JP2004119087A - Organic electroluminescent panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of element due to invasion of water after delivery of the panel, which is caused by remaining of uncured portion of the ultraviolet-curing resin that adheres the transparent substrate and the metal sealed container, in the organic electroluminescent panel in which the organic electroluminescent element formed on the transparent substrate is sealed by a metal sealed container. <P>SOLUTION: Remaining of the uncured portion is prevented by sufficiently irradiating ultraviolet rays on the adhesive 10 too in the region shaded by the drawing-out electrodes 6, 7 made of metal by applying surface finishing so that reflectivity of the adhered face of the metal sealed container 9 to the ultraviolet rays may be 50% or more. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescence (EL) panel used for a flat display.
[0002]
[Prior art]
The organic EL element is a self-luminous element having a basic structure of a laminated structure in which a light emitting layer made of an organic compound is sandwiched between an anode and a cathode. An organic EL panel in which the elements are arranged in a matrix has a high luminance and a wide field of view. It has the advantage that the response speed is fast at the corner. Therefore, the organic EL panel has attracted much attention in recent years as a display panel replacing the LCD (liquid crystal display), and a panel having a large screen, high definition, and low power consumption has been demanded.
[0003]
At least one of the electrodes of the organic EL element is formed of a transparent conductive material such as ITO (indium tin oxide). This transparent conductive material has a very large resistance value as compared with a metal, and particularly in a panel having a simple matrix configuration, a voltage drop due to resistance hinders a larger screen, higher definition, and lower power consumption of the panel. I have. For this reason, a method has been adopted in which a metal is used as an extraction electrode from an organic EL element constituting a panel to an external circuit to reduce wiring resistance.
[0004]
On the other hand, since the light emitting layer is made of an organic material, the organic EL element is easily affected by moisture, and a sealing structure for sealing the element is indispensable. Specifically, moisture causes deterioration of the organic material, separation of the light-emitting layer and the electrode, and generation and increase of a non-light-emitting portion called a dark spot, making it difficult to maintain long-term light-emitting performance. On the other hand, a method of bonding a metal sealing container to a transparent substrate on which an organic EL element is formed is often used. Inside the sealed container, a drying means such as a hygroscopic agent is usually arranged in order to maintain a dry state. Further, as another method, there is a method of forming a protective film on the laminate, but it is inevitable that stress of the protective film is applied to the organic EL element, and to form a highly reliable protective film. Requires a complicated process. In particular, in the case of a panel having a simple matrix configuration in which cost is important, a metal sealed container which is easy to form and is inexpensive is advantageous.
[0005]
For adhesion between the metal sealing container and the transparent substrate, an ultraviolet-curable resin is preferably used as an adhesive. This is because it is difficult to use a thermosetting resin in terms of heat resistance and workability of an organic EL element made of an organic material.
[0006]
[Problems to be solved by the invention]
When the transparent substrate on which the metal extraction electrode is formed and the metal sealing container are bonded with an ultraviolet-curing resin, ultraviolet light is directly applied to a region sandwiched between the extraction electrode and the bonding surface of the metal sealing container. Not irradiated. On the other hand, a method has been adopted in which the irradiation time of ultraviolet rays is extended, and the adhesive in the area is hardened by utilizing the wraparound due to the diffraction and scattering of light incident from the gap between the metal electrodes. However, in this method, an uncured portion tends to remain at the center of the region. In particular, when the width of the extraction electrode exceeds the light wrap limit, complete curing is impossible.
[0007]
If an uncured portion exists in the adhesive, minute peeling is likely to occur in that portion due to a temperature change or impact. Since this peeling occurs between the take-out electrode and the bonding surface of the metal sealing container, it is difficult to detect even if it occurs during manufacturing. Also, due to this minute peeling, the amount of water entering into the metal sealing container increases, but there is also a drying means arranged inside, so that the organic EL element is not rapidly destroyed. Since defects are found after the panel is shipped, the reliability of the panel may be impaired.
[0008]
The present invention has been made in view of the above problems, and performs complete sealing without leaving an uncured portion in an adhesive for bonding a metal sealing container and a transparent substrate. An object of the present invention is to provide a highly reliable organic EL panel by preventing deterioration.
