KR940002294B1 - Lcd device - Google Patents

Abstract

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Description

Liquid crystal display

1 is a block diagram illustrating the liquid crystal display circuit of the first embodiment according to the present invention.

2 is a block diagram showing an example of the configuration of the liquid crystal device 101. FIG.

3 is a timing diagram of a control signal 102 and a data signal 103. FIG.

4 shows an example of a circuit of the correction circuit 104. FIG.

5 illustrates an example of a circuit diagram of the voltage power supply circuit 105. FIG.

6 shows a display dot matrix of a liquid crystal panel.

7 is a diagram showing a voltage waveform illustrating the operation of the present invention.

8 is a block diagram showing a circuit of a liquid crystal display device of a sixth embodiment of the present invention.

9 is a diagram showing an example of the configuration of a liquid crystal device 801. FIG.

10 is a diagram showing an example of a circuit of a scan electrode driving circuit.

FIG. 11 shows an example of a circuit of the correction circuit 804. FIG.

12 shows an example of a voltage power supply circuit 805. FIG.

13, 15, 17, and 23 show the structure of a liquid crystal panel and a display dot matrix.

14 and 16 illustrate voltage waveforms used to illustrate the operation of the present invention.

18 to 22, 24 and 25 show voltage waveforms useful for explaining the prior art and the problems of the prior art.

* Explanation of symbols for main parts of the drawings

101: liquid crystal device 104: correction circuit

105: power supply circuit 108: sign circuit

109: strength signal 202: substrate

205: scan electrode driving circuit 208: signal electrode driving circuit

209: shift register circuit 501 to 509: resistor

511, 512 switch 810 flip-flop circuit

The present invention relates to a method of driving a liquid crystal display.

Conventionally, a driving method of a liquid crystal display device will be known as a voltage averaging method.

The driving method will be described with reference to FIGS. 17 to 19. In FIG. 17, the structure of a liquid crystal panel and the display dot matrix (henceforth a display substitute) are shown. Scan electrodes Y1 to Y6 arranged in the transverse direction are formed in one substrate 2, and signal electrodes X1 to X6 are formed in the other substrate 3. The display dots are formed at the intersections of the scan electrodes Y1 to Y6 and the signal electrodes X1 to X6. Display dots encoded by hatching (hatched) in FIG. 17 indicate a lighting state, and other display dots indicate a non-lighting state. Thereafter, display dots in the lit state are described as lit dots, and display dots in the non-lit state are described as non-lit dots. Further, the illustrated liquid crystal panel is based on the number of 6x6 dot metrics for simplicity of expression, but there are a number of dots for the liquid crystal.

The selection voltage or non-selection voltage is sequentially applied to scan electrodes Y1 to Y6. One frame means a period in which the selected or non-selected voltage is sequentially applied to the scan electrodes Y1 to Y6.

When applying a selection or non-selection voltage to scan electrodes Y1 to Y6 in turn, at the same time each signal electrode X1 to X6 is applied with a lit or non-illuminated voltage (the scan electrode to which the selection voltage is applied is known as the selected scan electrode). . In the case where the display dot located at the intersection of any scan electrode and any signal electrode is lit, the lit voltage is applied to the signal electrode when the scan electrode is selected. On the other hand, in the non-lighting state, the non-lighting voltage is applied. 18 and 19 show an example of an actual drive waveform (applied voltage waveform).

FIG. 18A shows the waveform of the signal voltage applied to the signal electrode X2 shown in FIG. FIG. 18B shows the waveform of the scan voltage applied to the scan electrode Y4, and FIG. 18C shows the waveform of the voltage applied to the display dot (lighted state) at the intersection of the signal electrode X2 and the scan electrode Y4.

19A shows the waveform of the signal voltage applied to the signal electrode X2. FIG. 19B shows the waveform of the scan voltage applied to the scan electrode Y3, and FIG. 19C shows the waveform of the voltage applied to the display dot (non-lighting state) at the intersection of the signal electrode X2 and the scan electrode Y2.

18 and 19, F1 and F2 denote frame periods. In frame period F1

Voltage = V0, non-voltage = V4

Steady Voltage = V5, Non-Ignition Voltage = V3

In frame period F2,

Voltage = V5, non-voltage = V1

Steady-voltage = V0, non-ignition voltage = V2

In addition, the following relation holds.

V0-V1 = V1-V2 = V

V3-V4 = V4-V5 = V

V0-V5 = n.V

Where n is an integer. The polarity of the voltage difference between the scan voltage waveform and the signal voltage waveform changes in accordance with the frame periods F1 and F2, which affects the AC driving process. Here, the time for inverting the polarity is referred to as the polarity inversion time.

As apparent by comparing Figs. 18 and 19, the display dot is changed into a lit state or a non-lit state according to the voltage, that is, the lit voltage or the non-lit voltage is selected for the scan electrode in which the related display dot is present. When a voltage is applied it is applied to the signal electrode. The driving method described above is known as a voltage averaging method.

However, when driving with the voltage averaging method, as shown in Figs. 18 and 19, no clear-cut spherical waveform is actually applied to the display dots. The first reason for this is that the display dot has an electric capacity determined by its area, the thickness of the liquid crystal layer and the dielectric constant of the liquid crystal material. The second reason is that the scan electrode and the signal electrode are generally composed of a transparent conductive film having a sheet resistance on the order of tens of ohms. This means that each of these electrodes has a constant electrical resistance.

Assuming that the clear-cut square waveforms shown in FIGS. 18 and 19 are applied from the drive circuit, the voltage waveform actually applied to the display dots is somewhat distorted. As a result, a difference occurs in the effective voltage between waveforms of the voltage applied to each display dot, and a problem arises in which the contrast is not constant.

This problem is one conventionally known problem. In this countermeasure, a method of inverting the polarity of a voltage applied to a plurality of circuit liquid crystal panels during one frame (hereinafter, referred to as a line inversion driving method) is disclosed in Japanese Patent Application Laid-Open Nos. 62-31825 and 60. Suggested in -19195 and 60-19196.

