JPH06259041A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make circuits compact by specifying the number of row electrodes and the number of row electrodes collectively selected to specific values and the driving voltage to a specific value or below by using ordinarily used standard liquid crystals and driving the liquid crystals by batteries supplying this voltage. CONSTITUTION:The row electrodes are so constituted that the voltage is impressed at Vr amplitude in a positive or negative direction with respect to an intermediate voltage at the time of selection and that the intermediate voltage is impressed thereto at the time of non-selection. An orthogonal matrix in which elements consist of +1 or -Vr corresponding to the voltage +Vr is selected as a selection voltage matrix. This selection voltage matrix is constituted to impress the voltages in such a manner that the elements of the column vectors of the selection voltage matrix and the voltage amplitude in the row electrodes constituting row electrode sub-groups correspond to each other, at the time of selection of the row electrode subgroups. The number N of the row electrodes is specified to 16<=N<=130 and the number L of the row electrodes to be collectively selected is set near N<2/1>. The driving voltage is set at <=5V. The electrodes are provided with the batteries for supplying this voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display driven by a battery.

[0002]

2. Description of the Related Art In recent years, simple matrix type liquid crystal display devices have been used in various fields, and in particular, there is an increasing demand for small or portable displays such as mobile phones, car audio systems and gas meters. In this case, it is necessary to unify the drive voltage with the IC used, and to drive with a battery, the drive voltage itself needs to be 5 V or less.

[0003]

The main countermeasure against this problem is to reduce the driving voltage of the liquid crystal panel itself. In this case, materials such as Florocyanoester having a large dielectric anisotropy are often used. Had to do. However, these materials have low reliability and have a problem in durability in practical use.

On the other hand, the conventional twisted nematic (TN) or super twisted nematic (ST)
A driving method called a voltage averaging method has been used for a simple matrix type liquid crystal display element such as N) (for example, Paul M. Alt and Peter Pleshko, IEEE Trans, E).
D-21 (2), pp.146-155 ('74)).

However, in the conventional driving method,
Duty number that is heavier than a certain amount (for example, 1/32
The supply voltage could not be reduced to 5 V or less at the duty or higher).

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the number of row electrodes of a liquid crystal display element having a plurality of row electrodes and a plurality of column electrodes is J (where J is Two
The above integer) row electrode sub-group, and the liquid crystal display device is driven by collectively selecting and driving the row electrode sub-group. The row electrodes are positive or negative with respect to the intermediate voltage when selected. Direction, a voltage is applied with an amplitude of V _r (V _r > 0), and the intermediate voltage is applied at the time of non-selection.
An orthogonal matrix consisting of +1 corresponding to the voltage + V _r or −1 corresponding to −V _r is selected, and when selecting the row electrode subgroup, the elements of the column vector of the selection voltage matrix and the row electrode subgroup are selected. In the liquid crystal display device configured such that the voltage is applied so as to correspond to the voltage amplitudes of the row electrodes to be formed, the number N of row electrodes is 16 ≦ N ≦ 130
The number L of row electrodes selected at the same time is set near N ^1/2 so that the driving voltage is 5 V or less, and a battery for supplying a voltage to the electrodes is provided and driven by the batteries. A liquid crystal display device is provided.

[0007]

EXAMPLES Examples will be described below according to the present invention.

Basically, the liquid crystal display element of the present invention is disclosed by the applicant in Japanese Patent Application Nos. 4-277864 and 4-3047.
It is driven in the same manner as the driving method proposed in No. 15. That is,
The row electrodes of a liquid crystal display element including a plurality of row electrodes and a plurality of column electrodes are divided into J (J is an integer of 2 or more) row electrode subgroups, and the row electrode subgroups are collectively selected. The liquid crystal display element is driven and has the following features.

(1) A voltage is applied to the row electrodes with an amplitude of V _r (V _r > 0) in the positive or negative direction with respect to the intermediate voltage when selected, and the intermediate voltage is applied when not selected. Be configured to.

(2) As the selection voltage matrix, the elements are voltage +
An orthogonal matrix consisting of +1 corresponding to V _r or −1 corresponding to −V _r is selected, and when the row electrode subgroup is selected, the elements of the column vector of the selection voltage matrix and the rows forming the row electrode subgroup are selected. It is configured to be applied with a voltage corresponding to the voltage amplitude at the electrodes.

