JP2011027892A - Electrooptical device, electronic device, and method and circuit for driving electrooptical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately reverse a polarity of a voltage applied to an electrooptical device without needing any electric discharging operation in a configuration where a potential of a common electrode is varied. <P>SOLUTION: A reversal potential LCCOMX sequentially varied from one of a high-side potential VH and a low-side potential VL to the other by unit period F is supplied to a reversal potential line 24. A pixel circuit PIX includes a liquid crystal element 50 including a pixel electrode 52 and a common electrode 54, and a first control switch TC1 interposed between the pixel electrode 52 and the reversal potential line 24. A common potential LCCOM obtained by reversing a potential of the reversal potential LCCOMX is supplied to the common electrode 54. A driving circuit controls the first control switch TC1 to an ON state during a reversal period W where the common potential LCCOM is varied after application of a voltage VA to the liquid crystal element 50, and the first control switch TC1 to an OFF state during a reversal period W where the common potential LCCOM is varied after application of a voltage VB (VB<VA) to the liquid crystal element 50. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for driving an electro-optical element such as a liquid crystal element.

  For driving an electro-optical element such as a liquid crystal element, an AC drive that sequentially reverses the polarity of the voltage between the pixel electrode and the common electrode (counter electrode) is employed. For example, in Patent Document 1, by changing the potential of the common electrode and inverting the polarity of the voltage applied to the liquid crystal element, the potential supplied from the signal line to the pixel electrode in accordance with the specified gradation (hereinafter referred to as “gradation potential”). ")" Is disclosed.

  However, in the technique of Patent Document 1, since the potential of the pixel electrode varies in conjunction with the potential of the common electrode, the resistance of the selection switch that controls the connection between the signal line and the pixel electrode may be reduced. For example, in the case where the selection switch is formed of an N-channel transistor, when the potential of the pixel electrode is decreased in conjunction with the potential of the common electrode, the voltage between the gate and the source of the selection switch is increased to be turned on. Therefore, there is a problem that the electric charge held in the electro-optical element is discharged. In order to avoid the above problems, by ensuring sufficient amplitude of the potential of the gate (scanning line) of the selection switch, the writing capability (low on-resistance) and insulation capability (high off-resistance) of the selection switch are ensured. Need to do.

  As a technique for solving the problem of Patent Document 1, Patent Document 2 describes that each period within the period (all scanning line selection periods) after the supply of the gradation potential to each liquid crystal element and before the inversion of the potential of the common electrode. A technique for performing an operation (hereinafter referred to as “discharge operation”) for discharging electric charges held in a liquid crystal element is disclosed.

Japanese Patent Laid-Open No. 8-334741 JP 2004-109824 A JP 2006-84846 A

  However, in the technique of Patent Document 2, since the charge of each electro-optical element is discharged before the potential of the common electrode is inverted, the contrast (brightness difference) of the image is reduced as compared with a configuration in which the charge is not discharged. There is. For example, in a configuration employing a normally-black mode liquid crystal element as an electro-optic element, each electro-optic element controlled to the highest gradation (for example, white) is controlled to the lowest gradation (for example, black) by the discharge operation. The gradation actually perceived by the observer is a lower gradation than the target gradation.

  For example, as disclosed in Patent Document 3, according to the configuration in which the storage circuit that holds data for instructing on / off of the electro-optical element is built in the pixel circuit, the electro-optic is performed without performing the discharge operation. It is possible to appropriately reverse the polarity of the voltage applied to the element. However, since it is necessary to incorporate a memory circuit that requires a large number of elements in the pixel circuit, there is a problem that high definition of the pixel is limited.

  Further, if a transistor having a high threshold voltage is used as a selection switch, the selection switch can be maintained in an OFF state even when the potential of the pixel electrode varies in conjunction with the potential of the common electrode. However, since it is necessary to increase the amplitude of the scanning signal for controlling the selection switch, there may arise a problem that a high-breakdown-voltage drive circuit is required and a problem that the power consumption of the drive circuit increases.

  In view of the above circumstances, an object of the present invention is to appropriately reverse the polarity of the voltage applied to the electro-optic element without requiring a discharge operation under a configuration in which the potential of the common electrode is varied.

  In order to solve the above-described problems, an electro-optical device according to the present invention includes an inversion potential line to which an inversion potential that is sequentially changed every unit period is supplied from one of a high-side potential and a low-side potential to the other. A common electrode supplied with a common potential that is set to a low potential in a unit period in which the inversion potential is a high potential and is set to a high potential in a unit period in which the inversion potential is a low potential An electro-optical element including a pixel electrode and a first control switch (for example, the first control switch TC1 in FIGS. 2 and 13) for controlling the connection between the pixel electrode and the inversion potential line are provided. In the above aspect, the first control switch controls conduction / non-conduction between the inversion potential line to which the inversion potential whose level is inverted from the common potential of the common electrode is supplied and the pixel electrode. Therefore, the first control switch is controlled to be in an ON state after the voltage is applied between both electrodes of the electro-optic element (the inversion potential is supplied to the pixel electrode), so that the common potential is reversed and both the electro-optic elements are turned on. Even when the polarity of the voltage between the electrodes is reversed, the gradation of the electro-optical element is maintained. In the above configuration, since the discharge operation required in the technique of Patent Document 2 is unnecessary, there is an advantage that a decrease in contrast due to the discharge operation is suppressed. Although the discharge operation is not necessary in principle according to the present invention, the aspect of executing the discharge operation under the configuration of the present invention is not intended to exclude from the scope of the present invention.

  An electro-optical device according to a preferred aspect of the present invention includes a drive circuit, and the drive circuit supplies a gradation potential corresponding to a specified gradation to the pixel electrode in a unit period, while both electrodes of the electro-optic element. In the case where a gray-scale potential whose voltage is the first voltage is supplied, the first control switch is controlled to be in an on state in a period including a time point when the common potential fluctuates after the supply of the gray-scale potential. When a gradation potential is supplied such that the voltage between the two electrodes is a second voltage different from the first voltage, the first control switch is turned on during a period including the time when the common potential fluctuates after the supply of the gradation potential. Control to off state. In the above aspect, the first control switch is controlled to be on when the common potential is changed when the first voltage is applied to the electro-optic element, and the common potential is changed when the second voltage is applied to the electro-optic element. Sometimes the first control switch is controlled to the off state. Accordingly, it is possible to reverse the polarity of the applied voltage while maintaining the gradation of the electro-optic element both when the first voltage is applied and when the second voltage is applied. The first voltage is, for example, a voltage corresponding to white in the normally black mode or a voltage corresponding to black in the normally white mode, and the second voltage is, for example, a voltage corresponding to black in the normally black mode. Or a voltage corresponding to white in normally white mode.

  The electro-optical device according to a preferred aspect of the present invention includes a control line to which a control signal for controlling the first control switch is supplied, and a second control switch for controlling connection between the gate of the first control switch and the control line ( For example, the second control switch TC2) of FIG. 2 or 13 and a first control capacitor (for example, the control capacitor C1 of FIG. 2 or 13) that holds the potential of the gate of the first control switch are provided. In the above aspect, since the potential of the control signal for controlling the first control switch is held in the first control capacitor, the first control switch is continuously turned on in a period including the time when the common potential changes. It can be kept off. The electro-optical device according to a more preferable aspect includes a common potential line to which a common potential is supplied, a storage capacitor interposed between the common potential line and the pixel electrode, a gate of the first control switch, and the common potential line. A second control capacitor (for example, a control capacitor C2 in FIG. 13) is provided between the first control switch and the inversion potential line. In the above aspect, since the action of the common potential and the action of the inversion potential with respect to the potential of the gate of the first control switch are canceled, the potential of the gate of the first control switch is effectively held. On the other hand, the opposite electrode of the first control capacitor to the first control switch is connected to the inversion potential line, and the opposite electrode of the second control capacitor to the first control switch is connected to the common potential line. Therefore, a wiring dedicated for holding the potential of the gate of the first control switch (for example, the capacitor line 26 in FIG. 2) is unnecessary. Therefore, there is an advantage that the configuration of the electro-optical device is simplified.

