Display device
First Claim
Patent Images
1. A display device provided with a display panel comprising:
- a pixel portion comprising a pixel, wherein the pixel comprises a liquid crystal display element and a first transistor including an oxide semiconductor layer;
a driver circuit portion configured to drive the pixel portion and display an image on a screen; and
a switching element comprising a second transistor including the oxide semiconductor layer,wherein the oxide semiconductor layer comprises a crystal,wherein a c-axis of the crystal is aligned in a direction perpendicular to a surface of the oxide semiconductor layer,wherein the first transistor and the second transistor are connected to each other with the liquid crystal display element,wherein the driver circuit portion has a function to write a first image signal and a second image signal to the pixel successively so as to display an image on the screen, and a function to stop a writing operation of the second image signal and turn the first transistor off so as to maintain one image written to the screen when a difference is not detected between the first image signal and the second image signal, andwherein an off current of each of the first transistor and the second transistor is lower than 10 zA/μ
m at room temperature and lower than 100 zA μ
m at 85 °
C.
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Abstract
A driver circuit portion of a display device has a function in which image signals are written to a selected pixel successively so as to display an image on a screen and a function in which writing operation of an image signal is stopped and a transistor is turned off so as to maintain one image written to the screen when the one image is continuously displayed on the screen. Such functions are achieved by a transistor whose off current per micrometer in channel width is reduced to an extremely low value that is lower than 10 zA/μm at room temperature and lower than 100 zA/μm at 85° C.
228 Citations
42 Claims
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1. A display device provided with a display panel comprising:
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a pixel portion comprising a pixel, wherein the pixel comprises a liquid crystal display element and a first transistor including an oxide semiconductor layer; a driver circuit portion configured to drive the pixel portion and display an image on a screen; and a switching element comprising a second transistor including the oxide semiconductor layer, wherein the oxide semiconductor layer comprises a crystal, wherein a c-axis of the crystal is aligned in a direction perpendicular to a surface of the oxide semiconductor layer, wherein the first transistor and the second transistor are connected to each other with the liquid crystal display element, wherein the driver circuit portion has a function to write a first image signal and a second image signal to the pixel successively so as to display an image on the screen, and a function to stop a writing operation of the second image signal and turn the first transistor off so as to maintain one image written to the screen when a difference is not detected between the first image signal and the second image signal, and wherein an off current of each of the first transistor and the second transistor is lower than 10 zA/μ
m at room temperature and lower than 100 zA μ
m at 85 °
C. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 16)
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11. A display device provided with a display panel comprising:
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a pixel portion comprising a pixel, wherein the pixel comprises a liquid crystal display element and a first transistor including an oxide semiconductor layer; a driver circuit portion configured to drive the pixel portion and display an image on a screen; and a switching element comprising a second transistor including the oxide semiconductor layer, wherein the oxide semiconductor layer comprises a crystal, wherein a c-axis of the crystal is aligned in a direction perpendicular to a surface of the oxide semiconductor layer, wherein the first transistor and the second transistor are connected to each other with the liquid crystal display element, wherein the driver circuit portion has a function to select a first operation mode and a second operation mode, wherein the first operation mode is to perform a writing operation by writing a first image signal and a second image signal to the pixel successively so as to display an image on the screen, and wherein the second operation mode is to stop a writing operation so as to maintain one image written to the screen when the a difference is not detected between the first image signal and the second image signal, and wherein an off current of each of the first transistor and the second transistor is lower than 10 zA/ μ
m at room temperature and lower than 100 zA/ μ
m at 85 °
C. - View Dependent Claims (12, 13, 14, 15, 17, 18, 19, 20)
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21. A display device provided with a display panel comprising:
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a pixel portion comprising a pixel, wherein the pixel comprises a liquid crystal display element and a first transistor including an oxide semiconductor layer; a driver circuit portion configured to drive the pixel portion and display an image on a screen; and a switching element comprising a second transistor including the oxide semiconductor layer, wherein the oxide semiconductor layer comprises a crystal, wherein a c-axis of the crystal is aligned in a direction perpendicular to a surface of the oxide semiconductor layer, wherein the first transistor and the second transistor are connected to each other with the liquid crystal display element, wherein the driver circuit portion has a function to write a first image signal and a second image signal to the pixel successively so as to display an image on the screen, and a function to stop a writing operation of the second image signal and turn the first transistor off so as to maintain one image written to the screen when a difference is not detected between the first image signal and the second image signal, wherein an off current of each of the first transistor and the second transistor is lower than 10 zA/ μ
m at room temperature and lower than 100 zA/ μ
m at 85 °
C., andwherein a source electrode and a drain electrode of each of the first transistor and the second transistor comprise metal nitride. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A display device provided with a display panel comprising:
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a pixel portion comprising a pixel, wherein the pixel comprises a liquid crystal display element and a first transistor including an oxide semiconductor layer; a driver circuit portion configured to drive the pixel portion and display an image on a screen; and a switching element comprising a second transistor including the oxide semiconductor layer, wherein the oxide semiconductor layer comprises a crystal, wherein a c-axis of the crystal is aligned in a direction perpendicular to a surface of the oxide semiconductor layer, wherein the first transistor and the second transistor are connected to each other with the liquid crystal display element, wherein the driver circuit portion has a function to select a first operation mode and a second operation mode, wherein the first operation mode is to perform a writing operation by writing a first image signal and a second image signal to the pixel successively so as to display an image on the screen, and wherein the second operation mode is to stop a writing operation so as to maintain one image written to the screen when the a difference is not detected between the first image signal and the second image signal, wherein an off current of each of the first transistor and the second transistor is lower than 10 zA/ μ
m at room temperature and lower than 100 zA/μ
m at 85 °
C., andwherein a source electrode and a drain electrode of each of the first transistor and the second transistor comprise metal nitride. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification