JPH09232079A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL(electroluminescence) element which has high electric power converting efficiency and is excellent in uniform light emitting performance and has a long element sevice life. SOLUTION: In this organic EL element, a positive electrode, an organic substance layer of a single layer structure or a multilayer structure having a light emitting layer containing an organic light emitting material and a negative electrode are laminated in order on a base board. The negative electrode is formed by successively arranging two areas of an alloy area which contains alkaline metal or alkaline earth metal having a work function not more than 2.9eV by 0.5 to 5at.% in the total amount of the alkaline metal and the alkaline earth metal and has a thickness of 5 to 50nm and an upper metallic area composed of metal having a work function not less than 3.0eV in this order when viewed from the organic substance layer side. The oxygen existent concentration in the negative electrode is set not more than 1at%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic electroluminescence (hereinafter, “electroluminescence” is abbreviated as “EL”) device.

[0002]

2. Description of the Related Art An organic EL device has a structure in which an anode, an organic material layer having a single layer structure or a multilayer structure having a light emitting layer containing an organic light emitting material, and a cathode are sequentially laminated. There is. When the organic material layer has a single layer structure, the organic material layer is composed of a light emitting layer, and when the organic material layer has a multilayer structure, the organic material layer is a hole injection layer-light emission in order from the anode side. The layer structure includes a layer, a light emitting layer-electron injection layer or a hole injection layer-light emitting layer-electron injection layer.

In the organic EL device having the above structure, holes injected directly into the light emitting layer from the anode or through the hole injection layer and holes injected directly into the light emitting layer from the cathode or through the electron injection layer. The emitted electrons are recombined to generate light. As means for improving the light emitting characteristics of an organic EL element based on such a light emitting mechanism, improvement of organic light emitting materials and injection materials (hole injection materials, electron injection materials), selection and improvement of cathode materials, etc. are known. Has been. Among these, the selection or improvement of the cathode material is intended to improve the injection efficiency of electrons injected from the cathode directly or through the electron injection layer into the light emitting layer, thereby improving the light emitting characteristics. From the viewpoint of improving the efficiency of electron injection into the light emitting layer, it is desirable to lower the injection barrier when injecting electrons from the cathode into the electron conduction level of the organic material layer (light emitting layer or electron injection layer). The use of a metal having a low work function as a material has been studied.

The most commonly used cathode for organic EL devices at present is to use silver (A) as the electron injecting metal using magnesium (Mg), which is one of the alkaline earth metals.
g) is a Mg-based electrode using as a stabilizing metal,
The formation of the cathode using another alkaline earth metal or an alkali metal having a work function smaller than that of Mg and an excellent electron injecting property has also been studied.

For example, in JP-A-60-165771, a light metal such as Al, Ca, Mg and Be is used as a base metal,
Alkali metal (Li, Na, K, Rb, C
There is disclosed an organic EL device in which a cathode having a single-layer structure is formed by an alloy containing 1 to 99% by weight of at least one of s).

Further, Japanese Patent Laid-Open No. 4-212287 discloses a metal (Mg, Al, In,
Sn, Zn, Zr, Ag, etc.) and alkali metal elements (L
i, Na, K, etc.) in an amount of 6 mol% or more, forming an organic EL device having a cathode having a single-layer structure, and Mg, Sn, Al, I on the layer made of the alloy.
There is disclosed an organic EL element in which a cathode having a two-layer structure is formed by providing a noncorrosive metal layer made of n, Ni, Cu, Ag, Au, Pt, Zn or the like.

Japanese Patent Laid-Open No. 5-121172 discloses (1) An organic EL device in which a cathode having a single layer structure is formed of an alloy containing 0.01 to 0.1 parts by weight of lithium with respect to 100 parts by weight of aluminum. (2) An organic EL in which a cathode having a two-layer structure is formed by providing a protective electrode made of aluminum or magnesium on the alloy cathode of (1) above.
Element, (3) organic EL element in which a cathode having a single layer structure is formed by an alloy containing 10 to 25 parts by weight of strontium with respect to 100 parts by weight of magnesium, (4) aluminum or magnesium on the alloy cathode of (3) above. Organic E having a double-layered cathode formed by providing a protective electrode
L element, (5) Aluminum or magnesium 1000
An organic EL device in which a cathode having a single-layer structure is formed of an alloy containing 50 parts by weight or less of lithium with respect to parts by weight, (6)
(5) An organic EL device in which a two-layer structure cathode is formed by providing a protective electrode made of aluminum or magnesium on the alloy cathode, (7) 400 parts of strontium for 1000 parts by weight of aluminum or magnesium.
An organic EL device in which a cathode having a single-layer structure is formed by an alloy containing by weight or less, and (8) a cathode having a two-layer structure is formed by providing a protective electrode made of aluminum or magnesium on the alloy cathode in (7) above. Organic EL device,
Is disclosed.

However, it is difficult to obtain an organic EL device having high power conversion efficiency, excellent uniform light emitting property, and long device life by simply using an alkali metal or an alkaline earth metal as the cathode material. .

An object of the present invention is to provide an organic EL device which has high power conversion efficiency, excellent uniform light emitting property, and can be easily obtained with a long device life.

[0010]

The organic EL device of the present invention which achieves the above object comprises an anode, an organic material layer having a single-layer structure or a multi-layer structure having a light emitting layer containing an organic light emitting material, and a cathode. Is an organic EL element sequentially laminated on a substrate, and the cathode is an alkali metal or a work function 2.
An upper metal comprising an alloy region having a thickness of 5 to 50 nm and containing a work function of 3.0 eV or more, containing an alkaline earth metal of 9 eV or less in a total amount of the alkali metal and the alkaline earth metal of 0.5 to 5 at%. Two regions, a region and a region, are sequentially formed when viewed from the organic layer side, and the existing concentration of oxygen in the cathode is 1 at% or less.

[0011]

Embodiments of the present invention will be described below in detail. As described above, in the organic EL element of the present invention, the cathode constituting the organic EL element is composed of two regions, a specific alloy region and an upper metal region, and the existing concentration of oxygen in the cathode is 1 at%. The cathode is first described because it has the following characteristics.

The cathode constituting the organic EL device of the present invention comprises an alloy region having a thickness of 5 to 50 nm and an upper metal region which are sequentially formed in this order when viewed from the organic material layer side described later. Here, when the thickness of the alloy region is less than 5 nm,
Since the form of the film is incomplete, there is a possibility that the film has not been formed in some places, and there is also a problem in terms of reproducibility of the film. On the other hand, the thickness of the alloy region is 5
If it exceeds 0 nm, the alkali metal or the alkaline earth metal having a work function of 2.9 eV or less contained in the alloy region will be distributed to the vicinity of the surface of the cathode, depending on the amount of the alkali metal or the alkaline earth metal. However, deterioration such as oxidation is likely to progress in these alkali metals or alkaline earth metals. Therefore, the thickness of the alloy region is set to 5 to 50 nm. The thickness of the alloy region is particularly preferably 10 to 30 nm from the viewpoint of maintaining the performance as a film, reproducibility of film formation, oxidation resistance and the like (performance of electron injection).

The alloy region contains an alkali metal or an alkaline earth metal having a work function of 2.9 eV or less in a total amount of 0.5 to 5 at% in total of the alkali metal and the alkaline earth metal.
It consists of the alloy contained. Here, the value of the “work function” used for each element in the present invention is “J. Appl. Phys.
48, p. 4729 (1977).

Specific examples of the alkali metal include lithium (Li; work function 2.9 eV), sodium (Na; work function 2.75 eV), potassium (K; work function 2.3).
eV), rubidium (Rb; work function 2.16 eV) and cesium (Cs; work function 2.14 eV). Specific examples of the alkaline earth metal having a work function of 2.9 eV or less include calcium (Ca; work function 2.
87 eV), strontium (Sr; work function 2.59)
eV) and barium (Ba; work function 2.7 eV).

The alloy forming the alloy region may contain only one or more of the above-mentioned alkali metals among the alkali metals and the alkaline earth metals having a work function of 2.9 eV or less. Only one or more kinds of alkaline earth metals may be contained, or one or more kinds of the alkali metals and one or more kinds of the alkaline earth metals may be contained respectively.

However, in any case, the alkali metal contained in the above alloy (alloy region) and the work function 2.
The total amount with an alkaline earth metal of 9 eV or less is 0.5 to 5
Within the range of at%. When the total amount of the alkali metal and the alkaline earth metal is less than 0.5 at%, the content of the low work function metal (the alkali metal and the alkaline earth metal) responsible for the electron injection property is too small. As a result, the electron injection property becomes insufficient, and the reproducibility of the alloy composition and thus the reproducibility of the device performance deteriorates. On the other hand, when the total amount of the above-mentioned alkali metal and the above-mentioned alkaline earth metal exceeds 5 at%, the amount of these active metals such as alkali metal and alkaline earth metal is too large and the oxidation resistance of the element is lowered, and The uniformity of light emission decreases, such as increasing the number of non-light emitting points. The total amount of the above-mentioned alkali metal and alkaline earth metal is 1 to 3.
At% is particularly preferable.

