Driving method for liquid crystal display device

Abstract

To reduce malfunction and reduce consumption power in a liquid crystal display device capable of displaying a moving image and a still image.SOLUTION: A first substrate where a terminal part, a switching transistor, a driving circuit part, and a pixel circuit part including a pixel transistor and a plurality of pixels are formed, and a second substrate where a common electrode electrically connected to the terminal part through the switching transistor is formed are provided. Between a pixel electrode and the common electrode, liquid crystal is held. In a period of displaying a still image, a first terminal and a second terminal of the switching transistor are set to a non-conductive state and the common electrode is electrically floated. In a period of changing the still image to a moving image, a first step of supplying a common potential to the common electrode, a second step of supplying a power source voltage to the driving circuit part, a third step of supplying a clock signal to the driving circuit part, and a fourth step of supplying a start pulse signal to the driving circuit part are performed in order.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for driving a liquid crystal display device. [Background technology]

[0002] Liquid crystal display devices are used in a wide range of applications, from large displays such as television sets to small displays such as mobile phones. In the future, there will be a demand for products with higher added value, and development will continue. In recent years, interest in the global environment has increased, and the convenience of mobile devices has improved. From this viewpoint, the development of low power consumption liquid crystal display devices has been attracting attention.

[0003] In Patent Document 1, in order to reduce the power consumption of a liquid crystal display device, all gate lines and signal In order to keep the potential of each signal line constant during the pause period when the signal lines are in the non-selected state, all data A configuration in which the signal line is electrically disconnected from the data signal driver and put into a high impedance state. The Company discloses the following:

[0004] In Non-Patent Document 1, in order to reduce the power consumption of a liquid crystal display device, a method for displaying moving images and still images is described. The document discloses a configuration in which the refresh rate is changed when displaying a still image. In this case, the drain-common voltage fluctuates due to signal switching between the idle period and the scanning period. To prevent flicker from being perceived, the signal line and the common electrode are connected simultaneously during the pause period. The present invention discloses a configuration for preventing fluctuations in the drain-common voltage by applying an AC signal of the same phase. . [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-312253 A [Non-patent literature]

[0006] [Non-Patent Document 1] Kazuhiko Tsuda et al.,IDW'02,pp295-298 Summary of the Invention [Problem to be solved by the invention]

[0007] When a complicated drive is performed as in the configuration of Patent Document 1 or Non-Patent Document 1, the liquid crystal display device The configuration and operation of the driver circuit that supplies signals to the gate lines and signal lines of the liquid crystal display become complicated. The power consumption of the device cannot be reduced sufficiently.

[0008] In addition, as in the configuration of Non-Patent Document 1, the refresh rate is made different for video display and still image display. In order to further reduce the power consumption of the liquid crystal display device, the reflection However, the refresh rate when displaying still images must be extremely reduced. If the surge rate is reduced too much, the charge that should be held in the pixel electrode will leak from the pixel transistor. and / or noise, etc., may cause problems such as a pixel electrode becoming discolored and becoming stuck between the pixel electrode and the common electrode. Due to the problem of image signal distortion, the image displayed during the image signal retention period may be blurred. It will deteriorate.

[0009] In view of the above, one embodiment of the present invention is a method for manufacturing a liquid crystal display device that does not require complicated operations in a drive circuit of the liquid crystal display device and that can realize a still image display. Suppresses deterioration of the displayed image by reducing the refresh rate when displaying the image. One of the goals of the project is to [Means for solving the problem]

[0010] According to one embodiment of the present invention, during a period in which a moving image is displayed, The pixel transistor, the semiconductor layer of which is electrically connected to the pixel transistor is an oxide semiconductor, is brought into a conductive state. A semiconductor that supplies an image signal to the element electrodes and is electrically connected to the terminal portion formed on the first substrate. The switching transistor, whose layer is an oxide semiconductor, is turned on. A common potential is applied to a common electrode formed on a second substrate, which is electrically connected to the terminal portion via a resistor. During the period when a still image is displayed, the pixel transistor is turned off to reduce the pixel voltage. The common electrode is electrically floating, the switching transistor is non-conducting, and the common electrode is In the period when the image changes from a still image to a moving image, the common electrode is electrically floating. A first step of supplying a power supply voltage to the drive circuit unit, a second step of supplying a power supply voltage to the drive circuit unit, A third step of supplying a clock signal to the drive circuit section and a start pulse signal to the drive circuit section. a fourth step of driving a liquid crystal display device, in that order.

[0011] Another embodiment of the present invention is a method for displaying a moving image by using a driving circuit formed on a first substrate. A pixel transistor having a semiconductor layer made of an oxide semiconductor, which is electrically connected to the pixel portion, is turned on. The semiconductor device supplies image signals to the pixel electrodes and electrically connects the semiconductor device to the terminal portion formed on the first substrate. The switching transistor, whose conductor layer is an oxide semiconductor, is turned on. A common electrode formed on the second substrate is electrically connected to the terminal portion via a transistor. During the period when a still image is displayed, the pixel transistor is turned off to display the image. The element electrode is electrically floating, and the switching transistor is non-conducting. The electrodes are electrically floating, and during the period when the image changes from moving to still, The first step is to stop the start pulse signal, and the second step is to stop the clock signal to the drive circuit. The second step is to stop the power supply voltage to the drive circuit section, and the third step is to stop the power supply voltage to the common electrode. a fourth step of stopping the common potential.

[0012] According to one embodiment of the present invention, there is provided a liquid crystal display device, comprising: a storage circuit for storing an image signal; A comparison circuit compares each pixel and calculates the difference, and a control circuit controls the drive circuit and reads out the image signal. and a display control circuit for comparing successive frames stored in the memory circuit with each other in the comparison circuit. The image signal for the period is read out, compared pixel by pixel, the difference is calculated, and the judgment is made as to whether it is a moving image or a still image. The present invention may also be applied to a method of driving a liquid crystal display device in which the above-mentioned

[0013] In one embodiment of the present invention, the switching transistor is switched by a display control circuit. In response to a signal supplied to the gate terminal of the transistor, a terminal portion to which a common potential is supplied is connected. The method may be a method for driving a liquid crystal display device that controls a conductive state or a non-conductive state with respect to a conductive electrode.

[0014] In one embodiment of the present invention, the switching transistor has an off-state current per μm of channel width. The current value is 10 zA / μm or less at room temperature, and the switching transistor A liquid that controls the conductive state or non-conductive state between the terminal portion to which the common potential is supplied and the common electrode. The present invention may also be applied to a method for driving a liquid crystal display device. Effect of the Invention

[0015] According to one aspect of the present invention, even if the refresh rate is reduced when displaying a still image, the image can be displayed. This makes it possible to suppress image degradation. [Brief description of the drawings]

[0016] [Figure 1] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Diagram 3] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 4] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Diagram 5] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 6] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 7] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 8] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 9] 1A to 1C are diagrams illustrating electronic devices of one embodiment of the present invention. [Figure 10] 1A to 1C are diagrams illustrating electronic devices of one embodiment of the present invention. [Figure 11] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 12] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. [Figure 13] 1A and 1B are diagrams illustrating a liquid crystal display device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the above-mentioned embodiments, and may be practiced in various different ways without departing from the spirit and scope of the present invention. It will be easily understood by those skilled in the art that the form and details of the present invention may be modified in various ways. The present invention should not be construed as being limited to the description of the present embodiment. In the structure of the invention, reference numerals indicating the same objects are common among different drawings.

[0018] In addition, the size of each component, the thickness of a layer, or the signal waveform shown in the drawings of each embodiment may be different. The figures may be exaggerated for clarity. This is not limited to rules.

[0019] In this specification, the terms first, second, third, through Nth (N is a natural number) refer to configurations. It is noted that this is added to avoid confusion of elements and is not intended to limit the number. do.

[0020] (Embodiment 1) In this embodiment mode, a block diagram and a timing chart of a liquid crystal display device are shown. And explain.

[0021] First, FIG. 1 shows a block diagram of a liquid crystal display device, and each component of the liquid crystal display device according to the present specification. This article explains:

[0022] The liquid crystal display device 100 shown in FIG. 1 includes a display panel 101, a memory circuit 102, and a comparison circuit 103. , a display control circuit 104 , and a selection circuit 109 .

[0023] The display panel 101 includes, for example, a drive circuit section 105, a pixel circuit section 106, a common electrode section The pixel electrode 110 (also referred to as a common electrode portion) and a switching transistor 111. The circuit section 105 includes a gate line side driver circuit 107A and a signal line side driver circuit 107B.

[0024] The gate line side driver circuit 107A and the signal line side driver circuit 107B are pixel circuits each having a plurality of pixels. The gate line side driving circuit 107A and the signal line side driving circuit 107B are driving circuits for driving the path portion 106. The gate line side driving circuit 107B has a shift register circuit. The side driving circuit 107B, the pixel circuit section 106, and the switching transistor 111 are the same. The circuit is composed of thin film transistors formed on the substrate. 07A and a signal line side driver circuit 107B, a pixel circuit section 106 and a switching transistor The capacitor 111 may be formed on a separate substrate.

