JP3233562B2 - Driving method of liquid crystal panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal panel, and relates to a matrix type used for various OA equipment and multimedia terminals such as personal computers and word processors, as well as game equipment and AV (audiovisual) equipment. The present invention relates to a driving method for performing gradation display on a liquid crystal panel.

[0002]

2. Description of the Related Art Conventionally, T which responds to an effective voltage
N (Twisted Nematic) liquid crystal and STN (Super Twisted
Nematic) A simple matrix type liquid crystal panel using liquid crystal has adopted a line sequential driving method. In this driving method, a selected row voltage is applied to the row electrodes so that row electrodes as scanning lines are sequentially selected one by one, and in synchronization with the selection of the row electrodes, a column electrode as a data line is applied to the column electrodes. , A column electrode voltage corresponding to the display data of the pixel on the selected row electrode is applied.

Further, with the recent development of multimedia, S
In the process where the high-speed response of the TN liquid crystal is advanced, ST
The possibility of displaying moving images with N liquid crystals has begun to appear, and with the realization of colorization of liquid crystal displays, there has been a demand for STN liquid crystals to provide color multi-gradation display such as television image display and amusement image display. Have been.

[0004] However, in a liquid crystal panel having a high-speed response to which a conventional line-sequential driving method is applied, the influence of a frame response becomes larger with an increase in the number of scanning lines.
The contrast decreases. Therefore, in view of such a factor of lowering the image quality, two driving methods for reducing the influence of the frame response have been proposed in recent years.

One is a method of simultaneously selecting and driving all the row electrodes constituting the display panel, which is called an active address method (TJScheffer e).
t al.; "Active Addressing Method for High-Contrast
Video-Rate STN Displays ", SID 92 DIGEST, p228).

The other is a method of dividing all the row electrodes constituting the display panel into a plurality of blocks and simultaneously selecting and driving all the row electrodes in each block, which is called a multiple line selection method. (TNRuckmongathan et
al.; "A New Addressing Technique for Fast Respond
ing STN LCDs ", JAPAN DISPLAY '92, p. 65).

[0007] The basic principle of image display by these two driving methods is that an orthogonal transformation of image data is performed using an orthogonal matrix represented by a Hadamard matrix or a Walsh matrix, and the orthogonally transformed image data is converted into a liquid crystal. Inverse conversion is performed on the panel. The liquid crystal drive waveform is such that a plurality or all of the row electrodes are simultaneously selected during one frame period. As described above, in the above two driving methods, a plurality of small scan selection pulses are dispersed and applied to one row electrode within one frame period, so that high-speed response is achieved by utilizing the cumulative response effect of the liquid crystal. High contrast is achieved.

As a gradation display method, a frame modulation method and a pulse width modulation method are widely used for the line sequential driving method. Here, the frame modulation method is basically a method in which an ON display voltage and an OFF display voltage are selectively applied to a pixel over a plurality of frames, and two or more gray scales are provided using temporal averaging. However, this modulation method has a problem that flicker, a waving phenomenon, and the like increase when this method is employed in a liquid crystal panel having a high-speed response.

The pulse width modulation method is a method of modulating the pulse width of a gradation voltage applied to a pixel to give two or more gradations. In this modulation method, a driving waveform of a large liquid crystal panel is particularly increased. Problems such as easy display unevenness due to high-frequency components become prominent.

[0010] Therefore, in order to drive such a high-speed responsive liquid crystal panel, a plurality of lines or all lines are selected and driven. JP-A-6-1
An amplitude modulation method such as that described in Japanese Patent No. 38854 has been proposed.

The modulation schemes disclosed in these publications are based on the same driving principle, and the amplitude modulation scheme will be briefly described below.

The amplitude modulation method is a method of performing gradation display by changing a voltage amplitude applied to a pixel according to gradation information of display data. Here, the effective voltage applied to the pixel can be changed by changing the amplitude of the column voltage.

However, since the effective voltage values of all the pixels on the column electrode differ depending on the contents of the display data, if the amplitude of the column voltage is simply changed, the effective voltage value of each pixel will not be constant. In addition, non-uniform crosstalk occurs due to display information.

Therefore, in the amplitude modulation method, a driving method is adopted in which the influence of the change in the amplitude of the column voltage on the pixels in the non-selected state is canceled within one frame.

Here, the j-th row electrode block of a plurality of row electrode blocks obtained by dividing all the row electrodes of the liquid crystal panel into L row electrodes is used.
A display data group corresponding to the row electrode block is _converted into a column display vector D _j having L elements (display data) I _ij.
(See equation (1)). Further, each element I _ij of the column vector D _j takes a value between a value 1 indicating OFF display and a value −1 indicating ON display according to the degree of gradation.

In this driving method, a signal G _j (t) (see equation (2) and FIG. 11) obtained by converting the column display vector D _j by an orthogonal matrix F (see FIG. 9) is applied to the column electrode. By substantially applying a signal V _j (t) (see equation (4)) to which two types of correction signals H shown in (3) are added, gradation display is performed. Note that G _j (t) and V _j (t)
Is a generalized value corresponding to each pixel for the number M of column electrodes.

