JP2006228493A - Organic electroluminescent element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-type organic EL element and its manufacturing method capable of taking out light from a top face by perfect solid sealing of moisture by a resin layer containing a desiccant, and moreover, with its deterioration restrained over a long period of time by making an organic luminous medium layer moisture-proof through absorption of outside moisture with desiccant. <P>SOLUTION: The organic EL element can be restrained from deterioration over a long period of time, and a top-emission system of a display using the EL element is realized by perfect solid-state sealing of moisture into an organic luminous medium layer by a resin layer containing a desiccant, and by avoiding arrangement of the resin layer containing the desiccant on a top face (a light-taking out face) of the organic luminous medium layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an organic electroluminescence element (hereinafter, referred to as an organic EL element) that is expected to be widely used as a display such as an information display terminal or a surface-emitting light source.

The organic EL element is expected as a flat panel display that is replaced with a cathode ray tube or a liquid crystal display because of advantages such as a wide viewing angle, a high response speed, and low power consumption.

An organic EL element has a structure in which an organic light emitting medium layer is sandwiched between two electrodes (anode and cathode), one of which has translucency. A self-luminous display element that emits light in a layer. The organic light-emitting medium layer is usually composed of a plurality of layers separated by function, and typical examples thereof include copper phthalocyanine for the hole injection layer and N, N′-di (1-naphthyl) for the hole transport layer. -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine, a low molecular EL element in which tris (8-quinolinol) aluminum is laminated on the phosphor layer, and polythiophene in the hole transport layer There is a polymer type EL device in which a polyalkylfluorene derivative is laminated on a derivative or light emitting layer

It is known that an organic EL element is deteriorated by moisture and oxygen in the atmosphere when the light emitting medium layer and the cathode layer are left exposed to the atmosphere. As a specific representative example, there is a phenomenon in which a non-light-emitting region called a dark spot occurs and expands with time.

As a method for solving this problem, there is a method of covering and sealing an organic EL element in a dry nitrogen atmosphere with a glass or metal sealing cap containing a desiccant (see Patent Documents 1 and 2). However, this method has a problem that the cost of processing the sealing cap to provide a space for containing the desiccant is high, and a problem that it is difficult to reduce the thickness and weight of the organic EL element.

In recent years, active matrix organic EL devices have become the mainstream for large-sized, high-definition panels, and a top emission type device structure that extracts light from the opposite side (sealing glass side) of the TFT substrate is essential to improve the aperture ratio. Therefore, there is a need for a sealing method in place of sealing using a conventionally used non-light-transmitting desiccant (BaO or CaO) and a metal can.

Further, by applying an adhesive to the entire surface of the organic EL element and attaching a plate-shaped sealing substrate, a completely solid-sealed organic EL element without a gap can be produced. Since there is no desiccant inside, it is difficult to block the moisture that gradually enters from the edge of the adhesive, especially when the sealing width is narrowed by narrowing the frame, the life is greatly reduced. There was a problem.

JP-A-5-182759 JP-A-5-36475

The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to suppress the influence of moisture penetrating from the end portion over a long period of time in complete solid sealing, and to achieve a long-life organic An object of the present invention is to provide an EL element and a manufacturing method thereof.

In the present invention, an anode layer 2, a resin layer 3 containing a desiccant 4, an organic light emitting medium layer 5, and a cathode layer 6 are sequentially formed on a support substrate 1, and the organic light emitting medium layer 5 and the cathode layer 6 are formed. It is an organic electroluminescent element sealed with the sealing base material 8 through the adhesive layer 7 so as to cover the surface.
Here, the resin layer 3 is partially provided on the anode layer 2, and the organic light emitting medium layer 5 is provided on the anode layer 2 on which the resin layer 3 is not formed.
Then, the cathode layer 6 is formed on the organic light emitting medium layer 5.
By setting it as such a structure, the organic light emitting medium layer 5 will be in the state protected by the resin layer 3, and can maintain a stable state for a long period of time.

