Abstract:
An electronic device capable of transmitting and receiving a mail through an internet usually has from 12 to 20 operation keys inclusive of numerical keys and special keys. In order to input Japanese characters inclusive of “kanji” and special characters as data, complex operations must be executed by changing over the input mode. A portable data terminal as represented by a cellular phone or an electronic device such as a data terminal as represented by a personal computer or a desk top telephone, has such a shape that the first center line of the first housing and the second center line of the second housing come into agreement and in parallel with each other only in a state where the first housing and the second housing are folded by the hinge.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to electronic devices such as an information terminal, a cellular phone, a PHS (personal handy phone system) and a PDA (personal digital assistant) that are connected to the Internet to transmit and receive data. In this specification, the electronic device stands for those that can be carried by a user, and is capable of transmitting and receiving data and information indoors and outdoors through a wireless phone, a wired phone or an internet. 
     2. Description of the Related Art 
     Electronic devices as represented by a cellular phone (portable phone) are finding a rapid and widespread use owing to the establishment of an information communication network utilizing a wireless communications network and the Internet compounded by a decrease in the fees, in the cost of the device and convenience. The cellular phone includes a communication circuit, a display unit, an operation unit, a receiving unit, a transmitting unit and an antenna, which are integrally incorporated in a housing. 
     The electronic devices as represented by a cellular phone are selected by the users not only by their appearance and functions but also by their weight, duration in which they can be continuously used before recharging and the like. Therefore, a variety of contrivances have been made to lengthen the time of use through one time of electric charging yet decreasing the weight of the electronic device. As a result, functions which are considered unnecessary have been removed as much as possible. 
     Owing to the development in the communications technology in recent years, it is now becoming possible to transmit and receive electronic mails using electronic devices. However, complex operations are necessary for preparing a mail by manipulating the keys provided in the operation unit. 
     Further, the electronic device makes a communication by using wireless electromagnetic waves, and it often happens that the voice is heard with difficulty depending upon an environment in which the user is placed. 
     SUMMARY OF THE INVENTION 
     The invention disclosed in this specification is concerned with an electronic device having a first housing and a second housing which are coupled together by a hinge, wherein a first center line of the first housing and a second center line of the second housing are in parallel with each other only in a state where the first housing and the second housing are folded via the hinge. 
     The invention disclosed in this specification is concerned with an electronic device having a first housing and a second housing which are coupled together by a hinge, wherein each of the first and second housings has a pair of lines opposing each other, wherein one of the pair of lines has a shorter length than the other one of the pair of lines. 
     The invention disclosed in this specification is concerned with an electronic device having a first housing and a second housing which are coupled together by a hinge, wherein each of the first and second housings has a trapezoid shape. 
     This constitution makes it possible to simplify the operation of the keys. When the electronic device is used as a cellular phone, further, the transmitting unit can be brought close to the mouth, enabling the voice to be clearly transmitted to a remote user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1F  are views illustrating the appearance of an electronic device according to the present invention; 
         FIGS. 2A to 2D  are views illustrating the construction of a hinge according to the present invention; 
         FIGS. 3A to 3E  are views illustrating the arrangement of a printed board in a housing and the hinge of the present invention; 
         FIGS. 4A and 4B  are views illustrating a mode of operating the electronic device according to the present invention; 
         FIGS. 5A and 5B  are views illustrating a mode of using a display unit according to the present invention; 
         FIGS. 6A and 6B  are views illustrating the arrangement of the printed board and a light-emitting device in the housing of Embodiment 1; 
         FIG. 7  is a system block diagram of the electronic device of Embodiment 2; 
         FIGS. 8A and 8B  are views illustrating a mode of using the electronic device of Embodiment 3; 
         FIGS. 9A and 9B  are views illustrating a mode of using the electronic device of Embodiment 3; 
         FIG. 10  is a sectional view of an active matrix liquid crystal display device of Embodiment 4; 
         FIG. 11  is a view illustrating the appearance of the active matrix liquid crystal display device of Embodiment 4; 
         FIGS. 12A and 12B  are block diagrams of a drive circuit in the active matrix liquid crystal display device of Embodiment 4; 
         FIGS. 13A and 13B  are a top view and a sectional view of the active matrix liquid crystal display device of Embodiment 5; 
         FIG. 14  is a sectional view of the light-emitting device of Embodiment 6; 
         FIGS. 15A and 15B  are a top view and a sectional view of the light-emitting device of Embodiment 6; 
         FIG. 16  is a circuit diagram of a pixel having a sensor (photodiode) of Embodiment 7; and 
         FIG. 17  is a sectional view of the pixel having the sensor (photodiode) of Embodiment 7. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the invention will now be described. 
       FIGS. 1A to 1F  are diagrams of a cellular phone which is an electronic device of this invention, wherein  FIG. 1A  is a diagram of when the electronic device having a first housing and a second housing coupled together by a hinge is opened from the inside,  FIG. 1B  is a view of when the electronic device of  FIG. 1A  is viewed from the side, and  FIG. 1C  is a view of when the electronic device is opened and is viewed from the outer side. 
