JPH021313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a liquid crystal display device including a dot matrix display section and a segment display section.

In recent years, matrix displays have been proposed for liquid crystal displays in small electronic devices such as digital watches and small electronic calculators in order to cope with the expansion of functions and diversification of displays. Some parts have been put into practical use. However, the dot matrix display is a combination of dots, and the conventionally used segment display is easier to see when displaying time or calculated values. For example, in the case of an electronic watch, a dot matrix display section and a 7-segment display section are combined in the same liquid crystal cell, and the 7-segment display section displays the time, and the dot matrix display section displays non-numeric characters such as the day of the week. The idea is to display information. However, when a dot matrix display section and a 7-segment display section are arranged in the same liquid crystal cell,
In order to equalize each effective value, the display must be driven using the same driving method, and the 7-segment display section is driven by the same high-order dynamic drive as the dot matrix display section, and a drive signal with the same waveform is applied. I had to drive. However, if a 7-segment type display section is driven with a drive signal having the same waveform as a high-order dynamic drive, a problem arises in that crosstalk occurs. In other words, if this crosstalk occurs on the dot matrix display, the entire display becomes crosstalk, so there is no misreading of the data, or if crosstalk occurs on the 7-segment display, the data is There was a risk of misreading. For example, when "5" should be displayed on a 7-segment display section, "6", "9", "day", etc. are displayed due to crosstalk.

This invention was made in view of the above points,
The purpose is to provide a method for driving a liquid crystal display device that can prevent crosstalk and provide accurate display when a dot matrix display section and a 7-segment display section are formed in the same liquid crystal cell. .

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the appearance of an electronic wristwatch having a dot matrix display section and a 7-segment display section within the same liquid crystal cell. In the same figure, 1
1 is the case body of the electronic wristwatch. And 1
Reference numeral 2 denotes a display section, in which a dot matrix display section 13 and a 7-segment type display section 14 are formed within the same liquid crystal cell. Further, switch _S1 is a mode change switch, switch _S2 is a stopwatch switch, and switch _S3 is a time adjustment switch. In the normal state, as shown in FIG. 2, the dot matrix display section 13 of the display section 12 displays the day of the week and the date, and the seven segment display section 14 displays the current time. In this example, "June 24th,
"Sunday, 10:08:35 a.m." is displayed.
Next, if you want to switch to stopwatch mode, operate switch _S1 . As a result, as shown in FIG. 3, the dot matrix display section 13 displays that the stop watch mode is present, and the 7-segment display section 14 displays "XX minutes XXX seconds XXX". FIG. 4 is a diagram showing the arrangement of the common electrodes of the display section 12. In the figure, 12a is the display section 1
X ₀ ~
_X7 is a common electrode of the dot matrix display section 13, and signal lines are extended from each common electrode to electrodes _a0 to _a7 . These electrodes a ₀ to _{a 7} receive signals via transfers from electrodes e ₀ to _{e 7} of the other substrate 12b, which will be described later. Further, l ₁ and l ₂ are common electrodes of the 7-segment display section 14, and signal lines are extended from each common electrode to electrodes b ₀ and b ₂ . These electrodes are the electrodes f ₀ and f ₁ of the other substrate 12b.
It is now receiving signals from

FIG. 5 is a diagram showing the arrangement of segment electrodes of the display section 12. In the figure, 12b is the other substrate facing the substrate 12a, and Y0 _{to Y0} are segment electrodes of the dot matrix display section 12, and electrodes _C0 to _C0 signal lines are extended from each segment electrode. There is. Also, m ₀ to m _o are each 7
In the segment electrodes of the segment type display section 14, signal lines extend from each segment electrode to electric wires _d0 to _d0 . Further, the electrodes e ₀ -e ₇ , f ₀ , f ₁ are electrodes that supply drive signals to the electrodes a ₀ -a ₇ , b ₀ , b ₁ of one substrate 12a, respectively. The electrodes c ₀ -c _o , e ₀ -e ₇ , f ₀ , f ₁ , d ₀ -d _o of the substrate 12b each receive a liquid crystal drive signal from a liquid crystal drive circuit (not shown).

