JP2524113B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a driving method of a liquid crystal display device for receiving a television image.

[Conventional technology]

In the conventional driving method of the liquid crystal display device, the polarity of the video signal applied to the liquid crystal is inverted every one field or each frame as in JP-A-60-3698.

[Problems to be solved by the invention]

However, in the above-described conventional technique, when performing interlaced scanning in a liquid crystal display device having a large number of scanning lines, in order to drive the liquid crystal with an alternating current, the polarity of the video signal must be inverted every frame.

FIG. 3 is a circuit diagram showing a driving state of a conventional liquid crystal display device, and FIG. 4 shows a timing chart of the circuit of FIG.

In FIG. 3, reference numeral 1 is an input terminal to which a video signal of a television is supplied, and a signal from the input terminal 1 is vertically (Y axis) through each of the switching elements M ₁ , M _2, ... M _m.
Direction lines L ₁ , L ₂ ··· L _m . Note that m is a number corresponding to the number of pixels in the horizontal (X axis) direction. Further, an m-stage shift register 2 is provided, a clock signal φH of m times the horizontal frequency is supplied to this shift register, and a drive pulse signal φH sequentially scanned by φH from each output terminal of the shift register 2. _{1, φH 2,} ·· _{φH m} is supplied to the control terminal of the switching-element M ₁ ~M _m.

In addition, for example, H channel FE is connected to each line L _{1 to} L _m.
Switching element consisting of T M ₁₁ , M ₂₁・ ・ M _n1 , M ₁₂ , M ₂₂・
・ One end of M _n2・ ・ M _1m , M _2m・ ・ M _nm is connected. Note that n
Is a number corresponding to a horizontal scanning line. The other ends of the switching elements M _{11 to} M _nm are connected to the common potential 3 through the liquid crystal cells C ₁₁ , C ₂₁ ... C _nm , respectively.

Further, n / 2-stage shift registers 4 and 5 are provided, and horizontal shift clock signals φ ₁ V and φ ₂ V are provided to the shift registers 4 and 5.
There are supplied, clock signal phi ₁ V, the driving pulse signal .phi.V ₁ which are sequentially scanned by phi ₂ V from the output terminal of the shift register 4,5, φV ₂ ·· φV _n is switching-element M ₁₁ ~ Each row of M _{nm in} the X-axis direction (M _{11 to} M _1m ), (M ₂₁
~ M _2m ) ··· (M _{n1 to} M _nm ) for each control terminal. The shift register 2 is supplied with a low potential (Vss _x ) and a high potential (V _DDx ), and the shift registers 4 and 5 are similarly supplied with a low potential (Vss _Y ) and a high potential (V _DDY ).

In this circuit, a clock signal as shown by A in FIG. 4 is input to the shift register 2, the drive pulse shown in FIG. 4C is output from the shift register 2, and the shift registers 4 and 5 are supplied with 4 Figure B to show φ ₁ V, φ ₂ V is respectively inputted from the shift register 4 and 5 is output driving pulse shown in Figure 4 D. At this time, φ ₁ V and φ ₂ V select an odd-numbered scanning line by operating the shift register 4 by applying a clock signal to φ ₁ V in the first field to perform interlaced scanning, and in the second field. A clock signal is applied to φ ₂ V to operate the shift register 5 to select odd-numbered scan lines and output drive pulses. When φV ₁ and φH ₁ are output, the switching elements M ₁ and M _{11 to} M _1m are turned on, and the loop of input terminal 1 → M ₁ → L ₁ → M ₁₁ → C ₁₁ → common potential 3 is generated. The liquid crystal cell C ₁₁ is formed with the input terminal 1
Is supplied to the liquid crystal cell C ₁₁ . In this way, the charge amount corresponding to the video signal of the television is written in each liquid crystal cell from C _{11 to} C _nm, and the light transmittance of each liquid crystal cell is changed by the charge amount to change the first field and the first field. The writing of 2 fields is combined to display a 1-frame television image.

By the way, when displaying with a liquid crystal, an AC drive is generally used in order to improve its reliability and life. In the case of this conventional example, the polarity of the video signal is inverted every frame and input to the input terminal 1 to obtain the waveform shown in FIG.

When a liquid crystal cell is driven with such a circuit and signal configuration, liquid crystal cells in which a video signal is written at the first field and liquid crystal cells in which a video signal is written at the second field are, for example, C ₁₁ and C ₂₁ . A comparison of changes in transmittance with time is as shown in FIG. In this case, when the switches M _{11 to} M _nm are unipolar switches such as N-channel transistors, a difference occurs between the write state and the charge holding state depending on the polarity of the charges applied to the liquid crystal cell. FIG. 6 shows such a state. As an example, when the video signal has a negative polarity with respect to the common potential 3, the writing state is good and the holding state is bad as compared with the positive polarity video signal. Shows.

