JP6894943B2 - Display device - Google Patents

Description

The technical field relates to display devices and methods for driving them.

In recent years, as a display device, development of an electronic book in which a display panel is spelled in a book shape has been promoted (for example, Patent Document 1). Such a display device is such that the screen can be viewed by turning over the display panel like a paper book.

JP-A-2009-175767

One of the purposes of the display device is to reduce power consumption.

The disclosed display device has a function of turning over the display panel, and drives the pixels when the display panel is turned over. An aspect of the present invention is shown below.

One aspect of the present invention is a display panel in which pixels having a memory property capable of holding a video signal are arranged, and a support portion that rotatably supports the other end of the display panel with one end of the display panel as a free end. A sensor that outputs a detection signal when the display panel is rotating, and a pixel that drives a pixel by inputting a video signal to the display panel when the detection signal is output and a pixel when the detection signal is not output. It is a display device having a drive circuit for stopping the drive of the above. In the present specification, the rotation refers to the operation of turning the display panel like a paper book.

In the display device, power consumption can be reduced by shortening the pixel drive time.

The figure which shows an example of the structure of a display device. The figure which shows an example of the structure of a display device. Timing chart. Timing chart. Timing chart. Timing chart. Timing chart. The figure which shows an example of the structure of a display device. The figure which shows an example of the structure of a display device. Timing chart. The figure which shows an example of the structure of a display device. The figure which shows an example of the structure of a display device. The figure which shows an example of a transistor. The figure which shows an example of a transistor. The figure which shows the characteristic of a transistor. The figure which shows an example of the structure of a display device. The figure which shows an example of the structure of a display device.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, the following embodiments can be implemented in many different embodiments, and those skilled in the art can easily change the embodiments and details without departing from the purpose and scope thereof. Understood. Therefore, the interpretation is not limited to the description of the embodiments shown below. In all the drawings for explaining the embodiment, the same parts or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.

(Embodiment 1)
In this embodiment, an example of the display device and its driving method will be described.

FIG. 1 is an example of a display device.

The display device includes a plurality of display panels 1001 and a support portion 100 of the plurality of display panels 1001.
Has 2 and. The display panel 1001 has a display screen 1003 on one side or both sides. The support portion 1002 rotatably supports the other end of the display panel 1001 with one end of the display panel 1001 as a free end. That is, the display device can be viewed by turning the page (display panel 1001) like a paper book with the support portion 1002 as a fulcrum. Also,
The number of display panels 1001 may be one. The display panel 1001 may have flexibility. In that case, it can be used with a feeling similar to paper.

FIG. 2 shows an example of a display panel of a certain page. The display panel includes a pixel unit 100, a signal line drive circuit 200, a scanning line drive circuit 300, a controller 400, and a controller 500.

The pixel unit 100 has a plurality of pixels 101. Each of the plurality of pixels 101 has a wiring S (1).
) To S (x) (x is a natural number), any one of the wirings G (1) to G (y) (y is a natural number), and the wiring 111 and the wiring 112 are connected. In addition, in this specification, a connection means an electrical connection, and corresponds to a state in which a current, a voltage or a potential can be supplied or transmitted.

The signal line drive circuit 200 has a function of controlling the timing of outputting a video signal to the wirings S (1) to S (x). The video signal is written to each pixel 101. Then, the video signal controls the gradation and the state of each pixel 101.

The scanning line drive circuit 300 has a function of controlling the timing of outputting a gate signal to the wirings G (1) to G (y). In this way, any of the wirings G (1) to G (y) is selected. A video signal can be written to the pixel 101 belonging to the selected line.

The controller 400 controls the timing at which the signal line drive circuit 200 and the scan line drive circuit 300 operate. Therefore, the controller 400 outputs a voltage, a control signal, or the like to the signal line drive circuit 200 and the scanning line drive circuit 300.

The controller 500 controls the potentials of the wiring 111 and the wiring 112.

The controller 400 and the controller 500 can be shared by each display panel. Further, by mounting the controller 400 and the controller 500 in the support portion 1002 of FIG. 1, the display device can be miniaturized.

