JP2826381B2 - Organic electroluminescent device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an organic electroluminescence device, that is, an organic electroluminescence (EL) device.

BACKGROUND ART Conventionally, as the above-mentioned organic EL device, U.S. Patent No. 3,995,29
There is one described in the specification of No. 9. This organic EL device is an anode / hole injection layer / polymer / electron injection layer / cathode type device, and the concept of a hole injection layer has been proposed for the first time. In this case, polyvinyl carbazole is mentioned as a typical example of the polymer as the light emitting layer. Here, the hole injection layer is formed by adding a strong electron-accepting compound to an existing polymer, and is an electrically conductive layer in which cations are present in the layer. This hole injection layer can inject holes into the existing polymer under application of an electric field.

The electron injection layer is formed by adding a strong electron donating compound, and is an electrically conductive layer in which an anion is present in the layer. The electron injection layer can inject electrons into the existing polymer under electric field application.

Further, RHPartridge, Polymer, 24, 247 (1983) discloses in detail a hole injection layer and an electron injection layer, which indicate that electrons and holes can be injected into an organic insulator at a low voltage. I have.

However, in the above method, stable luminescence cannot always be obtained because a highly oxidizable metal such as Ce is used as the strong electron donating compound. In addition, an oxidizing agent such as AlCl ₃ is used as the electron-accepting compound. Therefore, under the application of a high electric field, a stable light emitting operation cannot be obtained due to movement of ions such as AlCl ₃ ⁻ .

This type is MSISM (Metal Semiconductor Insulat
or Semiconductor Metal) type device.

According to Japanese Patent Publication No. 64-7635, in an anode / hole injection zone / emission zone / cathode type device, a porphyrin-based compound is used for a hole injection zone, and an organic luminous body having a binder is used for an emission zone. Is disclosed. According to this element, an applied voltage of about 30 V and 100 mA / c
At a current density of about m ² , light emission of about 160 cd / cm ² became possible. In addition, by using a porphyrin-based compound, it has become possible to stably inject holes into the emission band at a low voltage. However, this device has 50 cd
Low luminous efficiency at high brightness of / m ² or more, up to 0.018lm / W
It was about.

JP-A-59-194393 discloses an anode / hole injection zone / emission zone / cathode type device using a triphenylamine derivative in the hole injection zone. According to this element, an applied voltage of about 20 V and 100 mA / c
In m ² about the current density has enabled luminescence hundreds cd / m ^2. This emission characteristic could reach a practical use range.

By the way, it is already known to use a charge generation layer / charge transport layer type structure as a photoconductive member (for example,
The Journal of the Electrographic Society of Japan, Vol. 25, No. 3, pp. 62-76). In the structure of the charge generation layer / charge transport layer type, the above triphenylamine derivative is used for the charge transport layer to form holes. An element designed to be transported is also known (for example,
53-27033, 54-58445, U.S. Pat.
7,412).

It has also been known that holes are injected from the electrode into the charge transport layer when an electric field is applied, and are transported in the transport layer (for example, US Pat. No. 4,251,621, Japanese Patent Publication No. 59-8 / 1984).
No. 24).

While the hole injection layer disclosed in the above-mentioned U.S. Pat.No. 3,995,299 is electrically conductive, the derivative of triphenylamine used in the above-described charge transport layer is an insulator, and alone. Does not have holes to be transported. However, if an appropriate anode is used,
-27033, 54-58445, U.S. Pat.
No. 621, No. 4,127,412, and JP-B-59-
It is clear that holes can be transported from the anode to the emission band when an electric field is applied due to the properties disclosed in, for example, Japanese Patent No. 824, and attention was paid to this, and the invention described in JP-A-59-194393 was made. Things. Furthermore, since the hole injection zone using the triphenylamine derivative does not transport electrons, electrons are accumulated at the interface between the hole injection zone and the emission zone,
It has been proposed to increase the luminous efficiency of the device (see, for example, Appl. Phys. Lett. 51, 913, 1987 and J. Appl.
l.Phys. 65, 3610, 1989).

The problem with this device configuration is that the donor triphenylamine derivative used in the hole injection zone and the compound that is the luminescent material used in the emission zone often form an exciplex. is there. The exciplex is formed at the interface between the hole injection zone and the emission zone,
This leads to a decrease in luminous efficiency and causes deterioration of the interface during the light emitting operation, which is one of the causes of a reduction in the life of the element. Of course, a light-emitting material that does not form an exciplex may be selected, but there is a significant restriction on the selection of the light-emitting material, and only a small number of electron-transporting light-emitting materials disclosed in JP-A-59-194393 are practical. Given properties. For this reason, it was disadvantageous to obtain various luminescent colors using an organic fluorescent material.

On the other hand, there have been attempts to replace the triphenylamine derivative with another charge transporting material known for the above-mentioned photoconductive member (for example, Japan Society for the Promotion of Science,
125 committee, 129th meeting for the study group, p. 8), life is not always successful due to problems.

In addition, since the charge transporting material used as the photoconductive member always has an amine component that gives a donor property, it is difficult to avoid the problem of the exciplex caused by the light emitting material and the triphenylamine derivative.

By the way, according to Synthetic Metals Vol. 28, No. C, 1989, various MS junction elements using a conductive polymer as a semiconductor layer (S layer) have been developed. Since these conductive polymers function as semiconductors, diodes having good rectification (forward current value / reverse current value) have been manufactured.
In particular, according to Fish et al., A thiophene oligomer is a semiconductor, and since it is easy to form a thin film by a vapor deposition method, an MS junction device can be easily manufactured using the thiophene oligomer. Pp. 705, 1989). Furthermore, it has been shown that thiophene oligomers are usually P-type, but can also become N-type semiconductors by heat treatment.

However, a light emitting diode element cannot be obtained with these MS junction diodes.

DISCLOSURE OF THE INVENTION An object of the present invention is to achieve luminance and luminous efficiency in a practical range equivalent to or higher than that of an anode / hole injection layer / light emitting layer / cathode type device using a triphenylamine derivative as an insulator. ,
It is an object of the present invention to provide an organic electroluminescent element having a novel element configuration which can emit light in a plane, emit light stably, and can be easily manufactured.

Another object of the present invention is to provide an organic electroluminescent device capable of avoiding the problem of formation of an exciplex which is inevitable in a device using a hole injection layer such as the above triphenylamine derivative, and capable of realizing various emission colors. It is to provide.

Yet another object of the present invention is to use an organic semiconductor band.
Improved MS junction diode, MISM type (MS
Is to provide an organic electroluminescent device that is a diode (ISM).

The present invention is an organic electroluminescent device in which a member in which an organic semiconductor zone and an organic insulator zone are sandwiched between electrodes is arranged on a substrate, and has an organic light emitting region in the organic insulator zone.
It is characterized by having a luminous efficiency necessary for practical use of 0.02 lm / W or more at a high luminance of not less than / m ² .

Further, in the above structure, the organic semiconductor zone is a zone having semiconductivity (electric conductivity), and is characterized by being formed by a conductive polymer oligomer.

The organic insulator zone is a zone having a lower conductivity than the above-mentioned organic semiconductor zone, and is formed by an organic compound. A light emitting area is provided in this band. Further, an electron barrier region or a hole barrier region can be provided in this band.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view schematically showing an example of an organic EL device according to the present invention, and FIGS. 2 to 4 show states of holes and electron movement in the above organic EL device. It is a schematic diagram.

FIG. 5 shows the current density of the device obtained in Example 11-
5 is a graph showing voltage characteristics. FIG. 6 shows an infrared absorption spectrum of the compound obtained in Example 10. FIG. 7 is a graph showing current density-voltage characteristics of the device obtained in Example 13. FIG. 8 shows an infrared absorption spectrum of the compound obtained in Example 12.

14 ・ ・ Organic semiconductor band, 18 ・ ・ Organic insulator band, 12,20 ・
-Electrode, 10-Substrate Best Mode for Carrying Out the Invention As a specific example of the above-described element, the following element configuration examples can be considered.

