JPH0627907A - Method for driving liquid crystal display element - Google Patents

Abstract

PURPOSE:To suppress variation in an optical state small by selecting row electrode subgroups so that specific requirements are satisfied. CONSTITUTION:Selective voltages are applied to row electrodes R1-R4 and a time interval T is a time interval for selecting a row electrode subgroup once when N row electrodes are all divided into row electrode subgroups at every L row electrode. Here, the specific requirements are satisfied so as to select the row electrode subgroups. Namely, (1) voltages having a positive or negative amplitude Vr (V4>0) about an intermediate voltage are applied to the row electrodes R1-R4 when they are selected and the intermediate voltages are applied when not. (2) Orthogonal matrixes A and the inverse of A consisting of L rows and K columns of elements which are +1 corresponding to a voltage +Vr or -1 corresponding to -Vr are selected as selective voltage matrixes. Here, K is the least number among integers which are L<=K.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device at high speed.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display element has been attracting attention as an alternative to a CRT for realizing a thin, light and compact display of a large amount of information. As such a liquid crystal display element, those that drive each pixel of the twisted nematic type liquid crystal display element by a thin film transistor formed corresponding to each, so-called twisted nematic type and super twisted nematic type liquid crystal display element, It can be roughly classified into two types, one that is driven without using a thin film transistor (simple matrix type).

[0003]

Although a device using a thin film transistor can be driven at a relatively high speed, it has a problem that the device manufacturing process is complicated and the manufacturing cost is high. On the other hand, the simple matrix type has a relatively simple element manufacturing process, but has a problem in that high-speed display switching is difficult and it is difficult to support mouse display and video display in a terminal.

Among these, the reason why it is difficult to drive a simple matrix type liquid crystal display element at high speed is because the characteristics of the twisted nematic type and super twisted nematic liquid crystal display elements make it slow to follow the alignment of liquid crystal molecules with respect to the applied voltage. . That is, the normal 2
In a super twisted nematic liquid crystal display device having an average response speed of about 50 msec, display switching at 20 to 30 Hz which is usually required for video display (33
(Corresponding to display switching every 50 msec) cannot be realized at all.

For high speed driving, it may be considered to use a liquid crystal element having a high response speed to an applied voltage.
Such a liquid crystal element may be referred to as a fast response liquid crystal element. As a method for obtaining a high-speed response liquid crystal element, there are a method of using a low-viscosity liquid crystal, a method of reducing the thickness of a liquid crystal layer by using a liquid crystal having a large refractive index anisotropy, and the like.

The response time of a super twisted nematic liquid crystal display element is approximately proportional to the viscosity η of the liquid crystal,
It is proportional to the square of the thickness d of the liquid crystal layer. On the other hand, considering the requirement that the product of the refractive index anisotropy Δn of the super twisted nematic liquid crystal display element and the thickness d of the liquid crystal layer should be substantially constant, the response time of the super twisted nematic liquid crystal display element is It is proportional and inversely proportional to the square of the refractive index anisotropy Δn. That is,
It is preferable to reduce the thickness d of the liquid crystal layer and use a liquid crystal having a low viscosity and a large refractive index anisotropy as the liquid crystal used in this liquid crystal element.

However, even if a high-speed response liquid crystal device is obtained in this way, the use of this device has the following serious problems in reality.

A method called a voltage averaging method is usually used to drive a simple matrix type liquid crystal display element. The number of scanning lines (the number of row electrodes) is N and the frame period is T
The waveform of the row electrode applied voltage in the voltage averaging method when _F is 1 has one selection pulse within the time T _F , and is 1 / b of the ON voltage selection pulse except when the selection pulse is applied. There is a bias wave with a peak value. That, T _F / N is the selection period, the non-selection period are assigned time _{(N-1) T F /} N. A typical applied waveform is shown in A of FIG. The horizontal axis represents time and the vertical axis represents voltage. In many cases, two frames are used to achieve alternating current.

In this voltage averaging method, it is premised that the liquid crystal molecules respond with the effective value of the applied voltage.
This makes it possible to obtain a predetermined contrast ratio.
The state of the effective value response is shown in C of FIG. The horizontal axis represents time, and the vertical axis represents transmitted light intensity when polarizing plates are arranged on both sides of the liquid crystal layer and an ON voltage is applied to the column electrodes when selecting the row electrodes. Normally, the frame period is about 10 to several tens of msec, whereas the average response speed of a normal liquid crystal display device is about 250 msec. Will be completed.

However, when a high-speed response liquid crystal element is driven, the change in the direction of the molecular axis of the liquid crystal molecules easily follows the voltage. Therefore, as shown by B in FIG. 5B, the optical response waveform has a so-called peak. The value-responsive behavior is exhibited, and the value deviates from the effective value response (shown by the C line). That is, since the optical response waveform that rises in the selection period cannot be held and is attenuated in the non-selection period, the average level of the transmittance decreases and the contrast ratio decreases. Hereinafter, this phenomenon is referred to as "relaxation phenomenon" of liquid crystal.

The relaxation phenomenon becomes a serious problem when an average response speed of a so-called liquid crystal display element is about 150 msec or less when performing dynamic drive with a high duty of several hundreds or more. This is remarkable in liquid crystal display devices.

Here, the average response speed of the liquid crystal display device is defined in this specification as follows. That is, the light transmissivity at the off voltage after a sufficient time has elapsed is T _OFF , the light transmissivity at the on voltage is T _ON, and the time at which the off voltage is switched to the on voltage is t ₁ , and then the light transmissivity is set. Degree T is (T _ON
−T _OFF ) × 0.9 + T _OFF is the time t ₂ , and
Assuming that the time when the on-voltage is switched to the off-voltage is t ₃ , and then the time when the light transmittance T becomes (T _ON −T _OFF ) × 0.1 + T _OFF is t ₄ , the average response speed τ is τ = ( It is represented by (t ₄ −t ₃ ) + (t ₂ −t ₁ )) / 2.

In order to suppress this relaxation phenomenon, it is conceivable to increase the frame frequency to shorten the selection pulse interval. However, in this case, since the time (pulse width) for selecting one row electrode is inevitably short, the liquid crystal molecules are less likely to react to the selection pulse, and therefore the effect of improving the display contrast ratio is not large. Further, when the driving frequency is increased, the resistance value of the electrode cannot be ignored, and there is a problem that display unevenness occurs in the vicinity of the signal input portion of the electrode and other portions, or _Vth fluctuates to cause display unevenness. For this reason, it has been difficult to use a liquid crystal device having a high-speed response for display in practice.

On the other hand, TNRuckmongathan uses a method of collectively selecting and driving a plurality of row electrodes as a method for reducing the drive voltage and reducing the display unevenness (hereinafter referred to as IHAT.
Proposed law (1988 International Displ
ay Research Conference). The outline of the driving method is as follows.

The N row electrodes are divided into p (p = N / M) subgroups each consisting of M row electrodes, and M row electrodes are collectively selected and driven. Display data within a selected subgroup on any one column electrode,
[D _{kM + 1} , d _{kM + 2} , ..., d _{kM + M} ]; d _{kM + j} = 0 or 1
(0 is off, 1 is on, and k is an integer that varies from 0 to (p-1) depending on the selected subgroup.). The row electrode selection pattern is _defined as [a _{kM + 1} , a _{kM + 2} , ..., a _{kM + M} ]; a _{kM + j} = 0 or 1 2 ^M (= Q) kinds of M-bit words (w ₁ , W ₂ , ...
・ ・, W _Q )

The driving is performed as follows. (1) One subgroup is selected at once. (2) One M-bit word is selected as the row electrode selection pattern. (3) If the non-selected row electrodes to be grounded, the row electrode is selected, -V _r, with respect to the logic 1 + V _r is applied against the logic 0. (4) The row electrode pattern and the data pattern of the selected subgroup are compared bit by bit by exclusive OR, and these exclusive OR are obtained. (5) The number i of mismatches of the two patterns obtained by the above exclusive OR is obtained.

(6) The voltage applied to the column electrodes is selected as V _i if the above-mentioned number of mismatches is i. (7) The voltage applied to each column electrode is independently determined by repeating the above steps (4) to (6) in the matrix. (8) Voltage is simultaneously applied to the row electrodes and the column electrodes for the time T _R. (9) A new row electrode selection pattern is selected, and the voltage applied to the column electrode is determined by the steps (4) to (6). Similarly, the new row and column electrodes are simultaneously energized for a time T _R. (10) The cycle is for all subgroups
All 2 ^M selection patterns are chosen and completed. (11) The display is updated by continuously repeating this cycle.

In particular, if V _i = V ₀ (M−2i) / MV _r = V ₀ N ^1/2 / M is selected, the on / off ratio of the effective voltage value can be maximized.

Further, the ratio of the effective voltage of ON and OFF at this time is V _ON / V _OFF = ((N ^1/2 +1) / (N ^1/2 -1))
^It becomes ^1/2 , which is equal to V _ON / V _OFF in the voltage averaging method used conventionally. Therefore, the contrast becomes the same. Further, since the effective voltage value of each lighting portion in the matrix becomes uniform, there is an effect that uniform display can be obtained regardless of the display pattern.

However, although the IHAT method is effective in reducing display unevenness, it requires a long time interval for completing one cycle. Therefore, it is not suitable for gradation display using a method similar to frequency modulation. That is, as the number of row electrodes selected at the same time increases, the number of required selection pulses increases exponentially. That is, if the widths of one selection pulse are equal, one display has 2 ^M-1 / M of the conventional method.
Double the time required. For example, if M = 7, 64/7
= 9.1 times longer.

[0021]

The present invention has been made to solve the above-mentioned problems, and provides the following driving method for a liquid crystal display device.

In a driving method of a matrix type liquid crystal display device having a plurality of row electrodes and a plurality of column electrodes, the J of the row electrodes is
A driving method in which x L electrodes (J and L are each an integer of 2 or more) are divided into J row electrode subgroups each including L row electrodes, and the row electrode subgroups are collectively selected. A method for driving a liquid crystal display device, characterized in that the row electrode subgroup is selected under the following conditions. (1) When selected, a voltage is applied to the row electrodes in the positive or negative direction with respect to the intermediate voltage with an amplitude of V _r (V _r > 0),
The intermediate voltage is applied when not selected. (2) As the selection voltage matrix, the orthogonal matrixes A and -A of L rows and K columns whose elements are +1 corresponding to the voltage + V _r or -1 corresponding to -V _r are selected. Where K is L ≦ K
Is an integer and is the smallest. (3) When the jth row electrode subgroup is selected, the elements of the column vector of the selection voltage matrix (hereinafter referred to as the selection voltage vector) correspond to the voltage amplitudes of the row electrodes forming the jth row electrode subgroup. As such, the voltage is applied. This voltage application is performed for all of the selection voltage vectors.

In the above driving method, the liquid crystal display element is a liquid crystal display element using a liquid crystal composition containing a difluorostilbene type liquid crystal and / or a tolan type liquid crystal. It provides a driving method. Furthermore, in the above driving method, the voltage applied to the column electrodes is (L + 1) voltage levels V
₀ , V ₁ , ..., V _L , where V ₀ <V ₁ <...
<V _L , the display data consisting of binary values of the j-th row electrode subgroup in a specific column (where j is an integer varying from 1 to J), and L elements are When represented by a vector D _j (where the elements of the vector D _j consist of 1 indicating ON or 0 indicating OFF), the vector D _j is represented by the vector D _j when the j-th row electrode subgroup is selected. In order to display the expressed data, V _i (i is an integer from 0 to L), where i is the sum of the exclusive ORs of the corresponding selection voltage vector and vector D _j corresponding to each other. ) Is applied to the column electrodes, a method for driving a liquid crystal display device is provided. Further, in the above driving method, the display data of the j-th row electrode subgroup in the specific column is replaced with the display data consisting of binary values, and the gradation of (U + 1) stages (U is a natural number of 2 or more) is displayed. As display data to be possessed, as the selected voltage matrix, U orthogonal elements A and −A of L rows and K columns each consisting of +1 corresponding to voltage + V _r or −1 corresponding to −V _r are selected (here , Where K is an integer that is L ≦ K and is the minimum, and by displaying a total of U on and off at a predetermined ratio, (U +
The present invention provides a driving method of a liquid crystal display device, which is characterized by performing gradation display of 1) steps.

In the driving method of the present invention, as in the IHAT method, a plurality of row electrodes are collectively selected. In this specification, a group of row electrodes that are collectively selected will be referred to as a “row electrode subgroup”. In order to simplify the driving circuit, it is preferable to make the number of row electrodes constituting the row electrode subgroup equal to each other. Of course, in a general cell configuration, the total number of row electrodes is
Since it is not a multiple of the number of row electrodes forming the row electrode subgroup, it may not be possible to equalize the number of row electrodes forming each row electrode subgroup. The row electrode subgroup, which is present as a fractional number and has a smaller number of row electrodes than the other row electrode subgroups, will be described later. First, the number of row electrodes forming the row electrode subgroup is L. Driving of equal parts will be described below.

When the row electrodes are divided into row electrode subgroups, it is not always necessary for adjacent row electrodes to belong to one row electrode subgroup. If wiring problems on the substrate allow, distant row electrodes can be simultaneously selected as row electrodes in the same row electrode subgroup.

