JPH07119408B2 - Organic electroluminescent device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel organic electroluminescent device. More specifically, the present invention relates to an organic electroluminescence device which is suitable as a light emitting device for various display devices and which can output yellow and green light with high brightness at a particularly low voltage.

[Prior Art] In recent years, electroluminescence elements (hereinafter abbreviated as EL elements) have high visibility because they self-lumineze, and because they are completely solid elements, they have features such as excellent impact resistance, Attention has been paid to its use as a light emitting element in various display devices.

This EL element includes an inorganic EL element that uses an inorganic compound as a light emitting material and an organic EL element that uses an organic compound. Among these, the organic EL element can significantly reduce the applied voltage, Research for its practical application is being actively conducted.

Regarding the structure of the organic EL device, the structure of the anode / light emitting layer / cathode is basically used, and a hole injecting / transporting layer and an electron injecting / transporting layer are appropriately provided on the structure, for example, anode / hole injecting / transporting layer / light emitting layer. There are known structures such as / cathode and anode / hole injecting / transporting layer / light emitting layer / electron injecting / transporting layer / cathode. The hole injecting and transporting layer has a function of transmitting holes injected from the anode to the light emitting layer, and the electron injecting and transporting layer has a function of transmitting electrons injected from the cathode to the light emitting layer. There is. By interposing the hole injecting and transporting layer between the light emitting layer and the anode, many holes are injected into the light emitting layer at a lower electric field, and further injected into the light emitting layer from the cathode or the electron injecting and transporting layer. It is known that the generated electrons are accumulated at the interface of the light emitting layer and the hole injecting and transporting layer due to the barrier of the electrons present at the interface, and the luminous efficiency is increased [“Applied Physics Letters”]. 51, 913 (1987)].

Various organic EL devices have been known so far, for example, (1) a laminated device having an anode / hole injection zone / emission zone / cathode configuration (Japanese Patent Laid-Open No. 59-194393), (2). ) In response to recombination of holes and electrons, a host material having a structure of anode / hole injecting / transporting zone / emission zone / cathode, and the emission zone having a function capable of injecting electrons and holes, (3) A device using 12-phthalopurinone as a light-emitting material [3] A stacked device composed of a phosphor doped with a light-emitting material [“Japanese Journal of Applied Physics Letters (JJAppl.Phys.Let
t.) ”Vol. 27, L713 (1988)] and the like.

In the element of (1) above, at a low voltage of about 20 V,
High-luminance blue-green, blue, and orange luminescence of several hundred cd / m ² are obtained. For example, by using a triphenylamine derivative in the hole injection zone and an aluminum oxine complex in the emission zone, green emission of 340 cd / m ² can be obtained, and by using a benzoxazole-based fluorescent whitening agent in the emission zone, It has realized blue, green and orange light emission. On the other hand, in the device of (2), red, green, and blue-green light emission of high brightness are obtained at a low voltage, but in the device of (3), it can be visually recognized in a yellow bright place with an applied voltage of about 50V. Only light emission with an output of about 1 μW / cm ² is obtained. As described above, in the conventional organic EL device, yellow light emission of high output has not yet been obtained.

[Problems to be Solved by the Invention] Under the circumstances, the present invention has been made for the purpose of providing a novel organic EL element capable of outputting yellow light emission with high brightness, particularly at low voltage. It is a thing.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, an organic EL element using a distyrylpyrazine derivative as a light emitting material has a high brightness of yellow and It was found that green light emission can be output at a low voltage, and the present invention has been completed based on this finding.

That is, the present invention provides, as a light emitting material, a distyrylpyrazine derivative, particularly a general formula (X and Y in the formula are each a monovalent aromatic residue or a heteroaromatic residue, and they may be the same or different from each other.) An organic EL device characterized by being used.

Hereinafter, the present invention will be described in detail.

In the EL device of the present invention, as the distyrylpyrazine derivative used as the light emitting material, the above-mentioned general formula (I) is particularly preferable.
A compound having a distyrylpyrazine skeleton structure represented by is preferable, which exhibits fluorescence in the solid state and brings about mobility of electrons and holes, and further, due to the conjugate property of the distyrylpyrazine skeleton, ionization energy Is small and has a high electron affinity, so that it has characteristics such as easy injection of charges from electrodes and the like.