However, in the case of performing the driving operation by the voltage averaging method or the line inversion driving method, the density of the display dots on the scan electrode to which the selection voltage is applied immediately after inverting the polarity of the voltage applied to the liquid crystal panel is different. It is different from the density of dots displayed on. For these reasons, the linear contrast is uneven. When the line inversion driving is performed such that the position of the scan electrode that performs the polarity inversion changes with time, a series of uneven linear contrast is generated. This phenomenon causes the display quality of the liquid crystal display device to be noticeably inclined.

Under such conditions, the present inventor clarifies the mechanism for generating unevenness of linear contrast that is special for the conventional liquid crystal display.

An uneven contrast generating mechanism will be described with reference to FIG. 17 by taking the display mode shown in FIG. 17 as an example.

For convenience of description, the scan electrodes Y1 to Y6 are sequentially arranged to return to the first scan electrode Y1 after being sequentially selected from the first scan electrode Y1 to the sixth scan electrode Y6.

The polarity inversion by the line inversion driving method is performed between the scan electrodes Y3 and Y4 (this does not limit the polarity inversion processing number and the position at which the polarity inversion is performed, and if necessary, polarity inversion is performed any number of times at any position. do).

The liquid crystal panel 1 selects so-called positive display in which the density increases, such as the effective voltage applied to the display dot increases.

The absolute value of the difference between the non-selected voltage and the lit / non-lit voltage is set to V, and the absolute value of the difference between the selected voltage and the lit voltage is set to n.V. Where n is an integer and usually maintains a value of 3 to 50.

20A to 20C show the waveforms of the signal voltages applied to the signal electrode X2 of FIG. 17, the waveforms of the scan voltages applied to the scan electrode Y2, and the difference between these two voltage waveforms, respectively.

Similarly, FIGS. 21A to 21C illustrate waveforms of the signal voltage applied to the seventeenth signal electrode, waveforms of the scan voltage applied to scan electrode Y3, and differences between these two waveforms, respectively.

In FIG. 22, the voltage applied to the display dot (hereinafter referred to as D23) formed by combining the signal electrode X2 and the scan electrode Y3 of FIG. 17 is shown by the solid line with reference to the signal electrode X3 of this display dot matrix.

By comparing the waveforms shown by solid lines in FIGS. 21C and 22, the effective voltage for the waveform of the voltage applied to the display dot formed by combining the signal electrode X2 and the scan electrode Y3 becomes large. It will be understood as the difference between the voltage applied to the electrode X2 and the scan electrode Y3 (Fig. 21C).

The interpretation of this is described below. The voltage of the waveform indicated by the broken line in FIG. 22 is applied to the display dot (hereinafter referred to as D22) at the intersection of the signal electrode X2 and the scan electrode Y2. Therefore, upon selective movement from scan electrode X2 to scan electrode Y3, the electric discharge capacity Q1 discharged by the capacitor generated by display dot D22 is regarded as below the voltage waveform indicated by the broken line in FIG. 22, and the following relation is established. do.

Q ₁ = nVC-(-VC) = (n + l) VC

Where C is the capacitance of the capacitor. The amount of charge Q ₂ absorbed by the display dot 23 is expressed as follows.

Q ₂ = (n-2) VC-VC = (n-3) VC

Here, the difference ΔQ by this is as follows.

ΔQ = 4VC

17 shows that the display dots D22 and D23 are adjacent to each other. The capacitors generated by the display dots D22 and D23 having a lower resistance value of the shorter signal electrode X3 (1 mm or less) are electrically connected.

Therefore, the charge indicated by Q ₁ -ΔQ = (n-3) VC immediately flows into the display dot D22 into the display dot D23, and almost no voltage drop is generated by this current.

However, the charge of ΔQ flows into the scan electrodes Y2 and Y3 or the signal electrode X3, i.e., the portion from which the voltage is applied. The resistance values of the scan electrode and the signal electrode at this time depend on the position of the display dot and represent a considerably large value, and as a result, the flow of charge is disturbed. As a result, electric charges are difficult to be released, and when the voltage on the scan electrode Y2 drops from the level of the selection voltage to the non-select voltage, the voltage drops on the signal electrode X3. Thus, the effective voltage between the signal electrode X3 and the scan electrode Y3 increases. do.

In other words, if the difference between the charge / discharge amounts is positive before and after the selection, the effective value of the display dot at the next selected scan electrode becomes large. Conversely, in the case of negative, the effective value is reduced. The magnitude of the effective value changes depending on the absolute value of the charge / discharge amount. In general, this magnitude is calculated by the amount of charge / dust protection before and after selection.

The number of all display dots is set to K, the number of lit dots is N _ON , and the number of non-viscosity dots is N _{OFF at} any selected scan electrode. The number of all display dots K is as follows.

K = N _ON + N _OFF

Next, the number of lit dots is set to M _ON and the signal of non-lit degree XM is set to M _OFF in the selected scan electrode.

Set the capacitor capacity of the lit dot to C _ON and the capacitor capacity of the unlit dot to C _OFF . Then, the relation between them is as follows.

C _ON > C _OFF

Thus, the charge amount Q1 charged to all the display dots in the selected scan electrode is as follows.

Q ₁ = N _ON nV _ON + N _OFF (n-2) VC _OFF

Next, the charge amount Q ₂ at which the display dot is charged in the selected scan electrode is as follows.

Q ₂ = M _ON nVC _ON + M _OFF (n -2) VC _OFF

Therefore, the difference between these charge amounts is obtained as follows.

ΔQ = Q ₁ -Q ₂

= (N _ON -M _ON ) nVC _ON + (N _OFF -M _OFF ) (n -2) VC _OFF

Here, the difference given by = (N _ON -M _ON {n (C _ON -C _OFF ) + 2C _OFF } V (N _ON -M _ON )) is set to I by N _OFF = KN _ON and M _OFF = KN _OFF . Assume that B = {n (C _ON -C _OFF ) + 2C _OFF } V.

