JP2001210466A - Organic el element and manufacturing method of the same and driving method of organic el element and driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an organic EL element restraining the generation of short-circuit, and an element provided with the process of restoring a short-circuited part in a prescribed atmosphere, and to provide a driving method and a driving circuit of an element which is capable of emitting light without restoring the short-circuited part. SOLUTION: Combustion supporting gas generating reagent, especially oxygen generating reagent, oxygen gas generating compound generating oxygen by absorbing moisture of ammonium persulfate, are sealed in an sealing space 53 formed by a substrate 1 and an sealing member. By the above treatment, short-circuit is restrained and inside of the element is efficiently dehumidified. Further, short-circuited part is restored in advance by sealing under the atmosphere of inert gas such as nitrogen gas, after restoring the short-circuited part by passing the current with higher voltage than that of constant current drive, accordingly, by generating heat and oxidizing the short circuited part, and the organic EL element, preventing the generation and growth of dark spot, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL device in which occurrence of a short circuit is suppressed, and a method for manufacturing an organic EL device including a step of sealing after repairing a short-circuited portion. In addition, a driving method of an organic EL element capable of emitting light even when a minute short circuit occurs and a specific constant current circuit, and a driving circuit of the organic EL element capable of sustaining light emission even when a minute short circuit occurs About.

[0002]

2. Description of the Related Art In an organic EL element driven by a constant current, a specific pixel does not emit light due to a short circuit between an anode and a cathode, or the entire element does not emit light due to almost all of the current flowing through a short-circuited portion. (For example,
JP-A-11-40346). In addition, when exposed to a high-temperature atmosphere due to moisture, oxygen, or the like, or when used for a long period of time, dark spots may be generated and grow. Further, there is a need for a simple device, operation, and the like for suppressing the occurrence of such pixel defects and dark spots, or for repairing a short-circuit portion. Furthermore,
It is desired to provide a driving method or the like that can emit light without repairing a short-circuited portion.

[0003]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide an organic EL device capable of suppressing occurrence of a short circuit, and to generate heat and oxidize a short-circuit portion. It is an object of the present invention to provide a method for manufacturing an organic EL element, which comprises a step of sealing after repairing by an organic EL device. Further, it is an object of the present invention to provide a method for driving an organic EL element which can emit light without repair even if there is a minute short-circuit, and a drive circuit for an organic EL element having a specific structure capable of being driven as such. With the goal.

[0004]

According to a first aspect of the present invention, there is provided an organic EL device comprising: a substrate; an anode, an organic EL thin film, and a cathode laminated on the surface of the substrate in this order;
And an organic EL element including a sealing member for sealing the organic EL laminate, wherein a combustion supporting gas generating agent is sealed in a space formed by the substrate and the sealing member. . This sealing member is formed of a sealing material made of glass, metal, or the like, and a bonding layer that bonds the sealing material to the periphery of the substrate.

As the above-mentioned "combustible gas generating agent", a compound capable of releasing a combustible gas capable of suppressing the occurrence of a short circuit when the device is used can be used. The supporting gas is usually an oxygen gas generated by the decomposition of the supporting gas generating agent, and other gases or the like that impair the characteristics of the organic EL thin film and the electrodes forming the organic EL element with the decomposition. Preference is given to nonflammable gas generating agents. In addition, as this combustible gas generating agent, without particularly requiring heating,
In general, it is more preferable to easily emit a supporting gas such as oxygen gas at an environmental temperature at which the organic EL element is used. Further, from the viewpoint of ease of handling when enclosing and fixing in a sealed space, the combustible gas generating agent is preferably a solid such as a powder or a granule.

Examples of such a supporting gas generating agent include peroxides such as sodium peroxide, potassium peroxide and zinc peroxide, and peroxodicarbonates such as sodium peroxodicarbonate and potassium peroxodicarbonate. Ammonium peroxodisulfate, sodium peroxodisulfate,
And peroxodisulfates such as potassium peroxodisulfate and barium peroxodisulfate. Of these, many of the peroxyacid salts generate oxygen gas by absorbing moisture, and when used as a combustible gas generating agent, absorb moisture contained in the sealed space of the organic EL element, and This is particularly preferable because no decomposition products or the like which impair the characteristics of the above are produced.

