Abstract:
In a display device comprising a plurality of pixels arranged in matrix form, there are provided two or more row driving and/or column driving circuits aligned parallel to each other. This arrangement serves to reduce intervals between rows and/or columns driven by each of the parallel driving circuits so that the pixels of the matrix can be arranged at a higher density. With this parallel arrangement of the driving circuits, interlaced scanning as well as line inversion and dot inversion of video signals are simplified and the operating frequency of the driving circuits can be reduced.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention pertains generally to display devices and, more particularly, relates to driving circuits thereof. The invention can be applied to driving methods for either simple matrix or active matrix displays. The invention is also applicable to display devices including such flat-panel displays as liquid crystal displays (LCDs) and electroluminescent displays, in which light transmittance, reflectance, refractive index, luminous intensity or other properties are varied by applying electrical signals in a controlled manner, and not including cathode ray tubes (CRTs). 
     2. Description of the Related Art 
     Matrix display devices incorporating a plurality of display elements arranged in matrix form are employed particularly in flat-panel displays as large capacity display means. Conventionally known matrix display devices include simple matrix type in which individual display elements arrayed in rows and columns have no built-in actuating devices and active matrix type in which each individual display element is associated with an active device such as a transistor or a diode. In the following description, a column signal line refers to each signal line for transmitting an electrical signal which contains a video signal, and a row signal line refers to each signal line for transmitting an electrical signal which does not contain any video signal. 
     In either type of matrix display device, basic construction is such that peripheral driving circuits containing addressing circuits are arranged in the periphery of the matrix structure for providing signals to the row and column signal lines. These driving circuits are called the row driving circuit and column driving circuit. For example, Japanese Unexamined Patent Application No. 57-41078 discloses an arrangement employing a shift register as an addressing circuit for active matrix display devices, whereas Japanese Unexamined Patent Application No. 62-265696 discloses an arrangement employing a decoder including AND gates and NAND gates as an addressing circuit for active matrix display devices. 
     The peripheral driving circuit of the conventional, matrix display device used to be formed on an integrated semiconductor circuit of the prior art, and connected to the matrix structure formed on a glass substrate using such bonding technique as a tape automated bonding (TAB) operation. Spacings between individual row and column signal lines have decreased in recent years as a result of increasing demand for greater display capacity of matrix displays and more compact matrix structure. This necessitates that the peripheral driving circuit be formed on the same substrate as the matrix structure in monolithic form. It is difficult to connect the individual lines with line spaces of 100 μm or less by TAB technology since the TAB operation is based on application of mechanical pressure. In the aforementioned construction in which the peripheral driving circuit is formed on the same substrate as the matrix of display elements, it is possible to utilize photolithography. In an ideal case, photolithography enables reduction of line spacing to a level practically equal to the level of design rule requirements. 
     It has recently been recognized, however, that a reduction in the area of individual display elements could give rise to problems related to circuit configuration. More specifically, even when the peripheral driving circuit is formed on the same substrate as the matrix of display elements in monolithic form, a circuit for supplying electrical signals to individual signal lines should have such line widths that equal to or smaller than the spaces between the individual signal lines. As an example, each stage of a shift register contained in the peripheral driving circuit includes approximately 10 transistors, and it is essential that the circuit be designed in such a way that these transistors fall within widths of the individual signal lines. In a case where the circuit is designed based on a 5 μm design rule, for instance, permissible minimum width of each signal line is 30 μm and, therefore, dimensions of each display element become at least 30 μm by 30 μm. 
     According to prior art driving techniques for a matrix display device, its row signal lines are sequentially driven from top to bottom (or from bottom to top). This means that the conventional matrix display devices can not be operated by a commonly used interlaced scanning process, in which groups of odd-numbered horizontal lines and even-numbered horizontal lines are scanned in alternate vertical scans. This limitation of the matrix display devices is disadvantageous when displaying quickly moving images. Furthermore, it is essential to convert video signals from interlaced scanning to noninterlaced scanning in order to display an ordinary video input. 
     LCD display devices usually employ line inversion or dot inversion display techniques to prevent picture degradation due to mutual interference between accumulated charges (i.e., image information) in adjacent display elements. This requires an additional process of converting image information. 
