JPH1192915A - Vapor deposition method and organic electroluminescent device - Google Patents

Abstract

(57) [Problem] To provide an evaporation method for forming an organic material layer using an organic evaporation material, which can surely reduce contamination by gas, moisture, and the like. Provided is an organic EL device capable of ensuring excellent quality by reducing contamination by impurities. SOLUTION: An organic material layer is formed by using an organic vapor deposition material.
In vapor-depositing No. 4, a pellet-shaped material having a gas content of 1 mol% or less is used as an organic vapor-depositing material. Thereby, contamination due to gas, moisture, and the like can be surely reduced. Therefore, when the organic EL element 1 is manufactured, a high-quality organic EL element 1 having a long life and a low driving voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor deposition method and an organic EL device (organic electroluminescence device), and more particularly, to a vapor deposition method for forming an organic material layer using an organic vapor deposition material and a method for forming a film on a substrate. The present invention relates to an organic EL device provided with an electrode and an organic material layer.

[0002]

2. Description of the Related Art In recent years, an organic EL element, which is a light emitting device including an organic material layer, has attracted attention, and research has been conducted for use in displays and the like. This organic EL device generally includes an anode (transparent electrode), an organic layer such as a light emitting layer,
And a structure in which a cathode (a counter electrode) is laminated on a substrate. On the other hand, in Carlson type electrophotographic copying machines,
As an electrophotographic photoreceptor, an organic photoreceptor having a photosensitive layer made of an organic material is used. The formation of an organic material layer in these organic EL elements, electrophotographic photoreceptors, and the like is performed by a vacuum evaporation method in which an organic evaporation material made of an organic material is heated and evaporated. As the organic vapor deposition material, a powdery material obtained by melting, degassing, and pulverizing an organic material as a raw material is used.

However, organic substances tend to adsorb gas which is an impurity during pulverization or the like, and powdery organic vapor-deposited materials have a large contact area with the air, so that impurities such as moisture are easily adsorbed. The adsorbed gas, moisture and the like evaporate together with the organic vapor deposition material during the vapor deposition of the organic material layer and enter the organic material layer or adhere to the substrate or the like. Due to such contamination by impurities such as gas, an organic EL element, an electrophotographic photoreceptor, and the like may not be able to sufficiently achieve a target function. In order to solve such a problem, a method of suppressing gas evaporation at the time of vapor deposition by using an organic powder as a tablet obtained by pressing and molding as an organic vapor deposition material (Japanese Patent Application Laid-Open No. 5-204196). A method has been proposed in which a vaporized organic vapor deposition material is introduced into a cold trap to condense and remove impurities and then used for vapor deposition (Japanese Patent Application Laid-Open No. 50-3973).

[0004]

In the method of tableting an organic substance powder, the organic substance powder is simply formed by pressure molding. Therefore, a gas, especially an organic solvent taken into a crystal of an organic substance from a deposition material. However, there is a problem that gas contamination cannot be sufficiently reduced. On the other hand, the method of introducing into a cold trap can remove non-volatile components among impurities in the organic vapor deposition material, but cannot sufficiently remove volatile components such as gas, so that contamination by gas or the like cannot be avoided. Further, when an organic EL device is produced by these methods, contamination of a light emitting layer, a substrate, or the like cannot be sufficiently suppressed, and thus a problem occurs in that the device performance is reduced, particularly, the life is shortened.

An object of the present invention is to provide a vapor deposition method for forming an organic material layer using an organic vapor deposition material, which can reliably reduce contamination by impurities such as gas and moisture. Another object of the present invention is to provide an organic EL device having an electrode and an organic material layer formed on a substrate and capable of ensuring excellent quality by reducing contamination by impurities. It is in.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, depending on the nature of the gas contained in the organic vapor deposition material, 5 mol / m is contained in the organic vapor deposition material.
It has been found that when 1% or more of gas is contained, degassing occurs from the organic vapor deposition material during vapor deposition, and this gas contaminates the organic layer and the substrate. Note that the gas here refers to a substance that evaporates below the deposition temperature of the organic deposition material, and does not include a substance that evaporates at a temperature higher than a temperature near the deposition temperature. The present invention aims to achieve the above object by limiting the amount of gas in the organic vapor deposition material.

