Abstract:
In an apparatus for driving a gate storage type liquid crystal display panel having gate lines, two gate pulse signals are simultaneously supplied to two adjacent ones of the gate lines, to thereby drive them. The two gate pulses differ in that at least one of a rising edge and a falling edge of one of the two gate pulses differs from that of the other.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for driving a gate storage type liquid crystal display (LCD) panel. 
     2. Description of the Related Art 
     Active matrix LCD panels using thin film transistors (TFT&#39;s) have been developed in terms of resolution and performance. 
     In a prior gate storage type active matrix LCD panel (see: T. P. Brody: &#34;A 6×6 inch 20 lines-per-Inch Liquid-Crystal Display Panel&#34;, IEEE Trans. of Electron Devices, Vol. ED-20, No. 11, pp. 995-1001, Nov. 1973), each pixel has a storage capacitor formed on an adjacent gate line, to thereby increase the capacity of the pixels. As a result, the feed-through of gate pulse signals is reduced, and a pixel voltage deviation caused by the leakage current of liquid crystal cells and TFT&#39;s is reduced. This will be explained later in detail. 
     On the other hand, a two gate line driving method is applied to a storage capacitor line type active matrix LCD panel (see: Shinji Morozumi et al., &#34;4.25-in and 1.51-in B/W and Full-Color LC Video Displays Addressed by Poly-Si TFT&#39;s&#34;, SID 84 Digest, pp. 316-319, 1984; Masahiro Adachi et al., &#34;A High-Resolution TFT-LCD for a High-Definition Projection TV&#34;, SID 90 Digest, pp. 338-341, 1990). According to the two gate line driving method, in non-interlace scanning, the pulse width of a gate pulse signal applied to gate lines can be twice that of the conventional one gate driving method, to enlarge the margin of a write operation and reduce the frequency of operation. Also, when the ability of the TFT&#39;s is small or when the number of gate lines is large, effective use is made of the two gate line driving method. Further, since non-interlace scanning is used, the resolution is high and the flicker is small. This will be explained later in detail. 
     In the prior art, however, it is impossible to apply the two gate line driving method to a gate storage type active matrix LCD panel. This will also be explained later in detail. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide an apparatus for driving a gate storage type LCD panel capable of carrying out the two gate line driving method. 
     According to the present invention, in an apparatus for driving a gate storage type LCD panel having gate lines, two gate pulse signals are simultaneously supplied to two adjacent gate lines, to thereby drive them. The pulse widths of the two gate pulse signals are independently controlled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the description as set forth, in comparison with the prior art, with reference to the accompanying drawings, wherein: 
     FIG. 1 is a circuit diagram illustrating a prior art gate storage type active matrix LCD panel; 
     FIGS. 2A through 2F are timing diagrams showing the operation of the apparatus of FIG. 1; 
     FIG. 3 is a circuit diagram illustrating a prior art storage capacitor line type active matrix LCD panel; 
     FIGS. 4A through 4F are timing diagrams showing the operation of the apparatus of FIG. 3; 
     FIGS. 5A through 5F are timing diagrams explaining a first principle of the present invention; 
     FIG. 6 is a circuit diagram illustrating a first embodiment of the gate storage type active matrix LCD panel according to the present invention; 
     FIG. 7 is a partial circuit diagram of the vertical timing generating circuit of FIG. 6; 
     FIGS. 8A through 8D are timing diagrams showing the operation of the circuit of FIG. 7; 
     FIG. 9 is a detailed circuit diagram of the gate line scanning circuits of FIG. 6; 
     FIGS. 10A through 10N are timing diagrams showing the operation of the circuit of FIG. 9; 
     FIG. 11 is a circuit diagram illustrating a second embodiment of the gate storage type active matrix LCD panel according to the present invention; 
     FIG. 12 is a detailed circuit diagram of the gate line scanning circuit of FIG. 11; 
     FIGS. 13A through 13M are timing diagrams showing the operation of the circuit of FIG. 12; 
     FIGS. 14A through 14F are timing diagrams explaining a second principle of the present invention; 
     FIG. 15 is a circuit diagram illustrating a third embodiment of the gate storage type active matrix LCD panel according to the present invention; 
     FIG. 16 is a partial circuit diagram of the vertical timing generating circuit of FIG. 15; 
     FIGS. 17A through 17D are timing diagrams showing the operation of the circuit of FIG. 16; 
     FIGS. 18A through 18N are timing diagrams showing the operation of the circuit of FIG. 9 applied to the LCD panel of FIG. 15; 
     FIG. 19 is a circuit diagram illustrating a fourth embodiment of the gate storage type active matrix LCD panel according to the present invention; 
     FIGS. 20A through 20M are timing diagrams showing the operation of the circuit of FIG. 12 applied to the LCD panel of FIG. 19; 
     FIGS. 21A through 21F are timing diagrams illustrating a modification of the first principle of the present invention as illustrated in FIGS. 5A through 5F; and 
     FIGS. 22A through 22F are timing diagrams illustrating a modification of the second principle of the present invention as illustrated in FIGS. 14A through 14F. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the description of the preferred embodiments, prior art active matrix LCD panels will be explained with reference to FIGS. 1, 2A through 2F, 3 and 4A through 4F. 
