JP2005164704A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which occurrence of a flicker or the like can be suppressed to a minimum in two display methods of reflection display and transmission display with a simple configuration. <P>SOLUTION: The liquid crystal display device 1 is provided with a first confronted electrode voltage generating part 6 generating and outputting a first confronted electrode voltage Va for transmission display, a second confronted electrode voltage generating part 7 generating and outputting a second confronted electrode voltage Vb for reflection display, a back light ON/OFF detection part 3 detecting whether a back light for transmission display is in a lighting state or a non-lighting state, a confronted electrode voltage selecting part 4 outputting the voltage Va or Vb in accordance with the lighting state of the back light, a liquid crystal panel 2 including liquid crystal elements arranged in a matrix shape and a liquid crystal panel driving part 5 driving the liquid crystal elements. The voltages Va and Vb are set to values optimum for a corresponding display method. Thus, display is realized by the confronted electrode voltage which can suppress occurrence of the flicker or the like to the minimum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device using liquid crystal, and more particularly to a liquid crystal display device capable of performing two display modes, for example, reflective display and transmissive display.

  2. Description of the Related Art Conventionally, it is known that an active matrix type liquid crystal display device using a thin film transistor (TFT) such as amorphous silicon as a driving element causes a voltage drop due to the parasitic capacitance of the TFT due to its structure. In general, in order to prevent the deterioration of the liquid crystal, the liquid crystal display device performs AC driving for inverting the polarity of the data signal based on the video signal in accordance with vertical synchronization or horizontal synchronization. In this AC driving method, a DC component is superimposed and applied to the liquid crystal element due to the influence of a voltage drop due to the parasitic capacitance of the TFT. For this reason, flickering occurs when AC driving is performed in synchronization with vertical synchronization, and a stripe pattern is generated on the screen when AC driving is performed in synchronization with horizontal synchronization.

  Therefore, conventionally, in order to minimize the influence of the voltage drop due to the parasitic capacitance of the TFT, the voltage value of the counter electrode (common electrode) is adjusted by appropriately adjusting the resistance value of a predetermined variable resistor or the like. Correction is performed.

  Here, as a method of correcting the voltage value of the counter electrode, a liquid crystal display device capable of performing reflective display and transmissive display is the main of two display modes (display methods) corresponding to these displays. Either the method of correcting so as to match the voltage value suitable for the display mode, or the method of correcting so as to match the average value (intermediate value) of each voltage value suitable for the two display modes. Correction is performed.

Moreover, there is a liquid crystal display device that corrects the voltage value of the counter electrode so as to minimize flicker and the like based on the luminance value of the liquid crystal element without considering the above two display modes (see Patent Documents 1 and 2). reference). In this apparatus, since an appropriate voltage value is set by directly measuring flicker, which is a temporal change in luminance, flicker and the like can be minimized regardless of the display mode.
JP-A-3-293630 Japanese Utility Model Publication No. 4-133223

  However, in the liquid crystal display device that corrects the voltage value based on the luminance value of the liquid crystal element as described above, the configuration for performing the correction automatically becomes complicated. In the method of performing correction so as to match the voltage value suitable for the main display mode among the display modes for the reflective display and the transmissive display or the average value of the voltage suitable for the display mode, two displays are used. In both aspects, the occurrence of flicker or the like cannot be minimized.

  Accordingly, an object of the present invention is to provide a liquid crystal display device having a simple configuration and capable of minimizing the occurrence of flicker or the like in two display modes for reflective display and transmissive display, for example.

According to a first aspect of the present invention, there is provided a counter electrode driving means for driving a counter electrode which is one of two electrodes provided so as to sandwich a liquid crystal for performing display according to an applied voltage, and a plurality of arrangements. A liquid crystal display device having a predetermined first and second display mode, and an active element that provides a voltage to be applied to the pixel electrode that is the other electrode,
First voltage generating means for generating a first voltage to be applied to the counter electrode corresponding to the first display mode;
Second voltage generating means for generating a second voltage to be applied to the counter electrode corresponding to the second display mode;
Selecting means for selecting either the first voltage or the second voltage according to the display mode used of the two display modes;
The counter electrode driving unit applies the voltage selected by the selection unit to the counter electrode.