This result

Becomes

Next, the charge / discharge amount when the polarity is reversed at the same time during the selection movement is as follows. The charge amount Q ₁ charged in the display dot in the selected scan electrode is as follows.

Q ₁ = N _ON nVC _ON + N _OFF (n-2) VC _OFF

The next scan electrode is selected, and the following relational expression is established in consideration of the inversion of the polarity of the charge amount Q ₂ charged in the display dot on the scan electrode.

Q ₂ =-(M _ON nVC _ON + M _OFF (n-2) VC _OFF )

Therefore, the difference ΔQ between them is as follows.

-ΔQ = Q ₁ -Q ₂

= N _ON nVC _ON + N _OFF (n-2) VC _OFF + M _ON nVC _ON + N _OFF (n-2) VC _OFF

= (N _ON + M _ON ) nVC _ON + (N _OFF + M _OFF ) (N-2) VC _OFF

Where N _OFF = KN _ON and M _OFF = KM _ON = (N _ON + M _ON ) nVC _ON + (2K-N _ON -M _ON ) (n-2) VC _OFF = (N _ON + M _ON ) {n (C _ON -C _OFF ) + 2C _OFF } V + 2K (n-2) VC _OFF (N _ON + M _ON ) is the sum of F and D = 2K (n-2) VC _OFF , The following results are established.

-Q = FB + Dd

Thus, taking into account that the polarity is reversed, the equation obtains

According to formulas (1) and (2), if the number of lit dots on the selected scan electrode is greater than the number of lit dots on the next selected scan electrode at the time of selection movement when the polarity is not reversed, the difference I becomes positive, and then the selected The effective voltage applied to the display dots on the scan electrodes has a higher density. On the other hand, if the number of lit dots of the next scan electrode is larger than the number of lit dots on the scan electrode before the selection movement, the difference I is negative, and the effective voltage applied to the display dots on the scan electrodes after the selection movement is less than Perform an increase in density. This degree changes in response to the absolute value of the numerical value I.

During the selection shift during the polarity inversion execution, the effective voltage applied on the display dot of the next one selected disappears to a constant value and simultaneously decreases to a value corresponding to the sum F of the lit dots on the scan electrodes before and after the selection displacement. do.

In order to carry out the summation, uneven contrast at the polarity reversal and the next selective displacement occurs corresponding to the difference I between the number of lit dots before and after the displacement.

During the selective displacement at the polarity inversion, an uneven contrast corresponding to the sum F of lit dots before and after the displacement is executed, and at the same time, there is a regular uneven contrast.

In addition, one of the uneven contrasts generated during selective displacement in performing polarity reversal will be a subtle difference in the step of changing the polarity between the signal voltage waveform and the scan voltage waveform output by the actual drive circuit. This is defined as the first cause.

The selection voltage is applied before inverting the polarity. The voltage of each signal electrode forms a display dot as a scan electrode, and after the inversion is performed immediately, the applied unselected voltage has a magnitude corresponding to the amount of charge obtained by the formula (2), and at the side end of the selective voltage after the polarity inversion. Is changed to the voltage being dragged. This is evident with reference to FIGS. 23 to 25. FIG. 23 illustrates the same liquid crystal panel 1 as that in FIG. 17, but differs in display contents. 24 and 25 illustrate voltage waveforms at positions of display dots D33 and D43 when performing the display shown in FIG. FIG. 24A shows the signal voltage waveform at the dot D33 position. FIG. 24B shows the scan voltage waveform at the dot D33 position. 24C shows the waveform of the voltage applied to the dot D33.

Similarly, FIG. 25A illustrates the waveform of the scan voltage at the position of liquid crystal D43. 25B shows the waveform of the scan voltage at the dot D43 position. 25C shows the waveform of the voltage applied to the dot D43. As illustrated in FIG. 24A, for a signal electrode applying an optical voltage, the lighting voltage is dragged at the side end of the selection voltage immediately after the polarity inversion, and the effective voltage applied to the dot D33 is equal to the drag shown in FIG. 24C. Decrease to the same degree. As illustrated in FIG. 25A, for the signal electrode to which the non-lighting voltage is applied, the non-lighting voltage is dragged to the side end of the selection voltage, and the effective voltage applied to the dot D43 increases to the same degree for dragging. For this reason, the dot D33 (lighted state) becomes smaller in intensity than other lit dots, and the dot D43 (non-illuminated state) becomes larger in size than the non-illuminated display dots. The unevenness on the display is improved by the charge by the formula (2). More particularly, some constant unevenness occurs on the display. In addition, unevenness corresponding to the display contents is generated on the liquid crystal panel. This is defined as the second cause.

The first object of the present invention is to provide a new display capable of displaying a uniformly uniform contrast by correcting the variation in the effective voltage applied to the display dots due to the two causes described above, that is, correcting the distortion of the scan voltage waveform and the signal voltage waveform. It is to provide a liquid crystal display device.

For this purpose, one aspect of the present invention provides a liquid crystal display device. The display device includes a liquid crystal layer, a pair of substrates into which the liquid crystal layer is inserted, a group of scan electrodes formed on one substrate, and a group of signal electrodes formed on another substrate, wherein the display device includes a group of scan voltage waveforms. It is driven by being applied to the scan electrode, and driven by applying a signal voltage waveform to a group of signal electrodes and periodically inverts the polarity of the voltage difference between the scan voltage waveform and the signal voltage waveform, and at the time of polarity inversion, the scan voltage waveform and the signal voltage And means for changing at least one of the waveforms.

In another aspect of the present invention, the configured liquid crystal display further comprises means for controlling the amount of change for at least one of the scan voltage waveform and the signal voltage waveform upon polarity inversion by graphic or molecular pattern display displayed on the liquid crystal display. It is characterized by having.

In still another aspect of the present invention, the liquid crystal display device may change at least one of the scan voltage waveform and the signal voltage waveform in an amount corresponding to a graphic or character pattern displayed on the display device similarly in polarity inversion and other operations. It is characterized by further comprising means for.

