Indication device

Abstract

Reduces flicker in LCD displays operating in FFS mode at low refresh rates. Reduce. [Solution] In a liquid crystal display device in FFS mode, liquid crystal elements are configured on the element substrate side. A pixel electrode and a first common electrode are formed, and a second common electrode is formed on the other opposing substrate side. By making the first common electrode and the second common electrode equipotential, residual D is removed from the pixel. The generation of C voltage can be suppressed. Therefore, even if the refresh rate is reduced, Fluctuations in pixel transmittance during the data retention period are suppressed, thereby reducing flickering.

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal display device and a method for driving the same. Regarding the electronic equipment installed.

[0002] In this specification, semiconductor devices refer to semiconductor elements (transistors, diodes, etc.). This refers to a circuit that includes such a circuit, and a device that has such a circuit. It also refers to a device that functions by utilizing semiconductor properties. This refers to all types of devices. For example, integrated circuits, chips containing integrated circuits, display devices, and light-emitting devices. Lighting devices and electronic equipment are all semiconductor devices. [Background technology]

[0003] With the development of the information society, the means of obtaining information have shifted from paper media to smartphones and other digital media. Information terminals such as personal computers are increasingly being used. Therefore, at close range I strain my eyes on a daily basis because I stare at screens for long periods of time. The causes of eye strain are complex. Yes, there are some issues, and one of them is screen flickering.

[0004] On a display device, images are switched dozens of times per second. The number of switching cycles is called the refresh rate. Also, the refresh rate is the drive cycle. It is sometimes called wavenumber. Such high-speed screen switching that is imperceptible to the human eye This is considered a cause of eye strain. As a display method for information terminals, liquid crystal display devices ( LCDs are a typical example. Therefore, Non-Patent Documents 1 and 2 discuss the refresh rate of LCDs. It has been proposed to reduce the number of image rewrites by lowering the processing speed.

[0005] The driving methods (modes) of active-matrix LCDs involve controlling the orientation of liquid crystal molecules. They are distinguished as follows: for example, TN (Twisted Nematic) mode, VA (Vertical Nematic) mode. (Directional) mode, IPS (In-Plane Switching) mode, and FFS (Fringe Field Switching) mode These are some of the known types. The structure of LCD pixels differs depending on the driving method.

[0006] In TN mode and VA mode LCDs, the pixels have pixel electrodes on one of a pair of substrates and commo on the other. A common electrode (also called a counter electrode) is formed, and two bases are located between the pixel electrode and the common electrode. By forming an electric field perpendicular to the surface of the plate and controlling the orientation of liquid crystal molecules, the transmittance of the pixels can be controlled. It is.

[0007] On the other hand, in IPS mode and FFS mode LCDs, the common electrode is on the same substrate as the pixel electrode. In IPS mode LCDs, the common electrode and pixel electrode are comb-shaped, and the same insulating It is formed on the edge film. FFS mode is an improved display method of IPS mode, and the insulating film is The pixel electrode and common electrode are formed facing each other via a barrier. Pixel of an FFS mode LCD. The electrode has a structure in which multiple slits are formed, and the fringe of the pixel electrode and The electric field (fringe field) formed between the common electrodes controls the orientation of liquid crystal molecules. Therefore, FFS mode LCDs have a wider viewing angle and higher transparency than IPS mode LCDs. It has characteristics of an excess rate.

[0008] Various improvements have been made to LCDs in FFS mode. For example, Patent Document 1 describes the image A second common electrode is formed on a substrate on which no primary electrodes have been formed, and this second common electrode is supplied It has been disclosed that by applying a potential, the LCD can achieve a fast response and wide viewing angle.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] Based on such background art, one of the problems of one embodiment of the present invention is to provide a novel FFS-mode liquid crystal display device, its driving method, etc. Another problem of one embodiment of the present invention is to provide a liquid crystal display device capable of providing an eye-friendly display, its driving method, etc.

[0012] The description of a plurality of problems does not prevent the existence of each other's problems.

[0013] ​​The embodiment does not need to solve all of these problems. Furthermore, if there are problems other than those listed, the specification These issues will become clear from the drawings, claims, etc., and these issues will also be addressed in this invention. This could become a challenge for one aspect of the Ming Dynasty. [Means for solving the problem]

[0014] Embodiments of the present invention include opposing first and second substrates and the space between the first and second substrates. A liquid crystal layer, a pixel electrode and a first common electrode formed on the first substrate, and a shaped layer on the second substrate. The pixel electrode has a second common electrode and an insulating layer in between, and the pixel electrode has a first common electrode. Opposite each other, with the liquid crystal layer in between, the second common electrode faces the first common electrode, and the pixel electrode is A data signal corresponding to the image data is supplied, and the same signal is transmitted to the first and second common electrodes. This is a liquid crystal display device characterized by the application of an electric potential.

[0015] Another embodiment of the present invention involves opposing first and second substrates, and the first substrate and the second substrate The intermediate liquid crystal layer, pixels, gate lines and source lines connected to the pixels, and gate signal generation It consists of a gate driver that outputs to the gate line and a source driver that generates a data signal and outputs it to the source line. It includes a source driver, a controller that controls the gate driver and source driver, and The pixel comprises a transistor formed on the first substrate, a pixel electrode, and a first common electrode. The transistor has a second common electrode formed on a second substrate, and the gate is connected to the gate. The source line is connected and functions as a switch that controls the connection between the pixel electrode and the source line, and the pixel electrode The electrode faces the first common electrode across an insulating layer, and the second common electrode faces the liquid crystal layer across Opposite the first common electrode, the same potential as the first common electrode is applied, and control For gate drivers and source drivers, for a period longer than one frame, A liquid crystal display device characterized by having a control function that holds the data signal input to the pixel. It is placed there.

[0016] In the above configuration, the pixel transistor controls the connection between the pixel electrode and the source line. As an switch, a transistor is used in which the channel is formed by an oxide semiconductor layer. preferable. [Effects of the Invention]

[0017] According to one embodiment of the present invention, flickering associated with data rewriting can be reduced, so the eyes This makes it possible to provide a liquid crystal display device that is gentle on the user, and a driving method for the same. ru. [Brief explanation of the drawing]

[0018] [Figure 1] A diagram illustrating an example of the pixel configuration of an FFS mode LCD. A: Circuit diagram. B: Schematic cross-sectional view showing the electrode structure. C: Perspective view of the same. [Figure 2] A diagram illustrating an example of the configuration of an FFS mode LCD. A: Block diagram. B: Plan view showing an example of the configuration of a liquid crystal (LC) panel. [Figure 3] A schematic diagram illustrating one example of an LCD driving method. A: Normal driving. B: IDS driving. [Figure 4] A timing chart illustrating one example of an LCD driving method. A: Normal driving. B: IDS driving. [Figure 5] A, B: Diagrams illustrating an example of IDS operation. [Figure 6] A cross-sectional view showing an example of the configuration of an LC panel in FFS mode. [Figure 7] Figure 6 is a layout diagram showing an example of the pixel configuration of an LC panel. [Figure 8]Block diagram showing an example of the configuration of an information processing system. [Figure 9] A-F: Exterior views showing specific examples of the information processing system. [Figure 10] Graph of the measurement results of the amount of change in the transmittance of the LCD. A: Example 1. B: Comparative Example 1. [Figure 11] Graph of the subjective evaluation results regarding the display quality of the LCD. A: Example 1. B: Comparative Example 1.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can easily understand that the form and details thereof can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below.

[0020] In the drawings used in the description of the embodiments of the invention, the same parts or parts having the same function are denoted by the same reference numerals, and repeated descriptions thereof are omitted.

[0021] (Embodiment 1) Using FIGS. 1 to 4, in this embodiment, an LCD will be described as an example of a semiconductor device. In addition, in this embodiment, an FFS-mode LCD will be described.

[0022] <<Example of LCD Configuration>> FIG. 2A is a block diagram showing an example of the configuration of the LCD 100. As shown in FIG. 2A, the L CD 100 has a pixel portion 111, a gate driver 112, a source driver 113, and a con troller 180. In addition, in the LCD 100, the circuit block surrounded by the dashed-dotted line in FIG. 2A The lock is modularized and configured as a liquid crystal (LC) panel 110. The NEL 110 has a pixel section 111, a gate driver 112, and a source driver 113. do.

[0023] The LCD100 receives the image signal (Video) and the data of the LC panel 110. Control signals such as synchronization signals (SYNC) and reference clock signals (CLK) for controlling the system A number is input. Examples of synchronization signals include horizontal synchronization signals and vertical synchronization signals. The LCD100 receives the voltage necessary for operation from power supply 190.

