JPH10197846A - Driving method of liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drive a liquid crystal panel in simple matrix which has two metastable states at low cost by an existing driving IC without newly providing a custom driving IC. SOLUTION: Of the scanning-electrode side driving voltage waveform of the liquid crystal panel in simple matrix structure consisting of a reset pulse R and a write pulse W which is outputted successively to the reset pulse R and has the same polarity with the reset pulse R, the pulse width of the reset pulse R and the pulse width of the write pulse W are determined according to a scanning-side clock signal Ck which is the period of greatest common measure. Consequently, the voltage levels of the reset pulse R and write pulse W are made constant by clock signals Ck. Consequently, two of four voltage levels can be selected in a period of one frame in synchronism with the clock signals Ck to achieve simplification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal panel, and more particularly, to a method for driving a liquid crystal panel applied to a controller of a display device using a liquid crystal. It is suitably used for display devices of OA equipment.

[0002]

2. Description of the Related Art In a liquid crystal panel, at least one of the liquid crystal panels is provided in parallel with an inner surface of a transparent insulating support plate.
In addition to providing an O transparent electrode, an alignment film for aligning liquid crystal molecules is formed on the surface of the transparent electrode, a liquid crystal is filled and sealed in a space sandwiched between the alignment films, and the outer surface of the insulating support plate is polarized. This is a structure in which the surfaces are sandwiched by polarizing plates that are substantially perpendicular to each other. The liquid crystal panel thus configured controls an alignment state of liquid crystal molecules according to an electric field generated by selectively applying a voltage between the transparent electrodes, and forms an electro-optical shutter to display an image. Things. At present, the liquid crystal panel applied to general OA equipment has a liquid crystal filled with TN (Twis).
ted Nematic) or STN (SuperTwisted Nema)
tic) a liquid crystal, wherein a simple matrix system in which the transparent electrodes are arranged in a matrix with scanning electrode groups and signal electrode groups is used.

At present, research and development are being conducted on a simple matrix liquid crystal display device, such as improvement of high-speed response and suppression of crosstalk, and various driving methods have been proposed. The liquid crystal display having two metastable states described in JP 230751 has been noted for its high-speed response.

A method of driving a liquid crystal display device having two metastable states described in Japanese Patent Application Laid-Open No. Hei 6-230751 (hereinafter referred to as the prior art) has a chiral structure having a twist structure having a twist angle φ in an initial state. The present invention relates to a method of driving a liquid crystal display device using a nematic liquid crystal, wherein a voltage applied to cause a Frederick dislocation in the initial state is a voltage pulse equal to or higher than a threshold in the initial state and two metastable states. And then to select one of the two metastable states,
This is a method of applying a voltage pulse of a voltage selected based on a critical value that generates one of two metastable states. Hereinafter, a method of driving a liquid crystal having two metastable states according to the related art will be schematically described from the viewpoint of actually driving a liquid crystal panel.

FIG. 9 is a diagram showing a voltage waveform applied to a pixel in the prior art. In the prior art, one of the voltage waveforms applied to the pixel is shown in FIG. An AC waveform of large amplitude ± E (first voltage pulse) applied during the selection period, followed by 0 or ± E ₁ (second voltage pulse) of AC waveform of small amplitude, and | E ₂ | (<| E ₁ |). Less than,
For illustration purposes, the first voltage pulse is reset pulse R,
The second voltage pulse is a write pulse W. In the prior art, in addition to this, it is that it is possible to apply a reset pulse R and + E ₁ of the write pulse W of the AC rather than waveform, in unipolar + E as applied waveform shown in FIG. 9 (B).

In the driving method of applying the voltage waveform shown in FIG. 9, as described above, it is necessary to apply a reset pulse R in addition to the normal write pulse W to the selected pixel. Number) may be limited. As a solution to this point, in the related art, as shown in FIG. 10, a method of superimposing reset pulses R on adjacent scan electrodes (not shown) is proposed.

[0007]

In the driving method of the simple matrix liquid crystal display device according to the prior art described above, the first voltage pulse (reset pulse R) which is a voltage of the kind shown in FIG. It is necessary to apply a second voltage pulse (write pulse W) to the selected pixel,
FIG. 9A shows an example in which an AC waveform is applied during the pixel selection time. For this reason, the driving waveform becomes complicated, and it is difficult to drive a liquid crystal panel having two metastable states with a conventional driving IC for a liquid crystal panel such as TN and STN. Hereinafter, a drive IC for a TN and STN liquid crystal panel will be referred to as an existing drive IC with respect to a drive IC for a liquid crystal having two metastable states.

In the prior art, the possibility of applying only the positive electrode (or the negative electrode) shown in FIG. 9B other than the AC waveform as the voltage waveform applied to the pixel is shown. The method is not mentioned. For this reason,
In the prior art, a driving IC newly supporting this driving method
However, in this case, the drive IC becomes a custom product, and the product cost is significantly increased. However, the prior art does not provide any solution to this problem.

Furthermore, in order to remove the limitation on the display capacity, a method is proposed in which the reset pulse R is superimposed on adjacent scanning electrodes as shown in FIG.
The driving waveform to achieve this is more complicated,
Increasingly difficult to drive with existing drive ICs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in the method of driving a liquid crystal panel having two metastable states which is a method of driving a simple matrix liquid crystal, a new custom driving IC is required. It is intended to realize high display quality at low cost.

[0011]

According to a first aspect of the present invention, there is provided a method for driving a liquid crystal panel having two metastable states, wherein four voltage levels are outputted as output levels, and the voltage levels which can be selected at the time of the output are the same. It is characterized by using a drive IC having a function of two levels out of four levels, thereby realizing driving of a liquid crystal panel having two metastable states using an existing drive IC, thereby reducing the cost. Thus, a high quality panel display can be realized.

According to a second aspect of the present invention, in the method of driving a liquid crystal panel according to the first aspect, each of the voltage levels output from the drive IC is switchable. By switching, a driving IC is used and a liquid crystal panel having two metastable states is driven, whereby a high-quality panel display can be realized at low cost.

According to a third aspect of the present invention, in the method for driving a liquid crystal panel according to the second aspect, the voltage level switching means for switching each voltage level output from the driving IC is provided.
The present invention is characterized in that the voltage is switched to a preset voltage by a logic signal, so that the same effects as those of the first and second aspects are obtained.

According to a fourth aspect of the present invention, in the method of driving a liquid crystal panel according to any one of the first to third aspects, the driving IC for driving a liquid crystal panel having two metastable states is provided.
The two types of voltages output from the two levels are a first voltage pulse and a second voltage pulse, and the voltages of the first voltage pulse and the second voltage pulse are formed from the same reference signal. Accordingly, it is possible to easily produce a pulse with a logic circuit, to simplify the logic circuit, and to reduce the cost.

According to a fifth aspect of the present invention, in the method for driving a liquid crystal panel according to the fourth aspect, the first voltage pulse and the second voltage pulse are output based on a reference signal, and the period of the reference signal is changed. Is characterized in that the period is the greatest common divisor of the first voltage pulse width and the second voltage pulse width, so that the same effect as that of claim 4 can be obtained.

According to a sixth aspect of the present invention, in the driving method for driving a liquid crystal panel having two metastable states, the liquid crystal panel is driven by an IC, and at the time of output of the driving IC, a voltage level at which each output can be selected is at least. The liquid crystal display device is characterized by having three levels, so that the display capacity of the liquid crystal display device can be ensured and the display quality can be improved.

According to a seventh aspect of the present invention, in the driving method for driving a liquid crystal panel having two metastable states, the liquid crystal panel is driven by an IC, and a voltage level at which each output can be selected at the time of output of the driving IC is: The liquid crystal display device is characterized in that it has six or more levels, so that the display capacity of the liquid crystal display device can be improved with a large reduction in the number of parts and cost while maintaining the display quality.

According to an eighth aspect of the present invention, in the driving method of the liquid crystal panel according to the sixth or seventh aspect, the scanning-side driving IC of the liquid crystal panel sequentially selects an output voltage pattern predetermined by a digital input. Output, so that the display capacity of the liquid crystal display device can be reduced
The display quality can be improved while ensuring the display quality.

According to a ninth aspect of the present invention, in the liquid crystal panel driving method according to the eighth aspect, an output voltage pattern for selecting an output voltage on the scanning side of the liquid crystal panel is produced using a logic circuit. Thus, the same effect as the eighth aspect can be obtained.

The invention according to claim 10 is the invention according to claims 6, 7, 8,
10. The method of driving a liquid crystal panel according to claim 9, wherein the scanning-side driving IC of the liquid crystal panel uses a signal-side driving IC of the liquid crystal panel for voltage gradation by digital input. Thus, the same effect as that described above can be obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for driving a liquid crystal panel by an existing IC according to the present invention will be described below. As described above, the driving method of a liquid crystal panel having two metastable states is roughly classified into two methods depending on whether or not the reset pulse R is superimposed. In the present invention, these are driven by an existing drive IC.

First, a driving method in which the reset pulse R is not overlapped will be described. There are four voltage levels to be output as an existing driving IC, and two of the four voltage levels that can be selected at the time of output are used. A driving method of a liquid crystal having two metastable states is realized by using a driving IC. It is shown below. When this driving IC is used in a conventional driving method, since the signal IC side (hereinafter, referred to as a signal side) and the scanning electrode side (hereinafter, referred to as a scanning side) are operated by synchronized signals, signals having different pulse widths are used. It is difficult to apply each scan. Further, the voltage level is insufficient with the two-level voltage, and it is considered impossible to realize the voltage level as it is.

The inventor of the present invention decomposes a drive waveform composed of reset pulses R and write pulses W of the same polarity shown in FIG. 9B into output waveforms on the signal side and the scan side as shown in FIG. The waveform was examined.

FIG. 1 is a time chart for explaining an embodiment of a liquid crystal panel driving method according to the present invention.
That is, in FIG. 1, the scanning periods of n frames and n + 1 frames for achieving the AC conversion are shown in FIGS.
The output waveform on the scanning side shown in (D) and the output waveform on the signal side shown in FIG. 1 (E) are decomposed into output waveforms applied to one pixel shown in FIG. 1 (F). Note that the output signal on the scanning side includes the output waveform of the second (second scanning line) following the output waveform of the first (first scanning line) shown in FIG. FIG. 1B shows output waveforms of a third (third scanning line) and a fourth (fourth scanning line) sequentially in FIG.
(C) and FIG. 1 (D). As a result of examining the driving waveforms shown in FIG. 1, as a result of using a signal in which the period of the greatest common divisor of the pulse width of the reset pulse R and the pulse width of the write pulse W is one cycle, these signals having different pulse widths are used. It has been found that the output can be performed by the drive IC (hereinafter, this signal on the scanning side is referred to as a scanning clock signal Ck for the sake of explanation).

Further, when the scanning line voltage in each period indicated by the same clock was examined in detail, it was found that the voltage level simultaneously output to each output terminal was two levels. However, since four voltage levels are required as a whole, a function of switching the voltage to a preset voltage by a logic signal was devised and solved.

Next, a specific output waveform will be described. For the sake of explanation, it is assumed that the pulse width of the reset pulse R is a period that is three times the pulse width of the write pulse W (the present invention is not at all limited to this period. The pulse width can be optimized by the liquid crystal material used, cell parameters, etc.).
In the present invention, a signal is used in which the cycle of the pulse width of the reset pulse R and the common divisor of the pulse width of the write pulse W is one cycle. In this example, the scanning-side clock signal Ck is a signal having one cycle of one third period of the write pulse W.

FIG. 2 is a time chart showing scan-side output waveforms for explaining an embodiment of the liquid crystal panel driving method according to the present invention. FIG. 2A shows the scanning-side output waveform shown in FIG. 1A, and FIG. 2B shows the scanning-side clock signal Ck shown in FIG.
7A is an enlarged output waveform obtained by enlarging the scan-side output waveform of FIG.

As shown in FIG. 2B, both the reset pulse R and the write pulse W are divided into a single voltage pulse by the scanning clock signal Ck. The voltage of each divided voltage pulse on the scanning side is referred to as a scanning side clock signal C.
Tables 1 and 2 show the values for each k.

Table 1A shows FIGS. 1 (A), (B), (C),
10D is a table showing the relationship between the output waveforms of the first to fourth scanning lines on the scanning side of the n-th frame shown in (D) and the scanning-side clock signal Ck;

Table 1B is shown in FIGS. 1 (A), (B), (C),
9 is a table showing the relationship between the output waveforms of the first to fourth scan lines on the scan side of the (n + 1) frame shown in (D) and the scan side clock signal Ck.

[0031]

[Table 1]

In these Tables 1A and 1B, Table 1A
Then, the clock order of the scanning side clock signal Ck is 1,
In the scanning line 1 at the time of 2, 3, the voltage V1, the scanning lines 2, 3,
4, two voltage levels of voltage V4, and when the clock order of the clock signal Ck of the scanning side clock signal is 4, two voltage levels of voltage V2 for scanning line 1 and voltage V3 for scanning lines 2, 3, and 4 In the clock order 5, 6, 7 of the scanning side clock signal Ck, two voltage levels of the voltage V1 on the scanning line 2 and the voltage V4 on the other scanning lines 1, 3, 4,
In the clock order 8 of the scanning side clock signal Ck, the scanning line 2
, The voltages of the other scanning lines 1, 3 and 4 are two voltage levels of V3, and the clock order 9, 10, and 11 of the scanning side clock signal Ck are the voltages V1 and others of the scanning line 3 Are the two voltage levels of the voltage V4 on the scanning lines 1, 2, 4 of the scanning line 1, and both of them are the clock order 1 of the scanning clock signal Ck.
It is understood that each of the scanning lines 1 to 4 corresponding to each of the clock orders of Nos. 1 to 11 has two types of voltage levels.

Similarly, the relationship between the output waveforms of the first to fourth scan lines on the scan side in the (n + 1) frame shown in Table 1B and the scan side clock signal Ck also indicates the output voltage of each scan side clock signal Ck. There are four types of voltage V
It can be seen that there are two types of voltage levels among 1 to V4. At this time, since the number of voltage levels required as a whole is four, this was solved by a method of switching voltages.