In another aspect of the invention, the liquid crystal device is further characterized by means for changing an unselected voltage applied immediately after the polarity inversion with respect to the scan electrode, wherein the selected voltage is polarized in the case of polarity inversion. A voltage is applied immediately before the discharge and an unselected voltage is applied immediately after the polarity inversion between the groups of scan electrodes.

In another aspect of the present invention, the liquid crystal display further comprises means for controlling the amount of change in non-selection voltage applied immediately after polarity inversion by a graphic or character pattern displayed on the liquid crystal display in relation to a scan electrode. The selected voltage is applied immediately before the polarity inversion according to the polarity inversion, and the unselected voltage is applied immediately after the polarity inversion between the groups of scan electrodes.

With the above-described configuration, when driving the liquid crystal display device, the polarity inversion is corrected while correcting the difference between the effective voltage applied on the display dot, that is, changing at least one of the scan electrode waveform and the signal electrode waveform according to the polarity inversion. It is possible to protect the uneven contrast by correcting the change with an effective voltage generated due to the deformation of the waveform of the voltage applied to the display dot formed at the time.

Illustrative embodiments of the invention will be described in a particular manner in conjunction with the accompanying drawings.

First, an embodiment for clarifying an uneven problem on the display due to the first cause given above is shown.

Example 1

The contrast generated during polarity inversion is generated to some extent unevenly on the display pattern. As described above, an uneven contrast is added corresponding to F, which is the sum of the number of lit dots on the selected scan electrode just before the polarity inversion and the number of lit dots on the selected scan electrode immediately after the polarity inversion.

If the selected scan electrode moves to the next electrode in operation other than the polarity inversion, the waveform applied to the display dot is distorted according to the difference I on the number of lit dots on the selected scan electrode and the number of lit dots on the next selected electrode.

Therefore, in the operation of the liquid crystal display, waveform correction corresponding to the sum F and the difference I will be performed before calculation. One particular embodiment of a liquid crystal display for performing these corrections is illustrated in FIG.

In FIG. 1, reference numeral 101 shows a liquid crystal device composed of a liquid crystal panel and a driving circuit. Reference numeral 102 denotes a series of control signals for controlling the operation of the liquid crystal display device, such as latch signal LP, frame signal FR, data-in signal DIN, X driver displacement clock signal XSCL, and the like. Numeral 103 denotes a data signal, numeral 104 is a waveform correction signal generating circuit (hereinafter referred to as a correction circuit), and numeral 105 is a power supply circuit.

The correction circuit 104 calculates a numerical value F or I, and as a correction signal of a sign signal 108 indicating a positive or negative value of the numerical value F or I and an intensity signal 109 indicating an intensity of the absolute value F or I. Transfer to the power supply circuit 105. The power supply circuit 105 includes a scan electrode driving power supply (hereinafter referred to as a Y power supply) 106 supplied to the liquid crystal device 101 in accordance with the sign signal 108 and the intensity signal 109, and a signal electrode driving. It serves to form a power source (hereinafter referred to as X power source) 107. The power supply circuit 105 acts to correct the voltage of the Y power supply 106.

The basic operation of Embodiment 1 shown in FIG. 1 will be described next.

That is, the correction circuit 104 takes in the data signal 103 when an arbitrary scan electrode is selected, and then calculates the number M _ON of the lit dots on the selected scan electrode. Thus, the correction circuit 104 counts numerical values F and I which are the sum of the number of lit dots N _ON and the number of lit dots M _ON and the difference between the selected scan electrodes. When the selection is moved (at the time of polarity inversion), the resulting code signal and absolute value are output in the form of a code signal and a strength signal 109. When the polarity is reversed, the value F replaced by the value I is output in the same manner. In the above step, the number of lit dots M _ON is stored in connection with the number of lit dots N _ON on the selected scan electrode. Then, the power supply circuit 105 performs correction necessary for the voltage of the Y power supply 106 by the sign signal 108 and the intensity signal 109.

By the above-described operation, uneven contrast caused in the liquid crystal panel induced by the first cause can be prevented. This embodiment relates to a correction method, wherein a constant voltage is applied in one direction to cancel a distortion generated in a driving waveform applied to a liquid crystal panel during a period corresponding to the magnitude of the distortion. The distortion of the constant voltage is determined by the sign signal 108 during the application period according to the intensity signal 108.

Specific configurations and operations related to the constituent elements used in Embodiment 1 will be described later, and FIGS. 1 to 5 illustrate the constituent elements of FIG. 1 in detail.

2 shows an example of a specific configuration of the liquid crystal device 101.

In FIG. 2, the liquid crystal panel 201 is arranged in a manner overlapping between the pair of substrates 202 and 203, and scanning electrodes Y1 to Y6 arranged laterally on one substrate 202 are formed, The signal electrodes X1 to X6 arranged in layers on the other substrate 203 are formed. Then, display dots are formed at the intersections consisting of scan electrodes Y1 to Y6 and signal electrodes X1 to X6. Incidentally, the liquid crystal panel is composed of a (6x6) dot matrix for the sake of simplicity, but the dot matrix is not limited to the above examples.

Reference numeral 205 is a scan electrode driving circuit, which is composed of a shift register circuit 206 and a level shift circuit 207. The output of this level shift circuit 207 leads the liquid crystal panel 201 to the scan electrodes Y1 to Y6. The signal electrode drive circuit 208 is composed of a shift register circuit 209, a latch circuit 210, and a level shift circuit 211. The output of the level shift circuit 211 is directed to the liquid crystal panel 201 signal electrodes X1 to X6.

3 shows a timing diagram showing the signals DIN, LP, FR and XSCL and the data signal 103 combined to constitute the control signal 102 described above.

