JP4736335B2 - Electro-optical device and electronic apparatus - Google Patents

Description

  The present invention relates to a technical field of an electro-optical device such as a liquid crystal device and an electronic apparatus including the electro-optical device.

  In this type of electro-optical device, for example, as a liquid crystal device, a pair of substrates are arranged to face each other via an electro-optical material such as liquid crystal, and a plurality of pixels connected to a plurality of scanning lines and data lines on one substrate. In addition to the unit, a data line driving circuit for driving data lines and the like including a scanning line driving circuit for driving scanning lines, a sampling circuit for sampling image signals, and the like are built in. At the time of driving, the sampling circuit operates to sample the image signal supplied onto the image signal line at the timing of the sampling circuit drive signal and supply it to the data line.

  As the driving method, inversion driving methods such as line inversion and surface inversion are employed in order to prevent liquid crystal burn-in and deterioration. In these inversion driving methods, for example, the polarity of the liquid crystal driving voltage is inverted by changing the voltage level of the image signal applied to the pixel electrode with reference to the intermediate potential of the voltage amplitude. However, the time when the potential of the data line is actually inverted immediately after the polarity inversion is slightly delayed because the data line itself has a parasitic capacitance.

  Therefore, prior to the inversion of the polarity of the image signal, a precharge operation for charging and discharging the data line to the inverted potential is performed (see, for example, Patent Document 1). Specifically, for example, a precharge signal of a predetermined potential level corresponding to gray or intermediate color is written to each data line.

JP-A-10-171421

  However, when the precharge operation is introduced, the data line is supplied with an image signal from one end by a data line driving circuit including a sampling circuit and the like disposed on one end side, and the precharge circuit disposed on the other end side Thus, the precharge signal is supplied from the other end. If separate circuits are provided at both ends of the data line as described above, there is a technical problem that wiring is restricted and it is difficult to reduce the size of the substrate or the entire apparatus. Also, when these various circuits are constructed as external IC circuits, there are difficulties such as an increase in the number of ICs. On the other hand, for example, by superimposing the precharge signal on the image signal, the precharge signal is inserted between the effective image signals used for writing, and the signal supply wiring for the data line is unified with the image signal line. There is. In this case, it is necessary to add a circuit for inserting a precharge signal into the image signal forming circuit, which raises a problem of cost increase.

  In addition to the above problems, the occurrence of display spots due to variations in the precharge data lines is a problem. In a normal precharge circuit, a plurality of data lines are connected in parallel to a common line to which a precharge signal is supplied through a precharge switching element. Thus, a precharge signal is supplied. That is, since a signal with a large amplitude is suddenly applied to the thin and long common wiring, each data line is caused by wiring resistance and parasitic capacitance of the common wiring, insufficient on-current of the precharge switching element, characteristic variation, etc. As a result of variations in the applied precharge level, luminance spots may occur in the arrangement direction of the data lines, and the contrast ratio may decrease.

  The same problem occurs when precharging is performed from the image signal line. In this case, the image signal line is a common line, and the precharge is performed by the same mechanism as described above, in which the precharge signal is supplied to the data line through the sampling switching element of the sampling circuit.

  SUMMARY An advantage of some aspects of the invention is that it provides an electro-optical device capable of high-quality display without complicating a device configuration and a driving form, and an electronic apparatus using the same. And

In order to solve the above problems, an electro-optical device according to the present invention provides a plurality of pixel electrodes, a plurality of data lines for supplying image signals to the plurality of pixel electrodes, and the plurality of pixels via an electro-optical material. A counter electrode facing the electrode; a plurality of image signal lines to which the image signal is supplied; and sampling the image signal supplied to the image signal line in a sampling period to supply the data signal to the plurality of data lines , A sampling circuit including a plurality of sampling switches that are electrically connected to the image signal lines to enable charging and discharging by conducting in a precharge period preceding the sampling period; and In contrast, a predetermined potential is supplied during the sampling period, and at least a part of the precharge period preceding the sampling period. Characterized in that it comprises a power supply means for supplying a different precharge signal and a predetermined potential.

  According to the electro-optical device of the present invention, during the operation, the image signal sampled from the image signal line is supplied to the pixel electrode through the data line during the sampling period, and data writing to each pixel is performed. Prior to this sampling period, a precharge operation is performed. The precharge operation refers to control in which the data line is charged or discharged and the potential of the data line is brought close to the image signal potential in advance in order to prevent insufficient writing. Here, in particular, precharging is performed by applying a voltage to the counter electrode and charging and discharging charges in the data line in accordance with a potential difference from the counter electrode.

  A voltage is applied to the counter electrode by power supply means. In general, a reference potential is applied to the counter electrode during driving so as to form a liquid crystal holding capacitor by appropriately holding a potential difference from the pixel electrode. The power supply means of the present invention serves as both a “reference voltage source” and a “precharge circuit”, and supplies a reference potential in the sampling period. In the precharge period, the precharge voltage signal ( That is, a precharge signal) is supplied to change the potential of the counter electrode.