As for the signal side output, similarly to the scanning side output, the relationship between the voltage levels of the first to fourth scanning lines of the signal with respect to the clock orders 1 to 11 of the scanning clock signal Ck can be obtained.

FIG. 3 is a time chart showing signal-side output waveforms for explaining an embodiment of a liquid crystal panel driving method according to the present invention.

FIG. 3A shows the signal waveforms of the n-th and n + 1-th frames shown in FIG. 1E, and the enlarged signal waveforms corresponding to the clock orders 1 to 11 of the scanning clock signal Ck. FIG. 3 (B) is shown.

Table 2A shows the relationship between the output signals of the first to fourth scanning lines on the signal side shown in FIG. 3 and the clock order of the scanning-side clock signal Ck in the n-th AC frame.

Table 2B shows FIG. 3 for the alternating n + 1 frames.
3 shows the relationship between the output signals of the first to fourth scanning lines on the signal side and the clock order of the scanning clock signal Ck.

[0039]

[Table 2]

According to FIG. 3 and Tables 2A and 2B, the voltage level of the output signal on the signal side for each scanning clock signal Ck is one of V4 and V2 in Table 2A and V1 and V2 in Table 2B. This is one of the voltage levels V2 and V4. In FIGS. 2 and 3, each output changes at the rising edge of the scanning-side clock signal Ck, but, of course, there is no problem at the falling edge.
Below, the circuit configuration of the drive circuit according to the block diagram is shown.

FIG. 4 is an example of a block diagram of a driving circuit for explaining a method of driving a liquid crystal panel according to the present invention. In the drawing, 1 is a voltage input, 2 is an oscillator, 3 is a voltage control unit, and 4 is A voltage switching unit, 5 is a liquid crystal cell, 6 is a display data input, 7 is a signal side driving IC, 8 is a scanning side driving IC, 9 is a signal side IC control unit, and 10 is a scanning side IC control unit. In this figure, each function is shown by a block for the purpose of explanation, but the present invention is not limited by the description of the wiring and the like.

As described above, the voltage level required for driving is two levels in one cycle of the scanning clock signal Ck, but four levels on the scanning side and signal level in one frame for AC conversion. Requires 3 levels. Therefore, the power supply of each drive IC is synchronized with the scanning clock signal Ck,
Switching has solved this problem.

In FIG. 4, voltages of a total of four levels required for driving are input to the voltage switching unit 4 as a voltage input 1. The input voltage 1 can be produced, for example, by a method of impedance-converting each voltage divided by a resistor using an operational amplifier or the like, or by using an output of a DA converter or the like. The input voltage is supplied to a signal switching IC 7 and a scanning scanning IC by a voltage switching unit 4 according to a control signal from a voltage control unit 3.
8 is output to the voltage input. The present invention is not limited to the range of voltage used here, in addition to being influenced by the material of the liquid crystal of the liquid crystal cell 5 used and the cell parameters, and considering the voltage difference defined by the driving IC. Absent. Here, the potential difference of the drive IC refers to the definition of the potential difference between the voltage input pin and another voltage pin.

The voltage control unit 3 is a logic circuit such as a counter and a decoder, and generates a signal for switching a voltage at a timing required for display shown in Tables 1A and 1B. C-
It can be realized by a PLD, an FPGA, a gate array, or the like. The voltage switching unit 4 can be realized using an FET, a transistor, or an array thereof. on the other hand,
Control signals for driving the signal-side drive IC 7 and the scan-side drive IC 8 are synchronized with the voltage control unit 3 by signal-side I
It is manufactured by the C control unit 9 and the scanning-side IC control unit 10. In the block diagram shown in FIG. 4, each of these functions is shown as an individual block, but the present invention is not limited to this configuration.

The voltage control unit 3 of the logic circuit unit
C, the signal side IC control unit 9 and the scanning side IC control unit 1
In the case of 0, a controller that reduces the number of components and minimizes the influence of propagation delay between blocks is manufactured by integrating one logic element (C-PLD, FPGA, gate array, etc.) into one chip. be able to. Needless to say, the voltage switching unit 4 having an analog configuration can also reduce the number of components by molding this portion alone and hybridizing it with a logic circuit. According to this method, using the existing drive IC, (reset pulse R)
Driving of the liquid crystal cell 5 having two metastable states requiring + (write pulse W) can be realized at low cost.

Next, a driving method for superimposing the reset pulse R using an existing driving IC will be described. In the present invention, in contrast to this driving method, a method has been devised in which a signal-side IC for displaying a voltage gradation by a digital signal is used on the scanning line side, thereby realizing an inexpensive method without newly manufacturing a dedicated IC. . This will be described below. The present inventor disassembles this waveform into a signal side and a scanning side as shown in FIG. Was done.

