JP2004171806A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a thin and lightweight organic electroluminescent(EL) element at a low cost, and to restrain deterioration of the organic EL element over a long time by blocking moisture from the outside. <P>SOLUTION: This organic electroluminescent element is composed by sequentially stacking at least a transparent conductive layer 2, an organic luminescent medium layer 3 and a negative electrode layer 4 on a translucent substrate 1, and by stacking metal foil 6 by interlaying an adhesion layer 5. The surface roughness Ra on the adhesion layer side of the metal foil is set between 10-1,000 nm. In addition, by using aluminum foil as the metal foil 6, the lightweight organic EL element strong against corrosion can be manufactured. Since a wrinkle and a scratch can be prevented from being easily formed by using hard aluminum foil, even the organic EL element formed on a glass substrate can easily be sealed. By using soft aluminum foil as the aluminum foil, even the organic EL element excellent in flexibility and formed on a plastic film can easily be sealed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescent device (hereinafter, referred to as an organic EL device) which is expected to be widely used as a display such as an information display terminal or a surface light source, and more specifically, has excellent moisture resistance over a long period of time. The present invention relates to a sealing method for manufacturing an organic EL device.
[0002]
[Prior art]
The organic EL element is expected as a flat panel display replacing a CRT or a liquid crystal display due to advantages such as a wide viewing angle, a high response speed, and low power consumption.
[0003]
The organic EL element has a structure in which an organic light emitting medium layer is sandwiched between a transparent anode and a cathode, and light is generated in the organic light emitting medium layer by passing a current between both electrodes.
[0004]
The organic light-emitting medium layer often has a multilayer structure. Typical examples thereof are copper phthalocyanine for the hole injection layer and N, N'-di (1-naphthyl) -N, N 'for the hole transport layer. -Diphenyl-1,1'-biphenyl-4,4'-diamine, a low-molecular-weight organic EL element in which a phosphor layer is laminated with tris (8-quinolinol) aluminum and the like, and a poly (3,3) in a hole transport layer. There is a polymer EL element in which a mixture of 4-ethylenedioxythiophene) and polystyrenesulfonic acid, and a phosphor layer on which polyfluorene or the like is laminated.
[0005]
One of the major problems of the organic EL element is that when the light emitting medium layer and the cathode layer are left in the state of exposure to the air, the light emitting medium layer and the cathode layer are deteriorated by moisture, oxygen and the like in the air. As a specific example, there is a phenomenon that a non-light-emitting area called a dark spot occurs and expands with the passage of time.
[0006]
Means for solving this problem are disclosed in Patent Documents 1 and 2, and the like. In these, a luminescent medium layer and a cathode layer are continuously formed under vacuum on a glass substrate on which a transparent conductive layer serving as an anode is formed, and the EL element is covered with a metal or glass sealing can under a dry nitrogen atmosphere. This is a sealing method.
[0007]
However, since a sealing can made of glass or metal is used, there is a limit in reducing the thickness and weight of the organic EL element. In addition, in the manufacturing process, there are a process of applying a photocurable resin to the hermetic case, a process of bonding the translucent substrate and the hermetic case, and a process of curing the photocurable resin. Had a problem.
[0008]
On the other hand, in recent years, a polymer light emitting medium layer has been formed on a plastic film or glass by a wet method such as a spin coating method, a gravure printing method, or an ink jet method, and sealed with a film having a high barrier property such as a metal foil. Japanese Patent Application Laid-Open No. H11-163,086 and the like have proposed a method for performing the above. Thus, a more reliable sealing method is desired for the organic EL element.
[0009]
[Patent Document 1]
JP-A-5-182759 [Patent Document 2]
JP-A-5-36475 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2002-50470
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to produce a thin and lightweight organic EL element at low cost and to cut off moisture from the outside for a long time. It is to suppress the deterioration of the organic EL element.
[0011]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and a first invention according to claim 1 is to sequentially laminate at least a transparent conductive layer, an organic luminescent medium layer, and a cathode layer on a light-transmitting substrate. An organic electroluminescent device comprising a metal foil laminated via an adhesive layer, wherein the surface roughness Ra of the metal foil on the adhesive layer side is in the range of 10 nm to 1000 nm. is there.