The signals DIN and LP serve as data and shift clocks with respect to the shift register circuit 206 of the scan electrode driving circuit 205. In accordance with the signal LP and the final transition, the signal DIN is taken into the shift register circuit 206 and transmitted. The active signal DIN when assumed at the " H " level is output once at intervals typically defined by the number of signals LP that are greater than or equal to the number of scan electrodes Y1 to Y6 of the liquid crystal panel 201. Data "H" passes through the shift register circuit 206, and in other cases the signal DIN is assumed to be "L". If active, the selection voltage is supplied to scan electrodes Y1 to Y6 through level shift circuit 207 in accordance with the contents of shift correction circuit 206. On the other hand, if it is inactive, the non-selection voltage is supplied to the scan electrodes Y1 to Y6. The selection voltage and the non-selection voltage are supplied from the Y power supply 106.

The data signal 103 and the signals XSCL and LP function as data and shift clocks of the signal electrode driving circuit 208 and the shift register circuit 209, and also function as latch clocks of the latch circuit 210. In FIG. 3, the data signal becomes active when the "H" level is assumed to indicate the lighting state. The data signal 103 serves as a signal for determining the display dot 204 of the next scan electrode to be in a lit or unlit state when any scan electrode of the liquid crystal panel 201 is selected. During the selection period of any scan electrode, the data signal 103 is taken in the shift register circuit 209 with the displacement of the signal XSCL so that the data signal 103 acts as a signal corresponding to the display dot on the next selected scan electrode. All. After the data signal 103 is taken by the signal XSCL, the contents of the shift register circuit 209 are taken in the latch circuit 210 with the arrival of the signal LP. Thus, when the active state is supplied via the shift register circuit 211 in correspondence with the contents of the taking, the lighting voltage is supplied to the signal electrodes X1 to X6. On the other hand, in the non-active state, the non-lighting voltage is supplied to the signal electrodes X1 to X6. The lit and unlit voltages are supplied from the X power source 107.

The signal FR (frame signal) is connected to the drive circuits 205 and 206 to AC drive the liquid crystal panel 201. The signal FR is synchronously switched to the arrival of the signal LP to switch the selection for the potential of the drive voltage. More specifically, the drive voltage includes two groups of voltages, one group being a selection and non-selection voltage and the other group being a lighting and non-lighting voltage. The drive voltage is switched by the frame signal FR.

The configuration of the liquid crystal device 101 and the driving method thereof are exemplified as an embodiment for explaining the present invention, but the above-described configuration and method are not limited.

4 is a block diagram showing an example of a specific circuit of the correction circuit 104 shown in FIG.

In Fig. 4, reference numeral 401 denotes a coefficient circuit, 402 denotes a first coefficient holding circuit, 403 denotes a second coefficient retaining circuit, 404 denotes a numerical calculation circuit, and 405 denotes a pulse width control circuit. Indicates.

The counting circuit 401 calculates the number of lightings in the display dots on the (n + 1) th scanning electrodes while the nth scanning electrode of the liquid crystal panel 201 of FIG. 2 is selected and processed.

The counting circuit 401 is additionally executed only when the data signal 103 is active at the arrival of the signal XSCL during the period from the arrival of the signal LP of the control signal 102 to the next arrival (n + 1). Calculate the number of lit dots. At the arrival of the signal LP, the count value is output to the first coefficient holding circuit 402, and at the same time, the count value of the counting circuit 401 is reset to zero. At this stage, counting starts. These steps are repeated sequentially. Exact calculations in single-dot increments may not necessarily be possible in some cases. If the error of the coefficient is set to ± 16 dots under the condition of the number 640 of the signal electrodes X1 to X6, no problem occurs.

Next, the first coefficient holding circuit 402 sequentially takes in the count value immediately before the count value of the counting circuit 401 becomes zero at the arrival of the signal LP. The second coefficient holding circuit 403 sequentially takes in count values from the first coefficient holding circuit 402 just before the first coefficient holding circuit 402 takes the next count value from the counting circuit 401 at the arrival of the signal LP. To act. Therefore, when the first coefficient holding circuit 402 receives the number of lit dots M _ON of the display dots on the (n + 1) th order scanning electrode, the second coefficient holding circuit 403 is used to display the display dots on the nth order scan electrode. Lit The dispenser N _ON . The numerical values M _ON and N _ON are output to the numerical calculation circuit 404, respectively.

Next, the numerical calculation circuit 404 calculates the sum F and the difference I associated with the numerical values M _ON and N _ON from the first and second coefficient holding circuits 402, 403, where F = N _ON + M _ON and I = N _ON -M _ON . If the signal FR does not change (time other than polar inversion), the sign of the numerical value I is output in the form of the sign signal 108. At the same time, the absolute value of I is output to the pulse width control circuit 405. So the signal FR is changed. At this time (at polar inversion), the numerical value F is output in the same form. However, depending on the situation of the circuit, the inversion to the sign of the numerical value F is output as the sign signal 108.

In synchronization with the arrival of the control signal 102 to the signal LP, the pulse width control circuit 405 generates the active signal or the intensity signal 109 for a time corresponding to the absolute value F or I input from the numerical calculation circuit 404. Output

The relationship between the width W of the intensity signal 109 and the numerical value F.I can be obtained, for example, by an experimental method. The width W will depend on the positive or negative of the numerical value I. However, the width W in this embodiment is not limited to the positive or negative of the numerical value I. In other words,

W = a ₁ · I and _{W = a 1 · F + a} 0

The operation and function of the correction circuit 104 is described above. The specific circuit of each of the components 401 to 405 is appropriately actualized in the above-described manner, so the description is omitted here.

FIG. 5 shows an example of a specific circuit of the voltage power supply circuit 105 shown in FIG. 1A.

In Fig. 5, reference numerals 501 to 509 denote resistors connected in series, and are connected to the ends of the resistors at voltage V0U and voltage V5L.