  The counter electrode is in a positional relationship facing the data line and the pixel electrode, and is, for example, a solid electrode facing all the pixel electrodes. For this reason, since the potential distribution on the counter electrode is considered to be constant for any data line, the potential variation between the data lines after the precharge hardly causes any problem in practice.

  A normal precharge operation is performed by applying a precharge signal of a predetermined voltage directly to the data line, and the precharge signal is supplied to all data lines simultaneously from the common line. Therefore, the supply voltage for each data line varies due to the wiring resistance, the parasitic capacitance between the wirings, etc., and the potential of the data line after precharging varies. Here, in a data line with insufficient precharge, writing of an image signal is relatively insufficient, and as a result, display defects such as luminance spots and a partial decrease in contrast ratio occur.

  On the other hand, in the present invention, as described above, since the precharge signal is applied to the counter electrode, all the data lines can be precharged almost uniformly. Therefore, variations in subsequent image signal writing are suppressed, and high-quality display with reduced display spots is possible.

  During the precharge operation according to the present invention, the data line is brought into conduction for charging / discharging. In order to prevent current leakage and sneak current, a normal data line is separated from the signal wiring by a switch or the like and floated during a period other than the signal application period. However, here, in the precharge period, it is necessary to be in a conductive state by connecting to some wiring that is not floating in order to increase or decrease the charge. Examples of such wiring include an image signal line and a precharge signal supply wiring in a conventional precharge circuit. Note that these wirings are only required to conduct the data lines during the precharge period, and are not necessarily wirings for supplying any signals.

  In addition, since the precharge in the present invention is achieved by at least (1) applying a precharge signal to the counter electrode and (2) keeping the data line conductive, in the electro-optical device of the present invention, Except for the difference in the supply destination of the precharge signal, the normal circuit configuration is almost followed. Therefore, there is an advantage that it is possible to save the trouble of adding a new precharge circuit and to complicate the apparatus configuration and the drive form.

  In an aspect of the electro-optical device according to the aspect of the invention, the sampling circuit includes a plurality of sampling switches that sample the image signal and supply the sampled data to the plurality of data lines, and the sampling switch is within the precharge period. By conducting, the plurality of data lines are electrically connected to the image signal lines so that charging / discharging is possible.

  According to this aspect, the conduction of the data line in the precharge period is ensured by connecting to the image signal line. That is, in the sampling period, the conduction timing of the sampling switch is controlled according to the image signal supplied to the image signal line, and only the data line corresponding to the image signal is selectively turned on, but in the precharge period, the sampling switch is turned on. All the data lines are connected to the image signal lines and are ready to be charged / discharged.

  Accordingly, a normal circuit configuration can be used as it is for this portion, so that the apparatus is not complicated. In addition, in this “video precharge” type drive system, unlike the normal “video precharge”, no signal is applied to the image signal line during the precharge period, so a precharge signal is inserted into the image signal forming circuit. Therefore, it is not necessary to add a circuit and a cost increase for the circuit, and it is convenient.

  In the aspect in which the data line is connected to the image signal line during the precharge period, precharge means for replacing the second precharge signal having a predetermined potential with the image signal and supplying the image signal line within the precharge period is further provided. You may make it prepare.

  In this case, the image signal line not only conducts the data line in the precharge period but also directly supplies a voltage to the data line, so that the data line can be precharged more reliably. . This driving method is generally called “video precharge”. If only this is applied, as described above, charge variation between data lines is induced. However, this driving method is combined with or supplementarily to the precharge method of the present invention. By using it, the second precharge signal related to the video precharge can be made smaller than usual, and the charge variation between the data lines due to this can be reduced.

  Alternatively, in the aspect in which the data line is connected to the image signal line in the precharge period, the image signal is periodically inverted in polarity between the successive sampling periods, and the timing of the polarity inversion is the precharge It may be set after the end of the period.

  In this case, when performing inversion driving such as line inversion and surface inversion, the polarity inversion of the image signal is performed after the end of the precharge period. In the “video precharge” type drive, the data line is electrically connected to the image signal line during the precharge period. Therefore, if the image signal is inverted before the end of the precharge period, the potential of the image signal becomes the data level. Affects the amount of charge on the line. Therefore, if the precharge is set only by the potential change of the counter electrode, there arises a problem that an appropriate amount of precharge is not performed. Further, the potential change due to the polarity inversion may be transmitted with variation in the data line due to the wiring resistance, the parasitic capacitance between the wirings, or the like. In this case, the charge amount for each data line varies. Therefore, such inconvenience can be avoided by inverting the polarity of the image signal after the end of the precharge period.

