JPH0935868A - Sealing method for organic el element and organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strongly suppress growth of a dark spot in the organic EL element and to improve an element life by providing a specific seal layer in the periphery of an organic EL element of prescribed constitution. SOLUTION: A seal layer containing 1ppm or less as dissolved O2 concentration 20 and consisting of inert liquid (example: perfluoroalkane) containing an adsorbent 20b is provided in the periphery of an organic EL element 10 laminating an anode 12 and a cathode 16 through at least an emitting layer 14. As the adsorbent 20b, it is preferable to use an inorganic compound selected from active alumina, diatom earth, activated carbon, semihydrate gypsum, P2 O5 , Mg(ClO4 )2 , KOH, CaSO4 , CaBr2 , CaO, ZnCl2 , ZnBr2 and from anhydrous copper sulfate, metal selected from Li, Be, K, Na, Mg, Rb, Sr and from Ca, alloy of the metals selected from these metal groups or (metha) acrylic type water absorbing polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sealing an organic electroluminescence element (hereinafter abbreviated as an organic EL element) and a sealed organic EL element.

[0002]

2. Description of the Related Art EL devices have high visibility due to self-emission, and have excellent impact resistance because they are completely solid devices. Because of these features, at present,
Various inorganic EL devices using an inorganic compound as a light-emitting material and various organic EL devices using an organic compound (hereinafter, this compound is referred to as an organic light-emitting material) as a light-emitting material have been proposed and attempted to be put to practical use. Have been. Among them, the organic EL element can drastically reduce the applied voltage as compared with the inorganic EL element, and therefore, development for obtaining a higher performance organic EL element is being actively pursued.

The basic structure of an organic EL device is an anode, a light emitting layer,
The cathode has a structure in which the cathodes are sequentially laminated, and in many cases, this organic EL element is formed on a substrate. At this time, the positions of the anode and the cathode may be reversed. Further, in order to improve the performance, a hole transport layer is provided between the anode and the light emitting layer,
An electron injection layer may be provided between the cathode and the light emitting layer. The light emitting layer is usually formed of one or more kinds of organic light emitting materials, but may be formed of a mixture of an organic light emitting material and a hole transporting material and / or an electron injecting material.

Of the pair of electrodes (anode and cathode) forming the organic EL element, the electrode located on the light extraction surface side improves the light extraction efficiency and is also configured as a surface emitting element. Above, it consists of a transparent or translucent thin film. On the other hand, the electrode located on the side opposite to the light extraction surface (hereinafter referred to as the counter electrode) is made of a specific metal thin film (thin film of metal, alloy, mixed metal, etc.).

The organic EL element having the above structure is a current-driven type light emitting element, and a high current must be passed between the anode and the cathode in order to emit light. As a result, the element generates heat during light emission, and when oxygen or moisture is present around the element, oxidation of the element constituent material due to the oxygen or moisture is promoted to deteriorate the element. The typical deterioration of the device due to oxidation and water is the generation and growth of dark spots. The dark spot is a light emission defect point. Then, as the constituent material of the organic EL element is oxidized as the organic EL element is driven, the existing dark spots grow, and finally the dark spots spread over the entire light emitting surface.

In order to suppress the above deterioration, various methods have been conventionally proposed. For example, JP-A-5-41281 discloses a method of removing water, which is one of the causes of deterioration, by forming an organic EL device in an inert liquid compound prepared by adding a dehydrating agent such as synthetic zeolite to liquid fluorinated carbon. A method of retaining is disclosed. In addition, JP-A-5-114
In Japanese Patent Publication No. 486, a heat dissipation layer in which fluorocarbon oil is sealed is provided on at least one of an anode and a cathode, and the heat generated when the device is driven is dissipated from the heat dissipation layer to prolong the light emission life of the device. A method is disclosed.

[0007]

However, even with the above-mentioned conventional method, it is difficult to sufficiently suppress the generation and growth of dark spots. The reason is presumed as follows. That is, removing the water that enters the organic EL element with a dehydrating agent after or during the sealing process of the organic EL element is one of the useful means for suppressing the generation and growth of dark spots. The cause of dark spot formation and growth is not only the invasion of water, but oxygen dissolved in liquid fluorinated carbon or fluorocarbon oil has a greater effect. Liquid fluorinated carbon and fluorocarbon oil dissolve gas very well, for example, perfluoroamine (Sumitomo 3M Fluorinert FC-70 (trade name)) dissolves up to 22 ml of air in 100 ml (dissolved). Oxygen concentration 63 ppm).

An object of the present invention is to provide an organic EL device capable of strongly suppressing the growth of dark spots in an organic EL device.
An object of the present invention is to provide a method for sealing an L element and an organic EL element in which growth of dark spots is unlikely to occur.

[0009]

[Means for Solving the Problems] A method for sealing an organic EL device of the present invention that achieves the above object is to provide an adsorbent on the outer periphery of an organic EL device in which an anode and a cathode are laminated at least with a light emitting layer interposed therebetween. It is characterized in that a sealing layer having an oxygen concentration of 1 ppm or less composed of an inert liquid containing is provided.

The organic EL device of the present invention which achieves the above object is characterized by being sealed by the above-mentioned method of the present invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. First, the method for sealing the organic EL element of the present invention will be described. In this method, as described above,
A sealing layer made of an inert liquid containing an adsorbent and having a dissolved oxygen concentration of 1 ppm or less is provided on the outer periphery of the organic EL element.

Here, the adsorbent is used to prevent oxygen and moisture from entering the organic EL element from the outside during or after the sealing process of the organic EL element. The adsorbent is not particularly limited as long as it adsorbs oxygen and water, but it is desirable that the adsorbent has a large adsorption amount and has a property of hardly releasing once adsorbed oxygen and water.
The shape of the adsorbent is not particularly limited, but a powdery one is preferable because it has a larger adsorption area.