According to the present invention, light emission can be taken out from the upper surface with a thin shape by completely solid-sealing moisture by providing a resin layer containing a desiccant on the anode layer. Further, with the above-described configuration, moisture from the outside can be absorbed by the desiccant to keep the organic light emitting medium layer moisture-proof. Since the resin layer containing a desiccant does not exist on the upper surface (light extraction surface) of the organic light emitting medium layer, the present invention is optimal for the top emission method.

An example of an embodiment of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this.

In the present embodiment, the material of the support substrate 1 is preferably selected according to the emission direction of light emission. For example, when light is to be extracted from the support substrate 1 side, glass, quartz, polypropylene , Polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, etc., or metal such as silicon oxide, aluminum oxide, etc. Oxides, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride and aluminum nitride, metal oxynitrides such as silicon oxynitride, acrylic resins, epoxy resins, silicone resins, polyester resins, etc. A translucent base material in which a polymer resin film is monolayered or laminated can be used. When light is extracted from the sealing base material side without extracting light from the support base material 1 side, In addition to conductive substrates, metal foils and sheets such as aluminum and stainless steel, silicon substrates, and non-translucent substrates in which metal films such as aluminum, copper, nickel, and stainless steel are laminated on the plastic film and sheet are used. be able to.

The support base 1 may be used as a driving substrate by forming a thin film transistor (TFT) as necessary. As a material for the TFT, an organic TFT such as polythiophene, polyaniline, copper phthalocyanine, or perylene derivative may be used, or amorphous silicon or polysilicon TFT may be used.

Moreover, it is more preferable that these base materials reduce the water | moisture content adsorb | sucked in this base material inside or the surface as much as possible by performing heat processing previously. Further, in order to improve the adhesion, depending on the material laminated on the base material, it is preferable to perform surface treatment such as ultrasonic cleaning treatment, corona discharge treatment, plasma treatment, UV ozone treatment. Further, if necessary, a color filter layer, a light scattering layer, a light deflection layer, a planarization layer, or the like may be provided.

First, the anode layer 2 is formed on the support substrate 1 and patterned as necessary (FIG. 1A).

Examples of the material of the anode layer 2 include metal composite oxides such as ITO (indium tin composite oxide), indium zinc composite oxide and zinc aluminum composite oxide, metal materials such as gold and platinum, and these metal oxides. Alternatively, a fine particle dispersion film in which fine particles of a metal material are dispersed in an epoxy resin or an acrylic resin can be used as a single layer or a laminated layer.

Further, in order to reduce the wiring resistance of the anode layer 2, a metal material such as copper or aluminum may be provided as an auxiliary electrode in the anode layer 2. Further, before the organic light emitting medium layer 3 is formed, the surface of the anode layer 2 is subjected to ultrasonic cleaning, immersion in isopropyl alcohol or steam cleaning, wet cleaning with an acid or alkaline solution, plasma treatment, It is preferable to perform a dry treatment such as UV / O ₃ treatment.

The anode layer 2 can be formed by a dry film forming method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, a gravure printing method, a screen depending on the material. A wet film forming method such as a printing method can be used. As the patterning method for the anode layer 2, an existing patterning method such as a mask vapor deposition method, a photolithography method, a wet etching method, or a dry etching method can be used depending on the material and the film forming method.

Next, the resin layer 3 having a predetermined pattern is formed so as to cover the upper portion of the anode layer 2 (FIG. 1B).

The resin layer 3 may be a single layer or a multilayer structure as long as the desiccant 4 is contained at least inside. The material of the resin layer 3 is not particularly specified, and acrylic resin, epoxy resin, butyral resin, styrene-maleic acid copolymer, phenol resin, polyester resin, cresol resin, polyimide resin, and other existing ones. Thermoplastic resins, thermosetting resins, photocurable resins, and photosensitive resins can be used.

Moreover, there is no restriction | limiting in particular as thickness of this resin layer 3, If it is 1-100 micrometers, More preferably, if it is 5-20 micrometers, it can play the role as a moisture adsorption source.