The display device of the present embodiment has a function of outputting a video signal to drive the pixels when the display panel is rotating and stopping the driving of the pixels when the display panel is not rotating. ing. That is, before and after turning the display panel, the pixels are driven when the display panel is turned, and the driving of the pixels is stopped after the display panel is turned. By shortening the pixel drive time in this way, the power consumption of the display device can be reduced. A specific example of how to drive the display panel will be described below.

FIG. 3 is an example of the timing chart of the display panel. The timing chart has a period Ta and a period Tb.

The period Ta is a period when the page is turned, and a video signal is written to the pixel 101. Then, the gradation of the pixel 101 is controlled. Therefore, it is also called a writing period.

The period Tb is a period before turning the page and after turning the page, and the gradation of the pixel 101 is maintained. Therefore, it is also called a retention period.

Next, the operation of the display panel during the period Ta will be described.

FIG. 4 is an example of the timing chart of the period Ta. The scanning line drive circuit 300 includes a start pulse GSP, a clock signal GCK, and a clock signal GC from the controller 400.
KB etc. are input.

When the start pulse GSP reaches the H level, the output signal GOUT of the scanning line drive circuit 300
(1) to GOUT (y) become H level in order. In this way, the scanning line drive circuit 300
Wiring G (1) to G (y) are selected in order. Then, the pixel 10 connected to the selected wiring
A video signal is input to 1 from the signal line drive circuit 200 via the wirings S (1) to S (x), respectively.

As described above, in the period Ta, the video signal is input to each of the plurality of pixels 101, and the video signal is input.
Gradation is controlled.

Next, the operation of the display panel during the period Tb will be described.

FIG. 5 is an example of a timing chart of the period Tb. Since the video signal is not written to the pixel 101 during the period Tb, it is possible to stop the driving of the pixel 101. That is, it is not necessary to select the wirings G (1) to G (y) connected to the pixel 101.

As a means for deselecting the wirings G (1) to G (y), for example, the scanning line drive circuit 300
It is possible to control and not output a signal, or to output an L level signal.
In FIG. 5, the wirings G (1) to G (y) are set to the L level of the start pulse GSP.
) Is not selected, and the pixel drive is stopped. In this way, power consumption can be reduced by shortening the pixel drive time.

FIG. 6 is another example of the timing chart of the period Tb. In FIG. 6, not only the start pulse GSP but also the clock signal GCK and the clock signal GCKB are set to the L level to stop the pixel drive. The power consumption is further reduced as compared with the driving method of FIG.

In FIG. 6, the voltage supplied to the scanning line drive circuit 300 can also be set to the same value as the L level. In this way, the bias voltage of the transistor can be made substantially zero, so that deterioration of the transistor can be suppressed.

FIG. 7 is another example of the timing chart of the period Tb. In the timing chart shown in FIG. 7, the operation of the controller 400 is stopped. Therefore, start pulse GSP
, The clock signal GCK and the clock signal GCKB are not output, and the pixel drive is stopped.
The power consumption is further reduced as compared with the driving method of FIG.

FIG. 8 is an example of the configuration of the controller 400. The controller 400 is a power supply circuit 8
It has 01, a timing generator 802, a switch element 803, and a switch element 804. The controller 400 controls the output from the power supply circuit 801 and the timing generator 802 to the scanning line drive circuit 300. For example, in the period Ta, the switch element 803
Is turned on and the switch element 804 is turned off to control the timing of outputting the _{H level signal (VH} ) or the L level signal ( _{VL) from the power supply circuit 801.} In the period Tb, the switch element 803 is turned off and the switch element 804 is turned on, so that the power supply circuit 801 outputs an _{L level signal (VL).}

FIG. 9 is an example of the configuration of the wirings G (1) to G (y) and the scanning line drive circuit 300. A switch element 901 is provided between the wirings G (1) to G (y) and the scanning line drive circuit. The switch element 901 controls the output of signals from the scanning line drive circuit 300 to the wirings G (1) to G (y). For example, in the period Ta, the switch element 901 is turned on. Period Tb
Then, the switch element 901 is turned off.

