JP2939051B2 - EL device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 has been
ope et al. were observed in anthracene single crystals (J.
Chem. Phys. 38 (1963) 2042), followed by Helfinch and Schnei in 1965
Der succeeded in observing relatively strong injection-type electroluminescence (EL) by using a solution electrode system having high injection efficiency (Phys. Rev. Lett. 1).
4 (1965) 229). Since then, U.S. Pat.
U.S. Pat. No. 2,862, U.S. Pat. No. 3,173,050, U.S. Pat. Chem. Phys. 44
(1966) 2902; Chem. Phys. 50
(1969) 14364; Chem. Phys. 5
8 (1973) 1542 or Chem. Phys.
Lett. 36 (1975) 345, studies have been made on the formation of an organic luminescent material with a conjugated organic host material and a conjugated organic activator having a fused benzene ring. Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene,
Picene, carbazole, fluorene, biphenyl, tar
Phenyl, triphenylene oxide, dihalobiphenyl, trans-stilbene, 1,4-diphenylbutadiene and the like have been given as examples of organic host materials, and anthracene, tetracene and pentacene have been mentioned as examples of activators. However, each of these organic light-emitting substances exists as a single layer having a thickness exceeding 1 μm, and a high electric field is required for light emission. For this reason, research on a thin film element by a vacuum deposition 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 did not lead to obtaining a high-brightness element on a practical level.

Recently, Tanngs et al. (Appl.
Phys. Lett. 51 (1987) 913 or U.S. Pat. No. 4,356,429. An EL device in which two very thin layers (a charge transport layer and a light emitting layer) are stacked by vacuum deposition between an anode and a cathode is devised. Realized brightness. This type of stacked organic EL device has been actively studied since then. For example, JP-A-59-194393, U.S. Pat. No. 4,539,507, JP-A-59-194393, U.S. Pat. 63-264692,
Appl. Phys. Lett. 55 (1986) 14
67, JP-A-3-163188 and the like.

Further, Jpn. J. Appl. Phys
s. 27 (1988) L269 and L713 report an EL element having a three-layer structure in which the functions of carrier transport and light emission are separated, and the restriction on carrier transport performance is relaxed even when selecting a dye of a light-emitting layer that determines the emission color. It is suggested that the degree of freedom in selection is considerably increased, and furthermore, there is a possibility of effectively confining holes and electrons (or excitons) in the central light emitting layer to improve light emission.

Although a vacuum evaporation method is generally used for producing a stacked organic EL device, it has been reported that a device having a considerably high brightness can be obtained even by a casting method (for example, the 50th Chemical Society of Japan). Proceedings of Academic Lectures 1
006 (1989) and Proceedings of the 51st Academic Lecture Meeting of the Japan Society for Response Science 1041 (1990)).

Further, polyvinyl carbazole is used as a hole transport compound, and oxadiazo is used as an electron transport compound.
It has been reported that a considerably high luminous efficiency can be obtained even with a mixed single-layer EL device formed by a dip coating method from a solution in which coumarin 6 is mixed as a luminous derivative and a luminescent material (for example, the 38th Lecture Meeting on the Correspondence of Corresponding Substances). Proceedings 1086
(1991)).

[0007] As mentioned above, recent advances in organic EL devices have suggested a remarkably wide range of applications.
However, the history of those researches is still young, and the research on the materials and devices has not yet been sufficiently conducted.
At present, there are still problems in terms of durability such as light output with higher luminance, temporal change due to long-term use, and deterioration due to oxygen-containing atmospheric gas or moisture. Further, in consideration of application to a full-color display or the like, problems such as diversification of emission wavelengths for accurately selecting emission hues of blue, green, and red have not been sufficiently solved.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to firstly provide an electroluminescent device having a light output with extremely high luminance, and secondly, to have various emission wavelengths and exhibit various emission hues. Thirdly, it is to provide an electroluminescent element which is extremely durable, and thirdly, to provide an electroluminescent element material which is easy to manufacture and can be provided relatively inexpensively.

[0009]

According to the present invention, there is provided an electroluminescent device comprising an anode, a cathode, and one or more organic compounds sandwiched between the anode and the cathode. The electroluminescent device comprises an amine skeleton represented by the general formula ( 1 ) and a compound having a carbonyl group in the same molecule. General formula ( 1 )

Embedded image In the formula, Ar ₁ , Ar ₂ and Ar ₃ represent an aromatic or heterocyclic group which may have a substituent, and Ar ₂ and A
r ₃ is rather good also to form a ring together with the nitrogen atom bound to,
At least one of Ar ₁ , Ar ₂ and Ar ₃ is condensed
Ar ₁ , Ar ₂ and Ar ₃ are coumarin rings
And it is not name a pyrene ring.

For the groups represented by Ar _{1 to} Ar ₃ , specifically, groups such as phenyl, naphthyl, anthryl, and pyrenyl as aromatic ring groups, and groups such as pyridyl, thienyl, furyl and quinolyl as heterocyclic groups Is mentioned.

Examples of the substituent in the above group include an alkyl group having 1 to 6 carbon atoms, an aralkyl group such as benzyl, phenethyl and naphthylmethyl; an aromatic ring group such as phenyl, naphthyl, anthryl and pyrenyl;
Examples include a heterocyclic group such as thienyl, furyl and quinolyl, an alkoxy group such as methoxy, ethoxy and propoxy, a halogen atom such as fluorine, chlorine and bromine, a nitro group, a cyano group, a hydroxyl group or an amino group.

Tables 1 to 6 show typical examples of the compound having an amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule. However, the present invention is not limited to these compounds.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

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

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

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, as the luminescent material, a material having either a hole transporting property or an electron transporting property or both is used for each layer, and a simple hole transporting substance or an electron transporting substance having no light emitting property is used. This 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. It separates the functions of carrier transport and light emission, and is used in combination with a compound having each of hole transport, electron transport, and light emitting properties. This greatly increases the degree of freedom in material selection. Since various compounds having different emission wavelengths can be used, the emission hue can be diversified. Further, it is also possible to effectively confine holes and electrons (or excitons) in the central light emitting layer to improve the light emission efficiency.

Compounds selected from the compounds having an amine skeleton represented by the general formula (1) and having a carbonyl group in the same molecule are all compounds having extremely excellent luminescent properties as compared with conventional compounds. Therefore, any of the configurations shown in FIGS. 1, 2 and 3 can be used as needed. Further, depending on the structure of the compound, the compound has one or both of a hole transporting property and an electron transporting property, and in any of the embodiments shown in FIGS. 1, 2 and 3, the compound is represented by the general formula (1). If necessary, two or more compounds selected from compounds having an amine skeleton and having a carbonyl group in the same molecule may be used.

In the present invention, the light-emitting layer has an amine skeleton represented by the general formula (1) as a constituent component, and
Although a compound selected from compounds having a carbonyl group in the same molecule is used, a hole-transporting compound or an electron-transporting compound which has been studied in the field of electrophotographic photoreceptor, etc. Together with a known hole transporting luminescent compound (for example, compounds listed in Tables 7 and 8 ) or an electron transporting luminescent compound known so far (for example, compounds listed in Table 9 ). You can also.

Hole transporting compound

[Table 7]

[Table 8]

Electron transporting compound

[Table 9]

The electroluminescent device of the present invention using a compound having an amine skeleton represented by the above general formula (1) and having a carbonyl group in the same molecule can be prepared by vacuum deposition or suitable binding. A thin film is formed in combination with an 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 include, but are not limited to, polystyrene, polyvinyl acetal, diallyl phthalate resin, acrylic resin, methacrylic resin, phenolic resin, epoxy resin, silicone resin, polysulfone, and urea resin. These resins can be used alone or in combination of two or more kinds as a copolymer polymer.

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

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

Further, at least one of the materials used as the anode and the cathode is 5% in the emission wavelength region of the device.
Preferably, more than 0% of the light is transmitted.

As the transparent substrate used in the present invention, glass, plastic film and the like are used.

The electroluminescent device of the present invention comprises a conventional incandescent lamp,
Unlike fluorescent lamps or light-emitting diodes, they are large-area, high-resolution, thin, light-weight, high-speed, and fully solid-state devices, and are used for electroluminescence (EL) panels that may meet high demands.

[0028]

EXAMPLE 1 On a transparent anode of indium tin oxide (ITO) coated (50 nm) glass, a light emitting layer of Compound Example 2 having a thickness of 100 nm was prepared.
And a cathode 200 made of an Mg / Ag (10/1) alloy
nm was sequentially formed by vacuum evaporation, and an electroluminescent device having the configuration shown in FIG. 1 was produced.

The anode and the cathode of the prepared electroluminescent device are separated.
When a DC power supply was connected and a voltage of 8 V was applied, a current having a current density of 9.0 mA / cm ² flowed through the device,
An optical output of 0.11 mW / cm ² was confirmed.

The current density as it is (9.0 mA)
/ Cm ² ) for 48 hours, a light output of final output of 0.09 mW / cm ² was obtained at an applied voltage of 9.5 V even after 48 hours.

[0031] Instead of the compound Example 2 used in Example 2 and 3 Example 1, except that with each compound Example 11 and compound examples 40, in the same manner as in Example 1, Example 2 and Example 3 Was produced.

A current having a current density of 9.0 mA / cm ² was applied to each of the prepared electroluminescent devices for 48 hours. Table 10 shows the results.

[Table 10]

COMPARATIVE EXAMPLES 1 TO 4 In place of compound example 2 used in example 1 , comparative compound example 1 , comparative compound example 2 , comparative compound example 3 and comparative compound example 4 having the following structural formulas were used. Comparative example 1 in the same manner as in example 1, Comparative example 2 to prepare a light emitting element of Comparative example 3 and Comparative example 4. Comparative compound example 1

Embedded image Comparative compound example 2

Embedded image Comparative compound example 3

Embedded image Comparative compound example 4

Embedded image

An anode and a cathode of each of the prepared electroluminescent devices were connected with a lead wire, and a DC power supply was connected. A current having a current density of 9.0 mA / cm ² was supplied for 48 hours as in Example 1 . Table 11 shows the results.

[Table 11]

As is clear from Tables 10 and 11 ,
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 4 A light emitting layer of Compound Example 12 having a thickness of 55 nm was placed on a transparent anode of indium tin oxide (ITO) coated (50 nm) glass.
Electron transport layer 40n composed of compound ( A ) having the following structural formula
m and a cathode 1 made of an Mg / Ag (10/1) alloy
40 nm was sequentially formed by vacuum evaporation, and an electroluminescent device having a configuration shown in FIG. 2 was prepared. Compound ( A )

Embedded image

The anode and cathode of the prepared electroluminescent device are
When a DC power supply was connected and a voltage of 8.0 V was applied, a current having a current density of 9.1 mA / cm ² flowed through the device, and an optical output of 0.21 mW / cm ² was confirmed.

Then, the current density as it is (9.5 mA)
/ Cm ² ) for 48 hours, a light output of final output of 0.18 mW / cm ² was obtained at an applied voltage of 8.2 V even after 48 hours.

[0039] Instead of the compound Example 12 used in Example 5-7 Example 4, respectively Compound Example 3, except for using Compound Example 22 and the compound Example 32, the same procedure as in Example 4, Example 5 The electroluminescent devices of Examples 6 and 7 were produced.

A current having a current density of 9.5 mA / cm ² was applied to each of the prepared electroluminescent devices. Table 12 shows the results.
Shown in

[Table 12]

Comparative Examples 5 to 7 The same procedures as in Example 5 were carried out except that Comparative Example 5 , Comparative Compound 6 and Comparative Example 7 of the following structural formula were used instead of Compound Example 3 used in Example 5. Comparative Example 5 and Comparative Example
6 and Comparative Example 7 were produced. Comparative compound example 5

Embedded image Comparative compound example 6

Embedded image Comparative compound example 7

Embedded image

A current having a current density of 9.5 mA / cm ² was applied to each of the prepared electroluminescent devices in the same manner as in Example 5 . Table 13 shows the results.

[Table 13]

As is clear from Tables 12 and 13 ,
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 8 A 60 nm anode made of gold, a 50 nm hole transport layer made of the compound ( B ) having the following structural formula, a 60 nm light emitting layer made of Compound Example 14, and a 150 nm cathode made of aluminum were formed on a glass substrate. Sequentially formed by vacuum deposition,
An electroluminescent device having the configuration shown in FIG. 2 was produced. Compound ( B )

Embedded image

The anode and cathode of the prepared electroluminescent device are
When a DC power supply was connected and a voltage of 8.0 V was applied, a current having a current density of 7.5 mA / cm ² flowed through the device, and an optical output of 0.12 mW / cm ² was confirmed.

Example 9 An indium tin oxide (ITO) coated (50 nm) glass transparent anode was coated on a transparent anode made of a compound ( C ) having the following structural formula.
Light emitting layer 50n composed of compound example 10
m, an electron transport layer 45 comprising a compound ( D ) having the following structural formula
nm, and a cathode 150 nm made of an Mg / Ag (10/1) alloy were sequentially formed by vacuum evaporation to produce an electroluminescent device having the configuration shown in FIG. Compound ( C )

Embedded image Compound ( D )

Embedded image

The anode and cathode of the prepared electroluminescent device are
When a DC power supply was connected and a voltage of 6.0 V was applied, a current having a current density of 8.0 mA / cm ² flowed through the device, and an optical output of 0.26 mW / cm ² was confirmed.

Examples 10 to 13 Compound Example 21 , Compound Example 31 , Compound Example 38 and Compound Example 10 were used in place of Compound Example 10 used in Example 9 , respectively.
Example 1 was repeated in the same manner as in Example 9 except that 39 was used.
0 , Example 11 , Example 12 and Example 13 were prepared.

A current having a current density of 8.0 mA / cm ² was applied to each of the prepared electroluminescent elements in the same manner as in Example 9 . Table 14 shows the results.

[Table 14]

Comparative Examples 8 to 12 Instead of Compound Example 10 used in Example 9 , Comparative Compound Example 8 , Comparative Compound Example 9 , Comparative Compound Example 10 ,
Except for using comparative compound Example 11 and Comparative Example Compound 12 in the same manner as in Example 9, Comparative Example 8, Comparative Example 9, was created electroluminescent device of Comparative Example 10, Comparative Example 11 and Comparative Example 12. Comparative compound example 8

Embedded image Comparative compound example 9

Embedded image Comparative compound example 10

Embedded image Comparative compound example 11

Embedded image Comparative compound example 12

Embedded image

A current having a current density of 8.0 mA / cm ² was applied to each of the prepared electroluminescent devices in the same manner as in Example 9 . Table 15 shows the results.

[Table 15]

As is clear from Tables 14 and 15 ,
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.

[0053]

As described above, the electroluminescent device of the present invention can emit light with extremely high luminance at a low applied voltage, and is extremely excellent in durability. In addition, the electroluminescent device can also be manufactured by vacuum evaporation or casting, and has a remarkable effect that a relatively inexpensive and large-area device can be easily manufactured.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Anode 3 Light emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer

Continuation of the front page (56) References JP-A-2-260889 (JP, A) JP-A-3-195957 (JP, A) JP-A-5-295361 (JP, A) JP-A-4-304466 (JP) JP-A-4-175394 (JP, A) JP-A-5-21165 (JP, A) JP-A-4-300991 (JP, A) JP-A-3-105894 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 11/06 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (1)

(57) [Claims] 1. An electroluminescent device comprising an anode, a cathode, and one or more layers of an organic compound sandwiched therebetween, wherein at least one of the organic compound layers is represented by the following general formula ( 1 ). Having an amine skeleton,
An electroluminescent device comprising a compound having a carbonyl group in the same molecule. General formula ( 1 ) In the formula, Ar ₁ , Ar ₂ and Ar ₃ represent an aromatic or heterocyclic group which may have a substituent, and Ar ₂ and A
r ₃ also form a ring together with the nitrogen atom in the formula bonded rather good <br/>, at least one of Ar _1, Ar ₂ and Ar ₃
Is a condensed ring, and Ar ₁ , Ar ₂ and Ar ₃ are
Ring and pyrene ring .