JPH10104575A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To improve display in a multiple line simultaneous selection driving method (MLA method). SOLUTION: N (N is an integer of 200 or more) row electrodes 4
(Vertical) <4.5, and Δε =
3.5-6.5 liquid crystal layer 6 (twist angle θ = 100-3
60 °), the row electrodes are divided into four sub-groups, the sub-groups are simultaneously selected, and the selected column vectors (A1, A2, A) of the 4-by-4 selected orthogonal matrix (A) are selected.
A liquid crystal display device in which a row selection voltage based on a signal obtained by developing (3, A4) in a time series is applied to a row electrode and an effective value of a voltage applied to a pixel is displayed. According to the present invention, high-speed, high-contrast display with low crosstalk can be achieved without impairing the characteristics of the MLA method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MLA method (short for multiple line simultaneous selection driving method; Japanese Patent Application Laid-Open No. 6-27907, US Pat. No. 5,262,881), or Japanese Patent Application Laid-Open No. 8-23.
No. 4164, etc.) to improve a simple matrix type liquid crystal display device using multiplex driving. In particular, a novel structure of a super-twisted nematic (STN) type liquid crystal display device that performs high-speed and moving image display equivalent to a TFT will be described.

[0002]

2. Description of the Related Art The demand for information display media is increasing with the progress of the advanced information age. Various display devices are used according to various applications and uses, but liquid crystal display devices have advantages such as thinness, light weight, and low power consumption.
It has good compatibility with drive circuits using semiconductor technology, and is expected to be more widely used.

At present, among the liquid crystal display devices, there are an STN type liquid crystal display device (hereinafter abbreviated as STN) and an active matrix liquid crystal display device having a thin film transistor provided in each pixel (hereinafter abbreviated as TFT). It has become mainstream. Comparing the two, STN has the advantage that the manufacturing process is simpler than that of TFT, that a constant yield and good productivity can be stably maintained, and that cost performance is good.

[0004] In recent years, in order to meet the specifications of high-density information terminals in particular, the size of the screen of the liquid crystal display device, high definition, large-capacity display, and high-speed display have been demanded. The search has begun.

Conventionally, line-sequential multiplex driving has been performed to perform large-capacity display in STN. In this method, each row electrode is sequentially selected one by one, and a column electrode is selected in correspondence with a pattern to be displayed. When all the row electrodes are selected in order, the display of one screen is completed (hereinafter, referred to as “one row electrode”). In the present invention, a scanning electrode is called a row electrode and a data electrode is called a column electrode.)

However, in the line sequential driving method, a problem called a frame response occurs as the display capacity increases. In the line sequential driving method, a relatively large voltage is applied to the pixel when selected and a relatively small voltage is applied when not selected. Generally, this voltage ratio increases as the number of row lines increases, that is, as driving under a high duty condition.

For this reason, when the voltage ratio is small, the liquid crystal responding to the effective voltage value responds to the applied waveform itself. In other words, the frame response has a large amplitude in the selection pulse, so that the transmittance at the time of OFF increases, and since the period of the selection pulse is long, the transmittance at the time of ON decreases. As a result, a phenomenon that causes a decrease in contrast occurs.

In order to suppress the occurrence of the frame response, a method of increasing the frame frequency to be used and shortening the period of the selection pulse is known, but this has a serious drawback. In other words, when the frame frequency is increased, the frequency spectrum of the applied waveform is increased, causing non-uniform display and increasing power consumption. Therefore, there is a limit to increasing the frame frequency for the purpose of preventing the selection pulse width from becoming too narrow.

It has become important to eliminate the frame response without increasing the frequency spectrum. In order to solve this problem, a driving method called the above-mentioned MLA method for simultaneously selecting a plurality of row electrodes (selection electrodes) has been proposed. This method can simultaneously select a plurality of row electrodes and independently control the display pattern in the column direction, and can shorten the frame period while keeping the selection width constant. That is, high-contrast display with suppressed frame response can be performed.

