JPH11162641A - Electroluminescent device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new electroluminescent device with lower electric field strength and excellent luminous brightness by composing an element of a new principle. SOLUTION: In this electroluminescent device, a π electron conjugate molecule 7 which has a fluorescent segment and can accept both an electron and a positive hole is vaporized, or/and an ultra fine particle containing the molecule is floated, to stay between a pair of electrodes comprising a transparent electrode 4 and a thin cold cathode 6 in a sealed container, the π electron conjugate molecule 7 is charged through discharging between both electrodes 4, 6 under an electric field, and is made to emit fluorescent light by recombination of the charges of the π electron conjugate molecule. Thereby, a new electroluminescent device with lower electric field strength and excellent luminous brightness can be obtained, Devices with various structures to emit a laser beam are included in this electroluminescent device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electroluminescent device used for a light emitting display, a light emitting diode, a surface emitting light source, and the like.

[0002]

2. Description of the Related Art Conventionally, a display panel comprising an electroluminescent device (EL) is formed by forming a fluorescent light emitting layer between a pair of electrodes, and is characterized by high visibility, excellent display capability, and high speed response. have. The following reference is disclosed as an injection type electroluminescent device using an organic material.

JP-A-57-51781 discloses an EL cell having an organic luminous body (guest) and a binder (host), and having a porphyrin layer disposed between the luminous body and the anode. JP-A-63-264692 discloses an electroluminescent device having a thickness of 1 μm or less, comprising a host substance capable of injecting both holes and electrons, and a fluorescent substance (guest).

Japanese Patent Application Laid-Open No. 2-15595 discloses a configuration of an electroluminescent device having a cathode made of a plurality of metals other than alkali metals and having a work function of less than 4 eV. As an electron injection electrode of this injection type electroluminescent device, Mg-Ag, Ca, Ag, L having a small work function are used.
Metal thin-film electrodes such as i-Al, Li-Ag, and Al are disclosed in, for example, Japanese Patent Application Laid-Open Nos.
The electrode is also formed by vapor deposition.

[0005] Specific research reports related to these published inventions include Applied Physics Letters,
51, 913, 1987 (Applied Physics Lett
ers, 51, 1987, p. 913.). W. Ta
ng et al. disclose an injection type electroluminescent device having a structure in which an organic light emitting layer and a charge transport layer are laminated.

Here, an excellent injection type electroluminescent device is obtained by using a tris (8-quinolinol) aluminum complex (hereinafter abbreviated as Alq) having both high luminous efficiency and electron transport as a luminescent material.

Further, Journal of Applied Physics, Vol. 65, p. 3610, 1989 (Journal
f Applied Physics, 65, 1989, p. 3610) states that Alq forming an organic light emitting layer has a coumarin derivative or DCM1 (Eastman).
Chemicals) and other devices doped with fluorescent dyes,
It is reported that the emission color is changed by appropriate selection of the dye, and that the luminous efficiency is increased as compared with the undoped one.

Following this research, much research and development has been carried out, and fluorescent chelating metal complexes, electron-transporting organic molecules and hole-transporting organic molecules have been developed and studied as new functional materials.

An injection type electroluminescent device using these organic molecules, that is, an organic EL device, has a light emitting layer thickness of 20 to 10 mm.
Since the thickness is about 100 nm (about 40 nm in many cases) and about 100 nm in thickness together with the hole transport layer, and 3 to 15 V is applied thereto, the electric field strength is 3 * 10 ^{5 to} 1.5 * 10 ⁶ (V /
cm) and high.

[0010] Such a high electric field strength region is a region of normal conduction or more that causes avalanche, and it is said that the conduction is due to space charge limited conduction.

Further, an example of forming an organic light emitting device having a micro-resonant structure using the principle of the organic EL and obtaining an emission spectrum with a small half width is described in "Monthly Display",
Vol., July, p. 64 (1996).

On the other hand, attempts to develop a microsphere laser utilizing the light confinement effect in polymer microspheres have been reported in "Chemistry", Vol. 47, No. 3, page 156 (1992),
"Chemistry and Industry", Vol. 45, No. 6, page 1110 (199
It is disclosed in 2).

