JP3469224B2 - Driving method of matrix display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a TN liquid crystal, an STN
Liquid crystal, STB liquid crystal, ECB liquid crystal, and other various liquid crystal materials
And other materials with electro-optical response characteristics
The present invention relates to a display method for a elixir-type display device. In particular, the invention
Relates to a method for performing gradation display. [0002] 2. Description of the Related Art A large number of dots are arranged in a matrix.
Therefore, without providing an element having a non-linear characteristic,
Simply apply to rows (also called rows) and columns (also called columns)
The signals at the intersection
The matrix that tries to control the signal of the
TN liquid crystal, STN liquid crystal, STB liquid crystal, EC
For display devices using B liquid crystal and other various liquid crystal materials
Used. In such a matrix, conventionally, FIG.
As shown, the column electrodes are constantly flowing signals while the row electrodes
In the electrode, a pulse signal is applied to
When the signal is applied, the signal of the column electrode is
Have been adopted. However, this one
In the formulas, the matrix size is particularly large, and the number of rows is large.
When it becomes difficult, the decrease in contrast becomes a problem,
It was extremely difficult to display. This is especially true for materials such as the liquid crystal described above.
Due to its slow optical response speed, its optical characteristics (transmittance and
Scattering rate) is substantially the potential difference between the row electrode and the column electrode.
This is because it is proportional to the effective value. In particular, applied to the column electrodes
Since the signals to be included also include the signals of pixels in other rows,
Absolute optical characteristics depending on the magnitude of the signal in other rows of the column
Has been greatly influenced. If the shadow of the other row signal
If you try to reduce the sound, you can
Materials that show a steep rise must be used, and
Difficult to obtain intermediate optical properties with materials such as
So, I could only display black and white. Also, the row signal pal
The problem was that the size became large. On the other hand, recently, a new driving method has been proposed.
Was devised. FIG. 3 shows a conceptual diagram thereof. This method is
Active addressing (T. J. Scheffer and B. Clit
ton: 1992 SID Digest of Technical Papers XXIII, 228
-231 (1992)).
Since the concept has been eliminated, the power applied to the row and column signals
The pressure is low and low power consumption is possible. However, even with this method, the above problem can be solved.
It didn't come. Active address method
Is the orthonormal function system f_iA suitable function f of_nAdopt the line
The potential of one of the functions is applied to the electrodes, while
The electrode has a linear combination of these functions の a_if_iExpressed in
Is applied. Normal one frame is T
Then, the effective value voltage V during one frame_RMSIs the number 1
Indicated by [0007] (Equation 1) Here, N is the number of rows in the matrix. formula
As is clear from, the rows other than the row of interest (the n-th row)
A signal is contained therein. Therefore, active
Removes information of other rows (pixels) even in the address method
And absolute gradation display was difficult. [0009] SUMMARY OF THE INVENTION The present invention relates to the above description
Achieving absolute gradation display, which was a problem in
With the goal. That is, pixels other than the pixel of interest
The present invention provides a signal and a driving method in which the display information does not enter. [0010] A conventional matrix display method
In the method, the tone information is given by the signal strength
I was Sometimes given by the pulse width of the signal
However, when considered as an effective value, both effects are the same.
there were. On the other hand, in addition to the gradation information,
Had to give the information that the choice. this is
Mainly carried by row signals, but as effective value
If video appears, the effect will be on the column signal
Is obvious. That is, in the conventional method, the signal strength and
In one expression means, there are two methods, gradation and selection.
Attempts to express are severely limited in freedom.
It has been. The inventor has found that the disadvantages of such a crippled method are:
He called for another expression method for expressing gradation. Soshi
And found a way to express gradation information by phase
It is. In the present invention, the same as the active address method is used.
Thus, the orthonormal function system f_iSelect That is, f_i
Satisfies the relationship of Equation 2. here,^*Represents the complex conjugate
Is f_iIf is a real function, f_i= F_i ^*It is. [0012] (Equation 2) Further, in the present invention, α is an arbitrary number.
