JP2002175888A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element which has element reliability for element leakage inhibition or the like obtained when an insulating layer or a resistance layer is used as a hole injection layer, and further which prevents elevation of a drive voltage that is a drawback, and which has high reliability and in which the drive voltage is low. SOLUTION: This organic EL element has at least one organic layer, including an organic luminous layer between a pair of electrodes composed of the hole injection electrode and an electron injection electrode, and this has a metal layer containing a metal layer, having a larger work function than that of the hole injection electrode between the hole injection electrode and the organic layer; and this is made to be the organic EL element of a constitution, having an insulation layer or resistance layer between the metal layer and the organic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device (organic EL device) using an organic material which emits light by recombination of holes and electrons.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for flat panel displays from the viewpoint of reducing the occupied area, and a device using an electroluminescent element (hereinafter abbreviated as EL element) which is lightweight and does not require a backlight has been developed. Attention has been paid. EL elements include organic EL elements and inorganic EL elements. Among these, the organic EL element has an advantage that it can be driven at a low voltage of about 20 V, unlike the inorganic EL element.

[0003] The structure of the organic EL device is a two-layer structure having a hole injection / transport layer and an organic light emitting layer / electron injection / transport layer between a hole injection electrode and an electron injection electrode, or an organic light emitting layer / positive layer. 2 having a hole injection transport layer and an electron injection transport layer
There is one of layer Yasushizo.

As a structure having two or more layers, there is a structure having a hole injection / transport layer, an organic light emitting layer, and an electron injection / transport layer. Alternatively, a single-layer structure having a light-emitting layer, a hole injection / transport layer, and an electron injection / transport layer in one layer is also known.

In these organic EL devices, an injection layer for efficiently injecting and transporting holes and electrons into the organic light emitting layer as in the above-described structure is required in order to obtain practical brightness at practical power. become.

Techniques disclosed so far for producing an organic EL element with high efficiency include the following, for example.

Japanese Patent Application Laid-Open No. 6-5369 discloses a highly efficient organic EL device in which a metal having a larger work function than ITO is stacked in contact with a hole injection electrode ITO to lower an injection barrier to an organic layer. The method of making is disclosed. However, Pt, Au, and the like, which are shown as metals having a higher work function than ITO, have poor bonding properties with the organic layer, so that film separation easily occurs at the interface between the metal film and the organic film, and current leakage of the element and One of the problems is that the reliability such as the life is extremely low.

Japanese Patent Application Laid-Open No. 9-63771 discloses an attempt to lower the drive voltage by inserting a metal oxide thin film having a large work function between an anode and an organic compound to reduce the energy gap with the organic compound. ing. By using a metal oxide, the problem of a decrease in the bonding property can be avoided. However, in this method, since the metal oxide thin film is conductive, there is a problem that current leakage of the element cannot be prevented, and the reliability is also lowered.

The hole injecting / transporting layer in contact with ITO is usually made of an organic material. However, the organic material used for the organic EL device is relatively expensive, and there is a problem in terms of manufacturing cost. For this reason, there is also a purpose of suppressing leakage of the element,
Attempts have been made to replace the hole injecting and transporting layer with an inorganic material such as an inorganic insulating layer or an inorganic high resistance layer, which is inexpensive and has high leak resistance.

For example, JP-A-8-288069 reports a method of suppressing leakage and short circuit of an organic EL element by inserting an insulating thin film layer between an anode and a cathode and an organic compound. Although this method has an effect on the life of the device, on the other hand, since the insulating layer has a low hole injection function, the driving voltage increases, and the advantage of the organic EL device that the device is driven at a low voltage can be used. Power consumption also increases.

Similarly, in order to solve the problem of leakage, Japanese Patent Application Laid-Open No. H11-162646 has attempted to insert a dielectric thin film layer. Although the embodiments of this publication show a decrease in driving voltage, the structure of this publication requires a dielectric thin film layer on both the hole injection layer side and the electron injection layer side. As described, when the dielectric thin film layer is provided only on the hole injection layer side, the driving voltage increases. That is, it is considered that the voltage drop effect is not effectively exerted on the hole injection layer but is caused by the voltage drop caused by disposing the alkali metal on the electron injection layer side.

In Japanese Patent Application Laid-Open No. 2000-100575, an inorganic insulating hole-injecting layer is provided, and the hole-injecting layer contains Cu, Fe, Ni, Ru, Sn, and Au. It is disclosed that the injection property of the hole injection layer is improved. However, when a conductor is contained in the insulating layer, if the content is large, a low-resistance film is formed, which adversely affects the suppression of leakage. If the content is small, the hole injecting property is reduced as in JP-A-8-288069. There is a trade-off relationship in which the drive voltage decreases and the drive voltage increases, and it is difficult to achieve both at the same time. Furthermore, since some of these metals have higher or lower work functions than those of ITO, there is no way to match the work functions.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to have element reliability such as element leakage suppression obtained when an insulating layer or a resistive layer is used as a hole injection layer, and further have its disadvantages. An object of the present invention is to provide an organic EL device which prevents a rise in drive voltage and has a high reliability and a low drive voltage.

[0014]

A metal layer having a high work function is provided between an anode and an organic layer, and an insulating layer is provided between the metal and the organic layer. By the action of the high work function metal, the injection property into the organic layer is improved, the driving voltage is reduced, and the leak is suppressed by providing the insulating layer.

That is, the above object is achieved by the following constitution of the present invention. (1) An organic EL device having one or more organic layers including an organic light emitting layer between a pair of electrodes composed of a hole injection electrode and an electron injection electrode, wherein the organic EL element has a structure between the hole injection electrode and the organic layer. An organic EL device comprising: a metal layer containing a metal element having a work function larger than that of a hole injection electrode; and an insulating layer or a resistance layer between the metal layer and the organic layer. (2) The organic EL device according to (1), wherein the insulating layer or the resistance layer is formed of an inorganic material. (3) The organic EL device according to the above (2), wherein the insulating layer or the resistance layer contains silicon oxide or germanium oxide as a main component. (4) The metal layer is made of Pt, Au, Pd, Ni, Re,
The organic EL device according to any one of the above (1) to (3), containing one or more elements selected from Co, Se, and Ir. (5) The organic EL device according to any one of (1) to (4), wherein the thickness of the metal layer is 0.1 to 2 nm. (6) The above (1) to (1) to wherein the hole injection electrode, the metal layer, and the insulating layer or the resistance layer have a light transmittance of 80% or more.
The organic EL device according to any one of (5).

