JP3268834B2 - Organic electroluminescent device - Google Patents

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 thin film layer sandwiched between a pair of electrodes.

[0002]

2. Description of the Related Art With the diversification of information devices, various display devices have been researched and developed. Among them, an electroluminescent element has attracted attention in recent years. The electroluminescent device includes an inorganic electroluminescent device and an organic electroluminescent device, and the light emitting principles of the two devices are different from each other. The inorganic electroluminescent element is a collision type electroluminescence, that is,
The organic electroluminescent device is of an injection type, that is, a light emitting type by recombination of electrons and holes, whereas an organic light emitting device is of an excitation light emitting type by collision between accelerated electrons and a light emitting center. Due to such a difference in light emission principle, the drive voltage of the inorganic electroluminescent element is 100 to 200 V, whereas the organic electroluminescent element has a low drive voltage of about 5 to 20 V. It is excellent in that it can be driven at low voltage. In the case of an organic electroluminescent device, a light emitting device of three primary colors can be manufactured by selecting a fluorescent substance, and realization of a full-color display device can be expected.

As a general structure of the organic electroluminescent device, a structure in which a pair of electrodes are formed on a glass substrate so as to sandwich an organic layer as shown in FIG. One having a light-emitting layer, an electron transport layer, and a hole transport layer is called a three-layer structure, and one having a light-emitting layer, an electron transport layer, or a hole transport layer is called a two-layer structure. .

Meanwhile, in the conventional organic electroluminescent device, the above-mentioned organic electroluminescent device is partially modified in order to cause the device to emit light in a desired pattern in addition to simply emitting light, as shown in FIGS. Elements are used. 5A and 6A are cross-sectional views of the device, and FIG. 5B is a top view. In the device shown in FIG. 5, the electrode formed on the back side in the direction of taking out the emitted light indicated by arrow A as viewed from the organic layer is patterned in a desired shape, and a voltage is applied directly from the patterned electrode. This is an element having a configuration in which a lead wire is connected to the device.

In the device shown in FIG. 6, an electrode present in the direction of taking out emitted light indicated by arrow A when viewed from the organic layer is patterned, and a connection electrode for connecting a lead wire from the outside is provided. 51 is formed in contact with the patterned electrode. Further, when a voltage is applied to the element, an electrode serving as a counter electrode of the patterned electrode is provided on the portion facing the connection electrode 51 so that the light emitting layer formed on the portion facing the connection electrode 51 does not emit light. Is an element having no structure.

[0006]

However, although the above-mentioned organic electroluminescent device can emit light of a desired shape, it has the following problems. First, FIG.
In the case of patterning the electrode located on the back side in the direction of taking out light emission as seen from the organic layer shown in the above, a lead wire for applying voltage must be connected to the patterned electrode directly involved in light emission, At the time of connection, there was a problem that the electrodes were damaged and light emission was hindered.
For this reason, the connection of the lead wires must be carefully performed, and there has been a problem that the device fabrication becomes complicated. In addition, there is a problem that a screen viewed from the glass substrate at the time of non-light emission becomes non-uniform because a portion where electrodes are formed and a portion where electrodes are not formed are seen through.

On the other hand, when the electrodes positioned in the direction in which light emission is taken out as viewed from the organic light emitting layer shown in FIG. 6 are patterned, the electrode portions contributing to light emission are not damaged when the leads are taken out. As described above, in order to obtain a desired shape of light emission, an electrode serving as a counter electrode cannot be formed in a portion facing the connection electrode 51, and thus, as in the element of FIG. There is a problem that the viewed screen becomes uneven.

In view of the above situation, an object of the present invention is to provide an organic electroluminescent device in which a lead wire can be easily connected without damaging a patterned electrode directly involved in light emission, and a screen when light is not emitted is uniform. With the goal.

[0009]

The organic electroluminescent device according to the first aspect of the present invention comprises an organic thin film layer sandwiched between an anode and a cathode, and at least one electrode is patterned into a desired shape. In the organic electroluminescent device that has been
From the at least the side surface of the cathode provided on the back side in the direction of taking out the emitted light as viewed from the organic thin film layer to the entire exposed surface of the organic thin film layer on which the electrode is formed, a metal element simple substance having a larger work function than the cathode Or a metal film made of an alloy of a plurality of metal elements.

An organic electroluminescent device according to a second aspect of the present invention comprises an organic thin film layer sandwiched between an anode and a cathode, wherein at least one electrode is patterned into a desired shape. The work function is higher than that of the anode from at least the side surface of the anode provided on the back side in the direction of taking out the emitted light as viewed from the organic thin film layer to the entire exposed surface of the organic thin film layer on which the electrode is formed. A small metal film is covered.