     In FIG. 1, which illustrates a prior art gate storage type active matrix LCD panel, reference numeral 1 designates a pixel array including a plurality of pixels P 11 , P 12 , . . . connected to gate lines GL 1 , GL 2 , . . . driven by a gate line scanning circuit 2 and to signal lines SL 1 , SL 2 , . . . driven by a signal line driving circuit 3. In more detail, each of the pixels, such as P 31 , includes a liquid crystal cell L 31  connected to a common counter electrode E, a TFT Q 31  connected between the signal line SL 1  and the liquid crystal cell L 31  and controlled by the potential at the gate line GL 3 , and a storage capacitor C 31  connected between the liquid crystal cell L 31  and the gate line GL 2  adjacent to the gate line GL 3 . Thus, due to the presence of the storage capacitors, such as C 31 , the capacity of the pixels is increased. That is, only when each of the gate lines GL 1 , GL 2 , . . . are selected for a small time period, is the potential thereof made high as shown in FIGS. 2A through 2F. Otherwise, the gate lines GL 1 , GL 2 , . . . remain at a definite potential such as the ground potential GND. Therefore, the gate lines GL 1 , GL 2 , . . . can serve as counter electrodes of capacitors. Note that an additional gate line GL 0  is provided only for the storage capacitors of the pixels P 11 , P 12 , . . . and the potential at the gate line GL 0  always remains at the ground potential GND. 
     Thus, in FIG. 1, since the capacity of the pixels is increased, the availability of an area is increased as compared with a storage capacitor line type LCD panel (see: FIG. 3), so that the aperture ratio for light is enlarged. In other words, if the aperture ratio for light is the same, the feed-through of gate pulse signals is reduced, and also, a pixel voltage deviation caused by the leakage current of the liquid crystal cells and the TFT&#39;s is reduced. 
     In FIG. 3, which illustrates a prior art storage capacitor line type active matrix LCD panel, a pixel array 1&#39; includes a plurality of pixels P 11  &#39;, P 12  &#39;, . . . connected to the gate lines GL 1 , GL 2 , . . . driven by a gate line scanning circuit 2&#39; and to the signal lines SL 1 , SL 2 , . . . driven by the signal line driving circuit 3. In this case, each of the pixels P 11  &#39;, P 12  &#39;, . . . is the same as the pixels P 11 , P 12 , . . . of FIG. 1, except that the storage capacitors, such as C 31 , are connected to additional storage capacitor lines L 1 , L 2 , . . . . Also, the additional gate line GL 0  of FIG. 1 is not provided. 
     The scanning operation of the gate lines GL 1 , GL 2 , . . . of FIG. 3 is next explained with reference to FIGS. 4A through 4F. In an odd field mode, the gate line GL 1  is driven for a time period T 1  ; the gate lines GL 2  and GL 3  are simultaneously driven for a time period T 2  ; the gate lines GL 4  and GL 5  are simultaneously driven for a time period T 3  ; and the like. That is, a pair of the gate lines GL i  and GL i+1  (i=2, 3, . . . ) are simultaneously driven. On the other hand, in an even field mode, the gate lines GL 1  and GL 2  are simultaneously driven for a time period T 1  &#39;; the gate lines GL 3  and GL 4  are simultaneously driven for a time period T 2  &#39;; the gate lines GL 5  and GL 6  are simultaneously driven for a time period T 3  &#39;; and the like. That is, a pair of the gate lines GL i  and GL i+1  (i=1, 2, . . . ) are simultaneously driven. In FIGS. 4A through 4F, in non-interlace scanning, the pulse width of a gate pulse signal applied to the gate lines GL 1 , GL 2 , . . . can be twice that as shown in FIGS. 2A through 2F, to enlarge the margin of a write operation and reduce the frequency of operation. Also, when the ability of the TFT&#39;s is small or when the number of gate lines is large, effective use is made of the two gate line driving method. Further, since non-interlace scanning is used, the resolution is high and the flicker is small. 
     If the two gate line driving method as shown in FIGS. 4A through 4F is applied to the gate storage type active matrix LCD panel of FIG. 1, the following problem may occur. That is, for example, consider that the gate lines GL 4  and GL 5  are simultaneously driven for the time period T 3  as shown in FIGS. 4A through 4F. In this case, since a write operation upon the gate line GL 3  is completed so that the potential at the gate line GL 3  is definite, the potential at the gate line GL 3  hardly affects the potential at the liquid crystal cells belonging to the gate line GL 4 . However, since the potentials at the gate lines GL 4  and GL 5  are changed simultaneously from high to low, the potential at the gate line GL 4  may affect the potentials at the liquid crystal cells belonging to the gate line GL 5  due to the capacitive coupling therebetween by the storage capacitors connected to the gate line GL 4 . Note that, generally, the capacity of each storage capacitor is larger than or equal to that of each liquid crystal cell. Therefore, the potentials at the liquid crystal cells belonging to the gate line GL 5  may be fluctuated, that is, the pixel potentials may be fluctuated. 
     FIGS. 5A through 5F are timing diagrams for explaining a first principle of the present invention. For example, in the pair of the gate lines GL 4  and GL 5  simultaneously driven for the time period T 3 , the gate line GL 4  is changed from high to low by a time period ΔT prior to the change of the potential at the gate line GL 5 . For example, if each of the time periods T 1 , T 2 , . . . , T 1  &#39;, T 2  &#39;, . . . is about 30 μm, the time period ΔT is about 5 μm. As a result, since a write operation upon the gate line GL 4  is also completed so that the potential at the gate line GL 4  is definite, the potential at the gate line GL 4  also hardly affects the potential at the liquid crystal cells belonging to the gate line GL 5 . 
     In FIG. 6, which is a first embodiment of the present invention for realizing the first principle of FIGS. 5A through 5F, the pixel array 1 includes 1280×1024 pixels. A gate line scanning circuit 2-L is used for driving the gate lines GL 1 , GL 3 , . . . , and GL 1023 , and a gate line scanning circuit 2-R is used for driving the gate lines GL 2 , GL 4 , . . . , and GL 1024 . 
     A vertical timing generating circuit 4 receives a vertical synchronization signal VSYNC and a horizontal synchronization signal HSYNC, to generate a start pulse signal STL, an inhibit signal INHL, and clock signals φL and φL for the gate line scanning circuit 2-L, and to generate a start pulse signal STR, an inhibit signal INHR, and clock signals φR and φR for the gate line scanning circuit 2-R. 
     Similarly, a horizontal timing generating circuit 5 receives the horizontal synchronization signal HSYNC to generate a start pulse signal STH and a clock signal φH for the signal line driving circuit 3. Also, a signal processing circuit 6 receives color signals R, G and B, to thereby generate digital output signals and transmit then to the signal line driving circuit 3. 
     In FIG. 7, which is a partial circuit diagram of the vertical timing generating circuit 4 of FIG. 6, an inhibit signal INH as shown in FIG. 8A is supplied to NAND circuits 401 and 402 which are controlled by an odd/even field signal O/E as shown in FIG. 8B. That is, when the odd/even field signal O/E is &#34;0&#34; (odd field mode), the inhibit signal INHL for the gate line scanning circuit 2-L is inactive as shown in FIG. 8C and the inhibit signal INHR for the gate line scanning circuit 2-R is active as shown in FIG. 8D. Conversely, when the odd/even field signal O/E is &#34;1&#34; (even field mode), the inhibit signal INHL for the gate line scanning circuit 2-L is active as shown in FIG. 8C and the inhibit signal INHR for the gate line scanning circuit 2-R is inactive as shown in FIG. 8D. 