Specific examples of adsorbents that can be used in the method of the present invention include (1) activated alumina, diatomaceous earth,
Inorganic compounds selected from activated carbon, hemihydrate gypsum, phosphorus pentoxide, magnesium perchlorate, potassium hydroxide, calcium sulfate, calcium bromide, calcium oxide, zinc chloride, zinc bromide and anhydrous copper sulfate, (2) lithium , A metal selected from the group consisting of beryllium, potassium, sodium, magnesium, rubidium, strontium and calcium, (3) an alloy of metals selected from the above metal group, and (4) an acrylic water-absorbing polymer or And a methacrylic water-absorbing polymer. As the adsorbent, only one kind may be used, or two or more kinds may be used in combination.

It is desirable that the adsorbent is used while maintaining a sufficient adsorption force, and for that purpose, it is preferable to remove oxygen and water adsorbed on the adsorbent before use. (The treatment for removing oxygen and water adsorbed on the adsorbent is referred to as "activation treatment" in the present invention.). The activation process of the adsorbent depends on the type of adsorbent, but it heats the adsorbent, vacuums the adsorbent, leaves the adsorbent in an inert gas stream, and removes the surface of the adsorbent. And the like, or a combination of two or more of these methods.

The activation treatment for the adsorbent is preferably carried out by isolating the adsorbent from the outside air. Further, the adsorbent after the activation treatment is also preferably isolated from the outside air until it is used for forming the sealing layer described later, in order to prevent the activity of the adsorbent from being lowered. For example, activation treatment by heating or vacuuming is performed in a state where the adsorbent is stored in a container capable of blocking outside air such as a container with a vacuum cock, and after the activation treatment is completed, close the cock, It is preferable to store the adsorbent after the activation treatment until the time of use in a state where the outside air is blocked.

In the method of the present invention, a sealing layer containing the above-described adsorbent and containing an inert liquid and having a dissolved oxygen concentration of 1 ppm or less is provided on the outer periphery of the organic EL element. Use of the adsorbent at this time The amount can be appropriately selected depending on the type. Generally, the larger the amount of the adsorbent used is, the higher the adsorption effect is.However, if the amount of the adsorbent used is too large, the fluidity of the adsorbent when the mixture is prepared by including the adsorbent in an inert liquid described below. It is remarkably lowered and it becomes difficult to form the sealing layer, or the organic EL element is damaged by the adsorbent.

When the above-mentioned mixed solution is prepared using an adsorbent having a small particle size, it is more suitable than when the above-mentioned mixed solution is prepared using an adsorbent having the same weight and a larger particle size. The fluidity of the mixed solution decreases, and as a result, it becomes more difficult to form the sealing layer, but the adsorbent with a smaller particle size also has a larger effective surface area than the adsorbent with a large particle size, so the adsorption amount is also large. Many. Therefore, a small amount (weight) of the adsorbent does not necessarily mean that the sealing effect is small. The preferred amount of the adsorbent used depends on the type and particle size of the adsorbent, but is generally within the range of 1 mg to 10 g per 1 ml of the inert liquid described below, and more preferably per 1 ml of the inert liquid described below. About 30
It is within the range of mg to 3 g.

In the method of the present invention, the inert liquid which constitutes the sealing layer together with the above-mentioned adsorbent is a chemically and physically stable liquid, for example, a chemical reaction or a chemical reaction even when it is brought into contact with another substance. It means a stable liquid that does not dissolve. Specific examples of such an inert liquid include liquid fluorinated carbon such as perfluoroalkane, perfluoroamine, and perfluoropolyether. Liquid fluorinated carbon is (1) excellent in electrical insulation (for example, the dielectric breakdown voltage of Demnum S-20 shown in Table 1 below is 72 kV when the sample thickness is 2.5 mm), (2) Since it has the property of being insoluble in neither water nor oil, it practically does not dissolve the layers constituting the organic EL element.
(3) Since the wettability to the surface of metal or glass is low, even when the organic EL element is provided on the substrate, it enters the gap between the surface of the substrate and the electrode immediately above it (which constitutes the organic EL element). It is a particularly suitable inert liquid because it has advantages such as substantially no peeling of the electrode.

Although the above-mentioned inert liquid is commercially available,
The sealing layer provided on the outer periphery of the organic EL element by the method of the present invention has a dissolved oxygen concentration of 1 ppm or less as described above,
Since the dissolved oxygen concentration of the commercially available inert liquid is much higher than 1 ppm, it cannot be used as it is in the method of the present invention. Here, the reason for limiting the dissolved oxygen concentration of the sealing layer to 1 ppm or less in the method of the present invention is that it becomes difficult to strongly suppress the growth of dark spots when the dissolved oxygen concentration of the sealing layer exceeds 1 ppm. Is. The lower the dissolved oxygen concentration of the sealing layer is, the more preferable it is, but in practical use, it is preferably in the range of 0.01 to 1 ppm, particularly 0.1
ppm or less is preferred.

The inert liquid used to form the sealing layer has a dissolved oxygen concentration higher than 1 ppm before the adsorbent is contained, and the dissolved oxygen concentration is 1 ppm or less due to the adsorbent inclusion. May be,
From the standpoint of forming a sealing layer having a higher sealing effect, it is preferable that the dissolved oxygen concentration at the stage before containing the adsorbent is already 1 ppm or less. Therefore, it is preferable to use the inert liquid after reducing the dissolved oxygen concentration to 1 ppm or less by a method such as a room temperature vacuum degassing method, a freeze vacuum degassing method, or an inert gas replacement method. The method of reducing the dissolved oxygen concentration is appropriately selected according to the type of the inert liquid used.

For example, most of perfluoroalkanes and perfluoroamines have a vapor pressure of more than 10 ^-2 Torr at 25 ° C, but the vapor pressure at 25 ° C is 10 ^-2 Torr.
Even if vacuum deaeration at room temperature is attempted, the degree of vacuum cannot be raised to below its vapor pressure, and since evaporation easily proceeds at room temperature, it will be dissolved by the room temperature vacuum deaeration method. Reducing the oxygen concentration is extremely difficult. Therefore, the vapor pressure at 25 ° C is 10 ^-2.
For those exceeding Torr, it is preferable to reduce the dissolved oxygen concentration by a freeze vacuum degassing method or an inert gas replacement method.