DESCRIPTION OF THE PREFERRED EMBODIMENTS The organic EL device of the present invention has a hole injection electrode and an electron injection electrode on a substrate, and has an organic light emitting layer between these electrodes. Further, a metal layer containing a metal element having a higher work function than the hole injection electrode is provided between the hole injection electrode and the organic layer, and an insulating layer or a resistance layer is in contact with the metal layer.

Here, the insulating layer has a specific resistance of 10 ⁸ Ω · cm.
The resistance layer is a layer containing a material having a specific resistance in the range of 10 ⁸ cm to 10 ^-2 cm. The definition of the insulating layer is, for example, S.M. M. Jie's book, "Semiconductor Device", Sangyo Tosho Co., Ltd., 1987
Year, is listed in. The range of the specific resistance of the resistance layer is preferably lower than that of the insulating layer and higher than that of the organic material used for the organic EL device, and the above range is preferable.

As a material constituting the insulating layer in the organic EL device of the present invention, for example, JP-A-8-288069
The one described in Japanese Patent Application Laid-Open Publication No. H10-260, can be used. Specifically, AIN, BN, GaN, Li ₃ N, Si ₃ N
_4, TaN, nitrides such as _{TiN, Al 2 0 3, BaO} ,
_{CaO, Fe 2 0 3, GeO} , GeO 2, MgO, Ni
O, SiO, SiO ₂ , TiO, TiO ₂ , Ti _20
3, Y ₂ 0 oxide such as _{3, CuS, EuS, GeS,} S
Sulfides such as nS, SrS and ZnS, carbides such as SiC and TiC, AIF, BaF ₂ , FeF ₃ , LiF and MgF
_{For example} , fluorides such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polycarbonate, polyurethane, and polyimide can be used.

The insulating layer is preferably made of silicon oxide which is known as a good insulating film. Further, germanium oxide or silicon nitride may be used. The insulating layer preferably has a higher resistance than the organic layer, but may be a resistor obtained by adding indium oxide as a conductor to germanium oxide as an insulator.

As a method of forming the insulating layer, a sputtering method, a vacuum evaporation method, an EB evaporation method, a CVD method, and the like can be considered. However, the sputtering method is preferred because the film quality can be easily controlled and the apparatus can be easily maintained. preferable.

When the insulating layer is formed by a sputtering method, when a metal oxide is used for the insulating layer, it is possible to use an inert atmosphere such as nitrogen or Ar, but it is better to add oxygen to the atmosphere to supplement the oxygen. Denseness as an insulating film is further improved.

The resistive layer has the following formula: (Si _1-x Ge _x ) O _y [0 ≦ x ≦ 1, 1.7 ≦ y ≦ 2.2] Examples include those containing a conductor such as Fe, Ni, Ru, Sn, Au, or In. In the present invention, a resistance layer is preferable to the above-mentioned insulating layer.

The main component of the resistance layer is (Si _1-x Ge _x ) O _y
0 ≦ x ≦ 1, 1.7 ≦ y ≦ 2.2, preferably 1.85 ≦ y ≦ 2.1
It is. The resistance layer may be silicon oxide or germanium oxide, or a mixed thin film thereof. If y is larger and the silicon or germanium vacancy is less,
However, even if oxygen vacancies are large, the hole injection function is reduced. The composition of the resistive layer may be determined by, for example, Rutherford backscattering or chemical analysis.

The resistance layer is made of Cu, Fe, N
It contains any one or more of i, Ru, Sn and Au. Especially, it is preferable to contain Sn, Ni, Cu, especially Ni. The content of these elements is 10at% in total
Hereinafter, it is more preferably 0.05 to 10 at%, further preferably 0.1 to 10 at%, and particularly preferably 0.5 to 5 at%. If the content exceeds this, the hole injection function is reduced.

In the resistance layer, H, Ne, Ar, Kr, Xe, or the like used as a sputtering gas is added as an impurity in a total amount of 5%.
At% or less may be contained.

If the average value of the entire resistance layer is such a composition, the composition may not be uniform and may have a structure having a concentration gradient in the film thickness direction.

The resistance layer is usually in an amorphous state.

The thickness of the resistance layer is not particularly limited, but is preferably from 0.1 to 10 nm, particularly preferably from about 1 to 10 nm.
If the high resistance layer is thinner or thicker than this, hole injection cannot be performed sufficiently.

As a method of manufacturing the above-described resistance layer, various physical or chemical thin film forming methods such as a sputtering method and an EB vapor deposition method are considered, but the sputtering method is preferable.

When the resistance layer is formed by the sputtering method, the pressure of the sputtering gas during the sputtering is preferably in the range of 0.1 to 1 Pa. As the sputtering gas, an inert gas used in a normal sputtering apparatus, for example, Ar, Ne, Xe, Kr, or the like can be used. Further, N ₂ may be used if necessary. The atmosphere during sputtering is O.O.
Reactive sputtering may be performed by mixing ₂ to about 1 to 99%. As the target, any of the above oxides may be used, and single or multiple sputtering may be performed.

As the sputtering method, a high-frequency sputtering method using an RF power source, a DC sputtering method, or the like can be used, but RF sputtering is particularly preferred. The power of the sputtering apparatus is preferably in the range of 0.1 to 10 W / cm ² by RF sputtering, and the film formation rate is 0.5 to 10 nm / min.
Particularly, the range of 1 to 5 nm / min is preferable.

The substrate temperature during film formation is room temperature (25
C) to about 150C.

In the present invention, the hole injection electrode and the insulating layer,
Alternatively, a metal layer of a metal having a higher work function than the hole injection electrode is provided between the metal layer and the resistance layer. By providing a metal layer having a higher work function than the hole injecting electrode between the hole injecting electrode and the insulating layer / resistive layer, it is possible to prevent an increase in driving voltage due to the insulating layer / resistive layer. . Further, the presence of the insulating layer / resistance layer reduces the occurrence of leaks and dark spots.

At this time, if the hole injection electrode is an ITO film (work function: 4.6 eV), the metal layer preferably contains a metal element having a higher work function than the ITO film. By using a material having a higher work function than the hole injection electrode, hole injection efficiency can be increased, and voltage drop in the insulating layer and the resistance layer can be suppressed. In addition, since the hole injection electrode and the metal layer are conductors, even if the work function of the metal layer is higher than that of the hole injection electrode, ohmic connection occurs without any problem.

Specific examples of the material constituting the metal layer include Ir (4.7 eV), Se (4.72 eV), and Co (4.72 eV).
(4.97 eV), Re (5.0 eV), Ni (5.15 eV)
V), preferably contains one or more elements selected from Pd (5.17 eV), Au (5.2 eV), and Pt (5.43 eV). The mixing ratio when using two or more of these elements is arbitrary. It is desirable that these metal elements are elements that substantially constitute the metal layer except for unavoidable components that are mixed in from materials, manufacturing processes, and the like.

Considering the use of the present invention as a display, IT
When light is extracted from the O side, the metal layer is desirably transparent, and preferably has a transmittance of 80% or more. For example, in the case of Pt, the thickness is 1 nm and the transmittance is 82%, and the thickness is preferably 1 nm or less, particularly preferably 0.1 to 1 nm. If the film thickness is smaller than 0.1 nm, it becomes difficult to obtain the effect of providing a metal layer having a high work function.

As a method of forming the metal layer, a vacuum evaporation method, an EB evaporation method, a sputtering method and the like can be considered, but a sputtering method capable of increasing the adhesion between the ITO and the metal layer is preferable.

If the metal layer and the insulating layer / resistive layer are laminated in the order of the insulating layer / resistive layer, the metal layer, and the organic layer from the hole injection electrode side, the adhesion between the metal layer and the organic layer is problematic. And the element characteristics deteriorate, such as the occurrence of leakage. Accordingly, the order of lamination of the metal layer and the insulating layer / resistive layer is, in order from the hole injection electrode side, the metal layer, the insulating layer / resistive layer, and the organic layer, so that the organic layer does not directly contact the metal layer. Is good.

The hole injection electrode material is preferably a material capable of efficiently injecting holes into a hole injection layer or the like, and is preferably a substance having a work function of 4.5 eV to 5.5 eV. Specifically, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), indium oxide (In
₂ O ₃ ), tin oxide (SnO ₂ ) and zinc oxide (Zn
O) having a main composition of either of them is preferable. These oxides may deviate somewhat from their stoichiometric composition. The mixing ratio of SnO ₂ to In ₂ O ₃ is 1 to 20.
wt%, more preferably 5 to 12 wt%. Also, IZO
The mixing ratio of ZnO to In ₂ O ₃ is usually 12
About 32% by weight.

The electrode on the light extraction side has an emission wavelength band,
Usually, the light transmittance for light having a wavelength of 400 to 700 nm is 5
It is preferably at least 0%, more preferably at least 80%, particularly preferably at least 90%. If the transmittance is too low, the light emission itself from the light emitting layer is attenuated, and it becomes difficult to obtain the luminance required for the light emitting element.

The thickness of the electrode is 50-500 nm, especially 50
The range of -300 nm is preferred. The upper limit is not particularly limited. However, if the thickness is too large, there is a fear that the transmittance is reduced or the layer is peeled off. If the thickness is too small, a sufficient effect cannot be obtained, and there is a problem in film strength at the time of production and the like.

As the inorganic electron injecting and transporting layer, when combined with an organic electron injecting and transporting layer, the following materials can be used, if necessary, as having an electron injecting property. For example, K, Li, Na, Mg, La, Ce, C
a, a single metal element such as Sr, Ba, Sn, Zn, Zr,
Or two components containing them to improve stability,
Three-component alloy system, for example, Ag.Mg (Ag: 0.1 to 5)
0 at%), Al.Li (Li: 0.01 to 14 at%),
In.Mg (Mg: 50-80at%), Al.Ca (C
a: 0.01 to 20 at%).

The thickness of the inorganic electron injecting and transporting layer may be a certain thickness or more capable of sufficiently injecting electrons, and may be 0.1 nm or more, preferably 0.5 nm or more, particularly 1 nm or more. The upper limit is not particularly limited, but the thickness may be generally about 1 to 500 nm.

As the inorganic electron injecting and transporting layer, Si, Ge
An inorganic layer containing a semiconductor element such as a main component may be used, or an alkali metal salt such as lithium fluoride disclosed in JP-A-9-17574 may be formed to a thickness of about 1 nm.

When the electron injecting electrode is combined with the inorganic electron injecting and transporting layer, it is not necessary to have a low work function and an electron injecting property. it can. Among them, in terms of conductivity and ease of handling, Al, Ag, In, Ti, Cu, Au, Mo,
One or two or more metal elements selected from W, Pt, Pd and Ni, particularly Al and Ag are preferred.

The thickness of these electron injecting electrodes may be a certain thickness or more capable of giving electrons to the inorganic electron injecting and transporting layer, and may be 50 nm or more, preferably 100 nm or more. Although the upper limit is not particularly limited, the film thickness may be generally about 50 to 500 nm.

Further, when a protective layer is provided to protect the organic EL element from moisture in the atmosphere, it is possible to suppress the deterioration caused by the generation of dark spots (called dark spots) in the element. The protective film is made of SiN, SiON, S
A film having a high water-blocking ability such as iO ₂ and Al ₂ O ₃ is preferable.

As a method of forming the protective film, a vapor deposition method, a sputtering method, a CVD method and the like can be considered, but a plasma CVD method which can be formed at a low temperature and has good step coverage is preferable.

After the organic EL device is manufactured, it is preferable to form a protective film without exposing the device to the air. The thickness of the protective film is not particularly limited, but is preferably 100 to 5000 nm. If the thickness of the protective film is smaller than this, the water blocking ability is reduced. If the thickness is larger than this, film peeling due to the stress of the protective film and the characteristics of the organic EL element are affected.

The total thickness of the electron injecting electrode and the protective layer is not particularly limited, but may be generally about 50 to 500 nm.

Next, the organic layer of the organic EL device will be described in detail.

The organic EL device according to the present invention comprises at least one organic light-emitting layer between two electrodes, at least one of which is transparent, and the organic light-emitting layer is at least one or two types involved in the light-emitting function. Contains compounds.

In the organic EL device according to the present invention, the wavelength of light emitted from at least one organic light emitting layer is not particularly limited, but preferably, at least one organic light emitting layer has a wavelength of at least 380 to 780 nm. It is configured to emit white light having a continuous emission spectrum.

In the present invention, if at least one organic light emitting layer is configured to emit white light having a continuous emission spectrum of 430 nm to 650 nm or less,
Particularly preferred.

In the present invention, the organic light emitting layer contains a host material which is a hole transporting compound or an electron transporting compound or a mixture thereof, and has a hole and electron injecting function, a hole and electron transporting function, and a positive hole and electron transporting function. It preferably has a function of generating excitons by recombination of holes and electrons and contains a compound which is relatively neutral electronically.

Examples of the hole transporting compound used as a host material of the organic light emitting layer include a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a birazolin derivative, a birazolone derivative, a phenylenediamine derivative, an arylamine derivative, Amino-substituted chalcone derivatives, oxazole derivatives,
Examples include a styryl anthracene derivative, a fluorenone derivative, a hydrazone derivative, and a stilbene derivative. Further, a triphenyldiamine derivative can be preferably used.

As an example of the triphenyldiamine derivative, a tetraarylpendicine compound (triaryldiamine or triphenyldiamine: TPD) is particularly preferred.

Tetraarylbendicine compound (TDP)
Preferred specific examples are as follows.

[0058]

Embedded image

[0059]

Embedded image

[0060]

Embedded image

As the electron transporting compound used as the host substance in the organic light emitting layer, a quinoline derivative can be preferably used. Further, a metal complex having 8-quinolinol or a derivative thereof as a ligand, Tris (8-quinolinato) aluminum (A
lq3) is preferably used. Further, a phenylanthracene derivative or a tetraarylethene derivative can also be used as the electron transporting compound.

[0062]

Embedded image

In the present invention, the organic light-emitting layer preferably has a structure in which a host material, which is a hole-transporting compound or an electron-transporting compound, or a mixture thereof, is doped with dovant, a fluorescent substance. .

The organic EL device according to the present invention preferably has two organic light emitting layers stacked on each other. In the case of forming two organic light emitting layers, each of them is doped with a fluorescent substance having a different light emission wavelength, thereby securing a wide light emission wavelength band and improving a degree of freedom of a color of a light emission color. be able to.

In the present invention, examples of the fluorescent substance to be contained as a dopant include compounds disclosed in JP-A-63-264692, specifically, rubrene-based compounds, coumarin-based compounds, quinacridone-based compounds, and dicyano-based compounds. One or more compounds selected from the group consisting of compounds such as methylbiran compounds can be preferably used.

Examples of the fluorescent substance which can be preferably used in the present invention are as follows.

[0067]

Embedded image

[0068]

Embedded image

[0069]

Embedded image

[0070]

Embedded image

Further, according to the present invention, JP-A-2000-26
No. 334 and the naphthacene-based compound described in JP-A-2000-26337 can also be preferably used as a fluorescent substance to be contained as a dovant, and include a rubrene-based compound, a coumarin-based compound, a quinacridone-based compound, and dicyanomethyl. When used in combination with a pyran-based compound or the like, the life of the organic EL device can be significantly improved.

In the present invention, a naphthacene-based compound that can be preferably used as a fluorescent substance to be contained as a dopant has a basic skeleton represented by the formula (I).

[0073]

Embedded image In the formula (I), R ^{1 to} R ⁴ each represent an unsubstituted or substituted alkyl group, aryl group, amino group,
Represents any of a heterocyclic group and an alkenyl group. Also,
It is preferably any of an aryl group, an amino group, a heterocyclic group and an alkenyl group.

The aryl groups represented by R ^{1 to} R ⁴ may be monocyclic or polycyclic, and include condensed rings and ring assemblies. The total carbon number is preferably 6 to 30, and may have a substituent.

The aryl group represented by R ^{1 to} R ⁴ is preferably a phenyl group, (o-, m-, p-) tolyl group, pyrenyl group, perylenyl group, coronenyl group, (1)
-, And 2-) naphthyl group, anthryl group, (o-,
(m-, p-) biphenylyl group, terphenyl group, phenanthryl group and the like.

The amino groups represented by R ^{1 to} R ⁴ include
Any of an alkylamino group, an arylamino group, an aralkylamino group and the like may be used. These preferably have an aliphatic having 1 to 6 carbon atoms in total and / or 1 to 4 aromatic carbon rings. Specific examples include a dimethylamino group, a diethylamino group, a dibutylamino group, a diphenylamino group, a ditolylamino group, a bisdiphenylylamino group, and a bisnaphthylamino group.

The heterocyclic groups represented by R ^{1 to} R ⁴ include:
Examples thereof include a 5- or 6-membered aromatic heterocyclic group containing O, N, and S as a hetero atom, and a fused polycyclic aromatic heterocyclic group having 2 to 20 carbon atoms.

The alkenyl group represented by R ^{1 to} R ⁴ has a phenyl group in at least one of the substituents (1
-, And 2-) phenylalkenyl groups, (1,2-,
And 2,2-) diphenylalkenyl groups, (1,2,2)
2-) A triphenylalkenyl group or the like is preferable, but an unsubstituted one may be used.

Examples of the aromatic heterocyclic group and the condensed polycyclic aromatic heterocyclic group include a thienyl group, a furyl group, a pyrrolyl group, a pyridyl group, a quinolyl group, and a quinoxalyl group.

When R ^{1 to} R ⁴ have a substituent, at least two of these substituents are preferably any of an aryl group, an amino group, a heterocyclic group, an alkenyl group and an aryloxy group. Aryl group, amino group,
For the heterocyclic group and the alkenyl group, the above R ^{1 to} R ⁴
Is the same as

The aryloxy group which is a substituent of R ^{1 to} R ⁴ is preferably an aryloxy group having an aryl group having a total of 6 to 18 carbon atoms, specifically, an (o-, m-, p-) phenoxy group or the like. It is.

Two or more of these substituents may form a condensed ring. Further, it may be further substituted, and in that case, preferred substituents are the same as described above.

When R ^{1 to} R ⁴ have a substituent, it is preferred that at least two of them have the above substituent. The substitution position is not particularly limited, and may be any of meta, para, and ortho positions. Also, R
¹ and R ⁴ , and R ² and R ³ are preferably the same, but may be different.

Further, at least five or more, more preferably six or more, of R ^{1 to} R ⁸ are an unsubstituted or substituted alkyl group, aryl group, amino group, alkenyl group or heterocyclic group.

R ⁵ , R ⁶ , R ⁷ and R ⁸ each represent hydrogen or an optionally substituted alkyl, aryl, amino or alkenyl group.

The alkyl group represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ preferably has 1 to 6 carbon atoms.
It may be linear or branched. Preferred specific examples of the alkyl group include a methyl group, an ethyl group,
(N, i) propyl group, (n, i, sec, tert)
-Butyl group, (n, i, neo, tert) -pentyl group and the like.

The aryl group, amino group and alkenyl group represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ include the above-mentioned R ¹
For to R ⁴ is the same as. Further, R ⁵ and R ⁶ and R ⁷ and R ⁸ are preferably the same, but may be different.

