JP2003229248A - Sealing material for organic el element having excellent sealing and adhering property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing material suitable for airtight sealing of an organic EL element by arranging an organic resin coating film 5b having excellent adhering property against a UV-curable epoxy adhesive. <P>SOLUTION: The sealing material is at least composed of a metallic base plate 5a facing a transparent base plate 1 and the organic resin coating film 5b formed on the surface of the metallic base plate. The organic resin coating film 5b is made of resin paint containing epoxy resin paint and silane compound, and OH group are oriented on the surface of the paint. The OH group oriented on the surface of the paint acts as a polar group to improve the adhering property of UV-curable epoxy adhesive. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL suitable for a sealing can or the like for protecting an organic EL element from moisture and oxygen in the atmosphere.
The present invention relates to an element sealing material.

[0002]

2. Description of the Related Art An organic EL device has a laminated structure in which a thin film containing a fluorescent organic compound is sandwiched between an anode electrode and a cathode electrode. Specifically, the organic light emitting layer 3 and the cathode electrode 4 are laminated on the anode electrode 2 formed on the substrate 1, and the sealing member 5 covering each of the layers 2 to 4 is fixed to the substrate 1 (FIG. 1). The organic light emitting layer 3 is formed of copper phthalocyanine (Cu) with a thickness of several tens nm from the anode electrode 2 side.
Pc) Hole injection layer 3a formed with an organic material or the like, hole transport layer 3b formed with bis [N- (1-naphthyl-) benzidine] α-NPD organic material with a thickness of several tens nm, or several tens of nanometers It has a three-layer structure of a light emitting / electron transporting layer 3c in which a film of tris (8-quinolinolato) aluminum (Alq3) organic material or the like having a film thickness of nm is formed.

When a direct current voltage is applied between the anode electrode 2 and the cathode electrode 4, holes are injected into the hole injection layer 3a and electrons are injected into the light emitting / electron transport layer 3c. The holes move in the hole transport layer 3b and recombine with the electrons in the light emitting / electron transport layer 3c. Excitons are generated by the recombination, but fluorescence or phosphorescence generated when the excitons are deactivated is generated by the substrate 1
Is released to the outside via. At this time, the required image is displayed by dividing the organic light emitting layer 3 into an XY matrix and driving the organic light emitting layer 3 by a simple matrix method or an active matrix method to cause predetermined pixels to emit light. Since the image display by the organic EL element utilizes self-luminous light, a clear image which is not affected by the viewing angle is reproduced as compared with the liquid crystal.

In the organic EL device having the laminated structure shown in FIG.
Since the substrate 1 is on the light extraction side, glass having high insulation and transparency is used as the substrate material. In particular, a thin glass plate of about several mm is used as the substrate 1 in applications such as mobile phones and in-vehicle displays, which are strongly required to be lightweight and thin. The anode electrode 2 is also required to have transparency, and a transparent conductive film such as an ITO thin film is used. A film having a thickness of several tens to several hundreds nm was formed on the cathode electrode 4.
A conductive thin film such as l-Ti is used. Hole injection layer 3a,
An organic EL element having an organic light emitting layer 3 in which a hole transport layer 3b, a light emitting / electron transport layer 3c and the like are laminated has a tendency that the light emission life is extremely shortened in the presence of oxygen. In addition, if there is water in the atmosphere, dark spots, which adversely affect the sharpness of the image, are generated and enlarged. Performance deterioration due to oxygen and water is particularly noticeable in low molecular type organic EL devices.

In order to prevent the performance deterioration due to oxygen and water, the sealing member 5 is fixed to the glass substrate 1 in an inert gas atmosphere such as dry nitrogen from which water is removed as much as possible, and each layer 2
It covers ~ 4. The sealing member 5 is made of stainless steel foil having a plate thickness of about 0.1 to 1 mm, which is impermeable to oxygen and moisture. The metallic encapsulant is an optimal material for cost reduction because it can be easily formed into a target shape by pressing, but it exhibits conductivity, and if it comes into contact with the extraction electrode, it causes defects such as short circuits. .