Specifically, the present invention relates to a vapor deposition method for forming an organic material layer using an organic vapor deposition material, wherein the organic vapor deposition material is formed in a pellet shape and has a gas content of 1 mol%. It is characterized as follows.

[0008] Here, the gas refers to a substance, other than an organic or inorganic substance, other than the organic vapor deposition material to be vapor-deposited, that is, an impurity in the organic vapor deposition material that has a temperature lower than the temperature around the vapor deposition of the organic vapor deposition material. A substance that evaporates at temperature. This gas includes not only those that are gaseous in the atmosphere (normal temperature), but also those that are heated and vaporized during vapor deposition.

In the present invention, since the gas content of the organic vapor deposition material is set to 1 mol% or less, the amount of gas as an impurity that evaporates during the vapor deposition of the organic material layer can be greatly reduced, so that the contamination by the gas can be reliably prevented. Can be reduced to Further, since the organic vapor-deposited material is formed in the shape of a pellet, the area in contact with the atmosphere can be made smaller than that of a powdery material, so that adsorption of moisture, which is an impurity, can be minimized. Therefore, since evaporation of moisture and the like from the organic material is minimized, contamination by impurities such as moisture can be surely reduced. Moreover, unlike powder, the heat conduction of the powder itself becomes good, so that when a large amount of material is charged, the vapor deposition conditions are stabilized in a short time.

[0010] In the above, it is preferable that the organic vapor-deposited material is degassed by heating in a vacuum. In this way, if organic matter is heated in vacuum,
Since the gas such as the organic solvent taken into the organic crystal can be removed, the gas can be efficiently degassed, so that the gas content in the organic vapor deposition material can be surely reduced.

Further, the gas content of the organic vapor deposition material is more preferably 0.1 mol% or less, and the gas content is preferably low. In addition, since gas is generated from the vacuum chamber itself during vapor deposition, it is sufficient to use an organic vapor deposition material having a lower gas content based on the gas generated from the vacuum chamber. Is obtained. As a method for measuring the gas content, a method of estimating from a change in the degree of vacuum at the time of degassing, a gas chromatography method, a method of obtaining from a weight loss before and after degassing, or the like can be employed. In addition, the type of the organic vapor deposition material is not particularly limited, but if the molecular weight is too large, there is a risk of decomposition due to high temperature during vapor deposition, so that the molecular weight is preferably smaller, for example, a molecular weight of 2000 or less. is there.

The shape and size of the pellets are not particularly limited, but those which are easy to produce are preferable. As the shape of the pellet, for example, spherical, cylindrical,
A rectangular parallelepiped shape or the like can be adopted. Further, the size of the pellet is preferably such that the maximum diameter is 0.1 to 100 mm.

On the other hand, the present invention relates to an organic electroluminescence element comprising an electrode and an organic material layer formed on a substrate, wherein the organic material layer is formed by evaporating an organic vapor deposition material on the substrate. The organic vapor-deposited material is formed into a pellet and has a gas content of 1 mol.
1% or less.

In the present invention, since a pellet-shaped material having a gas content of 1 mol% or less is used as the organic vapor deposition material, impurities such as gas and moisture in the organic vapor deposition material can be reduced, and the organic layer and the substrate can be reduced. Since contamination can be reliably reduced, a high-quality organic EL element having a long life and a low driving voltage can be obtained.

In the type in which the organic EL element has a light extraction surface on the substrate side, as a specific example of the layer structure of the organic EL element, the lamination order on the substrate surface is as follows (1) to (4).
One. (1) anode / light emitting layer / cathode (2) anode / light emitting layer / electron injection layer / cathode (3) anode / hole injection layer / light emitting layer / cathode (4) anode / hole injection 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 may be formed of a mixture of an organic light emitting material and a hole injection material and / or an electron injection material. . In some cases, a protective layer may be provided on the outer periphery of the element having the above-described layer structure so as to cover the element and prevent moisture from entering the element.

In the case where the substrate side is a light extraction surface, the substrate has at least light emission (EL light) from an organic EL element.
It is made of a material that gives high permeability (approximately 80% or more) to concrete, specifically, transparent glass, transparent plastic,
A plate, sheet, or film made of quartz or the like can be used.

As the materials for the anode, cathode, light emitting layer, hole injection layer, electron injection layer, and protective layer, conventionally known materials can be used. For example, as the anode material, 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. Specific examples include metals such as gold and nickel, C
ul, ITO, SnO ₂ , ZnO, and other dielectric transparent materials. In particular, in terms of productivity and controllability, ITO
Is preferred. The thickness of the anode depends on the material.
It can be appropriately selected within the range of nm to 1 μm.

As the cathode material, metals, alloys, electrically conductive compounds, or mixtures thereof having a low work function (for example, 4 eV or less) are preferably used. Specific examples include sodium, sodium-potassium alloy, magnesium, lithium, alloy or mixed metal of magnesium and silver, aluminum, Al / Al ₂ O ₃ ,
Rare earth metals such as indium and ytterbium are exemplified. The thickness of the cathode depends on the material, but is usually from 10 nm to
It can be appropriately selected within a range of 1 μm. The sheet resistance of each of the anode and the cathode is preferably several hundred Ω / □ or less. 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 organic vapor-deposited material (organic light-emitting material) of the light-emitting layer, which is an organic layer, is a light-emitting layer for an organic EL device, that is,
Injection function that can inject holes from the anode or the hole injection layer when applying an electric field and also injects electrons from the cathode or the electron injection layer, and the injected charge (at least one of electrons and holes) Any layer can be formed as long as it can form a layer having a transport function of moving an electron by the force of an electric field and a light-emitting function of providing a field for recombination of electrons and holes and connecting the same to light emission. Specific examples thereof include benzothiazole-based, benzimidazole-based, 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, styrylamine derivative, coumarin-based compound , Aromatic dimethylidin compounds, and metal complexes of 8-quinolinol derivatives. The thickness of the light emitting layer is not particularly limited, but is usually appropriately selected within a range of 5 nm to 5 μm.

The organic vapor deposition material (hole injection material) of the hole injection layer serving as the organic material layer may be any material that has either a hole injection property or an electron barrier 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, styryl anthracene derivatives, and fluorenone derivatives. , A hydrazone derivative,
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, and the like. . Although the thickness of the hole injection layer is not particularly limited, it is usually 5 nm to 5 nm.
It is appropriately selected within the range of μm. The hole injection layer may have a single-layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

The electron injection layer, which is an organic layer, may have a function of transmitting electrons injected from the cathode to the light emitting layer. Specific examples of the material (electron injection material) include a nitro-substituted fluorenone derivative. , Anthraquinodimethane derivative, diphenylquinone derivative, thiopyrandioxide derivative, heterocyclic tetracarboxylic anhydride such as naphthalene perylene, carbodiimide, fluorenylidenemethane derivative, anthraquinodimethane derivative, anthrone derivative,
Examples include oxadiazole derivatives, metal complexes of 8-quinolinol derivatives, metal-free phthalocyanines and metal phthalocyanines, or those whose terminals are substituted with an alkyl group or a sulfone group, and distyrylpyrazine derivatives. Although the thickness of the electron injection layer is not particularly limited, it is usually appropriately selected in the range of 5 nm to 5 μm. The electron injection layer may have a single-layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of multiple layers having the same composition or different compositions.

As specific examples 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 a copolymer main chain,
Polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, water absorption 1%
The above water-absorbing substances and moisture-proof substances having a water absorption of 0.1% or less, In, Sn, Pb, Au, Cu, Ag, Al, T
i, metal such as Ni, MgO, SiO, SiO ₂ , Al
₂ O ₃ , GeO, NiO, CaO, BaO, Fe ₂
Examples include metal oxides such as O ₃ , Y ₂ O ₃ , and TiO ₂ , and metal fluorides such as MgF ₂ , LiF, AlF ₃ , and CaF ₂ .

The method of forming each layer (including the anode and the cathode) excluding the organic layer constituting the organic EL device is not particularly limited. As a method for forming the anode and the cathode, for example, a vacuum evaporation method, a spin coating method, a casting method, a sputtering method, an LB method, or the like can be applied. Further, for the protective layer, a vacuum evaporation method, a 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), reactive sputtering method, plasma C
VD method, laser CVD method, thermal CVD method, gas source C
The VD method or the like can be adopted.

The method of forming each layer except for the organic material layer can be appropriately changed depending on the material used. However, when forming each layer constituting the organic EL element by using a vacuum evaporation method, only the vacuum evaporation method is used. Since an organic EL element can be formed, it is advantageous in simplifying equipment and reducing production time.

The shape and size of each layer (including the protective layer) constituting the organic EL element are not always the same. Further, when the element is viewed in a plan view, not all other layers are necessarily accommodated on the electrode formed immediately above the substrate.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. <Structure of Organic EL Element> FIG.
The L element 1 is shown. The organic EL element 1 includes a substrate 11, an anode (transparent electrode) 12 made of an ITO film formed on the substrate 11, and a hole injection layer 13 formed on the anode 12 as an organic material layer. And a light emitting layer 14,
A cathode (counter electrode) 15 is formed on these organic layers 13 and 14.

The substrate 11 is a rectangular flat glass substrate, and a band-shaped anode 12 is formed on one surface thereof along the longitudinal direction. On the hole injection layer 13 and the light emitting layer 14 laminated on the anode 12, three strip-shaped cathodes 15 extending in a direction perpendicular to the longitudinal direction of the substrate 11, that is, a direction perpendicular to the anode 12, are formed. Have been. In the organic EL device 1 of the present embodiment, the anode 12 and the cathode 15 overlap when viewed in a plan view.
A planar rectangular light emitting surface 16 is formed in a region where the hole injection layer 13 and the light emitting layer 14 are interposed.

In such an organic EL device 1, the hole injection layer 13, which is an organic material layer, is formed by depositing an organic vapor deposition material for the hole injection layer 13 on the anode 12 of the substrate 11. Have been. Similarly, the light emitting layer 14 which is an organic material layer is formed by evaporating an organic vapor deposition material for the light emitting layer 14 on the hole injection layer 13 of the substrate 11. These organic vapor-deposited materials are formed into pellets and have a gas content of 1 mol% or less.

<Preparation of Organic Vapor Deposition Material> Each of the organic vapor deposition materials constituting the hole injection layer 13 and the light emitting layer 14 is prepared in the following procedure. In the present embodiment, degassing and molding of the organic substance are performed by heating the powdery organic substance in a vacuum. That is, the organic powder is placed in a container made of molybdenum and set in a vacuum chamber of a vacuum evaporation apparatus. This container has a plurality of concave portions having a shape corresponding to the pellets, and a predetermined amount of organic powder is put into each of these concave portions.

Next, the vacuum chamber is evacuated by a vacuum pump, and when the vacuum chamber reaches a predetermined degree of vacuum, the vessel is heated to a predetermined temperature. The degree of vacuum in the vacuum chamber is
What is necessary is just to measure using an ionization vacuum gauge. When the container is heated, the organic material powder in the concave portion is melted, and gas as an impurity contained in the organic material is released, whereby the degree of vacuum in the vacuum chamber is reduced. If the container is continuously heated to a predetermined temperature in this state, the amount of gas in the organic powder decreases, and the amount of evaporation decreases, thereby increasing the degree of vacuum in the vacuum chamber. When almost no gas is contained in the organic powder, the degree of vacuum in the vacuum chamber returns to the predetermined degree of vacuum (the degree of vacuum before heating). By such a degassing process, gas in the organic substance powder is removed. In particular, by heating the organic material powder, the gas such as the organic solvent taken into the crystal of the organic material can be surely removed. The heating temperature of the container at this time is set to a temperature at which the organic matter is melted and does not evaporate, and the heating time of the container is such that the degree of vacuum reduced by the generation of gas is reduced to a predetermined degree of vacuum (the degree of vacuum before heating). Set it longer than the time required to recover.

After the degree of vacuum in the vacuum chamber returns to the state before the heating, the heating of the vessel is terminated, and the molten organic matter is cooled.
After solidifying into a shape following the concave portion of the container, it is taken out of the vacuum chamber. Thereby, a pellet which is an organic vapor deposition material is obtained. In this manner, when the organic powder is heated in a vacuum and degassed until the degree of vacuum in the vacuum chamber returns to the state before the heating, the gas content of the obtained pellets becomes 1 mol% or less. Further, since the surface area of the pellet in contact with the atmosphere is smaller than that in a powder state, absorption of moisture and the like after the degassing treatment can be minimized.

