JPH10275682A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of dark spots by forming a protection layer with a fluorine family polymer such as polytetrafluoroethylene, filling a cap structure with an inert medium comprising an inert gas, or depositing an oxide insulator such as SiO2 on a cathode as an element protecting layer. SOLUTION: A transparent electrode 2 of indium oxide serving as an anode is formed on glass substrate, and a hole pouring transport layer 3 is formed thereon. A light emitting layer 4 is deposited thereon, and an electron transport layer 6 is formed, then aluminum is co-deposited to form a cathode 7, and an organic EL element is formed. As a protecting layer 8, a 10-100 nm thick insulator made of a metal oxide such as SiO2 , MgO, Al2 O3 is formed on the cathode 7 so as to cover the whole surface from the top to the side of the stacked films from the hole pouring transport layer to the cathode. Or as the protecting layer 8, at least one kind of fluorine family polymers such as PTFE, PCTFE, and PVDF is deposited on the cathode 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (EL) device, and more particularly to an organic EL device having an improved sealing structure.

[0002]

2. Description of the Related Art An organic EL device is a current-driven type light emitting device and requires a large current to flow between an anode and a cathode. As a result, when the element generates heat during light emission and there is oxygen or moisture around the element, oxidation is promoted and the element is deteriorated. The main cause of deterioration due to oxygen and moisture is a non-light emitting point called a dark spot due to deterioration of an organic material or peeling of a cathode. The dark spot grows as the deterioration proceeds, and stops emitting light. To prevent the above deterioration,
Various improvement plans have been proposed.

For example, Japanese Patent Application Laid-Open No. 5-41281 discloses a method for removing water by keeping an EL element in an inert liquid containing a fluorocarbon oil containing a dehydrating agent such as synthetic zeolite.

In Japanese Patent Application Laid-Open No. 5-114486, a heat radiation layer in which a fluorocarbon oil 12a is sealed with a sealing glass 9 is provided on at least one of the anode 2 and the cathode 7 as shown in FIG. A method of dissipating heat and extending the life of the device is disclosed.

Further, as shown in FIG. 6, a method is known in which a sealing protective layer 8 made of a carbonate compound is provided on an element to prevent intrusion of oxygen or moisture.

[0006]

In the above method,
Dark spots often occur and grow due to dissolved oxygen and dissolved moisture contained in the fluorocarbon oil itself. In addition, when the dehydrating agent is put in the sealing member, it must be put in a large amount, thereby damaging the element, and there is a problem that water taken in by the dehydrating agent by direct contact promotes oxidation of the element, It was difficult to suppress the generation and growth of dark spots. In addition, in the case of sealing only a resin or metal layer, there is a limit in preventing intrusion of oxygen and moisture from the outside, and it is difficult to extend the life of the element, which is called a product level, to several thousands to tens of thousands of hours. Was.

The present invention has been made in view of the above problems, and has been made in consideration of the occurrence of dark spots in an organic EL device.
A method for sealing an organic EL element capable of preventing and suppressing growth, and organic E which hardly causes dark spot growth.
An object is to provide an L element.

[0008]

In order to solve the above problem, in an organic EL device having a sealing portion having a cap structure provided outside the device, a polytetrafluoroethylene (hereinafter abbreviated as PTFE) is provided on a cathode. ), Polychlorotrifluoroethylene (hereinafter abbreviated as PCTFE), polyvinylidene fluoride (hereinafter abbreviated as PVDF) or the like to form a protective layer with a fluorine-based polymer, and the cap structure is made of an inert gas or fluorocarbon. It is characterized by being filled with an inert medium such as an inert liquid or vapor-depositing an oxide insulator such as SiO on a cathode as an element protection layer.

As a countermeasure against heat radiation, the sealing member is formed of a metal having good heat conductivity such as stainless steel (SUS), or a heat radiating plate or a heat radiating network is arranged in the sealing member so as to cover the element. The heat radiation plate and the heat radiation network are connected to a heat sink provided outside the sealing member to facilitate heat radiation.