The total content of the alkali metal and the alkaline earth metal having a work function of 2.9 eV or less in the above alloy (alloy region) is substantially uniform from the organic layer side to the upper metal side described later. Although it may exist, it is preferable that the concentration gradually changes from the high concentration to the low concentration from the organic material layer side to the upper metal side. At this time, the content at the interface with the organic layer and its vicinity may be as high as about 10 at%.

On the other hand, as a metal component (hereinafter referred to as "second metal") other than the alkali metal and the alkaline earth metal having a work function of 2.9 eV or less in the above alloy (alloy region), the alkali metal and the work function 2 are used. Depending on the type of alkaline earth metal of 1.9 eV or less, aluminum (A
l), magnesium (Mg), gold (Au), silver (A
g), copper (Cu), zinc (Zn), lead (Pb), tin (S
Various metals such as n) can be used alone or in combination of two or more, and an alloy having a good film property is preferable.
Examples of preferable combinations of the alkali metal and the second metal include the following (1) to (2), and the work function of 2.
Examples of preferable combinations of the alkaline earth metal of 9 eV or less and the second metal include the following (i) to (iii).

Preferred combination of alkali metal and second metal (1) When the alkali metal is Li The second metal is Al, Mg, Ag, Au, Cu, Z.
It is preferable to use n, Pb or Sn, and it is particularly preferable to use Al, Zn, Pb or Sn. (2) When the alkali metal is Na, K, Cs, or Rb As the second metal, Al, Mg, or Ag is preferably used, and among them, Al or Mg is preferably used.

Preferred combination of alkaline earth metal and second metal (i) When the alkaline earth metal is Ca The second metal is Al, Mg, Ag, Cu, Zn, Pb.
Alternatively, Sn is preferably used, and Al or Mg is particularly preferably used. ◎ (ii) When the alkaline earth metal is Sr As the second metal, Al, Mg, Au, Ag, Cu, Z
It is preferable to use n, Pb, or Sn, and it is particularly preferable to use Al or Mg. (iii) When the alkaline earth metal is Ba As the second metal, Al, Mg, Ag, Cu, Zn, Pb
Alternatively, it is preferable to use Sn. Among them, Al, M
It is preferable to use g, Sn or Pb. The method of forming the alloy region will be described later.

The cathode constituting the organic EL device of the present invention is formed by sequentially forming the above-mentioned alloy region and upper metal region in this order when viewed from the organic material layer side described later. Then, the upper metal region is made of a metal having a work function of 3.0 eV or more.

Here, as a specific example of a metal having a work function of 3.0 eV or more, aluminum (Al; work function 4.2)
8 eV), magnesium (Mg; work function 3.66 e)
V), gold (Au; work function 5.1 eV), silver (Ag; work function 4.26 eV), copper (Cu; work function 4.65 e)
V), zinc (Zn; work function 4.33 eV), lead (P
b; work function 4.25 eV), tin (Sn; work function 4.b).
42 eV) and the like.

The upper metal region may be formed of only one metal having a work function of 3.0 eV or more, or a mixture of two or more metals having a work function of 3.0 eV or more (solid solution, Alloys are included). In any case, good film property of the entire cathode is required, and therefore an upper metal region having good film property is formed in consideration of the composition of the above-mentioned alloy region which is the base of the upper metal region. The composition is appropriately selected as described above. Examples of preferable combinations of the alloy region and the upper metal region include the following (a) to (g).

(A) When the composition of the alloy region is Al-Li The upper metal region is composed of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, among which A
It is preferably composed of 1, Ag, Pb or Sn. (b) When the composition of the alloy region is Pb-Li The upper metal region is composed of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, among which A
It is preferably composed of 1, Ag, Pb or Sn. (c) When the composition of the alloy region is Sn-Li The upper metal region is composed of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, among which A
It is preferably composed of 1, Ag, Pb or Sn. (d) When the composition of the alloy region is Mg-Na The upper metal region is made of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, among which A
It is preferably composed of 1, Mg or Ag.

(E) When the composition of the alloy region is Al-Ca The upper metal region is made of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, and above all, Al
Alternatively, it is preferably made of Ag. (f) When the composition of the alloy region is Al-Sr The upper metal region is composed of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, and above all, Al
Alternatively, it is preferably made of Ag. (g) When the composition of the alloy region is Mg-Sr The upper metal region is composed of Al, Mg, Ag, Au, Cu, Zn,
It is preferably composed of Pb or Sn, among which A
It is preferably composed of 1, Mg or Ag.

The thickness of the above-mentioned upper metal region is not particularly limited, but if the thickness is too thin, it lacks the ability to protect the above-mentioned alloy region located below it and is contained in the alloy region. Alkali metal and work function 2.9
The presence of an alkaline earth metal of eV or less facilitates the deterioration. On the other hand, if the thickness is too thick, the element is likely to be damaged by heat during film formation. For these reasons, the thickness of the upper metal region is preferably approximately 50 to 300 nm, and approximately 100 to 100 nm, depending on its composition.
It is particularly preferable that the thickness is 200 nm. The method of forming the upper metal region will be described later.

In the present invention, the existing concentration of oxygen in the cathode composed of the two regions of the above-mentioned alloy region and the above-mentioned upper metal region is 1 at% or less as described above.
Here, "the oxygen existing concentration in the cathode is 1 at% or less" in the present invention means that the oxygen existing concentration measured at any place in the cathode is 1 at% or less. Also,
As used herein, "the existing concentration of oxygen in the alloy region is 1
"At% or less" means that the oxygen concentration measured at any place in the alloy region is 1 at% or less, and "the oxygen concentration in the upper metal region is 1 at% or less" means
It means that the existing concentration of oxygen measured at any place in the upper metal region is 1 at% or less.

When the existing concentration of oxygen in the cathode, particularly in the alloy region, exceeds 1 at%, a non-light emitting point is likely to occur in the organic EL element. When the non-light emitting point occurs, the non-light emitting point is continuously driven. Organic E will increase and increase with
The uniform light emitting property, the brightness and the device life of the L element are reduced.

In the organic EL device of the present invention, since the existing concentration of oxygen in the cathode composed of the two regions, the alloy region and the upper metal region, is as low as 1 at% or less, the alkali metal and the work function are 2.9 eV or less. It is possible to easily obtain a device in which the alkaline earth metal is contained in the alloy region in a state where it is not substantially oxidized. Unless an alkali metal or an alkaline earth metal having a work function of 2.9 eV or less is oxidized, the electron injection property of these metals is high,
In addition, since the total content of these metals is a specific amount of 0.5 to 5 at%, such an organic EL element has high power conversion efficiency and has extremely few non-light emitting points. Therefore, the organic EL element of the present invention is an organic EL element that has a high power conversion efficiency and can easily obtain one having a significantly small number of non-light emitting points. The fact that the number of non-light emitting points is extremely small means that the uniform light emitting property is excellent. Further, the work function 3.
Since the upper metal region made of a metal of 0 eV or more is formed, the upper metal region protects the alkali metal in the alloy region or the alkaline earth metal having a work function of 2.9 eV or less. As a result, the organic EL element of the present invention including the above-described cathode is an organic EL element that can easily obtain a long element life.

The organic EL element of the present invention having the above-mentioned characteristics is suitable as a surface light source such as a display backlight of a pager or a wristwatch, or a constituent member or pixel of a display panel for an organic EL display device.

The "composition of the alloy region" referred to in the present invention.
Means analyzed as follows. That is, an anode, an organic material layer and a cathode are sequentially formed on a substrate in this order to obtain an organic EL element, and the surface of the organic EL element from the cathode surface to the organic material layer side is sputtered at a constant sputtering rate by an Ar ion gun. Sputtering was performed, and the composition of the surface was measured by Auger electron spectroscopy (AE).
S) and secondary ion mass spectrometry (SIMS) analysis (so-called depth profile measurement is performed by AES and SIMS), and the composition determined based on the result is meant.

At this time, in AES, the composition of the contained metal and the impurities are identified at the at% level. In SIMS, several kinds of alloy ingots having the same constituent elements as the alloy region of the desired composition but different composition ratios are prepared in advance, and the composition of these alloy ingots whose compositions are known is analyzed by SIMS, Signal count ratio between alkali metal and second metal and work function 2.9e
The signal count ratios of the alkaline earth metal of V or less and the second metal are obtained, and calibration curves of these signal count ratios and the actual composition ratios are prepared. Then, from the SIMS depth profile of the organic EL element,
Depth profiles for the alkali metal and the alkaline earth metal are obtained according to the above calibration curves (calibration curve method). To discuss quantitativeness in SIMS,
This condition should be confirmed because it is necessary that the alloy ingot used to create the calibration curve contains no elements other than the above-mentioned alkali metals, alkaline earth metals and second metals (matrix effect). In order to do so, the results of quantification by SIMS will be discussed after confirming that no components other than alloys are contained by using the measurement by AES together. S
The appropriateness of the composition ratio determined by IMS as described above was confirmed by the average concentration in the entire cathode obtained by ICP analysis (inductively coupled plasma emission spectroscopy) with the entire cathode being eluted.