The method for forming the resin layer 3 is not limited as long as a predetermined pattern can be formed, and a known photolithography method may be used, and printing such as a gravure method, a flexo method, and a screen method may be used. A method, an inkjet method, a nozzle coating method, or the like can be used.

As the desiccant 4 mixed in the resin layer 3, a physical adsorption desiccant such as activated carbon, zeolite, magnesium sulfate, sodium sulfate, calcium chloride, or active aluminum oxide is preferably used.

There is no restriction | limiting in particular in the size, shape, and mixing amount of this desiccant 4, The thing of the magnitude | size about 1 micrometer-100 micrometers can be mixed with the material of the above-mentioned partition 3 in the ratio of about 1-50%. The desiccant 4 is more preferably microencapsulated before being mixed into the resin layer 3. Here, the microcapsule refers to a micro container in which a desiccant is enclosed. Since the microencapsulated desiccant 4 is weak and brittle in strength, the desiccant is easily crushed and causes a short circuit and a dark spot of the organic EL element, and has an effect of suppressing it. There is no restriction | limiting in particular in the method of encapsulation, Well-known methods, such as an interfacial polymerization method, a submerged drying method, a spray drying method, a dry-type mixing method, can be used.

More preferably, the resin layer 3 containing the desiccant 4 is baked at a predetermined temperature and time before forming at least the cathode layer 6. For example, in the case of zeolite, it may be baked at 150 ° C. for several hours, and it is more preferable to adjust the temperature and time according to the material and its content, or to dry under reduced pressure. Further, any number of heat treatments may be performed before the cathode layer 6 is formed.

Next, the organic light emitting medium layer 5 is formed (FIG. 1C). The organic light emitting medium layer 5 in the present invention can be formed of a single layer film containing a light emitting substance or a multilayer film. Examples of the configuration in the case of forming the multilayer film include a hole injecting and transporting layer, an electron transporting light emitting layer or a hole transporting light emitting layer, a two-layer structure comprising an electron transporting layer, a hole injecting and transporting layer, a light emitting layer, A three-layer structure composed of an electron injecting and transporting layer, and further by forming an injection layer and a transporting layer or inserting an electron blocking layer, a hole blocking layer, etc., can be formed in a multilayer.
Examples of the hole injecting and transporting material include metal phthalocyanines and metal-free phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine, quinacridone compounds, 1,1-bis (4-di-p-tolyl) Aminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) Aromatic amine-based low molecular hole injection and transport materials such as -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine, polyaniline, polythiophene, polyvinylcarbazole, poly (3,4-ethylene Of polymer hole transport materials such as mixtures of dioxythiophene) and polystyrene sulfonic acid, polythiophene oligomer materials, and other existing hole transport materials It is possible to choose from.
As the light-emitting material, 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolinolato) aluminum complex, tris (4-methyl-8-) Quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolato) aluminum complex, tris (4-methyl-5-cyano-8-quinolinolato) aluminum complex, Bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4- Cyanophenyl) phenolate] aluminum complex, tri (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-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor, porphyrin phosphor, quinacridone phosphor, N, N'-dialkyl-substituted quinacridone phosphor , Naphthalimide-based phosphors, N, N′-diaryl-substituted pyrrolopyrrole-based phosphors, low-molecular light-emitting materials such as phosphorescent phosphors such as Ir complexes, polyfluorene, polyparaphenylene vinylene, polythiophene, polyspiro, etc. Polymer materials and dispersion of the above-mentioned low molecular materials in these polymer materials Alternatively, a copolymerized material or other existing light emitting materials can be used.

Examples of the electron transporting material include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1-naphthyl)- 1,3,4-oxadiazole, an oxadiazole derivative, a bis (10-hydroxybenzo [h] quinolinolato) beryllium complex, a triazole compound, or the like can be used.

The film thickness of the organic light emitting medium layer 5 is 1000 nm or less, preferably 50 to 150 nm, even when formed by a single layer or a stacked layer. In particular, the hole transport material of the polymer EL element has a large effect of covering the surface protrusions of the support substrate 1 and the anode layer 2, and it is more preferable to form a film having a thickness of about 50 to 100 nm.

