JP2005322432A - Organic el element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element and its manufacturing method wherein it is possible to maintain a stable light emitting characteristic over a long period and possible to make it inexpensive in a manufacturing process by preventing leakage of water as much as possible. <P>SOLUTION: This is the organic EL element utilizing a material in which a filler having both thixotropic characteristic and a water adsorption action is internally attached as a sealing material of the outer peripheral face of the element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescent device capable of extracting light emission on the anode side of the device and a method for manufacturing the same, and more particularly to a sealing method for a thin type display that emits light by applying an electric field to an organic light emitting layer. is there.

  The structure of the organic EL element currently under development is a sandwich structure in which an organic light emitting layer is sandwiched between two electrodes on a lower glass substrate. In order to allow light from the organic light emitting layer to be extracted outside. In addition, one of the electrodes is transparent, and generally an ITO (Indium Tin Oxide) transparent electrode is used for the anode. Furthermore, the outer peripheral surface of the organic light emitting layer is sealed with a sealing material, and emits light when a voltage is applied by an external drive circuit.

  Organic EL elements that emit light based on the above principle are used for displays and display elements such as in-vehicle components and mobile phones because they are excellent in visibility and flexibility and have various coloring properties.

  By the way, although it is a display which has these characteristics, on the other hand, the problem that an organic EL element is generally very weak to moisture is known well. As an example, when the moisture contained in the environmental atmosphere at the time of sealing the glass substrate which forms the organic light emitting layer in the organic EL element or the moisture passing through the defective portion of the sealing layer enters, the dark spot and A non-light-emitting region is generated, and there is a problem of lifetime such that light emission cannot be maintained.

As a measure for solving the problem relating to the lifetime, conventionally, in contrast to claims 1 to 10, there is a method of sealing using a cationic curing type ultraviolet curing adhesive as a sealing member of the outer peripheral portion of the organic EL element. Known (Patent Documents 1 and 2). Furthermore, a method of sealing the outer peripheral portion of the organic EL element by using a barrier laminate structure in which two or more barrier substrates made of a barrier coat layer and a barrier layer base are laminated is also known.
JP-A-10-241858 JP-A-10-233283 JP 2002-134271 A

  As shown in Patent Documents 1 and 2, even if the organic EL element is sealed with a cationic curing type ultraviolet curable adhesive, moisture intrusion or sealing from the adhesive itself is performed. Intrusion from the interface cannot be completely prevented, and there is a problem that a dark spot is gradually generated or enlarged, and the element is deteriorated and finally becomes unusable. Also, as disclosed in Patent Document 3, there is a method of sealing using a barrier laminate structure, but there is a problem that the manufacturing process becomes complicated and the cost increases.

  Therefore, the present invention has been made in view of the above-mentioned problems. By preventing moisture from entering as much as possible, an organic material that can maintain stable emission characteristics over a long period of time and can be manufactured at low cost in the manufacturing process. It is an object of the present invention to provide an EL element and a manufacturing method thereof.

In order to solve the above-described problems, the present invention provides an organic EL element in which an organic compound is provided between a pair of electrodes composed of an anode and a cathode facing each other and the pair of electrodes. It is proposed to use an organic material containing a filler that has both thixotropic properties and moisture adsorption as a sealing material.
It is also proposed that the filler is a porous filler.
It is also proposed that the organic material to which the filler is internally added is an epoxy adhesive.
It is also proposed that the porous filler is silica-based.
It is also proposed that the epoxy adhesive is photocationic polymerization.
It is also proposed that the sealing material has a width of 3.0 mm or less and a thickness of 0.1 mm or less.

According to the present invention, the following effects can be obtained by internally adding a filler having both thixotropic properties and hygroscopic action into an organic material as an organic EL sealing material.
1. The organic EL element is excellent in long-term stability because the amount of water vapor reaching the inside of the element is reduced because the filler containing water vapor in the air entering from outside the sealing of the organic EL element actively absorbs moisture. Can be provided.
2. Since the sealing material has thixotropic properties, it can be precisely applied by a dispenser and can be manufactured at low cost.

