JP4367175B2 - 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 such as a liquid crystal projector including the same.

In this type of electro-optical device, for example, as a liquid crystal device, a plurality of pixel portions connected to a plurality of scanning lines and data lines, a data line driving circuit for driving the data lines, and a scanning line are provided on a substrate. A scanning line driving circuit for driving, a sampling circuit for sampling an image signal, and the like are built in. At the time of the operation, the sampling circuit samples the image signal supplied onto the image signal line and supplies it to the data line at the timing of the sampling circuit drive signal supplied from the data line drive circuit.
Furthermore, in order to realize a high-definition image display while suppressing an increase in drive frequency, a serial image signal is converted into a plurality of parallel image signals such as 3-phase, 6-phase, 12-phase, 24-phase, etc. A technique for supplying the electro-optical device via a plurality of image signal lines after phase expansion (that is, phase development) has already been put into practical use. In this case, a plurality of image signals are simultaneously sampled by a plurality of sampling switches and are simultaneously supplied to a plurality of data lines (see, for example, Patent Document 1). In this specification, such conversion is referred to as “serial-parallel conversion”.

JP 2002-49357 A JP 2002-49331 A Japanese Patent Laid-Open No. 2002-49052

  However, in this type of electro-optical device that simultaneously drives a plurality of data lines, a plurality of thin film transistors (hereinafter referred to as “TFTs” as appropriate) as a plurality of sampling switches constituting a sampling circuit and their wirings. Due to the parasitic capacitance in between, image signal interference occurs between the pixel columns along the data line, and more or less image defects occur.

  In particular, there is a technical problem that image defects such as ghost or crosstalk are noticeable at the boundary between groups of data lines that are driven simultaneously. Such image defects such as ghosts are adjacent to each other through the boundary of a group of data lines that are driven simultaneously among a plurality of thin film transistors constituting a sampling circuit, according to the research of the present inventors as will be described later. It is considered that this is caused by the parasitic capacitance between the two thin film transistors, and it has been found that an image defect is likely to appear at least at the boundary between the groups.

  The present invention has been made in view of the above-described problems, for example, and reduces image defects that are manifested at the boundary between groups of data lines that are driven simultaneously, particularly when a plurality of data lines are driven simultaneously. An object is to provide an electro-optical device such as a liquid crystal device and an electronic apparatus such as a liquid crystal projector.

  In order to solve the above problems, an electro-optical device according to an aspect of the invention includes a plurality of scanning lines and a plurality of data lines, a plurality of the scanning lines, and the plurality of data lines arranged in an image display region on the substrate. And n (where n is a natural number of 2 or more) image signals subjected to serial-parallel conversion are supplied to a peripheral region located around the image display region. n image signal lines; (i) a drain electrically connected to the data line; (ii) a source electrically connected to the image signal line; and (iii) the source and the drain Each of which has a gate for controlling the conduction of the channel between the plurality of thin film transistors, and a plurality of thin film transistors arranged corresponding to the plurality of data lines. Among the plurality of data lines, each group of n thin film transistors electrically connected to n data lines that are driven at the same time among the plurality of data lines is commonly connected to the gate through a common wiring. A data line driving circuit for supplying the sampling circuit driving signal to the gate for each group through the common wiring, and two of the plurality of thin film transistors adjacent to each other through the boundary of the group. At least one of the plurality of data lines has a characteristic different from that of the other thin film transistors except the at least one thin film transistor in the same group so that an output value of the image signal from the drain to the plurality of data lines is made constant. It has been.

  According to the electro-optical device of the present invention, the thin film transistors serving as the sampling switches constituting the sampling circuit are arranged corresponding to the plurality of data lines. During the operation, n image signals subjected to serial-parallel conversion (that is, phase expansion) supplied to n image signal lines are sampled for each group of n thin film transistors constituting the sampling circuit. Are simultaneously supplied to n data lines. On the other hand, for example, scanning signals are sequentially supplied from the scanning line driving circuit to the scanning lines. Accordingly, for example, in a pixel portion including a pixel switching TFT, a pixel electrode, a storage capacitor, and the like, an electro-optic operation such as liquid crystal driving is performed on a pixel basis by an active matrix method.

  According to the research of the present inventor, generally, when n data lines are driven simultaneously, the parasitic capacitance between adjacent thin film transistors in the sampling circuit and the thin film transistors connected to the thin film transistors are adjacent to each other. As a result of the parasitic capacitance between the plurality of wirings extending, mutual potential fluctuations affect n data lines that are driven simultaneously and the source wirings and drain wirings of the thin film transistors connected to the adjacent data lines. It has been confirmed that ghost or crosstalk occurs. In particular, among the parasitic capacitances between adjacent thin film transistors and wirings in the sampling circuit, it has been found that it is the parasitic capacitance via the group boundary that makes the adverse effect on the display image obvious. . More specifically, depending on the parasitic capacitance between adjacent thin film transistors and wirings in the same group, for example, lines adjacent to each other with a narrow wiring pitch of about several μm to several tens of μm (that is, data lines). Since only ghosts or the like between the adjacent pixel columns) are displayed, little or no discrimination is made on human vision. On the other hand, depending on the parasitic capacitance between the thin film transistors adjacent to each other through the boundary between the groups, a ghost or the like is identified on the human eye as follows under a situation where no countermeasure is taken.

  For example, it is assumed that only a plurality of thin film transistors in which the arrangement of the source wiring, the gate, and the drain wiring are unified throughout the sampling circuit are arranged. In this case, the first thin film transistor in the M (where M is a natural number) group and the first thin film transistor in the M + 1 group are connected to the same first image signal line. Here, the parasitic between the last thin film transistor in the Mth group (hereinafter simply referred to as “nth TFT”) and the first thin film transistor in the M + 1th group (hereinafter simply referred to as “n + 1 TFT”). Due to the capacitance, (i) the potential fluctuation of the first image signal line is transmitted from the source wiring of the (n + 1) th TFT to the drain wiring of the nth TFT. Then, when the n-th TFT former supplies the image signal of the n-th image signal line to the data line, the image signal is transmitted from the source region of the (n + 1) -th TFT by the parasitic capacitance via the above-mentioned boundary. This results in a potential fluctuation corresponding to the image signal on the first image signal line. Alternatively, (ii) the potential fluctuation of the nth image signal line is transmitted from the source wiring of the nth TFT to the drain wiring of the (n + 1) th TFT. Then, when the n + 1 TFT supplies the image signal of the first image signal line to the data line, the image signal is transmitted from the source region of the nth TFT to the image signal by the parasitic capacitance through the above-mentioned boundary. This results in a potential fluctuation corresponding to the image signal on the nth image signal line.

  In any case of (i) and (ii) above, due to the parasitic capacitance through the above-mentioned boundary, between the first and nth data lines in each group, for example, Depending on the brightness of the display image, a white line or a black line is displayed at the boundary of the group as a ghost or the like. Such ghosts and the like are located on the basis of the width of the data line group that is driven at the same time, for example, a distance of about several μm to several tens of μm × (n−1) distances. It is displayed as a ghost or the like that can be made or conspicuous.

  However, according to the present invention, at least one of two adjacent thin film transistors (that is, the nth TFT and the (n + 1) th TFT) passes through a boundary of a group of n thin film transistors that simultaneously drive n data lines. The other thin film transistors in the same group have different characteristics so that the output value from the drain of the image signal to the data line is constant.

  While ordinary thin film transistors are formed in the same layout at the same time and have the same characteristics, in the present invention, at least one of the characteristics of two thin film transistors located at both ends of the group is represented by at least one thin film transistor. By intentionally differing from the characteristics of the other thin film transistors in the same group except for, the voltage fluctuation of the data line due to the parasitic capacitance described above, in particular, the voltage fluctuation generated in the interval cycle of the data line group is compensated.

  For example, the output voltage to the data line of the nth TFT decreases due to the parasitic capacitance with the source of the (n + 1) th TFT, but the characteristics of the nth TFT are adjusted to increase the drain current for the same gate signal input as before. Thus, the effective output voltage to the data line is increased, and the voltage drop is guaranteed. Therefore, the output value of the image signal for the data line is made constant, and little or no ghost or the like due to parasitic capacitance occurs between the first and nth data lines in each group.

