JP2000048951A - Luminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen a using range for an organic EL luminescent element by imparting flexibility to the organic EL luminescent element, and/or imparting translucency to the element, and/or allowing a light emitting direction of the element to be directed to an element direction in the view from a substrate. SOLUTION: A flexible material such as plastics is used for a substrate 11 to impart flexibility to an organic EL luminescent element. Light transmittance of a negative electrode 15 in a visible light band is made 50% or more to impart translucency to the organic EL luminescent element. The organic EL luminescent element is constituted to put in order the negative electrode 15, a luminous layer, a hole transport layer, and a positive electrode 13 from a substrate side to direct a lighting direction to an upper face direction of the element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent light emitting device using an organic compound (hereinafter referred to as an organic EL device).
Element).

[0002]

2. Description of the Related Art In recent years, organic electroluminescent light emitting devices have been actively studied. This is achieved, for example, by using tin-doped indium oxide (IT) formed on a glass substrate 21.
O) or the like, a hole transport material such as tetraphenyldiamine (TPD) is thinned by vapor deposition or the like on a transparent electrode (positive electrode), and a fluorescent substance such as an aluminum quinolinol complex (Alq3) is laminated as a light emitting layer. Element having a basic structure in which a metal electrode (negative electrode) having a small work function is formed.
It is noted that a very high luminance of 00 cd / cm2 can be obtained.

As a material used as a negative electrode of such an organic EL element, a material that injects a large amount of electrons into a light emitting layer is effective, and a material having a smaller work function is more suitable as a negative electrode. There are various materials having a small work function. Examples of materials used as a negative electrode of an EL light-emitting element include alloys such as MgAg and MgIn described in JP-A-4-233194, alkali metals and the like. And a metal having a large work function as a combination of AlCa,
AlLi and the like are known.

However, in the case where the organic EL element has the above-described structure, since the negative electrode has no light-transmitting property, light is emitted from the positive electrode. For this reason, it cannot be used for applications in which an object behind the element needs to be visually recognized, and the application range has to be limited.

Further, the organic EL element is generally formed on a glass substrate, and the substrate itself has no flexibility. Therefore, it cannot be applied to, for example, a display having a curved surface, a show window, and the like. The range was limited.

Further, in the organic EL device having the conventional structure, the light emitting layer is located on the substrate side of the negative electrode, so that light can be mainly extracted only on the substrate side where the device is formed. It has been difficult to apply such a technique that another functional element is formed and the organic EL element functions as a backlight.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic EL light emitting device with flexibility and / or to provide an organic EL light emitting device with a light transmitting property and / or to provide an organic EL light emitting device. By allowing the light emitting direction to be configured in the element direction as viewed from the substrate, the range of use of the organic EL light emitting element is expanded.

[0008]

This and other objects are achieved by the present invention described below. (1) By using a material having a flexible property such as plastic for the substrate, the organic EL light emitting element has a flexible property. (2) The organic EL light emitting element is made to have a light transmitting property by making the negative electrode have a light transmittance of 50% or more in the visible light band. (3) By configuring the organic EL light-emitting device in the order of the negative electrode, the light-emitting layer, the hole transport layer, and the positive electrode from the substrate side, the lighting direction is the upper surface direction of the device. By implementing the above items, an organic EL light-emitting element having flexibility and / or translucency and / or having an arbitrary lighting direction can be realized, thereby contributing to expansion of its application range. Is what you do.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail.

Embodiment 1 FIG. 1 is a schematic diagram showing one configuration of an organic EL light emitting device of the present invention. On a flexible transparent substrate 11, a positive electrode 12, a hole injection / transport layer 13, a light emitting and electron injection / transport layer 14, and a negative electrode 15
Are formed.

In this embodiment, a transparent substrate 1 having flexibility is used.
As 1, a substrate containing polyethylene terephthalate as a main component was used. Here, the material of the transparent substrate is not limited to the above, and there is no problem even if other materials such as PES and PMMA are used.

The EL device of the present invention is not limited to the illustrated example, but may have various configurations. For example, the EL device may have a configuration in which an electron injection / transport layer is interposed between a light emitting layer and a negative electrode.

