JPH06301010A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which is high in response speed while suppressing flickers by using a selective driving method for plural scanning electrodes. CONSTITUTION:A liquid crystal element having 2.5 to 5.5mum thickness d of a liquid crystal layer and >=25cps viscosity at 20 deg.C of the liquid crystal compsn. to be sealed is used and is driven by using plural scanning electrodes for simultaneously selecting the plural scanning electrodes C1 to C4. The display having the high-speed response, high contrast ratio, lessened uneven display and decreased flickers even in gradation display is obtd.

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 device for simultaneously selecting and driving a plurality of scanning electrodes.

[0002]

2. Description of the Related Art In recent years, due to the development of super twisted nematic (STN) technology and thin film transistor (TFT) technology, a thin, light, compact and large-capacity information display can be realized by a liquid crystal display device instead of a CRT. Is being started.

[0003]

In the active matrix type using a TFT, each pixel is driven in almost the same state as in static driving, so that it can be driven at a relatively high speed and the display quality is similar to that of static driving in appearance. can get. However, the TFT type has a problem that the manufacturing process is complicated and the manufacturing cost is high.

On the other hand, the simple matrix type such as STN has a relatively simple element manufacturing process, but if the number of duty is increased, the contrast ratio is lowered and the response speed is slowed down. Therefore, there is a problem that it is difficult to support mouse display and video display on the terminal.

For this matrix type liquid crystal display device, a new driving method for simultaneously selecting a plurality of scanning electrodes by the 1992 SID was proposed. Using this driving method, if four scan electrodes are selected and driven at the same time, even if there are 480 scan electrodes, they are driven as if the duty was 1/120.

When this driving method is used, while a plurality of scan electrodes are selected, a plurality of signals are applied to the column electrodes orthogonal to the scan electrodes depending on the states of a plurality of pixels corresponding to the plurality of scan electrodes. . That is, in the conventional simple matrix driving, only one signal is applied to the column electrode when the scan electrode is selected, whereas in this new driving method, a plurality of signals are applied to the column electrode in a time division manner. It

However, in the case where the response speed of the liquid crystal is extremely fast and the number of lines to be selected at the same time is small, by turning on and off for each frame and displaying halftones in units of several frames, frame thinning is performed. When it is attempted to perform the adjustment drive, the time taken as a unit of several frames is several times as long as the period from the original selection of scan electrodes to the next selection depending on the gradation. For this reason, the state of the liquid crystal molecules of the pixels turned on in one frame cannot be held for one unit of time and is relaxed. Since the pixels are turned on again at the next selection, the flickering of brightness, that is, flicker, is apparent. It turned out that it seems to have occurred remarkably.

When a fast response liquid crystal cell is driven, the change in the direction of the molecular axis of the liquid crystal molecules easily follows the voltage, so that the optical response waveform exhibits a so-called peak value responsive behavior. For this reason, the effective response of the applied voltage deviates from the expected optical response. That is, the optical response waveform that rises during the selection period cannot be retained as the non-selection period becomes longer, and the average level of the transmittance decreases and the contrast ratio decreases. This is called a liquid crystal relaxation phenomenon.

Although this phenomenon is also called a frame response in the conventional driving method, it has been found that the magnitude of the flicker phenomenon in gradation display and the magnitude of the luminance of the frame response correspond well.

An object of the present invention is to suppress flicker due to the relaxation phenomenon of liquid crystal in a liquid crystal display device driven by the simultaneous selective driving method of a plurality of scanning electrodes without increasing the number of simultaneously selected electrodes. It is a thing.

[0011]

The present invention has been made to solve the above-mentioned problems, and uses a liquid crystal cell in which a liquid crystal composition is sandwiched between a pair of substrates with electrodes, and a plurality of scanning electrodes are simultaneously formed. A plurality of pixel electrodes are selected and applied with a selection voltage, and a plurality of pixel electrodes facing the plurality of scanning electrodes are applied to the column electrodes in a time division manner by applying a voltage according to the selection status of the pixel electrodes. In a liquid crystal display device driven by the scanning electrode selection driving method, the thickness d of the liquid crystal layer is 2.5 to 5.5 μm, and the viscosity of the liquid crystal composition to be encapsulated at 20 ° C. is 2
The present invention provides a liquid crystal display device characterized by using a liquid crystal display element of 5 cps or more.

A liquid crystal display device characterized in that the period from the selection of the scan electrode to the next selection of the scan electrode is 0.5 to 30 msec, and those liquid crystal cells have at least 200 scan lines. A liquid crystal display device having a liquid crystal cell having electrodes, wherein the twist angle of the liquid crystal is 180 to 360 °.

As the liquid crystal cell of the present invention, an ordinary simple matrix type liquid crystal cell can be used. Specifically, In ₂ O ₃ -SnO ₂ (I
It is possible to use a transparent electrode such as TO) or SnO ₂ formed in a stripe shape, arranged so that the electrode surfaces face each other, and the periphery is sealed with a sealing material, and liquid crystal is sealed inside. Used by forming an insulating layer such as SiO ₂ or TiO ₂ or a color filter on or below this electrode surface, or by forming an alignment film such as polyimide, polyamide, silicon, acryl, urethane or SiO ₂ on the electrode .

Although this liquid crystal cell can be used also in the TN type, it is substantially of the STN type and has at least 200 scanning electrodes and a liquid crystal twist angle of 180 to 360 °. Is advantageous.

According to the present invention, in this liquid crystal cell, a plurality of scan electrodes are simultaneously selected and a selection voltage is applied, and the column electrodes are time-divided into a plurality of pixel electrodes facing the plurality of scan electrodes. Then, the plurality of scanning electrodes are simultaneously driven by applying a voltage according to the selected state of the pixel electrodes. Specifically, a column voltage based on an orthogonal conversion signal obtained by converting an image signal corresponding to the position of a plurality of simultaneously selected scanning electrodes on the panel by an orthogonal function is applied to the column electrodes in a time division manner, and the orthogonal voltage is applied. This is performed by applying a scanning voltage based on an orthogonal function signal capable of restoring the converted signal to the scanning electrodes.

[0016] The roots of the method for simultaneously driving a plurality of scanning electrodes are as described by TN Lucmongathan in 1988 by International Dis
This is the method proposed at the play Research Conference,
In order to lower the driving voltage and reduce display unevenness, a plurality of scanning electrodes are collectively selected and driven.

This is a method in which, for example, 200 scanning electrodes are divided into 50 groups of 4 scanning electrodes, and 4 scanning electrodes are simultaneously selected and driven. In this case, each column electrode has a scan electrode selection time.
A signal determined by the data depending on the state of the pixel electrode corresponding to each scanning electrode is applied by dividing the time into 2 ⁴ = 16. Since this method takes a long time to write data,
It was extremely difficult to perform gradation display by thinning out frames.

A driving method improved on the above point is proposed in 1992 SID. When the present invention is applied to the driving method, flicker becomes less noticeable and the display quality is improved. The driving method will be described in more detail.

In the present invention, a plurality of scan electrodes (M
Book) scanning electrodes. When selected, -V _r + V _x , V _r +
V _x (where V _r > 0, V _x is 0 or a voltage shifted from it) is applied. For example, when driving 400 scan electrodes, four scan electrodes are divided into 100 groups and four scan electrodes are simultaneously selected and driven, or eight scan electrodes are divided into 50 groups and eight scan electrodes are simultaneously selected and driven. In this case, the scanning electrodes may be driven not as a group of 2 ⁿ lines but as a group of 2 ⁿ −x lines, specifically, 7 lines instead of 8.

In this case, the column electrode has (M + 1) voltage levels V ₀ , V ₁ , ..., V _M , and a voltage of V ₀ <V ₁ <... <V _M is applied. Total of this voltage level V ₀ + V ₁ + ... + V _M
Is usually 0, but when the scanning electrode side is shifted by the voltage V _{x, the} voltage applied to this column electrode is also shifted by V _x . For the sake of clarity, the following description will be given with V _x = 0.

The column electrodes are supplied with a plurality of column signals in a time division manner during the scanning electrode selection period, while the scanning electrodes are orthogonal functions for restoring the signals supplied to the column electrodes into video signals. The signals are distributed in a time division manner. When the column of scanning voltage supplied in this time division is called "selection voltage sequence", the product of the selected voltage sequence and its transposed matrix is a scalar multiple of the unit matrix when the components are 1 and -1. Is formed on the basis of a matrix of N rows and M columns having N elements in the horizontal direction and M elements in the vertical direction. Such a matrix is called a “selection voltage matrix”. Here, N ≧ M.

For example, when the number of simultaneously selected scan electrodes is M = 4, N = 4, 8, 16, ..., However, it is preferable to select the minimum number allowed by N ≧ M. This is because if it is unnecessarily increased, the time required to write one screen becomes longer and the frame frequency is lowered. Therefore, M =
In the case of four, it is preferable to set N = 4 and M = 8
In the case of a book, N = 8 is preferable. As an example of this matrix, an example of N = 4 and N = 8 is given by (A)
It shows in (B).

[0023]

[Equation 1]

The matrix in this example is a matrix called a Hadamard matrix, and if this matrix is adopted, it is very effective to suppress display unevenness in actual liquid crystal driving. M is 3
If it is not 2 ^k , such as a book or 7 books, by removing an arbitrary (NM) row from the Nth-order matrix whose product with its transposed matrix is a scalar multiple of the unit matrix, A matrix A of M rows and N columns can be constructed. For example, the following Expression 2 shows an example configured from the 8th order Hadamard matrix of Expression 1 (B).

[0025]

[Equation 2]

Equation 2 is derived from the 8 × 8 matrix of Equation 1 (B)
It is a matrix with 7 rows and 8 columns with the first row deleted. Not limited to this example, one of the second to eighth rows may be deleted. In each case, the product of their transposes is a scalar multiple of the identity matrix.

The matrix A is A = [A ₁ , A ₂ , ..., A _N ] (where A _n is a vertical vector having M elements, by regarding each column as one vector). n represents a natural number equal to or less than N.) In this case, the selection voltage sequence is selected by appropriately arranging the vectors including the vectors A ₁ , A ₂ , ..., A _N.

In order to make the explanation easy to understand, it is assumed that the display is binary (only on or off). In the case of frame gray scale display, this gray scale display may be apparently performed using a plurality of frames. Further, the applied voltage itself or the pulse width may be modulated for gray scale display. In the case of binary display, as a typical driving method, as described above, each voltage A _n appears once in the selection voltage sequence, and a selection voltage sequence consisting of N vectors can be selected. Good.

This selection voltage sequence does not necessarily have to consist of only one of each of the above vectors, and it is possible to add another vector whose elements are + V _r or −V _r, or to arrange the same vector in plural. It is possible within a range that does not impair the effects of the present invention.

For example, it is possible to consider a selection voltage sequence including all possible potential states (the number of selection voltage vectors in the selection voltage sequence is 2 ^M or more). For example, if one scan electrode group group (scan electrodes that are selected at the same time) is composed of four scan electrodes, there are 2 ⁴ = 16 possible potential states as a whole. Therefore, there are 16 or more selection voltage vectors in the selection voltage sequence in this case.
Then, the voltage corresponding to the selected voltage sequence becomes the scan electrode selection waveform in the driving method of the present invention.

In this method, the scanning electrode group group goes through all potential states, which is advantageous from the viewpoint of suppressing display unevenness. However, when the number M of simultaneously selected scanning electrodes increases, the number of selection pulses increases exponentially, and the time for one frame becomes extremely long. Therefore, as described above, A ₁ , A ₂ , ..., A _N
It is preferable to select a column of N vectors in which the selection voltage vectors are arranged. As a result, the number of selection pulses required for selecting the scan electrodes can be minimized, which is advantageous for high-speed display. Further, when the selected voltage thus selected is not converted into an alternating current, A ₁ , A ₂ , ..., A
_{N, -A 1, -A 2,} ..., if you choose the selection voltage rows such that -A _N, it is AC.

Selected voltage vector A _n forming the selected voltage string
The arrangement order of is arbitrary, and it can be used by exchanging it for each row or each column of the matrix. In order to suppress display unevenness in actual driving, it is often preferable to drive while appropriately performing the above replacement depending on the display state of the pixel electrodes.

In order to make the explanation easy to understand, the components of the selection voltage vector A _n represented by + V _r as 1 and −V _r as 0 are called “selection pattern”, and the selection pattern is Those arranged in time series will be referred to as a “selection pattern sequence”. Therefore, a selection voltage sequence (selection pattern sequence) suitable for high speed driving will be described below.

Select voltage vector A _n included in the select voltage string
Is 2L (L is a natural number of 2L ≧ 2N), and
The first half of the row of L selection voltage vectors and the second half of the row of L selection voltage vectors have the same absolute value and opposite positive and negative polarities. Is preferred. The reason why such a vector sequence suppresses the display unevenness of the drive is not clear, but the supply voltage waveform generated between the electrodes when one display is performed is converted into an alternating current in a uniform cycle regardless of the display data. Presumed to be. Hereinafter, the selection pattern sequence arranged in this manner will be particularly referred to as an “inversion pattern sequence”.

Specifically, when the selection pattern column voltage sequence is composed of 2L selection patterns, the nth (n
Is a natural number less than or equal to L) and a (n + L) th selection pattern has a negative relationship between the selection patterns. In particular, the inversion pattern sequence is applied to the selection voltage sequence consisting of 2N selection voltage vectors, [A ₁ , A ₂ , ..., A _N , -A ₁ , -A ₂ , ..., -A _N ]. It is preferable to select a sequence of vectors having the following order in terms of high-speed response and suppression of display unevenness in driving.

As an example of the scanning electrode selection pattern sequence, 4
The following Hadamard matrix is shown in Table 1. This is exactly 1 of 1 of the matrix of equation 1 (A),
It is the same as the 8-by-4 matrix in which the 4 × 4 matrix with -1 as 0 is placed in the first half and the negated matrix is placed in the second half.

[0037]

[Table 1]

The selection pattern sequence in Table 1 satisfies the condition of [A ₁ , A ₂ , ..., A _N , -A ₁ , -A ₂ , ..., -A _N ] as a selection voltage sequence. There is. Each scan electrode group group may drive the scan electrodes in the order of the pattern numbers shown in Table 1. In this case, for example, in the scan electrode group group 1, the pattern numbers 1, 2, 3, ... …, 8
Will be driven in this order.

Further, rows (scanning electrode group groups) or columns (selection voltage column (selection pattern) for each display data) of the matrix
Can also be used interchangeably. For example, in the scan electrode group group 1, the pattern numbers 1, 2, 3, ...
In the order of 8, scan electrode group group 2 has pattern number 2,
The scanning electrode group group 3 can be driven in the order of 3, ..., 8, 1 in the order of pattern numbers 3, 4 ,. In addition, the scanning electrode group groups can be shifted every two groups, or the order can be reversed.

In the above example, the selection pattern sequence is 8
Although a number suitable for fast response has been described, it is also possible to employ a selection of 2 ⁴ = 16 selection voltages that will include all possible potential states. Specifically, natural binary order, random code, gray code, frequency equalizing code, etc. can be adopted.

In the present invention, in order to suppress the flicker, a liquid crystal display device is used in which the thickness d of the liquid crystal layer is 2.5 to 5.5 μm and the viscosity of the liquid crystal composition to be sealed at 20 ° C. is 25 cps or more. In the conventional ordinary liquid crystal display device, when aiming at high-speed response, it is considered that a liquid crystal composition having a faster response speed is more preferable, and it has been considered that the lower the viscosity of the liquid crystal composition is, the better.

However, in the present invention, the viscosity of the liquid crystal composition is made higher than that of the conventional ordinary liquid crystal display element, and the deterioration of the appearance due to flicker when gradation display is performed by frame thinning is suppressed to some extent, and the liquid crystal layer is formed. To reduce the thickness and improve the response speed. The flicker is greatly improved by using the multiple scan electrode selection drive method in which the number of simultaneously selected lines is 2 to 8.

From the viewpoint of suppressing flicker, it is advantageous to repeat the selection of the scanning electrodes in a short time among the plural scanning electrode selection driving methods. For this reason, it is preferable that the selection pulses are dispersed and applied within a period in which one display data is displayed.

That is, instead of continuously applying the voltage corresponding to the selection voltage train to one scan electrode group at a time, the selection voltage train is divided into several stages and one stage is applied. Then, it can be achieved by moving to the selection of the next scan electrode group.

For example, if four scan electrodes are selected at the same time, a minimum of eight selection voltage trains are required. First, there is a driving method in which the first scan electrode group is selected, and after application of these eight selection voltage trains is completed, the scan electrode group is transferred to the next scan electrode group. In this case, since eight pulses are applied to select one scan electrode group, one frame time for scanning all scan electrode groups becomes long. Then, the flicker becomes conspicuous due to the relaxation phenomenon of the liquid crystal.

In this case, by dividing the eight pulses into eight, when the scan electrode group is selected for the first time, a pulse based on the data of the first selection voltage train is applied to sequentially scan all the scan electrode groups. . After that, at the time of the second selection, a pulse based on the data of the second selection voltage train is applied to sequentially scan all scan electrode groups.

This operation is repeated eight times to complete the entire scanning, but each scanning electrode group is selected eight times within the same time as described above, and the frame response, that is, the relaxation phenomenon within one frame, occurs. Suppressed. Of course, this suppression of frame response is not effective for all display patterns, but on the average, it is quite effective.

In the above description, the stage is divided into eight stages, but it goes without saying that it may be divided into two or four stages.
A comparison will be made with the dynamic driving method that is usually used for the conventional liquid crystal display element. In the conventional dynamic driving method, when there are 400 scan electrodes, assuming that the time of one pulse of the column electrodes is t, 400t time is required for one selection of all scan electrodes.

On the other hand, if the full-selection voltage train is applied during one scan by the above-mentioned multiple scanning electrode selection driving method, a time of at least 800 t is required, and flicker becomes more conspicuous than in the conventional driving method. In this case, if it is divided into two stages, it will take 400t, and if it is divided into four stages,
If you divide into 8 stages in 200t time, it will be 100t time. This is more effective as the number of simultaneous selections is increased.

On the other hand, as the number of simultaneously selected lines increases, the load on the circuit side increases at an accelerating rate. Therefore, considering the cost performance of display, it is preferable to keep the number of selected lines small. INDUSTRIAL APPLICABILITY The present invention provides a method in which a good effect can be obtained with a small number of selections by adapting the performance of liquid crystal display elements to be combined.

Although not essential, it is extremely preferable to equalize the number of selection voltage vectors included in each stage. This is because the drive circuit configuration can be simplified.

FIG. 1 shows the voltages applied to the scan electrodes according to the selection code in Table 1. C _{1 to} C ₄ represent each of the scanning electrodes, and the time interval T is selected once when all the scanning electrodes are divided into scanning electrode group groups each including M scanning electrodes. It becomes the time interval for. When the total number of scan electrodes / M is not an integer, some scan electrode group groups include scan electrodes of a number smaller than M. In this case, M
Assuming that there are imaginary scanning electrodes for a smaller number (the situation of pixels may be whatever), the same consideration may be applied.

Next, regarding the voltage applied to the column electrodes for displaying the specific data when the specific scan electrode group group is selected under the conditions as described above,
This will be described below.

In the multi-scan electrode selection driving method, (M + 1)
It is driven by applying a voltage selected from the individual voltage levels according to the selection pattern of the scan electrode group to the column electrode. Considering that it is advantageous that the voltage waveform is made alternating current from the viewpoint of preventing display unevenness, these (M + 1) voltage levels are at least voltage levels V ₀ , V ₁ , It is preferable that ... V _M (V ₀ <V ₁ <... <V _M ). The specific voltage of this voltage level is determined from the configuration of the liquid crystal display element and the like.

The display data and the selection voltage applied to the scan electrodes determine which of these voltage levels should be selected. This method will be described later.

Next, from the viewpoint of alternating voltage waveforms, n
(N is a natural number equal to or less than M) it is preferable that the relative, always satisfy the relation: V _n = -V _Mn. However, this is the case where the voltage applied to the scan electrodes when not selected is 0, and it is naturally possible to change the potentials of both the scan electrodes and the column electrodes in parallel by the same amount. This is because the potential difference between both electrodes does not change in this case.

Next, how to select the applied voltage from the above (M + 1) voltage levels when a specific display pattern is given will be described.

First, the case where the display data is binary will be described. Table 2 shows the eight scan electrodes C ₁ ~ which are part of the display pattern of the matrix display consisting of 400 scan electrodes.
₁ schematically shows C ₈ and twelve column electrodes S _{1 to} S ₁₂ . In Table 2, "1" indicates a lit pixel (on) and "0" indicates a non-lit pixel (off).

[0059]

[Table 2]

If four scan electrodes are selected at the same time, one scan line electrode for each scan electrode group group
It is divided into 4-bit data patterns. Display data of the jth scan electrode group (where j is a whole number of scan electrodes / M, which is a natural number less than or equal to J expressed by rounding up to the right of the decimal point),
A vertical vector D _j having M components (where the vector D _j
The component of is composed of 1 for ON or 0 for OFF). For example, in the column electrode S ₉ , D ₁ = ^t (d ₁ , d ₂ , d ₃ , d
₄ ) = ^t (1,0,1,0). t represents transposition.

Here, in order to determine the voltage to be applied to the column electrode, the vector of the selection pattern of the selection voltage applied to the scanning electrode (this is referred to as β) and the vector of the data of the column electrode are used. , The exclusive OR is taken for each corresponding component, and the total sum i is obtained. For example, one of the scan electrodes in Table 2
When the selection voltage of the second scan electrode group group is represented by the selection pattern [1,1,1,1] represented by the pattern number 1 in Table 1, the voltage to be applied to the column electrode S ₉ in Table 2 To decide. At this time, the sum i of the exclusive ORs is 2
Becomes

When i is obtained in this way, the voltage level to be applied to the column electrode is represented as V _i . For example, it is assumed that the scanning electrode selection pattern sequence is selected as shown in Table 1. In this case, when the display pattern of Table 2 is displayed, the voltages applied to the column electrodes S ₁ , S ₂ , S ₃ , and S ₉ are 5 levels of V _{0 to} V ₄ (V ₂ = 0), which is shown in FIG. Like

In FIG. 2, for example, C _{1 to} C ₄ indicate changes in voltage during the period when the scan electrode group group C _{1 to} C ₄ is selected. Wherein _{C 1 ~C 4, C 5 ~C} 8, C 9 ~C 12
Are drawn independently. For ease of viewing, the horizontal time axis is drawn with other scan electrode group group selection periods omitted. Therefore, in the present invention, when the selection pulses are dispersed and applied, the voltage application shown in FIG. 2 is not continuously performed, but one voltage application in FIG. The voltage is applied to the scan electrode group group of, and after the time has elapsed, the next voltage application on FIG. 2 is performed.

Explaining in a concrete example, when the scanning electrode group group of C _{1 to} C ₄ is selected, the column electrode S ₁ is V ₄ →
V ₈ → V ₂ → V ₂ → V ₀ → V ₂ → V ₂ → V ₂ is not applied continuously, but V ₄ is applied first, then C ₅ ~ The scan electrode group group of C ₈ is selected, the first V _{3 of} FIG. 2 is applied, and then the V ₄ of FIG. 2 of the scan electrode group group of C _{9 to} C ₁₂ is applied. Group up to groups are applied. After that, the scan electrode group group of C _{1 to} C ₄ is selected again, and the second V ₂ of FIG. ₂ is applied and driven.

When the maximum value of the column electrode voltage is V _c , V ₀ , V
It is preferable that ₁ ... V _{M be} −V _c = V ₀ <V ₁ <... <V _M = V _c, and the potential difference between the voltage levels be constant. Specifically, when M = 4 as shown in FIG. 2, V ₄ = + V _c , V ₃ = + V _{c
/ 2, V 2 = 0,} V 1 = may be selected so that _{-V c / 2, V 0 =} -V c. When the total number of scanning electrodes is H, V _r = V _c
It is preferably H ^0.5 / M. Under this condition, H = 4
Since 00 and M = 4, V _r = 5V _c . FIG. 3 shows voltage changes of C ₁ -S ₉ (on state) and C ₂ -S ₉ (off state) in FIG. 2 in this case. However, similarly to FIG. 2, the time axis of the horizontal axis is drawn with the selection periods of other scan electrode group groups omitted for ease of viewing.

In this way, one display data is displayed, but when a particular scan electrode group is focused,
It may be effective to reduce the display unevenness that the configuration of the selection voltage string (selection pattern) is changed every time one or more displays are completed. In particular, it is preferable that the selection voltage applied to each scan electrode is switched among the scan electrodes in a specific scan electrode group group in order to reduce display unevenness. That is, the matrix formed by exchanging the rows of the matrix A used for forming the selected voltage column in the previous data display is used again as the matrix A for forming the selected voltage column.

Specifically, the rows of the matrix of the selection pattern columns shown in Table 1 can be sequentially replaced and driven. That is, during the first scan is driven as shown in Table 1, at the time of the second scanning things to the scanning electrodes C ₁ which has been initially applied to C _2, the C ₂ have been initially applied to the C ₃ In addition, what was initially applied to C ₄ was applied to C _3, and what was initially applied to C ₁ was applied to C ₄ . Further, next, similarly, it is sufficient to shift line by line.

Next, the selection pattern 2 in Table 1 is applied to the first scan electrode group group. Next, the selection pattern 3 in Table 1 is applied to the second scan electrode group group, and this is repeated thereafter until the Jth scan electrode group group.

In this way, the selection patterns are sequentially applied to each scan electrode group, and this is performed until all the selection patterns are applied. This completes one display. (1 frame)

[0070] When performing display for the next display data, shifting the selected pattern sequence of the scanning electrodes in Table 1, those to the scanning electrodes C ₁ that was originally applied to C _2, to C ₂ is The one initially applied to C ₃ , the one initially applied to C ₄ to C _3, and the one initially applied to C ₁ to C ₄ are applied.

Further, when displaying the next display data, the scanning electrodes are further shifted row by row, and after selecting four times, the sequence returns to the selection pattern column of Table 1. In this way, the display based on each display data is sequentially performed.

In the multiple scanning electrode selection driving method, if the inverted pattern row is used as the selection pattern row, the frame frequency can be substantially doubled as compared with the conventional dynamic driving method. Therefore, this can increase the on-luminance and the contrast ratio. Moreover, since the optical response period of the liquid crystal is constant in any display pattern, uniform display can be obtained.

The display data is not binary display, but (I +
When the gradation has 1) steps (I is a natural number of 2 or more), it can be performed in substantially the same manner as in the case of binary display. In this case, as described above, as the selection voltage string,
The selection voltage vector that constitutes it is substantially A ₁ , A ₂ ,
, A _N , -A ₁ , -A ₂ , ...,-A _N are respectively I, and a vector column in which the selection voltage vectors are arranged is selected.

The gradation display of (I + 1) steps is performed by displaying a total of I ONs or OFFs at a predetermined ratio for each of these I selected voltage vectors (2NI in total). ,It can be carried out.

As a specific example, a case where M = N = 4 and four gradations are displayed will be described. The selection pattern sequence at this time is, for example, a pattern formed of a 4th order Hadamard matrix, and pattern numbers 1 to 4 in Table 1 are repeated 3 times in sequence, and then 5 to 8 are also repeated 3 times in sequence 24 rows and 4 columns. Becomes the matrix of. Further, it may be a matrix of 24 rows and 4 columns in which the pattern numbers 1 to 8 in Table 1 are sequentially repeated three times.

In the above case, the same kind of selection pattern appears three times. Gradation display is possible by allocating these three selection patterns on or off. For example, if two are turned on and one is turned off, a display corresponding to the second gradation counted from the on state is obtained. If one is turned on and two are turned off, display corresponding to the third gradation counted from the on state is achieved. It is visually advantageous to distribute the on / off distribution evenly.

In this case, as in the case of the conventional dynamic driving method, for the time being, it is possible to adopt a driving method by a frame gray scale method in which one frame is driven by binary display and gradation display is performed using a plurality of frames.

Next, with respect to the portion composed of the scan electrode group group composed of a smaller number of scan electrodes than the other scan electrode group group composed of M scan electrodes,
The voltage applied to the scan electrodes and the column electrodes is similar to that in the case where the number of scan electrodes forming the scan electrode group is M by virtually adding and driving the scan electrodes of the insufficient number. Can be driven to.

In this case, the display data on the virtual scanning electrode is also virtually selected. This display data is 0 or 1 in the case of binary display, and may be display data corresponding to any gradation in the case of gradation display.

For example, when M = 4 and a scan electrode group group consisting of three scan electrodes is driven, three scan electrodes of the selection pattern row configured when M = 4 are used. do it. Specifically, if the selection pattern sequence shown in Table 1 is adopted, for example, the scanning electrode 2
Apply the selection pulse using the selection pattern sequence for 3 lines corresponding to ~ 4. The selection method is not limited to those corresponding to the scan electrodes 2 to 4, and other selection methods may be used, such as the one corresponding to the scan electrodes 1 to 3.

Further, the voltage applied to the column electrode is determined as follows. That is, regarding the display data, the virtual display data is virtually added to the vector of the display data.
_Make up D _j . On the other hand, the selection pattern was used to construct the selection pattern sequence for the three scan electrodes.
The selection pattern in the selection pattern row of the scan electrodes of the book is used. Then, as described above, the voltage applied to the column electrodes is determined by taking the exclusive OR for each of these corresponding elements and finding the sum i.

In the above description, the M scan electrodes forming the scan electrode group are all actual electrodes, but some of them may be treated as virtual electrodes. It is possible.

In this case, the number of selection pulses necessary for selection and the number of voltage levels of the voltage to be applied to the column electrodes are larger than the minimum required value, as compared with the actual scanning electrodes forming the scanning electrode group group. become. However, there are cases where there is an advantage, for example, when the level of the voltage applied to the column electrode is shared with the voltage level applied to another device. Specifically, when a drive circuit that can use eight voltage levels is used, M = 7 and N = 8.

In the present invention, in order to suppress flicker, a liquid crystal display device is used in which the thickness d of the liquid crystal layer is 2.5 to 5.5 μm and the viscosity of the liquid crystal composition to be sealed at 20 ° C. is 25 cps or more. By setting the viscosity at 20 ℃ to 25 cps or more, especially 35 cps or more, relaxation is suppressed, and even when gradation display is performed by frame thinning,
Flicker is less noticeable. And the thickness of the liquid crystal layer
By making d as thin as 2.5 to 5.5 μm, a high-speed response can be obtained by compensating for the decrease in response speed due to the increase in the viscosity of the liquid crystal.

Normally, the response speed τ _d from ON to OFF and the response speed τ _r from OFF to ON of the liquid crystal display element are considered to have the following relationship. τ _r , τ _d = A · η · d ² (1) where A is the proportional coefficient, η is the viscosity of the liquid crystal, and d is the thickness of the liquid crystal layer, that is, the cell gap.

From this equation (1), it can be seen that even if the viscosity is increased to suppress flicker, the response speed improves as the square when the thickness of the liquid crystal layer is reduced. It was confirmed that in such a cell, when the viscosity of the liquid crystal alone was changed from 20 cps to 40 cps, the frame response amplitude was reduced to about half. It was found that when the liquid crystal layer thickness was the same, the response speed slowed down as the viscosity increased. However, the response speed can be improved by reducing the thickness of the liquid crystal layer according to equation (1).

If a liquid crystal having a high viscosity is to be injected into an empty cell having a narrow gap between substrates, there is a problem that the injection time is significantly increased when vacuum injection is performed. Practically, about 60 cps seems to be the limit of high viscosity. Therefore, in the present invention, the liquid crystal composition has a viscosity of 25 to 6 at 20 ° C.
It is preferable to use one having a viscosity of about 0 cps. However, even if the viscosity exceeds 60 cps at 20 ° C, the viscosity of the liquid crystal will decrease as the temperature rises, so it is possible to use by heating and injecting it, or by adopting a manufacturing method that seals and encloses the liquid crystal at the same time. it can.

The liquid crystal composition used may be a mixture of various known liquid crystal materials in order to obtain desired physical properties. If necessary, a non-liquid crystal material having a similar structure, a dye, a chiral agent, and other additives may be added and used.

Generally, it is possible to increase the viscosity by mixing a large amount of liquid crystal having a large molecular weight, but in general, T _NI (nematic-isotropic liquid transition point) is increased. High duty gray scale display computer as used, for applications such as OA equipment word processor, a significant increase of T _NI is, since the constraint for obtaining a uniform orientation, even T _NI is high 100 It is desirable to increase the viscosity while keeping it around ℃. From this point, in order to increase the viscosity,
The use of ester compounds is preferred.

As the ester compounds, those exhibiting liquid crystallinity are usually used. However, even a compound having a structure similar to that of an ester-based liquid crystal but not exhibiting liquid crystallinity can be used as long as it exhibits desired properties as a composition.

By the way, among the conventionally proposed liquid crystal structures, it is known that ester liquid crystals are materials that should be excluded as much as possible from mixed liquid crystals for the purpose of high-speed response. For this reason, ester-based liquid crystals are not included as normal high-speed response liquid crystals for high-duty gradation display. In the present invention, a method of increasing the viscosity by positively introducing such a material that has been conventionally considered unsuitable is particularly suitable.

The ester-based liquid crystal is a ring of liquid crystal molecules.
It is a liquid crystal having an ester group between Q ₁ and ring Q ₂ . Typical molecular structures include the following compounds. In the following general formula, R ₁ and R ₂ represent an alkyl group, a cyano group, a halogen atom, etc., some of which have an ether bond or a carbonyl bond, or some of which have hydrogen atoms substituted with halogen atoms. You may. Further, -Ph- represents a 1,4-phenylene group and -Cy- represents a trans-1,4-cyclohexylene group, and a part of hydrogen atoms thereof may be replaced with a halogen atom. R ₁ -Q ₁ -COO-Q ₂ -R ₂ (2)

Examples of compounds with two rings. R ₁ -Ph-COO-Ph-R ₂ (2A) R ₁ -Cy-COO-Ph-R ₂ (2B) R ₁ -Ph-COO-Cy-R ₂ (2C) R ₁ -Cy-COO-Cy -R ₂ (2D)

Further, those in which a part of carbon atoms of these 1,4-phenylene group and trans-1,4-cyclohexylene group are substituted with oxygen atoms and nitrogen atoms are also possible. It is also possible that some carbon atoms of the trans-1,4-di-substituted cyclohexylene group are double-bonded, or the 6-membered ring is substituted with another ring such as a 5-membered ring. .

