1. Field of the Invention
The present invention relates to a technique for forming an electrode used for a pixel electrode of a reflection type liquid-crystal display, and more particularly to a method of manufacturing a pixel electrode for a direct-sight type of reflection type liquid-crystal display.
2. Description of the Related Art
The reflection type liquid-crystal display has a function of conducting display with the combination of reflection of a light inputted from the exterior by a pixel electrode with optical modulation action of liquid crystal.
The reflection type liquid-crystal display is roughly classified into a direct sight type and a projection type. In the direct sight type, the pixel electrode is required to irregularly reflect a light to be reflected by the electrode so that it is seen that the reflected light is white-muddy. On the other hand, in the projection type, the pixel electrode is required to be finished into a mirror surface.
In the reflection type liquid-crystal display device, either of a state in which an incident light is reflected by the pixel electrode and outputted to the exterior of the device, or a state in which the incident light is not outputted to the exterior of the device is selectively obtained in each cell by utilizing the optical modulation action of the liquid crystal, thereby conducting a bright or dark display in each cell, and images are displayed in combination with the bright cells and dark cells.
In the direct-sight type liquid-crystal display, the incident light from the exterior is reflected by the pixel electrode and then outputted to the exterior of the device, i.e., which is the bright display. However, since the display is obtained by reflecting the incident light by the pixel electrode as is reflected by a mirror without any changes, there occurs such a phenomenon that the display is glittered or darkened depending on an angle of view. That is, there occurs a phenomenon that the angle of view is narrowed.
This is caused by a fact that the reflection state of the incident light is different according to the angle of view. In order to eliminate this problem, the pixel electrode needs to be devised so that the incident light is irregularly reflected. With the device that allows irregular reflection, the pixel electrode appears to be in a visually white muddy state (it is needless to say that in the case where special processing is conducted on the pixel electrode so that only a light of a specific wavelength is inputted to the pixel electrode, the pixel electrode is not always white-muddy).
In general, in a direct-sight type display device, the surface of a pixel electrode is subjected to light etching to form irregularities thereon, to thereby cause the above-mentioned irregular reflection.
It is a supreme demand to suppress the manufacture costs as much as possible for the direct-sight type of reflection type liquid-crystal display. This is because that since the direct-sight type of reflection type liquid-crystal display device requires no back light which is different from the transmission type, it facilitates a low power consumption and a weight-lighting. As a result, the direct-sight type of reflection type liquid crystal display is mainly used for a cheap display unit of an information processing terminal or a portable telephone.
Under the above circumstances, an important problem resides in reducing its manufacturing process as much as possible to suppress the production costs as much as possible.
A process of forming irregularities on the surface of the above pixel electrode through etching is so complicated that wet etching or dry etching is required in a final stage.
In particular, since this etching is conducted after most of the device is completed, the use of wet etching suffers from a problem that etchant enters the interior of the device. Also, the use of dry etching suffers from electrostatic breakdown, etc., which are caused by the application of a bias voltage. In particular, the structure of the active matrix type is employed, those problems become more serious.
In order to evade those problems, such a trouble-some labor as making a process management standard more strict is required. However, this makes the manufacture costs increase.