The exemplary embodiments relate to a method for manufacturing a display device, such as an organic electro luminescence (EL) display device, and more particularly a display device, for an improved etching process.
An organic EL display device has a fine structure in which a number of pixels each including an anode, a light-emitting film, and a cathode are arranged two-dimensionally on a substrate. The manufacturing process of the organic EL display device thus uses a plurality of highly accurate photolithography processes to pattern a number of thin films such as electrodes and wires. See Japanese Unexamined Patent Publication No. 2001-284609.
The photolithography process, however, needs a number of steps after depositing an object to be patterned, such as photoresist coating, resist pre-bake, pattern exposure, pre-development bake, development, post-bake, etching, ashing, resist stripping, and washing, resulting in higher cost of manufacturing facilities. In addition, a large amount of chemicals, deionized water, gas and the like needs to be used, leading to higher operation cost for materials, wastewater treatment and the like.
Accordingly, it is an advantage of the exemplary embodiments to provide a method for manufacturing a display device for allowing the manufacturing of a display device such as an organic EL display device with less use of photolithography, and to provide a display device.
In order to achieve the object described above, the exemplary embodiments provide a method for manufacturing a display device including at least a first electrode film, a light-emitting film, and a second electrode film over a substrate. The method includes patterning at least one of the films by laser etching.
Such a configuration allows the patterning of films each having a predetermined function, such as an electrode, wire, and light-emitting film, without using photolithography.
Preferably, the patterning is implemented for at least one of the first and second electrode films to form a pixel electrode. This can provide a display with a two-dimensional screen. With a transparent electrode as one electrode film and a non-transparent (preferably, reflective) electrode as the other electrode film, a bottom-emission or top-emission display can be formed.
The light-emitting film is preferably an organic EL film. This can provide an organic EL display device.
A method for manufacturing a display device according to the exemplary embodiments includes: forming a first electrode film on a substrate; patterning the first electrode film formed on the substrate by laser etching to form a plurality of pixel electrodes each having an edge part; forming an insulating film that isolates the pixel electrodes from each other and covers the edge part of each pixel electrode; forming a light-emitting film over each pixel electrode; and forming a second electrode over the light-emitting film.
Such a configuration allows the first electrode film to be formed by laser etching. In addition, the insulating film that covers the edge part of the electrode film can form the separation-wall structure, which can facilitate the deposition of the light-emitting film by ink jet.
In the forming of the insulating film, the insulating film is preferably formed to cover a rolled-up part (raised part) resulting from the laser etching and generated at the edge part of the pixel electrode. This can prevent non-uniform thickness of the light-emitting layer and a short circuit between the first and second electrode films.
The insulating film is preferably a separation-wall film defining a pixel region. This allows the use of a positioning structure (separation-wall film in a grid) for positioning droplets of a light-emitting film material discharged by ink jet.
The insulating film is preferably made of photoresist or silicon oxide. The photoresist can facilitate the patterning. The silicon oxide can provide higher insulation.
The light-emitting film is preferably an organic EL film. This can provide an organic EL display device.
The exemplary embodiments can pattern thin films for a display device with no use or less use of photolithography, which includes a number of processes such as resist coating, pattern exposure, development, and etching.
Laser etching is used in cathode patterning without the use of inversely-tapered resist films called a cathode separator to be described below, used in a related art cathode-patterning process. This can eliminate adverse affects on light-emitting layers due to the cathode separator, thereby improving the performance and reliability of the display device.
With reference to the appended drawings, a method for manufacturing a display device according to exemplary embodiments will be described below.
First, as shown in
As shown in
Note that an edge of the anode 11 that is etched by laser has a rolled-up part 11a resulted from the thermal melting and buildup of part of the ITO film. For example, the laser etching under the above-described condition may cause the rolled-up part 11a with a height of about 0.1 μm and a width (in the direction from side to side in
As shown in
As shown in
Note that a lyophilic and insulating film may be formed between the ITO film 11 and separation-wall film 12. Examples of this film may include a silicon oxide film. By partially exposing the lyophilic film along the opening edge 12a of a pixel, droplets of a high molecular-weight light-emitting material discharged into the opening of the pixel by ink jet spread uniformly over the whole top surface of the pixel electrode 11, preventing the short circuit between the anode and cathode.
As shown in
A cathode film (back electrode film) 14 is then formed over the light-emitting film 13. The cathode film 14 may be formed by depositing an aluminum film with a thickness of about 0.2 μm, by a method such as vacuum deposition that has less damage on the light-emitting film. An electron-injection layer made of calcium, lithium fluoride or the like may intervene between the aluminum film and the light-emitting film 13.
As shown in
In addition, the cathode needs to be patterned in an inert atmosphere excluding most of water and oxygen to prevent or reduce the degradation of the light-emitting layer.
Laser etching can pattern the cathode without forming a cathode separator 30 as shown in
Note that the above description of the manufacturing process of the organic EL display device does not refer to components such as electrode wiring, circuit wiring, and drive circuit, but those can be formed in the same way as in a related art image-display circuit.
As shown in
In this way, laser etching can be used to pattern electrode films, with raised parts (rolled-up parts) of the films due to the laser etching being covered by an insulating film. Organic EL display devices can thus be manufactured with no use or less use of photolithography.
Note that in the above-described exemplary embodiment, the laser etching patterns two electrode films to form an anode and cathode for a unit pixel, but the cathode may be formed as a common electrode for each pixel, for example. The electrode film may also be patterned to form a cathode for each unit pixel, and an anode for each pixel may be formed as a common electrode.
In addition, the manufacturing method according to the exemplary embodiment uses a transparent electrode (ITO) and metal electrode as an anode and cathode, respectively, to provide a bottom-emission organic EL display device. Alternatively, the manufacturing method according to the exemplary embodiments may use a transparent electrode (ITO) and metal electrode as a cathode and anode, respectively, to provide a top-emission organic EL display device. In this case, the electrodes can be formed by depositing various types of materials, allowing more adequate setting of energy levels of films.
The manufacturing method according to the exemplary embodiments can apply to both a passive and active organic EL display device.
After the electrode is laser etched, processes such as chemical mechanical polishing (CMP) may planarize the electrode surface and remove rolled-up parts due to the laser etching.
Number | Date | Country | Kind |
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2004-218955 | Jul 2004 | JP | national |