     Higher-speed scanning is required as the display capacity of matrix display devices increases. As an example, the video graphics array (VGA) standard (640 by 480 pixels) requires a 9 MHz clock whereas the engineering workstation (EWS) standard requires a clock frequency of more than 30 MHz. Since the peripheral driving circuits of the matrix display devices formed in monolithic form are produced by the use of such a semiconductor material as polycrystalline silicon, which is inferior to single-crystal, an increase in operating speed is not preferable. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a solution to at least one of the aforementioned problems of the prior art. 
     In one form of the invention, a display device comprises a plurality of display elements arranged on a substrate to form a matrix structure, and at least first and second row driving circuits for supplying signals to individual rows of the matrix structure, the row driving circuits being located separately from and parallel to each other on the same substrate as the matrix structure, wherein a signal for any row signal line adjacent to a given row signal line to which a signal is supplied from the first row driving circuit is supplied from other than the first row driving circuit. 
     The above defined display device may be constructed in such a way that one of the row driving circuits is located to the left of the matrix structure while another is located to the right of the matrix structure, or all the row driving circuits are located to the left or right of the matrix structure. 
     In another form of the invention, a display device comprises a plurality of display elements arranged on a substrate to form a matrix structure, and at least first and second column driving circuits for supplying signals to individual columns of the matrix structure, the column driving circuits being located separately from and parallel to each other on the same substrate as the matrix structure, wherein a signal for any column signal line adjacent to a given column signal line to which a signal is supplied from the first column driving circuit is supplied from other than the first column driving circuit. 
     Construction of this display device may be such that one of the column driving circuits is located above the upper edge of the matrix structure while another is located below the lower edge of the matrix structure, or all the column driving circuits is located above the upper edge or below the lower edge of the matrix structure. 
     In either form of the invention, the display device may be constructed in such a way that all the row driving and column driving circuits employ shift registers for use as addressing circuits, or all the row driving and column driving circuits employ decoders for use as addressing circuits. Alternatively, the construction of the display device may be such that each row driving circuit employs a shift register as an addressing circuit while each column driving circuit employs a decoder as an addressing circuit, or vice versa. 
     In a case where two or more row driving or column driving circuits employing shift registers as addressing circuits are provided separately from each other, the construction of the display device may be such that a select signal outputted from a last stage of the first driving circuit is entered to a first stage of the second driving circuit. 
     In a case where two or more row driving or column driving circuits employing decoders as addressing circuits are provided separately from each other, the construction of the display device may be such that these decoders are controlled by a common counter. 
     Where the display device comprises two or more column driving circuits, it may be constructed in such a way that signals for driving display elements in a plurality of columns of the matrix structure may be simultaneously supplied to the respective column signal lines. 
     In either the first or second form of the invention described above, it is possible to reduce the longitudinal dimension of each stage (to which each signal line is connected) of a driving circuit. If two column driving circuits are provided at separate sites from each other, for example, the number of column signal lines that branch out from each column driving circuit can be halved. This means that twice as many column signal lines can be laid by dividing a single column driving circuit into two, provided that the width of each signal line is unchanged. In other words, twice as many display elements (pixels) can be formed in a given surface area compared to the conventional matrix structure. 
     The aforementioned feature of the invention is described in more detail by way of example. Provided that the overall length of a column driving circuit of a conventional matrix display is 19.2 mm and 640 column signal lines branch out from the column driving circuit, the interval between successive column signal lines is 30 μm. In other words, each stage of the column driving circuit takes up a longitudinal dimension of 30 μm. If two such column driving circuits, designed with the same signal line intervals, are provided parallel to each other at separate sites according to the invention, the number of column signal lines is doubled. Specifically, a total of 1280 column signal lines branch out from the two column driving circuits so that the effective line-to-line interval becomes 15 μm, although the actual interval between the individual column signal lines branching out from each column driving circuit remains 30 μm. It is possible anyway to produce a matrix display of a larger scale. 
     In one variation of the invention, the length of each column driving circuit may be halved. Although the number of column signal lines that can be connected to each column driving circuit decreases to 320, the total number of column signal lines branching out from two column driving circuits remains 640. This results in a reduction in pixel dimensions and an increase in integration level. Three, four, or more separate column driving circuits may be provided to achieve three times, four times, or further higher integration level or larger matrix scale. 
     The above discussion also applies to the row driving circuits and row signal lines. 
     In another feature of the invention, it is possible to scan odd-numbered and even-numbered horizontal lines, or rows of display elements, in alternate vertical scans to perform interlaced scanning. This is achieved by configuring the first and second driving circuits in such a way that a select signal outputted from the last stage of the first driving circuit is entered to the first stage the second driving circuit in a case where the two driving circuits employ shift registers as addressing circuits. If the first and second driving circuits employ decoders as an addressing circuits, the decoders should be controlled by a common counter to perform interlaced scanning. 
     It is also possible to scan every second rows, every third rows, and so forth if there are provided three, four, or more separate column driving circuits and they are driven in a prescribed sequence. 
     On the other hand, video signals can be simultaneously supplied to a plurality of column driving circuits by driving them substantially at the same time (provided that there is no signal delay except for unavoidable delays caused by different wiring lengths, for instance). This makes it possible to reduce the operating frequency of the individual column driving circuits. As an example, if four column driving circuits are provided for driving a matrix display conforming to the VGA standard (640 horizontal lines), 160 column signal lines are to be connected to each column driving circuit and the operating frequency of each column driving circuit becomes 2.3 MHz, one-fourth the normal operating frequency. 
     Further, the foregoing another form of the invention where a given column signal line is supplied with a signal from a first column driving circuit and another column signal line adjacent to the given column signal line is supplied with a signal from a second column driving circuit can be used to supply a positive video signal and a negative video signal on the same display frame in line inversion, that is, polarities of video signals are different from each other between adjacent column signal lines by supplying the positive video signal from the first column driving circuit and supplying the negative video signal from the second column driving circuit. Dot inversion of the video signal polarity can also be performed easily in a similar way. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a block diagram of a matrix display according to a first embodiment of the invention; 
     FIGS. 1B and 1C are simplified circuit diagrams illustrating alternative circuit configurations for driving individual display elements of the first embodiment; 
     FIG. 2A is a block diagram of a matrix display according to a second embodiment of the invention; 
     FIGS. 2B and 2C are simplified circuit diagrams illustrating alternative circuit configurations for driving individual display elements of the second embodiment; 
     FIG. 3A is a block diagram of a matrix display according to a third embodiment of the invention; 
     FIGS. 3B and 3C are simplified circuit diagrams illustrating alternative circuit configurations for driving individual display elements of the third embodiment; 
     FIG. 4A is a block diagram of a matrix display according to a fourth embodiment of the invention; 
     FIGS. 4B and 4C are simplified circuit diagrams illustrating alternative circuit configurations for driving individual display elements of the fourth embodiment; 
     FIG. 5A is a block diagram of a matrix display according to a fifth embodiment of the invention; 
     FIG. 5B is a block diagram of a matrix display according to a sixth embodiment of the invention; 
     FIG. 6A is a block diagram of a matrix display according to a seventh embodiment of the invention; 
     FIG. 6B is a block diagram of a matrix display according to an eighth embodiment of the invention; 
     FIG. 7A illustrates a circuit configuration applicable for driving active matrix displays of the invention, in which row and column driving circuits comprise shift registers to constitute an addressing circuit; 
     FIG. 7B illustrates a decoder which may substitute for either one or both of the shift registers shown in FIG. 7A; 
     FIG. 8A is a block diagram of a matrix display according to a ninth embodiment of the invention; 
     FIG. 8B is a block diagram of a matrix display according to a tenth embodiment of the invention; 
     FIGS. 9A to  9 E are diagrams illustrating how line inversion of a video signal is performed according to an eleventh embodiment; 
     FIG. 10A is a simplified circuit diagram of an addressing circuit according to the eleventh embodiment; 
     FIG. 10B is a circuit diagram of decoders which may substitute for shift registers shown in FIG. 10A; 
     FIG. 11 is a diagram illustrating signals which may be entered to the decoder shown in FIG. 10B; and 
     FIG. 12 is a block diagram of a matrix display according to the eleventh embodiment employing decoders to constitute an addressing circuit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     FIGS. 1A to  1 C illustrate circuit configuration of a matrix display according to a first embodiment of the invention, in which FIG. 1A is a block diagram of the matrix display. Although the matrix display of this embodiment employs a matrix  106  of 6 rows by 14 columns for the sake of simplification, the embodiment is applicable to a larger matrix as well. As shown in FIG. 1A, there are provided a first column driving circuit  101  and a second column driving circuit  104  for driving the matrix  106 . In this embodiment, the first column driving circuit  101  is located above the upper edge of the matrix  106  while the second column driving circuit  104  is located below the lower edge of the matrix  106 , as illustrated in FIG.  1 A. The first and second column driving circuits  101  and  104  are connected to individual column signal lines  112  and  113  via output circuits  103  and  105 , respectively. On the other hand, a row driving circuit  102  supplies driving signals to individual row signal lines  114 . 
     Referring to FIG. 1A, video signals are supplied to the first and second column driving circuits  101  and  104  via video signal lines  107  and  109 , respectively, while a clock signal is supplied to the row driving circuit  102  via a clock signal line  108 . Although not specifically illustrated, clock signals are supplied to the first and second column driving circuits  101  and  104  as well. The individual output circuits  103  and  105  are driven by latch pulse signals which are synchronized with the clock signal supplied to the individual row signal lines  114 . Latch pulses are supplied to the output circuits  103  and  105  through latch signal lines  110  and  111 , respectively. 
     FIGS. 1B and 1C are alternative circuit diagrams particularly showing connections between one row signal line  114  and three column signal lines  112 ,  113 . In FIG. 1B which shows a simple matrix structure, display elements (pixels)  115  and  116  are formed at intersections of each row signal line  114  and column signal line  112 , and of each row signal line  114  and column signal line  113 , respectively. It is to be noted that signals for the individual column signal lines  112  are supplied from the first column driving circuit  101  whereas signals for the individual column signal lines  113  are supplied from the second column driving circuit  104 . 
     FIG. 1C shows an active matrix structure in which transistors are employed as active devices. In this structure the relationship between the column signal lines  112 ,  113  and the column driving circuits  101 ,  104  is exactly same as what has been described with reference to FIG.  1 B. However, each of the display elements (pixels)  115  and  116  comprises a transistor and a capacitive circuit element in FIG.  1 C. 
     FIGS. 7A and 7B are more detailed circuit diagrams illustrating circuit configurations for driving a matrix display device. More particularly, FIG. 7A shows a configuration in which row and column driving circuits comprise shift registers  701  and  702  to constitute an addressing circuit, whereas FIG. 7B shows a decoder which may substitute for either one or both of the shift registers  701  and  702  of FIG.  7 A. The circuit configurations of FIGS. 7A and 7B are applicable not only to the first embodiment but also to other embodiments which will be described later. 
     Referring to FIG. 7A, clock pulses are supplied to the shift register  701  of the column driving circuit via a clock signal line  703  so that the shift register  701  outputs sequentially shifting signals. The column driving circuit comprises analog switches  705  and analog memories  706  in addition to the shift register  701 . Video signals entered through video signal lines  713  are sampled by the analog switches  705  and held in the respective analog memories  706 . 
     As switches  707  are turned on and off by a latch signal line  714  in a controlled manner, the video signals amplified by analog buffers  708  are supplied to individual column signal lines  711  of a matrix  709 . In the example shown in FIG. 7A, the matrix  709  is an active matrix display device which employs transistors as active devices. 
     Clock pulses are supplied to the shift register  702  of the row driving circuit via a clock signal line  704  so that the shift register  702  outputs sequentially shifting signals. It is to be noted the clock pulses supplied to the shift register  702  are different from those supplied to the shift register  701 . This is because the operating frequency of the row driving circuit is lower than that of the column driving circuit. The row driving circuit is constructed with the shift register  702  as described above. 
     Select signals outputted from the shift register  702  are supplied to row signal lines  710  arranged on the matrix  709 . Since each row signal line  710  is connected to a gate of a transistor built in a display element (pixel)  712 , a video signal held in the analog memory  706  on a particular column signal line  711  is entered to the corresponding display element (pixel)  712 . 
     If it is desired to use a decoder as disclosed in Japanese Unexamined Patent Application No. 62-265696, the circuit shown in FIG. 7B could substitute for each of the shift registers  701  and  702  shown in FIG.  7 A. In this embodiment, it is possible to substitute the decoder for only the column driving circuit or the row driving circuit. 
