JP3302064B2 - 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 having a luminescent layer made of a luminescent substance and capable of directly converting electric field applied energy to light energy by applying an electric field. Specifically, unlike conventional incandescent lamps, fluorescent lamps, light emitting diodes, etc., it has the characteristics of large area, high resolution, thin, lightweight, high speed operation, and more complete solid state device, and may meet high demands The present invention relates to an electroluminescent element that can be used for an electroluminescence (EL) panel.

[0002]

2. Description of the Related Art Electroluminescent development of organic materials was observed in an anthracene single crystal by Pope et al. In 1963 (J. Chem. Phys. 38 (1963) 204).
2), followed by Helfinch and Sc in 1965
Huider succeeded in observing a relatively strong injection-type EL by using a solution electrode system with high injection efficiency (Phys. Rev. Lett. 14 (1965) 22).
9). Since then, US Pat. No. 3,172,862,
U.S. Pat. No. 3,173,050, U.S. Pat.
0,167 specification; Chem. Phys. 44 (1
966) 2902; Chem. Phys. 50 (1
969) 14364; Chem. Phys. 58
(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.

[0003] Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl, triphenylene oxide, dihalobiphenyl, trans-stilbene and 1,4-diphenylbutanediene are organic hosts. Examples of materials were given, such as anthracene, tetracene, and pentacene, and the like were mentioned as examples of activators. However, each of these organic light-emitting substances exists as a single layer having a thickness exceeding 1 μm or more, 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, Th
in Solid Films 94 (1982) 17
1, Polymer 24 (1983) 748, Jp
n. J. Appl. Phys. 25 (1986) L77
3). 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, however, Tangs et al. (Appl.
Phys. Lett. 51 (1987) 913 or U.S. Pat. No. 4,356,429), devised an EL device in which two extremely thin layers (a charge transport layer and a light emitting layer) were stacked by vacuum evaporation between an anode and a cathode. High brightness was achieved with the drive voltage. This type of stacked organic EL device has been actively researched thereafter, and is disclosed in, for example, JP-A-59-19439.
No. 3, U.S. Pat. No. 4,539,507, JP-A-59-194393, U.S. Pat.
2, JP-A-63-264692, App.
l. Phys. Lett. 55 (1989) 1467;
It is described in JP-A-3-163188.

Further, Jpn. J. Appl. Phys
s. 27 (1988) L269 and L713 report a three-layered EL device in which the functions of carrier transport and light emission are separated. Even when a dye for the light-emitting layer that determines the emission color is selected, the carrier transport performance is restricted. It is suggested that there is a possibility that the degree of freedom can be considerably increased due to relaxation, and furthermore, holes and electrons (or excitons) can be effectively confined in the central light emitting layer for improvement. To make a stacked organic EL device,
In general, a vacuum evaporation method is used, but it has been reported that a device having a considerably high brightness can be obtained by the casting method (for example, Proceedings of the 50th Academic Lecture Meeting of the Applicable Society of Japan 1006 (1989) and Proceedings of the 50th Annual Meeting of the Japan Society for Materials Science, 1041 (1990)). Furthermore,
It has been reported that even a mixed single-layer EL device formed by a dip coating method from a solution in which polyvinyl carbazole as a hole transport compound, an oxadiazole derivative as an electron transport compound, and coumarin 6 as a luminous body can obtain considerably high luminous efficiency. (For example, Proceedings of the 38th Federation of Response-Related Lectures 1086 (1991)). As noted above, recent advances in organic EL devices are significant, suggesting a wide range of potential applications.

[0006]

[Problems to be Solved by the Invention] However, the history of those researches is still short, and the research on the materials and devices has not yet been sufficiently performed. At present, there are still problems in terms of durability, such as light output with even higher luminance, a change with time due to long-term use, and deterioration due to an atmospheric gas containing oxygen or moisture. Furthermore, when the application to full-color display or the like is considered, the problem of diversification of emission wavelengths for accurately selecting the emission hues of blue, green, and red has not yet been sufficiently solved.

Accordingly, it is an object of the present invention to firstly provide an electroluminescent device having an extremely high-precision light output. Secondly, it is an object of the present invention to provide an electroluminescent device having various emission wavelengths, exhibiting various emission hues, and being extremely durable. Another object of the present invention is to provide an electroluminescent device material which can be easily manufactured and can be provided at relatively low cost.

[0008]

The above objects are achieved by the present invention described below. That is, the present invention provides an electroluminescent device comprising an anode and a cathode and one or more layers of an organic compound supported therebetween, wherein at least one of the organic compounds is represented by the following general formula [1]. An electroluminescent device characterized by containing a compound having no amine skeleton. (However, in the formula, Ar is a fluoro group which may have a substituent.
, Pyrene, triphenylene, chrysene, tetrase
And any one of monovalent groups of pentane, pentacene and coronene . R is an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aromatic group which may have a substituent, an alkoxy group which may have a substituent, It represents an aryloxy group, a hydroxyl group, or a hydrogen atom which may have a substituent. )

[0009]

The present inventors have made intensive studies in order to achieve the above object. As a result, according to the electroluminescent device of the present invention containing the above-mentioned specific organic compound layer, light emission with extremely high luminance is obtained at a low applied voltage. Was found, and the present invention was also found to be extremely excellent in durability. In addition, since the electroluminescent device can also be manufactured by vacuum evaporation or casting, it is possible to easily manufacture a large-area device at relatively low cost.

[0010]

Preferred Embodiment Next, the preferred embodiment
The invention will be described in more detail. The electroluminescent device of the present invention,
Anode and cathode with one or more layers sandwiched between them
It is composed of several layers of organic compounds.
At least one of which is represented by the following general formula [1];
Characterized by containing a compound having no amine skeleton
You. The above general formula [1]Ar is pyrene,LuoranTe
, TrifeElm, Chrysene, tetracene, pentacene
NOrCoronenMonovalentBaseAny ofIs shown. R is C₁
~ C_FourAlkyl group, benzyl, phenethyl, naphthyl
Aralkyl groups such as methyl, phenyl, naphthyl, anse
Aromatic groups such as ril, methoxyethoxy, propoxy, etc.
Aryl groups such as alkoxy groups, phenoxy and naphthoxy
It represents a xy group, a hydroxyl group, or a hydrogen atom. Note that Ar and
R may have a substituent. Optional substituents
As C₁~ C_FourAlkyl groups, methoxy and ethoxy
And halogen groups such as fluorine, chlorine and bromine
Atom, aromatic group such as phenyl and naphthyl, or nitro
Groups.

More specifically, A in the general formula [1]
r is selected from the following structural formulas which may have a substituent:
Monovalent condensation having at least three or more benzene rings
Compounds exhibiting a polycyclic aromatic group are exemplified.

[0012]

The typical examples of the compounds represented by the general formula [1] are shown below. However, it is not limited to these compounds.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

In the light emitting device of the present invention, the compound represented by the above general formula [1] is formed between an anode and a cathode by a vacuum deposition method, a solution coating method, or the like. The thickness of the organic layer is smaller than 2 μm, preferably smaller than 0.5 μm.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows a structure in which an anode, a light-emitting layer, and a cathode are sequentially provided on a substrate. The light emitting element used here is useful when it has a single hole transporting ability, electron transporting ability and luminous performance by itself, or when it is used by mixing compounds having the respective properties. FIG. 2 shows a structure in which an anode, a hole transport layer, an electron transport layer, and a cathode are sequentially provided on a substrate. In this case, a material having either a hole-transporting property or an electron-transporting property, or both functions, is used for each layer as a light-emitting substance, 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.

FIG. 3 shows a structure in which an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode are sequentially provided on a substrate. It separates the functions of carrier transport and light emission, and has carrier transport properties, electron transport properties,
It is used in a timely combination with a compound having each of the luminescent properties, so that the degree of freedom of material selection is greatly increased, and various compounds having different emission wavelengths can be used. It becomes possible. Further, it is possible to effectively confine holes and electrons (or excitons) in the central light emitting layer to improve the light emission efficiency.
The compound used in the present invention is a compound having extremely excellent light-emitting properties as compared with conventional compounds, and can be used in any of the forms of FIGS. 1, 2 and 3 as necessary. is there. Further, the compound used in the present invention has either a hole transporting property or an electron transporting property, or both properties depending on its structure. In the case of any of the forms of FIGS. If necessary, two or more compounds represented by the general formula [1] may be used.

In the present invention, the compound represented by the above general formula [1] is used as a component of the light-emitting layer. If necessary, the hole transport property studied in the field of electrophotographic photoreceptors and the like is used. Compounds, hitherto known hole transporting luminescent compounds, or electron transporting compounds, and hitherto known electron transporting luminescent compounds can also be used together. Examples of these hole transporting compounds, hole transporting luminescent compounds, or electron transporting compounds, and electron transporting luminescent compounds include the following compounds.

[Hole transport compound] (Hole transporter)

[0026]

(Hole transporting luminescent material)

[Electron transporting compound] (Electron transporter)

(Electron Transporting Light Emitting Body)

The electroluminescent device of the present invention forms a thin film using the above-described compound, and is generally formed by vacuum deposition or a combination with an appropriate binder resin. The binder used at this time can be selected from a wide range of binder resins, for example, polyvinyl carbazole resin, polycarbonate resin, polyester resin, polyarylate resin,
Examples include butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, phenol resin, epoxy resin, silicone resin, polysulfone resin, urea resin, and the like, but are not limited thereto. These may be used alone or in combination of two or more as a copolymer.

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

On the other hand, as a cathode material, silver, lead, tin, magnesium, aluminum, calcium, manganese, indium, chromium, or an alloy thereof having a small work function is used. It is preferable that at least one of the materials used as the anode and the cathode transmits more than 50% of light in the emission wavelength region of the device. Further, as the transparent substrate used in the present invention, glass, plastic film and the like are used.

[0033]

The present invention will be described more specifically below with reference to examples and comparative examples of the present invention. (Example 1) On a transparent anode of indium tin oxide (ITO) coated (50 nm) glass, a light emitting layer 80 nm made of the above-mentioned exemplified compound (18) and a cathode 200 nm made of an Mg / Ag (10/1) alloy were placed. Each of them was sequentially formed by a vacuum evaporation method, and an electroluminescent device of the present invention as shown in FIG. 1 was prepared.
The anode and cathode of the device thus created were connected by a lead wire, a DC power supply was connected, and a voltage of 10 V was applied.
A current with a current density of 7.5 mA / cm ² flows through the device,
An optical power of 07 mW / cm ² was confirmed. When the current density (7.5 mA / cm ² ) was maintained for 24 hours, the final output was 0.06 mW / cm even after 24 hours.
An optical output of ² was obtained with an applied voltage of 11.0V.

(Examples 2 and 3 ) Instead of the exemplified compound (18) used in Example 1 above,
An electroluminescent device of the present invention was prepared in the same manner as in Example 1 except that the above-described exemplified compounds (16) and (29 ) were used, respectively. Then, a current having a current density of 7.5 mA / cm ^{2 was} passed through the obtained devices for 24 hours. The results at that time are shown in Table 1 below.

[0035]

(Comparative Examples 1 to 3) Compounds (a), (b) and (c) having the following structural formulas were used instead of the exemplary compound (18) used in Example 1, respectively. An element for comparison was formed in the same manner as in Example 1.

[0037] The anode and cathode of each element thus formed were connected by a lead wire, a DC power supply was connected, and a current having a current density of 7.5 mA / cm ² was supplied for 24 hours as in Example 1. The results at that time are shown in Table 2 below.

[0038]

As is clear from Tables 1 and 2, the devices of the examples of the present invention are extremely superior in light output and durability as compared with those of the comparative examples.

(Example 4 ) On a transparent anode of indium tin oxide (ITO) coated (60 nm) glass, a light-emitting layer 45 nm composed of the above-mentioned exemplified compound (39) and electron transport composed of the following compound (A) A 40 nm layer and a cathode made of a Mg / Ag (10/1) alloy were sequentially formed by vacuum evaporation, respectively, and FIG.
An element as shown in was prepared.

[0041] When an anode and a cathode of the device thus prepared were connected by a lead wire, a DC power supply was connected, and a voltage of 9.0 V was applied, a current having a current density of 5.0 mA / cm ² flowed through the device.
An optical output of 0.19 mW / cm ² was confirmed. And
When the current density (5.0 mA / cm ² ) was maintained for 24 hours, the final output was 0.17 mA even after 24 hours.
/ Cm ² was obtained with an applied voltage of 8.4V.

(Examples 5 to 7 ) The procedure of Example 1 was repeated except that the exemplified compounds (19), (26) and (28) were used instead of the exemplified compound (39) used in Example 4. Similarly, an electroluminescent device of the present invention was prepared. Then, a current density of 5.
A current of 0 mA / cm ² was passed. The results at that time are shown in Table 3 below.

[0043]

(Comparative Examples 4 to 6) Compounds (d), (e) and (f) represented by the following formulas were used in place of the exemplary compound (39) used in Example 4 , respectively. In the same manner as in Example 1, a comparative electroluminescent element was prepared. Then, similarly to Example 4 , a current having a current density of 5.0 mA / cm ² was passed through the obtained devices. The results at that time are shown in Table 4 below.

[0045]

[0046] As is clear from Tables 3 and 4, the electroluminescent device of the present invention is superior in the light output as compared with the electroluminescent device of the comparative example.

Example 8 A 60 nm anode made of gold on a glass substrate, a 60 nm hole transport layer made of the compound (B) shown below, a 60 nm light emitting layer made of the above exemplified compound (25), and aluminum Cathodes of 150 nm were sequentially formed by vacuum evaporation, respectively, to produce an electroluminescent device of the present invention as shown in FIG.

[0048] When an anode and a cathode of the device thus fabricated were connected with a lead wire, a DC power supply was connected and a voltage of 8.5 V was applied, a current having a current density of 6.5 mA / cm ² flowed through the device.
An optical output of 0.11 mW / cm ² was confirmed.

Example 9 On a transparent anode of indium tin oxide (ITO) coated (60 nm) glass, a hole transport layer 45 nm composed of the following compound (C) and light emission composed of the above exemplified compound (31) Layer 65 nm, an electron transport layer 50 nm made of the compound (D) shown below, and Mg / Ag (10 /
1) A cathode made of an alloy was formed to a thickness of 150 nm in order by vacuum evaporation to produce an electroluminescent device of the present invention as shown in FIG.

[0050] When an anode and a cathode of the device thus prepared were connected with a lead wire, a DC power supply was connected, and a voltage of 8.0 V was applied, a current having a current density of 6.0 mA / cm ² flowed through the device.
An optical output of 0.18 mW / cm ² was confirmed.

[0051] Instead of (Example 1 0) exemplified compound used in Example 9 (31), wherein except for using Exemplified Compound (21), the electroluminescent device of the present invention in the same manner as in Example 9 Created. Then, a current having a current density of 6.0 mA / cm ² was passed through the obtained device. The results at that time are shown in Table 5 below.

[0052]

(Comparative Examples 7 to 9) The same procedures as in Example 9 were carried out except that the following compounds (g), (h) and (i) were used instead of the exemplary compound (31) used in Example 9. Similarly, an element was prepared. Then, a current having a current density of 6.0 mA / cm ² was applied to the obtained devices in the same manner as in Example 9 . The results at that time are shown in Table 6 below.

[0054]

[0055] As is clear from Tables 5 and 6, the electroluminescent device of the present invention is extremely superior in light output as compared with the device of the comparative example.

[0056] (Example 1 1) Exemplified Compound (20) 2 g, hole transporting compound represented by the following structural formula (E) 1 g, electron transport compound (F) 1 g and polycarbonate resin (weight average molecular weight 35,000) 3 g Was dissolved in 280 ml of tetrahydrofuran to prepare a coating solution. This coating liquid was applied on a transparent anode of indium tin oxide (ITO) glass (50 nm) glass with a Meyer bar to form a 450 nm layer. Then, aluminum was vacuum-deposited thereon, and an anode was formed to form an element.

[0057] When an anode and a cathode of the device thus prepared were connected with a lead wire and a DC power supply was connected, and a voltage of 13.0 V was applied, a current of 4.2 mA / cm ² flowed through the device,
An optical output of 0.02 mW / cm ² was confirmed.

[0058]

As described above, the electroluminescent device of the present invention can obtain extremely high-luminance light emission at a low applied voltage and is extremely excellent in durability. Also, the electroluminescent device can be manufactured by vacuum evaporation or casting, and a large-area device can be easily manufactured relatively inexpensively.

[Brief description of the drawings]

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

FIG. 2 is a typical sectional view of an electroluminescent device according to the present invention.

FIG. 3 is a typical sectional view of an electroluminescent device according to the present invention.

Continuation of the front page (56) References JP-A-4-55493 (JP, A) JP-A-4-320484 (JP, A) JP-A-3-791 (JP, A) JP-A-4-31488 (JP) JP-A-6-52989 (JP, A) JP-A-5-295361 (JP, A) JP-A-5-302081 (JP, A) JP-A-6-136360 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 33/14 C09K 11/06 REGISTRY (STN) CA (STN)

Claims (1)

(57) [Claims] 1. An electroluminescent device comprising an anode, a cathode and one or more layers of an organic compound supported therebetween, wherein at least one of the organic compounds is represented by the following general formula [1]. An electroluminescent device comprising a compound having no amine skeleton. (However, in the formula, Ar is a fluoro group which may have a substituent.
, Pyrene, triphenylene, chrysene, tetrase
And any one of monovalent groups of pentane, pentacene and coronene . R is an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aromatic group which may have a substituent, an alkoxy group which may have a substituent, It represents an aryloxy group, a hydroxyl group, or a hydrogen atom which may have a substituent. )