JP3557488B2 - Driving method of liquid crystal display element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for driving a liquid crystal display element, and more particularly to a method for driving a liquid crystal display element that enables high-contrast display by using a ferroelectric liquid crystal.
[0002]
[Prior art]
As a driving method of the liquid crystal display element, two types of a simple matrix driving method and an active matrix driving method are known. In the active matrix driving method, a switching element such as a TFT (thin film transistor) is formed in correspondence with each pixel arranged on a glass substrate, and the switching element turns on / off (transmits or blocks light) each pixel. ) And the memory property is obtained until the next switching time. On the other hand, in the simple matrix driving method, a voltage is applied to a scanning line electrode and an information signal line electrode, and pixels arranged on each scanning line electrode are turned on / off.
[0003]
In the active matrix driving method, switching elements corresponding to the number of pixels are required. Therefore, the production cost is increased, and very advanced technology is required to manufacture all the TFTs as switching elements so as to function completely.
[0004]
On the other hand, in the simple matrix driving method, a scanning signal line group and an information signal line group are arranged so as to intersect, a scanning line electrode and an information signal line electrode are formed at the intersection of both signal line groups, and the opposing portion is formed. To the formed pixels, a signal for designating ON / OFF of each pixel by the information signal line is given at the same time while sequentially designating the scanning signal line group. Such a simple matrix driving method is advantageous in terms of manufacturing cost and technical as compared with the above-described active matrix driving method, but from the time when one pixel is turned on / off, it is turned on / off next. There is a problem in the memory property until the off control.
[0005]
However, in recent years, a so-called bistable liquid crystal in which liquid crystal molecules themselves have a memory property is disclosed in U.S. Pat. S. P. No. No. 4,367,924 (JP-A-56-107216). As such a bistable liquid crystal, a ferroelectric liquid crystal is generally used.
[0006]
By setting the panel gap to 2 μm or less, the ferroelectric liquid crystal becomes a surface-stabilized ferroelectric liquid crystal (SSFLC), and bistability is obtained. That is, by applying a voltage exceeding the positive or negative threshold voltage to the liquid crystal, the state of the liquid crystal molecules changes to the first optical stable state and the second optical stable state according to the polarity of the applied voltage. Invert between When the voltage applied to the pixel is cut off or a voltage not exceeding the threshold voltage is applied, the liquid crystal molecules stably maintain their own state at that time. In other words, the ferroelectric liquid crystal itself has memory properties. Due to such features, a liquid crystal display device using a ferroelectric liquid crystal has a low manufacturing cost and is technically relatively easy without using an active matrix method which requires a high manufacturing cost and a high technology. A practically sufficient display is possible by a simple matrix system which can be manufactured in a short time.
[0007]
Hereinafter, as to the driving method using the simple matrix method, a line-sequential driving method in which an information signal is applied to an information signal line electrode to perform display while sequentially selecting the most common scanning line electrodes will be described. Note that, here, the voltage applied to the liquid crystal is a difference between the signal waveform applied to the scanning line electrode and the signal waveform applied to the information signal line electrode with reference to the information signal line electrode. The polarity and voltage of the waveform change the state of the liquid crystal, and as a result, each pixel performs, for example, white / black display.
[0008]
Since the ferroelectric liquid crystal has a polarity response and a threshold voltage, when information is not written to the pixel (in this case, the state before that is maintained), a voltage lower than the threshold is applied. You. However, the polarity of the voltage applied to the scanning line electrode and the information signal line electrode in this case is the same. When the polarity of the voltage applied to the scanning line electrode and the polarity of the information signal line electrode are different, information is written to the pixel, and white display or black display is performed according to the polarity of the applied voltage. .
[0009]
Specifically, when a white display is performed, a voltage exceeding the positive threshold is applied last, and when a black display is performed, a voltage exceeding the negative threshold is applied last. Applied. Accordingly, display corresponding to each of them is possible, and basically, writing of one pixel, that is, display can be performed by one pulse.
[0010]
However, in the simple matrix driving method, if the above-mentioned display continues for a long time, a cumulative bias of electric charges always occurs, and as a result, burn-in, decomposition of liquid crystal molecules, and the like occur. There is a possibility that the function as a display element cannot be performed. Therefore, a pulse of the opposite polarity is applied to each pixel immediately before applying a selection pulse (a pulse applied to the scanning line electrode for specifying a pixel to be switched), and then a non-selection pulse (not specified) It is necessary to eliminate the bias of the charges by always canceling the polarities of the pulses applied to the pixels, so that the cumulative bias of the charges does not occur.
