JP4175428B2 - Liquid crystal display device and portable terminal - Google Patents

Description

The present invention relates to a portable terminal beauty Oyo liquid crystal display device, and more particularly to a portable terminal equipped with the active matrix type liquid crystal display device and those of the liquid crystal display device of the precharge scheme as an output display unit.

  2. Description of the Related Art In recent years, a mobile terminal represented by a mobile phone, which has been rapidly spreading, uses a liquid crystal display device as an output display unit (see, for example, Patent Document 1). Since these mobile terminals are extremely frequently used outdoors, the mobile terminals are required to operate reliably in a wide temperature range. The operation compensation temperature range is set to a temperature that has a particularly low lower limit (for example, about −30 ° C.).

JP 2001-290460 A

  On the other hand, the liquid crystal display device has a problem that the contrast at the low temperature is lowered due to the deterioration of the frequency characteristic of the liquid crystal dielectric constant at the low temperature. That is, in the equivalent circuit of the unit pixel shown in FIG. 3, it appears that the resistance component R of the liquid crystal material has increased at a low temperature, and the pixel electrode of the liquid crystal capacitance Clc is not fully charged during the determined period. Since the target signal voltage cannot be written, the contrast is lowered.

  The problem of a decrease in contrast at low temperatures is particularly noticeable in the case of a liquid crystal display device in which the system voltage is lowered for the purpose of reducing power consumption and the voltage applied to the liquid crystal capacitance Clc is lowered. In order to solve this problem, when the voltage applied to the liquid crystal capacitor Clc is increased, the output circuit of the data driver that drives the data line needs a large current capability, and thus the current consumption of the output circuit increases. At the same time, there arises a new problem that the circuit area increases.

  Also, for example, in a color liquid crystal display device, the number of outputs of the data driver can be reduced by sampling three color signals corresponding to the three colors arranged side by side onto the data lines in the display area in time series within one horizontal period. A so-called selector drive system that can be reduced to 1/3 is known. In this selector-driven liquid crystal display device, since the three color signals are sampled in order within one horizontal period, the time for writing to the pixel is shortened especially for the third color in the sampling order, and as described above when the temperature is low. It appears prominently for the reason, and the target signal voltage cannot be written to the pixel, so that there is a problem that the contrast of the third color in the sampling order is greatly reduced and chromaticity shift (chromaticity deterioration) occurs.

The present invention has been made in view of the above problems, and its object is to improve the contrast characteristics at low temperature while suppressing power consumption, and to reduce the chromaticity shift at low temperature in the selector driving system. it is to provide a portable terminal equipped with a liquid crystal display device and those of the liquid crystal display device as an output display unit.

In order to achieve the above object, according to the present invention, before writing a display signal to each data line in the display area, the gradation level when no voltage is applied to the liquid crystal is used as a precharge signal level for each data line. On the other hand, the precharge operation is stopped in the 1F inversion driving mode in which the polarity of the display signal written to each of the pixels is inverted in one field period (1F) cycle . Here, the gradation level when no voltage is applied to the liquid crystal is a white level in a normal white type liquid crystal display device and a black level in a normal black type liquid crystal display device.

  In the liquid crystal display device, the resistance component of the liquid crystal material increases at a low temperature, so that the frequency characteristic of the liquid crystal dielectric constant deteriorates, and the target signal voltage cannot be written to the pixel electrode of the liquid crystal capacitor within a predetermined period. Therefore, by writing the gradation level when no voltage is applied to the liquid crystal as the precharge signal level prior to writing the signal to the pixel, it is only necessary to start driving the data line from the gradation signal level. The time required for writing the signal voltage can be shortened. Therefore, even if the frequency characteristic of the liquid crystal dielectric constant deteriorates at low temperatures, the target signal voltage can be written in the period determined for the pixel electrode of the liquid crystal capacitor, so that the contrast at low temperatures increases.