  An electro-optical device according to a preferred aspect of the present invention includes a scanning line and a signal line that intersect each other, and a selection switch that connects the signal line and the pixel electrode when the scanning line is selected. The switch is controlled by a common signal (for example, scanning signal Y [m]). In the above aspect, since the selection switch and the second control switch are controlled by a common signal, the configuration of the electro-optical device can be simplified (the number of wires) compared to a configuration in which both are controlled by separate signals. Reduction) is realized.

  An electro-optical device according to a specific aspect of the invention includes a plurality of scanning lines and a plurality of signal lines that intersect each other, and one for a reversal that sequentially changes from one of a high potential and a low potential to every other unit period. An inversion potential line to which a potential is supplied, a plurality of pixel circuits arranged corresponding to each intersection of the plurality of scanning lines and the plurality of signal lines, and a drive circuit for driving each pixel circuit, Each of the plurality of pixel circuits has a common potential that is set to a low potential in a unit period in which the inversion potential is a high potential and is set to a high potential in a unit period in which the inversion potential is a low potential. , An electro-optical element including a common electrode and a pixel electrode, a selection switch for connecting the signal line and the pixel electrode when the scanning line is selected, and a first for controlling the connection between the pixel electrode and the inversion potential line. Including a control switch and a drive circuit in a unit period. Each of the plurality of scanning lines is sequentially selected and a gradation potential corresponding to the designated gradation of each pixel circuit corresponding to the scanning line is supplied to each of the plurality of signal lines, while each of the plurality of pixel circuits In the case where a gradation potential in which the voltage between both electrodes of the electro-optic element is the first voltage is supplied, the first control switch is turned on in a period including the time when the common potential fluctuates after the supply of the gradation potential. And a period including a time point at which the common potential fluctuates after the supply of the gradation potential when the gradation potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage. The first control switch is controlled to be in the OFF state. Also in the above aspect, the expected effect that the discharge operation of Patent Document 2 is unnecessary is realized.

  The electro-optical device according to each aspect described above is used in various electronic apparatuses. A typical example of an electronic device is a device that uses an electro-optical device as a display device. Specifically, a mobile phone or a portable information terminal is exemplified as the electronic apparatus of the present invention. Further, a projection display device using the electro-optical device of each of the above aspects as a light modulator that modulates light emitted from a light source is also included in the concept of the electronic apparatus of the present invention. The projection display device includes a light source that emits a light beam, the electro-optical device according to each aspect described above that modulates light emitted from the light source, and an optical system that projects the modulated light from the electro-optical device onto a projection surface.

  The present invention is also specified as a driving method of the electro-optical device according to each of the above aspects. In the driving method according to the present invention, a grayscale potential corresponding to a designated grayscale is supplied to the pixel electrode in a unit period, while a grayscale potential at which the voltage between both electrodes of the electro-optic element becomes the first voltage is supplied. In this case, the first control switch is controlled to be in an ON state in a period including a time point when the common potential fluctuates after the supply of the gradation potential, and the voltage between both electrodes of the electro-optic element is different from the first voltage. In the case where a gradation potential as a voltage is supplied, the first control switch is controlled to be in an off state in a period including a time when the common potential fluctuates after the supply of the gradation potential. According to the above driving method, an effect similar to that of the electro-optical device of the present invention is realized.

  A driving method according to another aspect includes an inversion potential line that is supplied with an inversion potential that sequentially changes from one high-side potential and a low-side potential to the other for each unit period, and the inversion potential is a high-side potential. An electro-optic element including a common electrode and a pixel electrode that are supplied with a common potential set to a high potential in a unit period that is set to a low potential in a unit period and the inversion potential becomes a low potential When the grayscale potential at which the voltage between both electrodes of the electrooptic element is the first voltage is supplied, the common potential fluctuates after the grayscale potential is supplied. When a reversal potential is supplied to the pixel electrode in a period including the voltage and a grayscale potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage, the supply of the grayscale potential is performed. Pixels in a period including the time when the common potential fluctuates thereafter It prohibits the supply of the reversing potential for electrode.

  In addition, the drive circuit of the electro-optical device according to the present invention supplies the gradation potential corresponding to the designated gradation to the pixel electrode in a unit period, while the voltage between both electrodes of the electro-optical element becomes the first voltage. When the gradation potential is supplied, the first control switch is controlled to be in an ON state in a period including the time when the common potential fluctuates after the supply of the gradation potential, and the voltage between both electrodes of the electro-optic element is the first. When a gradation potential that is a second voltage different from the voltage is supplied, the first control switch is controlled to be in an off state in a period including a time point when the common potential fluctuates after the supply of the gradation potential. According to the above drive circuit, the same effect as the electro-optical device of the present invention is realized.

1 is a block diagram of an electro-optical device according to a first embodiment of the invention. FIG. It is a circuit diagram of a pixel circuit. 6 is a timing chart showing a relationship between a common potential and an inversion potential and a unit period. It is a graph which shows the relationship between the applied voltage of a liquid crystal element, and a gradation (transmittance, reflectance). It is a block diagram of a signal line drive circuit. It is explanatory drawing of operation | movement of a signal line drive circuit. It is a timing chart in the case of changing the voltage of a liquid crystal element from positive polarity to negative polarity. It is explanatory drawing of operation | movement of the pixel circuit in the case of displaying black. It is explanatory drawing of operation | movement of the pixel circuit in the case of displaying white. It is a timing chart in the case of changing the voltage of a liquid crystal element from negative polarity to positive polarity. It is explanatory drawing of operation | movement of the pixel circuit in the case of displaying black. It is explanatory drawing of operation | movement of the pixel circuit in the case of displaying white. FIG. 10 is a circuit diagram of a pixel circuit of an electro-optical device according to a second embodiment. It is a perspective view which shows the form (personal computer) of an electronic device. It is a perspective view which shows the form (cellular phone) of an electronic device. It is a perspective view which shows the form (mobile information terminal) of an electronic device.

<A: First Embodiment>
FIG. 1 is a block diagram of an electro-optical device 100 according to the first embodiment of the present invention. The electro-optical device 100 is a liquid crystal device that is employed in various electronic devices as a display body that displays an image. As shown in FIG. 1, an electro-optical device 100 includes an element portion (display area) 10 in which a plurality of pixel circuits PIX are arranged in a plane, a drive circuit 30 that drives each pixel circuit PIX, and each pixel circuit PIX. And a control circuit 44 that controls the drive circuit 30 and the potential generation circuit 42.

  In the element unit 10, M scanning lines 12 extending in the X direction and N signal lines 14 extending in the Y direction intersecting the X direction are formed (M and N are natural numbers). The plurality of pixel circuits PIX are arranged corresponding to the intersections of the scanning lines 12 and the signal lines 14 and are arranged in a matrix of vertical M rows × horizontal N columns. In the element unit 10, N control lines 16 extending in the Y direction corresponding to the signal lines 14 are formed, and M common lines extending in the X direction corresponding to the scanning lines 12 are formed. A potential line 22, M inversion potential lines 24, and M capacitance lines 26 are formed.

