JP2006278206A - Method for manufacturing organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an organic EL element with an organic light emitting layer of uniform thickness without defects, using letterpress. <P>SOLUTION: A letterpress used for printing has a dummy region of outer edge and an image forming region of its inside. The dummy region which tends to get uneven printing pressure at printing is not used to form the organic light emitting layer on an electrode but the inner image forming region which gets even printing pressure is only used to print the layer on the electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an organic EL element in which an organic light emitting layer is formed by a relief printing method.

  Research and development of lightweight, high-efficiency flat panel displays for computer information display or television screen display is underway. A cathode ray tube (CRT) that has been widely used as a display that has been mainly used in the past is a cathode ray tube (CRT) that has excellent luminance and color reproducibility. As panel displays, liquid crystal panel displays or plasma panel displays have been commercialized, and some products are being replaced. However, the liquid crystal panel display has a problem that the viewing angle is narrow and the responsiveness to high-speed pixel signals is not sufficient, and the plasma panel display consumes a large amount of power. There is a problem.

Recently, an organic electroluminescence element using an organic light emitting material (hereinafter referred to as an organic EL element) has been attracting attention. Even if the organic compound is used as a light emitting material, it is self-luminous. It is expected to realize a flat panel display with low power consumption and high response speed and no viewing angle dependency.
FIG. 5 shows an example of the structure of this type of organic EL element. The organic EL element 100 of this example is a transparent pixel electrode (anode) made of ITO (indium tin oxide) on a transparent glass substrate 101. 102, a hole transport layer 103, a light emitting layer 104, an electron transport layer 105, and a metal cathode 106 are sequentially formed by, for example, a vacuum deposition method.

In the organic EL element 100 having this configuration, when a DC voltage is applied between the anode pixel electrode 102 and the cathode 106 from the DC power source 107, holes (holes) as carriers injected from the pixel electrode 102 are transported by holes. Each of them moves through the layer 103, and in the light emitting layer 104, recombination of these electron-hole pairs occurs, and light emission 108 having a predetermined wavelength is generated therefrom, which can be observed from the outside of the transparent glass substrate 101. .
Further, as another example of the specific layer structure of the organic EL element 100 described above, as shown in FIG. 6, the material of the hole transport layer 103 is poly (3,4) -ethylenedioxythiophene (hereinafter abbreviated as PEDOT). ), And the electron of poly (2-methoxy-5- (2′-ethylhexyloxy) -1,4-phenylenevinylene) (hereinafter abbreviated as MEH-PPV) as a layer that doubles as an electron transport layer and a light-emitting layer A structure is also known in which a transporting light emitting layer 110 is used, and a cathode 106 made of an aluminum electrode layer and a calcium (Ca) layer 111 that enhances electron injectability is provided on the upper layer.

Next, FIG. 7 shows a configuration example in which the organic EL element having the basic structure shown in FIG. 5 or 6 is applied to a flat display device.
As shown in the drawing, an organic laminated structure composed of an electron transport layer 115 and a hole transport layer 116 is disposed between the cathode 117 and the anode 118 in a predetermined pattern. The cathode 117 and the anode 118 are provided in stripes crossing each other, and are selected by the luminance signal circuit 120 and the control circuit 121 with a built-in shift register, respectively, and applied with a signal voltage. Thus, the EL element portions existing at the positions (pixels) where the selected cathode 117 and anode 118 intersect each other are configured to emit light individually.

  Various methods for forming an organic light-emitting material by printing have been studied as a method for forming the light-emitting layer of the organic EL element, and one of them is a relief printing method. Patent Documents 1 to 3 describe production of an organic EL display using a relief printing method.

In the relief printing method, an organic light emitter is transferred to a relief plate such as a flexographic plate via an anilox roll, and this organic light emitter is printed on a substrate on which an electrode is formed from the flexographic plate, thereby forming an organic light emitting layer. Methods of forming are known. However, according to the relief printing method, the unevenness of the printing pressure is generated between the central portion where the printing pressure is uniform and the end portion where the printing pressure is higher than the central portion of the relief printing, so the pattern printed on the outer edge portion However, there was a problem in that defects or defects occurred, and the height of the pattern printed at the center and edge of the plate was uneven. Further, when a flexographic plate is used for the relief plate, there is a problem that the outer edge portion is easily damaged during plate development. For this reason, the organic light emitting layer printed by letterpress printing lacked pattern lines or caused uneven thickness of the layer.

Japanese Patent Laid-Open No. 10-77467 JP 2001-155858 A JP 2004-322329 A

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to manufacture an organic EL device having an organic light-emitting layer having a uniform thickness without defects in a method for manufacturing an organic EL device. It aims to provide a method.

  By the way, according to the study of the present inventor, a relief plate larger than the relief plate conventionally required for forming the organic light emitter on the electrode of the organic EL element is prepared, and only the central portion of the relief plate is prepared. The present inventors have found that when an organic light-emitting material is printed on an electrode, an organic EL device having an organic light-emitting layer having a uniform film thickness without defects is found.

The present invention has been made on the basis of such knowledge. The invention according to claim 1 is a method in which an organic light emitting material is printed by a relief printing method on a region where an electrode on a substrate is provided, and an organic light emitting layer is formed. In the manufacturing method of the organic EL element including the process of forming
The relief printing used for relief printing comprises an image forming area and a dummy area located at the outer edge of the image forming area, and when the relief printing plate and the base material are in contact, the image forming area of the relief printing is the base material. The method of manufacturing an organic EL element includes an area where the upper electrode is provided, and the dummy area of the relief plate does not include an area where the electrode is provided on the base material.

The invention according to claim 2 includes a line pattern in which the relief plate is composed of a plurality of parallel lines,
Of the letterpress, at least the area occupied by both ends of the parallel lines is a dummy area,
2. The method of manufacturing an organic EL element according to claim 1, wherein an inner region of the dummy region of the relief plate is an image forming region.

  The invention according to claim 3 is characterized in that the minimum distance between the outer edge of the image forming area and the outer edge of the dummy area is 100 μm or more. It is.

In the relief printing used for manufacture of the organic EL element including the process of printing an organic light emitting material by the relief printing method in the area | region in which the electrode on the base material was provided, and forming an organic light emitting layer in invention of Claim 4 ,
The relief plate includes an image forming area and a dummy area located at an outer edge of the image formation area, and when the relief plate and the base material are in contact with each other, the image forming area of the relief plate is an electrode on the base material. And the dummy area of the relief plate does not include the area where the electrode is provided on the substrate.

  The invention described in claim 5 is the relief printing plate according to claim 4, wherein a resin relief printing plate is used for the relief printing plate.

  The invention according to claim 6 is an organic EL element manufactured by the manufacturing method according to any one of claims 1 to 3.

  The invention according to claim 7 is an organic EL device characterized in that an organic effect material is printed by a relief printing method using the relief plate according to claim 4 or 5.

  According to the present invention, it was possible to solve the problems of the pattern defect and the layer thickness unevenness of the organic light-emitting layer caused by the uneven printing pressure generated between the central portion and the end portion of the relief printing plate. For this reason, an organic EL element having stable and good light emission characteristics could be manufactured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of a relief plate for producing an organic EL element in the present embodiment.
FIG. 1A is a view of the relief plate as viewed from above, and FIG. 1B is a cross-sectional view of the relief plate.

  The relief plate 1 for producing an organic EL element according to the present embodiment only needs to have a convex surface at least, and the material can be a plate material usually used for relief printing such as a metal plate or a resin plate. In addition, a shape such as a concave portion or a convex portion for holding ink at the tip of the convex portion 11 of the relief printing plate can be produced. Furthermore, ink repellency may be imparted to the concave portions of the relief printing plate. Needless to say, the relief plate 1 has the same convex pattern as the electrode 22 of the organic EL element at least in the image forming region 101. Since the dummy region 102 of the relief plate 1 is not used for forming the organic light emitting layer on the electrode, an arbitrary convex pattern can be formed.

  Further, when a flexographic plate is used for the relief plate 1, as described above, there is a problem that the end portion is easily damaged by the development. However, according to the present invention, the area susceptible to damage by development is not used for printing the organic light emitter on the electrode, and the area not damaged by development prints the organic light emitter on the electrode. Used for. For this reason, even when a flexographic plate is used as the relief plate, an organic light-emitting layer having a uniform film thickness can be formed without any defects.