The drive of the pixel can be controlled by the configuration as shown in FIG. 8 or 9. However, the present invention is not limited to these, and various configurations can be applied.

The pixel driving method shown above can be used not only before and after turning the display panel but also for other purposes. For example, the display device has a function of processing the image displayed on the display panel, and before and after processing, drives the pixels during processing and stops driving the pixels after processing. You may. Examples of processing include enlargement, reduction, deformation, and the like of an image. Power consumption can be reduced by controlling the drive of the pixels in this way.

This embodiment can be implemented in combination with other embodiments as appropriate.

(Embodiment 2)
In this embodiment, an example of a display panel driving method will be described.

FIG. 10 is an example of a timing chart of the display panel.

Similar to FIG. 3, the period Ta is the period when the page is turned, and the period Tb is the period before and after the page is turned.

The difference from FIG. 3 is that the period Ta has a plurality of periods Ta (1) to Ta (n) (n is a natural number). Then, in each of the periods Ta (1) to Ta (n), a video signal is written to the pixel 101.

In each of the periods Ta (1) to Ta (n) of FIG. 10, the pixel 1 is the same as the period Ta of FIG.
A video signal is input to 01. That is, in the period Ta, the video signal is input to the pixel 101 n times. Pixel initialization, gradation control, and the like are performed by inputting n times.

It is preferable to control the display element in the pixel 101 so that it is in an electric field-free state during the final period Ta (n) of the plurality of periods Ta (1) to Ta (n). By doing so, it becomes easy to maintain the gradation in the period Tb. Wiring 11 as a means of creating an electric field-free state
Writing a video signal having a value approximately equal to the potential of 1 (also referred to as the common potential Vcom) can be mentioned.

This embodiment can be implemented in combination with other embodiments as appropriate.

(Embodiment 3)
In this embodiment, a specific configuration of pixels of the display panel and an example of a driving method thereof are shown.

FIG. 11 shows an example of the pixel 101 belonging to the i (i is any one of 1 to y) rows and the j (j is any one of 1 to x) columns. The pixels shown in FIG. 11 are the transistor 102 and the display element 1.
It has 03 and a capacitive element 104. The transistor 102 functions as a switch element that controls the supply of a video signal to the display element 103.

One of the source and drain of the transistor 102 is connected to the wiring S (j). The other of the source or drain of the transistor 102 is connected to one electrode of the capacitive element 104 and one electrode 5001 (also referred to as a pixel electrode) of the display element 103. Transistor 102
The gate of is connected to the wiring G (i). The other electrode of the capacitive element 104 is connected to the wiring 112. The other electrode 5002 of the display element 103 (common electrode, common electrode, counter electrode,
The cathode electrode) is connected to the wiring 111.

The pixel 101 preferably has a memory property. Therefore, the display element 103 preferably has a memory property. The display element 103 is driven by a microcapsule type electrophoresis method, a microcup type electrophoresis method, a horizontally moving type electrophoresis method, a vertically moving type electrophoresis method, a twist ball method, a powder transfer method, and an electron powder fluid method. , Cholesteric liquid crystal element, chiral nematic liquid crystal, anti-strong dielectric liquid crystal, polymer dispersion type liquid crystal, charged toner, electrowetting method, electrochromism method, electrodeposition method and the like. An example of them will be described below.

Various forms can be applied to the transistor 102. For example, it can be formed by using silicon, an oxide semiconductor, or the like. In particular, since a display element having a memory property has a large driving voltage, it is preferably formed by using amorphal silicon, an oxide semiconductor, or the like.

FIG. 12 is a cross-sectional view of pixels when a microcapsule type electrophoresis method is used as the display element 103.

A plurality of microcapsules 5003 are arranged between the electrode 5001 and the electrode 5002. The plurality of microcapsules 5003 are fixed by the resin 5004. Resin 5
004 has a function as a binder.