The voltages generated at each end of resistors 501-509 are indicated by V0U, VON, V0L, V1, V2, V3, V4, V5U, V5N and V5L, each of

VON-V1

= V1-V2

= V3-V4

= V4-V5N

= (V2-V3) / (n-4)

Where n is a constant. or

(V0U -VON) / (VON -V1)

= (V5N -V5L) / (V4 -V5N)

(VON -V0L) / (VON -V1)

= (V5U-V5N) / (V4-V5N).

The resistance value of each of the resistors 2601 to 2607 is set to establish these relations.

510 is a voltage stabilization circuit for stabilizing the divided voltages VON, V0L, V1, V2, V3, V4, V5U and V5N generated by resistors 501 to 509. In the circuit 510, a voltage having the same level as the input voltage is output to generate a low impedance. In the above embodiment, the voltage stabilization circuit 510 is constituted by a voltage follower circuit by an operational amplifier circuit.

The switches 511 and 512 are switched in response to the sign signal 108 and the strength signal 109 of FIG. When outputting the sign signal 108 and the strength signal 109 associated with negative values I and F, the switches 511 and 512 of FIG. 5 are switched to voltages V0U and V5L while the strength signal is active.

When outputting the sign signal 108 and the strength signal 109 associated with the positive value I, the switch switches to voltages V0L and V5U while the strength signal 109 is active.

In some cases, when the intensity signal 109 becomes inactive, the switch switches to voltages VON and V5N.

The voltages output by the switches 511 and 512 are V0 and V5.

The voltages V0N and V2 are defined as a group of lighting and non-lighting voltages when the voltages V5N and V3 are the lighting and non-lighting voltages of the other groups, and these voltages are integrated into one to form the X power source 107.

Similarly, voltages V5 and V1 are defined as a group of select and unselected voltages during the other group of select and unselect voltages, and these voltages are integrated into one to make up the Y power source 106.

The X power source 107 and the Y power source 106 supply a voltage to the liquid crystal device 101 shown in FIG.

The configuration is described above, and the description is described in specific embodiments. FIG. 6 shows the liquid crystal panel 201 (shown in FIG. 2), and the diagonal display dots indicate a lighting state. 7A to 7C show driving voltage waveforms as an embodiment of the present invention when displaying. The polarity is inverted between scan electrodes Y3 and Y4 (polarity inversion number and position are not limited but are arbitrarily selected).

FIG. 7A shows the waveform of the signal voltage applied to the signal electrode X2.

7B shows the waveform of the scan voltage applied to the scan electrode Y4. Polarity reversal is performed with scan electrode Y4, and the selection voltage becomes V0U or V5L only for a period (shown as W in the figure) obtained by adding a time corresponding to the value F to any span of time.

FIG. 7C shows a waveform (shown in solid line) of the voltage actually applied to the display dot (hereinafter indicated by D24) composed of the signal electrode X2 and the scan electrode Y4. It will be understood that the waveform shown by the broken line is generated corresponding to the sum of some numerical value and the numerical value F generated during polarity inversion.

7A to 7C, upon polarity inversion, the correction circuit 104 in FIG. 1 outputs an intensity signal 109 that is active for a period obtained by adding a time span equal to the numerical value F. . Sign signal 108 indicates a negative state. When the strength signal 109 is active, the power supply circuit 105 outputs V0U and V5L as the selection voltages (voltages V0 and V5) coupled to constitute the Y power supply 107, and when the strength signal 109 is inactive Outputs VON and V6N.

For this reason, the curvature portion shown by the broken line in FIG. 7C is almost corrected because the selection voltage is switched to voltages V0U and V5L only for the time W shown in FIG. 7B.

As a result, the effective voltage is corrected to remove the uneven contrast caused by the first cause at the inversion polarity.

During the selective shift other than the polar discharge, the sign signal 108 and the intensity signal 109 of FIG. 1 are identical in operation except that they follow the value I instead of the value F. FIG.

That is, the strength signal 109 is configured to be active during the period corresponding to the numerical value I.

During the active period, in the case of the sign signal 108 being positive, the voltages V0L and V5U are output as voltages V0 and V5.

During the active period, for negative sign signal 108, voltages V0U and V5L are output as voltages V0 and V5.

During inactive periods, voltages V0N and V5N are output as voltages V0 and V5.

By the above-described operation, the distortion of the voltage waveform actually applied to the display dot generated by the numerical value I as in the case of polarity inversion will be corrected, and as a result, the effective voltage will be corrected and the contrast will be eliminated.

Example 2

In Example 1, if the correction by the numerical value I (correction at the selected shift time other than the polarity inversion) is omitted, almost the same effect will be obtained, and the circuit will be simplified.

Example 3

In Example 2, when correction by the numerical value F at the time of polarity inversion is omitted, correction is always performed for a certain time. In such a case, almost the same effect will be obtained, and the circuit is simplified simply.

Example 4

In Examples 1 to 4, the correction is performed by converting the selection voltage. However, other non-selective voltages, lighting voltages and non-lighting voltages will vary.

Example 5

In Examples 1 to 5, the correction is effective when the specified voltage is changed only for a period corresponding to the numerical values I and F. However, the voltages corresponding to the numerical values I and F will be applied for a predetermined time, and the voltages will be applied during the period corresponding to the numerical values I and F. In addition, the voltage waveform applied to perform the correction will be assumed to be a sphere as well as another configuration expressed in a triangular and ladder, exponential relationship.

There will be the described embodiment configured to eliminate the uneven contrast that appears due to the second cause.

Example 6

Inconsistent display due to the second cause is that the voltage of the signal electrode crossing the scan electrode (hereinafter referred to as scan electrode YS) is reversed in polarity so as to change from the selection voltage to the non-selection voltage upon polarity inversion toward the selection voltage. It is caused by the fact of turning off. Some degree of unevenness and other unevenness are added to the unevenness corresponding to the sum of the display dots on the selected scan electrode before and after the polarity inversion. Thus, when the liquid crystal display is operated, the amount of unselected voltage of the scan electrode YS is attracted toward the selected voltage when the voltage of the signal electrode is superimposed on the unselected voltage applied to the scan electrode YS corresponding to the calculated sum F. The voltage is changed to the selection voltage so that the effective voltage of the display dots on the scan electrode YS is equal to the effective voltage of the display dots on the scan electrodes other than the electrode YS. The above-described correction method can eliminate the unevenness of the display due to the second cause.

In FIG. 8, one embodiment of the liquid crystal device is shown in order to carry out the above-described correction.

In FIG. 8, the liquid crystal device 801 is composed of a liquid crystal panel and a driving circuit. 102 and 103 represent control signals and data signals and are the same as those shown in FIG. In FIG. 8, the waveform correction signal generating circuit (hereinafter referred to as the correction circuit 804) also generates a strength signal 809 that remains active for a time corresponding to the result of the calculation and before and after moving the selection. The sum of the lighting dots of the scan electrodes selected in Fig. 2 is calculated. 805 is a voltage power supply circuit for generating an X power supply 107 composed of two groups of ignition and non-lighting voltages, and a Y power supply 108 composed of two groups of selection, unselection, and correction unselection voltages. The correction unselected voltage changes in accordance with the intensity signal 809. 810 shows a polarity inversion detection circuit composed of a flip-flop circuit and an exclusive OR circuit. The circuit 810 outputs a signal (hereinafter referred to as signal DET) assuming an "H" level until the signal LP appears next when the signal FR is synchronized to the signal LP. That is, the circuit 810 serves to detect that the signal FR changes.

In the present embodiment, specific configurations and operations for each component will be described. 9 shows an embodiment of a specific configuration of the liquid crystal device 801. Reference numeral 201 denotes a liquid crystal panel which is configured and operated in the same manner as that of the liquid crystal panel 201. Reference numeral 208 denotes a signal electrode driving circuit ( 208 is a signal electrode driving circuit having the same operation and configuration. Thus, its components are denoted by like numerals and description is omitted. In FIG. 9, the scan electrode driving circuit 905 consists of at least a shift register 906 having a number of bits larger than the number of scan electrodes T1 to Y6, a multiplexer circuit 907 and switch circuits 908, 909. do.

Scan electrode driving circuit 905 will be fully described with reference to FIG. 906 represents a 7-bit shift register for shifting the "H" level from BIT0 to BIT1 and then to BIT2 at each arrival of signal LP, after being taken to signal DIN with the transition of signal LP. The multiplexer 907 outputs a signal for turning on the switches Son (n = 0 to 5) of the switch circuit 908 when the output of BITn (n = 0 to 5) of the shift register 906 is at the "H" level. . The multiplexer circuit 907 outputs a signal for turning on the switch Sn, assuming that the output of BITn is at the "L" level and the signal DET is "L", the output of the BITn is "L", and the signal DET is "H". "Assuming level, the output of BIT (n + 1) becomes" L ". In addition, when the circuit 907 outputs a signal for turning on the switch Sn2, the output of BITn is at the "L" level, the output of BIT (n + 1) is at "H", and the signal DET is at the "H" level. Assume At the same time, the circuit 907 outputs a signal for turning off the other switches Sn0 to Sn2, and outputs a signal for turning on any one of the switches Sn0 to Sn2. The switch circuit 908 is composed of six groups of switches, each group consisting of three switches Sn0 to Sn2 (n = 0 to 5). These switches take one voltage between the selection, non-selection, and correction non-selection voltages according to the output of the multiplexer circuit 907 and output these voltages to scan electrodes Y1 to Y6 of the liquid crystal panel 201. In FIG. 10, the switch circuit 909 is composed of switches S60, S61, and S62. The switch circuit 909, together with the signal FR, switches a group of voltages from two groups of select, unselect and correct unselected voltages for the Y power source 806.

The configuration has been described above, and the technique is described below with operation. The group of voltages is selected from two groups of select, unselect and correct unselected voltages by the signal FR. For the switching of the switch circuit 908, the switch Sn0 is turned on, and the selection voltage is output when the BITn is at the "H" level, that is, in the selection state, and the signal DET is assumed to be at the "H" level, and BIT (n + 1). ) Output becomes " H " level, in the case of non-select state, the polarity is reversed and the selection state is just before the polarity inversion.

The scan electrode driving circuit 905 serves in the manner described above. The configurations of the switch circuits 908, 909 and the multiplexer circuit 907 are not limited to those described above but are taken from the conditions under which similar voltages can be output.

In Fig. 9, the liquid crystal device 801 has the above-described configuration.

FIG. 11 shows the correction circuit 804 of FIG. In FIG. 11, reference numerals 401, 402, and 401 denote the same elements as those in FIG. These elements coded with like reference numerals function the same, and the description is omitted here. Reference numeral 804 denotes a calculation circuit, and 805 denotes a pulse width control circuit. The calculation circuit 804 outputs the sum of the values N _ON and M _ON given from the first and second count holding circuits 402, 403 to the pulse width control circuit 805, and the calculated value is F = N _ON. + M _ON . Synchronized with the arrival of the signal LP, the pulse width control circuit 805 is an active signal, for example, a magnitude signal 809 that is only active for a period obtained by adding a time from a certain time corresponding to the input value F. Outputs

The correction circuit 804 has the above circuit and functions in the manner described above.

FIG. 12 shows an embodiment of a specific circuit of the voltage power supply circuit 805 of FIG. In Fig. 12, reference numerals 1201 to 1207 denote resistors connected in series, and these two ends are supplied at voltages V0 and V5.

The voltages generated at each end of resistors 1201 through 1207 are V0, V1N, V1L, V2, V3, V4U, V4N and V5 as shown in the figure.

V0-V1N

= VlN-V2

= V3-V4N

= V4N-V5

= (V2-V3) / (n-4) ≡V, where n is a constant value.

V1N-V1L

= V4U-V4N.

The resistance value of each of the resistors 1201 to 1207 can be obtained by the above relationship.

The voltage stabilization circuitry indicated at 510 is configured in the same way and functions the same as that of the circuit 510 shown in FIG.