  Here, “stabilization” means that the characteristics of each thin film transistor is not considered at all as described above, and the characteristics of each thin film transistor are adjusted and the output voltage from each to the data line is compared with the case where the characteristics are almost uniform. It means to reduce the difference. Ideally, this means to make the difference zero or close to zero, but if the difference becomes somewhat smaller by adjusting the characteristics, it is included in the meaning of “constant” here.

  As a result of the above, according to the electro-optical device of the present invention, a high-quality image in which ghosts or the like generated at the boundary of the data line groups that are driven simultaneously is reduced due to the parasitic capacitance between the thin film transistors in the sampling circuit. An image can be displayed.

  In addition, since the pitch of the thin film transistors in the sampling circuit can be reduced while suppressing the adverse effect on the image display due to such parasitic capacitance, the data line can be narrowed, that is, the pixel pitch can be narrowed. It is also possible to display a fine image.

  In one aspect of the electro-optical device according to the aspect of the invention, the at least one thin film transistor includes the characteristic so as to cancel or reduce an electrical influence from the thin film transistor, the image signal line, and the common wiring in the adjacent group. Are made different.

  According to this aspect, at least one of the two thin film transistors positioned at the boundary of the group, for example, at least one of the nth TFT and the n + 1th TFT cancels an electrical influence from the thin film transistor, the image signal line, and the common wiring related to the adjacent group. In addition, since the characteristics are adjusted so as to reduce, it is possible to eliminate the influence of the parasitic capacitance particularly among the parasitic capacitances, and to reduce the ghost generated at the boundary of the data line group. Can be displayed.

  In another aspect of the electro-optical device of the present invention, among the two thin film transistors adjacent to each other through the boundary of the group, the characteristics of the thin film transistor adjacent to the drain are adjusted to be different from the characteristics of the other thin film transistors. Has been.

  According to this aspect, among the two thin film transistors located at the boundary of the group, the characteristics of the thin film transistor whose drain side is adjacent are further adjusted. The parasitic capacitance described above is actually a problem when it affects the potential on the drain side connected to the data line. By selecting the target whose characteristics are adjusted in this way, the effect of the parasitic capacitance actually Only the thin film transistor having a large thickness can be selectively adjusted.

  In the normal sampling circuit, since the positional relationship between the source and drain of the thin film transistors arranged is uniform, the nth TFT and the n + 1 TFT adjacent to each other through the group boundary are adjacent in the drain. Become either one.

  In another aspect of the electro-optical device of the present invention, the channel length is adjusted such that at least one characteristic of two thin film transistors adjacent to each other through the boundary is different from the characteristic of the other thin film transistor.

  According to this aspect, the above-described characteristic adjustment of the thin film transistor is performed by adjusting the channel length. In general, the characteristics of a transistor are strongly dependent on the channel length and the channel width, and it is known that the transistor resistance in the on state is proportional to the channel length and inversely proportional to the channel width. Therefore, by changing the channel length, the thin film transistor can be easily adjusted to a desired characteristic.

  In another aspect of the electro-optical device of the present invention, the channel width is adjusted so that at least one characteristic of two thin film transistors adjacent to each other via the boundary is different from the characteristic of the other thin film transistor.

  According to this aspect, the above-described characteristics adjustment of the thin film transistor is performed by adjusting the channel width. In a normal sampling circuit, the drain wiring, gate, and source wiring of the thin film transistor are extended in the direction in which the data line extends, for example, the vertical direction or the Y direction, and the plurality of thin film transistors correspond to the plurality of data lines, for example, in the horizontal direction. It is arranged in the direction or X direction. The channel length in this case refers to the dimension of the channel in the data line arrangement direction, and the channel width refers to the dimension in the direction in which the channel data line extends. Therefore, when the channel length is changed, it is necessary to consider the distance between adjacent thin film transistors, but the channel width can be changed without considering such influence between the thin film transistors.

  In another aspect of the electro-optical device of the present invention, among the plurality of thin film transistors, at least one of two thin film transistors adjacent to each other through the boundary and the other thin film transistors are different in whole or in part. It is configured as follows.

  According to this aspect, the above-described characteristic adjustment of the thin film transistor is realized by changing the layout of the transistor. In this case, the layout change means that the overall characteristics can be adjusted by changing the number of unit elements connected in parallel or in series in addition to changing the position shape of all or part of each transistor. included. However, it is considered that the former method is usually adopted because of the small difference in characteristics of the transistors to be adjusted and the space of the sampling circuit.

  The channel length and channel width adjustments and layout changes described above may be performed independently, but may be performed in combination.

  In order to solve the above-described problems, an electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention.

  Since the electronic apparatus of the present invention comprises the above-described electro-optical device of the present invention, a projection display device, a television receiver, a mobile phone, an electronic notebook, a word processor, capable of displaying a high-quality image display image, Various electronic devices such as a viewfinder type or a monitor direct-view type video tape recorder, a workstation, a videophone, a POS terminal, and a touch panel can be realized. In addition, as the electronic apparatus of the present invention, for example, an electrophoretic device such as electronic paper, an electron emission device (Field Emission Display and Conduction Electron-Emitter Display), and the like can be realized.

  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. In the following embodiments, the electro-optical device of the invention is applied to a liquid crystal device.

<First Embodiment>
First, a first embodiment of the present invention will be described with reference to FIGS.

(Configuration of display panel)
FIG. 1 shows a configuration of a display panel in the liquid crystal device of the present embodiment. The liquid crystal device includes a display panel 100 with a built-in drive circuit and a circuit unit (not shown) that performs overall drive control and various processes on image signals.

  The display panel 100 is configured by disposing a TFT array substrate 1 and a counter substrate (not shown) so as to face each other via a liquid crystal layer. The display panel 100 has a liquid crystal layer for each pixel unit 4 that is partitioned in the image display region 10. By applying an electric field, the amount of transmitted light between the two substrates is controlled, and an image is displayed in gradation. Further, this liquid crystal device adopts a TFT active matrix driving method. In the display panel 100, a plurality of scanning lines 2 and data lines 3 are arranged in the pixel display region 10 on the TFT array substrate 1 so as to cross each other. The pixel unit 4 is connected to each of the data lines 3. The pixel unit 4 forms a TFT as a switching element for selectively inputting the image signal Sv supplied to the data line 3 and a liquid crystal holding capacitor for applying and holding the input voltage to the liquid crystal layer, that is, together with the counter electrode. And a pixel electrode.

  The scanning line 2 is connected to scanning line drive circuits 5A and 5B that sequentially select and drive the scanning line 2 at both ends, for example. The scanning line drive circuits 5A and 5B are provided in the peripheral region of the image display region 10, and are configured to apply a voltage to each scanning line 2 from both ends simultaneously.

  The data line 3 is connected to an image signal line 6 that supplies an image signal Sv via a sampling circuit 7. The sampling circuit 7 is composed of a switching element attached to each data line 3 in order to select the data line 3 that receives the image signal Sv from the image signal line 6, and the switching operation is timing-controlled by the data line driving circuit 8. It is comprised so that. The precharge circuit 9 is provided to apply a precharge level to the data line 3 before the application of the image signal Sv. The switching element constituting the sampling circuit 7 is composed of, for example, a single-channel TFT, a CMOS TFT, or the like.

  In addition, the display panel 100 according to the present embodiment is configured to be driven using “serial-parallel conversion”. That is, as shown in the figure, a plurality of (in this case, four) image signal lines 6 are arranged, and the data lines 3 (that is, four lines) connected to each of the image signal lines 6 are arranged in one group. A switching element corresponding to the line 3 is connected to the data line driving circuit 8 for each group by a control wiring X (X1, X2,..., Xn). Then, pulses sequentially output from a shift register provided in the data line driving circuit 8 are sequentially input to the sampling circuit 7 through the control wirings X1, X2,..., Xn as sampling circuit driving signals. At this time, a plurality of switching elements forming a group connected to the same control wiring X are driven simultaneously. That is, the sampling circuit drive signal is supplied through a plurality of branch wirings that constitute an example of the “common wiring” according to the present invention and reach the sampling circuit 7 that branches off from the shift register. Thus, the image signal on the image signal line 6 is sampled for each group of the data lines 3. As described above, 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 simultaneously for each group. The driving frequency is suppressed.

(Functional configuration of sampling circuit)
FIG. 2 shows a circuit system related to data line driving in the display panel. For the sake of simplicity, FIG. 4 shows only the system of the data line 3 of the groups G1 and G2 connected to the control wirings X1 and X2, and the circuit system of these two groups is also shown below. Based on this, a more detailed description will be given.

  Here, the number of the image signal lines 6 is four, and the image signals Sv1 to Sv4 are respectively supplied. The switching element of the sampling circuit 7 is specifically configured as a sampling TFT 71 (hereinafter, abbreviated as TFT 71 as appropriate). Each of the TFTs 71 is connected to the data line 3 in series between the source and the drain, and the gate thereof is connected to the data line driving circuit 8. Each data line 3 is connected to a large number of pixel units 4 on the side opposite to the sampling circuit 7 and supplies a signal voltage to the liquid crystal capacitor Cs of the selected pixel unit 4. A storage capacitor may be separately connected in parallel to the liquid crystal capacitor Cs.

(Sampling circuit layout)
Next, the layout of the sampling circuit on the TFT array substrate will be described with reference to FIGS.

  In the sampling circuit 7 of the present embodiment, of the two TFTs 71 adjacent to each other via the boundary of the group, the TFT 71A adjacent to the drain wiring side (the left end of each group in FIG. 3) is an image for the data line 3. The characteristics are different from those of the other TFTs 71B in the same group so that the output value of the signal is fixed.

  Specifically, the TFTs 71 are arranged in the layout shown in FIG. The plurality of TFTs 71 are grouped into groups G1 and G2 corresponding to the control wirings X1 and X2. Each of the groups G1 and G2 includes a total of four TFTs 71, the leftmost TFT 71A and the other TFT 71B. The TFT 71A includes a source wiring 72S and a drain wiring 72D that extend in the direction in which the data line 3 extends, and a gate wiring 72G that extends between the source wiring 72S and the drain wiring 72D in the direction in which the data line 3 extends. ing. The TFT 71B includes 73S and drain wiring 73D extending in the direction in which the data line 3 extends, and a gate wiring 73G extending between the source wiring 73S and the drain wiring 73D in the direction in which the data line 3 extends. ing.

  FIG. 4 is an enlarged view of the cross-sectional configuration of the TFT 71A taken along line II ′. In the TFT 71A, for example, the source wiring 72S and the drain wiring 72D are respectively connected to the source region 74S and the drain region 74D of the semiconductor layer 74 provided on the TFT array substrate 1, and the channel region 74C is formed on the channel region 74C. A gate is formed by providing a gate wiring 72G so as to face the 74C via the gate insulating film 75. The source wiring 72S, the gate wiring 72G, and the drain wiring 72D are electrically insulated from each other by the interlayer insulating film 76. The basic configuration of the TFT 71B is the same as that shown in FIG.

  In this embodiment, the channel width Wch of the channel region 74C in the TFT 71A is set longer than the channel width Wch of the TFT 71B. In general, the resistance of a TFT strongly depends on the channel width dimension, and the resistance decreases as the channel width increases. That is, when an equivalent gate voltage is applied, a larger drain current flows when the channel width is wider. Here, as will be described in detail below, the channel width Wch is adjusted only for the TFT 71A in order to compensate for the influence of the parasitic capacitance on the TFT 71A. As a result, the output value of the image signal from the TFT 71 to the data line 3 is adjusted. Is constant.

(Operation of display panel 100)
In such a display panel 100, when the image signal Sv is supplied to each data line 3 during one horizontal scanning period, the data line driving circuit 8 sends control signals to the control lines X1, X2,. By sequentially inputting, on / off of the TFT 71 is controlled for each group. In synchronization with this sampling control, the TFT 71 of each group is turned on, and the image signals Sv1 to Sv4 corresponding to the data lines 3 of the group permitted to input signals are sampled on the image signal line 6, They are supplied simultaneously to the corresponding four data lines 3.

  Now, it is assumed that a voltage is applied to the control wiring X1 and the image signals Sv1 to Sv4 are supplied to the group G1 (see FIGS. 2 and 3). In this case, only the TFT 71 of the group G1 is in an on state, and all other TFTs 71 are in an off state. Therefore, in the group G1, a voltage corresponding to the input image signal Sv (Sv1 to Sv4) is applied to the source wiring 72S and drain wiring 72D of the TFT 71A and the source wiring 73S and drain wiring 73D of the TFT 71B.