[0024] The pixel section 111 consists of multiple pixels 121, multiple gate lines 122, and multiple source lines 123 It has. Multiple pixels 121 are arranged in a two-dimensional array, and the arrangement of pixels 121 Accordingly, gate lines 122 and source lines 123 are provided. Pixel 12 in the same row 1 is connected to the gate driver 112 by a common gate line 122, and the pixels 12 in the same column Line 1 is connected to source driver 113 by a common source line 123.

[0025] The controller 180 is a circuit that controls the entire LC panel 110 and constitutes the LCD 100. It generates control signals for the circuit. Controller 180 generates the control signals from the synchronization signal (SYNC). It has a control signal generation circuit that generates control signals for the drivers (112, 113). Synchronization signal ( SYNC refers to signals such as the vertical synchronization signal, horizontal synchronization signal, and reference clock signal.

[0026] The controller 180 uses the start pulse signal as a control signal for the gate driver 112. It generates GSP, clock signals (GCLK), etc., and uses them as control signals for the source driver 113. It generates a start pulse signal (SSP), a clock signal (SCLK), etc. Note that these control signals may be a group of signals rather than a single signal.

[0027] In the following description, the start pulse signal (GSP) may be simply referred to as GSP or signal GSP. This also applies to other signals, voltages, potentials, circuits, and wirings, etc. .

[0028] Further, the controller 180 includes a power management unit and has a function of controlling the power supply to and the stop of the drivers (112, 11 3).

[0029] When GSP is input to the gate driver 112, it generates a gate signal according to GCLK and sequentially outputs it to the gate line 122. The gate signal is a signal for selecting the pixel 121 where the data signal is written.

[0030] The source driver 113 has a function of processing an image signal (Video) to generate a data signal and outputting it to the source line 123. When SSP is input to the source driver 113, it generates a data signal according to SCLK and sequentially outputs it to the source line 123.

[0031] The pixel 121 has a switching element whose on and off are controlled by the gate signal. When the switching element is turned on, a data signal is written from the source driver 113 to the pixel 121. When the switching element is turned off, the pixel 121 enters a data holding state for holding the written data signal.

[0032] <<Configuration example of LC panel>> The LC panel 110 has substrates 21 and 22 that are provided opposite each other. Substrate 21, The substrate 22 is fixed by the sealing member 23 so as to have a gap. A liquid crystal layer 20 exists between layers 22 (see Figure 1B).

[0033] The substrate 21 is a support substrate for the backplane of the LC panel 110, and on the substrate 21, The circuits (111-113) and terminal section 24 are formed. The substrate 21 is referred to as an element substrate, a TFT (thin film transistor) substrate, etc.

[0034] Note that Figure 2B shows the gate driver 112 as two circuits (gate drivers 112a, 11 2b) shows an example configuration in which the components are divided and arranged on both sides of the pixel section 111. Of course, gate drivers It is also possible to configure the wire 112 as a single circuit and place it on one side of the pixel section 111.

[0035] Multiple terminals are formed on the terminal section 24. Electrodes and wiring formed on the substrate 21, The electrodes and wiring formed on the substrate 22 are connected to the terminals of the terminal section 24 by routing the wiring, etc. Connected. The terminal portion 24 is connected by a conductive material such as an anisotropic conductive film. A printed circuit (FPC) 25 is connected via FPC 25. Voltage and signals are then input to the circuits (111-113) on the circuit board 21.

[0036] Furthermore, an IC chip including the controller 180 may be mounted on the circuit board 21. Part or all of the Iba (112, 113) are made into IC chips and mounted on the circuit board 21. This is also good. Implementation methods include the COG (Chip On Glass) method and the COF (Chip On Glass) method. p On Film method, wire bonding method, and TAB (Tape Automated Bonding) method. Methods such as ated bonding exist.

[0037] Furthermore, as explained below, the substrate 21 has pixel electrodes and a condensing ring for driving liquid crystal molecules. A mon electrode is formed. The substrate 22 is called a counter substrate or color filter substrate, etc. This is a support substrate for the components, and a common electrode is also provided on the substrate 22.

[0038] <<Example of pixel configuration>> Figure 1A is a circuit diagram showing an example of the circuit configuration of pixel 121. Figures 1B and 1C are also shown. Figure 1B is a schematic diagram illustrating the electrode structure of pixel 121, and shows a cross-section of the main part of pixel 121. Figure 1C is a top view, and Figure 1C is a perspective view of the same.

[0039] <Circuit Configuration> As shown in Figure 1A, the pixel 121 consists of a transistor 130, a liquid crystal element 131, and a capacitor. It has element 132.

[0040] The gate of transistor 130 is connected to gate line 122, and the liquid crystal element 131 This is a switching element that controls the connection between the gate driver 112 and the source line 123. The gate signal output controls whether transistor 130 is turned on or off.

[0041] The liquid crystal element 131 has two electrodes (30, 31) and a liquid crystal layer 20 (Figure 1B). So, of the two electrodes of the liquid crystal element 131, the source line 123 is connected via the transistor 130. The electrode (30) connected to the other electrode (31) is called the "pixel electrode," and the other electrode (31) is called the "common electrode." We will refer to this as the "pole." The common voltage VCOM is applied to the common electrode 31.

[0042] Capacitive element 132 is connected in parallel with liquid crystal element 131, and acts as an auxiliary capacitance for liquid crystal element 131. It functions as follows. The capacitive element 132 has an insulating layer 40 as a dielectric, and the pixel electrode 30 and common This is a capacitive element with a MIM structure, where electrode 31 is a pair of electrodes (terminals) (Figure 1B).

[0043] <Pixel electrode, common electrode> As shown in Figure 1B, the pixel electrode 30 and the common electrode 31 are formed on the substrate 21. The pixel electrode 30 faces the common electrode 31 via an insulating layer 40.

[0044] As shown in Figure 1C, the pixel electrodes 30 are provided electrically isolated for each pixel 121. On the other hand, in order to supply the same voltage (VCOM) to all pixels 121 of the pixel section 111, common Electrode 31 is provided as a single electrode in the pixel section 111. Note that this is an actual common electrode. An opening is provided in 31 for connecting the pixel electrode 30 to the transistor 130.

[0045] In the example shown in Figure 1C, the planar shape of the pixel electrode 30 is a rectangle with multiple strip-shaped openings. However, it is not limited to this shape. The pixel electrode 30 is the pixel electrode 30 And a shape such that a fringe field is formed when a voltage is applied to the common electrode 31. That would be fine. The pixel electrode 30 is, for example, a part in which multiple strip-shaped structures are regularly arranged. The structure can then have connecting parts to connect them.

[0046] A common electrode 32 is provided on the substrate 22, opposite to the common electrode 31, with the liquid crystal layer 20 in between. The common electrode 32, like the common electrode 31, is also connected to all pixels 121. It is provided as one electrode (one conductive film). Also, when displaying, the common electrode 32 is set to the same potential as the common electrode 31, and a common voltage VCOM is applied.

[0047] To set the common electrode 31 and the common electrode 32 to the same potential, the common electrodes 31 and the common electrode 32 are connected within the LC panel 110, and are connected to the same terminal of the terminal portion 24 by a common wiring, and VCOM may be applied to this terminal. Alternatively, the common electrode 31 and the common electrode 32 are connected to different terminals by separate wirings, and VCOM may be applied to each terminal.

[0048] The supply of VCOM to the LC panel 110 can be performed by generating VCOM with the power supply 190 and supplying it to the LC panel 11 0. When setting VCOM to 0 V (ground potential), the common electrodes 31 and the common electrode 32 may be connected to the terminal for the ground potential (GND). In this case, the supply of the power supply voltage from the power supply 190 becomes unnecessary.

[0049] <<LCD Image Display Method>> When displaying an image, by setting the common electrodes formed on the two opposing substrates to the same potential, it becomes possible to provide an FFS-mode LCD that reduces flicker during image rewriting.

[0050] In an LCD, each time data is rewritten, an image is displayed by inversion driving that inverts the polarity of the signal (data signal) written to the pixel. Also, due to the nature of the liquid crystal material, the voltage-transmittance (V-T) characteristics of the pixel differ depending on the polarity of the data signal. Therefore, the fluctuation of the transmittance of the pixel accompanying the inversion of the polarity of the data signal is considered to be the cause of eye fatigue due to the LCD. ​​

[0051] Therefore, in this embodiment, the number of data rewrites (number of data polarity reversals) is reduced. This reduces the strain on the user's eyes. Therefore, the LCD100 has at least two drives It has a driving method (display mode). One is a driving method for displaying general videos. This is a drive method that rewrites the data every frame. This is called "normal drive". One method is a drive method that stops the data rewriting process after the data writing process has been executed. This is called "idle stop (IDS) drive." IDS drive is a normal drive This is a drive method that rewrites data at a lower frequency than manual operation.