  FIG. 2 is a schematic view of an organic EL element substrate. FIG. 2A is a view of the organic EL element substrate as viewed from above, and FIG. 2B is a cross-sectional view of the organic EL element substrate 2. In the organic EL element substrate 2, electrodes 22 are patterned on a substrate 21. As the pattern of the electrode 22 of the organic EL element, a known pattern such as a line pattern in which a plurality of parallel lines are provided, or a matrix pattern in which the line patterns are vertically intersected can be applied. 2 to 4 show examples of the line pattern.

FIG. 3 is a schematic view showing the positional relationship between the relief plate 1 and the organic EL element substrate 2 when the organic light emitter is transferred. FIG. 3A shows the relief 1 and FIG. 3B shows the organic EL element substrate 2.
As shown in FIG. 3A, the relief plate 1 includes an image forming area 101 (area shown by a hatched area) and a dummy area 102 (area outside the hatched area) located at the outer edge thereof. As described above, when the flexographic plate is used, the outer edge portion of the plate is more easily damaged than the central portion, and as a result, the printed organic EL element also causes a pattern defect at the outer edge portion of the substrate. However, according to the manufacturing method according to the present invention, as shown in FIG. 3B, the image forming region 101 includes the entire region occupied by the electrode 22 of the organic EL element substrate 2, and therefore the electrode 22 of the organic EL element. The organic luminescent material transferred to the image forming area 101 is transferred from the relief plate 1. That is, in the relief printing plate 1, the organic light-emitting body received in the dummy region 102 at the outer edge is not transferred onto the electrode 22, so the pattern of the organic light-emitting layer formed on the electrode 22 is free from defects and has a film thickness. It will be constant.

  Next, an example of the manufacturing method of the organic EL element using the relief plate 1 for producing the organic EL element of the present invention will be described in detail. FIG. 5 shows an example of an organic EL element manufacturing apparatus using the relief plate. The ink 43 containing the organic light emitting material is replenished from the ink replenishing device 41 to the inking device 42 on the relief printing plate, and the ink 43 containing the organic light emitting material replenished to the inking device 42 can be removed by the doctor device 44. . As the ink replenishing device, a coater such as a fountain roll, a slit coater, a die coater, a cap coater, or a combination thereof can be used in addition to the dropping type replenishing device. In addition to the doctor roll, a doctor blade can also be used for the doctor device 44.

  After the excess ink is removed by the doctor device 44, at least the surface is inked into the cylinder 45 having the relief plate 47 for producing the organic EL element. The inking to the relief plate 47 for producing the organic EL element may be performed at least on the image forming portion of the plate. The ink inked to the relief plate 47 for producing the organic EL element is printed on the transfer body 46. As a base material that can be used for the transfer object 46, a translucent base material such as a film having a barrier property against water vapor or the like can be used in addition to glass. The ink 43 containing the organic light emitting material printed on the transfer body 46 is dried to form an organic light emitting layer of the organic EL element.

  In FIG. 4, the schematic of an example of the organic EL element in which the organic light-emitting body was formed with the manufacturing method of this invention is shown. 4A is a top view, and FIG. 4B is a cross-sectional view thereof. On the electrode 22, an organic light emitting layer printed by the relief image forming area 101 is formed. In addition, when an organic light emitter is printed on the organic EL element base material 2 by the relief dummy area 102, an organic light emitter layer pattern 202 printed by the dummy area 202 is formed on the base material.

  The present invention is suitable for high-definition pattern printing, and particularly suitable for printing electronic materials. As an example, FIG. 6 shows one light emitting unit 30 of an organic EL element obtained by this manufacturing method. One light emitting unit 30 of the organic EL element includes a light transmissive substrate 31, a transparent conductive layer 32, a hole injection layer 33, an organic light emitting layer 34, and a cathode layer 35. In this organic EL element, the manufacturing method of the present invention is applied using the translucent substrate 31 as the base material 2, the transparent conductive layer 32 as the electrode 22, and the organic light emitting layer 34 as the organic light emitting body 201 transferred by the image forming region. be able to.