  FIG. 2 is a circuit diagram of each pixel circuit PIX. In FIG. 2, one pixel circuit PIX located in the nth column (n-1 to N) of the mth row (m = 1 to M) is representatively shown. As shown in FIG. 2, the pixel circuit PIX includes a liquid crystal element 50, three switches (selection switch TSL, first control switch TC1, second control switch TC2) and two capacitance elements (holding capacity CS, control). Capacitance C1). Each switch (TSL, TC1, TC2) is composed of, for example, an arbitrary conductive type (N-channel type in this embodiment) thin film transistor formed on the surface of the element substrate. However, if a complementary transistor (for example, a transfer gate) is employed as each switch (TSL, TC1, TC2), the voltage required for each drive can be reduced.

  The liquid crystal element 50 is an electro-optical element including a pixel electrode 52, a common electrode (counter electrode) 54, and a liquid crystal 56 between both electrodes. The pixel electrode 52 is formed independently for each pixel circuit PIX on the surface of the element substrate (not shown), and the common electrode 54 is formed on the surface of the counter substrate (not shown) facing the element substrate. (See FIG. 1). The liquid crystal 56 between the pixel electrode 52 and the common electrode 54 changes in gradation (transmittance and reflectance) in accordance with the voltage between both electrodes. The liquid crystal 56 of the first embodiment is set to a vertical alignment type (VA (Vertical Alignment)), and the gradation becomes the lowest (black) when the voltage between the pixel electrode 52 and the common electrode 54 is zero. Operates in normally black mode. The polarity of the voltage between both electrodes of the liquid crystal element 50 is sequentially reversed (details will be described later).

  The selection switch TSL of each pixel circuit PIX in the n-th column is interposed between the pixel electrode 52 and the signal line 14 in the n-th column and controls the electrical connection (conduction / non-conduction) between them. The holding capacitor CS of each pixel circuit PIX in the m-th row is interposed between the pixel electrode 52 and the common potential line 22 in the m-th row (that is, arranged in parallel with the liquid crystal element 50). It is. Specifically, the storage capacitor CS is composed of an electrode EA1 connected to the pixel electrode 52, an electrode EA2 connected to the common potential line 22, and a dielectric between both electrodes. The holding capacitor CS functions as an element that holds the potential of the pixel electrode 52 (voltage applied to the liquid crystal element 50).

  The first control switch TC1 of each pixel circuit PIX in the m-th row is interposed between the pixel electrode 52 and the inversion potential line 24 in the m-th row and controls the electrical connection therebetween. The control capacitor C1 of each pixel circuit PIX in the m-th row is a capacitance that is interposed between the gate of the first control switch TC1 and the capacitor line 26 in the m-th row. Specifically, the control capacitor C1 includes an electrode EB1 connected to the gate of the first control switch TC1, an electrode EB2 connected to the capacitor line 26, and a dielectric between the electrodes. The control capacitor C1 functions as an element that holds the potential of the gate of the first control switch TC1.

  The second control switch TC2 of each pixel circuit PIX in the n-th column is interposed between the gate of the first control switch TC1 and the control line 16 in the n-th column and controls the electrical connection between them. The gates of the selection switch TSL and the second control switch TC2 in each pixel circuit PIX in the m-th row are commonly connected to the scanning line 12 in the m-th row. Since the selection switch TSL and the second control switch TC2 have the same conductivity type, the selection switch TSL and the second control switch TC2 are controlled to be in the same state (on state / off state).

  The control circuit 44 in FIG. 1 generates various signals that define the operation of the electro-optical device 100 and supplies the signals to the drive circuit 30 and the potential generation circuit 42. For example, the control circuit 44 includes a synchronization signal SV that defines a period (hereinafter referred to as “unit period”) that is a unit for reversing the polarity of the voltage applied to the liquid crystal element 50, and the polarity of the voltage applied to the liquid crystal element 50 in each unit period. A polarity signal SP designating (positive / negative) is output to the drive circuit 30 and the potential generation circuit 42. In addition, the control circuit 44 generates an image signal VID that specifies the gradation of each pixel circuit PIX (each liquid crystal element 50) and supplies the image signal VID to the drive circuit 30 (signal line drive circuit 34).

  The potential generation circuit 42 includes a common potential LCCOM and an inversion potential LCCOMX, a positive side gradation potential VDATA [+] and a negative side gradation potential VDATA [−], an on potential VON and an off potential VOFF, and a holding potential VSL. Is generated. The common potential LCCOM is supplied in common to the M common potential lines 22 and the common electrode 54 on the counter substrate. The inversion potential LCCOMX is supplied in common to the M inversion potential lines 24. The positive side gradation potential VDATA [+], the negative side gradation potential VDATA [−], the ON potential VON, and the OFF potential VOFF are supplied to the signal line driver circuit 34. The holding potential VSL is a predetermined potential that is commonly supplied to the M capacitor lines 26.

  As shown in FIG. 3, the common potential LCCOM sequentially changes from one to the other of the high potential VH and the low potential VL every unit period (for example, field period) F defined by the control signal 44 by the synchronization signal SV. To do. The higher potential VH exceeds the lower potential VL. In the unit period F in which the polarity signal SP indicates positive polarity (positive sign (+) in FIG. 3), the potential generation circuit 42 sets the common potential LCCOM to the lower potential VL and the polarity signal SP has negative polarity (FIG. 3). In the unit period F instructing the negative sign (-)), the common potential LCCOM is set to the high potential VH. The applied voltage of the liquid crystal element 50 when the common potential LCCOM is set to the lower potential VL is defined as positive polarity, and the applied voltage of the liquid crystal element 50 when the common potential LCCOM is set to the higher potential VH is negative. It is defined as

  Similar to the common potential LCCOM, the inversion potential LCCOMX sequentially changes from one to the other of the high potential VH and the low potential VL every unit period F. However, the common potential LCCOM and the inversion potential LCCOMX have a relationship in which the potential level is inverted. That is, in the unit period F in which the common potential LCCOM is set to the high potential VH, the inversion potential LCCOMX is set to the low potential VL, and in the unit period F in which the common potential LCCOM is set to the low potential VL. LCCOMX is set to the higher potential VH. FIG. 3 illustrates a period W (hereinafter referred to as “inversion period”) in which the common potential LCCOM and the inversion potential LCCOMX vary from one of the high potential VH and the low potential VL to the other.

  The positive side gradation potential VDATA [+] and the negative side gradation potential VDATA [−] are potentials supplied to the pixel electrode 52 for controlling the gradation of the liquid crystal element 50. The positive gradation potential VDATA [+] exceeds the negative gradation potential VDATA [-]. Specifically, the positive gradation potential VDATA [+] is the same potential as the high potential VH, and the negative gradation potential VDATA [−] is the same potential as the low potential VL. The on potential VON and the off potential VOFF are potentials used for controlling the first control switch TC1. The first control switch TC1 transitions to the on state when the on potential VON is supplied to the gate, and transitions to the off state when the off potential VOFF is supplied to the gate.

  The drive circuit 30 in FIG. 1 controls the gradation (transmittance or reflectivity) of each liquid crystal element 50 by driving each of the plurality of pixel circuits PIX. Subfield driving is employed for driving each pixel circuit PIX by the driving circuit 30. That is, the drive circuit 30 determines which of the two kinds of voltages (VA, VB) is applied to the liquid crystal element 50 of each pixel circuit PIX in each of the plurality of subfields SF (SF1, SF2, SF3) divided into the unit periods F. Apply. As shown in FIG. 3, one unit period F is divided into three subfields SF (SF1, SF2, SF3). The time lengths of the three subfields SF in the unit period F are in a binary weighted relationship (SF1: SF2: SF3 = 1: 2: 4). However, the number and time length of the subfield SF in the unit period F are arbitrarily changed.

