JPH0594875A - Organic thin-film el element - Google Patents

Abstract

PURPOSE:To vary luminous colors of an EL element corresponding to applied voltages by using tetraphenyldiamine derivatives for a positive hole injected carrier layer, tetraarylebutadiene for an organic luminous layer and tris(8- hydroxyguinolynole)aluminum electron injected carrier layer respectively. CONSTITUTION:On a transparent substrate 1, a transparent anode 2 is provided, and on which a positive hole injected carrier layer 3 is produced with a material of tetraphenyldiamine derivatives. On the layer 3 an organic luminous layer 4 of 0.01-0.2mum in thickness is produced by vacuum evaporation method with tetraarylebutadiene. On the layer 4 an electron injected carrier layer 5 of 0.01-0.2mum in thickness is produced by vacuum evaporation method with tris(8- hydroxyquinolynole)aluminum. On the layer 5 a cathode 6 is produced, and on which a sealing layer 7 is provided, and a seal plate 9 is adhered to the layer 7 with an adhesive resin layer 8 to seal hermetically. Thereby when a power source 10 is connected to apply positive DC voltages to the layer 3, the luminous layer 4 can be made luminous in different colors corresponding to that the voltage is low or high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EL device using electroluminescence, that is, electroluminescence (hereinafter simply referred to as EL), and more specifically, at least an anode, a hole injecting and transporting layer, an organic light emitting layer. , An electron injecting and transporting layer, and a cathode in this order.

[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, a hole injecting and transporting layer, an electron transporting and emitting layer, and a cathode are formed in this order. , Is made as follows.

First, an anode of a transparent conductive film of a complex oxide of indium and tin (hereinafter abbreviated as ITO) is formed on a transparent insulating substrate such as glass or a resin film by vapor deposition or sputtering. Next, copper phthalocyanine as a hole injecting and transporting layer, or a compound represented by the following chemical formula:

[0004]

[Chemical 1]

1,1-bis (4-diparatolylaminophenyl) cyclohexane or a compound represented by the following chemical formula:

[0006]

[Chemical 2]

A layer of a tetraphenyl derivative such as N, N, N ', N'-tetra-P-tolyl-1,1'-biphenyl-4,4'-diamine is formed to a thickness of about 0.1 μm or less. It is formed by vapor deposition of a single layer or a laminated layer.

Next, an organic phosphor such as tris (8-quinolinol) aluminum is vapor-deposited on the hole injecting and transporting layer to a thickness of about 0.1 μm or less to form an organic electron transporting light emitting layer. Finally, Mg: Ag, Ag: E as a cathode thereon.
Alloys of u, Mg: Cu, Mg: In, Mg: Sn, etc. are vapor-deposited by about 2000 Å.

In addition, Adachi et al.
A device in which an organic light emitting layer and an electron injecting and transporting layer were separated was manufactured by stacking various kinds of materials. Applied Physics Letters Vol. 57, No. 6, pp. 531 (1990
According to the authors, this device shows that N, N'-diphenyl-N, N'- as a hole injecting and transporting layer (3) on the anode of ITO.
Bis (3-methylphenyl) -1,1'-biphenyl-
4,4′-diamine, 1- [4 as the organic light emitting layer (4)
-N, N-bis (P-methoxyphenyl) aminostyryl] naphthalene, 2- (4) as the electron injecting and transporting layer (5)
-Biphenyl) -5- (4-t-butylphenyl)-
1,3,4-oxadiazole (hereinafter simply referred to as BPBD) and an alloy of Mg and Ag as a cathode (6) are sequentially laminated.

A brightness of about 1000 cd / m ² was obtained by applying a DC low voltage of about 20 V or less to any of the elements, but it has not been reported that the emission spectrum changes depending on the applied voltage.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic thin film EL element capable of reversibly changing the emission color by changing the applied voltage.

[0012]

That is, the present invention relates to an organic thin film EL device comprising at least an anode, a hole injecting and transporting layer, an organic light emitting layer, an electron injecting and transporting layer, and a cathode in this order, and a hole injecting and transporting layer. As α, α, α ′, α′-tetramethyl-α, α′-bis (4-diparatolylaminophenyl) -para-xylene represented by the following (Chemical Formula 3) and the following (Chemical Formula 4) N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 'shown
An organic compound characterized by using a tetraphenyldiamine derivative such as -biphenyl-4,4'-diamine, tetraaryl butadiene as an organic light emitting layer, and tris (8-quinolinol) aluminum as an electron injecting light emitting layer. It is a thin film EL device.

[0013]

[Chemical 3]

[0014]

[Chemical 4]

An embodiment of the present invention will be described below with reference to FIG. 1 of the drawings. FIG. 1 shows an organic thin film EL device according to the present invention, which includes a transparent substrate (1), an anode (2), a hole injecting and transporting layer (3),
This is an example in which an organic light emitting layer (4), an electron injecting and transporting layer (5), a cathode (6), an inorganic sealing layer (7), an adhesive resin layer (8) and a sealing plate (9) are arranged in this order. Can also consist of a cathode on the substrate.

The transparent substrate (1) is a transparent glass or a transparent resin film such as polyethylene terephthalate or polyethylene naphthalate. A transparent conductive material such as ITO (work function 4.8 eV), tin oxide, indium oxide, and zinc aluminum oxide is provided on one side of the surface resistance by vacuum deposition or sputtering method with a surface resistance of 10 to 50 Ω / square and a visible light transmittance of 80%. The above transparent conductive film is coated in a desired pattern to form an anode (2).

Next, the hole injecting and transporting layer (3) is formed on the transparent anode (2). Preferred conditions of the hole injecting and transporting material are stable to oxidation, high hole mobility and high workability. The function lies between the anode material and the light emitting layer, and the film forming property must be good, and at least it must be substantially transparent in the fluorescence wavelength region of the light emitting layer material.

Specifically, a tetraphenyldiamine derivative or the like is used in a single layer or laminated layers. Typical materials for the tetraphenyldiamine derivative are 1,1-bis (4-diparatolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1, 1'-biphenyl-4,4'-diamine (work function 5.4 eV), N, N'-diphenyl-
N, N′-bis (paratolyl) -1,1′-biphenyl-4,4′-diamine (work function 5.4 eV) N,
N, N ', N'-tetra (paratolyl) -4,4'-
Examples thereof include diaminobiphenyl and a compound represented by (Chemical Formula 3) (work function 5.7 eV), but are not particularly limited to the above examples.

The hole injecting and transporting layer (3) using these compounds is formed to a thickness of about 0.01 to 0.2 μm by a vacuum vapor deposition method, a spin coating method or the like. Next, the organic light emitting layer (4) is formed on the hole injecting and transporting layer (3) by a vacuum deposition method to a thickness of 0.01 to 0.2 μm.

The organic light emitting layer material used in the present invention is 1,1,
In 4,4-tetraarylbutadiene, the aryl group is selected from a phenyl group, a tolyl group, a methoxyphenyl group and the like. The work function of 1,1,4,4-tetraphenylbutadiene was 6.0 eV, and the electron affinity was 3.1 eV.

Next, an electron injecting and transporting layer is formed on the organic light emitting layer. Preferred conditions of the electron injecting and transporting material used in the present invention are that the electron mobility is high, the electron affinity is the work function of the cathode and the organic light emitting layer. , Which is between the electron affinities, and has good film-forming properties and suppresses crystallization of the light-emitting layer. Specifically, tris (8-hydroxyquinolinol) aluminum (electron affinity 3.2 eV) is formed in a thickness of 0.01 to 0.2 μm by a vacuum deposition method.

In order to improve the heat resistance of the hole injecting and transporting layer, the organic light emitting layer, and the electron injecting and transporting layer, the organic molecules mentioned in the examples of the constituent materials of each layer include vinyl group, allyl group, methacryloyloxymethyl group and methacryloyl. An oxy group, a methacryloyloxyethyl group, an acryloyl group, an acryloyloxymethyl group, an acryloyloxyethyl group, a cinnamoyl group, or a polymerizable substituent such as a styrenemethyloxy group is introduced into each layer during or after film formation. heat,
It may be polymerized into light, radiation, plasma, etc., or one or more methyl groups may be added to the organic molecules mentioned in the examples of the constituent materials of each layer to improve the film-forming property of the constituent materials of each layer and form a smooth film. Alternatively, an alkyl group such as an ethyl group may be introduced.

Next, the cathode (6) is formed on the electron injecting and transporting layer (5). The cathode is made of a material having a low work function in order to effectively inject electrons, and Li, Na, Mg, Ca,
A single metal element such as Sr, Al, Ag, In, Sn, Zn, or Zr, or a two-component or three-component alloy system containing them for improving 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. The cathode (6) is co-deposited by a resistance heating method under a vacuum of the order of 10 ⁻⁵ Torr or less while monitoring the vapor deposition from different vapor deposition sources for each component with a crystal oscillator type film thickness meter. 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 (7) is formed on the device. The sealing layer (7) is shade
It is formed immediately after the pole (6) 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. Vapor deposition, 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 invasion of moisture, a sealing plate (9) such as a glass plate is adhered by using an adhesive resin layer (8) such as a low hygroscopic photocurable adhesive or an epoxy adhesive. And seal. Besides the glass plate, a metal plate, a plastic plate or the like can be used. Organic thin film E configured as described above
The L element has a positive side on the hole injecting and transporting layer (3) side and a power source (1
0) is connected with a lead wire (11) and a direct current voltage is applied, light is emitted in different colors when a low voltage is applied and when a high voltage is applied.

[0027]

EXAMPLES Example 1 An example of an EL device of the present invention will be described below with reference to FIG. First, as the transparent substrate (1), a glass plate having a thickness of 1.1 mm was used, and 1200 I
It was coated with TO to form an anode (2). After thoroughly washing this transparent conductive glass substrate, α, α, α ′, α′-tetramethyl-α, α′-bis (4-) represented by (Chemical Formula 3) as a hole injecting and transporting layer (3). Diparatolylaminophenyl) -para-xylene was vapor-deposited at 500Å. Next, as the organic light emitting layer (4), 1,1,4,4-tetraphenylbutadiene was vapor-deposited at 300 liters. Next, tris (8-quinolinol) aluminum (200 Å) was used as the electron injecting and transporting layer (5). Mg and L as a cathode (6) on the upper surface
i was co-deposited.

Next, 2 μ of GeO is used as the inorganic sealing layer (7).
m After vapor deposition, a glass plate was used as a sealing plate (9) and adhered with an ultraviolet curable adhesive resin (8) for sealing. This element is 3V ~
At an applied voltage of 6 V, red light emission with a peak of 590 nm was emitted. Further, at 7V to 12V, light-blue emission at a peak of 470 nm became dominant, and at 13V, white emission (30 cd / m ² , 1.85 mA / cm ² ) was obtained.
In addition, the emission color changed reversibly when the applied voltage was lowered.

Example 2 Instead of the hole injecting and transporting layer in Example 1, first, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1 was formed on the anode (2). ，
1'-Biphenyl-4,4'-diamine was vapor-deposited by 250Å, and the compound represented by (Chemical Formula 3) was vapor-deposited by 250Å to form a hole injecting and transporting layer (3). .. This device emitted red light with a peak of 590 nm from an applied voltage of 3 V, became light blue with a peak of 470 nm at 10 V or more, and emitted white light at 12 V or more (1200 cd / m ² , 71 mA / cm ^{2 at} 15 V). The emission color changed reversibly by the applied voltage.

Example 3 Instead of the hole injecting and transporting layer in Example 1, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,
The same construction as in Example 1 was carried out except that 500 Å of 4′-diamine was vapor-deposited. The device emitted light of 470 nm peak in light blue at 3 V or higher, and emitted white light at 14 V or higher (2330 cd / m ² , 129 mA / cm ^{2 at} 15 V). The emission color changed reversibly by the applied voltage.

Example 4 The light emitting surface of the device of Example 2 was partially heated to mix the hole injecting and transporting layer, the organic light emitting layer and the electron injecting and transporting layer. −
(Quinolinol) Green EL, which is the same as the fluorescent color of aluminum
It emitted light and could emit red, green, and light blue in the same device.

[0032]

As described above, with the above device structure, EL light emission with a peak wavelength of 470 nm and 59
The ratio of 0 nm EL emission can be changed, which is effective in changing the EL emission color. Organic thin film E having the constitution of the present invention
According to the L element, the emission color can be changed by the applied voltage, which is effective in making the organic thin film EL element multicolored.

[0033]

[Brief description of drawings]

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

[Explanation of symbols]

 (1) Transparent substrate (2) Anode (3) Hole injecting and transporting layer (4) Organic light emitting layer (5) Electron injecting and transporting layer (6) Cathode (7) Inorganic sealing layer (8) Adhesive resin layer (9 ) Sealing plate (10) Power supply (11) Lead wire (12) Cathode outlet

Claims (2)

[Claims] 1. In an organic thin film EL device comprising at least an anode, a hole injecting and transporting layer, an organic light emitting layer, an electron injecting and transporting layer, and a negative order, the EL emission color can be changed by changing the applied voltage. Organic thin film EL device. 2. The organic compound according to claim 1, wherein a tetraphenyldiamine derivative is used for the hole injecting and transporting layer, tetraaryl butadiene is used for the organic light emitting layer, and tris (8-quinolinol) aluminum is used for the electron injecting and transporting layer. Thin film EL
element.