Here, in the first half of one frame period, a positive correction signal is added to the orthogonally transformed signal, and in the second half, a negative correction signal is added. The influence of the change in the amplitude on the pixels in the non-selected state is canceled. However, the method of using the positive and negative correction signals is not limited to this. For example, a positive correction signal is used in the first frame period of two consecutive frame periods, and a negative correction signal is used in the next frame period. In this case, the influence of the change in the amplitude of the column voltage on the pixels in the non-selected state can be canceled in two frame periods.

[0018]

(Equation 1)

[0019]

(Equation 2)

[0020]

(Equation 3)

[0021]

(Equation 4)

FIG. 2 is a view for explaining the structure of a conventional liquid crystal display device. In the figure, reference numeral 200 denotes a conventional liquid crystal display device of a multiple line selection drive system. In the amplitude modulation method, a driving method is employed in which the variation of the effective voltage value of each pixel which causes the occurrence of non-uniform crosstalk is canceled within one frame.

The details will be described below.
As shown in FIG. 6, N row electrodes 62 and M column electrodes 61 are arranged so that their intersections are arranged in a matrix, and the row electrode 62 and the column electrode 61 at each intersection are arranged as shown in FIG. , A liquid crystal panel 6 sandwiching a display medium (liquid crystal layer) responsive to an effective voltage value, and applying a voltage having a waveform based on an orthogonal matrix F (see FIG. 9) to a column electrode 61. , And a plurality of row electrodes 62 simultaneously selected and driven. Here, the liquid crystal panel 6 corresponds to FIG.
, J row electrode blocks B ₁ , B ₂ , ..., B _j , ..., so that L row electrodes 62 form one group.
B _J is divided into the row electrode 62 constituting the liquid crystal panel 6 is adapted to be simultaneously selected for each L present for each row electrode block B _j.

The liquid crystal display device 200 includes an orthogonal matrix generator 1 for generating a row signal corresponding to a selected row voltage based on the orthogonal matrix F, and receives an output from the orthogonal matrix generator 1 and receives the output from the liquid crystal panel. A plurality of row drivers 5a and 5b for driving six row electrodes 62 are provided.

Further, the liquid crystal display device 200 includes a frame memory 2 for storing a matrix I (see FIG. 8) composed of a group of display data for one frame corresponding to pixels arranged in a matrix, and a plurality of row electrodes. , A column signal vector F (t) of an orthogonal matrix F whose elements are row signals applied simultaneously.
When, and a orthogonal transform circuit 3 taking the sum of the exclusive logical sum of the column display vector D _mj matrix I _B (see FIG. 10) whose elements are the display data I _imj. Here matrix I _B to the display data elements shown in FIG. 10, those from the matrix I consisting of one frame of the display data group shown in FIG. 8, was taken out element corresponding to the j-th row electrode blocks B _j It is.

It should be noted that D _j shown in the above equation (1) is
Is a generalization of the column display vector D _mj of the matrix shown in FIG. 4 for M column electrodes, that is, the column display vector D _j in the above equation (1) is obtained for all the column electrodes of the j-th row electrode block. Column display vectors D _1j , D _{2j ,.}
D _mj ,..., D _Mj.
Elements I _1j, I _2j in the formula, ..., I _ij, ..., I _Lj is the first row of display data matrix I _B for the j-th row electrode block shown in FIG. 10, the second row, ..., the L rows Are representative of each element.

The liquid crystal display device 200 performs a sum of squares calculation and a square root calculation for obtaining a correction signal voltage (see the above equation (3)) required for gradation display using an amplitude modulation method. A gradation correction operation circuit 8, an adder 9 for adding the operation results output from the orthogonal transformation circuit 3 and the gradation correction operation circuit 8, and a DA for DA-converting the output of the adder 9
It has a (digital-analog) converter 10 and a plurality of column drivers 4a, 4b, 4c for driving column electrodes of the liquid crystal panel 6 according to the output of the converter.

Next, the operation will be described.

In the liquid crystal display device 200 having such a configuration, in the display data matrix I (see FIG. 8) of N rows × M columns written in the frame memory 2, it corresponds to the one row electrode block _Bj . Display data matrix I of L rows × M columns
The element (display data) I _{imj of B} (see FIG. 10) is read in the column direction, and the orthogonal transformation circuit 3 and the gradation correction operation circuit 8 are read out.
Is output to At this time, the orthogonal matrix generator 1 uses the orthogonal matrix F to generate a row signal F (i, t) corresponding to the selected row voltage.
(See FIG. 9) is generated and output to the orthogonal transformation circuit 3.

Then, in the orthogonal transformation circuit 3, the column signal vector F (t) of the matrix F having the row signal as an element and the display data I _ij (I _imj : m = 1 to _M from the frame memory 2)
String display vector D of the matrix I _B for the representative values) and elements
_j (D _mj : representative value of m = 1 to M), and the sum G of exclusive OR of corresponding elements of both column vectors
_j (t) (G _mtj : representative value of m = 1 to M) is obtained (see FIG. 11). The sum G _j (t) of the exclusive OR is
A transform representative data orthogonal transform matrix I _B which is composed of a display data group, which corresponds to all combinations of the column signal vector F (t), a column display vector D _j are determined.

At this time, in the gradation correction operation circuit 8, based on the column display vector D _j read from the frame memory 2, the correction value H shown in the above equation (3) is calculated for each column display vector D _j. Required.