[0052] Furthermore, the mode in which the LCD100 is displaying an image, whether in normal drive or IDS drive, is... These are called "normal mode (state)" and "IDS mode (state)," respectively.

[0053] Videos are displayed using normal drive. Still images are displayed using either normal drive or IDS drive. This is done by inputting a signal to determine the display mode to the controller 180 of the LCD 100. Then, the controller 180 will display the information in that display mode, Control (112, 113).

[0054] Since still images do not change from frame to frame, when displaying a still image, one frame There is no need to rewrite the data for each frame. Therefore, when displaying still images, the LCD By operating the 100 in IDS mode, screen flickering is reduced, and power consumption is also reduced. This can reduce the amount of power required. Below, using Figures 3 and 4, we will compare normal drive and IDS drive. explain.

[0055] FIG. 3A is a diagram for explaining a method of displaying a still image by normal driving, and FIG. 3B is a diagram for explaining a method of displaying a still image by IDS driving. Also, FIG. 4A is for normal driving, and FIG. 4B is a timing chart showing an example of IDS driving. In FIG. 4, Video is an image signal input to the LC panel 110, GVDD is the high power supply voltage of the gate driver 112, and VData is a data signal output from the source driver 113 to the source line 123.

[0056] <Normal Driving> In normal driving, it is a driving method in which pixel data is periodically rewritten by performing inversion driving every one frame period (Tpd). Triggered by the input of GSP, the gate driver 112 generates a gate signal according to GCLK and outputs it to the gate line 122. In the source driver 113, when SSP is input, VData is generated according to SCLK and output to the source line 123.

[0057] Also, as shown in FIG. 4A, the polarity of VData input to each pixel 121 is inverted every one frame period. For inversion driving, typically, there are dot inversion driving, gate line inversion driving, and source line inversion driving.

[0058] Here, the polarity of VData is determined based on VCOM. When the voltage of VData is higher than VCOM, it has a positive polarity, and when it is lower, it has a negative polarity.

[0059] <IDS Driving> In IDS driving, data is periodically rewritten at a refresh rate lower than that of normal driving. Therefore, the data holding period becomes longer than one frame period. In FIG. 3B, 10 ​​​​​​​​​​​​​This shows an example of rewriting the image frame by frame. This enables IDS-driven refresh The refresh rate becomes 1 / 10 of the normal drive rate. For example, if the normal drive refresh rate is 60 If the refresh rate is Hz, then the refresh rate of the IDS drive in Figure 3B is 6 Hz.

[0060] As shown in Figures 3B and 4B, the data rewriting process in IDS-driven data writing It can be divided into replacement (or, it can also be called writing) and data retention. can.

[0061] First, at the same refresh rate (interval Tpd) as normal operation, data rewrites occur once. This is executed multiple times, and data is written to pixel 121. After data writing, the gate Stop generating gate signals in driver 112 and stop rewriting data. Therefore, all pixels 121 have transistor 130 turned off, and enter a data retention state. ru.

[0062] The number of times the data can be rewritten is either once or multiple times. This applies to both IDS-driven and normal-driven systems. The data can be rewritten at the same refresh rate. The number of data rewrites is typically: The settings should be adjusted considering the refresh rate of the IDS drive, etc. This is an example where the data has been rewritten three times.

[0063] Furthermore, the polarity of the VData written to pixel 121 last is the same as the data retention in the previous IDS mode. During the retention period, the polarity of the VData held by pixel 121 becomes the opposite polarity to the data. The number of rewrite cycles is adjusted. This suppresses the degradation of the liquid crystal element 131 due to IDS driving. This is possible. For example, if the number of data rewrites is odd, then in the first rewrite... This is the polarity of the VData that pixel 121 held during the data retention period of the previous IDS mode. To do this, you should write Vdata with the opposite polarity to pixel 121.

[0064] As is clear from Figures 3 and 4, still image display in IDS mode is more efficient than in normal mode. This reduces the number of data rewrites, allowing for the display of still images in IDS mode. This reduces screen flicker, thus alleviating eye strain.

[0065] Furthermore, as shown in Figure 4B, in IDS mode, the data retention period is set by the controller 180 The supply of control signals (GSP, GCLK) from there to the gate driver 112 is stopped. Therefore, in the controller 180, after stopping the supply of control signals (GSP, GCLK) Even if control is performed to stop supplying the power supply voltage GVDD to the gate driver 112, Good. Also, during the data retention period, control signals (SSP, SCLK) are sent to the source driver 113. Since the supply of () will also be stopped, similarly, the supply of power voltage to the source driver 113 will also be stopped. It is possible to perform control such as IDS driving. In other words, it is possible to provide eye-friendly displays. This allows us to provide an LCD100 that is both efficient and low power consumption.

[0066] In this specification, "not supplying signals and voltage to wiring, terminals, etc." means "not moving the circuit." Applying a signal or voltage of a different magnitude to wiring, etc., than the predetermined voltage required to perform the operation, This refers to putting wires or other components in an electrically floating state.

[0067] Whether in normal drive or IDS drive mode, the voltage supplied to pixel 121 is used to rewrite the next data. It needs to be held at this voltage. This voltage fluctuation will lead to a decrease in the display quality of the LCD100. In normal operation, data is rewritten at a frequency of 60Hz or 120Hz. Pixel 121 is driven by an AC voltage. On the other hand, IDS drive is used for much of the display period. Since this is a data retention period, it can be considered as a pseudo-DC drive. Therefore, In IDS drive, the conditions that induce residual DC voltage last longer than in normal drive. This can lead to the localization of ionic impurities in the liquid crystal and the accumulation of residual charge at the interface between the liquid crystal layer and the alignment film. The residual DC voltage causes the voltage held by pixel 121 to fluctuate, and as a result, the liquid crystal cell This will cause the transmittance to fluctuate.

[0068] One method to suppress flickering is to reduce the number of data rewrites, such as by using IDS (Intrusion Detection System). On the other hand, if residual DC voltage is present in the liquid crystal cell, the data retention time will be longer. The S-drive mode may result in greater fluctuations in the transmittance of the liquid crystal cells compared to the normal drive mode. As a result, IDS-driven displays make flickering associated with data rewriting more easily visible. This presents a new problem. This embodiment solves this problem.

[0069] In the LCD100 of this embodiment, the common electrode 31 and the common electrode 32 are made to be at the same potential. This suppresses the generation of residual DC voltage due to IDS drive. In other words, common electrode 31 and common By making the potential between the electrodes 32 equal, the substrate 21 applied to the liquid crystal cell during the data retention period ( This reduces the DC voltage component perpendicular to the common electrode 31). This suppresses the accumulation of residual charge, thereby reducing fluctuations in the transmittance of liquid crystal cells during the data retention period.

[0070] By suppressing fluctuations in the transmittance of the liquid crystal cell, flickering during data rewriting is reduced. This makes it possible to display images that are less tiring on the eyes using LCD100. Common electrode 31 and By making the Mon electrode 32 equipotential, the transmittance of the liquid crystal cell during operation in IDS mode changes. The ability to suppress this and reduce flickering will be demonstrated in Example 1.

[0071] Another factor that causes variations in the transmittance of liquid crystal cells is the leakage of charge held within the liquid crystal cells. This is a change in the holding voltage caused by the following. Therefore, the amount of fluctuation of the applied voltage to the liquid crystal element 131 is used To reduce this, transistor 130 is used, which has a very low off-current. It is preferable to use a material with high resistance as the liquid crystal material for the liquid crystal layer 20. This is preferable.

[0072] <Pixel transistors> The off-current of a transistor refers to the current that flows between the source and drain when the transistor is in the off state. Furthermore, the off state of a transistor, in the case of an n-channel transistor, refers to the gate voltage This refers to a state where the voltage is significantly lower than the threshold voltage.

[0073] The off-current of transistor 130 is preferable to be small. Transistor 130 is channel The off-current per 1 μm width should be less than 100 zA. A lower off-current is preferable. Therefore, this standardized off-current is 10 zA / μm or less, or 1 zA / μm or less. It is preferable that the current is 10 yA / μm or less, and more preferably 10 yA / μm or less.

[0074] To make the off-current extremely small in this way, a wider band gap is required than that of Si or Ge. It is preferable to construct the channel of transistor 130 with an oxide semiconductor (3.0 eV or higher). Here, a transistor in which the channel is formed by an oxide semiconductor (OS) is called an OS transistor. It's called Zista.

[0075] It reduces impurities such as water or hydrogen that act as electron donors, and also reduces oxygen deficiency. This process makes oxide semiconductors into type i (intrinsic semiconductors), or brings them as close to type i as possible. This is possible. Here, we will refer to such oxide semiconductors as high-purity oxide semiconductors. By forming a channel with a high-purity oxide semiconductor, the normalized off-current is reduced to a few y A / μm can be reduced to approximately a few zA / μm.

