JP2007293153A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption and to simplify a manufacturing step in a semitransmission type LCD (liquid crystal display). <P>SOLUTION: In the semitransmission type LCD, a second transparent pixel electrode 14B in a transmission region and reflection pixel electrodes 14A and 15 in a reflection region are electrically separated to make it possible to apply separate video signals to both electrodes. Cell gaps in the transmission region and the reflection region are made equal to each other, that is, the distance between the second transparent pixel electrode 14B and a transparent common electrode 21 and the distance between the reflection pixel electrodes 14A and 15 and the transparent common electrode 21 are made equal to each other and an amplitude of the video signal applied to the reflection pixel electrodes 14A and 15 is made to be narrower than the amplitude of the video signal applied to the second transparent pixel electrode 14B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transflective liquid crystal display device having a transmissive region and a reflective region.

  A liquid crystal display device (hereinafter referred to as an LCD) has a feature of being thin and has low power consumption, and is currently widely used as a monitor for a computer or a portable information device such as a mobile phone. There are transmissive LCDs and reflective LCDs. In the transmissive LCD, a transparent electrode is used as a pixel electrode for applying a voltage to the liquid crystal, a backlight light source is disposed behind the LCD panel, and the amount of light transmitted through the backlight is controlled by the LCD panel, thereby darkening the surroundings. Even bright display is possible. However, since the backlight light source is always turned on for display, power consumption is large, and there is a characteristic that sufficient contrast cannot be secured in an environment with strong external light such as outdoors in the daytime.

  On the other hand, in a reflective LCD, external light such as sunlight or room light is used as a light source, and the external light incident on the LCD panel is reflected by a reflective electrode formed on a substrate on the observation surface side. Then, display is performed by controlling the amount of light emitted from the LCD panel of light incident on the liquid crystal and reflected by the reflective electrode for each pixel. Since this reflective LCD uses external light as a light source, it cannot be displayed in an environment without external light. However, unlike a transmissive LCD, it has low power consumption and no external light. There is a characteristic that a sufficient contrast can be obtained.

  In recent years, transflective LCDs have been developed as LCDs that have both a transmissive function and a reflective function, and are easy to see in both bright and dark environments. 14A is a plan view of one pixel of a conventional active matrix transflective LCD having a thin film transistor (TFT) for each pixel, and FIG. 14B is a plan view of FIG. 14A. It is sectional drawing along XX.

  In this transflective LCD, a first insulating substrate 100 having a TFT 101 and a second insulating substrate 200 having a color filter (not shown) are bonded together, and a liquid crystal 300 is sealed between these substrates. Yes. A TFT 101 is formed on the surface of the first insulating substrate 100, and a transparent pixel electrode 103 is connected to the TFT 101 through a contact hole CH 1 opened in the planarization insulating film 102. The pixel electrode 103 extends to the reflective region and the transmissive region. A reflective plate 104 is formed below the pixel electrode 103 in the reflective region.

  On the other hand, a protrusion 201 is formed on the second insulating substrate 200 so as to face the pixel electrode 103 in the reflective region. The protrusion 201 covers the protrusion 201 and is transparent on the surface of the second insulating substrate 200. A common electrode 202 is formed. As a result, the cell gap of the reflective region is reduced to about ½ of the cell gap in the transmissive region, and the optical path lengths of the reflective region and the transmissive region are aligned, so that the optical characteristics of the reflective region and the transmissive region are optimized. . In addition, a light shielding region is formed by a black matrix 203 on the outer periphery of the pixel.

