Display device
阅读说明：本技术 显示设备 (Display device ) 是由 山崎舜平 小山润 三宅博之 津吹将志 野田耕生 于 2010-09-28 设计创作，主要内容包括：本发明涉及一种显示设备,包括：包括源极、漏极和沟道形成区的晶体管,所述沟道形成区包括氧化物半导体；电连接到所述晶体管的所述源极或所述漏极的像素电极；以及与所述像素电极相邻的液晶材料,其中,所述液晶材料在20℃测量的特定电阻率大于或等于1×10<Sup>12</Sup>Ω·cm。(The present invention relates to a display device comprising: a transistor including a source electrode, a drain electrode, and a channel formation region including an oxide semiconductor; a pixel electrode electrically connected to the source or the drain of the transistor; and a liquid crystal material adjacent to the pixel electrode, wherein the liquid crystal material has a specific resistivity of 1 × 10 or more measured at 20 ℃ 12 Ω·cm。)
1. A display device, comprising:
A pixel portion and a driving circuit for driving the pixel portion,
Wherein the pixel portion includes a transistor and a display element,
The transistor includes a gate electrode layer, a gate insulating layer over the gate electrode layer, and an oxide semiconductor layer over the gate insulating layer,
A first silicon oxide film is located on the oxide semiconductor layer,
A first silicon nitride film is located on the first silicon oxide film,
The gate insulating layer includes a second silicon nitride film and a second silicon oxide film on the second silicon nitride film,
The first silicon oxide film includes a region in contact with the oxide semiconductor layer,
The second silicon oxide film includes a region in contact with the oxide semiconductor layer,
The drive circuit has a function of writing a signal to the pixel portion,
And a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a still image is lower than a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a moving image.
2. A display device, comprising:
A pixel portion and a driving circuit for driving the pixel portion,
Wherein the pixel portion includes a transistor and a display element,
The transistor includes a gate electrode layer, a gate insulating layer over the gate electrode layer, and an oxide semiconductor layer over the gate insulating layer,
A first silicon oxide film is located on the oxide semiconductor layer,
A first silicon nitride film is located on the first silicon oxide film,
The gate insulating layer includes a second silicon nitride film and a second silicon oxide film on the second silicon nitride film,
The first silicon oxide film includes a region in contact with the oxide semiconductor layer,
The second silicon oxide film includes a region in contact with the oxide semiconductor layer,
The oxide semiconductor layer contains indium, gallium, and zinc,
The drive circuit has a function of writing a signal to the pixel portion,
And a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a still image is lower than a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a moving image.
3. A display device, comprising:
A pixel portion and a driving circuit for driving the pixel portion,
Wherein the pixel portion includes a transistor and a display element,
The transistor includes a gate electrode layer, a gate insulating layer over the gate electrode layer, and an oxide semiconductor layer over the gate insulating layer,
A first silicon oxide film is located on the oxide semiconductor layer,
A first silicon nitride film is located on the first silicon oxide film,
The gate insulating layer includes a second silicon nitride film and a second silicon oxide film on the second silicon nitride film,
The first silicon oxide film includes a region in contact with the oxide semiconductor layer,
The second silicon oxide film includes a region in contact with the oxide semiconductor layer,
The oxide semiconductor layer includes a crystalline portion,
The drive circuit has a function of writing a signal to the pixel portion,
And a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a still image is lower than a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a moving image.
4. A display device, comprising:
A pixel portion and a driving circuit for driving the pixel portion,
Wherein the pixel portion includes a transistor and a display element,
The transistor includes a gate electrode layer, a gate insulating layer over the gate electrode layer, and an oxide semiconductor layer over the gate insulating layer,
A first silicon oxide film is located on the oxide semiconductor layer,
A first silicon nitride film is located on the first silicon oxide film,
The gate insulating layer includes a second silicon nitride film and a second silicon oxide film on the second silicon nitride film,
The first silicon oxide film includes a region in contact with the oxide semiconductor layer,
The second silicon oxide film includes a region in contact with the oxide semiconductor layer,
The off-state current of the transistor is less than or equal to 1 × 10 -13A，
The drive circuit has a function of writing a signal to the pixel portion,
And a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a still image is lower than a frequency of writing the signal from the driving circuit to the display element through the transistor when the pixel portion is caused to display a moving image.