Further, in order to arrange the oxygen absorbent and the moisture absorbent so as not to come into contact with the element, they are formed into a sheet or a solid, and fixed on the side of the sealing member opposite to the element.

In the above-mentioned organic EL device, by forming a protective layer with a fluorine-based polymer, SiO or the like on the cathode, high moisture-proof and insulating properties can be obtained. By separating so that the element is not directly touched, the element is not damaged, and water absorbed by the oxygen absorbent and water taken in by the dehydrating agent due to direct contact with the element does not promote oxidation of the element.

By promoting heat radiation by forming the sealing member with a metal having good thermal conductivity such as SUS, deterioration of the material due to heat generated when the element is driven can be prevented.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views of an organic EL device according to one embodiment of the present invention.

On a glass substrate 1, indium oxide (ITO) is formed as a transparent electrode 2 by sputtering as an anode, and a hole injection / transport layer 3 is formed thereon by a vacuum deposition method, and a light emitting layer 4 is formed thereon. And then the electron transport layer 6
Is formed by vacuum evaporation. Next, Al: Li and Mg:
Ag is formed by co-evaporation to form the cathode 7 to form an organic EL device.

As a protective layer 8 of the organic EL device, an oxide insulator made of a metal oxide such as SiO, MgO or Al ₂ O ₃ is formed on the cathode 7 by a vacuum evaporation method from a hole injection and transport layer. A film having a thickness of about 10 nm to 100 nm is formed so as to cover the whole of the laminated film up to the side surfaces up to the cathode. A film is formed by evaporation using a resistance heating method or an electron beam heating method. The degree of vacuum during deposition is 1 × 10 ⁻³ Pa or less, preferably 5 × 10 ⁻⁴ Pa or less, and the deposition rate is 50 to
Control is performed so that the substrate temperature is 200 nm / sec and the substrate temperature is 100 ° C. or less.

Alternatively, PTFE is formed on the cathode as a protective layer.
The protective layer is formed by a vacuum evaporation method using one or more fluorine-based polymers such as PCTFE and PVDF as an evaporation source. At this time, the form of the evaporation source compound may be a powder, a pellet, or a particle. The average molecular weight of the protective film at the time of vapor deposition on the organic EL element is preferably about 2,000 to 400,000. Vacuum evaporation is performed by a resistance heating method or an electron beam heating method, the degree of vacuum at the time of evaporation is 1 × 10 ⁻³ Pa or less, preferably 4 × 10 ⁻⁴ Pa or less, the evaporation rate is 30 nm / sec, and the substrate temperature is Is formed so that the film thickness becomes 10 to 500 nm under the condition of 100 ° C. or lower. Generally, organic EL materials do not have good heat resistance. However, by controlling the substrate temperature and the deposition rate during the deposition of the protective film, the organic EL material can be used.
It is possible to prevent the properties of the L material from deteriorating, and prevent the organic layer and the cathode thin film from peeling off due to stress. The protective film thus deposited has a high moisture-proof property and a high electrical insulation property, and is a thin film without pinholes.

As a method for sealing the EL element manufactured as described above, a sealing member 9 having a cap structure made of glass or metal is provided on the outer periphery of the element, and a dehydrating agent 10 and an oxygen absorbing agent are provided therein. Filled with an inert liquid 12 made of fluorocarbon such as perfluoroalkane or perfluoroamine mixed with 11 (FIG. 1), or argon,
An inert gas 13 made of helium or nitrogen is sealed (FIG. 2).

When an inert liquid perfluoroalkane or perfluoroamine is used as a filler, these liquids are heated in a vacuum oven, deaerated and dehydrated one to several times, and the mixture is treated with silica gel, Filtered through a column filled with molecular sieves, Fe, and ascorbic acid, and subjected to deoxygenation and dehydration operations. As shown in FIG. 1, this inert liquid is made of a granular ascorbic acid having a volume center particle size of 10 to 100 μm as an oxygen absorber, or a salt or oxide containing Fe, Ti or ions thereof, as a dehydrating agent. Filler is prepared by dispersing silica gel, molecular sieve, diatomaceous earth, activated alumina, zeolite, etc., one or more in a liquid, each having a central particle diameter of 10 to 100 μm, in a liquid so as to have a concentration of 30 to 60 W% with respect to the liquid. Create

At the time of filling the filler, an inlet 14 having a diameter of about 1 to 2 mm is provided on the roof side of the sealing member 9, and after adhering the glass substrate and the sealing member, injection is performed using a syringe or a pipettor. This injection port is closed with a lid 15 which is slightly larger than the injection port of the same material as the sealing member and an epoxy resin adhesive.

Further, as shown in FIG. 2, the oxygen absorbent and the dehydrating agent are combined with non-woven fabric, polyester, polyethylene, P
One to several layers of a sheet carried and dispersed in a polymer film such as VA or the above material is baked to make a solid, and a dehydrated oxygen absorbing member 16 is formed. The inert medium may be filled by bonding and holding using an agent. This makes it possible to remove oxygen and water remaining at the time of sealing, and also to remove trace amounts of oxygen and water entering from outside such as an adhesive interface after sealing.

When the inert gas is charged, granular ascorbic acid, Fe, Ti, or a salt or oxide containing these low-valent metal ions as the oxygen absorbent is used as a dehydrating agent. As a volume center particle diameter of 10 to 500 μm granular silica gel, molecular sieve, diatomaceous earth, activated alumina, zeolite and the like are carried on a nonwoven fabric, polyester, polyethylene, PVA or other polymer film, and one to several layers of a dispersed sheet, or The above-mentioned material is baked, solidified, adhered to the roof side of the sealing cap using an adhesive such as epoxy resin, and held to seal the EL element.

By holding the oxygen absorbent and the dehydrating agent on the roof side of the sealing member as shown in FIG. 2, it is possible to prevent them from directly contacting the element. In addition, this makes it possible to remove oxygen and water remaining at the time of sealing, and to remove trace amounts of oxygen and water entering from outside such as an adhesive interface after sealing.

To fill the inert gas, a hole may be formed in the sealing member and the inert gas may be injected as in the case of filling the inert liquid, but the inert gas may be injected in a glove box into which argon or nitrogen is introduced. By performing sealing, sealing can be performed without exposure to the atmosphere, which is effective in suppressing dark spots.

In the bonding between the sealing member and the element substrate, the heat resistance of the organic EL element is about 100 to 150 ° C., and it is difficult to use a thermosetting adhesive.
An epoxy-based photocurable adhesive 17 having low moisture permeability is used (FIG. 3).

As shown in FIG. 3, the SU is attached to the sealing cap 9a.
When the Ni alloy of the S and Fe bases is used, the heat radiation efficiency is improved, but the adhesion strength to the glass substrate and the thermal expansion become problems. A low-melting glass 18 is welded to these metals, and this glass part is bonded to the glass substrate of the EL element with the epoxy 17. Thereby, the difference in the thermal expansion coefficient between metal and glass can be reduced.

When the above metal or glass cap is used, a heat radiating plate or heat radiating network 19 made of a non-corrosive metal such as SUS is disposed so as to cover directly above the organic thin film 20 having the protective film 8 in the cap as shown in FIG. Then, the heat is taken out of the cap to prevent heat generated at the time of driving the element from being accumulated inside. By connecting the heat radiating plate or the heat radiating net to the heat sink 21 provided on the upper portion of the cap or the like, the heat radiating effect is increased and the life of the element can be further extended.

Example 1 A glass substrate 1 having a thickness of 1.1 mm
Then, ITO is formed as a transparent electrode 2 as an anode, and a hole injection and transport layer 3 is formed thereon by vacuum deposition of α-NPD (diamine compound) to a thickness of 500 Å, and a light emitting layer 4 is formed thereon. An aluminum quinoline complex and quinacridone as a dopant were co-evaporated at 250 Å, and then an aluminum quinoline complex was formed as an electron transport layer 6 by 300 Å. Next, a cathode was formed by depositing Al: Li by co-evaporation at 300 angstroms, and then depositing only aluminum at 1700 angstroms, thereby forming an organic EL device.

As a protective layer of the organic EL device, SiO 2 was used.
Was formed by vacuum evaporation to a thickness of 30 nm so as to cover the entire organic thin film and the cathode. The evaporation was performed by using a resistance heating method, the degree of vacuum before the evaporation was 4 × 10 ⁻⁴ Pa, and the evaporation rate was 200 n.
The film was formed so that the substrate temperature was 60 ° C. or less at m / sec.

The device thus produced was covered with a glass cap 9 as shown in FIG. 2, and nitrogen was sealed therein.

At the time of filling with nitrogen gas, a sheet in which granular ascorbic acid having a volume center particle diameter of 100 μm as an oxygen absorbent and silica gel having a volume center particle diameter of 500 μm as a dehydrating agent dispersed in a polyester resin is further layered as a sealing member. The EL element was sealed while being held on the roof side. An epoxy photocurable adhesive was used as the adhesive.

When a standing test was performed at a temperature of 25 ° C. and a relative humidity of 50 to 70%, no non-light-emitting points (dark spots) were visually observed even after 3,500 hours had passed. A constant current power supply is connected to this element, and an initial luminance of 300 c
When the device was driven with the current value set to d / cm ² , the time required for the luminance to be reduced by half was about 3000 hours.

Example 2 An organic EL device was prepared in the same manner as in Example 1, and a vapor deposition film was formed on the cathode as a protective layer by a vacuum vapor deposition method using granular PCTFE as a vapor deposition source. The degree of vacuum before vapor deposition is 4 × 10 ^-4 P
a, the deposition rate is 30 nm / sec, and the substrate temperature is 70
The film was formed so that the film thickness was 100 nm and the average molecular weight was about 4,000 to 20,000 under the condition of lower than or equal to ° C.

This element was welded with a low-melting glass to a sealing member made of SUS, and the glass portion and the glass substrate of the EL element were bonded with an epoxy resin. The perfluoroamine was filled therein. As the perfluoroamine, a product obtained by performing heating, degassing, and dehydrating operations of Fluorinert FC-70 (boiling point: 215 ° C.) (trade name, manufactured by Sumitomo 3M) in a vacuum oven three times, and filtering this with a molecular sieve was used. .

When the inert liquid is filled, granular ferrous oxide having a volume center particle size of 60 μm is used as an oxygen absorbent, and a molecular sieve having a volume center particle size of 100 μm is used as a dehydrating agent. It sealed so that it might be set to 40 W%.

When a standing test was conducted at a temperature of 25 ° C. and a relative humidity of 50 to 70%, no non-emission point (dark spot) visually observed was generated even after 3,500 hours. A constant current power supply is connected to this element, and an initial luminance of 300 c
When the device was driven with the current value set to d / cm 2, the time required for the luminance to be reduced by half was about 3500 hours.

Example 3 An organic EL device was prepared in the same manner as in Example 1, and SiO was formed as a protective layer to a thickness of 30 nm by vacuum evaporation so as to cover the organic thin film and the entire cathode. The deposition was performed by a resistance heating method, the degree of vacuum before deposition was 4 × 10 ⁻⁴ Pa, and the deposition rate was 2
The film was formed so as to be 00 nm / sec and the substrate temperature was 60 ° C. or lower.

When the above element is sealed with a sealing member having a glass cap structure, as shown in FIG.
A heat radiation net made of was formed so as to cover immediately above the element in the sealing member, taken out of the sealing member, and connected to a heat sink provided above the sealing member. When bonding the element substrate and the glass cap, a particle size of 20
By disposing the spacer 22 of 0 to 300 μm, the organic EL element and the heat radiation net were kept at a constant distance. The sealing cap 9 was filled with argon gas. When filled with argon gas, the volume center particle size is 10
The EL element was sealed by holding a sheet in which a 0 μm granular ferrous oxide and a silica gel having a volume center particle diameter of 500 μm as a dehydrating agent were dispersed in a polyester resin, was further layered on the roof side of the sealing cap.

When a standing test was carried out at 25 ° C. and 50-70% humidity, no non-light-emitting points (dark spots) were visually observed even after 3500 hours. A constant current power supply was connected to this element, and the initial luminance was 300 cd / cm.
^{When the} current value was set and driven so as to be ² , 350
Even after the elapse of 0 hours, the luminance did not decrease to half.

As a comparative example, a storage test was performed at 25 ° C. and a relative humidity of 50 to 70% for a device in which a glass cap was used without a protective film and a nitrogen gas was sealed. A non-emission point (dark spot) visually observed at time was observed. When a constant current power supply was connected to the device and the device was driven by setting a current value so as to have an initial luminance of 300 cd / cm ² , the time required for the luminance to decrease by half was about 1600 hours.

[0040]

As described above, according to the present invention,
By providing a protective layer between the element and the sealing liquid or gas, the element does not come into direct contact with the oxygen absorbent and the dehydrating agent, and it is possible to prevent the element from being damaged and the liquid from being wetted by the damage. . Oxygen or moisture dissolved in the filler or present in the element can be absorbed by an oxygen absorbent or a dehydrating agent, and damage to the element can be suppressed. Further, by providing a heat radiation structure, deterioration of the material due to heat generated when the element is driven can be prevented. Thus, the generation and growth of dark spots in the organic EL element can be suppressed, and the life of the element can be extended.

[Brief description of the drawings]

FIG. 1 is a sectional view of an organic EL device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an organic EL device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an organic EL device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of an organic EL device according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of an organic EL element according to a first conventional example.

FIG. 6 is a sectional view of an organic EL element according to a second conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate 2 ITO 3 hole injection / transport layer 4 light emitting layer 6 electron transport layer 7 cathode 8 protective layer 9 sealing member 9 a metal sealing cap 10 dehydrating agent 11 oxygen absorbent 12 inert liquid 12 a fluorocarbon oil 13 non Active gas 14 Inlet 15 Lid 16 Dehydration / oxygen absorbing member 17 Epoxy resin (adhesive) 18 Low melting point glass 19 Heat dissipation network 20 Organic thin film 21 Heat sink 22 Spacer

Claims (6)

[Claims] 1. A sealing section having a cap structure is provided outside an organic EL element having a laminate in which an organic light emitting material is formed between a pair of opposed electrodes, at least one of which is transparent or translucent, An organic EL device having a sealing portion filled with an inert medium, comprising a protective layer formed of a fluorine-based polymer or an oxide insulator on a cathode serving as a device surface layer. 2. The method according to claim 1, wherein the sealing portion is made of a good heat conductive metal, and a low melting point glass bonding portion is provided at a contact portion of the sealing portion with the element substrate. 2
The organic EL device according to the above. 3. The organic EL device according to claim 1, wherein a heat radiating plate or a heat radiating net made of a non-corrosive metal is arranged so as to cover at least immediately above said device. 4. The organic EL device according to claim 1, wherein said inert medium contains an oxygen absorbent and a dehydrating agent. 5. The organic EL device according to claim 5, wherein the oxygen absorbent and the dehydrating agent are formed in a sheet or solid state and are arranged so as not to contact the device. 6. The oxygen absorbent ascorbic acid, iron,
6. The organic EL device according to claim 4, wherein one or more of titanium fine powder or an oxide or metal salt thereof is used as the dehydrating agent, and one or more of silica gel and molecular sieve are used.