The liquid crystal display element used in the present invention is preferably one having a high speed response. As described above, a liquid crystal display device having a high-speed response can be obtained by reducing the thickness d of the liquid crystal layer and using liquid crystal having low viscosity and large refractive index anisotropy. As such a liquid crystal having large refractive index anisotropy, for example, a tolan-based liquid crystal is useful.
As a liquid crystal of a tolan type, for example, JP-A-61-563
Some of them are described in Japanese Patent Publication No. 1 and some of them have a structure as shown in Chemical formula 1.

[0027]

[Chemical 1]

Here, -X- is -COO-, -OCO.
-, - CH ₂ CH ₂ -, or show what two carbon is triple bond. R ¹ and R ² are independently of each other an alkyl group having 1 to 10 carbon atoms, a halogen atom, a nitrile group,
-SCN group, and in the case of having a carbon-carbon bond, oxygen is inserted between the bonds or between the carbon-carbon bond between this group and the ring, or a part of the carbon-carbon bond is -COO.
It may be substituted with-, -OCO-, or -CH = CH-. Incidentally, these compounds are merely examples,
Various materials are selected and used, such as substitution of a hydrogen atom with a halogen atom, a cyano group, a methyl group, or the like.

Further, as a material having a large refractive index anisotropy and a low viscosity at the same time, a difluorostilbene type liquid crystal is useful. Examples of the difluorostilbene-type liquid crystal include those described in Japanese Patent Application Laid-Open No. 1-96475, and those having a structure shown in Chemical formula 2.

[0030]

[Chemical 2]

Here, -X- is -COO-, -OCO.
-, - CH ₂ CH ₂ -, or show what two carbon is triple bond. R ¹ and R ² are independently of each other an alkyl group having 1 to 10 carbon atoms, a halogen atom, a nitrile group,
-SCN group, and in the case of having a carbon-carbon bond, oxygen is inserted between the bonds or between the carbon-carbon bond between this group and the ring, or a part of the carbon-carbon bond is -COO.
It may be substituted with-, -OCO-, or -CH = CH-. Incidentally, these compounds are merely examples,
Various materials are selected and used, such as substitution of a hydrogen atom with a halogen atom, a cyano group, a methyl group, or the like.

The difluorostilbene type liquid crystal and the tolan type liquid crystal may be used separately or both may be used at the same time. Particularly, a liquid crystal composition containing 1 to 80%, preferably 5 to 70%, and more preferably 10 to 60% of difluorostilbene has a markedly reduced viscosity and can realize a high-speed response.

As proposed by the IHAT method, in order to select a row electrode in units of a subgroup consisting of a plurality of row electrodes, it is necessary to apply a selection voltage in a different pattern for each row electrode.

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

The voltage applied to a particular row electrode subgroup at the time of selection can be expressed by arranging L-th order vectors having the voltage applied to each row electrode as an element in time series. In this specification, this vector will be referred to as a “selection voltage vector”. A matrix including the selection voltage vector as its column is called a “selection voltage matrix”. That is, when a specific selection voltage matrix is determined, the elements of the L-th order selection vector forming the selection voltage matrix are made to correspond to the voltages of the row electrodes, and all selection voltage vectors forming the selection voltage matrix are sequentially arranged. By applying a voltage to each row voltage, the row electrode subgroup is selected.

As the selection voltage matrix, basically, an orthogonal matrix A = L having K elements whose elements are + V _r or −V _r and whose product with the transposed matrix is a scalar multiple of the unit matrix is A =
[Α ₁ , α ₂ , ..., α _q , ..., α _K ] (where α _q is a vertical vector having L elements) is selected. Here, K is an integer such that L ≦ 2 ^p = K, where p is a natural number. That is, specifically, when L is 2, K is K = 2 (p = 1), 4 (p = 2), 8 (p = 3), ...
And so on, and if L is 3,4, K is K = 4,8,1
, And so on, and when L is 5, 6, 7, and 8, K is K = 8, 16, 32 ,. If K is made too large, the number of selection pulses required for selecting the row electrodes also becomes large. Therefore, it is preferable to set K to the smallest possible value.

When L = 4, 8 and K is 4, 8 respectively, a concrete example of the matrix A is as shown in Equation 1.

[0038]

[Equation 1]

As a result of actually applying various matrices to driving, particularly when the matrix of the equations 1 (a) and (c) called Hadamard matrix is adopted, it is effective to suppress display unevenness in actual liquid crystal driving. Was found to be large.

When L = 2 ^p is not satisfied, from the Kth-order matrix whose product with the transposed matrix is a scalar multiple of the unit matrix,
The matrix A of L rows and K columns can be configured by deleting an arbitrary (KL) row. For example, number 1 (c)
An example configured from the Hadamard matrix of order 8 is shown in the following Expression 2.

[0041]

[Equation 2]

Formula 2 (a) is a matrix of 7 rows and 8 columns in which the first row is deleted from Formula 1 (c), and Formula 2 (b) is the first and eighth rows from Formula 1 (c). It is the deleted matrix with 6 rows and 8 columns. In each case, the product of their transposes is a scalar multiple of the identity matrix.

By considering each column of the selection voltage matrix as one vector, A = [α ₁ , α ₂ , ..., α
_q , ..., α _K ] (where α _q is a vertical vector having L elements).

In actual driving, A and -A are selected as the selection voltage matrix. If the data to be displayed is binary (that is, on or off), the selection voltage vector basically includes 2K vectors forming each selection voltage matrix.

The selection voltage vector used for selecting the row electrodes does not necessarily have to consist of only one vector selected as described above, and the elements are + V _r or -V _r.
It is also possible to add another vector consisting of or to use a plurality of the same vectors without departing from the effects of the present invention.

However, if the number of selection voltage vectors becomes too large, the number of selection pulses required for row electrode selection will increase significantly. Therefore, if the pulse width is the same, one display cycle is completed. Therefore, the time required for this will be extremely long.

In this sense, as the selection voltage vector, using the notation of the selection voltage matrix described above, substantially α
₁ , α ₂ , ・ ・ ・, α _K , −α ₁ , −α ₂ , ・ ・ ・, −
The set of vectors consisting of α _K is preferably the set of selection voltage vectors used for driving. in this case,
The number of selection voltage vectors is substantially 2K. By doing so, the number of selection pulses required for selecting the row electrodes can be substantially minimized, which is most advantageous for high-speed display.

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

For simplicity of description, a pattern in which + V _r is 1 and -V _r is 0 among the elements of the selection voltage vector is referred to as a "selection pattern". Those arranged in series are called “selection codes”.

Therefore, a selection voltage matrix (selection code) suitable for high speed driving will be described below.

As a result of actually applying an array of various selection voltage vectors to driving, the number of selection voltage vectors used for driving is set to 2I (I is a natural number of 2I ≧ 2K), and selection of the first half I is performed. It has been found that it is preferable from the viewpoint of suppressing display unevenness in driving that the column of voltage vectors and the column of I selection voltage vectors for the latter half have the same absolute value and opposite signs. The cause of suppressing the display unevenness of the drive by the arrangement of the selection vectors is not clear, but the supply voltage waveform generated between the electrodes during one display is converted into an alternating current at a uniform cycle regardless of the display data. It is supposed to be because. Hereinafter, the selection code arranged in this way will be particularly referred to as an “inversion code”.