     In FIG. 9, which is a detailed circuit diagram of the gate line scanning circuit 2-L and 2-R of FIG. 6, the gate line scanning circuit 2-L includes a shift register having 512 stages S 1 , S 2 , . . . , and S 512  for shifting the start pulse signal STL as shown in FIG. 10C in synchronization with the clock signal φL and φL as shown in FIGS. 10E and 10F to generate gate pulse signals for the gate lines GL 1 , GL 3 , . . . , and GL 1023 . In this case, the gate pulse signals are supplied via AND circuits G 1 , G 2 , . . . , and G 512  controlled by the inhibit signal INHL as shown in FIG. 10A and buffers B 1 , B 2 , . . . , and B 512  to the gate lines GL 1 , GL 3 , . . . , and GL 1023 . Therefore, the gate pulse signals applied to the gate lines GL 1 , GL 3 , and GL 5  are shown in FIGS. 10I, 10K and 10M, respectively. Similarly, the gate line scanning circuit 2-R includes a shift register having 512 stages S 1  &#39;, S 2  &#39;, . . . and S 512  &#39; for shifting the start pulse signal STR as shown in FIG. 10D in synchronization with the clock signal φR and φR as shown in FIGS. 10G and 10H to generate gate pulse signals for the gate lines GL 2 , GL 4 , . . . , and GL 1024 . In this case, the gate pulse signals are supplied via AND circuits G 1  &#39;, G 2  &#39;, . . . , and G 512  &#39; controlled by the inhibit signal INHR as shown in FIG. 10B and buffers B 1  &#39;, B 2  &#39;, . . . , and B 512  &#39; to the gate lines GL 2 , GL 4 , . . . , and GL 1024 . Therefore, the gate pulse signals applied to the gate lines GL 2 , GL 4 , and GL 6  are shown in FIGS. 10J, 10L and 10N, respectively. 
     In an odd field mode, the inhibit signal INHL is inactive and the inhibit signal INHR is active as shown in FIGS. 10A and 10B. Also, the phase of the start pulse signal STL associated with the clock signals φL and φL is advanced as compared with that of the start pulse signal STR associated with the clock signals φR and φR, as shown in FIGS. 10C, 10E and 10F and FIGS. 10D, 10G and 10H. Therefore, as shown in FIGS. 10I through 10N, the gate lines GL 2  and GL 3  are simultaneously driven, and the gate line GL 2  falls earlier than the gate line GL 3 , and also, the gate lines GL 4  and GL 5  are simultaneously driven, and the gate line GL 4  falls earlier than the gate line GL 5 . 
     In an even field mode, the inhibit signal INHL is active and the inhibit signal INHR is inactive as shown in FIGS. 10A and 10B. Also, the phase of the start pulse signal STL associated with the clock signals φL and φL is the same as that of the start pulse signal STR associated with the clock signals φR and φR, as shown in FIGS. 10C, 10E and 10F and FIGS. 10D, 10G and 10H. Therefore, as shown in FIGS. 10I through 10N, the gate lines GL 1  and GL 2  are simultaneously driven, and the gate line GL 1  falls earlier than the gate line GL 2 . Also, the gate lines GL 3  and GL 4  are simultaneously driven, and the gate line GL 3  falls earlier than the gate line GL 4 . Further, the gate lines GL 5  and GL 6  are simultaneously driven, and the gate line GL 5  falls earlier than the gate line GL 6 . 
     In FIG. 11, which is a second embodiment of the present invention for realizing the first principle of FIGS. 5A through 5F, a gate line scanning circuit 2&#39; is provided instead of the gate line scanning circuits 2-L and 2-R of FIG. 6, and a vertical timing generating circuit 4&#39; is provided instead of the vertical timing generating circuit 4 of FIG. 6. 
     The vertical timing generating circuit 4&#39; receives the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC, to generate an odd/even field signal O/E, its inverted signal O/E, a start pulse signal ST, an inhibit signal INHL, and clock signals φ and φ for the gate line scanning circuit 2&#39;. 
     In FIG. 12, which is a detailed circuit diagram of the gate line scanning circuit 2&#39; of FIG. 11, the gate line scanning circuit 2&#39; includes a shift register having 512 stages S 1  &#34;, S 2  &#34;, . . . and S 512  &#34; for shifting the start pulse signal ST as shown in FIG. 13E in synchronization with the clock signal φand φ as shown in FIGS. 13F and 13G to generate gate pulse signals for the gate lines GL 1 , GL 3 , . . . , and GL 1023 . In this case, the gate pulse signals are supplied via AND circuits G 1 , G 2 , . . . , and G 512  controlled by the inhibit signal INHL as shown in FIG. 13C and buffers B 1 , B 2 , . . . and B 512  to the gate lines GL 1 , GL 3 , . . . , and GL 1023 . Therefore, the gate pulse signals applied to the gate lines GL 1 , GL 3 , and GL 5  are shown in FIGS. 13, 13J and 13L, respectively. 