When f_iSatisfies the conditions of Equations 3 and 4
Shall be In the present invention, for example, a matrix of N rows
Rix, each row electrode has the above f_iIndicated by
The potential of an appropriate function system is applied. However, select
The functions performed depend on the line. For example, the nth row
And the potential of the n'th row is F_n(T), F
_{n '}(T) F_n(T) ≠ F_{n '}(T) It is. [0014] (Equation 3) [0015] (Equation 4) On the other hand, the column electrode has a functional system f_iLinear combination of
Potential G expressed by_m(T) is applied,
The phase of each function is determined by the target pixel (row) in that column.
Arbitrarily selected according to the gradation information. That is, the number
5 is expressed. On the other hand, the row voltage is F_n(T) =
V₀f_n(T). Where V₀Is the same for all rows
Is a constant. As will be described later, by optimizing V
Thus, the contrast can be improved. More than
Under the conditions, one frame of the pixel at the n-th row and the m-th column (time
T) Effective voltage V_RMSBecomes as shown in Expression 6. formula
Apparently from V _RMSContains the gradation information of the n-th row, g (α
_n) Does not include any gradation information of other pixels.
Further, the maximum selection ratio is given by Expression 7, and depending on g and N, V
By optimizing, you can choose the best
You. For example, f_iIf a sine wave function is adopted,
Since 1 ≦ g ≦ 1, the maximum selection ratio in this case is Equation 8.
The same as the maximum contrast ratio of the conventional matrix drive
It is. [0017] (Equation 5) [0018] (Equation 6) [0019] (Equation 7) [0020] (Equation 8) In the present invention, a function that satisfies the above conditions is used.
All numbers are available, but the most accessible is the sine wave
Number or cosine wave function (ie, exp (ikx), (i is
It is a function of the kind represented by imaginary unit)). Also three
Angle and square waves are also represented by linear combinations of sinusoidal functions.
Naturally, the above conditions are satisfied and the present invention
Can be used for In particular, sine wave functions and cosine wave functions
When numbers are used, only the characteristics of the present invention can be used.
Without the pulse signal shown in FIG. 2 or FIG.
Compared to driving with a square wave signal, the signal
The shape is rarely distorted. Also easy to generate
It is. The present invention also eliminates the concept of a selection pulse.
And therefore applied to the row and column electrodes
The absolute value of the voltage is calculated using the conventional pulse type display method (Fig. 2).
Small in comparison. Therefore, lower power consumption
Is possible. Furthermore, according to the present invention, one frame
Voltage is applied to both row and column electrodes on average.
Therefore, flicker is extremely low. The following is an example.
Examples showing further developments of the present invention, and practicing the present invention
Of the driving device for this will be described. [0023] EXAMPLES Example 1 Commercially available 480 rows × 640 columns
The effect of the present invention was confirmed using the STN simple matrix.
Was. The screen was divided into upper and lower parts. Drive is non-inter
The race was 60 frames / sec. And on the nth line
Is V₀sin120π (n + 500) t Is applied to each column electrode, and
Apply a voltage, display, and perform contra
Obtain strike ratio (up to 55) and gradation accuracy (up to 16)
Was completed. In particular, conventionally, control is performed based on information from other pixels.
So-called crosstalk, which raises and lowers the last, is a problem
However, according to the present embodiment, the present invention reduces crosstalk.
It was proven that there was little. [0024] (Equation 9) In this embodiment, the positive voltage applied to the matrix is
The frequency of the sine wave is about 30 kHz to 44 kHz.
You. Generally, liquid crystals have characteristics such as threshold voltage depending on the frequency.
Sex is known to change. However, 30kHz
The liquid crystal characteristics are almost flat between
There was no problem. If V₀signal of sin120πnt
Is used, the sine wave applied to the matrix
Frequency is wide band from 60Hz to 14kHz
The response characteristics of the liquid crystal also differ from row to row.
