JP2003017242A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of the element by preventing growth of black spots in the organic electroluminescent element (EL). SOLUTION: The element contains in an airtight sealed container a laminated body containing an organic light-emitting material layer and a chemical sorbent for carbon dioxide (for example, a metallic hydroxide and a copper compound such as a hydroxide of an alkaline earth metal and an alkaline metal) separately from the laminated body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device, and more particularly to an organic electroluminescence device in which deterioration of an organic light emitting material layer over time is prevented and the effective life is extended.

[0002]

2. Description of the Related Art An organic electroluminescence device (organic EL device) has an organic light emitting layer sandwiched between a pair of electrodes, and electrons are injected into the organic light emitting layer from one electrode and holes are injected from the other electrode. , Which utilizes the fact that electrons and holes combine in the organic light-emitting layer to emit light, but has a wider viewing angle, better contrast, and better visibility than liquid crystal elements, and a backlight It is unnecessary and can be made thin and lightweight, and it is also advantageous in terms of power consumption. Furthermore, it can be driven with a low DC voltage, has a fast response speed, and is solid, so it is resistant to vibration and has a wide operating temperature range. have.

Such an organic EL element is used for information processing such as a computer, household equipment such as audio equipment, in-vehicle measuring equipment, car navigation, etc., as well as an outdoor display,
Widely expected to be used for applications such as clocks and calendars. In the future, there is expected to be a great demand especially for use in mobile phones and personal digital assistants. The organic EL element operates with direct current and can be driven at a voltage much lower than that of the inorganic EL element. Moreover, since it has a laminated structure, it is possible to easily obtain a planar light-emitting body by making one of the electrodes transparent. As such an organic EL element, Kodak Company discloses a laminated body type organic EL element in which a hole injection layer is provided to adjust the supply of carriers (Japanese Patent Publication No. 1-7635, 6-67).
32307, etc.), the possibility of practical application is recognized,
It has been gaining courageous attention, and development has advanced rapidly. After that, research and development of organic light-emitting materials, charge transport layers, device configurations, drive circuits, manufacturing methods, etc. increased rapidly, and almost all the problems were solved, and it has reached the stage of commercialization.

At the beginning of the research and development of the organic EL device, low voltage driving, high efficiency light emission, and high brightness were the issues, but recently, it has reached the stage where long life is an important issue, Stability, heat resistance stability, durability, etc. have been studied. In such a situation, in order to extend the life of the organic EL element, it is necessary to cover the outer side of the entire EL element to block moisture and oxygen in the atmosphere (Japanese Patent Publication No. 8-21469).
Further, it is disclosed that an organic EL element is enclosed in a closed container and a hygroscopic agent coexists in the container (Japanese Patent Publication No. 60-
19636, Japanese Patent Publication No. 1-4314, and Japanese Patent Laid-Open No. 9-148066.

[0005]

As described above, the organic EL
Although efforts are being made to improve the durability of the device, if the organic EL device is used for a long time, the emission brightness, the uniformity of light emission, etc. will decrease, and the problem of growing non-emission parts (black dots) is a problem. It has not been completely solved, and it is desired to further extend the life.

In view of the current state of the art, it is an object of the present invention to further extend the life of the organic EL element.

[0007]

As a result of extensive investigations on the cause of the deterioration of the life of the organic EL element, the present inventor has found that the organic EL element is deteriorated and black spots are generated when the organic EL element is enclosed in a closed container. As a cause, not only water (humidity) but also a very small amount of carbon dioxide (CO ₂ ) is present and CO ₂
It has also been found that this also causes black spot growth, and that a chemical sorbent for carbon dioxide (CO ₂ ) is placed in a closed container that encloses the organic EL element, and the life of the organic EL element is significantly extended. The present invention has been completed.

[0008] That is, the present invention, in the hermetically sealed container,
An organic electroluminescence device comprising: a laminate including an organic light emitting material layer; and a chemical sorbent for carbon dioxide contained and contained separately from the laminate. The chemical sorbent is preferably at least one selected from the group consisting of metal hydroxide and copper compound, one or more thereof supported on an inorganic carrier, and a mixture thereof. The form of these chemical sorbents is preferably powdery from the viewpoint of specific surface area, but is preferably granular or press-molded from the viewpoint of handleability. It is preferable that a moisture absorbent (a desiccant containing a chemical moisture absorbent) is further placed in the hermetically sealed container.

