1. Field of the Invention
The present invention relates to a display device, such as a liquid crystal display device for a cellular phone, especially, a device having a function of altering a viewing angle of a liquid crystal display.
2. Description of the Related Art
A liquid crystal display having a wide viewing angle (hereafter called “wide viewing angle display”) is installed to a cellular phone. It is the mainstream device that has added the functions of E-mail, camera, and television as well as the function of a telephone call. The wide viewing angle display device is preferable to display images, such as picture image or television show image on the cell phone display, since two or more people can see the images at the same time.
However, in the case that a user use the E-mail function of the cellular phone in a public place, it appears an undesirable situation that the image or information which he/she doesn't want to be seen by other people is displayed on the wide viewing angle display. To solve this kind of problem, there is a solution that the viewing angle is made narrow by putting a sheet on the display to limit the viewing angle of the display (for example, Japanese Registered Utility Model No. 3058477). According to this technology, peeping can be prevented even if the wide viewing angle display device displays a private image or information. On the other hand, there is still a problem that the viewing angle is fixed.
Further, it is disclosed in, for example, the Japanese laid open patent TOKKAI-HEI 9-105958 that a display device which viewing angle is electrically changed from wide to narrow (hereafter called “narrow viewing angle”). In accordance with the method, it is easily achieved to change viewing angle of display from wide to narrow, and vise/versa. Such display device can be installed into the cellular phone apparatus. In that case, there may be a push button for the viewing angle change in the cellular phone, then, a user can select a preferable viewing angle by operating of the pushbutton. It, however, spends the user's time and effort to select the viewing angle manually in accordance with a displayed image on cellular phone. In addition users may forget such selection.