The problem arose. In this embodiment, the maximum
Since the ratio between the wave number and the minimum frequency is 2 or less, the above-described problem occurs.
Is avoided, and this allows the fundamental wave and twice its
The noise caused by the resonance of the frequency wave was also avoided. Embodiment 2 FIG. 4 shows this embodiment. Book
The embodiment divides one frame into a plurality of subframes.
By reducing the size of the apparent matrix,
Therefore, the function f used_iCharacterized by reducing the number of
You. In the present invention, f is equal to the number of rows of the matrix._iDo not prepare
Must have many circuits such as oscillation circuits.
And This is a factor that increases the cost of the drive circuit.
You. For example, in the first subframe, as shown in FIG.
The first row, the fifth row,. . . , The (4n + 1) th row, the
(4n + 5) rows, one of the matrices
A signal (for example, a sine wave) is applied only to the / 4 rows. other
Is 0. And in the second subframe
Are the second row, the sixth row,... As shown in FIG. . . ,
(4n + 2) line, (4n + 6) line, etc.
In the third subframe, the third row, the seventh row,. . . ,
(4n + 3) line, (4n + 7) line, fourth subframe
In line 4, lines 8, line 8,. . . , 4nth row, (4n
+4) row, and so on. At this time, paying attention to one pixel,
Of the four subframes, only one is selected
State (a state in which a signal is applied to the row electrode).
The effective value voltage of is given by
It is shown in FIG. On the other hand, in the other three subframes
Indicates that no signal is applied to the row electrode,
The effective value voltage is F√N. Therefore, the average effective
The value voltage is shown in equation 11, and f_iAs the sinusoidal function
Like, -1 ≦ g_n(Α) ≦ 1, the maximum
The selection ratio is given by Expression 12. The size of the matrix does not change
If this is not the case, as in this embodiment,
Whether you use the subframe or subframe
It was shown that only contrast was obtained. [0029] (Equation 10) [0030] [Equation 11] [0031] (Equation 12) This can be generalized to the matrix of the NL line.
L (N and L are natural numbers)
And obtain one frame by L subframes
When the driving method is adopted, the maximum selection ratio becomes
Shown. [0033] (Equation 13) As a result, the image quality is hardly impaired.
And the number of drive circuits could be reduced. On the other hand, the conventional method
Does not work as well. For example, traditional active
Address method (method shown in FIG. 2, A.R. Conner and T.
J. Scheffer: Proc. 12th Int'l Display Research Con
f. (Japan Display '92), 69-72 (1992).)
The selection ratio becomes as shown in Expression 14, and L becomes large.
As the maximum selection ratio approaches 1, the image quality (contrast
Etc.) are degraded. These differences are
The conventional active address method uses gradation information and selection information.
Was expressed as a single signal strength.
In contrast, in the present invention, these two expression elements are
Try to express them independently with two things, phase and signal strength
There is no other way. [0035] [Equation 14] Embodiment 3 FIG. 5 shows an embodiment of the present invention.
FIG. 1 shows a basic block diagram of a driving circuit for the present invention. actually,
It is necessary to provide various correction circuits and refresh circuits.
It is important, but it will not be described because the description is complicated. In addition,
For simplification, the number of lines is set to eight. Horizontal scan
The converted normal video signal is shifted by the shift register (1).
Was distributed to each row. And in each column, 8 steps shift
This signal is distributed for each line by the register (2).
No. (analog) is a memory with capacitance etc.
It is temporarily stored in (3). On the other hand, the carrier signal (f_iCorresponding to different laps
Generated by eight oscillator circuits (4) that oscillate wave numbers
You. For oscillation, for example, read a sine wave stored in ROM
It is performed in such a manner. As shown in FIG.
The circuit is common to all columns. Also, part of this output is
Also used as a row signal. Columns and oscillator circuits of interest
A voltage control type delay circuit (5) is provided between
The carrier signal is sent to the. Meanwhile, from memory (3)
, Image information is sent. And the image information
Changes the degree of delay and modulates the phase of the output sine wave.