[0025] The drive circuit unit 105 is controlled by the display control circuit 104 to supply a high power supply potential Vdd and a low power supply potential Vdd. Vss, a start pulse SP, a clock signal CK, and an image signal Data are supplied. The common electrode section 110 is provided with a switching transistor under the control of the display control circuit 104. A common potential Vcom is supplied via the transistor 111 .

[0026] The high power supply potential Vdd is a potential higher than the reference potential, and the low power supply potential is a potential higher than the reference potential. Note that both the high power supply potential and the low power supply potential are It is desirable that the high power supply potential Vdd and the low power supply potential Vs The potential difference between s is sometimes called the power supply voltage.

[0027] Voltage refers to the potential difference between a certain potential and a reference potential (for example, ground potential). Therefore, voltage can be called electric potential.

[0028] The common potential Vcom is a reference potential for the image signal Data supplied to the pixel electrodes. The image signal Da may be a ground potential, for example. ta is the dot inversion drive, source line inversion drive, gate line inversion drive, frame inversion drive The signal may be inverted appropriately depending on the drive or the like and input to the display panel 101 .

[0029] The image signal for displaying a moving image or a still image is supplied to the memory circuit 102 in an analog form. In the case of a signal, the signal is converted into a digital signal via an A / D converter or the like, and is stored in the memory circuit 102. By converting the image signal into a digital signal in advance, the image signal can be supplied to the This is preferable because it allows easy detection of the difference.

[0030] The memory circuit 102 includes a plurality of frame memory circuits for storing image signals relating to a plurality of frames. The number of frame memories 108 included in the memory circuit 102 is not particularly limited. It is not necessary to use a memory element that can store image signals related to a plurality of frames. The frame memory 108 is, for example, a dynamic random access memory (DRAM). s Memory), SRAM (Static Random Access Memo) ry) or other memory elements.

[0031] The frame memory 108 may be configured to store an image signal for each frame period. The number of frame memories is not particularly limited. The signal is selectively read out by a comparison circuit 103 and a selection circuit 109 .

[0032] In addition, the switching transistor is connected to the source terminal and the drain terminal in response to a voltage applied to the gate. A switching operation can be realized by selecting conduction or non-conduction between the two drain terminals. It is an element made of thin film transistors.

[0033] In the configuration of this embodiment, the pixel circuit section 106 and the switching transistor 11 The semiconductor layer of the thin film transistor constituting 1 is made of an oxide semiconductor. In order to remove n-type impurities such as hydrogen from the oxide semiconductor, impurities other than the main components of the oxide semiconductor are removed. By purifying it to the extent possible, it is made into true (i type), or it is made into true type. In other words, instead of adding impurities to make it i-type, we try to remove impurities such as hydrogen and water as much as possible. By removing the SiO2, the semiconductor is purified to produce an i-type (intrinsic semiconductor) or is close to it. Therefore, the oxide semiconductor layer of the thin film transistor is highly purified and electrically The oxide semiconductor layer is made i-type (intrinsic).

[0034] In addition, there are very few carriers (close to zero) in highly purified oxide semiconductors. Rear density is 1×10 14 / cm 3 Less than 1 x 10 12 / cm 3 Less than or equal to Preferably 1×10 11 / cm 3 is less than.

[0035] Since there are very few carriers in an oxide semiconductor, the off-state current of a transistor can be reduced. Specifically, the thin film transistor having the oxide semiconductor layer can be The off-state current per 1 μm of channel width at room temperature is 10 aA / μm (1×10 -17 A / μm), and further, 1aA / μm (1×10 -18 A / μm or less, Furthermore, 10zA / μm (1×10 -20 In other words, it is possible to make the thickness of the thin film When a transistor is in a non-conducting state, the oxide semiconductor can be considered as an insulator and used in circuit design. On the other hand, in the conductive state of a thin film transistor including an oxide semiconductor layer, , and has a higher current supply than a thin film transistor having a semiconductor layer formed of amorphous silicon. Ability can be predicted.

[0036] By using a thin film transistor with an extremely small off-current in the pixel circuit section 106, The pixel electrode can be electrically isolated from the signal line that may cause a fluctuation in the potential of the pixel electrode. In addition, the off-current is extremely small. By adopting a membrane transistor as the switching transistor 111, the common potential Vcom It can be separated from the external terminal to which power is supplied, and the common electrode is left in an electrically floating state. This makes it possible to reduce fluctuations in the voltage applied to the electrodes at both ends of the liquid crystal element due to noise or the like.

[0037] The thin film transistors constituting the pixel circuit section 106 and the switching transistor 111 By using an oxide semiconductor for the semiconductor layer, it is possible to reduce the refresh rate and display still images. The period during which the gate line side driver circuit and the signal line side driver circuit are in a stopped state is significantly extended. As a result, the complicated operation of the driving circuit can be eliminated. This eliminates the need for a gate line side driver circuit and a signal line side driver circuit. This significantly extends the period during which the pixel is turned on, thereby reducing power consumption. The period for refreshing the electrode potential is set to 1000 s for oxide semiconductors with extremely small off-state currents. By using thin film transistors that use silicon, there is no problem even if the time is longer than one minute. The thin-film transistors constituting the pixel circuit section 106 and the switching transistor 111 are By using an oxide semiconductor for the semiconductor layer of the LCD, the electrodes on both ends of the LCD element can be placed in a floating state. It is possible to reduce deterioration of a displayed image due to noise or the like.

[0038] As oxide semiconductors, there are four-component metal oxides, such as In-Sn-Ga-Zn-O films, Ternary metal oxide films: In-Ga-Zn-O, In-Sn-Zn-O, and In-Al -Zn-O film, Sn-Ga-Zn-O film, Al-Ga-Zn-O film, Sn-Al-Zn- O-based, binary metal oxide films such as In-Zn-O, Sn-Zn-O, and Al-Zn-O film, Zn-Mg-O film, Sn-Mg-O film, In-Mg-O film, In-O film, Sn-O The oxide semiconductor layer may be a Zn-O film or a Zn-O film. may contain SiO2.

[0039] In addition, the oxide semiconductor is InMO3(ZnO) m Using a thin film expressed as (m>0) Here, M is one or more metals selected from Ga, Al, Mn, and Co. For example, M is Ga, Ga and Al, Ga and Mn, or Ga and C. o, etc. InMO3(ZnO) m (m>0) The oxide semiconductor having a structure containing Ga as M is the In-Ga-Zn-O oxide semiconductor described above. The thin film is also called an In-Ga-Zn-O film.

[0040] Note that a thin film transistor including an oxide semiconductor layer has almost no temperature dependence of on-state current. No change is observed and the off-current remains very small, making this device suitable for use at high temperatures.

[0041] The comparison circuit 103 selects image signals of successive frame periods stored in the memory circuit 102. The image signals are read out sequentially, and the difference between successive frames is detected for each pixel. Depending on whether or not a difference is detected, the display control circuit 104 and the selection circuit 105 are The operation of the comparison circuit 103 is determined by comparing the image signals. When a difference is detected in any pixel, the consecutive frame period in which the difference is detected is On the other hand, by comparing the image signals in the comparator circuit 103, it is determined that the image is a moving image. When no difference is detected, the consecutive frame periods during which the difference is not detected are still images. That is, the comparison circuit 103 judges that the image signal of the consecutive frame periods is By detecting the difference in the line 103, it is possible to determine whether the image signal is for displaying a moving image or a still image. The purpose of this comparison is to determine whether the image signal is for displaying an image. The difference is set so that when it exceeds a certain level, it is determined that a difference has been detected. The comparison circuit 103 may determine the difference based on the absolute value of the difference, regardless of the magnitude of the difference. This may be set to determine whether a difference is detected.

[0042] In this embodiment, the comparison circuit 103 compares image signals in successive frame periods. We have shown a configuration in which the difference between the two images is detected to determine whether the image is a video or a still image. By supplying a signal to switch between still and video from Alternatively, the signal may be supplied in the form of the signal shown in FIG.

[0043] Video is created by switching between multiple frames of images at high speed, which is time-divided into multiple frames. Specifically, it refers to an image that moves 60 times per second (60 frames). By switching between these images, the human eye will perceive it as a video with less flicker. On the other hand, still images are different from video images in that multiple images are time-shared over multiple frame periods and are displayed at high speed. However, during consecutive frame periods, for example, the nth frame and (n+ 1) This refers to an image signal that has the same frame as the first frame.

