JP2006286242A - Flexible organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a long-lifetime flexible organic EL element, by preventing atmospheric air and oxygen from entering inside it from an adhesive at its side part or an outer periphery part of a sealing plate to degenerate its cathode layer and organic luminescent medium layer, in an organic EL element forming at least an anode layer, the organic luminescent medium layer and the cathode layer on a flexible transparent substrate. <P>SOLUTION: After carrying out a first sealing process by bonding together a transparent substrate with an anode layer, an organic luminescent layer, and a cathode layer formed and a sealing plate with an adhesive, a second sealing process is carried out, by melting the outer periphery part of the sealing plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible organic electroluminescence element (hereinafter referred to as a flexible organic EL element). Specifically, a flexible substrate and a flexible sealing plate having good water vapor and gas barrier properties are used instead of a glass substrate and a glass or metal sealing plate, are light and difficult to break, can easily be enlarged, and can be bent. The present invention relates to a flexible organic electroluminescence element.

  An organic EL element, which is one of flat panel displays, has a structure in which a plurality of organic light emitting medium layers including an organic light emitting layer are sandwiched between an anode layer and a cathode layer, and light emission occurs when a current is passed. Examples of the organic light emitting medium layer include a hole transport layer, a hole injection layer, an electron injection layer, and an electron transport layer in addition to the organic light emitting layer. Since the organic EL element is a self-luminous type, it has characteristics of high brightness, high viewing angle, and low voltage driving.

  The cathode layer used in the organic EL element is formed of a metal or an alloy such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, Yb, MgAg, AlLi, or CuLi. Or the alloy is chemically unstable. When the cathode layer comes into contact with moisture and oxygen, it causes oxidation and corrosion. The oxidized and corroded place becomes a non-light emitting portion called a dark spot. This non-light-emitting portion grows quickly, so that the device life is shortened with a decrease in device brightness. Also, the organic light emitting medium layer tends to be altered by moisture and oxygen. Therefore, when putting an organic EL element into practical use, it is necessary to seal the entire organic EL element for the purpose of protecting the cathode layer and the organic light emitting medium layer from moisture and oxygen. Currently, when the substrate is a glass substrate in an organic EL element, sealing of the entire element is realized by bonding a glass or metal sealing plate to the glass substrate via an adhesive.

  However, the organic EL element of the glass substrate has drawbacks such as being heavy and easily broken, difficult to increase in area, and not flexible. In order to solve these problems, a transparent film substrate and a film sealing plate made of plastic are used instead of a glass substrate and a glass or metal sealing plate. Thereby, a flexible organic EL element can be produced. However, since the film substrate generally has a low barrier property against moisture and oxygen, moisture and oxygen in the atmosphere permeate the film substrate and the film sealing plate and enter the organic EL element, and the cathode layer and the organic light emitting medium layer As a result, the life of the device is shortened.

  Therefore, a method for forming a transparent barrier layer of a metal oxide such as silicon oxide or a metal nitride such as silicon nitride on one side or both sides of the transparent film substrate and the film sealing plate has been proposed. As a result, a significant improvement in the barrier properties of the transparent film substrate with a transparent barrier layer and the film sealing plate was confirmed, and an improvement in the lifetime was recognized from the flexible organic EL elements produced with these substrates and the sealing plate. .

As the adhesive used for sealing the flexible organic EL element, a thermosetting resin or a UV curable resin is generally used. As a sealing method, there has been proposed a method in which a film substrate and a film sealing plate are bonded together with an adhesive (for example, see Patent Document 1). However, when the flexible substrate and the flexible sealing plate are bonded together with an adhesive in this way, oxygen and moisture are mixed into the element from the adhesive on the side portion of the organic EL element, that is, the outer peripheral portion of the sealing plate. As a result, the lifetime of the element is shortened. Although the lifetime of the element was greatly improved by using a film having a barrier property, there was a problem that the lifetime was still short compared with the case where a glass substrate and a glass or metal sealing plate were used.
JP 2004-105379 A

  As a problem in the present invention, in an organic EL element in which at least an anode layer, an organic light emitting medium layer and a cathode layer are formed on a flexible transparent substrate, and the transparent substrate and the sealing plate are bonded with an adhesive, Prevents moisture and oxygen in the atmosphere from entering the organic EL element from the adhesive on the side part of the organic EL element, that is, the outer periphery of the sealing plate, and altering the cathode layer and the organic light emitting medium layer of the organic EL element. An object is to obtain a long-life flexible organic EL device.

