JP2006114399A - Organic EL device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element in which light-emitting characteristics stabilized over a long period of time is maintained by preventing invasion of moisture from the outside, and which can be fabricated inexpensively in a manufacturing process. <P>SOLUTION: As a sealing film of the organic EL element, a sealing film satisfying following conditions is used. (a) The moisture amount contained in a transparent film is 100 ppm or less, (b) transmittance at 400 nm to 700 nm is 80% or more at 100 μm of film thickness, (c) linear expansion coefficient is 10 ppm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an organic light emitting device.

  An organic EL device having a sandwich structure in which an organic light emitting layer is sandwiched between two electrodes on a lower film substrate is known. In order to allow light from the organic light emitting layer to be extracted outside, One of them 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.

  An organic EL element that emits light based on the above principle is excellent in visibility or flexibility, and has various color development properties. Therefore, the organic EL element is used in displays and display elements such as in-vehicle components and mobile phones.

  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 with respect to gas and water vapor | steam is known well. As an example, the moisture and the gas permeating through the defective portion of the sealing layer enter in the environmental atmosphere when sealing the film substrate forming the organic light emitting layer in the organic EL element, A non-light-emitting region called a dark spot 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 of the organic EL element, a technique using a gas barrier film having a silicon oxide film formed by a plasma CVD method on one side or both sides of a film substrate as a sealing film is known. (Patent Document 1).

  Furthermore, a technique using a gas barrier film in which an inorganic thin film is provided on a support having a hydrophilic surface where a hydrophilic graft polymer chain exists as a sealing film is known (Patent Document 2).

JP 2002-192646 A JP 2004-136638 A

  As shown in Patent Documents 1 and 2, even if the gas barrier property is improved by forming a silicon oxide film on the film surface as a sealing film by a plasma CVD method, the film is subjected to a temperature impact test during a product durability test. There was a problem that the gas barrier property was impaired due to micro cracks generated in the inorganic film due to the stress due to the difference in linear expansion coefficient between the inorganic film and the inorganic film.

Therefore, the present invention has been made in view of the above-described problems, and by maintaining moisture emission characteristics stable over a long period of time by preventing moisture from entering from the outside, the present invention can be manufactured at a low cost in the manufacturing process. An object of the present invention is to provide an organic EL element capable of satisfying the requirements.

The present invention provides an organic EL in which an organic layer is provided between a pair of electrodes composed of an anode and a cathode opposed to each other and the pair of electrodes, and a sealing structure is provided on an outer peripheral portion of the organic EL element. In the element, as the sealing film of the organic EL element formed from the inside in the order of the organic EL protective layer, the filling layer, and the sealing film,
(A) The water content contained in the transparent film is 100 ppm or less.
(B) The transmittance from 400 nm to 700 nm is 80% or more at a film thickness of 100 μm.
(C) The linear expansion coefficient is 10 ppm or less.
An organic EL element characterized by using a sealing film showing the above is provided.

  According to the present invention, as a sealing film for the organic EL element, which is formed in the order of a film substrate, an organic EL element, an organic EL protective layer, a filling layer, and a sealing film as a filler for the organic EL element, (A) A structure using a sealing film having a water content of 100 ppm or less, (b) a transmittance from 400 nm to 700 nm of 80% or more at a film thickness of 100 μm, and (c) a linear expansion coefficient of 10 ppm or less. By doing so, the following effects can be obtained.

  Since the moisture content of the transparent film used as the sealing film for the organic EL element is 100 ppm or less during the assembly of the organic EL element, the moisture reaching the inside of the element can be reduced, and thus an organic EL element having excellent stability is provided. be able to.

  In addition, since the linear expansion coefficient of the film base material is as low as 10 ppm, a product durability test is performed after an inorganic film such as a silicon nitride film is formed on the film base material by CVD or vacuum evaporation as before. Stable element performance can be obtained without causing microcracks in the inorganic film due to the stress caused by the difference in linear expansion coefficient between the film and the inorganic film generated during the temperature shock test.

<Embodiment>
A typical view of the present invention is shown in FIG. In FIG. 1, an organic EL element 3 including a transparent electrode, an organic light emitting layer, and an electrode is formed on a film substrate 1 by a film forming apparatus such as a vapor deposition apparatus or a spin coater, and a protective film is further formed by a vapor deposition apparatus 4.

  Further, as shown in FIG. 2, after forming the inorganic film 5 on the sealing film surface 2 by a film forming apparatus such as CVD or vacuum vapor deposition in another process, it is bonded to the organic EL element 3 side. FIG. 3). Thereafter, the periphery of the film substrate 1 and the sealing film 2 is sealed with an epoxy sealant 6 with a precision dispenser to form an organic EL element (FIG. 4).

  After sealing, the organic EL element of the present invention emits light by connecting the electrode to an external circuit.

  Here, about the detail of the sealing film of this invention, the part of a film is expanded and it shows in FIG.