[0011]
Note that a pulse of the opposite polarity applied immediately before the application of the above-described selection pulse is called a reset pulse, and a pulse to be written next is called a set pulse.
[0012]
Under these circumstances, for example, a four-pulse method, a two-field method, and the like have been proposed as a driving method of a liquid crystal display element using a ferroelectric liquid crystal. The invention disclosed in Japanese Unexamined Patent Publication No. Hei 5-34659 will be described as a prior art.
[0013]
FIG. 1 is a schematic diagram showing a display state of a simple matrix of 4 × 4 pixels in which white display or black display is written, and FIG. 2 is a waveform of a scanning line electrode and an information signal line electrode according to the prior art corresponding to FIG. FIG. 3 and FIG. 3 are waveform diagrams of the voltage applied to the pixel according to the conventional technique corresponding to FIG. In this example, a scanning line electrode is formed on the upper substrate side and an information signal line electrode is formed on the lower substrate side, respectively, and white display is performed when the voltage applied to the pixel is positive, and when the voltage applied to the pixel is negative. It is assumed that the display becomes black.
[0014]
As shown in FIG. 2, the scanning line electrode has a period t.₁At scanning line electrode C₁For each pixel above, the period t₂At scanning line electrode C₂For each pixel above, the period t₃At scanning line electrode C₃For each pixel above, the period t₄At scanning line electrode C₄A selection pulse is applied to each of the upper pixels, and a non-selection pulse is applied to the pixels on each scanning line electrode during periods other than that period. In other words, the period t₁Is the scanning line electrode C₁And the period t₂Is the scanning line electrode C₂And the period t₃Is the scanning line electrode C₃And the period t₄Is the scanning line electrode C₄Is the selection period. Further, during each selection period, the information signal line electrode S₁, S₂, S₃, S₄To perform black display writing from₁  , T₂  , T₃  , T₄In the first half period t_AIf it is desired to apply a write signal and perform white display writing in_BA write signal is applied.
[0015]
Note that the period t_AAnd period t_BThe first half of each pulse is a reset pulse, and the second half is a set pulse for black display or white display writing (in FIG. 2, each is indicated by ● or ○). In each case, the reset pulse is set to have a polarity opposite to that of the set pulse, so that the charges applied to the pixel are not biased. As a result of performing such a series of operations, the waveform applied to the pixel becomes a composite waveform of white display writing and black display writing shown in FIG. In FIG. 3, the scanning line electrode C₁3 shows a composite waveform applied to each pixel.
[0016]
It should be noted that the selection voltage (+ 4V) applied to each pixel during the selection period₀And -4V₀) And half-select voltage (+ 2V)₀And -2V₀) And a non-selection voltage (+ V₀And -V₀) Must be determined so that the voltages applied to the scanning line electrode and the information signal line electrode are appropriate. That is, the threshold voltage (V_h), The voltage actually applied to the pixel is 2V₀<V_h<4V₀V so that₀Must be set appropriately. This V₀If the selection is not appropriate, the liquid crystal responds even when a half-selection voltage is applied, and black display cannot be performed, or writing cannot be performed with the selection voltage.
[0017]
By the way, the ferroelectric liquid crystal has a memory property because it does not respond to a voltage lower than the threshold voltage and maintains the previous state. Therefore, even if the liquid crystal panel has a large screen, it is possible to drive the liquid crystal display element without lowering the contrast by utilizing the feature of the ferroelectric liquid crystal having memory properties. However, in the conventional technique of the four-pulse driving method as described above, uniform white display and black display cannot be actually performed, and a phenomenon occurs in which pixels having high contrast and pixels having low contrast are mixed. This may be due to the relationship between the selection voltage or the half-selection voltage and the subsequently applied non-selection voltage.
[0018]
Hereinafter, a description will be given with reference to a graph shown in FIG. 4 showing a relationship between a voltage applied to a pixel and a transmitted light amount (electro-optical response characteristic) according to the related art. Period t₁At scanning line electrode C₁And information signal line electrode S₁The first state (T) written to the pixel at the intersection with₁) And period t₂At scanning line electrode C₂And information signal line electrode S₁The second state (T₂)
(T₁  , T₂) = (A) (black, white), (b) (black, black), (c) (white, black), (d) (white, white)
Scan line electrode C in the case of₁And information signal line electrode S₁The relationship between the voltage applied to the pixel at the intersection with the pixel and the electro-optical response characteristic, and (T) in FIG.₁  , T₂) = (Black, black) and (white, white), (black, white) and (white, black) The description will be given with reference to a graph of measured values when the pulse width of the contrast ratio is changed. The measurement temperatures are all the same.