     In  FIGS. 1A to 1F , reference numeral  100  denotes a hinge,  104  denotes a receiving unit,  105  denotes an operation key,  106  denotes buttons,  101  denotes a display unit, and reference numeral  103  denotes a transmitting unit. In this specification, a plurality of buttons  106  are collectively called operation key  105 . In this embodiment, further, the first housing includes the receiving unit  104 , operation key  105  and buttons  106 , and the second housing includes the display unit  101  and transmitting unit  103 . As shown in  FIGS. 1A-1C , each of the first and second housings has a pair of lines opposing each other, wherein one of the pair of lines has a shorter length than the other one. That is, each of the first and second housing has a trapezoid shape. The display unit  101  is provided with a liquid crystal display device or a light-emitting device. Further, the electronic device of the invention may be provided with a function for receiving the electromagnetic waves, such as an antenna or the like. The electronic device may be further provided with accessories (not shown) such as a strap, a shielding pad, etc. The receiving unit  104  and the transmitting unit  103  are incorporated in the first housing and in the second housing, respectively, the first hosing and the second housing being allowed to be folded via the hinge  100  to decrease the size. Since the device is foldable, a sufficient distance is maintained between the receiving unit  104  and the transmitting unit  103  from the standpoint of human engineering. In a state where the first housing and the second housing are opened via the hinge as shown in  FIGS. 1A to 1C , the center line A of the first housing and the center line B of the second housing are inclined relative to each other and are not in parallel. 
       FIGS. 1D to 1F  are illustrating a state where the first housing and the second housing of the electronic device shown in  FIGS. 1A to 1C  are folded via the hinge.  FIG. 1D  is a view of when the first housing and the second housing are folded, and the first housing is viewed from the upper side. It will be learned that the center line A of the first housing and the center line B of the second housing are in agreement and are in parallel.  FIG. 1E  is a view of when the electronic device of  FIG. 1D  is viewed from the side, from which it will be learned that the center line A and the center line B are in agreement and are in parallel.  FIG. 1F  is a view of when the second housing of the electronic device of  FIG. 1D  is viewed front the upper side. Like in  FIG. 1D , the center line A of the first housing and the center fine B of the second housing are in agreement and are in parallel. 
     In this invention, the center lines of the housings stand for lines along which the center line A of the first housing and the center line B of the second housing are in parallel with each other in a state where the first housing and the second housing are folded via the hinge  100  as shown in  FIGS. 1A to 1F . The center lines further stand for lines which are inclined relative to each other in a state where the first housing and the second housing are opened via the hinge  100 . In  FIGS. 1A to 1F , the housing of the electronic device of the invention has a shape surrounded by straight lines. The invention, however, is in no way limited thereto only but may have a shape surrounded by curves. Further, the electronic device shown in  FIGS. 1A to 1F  has the first housing and the second housing which are of the same shape. The invention, however, is in no way limited thereto only, and the first housing and the second housing may have different shapes. 
       FIGS. 2A to 2D  illustrate the electronic device of the invention of before being coupled by the hinge  100  and after being coupled by the hinge  100 .  FIGS. 2A and 2B  illustrate the device of before the first housing and the second housing are coupled together by the hinge  100 , wherein  FIG. 2B  is a view of when the first housing and the second housing are opened from the inside and are viewed, and  FIG. 2A  is a side view of  FIG. 2B . The first housing and the second housing have a plurality of cylinders  100   a  which are perforated on the inner side thereof. The hinge  100  is constructed by passing a rod  100   b  through the holes of the cylinders  100   a  to couple them together. In this specification, the cylinders  100   a  and the rod  100   b  in combination are referred as the hinge  100 . The hinge  100  is not limited to the one of the shape shown in  FIGS. 2A to 2D , but any widely known hinge can be applied to this invention. 
       FIGS. 2C and 2D  are views showing the first housing and the second housing coupled together by the hinge  100 , wherein  FIG. 2D  is a view of the first housing and the second housing coupled together by the hinge  100  and being opened from the inside, and  FIG. 2C  is a side view of  FIG. 2D . 
     Next, described below with reference to  FIGS. 3A to 3E  is the arrangement of the printed board, FPC connecting the printed board and hinge  100  used for the electronic device of the invention.  FIG. 3A  illustrates the electronic device of the invention and  FIG. 3B  illustrates a printed board  110   a  in the first housing and a printed board  110   b  in the second housing. The printed board  110   a  and the printed board  110   b  are connected together by an FPC  111 . The printed board  110   a  has a wiring for displaying the data input by buttons  106  on the display unit  101  of the second housing. The first housing and the second housing are connected together through the FPC  111 , and the data input by buttons  106  are displayed on the display unit  101  of the second housing through the FPC  111 . The printed boards  110   a  and  110   b  are further provided with a memory and a controller for controlling the receiving unit  104  and the transmitting unit  103  in addition to those shown in  FIG. 2B , which, however, are not shown in  FIG. 3B  for simplifying the description. 