The resin 5004 is preferably translucent. Instead of the resin 5004, a gas such as air or an inert gas may be filled. In that case, it is preferable to form a layer containing an adhesive, an adhesive or the like on one or both of the electrode 5001 and the electrode 5002 to fix the microcapsules 5003.

The microcapsules 5003 have a membrane 5011, a liquid 5012, particles 5013, and particles 5014. The liquid 5012, the particles 5013, and the particles 5014 are the film 5011.
It is enclosed in. The film 5011 is translucent.

The liquid 5012 has a function as a dispersion liquid. The liquid 5012 allows the particles 5013 and 5014 to be dispersed within the membrane 5011. The liquid 5012 is preferably translucent and uncolored.

The particles 5013 and the particles 5014 have different colors. For example, one may be black and the other white. It is assumed that the particles 5013 and the particles 5014 are charged so that their charge densities are different from each other. For example, one may be positively charged and the other negatively charged. As a result, when a potential difference is generated between the electrode 5001 and the electrode 5002, the particles 5013 and the particles 5014 move according to the direction of the electric field. In this way, the gradation can be controlled by changing the reflectance of the display element 103.

The structure of the microcapsules 5003 is not limited to the above. For example, liquid 501
2 may be colored. In addition, the color of the particles is not only white and black, but also red and green.
You can choose from blue, cyan, magenta, yellow emerald green, vermilion, and so on. Further, the type of particle color may be one type or three or more types.

Next, the operation of the pixels of the present embodiment will be described. The following can be applied to display devices other than the microcapsule type electrophoresis method.

The gradation of the display element 103 is the voltage applied to the display element 103 (electrode 5001 and electrode 50).
It is controlled by the potential difference between 02 and 02). The potential of the electrode 5001 is controlled by the video signal supplied from the wiring S (j). The video signal is supplied to the electrode 5001 from the wiring S (j) when the transistor 102 is on. Moreover, the potential of the electrode 5002 is
It is controlled by the voltage supplied from the wiring 111.

By driving so that no potential difference is generated between the electrodes 5001 and 5002, the two electrodes are in an electric field-free state, and the gradation of the display element 103 can be maintained.

In FIG. 11, when the driving method of FIG. 3 (or FIG. 10) is used, the transistor 102 is turned on in order to set the wiring G (i) to the H level during the period Ta (when turning the page). As a result, a video signal is supplied from the wiring S (j) to the electrode 5001 via the transistor 102. At that time, the capacitive element 104 maintains a potential difference between the electrode 5001 and the electrode 5002.

During the period Tb (before turning the page and after turning the page), the wiring G (i) is deselected (the driving of the pixel 101 is stopped), so that the transistor 102 is turned off. As a result, the electrode 5
001 is in a floating state. At that time, the capacitive element 104 holds a potential difference between the electrode 5001 and the electrode 5002 during the period Ta. Therefore, even if the transistor is off, a voltage based on the video signal is applied to the display element 103. Therefore, the display element 103
Gradation is retained.

As described above, the power consumption can be reduced by shortening the driving time of the pixel 101.

This embodiment can be implemented in combination with other embodiments as appropriate.

(Embodiment 4)
In this embodiment, an example of forming the transistor 102 of FIG. 11 using an oxide semiconductor will be described.

By using an oxide semiconductor for the transistor 102, the leakage current (off current) of the transistor 102 in the off state can be reduced.

By reducing the off-current of the transistor 102, it is possible to prevent the electric charge of the electrode 5001 of the display element 103 from leaking from the transistor 102 during the period Tb. That is,
The function of maintaining the gradation of the display element can be enhanced. Therefore, the display quality of the pixels can be improved in combination with the effect of using the display element having the above-mentioned memory property.

Further, by reducing the off-current of the transistor 102, it is possible to maintain the gradation even when a display element having no memory property is used. That is, by using a transistor in which the off-current is reduced, the pixel has a memory property. Examples of the display element having no memory property include a nematic liquid crystal and a smectic liquid crystal.

Specific examples of the structure and manufacturing method of the transistor using the oxide semiconductor are shown below.

FIG. 13 is a cross-sectional view of the transistor. The transistor 2000 is a bottom gate type inverted staggered thin film transistor formed on the insulator 2001, and is a gate electrode 20.
02, has a gate insulating film 2003, a semiconductor film 2004, an electrode 2005, and an electrode 2006. It also has an insulating film 2007 on the transistor 2000. Electrode 2005 and electrode 20
In 06, one is a source electrode and the other is a drain electrode.

First, as a factor for increasing the off-current of the transistor 2000, it can be mentioned that the oxide semiconductor used for the semiconductor film 2004 contains impurities such as hydrogen (for example, hydrogen, water, or hydroxyl group). Hydrogen and the like may become carrier donors in oxide semiconductors, and are a factor in generating current even in the off state. That is, if the oxide semiconductor contains a large amount of hydrogen or the like, the oxide semiconductor becomes N-type.

Therefore, the manufacturing method shown below purifies the oxide semiconductor by reducing hydrogen and the like in the oxide semiconductor as much as possible and increasing the concentration of oxygen as a constituent element. The highly purified oxide semiconductor is a true or substantially genuine semiconductor, and can reduce off-current.

An oxide semiconductor film is formed on the gate insulating film 2003 by a sputtering method.

As the target of the oxide semiconductor film, a target of a metal oxide containing zinc oxide as a main component can be used. For example, as a composition ratio, In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1
A target of 1: 1, that is, In: Ga: Zn = 1: 1: 0.5 can be used. Further, a target having a composition ratio of In: Ga: Zn = 1: 1: 1 or In: Ga: Zn = 1: 1: 2 can also be used. _{Further, SiO 2} is added in an amount of 2% by weight or more and 10% by weight.
Targets including the following can also be used.

When forming the oxide semiconductor film, the film may be formed in a rare gas (typically argon) atmosphere, an oxygen atmosphere, or a noble gas and oxygen mixed atmosphere. Here, the sputtering gas used for forming the oxide semiconductor film has a concentration of impurities such as hydrogen at the ppm level, preferably p.
Use a high-purity gas that has been removed to the pb level.

The oxide semiconductor film is formed by introducing a sputter gas from which hydrogen and water have been removed while removing residual water in the treatment chamber. In order to remove the residual water in the treatment chamber, it is preferable to use an adsorption type vacuum pump. For example, it is preferable to use a cryopump, an ion pump, or a titanium sublimation pump.

The film thickness of the oxide semiconductor film may be 2 nm or more and 200 nm or less, preferably 5 nm.
It is 30 nm or more and 30 nm or less. Then, the oxide semiconductor film is etched or the like to be processed (patterned) into a desired shape to obtain a semiconductor film 2004.

In the above, an example of using In-Ga-Zn-O as the oxide semiconductor film has been shown, but in addition, In-Sn-Ga-Zn-O, In-Sn-Zn-O, In-Al-Zn -O, S
n-Ga-Zn-O, Al-Ga-Zn-O, Sn-Al-Zn-O, In-Zn-O,
Sn-Zn-O, Al-Zn-O, Zn-Mg-O, Sn-Mg-O, In-Mg-O,
In-O, Sn-O, Zn-O and the like can be used. Further, the oxide semiconductor film may contain Si. Further, these oxide semiconductor films may be amorphous or crystalline. Alternatively, it may be a non-single crystal or a single crystal.

Further, as the oxide semiconductor film, _{a thin film represented by InMO 3} (ZnO) _m (m> 0) can also be used. Here, M is one or more metal elements selected from Ga, Al, Mn and Co. For example, M includes Ga, Ga and Al, Ga and Mn, or Ga and Co.

Next, the oxide semiconductor film (semiconductor film 2004) is subjected to the first heat treatment. The temperature of the first heat treatment is 400 ° C. or higher and 750 ° C. or lower, preferably 400 ° C. or higher, and is lower than the strain point of the substrate.

Impurities such as hydrogen can be removed (dehydrogenation treatment) from the oxide semiconductor film (semiconductor film 2004) by the first heat treatment. When these are contained in the oxide semiconductor film, they act as donors and increase the off-current of the transistor, so that the dehydrogenation treatment by the first heat treatment is extremely effective.

An electric furnace can be used for the first heat treatment. Further, it may be heated by heat conduction or heat radiation from a heating element such as a resistance heating element. In that case, for example, GRTA (Ga)
s Rapid Thermal Anneal device, LRTA (Lamp Rapi)
RTA (Rapid Thermal A) such as d Thermal Anneal equipment
nel) device can be used.

The LRTA device is a device that heats an object to be processed by radiation of light (electromagnetic waves) emitted from lamps such as halogen lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high-pressure sodium lamps, and high-pressure mercury lamps.

The GRTA device is a device that performs heat treatment using a high-temperature gas. As the gas, an inert gas (typically, a rare gas such as argon) or a nitrogen gas can be used. GR
By using the TA device, high-temperature heat treatment can be performed in a short time, which is particularly effective.

Further, the first heat treatment may be performed before patterning the oxide semiconductor film, or may be performed.
It may be performed after forming the electrodes 2005 and 2006, or after forming the insulating film 2007. However, in order to prevent the electrodes 2005 and 2006 from being damaged by the first heat treatment, it is preferable to perform the process before forming these electrodes.

Here, in the first heat treatment, oxygen deficiency may occur in the oxide semiconductor. Therefore, it is preferable to introduce oxygen (oxidation treatment) into the oxide semiconductor after the first heat treatment to purify the constituent element oxygen.

As a specific example of the oxidation treatment, a second heat treatment is continuously carried out in a nitrogen or oxygen-containing atmosphere (for example, nitrogen: oxygen volume ratio = 4: 1) or in an oxygen atmosphere. There is a method of performing the heat treatment of. It is also possible to use a method of performing plasma treatment in an oxygen atmosphere. As a result, the oxygen concentration in the oxide semiconductor film can be improved and the purity can be increased. The temperature of the second heat treatment is 200 ° C. or higher and 400 ° C. or lower, preferably 250 ° C. or higher and 350 ° C. or lower.

Further, as another example of the oxidation treatment, an oxide insulating film (insulating film 2007) such as a silicon oxide film is formed in contact with the semiconductor film 2004, and a third heat treatment is performed. The oxygen in the insulating film 2007 moves to the semiconductor film 2004, and the oxygen concentration of the oxide semiconductor can be improved to improve the purity. The temperature of the third heat treatment is 200 ° C. or higher and 400 ° C. or lower, preferably 250 ° C. or higher and 350 ° C. or lower. Even when the top gate type is used, the semiconductor film 2004
The oxide semiconductor can be highly purified by forming the gate insulating film in contact with the upper portion with a silicon oxide film or the like and performing the same heat treatment.

As described above, the oxide semiconductor film is highly purified by performing the dehydrogenation treatment by the first heat treatment and then the oxidation treatment by the second heat treatment or the third heat treatment. Is possible. By purifying the oxide semiconductor, the oxide semiconductor can be made genuine or substantially genuine.
The off-current of the transistor 2000 can be reduced.

The insulator 2001 may be a substrate having an insulating property, and a silicon oxide film may be formed on a desired substrate.
A film formed by a single layer or a laminate using a silicon nitride film or the like may be used. It may be formed by using a plasma CVD method or a sputtering method. A film formed by a coating method or the like of a resin film such as polyimide may be used. By forming the substrate with a resin, a flexible display panel can be obtained.

Further, the gate electrode 2002 is a single layer using a metal material such as molybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper, neodymium, scandium, or an alloy material containing these as a main component on the insulator 2001. Or it is formed by lamination. It may be formed by using a sputtering method or a vacuum vapor deposition method.

Further, the gate insulating film 2003 is formed by a single layer or a laminate using a silicon oxide film, a silicon nitride film, or the like. It may be formed by plasma CVD or sputtering method.