[0019]
As shown in FIG.₁From the state of T₂The electro-optical response characteristics, that is, the amount of transmitted light differs depending on whether the polarities at the time of transition to the state described above are the same or different. Specifically, in FIGS. 4A and 4D, T₁From the state of T₂4 (b) and (c), the polarity at the time of transition to the state of FIG.₁From the state of T₂Is the same polarity at the time of transition to the state. In FIG. 4B, T₁  From the state of T₂Is the same polarity at the time of transition to the state, but the period t₂  Thereafter, the amount of transmitted light increases to about 50%. Also, in FIG.₁  From the state of T₂  Although the polarity at the time of the transition to the state is reversed, the period t₂  Thereafter, the amount of transmitted light is reduced to about 50%.
[0020]
In other words, there is a display combination in which the half-selection voltage and the non-selection voltage having the same polarity continue to perform the same function as the selection pulse and the liquid crystal molecules respond, and the polarity is opposite to the selection voltage. In some combinations of non-selection voltages, there is a display combination in which writing cannot be sufficiently performed only by the selection voltage. For this reason, as shown in FIG. 5, there arises a problem that the margin of the pulse width at which a high contrast ratio is obtained becomes small or the contrast itself cannot be obtained.
[0021]
FIG. 5 shows actual measurement data obtained by an experiment conducted by the inventors of the present application, and as shown in FIG.Information signalWhen pixels adjacent to each other on the line are in the same display state, that is, white and white or black and black, the display state is such that the contrast ratio is reduced. On the other hand, as shown in FIG.Information signalWhen adjacent pixels on the line have different display states, that is, white and black, or black and white, the waveform has a high contrast ratio, but does not look very high in actual appearance. Therefore, in any case, high-contrast display cannot be performed.
[0022]
[Problems to be solved by the invention]
In view of the above-described circumstances, it is conceivable to add another signal at the end of the selection period. For example, in the invention of Japanese Patent Application Laid-Open No. 60-56935, a period corresponding to one pulse is added to the scanning line electrode and the information signal line electrode next to the four pulses during the selection period as a pause period. are doing. However, in the invention disclosed in Japanese Patent Application Laid-Open No. 60-56935, it is true that the influence of the first pulse in the next non-selection period is reduced, but a pause period equivalent to one pulse is added to the conventional four pulses. Therefore, if simply considered, the overall operation speed is reduced by 25%.
[0023]
In the invention disclosed in Japanese Patent Application Laid-Open No. 5-45621, four pulses are applied to the scanning line electrode during the selection period and two pulses are applied to the subsequent non-selection period during the selection period, and the information signal line electrode is applied to the information signal line electrode during the selection period. As before, four pulses are applied. However, among the six pulses applied to the scanning line electrode, the first, fourth, and sixth pulses have the same polarity, and the second, third, and fifth pulses have the same polarity, but the first, fourth, and fifth pulses have the same polarity. The polarity is opposite to that of six pulses. In the four pulses applied to the information signal line electrode, the first and second pulses have opposite polarities, the third and fourth pulses have opposite polarities, and the pixel (liquid crystal) is applied by the first and second pulses. The pixel (liquid crystal) is set to the first optically stable state (black or white) by the third and fourth pulses in the first optically stable state (white or black).
[0024]
However, in the invention of Japanese Patent Application Laid-Open No. 5-45621, the sameInformation signalWhen the pixels adjacent to each other on the line are in the same display state, that is, when there is no black and black, there is not much problem, but when it is white and white, the contrast ratio is reduced, or the actual appearance is reduced. Has a problem that it does not look very high contrast.
[0025]
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a driving method of a liquid crystal display element which realizes high contrast and requires only four pulses during a selection period.
[0026]
[Means for Solving the Problems]
In order to solve the above-described problem, a driving waveform capable of sufficiently performing white display writing or a driving waveform in which white display writing is not performed after black display writing is added to the end of the selection period. This is achieved by:
[0027]
The conventional example shown in FIG.Of the voltage applied to the pixelIn the waveform, the reason why the complete black display is not obtained even though the black display writing is performed is that the black display writing is continued for two pixels, specifically, the scanning line next to the pixel where the black display writing is performed. When black display writing is continuously performed on the pixels on the electrodes,FIG. (b) As shown in the waveform of the applied voltage to the pixel shown inPositive half-selection pulse applied at the end of the second black display write selection periodCircle 4Followed by non-selective pulse of positive polarity1 'Is applied, the liquid crystal molecules, which should not respond originally, respond by the combination of the pulses and become close to a white display state. To prevent such a phenomenon,FIG. (a) As shown in the waveform of the applied voltage to the pixel shown inPositive semi-selective pulseCircle 4Followed by a non-selective pulse of negative polarity1 'Should be applied.