When the dissolved oxygen concentration is reduced by the freezing vacuum degassing method, for example, a step of freezing an object to be degassed (an inert liquid whose dissolved oxygen concentration is to be reduced) using liquid nitrogen, The dissolved oxygen concentration in the degassed object is changed by performing a series of operations including a step of vacuuming the degassed object in the state of 10 ⁻² Torr or less and a step of melting the degassed object in the frozen state. Perform the desired number of times until it becomes 1 ppm or less. The deaeration target is Fluorinert F manufactured by Sumitomo 3M.
C-72, Fluorinert FC-84, Fluorinert FC
-77, Fluorinert FC-75 (all are trade names, all of which are one type of perfluoroalkane) and the company's Fluorinert FC-40, Fluorinert FC-43, Fluorinert FC-70 (all trade names. And all of these are one kind of perfluoroamine.), The target product can be obtained by repeating the above-mentioned operation approximately 5 times or more. Further, when the dissolved oxygen concentration is reduced by the inert gas replacement method, for example, 0.1 to 1 liter / min of an inert gas (argon gas, nitrogen gas, helium gas, neon gas with respect to the degassing target 50 cc) is used. Etc.) and bubbling is performed for about 4 to 8 hours until the dissolved oxygen concentration in the degassing target becomes 1 ppm or less, whereby the target product can be obtained. Among these two methods, the freeze vacuum degassing method is preferable because the dissolved oxygen concentration can be reduced by a relatively short time operation.

On the other hand, with perfluoropolyether, 25
The vapor pressure at ℃ is often less than 10 ^-2 Torr.
For vapor pressures below 10 ^-2 Torr at ℃, the vapor pressure at room temperature is low and the amount of evaporation at room temperature is small. The dissolved oxygen concentration can also be reduced by the vacuum degassing method.

When the dissolved oxygen concentration of an inert liquid having a vapor pressure of 10 ^-2 Torr or less at 25 ° C is reduced by a vacuum degassing method at room temperature, for example, a degassing target kept at 160 ° C or less is degassed. Evacuation is performed at 10 ^-2 Torr or less until the dissolved oxygen concentration in the gas target becomes 1 ppm or less. If the kinematic viscosity of the degassed object is 65 cSt or less during the degassing operation, the dissolved oxygen can be degassed relatively easily. When the kinematic viscosity of the degassed object during the degassing operation is high, oxygen and water are firmly entrapped between the molecules, which makes it difficult to degas sufficiently. However, in this case, the degassing operation becomes complicated.
Further, during degassing, stirring of the degassed object and / or addition of zeolite to the degassed object may be carried out as necessary.
When using zeolite, it is preferable to use one made of a porous material such as unglazed glass, glass, and polytetrafluoroethylene (Teflon). When the target product is obtained by the room temperature vacuum degassing method, if the kinematic viscosity of the degassing target is 65 cSt or less during the degassing operation, the time required for the degassing operation is approximately 0.1 to 2 hours.

The vapor pressure at 25 ° C. is 10 ^-2 Torr.
When reducing the dissolved oxygen concentration in the following inert liquid by the freeze vacuum degassing method or the inert gas replacement method, the same operation as the operation for the one whose vapor pressure at 25 ° C exceeds 10 ^-2 Torr is performed. . Vapor pressure at 25 ℃ is 10 ^-2 Torr
Regarding the following inert liquids, the dissolved oxygen concentration can be reduced by the room temperature vacuum degassing method because the dissolved oxygen concentration can be reduced by a short-time operation among the above three methods and the degassing operation is simple. It is preferable to reduce the oxygen concentration.

Dissolved oxygen concentration was 1 p by vacuum degassing at room temperature.
Specific examples of the inert liquid that can easily obtain pm or less include various perfluoropolyethers shown in Table 1.

[Table 1]

The Demnum S-20 in Table 1 above has an average molecular weight of 2700 and a dielectric breakdown voltage of 2.5 m.
72kV for m-thick sample, volume resistivity is about 20 ℃ under 1
It is 0 ¹³ Ωcm. The structural formula thereof is expressed by the following formula (1).

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The structural formula of Fomblin Z03 in Table 1 is represented by the following formula (2).

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The structural formula of Galden H250 in Table 1 is represented by the following formula (3).

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In the method of the present invention, the above-mentioned adsorbent and the above-mentioned inert liquid are used, and a sealing layer made of an inert liquid containing an adsorbent and having a dissolved oxygen concentration of 1 ppm or less is formed of organic E.
Although it is provided on the outer periphery of the L element, the sealing layer has a dissolved oxygen concentration of 1 ppm or less and a water content of 1
It is particularly preferably 0 ppm or less. The sealing layer having a dissolved oxygen concentration of 1 ppm or less and a water content of 10 ppm or less has an adsorbent and a dissolved oxygen concentration of 1 ppm or less and a water content of 10 pp by containing the adsorbent.
Although it can be formed by using an inert liquid having a volume of m or less, from the viewpoint of forming a sealing layer having a higher sealing effect, the adsorbent and the stage before containing the adsorbent are used. It is preferable to use an inert liquid having a dissolved oxygen concentration of 1 ppm or less and a water content of 10 ppm or less.

When the dissolved oxygen concentration in the inert liquid is set to 1 ppm or less by the room temperature vacuum degassing method, the dissolved oxygen concentration is set to 1 ppm or less by this method, or the degassing operation is further repeated to dissolve the dissolved oxygen. Oxygen concentration is 1
An inert liquid having a water content of not more than 10 ppm and a water content of not more than 10 ppm can be obtained. Further, when the dissolved oxygen concentration in the inert liquid is set to 1 ppm or less by the inert gas substitution method, the dissolved oxygen concentration is set to 1 pp by this method.
At the same time as m or less or by slightly lengthening the bubbling time, an inert liquid having a dissolved oxygen concentration of 1 ppm or less and a water content of 10 ppm or less can be obtained. When the dissolved oxygen concentration in the inert liquid is set to 1 ppm or less by the freeze vacuum degassing method,
Before making the dissolved oxygen concentration below 1 ppm by this method,
Alternatively, after adjusting the concentration to 1 ppm or less, the inert liquid is distilled in a vacuum to divide into an initial distillation, a main distillation, and a subsequent distillation. By removing the initial distillation and the subsequent distillation, the dissolved oxygen concentration is 1 ppm or less and the water content is reduced. An inert liquid of 10 ppm or less can be obtained. By providing a sealing layer having a dissolved oxygen concentration of 1 ppm or less and a water content of 10 ppm or less, it becomes possible to further strongly suppress the growth of dark spots.