  In the present invention, by adding a filler having both thixotropic properties and moisture adsorption action in the sealing material on the outer peripheral surface of the organic EL element, the moisture adsorption action can be applied to deterioration of the element due to moisture entering from the outside. It is possible to maintain the moisture blocking property for a long period of time by the filler having, and the thixotropic property enables precise sealing work by a dispenser which is a simple device, and a highly reliable organic EL element can be obtained. It can be provided at low cost.

  A typical view of the present invention is shown in FIG. In FIG. 1, after forming an organic EL element of reference numeral 3 composed of a transparent electrode, an organic light emitting layer, and an electrode on a glass substrate of reference numeral 1 by a film forming apparatus such as a vapor deposition device or a spin coater, reference numeral 2 as shown in FIG. The sealing material 4 is applied to the outer peripheral portion of the sealing glass by a dispenser, and the glass substrate 1 and the sealing glass 2 are sealed and cured through the sealing material 4, and then the electrode is connected to the external circuit. By connecting to, the organic EL element of the present invention emits light.

  Here, the details of the present invention are shown in FIG. Here, reference numeral 6 in FIG. 3 indicates a filler, and reference numeral 7 indicates an organic material.

  The filler of the code | symbol 6 is a filler which has a water | moisture-content adsorption | suction action and thixotropic property, and specifically, a silica (a synthetic silica is included), a kaolin, a delaminated kaolin, an aluminum hydroxide, titanium white, a heavy calcium carbonate, a light carbonate Calcium, calcium sulfate, barium sulfate, titanium dioxide, calcined kaolin, talc, zinc oxide, zinc carbonate, zinc sulfide, alumina, particulate alumina, diatomaceous earth, calcined diatomaceous earth, aluminum silicate, calcium silicate, magnesium silicate, magnesium oxide, Examples thereof include mineral pigments such as magnesium carbonate, aluminosilicate, colloidal silica, activated clay, bentonite, zeolite, sericite, and lithopone, fine particles such as porous pigments and organic pigments, porous fine particles, and hollow fine particles.

  Organic materials include epoxy resins, cyclic polyolefin resins, polyvinyl chloride resins, poly (meth) acrylic resins, polyethylene terephthalate resins, various nylon polyamide resins, polyimide resins, polyamideimide resins, and polyaryl phthalates. Examples include resins, silicone resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polyurethane resins, acetal resins, and copolymers obtained by copolymerizing the above-mentioned precursors.

  As an example, a photocationic polymerization liquid resin (KR695A / Asahi Denka Kogyo Co., Ltd.) is used as the organic material, and synthetic silica (trade name) is used as a filler having both thixotropic properties and hygroscopicity in the resin. : Microid / manufactured by Toyo Kagaku Kogyo Co., Ltd.) was prepared as a sealing material, and the sealing material was precisely applied to a width of 1 mm and a thickness of 4 microns with a dispenser, and cured with a UV irradiation apparatus.

  These sealing steps can suppress the generation of dark spots, which has been a major problem until now, immediately after assembly by controlling the moisture concentration in the glove box (not shown) to 10 ppm or less for sealing. became. Also, for long-term reliability, a continuous durability test of 1000 hours was performed under an atmospheric condition of 60 ° C./90% RH, but no deterioration in light emission characteristics such as luminance deterioration was confirmed, and there was no occurrence of dark spots or the like. An organic EL device and a method for producing the same were obtained.

(First embodiment)
A typical view of the present invention is shown in FIG. Reference numeral 1 denotes a glass substrate, and reference numeral 3 denotes an organic EL element including a transparent electrode, an organic light emitting layer, and an electrode by a film forming apparatus such as a vapor deposition apparatus or a spin coater. Here, a detailed manufacturing method of the organic EL element will be described below.

[Cr electrode formation]
On the glass substrate, a Cr target was formed into a thickness of 100 nm as a positive electrode by DC sputtering of a Cr target. At this time, a 3 mm stripe was formed using a film formation mask. Ar gas was used under the conditions of 0.2 Pa pressure and 300 W input Pw conditions.