According to the present invention, a plurality of row electrodes are collectively selected. A group of row electrodes that are collectively selected is called a “row electrode subgroup”. It is preferable to equalize the number of row electrodes forming each row electrode subgroup, but if it is not possible to equalize all the number of row electrodes forming each row electrode subgroup, virtual dummy row electrodes are used. The row electrodes may be driven assuming that the number of row electrodes included in all the row electrode subgroups is equal.

Regarding the voltage applied to the row electrodes, when the voltage in the non-selected state is 0, + V _r , -V _{r in the} selected state.
It is assumed to take any voltage level of (V _r > 0). Here, the voltage 0 when not selected does not necessarily mean grounding to the earth. The drive voltage of the liquid crystal element is the voltage (potential difference) applied between the row electrode and the column electrode.
This is because the potential difference between both electrodes does not change even if the potentials of both electrodes are changed in parallel by the same amount.

The voltage at the time of selection applied to a specific row electrode sub-group is represented by a time-series arrangement of L-th order vectors having the voltage applied to each row electrode as an element. This is called a “selection voltage vector”. A matrix including the selection voltage vector as its column is called a “selection voltage matrix”.

As for the selection voltage matrix, basically, the elements are +1 corresponding to the voltage + V _r or -1 corresponding to -V _r.
An orthogonal matrix consisting of and is chosen. The number of rows of the selection voltage matrix corresponds to the number of row electrodes included in the row electrode subgroup, and the number of columns corresponds to the number of selection pulses included in one cycle. When the selection voltage applied to each selection electrode is not AC-converted, it can be AC-converted by driving using the selection voltage matrix A after the selection voltage matrix A.

Further, it is particularly effective to employ a Hadamard matrix as the selection voltage matrix in order to suppress display unevenness.

The time-series arrangement order of the selection voltage vectors used for driving is arbitrary, and the selection voltage vectors can be used by substituting each subgroup or each display data. In order to suppress display unevenness in actual driving, it is often preferable to perform driving while appropriately performing the above replacement.

Next, the timing for applying the selection pulse represented by the selection voltage vector configured as described above to each row electrode was proposed in Japanese Patent Application Nos. 4-277864 and 4-304715. In the driving method, in order to suppress a frame response (liquid crystal relaxation phenomenon) in a liquid crystal element having a high-speed response, selection pulses are dispersed and applied within one cycle to shorten the length of the non-selection period for each row electrode.
However, in the present invention, such timing is not essential. However, this has the advantage that the high-speed response liquid crystal can be used with a high contrast ratio.

Regarding the voltage applied to the column electrode for displaying the specific data when the specific row electrode subgroup is selected under the conditions described above,
For example, it is selected under the following conditions.

(1) It is selected from (L + 1) voltage levels such that V ₀ <V ₁ <... <V _L. Here, L is the number of row electrodes selected at the same time. The absolute value is appropriately determined according to the threshold voltage of the liquid crystal element. Also, this value is preferably chosen such that the column signals are alternating.

(2) If the mismatch between the selected voltage vector and the corresponding display data vector (ON is 1 and OFF is -1) is _i , V _i is applied to the column electrode.

Letting V _{c be} the maximum value of the column electrode voltage, V _i
= V _c (2i-L) / L, V _r = V _c N ^1/2 / L (where N is the total number of row electrodes), the V _ON / V _OFF of the voltage effective value is maximized. It is preferable because it can be

Of course, regardless of the above conditions, V _r and V should be set so that the best contrast ratio can be obtained in the vicinity thereof.
You can adjust the level of _i .

When the display data is not binary display but has gradation, gradation can be realized by a so-called frame thinning method. Also, Japanese Patent Application No. 4-
Amplitude modulation, such as that disclosed in 269560, may also be used.

In the present invention, the number N of row electrodes is 16 ≦ N ≦ 13.
The number L of the row electrodes which is set to 0 and is selected at the same time is made substantially equal to N ^1/2 . This allows the standard V that is normally used.
Using a liquid crystal having _th , the drive voltage, that is, 2V _r or 2V _c , whichever is larger, is set to 5 v or less. Further, it is characterized in that a battery for supplying a voltage to the electrodes is provided and driven by the battery. From this perspective,
In particular, if 16 ≦ N ≦ 100 and 4 ≦ L ≦ 7, the above L,
It is preferable to satisfy the condition of N. further,
Particularly preferably, 16 ≦ N ≦ 64 and 4 ≦ L ≦ 7.