       FIG. 3C  is a sectional view of the electronic device cut along A-A′ in  FIG. 3A . The printed board  110   a  in the first housing and the printed board  110   b  in the second housing are coupled together through the hinge  100 , the printed board  110   a  and the printed board  110   b  being connected together through the FPC  111 . The FPC  111  is held in the hinge  100  permitting the first housing and the second housing to be folded via the hinge  100 . 
       FIG. 3D  illustrates a state where the first housing and the second housing are folded via the hinge  100 , and  FIG. 3E  illustrates, on an enlarged scale, a portion surrounded by a dotted line of the electronic device of the invention shown in FIG.  3 C. As shown in  FIG. 3E , the FPC  111  is held in the hinge  100  to connect the printed board  110   a  and the printed board  110   b  together. 
       FIGS. 4A and 4B  are views illustrating a mode of using the electronic device of this invention, wherein  FIG. 4A  is a view of when the operation key  105  is manipulated by the left hand, which is best suited for a left-handed person, and  FIG. 4B  is a view of when the operation key  105  is manipulated by the right hand, which is best suited for a right-handed person. Though the device is manipulated by one hand only in  FIGS. 4A to 4B , the device may be manipulated by both hands, as a matter of course. 
       FIGS. 5A to 5B  illustrate a housing having the display unit  101 , wherein reference numeral  103  denotes the transmitting unit.  FIG. 5A  is a view illustrating a picture displayed on the display unit  101  and  FIG. 5B  is a view illustrating symbols such as letters, characters, alphabets, numerals and pictographs displayed on the display unit  101 . 
     Embodiment 1 
     In the foregoing was described the case where the display device was used for the display unit only. In the electronic device of this embodiment, however, a display device is provided under the operation key  105 .  FIGS. 6A to 6B  are sectional views illustrating the constitution of the operation key  105  under which the light-emitting device is provided. 
     In  FIG. 6A , a printed board  202  made of a glass epoxy resin or a ceramic material exists inside the housing  201 . As a base band unit, there are formed signal processing circuits such as CPU (microprocessor), DSP (digital signal processor) and various memories (flush memory and SRAM) as well as transmitting/receiving circuit unit mounting a mixer and a frequency synthesizer. 
     A light-emitting device  204  is provided on the surface of the printed board  202  on the side opposite to the surface on where the above various circuits are formed. The light-emitting device  204  includes a substrate  212 , a unit display  205  and a covering member  213 . The unit display  205  is arranged under each button  203 . 
     The button  203  can be seen from the outer side of the housing  201  and permits light to pass through, and the light emitting device  204  is provided thereunder. Owing to this constitution, a symbol (character) displayed by the light-emitting device  204  can be seen through the light-transmitting (translucent) button  203 . 
     The light-emitting device  204  is connected to the wiring  206  formed on the substrate  212 . Though there is no particular limitation on the manner of connecting the circuit of the printed board  202  to the circuit of the substrate  212 , the wiring  206  may be connected to the circuit of the printed board  202  by using, for example, an FPC (flexible printed circuit)  210 . Reference numeral  271  indicates a connecting electrode. 
     Electrodes  209   a  and  209   b , a diaphragm  208  and a flexible sheet  207  to which the diaphragm  208  is secured, are provided between the light-transmitting button  203  and the substrate  212 . The diaphragm  208  is made of an alloy containing aluminum and copper as main components, and is electrically conducting. The diaphragm  208  is provided for the button  203 . The electrodes  209   a  and  209   b  are connected to a circuit that detects the input among the above various circuits. 
     Referring to  FIG. 6A , the diaphragm  208  in an ordinary state is in contact with the one electrode  209   a  only. When the user depresses the button  203  in the direction of an arrow as shown in  FIG. 6B , the flexible sheet  207  and the diaphragm  208  undergo a change; i.e., the diaphragm  208  comes in contact with both electrodes  209   a  and  209   b  to establish a conducting state. Thus, the input data is obtained by detecting whether the button is operated. 
     Though the above embodiment has dealt with the case of using the light-emitting device, it is also allowable to use the reflection-type or the transmission-type liquid crystal display device as the display device. 
     This embodiment can be used in free combination with the mode of use. 
     Embodiment 2 
       FIG. 7  is a block diagram illustrating a system using the electronic device of the invention. In the system shown in  FIG. 7 , a key input unit  522  includes a display device  523  and a key input detector unit  524 . A keyboard interface unit  508  in a CPU  506  controls the picture of symbols displayed by the display device  523  via a keyboard control circuit (controller)  520 . 
     A signal from the key input detector unit  524  is input to the keyboard interface unit  508  via an input signal processing circuit  521 , whereby the data is processed in the CPU  506 , a predetermined data is output to the control circuit  512 , and the data is displayed on the display device  513  or is transmitted. 
     The external circuit is constituted by a power source  504  which includes a stabilized power source and a high-speed and high-precision operational amplifier, a voice processing circuit  502 , an external interface port  505 , and a transmitting/receiving circuit  515 . The CPU  506  contains a video signal processing circuit  507 . To the CPU  506  are connected VRAM  511 , DRAM  509 , flush memory  510  and memory card  503 . The data processed by the CPU  506  is sent as a video signal (data signal) to the control circuit  512  from the video signal processing circuit  507 . The control circuit  512  supplies a video signal and a clock to the display device  513 . Concretely speaking, the control circuit has a function for distributing the video signals into data corresponding to the pixels in the display device, and a function for converting the horizontal synchronizing signals and vertical synchronizing signals input from the external unit into start signals for the drive circuit and into timing control signals for alternating the current in the embedded power-source circuit. In addition, a microphone  508  and a speaker  514  are also included in this system. 
