JPH10208880A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic layered thin film light emitting element, which can maintain the light emitting efficiency in the atmosphere of oxygen and which can be stably driven for a long time in any atmosphere, by interposing a layer, which includes a material for emitting light, between a positive electrode and a negative electrode, and aging the light emitting element with the electric energy in the atmosphere of oxygen. SOLUTION: Characteristic of an organic layered thin film light emitting element can be stabilized without lowering the light emitting efficiency by performing the constant current aging for a short time in the atmosphere of oxygen at a low current density. Content of oxygen in the atmosphere is desirably set at 20% of volume percentage. Non-light emitting phenomenon and luminance lowering phenomenon due to the generation of short circuits can be restricted for a long time, and stabilized light emitting luminance and stabilized driving voltage can be maintained, and practical and reliable display is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element capable of converting electric energy into light, and is applicable to fields such as display elements, flat panel displays, backlights, lighting, interiors, signs, signboards, and electrophotographic machines. It can be preferably used as a flat surface light emitter.

[0002]

2. Description of the Related Art An organic laminated thin-film light-emitting device that emits light when electrons injected from a cathode and holes injected from an anode recombine in an organic phosphor sandwiched between both electrodes is thin and has a low driving voltage. It is characterized by high brightness light emission and multicolor light emission. This organic laminated thin film element emits light with high luminance, as described by Kodak C.I. W. First shown by Tang et al. (App
l.Phys. Lett. 51 (12) 21, p.913, 1987).

[0003] A typical structure of an organic laminated thin film light emitting device presented by Kodak Company is a diamine compound having a hole transporting property on an ITO glass substrate, tris (8-quinolinolato) aluminum as a light emitting layer, and Mg as a cathode: Ag is sequentially provided, and a driving voltage of about 10 V
Green light emission of cd / m ² was possible. The feature of the present invention resides in that a diamine compound as a hole transport layer is provided between tris (8-quinolinolato) aluminum as an illuminant and ITO as an anode, thereby dramatically improving luminous brightness. . The present organic laminated thin-film light-emitting device has a different configuration, such as a device provided with an electron transport layer in addition to the above-described device components, but basically follows the configuration of Kodak Company.

However, it is difficult to stably emit light for a long period of time in an organic laminated thin film light emitting device. No. 14794, JP-A-5-182764, JP-A-8-185979).

[0005]

However, in the aging treatment used in the prior art, the luminous efficiency after the treatment is remarkably reduced, so that the luminous efficiency after the aging becomes very low even if the luminance retention rate is high. There was a problem that it would. Further, in the related art, there is a problem that light emission cannot be performed due to local growth of a short-circuit region caused by element deterioration due to long-time driving, and luminance is extremely reduced. In general, it is most preferable to place an element in a vacuum in order to stably store an unstable element for a long period of time.However, this short-circuit phenomenon is particularly noticeable when the element is driven in a vacuum, and is driven in an inert gas. In this case, a problem often arises that a short phenomenon occurs. An object of the present invention is to provide an organic laminated thin-film light-emitting device that can maintain a practical luminous efficiency even after aging treatment and can drive the device stably for a long time in any atmosphere.

[0006]

In order to achieve the above object, the present invention provides a device comprising a layer containing a substance which emits light between an anode and a cathode, and an element which emits light by electric energy is placed in an atmosphere containing oxygen. Light-emitting element characterized by aging below. "

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the anode is made of a conductive metal oxide such as tin oxide, indium oxide, indium tin oxide (ITO) or a metal such as gold, silver or chromium if it is transparent to extract light. Metals, and these metals and I
Although not particularly limited, such as a laminate with TO, copper iodide, an inorganic conductive substance such as copper sulfide, a conductive polymer such as polythiophene, polypyrrole, and polyaniline, and a laminate of these conductive polymers and ITO, It is particularly desirable to use ITO glass or Nesa glass. The resistance of the transparent electrode is not particularly limited as long as a current sufficient for light emission of the element can be supplied, but is preferably low from the viewpoint of power consumption of the element. For example, an ITO substrate having a resistance of 300 Ω / □ or less functions as an element electrode, but a low-resistance substrate can be supplied at present.
It is particularly desirable to use a substrate of Ω / □ or less. IT
The thickness of O can be arbitrarily selected according to the resistance value,
Usually, it is often used between 50 and 300 nm. In addition, the substrate of ITO is made of soda lime glass, non-alkali glass, transparent resin, or the like, and the thickness is sufficient if it has a sufficient thickness to maintain mechanical strength. It is enough. As for the material of the glass, non-alkali glass is preferable because it is preferable that the amount of ions eluted from the glass is small, but soda lime glass can also be used. In this case, since soda lime glass provided with a barrier coat such as SiO ₂ is commercially available, it is more preferable to use this. The method of forming the ITO film is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method. In addition, ITO is UV
-It is known that the driving voltage of the element can be reduced by ozone treatment, but this method is also applicable to the present invention.

