JP2568790B2 - Driving method of matrix type display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of a matrix type display device. The present invention relates to a matrix type display device in which a display response is controlled at least to a large extent by an effective voltage value.

In this specification, a matrix type simple liquid crystal display device will be described hereinafter, but this essence applies to a matrix type display device in which all effective voltage values are dominant mechanisms.

[0003]

2. Description of the Related Art A display device such as a liquid crystal display device is a technology that is absolutely necessary as a man-machine interface. In particular, recently, liquid crystal display devices have become indispensable in computer terminals and the like from the viewpoint of downsizing. Among them, the matrix type simple liquid crystal display device is in a reasonable range such as price, and is going to be widely used.

Conventionally, the driving method of these matrix type simple liquid crystal display devices uses line-sequential scanning of scanning lines in accordance with a voltage averaging method. In this method, mathematically, it can be considered as follows. Choosing one scan line at each moment is equivalent to generating an orthogonal function as a whole (reasonably defining the product between the functions), and at the same time a finite display pattern, here a display device For a set or mathematical space whose elements correspond to the vectors corresponding to the representation of a certain column, the function for selecting one of the entire scan lines to be scanned is mathematically complete. It has become something.

That is, a basis vector corresponding to line-sequential scanning can be considered. Here, the total number of scanning lines is M. Basis vectors corresponding to conventional line-sequential scanning, which are orthogonal and complete with each other. That is, when the n-th scanning line is selected in one frame, the basis vectors {0, 0,..., 0, 1 (n-th), 0,.
.., 0｝ (8). It can be seen that these M vectors are directly facing each other when the product of the vectors is defined as a normal inner product. Also, the state of the pixels in each column of the display panel to be displayed (in this one frame, ON
, Or OFF state—for example, -1 if ON, +1 if OFF)
When represented by an M-order vector, it can always be represented by a linear combination of M base vectors (17). M vectors (17) are complete with respect to this vector space. That is, the scanning line has been applied and driven by using the orthogonal function without knowing it.

Mathematically, expansion of a function space including finite elements by an orthogonally complete base function of each element, etc.
He is familiar with "Introduction to Analysis", Sadaharu Takagi, published by Iwanami Shoten. The voltage averaging method is detailed in "Basics and Application of Liquid Crystal Electronics", edited by Akio Sasaki and published by Ohmsha. For more information on matrix theory, see "Matrix and Determinant", Keizo Asano, published by Kyoritsu Shuppan.

More recently, driving methods have been devised using other orthogonal and complete mathematical space theories. For example, tea.
Shea Shepherd ETC. 92 92
(TJScheffer etc.SID 92 DIGEST pp228). This uses Walsh-Hadamard transform theory. Here, the voltage applied to the pixel has a voltage peak value lower than that of a line-sequential so-called voltage averaging method, and from this point, there is an advantage that crosstalk and a frame response can be reduced.

[0008]

Recently, a demand for high-quality display has become a reality in liquid crystal display devices used in computer terminals and the like. In these liquid crystal display devices, a simple mode liquid crystal display device such as STN is mainly used. In these liquid crystal display devices, although the display quality is deteriorated due to a crosstalk phenomenon or the like in the display, the liquid crystal display devices are currently used without any difficulty.

In the high-speed STN, the movement of the liquid crystal deviates from the assumption of the voltage averaging method, and slightly responds to the peak value of the voltage. In this case, light also slightly leaks in the black state due to the response of the liquid crystal to the half-selection voltage. That is, the contrast becomes considerably inferior to expected. In conventional line-sequential scanning, because of the scanning voltage applied to the selected scanning line having a relatively large peak value,
Since a relatively large voltage is applied instantaneously once per frame,
The brightness is instantaneously brightened within one frame due to the high-speed response of the liquid crystal, and soon becomes dark.

In a normal liquid crystal display, this state is maintained for one frame or more when the display becomes bright due to an instantaneous large voltage pulse due to the slow movement of the liquid crystal. These behaviors of the liquid crystal display are derived from a so-called frame response. The frame response is a phenomenon as described above.