You. Eight sine waves thus phase-modulated
Are mixed by the mixer (6) and output to the column electrodes.
It is. For example, if the number of columns is 640,
In the formula, 8 × 640 delay circuits are required. In this embodiment, eight lines are used.
In the case of a matrix, 240 oscillation circuits and 240 × 6
Forty delay circuits are required, which makes the drive circuit
The costs are enormous. If as described in Example 2
One frame is composed of 30 subframes
Then, it can be driven by 8 oscillators and 8 × 640 delay circuits
And lead to cost reduction. Embodiment 4 FIG. 6 shows an embodiment of the present invention.
FIG. 1 shows a basic block diagram of a driving circuit for the present invention. actually,
It is necessary to provide various correction circuits and refresh circuits.
It is important, but it will not be described because the description is complicated. In addition,
For simplification, the number of lines is set to eight. Horizontal scan
The converted normal video signal is shifted by the shift register (7).
Was distributed to each row. And in each column, 8 steps shift
This signal is distributed for each line by the register (8).
No. (analog) is a memory with capacitance etc.
It is temporarily stored in (9). On the other hand, the phase of each column is changed by voltage control.
There are provided eight oscillation circuits (10). oscillation
Is, for example, to read the sine wave stored in ROM
Readout is performed by an external control voltage.
The phase changes by adjusting the timing.
The information stored in the memory (3) is stored at the beginning of the frame.
The output sine wave sent to the oscillation circuit (10)
Oscillation starts according to the information. Eight sine waves thus phase-modulated
Are mixed by the mixer (11) and output to the column electrodes
Is done. For example, if the number of columns is 640,
In the system, 8 × 640 oscillation circuits are required. In this embodiment, eight lines are used.
In the case of a matrix, 240 × 640 oscillation circuits are required.
In other words, the cost of the driving circuit becomes enormous.
If 30 subframes are used in the manner described in the second embodiment,
If one frame is composed of frames, 8 × 640
It can be driven by an oscillation circuit, leading to cost reduction. [Embodiment 5] In the above description, simultaneous multi-line
Although the selection is described, in the present invention, the conventional selection is performed line by line.
Even with the method of selecting
Obtainable. The line-by-line selection refers to Example 2.
And N = 1 in generalized equation 13.
And nothing else. For example, a matrix of 640 columns × 256 rows
think of. In this case, only one of the 256 rows
, 16V₀Apply potential of sin (30720πt)
On the other hand, V₀sin (30720π)
A voltage of (t + α) is applied. Note that 30720π = 6
0 [frame / second] x 256 [subframe / frame
X 2π. As a result, the subframe of the selected row is
The effective value voltage of the beam is shown in Expression 15. On the other hand, unselected
The effective value voltage of the row is πV₀It is. Therefore, one
RMS voltage through the frame (= 256 subframes)
Becomes as shown in Expression 16. Therefore, the maximum selection
The selection ratio is 1.064. This number is the traditional matrix
Is the same as the value obtained by
Extremely clear images because no crosstalk occurs
Is obtained. [0047] (Equation 15) [0048] (Equation 16) To perform such driving for each row,
In the third embodiment, the oscillator and the voltage-controlled delay circuit
One by one in each column, or in the fourth embodiment, voltage control
Prepare only one oscillator whose phase changes according to the
I just need. Also, a memory for storing video signals
There is no need for a shift register in the previous stage. In such a row-by-row drive, the circuit is simplified.
On the other hand, when the frame speed is low, flicker is generated.
I will. Flicker increases the frame rate above 60Hz,
Preferably, the frequency is set to 120 Hz or more, so that
It is possible to suppress the car, but the drive
The operating speed of the circuit increases. [Embodiment 6] In the embodiment 5, it is used for driving.