It is known that moisture contributes to the generation of so-called dark spots and their growth over time.
The amount of moisture contained in the sealed space of the organic EL element is reduced by the combustible gas generating agent that generates oxygen gas by absorbing moisture. Therefore, in some cases, it is possible to reduce the amount of the hygroscopic agent, such as barium oxide powder and calcium oxide powder, which is usually sealed in the sealed space. In addition, ammonium peroxodisulfate, etc. is in a powder form and is easy to handle when sealed in a sealed space. You can also.

[0008] Oxygen gas can also contribute to the generation of dark spots and their growth with high concentration or over long periods of time. Therefore, it is preferable that the amount of oxygen gas released from the combustible gas generating agent is a minimum amount necessary to suppress occurrence of a short circuit. The amount of oxygen gas can be easily adjusted by adjusting the amount of the combustible gas generating agent to an appropriate amount according to the volume of the sealed space. The oxygen gas amount is 0.1% when the sealed space is 100% by volume.
-5% by volume, particularly preferably 0.5-2% by volume. When the amount of oxygen gas is less than 0.1% by volume, the effect of suppressing the occurrence of a short circuit cannot be sufficiently obtained. When the amount exceeds 5% by volume, dark spots are generated with time and may grow. Not preferred.

The method for manufacturing an organic EL device according to the second invention comprises the following steps:
In an atmosphere containing oxygen gas of at least volume%, a current is applied to the organic EL thin film formed on the substrate to generate heat at the short-circuited portion and oxidize the organic EL thin film.
The thin film is sealed.

In this manufacturing method, an anode, an anode,
After forming an organic EL thin film having at least a light emitting layer and a cathode in this order, and repairing a short-circuit portion with an oxygen gas, under an inert gas atmosphere such as a nitrogen gas or an argon gas,
A sealing material is attached to the periphery of the substrate via the bonding layer, and the organic EL
The thin film and both electrodes are sealed. In this way, after repairing the short-circuit portion in advance, sealing in an inert gas atmosphere can prevent oxygen gas from being mixed into the sealed space, and after repairing the short-circuit portion, In addition, the organic EL thin film and the like can be shielded from oxygen gas. Thereby,
The generation and growth of dark spots can be more reliably prevented.

The energization of the organic EL thin film can be performed in a closed space containing "1% by volume or more" of oxygen gas, and the apparatus to be used is not particularly limited. The upper limit of the oxygen gas concentration is not specified, but if the concentration is too high, organic E
Since the characteristics of the L element may be impaired, the content is preferably 20% by volume or less, particularly preferably 10% by volume or less. The oxygen gas concentration is preferably 1 to 5% by volume, more preferably 1 to 2% by volume.
It is preferable that the oxygen gas concentration is within this range, so that the short-circuit site can be efficiently and sufficiently repaired.
If the oxygen gas concentration is less than 1% by volume, it is not possible to sufficiently repair the short-circuit site, or it takes a long time to repair,
Not practical.

The voltage and current at the time of energization are not particularly limited as long as they can be oxidized to the extent that heat is generated in the short-circuit portion and conduction is lost. It is preferable that the voltage and the current be higher than the voltage and the current when the organic EL element is normally driven. By applying a high voltage and a large current and energizing for a short time, the element can be efficiently repaired without deteriorating the characteristics of the element. Further, by setting higher voltage and current, it is possible to short-circuit a defective portion that has not yet been short-circuited, generate heat, oxidize and repair the defective portion, and prevent a short-circuit from occurring during use.

A driving method of an organic EL element according to a third invention is characterized in that a predetermined constant current driving is performed after a high voltage is applied at the start of driving to cause the organic EL element to emit light.

According to this driving method, it is possible to emit light without repairing a minute short-circuited portion. If there is a short-circuited portion, current flows intensively in that portion, and the organic EL device driven at a constant current may not emit light as a whole. Therefore, at the start of driving, a high voltage exceeding the voltage applied at the time of constant current driving is applied. In this way, a current exceeding the amount of current that can flow through the short-circuit portion flows through another portion of the element, and the element emits light. Then, since a predetermined current flows and a resistance value of a portion where light emission starts is reduced, the light emission is continued as it is after a certain period of time, even if switching to normal constant current driving is performed.

According to a fourth aspect of the present invention, a driving circuit for an organic EL element is characterized in that a zener diode and a resistor are added to a constant current circuit of an organic EL element driven at a constant current.

In the device provided with this drive circuit, light can be emitted as it is without repairing a minute short-circuited portion, and the light can be sustained. In an organic EL element driven by a constant current, when a short circuit occurs, the voltage required to flow a constant current decreases, and the entire element may not emit light. Therefore, when the breakdown voltage is exceeded, a current suddenly flows, and a Zener diode that keeps the voltage almost constant regardless of the magnitude of the current and a resistor for controlling the amount of current are arranged in series with the element. And add it to the constant current circuit. In this way, when the resistance of the element is reduced due to the short circuit and the applied voltage is reduced, the current determined by the resistance is almost equal to the breakdown voltage of the Zener diode.
It flows through the added Zener diode and the resistor. As a result, the voltage applied to the element is maintained at a level required for light emission, and light emission is maintained as it is.

In this drive circuit, when a short circuit occurs, a current flowing through the Zener diode and the resistor is applied to the element in addition to the current generated by the constant current drive. It may be repaired. After the short-circuit portion is repaired in this way, the operation returns to the normal constant-current driving, and stable light emission is maintained.

The driving method according to the third invention requires an additional circuit for applying a high voltage at the start of driving, and the driving circuit according to the fourth invention adds a zener diode and a resistor to the constant current circuit. There is a need. Therefore, the driving method of the third invention and the driving circuit of the fourth invention are both more suitable for a segment type element having a small number of pixels than a dot matrix type element having a large number of pixels. In particular, the driving method of the third invention which requires a capacitor and a coil which are difficult to integrate is more suitable for a segment type element.

In the first to fourth inventions, the organic EL element includes a substrate, and an organic EL laminate formed by laminating an anode, an organic EL thin film, and a cathode on the surface of the substrate in this order. The organic EL thin film includes at least a light emitting layer and may have a hole transport layer and an electron transport layer.
Further, a hole injection layer may be provided between the anode and the hole transport layer, and an electron injection layer may be provided between the electron transport layer and the cathode.

As the substrate, in addition to glasses such as soda-lime glass, synthetic resins such as polyethylene terephthalate, polyether sulfone and polycarbonate, and transparent materials such as quartz can be used. Of these, a substrate made of glass is particularly frequently used.

The light emitting layer can be formed of a light emitting material such as an aluminum quinolium complex and a benzoquinolinol Be complex. Further, a doping agent such as a quinacridone derivative or a DCM derivative can be added to these light emitting materials. The hole transport layer can be formed of a triphenylamine derivative or the like, and the electron transport layer can be formed of an aluminum quinolium complex, a hydroxyflavone Be complex, or the like. The hole injection layer can be formed of a copper phthalocyanine complex or the like.
Fluoride or oxide of alkali metal such as LiF and Ba
It can be formed of a fluoride of an alkaline earth metal such as F ₂ or the like.

The anode can be formed of a simple metal such as gold or nickel, or a metal compound such as ITO, CuI, SnO ₂ or ZnO. Of these, ITO is particularly preferred from the viewpoints of productivity, stable conductivity, and the like. The cathode can be formed of aluminum, a Mg-Ag alloy, a Na-K alloy, or the like. Each layer constituting these organic EL laminates can be formed by a vacuum evaporation method, and can also be formed by other various methods such as a spin coating method, a casting method, a sputtering method, and an LB method.

The organic EL laminate can be sealed by joining a sealing material to the periphery of the substrate via a joining layer. As the sealing material, a metal such as stainless steel, aluminum or an alloy thereof, glass such as soda-lime glass and silicate glass, and a synthetic resin such as an acrylic resin and a styrene resin can be used. The bonding layer is formed of a cured body made of a thermosetting resin such as an epoxy resin or an acrylate resin, or a sealing resin such as a photocurable resin. Among these sealing resins, it is preferable to use a sealing resin that forms a cured body through which moisture and the like hardly permeate, in order to suppress a decrease in luminance and the like. Further, a photocurable resin which can reduce the thermal stress applied to the element and has a high curing rate is more preferable.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. Example 1 As shown in FIG. 1, a transparent substrate 1 made of glass, a transparent electrode 2 made of ITO, an organic EL thin film 3 having at least a light emitting layer, and a cathode 4 made of aluminum were formed on the surface of the transparent substrate 1. Organic E laminated and formed in order
L laminated body, a sealing material 52 made of stainless steel, and a bonding layer 5 for bonding the sealing material 52 to the periphery of the transparent substrate 1.
An organic EL element provided with the sealing member 5 made of No. 1 was produced. The light emitting area of this element is 7.2 × 3.6 cm ² , and the volume of the sealing space 53 is 4 cm ³ .