[0044] When a difference is detected by the difference calculation in the comparison circuit 103, i.e., when a difference is detected, the selection circuit 109 When the image displayed between successive frames is a moving image, the frame memory in which the image signal is stored This is a circuit for selecting an image signal from the image sensor 108 and outputting it to the display control circuit 104. The selection circuit 109 is configured to select when the comparison circuit 103 does not detect a difference between the image signals through calculation. That is, when the image displayed between successive frames is a still image, the display control is performed for the image signal. This is a circuit that does not output to the circuit 104. In the case of a still image, the selection circuit 109 selects the frame of the image signal. By configuring the display control circuit 104 not to output data from the frame memory 108, power consumption The selection circuit 109 is formed of a plurality of switches, for example, transistors. The switch can be configured to

[0045] The display control circuit 104 is a display control circuit that is selected by the selection circuit 109 in response to the detection of the difference by the comparison circuit 103. The image signal thus obtained is supplied to the driving circuit unit 105, and the high power supply potential Vdd and the low power supply potential Vss are supplied to the driving circuit unit 105. , a start pulse SP, a clock signal CK, and other control signals for controlling the drive circuit unit 105. This is a circuit for controlling the switching on and off of supply to the drive circuit unit 105. If the comparison circuit 103 judges that the image is a moving image, the image signal is selected from the storage circuit 102. The signal is read out via the selection circuit 109 and supplied to the drive circuit unit 105 by the display control circuit 104. In addition, a control signal is supplied from the display control circuit 104 to the drive circuit unit 105. If the comparator circuit 103 judges that the image is a still image, the display control circuit 104 selects the image signal. Since the image signal is not supplied from the selection circuit 109, the image signal is not supplied to the driver circuit unit 105. In addition, each control signal to the drive circuit unit 105 is stopped.

[0046] When the difference is detected by the comparison circuit 103, the display control circuit 104 The switching transistor 111 is turned on (also called the ON state), and the comparison circuit 10 If no difference is detected by the calculation of the difference in step 3, the switching transistor 111 is turned off. This is referred to as a conductive state (also called an off state).

[0047] Note that the supply of a signal means supplying a predetermined potential to a wiring. A wiring to which a predetermined fixed potential is supplied by stopping the supply of a predetermined potential of the low power supply potential Vs s is connected to a wiring that is supplied with a certain potential, or This refers to cutting the material and leaving it in a floating state.

[0048] In addition, when the period during which the image is determined to be a still image is short, the control signal Among these, a configuration may be adopted in which the high power supply potential Vdd and the low power supply potential Vss are not stopped in advance. The power consumption is increased by frequently turning off and on the high power supply potential Vdd and the low power supply potential Vss. This is preferable because it can reduce an increase in power consumption.

[0049] The image signal and the control signal are stopped when each pixel in the pixel circuit unit 106 can hold an image signal. Therefore, it is desirable to perform the process over a period during which each pixel can hold an image signal. The display control circuit 104 controls the image signal supplied in the previous period so that the image signal is supplied again after the previous period. The pixel circuit portion 106 may be configured to periodically supply a signal and a control signal. The semiconductor layer of the thin-film transistor uses an oxide semiconductor, and the period during which an image signal can be retained is can be made longer.

[0050] In addition, the gate line side driving circuit 107A and the signal line side driving circuit 107B of the driving circuit unit 105 are configured as The shift register is configured with a clock signal, an inverted clock signal, a start pulse, etc. It is sufficient that the circuit outputs pulses sequentially from the output terminal of the first stage.

[0051] Here, the shift registers constituting the gate line side driving circuit 107A and the signal line side driving circuit 107B are An example of the data is shown in FIG.

[0052] The shift register shown in FIG. 11A includes first pulse output circuits 10_1 to N-th pulse The shift register shown in FIG. The first pulse output circuit 10_1 to the N-th pulse output circuit 10_N are connected to a first wiring 1 A first clock signal CK1 is output from the first wiring 12, a second clock signal CK2 is output from the second wiring 13, and a third clock signal CK3 is output from the third wiring 14. A third clock signal CK3 is transmitted from the wiring 13, and a fourth clock signal CK 4 is supplied to the first pulse output circuit 10_1. The first start pulse SP1 (first start pulse) is input. In the output circuit 10_n (n is a natural number of 2≦n≦N), A signal (called the previous stage signal OUT(n-1)) (n is a natural number of 2 or more) is input. The pulse output circuit 10_1 receives a signal from a third pulse output circuit 10_3, which is two stages behind. Similarly, in the n-th pulse output circuit 10_n in the second stage or later, the (n The signal from the pulse output circuit 10_(n+2) (called the next stage signal OUT(n+2) Therefore, the pulse output circuit of each stage outputs the pulses of the following stage and / or the two stages before it. A first output signal (OUT(1)(SR) to OUT(N)( SR), the second output signal (OUT(1) to OUT(N)) is output, which is input to another circuit, etc. As shown in FIG. 11(A), the last two stages of the shift register are Since the subsequent signal OUT(n+2) is not input, for example, A second start pulse SP2 is output from the first wiring 17, and a third start pulse SP3 is output from the seventh wiring 18. Alternatively, a signal generated internally may be input. For example, The (N+1)th pulse output circuit 10 does not contribute to the pulse output to the pixel unit. (N+1) , th ( N+2) Pulse output circuit 10 (N+2) (also called a dummy stage) is provided, and the dummy stage Signals corresponding to the second start pulse (SP2) and the third start pulse (SP3) It is also possible to generate the following.

[0053] The first clock signal (CK1) to the fourth clock signal (CK4) are generated at regular intervals. It is a signal that repeats H and L signals. Also, the first clock signal (CK1) to the fourth clock signal (CK2) The clock signal (CK4) is delayed by 1 / 4 period in sequence. The pulse output circuit is driven using the fourth clock signal (CK1) to the fourth clock signal (CK4). The clock signal CK is either GCK or is sometimes called SCK, but here we will explain it as CK.

[0054] In addition, when it is explicitly stated that A and B are connected, it means that A and B are electrically connected. A and B are connected functionally, A and B are directly connected, Here, A and B are objects (e.g., devices, elements, circuits, etc.). , wiring, electrodes, terminals, conductive films, layers, etc.). Therefore, a given connection relationship, For example, the present invention is not limited to the connection relationships shown in the drawings or text, and may be modified in any way without departing from the spirit or scope of the present invention. This also includes matters other than those involved.

[0055] Each of the first pulse output circuit 10_1 to the N-th pulse output circuit 10_N has a first input terminal a first input terminal 21, a second input terminal 22, a third input terminal 23, a fourth input terminal 24, a fifth input terminal The input terminal 25, a first output terminal 26, and a second output terminal 27 (see FIG. 11(B)).

[0056] The first input terminal 21, the second input terminal 22, and the third input terminal 23 are connected to the first wiring 11 to It is connected to any one of the fourth wirings 14. For example, in FIGS. The first pulse output circuit 10_1 has a first input terminal 21 connected to a first wiring 11, The second input terminal 22 is connected to the second wiring 12, and the third input terminal 23 is connected to the third wiring 13. The second pulse output circuit 10_2 has a first input terminal 21 connected to a second The first input terminal 22 is connected to the wiring 12, the second input terminal 23 is connected to the third wiring 13, and the third input terminal 23 is connected to the fourth wiring 14 .

[0057] In addition, in FIG. 11(A) and (B), the first pulse output circuit 10_1 has a fourth input terminal A start pulse is input to the fifth input terminal 24, and a subsequent signal OUT(3) is input to the fifth input terminal 25. The first output terminal 26 outputs a first output signal OUT(1)(SR), and the second output The second output signal OUT( 1 ) is output from the input terminal 27 .

[0058] Next, an example of a specific circuit configuration of the pulse output circuit will be described with reference to FIG.

[0059] In FIG. 11C, the first transistor 31 has a first terminal connected to a power supply line 51, The second terminal is connected to the first terminal of the ninth transistor 39, and the gate electrode is connected to the fourth input terminal 24. The second transistor 32 has a first terminal connected to the power supply line 52, The second terminal is connected to the first terminal of the ninth transistor 39, and the gate electrode is connected to the fourth transistor The third transistor 33 has a first terminal connected to the gate electrode of the first The fourth transistor is connected to the input terminal 21 and the second terminal is connected to the first output terminal 26. The transistor 34 has a first terminal connected to the power supply line 52 and a second terminal connected to the first output terminal 26. The fifth transistor 35 has a first terminal connected to the power supply line 52 and a second terminal is connected to the gate electrode of the second transistor 32 and the gate electrode of the fourth transistor 34. The sixth transistor 36 is connected to the fourth input terminal 24. The first terminal is connected to the power supply line 51, and the second terminal is connected to the gate electrode of the second transistor 32 and The gate electrode of the fourth transistor 34 is connected to the fifth input terminal 25. The seventh transistor 37 has a first terminal connected to the power supply line 51 and a second terminal the gate electrode of the eighth transistor 38 is connected to the third input terminal 23; The eighth transistor 38 has a first terminal connected to the gate of the second transistor 32. and a gate electrode of a fourth transistor 34, the gate electrode of which is connected to the second input terminal The ninth transistor 39 has a first terminal connected to the first transistor 31. and a second terminal of the second transistor 32, the second terminal of which is connected to the third transistor The gate electrode of the tenth transistor 40 is connected to the gate electrode of the tenth transistor 33. The electrode of the tenth transistor 40 is connected to the power supply line 51. The tenth transistor 40 has a first terminal connected to the first input terminal. a gate electrode connected to the ninth input terminal 21, a second terminal connected to the second output terminal 27, and a gate electrode connected to the ninth The eleventh transistor 41 is connected to the first terminal The first terminal is connected to the power supply line 52, the second terminal is connected to the second output terminal 27, and the gate electrode is The gate electrode of the first transistor 32 and the gate electrode of the fourth transistor 34 are connected to There are.