In the MLA method, a constant voltage pulse train is applied to each of the simultaneously applied row electrodes in order to independently control a column display pattern. In the MLA method of simultaneously selecting a plurality of lines, a voltage pulse is applied to a plurality of row electrodes at the same time. At this time, in order to simultaneously and independently control the display patterns in the column direction, it is necessary to apply pulse voltages having different polarities to the row electrodes.

A pulse having a polarity is applied to the row electrode several times, and a voltage corresponding to data is applied to the column electrode. Thus, an effective voltage corresponding to ON and OFF is applied to each pixel as a whole.

The selection pulse voltage group applied to each row electrode can be represented as a matrix of L rows and K columns (hereinafter, referred to as a selection matrix (A)). Since the selection pulse voltage sequence can be expressed as a group of vectors orthogonal to each other, a matrix including these as column elements is an orthogonal matrix. At this time, each row vector in the matrix is orthogonal to each other. The number L of rows corresponds to the number of simultaneously selected rows, and each row corresponds to each line.

For example, line 1 in L selection lines
, The element of the first row of the selection matrix (A) is applied, and the selection pulse is applied in order of the element of the first column and the element of the second column. In this specification, in the notation of the selection matrix (A), 1
Denotes a positive selection pulse, and -1 denotes a negative selection pulse. FIG. 4 shows a Hadamard matrix as a typical example of the selection matrix (A). FIG. 4 (a) shows a 4-row, 4-column structure.
FIG. 4B shows an 8-row, 8-column configuration, and FIG. 4C shows a 7-row, 8-column configuration excluding the first row of the 8-row, 8-column configuration.

A voltage level corresponding to each column element of the matrix and the column display pattern is applied to the column electrodes. That is, the column electrode voltage sequence is determined by the matrix that determines the row electrode voltage sequence and the display pattern.

The sequence of the voltage waveform applied to the column electrode is determined as follows. FIG. 3 is an explanatory diagram showing the concept. A Hadamard matrix of 4 rows and 4 columns will be described as an example. It is assumed that the display data on the column electrode i and the column electrode j are as shown in FIG. The column display pattern is represented as a vector (d) as shown in FIG. Here, when the column element is −1, it indicates ON display, and 1
Represents off display.

Assuming that the row electrode voltage is applied to the row electrodes sequentially in the order of the columns of the matrix, the column electrode voltage level is as shown in FIG.
The waveform becomes like a vector (v) shown in (b), and its waveform becomes like FIG. 3 (c). In FIG. 3C, the vertical and horizontal axes are arbitrary units.

In the case of selecting a partial line, in order to suppress the frame response of the liquid crystal display device, it is preferable to apply voltages in a distributed manner within one display cycle. Specifically, for example, after the first element of the vector (v) for the first simultaneously selected row electrode group (hereinafter, referred to as a subgroup) is applied, the second simultaneously selected row electrode group is called a subgroup. The first element of the vector (v) for the row electrode group to be applied is applied, and the same sequence follows.

Therefore, the voltage pulse sequence actually applied to the column electrodes determines how the voltage pulses are dispersed in one display cycle, and what selection matrix for each of the simultaneously selected row electrode groups. It is determined by whether (A) is selected.

[0019]

In the case of displaying a window pattern which is used very frequently recently, a phenomenon called crosstalk occurs, which is a display problem on a liquid crystal display device. The case where the influence of the crosstalk is most remarkable appears when the bar is displayed as shown in FIG. In the area B below the bar of the area C, display unevenness appears.

The dielectric anisotropy of a liquid crystal usually used for a simple matrix such as STN is Δε> 0. Therefore, when a voltage is applied between the pixels and the liquid crystal molecules become parallel to the electric field and the display is turned on, the equivalent capacitance component of the liquid crystal becomes maximum (ε (vertical)> ε (parallel)). At this time, the column electrode voltage waveform is in the most distorted state. That is, regardless of the same ON state, a luminance difference of region A <region B appears as display unevenness.