  At this time, there is a parasitic capacitance between adjacent TFTs 71 between the wiring portions that function as capacitive electrodes by facing the interlayer insulating film 76 as a dielectric film. Such parasitic capacitance is particularly large between the closest wirings. The parasitic capacitance also increases as the pixel pitch is reduced due to high definition and the dielectric film becomes thinner as the distance between the TFTs 71 is reduced. Within the group in operation, depending on the magnitude of the parasitic capacitance coupled to the wiring system, the source wiring and the drain wiring that are adjacent to each other mainly influence the potential fluctuation. Therefore, more or less potential fluctuation is caused by an image signal different from the image signal originally supplied to the data line 3 and further to the pixel portion 4. These can all cause ghosting in the strict sense.

  However, the inventor of the present invention compares the parasitic capacitance between the TFTs 71 that belong to different groups and are adjacent to each other at the boundary between the groups as compared to the parasitic capacitance between the TFTs 71 in such a group. It has been found that the effect on the image quality is significantly larger.

  This point will be described with reference to FIG. FIG. 5 is an equivalent circuit diagram showing the state of the parasitic capacitance in the sampling circuit in the case of this embodiment.

  As shown in FIG. 5, in the case of the present embodiment, a parasitic capacitance is parasitic between the source wiring and the drain wiring adjacent to the source wiring regardless of the group or between the groups. Here, for convenience, the parasitic capacitance between the TFTs 71 in the group is C11, and the capacitance generated between the TFTs 71 belonging to different groups across the boundary R is the intergroup capacitance C21.

  Normally, it is known that an image does not change abruptly when viewed in units of pixels, and adjacent pixels perform similar display. That is, there is no difference in pixel signal voltage between adjacent pixels. Therefore, in the group, the adverse effect of the potential fluctuation between the adjacent wirings due to the parasitic capacitance C11 is basically small. Further, even if the pixel changes suddenly in units of pixels, if the change is rapid between adjacent pixels, the parasitic capacitance between adjacent TFTs 71 may cause a gap between pixel lines connected to adjacent data lines. Even if a ghost occurs, it is rather difficult to see it. For example, even if a black line or a white line is displayed near the boundary between a white image and a black image, the thin black line or white line that is separated by only one line, for example, only about a dozen μm, is almost or practical. In general, it cannot be seen at all.

  However, in the period when the image signal is to be supplied to the group G1, in the leftmost TFT 71A of the group G1, among the potential fluctuations in the image signal line 6, the potential fluctuation due to the image signal Sv1 is adjacent to the group G2 across the boundary R. Is transmitted from the source wiring 73S of the TFT 71B to the drain wiring 72D via the inter-group capacitance C21.

  As a specific example in this case, according to the inventor of the present invention, for example, when the image signal Sv1 for displaying the rightmost pixel portion 4 in black is given in the group G1, the phenomenon that the leftmost pixel portion 4 is displayed in white is observed. Has been. This is due to the fact that the inter-group capacitance C21 effectively reduces the applied voltage at the leftmost pixel unit 4 in accordance with the image signal Sv1.

  Further, since the inter-group capacitor C21 causes the potential of the data line 3 arranged on one end side in the group to act on the potential of the data line 3 on the other end side in this way, the effect is the pixel separated by the period of the group. Appear in Therefore, it is much easier to visually recognize than noise generated between adjacent pixels. As described above, when no countermeasure is taken, the adverse effect of the inter-group capacity C21 is visually recognized as a ghost that becomes apparent when the distance is separated on the display screen. .

  In contrast, in the present embodiment, the channel width Wch of the TFT 71A located at the left end of the group is increased. As the channel width Wch increases, the drain current of the TFT 71A increases as compared with the TFT 71B, and the decrease in the amount of current on the drain wiring 72D side due to the inter-group capacitance C21 is offset. As a result, the influence of the inter-group capacitance C21 on the image signal Sv applied to the data line 3 is reduced, and an appropriate voltage can be supplied to the pixel unit 4. Therefore, it is possible to prevent display noise that becomes apparent at the above-described group intervals.

  As described above, in this embodiment, the characteristics of the TFT 71A are made different from those of the TFT 71B so that the output value of the image signal from all the TFTs 71 to the data line 3 is constant. The output voltage from the received TFT 71A to the data line 3 approaches or coincides with the voltage value of the image signal Sv4 that should originally be supplied to the data line 3, and image display is performed with little or no image quality degradation due to ghost or the like. be able to.

  In addition, by simply changing the layout of the conventional sampling circuit only in part, a particularly large parasitic capacitance component such as inter-group capacitance can be reduced, and a great effect of dramatically improving the image quality can be obtained. In particular, in the present embodiment, the characteristic adjustment of the TFT 71A is performed by changing the channel width Wch. Therefore, in addition to the adjustment itself being easy, the layout can be easily changed.

  Further, by reducing the parasitic capacitance component that has a great influence on the image quality by such a method, the wiring pitch of the TFT 71 having a trade-off relationship with the parasitic capacitance can be narrowed (without degrading the image quality). Therefore, the display panel 100 can achieve higher definition than conventional.

Second Embodiment
Next, a second embodiment will be described with reference to FIGS.

  FIG. 6 shows the configuration of the sampling circuit according to the second embodiment, and FIG. 7 is an equivalent circuit diagram showing the state of the parasitic capacitance in the sampling circuit in this case. The main configuration of the electro-optical device according to the second embodiment is the same as that of the first embodiment, except that the layout of the sampling circuit is different. Therefore, 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 sampling circuit in FIG. 6 is configured by a group in which a total of four TFTs 81, that is, the rightmost TFT 81A and the other TFT 81B are taken as one unit. Here, the arrangement of the source wiring and the drain wiring of the TFT 81 is opposite to that of the TFT 71. That is, here, the structure of the TFT 81 may be regarded as a mirror image of the TFT 71. Of the two TFTs 81 adjacent to each other through the boundary of the group, the output value of the image signal to the data line 3 is constant in the TFT 81A adjacent to the drain wiring side (the right end of each group in FIG. 6). The characteristics have been adjusted as described.

  In this case, as shown in FIG. 7, parasitic capacitance is parasitic between the source wiring and the drain wiring adjacent to the source wiring. Therefore, in the rightmost TFT 81A of the group G2 during the period when the image signal is to be supplied to the group G2, among the potential fluctuations in the image signal line 6, the potential fluctuation due to the image signal Sv4 is adjacent to the group G1 across the boundary R. Is transmitted from the source wiring of the TFT 81B to the drain wiring via the inter-group capacitor C22.

  However, according to the TFT 81A in the present embodiment, the drain current is increased as compared with the TFT 81B by an amount corresponding to the increase of the channel width Wch, and the decrease in the current amount on the drain wiring side due to the inter-group capacitance C22 is offset. Therefore, the influence of the inter-group capacitance C22 on the image signal Sv applied to the data line 3 is reduced, and an appropriate voltage can be supplied to the pixel unit 4. Accordingly, it is possible to prevent display noise that becomes apparent in the above-described group interval period.

  As described above, in this embodiment, the characteristics of the TFT 81A are made different from those of the TFT 81B so that the output value of the image signal from all the TFTs 81 to the data line 3 is constant. The voltage fluctuation caused by the capacitor C22 is reduced, and image display can be performed with little or no image quality degradation due to ghost or the like.

  Furthermore, by reducing the parasitic capacitance component that has a particularly large influence on the image quality in this way, the wiring pitch of the TFT 71 having a trade-off relationship with the parasitic capacitance can be reduced (without degrading the image quality). Therefore, the display panel 100 can achieve higher definition than conventional.

  In the first and second embodiments, the case where the characteristics of the TFT of the sampling circuit are adjusted by changing the channel width Wch has been described. However, for example, the characteristics can also be changed by changing the channel length. Can be adjusted. In the TFT 71, the channel length is the horizontal length of the channel region 24C in FIG. 4 and is generally proportional to the transistor resistance. Therefore, if the channel length is increased, the same effect as that of shortening the channel width can be obtained.

  Such TFT characteristic adjustment may be performed by changing both the channel length and the channel width, and may be performed by changing not only the channel region but also the TFT layout.

  Furthermore, in the above-described embodiment, the case where the characteristics of one of two thin film transistors adjacent to each other via a group boundary is adjusted among the TFTs of the sampling circuit has been described. However, in the sampling circuit according to the present invention, for example, the circuit layout Depending on the driving method or the like, the characteristics of both of the two thin film transistors adjacent to each other may be adjusted via the boundary between the groups.