  First, it is preferable to internally add a filler 7 that adsorbs moisture from the outside and a very small amount of moisture remaining inside the element into the sealing film 5.

  Here, the filler 7 is a filler having a moisture adsorption action, and specifically, silica (including synthetic silica), kaolin, deramikaolin, aluminum hydroxide, titanium white, heavy calcium carbonate, light calcium carbonate, 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, magnesium carbonate, alumino Examples thereof include mineral pigments such as silicate, 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 phthalate resins. , Silicone resins, polysulfone resins, polyphenylene sulfide resins, polyether sulfone resins, polyurethane resins, acetal resins, and copolymers obtained by copolymerizing the above listed precursors.

  Here, for example, the sealing film 2 is used as a transparent film, and a molecular sieves (3A type / manufactured by Sakai Kogyo), which is a synthetic zeolite-based desiccant, is adsorbed in order to adsorb moisture from the outside. A polyimide film was used.

  Next, in order to remove the moisture contained in the polyimide film, the moisture content was reduced to 1 ppm by vacuum heating.

  In order to improve the gas barrier property of the transparent polyimide film with reduced moisture, a silicon oxide film is formed to a thickness of about 500 nm by a CVD apparatus (not shown).

  After the film formation, the organic EL element side substrate formed up to the protective film 4 and the sealing film surface on which the inorganic film is formed are bonded together.

  After bonding, the outer peripheral part of the sealing film 2 was sealed again by the side sealing 6 in order to ensure the stability of the organic EL element.

  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. In addition, in the long-term reliability, a continuous durability test for 1000 hours was performed under the atmospheric condition of 60 ° C./90% RH. An organic EL element and a manufacturing method thereof were obtained.

  The organic EL element of the present invention includes a light source for illumination, a light source for exposing an image on a photoreceptor in an electrophotographic image forming apparatus, an electrophotographic image forming apparatus having such a light source, a vehicle-mounted display, and a digital display. The present invention is applicable to a display unit of a camera or an electrophotographic image forming apparatus, a television, a display for a personal computer, and the like.

A typical view of the present invention is shown in FIG. Here, 1 is a film substrate, and 3 is an organic EL element comprising 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 DC sputtered to form a Cr film having a thickness of 100 nm as an anode A. At this time, a 3 mm stripe was formed using a film formation mask. Using Ar gas, the pressure was 0.2 Pa, and the input Pw was 300 W.
[Atmospheric release]
Next, the substrate was taken out from the sputtering apparatus, ultrasonically washed with acetone and isopropyl alcohol (IPA) in sequence, then boiled and washed with IPA, and then dried. Further, UV / ozone cleaning was performed.
[Preprocessing]
After moving to an organic EL element deposition apparatus and evacuating, an oxygen plasma cleaning process was performed by applying 50 W RF power to a ring electrode provided near the substrate in the pretreatment chamber. The oxygen pressure was 0.6 Pa and the treatment time was 40 seconds.
[Hole transport layer formation]
The substrate is moved from the pretreatment chamber to the film formation chamber, and after the film formation chamber is evacuated to 1 × 10E (−4) Pa, αNPD having a hole transporting property is formed by a resistance heating vapor deposition method at a film formation rate of 0.2˜ A film was formed under the condition of 0.3 nm / sec to form a 35 nm-thick hole transport layer. In addition, the hole transport layer, the light emitting layer, and the electron injection layer were vapor-deposited on predetermined portions by using the same vapor deposition mask. The predetermined portion is a portion where Cr is exposed on the substrate (pixel electrode).
[Light emitting layer formation]
Subsequently, Alq3, which is an alkylate complex, was formed on the hole transport layer by a resistance heating vapor deposition method under a film formation condition similar to that of the hole transport layer, and a light emitting layer was formed.
[Electron injection electrode layer formation]
Next, a film is formed on the light-emitting layer by adjusting each vapor deposition rate so that Alq3 and cesium carbonate (CsCO ₃ ) are mixed at a film thickness ratio of 9: 1 by resistance heating co-evaporation. A 35 nm thick electron injection layer was formed. Specifically, the material set in each evaporation boat is evaporated by resistance heating method, the organic layer is ~ 5A / S, and the co-deposition layer is also adjusted for each boat current value. Film formation was performed at a speed.
[Cathode (transparent conductive film) formation]
Finally, the substrate is moved to another film formation chamber, and the film thickness is 130 nm by DC magnetron sputtering using an ITO target on the electron injection layer, and the Cr pixel electrode is covered by mask film formation. The cathode K was formed so as to cross the Cr stripe.

During film formation, a 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 such that H is 5 × 10 ²¹ to 1 × 10 ²² atoms / cc in the vicinity of the interface of the electron injection electrode layer, the concentration is continuously decreased in the film thickness direction, and the vicinity of the film thickness center of the cathode K The H content was set to the order of 10 ²⁰ atoms / cc at (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.