[0012]
A second invention according to claim 2 is the organic electroluminescent device, wherein the metal foil is a rolled foil.
[0013]
The third invention according to a third aspect is the organic electroluminescent device according to the first or second aspect, wherein the adhesive layer is laminated on the entire surface of the metal foil.
[0014]
A fourth invention according to claim 4, wherein the light-transmitting substrate is a glass substrate, and the metal foil is a hard aluminum foil. It is an electroluminescent element.
[0015]
A fifth invention according to claim 5, wherein the translucent substrate is a plastic film substrate, and the metal foil is a soft aluminum foil. Is an organic electroluminescence element.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of the organic EL device of the present invention and a manufacturing process thereof will be described with reference to FIG.
[0017]
First, a transparent conductive layer 2 serving as an anode is formed on one surface of a translucent substrate 1 by a sputtering method or the like, and then the transparent conductive layer 2 is patterned by a photolithography method and a wet etching method (FIG. 1). (A)).
[0018]
Here, in the present embodiment, as the material of the translucent substrate 1, any substrate can be used as long as it has translucency and insulating properties. For example, glass or quartz, polypropylene, polyether sulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, etc., plastic film or sheet, or these plastic film or sheet Metal oxide such as silicon oxide, aluminum oxide, silicon nitride, metal oxide such as silicon oxide, aluminum oxide, chromium oxide, magnesium oxide, metal fluoride such as aluminum fluoride, magnesium fluoride, silicon nitride on one or both surfaces Metal nitride such as aluminum nitride, chromium nitride, metal oxynitride such as silicon oxynitride, metal material such as aluminum, copper, nickel, stainless steel, acrylic resin, epoxy resin, silicone resin The polymer resin film such as polyester resin, in the range without any problem on the transparent, can be used in single layer or laminated. In order to impart moisture resistance to the base material, an inorganic thin film such as a metal oxide is particularly preferable in terms of transparency and barrier properties. However, film defects such as pinholes are likely to occur. Therefore, it is more preferable that the surface of the substrate is prepared by laminating a polymer resin film or the like in advance, instead of a single inorganic thin film.
[0019]
Further, it is more preferable that these substrates are subjected to a heat treatment in advance, if necessary, to reduce the moisture adsorbed inside or on the surface of the substrates as much as possible. Further, in order to improve the adhesion between the light-transmitting substrate 1 and the transparent conductive layer 2, the surface of the light-transmitting substrate 1 is subjected to ultrasonic cleaning, corona discharge treatment, plasma treatment, UV ozone treatment, or the like. It is preferable to perform the treatment, and further insert a thin film such as an inorganic insulating thin film such as silicon oxide, silicon nitride, or silicon oxynitride, or a metal thin film such as chromium or titanium within a range that does not impair the translucency. Is more preferred.
[0020]
As a material of the transparent conductive layer 2 serving as an anode, a light-transmitting conductive material capable of being formed into a thin film, specifically, ITO (indium tin composite oxide), indium zinc composite oxide, zinc aluminum composite Metal composite oxides such as oxides, metal materials such as gold and platinum, or fine particle dispersion films in which fine particles of these metal oxides and metal materials are dispersed in epoxy resin or acrylic resin, etc. can do. In addition, in order to reduce the wiring resistance of the transparent conductive layer, a metal material such as copper or aluminum may be provided as an auxiliary electrode in addition to the transparent conductive layer.
[0021]
As a method for forming the transparent conductive layer 2, depending on the material, a dry film formation method such as a resistance heating evaporation method, an electron beam evaporation method, a reactive evaporation method, an ion plating method, a sputtering method, a gravure printing method, or a screen is used. A wet film forming method such as a printing method can be used. As a patterning method of the transparent conductive layer 2, an existing patterning method such as a mask evaporation method, a photolithography method, a wet etching method, and a dry etching method can be used depending on a material and a film formation method.
[0022]
Next, the organic light emitting medium layer 3 and the cathode layer 4 are sequentially formed (FIG. 1B).