Since the cathode must efficiently supply electrons to a substance which controls light emission or a substance adjacent to the substance which controls light emission (for example, an electron transport layer), the adhesion between the electrode and the adjacent substance and the ionization potential. It is important to make adjustments. In addition, it is particularly desirable to use a material that is relatively stable in the air in order to maintain stable performance for long-term use. However, it is possible to use a protective film, etc. It is not something to be done. Specifically, it is possible to use metals such as indium, gold, silver, aluminum, lead, and magnesium or rare earth elements, alkali metals, or alloys thereof, but in consideration of element characteristics, magnesium, lithium, potassium,
It is desirable to use a low work function metal such as sodium. However, since these metals are very active and unstable, alloys with silver or aluminum can be used. An electrode is manufactured by a resistance heating method, an electron beam method, a sputtering method, a coating method, or the like. A metal can be deposited alone or two or more components can be deposited simultaneously. Particularly, for forming an alloy, an alloy electrode can be easily formed by depositing a plurality of metals at the same time, or an alloy may be deposited. Further, as a more preferable example, a method of performing a doping treatment on a layer containing a substance which controls light emission and then forming a negative electrode is given. This has the advantage that co-evaporation is not required and that a stable single metal can be used for the electrode, but it need not be. The dopant to be doped is preferably an alkali metal such as lithium, sodium or potassium, an alkaline earth metal such as magnesium or calcium, or an organic donor molecule such as ammonia, tetrathiofulvalene or tetraselenofulvalene. The doping amount is very small and shows a sufficient effect, and is usually 1 nm or less as measured by a film thickness sensor. The doping process is
It is preferably performed in a vacuum, but can be performed in the air or in an inert atmosphere. After performing the doping process, the metal negative electrode is made into a predetermined shape, but metals such as indium, gold, silver, copper, iron, aluminum, chromium, tungsten, lead, and alloys containing these and carbon are mainly produced by vacuum evaporation. Can be used. Among them, aluminum, indium, and silver are particularly preferably used metals from the viewpoint of resistance value, ease of pattern formation, and the like.

In the present invention, the substance which controls light emission comprises a light emitting material and a hole transporting material and / or an electron transporting material.
Even in a multilayer structure such as a light emitting layer, 2) a hole transporting layer / a light emitting layer / an electron transporting layer, and 3) a light emitting layer / an electron transporting layer,
4) Any combination of the above combined substances in a single layer may be used.

As the hole transporting material, a hole transporting material such as a biscarbazolyl derivative, TPD, m-MTDATA, poly (N-vinylcarbazole), polysilane, metal or metal-free phthalocyanine can be laminated or mixed. Above all, the biscarbazolyl derivative represented by the following general formula sufficiently withstands the Joule heat generated during the aging process due to the high glass transition point due to the rigid structure, and does not cause a significant decrease in luminous efficiency even under severe conditions. Device performance can be stabilized.

[0011]

Embedded image (R is ethyl, phenyl, methylphenyl, dimethylphenyl, methoxyphenyl, diphenylaminophenyl, hydroxyphenyl, naphthyl, methylnaphthyl,
Represents phenanthrolinyl, anthracenyl or pyrenyl, wherein R1 to R7 may be the same or different,
Each represents hydrogen, methyl, ethyl, propyl, butyl, fluorine, chlorine, bromine, iodine, methoxy, dialkylamino, formyl group)

The formation of the hole transport layer is mainly performed by a vacuum evaporation method, and the coating from a solution or the above-mentioned monomer hole transport material is made of polyvinyl chloride, polycarbonate, polystyrene, poly (N-vinylcarbazole), poly (N-vinylcarbazole), or the like. Methyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, A
Solvent-soluble resins such as BS resin and polyurethane resin,
Coating is also possible by dissolving or dispersing in a solvent together with a phenol resin, xylene resin, petroleum resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicone resin and the like. The thickness of the hole transport layer is desirably reduced to the "limit film thickness" at which the leakage current of the element increases in consideration of the driving voltage, but slightly larger than the "limit film thickness" in consideration of the durability of the element. Is preferred. The preferred thickness of the hole transport layer is not limited because it varies depending on the surface condition of the ITO substrate, the constituent material of the hole transport layer, and the like.
The thickness is preferably about 0 nm, more preferably 50 to 300 nm.