As shown in FIG. 1, a moisture permeable resin film 6 is formed around the periphery of the concave portion 54 on the inner surface of the sealing material 52 of this element.
Is affixed. The concave portion 54 is filled with a mixed powder 7 of 0.2 g of barium oxide powder and 0.8 mg of ammonium peroxodisulfate powder. When the device is used, the ammonium peroxodisulfate is used for bonding layer 5.
The oxygen gas is released by absorbing moisture penetrating into the sealed space 53 from 1 etc., and the total amount of oxygen gas generated from the enclosed 0.8 mg of ammonium peroxodisulfate is 4 × 10 ⁻² c.
become m ^3. Therefore, the concentration of oxygen gas contained in the sealed space 53 is about 1% by volume. Thereby, when using the element,
The occurrence of a short circuit is suppressed.

Example 2 After a process for repairing a short-circuited portion was previously performed by the apparatus shown in FIG. 2, sealing was performed to produce an organic EL device. The steps will be described below in the order of steps with reference to FIG. Under vacuum in the film forming chamber 8, I
A transparent electrode 2 made of TO, an organic EL thin film 3 having at least a light-emitting layer, and a cathode 4 made of aluminum were formed in this order (this is called an intermediate product). When the intermediate product is driven at a constant current and there is a pixel that does not emit light due to a short circuit, the intermediate product is transferred to the restoration processing chamber 9 in a vacuum state, and then a mixed gas of 1% by volume of oxygen gas and 99% by volume of nitrogen gas is introduced Then, the internal pressure was adjusted to 0.1 MPa.

The intermediate product is connected to the aging circuit 91, and a voltage at the time of constant current driving, a high voltage exceeding the current is applied, a large current is applied, and the short-circuit portion is heated and oxidized (the aluminum of the cathode at the short-circuit portion). Is oxidized and becomes an aluminum oxide and no longer conducts.) The intermediate product was transferred to the sealing chamber 10, and once the sealing chamber 10 was evacuated to remove oxygen gas, nitrogen gas was introduced to adjust the internal pressure to 0.1 MPa. An ultraviolet curable resin was applied to the periphery of the glass substrate 1 and a glass or metal sealing material 52 was adhered to the resin, and then the resin was cured and sealed to produce an organic EL device.

By manufacturing an element by such a process, a short-circuited portion can be repaired in advance, and the incorporation of oxygen gas into the sealed space can be prevented. And its growth can also be prevented. In FIG. 2, P is a vacuum pump for bringing each processing chamber into a vacuum state, and O ₂ and N
₂ is a supply source of oxygen gas and nitrogen gas, respectively, and these are connected to each processing chamber via a valve.

Embodiment 3 By discharging the electric charge stored in a capacitor or the like,
The organic EL element was driven by a drive circuit capable of applying a high voltage, for example, a constant current circuit including a circuit similar to a drive circuit of a fuel injection valve of a direct injection gasoline engine.
FIG. 3 schematically shows a temporal change of the voltage or the current in this case. As described above, even when a minute short circuit occurs due to a high voltage at the time of discharging, the element emits light and the voltage is high, so that the luminance is higher than that during normal constant current driving. After that, the voltage or the current decreased, and after a certain period of time, even if the mode was switched to the constant current drive from t ₀ , the light emission continued once because the resistance of the element that once emitted light had decreased. In this driving method,
By adjusting the capacity of a capacitor or the like and the time for switching to the constant current drive, it is possible to drive each element having a different light emitting area under optimum conditions.

Embodiment 4 As shown in FIG. 4, a Zener diode Z having a breakdown voltage of 10 V is provided in a constant current circuit for driving the organic EL element L.
And a resistor R. When this was driven by a power supply voltage of 20 V, the voltage applied to the organic EL element was 13 V, and the element emitted light normally. In this case, since the voltage applied to the Zener diode side is 7 V, no current flows at all.

In this state, if driving is continued and a short circuit occurs somewhere in the element, the resistance of the organic EL element decreases,
The applied voltage decreases. When the voltage applied to the element falls below 10 V, the voltage applied to the Zener diode side exceeds 10 V, and as shown in FIG.
Flows, the voltage applied to the organic EL element is maintained at a voltage higher than the voltage required for light emission, for example, 5 to 10 V, and light emission is continued. On the other hand, as shown in FIG. 6, when the Zener diode and the resistor are not added, the voltage applied to the organic EL element due to the occurrence of the short circuit falls below the voltage required for light emission,
For example, the voltage drops to 2 V, and the element stops emitting light.

It should be noted that the present invention is not limited to the above embodiment, but may be variously modified within the scope of the present invention depending on the purpose and application. That is, in the second embodiment,
As long as the short-circuit portion can be repaired in advance by such a process, the device, operation, and the like to be used are not limited. Also,
In the third embodiment as well, it is sufficient that a high voltage can be applied at the start of driving, and another driving circuit may be used.

[0033]

According to the first aspect of the present invention, it is possible to easily adjust the amount of the combustible gas generating agent for releasing a necessary minimum amount of oxygen gas, and to suppress occurrence of a short circuit. At the same time, it is possible to prevent the element from being deteriorated due to excess oxygen gas. In addition, if a combustible gas generating agent that absorbs moisture and releases oxygen gas is used, moisture in the sealed space can be more efficiently absorbed. Further, according to the second aspect, the short-circuit portion can be repaired in advance, and
Since oxygen gas is not mixed into the sealing space, generation and growth of dark spots during use of the device are prevented.

Further, according to the third aspect of the invention, even if there is a minute short circuit, light can be emitted by slightly changing the driving method at the start of driving, and a simple, low-cost element having a short circuit can be provided. It can emit light. Further, according to the fourth aspect, even when a short circuit occurs during use of the element, light emission of the element can be continued, and in some cases, the short-circuited portion may be repaired.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an organic EL device of Example 1 in which a combustion supporting gas generating agent is sealed in a sealed space.

FIG. 2 is a schematic diagram illustrating an outline of an apparatus for performing sealing after repairing a short-circuited portion according to a second embodiment.

FIG. 3 is a graph showing a high voltage or a large current at the start of driving in Example 3 and a constant current driving thereafter with time.

FIG. 4 is a circuit diagram illustrating a constant current circuit to which a zener diode and a resistor according to a fourth embodiment are added.

FIG. 5 is a circuit diagram showing a state in which a current flows through a Zener diode and a resistor, and a voltage required for light emission is continuously applied to the element.

FIG. 6 is a circuit diagram illustrating a constant current circuit in which a zener diode and a resistor are not added.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Transparent substrate, 2; Anode, 3; Organic EL thin film, 4; Cathode, 5; Sealing member, 51; Bonding layer, 52;
3; sealing space, 54; concave portion, 6; moisture-permeable resin film, 7; mixed powder, 8; film forming chamber, 9;
1; aging circuit; 10; sealing chamber, L; organic EL element, Z; zener diode, R;

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Taku Kobayashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masahide 1 Toyota Town Toyota City, Toyota City A Toyota Motor Corporation F Terms (reference) 3K007 AB00 AB05 AB18 BA06 CA01 CA02 CA05 CB01 DA00 DB03 EB00 FA00 FA01 FA02

Claims (4)

[Claims] 1. A substrate, an anode and an organic EL on a surface of the substrate.
The thin film and the cathode are laminated in this order, and the organic E
In the organic EL device including the L laminate and the sealing member that seals the organic EL laminate, a combustible gas generating agent is sealed in a space formed by the substrate and the sealing member. An organic EL device comprising: 2. In an atmosphere containing 1% by volume or more of oxygen gas, an electric current is applied to the organic EL thin film formed on the substrate to generate heat and oxidize the short-circuited portion. A method for manufacturing an organic EL device, comprising sealing a thin film. 3. An organic EL device, wherein a high voltage is applied at the start of driving.
A method for driving an organic EL element, comprising: performing a predetermined constant current drive after the element emits light. 4. A driving circuit for an organic EL element, wherein a zener diode and a resistor are added to a constant current circuit of an organic EL element driven at a constant current.