According to a second invention, in the first invention,
Further comprising backlight means for emitting light through the liquid crystal from the opposite side of the liquid crystal display surface;
The selection means is a transmission mode that is a display mode for transmissive display by light from the backlight unit, and a display mode for reflective display by light from outside the liquid crystal display device that illuminates the display surface of the liquid crystal. Of the two display modes with a certain reflection mode, either the first voltage or the second voltage is selected according to the display mode to be used.

According to a third invention, in the second invention,
The selection means includes
Detecting means for detecting whether the backlight means is in a state of emitting light;
Based on the detection result by the detection means, the first voltage is selected when the backlight means emits light, and the second voltage is selected when the backlight means does not emit light. Means.

According to a fourth invention, in the third invention,
A display mode switching means for switching the display mode to be used to one of the two display modes;
The display mode switching means switches to the first display mode when the backlight means emits light based on the detection result by the detection means, and the second display when the backlight means does not emit light. It switches to a mode, It is characterized by the above-mentioned.

According to a fifth invention, in the first or second invention,
The selection means includes
An external light illuminance detecting means for detecting the illuminance of light from outside the liquid crystal display device that illuminates the display surface of the liquid crystal;
Based on the illuminance detected by the external light illuminance detection means, the first voltage is selected when the illuminance is less than a predetermined value, and the second voltage is selected when the illuminance is greater than or equal to a predetermined value. Means.

According to a sixth invention, in the fifth invention,
A display mode switching means for switching the display mode to be used to one of the two display modes;
The display mode switching means switches to the first display mode when the illuminance is less than a predetermined value based on the illuminance detected by the external light illuminance detection means, and the second display when the illuminance is greater than or equal to a predetermined value. It switches to a mode, It is characterized by the above-mentioned.

In a seventh invention according to the first or second invention,
The selection means includes
Receiving means for receiving a control signal indicating the display mode, which is a signal given from the outside of the liquid crystal display device;
The counter electrode driving means selects either the first voltage or the second voltage according to the display mode indicated by the control signal received by the receiving means, and uses the selected voltage as the driving voltage of the counter electrode. And a counter electrode voltage selection means to be applied to.

In an eighth aspect based on the seventh aspect,
A display mode switching means for switching the display mode to be used to one of the two display modes;
The display mode switching means switches to the first or second display mode according to the display mode indicated by the control signal received by the receiving means.

According to a ninth invention, in the first invention,
In addition to the first and second display modes, it further has a predetermined third display mode,
Further comprising third voltage generating means for generating a third voltage to be applied to the counter electrode corresponding to the third display mode;
The selection unit selects any one of the first to third voltages according to a display mode to be used among the three display modes.

According to a tenth aspect of the present invention, there is provided a counter electrode driving step for driving a counter electrode which is one of two electrodes provided so as to sandwich a liquid crystal for performing display according to an applied voltage, and a plurality of arrangements. A liquid crystal display method including a pixel electrode driving step using an active element that applies a voltage to be applied to the pixel electrode that is the other electrode,
In the counter electrode driving step, a first voltage to be applied to the counter electrode corresponding to a predetermined first display mode or a second voltage to be applied to the counter electrode corresponding to a predetermined second display mode. Any one of the voltages is applied to the counter electrode according to the display mode used of the two display modes.

  According to the first aspect, the counter electrode is driven based on the counter electrode voltage having an appropriate voltage value selected by the selection unit according to the display mode to be used. This makes it possible to perform appropriate display in the two display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the second aspect, the counter electrode is driven based on an appropriate counter electrode voltage selected by the selection unit in accordance with the display mode to be used in the transmission mode and the reflection mode. This makes it possible to perform appropriate display in the two display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the third aspect of the invention, the lighting state of the backlight unit is detected by the detecting unit, and based on the detection result, the counter unit is selected based on the counter electrode voltage corresponding to the transmissive display or the reflective display selected by the counter electrode voltage selecting unit. The electrode is driven. This makes it possible to perform appropriate display in the two display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the fourth aspect, since the display mode to be used is switched based on the detection result of the detection means, the display mode suitable for the current display state is automatically selected from the two display modes with a simple configuration. In addition to being switched, appropriate display can be performed in both of the two display modes.