When a transflective LCD is used in the transmissive mode, display can be performed by controlling the amount of light transmitted through the backlight by a video signal applied to the pixel electrode 103. In addition, when the above-described transflective LCD is used in the reflection mode, display is performed by controlling the amount of external light that is reflected by the reflection plate 104 by the video signal applied to the pixel electrode 103. Can do. The transflective LCD is described in Patent Document 1.
JP-A-2005-141110 JP 2002-31909 A JP-A-2005-49402

  As described above, in one pixel of the conventional transflective LCD, the transmissive region and the reflective region are driven by the same video signal applied to one pixel electrode 103. When the reflection mode is used, the power consumption is reduced due to the backlight light source being extinguished, but the capacitive load of the pixel electrode 103 viewed from the driving circuit for driving the pixel does not change, so the power consumption of the driving circuit is reduced. However, compared with a reflective LCD with a built-in memory circuit (see Patent Documents 2 and 3), there is a problem that power consumption is large.

  Further, in the conventional transflective LCD, it is necessary to form the protrusion 201 in order to optimize the optical characteristics of the transmissive region and the reflective region by aligning the optical path lengths of the reflective region and the transmissive region. It also had the problem of becoming complicated.

  In the liquid crystal display device of the present invention, in the transflective LCD, the transparent pixel electrode in the transmissive region and the reflective pixel electrode in the reflective region are electrically separated. This makes it possible to apply separate video signals to both electrodes, especially in the reflective mode, since there is no need to charge the transmissive pixel electrode, and the capacitive load seen from the drive circuit is reduced. It becomes possible to reduce electric power.

  In addition to the above configuration, the cell gap between the transmissive region and the reflective region is made the same, and the amplitude of the video signal applied to the reflective pixel electrode is made smaller than the amplitude of the video signal applied to the transparent pixel electrode. As a result, it is possible to optimize the optical characteristics of the transmission mode and the reflection mode without forming a protrusion, simplify the manufacturing process, and reduce the amplitude of the video signal. Furthermore, power consumption can be reduced.

  According to the liquid crystal display device of the present invention, in a transflective LCD, power consumption can be reduced and the manufacturing process can be simplified.

First Embodiment A first embodiment of the present invention will be described. FIG. 1A is a schematic plan view of one pixel of an active matrix transflective LCD, and FIG. 1B is a schematic cross-sectional view taken along line YY in FIG.

  In this transflective LCD, a first insulating substrate 10 provided with a first TFT 11 and a second TFT 12 and a second insulating substrate 20 provided with a color filter (not shown) are bonded together. A liquid crystal 30 is sealed between them. A first TFT 11 is formed on the surface of the first insulating substrate 10, and a first transparent pixel electrode 14 A made of ITO is connected to the first TFT 11 through a contact hole CH 2 opened in the planarization insulating film 13. ing. The first transparent pixel electrode 14A is disposed only in the reflection region. Under the first transparent pixel electrode 14A on the planarization insulating film 13, a reflector 15 made of aluminum is formed in contact therewith. A reflective pixel electrode is formed by the first transparent pixel electrode 14 </ b> A and the reflective plate 15.

  A second TFT 12 is formed on the surface of the first insulating substrate 10, and a second transparent pixel electrode 14 B made of ITO is formed on the second TFT 12 through a contact hole CH 3 opened in the planarization insulating film 13. Is connected. The second transparent pixel electrode 14B is disposed only in the transmissive region, and is electrically separated from the first transparent pixel electrode 14A and the reflecting plate 15. In FIG. 1B, the second TFT 12 seems to be formed in the transmissive region. However, it is preferable that the second TFT 12 is actually formed under the reflecting plate 15 to suppress a decrease in the aperture ratio of the transmissive region.

  The surface of the second insulating substrate 20 is flat, and the transparent common electrode 21 is formed on the surface. A light blocking area is formed by a black matrix 22 on the outer periphery of the pixel. As described above, according to the present invention, in the transflective LCD, the second transparent pixel electrode 14B in the transmissive region and the reflective pixel electrodes 14A and 15 in the reflective region are electrically separated. A video signal can be applied, and in the case of the reflection mode in particular, it is not necessary to charge the second transparent pixel electrode 14B, so that the capacitive load as seen from the drive circuit is reduced, thereby reducing power consumption. It becomes possible.

