JP2008033362A - Method for driving electro-optical panel, electro-optical device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain high image quality even when a field frequency is dynamically changed. <P>SOLUTION: In an image display area AA, control lines 4a are arranged respectively according to scanning lines 3a, and TFTs 50, 51, a pixel electrode 9a and a storage capacitor 52 are arranged at each intersection of the data lines 6a and the scanning lines 3a. A control signal SC supplied through the control line 4a controls the TFT 51 for an on/off operation. A timing signal generator circuit 300 activates the control signal SC when a field frequency is not higher than 60 Hz and deactivates the control signal SC when the frequency exceeds 60 Hz. Thereby, whether or not to connect the storage capacitor 52 to the pixel electrode 9a is controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electro-optical panel or a driving method thereof, an electro-optical device, and an electronic apparatus.

  A conventional electro-optical panel, for example, an active matrix liquid crystal display panel, is generally composed of an element substrate, a counter substrate facing the element substrate, and liquid crystal filled between the substrates. In the element substrate, a plurality of data lines, a plurality of scanning lines, and thin film transistors (hereinafter referred to as TFTs) are provided on each of the pixel electrodes arranged in a matrix corresponding to the intersections thereof, A common electrode and a color filter are formed on the counter substrate.

  FIG. 18 is a circuit diagram showing an equivalent circuit of a certain pixel used in a conventional electro-optical panel. As shown in this figure, the pixel includes a TFT 1 and a liquid crystal capacitor 2 and a storage capacitor 3 connected to its drain electrode. The gate electrode of the TFT 1 is connected to the scanning line 4, while its source electrode is connected to the data line 5. The liquid crystal capacitor 2 is configured by sandwiching liquid crystal between the pixel electrode and the common electrode.

  In such a configuration, when a scanning signal (selection voltage) is applied to the TFT 1 via the scanning line 4, the TFT 1 becomes conductive. When an image signal is applied to the pixel electrode via the data line 5 in this conductive state, a predetermined charge is accumulated in the liquid crystal capacitor 2 between the pixel electrode and the common electrode. When the TFT 1 is turned off by applying a non-selection voltage after charge accumulation, charge accumulation in the liquid crystal capacitor 2 is maintained. In this way, by controlling the amount of charge accumulated by driving each TFT 1, the alignment state of the liquid crystal changes for each pixel, and predetermined information can be displayed.

  However, since the off-resistance value of the TFT 1 is finite, the electric charge accumulated in the liquid crystal capacitor 2 is gradually discharged over time. The storage capacitor 3 is provided to increase the time constant of discharge. Thereby, the charge retention characteristics of the liquid crystal capacitor 2 can be improved. As a result, it is possible to improve the contrast ratio and further suppress the crosstalk in the vertical direction.

  By the way, since the field frequency of the image signal is 60 Hz in the NTSC system, the electro-optical panel is often driven at 60 Hz in synchronization therewith. However, depending on the application of the electro-optical panel, the field frequency may be as low as 30 Hz or 15 Hz, and conversely, the field frequency may be as high as 120 Hz or 240 Hz.

  Here, when the voltage of the data line 5 is written to the pixel, the TFT 1 is turned on in the selection period, and the voltage of the data line 5 is determined by the liquid crystal capacitance value, the holding capacitance value, and the on-resistance value of the TFT 1. It is written in the liquid crystal capacitor 2 according to the constant. Therefore, when the storage capacitor 3 is added to the liquid crystal capacitor 2, the writing time required for writing becomes long.

  That is, when the storage capacitor 2 is added, the voltage of the data line 5 cannot be sufficiently written to the liquid crystal capacitor 2 when the field frequency is high and the selection period is short. Conversely, the storage capacitor 2 is added. Otherwise, there is a problem that the write voltage cannot be held when the field frequency is low and the holding period is long.

  In other words, the conventional electro-optical panel has a storage capacitance value determined so as to correspond to a certain selection period and a storage period, and does not assume that these periods can be changed by changing a field frequency or the like. There was a problem.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to achieve both the writing of a voltage to a pixel and the holding of the written voltage even when the selection period and the holding period change.

  To achieve the above object, an electro-optical panel according to the present invention includes a first substrate on which a plurality of scanning lines and a plurality of data lines are formed, a second substrate facing the first substrate, An electro-optical material sandwiched between a first substrate and the second substrate, wherein the first substrate is formed by a plurality of controls formed corresponding to the scanning lines. Line, and corresponding to the intersection of the scanning line and the data line, and on / off is controlled based on a scanning signal supplied via the scanning line, and the data line and the pixel electrode A first switching element provided between the scanning line and the data line, each of which is provided corresponding to an intersection of the scanning line and the data line, and on / off is controlled based on a control signal supplied via the control line; Second switching provided between the pixel electrode and the storage capacitor Characterized in that it comprises a child.

  According to this electro-optical panel, the ON / OFF of the second switching element can be controlled by the control signal, so that the storage capacitor is connected to the pixel electrode as necessary, or the storage capacitor is disconnected from the pixel electrode. be able to. Accordingly, it is possible to change whether or not the storage capacitor is connected to the electro-optic material capacitor formed by the pixel electrode and the electro-optic material. The time constant when the voltage is taken into the pixel electrode from the data line via the first switching element is determined by the on-resistance value and the pixel capacitance value of the first switching element, while the time constant when each pixel holds the voltage. Is determined by the off-resistance value of the first switching element, the pixel capacitance value, and the like. Since the pixel capacitance value can be changed depending on whether or not the storage capacitor is connected to the electro-optic material capacitor, the voltage of the data line is applied to the pixel by generating a control signal according to the writing period or the holding period. It is possible to reliably write and hold the written voltage sufficiently. Thereby, even if the field frequency is dynamically changed, the image quality can be kept high.

  The electro-optical panel described above includes a first conversion unit that converts input image data into point-sequential image data, a second conversion unit that converts the point-sequential image data into line-sequential image data, and the line-sequential data. A data line signal supply unit that supplies each data line signal generated based on image data to each data line, and a scanning line drive that generates each scanning signal for sequentially selecting the scanning lines and supplies the scanning lines to each scanning line It is preferable to provide a part. In this case, since the drive circuit for driving the data line and the scanning line can be included in the electro-optical panel, it is not necessary to provide a drive circuit outside the electro-optical panel, and the apparatus using the electro-optical panel can be made compact. Can be achieved.

  Next, an electro-optical device according to the present invention includes the above-described electro-optical panel and a control signal generation unit that generates the control signal according to a field frequency. According to this electro-optical device, when the field frequency is high and the writing period is short, the second switching element can be controlled so as to cut the holding capacitor, and when the field frequency is low and the holding period is long, the holding capacitor is connected. Thus, the second switching element can be controlled. Therefore, even if the field frequency is dynamically changed, the image quality can be kept high.

Here, the control signal generation unit may generate control signals corresponding to the control lines and supply the control signals to the control lines. In this case, since it is possible to determine whether or not a storage capacitor is connected for each control line, more detailed control is possible.
The electro-optical device according to the present invention includes the above-described electro-optical panel and a control signal generation unit that generates the control signal according to whether the image to be displayed is a moving image or a still image. May be. According to this electro-optical device, when the image to be displayed is a moving image, the second switching element can be controlled so as to cut the storage capacitor. On the other hand, when the image to be displayed is a still image, the storage capacitor is reduced. The second switching element can be controlled to connect. Therefore, even if the property of the image to be displayed is dynamically changed, the image quality can be kept high.

  Next, an electro-optical panel according to the present invention includes a first substrate on which a plurality of scanning lines and a plurality of data lines are formed, a second substrate facing the first substrate, and the first substrate. And an electro-optic material sandwiched between the second substrate and the first substrate, wherein the first substrate includes a plurality of control lines formed corresponding to the scanning lines, Provided corresponding to the intersection of the scanning line and the data line, and on / off controlled based on a scanning signal supplied through the scanning line, and provided between the data line and the pixel electrode. The first switching element is provided corresponding to the intersection of the scanning line and the data line, and on / off is controlled based on a control signal supplied via the control line, and the pixel electrode A second switching element provided between the storage capacitor and the display A plurality of control circuits for generating each control signal to be supplied to each control line based on a common control signal indicating whether the image is a moving image or a still image and each scanning signal; It is characterized by that. According to the present invention, each control signal can be generated in units of control lines (in units of scanning lines), so it is possible to control whether or not the storage capacitors are connected in units of control lines.

  Here, the control circuit generates the control signal for turning off the second switching element when the common control signal indicates a moving image during an active period of the scanning signal, and the common control signal generates a still image. In the case of instructing, it is preferable to generate the control signal for turning on the second switching element, while generating the control signal so as to maintain the state in the immediately preceding active period in the inactive period of the scanning signal. .

  Further, the electro-optical panel described above includes a scanning line driving unit that generates the scanning signals for sequentially selecting the scanning lines and supplies the scanning lines to the scanning lines only during a period in which an enable signal supplied from the outside is active. It is preferable to provide.

  The first switching element and the second switching element are preferably thin film transistors. The thin film transistor has an advantage that it can be formed on a glass substrate or the like.

  Next, an electro-optical device according to the present invention switches and displays a moving image and a still image in field units, and the above-described electro-optical panel and the image to be displayed are a moving image or a still image. Accordingly, a common control signal generation unit that generates a common control signal that changes a binary signal level in units of fields and instructs a moving image at one signal level and a still image at the other signal level; In the moving image display period, the enable signal is generated to be active, while in the still image display period, the first field is active, the subsequent field or fields are inactive, and the active signal is inactive at a fixed period. And an enable signal generation unit that generates the enable signal so as to repeat active.

  According to the present invention, writing and holding can be performed in units of one field during the moving image display period, and one set of the writing period of one field and the holding period of a plurality of fields can be combined in the still image display period. The electro-optical panel can be driven as a cycle. Therefore, in the still image display, since the writing rate can be reduced, power consumption can be reduced.

  Here, the common control signal generation unit changes the signal level of the common control signal during a vertical blanking period, and the enable signal generation unit switches the switching between the active period and the inactive period of the enable signal. Preferably during the ranking period. Since the scanning line is not selected in the vertical blanking period, the quality of the display image can be improved.

  Next, an electro-optical device according to the present invention switches between a moving image and a still image for each scanning line and displays the moving image display period corresponding to the above-described electro-optical panel and the moving image area. Depending on whether it is the still image display period corresponding to the image area, the binary signal level is changed, and the common control signal for instructing the moving image at one signal level and the still image at the other signal level is generated. And the common control signal generation unit that generates the enable signal so as to be active in each moving image display period of each field, while the first field is active in each still image display period of each field. The enable signal is generated so as to be inactive in one or a plurality of fields subsequent to, and to repeat active and inactive at regular intervals. Characterized by comprising a Buru signal generator.

  According to the present invention, when there is a part that displays a moving image in a part of the display screen and there is a part that displays a still image in the other part, while the storage area is disconnected in the moving image area, A storage capacitor can be connected in the still image area. In addition, since the enable signal is always active in the moving image area, each scanning line is sequentially selected and the voltage of the data line is written to the electro-optic material capacitance. In the still image area, the enable signal is active at a constant cycle. After writing in the field, it can be held in the subsequent field. That is, in the still image area, since the writing rate can be reduced, power consumption can be reduced.

Here, the common control signal generation unit changes a signal level of the common control signal during a vertical blanking period or a horizontal blanking period, and the enable signal generation unit performs an inactive and an inactive period of the enable signal. It is desirable to switch the period during the vertical blanking period or the horizontal blanking period.
Since the scanning line is not selected in the vertical blanking period or the horizontal blanking period, the quality of the display image can be improved.

  Next, in the electro-optical panel driving method according to the present invention, the plurality of scanning lines, the plurality of data lines, and the intersections of the scanning lines and the data lines are arranged in a matrix. A method for displaying an image on an electro-optical panel having a first capacitor and a second capacitor, wherein the field frequency of the image to be displayed is determined to be higher or lower than a predetermined frequency, and the field When the frequency is high, the first capacitor and the second capacitor are disconnected, the scan lines are sequentially selected, and the voltage of the data line is written to the first capacitor, and the field frequency is low Is characterized in that the first capacitor and the second capacitor are connected, the scanning lines are sequentially selected, and the voltage of the data line is written into the first capacitor and the second capacitor. According to the present invention, since it is possible to determine whether the first capacitor and the second capacitor are connected or not according to the field frequency, the image quality can be improved even if the field frequency is dynamically changed. Quality can be kept.

  Next, in the electro-optical panel driving method according to the present invention, the plurality of scanning lines, the plurality of data lines, and the intersections of the scanning lines and the data lines are arranged in a matrix. A method for displaying an image on an electro-optical panel having a first capacitor and a second capacitor, wherein whether the image to be displayed is a moving image or a still image is determined, and the image to be displayed is a moving image If the first capacitor and the second capacitor are not connected, the scanning lines are sequentially selected and the voltage of the data line is written to the first capacitor, and the image to be displayed is stationary. In the case of an image, the first capacitor and the second capacitor are connected, the scanning lines are sequentially selected, and the voltage of the data line is written into the first capacitor.

  According to the present invention, it is possible to determine whether the first capacitor and the second capacitor are connected or not according to whether the image to be displayed is a moving image or a still image. Even if the image is changed, the image quality can be kept high.

  Next, in the electro-optical panel driving method according to the present invention, the plurality of scanning lines, the plurality of data lines, and the intersections of the scanning lines and the data lines are arranged in a matrix. A method for switching and displaying a moving image and a still image in a field unit on an electro-optical panel having a first capacitor and a second capacitor, wherein the pixel electrode and the With the two capacitors disconnected, the scanning lines are sequentially selected and the voltage of the data line is written to the first capacitor. In each field where a still image is to be displayed, the first capacitor and the second capacitor are displayed. In the first field, the scanning lines are sequentially selected, and the voltage of the data line is written to the first capacitor and the second capacitor. Holding said first capacitor and said second voltage written to the capacitor made unselected 査線, and repeating the holding and writing in a constant cycle.

  According to the present invention, it is possible to determine whether the first capacitor and the second capacitor are connected or not according to whether the image to be displayed is a moving image or a still image. Even when moving images and still images are changed, the image quality can be kept high.

  Next, in the electro-optical panel driving method according to the present invention, the plurality of scanning lines, the plurality of data lines, and the intersections of the scanning lines and the data lines are arranged in a matrix. A method for switching a moving image and a still image to be displayed on a scanning line unit on an electro-optical panel having a first capacitor and a second capacitor, wherein the pixel electrode And the second capacitor are disconnected, the respective scanning lines are sequentially selected, and the voltage of the data line is written to the first capacitor. For each scanning line corresponding to a still image display, the first capacitor and the second capacitor are The second capacitor is connected, and in the first field, the scanning lines are sequentially selected and the voltage of the data line is written to the first capacitor and the second capacitor, and in the one or more fields that follow this, Each scanning line Said first capacitor and voltage written in the second volume was retained as a non-selection, and repeating the holding and writing in a constant cycle.