[0013]

However, in the injection type electroluminescent device comprising the above-mentioned conventional organic molecules, the organic molecules are a molecular material, and the intermolecular force is weak, so that diffusion or electrophoresis can be performed under an electric field in a solid bulk. There is a problem that such a solid-state device is difficult to obtain a highly reliable device because it is apt to occur, and composition fluctuation and characteristic change are likely to occur.

Further, the above-mentioned injection type electrode comprising the organic molecule is used.
Field light-emitting devices are ultra-thin films with an element thickness of 1 μm or less.
Light emitting diode made in the area, DC voltage of 3-20V
(Including pulse voltage)
The electric field strength is 10 ^Five-10⁶High and poor conduction
There is a problem that stable and stable operating current cannot be obtained.
Was.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a novel electroluminescent device having a lower electric field strength and an excellent light emission luminance by forming an element based on a new principle.

[0016]

To achieve the above object, the present invention provides a liquid discharge head having at least one dischargeable gap between a pair of electrodes comprising a transparent anode and a thin-film cold cathode in a sealed container. And an electroluminescent device that excites and emits fluorescent pi-electron conjugated molecules in the layer having the dischargeable voids by discharge generated under an electric field. The electroluminescent device of the present invention includes a device that emits laser light, in addition to devices having various specific structures described below.

As a result, a novel electroluminescent device having a lower electric field intensity and an excellent luminance can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention (claim 1) forms a layer having at least one dischargeable gap between a pair of electrodes consisting of a transparent anode and a thin film cold cathode in a sealed container. The discharge generated under the electric field excites the luminescent pi-electron conjugated molecule in the layer having the dischargeable voids, thereby forming an electroluminescent device that emits fluorescent light. It has the effect of using a discharge to excite and emit fluorescent molecules in a region where the electric field intensity is smaller than that of the EL element.

Further, in the present invention, the excitation voltage of the fluorescent pi-electron conjugated molecule that carries the charge between the electrodes corresponds to the energy gap of the molecule (the energy difference between HOMO and LUMO), and the ionization voltage is the ionization voltage. The excitation voltage and the ionization voltage of the fluorescent pi-electron conjugated molecules used in the present invention are lower than those of the inert gas, and these molecules form ion radicals and discharge at a low voltage. When electric charges are carried by creeping discharge on the wall surface of the void, the solidified energy value of the fluorescent pi-conjugated molecule is reflected, and the excitation voltage is further reduced.

As the thin film cold cathode, a metal thin film containing an alkali metal or an alkaline earth metal and having a small work function is suitable, and it is preferable that the cold cathode be formed of a metal alloy thin film containing any of Ca, Mg and Li. That is, Al alloy, Al-
A Zn alloy, an Ag alloy, a Zn alloy, or the like is used. On the other hand, an indium-tin-oxide (ITO) thin film is mainly used for the transparent anode.

The layer having a dischargeable gap between the electrodes preferably has a thickness of 50 to 10000 nm. The electric field strength of the discharge threshold is the electric field strength of the dielectric breakdown of solid (10 ⁶ V / c).
(m order), 1.5 to 2 orders of magnitude lower at 1 atm of air, so the device of the present invention utilizing the discharge phenomenon can be driven at a low voltage even with such a large electrode spacing.

Although there are various types of discharges, glow discharges and corona discharges occur mainly in the present invention, and the threshold voltage of the discharges in air at 1 atm depends on humidity but about 10%. ⁴ (V / cm).

In various gases, the discharge threshold varies depending on the type and pressure of the gas. If the electric field intensity is equal to or higher than the discharge threshold, discharge occurs. 50 to 1000
The discharge length of 0 nm, the electric field strength in the application of 3~15V is ^{3 * 10 3 ~3 * 10 6} (V / cm) , and the various discharge occurs in each conditions. The discharge length is preferably selected in consideration of the mean free path and the driving voltage of the fluorescent molecules to be vaporized so that the luminance and the luminous efficiency are optimized.