  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. 8 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. 9 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 has a configuration in which a backlight is added to the above-described liquid crystal device 1005 as an electro-optical device.

(mobile phone)
Further, an example in which the liquid crystal device as the electro-optical device is applied to a mobile phone will be described. FIG. 10 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 block diagram illustrating a display panel of an electro-optical device according to a first embodiment of the invention. FIG. FIG. 2 is a circuit diagram showing a configuration of a data line driving circuit system in the display panel shown in FIG. 1. FIG. 3 is a wiring layout diagram of the sampling circuit shown in FIG. 2. It is I-I 'sectional drawing of FIG. FIG. 3 is a diagram for explaining a parasitic capacitance in the sampling circuit shown in FIG. 2. FIG. 6 is a wiring layout diagram of a sampling circuit according to a second embodiment. It is a figure for demonstrating the parasitic capacitance in the sampling circuit shown in FIG. It is sectional drawing which shows the structure of the projector which is an example of the electronic device to which the electro-optical apparatus 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 is applied. It is sectional drawing which shows the structure of the mobile telephone which is an example of the electronic device to which the electro-optical apparatus is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... TFT substrate, 2 ... Scan line, 3 ... Data line, 4 ... Pixel part, 5A, 5B ... Scan line drive circuit, 6 ... Image signal line, 7 ... Sampling circuit, 8 ... Data line drive circuit, 9 ... Pre Charge circuit, 10 ... Image display area, 71 (71A, 71B), 81 (81A, 81B) ... TFT, 72S, 73S ... Source, 72G, 73G ... Gate, 72D, 73D ... Drain, X, X1, X2 ... Control Wiring, G1, G2... (Group of simultaneously driven wiring system), R... Boundary between groups, Sv, Sv1 to Sv4... Image signal, Wch... Channel width, C11. , 100 ... display panel.

Claims (7)

The image display area on the substrate includes a plurality of scanning lines and a plurality of data lines arranged in a crossing manner, and a plurality of pixel portions connected to the plurality of scanning lines and the plurality of data lines,
In the peripheral area located around the image display area,
N image signal lines to which n (where n is a natural number of 2 or more) converted image signals are supplied;
(i) a drain electrically connected to the data line; (ii) a source electrically connected to the image signal line; and (iii) sampling a channel conduction between the source and the drain. A sampling circuit including a plurality of thin film transistors arranged corresponding to the plurality of data lines, each of which includes a gate controlled according to a circuit drive signal,
Among the plurality of thin film transistors, each of the n thin film transistors electrically connected to the n data lines driven simultaneously among the plurality of data lines is common to the gate through a common wiring. And a data line driving circuit that supplies the sampling circuit driving signal to the gate for each group through the common wiring, and
Among the plurality of thin film transistors, at least one of two thin film transistors adjacent to each other through the boundary of the group is the same so that the output value of the image signal from the drain for the plurality of data lines is constant. An electro-optical device having characteristics different from those of the other thin film transistors except the at least one thin film transistor in the group.   The at least one thin film transistor has different characteristics so as to cancel or reduce an electrical influence from the thin film transistor, the image signal line, and the common wiring in the adjacent group. The electro-optical device according to claim 1.   The characteristic of the thin film transistor adjacent to the drain among the two thin film transistors adjacent to each other through the boundary of the group is adjusted to be different from the characteristics of the other thin film transistors. 2. The electro-optical device according to 2.   4. The channel length is adjusted so that at least one characteristic of two thin film transistors adjacent to each other through the boundary is different from characteristics of the other thin film transistors. 5. The electro-optical device according to Item.   The channel width is adjusted so that at least one characteristic of two thin film transistors adjacent to each other via the boundary is different from the characteristic of the other thin film transistor. The electro-optical device according to Item.   The at least one of two thin film transistors adjacent to each other through the boundary and the other thin film transistors among the plurality of thin film transistors are configured such that the whole or a part of the layout is different. Item 4. The electro-optical device according to any one of Items 1 to 3. An electronic apparatus comprising the electro-optical device according to any one of claims 1 to 6.

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