JP2002025780A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which allows its film formation or lamination by application, capable of being easily manufactured not only as a single layer type but also as a lamination type, and capable of realizing low voltage drive, high luminance, a long service life and of being defect free. SOLUTION: This organic electroluminescent element has organic thin film layers, including at least a luminescent layer and a pair of electrodes formed by catching the organic thin film layer. In this case, the element is characterized in that at least one of the organic thin film layers is a three-dimensionally bridged layer, by using a three-dimensionally bridging charge transporting material and an electron-acceptor material at the same time.

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 using an organic material having a specific structure.

[0002]

2. Description of the Related Art Conventionally, a thin film type electroluminescent device (hereinafter, referred to as a thin film type electroluminescent device)
It may be referred to as “EL element”. ) Are ZnS, CaS, S, which are II-VI compound semiconductors of inorganic materials.
Rn and the like, such as Mn as a luminescence center and rare earth elements (Eu, C
e, Tb, Sm, etc.) are commonly used. EL elements made from such inorganic materials are:
1) AC drive is required (generally 50 to 1000 Hz),
2) High driving voltage (generally about 200 V) 3) It is difficult to achieve full color, and there is a problem particularly with blue color. 4) There is a problem that the cost of the peripheral driving circuit is high.

On the other hand, the organic EL element can greatly reduce the applied voltage, can be easily miniaturized, consumes low power, can emit light in a plane, and can easily emit light in three primary colors. Therefore, research and development have been made as a next-generation light-emitting element. In particular, in order to enhance the luminous efficiency, the efficiency of carrier injection from the electrode was improved by optimizing the type of the electrode, and a hole transport layer composed of an aromatic diamine and a luminous layer composed of an aluminum complex of 8-hydroxyquinoline were provided. Development of an organic electroluminescent device having a laminated structure (Appl. Ph.
ys. Lett. 51, p. 913, 1987), the luminous efficiency has been greatly improved as compared with a conventional EL device using a single crystal such as anthracene. In addition, various materials have been searched to extend the life of the device. For example, porphyrin derivatives and phthalocyanine compounds (Japanese Patent Application Laid-Open No. 63-295695) and star-bust type aromatic triamines (Japanese Patent Application Laid-Open No. -3
No. 08688), hydrazone compounds (Japanese Unexamined Patent Publication No. 4-3)
20483), an alkoxy-substituted aromatic diamine derivative (JP-A-4-220995), p- (9-
With the development of (anthryl) -N, N-di-p-tolylaniline and the like, practical properties have been approached. Further, in addition to the electroluminescent device using a low molecular material as described above, poly (p-phenylenevinylene), poly [2-methoxy-5- (2-ethylhexyloxy)-
1,4-phenylenevinylene], development of EL devices using polymer materials such as poly (3-alkylthiophene),
An element in which a low molecular light emitting material and an electron transfer material are mixed with a polymer such as polyvinyl carbazole is also being developed.

The structure of an organic EL device is based on the structure of anode / organic light emitting layer / cathode, and is provided with a hole injection / transport layer or an electron injection layer as appropriate, for example, anode / hole injection / transport layer / cathode. Known structures include an organic light emitting layer / cathode and an anode / hole injection / transport layer / organic light emitting layer / electron injection layer / cathode.

By the way, the biggest problem of the organic EL device is that
The development of the instability at the time of driving includes a decrease in light emission luminance, an increase in voltage at the time of constant current driving, generation of a non-light emitting portion (dark spot), and the like. Although there are several causes of these instabilities, deterioration of the thin film shape of the organic layer is dominant. It is considered that the deterioration of the thin film shape is caused by crystallization (or aggregation) of the organic amorphous film due to heat generated during element driving.

Further, as a material used for an organic EL device, an organic low-molecular compound or oligomer is conventionally often vacuum-deposited and used. However, these materials have low heat resistance and their improvement has been demanded. On the other hand, from the expectation that the thermal stability will be improved by polymerizing low molecules and the generation of defects due to crystallization etc. can be prevented, attempts have been made to improve the heat resistance using polymers. However, in this case, the hole mobility of the polymer was usually 10 ⁻⁵ cm ² / V · sec or less, and the resistance of the hole injection layer was a problem. Furthermore, attempts have been made to use a mixture of a polymer and an organic low-molecular compound, but also in this case, the hole injection layer has a conductivity of 10 ⁻¹⁰ S · cm ⁻¹ or less, and the resistance is still a problem. Had become.

On the other hand, WO 95/24056 states that
An organic EL device using an all-conjugated polymer for the hole injection layer is disclosed. The all-conjugated polymer is, for example, polyaniline or poly 3,4-ethylene-dioxythiophene. Further, as an element having a similar configuration, there is disclosed an element in which a polyaniline layer is provided on an anode, and a light emitting layer and a cathode are sequentially formed thereon (see International Publication 9).
7/32452). In these devices, the applied voltage can be lowered and the efficiency can be improved, but there are the following problems.

1) Since the material of the hole injection layer is an all-conjugated polymer, it exhibits strong color and is inferior in transparency. Therefore, if the film thickness is increased to 250 nm or more, the light transmittance becomes 3
Loss 0% or more. Accordingly, the thickness of the hole injection layer cannot be increased, the protrusions on the anode and the end of the anode cannot be sufficiently covered, and the element light-emitting surface is likely to have defects, and leaks and short circuits are likely to occur, In the case of an XY matrix type display element, a crosstalk defect was easily generated.

2) An all-conjugated polymer is actually an aggregate of various conductive units, and the effective length of the conjugated system is dispersed, which means that the energy level of the unit for transporting holes is dispersed. Means to do. Therefore, the level that traps holes cannot be essentially avoided, and the hole mobility, which is the hole mobility, was as low as 10 ⁻⁵ cm ² / V · sec or less. For this reason, when all conjugated polymers are used for the hole injection layer, the resistance of the hole injection layer becomes a problem. In particular, when high-intensity pulsed light needs to be emitted, an instantaneous 10 mA /
cm ² ~1A / cm ^2, in some cases it is necessary to energize the pulse current of up to 1 kA / cm ^2. However,
If the hole mobility is 10 ⁻⁵ cm ² / V · sec or less, there is a problem that a voltage drop occurs in the hole injection layer due to resistance and the voltage of the device is increased.

[0010] This is due to the so-called space-limited current phenomenon. To avoid this, it is necessary to improve the hole mobility. 2) There were essential problems as described above. On the other hand, U.S. Pat. No. 3,995,299 discloses the use of an amorphous polymer containing a strong electron-withdrawing substance as a hole injection zone. However, the disclosed amorphous polymer is limited to polyvinyl carbazole, which has a low hole mobility and has the same problem as the above all conjugated polymer. Further, since the π-conjugated system is not spread, the ionization energy is 5.
8eV, which is hard to be oxidized and has conductivity of 10 ^-8 S
There are problems such as the small size of cm -1 or less and the difficulty in injecting holes from the anode. Improvements have been demanded.

On the other hand, in Japanese Patent Application Laid-Open Nos. 11-283750 and 2000-36390, by doping an acceptor into a polymer having a hole transporting unit, the resistance value of the hole injection layer is reduced, and the film can be made thicker. In addition, it has been proposed that a layer can be formed by coating, a defect caused by unevenness on the surface of a substrate is concealed, and a device is stabilized.

[0012]

In the method of inserting a hole injection layer between an electrode (anode) and a hole transport layer, when a porphyrin derivative or a phthalocyanine compound is used as the hole injection layer, these films are used. There is a problem that the spectrum is changed due to light absorption by itself, and the external appearance is colored and becomes invisible. Star-bust type aromatic triallylamine, hydrazone compound, alkoxy-substituted aromatic diamine derivative, p- (9-anthryl) -N, N-di-
Although p-tolylaniline and the like have the advantage of low ionization potential and high transparency, they have poor heat resistance due to low glass transition point and melting point, have poor stability to local heating during continuous driving, and have low brightness and low brightness. Voltage rise becomes a problem.

On the other hand, polythienylenevinylene, poly-p
-For polymer materials such as phenylene vinylene and polyaniline, there is no report on lowering the driving voltage and improving the driving life. Also, a method of doping an acceptor into a polymer having a hole transporting unit is very effective, but on the other hand, there is still a problem in the transportability and film-forming properties of a base polymer, and an element with sufficient performance Has not yet gotten. Furthermore, the method of casting the solution after dissolving it in various solvents, taking advantage of the characteristics of the organic material, has a great merit in terms of manufacturing cost, but in the case of conventional polymers, due to its properties, the upper layer is further applied and laminated. In such a case, the element swells or dissolves and the interface is exposed, so that it has been difficult to produce an element exhibiting stable performance.

That is, the high voltage at the time of driving the organic EL element and the low stability including heat resistance are serious problems for a light source such as a facsimile, a copying machine, and a backlight of a liquid crystal display. In particular, it is not desirable as a display element such as a full-color flat panel display. Further, development of an organic EL device that can be driven at low voltage and high luminous efficiency, has good heat resistance, and can maintain stable luminescent characteristics for a long period of time is desired. . Further, it is desired that the film can be easily formed or laminated by coating from the viewpoint of cost reduction.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects.
That is, an object of the present invention is to be able to form a film or laminate by coating, to easily obtain not only a single layer type but also a laminated type, and to reduce the voltage, increase the brightness, extend the life, and eliminate defects. An object of the present invention is to provide an organic electroluminescent device capable of achieving the following.

[0016]

The above object is achieved by the following means. That is, the present invention provides <1> an organic electroluminescent element having at least an organic thin-film layer including a light-emitting layer, and a pair of electrode pairs sandwiching the organic thin-film layer. An organic electroluminescent device, wherein one layer is a three-dimensionally cross-linked layer using a three-dimensionally cross-linkable charge transport material and an electron-accepting material simultaneously. <2> The three-dimensionally crosslinkable charge transporting material is a charge transporting material having an aromatic amine skeleton having a structure represented by the following general formula (I) as a skeleton having a hole transporting function. An organic electroluminescent device according to <1>.

[0017]

Embedded image

(In the general formula (I), Ar ^{1 to} Ar ⁴ each independently represent a substituted or unsubstituted aryl group. Ar ⁵
Represents a substituted or unsubstituted aryl group or an arylene group. Ar ¹ and Ar ² , and Ar ³ and Ar ⁴ may form a ring. One to four of Ar ^{1 to} Ar ^{5 have} a bond that can be bonded by a covalent bond in the three-dimensionally crosslinked layer. k represents 0 or 1. )

<3> The charge transport material having an aromatic amine skeleton having the structure represented by the general formula (I) has a substituted silicon group containing a hydrolyzable group represented by the following general formula (II). The organic electroluminescent device according to <2>, wherein the organic electroluminescent device is characterized in that:

[0020]

Embedded image

(In the general formula (II), R ₁ represents hydrogen, an alkyl group, a substituted or unsubstituted aryl group, Q represents a hydrolyzable group, and a represents an integer of 1 to 3.)

<4> The electron accepting material is at least one selected from metal halides, Lewis acids, organic acids, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. <1
> To <3>. <5> The organic electroluminescent device according to <4>, wherein the electron-accepting material is a compound represented by the following general formula (III).

[0023]

Embedded image

(In the general formula (III), Y represents a halogen atom. R represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a cyano group, or a nitro group.)

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The organic electroluminescent device of the present invention has an organic thin film layer including at least a light emitting layer, and a pair of electrodes sandwiching the organic thin film layer. At least one layer is a three-dimensionally cross-linked layer (hereinafter, sometimes referred to as a “three-dimensional cross-linked film”) using a three-dimensional cross-linkable charge transport material and an electron-accepting material simultaneously. By using a three-dimensionally crosslinkable charge transport material and an electron-accepting material together, it is possible to form a thick three-dimensionally crosslinked film with excellent film-forming properties, no defects, and excellent charge injection properties. Properties, characteristics and stability can be greatly improved. In addition, compared to a device using a low-molecular-weight amorphous film, the heat resistance of the device is improved by using a three-dimensional cross-linkable charge transporting material that suppresses molecular motion and has a high glass transition temperature as a base of the three-dimensional cross-linked film. It is greatly improved. If a three-dimensionally crosslinked film obtained by using a three-dimensionally crosslinkable charge transporting material is formed first, it becomes stable to a solvent when further laminated and applied thereon. For this reason, the organic electroluminescent device of the present invention can be formed into a film or laminated by coating, so that not only a single-layer type but also a laminated type (separated type) can be easily obtained, and low voltage and high luminance can be obtained. , Longer life and defect-free operation can be achieved.

In the organic electroluminescent device of the present invention, the three-dimensional cross-linked film is formed by using at least a three-dimensional cross-linkable charge transport material and an electron-accepting material. Each material will be described in detail below.

Examples of the three-dimensional crosslinkable charge transporting material include JP-A-8-176293, JP-A-8-208820, JP-A-8-253568, and JP-A-9-11.
No. 0974, etc., having a specific repeating structure and a charge transporting polyester having a hydroxyl group or a carboxyl group at a terminal or a polycarbonate or the like having three or more functional isocyanate groups or epoxy groups in one molecule. Cross-linked using a cross-linking agent;
No. 147804, Japanese Patent Application Laid-Open No. 2000-147813, etc., in which a charge transporting agent having a heat or photocurable functional group at a terminal is crosslinked; [Macrom
ol. Rapid Commun. 20,224-22
8 (1999)], which is obtained by photocrosslinking a charge transport material having oxetane; Japanese Patent Application Laid-Open No. 9-124665.
Gazette, JP-A-11-38656, [Adv. M
ater. 1999, 11, no. 2, Adv. Mat
er. 1999, 11, no. 9] and the like, which are obtained by heating and crosslinking a charge transporting material having an alkoxysilyl group at a terminal; and the like.

Among these, those having a hole transporting property are preferable, and in particular, a charge transporting material having an aromatic amine skeleton having a structure represented by the following general formula (I) as a skeleton having a hole transporting function. It is preferable from the viewpoint that the charge transport ability is excellent. Since a material having a hole transporting property has a specific structure of an electron donating property, when it is mixed with an electron accepting material, charge transfer occurs, and as a result, holes serving as free carriers are generated. When the film is used as a hole injection layer, the electric conductivity is increased, and in particular, the electrical connection between the light emitting layer and the electrode (anode) is improved by providing the hole injection layer, and the driving voltage is reduced. Stability during continuous driving is also improved.

Further, the charge transporting material having an aromatic amine skeleton having a structure represented by the following general formula (I) may have a substituted silicon group containing a hydrolyzable group represented by the following general formula (II). , Si groups can cause a cross-linking reaction with each other to effectively form a three-dimensional Si—O—Si bond, that is, an inorganic vitreous network, as well as adhesion to a substrate mainly composed of an inorganic material. Excellent,
It is preferable from the viewpoint that the characteristics of the obtained organic electroluminescent device can be improved.

[0030]

Embedded image In the general formula (I), Ar ^{1 to} Ar ⁴ each independently represent a substituted or unsubstituted aryl group. Ar ⁵ represents a substituted or unsubstituted aryl group or an arylene group. Ar ¹ and Ar ² , and Ar ³ and Ar ⁴ may form a ring. Ar ^{1 to} A
1-4 of r ⁵ have a bond which can be covalently bonded to the layer in a crosslinked three-dimensionally. k represents 0 or 1.

[0031]

Embedded image

In the general formula (II), R ₁ represents hydrogen, an alkyl group, or a substituted or unsubstituted aryl group. Q represents a hydrolyzable group (for example, an alkoxy group, a methylethylketoxime group, a diethylamino group, an acetoxy group, a propenoxy group, a halogen, etc.). a shows the integer of 1-3.

Hereinafter, specific examples of the compound represented by formula (I) are shown, but the present invention is not limited to these specific examples. In addition, a symbol in which “II-” is added to a compound number in the following table is an example compound in the present specification (for example, a compound number “12” means “example compound (I-12)”). Shown).

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6]

[0040]

[Table 7]

[0041]

[Table 8]

[0042]

[Table 9]

[0043]

[Table 10]

[0044]

[Table 11]

[0045]

[Table 12]

[0046]

[Table 13]

[0047]

[Table 14]

[0048]

[Table 15]

[0049]

[Table 16]

[0050]

[Table 17]

[0051]

[Table 18]

[0052]

[Table 19]

[0053]

[Table 20]

[0054]

[Table 21]

[0055]

[Table 22]

[0056]

[Table 23]

[0057]

[Table 24]

[0058]

[Table 25]

[0059]

[Table 26]

[0060]

[Table 27]

[0061]

[Table 28]

[0062]

[Table 29]

[0063]

[Table 30]

[0064]

[Table 31]

[0065]

[Table 32]

[0066]

[Table 33]

[0067]

[Table 34]

[0068]

[Table 35]

[0069]

[Table 36]

[0070]

[Table 37]

[0071]

[Table 38]

[0072]

[Table 39]

[0073]

[Table 40]

[0074]

[Table 41]

[0075]

[Table 42]

[0076]

[Table 43]

[0077]

[Table 44]

[0078]

[Table 45]

[0079]

[Table 46]

[0080]

[Table 47]

[0081]

[Table 48]

[0082]

[Table 49]

[0083]

[Table 50]

[0084]

[Table 51]

[0085]

[Table 52]

[0086]

[Table 53]

[0087]

[Table 54]

[0088]

[Table 55]

The electron-accepting material is not particularly limited as long as it can reduce the resistance value of the film, but the reduction of the electron-accepting material is determined from the oxidation potential of the monomer which is the raw material of the three-dimensional crosslinkable charge transporting material. The value obtained by subtracting the potential is preferably 1 V or less, more preferably 0.7 V or less. Further, the content of the electron accepting material is preferably in the range of 0.1 to 50% by weight based on the charge transporting material capable of three-dimensionally crosslinking.

Specific examples of the electron accepting material include at least one selected from a metal halide, a Lewis acid, an organic acid, a salt of an arylamine and a metal halide, and a salt of an arylamine and a Lewis acid. Can be More specifically, a compound represented by the following general formula (III),
Although the compound shown by the following compound group 1 is mentioned, the compound shown by the following general formula (III) is especially preferable. Further, specific examples of the compound represented by the following general formula (III) are shown as the following compound group 2, but are not limited thereto.

[0091]

Embedded image

In the general formula (III), Y represents a halogen atom. R represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a cyano group, or a nitro group.

[0093]

Embedded image

[0094]

Embedded image

In the three-dimensionally crosslinked film, the layer containing the three-dimensionally crosslinkable charge transporting material and the electron accepting material can be formed by a usual coating method. The heating temperature for forming the three-dimensional crosslinked film is preferably from 50 to 200 ° C, and from 60 to 17 ° C.
0 ° C. is more preferred. The heating time is preferably from 5 minutes to 2 hours, more preferably from 10 minutes to 1 hour. In addition, when performing photocrosslinking, using an ultraviolet irradiator or the like, 100 to 100
It is preferable to carry out the treatment at 500 W for 5 to 120 seconds, but thermal crosslinking is preferred because the material is often decomposed by ultraviolet rays depending on the material used.

When another layer is laminated on this layer by a coating method after forming the three-dimensional crosslinked film, it is preferable to use a solvent which does not substantially dissolve the three-dimensional crosslinked film. Therefore, the solvent resistance is high, and the solvent can be selected from a wide range.

In the organic electroluminescent device of the present invention, the organic thin film layer sandwiched between the pair of electrodes may be of a single-layer type,
A stacked (separated function) element may be used. In case of single layer type,
The organic thin film layer has only a light emitting layer, and the three-dimensional crosslinked film using a light emitting material is further formed as the light emitting layer. In the case of the stacked type, as the organic thin film layer, in addition to the light emitting layer, a charge injection layer (hole injection layer, electron injection layer), a charge transport layer (hole transport layer, electron transport layer) or a function thereof as required. The three-dimensional cross-linked film has a charge injection / transport layer (hole injection / transport layer, electron injection / transport layer) or the like.
It is preferably formed as a hole injection layer. In addition, these electrodes and the organic thin film layer are usually formed on a substrate.

Hereinafter, the organic electroluminescent device of the present invention will be described in detail with reference to specific examples, but the present invention is not limited thereto. 1 to 3 are schematic cross-sectional views showing one example of the organic electroluminescent device of the present invention. The electroluminescent device shown in FIG. 1 has an anode (electrode) 11, a hole injection layer 12,
The light emitting layer 14 and the cathode (electrode) 16 are sequentially laminated. The organic electroluminescent device shown in FIG. 2 has the same configuration as the organic electroluminescent device shown in FIG. 1 except that a hole transport layer 13 is provided between the hole injection layer 12 and the light emitting layer 14. The organic electroluminescent device shown in FIG. 3 has the same configuration as the organic electroluminescent device shown in FIG. 2 except that an electron transport layer 15 is provided between the light emitting layer 14 and the cathode 16.

The substrate 10 serves as a support for the organic electroluminescent device, and includes a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet, and the like. Particularly, a glass plate or a substantially transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, and polysulfone is preferable. When a synthetic resin plate is used, it is necessary to pay attention to the gas barrier property. If the gas barrier property is too low, the organic electroluminescent element may be deteriorated by the outside air passing through the substrate 10, which is not preferable. Therefore, a method of providing a dense silicon oxide film or the like on one or both sides of the synthetic resin substrate to ensure gas barrier properties is also a preferable method.

The anode 11 is usually made of aluminum,
It is composed of metals such as gold, silver, nickel, palladium and platinum, metal oxides such as oxides of indium and / or tin, metal halides such as copper iodide, carbon black and the like. These can be generally formed by a sputtering method, a vacuum evaporation method, or the like. The anode 11
May be constituted by incorporating metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles and the like in a suitable binder resin. These can be usually formed by applying a binder resin coating solution. Further, the anode 11 may be laminated with a different material.

The thickness of the anode 11 varies depending on the required transparency. Generally, the higher the transparency, the more preferable.
Visible light transmittance is usually 60% or more, preferably 80%
It is preferable to make the above. In this case, the thickness is usually 1
It is about 0 to 1000 nm, preferably about 20 to 500 nm. The anode 11 may be the same as the substrate 10 when opaque, for example, when a metal deposition film is provided for the purpose of reflecting between the two electrodes for the purpose of laser oscillation from the end face or the like.

The hole injection layer 12 is usually provided between the anode 11 and the light-emitting layer 14. It is a material having high hole injection efficiency and capable of efficiently transporting injected holes. For that purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities serving as traps are unlikely to be generated during production or use. Required.
In addition to the above-mentioned general requirements, for example, in consideration of application for in-vehicle display, heat resistance of 100 ° C. or more, more preferably 120 ° C. or more is required. Therefore, by forming the three-dimensional crosslinked film as the hole injection layer 12, it becomes possible to simultaneously improve the light emitting characteristics and the heat resistance of the device. That is, the three-dimensionally crosslinked film using a three-dimensionally crosslinkable charge transporting material having a hole transporting ability is used as the hole injection layer 1.
When formed as 2, an electron-accepting material is used in combination with the electron-donating three-dimensionally crosslinkable charge-transporting material, so that the electrical junction between the light-emitting layer 14 and the anode 11 is improved as described above, The driving voltage can be lowered and the stability during continuous driving can be improved. In addition, by using a three-dimensionally crosslinkable charge transporting material having a high glass transition temperature as a base material of the hole injection layer 12, the heat resistance of the device can be improved. Is also greatly improved, which is the most preferable configuration.

The thickness of the hole injection layer 12 is usually 5 to 300
It is about 0 nm, preferably about 10 to 2000 nm. In forming the hole injection layer 12 composed of the three-dimensional cross-linked film, a predetermined amount of the three-dimensional cross-linkable charge transport material and the electron-accepting material may be added to a predetermined amount of a binder resin or a coating material that does not trap holes as necessary. Improvers can be added.
Further, for various purposes, other silane coupling agents, aluminum coupling agents, titanate coupling agents and the like can be added. By dissolving them, the coating solution is adjusted to a desired concentration, applied on the anode 11 by a method such as spin coating or dip coating, and dried to form the hole injection layer 12.

The light-emitting layer 14 is formed between the electrode (cathode) and the hole injection layer 1 between the electrodes to which an electric field is applied.
The holes injected from 2 (anode) are efficiently recombined, and are formed from the light emitting material efficiently by the recombination. Examples of the luminescent material satisfying such conditions include metal complexes such as an aluminum complex of 8-hydroxyquinoline (JP-A-59-194393) and metal complexes of 10-hydroxybenzo [h] quinoline (JP-A-6-322362). Publication), bisstyrylbenzene derivatives (Japanese Unexamined Patent Publication No. 1-24)
No. 5087, No. 2-222484), bisstyryl arylene derivatives (Japanese Patent Application Laid-Open No. 2-247278), metal complexes of (2-hydroxyphenyl) benzothiazole (Japanese Patent Application Laid-Open No. 8-315983), silole derivatives, etc. Is mentioned. These luminescent materials can be usually formed by a vacuum evaporation method or a coating method.

The light emitting layer 14 is formed, for example, by using an aluminum complex of 8-hydroxyquinoline as a host material for the purpose of improving the luminous efficiency of the device and changing the luminescent color.
Doping with a fluorescent dye for laser such as coumarin (J.
Appl. Phys. 65, 3610, 1989.
Year). The advantages of this method are: 1) improved luminous efficiency by high-efficiency fluorescent dye; 2) variable emission wavelength by selecting fluorescent dye; 3) fluorescent dye which causes concentration quenching can be used; Dyes can also be used,
And the like.

The light emitting layer 14 is effectively doped with a fluorescent dye using a light emitting material as a host material also for the purpose of improving the driving life of the device. For example, using a metal complex such as an aluminum complex of 8-hydroxyquinoline as a host material, naphthacene derivatives represented by rubrene (JP-A-4-335087), quinacridone derivatives (JP-A-5-70773), perylene, etc. By doping a condensed polycyclic aromatic ring (JP-A-5-198377) with 0.1 to 10% by weight based on the host material, it is possible to greatly improve the light-emitting characteristics of the device, especially the driving stability. . As a method of doping the above-mentioned fluorescent dye such as a naphthacene derivative, a quinacridone derivative, or perylene into a host material, there are a method of co-evaporation and a method of previously mixing an evaporation source at a predetermined concentration.

The light-emitting layer 14 is formed of poly (p-phenylenevinylene) or poly [2-methoxy-5- (2-ethylhexyloxy)-] as a polymer light-emitting material.
1,4-phenylenevinylene], a polymer material such as poly (3-alkylthiophene), a system in which a light-emitting material and an electron transfer material are mixed with a polymer such as polyvinylcarbazole, and the like. These materials can be formed by a method such as spin coating or dip coating.

The thickness of the light emitting layer 14 is usually 10 to 200 n.
m, preferably 30 to 100 nm. Light emitting layer 1
4 is formed on the hole injection layer 12 by a coating method,
It is preferable to use a solvent that does not substantially dissolve the hole injection layer 12, but since it is three-dimensionally crosslinked, the solvent resistance is high, and the solvent can be selected from a wide range.

The cathode 16 plays a role of injecting electrons into the light emitting layer 14. As the material used for the cathode 16, the same material as the anode 11 can be used, but for efficient electron injection, a metal having a low work function is preferable, and tin, magnesium, indium, calcium, aluminum, A suitable metal such as silver or an alloy thereof is preferably used. Specific examples include a low work function alloy electrode such as a magnesium-silver alloy, a magnesium-indium alloy, and an aluminum-lithium alloy.

The thickness of the cathode 16 is usually the same as that of the anode 11. For the purpose of protecting the cathode made of a low work function metal, it is effective to further stack a metal layer having a high work function and being stable to the atmosphere in order to increase the stability of the device. Such metals include aluminum, silver,
Examples include metals such as copper, nickel, chromium, gold, and platinum. Furthermore, it is also possible to insert an ultra-thin insulating film (about 0.1 to 5 nm in thickness) such as LiF, MgF ₂ , or Li ₂ O at the interface between the cathode 16 and the light emitting layer 14 or the electron transport layer 15 described later.
This is an effective method for improving the efficiency of the device (Appl.
Phys. Lett. 70, 152, 1997.
Year; JP-A-10-74586; IEEE Tran
s. Electron. Devices, 44, 12
45, 1997).

The hole transport layer 13 is provided to improve the light emitting characteristics of the device, has a high hole injection efficiency from the hole injection layer 12, and efficiently transports the injected holes. can do. For this reason, the material for forming the hole transport layer 13 is required to have a low ionization potential, a high hole mobility, excellent stability, and a low generation of impurities serving as traps during production or use. . As such a hole transport material, for example,
Aromatic diamine compounds linked with tertiary aromatic amine units such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane (JP-A-59-194393), 4,4'-bis [ Aromatic amines containing two or more tertiary amines represented by N- (1-naphthyl) -N-phenylamino] biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Application Laid-Open No. Hei 5-234681) No.),
Aromatic triamines having a starburst structure as derivatives of triphenylbenzene (US Pat. No. 4,923,77)
No. 4), N, N'-diphenyl-N, N'-bis (3-
Aromatic diamines such as methylphenyl) biphenyl-4,4′-diamine (US Pat. No. 4,764,625);
Triphenylamine derivatives which are sterically asymmetrical as a whole molecule (JP-A-4-129271), and compounds in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4-129271)
175395), an aromatic diamine having a tertiary aromatic amine unit linked by an ethylene group (JP-A-4-264)
No. 189), an aromatic diamine having a styryl structure (JP-A-4-290851), and an aromatic tertiary amine unit linked by a thiophene group (JP-A-4-3904).
No. 04466), a starburst type aromatic triamine (JP-A-4-308688), a benzylphenyl compound (JP-A-4-364153), and a tertiary amine linked by a fluorene group (JP-A-5-2547).
No. 3), triamine compounds (JP-A-5-23945)
No. 5), bisdipyridylaminobiphenyl (JP-A-5-320634), an N, N, N-triphenylamine derivative (JP-A-6-1972), and an aromatic diamine having a phenoxazine structure (JP-A-5-32073). 7-138
562), diaminophenylphenanthridine derivatives (JP-A-7-252474), silazane compounds (US Pat. No. 4,950,950), silanamine derivatives (JP-A-6-49079), phosphamine derivatives (JP-A-6-25659). These compounds may be used alone or, if necessary, in combination of two or more.

As the material of the hole transport layer 13, in addition to the above-described hole transport materials, polyvinyl carbazole, polysilane, polyphosphazene (JP-A-5-310949), and polyamide (JP-A-5-310949) ,
Polyvinyl triphenylamine (Japanese Patent Application Laid-Open No. 7-53953)
Japanese Patent Application Laid-Open (JP-A) No. 4-133965, a polymer having a triphenylamine skeleton (Japanese Patent Application Laid-Open No. 4-133065), and a polymer material such as polymethacrylate containing an aromatic amine.

The hole transport layer 13 can be formed by laminating the above hole transport material on the hole injection layer 12 by a coating method or a vacuum evaporation method. In the case of the coating method, one of the hole transport materials is used.
To the seed or two or more, if necessary, an additive such as a binder resin or a coatability improver that does not trap holes is added and dissolved to prepare a coating solution, and a method such as spin coating is used. Can be applied and dried to form. Here, examples of the binder resin include polycarbonate, polyarylate, and polyester.
Since a large amount of the binder resin decreases the hole mobility, a small amount is preferable, and usually 50% by weight or less is preferable. In the case of the vacuum evaporation method, the hole transporting material is put into a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ^-4 Pa by a suitable vacuum pump. The hole transport material can evaporate to form a hole transport layer 13 on the hole injection layer 12, which is placed facing the crucible.

The thickness of the hole transport layer 13 is usually from 10 to 30.
It is about 0 nm, preferably 30 to 100 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used. When the hole transport layer 13 is formed on the hole injection layer 12 by a coating method, it is preferable to use a solvent that does not substantially dissolve the hole injection layer 12, but since the solvent is three-dimensionally crosslinked, The solvent resistance is high, and the solvent can be selected from a wide range.

The electron transport layer 15 is provided for improving the light emitting characteristics of the device, and has a high electron injection efficiency from the cathode 16 and can efficiently transport the injected electrons. For this reason, the material for forming the hole transport layer 13 is required to be capable of easily injecting electrons from the cathode 16 and having a higher electron transport capability. Examples of such an electron transporting material include aluminum complexes of 8-hydroxyquinoline and oxadiazole derivatives (Appl. Phys. Lett., Vol. 55,
1489, 1989) or a system in which they are dispersed in a resin such as polymethyl methacrylate (PMMA), a phenanthroline derivative (JP-A-5-331559),
t-butyl-9,10-N, N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide and the like. The electron transport layer 15 can be formed in the same manner as the hole transport layer 13 described above. However, when the light-emitting layer 14 is formed by a coating method, it is preferable to use a solvent that does not substantially dissolve the light-emitting layer 14.

The thickness of the electron transport layer 15 is usually 5 to 200
nm, preferably 10 to 100 nm.

In the electroluminescent device shown in FIG. 1, for example, the reverse structure, that is, the cathode 16 and the light emitting layer 1
4, the hole injection layer 12 and the anode 11 can be laminated in this order. As described above, it is also possible to provide an organic electroluminescent element between two substrates, at least one of which is highly transparent. Further, when light is extracted from the film thickness direction, at least one of the substrates or the electrodes is configured to be transparent, but when light is extracted from a direction perpendicular to the film thickness direction,
It is also possible to adopt a configuration in which both substrates or electrodes reflect light. Similarly, in the electroluminescent device shown in FIGS. 2 and 3, it is also possible to laminate the respective constituent layers in an inverted structure. In order to further extend the life of the element, it is effective to form a sealing layer that is sealed with a material such as resin or metal and protects the element from air and water, and to have a structure in which the element itself operates in a vacuum system. is there.

[0118]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these embodiments do not limit the present invention.

(Example 1) First, a 150 nm-thick IT
A glass substrate provided with an O film electrode was prepared, and washed with oxygen plasma for 30 seconds using a plasma cleaning machine (BP1 manufactured by Samco International). 30 mg of a charge transporting material represented by the following structural formula (1) (the oxidation potential is 0.88 V with respect to a saturated calomel electrode (SCE)), 20 mg of an isocyanate represented by the following structural formula (2), and tris (4- A solution obtained by dissolving 5 mg of (bromophenyl) ammonium hexachloroantimonate (TBPHA) in 1 ml of dichloromethane was subjected to a rotation speed of 300 rpm.
, And then heated at 120 ° C. for 1 hour and cured to form a hole injecting and transporting zone (layer) having a thickness of 600 nm (measured with a stylus thickness meter).

[0120]

Embedded image

Then, tris (8-hydroxyquinoline) aluminum (Alq) as a luminescent material was vacuum-deposited to a thickness of 50 nm on the hole injection / transport zone (layer) to form a luminescent layer.・ 200n silver alloy cathode
An electrode was formed by vapor deposition to a thickness of m to produce an organic EL device.

In the obtained organic EL device, the ITO electrode was used as an anode, and the magnesium / silver alloy electrode was used as a cathode.
When 8 V DC was applied, current-voltage characteristics (applied voltage, current density) were determined, and luminance and efficiency were measured. Table 56 shows the results.

Example 2 50 mg of a polymer having the following structure (CTP-1: the molecular weight is a weight average molecular weight Mw = 56000 in terms of styrene), and the oxidation potential of the monomer is 0.79 V with respect to a saturated calomel electrode (SCE). And a solution of 5 mg of tris (4-bromophenyl) ammonium hexachloroantimonate (TBPHA) dissolved in 1 ml of dichloromethane was subjected to rotation at 1,000 rpm.
pm, and then heated at 120 ° C for 1 hour,
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that a hole injection transport zone (layer) having a thickness of 700 nm (measured with a stylus thickness gauge) was formed by curing. Done. The results are shown in Table 56.

[0124]

Embedded image

(Example 3) A charge transporting material represented by the following structural formula (3) (oxidation potential is a saturated calomel electrode (SCE)
0.79 V) and tris (4-bromophenyl) ammonium hexachloroantimonate (T
After dissolving 50 mg of BPHA) and 2 mg of 1N hydrochloric acid in butanol and spin-coating at 300 rpm, 1
By heating at 20 ° C. for 1 hour and curing, the film thickness becomes 50
An organic EL device was prepared in the same manner as in Example 1, except that a hole injection / transport zone of 0 nm (measured with a stylus film thickness meter) was formed.
An evaluation was performed. The results are shown in Table 56.

[0126]

Embedded image

(Embodiment 4) Instead of TBPHA, DD
Q (reduction potential is 0,0 with respect to a saturated calomel electrode (SCE).
52V) and a thickness of 100 nm (measured with a stylus thickness gauge)
An organic EL device was prepared and evaluated in the same manner as in Example 3, except that the hole injection transport zone (layer) was formed. The results are shown in Table 56.

Example 5 As a light emitting layer, poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-
[Phenylenevinylene] was spin-coated at a rotational speed of 1000 rpm with a solution of 10 mg dissolved in 1 ml of dichloromethane, and then heated at 120 ° C. for 1 hour to form a film having a film thickness of 60%.
An organic EL device was prepared and evaluated in the same manner as in Example 3 except that a film having a thickness of nm was formed. Table 56 shows the results.
Shown in

(Example 6) The hole injecting and transporting zone (layer) in Example 2 was formed, and poly [2- [2-]
Methoxy-5- (2-ethylhexyloxy) -1,4
-Phenylenevinylene] was spin-coated at a rotation speed of 1000 rpm, and then heated at 120 ° C. for 1 hour to form a film having a thickness of about 6
After forming a 0 nm film, an organic EL device was prepared and evaluated in the same manner as in Example 1. Table 56 shows the results.
Shown in

Comparative Example 1 A solution prepared by dissolving 50 mg of CTP-1 and 5 mg of tris (4-bromophenyl) ammonium hexachloroantimonate (TBPHA) in 1 ml of dichloromethane was prepared at 1000 rpm.
After spin coating at rpm, the film was heated at 120 ° C. for 1 hour to form a hole injecting and transporting band (layer) having a thickness of 600 nm (measured with a stylus film thickness meter).
-Methoxy-5- (2-ethylhexyloxy) -1,
4-phenylenevinylene] in 10 mg of dichloromethane
The solution dissolved in milliliter was rotated at 1000 rpm.
And then heated at 120 ° C. for 1 hour to form a film having a thickness of about 60 nm.
Swelling and dissolution of TP-1 occurred, and a film could not be formed uniformly. Otherwise, in the same manner as in Example 1,
An organic EL device was manufactured and evaluated. The results are shown in Table 56. In this comparative example, weak light emission was observed, but 5
Light emission stopped in about a minute.

Comparative Example 2 50 mg of a charge transporting material represented by the structural formula (1) and tris (4-bromophenyl) ammonium hexachloroantimonate (TBPHA)
After spin-coating a solution of 5 mg in 1 ml of dichloromethane at 300 rpm, 12
After heating at 0 ° C. for 1 hour, the charge transporting material represented by the structural formula (1) was crystallized, and a good film could not be obtained.

[0132]

[Table 56]

[0133]

As described above, according to the present invention, a film can be formed or laminated by coating, and not only a single-layer type but also a laminated type can be easily obtained, and low voltage, high luminance, and long It is possible to provide an organic electroluminescent device that can have a long life and no defects.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the organic electroluminescent device of the present invention.

FIG. 2 is a schematic sectional view showing another example of the organic electroluminescent device of the present invention.

FIG. 3 is a schematic sectional view showing another example of the organic electroluminescent device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Anode 12 Hole injection layer 13 Hole transport layer 14 Light emitting layer 15 Electron transport layer 16 Cathode

Claims (5)

[Claims] An organic thin film layer including at least a light emitting layer;
An organic electroluminescent device having a pair of electrodes sandwiching the organic thin film layer, wherein at least one of the organic thin film layers simultaneously contains a three-dimensional crosslinkable charge transport material and an electron accepting material. And an organic electroluminescent device, which is a three-dimensionally cross-linked layer. 2. The three-dimensionally crosslinkable charge transporting material is a charge transporting material having an aromatic amine skeleton containing a structure represented by the following general formula (I) as a skeleton having a hole transporting function. The organic electroluminescent device according to claim 1. Embedded image (In the general formula (I), Ar ^{1 to} Ar ⁴ each independently represent a substituted or unsubstituted aryl group. Ar ⁵ represents a substituted or unsubstituted aryl group or an arylene group. Ar ¹
And Ar ² , Ar ³ and Ar ⁴ may form a ring. Ar ¹ to
One to four of Ar ^{5 have} a bond that can be covalently bonded in the three-dimensionally crosslinked layer. k represents 0 or 1. ) 3. The charge transporting material having an aromatic amine skeleton having a structure represented by the general formula (I) has a substituted silicon group containing a hydrolyzable group represented by the following general formula (II). The organic electroluminescent device according to claim 2, wherein Embedded image (In the general formula (II), R ₁ represents hydrogen, an alkyl group, a substituted or unsubstituted aryl group, Q represents a hydrolyzable group, and a represents an integer of 1 to 3.) 4. The method according to claim 1, wherein the electron accepting material is at least one selected from metal halides, Lewis acids, organic acids, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. The organic electroluminescent device according to claim 1, wherein 5. An electron accepting material represented by the following general formula (II)
5. The compound represented by I)
3. The organic electroluminescent device according to claim 1. Embedded image (In the general formula (III), Y represents a halogen atom. R represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a cyano group, or a nitro group.)