JP2004134151A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL (electroluminescent) element for obtaining a stable light-emitting property and improving brightness of a display. <P>SOLUTION: An anode barrier layer 12 having a high barrier property against at least water is formed on a substrate 11. The water intruded from a side of the substrate 11 is shut off by the barrier layer 12 and an organic EL layer 14 is prevented from being intruded by the water. Thereby, deterioration of the EL layer 14 is suppressed even if the substrate 11 is composed of a plastic material. The barrier layer 12 has a transmittancy against light in a visible light region of 50% or higher and has a specific resistance of 0.001 Ωcm or lower. Thereby, light emitted from the EL layer 14 is passed through the barrier layer 12 and efficiently derived from a rear face of the substrate 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic EL element suitable for a display device as a light emitting element.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a display device (display), there is a stationary cathode ray tube, that is, a CRT (Cathode Ray Tube) device, and a flat panel display for satisfying demands for portable and thin devices. CRTs are widely used at present because of their high luminance and good color reproducibility, but problems such as large occupied capacity, heavy weight, and large power consumption have been pointed out. On the other hand, flat panel displays are lightweight and have higher luminous efficiency than cathode ray tubes, and are expected to be used for screen display of computers and televisions. Currently, as a flat panel display, an active matrix driving type liquid crystal display (LCD; Liquid Crystal Display) is commercialized. This LCD is a type of display that displays by receiving light (backlight) from the outside without emitting light by itself, and has a narrow viewing angle and is not a self-luminous type. Problems have been pointed out, such as high power consumption and insufficient response performance to high-definition, high-speed video signals expected to be put to practical use in the future.
[0003]
In recent years, an organic EL display has attracted attention as a display that can solve such various problems. The organic EL display has a configuration in which organic EL elements whose light emitting layers are made of an organic light emitting material are arranged in a matrix. In this organic EL element, an anode layer and a cathode layer, which are transparent electrodes, have a matrix structure. The pixel is made to emit light by applying a voltage between the selected anode layer and cathode layer and causing a current to flow through the organic EL layer. The generated light is taken out from the anode layer side.
[0004]
The organic EL display having such a configuration is a self-luminous type flat panel display that does not require a backlight, and has an advantage that a display with a wide viewing angle unique to the self-luminous type display can be realized. In addition, since only necessary pixels need to be turned on, it is possible to further reduce power consumption and to provide sufficient response performance to the high-definition high-speed video signal described above. It is believed that. Further, in recent years, such an organic EL display has attracted attention as a device having flexibility by using a plastic substrate as a substrate in order to utilize the flexibility inherent in the organic light emitting material.
[0005]
[Patent Document 1]
JP-A-6-124785 [Patent Document 2]
Japanese Patent Application Laid-Open No. H14-100469
[Problems to be solved by the invention]
By the way, the organic EL element constituting the organic EL display has a problem in the life of the organic light emitting material used for the light emitting layer. That is, one of the causes is the influence of moisture that enters the organic EL layer from the outside. When moisture enters the inside of the device, the cathode layer is oxidized or peels off at the interface with the organic compound, resulting in darkness. There is a problem that spots occur. This problem is particularly noticeable when a plastic substrate is used.
[0007]
For example, when a plastic substrate is used as a substrate of an organic EL element as in Patent Document 1, the organic EL layer deteriorates due to the penetration of moisture into the organic EL element through the plastic substrate. There was a problem that stable light emission characteristics could not be obtained. In addition, a technique for sealing a plastic substrate has been studied to solve such a problem, and for example, by forming an inorganic barrier layer on both surfaces of the plastic substrate, a good moisture-proof property is obtained. It has been reported (see Patent Document 2). However, since an inorganic film having a thickness of several hundred nm is formed on both surfaces of the substrate, there is a problem that the visible light transmittance and the flexibility are reduced, and thus the brightness is reduced. In addition, in a display using such an element, there is a problem that its storability is reduced.