<Preparation of Organic EL Element> In this embodiment,
A hole injection layer 13 and a light emitting layer 1 are formed on a substrate 11 having an anode 12.
4 and the cathode 15 are sequentially formed by a vacuum deposition method.
That is, a transparent support substrate 10 on which an ITO film 12 is formed in advance on a substrate 11 is prepared, and the transparent support substrate 10 is washed and then fixed to a substrate holder in a vacuum chamber of a vacuum evaporation apparatus. This vacuum evaporation apparatus is an existing one, and a substrate holder and a plurality of molybdenum resistance heating boats are arranged opposite to each other in the vacuum chamber. In such a vacuum deposition apparatus, a plurality of layers of films can be continuously deposited without breaking the vacuum of the vacuum chamber, and a film made of a plurality of types of materials can be deposited by simultaneously evaporating different types of deposition materials. It has become.

Next, the pellets for the hole injection layer 13 obtained by the above-described processing and the light emitting layer 14 obtained by the same processing
After putting the pellets for the cathode and the metal for the cathode 15 into separate resistance heating boats, the pressure inside the vacuum chamber is reduced to a predetermined degree of vacuum. The metal for the cathode 15 may be in the form of a powder or may be in the form of a pellet. The type of metal used is
The type is not limited to one type, and a plurality of types may be used. When a plurality of types of metals are used, they are placed in different resistance heating boats because the deposition conditions such as the deposition temperature are different for each material.

Thereafter, the resistance heating boat containing the pellets for the hole injection layer 13 is heated to a predetermined temperature to evaporate it, and is deposited on the anode 12 of the transparent support substrate 10 so that the hole injection layer 13 Form a film. At this time, the pellet for the hole injection layer 13 has a gas content of 1 m by the above-described deaeration treatment.
ol%, and almost no absorption of moisture and the like after the deaeration treatment. Therefore, at the time of vapor deposition, almost no impurities such as gas are generated from the pellets for the hole injection layer 13.

When the formation of the hole injection layer 13 is completed, the light emitting layer 1 can be used without removing the transparent support substrate 10 from the vacuum chamber.
4 is formed. That is, the resistance heating boat containing the pellets for the light emitting layer 14 is heated to a predetermined temperature and evaporated, and deposited on the hole injection layer 13 to form the light emitting layer 14. At this time, the pellet for the light emitting layer 14 is the hole injection layer 1
As in the case of No. 3, the gas content is set to 1 mol% by the above-described degassing process, and almost no moisture or the like is absorbed after the degassing process. do not do.

After the formation of the light emitting layer 14 is completed, the cathode 15 is formed. That is, the resistance heating boat containing the metal for the cathode is heated to a predetermined temperature and evaporated, and is deposited on the light emitting layer 14 to form the cathode 15. Note that three cathodes 15 of this embodiment are formed on the light emitting layer 14 at predetermined intervals using a mask or the like.

When the deposition of the cathode 15 is completed, the transparent support substrate 10 on which the hole injection layer 13, the light emitting layer 14, and the cathode 15 have been formed is taken out of the vacuum chamber and cut into three pieces. (ITO film) 12 / hole injection layer 13 / light emitting layer 1
4 / Three organic EL elements 1 having the cathode 15 are obtained.

According to this embodiment, the following effects can be obtained. That is, since the gas content of each of the pellets (organic vapor deposition material) constituting the hole injection layer 13 and the light emitting layer 14 is 1 mol% or less, the amount of gas as impurities evaporated during vapor deposition is greatly reduced. Each layer 12 constituting the organic EL element 1 by gas can be reduced.
To 15 and the substrate 11 can be reliably reduced. In addition, since each of the pellets (organic vapor deposition material) constituting the hole injection layer 13 and the light emitting layer 14 has a smaller area in contact with the atmosphere than a powdery material, the adsorption of impurities such as moisture can be minimized. From the hole injection layer 13 and the light emitting layer 14
The evaporation of moisture and the like from the pellets during vapor deposition can be minimized, and the contamination of each of the layers 12 to 15 and the substrate 11 constituting the organic EL element 1 by impurities such as moisture can be reliably reduced. Thereby, each layer 12 constituting the organic EL element 1 is formed.
Since the substrate 15 and the substrate 11 are hardly contaminated by gas, moisture, and the like at the time of vapor deposition, a high-quality organic EL device 1 having a long life and a low driving voltage can be obtained.

Further, the hole injection layer 13 and the light emitting layer 14
Each of the pellets was prepared by heating the organic powder in a vacuum, so it was possible to remove gases such as organic solvents taken into the crystals of the organic substance, and to efficiently degas, so that the gas content in the pellet was ensured. Can be reduced to

It should be noted that the present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and also includes the following modifications.
That is, in the above-described embodiment, the pelletization of the organic material powder and the deaeration treatment are performed at the same time, but the deaeration treatment may be performed after the organic material powder is formed into a pellet by pressure molding or the like, or The powder may be degassed and then pelletized.

In the embodiment described above, the case where the layer constitution of the organic EL element is anode / hole injection layer / light emitting layer / cathode has been described. However, the present invention is not limited to this.
The light emitting layer / cathode may be used, or the anode / light emitting layer / electron injection layer / cathode may be used, and further, the anode / hole injection layer / light emitting layer / electron injection layer / cathode may be used. Also,
A protective film may be provided so as to cover these layers.

[0043]

Next, the effects of the present invention will be described based on specific examples. [Example 1] In Example 1, based on the above embodiment, respective pellets (organic vapor deposition material) constituting the hole injection layer and the light emitting layer were manufactured, and an organic EL element was manufactured using these pellets. did. In the first embodiment, the following specific conditions are employed.

<About Pellets (Organic Vapor Deposition Material)> Raw Materials (Organic Powder) • Hole Injection Layer: Powdered N, N′-diphenyl-N,
N'- bis - (3-methylphenyl) - [I-I 'biphenyl] -4,4'-diamine (hereinafter referred to as TPD) · emitting layer: powdery tris (8-quinolinol) of aluminum (hereinafter Alq ₃・ Amount of each organic powder supplied to the container: 1g

Vacuum evaporation device (manufactured by Nippon Vacuum Engineering Co., Ltd.) ・ Volume of vacuum tank: 650 l ・ Evacuation capacity: 10 ⁴ l / sec Vessel ・ Number of recesses: 10 Heating of organic powder: vacuum degree of vacuum tank is 1 × 10 ^-5 Pa
After that, heating of the container was started, and the container was heated to 200 ° C. The degree of vacuum is reduced by the generation of gas,
After returning to 1 × 10 ⁻⁵ Pa again, heating was continued for another 10 minutes.

Based on the above conditions and the like, the TPD powder, which is an organic powder for the hole injection layer, was subjected to molding and deaeration, and as a result, 100 mg of TPD pellets were obtained.
0 were obtained. At the time of heating the TPD powder, the degree of vacuum in the vacuum chamber is temporarily reduced to 1 × 10 ⁻³ Pa due to generation of gas, and after this state continues for 30 seconds, 1 × 10 ⁻⁵ Pa again.
Returned to. The decrease in the degree of vacuum due to heating at this time is about 1
× 10 ⁻³ Pa, and this value and the evacuation speed of the vacuum chamber 10
^{From 4} l / sec, the amount of gas released from the TPD powder is estimated by the equation of state of gas to be about 4 × 10 -6 mol.
/ Sec. Since the release of the gas lasted for 30 seconds, about 1 × 10 -4 mol of gas was released from the TPD powder in the deaeration treatment by heating in the first embodiment. As a result, the proportion of gas in 1 g of the used TPD powder, that is, the gas content of the TPD powder before heating is about 5%.
mol%. Further, it is considered that the gas in the TPD was almost completely released because the degree of vacuum in the vacuum tank returned to 1 × 10 −5 Pa during the heating of the TPD. Therefore, the gas content of the TPD pellet, which is an organic vapor deposition material, is 5 × 10 ⁻³ m.
ol% or less.