  According to the fifth aspect, the ambient light illuminance detecting means detects the ambient light illuminance, and the counter electrode is driven based on the counter electrode voltage having an appropriate value selected by the counter electrode voltage selecting means based on the detection result. . This makes it possible to perform appropriate display in the two display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the sixth aspect of the invention, since the display mode (and the lighting state of the backlight unit) to be used is switched based on the external light illuminance detection unit, the current display state of the two display modes can be changed with a simple configuration. The display mode can be automatically switched to a suitable display mode, and appropriate display can be performed in both display modes.

  According to the seventh aspect of the invention, the receiving means receives the control signal given from the outside of the liquid crystal display device, and the counter electrode voltage having an appropriate value selected by the counter electrode voltage selecting means based on the control signal is opposed. The electrode is driven. This makes it possible to perform appropriate display in the two display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the eighth aspect of the invention, the display mode to be used (and the lighting state of the backlight means) is switched based on the control signal received by the receiving means, so that it can respond to the control signal from the outside of the apparatus with a simple configuration. Thus, appropriate display can be automatically performed in the two display modes.

  According to the ninth aspect, the counter electrode is driven based on the counter electrode voltage having an appropriate voltage value selected by the selection unit according to the display mode to be used. This makes it possible to perform appropriate display in the three display modes with a simple configuration, for example, display with minimal occurrence of flicker or the like.

  According to the tenth aspect, the counter electrode is driven based on the counter electrode voltage having an appropriate voltage value according to the display mode to be used. This makes it possible to perform appropriate display in the two display modes, for example, display with minimal occurrence of flicker, etc., with a simple operation.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
<1. Configuration>
A configuration of a display device according to an embodiment of the present invention will be described with reference to FIGS. This display device is an active matrix type liquid crystal display (LCD), such as a white light emitting diode (LED) or a cold cathode fluorescent tube (CCFT). The liquid crystal display device includes a backlight which is a planar illumination device including a light source and a predetermined light guide plate, and can display in two display modes (display methods) for reflective display and transmissive display. Here, the transmissive display refers to a state in which the liquid crystal display is performed by the transmitted light from the backlight, and the reflective display refers to a state in which the liquid crystal display is performed by light from outside the apparatus (hereinafter referred to as “external light”). It refers to the state that has been broken.

  The present liquid crystal display device is a liquid crystal display device for mobile use in which a transmissive display is used indoors and a reflective display is used outdoors, such as a mobile phone, an information terminal, a notebook computer, or a portable device. It is preferable to be used for

  Here, the present liquid crystal display device performs display in a display mode for reflection display (hereinafter referred to as “reflection mode”) when the backlight is not turned on, and displays for transmission display when the backlight is turned on. The display is performed in a mode (hereinafter referred to as “transmission mode”). In addition, this display mode (and turning on and off the backlight) is switched by a user operating a switch not shown here.

  In addition, when the backlight is not turned on, a reflective display is performed, and when the backlight is turned on, a transmissive display is mainly performed. However, external light is much more light than light from the backlight. When strong, reflection display may be performed mainly in spite of the transmission mode. In this case, the display mode is normally switched to the reflection mode by the user.

  FIG. 1 is a block diagram showing the configuration of the liquid crystal display device according to the present embodiment. FIG. 2 is an exploded perspective view of the liquid crystal display device according to the present embodiment. The liquid crystal display device 1 includes a first counter electrode voltage generator 6 that generates and outputs a predetermined first counter electrode voltage Va, and a second counter electrode that generates and outputs a predetermined second counter electrode voltage Vb. An electrode voltage generation unit 7; a backlight ON / OFF detection unit 3 that detects whether the backlight for transmissive display is in a lighting state or a non-lighting state; and the first counter electrode voltage Va or the second A counter electrode voltage selector 4 that selects and outputs one of the counter electrode voltages Vb, a liquid crystal panel 2 that includes liquid crystal elements, and a liquid crystal panel driver 5 that drives these liquid crystal elements are provided. The backlight is arranged on the side opposite to the display surface of the liquid crystal panel 2. Light from this backlight is emitted from the display surface of the liquid crystal via the liquid crystal in the liquid crystal panel 2.

  The liquid crystal panel 2 has a structure in which liquid crystal is disposed between a TFT substrate including a thin film transistor (TFT) and a substrate including a counter electrode (common electrode). The TFT substrate is provided with a plurality of source bus lines parallel to each other and a plurality of gate bus lines parallel to each other so as to extend in a direction orthogonal to the source bus lines. A TFT functioning as a switching element is provided in the vicinity of each intersection. A source drive signal having a predetermined source voltage is supplied from the source bus line to the source terminal of the TFT, and a gate drive signal having a predetermined gate voltage is supplied to the gate terminal from the gate bus line. The drain terminal is connected to a pixel electrode provided on the TFT substrate so as to be in contact with the liquid crystal. Further, a counter electrode is provided on the counter substrate so as to be in contact with the liquid crystal, and a predetermined counter electrode voltage described later is applied to the counter electrode.

  The first counter electrode voltage generator 6 uses the voltage that can minimize the influence of the voltage drop due to the parasitic capacitance of the TFT when the display mode is the transmission mode as the counter electrode voltage. Va is generated and output. Further, the second counter electrode voltage generation unit 7 uses the voltage that can minimize the influence of the voltage drop due to the parasitic capacitance of the TFT as the counter electrode voltage when the display mode is the reflection mode. An electrode voltage Vb is generated and output. For example, the first counter electrode voltage generation unit 6 and the second counter electrode voltage generation unit 7 are resistance voltage dividing circuits including a predetermined variable resistor, and are configured to divide a predetermined voltage as a reference. The first counter electrode voltage Va and the second counter electrode voltage Vb are output. Note that the first counter electrode voltage Va and the second counter electrode voltage Vb are set in advance to optimum values based on a predetermined measurement result (or calculation result).

  The backlight ON / OFF detector 3 receives a control signal for turning on or off the backlight, which is a signal given to a backlight drive circuit (not shown) for driving the backlight, and based on this control signal Whether the light is on or off is detected, and the detection result is given to the counter electrode voltage selector 4.

  Based on the detection result received from the backlight ON / OFF detector 3, the counter electrode voltage selector 4 determines that the backlight is in the transmissive mode and is in the reflective mode when the backlight is not lit. Is determined. When it is determined that the transmission mode is selected, the first counter electrode voltage Va generated by the first counter electrode voltage generation unit 6 is selected and applied to the liquid crystal panel driving unit 5 as the counter electrode voltage, and in the reflection mode. If it is determined that there is, the second counter electrode voltage Vb generated by the second counter electrode voltage generator 7 is selected and applied to the liquid crystal panel driver 5 as a counter electrode voltage. Thus, the backlight ON / OFF detection unit 3 and the counter electrode voltage selection unit 4 function as a selection unit that selects the counter electrode voltage to be supplied to the liquid crystal panel driving unit 5.

  The liquid crystal panel drive unit 5 includes a common electrode drive circuit connected to the common electrode, and drives the common electrode based on the common electrode voltage received from the common electrode voltage selection unit 4. As described above, the counter electrode voltage is set to a voltage that minimizes the influence of the voltage drop due to the parasitic capacitance of the TFT in the display mode currently being performed. Therefore, flicker or the like is suppressed most in any display mode.

  The liquid crystal panel driving unit 5 includes a gate driver connected to the gate bus line and a source driver connected to the source bus line. The gate driver controls a TFT connected to the gate bus line to be turned on or off by applying a predetermined gate voltage to the gate bus line. In addition, the source driver applies a predetermined source voltage to the TFT in the selected state that is turned on, thereby realizing display by liquid crystal according to the voltage difference between the pixel electrode connected to the drain terminal and the counter electrode. That is, in the case of transmissive display, the amount of transmission of illumination light from the backlight that is emitted from the display surface through the liquid crystal is controlled by the liquid crystal, and in the case of reflective display, incident light from the outside and The amount of transmitted reflected light is controlled by the liquid crystal.