     Also, switches SW1, SW2, . . . , and SW512 are provided. When the odd/even field signal O/E is &#34;0&#34; (odd field mode) as shown in FIGS. 13A and 13B, the switches SW1, SW3, . . . , and SW511 are turned OFF and the switches SW2, SW4, . . . , and SW512 are turned ON. As a result, the gate pulse signal applied to the gate line GL 3  is applied to the gate line GL 2 , the gate pulse signal applied to the gate line GL 5  is applied to the gate line GL 4 , and so on. Conversely, when the odd/even field signal O/E is &#34;1&#34; (even field mode), as shown in FIGS. 13A and 13B, the switches SW1, SW3, . . . , and SW511 are turned ON and the switches SW2, SW4, . . . , and SW512 are turned OFF. As result, the gate pulse signal applied to the gate line GL 1  is applied to the gate line GL 2 , the gate pulse signal applied to the gate line GL 3  is applied to the gate line GL 4 , and so on. In this case, the gate pulse signals are supplied via the AND circuits G 1  &#39;, G 2  &#39;, . . . , and G 512  &#39; controlled by the inhibit signal INHR as shown in FIG. 13D and the buffers B 1  &#39;, B 2  &#39;, . . . , and B 512  &#39; to the gate lines GL 2 , GL 4 , . . . , and GL 1024 . Therefore, the gate pulse signals applied to the gate lines GL 2 , GL 4 , and GL 6  are shown in FIGS. 13I, 13K and 13M, respectively. 
     In an odd field mode, the inhibit signal INHL is inactive and the inhibit signal INHR is active as shown in FIGS. 13C and 13D. Therefore, as shown in FIGS. 13H through 13M, the gate lines GL 2  and GL 3  are simultaneously driven, and the gate line GL 2  falls earlier than the gate line GL 3 , and also, the gate lines GL 4  and GL 5  are simultaneously driven, and the gate line GL 4  falls earlier than the gate line GL 5 . 
     In an even field mode, the inhibit signal INHL is active and the inhibit signal INHR is inactive as shown in FIGS. 13C and 13D. Therefore, as shown in FIGS. 13H through 13M, the gate lines GL 1  and GL 2  are simultaneously driven, and the gate line GL 1  falls earlier than the gate line GL 2 . Also, the gate lines GL 3  and GL 4  are simultaneously driven, and the gate line GL 3  falls earlier than the gate line GL 4 . Further, the gate lines GL 5  and GL 6  are simultaneously driven, and the gate line GL 5  falls earlier than the gate line GL 6 . 
     In FIGS. 6 and 11, the storage capacitors belonging to the gate line GL i  are connected to the gate line GL i-1  located upstream along the scanning direction. However, the present invention can be applied to a case where the storage capacitors belonging to the gate line GL i  are connected to the gate line GL i+1  downstream along the scanning direction. In this case, a second principle of the present invention as shown in FIGS. 14A through 14F is adopted, and a third embodiment of the present invention for realizing this second principle is illustrated in FIG. 15. In FIG. 15, a pixel array 1&#34; and a vertical timing generating circuit 4&#34; are provided instead of the pixel array 1 and the vertical timing generating circuit 4 of FIG. 6. For example, in the pair of the gate lines GL 4  and GL 5  simultaneously driven for the time period T 3 , the gate line GL 5  is changed from high to low by a time period ΔT prior to the change of the potential at the gate line GL 4 . As a result, since a write operation upon the gate line GL 5  is also completed so that the potential at the gate line GL 5  is definite, the potential at the gate line GL 5  also hardly affects the potential at the liquid crystal cells belonging to the gate line GL 4 . 
     In FIG. 16, which is a partial circuit diagram of the vertical timing generating circuit 4&#34; of FIG. 15, an inhibit signal INH as shown in FIG. 17A is supplied to NAND circuits 401&#39; and 402&#39; which are controlled by an odd/even field signal O/E as shown in FIG. 17B. That is, when the odd/even field signal O/E is &#34;0&#34; (odd field mode), the inhibit signal INHL for the gate line scanning circuit 2-L is active as shown in FIG. 17C and the inhibit signal INHR for the gate line scanning circuit 2-R is inactive as shown in FIG. 17D. Conversely, when the odd/even field signal O/E is &#34;1&#34; (even field mode), the inhibit signal INHL for the gate line scanning circuit 2-L is inactive as shown in FIG. 17C and the inhibit signal INHR for the gate line scanning circuit 2-R is active as shown in FIG. 17D. 