     Although the matrix driving circuit of FIGS. 7A and 7B is of an analog type employing the analog switches  705  and analog memories  706 , an equivalent digital-type circuit can be easily configured by use of prior art digital techniques. 
     There are a total of 14 column signal lines  112 ,  113  in the first embodiment described above, and seven each column signal lines  112 ,  113  are connected to the first column driving circuit  101  and the second column driving circuit  104 . It is possible to double the density of display elements (pixels) by providing two column driving circuits  101 ,  104  in this manner. 
     Second Embodiment 
     FIGS. 2A to  2 C illustrate circuit configuration of a matrix display according to a second embodiment of the invention, in which FIG. 2A is a block diagram of the matrix display. The matrix display of this embodiment employs a matrix  206  of 6 rows by 14 columns for the sake of simplification. As shown in FIG. 2A, there are provided a first column driving circuit  201  and a second column driving circuit  202  for driving the matrix  206 . In this embodiment, both the first column driving circuit  201  and the second column driving circuit  202  are located above the upper edge of the matrix  206 , as illustrated in FIG.  2 A. The first and second column driving circuits  201  and  202  are connected to individual column signal lines  214  and  213  via output circuits  203  and  204 , respectively. On the other hand, a row driving circuit  205  supplies driving signals to individual row signal lines  212 . 
     Referring to FIG. 2A, video signals are supplied to the first and second column driving circuits  201  and  202  via video signal lines  207  and  208 , respectively, while a clock signal is supplied to the row driving circuit  205  via a clock signal line  209 . Although not specifically illustrated, clock signals are supplied to the first and second column driving circuits  201  and  202  as well. The individual output circuits  203  and  204  are driven by latch pulse signals which are synchronized with the clock signal supplied to the individual row signal lines  212 . Latch pulses are supplied to the output circuits  203  and  204  through latch signal lines  210  and  211 , respectively. 
     FIGS. 2B and 2C are alternative circuit diagrams particularly showing connections between one row signal line  212  and three column signal lines  213 ,  214 . In FIG. 2B which shows a simple matrix structure, display elements (pixels)  215  and  216  are formed at intersections of each row signal line  212  and column signal line  214 , and of each row signal line  212  and column signal line  213 , respectively. It is to be noted that signals for the individual column signal lines  214  are supplied from the first column driving circuit  201  whereas signals for the individual column signal lines  213  are supplied from the second column driving circuit  202 . 
     FIG. 2C shows an active matrix structure in which transistors are employed as active devices. In this structure the relationship between the column signal lines  213 ,  214  and the column driving circuits  201 ,  202  is exactly same as what has been described with reference to FIG.  2 B. However, each of the display elements (pixels)  215  and  216  comprises a transistor and a capacitive circuit element in FIG.  2 C. 
     Third Embodiment 
     FIGS. 3A to  3 C illustrate circuit configuration of a matrix display according to a third embodiment of the invention, in which FIG. 3A is a block diagram of the matrix display. The matrix display of this embodiment employs a matrix  305  of 11 rows by 7 columns for the sake of simplification. As shown in FIG. 3A, there are provided a first row driving circuit  303  and a second row driving circuit  304  for driving the matrix  305 . In this embodiment, the first row driving circuit  303  is located to the left of the matrix  305  while the second row driving circuit  304  is located to the right of the matrix  305 , as illustrated in FIG.  3 A. Signals are supplied from the first and second row driving circuits  303  and  304  to individual row signal lines  312  and  311 , respectively. On the other hand, a column driving circuit  301  supplies video signals to individual column signal lines  310  via respective output circuits  302 . 
     Referring to FIG. 3A, a video signal is supplied to the column driving circuit  301  via a video signal line  306  while clock signals are supplied to the first and second row driving circuits  303  and  304  via clock signal lines  307  and  308 , respectively. This configuration makes it easier to choose whether to sequentially scan all successive rows, or horizontal lines, in a single vertical scan (noninterlaced scanning) or to scan odd-numbered and even-numbered horizontal lines in alternate vertical scans (interlaced scanning) by controlling the timing of clock pulses fed through the clock signal lines  307  and  308 . Although not specifically illustrated, a clock signal is supplied to the column driving circuit  301  as well. The individual output circuits  302  are driven by a latch pulse signal. Latch pulses are supplied to the output circuits  302  through a latch signal line  309 . 