Further, the driving method using the above-mentioned various orthogonal and complete mathematical space theories is excellent. In other words, during driving, the effective voltage applied to each pixel is dispersed within one frame, thus contributing to the reduction of crosstalk and frame response, and the improvement of image quality. This method relies on the Walsh-Hadamard transform of the idea and uses the underlying Hadamard matrix.

First, an Nth-order Walsh-Hadamard transform matrix W will be described. N-order Walsh - For Hadamard transform matrix W, becomes N = 2 ^w, the N present is natural number, construction method of the matrix W are known. Of course, each element of the unitary property ^{W · t W = t W ·} W = E matrix W is composed of only 1 or -1. Of course, the matrix W is a square matrix.

The row or column vector of the matrix W is
It shows the applied voltage pattern of the entire scanning side electrode group at the moment,
It is desirable that the order of this vector matches the number of scanning electrodes. Otherwise, the ON state voltage of the pixel and the OF
The ratio at which the voltage in the F state can reach (ON-OFF selection ratio) decreases. However, as described above, there is a great restriction that the order of the row vector or the column vector forming the matrix W cannot be arbitrarily selected.

When a specific display pattern, particularly a solid display or a vertical ruled line, which often appears in an OA display device, is displayed.
The voltage value becomes considerably high, and in this display, crosstalk and frame response may become severe.

Also, for example, 2 pixels of 480 × 600 pixels
In the case of a matrix-type liquid crystal display device,
Although 240 × 600 pixels are considered, in the case where there are 240 scanning lines as described above, when driving using such a Walsh-Hadamard transform is performed, the scanning-side voltage or the driving-side voltage considerably increases, and High-voltage design for the IC. That is, as long as this driving method is used, there is an optimum number of scanning lines for the voltage of the IC. This fact is not grateful.

[0016]

According to the present invention, in order to solve the above-mentioned problem, each element can take three values of -1, 0 and +1, an element taking a value -1, and an element taking a value 0. , And value +
There is at least one element each taking 1 and all column or row vectors have the same length, and different column or row vectors are orthogonal when defining the multiplication between the vectors as appropriate. The transformation matrix U is
This paper proposes a new orthogonal matrix construction method using the binary system.

Further, according to the present invention, each element is -1 and 0 and +
An element that can take three values of 1 and takes a value of -1;
Element and at least one element each taking the value +1
Where all column or row vectors have the same length, and different column or row vectors, when appropriately defining the multiplication between the vectors, have a higher order , Each element is -3, 0 and +1
Elements that can take values and take the value -1, elements that take the value 0, and
There is at least one element each taking the value +1 and all column or row vectors have the same length;
Different column or row vectors define orthogonal transformation matrices V when appropriately defining the multiplication between the vectors.

[0018]

(Equation 2)

We propose a method of constructing an orthogonal matrix as obtained according to Further, according to the present invention, each element is a 3 of -1, 0 and +1.
Elements that can take values and take the value -1, elements that take the value 0, and
There is at least one element each taking the value +1 and all column or row vectors have the same length;
Different column vectors or row vectors are provided with a generator of a transformation matrix H that is orthogonal when appropriately defining multiplication between the vectors, and N corresponding to a display pattern of one frame.
The matrix A rows and M columns, as rows and columns of the matrix A corresponds to the order in the row and column of the matrix display device, moreover,
-1 corresponds to the ON pixel, +1 corresponds to the OFF pixel, or
+1 for ON pixels and -1 for OFF pixels
Is defined so that

[0020]

[Formula 3] H · A = B

As described above, a conversion display pattern matrix B is obtained by conversion using this conversion matrix H, and one frame period T is divided into N slots, and in one frame period T = t _n −t ₀ ,
_{t 0 ~t 1, t 1 ~t} 2, t 2 ~t 3, ......, in updating the voltage applied to all pixels in t _n-1 ~t _n, timing,
At timing t _i-1 ~t _i, scanning lines, and signal electrodes, the voltage specified individually, yet the whole, at the same time, by applying a scanning voltage and the signal voltage, this time, the scan lines of k rows, A scan voltage proportional to the values of the k-th column and the i-th row of the conversion matrix H is applied to the j-th signal electrode at the same timing to the values of the i-th row and the j-th column of the conversion display pattern matrix B. A driving method of a matrix type display device in which a proportional signal voltage is applied will be clarified.

At this time, it is desirable to invert the scanning side potential and the signal side potential for each frame.

[0023]

The rows and columns of the matrix are defined by mathematics. The definition of the rows and columns in the panel of the matrix display device is such that the rows correspond to the scanning lines and the columns correspond to the signal lines. Correspond.

The present invention pertains, in part, to a matrix-type display device that is rms responsive.

First, a description will be given of a method of constructing a square matrix composed of column vectors or row vectors having an arbitrary degree and having orthogonality (automatically completed automatically). Of course, the lengths of such vectors are equal. The length of a vector is defined as the square root of the inner product of the vector itself.

By doing so, the order can be matched with the number of scanning lines of the display device, and the ON-OFF selection ratio can be increased as compared with the known example.

Each element of the Walsh function (also represented by a column vector or a row vector of the Hadamard matrix W) is composed of only +1 and -1 values. Such matrices are mathematically of this kind only.

As a result of consideration, the present inventors have found that, in the case of a display device, it is more flexible and more practical to consider a vector in which each element is composed of only three values of +1, 0 and -1. It is at the outset of the present invention that it was considered easy.
Mathematically, it has not been clarified how to construct a basis vector of an orthogonally complete space in which each element can take three values. In other words, this idea itself is very novel. The fact that each element can be ternary, especially 0, provides the following features.

That is, in driving using the Walsh function, (+ 1, + 1,..., + 1)... (9) when displaying a unique pattern such as a solid display or a vertical ruled line often appearing in the display for OA use. ), The applied voltage concentrates in the pattern of the applied voltage on the scanning side, and as a result, the driving voltage at this time increases. Only at this time, crosstalk and frame response increase. As can be seen from this, this situation can be prevented if the elements of the vector can be made ternary, especially 0, and there is a possibility that the vector as in (9) is not a base vector. Actually, it was found that this situation could be prevented if each element could take three values.

In driving using the Walsh function, a voltage proportional to -1 or +1 is always applied to the scanning line. For this reason, for example, in the case of realistic 240 scanning lines, a considerable voltage is applied to the driver IC. However, since a voltage proportional to 0, that is, some scanning lines can be instantaneously dropped to 0 potential, even in the case of realistic 240 scanning lines, a considerable voltage can be considerably reduced to the driver IC. This will be apparent from computer simulation.

Now, the method of constructing the matrix according to the present invention will be specifically described.

Each element can take three values, -1 and 0 and +1 .
Elements taking the value -1, elements taking the value 0, and taking the value +1
There is at least one element each , all column or row vectors have the same length, and different column or row vectors are orthogonal transformation matrices U, when appropriately defining the multiplication between the vectors. Is not so mathematically clear. The inventors have found a method of specifically calculating such a matrix using a computer. This is a part of the present invention.

First, in order for each column vector forming the matrix to have the same length (which necessarily results in each row vector also having the same length), the 0 element in each column vector must have the same length. It is necessary and sufficient that the numbers be the same. Under this constraint, for example, a certain column vector (degree is G) (1, -1, 0,..., -1) (10) is converted into the following vector (2, 0, 1,. …, 0) and convert this vector to
Assuming that it is a ternary representation, X = 2 × 3 ^G-1 + 0 × 3 ^G-2 + 1 × 3 ^G-3 +... + 0 × 3 ⁰ (11) There is a basis for the present invention. More specifically, the embodiment shows a schematic program.