FIG. 5 is a time chart for explaining an embodiment of the liquid crystal panel driving method according to the present invention.
FIG. 5A shows a voltage waveform applied to a first scanning line, and FIG. 5B shows a voltage waveform applied to a second scanning line. FIG. 5C shows a voltage waveform applied to the third scanning line, FIG. 5D shows a voltage waveform applied to the first signal line, and FIG.
(E) is a composite waveform applied to the (1,1) pixel.
The solid line shows the ON waveform, and the dotted line shows the OFF waveform.

As shown in FIG. 5, in the case of the method in which the reset pulse R is overlapped, the greatest common divisor of the pulse width of the reset pulse R and the pulse width of the write pulse W is the same as in the method in which the reset pulse R is not overlapped. It has been found that a method using a signal having a width of one cycle is effective. In FIG. 5, this signal is referred to as a scanning cook signal Ck (not shown) for the sake of explanation. Also, the reset pulse R
Of the pulse width of the write pulse W to the pulse width of the write pulse W is 3: 1.
And

In the method of superimposing the reset pulse R,
Similar to the above-described method in which the reset pulse R is not overlapped, the relationship between the order of the scan-side clock signal Ck and the scan-side output and the relationship between the order of the scan-side clock signal Ck and the signal-side output are shown. The scanning-side output and the signal-side output divided by are combined into n-th AC frame and n + 1-th AC frame for each scanning line.

FIG. 6 is a time chart showing the relationship between the order of the scanning clock signal Ck and the scanning output for explaining an embodiment of the liquid crystal panel driving method according to the present invention, and FIG. FIG. 6B shows a voltage waveform applied to one scanning line, and FIG. 6B shows a voltage waveform applied to the second scanning line.
(C) is a voltage waveform applied to the third scanning line, FIG.
Is a scanning side clock signal Ck.

Table 3A is a table showing the relationship between the output of the scanning lines (1 to 4) and the scanning side clock signal Ck in the n-th AC frame shown in FIG. 6, and Table 3B is the n + 1-th AC frame shown in FIG.
6 is a table showing a relationship between an output of a scanning line (1 to 4) and an AC clock signal Ck in a frame.

[0052]

[Table 3]

In Table 3A, the voltage level required by each drive IC simultaneously (same clock signal Ck) is V
5, V4 and V1. Similarly, in Table 3B, the number of voltage levels for each clock signal Ck is V2, V
3, maximum of V6.

FIG. 7 is a time chart showing the relationship between the scanning clock signal Ck and the signal output for describing an embodiment of the liquid crystal panel driving method according to the present invention.

Table 4A shows the signal outputs of the scanning lines (1 to 4) and the scanning-side clock signal C in the n-th AC frame shown in FIG.
is a table showing the relationship with k.

Table 4B is a table showing the same relationship as Table 7 in the AC n + 1 frame shown in FIG.

[0057]

[Table 4]

In Table 4A, clock signal Ck (1
To 3), V6 for the clock signal Ck (4 to 11).
6 / V4 and Table 4B, the clock signals Ck (1 to
3) is V1 and the clock signal Ck (4 to 11) is V1.
/ V3.

As described above, the output waveforms of the driving ICs on the scanning side and the signal side are divided by the scanning side clock signal Ck as shown in FIG. 6 (scanning side) and FIG. 7 (signal side). As a result of arranging each voltage level for each scanning-side clock signal Ck, Tables 3A and 3B (scanning side) and Tables 4A and 4B
The voltage combinations shown on the (signal side) were obtained, and it was found that three voltage levels were required simultaneously for each drive IC. Therefore, at least three levels of voltage can be selected from the driving IC and each voltage is switched, so that the driving with the existing IC can be realized in this case as well. Further, since the necessary voltage levels are six levels (V1 to V6 in Tables 4A and 4B) between frames for AC conversion, a driving IC (scanning side) capable of selecting a voltage of six levels or more is used. By using it, it is possible to realize at lower cost without using voltage switching.

The method of using the signal side driving IC on the scanning side can be realized by sequentially inputting data for selecting a voltage to be output. As is clear from Tables 3A and 3B, since a certain output pattern is sequentially output as the output voltage, the output pattern can be easily realized by a method of storing the output pattern in a storage element and sequentially reading the output pattern. Further, since the number of outputs of the repetition pattern is small, the output can be realized by using a logic circuit without using a storage element, and the number of parts and product cost can be reduced.

The problem at this time is that a combination which is difficult to realize with the shift register inside the driving IC occurs at the voltage level on the scanning side. As is clear from Tables 3A and 3B, during the period of the scanning side clock signal 1, the signal of the scanning side 2 line and thereafter, and during the period of the scanning side clock signal 2, the signal of the scanning side 3 line and thereafter are supplied to the input terminal of the scanning side driving IC8. The operation must be determined before the signal is input from.
Therefore, in the present invention, a step of inputting a signal of V5 (in the case of Table 3A) or V2 (in the case of Table 3B) to the shift register inside the scan driving IC 8 before the start of scanning of one screen is provided on the scanning side. Was realized. The details are shown below.