In another aspect of the electro-optical device of the present invention, a plurality of pixel electrodes, a plurality of data lines for supplying image signals to the plurality of pixel electrodes, and the plurality of pixel electrodes are opposed to each other through an electro-optical material. A plurality of image signal lines to which the image signal is supplied, a sampling circuit that samples the image signal supplied to the image signal line during a sampling period and supplies the image signal to the plurality of data lines, Power supply means for supplying a predetermined potential to the counter electrode during the sampling period and supplying a precharge signal different from the predetermined potential to at least a part of the precharge period preceding the sampling period; and the image signal line And a precharge wiring connected to the plurality of data lines via a precharge switch. By conducting the pre-charge period Jisuitchi, characterized in that makes it rechargeable said plurality of data lines connected the electrically to the precharge wirings

  According to this aspect, the continuity of the data line in the precharge period is ensured by connecting to the wiring routed separately from the image signal line for precharging. The precharge wiring is connected to the data line when the precharge switch is turned on, and functions to make the data line conductive. Such a configuration is realized by, for example, a commonly used precharge circuit. The normally used precharge circuit is a circuit that is connected to each data line via a switch on the side opposite to the sampling circuit and supplies a precharge signal. On this circuit, the above function can be achieved by simply turning on the switch during the precharge period. Accordingly, a normal circuit configuration can be used as it is for this portion, so that the apparatus is not complicated.

  In the aspect in which the data line is connected to the precharge wiring during the precharge period, a precharge circuit for supplying a second precharge signal having a predetermined potential to the precharge wiring within the precharge period is further provided. Also good.

  In this case, it is possible to precharge the data line more reliably by combining or supplementarily using a normal precharge system in which a voltage is directly applied to the data line to the precharge system of the present invention. It becomes. At the same time, the second precharge signal by the normal method can be reduced, and the charge variation between the data lines due to this can be reduced.

  In another aspect of the electro-optical device according to the aspect of the invention, the power supply unit periodically inverts the polarity of the voltage applied to the counter electrode between the sampling periods.

  According to this aspect, when performing inversion driving such as line inversion and surface inversion, the potential of the counter electrode is inverted instead of or in addition to the pixel electrode. Therefore, the amplitude of the image signal can be made relatively small compared to the case where the polarity of only the pixel electrode is reversed, and the withstand voltage of the IC of the drive circuit on the pixel electrode side can be lowered.

  In order to solve the above-described problems, an electronic apparatus of the present invention includes the above-described electro-optical device of the present invention (including various aspects thereof).

  According to the electronic apparatus of the present invention, since the above-described electro-optical device of the present invention is provided, high-quality display is possible, and at the same time, the configuration of the apparatus and the driving form can be simplified. The electronic apparatus includes, for example, various display devices such as a liquid crystal device, an electrophoretic device such as electronic paper, a display device using an electron-emitting device (Field Emission Display and Surface-Conduction Electron-Emitter Display), a projection type or a reflection type. It can be realized as various devices such as a projector, a television receiver, a mobile phone, an electronic notebook, a word processor, a viewfinder type or a monitor direct-view type video tape recorder, a workstation, a video phone, a POS terminal, and a touch panel.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

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

<First Embodiment>
A first embodiment of the electro-optical device according to the invention will be described with reference to FIGS. In the following embodiments, the electro-optical device of the present invention is applied to a liquid crystal device.

  First, the overall configuration of the liquid crystal device according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a plan view of the liquid crystal device viewed from the counter substrate side, and FIG. 2 is a cross-sectional view taken along line H-H ′ of FIG. 1. FIG. 3 is a block diagram illustrating a main configuration of the liquid crystal device. FIG. 4 shows a drive system related to the precharge operation in the configuration shown in FIG. Note that the liquid crystal device according to the present embodiment includes a display panel 100 with a built-in drive circuit, and a circuit unit that performs overall drive control and various processes on image signals.

  In the display panel 100 in FIGS. 1 and 2, the TFT array substrate 10 and the counter substrate 20 are disposed to face each other. A liquid crystal layer 50 is sealed between the TFT array substrate 10 and the counter substrate 20, and the TFT array substrate 10 and the counter substrate 20 are provided in a seal material provided in a seal region around the image display region 10a. 52 are bonded to each other. The sealing material 52 is made of, for example, an ultraviolet curable resin, a thermosetting resin, or the like for bonding the two substrates, and is applied on the TFT array substrate 10 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like. It is. Further, in the sealing material 52, a gap material such as glass fiber or glass beads for dispersing the distance (inter-substrate gap) between the TFT array substrate 10 and the counter substrate 20 to a predetermined value is dispersed. A light-shielding frame light-shielding film 53 that defines the frame area of the image display area 10a is provided on the counter substrate 20 side in parallel with the inside of the seal area where the sealing material 52 is disposed. However, part or all of the frame light shielding film 53 may be provided as a built-in light shielding film on the TFT array substrate 10 side.