As a method for forming the organic light emitting medium layer 5, depending on the material, a vacuum deposition method, a coating method such as spin coating, spray coating, flexo, gravure, micro gravure, intaglio offset, printing method, ink jet method or the like is used. Can be used. When the polymer light emitting medium layer is made into a solution, it is preferable to control the vapor pressure, solid content ratio, viscosity, etc. of the solvent according to the forming method. Solvents include water, xylene, anisole, cyclohexanone, mesitylene, tetralin, cyclohexylbenzene, methyl benzoate, ethyl benzoate, toluene, ethanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, isopropyl alcohol, ethyl acetate, butyl acetate, etc. These may be a single solvent or a mixed solvent. In order to improve coatability, it is more preferable to mix an appropriate amount of additives such as surfactants, antioxidants, viscosity modifiers and ultraviolet absorbers as necessary. As a method for drying the coating solution, the solvent may be removed to such an extent that the EL characteristics are not hindered, and heating, decompression, or heating / decompression may be performed.

Next, the cathode layer 6 is formed (FIG. 1D). As the material of the cathode layer 6, a substance having a high electron injection efficiency is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface in contact with the light emitting medium, and Al or Cu having high stability and conductivity. Are used in a stacked manner. 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, Al An alloy system with a metal element such as Cu or Cu is used. Specifically, alloys such as Mg, Ag, Al, Li, Cu, and Li can be used. The cathode layer 6 can be formed by a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method, depending on the material. The thickness of the cathode layer 6 is preferably about 10 nm to 1000 nm, but when used as a light-transmitting cathode layer, ITO (indium tin composite oxide) is formed after laminating these metal materials as a thin film of about 1 to 10 nm. ), A metal composite oxide such as indium zinc composite oxide, zinc aluminum composite oxide or the like is preferably laminated to have a thickness of 10 to 150 nm so as to achieve both electron injecting property and light transmitting property.

Finally, the sealing substrate 8 is laminated via the adhesive layer 7 (FIG. (E)). As a material of the adhesive layer 7, a thermosetting adhesive resin such as an epoxy resin, an acrylic resin, silicone, a phenol resin, or a polypropylene resin, a photocurable adhesive resin, a thermoplastic adhesive resin, or the like can be used. . In particular, it is preferable to use an epoxy resin adhesive resin that is excellent in moisture resistance and water resistance and has little shrinkage during curing. As a method for forming the adhesive layer 7, a coating method such as roll coating, spin coating, screen printing, spray coating, or the like can be used depending on the material. The adhesive layer 7 preferably contains as little water as possible. In addition, in the adhesive layer 7, rubber fine particles such as plastic fine particles, acrylic rubber, and nitrile rubber are mixed with a single-component or multi-component filler in order to relieve residual stress at the time of curing and improve adhesiveness. May be. Although there is no restriction | limiting in particular as thickness of this contact bonding layer 7, It is preferable that it is a thin film as much as possible, and it is more preferable that it is about 1-100 micrometers, and also 5-20 micrometers.

As the sealing substrate 8, a metal oxide such as silicon oxide or aluminum oxide, or a metal nitride such as silicon nitride or aluminum nitride is formed on a plastic film such as glass or polyethylene terephthalate, polyethylene naphthalate or polycarbonate. Also, metal fluorides such as aluminum fluoride, films deposited with metals and alloys such as aluminum, nickel, copper, metal foils and alloy foils made of these metal materials, glass plates, metal plates, etc. can be used. . In order to improve the adhesiveness with the adhesive layer 7, it is preferable to perform surface treatment such as ultrasonic cleaning treatment, corona discharge treatment, plasma treatment, UV ozone treatment, etc. Among them, an inorganic insulating thin film such as silicon oxide, silicon nitride, or silicon oxynitride, or a thin film such as a metal thin film such as chromium or titanium may be inserted. In addition, when extracting light from the sealing substrate 8 side, a color filter layer, a color conversion layer, an antireflection film, a deflection film, an antifouling film, an anti-scratch film, etc., if necessary A base material provided may be used.