The light emitting material may be a single light emitting material or a mixture of two or more light emitting materials. The doping method is a method in which a dopant serving as a guest is mixed with a phosphor substance serving as a host to emit light from the dopant. As the host material, JP-A-63-264892
Metal oxide derivatives such as tris (8-quinolinolato) aluminum, 1,4-diphenylbutadiene, 1,1,4,4-tetraphenylbutadiene (JP-A-59-194393), styryl compounds (JP-A-2-247278, JP-B-7-9)
8787), benzoxazole derivatives, benzothiazole derivatives, transstilbene and the like. On the other hand, as a dopant as a guest material, coumarin derivatives known to be useful as laser dyes such as 7-dimethylamino-4-methylcoumarin and the like (J. Appl. Phys. 65 (9) 3610) (1989), JP-A-63-264692, JP-A-6-240243), dicyanomethylenepyran dye, dicyanomethylenethiopyran dye, cyanine dye, xanthene dye, pyrylium dye, carbostyril dye, perylene dye JP-A-63-264892), perylene, tetracene, pentacene (JP-A-2-261889),
-(Dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4Hpyran, 3- (2'-benzimidazoyl) -7-N, N-diethylaminocoumarin (Japanese Unexamined Patent Publication No. 3-26780) ), Quinacridone compounds, quinazoline compounds (JP-A-5-70773,
JP-A-3-255190), pyrrolopyridine, a compound having a diazaindacene skeleton, furopyridine (JP-A-5-222360), 1,2,5-thiadiazolopyrene derivative (JP-A-5-222361),
Perinone derivatives (JP-A-5-279662, Jpn.
J. Appl. Phys., 27, L713 (1988)), a pyrrolopyrrole compound (JP-A-5-320633), a squarylium compound (JP-A-6-93257), a rare earth complex (Patent No. 2505244), Eu (dibenzoylmethide) ₃
(phenanthroline) (41st Joint Lecture Meeting on Applied Physics)
28p-N-8), Eu (thenoyltrifluoroacetone) -1,10-phenant
hroline (Jpn.J.Appl.Phys.Vol.34,1883 (1995)), Tb (ace
tylacetonate) ₃ (Chem. Lett., 657 (1990)), Eu (thenoyl
Light emitters such as trifluoroacetonate) ₃ (Chem. Lett., 1267 (1991)) are known. Since the concentration quenching phenomenon occurs when the doping amount is usually too large, the doping amount is preferably used in an amount of 10% by weight or less, more preferably 2% or less, based on the host material. As a doping method, it can be formed by a co-evaporation method with a host material. There is a method of separately depositing in a deposition boat partitioned into two rooms, heating them at the same time, and then depositing. It is also possible to use a small amount of guest molecules sandwiched between host materials. The method for forming the light-emitting layer is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating. However, resistance heating evaporation and electron beam evaporation are usually preferable in terms of characteristics. The thickness of the light-emitting layer cannot be limited because it depends on the resistance of the substance that controls light emission,
Empirically, it is selected from the range of 10 to 1000 nm.

As an electron transport layer material, it is important to efficiently transport electrons from the cathode between the electrodes to which an electric field is applied, and it is desirable to have a high electron injection efficiency and to efficiently transport the injected electrons. . For this purpose, it is required that the material has a high electron affinity, a high electron mobility, a high stability, and a small amount of impurities serving as traps during production and use. Oxin-based complexes such as tris (8-quinolinolato) aluminum, tris (benzquinolinolato) aluminum, oxadiazole derivatives, triazine derivatives, and perylene derivatives, which are light-emitting substances having an electron-transporting ability, satisfying such conditions. , Perinone derivatives, naphthalene, coumarin, oxadiazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, pyridine derivatives, and phenanthroline derivatives. The electron transport layer material can take any form of single, laminated, or mixed, and can take an optimal form in combination with a light emitting layer and a cathode.