Before starting scanning (or at the end of previous scanning)
Then, data is read into all the shift registers on the scanning side by using a clock signal faster than the scanning clock on the signal side. At this time, if the clock signal to be used is equal to or less than the upper limit value of the clock signal for reading data of the scanning side driving IC 8 used for the scanning side, the higher the frequency is, the shorter the period not used for display can be. Becomes

In particular, in the present invention, since the signal-side drive IC is used as the scan-side drive IC, the clock frequency is sufficiently higher than the normal scan-side drive IC.
For example, the data on the scanning side can be input with a clock signal for reading the display data on the signal side. In this case, the display capacity is 640 × 480 (data side 8-bit parallel transfer, binary display, frame frequency 60
Hz) is 1 scan time x 4
80 / (640/8) = 208.33 μs, which does not affect the display. Further, in this configuration, it is not necessary to newly create a clock for the data of the scanning-side driving IC 8, so that the circuit configuration can be simplified and the cost can be reduced. The overall configuration of the drive circuit is shown in FIG.

FIG. 8 is a block diagram of a drive circuit for explaining a method of driving a liquid crystal panel according to the present invention.
Reference numeral 1 denotes a scanning-side data generation unit, and 12 denotes a scanning-side data control unit. Parts having the same functions as those in FIG. 4 are denoted by the same reference numerals as in FIG. FIG. 8 illustrates each function as one block for explanation, and the present invention is not limited by the description method of the number of electrode lines and the like.

In the drive circuit shown in FIG. 8, a signal driver IC 7 and a scan driver IC 8 having three levels of output will be described. In FIG. 8, a total of six levels of voltages necessary for driving are input as voltage inputs. The input voltage 1 can be produced, for example, by a method of impedance-converting each voltage divided by a resistor using an operational amplifier or the like, or by using an output of a DA converter or the like.
The input voltage is output to the voltage input of each of the driving ICs 7 and 8 on the signal side and the scanning side by the voltage switching unit 4 according to a control signal from the voltage control unit 3. The range of the voltage used here is influenced by the material of the liquid crystal used in the liquid crystal cell 5 and the cell parameters, and also the driving ICs 7 and 8 on the signal side and the scanning side.
The present invention is not limited except by taking into account the voltage difference defined by Here, the potential difference of the drive IC refers to the definition of the potential difference between the voltage input pin and another voltage input pin.

The voltage control section 3 is a logic circuit such as a counter and a decoder, and generates a signal for switching a voltage at a timing required for display (Tables 3A and 3B). CP
It can be realized by an LD, an FPGA, a gate array, or the like. The output switching here is performed for each frame for AC conversion. The voltage switching unit 4 can be realized using an FET, a transistor, or an array thereof.
On the other hand, in synchronization with the voltage control unit 3, the signal side and the scanning side drive I
Control signals for driving C7 and C8 are generated by the signal-side IC control unit 9 and the scanning-side IC control unit 10, respectively.

Data for controlling the output on the scanning side is as follows:
It is created by the scanning-side data creating unit 11. Here, sequentially output waveforms are created based on a clock signal or the like. The data controller 12 on the scanning side starts the display of the frame described in the configuration (or after the display of the previous frame is completed).
It controls the operation of reading data into all shift registers of the scanning drive IC 8 and the reading of data for normal display after the start of display. In the block diagram of the drive circuit illustrated in FIG. 9, each of these functions is illustrated by an individual block; however, the present invention is not limited to this configuration.

The IC of the voltage control unit 3, which is a logic circuit, the signal-side IC control unit 9, and the scanning-side IC control unit 10 are integrated into one chip for one logic element (C-PLD, FPGA, gate array, etc.). By doing so, it is possible to manufacture a controller that reduces the number of components and minimizes the influence of propagation delay between blocks. Needless to say, the voltage switching unit 4 having an analog configuration can also reduce the number of parts by molding this part alone and hybridizing it with a logic circuit.

On the other hand, when the signal-side and scanning-side drive ICs 7 and 8 having a voltage output of 6 levels are used, all the voltage outputs for the alternating current can be output with respect to the above configuration. In addition, the voltage switching unit 4 becomes unnecessary. Each voltage 1 can be directly input to the signal side and scanning side drive ICs 7 and 8. For data for scanning,
You will need to switch between the frames to be exchanged,
Both the cost and the number of parts can be greatly reduced as compared with the case where the voltage is switched. According to this method, the signal-side drive IC 7 that realizes a voltage gradation by a commonly used digital signal is used on the scanning side, thereby having two metastable states in which the reset pulse R is superimposed on adjacent scanning lines. It becomes possible to realize driving of the liquid crystal panel at low cost.