     FIGS. 3B and 3C are alternative circuit diagrams particularly showing connections between one column row signal line  310  and three row signal lines  311 ,  312 . In FIG. 3B which shows a simple matrix structure, display elements (pixels)  313  and  314  are formed at intersections of each column signal line  310  and row signal line  311 , and of each column signal line  310  and row signal line  312 , respectively. It is to be noted that signals for the individual row signal lines  312  are supplied from the first row driving circuit  303  whereas signals for the individual row signal lines  311  are supplied from the second row driving circuit  304 . 
     FIG. 3C shows an active matrix structure in which transistors are employed as active devices. In this structure the relationship between the row signal lines  311 ,  312  and the row driving circuits  303 ,  304  is exactly same as what has been described with reference to FIG.  3 B. However, each of the display elements (pixels)  313  and  314  comprises a transistor and a capacitive circuit element in FIG.  3 C. 
     Fourth Embodiment 
     FIGS. 4A to  4 C illustrate circuit configuration of a matrix display according to a fourth embodiment of the invention, in which FIG. 4A is a block diagram of the matrix display. The matrix display of this embodiment employs a matrix  405  of 11 rows by 7 columns for the sake of simplification. As shown in FIG. 4A, there are provided a first row driving circuit  403  and a second row driving circuit  404  for driving the matrix  405 . In this embodiment, both the first row driving circuit  403  and the second row driving circuit  404  are located to the left of the matrix  405 , as illustrated in FIG.  4 A. Signals are supplied from the first and second row driving circuits  403  and  404  to individual row signal lines  411  and  412 , respectively. On the other hand, a column driving circuit  401  supplies video signals to individual column signal lines  410  via respective output circuits  402 . 
     Referring to FIG. 4A, a video signal is supplied to the column driving circuit  401  via a video signal line  406  while clock signals are supplied to the first and second row driving circuits  403  and  404  via clock signal lines  407  and  408 , respectively. This configuration makes it easier to choose whether to sequentially scan all successive rows, or horizontal lines, in a single vertical scan (noninterlaced scanning) or to scan odd-numbered and even-numbered horizontal lines in alternate vertical scans (interlaced scanning) by controlling the timing of clock pulses fed through the clock signal lines  407  and  408 . Although not specifically illustrated, a clock signal is supplied to the column driving circuit  401  as well. The individual output circuits  402  are driven by a latch pulse signal. Latch pulses are supplied to the output circuits  402  through a latch signal line  409 . 
     FIGS. 4B and 4C are alternative circuit diagrams particularly showing connections between one column signal line  410  and three row signal lines  411 ,  412 . In FIG. 4B which shows a simple matrix structure, display elements (pixels)  413  and  414  are formed at intersections of each column signal line  410  and row signal line  411 , and of each column signal line  410  and row signal line  412 , respectively. It is to be noted that signals for the individual row signal lines  411  are supplied from the first row driving circuit  403  whereas signals for the individual row signal lines  412  are supplied from the second row driving circuit  404 . 
     FIG. 4C shows an active matrix structure in which transistors are employed as active devices. In this structure the relationship between the row signal lines  411 ,  412  and the row driving circuits  403 ,  404  is exactly same as what has been described with reference to FIG.  4 B. However, each of the display elements (pixels)  413  and  414  comprises a transistor and a capacitive circuit element in FIG.  4 C. 
     Fifth Embodiment 
     FIG. 5A is a block diagram of a matrix display according to a fifth embodiment of the invention. The matrix display of this embodiment employs a matrix  505  of 8 rows by 14 columns for the sake of simplification. There are provided a first row driving circuit  502  and a second row driving circuit  503  for driving the matrix  505 . In this embodiment, the first row driving circuit  502  is located to the left of the matrix  505  while the second row driving circuit  503  is located to the right of the matrix  505 , as illustrated in FIG.  5 A. Signals are supplied from the first and second row driving circuits  502  and  503  to individual row signal lines. On the other hand, a first column driving circuit  501  and a second column driving circuit  504  supply video signals to individual column signal lines via respective output circuits. In this embodiment, the first column driving circuit  501  is located above the upper edge of the matrix  505  while the second column driving circuit  504  is located below the lower edge of the matrix  505 . The density of display elements (pixels) is quadrupled by separately providing two each row driving circuits  502 ,  503  and column driving circuits  501 ,  504  in this manner. 