The above-mentioned cathode constituting the organic EL device of the present invention is formed by forming the alloy region on the organic layer described later and then forming the upper metal region on the alloy region, or after forming the upper metal region. It can be produced by forming an alloy region on the upper metal region (in this case, an organic material layer described later is formed on the alloy region). The alloy region and the upper metal region are respectively formed by vacuum vapor deposition (resistance heating vapor deposition, electron beam vapor deposition, high frequency induction heating,
Hot wall deposition method), molecular beam epitaxy method, ion plating method, cluster ion beam deposition method, sputtering method and the like. When the alloy region or the upper metal region composed of two or more components is formed by, for example, the vacuum deposition method,
The vacuum deposition may be one-source deposition or multi-source simultaneous deposition of two or more sources. The same applies to the case where the alloy region or the upper metal region composed of two or more components is formed by a method other than the vacuum deposition method.

In any method of forming the cathode, from the formation of the alloy region on the organic layer to the formation of the upper metal region on the alloy region, or from the formation of the alloy region on the alloy region. In order to prevent the alloy region from being oxidized or dust being mixed into the element during the formation of the organic material layer in, rather than forming the alloy region and the upper metal region by different methods, It is preferable to continuously form the alloy region and the upper metal region by the same method, practically the same apparatus. Here, the term "continuously forming the alloy region and the upper metal region" as used herein means from the formation of the alloy region to the formation of the upper metal region on the alloy region, or the alloy. This means that the alloy region and the upper metal region or the organic layer are sequentially formed so that the alloy region does not come into contact with air from the formation of the region to the formation of the organic layer on the alloy region.

In forming the alloy region by the above-exemplified method, the concentration of oxygen in the alloy region is set to 1 at% or less, and therefore the following (I) or (I
It is preferable to carry out film formation as in I). (I) When performing film formation in a vacuum environment in which the total pressure of the atmosphere during film formation (hereinafter referred to as “vacuum degree during vapor deposition”) is 5.0 × 10 ⁻⁷ to 5.0 × 10 ⁻⁶ Torr (I) The partial pressure of water gas in the atmosphere is approximately 3.0 as measured by a quadrupole mass spectrometer.
X10 ^{-7 to} 3.0 x 10 ^-6 Torr, and the partial pressure of oxygen gas in the atmosphere is 5% or less of the partial pressure of the water gas measured by a quadrupole mass spectrometer. Do membranes, or
(ii) The partial pressure of hydrogen gas in the atmosphere is approximately 4.0 × 10 ^{−7 to} 4.0 × 10 ⁻⁶ Torr measured by a quadrupole mass spectrometer, and the atmosphere is hydrogen gas. The film formation is performed in a reducing atmosphere in which the partial pressure is higher than the partial pressure of water gas measured by a quadrupole mass spectrometer. (II) The degree of vacuum during vapor deposition is 5 × 10 ^{−9 to} 2.0 × 10 ⁻⁷ Torr.
The film is formed in a high vacuum or ultra high vacuum environment.

Even when the film formation in the alloy region is performed as in the above (I) or (II), the incidence frequency of the alkali metal or the alkaline earth metal having a work function of 2.9 eV or less on the film formation substrate is oxygen. If the film forming conditions are higher than the incidence frequency of water or water, it becomes difficult to form an alloy region in which the existing concentration of oxygen is 1 at% or less.

For example, the degree of vacuum during vapor deposition is 5.0 × 10 ⁻⁷
When the alloy region is formed by the unitary vacuum vapor deposition method with 5.0 × 10 ⁻⁶ Torr, the vapor deposition rate measured by a crystal oscillator type film thickness meter (the same applies hereinafter) is 0.005 to 10.
By setting it to be nm / s, an alloy region having a desired metal composition ratio can be stably formed on the organic layer described later, but the degree of vacuum during vapor deposition is set to a pressure higher than 5 × 10 ⁻⁶ Torr and 0 When the film formation is performed at a deposition rate of 0.5 to 2 nm / s, it becomes difficult to form an alloy region having a desired metal composition ratio in which the oxygen concentration is 1 at% or less on the organic material layer described later.
The degree of vacuum during vapor deposition is 5.0 × 10 ⁻⁷ to 5.0 × 10 ^−6.
When the alloy region is formed by the multi-source vacuum deposition method using Torr, the deposition rate of the alkali metal or the alkaline earth metal having a work function of 2.9 eV or less to be contained in the alloy region is 0.005 to 0. By setting it to about 1 nm / s, it becomes possible to stably form an alloy region having a desired metal composition ratio on the organic material layer described later, but the degree of vacuum during vapor deposition is 1.0 × 10 ⁻⁵ Torr or more. High pressure to 0.
When the film is formed at a vapor deposition rate of 005 to 0.01 nm / s,
It becomes difficult to form an alloy region having a desired metal composition ratio in which the existing concentration of oxygen is 1 at% or less on the organic material layer described later.

Therefore, in forming the alloy region, the alkali metal to the substrate or the work function of 2.9 eV is used.
The film forming conditions are appropriately selected in consideration of the incidence frequency of the following alkaline earth metals and the incidence frequencies of oxygen and water on the substrate.
In order to maintain the above vapor deposition rate when forming the alloy region by the one-source vacuum vapor deposition method or the multi-source vacuum vapor deposition method, it is preferable to monitor and control the vapor source temperature with an accuracy of 0.5 ° C. or less.

On the other hand, when the upper metal region is formed by the above-described method, the upper metal region does not contain an alkali metal or an alkaline earth metal having a work function of 2.9 eV or less. The existing concentration of oxygen can be set to 1 at% or less more easily than when it is formed.

When the cathode is formed by the vacuum deposition method,
Considering the uniformity of the thickness of the obtained film (alloy region and upper metal region) and the loss due to the deposition on other than the substrate, the distance between the substrate and the evaporation source is preferably 15 to 50 cm.

The above-mentioned "deposition rate" for the alkali metal and alkaline earth metal referred to in the present specification is actually the film-forming rate because the adhesion probability of these metals to the organic layer described later is not 1. It does not mean the deposited rate. From the study by the present inventors, it was found that the above-mentioned sticking probability is extremely small. Therefore, the above-mentioned "vapor deposition rate" in the present specification means the concentration (vapor pressure) of evaporated metal near the film thickness meter.

In forming the alloy region,
Since water gas in the atmosphere during film formation can serve as a supply source of oxygen, it is preferable to keep the partial pressure of the water gas as low as possible. For that purpose, it is possible to use a film forming apparatus having a cryopump having a pumping speed effective for water, or a film forming apparatus having an exhaust system having a trap mechanism cooled by liquid nitrogen or the like. preferable.

The organic EL device of the present invention may be any one provided with the above-mentioned cathode which can be formed as described above, and its layer structure is particularly limited as long as it functions as an organic EL device. It is not something that will be done. Organic E
There are various layer configurations of the L element. As a specific example of the layer structure of an organic EL element of a type formed on a transparent substrate and using the transparent substrate as a light extraction surface, for example, the order of stacking on the transparent substrate is (1) to (4) below. ). When the substrate is not the light extraction surface, the order of stacking on the substrate may be the reverse of the following (1) to (4).

(1) Anode / light emitting layer / cathode (2) Anode / hole injection layer / light emitting layer / cathode (3) Anode / light emitting layer / electron injection layer / cathode (4) Anode / hole injection layer / light emitting Layer / electron injection layer / cathode

In the organic EL device of the above type (1) and the organic EL device of the type in which the stacking order is reverse to that of the above (1), the light emitting layer corresponds to the organic material layer of the single layer structure in the present invention. In the organic EL element of type 2) and the organic EL element of the type in which the stacking order is the reverse of the above (2), the hole injection layer and the light emitting layer correspond to the organic material layer of the multilayer structure in the present invention,
In the organic EL device of the type (3) and the organic EL device of the type having a reverse stacking order to the above (3), the light emitting layer and the electron injection layer correspond to the organic material layer of the multilayer structure referred to in the present invention. In the organic EL element of type 4) and the organic EL element of the type in which the order of lamination is the reverse of the above (4), the hole injection layer, the light emitting layer and the electron injection layer correspond to the organic material layer of the multilayer structure in the present invention. .

The light emitting layer is usually formed of one or more kinds of organic light emitting materials, and a mixture of the organic light emitting material and the electron injecting material and / or the hole injecting material, or the mixture or the organic light emitting material is dispersed. It may be formed of a polymer material or the like. In some cases, a sealing layer is provided around the organic EL element having the above-described layer structure so as to cover the organic EL element and prevent moisture and oxygen from entering the organic EL element.

In the organic EL device of the present invention, the material for the layers other than the cathode is not particularly limited, and various materials can be used. Each layer other than the cathode, including the substrate, will be described in detail below.

(A) Substrate When the substrate is used as the light extraction surface, the transparent substrate is used as described above. The transparent substrate may be made of a material that gives high transmittance (approximately 80% or more) to light emission (EL light) from the light emitting layer, and specific examples thereof include transparent materials such as alkali glass and alkali-free gas. Plates made of glass, transparent resin such as polyethylene terephthalate, polycarbonate, polyethersulfone, polyetheretherketone, polyvinyl fluoride, polyacrylate, polypropylene, polyethylene, amorphous polyolefin, fluorine resin, or quartz, A sheet-like material or a film-like material may be used. What kind of transparent substrate is used can be appropriately selected according to the intended use of the organic EL element and the like. On the other hand, when the substrate is not used as the light extraction surface, a substrate other than the transparent substrate described above can be used as the substrate. In this case, the substrate may be an inorganic substance or an organic substance.

(B) Anode As a material for the anode, a material having a large work function (for example, 4 eV) is used.
Above) Metals, alloys, electrically conductive compounds or mixtures thereof are preferably used. Specific examples include conductive transparent materials such as metals such as Au and CuI, ITO, tin oxide, zinc oxide. The anode can be manufactured by forming a thin film of the above material by a method such as a vapor deposition method or a sputtering method. When the emitted light (EL light) from the light emitting layer is taken out from the anode side, the transmittance of the EL light at the anode is 1
It is preferably 0% or more. The sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness of the anode depends on the material, but is usually 10 nm to 1 μm, preferably 10 to 20.
It is selected in the range of 0 nm.

(C) Light-Emitting Layer The organic light-emitting material used as the material for the light-emitting layer is (a) having a function of injecting charges, that is, capable of injecting holes from the anode or the hole injecting layer when an electric field is applied, and the cathode. Alternatively, a function capable of injecting electrons from the electron injection layer, (b) a transport function, that is, a function of moving injected holes and electrons by the force of an electric field, and (c) a light emitting function, that is,
It is sufficient as long as it has the three functions of providing a field for recombination of electrons and holes and connecting them to light emission, but sufficient performance for each of the above functions (a) to (c). It is not always necessary to have both of them, and, for example, among the materials having a hole injection / transport property which is far superior to the electron injection / transport property, there is a material suitable as an organic light emitting material.
As the organic light emitting material, for example, a fluorescent brightening agent such as benzothiazole-based, benzimidazole-based, or benzoxazole-based, a styrylbenzene-based compound, or the like can be used.

Specific examples of the above-mentioned optical brightener include benzoxazole-based 2,5-bis (5,7-di-t-).
Pentyl-2-benzoxazolyl) -1,3,4-thiadiazole, 4,4'-bis (5,7-t-pentyl-2-benzoxazolyl) stilbene, 4,4'-bis [5 , 7-Di- (2-methyl-2-butyl) -2-benzoxazolyl] stilbene, 2,5-bis (5,7
-Di-t-pentyl-2-benzoxazolyl) thiophene, 2,5-bis [5-α, α-dimethylbenzyl-
2-benzoxazolyl] thiophene, 2,5-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl] -3,4-diphenylthiophene,
2,5-bis (5-methyl-2-benzoxazolyl)
Thiophene, 4,4'-bis (2-benzoxazolyl) biphenyl, 5-methyl-2- [2- [4- (5-
Methyl-2-benzoxazolyl) phenyl] vinyl]
Examples thereof include benzoxazole and 2- [2- (4-chlorophenyl) vinyl] naphtho [1,2-d] oxazole, and benzothiazole-based compounds include 2,2 ′-(p-phenylenedivinylene) -bisbenzothiazole. In the benzimidazole system, 2- [2- [4- (2-
Examples thereof include benzimidazolyl) phenyl] vinyl] benzimidazole and 2- [2- (4-carboxyphenyl) vinyl] benzimidazole. Still other useful compounds are the chemistry of synthetic soybean (1971), pages 628-637 and 6
Listed on page 40.

Specific examples of the above-mentioned styrylbenzene compound include 1,4-bis (2-methylstyryl).
Benzene, 1,4-bis (3-methylstyryl) benzene, 1,4-bis (4-methylstyryl) benzene, distyrylbenzene, 1,4-bis (2-ethylstyryl) benzene, 1,4-bis (3-Ethylstyryl) benzene, 1,4-bis (2-methylstyryl) -2-methylbenzene, 1,4-bis (2-methylstyryl)-
2-ethylbenzene etc. are mentioned.

Further, in addition to the above-described optical brightener and styrylbenzene compound, for example, 12-phthaloperinone, 1,4-diphenyl-1,3-butadiene, 1,
1,4,4-tetraphenyl-1,3-butadiene, naphthalimide derivative, perylene derivative, oxadiazole derivative, aldazine derivative, pyrazin derivative, cyclopentadiene derivative, pyrrolopyrrole derivative, styrylamine derivative, coumarin compound, international Publication WO
90/13148 and Appl.Phys.Lett., Vol 58,18, P1982
(1991), a polymer compound, an aromatic dimethylidyne compound, the following general formula (I)

Embedded image A compound represented by and the like can also be used as the organic light emitting material.

Here, specific examples of the aromatic dimethylidyne-based compound include 1,4-phenylene dimethylidene, 4,4'-phenylene dimethylidene, 2,5-xylylene dimethylidene, and 2,6. -Naphthylene dimethylidene, 1,4-biphenylene dimethylidene, 1,4
-P-Terephenylene dimethylidene, 4,4'-bis (2,2-di-t-butylphenylvinyl) biphenyl, 4,4'-bis (2,2-diphenylvinyl) biphenyl, and the like Examples include derivatives. Also,
Specific examples of the compound represented by the general formula (I) include:
Examples thereof include bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminum (III) and bis (2-methyl-8-quinolinolato) (1-naphtholate) aluminum (III).

In addition, a compound obtained by using the above-mentioned organic luminescent material as a host and doping the host with a strong fluorescent dye of blue to green color, for example, a coumarin-based or a fluorescent dye similar to the above host, is also suitable as the organic luminescent material. .
When the above compound is used as the organic light emitting material, blue to green light emission (emission color varies depending on the kind of dopant) can be obtained with high efficiency. Specific examples of the host which is the material of the compound include organic light-emitting materials having a distyrylarylene skeleton (particularly preferably 4,
4'-bis (2,2-diphenylvinyl) biphenyl)
Specific examples of the dopant which is a material of the compound include diphenylaminovinylarylene (particularly preferably N, N-diphenylaminobiphenylbenzene) and 4,4′-bis [2- [4- (N , N-di-p-tolyl) phenyl] vinyl] biphenyl).

As a method for forming a light emitting layer using the above organic light emitting material, for example, a vapor deposition method, a spin coating method,
Known methods such as the casting method and the LB method can be applied, but it is preferable to apply a method other than the sputtering method. Further, the light emitting layer is particularly preferably a molecular deposition film. Here, the molecular deposition film refers to a thin film formed by deposition from a material compound in a gaseous state or a film formed by solidification from a material compound in a solution state or a liquid phase state. Can be distinguished from a thin film (molecule accumulation film) formed by the LB method by a difference in an aggregated structure and a higher-order structure and a functional difference caused by the difference. Further, the light emitting layer can also be formed by dissolving a binder such as a resin and an organic light emitting material in a solvent to form a solution, and then thinning the solution by a spin coating method or the like. The thickness of the light emitting layer formed in this manner is not particularly limited and can be appropriately selected depending on the situation, but is usually preferably in the range of 5 nm to 5 μm.

(D) Hole Injecting Layer The material of the hole injecting layer (hereinafter referred to as “hole injecting material”), which is provided if necessary, has a hole injecting property or an electron barrier property. Any material may be used, for example, a material conventionally used as a hole injecting material for an electrophotosensitive material can be appropriately selected and used, and the hole mobility is 10
^-5 cm ² / Vs (electric field strength 10 ⁴ to 10 ⁵ V / cm)
Those described above are preferred. The hole injection material may be either organic or inorganic.

Specific examples include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives,
Styrylanthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative, silazane derivative,
Polysilanes, aniline-based copolymers, conductive polymer oligomers (particularly thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, styrylamine compounds, the above-mentioned aromatic dimethylidyne compounds shown as organic light-emitting materials, p-type Examples thereof include inorganic semiconductors such as -Si and p-type SiC. As the hole injection material, it is preferable to use a porphyrin compound, an aromatic tertiary amine compound or a styrylamine compound, and it is particularly preferable to use an aromatic tertiary amine compound.

Specific examples of the porphyrin compound include porphine, 1,10,15,20-tetraphenyl-21H, 23H-porphin copper (II), 1,10,
15,20-tetraphenyl-21H, 23H-porphine zinc (II), 5,10,15,20-tetrakis (pentafluorophenyl) -21H, 23H-porphine, silicon phthalocyanine oxide, aluminum phthalocyanine chloride, phthalocyanine (metal-free ),
Examples thereof include dilithium phthalocyanine, copper tetramethyl phthalocyanine, copper phthalocyanine, chromium phthalocyanine, zinc phthalocyanine, lead phthalocyanine, titanium phthalocyanine oxide, magnesium phthalocyanine, and copper octamethyl phthalocyanine.