Then, the adder 9 adds the transformed display data G _j (t) obtained by orthogonally transforming each column display vector and the correction value H corresponding to each column display vector, and the added value is substantially calculated. The voltage value V to be applied to the column electrode
_j (t), the column driver 4 via the DA converter 10
a, 4b, and 4c. Thus, each column driver outputs a drive signal corresponding to the voltage value V _j (t) to the column electrode.

At this time, the row drivers 5a and 5b output the column signal vector F of the orthogonal matrix used for the orthogonal transformation.
A voltage corresponding to the element F (i, t) of (t) is output as L selected row voltages in synchronization with the column electrode drive signal.

As a result, the converted display data is inversely converted on the liquid crystal panel 6, and a gradation display corresponding to the original display data is performed.

[0035]

However, in a liquid crystal display device employing a conventional amplitude modulation method, a square sum calculation is required to obtain a predetermined gradation correction voltage H as shown in the above equation (3). It is necessary to perform square root calculation, and as a means for realizing this, it is necessary to use a complicated circuit such as a gradation correction operation circuit 8 and an adder 9 as shown in FIG.

In general, the solution of the square root calculation is irrational, and it is necessary to increase the number of effective bits in terms of accuracy. Therefore, it is necessary to use a high-precision DA converter 10 constituting the liquid crystal display device. Was.

As described above, the liquid crystal display device employing the conventional amplitude modulation method has a problem that the circuit scale is further increased, and as a result, the power consumption is increased and the cost is increased.

The present invention has been made to solve the above problems, and can suppress flicker and crosstalk which occur in the frame modulation system without increasing the circuit scale. It is an object of the present invention to obtain a liquid crystal display device which can display multi-gradation display at low power consumption.

[0039]

According to a first aspect of the present invention, there is provided a method of driving a liquid crystal panel in which a plurality of row electrodes and a plurality of column electrodes are arranged such that their intersections are arranged in a matrix. A liquid crystal panel comprising a display medium responsive to an effective voltage value between a row electrode and a column electrode at each intersection.
In this method, a voltage having a waveform based on an orthogonal matrix is applied to a column electrode and a plurality of row electrodes selected at the same time to drive.

According to this driving method, the table corresponding to the i-th row in the entire area of one frame of the display image or the block area obtained by dividing the one frame of the display image in the vertical scanning direction is used.
The display data indicates the display off corresponding to the gradation level.
Switch between a value of +1 and a value of -1 indicating display ON.
Assuming values that do not require calculation,
Y (≧ 1) virtual rows for each of the row electrodes
And for each assumed virtual row,
No need to calculate open / close of virtual data corresponding to each display data
A / b (a and b are integers),
Moreover, the square of the corresponding display data and the display data
Is the sum of the squares of all virtual data with
Each is assumed to be a constant value P near one.

[0041] In this driving method, sequentially applied to the display data, the virtual data is also included to orthogonal transformation by using the orthogonal matrix, the column voltage corresponding to the converted display data the orthogonal transformation to all the column electrodes And simultaneously selecting all the rows of electrodes corresponding to the entire area or the block area of the one frame of the display image and removing columns corresponding to virtual rows from the orthogonal matrix used for the orthogonal transformation. By sequentially applying a row signal corresponding to a vector element as a row selection pulse, the converted display data is inversely converted on the liquid crystal panel, and a gradation display indicated by the original display data is performed. Thereby, the above object is achieved.

According to a second aspect of the present invention, in the method for driving a liquid crystal panel, the orthogonal transformation includes, as an orthogonal matrix, a half of the number of rows including simultaneously selected row electrodes and virtual rows. Is used.

In the method of driving a liquid crystal panel according to the present invention (claim 3), a plurality of row electrodes and a plurality of column electrodes are arranged such that their intersections are arranged in a matrix, and each intersection is arranged in a matrix. This is a method of driving a liquid crystal panel having a display medium responsive to an effective voltage value between a row electrode and a column electrode by applying a waveform voltage based on an orthogonal matrix to the column electrode and the row electrode.

In this driving method, the display data corresponding to the i-th row in the entire area of one frame of the display image is
In accordance with the degree of gradation, a value indicating display off +1 and a display off
Values that do not require opening and closing calculations
Each of the plurality of sequentially selected row electrodes is assumed.
On the other hand, assuming Y (≧ 1) virtual rows,
For each supposed virtual line, there is a corresponding
The corresponding virtual data is converted to a / b (a and
And b are integers), and the corresponding
The square of the display data and all temporary
The sum of the squares of the hypothetical data and the square is not always 1 but constant around 1
Each is assumed to be the value P.

[0045] In this driving method, the display data for the respective row electrodes, the virtual data is also included to orthogonal transformation by using the orthogonal matrix, all the column electrodes a column voltage corresponding to the converted display data the orthogonal transform Are sequentially applied, and a row signal corresponding to a column vector element of a matrix excluding an element corresponding to a virtual row in the orthogonal matrix used for the orthogonal transformation is applied to each row electrode of the entire area of the display image 1 frame. By sequentially applying the converted display data as a row selection pulse, the converted display data is inversely converted on the liquid crystal panel, and gradation display indicated by the original display data is performed. Thereby, the above object is achieved.

The operation of the present invention will be described below.