     Sixth Embodiment 
     FIG. 5B is a block diagram of a matrix display according to a sixth embodiment of the invention. The matrix display of this embodiment employs a matrix  510  of 8 rows by 14 columns for the sake of simplification. There are provided a first row driving circuit  508  and a second row driving circuit  509  for driving the matrix  510 . In this embodiment, the first row driving circuit  508  is located to the left of the matrix  510  while the second row driving circuit  509  is located to the right of the matrix  510 , as illustrated in FIG.  5 B. Signals are supplied from the first and second row driving circuits  508  and  509  to individual row signal lines. On the other hand, a first column driving circuit  506  and a second column driving circuit  507  supply video signals to individual column signal lines via respective output circuits. In this embodiment, both the first column driving circuit  506  and the second column driving circuit  507  are located above the upper edge of the matrix  510 . 
     Seventh Embodiment 
     FIG. 6A is a block diagram of a matrix display according to a seventh embodiment of the invention. The matrix display of this embodiment employs a matrix  605  of 8 rows by 14 columns for the sake of simplification. There are provided a first row driving circuit  602  and a second row driving circuit  603  for driving the matrix  605 . In this embodiment, both the first row driving circuit  602  and the second row driving circuit  603  are located to the left of the matrix  605 , as illustrated in FIG.  6 A. Signals are supplied from the first and second row driving circuits  602  and  603  to individual row signal lines. On the other hand, a first column driving circuit  601  and a second column driving circuit  604  supply video signals to individual column signal lines via respective output circuits. In this embodiment, the first column driving circuit  601  is located above the upper edge of the matrix  605  while the second column driving circuit  604  is located below the lower edge of the matrix  605 . 
     Eighth Embodiment 
     FIG. 6B is a block diagram of a matrix display according to an eighth embodiment of the invention. The matrix display of this embodiment employs a matrix  610  of 8 rows by 14 columns for the sake of simplification. There are provided a first row driving circuit  608  and a second row driving circuit  609  for driving the matrix  610 . In this embodiment, both the first row driving circuit  608  and the second row driving circuit  609  are located to the left of the matrix  610 , as illustrated in FIG.  6 B. Signals are supplied from the first and second row driving circuits  608  and  609  to individual row signal lines. On the other hand, a first column driving circuit  606  and a second column driving circuit  607  supply video signals to individual column signal lines via respective output circuits. In this embodiment, both the first column driving circuit  606  and the second column driving circuit  607  are located above the upper edge of the matrix  610 . 
     Ninth Embodiment 
     FIG. 8A is a block diagram of a matrix display according to a ninth embodiment of the invention. The matrix display of this embodiment employs a matrix  806  of 11 rows by 27 columns for the sake of simplification. There are provided a first row driving circuit  804  and a second row driving circuit  805  for driving the matrix  806 . In this embodiment, the first row driving circuit  804  is located to the left of the matrix  806  while the second row driving circuit  805  is located to the right of the matrix  806 , as illustrated in FIG.  8 A. Signals are supplied from the first and second row driving circuits  804  and  805  to individual row signal lines. On the other hand, a first column driving circuit  801 , a second column driving circuit  802  and a third column driving circuit  803  supply video signals to individual column signal lines via respective output circuits (not shown). In this embodiment, all the column driving circuits  801 - 803  are located above the upper edge of the matrix  806 . According to this circuit configuration, the operating frequency of the individual column driving circuits  801 - 803  can be made one-third as low as the normal operating frequency by simultaneously driving the three column driving circuits  801 - 803  and feeding different video signals to them. 
