JPH06240244A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain an org. electroluminescent element which can emit a blue light at a high luminance with a high stability by incorporating a specific material represented by a specific formula into an org. compd. layer. CONSTITUTION:A compd. of formula I (wherein n is 2 or 3; A is a group of formula II or III; R1 to R16 are each alkyl, aralkyl, alkoxy, H, halogen, or aryl provided when n is 3, then R13 and R16 are excluded) is incorporated into at least one org. compd. layer of an electroluminescent element which comprises an anode, a cathode, and at least one org. compd. layer including the above- mentioned layer and sandwiched between the two electrodes. The obtd. element can emit a blue light at a high luminance with a high stability. Formula IV shows an example of the compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device capable of emitting blue light.

[0002]

2. Description of the Related Art In recent years, with the diversification of information equipment, CR
There is an increasing need for a flat panel display device that consumes less power and occupies less space than T. Liquid crystal, plasma display, and the like are available as such flat display elements. Recently, electroluminescent elements (EL elements), which are luminescent type and have a clear display, have recently been developed.
Is attracting attention. Here, the EL element can be roughly classified into an inorganic EL element and an organic EL element depending on the constituent material, and the inorganic EL element has already been put into practical use. However, the driving method of the above-mentioned inorganic EL element is a so-called collision excitation type light emission in which electrons accelerated by application of a high electric field collide and excite the emission center to emit light,
It needs to be driven at a high voltage. Therefore, there is a problem that the cost of the peripheral device is increased.

On the other hand, the above-mentioned organic EL element has a structure in which opposed electrodes having different work functions are arranged with an organic light emitting layer interposed therebetween, and holes injected from the anode and electrons injected from the cathode are emitting light. This is so-called injection type light emission in which the light having the same wavelength as the fluorescence of the light emitting layer is recombined at. Therefore, it is possible to drive at a low voltage, and it is possible to obtain an arbitrary emission color by changing the material of the light emitting layer.

In addition, since the organic compound used in the organic EL element has different properties by changing the substituents, the degree of freedom in material design is higher than that of the inorganic compound. Therefore, it is considered that an arbitrary light emitting material can be obtained by changing the molecular structure of the organic compound while considering the electronic state of the molecule. Therefore, in theory,
It is possible to emit all colors from blue to red, and various stable constituent materials that actually emit green, yellow, and orange have been proposed. However, those which emit blue light stably and with high brightness are inorganic EL elements and organic EL elements.
Regardless of the L element, it is in the present state of being not developed yet. For example, as a blue light emitting material in an organic EL element,
An element using a 1,1,4,4-tetraphenyl-1,3-butadiene derivative or a styrylbenzene derivative has been proposed, but all of them have poor film-forming properties and can provide satisfactory brightness and stability. Does not reach. Further, as an electron transport material, 2- (4-tert-butylphenyl) -5- (p
An element using -biphenylyl) -1,3,4-oxadiazole has been proposed, but this element is easily crystallized and satisfactory stability is not obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electroluminescent device capable of obtaining sufficient brightness and stability in blue light emission.

[0006]

Means for Solving the Problems The inventors of the present invention have made earnest studies on the constituent elements of an organic EL device for solving the above problems, and as a result, have formed an anode and a cathode and one or more layers sandwiched between them. In the electroluminescent device constituted by the organic compound layer of, an electroluminescent device in which at least one of the organic compound layers is a layer containing a specific pyrene compound as a constituent component is found to be effective for the above problems. It was

Further, in an organic electroluminescent device containing at least one electron transport layer as a constituent element between an anode and a cathode, the electron transport layer is a layer containing a specific fused polycyclic compound as a constituent element. It has been found that the light emitting element is also effective.

That is, according to the present invention, in an electroluminescent device composed of an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, at least one of the organic compound layers is generally used. There is provided an electroluminescent device comprising a layer containing a compound represented by formula (I) (Chemical formula 1) as a constituent component. .