[0076] The oxide semiconductor of the OS transistor contains at least indium (In) or zinc (Zn). It is preferable that it contains [a certain component]. In addition, oxide semiconductors are used to reduce variations in electrical properties. It is preferable that the material contains an element that acts as a stabilizer. Such elements include Ga, Sn, and Hf. Examples include Al, Zr, etc. In-Ga -Zn oxides and In-Sn-Zn oxides are typical. In Embodiment 4, acid Let's explain ion semiconductors in more detail.

[0077] <Liquid crystal materials> In order to suppress the amount of charge leaking through transistor 130, the resistor of transistor 130 It is desirable to increase the resistivity. Therefore, the resistivity of the liquid crystal material in the liquid crystal layer 20 is 1.0 × 10⁻⁶. 1 3 It is preferable that the density be Ωcm or greater, and 1.0 × 10 14 It is preferable that the value be greater than Ωcm. For example, as a liquid crystal material, the resistivity is 1.0 × 10⁻⁶.13 above 1.0×1 Ωcm 0 16 a material of below 1.0×10 Ωcm, preferably 14 above 1.0×10 Ωcm 16 Ω it is advisable to select a material of below 1.0×10 cm. The resistivity of the liquid crystal material is the value measured at 20 °C thereof.

[0078] As described above, according to this embodiment, it is possible to provide a display that is less likely to cause eye fatigue and an LCD that can be powered with low power consumption.

[0079] This embodiment can be appropriately combined with other embodiments and examples.

[0080] (Embodiment 2) In this embodiment, another example of IDS driving will be described.

[0081] <IDS driving> The IDS driving in FIG. 3B rewrites data periodically at a refresh rate lower than normal driving. In the display of a still image, data rewriting can be stopped as long as the displayed image does not change. Therefore, instead of performing data rewriting periodically, a still image can be displayed by a driving method that performs data rewriting when the displayed image changes. Here, this driving method is called the second IDS driving, and the IDS driving in FIG. 3B is called the first IDS driving for the sake of clarity. Hereinafter, the second IDS driving will be described using FIG. 5.

[0082] Here, a case where a still image IM2 is displayed after displaying a still image IM1 as shown in FIG. 5A will be described as an example. As shown in FIG. 5B, the image data of the still image IM1 is written into the pixel 121 by IDS driving. The data writing can be performed in the same manner as the first IDS driving ​​​​ Yes, it's possible. The data can be rewritten once at the same refresh rate (interval Tpd) as normal operation. Alternatively, this is executed multiple times, and data is written to pixel 121. In the example in Figure 5B, the data is written The equipment is changed three times.

[0083] After data writing, data rewriting is stopped and the system enters a data retention state. Second IDS During operation, the data retention state continues until the displayed image changes. Still image IM2 The data rewriting for displaying the image is done in the same way as for the still image IM1. First, the data is written The system is switched three times, after which data rewriting is stopped and the system is returned to a data retention state.

[0084] Furthermore, in order to smoothly switch between still image IM1 and still image IM2, Between the display of IM1 and still image IM2, the normal drive process from still image IM1 to still image IM2 You may display a video to guide the screen transitions.

[0085] LCD100 is designed to perform both first and second IDS drives. Alternatively, one or the other may be performed. The semiconductor device to which LCD100 is applied Depending on the application and the materials that make up pixel 121 (alignment film, liquid crystal, etc.), appropriate IDS driving can be implemented. The goal is to make it possible to do so.

[0086] This embodiment can be appropriately combined with other embodiments and examples.

[0087] (Embodiment 3) In this embodiment, with reference to Figures 6 and 7, a more specific configuration of the liquid crystal panel in FFS mode is described. Let me explain about the formation.

[0088] <<FFSモードのLCパネル> > Figure 6 is a cross-sectional view showing an example of the configuration of the LC panel 210. The LC panel 210 is also an LC Similar to panel 110, the pixel section and drivers (gate drivers and soles) are placed on the same substrate. A driver is formed. Here, the transistors that make up these circuits are OS Let's consider it a transistor. An OS transistor is an n-channel type transistor.

[0089] Figure 6 shows typical pixel sections 211 and terminal sections 224 of the LC panel 210. Also, as the pixel section 211, typically there is a pixel 221 and a common electrode 331 (COM-1 The connection part 222 of ) is shown.

[0090] Figure 7 is a layout diagram showing an example of the configuration of pixel 221. The circuit configuration of pixel 221 is: The circuit configuration is similar to that of pixel 121 in Figure 1A.

[0091] As shown in Figure 6, the space between substrate 301 and substrate 302 is sealed by a sealing member 304. A liquid crystal layer 303 exists. As mentioned above, the liquid crystal layer 303 has a resistivity of 1.0 × 10⁻⁶. 13 It is preferable to use a liquid crystal material with a density of Ωcm or greater.

[0092] As a component to maintain the cell gap of the LC panel 210, spacer 3 is attached to the substrate 302. 83 is formed. As shown in Figure 7, the spacer 383 is formed by the gate line 311 and the socket It exists in the region where line 321 overlaps. Such regions are regions where the orientation of the liquid crystal material is disrupted. and does not contribute to display. By forming the spacer 383 in such a region, pixel 22 The aperture ratio of 1 can be increased. Note that the spacer 383 should be provided on the substrate 301 side. It's also possible.

[0093] The area outside the sealing member 304 of the substrate 301 has a terminal portion 224 which includes a plurality of terminals 324. These terminals 324 are formed. These terminals 324 are connected to the FPC 225 by an anisotropic conductive film 226. Terminal 324 is connected to wiring 312.

[0094] An insulating layer 391 is formed on the surface of the substrate 302, and a light-shielding layer 381 and a carbon A filter layer 382 is formed. The insulating layer 391 is formed of, for example, a silicon nitride film. The light-shielding layer 381 and the color filter layer 382 are formed of, for example, resin. Layer 381 is designed to hide areas that do not contribute to display, such as wiring and electrodes formed on pixel 221. It is provided.

[0095] An insulating layer 392 made of resin or the like is formed covering the light-shielding layer 381 and the color filter layer 382. It is formed on the insulating layer 392, and the common electrode 332 (COM-2) is formed on the insulating layer 392. A spacer 383 is formed on 332. The spacer 383 is formed from a photosensitive resin material. This can be achieved. The alignment film 352 covers the common electrode 332 and the spacer 383. It is formed. The common electrode 332 is similar to the counter electrode of an LCD panel in TN mode. The terminals of the connection part (common contact) formed on the substrate 301 by the anisotropic conductive film are connected. This terminal is connected to terminal 324 of terminal section 224 via wiring 312. Yes, they are.

[0096] Transistor 231 has gate wire 311 (GL), source wire 321 (SL), and electrode 322 and has an oxide semiconductor (OS) layer 340. Electrode 322 has a pixel electrode 330 (PX ) is connected. OS layer 340 has fewer oxide semiconductor layers in which channels are formed. It also has one layer. The insulating layer 371 constitutes the gate insulating layer of transistor 231.

[0097] Furthermore, the driver also has a transistor with a similar element structure to transistor 231. It will be done.

[0098] In the example in Figure 6, transistor 231 is a bottom-gate type transistor, but It may also be a gate-type design. Alternatively, a dual gate-type design with two gate electrodes on either side of the channel may be used. It may also be a dual-gate type. By using a dual-gate type, the current drive characteristics of the OS transistor can be improved. This can improve performance. Furthermore, in the driver, some drivers can be adapted to suit their intended use. By making the lunger a dual-gate type and the others a bottom-gate or top-gate type... It can also be done this way.

[0099] The common electrode 331 (COM-1) is provided facing the pixel electrode 330 via an insulating layer 375. While a pixel electrode 330 is formed for each pixel 221, a common electrode 331 It is formed from a single conductive film and is shared by all pixels 221. (Figures 6 and 7) As shown, the common electrode 331 is connected to the transistor 231 and the pixel electrode 330. An aperture for this purpose is provided for every 221 pixels.

[0100] The electrodes (330-332) are formed from a translucent conductive film. The materials include indium oxide containing tungsten oxide, and indium oxide containing tungsten oxide. Indium oxide containing zinc oxide, titanium oxide containing indium tin oxide, and titanium oxide containing indium tin oxide. Oxides, indium tin oxide (hereinafter referred to as ITO), indium zinc oxide, sulfite oxide Examples include indium tin oxide with added polycarbonate. Films made from these conductive materials are spalled. It can be formed using the taring method.