<2. Effect>
As described above, in the present liquid crystal display device, the counter electrode voltage having an appropriate value selected by the counter electrode voltage selection unit 4 based on the lighting state of the backlight detected by the backlight ON / OFF detection unit 3 is obtained. It is given to the liquid crystal panel driving unit 5. This makes it possible to minimize the occurrence of flicker, screen stripes, and the like in the two display modes of the reflection mode and the transmission mode with a simple configuration.

<3. Modification>
In the one embodiment, the backlight ON / OFF detection unit 3 detects whether the backlight is in a lighting state or a non-lighting state based on a control signal given to the backlight driving circuit. Therefore, it is not necessary to receive a control signal given to the backlight driving circuit, for example, a configuration for receiving an operation signal based on an operation of a predetermined switch by a user for turning on or off the backlight. May be.

  In the above embodiment, the two display modes (and turning on and off of the backlight) are switched by the user operating a switch (not shown). However, automatic operation is not required without any special operation by the user. The structure which can be switched automatically may be sufficient. For example, the detection result received from the backlight ON / OFF detection unit 3 is also used when the user does not perform any special operation such as the backlight is automatically turned on for a predetermined period from when the user starts the apparatus. Based on this, when the backlight is in the lit state, the mode is switched to the transmission mode, and when the backlight is not lit, the mode is switched to the reflection mode. This operation is performed by a display mode switching unit included in the liquid crystal panel driving unit 5. Note that this display mode switching unit may be included in a control unit (not shown) for controlling various operations of the apparatus. The counter electrode voltage selection unit 4 determines that the backlight is in the transmissive mode based on the detection result received from the backlight ON / OFF detection unit 3, and the reflection mode when the backlight is in the non-lit state. It is determined that This makes it possible to automatically switch to a display mode (either transmission mode or reflection mode) with a simple configuration, and to minimize the occurrence of flickers, screen stripes, and the like.

  Further, the present liquid crystal display device 1 may include an external light illuminance detection unit that detects the illuminance of external light instead of the backlight ON / OFF detection unit 3. FIG. 3 is a block diagram illustrating a configuration of a liquid crystal display device including the external light illuminance detection unit. The external light illuminance detector 13 shown in FIG. 3 includes a light receiving element for detecting the illuminance of external light (regardless of the brightness of the liquid crystal panel) that illuminates the display surface of the liquid crystal display device. Here, by using the detection result of the external light illuminance detection unit 13, switching between the two display modes of the transmission mode and the reflection mode is automatically performed without the user's switch operation or the like. That is, based on the external light illuminance detected by the external light illuminance detection unit 13, the display mode is switched to the reflection mode when the external light illuminance is a predetermined value or more by the display mode switching unit included in the liquid crystal panel driving unit 5. When the external light illuminance is less than a predetermined value, the display mode is switched to the transmission mode (and the backlight is turned on at the same time). Note that the display mode switching unit may be included in the control unit (not shown).

  The counter electrode voltage selection unit 4 determines that the mode is the transmission mode when the ambient light illuminance is less than a predetermined value based on the ambient light illuminance detected by the ambient light illuminance detection unit 13, and generates the first counter electrode voltage. The first counter electrode voltage Va generated by the unit 6 is selected and applied to the liquid crystal panel driving unit 5 as a counter electrode voltage. Further, when the ambient light illuminance is equal to or higher than a predetermined value, it is determined that the reflection mode is selected, and the second counter electrode voltage Vb generated by the second counter electrode voltage generator 7 is selected as the counter electrode voltage. This is given to the liquid crystal panel drive unit 5.

  Thus, with a simple configuration, one of the two display modes of the reflection mode and the transmission mode is suitable for the current display state (either the transmission display or the reflection display) (either the transmission mode or the reflection mode). It is possible to automatically switch to the display mode and to minimize the occurrence of flicker, screen stripes, and the like.

  Note that the switching between the lighting state and the non-lighting state of the backlight may be determined based on, for example, a user operation regardless of the display mode to be used, but the necessity of lighting the backlight is excluded. Since there is a strong correlation with the light illuminance, it is preferable to determine based on the external light illuminance.