[0011]

The above-described structure operates as follows. First, when the electrode provided on the back side in the direction of taking out the emitted light as viewed from the organic thin film layer is patterned, the electrode is formed from a side surface of the electrode by a metal having a lower carrier injection property than the electrode. By covering the entire exposed surface of the organic thin film layer, first, it is sufficient to connect the lead wire to the metal film portion, so that the patterned electrode involved in light emission is not damaged, and the complexity of element fabrication is also eliminated. .

In addition, by using a metal of the same color as the above-mentioned electrode as a material of the metal film, a non-light emitting screen can be made uniform. On the other hand, when the electrode formed in the direction of taking out the emitted light as viewed from the organic thin film layer is patterned, the organic thin film layer is exposed from the side of the electrode on the back side in the direction of taking out the emitted light as viewed from the organic thin film layer. As described above, the carrier injection 0 is low over the entire surface, and by covering with a metal film of the same color, a non-emission screen becomes uniform.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an organic electroluminescent device according to one embodiment of the present invention, in which an electrode formed on a back surface in a direction in which light emitted from an organic layer is extracted is patterned.

Hereinafter, the electrode formed on the back side in the direction of taking out the emitted light as viewed from the organic layer is referred to as an upper electrode, and the electrode formed in the direction of taking out the emitted light as viewed from the organic layer is referred to as a lower electrode. In FIG. 1, a flat glass substrate 1
A hole injection electrode 2, a hole transport layer 3, and an organic light emitting layer 4 having the same area as the glass substrate 1
Are formed in order. On this, an electron injection electrode 5 patterned in a desired shape, for example, a star shape, as an upper electrode
Are formed, and an electron injection electrode 5 and an organic light emitting layer 4 which is exposed because the electron injection electrode is not formed.
And a metal film 6 is formed on the entire upper surface of the light emitting element. The state in which the metal film 6 in FIG. 1 is provided is such that the metal film is covered up to the upper part of the electron injection electrode 5, but the metal film is formed at least from the side surface of the electron injection electrode 5 in the organic thin film layer. It is only necessary that the organic light emitting layer 4 be covered over the entire exposed surface.

A lead wire 7 for applying a voltage is connected to the metal film 6 and the hole injecting electrode 2, respectively, so that light is extracted in the direction of arrow A by applying the voltage. As a material of the hole injection electrode 2 serving as the lower electrode, transparent ITO is used to extract light emitted from the organic light emitting layer 4 from the glass substrate 1.

The material of the hole transport layer 3 is poly-N-
Vinyl carbazole is used, and tris (8-quinolinol) aluminum is used as a material of the organic light emitting layer 4. As a material of the electron injection electrode 5 as the upper electrode, a silver-white magnesium-indium alloy having a work function of 3.7 eV is used. As the material of the metal film 6, a material having a lower carrier injecting property than the upper electrode formed on the side where the metal film is formed must be used, so that the electron injecting property is lower than the metal used for the electron injecting electrode 5. Therefore, a metal having a large work function must be used.
In the case of this embodiment, the work function is 3.7 eV as described above.
Is used as the material of the electron injecting electrode 5, so aluminum (work function: 4.3 eV, silver white) having a higher work function was used.

Further, by using the same color metal for the electron injection electrode 5 and the metal film 6, a non-light-emitting screen becomes uniform. In addition, when silver-white as in this example,
The screen when no light is emitted has a mirror surface. The electroluminescent device having the above configuration was manufactured as follows. An ITO film is formed as a hole injection electrode 2 on a glass substrate 1. Poly-N-vinyl carbazole as a hole transport layer 3 is further coated with 100
{Tris (8-quinolinol) aluminum 900} is sequentially deposited as the organic light emitting layer 4 at a vacuum of about 10 ⁻⁶ Torr. Then, a magnesium-indium alloy (silver white, work function 3.7 e) was used as the electron injection electrode 5.
V) is deposited in a star shape using a metal mask. This shape can be arbitrarily selected by using different masks. Further, aluminum (silver white, work function 4.3 eV) was deposited as a metal film 6 covering the entire top surface of the device including the electron injection electrode 5.

A voltage between 6 V and 6 V is applied between both poles of the organic electroluminescent device.
When a voltage of 13 V is applied, only the organic light emitting layer facing the patterned electron injection electrode 5 emits light, and star-shaped light is extracted from the glass substrate side.
Further, when no light was emitted, the entire light emitting surface of the element was a uniform silver-white mirror surface. As described above, when the star-shaped light emission is performed, 6 V to 1
Driving in the range of 3 V is based on the data shown in FIG.

That is, when an electroluminescent device using a magnesium-indium alloy and a light emitting device using aluminum as materials of an electron injection electrode were manufactured and driven, respectively, the work function was as shown in FIG. The driving voltage is lower when a magnesium-indium alloy having a smaller value is used as the material of the electron injection electrode, and in the range of 6 V to 13 V,
This is because only the one using the magnesium-indium alloy as the material of the electron injection electrode emitted light.