[0006]

A metallic sealing material (Japanese Patent Laid-Open No. 2000-43970) in which the occurrence of defects such as a short circuit is suppressed by providing an insulating property with an organic resin layer is partially used. . However, when the organic EL element is sealed using a metal plate provided with an organic resin coating and the metal plate is bonded to a transparent substrate such as glass, white discoloration is likely to occur on the flange of the bonded portion. Detailed observation of the white-discolored organic resin coating film revealed that peeling occurred at the interface of the adhesive / organic resin coating film, and it was clarified that the interfacial peeling is the cause of the white discoloration. When a gap is created at the interface between the adhesive and the organic resin coating film due to the peeling of the interface, moisture and oxygen in the atmosphere penetrate into the element through the gap and deteriorate the organic EL element, which makes it practical for use as a display device. It will be difficult.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem, and by providing an organic resin coating film in which OH groups are oriented on the surface, UV-curable epoxy adhesion is provided. It is an object of the present invention to provide an encapsulant for an organic EL element, which enhances the adhesiveness to the agent, prevents the interfacial peeling of the adhesive / organic resin coating film, and can maintain the emission characteristics of the organic EL element at a high level for a long period. .

In order to achieve the object, the encapsulant for organic EL devices of the present invention has an organic resin coating film on at least the surface of a base metal plate or metal foil facing the transparent substrate of the organic EL device. OH groups are oriented on the surface of the organic resin coating film. The organic resin coating film is formed with an epoxy resin coating material or an organic resin coating material containing a silane compound. If necessary, a dehydrating agent is added to the organic resin paint.

[0009]

With regard to the interfacial peeling of the adhesive / organic resin coating film which tends to occur when the conventional organic resin-coated metal plate is used as the sealing material to seal the organic EL element, the present inventors have the following. Considered. A UV curable epoxy adhesive having a small amount of water permeation is mainly used for sealing and adhering the organic EL element. UV-curable epoxy adhesive is a type that is easily bonded to surfaces with polar groups such as metals and ceramics, so when used as a stainless steel encapsulant, peels off at the encapsulant / adhesive interface. Does not occur. However, when it is applied to a metal sealing material provided with an organic resin coating film having no polar group, the adhesive force to the organic resin coating film is weak and the interface between the adhesive / organic resin coating film is easily peeled off.

Assuming that the surface state of the organic resin coating film causes interfacial peeling, various investigations were conducted on the influence of the surface state of the organic resin coating film on the sealing adhesiveness. When an organic resin coating film oriented on the coating film surface is provided on the surface of the metal plate, excellent adhesiveness of the UV-curable epoxy adhesive is developed, and the organic adhesive film does not peel off at the adhesive / organic resin coating film interface. It has been found that the EL element can be sealed.

In order to form an organic resin coating film in which OH groups are oriented on the surface of the coating film, a paint based on an epoxy group having an OH group or a polyol system having a relatively low molecular weight is used. Even if the resin has no OH group, it has the formula R ¹ _4-n Si (O
R ² ) _n [wherein R ^{1 is} an alkyl group or an alkoxyl group,
R ² : alkyl group, n: 3 or 4] and a silane compound represented by the formula, and if necessary, a dehydrating agent, to achieve a given object. In the silane compound thus blended, the condensation cross-linked product is concentrated on the surface of the coating film, and the alkoxyl group is hydrolyzed into the OH group by the moisture in the atmosphere. As a result, an organic resin coating film in which OH groups are oriented on the coating film surface is formed, and excellent sealing adhesiveness is exhibited.