In the present invention, the following compounds can be preferably used as the fluorescent substance to be contained as a dopant.

[0089]

Embedded image

[0090]

Embedded image

When two organic light emitting layers are provided, it is preferable that each organic light emitting layer contains two or more kinds of these fluorescent substances, and that two or more kinds of fluorescent substances have different emission wavelengths. .

In the present invention, the content of the dopant in the organic light emitting layer is preferably from 0.01 to 20% by weight, more preferably from 0.1 to 15% by weight.

In the present invention, the thickness of the organic light emitting layer is not particularly limited, and the preferable thickness is usually from 5 to 500 nm, more preferably from 10 to 300 nm, depending on the forming method. .

In the present invention, when two or more organic light emitting layers are formed, the thickness of each organic light emitting layer ranges from a thickness corresponding to one molecular layer to a thickness less than the total thickness of the organic light emitting layer. Yes, specifically, 1 to 85 nm, preferably 5 to 60 n
m, more preferably 5 to 50 nm.

In the present invention, preferably, the organic light emitting layer is formed by vapor deposition.

In the present invention, the conditions for forming the organic light-emitting layer by vapor deposition are not particularly limited, but are not more than 1 × 10 ^-4 Pascal and the steaming speed is 0.01 to 10 Pa.
It is preferred to be about 1 nm / sec.

In the present invention, the organic light emitting layer preferably contains a mixture of a hole transporting compound and an electron injecting and transporting compound.

When the organic light emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, a hopping conduction path for carriers is formed, and each carrier is formed of a material having a polarity predominantly. And carrier injection of the opposite polarity is less likely to occur, and therefore, the compound contained in the organic light emitting layer is prevented from being damaged.
There is an advantage that the life of the element can be improved.

Further, a dobant made of a fluorescent substance is
By including the mixture of the hole transporting compound and the electron injecting and transporting compound in the organic light emitting layer, the emission wavelength characteristics of the organic light emitting layer itself can be changed, and the emission wavelength is shifted to the longer wavelength side. At the same time, the emission intensity can be improved, and further, the stability of the organic EL element can be improved.

When the organic light emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, the mixing ratio between the hole transporting compound and the electron injecting and transporting compound is determined by the carrier mobility and the carrier mobility. Although it is determined according to the concentration, it is generally 1/99 to 99/1, preferably 10/90 to 90/10, more preferably 20/80 to 80, by weight.
/ 20, most preferably 40/60 to 60/40.

When forming an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the hole transporting compound and the electron injecting and transporting compound are put in different evaporation sources and evaporated. It is preferable to perform co-evaporation,
When the hole transporting compound and the electron injecting and transporting compound have the same or very similar vapor pressure, they can be mixed in advance in the same vapor deposition source and then subjected to steaming.

When an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound is formed, the hole transporting compound and the electron injecting and transporting compound are uniformly mixed in the organic light emitting layer. However, it is not always necessary to mix them uniformly.

In the present invention, the organic material layer preferably has at least one organic light-emitting layer, a hole transport layer having a function of stably transporting holes, and a function of stably transporting electrons. And an electron transport layer having the following formula: By providing these layers, it is possible to increase the number of holes and electrons injected into the organic light emitting layer, to confine the organic light emitting layer, to optimize the recombination region, and to improve the light emission efficiency. .

In the present invention, compounds that can be preferably used in the hole transport layer include, for example, tetraarylbendicine compounds (triaryldiamine or triphenyldiamine: TPD), aromatic tertiary amines,
Hydrazone derivatives, carbazole derivatives, triazole derivatives ", imidazole derivatives, oxadiazole derivatives having an amino group, polythiophenes, and the like. Among them, tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD) and triarylamine multimer (ATP) described in WO / 98/30071 can be particularly preferably used. .

Preferred specific examples of the triarylamine multimer (ATP) are as follows.

[0106]

Embedded image

[0107]

Embedded image

[0108]

Embedded image

In the present invention, further, JP-A-63-29
No. 5695, JP-A-2-191694, JP-A-3-792
JP-A-5-234681, JP-A-5-239455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226-1 and JP-A-8-100172 And various organic compounds described in JP-A No. 650955Al can also be used for the hole injection / transport layer, the hole injection layer, and the hole transport layer.

In the present invention, two or more of these compounds may be used in combination, and when two or more of these compounds are used in combination, they may be mixed in one layer or formed as two or more layers. , May be laminated.

In the present invention, the hole transport layer can be formed by depositing the above compound. When a device is formed by vapor deposition, a uniform, thin film having a thickness of about 1 to 10 nm without pinholes can be formed. Therefore, a compound having a small ionization potential and absorbing light of a visible wavelength is formed in the hole injection layer. Even if it is used, it is possible to prevent a decrease in the luminous efficiency due to a change in the color tone of the luminescent color or reabsorption.

In the present invention, compounds that can be preferably used in the electron transport layer include, for example, 8- (quinolineolato) aluminum (Alq3) such as tris (8-quinolinolato) aluminum.
Examples thereof include an organometallic complex having quinolinol or a derivative thereof as a ligand, an oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, and a quinoxaline derivative.

In the present invention, the electron transport layer can be formed by depositing the above compound.

In the present invention, an organic light emitting layer, a hole injection / transport layer or a hole injection layer and a hole transport layer;
Each layer of the electron injection transport layer or the electron injection layer and the electron transporting layer is not specifically limited condition to be formed by vapor deposition, in 1 × 10 ^-4 Pa or less, the deposition rate 0.01 to 1 / sec It is preferable to set the degree. Each layer is preferably formed continuously under a reduced pressure of 1 × 10 ⁻⁴ Pa or less. By continuously forming each layer under a reduced pressure of 1 × 10 ⁻⁴ Pa or less, it is possible to prevent impurities from being adsorbed at the interface of each layer, and to obtain a high-performance organic EL device. In addition, the driving voltage of the organic EL element can be reduced, and the generation and growth of dark spots can be suppressed.

In the present invention, when two or more compounds are contained in the organic light emitting layer, the hole transporting layer, and the electron transporting layer, each boat containing the compounds is individually temperature-controlled.
It is preferable to form an organic light emitting layer, a hole transport layer, an electron injection transport layer, an electron injection layer or an electron transport layer by co-evaporation.

In the present invention, instead of or in addition to the electron transport layer, a high-resistance inorganic electron injection / transport layer having an electron conduction path and having a function of blocking holes may be provided.

