JP2001085158A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the stability and uniform luminescent property of an organic EL element which emits light at high brightness. SOLUTION: This organic EL element has a first electrode 20, an organic compound layer 22 and a second electrode 24, all provided in a luminescent area on a substrate, with a current supplied from a source of current to the organic compound layer 22 via the first and second electrodes 20, 24. The first and second electrodes 20, 24 are connected to the source of current via extension terminals 20T, 24T extended out to the peripheral edge of the substrate from the electrodes, and the terminal width of the extension terminal 20T of at least one of the electrodes 20 formed from a transparent conductive material such as ITO(indium tin oxide) is about 50% or more of the width of the electrode. In particular, the terminal width of the extension terminal 20T is desirably equal to or greater than the electrode width. Further, the terminals 20T, 24T are formed at both ends of each electrode to reduce wiring resistance and nonuniformity of charge density. A conductive metal oxide material is used for the extension terminal 24T of the second electrode 24 of a metal that is prone to oxidation, to thereby prevent an increase in wiring resistance due to oxidation of the terminal.

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 (hereinafter, referred to as an organic EL device), and more particularly to a lead terminal for an electrode of the device.

[0002]

2. Description of the Related Art An organic EL element is a self-luminous element which emits light from an organic compound layer sandwiched between electrodes, is capable of emitting high luminance, has no restriction on a viewing angle, is driven at a low voltage, and has a fast response. In addition to the use as a display element of a display, the use as a high-luminance flat light source such as a backlight of a liquid crystal display device is promising.

FIG. 4 shows a cross-sectional structure of a conventional organic EL device for a flat light source, and FIG. 5 shows a plan structure of the device. As illustrated, an ITO electrode (anode) is formed as a single first electrode 2 in a light emitting region of the glass substrate 10, and an organic compound layer 22 including a light emitting layer is formed on the first electrode 2. Further, a metal electrode (cathode) is formed on the organic compound layer 22 as the second electrode 4. Further, the sealing container 40 is covered so as to cover the light emitting region of the element from the second electrode side, and is adhered to the substrate 10 by the resin 42.

[0005] As shown in FIG. 5, at the end of the substrate 10, a lead terminal 2T drawn from the first electrode 2 and a second lead terminal 4T drawn from the second electrode 4 are respectively provided. It is formed integrally with the electrode.

External terminals (not shown) are connected to the extraction terminals 2T and 4T, respectively.
, Holes are injected from the first electrode 2 and electrons are injected from the second electrode 4 through the extraction terminals 2T and 4T. The injected holes and electrons move in the organic compound layer 22 and collide with each other,
Recombination occurs and disappears, and the energy generated by the recombination causes the light-emitting molecule to be in an excited state, thereby causing light emission.

[0006]

A lead terminal formed on the same substrate as the electrode for connection between the electrode of the element and an external power supply or the like is formed on the periphery of the substrate and connected to an external power supply or the like. You. In the conventional organic EL element for a flat light source, the lead terminals 2T and 4T have a minimum size at the end of the substrate 10 for connection to an unillustrated external current source, as shown in FIG. The design is adopted.

Here, in an organic EL element used for an application such as a flat light source, it is necessary to emit light with high luminance over the entire surface. In such an application, a large current is supplied to the first electrode and the second electrode. There is a need. However, as a material of the first electrode 2, a transparent conductive material such as ITO is used in order to enable light emission to the substrate side. This transparent conductive material has a higher electric resistance than a general metal electrode, and in applications such as a flat light source to which a large current is supplied, Joule heat generated on the ITO electrode side of the element becomes considerably large. I will. Then, the lead terminal 2T having a narrow width formed integrally with the ITO electrode has a smaller area, so that the wiring resistance is higher than that of the electrode portion, and the temperature becomes considerably high due to the generated Joule heat.

On the other hand, the organic compound layer 22 using the materials proposed at present has insufficient heat resistance and stability, and tends to deteriorate in characteristics at high temperatures. Therefore,
In particular, it is desired to suppress a rise in temperature due to Joule heat generation.

An organic compound layer 22 is formed between the first and second electrodes near the boundary between the lead terminal 2T and the first electrode 2, and an organic compound layer 22 near the narrow lead terminal 2T is formed. Since the electric field is concentrated on the layer 22, there is a possibility that the light emission intensity is locally increased, and further, a dielectric breakdown occurs.

Therefore, an object of the present invention is to improve the stability, reliability and uniform light emission of an organic EL device.

It is another object of the present invention to provide an organic EL device suitable for use in which a large current is supplied to an organic compound layer to emit light, such as a flat light source.

[0012]

In order to achieve the above object, an organic EL device according to the present invention comprises, in a light emitting region, a first electrode formed on a substrate and an organic compound layer formed on the first electrode. A second electrode sandwiched therebetween.
And an organic EL element for supplying a current from a current source to the organic compound layer through a second electrode to emit light,
And the second electrode is connected to the current source via a lead terminal drawn from each electrode to the peripheral portion of the substrate, and for the electrode composed of at least the transparent conductive material among the first and second electrodes. The terminal width of the lead terminal is at least 50% of the electrode width of the electrode in the light emitting region.

It is more preferable that the terminal width of the lead terminal of the electrode made of a transparent conductive material is equal to or larger than the electrode width in the light emitting region.

A transparent conductive material, for example, ITO (Indium)
A lead terminal for an electrode made of Tin Oxide is formed integrally with the electrode, and the same transparent conductive material is often used. In such a case, the wiring resistance of the terminal portion can be reduced by setting the width of the extraction terminal to at least 50% or more of the electrode width in the light emitting region, particularly, equal to or more than the electrode width. Therefore, when a large current from an external current source is supplied to the electrode via the extraction terminal, Joule heat which is particularly easily generated in the extraction terminal can be reduced. Further, it is possible to prevent the electric field from being concentrated on the organic compound layer at the boundary between the extraction terminal and the electrode. Further, not only the electrode formed of the transparent conductive material but also the lead terminal for a metal electrode having a lower resistance, if the terminal width is 50% or more of the width of the metal electrode, the wiring resistance is reduced. be able to.

Another feature of the present invention is that in the light emitting region,
A first electrode formed on the substrate; and a second electrode formed on the first electrode with an organic compound layer interposed therebetween, and a current is applied to the organic compound layer via the first and second electrodes. An organic electroluminescent element that supplies current from a source and emits light, wherein the first and second electrodes are connected to the current source via extraction terminals drawn from each electrode to a peripheral portion of the substrate; And the extraction terminal for the second electrode is formed of a conductive metal oxide material. In this configuration, at least one of the first and second electrodes, which is an extraction terminal for an electrode made of a transparent conductive material, has a terminal width of 50% or more of the electrode width of the electrode in the light emitting region. Is more preferable.

If the lead terminals are formed of a metal material, the wiring resistance can be reduced, but the metal material is generally easily oxidized. In particular, the extraction terminal formed at the end of the substrate is exposed to the atmosphere, so that it is easily oxidized, and the oxidation causes an increase in resistance. In addition, as shown in FIG. 7, when the oxidation of the metal extraction terminal proceeds from the end of the substrate into the sealing container and reaches the organic compound layer, the organic compound layer may be broken. However, if a conductive metal oxide material is used for the extraction terminal as in the present invention, this material is hard to be oxidized, so that it is possible to prevent the resistance from being increased by oxidation and the destruction of the organic compound layer. Therefore, it is possible to improve the reliability and life time of the organic EL element.

Further, another feature of the present invention is that in each of the above elements, at least both ends of the first and second electrodes formed of a transparent conductive material are provided at both ends of the first and second electrodes.
The lead terminals drawn from the electrodes are respectively formed.