  Furthermore, the liquid crystal display device 1 may include a switching signal receiving unit that receives a predetermined counter electrode voltage switching signal from the outside of the device, instead of the backlight ON / OFF detection unit 3. FIG. 4 is a block diagram illustrating a configuration of a liquid crystal display device including the switching signal receiving unit. The switching signal receiving unit 23 shown in FIG. 4 receives a predetermined counter electrode voltage switching signal Ss output from an external device such as a notebook personal computer or a portable information device terminal that uses the present liquid crystal display device for various displays. Receive via input terminal. The common electrode voltage selection unit 4 generates the first common electrode voltage Va generated by the first common electrode voltage generation unit 6 or the second common electrode voltage Va based on the common electrode voltage switching signal Ss received by the switching signal reception unit 23. Any one of the second counter electrode voltages Vb generated by the counter electrode voltage generator 7 is selected and applied to the liquid crystal panel drive unit 5 as the counter electrode voltage. Here, in accordance with the control signal received by the switching signal receiving unit 23, the display mode switching unit included in the liquid crystal panel driving unit 5 switches between the two display modes of the transmission mode and the reflection mode (and the backlight mode). (Lit or extinguished) shall be performed automatically.

  As a result, the two display modes of the reflection mode and the transmission mode are automatically and appropriately switched according to the control signal from the outside of the apparatus with a simple configuration, and the occurrence of flicker, screen stripes, etc. is minimized. Can be suppressed.

  Note that switching between the lighting state and the non-lighting state of the backlight may be determined based on, for example, a user operation regardless of the display mode used, but is determined according to the display mode used. Is preferable.

  In the above-described embodiment, the liquid crystal display device having two display modes (display methods) of the transmission mode and the reflection mode has been described, but the display mode is not limited to these. For example, a liquid crystal display device having two display modes such as a high luminance mode and a low luminance mode, a low power consumption mode (low frequency driving mode) and a high quality mode (high frequency driving mode), or a 3D liquid crystal mode and a normal mode. May be. Note that the 3D liquid crystal mode is a driving mode for three-dimensional display, for example, a predetermined switch liquid crystal provided between the backlight and the liquid crystal panel so that different light reaches the left and right eyes of the user. The driving mode in which the optical parallax barrier is formed is referred to as the normal mode, and the normal mode refers to the driving mode in which the optical parallax barrier is not formed.

  Further, it may be a liquid crystal display device having three display modes, for example, a transmission mode, a reflection mode, and an intermediate mode. Here, the intermediate mode refers to a drive mode corresponding to an intermediate (compatible) display state between transmissive display and reflective display. In this case, a third counter electrode voltage generation unit that generates and outputs a predetermined third counter electrode voltage Vc is further provided, and the counter electrode voltage selection unit 4 includes the first counter electrode voltage Va and the second counter electrode voltage Va. One of the counter electrode voltage Vb and the third counter electrode voltage Vc is selected and output.

  Furthermore, it may be a liquid crystal display device having four or more other display modes. Also in this case, the number of counter electrode voltage generation units corresponding to the display mode is further provided, and the counter electrode voltage selection unit 4 is any one of the counter electrode voltages generated by the plurality of counter electrode voltage generation units. Select and output. Moreover, the liquid crystal display device from which a display mode changes continuously may be sufficient. In this case, a counter electrode voltage that continuously changes corresponding to a continuous display state is generated, and this counter electrode voltage is applied to the liquid crystal panel drive unit 5.