  According to the present invention, when there is a part that displays a moving image in a part of the display screen and there is a part that displays a still image in the other part, the second capacitor is disconnected in the moving image area. In the still image area, the second capacitor can be connected. In addition, since the enable signal is always active in the moving image area, each scanning line is sequentially selected and the voltage of the data line is written to the first capacitor. In the still image area, the enable signal becomes active at a constant period. After writing, it can be held in the subsequent field. That is, in the still image area, since the writing rate can be reduced, power consumption can be reduced.

  Next, an electronic apparatus according to the present invention includes the above-described electro-optical device, and includes, for example, a viewfinder used in a video camera, a mobile phone, a notebook computer, a video projector, and the like.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<1. First Embodiment>
<1-1: Overall Configuration of Liquid Crystal Device>
First, as an electro-optical device according to the present invention, a liquid crystal device using liquid crystal as an electro-optical material will be described as an example. The main part of the liquid crystal device is, as will be described later, an element substrate on which a TFT is formed as a switching element and a counter substrate are attached to each other with the electrode forming surfaces facing each other and maintaining a certain gap. A liquid crystal panel AA in which liquid crystal is sandwiched is provided.

FIG. 1 is a block diagram showing the overall configuration of the liquid crystal device according to the first embodiment.
The liquid crystal device includes an image display area A, a data line driving circuit 100, and a scanning line driving circuit 200 on an element substrate of the liquid crystal panel AA, and a timing generation circuit 300 as an external processing circuit of the liquid crystal panel AA. ing.

  The input image data Din supplied to the liquid crystal device is in a 3-bit parallel format. In this example, in order to simplify the following description, the input image data Din is described as corresponding to one color. However, the present invention is not limited to this and corresponds to the three primary colors of RGB. Of course, it may be.

  Here, the timing generation circuit 300 synchronizes with the input image data Din, the Y clock signal YCK, the inverted Y clock signal YCKB, the X clock signal XCK, the inverted X clock signal XCKB, the Y transfer start pulse DY, and the X transfer start pulse DX. And the latch pulse LAT and the like are generated and supplied to the data line driving circuit 100 and the scanning line driving circuit 200.

  In addition, the timing generation circuit 300 generates a control signal SC for controlling whether a storage capacitor 52 described later is connected to or disconnected from the pixel electrode 9a (liquid crystal capacitor LC), and outputs the control signal SC to the image display area A. ing. More specifically, the timing generation circuit 300 detects a field frequency corresponding to the driving method, compares it with a predetermined reference frequency, and generates a control signal SC based on the comparison result. In this example, the reference frequency is 60 Hz, and when the frequency is 60 Hz or less, an H level control signal SC that instructs connection is generated, while when the frequency exceeds 60 Hz, an L level control signal SC that instructs disconnection is generated. In the present embodiment, the field frequency is a frequency given by 1 / Tx, where Tx is one period required to sequentially select all the scanning lines 3a.

<1-2: Image display area>
Next, as shown in FIG. 1, in the image display area A, m scanning lines 3a and control lines 4a are formed in parallel along the X direction, while n data lines 6a. Are arranged in parallel along the Y direction. In the vicinity of the intersection of the scanning line 3a and the data line 6a, the gate electrode of the TFT 50 is connected to the scanning line 3a, while the source electrode of the TFT 50 is connected to the data line 6a, and the drain electrode of the TFT 50 is connected to the pixel. It is connected to the electrode 9a. The gate electrode of the TFT 51 is connected to the control line 4 a, the source electrode of the TFT 51 is connected to the pixel electrode 9 a, and the drain electrode of the TFT 51 is connected to the storage capacitor 52.

  Each pixel includes TFTs 50 and 51, a storage capacitor 52, and a liquid crystal capacitor LC. The liquid crystal capacitor LC is composed of a pixel electrode 9a, a counter electrode (described later) formed on the counter substrate, and a liquid crystal sandwiched between these electrodes. As a result, the pixels are arranged in a matrix corresponding to each intersection of the scanning line 3a and the data line 6a. The TFTs 50 and 51 in this example are N-channel transistors, which are turned on when the gate voltage is at the H level, and turned off when the gate voltage is at the L level. Therefore, by controlling the gate voltage of the TFT 50, the data line signal supplied to the data line 6a can be written to the liquid crystal capacitor LC, and by further controlling the gate voltage of the TFT 51, the storage capacitor 52 is made to be a liquid crystal capacitor. It is possible to control whether to connect to or disconnect from the LC.

  The scanning signals Y1, Y2,..., Ym are applied to each scanning line 3a to which the gate of the TFT 50 is connected in a pulse-sequential manner. Therefore, when a scanning signal is supplied to a certain scanning line 3a, the TFT 50 connected to the scanning line 3a is turned on, so that data line signals X1, X2,. Xn is sequentially written in the corresponding pixels and then held for a predetermined period.

  Here, since the orientation and order of liquid crystal molecules change according to the voltage level applied to each pixel, gradation display by light modulation becomes possible. For example, in the normally white mode, the amount of light passing through the liquid crystal is limited as the applied voltage increases. In the normally black mode, the amount of light that passes through the liquid crystal is reduced as the applied voltage increases. Then, light having contrast according to the gradation to be displayed is emitted for each pixel. For this reason, a predetermined display is possible.

  Further, as described above, the control signal SC supplied to the control line 4a becomes H level when the field frequency is 60 Hz or less. Therefore, when the field frequency is low, the TFT 51 is turned on and the storage capacitor is turned on. 52 is added in parallel to the liquid crystal capacitor LC. On the other hand, the control signal SC becomes L level when the field frequency exceeds 60 Hz. Therefore, when the field frequency is high, the TFT 51 is turned off and the storage capacitor 52 is disconnected from the liquid crystal capacitor LC. Become.

  Therefore, the pixel capacitance value Cg when the field frequency is low is given as the sum of the liquid crystal capacitance value CLC and the holding capacitance value CST. This increases the writing time for writing the data line signal to the pixel, but can improve the holding characteristics. On the other hand, the pixel capacitance value Cg when the field frequency is high matches the liquid crystal capacitance value CLC. Thereby, the writing time for writing the data line signal to the pixel can be shortened. In this case, the holding characteristics of the liquid crystal capacitor LC are lowered, but the holding period when the field frequency is high is shortened, so that the voltage change of the liquid crystal capacitor LC is small and does not cause a problem in practice.

<1-3: Data Line Drive Circuit>
Next, the data line driving circuit 100 includes an X shift register 110, image data supply lines L1 to L3 to which input image data Din0 to Din2 are supplied, switches SW1 to SW3n, a first latch 120, a first latch 120, as shown in FIG. 2 latch 130 and D / A converter 140.

  First, the X shift register 110 sequentially generates X sampling pulses SR1, SR2,..., SRn by sequentially shifting the X transfer start pulse DX in accordance with the X clock XCK and the inverted X clock XCKB.

  Next, the image data supply lines L1 to L3 are connected to the first latch 120 via the switches SW1 to SW3n, and sampling pulses SR1, SR2,... SRn are connected to the control input terminals of the switches SW1 to SW3n. Is to be supplied. The switches SW1 to SW3n have a set of three in correspondence with the input image data Din0 to Din2. Therefore, the input image data Din0 to Din2 are simultaneously supplied to the first latch 120 in synchronization with the sampling pulses SR1, SR2,.

  Next, the first latch 120 latches the input image data Din0 to Din2 supplied from the switches SW1 to SW3n, thereby obtaining the dot sequential image data d1 to dn scanned in a dot sequential manner. It is done. The second latch 130 latches each point sequential image data d1 to dn of the first latch 120 by a latch pulse LAT. Here, the latch pulse LAT is a signal that becomes active every horizontal scanning period. Therefore, the second latch 130 generates line sequential image data D1 to Dn by aligning the phases of the dot sequential image data d1 to dn for each horizontal scanning period.

  Next, the D / A converter 140 converts the 3-bit line sequential image data D1 to Dn from digital signals to analog signals, generates the data line signals X1 to Xn, and supplies them to the data lines 6a. is doing. In other words, the D / A converter 140 functions as a data line signal supply unit that supplies each data line signal X1 to Xn generated based on each line sequential image data D1 to Dn to each data line 6a.

<1-4: Configuration example of liquid crystal panel>
Next, the overall configuration of the liquid crystal panel AA according to the electrical configuration described above will be described with reference to FIGS. Here, FIG. 3 is a perspective view showing the configuration of the liquid crystal panel AA, and FIG. 4 is a sectional view taken along the line ZZ ′ in FIG.

  As shown in these drawings, the liquid crystal panel AA includes an element substrate 151 such as glass or a semiconductor on which pixel electrodes 9a are formed, and a transparent counter substrate 152 such as glass on which a common electrode 158 is formed. In addition, the sealing material 154 mixed with the spacer 153 is bonded so that the electrode forming surfaces face each other while maintaining a certain gap, and a liquid crystal 155 as an electro-optical material is sealed in the gap. Note that the sealant 154 is formed along the periphery of the counter substrate 152, but a part thereof is opened to enclose the liquid crystal 155. Therefore, after the liquid crystal 155 is sealed, the opening is sealed with the sealing material 156.

  Here, on the opposite surface of the element substrate 151 and on the outer side of the sealing material 154, the data line driving circuit 100 described above is formed to drive the data line 6a extending in the Y direction. ing. Further, a plurality of connection electrodes 157 are formed on one side, and various signals from the timing generation circuit 300 and image data D0 to D2 are input. Further, a scanning line driving circuit 200 is formed on one side adjacent to the one side, and the scanning line 3a extending in the X direction is driven from both sides.

  On the other hand, the common electrode 158 of the counter substrate 152 is electrically connected to the element substrate 151 by a conductive material provided in at least one of the four corners of the bonding portion with the element substrate 151. In addition, the counter substrate 152 is provided with, for example, a color filter arranged in a stripe shape, a mosaic shape, a triangle shape, or the like according to the use of the liquid crystal panel AA. And a black matrix such as resin black in which carbon or titanium is dispersed in a photoresist, and third, a backlight for irradiating the liquid crystal panel AA with light. Particularly in the case of color light modulation, a black matrix is provided on the counter substrate 152 without forming a color filter.

  In addition, the opposing surfaces of the element substrate 151 and the counter substrate 152 are each provided with an alignment film or the like that is rubbed in a predetermined direction, and a polarizing plate (not shown) corresponding to the alignment direction on each back side. Are provided respectively. However, if a polymer-dispersed liquid crystal dispersed as fine particles in a polymer is used as the liquid crystal 155, the above-described alignment film, polarizing plate, and the like are not required. This is advantageous in terms of reducing power consumption.

  Instead of forming part or all of the peripheral circuits such as the data line driving circuit 100 and the scanning line driving circuit 200 on the element substrate 151, the peripheral circuit is mounted on a film using, for example, a TAB (Tape Automated Bonding) technique. The driving IC chip may be electrically and mechanically connected via an anisotropic conductive film provided at a predetermined position of the element substrate 151. The driving IC chip itself may be a COG (Chip On Grass). A technique may be used to electrically and mechanically connect to a predetermined position of the element substrate 151 via an anisotropic conductive film.

<1-5: Operation of liquid crystal device>
Next, the operation of the liquid crystal device will be described. FIG. 5 is a timing chart showing the overall operation of the liquid crystal device, and FIG. 6 is a timing chart showing the operation of writing the data line signal to the pixel. In these drawings, the vertical blanking period is omitted to simplify the description.

  First, when the Y transfer start pulse DY is supplied to the scanning line driving circuit 200, the scanning line driving circuit 200 sequentially transfers the Y transfer start pulse DY based on the Y clock signal YCK and the inverted Y clock signal YCKB. Scan line signals Y1, Y2,..., Ym shown in FIG. The active period of each of the scanning line signals Y1, Y2,..., Ym is one horizontal scanning period, which is sequentially shifted. Thereby, each scanning line 3a is sequentially selected.

  On the other hand, when the X transfer start pulse DX is supplied to the data line driving circuit 100, the X shift register 110 sequentially shifts the generated pulses and generates sampling pulses SR1, SR2,. The switches SW1 to SWn sample the input image data Din based on the sampling pulses SR1, SR2,..., SRn, and the first latch 120 latches the sampling result, so that the dot sequential image data d1, d2,. , As shown in FIG.

  Thereafter, the second latch 130 latches the point sequential image data d1d1, d2,..., Dn at the start of the horizontal scanning period, thereby generating the line sequential image data D1, D2,. Is done. The line sequential image data D1, D2,..., Dn are DA-converted by the DA converter 140 and supplied to the data lines 6a as data line signals X1, X2,.

  Here, since the total number of scanning lines 3a is m, assuming that the field frequency is 60 Hz, a certain scanning signal Yj has an active period of 1 / (60 · m) as shown in FIG. Become. In this case, since the control signal SC becomes H level, the TFT 51 of each pixel is turned on, and the holding capacitor 52 is connected to the liquid crystal capacitor LC. Therefore, the pixel capacitance value Cg is Cg = CLC + CST. CLC is a liquid crystal capacitance value, and CST is a holding capacitance value. Here, when the on-resistance value of the TFT 50 is Ron and the off-resistance value is Roff, the voltage Vc on the pixel electrode side of the liquid crystal capacitor LC is in accordance with the time constant Ron · (CLC + CST) as shown in FIG. It rises relatively slowly from time t1, and becomes substantially constant before time t2 when the active period of the scanning signal Yj ends. At time t2, when the scanning signal Yj becomes L level and the TFT 51 is turned off, the voltage Vc decreases according to the time constant Roff · (CLC + CST). In this example, since the holding capacitor 52 is connected to the liquid crystal capacitor CLC, the writing time Tw for writing the image signal to the liquid crystal capacitor LC is relatively long, but the discharge time constant Roff · (CLC + CST) is large. Even if the holding period is long, the change voltage ΔVc of the voltage Vc can be reduced.

  Next, assuming that the field frequency is switched from 60 Hz to 120 Hz, a certain scanning signal Yj has an active period of 1 / (120 · m) as shown in FIG. In this case, since the control signal SC becomes L level, the TFT 51 of each pixel is turned off, and the storage capacitor 52 is separated from the liquid crystal capacitor LC. Therefore, the pixel capacitance value Cg is Cg = CLC. In this case, the voltage Vc on the pixel electrode side of the liquid crystal capacitor LC rises sharply from the time t1 according to the time constant Ron · CLC as shown in FIG. 4D, and the time when the active period of the scanning signal Yj ends. It becomes a substantially constant value before t2. At time t2, when the scanning signal Yj becomes L level and the TFT 51 is turned off, the voltage Vc decreases according to the time constant Roff · CLC. In this example, since the storage capacitor 52 and the liquid crystal capacitor CLC are disconnected, the write time Tw for writing the data line signal to the liquid crystal capacitor LC is relatively short, but the time constant Roff · CLC of the discharge is small. However, since the holding period is substantially half compared with the case where the field frequency is 60 Hz, the change voltage ΔVc of the voltage Vc can be reduced.

That is, according to the present embodiment, whether or not the storage capacitor is connected to the liquid crystal capacitor is controlled according to the field frequency, so that the applied voltage of the liquid crystal capacitor can be held well when the field frequency is low. In addition, when the field frequency is high, the data line signal can be reliably written in the liquid crystal capacitor in a short writing time.
This makes it possible to display an image with high quality even if the field frequency is varied.

<1-6: Modification of First Embodiment>
<1-6-1: Control signal supply method>
In the first embodiment described above, the common control signal SC is supplied to each control line 4a. However, the present invention is not limited to this, and a different control signal SC is supplied to each control line 4a. Then, on / off of the TFT 51 may be controlled in units of horizontal lines. This makes it possible to switch whether or not the storage capacitor 52 is connected to the liquid crystal capacitor LC for each control line 4a. In this case, m control signals SC need to be supplied to each control line 4a, but the control signal SC is generated based on the scanning signals Y1, Y2,..., Ym, or the scanning line driving circuit. As in the case of 200, a control line driving circuit including a shift register or the like may be provided separately to generate m control signals SC.

  Further, in this modification, in particular, a driving method in which one field period of the input image data Din is divided into a plurality of periods according to the weight of the bit and all the scanning lines 3a are sequentially selected for each period. Is preferred. In this case, since the time for each divided period changes according to the weight of the bit, the field frequency is different for each divided period, and the storage capacitor 52 is connected during the period when the field frequency is low. On the other hand, the storage capacitor 52 is disconnected during a period when the field frequency is high.

<1-6-2: Switching between video and still image by control signal>
In the first embodiment described above, when the field frequency is 60 Hz or less, the control signal SC is set to H level to connect the holding capacitor 52 to the liquid crystal capacitor LC, while when the field frequency exceeds 60 Hz. The control signal SC is set to L level to disconnect the holding capacitor 52 and the liquid crystal capacitor LC. However, the signal level of the control signal SC is switched depending on whether the image to be displayed is a moving image or a still image. Also good.

  In this case, the supply device of the input image data Din detects whether the image to be displayed is a moving image or a still image, generates a switching signal indicating the type of display image, and uses this to generate a timing generation circuit 300. The control signal SC may be generated based on the switching signal. Alternatively, the timing generation circuit 300 may determine the type of moving image / still image based on the input image data Din and generate the control signal SC based on the determination result. A known discrimination method can be used to discriminate the type of moving image / still image. For example, a correlation value indicating the correlation between fields is detected, and the correlation value is compared with a threshold value. While it is determined as a still image, it may be determined as a moving image if the correlation is low.

  By the way, when the signal level of the control signal SC is changed, since the storage capacitor 52 is connected / disconnected, the display image is affected. For this reason, the timing for changing the signal level of the control signal SC is performed in a period that does not affect the image display. Specifically, it is desirable to carry out during the vertical blanking period.

  FIG. 7 is a timing chart showing an example of the switching timing of the control signal SC. In this example, a moving image is displayed during the period from the first field f1 to the sixth field f6, while a still image is displayed after the seventh field f7. In this example, the moving image is displayed at 60 Hz, and the still image is displayed at 15 Hz. The vertical blanking signal VB shown in this figure indicates a vertical blanking period when the signal level is H level. This signal is generated inside the timing generation circuit 300 and is used to generate a Y transfer start pulse DY and the like. The scanning signals Y1, Y2,... Ym are sequentially activated (H level) during the period when the vertical blanking signal VB is at L level. Here, the control signal SC changes from the L level to the H level in the vertical blanking period of the seventh field f7. That is, the signal level of the control signal SC is selected to transition during the period in which the TFTs 50 of all the pixels are off. Therefore, during the period in which the data signals X1, X2,... Xn are taken into each pixel, the signal level of the control signal SC does not change, so that the connection / disconnection of the storage capacitor 52 is not switched in this period. As a result, since the data signals X1, X2,... Xn can be stably taken into each pixel, the quality of the display image is not impaired at the switching timing even when switching from a moving image to a still image.

<2. Second Embodiment>
Next, a second embodiment according to the present invention will be described with reference to the drawings.

<2-1: Overall configuration of liquid crystal device>
FIG. 8 is a block diagram showing the overall configuration of the liquid crystal device according to the second embodiment. In this liquid crystal device, a scanning line driving circuit 300B is used instead of the timing generation circuit 300, a scanning line driving circuit 200B is used instead of the scanning line driving circuit 200 in the liquid crystal display panel BB, and control circuits C1, C2, ... Except for the addition of Cm, the configuration is the same as that of the liquid crystal device of the first embodiment shown in FIG.

  The timing generation circuit 300B is configured in the same manner as the timing generation circuit 300 of the first embodiment except that the enable signal EN is generated. The enable signal EN is controlled to activate each scanning signal Y1, Y2,... Ym when the signal level is H level, and to activate each scanning signal Y1, Y2,. To do.

<2-2: Scanning line driving circuit>
FIG. 9 is a block diagram of the scanning line driving circuit 200B. As shown in this figure, the scanning line driving circuit 200B includes the scanning line driving circuit 200 of the first embodiment and AND circuits A1, A2,... Am. Each output signal of the scanning line driving circuit 200 is supplied to one input terminal of each AND circuit A1, A2,... Am, and an enable signal EN is supplied to the other input terminal. Yes. Therefore, when the enable signal EN is at the H level, each scanning signal Y1, Y2,... Ym coincides with each output signal of the scanning line driving circuit 200. When the enable signal EN is at the L level, each scanning signal Y1, Y2,... Ym is at the L level (inactive).

  In the liquid crystal device shown in FIG. 8, the control signal SC is not supplied to the control lines 4a in common, but the control signals SC1, SC2,... SCm from the control circuits C1, C2,. Is to be supplied. Therefore, whether or not the storage capacitor 52 is added to the liquid crystal capacitor LC is controlled in units of scanning lines. In the following description, the control signal SC is referred to as a common control signal SC and is distinguished from the control signals SC1, SC2,.

<2-3: Control circuit>
FIG. 10 is a circuit diagram showing a configuration of the control circuit C1. The other control circuits C2 to Cm are configured similarly to the control circuit C1. As shown in this figure, the control circuit C1 includes inverters INV1 to INV3 and a switch SW. Here, the inverter INV3 has an inversion control input terminal. When an L level signal is supplied to the inversion control input terminal, the inverter INV3 functions as an inverting circuit, and when an H level signal is supplied to the inversion control input terminal. The output terminal is set to a high impedance state. Therefore, the inverter INV2 and the inverter INV3 function as a latch circuit when the scanning signal Y1 is at L level (inactive), and function as an inverting circuit when the scanning signal Y1 is at H level.

  The scanning signal Y1 is supplied to the control input terminal of the switch circuit SW, while the scanning signal Y1 is supplied to the inversion control input terminal via the inverter INV1. Accordingly, when the scanning signal Y1 is at the H level, the switch circuit SW is turned on, and the common control signal SC is supplied to the input terminal of the inverter INV2. When the scanning signal Y1 is at L level, the switch circuit SW is turned off, and the common control signal SC is not supplied to the input terminal of the inverter INV2. In this case, since the inverter INV2 and the inverter INV3 function as a latch circuit, the signal level of the control signal SC1 is held at the previous signal level.