The lead-out terminal for one electrode may be formed at one place at the end of the substrate from the viewpoint of securing the connection with the outside. However, in the case of a lead terminal for an electrode that supplies a large current, the lead resistance is formed at both ends of the electrode of the substrate (two opposite sides of the substrate) as in the present invention, so that the wiring resistance at the lead terminal portion is reduced. Can be further reduced. In particular, since the electrodes and the lead terminals formed of a transparent conductive material have high wiring resistance, forming the lead terminals on both sides of the electrodes is very excellent from the viewpoint of reducing the wiring resistance. The wiring resistance can be reduced by forming not only the electrode formed of the transparent conductive material but also a lead terminal for a metal electrode having a lower resistance at both ends of the metal electrode. In addition, when current is supplied to one electrode through the lead terminals formed on both sides of the substrate, the bias of the charge density in the light emitting region can be reduced, and the in-plane light emission is uniformly improved. It becomes possible.

In the present invention, when each of the first electrode and the second electrode is a single electrode extending over the entire light emitting region, a large current is supplied to the electrodes, for example, a flat light source. In this case, the lead terminal is widened, the lead terminals are formed at both ends of the electrode, or a transparent conductive metal oxide material that is hardly oxidized is used as a terminal material. By doing this,
It is possible to reduce the resistance in a wiring path through which a large current flows, prolong the life of the element, and improve the reliability of the element.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 conceptually shows a plan configuration of an organic EL device according to Embodiment 1 of the present invention. FIG. 2 shows a cross section of the element taken along line AA in FIG. As shown in the figure, in the organic EL element, a first electrode 20, an organic compound layer 22, and a second electrode 24 are laminated in this order in a light emitting region on the substrate 10.

As the substrate 10, a transparent glass substrate, a transparent ceramics substrate, a diamond substrate or the like is used.

The first electrode 20 functions as an anode, and a transparent electrode having high light transmittance and conductivity is used.
Examples of such a material include a conductive metal oxide material, for example, indium tin oxide (ITO).
e), indium zinc oxide (InZnO), aluminum
A thin film material such as zinc oxide (ZnO: Al), SnO ₂ , indium oxide (In ₂ O ₃ ), or a thin film material such as polyaniline can be used. Au, Al, M
It is also possible to use an extremely thin metal film made of g or the like. The organic compound layer 20 is formed to a thickness of, for example, about several tens to several hundreds of nm, and has a two-layer structure of a hole transport layer and a light-emitting layer, a single-layer structure of a light-emitting layer, and a light-emitting layer. It has a three-layer structure of a layer and an electron transport layer.

On the organic compound layer 22, a second electrode 24 functioning as a cathode is formed. This second electrode 2
4, as Mg or Ag alone or an alloy, or
A laminated structure of LiF and Al, a laminated structure of Li ₂ O and Al,
Laminated body of Ca and Al or alloy containing both materials, MgF ₂
A metal material having a small ionization potential, such as a laminated structure of Al and Al, or an AlLi alloy, is used. However, it may be constituted by a transparent electrode.

The anode / organic compound layer / cathode laminate as described above is formed in the light emitting region of the device, and a sealing container 40 made of glass or metal is sealed with UV to seal the laminate.
It is adhered to the substrate by a resin 42 such as a curable resin.

In this embodiment, the extraction terminal 20T of the first electrode 20 formed of a transparent conductive material is connected to the electrode 2
0, that is, formed of the same transparent conductive material. Further, the lead terminal 20T is connected to the first electrode 20T.
And formed along two opposing sides of the substrate. The terminal width of the extraction terminal 20T is 50% or more of the electrode width of the electrode 20 in the light emitting region. In the example shown in FIG. 1, the terminal width of the extraction terminal 20T is
The width is set substantially equal to the electrode width of the first electrode 20.