In providing the sealing layer on the outer circumference of the organic EL element, the entire organic EL element is immersed in a container containing an inert liquid containing an adsorbent to form the sealing layer on the outer circumference of the organic EL element. Although it may be provided, when the organic EL element is formed on the substrate, it is more preferable to provide the sealing layer as follows. That is, a housing material is provided outside the organic EL element formed on the substrate to cover the organic EL element in cooperation with the substrate while forming a gap between the organic EL element and the organic EL element. It is preferable to form a sealing layer in the space formed by the housing material.

As a specific example of the method of providing the sealing layer on the outer periphery of the organic EL element using the housing material, the following (A)
And the method (B).

(A) An adsorbent and an inert liquid are mixed to prepare a mixed liquid, and then the mixed liquid is used as a substrate material for covering the substrate on which the organic EL element is provided and the organic EL element on the substrate. A method for forming a sealing layer by filling the space formed by the above. When the sealing layer is provided by this method, the above mixed solution should not be prepared in the air, but in a dry inert gas atmosphere (nitrogen gas atmosphere, argon gas atmosphere, etc.), for example, with a dry inert gas. It is preferable to carry out in a glove box whose atmosphere is replaced. In preparing the mixed liquid, the inert liquid may be poured into the container containing the adsorbent, or the adsorbent may be put into the container containing the inert liquid. Furthermore, in addition to the container containing the adsorbent and the container containing the inert liquid, a container for preparing a mixed solution is separately prepared,
The container may contain the adsorbent and the inert liquid simultaneously or separately. When the adsorbent and the inert liquid are separately put in the container for preparing the mixed liquid, either one may be put first.

The formation of the sealing layer using the above mixed solution is
The space is filled with the mixed solution from an injection port previously provided in the substrate on which the organic EL element is provided or the housing material covering the organic EL element on the substrate, and the injection port is sealed after the filling. This can be done by The formation of the sealing layer is also preferably performed in a dry inert gas atmosphere. This method is suitable when the sealing layer is provided by a liquid mixture having high fluidity (inert liquid containing an adsorbent).

(B) An adsorbent and an inert liquid are separately put in the space defined by the substrate on which the organic EL element is provided and the housing material covering the organic EL element on the substrate, and sealed. A method of forming a stop layer. This method can be further divided into the following three (b1) to (b3), but in each case, it is preferable that the sealing layer is formed in a dry inert gas atmosphere.

(B1) After placing an adsorbent on the organic EL element and on the substrate on which the organic EL element is provided and in the area that fits in the space, a housing material is provided on the substrate. The space is filled with an inert liquid from an inlet provided in the substrate or the housing material in advance to form a sealing layer. The inlet is sealed after filling with the inert liquid.

(B2) An adsorbent is placed in a recess in the housing material that is involved in the formation of the above space, and the housing material is provided on the substrate on which the organic EL element is provided. The sealing layer is formed by filling the above space with the inert liquid from the inlet provided in the housing material in advance. The inlet is sealed after filling with the inert liquid.

(B3) A housing material is provided on a substrate on which an organic EL element is provided to form the above space, and an adsorbent and an inert liquid are introduced from an injection port previously provided in the substrate or the housing material. The sealing layer is formed by putting and in the above-mentioned space in no particular order. The inlet is sealed after filling with adsorbent and inert liquid.

When a sealing layer is provided on the outer periphery of an organic EL element by using a housing material, the housing material is a cap-shaped article having a recess whose inner dimension is larger than the outer dimension of the organic EL element to be sealed. , Plate-shaped objects (eg counterbore substrate),
The housing material is a sheet or a film, and the housing material is fixed on the substrate so as to form a substantially closed space together with the substrate. At this time, the organic EL element to be sealed is in a state of being housed in the recess. When a plurality of organic EL elements are formed on the substrate, the housing material may be provided for each organic EL element, or only one common to all organic EL elements may be provided. It is also possible to provide a plurality of common elements among all the organic EL elements. Similarly, the recess formed in the housing material may correspond to each organic EL element, or may have a size capable of accommodating all the organic EL elements, All organic EL
It may be of a size capable of accommodating a plurality of elements.

The housing material can be arranged on the substrate by fixing it with various adhesives such as epoxy resin adhesives and acrylate resin adhesives. The backing material is preferably one that is less likely to allow water and oxygen to pass through, and specific examples thereof include Araldite AR-R30 (trade name of epoxy resin adhesive manufactured by Ciba-Geigy). In addition, various resins such as thermosetting resins and photocurable resins may be used instead of the above adhesive.

The material of the housing material is preferably an electrically insulating substance such as glass or polymer, and specific examples thereof include soda lime glass, borosilicate glass, silicate glass, silica glass, non-fluorescent glass, Examples thereof include quartz, acrylic resin, styrene resin, polycarbonate resin, epoxy resin, polyethylene, polyester, and silicone resin. In addition, when the organic EL element to be sealed is one in which an insulating coated electrode wire is used for electrode extraction, or when the housing material is fixed on the substrate by an electrically insulating adhesive or an electrically insulating resin. If done, the housing material may be made of a conductive metal such as stainless steel or aluminum alloy.

By providing a predetermined sealing layer on the outer periphery of the organic EL element as described above, the intended sealing of the present invention can be performed. At the same time, the target organic EL device of the present invention can be obtained.

Organic EL to be sealed by the method of the present invention
The element configuration of the element is not particularly limited, and it is possible to target organic EL elements having various element configurations. Therefore, the device configuration of the organic EL device of the present invention also takes various configurations.

Specific examples of the layer structure of the organic EL element of the type in which the substrate side is the light extraction surface include the following (1) to (4) in the stacking order on the substrate surface. (1) Anode / light emitting layer / cathode (2) Anode / light emitting layer / electron injection layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / electron Injection layer / cathode

Here, the light emitting layer is usually formed of one or more kinds of organic light emitting materials, but it may be formed of a mixture of an organic light emitting material and a hole injecting material and / or an electron injecting material. In addition, a protective layer may be provided on the outer periphery of the element having the above-mentioned layer structure so as to cover the element and prevent moisture from entering the element.