Specific examples of the aromatic tertiary amine compound and the styrylamine compound include N, N,
N ', N'-tetraphenyl-4,4'-diaminophenyl, N, N'-diphenyl-N, N'-bis- (3-
Methylphenyl)-[1,1'-biphenyl] -4,
4'-diamine, 2,2-bis (4-di-p-tolylaminophenyl) propane, 1,1-bis (4-di-p-
Tolylaminophenyl) cyclohexane, N, N,
N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl, 1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane, bis (4-
Dimethylamino-2-methylphenyl) phenylmethane, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N'-diphenyl-N, N'-di (4-
Methoxyphenyl) -4,4′-diaminobiphenyl,
N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis (diphenylamino) quadriphenyl, N, N, N-tri (p-
Tolyl) amine, 4- (di-p-tolylamino) -4 '
-[4 (di-p-tolylamino) styryl] stilbene, 4-N, N-diphenylamino- (2-diphenylvinyl) benzene, 3-methoxy-4'-N, N-diphenylaminostilbene, N-phenylcarbazole ,
4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl having two condensed aromatic rings in the molecule, three triphenylamine units linked in starburst type 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino]
Triphenylamine and the like.

The hole injection layer can be formed by thinning the above compound by a known method such as a vacuum vapor deposition method, a spin coating method, a casting method or an LB method. The thickness of the hole injection layer is not particularly limited, but is usually 5 nm to 5 μm. This hole injection layer is
It may have a single-layer structure composed of one or more of the above-mentioned materials, or may have a multi-layer structure composed of a plurality of layers having the same composition or different compositions.

(E) Electron Injection Layer The material of the electron injection layer (hereinafter referred to as “electron injection material”) provided as necessary has a function of transmitting electrons injected from the cathode to the light emitting layer. Anything will do. In general, it is desirable that the electron affinity is larger than the electron affinity of the organic light emitting material and smaller than the work function of the cathode (the minimum when the cathode is composed of multiple components). However, where the difference in energy level is extremely large, a large electron injection barrier exists there, which is not preferable.
The electron affinity of the electron injection material is preferably as large as the work function of the cathode or the electron affinity of the organic light emitting material. The electron injection material may be either organic or inorganic.

Specific examples include nitro-substituted fluorenone derivatives, anthraquinodimethane derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthaleneperylene, carbodiimides, phenylenylidene methane derivatives, and anthrone. Derivatives, oxadiazole derivatives, JP-A-59-19439
Patent Document 3 discloses a series of electron-transporting compounds disclosed as materials for a light-emitting layer, a thiazole derivative in which an oxygen atom of an oxadiazole ring is substituted with a sulfur atom, and a quinoxaline having a quinoxaline ring known as an electron-withdrawing group. Derivatives, metal complexes of 8-quinolinol derivatives (e.g., tris (8-quinolinol) aluminum, tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, tris (2 -Methyl-8-quinolinol)
Aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc and the like, and the central metal of these metal complexes is In, Mg, C
u, Ca, Sn, Ga or Pb) or a metal-free or metal phthalocyanine or a compound in which the terminal thereof is substituted with an alkyl group, a sulfone group, or the like, and the above-mentioned diamines as organic light-emitting materials. Examples thereof include styrylpyrazine derivatives and inorganic semiconductors such as n-type-Si and n-type-SiC.

The electron injection layer can be formed by forming the above compound into a thin film by a known method such as a vacuum vapor deposition method, a spin coating method, a casting method and an LB method. The thickness of the electron injection layer is not particularly limited, but is usually 5 nm to 5 μm. This electron injection layer
It may have a single-layer structure composed of one or more of the above-mentioned materials, or may have a multi-layer structure composed of a plurality of layers having the same composition or different compositions.

As described above, in the organic EL device of the present invention, various materials including the substrate can be used for each layer other than the cathode, and the layer structure, especially the layer of the organic material layer in the present invention is used. The configuration can also be various configurations. Further, the anode, each layer constituting the organic material layer, and the cathode can be formed by various methods as described above. However, if a vacuum vapor deposition method is used for forming each layer, the organic EL element can be formed only by this vacuum vapor deposition method. Since it can be formed, it is advantageous in simplifying equipment and shortening production time. At that time, when the target organic EL device is one in which an anode, an organic material layer and a cathode are sequentially formed on a substrate in this order, at least each layer constituting the organic material layer (when the organic material layer has a single layer structure) From the formation of the cathode to the formation of the cathode, and in the case where the target organic EL element is one in which the cathode, the organic material layer and the anode are formed in this order on the substrate, the formation of the cathode Until formation, each is performed continuously, that is,
After forming a certain layer A (including the case of an alloy region or an upper metal region forming the cathode), the next layer B (including the case of an alloy region or an upper metal region forming the cathode) is formed. It is preferable that the layer A is not exposed to air during the period.

Further, the organic EL element of the present invention may have a sealing layer for preventing moisture and oxygen from entering the element, as in the conventional organic EL element. Specific examples of the material for the sealing layer include a copolymer obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer, and a fluorinated copolymer having a cyclic structure in the copolymer main chain. , Polyethylene, polypropylene, polymethylmethacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymers of chlorotrifluoroethylene and dichlorodifluoroethylene, water absorption of 1% or more Substance and water absorption rate 0.1
% Or less moisture-proof material, In, Sn, Pb, Au, Cu,
Metals such as Ag, Al, Ti, Ni, MgO, SiO, S
iO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, Ba
Metal oxides such as O, Fe ₂ O ₃ , Y ₂ O ₃ and TiO ₂ ,
Metal fluorides such as MgF ₂ , LiF, AlF ₃ and CaF ₂ , liquid fluorinated carbon such as perfluoroalkane, perfluoroamine and perfluoropolyether, and an adsorbent for adsorbing water and oxygen to the liquid fluorinated carbon are used. Examples include dispersed materials.

In forming the sealing layer, a vacuum deposition method, a spin coating method, a sputtering method, a casting method, MBE
(Molecular beam epitaxy) method, cluster ion beam deposition method, ion plating method, plasma polymerization method (high frequency excitation ion plating method), reactive sputtering method, plasma CVD method, laser CVD method, thermal CVD
Method, gas source CVD method, or the like can be applied as appropriate. When liquid fluorinated carbon or a liquid fluorinated carbon in which an adsorbent that adsorbs water or oxygen is dispersed is used as the material of the sealing layer, the organic E formed on the substrate is used.
Outside the L element (which may already have another sealing layer),
A housing material is provided in cooperation with the substrate to cover the organic EL element while forming a gap between the organic EL element and the liquid fluorination in the space formed by the substrate and the housing material. The sealing layer is preferably formed by filling carbon or a liquid fluorinated carbon in which an adsorbent that adsorbs water or oxygen is dispersed. As the housing material, a material made of glass or a polymer (for example, ethylene trifluoride chloride) having a small water absorption is preferably used. When using a housing material, only the housing material may be provided without providing the above-described sealing layer, or after the housing material is provided, a space formed by the housing material and the substrate may be used. A layer of an adsorbent for adsorbing oxygen or water may be provided, or particles of the adsorbent may be dispersed.

[0068]

Embodiments of the present invention will be described below. Example 1 (1) Preparation of organic EL device In which an ITO transparent electrode (corresponding to an anode) having a thickness of 100 nm was formed on a glass substrate having a size of 25 × 75 × 1.1 mm (hereinafter referred to as “anode-bearing substrate”). Said)) was prepared. The substrate with the anode was subjected to ultrasonic cleaning in an organic solvent, and then blown with dry nitrogen gas to remove the organic solvent from the surface of the ITO transparent electrode. Then, UV ozone cleaning was performed to remove organic substances from the surface of the ITO transparent electrode.

A commercially available vacuum vapor deposition apparatus (high vacuum vapor deposition apparatus manufactured by Nippon Vacuum Technology Co., Ltd.) equipped with a cryopump having an effective pumping speed for water as a main exhaust pump is used, and the vacuum vapor deposition is performed. A trap mechanism is provided near the substrate support part of the device to prevent residual gas such as water and oxygen from adhering to the substrate, and above the cleaned substrate with an anode (on the surface where the ITO transparent electrode is provided) A hole injecting layer, a light emitting layer, an electron injecting layer and a cathode were sequentially laminated in this order under the following conditions to obtain an organic EL device. At this time, without breaking the vacuum on the way from the formation of the hole injection layer to the formation of the cathode, 1
An organic EL element was produced by vacuuming twice. In addition, all the organic materials used were purified so that no degassing occurred at the start of vapor deposition and no impurities were generated.

First, 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (hereinafter referred to as" MTDATA "was used as a hole injection material for the first hole injection layer. Is used for this MTD.
At the time of vapor deposition, ATA was vapor-deposited under the conditions of a vacuum degree of 1.0 × 10 ⁻⁶ Torr or less and a vapor deposition rate of 0.1 to 0.3 nm / s to obtain a film thickness of 6
A 0 nm first hole injection layer was formed. At this time, the above-mentioned substrate with an anode was not particularly heated or cooled. next,
As the hole injection material for the second hole injection layer, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as “NPD”) was used.
PD was vapor-deposited under the same conditions as when forming the first hole injection layer to form a second hole injection layer having a film thickness of 20 nm.