  With the above configuration, the truth table of the control circuit C1 is as shown in FIG. As is apparent from this truth table, each control circuit C1 inverts and outputs the common control signal SC when the scanning signal Y1 becomes H level, while holding the previous state when the scanning signal Y1 is L level, SC1 is generated.

<2-4: Operation of liquid crystal device>
Next, the operation of the liquid crystal device according to the second embodiment will be described with reference to the drawings.

<2-4-1: Operation when switching between video and still image in field units>
First, the operation when switching between moving images and still images in the field unit for the entire screen will be described. Here, a case where a moving image is displayed in the first field f1 and the second field f2 and a still image is displayed after the third field f3 will be described as an example. FIG. 12 is a timing chart illustrating an operation example of the liquid crystal device. In this example, since a still image is displayed after the third field f3, the common control signal SC changes from the H level to the L level at time t3, which is the start timing of the third field f3. Strictly speaking, the signal level transition of the common control signal SC is performed in the vertical blanking period of the third field as described in the modification of the first embodiment with reference to FIG. Similarly, the signal level of the enable signal EN is also changed during the vertical blanking period.

  The enable signal EN becomes the H level in the first field f1 and the second field f2 that are the moving image display period, and becomes the H level in the four field period after the third field f3.

  Here, paying attention to the second field f2 which is the moving image display period, since the enable signal EN is at the H level in the period, the scanning signals Y1, Y2,... Ym sequentially become the H level similarly to the normal operation. . Therefore, each scanning line 3a is sequentially selected, and data signals X1, X2,... Xn are supplied to each pixel in units of scanning lines. In this case, since the common control signal SC is at the H level, each of the control signals SC1, SC2,... SCm is at the L level. For this reason, in this period, the TFT 51 is turned off and the storage capacitor 52 is not connected to the liquid crystal capacitor LC. Therefore, during the moving image display period, the load viewed from the data line driving circuit 100 is reduced.

  Next, paying attention to the third field f3, which is the first field in the still image display period, the enable signal EN is at the H level in the period, so that the scanning signals Y1, Y2,. Is done. On the other hand, the common control signal SC is at the L level during this period. As described above, each control circuit C1, C2,... Cm inverts and outputs the common control signal SC when each scanning signal Y1, Y2,. Since the state is maintained, as shown in FIG. 12, when each scanning signal Y1, Y2,... Ym transitions from L level to H level in the third field f3, each control signal SC1, SC2,. Then, it becomes H level and maintains that state. Accordingly, in the first field of the still image display period, the TFT 51 is turned on, the storage capacitor 52 is connected to the liquid crystal capacitor LC, and voltage is written to these.

  Next, paying attention to the fourth field f4, which is the second field in the still image display period, since the enable signal EN is at the L level during the period, the scanning signals Y1, Y2,... Ym are at the L level. Therefore, no voltage is written to each pixel during this period, and the control signals SC1, SC2,..., SCm are maintained at the H level, and the storage capacitor 52 remains connected to the liquid crystal capacitor LC.

  Next, in the fifth and sixth fields f5 and f6, which are the third and fourth fields in the still image display period, as in the third field f3, no voltage is written to each pixel, and the storage capacitor 52 is not liquid crystal. It remains connected to the capacitor LC. Thereafter, the period from the seventh field f7 to the tenth field f10 operates similarly to the period from the third field f3 to the sixth field f6.

  Therefore, in the still image display period, writing is performed at a rate of 1 field per 4 fields, and the written voltage is held in the other 3 fields. That is, in the still image display period, the field frequency can be substantially reduced to ¼ compared to the moving image display period. In this still image display period, since the storage capacitor 52 is connected to the liquid crystal capacitor LC, the voltage written to the pixel can be held well, and the writing operation per unit time is compared with the moving image display period. Therefore, power consumption can be reduced.

<2-4-2: Operation when displaying moving images and still images together on one screen>
Next, an operation in the case where a moving image and a still image are mixedly displayed on one screen will be described. Here, the scanning line 3a has m (= 2k, k is a natural number), and a moving image is displayed on the first to kth scanning lines 3a corresponding to the upper half of the screen, and corresponds to the lower half of the screen. A still image is displayed on the (k + 1) th to 2kth scanning lines 3a.

  FIG. 13 is a timing chart illustrating an operation example of the liquid crystal device. In this example, in each field f1 to f8, those first half periods are referred to as moving image display periods M1 to M8, and those latter half periods are referred to as still image display periods S1 to S8.

  In this example, while the moving image is displayed on the upper half of the screen and the still image is displayed on the lower half of the screen, the common control signal SC is at the L level in each moving image display period M1 to M8 as shown in FIG. It becomes H level in each still image display period S1 to S8. In this example, the signal level of the common control signal SC changes during one field period, but this is performed during the horizontal blanking period.

  FIG. 14 is a timing chart showing an example of switching timing of the common control signal SC. The horizontal blanking signal HB shown in this figure indicates a horizontal blanking period when the signal level is H level. This signal is generated inside the timing generation circuit 300B and is used to generate an X transfer start pulse DX and the like. The sampling signals SR1, SR2,... SRn are sequentially activated (H level) during a period when the horizontal blanking signal HB is at L level. Here, the common control signal SC changes from the H level to the L level in the horizontal blanking period of the (k + 1) th horizontal scanning period Hk + 1. That is, it is selected so that the signal level of the common control signal SC changes during the period in which the TFTs 50 of all the pixels are off. Therefore, during the period in which the data signals X1, X2,... Xn are taken into each pixel, the signal level of the common control signal SC does not change, and the connection / disconnection of the storage capacitor 52 is not switched in this period. As a result, since the data signals X1, X2,... Xn can be stably taken into each pixel, the quality of the display image is not impaired at the switching timing even when switching from a moving image to a still image.

  Next, returning to FIG. 13, the enable signal EN is always at the H level in each of the moving image display periods M1 to M8. Therefore, during these periods, the scanning signals Y1, Y2,... Yk are sequentially at the H level. In addition, the enable signal EN becomes H level in the still image display periods S1 and S5, and the enable signal EN becomes L level in the still image display periods S2 to S4 and S6 to S8. That is, in the still image display periods S1 to S8, the H level is set at a rate of one cycle in four cycles, such as H level → L level → L level → L level.

  Here, operations of the first field f1 and the second field f2 will be described in detail. First, in the video display periods M1 and M2, since the enable signal EN is at the H level, the scanning signals Y1, Y2,... Yk are sequentially activated, and the data signals X1, X2,. It is written in each pixel. In this case, since the common control signal SC is at the H level, the control signals SC1 to SCk are at the L level as shown in the figure, and the storage capacitor 52 is in a non-connected state. Therefore, voltage is written only to the liquid crystal capacitor LC for each pixel in the upper half of the screen.

  Next, since the enable signal EN is at the H level in the still image display period S1, the scanning signals Y1, Y2,... Yk are sequentially activated in the same manner as the moving image display period M1, and the data signals X1, X2 ... Xn is written to each pixel. In this case, since the common control signal SC is at the L level, the control signals SCk + 1 to SC2k are at the H level in synchronization with the rising timings of the scanning signals Y1, Y2,. 52 is connected. Therefore, voltage is written to the liquid crystal capacitor LC and the storage capacitor 52 for each pixel in the lower half of the screen.

  Next, in the still image display period S2, since the enable signal EN is at L level, each scanning signal Y1, Y2,... Yk maintains L level, so that the data signals X1, X2,. Never written. That is, this period acts as a holding period for holding the voltage written in the still image display period S1. In addition, since the control signals SCk + 1 to SC2k maintain the H level, the storage capacitor 52 remains connected to the liquid crystal capacitor LC.

  Further, in the still image display periods S3 and S4, as in the still image display period S2, the enable signal EN becomes L level, so that each pixel in the lower half of the screen holds the voltage and maintains the connection state of the holding capacitor 52. To do.

In this way, in the upper half area of the screen for displaying moving images, writing is performed for each field while the holding capacity 52 is disconnected as in the normal operation, while in the lower half area of the screen for displaying still images, the holding capacity is set. 52 can be connected and writing can be performed at a rate of 1 field per 4 fields. As a result, in the still image display area, writing is performed at a rate of one field in four fields, and the written voltage is held in the other three fields. That is, in the still image display basin, the field frequency can be substantially reduced to ¼ compared to the moving image display region.
In this still image display area, since the holding capacitor 52 is connected to the liquid crystal capacitor LC, the voltage written to the pixel can be held well, and the writing operation per unit time is compared with the moving image display area. Therefore, power consumption can be reduced.

<3. Application example>
<3-1: Configuration of element substrate>
In each of the above-described embodiments, the TFTs 51 and 52 constituting the pixel are described as examples using N-channel transistors. However, the present invention is not limited to this, and the TFTs 51 and 52 are P-channel transistors. Of course, a TFT may be used. In this case, the scanning signals Y1, Y2,..., Ym and the control signal SC may be generated so as to be active at the L level. Further, it can be used for a CMOS transistor.

  In each of the above-described embodiments, the element substrate 151 of the liquid crystal panels AA and BB is configured by a transparent insulating substrate such as glass, and a silicon thin film is formed on the substrate, and a source, drain, Although it has been described that the TFT in which the channel is formed constitutes the pixel switching element (TFT 50), the data line driving circuit 100, and the scanning line driving circuit 200, the present invention is not limited to this.

  For example, the element substrate 151 is composed of a semiconductor substrate, and a pixel switching element or various circuit elements are composed of insulated gate field effect transistors in which a source, a drain, and a channel are formed on the surface of the semiconductor substrate. Also good. When the element substrate 151 is formed of a semiconductor substrate in this manner, it cannot be used as a transmissive display panel. Therefore, the pixel electrode 9a is formed of aluminum or the like and used as a reflective type. Alternatively, the element substrate 151 may be a transparent substrate and the pixel electrode 9a may be a reflection type.

<3-2: Electronic equipment>
Next, the case where the above-described liquid crystal device is applied to various electronic devices will be described.

<3-2-1: Projector>
First, a projector using the liquid crystal panel AA as a light valve will be described. FIG. 15 is a plan view showing the configuration of the projector. As shown in this figure, a lamp unit 1102 including a white light source such as a halogen lamp is provided inside the projector 1100. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by three mirrors 1106 and two dichroic mirrors 1108 disposed therein, and a liquid crystal panel as a light valve corresponding to each primary color 100R, 100B and 100G, respectively. Here, the light of B color has a long optical path as compared with other R colors and G colors. Therefore, in order to prevent the loss, the light of B color passes through a relay lens system 1121 including an incident lens 1122, a relay lens 1123, and an exit lens 1124. Be guided.

  The configurations of the liquid crystal panels 100R, 100B, and 100G are the same as those of the liquid crystal panel AA described above, and are driven by R, G, and B primary color signals supplied from an image signal processing circuit (not shown). is there. The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In the dichroic prism 1112, the R and B light beams are refracted at 90 degrees, while the G light beam goes straight. Therefore, as a result of the synthesis of the images of the respective colors, a color image is projected onto the screen 1120 via the projection lens 1114.

  Here, paying attention to the display images by the liquid crystal panels 100R, 100B, and 100G, the display image by the liquid crystal panel 100G needs to be horizontally reversed with respect to the display images by the liquid crystal panels 100R and 100B. Therefore, the horizontal scanning direction is in the opposite direction between the liquid crystal panel 100G and the liquid crystal panels 100R and 100B. Since light corresponding to the primary colors R, G, and B is incident on the liquid crystal panels 100R, 100B, and 100G by the dichroic mirror 1108, it is not necessary to provide a color filter.

<3-2-2: Mobile computer>
Next, an example in which the liquid crystal panel AA is applied to a mobile personal computer will be described. FIG. 16 is a perspective view showing the configuration of this personal computer. In the figure, a computer 1200 includes a main body 1204 having a keyboard 1202 and a liquid crystal display unit 1206. The liquid crystal display unit 1206 is configured by adding a backlight to the back surface of the liquid crystal panel 100 described above.

<3-2-3: Mobile phone>
Further, an example in which the liquid crystal panel AA is applied to a mobile phone will be described. FIG. 17 is a perspective view showing the configuration of this mobile phone. In the figure, a cellular phone 1300 includes a liquid crystal panel AA in addition to a plurality of operation buttons 1302 as well as an earpiece 1304 and a mouthpiece 1306. The liquid crystal panel 100 is also provided with a backlight on the back as necessary.

  In addition to the electronic devices described with reference to FIGS. 15 to 17, the electronic devices include a liquid crystal television, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, and a word processor. , Workstations, videophones, POS terminals, devices with touch panels, and the like. Needless to say, the liquid crystal panel of each embodiment and further the electro-optical device can be applied to these various electronic devices.

  As described above, according to the present invention, it is possible to reliably write the voltage of the data line to the pixel and sufficiently hold the written voltage by generating the control signal according to the writing period and the holding period. It becomes. Thereby, even if the field frequency is dynamically changed, the image quality can be kept high.

1 is a block diagram illustrating an overall configuration of a liquid crystal device according to a first embodiment of the present invention. It is a block diagram which shows the structure of the data line drive circuit of the apparatus. It is a perspective view for demonstrating the structure of the liquid crystal panel of the apparatus. 4 is a partial cross-sectional view for explaining the structure of the liquid crystal panel. FIG. It is a timing chart for demonstrating the whole operation | movement of the apparatus. It is a timing chart which shows the operation | movement which writes a data line signal to a pixel. It is a timing chart which shows an example of the switching timing of a control signal. It is a block diagram which shows the whole structure of the liquid crystal device concerning 2nd Embodiment of this invention. It is a block diagram of the scanning line drive circuit used for the apparatus. It is a circuit diagram which shows the structure of the control circuit used for the apparatus. It is a truth table showing operation of the control circuit. It is a timing chart which shows the operation example of the same apparatus. It is a timing chart which shows the other operation example of the same apparatus. It is a timing chart which shows an example of the switching timing of the common control signal in the apparatus It is sectional drawing of the video projector which is an example of the electronic device to which a liquid crystal device is applied. It is a perspective view which shows the structure of the personal computer which is an example of the electronic device to which the liquid crystal device is applied. It is a perspective view which shows the structure of the mobile telephone which is an example of the electronic device to which a liquid crystal device is applied. It is a circuit diagram which shows the equivalent circuit of a certain pixel used for the conventional electro-optical panel.

Explanation of symbols

  3a ... scanning line, 4a ... control line, 6a ... data line, 9a ... pixel electrode, 50, 51 ... TFT (first switching element, second switching element), 52 ... retention capacitor, SC ... control signal, Y1 to Ym ... Scanning signal, X1 to Xn ... Data line signal, Din ... Input image data, d1 to dn ... Dot sequential image data, D1 to Dn ... Line sequential image data, 100 ... Data line driving circuit, 110 ... X shift register (first) 1 conversion unit), 120... First latch (first conversion unit), 130... Second latch (second conversion unit), 140... D / A converter (data line signal supply unit), 200. Scanning line drive unit), C1 to Cm... Control circuit.