     Tenth Embodiment 
     FIG. 8B is a block diagram of a matrix display according to a tenth embodiment of the invention. The matrix display of this embodiment employs a matrix  813  of 11 rows by 27 columns for the sake of simplification. There are provided a first row driving circuit  809  and a second row driving circuit  810  for driving the matrix  813 . In this embodiment, the first row driving circuit  809  is located to the left of the matrix  813  while the second row driving circuit  810  is located to the right of the matrix  813 , as illustrated in FIG.  8 B. Signals are supplied from the first and second row driving circuits  809  and  810  to individual row signal lines. On the other hand, a first column driving circuit  807 , a second column driving circuit  808 , a third column driving circuit  811  and a four the column driving circuit  812  supply video signals to individual column signal lines via respective output circuits (not shown). In this embodiment, the first column driving circuit  807  and the second column driving circuit  808  are located above the upper edge of the matrix  813  while the third column driving circuit  811  and the fourth column driving circuit  812  are located below the lower edge of the matrix  813 . According to this circuit configuration, the operating frequency of the individual column driving circuits  807 ,  808 ,  811 ,  812  can be made one-fourth as low as the normal operating frequency by simultaneously driving the four column driving circuits  807 ,  808 ,  811 ,  812  and feeding different video signals to them. 
     Eleventh Embodiment 
     Referring now to FIGS. 9 to  12 , a method of line inversion according to an eleventh embodiment of the invention is described. FIG. 9A shows a video signal for a particular row of a matrix display. A conventional technique used for line inversion of this type of video signal input which has a relatively featureless pattern involves a process of converting the video signal input so that its polarity is alternately inverted as shown in FIG.  9 B. Sequentially varying values of the video signal are entered to a matrix addressing circuit and distributed to successive columns a through z. The present invention remarkably simplifies polarity inverting operation. 
     According to the eleventh embodiment, the video signal for a single row of the matrix display is compressed, or shortened in time, to half the original length. This compressed video signal in its normal polarity is combined with a reversal of the same video signal so that the former is immediately followed by the latter, as shown in FIG.  9 C. 
     As the resultant video signal input shown in FIG. 9C is sampled at specific points in time, a signal shown in FIG. 9D is obtained. The input signal thus obtained is entered to a shift register which is configured as shown in FIG. 10A, for instance, to distribute individual values of the video signal to successive columns of the matrix display. Although the matrix display shown in FIG. 10A has only 16 columns (a through p) for the sake of simplification, it may be expanded to include 26 columns (a through z), for instance. What is to be noted in the circuit configuration of FIG. 10A is that a select signal output from a last stage (column o) of a first shift register SRI is entered to a first stage (column b) of a second shift register SR 2 . 
     Referring to FIG. 10A, the matrix display comprises successive columns a, b, c, d, e, and so forth but the first shift register SR 1  and the second shift register SR 2  are alternately connected to these columns. Accordingly, if the individual values of the video signal shown in FIG. 9D are distributed to successive stages of the first shift register SR 1  and the second shift register SR 2 , the signal entered to a given row of the matrix is depicted as shown in FIG.  9 E. This is exactly the same as obtained by the conventional line inversion technique. It would be recognized from the above discussion of the embodiment that line inversion operation is remarkably simplified by the invention. 
     Although the foregoing discussion is based on the circuit diagram of FIG. 10A which employs the shift registers SR 1  and SR 2  to constitute an addressing circuit, decoders DC 1  and DC 2  as shown in FIG. 10B which may substitute for the shift registers SR 1  and SR 2 . Although a counter for the circuit of FIG. 10B outputs four digital values, or four bits designated by 2 0  to 2 3 , to deliver signals to 16 columns, this is just for simplifying the circuit diagram. It is possible to drive a 26-column matrix display only by expanding the circuit of FIG. 10B so that it can handle one more bit. 
     When signals shown in FIG. 11 are entered to individual bit lines 2 0  to 2 3  of the circuit of FIG. 10B, the first decoder DC 1  sequentially outputs signals for columns a, c, e, g, i, k, m and o and then the second decoder DC 2  sequentially outputs signals for columns b, d, f, h, j, l, n and p. This means that the first and second decoders DC 1  and DC 2  perform the same function as the first and second shift registers SR 1  and SR 2  shown in FIG.  10 A. 
     FIG. 12 is a block diagram of a matrix display based on the above-described line inversion operation. Although there are provided separate decoders  1201  and  1202 , they are driven by a single counter  1203 . The matrix display driving circuit of FIG. 12 is characterized in that line inversion operation is performed by supplying a video signal from a video controller  1204  to a matrix  1205 .