Liquid crystal display device and electronic device

Abstract

To provide a liquid crystal display device which can perform image display in both modes: a reflective mode where external light is used as an illumination light source; and a transmissive mode where a backlight is used. In one pixel, a region where incident light through a liquid crystal layer is reflected to perform display (reflective region) and a region through which light from the backlight passes to perform display (transmissive region) are provided, and image display can be performed in both modes: the reflective mode where external light is used as an illumination light source; and the transmissive mode where the backlight is used as an illumination light source. In addition, two transistors connected to respective pixel electrode layers are provided in one pixel, and the two transistors are separately operated, whereby display of the reflective region and display of the transmissive region can be controlled independently.

1 . (canceled) 
     
     
         2 . A liquid-crystal display device comprising:
 a display panel comprising a pixel;   a backlight; and   an image processing circuit,   wherein the pixel comprises a first subpixel,   wherein the first subpixel comprises a first pixel electrode and a first transistor,   wherein the backlight comprises a first light-emitting element emitting light of a first wavelength, a second light-emitting element emitting light of a second wavelength, and a third light-emitting element emitting light of a third wavelength corresponding to blue light,   wherein the first transistor has a function of transmitting an image signal to the first pixel electrode,   wherein the image processing circuit comprises a field sequential signal generation circuit,   wherein the field sequential signal generation circuit has a function to control a display period of one frame,   wherein the display period of the one frame includes a first period, a second period, and a third period,   wherein in the first period, the first light-emitting element is continuously lit and the third light-emitting element emits light,   wherein in the second period, the second light-emitting element is continuously lit and the third light-emitting element emits light, and   wherein in the third period, the third light-emitting element emits light.   
     
     
         3 . A liquid-crystal display device comprising:
 a display panel comprising a pixel;   a backlight; and   an image processing circuit,   wherein the pixel comprises a first subpixel,   wherein the first subpixel comprises a first pixel electrode and a first transistor,   wherein the backlight comprises a first light-emitting element emitting light of a first wavelength, a second light-emitting element emitting light of a second wavelength, a third light-emitting element emitting light of a third wavelength corresponding to blue light, a fourth light-emitting element emitting light of a fourth wavelength corresponding to blue light, and a fifth light emitting element emitting light of a fifth wavelength,   wherein the first transistor has a function of transmitting an image signal to the first pixel electrode,   wherein the image processing circuit comprises a field sequential signal generation circuit,   wherein the field sequential signal generation circuit has a function to control a display period of one frame,   wherein the display period of the one frame includes a first period, a second period, a third period, a fourth period, a fifth period, and a sixth period,   wherein in the first period, the first light-emitting element is continuously lit and the third light-emitting element emits light,   wherein in the second period, the second light-emitting element is continuously lit and the fourth light-emitting element emits light,   wherein in the third period, the third light-emitting element is continuously lit and the fourth light-emitting element emits light,   wherein in the fourth period, the fifth light-emitting element is continuously lit and the fourth light-emitting element emits light,   wherein in the fifth period, the second light-emitting element is continuously lit and the third light-emitting element emits light, and   wherein in the sixth period, the fourth light-emitting element is continuously lit and the third light-emitting element emits light,   
     
     
         4 . The semiconductor device according to  claim 2 , wherein no grain boundary is observed in the metal oxide film in a high-resolution TEM image. 
     
     
         5 . The semiconductor device according to  claim 3 , wherein no grain boundary is observed in the metal oxide film in a high-resolution TEM image. 
     
     
         6 . A semiconductor device comprising:
 a transistor, the transistor comprising:
 an oxide semiconductor film; 
 a gate insulating film comprising any one of silicon oxide, silicon nitride, and silicon nitride oxide over the oxide semiconductor film; 
 a metal oxide film over the gate insulating film; 
 a first conductive film, having a region overlapping with the oxide semiconductor film with the gate insulating film and the metal oxide film provided therebetween, over the metal oxide film; 
 an insulating film comprising hydrogen over the first conductive film; and 
 a second conductive film and a third conductive film, electrically connected to the oxide semiconductor film, over the insulating film comprising hydrogen, 
   wherein the first conductive film functions as a gate electrode,   wherein, in a cross-sectional view in a channel-length direction of the transistor, a width of the gate insulating film is greater than a width of the metal oxide film,   wherein a top surface of the gate insulating film has a first region in contact with a first portion of the insulating film comprising hydrogen, a second region in contact with a second portion of the insulating film comprising hydrogen, and a third region in contact with the metal oxide film between the first region and the second region, and   wherein the oxide semiconductor film has a fourth region in contact with a third portion of the insulating film comprising hydrogen, a fifth region in contact with a fourth portion of the insulating film comprising hydrogen, and a sixth portion in contact with the gate insulating film between the fourth region and the fifth region.   
     
     
         7 . A semiconductor device comprising:
 a transistor, the transistor comprising:
 a first conductive film; 
 a first gate insulating film over the first conductive film; 
 an oxide semiconductor film over the first gate insulating film; 
 a second gate insulating film comprising any one of silicon oxide, silicon nitride, and silicon nitride oxide over the oxide semiconductor film; 
 a metal oxide film over the second gate insulating film; 
 a second conductive film, having a region overlapping with the oxide semiconductor film with the second gate insulating film and the metal oxide film provided therebetween, over the metal oxide film; 
 an insulating film comprising hydrogen over the second conductive film; and 
 a third conductive film and a fourth conductive film, electrically connected to the oxide semiconductor film, over the insulating film comprising hydrogen, 
   wherein each of the first conductive film and the second conductive film functions as a gate electrode,   wherein, in a cross-sectional view in a channel-length direction of the transistor, a width of the second gate insulating film is greater than a width of the metal oxide film and smaller than a width of the first conductive film,   wherein a top surface of the second gate insulating film has a first region in contact with a first portion of the insulating film comprising hydrogen, a second region in contact with a second portion of the insulating film comprising hydrogen, and a third region in contact with the metal oxide film between the first region and the second region, and   wherein the oxide semiconductor film has a fourth region in contact with a third portion of the insulating film comprising hydrogen, a fifth region in contact with a fourth portion of the insulating film comprising hydrogen, and a sixth portion in contact with the second gate insulating film between the fourth region and the fifth region.   
     
     
         8 . The semiconductor device according to  claim 2 , wherein each of the oxide semiconductor film and the metal oxide film comprises In, Ga, and Zn. 
     
     
         9 . The semiconductor device according to  claim 3 , wherein each of the oxide semiconductor film and the metal oxide film comprises In, Ga, and Zn. 
     
     
         10 . The semiconductor device according to  claim 6 , wherein each of the oxide semiconductor film and the metal oxide film comprises In, Ga, and Zn. 
     
     
         11 . The semiconductor device according to  claim 7 , wherein each of the oxide semiconductor film and the metal oxide film comprises In, Ga, and Zn.