According to the present invention, when the precharge operation is performed prior to writing the display signal to the pixel, the gradation level when no voltage is applied to the liquid crystal is used as the precharge signal, thereby reducing the resistance of the liquid crystal material at a low temperature. Even if the component increases, the target signal voltage can be reliably written to the pixel, so that the contrast characteristics at low temperatures can be improved without increasing the power consumption. In the 1F inversion drive mode, the power consumption can be reduced by stopping the precharge operation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration of an active matrix liquid crystal display device according to an embodiment of the present invention. Here, for the sake of simplicity, the case of a pixel array of 4 rows and 6 columns is shown as an example.

  In FIG. 1, each of gate lines 11-1 to 11-4 and each of data lines 12-1 to 12-6 are wired in a matrix. Pixels 13 are arranged in a matrix at the intersections of these wirings to form a display area 14. The pixel 13 includes a pixel transistor TFT (Thin Film Transistor) having a gate electrode connected to the gate lines 11-1 to 11-4 and a source electrode (or drain electrode) connected to the data lines 12-1 to 12-6. The liquid crystal cell LC has a pixel electrode connected to the drain electrode (or source electrode) of the pixel transistor TFT, and a storage capacitor Cs connected in parallel to the liquid crystal cell LC.

  In this pixel structure, the counter electrode of the liquid crystal cell LC is connected in common between the pixels. A common voltage VCOM is commonly applied to the counter electrode of the liquid crystal cell LC. In the case of performing IH (H is a horizontal period) inversion driving or 1F (F is a period corresponding to one field) inversion driving, which will be described later, the display signal written to the data lines 12-1 to 12-6 uses this common voltage VCOM. Polarity inversion is performed as a reference.

  Further, in the liquid crystal display device according to the present embodiment, the VCOM inversion driving for inverting the polarity of the common voltage VCOM in the 1H cycle or 1F cycle is used in combination. By using this VCOM inversion driving together with IH inversion driving or 1F inversion driving, half of the operation power supply voltage of the output circuit of the data driver, which will be described later, is not required, so the voltage of the data driver can be reduced.

  As the common voltage VCOM, an AC voltage having substantially the same amplitude is used when the amplitude of the display signal is 0 to 3.3 V, for example. Actually, when a signal is written from the data lines 12-1 to 12-6 to the pixel electrode of the liquid crystal cell LC through the pixel transistor TFT, a voltage drop occurs in the pixel transistor TFT due to a parasitic capacitance or the like. As the voltage VCOM, an AC voltage having an amplitude shifted by the voltage drop is used. With this VCOM inversion driving, the polarity of the electrode on the counter electrode side of the holding capacitor Cs is inverted in synchronization with the common voltage VCOM, and a voltage having the same amplitude as the common voltage VCOM is connected to the Cs line (counter electrode side wiring) 15. Given through.

  On the left side of the display area 14, for example, a scan driver 16 that is vertical driving means is arranged. The scan driver 16 performs a process of sequentially driving the gate lines 11-1 to 11-4 for each field period to select the pixels 13 in units of rows. For example, a data driver 17 is arranged above the display area 14, a selector switch 18 is arranged between the data driver 17 and the display area 14, and a precharge switch 19 is arranged below the display area 17, for example. Has been.

  The data driver 17 repeatedly outputs display signals of the three primary colors of B (blue), G (green), and R (red) for every three columns of the pixel array of the display area 14 in the order of B, G, and R, for example. This repetition cycle is usually a 1H cycle. That is, the B, G, and R color signals are output in time series within the 1H period. At this time, the polarities of these color signals are inverted every 1H with respect to the common voltage VCOM. Thereby, 1H inversion driving is realized in which the polarity of the display signal applied to each pixel 12 is inverted every 1H.