  In the peripheral region located around the image display region 10 a on the TFT array substrate 10, the data line driving circuit 101 and the external circuit connection terminal 102 are provided along one side of the TFT array substrate 10. The scanning line driving circuit 104 is provided along two sides adjacent to the one side so as to be covered with the frame light shielding film 53. Further, in order to connect the two scanning line driving circuits 104 provided on both sides of the image display region 10 a in this way, a plurality of the light-shielding films 53 are covered along the remaining one side of the TFT array substrate 10. A wiring 105 is provided. Further, between the TFT array substrate 10 and the counter substrate 20, a vertical conduction terminal 106 is arranged for ensuring electrical conduction between the two substrates.

  In FIG. 2, on the TFT array substrate 10, a pixel electrode 9a is formed on a pixel switching TFT and various wirings, and an alignment film is formed thereon. On the other hand, in the image display region 10 a on the counter substrate 20, a counter electrode 21 that faces the plurality of pixel electrodes 9 a through the liquid crystal layer 50 is formed. In other words, a liquid crystal holding capacitor is formed between the pixel electrode 9 a and the counter electrode 21 by applying a voltage to each. On the counter electrode 21, a lattice-shaped or striped light-shielding film 23 is formed, and the alignment film covers the light-shielding film 23. The liquid crystal layer 50 is made of, for example, a liquid crystal in which one or several types of nematic liquid crystals are mixed, and takes a predetermined alignment state between the pair of alignment films.

  Although not shown here, in addition to the data line driving circuit 101 and the scanning line driving circuit 104, a sampling circuit 7 to be described later is formed on the TFT array substrate 10. In addition to this, an inspection circuit or the like for inspecting the quality, defects and the like of the liquid crystal device during manufacture or at the time of shipment may be formed. In addition, for example, the TN (twisted nematic) mode, the STN (super TN) mode, and the D-STN (double- A polarizing film, a retardation film, a polarizing plate, and the like are arranged in a predetermined direction according to an operation mode such as an STN mode or a normally white mode / normally black mode.

  In FIG. 3, a display panel 100 includes a TFT array substrate 10 made of, for example, a quartz substrate, a glass substrate, or a silicon substrate, and a counter substrate 20 (not shown here) facing each other with a liquid crystal layer interposed therebetween. The voltage applied to the pixel electrodes 9a partitioned and arranged in 10a is controlled to modulate the electric field applied to the liquid crystal layer for each pixel. Thereby, the amount of transmitted light between the two substrates is controlled, and the image is displayed in gradation. The display panel 100 employs a TFT active matrix driving method, and a plurality of pixel electrodes 9 a arranged in a matrix and a plurality of scanning lines 2 arranged so as to intersect with each other in the pixel display region 10 a of the TFT array substrate 10. And a data line 3 are formed, and a pixel portion corresponding to the pixel is constructed. Although not shown here, between each pixel electrode 9a and the data line 3, a TFT or a pixel electrode whose conduction or non-conduction is controlled according to a scanning signal supplied via the scanning line 2 respectively. A storage capacitor for maintaining the voltage applied to 9a is formed. In addition, a drive circuit such as the data line drive circuit 101 is formed in the peripheral area of the image display area 10a.

  The data line driving circuit 101 drives the sampling circuit 7, and converts the image signals VID1 to VID6 supplied to the image signal line 6 into sampling circuit driving signals Si (i = 1,...) As reference clock signals for applying data signals. n), and each is applied to the data line 3 as a data signal.

  That is, the image signals VID <b> 1 to VID <b> 6 are serially / parallel-developed into six phases by an external image signal processing circuit and input to the sampling circuit 7 via the six image signal lines 6. For example, as shown in FIG. 4, the sampling circuit 7 includes a sampling switch 71 formed of a P-channel or N-channel single-channel TFT or a complementary TFT. On the other hand, the sampling circuit drive signal Si (i = 1,..., N) generated based on the X-side clock signal CLX (and its inverted signal CLX ′) and the shift register start signal DX input into the data line drive circuit 101. ) Are input to six adjacent sampling switches 71 via control signal lines X1,. Accordingly, the sampling circuit 7 is driven for every six sampling switch 71 groups. In this way, when parallel image signals obtained by converting serial image signals are simultaneously supplied to a plurality of image signal lines 6, image signals can be input to the data lines 3 for each group and driven. The frequency is suppressed.

  The scanning line driving circuit 104 scans a plurality of pixel electrodes 9a arranged in a matrix in the array direction of the scanning lines 2 by a data signal and a scanning signal, and a Y-side clock signal that is a reference clock for applying a scanning signal. A scanning signal generated based on CLY (and its inverted signal CLY ′) and shift register start signal DY is sequentially applied to a plurality of scanning lines 2. In that case, a voltage is simultaneously applied to each scanning line 2 from both ends.

