JP2000036382A - Light emitting element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability while restricting the moisture in the gas and preventing the deterioration of a characteristic due to the moisture by sealing a light emitting element, and sealing the gas having a dew point at a specified temperature or less between the light emitting element and the sealing material. SOLUTION: The predetermined positive electrode 2, an organic layer 2 formed of the hole transporting material, the light emitting material and the electron transmitting material or the like, and a negative electrode 4 are laminated on a board 1 so as to form an element for emitting the light with the electric energy, and it is sealed by the predetermined sealing material 6 for preventing infiltration of moisture. At this stage, in order to avoid generation of damage to the light emitting element due to a contact with the sealing material 6, a clearance is provided between the sealing material 6, and the work and sealing are performed in the atmosphere of the gas having a dew point at 0 deg.C or less, desirably, at -70 deg.C or less such as argon and helium and the clearance is filled with this gas. With this structure, adsorption of moisture can be prevented without eliminating the moisture through a complicated drying process, and deterioration of the characteristic due to the adsorption of moisture can be restricted after manufacturing the light emitting element.

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 relates to a display element, a flat panel display, a backlight, lighting, an interior, a sign, a sign, an electrophotographic device, an optical signal generator, and the like. The present invention relates to a light emitting element that can be used in the field of (1).

[0002]

2. Description of the Related Art In recent years, active research has been conducted on organic thin-film light emitting devices that emit light when electrons injected from a negative electrode and holes injected from a positive electrode recombine in an organic phosphor sandwiched between both electrodes. I have. This element is characterized by thinness, high luminance light emission under a low driving voltage, and multicolor light emission by selecting a fluorescent material.

[0003] It is known from Kodak's C.I. W. Tang et al. (Appl. Phys. Lett. 51 (12)
21, p. 913, 1987). A typical configuration of the organic laminated thin-film light emitting device presented by Kodak Company is a hole transporting diamine compound and a light emitting layer on an ITO glass substrate,
8-Hydroxyquinoline aluminum, which also has an electron transporting property, and Mg: Ag as a negative electrode were sequentially provided, and green light emission of 1000 candela / m 2 was possible at a driving voltage of about 10 V. The current 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. I have.

By the way, low work function metals are often used as a cathode material of an organic thin film laminated element in order to obtain a high luminous efficiency by lowering a driving voltage. However, these materials have characteristics easily due to moisture in the atmosphere. to degrade. In addition, deterioration of characteristics due to moisture is unavoidable even in an organic material constituting an element. Specifically, a dot-shaped non-light-emitting portion called a dark spot (DS) is generated. As the deterioration progresses, the non-light-emitting portion spreads like a spot, and eventually stops emitting light. In order to prevent the influence of moisture on durability as described above, a resistance heating evaporation method generally used for device fabrication employs a hole transport layer, a light emitting layer, an electron transport layer if necessary, and a cathode on an ITO substrate. In manufacturing, a device has been devised so as not to be exposed to the outside air by vacuum deposition. However, in order to have practical durability, it is necessary to provide a seal for shutting off outside air even after production, and various attempts have been made so far.

Specifically, a method of forming a polyparaxylene film as a sealing layer by a gas phase polymerization method (Japanese Patent Laid-Open No.
7483) and a method of forming a silica protective film (JP-A-4-73886). However, there has been a problem that the sealing effect is not sufficient, and cracks occur when the film thickness is increased to increase the sealing effect.

A method of coating a resin has also been devised. However, even when a solvent contained affects the organic thin-film laminated structure, or when a thermosetting resin or a photo-setting resin is used, the effect of heat or the curing may be accompanied. The element is destroyed due to the shrinkage of the resin.

As a method having a higher sealing effect, an organic thin-film laminated element is sealed in a container, or a substrate on which the organic thin-film laminated element is formed and a sealing material such as a glass plate or a stainless steel plate are used. A method of sandwiching a thin-film laminated element, bonding the thin-film laminated element with an adhesive, and blocking the outside air (Japanese Patent Laid-Open No. 4-212284)
Publication). However, these are not sufficiently satisfactory, and further improvement in durability has been desired.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the prior art and to provide a light emitting device with improved durability and a method for manufacturing the same.

[0009]

According to the present invention, there is provided an element which emits light by electric energy, wherein a substance which controls light emission is present between a positive electrode and a negative electrode. And a gas having a dew point of 0 ° C. or less between the element and the sealing material.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A positive electrode according to the present invention is made of a conductive metal oxide such as tin oxide, indium oxide, indium tin oxide (ITO), or gold, silver, chromium, if it is transparent to extract light. Such metals, copper iodide, inorganic conductive substances such as copper sulfide, and conductive polymers such as polythiophene, polypyrrole, and polyaniline are not particularly limited. However, it is preferable to use ITO glass or Nesa glass. It is desirable to use. The resistance of the transparent electrode is not 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, 300Ω /
If it is an ITO glass substrate of □ or less, it functions as an element electrode, but it is now possible to supply a substrate of about 10 Ω / □, so it is particularly preferable to use a low-resistance substrate of 20 Ω / □ or less. desirable. The thickness of the ITO can be arbitrarily selected according to the resistance value.
Often used between nm. Further, as the glass substrate, soda lime glass, non-alkali glass or the like is used, and the thickness only needs to be sufficient to maintain the mechanical strength. As for the material of the glass, alkali-free glass is preferred because it is better that ions eluted from the glass are small.
Soda lime glass with a barrier coat such as ₂ is also commercially available and can be used. Even when a substrate other than glass is used, any substrate may be used as long as it is transparent and has a high sealing effect. The method of forming the ITO film is not particularly limited, such as an electron beam evaporation method, a sputtering method, and a chemical reaction method. It is desirable that the ITO glass substrate be well cleaned and well dried.

In the present invention, the structure of the substance that controls light emission is as follows:
1) a hole transporting material / a light emitting material, 2) a hole transporting material / a light emitting material / an electron transporting material, 3) a light emitting material / an electron transporting material, and 4) a form in which a combination of the above substances is mixed.
Any of these may be used. That is, in addition to the multi-layer structure of 1) to 3), a layer containing a luminescent material alone or a luminescent material and a hole transporting material, or a layer containing a luminescent material, a hole transporting material and an electron transporting material as in 4) is further provided. It may just be provided. The light emitting material may be either a host material alone or a combination of a host material and a dopant material.
In addition, the dopant material may be included in the entire host material, partially, or may be included. The dopant material may be stacked, dispersed, or the like.

The hole transporting material in the present invention is required to efficiently transport holes from the positive electrode between the electrodes to which an electric field is applied, and has a high hole injection efficiency. Good transport is desirable. For that purpose, it is required that the ionization potential be small, the hole mobility be large, the stability be further improved, and impurities serving as traps be hardly generated during production and use. The substance satisfying such conditions is not particularly limited, but is a biscarbazolyl derivative,
Known triphenylamine derivatives such as TPD, m-MTDATA, α-NPD, pyrazoline derivatives, stilbene compounds, hydrazone compounds, heterocyclic compounds represented by oxadiazole derivatives and phthalocyanine derivatives, polyvinyl carbazole, polysilane and the like Hole transport materials can be used. These hole transport materials may be used alone or may be laminated or mixed with different hole transport materials.

Among the luminescent materials in the present invention, the host material is not particularly limited, but tris (8-quinolinolato) aluminum, a condensed ring derivative such as anthracene or pyrene, which has been known as a luminescent material before, may be used. Metal chelated oxinoid compounds, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole For derivatives, thiadiazolopyridine derivatives, and polymer systems, polyphenylenevinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives can be used.

The dopant material to be added to the host material is not particularly limited, but specific examples thereof include condensed ring derivatives such as perylene and rubrene, quinacridone derivatives, phenoxazone 660, DC
M1, perinone, coumarin derivatives and the like can be used as they are. These dopant materials may be used alone or in combination with different dopant materials.

As the electron transporting material in the present invention,
It is necessary to efficiently transport electrons from the negative electrode between the electrodes to which an electric field is applied, and it is desirable that the electron injection efficiency is high and the injected electrons are transported efficiently. 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. Materials satisfying such conditions include quinolinol derivative metal complexes represented by 8-hydroxyquinoline aluminum, tropolone metal complexes, flavonol metal complexes, perylene derivatives, perinone derivatives, naphthalene,
There are coumarin derivatives, oxadiazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, and the like, but are not particularly limited. Although these electron transport materials are used alone,
They may be laminated or mixed with different electron transport materials.

The above materials used for the hole transporting layer, the light emitting layer and the electron transporting layer can be used alone to form each layer. Examples of the polymer binder include polyvinyl chloride, polycarbonate, polystyrene, and the like. Poly (N-vinyl carbazo-
), Polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose
Curing of solvent-soluble resins such as water, vinyl acetate, ABS resin and polyurethane resin, phenol resin, xylene resin, petroleum resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicone resin, etc. It is also possible to use it by dispersing it in a conductive resin or the like.