  In each unit 30 of the organic EL element, a glass substrate or a plastic film or sheet can be used as the translucent substrate 31. If a plastic film is used, an organic light emitting device can be manufactured by winding, and the device can be provided at low cost. As the plastic, for example, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate and the like can be used. Moreover, you may laminate | stack other gas barrier films, such as a ceramic vapor deposition film, a polyvinylidene chloride, a polyvinyl chloride, an ethylene-vinyl acetate copolymer saponified material, on the side which does not form the transparent conductive layer 32 into a film.

Examples of the material forming the transparent conductive layer 32 include a composite oxide of indium and tin (hereinafter referred to as ITO). In addition, a semi-transparent metal such as aluminum, gold, or silver, or an organic semiconductor such as polyaniline may be used.
Examples of the material forming the hole injection layer 33 include conductive polymer materials such as a polyaniline derivative, a polythiophene derivative, a polyvinylcarbazole derivative, and a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid.

  The organic light emitting layer 34 is a layer containing an organic light emitter, and emits light when a voltage is applied. Examples of organic light emitting materials include coumarin, perylene, pyran, anthrone, porphyrin, quinacridone, N, N′-dialkyl substituted quinacridone, naphthalimide, N, N′-diaryl substituted pyrrolopyrrole. Organic light-emitting materials soluble in organic solvents such as iridium complexes, organic light-emitting materials dispersed in polymers such as polystyrene, polymethyl methacrylate, polyvinyl carbazole, polyarylenes, polyarylene vinylenes, Examples thereof include polymer organic light emitting materials such as polyfluorene-based materials.

As a material for forming the cathode layer 35, a material corresponding to the light emitting characteristics of the organic light emitting medium layer can be used.
Examples thereof include simple metals such as lithium, magnesium, calcium, ytterbium, and aluminum, and alloys of these with stable metals such as gold and silver. Alternatively, a conductive oxide such as indium, zinc, or tin can be used.

  In order to manufacture the above-described organic light-emitting device using the present invention, a material in which a transparent conductive layer 32 and a hole injection layer 33 are laminated on a translucent substrate 31 is used as the transfer target 26, and organic light-emitting is used as the ink 22. Use ink containing material.

The ink containing the organic light emitting material is supplied to the convex portion of the relief printing as described above, and is printed on the transfer substrate 26 described above. Solvents used in inks that dissolve or disperse luminescent materials include, for example, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, chloroform, chloride. Examples thereof include methylene, dichloroethane, trichloroethane, tetrachloroethylene, water alone or a mixed solvent thereof. In particular, aromatic solvents and halogen solvents are excellent for dissolving organic light emitting materials.
Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, a desiccant, etc. may be added to the ink containing an organic luminescent material as needed.

Hereinafter, specific embodiments of the present invention will be described in detail using examples and comparative examples.
<Example 1>
The flexo proofing machine as the organic EL element manufacturing apparatus in the above embodiment has a line pattern with a convex portion width of 120 μm and a concave portion width of 380 μm, and includes a 32 mm × 35 mm image forming region and a dummy region, 35 mm × 37 mm. Resin letterpress was used.
As the organic light emitter, a 1.0% by weight toluene solution of polyarylene vinylene containing an organic light emitting material was used. Furthermore, it was set as the to-be-transferred board | substrate which laminated | stacked the mixture of ITO, poly (3,4-ethylene dioxythiophene), and polystyrene sulfonic acid on the glass substrate. After printing using the above relief printing on this transfer substrate, 10 nm of calcium and 300 nm of silver were vapor-deposited as a cathode, and glass sealing was performed. When the light emission characteristics of the organic EL element were observed, uniform light emission was observed over the entire light emitting surface.

<Example 2>
The flexo proofing machine similar to Example 1 as the organic EL element manufacturing apparatus in the above embodiment has 70 line patterns having a convex portion of 120 μm and a concave portion of 380 μm, of which three patterns are occupied at both ends. The area was a dummy area, and the area occupied by 64 patterns inside the dummy pattern was an image forming area.
A mixture of ITO, poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid is laminated on glass using a toluene solution of 1.0% by weight of polyarylene vinylene containing an organic light emitting material as an organic light emitter. After printing using the above-mentioned relief printing on the transferred substrate, calcium was deposited at a thickness of 10 nm and silver at a thickness of 300 nm as a cathode, followed by glass sealing. When the light emission characteristics of the organic EL element were observed, uniform light emission was observed over the entire light emitting surface.