The cathode is formed by vapor deposition or sputtering.
The organic layer such as the light emitting layer can be formed by vacuum evaporation or the like, and the positive electrode can be formed by the above-described method. Each of these films is patterned by a method such as mask evaporation or etching after forming the film as necessary. Thus, a desired light emission pattern can be obtained. Further, the substrate is a thin film transistor (TFT), and by forming each film according to the pattern, a display and drive pattern can be used as it is. Finally, Si
A protective layer made of an inorganic material such as OX or an organic material such as Teflon may be formed.

As a constituent material of the negative electrode, as a material having a low work function, for example, for effective electron injection, for example,
K, Li, Na, Mg, La, Ce, Ca, Sr, B
a, a metal element such as Al, Ag, In, Sn, Zn, Zr, etc., or a metal element containing them in order to improve stability.
It is preferable to use a three-component alloy system. As an alloy system, for example, Ag · Mg (Ag: 1 to 20 at)
%), Al.Li (Li: 0.5 to 10 at%), In
-Mg (Mg: 50-80 at%), Al-Ca (C
a: 5 to 20 at%).

The thickness of the cathode electrode thin film may be a certain thickness or more for sufficiently injecting electrons.
Preferably, the thickness may be 100 nm or more. The upper limit is not particularly limited, but is usually 100 to 500.
It may be about nm.

The protective layer may be transparent or opaque, and when transparent, a transparent material (for example, Si
O2, SIALON, etc.), or by controlling the thickness to be transparent (preferably, the transmittance of emitted light is 80%).
% Or more). Generally, the thickness of the protective layer is about 50 to 1200 nm. The method for forming the protective layer is not particularly limited, and may be evaporation or the like. However, according to the sputtering method, continuous film formation with the negative electrode is possible.

Next, the organic layer provided in the EL device of the present invention will be described.

The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The charge transport layer has a function of facilitating injection of holes from the positive electrode, a function of transporting holes, and a function of blocking electrons, and is also called a hole injection transport layer.

In addition, if necessary, for example, when the electron injecting / transporting function of the compound used in the light emitting layer is not so high, injection of electrons from the negative electrode between the light emitting layer and the negative electrode as described above. May be provided with an electron injecting and transporting layer having a function of facilitating electron transport, a function of transporting electrons, and a function of blocking holes.

The hole injection transport layer and the electron injection transport layer are
Increases and confines holes and electrons injected into the light emitting layer,
Optimize the recombination region and improve luminous efficiency.

The hole injecting / transporting layer and the electron injecting / transporting layer may be separately provided in a layer having an injection function and a layer having a transport function.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
It is preferable to set the thickness to 0 to 100 nm.

The thickness of the hole injecting / transporting layer and the thickness of the electron injecting / transporting layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. . When the injection layer and the transport layer for electrons or holes are separated from each other, the thickness of the injection layer is preferably 1 nm or more, and the thickness of the transport layer is preferably 20 nm or more. At this time, the upper limits of the thicknesses of the injection layer and the transport layer are generally about 100 nm for the injection layer and about 100 nm for the transport layer. Such a film thickness is the same when two injection / transport layers are provided.

Further, by controlling the film thickness in consideration of the carrier mobility and carrier density (determined by ionization potential and electron affinity) of the combined light emitting layer, electron injection transport layer and hole injection transport layer, recombination is achieved. It is possible to freely design the region and the light emitting region, and it is possible to design the light emission color, control the light emission luminance and light emission spectrum by the interference effect of both electrodes, and control the spatial distribution of light emission.

The light emitting layer of the EL device of the present invention contains a fluorescent substance which is a compound having a light emitting function. Examples of the fluorescent substance include metal complex dyes such as tris (8-quinolinolato) aluminum disclosed in JP-A-63-264692. In addition, or in addition, or alone, quinacridone, coumarin, rubrene, styryl dye, other tetraphenylbutadiene, anthracene, perylene, coronene,
A 2-phthaloperinone derivative or the like can also be used. The light emitting layer may also serve as the electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited or the like.

The electron injecting / transporting layer provided as necessary includes an organic metal complex such as tris (8-quinolinolato) aluminum, an oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoline derivative, and a quinoxaline derivative. , A diphenylquinone derivative,
Nitro-substituted fluorene derivatives and the like can be used.
As described above, the electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The formation of the electron injecting and transporting layer may be performed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is provided separately for the electron injecting layer and the electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the higher electron affinity from the cathode side. This stacking order is the same when two or more electron injection / transport layers are provided.