[0009]

EXAMPLES The organic EL device of the present invention comprises, as essential components, a hermetically sealed container, a laminate containing an organic light emitting material layer, and a carbon dioxide chemical sorbent. A laminate including an organic light emitting material layer is formed by sandwiching an organic light emitting material layer between a pair of electrodes, and further, a hole transporting layer between the anode and the organic light emitting material layer and an electron transporting layer between the cathode and the organic light emitting material layer. It can include layers. Each of the organic light emitting material layer, the electrode, the hole transport layer, and the electron transport layer does not have to be a single layer, and may have a multilayer structure. The hole transport layer and the electron transport layer are not essential, and both or one of them may be used. In some cases, the distinction between the organic light emitting material layer, the hole transport layer, and the electron transport layer is not always clear.

As an organic light emitting material which can be used in the present invention, aluminum complex 198 of 8-oxyquinoline, which was published by Tang et al., Is well known, and a fluorescent quantum yield such as coumarin dye, quinaxone 199 or dicyanomethylene is used as a dopant. It has been reported that the emission wavelength can be changed by doping with a dye having a high ratio to further increase the brightness and the yield, but there is no particular limitation, and (1) polycyclic aromatic compounds such as terphenyl, anthracene, perylene, etc. Condensed polycyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons such as arylalkylenes in which phenyl groups are linked via a carbon-carbon double bond, diarylethylenes, polyarylbutadienes and derivatives thereof, (2) furan , Thiophene, pyrrole-containing compounds, benzofuran, benzothiophene, India Five-membered compounds such as compounds having a ru nucleus, compounds in which diphenyl is bridged by heteroatoms, structures in which pyrrole rings such as porphyrins and phthalocyanines are linked by conjugated chains, and compounds containing a skeleton of pyridine, quinoline, and pyrazine. Ring, 6-membered heterocyclic compound, (3) porphyrin, phthalocyanine, quinolyl metal complex, for example, 8-quinolyl aluminum complex,
(4) Other examples include, but not limited to low molecular weight compounds, polymer compounds such as polyparaphenylene vinylene type, polyparaphenylene type, polythiophene type, polyalkylfluorene type, polysilane type may be used.

The hole transporting material that can be used in the present invention is not particularly limited, but examples thereof include triphenylamine derivatives (TPD). The electron transporting material that can be used in the present invention is not particularly limited, and examples thereof include an oxadiazole derivative (PBD). The anode that can be used in the present invention is not particularly limited, but preferably a metal, alloy, or conductive compound having a large work function, such as ITO, indium tin, tin, zinc oxide, platinum, or the like can be given as an example. it can.

The cathode that can be used in the present invention is not particularly limited, but metals, alloys and conductive compounds having a low work function, such as magnesium, aluminum, indium, lithium and sodium are preferably exemplified. it can. For encapsulating the thin film laminate of the organic EL device of the present invention in an airtight container, for example, referring to FIG. 1, a transparent substrate, here, a glass substrate 1 is typically formed on a surface of an ITO (anode) transparent electrode. ) 2 is formed into a film, and if necessary, a hole transport layer 3, an organic light emitting layer 4, an electron transport layer 5, and a cathode 6 are laminated and manufactured, and then the can-shaped lid 7 is sealed in the glass substrate 1. . The carbon dioxide chemical sorbent 8 of the present invention is arranged, for example, on the bottom of the can-shaped lid 7 using a partition, a bag, a package, or the like, or the molded body is fixed by adhesion or another method, It can be arranged by using an appropriate method such as forming a film by sputtering or a coating method. It is preferable to dispose the carbon dioxide chemical sorbent 8 on the entire surface of the can-shaped lid 7 because a large amount of the chemical sorbent can be arranged in a thin shape. The inside of the closed container is generally sealed with nitrogen or an inert gas, but may be vacuum sealed.

The organic EL device of the present invention is characterized in that a chemical sorbent for carbon dioxide is contained in advance in an airtight container. The chemical sorbent for carbon dioxide may be any one that can chemically absorb or adsorb a small amount of carbon dioxide present in the airtight container, and as a material having such an action, a metal hydroxide can be used. Examples thereof include alkaline earth metal hydroxides and alkali metal hydroxides, particularly calcium hydroxide, barium hydroxide and magnesium hydroxide. Further, copper compounds such as copper, copper chloride, copper nitrate and copper hydroxide are also effective. In addition, these chemical sorbents can be used as synthetic alumina such as alumina (or activated alumina), silica-alumina, silica gel, silica, activated carbon, molecular sieve, natural zeolite such as erionite, perlite, sepiolite, diatomaceous earth, activated clay. It may be used by supporting it on an inorganic carrier such as clay mineral. Of course, a mixture of these may be used.