  In the present embodiment, a precharge timing signal NRG (Noise Reduction Gate) can be input to the control signal lines X1,... Xn separately from the sampling circuit drive signal Si. More specifically, each signal line for supplying the sampling circuit drive signal Si and the precharge timing signal NRG is connected to the control signal lines X1,... Xn via the OR circuit 51. The precharge timing signal NRG defines a precharge period prior to the writing period (that is, the sampling period) of the image signals VID1 to VID6, and is supplied all at once to the control signal lines X1,. Accordingly, all the sampling switches 71 are simultaneously turned on by the precharge timing signal NRG, and all the data lines 3 are simultaneously connected to the pixel signal lines 6. Here, in particular, the data line 3 is only made conductive by the image signal line 6 in the precharge period, and no signal is supplied from the image signal line 6. Alternatively, the data line 3 is connected to a predetermined potential different from the potential of the image signal via the image signal line 6 which is in a conductive state during the precharge period.

  Various timing signals such as a precharge timing signal NRG and a clock signal are generated by a timing generator (not shown) provided in the circuit unit and supplied to the display panel 100. In addition, a power supply voltage necessary for driving each drive circuit is also supplied into the display panel 100 from the outside.

  Further, the counter electrode potential LCC is supplied to the signal line 8 drawn from the vertical conduction terminal 106 from the voltage source 200 which is an example of the “power supply means” of the present invention. The counter electrode potential LCC is supplied to the counter electrode 21 via the signal line 8 and the vertical conduction terminal 106. Here, the voltage source 200 has a reference potential for forming a liquid crystal storage capacitor by appropriately holding a potential difference from the pixel electrode 9a as a counter electrode potential LCC, and a reference potential at least during a precharge period. It is configured to generate and output precharge potentials of different voltages. The counter electrode 21 is formed as a solid electrode on the entire surface of the image display region 10a in the counter substrate 20.

  Next, the operation of this liquid crystal device, particularly the precharge operation, will be described with reference to FIGS. FIG. 5 is a timing chart of various signals in the drive system shown in FIG. 4, and FIG. 6 is a timing chart in a normal precharge operation as a comparative example.

  As shown in the timing chart of FIG. 5, when the precharge timing signal NRG is input prior to the data writing period of the image signals VID1 to VID6, that is, the sampling period 32, in each field period, this signal becomes the control signal. Input to the gates of all sampling switches 71 through lines X1,... Xn, and all the data lines 3 are brought into conduction with the image signal lines 6. That is, during the precharge period 31 defined by the precharge timing signal NRG, the data line 3 becomes conductive. In the meantime, the image signals VID1 to VID6 on the image signal line 6 are supplied to the data line 3, but the image signals VID1 to VID6 in the precharge period 31 are continuously set to a constant reference potential from the previous field, and the data No potential variation is applied to the line 3. That is, the polarity of the image signals VID <b> 1 to VID <b> 6 of each field is inverted at least every sampling period 32 by the surface inversion driving, but the inversion timing is set to be delayed by Δt from the precharge period 31.

  During the precharge period 31, a precharge level 35 is applied to the counter electrode 21 from the voltage source 200 as the counter electrode potential LCC. The precharge level 35 is inverted in polarity around the potentials Vp + and Vp− and the reference level Vs for each field, and the potential difference between the image signals VID1 to VID6 with respect to the precharge level 35, that is, the data line 3 viewed from the counter electrode 21. The potential is a potential difference V1 +, V1-. Due to the potential differences V1 + and V1−, as shown in FIG. 4, a capacitance Cd is generated between the data line 3 and the counter electrode 21, and the capacitance Cd, the transistor capacitance of the sampling switch 71, and the image signal line 6 The wiring capacity is charged through the image signal line 6 according to the potential difference V1 + in the positive polarity field, and discharged according to the potential difference V1− in the negative polarity field.

  At this time, since the counter electrode 21 is a solid electrode, the resistance of the electrode itself is low, and an element such as a TFT is not connected. Therefore, the potential difference of the counter electrode 21 with respect to any data line 3 is considered to be substantially constant. It is done. Therefore, the potential variation between the data lines 3 after the precharge hardly becomes a problem at all in practice. As a result, the writing variation of the data signal in the subsequent sampling period 32 is suppressed, and a high-quality display with reduced display spots becomes possible.

  Note that the precharge level 35 is supplied here for a longer period including the precharge period 31, but in order to precharge the data line 3 as described above, it is supplied to at least a part of the precharge period 31. It will be enough if it is done.

  After the precharge period 31, the polarity of the image signals VID1 to VID6 is inverted to the polarity to be written in the field, and the sampling period 32 is started. Since the data line 3 is electrically connected to the image signal line 6 during the precharge period 31, if the image signals VID1 to VID6 are inverted before the end of the precharge period 31, the potentials of the image signals VID1 to VID6 affect the charge amount of the data line 3. As a result, there is a risk that a proper amount of precharge is not performed. Further, the potential change due to the polarity inversion of the image signals VID <b> 1 to VID <b> 6 may be transmitted to the data line 3 with variation due to the influence of the resistance and capacitance of the image signal line 6 and the sampling switch 71. Therefore, such inconvenience is avoided by inverting the polarity of the image signals VID1 to VID6 after the end of the precharge period 31. The counter electrode potential LCC is returned from the precharge level 35 to the reference potential Vs after the end of the precharge period 31 and before the start of the sampling period 32.