[0028]
On the other hand, contrary to the above-described case, when white display writing is continued for two pixels, specifically, white display writing is continuously performed on a pixel on the scanning line electrode next to the pixel on which white display writing is performed. IfFIG. (d) As shown in the waveform of the applied voltage to the pixel shown inPositive selection pulseCircle 4Followed by a non-selective pulse of negative polarity1 'In this combination of pulses, although the liquid crystal molecules are apparently inverted, the liquid crystal molecules cannot be sufficiently inverted. Therefore,FIG. (c) As shown in the waveform of the applied voltage to the pixel shown inPositive selection pulseCircle 4Followed by non-selective pulse of positive polarity1 'Is applied to assist the state inversion of the liquid crystal molecules. By doing so, it is possible to always realize high-contrast display.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. Note that the ferroelectric liquid crystal display element used in the method for driving a liquid crystal display element of the present invention has a layer structure called a bookshelf structure by a surface stabilization treatment.
[0030]
By the way, the driving method of the liquid crystal display element of the present invention takes into consideration the problem that sufficient white / black writing cannot be performed by applying the driving waveform applied to the pixel by the conventional four-pulse driving method. By adding at least two auxiliary pulses between the selection period and the next non-selection period, writing can be performed more sufficiently from the state in which writing has been performed in the selection period.
[0031]
Specifically, the waveform obtained by synthesizing the scanning line electrode and the information signal line electrode actually applied to each pixel has a fifth pulse having a positive polarity and a sixth pulse having a negative polarity in the case of white display writing. In contrast, in the case of black display writing, the waveform applied to the scanning line electrode and the waveform applied to the information signal line electrode are changed so that the fifth pulse has a negative polarity and the sixth pulse has a positive polarity. decide. Hereinafter, some embodiments of such an information signal line electrode of the present invention will be described.
[0032]
[First Embodiment]
FIG. 6 is a waveform chart showing signal waveforms for realizing the liquid crystal display element driving method according to the present invention, that is, the first embodiment of the six-pulse driving method. FIG. 7 shows an example in which the first embodiment of the driving method of the liquid crystal display element of the present invention shown in FIG. 6 is applied to each electrode in order to realize the above-mentioned display state shown in FIG. FIG. 8 is a waveform diagram showing an actual driving waveform applied to each pixel.
[0033]
Specifically, in the first embodiment, the selection pulse applied to the scanning line electrode is such that the first pulse is + 2V₀, The second pulse is -2V₀, The third pulse is -2V₀, The fourth pulse is + 2V₀, The fifth pulse is + V₀, The sixth pulse is -V₀Are set respectively. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity.
[0034]
In addition, the first non-selection pulse is -V₀, The second pulse is + V₀, The third pulse is + V₀, The fourth pulse is -V₀, The fifth pulse is + V₀, The sixth pulse is -V₀Are set respectively. Speaking only of the polarity, the second, third, and fifth pulses have a positive polarity, and the first, fourth, and sixth pulses have a negative polarity.
[0035]
The ON (white display) pulse applied to the information signal line electrode has a first pulse of -2 V₀, The second pulse is + 2V₀, The third pulse is + 2V₀, The fourth pulse is -2V₀, The fifth pulse is set to 0, and the sixth pulse is set to 0. Speaking only of the polarity, the second and third pulses have a positive polarity, the first and fourth pulses have a negative polarity, and the fifth and sixth pulses have no polarity.
[0036]
The OFF (black display) pulse applied to the information signal line electrode has a first pulse of -2 V₀, The second pulse is + 2V₀, The third pulse is 0, the fourth pulse is 0, and the fifth pulse is + 2V₀, The sixth pulse is -2V₀Are set respectively. Speaking only of the polarity, the second and fifth pulses have a positive polarity, the first and sixth pulses have a negative polarity, and the third and fourth pulses have no polarity.
[0037]
As described above, the composite waveform of the voltage applied to each pixel is the difference between the signal waveform applied to the scanning line electrode and the signal waveform applied to the information signal line electrode with reference to the information signal line electrode. Therefore, the composite waveform applied to the pixel selected by the scanning line electrode and subjected to white display writing has a first pulse of + 4V.₀, The second pulse is -4V₀, The third pulse is -4V₀, The fourth pulse is + 4V₀, The fifth pulse is + V₀, The sixth pulse is -V₀become. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity.
[0038]
That is, in the first embodiment, the fifth pulse is + V₀(Positive polarity), the sixth pulse is -V₀(Negative polarity).
[0039]
On the other hand, the composite waveform applied to the pixel selected by the scanning line electrode and subjected to black display writing has a first pulse of +4 V₀, The second pulse is -4V₀, The third pulse is -2V₀, The fourth pulse is + 2V₀, The fifth pulse is -V₀, The sixth pulse is + V₀become. In terms of only the polarity, the first, fourth and sixth pulses have a positive polarity, and the second, third and fifth pulses have a negative polarity.
[0040]
That is, in the first embodiment, in the black display writing, the fifth pulse is -V₀(Negative polarity), the sixth pulse is + V₀(Positive polarity).
like thisWhen the above-described display state shown in FIG. 1 is realized by the first embodiment of the driving method of the liquid crystal display element of the present invention, the scanning line electrode, the information signal line electrode, and the voltage applied to each pixel Is as shown in the waveform diagram of FIG. That is, the first and second pulses are a reset unit, the third and fourth pulses are a black writing unit, and the fifth and sixth pulses are a white writing unit.
[0041]
Here, the scanning line electrode C₁During the period in which the information signal line electrode S is selected.₁, S₂, S₃, S₄A display pulse is applied to the scanning line electrode C in the order of black, black, white, and white.₁And information signal line electrode S₁Pixel at the intersection with (C₁-S₁) Is applied to the scanning line electrode C (shown by ●).₂During the period in which the information signal line electrode S is selected.₁, S₂, S₃, S₄A display pulse is applied to the scanning line electrode C in the order of white, black, white, and black.₂And information signal line electrode S₃Pixel at the intersection with (C₂-S₃) Shows a state in which a composite pulse (shown by ○) in white display is applied.
[0042]
[Second embodiment]
FIG. 9 is a waveform chart showing signal waveforms for realizing the liquid crystal display element driving method according to the present invention, that is, the second embodiment of the six-pulse driving method. Further, FIG. 10 shows a state in which each of the electrodes is applied to realize the display state shown in FIG. 1 according to the second embodiment of the driving method of the liquid crystal display element of the present invention shown in FIG. FIG. 11 is a waveform diagram showing an actual driving waveform applied to each pixel.
[0043]
Specifically, in the second embodiment, the selection pulse and the non-selection pulse applied to the scanning line electrode and the OFF (black display) pulse applied to the information signal line electrode are shown in FIG. Since the third embodiment is similar to the first embodiment, the description thereof is omitted, and only the waveform of an ON (white display) pulse applied to the information signal line electrode different from the first embodiment will be described. .
[0044]
In the second embodiment, the ON (white display) pulse applied to the information signal line electrode is such that the first pulse is 0, the second pulse is 0, and the third pulse is + 2V.₀, The fourth pulse is -2V₀, The fifth pulse is set to 0, and the sixth pulse is set to 0. Speaking only of the polarity, the third pulse has a positive polarity, the fourth pulse has a negative polarity, and the first, second, fifth, and sixth pulses have no polarity.
[0045]
In the second embodiment, the composite pulse applied to the pixel selected by the scanning line electrode and subjected to white display writing has a first pulse of + 2V.₀, The second pulse is -2V₀, The third pulse is -4V₀, The fourth pulse is + 4V₀, The fifth pulse is + V₀, The sixth pulse is -V₀become. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity, as in the first embodiment.
[0046]
That is, in the second embodiment, as in the first embodiment, the fifth pulse is + V in white display writing.₀(Positive polarity), the sixth pulse is -V₀(Negative polarity).
[0047]
On the other hand, the composite waveform applied to the pixel selected by the scanning line electrode and subjected to black display writing is the same as that in the first embodiment.
[0048]
When the above-described display state shown in FIG. 1 is realized by the second embodiment of the liquid crystal display element driving method of the present invention, the scanning line electrode, the information signal line electrode, and each pixel are connected to each other. The waveform of the applied voltage is as shown in the waveform diagram of FIG.
[0049]
Here, the scanning line electrode C₁During the period in which the information signal line electrode S is selected.₁, S₂, S₃, S₄A display pulse is applied to the scanning line electrode C in the order of black, black, white, and white.₁And information signal line electrode S₁Pixel at the intersection with (C₁-S₁) Is applied to the scanning line electrode C (shown by ●).₂During the period in which the information signal line electrode S is selected.₁, S₂, S₃, S₄A display pulse is applied to the scanning line electrode C in the order of white, black, white, and black.₂And information signal line electrode S₃Pixel at the intersection with (C₂-S₃) Shows a state in which a composite pulse (shown by ○) in white display is applied.