Similarly, Alq ₃ powder, which is an organic material powder for the light emitting layer, was subjected to molding and degassing, and as a result, 10 100 mg Alq ₃ pellets were obtained. In the same manner as in the case of the TPD, the gas amount was determined from the change in the degree of vacuum in the vacuum chamber during heating.
The gas content of the lq ₃ powder was about 8 mol%.
Further, since the degree of vacuum returned to 1 × 10 ⁻⁵ Pa during heating of Alq ₃ , it can be said that the gas content of the Alq ₃ pellets as the organic vapor deposition material is 5 × 10 ⁻³ mol% or less.

<Organic EL Element> Element Configuration ・ Substrate Dimensions: 25 mm long × 75 mm wide × 1.1 mm thick ・ Anode Film Thickness: 10 nm ・ Hole Injection Layer Organic Evaporation Material: TPD Pellet Thickness: 60 nm ・ Emission Layer Organic vapor deposition material: Alq ₃ pellet Thickness: 60 nm Cathode: Made of mixed metal of magnesium and silver. Deposition material: Magnesium and silver Film thickness: 150 nm Plane dimensions: 3 mm x 15 mm (one cathode)-Light emitting surface Plane dimensions: 3 mm x 5 mm

Vacuum evaporation apparatus: The same as that used in the preparation of the organic evaporation material Cleaning of the transparent support substrate: After ultrasonic cleaning with isopropyl alcohol for 30 minutes, cleaning with pure water for 30 minutes, and again with isopropyl alcohol for 30 minutes. Ultrasonic cleaning for minutes. Pressure in vacuum chamber during vapor deposition: 1 × 10 ⁻⁵ Pa

Deposition conditions of hole injection layer ・ Use amount of TPD pellet: 200 mg ・ Heating temperature of boat containing TPD pellet: 215 to 220 ° C. ・ Deposition rate of TPD pellet: 0.1 to 0.3 nm / sec Emission the amount of deposition conditions · Alq ₃ pellets layer: 200 mg · Alq ₃ of boat containing the pellet heating temperature: 275 ℃ · Alq ₃ pellets deposition rate: 0.1 to 0.2 nm / sec

Cathode deposition conditions: Magnesium and silver were placed in separate resistance heating boats and evaporated at the same time. ・ Amount of magnesium used: 1 g ・ Heating temperature of boat containing magnesium: about 500 ° C. ・ Magnesium deposition rate : About 1.7 to 2.8 nm / sec. ・ Amount of silver used: 500 mg ・ Heating temperature of resistance heating boat containing silver: about 800 ° C. ・ Silver deposition rate: 0.03 to 0.08 nm / sec

Under the above conditions, a hole injection layer, a light emitting layer, and a cathode were sequentially deposited on the basis of the above embodiment to obtain an organic EL device of Example 1. The initial luminance of this organic EL element reached 100 cd / m ² under the conditions of a voltage of 6.5 V and a current density of 3 mA / cm ² , and the power conversion efficiency at this time was 1.6 lm / W.

[Comparative Example 1] In Example 1, as the organic vapor deposition materials for the hole injection layer and the light emitting layer,
TPD powder and Al not deaerated by heating
except for using the q ₃ powder to obtain an organic EL device of Comparative Example 1 in the same manner as in Example 1. Thus, TPD
If the degassing treatment of Alq ₃ is omitted, the gas content of the organic vapor deposition material becomes larger than 1 mol%. For this reason, at the time of vapor deposition of the hole injection layer and the light emitting layer, more gas was released from TPD and Alq ₃ than in the case of Example 1, and the degree of vacuum in the vacuum chamber was reduced. The initial luminance of the organic EL element of Comparative Example 1 was a voltage of 7 V and a current density of 3.5
reaches 100 cd / m ² under the condition of mA / cm ² ,
The power conversion efficiency at this time was 1.3 lm / W.

[Evaluation of Organic EL Device (1)] With respect to each of the organic EL devices obtained in Example 1 and Comparative Example 1, the half life and the change over time of the driving voltage were evaluated. These results are shown in FIG. 2 and FIG. The half-life was evaluated by setting the initial luminance to 300 cd / m ² ,
It was performed by determining the time required to reach cd / m ² . The evaluation of the driving voltage was performed by obtaining a voltage necessary for continuously obtaining an initial current.