The degree of orientation of OH groups on the surface of the coating film is preferably 0.4 or more as a value X obtained by substituting the amounts of OH groups and CH measured by an infrared spectrophotometer into the following equation. X value indicating the degree of orientation is 0.
When it is 4 or more, the influence of the OH groups oriented on the surface of the coating film becomes remarkable and the sealing adhesiveness is improved. X value = (O in the wavelength range of 3600 to 3000 / cm
H peak intensity) / (CH peak intensity in the wavelength range of 3600 to 3000 / cm)

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The insulating sealing member for an organic EL element according to the present invention is made of stainless steel, ordinary steel, various plated steels, copper,
A metal thin plate or metal foil of copper alloy, aluminum, aluminum alloy or the like is used as the base material of the sealing member 5, and the organic resin coating film 5 is formed on at least the surface of the base metal plate 5a facing the transparent substrate 1.
b is formed (FIG. 2). Since the metal thin plate or the metal foil that does not allow moisture or oxygen to pass through is used as the base metal plate 5a, the performance deterioration of the organic EL element due to moisture or oxygen can be prevented.

In order to orient the OH groups on the surface of the organic resin coating film 5b, a polyol-based resin-based paint is used. However, a relatively high molecular weight resin such as polyester is not effective in improving the sealing adhesiveness because the amount of OH groups remaining in the organic resin coating film 5b is insufficient. In this respect, the coating material based on the epoxy resin having a relatively small molecular weight has a large amount of OH groups remaining in the organic resin coating film 5b after being dried and baked, and thus has excellent sealing adhesiveness to the UV curable epoxy adhesive agent. Express.

Examples of the epoxy resin include a bisphenol type epoxy resin, a novolac type epoxy resin, a polyester modified epoxy resin obtained by modifying these, and an acrylic modified epoxy resin. Amino resins represented by etherified melamine resins and polyisocyanates such as hexamethylene diisocyanate and diphorone diisocyanate are used as the curing agent.

Even if it is an organic paint having no OH group,
By adding a silane compound or a condensation cross-linked product thereof, OH groups can be oriented on the surface of the organic resin coating film 5b and the sealing adhesiveness can be improved. Examples of organic paints of this type include mixed resins of polyvinylidene fluoride resin and acrylic resin that have been developed for precoated metal plates, solvent-soluble fluororesins, polyester resins, silicone polyester resins,
Acrylic resin, urethane resin, vinylidene chloride resin, etc. may be mentioned.

The silane compound or its condensation cross-linked product added for imparting the sealing adhesiveness is preferably of the formula R ¹ _4-n Si
(OR ² ) _n [wherein R ^{1 is} an alkyl group or an alkoxyl group, R ^{2 is} an alkyl group, n is 3 or 4], and a monomer such as tetramethoxysilane, tetraethoxysilane, or tetrapropoxysilane is mixed with water and An oligomer obtained by adding a catalyst and performing hydrolysis and dehydration condensation is used.
The silane compound or its condensation cross-linked product is preferably blended in a ratio of 1 to 20 parts by mass with respect to 100 parts by mass of the coating resin. If the compounding amount is less than 1 part by mass, the effect of improving the sealing adhesiveness by adding the silane compound or its condensation cross-linked product is small, and when the sealing member 5 is bonded to the transparent substrate 1 with the UV curable epoxy adhesive, the adhesive / Peeling easily occurs at the interface of the organic resin coating film. On the contrary, when the compounding amount exceeds 20 parts by mass,
The reaction of the silane compound or its condensation cross-linked product is accelerated, and the storage stability of the coating composition deteriorates due to gelation.