Specifically, when the selection code voltage string is made up of 2I selection patterns, the first to the Ith selection code voltage strings are formed.
The second selection pattern column and the (I + 1) th to the second
Considering two columns, the column of the I-th selection pattern,
It is characterized by using a selection code such that the contents of the sth selection pattern and the (I + s) th selection pattern have a negative relationship. That is, when the s-th selection pattern is expressed as W _s , the row electrode selection code is formed so as to satisfy the relationship as shown in Expression 3.

[0053]

[Equation 3]

By applying the inversion code to the one consisting of 2K selection voltage vectors, that is,
[Α ₁ , α ₂ , ..., α _K , −α ₁ , −α ₂ , ...
,, −α _K ], then choosing a sequence of vectors
It was found to be preferable from the viewpoint of suppressing drive display unevenness.

Table 1 shows, as an example of the row electrode selection code, a code formed of a 4th order Hadamard matrix.

[0056]

[Table 1]

The selection code of Table 1 is [α ₁ , α ₂ , ..., α _K , −α ₁ , −, as an array of selection voltage vectors.
[alpha] ₂ , ...,-[alpha] _K ] is satisfied. In addition, when the array (selection pattern) of the selection voltage vectors is replaced for each subgroup or each display data, selection codes as shown in Table 2 or Table 3 can be adopted. The numbers in the table indicate the selection pattern numbers in Table 1, and the selection patterns are applied to the row electrodes in time series from left to right. Table 2 shifts the selection pattern each time one row electrode subgroup is selected, and Table 3 shifts the selection pattern each time two row electrode subgroups are selected.

[0058]

[Table 2]

[0059]

[Table 3]

Table 4 shows another example of the inversion code when L = 3.

[0061]

[Table 4]

Thus, in the above inverted code, the first
The negative row electrode selection patterns from the fourth row to the fourth row are arranged in order from the fifth row to the eighth row.

On the other hand, the display data is not binary display,
When the gradation has (U + 1) stages (U is a natural number of 2 or more), at least α ₁ , α ₂ , ..., α _K , −α ₁ , −α ₂ , ...
Selected from the set of vectors containing U each of −α _K.

As in the case of the binary display, the selection voltage vector used for driving does not necessarily have to consist of only the above-mentioned vector U (in this case, 2KU in total), and the elements may be + V _r or −. It is possible to add another vector composed of V _r or the same vector as long as the effect of the present invention is not impaired. In addition, if the selection voltage vector used for driving is substantially composed of the above-mentioned U vectors (2KU in total), the number of selection pulses required for selecting the row electrodes is reduced. This is preferable for high-speed display, and in particular, if the selection voltage vector used for driving is made up of only U of each of the above vectors (2KU in total), it is necessary for selection of the row electrodes. The number of selection pulses can be minimized, which is highly desirable for high speed display.

The selection voltage vectors may be arranged in any order, and the selection voltage vectors may be arranged randomly, or the arrangement may be changed for each subgroup or for each display data. In order to suppress the display unevenness in the actual driving, it is often preferable to drive while appropriately performing the above replacement, as in the case of the binary display.

Also in the case of (U + 1) -stage gradation display, various arrangements of the selection voltage vector forming the selection voltage can be adopted. For example, the vector sequence [α ₁ , α ₂ ,
..., expressed as S the alpha _K] as a unit, [S, S,
..., S, -S, -S, ..., -S], or [S, -S, S, -S, ..., S, -S]. . Particularly, from the viewpoint of preventing flicker, [S, S, ..., S, −S, −S, ..., −
S] is preferable.

Next, the timing of applying the selection pulse represented by the selection voltage vector configured as described above to each row electrode will be described.

In the case of driving for switching the display at high speed, it is preferable to use a liquid crystal display element having a high-speed response in order to make the rising of the liquid crystal molecules with respect to the voltage application steep. In this case, there is a problem that the alignment of the liquid crystal molecules is relaxed when the selection pulse is not applied to the liquid crystal molecules as described above. This problem becomes serious when the so-called average response speed of the liquid crystal display element is 150 msec or less when performing dynamic driving with a high duty ratio of several hundreds or more. This is remarkable in liquid crystal display devices.

In order to suppress the liquid crystal relaxation phenomenon, it is preferable to adjust the length of the non-selection period in which the selection voltage is not applied to each row electrode. This adjustment is specifically
In the method of the present invention, the selection pulse can be 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 vector to one row electrode subgroup at one time, the arranged selection voltage vector is divided into several stages to form one row. When the stage is applied, the next row electrode subgroup is selected. Specifically, the following sequence is taken. (A) A voltage corresponding to a vector included in one stage is continuously applied to each row electrode forming the row electrode subgroup in the order of the selection voltage vector (hereinafter, referred to as step a). . (B) The step a is performed on all the row electrode subgroups (hereinafter, this is referred to as step b). (C) The steps a and b are performed according to their order for all stages.

In this way, it becomes possible to adjust the length of the non-selection period in which the selection voltage is not applied to each row electrode.

In the conventional so-called voltage averaging method,
This is because the selection voltage is made alternating by applying two selection pulses having different phases to each row electrode while displaying one display data, and therefore two selection pulses are in one cycle in a unit.

On the other hand, in the present invention, as many selection pulse trains as the number obtained by dividing the array of selection voltage vectors into each stage appear. Therefore, if the column of selection voltage vectors is divided into three or more, the number of selection pulses that appear during the display of one display data can be increased as compared with the conventional method.

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.

The length of the non-selection period in which the selection voltage is not applied to each row electrode can be adjusted according to the high-speed response of the liquid crystal display element. In general, increasing the number of divisions of the selection voltage vector sequence shortens the non-selection period, which is more effective in preventing the relaxation phenomenon of the liquid crystal. That is, if the selection pulse is dispersed more, the optical response waveform that rises in the selection period can be easily held in the non-selection period. Therefore, it is possible to suppress the decrease in average transmittance level,
Most preferably, each stage consists of one selection voltage vector to prevent a reduction in contrast ratio. For simplicity of explanation, this case will be mainly described below.

In the present invention, when N row electrodes are selected as a whole and L rows are collectively selected for binary display, the number of selection pulses to be applied to each row electrode for one display is , The minimum is 2K · (N / L) lines, which is almost the same as the 2N lines in the conventional voltage averaging method. Therefore, if the display switching speeds are the same in both methods, the widths of the selection pulses corresponding to one selection pattern are almost the same. On the other hand, regarding each row electrode, the number of selection pulses applied during one display is, for example, 2L if L = 2 ^p (p is an integer), and by applying all of them in a distributed manner, The time during which the selection voltage is not applied to the row electrodes can be reduced to 1 / L as compared with the conventional method. That is, it is a feature of the method of the present invention that the number of selection pulses can be increased without substantially changing the width of the selection pulse.