In the present invention, one of the most suitable embodiments is an element in which an anode / a hole transport layer / a light emitting layer doped with diazaindacene / an electron transport layer / a cathode are laminated in this order, but this element is not necessarily required. It is not limited to the configuration.

The driving method of the light emitting device according to the present invention can be classified according to the driving electrode. That is, segment display, symbol display suitable for numeric display, analog bar graph display,
Fixed pattern display suitable for pattern display, character display, graphic display, matrix display suitable for video display, and the like can be given. In the matrix display, an anode and a cathode constitute a strip row electrode or the other strip column electrode, respectively, and an arbitrary pattern can be displayed by selectively applying a voltage to an arbitrary intersection. The driving method is applied to a case where a relatively large number of segment electrodes are used as in the case of static driving in which segment electrodes to be displayed are individually and simultaneously driven, a large number of digits are displayed, or a matrix electrode configuration. Multiplex drive (line-sequential drive), and active elements that add and integrate switch elements and capacitor elements as necessary for each pixel at the intersection of the scanning electrode and signal electrode matrix to improve display characteristics such as contrast and response Matrix driving is exemplified. A particularly preferable driving method is not limited since an appropriate driving method differs depending on the application. For example, in the case of a small display using matrix driving, a line sequential driving method having a simple structure can be cited as a preferable example. Further, in order to emit light only in a predetermined region, the anode or the cathode can be processed into a predetermined shape, and can emit light in that shape, or can be used as a planar light emitting body. Further, any one of a direct current, an alternating current, and a pulse power source may be used for driving the element of the present invention.

The decrease in luminance usually tends to be sharper as the drive current density increases. Roughly speaking, the rate of decrease in luminance is almost the same in terms of the accumulated charge, which is the product of current density and time. That is, the element driven at 5 mA / cm ² has 1
Luminance is reduced five times faster than a device driven at mA / cm ² . 20m from a practical point of view
The luminance retention ratio after 1 hour of the device driven at A / cm ² was 70.
% Is preferable. The organic layered electroluminescent device of the present invention has a large initial decrease in luminance and gradually decreases in luminance. Therefore, it can be said that the organic EL device is practical if the retention rate in the first hour is 70% or more.

The present inventors surprisingly performed an aging treatment on an organic laminated thin-film light emitting device in an atmosphere in which oxygen is present, thereby maintaining a low current density, a high luminous efficiency in a short time, and a long continuous operation. It has been found that quenching and reduction in luminance due to short-circuiting of the element in light emission, particularly in a vacuum atmosphere, can be significantly suppressed. Thus, it has become possible to obtain an organic laminated thin-film light-emitting device capable of driving the device stably for a long time in any atmosphere.

The oxygen content of the aging treatment atmosphere is as follows:
If the volume percentage is 5% or more, the effect can be exhibited, but the higher the content, the more the effect can be obtained. The oxygen content of the atmosphere is preferably 20% or more by volume percentage. Usually, a convenient atmosphere is air, whose volume percentage of oxygen is 20.93%
It is. However, when air is used, humidity is a problem. That is, the aging process usually requires several hours or more. At this time, if the humidity in the air is high, a non-light-emitting portion called a dark spot appears during aging, causing deterioration of the element. As one standard, the relative humidity is desirably 70% or less, but the lower the better, the better. In order to lower the humidity of the gas to be subjected to the aging treatment, those which are usually used as a dehydrating agent can be used. Specifically, silica gel, zeolite, activated carbon, phosphorus pentoxide, calcium chloride, magnesium perchlorate and the like can be used, but from the viewpoint of ease of handling and hygroscopicity, a combination of silica gel and magnesium perchlorate is one preferable example. It can be mentioned as. The aging effect is determined by the product of the current density and the aging processing time. That is, if the current density is high, the processing time is short, and if the current density is low, the processing time is long.
However, the higher the current density is, the better it is not. If the current density is too high, dielectric breakdown occurs or the element is broken by Joule heat. One preferable specific current density in consideration of Joule heat is 0.1 A / cm ² or less.
When performing line-sequential driving, an instantaneous high luminance is required. In the maximum case, a current of 1 to 0.5 A / cm ² flows through the element.
A current of 02 A / cm ² flows through the device. Therefore, it is desirable that the current density of the aging process is 5 times or less of the maximum current density at the time of driving. However, the driving method other than this example is not limited to this. When a large number of elements for performing the static drive, the multiplex drive (line-sequential drive), and the active matrix drive are incorporated in one display device, all the elements may be aged at the same time or may be fixed. May be processed by the number of pieces. However, it is usually preferable to simultaneously age all elements in order to increase the efficiency of the aging process.

