JPH02267888A - Electroluminescence display element - Google Patents

Abstract

PURPOSE:To maintain high luminescence brightness for a long period of time through low voltage driving and permit large-area application by providing a luminescence layer composed of a polymer in which an organic fluorescent material is dispersed, between a pair of electrodes. CONSTITUTION:A polypyrrole electrode film 2 is formed by the electrolytic polymerization method on a glass base 1. Then, a polymer luminescence layer 3 of 2 micron meters in thickness is deposited through spin coating by using a slurry in which 30weight% of perylene against an acrylic resin is dissolved in chloroform employed as a common solvent. Further on top of it, indium which serves as an upper electrode 4 is vacuum-evaporation coated. By this constitution, when a 5V DC voltage is applied to the electrode 4 used as a minus-side, orange-colored luminescence of a few hundred Cd/cm<2> in brightness is produced, and this brightness is not reduced even with the voltage applied continuously for 1000 hours.

Description

[Detailed Description of the Invention] [Industrial Application Field 1 Electroluminescence (hereinafter referred to as EL) suitable for display
(described as)) regarding elements.

[Prior art 1] Conventionally used inorganic compounds such as zinc sulfide require a high voltage of at least 200 volts to emit light. Furthermore, the color tone of the emitted light was also limited. Recently, organic compounds with high fluorescence quantum efficiency have come to be used in EL devices, and organic thin 11iEL devices that emit light below 10 volts have also been reported (C, W, Tang, Appl, P
hys.

Lett,,51. P913. (1987)).

[Problems to be Solved by the Invention] However, in the organic thin film EL devices that have been studied in the past, the luminous efficiency significantly decreases in a short period of time. In addition, conventional organic thin films have been formed using vacuum deposition or the LB (Langmuir-Blodgett) method, which poses problems in mass production and large-area production.

Therefore, in order to solve these conventional problems, the present invention has the following features:
An object of the present invention is to provide an EL display element that can be driven at a low voltage, maintains high luminance for a long time, and can easily be made to have a large area.

[Means for Solving the Problems 1] The EL display element of the present invention is characterized by having a light emitting layer made of a polymer in which at least an organic fluorescent substance is dispersed between a pair of electrodes.

[Example 1 Example 1] FIG. 1 is a cross-sectional view schematically showing an EL display element in Example 1 of the present invention.

A polypyrrole film electrode 2 was formed on a glass substrate 1 by electrolytic polymerization. 30% by weight of perylene was dissolved in chloroform, a common solvent, in a zero-order acrylic resin, and a 2 micrometer thick film was formed by spin coating. A polymer light emitting layer 3 was formed. Furthermore, indium was laminated by vacuum evaporation to form the electrode 4 described above. Through microscopic observation, it was confirmed that perylene was dispersed in the acrylic resin in the form of polycrystals.

When a DC voltage of 5 V was applied with the indium upper electrode on the negative side, orange light emission with a brightness of several hundred cd/m2 was detected.

Even when the voltage application was continued for 1000 hours, no decrease in brightness was observed.

Example 2 FIG. 2 is a cross-sectional view schematically showing an EL display element in Example 2 of the present invention.

After forming an ITO electrode 2 on a polypropylene substrate 1 by vacuum evaporation, ladder polysilane was dissolved in an organic solvent, and a hole injection layer 5 was formed by roll coking.

Next, 40% by weight of anthracene based on polystyrene was dissolved in carbon tetrachloride as a common solvent, and a polymer light emitting layer 3 with a thickness of 3 micrometers was coated using a roll coater.
was formed. Furthermore, aluminum was laminated by vacuum evaporation to form the upper electrode 4. By observation using a microscope Ia, it was confirmed that anthracene was dispersed in polystyrene in the form of polycrystals.

When 20 V of 60 Hz alternating current was applied between the electrodes, blue light emission with a brightness of several hundred cd/m'' was detected. Even if the voltage application was continued for 1000 hours, no decrease in Ii degree was observed. There wasn't.

Example 3 FIG. 3 is a cross-sectional view schematically showing an EL display element in Example 3 of the present invention.

After forming an ITO electrode 2 on a glass substrate 1 by vacuum evaporation, a diamine-based hole injection layer 5 was formed by vacuum evaporation using 0-order acrylic resin, 20% by weight of coronene, and tetrachloride as a common solvent. A polymer light-emitting layer 3 having a thickness of 1 micrometer was formed by dissolving it in carbon and spin coating. Furthermore, after forming an electron conductive layer 6 made of a perylenetetracarboxy derivative by vacuum evaporation,
An aluminum electrode 4 was formed.

When an alternating current of 200F (z) was applied between the electrodes at IOV,
Green light emission with a brightness of several hundred cd/m'' was detected. No decrease in brightness was observed even after applying the AC voltage for 1000 hours.

[Effects of the Invention J As described above, according to the present invention, by having a light emitting layer made of a polymer in which at least an organic fluorescent substance is dispersed between a pair of electrodes, high luminance can be maintained for a long time with low voltage drive. Moreover, it was possible to provide an EL display element that can be easily made large in area.

FIG. 1 is a cross-sectional view schematically showing an EL display element in Example 1 of the present invention. Similarly, FIG. 2 is a diagram showing the second embodiment, and FIG. 3 is a diagram corresponding to the third embodiment.

·substrate ·electrode ・Polymer light emitting layer ·electrode ・Hole injection layer ・Electronic conductive layer that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Kisanbe Suzuki (1 other person)

[Brief explanation of drawings]

Grass 3

Claims (1)

[Claims] An electroluminescent display element characterized by having a polymer light emitting layer in which at least an organic fluorescent substance is dispersed between a pair of electrodes.