     Referring to  FIG. 7 , the electronic device of this invention is so constituted that the display devices provided under the buttons are controlled solely by the CPU. 
     This embodiment can be used in free combination with the mode of use and with the embodiment 1. 
     Embodiment 3 
     Next,  FIGS. 8A to 8B  show the appearance of the electronic device using the display device for the operation key dealt with in the embodiments 1 and 2.  FIG. 8A  illustrates a case where, when the first housing and the second housing are arranged in the vertical direction, the direction of symbols displayed on the display unit  101  and the direction of symbols displayed on the buttons  106  in the operation key  105 , are in what they should be as viewed from the side of the user. 
       FIG. 8B  illustrates a case where, when the first housing and the second housing are arranged in the lateral direction, the direction of symbols displayed on the display unit  101  and the direction of symbols displayed on the buttons  106  in the operation key  105 , are in what they should be as viewed from the side of the user. 
     The electronic device of the invention is capable of changing the direction of the symbols displayed on the display unit  101  and the direction of the symbols displayed on the buttons  106  in the operation key  105  over to the direction shown in  FIG. 8A  and over to the direction shown in  FIG. 8B  to meet the user&#39;s choice. 
     In the foregoing was described the case where the direction of pictures displayed on the display unit  101  was the same as the direction of symbols displayed on the operation key  105  with reference to  FIGS. 8A to 8B . The invention, however, is in no way limited thereto only. The direction of pictures displayed on the display unit  101  may be different from the direction of symbols displayed on the operation key  105 . The symbols displayed by the operation key  105  shown in  FIGS. 8A to 8B  are only some examples of the symbols, and the electronic device of this invention is not limited to these symbols only. 
     Further, the direction of pictures displayed on the display unit  101  and the direction of pictures such as symbols displayed on the operation key  105 , may be automatically changed relying upon the angle θ in the connection portion  100  between the surface of the first housing having the display unit  101  and the surface of the second housing having buttons  106  in the operation key  105 . 
     Further, the brightness of display of the operation key  105  may be changed. The operation key  105  shown in  FIG. 9A  displays one or a plurality of black symbols on a white background. The operation key  105  shown in  FIG. 9B  displays one or a plurality of white symbols on a black background. 
     Though  FIGS. 9A and 9B  have illustrated the operation keys producing a black display and a white display, it should be noted that the invention is not limited to these constitutions only. The operation key may produce a display of a color other than white. For example, a yellow display may be made on the black background, a green display may be made on the white background or a black display may be made on the blue background. 
     Owing to the above constitution, the electronic device consumes the electric power in suppressed amounts. 
     This embodiment can be used in free combination with the mode of use and with the embodiments 1 and 2. 
     Embodiment 4 
     In this embodiment, an example of a display device used in a display portion  101  or provided under an operation key is shown. In this embodiment, a liquid crystal display device will be described as a display device. An example of the liquid crystal display device having a pixel portion and a driver circuit for driving it on a substrate with an insulating surface (note that it is in a state before a liquid crystal material sealing) is shown in  FIG. 10 . 
     Note that a CMOS circuit as a basic unit is shown as the driver circuit and one pixel is shown as the pixel portion. 
     In  FIG. 10 , a driver circuit  601  composed of n-channel TFTs  605  and  606  and p-channel TFTs  603  and  604  and a pixel portion  602  composed of a pixel TFT  607  as an n-channel TFT and a storage capacitor  608  are formed on a substrate. In the driver circuit  601 , combining n-channel TFTs and p-channel TFTs, a logic circuit  609  and a sampling circuit  610  are also formed. 
     The pixel TFT  607  has a structure (double gate structure) where two channel forming regions are located between a source region and a drain region. However, this embodiment is not limited to the double gate structure. A single gate structure where one channel forming region is formed or a triple gate structure where three channel forming regions are formed may be used. 
     Also, in this embodiment, a pixel electrode connected with the drain region of the pixel TFT  607  is formed as a reflection electrode. As the material of the pixel electrode, it is desirable that a material with superior reflectivity, such as a film containing mainly Al or Ag or a laminate film of these be used. Also, it is preferable that after the formation of the pixel electrode, its surface is made uneven by a process using a sandblast method, an etching method, or the like, which is known. Thus, mirror reflection is prevented and reflection light is scattered to increase the degree of whiteness. 
     Note that in this embodiment, the example of the reflection liquid crystal display device using the reflection electrode as the pixel electrode is shown. However, a transmission liquid crystal display device using a transparent conductive film as the pixel electrode instead of the reflection electrode may be used. 
     After the state in  FIG. 10  is obtained, an orientation film is formed on the pixel electrode and then rubbing processing is performed. Note that in this embodiment, before the formation of the orientation film, an organic resin film such as an acrylic resin film is patterned to form column-shaped spacers for keeping a substrate interval in predetermined positions. Instead of the column-shaped spacers, spherical spacers may be dispersed over the entire surface of the substrate. 
     Next, a counter (opposite) substrate is prepared. After colored layers and a light shielding layer are formed on the counter substrate, a planarization film is formed. Then, a counter electrode made of a transparent conductive film is formed in at least the pixel portion on the planarization film, an orientation film is formed on the entire surface of the counter substrate, and rubbing processing is performed. 
     Then, a stainless substrate in which the pixel portion  602  and the driver circuit  601  are formed and a fixing substrate are adhered to each other through an adhesion layer (seal member in this embodiment). Fillers are mixed with the adhesion layer. The two substrates are adhered to each other at a uniform interval by the fillers and the column-shaped spacers. After that, a liquid crystal material is injected between both substrates and completely seated using a sealing agent (not shown). A known liquid crystal material may be used as the liquid crystal material. 
     Next, after the liquid crystal sealing (or filling) process is completed, a substrate holder is separated as described in the embodiment mode and in Embodiment 1. A state of the liquid crystal display device after that will be described using  FIG. 11 . 
     In the top view shown in  FIG. 11 , a stainless substrate  82   a  and a counter substrate  82   b  on which a color filter and the like are provided are adhered to each other through a seal member  83 . In the stainless substrate  82   a , a pixel portion, driver circuits, an external input terminal  80  to which an FPC (flexible printed circuit)  89  is adhered, wiring  81  for connecting the external input terminal with input portions of the respective circuits, and the like are formed. 
     A light shielding layer  86   a  is provided on the counter substrate side so as to overlap a gate side driver circuit  84  and a light shielding layer  86   b  is provided on the counter substrate side so as to overlap a source side driver circuit  85 . Also, in a color filter  88  which is provided on the counter substrate on a pixel portion  87 , the light shielding layers and colored layers of respective colors of red (R), green (G), and blue (B) are provided corresponding to each pixel. In actual display, color display is made by three colors of the red (R) colored layer, the green (G) colored layer, and the blue (B) colored layer. The colored layers of the respective colors are arbitrarily arranged. 
     In this embodiment, the color filter  88  is provided in the counter substrate for colorization. However, in particular, the present invention is not restricted to this. When an element is formed on a substrate, a color filter may be formed over the substrate. 
     Also, the light shielding layer is provided between adjacent pixels in the color filter to light-shield a portion except for a display region. Further, the light shielding layers  86   a  and  86   b  are provided in a region covering the driver circuits. However, when the liquid crystal display device is incorporated as the display portion of the electronic equipment, the region covering the driver circuits is covered with a cover. Thus, a structure where the shielding layers are not provided may be used. When a necessary element is formed on a substrate, light shielding layers may be formed on the substrate. 
     Also, without providing the above light shielding layers, the colored layers composing the color filter may be suitably arranged between the counter substrate and the counter electrode such that light shielding is made with a laminate layer in which a plurality of layers are laminated. Thus, a portion (gap between respective pixel electrodes) except for the display region and the driver circuits are light-shielded. 
     Also, an FPC  89  made of a base film and wiring is adhered to the external input terminal through an anisotropic conductive resin. A reinforced plate is further provided to improve the mechanical strength. 
     Also, a polarization plate (not shown) is adhered to only the counter substrate. 
     The liquid crystal display device thus manufactured can be used as a display portion of electronic equipments used in this invention. 
     An example of a circuit structure of the liquid crystal display device of this embodiment is shown in  FIGS. 12A and 12B . 
     First, a circuit structure for analog drive will be explained by using  FIG. 12A . In this embodiment, the liquid crystal display device has a source side driver circuit  90 , a pixel portion  91 , and a gate side driver circuit  92 . Note that the term driver circuit in this specification covers the source side driver circuit and the gate side driver circuit. 
     In the source driver circuit  90 , a shift register  90   a , a buffer  90   b , and a sampling circuit (transfer gate)  90   c  are provided. Also, in the gate side driver circuit  92 , a shift register  92   a , a level shifter  92   b , and a buffer  92   c  are provided. If necessary, a level shifter circuit may be provided between the sampling circuit and the shift register. 
     Also, in this embodiment, the pixel portion  91  includes a plurality of pixels and a TFT element is provided for the respective pixels. Note that the source side driver circuit  90  and the gate side driver circuit  92  can be formed using p-channel TFTs or n-channel TFTs. 
     Note that, although not shown, another gate side driver circuit may be provided on the opposite side of the gate side driver circuit  92  with the pixel portion  91  therebetween. 
     Next, a circuit structure for digital drive will be explained by using  FIG. 12B . In the case of digital drive, as shown in  FIG. 12B , instead of the sampling circuit, a latch (A)  93   b  and a latch (B)  93   c  may be provided. In a source side driver circuit  93 , a shift register  93   a , the latch (A)  93   b , the latch (B)  93   c , a D/A converter  93   d , and a buffer  93   e  are provided. Also, in the gate side driver circuit  95 , a shift register  95   a , a level shifter  95   b , and a buffer  95   c  are provided. If necessary, a level shifter circuit may be provided between the latch (B)  93   c  and the D/A converter  93   d.    