5. The display device according to any one of claims 1 to 4,
The first silicon oxide film has a function of supplying oxygen to the oxide semiconductor layer.
Technical Field
The present invention relates to a liquid crystal display device. The present invention relates to an electronic apparatus having a liquid crystal display device.
Background
As commonly seen in liquid crystal display devices, thin film transistors formed on a flat plate such as a glass substrate have been manufactured using amorphous silicon, polysilicon, or the like. A thin film transistor manufactured using amorphous silicon has low field effect mobility, but can be formed on a larger glass substrate. On the other hand, a thin film transistor manufactured using crystalline silicon has high field effect mobility, but such a transistor is not necessarily suitable for formation on a large glass substrate due to a crystallization step such as laser annealing.
In view of the above, a technique of manufacturing a thin film transistor using an oxide semiconductor has been noted, and such a transistor is applied to an electronic device or an optical device. For example,
[ reference documents ]
Patent document 1: japanese published patent application No.2006-165528
Disclosure of Invention
It is said that a thin film transistor in which an oxide semiconductor is used to form a channel region realizes higher field effect mobility than a thin film transistor in which amorphous silicon is used to form a channel region. It is desirable to apply a pixel including such a thin film transistor using an oxide semiconductor to a display device such as a liquid crystal display device.
Each pixel included in the liquid crystal display device is provided with a storage capacitor in which a voltage for controlling the orientation of the liquid crystal element is held. Off-leak current (hereinafter referred to as off-state current) of the thin film transistor is one factor determining the holding capacitance. When displaying a still image or the like, it is important to reduce the off-state current (which results in an increase in the period of holding the voltage in the storage capacitor) to reduce power consumption.
Further, it is important to increase the added value of the display device to manufacture the display device so that a moving image can be displayed in addition to low power consumption in displaying a still image or the like. Therefore, it is important to determine whether an image is a still image or a moving image, and to perform display by switching between the still image and the moving image, thereby further reducing power consumption by reducing power consumption when displaying the still image.
Note that in this specification, an off-state current is a current flowing between a source electrode and a drain electrode when a thin film transistor is in an off state (also referred to as a non-conductive state). In the case of an n-channel thin film transistor (e.g., having a threshold voltage of about 0 to 2V), the off-state current refers to a current flowing between the source and the drain when a negative voltage is applied between the gate and the source.
Further, in a liquid crystal display device having a higher added value (such as a 3D display or a 4k2k display), the area per pixel is expected to be small, and an improvement in aperture ratio is required. To improve the aperture ratio, it is important to reduce the area of the storage capacitor. Therefore, it is necessary to reduce off-state current of the thin film transistor.
In view of the above, an object of one embodiment of the present invention is to provide a liquid crystal display device with reduced power consumption in which off-state current of a thin film transistor using an oxide semiconductor is reduced in a pixel.
One embodiment of the present invention is a liquid crystal display device including: a display panel including a driver circuit portion, and a pixel portion in which a transistor including a semiconductor layer using an oxide semiconductor is provided in each pixel; a signal generation circuit for generating a control signal for driving the drive circuit portion and an image signal supplied to the pixel portion; a memory circuit for storing an image signal for each frame period; a comparison circuit for detecting a difference in image signals for a series of frame periods among the image signals for the respective frame periods stored in the memory circuit; a selection circuit that selects and outputs the image signals of the series of frame periods when the difference is detected in the comparison circuit; and a display control circuit which supplies the control signal and the image signal output from the selection circuit to the drive circuit portion when the difference is detected in the comparison circuit, and stops the supply of the control signal to the drive circuit portion when the difference is not detected in the comparison circuit.