[0060] In FIG. 11C, the gate electrode of the third transistor 33, the gate electrode of the tenth transistor The connection point of the gate electrode of the ninth transistor 40 and the second terminal of the ninth transistor 39 is a node NA. In addition, the gate electrode of the second transistor 32 and the gate electrode of the fourth transistor 34 , the second terminal of the fifth transistor 35, the second terminal of the sixth transistor 36, The connection point of the first terminal of the eleventh transistor 38 and the gate electrode of the eleventh transistor 41 is It will be called DoNB.

[0061] When the pulse output circuit in FIG. 11C is the first pulse output circuit 10_1, A first clock signal CK1 is input to the input terminal 21, and a second clock signal CK2 is input to the second input terminal 22. The clock signal CK2 is input to the third input terminal 23, and the third clock signal CK3 is input to the third input terminal 24. A start pulse SP is input to the fourth input terminal 24, and a The second output terminal 26 outputs OUT(1)(SR). and OUT(1) is output from the second output terminal 27.

[0062] Also, the timing of the shift register having a plurality of pulse output circuits shown in FIG. FIG. 12 shows a schematic diagram of the shift register as a gate line side driver circuit. In FIG. 12, period 61 is a vertical blanking period, and period 62 corresponds to a gate selection period.

[0063] Next, the switch connected to the common electrode portion 110 in the display panel 101 shown in FIG. The advantages of providing the feedback transistor 111 are shown in FIG. In FIG. 2, a circuit such as a display control circuit (not shown) is provided outside the display panel. The configuration is such that a predetermined signal (high power supply potential Vdd, low power supply potential Vss, Start pulse SP, clock signal CK, image signal Data, common potential Vcom, etc.) are input. The configuration shown is as follows:

[0064] The display panel shown in FIG. 2A is composed of a first substrate 201 and a second substrate 202. The first substrate 201 includes a pixel circuit section 203, a gate line side driving circuit 204, a signal line side driving circuit 205, a terminal portion 206, and a switching transistor 207. 2, a common connection portion 208 (also called a common contact), a common electrode 209 (also called a counter electrode), (u)

[0065] In this embodiment, the common electrode 209 is connected to the second substrate 2 via a common connection portion 208. However, it may be provided on the first substrate.

[0066] The first substrate 201 and the second substrate 202 are made of a material that has light transmitting properties and is resistant to subsequent heat treatment. It is necessary to have a heat resistance that is as high as possible. Aluminosilicate glass, aluminum Glass bases used in the electronics industry, such as borosilicate glass and barium borosilicate glass Plates (also called "alkali-free glass substrates"), quartz substrates, ceramic substrates, plastic A substrate such as a quartz substrate can be used.

[0067] Note that the pixel circuit section 203, the gate line side driving circuit 204, and the signal line side driving circuit 205 shown in FIG. 205 and the switching transistor 207 are thin films formed on the first substrate 201. The circuit may be configured by transistors. The signal line side driver circuit 205 is composed of thin film transistors formed on the first substrate 201. It is not necessary to form the first substrate 201 on the first substrate 201, but it is sufficient to form the first substrate 201 on another substrate as shown in FIG. .

[0068] The pixel circuit section 203 includes a gate line side driver circuit 204 and a signal line side driver circuit 205. A plurality of gate lines and signal lines are provided extending from the substrate. A plurality of pixels are provided, each of which is arranged in a corresponding position.

[0069] Furthermore, a signal controlled by the display control circuit 104 shown in FIG. That is, a pulse signal for displaying in the pixel circuit section 203 is output from the terminal section 206. In order to receive the specified signals (high power supply potential Vdd, low power supply potential Vss, A start pulse SP, a clock signal CK, an image signal Data, a common potential Vcom, etc. are provided. It will be provided.

[0070] The common connection portion 208 is connected to the second terminal of the switching transistor 207 on the first substrate 201. The electrode 204 is provided for electrical connection to the common electrode 209 on the second substrate 202. The switching transistor 207 and the common connection portion 208 are connected to the terminal portion 206. Thus, a common potential is supplied to the common electrode 209. For this purpose, electrical connection can be achieved by using conductive particles, which are insulating spheres coated with a thin metal film. The common connection portion 208 is provided at a plurality of locations between the first substrate 201 and the second substrate 202. The configuration may be such that

[0071] The common electrode 209 is preferably provided so as to overlap with a pixel electrode of the pixel circuit portion 203. In addition, the common electrode 209 and the pixel electrodes of the pixel circuit section 203 may have various aperture patterns. The shape may be one having a groove.

[0072] Next, in FIG. 2B, in the schematic diagram of the display panel in FIG. 2A, particularly the pixel circuit section 20 A detailed circuit diagram of the configuration of 3 is shown below.

[0073] The liquid crystal display device shown in FIG. 2B includes a first substrate 201, a second substrate 202, and a The first substrate 201 is provided with a pixel circuit section 203, a gate line side driver 204, and a gate electrode 205. A driving circuit 204, a signal line side driving circuit 205, a terminal portion 206, a switching transistor 20 The second substrate 202 has a common connection portion 208 and a common electrode 209.

[0074] In FIG. 2B, a pixel circuit portion 203 includes a plurality of gate lines 211 and a plurality of signal lines 212. Lines 212 are arranged vertically and horizontally, and include gate lines 211, signal lines 212, thin film transistors ( Hereinafter, the pixel transistor 214 is a pixel transistor having a first electrode and a second electrode, and a liquid crystal is sandwiched between the first electrode and the second electrode. A pixel 213 having a liquid crystal element 215 and a capacitor element 210 formed by the liquid crystal element 215 and the capacitor element 210 is provided. In FIG. 2B, the source terminal of the pixel transistor 214 One of the drain terminals is called the first terminal, and the other of the source terminal or drain terminal is called the second terminal. The first terminal is connected to the signal line 212, the gate terminal is connected to the gate line 211, The second terminal is connected to the first electrode of the liquid crystal element 215. In FIG. One electrode of the liquid crystal element 210 is connected to a first electrode of the liquid crystal element 215, and the other electrode is connected to another wiring. The first electrode of the liquid crystal element 215 corresponds to a pixel electrode. The second electrode of the liquid crystal element 215 corresponds to the above-mentioned common electrode 209 .

[0075] In FIG. 2B, a structure in which a capacitor 210 is provided in the pixel 213 is shown. It is also possible to adopt a configuration in which no quantum element is provided.

[0076] Next, a circuit diagram of one pixel having a pixel electrode is shown in FIG. ) focuses on the pixel transistor 214 and the switching transistor 207. The gate terminal of the pixel transistor 214 is connected to the gate line 211. A first terminal of the pixel transistor 214 is connected to the signal line 212, and a second terminal of the pixel transistor 214 is connected to the signal line 212. The gate terminal of the switching transistor 207 is connected to the pixel electrode 221. A first terminal of the switching transistor 207 is connected to a terminal 206A of the slave unit 206. A second terminal of the switching transistor 207 is connected to the terminal 206B of the terminal section 206. The pixel electrode 221 is electrically connected to the common electrode 222 via the common connection portion 208. A liquid crystal 223 is sandwiched between the pixel electrode 221 and the common electrode 222. The liquid crystal 223 and the liquid crystal 225 may be collectively called a liquid crystal element.

[0077] 4, the terminals in the circuit diagram shown in FIG. 2C, the gate line side driving circuit 204, FIG. 2 is a timing chart showing the state of signals supplied to the signal line side driver circuit 205. For the sake of explanation, the period 401 shown in FIG. 4 is a moving image writing period. The period 402 corresponds to a still image display period, and is determined by the result of the above-mentioned determination of whether the image is a moving image or a still image. In FIG. 4, GCK is supplied to the gate line side driving circuit 204. GSP is a start pulse supplied to the gate line side driver circuit 204. SCK is a clock signal supplied to the signal line side driver circuit 205, and SSP is a signal This is a start pulse supplied to the line side driver circuit 205. Also, in FIG. potential, the potential of the pixel electrode 221, the potential of the terminal 206A, the potential of the terminal 206B, the common electrode 22 The potential of the clock signal GCK and the start GSP, which is a pulse, and SCK, which is a clock signal, and GSP, which is a start pulse The configuration of the shift register of the driving circuit section to which the signal is supplied is the same as that described with reference to FIGS. A circuit can be used.

