JP2003303680A - El element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life organic EL element with stable luminous characteristics maintained for a long time by preventing degradation of the luminous characteristics due to oxygen or moisture, and to provide a long-life EL element with stable luminous characteristics maintained for long time by preventing mechanical degradation of the element due to a temperature cycle. <P>SOLUTION: With the EL element sealing a luminous medium consisting of at least a positive electrode layer, a luminous layer and a negative layer in an enclosed space, two kinds or more of desiccants are to be contained in the space. Preservation life is greatly elongated by removing moisture already contained in an element such as an adhesive and a base material at manufacturing of elements and removing moisture infiltrating from outside in a long time span by a desiccant with a large absorption capacity. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film EL device utilizing the electroluminescence (hereinafter simply referred to as EL) phenomenon of an organic thin film, and more particularly to a polymer EL device having an organic light emitting layer made of a polymeric fluorescent substance. is there.

[0002]

2. Description of the Related Art Organic thin film EL elements are generally anodes,
An organic light emitting layer and a cathode are laminated. The organic light emitting layer may also have a multi-layer structure in which a hole injection layer, a hole transport layer, a phosphor layer, an electron injection layer, etc. are laminated. Light emission occurs in the organic phosphor layer by passing a current between the anode and the cathode, and light can be extracted to the outside by making one electrode transparent.

As a typical example of the organic light emitting layer, copper phthalocyanine is used for the hole injection layer and N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1 'is used for the hole transport layer. −
Examples thereof include biphenyl-4,4′-diamine and a phosphor layer containing tris (8-quinolinol) aluminum. Each of these organic layers is a low molecular weight compound, and each layer is laminated with a thickness of about 0.01 to 0.1 μm by a vacuum deposition method such as a resistance heating method.

In recent years, polymer EL devices using polymers as organic layers have been proposed. Polymers used as the organic layer, such as polystyrene, polymethylmethacrylate, polyvinylcarbazole, etc., in which a low-molecular fluorescent dye is dissolved, polythiophene derivatives,
Polyparaphenylene derivative, polyphenylene vinylene derivative (PPV), polyalkylfluorene derivative (PA
A polymeric fluorescent substance such as F) is used. By making these polymeric light emitters soluble in a solution, they can be formed into a film by a wet method such as spin coating or flexographic printing.

As the cathode, a metal material such as calcium, barium, lithium fluoride, aluminum, magnesium or silver is deposited by a vacuum deposition apparatus such as vacuum deposition or sputtering.

It is known that when such an organic EL element is driven continuously or discontinuously for a certain period of time, the light emission characteristics such as light emission luminance, light emission efficiency and light emission uniformity are significantly reduced as compared with the initial case. ing. The cause of such deterioration of the light emission characteristics may be oxidation of the electrode due to oxygen or water entering the organic EL element, modification of organic substances, etc., and various proposals have been made regarding a sealing technique for preventing such entry. Has been done.

The following proposals have been made as a sealing method for preventing the deterioration of the light emitting characteristics. An outer surface of the laminated structure of the organic EL device is provided with a protective layer made of an electrically insulating inorganic compound, and an electrically insulating glass, and an electrically insulating polymer compound such as an epoxy resin or a silicone resin are provided outside the protective layer. Sealing method in which a shield layer made of a substance selected from the group consisting of electrically insulating airtight fluid is provided (JP-A-5-89959). Solid or gel-like insulating material having a back substrate and a moisture absorber. By thin film E
Organic thin film panel in which L element is sealed (Japanese Patent Laid-Open No. 2-1
2792) A method in which an EL element is packed in a box and diphosphorus pentoxide is shared therein so as not to touch the EL element (JP-A-3-261091) The EL element is immersed in fluorocarbon oil, and a dehydrating agent is mixed in the fluorocarbon oil. , Method for removing water (Japanese Patent Laid-Open No. 5-41281, 114486)
Sealing technology with high airtightness and moisture resistance using a photocurable resin (Japanese Patent Laid-Open No. 5-182759) Epoxy adhesive is mixed with a desiccant, and the adhesive is directly applied onto the organic EL element to form a sealing base. A method for adhering materials is disclosed.

When the cathode is formed by vacuum film formation, the vapor-deposited layer has a thickness of about 1 μm at most, so that invasion of water vapor, oxygen and the like into the element cannot be prevented, and a metal lid, a glass lid or the like is sealed. However, there is a problem in that the entire device becomes thicker and heavier, and particularly when a plastic film is used as a substrate, these methods could not be substantially adopted.

In the above-mentioned sealing method, the effect of sealing oxygen is not always satisfactory, and in the thin film EL panel, the effect of sealing oxygen is also insufficient, and the method of Since the EL device must be packaged in a box and a separate container containing diphosphorus pentoxide must be made, the device is complicated to make, and diphosphorus pentoxide reacts violently with the electrodes and organic substances of the EL device. Since it is necessary to consider impact resistance, the method of is not practical because of the risk of liquid leakage at the time of destruction, and the method of is not practical when curing such resin. There is a problem that the element is mechanically deteriorated and eventually destroyed due to contraction or a difference in expansion coefficient (temperature cycle) between the EL element and the sealing layer.

In the method of (1), since the adhesive is solidly coated on the EL element, it is possible to take a relatively wide adhesive surface without alignment, so that strong adhesion can be obtained. A desiccant is mixed into the adhesive. If this is done, there is an advantage that the element can be made thinner because it is not necessary to provide a cavity in the backside sealing plate and separately put a desiccant, but the desiccant to be mixed is generally barium oxide, calcium oxide, or the like. Although those with a high adsorption rate for water are used, they often have a small adsorption capacity, and they are very effective for removing the water already contained in the adhesive etc. at the time of production, but long-term storage It is hard to say that it is a desiccant that is very suitable for.

Further, the problem that the EL element is peeled off from the base material or the sealing base material is peeled off due to the stress of the adhesive generated at the time of curing is vapor-deposited with a protective layer or
Even if it was coated, it could not be prevented. Moreover, the mixed desiccant has been a cause of damaging the element.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and prevents deterioration of the light emission characteristics due to oxygen and moisture, maintains stable light emission characteristics for a long time, and has a long life. It aims at providing the organic EL element of. Another object of the present invention is to provide an EL device which prevents mechanical deterioration of the device due to temperature cycling and maintains stable light emission characteristics for a long period of time and has a long life.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first aspect of the present invention is a light emitting medium including at least an anode layer, a light emitting layer and a cathode layer in a sealed region. In the EL element in which the
The EL element is characterized by containing more than one kind of desiccant.

In contrast to the sealing of EL elements, moisture already contained inside the element such as an adhesive or a base material at the time of manufacturing the element is removed by a desiccant having a high adsorption rate, and moisture that invades from the outside for a long period of time is removed. By removing with a desiccant having a large adsorption capacity, it is possible to provide an EL element having a very long storage life.

A second aspect of the present invention is the EL element, wherein the desiccant is made of a material that is chemically adsorbed and a material that is physically adsorbed.

A material that is chemically adsorbed has a strong adsorbing power for water and oxygen, but has a small adsorbing capacity. In addition, a material that physically adsorbs has a weak adsorption power, but has a large adsorption capacity. Therefore, it is possible to provide an EL element having a very long storage life by removing moisture invading from the outside for a long term with a desiccant having a large adsorption capacity.

A third aspect of the present invention is an EL element characterized in that the region comprises a base material, an adhesive layer and a sealing layer, and a desiccant is mixed in the adhesive layer. .

When a desiccant is mixed in the adhesive layer, it is not necessary to provide a cavity in the sealing layer on the back surface of the element and separately put a desiccant, so that the thickness can be reduced.

A fourth aspect of the present invention is an EL element having a protective layer composed of at least a hydrophobic liquid and a protective film between the base material and the adhesive layer.

Since the stress caused by the curing of the adhesive can be relieved, the EL element is peeled off from the base material.
It is possible to solve the problem that the sealing base material is peeled off. In addition, it is not possible to prevent the problem that the desiccant particles damage the EL element and create a non-light emitting part or a cause of a short circuit by directly providing a thin protective film on the light emitting medium etc. By sandwiching the film, the EL element layer can be completely protected and a short circuit can be prevented.

[Detailed Description of the Invention] The EL device according to the present invention is provided with a sealed region that substantially blocks oxygen and moisture from the outside.
It is formed by sealing a light emitting medium including at least an anode layer, a light emitting layer, and a cathode layer. The sealed region of such an EL element is preferably composed of a base material and a sealing layer, or a base material, an adhesive layer and a sealing layer in the manufacturing process. Less than,
A structure in which the anode layer is sequentially laminated on the base material will be described.

As the base material, a glass substrate or a plastic film or sheet can be used. If a plastic film is used, a polymer EL device can be manufactured by winding, and the device can be provided at low cost. As the plastic film, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyether sulfone,
Polymethylmethacrylate, polycarbonate, etc. can be used. On the side where the anode layer is not formed, a ceramic vapor deposition film or other gas barrier film such as polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer saponification product is laminated, or a color filter layer is provided by printing. You may

The luminescent medium according to the present invention comprises at least an anode layer, a luminescent layer and a cathode layer. As the anode layer, a transparent or semitransparent conductive material such as a complex oxide of indium and tin (hereinafter referred to as ITO) can be used, and a film can be formed on the base material by vapor deposition or sputtering. Alternatively, a precursor such as indium octylate or indium acetone can be applied on the base material and then formed by a coating pyrolysis method in which an oxide is formed by thermal decomposition. Alternatively, a metal such as aluminum, gold, or silver vapor-deposited semitransparently can be used.

The glass or plastic substrate on which the anode layer is laminated does not need to be specially manufactured for the present invention, and a commercially available substrate may be used depending on the resistivity and light transmittance of the anode layer. it can.

If necessary, the anode layer may be patterned by etching, or the surface thereof may be activated by UV treatment, plasma treatment or the like. Instead of etching, nitrocellulose, polyamide, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, acrylic resin, urethane resin, etc. may be printed as an insulating layer.

The light-emitting layer that can be used in the present invention may be a single layer of an organic phosphor or a multi-layer structure composed of a hole transport layer, a polymeric phosphor layer and the like. When a hole transport layer is provided, copper phthalocyanine or its derivative, 1,1
-Bis (4-di-p-tolylaminophenyl) cyclohexane, N, N'-diphenyl-N, N'-bis (3-
Methylphenyl) -1,1'-biphenyl-4,4'-
Diamine, N, N'-di (1-naphthyl) -N, N'-
Although low molecular weight compounds such as aromatic amines such as diphenyl-1,1'-biphenyl-4,4'-diamine can be used, polyaniline, polythiophene, polyvinylcarbazole, poly (3,4-ethylenedioxythiophene) It is possible to form a film by a wet method using a mixture of styrene and polystyrene sulfonic acid.

As the phosphor layer, coumarin type, perylene type, pyran type, anthuron type, porphyrene type, quinacridone type, N, N'-dialkyl substituted quinacridone type,
Naphthalimide-based, N, N'-diaryl-substituted pyrrolopyrrole-based, or these fluorescent dyes dissolved in a polymer such as polystyrene, polymethylmethacrylate, polyvinylcarbazole, polyarylvinylene-based or polyfluorene-based, etc. The polymeric fluorescent substance can be used.

These phosphor layers are vacuum-deposited or
Toluene, xylene, acetone, methyl ethyl ketone,
The phosphor material can be dissolved in a single solvent or a mixed solvent such as methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, and water to form a film using a printing method. When the substrate is glass, spin coating, roll coating, spray coating, slot coating, flexography, offset, intaglio offset, and other methods can be used. When using a film wound as a substrate,
Various coating methods such as flexo, gravure, gravure offset, microgravure, flexo, die coating and roll coating can be used. In particular, a method in which patterning such as flexo, offset, intaglio offset, and gravure can be performed simultaneously with coating is preferable. Further, when the polymer light emitting layer is composed of two or more layers, in consideration of the solubility of the material forming each layer, for example, the difference in solubility between the water-soluble and oil-soluble resins is used. Or shorten the time from coating to drying,
The coating conditions may be selected so as not to substantially affect the lower layer. The thickness of the coating depends on the structure of the device, but is 0.01 to 10 μm, preferably 0.05 to 0.5 μm.

If necessary, an electron injection layer may be provided. The electron injection layer may have a function of transmitting the electrons injected from the cathode to the light emitting layer, and the material thereof is conventionally used. Any known compound can be selected and used. For example, nitro-substituted fluorenone derivative, anthraquinone derivative, quinone derivative, thiopyrazine dioxide derivative, oxadiazole derivative,
A quinoline derivative, a quinolinol derivative, a quinoxaline derivative, or the like can be used.

Further, the light emitting layer may be made of an inorganic light emitting material.

For the cathode, any material can be used according to the energy level of the laminated materials. For example,
Metal materials such as calcium, barium, lithium fluoride, aluminum, magnesium and silver are deposited by a vacuum deposition apparatus such as vacuum deposition or sputtering.

As the hydrophobic liquid used for the protective layer,
Boiling point 150 ° C or higher, viscosity 10-2000 cP (25
It is desirable to use the one of (° C). The type of liquid is, for example, an alkane-based, fluoroalkane-based, or siloxane-based liquid, and does not react with a cathode material such as an oligomer or a polymer having these as a structural unit, and does not melt a base light-emitting material or an adhesive. Solvents free of can be used. It is desirable that these solvents have high purity. Further, since the EL element is very sensitive to moisture, it needs to be sufficiently dried.

As the protective film, a plastic film can be used. As the plastic film, polyethylene terephthalate, polypropylene,
Cycloolefin polymer, polyamide, polyether sulfone, polymethylmethacrylate, polycarbonate and the like can be used. These films need to be thoroughly dried and moisture removed before use. The film thickness must be smaller than the thickness of the adhesive, and is preferably 100 μm or less.

As the adhesive, a photocurable resin or a thermosetting resin can be used. Water vapor transmission rate is 80 ° C, 90%
RH is preferably 500 g / m ² · 24 h or less.
Further, since the thermosetting resin causes deterioration and crystallization of the material due to heat during curing, the curing temperature is preferably 150 ° C. or lower, more preferably 100 ° C. or lower. As the adhesive that can be used, for example, acrylic resin, epoxy resin, fluorine resin, silicone resin, chloroprene resin,
Examples thereof include butyl rubber-based resin and styrene-butadiene rubber-based resin. Further, those which do not generate gas during curing are preferable, and epoxy resins are particularly preferable.

As the desiccant, two or more kinds can be arbitrarily selected. For example, materials that chemically adsorb moisture and oxygen (such as alkali metals, alkaline earth metals, oxides of alkaline earth metals, etc.) that chemically adsorb water and oxygen (strong adsorption power but small adsorption capacity), activated carbon, zeolite, magnesium sulfate. , Sodium sulfate, calcium chloride, activated aluminum oxide, and other materials that physically adsorb water and oxygen (adsorption power is weak but adsorption capacity is large) are preferably used together. These desiccants can be formed as a layer independent of the adhesive layer and the sealing layer that form the sealed region, but are preferably mixed in the adhesive layer in view of thinning the element and in the manufacturing process ( 1 and 2).

As the sealing layer, a glass plate, a metal plate, a metal foil, a film having a barrier property against water vapor, oxygen or the like can be used. These backside sealing materials may be subjected to surface treatment such as ultraviolet ray, electron beam, corona or the like as a pretreatment for laminating to improve adhesion with an adhesive.

Although the structure in which the anode layer and the following layers are sequentially formed on the substrate has been described above, it goes without saying that the effect of the present invention can be obtained even if the cathode layer is first formed on the substrate.

[0038]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

(Embodiment 1) A description will be given below with reference to FIG.
Poly (3,4-ethylenedioxythiophene) as represented by the following chemical formula 2 as a hole transport layer 2 on a patterned glass substrate 1 with ITO having a size of 50 × 50 mm.
And a mixture of polystyrene sulfonic acid (hereinafter PEDOT /
PSS) was applied by spin coating to a thickness of 0.1 μm, and the excess hole transport layer was wiped off.

[0040]

[Chemical 1]

[0041]

[Chemical 2]

Next, as the polymer light emitting layer 3, poly [2-methoxy-5- (2'-ethyl-hexyloxy) -1,4-phenylene vinylene (Po is represented by the following chemical formula 1.
ly [2-methoxy-5- (2'-ethyl-hexyloxy) -1,4-phenylene
vinylene] (hereinafter referred to as MEH-PPV), and is coated with a thickness of 0.1 μm by a spin coating method.
The excess polymer light emitting layer was wiped off and removed. Then
0.01 μm calcium and 0.2 μm silver 4 were formed into a film by vacuum evaporation. This is the first substrate 8.

Further, 5 wt% each of calcium oxide and zeolite 6 as a desiccant is mixed with the thermosetting epoxy adhesive 5 and a glass plate which has been corona-treated in advance is used as the backside sealing plate 7 and the epoxy adhesive is applied and spread sufficiently. Let This is the second substrate 9. By laminating the first substrate and the second substrate, the polymer E as shown in FIG.
An L element was produced.