Further, according to the present invention, each element is -1 and 0 and +
An element that can take three values of 1 and takes a value of -1;
Element and at least one element each taking the value +1
Where all column or row vectors have the same length, and different column or row vectors, when appropriately defining the multiplication between the vectors, have a higher order , Each element is -3, 0 and +1
Elements that can take values and take the value -1, elements that take the value 0, and
There is at least one element each taking the value +1 and all column or row vectors have the same length;
A different column vector or row vector proposes a method of constructing an orthogonal matrix so as to obtain an orthogonal transformation matrix V according to (Equation 3) when multiplication between vectors is appropriately defined. This can be understood by calculation. Such a procedure for expanding a matrix is first revealed.

Next, an outline of driving using this will be described. In the present invention, each element can take three values of -1, 0 and +1 ;
Elements taking the value -1, elements taking the value 0, and taking the value +1
There is at least one element each , all the column or row vectors have the same length, and the different column or row vectors are orthogonal transformation matrices H when appropriately defining the multiplication between the vectors. comprising a generator, the 1-frame display pattern of - the matrix a of N rows M columns corresponding to down, as rows and columns of the matrix a corresponds to the order in the row and column of the matrix display device, moreover, -1 for ON pixels, +1 for OFF pixels, or ON pixels
Is +1 and OFF pixel is -1.
So that, by definition, equation (3) as conversion display pattern is converted in this transformation matrix H - give the emission matrix B, by dividing one frame period T into N slots, one frame period T =
In _{t n -t 0, t 0 ~t} 1, t 1 ~t 2, t 2 ~t 3, ··
...., in updating the voltage applied to all pixels in t _n-1 ~t _n, the timing, at the timing t _i-1 ~t _i,
Scanning lines, and the signal electrode, the voltage specified individually, yet the whole, at the same time, to apply the scanning voltage and the signal voltage
At this time, a scanning voltage proportional to the value of the k-th column and the i-th row of the conversion matrix H is applied to the k-th scanning line, and the conversion display pattern matrix B is applied to the j-th signal electrode at the same timing. Among them, a driving method of a matrix type display device in which a signal voltage proportional to the numerical value of the i-th row and the j-th column is applied will be clarified.

The features are as described above. Note that each column vector of the transformation matrix H was generated in a ROM memory.

The present invention also proposes that the scanning-side potential and the signal-side potential are inverted for each frame in the above-described driving method.

[0038]

【Example】

(Example 1) A matrix having four rows and four columns according to the present invention was calculated using a small computer.

First, a column vector having a length of √3 (corresponding to one element of a vector consisting of 0), a column vector having a length of √2 (two elements of a vector become 0 ... this one does not exist),
The program is divided into cases of $ 1 (three elements of the vector become 0). Further, as described above, the vector is represented by a ternary number, and a calculation corresponding to the inner product of the vector is advanced while imposing a restriction on the number of zero elements of the vector, to obtain four orthogonal column vectors. Mathematically, from these four column vectors, the row vectors of the constructed matrix are also automatically orthogonal. In addition, although the matrix code is changed, and the rows and columns are exchanged, the column vectors and the row vectors are also the same in length and orthogonal to each other.

An example of a matrix obtained by calculation is

[0041]

(Equation 4)

Shown in FIG. In the calculation, (Equation 4)
To (d) are obtained. In the present invention, the above (b) is used.
Absent. Further, as shown in (Equation 2), a 240-order matrix according to the present invention was obtained from the 15th-order unit matrix E. This was exactly the case where the length of each column vector was constant and orthogonal to each other.

(Embodiment 2) An embodiment of the driving method according to the present invention will be described below. However, most of the circuits are composed of logic circuits, and an outline thereof is shown in FIG. (FIG. 1) is a block diagram. In the figure, 1 is a 240 × 640-frame-buffer memory, 2 is a 240 × 640 pixel matrix type simple liquid crystal display device, 3 is a matrix element generating ROM, 4 is a scanning side voltage register, and 5 is a signal side signal operation circuit. , 6
Is a high-speed digital-analog converter (DAC), 7 is an analog-signal side-driver, and 8 is a ternary-scanning side-driver.

In practice, a commercially available STN panel (240 scanning lines × 640 signal lines) was devised, and a commercially available analog TFT driver was used as the signal driver. Further, the proportional constant in generating the scanning line side voltage of the panel and the proportional constant in generating the signal side voltage can be independently fixed. These values seem to have different optimum values depending on the threshold value of the liquid crystal panel and the scale of display.