  Further, since the surface of the second insulating substrate 20 is flat, the cell gap between the transmissive region and the reflective region is the same, that is, the distance between the second transparent pixel electrode 14B and the transparent common electrode 21, and the reflective pixel. The distance between the electrodes 14A, 15 and the transparent common electrode 21 is the same, and the amplitude of the video signal applied to the reflective pixel electrodes 14A, 15 is determined from the amplitude of the video signal applied to the second transparent pixel electrode 14B. It is set small. That is, as shown in FIG. 2, the reflectivity vs. voltage curve of the present invention shifts to a lower voltage side than the conventional reflectivity vs. voltage curve (the cell gap in the reflection region is ½ of the gap in the transmission region). . Therefore, the black voltage in the reflection mode is set lower than the black voltage in the transmission mode.

  As a result, the optical characteristics of the transmission mode and the reflection mode can be optimized without forming protrusions as in the conventional case, the manufacturing process can be simplified, and the amplitude of the video signal can be reduced. As a result, power consumption can be further reduced.

  Next, a layout of pixels on the first insulating substrate 10 and an equivalent circuit will be described in detail. FIG. 3 is a layout diagram of pixels, and shows two pixels. FIG. 4 is an equivalent circuit diagram of one pixel. As shown in FIG. 3, the first TFT 11 and the second TFT 12 are disposed under the reflective pixel electrodes 14A and 15 in the reflective region. The drain of the first TFT 11 is connected to the first data line DL1 extending in the vertical direction at the left end of the pixel, and the first gate line GL1 extending in the horizontal direction crosses the channel of the first TFT 11.

  The source of the first TFT 11 is connected to the first transparent pixel electrode 14A through the contact hole CH2. The source of the first TFT 11 also serves as the first lower electrode 16 of the first storage capacitor SC1, and the storage capacitor line SCL serving as the upper electrode overlies the first lower electrode 16 via an insulating film. Wrapping.

  On the other hand, the drain of the second TFT 12 is connected to the second data line DL2 that extends in the vertical direction at the right end of the pixel, and the second gate line GL2 that extends in the horizontal direction on the channel of the second TFT 12 traverses. Yes. The source of the second TFT 12 is connected to the second transparent pixel electrode 14B through the contact hole CH3.

  The source of the second TFT 12 also serves as the second lower electrode 17 of the second storage capacitor SC2, and the storage capacitor line SCL serving as the upper electrode overlies the second lower electrode 17 via an insulating film. Wrapping. The source of the first TFT 11 and the source of the second TFT 12 are separated.

As shown in FIG. 4, the first storage capacitor SC <b> 1 is connected to the first TFT 11, and the second storage capacitor SC <b> 2 is connected to the second TFT 12. A common potential Vcom is applied to the transparent common electrode 21. The operation of the transflective LCD is performed independently for the reflective area and the transmissive area. That is, in the reflection mode, the first TFT 11 is turned on in response to the first gate signal G1 from the first gate line GL1, and the video signal from the first data line DL1 is reflected through the first TFT 11. It is applied to the pixel electrodes 14A and 15. At this time, the video signal is held by the first holding capacitor SC1.

  On the other hand, in the transmissive mode, the second TFT 12 is turned on in response to the second gate signal G2 from the second gate line GL2, and the video signal from the second data line DL2 passes through the second TFT 12 and passes through the second TFT 12. The second transmissive pixel electrode 14B is applied. At this time, the video signal is held by the second holding capacitor SC2.

Second Embodiment In this embodiment, the first data line DL1 and the second data line DL2 of the first embodiment are shared. As shown in the pixel layout of FIG. 5 and the equivalent circuit diagram of one pixel of FIG. 6, one data line DL extends in the vertical direction corresponding to one pixel. A first TFT 11 and a second TFT 12 are connected to the data line DL.