The aging process includes a DC constant current (voltage),
Constant current (voltage) pulse, alternating current, stepped current (voltage), gradually increasing current (voltage), gradually decreasing current (voltage), etc. are used.
The constant current process is the most preferable example in that the luminous efficiency after the process can be kept high and the process is simple. Although the processing time is not particularly limited, it is desirable to end the processing when the luminance decrease during aging becomes gentle. This is because, in many cases, the element is stabilized when the change in luminance becomes gentle, so that stoppage of light emission due to luminance retention or short circuit during long-term driving is suppressed. However, until such a state is usually attained, a long time treatment is required, so that the deterioration of the element cannot be ignored, and therefore the luminous efficiency of the element after the aging treatment is remarkably reduced. However, the constant current aging treatment in the presence of oxygen according to the present invention has a low current density,
Under mild conditions of short time, the characteristics can be stabilized without significantly lowering the luminous efficiency of the device, and a non-light emitting phenomenon and a luminance lowering phenomenon due to a short circuit can be suppressed.

[0021]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A glass substrate (15 Ω / □, manufactured by Asahi Glass Co., electron beam deposited) on which an ITO transparent conductive film was deposited to a thickness of 150 nm was cut into a predetermined size and etched. The obtained substrate was subjected to ultrasonic cleaning with acetone and semicocrine 56 for 15 minutes each, and then with ultrapure water. Subsequently, the substrate is subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes and then to hot methanol for 15 minutes.
Dipped for a minute and dried. After cleaning the ITO substrate before producing the element, the substrate was subjected to UV-ozone treatment for 1 hour, and then mounted in a vacuum evaporation machine, and the pressure was reduced to 8 × 10 ⁻⁴ Pa. Without heating the substrate, copper phthalocyanine was added to the substrate by a resistance heating method.
m, bis (m-methylphenylcarbazole) 100 n
m, 100 parts of tris (8-quinolinolato) aluminum
nm, 1 nm of lithium and 200 nm of aluminum were sequentially deposited to prepare a 5 × 5 mm element. Here, the film thickness referred to here is a crystal oscillation type film thickness monitor display value corrected by a value measured by a surface roughness meter. After leaving for a day,
This element was aged for 2 hours at a constant current of 40 mA / cm ² (8.83 V) in air at a relative humidity of 62%. The luminance at the start of aging was 1,522 cd / m ² , and the emission luminance at the end was 1,190 cd / m ² . When this device was allowed to emit light under a constant current condition of 4 mA / cm ² under vacuum, the initial luminance was 83 cd / m ² (6.26 V), and the luminous efficiency was 2.0.
8 cd / A was changed to 81 cd / m ² after 7 hours (6.
47V), 78 cd / m ² (7.58) after 307 hours.
V).

Comparative Example 1 An evaluation was performed in the same manner as in Example 1 except that aging was not performed. The initial luminance was 134 cd / m ² (6.
87 V), but no light emission was observed after 6.5 hours.

Comparative Example 2 The same evaluation as in Example 1 was carried out except that aging was performed in a vacuum, and the initial luminance was 98 cd / m ² (6.3).
6 V), but no light emission was observed after 6.5 hours.

Example 2 A glass substrate (15 Ω / □, manufactured by Asahi Glass Co., Ltd., electron beam deposited) on which an ITO transparent conductive film was deposited to a thickness of 150 nm was cut into a predetermined size and etched. The obtained substrate was subjected to ultrasonic cleaning with acetone and semicocrine 56 for 15 minutes each, and then with ultrapure water. Subsequently, the substrate is subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes and then to hot methanol for 15 minutes.
Dipped for a minute and dried. After cleaning the ITO substrate before producing the element, the substrate was subjected to UV-ozone treatment for 1 hour, and then mounted in a vacuum evaporation machine, and the pressure was reduced to 8 × 10 ⁻⁴ Pa. Without heating the substrate, copper phthalocyanine was added to the substrate by a resistance heating method.
m, bis (m-methylphenylcarbazole) 100 n
m, 100 parts of tris (8-quinolinolato) aluminum
nm, 1 nm of lithium and 200 nm of aluminum were sequentially deposited to prepare a 5 × 5 mm element. Here, the film thickness referred to here is a crystal oscillation type film thickness monitor display value corrected by a value measured by a surface roughness meter. The device was aged at a constant current of 80 mA / cm ² for 2 hours in air having a relative humidity of 62%.
90 cd / m ² and the emission luminance at the end was 1681 cd / m ²
m ² . When this device was made to emit light under a constant current condition of 20 mA / cm ² under vacuum, the initial luminance was 468 cd / m ^2.
(8.67V), the at a luminous efficiency 2.34cd / A was 362cd / m ² after 1 hour (8.62V), 181cd / m ² after 203 hours (11.12V).