Further, the electrodes 2005 and 2006 are the gate insulating film 2003 and the semiconductor film 2004.
A single layer is used on top of a metal such as molybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper, and yttrium, an alloy material containing these as the main component, or a conductive metal oxide such as indium oxide. Or it is formed by lamination. It may be formed by using a sputtering method or a vacuum vapor deposition method. The electrode 2005 and the electrode 2006 are preferably formed so as to overlap with the gate electrode 2002. By doing so, the current driving ability of the transistor 102 can be improved. In particular, it is effective when a highly purified oxide semiconductor (intrinsic or substantially intrinsic oxide semiconductor) is used.

The highly purified oxide semiconductor and the transistor using the same will be described in detail below.

As an example of a highly purified oxide semiconductor, the carrier concentration is ^{less than 1 × 10 14} / cm ³ , preferably less than 1 × 10 ¹² / cm ³ , and more preferably less than 1 × 10 ¹¹ / cm ³ , or 6 less than .0 × ^{10 10} / cm ³ oxide semiconductor can be mentioned.

A transistor using a highly purified oxide semiconductor has a feature that the off-current is very small as compared with a transistor having a semiconductor using silicon or the like.

The results of measuring the off-current characteristics of the transistor using an evaluation element (also called TEG) are shown below. In addition, here, it is described assuming that it is an n-channel type transistor.

200 transistors with L / W = 3 μm / 50 μm (film thickness d: 30 nm) are used in the TEG.
L / W = 3 μm / 10000 μm transistors manufactured by connecting the transistors in parallel were provided.
The initial characteristics are shown in FIG. Here, VG is shown in the range of −20V to + 5V. In order to measure the initial characteristics of the transistor, the substrate temperature is set to room temperature, the source-drain voltage (hereinafter referred to as drain voltage or VD) is set to 10V, and the source-gate voltage (hereinafter referred to as gate voltage or VG) is set to -20V. Source when changed to ~ + 20V-
Change characteristics of drain current (hereinafter referred to as drain current or ID), that is, VG-ID
The characteristics were measured.

As shown in FIG. 15, a transistor having a channel width W of 10000 μm has an off current of 1 × 10 ^-13 A or less regardless of whether the VD is 1 V or 10 V, and the measuring machine (
The resolution (100 fA) or less of the semiconductor parameter analyzer, Agilent 4156C; manufactured by Agilent. This off-current value corresponds to 10 aA / μm when converted to a channel width of 1 μm, and can be regarded as substantially zero when applied to pixels.

In this specification, the off-current is an n-channel transistor with a threshold value of Vth.
When is positive, it refers to the current flowing between the source and drain of the transistor when an arbitrary gate voltage in the range of -20V or more and -5V or less is applied at room temperature. The room temperature is 15 degrees or more and 25 degrees or less. The transistor using the oxide semiconductor disclosed in the present specification has a current value per unit channel width (W) of 100 aA / μm or less, preferably 1 aA / μm or less, and more preferably 10 zA / μm or less at room temperature. ..

Further, in the pixel 101 of FIG. 11, by reducing the off-current of the transistor 102, the function of maintaining the gradation of the display element 103 is enhanced, so that it is possible to configure the pixel 101 without the capacitance element 104. By not providing the capacitive element 104, the aperture ratio of the pixel 101 can be improved.

Further, a transistor using a highly purified oxide semiconductor has good temperature characteristics. Typically, in the current-voltage characteristics of a transistor in the temperature range from -25 ° C to 150 ° C, there is almost no fluctuation in on-current, off-current, field effect mobility, S value, and threshold voltage, depending on the temperature. Almost no deterioration of current-voltage characteristics is seen. In addition, since highly purified oxide semiconductors are less likely to deteriorate due to light irradiation, devices that use light, such as display devices, are used.
In particular, reliability can be improved.

In this embodiment, an example in which the transistor is a bottom gate type is shown, but FIG. 14
The top gate type transistor 3000 may be used as described above. The transistor 3000 has a semiconductor film 3004, an electrode 3005, an electrode 3006, a gate insulating film 3003, and a gate electrode 3002. One of the electrodes 3005 and 3006 is a source electrode, and the other is a drain electrode.