  As shown in FIG. 7, a first vertical drive circuit 41 that outputs a first gate signal G1 to the first gate line GL1 is arranged on the LCD panel 40 along the right side. A second vertical drive circuit 42 that outputs a second gate signal G2 is disposed along the second gate line GL2. A horizontal drive circuit 43 that outputs a video signal to the data line DL is disposed along the lower side of the LCD panel 40.

  In this transflective LCD, video signals are written in a time division manner in the reflective area and the transmissive area. That is, as shown in the timing chart of FIG. 8, the first gate signal G1 becomes high in the first half of one horizontal period (1H), and the first TFT 11 is turned on. While the first TFT 11 is on, a video signal is applied from the data line DL to the reflective pixel electrodes 14A and 15 through the first TFT 11. At this time, when the transflective LCD has RGB pixels, the first horizontal switch, the second horizontal switch, and the third horizontal switch respectively connected to the plurality of data lines DL are respectively the first horizontal switch. In response to the horizontal switch signal (R), the second horizontal switch signal (G), and the third horizontal switch signal (B), the signals are sequentially turned on, and the RGB video signals are transmitted from the data lines DL in synchronization therewith. Are written in the corresponding RGB pixels.

  In the second half of one horizontal period (1H), the first gate signal G1 goes low, the first TFT 11 turns off, the second gate signal G2 goes high, and the second TFT 12 turns on.

  While the second TFT 12 is on, a video signal is applied from the data line DL to the second transmissive electrode 14B through the second TFT 12. At this time, when the transflective LCD has RGB pixels, similarly, the first horizontal switch, the second horizontal switch, and the third horizontal switch are respectively connected to the first horizontal switch signal (R). In response to the second horizontal switch signal (G) and the third horizontal switch signal (B), the signals are sequentially turned on, and the RGB video signals are written from the data lines DL to the corresponding RGB pixels in synchronization therewith. It is.

  In a transflective LCD in which the first data line DL1 and the second data line DL2 are not shared, the horizontal drive circuit 43 is provided on the lower side and the upper side of the LCD panel 40 corresponding to each data line. It may be divided and arranged.

Third Embodiment Next, a third embodiment of the present invention will be described. This embodiment is based on the first and second embodiments, and the transmissive region is the same as the first and second embodiments, but a memory circuit is built in the reflective region, and the memory circuit The display is performed based on the video signal stored in. Thereby, the power consumption in the reflection mode can be further reduced to several tens of μW.

  FIG. 9 is an equivalent circuit diagram of one pixel of a transflective LCD incorporating a memory circuit. The memory circuit MC includes TFTs 11A and 11B, and a first inverter INV1 and a second inverter INV2 that are feedback-connected so as to form a video signal holding loop. The memory circuit MC is the same as a 1-bit SRAM cell. A first data line DL11 for reflection is connected to the drain of the TFT 11A, and a second data line DL12 for reflection is connected to the TFT 11B.

  A first gate line GL1 is commonly connected to the gates of the TFTs 11A and 11B. A video signal is supplied to the first data line DL11, and an inverted video signal is supplied to the second data line DL12. A first inverter INV1 and a second inverter INV2 forming a holding loop are connected to the sources of the TFTs 11A and 11B.

  The output of the memory circuit MC is applied to the control terminals of the first and second transfer gates TG1 and TG2, and the first and second transfer gates TG1 and TG2 are 1-bit video signals held in the memory circuit MC. Switching selectively according to ("1" or "0").

  A first voltage Von that turns on the liquid crystal 30 is input to the first transfer gate TG1, and a second voltage Voff that turns off the liquid crystal 30 is input to the second transfer gate TG2. Accordingly, when the video signal “1” is output from the memory circuit MC, the first transfer gate TG1 is turned on, and the second voltage Voff is applied to the reflective pixel electrodes 14A and 15, thereby the liquid crystal 30 is Turn off (in this case, for example, black display).