FIG. 1 shows the voltages applied to the row electrodes according to the selection code in Table 1. R _{1 to} R ₄ represent each of the row electrodes, and the time interval T is N in total.
When one row electrode is divided into row electrode subgroups each including L row electrodes, the time interval is for selecting the row electrode subgroup once.

Similar to FIG. 1, the time-series changes of the applied voltage for the row electrode subgroups R _{1 to} R _{3 in} the case of the selection codes shown in Table 4 are shown in FIG. Here, the total number of row electrodes N = 240.

Next, the voltage applied to the column electrode for displaying the specific data when the specific row electrode subgroup is selected under the conditions described above will be described below.

In the present invention, the driving is performed by applying the voltage selected from the (L + 1) voltage levels according to the selection pattern of the row electrode subgroup 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 (L + 1) voltage levels satisfy at least the voltage level V satisfying the following condition.
₀ , V ₁ , ..., V _L are preferable.

First, V ₀ <V ₁ <... <V _L. From the display data and the selection voltage applied to the row electrodes,
Which of these voltage levels should be selected is determined. This method will be described later.

Next, from the viewpoint of making the voltage waveform alternating, L
Is an odd number (i.e., n is an integer, L + 1 = 2
n), the _{V 2n-m-1 = -V} m (m is a _{V 2n-m-1> 0} ) with 0 ≦ m ≦ n-1 integers, when M is an even number (M = 2
n), V _2n-m = -V _m (m is an integer of 0≤m≤n-1 and is V
_2n-m > 0). However, this is the case where the voltage applied to the row electrodes when not selected is 0, and it is naturally possible to change the potentials of both the row electrodes and the column electrodes in parallel by the same amount. This is because the potential difference between both electrodes does not change.

Further, the absolute values of V ₀ , V ₁ , ..., V _L need to be appropriately determined depending on the configuration of the liquid crystal element and the like.

Next, how to select the applied voltage from the above (L + 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. FIG. 2 schematically shows a part of a display pattern of a matrix display including 400 row electrodes. When a display pattern as shown in FIG. 2 is displayed, the data pattern corresponding to this is as shown in the table when ON is 1 and OFF is 0. If four row electrodes are selected at once, one column electrode is divided into data patterns of 4 bits for each subgroup. The display data of the j-th row electrode subgroup (where j is an integer varying from 1 to J) is used as a vertical vector D _j having L elements (where the elements of the vector D _j indicate ON). Or it consists of 0 which indicates off).
For example, in the column electrode C 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 row electrode (this is β) and the vector of the data of the column electrode are used. , The exclusive OR is taken for each corresponding element, and the total sum i is obtained. For example, when the selection voltage of the first subgroup of row electrodes in FIG. 2 is represented by a selection pattern [1, 1, 1, 1], the voltage to be applied to the column electrode C ₉ in FIG. 2 is determined. To do. At this time, the sum i of the exclusive ORs is expressed by Equation 4.

[0087]

[Equation 4]

When i is obtained in this way, the voltage level to be applied to the column electrode is represented as V _i .

For example, the row electrode selection code is selected as shown in Table 1. In this case, when the display pattern of FIG. 2 is displayed, the voltages applied to the column electrodes C ₁ , C ₂ , C ₃ and C ₉ are as shown in FIG. In the figure, for example, R _{1 to} R ₄ indicate voltage changes during a period in which the row electrode subgroups R _{1 to} R ₄ are selected. Where R ₁ ~ R
₄ , R _{5 to} R ₈ and R _{9 to} R ₁₂ are drawn independently. Further, for ease of viewing, the horizontal time axis is drawn with other subgroup selection periods omitted. Therefore, in the present invention, when the select pulse is dispersed and applied, the voltage application shown in the graph is not continuously performed, but one voltage application on the graph is performed and then the other lines are applied. A voltage is applied to the electrode subgroup, and after the time has elapsed, the next voltage application on the graph is performed.

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

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

When L = 4 as shown in FIG. 2, V ₄ = + V
_{c, V 3 = + V c} / 2, V 2 = 0, V 1 = -V c / 2,
Select V ₀ = -V _c or the like. Further, under the above conditions, V _r =
It becomes 5 V _c . FIG. 4 shows the voltage changes of R ₁ -C ₉ (on state) and R ₂ -C ₉ (off state) in FIG. 2 in this case. However, as in FIG. 3, the horizontal axis is drawn with the other subgroup selection periods omitted for ease of viewing.

In this way, one display data is displayed, but when attention is paid to a specific row electrode subgroup,
It may be effective to reduce the display unevenness that the configuration of the selection voltage matrix (selection pattern) is changed each time one or more displays are completed. In particular, it is preferable that the selection voltage applied to each row electrode is switched among the row electrodes in a specific subgroup 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 vector in the previous data display is used again as the matrix A for forming the selected voltage vector.

Specifically, when the selection codes shown in Table 1 are adopted for the first display, the selection codes shown in Table 5, Table 6, and Table 7 can be sequentially used every time the display data is switched. it can. The selection codes in each table are obtained by shifting the selection pressure applied to each row electrode.

[0095]

[Table 5]

[0096]

[Table 6]

[0097]

[Table 7]

As described above, in the sequence of the driving method of the present invention for displaying binary display data as described above, the number of row electrodes to be collectively selected is 4 (L = 4), and the row electrode sub-group is selected. A representative example in which the number is J will be summarized.

A basic selection code is determined in advance. In this example, the selection code of Table 1 is adopted.

First, the selection pattern 1 in Table 1 is applied to the first row electrode subgroup. At the same time, a voltage determined from this selection pattern and display data is applied to each column electrode. Next, the selection pattern 2 in Table 1 is applied to the second row electrode subgroup, and at the same time, the selection pattern and the voltage determined from the display data are applied to each column electrode. Then, the selection pattern 3 in Table 1 is applied to the third row electrode subgroup, and the same is applied to each column electrode. Then, this process is repeated until the J-th sub group.

Next, the selection pattern 2 of Table 1 is applied to the first row electrode subgroup. Next, the selection pattern 3 of Table 1 is applied to the second row electrode subgroup, and this is repeated until the Jth subgroup.

In this way, the selection pattern is sequentially applied to each row electrode subgroup, and this is performed until all selection patterns are applied. This completes one display.

When displaying the next display data, the selection code of Table 5 is adopted. This is obtained by shifting the selection voltage applied by the selection code in Table 1 for each row electrode.