Example 3 When aging was performed in the same manner as in Example 2 except that the current density was changed to 60 mA / cm ² , the luminance at the start of aging was 2080 cd / m ² and the emission luminance at the end was 1415 cd / m 2. ^{Was 2} . This element is 20m under vacuum
When the light was emitted under the constant current condition of A / cm ² , the initial luminance was 4
29 cd / m ² (8.69 V), luminous efficiency 2.15 cd /
A was 426 cd / m ² (8.61) after one hour.
V), 173 cd / m ² (11.22) after 203 hours
V).

Example 4 In Example 2, the current density was 44.5 mA / cm ² on average.
When the aging was performed in the same manner except that the pulse (Duty 1/21, 936 mA / cm ² ) was obtained, the luminance at the start of aging was 920 cd / m ² and the emission luminance at the end was 855 cd / m ² . This element is 20m under vacuum
When the light was emitted under the constant current condition of A / cm ² , the initial luminance was 4
35 cd / m ² (8.81 V), luminous efficiency 2.18 cd /
A was 432 cd / m ² (8.62) after one hour.
V), 194 cd / m ² (10.87) after 203 hours
V).

Example 5 The same procedure as in Example 2 was carried out except that the aging time was changed to 4 hours.
6 cd / m ² and the emission luminance at the end is 954 cd / m ²
Met. When this device was made to emit light under a constant current condition of 20 mA / cm ² under vacuum, the initial luminance was 467 cd / m 2.
² (7.37 V) and luminous efficiency of 2.34 cd / A after 1 hour, 447 cd / m ² (7.28 V), 251
After an hour, it was 187 cd / m ² (7.94 V).

Example 6 Example 2 was repeated except that the aging time was changed to 6 hours.
6 cd / m ² and the emission luminance at the end is 978 cd / m ²
Met. When this device was made to emit light under a constant current condition of 20 mA / cm ² under vacuum, the initial luminance was 459 cd / m 2.
² (7.32 V) and luminous efficiency of 2.30 cd / A after 1 hour, 442 cd / m ² (7.24 V), 251
After time, it was 190 cd / m ² (7.91 V).

Example 7 The procedure of Example 2 was repeated, except that aging was performed in dry air (dried with silica gel and magnesium perchlorate). The luminance at the start of aging was 1,422 cd /
m ² , the emission luminance at the end was 1143 cd / m ² . When this device was made to emit light under a constant current condition of 20 mA / cm ² under vacuum, the initial luminance was 573 cd / m ² (9.14).
V), the luminous efficiency of 2.87 cd / A was 547 cd / m ² (9.43 V) after 9 hours, and 27 after 234 hours.
7 cd / m ² (10.24 V), 10 after 1218 hours
It was 5 cd / m ² (12.97 V).

Example 8 When a device was prepared and aged in the same manner as in Example 7, the luminance at the start of aging was 1435 cd / m ² .
The emission luminance at the end was 1097 cd / m ² . When this device was made to emit light under a constant current condition of 10 mA / cm ² under vacuum, the initial luminance was 275 cd / m ² (8.40 V) and the luminous efficiency was 2.75 cd / A.
/ M ² (8.69 V), 174 cd / m after 234 hours
² (9.20 V), 92 cd / m after 1218 hours
² (10.97 V).

Comparative Example 3 In Example 7, when aging was performed in the air having a relative humidity of 92%, a non-light-emitting portion (dark spot) was formed on the light-emitting surface at the end of the aging so as to be visually confirmed.

Example 9 In Example 1, when drying was performed in an atmosphere of dry oxygen (drying with silica gel and magnesium perchlorate) instead of air, the luminance at the start of aging was 1515 cd / m ² .
The emission luminance at the end was 1187 cd / m ² . When this device was made to emit light under vacuum at a constant current of 4 mA / cm ² , the initial luminance was 92 cd / m ² (6.64 V) and the luminous efficiency was 2.3 cd / A. ^Two
(6.77 V), 81 cd / m ² after 212 hours (6.
94V).