  In order to solve the above-mentioned problems, the invention according to claim 1 is to provide a flexible sealing by forming at least an anode layer, an organic light emitting medium layer including an organic light emitting layer, and a cathode on a flexible transparent substrate. In a flexible organic EL element sealed with a plate, a transparent substrate on which an anode layer, an organic light emitting medium layer, and a cathode layer are formed and a sealing plate are bonded together by an adhesive, and then sealed. A flexible organic EL element characterized in that the second sealing was performed by melting the outer peripheral portion of the plate.

  The invention according to claim 2 is characterized in that the sealing plate is a glass film, and the glass film is melted by laser irradiation and sealed with a transparent substrate. A flexible organic EL element was obtained.

  In the present invention, the transparent substrate on which the organic light emitting medium layer is formed and the sealing plate are bonded and sealed with an adhesive, and the first sealing is performed. By performing the second sealing with the sealing plate and performing double sealing, moisture and oxygen in the atmosphere are released from the side portion of the organic EL element, that is, from the outer peripheral portion of the sealing plate even when used for a long time. Intrusion was prevented and a long-life organic EL device could be obtained.

  In particular, a long-life organic EL device could be obtained by using a glass film that can be melted by a laser and has excellent moisture and oxygen barrier properties.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a schematic cross-sectional view showing one embodiment of the flexible organic EL element of the present invention. In the flexible organic EL device 100 of the present invention, an anode layer 21, an organic light emitting medium layer 31, and a cathode layer 22 are formed on a flexible transparent substrate 11, and a flexible sealing plate 12 is bonded to an adhesive 41. In this structure, the organic EL element side portion 51, that is, the outer peripheral portion of the sealing plate, is further sealed by being bonded and sealed.

  As described above, in the flexible organic EL element 100 of the present invention, the organic light emitting medium layer 31 and the second electrode 22 sandwiched between the transparent substrate 11 and the sealing plate 12 are bonded to the adhesive sealing layer 41 and the second electrode 22. In particular, it is possible to obtain a flexible organic EL element that is excellent in moisture and oxygen barrier properties from the organic EL element side portion 51 and is reliable.

Hereinafter, a method for producing the flexible organic EL element of the present invention will be described with reference to FIG. 2A to 2E are schematic cross-sectional views showing one of the methods for producing a flexible organic EL element of the present invention.

  First, the anode 21 is formed on the flexible transparent substrate 11 (see FIG. 2A). As the flexible transparent substrate 11, a resin material having excellent heat resistance, translucency, and flatness is preferable. Specific examples include polyethylene terephthalate (PET), polyethersulfone (PES), polyvinyl butyral (PVB), polyethylene-2,6-naphthalate (PEN), polyarylate (PAR), polyimide (PI), polyvinyl alcohol ( PVA), polycarbonate (PC), polyetherimide (PEI), cellulose triacetate (TAC) vinyl fluoride (PVF), and the like. More preferred is polyethersulfone (PES). Moreover, a glass film can also be used.

  The thickness of the flexible transparent substrate 11 needs to be comprehensively determined such as flexibility, transparency, and workability, but is generally 5 to 400 μm. Preference is given to 150 μm to 250 μm.

  In addition, a barrier layer (not shown) can be formed on one side or both sides of the first substrate in order to increase the moisture and oxygen barrier properties of the flexible transparent substrate 11. As a material used for the barrier layer, a metal oxide such as silicon oxide, silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxide, or a metal nitride can be used. Specifically, silicon nitride and silicon oxynitride having particularly good barrier properties, solvent resistance, and transparency are preferable.

  As a method for forming the barrier layer, a sputtering method or a CVD method is often used. Silicon oxide can be produced by sputtering and silicon nitride can be produced by CVD. The film thickness is in the range of 10 nm to 1000 nm, preferably 50 to 300 nm.

  In the present invention, if necessary, the surface of the transparent substrate 11 may be flattened to alleviate the unevenness of the surface of the transparent substrate 11, or the barrier layer may be protected from chemicals or mechanical shock by thermosetting or Using a UV curable resin, a planarizing layer can be formed on the surface of the transparent film substrate, and a protective layer can be formed on the surface of the barrier layer. Examples of the thermosetting resin include melamine type, acrylic type, 0-cresol novolac type, bisphenol type epoxy type, and urethane type. Examples of the UV curable resin include urethane diacrylate, epoxy diacrylate, and polyester diacrylate. The thickness of the planarization layer and the protective layer in the present invention is 0.5 μm to 20 μm. Preference is given to 1 μm to 5 μm.