In the present invention (claim 1), one or a plurality of virtual rows are assumed for each of a plurality of row electrodes selected at the same time, and virtual data is assumed corresponding to each virtual row. Since the sum of the squares of the display data corresponding to each row electrode and the virtual data of the virtual row corresponding to each row electrode is constant and each virtual data is a rational number, the virtual data is set. When each row electrode and a virtual row assumed for each row electrode are collectively viewed, the effective applied voltage corresponding to the display data applied to each row electrode in one column electrode and the corresponding virtual row is Is constant for all row electrodes regardless of the display data. Thus, it is possible to prevent a change in the amplitude of the column voltage in the amplitude modulation method from affecting the pixels in the non-selected state.

Further, since rational numbers can be set as the values of the respective virtual data, an arithmetic circuit for performing a complicated operation such as a square sum calculation or a square root calculation is not required, and the converted display data after the orthogonal transformation is also a rational number. Therefore, the converted display data can be supplied to the column driver without performing a process such as DA conversion.

As a result, it is possible to obtain a liquid crystal display device capable of multi-tone display with a simple and inexpensive system configuration.

In the present invention (claim 2), in the orthogonal transformation, an orthogonal matrix having half the number of rows including simultaneously selected row electrodes and virtual rows is used as the orthogonal matrix. Accordingly, the scale of the orthogonal transform circuit can be reduced.

In the present invention (claim 3), one or a plurality of virtual rows are assumed for each row electrode sequentially selected, and virtual data is assumed to correspond to each virtual row. Virtual data is set so that the sum of the squares of the display data to be displayed and the virtual data of the virtual row corresponding to each row electrode is constant and each virtual data is a rational number. When the assumed virtual rows for each row electrode are viewed together, the effective applied voltage corresponding to the display data applied to each row electrode in one column electrode and the corresponding virtual row is:
It is constant for all row electrodes regardless of the display data.
Thereby, in the liquid crystal display device of the line sequential drive system,
By the amplitude modulation method, multi-gradation display can be performed while preventing a change in the amplitude of the column voltage from affecting a pixel in a non-selected state.

Further, in this case, since a rational number can be set as a value of each virtual data, an arithmetic circuit for performing a complicated operation such as a square sum calculation or a square root calculation is not required.
Since the transformed display data after the orthogonal transformation is also a rational number, the transformed display data can be supplied to the column driver without performing a process such as DA conversion.

As a result, it is possible to obtain a liquid crystal display device of a line-sequential drive system capable of multi-gradation display with a simple and inexpensive system configuration.

[0054]

Embodiments of the present invention will be described below.

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a diagram for explaining a method of driving a liquid crystal panel according to the present invention, and shows a block configuration of a liquid crystal display device employing the driving method.

In the figure, reference numeral 100 denotes a liquid crystal display device employing the liquid crystal panel driving method of the present invention. The liquid crystal display device 100 includes a data conversion circuit 7 for converting display data from a frame memory. The output of the circuit 7 is supplied to the orthogonal transformation circuit 3, and a gradation correction operation circuit for performing a complex square sum calculation and a square root calculation for obtaining a correction value H in the conventional liquid crystal display device 200 shown in FIG. 8 and an adder 9 for adding the operation result and the orthogonal transformation result are not used, and each column driver 4a,
A DA converter 10 for DA-converting a signal to be input to the column driver in a stage preceding 4b and 4c is also omitted.

The data conversion circuit 7 has a circuit configuration including a ROM (Read Only Memory) or a decoder circuit including a gate element and a multiplexer circuit. In this data conversion circuit 7, the L from the frame memory 2 corresponding to each row electrode block B _j (see FIG. 7)
A predetermined conversion process is performed on the display data groups I _i = (I ₁ ,..., I _L ), and these display data groups are newly L × (Y + 1) data groups D ′ _j = (I ₁ , ...,
I _L , α ₁₁ , ..., α _L1 , α ₁₂ , ..., α _L2 , ..., α _1Y ,
.., Α _LY ). Here, α _iy is virtual data, and its value is obtained from the following two relational expressions. Here, the display data group I _i and the data group D ′ _j represent a generalized case where Y virtual rows are provided for each of the M column electrodes.

[0058] _{^{I i 2 + α i1 2 +}} α i2 2 + ... + α iy 2 + ... + α iY 2 = P ··· (A) α iy = a / b also (a, b is an integer) ··· (B) , The orthogonal matrix generator 1 extracts L × (Y + 1) row vectors from a K (= 2 ^S ) -order square orthogonal matrix, that is, a matrix F ′ having L × (Y + 1) rows and K columns, into a ROM
Alternatively, it is configured to generate using a counter circuit or a decoder circuit using a gate element or the like. here,
L × (Y + 1) is the total number of simultaneously selected L row electrodes corresponding to each row electrode block, and Y virtual rows provided for each selected row, and K is L × (Y + 1). ) Or more.

Further, the orthogonal transformation circuit 3 includes a column vector element F ′ (t) of the matrix F ′ output from the orthogonal matrix generator 1 and a data group D output from the data conversion circuit 7. ' _j , the data group D' _j is orthogonally transformed using the output F' (t) to determine the column electrode voltage level.

Further, a plurality of column drivers 4a, 4b, 4c
Drives the column electrodes of the liquid crystal panel 6 based on the column electrode voltage output from the orthogonal transform circuit 3.

The plurality of row drivers 5a and 5b output the output F '(t) from the orthogonal matrix generator 1 in synchronization with the data group D' _j being supplied from the orthogonal transformation circuit 3 to the column driver. ), The row electrodes of the liquid crystal panel 6 are driven based on the output.

Next, the function and effect will be described.

First, the operation of the liquid crystal display device 100 according to the first embodiment will be briefly described.

In the liquid crystal display device 100, a display data matrix I of N rows × M columns written in the frame memory 2 is used.
8 (see FIG. 8), the display data matrix I _B (see FIG. 10) of L rows × M columns corresponding to the one row electrode block B _j is read in the column direction and output to the data conversion circuit 7. Is done. Then, the data conversion circuit 7 performs a predetermined conversion process on the _L display data groups I _i = (I ₁ ,..., I _L ) corresponding to each row electrode block B _j from the frame memory 2. Then, these display data groups are newly L
× (Y + 1) data D ′ _j = (I ₁ ,..., I _L ,
α ₁₁ ,…, α _L1 , α ₁₂ ,…, α _L2 ,…, α _1Y ,…,
α _LY ) is output to the orthogonal transformation circuit 3.

At this time, in the orthogonal matrix generator 1, K (= 2
^S ) A matrix F ′ is generated by extracting L × (Y + 1) row vectors from the next square orthogonal matrix, and is output to the orthogonal transformation circuit 3.

Further, in the orthogonal transformation circuit 3, a column signal vector F '(t) of a matrix F' having row signals as an element and a matrix D' _j having data group D' _j from the data conversion circuit 7 as an element. ', The sum V of the exclusive OR of the corresponding elements of the two column vectors
_col (t) is required. Sum V of the exclusive OR
_col (t) is transform data obtained by orthogonally transforming the data group D' _j , and data corresponding to all combinations of the column signal vector and the column data vector is obtained.

The level of the column electrode voltage, which is the output of the orthogonal transform circuit 3, is supplied to the column drivers 4a, 4b, and 4c, whereby each column driver outputs the voltage value V _col (t). Is output to the column electrodes.

At this time, from the row drivers 5a and 5b, the elements of the column signal vector F '(t) of the orthogonal matrix used for the orthogonal transform are synchronized with the drive signals of the column electrodes for L lines. Is output to the row electrode of one row electrode block as the selected row voltage.

As a result, on the liquid crystal panel 6, the converted display data is inversely converted, and gradation display corresponding to the original display data is performed.

Next, the operation when the example of the solution satisfying the above relational expressions (A) and (B) is specifically set will be described.

[0071] First, the number of gradation level of the display data I _i is 4
The case where the gradation is (1, 1/3, -1/3, -1) will be described. Table 1 shows an example of a solution satisfying the above relational expression in this case.

[0072]

[Table 1]

In this example, the virtual row is each selected row (row electrode)
(Y = 1), and the virtual data α _i1 is set to a value that does not require the square root calculation for each gradation level, similarly to the display data I _i .

In the example of this solution, only one virtual row (Y = 1) needs to be provided for each selected row, and the sum of squares (= P) of the display data and the virtual data is represented by the display content. Irrespective of, the constant value (P = 10/9 in Table 1) is always maintained, so that non-uniform crosstalk does not occur.

[0075] Examples of the above solution, a simultaneous selection number L is 4, a description will be given of a specific circuit operation when applied to the case given the display data I _i, as shown in FIG.

FIG. 3 shows the display data I _i for a certain four rows selected simultaneously and the virtual data α _i1 based on Table 1 above.
In FIG. 3, the pixel density corresponds to the gradation level.

The four display data I _i = (1, 1/3, − ／, −1) output from the frame memory 2 are input to the data conversion circuit 7. The data conversion circuit 7 refers to the ROM in which the virtual data based on Table 1 has been written in advance from these input data, and _obtains eight new data D ' _j1 = (1,1 / 1 /
3, -1/3, -1, 1/3, 1, -1, -1/3) are created. Here, a ROM is used to create display data including virtual data, but the present invention is not limited to this, and a decoder circuit or a multiplexer circuit using gate elements or the like can be used.

In the orthogonal matrix generator 1, eight rows and eight columns represented by the following equation (5) are applied to the selected four row electrodes and one virtual row provided for each selected row. Orthogonal matrix F ₁
Generate

[0079]

(Equation 5)

The first to fourth rows in the above equation (5) correspond to the selected four row electrodes, and the fifth to eighth rows correspond to the four virtual rows. The orthogonal transformation circuit 3 orthogonally transforms the input data D ′ _j1 using the orthogonal matrix F ₁ , and determines the column electrode voltage level V _col (t) represented by _Expression 6.

[0081]

(Equation 6)

Here, D ′ _j1 (s) is the input data D ′
_{j 1} is an individual value, F ₁ (s, t) is an element of the orthogonal matrix F ₁ , and s is an integer of 1 to 8.

As a result of driving an actual liquid crystal panel by the above-described method, a high-quality four-gradation display with very little flicker and crosstalk was obtained.

In the orthogonal matrix F ₁ used in this example,
The influence of the fifth row vector, since the DC component to the liquid crystal panel 6 is to be applied, so that this effect does not appear, prevented the deterioration of liquid crystal by inverting the polarity of the orthogonal matrix F ₁ for each frame .

(Embodiment 2) Next, Embodiment 2 of the present invention
A method for driving a liquid crystal panel according to the present invention will be described.