[0023]
The organic light emitting medium layer 3 in the present invention can be formed of a single layer film containing a fluorescent substance or a multilayer film. When the organic light emitting medium layer is formed of a multilayer film, examples of the structure of the organic light emitting medium layer include a hole injection transport layer, an electron transport light emitting layer or a hole transport light emitting layer, a two-layer structure including an electron transport layer, a hole injection transport layer, And a three-layer structure including an electron transport layer. It is also possible to form more layers, and each layer is sequentially formed on the transparent conductive layer 2. Specific materials of each layer are listed below, but there is no particular limitation as long as the material is generally used.
[0024]
Examples of the hole injecting and transporting material include metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine, and metal-free phthalocyanines, quinacridone compounds, 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'-diphenyl-1,1'-biphenyl-4,4'-diamine and other aromatic amine-based low-molecular-weight hole injection / transport materials, high-molecular-weight hole transport materials such as polythiophene and polyaniline, polythiophene oligomer materials, and others You can choose from existing hole transport materials.
[0025]
Examples of light emitting materials include 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolinolato) aluminum complex, tris (4-methyl- 8-quinolinolate) aluminum complex, bis (8-quinolinolate) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolate) aluminum complex, tris (4-methyl-5-cyano-8-quinolinolate) aluminum Complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolate) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolate) [4- ( 4-cyanophenyl) phenolate] aluminum complex, Lis (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, poly-2,5 -Diheptyloxy-para-phenylenevinylene, coumarin-based phosphor, perylene-based phosphor, pyran-based phosphor, anthrone-based phosphor, porphyrin-based phosphor, quinacridone-based phosphor, N, N'-dialkyl-substituted quinacridone-based phosphor Low molecular materials such as phosphor, naphthalimide phosphor, N, N'-diaryl-substituted pyrrolopyrrole phosphor, polymer materials such as polyfluorene, polyparaphenylenevinylene, polythiophene, and other existing light emitting materials Can be.
[0026]
Examples of the organic electron transporting material include 2- (4-bifinylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole and 2,5-bis (1-naphthyl) -1 , 3,4-oxadiazole, oxadiazole derivatives synthesized by Hamada et al. (Journal of the Chemical Society of Japan, p. 1540, 1991), bis (10-hydroxybenzo [h] quinolinolate) beryllium complex, JP-A-7-90260 And the like.
[0027]
Depending on the material, the organic light emitting medium layer 3 can be formed by a vacuum evaporation method, a coating method such as spin coating, spray coating, flexo, gravure, microgravure, intaglio offset, or a printing method. The thickness of the organic light emitting medium layer is 1000 nm or less even when it is formed as a single layer or a stacked layer, and is preferably 50 to 150 nm for reducing the thickness of the entire organic EL element.
[0028]
As a material of the cathode layer 4, a substance having a high electron injection efficiency is used. Specifically, a single metal such as Mg, Al, Yb, or the like is used, or a compound such as Li, Li oxide, or LiF is sandwiched by about 1 nm at an interface in contact with a light emitting medium, and Al or Cu having high stability and conductivity is laminated. Used. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function, and stable Ag and Al And an alloy system with a metal element such as Cu. Specifically, alloys such as MgAg, AlLi, and CuLi can be used.
[0029]
As a method for forming the cathode, a resistance heating evaporation method, an electron beam evaporation method, a reactive evaporation method, an ion plating method, or a sputtering method can be used depending on a material. The thickness of the cathode is desirably about 10 nm to 1000 nm.
[0030]
Finally, a metal foil 6 is laminated via an adhesive layer 5 in order to block moisture from the outside and suppress deterioration of the organic EL element for a long period of time (FIG. 1C).
[0031]
Examples of the material of the adhesive layer 5 include a photo-curable adhesive resin such as an epoxy resin, an acrylic resin, and a silicone resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and an acid such as polyethylene and polypropylene. A thermoplastic adhesive resin made of a modified product can be used. In particular, it is preferable to use an epoxy-based thermosetting adhesive resin that has excellent moisture resistance and water resistance and has little shrinkage during curing.
[0032]
In addition, as a method for forming the adhesive layer 5, a coating method such as roll coating, spin coating, screen printing, spray coating, or a printing method can be used depending on the material. In addition, a desiccant such as barium oxide or calcium oxide may be mixed in to remove moisture contained in the adhesive layer 5.
When a soft aluminum foil is used as the metal foil, it is particularly desirable to apply a resin material to be an adhesive layer to the cathode layer and the entire surrounding area. As a result, the completed organic EL element has a smooth and uniform thickness, and it is possible to prevent excess gas and moisture from remaining in the organic EL element.
[0033]
As a material of the metal foil 6, a metal material such as aluminum, copper, and nickel, or an alloy material such as stainless steel and an aluminum alloy can be used. It is preferable to use a metal or alloy having foil workability, and most preferably, aluminum which is flexible, excellent in foil workability and cost, has low specific gravity, and is resistant to corrosion.
Further, in order to facilitate handling during manufacture, an aluminum foil in which a film of polyethylene terephthalate, nylon, or the like is preliminarily laminated may be used as a base material. In this case, the surface opposite to the organic EL element (ie, the outer surface) ) Is desirably laminated.
[0034]
In addition, in the production of aluminum foil, usually, two aluminum foils are rolled while being overlapped in the final step (polymerization rolling), so that the surface that comes into contact with the rolling roll has a specular gloss (glossy surface) and the two foils The surfaces that come into contact with each other have a glossy white luster (popping surface) having fine irregularities. Therefore, it is more preferable to dispose a matte ash surface on the adhesive layer 5 side, because the contact area is improved, a stronger adhesive force is obtained, and deterioration of the organic EL element can be suppressed for a long time.
The surface roughness Ra of the shiny non-glossy surface of the aluminum foil disposed on the adhesive layer side needs to be 10 nm or more, more preferably 50 nm, and most preferably 100 nm or more. When this value is small, as shown in the comparative example, the glossy surface easily peels off from the adhesive layer, which causes a light emission failure in the organic EL element. It is preferable that the surface roughness Ra is large because the contact area with the adhesive layer is increased, so that a larger adhesive force can be obtained, but if the surface roughness Ra is too large, the adhesive cannot fill the unevenness and a gap is generated. It is necessary that such an inconvenience such as generation or damage to the organic EL element does not occur, and the upper limit is about 1000 nm.
The thickness of the aluminum foil may be 5 μm or more in terms of handling, but is preferably 15 μm or more in order to prevent pinholes in the aluminum foil.
[0035]
During the production of the aluminum foil, a heat treatment is performed to remove the rolling oil adhering in the rolling step, but when this treatment is performed, the aluminum foil is in a soft state. Since this soft aluminum foil has flexibility, it is suitable for roll pressing. Therefore, if a flexible plastic film or the like is used as the base material of the organic EL element and a soft aluminum foil is used for encapsulation, all manufacturing steps can be performed by roll winding, which is very advantageous for mass production. It is.
[0036]
In addition, when a base material having a certain degree of hardness, such as a glass base material that is commonly used, is used as the light-transmitting base material. Not only can be prevented, but also the warpage of the organic EL element can be prevented, and a higher quality organic EL element can be provided. In this case, the rolling oil is more preferably removed by an organic solvent such as acetone, UV ozone cleaning, plasma cleaning, or the like.
[0037]
【Example】
Example 1 and Comparative Examples 1 and 2 based on the embodiment will be described with reference to FIG.
[0038]
<Example 1>
First, a glass substrate was used as the light-transmissive substrate 1, an ITO film was formed as a transparent conductive layer 2 to a thickness of 150 nm by a sputtering method, and then the ITO film was patterned by a photolithography method and a wet etching method (FIG. 1). (A)).
Next, as the organic light emitting medium layer 3, a mixture (20 nm) of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid was used for the hole transport layer, and poly [2-methoxy-5- ( After 2′-ethyl-hexyloxy) -1,4-phenylenevinylene] (MEHPPV) (100 nm) was formed by spin coating, Ca (20 nm) and Ag (200 nm) were formed as the cathode layer 4 by vacuum evaporation. The layers were formed in this order (FIG. 1B). Next, after laminating an epoxy resin-based thermosetting adhesive as the adhesive layer 5, using a single-sided luster of a hard aluminum foil (50 μm) as the metal foil 6, laminating a non-glossy brush side on the adhesive layer 5 side. Thus, an organic EL device was produced (FIG. 1C). The surface roughness of the unpolished brushed surface of this aluminum foil was Ra = 470 nm, and the surface roughness Ra of the glossy surface was 1 nm or less. Even when the obtained EL element was stored in a constant-temperature constant-humidity layer at 60 ° C. and 90 RH%, peeling of the aluminum foil did not occur.