In some cases, a gas is sealed in anticipation of the Penning effect or the like, and various gases such as an inert gas and nitrogen can be used as the gas. However, water and oxygen have high reactivity with element constituting materials. It must be avoided because it causes deterioration.

The electroluminescent device of the present invention is not limited to forming only a layer having the above-mentioned dischargeable gap between the above-mentioned electrodes, but also comprises a hole transport layer used in a general organic EL device, and an anode. , A buffer layer, a dopant layer, an electron transport layer, a charge injection layer, and the like at the interface can be provided together.

According to the present invention (claim 2), the fluorescent pi-electron conjugated molecule is a sublimable aromatic molecule, and the sublimable molecule having no melting point has a higher melting point than the evaporable thermofusible molecule. Is vaporized without passing through a liquid state, and thus is preferable in the present invention without affecting the element shape. In addition, the aromatic molecule has a function that the pi electron is delocalized and the molecular structure is not broken when the electron is transferred, so that the aromatic molecule is stable.

As the sublimable aromatic molecule which acts as a fluorescent pi-electron conjugated molecule, a molecule which does not form a dense and large crystalline solid and which easily forms a powder form is rather suitable. Suitable for high quality light emitting layer.

Specifically, a fluorescent organic metal complex is suitable, and a metal complex having an aromatic organic molecule in which a pi electron is delocalized in the whole molecule as a ligand is preferable because of its high stability. This metal complex has a property that both electrons and holes are easily injected. Specifically, dyes having various structures such as fluorescent dyes and laser dyes can be used. Further, an organic complex having a rare earth element as a central metal can also be used.

As the organometallic complex, nitrogen or / and / or
And a metal complex having a sulfur-containing compound as a ligand,
As the nitrogen-containing compound, an aromatic tertiary polyamine in which a plurality of aromatic rings are bonded to nitrogen is mainly used.
Further, nitrogen-containing heterocyclic compounds are also suitable as the nitrogen-containing compound, and various derivatives such as pyrrole, imidazole and triazole (polycyclic derivatives, substituent-added derivatives, etc.) as 5-membered ring compounds, pyridine as 6-membered ring compounds, There are various derivatives such as pyrimidine and triazine (polycyclic derivatives such as naphthoquinoline, derivatives with substituents, etc.).

In addition, many aromatic condensed polycyclic compounds containing a hetero element are suitable for the present invention. Specifically, porphine derivatives such as carbazoles, quinolines, acridines and phthalocyanines, phenanthroline derivatives, There are tetrathiofulvalenes, thiophenes, bismaleimides, cyanoquinones, cyanoquinodimethanes and the like.

As the nitrogen-containing heterocyclic compound, quinoline, imidazole, triazole, oxadiazole and oxyquinazoline compounds are suitable.
The quinoline-based metal complex has high fluorescence and electronic (redox) stability, and is one of the most excellent specific materials. Examples of the quinoline-based compound used in the present invention include quinolinols, naphthoquinolines, and quinoline complexes.

Suitable imidazole compounds include benzimidazoles and aromatic derivatives such as phenyl-substituted, diphenyl-substituted and pyridyl-substituted compounds.

Examples of the triazole compound include benzotriazoles, phenyl-substituted, diphenyl-substituted, and the like.
Aromatic derivatives such as pyridyl substitution are suitable, and a triazine derivative is a similar structure having an effect similar to these.

As the oxadiazole compound, similarly, aromatic derivatives such as phenyl-substituted, diphenyl-substituted and pyridyl-substituted compounds are suitable. As oxyquinazoline-based compounds, there are many derivatives like the above-mentioned quinolines.

According to the present invention (claim 3), the fluorescent pi-electron conjugated molecule is a pi-electron conjugated molecule having a fluorescent segment and capable of accepting both electrons and holes. And / or the presence of suspended ultrafine particles containing the molecule, charging of the pi-electron conjugate molecule through electric discharge between the two electrodes under an electric field, and fluorescence due to recombination of the charge of the pi-electron conjugate molecule. A pi-electron conjugated molecule having a fluorescent segment and capable of accepting both electrons and holes, which is vaporized and / or vaporized; By allowing the ultrafine particles containing molecules to be present in a floating state, it is possible to continuously maintain the movement of electric charge due to discharge, and discharge the electric field in a region where the electric field intensity is smaller than that of the EL element as a solid light emitting element. An effect that can form a highly efficient light-emitting devices uniform continuous utilized.

The vaporized fluorescent molecules and floating particles present between the above-mentioned electrodes are charged and form ion radicals and are discharged. However, the light emission by the discharge of the present invention requires the vaporization between the electrodes to be positive or negative. When the charged fluorescing pi-electron conjugated molecule recombines with another oppositely charged fluorescent molecule, and when one fluorescent molecule has the highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO), In some cases, holes and electrons enter and charge is recombined in one molecule to emit fluorescence.

Excitation and ionization characteristics of the vaporized fluorescent pi-electron conjugated molecule in the discharge space occur by reflecting the energy gap and ionization potential of the molecule and are reflected in the discharge characteristics. In the case of suspended particles, the solidified energy value of the molecule is reflected. The concentration of the vaporized fluorescent molecule between the electrodes has a concentration at which the strongest fluorescent light is emitted, and this varies depending on the type of the molecule and the pressure in the container.

In the case of using suspended particles, the above-mentioned vaporization is carried out by forming an aerosol between the electrodes by using ultrafine particles having a particle diameter of 100 nm or less containing at least a luminescent pi-electron conjugated molecule on the surface. Like molecules, it exists as vaporized particles and emits fluorescent light through discharge. In this case, particles of the aerosol may collide with the electrode and receive charge injection from the electrode.

According to the present invention (claim 4), the layer having at least one dischargeable void contains a pi-electron conjugated molecule having a fluorescent segment and capable of accepting both electrons and holes at least on the surface of the hole. Thus, a porous light-emitting layer having continuous voids is formed, and the porous layer having the above structure has a feature that a pseudo-solid discharge space can be easily formed in the device.

The present invention also includes the use of creeping discharge for discharging the surface (particle surface) of the void in the porous light emitting layer.

According to the present invention (claim 5), the porous light-emitting layer is composed of a group of particles containing at least a surface of a fluorinated pi-electron conjugated molecule, and there is a gap between the particles. It has the effect that discharge occurs in this gap. As the particles, in addition to single crystal particles, ultrafine particles whose surface is modified with a fluorescent light-emitting electron-accepting molecule may be used. Desirable particle size is 20 to 2000 nm. In this case, the layer thickness of the porous light emitting layer is 50 to 10,000 n
m is desirable.

The structure composed of the porous particles in which the pi-electron conjugated molecules are adsorbed on the surface layer as the particles has voids between the particles and in the particles, the surface area of the particles is large, and the fluorescent molecules are in the air. It is preferable because the discharge phenomenon easily occurs in a stable manner.

In addition to the adsorption and carrying method, various methods of particle surface coating such as fluid coating and dipping can be used.

In the case where transparent or white spherical particles made of a metal oxide or a polymer are used as the porous particles, these spherical particles have an effect of easily modifying the surface. As the metal oxide, there are spherical particles represented by silica and alumina. Spherical particles can be easily prepared from polymers, and monodisperse particles having a uniform particle size can be used, and variations in device characteristics can be suppressed and stabilized.

Further, a pigment may be added to these particles to be colored so as to have a function of absorbing reflected light in color display.

In addition, since these particles also function as spacers between the electrodes, they also have a feature of preventing short-circuiting and forming an element having no short-circuited portion.

According to the present invention (claim 6), the porous light-emitting layer is composed of an internal transparent particle group containing at least the surface of a fluorinated pi-electron conjugated molecule, and the internal transparent particle group is formed. Laser light is emitted by the light confinement effect of the particles, and has the effect of emitting laser light by the light confinement effect of the transparent particles.