The method for forming the substance which controls light emission in the present invention is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating. Beam evaporation is preferred in terms of properties. The thickness of the layer depends on the resistance of the substance that controls light emission and cannot be limited, but is selected from the range of 10 to 1000 nm.

The negative electrode of the present invention efficiently converts electrons,
The substance is not particularly limited as long as it can be injected into the substance that controls light emission. Generally, platinum, gold, silver, copper, iron, tin, aluminum, indium, lithium, sodium, potassium,
Examples include calcium and magnesium. In order to increase the electron injection efficiency and improve the device characteristics, a low work function metal such as lithium, sodium, potassium, calcium, and magnesium is effective. However, since these low work function metals are generally unstable, it is desirable to form an alloy or a laminated structure with the stable metal. Alternatively, a method of doping a substance which controls light emission is also effective.
For the method of manufacturing the electrodes, resistance heating evaporation, electron beam evaporation, sputtering, ion plating,
There is no particular limitation as long as conduction can be achieved by a coating method or the like, but a resistance heating evaporation method or an electron beam evaporation method is preferable in terms of characteristics.

Before the sealing in the present invention, a protective layer may be provided to protect the organic thin film laminated element. As a material of the protective layer, platinum, gold, silver, copper, iron, tin, lead, aluminum, titanium, nickel, metals such as indium, or an alloy using these metals, and silica,
Metal oxides such as titania, alumina, magnesium oxide, yttrium oxide, germanium oxide, nickel oxide, barium oxide, calcium oxide, iron oxide, magnesium fluoride, lithium fluoride, aluminum fluoride,
Examples thereof include metal fluorides such as calcium fluoride and resins such as fluororesins, but are not particularly limited. For the method of forming the protective layer, a resistance heating evaporation method,
Although not particularly limited, such as an electron beam evaporation method, a sputtering method, an ion plating method, an MBE method, and a CVD method, a resistance heating evaporation method or an electron beam evaporation method is preferable in terms of characteristics.

The sealing material in the present invention is not particularly limited as long as it prevents moisture from entering the organic thin film laminated device. Specifically, soda-lime glass, borosilicate glass, silicate glass, silica glass, non-fluorescent glass, quartz, inorganic substances such as ceramics, metals such as stainless steel and aluminum alloy, fluorine resin, acrylic resin, Resins such as polycarbonate resin, epoxy resin, polyester resin, polyamide resin, polystyrene resin, polyethylene resin, polypropylene resin, polyolefin resin, and silicone resin are exemplified. The sealing method is not particularly limited, and the organic thin-film laminated element (the positive electrode 2, the organic layer 3,
A method of inserting the negative electrode 4) and the gas 5 and a method of sandwiching the organic thin film laminated element and the gas 5 between the substrate 1 on which the organic thin film laminated element is formed as shown in FIG. . In order to make use of the thinness characteristic of the organic thin film laminated element, it is desirable to make the sealing material thinner,
If it is too thin, it may be broken by an external impact, so it is desirable to design the thickness according to the material of the sealing material.

The adhesive used for sealing is not particularly limited as long as it has a sealing effect. In particular,
An epoxy resin-based adhesive, an acrylate resin-based adhesive, or the like can be used. In addition, a photocurable resin adhesive, a thermosetting resin adhesive, an anaerobic resin adhesive, or the like can be used.

Although there is no particular limitation on the form of sealing in the present invention, if the sealing material is directly in contact with the light emitting element, the light emitting element may be destroyed. It is desirable that there be a slight gap. Evacuating the gap to create a vacuum or refilling with a dry liquid is complicated, and actually involves the gas in the atmosphere of the sealing step. If the gas is wet, the sealing effect is significantly reduced, so that a gas having a dew point of 0 ° C. or less is included between the light emitting element and the sealing material in the present invention. In order to further improve the durability, a gas having a dew point of −70 ° C. or less is preferable, and a gas of −100 ° C. or less is more preferable. Even if the enclosed gas is wet, it can be dried by enclosing the adsorbent. However, since the deterioration of the element progresses quickly, it is desirable that the gas in the atmosphere of the sealing step be dried in advance. When a vacuum deposition process is included in the manufacturing process of a light emitting element, if a wet gas is used at the time of leakage, moisture is instantaneously adsorbed. It can be evacuated again to remove some water, but recovery from deterioration cannot be expected. Therefore, when leaking, the dew point is 0
It becomes important to use a gas at a temperature of not more than ° C. In order to further improve the durability, a gas having a dew point of −70 ° C. or less is preferable, and a gas of −100 ° C. or less is more preferable. Although it is desirable that the device is manufactured in a vacuum process, it is also effective when a leak is required during device manufacture.