Claims (18)

A first substrate on which a plurality of scanning lines and a plurality of data lines are formed, a second substrate facing the first substrate, and a gap between the first substrate and the second substrate An electro-optic panel comprising:
The first substrate is
A plurality of control lines formed corresponding to the scanning lines;
Provided corresponding to the intersection of the scanning line and the data line, and on / off controlled based on a scanning signal supplied via the scanning line, provided between the data line and the pixel electrode. A first switching element,
Provided corresponding to the intersection of the scanning line and the data line, and controlled on / off based on a control signal supplied via the control line, and provided between the pixel electrode and the storage capacitor. An electro-optical panel comprising: the second switching element. A first conversion unit that converts input image data into point-sequential image data;
A second conversion unit for converting each point sequential image data into each line sequential image data;
A data line signal supply unit for supplying each data line signal generated based on each line sequential image data to each data line;
The electro-optical panel according to claim 1, further comprising: a scanning line driving unit that generates each scanning signal for sequentially selecting the scanning lines and supplies the scanning signal to each scanning line. The electro-optical panel according to claim 1 or 2,
An electro-optical device comprising: a control signal generation unit that generates the control signal according to a field frequency.   The electro-optical device according to claim 3, wherein the control signal generation unit generates each control signal corresponding to each control line and supplies the control signal to each control line. The electro-optical panel according to claim 1 or 2,
An electro-optical device comprising: a control signal generation unit that generates the control signal according to whether an image to be displayed is a moving image or a still image. A first substrate on which a plurality of scanning lines and a plurality of data lines are formed, a second substrate facing the first substrate, and a gap between the first substrate and the second substrate An electro-optic panel comprising:
The first substrate is
A plurality of control lines formed corresponding to the scanning lines;
Provided corresponding to the intersection of the scanning line and the data line, and on / off controlled based on a scanning signal supplied via the scanning line, provided between the data line and the pixel electrode. A first switching element,
Provided corresponding to the intersection of the scanning line and the data line, and controlled on / off based on a control signal supplied via the control line, and provided between the pixel electrode and the storage capacitor. A second switching element,
A plurality of control circuits for generating the respective control signals to be supplied to the respective control lines based on a common control signal for instructing whether an image to be displayed is a moving image or a still image and the respective scanning signals; An electro-optical panel comprising:   The control circuit generates the control signal for turning off the second switching element when the common control signal indicates a moving image during an active period of the scanning signal, and the common control signal indicates a still image And generating the control signal for turning on the second switching element, and generating the control signal so as to maintain the state in the previous active period during the inactive period of the scanning signal. Item 7. The electro-optical panel according to Item 6.   And a scanning line driving unit that generates and supplies the scanning signals for sequentially selecting the scanning lines to the scanning lines only during a period in which an enable signal supplied from the outside is active. Item 8. The electro-optical panel according to Item 7.   The electro-optical panel according to claim 1, wherein the first switching element and the second switching element are thin film transistors. An electro-optical device that switches between a moving image and a still image on a field basis,
An electro-optical panel according to claim 8,
According to whether the image to be displayed is a moving image or a still image, the binary signal level is changed in units of fields to indicate a moving image at one signal level and to indicate a still image at the other signal level A common control signal generator for generating a common control signal;
In the moving image display period, the enable signal is generated to be active, while in the still image display period, the first field is active, the subsequent field or fields are inactive, and the active signal is inactive at a fixed period. An electro-optical device comprising: an enable signal generating unit that generates the enable signal so as to repeat active. The common control signal generation unit changes the signal level of the common control signal during a vertical blanking period,
The electro-optical device according to claim 10, wherein the enable signal generation unit performs switching between an active period and an inactive period of the enable signal during a vertical blanking period. An electro-optical device that switches between a moving image and a still image for each scanning line.
An electro-optical panel according to claim 8,
Depending on whether it is a moving image display period corresponding to a moving image area or a still image display period corresponding to a still image area, the binary signal level is changed and a moving image is indicated by one signal level, and the other signal level is indicated. A common control signal generation unit for generating the common control signal for instructing a still image with
The enable signal is generated so as to be active in each moving image display period of each field, while in each still image display period of each field, the first field is active, and in one or more following fields An electro-optical device, comprising: an enable signal generating unit configured to generate the enable signal so as to be inactive and repeat active and inactive at a constant period. The common control signal generation unit changes the signal level of the common control signal during a vertical blanking period or a horizontal blanking period,
The electro-optical device according to claim 12, wherein the enable signal generation unit performs switching between an active period and an inactive period of the enable signal during a vertical blanking period or a horizontal blanking period. An image is displayed on an electro-optical panel having a plurality of scanning lines, a plurality of data lines, and first capacitors and second capacitors arranged in a matrix corresponding to the intersections of the scanning lines and the data lines. An electro-optical panel driving method for
Determine whether the field frequency of the image to be displayed is higher or lower than a predetermined frequency,
When the field frequency is high, the first capacitor and the second capacitor are disconnected, the scan lines are sequentially selected, and the voltage of the data line is written to the first capacitor.
When the field frequency is low, the first capacitor and the second capacitor are connected, the scanning lines are sequentially selected, and the voltage of the data line is written to the first capacitor and the second capacitor. A method for driving an electro-optical panel. An image is displayed on an electro-optical panel having a plurality of scanning lines, a plurality of data lines, and first capacitors and second capacitors arranged in a matrix corresponding to the intersections of the scanning lines and the data lines. An electro-optical panel driving method for causing
Determine whether the image to be displayed is a video or a still image,
When the image to be displayed is a moving image, the first capacitor and the second capacitor are disconnected, the scan lines are sequentially selected, and the voltage of the data line is written to the first capacitor.
When the image to be displayed is a still image, the first capacitor and the second capacitor are connected, the scanning lines are sequentially selected, and the voltage of the data line is written to the first capacitor. A method for driving an electro-optical panel. An electro-optical panel having a plurality of scanning lines, a plurality of data lines, and a first capacitor and a second capacitor arranged in a matrix corresponding to the intersection of the scanning line and the data line, in a field unit. A method of driving an electro-optic panel for switching between a moving image and a still image,
For each field that should display a video,
The pixel electrode and the second capacitor are disconnected, the scan lines are sequentially selected, and the voltage of the data line is written to the first capacitor.
In each field where still images should be displayed,
Connecting the first capacitor and the second capacitor;
In the first field, each of the scanning lines is sequentially selected to write the voltage of the data line to the first capacitor and the second capacitor,
In one or a plurality of subsequent fields, the voltages written in the first capacitor and the second capacitor are held while the scanning lines are not selected.
A method for driving an electro-optical panel, wherein writing and holding are repeated at a constant cycle. An electro-optical panel having a plurality of scanning lines, a plurality of data lines, and a first capacitor and a second capacitor arranged in a matrix corresponding to the intersection of the scanning lines and the data lines. A method of driving an electro-optical panel for switching between a moving image and a still image for display,
For each scanning line corresponding to moving image display, the pixel electrode and the second capacitor are disconnected, the scanning lines are sequentially selected, and the voltage of the data line is written to the first capacitor.
For each scanning line corresponding to still image display, the first capacitor and the second capacitor are connected, and in the first field, the scanning lines are sequentially selected to set the voltage of the data line to the first capacitor. In the one or more fields that follow, the scanning lines are not selected and the voltages written in the first capacitor and the second capacitor are held, and the writing and holding are performed at a constant cycle. The method of driving the electro-optical panel is characterized by repeating the above.   An electronic apparatus comprising the electro-optical device according to claim 4.

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