<Comparative example>
As an organic EL element manufacturing apparatus in the above embodiment, a relief printing machine similar to that in Example 1 is provided with a relief plate having a line pattern having a convex portion of 120 μm and a concave portion of 380 μm and having only an image forming area of 32 mm × 35 mm. Using. A mixture of ITO, poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid is laminated on glass using a toluene solution of 1.0% by weight of polyarylene vinylene containing an organic light emitting material as an organic light emitter. After printing on the transferred substrate, the glass was sealed by depositing 10 nm of calcium and 300 nm of silver as a cathode. As a result of examining the light emission characteristics of the organic EL element, uneven light emission was observed at the end of the light emitting surface. Pressure unevenness during printing was measured with a Fujifilm prescale. The result is shown in FIG. The higher the pressure, the darker the color is displayed. As shown in FIG. 7, uneven printing pressure was observed at the end of the image forming area. The non-uniform light emission seems to be due to the non-uniformity in the film thickness of the organic light-emitting layer due to this uneven printing pressure.

It is the schematic of the letterpress used for the manufacturing method of this invention. It is the schematic of the organic EL element used for the manufacturing method of this invention. It is the schematic of the letterpress used for the manufacturing method of this invention, and an organic EL element. It is the schematic of an example of the organic EL element produced with the manufacturing method of this invention. It is the schematic of an example of the manufacturing apparatus used for the manufacturing method of this invention. It is the schematic of an example of an organic EL element. It is the figure which showed the pressure distribution at the time of printing of the relief printing used in the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Letterpress 11 Protrusion part 2 Organic EL element base material 21 Base material 101 Image formation area 102 Dummy area 201 Organic light-emitting body 202 transferred by image formation area Organic light-emitting body 41 transferred by dummy area Ink replenishing apparatus 42 Inking apparatus 43 Ink 44 Doctor Device 45 Cylinder 46 Transferred Material 47 Letterpress 30 for Organic EL Element Production One Unit of Organic EL Element 31 Translucent Substrate 32 Transparent Conductive Layer 33 Hole Injection Layer 34 Organic Light-Emitting Layer 35 Cathode Layer

Claims (7)

In the method of manufacturing an organic EL element including a step of printing an organic light emitting material by a relief printing method on a region where an electrode on a substrate is provided, and forming an organic light emitting layer,
The letterpress used for letterpress printing is
An image forming area;
A dummy area located at the outer edge of the image forming area, and when the relief plate and the substrate come into contact,
The image forming area of the relief plate includes an area where an electrode on the substrate is provided,
The method for manufacturing an organic EL element, wherein the dummy area of the relief plate does not include an area where an electrode is provided on the substrate. The letterpress includes a line pattern composed of a plurality of parallel lines,
Of the letterpress, at least the area occupied by both ends of the parallel lines is a dummy area,
2. The method of manufacturing an organic EL element according to claim 1, wherein an inner region of a dummy region of the relief printing plate is an image forming region.   3. The method of manufacturing an organic EL element according to claim 1, wherein a minimum interval between the outer edge of the image forming area and the outer edge of the dummy area is 100 [mu] m or more. In the relief printing used for the manufacture of the organic EL element including the step of printing the organic light emitting material by the relief printing method and forming the organic light emitting layer in the region provided with the electrode on the substrate,
The letterpress is
An image forming area;
A dummy area located at the outer edge of the image forming area, and when the relief plate and the substrate come into contact,
The image forming area of the relief plate includes an area where an electrode on the substrate is provided,
The relief printing plate according to claim 1, wherein the dummy region of the relief printing plate does not include a region provided with electrodes on the substrate.   The relief printing plate according to claim 4, wherein a resin relief printing plate is used for the relief printing plate.   An organic EL device manufactured by the manufacturing method according to claim 1.   6. An organic EL element, wherein an organic effect material is printed by a relief printing method using the relief plate according to claim 4 or 5.