Then, 4,4'-bis [2- [4- (N, N-di-p-tolyl) phenyl] was used as an organic light emitting material.
Vinyl] biphenyl (hereinafter abbreviated as “DTAVBi”) and 4,4′-bis (2,2-diphenylvinyl)
Biphenyl (hereinafter abbreviated as "DPVBi") was used to perform binary simultaneous vapor deposition so that DTAVBi was 2.5 wt% with respect to DPVBi to form a light emitting layer having a thickness of 40 nm. The degree of vacuum during vapor deposition, the substrate temperature, and the vapor deposition rate of DPVBi at this time were the same as those at the time of forming the above-described first hole injection layer.

Next, tris (8-quinolinol) aluminum (hereinafter abbreviated as "Alq") is used as an electron injecting material, and this Alq is subjected to the same conditions as the above-mentioned formation of the first hole injecting layer. Evaporation was performed to form an electron injection layer having a film thickness of 20 nm.

Next, the Li concentration of 1 consisting of Al and Li was 1
The alloy base material of 0 at% was used as the vapor deposition material for forming the alloy region, and the vacuum degree during vapor deposition was 1.0 × 10 ⁻⁶ Torr and the vapor deposition rate was 0.5
The vapor deposition material is vapor-deposited under the condition of ~ 1.0 nm / s,
A 20 nm thick alloy region was formed. At this time, prior to the formation of the alloy region, the above alloy base material was gradually heated and degassed while being monitored with a crystal oscillator type film thickness meter so that evaporation of the alloy base material did not occur. When observing the atmosphere in the vacuum chamber at the time of degassing with a quadrupole mass spectrometer, in addition to the growth of hydrogen gas, the growth of gas such as CO ₂ due to heating near the evaporation source by thermal radiation was observed. It was After confirming that degassing such as CO ₂ gas has settled, the alloy region is formed by further heating the evaporation source until the jump of the alloy from the evaporation source is observed by the crystal oscillator type film thickness meter. With the source shutter closed, the deposition rate is gradually approached to the above rate while emptying, and the deposition rate is controlled by controlling the power input to the evaporation source so that the deposition rate stabilizes at the target rate. Was confirmed to be stable with a crystal oscillator type film thickness meter.

When the atmosphere in the vacuum chamber at the time of forming the alloy region was observed by a quadrupole mass spectrometer, the oxygen gas was 3
% Partial pressure strength (about 2.0 × 10 ⁻⁹ Torr),
It was confirmed that the partial pressure intensity of water gas decreased and hydrogen gas had the first peak. After the alloy area is formed, the evaporation source shutter is quickly closed to turn off the power supply to the alloy base material, and the substrate (the above-mentioned substrate with an anode formed up to the alloy area)
Was isolated from the evaporation source.

After the temperature of the alloy base material is sufficiently lowered, Al is used as a vapor deposition material for the upper metal region, degassing of the Al is performed, and then the vacuum degree during vapor deposition is 1.0 × 10 ^−6.
The vapor deposition material (Al) was vapor-deposited under the conditions of Torr and vapor deposition rate of about 1.0 nm / s to form an upper metal region having a thickness of 200 nm.

By forming the alloy region and the upper metal region described above, a cathode composed of these two regions is formed. By forming this cathode, the anode (ITO) is formed.
Transparent electrode), hole injection layer (MTDATA layer and NPD
Layer), a light emitting layer (layer consisting of DTAVBi and DPVBi), an electron injection layer (Alq layer) and a cathode (Al-Li).
Thus, an organic EL device was obtained in which the alloy region consisting of Al and the upper metal region consisting of Al) were sequentially laminated on the glass substrate. In this organic EL device, the hole injecting layer, the light emitting layer and the electron injecting layer correspond to the “multi-layered organic substance layer including the light emitting layer containing the organic light emitting material” in the present invention.

(2) Luminescence test of organic EL device 6 Anode-cathode 6 of the organic EL device obtained in the above (1)
When a DC voltage of V was applied, a current of 1.23 mA / cm ² flowed, and blue light emission with a brightness of 128 cd / m ² was obtained. The power conversion efficiency at this time was 5.45 lm / W. In addition, visual inspection and a luminance meter (CS-1 manufactured by Minolta Co., Ltd.
As long as it was observed with No. 00), no non-light emitting point was observed in the light emitting surface, and the uniformity of light emission was excellent. When the above organic EL device was continuously driven with a constant direct current in a dry nitrogen gas atmosphere under the condition of an initial brightness of 300 cd / m ² , it took a long time of 2600 hours until the brightness was reduced to half. During this period, the emission chromaticity did not change, and no emission point was observed.

(3) Composition Analysis of Cathode Another organic EL element was prepared in the same manner as in the above (1), and the composition of the cathode constituting this organic EL element was as follows. analyzed. That is, from the cathode side to the anode side, 1.5 n is generated by Ar ⁺ ions.
The first AES and SI after sputtering the cathode surface by 10 nm with a sputtering rate of m / s
The measurement was performed by MS, and thereafter, the sputtering was stopped every 15 nm for the upper metal region and every 5 nm for the alloy region, and the composition analysis was performed by AES and SIMS each time. In SIMS, since the sample surface is irradiated with ions, the sample surface is scraped by about 5 nm at each measurement. Sputtering and compositional analysis were repeated at the depth at which the carbon signal was observed by AES.

In the ninth SIMS measurement, a region having a depth of approximately 170 to 175 nm was measured from the initial cathode surface, and in the eleventh SIMS measurement, a region having a depth of approximately 200 to 205 nm was measured from the initial cathode surface. ,
In the twelfth SIMS measurement, a region having a depth of about 210 to 215 nm is measured from the initial cathode surface, and in the thirteenth SIMS measurement, the depth is approximately 2 from the original cathode surface.
The area from 20 to 225 nm was measured.

As a result, oxygen was not detected by AES in both the upper metal region and the alloy region, and the existing concentration of oxygen in these regions was below the detection limit, that is, less than 1 at%. In the alloy area, AE
In S, only Al is detected, and the Li concentration is the detection limit (1 at
%). Table 1 shows the measurement results of the Li concentration in the cathode by SIMS.

[0081]

[Table 1]

Here, the depth in Table 1 is 200 to 205 nm.
Is considered to be data at the interface between the upper metal region and the alloy region, and the data at a depth of 220 to 225 nm is considered to be data at the interface between the alloy region and the electron injection layer. Therefore, approximately 0.5 at% Li is present in the alloy region.

Example 2 (1) Fabrication of organic EL device In forming an alloy region, the vapor deposition rate was 1.2 to
1.3 nm, and the thickness of the alloy region is 50 nm
In the same manner as in Example 1 (1) except that the organic E
An L element was produced. The partial pressure intensities of oxygen gas and water gas in the atmosphere in the vacuum chamber at the time of formation, which were observed by the degree of vacuum during vapor deposition at the time of forming the alloy region and the quadrupole mass spectrometer, were the same as in Example 1 (1). It was similar.

(2) Light-emission test of organic EL device 6 between the anode and the cathode of the organic EL device obtained in the above (1).
When a DC voltage of V was applied, a current of 0.84 mA / cm ² flowed, and blue light emission with a luminance of 68 cd / m ² was obtained. The power conversion efficiency at this time was 4.21 lm / W. Further, as far as visual observation and observation with a luminance meter were observed, no light-emitting point was observed in the light-emitting surface, and the light emission was excellent in uniformity as in the organic EL produced in Example 1 (1). When the above organic EL device was continuously driven under the same conditions as in Example 1 (2), it took a long time of 2000 hours until the brightness thereof was reduced to half. During this period, the emission chromaticity did not change, and no emission point was observed.

(3) Composition Analysis of Cathode Another organic EL element was prepared in the same manner as in the above (1), and the composition of the cathode constituting this organic EL element was determined as in Example 1 (3). ).
As a result, oxygen was not detected by AES in both the upper metal region and the alloy region. Table 2 shows the measurement results of the Li concentration in the alloy region by SIMS.

[0086]

[Table 2]

As shown in Table 2, approximately 0.5 to 2.5 at% Li is present in the alloy region. For confirmation, an Al—Li alloy layer having a film thickness of 50 nm was formed on a quartz glass substrate under the same conditions as the alloy region forming conditions in the above (1), and the composition thereof was determined by ICP analysis. As a result, the Li concentration was 1.74 at%, which almost coincided with the above-mentioned result by SIMS.

Comparative Example 1 After forming the electron injection layer in exactly the same manner as in Example 1 (1), the degree of vacuum during vapor deposition was 7.0 × 10 ⁻⁷ Torr, and the total vapor deposition rate was 1.4 to 1.5 nm / s. Under the conditions of Mg and Ag, Mg:
Vapor was vapor-deposited on the electron injection layer at an atomic ratio of Ag = 10: 1 to form a cathode having a thickness of 200 nm. In forming the cathode, the vapor deposition material was degassed and evacuated in the same manner as in Example 1 (1). An organic EL device was obtained by forming this cathode.