[0009]
[Means for Solving the Problems]
The present invention, a transparent substrate,
On the transparent substrate, a first electrode having a light-transmitting property, an organic layer having at least a light-emitting layer made of an organic compound, and a laminated structure obtained by sequentially laminating a second electrode,
A metal sealed container including the laminated structure and bonded to the transparent substrate,
An extraction electrode connected to the first electrode and the second electrode, formed on a transparent substrate, and drawn out of the metal sealing container;
In an organic electroluminescence panel having
The metal sealing container and the transparent substrate are bonded by an ultraviolet-curable resin,
The extraction electrode is formed of at least a metal,
An organic electroluminescent panel characterized in that at least a region of the bonding surface of the metal sealing container sandwiching the extraction electrode has a reflectance of 50% or more with respect to ultraviolet rays.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the organic EL panel of the present invention, by setting the ultraviolet reflectance of the bonding surface of the metal sealing container to 50% or more in the region sandwiched between the bonding surface of the metal sealing container and the extraction electrode, the organic EL panel can be disposed between the extraction electrodes. The penetrated light is reflected on the bonding surface, and sufficient light can be applied to the part shielded by the extraction electrode, and good sealing can be realized without leaving uncured part in the adhesive. .
[0011]
According to the present invention, an extraction electrode having a width of 100 μm or more can be used, and the wiring resistance of the extraction electrode can be reduced.
[0012]
Hereinafter, the present invention will be described in detail with reference to embodiments.
[0013]
FIG. 1 shows a basic configuration of the organic EL panel of the present invention. In the figure, 1 is a transparent substrate, 2 is a laminated structure of an organic EL element, and a first electrode 3 having a light transmitting property and an organic layer 4 having at least a light emitting layer made of an organic compound on the transparent substrate 1. And the second electrode 5 are laminated. Reference numeral 6 denotes an extraction electrode of the first electrode 3, reference numeral 7 denotes an extraction electrode of the second electrode 5, reference numeral 8 denotes a drying means, reference numeral 9 denotes a metal sealing container, and reference numeral 10 denotes an adhesive made of an ultraviolet curing resin. In addition, since FIG. 1 is a schematic diagram, the second electrode 5 is extended to reach the transparent substrate 1 and is in contact with the end of the anode 3. However, actually, the first electrode 3 and the second electrode 5 are Insulated by insulating material.
[0014]
In the present invention, a glass substrate is preferably used as the transparent substrate 1. The same structure as that of a conventional organic EL element can be used as the laminated structure 2. For example, an ITO formed on the transparent substrate 1 by sputtering is used for the first electrode 3 having light transmittance. Etc. can be used. The organic layer 4 only needs to have at least a light-emitting layer, and the light-emitting layer can be formed by vapor deposition using, for example, an aluminum quinolinol complex (Alq3). In addition to the light emitting layer, the organic layer 4 preferably includes a hole transport layer formed by spin-coating triphenyldiamine (TPD) or the like. In addition, an electron transport layer or a hole injection layer Layers that constitute an organic layer of a conventional organic EL element, such as an electron injection layer, can be added as appropriate. Further, as the second electrode 5, an Al film formed by vacuum evaporation can be used.
[0015]
The extraction electrodes 6 and 7 are connected to the first electrode 3 and the second electrode 5, respectively. The extraction electrodes 6 and 7 are formed on the transparent substrate 1 and are drawn out of the metal sealing container 9. The extraction electrodes 6 and 7 are made of at least a metal and are formed of, for example, Al. Further, the extraction electrodes 6 and 7 may be a laminate of a transparent conductive layer such as ITO and a metal layer. The extraction electrodes 6 and 7 are formed by forming a base layer such as Ti or Mo on the transparent substrate 1 and then forming a metal layer on the transparent substrate 1 in order to improve the adhesiveness with the transparent substrate 1 or the first electrode 3 when the electrode is made of ITO. Layers may be stacked.
[0016]
A stainless material having a thickness of about 0.2 to 0.5 mm is preferably used for the metal sealing container 9, and an adhesive surface and a holding portion of the drying unit 8 are formed by press molding or the like. In the present invention, the bonding surface of the metal sealing container 9 is surface-finished by polishing or the like so that the reflectance to ultraviolet rays becomes 50% or more. The region having a reflectance of 50% or more with respect to the ultraviolet rays may be at least a region sandwiching the extraction electrodes 6 and 7. However, in order to allow more ultraviolet light to enter the region, the regions corresponding to the extraction electrodes 6 and 7 are required. It is preferable that the peripheral portion of the region to be finished be finished to have the same reflectance. This surface finishing may be performed in advance by pressing using a mirror-finished material or the like, instead of being performed after molding.