The liquid crystal display device to which the driving method of the second embodiment is applied is configured to display an image with the number of gradation levels of the display data being 8 gradations, and the other constitutions are the same as those of the liquid crystal display device of the first embodiment. It is the same as the display device 100. For this reason, in the description of the second embodiment, portions that are the same as those in the first embodiment will be omitted.

[0087] In the second embodiment, the gradation level number is 8 gradation display data _{I i (1,5 / 7,3 / 7,1} / 7, -
1/7, −3/7, −5/7, 11), and the circuit operation in this case will be described below. Table 2 shows an example of a solution satisfying the above relational expressions (A) and (B) in this case.

[0088]

[Table 2]

In the example of this solution, there are two (Y = 2) virtual rows for each selected row, and the virtual data α _i1 and α _i
i2, like the display data I _i, is set to a value that does not require Unexamined calculated for each tone level. Further, the sum of squares (= P) of the display data and the virtual data is always kept at a constant value (P = 50/49 in Table 2) irrespective of the display contents, so that non-uniform crosstalk does not occur.

[0090] Examples of the above solution, a simultaneous selection number L is 4, a description will be given of a specific circuit operation when applied to the case given the display data I _i, as shown in FIG.

FIG. 4 shows the display data I _i for a certain four rows selected simultaneously and the virtual data α _i1 based on Table 2 above.
And α _i2 , and in FIG. 4, the pixel density corresponds to the gradation level.

The four display data I _i output from the frame memory 2 = (1, 3/7,-1/7, -5 /
7) is input to the data conversion circuit 7. The data conversion circuit 7 refers to the ROM in which the virtual data based on Table 2 is written in advance from these input data, and obtains 12 new data D ′ _j2 including the virtual data.
= (1,3 / 7, -1 / 7, -5 / 7,1 / 7,5 /
7, −1, −5/7, 0, 4/7, 0, 0). Here, a ROM is used to create display data including virtual data, but the present invention is not limited to this, and a decoder circuit or a multiplexer circuit using gate elements or the like can be used.

In the orthogonal matrix generator 1, for the four selected row electrodes and two virtual rows provided for each selected row, 12 orthogonal rows of 16 rows and 16 columns are obtained. An orthogonal matrix of 12 rows and 16 columns is generated by extracting a row vector.
The following equation (7) represents an example of such an orthogonal matrix.

[0094]

(Equation 7)

The first to fourth rows in the above equation (7) correspond to the selected four row electrodes, and the fifth to twelfth rows correspond to eight virtual rows. The orthogonal transformation circuit 3 orthogonally transforms the input data D ′ _j2 using the orthogonal matrix F ₂ , and determines a column electrode voltage level V _col (t) represented by the following equation (8). .

[0096]

(Equation 8)

Here, D ′ _j2 (s) is the input data D ′
_{j 2} is an individual value, F ₂ (s, t) is an element of the orthogonal matrix F ₂ , and s is an integer of 1 to 12.

As a result of driving an actual liquid crystal panel by the above method, a high-quality 8-gradation display with extremely little flicker and crosstalk was obtained.

In this example, since the orthogonal matrix F ₂ containing no DC component was used, the polarity inversion for each frame was unnecessary, but an orthogonal matrix containing the DC component as shown in the above equation (5) is used. In this case, it is necessary to invert the polarity of the orthogonal matrix for each frame so that no DC component is applied to the liquid crystal panel.

(Embodiment 3) Next, Embodiment 3 of the present invention.
A method for driving a liquid crystal panel according to the present invention will be described.

In the liquid crystal display device to which the driving method according to the third embodiment is applied, similar to the first embodiment, an image is displayed by setting the number of gradation levels of the display data to four. However, in the four-gradation display method described in the first embodiment, the column electrode voltage is obtained by performing a predetermined orthogonal transformation on the display data and the virtual data using an 8 × 8 orthogonal matrix. On the other hand, in the third embodiment, orthogonal transformation is performed on display data and virtual data using an orthogonal matrix of 4 rows and 8 columns.

The driving principle of the third embodiment will be described below.

The 8-row, 8-column orthogonal matrix (see equation (5)) used in the first embodiment includes a 4-row, 8-column matrix from the first row to the fourth row, and a 5-row to 8-row matrix. Is divided into two matrices, that is, a matrix of 4 rows and 8 columns. Comparing the former and the latter column vectors, the first to fourth columns are the same, and the fifth to eighth columns have the same sign. It turns out that it is only inverted. From this and the above equation (6), the following (9)
A) and (9B) are derived.

[0104]

(Equation 9)

That is, the expressions (9A) and (9B) are
The display data of the selected row and the virtual data of the virtual row corresponding thereto are added in advance, and a predetermined orthogonal transformation is performed using an orthogonal matrix of 4 rows and 8 columns to determine the column electrode voltage. Means.

More specifically, the first half of one frame period is the first half.
In the first cycle, the above (9A)
Determine the column electrode voltage level V _col (t) using the equation:
The second cycle of the second half of one frame period is referred to as a second cycle.
In the cycle, the level V _col (t) of the column electrode voltage is determined by using the above equation (9B), and the orthogonality of the display data for a predetermined row electrode block corresponding to one frame is determined by both the first and second cycles. The conversion is completed.