The lead terminal 24T for the second electrode 24 made of a metal material is separate from the second electrode 24 as shown in the sectional view of FIG. When the terminal 20T is formed of a transparent conductive metal oxide such as ITO, it is formed of the same material.
The lead terminals 24T are also formed on both ends of the second electrode 24, respectively. Then, the terminal width of the lead terminal 24T is formed to be 50% or more of the electrode width of the second electrode 24, and particularly to the same width as the second electrode 24 in the example of FIG.

As described above, in the first embodiment, the terminal width of the lead terminals 20T and 24T of the first and second electrodes 20 and 24 is set to 50% or more of the corresponding electrode width. In particular, at least the lead terminal 20T of the first electrode using a high-resistance transparent conductive material has a large terminal width to reduce the wiring resistance at the lead terminal 20T. Further, by setting the terminal width as described above, the lead terminal 20T and the first electrode 2
The concentration of the electric field on the organic compound layer 22 at the boundary with zero can be reduced, and the Joule heat generated at the extraction terminal 20T can be reduced. Also, as shown by the dashed line in FIG. 1, if the terminal width is formed larger than the electrode width, it is possible to further reduce the wiring resistance of the extraction terminal.

In the first embodiment, lead terminals are formed on two sides facing each other on the substrate, that is, both ends of each electrode, and one electrode is connected to an external current source via the two lead terminals. . Therefore, it is possible to further reduce the wiring resistance and the amount of generated heat. In addition, since current can be supplied to the electrodes from both sides of the substrate, not only can the resistance of the wiring be reduced, but also the amount of current supplied within the light emitting area can be made uniform, and the uniformity of the light emission intensity in the plane can be improved It becomes possible to greatly increase.

Further, in the first embodiment, the lead-out terminal 24 for the second electrode 24 made of a metal material which is easily oxidized is used.
As T, a conductive metal oxide material that is difficult to oxidize is used,
The resistance of the lead terminal 24T is prevented from increasing due to oxidation.
Further, it also prevents the organic compound layer 22 formed near the terminal from being affected by oxidation and causing dielectric breakdown or the like. When a transparent conductive metal oxide material is used as the material of the first electrode 20 and the lead terminal 20T, the same metal oxide material can be used for the lead terminal 24T. If the same material is used, the lead terminal 24T can be formed on the substrate simultaneously with the first electrode 20 and the lead terminal 20T.

In the above description, the lead terminal 20
Although T and 24T are each described as a solid electrode, a slit or the like may be formed as long as a sufficient area is secured from the viewpoint of reducing the wiring resistance.

[0032]

EXAMPLE An example of the organic EL device according to Embodiment 1 will be described below with reference to FIGS.

As the substrate 10, a Corning 7059 glass substrate polished on both sides was used. The substrate 10 was subjected to ultrasonic cleaning using acetone and isopropyl alcohol in this order, rinsed with pure water, and dried in a super clean oven. Next, the metal mask for forming the ITO film and the glass substrate are set in the sputtering apparatus, and the first electrode 20, its lead terminal 20T and the second electrode lead terminal 2 are placed in a vacuum.
A 120 nm thick ITO film of 4T was formed. Film formation is A
r: flowing 1% O ₂ gas, degree of vacuum 3.5 × 10 ^{- 3,} was performed at a substrate temperature of 300 ° C..

After the formation and patterning of the ITO, the substrate is ultrasonically cleaned using an organic alkali cleaning semico clean 56 (manufactured by Furuuchi Chemical Co., Ltd.), rinsed with pure water, and sequentially heated using isopropyl alcohol, acetone and isopropyl alcohol. Ultrasonic was applied and rinsed with pure water. afterwards,
It was dried in a super clean oven, subjected to UV ozone treatment to remove organic contaminants on the ITO surface, and quickly set in a vapor deposition apparatus. Next, after mounting a mask for forming an organic layer in a vacuum, heating the carbon crucible to form a copper phthalocyanine (CuPc) and a hole transport layer [TEL02 which is a triphenylamine tetramer] as the organic compound layer 22.
2], a light emitting layer [a quinolinolamine Al complex (Alq3) layer doped with 1% quinacridone (Qd), and an Alq3 single layer]. The deposition rate is 2
6 nm / min. In addition, TPTE can be used as the hole transporting material in addition to TEL022.