  FIG. 4 is a graph showing the relationship between the voltage (absolute value) between both electrodes of the liquid crystal element 50 and the gradation (transmittance or reflectance) of the liquid crystal element 50. The voltage VA in FIG. 4 is a voltage for changing the gradation of the liquid crystal element 50, and the voltage VB is a voltage different from the voltage VA (in this embodiment, a voltage lower than the voltage VA). The voltage VB is typically set to 0V. As shown in FIG. 3, the potential difference between the higher potential VH (positive gradation potential VDATA [+]) and the lower potential VL (negative gradation potential VDATA [-]) corresponds to the voltage VA. As shown in FIG. 4, the liquid crystal element 50 is controlled to the gradation GW by the application of the voltage VA and is controlled to the gradation GB by the application of the voltage VB. In this embodiment in which the liquid crystal element 50 operates in the normally black mode, the gradation GW corresponds to the highest gradation (white) and the gradation GB corresponds to the lowest gradation (black). In the unit period F, the ratio of the time during which the voltage VA is applied to the liquid crystal element 50 and the time during which the voltage VB is applied (number ratio of the subfield SF) is variably controlled according to the designated gradation of each pixel circuit PIX. The

  As shown in FIG. 1, the drive circuit 30 includes a scanning line drive circuit 32 and a signal line drive circuit 34. The scanning line driving circuit 32 sequentially selects each of the M scanning lines 12. Specifically, the scanning line driving circuit 32 outputs the scanning signals Y [1] to Y [M] to each scanning line 12, so that M scanning lines in the subfield SF of each unit period F are output. Each of 12 is selected sequentially. The scanning signal Y [m] output to the m-th row scanning line 12 is a voltage signal instructing selection / non-selection of the m-th row. That is, as shown in FIG. 3, the scanning signal Y [m] has a selection potential VSEL_ON (potential meaning selection of the scanning line 12) in the m-th horizontal scanning period H [m] in each subfield SF. And is set to the non-selection potential VSEL_OFF (potential meaning non-selection of the scanning line 12) in other periods.

  The signal line drive circuit 34 in FIG. 1 outputs gradation signals X [1] to X [N] to each signal line 14 in synchronization with the selection of each scan line 12 by the scan line drive circuit 32 and a control signal. Z [1] to Z [N] are output to each control line 16. The gradation signal X [n] supplied to the signal line 14 in the n-th column in the horizontal scanning period H [m] is the gradation GW (white) for the liquid crystal element 50 in the pixel circuit PIX in the m-th row and the n-th column. Display) and gradation GB (black display), and is set to either the positive gradation potential VDATA [+] or the negative gradation potential VDATA [-]. The control signal Z [n] supplied to the control line 16 in the n-th column in the horizontal scanning period H [m] is the state (ON state) of the first control switch TC1 in the pixel circuit PIX in the n-th column of the m-th row. / Off state) and is set to either the on voltage VON or the off voltage VOFF.

  FIG. 5 is a block diagram of the signal line driving circuit 34. As shown in FIG. 5, the signal line drive circuit 34 includes a distribution circuit 62 and an output circuit 64. The distribution circuit 62 generates gradation data D [1] to D [N] corresponding to the N pixel circuits PIX in the m-th row from the image signal VID, and in parallel in each horizontal scanning period H [m]. It is a circuit to output. The gradation data D [n] output from the distribution circuit 62 in the horizontal scanning period H [m] is the gradation GW (white display) for the liquid crystal element 50 of the pixel circuit PIX located in the nth column of the mth row. This is data specifying either voltage VA) or gradation GB (black display voltage VB).

  As shown in FIG. 5, the distribution circuit 62 includes a selection circuit 621, a first latch circuit 623, and a second latch circuit 625. The selection circuit 621 sequentially sets the N selection signals SEL [1] to SEL [N] to active in each horizontal scanning period H [m]. For example, an N-stage shift register that sequentially transfers start pulses is employed as the selection circuit 621. The first latch circuit 623 receives the image signal VID supplied from the control circuit 44 at the time when each of the selection signals SEL [1] to SEL [N] (SEL [n]) is set to active, and the gradation data D Output and hold as [n]. That is, the gradation data D [1] to D [N] are output in parallel from the first latch circuit 623 in dot order. The second latch circuit 625 simultaneously outputs (line-sequential output) and holds the gradation data D [1] to D [N] output from the first latch circuit 623 every horizontal scanning period H [m].

  The output circuit 64 generates gradation signals X [1] to X [N] and control signals Z [1] to Z [N] according to the gradation data D [1] to D [N] and outputs them. To do. As shown in FIG. 5, the output circuit 64 includes N unit circuits U [1] to U [N] corresponding to the number of columns of the pixel circuit PIX. The n-th unit circuit U [n] generates and outputs a gradation signal X [n] and a control signal Z [n] according to the gradation data D [n] output from the distribution circuit 62. As shown in FIG. 5, the unit circuit U [n] includes a potential selection circuit 641 that generates a gradation signal X [n] and a potential selection circuit 643 that generates a control signal Z [n]. . FIG. 6 is a chart for explaining operations of the potential selection circuit 641 and the potential selection circuit 643 (setting of the potentials of the gradation signal X [n] and the control signal Z [n]).

  The potential selection circuit 641 in FIG. 5 uses either the positive gradation potential VDATA [+] or the negative gradation potential VDATA [−] generated by the potential generation circuit 42 as the gradation data D [n] and the polarity signal SP. Is selected according to the output signal and output to the signal line 14 as the gradation signal X [n]. Specifically, the potential selection circuit 641 adjusts the voltage (VA, VB) corresponding to the gradation (GW, GB) indicated by the gradation data D [n] so as to be applied to the liquid crystal element 50. The potential of the adjustment signal X [n] is set to either the positive side gradation potential VDATA [+] or the negative side gradation potential VDATA [-].

  For example, in the unit period F in which the polarity signal SP indicates positive polarity (the period in which the common potential LCCOM is set to the lower potential VL), the potential selection circuit 641 performs the gradation data D [n as shown in FIG. ] Indicates the gradation GW, the positive side gradation potential VDATA [+] is selected, and when the gradation data D [n] indicates the gradation GB, the negative side gradation potential VDATA [-] is selected. Select. On the other hand, in the unit period F in which the polarity signal SP indicates the negative polarity (period in which the common potential LCCOM is set to the higher potential VH), the potential selection circuit 641 indicates that the gradation data D [n] indicates the gradation GW. In this case, the negative gradation potential VDATA [-] is selected, and when the gradation data D [n] indicates the gradation GB, the positive gradation potential VDATA [+] is selected.

  The potential selection circuit 643 in FIG. 5 selects either the ON potential VON or the OFF potential VOFF generated by the potential generation circuit 42 according to the gradation data D [n], and uses the control line 16 as the control signal Z [n]. Output to. Specifically, as shown in FIG. 6, the potential selection circuit 643 selects the ON potential VON when the gradation data D [n] indicates the gradation GW (voltage VA), and the gradation data D When [n] indicates the gradation GB (voltage VB), the off potential VOFF is selected.

  Next, the operation of the electro-optical device 100 will be described with reference to FIGS. The gradation data D for each of the unit period F (FIGS. 7 to 9) in which the common potential LCCOM is set to the lower potential VL and the unit period F (FIGS. 10 to 12) set to the higher potential VH. The operation when [n] indicates the gradation GB (FIGS. 8 and 11) and when the gradation GW is specified (FIGS. 9 and 12) will be described below. In the following, the operation will be described focusing on the pixel circuit PIX in the m-th row and the n-th column. A similar operation is performed for each pixel circuit PIX in the element unit 10.

  In the following, as shown in FIG. 7 and FIG. 10, the non-selection potential VSEL_OFF, the low potential VL, the negative gradation potential VDATA [-], and the off potential VOFF are set as a reference (0 V) as the reference (0 V). The positive gradation potential VDATA [+] is set to 5V, the ON potential VON is set to 7V, and the selection potential VSEL_ON is set to 9V. It is assumed that the threshold voltage of each switch (TSL, TC1, TC2) of the pixel circuit PIX is 2V or less. The voltage VB corresponding to the gradation GB (black display) is 0 V, but the voltage + VB applied to the liquid crystal element 50 in the unit period F in which the polarity signal SP indicates positive polarity and the polarity signal SP is negative. For the sake of convenience, the voltage -VB applied to the liquid crystal element 50 in the unit period F instructing the above is distinguished.

[A] Unit period F in which polarity signal SP indicates positive polarity (FIGS. 7 to 9)
[A1] When gradation data D [n] indicates gradation GB (black display) (FIG. 8)
In the unit period F in which the polarity signal SP indicates positive polarity, as shown in FIG. 7, the common potential LCCOM is set to the low potential VL and the inversion potential LCCOMX is set to the high potential VH. Further, since the gradation data D [n] indicates the gradation GB, the gradation signal X [n] of the signal line 14 is shown in the horizontal scanning period H [m], as shown in part (A) of FIG. Is set to the negative gradation potential VDATA [−] which is the same potential as the common potential LCCOM (low potential VL), and the control signal Z [n] of the control line 16 is set to the OFF potential VOFF.

  As shown in FIG. 7, in the horizontal scanning period H [m], the scanning signal Y [m] is set to the selection potential VSEL_ON, so that the selection switch TSL and the second control switch TC2 are turned on. Therefore, the potential VP of the pixel electrode 52 is, as shown in the part (i) of FIG. 7 and the part (A) of FIG. 8, the negative gradation potential VDATA [supplied from the signal line 14 via the selection switch TSL. -] (Low potential VL). Since the common potential LCCOM of the common electrode 54 is maintained at the lower potential VL, a voltage + VB (0 V) is applied between both electrodes of the liquid crystal element 50 as shown in part (A) of FIG. Therefore, the liquid crystal element 50 is controlled to the gradation GB (black display). On the other hand, the OFF potential VOFF is supplied from the control line 16 to the gate of the first control switch TC1 via the second control switch TC2. Therefore, the first control switch TC1 is controlled to the off state. That is, the pixel electrode 52 and the inversion potential line 24 are electrically insulated.

  The potential VP of the pixel electrode 52 is held by the holding capacitor CS, and the off-potential VOFF supplied from the control line 16 is held by the control capacitor C1. Therefore, as shown in part (B) of FIG. 8, even after the horizontal scanning period H [m] has elapsed and the scanning signal Y [m] has changed to the non-selection potential VSEL_OFF, the applied voltage of the liquid crystal element 50 remains the voltage. The voltage is maintained at + VB, and the first control switch TC1 is maintained in the off state. The above operation is sequentially executed in each subfield SF in the unit period F.

  As shown in FIG. 7, in the inversion period W after the lapse of the unit period F, the common potential LCCOM changes from the low potential VL to the high potential VH and the inversion potential LCCOMX changes from the high potential VH to the low potential VL. To change. On the other hand, after the elapse of the horizontal scanning period H [m], the selection switch TSL and the first control switch TC1 are controlled to be turned off, so that the pixel electrode 52 is maintained in an electrically floating state. Since the pixel electrode 52 is capacitively coupled to the common potential line 22 via the storage capacitor CS, the potential VP of the pixel electrode 52 is interlocked with the potential of the electrode EA2 of the storage capacitor CS within the inversion period W (common potential LCCOM). Change. The amount of change in the potential VP of the pixel electrode 52 is substantially the same as the amount of change in the common potential LCCOM. That is, as shown in part (i) of FIG. 7 and part (C) of FIG. 8, the potential VP of the pixel electrode 52 changes from the lower potential VL before the start of the inversion period W to the higher potential VH. Maintained. Therefore, the voltage applied to the liquid crystal element 50 is a negative voltage −VB (0 V) corresponding to the high potential VH after the change of the common potential LCCOM of the common electrode 54 and the high potential VH after the change of the pixel electrode 52. Set to As described above, the gradation of the liquid crystal element 50 is maintained at the gradation GB (black display) before and after the change of the common potential LCCOM within the inversion period W. On the other hand, since the first control switch TC1 maintains the OFF state, the change in the inversion potential LCCOMX within the inversion period W does not affect the potential VP of the pixel electrode 52.

[A2] When gradation data D [n] indicates gradation GW (white display) (FIG. 9)
In the case where the gradation data D [n] indicates the gradation GW in the unit period F (LCCOM = VL) in which the polarity signal SP indicates positive polarity, in the horizontal scanning period H [m], the portion (A ), The gradation signal X [n] is set to the positive gradation potential VDATA [+] (that is, a potential different from the common potential LCCOM), and the control signal Z [n] is set to the ON potential VON. Is set.

  Therefore, in the horizontal scanning period H [m] in which the scanning signal Y [m] is set to the selection potential VSEL_ON, as shown in part (A) of FIG. To the pixel electrode 52 via the selection switch TSL. The ON potential VON is supplied from the control line 16 to the gate of the first control switch TC1 via the second control switch TC2. The inversion potential LCCOMX (source potential of the first control switch TC1) is set to the higher potential VH (5 V), but the voltage between the gate and source of the first control switch TC1 exceeds the threshold voltage (2 V or less). Thus, the ON potential VON (7V) is set, so that the first control switch TC1 transitions to the ON state, and the pixel electrode 52 and the inversion potential line 24 are electrically connected. That is, both the signal line 14 of the positive gradation potential VDATA [+] and the inversion potential line 24 of the inversion potential LCCOMX (higher side potential VH) are connected to the pixel electrode 52. Since the positive side gradation potential VDATA [+] and the higher potential VH are the same potential, the potential VP of the pixel electrode 52 is higher as shown in part (ii) of FIG. 7 and part (A) of FIG. It is set to the side potential VH (positive side gradation potential VDATA [+]). Since the common potential LCCOM of the common electrode 54 is maintained at the lower potential VL, a positive voltage + VA (5 V) is applied between both electrodes of the liquid crystal element 50 as shown in part (A) of FIG. Accordingly, the liquid crystal element 50 is controlled to the gradation GW (white display).

  The potential VP of the pixel electrode 52 is held by the holding capacitor CS, and the ON potential VON of the control signal Z [n] is held by the control capacitor C1. Therefore, even after the horizontal scanning period H [m] has elapsed, as shown in part (B) of FIG. 9, the voltage + VA is continuously applied between both electrodes of the liquid crystal element 50, and the first control switch TC1 is turned on. Thus, the inversion potential LCCOMX (high potential VH) is continuously supplied from the inversion potential line 24 to the pixel electrode 52. The above operations are sequentially executed in the subfield SF in the unit period F.