X and Y in the general formula (I) are each a monovalent aromatic residue or a heteroaromatic residue, and examples of the aromatic residue include a phenyl group, a naphthyl group, an antonyl group, a styryl group, and the like. However, as the heteroaromatic residue, for example, a furyl group, a thienyl group, a pyrrolyl group, a pyridyl group, a quinolyl group, a thiazolyl group, an oxazolyl group, an imidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzimidazolyl group, a carbazolyl group. A monovalent group consisting of a triazole group and a pyrazoline group.

Various substituents may be introduced into these aromatic residues and heteroaromatic residues as long as the above characteristics are not impaired. Examples of the substituent include an alkyl group such as a methyl group, an ethyl group, an isopropyl group, and a t-butyl group or a halogen-substituted alkyl group thereof, a methoxy group, an ethoxy group, a propoxy group, an alkoxy group such as a butoxy group, a formyl group, Acyl group such as acetyl group, propionyl group, butyryl group, aralkyl group such as benzyl group, phenethyl group, phenoxy group, aryloxy group such as tolyloxy group, methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group, etc. Alkoxycarbonyl group, acetyloxy group, propionyloxy group, butyryloxy group and other acyloxy groups, acetylamino group, propionylamino group, butyrylamino group and other acylamino groups, carbamoyl group,
Dimethylaminocarbonyl group, aminocarbonyl group such as carbonyl group, phenoxycarbonyl group, tolyloxycarbonyl group, aryloxycarbonyl group such as xylyloxycarbonyl group, various halogen atoms, carboxyl group, hydroxyl group, further methyl group, ethyl group A phenyl group with or without a substituent such as an alkyl group such as a propyl group, an alkoxy group such as a methoxy group and an ethoxy group, and a general formula (R ¹ and R ² in the formula are each a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a formyl group, an acetyl group, an acyl group such as a propionyl group,
A phenyl group or a substituted phenyl group such as a tolyl group or a xylyl group, which may be the same or different from each other, and are bonded to each other to form a substituted or unsubstituted saturated five-membered ring or A saturated 6-membered ring may be formed, or a substituted or unsubstituted saturated 5-membered ring or saturated 6-membered ring may be formed by combining with a group substituted for X and Y). And the like.

X and Y in the general formula (I) may be the same or different from each other, and a saturated or unsaturated ring structure may be formed by bonding between the groups substituting for them. It may be formed.

Among the distyrylpyrazine derivatives represented by the general formula (I), those in which the double bond site has a trans structure are particularly preferable from the viewpoint of having strong fluorescence in the solid state. Among these, an alkyl group and an alkoxy group are preferable for the same reason.

Specific examples of the distyrylpyrazine derivative represented by the general formula (I) used as a light emitting material in the EL device of the present invention include the following compounds.

Among these compounds, 2,5-bis- [2- of (4)
(4-Biphenyl) ethenyl] pyrazine is a novel compound that has not been published in the literature, and can be produced, for example, by reacting p-phenylbenzaldehyde with 2,5-dimethylpyrazine in the presence of an acid anhydride. it can. Also,
Compounds other than (4) include, for example, “Journal of Polymer Science Polymer Physics Edition” (J. Polymer Sci. Polymer Phys. Ed.) No. 16
Vol. 1, p. 1365 (1968).

The light emitting layer in the EL device of the present invention is prepared by using the distyrylpyrazine derivative represented by the general formula (I), for example, by a vapor deposition method,
It can be formed by thinning it by a known method such as a spin coating method, a casting method or an LB method, but a molecular deposition film is particularly preferable. Here, the molecular deposition film is a thin film formed by depositing the distilpyrazine derivative from a vapor phase state, or a film formed by solidifying from a solution state or a liquid phase state of the derivative, for example, vapor deposition. The membrane corresponds to this. Usually, this molecular deposition film can be distinguished from a thin film (molecular cumulative film) formed by the LB method. Further, the light emitting layer, as disclosed in JP-B-64-7636, etc., an adhesive such as a resin and the distyrylpyrazine derivative are dissolved in a solvent to prepare a solution, which is then spin-coated. It can also be formed into a thin film by a method such as. The thickness of the light emitting layer thus formed is not particularly limited and may be appropriately selected depending on the circumstances, but is usually selected in the range of 5 nm to 5 μm.

The light emitting layer in the EL device of the present invention is (1) injection capable of injecting holes from an anode or a hole injection / transport layer and electrons from a cathode or an electron injection / transport layer when an electric field is applied. It has a function, (2) a transport function that moves injected charges (electrons and holes) by the force of an electric field, and (3) a light emitting function that provides a field for recombination of electrons and holes and connects them to light emission. is doing. In addition, the ease with which holes are injected,
The electron injection may be different, and the transport function represented by the mobility of holes and electrons may be large or small, but it is preferable to transfer either one of the charges.

The distyrylpyrazine derivative represented by the general formula (I) used for the light emitting layer generally has an ionization energy
Since it is less than about 6.0eV, it is relatively easy to inject holes by selecting an appropriate anode metal or anode compound.
Since it is larger than about V, if an appropriate cathode metal or cathode compound is selected, it is relatively easy to inject electrons, and the electron and hole transporting function is also excellent. Furthermore, since the solid-state fluorescence is strong, it has a large ability to convert the excited state of the distyrylpyrazine derivative formed at the time of recombination of electrons and holes, its associated body or crystal into light.

Although the EL device of the present invention has various configurations, it is basically configured such that the light emitting layer is sandwiched between a pair of electrodes (anode and cathode), and if necessary, hole injection is performed. A transport layer and an electron injection transport layer may be interposed. Specifically (1)
Anode / light emitting layer / cathode, (2) anode / hole injection / transport layer / light emitting layer / cathode, (3) anode / hole injection / transport layer / light emitting layer / electron injection / transport layer / cathode it can.
The hole injecting and transporting layer and the electron injecting and transporting layer are not always necessary, but the presence of these layers further improves the light emitting performance.

Further, in the element having the above-mentioned configuration, it is preferable that all are supported by a substrate, and there is no particular limitation on the substrate, and those conventionally used for organic EL elements such as glass, transparent plastic, quartz and the like are conventionally used. Can be used.

As the anode in the organic EL device of the present invention, those having an electrode substance of a metal, an alloy, an electrically conductive compound having a large work function (4 eV or more) and a mixture thereof are preferably used. Specific examples of such electrode materials include Au and Cu.
Examples thereof include metals such as I, ITO, SnO ₂ and ZnO, and conductive transparent materials. The anode can be prepared by forming a thin film of these substances by a method such as vapor deposition or sputtering. When the emitted light is taken out from this electrode, it is desirable that the transmittance is higher than 10%, and the sheet resistance as the electrode is preferably several hundred Ω / □ or less. Furthermore, the film thickness depends on the material, but is usually 10 nm to 1 μm.
m, preferably in the range of 10 to 200 nm.

On the other hand, as the cathode, one having a low work function (4 eV or less) metal, alloy, electrically conductive compound or a mixture thereof as an electrode substance is used. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, Al / AlO ₂ , and isodium. The cathode can be produced by forming a thin film of these substances by a method such as vapor deposition or sputtering. The sheet resistance as an electrode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 nm to 1 μm, preferably
It is selected in the range of 50 to 200 nm. In the device of the present invention, it is preferable that either the anode or the cathode is transparent or semi-transparent, because the emitted light is transmitted and the extraction efficiency is good.

The EL device of the present invention has various configurations as described above, and the hole injecting / transporting layer in the EL device of the above (2) or (3) is a layer composed of a hole transporting compound. Has a function of transmitting holes injected from the anode to the light emitting layer. By interposing this hole injecting and transporting layer between the anode and the light emitting layer, many holes emit light at a lower electric field. The electrons injected into the light emitting layer and further injected into the light emitting layer from the cathode or the electron injecting and transporting layer are near the interface in the light emitting layer due to the electron barrier existing at the interface between the light emitting layer and the hole injecting and transporting layer. The device is excellent in light emission performance because it is accumulated and the light emission efficiency is improved.

The hole transporting compound used in the hole injecting and transporting layer is disposed between two electrodes to which an electric field is applied, and when holes are injected from the anode, the hole transporting compound is appropriately transferred to the light emitting layer. A compound capable of undergoing an electric field application of, for example, 10 ⁴ to 10 ⁶ V / cm,
Those having a hole mobility of at least 10 ⁻⁶ cm ² / V · S are preferable.

The hole transporting compound is not particularly limited as long as it has the above-mentioned preferable properties, and is conventionally used as a charge transporting material for holes in photoconductive materials and hole of EL elements. Any known material can be selected and used from the known materials used for the injecting and transporting layer.
Examples of the charge transport material include triazole derivatives (described in US Pat. No. 3,112,197), oxadiazole derivatives (described in US Pat. No. 3,189,447), imidazole derivatives (JP-B-37). −16
096 and the like), polyarylalkane derivatives (U.S. Pat.Nos. 3,615,402, 3,820,989, 3,542,544, Japanese Patent Publication No. 45-555,
JP-A-51-10983, JP-A-51-93224, JP-A-55-17.
No. 105, No. 56-4148, No. 55-108667,
55-1556953, those described in 56-36656, etc.), pyrazoline derivatives and pyrazolone derivatives (U.S. Pat.Nos. 3,180,729, 4,278,746, JP-A-55-88064, 55-88065, 49-105537
No. 55, No. 55-51086, No. 56-80051, No. 56
-88141, 57-45545, 54-112637, 55-74546, etc.), phenylenediamine derivatives (U.S. Pat. No. 3,615,404, JP-B-51-10105) Gazette, No. 46-3712, Gazette 47-25336
JP-A-54-53435, JP-A-54-110536, JP-A-54-119925, etc.), arylamine derivatives (U.S. Pat.Nos. 3,567,450 and 3,18).
No. 0,703, No. 3,240,597, No. 3,658,520, No. 4,232,103, No. 4,175,961
4,012,376, JP-B-49-35702, 39-
27577, JP-A-55-144250, 56-119132
JP-A No. 56-22437, those described in West German Patent No. 1,110,518, etc.), amino-substituted chalcone derivatives (such as those described in US Pat. No. 3,526,501),
Oxazole derivatives (described in US Pat. No. 3,257,203, etc.), styrylanthracene derivatives (described in JP-A-56-46234, etc.), fluorenone derivatives (described in JP-A-54-110837, etc.) Stuff),
Hydrazone derivatives (U.S. Pat.No. 3,717,462, JP-A-54-59143, JP-A-55-52063, JP-A-55-5206)
No. 4, No. 55-46760, No. 55-85495, No. 5
Nos. 7-11350 and 57-148749) and stilbene derivatives (Japanese Patent Laid-Open Nos. 61-210363, 61-228451, 61-14642, and 61- 7
No. 2255, No. 62-47646, No. 62-36674,
62-10652, 62-30255, 60-93445.
No. 60, No. 60-94462, No. 60-174749, No. 6
Those described in JP-A No. 0-175052) and the like.

In the present invention, these compounds can be used as a hole transfer compound, but the following porphyrin compounds (described in JP-A-63-295695 and the like), aromatic tertiary amine compounds and Styrylamine compound (U.S. Pat.No. 4,127,412, JP-A-53-27033,
54-58445, 54-149634, 54-64299
No. 55, No. 55-79450, No. 55-144250, No. 5
6-119132, 61-295558, 61-98353, 63-295695, etc.), and it is particularly preferable to use the aromatic tertiary amine compound.

As a typical example of the porphyrin compound, porphine,
1,10,15,20-Tetraphenyl-21H, 23H-porphine copper (II), 1,10,15,20-Tetraphenyl-21H, 23H-porphine zinc (II), 5,10,15,20- Tetrakis (pentafluorophenyl) -21H, 23H-porphine, silicon phthalocyanine oxide, aluminum phthalocyanine chloride, phthalocyanine (metal free), dilithium phthalocyanine, copper tetramethyl phthalocyanine, copper phthalocyanine, chromium phthalocyanine, zinc phthalocyanine,
Examples thereof include lead phthalocyanine, titanium phthalocyanine oxide, magnesium phthalocyanine, and copper octamethylphthalocyanine. Further, as typical examples of the aromatic tertiary amine compound and the styrylamine compound,
N, N, N ', N'-tetraphenyl-4,4'-diaminobiphenyl, N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl, 2 , 2-bis (4-
Di-p-tolylaminophenyl) propane, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, N, N, N ', N'-tetra-p-tolyl-4,4'-diamino Biphenyl, 1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane, bis (4-
Dimethylamino-2-methylphenyl) phenylmethane, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N'-diphenyl-N, N'-di (4-methoxyphenyl) -4,4 ' -Diaminobiphenyl, N, N, N ',
N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis (diphenylamino) quadriphenyl, N, N, N-tri (p-tolyl) amine, 4- (di-p-tolylamino) ) -4 '-[4 (di-p-tolylamino) styryl] stilbene, 4-N, N-diphenylamino- (2-diphenylvinyl) benzene, 3-methoxy-4'-N, N-diphenylaminostilbene, Examples thereof include N-phenylcarbazole.

The hole injecting and transporting layer in the device of the present invention may be composed of one layer composed of one kind or two or more kinds of these hole transporting compounds, or a hole composed of a compound different from the layer. It may be a stack of injecting and transporting layers.

On the other hand, the electron injecting and transporting layer in the EL device having the above configuration (3) is made of an electron transporting compound and has a function of transmitting the electrons injected from the cathode to the light emitting layer.
There is no particular limitation on such an electron transfer compound, and any compound can be selected and used from conventionally known compounds. Preferred examples of the electron transfer compound include: Nitro-substituted fluorenone derivatives, such as Thiopyran dioxide derivatives such as And other diphenylquinone derivatives ["Polymer Preprints, Japan", Volume 37, Volume 3
No., page 681 (1988)], or And other compounds ["Japanese Journal of Applied Physics (JJApply.Phys.)" No. 27
Vol., L269 (1988), etc.] and anthraquinodimethane derivatives (JP-A-57-149259, 58-55).
No. 450, No. 61-225151, No. 61-233750, No. 63-104061, etc.), a fluorenylidene methane derivative (JP-A-60-69657, No. 61).
-143764, JP-A 61-148159, etc.), anthrone derivative (JP-A 61-225151, JP-A 61-225151,
61-233750, etc.) and the like.

Next, an example of a suitable method for producing the organic EL element of the present invention will be described for each element of each constitution. Explaining the method for producing an EL device composed of the above-mentioned anode / light-emitting layer / cathode, first, a thin film of a desired electrode material, for example, a material for an anode, of 1 μm or less, preferably 10
After forming the anode by a method such as vapor deposition or sputtering so as to have a film thickness in the range of up to 200 nm,
A thin film of a distyrylpyrazine derivative represented by the general formula (I), which is a light emitting material, is formed on this to provide a light emitting layer. Examples of methods for thinning the light-emitting material include spin coating, casting, LB, vapor deposition, and the like. However, vapor deposition is preferable because a homogeneous film is easily obtained and pinholes are not easily generated. Method is preferred. When this vapor deposition method is used for thinning the light emitting material, the vapor deposition conditions generally differ depending on the type of organic compound used for the light emitting layer used, the target crystal structure of the molecular deposited film, the association structure, etc. Boat heating temperature 50 to 400 ° C, vacuum degree 10 ^-5 to 10 ^-3 Pa, deposition rate 0.01 to 50 nm / sec, substrate temperature -50 to + 300 ° C, film thickness 5
It is desirable to properly select in the range of nm to 5 μm. Next, after forming this light emitting layer, a thin film made of a substance for the cathode is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm. By providing the desired organic EL
The device is obtained. In the production of this EL element,
It is also possible to reverse the manufacturing order and manufacture the cathode, the light emitting layer and the anode in this order.

Next, EL consisting of anode / hole injecting / transporting layer / light emitting layer / cathode
Explaining the manufacturing method of the element, first, the anode is
After forming in the same manner as in the case of EL element, a thin film made of a hole transfer compound is formed thereon by a vapor deposition method or the like,
A hole injecting and transporting layer is provided. The vapor deposition conditions at this time may conform to the vapor deposition conditions for forming the thin film of the light emitting material. Next, a light emitting layer and a cathode were sequentially formed on the hole injecting and transporting layer,
A desired EL element can be obtained by providing the EL element in the same manner as in the case of manufacturing the EL element. Also in the production of this EL element, the production order may be reversed to produce the cathode, the light emitting layer, the hole injecting and transporting layer, and the anode in this order.

Furthermore, a method of manufacturing an EL device composed of anode / hole injecting / transporting layer / light emitting layer / electron injecting / transporting layer / cathode will be described.
First, in the same manner as in the case of manufacturing the EL element, the anode,
After the hole injecting and transporting layer and the light emitting layer are sequentially provided, a thin film made of an electron transfer compound is formed on the light emitting layer by a vapor deposition method or the like to provide the electron injecting and transporting layer, and then, on this,
A desired EL element can be obtained by providing the cathode in the same manner as in the case of manufacturing the EL element. Also in the production of this EL element, the production order may be reversed, and the cathode, the electron injecting and transporting layer, the light emitting layer, the hole injecting and transporting layer, and the anode may be produced in this order.

When a direct current voltage is applied to the thus obtained organic EL element of the present invention, when a voltage of about 5 to 40 V is applied with the positive polarity of the anode and the negative polarity of the cathode, the light emission is transparent or semitransparent. It can be observed from the electrode side. Moreover, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. further,
When an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the − state. The waveform of the alternating current applied may be arbitrary.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Production Example 1 Production of 2,5-bis- [2- (4-biphenyl) ethenyl] pyrazine [compound of formula (4)] 7.18 g of p-phenylbenzaldehyde, 1.00 g of 2,5-dimethylpyrazine and benzoic anhydride After mixing 9.95 g and refluxing for 21 hours, the reaction mixture was poured into 100 ml of ethyl alcohol to generate a precipitate. Then, the precipitate is filtered off,
After washing with ethyl alcohol, it was dried in vacuum to obtain 0.48 g of a crude product.

Next, this crude product was purified by sublimation to obtain a yellow powder, which was then recrystallized with 400 ml of xylene (activated carbon treatment),
300 ml of yellow needle crystals were obtained. The melting point of this product is 310 to 313.
It was ℃ (decomposition).

Other distyrylpyrazine derivatives are described in "Journal of Polymer Science Polymer Physics Edition (J.Polymer Sci.Polymer Phys.E
d.) ”, Volume 16, page 1365 (1968).

Example 1 A glass substrate (25 × 75 × 1.1 mm size, manufactured by HOYA) having a 100 nm-thick ITO transparent electrode was used as a transparent supporting substrate, and this was ultrasonically cleaned with isopropyl alcohol for 30 minutes, and further, It was immersed in isopropyl alcohol and washed. This transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus, while a molybdenum resistance heating boat was used, N, N'-diphenyl-N, N'-.
Bis (3-methylphenyl)-(1,1'-biphenyl)
200 mg of -4,4'-diamine (TPD) was put into another resistance heating boat made of molybdenum, and the all-trans structure 2,5-bis- [2- (4-biphenyl) obtained in Production Example 1 was used.
200 mg of ethenyl] pyrazine [compound of formula (4)] was charged and attached to a vacuum vapor deposition apparatus. Then vacuum chamber 1.2
After reducing the pressure to × 10 ^-4 Pa, the heating boat containing TPD is energized to heat it to 230 ° C, and the deposition rate is 0.1 to 0.3 nm /
It was vapor-deposited on a transparent support substrate for sec, and a hole injecting and transporting layer having a film thickness of 60 nm was provided. Further, the boat containing 2,5-bis [2- (4-biphenyl) ethenyl] pyrazine was energized and heated to 285 ° C., and the deposition rate of 0.1 to 0.3 nm / sec was applied to the hole injecting and transporting layer. A 70-nm-thick light-emitting layer was provided by vapor deposition on top. The temperature of the substrate during vapor deposition was room temperature.

Next, open a vacuum chamber, install a stainless steel mask on the light emitting layer, while placing 3 g of magnesium in a resistance heating boat made of molybdenum and copper in the crucible of the electron beam evaporation apparatus, and again in the vacuum chamber. After reducing the pressure to 2 × 10 ^-4 Pa, the magnesium-containing boat is energized, and the deposition rate is 4-5 nm /
By vaporizing magnesium in sec, at this time, heating copper by an electron beam at the same time, vapor depositing copper at a vapor deposition rate of 0.1 to 0.3 nm / sec, and forming a counter electrode composed of a mixture of the magnesium and copper, The target EL device was produced.

When a direct current of 17 V was applied with the ITO electrode of this device as a positive electrode and the counter electrode made of a mixture of Mg and copper as a negative electrode, a current having a current density of 300 mA / cm ² was flowed and yellow light emission was obtained.
The maximum emission wavelength at this time was 548 nm, and the emission luminance was 100 cd / m ^2. Example 2 A glass substrate (25 × 75 × 1.1 mm size, manufactured by HOYA) provided with ITO transparent electrodes with a film thickness of 100 nm was used. A transparent support substrate was obtained, which was ultrasonically cleaned with isopropyl alcohol for 30 minutes and further immersed in isopropyl alcohol for cleaning. This transparent support substrate is dried with dry nitrogen gas and fixed to the substrate holder of a commercially available vacuum evaporation system, while TPD200mg is put in a resistance heating boat made of molybdenum, and another resistance heating boat made of molybdenum has an all-trans structure. of 2,
5-bis- (4-ethylstyryl) pyrazine [formula (2)
200 mg] of the above compound and attached to a vacuum vapor deposition apparatus.
Next, after depressurizing the vacuum chamber to 3 × 10 ⁻⁴ Pa, the heating boat containing TPD is energized to heat it to 230 ° C.,
A hole injecting and transporting layer having a film thickness of 70 nm was provided by vapor deposition on a transparent supporting substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec. Further, the boat containing 2,5-bis (4-ethylstyryl) pyrazine is energized and heated to 200 ° C., and the deposition rate is 0.1 to 0.3 nm / sec.
Then, vapor deposition was performed on the hole injecting and transporting layer to form a light emitting layer having a film thickness of 80 nm. The temperature of the substrate during vapor deposition was room temperature.

Next, open a vacuum chamber, install a stainless steel mask on the light emitting layer, while placing 3 g of magnesium in a resistance heating boat made of molybdenum and copper in the crucible of the electron beam evaporation apparatus, and again in the vacuum chamber. After reducing the pressure to 2 × 10 ^-4 Pa, the magnesium-containing boat is energized, and the deposition rate is 5 to 6 nm /
By vaporizing magnesium in sec, at this time, copper is simultaneously heated by an electron beam to vapor deposit copper at a vapor deposition rate of 0.2 to 0.3 nm / sec, thereby forming a counter electrode composed of a mixture of the magnesium and copper, The target EL device was produced.

When a direct current of 13 V was applied using the ITO electrode of this device as a positive electrode and the counter electrode made of a mixture of Mg and copper as a negative electrode, a current having a current density of 33 mA / cm ² was flowed and green light emission was obtained. At this time, the maximum wavelength of emission was 512 nm and the emission luminance was 270 cd / m ² .

Example 3 A glass substrate (25 × 75 × 1.1 mm size, manufactured by HOYA) having a 100 nm-thick ITO transparent electrode was used as a transparent support substrate, and this was ultrasonically cleaned with isopropyl alcohol for 30 minutes. It was immersed in isopropyl alcohol and washed. This transparent support substrate is dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum evaporation system.On the other hand, TPD200mg is put in a resistance heating boat made of molybdenum, and all transformers are put in another resistance heating boat made of molybdenum. Structural
2,5-bis- (4-methoxystyryl) pyrazine [formula (1
Compound of 8)] 200 mg was put and attached to a vacuum vapor deposition apparatus. Next, after depressurizing the vacuum chamber to 2 × 10 ^-4 Pa, TP
The heating boat containing D was energized, heated to 220 ° C., and vapor-deposited on the transparent supporting substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec to form a hole injecting and transporting layer having a film thickness of 60 nm. In addition, 2,5
The boat containing -bis- (4-methoxystyryl) pyrazine was energized and heated to 230 ° C, and the deposition rate was 0.1 to 0.
At a thickness of 3 nm / sec, vapor deposition is performed on the hole injecting and transporting layer to obtain a film thickness of 9
A 0 nm emission layer was provided. The temperature of the substrate during vapor deposition was room temperature.

Next, open a vacuum chamber, install a stainless steel mask on the light emitting layer, while placing 3 g of magnesium in a resistance heating boat made of molybdenum and copper in the crucible of the electron beam evaporation apparatus, and again in the vacuum chamber. After reducing the pressure to 2 × 10 ^-4 Pa, energize the boat containing magnesium to vapor deposition rate 6 nm / sec.
At this time, the magnesium is vapor-deposited, at the same time, the copper is heated by the electron beam at the same time, the copper is vapor-deposited at the vapor deposition rate of 0.1 to 0.3 nm / sec, and the counter electrode is made of a mixture of the magnesium and the copper. An EL element was manufactured.

When a direct current of 17 V was applied with the ITO electrode of this device as the positive electrode and the counter electrode made of a mixture of Mg and copper as the negative electrode, a current having a current density of 190 mA / cm ² flowed and blue-green light emission was obtained. In this case, the maximum emission wavelength is 497 nm and the emission brightness is 160 cd / m.
^{Was 2} .

Example 4 A glass substrate (25 × 75 × 1.1 mm size, manufactured by HOYA) having a 100 nm-thick ITO transparent electrode was used as a transparent support substrate, which was ultrasonically cleaned with isopropyl alcohol for 30 minutes, and further, It was immersed in isopropyl alcohol and washed. This transparent support substrate was dried with dry nitrogen gas and fixed to a substrate holder of a commercially available vacuum evaporation system, while a 1,4-bis- (4-methylstyryl) pyrazine [formula ( 1) compound] 200mg,
It was attached to a vacuum vapor deposition device. Then, the vacuum chamber is set to 2 × 10 ^-4 Pa
Depressurize to, heat to 210 ℃ by energizing the boat containing 1,4-bis- (4-methylstyryl) pyrazine,
It vapor-deposited on a transparent support substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec to provide a light-emitting layer having a film thickness of 500 nm. The temperature of the substrate during vapor deposition was room temperature.

Next, open a vacuum chamber, install a stainless steel mask on the light emitting layer, while placing 3 g of magnesium in a resistance heating boat made of molybdenum and copper in the crucible of the electron beam evaporation apparatus, and again in the vacuum chamber. After reducing the pressure to 2 × 10 ^-4 Pa, the magnesium-containing boat is energized, and the deposition rate is 4-5 nm /
By vaporizing magnesium in sec, at this time, copper is simultaneously heated by an electron beam to vapor deposit copper at a vapor deposition rate of 0.2 to 0.3 nm / sec, thereby forming a counter electrode composed of a mixture of the magnesium and copper, The target EL device was produced.

When a direct current of 30 V was applied with the ITO electrode of this device as a positive electrode and the counter electrode made of a mixture of Mg and copper as a negative electrode, a current with a current density of 30 mA / cm ² was flowed and green light emission was obtained. At this time, the maximum wavelength of emission was 520 nm and the emission luminance was 0.5 cd / m ² .

Example 5 A glass substrate (25 × 75 × 1.1 mm size, manufactured by HOYA) with ITO having a film thickness of 100 nm used as a transparent electrode was used as a transparent support substrate, and this was ultrasonically cleaned with isopropyl alcohol for 30 minutes, Furthermore, it was immersed in isopropyl alcohol and washed. This transparent support substrate is dried with dry nitrogen gas, fixed to a substrate holder of a commercially available vacuum evaporation system, 200 mg of TPD is put in a resistance heating boat made of molybdenum, and another resistance heating boat made of molybdenum has an all-trans structure. is there
200 mg of 2,5-bis {2- (1-naphthyl) vinyl} pyrazine (Specific Example 21 of the light emitting material) was put and attached to a vacuum vapor deposition apparatus. After this, depressurize the vacuum chamber to 4 × 10 ^-4 Pa,
Energize the boat containing TPD, heat to 230 ℃, vapor deposition on a transparent support substrate at a vapor deposition rate of 0.1 ~ 0.3 nm / sec, film thickness
The hole injection layer (hole injection / transport layer) had a thickness of 50 nm. Two more
The boat containing 5-bis {2- (1-naphthyl) vinyl} pyrazine is energized, heated to 242 ° C, and the deposition rate is
Vapor deposition was performed at 0.3 nm / sec on the hole injection layer on the transparent supporting substrate to obtain a light emitting layer having a thickness of 60 nm. The temperature of the substrate during vapor deposition was room temperature. After this, open the vacuum chamber, place a stainless steel mask on the light emitting layer, put 3 g of magnesium in a molybdenum resistance heating boat, put copper in the crucible of the electron beam evaporation system, and set the vacuum chamber to 2 again. The pressure was reduced to × 10 ^-4 Pa, and then a boat containing magnesium was energized to deposit magnesium at a deposition rate of 4 to 6 nm / sec. At this time, simultaneously heat the copper with an electron beam to 0.1 to 0.3 nm / sec.
Then, copper was vapor-deposited, and the magnesium was mixed with copper to form a counter electrode. Through the above steps, the fabrication of the electroluminescent element was completed.

When the ITO electrode of this device was used as a positive electrode and the counter electrode made of a mixture of Mg and copper was used as a negative electrode and a direct current of 12 V was applied, a current with a current density of 213 mA / cm ² flowed, and yellow light emission was obtained. At this time, the maximum emission wavelength is 565 nm, the CIE chromaticity coordinate is x = 0.40, y
= 0.53 (Yellow Green), the emission luminance was 932 cd / m ² , which was extremely high luminance.

[Advantages of the Invention] The organic EL element of the present invention uses a distyrylpyrazine derivative as a light emitting material, and can obtain yellow and green light emission with high brightness, particularly at low voltage, and can be used in various display devices. It is preferably used as a light emitting element.

Claims (5)

[Claims] 1. An organic electroluminescence device comprising a distyrylpyrazine derivative as a light emitting material. 2. A distyrylpyrazine derivative having the general formula (X and Y in the formula are each a monovalent aromatic residue or a heteroaromatic residue, and they may be the same or different from each other) The organic electroluminescence device according to claim 1. 3. The organic electroluminescence device according to claim 1, which has a thin-film light emitting layer made of a distyrylpyrazine derivative represented by the general formula (I). 4. The organic electroluminescence device according to claim 3, wherein a light emitting layer is interposed between a pair of electrodes. 5. The organic electroluminescence device according to claim 4, wherein the anode, the hole injecting and transporting layer, the light emitting layer and the cathode are laminated in this order.