[0050]
With such a driving method, a high-contrast display which has been difficult to be realized by the conventional four-pulse driving method can be realized.
[0051]
[Third Embodiment]
By the way, in the above-described first and second embodiments, six pulses are required during the selection period. If the time width of each pulse is the same, the operation is simpler than the conventional four-pulse method. Speed is reduced by 50%. Therefore, an embodiment in which the 6-pulse method is simulated and the 4-pulse drive method is applied by applying the above-described first and second embodiments will be described below.
[0052]
In short, this pseudo four-pulse driving method simply starts selecting the (n + 1) th line at the same time as the application timing of the fifth pulse during the period during which the nth line (scanning line) is being selected, and Start application of. According to such a driving method, it is possible to perform driving in the same operation time as when driving by the four-pulse driving method. Hereinafter, a specific description will be given.
[0053]
FIGS. 12 and 13 show a third embodiment for driving a liquid crystal display element according to the present invention (hereinafter referred to as a pseudo four-pulse driving method), that is, a pseudo four-pulse driving method instead of a six-pulse driving method. It is a waveform diagram which shows each signal waveform which implement | achieves a form. FIGS. 14 and 15 show the above-described display state shown in FIG. 1 according to the third embodiment of the method of driving the liquid crystal display element of the present invention shown in FIGS. 12 and 13. FIG. 16 is a waveform diagram showing an actual driving waveform applied to each pixel, and FIG. 16 is a waveform diagram showing an actual driving waveform applied to each pixel.
[0054]
Specifically, in the third embodiment, the selection pulse applied to the scanning line electrode is, as shown in FIGS.₀, The second pulse is -6V₀, The third pulse is -4V₀, The fourth pulse is + 4V₀, The fifth pulse is + V₀, The sixth pulse is -V₀Are set respectively. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity.
[0055]
In addition, the first non-selection pulse is + V₀, The second pulse is -V₀, The third pulse is -V₀, The fourth pulse is + V₀, The fifth pulse is + V₀, The sixth pulse is -V₀Are set respectively. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity.
[0056]
As shown in FIG. 12, two types of ON (white display) pulses applied to the information signal line electrode are prepared, and the first ON (white display) pulse is one of the first to sixth pulses. All are set to 0 respectively. Further, the second ON (white display) pulse is such that the first pulse is +2 V₀, The second pulse is -2V₀, And the third to sixth pulses are set to 0. Speaking only of the polarity, the first pulse has a positive polarity, the second pulse has a negative polarity, and the other pulses have no polarity.
[0057]
On the other hand, two types of OFF (black display) pulses applied to the information signal line electrode are prepared as shown in FIG. 13, and the first OFF (black display) pulse has a first pulse of + 2V.₀, The second pulse is -2V₀, The third pulse is -2V₀, The fourth pulse is + 2V₀, 5th pulse is + 2V₀, The sixth pulse is -2V₀Are set respectively. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity. The second OFF (black display) pulse is such that the first pulse is 0, the second pulse is 0, and the third pulse is -2V.₀, The fourth pulse is + 2V₀, 5th pulse is + 2V₀, The sixth pulse is -2V₀Are set respectively. Speaking only of the polarity, the fourth and fifth pulses have a positive polarity, the third and sixth pulses have a negative polarity, and the other pulses have no polarity.
[0058]
In the third embodiment, as shown in FIG. 12, a composite waveform applied to a pixel selected by the scanning line electrode and subjected to white display writing has a first ON (white display) pulse. Then, the first pulse is + 6V₀, The second pulse is -6V₀, The third pulse is -4V₀, The fourth pulse is + 4V₀, The fifth pulse is + V₀, The sixth pulse is -V₀become. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity. In the second ON (white display) pulse, the first pulse is + 4V.₀, The second pulse is -4V₀, The third pulse is -4V₀, The fourth pulse is + 4V₀, The fifth pulse is + V₀, The sixth pulse is -V₀become. Speaking only of the polarity, the first, fourth, and fifth pulses have a positive polarity, and the second, third, and sixth pulses have a negative polarity.
[0059]
That is, in the third embodiment, the fifth pulse is + V in any ON (white display) pulse.₀(Positive polarity), the sixth pulse is -V₀(Negative polarity).