  As shown in FIG. 7, in the inversion period W after the lapse of the unit period F, the common potential LCCOM changes from the low potential VL to the high potential VH and the inversion potential LCCOMX changes from the high potential VH to the low potential VL. To change. On the other hand, the supply of the inversion potential LCCOMX to the pixel electrode 52 (the ON state of the first control switch TC1) is maintained even during the inversion period W. That is, in the inversion period W when the gradation GB is instructed, the pixel electrode 52 is set in an electrically floating state, whereas when the gradation GW is instructed, the pixel electrode 52 is in an inversion potential LCCOM. Is set to the supplied state. Therefore, the potential VP does not fluctuate due to the capacitive coupling between the pixel electrode 52 and the common potential line 22 (the electrode EA2 of the storage capacitor CS), and the potential VP of the pixel electrode 52 is equal to the portion (ii) in FIG. As shown in part (C) of FIG. 9, within the inversion period W, the inversion potential LCCOMX changes from the higher potential VH to the lower potential VL. Therefore, the voltage applied to the liquid crystal element 50 is a negative voltage corresponding to the potential difference between the high potential VH after the change of the common potential LCCOM of the common electrode 54 and the low potential VL after the change of the potential VP of the pixel electrode 52. Set to -VA. That is, the polarity of the voltage applied to the liquid crystal element 50 is reversed before and after the change of the common potential LCCOM within the inversion period W while the liquid crystal element 50 is maintained at the gradation GW (white display).

[B] Unit period F in which polarity signal SP indicates negative polarity (FIGS. 10 to 12)
[B1] When gradation data D [n] designates gradation GB (black display) (FIG. 11)
In the unit period F in which the polarity signal SP indicates negative polarity, as shown in FIG. 10, the common potential LCCOM is set to the high potential VH and the inversion potential LCCOMX is set to the low potential VL. Further, when the gradation data D [n] indicates the gradation GB, as shown in the part (A) of FIG. 11, in the horizontal scanning period H [m], the gradation signal X [n] The adjustment potential VDATA [+] is set and the control signal Z [n] is set to the OFF potential VOFF.

  When the scanning signal Y [m] is set to the selection potential VSEL_ON in the horizontal scanning period H [m], the potential VP of the pixel electrode 52 is set to the positive side of the signal line 14 as shown in part (i) of FIG. The gradation potential changes to VDATA [+]. Therefore, as shown in part (A) of FIG. 11, the voltage applied to the liquid crystal element 50 includes the common potential LCCOM (high potential VH) of the common electrode 54 and the positive gradation potential VDATA [+] of the pixel electrode 52. Is set to a negative polarity voltage -VB (0 V). That is, the liquid crystal element 50 is controlled to the gradation GB (black display). On the other hand, since the first control switch TC1 is controlled to be turned off by supplying the off potential VOFF, the pixel electrode 52 and the inversion potential line 24 are electrically insulated. As shown in part (B) of FIG. 11, the above state is maintained even after the horizontal scanning period H [m] has elapsed.

  As shown in FIG. 10, in the inversion period W after the lapse of the unit period F, the common potential LCCOM changes from the high potential VH to the low potential VL and the inversion potential LCCOMX changes from the low potential VL to the high potential VH. To change. Since the pixel electrode 52 is in an electrically floating state, the potential VP of the pixel electrode 52 is changed from the higher potential VH in conjunction with the common potential LCCOM of the common potential line 22 as shown in part (i) of FIG. The low potential VL is changed and maintained. Therefore, the voltage applied to the liquid crystal element 50 is a positive voltage + VB (0 V) corresponding to the lower potential VL of the common electrode 54 and the lower potential VL of the pixel electrode 52, as shown in part (C) of FIG. ). That is, the gradation of the liquid crystal element 50 is maintained at the gradation GB (black display) before and after the change of the common potential LCCOM within the inversion period W. Since the first control switch TC1 is kept off, the change in the inversion potential LCCOMX within the inversion period W does not affect the potential VP of the pixel electrode 52.

[B2] When gradation data D [n] indicates gradation GB (black display) (FIG. 12)
When the gradation data D [n] indicates the gradation GW in the unit period F (LCCOM = VH) in which the polarity signal SP indicates negative polarity, in the horizontal scanning period H [m], the portion (A ), The gradation signal X [n] is set to the negative gradation potential VDATA [−]. Further, the control signal Z [n] is set to the ON potential VON, whereby the first control switch TC1 is controlled to be in the ON state. That is, in the horizontal scanning period H [m], the negative gradation potential VDATA [−] is supplied from the signal line 14 to the pixel electrode 52, and the lower potential VL of the inversion potential LCCOMX is supplied from the inversion potential line 24. The pixel electrode 52 is supplied via the first control switch TC1. Therefore, a negative voltage −VA corresponding to the potential difference between the higher potential VH of the common electrode 54 and the lower potential VL (negative gradation potential VDATA [−]) of the pixel electrode 52 is between the electrodes of the liquid crystal element 50. The liquid crystal element 50 is controlled to a gradation GW (white display). As shown in part (B) of FIG. 12, the above state is maintained even after the horizontal scanning period H [m] has elapsed.

  As shown in FIG. 10, in the inversion period W, the common potential LCCOM changes from the high potential VH to the low potential VL and the inversion potential LCCOMX changes from the low potential VL to the high potential VH. Since the connection between the pixel electrode 52 and the inversion potential line 24 is maintained even during the inversion period W, as shown in the part (ii) of FIG. 10 and the part (C) of FIG. Along with the inversion potential LCCOMX, the low potential VL changes to the high potential VH. That is, the applied voltage of the liquid crystal element 50 is set to a positive voltage + VA corresponding to the potential difference between the lower potential VL after the change of the common potential LCCOM and the higher potential VH after the change of the pixel electrode 52. That is, the polarity of the voltage applied to the liquid crystal element 50 is reversed before and after the change of the common potential LCCOM within the inversion period W while the liquid crystal element 50 is maintained at the gradation GW (white display).

  As described above, in the first embodiment, since the common potential LCCOM sequentially changes from one of the high potential VH and the low potential VL to the other, it is compared with the configuration in which the common potential LCCOM is fixed. It is possible to reduce the amplitude of the tone signal X [n] (potential difference between the positive gradation potential VDATA [+] and the negative gradation potential VDATA [−]). Further, since the amplitude of the gradation signal X [n] is reduced, the selection potential VSEL_ON necessary for controlling the selection switch TSL is also reduced. Therefore, there is an advantage that the withstand voltage performance required for the scanning line driving circuit 32 and the signal line driving circuit 34 is reduced and the power consumption is reduced.

  In the first embodiment, when the voltage VA (± VA) corresponding to the gradation GW is applied to the liquid crystal element 50, the pixel electrode is connected from the inversion potential line 24 within the inversion period W in which the common potential LCCOM varies. The inversion potential LCCOMX is supplied to 52. That is, the fluctuation of the common potential LCCOM within the inversion period W does not affect the potential VP of the pixel electrode 52. Therefore, the polarity of the voltage VA of the liquid crystal element 50 can be reversed before and after the change of the common potential LCCOM while the liquid crystal element 50 is maintained at the gradation GW. With the above configuration, since the discharge operation required by the technique of Patent Document 2 is unnecessary, there is an advantage that a reduction in contrast due to the discharge operation is suppressed. Further, since it is not necessary to incorporate in the pixel circuit PIX a storage circuit that holds data for instructing turning on / off of the electro-optic element, the pixel circuit PIX can be downsized (and further displayed images can be compared with the technique of Patent Document 3). (High definition) is also easy. Further, since the configuration of the pixel circuit PIX is simplified, it is possible to improve the yield as compared with the technique of Patent Document 3.