The porous light-emitting layer functions as a microsphere laser layer. The porous light-emitting layer has a suitable thickness of 300 to 10000 nm. Is composed of transparent fine particles. With this configuration, even when laser oscillation cannot be obtained, the half width of light emission is reduced, and light emission with high monochromaticity can be obtained.

As the transparent fine particles used for the microsphere laser layer, perfectly spherical monodisperse particles having a diameter of 300 to 10000 nm are suitable, and since the monodisperse fine particles do not have a variation in particle diameter, resonance easily occurs and laser oscillation easily occurs. Further, since these fine particles are present in the gaseous medium forming the porous light emitting layer, the difference in the refractive index of the surface is large, the reflectance is high, and the light confinement effect is high.

As the internal transparent particles containing the fluorescent pi-electron conjugated molecule at least on the surface thereof used in the present invention, the dye may be contained only on the particle surface even if the dye is contained throughout the transparent particles. May be either. As a material of the transparent particles, a glass or a polymer can be used because spherical monodispersed particles can be easily obtained.

According to the present invention (claim 7), the transparent anode is formed on a transparent substrate having a translucent reflective film, and a thin-film cold cathode having total reflection is further formed to form a microresonant structure between the substrate and the cathode. Formed, exciting the fluorescence emitting pi-electron conjugated molecule through discharge under an electric field, and emitting laser light,
This has the function of emitting laser light by the micro-resonance structure.

This microresonance structure has a distance between mirrors of 300 to
Although formed with a thickness of 10,000 nm, unlike the above-mentioned conventional organic EL element, there is a feature that the length of the resonator can be made longer than before because it is a discharge type.

Further, the microsphere laser emitting layer made of the transparent particles is formed on at least one of the inside of the microresonance structure between the substrate and the cathode and the outside of the translucent reflection film of the microresonance structure. An electroluminescent device having a kind of resonance structure can also be configured.

In this configuration, a novel organic laser element having high conversion efficiency can be obtained by combining the microsphere laser light emitting layer and the mirror type microresonance structure in this manner.

That is, the microsphere laser light-emitting layer can be formed either inside or outside the mirror-shaped microresonance structure, and light emission can be extremely enhanced by using a matched composite resonance structure.

According to the present invention (claim 8), the gas pressure in the sealed container is adjusted, and the pressure (vacuum degree) in the container, that is, the gap between the electrodes is adjusted so as to optimize light emission. It has the effect of adjusting the gas pressure. In the present invention, it is also possible to seal a suitable gas in the container, which has the effect of optimizing the discharge between the electrodes and the fluorescent emission of the gaseous fluorescent pi-electron conjugated molecule by gas pressure. Various gases can be sealed as the sealing gas, and the light emission characteristics are greatly affected.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a view schematically showing a configuration of an electroluminescent device according to Embodiment 1 of the present invention.
And a transparent substrate 2 constitute a sealed container, and have a fluorescent segment between a pair of electrodes composed of a transparent anode 3 and a thin-film cold cathode 6 formed on the transparent substrate 2 and have both an electron and a hole. A porous light-emitting layer 5 having a void containing at least a surface thereof containing an acceptable pi-electron conjugated molecule 7 is formed, in which the pi-electron conjugated molecule 7 is vaporized or /
And the ultrafine particles containing the molecule are floating, the pi-electron conjugated molecule is charged through a discharge between the two electrodes under an electric field, and the pi-electron conjugated molecule is caused to emit fluorescence by recombination of its charge. Has an action.

Reference numeral 4 denotes a lead wire. (Embodiment 2) FIG. 2 is a view showing an example of particles constituting the porous light emitting layer 5 according to the present invention. The pi-electron conjugated molecule 7 having a fluorescent segment and capable of accepting both electrons and holes. Particles 9 having a surface layer 8 containing The pi-electron conjugated molecule 7 sublimes from the surface of the particle, and becomes a charge carrier for discharge during device operation. Further, the surface of the particles may cause a creeping discharge. When the particles 9 are transparent particles,
The light incident on the particles acts as a microsphere laser due to the light confinement effect of the particles. Laser oscillation may occur.