[0008]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an organic EL device which can obtain stable light emission characteristics and sufficient luminance and can improve the storage property as a display. Is to do.
[0009]
[Means for Solving the Problems]
The organic EL device according to the present invention includes a substrate, an element portion in which an anode layer, an organic EL layer, and a cathode layer are laminated in this order on one surface of the substrate, and an organic EL layer of the substrate and the element portion. And one or more barrier layers having at least a barrier property against moisture formed therebetween.
[0010]
In the organic EL device according to the present invention, the barrier layer between the substrate and the organic EL layer blocks moisture that has entered from the substrate side and prevents entry into the organic EL layer. As a result, deterioration of the organic EL layer is suppressed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 shows a cross-sectional configuration of an organic EL device 10 according to one embodiment of the present invention. The organic EL element 10 includes a substrate 11, on which an anode barrier layer 12 is formed. The anode barrier layer 12 has a particularly high barrier property against moisture. An anode layer 13 is formed on the anode barrier layer 12. On the anode layer 13, an organic EL layer 14, a buffer layer 15, and a cathode layer 16 are formed in this order.
[0013]
The substrate 11 is made of, for example, a plastic material that is sufficiently transparent to light in the visible light region and has flexibility. Light emitted by the organic EL layer 14 is extracted from the back surface of the substrate 11. Note that the substrate 11 may be made of a glass material.
[0014]
The anode barrier layer 12 is made of a material having a high barrier property against moisture and oxygen (O ₂ ), especially moisture, for example, zinc oxide (ZnO) doped with gallium (Ga), and has a thickness of 50 nm. Electrodes. The anode barrier layer 12 blocks moisture entering from the substrate 11 side, and prevents moisture from entering the organic EL layer 14.
[0015]
Since the light emitted from the organic EL layer 14 passes through the anode barrier layer 12 and is extracted from the back side of the substrate 11, the anode barrier layer 12 has a transmittance of 50% or more for light in the visible light region. Is preferred. Furthermore, since the anode barrier layer 12 is an electrode for injecting holes into the organic EL layer 14 together with the anode layer 13, the anode barrier layer 12 preferably has a low resistance, for example, a specific resistance of 0.001 Ωcm or less. Here, examples of the material of the anode barrier layer 12 include ZnO doped with aluminum (Al) and undoped ZnO in addition to ZnO doped with Ga.
[0016]
The anode layer 13 has a thickness of, for example, 200 nm, has a large work function from a vacuum level so that holes can be efficiently injected into the organic EL layer 14, and transmits light so that light from the organic EL layer 14 can be extracted. It is made of a material having properties. Examples of the anode material include indium tin oxide (ITO), tin oxide (SnO ₂ ), and the like.
[0017]
The organic EL layer 14 is, for example, a layer in which a hole transport layer 14A, a light emitting layer 14B, and an electron transport layer 14C are sequentially stacked from the anode layer 13 side.
[0018]
The hole transport layer 14A is provided for transporting holes injected from the anode layer 13 to the light emitting layer 14B. Examples of the material of the hole transport layer 14A include benzene, styrylamine, triphenylamine, porphyrin, triazole, imidazole, oxadiazole, polyarylalkane, phenylenediamine, arylamine, oxazole, anthracene, fluorenone, hydrazone, stilbene Or a derivative thereof, or a heterocyclic conjugated monomer, oligomer, or polymer such as a polysilane compound, a vinylcarbazole compound, a thiophene compound, or an aniline compound. Specifically, α-naphthylphenyldiamine, porphyrin, metal tetraphenylporphyrin, metal naphthalocyanine, 4,4,4-tris (3-methylphenylphenylamino) triphenylamine) triphenylamine, N, N, N , N-tetrakis (p-tolyl) p-phenylenediamine, N, N, N, N-tetraphenyl 4,4-diaminobiphenyl, N-phenylcarbazole, 4-di-p-tolylaminostilbene, poly (paraphenylene) Vinylene), poly (thiophenvinylene), poly (2,2-thienylpyrrole) and the like.
