JPH05271652A - Organic thin-film el element - Google Patents

Abstract

PURPOSE:To obtain an organic thin-film EL element having high heat resistance, high solvent resistance, high performances and stable quality by forming an organic thin-film EL element consisting of an anode, an organic hole injection and transport layer, an organic electron transport layer containing a product of crosslinking of a specified compound, and a cathode. CONSTITUTION:This EL element is one essentially consisting of an anode, an organic hole injection and transport layer, an organic electron transport layer and a cathode, and the organic hole injection and transport layer contains a product of crosslinking of a compound of the formula. The tetraallyldiamine compound of the formula can be obtained by reacting N,N'-bis(hydroxyphenyl)- N,N'-diphenylbenzidine with chloromethylstyrene. In order to improve the hole mobility, a plurality of methyl groups may be introduced into the skeleton of N,N',N'-tetraphenylbenzidine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film EL device utilizing the electroluminescence (hereinafter simply referred to as EL) phenomenon of an organic thin film.

[0002]

2. Description of the Related Art C. of Eastman Kodak Company. W. T
The organic thin film EL device developed by ang et al.
-194393, JP-A-63-264692, JP-A-63-295695, Applied Physics Letter Vol. 51 No. 12, page 913 (19)
1987), and Journal of Applied Physics Vol. 65, No. 9, page 3610 (1989) and the like, generally, an anode, an organic hole injecting and transporting layer, an electron transporting and emitting layer, and a cathode in this order. It is composed and made as follows.

As shown in FIG. 1, first, on a transparent insulating substrate (1) such as glass or a resin film, a transparent conductive material of a complex oxide of indium and tin (hereinafter referred to as ITO) is formed by a vapor deposition or sputtering method. The positive electrode (2) of the functional coating is formed. Next, copper phthalocyanine as the organic hole injecting and transporting layer (3) or a compound represented by the following chemical formula:

[0004]

[Chemical 2]

1,1-bis (4-di-p-tolylaminophenyl) cyclohexane (melting point 181.4 ° C.-18
2.4 ° C.) or a compound represented by (Chemical Formula 3):

[0006]

[Chemical 3]

N, N, N ', N'-tetra-p-tolyl-1,1'-biphenyl-4,4'-diamine (melting point 1
20 ° C.) tetraaryldiamine or the like having a thickness of about 0.1 μm or less is formed in a single layer or by stacking and vapor deposition.

Then, an organic phosphor such as tris (8-quinolinol) aluminum is vapor-deposited on the organic hole injecting and transporting layer (3) to a thickness of about 0.1 μm or less to form an organic electron transporting and emitting layer (4). Form. Finally, Mg: Ag, Ag: Eu, Mg: Cu, Mg: In, as a cathode (5) thereon.
An alloy such as Mg: Sn is vapor-deposited on the order of 2000Å.

In addition, Adachi et al.
A device in which an organic light emitting layer (6) and an organic electron injecting and transporting layer (7) were divided was produced by stacking various kinds of materials. Applied Physics Letter Vol. 57, No. 6, No. 5
According to p. 31 (1990), the device has N, N'-diphenyl-N, N'-bis (3-methylphenyl)-as an organic hole injecting and transporting layer (3) on an anode of ITO.
1,1'-biphenyl-4,4'-diamine (melting point 15
9-163 ° C.) 1- [4-N, as the organic light emitting layer (6)
N-bis (p-methoxyphenyl) aminostyryl] naphthalene, 2- (4-) as the organic electron injecting and transporting layer (7)
Biphenylyl) -5- (4-t-butylphenyl)-
1,3,4-oxadiazole (hereinafter simply referred to as BPBD) and an alloy of Mg and Ag as a cathode (5) are sequentially laminated.

However, in the organic hole injecting and transporting material shown above, copper phthalocyanine is heat-resistant, but has a large absorption in the visible light wavelength region, and since it is crystalline, the vapor-deposited film becomes uneven, and the device is There was a problem that it became easy to short-circuit. The compounds shown in (Chemical Formula 2) and (Chemical Formula 3) are amorphous and have a smooth vapor-deposited film, and have no absorption in the visible light wavelength region, but have a low melting point and generate heat during the device manufacturing process or device driving. Therefore, there is a problem in that it melts and mixes with the light emitting layer.
For example, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine is formed into a thin film of about 500Å and laminated with (8-quinolinol) aluminum. In this case, there is a problem that mixing is performed at a temperature of about 95 ° C.