The control signal in the liquid crystal display device may be any one of a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, and a reset signal.
The oxide semiconductor in the liquid crystal display device may have 1 × 10 or less detected by secondary ion mass spectrometry 16/cm3The hydrogen concentration of (c).
The oxide semiconductor in the liquid crystal display device may have a size of less than 1 × 10 14/cm3The carrier density of (2).
According to the present invention, in a pixel including a thin film transistor using an oxide semiconductor, off-state current can be reduced. Accordingly, the period of holding the voltage in the storage capacitor can be extended, so that a liquid crystal display device in which power consumption in displaying a still image or the like can be reduced can be provided. In addition, the aperture ratio can be improved, so that a liquid crystal display device including a high-resolution display portion can be provided.
Further, a display device which displays not only a still image but also a moving image can be provided, so that the added value of the display device can be improved. Whether an image is a still image or a moving image is determined, and display is performed by switching between the still image and the moving image, so that power consumption in displaying the still image can be reduced.
Drawings
Fig. 1 is a diagram showing one example of a block diagram of a liquid crystal display device;
Fig. 2A to 2C are diagrams illustrating one example of a driving circuit.
Fig. 3 is a timing diagram of the driving circuit.
Fig. 4A to 4C are diagrams illustrating one example of a driving circuit.
Fig. 5A and 5B illustrate a thin film transistor.
Fig. 6A to 6E illustrate a method for manufacturing a thin film transistor.
Fig. 7A and 7B illustrate a thin film transistor.
Fig. 8A to 8E illustrate a method for manufacturing a thin film transistor.
Fig. 9A and 9B each show a thin film transistor.
Fig. 10A to 10E illustrate a method for manufacturing a thin film transistor.
Fig. 11A to 11E illustrate a method for manufacturing a thin film transistor.
Fig. 12A to 12D illustrate a method for manufacturing a thin film transistor.
Fig. 13A to 13D illustrate a method for manufacturing a thin film transistor.
Fig. 14 shows a thin film transistor.
Fig. 15A to 15C illustrate a liquid crystal panel.
Fig. 16A to 16C each show an electronic device.
Fig. 17A to 17C each show an electronic device.
Fig. 18A and 18B illustrate a display panel and a thin film transistor.
Fig. 19 is a diagram for describing
Fig. 20A and 20B are diagrams for describing
Fig. 21A and 21B are diagrams for describing
FIG. 22 is a diagram for describing
FIG 23 is a graph for describing example 14.
FIGS. 24A and 24B are photographs for describing example 14.
Fig. 25A and 25B are graphs for describing example 14.
Fig. 26A to 26D are diagrams for describing
Fig. 27 is a photograph for describing example 1.
Fig. 28 is a graph for describing example 1.
Fig. 29 is a photograph for describing example 2.
Fig. 30 is a graph for describing example 2.
Fig. 31 is a photograph for describing example 3.
Fig. 32 is a graph for describing example 3.
Fig. 33 is a photograph for describing example 4.
Fig. 34 is a diagram for describing example 5.
Detailed Description
Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings. However, it will be readily understood by those skilled in the art that the modes and details disclosed herein may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments and examples. Note that in the structure of the present invention described below, the same portions are denoted by the same reference numerals in all the drawings.
Note that the size, the thickness of a layer, or an area of each structure shown in the drawings and the like in the embodiments is enlarged for simplicity in some cases. Thus, embodiments of the invention are not limited to such scaling.
In this specification, ordinal numbers such as "first", "second", and "third" are used to avoid confusion among components, and these terms do not numerically limit the components.
(example 1)
In this embodiment, a block diagram of a display device, and a stop order and a start order of operations in a driving circuit are described. First, a block diagram of a display apparatus is described using fig. 1.