  By the way, in the precharge operation that is normally performed, so-called “video precharge”, as shown in the timing chart of FIG. 6, the precharge period 41 is preliminarily applied to the image signal line 6 with the input of the precharge timing signal NRG. A charge level 45 is supplied and applied to all data lines 3 simultaneously. That is, the precharge level 45 is inserted in the image signals VID11 to VID16, and the data line 3 is precharged by direct application of the precharge level 45.

  In order to perform substantially the same precharge as in the present embodiment by this driving method, the polarity of the potential of the precharge level 45 is inverted for each field from the reference level Vs to the potentials Vp2 + and Vp2−. The potential difference between the charge level 45 and the image signals VID11 to VID16 during the sampling period may be set to V1 + and V1−.

  When the voltage is directly applied to the data line 3 and precharged in this way, the supply voltage for each data line 3 varies due to the resistance and capacitance of the data line 3, the sampling switch 71, and the image signal line 6. The potential of the data line 3 varies. In the data line 3 with insufficient precharge, the subsequent writing of the image signals VID11 to VID16 is relatively insufficient, and as a result, the luminance unevenness and the partial reduction in the contrast ratio according to the potential variation of the data line 3 occur. Such a display defect occurs. On the other hand, in the present embodiment, the precharge level 35 is applied to the counter electrode 21 as described above, so that all the data lines 3 can be precharged almost uniformly.

  Data writing in the sampling period 32 may be performed in the same manner as usual. 3, the data line driving circuit 101 generates sampling circuit driving signals S1, S2, S3,... By the input of the clock signal CLX (and its inverted signal CLX ′) and the shift register start signal DX, and the sampling circuit. 71 are sequentially supplied. These sampling circuit drive signals Si drive the sampling circuit 7 for each group of six sampling switches 71 through the control signal lines X1,... Xn, and for each set of six data lines 3 corresponding to the sampling switches 71. Image signals VID1 to VID6 are supplied from the image signal line 6. These image signals VID1 to VID6 are applied from each data line 3 to the pixel electrode 9a of the selected pixel column, and data writing is performed. In this sampling period 32, the data line 3 to which the image signals VID1 to VID6 are not supplied is floated because the corresponding sampling switch 71 is in a non-conducting state, and the charged potential is maintained when it is finally energized. ing. On the other hand, the counter electrode potential LCC supplied from the voltage source 200 is at the reference level Vs except during the precharge period 31, and forms a liquid crystal storage capacitor with the pixel electrode 9a in which the data signal is written.

  As described above, according to the present embodiment, the precharge operation is not performed by directly applying a voltage to the data line 3 but by applying the precharge level 35 and changing the potential of the counter electrode 21. As a result, the potential variation of the data line 3 after precharging is reduced. Therefore, the writing variation of the image signals VID1 to VID6 for each data line 3 is suppressed, and high-quality display with reduced display spots becomes possible. Further, this driving method is common in that the data line 3 is electrically connected to the image signal line 6 as compared with the normal “video precharge”, and the precharge level 35 is not the image signals VID1 to VID6 but the counter electrode. The only difference is that it is inserted into the potential LCC. Therefore, the configuration other than the voltage source 200 can follow the normal circuit configuration almost as it is, and the trouble of adding a precharge circuit can be saved, and the device configuration and the drive form can be simplified.

  In the first embodiment, the precharge operation is performed exclusively based on the counter electrode potential LCC, but “video precharge” may be combined therewith. That is, in this case, precharging is performed according to the relative potential difference between the two types of precharge levels. Specifically, within the precharge period 31, for example, the image signal forming circuit is modified so that the second precharge level of a predetermined potential is replaced with the image signals VID1 to VID6 and supplied to the image signal line 6, and the image signal forming circuit is modified. The signals VID1 to VID6 and the second precharge level supply means may be used. As described above, the second precharge level is set smaller than the normal “video precharge” by combining with or supplementarily using the precharge method of the present invention, and the charge between the data lines 3 due to this is set. Variations can be reduced. Further, in this case, since the voltage is directly supplied to the data line 3 not a little, more reliable precharge is possible.

Second Embodiment
Next, a second embodiment will be described with reference to FIG. FIG. 7 is an overall block diagram of a liquid crystal device as an example of an electro-optical device.

  The present embodiment includes a precharge circuit 80 for conducting the data line 3 to the precharge wiring 82 in accordance with the precharge timing signal NRG, and supplies the precharge timing signal NRG to the precharge circuit 80 instead of the sampling circuit 7. Except for the configuration, the second embodiment is the same as the first embodiment. Therefore, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  The precharge circuit 80 includes a plurality of precharge switches 81 such as TFTs arranged in correspondence with the data lines 3. These precharge switches 81 are switched to a conductive state all at once by a precharge timing signal NRG, and are configured to connect the data line 3 to the precharge wiring 82. The precharge wiring 82 is drawn out of the display panel 100 and is directly or indirectly connected to the power supply of the circuit unit, for example. The precharge circuit having such a configuration normally has a function of supplying a precharge level from the precharge wiring 82 to the data line 3 when the precharge switch 81 is turned on. In this embodiment, the precharge wiring 82 is provided. Is simply used to make the data line 3 conductive. That is, the data line 3 is rendered conductive by the precharge wiring 82 instead of the image signal line 6 in the precharge period 31. Other than that, it drives similarly to 1st Embodiment.

  As described above, according to the second embodiment, since the precharge operation described in the first embodiment is performed using the precharge circuit 80 using a normal precharge circuit, the apparatus is not complicated. Operations and effects similar to those of the first embodiment can be obtained.

  In the second embodiment, as in the first embodiment, the precharge operation is performed exclusively based on the counter electrode potential LCC. However, in combination with the normal precharge method, two types of precharge levels are used. Precharging may be performed according to a relative potential difference. Specifically, the second precharge level having a predetermined potential is supplied to the precharge wiring 82 within the precharge period 31. The second precharge level can be set smaller than usual by combining or supplementarily using the precharge method of the present invention, and the charge variation between the data lines 3 due to this can be reduced. Is possible. Further, in this case, since the voltage is directly supplied to the data line 3 not a little, more reliable precharge is possible.

<Third Embodiment>
Next, a third embodiment will be described with reference to FIG. FIG. 8 is a timing chart in the liquid crystal device as an example of the electro-optical device according to the present embodiment.

  In the present embodiment, the image signals VID21 to VID26 and the counter electrode potential LCC2 having different voltage amplitudes from the first embodiment are supplied to the apparatus having the same configuration as that of the first embodiment. Except for this point, the configuration is the same as that of the first embodiment. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  In the timing chart of FIG. 8, the polarity of the counter electrode potential LCC2 is inverted for each field, and the image signals VID21 to VID26 are signals obtained by inverting the potential polarity with respect to the counter electrode potential LCC2 for each field. In this case, the liquid crystal holding capacitor is relatively charged with the same polarity and the same potential as in the first embodiment in the sampling period 52, and as a result, each pixel is driven in an inverted manner as in the first embodiment.

  Further, the precharge level 55 of the counter electrode potential LCC2 is applied at the same timing as the precharge level 35, for example, and the potential is inverted to the potentials Vp3 + and Vp3− for each field, and the potential difference between the image signals VID21 to VID26 is For example, V1 + and V1- are set. Therefore, in the precharge period 51, the data line 3 is precharged relatively as in the first embodiment.

  Therefore, according to the third embodiment, the same operation and effect as the first embodiment can be obtained. In addition, by performing inversion driving by changing the amplitude of the counter electrode potential LCC, the amplitude of the image signals VID21 to VID26 can be made relatively smaller than in the case of inversion driving by changing the image signal. It is possible to reduce the IC withstand voltage in the supply side circuit of the image signals VID21 to VID26, such as an image signal forming circuit.

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

  (Projector) First, a projector in which a liquid crystal device as an example of the “electro-optical device” of the present invention is applied to a light valve will be described. FIG. 9 is a plan view showing a configuration example of the projector. As shown in the figure, a projector 1100 is provided with a lamp unit 1102 composed of a white light source such as a halogen lamp. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and serves as a light valve corresponding to each primary color. It enters the liquid crystal devices 1110R, 1110B, and 1110G. The configurations of the liquid crystal devices 1110R, 1110B, and 1110G are the same as, for example, the liquid crystal devices in the above-described embodiments. In each of them, R, G, and B primary color signals supplied from an image signal processing circuit (not shown) are modulated. The Light modulated by these liquid crystal devices is incident on the dichroic prism 1112 from three directions. In the dichroic prism 1112, R and B light is refracted by 90 degrees, while G light travels straight. As a result, the images of the respective colors are synthesized and a color image is projected onto the screen or the like via the projection lens 1114.

  (Mobile Computer) Next, an example in which the liquid crystal device as the electro-optical device is applied to a mobile personal computer will be described. FIG. 10 is a perspective view showing the configuration of this personal computer. The personal 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 liquid crystal device 1005.

  (Mobile Phone) An example in which the liquid crystal device as the electro-optical device is applied to a mobile phone will be described. FIG. 11 is a perspective view showing the configuration of this mobile phone. A cellular phone 1300 in the figure includes a liquid crystal device 1005 together with a plurality of operation buttons 1302 and a built-in circuit. Here, the liquid crystal device 1005 is of a reflective type, and a front light is provided on the front surface thereof as necessary.