As described above, by providing a high-resistance inorganic electron injecting and transporting layer having an electron conduction path and having a function of blocking holes, between the organic light emitting layer and the electron injecting electrode, organic light emitting can be achieved. Electrons can be efficiently injected into the layer, so that the luminous efficiency can be improved and the driving voltage can be reduced. Furthermore, by providing a high-resistance inorganic electron injecting and transporting layer having an electron conduction path and a function of blocking holes, it is possible to reduce the thickness of the organic EL display panel and the organic EL element, Accordingly, it is possible to further reduce the thickness of the organic EL display panel and the organic EL element which are thinned by forming a color filter layer or a color filter.

The high resistance inorganic electron injecting and transporting layer preferably has a work function of 4 eV or less as a first component, more preferably 1 eV or less.
４4 eV, preferably Li, Na, K, Rb, C
one or more alkali metal elements selected from s and Fr, or one or more alkaline earth metal elements preferably selected from Mg, Ca and Sr, or 1 preferably selected from La and Ce Contains oxides of any one or more of the lanthanoid elements. Of these, lithium oxide, magnesium oxide, calcium oxide, and cerium oxide are particularly preferred. When these are mixed and used, the mixing ratio is arbitrary. Lithium oxide is 50 mol% in terms of Li ₂ O in these mixtures.
It is preferable to contain the above.

The inorganic electron injection layer further contains one or more elements selected from Zn, Sn, V, Ru, Sm and In as the second component. In this case, the content of the second component is preferably 0.2 to 40 mol%, more preferably 1 to 20 mol%. If the content is small, the electron injection function is reduced, and if the content is large, the hole blocking function is reduced. When two or more kinds are used in combination, the total content is preferably in the above range. The second component may be in a metal element state or an oxide state.

As described above, in the high resistance first component,
As the second component, Zn, Sn, V, Ru, Sm and I
n or more elements selected from the group consisting of
By forming the conductive path at a content of 40 mol%, electrons can be efficiently injected from the electron injection electrode into the organic light emitting layer. This is considered to be due to the fact that the inclusion of the second component in the first component causes the conductive material to be present in the form of islands in the insulating material, thereby forming a hopping path for electron injection. .

In the first component, the second component is added in an amount of 0.2 to 40.
By containing mol%, the movement of holes from the organic light emitting layer to the electron injection electrode can be further suppressed, and the holes and electrons can be efficiently recombined in the organic light emitting layer. .

When a high-resistance inorganic electron injecting and transporting layer is provided, it is equivalent to a conventional organic electron injecting and transporting layer, an organic electron injecting layer, and an organic EL element having an organic electron transporting layer. In addition, higher brightness can be obtained, and the heat resistance and weather resistance are high, so the life is long, and the connectivity with the electron injection electrode, which is an inorganic material, is good. There is also an advantage that there is less. Furthermore, unlike relatively expensive organic materials, the inorganic materials for forming the inorganic electron injecting and transporting layer are inexpensive, easily available, and easy to form. The manufacturing cost of the element or the organic EL display panel can be reduced.

The resistivity of the high-resistance inorganic electron injecting and transporting layer is as follows:
It is preferably 1 × 10 ⁻² Ω · cm to 1 × 10 ⁻⁸ Ω · cm. By setting the resistivity of the inorganic electron injecting and transporting layer to such a range, while maintaining high hole blocking properties,
The electron injection efficiency can be dramatically improved.

The oxide of the first component usually has a stoichiometric composition, but it deviates somewhat from this, and the non-stoichiometric composition is non-stoichiometric.
ry). The same applies to the oxide of the second component.

The high-resistance inorganic electron injecting and transporting layer further comprises
As impurities, H, Ne used as a sputtering gas,
Ar, Kr, Xe and the like may be contained in a total of 5 at% or less.

The inorganic electron injecting and transporting layer having a high and low resistance is usually in an amorphous state.

The high-resistance inorganic electron injecting and transporting layer has a thickness of 0.2 to 0.2.
It preferably has a thickness of 30 nm,
It is particularly preferable that the film has a thickness of 0. Even if the thickness of the high-resistance inorganic electron injecting and transporting layer is less than 0.2 nm, it is 30 nm.
, The function of electron injection cannot be sufficiently exhibited.

The high-resistance inorganic electron injecting and transporting layer can be formed by various physical or chemical thin film forming methods such as sputtering and vapor deposition, but is preferably formed by a sputtering method. In particular, it is preferable to form the inorganic electron injecting and transporting layer by a multiple spattering method in which the first component and the second component are targets and separately sprinkled. According to the multi-source sputtering method, sputtering can be performed under conditions suitable for each target. Further, the inorganic electron injecting and transporting layer can be formed by a one-way sparging method using a mixed target of the first component and the second component.

When the inorganic electron injecting and transporting layer is formed by the sparging method, the pressure of the sputtering gas is 0.1 to
It is preferable to set the range to 1 Pascal. As the sputtering gas, an inert gas usually used in the sputtering method, for example, Ar, Ne, Xe, Kr, or the like can be used, and if necessary, a nitrogen gas can be used. At the time of sputtering, an oxygen gas of 1 to 99% may be mixed in addition to these sputtering gases.

As the sputtering method, a high-frequency sputtering method using an RF power source or a DC sputtering method can be used. The power of the high-frequency sputtering using the RF power source is preferably in the range of 0.1 to 10 W / cm 2, The deposition rate is 0.5 to 10 nm / min.
A range of 1 to 5 nm is preferred.

The substrate temperature during film formation is about 25 to 150 ° C.

In the present invention, the substrate on which the organic EL structure is formed is an amorphous substrate such as glass or quartz, or a crystalline substrate such as Si, GaAs, ZnSe, or Z.
Examples thereof include nS, GaP, and InP, and a substrate in which a crystalline, amorphous, or metal buffer layer is formed on these crystalline substrates can also be used. As the metal substrate, Mo, Al, Pt, Ir, Au, Pd, or the like can be used. Further, a resin material such as plastic or a material having flexibility can be used. The substrate material is
Preferably, a glass substrate or a resin material is used. When the substrate is on the light extraction side, it is preferable that the substrate has the same light transmittance as the above-mentioned electrodes.

As the glass material, alkali glass is preferable from the viewpoint of cost, and in addition, glass materials such as soda lime glass, lead alkali glass, borosilicate glass, aluminosilicate glass, and silica glass are also preferable. In particular, soda glass, which has no surface treatment, can be used at low cost.

Further, in order to prevent oxidation of the organic layer and the electrodes of the element, it is preferable to seal the element with a sealing plate or the like. The sealing plate adheres and seals the sealing plate using an adhesive resin layer in order to prevent moisture from entering. The sealing gas is A
An inert gas such as r, He, N ₂ or the like is preferable. Further, the moisture content of the sealing gas is preferably 100 ppm or less, more preferably 10 ppm or less, and particularly preferably 1 ppm or less. Although there is no particular lower limit for the water content, it is usually about 0.1 ppm.

As the material of the sealing plate, it is possible to use a material different from the above-mentioned substrate, but it is preferable to use the same material as the substrate material, or a material having the same thermal expansion coefficient and mechanical strength.

The height of the sealing plate may be adjusted by using a spacer, and may be maintained at a desired height. Examples of the material of the spacer include resin beads, silica beads, glass beads, and glass fibers, and glass beads are particularly preferable. When a recess is formed in the sealing plate, the spacer may or may not be used.

The spacer may be mixed in the sealing adhesive in advance, or may be mixed at the time of bonding. The content of the spacer in the sealing adhesive is preferably 0.01
-30 wt%, more preferably 0.1-5 wt%.

The adhesive is not particularly limited as long as it can maintain stable adhesive strength and has good airtightness, but it is preferable to use a cationic curing type ultraviolet curing epoxy resin adhesive. .

The luminescent color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

For the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL element to optimize the extraction efficiency and the color purity.

When a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance of the element and the contrast of display are improved.

In addition, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film performs color conversion of the emission color by absorbing the light of the EL light emission and emitting the light from the phosphor in the fluorescence conversion film. It is formed from a fluorescent material and a light absorbing material.

Basically, a fluorescent material having a high fluorescence quantum yield may be used, and it is desirable that the material has strong absorption in the EL emission wavelength region. In practice, laser dyes and the like are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalocyanines, etc.) naphthalimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds A styryl compound, a coumarin compound or the like may be used.

As the binder, basically, a material that does not quench the fluorescence may be selected, and a binder that can be finely patterned by photolithography, printing, or the like is preferable. In the case where the hole injection electrode is formed on the substrate in contact with the hole injection electrode, a material which does not damage the film during formation of the hole injection electrode (ITO, IZO, or the like) is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

The organic EL device of the present invention comprises, for example, as shown in FIG. 1, a substrate 1 / hole injection electrode 2 / metal layer 3 / insulating layer or resistance layer 4 / hole injection / transport layer 5a, light emitting layer 5b, Organic layer including electron injection / transport layer 5c / inorganic electron injection / transport layer 6
/ Electron injection electrodes 7 are sequentially laminated. In addition, a reverse stack in which the electron injection electrode 7 is formed on the substrate 1 side may be used. The stacked configuration may be an optimum stacked configuration according to required performance and specifications. The organic layer may have a multilayer structure in which a hole injection / transport layer, a light emitting layer, an electron injection / transport layer, and the like are stacked, or a single layer structure in which the light emitting layer has an electron injection / transport function, a hole transport function, and the like. It may be.

The organic EL element can be driven by DC or pulse, and can be driven by AC. The applied voltage is usually 2
It is about 30V.

[0149]

[Example 1] As shown in FIG. 2, an organic EL device described in this example has a transparent conductive film ITO, which is a hole injection electrode 2, having a thickness of 100 nm on a glass substrate 1. Pt: 0.5 nm for the metal layer 3 and GeO ₂ : In ₂ O ₃
(Sputter target composition, 85:15 mol%) An inorganic hole injection layer 4 composed of 1 nm, and a distyrylaryleneamine derivative also represented by the following chemical formula 2 in addition to a distyrylarylene derivative represented by the following chemical formula 1 Organic light-emitting layer 5 with a thickness of 100 nm added with 3% by volume, inorganic electron injection layer 6 with lithium fluoride: 0.3 nm, and electron injection with a thickness of 200 nm with silver added to magnesium at 2% by volume. It has a structure in which the electrodes 7 are sequentially stacked.

[0150]

Embedded image

[0151]

Embedded image

A method for manufacturing the organic EL device will be specifically described.

First, the glass substrate 1 on which the hole injection electrode 2 was formed was ultrasonically cleaned for 10 minutes, and then rinsed with pure water. Thereafter, baking was performed in an oven at 110 ° C. for 8 hours or more. After the substrate with ITO was subjected to UV / O ₃ cleaning, the substrate was introduced into a vacuum device and the pressure in the tank was reduced to 1 × 10 ⁴ Pa or less.

Then, as the hole injection metal layer 3, 0.5 nm of Pt was formed by EB evaporation at an evaporation rate of 0.01 nm / sec. The conditions at this time are as follows: a voltage of 4.6 keV and a current value of 2
00 mA.

While maintaining the decompressed state, Ge was applied to the target.
Using O ₂ : In ₂ O ₃ (85:15 mol%), an inorganic high resistance layer is formed to a thickness of 1 nm, and a hole injection layer is formed to a total thickness of 1.5.
nm. The conditions at this time are as follows: 10%
Using O ₂ / Ar, pressure: 0.15 Pa, input power: 0.
8W / cm ^2, the film formation rate: was 0.05nm / sec.

While maintaining the reduced pressure, 3% by volume of the compound of formula 16 was added to the compound of formula 15, and the deposition rate was:
The organic light emitting layer 5 was deposited to a thickness of 100 nm by a resistance heating method at a rate of 0.1 nm / sec.

Then, the electron injection layer 6 was formed to a thickness of 0.1 nm with a deposition rate of 0.01 nm / sec by resistance heating using lithium fluoride.
Evaporated to a thickness of 3 nm.

Further, 2% by volume of silver was added to magnesium, and the electron injection electrode 7 was evaporated to a thickness of 200 nm at a deposition rate of 0.1 nm / sec. Organic EL with the above process
An element was manufactured.

Example 2 The inorganic high resistance layer was made 3 nm and Pt was
The structure was the same as that of Example 1 except that a hole injection layer of 3.5 nm was combined with the layer of 0.5 nm.

Example 3 The organic light emitting layer 4 was made of tris (8-quinolinol) aluminum (hereinafter abbreviated as Alq3).
Was constructed in the same manner as in Example 2 except that the film was formed with a film thickness of 100 nm.

Example 4 As shown in FIG. 3, N, N'-diphenyl-N, N'- was used as the organic hole injection layer 5a.
Bis (3-methylphenyl) -1,1'-biphenyl-
The structure was the same as that of Example 3 except that a 4,4′-diamine (abbreviated as TPD) film thickness of 20 nm was inserted between the inorganic hole injection layer 4 and the organic light emitting layer 5b.