(Embodiment 3) FIG. 3 is a view schematically showing the principle of an electroluminescent device according to the present invention, in which a fluorescent segment is provided between a pair of electrodes comprising a transparent anode 3 and a thin-film cold cathode 6. A porous light-emitting layer 5 having a void containing at least a surface containing both electron and hole acceptable pi-electron conjugated molecules 7 is formed, and the pi-electron conjugated molecules 7 are vaporized in the void between the electrodes. Or / and super-fine particles containing the pi-electron conjugated molecule 7 are allowed to exist in a floating state, and the pie-electron conjugated molecule 7 is charged via electric discharge between the two electrodes under an electric field, and the charge of the pi-electron conjugated molecule 7 is charged. Has the effect of causing fluorescence emission by recombination.

The porous light-emitting layer 5 of FIG. 3 is a schematic diagram in the case where particles containing at least the surface of the pi-electron conjugated molecule 7 having a fluorescent property are deposited and formed. The voids in the layer are filled with the vaporized fluorescent pi-electron conjugated molecules 7 and contribute to discharge and light emission.

[0061]

Next, specific examples of the present invention will be described.

Example 1 A pi-electron conjugated molecule 7 having a fluorescent segment and capable of injecting both electrons and holes was formed on a glass substrate 2 on which a transparent anode 3 made of an ITO thin film was formed.
Aluminum quinolium complex (Alq) as the
White silica particles 9 having an average particle diameter of 800 nm, which easily adsorb lq, were dispersed in a solution containing a small amount of a binder, and cast to form a porous light-emitting layer 5 having a thickness of 2500 nm. Furthermore, Al-Li containing 3% of lithium thereon
A 260 nm thick thin film cold cathode 6 made of an alloy was formed by vapor deposition. The device thus obtained had a structure as schematically shown in FIG.

The thus obtained electroluminescent device is shown in FIG.
After covering with the cover container 1 and sealing it in a structure capable of reducing the pressure as described above, applying a DC voltage and measuring the light emission characteristics thereof, a current of 2.4 mA / cm ² flows when 6 V is applied under normal pressure. , 95 cd / m ² . When a DC voltage was applied to the device to measure the relationship between the reduced pressure, the emission luminance, and the current, the luminance and the current changed significantly depending on the reduced pressure.

(Example 2) A pi-electron conjugated molecule 7 having a fluorescent segment and capable of injecting both electrons and holes was formed on a glass substrate 2 on which a transparent anode 3 made of an ITO thin film was formed.
Was dissolved in acetone, and a surface coating layer of Alq was formed on the surface of the transparent polystyrene particles 9 having an average particle size of 750 nm by a fluid coating method. The particles were dispersed in a solution containing a binder and a foaming agent, and cast to form a porous light-emitting layer 5 having a thickness of 3600 nm. Further, a thin film cold cathode 6 of 230 nm thickness made of an Al-Li alloy containing 3% of lithium was formed thereon by vapor deposition.

The thus obtained electroluminescent device was covered with a cover container 1 as shown in FIG. 1 and sealed under reduced pressure. Then, a DC voltage was applied to measure the light emitting characteristics. At 3.6 mA / cm ² flows,
A high luminance of 160 cd / m ² was obtained.

When a drop of n-decane, which is an insulating non-solvent, was poured onto the surface of the electroluminescent device not covered with the cover container 1 while applying a voltage of 8 V, the voids in the porous light emitting layer became n-decane. The discharge was stopped by filling with decane, and the light emission disappeared. After several tens of seconds, the light emission started again with the evaporation of n-decane, and after several minutes, it returned to its original state and emitted light neatly.

Example 3 A pi-electron conjugated molecule 7 having a fluorescent segment and capable of injecting both electrons and holes was formed on a glass substrate 2 on which a transparent anode 3 made of an ITO thin film was formed.
The ultrafine silica particles 9 having an average particle diameter of 2 nm to which Alq was adsorbed were dispersed in a solution containing a small amount of a foaming agent and a binder, and cast to form a porous light-emitting layer 5 having a thickness of 2500 nm. 3% lithium on top
A thin film cold cathode 6 having a thickness of 230 nm and made of an Al-Li alloy containing the same was formed by vapor deposition.

After the thus obtained electroluminescent device was covered with a cover container 1 as shown in FIG. 1 and sealed under reduced pressure, a direct current voltage was applied to measure the light emitting characteristics. The fine particles fly and the above thickness 2500
An aerosol was formed in the porous light emitting layer 5 of nm, and light emission was observed from flying particles. The light emission characteristic is 7V
When applied, a current of 4.1 mA / cm ² flows, and 180 cd /
A high luminance of m ² was obtained.

Example 4 A glass substrate 2 on which a transparent anode 3 made of an ITO thin film was formed was prepared, and Alq was converted to acetone as a pi-electron conjugated molecule 7 having a fluorescent segment and capable of injecting both electrons and holes. And an Alq surface coating layer was formed on each of the 1100 nm monodisperse spherical transparent polystyrene particles having a uniform particle size by a fluid coating method to obtain surface-modified particles.

The particles were dispersed in a solution containing a small amount of a binder and cast to form a porous light-emitting layer having a thickness of 2700 nm. Furthermore, a 220 nm thick thin film cold cathode 6 made of an Al-Li alloy containing 3% of lithium is further formed thereon.
Was formed by vapor deposition.

The thus obtained electroluminescent device is shown in FIG.
After covering the cover container 1 and sealing it under reduced pressure, a DC voltage was applied to measure the light emission characteristics. As a result, a current of 2.9 mA / cm ² flowed when 6 V was applied, and the luminance was 100 cd / m 2. ² luminescence was obtained. When this emission spectrum was measured, the half width of the spectrum was 1/15 of the half width of the spectrum of the comparative example. Based on these, we proceeded to study for laser oscillation.

Example 5 A transparent anode 3 made of an ITO thin film was formed on a transparent glass substrate having a translucent reflective film.
As a pi-electron conjugated molecule 7 having a fluorescent segment and capable of injecting both electrons and holes, silica particles 9 having an average particle diameter of 750 nm on a fine porous surface on which Alq is adsorbed are dispersed in a solution containing a small amount of a binder. Then, this was cast on a substrate on which the transparent solid thin film 4 was formed to form a porous light emitting layer 5 having a thickness of 2300 nm.

Further, Al-containing 3% of lithium
A 250 nm-thick total-reflection thin-film cold cathode 6 made of a Li alloy was formed by vapor deposition, and a micro-resonant structure was formed between the substrate and the cathode.

The thus obtained electroluminescent device is shown in FIG.
After sealing with a structure capable of reducing the pressure by covering the cover container 1 as described above, the luminescence characteristics were measured by applying a DC voltage, and depending on the pressure, it was 6.4 mA / cm when 8 V was applied.
² and a luminance of 350 cd / m ² was obtained.

When this emission spectrum was measured, the half width of the spectrum was 1% of the half width of the spectrum of the comparative example.
/ 7. Based on these, we proceeded to study for laser oscillation.

Comparative Example A glass substrate on which a transparent anode for injecting holes made of a transparent ITO thin film was formed was set as an evaporation target in an evaporation apparatus. Each of the four heating boats of the evaporation source has T as a heat-meltable hole transporting organic molecule.
PD, Alq as a fluorescent electron-accepting organic molecule,
Aluminum metal and lithium metal were put and set.

Close the bell jar and reduce the vacuum to 3 * 10 ^-6 T
After pulling to orr, a current was passed through the boat of the TPD and resistance heating was performed.
An 80 nm-thick TPD was deposited at a speed of about 30 nm.
Next, an electric current is applied to the Alq boat to perform resistance heating, and the film thickness is set to 5 at a deposition rate of about 0.1 nm / sec.
0 nm of Alq was deposited.