[0019]
When a potential difference occurs between the cathode layer 16 and the anode layer 13, electrons and holes are injected from the cathode layer 16 and the anode layer 13, respectively, and the electrons and holes recombine to emit light. Area where The light emitting layer 14B is made of a material having a high luminous efficiency, for example, an organic material such as a low-molecular fluorescent dye, a fluorescent polymer, and a metal complex. Specifically, for example, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, tris (8-quinolinolato) aluminum complex, bis (benzoquinolinolato) beryllium complex, tri (dibenzoyl) Methyl) phenanthroline europium complex ditolylvinylbiphenyl.
[0020]
The electron transport layer 14C is provided to transport electrons injected from the cathode layer 16 to the light emitting layer 14B. Examples of the material of the electron transport layer 14C include quinoline, perylene, bisstyryl, pyrazine, and derivatives thereof. Specific examples include 8-hydroxyquinoline aluminum, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, and derivatives thereof.
[0021]
The buffer layer 15 is made of, for example, lithium oxide (Li ₂ O). This buffer layer 15 makes it possible to lower the light emission start voltage.
[0022]
The cathode layer 16 is made of, for example, aluminum (Al), gold (Au), Cu (copper), or an alloy thereof.
[0023]
The organic EL element 10 having such a configuration can be manufactured, for example, as follows. First, an anode barrier layer 12 made of ZnO doped with Ga is formed on a substrate 11 by, for example, a sputtering method. Next, the anode layer 13 made of ITO is formed by using, for example, a reactive DC sputtering method. Next, the organic EL layer 14 is formed by sequentially forming the hole transport layer 14A, the light emitting layer 14B, and the electron transport layer 14C on the anode layer 13 by a vacuum evaporation method. Next, a buffer layer 15 made of Li ₂ O is formed on the organic EL layer 14 by a vacuum evaporation method. Finally, the organic EL element 10 is completed by forming the cathode layer 16 by a vacuum evaporation method.
[0024]
In the organic EL element 10 of the present embodiment, the anode barrier layer 12 having a barrier property against moisture is provided on the substrate 11, so that the moisture entering from the substrate 11 is blocked by the anode barrier layer 12. As a result, penetration of moisture into the organic EL layer 14 is prevented. Therefore, even when the substrate 11 is made of a plastic material, deterioration of the organic EL layer 14 is suppressed, and as a result, stable light emission characteristics can be obtained.
[0025]
Further, since the anode barrier layer 12 has a transmittance for light in a visible light region of 50% or more and a specific resistance of 0.001 Ωcm or less, light emitted from the organic EL layer 14 is transmitted through the anode barrier layer 12, It can be efficiently taken out from the substrate 11 side. Therefore, when the organic EL element 10 of the present embodiment is applied to a display, the luminance of the display can be improved.
[0026]
Furthermore, since it is not necessary to form an inorganic film on both sides of the substrate as in the conventional device in order to prevent the deterioration of the organic EL layer, the substrate 11 may be formed of a thin film made of a plastic material as in the present embodiment. Thus, the storage of the display can be improved.
[0027]
As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, one anode barrier layer 12 is formed between the substrate 11 and the anode layer 13, but a plurality of anode barrier layers may be formed. For example, an anode barrier layer 21 may be further provided between the anode layer 13 and the organic EL layer 14, as in the organic EL element 20 shown in FIG.