  When the energy saving (power saving) mode is set, the data driver 17 outputs B, G, and R color signals at a repetition period of one field period (1F). At this time, the polarities of these color signals are inverted every 1F with respect to the common voltage VCOM. Thereby, 1F inversion driving is realized in which the polarity of the display signal applied to each pixel 12 is inverted every 1F. Here, in the case of 1F inversion driving, the polarity inversion of the color signal is extremely less than in the case of 1H inversion driving, and power consumption in the output circuit of the data driver 17 can be suppressed. Can be reduced (energy saving).

  As described above, the display signals Sig1, Sig2,..., Which are time-series signals of the B, G, R color signals, are supplied from the data driver 17 to a plurality of adjacent ones in the same row in the pixel array of the display area 14, for example, 3 It is output in units of pixels and supplied to the selector switch 18. The selector switch 18 realizes a selector driving system that samples display signals of pixels corresponding to three colors arranged horizontally in the display area 14 to the data lines 12-1 to 12-6 in time series within one horizontal period. It is a switch to do.

  Specifically, the selector switch 18 includes a set of three analog switches SWsB-1, SWsG-1, and SWsR-1 for the display signal Sig1, and three analog switches SWsB-2 for the display signal Sig2. SWsG-2, SWsR-2 are combined, and so on. The input terminals of the analog switches are connected in common to each set, and the output terminals are connected to one ends of the data lines 12-1 to 12-6 in the display area 14, respectively.

  In the selector switch 18, the analog switches of the same color are turned on / off at the timing of select pulses SEL-B, SEL-G, and SEL-R given in time series from the outside. Specifically, the analog switches SWsB-1 and SWsB-2 are at the timing of the B select pulse SEL-B, the analog switches SWsG-1 and SWsG-2 are at the timing of the G select pulse SEL-G, and the analog switch SWsR. -1 and SWsR-2 perform on / off operations at the timing of the R select pulse SEL-R, respectively.

  By using this selector switch 18, the display signals Sig1 and Sig2 are sampled in time series within one horizontal period, and the display signals corresponding to the pixels arranged in the horizontal direction, that is, the pixels in row units, are collected in one horizontal period. By adopting a selector driving system that supplies data lines 12-1 to 12-6 in the display area 14, the number of outputs of the data driver 17 is set to the number of data lines 12-1 to 12-6 in the display area 14. There is an advantage that can be reduced to 1/3.

  The precharge switch 19 precharges writing the precharge signal Psig to the data lines 12-1 to 12-6 immediately before the display signals Sig1 and Sig2 are written to the data lines 12-1 to 12-6 by sampling by the selector switch 18. This is a switch for realizing the method.

  Specifically, the precharge switch 19 includes analog switches SWp-1 to SWp-6 corresponding to the number of columns in the pixel array of the display area 12. One end of each of the analog switches SWp-1 to SWp-6 is connected in common to serve as an input end of the precharge signal Psig, and the other end is each of the data lines 12-1 to 12-6 in the display area 14. Each is connected to the other end. The analog switches SWp-1 to SWp-6 perform an on / off operation at the timing of the precharge pulse PCG given from the outside prior to the first select pulse SEL-B.

  Here, in the analog dot sequential type liquid crystal display device, when the precharge is not performed, that is, prior to the writing of the display signals Sig1 and Sig2, the precharge signal Psig is not written to the data lines 12-1 to 12-6 in advance. Considering the case, when the 1H inversion driving described above is performed, if a charge / discharge current due to signal writing to the data lines 12-1 to 12-6 is large, noise such as vertical stripes appears on the display screen. On the other hand, the precharge signal Psig is written in advance to the data lines 12-1 to 12-6. Generally, in the normally white type, the gray or black level is written as the precharge signal Psig, so that signal writing is performed. Since charging / discharging current can be suppressed, noise can be reduced.

