Recently, a small-size, lightweight, and thin-shaped display element has become available, and through use of a display element, a portable display device has been commercialized which imports an image from an external device and displays the image. Not only a portable display device but also a display device using such a display element are required to be about as close as possible to the same size possible as a display section of the display device, and hence a size of a frame section of the display device is under very tight limitations.
The frame section is a section which is provided around the display section of the display device and does not contribute to display. The display device includes the element (hereinafter referred to as “display element”) having a display function, which display element forms the display section. Provided around the display section is a terminal part or the like, which terminal part is for inputting a signal into the display section. When the display device is formed, the display element is incorporated into such a section that does not contribute to display, the section is covered by a bezel.
In order to provide the functions of a speaker (sound source element), a microphone (sound collection element), and the like, a conventional portable display device needs to separately include, in addition to the display element, an element (voice element) having a voice function.
Today, such a portable display device is being commercialized as a very easily portable card-like display device that is about the same size as a normal credit card or business card.
“Nikkei Electronics (Feb. 17, 2003) p. 123-130” describes a technique of forming an 8-bit microprocessor on a glass substrate. According to this technique, a continuous grain boundary crystal silicon (hereinafter referred to as “CG silicon”) technique is used to form on a glass substrate a thin film layer containing CG silicon. As compared with low-temperature polycrystalline silicon, CG silicon has large crystal grains with regular boundaries therebetween. Because CG silicon has a high electron transfer degree of 200 to 300 cm2/Vs, it allows a logic circuit to operate at high speeds. By using this technique, a microprocessor can be incorporated into substrates sandwiching liquid crystal.
Meanwhile, Japanese Unexamined Patent Publication No. 29288/2003 (Tokukai 2003-29288; published on Jan. 29, 2003) describes a display device including: an FPC (liquid crystal panel FPC) for a liquid crystal panel; and an FPC (heater FPC) for a heater designed to warm up the liquid crystal panel, wherein the heater FPC is connected to the liquid crystal panel FPC in advance so as to decrease the number of operations required to form electrical connections.
However, as described above, the conventional portable display device needs to separately include functional elements such as a voice element so as to provide the functions of a speaker, a microphone, and the like, as well as a display. In order to achieve this while limiting an increase in outer dimensions, a method can be used in which the display device includes therein these elements. Further, a method is proposed in which the functional elements are laminated on the display element so that the display device has multiple functions. However, also in this case, the functional elements need to be laminated on the display element in a special manner. Otherwise, a thin-shaped display device cannot be achieved even if a size of a frame section is within the limits, as there will be an unnecessary increase in a size of a circuit necessary for normal and external processes. As a result, even if a small-size and lightweight laminated part is achieved, a thin-shaped display device cannot be achieved in view of a signal line connection for inputting and outputting signals.
Particularly, the card-like display device, which is being commercialized today, is unable to have multiple functions while keeping its card-like size, which is a hindrance to further development. Further, as the display device comes to have multiple functions, an increase in cost cannot be avoided, the reduction of which will be a significant issue in the future.
Further, now that a microprocessor can be incorporated into a constituent substrate of a liquid crystal panel, it is expected that the liquid crystal panel will have more and more multiple functions. However, also in this case, functional elements need to be laminated on and connected to a display element in a special manner. Otherwise, a thin-shaped display device cannot be achieved due to the number of connections, and the cost of the display device becoming high.
The present invention has been completed in view of the foregoing problems and has as an object to provide a multifunctional display device which can be achieved at low cost by efficiently using a limited space around the display element without sacrificing the advantages of a lightweight and thin-shaped flat display device.