  Incidentally, the gradation (transmittance or reflectance) of the liquid crystal element 50 ideally saturates to the gradation GW when the applied voltage exceeds a predetermined threshold VTH, as shown by the solid line in FIG. However, in practice, as shown by the chain line in FIG. 4, the gradation of the liquid crystal element 50 may change depending on the voltage even within the range exceeding the threshold value VTH. Therefore, in the configuration in which the pixel electrode 52 is set in an electrically floating state after the gradation signal X [n] corresponding to the gradation GW is supplied, for example, due to the leakage of the current of the storage capacitor CS, the pixel electrode 52 When the potential VP fluctuates, the gradation of the liquid crystal element 50 may change. That is, it is difficult to set the gradation of the liquid crystal element 50 with high accuracy. On the other hand, in the first embodiment, the potential VP of the pixel electrode 52 is maintained at the inversion potential LCCOMX after application of the voltage VA corresponding to the gradation GW. Therefore, even when the liquid crystal element 50 having the characteristics shown by the chain line in FIG. 4 is employed, there is an advantage that the gradation (operating point) of the liquid crystal element 50 can be set with high accuracy.

<B: Second Embodiment>
FIG. 13 is a circuit diagram of the pixel circuit PIX of the electro-optical device 100 according to the second embodiment of the present invention. The pixel circuit PIX of the second embodiment has a configuration in which the capacitor line 26 is omitted from the pixel circuit PIX of the first embodiment and a control capacitor C2 is added. Detailed descriptions of elements of the second embodiment that have the same functions and functions as those of the first embodiment will be omitted.

  As shown in FIG. 13, the control capacitor C1 is interposed between the gate of the first control switch TC1 and the inversion potential line 24 in the m-th row. That is, the electrode EB1 is connected to the gate of the first control switch TC1, and the electrode EB2 is connected to the inversion potential line 24. On the other hand, the control capacitor C2 is interposed between the gate of the first control switch TC1 and the common potential line 22 in the m-th row. Specifically, the control capacitor C2 is composed of an electrode EC1 connected to the gate of the first control switch TC1, an electrode EC2 connected to the common potential line 22, and a dielectric between the electrodes.

  As described above, the inversion potential LCCOMX is supplied to the electrode EB2 of the control capacitor C1, and the common potential LCCOM is supplied to the electrode EC2 of the control capacitor C2. The common potential LCCOM and the inversion potential LCCOMX are in a relationship of inverting the potential. Specifically, when the inversion potential LCCOMX of the electrode EB2 changes from one of the higher potential VH and the lower potential VL to the other, the common potential LCCOM of the electrode EC2 changes in the reverse direction. Therefore, the action of the gate potential of the first control switch TC1 changing in conjunction with the common potential LCCOM of the electrode EC2 and the action of changing in conjunction with the inversion potential LCCOMX of the electrode EB2 are offset. That is, the function of holding the gate potential of the first control switch TC1 (the same function as the control capacitor C1 of the first embodiment) is realized in cooperation with the control capacitor C1 and the control capacitor C2.

  Even in the above configuration, the same operations and effects as those of the first embodiment are realized. In the second embodiment, since the M capacitor lines 26 of the first embodiment are omitted from the element unit 10, there is an advantage that the configuration of the element unit 10 is simplified.

<C: Modification>
Various modifications are added to the above embodiments. Specific modifications are exemplified below. Two or more aspects arbitrarily selected from the following examples may be merged.

(1) Modification 1
The configuration of the pixel circuit PIX is changed as appropriate. For example, in the above embodiments, the selection switch TSL and the second control switch TC2 are connected to the common scanning line 12. However, the selection switch TSL and the second control switch TC2 are different from each other after being connected to separate wirings. A configuration controlled by signals is also employed. However, according to the configuration in which the selection switch TSL and the second control switch TC2 are connected to the common scanning line 12, the element unit 10 is simplified (reduction in the number of wirings) compared to the configuration in which both are connected to separate wirings. ) Is realized.

  In each of the above embodiments, the common potential line 22, the inversion potential line 24, and the capacitance line 26 are formed independently for each row. However, one wiring (the common potential line 22, the inversion potential line 24, and the capacitance is provided for each row. A configuration in which the line 26) is formed and shared for driving the pixel circuits PIX in a plurality of rows is also employed. Further, if the capacitance value of the liquid crystal element 50 is sufficiently secured, the storage capacitor CS can be omitted. Further, for example, if a capacitance associated with the gate of the first control switch TC1 (for example, a gate capacitance or a parasitic capacitance of the first control switch TC1) is sufficiently secured, the control capacitor C1 (the control capacitor C2 of the second embodiment). ) May be omitted.

(2) Modification 2
Each of the above forms is the same for the electro-optical device 100 employing the normally white mode liquid crystal element 50 in which the gradation is highest (white) when the voltage between the pixel electrode 52 and the common electrode 54 is zero. Applies to That is, the pixel electrode 52 is set in an electrically floating state during the inversion period W when the gradation data D [n] indicates the gradation GW corresponding to white (when the voltage ± VB is applied to the liquid crystal element 50). The inversion potential LCCOMX is supplied to the pixel electrode 52 in the inversion period W when the gradation data D [n] indicates the gradation GB corresponding to black (when the voltage ± VA is applied to the liquid crystal element 50). The That is, in the driving methods in the above embodiments, when the voltage ± VA is applied to the liquid crystal element 50, the first control switch TC1 is controlled to be in an ON state (that is, the pixel electrode 52 and the inversion potential line 24 are connected). ), When applying a voltage ± VB different from the voltage ± VA to the liquid crystal element 50, the first control switch TC1 is controlled to be turned off (that is, the pixel electrode 52 and the inversion potential line 24 are insulated). It is included.

(3) Modification 3
In each of the above embodiments, when the voltage ± VA is applied to the liquid crystal element 50, the first control switch TC1 is in the ON state from the elapse of the horizontal scanning period H [m] until the start of the next horizontal scanning period H [m]. Maintained. However, since the change in the potential VP of the pixel electrode 52 due to the common potential LCCOM becomes noticeable when the common potential LCCOM changes, during a predetermined period (for example, the inversion period W) including the change in the common potential LCCOM. If the inversion potential LCCOMX is supplied to the pixel electrode 52, the expected effect of the present invention is realized regardless of the conduction / non-conduction between the pixel electrode 52 and the inversion potential line 24 in other periods. Is done. However, from the viewpoint of preventing fluctuations in the potential VP of the pixel electrode 52 due to factors other than fluctuations in the common potential LCCOM (for example, current leakage in the storage capacitor CS and the selection switch TSL), the voltage ± When VA is applied, it is preferable to supply the inversion potential LCCOMX to the pixel electrode 52 even during a period other than the inversion period W as illustrated in the above embodiments.

(4) Modification 4
The cycle of fluctuation of the common potential LCCOM and the inversion potential LCCOMX is arbitrarily changed. For example, a configuration in which the common potential LCCOM and the inversion potential LCCOMX are changed from one of the higher potential VH and the lower potential VL to the other for each subfield SF (configuration in which the subfield SF is a unit period for polarity inversion) is also employed. The

(5) Modification 5
The liquid crystal element 50 is an example of an electro-optical element. For example, the structure which substituted the electrophoretic element and the light emitting element (for example, organic EL element) by the liquid crystal element 50 of each above form is also employ | adopted. In other words, the electro-optical element is included as a driven element whose gradation (optical characteristics such as transmittance and luminance) changes according to an electrical action such as application of voltage (electric field) or supply of current. .