Switches 1209 and 1210 output voltages V1L and V4U during the active period of intensity signal 809 of FIG. During periods of inactivity, switches 1209 and 1210 output voltages VlN and V4N. The output voltages of switches 1209 and 1219 are updated to voltages V1 'and V4'.

The voltage power supply circuit 805 outputs the X power supply 107, and the voltages V0 and V2 are defined as a group of on and off lights, and the voltages V5 and V3 are defined as other groups on and off. Circuit 805 also outputs Y power supply 806, where voltages V5, V1n and V1 'are defined as a group of select, unselect and correct unselected voltages, and voltages V0, V4N and V4' select other groups. , Non-selection and correction are defined as non-select voltages.

Thus, the voltage stabilization circuit 510 is configured. The operation of the circuit 510 will be described by the method of the specific embodiment.

FIG. 13 shows the liquid crystal panel 201 (see FIG. 9), and the display dots indicated by the lines are in the lit state.

14A to 14C show driving voltage waveforms according to an embodiment of the present invention when performing display. The polarity is inverted between scan electrodes Y3 and Y4 (the polar inversion and the number of positions are not limited but are arbitrarily selected as needed).

FIG. 14A shows the voltage waveform at the position of dot D33 on the signal electrode X3. When the polarity is reversed, it is dragged to the selected voltage.

14B shows the voltage waveform at the position of dot D33 on scan electrode Y3. During the polarity inversion, the corrected non-selection voltage biased from the non-selection voltage to the select voltage is applied only to the scan electrodes Y3 and Y4 for a period obtained by adding a certain time to the sum of the lit dots in time.

FIG. 14C shows the difference between 14a and 14b which are waveforms of the voltage applied to the dot D33.

As shown in Fig. 14C, the voltage waveform formed on the scan electrode Y3 is deflected to the selection voltage when the voltage waveform of the signal electrode X3 is dragged to the lighting voltage. As a result, the difference in the effective value is almost corrected, resulting in uneven contrast on the display.

In this manner, a correction non-selection voltage is applied to the selected scan electrode immediately before the polarity inversion according to the case where the polarity is inverted only during a period (hereinafter referred to as a correction period) obtained by loading a time with a time corresponding to the sum F, This eliminates uneven contrast on the display.

Example 7

In the sixth embodiment, the period for applying the corrected unselected voltage, which is a voltage different from the unselected voltage, is increased or decreased depending on the sum F. The forward difference associated with the other voltage can be increased or decreased by the sum F. The potential difference and the period will be changed by the sum F. The other voltages described above will be replaced by other waveforms represented by waveforms and exponential functions assuming triangular and ladder configurations.

Example 8

In Example 6, the amount of correction is increased or decreased by the sum F. The increase or decrease according to the sum F can be eliminated. Instead, a corrected non-selection voltage is applied to the selected scan electrode just before the polarity reversal, according to the case of polarity reversal, only during a period of time in which it is added. Significantly improves unevenness on the display The correction period is specially set to one size of the signal LP to simplify the circuit 1. The switches 1209 and 1210 of the correction circuit 804 and the power supply circuit 805 Can be removed.

Example 9

Example 1 is provided to replace the unevenness of the display due to the first cause, and the selection voltage is overlapped with the correction voltage. On the other hand, Example 6 is given to cope with the unevenness of the display due to the second cause, and the non-selection voltage is overlapped with the correction voltage. Under such conditions, it is possible to eliminate the unevenness on the display by the first cause and the second cause.

Example 10

In Examples 1 to 9, the liquid crystal display device provides a device for changing the correction amount by the ambient temperature so as not to indicate an unevenness even at the ambient temperature of the width region.

As described above, the unevenness of the contrast can be corrected by correcting the difference between the effective voltages generated during the polarity inversion upon changing the scan or voltage waveform according to the polarity inversion.

The uneven contrast can be improved by making corrections corresponding to the value F.

In addition to the above, it can be provided by varying the scan or signal voltage waveform according to the value I under polarity reversal and other situations under more improved conditions in relation to uneven contrast.

By adding a certain time to the time corresponding to the sum F, a correction non-selection voltage can be applied to the selected scan electrode immediately before the polarity inversion according to the polarity inversion only to eliminate the uneven contrast on the display.

Although the illustrated embodiments are described in detail with reference to the accompanying drawings, the present invention is not limited to these embodiments, and many variations or modifications may be made by those skilled in the art without departing from the spirit and spirit of the present invention.

Claims (5)

One liquid crystal layer, a pair of substrates for inserting the liquid crystal layer, a group of scan electrodes formed on the one substrate, and a group of signal electrodes formed on the other substrate, provide a scan voltage to the scan electrode group A liquid crystal display device which applies a waveform, applies a signal voltage waveform to the signal electrode group, and periodically inverts the polarity of the voltage difference between the scan voltage waveform and the voltage waveform. And means for changing at least one of the scan voltage waveform and the signal voltage waveform. The liquid crystal display device according to claim 1, further comprising means for controlling an amount of change in any one of the scan voltage waveform and the signal voltage waveform corresponding to a graphic or a character pattern displayed on the liquid crystal display when the polarity is inverted. . 3. The apparatus of claim 2, further comprising means for changing at least one of the scan voltage waveform and the signal voltage waveform to an amount corresponding to the graphic or character pattern displayed on the liquid crystal display during an operation different from the polarity inversion operation. Liquid crystal display. The non-selection voltage applied immediately after the polarity inversion is applied immediately before the polarity inversion according to the polarity inversion, and the non-selection voltage is applied immediately after the polarity inversion between the scan electrode groups. And means for varying in association with the scan electrode being applied. The scanning electrode of claim 4, wherein the selection voltage is applied immediately before the polarity inversion according to the polarity inversion and the non-selection voltage is applied immediately after the inversion of the polarity between the scan electrode groups. And means for controlling the amount of change in the non-selected voltage applied immediately after the polarity inversion in correspondence with the graphic or character pattern displayed on the liquid crystal display.

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