  In the above, the electro-optical device of the present invention has been specifically described by taking a liquid crystal device as an example. However, the electro-optical device of the present invention also performs driving by “serial-parallel conversion”. The present invention can be widely applied to all devices using TFTs as sampling switching elements. Examples of such a device include an electrophoretic device such as electronic paper, and a display device (Field Emission Display and Surface-Conduction Electron-Emitter Display) using an electron-emitting device.

  In addition to the above-described electronic apparatus, the electro-optical device of the present invention includes a television receiver, a viewfinder type or a monitor direct-view type video tape recorder, a car navigation device, a pager, and an electronic notebook. It can be applied to a calculator, a word processor, a workstation, a video phone, a POS terminal, a device equipped with a touch panel, and the like.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an electro-optical device with such a change, In addition, an electronic device including the same is also included in the technical scope of the present invention.

1 is a plan view illustrating a configuration of a liquid crystal device according to a first embodiment of an electro-optical device of the invention. It is H-H 'sectional drawing of FIG. It is a block diagram showing the principal part structure of the liquid crystal device in 1st Embodiment. FIG. 3 is a circuit diagram of a drive system related to a precharge operation in the liquid crystal device according to the first embodiment. 5 is a timing chart of the drive system shown in FIG. 6 is a timing chart of a comparative example for the liquid crystal device of the first embodiment. It is a block diagram showing the whole structure of the liquid crystal device which concerns on 2nd Embodiment. It is a timing chart of the liquid crystal device concerning a 3rd embodiment. FIG. 3 is a cross-sectional view illustrating a configuration of a projector as an example of an electronic apparatus to which the electro-optical device of the invention is applied. 1 is a cross-sectional view illustrating a configuration of a personal computer as an example of an electronic apparatus to which an electro-optical device of the invention is applied. 1 is a cross-sectional view illustrating a configuration of a mobile phone as an example of an electronic apparatus to which an electro-optical device of the invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10a ... Image display area, 2 ... Scan line, 3 ... Data line, 6 ... Image signal line, 7 ... Sampling circuit, 9a ... Pixel electrode, 10 ... TFT array substrate, 11 ... Pixel electrode, 20 ... Counter substrate, 21 ... Counter electrode 35, 45, 55 ... Precharge level, 100 ... Display panel, 101 ... Data line drive circuit, 104 ... Scan line drive circuit, 200 ... Voltage source, LCC ... Counter electrode potential, NRG ... Precharge timing signal, S1 to Sn: sampling circuit drive signals, VID1 to VID6, image signals.

Claims (7)

A plurality of pixel electrodes;
A plurality of data lines for supplying image signals to the plurality of pixel electrodes;
A counter electrode facing the plurality of pixel electrodes via an electro-optic material;
A plurality of image signal lines to which the image signal is supplied;
The image signal supplied to the image signal line is sampled during a sampling period and supplied to the plurality of data lines, and the plurality of data lines are connected to the image by conducting in a precharge period preceding the sampling period. A sampling circuit including a plurality of sampling switches that are electrically connected to a signal line to enable charging and discharging; and
Power supply means for supplying a predetermined potential to the counter electrode in the sampling period and supplying a precharge signal different from the predetermined potential in at least a part of the precharge period preceding the sampling period. Electro-optical device characterized.   2. The electro-optical device according to claim 1, further comprising precharge means for replacing a second precharge signal having a predetermined potential with the image signal and supplying the image signal line within the precharge period.   2. The image signal according to claim 1, wherein the polarity of the image signal is periodically inverted between the sampling periods that follow each other, and the timing of the polarity inversion is set after the end of the precharge period. The electro-optical device described. A plurality of pixel electrodes;
A plurality of data lines for supplying image signals to the plurality of pixel electrodes;
A counter electrode facing the plurality of pixel electrodes via an electro-optic material;
A plurality of image signal lines to which the image signal is supplied;
A sampling circuit that samples the image signal supplied to the image signal line in a sampling period and supplies the sampled signal to the plurality of data lines;
Power supply means for supplying a predetermined potential to the counter electrode during the sampling period and supplying a precharge signal different from the predetermined potential to at least a part of the precharge period preceding the sampling period;
And a precharge line connected via a precharge switch to the plurality of data lines together provided separately from the image signal lines,
An electro-optical device, wherein the plurality of data lines are electrically connected to the precharge wiring so as to be chargeable / dischargeable by conducting the precharge switch during the precharge period.   5. The electro-optical device according to claim 4, further comprising a precharge circuit that supplies a second precharge signal having a predetermined potential to the precharge wiring within the precharge period.   6. The electro-optical device according to claim 1, wherein the power supply unit periodically inverts the polarity of the voltage applied to the counter electrode between the sampling periods. .   An electronic apparatus comprising the electro-optical device according to any one of claims 1 to 6.

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