FIG. 6 shows that the change in the light transmittance of the liquid crystal cell C ₁₁ is shown by the solid line 10 in the figure, and the change in the light transmittance of the liquid crystal cell C ₂₁ is shown by the broken line 11. In FIG. 6, the size of the shaded area indicates the amount of light blocking,
It is shown that when the changes 10 and 11 in the light transmittance are added, the light transmittance changes as shown in FIG. The change of light in FIG. 7 has a periodicity, and in the driving by the conventional method as described above, it changes in a cycle of one cycle in two frames (four fields). On the other hand, the video signal of the television is sent at a cycle of 60Hz for one field, and as described above, it becomes 15Hz for one cycle with four fields. At that frequency, the light transmittance vibrates and flickers, resulting in remarkable image quality. There was a problem that it would decrease. Therefore, the present invention solves such a problem, and an object of the present invention is to provide a liquid crystal display device of high image quality in which flickering does not occur even when interlaced scanning is performed.

[Means for solving problems]

The present invention will be described with reference to the reference numerals in FIG. 1. The liquid crystal cells are arranged in a matrix in the row direction and the column direction, and the first (odd row) liquid crystal cell row and the second (even row) liquid crystal cell are arranged. A liquid crystal in which cell rows are arranged alternately in the column direction, and a first (odd row) liquid crystal cell row and a second (even row) liquid crystal cell row are arranged alternately in the row direction. In a liquid crystal display device that drives a panel based on a video signal in which one frame is composed of two fields and a predetermined DC potential other than the video signal, in one (first) field, A video signal (16) having a (negative) polarity is selected and output, and in the other (second) field, a video signal (6) having the other (positive) polarity with respect to the reference potential is selected. The first switch (12) for outputting and the one (first) In the field, the predetermined DC potential (7) having the other (positive) polarity with respect to the reference potential is selected and output, and in the other (second) field, the one with respect to the reference potential. A second switch (13) for selecting and outputting the predetermined DC potential (17) having a (positive) polarity; and the other (positive) with respect to the reference potential in the one (first) field. And outputs the video signal (6) having the polarity, and in the other (second) field, selects and outputs the video signal (16) having the one (negative) polarity with respect to the reference potential. And a third switch (14) for switching, and in the one (first) field, selecting and outputting the predetermined DC potential (17) having the one (negative) polarity with respect to the reference potential, In the other (second) field, the reference A fourth switch (15) for selecting and outputting the predetermined DC potential (7) having the other (positive) polarity with respect to the position, and in the one (first) field, the first row Selecting the first liquid crystal cell rows in the arrangement order along the column direction for each scanning period based on the selection timing signal (φ1V),
In the other (second) field, based on the timing signal (φ1V) having a phase opposite to that of the first row selection signal, the first liquid crystal cell is returned every blanking period between scanning periods of each row. First row selecting means (4) for selecting rows in the arrangement order along the column direction, and in the one (first) field, based on a second row selection timing signal (φ2V), The second liquid crystal cell rows are selected in the arrangement order along the column direction for each blanking period during the scanning period, and in the other (second) field, the second row selection signal is opposite to the second row selection signal. Row selection means (5) for selecting the second liquid crystal cell rows in the order of arrangement in the column direction based on the phase timing signal (φ2V), and during the scanning period, Select the liquid crystal cell column of each column in the order of arrangement along the row direction, and during the blanking period, Column selecting means and (2,9 selecting said liquid crystal cell in each column simultaneously, .theta.1, .theta.2
, M1, M2, ...) In the blanking period, the output of the second switch (13) is selected and output to the second liquid crystal cell row, and in the scanning period, the second switch (13) is output. For the liquid crystal cell column of
And a fifth switch (8) for selecting and outputting the output of the switch (12), and for selecting the output of the fourth switch (15) for the first liquid crystal cell row in the blanking period. And a sixth switch (18) for selecting and outputting the output of the third switch (14) to the first liquid crystal cell column in the scanning period. To do.