  On the other hand, if precharge using a signal similar to this is performed to improve low temperature characteristics, power consumption increases. In order to suppress an increase in power consumption due to this precharge, in the liquid crystal display device according to the present embodiment, as the precharge signal Psig, the gradation level when no voltage is applied to the liquid crystal, that is, a normally white liquid crystal The display device uses a white level, and the normally black liquid crystal display device uses a black level. Specifically, taking the case of a normally white liquid crystal display device as an example, the common voltage VCOM corresponds to the gradation level when no voltage is applied to the liquid crystal, that is, the white level, so the liquid crystal according to the present embodiment. In the display device, the common voltage VCOM is used as the precharge signal Psig.

  In this way, in the precharge type active matrix liquid crystal display device, the target display supplied from the data driver 17 using the gradation level when no voltage is applied to the liquid crystal, for example, the common voltage VCOM, as the precharge signal Psig. Just before the signals Sig1, Sig2,... Are sampled by the selector switch 18, the precharge switch 19 is turned on / off at the timing of the precharge pulse PCG, and the common voltage VCOM is preliminarily applied to the data lines 12-1 to 12-6. Then, the selector switch 18 is sequentially turned on / off at the timing of select pulses SEL-B, SEL-G, and SEL-R, and a target signal is sent to each pixel 13 through the data lines 12-1 to 12-6. By performing the write operation, the following effects can be obtained. Can.

  For example, in a normally white liquid crystal display device, a case where, for example, a black signal is written to the second G pixel when sampling in the order of BGR will be described with reference to the timing chart of FIG. Due to the VCOM inversion drive, the common voltage VCOM is in reverse phase with the output signal Sig of the data driver 17.

  Here, in the case of no precharge, the data line potential Sig-G of G before writing is affected by the opposite-phase common voltage VCOM so that the original potential level as shown by the dotted line in FIG. Less than. Thereby, in the equivalent circuit of the unit pixel shown in FIG. 3, the pixel electrode potential Vp of the liquid crystal capacitance Clc is similarly lowered (dotted line in FIG. 2). Here, when the resistance component R of the liquid crystal material becomes large at a low temperature, the target signal voltage cannot be sufficiently written to the pixel within a predetermined period, so that a problem of a decrease in contrast occurs.

  On the other hand, prior to the writing of the black signal, the precharge pulse PCG (active at low level) G is preliminarily applied to the data line as a precharge signal Psig, a gradation signal when no voltage is applied to the liquid crystal, in this example common By precharging the voltage VCOM, the G data line potential Sig-G becomes an intermediate level as shown by a solid line in FIG. 2, and accordingly, the pixel electrode potential Vp of the liquid crystal capacitor Clc also becomes an intermediate level. When the selector switch SWsG is turned on by the G selector pulse SEL-G, the signal Sig-G rises from the intermediate level. Therefore, even if the resistance component R of the liquid crystal material increases at low temperatures, the pixel electrode of the liquid crystal capacitance Clc can be sufficiently charged within a predetermined period, and the target signal voltage can be reliably written to the pixels. The contrast of the hour increases.

  In addition, when there is no precharge, as indicated by the dotted line in FIG. 2, the pixel electrode potential Vp of the liquid crystal capacitor Clc cannot reach the target signal level within a predetermined period, and sampling is performed in the order of BGR. In the case of the last R, however, this becomes conspicuous and the contrast of R is greatly reduced at low temperatures. However, by performing the above-described precharge and setting the pixel electrode potential Vp of the liquid crystal capacitance Clc to an intermediate level, the liquid crystal Since the pixel electrode potential Vp of the capacitor Clc can sufficiently reach the target signal level within the determined period, the chromaticity shift at a low temperature can be greatly reduced.

  In the above embodiment, the case where the common voltage VCOM applied to the counter electrode of the liquid crystal cell LC is used as the gradation level when no voltage is applied to the liquid crystal has been described as an example. However, the embodiment is limited to the common voltage VCOM. For example, since the voltage applied to the Cs line side electrode of the storage capacitor Cs is almost the same level as the common voltage VCOM, the voltage is used as the gradation level when no voltage is applied to the liquid crystal, that is, the precharge signal Psig. Is also possible.