[0017]
As the drying means 8 disposed in the metal sealing container 9, a commonly used sheet-like or powdery hygroscopic agent can be used, but it is preferable to use a chemisorbing device which hardly releases the adsorbed moisture. For example, an alkali metal oxide, an alkaline earth metal oxide and the like can be mentioned. When a powdery hygroscopic agent is used, it is preferable that the powdery hygroscopic agent is fixed to the metal sealing container 9 using a moisture-permeable film or the like.
[0018]
As the adhesive 10 used for bonding the transparent substrate 1 and the metal sealing container 9, an ultraviolet-curable resin is used, and specifically, an ultraviolet-curable epoxy resin can be used. The epoxy resin used here is preferably designed to have low moisture permeability, and in recent years, those developed for use in organic EL panels are also on the market.
[0019]
Suitable curing conditions for such an epoxy resin are an ultraviolet irradiance of about 100 to 400 mW / cm ^2. If it is lower than this, the polymerization reaction is insufficient and the strength of the resin decreases. And a decrease in interfacial bonding force due to excessive cohesive force occurs, and sufficient adhesive strength cannot be obtained. Further, an appropriate amount of ultraviolet irradiation is about 4 to 6 J / cm ^{2. As} with the illuminance, if the irradiation amount is insufficient, an uncured portion remains, and if it is excessive, deterioration and a decrease in interface bonding force occur. The limit of this excessive irradiation amount is about three times the proper amount, and if it exceeds this, peeling due to intrusion of moisture into the bonding interface or the like is likely to occur. Further, it is said that the hardening due to the wraparound of the ultraviolet rays to the region where the ultraviolet rays are blocked by the extraction electrodes 6 and 7 is limited to 30 to 50 μm. However, complete curing of the resin was not possible.
[0020]
In the present invention, as shown in FIG. 2, even if the electrode width is 100 μm or more, ultraviolet rays are guided to the central portion to reduce the residual uncured portion even if the electrode width is not less than 100 μm. Can be prevented. In the case where ultraviolet irradiation is performed for a certain period of time, the illuminance of the ultraviolet rays reaching the vicinity of the center of the extraction electrodes 6 and 7 must be adjusted so that the amount of excessive ultraviolet irradiation is within three times the appropriate value. It is necessary that the illuminance of the region is not less than 1/3 of the ultraviolet illuminance. The appropriate value range of the ultraviolet intensity is three times or more as large as the minimum value. Therefore, the ultraviolet rays are irradiated within the above-mentioned appropriate value range in any of the central portions of the extraction electrodes 6 and 7 and the regions other than the extraction electrodes 6 and 7. It is possible to do.
[0021]
The ultraviolet transmittance of the adhesive 10 is usually about 80% at a thickness of 30 μm with respect to ultraviolet rays having a wavelength of 365 nm used for curing the resin. Ultraviolet rays incident between the adjacent extraction electrodes 6 and 7 penetrate the resin, are reflected on the bonding surface of the metal sealing container 9, transmit the resin again, and are on the back side (adhesive 10 side) of the extraction electrodes 6 and 7. Considering the route of arrival, the intensity of the arriving ultraviolet light is represented by the product of the square of the incident light intensity, the transmittance of the resin, and the reflectance of the bonding surface. In order to obtain 1/3 of the incident light intensity on the back side of the extraction electrodes 6 and 7, the adhesive surface needs to have a reflectance of 50% or more. Actually, not only such a simple path, but also a complicated path due to diffusion or scattering at the bonding surface exists, but if the bonding surface has a reflectance of 50% or more, the present invention Enough to get the effect.
