JPH06256759A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain an electroluminesent element comprising an anode, a cathode, and an organic compound layer nipped therebetween and containing a specific compound, having a highly brilliantly light-emitting ability at low application voltages, having good diversity on light-emitting wavelengths, and excellent in durability. CONSTITUTION:This electroluminescent element comprises an anode, a cathode, and a monolayered or plurally layered organic compound layer which is nipped between the electrodes and which contains a compound having an amine skeleton of formula I (R1-R3 are alkyl, aralkyl, aromatic ring, heterocyclic ring, alkoxy, halogen, nitro, cyano, etc.; (n), (m) and (p) are 0-5) and having a carbonyl group in the same molecule, such as a compound of formula II.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroluminescent device.

[0002]

2. Description of the Related Art The electroluminescence phenomenon of organic materials is 1963 P.
observed in anthracene single crystal (J.
Chem. Phys. 38 (1963) 2042), followed by 1965 Helfinnch and Schnei.
der has succeeded in observing relatively strong injection electroluminescence (EL) by using a solution electrode system having a high injection efficiency (Phys. Rev. Lett. 1).
4 (1965) 229). Since then, US Patent 3,17
2,862, U.S. Pat. No. 3,173,050, U.S. Pat. No. 3,710,167, J. Chem. Phys. 44
(1966) 2902, J. Chem. Phys. Fifty
(1969) 14364, J. Am. Chem. Phys. 5
8 (1973) 1542 or Chem. Phys.
Lett. 36 (1975) 345, etc., studies have been conducted on forming an organic light-emitting substance from a conjugated organic host substance and a conjugated organic activator having a condensed benzene ring. Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene,
Picene, carbazole, fluorene, biphenyl, tar
Phenyl, triphenylene oxide, dihalobiphenyl, trans-stilbene, 1,4-diphenylbutadiene, etc. were shown as examples of organic host materials, and anthracene, tetracene, pentacene, etc. were mentioned as examples of activators. However, all of these organic light-emitting substances existed as a single layer having a thickness exceeding 1 μm, and a high electric field was required for light emission. For this reason, research on thin film devices by the vacuum evaporation method has been advanced (for example, Thinn Solid Films 94 (19).
82) 171, Polymer 24 (1983) 74.
8, Jpn. J. Appl. Phys. 25 (198
6) L773). However, although thinning was effective in reducing the driving voltage, it was not possible to obtain a practically high brightness device.

Recently, Tanngs et al. (Appl.
Phys. Lett. 51 (1987) 913 or US Pat. No. 4,356,429) We devised an EL device in which two very thin layers (a charge transport layer and a light emitting layer) were laminated by vacuum evaporation between an anode and a cathode, and a high driving voltage was obtained at a low driving voltage. Realized brightness. This type of laminated organic EL device has been actively researched since then, and is disclosed in, for example, JP-A-59-194393, US Pat. No. 4,539,507, JP-A-59-194393, US Pat. 63-264692,
Appl. Phys. Lett. 55 (1986) 14
67, JP-A-3-163188 and the like.

Furthermore, Jpn. J. Appl. Phy
s. 27 (1988) L269, L713, an EL device having a three-layer structure in which the functions of carrier transport and light emission are separated has been reported, and restrictions on carrier transport performance are alleviated when selecting a dye for the light-emitting layer that determines the emission color. It also suggests that the degree of freedom in selection is considerably increased, and further that holes and electrons (or excitons) are effectively confined in the central light emitting layer to improve the light emission.

A vacuum evaporation method is generally used for producing a laminated organic EL element, but it has been reported that an element having a considerable brightness can be obtained also by a casting method (for example, the 50th Society of Applied Physics). Academic Lecture Lecture Proceedings 1
006 (1989) and Proceedings of the 51st Academic Meeting of the Society of Biological Sciences 1041 (1990)).

Further, polyvinylcarbazole is used as a hole transport compound, and oxadiazo is used as an electron transport compound.
It has been reported that even a mixed single-layer type EL device formed by a dip coating method from a solution in which a carboxylic acid derivative and coumarin 6 as a luminescent material are mixed can provide a considerably high luminous efficiency (for example, the 38th Joint Meeting on Vehicular Relations). Lecture Proceedings 1086
(1991)).

As mentioned above, the recent advances in organic EL devices suggest a remarkably wide range of potential applications.
However, the history of those studies is still shallow, and the researches for materials and devices have not been sufficiently conducted.
At present, there are still problems in terms of durability such as higher brightness light output, deterioration with time due to long-term use, and deterioration due to atmospheric gas containing oxygen or moisture. Further, in consideration of application to full-color displays and the like, problems such as diversification of emission wavelengths for precisely selecting emission hues of blue, green and red have not yet been sufficiently solved.

[0008]

An object of the present invention is to firstly provide an electroluminescent device having a light output of extremely high brightness, and secondly, there are various emission wavelengths and various emission hues. At the same time, it is to provide an electroluminescent device having extremely high durability, and thirdly to provide an electroluminescent device material which is easy to manufacture and can be provided at a relatively low cost.

[0009]

The present invention provides an electroluminescent device comprising an anode and a cathode and one or more organic compound layers sandwiched therebetween, and at least one of the organic compound layers is The electroluminescent element is characterized by having a compound having an amine skeleton represented by the following general formula (1) and having a carbonyl group in the same molecule. General formula (1)

[Chemical 2] In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group, an aralkyl group, an aromatic ring group, a heterocyclic group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a hydroxyl group or an amino group, m, n and p each represent an integer of 0-5.

With respect to the groups represented by R _{1 to} R ₃ , specifically, the alkyl group has 1 to 6 carbon atoms,
The aralkyl group is a group such as benzyl, phenethyl, naphthylmethyl, the aromatic ring group is a group such as phenyl, naphthyl, anthryl and pyrenyl, the heterocyclic group is a group such as pyridyl, thienyl, furyl and quinolyl, and the alkoxy group is Examples thereof include groups such as methoxy, ethoxy and propoxy, examples of aryloxy groups include groups such as phenoxy and naphthoxy, and examples of halogen atoms include fluorine atom, chlorine atom and bromine atom.

Typical examples of compounds having the amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule are shown in Tables 1 to 7. However, the present invention is not limited to these compounds.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

The electroluminescent device of the present invention has a compound selected from compounds having an amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule, such as a vacuum deposition method and a solution coating method. To form between the anode and the cathode. The thickness of the organic layer is smaller than 2 μm, preferably smaller than 0.5 μm and is preferably thin.

The present invention will be described in detail with reference to the drawings. FIG. 1 shows a structure in which an anode 2, a light emitting layer 3 and a cathode 4 are sequentially provided on a substrate 1. The light emitting device used here is useful when it has a single hole transporting ability, an electron transporting ability and a light emitting ability by itself, or when compounds having respective properties are mixed and used.

FIG. 2 shows a structure in which an anode 2, a hole transport layer 5, an electron transport layer 6 and a cathode 4 are sequentially provided on a substrate 1. In this case, the light-emitting substance is a material having a hole-transporting property, an electron-transporting property, or both, for each layer, and a mere hole-transporting substance or electron-transporting substance having no light-emitting property is used. It is useful when used in combination with.

FIG. 3 shows a structure in which an anode 2, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6 and a cathode 4 are sequentially provided on a substrate 1. This is one in which the functions of carrier transport and light emission are separated, and it is used in combination with a compound having hole transportability, electron transportability, and light emission properties as appropriate, and the degree of freedom in selecting materials is greatly increased. Since various compounds having different emission wavelengths can be used, the emission hue can be diversified. Further, it becomes possible to effectively confine holes and electrons (or excitons) in the central light emitting layer to improve the light emitting efficiency.

The compounds selected from the compounds having the amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule are all compounds having extremely excellent light emission characteristics as compared with conventional compounds. It is possible to use any of the configurations shown in FIGS. 1, 2 and 3 as required. Further, depending on the structure of the compound, it has a hole transporting property, an electron transporting property, or both, and is represented by the general formula (1) in any of the forms shown in FIGS. 1, 29 and 3. Has an amine skeleton,
In addition, two or more kinds of compounds selected from compounds having a carbonyl group in the same molecule may be used if necessary.

In the present invention, the amine skeleton represented by the above general formula (1) is contained as a constituent of the light emitting layer, and
A compound selected from compounds having a carbonyl group in the same molecule is used, but if necessary, a hole transporting compound or an electron transporting compound which has been studied in the field of electrophotographic photoconductors, or a compound known until now. Used together with known hole transporting luminescent compound (for example, compounds listed in Tables 8 and 9) or hitherto known electron transporting luminescent compound (such as compounds listed in Table 10). You can also do it.

Hole-transporting compound

[Table 8]

[Table 9]

Electron transporting compound

[Table 10]

The electroluminescent device of the present invention, which uses the compound having the amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule, is vacuum-deposited or appropriately bonded. A thin film is formed in combination with the agent resin.

The binder resin can be selected from a wide range of binder resins, such as polyvinyl carbazole and polycarbonate.
Polyester, polyarylate, butyral resin,
Examples thereof include, but are not limited to, polystyrene, polyvinyl acetal, diallyl phthalate resin, acrylic resin, methacrylic resin, phenol resin, epoxy resin, silicone resin, polysulfone, and urea resin. These resins may be used alone or in combination of two or more as a copolymer polymer.

The anode material preferably has a work function as large as possible, and examples thereof include nickel, gold, platinum, palladium, selenium, rhenium, iridium and alloys thereof, tin oxide, indium tin oxide (ITO), and copper iodide. preferable. Further, a conductive polymer such as poly (3-methylthiophene), polyphenylene sulfide or polypyrrole can also be used.

As the cathode material, silver having a small work function,
Lead, tin, magnesium, aluminum, calcium, manganese, indium, chromium or alloys thereof are used.

At least one of the materials used as the anode and the cathode is 5 in the emission wavelength region of the device.
It is preferable to transmit more than 0% of the light.

As the transparent substrate used in the present invention, glass, plastic film or the like is used.

The electroluminescent element of the present invention is a conventional incandescent lamp,
Unlike fluorescent lamps or light-emitting diodes, it is a large-area, high-resolution, thin, lightweight, high-speed operation, complete solid-state device, and is used for electroluminescence (EL) panels that may meet high requirements.

[0027]

【Example】

Example 1 On a transparent anode of indium tin oxide (ITO) coated (50 nm) glass, a light emitting layer of Compound Example 3 having a thickness of 110 nm,
And a cathode 150 made of Mg / Ag (10/1) alloy
nm were sequentially formed by vacuum vapor deposition to prepare an electroluminescent device having the structure shown in FIG.

The anode and cathode of the prepared electroluminescent device were read.
When a direct current power supply was connected and a voltage of 6.0 V was applied by connecting with a lead wire, a current with a current density of 7.0 mA / cm ² was passed through the element, and an optical output of 0.15 mW / cm ² was confirmed.

Then, the current density as it is (7.0 mA
/ Cm ² ) for 48 hours, a light output with a final output of 0.12 mW / cm ² was obtained with an applied voltage of 7.1 V even after 48 hours.

Examples 2 to 6 Example 1 was repeated except that Compound Example 5, Compound Example 9, Compound Example 14, Compound Example 31 and Compound Example 49 were used instead of Compound Example 3 used in Example 1, respectively. In the same manner as in Example 2, Example 3, Example 3, Example 4, Example 5, and Example 6
The electroluminescent element of was produced.

A current having a current density of 7.0 mA / cm ² was applied to each of the prepared electroluminescent devices for 48 hours. The results are shown in Table 11.

[Table 11]

Comparative Examples 1-5 Instead of the compound example 3 used in Example 1, comparative compound example 1, comparative compound example 2, comparative compound example 3, comparative compound example 4 and comparative compound example 5 having the following structural formulas were used. The electroluminescent elements of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 were prepared in the same manner as in Example 1 except that they were used. Comparative compound example 1

[Chemical 3] Comparative compound example 2

[Chemical 4] Comparative compound example 3

[Chemical 5] Comparative compound example 4

[Chemical 6] Comparative compound example 5

[Chemical 7]

The anode and cathode of each of the prepared electroluminescent devices were connected by a lead wire and connected to a DC power source, and a current having a current density of 7.0 mA / cm ² was supplied for 48 hours as in Example 1. The results are shown in Table 12.

[Table 12]

As is clear from Tables 11 and 12,
It is known that the electroluminescent device of the present invention is extremely superior in light output and durability as compared with the electroluminescent device of the comparative example.

Example 7 On a transparent anode of indium tin oxide (ITO) coated (60 nm) glass, a light emitting layer of Compound Example 13 of 60 nm,
Electron transport layer 50 nm composed of compound A having the following structural formula, and cathode 200n composed of Mg / Ag (10/1) alloy
m were sequentially formed by vacuum vapor deposition to produce an electroluminescent device having the structure shown in FIG. Compound A

[Chemical 8]

The anode and cathode of the prepared electroluminescent device were read.
When a direct current power supply was connected and a voltage of 7.5 V was applied by connecting a dead line, a current having a current density of 8.8 mA / cm ² was passed through the element, and an optical output of 0.26 mW / cm ² was confirmed.

Then, the current density as it is (8.8 mA
/ Cm ² ) for 48 hours, a light output with a final output of 0.24 mW / cm ² was obtained with an applied voltage of 7.8 V even after 48 hours.

Examples 8 to 10 Example 8 was repeated in the same manner as Example 7 except that Compound Example 18, Compound Example 21 and Compound Example 25 were used instead of Compound Example 13 used in Example 7. The electroluminescent elements of Example 9 and Example 10 were prepared.

A current having a current density of 8.8 mA / cm ² was passed through each of the prepared electroluminescent devices. The results are shown in Table 13.
Shown in.

[Table 13]

Comparative Examples 6 to 7 Comparative Example 6 was carried out in the same manner as Example 8 except that Comparative Compound Example 6 and Comparative Compound Example 7 having the following structural formulas were used in place of Compound Example 18 used in Example 8. 6 and Comparative Example 7 were prepared. Comparative compound example 6

[Chemical 9] Comparative compound example 7

[Chemical 10]

The anode and cathode of each of the prepared electroluminescent devices were connected by a lead wire and connected to a direct current power source, and a current having a current density of 8.8 mA / cm ² was supplied in the same manner as in Example 8. The results are shown in Table 14.
Shown in.

[Table 14]

As is clear from Tables 13 and 14,
It is known that the electroluminescent device of the present invention is extremely superior in light output as compared with the electroluminescent device of the comparative example.

Example 11 Anode 50 nm made of gold on a glass substrate, hole transport layer 50 nm made of compound B having the following structural formula, compound example 50
2 and a cathode 200 nm each made of aluminum are sequentially formed by vacuum vapor deposition.
An electroluminescent device having the structure shown in was prepared. Compound (B)

[Chemical 11]

The anode and cathode of the prepared electroluminescent device were read.
When a direct current power supply was connected and a voltage of 10.0 V was applied by connecting a dead line, a current having a current density of 10.4 mA / cm ² was passed through the device, and an optical output of 0.18 mW / cm ² was confirmed.

Example 12 On a transparent anode of indium tin oxide (ITO) coated (50 nm) glass, a hole transport layer of compound C having the following structural formula: 60 nm, a light emitting layer of compound example 51: 70 nm,
Electron transport layer 60 nm composed of compound D having the following structural formula, and cathode 150 n composed of Mg / Ag (10/1) alloy
m were sequentially formed by vacuum vapor deposition to prepare an electroluminescent device having the structure shown in FIG. Compound C

[Chemical 12] Compound D

[Chemical 13]

The anode and cathode of the prepared electroluminescent device were read.
When a direct current power supply was connected and a voltage of 6.2 V was applied by connecting with a lead wire, a current with a current density of 7.0 mA / cm ² was passed through the element, and an optical output of 0.24 mW / cm ² was confirmed.

Examples 13 to 17 Instead of the compound example 51 used in the example 12, the compound example 10, the compound example 12, the compound example 26 and the compound example 4 respectively.
Electroluminescent devices of Example 13, Example 14, Example 15, Example 16 and Example 17 were prepared in the same manner as in Example 12, except that 4 and Compound Example 48 were used.

A current having a current density of 7.0 mA / cm ² was passed through each of the prepared electroluminescent devices. The results are shown in Table 15.
Shown in.

[Table 15]

Comparative Examples 8 to 12 Instead of the compound example 10 used in Example 13, comparative compound example 8, comparative compound example 9 and comparative compound example 1 having the following structural formulas.
0, Comparative Compound Example 11 and Comparative Compound Example 12 were used, and Comparative Example 8 and Comparative Example 9 were carried out in the same manner as in Example 13.
Electroluminescent devices of Comparative Example 10, Comparative Example 11 and Comparative Example 12 were prepared. Comparative compound example 8

[Chemical 14] Comparative compound example 9

[Chemical 15] Comparative compound example 10

[Chemical 16] Comparative compound example 11

[Chemical 17] Comparative compound example 12

[Chemical 18]

A current having a current density of 7.0 mA / cm ² was applied to each of the prepared electroluminescent devices in the same manner as in Example 13. The results are shown in Table 16.

[Table 16]

As is clear from Tables 15 and 16,
It is known that the electroluminescent device of the present invention is extremely superior in light output as compared with the electroluminescent device of the comparative example.

Example 18 2 g of the compound of Compound Example 2, 1 g of a hole transport compound E of the following structural formula, and an electron transport compound F of the following structural formula
1 g and polycarbonate (weight average molecular weight 35,
000) 2 g was dissolved in 300 ml of tetrahydrofuran to prepare a coating solution. This coating liquid was applied on a transparent anode of indium tin oxide (ITO) coated (50 nm) glass with a Mayer bar to form a 400 nm layer.
And aluminum is vacuum-deposited on it and 150 nm
The cathode of No. 1 was formed to prepare an electroluminescent device. Compound E

[Chemical 19] Compound F

[Chemical 20]

The anode and cathode of the prepared electroluminescent device were read out.
When a voltage of 10.0 V was applied by connecting with a DC line and connecting a DC power supply, a current having a current density of 9.6 mA / cm ² was passed through the element, and an optical output of 0.38 mW / cm ² was confirmed.

[0054]

EFFECT OF THE INVENTION The electroluminescent element of the present invention is capable of obtaining light emission with extremely high brightness at a low applied voltage and is also extremely excellent in durability. Further, the electroluminescent element can be produced by vacuum vapor deposition or casting method, and the remarkable effect that an element having a relatively large area and a large area can be easily produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of an electroluminescent device of the present invention.

FIG. 2 is a cross-sectional view of an example of the electroluminescent device of the present invention.

FIG. 3 is a cross-sectional view of an example of the electroluminescent device of the present invention.

[Explanation of symbols]

 1 Substrate 2 Anode 3 Light-emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer

Claims (1)

[Claims] 1. An electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, wherein at least one of the organic compound layers has the following general formula (1): An electroluminescent device comprising a compound having the amine skeleton shown and having a carbonyl group in the same molecule. General formula (1) In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group, an aralkyl group, an aromatic ring group, a heterocyclic group, an alkoxy group, an aryloxy group, a halogen atom, a nitro group, a cyano group, a hydroxyl group or an amino group, m, n and p each represent an integer of 0-5.