FIG. 1 shows an example of a circuit adopted to realize the driving method of the present invention. The display data is input as an analog signal separately for R, G, and B. This is converted into digital data by A / D converters 1, 1, 1 each having 6 bits of R, G, B, and this is corrected according to the optical characteristics of the liquid crystal.
Is corrected (so-called γ correction), converted into gradation data having a predetermined number of bits determined by gradation, and stored in the display memory 3 once. Next, the data is read from the display memory 3 in a predetermined order, and the data selector 4 allocates the data to the L sub-group memories 5, 5, 5 ... The L pieces of data are supplied to the gradation control circuits 6, 6, respectively.
, 6 is converted into 1-bit ON / OFF display data string (L pieces) data as a group in 15 cycles and sent to the exclusive OR and the adder 7.

Then, an exclusive OR of the L-bit data and the L-bit row selection pattern sent from the row electrode selection pattern generating circuit 11 is calculated, and then the addition is performed to the column electrode driver 8. Sent. The row selection pattern generation circuit 12 delays the selection time for one row and sends it to the row electrode driver 13. The outputs of the row electrode driver 13 and the column electrode driver 8 are input to each electrode of the liquid crystal panel 9. Reference numeral 10 is a timing generation circuit.

The following table shows the results when the liquid crystal display panel was driven using the above circuit configuration.

Table 1 is a comparison between the driving method according to the present invention and the conventional driving method. Table 2 shows changes in operating voltage when the duty ratio is changed by the driving method according to the present invention. In the table, L is the number of simultaneously selected lines (line),
N is the number of row electrodes (number), D is the duty ratio, V _D is the drive voltage (v), and V _th is the threshold voltage of the liquid crystal used.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, by operating on a battery, a simple matrix type, such as TN and S, can be used.
It is possible to significantly reduce the operating voltage in the display elements such as mobile phones, pagers, and gas meters that use the TN liquid crystal display element as a display device. For this reason, the booster circuit that has been used to obtain the desired drive voltage is no longer needed, and the circuit can be made compact and the cost will be reduced accordingly, so a large expansion of these applications is expected. it can.

Further, since a highly reliable liquid crystal material can be used, stable display can be performed for a long period of time, and deterioration of the liquid crystal display element due to occurrence of display unevenness can be prevented or suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an example of the present invention.

[Explanation of symbols]

 1: A / D converter 2: Corrector 3: Display memory 4: Data selector 5: Subgroup memory 6: Grayscale control circuit 7: Exclusive OR and adder 8: Column electrode driver 9: Liquid crystal panel 10: Timing generation circuit 11: Row electrode selection pattern generation circuit 12: Delay circuit 13: Row electrode driver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoshi Nakazawa Satoshi Nakazawa 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Kanagawa Prefecture A-G Technology Co., Ltd. (72) Takeshi Kuwata Matsubara Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Address 1160, within AG Technology Co., Ltd.

Claims (1)

[Claims] 1. A row electrode of a liquid crystal display device comprising a plurality of row electrodes and a plurality of column electrodes is divided into J (J is an integer of 2 or more) row electrode subgroups, and the row electrode subgroups are collectively processed. In the liquid crystal display device, the row electrodes are applied with a voltage of V _r (V _r > 0) in a positive or negative direction with respect to the intermediate voltage when selected, and
When not selected, the intermediate voltage is applied, and as the selection voltage matrix, an orthogonal matrix whose elements are +1 corresponding to the voltage + V _r or -1 corresponding to -V _r is selected, and the row is selected. When selecting the electrode subgroup,
In a liquid crystal display device configured such that a voltage is applied so that the elements of the column vector of the selection voltage matrix correspond to the voltage amplitudes of the row electrodes forming the row electrode subgroup, the number N of row electrodes is 16 ≦ N. ≦ 130, the number L of row electrodes selected at the same time is set to near N ^1/2 , and the drive voltage is set to 5 v.
In addition to the following, a liquid crystal display device comprising a battery for supplying a voltage to an electrode and being driven by the battery.