These chemical sorbents are mainly used in the form of powder from the viewpoint of specific surface area, but it is preferable to press-mold the powder or use it in the form of granules from the viewpoint of handleability. The amount of the chemical sorbent used is preferably such that CO ₂ generated when the organic EL element is used for a long period of time can be sufficiently absorbed and adsorbed, so that the organic EL element can be downsized and thinned. It is desirable to use a large amount as long as the requirements are not hindered. Specifically, although not particularly limited, and depending on the absolute amount used, the amount of the CO ₂ chemical sorbent used is, for example, an alkaline earth metal or an alkali metal oxide as a desiccant. When used, it is preferably used within the range of 5 to 60% by weight, more preferably within the range of 10 to 45% by weight, based on the total amount of the drying agent.

The concentration of carbon dioxide in the closed container of the organic EL device of the present invention is not limited, but is 100 ppm.
The following control is preferable. According to the present invention, by disposing the carbon dioxide chemical sorbent in the closed container, the concentration in the closed container can be maintained at such a low value for a long time.

The method of enclosing the chemical sorbent is not particularly limited, and various methods as described above can be adopted. As shown in FIG. 2, the chemical sorbent is housed in a package or a press-molded body. As a result, it is preferable to dispose and fix this in the container of the organic EL element. Exemplarily referring to FIG. 2, a polyethylene-aluminum laminated film (thickness 70 μm), a chemical sorbent 12 is placed on a lid 13, and a polyethylene fiber film (thickness 150 μm) is provided.
) 11 and the peripheral region 14 of the chemical sorbent 12 is heat sealed to the polyethylene fiber film 11. The polyethylene fiber film 11 is
It does not allow fine powder of the chemical sorbent 12 to pass through, but has gas permeability. Chemical sorbent 1 contained in this package
2 is, for example, a thickness of 200 μ formed by pressing powder.
It is a porous molded body of about m 2. It does not necessarily have to be a press-molded body, and may be filled in a powder form. The chemical sorbent is, for example, a mixture of CaO as a hygroscopic agent (drying agent) and Ca (OH) ₂ as a chemical sorbent of carbon dioxide. Such a package is preferably arranged on the entire surface of the can-like lid of the closed container of the organic EL element as shown in FIG. 1, but is fixed to the can-like lid by a suitable method such as fitting or bonding, You may arrange | position only in a can-shaped lid body and it may be made to provide a space | interval with an organic EL laminated body or a glass substrate using a spacer.

In the organic EL device of the present invention, a moisture absorbent (particularly a water chemical sorbent, for example, an oxide of an alkali metal or an alkaline earth metal) is stored together with a chemical sorbent of carbon dioxide in an airtight container. Insertion is preferable in practice, but not limited. According to the present invention, the life of the organic EL element can be remarkably extended by removing the carbon dioxide from the organic EL element sealed in the hermetically sealed container by using the carbon dioxide chemical sorbent. The effect is played.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an organic EL element of the present invention.

FIG. 2 is a schematic cross-sectional view of a sorbent package used in the organic EL device of the present invention.

[Explanation of symbols]

1 ... Glass substrate 2 ... Anode 3 ... Hole transport layer 4 ... Organic light emitting layer 5 ... Electron transport layer 6 ... Cathode 7 ... Can-shaped lid 8 ... sorbent 11 ... Polyethylene fiber film 12 ... Sorbent 13 ... Polyethylene-aluminum laminated film 14 ... Heat seal

Claims (3)

[Claims] 1. An organic electroluminescence device comprising a hermetically sealed container, a laminate containing an organic light-emitting material layer, and a chemical sorbent for carbon dioxide contained separately from the laminate. . 2. The chemical sorbent is at least one selected from one or more of metal hydroxides and copper compounds, those supported on an inorganic carrier, and mixtures thereof. 1. The organic electroluminescence device according to 1. 3. The organic electroluminescence device according to claim 1, further comprising a hygroscopic agent in the hermetically sealed container.