This is because the effective voltage applied to the liquid crystal is in the region A
<Area B>. A display pattern such as a window display is a combination of the displays in FIG. 4 and is assumed to be used most frequently, and reducing display unevenness (crosstalk) is a major issue.

The magnitude of this crosstalk is determined by the bar width W
Alternatively, the length H changes. When the width W of the bar of the display pattern is increased, the luminance difference between the area A and the area B decreases. When the length H of the bar is increased, the luminance difference between the area A and the area B increases.

It is considered that these phenomena are caused by distortion of the column electrode waveform between the ON waveform and the OFF waveform.
In other words, the ON waveform is a waveform that is distorted to some extent, whereas the OFF waveform is a waveform that is almost ideal.

There are mainly two causes of distortion of the ON waveform. One is that a driving circuit (hereinafter referred to as a driving system) for driving a matrix electrode sandwiching a liquid crystal layer is not constituted by an ideal power supply and an ideal driver. In the display of FIG. 2, most of the column electrodes (W _OFF
), An ON waveform is output. At this time, in the drive system, a large load is applied to the voltage level for outputting the ON waveform among the column electrode voltage levels, which causes distortion.

The other is the effect of the capacitance inside the liquid crystal panel. In the ON state, the capacitance of the liquid crystal connected in series to the column electrode is maximized. Therefore, if there are many ON waveforms, the waveform in the liquid crystal panel becomes the most distorted state. On the other hand, as the off waveform, a waveform close to the ideal is output. This is because the condition that the waveform is distorted compared to the ON waveform does not apply.

In FIG. 2, in the area A, only the column electrode waveforms that are substantially on are applied, but in the area B, both the on and off column electrode waveforms are applied. Therefore, area A
In the column voltage waveform of (1), only a very distorted waveform is output, whereas in the region B, the distortion of the column voltage as a whole is not so large as compared with the region A. Therefore, in the region B, the decrease in the effective voltage applied to the liquid crystal is small.

As described above, although the MLA method is a very effective method for suppressing a frame response, it has been found that display unevenness due to crosstalk is more noticeable than the conventional driving method.

This is presumed to be due to the fact that the row electrode voltage level is lower in the driving method for simultaneously selecting a plurality of rows than in the line sequential driving. That is, when a plurality of rows are selected at the same time, the bias ratio between the row electrode voltage and the column electrode voltage is reduced, and the effect of the column electrode voltage on the effective voltage is much greater than in the conventional driving method. As a result, if there is a waveform distortion in the column electrode voltage sequence, the influence of the waveform distortion on the display quality is greater than that of the conventional one.

Actually, the power supply used in the driving system and the driving ability in the final stage are finite, so that the voltage waveform always has distortion at the input terminal, and the electric impedance of the liquid crystal panel is the series of the capacitance component of the liquid crystal itself and the electrode resistance. The voltage waveform to be output to the column electrode is considerably distorted and output because it is considered to be coupling. Therefore, when a plurality of rows are selected at the same time, display unevenness due to crosstalk may be conspicuous. This phenomenon becomes remarkable when the number L of row electrodes to be simultaneously selected is 5 or more.

Another major problem is crosstalk in halftone display. The halftone display method includes a frame rate control method, an amplitude modulation method, a combination with a dither method, and the like. The frame rate control method is most frequently used as a driving method of a liquid crystal display device. At this time, in order to make the occurrence of flicker less noticeable, a combination with spatial modulation that spatially (between adjacent pixels) makes a phase difference and cancels flicker is often used.

In this case, unlike the monochrome solid display based on the binary display, the spatial frequency of the image may be extremely high for each frame. For this reason, crosstalk occurs and the quality of the image is degraded. Similarly, when the dither method is used, the spatial frequency is high and there is a problem of crosstalk.

Further, when displaying a moving image such as a video display, there is a problem of image deterioration. In a video display, unlike a basically geometric display such as a window, many spatially complicated displays (that is, high spatial frequencies) appear.