[0101] As the first layer of wiring and electrodes, gate wires 311 and routing wires 312 are formed. It is there. The first layer of wiring and electrodes (311, 312) is covered, and an insulating layer 371 is formed. .

[0102] An OS layer 340 is formed on the insulating layer 371, and a second layer is formed on the insulating layer 371 and the OS layer 340. The wiring and electrodes (321-324) of the next layer are formed. Wiring 323 connects to the common electrode 331. This is the wiring for connecting to the routing wiring 312. Second layer wiring / electrodes (321-32 Before the formation of (4), an opening is formed in the insulating layer 371 to expose the routed wiring 312. Wiring 323 and terminal 324 are connected to routing wiring 312 in this opening. .

[0103] The second layer of wiring and electrodes (321-324) is covered by an insulating layer 372, 3 made of inorganic material. 73 is formed. The second layer of wiring / electrodes (322-32) is formed on the insulating layers 372 and 373. After forming an opening that exposes 4), an insulating layer 374 made of, for example, a resin material is formed. By using a photosensitive resin material, an insulating layer 3 with openings can be formed without using an etching process. 74 can be formed. The insulating layer 374 has openings for connection as well as sealing member 304 An opening is formed in the region where it is formed.

[0104] A common electrode 331 is formed on the insulating layer 374. The insulating layer covers the common electrode 331. Layer 375 is formed. The insulating layer 375 contains the second layer of wiring and electrodes (322-324). An opening is formed that exposes the pixel electrode 330 on the insulating layer 375. An alignment film 351 is formed covering the pixel electrode 330. The pixel electrode 330 is covered by an insulating layer 375 The region overlapping with the common electrode 331 via this region functions as an auxiliary capacitance for the liquid crystal element.

[0105] Examples of substrates applicable to substrates 301 and 302 include alkali-free glass substrates, and variable glass substrates. Borosilicate glass substrate, aluminoborosilicate glass substrate, ceramic substrate, quartz substrate, Sapphire substrates, metal substrates, stainless steel substrates, plastic substrates, polyethylene terephthalate Examples include ray substrates and polyimide substrates.

[0106] Substrates 301 and 302 are used to fabricate pixels 221, common electrodes 332, etc. It does not have to be a support substrate (such as a glass substrate). After manufacturing pixels 221, etc., the support substrate The flexible substrate may be attached by peeling off the adhesive layer. Typical flexible substrates include Plastic substrates are one example, and the thickness is between 50 μm and 500 μm. Thin glass substrates can also be used. Substrates 301 and 302 can be made into flexible substrates. This makes it possible to bend the LC panel 210.

[0107] The wiring and electrodes of the first and second layers (311, 312, 321-324) are made of a single-layer conductive film. It can be formed by or by two or more conductive films. Such conductive films include aluminum Titanium, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tan Gusten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, Metal films such as beryllium can be used. In addition, alloy films and Compound films, polycrystalline silicon films containing impurity elements such as phosphorus, etc., can be used. .

[0108] The insulating layer (371-375, 391, 392) is a single insulating film or two or more insulating layers. It can be formed as a film. Examples of inorganic insulating films include aluminum oxide and magnesium oxide. , silicon oxide, silicon nitride, silicon nitride, silicon gallium oxide, Germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide Examples include films made of hafnium oxide and tantalum oxide, etc. Furthermore, these insulating films are Formed using sputtering, CVD, MBE, ALD, or PLD methods. This can be done. In addition, as resin films, acrylic resin, polyimide resin, benzocyclobuterol There are organic resin films such as siloxane resins, polyamide resins, and epoxy resins. In this specification, an oxidized nitride refers to a compound in which the oxygen content is greater than the nitrogen content. Nitride oxides are compounds that contain more nitrogen than oxygen.

[0109] This embodiment can be appropriately combined with other embodiments and examples.

[0110] (Embodiment 4) In this embodiment, the oxide semiconductor that forms the channel of the OS transistor will be described. ru.

[0111] Indium oxide, tin oxide, zinc oxide, In- Zn oxides, Sn-Zn oxides, Al-Zn oxides, Zn-Mg oxides, Sn- Mg oxides, In-Mg oxides, In-Ga oxides, In-Ga-Zn oxides ( Also written as IGZO), In-Al-Zn oxide, In-Sn-Zn oxide, Sn -Ga-Zn oxides, Al-Ga-Zn oxides, Sn-Al-Zn oxides, In- Hf-Zn oxides, In-Zr-Zn oxides, In-Ti-Zn oxides, In-S c-Zn oxides, In-Y-Zn oxides, In-La-Zn oxides, In-Ce- Zn oxides, In-Pr-Zn oxides, In-Nd-Zn oxides, In-Sm-Z n-based oxides, In-Eu-Zn oxides, In-Gd-Zn oxides, In-Tb-Zn In-Dy-Zn oxides, In-Ho-Zn oxides, In-Er-Zn oxides Oxides, In-Tm-Zn oxides, In-Yb-Zn oxides, In-Lu-Zn ​​acids In-Sn-Ga-Zn oxides, In-Hf-Ga-Zn oxides, In-Al -Ga-Zn oxides, In-Sn-Al-Zn oxides, In-Sn-Hf-Zn acids In-Hf-Al-Zn oxides can be used.

[0112] The oxide semiconductor of the OS transistor contains at least indium (In) or zinc (Zn). It is preferable that it contains [a certain component]. In addition, oxide semiconductors are used to reduce variations in electrical properties. It is preferable that the material contains an element that acts as a stabilizer. Such elements include Ga, Sn, and Hf. Examples include Al, Zr, etc. In-Ga Typical examples include -Zn oxides and In-Sn-Zn oxides.

[0113] Here, an In-Ga-Zn oxide is an oxide that has In, Ga, and Zn as its main components. This means that the ratio of In, Ga, and Zn is not important. Also, other than In, Ga, and Zn... It may contain metallic elements.

[0114] Also, as the oxide semiconductor, InMO3(ZnO) m (where m > 0) may be used Here, M represents one metal element or a plurality of metal elements selected from Ga, Fe, Mn, and Co, or an element as the above stabilizer. Also, as the oxide semiconductor In2SnO5(ZnO) (where n > 0) may be used n (where n > 0) may be used

[0115] For example, In-Ga-Zn-based oxides with an atomic ratio of In:Ga:Zn = 1:1:1, In:Ga:Zn = 1:3:2, In:Ga: Zn = 3:1:2, or In:Ga:Zn = 2:1:3, or oxides in the vicinity of the composition thereof may be used For example, In-Ga-Zn-based oxides with an atomic ratio of In:Ga:Zn = 1:1:1, In:Ga:Zn = 1:3:2, In:Ga:Zn = 3:1:2, or In:Ga:Zn = 2:1:3, or oxides in the vicinity of the composition thereof may be used

[0116] When a large amount of hydrogen is contained in the oxide semiconductor film, by combining with the oxide semiconductor, a part of the hydrogen becomes a donor and generates electrons as carriers. As a result, the threshold voltage of the OS transistor shifts in the negative direction. Therefore, after forming the oxide semiconductor film, it is preferable to perform a dehydration treatment (dehydrogenation treatment) to remove hydrogen or moisture from the oxide semiconductor film and purify it to contain as few impurities as possible shifts in the negative direction. Therefore, after forming the oxide semiconductor film, it is preferable to perform a dehydration treatment (dehydrogenation treatment) to remove hydrogen or moisture from the oxide semiconductor film and purify it to contain as few impurities as possible shifts in the negative direction. Therefore, after forming the oxide semiconductor film, it is preferable to perform a dehydration treatment (dehydrogenation treatment) to remove hydrogen or moisture from the oxide semiconductor film and purify it to contain as few impurities as possible shifts in the negative direction. Therefore, after forming the oxide semiconductor film, it is preferable to perform a dehydration treatment (dehydrogenation treatment) to remove hydrogen or moisture from the oxide semiconductor film and purify it to contain as few impurities as possible

[0117] Note that, by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, oxygen in the oxide semiconductor film may also be reduced at the same time. Therefore, in order to compensate for the oxygen deficiency increased by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, it is preferable to perform a treatment of adding oxygen to the oxide semiconductor film Note that, by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, oxygen in the oxide semiconductor film may also be reduced at the same time. Therefore, in order to compensate for the oxygen deficiency increased by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, it is preferable to perform a treatment of adding oxygen to the oxide semiconductor film Note that, by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, oxygen in the oxide semiconductor film may also be reduced at the same time. Therefore, in order to compensate for the oxygen deficiency increased by the dehydration treatment (dehydrogenation treatment) of the oxide semiconductor film, it is preferable to perform a treatment of adding oxygen to the oxide semiconductor film Here, the treatment of supplying oxygen to the oxide semiconductor film is sometimes called an oxygen addition treatment or a peroxygenation treatment Here, the treatment of supplying oxygen to the oxide semiconductor film is sometimes called an oxygen addition treatment or a peroxygenation treatment

[0118] Thus, oxide semiconductor films undergo dehydration treatment (dehydrogenation treatment) to remove hydrogen or water. It is removed and the oxygen deficiency is compensated for by oxygenation treatment, resulting in type i (true) or It is possible to create an oxide semiconductor film that is very close to type i and is practically type i (intrinsic). In essence, true means that there are very few donor-derived carriers in the oxide semiconductor film. (Close to zero), carrier density is 1 × 10⁻⁶ 17 / cm 3 Below, 1 x 10 16 / cm 3 below, 1 x 10 15 / cm 3 Below, 1 x 10 14 / cm 3 Below, 1 x 10 13 / cm 3 Below It means to do something.