[0078] The period 401 corresponds to a period for writing an image signal for displaying a moving image. The period 402 corresponds to a period during which a still image is displayed. An electric potential is supplied to each pixel and the common electrode of the pixel circuit unit 203 . On the other hand, during a period 402, an image signal is sent to each pixel of the pixel circuit unit 203, and a common potential is sent to the common electrode. In the period 402 in FIG. 4, the operation of the driving circuit unit is stopped. However, depending on the length of the period 402, the signal may be periodically supplied to stop the It is preferable to prevent deterioration of the image quality of a still image by writing an image signal to the pixel.

[0079] In period 401, the clock signal GCK is constantly supplied as shown in FIG. In the period 401, the start pulse GSP is vertically shifted as shown in FIG. In the period 401, the clock signal As shown in FIG. 4, SCK constantly supplies a clock signal. As shown in Figure 4, the start pulse SSP is generated according to one gate selection period. During the period 401, the signal line 212 is supplied with the An image signal Data to be supplied to the pixel is supplied, and the pixel is turned on in response to the potential of the gate line 211. The potential of the signal line 212 is supplied to the pixel electrode 221 in the pixel region 221. As shown, the potential of terminal 206A, which corresponds to the gate terminal of switching transistor 207, is a potential that causes the switching transistor 207 to be in a conductive state by the display control circuit 104. The common potential, which is the potential of the terminal 206B, is supplied to the common electrode 222. do.

[0080] In period 402, the clock signal GCK and the start pulse GSP are as shown in FIG. During period 402, the clock signal SCK and the start pulse SSP are During the period 402, the image signal supplied to the signal line 212 is turned off. The image signal Data stops as shown in FIG. K and the start pulse GSP are both stopped as shown in FIG. 214 becomes non-conductive, the supply of the image signal Data stops, and the potential of the pixel electrode 221 becomes In addition, the gate terminal of the switching transistor 207 The potential of the terminal 206A corresponding to the terminal 206A makes the switching transistor 207 non-conductive. When the supply of the common potential, which is the potential of the terminal 206B, is stopped, the common electrode 222 The potential becomes floating.

[0081] That is, in the period 402, the electrodes on both ends of the liquid crystal 223, that is, the pixel electrode 221 and the common electrode By making the potential of 222 floating, a still image can be displayed without supplying any new potential. The clocks supplied to the gate line side driver circuit 204 and the signal line side driver circuit 205 can be By stopping the clock signal and the start pulse, it is possible to reduce power consumption. The present invention provides a liquid crystal element using an oxide semiconductor layer capable of reducing an off-current when both ends of the liquid crystal element are in a non-conducting state. The pixel transistor 214 and the switching transistor 215 are thin film transistors having a semiconductor layer. By forming the transistor 207, the current flowing through the liquid crystal element can be reduced.

[0082] Next, in FIG. 5(A) and (B), the period 401 in the timing chart of FIG. 4, that is, the period when the moving image is switched to the still image (period 4 in FIG. 4). 03), and the period from period 402 to period 401, i.e., the period from the still image to the moving image. During the switching period (period 404 in FIG. 4), the high power supply potential Vdd and the clock signal (here, GCK), a start pulse signal (here GSP), the potential of terminal 206A, i.e., the display control 1 shows a timing chart of signals from the control circuit 104.

[0083] As shown in FIG. 5A, in the period when a moving image is switched to a still image, the display control circuit 104 The start pulse GSP is stopped (E1 in FIG. 5(A), first step). Then, After the pulse signal SP stops, the pulse output reaches the final stage of the shift register, and then multiple The clock signal GCK is stopped (E2 in FIG. 5A, second step). The high power supply potential Vdd of the voltage is changed to the low power supply potential Vss (E3 in FIG. 5A, the third step Then, the potential of the terminal 206A is changed to the non-conducting state by the switching transistor 111. (E4 in FIG. 5(A), the fourth step).

[0084] Through the above procedure, the signal supplied to the drive circuit unit 105 is stopped due to an error in the drive circuit unit 105. This can be done without inducing any motion. When displaying a still image, the charge on the pixel electrode This maintains the voltage applied to the liquid crystal, so there is no noise caused by malfunction. By performing the operation of the circuit unit 105, a liquid crystal display capable of displaying still images with little image degradation is provided. A method for operating the device may be provided.

[0085] Also, as shown in FIG. 5B, during the period when the still image is switched to the moving image, the display control circuit 104 , the potential of the terminal 206A is set to a potential at which the switching transistor 111 is in a conductive state. (S1 in FIG. 5B, first step). Next, the power supply voltage is changed from the low power supply potential Vss to the high power supply potential Vss. The power supply potential Vdd is applied (S2 in FIG. 5B, second step). Next, multiple clock signals are Then, the start pulse signal GCK is supplied (S3 in FIG. 5B, the third step). GSP is supplied (S4, fourth step in FIG. 5(B)).

[0086] Through the above procedure, the supply of the signal to the drive circuit unit 105 is resumed. This can be done without causing malfunctions. The potential of each wiring is adjusted in sequence as needed to display a moving image. By returning the power supply voltage to the normal level, the drive circuit unit can be driven without malfunction.

[0087] In FIG. 6, the horizontal axis represents time, with a period 601 for displaying moving images and a period 602 for displaying still images. 02, for example, for each frame period. In FIG. 6, "W" indicates the writing period of the image signal, and "H" indicates the In FIG. 6, the period 603 is a period for holding a signal. Although the time period is shown as a time period, it may be another time period.

[0088] As can be seen from FIG. 6, in the configuration of the liquid crystal display device of this embodiment, the comparator When no difference is detected in the image signal between frames, that is, when a still image is displayed during the period 602, The image signal supplied to the pixel is written during the period when the image signal is switched (period 604 in FIG. 6). ) during the other period of the period 602. This is the period during which the signal is held.

[0089] As described above, during the period in which a still image is displayed according to the configuration of this embodiment, images are frequently This reduces the number of operations required to write image signals multiple times. When viewing an image created by a camera, the human eye sees an image that switches multiple times. Therefore, this may appear as fatigue to the human eye. As mentioned above, by reducing the number of times that image signals are written, eye fatigue can be reduced. There are also other effects.

[0090] In this embodiment, a thin film transistor using an oxide semiconductor is provided in the pixel. The off-current of the thin film transistor is controlled by providing a transistor for each pixel. This allows the voltage to be held by the storage capacitor for a longer period. This makes it possible to provide a liquid crystal display device that can achieve low power consumption when displaying a still image. Cut.

[0091] This embodiment mode can be implemented in appropriate combination with the configurations described in other embodiments. It is.

[0092] (Embodiment 2) The configuration of the display panel in the liquid crystal display device described in the first embodiment will be described with reference to FIG. Specific top views and cross-sectional views will be shown and described.

[0093] 7A shows a top view of a display panel. 7(B) is a top view of the display panel before the conductive particles and the connection wiring are attached. FIG. 7C is a cross-sectional view of the pixel circuit and the connection wiring. 7(B) is a cross-sectional view of EF in FIG. 7(A) showing the connecting region.

[0094] In FIG. 7(A) to (C), an active matrix substrate on which pixel electrodes are formed is shown. The first substrate 1210 and the second substrate 1204 on which the common electrode 1291 is formed are sandwiched between the sealing material 12 The inside of the sealant 1205 is filled with liquid crystal 1280. On the first substrate 1210, a signal line side driving circuit 1200 and a gate line side driving circuit 12 12.01 and a pixel circuit 1202 in which pixel electrodes are formed in a matrix are formed.

[0095] Liquid crystal 1280 is a thermotropic liquid crystal, a low molecular weight liquid crystal, a high molecular weight liquid crystal, a polymer dispersion liquid, These liquid crystal materials are used as follows: The phases shown are steric, smectic, cubic, chiral nematic, and isotropic. vinegar.

[0096] In FIG. 7B, the common electrode 1291 is connected to the connection wiring 120 extending from the terminal portion 1240. 8, a switching transistor 1261, and conductive particles disposed between a pair of substrates are provided. The resin layer 1235 is electrically connected to the terminal portion 1240. Although an example in which there are four locations is shown in FIG. 7(A), at least one location is sufficient, and multiple locations are also acceptable. This is also possible.

[0097] In FIG. 7C, a thin film transistor for a driver circuit is formed on a first substrate 1210 as a driver circuit portion. The signal line side driver circuit 1200 is provided with a circuit having a driver 1223. A gate line side driving circuit having a driving circuit thin film transistor on the first substrate. It has 1201.

[0098] In FIG. 7C, the pixel circuit 1202 includes a pixel transistor 1211. A pixel electrode 1250 connected to the pixel transistor 1211 is provided on the insulating layer 1214. It is being done.

[0099] In FIG. 7(A) to (C), a pixel transistor 1211, a thin film transistor for a driver circuit The switching transistor 1261 includes an oxide semiconductor layer, a gate insulating layer, and and a gate electrode layer.