6 V is applied between the anode and the cathode of the above organic EL device.
When a direct current voltage of 0.80 mA / cm ² was applied, a blue light emission with a brightness of 31 cd / m ² was obtained.
The power conversion efficiency at this time was 2.1 lm / W. In addition, as a result of observation with a luminance meter (?), A slight non-emission point was observed in the light emission surface. The voltage required to obtain light emission with a brightness of about 120 cd / m ² by this organic EL element is 7 V, and the power conversion efficiency in the same brightness range (around 100 cd / m ² ) is the organic EL of each of the first and second embodiments. It was 1/2 or less as compared with the device.

When this organic EL device was continuously driven under the same conditions as in Example 1 (2), its luminance was halved within a relatively short time of about 1000 hours. During this period, the emission chromaticity did not change, but a slight increase in the non-emission point was observed. In addition, in the same manner as above, another organic E
An L element was produced, and the composition of the cathode constituting this organic EL element was determined by AES. as a result,
In addition to Mg and Ag, about 3 at% of oxygen originated from Mg oxide was detected near the interface between the cathode and the electron injection layer.

COMPARATIVE EXAMPLE 2 AND COMPARATIVE EXAMPLE 3 In forming the alloy region, an Al—Li alloy base material having a Li concentration shown in Table 3 below was used as a vapor deposition material, the vapor deposition rate was set to the rate shown in Table 3, and the alloy was formed. Table 3 shows the thickness of the area
An organic EL device was obtained for each comparative example in exactly the same manner as in Example 1 (1) except that the thickness was as shown in. In forming the alloy region, the vapor deposition material was degassed and evacuated in the same manner as in Example 1 (1).

[0092]

[Table 3]

The luminance and power conversion efficiency when a DC voltage of 6 V was applied to each of the above organic EL elements, and the luminance was halved when these organic EL elements were continuously driven under the same conditions as in Example 1 (2). Table 4 below shows the time required for this (luminance half-life time). Further, Table 4 also shows the Li concentration in the alloy region obtained by SIMS in the same manner as in Example 1 (3).

[0094]

[Table 4]

As shown in Table 4, the organic EL devices of Comparative Example 2 and Comparative Example 3 each had a Li concentration in the alloy region outside the range defined by the present invention, and the power consumption of these organic EL devices was low. The conversion efficiency is lower than that of each of the organic EL devices of Example 1 and Example 2, and the luminance half time is also Example 1.
And each organic EL device of Example 2 was shorter. It should be noted that any of the organic ELs of Comparative Example 2 and Comparative Example 3
Regarding the device as well, oxygen was not detected in the cathode by composition analysis by AES. Further, regarding the uniformity of light emission, these organic ELs were good.

Comparative Example 4 A main vacuum system is an oil diffusion pump, a high vacuum vapor deposition apparatus having no trap mechanism near the substrate holding section is used, and
Example 1 except that the degree of vacuum during vapor deposition in forming the alloy region was 5 × 10 ⁻⁶ Torr and the vapor deposition rate was 1.5 to 3.0 nm / s.
An organic EL device was obtained in exactly the same manner as (1). When the atmosphere in the vacuum chamber when the alloy region was formed was observed with a quadrupole mass spectrometer, the partial pressure strength of water gas was higher than the partial pressure strength of hydrogen gas. Was the first peak. The partial pressure strength of this water gas is the same as in Example 1.
It was 5 times that when the alloy region was formed in (1).

The brightness when a DC voltage of 6 V was applied to the above organic EL element was 15.8 cd / m ² , and the power conversion efficiency at this time was 4.59 lm / W. Further, when this organic EL device was continuously driven under the same conditions as in Example 1 (2), its luminance was halved in 1000 hours. Further, as in Example 1 (3), Li in the alloy region
When the concentration was determined, it was 4.2 at%. However, since 1 to 2 at% oxygen was detected by AES at the interface between the alloy region and the electron injection layer and in the vicinity thereof, the Li concentration in the alloy region excludes the values at the interface and the vicinity thereof. is there. The oxygen is not of organic origin because the carbon signal was not detected simultaneously.

As described above, the power conversion efficiency of this organic EL element is equal to or higher than that of each of the organic EL elements of Example 1 and Example 2, but the luminance half time is as short as 1000 hours as described above. . In addition, the organic EL element had a non-light emitting point in the initial stage. It is speculated that the existence of these non-luminous points is due to the presence of 1 to 2 at% oxygen at the interface between the alloy region and the electron injection layer and in the vicinity thereof. The number of non-light emitting points was increased by continuous driving of the element, and each non-light emitting point was expanded by continuous driving of the element.

Comparative Example 5 The same high vacuum vapor deposition apparatus as used in Comparative Example 4 was used, and
Example 1 except that the degree of vacuum during vapor deposition during formation of the alloy region was 1 × 10 ⁻⁵ Torr and the vapor deposition rate was 2.0 to 3.0 nm / s.
An organic EL device was obtained in exactly the same manner as (1). When the atmosphere in the vacuum chamber at the time of forming the alloy region was observed by a quadrupole mass spectrometer, the partial pressure strength of oxygen gas was about 10% (7.0 × 10 ⁻⁷ Torr) of the partial pressure strength of water gas. Was about).

The luminance when a DC voltage of 6 V was applied to the above organic EL element was 20 cd / m ² , and the power conversion efficiency at this time was 4.63 lm / W. Further, when this organic EL device was continuously driven under the same conditions as in Example 1 (2), its luminance was halved in 1000 hours. Furthermore, when the Li concentration in the alloy region was determined in the same manner as in Example 1 (3), it was 1.2 at%. However, at the interface between the alloy region and the electron injection layer and its vicinity, AES
Since 3 at% oxygen was detected by, the Li concentration in the alloy region excludes the values at the interface and its vicinity. The oxygen is not of organic origin because the carbon signal was not detected simultaneously.

As described above, the power conversion efficiency of this organic EL element is equal to or higher than that of each of the organic EL elements of Example 1 and Example 2, but the luminance half time is as short as 1000 hours as described above. . In addition, the organic EL element had a non-light emitting point in the initial stage. It is speculated that the existence of these non-light emitting points is due to the presence of 3 at% oxygen at the interface between the alloy region and the electron injection layer and in the vicinity thereof. The number of non-light emitting points was increased by continuous driving of the element, and each non-light emitting point was expanded by continuous driving of the element.

Example 3 (1) Preparation of organic EL device After forming an electron injection layer in exactly the same manner as in Example 1 (1), vapor deposition was performed by a binary simultaneous vapor deposition method using Al and Li as vapor deposition materials. Hour vacuum degree 5.0 × 10 ⁻⁷ Torr, Al vapor deposition rate 2.0 nm / s, Li vapor deposition rate 0.01 nm /
An alloy region having a thickness of 50 nm was formed under the condition of s. In forming the alloy region, each vapor deposition material was degassed and evacuated in the same manner as in Example 1 (1). After that, an upper metal region made of Al and having a thickness of 200 nm was formed in the same manner as in Example 1 (1) to obtain an organic EL device.

(2) Luminescence test of organic EL device 6 Anode-cathode 6 of the organic EL device obtained in (1) above.
When a DC voltage of V was applied, a current of 1.63 mA / cm ² flowed, and blue light emission with a brightness of 167 cd / m ² was obtained. The power conversion efficiency at this time was 5.36 lm / W. Further, as far as visual observation and observation with a luminance meter were observed, no light-emitting point was observed in the light-emitting surface, and the light emission was excellent in uniformity as in the organic EL produced in Example 1 (1). When the above organic EL device was continuously driven under the same conditions as in Example 1 (2), it took a long time of about 2500 hours until the brightness thereof was reduced to half. During this period, the emission chromaticity did not change, and no emission point was observed.

(3) Composition Analysis of Cathode Another organic EL element was prepared in the same manner as in (1) above, and the composition of the cathode constituting this organic EL element was determined as in Example 1 (3). ).
As a result, in the cathode, as in Example 1 (3), AE
No oxygen was detected in S. Moreover, the Li concentration in the alloy region measured by SIMS was 0.8 at%.

Example 4 (1) Preparation of Organic EL Element Pb was used as a vapor deposition material for forming the upper metal region, and the degree of vacuum during vapor deposition at the time of forming the upper metal region was 1.2 × 10.
An organic EL device was obtained in exactly the same manner as in Example 1 (1) except that the deposition rate was ⁻⁶ Torr and the deposition rate was 2.0 nm / s.

(2) Luminescence test of organic EL device [0106] Between the anode and the cathode of the organic EL device obtained in the above (1), 6
When a DC voltage of V was applied, a current of 1.52 mA / cm ² flowed, and blue light emission with a brightness of 153 cd / m ² was obtained. The power conversion efficiency at this time was 5.27 lm / W. Further, as far as visual observation and observation with a luminance meter were observed, no light-emitting point was observed in the light-emitting surface, and the light emission was excellent in uniformity as in the organic EL produced in Example 1 (1). When the above organic EL device was continuously driven under the same conditions as in Example 1 (2), it took a long time of about 2450 hours until the brightness thereof was reduced to half. During this period, the emission chromaticity did not change, and no emission point was observed.