  As an anode material for forming the anode layer 21 in the present invention, transparent electrode materials such as ITO (indium tin composite oxide), IZO (indium zinc composite oxide), tin oxide, zinc oxide, indium oxide, zinc aluminum composite oxide, etc. Is mentioned. ITO is preferable from the viewpoints of low resistance, solvent resistance, and transparency.

  The formation method of the anode layer 21 is roughly classified into a wet method, a physical method, and a chemical method. Examples of the wet method include a printing method and a coating method. Examples of physical methods include ion plating, sputtering, and vacuum deposition. Chemical methods include CVD and plasma CVD. In general, a sputtering method is employed when forming ITO. The thickness of the ITO film is in the range of 10 nm to 1000 nm. Preferable is 50 to 200 nm.

  Next, the organic light emitting medium layer 31 is formed on the anode layer 21 (see FIG. 2B). The organic light emitting medium layer 31 has an organic light emitting layer, and layers such as a hole transport layer, a hole injection layer, an electron injection layer, and an electron transport layer are stacked as necessary. The organic medium layer can be formed by vacuum deposition in vacuum, sputtering, ion plating, magnetron sputtering, CVD, plasma CVD, spin coating in air, dip coating, spray coating. There are various printing methods such as coating methods, gravure printing methods, offset printing methods, flexographic printing methods, and inkjet printing methods. When forming an organic light emitting medium layer by various coating methods and various printing methods in the atmosphere, it is necessary to dissolve or stably disperse the organic light emitting material in a solvent.

  In the case of forming the organic light emitting medium layer in a multilayer structure, examples of the organic light emitting medium layer include a two-layer structure including a hole transport layer and an organic light emitting layer from the anode side, an organic light emitting layer and an electron transport layer, and from the anode side. There are a three-layer structure including a hole transport layer, an organic light emitting layer, and an electron transport layer. Furthermore, it is possible to take a multilayer structure, and each layer may be formed on the anode layer sequentially. The film thickness of the organic light emitting medium layer is 500 nm or less, preferably 50 to 150 nm, even in a single layer configuration or a multilayer configuration.

  Examples of the hole transport material forming the hole transport layer include metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine, and metal-free phthalocyanines, quinacridone compounds, 1,1-bis (4-di- p-tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1 -Naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine and other aromatic amine-based low molecular hole injection and transport materials, poly (para-phenylene vinylene), polyaniline and other high It can be selected from molecular hole transport materials, polythiophene oligomer materials, and other existing hole transport materials.

  Examples of the organic light-emitting material forming the organic light-emitting layer include 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, and tris (8-quinolinolato) aluminum complex. , Tris (4-methyl-8-quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolato) aluminum complex, tris (4-methyl-5- Cyano-8-quinolinolato) aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8) -Quinolinolato) [4- (4-cyanophenyl) phenola G] aluminum complex, tris (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, Poly-2,5-diheptyloxy-para-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor, porphyrin phosphor, quinacridone phosphor, N, N'- Examples include dialkyl-substituted quinacridone phosphors, naphthalimide-based phosphors, N, N′-diaryl-substituted pyrrolopyrrole phosphors, and these are used alone or mixed with other low-molecular materials or polymer materials. Can do.

  Examples of the electron transport material forming the electron transport layer include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1 -Naphthyl) -1,3,4-oxadiazole and oxadiazole derivatives synthesized by Hamada et al. (Journal of Chemical Society of Japan, 1540, 1991) and bis (10-hydroxybenzo [h] quinolinolato) beryllium complex, Examples thereof include triazole compounds described in JP-A-7-90260.

  Next, the cathode layer 22 is formed on the transparent substrate 11 on which the anode layer 21 and the organic light emitting medium layer 31 are formed (see FIG. 2C).

  As the material of the cathode layer 22, a substance having a high electron injection efficiency is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface in contact with the organic layer, and highly stable and conductive Al or Cu is laminated. And use.

  Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, Al An alloy system with a metal element such as Cu is used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used.

  The cathode layer 22 can be formed by a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method depending on the material. The thickness of the cathode layer 22 is desirably about 10 nm to 1 μm.

  Next, an adhesive made of a thermosetting resin is applied, the sealing plate 12 is overlaid, and heated at a predetermined temperature to form an adhesive layer 41. The sealing plate 12, the anode layer, the organic light emitting medium layer, The transparent substrate 10 on which the cathode layer is formed and the sealing plate are bonded and sealed, and the first sealing is performed (see FIG. 2D).