  Here, when the voltage applied to the Cs line side electrode of the storage capacitor Cs is used as the precharge signal Psig, a Cs driver (not shown) for driving the Cs line 15 is connected to a precharge switch (precharge). Driver) 19 can be used also. At this time, since the Cs driver can be generally composed of a CMOS inverter, almost no direct current flows through the circuit. On the other hand, by performing the precharge operation, in the output circuit (analog circuit) of the data driver 17, half of the necessary charge / discharge charge amount is assigned to the precharge driver (Cs driver). Current consumption can be reduced. Therefore, it can greatly contribute to the reduction in power consumption of the entire liquid crystal display device.

  In the above embodiment, the case where the present invention is applied to a liquid crystal display device of the VCOM inversion driving method has been described as an example. However, the present invention is not limited to the VCOM inversion driving, and the common voltage VCOM is fixed to a predetermined DC voltage. This is also applicable to the case. At this time, the voltage applied to the Cs line side electrode of the storage capacitor Cs (the potential of the Cs line 15) is also fixed to the common voltage VCOM or another DC level.

  Further, in the above-described embodiment, the case where the present invention is applied to a selector driving type liquid crystal display device has been described as an example. However, the present invention is a driving method other than the selector driving method, for example, a display corresponding to a row unit pixel in the display area 14. A line sequential driving method in which signals are sampled collectively within one horizontal period and supplied to each of the data lines, and display signals corresponding to pixels in units of rows in the display area 14 are sampled sequentially within one horizontal period. Thus, the present invention can be similarly applied to the dot sequential driving method in which each data line is supplied. In particular, when applied to the dot sequential driving method, the signal writing period for the pixel at the end of sampling is shortened, so that an effect of reducing shading at a low temperature can be obtained.

  FIG. 4 is a block diagram showing a specific configuration example of the liquid crystal display device according to the above-described embodiment. In FIG. 4, the same parts as those in FIG.

  In this configuration example, the data driver 17 is made of an IC and is mounted on the glass substrate 21 by COG (Chip On Glass). The arrangement relationship of the data driver 17, the selector switch 18, and the precharge switch 19 with respect to the display area 14 on the glass substrate 21 is the same as in the case of FIG. However, the scan driver 16 is omitted here. Setting signals PRM1, 2, and 3 for setting a method of outputting a control signal PRS (described later) are input to the data driver 17 from the outside via the flexible printed circuit board 22.

  The data driver 17 outputs a control signal PRS that defines whether or not the precharge switch 19 is activated during the horizontal blanking period in the non-display area period in the 1F inversion driving mode or the partial mode. The data driver 17 further outputs a gradation signal when no voltage is applied to the liquid crystal as the precharge signal Psig. In this embodiment, the common voltage VCOM is used as the gradation signal when no voltage is applied to the liquid crystal.

  The output terminal of the control signal PRS of the data driver 17, the PRS terminal of the test pad 23, and the level shift circuit 24 formed on the glass substrate 21 are electrically connected by a wiring 25. The control signal PRS output from the data driver 17 is supplied to the level shift circuit 24 through the wiring 25.

  The level shift circuit 24 converts the level of the control signal PRS from a first voltage level, eg, 3.3V, to a second voltage level higher than that, eg, 7.0V (level shift). The level-converted control signal PRS is supplied to a pulse generation circuit 26 that generates a precharge pulse PCG, and controls whether or not to generate the precharge pulse PCG. The precharge pulse PCG generated by the pulse generation circuit 26 is supplied to the precharge switch 19.

  The output terminal of the precharge signal Psig of the data driver 17, the Tsig terminal of the test pad 27, and the precharge switch 19 are electrically connected by a wiring 28. The precharge signal Psig output from the data driver 17 is supplied to the precharge switch 19 through the wiring 28.