Further, as a thin film cold cathode, the boat of the evaporation source containing lithium metal was heated, and the film thickness sensor was adjusted so that the evaporation rate of lithium was about 0.015 nm / sec. After heating to melt and evaporate Al to set the evaporation rate to 1.5 nm / sec, a lithium-containing metal alloy thin film was immediately deposited at a thickness of 140 nm by simultaneous vapor deposition.

The thus obtained electroluminescent device is shown in FIG.
After covering and sealing the cover container 1 as described above, a DC voltage was applied to measure the light emission characteristics. As a result, a current of 2.5 mA / cm ² flowed by applying 6 V, and a luminance of 55 cd / m ² was obtained Was done. The half width of the emission spectrum was about 100 nm.

[0080]

As described above, the present invention provides a pi-electron conjugated molecule having a fluorescent segment between a pair of electrodes consisting of a transparent anode and a thin film cold cathode and capable of accepting both electrons and holes. Vaporization or / and super-fine particles containing the molecule are suspended and present, and the pi-electron conjugated molecule is charged via electric discharge between the two electrodes under an electric field, and the charge of the pi-electron conjugated molecule is recombined. It has the characteristic that it is composed of an electroluminescent device based on a new principle of causing the device to emit fluorescent light. Since the present invention utilizes discharge, the brightness in the discharge space becomes uniform, and element defects are less noticeable, self-repair is easy, and the life is long.

According to the present invention, since the electric field intensity can be made lower than before, a thick film can be formed, and an advantageous effect that a new electroluminescent device having excellent emission luminance and long life can be obtained can be obtained. The electroluminescent device of the present invention includes a device that emits laser light, and enables a surface emitting laser to be configured.

As described above, the present invention is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of an electroluminescent device according to a first embodiment of the present invention.

FIG. 2 is a view showing an example of particles constituting a porous light emitting layer according to a second embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating the principle of an electroluminescent device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cover container 2 Transparent substrate 3 Transparent anode 4 Lead wire 5 Porous light emitting layer 6 Thin film cold cathode 7 Pi electron conjugated molecule having a fluorescent segment 8 Surface layer containing pi electron conjugated molecule 9 Particles

Claims (8)

[Claims] 1. A layer having at least one dischargeable gap is formed between a pair of electrodes comprising a transparent anode and a thin-film cold cathode in a sealed container. An electroluminescent device, wherein a fluorescent pi-electron conjugated molecule in the layer having a dischargeable void is excited to emit fluorescent light. 2. The electroluminescent device according to claim 1, wherein the fluorescent pi-electron conjugated molecule is a sublimable aromatic molecule. 3. The fluorinated pi-electron conjugated molecule is a pi-electron conjugated molecule having a fluorescent segment and capable of accepting both electrons and holes, vaporizing it and / or containing the molecule. The ultrafine particles are suspended and present, the pi-electron conjugated molecule is charged through a discharge between the two electrodes under an electric field, and the pi-electron conjugated molecule emits fluorescence by recombination of the electric charge. 3. The electroluminescent device according to 2. 4. A continuous void comprising a layer having at least one dischargeable void comprising a fluorescent segment and containing at least a pi-electron conjugated molecule accepting both electrons and holes at the pore surface. The electroluminescent device according to claim 3, wherein a porous light emitting layer having the following is formed. 5. The electroluminescent device according to claim 4, wherein the porous light-emitting layer comprises a group of particles containing at least a surface of a pi-electron conjugated molecule having a fluorescent property. 6. A porous light-emitting layer comprising a group of internal transparent particles containing at least a luminescent pi-electron conjugated molecule on the surface, and a laser confined by the internal transparent particles. The electroluminescent device according to claim 4, wherein the device emits light. 7. A transparent substrate having a translucent reflective film, wherein the transparent anode is formed, a thin-film cold cathode having total reflection is formed to form a micro-resonant structure between the substrate and the cathode, and discharge is performed under an electric field. To excite the fluorescent pi-electron conjugated molecule through
The electroluminescent device according to claim 3, wherein the device emits laser light. 8. The electroluminescent device according to claim 1, wherein the gas pressure in the sealed container is adjusted.