[0119] The structure of oxide semiconductor films will be described below.

[0120] The oxide semiconductor film can be either a single-crystal oxide semiconductor film or a non-single-crystal oxide semiconductor film. Non-single-crystal oxide semiconductor films include amorphous oxide semiconductor films, microcrystalline oxide semiconductor films, and polycrystalline oxide films. Compound semiconductor film, CAAC-OS (C Axis Aligned Crystallin This refers to films such as (e) Oxide Semiconductor films.

[0121] The oxide semiconductor film of an OS transistor may be a single-layer structure, or, for example, an amorphous oxide semiconductor A multilayer film having two or more of the following: body film, microcrystalline oxide semiconductor film, and CAAC-OS film. That's fine.

[0122] Amorphous oxide semiconductor films have a disordered atomic arrangement within the film and do not contain crystalline components. It is an oxide semiconductor film. One example is an oxide semiconductor film that has an amorphous state, such as quartz. Crystalline oxide semiconductor films do not allow for the identification of crystalline regions in high-resolution TEM images. When structural analysis of crystalline oxide semiconductor films is performed using an XRD device, out-of-pl Analysis using the ANE method does not detect any peaks indicating crystal planes. Furthermore, amorphous oxide semiconductors... When electron diffraction is performed on a body film, a halo pattern is observed. Furthermore, amorphous oxide semiconductors... When nanobeam electron diffraction is performed on a body membrane, no spots are observed, and a halo pattern is not visible. It is measured.

[0123] Microcrystalline oxide semiconductor films have areas where crystalline regions can be confirmed in high-resolution TEM images. It has regions where a clear crystalline portion cannot be observed and regions where a clear crystalline portion cannot be observed. The crystalline portion included is, for example, between 1 nm and 100 nm, or between 1 nm and 10 nm. They are often the size of microcrystals (nc:n) with a size of 1 nm to 10 nm. An oxide semiconductor film having an anocrystal is made nc-OS (nanocrysta It is called an nc-OS film (L-Oxide Semiconductor). For example, in high-resolution TEM images, grain boundaries may not be clearly visible. OS films are oxide semiconductor films with higher orderliness than amorphous oxide semiconductor films. Therefore, nc-OS films have a lower defect level density than amorphous oxide semiconductor films. However, nc- OS films do not exhibit regularity in crystal orientation between different crystalline regions. Therefore, nc-OS films are Compared to CAAC-OS films, the defect level density is higher.

[0124] CAAC-OS film is an oxide semiconductor film having multiple c-axis oriented crystalline regions. The following provides a detailed explanation of the CAAC-OS membrane.

[0125] Transmission Electron Microscope (TEM) A composite analysis image of the CAAC-OS film's bright-field image and diffraction pattern (using a scope) Also known as a high-resolution TEM image, multiple crystalline regions can be identified by observing it. On the other hand, high-resolution TEM images also clearly show the boundaries between crystalline parts, i.e., grain boundaries. Also called boundary.) It is not possible to confirm. Therefore, the CAAC-OS membrane is granular. It can be said that a decrease in electron mobility due to the field is less likely to occur.

[0126] When observing a high-resolution TEM image of the cross-section of the CAAC-OS film from a direction roughly parallel to the sample surface, In the crystalline region, it can be confirmed that the metal atoms are arranged in layers. Each layer of metal atoms is This reflects the unevenness of the surface (also called the surface to be formed) or the upper surface of the CAAC-OS film. It has a specific shape and is arranged parallel to the surface or top surface of the CAAC-OS film to be formed.

[0127] On the other hand, a high-resolution TEM image of the CAAC-OS film plane was observed from a direction roughly perpendicular to the sample surface. Then, it was confirmed that the metal atoms in the crystalline region are arranged in a triangular or hexagonal shape. Yes, it is possible. However, no regularity is observed in the arrangement of metal atoms between different crystalline regions.

[0128] X-ray diffraction (XRD) applied to the CAAC-OS film. When structural analysis is performed using this method, for example, a CAAC-OS film having InGaZnO4 crystals is found. In the out-of-plane analysis, the diffraction angle (2θ) shows a peak near 31°. may appear. This peak is attributed to the (009) plane of the InGaZnO4 crystal Therefore, it can be confirmed that the crystal of the CAAC-OS film has c-axis orientation, and the c-axis is oriented in a direction substantially perpendicular to the formed surface or the upper surface

[0129] The crystal part is formed when the CAAC-OS film is formed or when crystallization treatment such as heat treatment is performed. As described above, the c-axis of the crystal is oriented in a direction parallel to the normal vector of the formed surface or the upper surface of the CAAC-OS film. Therefore, for example, when the shape of the CAAC-OS film is changed by etching or the like, the c-axis of the crystal may not be parallel to the normal vector of the formed surface or the upper surface of the CAAC-OS film In addition, the crystallinity in the CAAC-OS film does not have to be uniform. For example, when the crystal part of the CAAC-OS film is formed by crystal growth from near the upper surface of the CAAC-OS film, the crystallinity in the region near the upper surface may be higher than that in the region near the formed surface. Also, when impurities are added to the CAAC-OS film, the crystallinity in the region where the impurities are added changes, and regions with different crystallinities may be formed partially

[0130] In the out-of-plane analysis of the CAAC-OS film having InGaZnO4 crystals, in addition to the peak at around 2θ = 31°, a peak may also appear at around 2θ = 36°. The peak at around 2θ = 36° is attributed to the (311) plane of the ZnGa2O4 crystal, indicating that a part of the CAAC-OS film having InGaZnO4 crystals contains ZnGa2O4 crystals. The CAAC-OS film has a peak at around 2θ = 31

[0131] ​​​​​​​​​​​​​It is preferable that it shows a peak at [specific condition] and does not show a peak when 2θ is near 36°.

[0132] The CAAC-OS film is an oxide semiconductor film with a low impurity concentration. Impurities are elements other than the main components of the oxide semiconductor film, such as hydrogen, carbon, silicon, transition metal elements, etc. In particular, elements such as silicon, which have a stronger binding force with oxygen than the metal elements constituting the oxide semiconductor film, will disrupt the atomic arrangement of the oxide semiconductor film and reduce the crystallinity by depriving oxygen from the oxide semiconductor film. This becomes a factor for Moreover, heavy metals such as iron and nickel, argon, carbon dioxide, etc., due to their large atomic radius (or molecular radius), when contained inside the oxide semiconductor film, will disrupt the atomic arrangement of the oxide semiconductor film and become a factor for reducing the crystallinity. Incidentally, impurities contained in the oxide semiconductor film may become carrier traps or carrier generation sources.

[0133] In addition, the CAAC-OS film is an oxide semiconductor film with a low defect level density. For example, oxygen deficiencies in the oxide semiconductor film may become carrier traps or may become carrier generation sources by capturing hydrogen.

[0134] A low impurity concentration and a low defect level density (few oxygen deficiencies) are called high purity intrinsic or substantially high purity intrinsic. An oxide semiconductor film with high purity intrinsic or substantially high purity intrinsic has few carrier generation sources, so the carrier density can be lowered. Therefore, a transistor using the oxide semiconductor film is less likely to have an electrical characteristic where the threshold voltage becomes negative ( also called normally-on).) Also, an oxide semiconductor film with high purity intrinsic or substantially high purity intrinsic has few carrier traps. Therefore, for the oxide semiconductor Transistors using body membranes exhibit less variation in electrical characteristics and are highly reliable. Furthermore, the charge trapped in the carrier trap of the oxide semiconductor film requires time to be released. It can remain dormant for a long time, behaving almost like a fixed charge. Therefore, the impurity concentration Transistors using oxide semiconductor films with high defect level density have unstable electrical properties. It can happen.

[0135] Transistors using CAAC-OS film exhibit changes in electrical properties due to irradiation with visible light and ultraviolet light. Its value is small. Therefore, this transistor is highly reliable.

