Driving method of liquid crystal display device
First Claim
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1. A liquid crystal display device comprising:
- a pixel portion comprising;
first to fourth conductive layers;
a semiconductor layer;
first and second insulating layers; and
a liquid crystal,wherein;
the first insulating layer is located over the first conductive layer;
the semiconductor layer is located over the first insulating layer;
the second and third conductive layers are in the same layer and located over the semiconductor layer;
the second insulating layer is located over the second and third conductive layers;
the fourth conductive layer is located over the second insulating layer;
the third conductive layer is electrically connected to the fourth conductive layer in a contact hole which is located in the second insulating layer;
a part of the first conductive layer is configured to be a gate of a transistor;
a part of the first insulating layer is configured to be a gate insulating layer of the transistor;
the second conductive layer is configured to be one of a source and a drain of the transistor;
the second conductive layer is configured to supply an image signal;
the third conductive layer is configured to be the other of the source and the drain of the transistor;
the fourth conductive layer is configured to apply an electric field to the liquid crystal;
the first conductive layer extends in a first direction in the pixel portion;
the second conductive layer extends in a second direction in the pixel portion;
the first direction intersects with the second direction;
the whole of the semiconductor layer overlaps with the first conductive layer in the pixel portion;
in a periphery of the semiconductor layer in the pixel portion, the third conductive layer comprises a region in which the third conductive layer overlaps with the first conductive layer with the first insulating layer therebetween;
no capacitor line is located in the pixel portion;
the semiconductor layer comprises an oxide semiconductor;
the oxide semiconductor comprises indium, gallium, and zinc and comprises a region where a carrier density is less than 1×
1014/cm3; and
the oxide semiconductor comprises a crystal which is c-axis-aligned.
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Abstract
An object is to provide a driving method of a liquid crystal display device with a low power consumption and a high image quality. A pixel includes a liquid crystal element and a transistor which controls supply of an image signal to the liquid crystal element. The transistor includes, in a channel formation region, a semiconductor which has a wider band gap than a silicon semiconductor and has a lower intrinsic carrier density than silicon, and has an extremely low off-state current. In inversion driving of pixels, image signals having opposite polarities are input to a pair of signal lines between which a pixel electrode is disposed. By employing such a structure, the quality of the displayed image can be increased even in the absence of a capacitor in the pixel.
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Citations
14 Claims
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1. A liquid crystal display device comprising:
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a pixel portion comprising; first to fourth conductive layers; a semiconductor layer; first and second insulating layers; and a liquid crystal, wherein; the first insulating layer is located over the first conductive layer; the semiconductor layer is located over the first insulating layer; the second and third conductive layers are in the same layer and located over the semiconductor layer; the second insulating layer is located over the second and third conductive layers; the fourth conductive layer is located over the second insulating layer; the third conductive layer is electrically connected to the fourth conductive layer in a contact hole which is located in the second insulating layer; a part of the first conductive layer is configured to be a gate of a transistor; a part of the first insulating layer is configured to be a gate insulating layer of the transistor; the second conductive layer is configured to be one of a source and a drain of the transistor; the second conductive layer is configured to supply an image signal; the third conductive layer is configured to be the other of the source and the drain of the transistor; the fourth conductive layer is configured to apply an electric field to the liquid crystal; the first conductive layer extends in a first direction in the pixel portion; the second conductive layer extends in a second direction in the pixel portion; the first direction intersects with the second direction; the whole of the semiconductor layer overlaps with the first conductive layer in the pixel portion; in a periphery of the semiconductor layer in the pixel portion, the third conductive layer comprises a region in which the third conductive layer overlaps with the first conductive layer with the first insulating layer therebetween; no capacitor line is located in the pixel portion; the semiconductor layer comprises an oxide semiconductor; the oxide semiconductor comprises indium, gallium, and zinc and comprises a region where a carrier density is less than 1×
1014/cm3; andthe oxide semiconductor comprises a crystal which is c-axis-aligned. - View Dependent Claims (2, 3, 4, 5)
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6. A liquid crystal display device comprising a plurality of pixels over a substrate, at least one of the plurality of pixels comprising:
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a signal line over the substrate; a gate electrode over the substrate; a gate insulating film over the gate electrode, the gate insulating film comprising a metal oxide of a Group 13 element; an oxide semiconductor film over the gate insulating film, the oxide semiconductor film having a band gap wider than a silicon semiconductor; a first conductive film and a second conductive film over the oxide semiconductor film; and a liquid crystal element comprising a pixel electrode, wherein the first conductive film is electrically connected to the signal line, wherein the second conductive film is electrically connected to the pixel electrode, and wherein the metal oxide is configured to supply oxygen to the oxide semiconductor film when the metal oxide is heated. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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Specification
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Current AssigneeSemiconductor Energy Laboratory Co., Ltd.
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Original AssigneeSemiconductor Energy Laboratory Co., Ltd.
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InventorsMiyake, Hiroyuki, Shishido, Hideaki, Arasawa, Ryo
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Primary Examiner(s)BOYD, JONATHAN A
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Application NumberUS15/646,452Publication NumberTime in Patent Office350 DaysField of SearchUS Class CurrentCPC Class CodesG06F 1/3265 Power saving in display deviceG06F 3/038 Control and interface arran...G09G 3/3614 Control of polarity reversa...G09G 3/3648 using an active matrix G09G...H01L 27/1225 with semiconductor material...H01L 29/02 Semiconductor bodies ; Mult...Y02D 10/00 Energy efficient computing,...