Embodiment 1 (corresponding to claims 1 to 5) A liquid crystal display controller having two metastable states (without overlapping reset pulses) is a C-PLD LATTIC
Designed and prototyped with plsi1048 of E company, normal STN drive IC
The TMS57202 manufactured by TI was used for the signal side and the scanning side (the TMS57202 can be used for both the signal side and the scanning side by switching signals). Power supply switching circuit
It was configured using an FET. As the liquid crystal panel, a liquid crystal panel having a display capacity of 160 × 160 having two metastable states was manufactured. For comparison, a normal STN liquid crystal panel was manufactured using the same driving IC and liquid crystal material.

When the two prototype display devices were driven and compared with each other, the display device according to the present invention showed that the two display devices despite the use of the conventional STN driving IC were used.
It was possible to drive a liquid crystal panel having two metastable states, confirming that high-speed response and contrast were improved.

Embodiment 2 (corresponding to claims 6 and 8 to 10) A liquid crystal panel having two metastable states with the same configuration as in Embodiment 1 is manufactured, and the controller (the one on which the reset panel R overlaps) is a Lattice Design prototype using plsi1048
Hitachi HD6631 for both signal side and scanning side as drive IC
A display device using 0 was produced. The HD66310 is a signal driver IC for voltage gradation capable of outputting a voltage of eight levels in response to digital signals. As in Example 1,
For comparison, a normal STN panel was manufactured using the same driving IC and liquid crystal material.

A comparison was made by driving the two prototype display devices. The display device according to the present invention drives a liquid crystal panel having two metastable states despite the use of a conventional drive IC. It was confirmed that the high-speed response and the contrast were improved. Further, it was found that the frame frequency can be increased as compared with the first embodiment, and that it is possible to cope with a large display capacity (increase in the number of scanning lines) as compared with the first embodiment. .

Embodiment 3 (corresponding to claims 7 to 10) A liquid crystal panel having two metastable states with the same configuration as in Embodiment 1 was manufactured, and a controller was designed and manufactured by using Lattice plsi1048, and a drive was performed. A display device using Hitachi's HD66310 for both the signal side and the scanning side as an IC was manufactured.
In this embodiment, the HD66310 is a signal driver IC for voltage gradation capable of outputting eight levels of voltage in response to digital signals, but of these eight levels, three levels are used for AC conversion. And the circuit configuration in which the voltage is not required to be switched between the alternating frames was prepared, and the circuit configuration was compared.

When the two prototype display devices are driven and compared, the display quality is the same, and the liquid crystal panel having two metastable states by using the conventional driving IC by the display device according to the present invention is driven. Although it was confirmed that the output of the drive IC used 6 levels, 3
For level use, the number of parts and mounting man-hours can be reduced,
It has been found that the use of six levels as the number of outputs can effectively reduce the number of parts and product cost.

[0076]

According to a first aspect of the present invention, in the method of driving a liquid crystal panel having two metastable states, four voltage levels are output as voltage levels, and the voltage levels that can be simultaneously selected during the output are the four level levels. Of these, a drive IC having two levels of functions was used, so that inexpensive and high-quality display could be realized.

According to a second aspect of the present invention, in the method for driving a liquid crystal panel according to the first aspect, the respective voltage levels output from the drive IC are switchable. Since an IC can be used, high quality display can be realized at low cost.

According to a third aspect of the present invention, in the liquid crystal panel driving method according to the second aspect, the voltage level switching means for switching each voltage level output from the driving IC is set to a voltage set in advance by a logic signal. Since the switching was performed, the same effect as the second aspect of the invention was obtained.

The effect corresponding to claim 4: claims 1 to 3
In the method for driving a liquid crystal panel according to any one of the above, the two types of two-level voltages output from the driving IC for driving a liquid crystal panel having two metastable states are a first voltage pulse and a second voltage pulse. Since the two voltage pulses are used and the voltages of the first voltage pulse and the second voltage pulse are generated from the same reference signal, a low-cost voltage pulse can be obtained.

According to a fifth aspect of the present invention, in the liquid crystal panel driving method according to the fourth aspect, the first voltage pulse and the second voltage pulse are output based on a reference signal, and Since the period is a period of the greatest common divisor of the first voltage pulse width and the second voltage pulse width, a pulse can be easily produced by a logic circuit, and the logic circuit can be simplified and the cost can be reduced. Was realized.

According to a sixth aspect of the present invention, in the driving method for driving a liquid crystal panel having two meta-stable states, the driving is performed using a driving IC in which at least three voltage levels can be selected at the time of output. Thus, the display capacity of the liquid crystal display device could be improved while maintaining the display quality.