[0136] In the description of crystal structures, "parallel" means that two straight lines are at an angle of -10° or more and 10° or less. This refers to a state where objects are arranged at an angle. Therefore, it also includes cases where the angle is between -5° and 5°. "Perpendicular" refers to a state where two lines are positioned at an angle of 80° to 100°. Therefore, this also includes cases where the angle is between 85° and 95°.

[0137] CAAC-OS films are produced, for example, by sputtering using a polycrystalline metal oxide target. The film is formed by this process. When ions collide with the target, the crystalline region contained in the target A plate-shaped or pellet-shaped splice whose region cleaves from the ab plane and has a surface parallel to the ab plane. They may detach as taring particles. In this case, the flat or pellet-shaped spalls may detach. The uttering particles reach the substrate while maintaining their crystalline state, thereby forming the CAAC-OS film. It can be used to form a thin film.

[0138] Furthermore, it is preferable to apply the following conditions for forming the CAAC-OS film.

[0139] By reducing the incorporation of impurities during film formation, it is possible to suppress the breakdown of the crystal state due to impurities. For example, the impurity concentration (such as hydrogen, water, carbon dioxide, and nitrogen) present in the processing chamber may be reduced. Also, the impurity concentration in the film-forming gas may be reduced. Specifically, a film-forming gas having a dew point of -80°C or lower, preferably -100°C or lower, is used.

[0140] Further, by increasing the substrate heating temperature during film formation, when flat or pellet-shaped sputtering particles reach the substrate, migration occurs on the substrate, and the flat surface of the sputtering particles adheres to the substrate. For example, the substrate heating temperature may be 100°C or higher and 740°C or lower, preferably 200°C or higher and 500°C or lower.

[0141] Also, by increasing the oxygen ratio in the film-forming gas and optimizing the power, plasma damage during film formation can be reduced. For example, the ratio of oxygen in the film-forming gas may be 30% by volume or higher, preferably 100% by volume.

[0142] This embodiment can be appropriately combined with other embodiments and examples.

[0143] (Embodiment 5) In this embodiment, an electronic device in which an LCD is used for a display unit will be described. By applying Embodiments 1 to 4, it is possible to provide an electronic device that enables an eye-friendly display and has low power consumption.

[0144] (Example Configuration of Information Processing System) FIG. 8 is a block diagram showing an example of the configuration of an information processing system including an LCD in a display unit. The information processing system 500 includes an arithmetic unit 510, an LCD 520, an input device 530, and a memory It is equipped with a memory device 540.

[0145] The arithmetic unit 510 has the function of controlling the entire information processing system 500. , processor 511, storage device 512, input / output (I / O) interface 513, and It has a bus 514. The bus 514 connects the processor 511, the storage device 512 and I The I / O interfaces 513 are connected to each other. The arithmetic unit 510 is an I / O interface. Communication with the LCD 520, input device 530, and storage device 540 via face 513. For example, the input signal from input device 530 is sent to I / O interface 513 and The data is transmitted to the processor 511 and storage device 512 via bus 514.

[0146] The storage device 512 contains data (including programs) necessary for processing by the processor 511, Data input via I / O interface 513 is stored.

[0147] The processor 511 executes a program to operate the information processing system 500. The decoder 511 analyzes, for example, the input signal from the input device 530, and the storage device 540 The LCD 5 reads information, writes data to storage devices 512 and 540, This process involves generating a signal to output to 20, and other related operations.

[0148] The LCD520 is provided as an output device and constitutes the display unit of the information processing system 500. It accomplishes. In addition, the information processing system 500 has, as an output device, a display device, as well as a speed It may also be equipped with other output devices such as a printer.

[0149] The input device 530 is a device for inputting data to the calculation unit 510. The user is an input device By operating the device 530, the information processing system 500 can be operated. The device 530 can use various human interfaces and has multiple input devices. The input device 530 can be provided in the information processing system 500. It has a touch panel, keyboard, and control buttons. These are operated directly by the user. This allows for the operation of the information processing system 500. In addition, voice, eye gaze, and gestures are also supported. An input device incorporating a device for detecting things like ya is provided, and the information processing system 50 You may also manipulate 0. For example, a microphone, camera (imaging system), etc. It may be established.

[0150] The storage device 540 stores various types of data, such as programs and image signals. The storage capacity of 40 is greater than that of storage device 512. As for storage device 540, flash memory These include Mori, DRAM, and hard disk drives (HDDs). Also, storage device 540 is It should be provided as needed.

[0151] The information processing system 500 has all its components, including the arithmetic unit 510, housed in a single enclosure. It may be a device of a certain form, or some devices may connect to the arithmetic unit 510 by wire or wireless connection. It may also be a device in a continuous form. For example, as the former form, a notebook personal computer Computers (PCs), tablet PCs (devices), e-book readers (devices), and smartphones Examples include smartphones, etc. The latter form includes desktop PCs, keyboards, and mice. And there is a set of monitors.

[0152] The LCD520 of the information processing system 500 can display images using both normal drive and IDS drive. Furthermore, the IDS drive may consist of either the first or second IDS drive, or both. For example, the preferred method of an information processing system 500 that displays still images using a second IDS drive (see Figure 5) Suitable uses include reading ebooks and viewing photos taken with a digital camera. In other words, the same image remains for a relatively long time, and the entire screen can be displayed depending on the user's actions. By switching this, when using the information processing system 500, the second IDS drive provides a quieter experience. It is preferable to display a still image.

[0153] Refer to Figures 9A-9F to see some specific examples of the information processing system 500. Figure 9A —Figure 9F is an external view showing an example of an information processing system in which the display unit is composed of an LCD.

[0154] The portable game console 700 shown in Figure 9A consists of a casing 701, a casing 702, a display unit 703, and a display unit 704, microphone 705, speaker 706, control button 707, and stylus It has 708 etc. Display unit 703 and / or display unit 704 have an input device 530 A touch panel may be provided.

[0155] The video camera 710 shown in Figure 9B consists of a housing 711, a housing 712, a display unit 713, and operation buttons. It has a 714, a lens 715, and a connecting part 716, etc. Operation button 714 and lens The Z 715 is located in the housing 711, and the display unit 713 is located in the housing 712. Furthermore, housing 711 and housing 712 are connected by a connecting part 716, and housing 711 The angle between the housing 712 and the display unit 713 is movable by the connecting part 716. The switching is performed according to the angle between housing 711 and housing 712 at the connection part 716. This configuration is also possible. A touch panel may be provided on the display unit 713.

[0156] The tablet terminal 720 shown in Figure 9C includes a display unit 722 built into the housing 721, Operation button 723, speaker 724, and other microphones and stereo headphones (not shown in the diagram) It is equipped with a jack, memory card slot, camera, USB connector and other external connection ports. The display unit 722 is equipped with a touch panel as an input device 530.

[0157] The foldable tablet terminal 730 shown in Figure 9D consists of a housing 731, a housing 732, and a front It has a display unit 733, a display unit 734, a connection unit 735, and an operation button 736, etc. Display unit 733 and the display unit 734 are composed of LCD520. Display units 733 and 734 A touch panel is provided as an input device 530.

[0158] The smartphone 740 shown in Figure 9E consists of a housing 741, operation buttons 742, and a microphone. It includes 743, a display unit 744, a speaker 745, and a camera lens 746, etc. Since the camera lens 746 is located on the same plane as part 744, video conferencing is possible. The display unit 744 is equipped with a touch panel as an input device 530.

[0159] The notebook PC 750 shown in Figure 9F consists of a casing 751, a display unit 752, a keyboard 753, and It also has a pointing device 754, etc. An LCD 520 is used for the display unit 752. It is possible to also provide a touch panel as an input device 530 on the display unit 752.

[0160] This embodiment can be appropriately combined with other embodiments and examples.

Example

[0161] <LC panel specifications> An FFS-mode LC panel of Embodiment 3 (see FIGS. 6 and 7) was fabricated, and its operation was verified. The specifications of the prototype LC panel (hereinafter referred to as the test panel) are shown in Table 1. In actual verification, a backlight module etc. was incorporated into the test panel and it was operated as a transmissive LCD.

[0162]

Table 1

[0163] The two substrates of the test panel are glass substrates. The gate driver and the source driver are integrated on the element substrate together with the pixel portion. The fabricated transistor is an OS transistor, and its oxide semiconductor layer is formed of an In-Ga-Zn-based oxide film having a CAAC structure.

[0164] <<Evaluation of test panel>> The common voltage VCOM (voltage of the common electrode COM-1) of the test panel was set to 0V. Also, the voltage VCOM2 of the common electrode COM-2 was also set to 0V, and the test panel was operated in a state where the common electrode COM-1 and the common electrode COM-2 were at the same potential, and objective and subjective evaluations were performed regarding flicker.