Therefore, in particular, when an attempt is made to display a video display in a specific window, there arises a problem that not only the quality of the video display itself is degraded due to the generated crosstalk but also the surrounding windows are affected. I was

Here, the behavior of the liquid crystal layer itself acting as a load in a liquid crystal display device for realizing display utilizing the change in the state of the liquid crystal layer, particularly in a simple matrix drive system such as STN will be described.

As described above, the liquid crystal is approximated as a series combination of a capacitive load and a resistive load. The former is due to the liquid crystal capacitance (at the time of off and on), and the latter is due to the electrode resistance. The display area and display resolution are strongly related to these loads. When the area is large, the high-frequency characteristics are deteriorated due to the increase in the capacitive load, the waveform distortion is increased, and the crosstalk is increased.

Also, when the resolution increases, the high frequency component of the drive increases, which also leads to an increase in crosstalk. Generally, a practical problem arises when the diagonal size is 9 inches or more and the number of display lines is 200 scan lines or more (corresponding to 400 lines or more when driving two screens).

In addition, as the resolution increases, the required row voltage (amplitude value) increases. Therefore, the feasibility of a drive driver circuit that can be used (mainly the technical limit in semiconductor IC technology, such as withstand voltage, current value, switching, etc.) Speed, power consumption, etc.), the drive voltage must be reduced, and the crosstalk condition has become increasingly severe.

For this reason, means for lowering the resistance value of the transparent electrode has been used, but reducing the electrical resistance value while maintaining optical transparency is approaching its limit. In addition, it is obvious that this causes an increase in production cost and a variation in performance, and is not suitable for manufacturing general-purpose products.
Next, a display failure phenomenon peculiar to the MLA method will be described.

In the MLA method, there is a special crosstalk called a ghost. A ghost is a phenomenon in which a certain image is slightly displayed at a location near the ghost, and appears as a double image like a ghost due to a radio wave interference of a TV. The cause was clarified and the following conclusions were obtained.

Ghosts in the MLA method are selected (rows).
This is due to the waveform distortion of the waveform. This is a phenomenon that occurs because a selected waveform is applied to a time interval that should be a non-selection period. In the MLA method, a plurality of (L
Since the lines of (1) and (2) are selected at the same time, ghosts for a plurality of lines can be seen, and the ghosts are more easily recognized than in the conventional driving method.

Although the same phenomenon occurs in the conventional driving method APT, the ghost occurs only for one line because the row is selected in units of one line. Therefore, since it appears only to the extent of slight image blurring (that is, a decrease in resolution), it does not appear as a “double image”. Therefore,
In the APT method, it can be said that ghosts are hardly observed.

As one means for solving this problem, the above-mentioned Japanese Patent Application Laid-Open No. 8-234164 has proposed an MLA driving method for reducing crosstalk. It has been shown that crosstalk can be reduced by optimizing the orthogonal matrix and suppressing the signal voltage waveform from largely changing depending on the pattern.

However, in order to construct an advanced display system that provides high-resolution and high-quality images, such as multimedia support including recent moving pictures and Windows display on a personal computer, a drive system, a liquid crystal cell structure, and a liquid crystal display are required. It was found that higher image quality improvement by integrating materials and circuit design was necessary.

[0044]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem. That is, the present invention provides an N-row electrode (N is an integer of 200 or more) arranged in a matrix. And a plurality of column electrodes provided with a liquid crystal cell in which a liquid crystal layer is sandwiched. The twist angle θ of the liquid crystal layer is 100 to 360.
And the row electrodes are divided into L subgroups (L is 2, 3 or 4), the subgroups are selected collectively, and the selected columns of the selected orthogonal matrix (A) of L rows and M columns A row selection voltage based on a signal obtained by developing the vector (A1, A2, A3, A4) in time series is applied to the row electrode, and display is performed with respect to the effective value of the voltage applied to the pixel. ε (vertical) <4.5 and dielectric anisotropy Δε = 3.5
To 6.5, which is a liquid crystal display device.