  Further, the TMS terminal of the flexible printed circuit board 22, the TMS terminal of the test pad 27, and the precharge switch 19 are electrically connected by a wiring 29. A control signal TMS is input from the outside to the TMS terminal of the flexible printed circuit board 22 and further supplied to the precharge switch 19 through the wiring 29. The control signal TMS is a signal for selecting whether the precharge switch 19 is set to a test mode or a precharge drive mode.

  In the liquid crystal display device according to the specific example of the above configuration, when the precharge switch 19 is set to the test mode by the control signal TMS input through the TMS terminal of the flexible printed circuit board 22, the test signal is output from the Tsig terminal of the test pad 27. By inputting the signal Tsig and supplying the test signal Tsig to the precharge switch 19 through the wiring 28, a panel display test when the driver IC (data driver 17) is not mounted can be performed. At this time, the precharge switch 19 functions as a test switch.

  In the state where the data driver 17 is mounted, the precharge switch 19 is activated during the horizontal blanking period by the control signal PRS output from the data driver 17, and as described in the previous embodiment, the data Before the driver 17 writes a signal to each data line in the display area 14, a precharge operation for writing the precharge signal Psig by the precharge switch 19 is performed.

  Further, the control signal PRS output from the data driver 17 causes the precharge switch 19 to be inactive during the horizontal blanking period in the 1F driving inversion mode or in the non-display region period in the partial mode, so that the 1F inversion driving is performed. The precharge operation is stopped in the non-display area period in the mode or the partial mode. Thereby, the power consumption of the present liquid crystal display device can be further reduced.

  In other words, in the 1F inversion driving mode, the signal writing time to the pixel can be made longer than in the 1H inversion driving mode, so that the problem of a decrease in contrast at a low temperature hardly occurs. Therefore, by stopping the precharge operation, the power consumption can be reduced by the amount of power required to drive the precharge switch 19.

  In the non-display area period in the partial mode, for example, in the case of a normal white liquid crystal display device, white is displayed in the non-display area, and a white signal is written in the data line. This is equivalent to writing the common voltage VCOM to the data line as the precharge signal Psig, and means that it is not necessary to perform the precharge operation. Therefore, similarly to the above case, power consumption can be reduced by stopping the precharge operation.

  FIG. 5 is an external view showing a schematic configuration of a mobile terminal device, for example, a mobile phone, according to the present invention.

  The mobile phone according to the present example has a configuration in which a speaker unit 42, an output display unit 43, an operation unit 44, and a microphone unit 45 are arranged in this order from the upper side on the front side of the device casing 41. In the mobile phone having such a configuration, a liquid crystal display device is used for the output display unit 43, and the liquid crystal display device according to the above-described embodiment or a specific example thereof is used as the liquid crystal display device.

  The output display unit 43 in this type of mobile phone has a partial display mode (partial display mode) for displaying an image only in a partial area in the vertical direction of the screen as a display function in a standby mode or the like. As an example, in the standby mode, as shown in FIG. 6, information such as the remaining battery level, reception sensitivity or time is always displayed in a partial area of the screen. In the remaining non-display area, white display is performed in the normally white liquid crystal display device and black display is performed in the normally black liquid crystal display device.

  As described above, in the mobile phone equipped with the output display unit 43, the liquid crystal display device according to the above-described embodiment or its modification is used as the output display unit 43, and the precharge is performed prior to the writing of the display signal to the pixel. By operating, even in the case of a mobile phone with a wide operating compensation temperature range, it is possible to improve contrast characteristics, especially at low temperatures, so that even higher temperature images can be displayed. Become.

  Further, when performing partial display in the standby mode or the like, the power consumption of the output display unit 43 can be reduced by the amount consumed by the precharge driver by stopping the precharge operation in the non-display area. There is also an advantage that the use time can be extended by one charge of the battery as the main power source.