Here, one frame period is divided into the first half and the second half, and the column electrode voltage level V _col (t) is determined. However, the column electrode voltage is determined using two different orthogonal transformation equations as described above. The method for determining the voltage level is not limited to this. For example, in the first frame period of two consecutive frame periods, the level V _col (t) of the column electrode voltage is determined using the above equation (9A), and in the next frame period, the above equation (9B) is used. And the column electrode voltage level V _col
(T) may be determined. In this case, the orthogonal transformation of the display data is completed in the two consecutive frame periods.

Table 3 shows the result of addition of the display data of the selected row and the virtual data of the corresponding virtual row in the driving method of the third embodiment.

[0109]

[Table 3]

From Table 3, (I _i + α _i1 ) and (I _i −
α _i1 ) is (D ′ _j1 (s) +
D ' _j1 (s + 4)) and (D' _{j in the} above equation (9B))
_j1 (s) −D ′ _j1 (s + 4)),
It can be seen that both are expressed as binary data. These values may be written to the ROM or the like in the data conversion circuit 7 for the gradation display data as in the first embodiment.

By the way, when the display by the binary (no gradation) data is originally performed by the four-line selection driving method, (+
The column electrode voltage level obtained by orthogonally transforming the binary data using an orthogonal matrix having elements 1) and (-1) is 5 (=
It becomes the number of selected lines + 1) level. Therefore, the above (9)
A) and (9B), the conversion _yields (I _i + α _i1 )
And (I _i −α _i1 ), five levels are similarly obtained as orthogonal transformation results. Also here
Since the absolute value of the value (I _i + α _i1) is twice the absolute value of the value (I _i -α _i1), the relative (I _i + α _i1) 1
The second, third, and fourth levels of the first to fifth column electrode voltage levels correspond to the first, third, and third levels of the first to fifth column electrode voltage levels corresponding to the value (I _i −α _i1 ). 5, and these values (I _i + α _i1 ) and (I _i −α _i1 )
There are three common levels of column electrode voltage.

For this reason, in the third embodiment, four gradation display can be performed using the above values (I _i + α _i1 ) and (I _i −α _i1 ) as the display data. 5 + 5
-3) Four-gradation display is possible with only one column electrode voltage level.

As a result of driving the actual liquid crystal panel by the driving method according to the third embodiment, a high-quality display with very little flicker and crosstalk was obtained as in the first embodiment.

Further, needless to say, by performing the same data conversion even when the number of gradation levels is increased, a high-quality multi-gradation display with extremely little flicker and crosstalk can be obtained.

As described above, Embodiments 1 to 5 of the present invention
In No. 3, there is no need to perform a square sum calculation or a square root calculation to determine the level of the column electrode voltage, and the square sum calculation and the square root calculation for obtaining the gradation correction voltage, which are required in the conventional method, are performed. This eliminates the need for a complicated circuit configuration and a high-precision DA converter that increases the number of effective bits in terms of accuracy. Thus, a multi-gradation display can be achieved with a simple and inexpensive system configuration.

Here, the correlation between the value of the constant P in the above-mentioned relational expression (A) and the on / off ratio of the liquid crystal applied voltage is shown in FIG.
Shown in The horizontal axis in FIG. 5 shows the value of the constant P, and the vertical axis shows the on / off ratio of the liquid crystal applied voltage. The on / off ratio of the liquid crystal applied voltage shown here is a value when a liquid crystal panel having 480 row electrodes is driven by dividing the screen into upper and lower screens (that is, a duty ratio of 1/240). The maximum on / off ratio is 1.066.

Therefore, it is understood that it is preferable to set the value of the constant P to a value as close to 1 as possible. However, in practice, there is no problem if the on / off ratio of the liquid crystal applied voltage of 1.06 or more is obtained, that is, the constant P is set to a value within about 1.22.

In the above-described embodiment, the number of gradations is four.
Although the description has been given of the case where the level is 8 levels and the duty ratio is 1/240, the present invention is not limited to this, and can be widely applied to other gradation numbers, duty ratios 1/300, 1/480, and the like. In such a case, if the value of the constant P is set so that an on / off ratio of about 99.5% or more with respect to the maximum on / off ratio of the liquid crystal applied voltage can be obtained, A high-quality image display can be obtained without any problem.

In each of the embodiments described above, the driving method for simultaneously selecting a plurality of lines has been described. However, the present invention is not limited to this driving method, and can be applied to a conventional line-sequential driving method.

For example, an orthogonal matrix F ₃ ((1
By using the formula (0)), multi-gradation display is possible even in the line sequential driving method.

[0121]

(Equation 10)

That is, the first row in the above formula (10) may be made to correspond to the row electrodes to be sequentially selected, and the second row may be made to correspond to the virtual row provided one by one (Y = 1) for each row electrode. .

At this time, as the orthogonal matrix for performing the orthogonal transformation of the display data and the virtual data, the orthogonal matrix F ₃ and the orthogonal matrix −F _{3 in} which the signs of all the elements are inverted are used together. Thereby, the AC driving of the liquid crystal panel can be performed so that the DC component is not applied to the liquid crystal panel.

[0124]

As described above, according to the liquid crystal panel driving method according to the present invention, the circuit scale is greatly reduced as compared with the conventional liquid crystal display device employing the gray scale driving method, and the power consumption is low and the cost is low. A liquid crystal display device capable of multi-gradation can be obtained. Also,
Since the amplitude modulation method is also used in the present invention, there is an effect that a high-quality image display with very little flicker and crosstalk as occurs in the frame modulation method can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a driving method of a liquid crystal panel according to an embodiment of the present invention, and shows a block configuration of a liquid crystal display device to which the driving method is applied.