Further, according to the present invention, the gap d of the liquid crystal cell is 4 to 6 μm, and the twist angle θ is 220 to 260 °.
2. The liquid crystal display device according to claim 1, wherein:

Further, the invention according to claim 3 employs a driving method in which the polarity of the row selection voltage and the column voltage is inverted with a periodicity of S times the selection pulse width, and satisfies the relationship of equation (1). 3. The liquid crystal display device according to claim 1, wherein:

[0047]

S <(N / L) * M * 0.5 (1)

The invention according to claim 4 is characterized in that the voltage amplitude Vr (pp) of the row voltage and the voltage amplitude Vc (pp) of the column voltage satisfy the relationship of equation (2). 2 or 3 liquid crystal display devices.

[0049]

N ^0.5 /L≦Vr/Vc(max)≦1.4*N ^0.5 / L (2)

Hereinafter, the present invention will be described. When trying to reduce various types of crosstalk in a liquid crystal display device employing a simple matrix driving method, it is important that the characteristics of the waveform, load (such as liquid crystal capacitance and electrode resistance), It is a parameter such as a current supply power supply to the liquid crystal. They are strongly involved and interact with each other to determine the voltage actually applied to the pixel.

In particular, depending on the characteristics of the waveform and the characteristics of the load, it is difficult to reduce the crosstalk even if the external current supply power source is reinforced. In this sense, the relationship between the waveform and the load is an essential element for reducing crosstalk.

In the present invention, in order to provide a high-quality image in a liquid crystal display device using the MLA method, a liquid crystal cell acting as a load when viewed from a driving system and an element for determining a waveform in the MLA method is provided. Shows the overall optimal configuration of

When considering the characteristics of the waveform involved in the crosstalk of the MLA method, first, the number of simultaneous selections is important. M
In the LA method, a selection waveform, which was conventionally one per row line in a display frame, is applied a plurality of times and a column voltage is determined so as to correspond thereto.

Therefore, according to the number of simultaneously selected lines,
The row and column voltage balance changes, and the crosstalk occurrence situation changes. First, in order to facilitate a simple understanding, a description will be given on the condition that an optimum bias at which the voltage ratio between the ON waveform and the OFF waveform is theoretically maximum is used.

The liquid crystal layer in the liquid crystal display has a constant threshold voltage (V _th , rms). When this is supplied by multiplex drive, it is necessary to consider the final effective voltage obtained by combining the row and column waveforms. When the column voltage Vc of the APT method which is a conventional line sequential driving method is set to 1, M
The maximum values of the row voltage Vr and the column voltage Vc in the LA method are given in Table 1 below with respect to the number L of simultaneous selections.

[0056]

[Table 1]

Here, N is the total number of selected lines, which is the case of the optimum bias as described above. As is clear from Table 1, as L increases, the row voltage decreases and the column voltage increases. Therefore, if L changes, the intensity changes depending on the type of crosstalk that occurs in the row direction and the column direction.

In the MLA method, a column electrode display pattern vector (x) = (x1) having a display pattern (off = 1, on-1) corresponding to a simultaneously selected row electrode on a specific column electrode. , X2, x3, x4...) And the inner product of the selected column vector (Ai: i = 1, 2, 3, 4,...), Ii = (x1, x2, x3, x4. Since a voltage is applied to the column electrodes, the (x) pattern is an important factor that directly determines the voltage.

The present inventor has examined the characteristics of such waveforms, and determined what the load of the liquid crystal cell should be, what the drive waveform should be, the drive system at that time, mainly the actual circuit configuration and the like.
Taking into account the effects on the driver and other factors, the optimum configuration was obtained. Table 2 below summarizes the effects of the main factors on crosstalk and the like.

[0060]

[Table 2]

(1) and (2) in Table 2 clearly contradict from the theory of the conventional liquid crystal technology. This is because the driving voltage of the liquid crystal depends on the dielectric anisotropy Δε of the liquid crystal, and in order to lower the voltage of the liquid crystal, it is necessary to increase the dielectric anisotropy Δε, which leads to an increase in the capacitance load. It is.