     The gate line scanning circuits 2-L and 2-R of FIG. 15 are operated as shown in FIGS. 18A through 18N. That is, in an odd field mode, the inhibit signal INHL is active and the inhibit signal INHR is inactive as shown in FIGS. 18A and 18B. Also, the phase of the start pulse signal STL associated with the clock signals φL and φL is advanced as compared with that of the start pulse signal STR associated with the clock signals φR and φR, as shown in FIGS. 18C, 18E and 18F and FIGS. 18D, 18G and 18H. Therefore, as shown in FIGS. 18I through 18N, the gate lines GL 2  and GL 3  are simultaneously driven, and the gate line GL 3  falls earlier than the gate line GL 2 , and also, the gate lines GL 4  and GL 5  are simultaneously driven, and the gate line GL 5  falls earlier than the gate line GL 4 . 
     In an even field mode, the inhibit signal INHL is inactive and the inhibit signal INHR is active as shown in FIGS. 18A and 18B. Also, the phase of the start pulse signal STL associated with the clock signals φL and φL is the same as that of the start pulse signal STR associated with the clock signals φR and φR, as shown in FIGS. 18C, 18E and 18F and FIGS. 18D, 18G and 18H. Therefore, as shown in FIGS. 18I through 18N, the gate lines GL 1  and GL 2  are simultaneously driven, and the gate line GL 2  falls earlier than the gate line GL 1 . Also, the gate lines GL 3  and GL 4  are simultaneously driven, and the gate line GL 4  falls earlier than the gate line GL 3 . Further, the gate lines GL 5  and GL 6  are simultaneously driven, and the gate line GL 6  falls earlier than the gate line GL 5 . 
     In FIG. 19, which is a fourth embodiment of the present invention for realizing the second principle of FIGS. 14A through 14F, a gate line scanning circuit 2&#39; is provided instead of the gate line scanning circuit 2-L and 2-R of FIG. 15, and a vertical timing generating circuit 4&#34;&#39; is provided instead of the vertical timing generating circuit 4&#34; of FIG. 15. 
     The vertical timing generating circuit 4&#34;&#39; is the same as the vertical timing generating circuit 4&#39; of FIG. 11 except for the inhibit signals INHL and INHR. 
     The gate line scanning circuit 2&#39; of FIG. 19 is operated as shown in FIGS. 20A through 20M. 
     In an odd field mode, the inhibit signal INHL is active and the inhibit signal INHR is inactive as shown in FIGS. 20C and 20D. Therefore, as shown in FIGS. 20H through 20M, the gate lines GL 2  and GL 3  are simultaneously driven, and the gate line GL 3  falls earlier than the gate line GL 2 , and also, the gate lines GL 4  and GL 5  are simultaneously driven, and the gate line GL 5  falls earlier than the gate line GL 4 . 
     In an even field mode, the inhibit signal INHL is inactive and the inhibit signal INHR is active as shown in FIGS. 20C and 20D. Therefore, as shown in FIGS. 20H through 20M, the gate lines GL 1  and GL 2  are simultaneously driven, and the gate line GL 2  falls earlier than the gate line GL 1 . Also, the gate lines GL 3  and GL 4  are simultaneously driven, and the gate line GL 4  falls earlier than the gate line GL 3 . Further, the gate lines GL 5  and GL 6  are simultaneously driven, and the gate line GL 6  falls earlier than the gate line GL 5 . 
     In FIGS. 21A through 21F, which are timing diagrams showing a modification of the first principle of the present invention as shown in FIGS. 5A through 5F, the pulse widths of the gate pulse signals are the same. Also, in FIGS. 22A through 22F, which are timing diagrams showing a modification of the second principle of the present invention as shown in FIGS. 14A through 14F, the pulse widths of the gate pulse signals are the same. These modifications may simplify the circuits as illustrated in FIGS. 6, 11, 15 and 19. 
     As explained hereinbefore, according to the present invention, in a gate storage type LCD panel, the two gate line driving method can be carried out.