Embedded image

Next, the mask was changed to a film for forming a cathode electrode (second electrode) in vacuum, and Mg was changed to 6 nm / min and Ag was changed to 0.
At a deposition rate of 6 nm / min, 160 nm of Mg, Ag
Was deposited to a thickness of 16 nm. Each layer has a degree of vacuum of 5 × 10 ^−7.
The film was formed under the condition of Torr or less.

Through the above steps, the first electrode (IT
The lead terminals 20T of O) are formed at the same width as the first electrode width and at both ends of the first electrode 20 as shown in FIG. At the same time, ITO lead terminals 24T for the second electrode (metal) were formed on both end sides of the second electrode 24 with the same width as the second electrode 24, respectively. The connection between the lead terminal 24T made of ITO and the second electrode 24 made of MgAg is performed by forming the second electrode 24 at the end of the substrate so as to overlap the lead terminal 24T as shown in the sectional view of FIG. It is done by doing.

Next, in a glove box in a nitrogen atmosphere, U
The sealing container 40 coated with the V-cured resin 42 was brought into close contact with the substrate. Since a glass container was used as the sealing container 40 in this embodiment, the organic pattern was covered with aluminum foil to protect the light emitting area, and only the resin-coated portion was irradiated with UV light for 5 minutes to cure the resin 42 and seal with the substrate 10. The stop container 40 was adhered.

The organic compound layer 22 of the obtained organic EL device
Then, holes were injected from the first electrode 20 and electrons were injected from the second electrode 24, and the device was driven under the light emission condition of an initial luminance of 5000 cd / m ^{2. As} a result, bright and uniform light emission was observed in the light emitting region. In particular, in the conventional device, the light emission intensity was higher than in other regions due to the electric field concentration near the boundary between the first electrode and the extraction terminal, but in the device according to the example, the connection between the extraction terminal 20T and the first electrode 20 was large. Even in the vicinity of the boundary, uniform and bright light emission was achieved, which was the same as the light emission intensity in other regions. When the initial luminance was driven under the above-described high luminance condition, the conventional organic EL element having a narrow lead terminal as shown in FIGS. 4 and 5 had a luminance half time of only several tens of minutes. On the other hand, in the device according to the present example, the luminance half time was able to be attained on the order of several hours.

[Embodiment 2] In the device configuration of Embodiment 1 described above, the first electrode 20 is constituted by a solid electrode. In Embodiment 2, however, the first electrode 20 is formed as shown in FIGS. 30 was constituted by a pattern having a gap in the light emitting region, such as a matrix (or mesh or lattice) pattern. However, the lead terminal 20T for the first electrode 30 is a solid terminal similar to the first embodiment from the viewpoint of increasing the area as much as possible and reducing the wiring resistance. Other configurations are common to the first embodiment.

As described above, the transparent conductive material ITO
Has a relatively high resistance. Therefore, when this is used as the first electrode 30 of an organic EL element used for a flat light source (the same is true for the extraction terminal 20T), generation of Joule heat is avoided in the first electrode 30 through which a large current flows. I can't. Also, the first electrode 30
In some cases, poor conduction may occur in the interior. If the first electrode 30 made of ITO or the like has a pattern with a gap in the light emitting region as in the second embodiment, the generated Joule heat can be radiated through the gap between the patterns, and the organic compound layer 22 generated by the heat is generated. Characteristics deterioration can be prevented. Further, even when there is a conduction failure in a part of the electrode, it is possible to prevent the influence of the failure of the light emission from occurring on the entire light emitting region of the electrode.

