JP2777179B2 - Thin-film electroluminescence device - Google Patents

Description

The present invention relates to a thin-film electroluminescent device of the present invention.
Specifically, the present invention relates to a thin-film electroluminescence element used as a light-emitting body of various display devices.

[Problems to be solved by conventional technology and invention]

Electroluminescence device (hereinafter referred to as EL device)
Is characterized by high visibility due to self-luminescence and excellent impact resistance because it is a completely solid-state device. Currently, various EL devices using inorganic and organic compounds for the light-emitting layer have been proposed. Has been attempted for practical use. Among these, various materials are being developed for the organic thin film EL element because the applied voltage can be greatly reduced.

For example, Japanese Patent Application Laid-Open No. Sho 59-194393 discloses an organic thin-film EL device which exhibits high luminance when a low voltage of 25 V or less is applied. This EL device is a stacked type having an anode / a hole injection layer / a light emitting layer / a cathode, and the film thickness between the electrodes needs to be 1 μm or less. In some cases, there is a problem that pinholes are easily generated and the productivity is low, and in the embodiment using tetraphenylbutadiene for the light emitting layer, the luminous efficiency in blue light emission is extremely small. Further, according to European Patent Publication No. 0281381, a laminated type of anode / hole injection / transport zone / emission zone / cathode is disclosed. Here, the emission band is composed of a thin film made of a host material and a small amount of a fluorescent material in the host material. However, the EL disclosed here
The device can achieve high output by applying a low voltage with respect to light emission in the green to red regions, but cannot realize blue light emission.

Further, U.S. Pat. Nos. 4,672,265, 4,725,513, 4,734,338, 4,747,767,
JP-B-4775820 and JP-A-61-37890 disclose a two-layer structure of a light-emitting layer composed of an electron-accepting electroluminescent compound and a light-emitting layer composed of an electron-donating electroluminescent compound. An EL device having a stacked structure including a stacked structure as a basic structure is disclosed. Here, the electroluminescent compound is a compound that has high emission quantum efficiency, has a π-electron system that easily undergoes external perturbation, and can be electrically excited.

However, in these odors, it is essential that the light-emitting layer has two layers, and various types of interaction represented by the formation of an exciplex of an electron-donating compound and an acceptor compound forming the two layers near the interface between the two layers. Since the light emission performance greatly depends on the state of the interface, manufacturing conditions are difficult, and the decrease in light emission due to deterioration of the interface is remarkable.

In the EL device described in US Pat. Nos. 4,672,265 and 4,725,513, at least one of the two light-emitting layers is a molecular accumulation film formed by an LB method, and a long chain used in the molecular accumulation film is used. Since the alkyl chain has a heat resistance temperature of about 100 ° C., it is susceptible to heat (Journal of the Society of Polymer Science, 36,267 (1987)).
Therefore, the above-described molecular accumulation film and the like are damaged during the deposition of the counter electrode, and the yield of the element is poor. A further important drawback in this regard is that the long alkyl chains generally have very low mobilities, thereby significantly alienating charge mobility, which makes the light emitting performance of this device inadequate and lacks practicality. .

U.S. Patent Nos. 4,734,338 and 4,741,976,
No. 4,775,820 discloses a light emitting layer 2 having an insulating layer added.
Although the layer structure is disclosed, the light emitting performance is not sufficient because of the unavoidable mobility of the electric charge, and the practicability is lacking.

As a document mentioning the use of a distyrylbenzene derivative in an organic thin film EL device, there is the aforementioned European Patent Publication No. 281381. This reference describes p-bis- (o
-Methylstyryl) benzene and bis (styryl) benzene-based dyes are used as fluorescent substances, and used by embedding them in a trace amount in a host substance. At this time, the thin-film host material in which a trace amount of the fluorescent substance is embedded is a light emitting band, and an injection function to be possessed by the light emitting band (light emitting layer) (hole injection from an electrode or a hole injection layer by electrolytic application). And the ability to inject electrons from the electrodes or the electron injection layer), the transport function (the ability to transport holes and electrons by an electric field), and the light-emitting function (the field of recombination of holes and electrons). The host substance is responsible for some of the injection, transport, and luminescence functions, and the fluorescent substance (distyrylbenzene derivative) responds to the recombination of holes and electrons. Due to the property of emitting light, that is, only a part of the light emitting function is used, the host substance is only used in a small amount (about 5 mol%). What is disclosed There.

Further, U.S. Pat. Nos. 4,672,265 and 4,755,513.
No. 4,731,338, No. 4,747,761 and No. 4,775,320, JP-A-61-37890, etc., as examples of electroluminescent compounds, 1,4- Screw (2
-Methylstyryl) benzene and its substituents such as alkyl group, alkoxy group and amino group are described.
There is no disclosure as to the light emitting performance of devices using these compounds. Further, as described above, since the light emission is caused by the interaction between the two light emitting layers, the present invention is an invention in which the light emitting function is specified to be based on the exciplex. Without this specific light emitting function, that is, without taking the two-layer structure of the light emitting layer,
There is no technical disclosure that a thin film made of a distyrylbenzene derivative can function as a light emitting layer. A device using a distyrylbenzene derivative alone as a light emitting layer is disclosed in Japanese Patent Application No. 63-308859. The EL element shown here is of a single-layer type having only a light-emitting layer, and has good emission intensity and luminous efficiency as a single-layer type, but there is still room for improvement in practical use.

[Means for solving the problem]

Therefore, the present inventors have solved the above disadvantages of the prior art,
We have conducted intensive research to develop an EL device that is simple in structure, has excellent heat resistance, has a good yield, and can obtain highly efficient light emission.

As a result, by using a 1,4-bis (alkylstyryl) benzene derivative with a specific structure as a light-emitting material and stacking a charge injection / transport layer on it,
It has been found that the luminous efficiency can be remarkably improved, and the above object can be sufficiently achieved. The present invention has been completed based on such findings.

That is, the present invention relates to the general formula (Wherein, R ¹ and R ² each represent an alkyl group having 1 to 4 carbon atoms, and R ³ represents hydrogen or an alkyl group having 1 to 4 carbon atoms). An alkylstyryl) benzene derivative is used as a material for the light emitting layer, and (1) an anode, a hole injection / transport layer, a light emitting layer and a cathode are stacked in this order, and (2) an anode, a hole injection / transport layer, a light emitting layer, An object of the present invention is to provide a thin film EL device in which an electron injection / transport layer and a cathode are stacked in this order, or (3) an anode, a light emitting layer, an electron injection / transport layer and a cathode are stacked in this order.

In the present invention, the compound used as the light emitting layer material is a 1,4-bis (alkylstyryl) benzene derivative represented by the above general formula (I). Here, each symbol in the formula is as described above. That is, R ¹ and R ² each represent an alkyl group having 1 to 4 carbon atoms (eg, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, and an s-butyl group). , t-butyl group), which may be the same or different. R ³ represents hydrogen or an alkyl group having 1 to 4 carbon atoms as in R ¹ and R ² described above.
There are various types of 1,4-bis (alkylstyryl) benzene derivatives represented by the general formula (I).
1,4-bis (2-methylstyryl) benzene; 1,4-bis (3-methylstyryl) benzene; 1,4-bis (4-methylstyryl) benzene; 1,4-bis (2-ethylstyryl) Benzene; 1,4-bis (3-ethylstyryl) benzene; 1,4-bis (4-ethylstyryl) benzene; 1,4-bis (2-methylstyryl) -2-methylbenzene; 1,4-
Bis (2-methylstyryl) -2-ethylbenzene and the like can be mentioned. Of these, 1,4-bis (2-methylstyryl) benzene represented by 1,4-bis (4-methylstyryl) benzene represented by the following formula is preferably used.

In the EL device of the present invention, the 1,4-bis (alkylstyryl) benzene derivative of the above general formula (I) is used as a material for the light emitting layer, and at the same time, it is used as a material for the hole injection / transport layer and / or the electron injection / transport layer. It is necessary to have a laminated structure.
With such a laminated structure, the luminous intensity can be greatly improved as compared with a single-layer type having only the luminescent layer.

The laminated structure in the EL device of the present invention includes (1) anode / hole injection / transport layer / light emitting layer / cathode, (2) anode / hole injection / transport layer / light emitting layer / electron injection / transport layer / cathode, or (3) The anode / light-emitting layer / electron injection / transport layer / cathode were laminated in this order.

Note that these EL elements are preferably formed over a supporting substrate.

The light emitting layer in the EL device of the present invention has the following three functions. Injection function When an electric field is applied, holes can be injected from the anode or the hole injection / transport layer, and electrons can be injected from the cathode or the electron injection / transport layer. Transport function Injected charges (electrons and holes) ) The function of moving the) by the force of an electric field. Light-emitting function Provides a field for recombination of electrons and holes, and connects it to light emission. However, there is a difference between the ease of hole injection and the ease of electron injection. Although the transport ability represented by the mobility of holes and electrons may be large or small, it is preferable to transfer either one of the charges.

In the EL device of the present invention, the 1,4-bis (alkylstyryl) benzene derivative of the general formula (I) used as a light-emitting material (light-emitting layer) has an ionization energy of preferably 6.0 eV or less and a suitable anode metal. Alternatively, if an anode compound is selected, holes are relatively easily injected. The electron affinity is preferably 2.5 eV or more, and if an appropriate cathode metal or cathode compound is selected, electrons can be relatively easily injected. Moreover, the electron and hole transport functions are excellent. Further, since the solid-state fluorescence is strong, the ability to convert the excited state of the above-mentioned compound, its aggregate or crystal formed at the time of recombination into light is large.

The substrate that can be used in the EL device of the present invention is preferably a substrate having transparency, and generally, glass, transparent plastic, quartz, or the like is applied. The electrodes (anode, cathode) are made of a metal such as gold, aluminum, or indium, an alloy, a mixture, or a transparent material such as indium tin oxide (a mixed oxide of indium oxide and tin oxide; ITO), SnO ₂ , and ZnO. Preferably, it is used. For the anode, a metal or an electrically conductive compound having a large work function is preferable.
A metal having a small work function or an electrically conductive compound is suitable for the cathode. Preferably, at least one of these electrodes is transparent or translucent.

In order to produce an EL device having the above-mentioned constitution (1) consisting of anode / hole injection / transport layer / light-emitting layer / cathode, for example, the following procedure may be followed. That is, first, an electrode is formed on a substrate by vapor deposition or sputtering. At this time, the film-like electrode generally has a thickness of 10 nm to 1 μm, particularly 200 nm or less.
It is preferable to increase the transmittance of light emission. Next, a hole injection / transport material is formed in a thin film on the electrode to form a hole injection / transport layer. In this case, the thinning method includes spin coating, casting, vapor deposition, and the like, but a vacuum vapor deposition method is particularly preferable because a uniform film is easily obtained and pinholes are not generated. When using a vapor deposition method for thinning,
The conditions for the deposition are, for example, a boat heating temperature of 50 to 400 ° C.
The thickness may be selected so that the film thickness is 5 nm to 5 μm in a range of a vacuum degree of 10 ⁻⁵ to 10 ⁻³ Pa, a deposition rate of 0.01 to 50 nm / sec, and a substrate temperature of −50 to + 300 ° C.

The above-mentioned conditions differ depending on the type of the compound and the target crystal structure, association structure, etc. of the molecular deposition film, and cannot be uniquely determined. preferable.

After the formation of the hole injecting and transporting layer, the luminescent material is formed into a thin film on the hole injecting and transporting layer by, for example, a vacuum evaporation method. The deposition conditions at this time are the same as the conditions for forming the hole injection transport layer.

After that, the counter electrode is formed with a film thickness of 50 to
If formed at 200 nm, an EL element is created.

Further, in order to prepare an EL device having the constitution of (2) anode / hole injection / transport layer / light-emitting layer / electron injection / transport layer / cathode, first, an electrode, a hole injection / transport layer, and a light-emitting layer were prepared according to the above (1). Formed in the same way as an EL device, and then an electron injection material (electron transfer compound)
By forming a thin film by vapor deposition to form an electron injection / transport layer on the light emitting layer, and finally forming a counter electrode in the same manner as in the case of producing the EL element of (1) above, An EL element having the configuration of the above (2) is created. Here, the order of the hole injecting and transporting layer / light emitting layer / electron injecting and transporting layer is changed to the electron injecting and transporting layer / light emitting layer / hole injecting and transporting layer. A transport layer and an electrode may be formed in this order.

Further, in order to prepare an EL device having the structure of (3) anode / light-emitting layer / electron injection / transport layer / cathode, the above-mentioned (2)
When the EL element is manufactured, the formation of the hole injection / transport layer may be omitted.

In the EL device of the present invention, at least one of the hole injecting and transporting layer and the electron injecting and transporting layer is required, and a device having both layers is more preferable, and the light emitting performance is further improved. Here, the hole injection transport layer (hole injection layer) is made of a hole transport compound (hole injection material) and has a function of transmitting holes injected from the anode to the light emitting layer. By sandwiching this layer between the anode of the EL element and the light emitting layer, more holes are injected into the light emitting layer at a low voltage, and the luminance of the element is improved.

The hole transport compound of the hole injecting and transporting layer used here is disposed between two electrodes to which an electric field is applied to facilitate the injection of holes from the anode, and appropriately converts the holes into the light emitting layer. A compound that can be transmitted to By interposing the hole injection transport layer between the anode and the light emitting layer, many holes are injected into the light emitting layer with a lower electric field. Furthermore, electrons injected from the cathode or the electron injection / transport layer into the light emitting layer are blocked by electrons at the interface between the light emitting layer and the hole injection / transport layer.
The light is accumulated near the interface in the light emitting layer, and the luminous efficiency is improved. Preferred hole transport compounds here are 10 ⁴ to 10 ⁶ volts
If a layer is placed between electrodes given an electric field of / cm,
It has a hole mobility of at least 10 ^-6 cm ² / volt-second. Therefore, preferred examples include various compounds used as a hole charge transporting material in a photoconductive material.

As described above, examples of the charge transport material include the following.

Triazole derivatives described in U.S. Patent No. 3,112,197, etc., oxadiazole derivatives described in U.S. Patent No. 3,189,447, etc., imidazole derivatives described in JP-B-37-1696, etc. U.S. Patent Nos. 3615402, 3820989, 3542544, JP-B Nos. 45-555, 51-10983, and JP-A-51-93224, 55-17105, 56-4148. , Id 55
Polyarylalkane derivatives described in JP-A-108667, JP-A-55-156953, JP-A-56-36656 and the like; U.S. Patent Nos. 3,180,729 and 4,278,746;
-88064, 55-88065, 49-105537, 55-51
Nos. 086, 56-80051, 56-88141, 57-45545
Pyrazoline derivatives and pyrazolone derivatives described in U.S. Pat. Nos. 6,115,105, 54-112637, 55-74546, and the like.
46-3712, 47-25336 and JP-A-54-534.
Phenylenediamine derivatives described in JP-A Nos. 35, 54-110536 and 54-119925; U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,597;
Nos. 3,658,520, 4,322,103, 4,117,961 and 4,012,376, and JP-B-49-35702, JP-A-39-27577, and JP-A-55-144250, JP-A-56-119132, and JP-A-56-119. 22437
No. 3,085,086, an arylamine derivative described in West German Patent No. 1110518, an amino-substituted chalcone derivative described in US Pat. No. 3,235,501, and a US Pat. No. 3,257,203. Oxazole derivatives, styryl anthracene derivatives described in JP-A-56-46234, etc., fluorenone derivatives described in JP-A-54-110837, etc., U.S. Pat. 54-59143, same
55-52063, 55-52064, 55-46760, 55-8
Hydrazone derivatives described in JP-A-5495, JP-A-57-11350, JP-A-57-148749, etc., and JP-A-61-210363, JP-A-61-228451, JP-A-61-14642.
Nos. 61-72255, 62-47646, 62-36674,
No. 62-10652, No. 62-30255, No. 60-93445, No. 60
Stilbene derivatives and the like described in JP-A-94462, JP-A-60-174749, JP-A-60-175052 and the like can be listed.

More particularly preferred examples include a compound as a hole transport layer (aromatic tertiary amine) and a compound as a hole injection zone (porphyrin compound) disclosed in JP-A-63-295695. .

Further preferred examples of the hole transport compound are described in JP-A-53-27033, JP-A-54-58445, and JP-A-54-149634.
JP-A-54-64299, JP-A-55-79450, and 55
No. 144250, No. 56-119132, No. 61-295558, No. 61-98353, and U.S. Pat. No. 4,127,412. Examples of these are as follows.

A hole injecting and transporting layer is formed from these hole transporting compounds, and the hole injecting and transporting layer may be composed of a single layer or a layer in which a hole injecting and transporting layer using a different kind of compound is stacked. Is also good.

On the other hand, the electron injection transport layer (electron injection layer) is made of a compound that transmits electrons. Preferred examples of the electron transfer compound (electron injection material) for forming the electron injection transport layer include: Nitro-substituted fluorenone derivatives such as JP-A-57-149259, JP-A-58-55450 and JP-A-63-104061.
No. 3 (1988), p.68, anthraquinodimethane derivatives described in Japanese Unexamined Patent Publication No.
Listed in 1 etc. Diphenylquinone derivatives such as, Thiopyran dioxide derivatives such as those described in JJAPPl. Phys., 27, L269 (1988), etc. Compounds represented by the following formulas: JP-A-60-69657, JP-A-61-143764, JP-A-61-148159
And the anthraquinodimethane derivatives and anthrone derivatives described in JP-A Nos. 61-225151 and 61-233750.

In the EL element of the present invention, when the applied voltage is AC (AC drive), light emission is observed only in a bias state in which a positive voltage is applied to the anode side. When the applied voltage is direct current (direct current drive), light emission is always observed by applying a positive voltage to the anode side.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 ITO was deposited on a 25 mm × 75 mm × 1.1 mm glass substrate by vapor deposition.
A transparent support substrate was formed with a thickness of 100 nm. This transparent support substrate is supplied to a commercially available vapor deposition device (Nihon Vacuum Technology Co., Ltd.)
And a molybdenum resistance heating boat and N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4 ' -Add 200 mg of diamine (TPDA), and add another 1,4-bis (2-methylstyryl) benzene (OMS
200 mg of B) was placed therein, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Thereafter, the boat containing TPDA was heated to 215 to 220 ° C., and TPDA was deposited on the transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec to form a hole injection layer having a thickness of 80 nm. The substrate temperature at this time was room temperature. Without removing this from the vacuum chamber, place the OM on another hole
90 nm was stacked and deposited as a light emitting layer using SB. The deposition conditions were a boat temperature of 145 to 155 ° C., a deposition rate of 0.1 to 0.2 nm / sec, and a substrate temperature of room temperature.

This was taken out of the vacuum chamber, a stainless steel mask was placed on the light emitting layer, and fixed again to the substrate holder.

Next, 1 g of a magnesium ribbon was placed in a molybdenum resistance heating boat, and a copper pellet was mounted as a target of an electron gun for electron beam evaporation located below the substrate holder in the center of the vacuum chamber. Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and then copper was deposited at 0.03 to 0.08 nm / cm by electron beam evaporation.
At the same time, magnesium was vapor-deposited from the molybdenum boat at a deposition rate of 1.7 to 2.8 nm / sec by the resistance heating method. The emission current of the filament of the electron gun was 200 to 230 mA, and the acceleration voltage was 4 kV. The temperature of the boat was about 500 ° C. Under the above conditions, a mixed metal electrode of magnesium and copper was deposited on the light emitting layer in a thickness of 60 nm to form a counter electrode.

When applying 10V DC to this device with the ITO electrode as the anode and the mixed metal electrode of magnesium and copper as the cathode, the current is 140mA
/ cm ² and blue emission was obtained. The maximum emission wavelength was 463 nm from spectral measurement, and the emission luminance was 100 cd / m ² .

When this is compared with Comparative Example 1 described later, the emission maximum wavelength is
Although the wavelength was increased by about 10 nm, high-intensity blue light emission at low voltage was obtained by lamination.

Example 2 ITO was deposited on a 25 mm × 75 mm × 1.1 mm glass substrate by vapor deposition.
A transparent support substrate was formed with a thickness of 100 nm. This transparent support substrate is supplied to a commercially available vapor deposition device (Nihon Vacuum Technology Co., Ltd.)
And a molybdenum resistance heating boat and N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4 ' -200 mg of diamine (TPDA) and another molybdenum boat in 1,4-bis (4-methylstyryl) benzene (PMSB)
Was placed in a vacuum tank, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Thereafter, the boat containing TPDA was heated to 215 to 220 ° C., and TPDA was deposited on the transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec to form a hole injection layer having a thickness of 85 nm. The substrate temperature at this time was room temperature. Without taking it out of the vacuum chamber, put PM on another hole boat
SB was used as a light emitting layer, and was deposited in a thickness of 80 nm. The deposition conditions were a boat temperature of 220 to 225 ° C., a deposition rate of 0.1 to 0.2 nm / sec, and a substrate temperature of room temperature.

This was taken out of the vacuum chamber, a stainless steel mask was placed on the light emitting layer, and fixed again to the substrate holder.

Next, 1 g of a magnesium ribbon was placed in a molybdenum resistance heating boat, and a copper pellet was mounted as a target of an electron gun for electron beam evaporation located below the substrate holder in the center of the vacuum chamber. Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and then copper was deposited at 0.03 to 0.08 nm / cm by electron beam evaporation.
At the same time, magnesium was vapor-deposited from the molybdenum boat at a deposition rate of 1.7 to 2.8 nm / sec by the resistance heating method. The emission current of the filament of the electron gun was 200 to 230 mA, and the acceleration voltage was 4 kV. The temperature of the boat was about 500 ° C. Under the above conditions, a mixed metal electrode of magnesium and copper was deposited on the light emitting layer in a thickness of 60 nm to form a counter electrode.

When a 12 VDC current is applied to this device using the ITO electrode as the anode and the mixed metal electrode of magnesium and copper as the cathode, a current of 140 V is applied.
mA / cm ² flow and blue-green emission was obtained. The maximum emission wavelength was 493 nm from spectral measurement, and the emission luminance was 150 cd / m ² .

Compared with Comparative Example 2 described below, low-voltage and high-luminance bluish green (the same luminescent color as the single-layer type) was obtained by lamination.

Example 3 ITO was deposited on a 25 mm × 75 mm × 1.1 mm glass substrate by vapor deposition.
A transparent support substrate was formed with a thickness of 100 nm. This transparent support substrate is supplied to a commercially available vapor deposition device (Nihon Vacuum Technology Co., Ltd.)
And a molybdenum resistance heating boat and N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4 ' -Add 200 mg of diamine (TPDA), and add another molybdenum boat to 1,4-bis (4-ethylstyryl) benzene (ESB)
Was placed in a vacuum tank, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Thereafter, the boat containing TPDA was heated to 215 to 220 ° C., and TPDA was deposited on the transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec to form a hole injection layer having a thickness of 80 nm. The substrate temperature at this time was room temperature. Without taking it out of the vacuum chamber, put ES on another hole boat
B was deposited as a light emitting layer by 80 nm deposition. The deposition conditions were a boat temperature of 220 to 225 ° C., a deposition rate of 0.1 to 0.3 nm / sec, and a substrate temperature of room temperature. Take this out of the vacuum chamber, place a stainless steel mask on the light emitting layer,
It was fixed to the substrate holder again. Next, 1 g of a magnesium ribbon was placed in a molybdenum resistance heating boat, and a copper pellet was mounted as a target of an electron gun for electron beam evaporation located below the substrate holder in the center of the vacuum chamber. Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and then copper was deposited at a deposition rate of 0.03 to 0.08 nm / sec by electron beam deposition, and simultaneously magnesium was removed from the molybdenum boat by resistance heating at a rate of 1.
Deposition began at a deposition rate of 7-2.8 nm / sec. The emission current of the filament of the electron gun is 200 to 230 mA, and the acceleration voltage is
It was 4 kV. The temperature of the boat was about 500 ° C.
Under the above conditions, a mixed metal electrode of magnesium and copper was deposited to a thickness of 500 nm on the light emitting layer to form a counter electrode.

Applying DC 10V to this device with the ITO electrode as the anode and the mixed metal electrode of magnesium and copper as the cathode, the current becomes 100mA
/ cm ² and blue-green emission was obtained. The maximum emission wavelength was 486 nm from the spectroscopic measurement, and the emission luminance was 80 cd / m ² .

When this was compared with Comparative Example 3 described later, blue-green light emission with low voltage and high luminance was obtained by lamination.

Example 4 ITO was deposited on a 25 mm × 75 mm × 1.1 mm glass substrate by vapor deposition.
A transparent support substrate was formed with a thickness of 100 nm. This transparent support substrate is supplied to a commercially available vapor deposition device (Nihon Vacuum Technology Co., Ltd.)
And a molybdenum resistance heating boat and N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4 ' -Add 200 mg of diamine (TPDA), and put another molybdenum boat in 1,4-bis- (2-ethylstyryl) benzene (ES
200 mg of B) was placed therein, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. Then heat the boat containing TPDA to 215-220 ° C,
TPDA was deposited on the transparent support substrate at a deposition rate of 0.1 to 0.3 nm / sec to form a 60-nm thick hole injection layer. The substrate temperature at this time was room temperature. Without taking this out of the vacuum chamber, a 60 nm layer of ESB was deposited as a light emitting layer from another boat on the hole injection layer. The deposition conditions were a boat temperature of 220 to 225 ° C., a deposition rate of 0.1 to 0.3 nm / sec, and a substrate temperature of room temperature.

The vacuum chamber was then returned to atmospheric pressure and the two molybdenum boats were removed from the vacuum chamber and replaced with [3 ″,
4 ″: 3,4,5: 10 ″, 9 ″: 3 ′, 4 ′, 5 ′)-dipyridino [1,2
-A: 1 ', 2'-a'] bisbenzimidazole-6,18-
A molybdenum boat containing 200 mg of dione was set in a vacuum chamber. Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and the boat was heated to 500 ° C., and the material was deposited in a thickness of 60 nm as an electron injection layer on the light emitting layer. After that, the vacuum chamber was returned to the atmospheric pressure, the laminated sample was once removed from the substrate holder, and then a stainless steel mask was installed.
It was fixed to the substrate holder again.

Next, 1 g of a magnesium ribbon was placed in a molybdenum resistance heating boat, and a copper pellet was mounted as a target of an electron gun for electron beam evaporation located below the substrate holder in the center of the vacuum chamber. Thereafter, the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa, and then copper was deposited at 0.03 to 0.08 nm / cm by electron beam evaporation.
At the same time, magnesium was vapor-deposited from the molybdenum boat at a deposition rate of 1.7 to 2.8 nm / sec by the resistance heating method. The emission current of the filament of the electron gun was 200 to 230 mA, and the acceleration voltage was 4 kV. The temperature of the boat was about 500 ° C. Under the above conditions, a mixed metal electrode of magnesium and copper was deposited to a thickness of 100 nm on the light emitting layer to form a counter electrode.

Applying 10V DC to this device using the ITO electrode as the anode and the mixed metal electrode of magnesium and copper as the cathode, the current becomes 120mA
/ cm ² and blue-green light emission similar to that of Example 3 was obtained. The peak wavelength was 486 nm, and the emission luminance was 100 cd / m ² .

Compared with Comparative Example 3 described below, by laminating the hole injection layer and the electron injection layer, blue-green light emission with lower voltage and higher luminance was obtained than in the single layer type having only the light emitting layer.

Comparative Example 1 A transparent support substrate was formed by sputtering ITO (indium tin oxide) to a thickness of 50 nm on a glass substrate of 25 mm × 75 mm × 1.1 mm by a sputtering method. Fixed to a substrate holder manufactured by Japan Vacuum Technology Co., Ltd., 100 mg of 1,4-bis (2-methylstyryl) benzene was placed in a molybdenum resistance heating boat, and the pressure in the vacuum chamber was reduced to 5 × 10 ⁻⁵ Pa. . 160 ° C
Then, 1,4-bis (2-methylstyryl) benzene was deposited on the transparent support substrate at a deposition rate of 1.0 nm / sec.
A 7 μm phosphor thin film was obtained. At this time, the substrate temperature was room temperature. Take this out of the vacuum chamber, place a stainless steel mask on the luminous body thin film, fix it again on the substrate holder, and place it on a molybdenum resistance heating boat with 200 m of gold.
g, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. Thereafter, the boat was heated to 1400 ° C., and finally a 50 nm gold electrode was formed on the luminescent thin film to produce an EL device.

When a DC voltage of 20 V was applied to this element, the current was 2.0
mA flow and blue emission were obtained. The emission maximum wavelength at this time is 45
The emission luminance was 0 cd / m ² at 0 nm.

Comparative Example 2 ITO was deposited on a 25 mm × 75 mm × 1.1 mm glass substrate by vapor deposition.
A film formed to a thickness of 50 nm is used as a transparent support substrate, and this transparent support substrate is used as a commercially available vapor deposition device (manufactured by Japan Vacuum Engineering Co., Ltd.)
200 mg of 1,4-bis (4-methylstyryl) benzene in a molybdenum resistance heating boat
And the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Further, the boat was heated to 240 to 246 ° C., and 1,4-bis (4-methylstyryl) benzene was deposited at a rate of 0.5 to 1.0.
Vapor deposition was performed on the transparent support substrate at a rate of nm / sce to obtain a light emitting thin film having a thickness of 0.5 μm. At this time, the substrate temperature was room temperature. This is taken out of the vacuum chamber, a stainless steel mask is placed on the luminescent thin film, and 200 mg of gold is again put into a molybdenum resistance heating boat fixed to the substrate holder, and the vacuum chamber is evacuated to 2 × 10 ^-4 Pa. did.

Thereafter, the boat was heated to 1400 ° C., and a gold electrode having a thickness of 20 nm was formed on the luminous body thin film, and used as a counter electrode. When a direct current of 30 V was applied to the device using a gold electrode as a positive electrode and an ITO electrode as a negative electrode, a current of 20 mA was emitted to emit blue-green light.

The emission maximum wavelength at this time is 490 nm, and the emission band is 440 nm ~
The emission range was 560 nm, and the emission luminance was 60 cd / m ² .

Comparative Example 3 ITO was deposited on a 25 mm x 75 mm x 1.1 mm glass substrate by vapor deposition.
A film formed to a thickness of 50 nm is used as a transparent support substrate, and this transparent support substrate is used as a commercially available vapor deposition device (manufactured by Japan Vacuum Engineering Co., Ltd.)
200mg 1,4-bis (4-ethylstyryl) benzene in a molybdenum resistance heating boat
And the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

Further, the boat was heated to 237 ° C, and 1,4-bis (4
-Ethylstyryl) benzene was deposited on the transparent support substrate at a deposition rate of 0.5 nm / sce to obtain a light emitting thin film having a thickness of 0.5 μm. At this time, the substrate temperature was room temperature. This was taken out of the vacuum chamber, a stainless steel mask was placed on the luminous body thin film, fixed again to the substrate holder, 200 mg of gold was put into a molybdenum resistance heating boat, and the vacuum chamber was set to 2 × 10 ^-4 P
The pressure was reduced to a.

Thereafter, the boat was heated to 1400 ° C., and a gold electrode having a thickness of 20 nm was formed on the luminous body thin film, and used as a counter electrode. When a direct current of 30 V was applied to this device using a gold electrode as a positive electrode and an ITO electrode as a negative electrode, a current of 1 mA was emitted to emit blue-green light.

The emission maximum wavelength at this time is 480 nm, and the emission band is 440 nm
The emission range was 600 nm, and the emission luminance was 0.1 cd / m ² .

〔The invention's effect〕

As described above, the EL device of the present invention can obtain high luminance only by applying a low voltage, has a simple configuration, and can be easily manufactured. Further, according to this EL element, it is possible to achieve blue light emission, which has been conventionally difficult, with high luminance and high efficiency.

In addition, there are few defects such as pinholes, and it is easy to enlarge the area, high productivity, and EL for display of various devices
It is possible to provide an inexpensive and stable product as an element.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-59-194393 (JP, A) JP-A-63-295695 (JP, A) Chemical Abstract Vol. 78, 50479, P483, 1973 Steblin V. I. et al, 2h. prikl. Spektros k. , Vol. 19, No. 4, P724-726.1973 (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 11/06 Z CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] An anode, a hole injection / transport layer, a light emitting layer and a cathode are laminated in this order. (Wherein, R ¹ and R ² each represent an alkyl group having 1 to 4 carbon atoms, and R ³ represents hydrogen or an alkyl group having 1 to 4 carbon atoms). A thin-film electroluminescent device, wherein an alkylstyryl) benzene derivative is used as a material for the light emitting layer. 2. An anode, a hole injecting and transporting layer, a light emitting layer, an electron injecting and transporting layer and a cathode are laminated in this order.
2. A thin-film electroluminescence device comprising the 1,4-bis (alkylstyryl) benzene derivative according to claim 1 as a material for the light-emitting layer. 3. An anode, a light emitting layer, an electron injection / transport layer and a cathode are laminated in this order.
A thin-film electroluminescent device, wherein a bis (alkylstyryl) benzene derivative is used as a material of the light emitting layer.