When a coating material to which a silane compound or a condensation cross-linked product thereof is added is applied to a metal plate and dried and baked, the condensation cross-linked product of the silane compound is concentrated on the surface of the coating film. Since the concentrated silane compound or the alkoxyl group of the condensation cross-linked product is hydrolyzed to the OH group by the moisture in the atmosphere, the OH group effective for developing the sealing adhesiveness is oriented on the surface of the coating film. If a resin coating containing a silane compound or a condensation cross-linked product thereof is stored, a condensation reaction progresses and polymerizes. It may not be distributed on the film surface. Further, when the moisture derived from the coating material or the moisture absorbed by the coating from the atmosphere comes into contact with the silane compound or the condensation crosslinked product, hydrogen ions or the like are generated, which also accelerates the dehydration condensation. as a result,
The reaction of the silane compound or the condensation cross-linked product is promoted, the coating is gelated, and the condensation cross-linked product of the silane compound effective for developing the sealing adhesiveness is not concentrated on the coating film surface.

Condensation crosslinking or dehydration condensation which adversely affects the sealing adhesiveness can be prevented by adding a dehydrating agent. As the dehydrating agent, one type or two or more types of trialkyl orthoformate, trialkyl orthoacetate, trialkyl orthoborate and the like are used. When the dehydrating agent is blended in a proportion of 1 part by mass or more with respect to 100 parts by mass of the coating resin, the effect of addition becomes remarkable, and the reaction between the silane compound or its condensation crosslinked product and water is effectively suppressed. However, when an excessive amount of the dehydrating agent exceeding 50 parts by mass is blended, the paint clay is lowered and the paintability is deteriorated. Epoxy resin paints and resin paints containing silane compounds or condensation cross-linked products are applied to the base metal plate by methods such as roll coating, spraying, spin coating, dipping and screen printing, and organic resin coatings by dry baking. 5b. The thickness of the organic resin coating film 5b is 1 to 50 μm.
m is preferred. If the film thickness is 50 μm or more, the outer ring of the coating film is likely to deteriorate due to cracking or blistering during drying / baking. On the contrary, if the film thickness is less than 1 μm, the adhesiveness may decrease due to the unpainted part. .

[0020]

[Example] Three kinds of sealing materials A to C were prepared. Sealing material A (example of the present invention): degreased SU having a thickness of 0.3 mm
Apply epoxy resin coating on S430 stainless steel plate,
An organic resin coating film 5b having a dry film thickness of 11 μm was provided by drying and baking. Sealing material B (Example of the present invention): Based on polyester resin, 5 parts by mass of oligotetramethoxysilane (silane compound) and 2 parts by mass of triethyl orthoformate (dehydrating agent) are mixed with 100 parts by mass of the coating resin. Was prepared. The resin paint was applied to a degreased SUS430 stainless steel plate having a thickness of 0.3 mm, and dried and baked to form an organic resin coating film 5b having a dry film thickness of 20 μm. Sealant C (comparative example): SUS degreased with a thickness of 0.3 mm
A 430 compound stainless steel sheet was coated with a polyester resin paint containing no silane compound and no dehydrating agent, and dried and baked to form an organic resin coating film 5b having a dry film thickness of 14 μm.

(Evaluation of Sealing Adhesiveness) A 25 mm × 100 mm test piece was cut out from each sealing material A to C and a glass plate,
Adhesive area 3.125 using UV curable epoxy adhesive
Each of the sealing materials A to C was bonded to a glass plate (transparent substrate 1) with a cm ² . The bonded test piece was subjected to a shear strength test, and a shearing force was applied until the sealing materials A to C were separated from the glass substrate. Observing the broken state of the adhesive part, the sealing adhesiveness is evaluated by ◯ for the test piece where the glass is broken, Δ for the test piece where the adhesive has undergone cohesive failure, and x for the test piece where the coating / adhesive interface has peeled off. did.

(Evaluation of Light Emission Yield of Organic EL Element) After forming an ITO thin film (anode electrode 2) on a cleaned glass substrate (transparent substrate 1) by a sputtering method, the ITO thin film was patterned by a photolithography method. Then, the hole injection layer 3a, the hole transport layer 3b, and the light emitting / electron transport layer 3c are sequentially laminated on the ITO thin film according to a conventional method to provide the organic light emitting layer 3, and then the Al thin film (cathode electrode 4) is deposited by the vapor deposition method. To form a film on the organic light emitting layer 3. In order to seal the produced organic EL element, the sealing member 5 in which each of the sealing materials A to C was processed into a sealing can shape by extrusion molding was used. The organic EL element was hermetically sealed by stacking the sealing member 5 on the transparent substrate 1 in an inert atmosphere and fixing it with a UV-curable epoxy adhesive.

When the sealing adhesiveness of the sealing member 5 to the transparent substrate 1 is low, outside air and moisture enter the inside of the organic EL element through the gap created by the peeling of the adhesive / organic resin coating film interface, Defects such as dark spots are likely to occur. Therefore, the hermetically sealed organic EL element is kept at 40 ° C. and 90 ° C.
After continuously driving in an atmosphere of% RH for 1000 hours, the light emitting surface was observed to examine the occurrence of dark spots. The organic EL device in which no dark spot was detected on the light emitting surface was evaluated as ◯, and the organic EL device in which dark spot was generated was evaluated as × to evaluate the light emission yield.

As can be seen from the investigation results in Table 1, in the organic EL element hermetically sealed by using the sealing member 5 provided with the organic resin coating film 5b according to the present invention, the sealing adhesiveness, the light emission step It was excellent for any of the distillates. On the other hand, when the encapsulant C having the organic resin coating film 5b made of a normal polyester resin coating material is used, the adhesive / organic resin coating film interface peels in the shear test, and the luminescence yield is low. It was an evaluation. A low emission yield means that oxygen, moisture, etc. have penetrated into the inside of the organic EL element through the gap generated by the interfacial peeling to deteriorate the organic light emitting layer 3.

[0025]

[0026]

As described above, the organic E of the present invention is used.
The encapsulant for L elements has an organic resin coating film in which OH groups are oriented on the surface of the coating film provided on the base metal plate. Therefore, UV curing epoxy adhesive is used to seal and adhere to a transparent substrate such as glass. At this time, the organic EL element is hermetically sealed with a high airtightness without causing the interfacial peeling of the adhesive / organic resin coating film which causes a gap that causes the penetration of oxygen, water and the like. for that reason,
Provided is an organic EL element which exhibits excellent emission characteristics for a long period without deterioration of the organic emission layer due to oxygen, moisture and the like. Moreover, since the organic resin coating film acts as an insulator, a short circuit due to the contact between the organic EL element and the base metal plate is prevented, and the organic resin coating film is used as a sealing material suitable for a display panel that is strongly required to be thin. .

[Brief description of drawings]

FIG. 1 Organic EL that is hermetically sealed using a conventional sealing can
Cross section of the device

FIG. 2 is a sectional view of an organic EL element hermetically sealed using a sealing can according to the present invention.

[Explanation of symbols]

1: Transparent substrate 2: Anode electrode 3: Organic light emitting layer 4: Cathode electrode 5: Sealing member Base metal plate 5a: 5b: Organic resin coating film in which OH groups are oriented on the coating film surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuma Awa             7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel             Technical Research Institute Co., Ltd. (72) Inventor Kenji Koshiishi             7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel             Technical Research Institute Co., Ltd. F-term (reference) 3K007 AB08 AB11 AB12 AB13 AB15                       BB01 DB03 FA02

Claims (3)

[Claims] 1. An organic resin coating film is provided on at least a surface of a base metal plate or a metal foil facing a transparent substrate of an organic EL device, and OH groups are oriented on the surface of the organic resin coating film. A sealing material for an organic EL element, which is excellent in sealing adhesion. 2. The encapsulating material for an organic EL device according to claim 1, wherein the organic resin coating film is made of an epoxy resin paint. 3. The organic EL film according to claim 1, wherein the organic resin coating film is formed from an organic resin coating material containing a silane compound.
Device encapsulant.