When the substrate side is used as the light extraction surface, at least the substrate emits light (EL light).
It is made of a substance that gives a high transparency (about 80% or more) to, and specifically, a plate-like material, a sheet-like material, or a film-like material made of transparent glass, transparent plastic, quartz or the like is used.

Various materials can be used as the materials for the anode, the cathode, the light emitting layer, the hole transport layer, the electron injection layer and the protective layer. For example, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (for example, 4 eV or more) is preferably used as the anode material.
Specific examples are metals such as gold and nickel, CuI, and IT.
Examples include dielectric transparent materials such as O, SnO ₂ , and ZnO. In particular, ITO is preferable in terms of productivity and controllability.
Although the film thickness of the anode depends on the material, it can be appropriately selected usually within the range of 10 nm to 1 μm.

As the cathode material, a metal, an alloy, an electrically conductive compound having a small work function (for example, 4 eV or less),
Alternatively, a mixture thereof or the like is preferably used. Specific examples include sodium, sodium-potassium alloys, magnesium, lithium, alloys or mixed metals of magnesium and silver, rare earth metals such as aluminum, Al / AlO ₂ , indium and ytterbium. Although the film thickness of the anode depends on the material, it can be appropriately selected usually within the range of 10 nm to 1 μm. The sheet resistance of both the anode and the cathode is preferably several hundreds Ω / □ or less. Note that the size of the work function used as a reference when selecting the anode material and the cathode material is not limited to 4 eV.

The material of the light emitting layer (organic light emitting material) is organic E
A light emitting layer for an L element, that is, an injection function capable of injecting holes from an anode or a hole transporting layer when an electric field is applied and electrons from a cathode or an electron injecting layer, and injected charges (electrons). And / or holes)
Any layer can be formed as long as it can form a layer having a transporting function of moving an electron by an electric field and a light emitting function of providing a field for recombination of electrons and holes and connecting it to light emission. Specific examples thereof include benzothiazole-based, benzimidazole-based, and benzoxazole-based fluorescent whitening agents, metal chelated oxinoid compounds, styrylbenzene-based compounds, distyrylpyrazine derivatives, polyphenyl-based compounds, 12- Phthaloperinone, 1,4-diphenyl-
1,3-butadiene, 1,1,4,4-tetraphenyl-1,3-butadiene, naphthalimide derivative, perylene derivative, oxadiazole derivative, aldazine derivative, pyrazirine derivative, cyclopentadiene derivative, pyrrolopyrrole derivative, styryl Examples thereof include amine derivatives, coumarin-based compounds, aromatic dimethylidin compounds, and metal complexes of 8-quinolinol derivatives. The thickness of the light emitting layer is not particularly limited, but is usually 5 nm to 5 μm.
Is appropriately selected within the range.

The material for the hole-transporting layer (hole-transporting material) may be any material having either a hole-transporting property or an electron-blocking property. Specific examples thereof include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, and fluorenone derivatives. , Hydrazone derivatives, stilbene derivatives, silazane derivatives, polysilane compounds, aniline copolymers, conductive polymer oligomers such as thiophene oligomers, porphyrin compounds, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds Etc. Although the thickness of the hole transport layer is not particularly limited, it is usually appropriately selected within the range of 5 nm to 5 μm.
The hole transport layer may have a single-layer structure made of one or more of the above-mentioned materials, or a multi-layer structure made of a plurality of layers having the same composition or different compositions.

The electron injection layer has only to have a function of transmitting electrons injected from the cathode to the light emitting layer. Specific examples of the material (electron injection material) include nitro-substituted fluorenone derivatives and anthraquinodimethane. Derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthalene perylene, carbodiimides, phenylenylidene methane derivatives, anthraquinodimethane derivatives, anthrone derivatives, oxadiazole derivatives, 8-quinolinol derivatives And metal-free phthalocyanines, metal phthalocyanines, those in which the ends thereof are substituted with alkyl groups, sulfone groups, etc., and distyrylpyrazine derivatives. Although the thickness of the electron injection layer is not particularly limited, it is usually appropriately selected within the range of 5 nm to 5 μm. The electron injection layer may have a single-layer structure made of one or more of the above-mentioned materials, or a multi-layer structure made of a plurality of layers having the same composition or different compositions.

As a specific example of the material of the protective layer,
A copolymer obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer, a fluorine-containing copolymer having a cyclic structure in the copolymer main chain,
Polyethylene, polypropylene, polymethylmethacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, water absorption 1%
The above water-absorbing substance and moisture-proof substance having a water absorption rate of 0.1% or less, In, Sn, Pb, Au, Cu, Ag, Al, T
Metals such as i and Ni, MgO, SiO, SiO ₂ , Al ₂
O ₃ , GeO, NiO, CaO, BaO, Fe ₂ O ₃ ,
Metal oxides such as Y ₂ O ₃ and TiO ₂ , MgF ₂ and Li
Examples thereof include metal fluorides such as F, AlF ₃ , and CaF ₂ .

Further, the method for forming each layer (including the anode and the cathode) constituting the organic EL element to be sealed is not particularly limited. As a method for forming the anode, the cathode, the light emitting layer, the hole transporting layer, and the electron injecting layer, for example, a vacuum vapor deposition method, a spin coating method, a casting method, a sputtering method, an LB method or the like can be applied. It is preferable to apply a method other than the sputtering method (vacuum vapor deposition method, spin coating method, casting method, LB method, etc.). The light emitting layer is preferably a molecular deposition film. Here, the molecular deposition film is a thin film formed by depositing a material compound in a vapor phase state, or a film formed by solidifying a material compound in a solution state or a liquid phase state. , A thin film (molecular cumulative film) formed by the LB method can be classified according to a difference in agglomeration structure, a higher-order structure, or a functional difference due to the difference. When the light emitting layer is formed by spin coating or the like, a coating solution is prepared by dissolving a binder such as a resin and a material compound in a solvent.

For the protective layer, vacuum deposition method, spin coating method, sputtering method, casting method, MBE (molecular beam epitaxy) method, cluster ion beam method, ion plating method, plasma polymerization method (high frequency excitation ion plating method) A reactive sputtering method, a plasma CVD method, a laser CVD method, a thermal CVD method, a gas source CVD method, or the like can be applied.

The method of forming each layer can be appropriately changed depending on the material used. If a vacuum vapor deposition method is used for forming each layer constituting the organic EL element, the organic EL element can be formed only by this vacuum vapor deposition method.
This is advantageous in simplifying equipment and shortening production time.

In the organic EL element of the present invention which is sealed by providing the above-mentioned sealing layer on the outer periphery of the above-mentioned organic EL element to be sealed, the presence of the sealing layer causes the generation of dark spots or dark spots. Growth is strongly suppressed, resulting in a long device life.

[0058]

EXAMPLES Hereinafter, examples of the present invention will be described in comparison with comparative examples. A method for manufacturing an organic EL element used as a sealing target in each example and each comparative example will be described in advance. When manufacturing the organic EL element to be sealed,
First, a transparent support substrate was prepared by depositing an ITO film having a film thickness of 100 nm on a glass substrate of 25 mm × 75 mm × 1.1 mm by a vapor deposition method. When the light transmittance of this substrate was measured by UV-3100PC manufactured by Shimadzu Corporation, it was about 80% in the wavelength range of 400 to 600 nm.
The substrate is ultrasonically cleaned in isopropyl alcohol for 5 minutes and then in pure water for 5 minutes, and further,
UV ozone cleaning was performed for 10 minutes using an apparatus manufactured by Samco International Laboratories Inc.

Next, while fixing this substrate to a substrate holder of a commercially available vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), N, N'-bis (3-methylphenyl-) was placed in a resistance heating boat made of molybdenum. 200 mg of N, N'-diphenyl [1,1'-biphenyl] -4,4'-diamine (hereinafter abbreviated as TPD) was put, and 4,4'-bis (was added to a different molybdenum resistance heating boat. 2,2′-diphenylvinyl) biphenyl (hereinafter abbreviated as DPVBi)
After adding 00 mg, the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

After that, the boat with TPD is loaded with 215
Up to 220 ° C. to deposit TPD at a deposition rate of 0.1 to 0.1 ° C.
Deposited on the ITO film at 3 nm / s to a film thickness of 60 n
m of the hole transport layer was formed. At this time, the substrate temperature was room temperature. Without removing this from the vacuum chamber, the boat containing DPVBi was placed in the boat for 2 hours after the formation of the hole transport layer.
Heat to 40 ° C. to deposit DPVBi at a deposition rate of 0.1 to 0.1.
The film is deposited on the hole transport layer at 3 nm / s to have a thickness of 40 nm.
A light emitting layer of nm was formed. The substrate temperature at this time was also room temperature.

This was taken out from the vacuum chamber, a stainless steel mask was placed on the above light emitting layer, and it was fixed to the substrate holder again. Next, tris (8-quinolinol) aluminum (hereinafter referred to as Alq ₃
200 mg), 1 g of magnesium ribbon in a different molybdenum boat, and 500 mg of silver wire in a tungsten basket, and these boats were mounted in a vacuum tank.

Next, the vacuum chamber was decompressed to 1 × 10 ⁻⁴ Pa, and the boat containing Alq ₃ was heated to 230 ° C. to emit Alq ₃ at a vapor deposition rate of 0.01 to 0.03 nm / s. An electron injection layer having a film thickness of 20 nm was formed by vapor deposition on the layer. Further, silver is vapor-deposited on the adhesive layer at a vapor deposition rate of 0.1 nm / s, and at the same time, magnesium is vapor-deposited on the adhesive layer at a vapor deposition rate of 1.4 nm / s to form a film of a mixed metal of magnesium and silver. A counter electrode having a thickness of 150 nm was formed. When the reflectance of this counter electrode was measured by Shimadzu Corporation UV-3100PC, it was 400-6.
It was 80% in the wavelength range of 00 nm.

By forming the counter electrode as described above, the intended organic EL element to be sealed was obtained. In this organic EL device, an ITO film as an anode, a TPD layer as a hole transport layer, a DPVBi layer as a light emitting layer, and an Alq as an electron injection layer are formed on one main surface of a glass substrate.
_Three layers and a magnesium-silver mixed metal layer as a counter electrode are sequentially laminated. Part of the ITO film and part of the magnesium-silver mixed metal layer also serve as electrode wires for extracting electrodes, and the size of the light emitting layer in plan view is 6 mm × 10 mm.

Example 1 (1) Preparation of Inert Liquid with Dissolved Oxygen Concentration of 1 ppm or Less First, as an inert liquid before adjusting the dissolved oxygen concentration, perfluoropolyether (Demnum S-20 manufactured by Daikin Industries, Ltd.) was used. (Product name: vapor pressure at 25 ° C 10 ^-6
Torr, kinematic viscosity at 25 ° C. 53 cSt)) is prepared,
An appropriate amount of this Demnum S-20 was placed in a glass sample container with a vacuum cock, and this sample container and a vacuum pump with a diffusion pump (ULVAC VPC-manufactured by Nippon Vacuum Technology Co., Ltd.)
050) and was connected using a flange. Next, insert a zeolite made of polytetrafluoroethylene (Teflon) into the demnum S-20 contained in the above sample container, and evacuate the sample container to 10 ^-4 Torr while stirring at room temperature. Then, the dissolved oxygen was discharged by the vacuum degassing method at room temperature for about 30 minutes until foaming disappeared. After this, the vacuum cock was closed and stored.

A part of the thus prepared inert liquid was sampled and the dissolved oxygen concentration and the water content were measured. As a result, the dissolved oxygen concentration was 0.05 ppm and the water content was 5 ppm. In addition, SUD-1 (trade name of measuring device) manufactured by Central Science Co., Ltd. was used for measuring the dissolved oxygen concentration, and an inert liquid was used for the sensor part of the device in a glove box whose atmosphere was replaced with nitrogen gas. 5
Flowing at a constant flow rate of 0 ml / min, and after about 20 seconds, the measured value was read after the displayed numerical value became stable. Further, the water content in the inert liquid was measured by the Karl Fischer titration method.

(2) Activation treatment of adsorbent Activated alumina (made by Hiroshima Wako Pure Chemical Industries, Ltd .: particle size of about 300 mesh) was prepared as an adsorbent, and an appropriate amount of this activated alumina was made of glass with a vacuum cock. It was put in a sample container and the sample container and the vacuum pump were connected using a flange.
Next, the inside of the sample container was evacuated to 10 ⁻⁴ Torr at room temperature, and the part in which the activated alumina was stored was heated to 280 ° C. by a heater and further evacuated. The vacuum evacuation while heating was continued for 5 hours until no gas was generated from the activated alumina and the degree of vacuum became stable, after which the vacuum cock was closed and stored.

(3) Sealing First, a cap-type housing material made of glass (a spot facing substrate manufactured by Howa Sangyo Co., Ltd.) was prepared. This housing material has one recess having an inner dimension of 13 mm × 13 mm × 1 mm, and the outer dimension thereof is 15 mm × 15 mm × 1.8 mm. An injection port for injecting an inert liquid or the like is provided at the bottom of the recess of the housing material. Next, the glass substrate on which the organic EL element is formed and the housing material are covered with an epoxy resin adhesive (made by Ciba-Geigy Co., Ltd.) so that the organic EL element to be sealed is housed in the recess. It was pasted by Araldite AR-R30). At this time, the organic EL element is in the space formed by the recess of the housing material and the substrate, and the organic EL element and the housing material are not in contact with each other.

After being left for 3 hours to solidify the adhesive, it was vacuum dried using a vacuum desiccator. The material after vacuum drying was transferred into a glove box whose atmosphere was replaced with dry nitrogen gas. In addition, the sample container containing the inert liquid prepared in the above (1) and the sample container containing the adsorbent activated in the above (2) Moved inside. Then, a predetermined amount of the adsorbent is added to the sample container containing the inert liquid, and the mixture is stirred, and the inert liquid containing the adsorbent (hereinafter referred to as "mixed liquid") is added.
Say. ) Was prepared. This mixed liquid contains 500 mg of the adsorbent per milliliter of the inert liquid, and the dissolved oxygen concentration is 1 ppm or less. Then, the mixed solution was injected from an injection port provided in the housing material to fill the space defined by the recess of the housing material and the substrate with the mixed solution.

After filling the mixed solution, the inlet was closed in the glove box with an epoxy adhesive (Araldite AR-R30 manufactured by Ciba-Geigy), and the mixture was placed in the glove box for about 3 hours until the adhesive solidified. I left it.

The space formed by the recess of the housing material and the substrate is filled with the above-mentioned mixed liquid, so that a sealing layer is formed on the outer periphery of the organic EL element to be sealed, whereby the desired sealing is achieved. It was stopped. At the same time, the target organic EL device was obtained. A schematic cross section of this organic EL element (sealed) is shown in FIG. As shown in FIG. 1, the above-obtained organic EL device 1 after encapsulation has the inert liquid 20a prepared in (1) above and (2) above the outer periphery of the organic EL device 10 to be encapsulated. ), The sealing layer 20 made of a mixed liquid (inert liquid containing an adsorbent) with the adsorbent 20b that has been subjected to the activation treatment is provided.

The organic EL element 10 to be sealed has an ITO film 12 as an anode, a TPD layer 13 as a hole transport layer, a DPVBi layer 14 as a light emitting layer, on a glass substrate 11.
An Alq ₃ layer 15 as an electron injection layer and a magnesium-silver mixed metal layer 16 as a counter electrode (cathode) are sequentially laminated. Then, a part 1 of the ITO film 12
2a and a part 16a of the magnesium-silver mixed metal layer 16 are electrode wires for extracting electrodes. The organic EL element 10 is present in the space formed by the concave portion of the housing material 18 fixed on the glass substrate 11 by the epoxy resin system 17 and the glass substrate 11,
This space is filled with the above mixed liquid. As a result, the sealing layer 20 is formed on the outer periphery of the organic EL element 10. The sealing layer 20 was provided in the housing member 18 with a mixed liquid obtained by mixing the inert liquid 20a prepared in (1) above and the adsorbent 20b activated in (2) above. It is formed by injecting from the injection port 19, and the injection port 19 is sealed with the epoxy resin adhesive 17a after the sealing layer 20 is formed.

(4) Evaluation of sealing effect Organic EL element obtained in (3) above (sealed)
A DC constant current power supply is connected to the organic EL device via two electrode wires of the organic EL device, and the initial brightness is 100 c at 25 ° C. under atmospheric pressure.
Electricity was applied so that the pressure would be d / m ² . At this time, the current value was 0.56 mA and the voltage value was 9V. The brightness is measured by a color difference meter (trade name CS-1 manufactured by Minolta Camera Co., Ltd.).
00). Subsequent to the above energization, an enlarged photograph of the light emitting surface (magnification 10 times) was taken, and from this photograph, the ratio of the total area of the dark spot in plan view to the area of the light emitting surface in plan view (hereinafter referred to as “non-light emitting area ratio It was 0.20%. Further, the diameter of a certain dark spot was 15 μm. Next, 5 and 30 days after the start of energization, the non-emission area ratio was determined by the same method as above, and at the same time, the diameter of the same dark spot as above was determined. Table 2 shows the results.

Example 2 As an adsorbent, Mg powder (manufactured by Kojundo Chemical Laboratory Co., Ltd .: particle size of 80 mesh or less) was prepared, and the M
The g powder was activated. First, an appropriate amount of Mg powder is put in a beaker, 1M hydrochloric acid aqueous solution is put in this beaker, left for several minutes and then filtered, and the residue (Mg powder) is rinsed with a sufficient amount of absolute ethanol. Residue after rinsing (Mg
Powder) is transferred to a glass sample container with a vacuum cock, and the cock of the sample container is closed. All the operations up to here,
It is carried out in a glove box with a flow of dry nitrogen gas. Remove the sample container (containing the residue (Mg powder)) after closing the cock from the glove box,
The Mg powder in the sample container is evacuated in the same manner as in Example 1 until ethanol is evaporated and the degree of vacuum is stabilized. The evacuation at this time is performed at room temperature without heating the portion of the sample container accumulating the Mg powder with a heater.