The hole injecting and transporting layer is described in, for example, JP-A-63-295695 and JP-A-2-191694.
JP, JP-A-3-792, JP-A-5-2346
No. 81, JP-A-5-239455, JP-A-5
JP-A-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100
Various organic compounds described in JP-A-172, EP0650955A1, and the like can be used. For example, a tetraarylbendicine compound (tetraaryldiamine or tetraphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, polythiophene, or the like. . Two or more of these compounds may be used in combination, and when they are used in combination, they may be stacked as separate layers or mixed.

When the hole injecting and transporting layer is provided separately as a hole injecting and transporting layer, a preferable combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the smaller ionization potential in order from the positive electrode (ITO or the like) side. It is preferable to use a compound having a good thin film property on the surface of the positive electrode. Such a stacking order is the same when two or more hole injection / transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In the case of forming an element, a thin film having a thickness of about 1 to 10 nm can be made uniform and pinhole-free because evaporation is used, so that the hole injection layer has a small ionization potential and has absorption in the visible part. Even when such a compound is used, it is possible to prevent a change in the color tone of the emission color or a decrease in efficiency due to reabsorption.

The hole injection transport layer may be formed by depositing the above compound in the same manner as the light emitting layer.

In the present invention, the material and thickness of the transparent electrode used as the positive electrode are preferably determined so that the transmittance of emitted light is preferably 80% or more. Specifically, for example, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZ)
O), SnO2, polypyrrole doped with a dopant, or the like is preferably used for the positive electrode. The thickness of the positive electrode is preferably about 10 to 500 nm. Further, it is necessary that the driving voltage be low in order to improve the reliability of the element.

As a substrate material, a transparent or translucent material such as a flexible resin is used. Further, the emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

The organic EL device of the present invention is generally used as a DC drive type EL device, but it can be AC drive or pulse drive. The applied voltage is usually 5 to 2
It is about 0V.

Since the organic EL element of the present invention has flexibility, it can be applied to, for example, a window display having a curved surface, and has the effect of expanding the application of the organic EL element.

(Embodiment 2) Next, another embodiment of the present invention will be described. FIG. 2 is a schematic diagram for explaining another embodiment according to the present invention. In this embodiment, a positive electrode 22, a hole injecting / transporting layer 23, a light emitting and electron injecting / transporting layer 24,
A negative electrode 25 is formed. In this embodiment, the negative electrode 25 is composed of two layers, a 5 nm-thickness magnesium-silver alloy layer 26 on the side in contact with the light-emitting layer, and an ITO transparent electrode layer 27 on the opposite side. Is formed. Here, the magnesium-silver alloy layer 26 on the side in contact with the light emitting layer
Has a thickness of 1 nm to 20 nm, preferably 3 nm to 1 nm.
What is necessary is just to set in the range of 0 nm. Further, as the transparent electrode layer 27 on the opposite side, tin-doped indium oxide (IT
O), an electrode material such as zinc-doped indium oxide (IZO) or antimony-doped tin oxide, and a transparent electrode formed by forming an electrode material such as gold to be extremely thin so as to have a visible light transmittance of 50% or more. Can be used.

In this embodiment, the element can be made translucent by making the configuration of the negative electrode as described above. In this embodiment, the selection of the substrate is not limited to a flexible substrate. Other films other than the negative electrode configuration can be formed by the same process as in the first embodiment.

By using the method of this embodiment, the organic EL
The element can be made to have a light-transmitting property. For example, it can be used in a box for a product display, for example, to illuminate while showing an internal product, and the application range of the organic EL element can be expanded. .

(Embodiment 3) Next, another embodiment of the present invention will be described. FIG. 3 is a schematic diagram for explaining another embodiment according to the present invention. In this embodiment, a negative electrode 32, a hole injection / transport layer 33, a light emitting and electron injection / transport layer 34,
A positive electrode 35 is formed.