     Also, although only the structures of the pixel portion  91  or  94  and the driver circuit are described in this embodiment, a memory or a microprocessor further may be formed. 
     Note that this embodiment can be combined the embodiment mode and Embodiments 1 to 3. 
     Embodiment 5 
     In this embodiment, an example, in which the TFT for a pixel portion and driver circuits of the liquid crystal display device used in a display portion of electronic equipments of this invention is formed by an inverted stagger TFT, will be described using  FIGS. 13A and 13B .  FIG. 13A  is a top view in the case where one of pixels in the pixel portion is enlarged and a sectional view taken along a dot line A-A′ in  FIG. 13A  is shown in  FIG. 13B . 
     In  FIG. 13B , reference numeral  51  denotes a substrate having an insulating surface. A pixel TFT portion  72  is formed of n-channel TFTs. A gate electrode  52  is formed on a substrate  51 , and a first insulating film  53   a  of silicon nitride and a second insulating film  53   b  of silicon oxide are provided thereon. As active layers on the second insulating film  53   b , n +  type regions  54  to  56 , channel forming regions  57  and  58 , and n −  type regions  59  and  60  located between the n −  type regions and the channel forming regions are formed. The channel forming regions  57  and  58  are protected by insulating layers  61  and  62 . After contact holes are formed in a first interlayer insulating film  63  which covers the insulating layers  61  and  62  and the active layers, wiring  64  connected with the n +  type region  54  is formed, a pixel electrode  65  of Al, Ag, or the like is connected with the n −  type region  56 . Reference numeral  70  denotes a pixel electrode. 
     Note that in this embodiment, the gate wiring of the pixel TFT in the pixel portion is formed in a double gate structure. However, a multi-gate structure such as a triple gate structure may be used in order to reduce a variation in an off current. Further, a single gate structure may be used to improve an aperture ratio. 
     Also, a capacitor portion  73  in the pixel portion is composed of the first insulating film  53   a  and the second insulating film  53   b  as dielectric, capacitor wiring  71 , and the n −  type region  56 . 
     Note that the pixel portion shown in  FIGS. 13A and 13B  is merely shown as one example, and the present invention is not restricted to the above structure in particular. 
     Note that this embodiment can be combined the embodiment mode and Embodiments 1 to 4. 
     Embodiment 6 
     In this embodiment, an example of a display device used in a display portion  101  or provided under an operation key will be described. In this embodiment, a light emitting device used as a display device will be explained. 
     An example of a light emitting device having a pixel portion  705  and a driver circuit  704  for driving it on the same substrate (note that a state before sealing) is shown in  FIG. 14 . Note that a CMOS circuit as a basic unit is shown in the driver circuit  704  and one pixel is shown in the pixel portion  705 . 
     In  FIG. 14 , reference numeral  701  denotes a substrate. An insulating film is formed on the substrate. A driver circuit  704  composed of an n-channel TFT  720  and a p-channel TFT  721 , and a pixel portion  705  comprising a switching TFT  702  composed of the a p-channel TFT and a current control TFT  703  composed of an n-channel TFT are formed thereon. Also, in this embodiment, all TFTs are formed as top gate TFTs. 
     Also, the switching TFT  702  has a structure (double gate structure) where two channel forming regions are located between a source region and a drain region. However, this embodiment is not restricted to the double gate structure. A single gate structure where one channel forming region is formed or a triple gate structure where three channel forming regions are formed may be used. 
     Also, before a second interlayer insulating film  708  is provided, a contact hole is provided in a first interlayer insulating film  707  on a drain region  706  of the current control TFT  703 . This is because an etching process is simplified in the case where a contact hole is formed in the second interlayer insulating film  708 . The contact hole is formed in the second interlayer insulating film  708  so as to reach the drain region  706  and a pixel electrode  709  connected with the drain region  706  is provided. The pixel electrode  709  is an electrode which functions as the cathode of a light-emitting element and formed using a conductive film containing an element belonging to group 1 or 2 of the periodic table. In this embodiment, a conductive film made of a compound of lithium and aluminum is used. 
     Reference numeral  713  denotes an insulating film provided to cover end portions of the pixel electrode  709  and this insulating film is called a bank in this specification. The bank  713  may be formed using an insulating film containing silicon or a resin film. In the case where the resin film is used, when a carbon particle or a metal particle is added to the resin film such that resistivity thereof becomes 1×10 6  to 1×10 12  Ωm (preferably, 1×10 8  to 1×10 10  Ωm), the occurrence of dielectric breakdown at film formation can be suppressed. 
     Also, a light-emitting element  710  is composed of the pixel electrode (cathode)  709 , an organic compound layer  711 , and an anode  712 . As the anode  712 , a conductive film having a large work function, typically an oxide conductive film is used. As the oxide conductive film, indium oxide, tin oxide, zinc oxide or a compound of these may be used. The light emitting device of this embodiment becomes a light emitting device for emitting light upward. Note that this embodiment is not restricted to the light emitting device for emitting light upward. If the structure of the light emitting device is suitably modified, the light emitting device for emitting light downward can be obtained. 