It is a block diagram which shows the structure of the liquid crystal display device which concerns on one Embodiment of this invention. It is a disassembled perspective view of the liquid crystal display device which concerns on the said one Embodiment. It is a block diagram which shows the structure of a liquid crystal display device provided with the external light illumination intensity detection part in the modification of the said one Embodiment. It is a block diagram which shows the structure of a liquid crystal display device provided with the switching signal receiving part in the modification of the said one Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Liquid crystal panel 3 ... Backlight ON / OFF detection part 4 ... Counter electrode voltage selection part 5 ... Liquid crystal panel drive part 6 ... 1st counter electrode voltage generation part 7 ... 2nd counter electrode voltage generation Unit 13 ... External light illuminance detection unit 23 ... Switching signal receiving unit Ss ... Counter electrode voltage switching signal

Claims (10)

A plurality of counter electrode driving means for driving the counter electrode, which is one of the two electrodes provided so as to sandwich the liquid crystal for displaying according to the applied voltage, and the other An active element for applying a voltage to be applied to a pixel electrode as an electrode, and having a predetermined first and second display mode,
First voltage generating means for generating a first voltage to be applied to the counter electrode corresponding to the first display mode;
Second voltage generating means for generating a second voltage to be applied to the counter electrode corresponding to the second display mode;
Selecting means for selecting either the first voltage or the second voltage according to the display mode used of the two display modes;
The liquid crystal display device, wherein the counter electrode driving unit applies the voltage selected by the selection unit to the counter electrode. Further comprising backlight means for emitting light through the liquid crystal from the opposite side of the liquid crystal display surface;
The selection means is a transmission mode that is a display mode for transmissive display by light from the backlight unit, and a display mode for reflective display by light from outside the liquid crystal display device that illuminates the display surface of the liquid crystal. 2. The liquid crystal display device according to claim 1, wherein either one of the first voltage and the second voltage is selected according to a display mode to be used among two display modes with a certain reflection mode. The selection means includes
Detecting means for detecting whether the backlight means is in a state of emitting light;
Based on the detection result by the detection means, the first voltage is selected when the backlight means emits light, and the second voltage is selected when the backlight means does not emit light. The liquid crystal display device according to claim 2, further comprising: means. A display mode switching means for switching the display mode to be used to one of the two display modes;
The display mode switching means switches to the first display mode when the backlight means emits light based on the detection result by the detection means, and the second display when the backlight means does not emit light. The liquid crystal display device according to claim 3, wherein the liquid crystal display device is switched to a mode. The selection means includes
An external light illuminance detecting means for detecting the illuminance of light from outside the liquid crystal display device that illuminates the display surface of the liquid crystal;
Based on the illuminance detected by the external light illuminance detecting means, the first voltage is selected when the illuminance is less than a predetermined value, and the second voltage is selected when the illuminance is greater than or equal to a predetermined value. The liquid crystal display device according to claim 1, further comprising: means. A display mode switching means for switching the display mode to be used to one of the two display modes;
The display mode switching means switches to the first display mode when the illuminance is less than a predetermined value based on the illuminance detected by the external light illuminance detection means, and the second display when the illuminance is greater than or equal to a predetermined value. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is switched to a mode. The selection means includes
Receiving means for receiving a control signal indicating the display mode, which is a signal given from the outside of the liquid crystal display device;
The counter electrode driving means selects either the first voltage or the second voltage according to the display mode indicated by the control signal received by the receiving means, and uses the selected voltage as the driving voltage of the counter electrode. The liquid crystal display device according to claim 1, further comprising a counter electrode voltage selection unit for applying to the liquid crystal display. A display mode switching means for switching the display mode to be used to one of the two display modes;
The liquid crystal display according to claim 7, wherein the display mode switching unit switches to the first or second display mode according to a display mode indicated by the control signal received by the receiving unit. apparatus. In addition to the first and second display modes, it further has a predetermined third display mode,
Further comprising third voltage generating means for generating a third voltage to be applied to the counter electrode corresponding to the third display mode;
2. The liquid crystal according to claim 1, wherein the selection unit selects any one of the first to third voltages according to a display mode to be used among the three display modes. Display device. A plurality of counter electrode driving steps for driving the counter electrode, which is one of the two electrodes provided so as to sandwich the liquid crystal for display according to the applied voltage, and the other A liquid crystal display method including a pixel electrode driving step using an active element that applies a voltage to be applied to a pixel electrode that is an electrode,
In the counter electrode driving step, a first voltage to be applied to the counter electrode corresponding to a predetermined first display mode or a second voltage to be applied to the counter electrode corresponding to a predetermined second display mode. One of the voltages is applied to the counter electrode in accordance with the display mode used out of the two display modes.

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