The deposition conditions are room temperature deposition without substrate heating, deposition pressure of 1.0 Pa, Ar, H ₂ O and O ₂ gases, flow rates of 500, 1.5 and 5.0 sccm, respectively, applied to the target. The film was formed with an input power of ITO: 500 W. 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 moves to a sealing process.

  As the transparent film of the sealing film of reference number 2 used here, a transparent film having a thickness of 50 μm is added with 20% by weight of molecular sieves (3A type / manufactured by Sakai Kogyo Co., Ltd.), a synthetic zeolite-based desiccant to adsorb moisture from the outside. A polyimide film was used.

  Next, in order to remove the moisture contained in the polyimide film, the moisture content was reduced to 1 ppm by vacuum heating.

  In order to improve the gas barrier property of the transparent polyimide film with reduced moisture, a silicon oxide film is formed to a thickness of about 500 nm by a CVD apparatus (not shown).

  After the film formation, the organic EL element side substrate formed up to the protective film 4 and the sealing film surface on which the inorganic film is formed are bonded together.

  After bonding, the outer peripheral part of the sealing film 2 was sealed again by the side sealing 6 in order to ensure the stability of the organic EL element.

  Here, as the sealing material 6, a photocationic polymerization type liquid resin (KR695 / manufactured by Asahi Denka) is used, and here, synthetic silica (trade name: Microid / A material in which 50 wt% was internally added by a mixing / dispersing device was used.

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 and sealing. became.
[Element evaluation]
As for long-term reliability, as shown in Table 1, a continuous durability test was performed for 1000 hours under an atmospheric condition of 60 ° C./90% RH, but almost no deterioration in light emission characteristics such as luminance deterioration was confirmed (luminance: 95 %), No dark spots and the like, and a stable organic EL device and a method for producing the same were obtained.
<Comparative Example 1>
The first comparative example shows a case where a transparent polyimide film having a large amount of moisture contained in the film and a large linear expansion coefficient is used as the sealing film for the organic EL element, as compared with Example 1.

  After forming an inorganic film with a thickness of about 500 nm by CVD on the sealing film 2 having physical properties of the organic EL element substrate formed up to the protective film 4 on the film substrate 1 and moisture content of 3500 ppm and linear expansion coefficient of 50 ppm, sealing The process proceeds to the sealing step with the material 6.

  As the sealing material 6 used here, the photocation polymerization type liquid resin (KR695 / manufactured by Asahi Denka) and the moisture adsorbing filler were the same as those in Example 1.

  The said sealing material 6 was inject | poured in the syringe for precision dispensers, and as shown in FIG. 4, the sealing material 6 was precisely apply | coated to the outer peripheral part of the sealing film 2 with the dispenser after injection | pouring.

  After the application, the film substrate 1 and the sealing film 2 were sealed with a sealing material 6 and cured by heating. The heating condition at that time is 80 ° C./30 minutes.

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 penetrated from the sealing material and the sealing interface, and the luminance was as shown in Table 1. Deterioration progressed (luminance: 30.5%), resulting in an organic EL device with poor stability.

It is sectional drawing of the organic EL element of this invention. It is the figure which formed the inorganic film | membrane on the sealing film by CVD. It is a figure at the time of bonding the glass substrate formed even to the protective film, and the sealing film which formed the inorganic film. It is a figure which has applied the sealing agent to the outer peripheral part of the sealing film with the precision dispenser (side sealing). It is an enlarged view of the sealing film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film substrate 2 Sealing film 3 Organic EL element 4 Protective film 5 Transparent filling layer 6 Sealing material 7 Moisture adsorption filler

Claims (8)

In an organic EL element in which an organic layer is provided between a pair of electrodes composed of an anode and a cathode facing each other and the pair of electrodes, and a sealing material is provided on an outer peripheral portion of the organic EL element.
As the sealing film of the organic EL device formed from the inside in the order of the organic EL protective layer, the filling layer, and the sealing film, the following conditions:
(A) The water content contained in the transparent film is 100 ppm or less. (B) The transmittance at 400 nm to 700 nm is 80% or more when the film thickness is 100 μm. (C) A transparent film satisfying a linear expansion coefficient of 10 ppm or less is used. Organic EL element to be used.   2. The organic EL device according to claim 1, wherein a gas barrier layer made of silicon oxide and / or silicon nitride is laminated on at least one of the sealing film substrates.   The organic EL device according to claim 1, wherein the sealing film contains a solid hygroscopic agent.   3. The organic EL device according to claim 2, wherein the solid moisture absorbent is a porous moisture absorbent such as zeolite or silica.   The organic EL device according to claim 2, wherein an average particle size of the solid moisture absorbent is 1 μm or less.   The organic EL element according to claim 1, wherein the sealing film has a thickness of 1 μm to 100 μm.   The organic EL element according to claim 1, wherein a polyimide film is used as the sealing film.   8. The organic EL device according to claim 1, wherein the organic EL device has a top emission structure.

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