Further, when displaying the next display data, the selection code of Table 6 is adopted, and each time the display data is switched, the selection code of Table 7 and the return code of Table 1 are used.
The selection code of and the selection code to be adopted are switched. In this way, the display based on each display data is sequentially performed.

Further, the case of selecting the selection code in Table 4 is as follows. As shown in Table 4, there are 8 possible states of the data pattern D = ^t (d ₁ , d ₂ , d ₃ ) in the row electrode subgroup for one column electrode in total, and any of these combinations can be used. Display patterns can be configured. The sum i of bitwise exclusive ORs of each row electrode selection pattern and the data pattern, and its i
Table 8 shows the result of calculation of V _{i according} to V _i = V _c (2i−L) / L. However, the value of V _i is shown by representing only the coefficient of V _c .

[0106]

[Table 8]

Based on this table, the voltage waveform to be applied to the column electrodes during the period when one subgroup is selected is determined, and becomes as shown in FIG. Arbitrary display is possible by combining eight kinds of waveforms in this figure.

The waveform of the applied voltage on R ₃ in FIG. 7 is a data pattern of full-on ((d ₁ , d ₂ , d ₃ ) = (1, 1, 1)) and full-off ((d ₁ , d ₂ , d
FIG. 11 shows a data pattern of ₃ ) = (0,0,0)). From this, it can be seen that the same voltage is always applied after four stages. This is the same for data patterns other than full off and full on.

That is, by adopting the above-mentioned inversion code as the selection code, a potential having the same absolute value is applied during a period for scanning one screen (hereinafter, referred to as a frame period, and its reciprocal is referred to as a frame frequency). It can be repeated twice.

That is, when the display is turned on, of the pulses of the applied voltage, the absolute voltage has the maximum voltage +
_{(V r + V c),} - although the application of (V _r + V _c) is believed to contribute most to the movement of the liquid crystal molecules, which also every four stages, i.e. to appear exactly at twice the frequency of the frame frequency become.

That is, in the conventional voltage averaging method, the frequency of the optical response of the liquid crystal was equal to the frame period.
If an inverted code is used as the selection code in the driving method of the present invention, the frame frequency can be substantially doubled. 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 a binary display but (U +
When the gradation has 1) steps (U 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, the selection voltage vectors constituting it are substantially α ₁ , α ₂ , ..., α _K ,
A column of vectors, each of which is U in number of −α ₁ , −α ₂ , ..., −α _K and in which the selected voltage vectors are appropriately arranged, is selected.

The gradation display of (U + 1) stages is performed by displaying a total of U on or off at a predetermined ratio for each of these U selected voltage vectors (2KU in total). It can be carried out.

As a specific example, a case where L = K = 4 and four gradations are displayed will be described. The selection code at this time is, for example, as shown in Table 9 as a selection code composed of a fourth-order Hadamard matrix. It is assumed that the selection pattern progresses from left to right, and the vertical steps correspond to the row electrodes.

[0115]

[Table 9]

Alternatively, there is one as shown in Table 10.

[0117]

[Table 10]

In the above case, the same kind of selection pattern appears three times each. 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.

Next, with respect to the portion composed of the row electrode subgroup composed of L _r row electrodes smaller than the other row electrode subgroup composed of L row electrodes, the row electrode and the column electrode are For the applied voltage, see (L-L
_r ) By virtually adding and driving row electrodes,
Driving can be performed in the same manner as when the number of row electrodes forming the row electrode subgroup is L.

That is, when driving a sub-group consisting of L _r row electrodes, (L−L _r ) rows corresponding to the L _r- th, (L _r +1) -th, ..., L-th row. The electrodes are virtually considered, and the display data on the virtual row electrodes are 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 driving a row electrode subgroup of L = 4 and L _r = 3, three row electrodes of the selection code configured when L = 4 are used. Specifically, if the selection code shown in Table 1 is adopted, for example, the selection pulse is applied using the selection codes for three lines corresponding to the row electrodes 2 to 4. The selection method is not limited to the one corresponding to the row electrodes 2 to 4, and may be another selection method such as using one corresponding to the row electrodes 1 to 3.

Further, the voltage applied to the column electrode is determined as follows. That is, for display data, virtual display data is virtually added to form a display data vector D _j . On the other hand, regarding the selection pattern,
The selection pattern in the selection code of the L row electrodes used to construct the selection code for the L _r row electrodes 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 L row electrodes forming the row electrode subgroup 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 required for selection and the number of voltage levels of voltages to be applied to the column electrodes are larger than the minimum required value, as compared with the row electrodes which actually form the row electrode subgroup. It will be. 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.

[0125]

FIG. 6 shows an example of a circuit adopted to implement the driving method of the present invention. The following description is for the case of performing 16 gradation display. The display data is input as an analog signal separately for R, G and B. This is R, G, B each 6
The bit A / D converters 1, 1, 1 convert the data into digital data, and the compensator 2 corrects the data according to the optical characteristics of the liquid crystal (so-called γ correction) to obtain a predetermined number of bits determined by gradation. It is converted into gradation data and stored in the display memory 3 once. Next, the data is read from the display memory 3 in a predetermined order and distributed by the data selector 4 to each of the L sub-group memories 5, 5 ,. The L pieces of data are respectively supplied to the gradation control circuits 6, 6, ...
In 6 the 15 cycles are collectively converted into 1-bit ON / OFF display data string (L pieces) data and sent to the exclusive OR and the adder 7.

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

Example 1 An STN liquid crystal display element having an average response speed of 50 msec (25 ° C.) using the above-mentioned circuit configuration has a row electrode number N of 490, L = 7, J = 7.
When 0 and K = 8 were set and the selection pulse width corresponding to one selection pattern was changed and driving was performed by the driving method of the present invention, the maximum contrast ratio at 25 ° C. is as shown by the triangle marks in FIG. It was

This liquid crystal contains 30 wt% of difluorostilbene type liquid crystal and 43% of tolan type liquid crystal.
The characteristics as a whole are that the refractive index anisotropy Δn is 0.237,
The viscosity η was 12.1 cSt and the clearing point T _c was 86.7 ° C. The liquid crystal layer thickness d used was 3.7 μm.

At this time, the selection code shown in Table 11 was used. This is because the row electrode 2 to the selection code composed of the 8th order Hadamard matrix as shown in Table 12
The selection code corresponding to the row electrode 8 is used.

Further, each time a selection pattern is applied to a row electrode, the next row electrode subgroup is applied,
V _i = V _c (2i−L) / L and V _r = V _c N ^1/2 / L were selected, and the absolute value of the voltage was adjusted so that the maximum contrast ratio was obtained. In all the examples below, the next row electrode subgroup is applied each time one selection pattern is applied to the row electrode.

[0131]

[Table 11]

[0132]

[Table 12]

(Comparative Example 1) 1/4 by the conventional voltage averaging method
When the element of Example 1 was driven while changing the 80 duty, the 1/15 bias, and the selection pulse width, the maximum contrast ratio was as shown by the circle in FIG. From FIG. 9, a pulse width of 20 μsec (frame frequency 100 Hz, which is normally used in the 1/480 duty voltage averaging method).
It is understood that there is a large difference in the contrast ratio between the present invention and the conventional method in the vicinity of about (degree), and the relaxation phenomenon of the liquid crystal is suppressed and the contrast ratio becomes extremely high in the present invention.

(Embodiment 2) An STN liquid crystal display element having an average response speed of 250 msec (25 ° C.) using the above circuit configuration has a row electrode number N of 490, L = 7, J =
When the driving method of the present invention was performed with 70, K = 8 and the selection pulse width corresponding to one selection pattern was changed, the maximum contrast ratio at 25 ° C. is as shown by the triangle marks in FIG. It was

This liquid crystal contains neither difluorostilbene-type liquid crystal nor tolan-type liquid crystal, and the overall characteristics are that the refractive index anisotropy Δn is 0.131 and the viscosity η is 18.
9cSt and _Tc were 93.9 degreeC. Further, the liquid crystal layer thickness d was used at 6.7 μm.

At this time, the same selection code as in Example 1 was used. Further, each time one selection pattern is applied to the row electrode, the next row electrode subgroup is applied, and V _i = V _c (2i−L) / L and V _r = V _c / N ^1/2
L was selected and the absolute value of the voltage was adjusted so that the maximum contrast ratio was obtained.

(Comparative Example 2) 1/4 by the conventional voltage averaging method
When the device of Example 2 was driven while changing the 80 duty, the 1/15 bias, and the selection pulse width, the maximum contrast ratio was as indicated by the circle in FIG. Figure 10
Therefore, the pulse width of 20 μsec (frame frequency 100H, which is normally used in the 1/480 duty voltage averaging method).
It is understood that the effect of the relaxation phenomenon of the liquid crystal has already been exerted in the vicinity of z) by the conventional method, and the contrast ratio is decreased as compared with the present invention.

(Embodiment 3) Average response speed is 80 msec.
(25 ° C) STN liquid crystal display device has 24 row electrodes N
For 0 lines, L = 7, J = 34, K = 8, and L _r = 5, and the selection pulse width corresponding to one selection pattern is 20.
When the driving was performed by the driving method of the present invention using the selection code of Table 11, the maximum contrast ratio was 80: 1 at 25 ° C.

This liquid crystal does not contain difluorostilbene type liquid crystal but contains 61% of tolan type liquid crystal. The overall characteristics are: refractive index anisotropy Δn is 0.229, viscosity η is 17.4 cSt, _Tc was 89.2 ° C. The liquid crystal layer thickness d used was 3.9 μm.

(Example 4) The STN liquid crystal display element of Example 3 was set to L = 7. However, one of the row electrode subgroups was a dummy electrode and the actual electrode was six.
= 40 sub-groups, the selection pulse width corresponding to one selection pattern was set to 20 μsec, and the same selection code as in Example 2 was used to drive by the driving method of the present invention. It became 75: 1.

However, one display cycle was slightly longer because the number of row electrode subgroups was larger than that in Example 3.

Comparative Example 3 The STN liquid crystal display element of Example 3 was subjected to the conventional voltage averaging method at 1/240 duty and 1
When driven with a / 15 bias and a selection pulse width of 20 μsec, the maximum contrast ratio was 55: 1.

(Embodiment 5) Average response speed is 45 msec.
(25 ° C) STN liquid crystal display element, the number of row electrodes N is 2
For 40 lines, L = 7, J = 34, K = 8, L _r = 5
And the selection pulse width corresponding to one selection pattern is 2
When the driving method of the present invention was used for 0 μsec,
The maximum contrast ratio was 54: 1 at 25 ° C.

This liquid crystal contains 44 wt% of the difluorostilbene type liquid crystal and does not contain the tolan type liquid crystal. The overall characteristic is that the refractive index anisotropy Δn is 0.18.
5, the viscosity η was 13.8 cSt and T _c was 92.2 ° C. The liquid crystal layer thickness d used was 4.7 μm.

Sixth Embodiment In the fifth embodiment, as the row electrode selection pattern, the selection pattern shown in Table 10 is used, and the selection pattern to be used is moved to the right in Table 10 every time two row electrode subgroups are selected. The same procedure was performed except that the staggered one was used. The maximum contrast ratio was 54: 1, which was almost the same as in Example 5, but the display unevenness was smaller and a good-looking display was obtained.

(Embodiment 7) In Embodiment 6, the correspondence between the row electrodes in the row electrode subgroup and the elements of the selection pattern was shifted one by one and selected each time one display cycle was completed. The maximum contrast ratio was 54: 1, which was almost the same as that in Example 6, and a display with good appearance with smaller display unevenness than in Example 6 was obtained.

(Comparative Example 4) The STN liquid crystal display element of Example 5 was used in the conventional voltage averaging method at 1/240 duty and 1
When driven with a / 15 bias and a selection pulse width of 20 μsec, the maximum contrast ratio decreased to 11: 1.

(Embodiment 8) An STN liquid crystal display element having an average response speed of 45 msec (25 ° C.) different from that of Embodiment 5 was used.
When the inversion code shown in Table 6 was used as the row electrode selection code and driving was performed with N = 240, L = 3, and a selection pulse width of 23 μsec, the maximum contrast was 50: 1.

This liquid crystal contains 44% by weight of difluorostilbene type liquid crystal and 31% by weight of tolan type liquid crystal. The overall characteristics are that the refractive index anisotropy Δn is 0.187 and the viscosity η is 15. 1 cSt, T _c is 84.9
It was ℃. The liquid crystal layer thickness d used was 4.7 μm.

(Embodiment 9) The STN liquid crystal display element of the embodiment 8 has N = 240, L = 3 and a selection pulse width of 23 μsec.
As a row electrode selection code, a frequency uniformization code was selected and driven by the method of the present invention, and the maximum contrast was 25: 1.

(Embodiment 10) Under the same conditions as in Embodiment 8 except that the selection pulse width is set to 12 μsec in Embodiment 8, the maximum contrast is 62: 1.

(Comparative Example 5) The STN liquid crystal display element of Example 8 was subjected to the conventional voltage averaging method at 1/240 duty and 1
/ 15 bias, frame frequency 90Hz (pulse width 2
When driven for 3 μsec), the maximum contrast ratio was 18: 1.

(Example 11) The STN liquid crystal display element of Example 5 was subjected to RGB color 4-gradation display while shifting the selection pattern as in Example 7. As the selection pattern, the matrix S is used up to the eighth selection pattern in Table 10.
In this case, the one represented by [S, S, S, -S, -S, -S] was used. It was possible to drive with high contrast ratio and small display unevenness.

(Embodiment 12) As the selection pattern in Embodiment 11, the one composed of [S, -S, S, -S, S, -S] was used. Compared with the eleventh embodiment, a display having substantially the same contrast ratio and the degree of display unevenness was obtained.
Some flicker was observed.

[0155]

As described above, according to the present invention, a plurality of selection pulses are dispersed in one frame, so that the voltage averaging method in the conventional simple matrix system has only one selection pulse in one frame. It has become possible to suppress changes in the optical state to a small extent. This is effective in driving a liquid crystal display device having an average response speed of 100 msec or less, particularly 50 msec or less during dynamic driving.

Further, since the present invention basically utilizes the characteristics of the IHAT method, if L ≧ 4, the supply voltage can be reduced as compared with the conventional voltage averaging method. ing.

In this case, the supply voltage is further reduced as L is increased. However, if the number of L is large, the level number (L + 1) of the waveform applied to the column electrode also increases, and the hardware becomes complicated. , So far L is 32 or less, especially 7
Around 15 is preferable.

Further, according to the present invention, the number of selection pulses required for displaying one display data is substantially the same as that of the conventional voltage averaging method. Has an advantage. Further, it has become possible to perform gradation display and color display with a high contrast ratio.

Similarly, with respect to the display uniformity by driving, the effect is large as compared with the conventional voltage averaging method.

In the conventional method, the frequency component of the drive waveform is greatly different depending on the display pattern, which causes display unevenness. However, in the present invention, the variation of the frequency component due to the display pattern is small, and thus display unevenness is less likely to occur. it is conceivable that.

[Brief description of drawings]

FIG. 1 is a graph showing a time-series change in potential for row electrode subgroups R _{1 to} R ₄ according to the selection codes in Table 1.

FIG. 2 is a conceptual diagram showing a display pattern of a liquid crystal display element.

FIG. 3 is a graph showing voltages applied to the column electrodes C ₁ , C ₂ , C ₃ and C ₉ in the display pattern of FIG. 2 according to the selection code of Table 1.

4 is a graph showing the voltages of R ₁ -C ₉ and R ₂ -C _{9 in} the display pattern of FIG. 2 when the selection code of Table 1 is followed.

FIG. 5 is a graph showing an effective value response and a peak value response.

FIG. 6 is a block diagram showing an example of a circuit that realizes the driving method of the present invention.

FIG. 7 is a graph showing a time-series change in the potentials of the row electrode subgroups R _{1 to} R ₃ according to the selection code of Table 4.

FIG. 8 is a graph showing voltage waveforms to be applied to the column electrodes in each display pattern when the selection codes in Table 4 are followed.

FIG. 9 is a graph of contrast ratio change when the selection pulse width is changed by the conventional method and the method of the present invention.

FIG. 10 is a graph of contrast ratio change when the selection pulse width is changed by the conventional method and the method of the present invention.

11 is a graph showing the waveform of the applied voltage on R ₃ in FIG.

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hidemasa Taka Inaka, 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Hideyuki Nagano, Hazawa-machi, Kanagawa-ku, Yokohama 1150 Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Takanori Onishi 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture AZ Technology Co., Ltd.

Claims (9)

[Claims] 1. A method of driving a matrix type liquid crystal display device comprising a plurality of row electrodes and a plurality of column electrodes, wherein J × L row electrodes (J and L are each an integer of 2 or more) are respectively used. This is a driving method that is performed by dividing the row electrode subgroups into J row electrode subgroups and collectively selecting the row electrode subgroups. The row electrode subgroups are selected by satisfying the following conditions. A method for driving a liquid crystal display device, which is characterized by being performed. (1) When selected, a voltage is applied to the row electrodes in the positive or negative direction with respect to the intermediate voltage with an amplitude of V _r (V _r > 0),
The intermediate voltage is applied when not selected. (2) As the selection voltage matrix, the orthogonal matrixes A and -A of L rows and K columns whose elements are +1 corresponding to the voltage + V _r or -1 corresponding to -V _r are selected. Where K is L ≦ K
Is an integer and is the smallest. (3) When the jth row electrode subgroup is selected, the elements of the column vector of the selection voltage matrix (hereinafter referred to as the selection voltage vector) correspond to the voltage amplitudes of the row electrodes forming the jth row electrode subgroup. As such, the voltage is applied. This voltage application is performed for all of the selection voltage vectors. 2. The liquid crystal display element is a liquid crystal display element using a liquid crystal composition containing a difluorostilbene type liquid crystal and / or a tolan type liquid crystal.
A method for driving the described liquid crystal display device. 3. The method of driving a liquid crystal display device according to claim 1, wherein the voltage applied to the column electrodes is (L + 1) voltage levels V ₀ , V ₁ , ..., V _L. And V ₀ <V ₁
<... <V _L, and display data consisting of binary values of the j-th row electrode subgroup in a specific column (where j is an integer varying from 1 to J), L A vector D _j having n elements (where the elements of the vector D _j are 1 for ON or 0 for OFF)
Corresponding to the applied selection voltage vector and the vector D _j in order to display the data represented by the vector D _j when the j-th row electrode subgroup is selected. A driving method of a liquid crystal display element, wherein V _i (i is an integer of 0 to L) is applied to the column electrode, where i is a total of exclusive ORs of the elements. 4. The liquid crystal display device driving method according to claim 3, wherein the display data of the j-th row electrode subgroup in a specific column is replaced by (U +
1) Display data having gradations of U steps (U is a natural number of 2 or more), and the selected voltage matrix has elements of +1 corresponding to the voltage + V _r.
Alternatively, U orthogonal matrices A and −A of L rows and K columns each consisting of −1 corresponding to −V _r are selected (where K is L ≦
K is assumed to be the smallest and smallest), and by displaying a total of U on and off at a predetermined ratio,
A driving method of a liquid crystal display device, which is characterized by performing gradation display of (U + 1) steps. 5. A selection voltage is applied to the next row electrode subgroup every time a voltage corresponding to one selection voltage vector forming the selection voltage matrix is applied to the row electrode subgroup. The method for driving a liquid crystal display element according to claim 1, wherein 6. The selection voltage matrix for selecting one row electrode sub-group is a selection voltage matrix for selecting another row electrode sub-group, wherein the vectors are arranged in a different order. Item 6. A method for driving a liquid crystal display device according to any one of items 1 to 5. 7. The selection voltage matrix A used in the previous data display cycle, which is formed by replacing the rows, is used again as the selection voltage matrix in the next display cycle. 13. A method for driving a liquid crystal display device according to any one of items. For 8. row electrode subgroups composed of L _r of row electrodes (L _r <L), claims and drives the addition of (L-L _r) of row electrodes virtually Items 1-7
13. A method for driving a liquid crystal display device according to any one of 1. 9. The liquid crystal display element according to claim 1, wherein some of the L row electrodes forming the row electrode subgroup are virtual electrodes. Driving method.