Further, when the hole injecting and transporting layer is laminated by the coating method using an organic solvent such as the spin coat method, or the light emitting layer is formed on the hole injecting and transporting layer, the conventional three-dimensional method is used. In many cases, the hole injecting and transporting layer composed of non-crosslinked low molecular weight compounds was dissolved by the solvent of the light emitting layer material.

[0012]

DISCLOSURE OF THE INVENTION As described above,
The following three points are required for the hole injecting and transporting layer of the organic thin film EL device. 1. Capable of forming a film that is colorless and transparent and has a smooth thickness of 0.1 μm or less. 2. High ability to inject and transport holes from the anode to the light emitting layer. 3. Heat resistance of 200 ° C or higher and insolubility in organic solvents. The present invention has been made for the purpose of providing an organic thin film EL device having a hole injecting and transporting layer which solves the above problems.

[0013]

The present invention has been made in view of the above problems, and is an organic thin film EL device including at least an anode, an organic hole injecting and transporting layer, an organic electron transporting layer, and a cathode. 2. In the organic thin film EL element, the organic hole injecting and transporting layer contains a cross-linked body of the compound represented by the general formula (Formula 1). After forming a film of the novel tetraaryldiamine compound represented by the above (Chemical Formula 1) as a hole injecting and transporting layer, three-dimensionally cross-linking it to make it infusible at high temperatures and insoluble in solvents. Settled.

The organic thin film EL device of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 shows an organic thin film EL device according to the present invention, in which an anode (2), an organic hole injecting and transporting layer (3), an organic electron transporting and emitting layer (4), a cathode (5), and an encapsulation are formed on a substrate (1). This is a case where the layers (8) are formed in this order, and the glass plate (9) is adhered with an adhesive (10) and sealed.

As shown in FIG. 2, a plurality of materials including the hole injecting and transporting material according to the present invention are used in the hole injecting and transporting layer (3) to enhance the hole injecting ability. The layer (11) and the second hole injecting and transporting layer (12) may be laminated and formed.

Further, as shown in FIG. 3, the organic electron transporting light emitting layer (4) is divided into an organic light emitting layer (6) and an organic electron injecting and transporting layer (7), and an anode (2) is formed on the substrate (1). ),
The hole injecting and transporting layer (3), the organic light emitting layer (6), the organic electron injecting and transporting layer (7), the cathode (5) and the sealing layer (8) can be formed in this order, or the same configuration can be obtained on the substrate. The cathode may be arranged in the reverse order.

The cathode (2) is a transparent insulating substrate (1) such as glass coated with a transparent conductive material such as ITO or zinc aluminum oxide by vacuum deposition or sputtering, and has a surface resistance of 10 to 50 Ω /. Square, visible light transmittance 80%
The transparent electrode described above or a semitransparent electrode in which gold or platinum is thinly vapor-deposited is desirable.

In another case, however, the anode (2) is opaque and the hole injection / transport layer (3) facilitates hole injection into the organic electron transport light emitting layer (4) or the organic light emitting layer (6). A metal plate having a large function such as gold, platinum, or nickel, a semiconductor substrate such as silicon, gallium phosphide, or amorphous silicon carbide having a work function of 4.8 eV or more, or those metals or semiconductors on an insulating substrate (1) The cathode (5) can be a transparent electrode or a semi-transparent electrode by using it for the anode (2) coated on. If the cathode (5) is also opaque, the organic electron transport light emitting layer (4) or the organic light emitting layer (6)
Must be transparent on at least one end.

Next, the organic hole injecting and transporting layer (3) of the present invention
Are formed on the anode (2). The hole transport layer used in the present invention is formed by using the tetraaryldiamine compound represented by the general formula (1) (hereinafter abbreviated as STTPD). This compound is a molecule having N, N, N ′, N′-tetraphenylbenzidine as a skeleton, which has a large hole mobility of about 10 ⁻³ cm ² / v · sec, and is colorless and transparent in the visible region.
An amorphous and smooth film can be formed. A styrylmethoxy group was introduced into the two phenyl groups as a group for three-dimensionally crosslinking the molecules with heat and light.

STTPD is Euro Patent 02951
It can be obtained by reacting N, N′-bis (hydroxyphenyl) -N, N′-diphenyl-benzidine with chloromethylstyrene described in JP-A No. 15-58, but for the purpose of further improving hole mobility, N, Plural methyl groups may be introduced on the N, N ′, N′-tetraphenylbenzidine skeleton.

The film formation method of STTPD is carried out by vacuum vapor deposition or by dissolving in an organic solvent such as toluene and spin coating, and the thickness of the hole injecting and transporting layer is 1 μm when formed as a single layer or a laminated layer. It is below, and preferably 0.03 to 0.1 μm. STTP
Cross-linking between D molecules is performed by irradiating with ultraviolet rays while heating at 70 ° C. to 240 ° C. after film formation. On this occasion,
It is desirable that there is no oxygen such as in an inert gas atmosphere or in a vacuum.

In the present invention, as shown in FIG.
Although the organic hole injecting and transporting layer (3) can be formed by a single layer of a crosslinked body of TTPD, it can also be used by laminating it with another organic hole injecting and transporting material as shown in FIG. At this time, the crosslinked body of STTPD is used as the second hole injecting and transporting layer (12).
In this case, it is possible to form an EL element which is unlikely to cause short circuit even if a vapor deposition film of a material such as crystalline copper phthalocyanine is used for the first hole injecting and transporting layer (11).

The crosslinked body of STTPD is used as the first hole injecting and transporting layer (11), and other materials are used as the second hole injecting and transporting layer (12).
It is also possible to use the above, and it is also possible to stack three or more layers. It is also possible to spin-coat an organic solvent-soluble substance on the hole injecting and transporting material of the crosslinked product of STTPD to form a film, and to form a low molecular weight hole transporting material, vinyl group, allyl group, methacryloyloxy in STTPD. Others having polymerizable and crosslinkable substituents such as methyl group, methacryloyloxy group, methacryloyloxyethyl group, acryloyl group, acryloyloxymethyl group, acryloyloxyethyl group, cinnamoyl group, styrylmethoxy group, propioloyl group, propargyl group, etc. It is also possible to polymerize and crosslink by mixing the hole transporting material, the fluorescent molecule and the like.

Other organic hole injecting and transporting layer materials to be laminated with the hole injecting and transporting layer composed of a cross-linked body of STTPD include polyaniline, polypyrrole, polythiophene, polythienylenevinylene, polyphenylenevinylene and alkyl groups and alkoxy groups thereof. , A conductive polymer that was made soluble by solvent, Buckminster fullerene (C60)
Such as spherical carbon clusters, copper phthalocyanines, phthalocyanines such as metal-free phthalocyanines, or 1, 1
-Bis (4-di-p-tolylaminophenyl) cyclohexane, N, N'-diphenyl-N, N'-bis (3-
Methylphenyl) -1,1'-biphenyl-4,4'-
Diamine, N, N'-diphenyl-N, N'-bis (p
Toluryl) 1,1′-biphenyl-4,4′-diamine, N, N, N ′, N′-tetra (p-tolyl) -4,
Examples thereof include triphenylamine and tetraphenyldiamine derivatives such as 4′-diaminobiphenyl and their methyl group-, fluorine- or trifluoromethyl group-substituted compounds, but are not particularly limited to the above examples.

Next, the organic electron transporting light emitting layer (4) is formed on the organic hole injecting and transporting layer (3). The phosphor used for the organic electron transporting light emitting layer (4) has fluorescence in the visible region. However, any phosphor that can be formed into a film by an appropriate method is possible. For example, anthracene, salicylate, pyrene, coronene,
Perylene, tetraphenyl butadiene, 9,10-bis (phenylethynyl) anthracene, 8-quinolinol lithium, tris (8-quinolinol) aluminum,
Tris (5,7-dichloro, 8-quinolinol) aluminum, tris (5-chloro-8-quinolinol) aluminum, bis (8-quinolinol) zinc, tris (5
Examples include -fluoro-8-quinolinol) aluminum, bis [8- (paratosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, and pentaphenylcyclopentadiene.

The phosphor in the organic electron transporting light emitting layer (4) is
In order to convert the emission wavelength and improve the emission efficiency, two or more kinds of phosphors such as coumarin-based, quinacridone-based, perylene-based and pyran-based phosphors are mixed, or two or more light-emitting layers of multiple kinds of phosphors are laminated. Alternatively, one of them may exhibit fluorescence in the infrared region or the ultraviolet region.

The method of forming the organic electron transporting light emitting layer (4) is as follows.
It is carried out by a vacuum vapor deposition method, a cumulative film method, or by dispersing in a suitable resin binder and coating by a method such as spin coating. The film thickness of the organic electron transporting light emitting layer (4) is 1 μm or less even when it is formed by a single layer or a laminated layer, and preferably 50Å to 1000Å.

Next, when the organic electron transporting light emitting layer (4) is functionally separated into the organic light emitting layer (7) and the electron injecting and transporting layer (8), the preferable condition of the electron injecting and transporting material is electron mobility. Is large, the LUMO energy level is between the same level as the LUMO energy level of the organic light emitting layer material and the Fermi level of the cathode material, the work function is larger than that of the organic light emitting layer material, and the film forming property is good. Further, in the element in which the anode (2) is opaque and the light is extracted from the transparent or semitransparent cathode (5), it is necessary that it is substantially transparent at least in the fluorescence wavelength region of the organic light emitting layer material. Examples include BPBD, 3,4,9,10-
Examples include perylene tetracarboxyl-bis-benzimidazole, but not limited to the above examples.

The method for forming the organic electron injecting and transporting layer (7) is as follows.
It is carried out by a vacuum vapor deposition method, a cumulative film method, or by dispersing in a suitable resin binder and coating by a method such as spin coating. Next, the cathode (5) is formed on the organic electron injecting and transporting layer (7). For the cathode, a low work function material is used to effectively inject electrons, and Li, N
a, Mg, Ca, Sr, Al, Ag, In, Sn, Z
A single metal element such as n, Zr or the like, or a binary or ternary alloy system containing them for improving the stability is used.

As an example of the work function, Mg alone is about 3.6.
It is eV and decreases to 3.1 to 3.2 eV when an alkali metal such as Li is added to Mg. As a method of forming the cathode (5), co-evaporation is performed by a resistance heating method under a vacuum degree of 10 ⁻⁵ Torr order or less while monitoring the crystal oscillator film thickness type from different vapor deposition sources for each component. At this time,
The film is formed with a film thickness of about 0.01 to 0.3 μm, but it is also possible to use an alloy target instead of co-deposition by the electron beam evaporation method, the ion plating method or the sputtering method.

Next, in order to prevent oxidation of the organic layers and electrodes of the device
A sealing layer (8) is formed on the device. The sealing layer (8) is shade
It is formed immediately after the pole (5) is formed. As an example of sealing layer material
For SiO₂, SiO, GeO, MoO₃Oxidation of etc.
Thing, MgF₂, LiF, BaF ₂, AlF₃, FeF₃
Barrier properties of fluorinated compounds such as GeS, SnS, etc.
Inorganic compounds with high
Not a thing. These can be used alone or in combination to deposit and spa
The film is formed by the tattering method, the ion plating method, etc.
It When using the resistance heating method, you can deposit at a low temperature.
GeO is excellent.

Further, in order to prevent the infiltration of moisture, an adhesive resin layer (1) having a low hygroscopicity, such as a photocurable adhesive or an epoxy adhesive.
0) is used to adhere and seal a sealing plate (9) such as a glass plate. Besides the glass plate, a metal plate, a plastic plate or the like can be used. Organic thin film EL constructed as described above
The device emits light by connecting the power source (13) to the power supply (13) with the lead wire (14) with the positive side of the organic hole injecting and transporting layer (3) side and applying a direct current voltage. Light is emitted while a positive voltage is applied to the electrode on the hole injecting and transporting layer (3) side.

[0033]

After the tetraaryldiamine compound is formed into a film, it is three-dimensionally crosslinked to make it infusible at a high temperature and insoluble in a solvent, thereby solving the problem. That is, a colorless transparent and smooth film having a thickness of 0.1 μm or less can be formed, and the capability of injecting and transporting holes from the anode to the light emitting layer is high.
It has a high heat resistance of more than 00 ° C and is hardly soluble in general organic solvents.

[0034]

【Example】

Example 1 An example of the EL device of the present invention will be described below with reference to FIG. First, as the transparent insulating substrate (1), a glass plate having a thickness of 1.1 mm was used, and a glass plate 120
The anode (2) was coated with 0Å ITO. After thoroughly cleaning this transparent conductive glass substrate, STTPD is applied to about 500
Å After vacuum deposition, irradiate Hg-Xe lamp for 1 hour in vacuum (ultraviolet intensity is 2.8 mW / c measured by UV-25 silicon photodiode sensor manufactured by Oak Manufacturing Co., Ltd.)
m ² ) while heating to 200 ° C. to cross-link the molecules three-dimensionally.

Next, tris (8-quinolinol) aluminum was vapor-deposited as an organic electron-transporting light-emitting layer (4) at a rate of 500 Å, and Mg and Ag as a cathode were vapor-deposited at a rate ratio of 1 on the upper surface thereof.
2200Å was vapor-deposited at 0: 1. Finally, GeO was deposited to a thickness of 2.2 μm as a sealing layer (8), and then a glass plate (9) was bonded and sealed with an ultraviolet curing adhesive. This device emits yellowish green light when a DC voltage of 5V or more is applied, and it is 20V at 18V.
A brightness of 70 cd / m ² was obtained.

Example 2 Anode (2) similar to Example 1
On top of it, copper phthalocyanine is used as the first hole injecting and transporting layer.
00Å was vapor-deposited, and STTPD was further vapor-deposited thereon as a second hole injecting and transporting layer. After that, an element was manufactured in the same manner as in Example 1. This device is 1100 cd at 11V
The brightness was / m ² .

<Example 3> Anode (2) similar to Example 1
On top, 1 layer of copper phthalocyanine is formed as the first hole injecting and transporting layer.
50Å evaporated. Next, as a second hole injecting and transporting layer, STT
PD was deposited by 400Å, and STTPD was crosslinked in the same manner as in Example 1. Next, as a third hole injecting and transporting layer, N,
N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine was added to 1
50Å evaporated. Next, tris (8-quinolinol) aluminum containing coumarin 540 was vapor-deposited as an organic electron-transporting light emitting layer at 450 Å, and Mg containing Li as a cathode was vapor-deposited at 2200 Å on the upper surface thereof.

Finally, Geo was deposited to a thickness of 1.5 μm as a sealing layer, and a glass plate was adhered and sealed with an ultraviolet curing adhesive.
This device emits green light by applying a DC voltage of 3 V or more, and has a luminance of 9720 cd / m ² and a current density of 25 V at 16 V.
It was 0 mA / cm ² .

<Example 4> 50 STTPDs were placed on a quartz plate.
It was vapor-deposited with 0Å and crosslinked under the same conditions as in Example 1. This film is transparent at wavelengths in the visible light range and includes ethanol, toluene,
It was insoluble in an organic solvent such as 700 form. In addition, the layer of chloro STTPD of the devices of Examples 1 to 3 was formed into STTPD.
The device could also be produced by spin-coating the toluene solution of 1.

[0040]

As described above, the organic thin film E of the present invention is
According to the L element, by using a cross-linked tetraaryldiamine compound in the hole injecting and transporting layer, a hole injecting and transporting layer that is insoluble in an organic solvent, has high heat resistance, is smooth, and is transparent, and has a substrate temperature of 100. It has an effect of enabling various organic thin film element manufacturing processes such as a process of increasing the temperature above ℃ and a spin coating method. According to the organic thin film EL element of the present invention, the organic thin film EL element withstands harsh conditions in the manufacturing process and has high performance and stable quality.

[0041]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an organic thin film EL element of the present invention.

FIG. 2 is an explanatory view showing another embodiment of the organic thin film EL element of the present invention.

FIG. 3 is an explanatory view showing another embodiment of the organic thin film EL element of the present invention.

[Explanation of symbols]

 (1) Substrate (2) Anode (3) Organic hole injecting and transporting layer (4) Organic electron transporting and emitting layer (5) Cathode (6) Organic light emitting layer (7) Organic electron injecting and transporting layer (8) Sealing layer ( 9) Glass plate (10) Adhesive resin layer (11) First hole injecting and transporting layer (12) Second hole injecting and transporting layer (13) Power supply (14) Lead wire (15) Cathode outlet

Claims (2)

[Claims] 1. In an organic thin film EL device comprising at least an anode, an organic hole injecting and transporting layer, an organic electron transporting layer and a cathode, the organic hole injecting and transporting layer is represented by the following general formula (Formula 1). An organic thin film EL device comprising a cross-linked compound. [Chemical 1] 2. The organic hole transport layer has a laminated structure of a layer formed using a compound represented by the general formula (Formula 1) and a layer formed of another organic hole transport material. The organic thin film EL element according to claim 1, wherein