Example 10 A glass substrate on which an ITO transparent conductive film was deposited to a thickness of 150 nm (a product of Asahi Glass Co., Ltd., 15 Ω / □, electron beam deposited) was cut into a predetermined size and etched. The obtained substrate was subjected to ultrasonic cleaning with acetone and semicocrine 56 for 15 minutes each, and then with ultrapure water. Subsequently, the substrate is subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes and then to hot methanol for 15 minutes.
Dipped for a minute and dried. After cleaning the ITO substrate before producing the element, the substrate was subjected to UV-ozone treatment for 1 hour, and then mounted in a vacuum evaporation machine, and the pressure was reduced to 8 × 10 ⁻⁴ Pa. Without heating the substrate, copper phthalocyanine was added to the substrate by a resistance heating method.
m, 100 nm of N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4′-diamine, 100 nm of tris (8-quinolinolato) aluminum, and lithium of 1 nm and aluminum were sequentially vapor-deposited to 200 nm to produce a 5 × 5 mm element. Here, the film thickness referred to here is a crystal oscillation type film thickness monitor display value corrected by a value measured by a surface roughness meter.
This element was aged for 2 hours at a constant current of 40 mA / cm ^{2 in} air at a relative humidity of 62%. The luminance at the start of aging is 1269 cd / m ² and the emission luminance at the end is 98.
It was 8 cd / m ² . This device was vacuumed at 4 mA / cm ²
When the light was emitted under the constant current condition, the initial luminance was 86 cd /
m ² (6.57 V) and luminous efficiency of 2.15 cd / A were found to be 84 cd / m ² (7.21 V) and 29 after 49 hours.
72cd / m ² after 1 hour (8.7V), was 44cd / m ² (13.03V) after 881 hours.

[0035]

The light emitting device to which the present invention is applied can maintain stable light emission luminance and driving voltage for a long period of time, and can realize a practical and reliable display. is there.

Claims (13)

[Claims] 1. A light-emitting element in which a layer containing a substance which emits light is present between an anode and a cathode, and an element which emits light by electric energy is subjected to aging treatment in an atmosphere containing oxygen. 2. The light emitting device according to claim 1, wherein the luminous efficiency after the aging treatment is 2 cd / A or more. 3. The light emitting device according to claim 1, wherein the luminance retention after driving for one hour is 70% or more. 4. The light emitting device according to claim 1, wherein the atmosphere has an oxygen concentration of 20% or more by volume percentage. 5. The light emitting device according to claim 1, wherein the atmosphere has a relative humidity of 70% or less. 6. The method according to claim 1, wherein the aging process is performed at a current density not more than 5 times the maximum current density during driving.
5. The light-emitting element according to any one of 5. 7. The light emitting device according to claim 1, wherein aging is performed at a current density of 0.1 A / cm ² or less. 8. The light emitting device according to claim 1, wherein aging is performed at a constant current density. 9. The light-emitting substance according to claim 1, wherein the light-emitting substance has a laminated structure of at least a hole transport layer and a light-emitting layer.
9. The light-emitting device according to any one of items 1 to 8. 10. An anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode, which are sequentially laminated.
The light-emitting element according to any one of the above. 11. The light emitting device according to claim 9, wherein the hole transport layer has a biscarbazolyl skeleton represented by the following general formula. Embedded image (R is ethyl, phenyl, methylphenyl, dimethylphenyl, methoxyphenyl, diphenylaminophenyl, hydroxyphenyl, naphthyl, methylnaphthyl,
Represents phenanthrolinyl, anthracenyl or pyrenyl, wherein R1 to R7 may be the same or different,
Each represents hydrogen, methyl, ethyl, propyl, butyl, fluorine, chlorine, bromine, iodine, methoxy, dialkylamino, formyl group) 12. An anode and a cathode each constitute a strip row electrode or the other strip column electrode, and have a matrix electrode capable of displaying an arbitrary pattern by selectively applying a voltage to an arbitrary intersection. A light-emitting device according to claim 1. 13. The light emitting device according to claim 1, wherein a switching device is provided for each pixel at a matrix intersection of the scanning electrode and the signal electrode.