As shown in FIG. 2, in Example 1, the hole injecting layer and the light emitting layer were deposited by using pellets having a gas content of 1 mol% or less by degassing TPD powder and Alq ₃ powder, respectively. In addition, generation of gas during deposition is almost eliminated. Therefore, it can be understood that contamination of the element by gas can be reduced, and an organic EL element of excellent quality having a longer half-life and a smaller increase in driving voltage over time than in Comparative Example 1 can be obtained. On the other hand, in Comparative Example 1, TP
Since the degassing process and pelletization of the D powder and Alq ₃ powder were not performed, the device was contaminated by the gas released at the time of vapor deposition, the half life was shorter than that of the organic EL device of Example 1, and the time elapsed. It can be seen that the voltage increase accompanying the

[Example 2] In Example 1, as the organic vapor deposition material for the hole injection layer, the gas content was 0.1 mol.
An organic EL device of Example 2 was obtained in the same manner as in Example 1 except that 1% of TPD pellets were used.

Example 3 In Example 1, the gas content was 1 mol% as the organic vapor deposition material for the hole injection layer.
An organic EL device of Example 3 was obtained in the same manner as in Example 1 except that TPD pellets of Example 1 were used.

Example 4 In Example 1, as the organic vapor deposition material for the hole injection layer, the gas content was 5 × 10 −2.
An organic EL device of Example 4 was obtained in the same manner as in Example 1 except that a mol% TPD pellet was used.

[Comparative Example 2] In Example 1, the gas content was 5 mol% as the organic vapor deposition material for the hole injection layer.
An organic EL device of Comparative Example 2 was obtained in the same manner as in Example 1 except that TPD pellets of Example 1 were used.

[Evaluation of Organic EL Device (2)]
The half life of each of the organic EL devices obtained in Comparative Examples 3 and 4 and Comparative Example 2 was determined in the same manner as in the evaluation (1) of the organic EL device. These results are shown in FIG. 4 as a relationship between the gas content of the TPD pellet and the half life. FIG. 4 shows that the smaller the gas content of the TPD pellet, the higher the quality of the organic EL device with a long half-life can be obtained.

[0061]

As described above, according to the present invention,
In forming an organic layer using an organic vapor deposition material,
Since the gas content of the organic vapor deposition material is set to 1 mol% or less, the amount of gas as an impurity that evaporates at the time of vapor deposition of the organic layer can be significantly reduced, so that contamination by the gas can be surely reduced. Further, since the organic vapor-deposited material is formed in the shape of a pellet, the area in contact with the atmosphere can be made smaller than that of a powdery material, so that the adsorption of impurities such as moisture can be minimized. Therefore, since evaporation of moisture and the like from the organic material is minimized, contamination by impurities such as moisture can be surely reduced.

Further, when an organic vapor deposition material was vapor-deposited on a substrate to form an organic material layer of an organic EL device, a pellet-like material having a gas content of 1 mol% or less was used as the organic vapor deposition material. Since contamination of the organic layer and the substrate can be reliably reduced, a high-quality organic EL device having a long life and a low driving voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 shows each organic EL of Example 1 and Comparative Example 1 of the present invention.
4 is a graph showing the half life of the device.

FIG. 3 is a graph showing a voltage rise of each organic EL element of Example 1 and Comparative Example 1.

FIG. 4 is a graph showing the gas content of TPD and the half life of the organic EL element in Examples 2 and 3 and Comparative Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic electroluminescent element 10 Transparent support substrate 11 Substrate 12 Anode 13 Hole injection layer (organic material layer) 14 Light emitting layer (organic material layer) 15 Cathode 16 Light emitting surface

Claims (3)

[Claims] 1. A vapor deposition method for forming an organic layer using an organic vapor deposition material, wherein the organic vapor deposition material is formed in a pellet shape and has a gas content of 1 mol% or less. Characteristic evaporation method. 2. The vapor deposition method according to claim 1, wherein
The vapor deposition method, wherein the organic vapor deposition material is degassed by heating in a vacuum. 3. An organic electroluminescence device comprising an electrode and an organic material layer formed on a substrate, wherein the organic material layer is formed by evaporating an organic vapor deposition material on the substrate. An organic electroluminescence device, wherein the vapor deposition material is formed in a pellet shape and has a gas content of 1 mol% or less.