  On the other hand, when the video signal “0” is output from the memory circuit MC, the second transfer gate TG2 is turned on, and the first voltage Von is applied to the reflective pixel electrodes 14A and 15, whereby the liquid crystal 30 is Turn on (in this case, for example, white display).

Thus, in the reflection mode, the display is performed based on the video signal written and held in the memory circuit MC, so that the first vertical drive circuit 41, the second vertical drive circuit 42, the horizontal drive circuit 43, etc. Since the operation of the peripheral circuit can be stopped, the power consumption of the entire LCD panel can be reduced to several tens of μW.

  The first vertical drive circuit 41 (for reflection) and the second vertical drive circuit 42 (for transmission) have the same arrangement as in FIG. 7, but the horizontal drive circuit 43 corresponds to each data line. The LCD panel 40 is preferably divided into a lower side and an upper side. In the transmissive mode, it is preferable to store a video signal for displaying black in the reflective area in the memory circuit MC so that the reflective area functions as a black matrix.

  The transmissive region is the same as the circuit of FIG. 4, and a third data line DL13 is provided as a transmissive data line.

Fourth Embodiment In this embodiment, the first data line DL11 and the third data line DL13 of the third embodiment are shared. As shown in the equivalent circuit diagram of one pixel in FIG. 10, these data lines are shared by one data line DL14. Further, it is preferable that a third inverter INV3 for inverting the video signal from the data line DL14 is provided in the pixel, and the inverted video signal is supplied to the TFT 11B. As a result, the second data line DL12 can be omitted. In this case, the writing of the video signal to the reflection area and the transmission area is performed by time division driving as shown in FIG.

Fifth Embodiment Next, a fifth embodiment of the present invention will be described. According to the third and fourth embodiments, since the memory circuit MC is provided in the reflection region of one pixel, the number of wirings and the number of TFT elements in one pixel is very large. In general, the optical characteristics required for the reflective LCD are lower than that of the transmissive LCD, and it is often required only to increase the reflectance. Therefore, only the reflective area is displayed in monocolor (monochrome). Transflective LCDs have also been put into practical use. Therefore, by combining the two, high optical characteristics can be obtained in the transmissive mode, mono-color display is performed in the reflective mode, the reflectivity is high, and the memory circuit MC is built in, so that the power consumption is further reduced. Type LCD can be realized.

  FIG. 11 is an equivalent circuit diagram of such a transflective LCD. One monochromatic reflective pixel GSM is arranged adjacent to three transmissive pixels corresponding to the three primary colors of RGB. Each of these pixels is sometimes called a subpixel.

  The configuration of the reflective pixel GSM is the same as the configuration of the reflective region in FIG. 9, and includes a memory circuit MC and first and second transfer gates TG1 and TG2. Reflecting data lines DL21 and DL22 are connected to the TFTs 11A and 11B, respectively.

  The transmissive pixels GS (R), GS (G), and GS (B) each have a TFT 12 and a storage capacitor SC, and each have independent transparent pixel electrodes 14B (R), 14B (G), and 14B (B). Yes. These transparent pixel electrodes 14B (R), 14B (G), 14B (B) and the reflective pixel electrodes 14A, 15 of the reflective pixel GSM are electrically separated. The TFT 12 of the transmission pixel GS (R) has a transmission data line DL (R), and the TFT 12 of the transmission pixel GS (G) has a transmission data line DL (G) and a transmission pixel GS (B). A transmission data line DL (B) is connected to the TFT 12.

  FIG. 12 is a plan view showing the layout of transparent pixels, reflective pixels, and signal wiring. The Vdd wiring is a power supply wiring, and the Vss wiring is a ground wiring, and is connected to the first and second inverters INV1 and INV2 of the memory circuit MC.

  Further, by sharing two of the transmission data lines DL (R), DL (G), DL (B) with the reflection data lines DL21, DL22, the transmission type pixels GS (R), GS (G ), The aperture ratio of GS (B) can be improved.