[0022]
【Example】
(Example 1)
On a glass substrate, ITO having a thickness of 150 μm as a first electrode, TPD having a thickness of 20 nm as a hole transport layer, Alq3 having a thickness of 40 nm as a light emitting layer, and Al having a thickness of 100 nm as a second electrode were sequentially laminated, respectively. A laminated structure was formed. As the extraction electrode, a laminate in which an Al film having a thickness of 100 nm was formed on ITO having a thickness of 150 nm was used. The pattern of the extraction electrode has a width of 120 μm and an interval of 120 μm. The metal sealing container was made of stainless steel SUS304 having a surface finish of # 800 and having a thickness of 0.4 mm, and the bonding surface and the holding portion for the moisture absorbent were formed by press working. The reflectance of the bonded surface after formation to light with a wavelength of 365 nm was in the range of 55 to 60%. After pre-treatment was performed on the bonding surface with a UV / O ₃ washer, bonding was performed using an ultraviolet-curable epoxy resin. The curing of the resin was performed by an ultraviolet irradiation device in which a high-pressure mercury lamp was arranged, and the illuminance of the ultraviolet light incident on the resin was about 300 mW / cm ² . At an irradiation time of 60 seconds, the irradiation amount between the extraction electrodes was 18 J / cm ² , the illuminance on the back side of the extraction electrode was 100 mW / cm ² or more, and the irradiation amount was 6 J / cm ² or more.
[0023]
The organic EL panel sealed under the above conditions was subjected to a 300-hour durability test under high-temperature and high-humidity conditions of 80 ° C. and 90% RH. Here, in order to confirm the sealing performance, the organic EL element was exposed to humidity when moisture entered the organic EL panel without using a normally installed moisture absorbent. Microscopic observation of the light emitting portion after the durability test showed no noticeable deterioration such as an increase in dark spots as compared to before the test. In addition, a peel test of the metal-sealed container was performed, and it was confirmed that almost the entire bonding surface was cohesively fractured, and that the interfacial adhesive force on the back side of the extraction electrode was sufficiently obtained.
[0024]
(Comparative Example 1)
The organic EL panel was sealed in the same manner as in Example 1 except that the surface finish of the metal-sealed container was # 400 and the reflectance of the bonding surface to ultraviolet rays was 20%, and a durability test was performed. As a result, in the microscopic observation of the light emitting portion after the test, a clear increase in the dark spot was observed as compared with before the test. Further, in the peeling test, it is presumed that a large amount of interface peeling occurred on the back side of the take-out electrode, and the vicinity of the interface where the uncured portion remained due to the insufficient amount of ultraviolet irradiation became a water entry port.
[0025]
(Comparative Example 2)
An organic EL panel was sealed in the same manner as in Example 1 except that the width of the extraction electrode was set to 80 μm and the interval was set to 160 μm using the metal sealing container used in Comparative Example 1, and a durability test was performed. As a result, in the microscopic observation of the light emitting portion after the test, no noticeable deterioration was observed compared to before the test.
[0026]
(Example 2, Comparative Example 3)
The width of the extraction electrode was set to 80 μm, and the interval was set to 160 μm. , The organic EL panel was sealed, and a durability test was performed. As a result, in Comparative Example 3, an increase in dark spots was observed in the light emitting portion, whereas in Example 2, no noticeable deterioration was observed. The effect that the time required for curing the adhesive can be significantly reduced is obtained even with an extraction electrode having a width that allows ultraviolet light to pass around.
[0027]
【The invention's effect】
As described above, according to the present invention, even when the width of the extraction electrode is wide, an organic EL panel having high sealing properties without peeling due to the remaining uncured portion of the adhesive is obtained. Therefore, according to the present invention, the deterioration of the organic EL element due to the invasion of water over time is greatly suppressed, and a highly reliable organic EL panel is provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a basic configuration of an organic EL panel of the present invention.
FIG. 2 is a schematic cross-sectional view in which a part of an adhesive portion between a transparent substrate and a metal sealing container of the organic EL panel of the present invention is enlarged.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Laminated structure 3 1st electrode 4 Organic layer 5 2nd electrode 6, 7 Extraction electrode 8 Drying means 9 Metal sealing container 10 Adhesive

Claims (2)

A transparent substrate,
On the transparent substrate, a first electrode having a light-transmitting property, an organic layer having at least a light-emitting layer made of an organic compound, and a laminated structure obtained by sequentially laminating a second electrode,
A metal sealed container including the laminated structure and bonded to the transparent substrate,
An extraction electrode connected to the first electrode and the second electrode, formed on a transparent substrate, and drawn out of the metal sealing container;
In an organic electroluminescence panel having
The metal sealing container and the transparent substrate are bonded by an ultraviolet-curable resin,
The extraction electrode is formed of at least a metal,
An organic electroluminescent panel characterized in that at least a region of the adhesive surface of the metal sealing container sandwiching the extraction electrode has a reflectance of at least 50% with respect to ultraviolet rays. The organic electroluminescent panel according to claim 1, wherein the width of the extraction electrode is 100 µm or more.

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