[Chemical 1]

[Chemical 2] Further, according to the present invention, in the organic electroluminescent device containing at least one electron transport layer as a constituent element between the anode and the cathode, the electron transport layer comprises a compound represented by the following general formula (II) as a constituent component. An electroluminescent device is provided which is a layer having B-X-C (II) (In the formula, B and C each represent a substituted or unsubstituted fused polycyclic hydrocarbon residue in which two or more rings are condensed, and X is an alkylene group or an alkylene group containing an arylene group therebetween. Represents.)

Specific examples of the compound represented by the general formula (I) are as follows.

[Table 1- (1)] No. 1 No. Two No. Three No. Four

[0010]

[Table 1- (2)] No. 5 No. 6 No. 7 No. 8

[0011]

[Table 1- (3)] No. 9 No. 10

Specific examples of the compound represented by the general formula (II) include the followings in addition to the compounds represented by the general formula (I).

[0013]

[Table 2- (1)] No. 11 No. 12

[0014]

[Table 2- (2)] No. Thirteen No. 14 No. 15 No. 16 No. 17

[0015]

[Table 2- (3)] No. 18 No. 19 No. 20 No. 21 No. 22

[0016]

[Table 2- (4)] No. 23 No. 24 No. 25 No. 26 No. 27

[0017]

[Table 2- (5)] No. 28 No. 29 No. Thirty No. 31 No. 32

[0018]

[Table 2- (6)] No. 33 No. 34 No. 35 No. 36 No. 37

[0018]

[Table 2- (8)] No. 38 No. 39

In the electroluminescent device of the present invention, the compound described above is made into a thin film by vacuum vapor deposition, solution coating, etc.
It is constituted by sandwiching the anode and cathode directly or indirectly. At that time, a plurality of other substances may be added as an additive to the compound.

As the anode material, nickel, gold, platinum,
Palladium, alloys of these or tin oxide (SnO ₂ ),
Indium tin oxide (ITO), metals having a large work function such as copper iodide, their alloys and compounds, and poly (3-
A polyalkylthiophene such as methylthiophene) or a conductive polymer such as polypyrrole can be used. Alternatively, it may be a laminate of a metal and a conductive polymer.

On the other hand, as the cathode material, silver, tin, lead, magnesium, manganese, aluminum, or an alloy thereof having a small work function is used. At least one of the materials used as the anode and the cathode is preferably sufficiently transparent in the emission wavelength region of the device. Specifically, it is desirable to have a light transmittance of 80% or more. However, in the case of an edge emitting device, it is preferable that both electrodes have high light reflectance.

FIG. 1 shows a typical configuration example of the electroluminescent device according to the present invention. In FIG. 1, 1 is a substrate, 2 and 4 are electrodes, 3a is a light emitting layer, 3b is an electron transport layer, and 3c is a hole transport layer. FIG. 1 shows that an electrode 2 is provided on a substrate 1
The light emitting layer 3a is independently provided on the top, and the electrodes are provided on the light emitting layer 3a. 2 shows a structure in which the hole transport layer 3c is provided between the electrode 2 and the light emitting layer 3a in FIG.
In FIG. 1, an electron transport layer 3b is provided between the light emitting layer 3a and the electrode 4 in FIG. FIG. 4 shows the electrode 2 in FIG.
The hole transport layer 3c is provided between the light emitting layer 3a and the light emitting layer 3a. Of these, the invention according to claim 2 is intended for the configurations of FIGS. 3 and 4.

Although the typical constitutional examples are illustrated above, these are the most basic constitutional examples, and layers for improving the charge transporting property may be inserted in various places.
It is also applied to the case where a tandem type laminated structure having a plurality of light emitting layers is adopted. The electroluminescent device of the present invention is configured as an element by sequentially laminating the above layers on a transparent substrate such as glass, but improving the stability of the element,
In particular, in order to protect against moisture in the atmosphere, a separate protective layer may be provided, or the entire element may be placed in a cell and silicon oil or the like may be enclosed.

As the various materials used in combination in the present invention, any materials can be used as long as they have functions such as hole transporting property, electron transporting property and light emitting property.
For example, the following conventionally known ones can be used. As the organic compound used in the light emitting layer, any compound can be used as long as it exhibits strong fluorescence in the solid state and has an excellent hole transporting ability. Examples of such substances include triphenylamines, stilbene derivatives, pyrazoline derivatives, and the like, and specific examples thereof include the following.

[0025]

[Table 3- (1)]

[0026]

[Table 3- (2)]

Of the above compounds, the compounds represented by (E2), (E3), (E4) and (E5) are particularly preferred for blue emission. These compounds are also used for the light emitting layer in the structure shown in FIG. As the material used for the hole transport layer in the structure shown in FIGS. 2 and 4, the following conventionally known materials are used, for example. (1) Triazole derivatives described in U.S. Pat. No. 3,121,197; (2) U.S. Pat. No. 31,894.
47, oxadiazole derivatives, (3) imidazole derivatives described in JP-B-37-16096, and (4) US Pat. No. 3,615.
No. 402, No. 3820989, No. 3542544, Japanese Patent Publication Nos. 45-555, 51-10983, and JP-A Nos. 51-93224 and 55-171.
No. 05, No. 56-4148, No. 55-108667.
Nos. 55-156953 and 56-36656, and the like, polyarylalkane derivatives,
(5) U.S. Pat. Nos. 3,180,729 and 4,278,746
Specification and JP-A-55-88064 and JP-A-55-880
No. 65, No. 49-105537, No. 55-51086.
No. 56-80051, No. 56-88141, No. 57-45545, No. 54-112637, No. 55.
-74546 and other pyrazoline and pyrazolone derivatives, (6) US Pat. No. 3615
No. 404 and JP-A Nos. 51-10105 and 46-
3712, 47-25336, and JP-A-54-53435, 54-110536, and 54.
Phenylenediamine derivatives described in JP-A-119925, (7) U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,597, and 36,585.
No. 20, No. 4232103, No. 4175961, No. 4012376 and Japanese Patent Publication No. 49-35702.
JP-A-39-27577 and JP-A-55-144.
250, 56-119132, 56-2243.
Arylamine derivatives described in Japanese Patent No. 7 and West German Patent No. 1110518, and (8) US Patent No. 3
Amino-substituted chalcone derivatives described in Japanese Patent No. 526501, (9) Oxazole derivatives described in US Pat. No. 3,257,203, and (10) Japanese Patent Application Laid-Open No. 56-46234. Styrylanthracene derivative, (11) JP-A-54-1108
Fluorenone derivatives described in Japanese Patent No. 37, etc.,
(12) US Pat. No. 3,717,462 and JP-A-5
4-59143, 55-52063, 55-5
No. 2064, No. 55-46760, No. 55-8549
No. 5, No. 57-11350, No. 57-14874, and the like, (13) JP-A-61-1210363, No. 61-228451, No. 61-14642, and No. 61- No. 72255, No. 62-
47646, 62-36674, 62-106.
No. 52, No. 62-30255, No. 60-93445.
No. 60-94462, No. 60-174749,
Examples thereof include stilbene derivatives described in JP-A-60-175052.

A more particularly preferable example is Japanese Patent Laid-Open No.
Examples thereof include a compound (aromatic tertiary amine) as a hole transport layer and a compound (porphyrin compound) as a hole injection zone disclosed in JP-A-3-295695.

More preferable examples of the hole transfer compound are disclosed in JP-A-53-27033 and JP-A-54-584.
No. 45, No. 54-149634, No. 54-6.
4299, 55-79450, 55-
No. 144250, No. 56-119132, No. 61-295558, No. 61-98353, and U.S. Pat. No. 4,127,412. The examples are as follows.

[0030]

[Table 4- (1)]

[0031]

[Table 4- (2)]

The hole-transporting layer is formed from these compounds, and the hole-transporting layer may be composed of one layer, or a hole-transporting layer using a compound of a different kind from the above-mentioned one layer may be laminated.

[0033]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 On a glass substrate having an ITO anode having a surface resistance of 20 Ω / □, a hole transporting layer having a thickness of 50 nm made of the arylamine derivative represented by H8, Compound No. A 50-nm-thick light-emitting layer of 1 and a 200-nm-thick cathode of a MgAg alloy with an atomic ratio of 10: 1 were sequentially laminated by vacuum evaporation to produce an electroluminescence device as shown in FIG. The device thus obtained exhibited blue light emission with a wavelength of 461 nm at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 2 In Example 1, the compound No. An electroluminescent device was produced in the same manner except that 2 was used. The device thus obtained was a device which emitted blue light with a wavelength of 468 nm at a drive voltage of 20 V or less and which was less deteriorated with time.

Example 3 In Example 1, the compound No. An electroluminescent device was produced in the same manner except that No. 3 was used. The device thus obtained exhibited blue light emission with a wavelength of 474 nm at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 4 In Example 1, the compound No. An electroluminescent device was produced in the same manner except that 9 was used. The device thus obtained exhibited blue light emission with a wavelength of 474 nm at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 5 A glass substrate having an ITO anode having a surface resistance of 20 Ω / □ and having a thickness of 5 consisting of the stilbene derivative represented by E5 above.
0 nm emission layer, compound no. 50 nm thickness consisting of 1
An electron-transporting layer of No. 2 and a cathode of MgAg alloy having an atomic ratio of 10: 1 and having a thickness of 200 nm were sequentially laminated by vacuum vapor deposition to manufacture an electroluminescent device as shown in FIG. The device thus obtained has a wavelength of 4 V at a driving voltage of 20 V or less.
The device showed blue light emission of 60 nm and showed little deterioration over time.

Example 6 In Example 5, the compound No. An electroluminescent device was produced in the same manner except that 2 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 7 In Example 5, the compound No. An electroluminescent device was produced in the same manner except that No. 3 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 8 In Example 5, the compound No. 3 was added to the electron transport layer. An electroluminescent device was produced in the same manner except that No. 4 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 9 In Example 5, the compound No. An electroluminescent device was produced in the same manner except that 5 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 10 In Example 5, the compound No. 3 was added to the electron transport layer. An electroluminescent device was produced in the same manner except that 9 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 11 In Example 5, the compound No. 3 was added to the electron transport layer. An electroluminescence device was produced in the same manner except that No. 14 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 12 In Example 5, compound No. 4 was added to the electron transport layer. An electroluminescence device was produced in the same manner except that No. 18 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 13 In Example 5, compound No. 3 was added to the electron transport layer. An electroluminescent device was produced in the same manner except that No. 19 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

Example 14 In Example 5, the compound No. An electroluminescent device was produced in the same manner except that 35 was used. The device thus obtained showed clear blue light emission at a drive voltage of 20 V or less, and was a device with little deterioration over time.

[0047]

The electroluminescent device of the present invention provides blue light emission with high brightness and high stability because the organic compound layer contains the specific material represented by the general formula (I).
Further, by using the specific material represented by the general formula (II) for the electron transport layer, blue light emission having higher brightness and higher stability is further provided.

[Brief description of drawings]

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

FIG. 2 is a schematic cross-sectional view of another electroluminescent device according to the present invention.

FIG. 3 is a schematic cross-sectional view of another electroluminescent device according to the present invention.

FIG. 4 is a schematic cross-sectional view of still another electroluminescent device according to the present invention.

[Explanation of symbols]

1 ... Substrate, 2, 4 ... Electrode, 3a ... Light emitting layer, 3b ... Electron transport layer, 3c ... Hole transport layer.

Front page continuation (72) Inventor Masafumi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (2)

[Claims] 1. An electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, at least one of the organic compound layers having the general formula (I) An electroluminescent device comprising a layer containing the compound represented by 1) as a constituent. [Chemical 1] [Chemical 2] 2. An organic electroluminescent device comprising, as a constituent, at least one electron-transporting layer between an anode and a cathode, the electron-transporting layer comprising a compound represented by the following general formula (II) as a constituent. An electroluminescent device characterized by: B-X-C (II) (In the formula, B and C each represent a substituted or unsubstituted fused polycyclic hydrocarbon residue in which two or more rings are condensed, and X is an alkylene group or an alkylene group containing an arylene group therebetween. Represents.)