From the 15th-order unit matrix E, the 240th-order matrix according to the present invention is expressed as

[0046]

(Equation 5)

The above expansion method was repeated four times.
This matrix was used as a transformation matrix H. This is literally -1
And an orthogonal matrix consisting of 0 and +1. In addition, each column vector or each row vector has the same length.

First, one frame of image information is transmitted from outside. It is stored in a 240 × 640 frame-buffer-memory 1. This stored information corresponds to the matrix A in this specification. When obtaining the matrix A, -1 is associated with ON pixels and +1 is associated with OFF pixels. Matrix element generation ROM 3 (conversion matrix H
The conversion display pattern matrix B is substantially generated in accordance with (Equation 3) using the scanning-side voltage register 4 and the signal-side signal operation circuit 5. In this calculation, the contents of both the matrix H and the matrix A are −1 and 0
And + B, and is therefore composed of a simple gate circuit. Therefore, the operation is performed at a very high speed.

The column matrix of the transformation matrix H gives the voltages of the individual scanning lines during the so-called 1H period. This is performed substantially by the matrix element generating ROM 3 and the scanning side voltage register 4.

The response speed (= the time required for the rise of the response + the time required for the fall after the signal is turned off) is 1
In the high-speed STN display device of 20 ms, the crosstalk and the frame response could be greatly improved, and the contrast could be improved to 5 times or more and the brightness could be improved to about 2 times as compared with the prior art. This display device impresses the possibility of displaying moving images in the future.

During display, the voltage applied to the scanning line and the signal line was monitored almost 100% in time, and the voltage value was reduced to 1/2 to 1/4 as compared with the conventional case. I guess they are doing this together with the rut.
Crosstalk was significantly reduced.

In the driving method of the above-mentioned shepherds, special patterns such as vertical ruled lines often appearing in OA display are used.
In the period of 1H, the voltage value on the signal side needs to be extremely large, and adverse effects such as crosstalk and frame response appear. According to the present embodiment, this phenomenon is suppressed. This is because the elements of the orthogonal matrix H used for the transformation can take three values, that is, −1, 0, and +1. Therefore, the configuration of the column vector becomes more diverse, and the orthogonal matrix Can be configured. Incidentally, the elements of the transformation matrix used by the Scheffers consist of only -1 and +1, which is a very restrictive environment.

In the column vector of the transformation matrix H of this embodiment, the number of elements from -1 to +1 is 16, and the other 224 are 0. As a result, the voltage on the scanning side is greatly reduced as compared with the above-mentioned Shepher method. This is also because the domain that the elements of the transformation matrix H can take is ternary.

Also, compared to the above-mentioned method of Scheffers,
Any horizontal crosstalk along the scan line has also been greatly improved. This is the pseudo-frequency of the row vector of the Hadamard matrix used by the Scheffers (which represents the temporal voltage transition within one frame of each scan line), which is the Fourier transform of the temporal transition of the voltage. ) Varies greatly depending on the scanning line, but in this case, the width of the pseudo frequency distribution can be considerably reduced. This is because, as one element of the transformation matrix H, three values, that is, −1
And 0 and +1. Shepherds are -1
And +1 only. As a scanning driver, there is no great difference in the configuration of the IC between the driving in proportion to −1, 0 and +1 and the driving in proportion to −1 and +1.

Further, in the scanning within one frame, in the voltage pattern of the entire scanning line applied simultaneously and instantaneously, even if the application of the voltage to the entire scanning line corresponding to the one with extremely low frequency component is omitted. In the case of a natural picture, it was perfectly acceptable. This has remarkably relaxed the requirements for the circuit configuration.

The polarity of the scanning side voltage and the signal side voltage was inverted for each frame. This tendency tends to be smaller when the printing of the liquid crystal display device is performed for a long time.