[0060]
On the other hand, as shown in FIG. 13, the composite waveform applied to the pixel selected by the scanning line electrode and subjected to black display writing has a first OFF (black display) pulse of +4 V as shown in FIG.₀, The second pulse is -4V₀, The third pulse is -2V₀, The fourth pulse is + 2V₀, The fifth pulse is -V₀, The sixth pulse is + V₀become. In terms of only the polarity, the first, fourth and sixth pulses have a positive polarity, and the second, third and fifth pulses have a negative polarity. In the second OFF (black display) pulse, the first pulse is +6 V₀, The second pulse is -6V₀, The third pulse is -2V₀, The fourth pulse is + 2V₀, The fifth pulse is -V₀, The sixth pulse is + V₀become. In terms of only the polarity, the first, fourth and sixth pulses have a positive polarity, and the second, third and fifth pulses have a negative polarity.
[0061]
That is, in the third embodiment, in the black display writing, the fifth pulse is -V₀(Negative polarity), the sixth pulse is + V₀(Positive polarity).
[0062]
When the above-mentioned display state shown in FIG. 1 is realized by the third embodiment of the liquid crystal display element driving method of the present invention, the scanning line electrode, the information signal line electrode, and each pixel are connected to each other. As shown in the waveform diagrams of FIG. 14, FIG. 15, and FIG. 16, the waveform of the applied voltage at the same time as the application timing of the fifth pulse during the period when the n-th line (scanning line electrode) is selected. The selection of the (n + 1) th line (scanning line electrode) is started, and the application of the first pulse is started. At this time, the second ON (white display) pulse is used when the black display is changed to the white display, and the first ON (white display) pulse is used for the subsequent continuous white display. The second OFF (black display) pulse is used when the display is switched to the display, and the first OFF (black display) pulse is used for the subsequent continuous black display.
[0063]
Here, the scanning line electrode C₁During the period in which the information signal line electrode S is selected.₁, S_Two, S_Three, S_FourA display pulse is applied to the scanning line electrode C in the order of black, black, white, and white.₁And information signal line electrode S₁ And S _Three Pixel at the intersection with (C₁-S₁) And (C₁−S _Three ) Is applied to the scanning line electrode C (shown by ●)._TwoDuring the period in which the information signal line electrode S is selected.₁, S_Two, S_Three, S_FourA display pulse is applied to the scanning line electrode C in the order of white, black, white, and black._TwoAnd information signal line electrodeS ₁ Pixel at the intersection with (C_Two−S ₁ ) Shows a state in which a composite pulse (shown by ○) in white display is applied.
[0064]
With such a driving method, a high-contrast display, which has been difficult to be realized by the conventional four-pulse driving method, can be apparently realized with the same four pulses as the conventional one.
[0065]
【The invention's effect】
As described in detail above, according to the driving method of the liquid crystal display element of the present invention, it is possible to sufficiently perform white writing and black writing during the selection period, and further, it is possible to perform complete writing during the non-selection period and during the memory state. Since the white or black writing state is maintained, a very high-contrast display can be performed. Then, the contrast is always increased by such driving, so that the visibility becomes very good when applied to a reflective display.
[0066]
In addition, according to the third embodiment, it operates at the apparently similar speed with four pulses as in the conventional case.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a display state of a simple matrix.
FIG. 2 is a waveform diagram of a conventional scanning line electrode and information signal line electrode.
FIG. 3 is a waveform diagram of a voltage applied to a pixel according to the related art.
FIG. 4 is a graph showing a relationship between a voltage applied to each pixel and a transmitted light amount (electro-optical response characteristic) according to a conventional technique.
FIG. 5 shows (T₁  , T₂7) is a graph showing the contrast ratio of the waveforms of (black, black) and (white, white), (black, white), and (white, black).
FIG. 6 is a waveform chart showing signal waveforms for realizing the first embodiment of the present invention.
FIG. 7 is a waveform chart showing actual driving waveforms applied to respective electrodes according to the first embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 8 is a waveform chart showing an actual driving waveform applied to each pixel according to the first embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 9 is a waveform chart showing signal waveforms for realizing a second embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 10 is a waveform chart showing actual applied waveforms applied to respective electrodes according to the second embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 11 is a waveform chart showing an actual applied waveform applied to each pixel according to the second embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 12 is a waveform chart showing signal waveforms for implementing a third embodiment of the method for driving a liquid crystal display element according to the present invention.
FIG. 13 is a waveform chart showing signal waveforms for realizing a third embodiment of the method for driving a liquid crystal display element according to the present invention.
FIG. 14 is a waveform chart showing actual applied waveforms applied to respective electrodes according to the third embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 15 is a waveform chart showing actual applied waveforms applied to respective electrodes according to the third embodiment of the method for driving a liquid crystal display element of the present invention.