〔Example〕

In the present invention, as shown in FIG. 1, a positive DC signal 6, a negative video signal 16 and a constant DC potential are used as potentials other than the video signal (hereinafter, referred to as constant DC potential). With constant polarity DC potential 7 and constant negative polarity DC potential 17 as signal source, and signal switching switches 12, 13, 14, 1
The 5,8,18 controls the signal input to the input terminal 1 and 21 at the timing described below, and the input terminal 21, vertical signal lines L ₁ of the odd-numbered columns of the panel portion, L ₃ switch to · · M ₁ , M ₃ ···, and the input terminal 1 is a vertical signal line in an even column
The horizontal retrace period of the video signal of the television shown in FIG. 2 is shown as an example, which is driven by a configuration in which the switches are connected to L ₂ , L ₄ ··· L _m via switches M ₂ , M ₄ ·· M _m . 1 jumped in
A method of applying a constant DC potential to the display liquid crystal cells of the rows will be described below.

In FIG. 1, the signal switching switches 12, 13, 14, 15 select the positive polarity video signal and a certain direct current when the level is "L" by the control signal φA, ▲ ▼, and when the level is "H". , A negative video signal and a constant DC level are selected. φA and ▲ ▼ are control signals in which “H” and “L” are alternated for each field as shown in FIG.

Next, input terminals 1 and 21 receive φ
When s is at "H" level (during the horizontal retrace period), a constant DC potential 7,17 is connected to the input terminals 1,21, and φs
At the “L” level (during the horizontal scanning period), input switching circuits 8 and 18 for controlling the video signals 6 and 16 to be connected are added, and at the same time, the switches M ₁ ... M _n are externally connected. OR gate θ ₁ θ ₂ ·· θ
_{Append n} . The input switching signal φs is applied to the all-on terminal 9. When each signal is input to such a circuit configuration at the timing shown in FIG.
The video signals 6 and 16 and the constant DC potentials 7 and 17 shown in FIG. 8 have a switched waveform.

In the first field, φ ₁ V is the shift register 4
Input to ΦV ₁ , ΦV ₂
A drive pulse is generated when 6 is input (during the horizontal scanning period), and a liquid crystal cell connected to an odd-numbered line.
_{C 11 C 12 ·· C 1m,} C 31, C 32 ·· C 3m ·· to the video signal 6 and 16 are written alternately in the row direction. At this time, during each horizontal blanking period, no drive pulse is generated from the shift register 4 and φ ₂ V
Drive pulse is generated in synchronization with the above horizontal retrace period in which a constant DC potential 7,17 is input to the input terminals 1,21 from the shift register 5 which is input Liquid crystal cell C ₂₁ , C ₂₂・ ・ C _2m , C ₄₁ , C ₄₂・ ・ C _4m
..Constant DC potentials 7,17 are written alternately in the row direction in C _nm .

In the second field, the phases of φ ₁ V and φ ₂ V are opposite to the first field, and a constant DC potential of 7,17 is applied to the liquid crystal cells connected to the odd-numbered lines.
Is applied during the horizontal blanking period, and the video signals 6 and 16 are applied to the liquid crystal cells connected to the even-numbered lines during the horizontal scanning period.

The temporal change in the light transmittance of the liquid crystal cell in this driving is shown in FIG.

In FIG. 9, a solid line 10 indicates changes in light transmittance of liquid crystal cells for display in odd-numbered columns and odd-numbered rows, and a dashed-dotted line 19 indicates odd-numbered columns, even-numbered columns,
The broken line 11 shows the change in light transmittance of the liquid crystal cells for display in the even-numbered columns and the odd-numbered lines, and the two-dot chain line 20 shows the change in the light transmittance of the display liquid crystal cells.

The change in light transmittance of the entire liquid crystal display device is shown in the above 10, 19, 1
The value is the sum of the areas of 1,20 and is shown in Fig. 10. First
The periodicity of the change in the light transmittance in FIG. 10 is 1 field, and the flickering does not occur because the vibration of the light transmittance is 60 Hz.

The embodiment of the present invention has been described above by using the method of inputting a constant DC potential during the horizontal line period. However, a video signal memory corresponding to one scanning line is provided for two scanning lines, and an image of the next scanning line is provided. While reading and storing the signal, the method of writing the previously stored video signal and the constant DC potential line by line for 1/2 horizontal scanning period, or L ₁ , L
₂ ... switches the L content which has been stored corresponding to the _{m M 1, M 2} ·
・ By turning on M _m at the same time and writing line by line,
Similar effects can be obtained by applying a video signal and a constant DC potential.