  As the thermosetting resin, melamine type, acrylic type, O-cresol novolac type, bisphenol type epoxy type, urethane type and the like can be used.

  Next, in the side part 51 of the organic EL element, the outer peripheral part of the sealing plate is irradiated with a laser and melted to perform second sealing, thereby producing a double-sealed flexible organic EL element (FIG. 2 ( e)).

  The material of the sealing plate and the type of laser are appropriately selected. The sealing plate needs to be melted when irradiated with a laser. Further, it is necessary to prevent the transparent substrate from being deformed or altered when irradiated with a laser.

  When a sealing plate that is a glass film is used and the organic EL element side portion 51 is irradiated with a YAG laser, the outer peripheral portion of the sealing plate is melted, and the softened glass film is in close contact with the transparent substrate to be sealed. it can. As the material of the glass used for the glass film, almost any glass composition such as soda lime glass, borosilicate glass, non-alkali glass, etc. can be applied, and those subjected to secondary processing such as tempering and surface treatment can also be used. In principle, the glass film can be prepared by stretching the glass melt at a temperature above the temperature at which the glass melt solidifies. The film thickness of the glass film is 500 μm or less and preferably around 100 μm. The glass film is very excellent in moisture and oxygen barrier properties, and even when melted by a YAG laser, the barrier properties are maintained after cooling.

  Examples are shown below. First, a barrier layer against moisture and oxygen made of 200 nm thick silicon nitride is formed by plasma CVD on both sides of a flexible transparent substrate made of a 200 μm thick PES transparent film substrate (manufactured by Sumitomo Bakelite Co., Ltd.), and further by sputtering. An anode 21 made of an ITO film having a thickness of 150 nm was formed.

  Next, copper phthalocyanine (hole transport layer), N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (hole transport layer) , Tris (8-quinolinolato) aluminum complex (organic light emitting layer) were sequentially deposited in a thickness of 20 nm, 60 nm and 70 nm to form an organic light emitting medium layer.

  Next, Al was vacuum-deposited while rotating the substrate to form a cathode layer having a thickness of 0.5 μm on the transparent substrate on which the anode layer and the organic light emitting medium layer were formed.

  Next, an adhesive made of a thermosetting resin (20X-325C: Three Bond Co.) is applied on the first base material 10, a sealing plate made of a 200 μm thick glass film is overlaid, and heated at 90 ° C. for 1 hour. Then, the transparent substrate on which the anode layer, the organic light emitting medium layer, and the cathode layer were formed and the sealing plate were sealed (first sealing).

  Finally, the peripheral portion of the sealing plate is irradiated with a YAG laser to seal the peripheral portion of the transparent substrate and the sealing plate (second sealing), and a double-sealed flexible organic EL element Got.

(Comparative example)
In the examples, only the first sealing was performed and the second sealing was not performed as a comparative example.

  About the flexible organic EL element obtained by the Example and the comparative example, the anode layer and the cathode layer were wired with the power supply, and it was made to light-emit. When light emission was confirmed after storage for 500 hours in an environment of 60 ° C. and 90% RH, a dark spot was confirmed from the edge of the flexible organic EL element obtained in the comparative example, and the area of the dark spot over time. It was confirmed that gradually increased. On the other hand, in the flexible organic EL element obtained in the example, dark spots were not confirmed and normal light emission was shown.

It is a cross-sectional schematic diagram of the flexible organic EL element of this invention. (A)-(e) is the schematic diagram of the cross section which showed the manufacturing method of the flexible organic EL element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transparent substrate 21 Anode layer 22 Cathode layer 31 Organic luminescent medium layer 41 Adhesive layer 51 Organic EL element side part 100 Flexible organic EL element

Claims (2)

  In a flexible organic EL device in which an anode layer, an organic light emitting medium layer including an organic light emitting layer, and a cathode are formed on a flexible transparent substrate and sealed with a flexible sealing plate, the anode layer, organic After the first sealing is performed by laminating the transparent substrate on which the light emitting medium layer and the cathode layer are formed and the sealing plate with an adhesive, the second sealing is performed by melting the outer peripheral portion of the sealing plate. A flexible organic EL element characterized by having been performed.   The flexible organic EL device according to claim 1, wherein the sealing plate is a glass film, and the glass film is melted by laser irradiation to be sealed with a transparent substrate.

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