Sixth Embodiment In the fifth embodiment, one mono color corresponding to three transmissive pixels GS (R), GS (G), and GS (B) corresponding to the three primary colors of RGB. In this embodiment, as shown in FIG. 13, the reflective pixels GSM are arranged in correspondence with 12 transmissive pixels GS (R), GS (G), GS (B). Monochromatic reflective pixels GSM are arranged.

  When the definition is increased, it is practically difficult to dispose a memory circuit built-in pixel having a large number of wirings and elements in one pixel or for every three transmissive pixels. Therefore, by reducing the resolution of the reflection mode, which requires a lower level of display quality than the transmission mode, the power consumption of the reflection mode can be reduced accordingly.

  As a specific layout example, as shown in FIG. 13, three transmissive pixels GS (R), GS (G), and GS (B) corresponding to the three primary colors of RGB are set as one picture element. Arranged in two columns, one reflective pixel GSM is arranged between the first and second rows. The horizontal width of the reflective pixel GSM corresponds to six transmissive pixels. By taking advantage of the large area of the reflective pixel GSM as described above, the memory circuit MC in the reflective pixel GSM can be increased to 2 or more bits instead of 1 bit to increase the display gradation. Become.

  In the fifth and sixth embodiments, the case where one reflective pixel is arranged adjacent to three transmissive pixels corresponding to the three primary colors of RGB has been described. One reflective pixel may be arranged adjacent to four or more transmissive pixels corresponding to four or more colors including colors such as C (cyan).

1 is a schematic plan view and a schematic cross-sectional view of one pixel of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the transmittance | permeability vs. voltage curve and the reflectance vs. voltage curve. 1 is a plan view of one pixel of a liquid crystal display device according to a first embodiment of the present invention. 1 is an equivalent circuit diagram of one pixel of a liquid crystal display device according to a first embodiment of the present invention. It is a top view of one pixel of the liquid crystal display device by the 2nd Embodiment of this invention. FIG. 6 is an equivalent circuit diagram of one pixel of a liquid crystal display device according to a second embodiment of the present invention. It is a top view of the LCD panel by the 2nd Embodiment of this invention. FIG. 6 is a timing chart of a liquid crystal display device according to a second embodiment of the present invention. FIG. 7 is an equivalent circuit diagram of one pixel of a liquid crystal display device according to a third embodiment of the present invention. It is an equivalent circuit schematic of one pixel of the liquid crystal display device by the 4th Embodiment of this invention. It is an equivalent circuit schematic of the liquid crystal display device by the 5th Embodiment of this invention. It is a layout figure of the liquid crystal display device by the 5th Embodiment of this invention. It is a layout figure of the liquid crystal display device by the 6th Embodiment of this invention. It is the schematic plan view and schematic sectional drawing of 1 pixel of the liquid crystal display device of a prior art example.

Explanation of symbols

10, 100 First insulating substrate 11 First TFT
11A, 11B, 101 TFT 12 Second TFT
13, 102 Planarization insulating film 14A First transparent pixel electrode (reflection pixel electrode)
14B Second transparent pixel electrode 14B (R), 14B (G), 14B (B) Transparent pixel electrode 15 Reflective film (reflective pixel electrode) 16 First lower electrode 17 Second lower electrode 20, 200 Second Insulating substrate 21 Transparent common electrode 22,203 Black matrix
30, 300 Liquid crystal 40 LCD panel 41 First vertical drive circuit 42 Second vertical drive circuit 43 Horizontal drive circuit 103 Pixel electrode 104 Reflector 201 Protrusion 202 Common electrodes CH1 to CH3 Contact holes DL1, DL11 First data line DL2, DL12 Second data line DL13 Third data line DL14 Data lines DL21, DL22 Reflection data lines DL (R), DL (G), DL (G) Transmission data line G1 First gate signal G2 First 2 gate signal GL1 first gate line GL2 second gate line GS (R), GS (G), GS (B) transmissive pixel INV1 first inverter INV2 second inverter INV3 third inverter MC memory Circuit SC holding capacitor SC1 first holding capacitor SC2 second holding capacitor Capacity SCL storage capacitor line TG1 first transfer gate TG2 second transfer gate