  Here, the case where the present invention is applied to a mobile phone has been described as an example. However, the present invention is not limited to this, and can be applied to all mobile terminals such as PDA (Personal Digital Assistants).

1 is a circuit diagram illustrating a configuration of an active matrix liquid crystal display device according to an embodiment of the present invention. 5 is a timing chart for explaining an operation when a black signal is written to a G pixel when sampling in the order of BGR in a normally white liquid crystal display device. It is an equivalent circuit diagram of a unit pixel. It is a block diagram which shows the specific structural example of the liquid crystal display device which concerns on one Embodiment of this invention. It is an external view which shows the outline of a structure of the mobile telephone which concerns on this invention. It is a figure which shows the example of a display of an output display part.

Explanation of symbols

  11-1 to 11-4: gate lines, 12-1 to 12-6 ... data lines, 13 ... pixels, 14 ... display area, 16 ... scan driver, 17 ... data driver, 18 ... selector switch, 19 ... precharge Switch, Cs ... Holding capacitor, LC ... Liquid crystal cell, TFT ... Pixel transistor

Claims (10)

Signal writing means for writing a display signal to each of data lines in a display area in which pixels are arranged in a matrix;
Before writing the display signal to each data line by the signal writing means, the gradation level when no voltage is applied to the liquid crystal is written to each of the data lines as a precharge signal level, and the display is written to each of the pixels. Precharge means for stopping the precharge operation in the 1F inversion driving mode in which the polarity of the signal is inverted in one field period (1F) cycle ;
A liquid crystal display device, wherein the precharge signal level is white level when normal white and black level when normal black. The signal writing means samples a plurality of pixels arranged adjacent to each other in the same row in the display area as a unit, and sequentially samples display signals corresponding to the plurality of pixels in one horizontal period in time series. Supply to each of the data lines,
The liquid crystal display device according to claim 1, wherein the precharge unit writes the precharge signal to each of the data lines before the signal writing unit performs sampling. The signal writing means sequentially samples a display signal corresponding to a pixel in a row in the display area within one horizontal period and supplies the sampled signal to each of the data lines.
The liquid crystal display device according to claim 1, wherein the precharge unit writes the precharge signal to each of the data lines before the signal writing unit performs sampling. The signal writing means samples the display signals corresponding to the pixels in row units in the display area and supplies them to each of the data lines in one horizontal period.
The liquid crystal display device according to claim 1, wherein the precharge unit writes the precharge signal to each of the data lines before the signal writing unit performs sampling. The liquid crystal display device according to claim 1, wherein the gradation signal is a common voltage applied to a counter electrode of a liquid crystal cell constituting the pixel. The liquid crystal display device according to claim 1, wherein the gradation signal is a voltage applied to the other end of a storage capacitor having one end connected to the pixel electrode of the liquid crystal cell constituting the pixel and the other end connected to the counter electrode. The liquid crystal display device according to claim 1, wherein the precharge unit stops a precharge operation in a non-display region period in a partial mode in which display driving is performed only on a partial region of the display area. The liquid crystal display device according to claim 1, wherein the precharge unit writes a test signal supplied from the outside in place of the precharge signal to each of the data lines. An output display unit is provided, and a liquid crystal display device is used as the output display unit.
The liquid crystal display device
Signal writing means for writing a display signal to each of data lines in a display area in which pixels are arranged in a matrix;
Before writing the display signal to each data line by the signal writing means, the gradation level when no voltage is applied to the liquid crystal is written to each of the data lines as a precharge signal level, and the display is written to each of the pixels. Precharge means for stopping the precharge operation in the 1F inversion driving mode in which the polarity of the signal is inverted in one field period (1F) cycle ;
A mobile terminal, wherein the precharge signal level is white level when normal white and black level when normal black. The output display unit can set a partial mode for performing display driving only for a partial area of the display area,
The portable terminal according to claim 9 , wherein the precharge unit stops a precharge operation during a non-display region period in the partial mode.

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