The sine wave function was used as the
Square wave can be used in the same way as
You. An example is shown in FIG. The square wave, as explained earlier
Satisfy the conditions required by the present invention. Also, with a square wave
Is easy to use because it has the relationship shown in Equation 17. [0052] [Equation 17] FIG. 7A shows one line at a time, similarly to the fifth embodiment.
FIG. 3 is a conceptual diagram of a driving method when the driving is performed. line
One-period rectangular wave is applied to the electrode independently.
May have a multi-period. The selection of the n-th row
When completed, the next row (the (n + 1) th row in the figure)
Is applied. On the other hand, a rectangular wave is applied to the column electrode (m-th column).
The applied voltage is applied. At this time, FIG.
A method of synthesizing the applied voltages will be described. In the figure,
(A) and (b) are rectangular waves vibrating in the same phase.
You. Now, in the n-th row, a rectangular wave delayed by α
The case where a rectangular wave delayed by β is applied to the (n + 1) -th row
Think. Square wave delayed by α and rectangle delayed by β
The waves are as shown in (c) and (d), respectively. Now
What is important is that the nth and (n + 1) th rows are selected.
Cut off each part because it is only the wave when
Then, (e) and (f) are obtained. When this is superimposed, as shown in (g),
The components of the n-th row and the (n + 1) -th row of the signal of the m-th column are obtained.
You. Actually, the time when the square wave starts due to the gradation signal
Can be changed, and the circuit configuration is the same as that of the fifth embodiment.
Is the same as In the rectangular wave of the present embodiment, the voltage is
Since it is only binary, use a commercially available digital circuit
Therefore, cost can be easily reduced. In this case as well,
As in the fifth embodiment, when the frame speed is low, flicker is reduced.
It should be noted that this occurs. [0056] The present invention is extremely superior to the conventional method.
It will be clear from the above description that the order is high. This
There are many benefits that the present invention
Image information is displayed by phase control (phase modulation)
This results in adopting the method of manifestation. Departure
Ming is also very clean in theory. Conventionally, a large-scale matrix of STN liquid crystal is as follows.
It is inexpensive, but for color display that requires gradation display
It was not suitable. However, according to the present invention,
That the same gradation display characteristics as the active matrix can be obtained.
And As a result, relatively active matrix
Will be less competitive. Of course, the present invention does not apply to STN liquid crystal or less.
Besides, like TN liquid crystal, STB liquid crystal, ECB liquid crystal,
Materials whose optical properties depend on the RMS voltage
It goes without saying that it can be applied. Thus, the present invention
Effect of LCD on flat panel display industry such as liquid crystal
The fruit is extremely large and therefore of great industrial value
It can be said that this is an invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a conceptual diagram of a driving method of a matrix display device of the present invention. FIG. 2 shows a conceptual diagram of a driving method of a conventional matrix display device. FIG. 3 shows a conceptual diagram of a driving method of a conventional matrix display device. FIG. 4 is a conceptual diagram of a driving method of the matrix display device according to the embodiment. FIG. 5 is a conceptual diagram of a driving device of the matrix display device according to the embodiment. FIG. 6 is a conceptual diagram of a driving device of the matrix display device according to the embodiment. FIG. 7 is a conceptual diagram illustrating a driving method of the matrix display device according to the embodiment. [Description of Signs] 1, 7 shift register 2, 8 shift register (8 stages) 3, 9 memory device 4 oscillation circuit (8 frequencies) 5 voltage-controlled delay circuit 6, 11 mixer 10 voltage-controlled oscillation circuit

Claims (1)

(57) [Claims 1] In a matrix display device, an electro-optic material used for display responds to an effective value voltage, and in the display, a signal satisfying an orthonormal function is applied to a row electrode. And the column electrode includes the gradation information of the pixels included in the column.
When a display is performed by applying a signal represented by a linear combination of an orthonormal function, at least a part of gradation information is given by modulation of a phase of a signal applied to the column electrode, and the orthonormal function is applied. Is a sine wave function or a cosine wave function.