When a voltage of 5 V was applied to this polymer EL device, a uniform emission of 800 cd / m ² could be obtained. Further, in 60 ° C. and 90% RH, there was no breakage of the device such as a decrease in brightness and peeling for at least 6 months, but peeling of the sealing layer came to be seen at 7 months. The area ratio of the non-light emitting portion immediately after fabrication was 0.07%, which was 6
It was 0.07% even after a month, and the area ratio of the non-light emitting portion did not increase. Of 100 devices, 15 devices were short-circuited.

(Embodiment 2) A description will be given below with reference to FIG.
PEDOT / PSS as a hole transporting layer 11 is coated on the patterned glass substrate 10 with ITO in a size of 50 × 50 mm to a thickness of 0.1 μm by a spin coating method to form an extra hole transporting layer. I wiped it off.

Next, as the polymer light emitting layer 12, poly [2-methoxy-5- (2'-ethyl-hexyloxy) -1,4-phenylene vinylene (Po
ly [2-methoxy-5- (2'-ethyl-hexyloxy) -1,4-phenylene
vinylene] (hereinafter referred to as MEH-PPV), and is coated with a thickness of 0.1 μm by a spin coating method.
The excess polymer light emitting layer was wiped off and removed. Then
0.01 μm of calcium and 0.2 μm of silver 13 were formed into a film by vacuum evaporation. Next, 50 μl of sufficiently dried silicone oil 14 was dropped as a protective layer, and a protective film with a thickness of 12 μm was formed on it by 27 × 27.
A pet film 15 having a size of mm was covered, and silicon oil was sufficiently spread under the PET film 15. This is the first substrate 1
Set to 9.

Then, 5 wt% of calcium oxide and zeolite 17 are mixed as a desiccant in the thermosetting epoxy adhesive 16, and the glass plate 18 which has been corona-treated in advance is used as a sealing layer to apply the epoxy adhesive sufficiently. I spread it.
This is the second substrate 20. By laminating the first substrate and the second substrate, a polymer EL device as shown in FIG. 2 was produced.

When a voltage of 5 V was applied to this polymer EL device, a uniform emission of 800 cd / m ² could be obtained. Further, in 60 ° C. and 90% RH, there was no breakdown of the device such as a decrease in brightness and peeling for at least 6 months. The area ratio of the non-light emitting portion was 0.07% immediately after the production and was 0.07% even after 6 months, and the area ratio of the non-light emitting portion did not increase. None of the 100 devices caused a short circuit.

(Comparative Example 1) In comparison with Example 1, a desiccant containing only calcium oxide was prepared. When a voltage of 5 V was applied to this organic EL element, it was 800 cd /
It was possible to obtain uniform light emission of m ² . Also, 60 ℃ 9
A decrease in luminance and an increase in the area ratio of the non-light emitting portion were observed after 3 months in 0% RH. The ratio of the area of the non-light emitting portion was 0.07% immediately after production and 5.5% after 3 months.

[0050]

According to the EL device of the present invention, a longer device life can be obtained. Further, the relaxation of the stress caused by the curing of the adhesive at that time can prevent the element from peeling off, and prevent the element from being short-circuited due to the desiccant.

[0051]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a polymer EL device of the present invention.

FIG. 2 is an explanatory view showing another embodiment of the polymer EL device of the present invention.

[Explanation of symbols]

1 ... ITO glass substrate 2 ... Hole transport layer: PEDOT / PSS 3 ... Polymer light emitting layer 4 ... Calcium, silver deposition layer 5: Epoxy adhesive 6 ... Calcium oxide, zeolite 7 ... Glass sealing layer 8 ... First substrate 9 ... second substrate 10 ... ITO glass substrate 11 ... Hole transport layer: PEDOT / PSS 12 ... Polymer light emitting layer 13 ... Calcium, silver deposition layer 14 ... Silicon oil 15 ... PET film 16 ... Epoxy adhesive 17 ... Calcium oxide, zeolite 18 ... Glass sealing layer 19: First substrate 20 ... second substrate

Claims (4)

[Claims] 1. An EL device in which a light emitting medium including at least an anode layer, a light emitting layer, and a cathode layer is sealed in a sealed region, and the region further contains two or more kinds of desiccants. EL element. 2. The EL device according to claim 1, wherein the desiccant is made of a material that physically adsorbs and a material that chemically adsorbs. 3. The EL element according to claim 1, wherein the region is composed of a base material, an adhesive layer and a sealing layer, and a desiccant is mixed in the adhesive layer. . 4. The EL device according to claim 1, further comprising a protective layer composed of at least a hydrophobic liquid and a protective film between the base material and the adhesive layer.