The gas taken in at the time of leakage and at the time of sealing includes, for example, argon, neon, helium, nitrogen, oxygen, carbon dioxide and the like. May also be mixed like air. If oxygen is contained in the gas like air, the temporary short-circuit (short) due to dust and protrusions / defects of ITO is oxidized and becomes an insulator, preventing the occurrence of permanent short-circuit. Can be done. Moreover, it is preferable to use air because it can be used easily. The gas taken in at the time of leakage and at the time of sealing may be the same or different.

An adsorbent may be included between the light emitting element and the sealing material in the present invention. The adsorbent is not particularly limited as long as it adsorbs moisture that enters from outside after sealing. Specifically, activated alumina, diatomaceous earth, activated carbon, phosphorus pentoxide, magnesium perchlorate, potassium hydroxide, calcium nitrate, calcium bromide, calcium oxide, barium oxide, barium carbonate, zinc chloride, zinc bromide, sulfuric anhydride Examples include inorganic compounds such as copper, metals such as lithium, beryllium, potassium, sodium, magnesium, rubidium, strontium, and calcium and alloys thereof, and acrylic and methacrylic water-absorbing polymers.

The electric energy in the present invention mainly refers to a direct current, but it is also possible to use a pulse current or an alternating current. The current value and voltage value are not particularly limited,
In consideration of the power consumption and life of the device, it is necessary to obtain the maximum brightness with the lowest possible energy.

It is preferable that the light emitting device of the present invention constitutes a display for displaying by a matrix or segment system or a combination of both.

The matrix in the present invention refers to a matrix in which pixels for display are arranged in a lattice, and displays a character or an image by a set of pixels. The shape and size of the pixel depend on the application. For example, for the display of images and characters on personal computers, monitors, televisions, and the like, generally square pixels with a side of 300 μm or less are used, and in the case of a large display such as a display panel, pixels with a side on the order of mm are used. Become. In the case of monochrome display, pixels of the same color may be arranged, but in the case of color display, red, green and blue pixels are displayed side by side. In this case, there are typically a delta type and a stripe type. Note that the light-emitting element of the present invention can emit red, green, and blue light, so that multi-color or full-color display can be performed by using the display method. The matrix may be driven by either a line-sequential driving method or an active matrix. The line-sequential driving has the advantage of a simpler structure, but the active matrix is sometimes superior in consideration of the operating characteristics. Therefore, it is necessary to use this depending on the application.

In the segment type according to the present invention, a pattern is formed so as to display predetermined information, and a predetermined area emits light. For example, there are a time display and a temperature display on a digital clock or a thermometer, an operation state display of an audio device, an electromagnetic cooker, or the like, and a panel display of an automobile. The matrix display and the segment display may coexist in the same panel.

The light emitting device of the present invention is also preferably used as a backlight. The backlight in the present invention,
It is mainly used for improving the visibility of a display device that does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel, a sign, and the like. In particular, as for the backlight for liquid crystal display devices, particularly for personal computer applications where thinning is an issue, the present invention is considered to be difficult because the conventional type is made of a fluorescent lamp or a light guide plate, and it is difficult to make it thin. Is characterized by its thinness and light weight.

[0030]

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 / □, electron beam vapor-deposited product, manufactured by Asahi Glass Co., Ltd.) on which a 150 nm ITO transparent conductive film was deposited was used for 30
The wafer was cut into a size of 40 mm 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 was subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes, immersed in hot methanol for 15 minutes, and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the element, placed in a vacuum evaporation apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. First, 4,4′-bis (N- (m-tolyl) -N-phenylamino) biphenyl was deposited as a hole transporting material to a thickness of 100 nm by a resistance heating method. Next, 100 nm of trisquinolinolate aluminum (III) was deposited as a host material. Next, lithium was added to 0.
5 nm, 200 nm of aluminum is deposited to form a cathode,
An element having a size of 5 × 5 mm was manufactured as part of the vacuum. The film thickness referred to here is a value displayed on a crystal oscillation type film thickness monitor corrected by a value measured by a surface roughness meter. Leakage was caused using argon having a dew point of 0 ° C., moved to a dry box in an argon atmosphere having a dew point of 0 ° C., and a stainless sealing material having a thickness of 0.4 mm was bonded using an epoxy resin. The gap was 2 mm. The light emitting device was taken out into the atmosphere and allowed to emit light after being allowed to stand. When left for one week, a non-light-emitting portion was slightly observed with a microscope, and when left for one month, a non-light-emitting portion was slightly observed with the naked eye.

Comparative Example 1 Leakage occurred in an argon atmosphere having a dew point of 0 ° C.
The device manufactured in exactly the same manner as in Example 1 except that sealing was performed at a temperature of 80 ° C. and a humidity of 80%) was taken out into the air and allowed to emit light after being allowed to stand. When left for one day, the non-light-emitting portion was observed with the naked eye, and when left for one week, the non-light-emitting portion became larger than the light-emitting portion.

Comparative Example 2 Leakage occurred in the air (25 ° C., humidity 80%) and the dew point was 0 ° C.
A device manufactured in the same manner as in Example 1 except that the sealing was performed in an argon atmosphere was taken out into the air and allowed to stand, and then emitted light. When left for one day, the non-light-emitting portion was observed with the naked eye, and when left for one week, the non-light-emitting portion became larger than the light-emitting portion.

Comparative Example 3 A device produced in the same manner as in Example 1 except that leakage and sealing were performed in the air (25 ° C., humidity 80%) was taken out into the air and left to emit light. After one day, the non-light-emitting portion was observed with the naked eye, and after three days, the non-light-emitting portion became larger than the light-emitting portion.

Example 2 A device produced in exactly the same manner as in Example 1 except that leakage and sealing were carried out in argon at a dew point of -70 ° C. was taken out to the atmosphere, allowed to emit light, and then emitted. After leaving for one month, a non-light-emitting portion was slightly observed with a microscope.

Example 3 A device manufactured in exactly the same manner as in Example 1 except that leakage and sealing were performed in argon having a dew point of -100 ° C. was taken out into the air and allowed to emit light after leaving. The non-light-emitting portion was not observed under a microscope even after being left for one month.

Example 4 A device manufactured in exactly the same manner as in Example 1 except that leakage and sealing were performed in nitrogen having a dew point of -100 ° C. was taken out into the air and left to emit light. The non-light-emitting portion was not observed under a microscope even after being left for one month.

Example 5 A device manufactured in exactly the same manner as in Example 1 except that leakage and sealing were carried out in air having a dew point of -100 ° C. was taken out to the atmosphere, allowed to emit light, and then emitted. The non-light-emitting portion was not observed under a microscope even after being left for one month. Examples 1-4
In comparison with this, the ratio of occurrence of short circuit in this device was reduced.

[0039]

According to the present invention, it is possible to provide a light emitting device having improved durability and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a method for putting an organic thin-film laminated element in a container with a sealing material.

FIG. 2 is a schematic cross-sectional view of a method of sandwiching an organic thin-film laminated element between a substrate on which the organic thin-film laminated element is formed and a thin plate-like sealing material.

[Explanation of symbols]

 1, substrate 2, positive electrode 3, organic layer 4, negative electrode 5, gas 6, sealing material 7, adhesive 8, conducting wire 9, power supply

Claims (8)

[Claims] An element which emits light by electric energy between a positive electrode and a negative electrode and which emits light by electric energy, wherein the element is sealed with a sealing material. A light-emitting element comprising a gas having a dew point of 0 ° C. or lower between the two. 2. An element which emits light by electric energy, in which a substance responsible for light emission exists between a positive electrode and a negative electrode, wherein a process of manufacturing the element includes a vacuum deposition step, and a dew point of 0 ° C. or less at the time of leakage. A method for manufacturing a light-emitting element, wherein a gas is used. 3. The light emitting device according to claim 1, wherein the dew point is -70 ° C. or less. 4. The light emitting device according to claim 1, wherein the dew point is -100 ° C. or lower, and a method for manufacturing the same. 5. The light emitting device according to claim 1, wherein the gas between the device and the sealing material and / or the gas used at the time of the leak contains oxygen. 6. The light emitting device according to claim 1, wherein the gas containing oxygen is air. 7. The light emitting device according to claim 1, wherein said light emitting device constitutes a display for displaying in a matrix and / or segment system. 8. The light emitting device according to claim 1, wherein said light emitting device is a backlight.