Based on the above, a configuration that makes use of the features of the MLA method and can reduce the crosstalk will be considered. At this time, a drive waveform of the MLA method and a preferable configuration of the liquid crystal cell as a load are considered simultaneously. Table 3 shows the main factors.

[0063]

[Table 3]

The trade-off relationship between (3) and (4) is
This means that there is an optimum point in the driving method and the liquid crystal load in the MLA method. In the present invention, these relationships were theoretically considered and experimentally verified, and the following conclusions were reached.

Crosstalk can be reduced by the MLA method when the following three conditions (a), (b), and (c) in Table 4 are satisfied.

[0066]

[Table 4]

The basic configuration shown in (a), (b), and (c) in Table 4 reduces the capacity load by 30 to 50% as compared with the conventional STN, and allows the transparent electrode to cross without significantly lowering its resistance. The whole talk can be reduced.

Further, it is more effective to set the polarity inversion period S of the driving waveform (d) in Table 4 to a half frame length or less. This is for setting the frequency component of the waveform to an intermediate frequency region. The last condition is S <
(N / L) * M * 0.5 means satisfying the relationship of (1).

This configuration is effective particularly when a high-speed response is required. In order to achieve high-speed response, it is common to lower the viscosity of the liquid crystal itself and increase the interface regulation force from the substrate to the liquid crystal to increase the speed, but this increase in regulation force is due to the gap in the liquid crystal cell. , Which leads to an increase in capacity load. Since the reduction of the gap hardly changes the drive voltage itself, the increase in crosstalk with the increase in load becomes very noticeable.

In the configuration of the present invention, since the absolute value of the voltage and the magnitude of the load are essentially optimized, a large margin for reducing the gap and increasing the speed can be obtained. For example, when other parameters are equal, the gap d is 6.5 μm and the dielectric anisotropy Δε = 9 (ε
When the MLA method is used, the gap d can be set to 4.5 μm and the dielectric anisotropy Δε = 4.5 (ε vertical = 4).

Therefore, load reduction (maximum load is about 6
% Reduction), the reduction of the maximum voltage (row voltage) (about 30% reduction in the case of simultaneous selection of four lines), and the speeding up (the response time can be reduced by about 50%) can all be achieved at the same time.

In particular, the gap d of the liquid crystal cell is 4 to 6 μm.
m and the twist angle θ = 220 to 260 °, the physical properties of the liquid crystal used are ε (vertical) ≦ 4.5 and Δε =
It is preferable to be 3.5 to 6.5. Furthermore, Δε
= 4.0-6.0 is more preferable.

In addition, naturally, the contrast of the MLA method is increased at the same time, and conventionally, the ratio is 20: 1 to 30: 1.
Contrast ratio (on / off luminance ratio)
Became possible at 40: 1 or more.

As described above, the driving waveform of the MLA method and the configuration of the liquid crystal display element adapted to the MLA method achieve higher contrast and higher speed than those of the conventional driving method and the liquid crystal display element configuration. Low crosstalk and reduction of the maximum power supply voltage are achieved. This indicates that high-quality images can be provided at low cost and with low power consumption.

In the present invention, since the above load requirements are adopted, driving with a bias ratio different from the conventional one becomes possible. Here, the bias ratio is defined by the maximum value of the row voltage / the column voltage.
(N) ^0.5 / L In the APT driving method, since the column voltage becomes extremely high, the bias ratio is generally set to be smaller than the optimum bias. However, in the MLA method, this voltage ratio is set to be larger than the optimum bias rather than the characteristic of the waveform. It is preferable to use it.

The reasons are as follows. (1) APT
Since the method has a frame response, the smaller the bias, the higher the contrast, but the MLA method suppresses the frame response by the method itself. (2) The row voltage is lower in the MLA method than in the APT method.

Therefore, it is necessary that the voltage amplitude Vr of the row voltage and the maximum voltage Vc (max) of the column voltage satisfy the relationship of the expression (2) in order to obtain a higher quality image in the liquid crystal display device of the present invention. It is a preferable condition.

The driving method of the present invention can be easily realized by using a known MLA circuit. For example, as the gradation method, F
When RC (Frame Rate Control) is used, spatial modulation FR
C is in the stage before storing the first-stage multi-bit data in the memory, stores 1-bit (one frame) data after FRC in the memory, sequentially reads out the data, and calculates the column electrode voltage waveform by MLA operation. Good. Alternatively, the multi-bit data may be stored in the memory as it is, and may be converted into 1-bit FRC data by referring to the spatial modulation FRC table before the column voltage calculation.

The spatial modulation table may be stored in a ROM and read out sequentially for use. However, a configuration using a logic circuit can be easily realized. Display is achieved by inputting a column voltage waveform calculated by these circuits to a column signal driver having a plurality of voltage levels and applying a voltage to the liquid crystal.

The gradation display method of the liquid crystal display device of the present invention is not limited to the above-mentioned FRC, but may be AM (Amplitude).
ude Modulation (amplitude modulation), PWM
(Pulse Width Modulation). When displaying gradation, crosstalk generally increases due to the complexity of the drive waveform,
Although a shift in gradation occurs due to a change in voltage, in the present invention, since crosstalk is reduced, fine gradation can be realized even during gradation display without deteriorating the display quality.

[0081]

【Example】

(Example 1) VGA (640 × 480 × 3 (RGB))
The color STN of the size is divided into upper and lower two screens to drive two screens. The number of row lines in one screen was 240, and the MLA method was driven with the number of simultaneous selections L = 4 (that is, the number of subgroups = 60). The size of the display screen is 10.4 inches diagonal, the transparent electrode used is ITO, and the sheet resistance is 5Ω.
It was.

The liquid crystal cell has a gap of 4 μm, a dielectric constant (vertical) of the liquid crystal of 3.7, a dielectric constant (parallel) of 9.0 (dielectric anisotropy Δε = 5.3), and a maximum driving voltage (dielectric anisotropy Δε = 5.3). Vr) was about 16V. The bias ratio was 3.9, which is the optimum bias condition.

FIG. 1 is an explanatory diagram of the configuration of this embodiment. The liquid crystal cell includes a front polarizer, a front substrate, a row electrode 4, a liquid crystal layer 6, and a column electrode 5. Further, an MLA controller and an external interface are provided as a drive system. A TFT interface signal is supplied from outside, and a drive signal is supplied to a row drive driver and a column drive driver via an external interface and an MLA controller (which performs data conversion and the like, and employs an FRC gray scale method). . Thus, the liquid crystal display device is driven by the MLA method. The orthogonal matrix used in the driving method of the MLA method is shown in Expression 5, and the gray scale display is FRC
The method was used.

[0084]

(Equation 5)

When a video was displayed on Windows, almost no flicker or crosstalk was observed.
Delicate gradation display was obtained. The frame frequency is 1
Drive was performed at 20 Hz, the contrast ratio was 50: 1, and the response time (average of rising and falling) was 50 ms.

Example 2 SVGA (800 × 600 ×
3 (RGB)) color STN is divided into upper and lower two screens.
Screen drive. The line line of one screen is 300,
MLA driving was performed with the number of simultaneous selections L = 4 (that is, the number of subgroups = 75). Display screen size is 12.1 diagonal
The transparent electrode used was an inch size and had a sheet resistance of 4Ω.

The orthogonal matrix used is shown in Expression 5, and the FRC method is used for gradation display. The liquid crystal display element
The gap is 5 μm, the permittivity of the liquid crystal is 3.5 for vertical and 8.5 for horizontal (Δε = 5.0), and the maximum driving voltage (Vr)
Was about 18V. The bias ratio was (optimal bias × 1.2) of 5.2.

When a video was displayed on Windows, almost no flicker or crosstalk was observed.
Delicate gradation display was obtained. The frame frequency is 1
Drive was performed at 20 Hz, the contrast ratio was 50: 1, and the response time (average of rising and falling) was 65 ms.

Comparative Example SVGA (800 × 600 × 3)
(RGB)), the color STN display element was divided into upper and lower two screens, and two screens were driven. The number of row lines in one screen was 300, and line-sequential driving (APT) was performed. The size of the display screen is 12.1 inches diagonally, and the transparent electrode used is ITO
And a sheet resistance of 4Ω. Gray scale display is FRC
The method was used.

The liquid crystal display element has a gap of 6 μm, and the liquid crystal has a dielectric constant of 4.0 for vertical and 13.0 for horizontal (Δε = 9.
0), and the maximum drive voltage (Vr) was about 26V. Note that the bias ratio was an optimum bias.

When video display was performed on Windows, delicate gradation display with almost no flicker was obtained, but the level of crosstalk was worse than that of the second embodiment. The frame frequency was driven at 120 Hz, the contrast ratio was 30: 1, the response time (average of rise and fall) was 150 ms, and a strong afterimage was seen in video display.

[0092]

According to the first aspect of the present invention, the performance of a multiple line simultaneous selection method (MLA) and a high-speed liquid crystal display element is completely derived, and high-speed and high-contrast display with low crosstalk can be realized. This makes it possible to display moving images and multiple gradations using a simple matrix that has never existed before. In addition, the power supply voltage can be reduced as compared with the conventional driving method.

According to the second aspect of the invention, a higher quality display can be obtained in a liquid crystal cell having a specific configuration.

According to the third aspect of the invention, the capacitance load can be reduced, and the overall crosstalk can be reduced without significantly reducing the resistance of the transparent electrode.

According to the fourth aspect of the present invention, the power supply voltage system is not complicated, and the drive system can be simplified.

The present invention can be applied to other liquid crystal display devices and the like as long as the effect is not impaired.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of the present invention.

FIG. 2 is a conceptual diagram for explaining crosstalk.

FIGS. 3A to 3C are a conceptual diagram and a waveform diagram illustrating a voltage application method in the MLA method.

FIGS. 4A to 4C are explanatory diagrams showing Hadamard matrices.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Asako Kubo 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside the Central Research Laboratory of Asahi Glass Co., Ltd. Inside the Central Research Laboratory (72) Inventor Satoshi Nakazawa 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside the Central Research Laboratory Asahi Glass Co., Ltd.

Claims (4)

[Claims] 1. N lines (N is 20) arranged in a matrix
A liquid crystal cell in which a liquid crystal layer is sandwiched between a row electrode having an integer of 0 or more and a plurality of column electrodes is provided. The twist angle θ of the liquid crystal layer is 100 to 360 °, and the number of row electrodes is L ( L is divided into 2, 3 or 4) subgroups, and the subgroups are collectively selected, and the selected column vector (A1, A2, A3, A4) of the selected orthogonal matrix (A) having L rows and M columns is selected. A row selection voltage based on the signal developed in time series is applied to the row electrode, display is performed on the effective value of the voltage applied to the pixel, the dielectric constant ε (vertical) of the liquid crystal <4.5, and A liquid crystal display device, wherein dielectric anisotropy Δε = 3.5 to 6.5. 2. The liquid crystal display device according to claim 1, wherein the gap d of the liquid crystal cell is 4 to 6 μm and the twist angle θ is 220 to 260 °. 3. A driving method in which the polarity of a row selection voltage and a column voltage is inverted with a periodicity of S times the selection pulse width, and satisfies the relationship of equation (1). The liquid crystal display device of 1 or 2. S <(N / L) * M * 0.5 (1) 4. The liquid crystal display device according to claim 1, wherein the voltage amplitude Vr (pp) of the row voltage and the voltage amplitude Vc (pp) of the column voltage satisfy a relationship represented by the following expression (2). . ## EQU2 ## N ^0.5 /L≦Vr/Vc(max)≦1.4*N ^0.5 / L (2)