FIG. 16 is a waveform chart showing an actual applied waveform applied to each pixel according to the third embodiment of the method for driving a liquid crystal display element of the present invention.
[Explanation of symbols]
C₁~ C₄  Scan line electrode
S₁~ S₄  Information signal line electrode

Claims (4)

A plurality of scanning line electrodes and a plurality of information signal line electrodes are arranged so as to intersect, and a plurality of liquid crystal pixels are sandwiched between ferroelectric liquid crystals at intersections of the plurality of scanning line electrodes and the plurality of information signal line electrodes. Each liquid crystal pixel of the configured liquid crystal display element is
First to fourth pulses are applied to the scanning line electrode during the selection period, and fifth and sixth pulses are applied to the scanning line electrode following the selection period. The first to fourth pulses are applied to the information signal line electrode during the selection period. Of the liquid crystal display element in which a first stable state for white display or a second stable state for black display is obtained by applying the fifth and sixth pulses respectively following the selection period. At
Pulses synthesized by taking the difference between the pulse of the signal waveforms applied to the information signal line electrodes and the signal waveform of the pulse applied to the scan line electrode, if should be the first stable state to the fifth The scan line electrode is set so that the pulse becomes positive, the sixth pulse becomes negative, and if the second stable state is to be established, the fifth pulse becomes negative and the sixth pulse becomes positive. And setting the polarity of a pulse applied to the information signal line electrode. In the pulse applied to the scanning line electrode, the first and fourth pulses have a positive polarity of a first value , and the fifth pulse has a positive polarity of a second value smaller than the first value . The second and third pulses have a negative polarity of the first value greater than the second value , the sixth pulse has a negative polarity of the second value ,
In order to bring each liquid crystal pixel into the first stable state, the pulse applied to the information signal line electrode is such that the first and fourth pulses have the negative polarity of the first value and the second and third pulses Is the positive polarity of the first value , the fifth and sixth pulses are non-polar,
In order to bring each liquid crystal pixel into the second stable state, the pulse applied to the information signal line electrode is such that the first and sixth pulses have the negative polarity of the first value and the second and fifth pulses 2. The method of driving a liquid crystal display element according to claim 1, wherein the first value has a positive polarity, and the third and fourth pulses have no polarity. In the pulse applied to the scanning line electrode, the first and fourth pulses have a positive polarity of a first value , and the fifth pulse has a positive polarity of a second value smaller than the first value . The second and third pulses have a negative polarity of the first value greater than the second value , the sixth pulse has a negative polarity of the second value ,
In order to bring each liquid crystal pixel into the first stable state, the first, second, fifth, and sixth pulses of the pulse applied to the information signal line electrode are nonpolar, and the third pulse is the third pulse . A fourth pulse having a positive polarity of a value of 1 and a fourth pulse having a negative polarity of the first value ;
In order to bring each liquid crystal pixel into the second stable state, the pulse applied to the information signal line electrode is such that the first and sixth pulses have the negative polarity of the first value and the second and fifth pulses 2. The method of driving a liquid crystal display element according to claim 1, wherein the first value has a positive polarity, and the third and fourth pulses have no polarity. In the pulse applied to the scanning line electrode, a first pulse has a positive polarity of a first value, a second pulse has a negative polarity of the first value , and a third pulse has a higher polarity than the first value. Is also a negative value of a second value that is smaller , a fourth pulse is a positive polarity of the second value , and a fifth pulse is a positive polarity of a third value that is smaller than the second value . , A sixth pulse having a negative polarity of the third value ,
The pulse applied to the information signal line electrode for bringing each liquid crystal pixel into the first stable state is such that all of the first to sixth pulses are non-polar, or the first pulse is the second value. A fourth pulse having a positive polarity of a fourth value smaller than and larger than the third value , a second pulse having a negative polarity of the fourth value , and third to sixth pulses having no polarity;
Pulses applied to the information signal line electrode to bring each liquid crystal pixel into the second stable state are such that first, fourth, and fifth pulses have the positive polarity of the fourth value , and The third and sixth pulses have a negative polarity of the fourth value , or the first and second pulses have no polarity, and the third and sixth pulses have a negative polarity of the fourth value ; Fourth and fifth pulses have the positive polarity of the fourth value ,
2. The method of driving a liquid crystal display element according to claim 1, wherein the first pulse of the next scanning line electrode is applied at a timing of applying the fifth pulse during the selection period of an arbitrary scanning line electrode.

Images