(3) Cathode Composition Analysis Another organic EL device was prepared in the same manner as in (1) above, and the composition of the cathode constituting this organic EL device was determined as in Example 1 (3). ).
As a result, in the cathode, as in Example 1 (3), AE
No oxygen was detected in S. Further, the Li concentration in the alloy region measured by SIMS was 0.6 at%.

Examples 5 to 7 (1) Preparation of Organic EL Element After forming alloy regions in exactly the same manner as in Example 1 (1), except that the materials shown in Table 5 below were used as vapor deposition materials, respectively. An upper metal region having a thickness of 200 nm was formed under the same conditions as in Example 1 (1), and an organic EL element was obtained for each example.

(2) Luminescence test of organic EL element For each of the above organic EL elements, the luminance and power conversion efficiency when a DC voltage of 6 V was applied between the anode and the cathode, and the same as Example 1 (2) Table 5 below shows the time required for the luminance to decrease to half when continuously driven under the conditions (luminance half time).

[0110]

[Table 5]

As shown in Table 5, Example 5 and Example 6
The power conversion efficiency of any of the organic EL devices of Example 7 is as high as 5.15 lm / W, 5.10 lm / W or 4.93 lm / W. The luminance half-life of these organic EL devices is 2400 hours, 2500 hours or 2 hours.
It is as long as 300 hours. Furthermore, these organic EL devices are
As far as visual observation and observation with a luminance meter were observed, no light-emitting point was observed in the light-emitting surface, and the uniformity of light emission was excellent as in the organic EL produced in Example 1 (1). In any of the organic EL devices of Example 5, Example 6 and Example 7,
The emission chromaticity did not change during continuous driving, and no emission point was observed.

(3) Cathode composition analysis Another organic EL element was prepared in each of the examples in the same manner as in the above (1), and the composition of the cathodes constituting these organic EL elements was determined. Each was analyzed in the same manner as in Example 1 (3). As a result, in any of the organic EL elements, the AE was the same in the cathode as in Example 1 (3).
No oxygen was detected in S. Further, the Li concentration in the alloy region measured by SIMS is the same as the organic E of Example 5.
0.6 at% in L element, Example 6 and Example 7
It was 0.5 at% in each of the organic EL devices.

Examples 8 to 9 (1) Preparation of Organic EL Element After forming the electron injection layer in exactly the same manner as in Example 1 (1), the alloy base materials shown in Table 6 below were used as vapor deposition materials. An alloy region was formed in exactly the same manner as in Example 1 (1) except that the vapor deposition rate was 1.2 to 1.3 nm / s. After that, an upper metal region was formed in exactly the same manner as in Example 1 (1) except that the materials shown in Table 6 below were used as vapor deposition materials and the vapor deposition rate was set to 1.5 nm / s. An organic EL device was obtained for each example.

[0114]

[Table 6]

(2) Luminescence test of organic EL device For each of the above organic EL devices, the luminance and power conversion efficiency when a DC voltage of 6 V was applied between the anode and the cathode, and the same as in Example 1 (2) Table 7 below shows the time required for the luminance to be reduced to half when continuously driven under the conditions (luminance half-life time).

[0116]

[Table 7]

As shown in Table 7, the power conversion efficiency of each of the organic EL devices of Examples 8 and 9 is as high as 4.56 lm / W or 3.85 lm / W. Further, the luminance half-life of these organic EL elements is as long as 2400 hours or 2200 hours. Furthermore, these organic E
As for the L element, no non-light emitting point was observed in the light emitting surface as observed visually and with a luminance meter, and it was excellent in light emission uniformity as in the organic EL produced in Example 1 (1). In any of the organic EL elements of Example 8 and Example 9,
The emission chromaticity did not change during continuous driving, and no emission point was observed.

(3) Composition Analysis of Cathode Another organic EL element was prepared for each example in the same manner as in the above (1), and the composition of the cathodes constituting these organic EL elements was determined. Each was analyzed in the same manner as in Example 1 (3). As a result, in any of the organic EL elements, the AE was the same in the cathode as in Example 1 (3).
No oxygen was detected in S. In addition, the Li concentration in the alloy region measured by SIMS is the same as the organic E of Example 8.
It is 2.5 at% in the L element, and is the organic E of Example 9.
It was 1.3 at% in the L element.

Examples 10 to 11 (1) Preparation of Organic EL Element After forming an electron injection layer in exactly the same manner as in Example 1 (1), in Example 10 Al and a work function of 2.9 eV or less were used. In Example 11, an alloy base material (Ca concentration = 5 at%) made of Ca, which is one of the alkaline earth metals, is used as Al and S which is one of the alkaline earth metals having a work function of 2.9 eV or less.
Alloy base materials (concentration of Sr = 5 at%) each of which is used as a vapor deposition material, and the vapor deposition rate is 1.2 to 1.
An alloy region was formed in exactly the same manner as in Example 1 (1) except that the thickness was 3 nm / s. After that, an upper metal region is formed in exactly the same manner as in Example 1 (1), and organic E
An L element was obtained.

(2) Luminescence test of organic EL device For each of the above organic EL devices, the luminance and power conversion efficiency when a DC voltage of 6 V was applied between the anode and the cathode, and the same as in Example 1 (2) Table 8 below shows the time required for the luminance to be reduced to half when continuously driven under the conditions (luminance half-life time).

[0121]

[Table 8]

As shown in Table 8, in any of the organic EL elements of Example 10 and Example 11, the power conversion efficiency was as high as 4.93 lm / W or 4.85 lm / W. In addition, the luminance half time of these organic EL elements is 23.
It is as long as 00 hours or 2500 hours. Furthermore, these organic EL devices showed no non-emission point in the light emitting surface as observed visually and with a luminance meter, and were excellent in uniformity of light emission as in the organic EL device produced in Example 1 (1). It was In addition,
In each of the organic EL devices of Example 10 and Example 11, the emission chromaticity did not change during continuous driving, and no emission point was observed.

(3) Composition Analysis of Cathode Another organic EL element was prepared for each example in the same manner as in the above (1), and the composition of the cathodes constituting these organic EL elements was determined. Each was analyzed in the same manner as in Example 1 (3). As a result, in any of the organic EL elements, the AE was the same in the cathode as in Example 1 (3).
No oxygen was detected in S. The Ca concentration in the alloy region of the organic EL device of Example 10 measured by SIMS was 1.5 at%.
The Sr concentration in the alloy region of the L element measured by SIMS was 3.2 at%.

[0124]

As described above, according to the present invention, it is possible to easily provide an organic EL device having high power conversion efficiency, excellent uniform light emitting property, and long device life.

Claims (8)

[Claims] 1. An organic EL device in which an anode, an organic material layer having a single-layer structure or a multilayer structure including a light-emitting layer containing an organic light-emitting material, and a cathode are sequentially laminated on a substrate, wherein the cathode is A thickness of 5 to 50 containing an alkali metal or an alkaline earth metal having a work function of 2.9 eV or less in a total amount of 0.5 to 5 at% of the alkali metal and the alkaline earth metal.
nm alloy region and an upper metal region made of a metal having a work function of 3.0 eV or more are sequentially formed as viewed from the organic material layer side, and the existing concentration of oxygen in the cathode is 1 at% or less. An organic EL device characterized in that 2. The alloy region is made of an alloy containing only an alkali metal among an alkali metal and an alkaline earth metal having a work function of 2.9 eV or less, and the alkali metal is lithium (Li). 1. The organic EL device according to 1. 3. The alloy region comprises an alloy containing only an alkaline earth metal having a work function of 2.9 eV or less among an alkali metal and an alkaline earth metal having a work function of 2.9 eV or less. Metal is calcium (Ca)
The organic EL device according to claim 1, which is 4. The alloy region comprises an alloy containing only an alkaline earth metal having a work function of 2.9 eV or less among an alkali metal and an alkaline earth metal having a work function of 2.9 eV or less. The metal is strontium (S
The organic EL device according to claim 1, which is r). 5. The metal forming the upper metal region is aluminum (Al), magnesium (Mg), gold (A).
u), silver (Ag), copper (Cu), zinc (Zn), lead (P
The method according to any one of claims 1 to 4, comprising one elemental metal selected from the group consisting of b) and tin (Sn) or a mixture of two or more kinds of metals selected from the group. The organic EL device described. 6. The alloy region is formed in a vacuum environment in which the partial pressure of oxygen gas is 5% or less of the partial pressure of water gas when the partial pressure of gas components is measured by a quadrupole mass spectrometer. The organic E according to any one of claims 1 to 5, which is
L element. 7. The alloy region is formed in a vacuum environment of a reducing atmosphere in which the partial pressure of hydrogen gas is larger than the partial pressure of water gas when the partial pressure of gas components is measured by a quadrupole mass spectrometer. The organic EL element according to any one of claims 1 to 6, which is a product. 8. The organic E according to claim 1, wherein the alloy region is formed by a film forming apparatus equipped with a cryopump or a trap mechanism.
L element.