[0028]
In the above embodiment, the anode barrier layer 12 is provided separately from the anode layer 13. However, as in the organic EL device 30 shown in FIG. It may be the anode / barrier layer 31 which itself has a barrier function. Further, like the organic EL element 40 shown in FIGS. 4 and 5, an auxiliary electrode 41 having an opening 41A is formed on the substrate 11, and a barrier layer 42 is formed in the opening 41A. Is also good. The barrier layer 42 has a high barrier property against moisture similarly to the above-described anode barrier layer 12, and is a transparent material in a visible light region, for example, silicon nitride (SiN _x : x is a positive number), silicon oxide ( It is made of an insulating material such as SiO _x : where x is a positive number, or silicon nitride oxide (SiO _x N _y : where x and y are positive numbers). The opening 41A preferably has an area of 50% or more of the entire surface of the substrate 11 so that light emitted from the organic EL layer 14 is sufficiently transmitted.
[0029]
【The invention's effect】
As described above, according to the organic EL device according to any one of claims 1 to 9, one or two or more layers having at least a barrier property against moisture between the substrate and the organic EL layer. Since the barrier layer is provided, the barrier layer blocks moisture that has entered from the substrate side, and can prevent entry into the organic EL layer. Therefore, even when the substrate is made of a plastic material, deterioration of the organic EL layer is suppressed, and as a result, stable light emission characteristics can be obtained.
[0030]
According to the organic EL device of the third aspect, since the barrier layer has a transmittance of 50% or more for light in a visible light region and a specific resistance of 0.001 Ωcm or less, the organic EL layer passes through the barrier layer. The light emitted therefrom is transmitted, and can be efficiently extracted from the substrate side. Therefore, when the present invention is applied to a display, the luminance of the display can be improved.
[0031]
According to the organic EL device of the eighth aspect, it is not necessary to form an inorganic film on both sides of the substrate as in the conventional device in order to prevent deterioration of the organic EL layer. By providing the element, the entire element has flexibility, and as a result, when the present invention is applied to a display, the storability of the display can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an organic EL device according to an embodiment of the present invention.
FIG. 2 is a modification of the organic EL element.
FIG. 3 is a modification of the organic EL element.
FIG. 4 is a modification of the organic EL element.
FIG. 5 is a reduced cross-sectional view taken along a plane including a barrier layer of a modification of the organic EL element shown in FIG.
[Explanation of symbols]
10, 20, 30, 40 ... Organic EL element, 11 ... Substrate, 12, 21, ... Anode barrier layer, 13 ... Anode layer, 14 ... Organic EL layer, 14A ... Hole transport layer, 14B ... Light emitting layer, 14C ... Electron transport layer, 15 ... Buffer layer, 41A ... Opening, 31 ... Anode / barrier layer, 42 ... Barrier layer

Claims (9)

Board and
An element portion in which an anode layer, an organic EL layer, and a cathode layer are laminated in this order on one surface of the substrate;
An organic EL device comprising: at least one or two or more barrier layers formed between the substrate and the organic EL layer of the element portion and having at least a barrier property against moisture. 2. The organic EL device according to claim 1, wherein the anode layer also functions as the barrier layer. 2. The organic EL device according to claim 1, wherein the barrier layer is a transparent electrode having a transmittance for light in a visible light region of 50% or more and a specific resistance of 0.001 Ωcm or less. 2. The organic EL device according to claim 1, wherein the barrier layer is a transparent electrode made of zinc oxide (ZnO) or zinc oxide (ZnO) doped with gallium (Ga) or aluminum (Al). . The organic EL device according to claim 1, further comprising an auxiliary electrode having an opening between the anode layer and the substrate, wherein the barrier layer is formed in the opening. The organic EL device according to claim 5, wherein the opening has an area of 50% or more of the entire surface of the substrate. The barrier layer is made of silicon nitride (SiN _x : x is a positive number), silicon oxide (SiO _x : x is a positive number), or silicon nitride oxide (SiO _x N _y : x and y are positive). 6. The organic EL device according to claim 5, comprising: The organic EL device according to claim 1, wherein the substrate has flexibility. 9. The organic EL device according to claim 8, wherein the substrate is made of a plastic material.

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