Since the second electrode 24 is made of a low-resistance metal material, it may be a solid electrode as in the first embodiment. It may be a pattern. However, the second electrode 2
Regarding the lead terminal 24T for the fourth, it is more appropriate to use a solid terminal as in the first embodiment from the viewpoint of reducing the wiring resistance.

[0042]

As described above, in the present invention, the terminal width of at least the lead terminal of the electrode using a transparent conductive material among the first and second electrodes for supplying a current to the organic compound layer is increased. Thereby, the wiring resistance can be reduced. Further, since the terminal width is wide, the concentration of the electric field in the organic compound layer formed near the boundary between the terminal and the electrode can be reduced. Therefore, an organic EL element having a uniform emission intensity in a plane, a long life and high reliability can be obtained, and an organic EL element which is very suitable for applications such as a flat light source can be provided.

Further, by forming the lead terminals of one electrode at both ends of the electrode, the wiring resistance can be further reduced and the charge density can be made uniform, and the light emission within the plane can be made more uniform. Things.

Further, by using a conductive metal oxide material as a lead terminal for a metal electrode which is easily oxidized, it is possible to prevent the lead terminal exposed to the atmosphere or the like from being oxidized. Can be prevented from reaching the organic compound layer and destroying the organic compound layer.

[Brief description of the drawings]

FIG. 1 is a view conceptually showing a planar configuration of an organic EL device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of the element along the line AA in FIG.

FIG. 3 is a diagram showing a plan configuration of an organic EL device according to another embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional configuration of a conventional organic EL element.

FIG. 5 is a diagram showing a plan configuration of the organic EL element shown in FIG.

FIG. 6 is a plan view illustrating a problem in the vicinity of a lead terminal of a conventional organic EL element.

FIG. 7 is a cross-sectional view illustrating a problem in the vicinity of a lead terminal of a conventional organic EL element.

[Explanation of symbols]

10 transparent substrate, 20, 30 first electrode (transparent electrode),
20T extraction terminal (for first electrode), 22 organic compound layer, 24 second electrode (for metal electrode), 24T extraction terminal (for second electrode), 40 sealed container, 42 resin.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasukun Taga 41-41, Oku-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi F-term in Toyota Central R & D Laboratories, Inc. (reference) 3K007 AB00 AB01 AB02 BB01 CA00 CA01 CA02 CB01 CC05 DA00 FA01 FA02

Claims (4)

[Claims] A first electrode formed on a substrate in a light emitting region; and a second electrode formed on the first electrode with an organic compound layer interposed therebetween, wherein the first and second electrodes are provided. An organic electroluminescent element that supplies a current from a current source to the organic compound layer and emits light through the first and second electrodes, and the first and second electrodes are connected to a lead terminal that is led to a peripheral portion of the substrate from each electrode. A terminal width of the lead terminal for an electrode which is connected to a current source and which is formed of at least a transparent conductive material among the first and second electrodes,
An organic electroluminescent device, wherein the width is 50% or more of the electrode width of the electrode in a light emitting region. 2. A light-emitting region, comprising: a first electrode formed on a substrate; and a second electrode formed on the first electrode with an organic compound layer interposed therebetween. An organic electroluminescent element that supplies a current from a current source to the organic compound layer and emits light through the first and second electrodes, and the first and second electrodes are connected to a lead terminal that is led to a peripheral portion of the substrate from each electrode. An organic electroluminescent device connected to a current source, wherein the extraction terminal for an electrode composed of at least a metal material among the first and second electrodes is formed of a conductive metal oxide material. element. 3. The organic electroluminescent device according to claim 1, wherein at least both ends of the first and second electrodes made of a transparent conductive material are drawn out from the electrodes. An organic electroluminescent element, wherein each of the drawn out terminals is formed. 4. The organic electroluminescent device according to claim 1, wherein each of the first electrode and the second electrode is a single electrode extending over the entire light emitting region. Characteristic organic electroluminescent device.