[Atmospheric release]
Next, the substrate was taken out of the sputtering apparatus, ultrasonically cleaned with acetone and isopropyl alcohol (IPA) in sequence, then boiled and washed with IPA, and then dried. Further, UV / ozone cleaning was performed.

[Preprocessing]
The sample was transferred to an organic EL vapor deposition apparatus and evacuated, and 50 W RF power was applied to a ring electrode provided near the substrate in the pretreatment chamber to perform an oxygen plasma cleaning process. The oxygen pressure was 0.6 Pa and the treatment time was 40 seconds.

[Hole transport layer formation]
The substrate was moved from the pretreatment chamber to the film formation chamber, and the film formation chamber was evacuated to 1 × 10E (−4) Pa. Then, αNPD having hole transportability was formed at a film formation rate of 0.2 by resistance heating vapor deposition. A film was formed under a condition of ˜0.3 nm / sec, and a 35 nm-thick hole transport layer was formed. Note that the hole transport layer, the light emitting layer, and the electron injection layer were deposited on predetermined portions by using the same deposition mask. The predetermined portion is a portion where the Cr is exposed on the substrate (pixel electrode).

[Light emitting layer formation]
Subsequently, Alq ₃ as an alkylate complex was formed on the hole transport layer by a resistance heating vapor deposition method under the same film formation conditions as the hole transport layer to form a 15 nm-thick film and a light emitting layer.

[Electron injection electrode layer formation]
Next, each deposition rate is adjusted to form a film on the light emitting layer by resistance heating co-evaporation so that Alq ₃ and cesium carbonate (Cs ₂ CO ₃ ) are mixed at a film thickness ratio of 9: 1. An electron injection layer having a thickness of 35 nm was formed. Specifically, the material set in each evaporation boat is evaporated by resistance heating method, the organic layer is ~ 5 A / S, and the co-deposition layer is also adjusted to the respective boat current value. Film formation was performed at a speed.

[Cathode (transparent conductive film) formation]
Finally, the substrate is transferred to another film formation chamber, and the Cr pixel electrode is covered by a mask film formation so that the film thickness becomes 130 nm by a DC magnetron sputtering method using an ITO target on the electron injection layer to form a Cr stripe. A cathode K was formed so as to intersect.

During film formation, an H concentration gradient was formed in the film thickness direction of the cathode K by decreasing the H ₂ O gas supply amount as the film formation time elapses. The concentration gradient of H is 5 × 10 ²¹ to 1 × 10 ²² atom / cc in the vicinity of the electron injection electrode layer interface, and the concentration is decreased continuously in the film thickness direction, near the film thickness center of the cathode K. The H content was on the order of 10 ²⁰ atoms / cc (65 nm from the electron injection electrode layer interface). As described above, a strong magnetic field type magnet is disposed on the back surface of the ITO target, and low voltage sputtering is possible.

Deposition conditions include room temperature film formation without substrate heating, film formation pressure of 1.0 Pa, Ar, H ₂ O and O ₂ gases, flow rates of 500, 1.5, 5.0 scccm, and input power applied to the target. Formed a film with ITO: 500W. The transmittance was 85% (at 450 nm), and the specific resistance value was 8.0E ⁻⁴ Ωcm.

  As described above, the anode, the hole transport layer, the light emitting layer, the electron injection electrode layer, and the cathode were provided on the glass substrate denoted by reference numeral 1 to form an organic EL light emitting device.

[Sealing process]
Next, in order to give barrier property with the sealing material which the water vapor | steam in air does not permeate into the formed organic electroluminescent light emitting element, it transfers to a sealing process.

  As the sealing material used here, a photocationic polymerization liquid resin (KR695 / manufactured by Asahi Denka) is used. As a filler having thixotropic properties and moisture adsorption action in the liquid resin, here, synthetic silica (trade name) : Microid / manufactured by Tokai Chemical Industry Co., Ltd.) was prepared as a sealing material 4 with a 50 wt% internal addition using a mixing / dispersing device.