FIG. 2 is a block diagram illustrating a liquid crystal display device of a multi-line selection drive system to which a conventional amplitude modulation system is applied.

FIG. 3 is a diagram showing display data and virtual data in a case where an image is displayed by a four-gradation display method in a liquid crystal display device employing the driving methods according to the first and third embodiments of the present invention.

FIG. 4 is a diagram showing display data and virtual data when an image is displayed by an 8-gradation display method in a liquid crystal display device employing a driving method according to a second embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a value of a sum of squares of display data and virtual data and an on / off ratio of a liquid crystal applied voltage when the liquid crystal panel driving method according to the present invention is used. is there.

FIG. 6 is a diagram schematically showing a configuration of a liquid crystal panel having M column electrodes and N row electrodes, which constitute the liquid crystal display device of the related art and the embodiment of the present invention.

FIG. 7 is a diagram schematically showing a state in which a row electrode of the liquid crystal panel is divided into J row electrode blocks.

FIG. 8 is a diagram showing display data for one frame corresponding to pixels of N rows × M columns arranged in a matrix.

FIG. 9 is a diagram illustrating an orthogonal matrix F having a size of L rows and K columns created from an orthogonal matrix having a size of K rows and K columns.

10 is a diagram showing a display data matrix I _B of L rows × M columns corresponds to one row electrode blocks B _j of the liquid crystal panel.

[11] The display data matrix I _B of L rows × M columns corresponds to one row electrode blocks B _j of the liquid crystal panel, converts the display data matrix G of the orthogonal transformed M rows × K column orthogonal matrix F it is a diagram showing a _B.

[Explanation of symbols]

 Reference Signs List 1 orthogonal matrix generator 2 frame memory 3 orthogonal transformation circuit 4a, 4b, 4c column driver 5a, 5b row driver 6 liquid crystal panel 7 data conversion circuit 100 liquid crystal display device

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 505-580 G09G 3/36

Claims (3)

(57) [Claims] 1. A plurality of row electrodes and a plurality of column electrodes are arranged such that their intersections are arranged in a matrix, and a response to an effective voltage value is provided between the row electrodes and the column electrodes at each of the intersections. A method of driving a liquid crystal panel sandwiching a display medium by applying a voltage having a waveform based on an orthogonal matrix to a column electrode and a plurality of row electrodes selected at the same time, comprising: Alternatively, as display data corresponding to the i-th row in a block area obtained by dividing one frame of the display image in the vertical scanning direction,
Accordingly, a value +1 indicating display off and a value -1 indicating display on
Assuming values that do not require opening and closing calculations between
For each of the plurality of simultaneously selected row electrodes, Y
Assuming (≧ 1) virtual rows,
For each thought, the virtual data corresponding to each display data
A / b (a and b are integers) that do not require open / close calculation
And the value of the corresponding display data
The square and the square of all virtual data for that display data
The sum with the power is always a constant value P near 1 that is not 1.
Assuming respectively, the display data is orthogonally transformed using the orthogonal matrix including the virtual data, and a column voltage corresponding to the orthogonally transformed display data is sequentially applied to all the column electrodes. The entire region of one frame of the image or all the row electrodes corresponding to the block region are simultaneously selected, and correspond to the column vector elements of the matrix obtained by removing the elements corresponding to the virtual rows in the orthogonal matrix used for the orthogonal transformation. A liquid crystal panel driving method in which the converted display data is inversely converted on the liquid crystal panel by sequentially applying a row signal to be applied as a row selection pulse, and a gradation display indicated by the original display data is performed. 2. The method of driving a liquid crystal panel according to claim 1, wherein the orthogonal transformation includes, as an orthogonal matrix, half of the number of rows including simultaneously selected row electrodes and virtual rows. A method of driving a liquid crystal panel using a matrix. 3. A plurality of row electrodes and a plurality of column electrodes are arranged such that their intersections are arranged in a matrix, and a response is made between the row electrodes and the column electrodes at each of the intersections to an effective voltage value. A method of driving a liquid crystal panel sandwiching a display medium by applying a voltage having a waveform based on an orthogonal matrix to a column electrode and a row electrode, wherein the liquid crystal panel corresponds to an i-th row in an entire region of one frame of a display image. Display data corresponding to the gradation level
Between the value +1 indicating display and the value -1 indicating display ON.
Assuming each value I _i that does not require a closed calculation,
Y (≧ 1) provisional for each of the plurality of row electrodes
Imagined behavior, and for each imagined virtual row
Open and close virtual data α corresponding to each display data
Value represented by a / b (a and b are integers) that do not require calculation
And the square of the corresponding display data and its
Sum of squares of all virtual data to display data
Is always a constant value P near 1 which is not 1.
Assuming that the display data for each row electrode is orthogonally transformed using the orthogonal matrix including the virtual data, and a column voltage corresponding to the orthogonally transformed display data is sequentially applied to all column electrodes, A row signal corresponding to a column vector element of a matrix excluding an element corresponding to a virtual row in the orthogonal matrix used for the orthogonal transformation is sequentially applied as a row selection pulse to each row electrode of the entire area of the display image 1 frame. The method of driving a liquid crystal panel performs inverse conversion of the converted display data on the liquid crystal panel to thereby perform gradation display indicated by the original display data.