<D: Application example>
Next, electronic devices using the electro-optical device 100 according to each of the above aspects will be described. FIGS. 14 to 16 show forms of electronic devices that employ the electro-optical device 100 as a display device.

  FIG. 14 is a perspective view illustrating a configuration of a portable personal computer that employs the electro-optical device 100. The personal computer 2000 includes an electro-optical device 100 that displays various images, and a main body 2010 on which a power switch 2001 and a keyboard 2002 are installed.

  FIG. 15 is a perspective view illustrating a configuration of a mobile phone to which the electro-optical device 100 is applied. The cellular phone 3000 includes a plurality of operation buttons 3001 and scroll buttons 3002, and the electro-optical device 100 that displays various images. By operating the scroll button 3002, the screen displayed on the electro-optical device 100 is scrolled.

  FIG. 16 is a perspective view illustrating a configuration of a personal digital assistant (PDA) to which the electro-optical device 100 is applied. The portable information terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the electro-optical device 100 that displays various images. When the power switch 4002 is operated, various information such as an address book and a schedule book are displayed on the electro-optical device 100.

  The electronic apparatus to which the electro-optical device according to the invention is applied includes, in addition to the apparatuses illustrated in FIGS. 14 to 16, a projector, a digital still camera, a television, a video camera, a car navigation device, a pager, an electronic notebook, Examples include electronic paper, calculators, word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, devices equipped with touch panels, and the like.

DESCRIPTION OF SYMBOLS 100 ... Electro-optical device, 10 ... Element part, PIX ... Pixel circuit, 12 ... Scanning line, 14 ... Signal line, 16 ... Control line, 22 ... Common potential line, 24 ... Inversion potential , 26... Capacitance line, 30... Drive circuit, 32... Scan line drive circuit, 34... Signal line drive circuit, 42. ... Common electrode, 56 ... Liquid crystal, TSL ... Selection switch, TC1 ... First control switch, TC2 ... Second control switch, CS ... Holding capacity, C1, C2 ... Control capacity, 62 ... Distribution circuit, 621 ... selection circuit, 623 ... first latch circuit, 625 ... second latch circuit, 64 ... output circuit, U [1] to U [N] ... unit circuit, 641 ... potential selection Circuit, 643... Potential selection circuit.

Claims (9)

An inversion potential line that is supplied with an inversion potential that sequentially changes every unit period from one of the high potential and the low potential to the other;
A common potential that is set to the low potential in the unit period in which the inversion potential becomes the high potential and supplied to the high potential in the unit period in which the inversion potential becomes the low potential is supplied. An electro-optic element including a common electrode and a pixel electrode,
A driving method of an electro-optical device comprising: a first control switch that controls connection between the pixel electrode and the inversion potential line;
While supplying a gradation potential corresponding to a specified gradation to the pixel electrode in the unit period,
In the case where a gradation potential is supplied at which the voltage between both electrodes of the electro-optic element is the first voltage, the first control switch is turned on during a period including the time when the common potential fluctuates after the supply of the gradation potential. Control to ON state,
When a gradation potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage, the period including the time when the common potential fluctuates after the gradation potential is supplied. A method for driving the electro-optical device, wherein the first control switch is controlled to be in an OFF state. An inversion potential line that is supplied with an inversion potential that sequentially changes every unit period from one of the high potential and the low potential to the other;
A common potential that is set to the low potential in the unit period in which the inversion potential becomes the high potential and supplied to the high potential in the unit period in which the inversion potential becomes the low potential is supplied. An electro-optic element including a common electrode and a pixel electrode,
An electro-optical device comprising: a first control switch that controls connection between the pixel electrode and the inversion potential line. Comprising a drive circuit;
The drive circuit is
While supplying a gradation potential corresponding to a specified gradation to the pixel electrode in the unit period,
In the case where a gradation potential is supplied at which the voltage between both electrodes of the electro-optic element is the first voltage, the first control switch is turned on during a period including the time when the common potential fluctuates after the supply of the gradation potential. Control to ON state,
When a gradation potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage, the period including the time when the common potential fluctuates after the gradation potential is supplied. The electro-optical device according to claim 2, wherein the first control switch is controlled to be in an OFF state. A control line to which a control signal for controlling the first control switch is supplied;
A second control switch for controlling connection between the gate of the first control switch and the control line;
The electro-optical device according to claim 2, further comprising: a first control capacitor that holds a potential of the gate of the first control switch. A common potential line to which the common potential is supplied;
A storage capacitor interposed between the common potential line and the pixel electrode;
A second control capacitor interposed between the gate of the first control switch and the common potential line;
The electro-optical device according to claim 4, wherein the first control capacitor is interposed between a gate of the first control switch and the inversion potential line. Crossing scan lines and signal lines;
A selection switch for connecting the signal line and the pixel electrode when the scanning line is selected;
The electro-optical device according to claim 4, wherein the selection switch and the second control switch are controlled by a common signal. A plurality of scanning lines and a plurality of signal lines intersecting each other;
An inversion potential line that is supplied with an inversion potential that sequentially changes every unit period from one of the high potential and the low potential to the other;
A plurality of pixel circuits arranged corresponding to each intersection of the plurality of scanning lines and the plurality of signal lines;
A drive circuit for driving each of the pixel circuits,
Each of the plurality of pixel circuits is
A common potential that is set to the low potential in the unit period in which the inversion potential becomes the high potential and supplied to the high potential in the unit period in which the inversion potential becomes the low potential is supplied. An electro-optic element including a common electrode and a pixel electrode,
A selection switch for connecting the signal line and the pixel electrode when the scanning line is selected;
A first control switch for controlling connection between the pixel electrode and the inversion potential line;
The drive circuit is
While each of the plurality of scanning lines is sequentially selected in the unit period, a gradation potential corresponding to a designated gradation of each pixel circuit corresponding to the scanning line is supplied to each of the plurality of signal lines. ,
For each of the plurality of pixel circuits,
In the case where a gradation potential is supplied at which the voltage between both electrodes of the electro-optic element is the first voltage, the first control switch is turned on during a period including the time when the common potential fluctuates after the supply of the gradation potential. Control to ON state,
When a gradation potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage, the period including the time when the common potential fluctuates after the gradation potential is supplied. An electro-optical device that controls the first control switch to an OFF state.   An electronic apparatus comprising the electro-optical device according to claim 2. An inversion potential line that is supplied with an inversion potential that sequentially changes every unit period from one of the high potential and the low potential to the other;
A common potential that is set to the low potential in the unit period in which the inversion potential becomes the high potential and supplied to the high potential in the unit period in which the inversion potential becomes the low potential is supplied. An electro-optic element including a common electrode and a pixel electrode,
A drive circuit for an electro-optical device comprising: a first control switch that controls connection between the pixel electrode and the inversion potential line;
While supplying a gradation potential corresponding to a specified gradation to the pixel electrode in the unit period,
In the case where a gradation potential is supplied at which the voltage between both electrodes of the electro-optic element is the first voltage, the first control switch is turned on during a period including the time when the common potential fluctuates after the supply of the gradation potential. Control to ON state,
When a gradation potential is supplied such that the voltage between both electrodes of the electro-optic element is a second voltage different from the first voltage, the period including the time when the common potential fluctuates after the gradation potential is supplied. A drive circuit for the electro-optical device that controls the first control switch to an OFF state.

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