  The prepared sealing material 4 is poured into a syringe for a dispenser with a reference number 5, and after the injection, as shown in FIG. 2, the sealing material 4 is placed on the outer periphery of the sealing glass with a reference number 2 by a dispenser with a width of 1 mm, Precision coating was performed with a thickness of 4 microns. Here, precise application to the outer periphery of the organic EL element with the above dimensions is impossible with a liquid resin having no thixotropic property, and thixotropic property is imparted by a filler as in the present sealing material (thixotropic coefficient: 4). .5) It becomes possible by doing.

Next, the glass substrate 1 and the sealing glass 2 were sealed with a sealing material 4 and cured by an ultraviolet irradiation device (manufactured by EX250 HOYA-SHOTT) 8. In addition, the ultraviolet irradiation intensity at that time is 100 mW / cm ² and the amount of light is 3,000 mJ / cm ² .

  The sealing process described above can suppress the generation of dark spots, which has been a major problem until now, immediately after assembly by controlling the moisture concentration in the glove box (not shown) to 10 ppm or less for sealing. It became.

[Element evaluation]
In long-term reliability, as shown in Table 1, a continuous durability test was conducted for 1000 hours under an atmospheric condition of 60 ° C./90% RH. Since there was no permeation of moisture, there was almost no decrease in light emission characteristics such as luminance deterioration, and there was no occurrence of dark spots and the like, and a stable organic EL device and a method for producing the same could be obtained.

(First comparative example)
The first comparative example shows a case where a filler having both thixotropic properties and moisture adsorption action is not added as an organic EL sealing material to the first embodiment.

  As the sealing material used here, a photocationic polymerization type liquid resin (KR695 / manufactured by Asahi Denka) was used, and no filler was added.

  The said sealing material 4 is inject | poured in the syringe for dispensers of the code | symbol 5, and after injection | pouring, as shown in FIG. Precision coating was performed with micron.

Next, the glass substrate 1 and the sealing glass 2 were sealed with a sealing material 4 and cured by an ultraviolet irradiation device (manufactured by EX250 HOYA-SHOTT) 8. In addition, the ultraviolet irradiation intensity at that time is 100 mW / cm ² and the amount of light is 3,000 mJ / cm ² .

  In the sealing step described above, sealing was performed by controlling the water concentration in the glove box (not shown) to 10 ppm or less.

[Element evaluation]
The assembled organic EL device was subjected to a continuous durability test for 1000 hours under an atmospheric condition of 60 ° C./90% RH. Excess water entered from the sealing material and the sealing interface, and the luminance was as shown in Table 1. It became an organic EL device having poor stability and poor stability.

It is sectional drawing of the organic EL element of this invention. It is the figure which has apply | coated the sealing material on sealing glass with the dispenser. It is an enlarged view of the sealing part of this invention. It is the figure which has hardened the sealing material with UV lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Sealing glass 3 Organic EL element 4 Sealing material 5 Syringe for dispenser 6 Filler 7 Organic material 8 UV irradiation apparatus

Claims (6)

  In an organic EL element in which an organic compound is provided between a pair of electrodes, which are an anode and a cathode facing each other, and an organic compound between the pair of electrodes, thixotropic property and moisture adsorption action are used as a sealing material for the outer peripheral surface of the organic EL element. An organic EL element characterized by using an organic material internally added with a filler.   The organic EL device according to claim 1, wherein the filler according to claim 1 is a porous filler.   2. An organic EL device, wherein the organic material to which the filler according to claim 1 is internally added is an epoxy adhesive.   3. The organic EL device according to claim 2, wherein the porous filler is based on silica.   4. The organic EL device according to claim 3, wherein the epoxy adhesive according to claim 3 is cationic photopolymerization.   6. The organic EL manufacturing method according to claim 1, wherein the sealing material has a width of 3.0 mm or less and a thickness of 0.1 mm or less.

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