According to a seventh aspect of the present invention, in the driving method for driving a liquid crystal panel having two meta-stable states, the driving is performed using a driving IC in which the output can select six or more voltage levels at the time of output. As a result, the display capacity of the liquid crystal display device was able to be improved along with a significant reduction in the number of parts and cost while maintaining the display quality.

According to an eighth aspect of the present invention, in the liquid crystal panel driving method according to the sixth or seventh aspect, the scanning side driving IC of the liquid crystal panel sequentially selects a predetermined output voltage pattern by digital input. Output, the display capacity of the liquid crystal display device can be improved while the number of parts and the cost are significantly reduced while maintaining the display quality.

According to a ninth aspect of the present invention, in the liquid crystal panel driving method according to the eighth aspect, the output voltage pattern for selecting an output voltage on the scanning side of the liquid crystal panel is formed using a logic circuit. Therefore, the display capacity of the liquid crystal display device can be greatly reduced while maintaining the display quality.
It was able to improve with cost reduction.

The effect corresponding to claim 10: claim 6
10. The method for driving a liquid crystal panel according to 7, 8, or 9, wherein the scan-side drive IC of the liquid crystal panel uses the signal-side drive IC of the liquid crystal panel for voltage gradation by digital input. The capacity was able to be improved with a significant reduction in the number of parts and cost while maintaining the display quality.

[Brief description of the drawings]

FIG. 1 is a time chart for explaining a driving method according to the present invention.

FIG. 2 is a time chart showing a scan-side output waveform of the driving method according to the present invention.

FIG. 3 is a time chart showing a signal-side output waveform of the driving method according to the present invention.

FIG. 4 is a block diagram showing an example of a drive circuit according to the present invention.

FIG. 5 is a time chart for explaining a driving method according to the present invention.

FIG. 6 is a time chart showing a scan-side output waveform of the driving method according to the present invention.

FIG. 7 is a time chart showing a signal-side output waveform of the driving method according to the present invention.

FIG. 8 is a block diagram showing an example of a drive circuit according to the present invention.

FIG. 9 is a diagram showing an example of a driving waveform of a liquid crystal having two semi-low states according to the related art.

FIG. 10 is a diagram illustrating an example of a driving waveform of a liquid crystal having two metastable states according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Voltage input, 2 ... Oscillator, 3 ... Voltage control part, 4 ... Voltage switching part, 5 ... Liquid crystal cell, 6 ... Display data input, 7 ... Signal side driving IC, 8 ... Scanning side driving IC, 9 ... Signal side IC control unit, 10: scanning-side IC control unit, 11: scanning-side data creation unit, 12: scanning-side data control unit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Fumiyoshi Matsumoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hiroyuki Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Kazuya Miyagaki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd.

Claims (10)

[Claims] 1. A method of driving a liquid crystal panel having two meta-stable states, wherein four voltage levels are output as voltage levels, and the voltage levels that can be simultaneously selected during the output are four levels.
A method for driving a liquid crystal panel, comprising using a drive IC having a function of two levels among levels. 2. The method according to claim 1, wherein the respective voltage levels output from the driving IC are switchable. 3. The liquid crystal panel driving method according to claim 2, wherein the voltage level switching means for switching each voltage level output from the driving IC switches to a voltage set in advance by a logic signal. 4. The two-level two-level voltages output from the driving IC for driving a liquid crystal panel having two metastable states are defined as a first voltage pulse and a second voltage pulse. 4. The method according to claim 1, wherein the voltage of the first voltage pulse and the voltage of the second voltage pulse are generated from the same reference signal. 5. The method according to claim 1, wherein the first voltage pulse and the second voltage pulse are output based on a reference signal, and the cycle of the reference signal is the same as the first voltage pulse width and the second voltage pulse width. 5. The method according to claim 4, wherein the period is the greatest common divisor. 6. A driving method for driving a liquid crystal panel having two metastable states, wherein the liquid crystal panel is driven by an IC, and at the time of output of the driving IC, each output can select at least three voltage levels. A method for driving a liquid crystal panel. 7. A driving method for driving a liquid crystal panel having two metastable states, wherein the liquid crystal panel is driven by an IC, and a voltage level at which each output can be selected at the time of output of the driving IC is 6 levels or more. A method for driving a liquid crystal panel, comprising: 8. The liquid crystal panel driving method according to claim 6, wherein the scanning-side driving IC of the liquid crystal panel sequentially selects and outputs a predetermined output voltage pattern by digital input. . 9. The method of driving a liquid crystal panel according to claim 8, wherein the output voltage pattern for selecting the output voltage on the scanning side of the liquid crystal panel is created using a logic circuit. 10. The scanning-side drive IC of the liquid crystal panel,
8. The liquid crystal panel according to claim 6, wherein a signal driving IC for voltage gradation by digital input is used.
10. The method for driving a liquid crystal panel according to 8 or 9.