[0039]
<Example 2>
In the organic EL device described in Example 1, an acrylic resin (thickness: 3 μm), silicon oxide (thickness: 100 nm), an acrylic resin (thickness: 3 μm), and a light-transmitting base material 1 were coated on a polyethylene terephthalate film (thickness: 100 μm). Using a conductive barrier substrate in which silicon nitride (thickness: 1 nm) and ITO (thickness: 150 nm) were laminated in this order, soft aluminum was laminated as a metal foil instead of hard aluminum foil.
Even when the obtained EL element was stored in a constant-temperature constant-humidity layer at 60 ° C. and 90 RH%, peeling of the aluminum foil did not occur.
[0040]
<Comparative Example 1>
In the organic EL device described in Example 1, when the aluminum foil was laminated, the glossy surface was laminated on the adhesive layer 6 side. The obtained organic EL device was stored in a constant-temperature and constant-humidity layer at 60 ° C. and 90 RH% for 1000 hours. As a result, peeling occurred at the edge of the aluminum foil at the interface with the adhesive layer, and a non-light emitting portion was generated in the organic EL device. did.
[0041]
<Comparative Example 2>
In the organic EL device described in Example 1, a soft aluminum foil was laminated instead of the hard aluminum foil. In the obtained organic EL element, wrinkles were generated in the soft aluminum foil during the handling of the sealing, and as a result of storing for 1000 hours in a 60 ° C., 90 RH% constant temperature and humidity layer, water was removed from the wrinkles generated in the soft aluminum foil. Penetrated, and a non-light emitting portion was generated in the organic EL element.
[0042]
<Comparative Example 3>
In the organic EL device described in Example 2, a hard aluminum foil was laminated instead of the soft aluminum foil. In the obtained organic EL device, the aluminum foil could not be stuck to the organic EL device uniformly because the hard aluminum foil was warped when the roll was wound up.
[0043]
【The invention's effect】
According to the present invention, when sealing the organic EL element with the metal foil, by laminating the non-glossy surface of the metal foil on the adhesive layer side, moisture from the outside is shut off, and the organic EL element is deteriorated for a long time. And a thin, lightweight, low-cost organic EL element can be provided. Aluminum is most preferable for use as a metal foil for encapsulating an organic EL element because aluminum is flexible, has excellent workability, is lightweight, is resistant to corrosion, and is resistant to rust. By using a hard aluminum foil as the aluminum foil, wrinkles and scratches are unlikely to occur, so that even an organic EL element manufactured on a glass substrate can be easily sealed. In addition, by using a soft aluminum foil as the aluminum foil, it is excellent in flexibility, and even an organic EL element manufactured on a plastic film can be easily sealed.
[0044]
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a cross-sectional structure of an organic EL device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Translucent base material 2 ... Transparent conductive layer 3 ... Organic light emitting medium layer 4 ... Cathode layer 5 ... Adhesive layer 6 ... Metal foil 6a ...
6b: glossy surface of metal foil (smooth surface)

Claims (5)

On a translucent substrate, at least a transparent conductive layer, an organic light emitting medium layer, and a cathode layer are sequentially laminated, and in an organic electroluminescent element in which a metal foil is laminated via an adhesive layer, the adhesive layer side of the metal foil The organic electroluminescent device according to claim 1, wherein the surface roughness Ra is in the range of 10 nm to 1000 nm. The organic electroluminescence device according to claim 1, wherein the metal foil is a rolled foil. The organic electroluminescence device according to claim 1, wherein the adhesive layer is laminated on an entire surface of the metal foil. 4. The organic electroluminescent device according to claim 1, wherein the translucent substrate is a glass substrate, and the metal foil is a hard aluminum foil. 4. The organic electroluminescent device according to claim 1, wherein the translucent substrate is a plastic film substrate, and the metal foil is a soft aluminum foil.

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