Examples and Comparative Examples 1 and 2 based on the best mode for carrying out the invention will be described with reference to FIG.

First, a glass substrate was used as the supporting substrate 1, and an ITO film having a thickness of 150 nm was formed as the anode layer 2 on the supporting substrate 1 by a sputtering method, and then the ITO film was patterned by a photolithography method and a wet etching method ( FIG. 1 (a)).

Next, the resin layer 3 was patterned on the anode layer 2 by using a photo-sensitive resin made of a cresol resin by using a photolithography method (FIG. 1B). At this time, the desiccant 4 in the form of microcapsules encapsulating zeolite having a particle diameter of 1 μm was mixed in the resin layer 3 in advance.

Next, as the organic light-emitting medium layer 5, a poly 3,4-ethylenedioxythiophene and polystyrenesulfonic acid mixture (20 nm) is used for the hole transport layer, and poly [2-methoxy-5- (2 ′) is used for the phosphor layer. -Ethyl-hexyloxy) -1,4-phenylene vinylene] (MEHPPV) (100 nm) was formed by spin coating (FIG. 1 (c)).

Next, before forming the cathode layer, the drying agent 4 was dehydrated by heating in vacuum at 150 ° C. for 6 hours.

Next, Ca (5 nm) and Ag (100 nm) were laminated in this order as a cathode layer 6 on the organic light emitting medium layer 5 in this order (FIG. 1D).

Next, sealing was performed using a two-component curable epoxy adhesive as the adhesive layer 7 and a glass substrate as the sealing substrate 8 to produce an organic EL element (FIG. 1 (e)).

The organic EL element thus obtained emitted light of 1000 cd / m ² under a voltage of 5V. Further, even when stored at 60 ° C. and 90% RH for 4000 hours, no expansion of dark spots was observed.

<Comparative Example 1>
An organic EL device was obtained in the same manner as in Example except that the cathode layer 6 was formed without baking before the cathode layer 6 was formed. As a result of applying a voltage of 5 V to the organic EL element, light emission of 1000 cd / m ² was obtained, but a dark spot was already generated in the early stage of light emission. In addition, as a result of storage at 60 ° C. and 90% RH for 500 hours, the moisture entering from the end of the organic EL element causes the adhesive interface between the resin layer 3 and the sealing substrate 8 as a partition wall to moisture. As described above, since the organic EL element was made non-light emitting, the pixel area was 20% with respect to the initial 100%.

<Comparative example 2>
The said organic EL element was produced by the structure similar to the Example except not having mixed the said desiccant 4 in the resin layer 3 inside. As a result of applying a voltage of 5 V to the organic EL element, light emission of 1000 cd / m ² was obtained by applying a voltage of 5 V. Further, the dark spot started to expand when stored at 60 ° C. and 90% RH for 2000 hours, and did not emit light when stored for 4000 hours.

The above-described invention can be used as a display such as an information display terminal or a surface emitting light source.

It is sectional drawing which shows an example of the organic EL element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Support base material 2 ... Anode layer 3 ... Resin layer 4 ... Desiccant 5 ... Organic luminescent medium layer 6 ... Cathode layer 7 ... Adhesive layer 8 ... Sealing Stop base material

Claims (4)

In an organic electroluminescence device comprising at least a support substrate, an anode layer, an organic light emitting medium layer, a resin layer, a cathode layer, an adhesive layer, and a sealing substrate, a desiccant is contained on the anode layer. An organic electroluminescence element comprising a resin layer. The organic electroluminescent device according to claim 1, wherein the desiccant is a physical adsorption desiccant such as zeolite or silica gel. The organic electroluminescence device according to claim 1, wherein the desiccant is a desiccant encapsulated in a microcapsule. Form a cathode layer in the production of an organic electroluminescent device that at least forms an anode layer, a resin layer containing a desiccant, an organic light-emitting medium layer, a cathode layer, an adhesive layer, and a sealing substrate on a supporting substrate in order. A method for producing an organic electroluminescence element, comprising a step of drying the resin layer in a step before the step.

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