JP2869447B2 - EL device - Google Patents

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 electric field applied energy to light energy by applying an electric field. The present invention relates to an electroluminescent device that can realize a large-area planar light emitting body unlike a fluorescent lamp or a light emitting diode.

[Conventional technology]

The electroluminescent device has (1)
An intrinsic electroluminescent element that excites the luminous body by local movement of electrons and holes in the luminescent layer and emits light only in an alternating electric field;
(2) A carrier injection type electroluminescent device that excites a luminous body by injecting electrons and holes from an electrode and recombines the electrons and holes in a light emitting layer and operates by a DC electric field. The intrinsic electroluminescent light emitting device of (1) generally uses an inorganic compound obtained by adding Mn, Cu, or the like to ZnS as a light emitting body.
There are many problems, such as the necessity of a high AC electric field of 200 V or more, high manufacturing cost, and insufficient luminance and durability.

The carrier-injection type electroluminescent device of (2) has obtained a high-luminance device since a thin-film organic compound was used as a light-emitting layer. Such examples are described in, for example, JP-A-59-194393, U.S. Pat.No. 4,720,432, Jpn. Journal of A
pplied Physics, vol. 27, pages 713-715,
Usually, a hole injection layer or an electron injection layer is provided on one side or both sides of the light emitting layer, and emits light with high luminance under a DC electric field of 100 V or less.

However, the conventional carrier-injection type electroluminescent device has a drawback that the device manufacturing is complicated because the multilayer structure must be formed by vacuum evaporation, so that the manufacturing cost is increased or the durability is inferior.

[Problems to be solved by the invention]

The present invention has been made in view of the circumstances of the above-mentioned prior art, and has an object of being easy to manufacture, exhibiting high luminance emission, and having excellent durability in which the light emission performance is maintained for a long time. To provide an electroluminescent device.

[Means for solving the problem]

The present inventors have conducted intensive studies on the components of the light-emitting layer in order to solve the above-mentioned object. High brightness is obtained when a fluorescent organic compound having electron transporting ability is mixed with a substance having hole transporting ability, and a mixed thin film formed by wet film forming such as spin coating is used as a light emitting layer. Thus, the present inventors have found that an electroluminescent device which is rich in durability and easy to manufacture can be obtained, and has completed the present invention.

That is, according to the present invention, in an electroluminescent device in which a light emitting layer composed of an organic thin film layer is provided between two electrodes, a substance constituting the light emitting layer is selected from triphenylamines, stilbene derivatives, and oxadiazoles. And a fluorescent organic compound having an electron transporting ability comprising an organic compound having a hole transporting ability and a perinone derivative, wherein the composition ratio of the organic compound having a hole transporting ability and the fluorescent organic compound having an electron transporting ability is An electroluminescent device comprising a mixture having a weight of 10/90 to 90/10 and using a mixture thin film formed by a wet film forming method. Is provided.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of the electroluminescent device of the present invention.
1 is a glass substrate or a synthetic resin substrate, and 2 is an anode formed on the substrate. 2 is formed by vapor deposition of metal such as gold, platinum, palladium, sputtered film or tin, indium-tin oxide thin film, organic conductive thin film, etc., and is transparent in a wavelength region of 400 nm or more in order to extract light emission. desirable. Reference numeral 3 denotes a thin film obtained by forming a mixture of an organic compound having a hole-transporting ability and a fluorescent organic compound having an electron-transporting ability by a wet film-forming method.
And preferably 400 to 1500 °.

Examples of the organic compound having a hole transporting ability include a high molecular weight compound having an excellent hole transporting ability such as polyvinyl carbazole and a low molecular weight compound having an excellent hole transporting ability. Examples of the low molecular weight compound include triphenylamines, stilbene derivatives, oxadiazoles, and the like, and specific examples thereof include the following.

If necessary, a resin binder such as bisphenol-A-polycarbonate or polystyrene may be added to the light emitting layer.

The fluorescent organic compound does not need to be particularly excellent in thin film-forming ability as long as it has a substance capable of transporting electrons and emits strong fluorescence in a solid state. Examples of such a substance include a perinone derivative, and specific examples thereof include the following substances.

The mixed composition of the organic compound having a hole transporting ability and the fluorescent organic compound used in the present invention is 10/90 to 9 by weight.
Although it can be changed to 0/10, the optimum mixing ratio is determined from the viewpoint of the ability of the mixture to form a thin film.

When a resin binder is compounded in the light emitting layer, it is preferable to use 5 to 50 parts by weight of the resin binder based on 100 parts by weight of the total amount of the organic compound having the hole transporting ability and the fluorescent organic compound.

In the wet film forming method of the present invention, in order to form a light emitting layer, a mixture of the organic compound having a hole transporting ability and a fluorescent organic compound or a mixture obtained by adding a resin binder to these is dissolved or dispersed in a solvent such as dichloromethane. And concentration 1.0
A solution or dispersion of up to 6.0% by weight is formed on a substrate by spin coating.

In this case, it is also possible to prepare a thin film or a property of the light emitting layer by devising a method of lifting the substrate from the solution or the dispersion.

Reference numeral 4 denotes a cathode, which is formed on the mixed film by vacuum evaporation of metal. As the material, any metal that can be vacuum-deposited can be used, and particularly, a metal having a small work function, such as Mg, Al, Ag, or In, is desirable.

The organic thin film layer of the electroluminescent device of the present invention is characterized in that it is a single layer, but in order to improve the durability of the device and further improve the hole and electron injection efficiency, the organic thin film layer and the electrode One or several organic layers may be inserted between them.

〔effect〕

The electroluminescent device of the present invention uses a mixture thin film layer formed by a wet film forming method using a mixture of an organic compound having a hole transporting ability and a fluorescent organic compound as the light emitting thin film layer, thereby producing the device. In addition, the device has many advantages such as realizing high-luminance light emission and durability of the device, and being able to use a wide range of organic fluorescent substances as light-emitting materials for electroluminescent devices.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 As an anode, indium-tin oxide (ITO) glass (manufactured by HOYA) was washed with a neutral detergent, and then ultrasonically washed in ethanol for about 10 minutes. This was put in boiling ethanol for about 1 minute, taken out, and immediately blow-dried. Next, an equimolar mixture of polyvinyl carbazole, an organic compound having a hole transporting ability, and a perinone derivative (I) represented by the following formula, which is a fluorescent organic compound, is dissolved in dichloromethane to form a solution having a concentration of about 4.0% by weight.
A film was formed on the substrate by spin coating. Thickness is about 1000
Was Å. The rotation speed at this time was 1500 rpm.

Next, on this light emitting layer, 0.1 cm ² , 1500 mm thick Mg-Ag
Electrodes were deposited. The light emitting device thus obtained is
When a positive bias was applied to the ITO side, yellow emission having a peak at 550 nm was exhibited. At a driving voltage of 60 V and a current density of 100 mA / cm ² , the luminance was 50 cd / m ² . Further, this light-emitting element could be operated in air in a state where humidity was sufficiently removed.

Example 2 A light emitting device was produced in the same manner as in Example 1 except that the following cyclopentadiene derivative was used as the fluorescent organic compound.

The obtained light-emitting element emitted blue light with a peak at 460 nm when a positive bias was applied to the ITO side.
Further, the driving voltage 72V, a current density of 100 mA / cm ^2, 105c
It showed a luminance of d / m ² .

Example 3 A light emitting device was produced in the same manner as in Example 1, except that the components for forming the light emitting layer were changed to the following.

(Emitting layer forming component)

N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine, which is an organic compound having a hole transporting ability, and the fluorescent organic compound, Perinone derivative (I) and bis-phenol A-polycarbonate (resin binder) dissolved and dispersed in dichloromethane at a weight ratio of 4: 4: 1.

The obtained light-emitting element emitted yellow light with a peak at 550 nm. The driving voltage 55V, current density 100mA / m ² 75cd / m ²
Luminance was shown.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an example of an electroluminescent device according to the present invention. 1 is a substrate, 2 is an anode, 3 is a thin film layer of a mixture of an organic compound having a hole transporting ability and a fluorescent organic compound, and 4 is a cathode.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-37886 (JP, A) JP-A-57-51781 (JP, A) JP-A-2-291696 (JP, A) JP-A-1- 254791 (JP, A) JP-A-62-50383 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 33/00-33/28 C09K 11/06 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. An electroluminescent device in which a light emitting layer comprising an organic thin film layer is provided between two electrodes, wherein a substance constituting the light emitting layer is a hole selected from triphenylamines, stilbene derivatives, and oxadiazoles. It is composed of an organic compound having an electron transporting ability and a fluorescent organic compound having an electron transporting ability comprising a perinone derivative, and the composition ratio of the organic compound having an electron transporting ability to the organic compound having an electron transporting ability is 10% by weight. An electroluminescent device, comprising a mixture thin film formed by a wet film-forming method and comprising a mixture of / 90 to 90/10.