     Note that a laminate in which a hole injection layer, a hole transport layer, a hole blocking layer, an electron transport layer, an electron injection layer, or an electron blocking layer is combined with a luminescent layer is defined as an organic compound layer in this specification. Also, if an organic compound material is used, the luminescent layer is not limited to a specific material. For example, a thin film made of a luminescent material (singlet compound) for luminescence by singlet excitation or a thin film made of a luminescent material (triplet compound) for luminescence by triplet excitation can be used. 
     Note that, although not shown here, after the anode  712  is formed, it is effective that a passivation film is provided so as to completely cover the EL layer  710 . As the passivation film, an insulating film including a carbon film, a silicon nitride film, or a silicon oxynitride film as a single layer, or a laminate layer of those is used. 
     Next, a process up to a sealing (or filling) process for protecting the light-emitting element is performed. The EL display device after the process will be described using  FIGS. 15A and 15B . 
       FIG. 15A  is a top view showing a state where a process up to sealing of the EL element is performed and  FIG. 15B  is a cross sectional view taken along a line A-A′ in  FIG. 15A . As shown by dot lines, reference numeral  801  denotes a pixel portion, numeral  802  denotes a source side driver circuit, and numeral  803  denotes a gate side driver circuit. Also, reference numeral  804  denotes a cover member, numeral  805  denotes a first seal member, and numeral  806  denotes a second seal member. 
     Note that reference numeral  808  denotes FPC, and  807  is a wiring for transmitting signals to be inputted to the source side driver circuit  802  and the gate side driver circuit  803 . Note that, although only the FPC is shown in  FIGS. 15A and 15B , a printed wiring board (PWB) may be attached to the FPC. 
     Next, the cross sectional structure will be described using  FIG. 15B . The pixel portion and the source side driver circuit  809  are formed over a substrate  800 . The pixel portion is composed of a plurality of pixels. Each of the pixels includes a current control TFT  810  and a pixel electrode  811  electrically connected with the drain thereof. The source side driver circuit  809  is constructed using a CMOS circuit in which an n-channel TFT and a p-channel TFT are combined with each other. Note that a polarization plate (typically a circular polarization plate) may be attached to the substrate  800 . 
     Banks  812  are formed at both ends of the pixel electrode  811  and an organic compound layer  813  and an anode  814  of the light-emitting element are formed on the pixel electrode  811 . The anode  814  also function as wiring common to all pixels and is electrically connected with an FPC  808  through a connection wiring  815 . Further, all elements included in the pixel portion and the source side driver circuit  809  are covered with a passivation film (not shown). 
     Also, the cover member  804  is adhered to the substrate  800  through the first seal member  805 . Note that spacers may be provided to secure an interval between the cover member  804  and the EL element constant. A gap (space)  817  is produced inside the first seal member  805  and the substrate  800 . It is desirable that the first seal member  805  is a material to which moisture or oxygen is not transmitted. It is effective that a substance having a hygroscopic effect or a substance having an antioxidant effect is provided in the gap  817 . 
     A carbon film (specifically, a diamond like carbon film) is preferably provided as a protective film on the front surface and the rear surface of the cover member  804  with a thickness of 2 to 30 nm. Such a carbon film (not shown here) has the functions of preventing penetration of oxygen and water and mechanically protecting the surface of the cover member  804 . 
     After the adhesion of the cover member  804 , the second seal member  806  is provided so as to cover the exposed surface of the first seal member  805 . The same material as the first seal member  805  can be used for the second seal member  806 . 
     When the light-emitting element is filled with the above structure, the light-emitting element can be completely shielded from the exterior and the penetration of a substance which causes deterioration of the organic compound layer by oxidation, such as moisture or oxygen, from the exterior can be prevented. Therefore, the light emitting device having high reliability is obtained. 
     Note that this embodiment can be combined the embodiment mode and Embodiments 1 to 5. 
     Embodiment 7 
     This embodiment deals with a case where a photoelectric conversion element (photodiode) is incorporated in each pixel of the display device. In this embodiment, each pixel in the light-emitting device has a photoelectric conversion element incorporated therein. 
       FIG. 16  closely illustrates the constitution of a pixel  1002 . A region surrounded by a dotted line represents the pixel  1002 . 
     The pixel  1002  includes a switching TFT  1004 , a driving TFT  1005  and a light-emitting element  1006 . In  FIG. 16 , the pixel  1002  is provided with a capacitor  1007 . The capacitor  1007 , however, may not be provided. 
     The light-emitting element  1006  comprises an anode, a cathode and an organic compound layer provided between the anode and the cathode. When the cathode is connected to the source region or the drain region of the driving TFT  1005 , the anode works as an opposing electrode, the cathode works as a pixel electrode, and light is emitted toward the lower direction. Conversely, when the anode is connected to the source region or the drain region of the driving TFT  1005 , the anode works as the pixel electrode, the cathode works as the opposing electrode, and light is emitted toward the upper direction. 