Example 5 The inorganic insulating layer was made of SiO ₂ : 3 nm.
The structure was the same as that of Example 4 except that the hole injection layer was 3.5 nm in total including the Pt layer: 0.5 nm.

Comparative Example 1 The structure was the same as that of Example 1 except that the inorganic hole injecting layer was only the inorganic high resistance layer GeO ₂ : In ₂ O ₃ : 1 nm and no Pt metal layer was provided.

Comparative Example 2 The structure was the same as that of Example 2 except that the inorganic hole injecting layer was only the inorganic high-resistance layer GeO ₂ : In ₂ O ₃ : 3 nm and the Pt metal layer was not provided.

Comparative Example 3 The structure was the same as that of Example 3 except that the inorganic hole injecting layer was only the inorganic high resistance layer GeO ₂ : In ₂ O ₃ : 3 nm and the Pt metal layer was not provided.

Comparative Example 4 The structure was the same as that of Example 4 except that the inorganic hole injecting layer was only the inorganic high-resistance layer GeO ₂ : In ₂ O ₃ : 3 nm and the Pt metal layer was not provided.

Comparative Example 5 The structure was the same as that of Example 5 except that the inorganic hole injecting layer was made of only the inorganic insulating layer SiO ₂ : 3 nm and the Pt metal layer was not provided.

[Comparative Example 6] Pt was used as the inorganic hole injecting layer.
Instead of Mg, a 0.5 nm film of Mg is formed, and then the inorganic high resistance layer G is formed.
eO ₂ : In ₂ O ₃ was formed to a thickness of 3 nm, and the structure was the same as that of Example 2 except that the total thickness was set to 3.5 nm.

[Comparative Example 7] GeO ₂ : In ₂ on ITO
An element was fabricated in the same manner as in Example 1, except that the O ₃ hole injection layer was formed first, and then the Pt layer was formed.

In this device, when an organic layer was formed on the metal layer, the organic layer was repelled, and an organic thin film could not be formed uniformly.

A predetermined voltage was applied to each of the organic EL devices of Examples 1 to 5 and Comparative Examples 1 to 7 with the ITO electrode side being plus and the electron injection electrode side being minus.
The voltage when the current was mA / cm ² and the voltage when the luminance was 100 cd / m ² were measured.

The results are shown in Table 1 below.

[0173]

[Table 1]

The measured values of the resistivity of the insulating layer and the high-resistance layer used in each of the above embodiments are shown below. The measurement was performed by masking the sample to a predetermined area and using IT
It was sandwiched between an O transparent electrode and an Al electrode and determined from the applied voltage and current. The measured value is easily affected by the environmental humidity and the noise level, and is considered to be a value including an error.

[0175]

[Table 2]

From the above results, Comparative Examples 1 to 5 and Examples 1 to 5
Sample No. 5 even corresponds to each sample, for example, Example 1 (driving voltage 6.6 V, 10 mA / cm ² ) and Comparative Example 1
(At a driving voltage of 12.6 V, at 10 mA / cm ² ), it can be seen that the driving voltage of the sample of the present invention is significantly reduced. In Comparative Example 3, when a voltage at a luminance of 100 cd / m ² was used for measurement, the element was broken before the measurement.

On the other hand, if the work function is ITO (work function 4.6)
e) lower than magnesium (work function 3.6 eV)
Even when t was inserted instead of t (work function: 5.4 eV), the results of Comparative Example 6 did not show a decrease in drive voltage.

In Comparative Example 7, no luminance was obtained.
The voltage drive voltage at cd / m ² could not be measured. This is probably because the leakage portion burned out first, and then the drive voltage abnormally increased. In addition, luminance unevenness in the light emitting portion was severe, and a bright spot was observed.

From the above results, it was clarified that the drive voltage was reduced by inserting a metal having a higher work function than the hole injection electrode.

Example 6 The devices of Example 1 and Comparative Example 1 were continuously illuminated with a constant current of 100 mA / cm ^{2 in} an argon atmosphere, and the life of each organic EL device was measured. FIG. 4 shows the results.

From the above results, it was found that the organic EL in Example 1 was
It was found that the decrease in the light emission luminance of the element was much slower than that in Comparative Example 1. This is considered to be due to the suppression of leakage due to the insertion of the high resistance layer and the decrease in the amount of heat generated due to the decrease in drive voltage due to the insertion of the metal layer.

As described above, according to the present invention, by using a metal layer having a high work function and an insulating layer or a high resistance layer as an inorganic hole injection layer, it is possible to suppress leakage and, in addition, to use an insulating layer. By reducing the energy barrier with the organic layer, the driving voltage of the element can be reduced and the life of the element can be prolonged. Therefore, the present invention can be applied to various display devices using the organic EL element, and the effect is great.

[0183]

As described above, according to the present invention, device reliability such as device leakage suppression obtained when an insulating layer or a resistive layer is used as a hole injection layer is a disadvantage. An increase in driving voltage can be prevented, and an organic EL element with high reliability and low driving voltage can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an organic EL device of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a basic configuration of the organic EL element of Example 1.

FIG. 3 is a schematic cross-sectional view illustrating a basic configuration of an organic EL device of Example 4.

FIG. 4 is a graph showing measurement results of life characteristics of Example 6.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Hole injection electrode 3 Metal layer 4 Insulating layer / resistance layer 5 Organic layer 5a Hole injection transport layer 5b Light emitting layer 5c Electron injection transport layer 6 Inorganic electron injection layer 7 Electron injection electrode

Claims (6)

[Claims] 1. An organic EL device having one or more organic layers including an organic light emitting layer between a pair of electrodes composed of a hole injection electrode and an electron injection electrode, An organic EL device having a metal layer containing a metal element having a work function larger than that of a hole injection electrode between the metal layer and an organic layer. 2. The organic EL device according to claim 1, wherein the insulating layer or the resistance layer is formed of an inorganic material. 3. The organic electroluminescent device according to claim 2, wherein said insulating layer or said resistive layer contains silicon oxide or germanium oxide as a main component.
L element. 4. The metal layer is made of Pt, Au, Pd, Ni,
The organic EL device according to any one of claims 1 to 3, further comprising one or more elements selected from Re, Co, Se, and Ir. 5. The organic EL device according to claim 1, wherein said metal layer has a thickness of 0.1 to 2 nm. 6. The light transmittance of the hole injection electrode, the metal layer, and the insulating layer or the resistance layer is 80% or more.
5. The organic EL device of any one of items 1 to 5.