1. Field of the Invention
The present invention relates to a dimming method of an organic EL (electroluminescence) displaying apparatus as one kind of restoring techniques of the organic EL displaying apparatus in which organic EL elements are arranged in a matrix form.
2. Description of the Related Art
An organic EL displaying apparatus is an apparatus constructed in such a manner that a plurality of pixels each having an organic EL element and a driving circuit for driving the organic EL element are arranged on a substrate in a matrix form.
There is a case where a defect occurs in the driving circuit provided every pixel due to a defect in a manufacturing step of the organic EL displaying apparatus, so that defective display occurs in the organic EL displaying apparatus. As an example of the defective display, there is such a defect (defective bright-spot) that a bright-spot pixel in which the organic EL element is turned on even in a black displaying mode occurs.
Japanese Patent Application Laid-Open No. 2004-006339 discloses a method whereby, in an organic EL displaying apparatus, a laser beam is selectively irradiated to a part of a semiconductor layer included in a thin film transistor (hereinbelow, called a TFT) in a driving circuit which a bright-spot pixel has. By irradiating the laser beam to (a part of) the semiconductor layer, a resistance of the laser-irradiated semiconductor layer increases, so that dimming of the bright-spot pixel can be performed (that is, light of the bright-spot pixel can be dimmed).
Further, Japanese Patent Application Laid-Open No. 2004-006339 also discloses a method whereby a region to which the laser beam is irradiated is set to a region where a gate electrode layer is arranged upward in the semiconductor layer included in the TFT. According to such a method, the laser beam irradiated from a downward direction is reflected by the gate electrode layer, thereby enabling the dimming to be efficiently performed (that is, enabling the light to be efficiently dimmed).
However, if the method disclosed in Japanese Patent Application Laid-Open No. 2004-006339 is applied to the organic EL displaying apparatus, there are the following problems. That is, when the laser beam is irradiated from the downward direction of the substrate toward the semiconductor layer in order to perform the dimming of the bright-spot pixel, there is a possibility that the laser beam is irradiated to the region where the gate electrode layer provided over the semiconductor layer is arranged. There is such a problem that if the laser beam is irradiated to the gate electrode layer, the semiconductor layer and the gate electrode layer are short-circuited, so that the dimming of the bright-spot pixel is not performed.
There is also a case where even if the resistance of the TFT semiconductor layer is increased, the dimming of the bright-spot pixel is not sufficiently performed due to a variation in shape of the TFT by a process variation, a variation in characteristics, or a variation in laser beam which is irradiated. Therefore, it is necessary to increase an energy of the laser beam which is irradiated. In this case, according to the method in the related art, that is, the method whereby the laser beam is irradiated from the downward direction of the substrate toward the region where the gate electrode layer provided over the semiconductor layer is arranged, the foregoing problem of the short-circuit between the semiconductor layer and the gate electrode layer becomes more conspicuous.