(1) Anode / P-type semiconductor band (PS) / Emission area (Em)
/ Cathode (2) Anode / PS / E-barrier region (eB) / Em / Cathode (3) Anode / PS-eB / Em / n-type semiconductor band / (NS) /
Cathode (4) Anode / P-S / eB / Em / Hole Barrier Area (hB) / N-S / Cathode (5) Anode / PS-Em / hB / Cathode (6) Anode / PS- Em / hB / N−S / cathode Note) Em, eB and hB are all included in the insulator band.
In particular, (3), (4) and (6) are MSISM types, which are considered to be developed types of the MIS type.

Hereinafter, the organic electroluminescent device according to the present invention will be described for each component.

Substrate It is preferable that each of the above elements is supported by a substrate. The material of the substrate is not particularly limited, and materials conventionally used for organic EL elements, for example, glass, transparent plastic, quartz, and the like can be used.

Electrode (Anode) As the anode in the organic EL device of the present invention, it is preferable to use a material having a high work function (for example, 4 eV or more) made of a metal, an alloy, an electrically conductive compound, or a mixture thereof. A specific example of such a material is A
u, CuI, ITO, SnO ₂ , ZnO and the like. The anode is produced by, for example, performing a process such as vapor deposition or sputtering on these materials to form a thin film on the surface thereof.

When taking out light from this electrode, set the transmittance to 10%
Preferably, the sheet resistance of the electrode is several hundred Ω / □ or less. In addition, the thin film
Although it depends on the material, it is usually 500 nm or less, preferably 10 to 22 n
It is selected in the range of m.

Electrode (cathode) On the other hand, the cathode has a small work function (for example, 4e
(V or less) metals, alloys, electrically conductive compounds and mixtures thereof are used as electrode materials. Specific examples of such an electrode material include sodium, sodium-
Potassium alloy, magnesium, lithium, magnesium / copper mixture, Al / AlO ₃ , yttrium, indium and the like. A cathode can be manufactured by performing a process such as evaporation or sputtering on these electrode materials to form a thin film.

Further, the sheet resistance as an electrode is preferably several hundred Ω / □ or less, and the film thickness is usually 500 nm or less, preferably 10 to 200 nm.
Is selected in the range.

In the device of the present invention, it is preferable that one of the above-described anode and cathode is transparent or translucent. Thereby, the emitted light can be efficiently transmitted and extracted.

Organic semiconductor band composed of oligomers of conductive polymers Conductive polymers of main chain conjugate type are known to be semiconductors in an undoped state, such as polyacetylene, polythiophene, polypyrrole, polyphenylenevinylene, polyparaphenylene, and polyaniline. Is synthesized by a chemical synthesis method, electrolytic polymerization, or the like. Oligomers of these conductive polymers and copolymers thereof (eg, polyphenylenevinylene) include those which are semiconductors such as thiophene oligomers and polytriphenylamine oligomers. While thin films cannot be formed by the vapor deposition method, thin films can be easily formed by the vapor deposition method (Synthetic Metals, Vol. 28, p. C705, 1989, U.S. Pat. No. 4,565,860 and Synthetic Metals,
25, page 121, 1988). Then, the thin film formed by vapor deposition is superior to the conductive polymer formed by the electrolytic polymerization method in the thin film quality, the surface is smooth, and the number of pinballs is small.

When a semiconductor zone is formed by oligomers of these conductive polymers, and is preferably used as a thin film layer sandwiched between an electrode and an insulating zone, it has been found that significant charge injection occurs from the semiconductor zone to the insulator zone when electrolysis is applied. Was done.
When PS (P-type semiconductor band) is used, hole injection occurs in the insulator band, while when NS (N-type semiconductor band) is used, electron injection occurs in the insulator band. When this band is a thin film layer, the thin film preferably has a thickness of 10 nm to
100 nm. If it is less than 10 nm, it becomes difficult to form a thin film, which is not preferable.

When light is extracted through this thin film layer,
The thickness of the thin film is preferably 100 nm or less. Above that, light is absorbed by the thin film, and the amount of extracted light is reduced.

Various thinning methods such as spin coating, casting, LB, and vacuum deposition can be used as a method for forming the thin film layer in the semiconductor zone. The vacuum deposition method is most preferable in that a uniform thin film without pinholes can be formed.

When a thin film layer composed of the above-mentioned semiconductor zone is formed using a vacuum deposition method, the following processing is performed. First, a vacuum tank is prepared, and a resistance heating boat or a crucible is installed therein. The resistance heating boat or crucible can be energized in advance. In this state, the organic compound forming the thin film layer is put into a resistance heating boat or crucible in a vacuum chamber. Thereafter, the vacuum chamber is evacuated to a vacuum of preferably 10 ^-5 to 10 ^-3 Pa, and the temperature is increased by supplying electricity to the boat or crucible. At this time, from the crystal oscillator type film thickness monitor,
The temperature is increased so that the compound sublimates at a deposition rate of 0.01 to 50 nm / sec. This temperature is substantially determined by the type of the organic compound used and the desired deposition temperature, but it is 150 ° C. to 500 ° C.
In the range of ° C. The substrate temperature is set to a temperature at which a thin film made of an organic compound deposited by vapor deposition is brought into a desired state. In addition, care must be taken to prevent the deposition temperature from becoming excessively high. Otherwise, decomposition of the organic compounds will occur, which will adversely affect the performance of the semiconductor zone.

The above evaporation conditions are typical examples, and the sublimation temperature of the organic compound used, selection of the target thin film state (for example, microcrystalline system, amorphousness, etc.), thin film property (flatness), and crystal orientation state For example, it is determined under specific conditions.

Among the above conductive polymer oligomers, thiophene-containing oligomers are preferred. These are particularly preferable because they can be vacuum-deposited and α-quinkthiophene and α-sexithiophene can be easily formed even in a thin film having a thickness of 100 nm or less. Furthermore, α-sexithiophene is particularly suitable in view of keeping a thin film. Polythiophene oligomers such as α-kinkthiophene can be synthesized according to known literature (Synthetic Metal
s, vol. 28, p. C705, 1989 and references cited therein).

The important point is that these synthesized products are further purified. α-kinkthiophene can be purified by recrystallization from a solution, but α-sexithiophene (moreover, a multimer, etc.) is hardly soluble, cannot be purified by recrystallization, and is subjected to temperature gradient sublimation purification. (Guttman and Lyons, Organic semiconductor Part
A, Robert Krieger Publishing Company, Florida, 1981,
Chapter 3). Similarly, oligomers that are multimers are preferably used in the above-described sublimation purification because they are hardly soluble.

Furthermore, various substituents, for example, an alkyl group, a cyclohexyl group, and an alkoxy group can be introduced into the oligomer of the conductive polymer as long as the properties as a semiconductor zone are not impaired. With this introduction, the improvement of thin film properties,
It is possible to improve the ease of charge injection from the anode and the cathode (increase the ohmic junction property). Further, particularly, an oligomer of a copolymer of the above conductive polymer, for example, It is possible to widen the gap by using the method and the like to improve the charge injection into the insulator band.

Examples of the conductive polymer oligomer that can be used as the semiconductor band are as follows.

Here, in the examples (1) to (14), Or including Have P-type semiconductor properties, Had N-type semiconductor properties. The compounds (1) to (14) can be generally synthesized by the Grignard method (see Examples 10 and 12) as shown in Examples 10 and 12. However, compound (12) is synthesized by the Wittig method.

Organic insulator zone This zone has a lower conductivity than the semiconductor zone. This band contains a light emitting region made of an organic fluorescent compound. This light-emitting region is a thin film layer, may be in contact with another region, a thin film layer, to form an insulating band, may be a granular region dispersed in another region, or may be a region other than the other region. Mixed insulating bands may be used. The other region described here is an electron barrier region or a hole barrier region.

When an electron barrier region is used, a thin film layer is preferably used, and a light emitting layer which is a thin film layer is more preferably used.

Note that the light emitting region may be an insulator band together with a region other than the electron barrier region, for example, a region formed of a mere binder-like material (binder). In that case, it is preferable that injection of charges into the light-emitting region and transport of charges in the light-emitting region be not hindered. In addition, a hole transporting region that simply transports holes and an electron transporting region that simply transports electrons exist as the regions corresponding to the above.