     The gate electrode of the switching TFT  1004  is connected to the gate signal line G. As for the source region and the drain region of the switching TFT  1004 , either one of them is connected to the source signal line S and the other one is connected to the gate electrode of the driving TFT  1005 . 
     The source region of the driving TFT  1005  is connected to a power-source supply line V, and the drain region of the driving TFT  1005  is connected to the light-emitting element  1006 . The capacitor  1007  is connected to the gate electrode of the driving TFT  1005  and to the power-source supply line V. 
     The pixel  1002  includes a reset TFT  1010 , a buffer TFT  1011 , a selection TFT  1012  and a photodiode  1013 . 
     The gate electrode of the reset TFT  1010  is connected to a rest gate signal line RG. The source region of the reset TFT  1010  is connected to a sensor power-source line VB. The power-source line VB for sensor is maintained at a constant potential (reference potential) at all times. The drain region of the reset TFT  1010  is connected to the photodiode  1013  and to the gate electrode of the buffer TFT  1011 . 
     Though not diagramed, the photodiode  1013  includes an N-type semiconductor layer, a P-type semiconductor layer, and a photoelectric conversion layer provided between the N-type semiconductor layer and the P-type semiconductor layer. Concretely speaking, the drain region of the reset TFT  1010  is connected to the P-type semiconductor layer or to the N-type semiconductor layer of the photodiode  1013 . 
     The drain region of the buffet TFT  1011  is connected to the power-source line VB for sensor and is maintained at a constant reference potential at all times. The source region of the buffer TFT  1011  is connected to the source region or the drain region of the selection TFT  1012 . 
     The gate electrode of the selection TFT  1012  is connected to a sensor gate signal line SG. One of the source region and the drain region of the selection TFT  1012  is connected to the source region of the buffer TFT  1011  as described above and the other one thereof is connected to the sensor output wiring SS. The sensor output wiring SS is connected to a constant current source  1003  to flow a constant current at all times. 
       FIG. 17  is a sectional view of the pixel according to the embodiment. Reference numeral  1101  denotes a switching TFT,  1102  denotes a driving TFT,  1103  denotes a reset TFT,  1104  denotes a buffer TFT, and  1105  denotes a selection TFT. 
     Further, reference numeral  1108  denotes a P-type semiconductor layer,  1109  denotes a photoelectric conversion layer and  1107  denotes an N-type semiconductor layer. A photodiode  1106  is formed by the P-type semiconductor layer  1108 , photoelectric conversion layer  1109  and N-type semiconductor layer  1107 . Reference numeral  1111  denotes a sensor wiring which electrically connects the P-type semiconductor layer  1108  to an external power source. Further, the P-type semiconductor layer  1108  of the photodiode  1106  is electrically connected to the drain region of the reset TFT  1103 . 
     Reference numeral  1110  denotes a pixel electrode (anode),  1112  denotes an organic compound layer and  1113  denotes an opposing electrode (cathode). A light-emitting element  1114  is formed by the pixel electrode (anode)  1110 , organic compound layer  1112  and opposing electrode (cathode)  1113 . Reference numeral  1115  denotes a bank partitioning the organic compound layer  1112  of the neighboring pixels. 
     Reference numeral  1116  denotes a subject. Light emitted from the light-emitting element  1114  is reflected by the subject  1116  to fall on the photodiode  1106 . In this embodiment, the subject  1116  is provided on the side where no TFT has been formed in the substrate  1100 . 
     In this embodiment, the switching TFT  1101 , buffer TFT  1104  and selection TFT  1105  are all N-channel TFTs. The driving TFT  1102  and the reset TFT  1103  are P-channel TFTs. This invention is not limited to this constitution only. Namely, the switching TFT  1101 , driving TFT  1102 , buffer TFT  1104 , selection TFT  1105  and reset TFT  1103  may be either the N-channel TFTs or the P-channel TFTs. 
     Here, however, when the source region or the drain region of the driving TFT  1102  is electrically connected to the anode  1113  of the light-emitting element  1114  as in this embodiment, it is desired that the driving TFT  1102  is the P-channel TFT. Conversely, when the source region or the drain region of the driving TFT  1102  is electrically connected to the cathode of the light-emitting element  1114 , it is desired that the driving TFT  1102  is the N-channel TFT. 
     In this embodiment, the photodiode can be formed simultaneously with other TFTs making it possible to suppress the number of the steps. With the photoelectric conversion element being incorporated in each pixel, furthermore, the display portion of the electronic device of the invention can be used as an image sensor. This embodiment can be used in free combination with the mode of use and with the embodiments 1 to 6. 
     The electronic device of the invention is allowed to be folded and is realized in a small size since the first housing and the second housing are coupled together by a hinge. Further, the electronic device of this invention has such a shape that the first center line of the first housing and the second center line of the second housing come into agreement and in parallel with each other only in a state where the first housing and the second housing are folded by the hinge. At the time of using the electronic device having the transmitting unit, therefore, the transmitting unit can be easily brought close to the mouth and the voice is transmitted to a remote user more clearly.