Mg which has been activated as described above
The organic EL device was sealed in the same manner as in Example 1 except that the powder was used as the adsorbent, and at the same time, the desired organic EL device was obtained. At this time, the sealing layer contains 500 mg of the adsorbent per 1 ml of the inert liquid, and the dissolved oxygen concentration is 1 ppm or less. Organic EL after sealing
The element was evaluated for sealing effect in the same manner as in Example 1 (4). The results are shown in Table 2.

Example 3 As an adsorbent, CaSO ₄ .1 / 2H ₂ O (Wako Pure Chemical Industries, Ltd .: Baked Gypsum) powder (particle size 300 mesh or less) was used, and the adsorbent was activated. In the same manner as in Example 1 except that the heating temperature by the heater for application was 240 ° C., and 200 mg of the adsorbent was added to 1 ml of the inert liquid to prepare a mixed liquid (inert liquid containing the adsorbent). To seal the organic EL device,
At the same time, the target organic EL device was obtained. The dissolved oxygen concentration of the sealing layer at this time is 1 ppm or less. The sealing effect of the sealed organic EL element was evaluated in the same manner as in Example 1 (4). The results are shown in Table 2.

Comparative Example 1 An organic EL device was sealed in the same manner as in Example 1 except that no adsorbent was used. Then, the sealing effect of the sealed organic EL element was evaluated in the same manner as in Example 1 (4). The results are shown in Table 2.

Comparative Example 2 In the same manner as in Example 1 except that perfluoropolyether (Demnum S-20 (trade name) manufactured by Daikin Industries, Ltd.) was used as an inert liquid without vacuum degassing. The organic EL device was sealed. And the organic E after sealing
The sealing effect of the L element was evaluated in the same manner as in Example 1 (4). The results are shown in Table 2.

Comparative Example 3 As in Example 1 except that activated alumina (manufactured by Hiroshima Wako Pure Chemical Industries, Ltd .: particle size of about 300 mesh) was once exposed to the atmosphere and then used as an adsorbent without activation treatment. Similarly, the organic EL element was sealed. The dissolved oxygen concentration of the mixed liquid (inert liquid containing an adsorbent) used for forming the sealing layer was 5.0 ppm because the oxygen adsorbed in the adsorbent was dissolved in the inert liquid. there were. Then, the sealing effect of the sealed organic EL element was evaluated in the same manner as in Example 1 (4). The results are shown in Table 2.

[0079]

[Table 2]

As is clear from Table 2, in each of the organic EL devices sealed in Examples 1 to 3, both the increase in the non-light emitting area ratio with time and the growth of dark spots with time are strongly suppressed. Was done. On the other hand, in the organic EL device sealed in Comparative Example 1, although the increase in the non-light emitting area ratio with time and the growth of dark spots with time were relatively suppressed, in Examples 1 to 3 Sealed organic EL
The sealing effect is lower than that of the device. Comparative Example 2
In the organic EL element sealed with, the non-light emitting area ratio increases with time and the dark spots grow with time, and the sealing effect is low. Then, in Comparative Example 3 in which the adsorbent was once exposed to the atmosphere and then used without activation treatment to form a sealing layer having a dissolved oxygen concentration of 5.0 ppm, Comparative Example in which no adsorbent was used Similar to the organic EL device sealed with 2, the non-light emitting area ratio increased with time and the growth of dark spots with time was large, and the effect of using the adsorbent was not observed.

[0081]

As described above, according to the method of the present invention, the growth of dark spots in the organic EL device can be strongly suppressed. Therefore, by implementing the present invention, it becomes possible to provide an organic EL element having a long element life.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of an organic EL element (sealed) obtained in Example 1.

[Explanation of symbols]

 1 Organic EL Element after Encapsulation 10 Organic EL Element to be Encapsulated 11 Glass Substrate 17 Epoxy Resin Adhesive 17a Epoxy Resin Adhesive 18 Housing Material 19 Injection Port 20 Encapsulation Layer 20a Inert Liquid 20b Adsorbent

Claims (9)

[Claims] 1. A sealing layer made of an inert liquid containing an adsorbent and having a dissolved oxygen concentration of 1 ppm or less is provided on the outer periphery of an organic EL element in which an anode and a cathode are laminated with at least a light emitting layer interposed therebetween. And a method for sealing an organic EL element. 2. As an adsorbent, (1) activated alumina, diatomaceous earth, activated carbon, gypsum hemihydrate, phosphorus pentoxide, magnesium perchlorate, potassium hydroxide, calcium sulfate, calcium bromide, calcium oxide, zinc chloride, Inorganic compounds selected from zinc bromide and anhydrous copper sulfate, (2) lithium,
A metal selected from the group of metals consisting of beryllium, potassium, sodium, magnesium, rubidium, strontium and calcium, (3) an alloy of metals selected from the group of metals, or (4) an acrylic water-absorbing polymer or meta The method according to claim 1, wherein an acrylic water-absorbing polymer is used. 3. The method according to claim 1, wherein an activated adsorbent is used as the adsorbent. 4. The method according to claim 1, wherein 1 mg to 10 g of the adsorbent is contained in 1 ml of the inert liquid. 5. An inert liquid having a dissolved oxygen concentration of 1 pp.
The method according to any one of claims 1 to 4, wherein m or less of an inert liquid is used. 6. The method according to claim 1, wherein liquid fluorocarbon having a vapor pressure at 25 ° C. of 10 ⁻² Torr or less is used as the inert liquid. 7. An inert liquid having a water content of 10 ppm
The method according to claim 1, wherein the following inert liquids are used. 8. A housing member is provided outside the organic EL element formed on the substrate to cover the organic EL element in cooperation with the substrate while forming a gap between the organic EL element and the organic EL element, The method according to any one of claims 1 to 7, wherein a sealing layer is formed in a space formed by the substrate and the housing material. 9. An organic E, which is sealed by the method according to any one of claims 1 to 8.
L element.