There are also compounds having three or more rings.
In this case, R ₁ and R _{2 in} the compound of the above formula (2) may be regarded as a structure containing a ring structure. To give a concrete example,
There are the following compounds.

R ₁ -Ph-Ph-COO-Ph-R ₂ R ₁ -Ph-COO-Ph-COO-Ph-R ₂ R ₁ -Ph-COO-Ph-OCO-Ph-R ₂ R ₁ -Ph -CH≡CH-Ph-COO-Ph-R ₂ R ₁ -Ph-COO-Cy-Cy-R ₂ R ₁ -Ph-Cy-COO-Cy-R ₂

Such an ester type liquid crystal has a property that the interaction of liquid crystal molecules is increased by the ester bond at the center. Further, a cyanoester liquid crystal in which R ₂ is a cyano group or a fluoroester liquid crystal in which R ₂ is a fluorine atom is a chemically unstable material due to the presence of a polar group at the end. Although it has the effect of addition, it is preferable that it is not contained as much as possible.

Therefore, a material having an ester bond between rings and having both ends (R ₁ , R ₂ ) nonpolar with alkyl or alkoxy is the most preferable material.
In order to obtain the effect of increasing the viscosity of this ester-based liquid crystal, it is necessary to add at least 5 wt% to the liquid crystal composition, and the higher the content, the higher the viscosity. The upper limit of the addition is not limited as such, but there is a limit due to the upper limit of the viscosity and a constraint such as Δn required in consideration of the thickness of the liquid crystal layer used. That is, the addition amount may be determined within a range where the required parameters can be balanced.

The viscosity of the liquid crystal composition also depends on the chiral material used. Cholesteryl nonanoate (CN), which is one of the cholesteric liquid crystals, is a liquid crystal component that requires a large amount of addition because it is a material having a small twisting power and has a high viscosity. Such materials are suitable for use by adding to the liquid crystal composition of the present invention.

In the present invention, a liquid crystal composition having such a viscosity is used, and the thickness d of the liquid crystal layer is 2.5 to 5.5 μm.
By doing so, the decrease in response speed with the increase in viscosity is hardly or further improved, and the flicker in the case of performing frame gradation is significantly improved. If the thickness d of the liquid crystal layer is not less than 5.5 μm, the response speed will not be sufficiently fast, and if it is less than 2.5 μm, it will take too much time for injection and display unevenness will easily occur. further,
The thickness is preferably 3 to 5.0 μm.

In the present invention, it is preferable that the response speed when driven by the static drive method using the same liquid crystal display element is higher than a certain level. Specifically, a square wave with a frequency of 100 Hz is used in the static drive method, and the rising (τ
Select a voltage such that the response times of _r ) and the fall (τ _d ) are almost equal, and apply the voltage, and measure the total response time (τ _r + τ _d ). In the present invention, considering that it is compatible with mice, the total response time is 80
It is preferable to adopt a configuration such that the time is msec or less.

In the present invention, liquid crystal is injected into an empty cell formed of a pair of substrates with electrodes, and a polarizing film, a retardation film, a reflecting film and the like are further arranged as necessary to provide a liquid crystal display device. And In particular, the present invention is suitable for performing gradation display by time-division driving with a duty of 1/200 or more, and is suitable for an STN type liquid crystal display element in which the twist angle of the liquid crystal is about 180 to 360 °. Further, among them, it is also suitable for an STN type liquid crystal display element for black and white display in which a retardation plate and a compensating liquid crystal cell are laminated on the STN type liquid crystal cell or a liquid crystal display element for multicolor display in which the color is formed. .

In this case, the time from the selection of the scan electrode group group to the selection of the next scan electrode group group is
It is preferably 0.5 to 30 msec. For example, in the above example, when the total number of scanning electrodes is 400 and eight selection pattern rows are sequentially driven with M = 4, the frame frequency is
At 70Hz, 8 times x 70Hz = 560, therefore 1/560 = approx. 1.8m
It becomes sec. When driving by frame thinning, for example, in the case of gradation display with 5 frames, considering the worst, 8 times × 70 Hz ÷ 5 = 112, so 1/112 = approximately 9 msec.

A liquid crystal display device of this kind is used by connecting it to a driving method for selecting a plurality of scanning electrodes with a high duty ratio, in particular a gradation display. At that time, CCT, LE
Light sources such as D and EL, and illumination such as a light guide plate may be combined. Also, a transparent touch switch may be provided on the surface.

[0105]

The reason why flicker is reduced and the response speed is hardly reduced or can be increased by the present invention is considered as follows. That is, the response from on to off changes depending on the elastic constant ratio of the liquid crystal. The response phenomenon shows a property as an elastic body, and is a phenomenon in which internal strain induced by an applied electric field is relaxed in a direction different from the alignment direction of liquid crystal molecules regulated on the surface of the alignment film. This phenomenon is governed by the distance from the interface, that is, the thickness of the liquid crystal layer (cell gap). That is, the thinner the liquid crystal layer, the faster the response speed.

On the other hand, the flicker is a vibration of liquid crystal molecules on the order of 10 msec, and it can be said from the observation result that the flicker is a phenomenon that the alignment film surface is not regulated at all. The thermal fluctuation of liquid crystal molecules has the same property, and flicker can be interpreted as a phenomenon in which the thermal fluctuation phenomenon is synchronized with the frame frequency. That is, it is considered that the liquid crystal molecules, which normally have no regularity and are fluctuating, are synchronized by the regularly oscillating external field, and as a result, the vibration as a group occurs.