Claims (13)

A first insulating substrate;
A transparent pixel electrode disposed on the first insulating substrate;
A reflective pixel electrode disposed on the first insulating substrate and electrically separated from the transparent pixel electrode;
A second insulating substrate disposed opposite the first insulating substrate;
A transparent common electrode disposed on the second insulating substrate;
A liquid crystal display device comprising: a liquid crystal sealed between the first insulating substrate and the second insulating substrate. A first TFT that is turned on in response to a first gate signal and applies a video signal from a first data line to the transparent pixel electrode;
The liquid crystal display device according to claim 1, further comprising: a second TFT that is turned on in response to a second gate signal and applies a video signal from a second data line to the reflective pixel electrode. . The first and second data lines are common, and a control circuit for controlling the first and second gate signals is provided so that the first and second TFTs are turned on in different periods. The liquid crystal display device according to claim 2. The distance between the transparent pixel electrode and the transparent common electrode is the same as the distance between the reflective pixel electrode and the transparent common electrode, and the amplitude of the video signal applied to the reflective pixel electrode is the transparent 2. The liquid crystal display device according to claim 1, wherein the amplitude of the video signal applied to the pixel electrode is smaller. 4. The liquid crystal display device according to claim 2, wherein the first and second TFTs are disposed below the reflective pixel electrode. Below the reflective pixel electrode, a first storage capacitor for holding data connected to the first TFT and a second storage capacitor for holding data connected to the second TFT are arranged. The liquid crystal display device according to claim 5. A first insulating substrate;
A transparent pixel electrode disposed on the first insulating substrate;
A reflective pixel electrode disposed on the first insulating substrate and electrically separated from the transparent pixel electrode;
A memory circuit disposed on the first insulating substrate for storing a video signal;
A drive signal selection circuit that selectively applies a first drive signal or a second drive signal to the reflective pixel electrode according to a video signal stored in the memory circuit;
A second insulating substrate disposed opposite the first insulating substrate;
A transparent common electrode disposed on the second insulating substrate;
A liquid crystal display device comprising: a liquid crystal sealed between the first insulating substrate and the second insulating substrate. A first TFT that is turned on in response to a first gate signal and applies a video signal from a first data line to the transparent pixel electrode;
The liquid crystal display device according to claim 7, further comprising: a second TFT that is turned on in response to a second gate signal and writes a video signal from a second data line to the memory circuit. The first and second data lines are common, and a control circuit for controlling the first and second gate signals is provided so that the first and second TFTs are turned on in different periods. The liquid crystal display device according to claim 8. A liquid crystal display device comprising one monochromatic reflective pixel corresponding to a plurality of transmissive pixels,
The transmissive pixel includes a transparent pixel electrode,
The reflective pixel includes a reflective pixel electrode separated from the transparent pixel electrode, a memory circuit for storing a video signal, and a first drive signal or a second signal depending on the video signal stored in the memory circuit. A liquid crystal display device comprising: a drive signal selection circuit that selectively applies a drive signal to the reflective pixel electrode. The liquid crystal display device according to claim 10, wherein one reflective pixel is disposed adjacent to a plurality of transmissive pixels corresponding to a plurality of colors. The plurality of transmissive pixels corresponding to a plurality of colors are arranged in 2 rows × 2 columns, and one reflective pixel is arranged between the first row and the second row. The liquid crystal display device described. The liquid crystal display device according to claim 12, wherein the memory circuit of the reflective pixel has a storage capacity of 2 bits or more.

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