[0100] An example of the structure of a transistor has been described above. The structure is not limited to the above, and various other structures are possible. For example, a transistor The transistor may have a multi-gate structure with two or more gate electrodes. A transistor has a structure in which a gate electrode is placed above a channel region, and a A structure in which a gate electrode is arranged, a positive staggered structure, an inverse staggered structure, a structure in which a channel region is divided into multiple regions, In the reverse staggered structure, it is possible to use a channel protection type, The structure may be a channel etching type.

[0101] A gate electrode is formed on the thin film transistor 1223 for the driver circuit shown in FIG. 7(C) via an insulating layer 1214. 129 shows a structure including a conductive layer 1293 overlapping with the oxide semiconductor layer and the oxide electrode layer.

[0102] In the thin film transistor 1223 for the driver circuit, an oxide semiconductor layer is formed as a gate electrode layer and a conductive layer. By sandwiching the thin film transistor 1223 for the driver circuit with the thin film transistor 1293, This thin-film transistor for driver circuits has stable electrical characteristics and can reduce the variation in values. A display panel including a transistor 1223 can be provided. The conductive layer 1293 is a gate It may be at the same potential as the electrode layer, a floating potential, or a fixed potential, e.g., GN It may be a D potential or 0V. In addition, by applying an arbitrary potential to the conductive layer 1293, The threshold voltage of the thin film transistor 1223 can be controlled.

[0103] The switching transistor 1261 in FIG. 7B is a conductive particle provided in a resin layer 1235. It is electrically connected to a common electrode 1291 via a terminal 1270 .

[0104] In FIG. 7A, the switching transistor 1261 is disposed outside the sealing material 1205. However, the sealing material 1205 is provided in the region of the signal line side. The switching transistor 126 may be provided in the same area as the driving circuit 1200. 1 is provided in the inner area of ​​the seal material 1205, thereby providing protection from external impacts, etc. Therefore, the life of the switching transistor 1261 can be extended. do.

[0105] In FIGS. 7A to 7C, the first substrate 1210 and the second substrate 1204 are Aluminosilicate glass, aluminoborosilicate glass, barium borosilicate glass, etc. Glass substrates used in the electronics industry (also called "alkali-free glass substrates"), quartz A substrate, a ceramic substrate, a plastic substrate, or the like can be used as appropriate. 10 and the second substrate 1204 are made of a flexible plastic substrate. Flexible display panels can be made.

[0106] In FIG. 7(A) to (C), the sealant 1205 is formed by screen printing, inkjet printing, etc. The sealant is applied onto the first or second substrate using a coating or dispensing device. 1205 is a material that typically contains visible light curable, ultraviolet light curable or heat curable resin. For example, bisphenol A liquid resin, bisphenol A solid resin, etc. Epoxy resins containing bromine, bisphenol F type resins, bisphenol AD ​​type resins, phenol Nol type resin, cresol type resin, novolac type resin, cyclic aliphatic epoxy resin, epib type epoxy resin, glycidyl ester resin, glycidylamine resin, heterocyclic epoxy Resins, modified epoxy resins, and other epoxy resins can be used as the sealing material 1205. The viscosity of the filler is 40 to 400 Pa·s. The sealing material may be a material that does not dissolve in the liquid crystal that will come into contact with the sealing material later. It is preferable to select.

[0107] Conductive particles 1270 may be insulating spheres coated with a thin metal film. The insulating sphere is made of silica glass, hard resin, etc. The metal thin film is made of gold, silver, It can be a single layer or multilayer structure of radium, nickel, ITO, and IZO. Examples For example, a gold thin film or a laminate of a nickel thin film and a gold thin film can be used as the metal thin film. By using conductive particles with insulating spheres at the center, the elasticity is increased and the material is more resistant to external pressure. This can reduce damage to the

[0108] The type of pixel electrode 1250 differs between a transmissive display panel and a reflective display panel. In the case of a transmissive display panel, the pixel electrode 1250 is formed using a light-transmitting material. The materials that have optical properties are indium tin oxide (ITO), zinc oxide (ZnO), and indium oxide. Examples include gallium-doped zinc oxide (IZO), and gallium-doped zinc oxide (GZO).

[0109] The pixel electrode 1250 is made of a conductive material including a conductive polymer. The pixel electrode formed by using the conductive composition can be formed by a sheet. Resistance is 10000Ω / □ or less, and light transmittance at a wavelength of 550nm is 70% or more. It is also preferable that the resistivity of the conductive polymer contained in the conductive composition is 0.1 Ω cm or less. It is preferable that:

[0110] As the conductive polymer, a so-called π-electron conjugated conductive polymer can be used. For example, polyaniline or its derivatives, polypyrrole or its derivatives, polythiophene or or a derivative thereof, or a copolymer of two or more of these.

[0111] On the other hand, in the case of a reflective display panel, a metal electrode with high reflectivity is used for the pixel electrode. Typically, aluminum, silver, etc. are used. Also, by making the surface of the pixel electrode uneven, Therefore, the base film of the pixel electrode may be made uneven.

[0112] In the case of a semi-transmissive display panel, the pixel electrodes are made of both transmissive and reflective materials. can be done.

[0113] In addition, a terminal portion 1240 is formed at an end portion of the first substrate 1210. A connection terminal 1241 is formed on the connection wiring 1208 .

[0114] FIG. 7B is a cross-sectional view of a region where the conductive particles 1270 and the connection terminal are connected. A connection wiring 1208 and a switching transistor 1261 are formed on a substrate 1210 . A connection terminal 1241 is formed on the connection wiring 1208 at the same time as the pixel electrode 1250. The connection terminal 1241 is connected to the connection wiring 1208, the switching transistor 1261, and The connecting terminal 1291 is electrically connected to the common electrode 1291 via the conductive particles 1270. 1241 is connected to an FPC (not shown). 70 is fixed by a resin layer 1235. The resin layer 1235 is made of a seal material 12 An organic resin material such as that used in 05 can be used.

[0115] 7C is a cross-sectional view of a region where the pixel electrode and the connection terminal are connected. A connection wire is formed on the thin film transistor at the same time as the source electrode layer and the drain electrode layer. A line 1242 is formed. A pixel electrode 1250 is formed on the connection wiring 1242 at the same time. A connection terminal 1243 is formed. The connection terminal 1243 is connected to the pixel via the connection wiring 1242. It is electrically connected to the electrode 1250. In this embodiment, the active matrix type Since the display panel is configured as shown in FIG. 1, the pixel electrode 1250 and the connection wiring 1242 are directly connected. 12. Instead, they are connected via the pixel transistor 1211 or the signal line side driver circuit 1200.

[0116] An alignment film 1206 is provided on the pixel electrode 1250 and is subjected to a rubbing treatment. This alignment film 1206 and rubbing treatment may or may not be required depending on the mode of the liquid crystal used. It may be unnecessary.

[0117] The second substrate 1204, which is the opposing substrate, has a blank at a position overlapping the signal line side driver circuit 1200. A color filter is placed over the pixel circuit 1202, and a protective layer is placed over the pixel matrix. A common electrode 1291 may be formed, and an alignment film 120 may be formed on the common electrode 1291. The second substrate 1204 is also the same as the first substrate 12. As with 10, alignment films and rubbing treatments may or may not be required depending on the liquid crystal mode used. There may be cases where this is necessary.

[0118] The second substrate 1204 on which the common electrode 1291 is formed or the pixel electrode 1250 is formed A columnar spacer 1255 is provided on the first substrate 1210. is for maintaining the gap between the first substrate 1210 and the second substrate 1204, In this embodiment, an example is shown in which the columnar spacer is provided on the second substrate 1204 side. Also known as trisospacer, postspacer, scallop spacer, and column spacer In addition, a spherical spacer may be used. In this embodiment, a columnar spacer is used. The columnar spacer 1255 is fabricated using an organic insulating material such as photosensitive acrylic. The substrate is coated with a border material by spin coating, and then the border material is subjected to a series of photolithography processes. By carrying out this process, the photosensitive acrylic remaining on the substrate acts as a spacer. This method allows exposure to the desired location of the spacer depending on the mask pattern used during exposure. Therefore, by arranging this column spacer in the area where the liquid crystal is not driven, Not only can it maintain the gap between the plates, but it also prevents the liquid crystal from leaking light. The Pacer 1255 uses the inkjet method to eject and bake a composition containing an organic insulating material. It can be formed by:

[0119] The conductive particles 1270 may be filled with a conductive polymer. Examples include conductive polyaniline, conductive polypyrrole, conductive polythiophene, and polyether. Complexes of ethylenedioxythiophene (PEDOT) and polystyrene sulfonate (PSS), etc. In addition, the following conductive polymers can be used for the pixel electrode 1250: The above-listed materials can be used as appropriate. Conductive polymers are used in ink-jet devices, The conductive polymer is applied to the common electrode or the connection wiring by a dispenser device. The polymer contacts the conductive particles 1270 and the conductive polymer, forming a common electrode In addition, the connection resistance of the connection wiring can be reduced.

[0120] The connection wiring 1208 and the common electrode 1291 formed on the second substrate 1204 are electrically conductive. Conduction occurs through particles 1270.

[0121] The sealing material 1205 and the conductive particles 1270 are applied to the first substrate 1210 or the second substrate 12 1204, and then the liquid crystal is discharged on the inside of the sealant 1205. After this, The plate 1210 and the second substrate 1204 are bonded together in a reduced pressure atmosphere, and then irradiated with UV light to form a sealant. After the sealant 1205 is hardened, it is heated to further harden the sealant 1205 and the first substrate 1210. Then, the first substrate 1202 is fixed to the second substrate 1204. The liquid crystal orientation is made uniform by the heating.

[0122] As a result, the first substrate 1210 and the second substrate 1204 can be bonded together.

[0123] Then, the first substrate 1210 and the second substrate 1204 are cut into panels. In order to enhance contrast, a first polarizing plate 1290 and a second polarizing plate 1291 are provided on the outside of the first substrate 1210. A second polarizing plate 1295 is provided on the outer side of the substrate 1204. In this case, the first polarizing plate 1290 may not be necessary.

[0124] Although not shown in the present embodiment, a black matrix (light-shielding layer), a polarizing member, a phase Optical members (optical substrates) such as a polarizing member and an anti-reflection member are provided as appropriate. A circularly polarized light source using a retardation substrate may be used. Alternatively, threads or the like may be used.

[0125] In an active matrix display panel, pixel electrodes arranged in a matrix are By driving the selected pixel, a display pattern is formed on the screen. When a voltage is applied between the pixel electrode and the common electrode corresponding to the pixel electrode, The liquid crystal layer disposed between the common electrodes is optically modulated, and this optical modulation corresponds to a display pattern. and is perceived by the observer.

[0126] In the above-described configuration of a display panel having a thin film transistor using an oxide semiconductor layer, As in the first embodiment, power consumption can be reduced when displaying a still image. .

[0127] This embodiment mode can be implemented in appropriate combination with the configurations described in other embodiments. It is.

[0128] (Embodiment 3) In this embodiment mode, a touch panel function is added to the liquid crystal display device shown in the above embodiment mode. The structure of the liquid crystal display device having the added structure will be described with reference to FIGS.

[0129] FIG. 8(A) is a schematic diagram of a liquid crystal display device according to the present embodiment. A touch panel unit 802 is superimposed on a liquid crystal display panel 801, which is a liquid crystal display device in the form of The touch panel is attached to a housing 803 (case). The unit 802 uses a resistive film type, a surface type capacitive type, a projected type capacitive type, etc. It is possible.

[0130] As shown in FIG. 8A, a liquid crystal display panel 801 and a touch panel unit 802 are separately provided. By fabricating and stacking these devices separately, we have developed a liquid crystal display device with touch panel functionality. Cost reduction can be achieved.

[0131] Regarding the configuration of a liquid crystal display device with a touch panel function different from that shown in FIG. A liquid crystal display device 804 shown in FIG. 8B has a plurality of pixels 805. The touch panel has a sensor 806 and a liquid crystal element 807. Since there is no need to fabricate the liquid crystal display device by stacking the liquid crystal units 802, the liquid crystal display device can be made thinner. In addition to the pixel 805, a gate line side driver circuit 808, a signal line side driver circuit 809, By forming the optical sensor driver circuit 810 on the same substrate as the pixel 805, The optical sensor 806 is made of amorphous silicon or the like. The insulating film may be formed so as to overlap with a thin film transistor including an oxide semiconductor.

[0132] According to the present embodiment, in a liquid crystal display device to which a touch panel function is added, By using thin film transistors with a thin film, the image retention characteristics when displaying still images can be improved. During this time, the operation of the driver circuitry is stopped, resulting in low power consumption. This will enable us to strengthen our capabilities.

[0133] In addition, a display panel using the same oxide semiconductor as that used in the pixel circuit is formed on the display panel shown in FIGS. A thin film transistor manufactured using the above method can be provided to provide a memory element. The memory element provided on the display panel may be, for example, a touch panel, which stores the voltage of the touch panel. As an example, the threshold value of the optical signal may be stored in the memory. FIG. 13 shows a configuration in which a memory element 811 is provided in addition to the display panel configuration. FIG. 13 shows the basic configuration of a memory element. In the following, a transistor including an oxide semiconductor is denoted by the symbol OS. is.

[0134] In the memory element shown in FIG. 13, the gate electrode of the transistor 160 and the gate electrode of the transistor 162 The first transistor is electrically connected to one of the source electrode and the drain electrode. The line (also called the 1st Line: source line) and the source electrode of the transistor 160 are connected to each other. The second line (also called the bit line) and the transistor 1 are electrically connected to each other. The drain electrode of the third wiring (3rd Lin e: also referred to as a first signal line) and the other of the source electrode or drain electrode of the transistor 162 The fourth line (also called the second signal line) and the third line (also called the fourth line) are electrically connected to each other. The gate electrode of the transistor 162 is electrically connected to the The gate electrode of the transistor 60 and one of the source electrode and drain electrode of the transistor 162 are connected to a capacitor. A fifth line (5th Line: word line) is electrically connected to one of the electrodes of the capacitance element 164. The other electrode of the capacitor 164 is electrically connected to a line (also referred to as a line).

[0135] The transistor 160 and the transistor 162 each using an oxide semiconductor have an extremely low off-state current. Therefore, when the transistor 162 is turned off, , the potential of the gate electrode of the transistor 160 can be maintained for an extremely long period of time. By including the capacitor 164, the gate electrode of the transistor 160 This makes it easier to hold the charge applied to the memory cell and easier to read out the stored contents.

[0136] In the memory element described in this embodiment, the potential of the gate electrode of the transistor 160 can be held. By taking advantage of this feature, it is possible to write, retain, and read information as follows: .

[0137] First, the writing and holding of information will be explained. The transistor 162 is turned on by applying a potential that turns on the transistor 162 . As a result, the potential of the third wiring is applied to the gate electrode of the transistor 160. That is, a predetermined charge is applied to the gate electrode of the transistor 160 (write). After that, the potential of the fourth wiring is set to a potential at which the transistor 162 is turned off. By turning off the transistor 162, the voltage applied to the gate electrode of the transistor 160 is The charge is retained (retention).

[0138] Since the off-state current of the transistor 162 is extremely small, the gate electrode of the transistor 160 The charge is held for a long time. For example, when a read potential is applied to the fifth wiring, A potential is applied to the gate electrode of the transistor 160 so that the transistor 160 is turned on. By doing so, the on state of the transistor 160 is maintained for a long period of time. Similarly, a potential that turns off the transistor 160 is applied to the By applying a current to the gate electrode, the transistor 160 is kept in an off state for a long period of time. Here, the read potential is the potential that changes depending on the charge held in the gate electrode. The potential of the fifth wiring at which the resistor 160 is turned on or off is referred to as the potential of the fifth wiring at which the resistor 160 is turned on or off.

[0139] Next, the reading of information will be described. As described above, when the transistor 160 is in the on state, Alternatively, in a state in which the off state is maintained, a read potential is applied to the fifth wiring, and the first wiring When a predetermined potential (low potential) is applied to the line, the transistor 160 is turned on or off. In response, the potential of the second wiring has a different value. In this case, the potential of the second wiring is lower than the potential of the first wiring. When the transistor 160 is off, the potential of the second wiring does not change.

[0140] In this manner, in a state in which information is held, the potential of the first wiring and the potential of the second wiring are By comparing, information can be read out.

[0141] When no information is read, the transistor remains in the ON state regardless of the charge held in the gate electrode. A potential at which the fifth switch 160 is turned off (or turned on) is applied to the fifth switch 160. Just give it to the wiring.

[0142] Next, the rewriting of information will be described. The rewriting of information includes the above-mentioned writing of information and That is, the potential of the fourth wiring is held in the same manner as when the transistor 162 is turned on. This causes the transistor 162 to be turned on. (a potential related to new information) is applied to the gate electrode of transistor 160. Then, The potential of the fourth wiring is set to a potential at which the transistor 162 is turned off. By turning off 62, the new information is held.

[0143] In this way, the memory element shown in FIG. 13 directly writes information by rewriting information. This allows the erase operation required in flash memories, etc. This eliminates the need for an erase operation, and can suppress the decrease in operation speed caused by the erase operation. High speed operation of the memory element is achieved.

[0144] The source electrode or drain electrode of the transistor 162 is connected to the gate of the transistor 160. The flow cell is electrically connected to a gate electrode, and is used as a non-volatile memory element. This provides the same effect as the floating gate of a floating gate type transistor. In the figure, the source electrode or drain electrode of the transistor 162 and the gate of the transistor 160 The portion to which the gate electrode is electrically connected is sometimes called the floating gate portion FG. When the transistor 162 is off, the floating gate portion FG is embedded in an insulator. The floating gate FG holds charge. In the transistor 162 using a conductor, the off-state current is generated by a transistor formed by a silicon semiconductor or the like. Since the transistor 162 is 1 / 100,000th of the transistor, the leakage current of the transistor 162 is Therefore, it is possible to ignore the loss of the charge stored in the gate portion FG.

[0145] This configuration provides the following problems that have been pointed out in the conventional floating gate type transistors: This avoids the problem of deterioration of the gate insulating film (tunnel insulating film) that is being used. This solves the problem of deterioration of the gate insulating film when electrons are injected into the floating gate. This allows the memory element shown in FIG. There is no limit on the number of times.

[0146] Note that this embodiment mode can be appropriately combined with other embodiment modes.

[0147] (Embodiment 4) In this embodiment, an electronic device including the liquid crystal display device described in the above embodiment is An example will be described.

[0148] FIG. 9(A) shows a portable game machine, which includes a housing 9630, a display portion 9631, a speaker 9633, It may have operation keys 9635, a connection terminal 9636, a recording medium reading unit 9672, etc. The portable gaming machine shown in FIG. 9(A) uses a program or data recorded on a recording medium. The function to read the information and display it on the display unit, and to share information with other portable gaming machines by wireless communication. The functions of the portable gaming machine shown in FIG. The function is not limited to this and may have various functions.

[0149] FIG. 9B shows a digital camera, which includes a housing 9630, a display portion 9631, and a speaker 9633. , operation keys 9635, connection terminal 9636, shutter button 9676, image receiving unit 9677, The digital camera shown in FIG. 9B has a function of taking still images, It has a variety of functions, including video shooting, automatic or manual image correction, and antennas. A function to acquire information, a function to store images captured or information acquired from the antenna, The device has the function of displaying captured images or information obtained from the antenna on the display unit. The functions of the digital camera shown in FIG. 9B are not limited to those described above. It can have various functions.

[0150] FIG. 9C shows a television receiver, which includes a housing 9630, a display portion 9631, a speaker 9633, It may have operation keys 9635, a connection terminal 9636, etc. A television receiver has the functions of processing television radio waves and converting them into image signals, and processing and displaying image signals. The function of converting the image signal into a signal suitable for the application, the function of converting the frame frequency of the image signal, etc. The functions of the television receiver shown in FIG. 9C are not limited to those described above, and various functions may be used. It can have various functions.

[0151] FIG. 9(D) shows a monitor for use in a personal computer. 30, a display unit 9631, etc. The monitor shown in FIG. In the example shown, the C-shaped display unit 9653 is located on the display unit 9631. Although a window-type display unit 9653 is shown in the display unit 9631, other symbols, such as icons, may be used. In the case of a monitor for a personal computer, the image is displayed only when the input is made. In many cases, image signals are rewritten, and the driving method of the liquid crystal display device according to the above embodiment is It is preferable to apply the monitor shown in FIG. 9(D) to the above-mentioned applications. It can have a variety of functions.

[0152] FIG. 10A shows a computer, which includes a housing 9630, a display portion 9631, and a speaker 9633. , operation keys 9635, connection terminals 9636, pointing devices 9681, external connection points The computer shown in FIG. 10A can store various information. The function to display images (still images, videos, text images, etc.) on the display, A function to control processing by a program, a communication function such as wireless communication or wired communication, The ability to connect to various computer networks using the communication function, The code shown in FIG. 10(A) can have a function to transmit or receive data. The functions possessed by the computer are not limited to those described above, and the computer may have a variety of functions.

[0153] Next, FIG. 10B shows a mobile phone, which includes a housing 9630, a display portion 9631, and a speaker 963. 3, operation keys 9635, a microphone 9638, etc. The mobile phone shown in has the following functions: A function to display the calendar, date, time, etc. on the display, and to operate or It has the functions of editing, controlling the processing by various software (programs), etc. However, the functions of the mobile phone shown in FIG. 10(B) are not limited to these. It can have a variety of functions.

[0154] Next, FIG. 10C shows an electronic paper (also called an E-book). The electronic pen 9630 may have a display unit 9631, an operation key 9632, etc. The user interface has the functions to display various information (still images, videos, text images, etc.), a calendar, , a function to display the date or time on the display unit, and a function to operate or edit the information displayed on the display unit Functions such as the ability to control processing using various software (programs) Note that the functions of the electronic paper shown in FIG. 10(C) are not limited to these. It can have various functions. Another structure of electronic paper is shown in FIG. The electronic paper shown in FIG. 10(D) is the same as the electronic paper shown in FIG. 10(C) except that a solar cell 9651 The display unit 9631 is a reflection type. When using a projection type liquid crystal display device, it is expected to be used in a relatively bright environment. It is ideal for efficiently generating power with the 651 and charging the battery 9652. If a lithium-ion battery is used as the battery 9652, it can be made smaller. This has the advantage that

[0155] The electronic device described in this embodiment is designed to reduce power consumption when displaying a still image. can be done.

[0156] This embodiment mode can be implemented in appropriate combination with the configurations described in other embodiments. It is. [Explanation of symbols]

[0157] 10 Pulse output circuit 11 First Wire 12 Second Wire 13 Third Wire 14 Fourth Wire 15 The fifth wire 17 6th Wire 18 Seventh Wire 21 First input terminal 22 Second input terminal 23 Third input terminal 24 4th input terminal 25 5th input terminal 26 First output terminal 27 Second output terminal 31 First transistor 32 Second transistor 33 The third transistor 34 The Fourth Transistor 35 The fifth transistor 36 The 6th Transistor 37 The Seventh Transistor 38 The 8th Transistor 39 The ninth transistor 40 The 10th Transistor 41 The 11th transistor 51 Power line 52 Power line 61 period 62 period 100 LCD display device 101 Display Panel 102 Memory circuit 103 Comparison circuit 104 Display control circuit 105 Drive circuit section 106 Pixel circuit section 107A Gate line side driving circuit 107B Signal line side driver circuit 108 Frame Memory 109 Selection circuit 110 Common electrode section 111 Switching transistor 221 Pixel electrode 222 Common electrode 223 Liquid crystal 160 Transistors 162 Transistor 164 Capacitive element 201 First Substrate 202 Second Substrate 203 Pixel circuit section 204 Gate line side driving circuit 205 Signal line side driver circuit 206 Terminal section 206A Terminal 206B Terminal 207 Switching Transistor 208 Common Connection 209 Common electrode 210 Capacitive element 211 Gate Line 212 Signal Line 213 pixels 214 Pixel transistor 215 Liquid crystal element 221 Pixel electrode 222 Common electrode 223 Liquid crystal 401 period 402 period 403 period 404 period 601 period 602 period 603 period 604 period 801 Liquid crystal display panel 802 Touch panel unit 803 Case 804 LCD display device 805 pixels 806 Light Sensor 807 Liquid crystal element 808 Gate line side driver circuit 809 Signal line side driver circuit 810 Driver circuit for optical sensor 811 Memory elements 1200 Signal line side driver circuit 1201 Gate line side driver circuit 1202 Pixel circuit 1204 Second Board 1205 Sealing material 1206 Alignment film 1207 Orientation film 1208 Connection Wiring 1210 First substrate 1211 Pixel transistor 1214 Insulating layer 1223 Thin film transistor for driver circuits 1235 Resin layer 1240 Terminal section 1241 Connection terminal 1242 Connection Wiring 1243 Connection terminal 1250 pixel electrode 1255 Pillar Spacer 1261 Switching transistor 1270 Conductive Particles 1280 LCD 1290 1st polarizing plate 1291 Common electrode 1293 Conductive layer 1295 Second polarizing plate 9630 Case 9631 Display section 9632 Operation key 9633 Speaker 9635 Operation Key 9636 Connection terminal 9638 Microphone 9651 Solar Cell 9652 Battery 9653 Window type display 9672 Recording medium reading unit 9676 Shutter button 9677 Image receiving unit 9680 External connection port 9681 Pointing Device

Claims

[Claim 1] during a period in which moving images are displayed, a pixel transistor having a semiconductor layer made of an oxide semiconductor and electrically connected to a drive circuit section formed on a first substrate is brought into a conductive state to supply an image signal to a pixel electrode, a switching transistor having a semiconductor layer made of an oxide semiconductor and electrically connected to a terminal section formed on the first substrate is brought into a conductive state, and a common potential is supplied to a common electrode formed on a second substrate and electrically connected to the terminal section via the switching transistor; during a period in which a still image is displayed, the pixel transistor is made non-conductive to make the pixel electrode electrically floating, the switching transistor is made non-conductive, and the common electrode is made electrically floating; A method for driving a liquid crystal display device, characterized in that, during a period when the still image is switched to the moving image, the following steps are carried out in that order: a first step of supplying the common potential to the common electrode, a second step of supplying a power supply voltage to the drive circuit unit, a third step of supplying a clock signal to the drive circuit unit, and a fourth step of supplying a start pulse signal to the drive circuit unit.

Images