Light-Emitting Region This region is made of an organic compound having fluorescence in a solid state, and is preferably a thin film (light-emitting layer) having a thickness of about 5 nm to 5 μm, and further has the following three functions.

(1) Anode, P-S (P-type semiconductor band) or
An injection function capable of injecting holes from outside such as eB (electron obstruction region), and also capable of injecting electrons from outside such as a cathode or NS (N-type semiconductor band).

(2) A transport function for moving the injected charges by the force of an electric field.

(3) A light-emitting function that provides a field for recombination of electrons and holes, and connects this to light emission.

It should be noted that there may be a difference between the ease of hole injection and the ease of electron injection, and a difference between the transport abilities represented by the mobility of holes and electrons.

In the above-described injection function, the ionization energy of the light emitting layer is preferably 6.0 eV or less from the viewpoint that holes can be relatively easily injected by selecting an appropriate anode material. On the other hand, the electron affinity is preferably 2.5 eV or more, since it is relatively easy to inject electrons when an appropriate cathode material is selected.

As for the light emitting function, it is desirable that the solid state has strong fluorescence. This is because such a light emitting layer has a large ability to convert the excited state of the compound itself, its aggregate or crystal, etc. forming the light emitting layer.

The organic compound used in the light-emitting region in the organic EL device of the present invention is not particularly limited as long as it has a thin film forming property having the above properties, and any one can be selected from conventionally known compounds. Can be used. As the organic compound, for example, polycyclic condensed aromatic compounds, benzothiazole-based, benzimidazole-based, benzothiazole-based fluorescent whitening agents, metal-chelated oxanoid compounds, distyrylbenzene-based compounds, and the like can be used. .

Examples of the above-mentioned condensed polycyclic aromatic compound include a condensed ring light-emitting substance containing an anthracene, naphthalene, phenanthrene, pyrene, chrysene, and perylene skeleton, and other condensed ring light-emitting substances containing about eight condensed rings. Can be.

Further, as the fluorescent whitening agent of each system described above, for example, those described in JP-A-59-194393 can be used,
Representative examples are 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-benzooxazolyl) thiophene; 4,4'-bis (2-benzoxazolyl ) Biphenyl; 5-methyl-2- [2- [4- (5
Benzoxazoles such as -methyl-2-benzoxazolyl) phenyl] vinyl] benzoxazole; 2- [2- (4-chlorophenyl) vinyl] naphtho [1,2-d] oxazole, 2,2 '-( benzothiazoles such as p-phenylenedivinylene) -bisbenzothiazole;
Examples of the fluorescent whitening agent include benzoimidazoles such as 2- [2- [4- (2-benzimidazolyl) phenyl] vinyl] benzimidazole; 2- [2- (4-carboxyphenyl) vinyl] benzimidazole.

As the metal chelated oxanoid compound,
For example, those described in JP-A-63-295695 can be used. As typical examples, tris (8-quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo [f] -8-quinolinol) zinc, bis (2-methyl-8-quinolinolate) aluminum oxide, tris ( 8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, lithium 8-quinolinol, tris (5-chloro-
8-quinolinol) gallium, bis (5-chloro-8-
Quinolinol) calcim, poly [zinc (II) -bis (8
-Hydroxy-5-quinolinonyl) methane] and dilithium epindridione.

Further, as the distyrylbenzene-based compound,
For example, those described in Japanese Patent Application No. 1-029681 can be used.

Further, besides the above-mentioned compounds, for example, phthaloperinone derivatives (JSPS, Photoelectric Interconversion, 125th Committee,
Materials from the 129th meeting), stilbene compounds (Japanese Patent Application No. Sho 62)
−312356, 63-80257, 63-313932, 63-3
No. 08859), coumarin compounds (Japanese Patent Application No. 64-009995,
Japanese Patent Application Nos. 1-054957, 1-060665, 1-068387
And No. 1-075035) and distyrylpyrazine derivatives (Japanese Patent Application No. 4-075936) can also be used in the light emitting layer.

The light-emitting layer composed of the above-mentioned organic compound may be used, if desired.
It may take a laminated structure of more than one layer, U.S. Pat.
As disclosed in the specification of Japanese Patent No. 292, it may be formed from a host substance and a fluorescent substance. In this case, the host material is a thin film-like layer and has a part of an injection function, a transport function, and a light emitting function among the functions of the light emitting region. On the other hand, a trace amount of the fluorescent material is contained in the host material layer. (Several mole% or less), and has only a part of the light emitting function of emitting light in response to the binding of electrons and holes.

Further, the organic compound used for the light emitting region may be a compound having no thin film property, for example, 1,4-diphenyl-1,3
-Butadiene, 1,1,4,4-tetraphenyl-1,3-butadiene; tetraphenylcyclopentadiene and the like can also be used.

The method for forming the light-emitting layer, which is the light-emitting region, may be in accordance with the above-described method for forming a semiconductor band as a thin film layer, but it is more preferable to use a vapor deposition method. The formation of the thin film by the vapor deposition method may be performed in accordance with the description when the semiconductor zone is formed into a thin film by vapor deposition.

Electron barrier region This region has the function of retaining electrons transported inside Em to the anode side when an electric field is applied, within Em, and has an electron affinity smaller than the electron affinity (solid phase) of the organic compound in the light emitting region. (Solid phase). The difference between the electron affinities is preferably 0.5 eV or more.

The element configuration including this region has higher luminous efficiency than the element configuration example (1) described above, and provides a high-luminance and high-efficiency element. The electron barrier region is used as an electron barrier layer, which is preferably a thin film layer. Many of the light-emitting layers are used to keep electrons in the light-emitting region adjacent thereto.
Since it has an electron affinity around 3 eV, at least 3 eV or less,
It is noted that there is an additional property that it preferably has an electron affinity of 2.6 eV or less. This means that the barrier against electrons does not necessarily have to have the property of not transporting electrons, and it is sufficient that electrons are hardly injected from the light emitting region. (Apply. Phys. Lett. 51, 913, 198
7) is significantly different from the case where a triphenylamine derivative having no electron transporting property is required.

Preferred examples of the material of the electron barrier region include the following general formula (I).

General formula (I) Here, X is the following A, B or C, and a combination of A, B and C is -ABBA-, -BBA, -CAB, -C
-BB-, -CCCC- or the like. Here, Y and Y 'are -N = or -CR' =, and Z is -O-,
-S-, NR'-. Here, R 'is a hydrogen atom, an alkyl group, an aryl group, or the like.

[Where R ¹ and R ² are independently hydrogen, Ar, an alkyl group or a cyclohexyl group. Ar is an aryl group such as phenyl and naphthyl. Various substituents may be introduced into the compound of the above general formula (I) as long as the properties of the material of the electron barrier region are preserved, but an alkyl group, an aryl group, an alkoxy group and the like are preferable. .

further, Can also be used as a material for the electron barrier region.

The electron barrier layer made of the above-mentioned material may be a microcrystalline thin film or amorphous, but is limited by a need to have good thin film properties. In the case of a microcrystalline thin film, an organic crystal has a hole transporting property as long as it is an aromatic compound (M.
Pope and CESenberg, Electronic Processes in Org
anic Crystals, Clarenndon Press, New York, 1982,337
Page), unlike the prior art hole transport compounds, it is not necessary to have a specific molecular structure, for example, an aromatic amine, and as described above, it is only necessary to satisfy certain conditions of electron affinity. Give range expansion.

Electron barrier materials with poor thin film properties should not be used because they do not function as barrier layers due to pinholes.

More important points in selecting a material for the electron barrier region are the material for the light emitting region and the exciplex (excited complex).
Is to choose one that does not form In many cases, exciplexes result in reduced efficiency of EL emission and longer wavelength emission. Therefore, when an insulator band is formed in such a combination as to form an exciplex and a MISM or MSISM element is obtained, it is easy to obtain EL emission that can be visually recognized under normal illumination, but the luminous efficiency is small and practical. Often not.