(Embodiment 3) Fifteenth-order matrix F

[0058]

(Equation 6)

From the above, a matrix of the 240th order according to the present invention is expressed as follows.
It was obtained by repeating the expansion method of (Equation 5) four times. This matrix was used as a transformation matrix H. This is literally -1 and 0
And +1. In addition, each column vector or each row vector has the same length.

As in (Example 2), a 240 × 640 pixel matrix type liquid crystal panel was driven using this conversion matrix. The results also show a significant improvement in properties.

(Embodiment 4) Fourth-order matrix D

[0062]

(Equation 7)

From the above, a matrix of order 256 according to the present invention is expressed as follows:
It was obtained by repeating the expansion method of (Equation 5) four times. This matrix was used as a transformation matrix H. This is literally -1 and 0
And +1. In addition, each column vector or each row vector has the same length.

Similarly to (Example 2), a 240 × 640 pixel matrix type liquid crystal panel was driven using this conversion matrix. However, an area corresponding to 256 × 640 display is prepared as a frame-buffer-memory,
For the 241st and subsequent fictitious scanning lines, 1 or-
1 fictitious data was inserted.

As a result, the characteristics were also significantly improved.
In the present embodiment, a so-called single matrix display device has been described. However, for example, a so-called double matrix display device may, of course, carry out the present invention one by one.

Although the description has been limited to the liquid crystal display device, as will be understood from the gist, the present invention is applicable to a matrix type display device, and the present invention includes all the display devices of this type. Things.

[0067]

The present invention is applicable not only to liquid crystal display devices but also to matrix type display devices based on a similar principle, and has great industrial value.

A conventional or known orthogonal function takes a continuous numerical value as a domain of a function, or in the case of a discrete domain,
It is only a binary value such as +1 and -1.

However, in terms of engineering, ternary values (−1, 0, and +1)
Was found to be of great use value.
I am convinced that this can be a big deal, as it also contributes to other engineering applications.

[Brief description of the drawings]

FIG. 1 is a block diagram of a system for realizing the present invention.

[Explanation of symbols]

 Reference Signs List 1 240 × 640-frame-buffer memory 2 240 × 640 pixel matrix type simple liquid crystal display device 3 Matrix element generation ROM 4 Scan-side voltage register 5 Signal-side signal operation circuit 6 High-speed digital-analog converter (DAC) 7 Analog- Signal side-Driver 8 Tri-level-Scanning side-Driver

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naohide Wakita 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-27904 (JP, A) JP-A-6-27 27905 (JP, A) JP-A-6-27906 (JP, A) SID 92 DIgest, T.A. J. Scheffer et al, "Active Addressing Method for High-Contrast Video-Rate STN Displays", p. 228-231

Claims (1)

(57) [Claims] 1. Each element can take three values of -1, 0 and +1. An element having a value of -1, an element having a value of 0, and a value of +1.
Each column or row vector has at least one element , all column or row vectors have the same length, and different column or row vectors are orthogonal transformation matrices when appropriately defining the multiplication between the vectors. comprising a H of the generator, a display pattern of a frame - a matrix a of N rows M columns corresponding to down, as rows and columns of the matrix a corresponds to the order in the row and column of the matrix display device, yet , ON pixel, -1 for OFF pixel, or ON pixel
Is +1 and OFF pixels are -1.
So as to engage, defining, as in Equation 1] H · A = B, converts the display pattern is converted in this transformation matrix H - give the emission matrix B, dividing one frame period T into N slots Then, in one frame period T = t _n −t ₀ , t _{0 to} t ₁ ,
_{t 1 ~t 2, t 2 ~t} 3, ······, in updating the voltage applied to all pixels in t _n-1 ~t _n, the timing, at the timing t _i-1 ~t _i , Scanning lines, and signal electrodes , when individually applying the scanning voltage and the signal voltage simultaneously and as a whole, the k rows of scanning lines have k columns and i rows of the conversion matrix H. And a signal voltage proportional to the values of the i-th row and j-th column of the conversion display pattern matrix B is applied to the j-th signal electrode at the same timing. A method for driving a matrix-type display device, comprising: