JP2869446B2 - 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,
In these, usually, a hole injection layer or an electron injection layer is provided on one side or both sides of a light emitting layer, and emits light with high luminance under a DC electric field of 100 V or less.

However, the carrier injection type electroluminescent device of (2) requires that the organic compound forming each layer has a capability of forming a uniform and pinhole-free thin film having a thickness of 1000 mm or less, and thus can be used. However, there are disadvantages in that the device is limited and that the multilayer structure must be formed by vacuum evaporation, so that the device production is complicated. In particular, since few fluorescent organic compounds have the ability to form a uniform thin film of 1000 ° or less, devices using such a light emitting layer inevitably have poor durability, and improvement of this point has been strongly desired. .

[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 honored elements of the light-emitting layer in order to solve the above-mentioned object, and as a result, mixed a fluorescent organic compound having an electron transporting ability with an organic compound having a hole transporting ability. It has been found that an electroluminescent device having high luminance, high durability and easy manufacture can be obtained when the light emitting layer is used, and the present invention has been completed.

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 is provided, which is a mixed thin film having a weight of 10/90 to 90/10.

 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. Numeral 2 is formed by vapor deposition of a metal such as gold, platinum, or palladium, a sputtered film or a thin oxide film of tin or indium-tin, and is preferably transparent in a wavelength region of 400 nm or more in order to extract light emission. Reference numeral 3 denotes a thin film made of a mixture of an organic compound having hole transport and a fluorescent organic compound having an electron transporting ability.
It is 0 to 3000 °, preferably 400 to 1500 °.

As the organic compound having a hole transporting ability, a compound which easily forms an amorphous solid is preferable, and a transparent organic compound in a wavelength region of 400 nm or more is preferably used. Such organic compounds include triphenylamines, stilbene derivatives, and oxadiazoles, and specific examples thereof include the following.

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. Such a substance is 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.
Can be changed to 0/10. The formation of the mixed thin film can be performed by a vacuum evaporation method, a canting, a melting method, or the like. In the case of the vacuum evaporation method, the evaporation can be performed by simultaneous evaporation from two resistance heating evaporation sources that can independently measure the heating temperature and control the evaporation rate. Also, a mixture of fine powders of both substances in advance is installed in one resistance heating source,
A good mixed thin film can be formed even by the method of vapor deposition. Further, it is also possible to form a mixed film having a composition change in the film thickness direction by performing evaporation while independently changing the evaporation rates of the two substances by using two independent heating evaporation sources.

Reference numeral 4 denotes a cathode, and as the cathode material, metals and organic conductors capable of being vacuum-deposited can be used. In particular, Mg, Al, Ag, In
A metal having a small work function, such as a metal, is desirable.

The light emitting layer of the electroluminescent device of the present invention is characterized in that it is a single layer, but one or more organic material layers between the light emitting layer and the electrode in order to improve the durability of the device and improve the luminous efficiency. May be inserted.

〔effect〕

Since the electroluminescent device of the present invention uses a uniform mixed layer of an organic compound having a hole transporting ability and a fluorescent organic compound,
It has advantages such as facilitating the manufacture of the device and realizing high-luminance emission and improved durability of the device.

〔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, N, which is an organic compound having a hole transporting ability,
N'-diphenyl-N, N '-(3-methylphenyl) -1,
1′-biphenyl-4,4′-diamine (TPD) and a perinone derivative represented by the following formula, which is a fluorescent organic compound, are glass from two resistive heating sources capable of controlling the deposition rate by independently setting the heating temperature. A light emitting layer was formed on the plate by simultaneous vapor deposition. That is, the temperature controller keeps the tantalum boat containing the TPD at 200 ° C and the boat containing the perinone derivative at 250 ° C.
Controlled to be s. Therefore, the deposition rate is 4
Å / s, and the degree of vacuum at the time of vapor deposition was 0.7 × 10 ⁻⁶ torr. The substrate temperature was 20 ° C. The thickness of the deposited layer formed on ITO was 1500 °.

Next, a 0.1 cm ² , 1500 mm thick Mg-Ag electrode was deposited on the deposition layer. The light emitting device obtained in this way is ITO
When a positive bias was applied to the side, it emitted orange light with a peak at 580 nm. In addition, drive voltage 20V,
At a current density of 100 mA / cm ² , the luminance was 500 cd / m ² . Further, this light-emitting element could be operated in air in a state where humidity was sufficiently removed. Further, when the light emitting device of the present invention was driven under the conditions of a current density of 10 mA and a luminance of 50 cd / m ² , no decrease in luminance was observed even after 40 hours.

Example 2 The following stilbene derivative was used as an organic compound having a hole transporting ability, and the temperature of a boat containing this substance was adjusted to
A light emitting device was manufactured in the same manner as in Example 1 except that the deposition rate was kept at 160 ° C. and the deposition rate was controlled to be 2 ° / s, that is, 4 ° / s in total. The thickness of the deposited film formed on this ITO was 1000 mm.

The obtained light emitting device emitted orange light with a peak at 580 nm when a positive bias was applied to the ITO side. At a driving voltage of 20 V and a current density of 100 mA / cm ² , the luminance was 500 cd / m ² .

Example 3 Compound (P-1) shown below as a fluorescent organic compound
A light emitting device was produced in the same manner as in Example 1 except that the temperature of the boat containing this substance was kept at 210 ° C., and the vapor deposition rate was controlled to 2 ° / s, that is, 4 ° / s in total. . The thickness of the deposited film formed on the ITO was 1000 mm.

The obtained light-emitting element emitted yellow light with a peak at 550 nm. The driving voltage 19V, current density 100mA / m ² 50cd / m ²
Luminance was shown.

Comparative Example TPD, an organic compound having a hole transporting ability, was
The hole transport layer was formed by vapor deposition at 0 °. Next, on the hole transport layer, (P-1) as a fluorescent substance was vapor-deposited at 500 [deg.] To form a light emitting layer. Next, an Mg-Ag electrode was
A light emitting device of a comparative example was produced by vapor deposition at 500 °. In addition, TPD
Was maintained at 190 ° C., the boat temperature of P-1 was maintained at 210 ° C., and the vapor deposition rate was controlled at 2 ° / s.

This light emitting device emitted yellow light having a peak at 550 nm. However reluctant, driving voltage 14 V, at a current density of 100mA / cm ² 0.
Only a luminance of 5 cd / m ² was obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of the 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-63-264692 (JP, A) JP-A-63-295695 (JP, A) JP-A-58-1983 30758 (JP, A) JP-A-2-220394 (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. An organic compound having a transport ability and a perinone derivative, comprising a fluorescent organic compound having an electron transport ability, the composition ratio of the organic compound having a hole transport ability and the fluorescent organic compound having an electron transport ability is represented by weight. An electroluminescent device, wherein the electroluminescent device is a mixed thin film having a ratio of 10/90 to 90/10.