As a result, it is the strength of the interaction between adjacent liquid crystal molecules, that is, the viscosity, that regulates this movement.
Therefore, it is considered that the flicker phenomenon can be suppressed by using the high-viscosity liquid crystal independently of the response speed.
Therefore, it seems that the flicker phenomenon is not affected even when the thickness of the liquid crystal layer is reduced. As a result, both high-speed response and flicker reduction effects can be produced.

[0108]

【Example】

Example 1 1/200 A duty-driven 640 × 400-dot STN liquid crystal display device was produced under the following conditions. An empty cell was formed with a cell gap of 4.0 μm, and the mixed liquid crystal of the matrix contained 10 wt% of an ester material. Cholesteryl nonanoate was added to this material as a chiral material until a pitch at which d / P became 0.52 was exhibited to prepare a liquid crystal composition.
The viscosity after addition was 35 cps. This liquid crystal composition was injected into an empty cell, the injection port was sealed, and a retardation plate and a polarizing film were laminated to obtain a black and white STN type liquid crystal display device.

Τ in the static drive of this liquid crystal display element (using a rectangular wave with a frequency of 100 Hz, and selecting and applying a voltage such that the response times of rising (τ _r ) and falling (τ _d ) are almost equal) _r + τ _d was 30 msec.

In the multiple scan electrode selection driving method, when the number of simultaneously selected electrodes is set to 4, and binary display driving is performed, τ _r + τ
It was _d = 250 msec. When this was driven with 16 gradations using a frame thinning method and area gradation, the flicker phenomenon was significantly reduced and was hardly visible.

Example 2 A 1/200 duty driven 640 × 400 dot STN type liquid crystal display device was produced under the following conditions. An empty cell was formed with a cell gap of 5.0 μm, and the mixed liquid crystal of the matrix contained 10 wt% of an ester material. Cholesteryl nonanoate was added to this material as a chiral material until a pitch at which d / P became 0.52 was exhibited to prepare a liquid crystal composition.
The viscosity after addition was 25 cps. This liquid crystal composition was injected into an empty cell, the injection port was sealed, and a retardation plate and a polarizing film were laminated to obtain a black and white STN type liquid crystal display device. Τ _r + τ _d in static drive of this liquid crystal display element was 24 msec.

In the multi-scan electrode selection drive method, when the number of simultaneously selected lines is set to 4, and binary display drive is performed, τ _r + τ
It was _d = 200 msec. Using this, when performing 16 gradation display using frame thinning method and area gradation,
The flicker phenomenon was greatly reduced and was hardly visible.

Comparative Example 1 A 1/200 duty driven 640 × 400 dot STN type liquid crystal display device was produced under the following conditions. An empty cell was formed with a cell gap of 4.0 μm, and the mixed liquid crystal of the matrix was a liquid crystal composition containing no ester-based material. To this material, as a chiral material, "S-811" manufactured by Merck & Co.
A liquid crystal composition was prepared by adding until P 2 showed a pitch of 0.52. The viscosity after addition was 15 cps. This liquid crystal composition was injected into an empty cell, the injection port was sealed, and a retardation plate and a polarizing film were laminated to obtain a black and white STN type liquid crystal display device. Τ _r + τ _d in static drive of this liquid crystal display device
Was 15 msec.

In the multiple scan electrode selection drive method, when the number of simultaneously selected lines is set to 4, and binary display drive is performed, τ _r + τ
_{It was d} = 120 msec, and it was in a state that it could be used without any problem even if a mouse was used. When this was used to perform 16-gradation display using the frame thinning method and area gradation, the flicker phenomenon occurred severely and it was difficult to see.

[0115]

INDUSTRIAL APPLICABILITY The present invention uses a specific high-viscosity and low-gap liquid crystal cell by using a multiple scanning electrode selection driving method which can easily obtain a high-speed response, a high-contrast gradation display and a highly uniform display. As a result, it is possible to obtain a high-speed response liquid crystal display device in which flicker and display unevenness are less noticeable.

The present invention can be applied in various ways within a range that does not impair the effects of the present invention.

[Brief description of drawings]

FIG. 1 is a waveform chart showing a time-series change of potentials of C _{1 to} C _{4 in} one scan electrode group group according to the selection pattern sequence in Table 1.

FIG. 2 Scanning electrode group groups C _{1 to} C ₄ , C _{5 to} C ₈ , C _{9 to} C ₁₂
5 is a waveform diagram of voltages applied to the column electrodes S ₁ , S ₂ , S ₃ , and S ₉ in the selection period of FIG.

FIG. 3 is a waveform diagram showing the voltages of C ₁ -S ₉ and C ₂ -S ₉ when displayed in the display pattern of Table 2 according to the selection pattern column of Table ₁ .

[Explanation of symbols]

Scan electrodes: C _{1 to} C ₄ , C _{5 to} C ₈ , C _{9 to} C ₁₂ column electrodes: S ₁ , S ₂ , S ₃ , S ₉

Claims (3)

[Claims] 1. A liquid crystal cell in which a liquid crystal composition is sandwiched between a pair of electrodes-attached substrates, a plurality of scanning electrodes are selected at the same time and a selection voltage is applied to the column electrodes. In a liquid crystal display device driven by a multiple scanning electrode selection driving method in which a plurality of pixel electrodes facing each other are time-divisionally applied with a voltage according to the selection status of those pixel electrodes, the liquid crystal layer thickness d Is 2.5-5.5 μm, and the liquid crystal composition to be enclosed has a viscosity at 20 ° C. of 25 cps or more. 2. The liquid crystal display device according to claim 1, wherein the period from the selection of the scan electrode to the next selection of the scan electrode is 0.5.
Liquid crystal display device characterized by ~ 30 msec. 3. The liquid crystal display device according to claim 1 or 2, wherein the liquid crystal cell is a liquid crystal cell having at least 200 scanning electrodes, and the twist angle of the liquid crystal is 180 to 360.
A liquid crystal display device characterized by being defined as °.