Next, drive signals applied to the liquid crystal cell configured as described above will be explained. First, FIG. 6A shows a driving waveform when the dots on the dot matrix display section 13 are lit. Further, FIG. B shows the driving waveform when the dot is not lit. That is, FIG. 6A shows a drive waveform of 1/4 bias and 1/8 duty. Let us now calculate the drive voltage V _pp when using a 1/4 bias 1/N duty drive waveform. Here, if the effective voltage when the dot is lit is ν _po and the effective voltage when the dot is not lit is ν _pff , then Now, set the threshold voltage of the liquid crystal to be used.
If V _th , then from equations (1) and (2) The drive voltage V _pp must be determined so that

Incidentally, FIG. 7 shows a drive waveform of 1/2 bias and 1/2 duty applied to a conventional 7-segment type display section. Here, A
is a common signal, B is a segment signal, and C is a segment signal.
is the drive waveform when the segment lights up, and is D in the same figure.
shows the drive waveform when the segment is not lit. Now, the effective voltage when the segment is lit is
U _po , when the effective voltage when not lit is U _pff In this case, the threshold voltage of the liquid crystal
If U _{th is U th} , then U _pp is from equations (4) and (5) above. becomes. By the way, since the dot matrix display section 13 and the 7-segment type display section 14 are driven in the same liquid crystal cell as shown in FIG. 1, V _th =U _th must be satisfied. However, as can be seen by comparing equations (3) and (6), if "V _th = U _th " is included, V _pp = U _pp does not generally hold. Therefore, in the present invention, when selecting a liquid crystal, priority is given to one suitable for the dot matrix display section 13, where the contrast of the applied voltage cannot be very large due to crosstalk problems, and the seven segment display section 14 is suitable for the dot matrix display section 13. The drive waveform applied to is changed so that V _pp = U _pp (7).

Therefore, FIG. 8 shows the driving waveforms applied to the 7-segment display section, where A is the common signal, B is the segment signal, and C is the driving waveform when the segments are lit. D in the figure shows a drive waveform when the segment is not lit.
Here, Figure B shows the waveform of a segment signal devised to achieve the object of the present invention. When using the waveform shown in Figure B, the effective voltage W _po when the segment is lit and the effective voltage W _pff when the segment is not lit.
teeth The driving voltage _Wpp in this case is becomes.

Therefore, when the dot matrix display section 13 and the 7-segment display section 14 are provided in the same liquid crystal cell as shown in FIG. 1, and when the same driving voltage is used, equations (3) and (10) are Than In other words, the value of m may be determined so as to satisfy equation (11).

As described in detail above, according to the present invention, when a dot matrix display section and a segment type display section are formed in the same liquid crystal cell, the width of the voltage waveform applied to the segment type display section is modulated to increase the effective voltage. Since the voltage is lowered, the dot matrix display section and the segment display section can be displayed with good contrast even when the power supply voltages are made equal, that is, even when a single power supply is used.

[Brief explanation of drawings]

1 to 6 and 8 show an embodiment of the present invention, and FIG. 1 shows an external appearance of an electronic wristwatch equipped with a dot matrix display section and a 7-segment display section within the same liquid crystal cell. Figures 2 and 3 are diagrams showing the display state, Figure 4 is a diagram showing the arrangement of common electrodes, Figure 5 is a diagram showing the arrangement of segment electrodes, and Figures 6A and B are diagrams showing the dots. A diagram showing the drive waveform applied to the matrix display section, FIG. 8A
to D are diagrams showing drive waveforms applied to a 7-segment display section, and FIG. 7 is a diagram showing a conventional drive waveform applied to a 7-segment display section. DESCRIPTION OF SYMBOLS 11...Case body, 12...Display part, 13...Dot matrix display part, 14...7 segment type display part.

Claims (1)

[Claims] 1 A dot matrix display section and a segment display section are provided in the same liquid crystal cell, each dynamically driven at a different number of time divisions, and a common signal in which a predetermined potential is repeated is supplied to the common electrode of the segment display section. The segment electrode of the segment display section is provided with one of the common signals.
During the repetition period, a segment signal consisting of a voltage whose height is opposite to the potential of the common signal and a voltage of the same potential for a predetermined period is supplied, and the segment signal is generated between the common electrode in the lighting state and the segment electrode. A segment signal in a lighting state in which an effective voltage applied to the segment signal is equal to a voltage waveform in a lighting state applied to the dot matrix display section, and a pulse width is narrowed by a period during which a voltage of the same potential as the segment signal is supplied. , has a pulse voltage having a width corresponding to a period during which a voltage of the same potential of the segment signal is supplied between the common electrode and the segment electrode in the non-lighting state, and has a phase inverted with respect to the segment signal in the lighting state. A method for driving a liquid crystal display device, comprising a segment signal in a non-lighting state.