This embodiment can be implemented in combination with other embodiments as appropriate.

(Embodiment 5)
In this embodiment, an example is shown of a configuration for detecting that the display panel has been turned over.

In the display device of FIG. 16, a sensor is provided on the display panel 1001, the support portion 1002, or the housing 1004. By providing a sensor, it is possible to automatically detect that the display panel has been turned over.

For example, the display panel 1001 may be provided with the photo sensor 1010. The photo sensor 1010 can detect the light incident when the display panel 1001 is turned over and detect that the display panel 1001 is turned over.

Further, the pressure sensor 1011 may be provided on the support portion 1002. The pressure sensor 1011 can detect the pressure generated when the display panel 1001 is turned over and detect that the display panel 1001 is turned over.

Further, FIG. 17 is a cross-sectional view of the display device of FIG. 16 as viewed from above. Here, the display panel 1001 has a magnetic sensor 1012, and the housing 1004 has a magnet 1013. The magnetic sensor 1012 has a magnet 10 when the display panel 1001 is turned in the direction of the arrow.
It is possible to detect that the magnetic energy has been turned over by detecting the change in magnetic energy generated from 13. The positions of the magnetic sensor 1012 and the magnet 1013 may be reversed. When a plurality of display panels are provided, by providing each display panel with a magnetic sensor 1012 or a magnet 1013, it is possible to detect a change in magnetic energy when the display panel is turned over.

In FIG. 17, instead of the magnetic sensor 1012 and the magnet 1013, two electrodes may be provided. By detecting the current generated by the contact between the two electrodes, it is possible to detect that the two electrodes have been turned over. Further, the change in electrostatic energy caused by the proximity of the two electrodes may be detected.

In addition to the above, a sensor (accelerometer) for detecting the acceleration at the time of turning, a sensor for detecting the turning angle (angle sensor), and the like may be provided. The detection signals from these sensors are output to the controller 400 (see FIG. 2). Then, the scanning line drive circuit 300 drives the pixels when the detection signal from the sensor is output, and stops the operation of the pixels when the detection signal is not output. By shortening the pixel drive time, the power consumption of the display device can be reduced.

This embodiment can be implemented in combination with other embodiments as appropriate.

100 Pixel section 101 Pixel 102 Transistor 103 Display element 104 Capacitive element 111 Wiring 112 Wiring 200 Signal line drive circuit 300 Scan line drive circuit 400 Controller 500 Controller 801 Power supply circuit 802 Timing generator 803 Switch element 804 Switch element 901 Switch element 1001 Display panel 1002 Support 1003 Display screen 1004 Housing 1010 Photosensor 1011 Pressure sensor 1012 Magnetic sensor 1013 Magnet 2000 Transistor 2001 Insulation 2002 Gate electrode 2003 Gate insulation film 2004 Semiconductor film 2005 Electrode 2006 Electrode 2007 Insulation film 3000 Transistor 3002 Gate electrode 3003 Gate insulation film 3004 Semiconductor film 3005 Electrode 3006 Electrode 5001 Electrode 5002 Electrode 5003 Microcapsule 5004 Resin 5011 Film 5012 Liquid 5013 Particle 5014 Particles

Claims (1)

With multiple display panels
Support part and
With a sensor,
Each of the plurality of display panels has a display screen on one side or both sides.
The display screen has pixels having a memory property, and the display screen has pixels.
The pixel has a transistor having a channel forming region in an oxide semiconductor and a liquid crystal display element.
Each of the first sides of the plurality of display panels is connected to the support portion, and is connected to the support portion.
Each of the plurality of display panels can be moved with the support portion as a fulcrum.
The sensor has a function of detecting that the display panel has been turned over and outputting a detection signal.
The plurality of display panels, the said pixel is driven while the detection signal is output, the display device to stop driving of the pixel when the detection signal is not output.

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