JPH04178488A - Electric field luminescent element - Google Patents

Abstract

PURPOSE:To provide the title electric field luminescent element excellent in hole transferability, electron transferability and luminescent characteristics, in which at least one layer of organic compound layers consists of an aromatic organic compound. CONSTITUTION:The objective electric field luminescent element in which at least one layer of organic compound layers sandwiched by anode and cathode consists of an organic compound of the formula [R1 to R6 are each H, halogen, cyano, nitro, or (each substituted) alkoxy, amino, carbon cyclic aromatic ring or heterocyclic aromatic ring; R3 and R4, R4 and R5, or R5 and R6 may form a ring jointly; n is 1 or 2].

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a light-emitting layer made of a light-emitting substance, and can directly convert electrical energy into light energy by applying an electric field. The present invention relates to an electroluminescent device that, unlike lamps or light emitting diodes, enables the realization of large-area planar light emitters.

[Conventional technology]

Electroluminescent elements differ in their luminescence excitation mechanisms; (+) intrinsic electroluminescent elements, which excite the luminescent body by local movement of electrons and holes within the luminescent layer, and emit light only in an alternating electric field;
2) Carrier injection type electroluminescent devices that excite a luminescent material by injecting electrons and holes from an electrode and recombining them within a luminescent layer, and operate in a DC electric field. (1) Intrinsic electroluminescence type light emitting device is generally made of ZnS with Mn and Cu.
The luminescent material is an inorganic compound added with
It has many problems such as requiring a high alternating current electric field of 2 (IOV or more) for driving, high manufacturing cost, and insufficient brightness and durability.

The carrier injection type electroluminescent device (2) has become capable of achieving high luminance since thin film-like organic compounds have been used as the light emitting layer. For example, JP-A-59-19
4393, U.S. Patent No. 4,539,507, JP-A-63
-295695, U.S. Patent No. 4,720,432, and JP-A No. 63-264692 disclose electroluminescent devices consisting of an anode, an organic hole injection transport band, an organic electron injection luminescent material, and a cathode, and are used in these devices. Typical examples of the material include aromatic tertiary amine as an organic hole injecting and transporting material, and aluminum trisoxine as an organic electron-injecting light-emitting material.

Also, Jpn, Journals o(^pplied
Ph7sicd, vol.

27, p. 713-715, an electroluminescent device consisting of an anode, an organic hole transport layer, a light emitting layer, an organic electron transport layer, and a cathode is reported, and the materials used for these include N as the organic hole transport material. .

N'-diphenyl-N, N'-bis(3-methylphenyl)-1゜1'-biphenyl-4,4'-diamine, and 3.4, 9.1 as organic electron transport materials.
Bisbenzimidazole 0-perylenetetracarboxylate is exemplified, and phthaloperinone is exemplified as a luminescent material.

These examples demonstrate that in order to use organic compounds as hole-transporting materials, luminescent materials, and electron-transporting materials, it is necessary to explore various properties of these organic compounds and effectively combine these properties to create electroluminescent devices. In other words, it shows that research and development of a wide range of organic compounds is necessary.

Furthermore, research on carrier injection electroluminescent devices using organic compounds as light emitters, including the examples mentioned above, has a short history, and research into materials and device development has not yet been sufficiently conducted. However, there are many issues to be solved, such as further improvement in brightness, diversification of emission wavelengths to enable precise selection of blue, green, and red emission hues when considering application to full-color displays, and improvement of durability. The reality is that there are.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned state of the prior art, and its purpose is to provide an electroluminescent element that has diversity in emission wavelength, exhibits various emission hues, and has excellent durability.

[Means to solve the problem]

As a result of intensive studies on the constituent elements of a light-emitting layer to solve the above problems, the present inventors found that an electroluminescent layer composed of an anode, a cathode, and one or more organic compound layers sandwiched between the anode and cathode. An electroluminescent device in which at least one of the organic compound layers is a layer containing an organic compound represented by the following general formula (I) as a component is effective for solving the above problem. This discovery led to the completion of the present invention.

(However, R1r R2r R3+ R4y '6+ R
6 each independently represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amine group, or a substituted or unsubstituted carbocyclic aromatic group. ring, substituted or unsubstituted heteroaromatic ring, and R3 and R4
, R4 and R5, R6 and R6 may jointly form a ring (n is l or 2). In general formula (1), as R1, R2, R3, R4, R5, R6 The alkyl groups used are preferably Cl-C20, especially C1
~C1□ straight-chain or branched alkyl group, and the alkyl of the alkoxy group is as described above.

Amino groups are mono-substituted or di-substituted.

Examples of carbocyclic or heterocyclic aromatic rings used as 'l+R2+R3+'4+R5+R6 are:
Phenyl, naphthyl, anthryl, acenaphthynyl, fluorenyl, phenanthryl, pyridyl, pyrimidyl,
Examples include furanyl, pyrrolyl, thiophenyl, quinolyl, benzofuranyl, benzothiophenyl, indolyl, carbazolyl, benzoxacylyl, quinoxalyl, and the like.

Also, 'I + R2+ R3+ in general formula (1)
R4+ R6+ Examples of substituents for R6 include the following.

(1) Halogen atom, trifluoromethyl group, cyan group, nitro group, (2) Alkyl group; preferably 0l-C20, especially 0
l-CI2 is a linear or branched alkyl group, and these alkyl groups further include a hydroxyl group, a cyan group, a 01-C
I2 alkoxy group, phenyl group or halogen atom,
It may contain a phenyl group substituted with a C, -C, □ alkyl group or a C1 to C1□ alkoxy group.

(3) Aryl group: phenyl group, naphthyl group, anthryl group, pyridyl group, furanyl group, thiophenyl group, etc., and these aryl groups further include 01-C1□ alkyl group, C1-CI2 alkoxy group, 01-CI2 alkoxy group, C1□ may be substituted with an alkylamino group, dialkylamino group, cyan group, halogen atom, or phenyl group.

(4) Alkoxy group (-OR');R' represents the alkyl group defined in (2).

(5) Aryloxy group: The aryl group represents the aryl group defined in (3).

(6) Alkylthio group (-3R');R' represents the alkyl group defined in (2).

\R3 Any acyl group such as an alkyl group, acetyl group or benzoyl group defined in (2) or an aryl group defined in (3). Also, like piperidyl and morpholyl groups, R
2 and R3 may form a ring together with the nitrogen atom. Furthermore, a ring may be formed jointly with a carbon atom on an aryl group, as in the case of a eurolidyl group. Alkoxycarbonyl group (-CO
OR4); R4 represents the alkyl group defined in (2) or the aryl group defined in (3).

(8) Acyl group (-COR'), sulfonyl group (-3O
2R'), represents the meaning defined in \R3. However, this excludes the case where R2 and R3 jointly form a ring with the polyatom on the aryl group.

(9) Alkylene dioxy group or alkylene dithio group such as methylene dioxy group or methylene dithio group Next, specific examples of the compound represented by the general formula (1) used in the present invention are shown, but the present invention is limited to these. It is not something that will be done.

I13 υ The electroluminescent device of the present invention is produced by depositing the organic compound described below in vacuum evaporation, solution coating, etc., so that the total thickness of the organic compound is less than 2 tones, more preferably 0.05 mm.
It is constructed by forming an organic compound layer by thinning it to a thickness of μs to 0.5 μs and sandwiching it between an anode and a cathode.

Hereinafter, the present invention will be explained in more detail along the drawings.

FIG. 1 shows a typical example of the electroluminescent device of the present invention,
It has a structure in which an anode, a light emitting layer, and a cathode are sequentially provided on a substrate.

The electroluminescent device shown in FIG. 1 is particularly useful when a single compound is used that has hole-transporting properties, electron-transporting properties, and luminescent properties, or when a mixture of compounds having each of these properties is used. .

FIG. 2 shows a light-emitting layer formed by a combination of a hole-transporting compound and an electron-transporting compound. This configuration combines the favorable properties of organic compounds, and by combining compounds with excellent hole transport properties or electron transport properties, it is possible to smoothly inject holes or electrons from the electrodes to obtain an element with excellent light emitting properties. That is. Note that in the case of this type of electroluminescent device, since the luminescent substances differ depending on the organic compounds used in combination, it is not possible to unambiguously determine which compound emits light.

Figure 3 shows a light-emitting layer formed by a combination of a hole-transporting compound, a luminescent compound, and an electron-transporting compound, and this can be considered to be a type of layer that further advances the above idea of functional separation. The second type of electroluminescent device can be obtained by appropriately combining compounds that have hole-transporting properties, electron-transporting properties, and luminescent properties, so the range of compounds that can be used is extremely wide.

It not only makes selection easy, but also allows the use of various compounds with different emission wavelengths, which has many advantages, such as diversifying the emission hues of the device.

All of the compounds of the present invention have excellent luminescent properties, and can have structures as shown in FIGS. 1, 2, and 3, if necessary.

Further, in the present invention, RI in the general formula (1)
By appropriately selecting the type of IR21R31R41R51R6 or the substituent, it is possible to provide both a compound with excellent hole transport properties and a compound with excellent electron transport properties.

Therefore, in the case of the configurations shown in FIGS. 2 and 3, two or more types of compounds represented by the general formula (1) may be used as components for forming the light emitting layer.

In the present invention, the above general formula (
The compound shown in 1) is used, but if necessary, an aromatic primary amine or N,N'-diphenyl-N,N'-bis(3-methylphenyl) to 1,1'-biphenyl-4,4'-diamine, etc., and as an electron transporting compound, aluminum trisoxine, or perylentithoracarboxylic acid derivatives, etc. can be used.

The electroluminescent device of the present invention emits light by applying an electrical bias to the light-emitting layer, but a slight pinhole may cause a short circuit and cause the device to no longer function, so film formation is necessary to form the light-emitting layer. It is desirable to use compounds with excellent properties. Furthermore, a light-emitting layer can be formed by combining such a compound with excellent film-forming properties with, for example, a polymer binder. Polymer binders that can be used in this case include polystyrene, polyvinyltoluene, poly-N-vinylcarbazole, polymethyl methacrylate, polymethyl acrylate, polyester,
Examples include polycarbonate and polyamide. In addition, in order to improve the charge injection efficiency from the electrode,
It is also possible to separately provide a charge injection transport layer between the electrodes.

Examples of anode materials include nickel, gold, platinum, palladium, alloys thereof, metals with large work functions such as tin oxide (Sn02), indium tin oxide (ITO), and copper iodide, their alloys, and compounds, as well as positive ( 3-methylthiophene), polypyrrole, and other conductive polymers.

On the other hand, as the cathode material, silver, tin, lead, magnesium, manganese, aluminum, or an alloy thereof, which has a small work function, is used. It is desirable that at least one of the materials used for the anode and the cathode be sufficiently transparent in the emission wavelength region of the device. Specifically, it is desirable to have a light transmittance of 80% or more.

In the present invention, it is preferable to form a transparent anode on a transparent substrate and have a structure as shown in FIGS. 1 to 3, but the opposite structure may be used depending on the case. Moreover, glass, plastic film, etc. can be used as the transparent substrate.

In addition, in the present invention, in order to improve the stability of the electroluminescent device obtained in this way, and in particular to protect it from atmospheric moisture, it is possible to provide a separate protective layer, or to place the entire device in a cell and use silicone. It is also possible to enclose oil or the like.

〔Example〕

The present invention will be described in more detail below based on Examples.

Example 1 An Mh electrode made of indium tin oxide (ITO) having a size of 3III11×3 mIn and a thickness of 500 A was formed on a glass substrate, and a hole transporting electrode made of a triphenylamine derivative represented by the following compound (ITO) was formed on it. layer 500 people,
Electron transport layer consisting of compound No. 2, silver/
Magnesium alloy (7.7 atomic percent silver, purity 99
．． 9%) were each formed by vacuum evaporation to produce an electroluminescent device. The degree of vacuum during vapor deposition was approximately 1×10''' Torr, and the substrate temperature was room temperature.

When a direct current power source was connected to the anode and cathode of the device thus fabricated via lead wires and a voltage was applied, clear blue-violet light emission was observed for a long period of time.

From this example, it is understood that the compound No. 2 used in the present invention functioned as an electron-transporting luminescent material.

Example 2 Example 1 except that compound No. 8 was used as the luminescent material
A light emitting device was produced in the same manner as above. The obtained light emitting device exhibited clear light emission when a positive bias voltage was applied to the anode side.

Furthermore, this light emitting device could be operated in air with sufficient humidity removed.

Example 3 Example 1 except that compound No. 9 was used as the luminescent material
A light emitting device was produced in the same manner as above. The obtained light emitting device exhibited clear light emission when a positive bias voltage was applied to the anode side.

Furthermore, this light emitting device could be operated in air with sufficient humidity removed.

Example 4 A light emitting device was produced in the same manner as in Example 1 except that Compound No. 20 was used as the light emitting substance. The obtained light emitting device exhibited clear light emission when a positive bias voltage was applied to the anode side.

Furthermore, this light emitting device could be operated in air with sufficient humidity removed.

Example 5 A light emitting device was produced in the same manner as in Example 1 except that compounds No. 12 were used as the light emitting substance. The obtained light emitting device exhibited clear light emission when a positive bias voltage was applied to the anode side.

Furthermore, this light emitting device could be operated in air with sufficient humidity removed.

Example 6 Size: 3 mm x 3 mm, thickness: 500 mm on a glass substrate
A hole transport layer 800A made of the compound NO, I4, an electron transport layer 500A made of an oxadiazole derivative represented by the following structural formula (b), and silver/ A cathode made of a magnesium alloy (silver 7.7 atomic percent, purity 9949%) +50 OA was formed by vacuum evaporation, and an element as shown in FIG. 2 was produced. The degree of vacuum during vapor deposition was approximately I x 10-6 Torr, and the substrate temperature was room temperature. When a direct current power source was connected to the anode and cathode of the device thus produced through lead wires and a voltage was applied, clear blue-green light emission was observed for a long period of time.

From this example, it is understood that compound NO,+4 functioned as a hole-transporting luminescent material.

Example 7 A light emitting device was produced in the same manner as in Example 6 except that Compound No. and Il were used as the light emitting substances. The obtained light emitting device exhibited clear light emission when a positive bias voltage was applied to the anode side.

Furthermore, this light emitting device could be operated in air with sufficient humidity removed.

Example 8 Size: 3 mm x 3 mm, thickness: 500 mm on a glass substrate
Forming an anode with indium tin oxide (ITO) of A,
On top of that is a light emitting layer consisting of the compound No. 22 +000
A, silver/magnesium alloy (silver 7.7 atomic percent,
1500 A of cathodes each having a purity of 99.9% were formed by vacuum evaporation to produce a device as shown in FIG.

The degree of vacuum during vapor deposition was approximately IXIG"-'To++, and the substrate temperature was room temperature. When a DC power source was connected to the anode and cathode of the device thus fabricated via lead wires, and a voltage was applied, a blue Clear green light emission was observed for a long time.

〔Effect of the invention〕

Since the electroluminescent device of the present invention uses the compound represented by the general formula (1) as the sliding material of the organic compound layer,
Even with a low driving voltage, it is possible to obtain high-brightness light emission for a long period of time, and it is also possible to exhibit various color tones.

In addition, since the device can be easily produced by vacuum evaporation or the like, it has the advantage of being able to efficiently produce large-area devices at low cost.

[Brief explanation of drawings]

1 to 3 are schematic cross-sectional views of an electroluminescent device according to the present invention. Patent applicant Rico Co., Ltd. −

Claims (1)

[Claims] (1) In an electroluminescent device composed of an anode and a cathode, and one or more organic compound layers sandwiched between them, at least one of the organic compound layers is represented by the following general formula (I). An electroluminescent device characterized by having a layer containing an organic compound as a constituent component. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R_1, R_2, R_3, R_4, R_5, R
_6 each independently represents a hydrogen atom, a halogen atom, a cyano group,
Represents a nitro group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted carbocyclic aromatic ring, or a substituted or unsubstituted heterocyclic aromatic ring. , R_3 and R_4, R_4 and R_5, R_5 and R_6 may jointly form a ring, and n represents 1 or 2. )