This voltage range varies depending on the device manufacturing conditions, the type of organic material, and the type of metal. [Other Matters] In the above embodiment, aluminum was used as the metal film, but other than this, a high work function metal such as gold, silver,
Copper, iron, platinum, lead, tin, chromium, cobalt, indium, manganese, nickel, palladium, beryllium, bismuth, cadmium, gallium, iridium, molybdenum, niobium, osmium, rhenium, ruthenium, antimony, tantalum, titanium, vanadium, Similar effects were obtained when using tungsten, zirconium, and alloys containing these.

In particular, when the electrode is silver-white such as a magnesium-indium alloy, the metal film is silver-white silver, beryllium, chromium, indium, molybdenum, manganese,
Nickel, palladium, platinum, rhenium, ruthenium,
When antimony or tin is used, the screen at the time of non-emission becomes a mirror surface, which is useful for various uses such as a display element. Although not shown in the above embodiment, a similar effect can be obtained by providing a metal film even when the patterned upper electrode is a hole injection electrode.

At this time, it is necessary to use a material having a lower hole injecting property than the hole injecting electrode, that is, a metal having a small work function, as a material of the metal film. Specific materials include lithium, sodium, calcium, barium, cerium, cesium, erbium, europium, gadolinium, potassium, lanthanum, neodymium, rubidium, scandium, samarium, yttrium, ytterbium, zinc, and alloys containing these metals. Can be mentioned. Even when the lower electrode is patterned, as shown in FIG. 3, at least the entire exposed portion of the organic layer from the side surface of the upper electrode is made of a material having a lower carrier injection property than the upper electrode and the same color as the upper electrode. By covering with a metal film made of, a non-light-emitting screen can be made uniform.

In the case of an element having such a structure, a non-conductive fibrous substance or the like having the same color as the upper electrode may be provided on the exposed portion of the organic layer instead of the metal film. Even when the organic light emitting device has a three-layer structure or when both electrodes are patterned, the same effect can be obtained by providing the metal film.

[0024]

As described above, according to the present invention,
Since the upper electrode does not need to connect a lead wire to an electrode directly involved in light emission, the element manufacturing process can be simplified without damaging the electrode directly involved in light emission. In addition, by using a metal of the same color as that of the electrode on which the metal film is formed as the material of the metal film, the screen when light is not emitted becomes uniform, and the display element can be easily viewed. In particular, electrodes,
Also, in the case of an element having a silver-white material in the metal film, since the screen when light is not emitted has a uniform mirror surface, a unique application utilizing the fact that an image appears in the mirror surface only when energized can be expected. .

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a graph showing a difference in light emission characteristics when electron injection electrodes having different work functions are used.

FIG. 3 is a side view showing one embodiment of the present invention.

FIG. 4 is a sectional view of an organic electroluminescent device.

FIG. 5 is a side cross-sectional view and a top view of an electroluminescent device in a case where an electrode is patterned in the related art.

FIG. 6 is a side cross-sectional view and a top view of an electroluminescent element when electrodes are patterned in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Hole injection electrode 3 Hole transport layer 4 Organic light emitting layer 5 Electron injection electrode 6 Metal film

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Nishio 2-18-18 Keihanhondori, Moriguchi City Sanyo Electric Co., Ltd. (72) Inventor Yuji Hamada 2-18-18 Keihanhondori, Moriguchi City Sanyo Electric Co., Ltd. (72) Inventor Kenichi Shibata 2-18 Keihanhondori, Moriguchi City Sanyo Electric Co., Ltd. (56) References JP-A-5-205878 (JP, A) JP-A-4-212284 (JP, A) JP JP-A-4-132191 (JP, A) JP-A-4-19993 (JP, A) JP-A-6-45074 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 33 / 00-33/28

Claims (2)

(57) [Claims] An organic thin film layer is sandwiched between an anode and a cathode.
And at least one of the electrodes has a pattern
Organic thin-film layer
It is provided on the back side in the direction of taking out the emitted light
The electrode is formed at least from the side of the cathode
From the cathode, the work surface is exposed over the entire exposed surface of the organic thin film layer.
Large number of metal elements alone or a combination of multiple metal elements
Characterized by being coated with a metal film made of gold
Electroluminescent device. 2. An organic thin film layer is sandwiched between an anode and a cathode.
And at least one of the electrodes has a pattern
Organic thin-film layer
It is provided on the back side in the direction of taking out the emitted light
The electrode is formed at least from the side of the anode
From the anode, the work surface is exposed over the entire exposed surface of the organic thin film layer.
Characterized by being coated with a small number of metal films
Electroluminescent device.