In this embodiment, by forming the negative electrode on the substrate side, the emission direction of the emitted light can be changed to the general organic E
The direction can be opposite to that of the L element. For example, it is possible to apply another function element on the organic EL element and use it as a pack light. The structure of each film can be formed by a process similar to that of the first or second embodiment.

Further, by using the method of the present embodiment, it is possible to first form a transparent electrode such as ITO on a substrate, which is advantageous in terms of process.

[0042]

According to the present invention, the organic EL element is made flexible and / or the organic EL element is made transparent, and / or the light emitting direction of the organic EL element is changed to the substrate. By being configured in the element direction from the viewpoint, the range of use of the organic EL light emitting element can be expanded.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing another embodiment of the present invention.

FIG. 3 is a conceptual diagram showing another embodiment of the present invention.

[Explanation of symbols]

 11 Flexible Transparent Substrate 12 Positive Electrode 13 Hole Injection / Transport Layer 14 Emission and Electron Injection / Transport Layer 15 Negative Electrode 21 Transparent Substrate 22 Positive Electrode 23 Hole Injection / Transport Layer 24 Light Emission and Electron Injection / Transport Layer 25 Negative electrode 26 Alloy layer of magnesium and silver 27 Transparent electrode layer 31 Transparent substrate 32 Negative electrode 33 Hole injection / transport layer 34 Light emission and electron injection / transport layer 35 Positive electrode

Claims (16)

[Claims] 1. An organic electroluminescent light emitting device having a light emitting layer between a negative electrode and a positive electrode, wherein a substrate on which the device is formed has flexibility. 2. The light emitting device according to claim 1, wherein the substrate is a transparent substrate made of a flexible resin or the like. 3. The light emitting device according to claim 2, wherein the negative electrode and the positive electrode have translucency. 4. The negative electrode comprises tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO),
Alternatively, a light-transmitting property can be provided between a light-emitting layer and a transparent electrode formed by forming an electrode material such as antimony-doped tin oxide and gold so as to have a transmittance of visible light of 50% or more so as to be extremely thin. 4. The light emitting device according to claim 3, wherein the light emitting device is formed of a material having a thickness that does not impair and having a small work function. 5. The light emitting device according to claim 4, wherein the material having a low work function used for the cathode is an alloy of magnesium and silver. 6. The light emitting device according to claim 5, wherein the thickness of the alloy layer of magnesium and silver used for the negative electrode is in the range of 1 nm to 20 nm, preferably in the range of 3 nm to 10 nm. . 7. The positive electrode comprises tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO),
Or a metal oxide conductor such as antimony-doped tin oxide,
4. The light emitting device according to claim 3, wherein the light emitting device is an organic conductor such as polypyrrole or polyaniline to which a dopant is added. 8. An organic electroluminescent light-emitting device having a light-emitting layer between a cathode and a cathode, wherein the structure from the substrate side on which the device is formed is formed in the order of a cathode, a light-emitting layer, and a cathode. A light emitting element characterized by the above-mentioned. 9. The light emitting device according to claim 8, wherein the negative electrode and the positive electrode have translucency. 10. The negative electrode comprises tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), or antimony-doped tin oxide formed on a substrate;
And a transparent electrode formed by forming an electrode material such as gold so as to have a visible light transmittance of 50% or more so as to be extremely thin, so as to have a film thickness which does not impair the light transmittance and a work function of The light emitting device according to claim 9, wherein a small material is formed. 11. The light emitting device according to claim 10, wherein the material having a small work function used for the cathode is an alloy of magnesium and silver. 12. The light emitting device according to claim 11, wherein the thickness of the magnesium-silver alloy layer used for the cathode is in the range of 1 nm to 20 nm, preferably in the range of 3 nm to 10 nm. . 13. The positive electrode is made of tin-doped indium oxide (ITO) or zinc-doped indium oxide (IZ).
O) or a metal oxide conductor such as antimony-doped tin oxide, or an organic conductor such as polypyrrole or polyaniline to which a dopant is added.
The light-emitting element according to any one of the preceding claims. 14. The light emitting device according to claim 8, wherein said substrate is a transparent substrate made of glass, transparent resin or the like. 15. The light emitting device according to claim 8, wherein the substrate has flexibility. 16. The substrate according to claim 14, wherein said substrate is a transparent substrate made of a flexible resin or the like.
5. The light-emitting device according to 5.