In the device configuration of the present invention, since the material used for the electron barrier layer has a wide selection range as described above and does not need to have an amine component having a donor property, the exciplex property in the electron barrier layer / light emitting layer is not required. Can easily be avoided, and an element having high luminous efficiency can be obtained.
Therefore, the selection range of the material of the light emitting region is expanded, and red, blue,
It can provide the possibility of realizing elements of various emission colors such as yellow, green, purple, and orange.

The electron barrier region is preferably used as a thin film layer, and more preferably forms an insulator band together with the light emitting region formed as a thin film layer. The method of forming the electron barrier region (electron barrier layer) as this thin film layer may be in accordance with the above-described method of forming the semiconductor zone as a thin film layer, but it is more preferable to use an evaporation method. In this case, the above description for forming the semiconductor zone by vapor deposition to form a semiconductor layer may be used. At this time, the film thickness is preferably from 0 nm to 50 nm, particularly preferably 5 nm.
nm to 30 nm.

Examples of compounds that can be used for the electron barrier region are as follows.

Here, the compounds (1) to (5) are commercially available (manufactured by Lambda Physics), and the compounds (6) to (5) are
(8) is a commercially available product manufactured by Aldrich, and is easily available. Compounds (9) and (10) are known and can be easily synthesized. The compounds (11) and (12) can be easily synthesized according to the Grignard method, and the compounds (14) to (16) can be easily synthesized according to the Wittig method.

Hole barrier region The concept of an electron barrier is a hole barrier region.
This region retains the function of retaining holes transported in Em to the cathode side in Em when an electric field is applied, and has a higher ionization energy (solid phase) than that of the light emitting region. It consists of Therefore, if the absolute ionization energy is 5.9 eV or more, it is used because it is larger than most compounds that form a light emitting region. The element configuration including this region is the element configuration (1)
In some cases, the luminous efficiency may increase. Preferred examples of the material of the hole barrier region include those of the general formula (II).

General formula (II) Any combination of -A-, -B-, -C-, -AB-,
-A-C-, -A-D-A-, -A-D-, -B-C
-, -C-D-, -D-D-, -D-C-A- and the like.

The compound of the general formula (II) may be substituted with various substituents such as an alkyl group and an aryl group as long as the properties are maintained. Examples of compounds that can be used are as follows.

Device manufacturing method (1) Anode / semiconductor band / light-emitting region: production of cathode type device: A thin film made of a material for an anode is deposited on a suitable substrate so as to have a thickness of 1 μm or less, preferably 10 to 200 nm. ,
It is formed by a method such as sputtering. After preparing the anode, the material of the semiconductor zone is preferably formed as a thin film layer to provide the semiconductor zone.

Spin coating method, casting method,
Although there are vapor deposition methods and the like, a vapor deposition method is preferable in order to obtain a uniform, smooth, and pinhole-free film. When this evaporation method is used, the conditions are as described above. The thickness is preferably 100 nm or less when light emission is viewed through a semiconductor band, and is preferably 10 nm or more in order to avoid difficulty in forming a thin film.

Further, a light emitting region, preferably a thin film, is formed on this layer in the same manner as in the semiconductor zone. Preferably,
At this time, the thin film has a thickness of 5 nm to 5 μm, particularly preferably 30 nm to 1 μm.
50 nm. Further, a cathode material is thinned thereon by a sputtering method or a vapor deposition method, and an organic EL element having a desired MISM configuration is obtained.

The EL element may be formed by forming the cathode, the light emitting layer, the semiconductor layer, and the anode in this order.

(2) Preparation of anode / semiconductor band / electron barrier region / light emitting region / cathode type device: An anode and a semiconductor layer are formed in the same manner as in (1), and an electron barrier material is further formed on the semiconductor band. In the same manner as in the above method, the film is thinned to form an electron barrier layer. The thin film at this time is preferably 0 to 50 nm, particularly preferably 5 nm to 30 nm.
It is. Further, a light emitting layer and a cathode are sequentially formed in the same manner as in (1) to obtain a desired EL device.

The order may be reversed, and the cathode, the light emitting layer, the electron barrier layer, the semiconductor layer, and the anode may be formed in this order.

(3) In the case of other device configurations such as anode / semiconductor band / light emitting region / semiconductor band / cathode, the device may be manufactured according to (1) or (2). For other element configurations (1),
The device is manufactured according to (2).

 Next, the light emitting mechanism of the organic EL element will be described.

FIG. 1 is a view schematically showing an anode / P-type semiconductor zone / insulator zone / cathode type element which is an example of an organic EL element. In FIG. 1, an anode 12 and a P-type semiconductor band are formed on a substrate 10.
14, the insulator zone 18, and the cathode 20 are joined in order.

FIG. 2 shows a state when no electric field is applied to the element. Holes (+) are present in the P-type semiconductor zone 14, while no charge is present in the insulator zone 18.

FIG. 3 shows an initial state of the device when a positive potential is applied to the anode 12 and a negative potential is applied to the cathode 20. Holes present in the P-type semiconductor zone 14 are injected into the insulator zone 18. At the same time, the depleted holes are promptly supplied from the anode 12. On the other hand, electrons (−) are injected from the cathode 20 into the insulator zone 18.

FIG. 4 shows a state immediately after FIG. The state shown in FIG. 3 is immediately shifted to this state. The holes in the insulator zone 18 move toward the interface with the cathode 20. At the same time, electrons injected from the cathode 20 into the insulator zone 18 are P
It moves toward the interface with the mold semiconductor zone 14. In this charge transfer process, holes and electrons meet and recombine, creating an excited state in the light-emitting region. Is formed. This excited state is canceled by light emission,
Light is emitted from the device. An undesired condition may occur in which electrons injected into the insulator zone 18 from the cathode 20 sometimes pass through the insulating zone 18 and into the P-type semiconductor region 14. If this is desired to be prevented, an electron barrier region that contacts the P-type semiconductor zone 14 may be formed in the insulator zone 18. On the other hand, there may be an undesirable case in which holes injected from the P-type semiconductor zone 14 into the insulator zone 18 pass through the insulator zone 18 to the cathode 20. If you want to prevent this, a cathode
What is necessary is just to form the hole barrier area | region which contacts 20.

Operating state of the organic EL element When a DC voltage is applied to the organic EL element of the present invention obtained in this manner, when a voltage of about 1 to 30 V is applied with the positive polarity of the anode and the negative polarity of the cathode, light emission occurs. Can be observed from the transparent or translucent electrode side. Also, even if a voltage is applied with the opposite polarity, no direct current flows and no light emission occurs because the element is a diode. Furthermore, when applying an AC voltage,
It emits light only when the anode becomes + and the cathode becomes-.
The waveform of the applied alternating current may be arbitrary.

Synthesis Example 1 (Synthesis of α-sexithiophene) Known literature (eg, HETEROCYCLES, Vol. 20, No. 10, 19)
37, 1983) to obtain a red-black powder.
This was purified by a sublimation purification method to obtain a dark red powder. This powder has a melting point of 304 ° C. to 306 ° C., and has a m / e = 4 in FD mass.
94 and was identified as α-sexithiophene.

Synthesis Example 2 (Synthesis of α-kinkthiophene) Known literature (eg, Tetrahedron, No. 38, p. 3347, 1985)
Year) and recrystallized from a THF solution to obtain a dark orange powder. This product had a melting point of 256.5 to 258 ° C and was mainly FD mass m / e = 412, but it was found that there were some pentamers or more multimers. Further, the powder was purified by a sublimation purification method to obtain a light orange powder, and the m / e was measured to be 412 using an FD mass. There was no peak due to the multimer, and it was identified as α-quinkthiophene.

Hereinafter, these will be described with reference to some examples, but the present invention is not limited thereto. As shown in the examples, various luminescent colors can reach with high luminance and high luminous efficiency. It is emphasized that this is a result of using the device configuration of the present invention and avoiding the exciplex. Therefore, if the device configuration of the present invention is used,
It is clear that good results are obtained with various materials.

Example 1 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning.

The transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum vapor deposition device. On the other hand, α-sexithiophene (T6) was placed in a molybdenum resistance heating boat, and then placed in another molybdenum resistance heating boat.
(2'-N-methylbenzimidazolyl) -7-N, N-
Diethylaminocoumarin (KU30) was charged and attached to a vacuum evaporation apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 3 × 10 ⁻⁴ Pa, and the boat containing T6 was energized and heated to 297 ° C., and the deposition rate was 0.1 to 0.1 Pa.
Evaporation was performed on a transparent support substrate at a rate of 0.3 nm / sec to form a semiconductor band having a thickness of 20 nm. The boat containing KU30 was energized and
It was heated to 0 ° C. and vapor-deposited at a vapor deposition rate of 0.1 to 0.3 nm / sec on the semiconductor band on the transparent support substrate to obtain an 80 nm-thick insulator band (also a light-emitting region). The temperature of the substrate during each deposition was room temperature.

Thereafter, the vacuum chamber was opened, a stainless steel mask was placed on the light-emitting layer, 3 g of magnesium was put in a molybdenum resistance heating boat, copper was put in the crucible of the electron beam evaporation apparatus, and the vacuum tank was set up again. The pressure was reduced to × 10 ⁻⁴ Pa.

Thereafter, electricity was supplied to the boat containing magnesium, and magnesium was deposited at a deposition rate of 4 to 5 nm / sec. At the same time, simultaneously heat the copper with an electron beam and evaporate at a rate of 0.1 to 0.2 nm.
The copper was vapor-deposited at a rate of / sec, whereby the magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When the ITO electrode of this device was used as a positive electrode, the opposite electrode made of a mixture of Mg and copper was used as a negative electrode, and a DC voltage of 10 V was applied between the ^two electrodes, an electrode having a current density of 133 mA / cm2 flowed and green light was emitted. . At this time, the maximum emission wavelength was 502 nm, the CIE chromaticity coordinates were x = 0.19, y = 0.49, the emission luminance was 136 cd / m ² , and the emission efficiency was 0.03 lm / W.

Example 2 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning.

The transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum vapor deposition device. On the other hand, α-quinkthiophene (T5) was put into a molybdenum resistance heating boat, KU30 was put into another molybdenum resistance heating boat, and they were incorporated in a vacuum evaporation apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and electricity was supplied to the boat containing T5 to heat it.
Vapor deposition was performed on the transparent support substrate at a rate of nm / sec to form a semiconductor band with a thickness of 20 nm.

Further, the boat containing KU30 was energized, heated to 220 ° C., and vapor-deposited on the semiconductor band on the transparent support substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec to obtain a light-emitting layer having a thickness of 80 nm. The temperature of the substrate during each deposition was room temperature.

Thereafter, the vacuum chamber was opened, and a stainless steel mask was placed on the light emitting layer. Further, 3 g of magnesium was placed in a molybdenum resistance heating boat, copper was placed in a crucible of an electron beam evaporation apparatus, and the pressure in the vacuum chamber was reduced again to 1.2 × 10 ⁻⁴ Pa.

Thereafter, electricity was supplied to the boat containing magnesium, and magnesium was deposited at a deposition rate of 5 to 6 nm / sec. At the same time, the copper was vapor-deposited at a rate of 0.1 to 0.3 nm / sec by heating the copper with an electron beam, and then the magnesium was mixed with the copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When the ITO electrode of this device was used as a positive electrode, the counter electrode made of a mixture of Mg and copper was used as a negative electrode, and a direct current of 5 V was applied between the two electrodes, green light emission was clearly observed under ordinary illumination. However, when measured 3 hours later, the thin film portion made of T5 became cloudy, indicating that the thin film property was lost.

Example 3 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning.

The transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum vapor deposition device. On the other hand, α-sexithiophene (T6) was placed in a molybdenum resistance heating boat, and 2- (4-) was added to another molybdenum resistance heating boat.
Biphenylyl) -5- (4-t-butylphenyl) -1,
3,4-Oxadiazole (t-BuPBD) was charged, and another boat was charged with KU30, and they were attached to a vacuum deposition apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 3 × 10 ⁻⁴ Pa, and the boat containing T6 was energized and heated, and the deposition rate was 0.1 to 0.3 nm /
In seconds, it was vapor-deposited on a transparent support substrate to form a semiconductor band with a thickness of 20 nm. Further, the boat containing t-BuPBD is energized for 1
It was heated to 64 ° C. and deposited on the semiconductor zone on the transparent support substrate to obtain a 20 nm-thick insulator zone (electron barrier region).

Further, the boat containing the KU30 was energized and heated, and the semiconductor band on the transparent support substrate was deposited at a deposition rate of 0.1 to 0.3 nm / sec.
Evaporation was performed on the electron barrier region to obtain an insulator region (light-emitting region) having a thickness of 60 nm. The temperature of the substrate during each deposition was room temperature.

After this, the vacuum chamber was opened, a stainless steel mask was placed on the light emitting layer, 3 g of magnesium was put into a molybdenum resistance boat, copper was put into the crucible of the electron beam evaporation apparatus, and the vacuum tank was opened again. The pressure was reduced to 2 × 10 ⁻⁴ Pa. Thereafter, the boat containing magnesium is energized, and the deposition rate is 4 to
Magnesium was deposited at 5 nm / sec. At this time, at the same time, copper was heated by an electron beam to deposit copper at 0.1 nm / second, and copper was mixed with the above magnesium to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When the ITO electrode of this device was used as a positive electrode, the opposite electrode made of a mixture of Mg and copper was used as a negative electrode, and when DC 12 V was applied between both electrodes, a current density of 80 mA / cm ² flowed, and green light was emitted. . At this time, the maximum emission wavelength was 493 nm: the CIE chromaticity coordinates were x = 0.18, y = 0.44, the emission luminance was 426 cd / m ² , and the emission efficiency was 0.14 lm / W.

Example 4 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning. This transparent support substrate is dried with dry nitrogen gas,
It was fixed to a substrate holder of a commercially available vacuum evaporation apparatus. on the other hand,
Add α-sexithiophene (T6) to a molybdenum resistance heating boat and add 3,3 to another molybdenum resistance heating boat.
Add 5,3 ", 5" -tetra-t-butyl-p-sexiphenyl (TBS) and add 1,4-bis (2,2
-Di-p-tolylvinyl) benzene (DTVB) and charged them to a vacuum deposition apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 3 × 10 ⁻⁴ Pa, the boat containing T6 was energized and heated, and was deposited on a transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec. Semiconductor band. Furthermore, energize and heat the boat containing TBS,
Deposited on the semiconductor zone on the transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec., A 20 nm thick insulator zone (electron barrier region)
I got Further, the boat containing the DTVB is energized and heated, and is vapor-deposited on the semiconductor band / electron barrier region on the transparent support substrate at a vapor deposition rate of 0.1 to 0.5 nm / sec. ) Got. The temperature of the substrate during each deposition was room temperature.

After this, open the vacuum chamber, further set a stainless steel mask on the light emitting layer, put 3 g of magnesium in a molybdenum resistance heating boat, put copper in the crucible of the electron beam evaporation apparatus, and reopen the vacuum chamber. The pressure was reduced to 2 × 10 ⁻⁴ Pa. After that, power is supplied to the boat containing magnesium, and the deposition rate is 4
Magnesium was deposited at 55 nm / sec. At the same time, the copper is heated by the electron beam at a deposition rate of 0.1 to 0.3 nm /
The copper was vapor-deposited in seconds, whereby the magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When the ITO electrode of this device was used as a positive electrode, the opposite electrode made of a mixture of Mg and copper was used as a negative electrode, and a DC current of 8.3 mA / cm2 flowed when a direct current of 14 V was applied between the ^two electrodes, a blue-green stable Luminescence was obtained. The emission maximum wavelength at this time is 487 nm, CIE
The chromaticity coordinates were x = 0.15, y = 0.28, the luminance was 80 cd / m ² , and the luminous efficiency was 0.22 lm / W. When the voltage was further increased to 17.5 V, the light emission luminance was 396 cd / m ² when the current density was 73 mA / cm ² . When the applied voltage was further increased, green light emission of 1000 cd / m ² or more was obtained.

Comparative Example 1 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning. This transparent support substrate is dried with dry nitrogen gas,
It was fixed to a substrate holder of a commercially available vacuum evaporation apparatus. on the other hand,
N, N'-diphenyl- molybdenum resistance heating boat
Put N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (TPD), put KU30 in another molybdenum resistance heating boat, and put them in a vacuum evaporation system Attached to.

Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, the boat containing the TPD was energized and heated to 220 ° C., and the deposition rate was set to 0.1.
Vapor deposition was performed on the transparent support substrate at a rate of about 0.3 nm / sec to a film thickness of 100 nm. Further, the boat containing KU30 was energized and heated to 235 ° C., and the T on the transparent support substrate was deposited at a deposition rate of 0.1 to 0.3 nm / sec.
Evaporation was performed on the PD layer to obtain a KU30 layer having a thickness of 100 nm. The temperature of the substrate during each deposition was room temperature.

After this, the vacuum chamber was opened, a stainless steel mask was placed on the light-emitting chamber, 3 g of magnesium was placed in a molybdenum resistance heating boat, copper was placed in the crucible of the electron beam evaporation apparatus, and the vacuum tank was opened again. The pressure was reduced to 2 × 10 ⁻⁴ Pa.

Thereafter, electricity was supplied to the boat containing magnesium, and magnesium was deposited at a deposition rate of 4 to 5 nm / sec. At this time, simultaneously, the copper is heated by the electron beam and the deposition rate is 0.2 to 0.3.
The copper was vapor-deposited at nm / sec, whereby the magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

The ITO electrode of this device was used as a positive electrode, the counter electrode made of a mixture of Mg and copper was used as a negative electrode, and a current of 87 mA / cm2 flowed when a direct current of 20 V was applied between the ^two electrodes. . At this time, the maximum emission wavelength was 510 nm, the emission luminance was 440 cd / m ² , and the emission efficiency was 0.08 lm / W.

Comparative Example 2 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm used as a transparent electrode was used as a transparent support substrate, and this was ultrasonically cleaned with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning. This transparent support substrate is dried with dry nitrogen gas,
It was fixed to a substrate holder of a commercially available vacuum evaporation apparatus. on the other hand,
The TPD was placed in a molybdenum resistance heating boat, the MPVB was placed in another molybdenum resistance heating boat, and these were attached to a vacuum evaporation apparatus.

Then, the pressure in the vacuum chamber was reduced to 1 × 10 ^-4 Pa, and the boat containing the TPD was energized and heated to 220 ° C.
The film was deposited on the transparent support substrate at a rate of 0.1 to 0.3 nm / s to a film thickness of 75 nm.

Further, the boat containing DTVB was energized and heated, and was deposited on the TPD layer on the transparent support substrate at a deposition rate of 0.1 to 0.2 nm / sec to obtain a DTVB layer having a thickness of 60 nm. The temperature of the substrate during each evaporation was room temperature.

After this, the vacuum chamber was opened, a stainless steel mask was placed on the light emitting layer, 3 g of magnesium was put into a molybdenum resistance heating boat, copper was put into the crucible of the electron beam evaporation apparatus, and the vacuum tank was opened again. The pressure was reduced to 2 × 10 ⁻⁴ Pa.

Thereafter, electricity was supplied to the boat containing magnesium, and magnesium was deposited at a deposition rate of 1.7 to 2.8 nm / sec. At the same time, the copper is heated by the electron beam and the deposition rate is 0.03-
Vapor deposition was performed at 0.08 nm / sec, whereby magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When a direct current of 18 V was applied between the ^two electrodes using the ITO electrode of this element as a positive electrode and a negative electrode made of a mixture of Mg and copper as a negative electrode, a current density of 85 mA / cm2 flowed to obtain blue light emission. Was. At this time, the maximum emission wavelength was 487 nm, the emission luminance was 400 cd / m ² , and the emission efficiency was 0.08 lm / W.

When Examples 3 and 4 were compared with Comparative Examples 1 and 2, it was shown that in the Example, luminous efficiency and high luminance equal to or higher than those of the Comparative Example were realized.

Example 5 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) provided with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol for cleaning. This transparent support substrate is dried with dry nitrogen gas,
It was fixed to a substrate holder of a commercially available vacuum evaporation apparatus. on the other hand,
Add α-sexithiophene (T6) to a molybdenum resistance heating boat and add TB to another molybdenum resistance heating boat.
S was put, and KU30 was put in yet another boat, and these were attached to a vacuum evaporation apparatus.

Then, the pressure in the vacuum chamber was reduced to 3 × 10 ⁻⁴ Pa, and the boat containing T6 was energized and heated to 300 ° C., and the deposition rate was set to 0.1.
Vapor deposition was performed on a transparent support substrate at a rate of about 0.3 nm / sec to form a semiconductor band having a film thickness of 20 nm. Further, the boat containing TBS was energized and heated to 150 ° C., deposited at a deposition rate of 0.1 to 0.3 nm / sec on the semiconductor zone on the transparent support substrate, and formed into a 20 nm-thick insulator zone (electron barrier). Area).

Further, the boat containing KU30 is energized and heated to 220 ° C., and is vapor-deposited on a semiconductor band / electron barrier region on a transparent support substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec. (Light emitting region) was obtained. The temperature of the substrate during each evaporation was room temperature.

After that, the vacuum chamber was opened, a stainless steel mask was placed on the light emitting chamber, 3 g of magnesium was put into a molybdenum resistance heating boat, copper was put into the crucible of the electron beam evaporation apparatus, and the vacuum tank was set up again. The pressure was reduced to × 10 ⁻⁴ Pa. After that, the boat containing magnesium was energized and the deposition rate was 4
Magnesium was deposited at 55 nm / sec. At the same time, the copper was heated by an electron beam to deposit the copper at a deposition rate of 0.1 to 0.3 nm / sec. Thereby, the magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When an ITO electrode of this element was used as a positive electrode, and a counter electrode made of a mixture of Mg and copper was used as a negative electrode, when a DC voltage of 13 V was applied between the two electrodes, a current density of 60 mA / cm ² flowed, and green light was emitted. . At this time, the emission maximum wavelength was 502 nm, the CIE chromaticity coordinates were x = 0.22, y = 0.47, the emission luminance was 60 cd / m ² , and the emission efficiency was 0.02 lm / W. In the emission spectrum, the intensity of the tail on the long wavelength side was increased, and contributions other than the emission originating from the KU30 layer (presumed to be due to exciplex) were recognized.

Example 6 A glass substrate (size: 25 mm × 75 mm × 1.1 mm: manufactured by HOYA) with ITO having a thickness of 100 nm to be used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol. The transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum vapor deposition device. On the other hand, α-sexithiophene (T6)
Into another molybdenum resistance heating boat.
Bis- (2-butyloctyloxy) -p-quarterphenyl (BiBuQ) was charged, and another boat was charged with KU30, and these were attached to a vacuum evaporation apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 3 × 10 ⁻⁴ Pa, the boat containing T6 was energized and heated, and the deposition rate was 0.1 to 0.3 nm /
In seconds, it was vapor-deposited on a transparent support substrate to form a semiconductor band having a thickness of 200 nm.

Further, the above-mentioned boat containing BiBuQ is energized and heated, and is deposited on the semiconductor zone on the transparent support substrate at an evaporation rate of 0.1 to 0.3 nm / sec, and a 20 nm-thick insulator zone (electron barrier region). I got

Further, the boat containing KU30 is energized and heated, and the semiconductor band on the transparent support substrate is deposited at a deposition rate of 0.1 to 0.3 nm / sec.
Evaporation was performed on the electron barrier region to obtain a 60 nm-thick insulator band (light-emitting region). The temperature of the substrate during each evaporation was room temperature.

After that, the vacuum chamber was opened, a stainless steel mask was placed on the light emitting chamber, 3 g of magnesium was put in a molybdenum resistance heating boat, copper was put in the crucible of the electron beam evaporation apparatus, and the vacuum tank was set up again. The pressure was reduced to × 10 ⁻⁴ Pa.

Thereafter, electricity was supplied to the boat containing magnesium, and magnesium was deposited at a deposition rate of 4 to 5 nm / sec. At the same time, the copper is heated by the electron beam and the deposition rate is 0.1 to 0.3.
The copper was vapor-deposited at a rate of nm / second, whereby the magnesium was mixed with copper to form a counter electrode.

Thus, the fabrication of the electroluminescent device was completed.

When an ITO electrode of this device was used as a positive electrode, and a counter electrode made of a mixture of Mg and copper was used as a negative electrode, a DC of 15 V was applied between the ^two electrodes. Was obtained. The emission maximum wavelength at this time was 528 nm. Compared to the normal KU30 emission spectrum, the emission spectrum shifted to the longer wavelength side and the emission bandwidth became larger, and the contribution of exciplex-derived emission was recognized.

Example 7 In order to examine the presence or absence of formation of an exciplex of KU30 and TBS or BiBuQ, respective dioxane solutions were prepared, and KU30 and TBS, and KU30 and BiBuQ solutions were mixed, respectively.
Further, it was spread on a microplate and dried and solidified.
Further, irradiation with ultraviolet light in the wavelength range of 360 to 380 nm was performed, and the fluorescent color was examined. As a result, a mixture of KU30 and TBS produced yellow fluorescence, but the fluorescence decreased. Further, it was observed that the fluorescence of the mixed solidified product of KU30 and BiBuQ was remarkably reduced and the fluorescence was yellow fluorescence.

The solid state fluorescence of KU30, TBS, and BiBuQ is green, blue-violet, and purple, respectively, indicating that the fluorescent color of the above-described mixed solid forms an exciplex. KU30 and t-BuPBD, MPVB and TBS did not show exciplex formation. From Examples 3 to 7, it is concluded that it is preferable that the compound used for the electron barrier region does not form an exciplex used for the light-emitting region, from the viewpoint of increasing luminous efficiency. This is because the exciplex formed at the interface between the electron barrier region and the light emitting region becomes a non-radiative recombination field.

Examples 3 to 7 show that the problem of the exciplex can be avoided by selecting the material of the electron barrier region.

Example 8 The ionization energies Ip of the compounds used in the light-emitting region and the electron barrier region used in Examples 1 to 7 were measured by an atmospheric photoelectron spectrometer AC-1 manufactured by Riken Keiki Co., Ltd. Also,
Photocurrent measurement of energy gap Eg (M.Pope and CES
Electronic processes in Organic crystals, by wenberg
Clarennd on Press, New York, 1982, P207). The electron affinity Af was determined by Af = Ip−Eg. Table 1 shows the above results.

As shown in Table 1, the electron barrier region has a smaller electron affinity than the light emitting region. Thereby, a function of retaining electrons in the light emitting layer is generated. Note that the electron barrier region does not need to have the property of not transporting electrons. This is different from the hole injection zone disclosed in JP-A-63-194393. Actually, ITO / TPD / KU30 / t-BuPBD /
The Mg: Cu type EL device showed high brightness and high efficiency light emission at low voltage by KU30. This indicates that electrons are being transported through the t-BuPBD layer.

Example 9 The MISM elements of Examples 1 and 3 to 6 had no pinholes.
To check that it is working properly as a diode,
The commutation ratio was measured. A forward voltage V was applied to the device to measure a current, which was defined as a forward current. Next, a reverse voltage V was applied to measure the current, which was used as a reverse current.
Then, rectification ratio = forward current value / reverse current value.
The results are as shown in Table 2.

As shown in Table 2, MISM with excellent rectification ratio of 10 ³ or more
It turns out that it works as a type diode element.

Example 10 5,5'-bis (2- (5-cyclohexyl) thienyl)
Synthesis of Bithiophene 9.32 g of 2-bromo-5-cyclohexylthiophene was dissolved in 40 ml of anhydrous tetrahydrofuran, and this was added dropwise to 1.4 g of magnesium. After the addition was completed in 15 minutes, the mixture was stirred at 60 ° C. for 1 hour (Grignard reagent synthesis).

Then, in a separate container, 4.9 g of 5,5'-dibromodithienyl was dissolved in 40 ml of anhydrous tetrahydrofuran, and 0.28 g of 1,2-bis (diphenylphosphino) ethane nickel chloride was dissolved.
After the addition, the Grignard reagent synthesized above was added dropwise.

After the dropwise addition, the mixture was stirred under reflux overnight. After the reaction, the reaction solution was poured into a dilute aqueous hydrochloric acid solution, and the precipitated crystals were collected by filtration under reduced pressure.
Washed with 0 ml. Next, sublimation purification was repeated twice, and the mixture was washed by stirring with 300 ml of acetone, filtered, and dried.

3.3 g (yield 43.9%) of orange yellow powder was obtained. Melting point was 240 ° C. From the mass spectrum, only the molecular ion peak m / Z = 494 of the target substance was detected. Table 3 shows the results of elemental analysis and logical values (calculated values).

In addition, their infrared absorption spectra (KBr tablet method)
Is shown in FIG.

From the above, the yellow powder has the following formula 5,5-bis [2- (5-cyclohexyl) thienyl] bithiophene (thiophene oligomer derivative) represented by
Was confirmed.

Example 11 (Lighting that the compound obtained in Example 10 is a P-type organic semiconductor) A transparent glass substrate with ITO (manufactured by HOYA CORPORATION) was immersed in isopropyl alcohol, and ultrasonic cleaning was performed. This was performed for 30 minutes, and then this was sequentially immersed in pure water and an isopropyl alcohol layer, and then dried by blowing dry nitrogen.
Next, the substrate was cleaned for 120 seconds by a UV ozone cleaning apparatus (manufactured by Samco International). Thus, the cleaning process is completed.

Next, the transparent glass with ITO washed above was attached to a substrate holder of a vacuum deposition apparatus manufactured by ULVAC, and further 40
A resistance heating boat (manufactured by molybdenum) containing 0 mg of the powder of the thiophene derivative A (5,5'-bis (2- (5-cyclohexyl) thienyl) bithiophene) was attached to a current-carrying terminal of a vacuum evaporation apparatus. Thereafter, the inside of the vacuum layer was evacuated to 10 ^-5 Torr, and the boat was heated by heating the boat.
An evaporated thin film having a thickness of 1500 mm was formed on the substrate at an evaporation rate of 2 to 4 mm / sec. The film thickness was measured by a stylus-type film thickness meter (Detac 3030, available from ULVAC, Inc.) after the deposition was completed. The vacuum layer was returned to atmospheric pressure, the substrate on which the deposited thin film of the thiophene derivative A was formed was taken out, a stainless steel mask was put on the top of the substrate, and the substrate was mounted again on the substrate holder. Further, aluminum was put into a tungsten filament as another resistance heating source, and the inside of the vacuum layer was again evacuated to 10 ^-5 Torr. Apply electricity to the filament, and evaporate at a rate of 1-4 °
An aluminum electrode having a film thickness of 500 mm / sec was produced.

Through the above steps, a diode element was formed by sequentially laminating an ITO electrode, a thiophene derivative A layer, and an Al electrode on a substrate. The substrate temperature was kept at room temperature throughout the above steps.

The evaluation of the current density (mA / cm ² ) -voltage (V) characteristics in the forward direction was performed as follows. That is, using the ITO electrode as the anode and the Al electrode as the cathode, the DC voltage was increased every 0.2 V, and the current when the voltage was applied was measured with an electrometer (type 617, manufactured by Keithley Co.). The voltage change range was 0-6V. The resulting current density-voltage is shown in FIG. In the voltage range of 1 to 3 V, there was a linear region {current {exp (voltage)}} which is common in MS diodes. (Reference, SMSze, "Physics of Semiconductor," John Wile
y & Sons, 1981, 2nd edition, p89 and 262).

Next, the current density-voltage characteristics in the opposite direction to the above were evaluated using the ITO electrode as a cathode and the Al electrode as an anode. The current when the voltage was applied was measured in the same manner as above. Voltage change range is 0-
It was 6V. The voltage in the opposite direction is indicated by a minus sign.

The current in the reverse direction hardly depends on the voltage, and showed an extremely small value (10 ⁻⁸ A / cm ² or less). The rectification ratio at an applied voltage of ± 6 V was 1.2 × 10 ⁺⁶ . The above results prove that the compound of Example 10 functioned as an organic P-type semiconductor.