〔The invention's effect〕

As described above, according to the present invention, by inputting a constant DC potential to an interlaced liquid crystal cell having no video signal and alternately driving the DC voltage and the video signal that is normally sent, a) each Since one of the video signal and a predetermined DC potential is applied to the liquid crystal cell for each field, it is possible to prevent a reduction in contrast.

b) A video signal or a predetermined DC potential applied to each liquid crystal cell for each field has a positive polarity or a negative polarity with respect to a reference potential, and each liquid crystal cell has a positive polarity and a negative polarity for each field. Since the potentials of 1 are alternately applied, deterioration of the life of the liquid crystal can be prevented.

c) Since a liquid crystal cell to which a video signal is applied and a liquid crystal cell to which a predetermined DC potential is applied are alternately arranged in one screen formed by a video signal of one field, the screen for each field is The transmittance is balanced and the screen flicker is reduced. Further, since the cycle of change in transmittance is one field, flicker is reduced.

d) It is possible to drive a high-quality liquid crystal display device having more liquid crystal cell rows than the number of scanning lines in one field of a video signal.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a driving method of a liquid crystal display device of the present invention. FIG. 2 is a timing chart of respective signals showing an embodiment of a driving method of a liquid crystal display device of the present invention. FIG. 4 is a circuit configuration diagram showing a driving method of a liquid crystal display device. FIG. 4 is a timing chart of each signal showing a driving method of a conventional liquid crystal display device. FIG. 5 is an input signal diagram to the conventional liquid crystal display device. FIG. 8 is a state diagram showing a change in light transmittance according to a conventional driving method. FIG. 8 is an input signal diagram to a liquid crystal display device according to the present invention. FIGS. 9 and 10 are light transmission according to the driving method according to the present invention. State diagram showing rate change 1,21 …… Input terminals to liquid crystal display device 2,4,5 …… Shift register 3 …… Common potential 6 …… Video signal 7,12,13,14,15 …… Video Potential other than signal (constant DC potential) 8,18 …… Switching circuit 9 …… All-on terminal 10,11,19,20 …… Liquid Permeabilizing factor M is switching-element cell with a light, C is the liquid crystal cell, L is the vertical signal lines.

Claims (1)

(57) [Claims] 1. Liquid crystal cells are arranged in a matrix in a row direction and a column direction, a first liquid crystal cell row and a second liquid crystal cell row are alternately arranged in the column direction, and a first liquid crystal cell row is arranged. A liquid crystal panel in which liquid crystal cell columns and second liquid crystal cell columns are alternately arranged in the row direction is provided with a video signal in which one frame is composed of two fields and a predetermined DC potential other than the video signal. In a liquid crystal display device driven based on, a video signal having one polarity with respect to a reference potential is selected and output in one field, and a video signal having the other polarity with respect to the reference potential is output in the other field. A first switch for selecting and outputting; in the one of the fields, the predetermined DC potential having the other polarity with respect to the reference potential is selected and output; and in the other field, the predetermined DC potential is output. A second switch for selecting and outputting the predetermined DC potential having the one polarity with respect to the sub-potential, and a video signal having the other polarity for the reference potential in the one field. And a third switch for selecting and outputting the video signal having the one polarity with respect to the reference potential in the other field, and the one field with respect to the reference potential in the one field. A fourth switch for selecting and outputting the predetermined DC potential having a polarity, and for selecting and outputting the predetermined DC potential having the other polarity with respect to the reference potential in the other field; In one field, the first liquid crystal cell rows are selected in the arrangement order along the column direction for each scanning period based on the first row selection timing signal, and the other row is selected. In the field, the first liquid crystal cell rows are arranged in the arrangement order along the column direction for each blanking period during the scanning period of each row based on a timing signal having a phase opposite to that of the first row selection signal. First row selecting means for selecting; and in the one field, the second liquid crystal cell row is set for each blanking period during the scanning period of each row based on a second row selection timing signal. In the other field, the second liquid crystal cell rows are selected in each column based on a timing signal having a phase opposite to that of the second row selection signal in the order of arrangement in the column direction. Second row selecting means for selecting an array order along the direction; and liquid crystal cell columns of each column during the scanning period for selecting an array order along the row direction, and for selecting each column during the blanking period. A column selecting means for selecting the liquid crystal cells at the same time; The output of the second switch is selected and output to the second liquid crystal cell row, and the output of the first switch is selected to the second liquid crystal cell row during the scanning period. A fifth switch for outputting, and a fourth switch for the first liquid crystal cell row in the blanking period.
A sixth switch for selecting and outputting the output of the third switch with respect to the first liquid crystal cell column during the scanning period. Liquid crystal display device.