[0165] Also, as Comparative Example 1, the test panel was operated in a state where there was a potential difference between the common electrode COM-1 and the common electrode COM-2, and the same evaluation was performed. In Comparative Example 1, VCOM2 = -1 .7V. Also, VCOM was set to a constant voltage in the range of -1.8 to -1.7V. The value of VC OM differed for each test panel and was determined so that intermediate tone display would be optimal. ​​​

[0166] <Measurement of Transmittance> As an objective evaluation, the transmittance of the test panel was measured. The test panel was driven by IDS. A gray still image was displayed on the screen. The refresh rate is 1Hz, meaning every second. The data was rewritten. Also, in IDS drive, in one screen refresh The data was written three times (see Figures 3B and 4B). This was also reflected in the subjective evaluation below. It is the same.

[0167] In both Example 1 and Comparative Example 1, the transmittance was measured immediately after IDS activation and after 6 hours. The results are shown in Figure 10. Figure 10A is a graph showing the variation in transmittance in Example 1, and Figure 10B This is the graph for Comparative Example 1.

[0168] As shown in Figure 10B, in Comparative Example 1, the test panel after 6 hours had a data retention period. The transparency level cannot be maintained immediately after data rewriting, and the transparency level has decreased by more than 1%. On the other hand, Figure As shown in 10A, in Example 1, even when the IDS was driven continuously for 6 hours, the transmittance did not change. The motion is about the same as immediately after activation.

[0169] From Figure 10, the variation in the transmittance of the LCD in FFS mode is due to the common electrode COM-1 and the common electrode It was found that the potential difference between electrodes COM-2 was the cause. Two common electrodes (COM-1, By setting COM-2) to equipotential, fluctuations in transmittance are suppressed even when IDS is driven for a long time. This was confirmed. Since IDS drive is a pseudo DC drive, two common electrodes (CO If there is a potential difference between M-1 and COM-2, and the IDS is driven continuously for several hours, the liquid crystal will... It is thought that charge segregation occurred within the cell, which caused the fluctuation in transmittance.

[0170] In the typical VT (voltage-transmittance) characteristics of LCDs, halftones (gray) are lower in intensity. The variation in transmittance with respect to voltage is greater than in low-tone (black display) or high-gradation (white display). Figure 1 In Example 1, the fluctuation in transmittance of gray display due to IDS driving is suppressed in 0A. This has been shown to be the case. In other words, the two common electrodes (COM-1, COM-2) are at the same potential. By doing so, even with IDS drive, natural images expressed in midtones can be displayed in high quality. I realized it would be Noh.

[0171] <Subjective evaluation regarding flickering> By adjusting the potential difference between common electrode COM-1 and common electrode COM-2, the potential difference can be perceived by the human eye. Subjective evaluation confirmed that the flickering could be reduced. Figures 11A and 11B show Example 1. The subjective evaluation results for Comparative Example 1 are shown below.

[0172] The subjective evaluation involved preparing two test panels, one of which was driven under normal conditions (refresh rate 60Hz). One was operated at z) and the other at IDS drive (refresh rate 1Hz). By concealing the code and having subjects compare the screens of two test panels, We had them evaluate the quality of each display.

[0173] To avoid giving subjects preconceived notions about the evaluation objective, items other than "flicker" were used as indicators. We established evaluation criteria related to the position. The evaluation criteria include "flicker," "color tone," and "resolution." These are "reflection on the screen," "unevenness," and "readability of text." Regarding these, please select "very good," "somewhat good," "neither good nor bad," "somewhat bad," and "not good." Participants were asked to rate the experience on a 5-point scale, from "always bad" to "always bad".

[0174] The evaluation includes 13 nature illustrations, such as animals and landscapes, and 7 texts (alphabetical and hiragana). Twenty still images were used. These still images were displayed in a slideshow format at 5-second intervals. The results were displayed on the test panel. In both Example 1 and Comparative Example 1, the two test panels were subjected to 6 hours of testing. The system was kept running continuously. During this time, the subjects made evaluations as needed, and therefore the test panel was evaluated by the subjects. The elapsed time from the start of the operation to the evaluation time differs. Table 2 shows the breakdown of subjects. (a) is (b) is Example 1, and (b) is Comparative Example 1.

[0175] [Table 2]

[0176] As shown in Figure 11A, in Example 1, the evaluation of flicker was performed for normal drive and IDS drive. The difference in evaluation results was small. Out of 86 people, 3 felt more flicker with IDS-driven, and 6 felt more flicker. The response indicated that the constant drive mode caused more flickering. Example 1 provided an overall evaluation. The results showed that IDS drive resulted in less noticeable flickering than normal drive.

[0177] As shown in Figure 11B, the evaluation results regarding flicker show differences depending on the display mode. Example 1 was larger than Example 1. Out of 84 people, 11 people found the IDS-driven method to be more effective. The results showed that three people felt more flickering with the normal operation mode. In section 1, the overall evaluation results indicated that IDS drive resulted in more noticeable flickering than normal drive. Furthermore, the longer the test continued, the more noticeable the flickering became with the IDS-driven system. Many respondents gave the answer "yes." The subjective evaluation results for Comparative Example 1 are shown in Figure 10B, which shows the change in transparency over time. This aligns with the objective assessment of an increase in the fluctuation of the excess rate.

[0178] As described above, the two common electrodes (COM-1, COM-2) are set to the same potential. Therefore, even when using IDS drive, which is a pseudo-DC drive, for a long period of time, fluctuations in transmittance can be suppressed. It was confirmed that this is possible. In addition, it was possible to reduce the flickering caused by data rewriting when the IDS is running. It was confirmed that this is possible.

[0179] Furthermore, the subjective evaluation results in Figure 11 show that in Example 1, the display quality differed between IDS drive and normal drive. Although there was no significant difference in the evaluation results, in Comparative Example 1, the IDS drive performed better than the normal drive. This indicates that the quality of the display deteriorates. This is due to the two common electrodes (COM-1, C By making the potentials of OM-2 equal, even LCDs that have been driven in IDS mode for a long time can be driven normally. This indicates that it is possible to maintain the same display quality as during normal operation. [Explanation of Symbols]

[0180] 20 liquid crystal layers 21 circuit boards 22 circuit boards 23 Sealing member 24 Terminal section 25 FPC 30 Pixel Electrodes 31 Common Electrode 32 Common Electrodes 40 Insulating layer 100 Liquid crystal display (LCD) 110 LCD (LC) Panel 111 pixel section 112 Gate Driver 113 Source Driver 121 pixels 122 Gate Line 123 Source Line 130 transistors 131 Liquid crystal elements 132 Capacitive elements 180 Controllers 190 Power supply

Claims

[Claim 1] Transistors and A first conductive film having a region that functions as a pixel electrode, A second conductive film having a region that functions as a common electrode, A third conductive film having a region that functions as wiring, The first insulating layer, The second insulating layer, A third insulating layer, It has a fourth insulating layer, The aforementioned transistor is A fourth conductive film having a region that functions as a gate electrode, A fifth insulating layer having a region on the fourth conductive film that functions as a gate insulating layer, The oxide semiconductor layer on the fifth insulating layer, A fifth conductive film having a region on the oxide semiconductor layer that functions as either a source electrode or a drain electrode, The oxide semiconductor layer comprises a sixth conductive film having a region that functions as either a source electrode or a drain electrode, The first insulating layer has silicon oxide and includes a region in contact with the upper surface of the fifth conductive film and a region in contact with the upper surface of the sixth conductive film. The second insulating layer has silicon nitride and a region in contact with the upper surface of the first insulating layer. The third insulating layer has an organic material and a region in contact with the upper surface of the second insulating layer. The fourth insulating layer has silicon nitride and includes a region in contact with the upper surface of the second insulating layer and a region in contact with the upper surface of the third insulating layer. The first conductive film has a region in contact with the upper surface of the fourth insulating layer, The first conductive film has a region in contact with the side surface of the first insulating layer and a region in contact with the side surface of the second insulating layer. The oxide semiconductor layer has a region that overlaps with the fourth conductive film and a region that does not overlap with the fourth conductive film. The first conductive film has a region that overlaps with the second conductive film, with the fourth insulating layer in between. The second conductive film is light-transmitting, The second conductive film has a region in contact with the third conductive film, The second conductive film has an opening, The second conductive film has a region that overlaps with the fifth conductive film. The first conductive film has a region that contacts the upper surface of the sixth conductive film through the opening, In a plan view, the fifth conductive film is A first region having a first width and positioned along the edge of the first conductive film, A display device comprising: a second region positioned at a location intersecting the fourth conductive film and having a second width smaller than the first width.

Images