Example 12 (Synthesis of thiophene oligomer derivative) Synthesis of 4,4'-bis [5- (2,2-dithienyl)] biphenyl 10.8 g of 5-bromo-2,2'-dithienyl was dissolved in 40 ml of anhydrous tetrahydrofuran, This was added dropwise to 1.6 g of magnesium. After completion of the dropwise addition, the mixture was stirred at 60 ° C. for 1 hour (Grignard reagent synthesis).

Next, 5.5 g of 4,4'-dibromobiphenyl was dissolved in 40 ml of anhydrous tetrahydrofuran, 0.6 g of bis (triphenylphosphine) palladium chloride and 2.37 ml of bis (isobutyl) aluminohydride were added, and the mixture was stirred at room temperature under a nitrogen stream for 30 minutes. did. After the stirring, the previously synthesized Grignard reagent was added dropwise, and the mixture was stirred under reflux overnight.

After the reaction, the reaction solution was poured into a dilute aqueous hydrochloric acid solution, and the precipitated crystals were collected by filtration under reduced pressure, washed with 300 ml of acetone, further washed with stirring with 600 ml of hot benzene, and filtered. The sublimation purification of the obtained crude product was repeated twice, and the obtained crystals were washed by stirring twice with 300 ml of hot benzene, filtered, and dried. As a result, 3.9 g (yield 46%) of a yellow powder was obtained. Of this one
Upon DSC analysis, the melting point was 318 ° C. From the mass spectrum, only the molecular ion peak m / Z = 482 of the target substance was detected. Table 4 shows the results of elemental analysis and logical values (calculated values).

In addition, their infrared absorption spectra (KBr tablet method)
Is shown in FIG.

From the above, the yellow powder has the following formula 4,4'-bis [5- (2,2'-dithienyl)]
It was confirmed to be biphenyl (thiophene oligomer derivative).

Example 13 (Proof that the compound obtained in Example 12 is a P-type organic semiconductor) Instead of the compound obtained in Example 10, the compound of Example 12 was used.
A diode element was produced in the same manner as in Example 11, except that the compound obtained in the above was used, the film thickness was 500 mm, and the deposition rate of the Al electrode was 10 to 20 mm / sec. Further, in the same manner as in Example 11, the current at the time of applying the voltage was measured. The voltage change range was 0 to 4.2V. The resulting current density-voltage characteristics are shown in FIG. Similarly, a linear region {current {exp (voltage)} was clearly present at a voltage of 0.4-1.5V.

Next, in the same manner as in Example 11, the current when a voltage was applied in the reverse direction was measured. The voltage change range was 0 to -4.2V. The voltage in the opposite direction is indicated by a minus sign.

The current in the reverse direction did not depend on the voltage and showed an extremely small value. For example, at an applied voltage of -4.2 V, only a current of 4.0 × 10 ⁻⁹ A / cm ² flows. Therefore, the rectification ratio at an applied voltage of ± 4.2 V was 6 × 10 ⁶ . As described above, this indicates that the compound obtained in Example 12 is a P-type organic semiconductor.

Example 14 A 100-nm-thick glass plate with ITO (size 25 mm × 75 mm × 1.1 mm, manufactured by HOYA) used as a transparent electrode was used as a transparent support substrate, which was subjected to ultrasonic cleaning with isopropyl alcohol for 30 minutes, and further isopropyl alcohol. It was immersed in alcohol, taken out and blow-dried with dry nitrogen. After that, UV ozone cleaning equipment (Samco International, UV300)
For 2 minutes.

The compound obtained in Example 12 was placed in a molybdenum resistance heating boat fixed to a substrate holder of a commercially available vacuum evaporation apparatus, and the electron barrier material represented by Table 5 (Formula D) was placed in another boat. Further, tris (8-quinolinol) aluminum was placed in another boat, and these resistance heating boats were attached to a vacuum evaporation apparatus.

Thereafter, the pressure in the vacuum chamber was reduced to 1 × 10 ⁵ Torr, and
Electric heating of the boat containing the compound of
Vapor deposition was performed at 0.3 nm / sec to form a semiconductor band with a thickness of 20 nm. Next, the boat containing the electron barrier material represented by Table 5 (Formula D) was heated and deposited at a deposition rate of 0.1 to 0.3 nm / sec.
Electron barrier region. Further, the boat was heated in a boat containing tris (8-quinolinol) aluminum, and the deposition rate was set at 0.
Evaporation was performed at a rate of 1 to 0.2 nm / sec to form a light emitting layer having a thickness of 60 nm. The substrate temperature during each deposition was room temperature.

Thereafter, the vacuum chamber was opened, a stainless steel mask was placed on the light-emitting layer, and magnesium was put into a molybdenum resistance heating boat and attached. Further, indium is put into a filament-type resistance heating source, and a vacuum chamber is attached to the heating source.
The pressure was reduced to × 10 ⁻⁶ Torr.

Electric current was supplied to the boat containing magnesium, and Mg was deposited at a deposition rate of 1 nm / sec. At this time, the filament containing indium was energized at the same time, and vapor deposition was performed at a vapor deposition rate of 0.1 nm / second to form an Mg: In electrode with a film thickness of 100 nm. Thus, the fabrication of the electroluminescent device was completed.

When ITO was used as an anode and Mg; In was used as a cathode and a DC voltage of 7 V was applied, a current of 50 mA / cm ² flowed and yellow-green light emission with a luminance of 920 cd / m ² was obtained. The luminous efficiency was 0.83 lm / W.

Example 15 The material of the light emitting layer used was t-BuVPBi (* 6 in Table 5).
A compound up to the light-emitting layer was produced in the same manner as in Example 14, except that the compound was used.

Thereafter, the resistance heating boat containing the t-Bu PBD attached in advance was heated to form a hole barrier region having a thickness of 20 nm. Thereafter, an Mg: In electrode was formed in the same manner as in Example 14.

ITO anode, Mg: the In a negative electrode: were added to DC 9V, current 53 mA / cm ² flows, blue light emission of 1200 cd / cm ² occurs. The luminous efficiency at this time was 0.8 lm / W, which was extremely excellent as a blue EL device.

Examples 16 to 20 In the same manner as in Example 14, an element was manufactured using the materials of the semiconductor band, the electron barrier material, and the material of the light emitting layer shown in Table 5, and a DC voltage was applied in the same manner as described above to apply a current density and an emission intensity. The emission color was evaluated. Table 5 shows the results.

INDUSTRIAL APPLICABILITY According to the present invention, an anode / hole injection layer / light emitting layer / cathode type device using a triphenylamine derivative as an insulator as a hole injection layer can be put to practical use. An EL element having high performance can be obtained. Further, surface light emission is possible, light emission is stable, and the device can be easily manufactured.

Further, it is possible to avoid the problem of exciplex, which causes a decrease in luminous efficiency and a lack of device stability. Further, a light emitting element can be realized in the organic MISM type diode element.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-142081 (JP, A) JP-A-3-77299 (JP, A) JP-A-2-10693 (JP, A) JP-A-2- 12795 (JP, A) JP-A-3-8375 (JP, A) JP-B-2-6767 (JP, B2) POLYMER, 1983, Vol. 24, pp. 748-754 Appl Phys Lett, Vol. 51, No. 12, p913-915 (1987) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 33/00-33/28 C09K 11/06

Claims (4)

(57) [Claims] An organic electroluminescent device comprising an organic semiconductor zone and an organic insulator zone sandwiched between electrodes, having an organic light emitting region in the organic insulator zone and emitting light at a high luminance of 50 cd / m ² or more. In an organic electroluminescent device having an efficiency of 0.02 lm / W or more,
An organic electroluminescent device, wherein the organic semiconductor zone is made of a conductive polymer oligomer. 2. The organic electroluminescent device according to claim 1, further comprising an electron barrier region in the organic insulator zone. 3. The organic electroluminescent device according to claim 1, further comprising a hole barrier region in the organic insulating pair zone. 4. The organic electroluminescent device according to claim 1 carrying a diode action of 10 ² or more rectification ratio during light emission operation.