In recent years, concomitant with the trend toward advanced information performance, flat panel displays have been increasingly needed. For example, a non-self-luminous liquid crystal display (LCD), a self-luminous plasma display (PDP), an inorganic electroluminescence (inorganic EL) display, and an organic electroluminescence (hereinafter referred to as “organic EL”) display have been known. In particular, among those flat panel displays, the organic EL display has been significantly advanced.
In the organic EL display, there has been known a technique performing movie display by a simple matrix drive or a technique performing movie display by an active matrix drive of organic EL elements using thin film transistors (TFTs).
In addition, in a related display, pixels emitting red (R), green (G), and blue (B) light are used as one unit, and those pixels are arranged in a two-dimensional manner, so that many types of light having various color tones, such as white light, are produced to perform a full color display.
In order to realize the full color display as described above, in the case of organic EL, a method has been generally performed in which red, green, and blue pixels are separately formed from corresponding organic light emitting layers by a mask deposition method using a shadow mask. However, in the method as described above, it has been difficult to achieve an improvement in processing accuracy of the mask, an improvement in alignment accuracy of the mask, and an increase in size of the mask. In particular, in a large display field including a flat-screen television as a representative example, the size of a substrate has been increased from G6 to G8 and G10. Accordingly, in a related manufacturing method, a mask having a size approximately equivalent to or larger than that of the substrate is required, and as a result, it is necessary to form a mask corresponding to a large substrate.
Since the mask as described above requires a very thin metal (having a thickness, for example, of 50 to 100 nm), it is difficult to form a mask corresponding to a large substrate. Degradation in processing accuracy of the mask and alignment accuracy of the evaporation equipment may cause mixing among different types of emission light due to light emitting layers overlapped with each other. In order to prevent the phenomenon described above, in general, insulating layers of a specific width are required to be provided between pixels. However, when the area of each pixel is limited, the area of a light emitting portion or aperture ratio of the pixel is decreased, therefore, luminance may be lowered, power consumption increased, and lifetime decreased.
In addition, in the related manufacturing method, an organic layer is deposited in an upward direction using an organic material deposition source disposed below a substrate. Hence, as the size of the substrate (the size of the mask) is increased, the mask warps at a central portion thereof. The warp of the mask may be responsible in some cases for the mixing among different types of emission light described above. In an extreme example, a portion at which no organic layer is formed is unfavorably generated, and as a result, a leak may occur between an upper electrode and a lower electrode. In addition, in the related manufacturing method, since the mask is degraded when used a predetermined number of times, the mask may not be further used. Hence, the increase in size of the mask results in an increase in manufacturing cost of displays.
In order to overcome various phenomena in the large organic EL display as described above, a method has been proposed in which a plurality of organic EL displays (organic EL display units) are arranged to form one large display as a whole. However, when a plurality of organic EL display units are used in combination, a seam formed between organic EL display units arranged adjacent to each other becomes conspicuous, and the display quality as the display is degraded.
As a method to solve the problem relating to gaps formed when a plurality of organic EL display units are arranged in combination to realize one large organic EL display as a whole, for example, a method has been proposed in which at the expense of the aperture ratio, four organic EL panels are further sealed from the rear sides thereof to eliminate the seams (for example, see PTL 1).
In addition, a method has also been proposed in which after sealing portions of two organic EL panels are arranged so as to be overlapped with each other, an optically transparent plate having an adjusted refractive index is adhered to a substrate forming one of the two panels to eliminate the seam (for example, see NPL 1).