JP2524112B2 - 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 denotes 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 , ... Mm.
Directional lines L ₁ , L ₂ , ... Lm are supplied. 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 the output is sequentially scanned by φ ₁ H and φ ₂ H from each output terminal of the shift register 2. The drive pulse signals φH ₁ , φ ₂ H, ... φHm are supplied to the control terminals of the switching elements M _{1 to} Mm.

Further, for example, N-channel FE is provided in each line L _{1 to} Lm.
Switching element consisting of T M ₁₁ , M ₂₁ , ... Mn ₁ , M ₁₂ , M ₂₂ ...
… Mn ₂ …… M ₁ m, M ₂ m …… One end of Mnm is connected. Note that n
Is the number corresponding to the horizontal scanning line. The other ends of the switching elements M _{11 to} Mnm are connected to the common potential 3 through the liquid crystal cells C ₁₁ , C ₂₁ ... Cnm, 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 respectively supplied to the shift registers 4 and 5, and the output terminals of the shift registers 4 and 5 respectively. Drive pulse signals φV ₁ , φV ₂ ... φVn sequentially scanned by the clock signals φ ₁ V, φ ₂ V of each of the switching elements M _{11 to} Mnm in the X-axis direction columns (M _{11 to} M ₁ m), (M ₂₁ ~ M ₂ m) …… (Mn ₁
~ Mnm) is supplied to each control terminal. The shift register 2 is supplied with a low potential (V _ssx ) and a high potential (V _DDX ), and the shift registers 4 and 5 are similarly supplied with a low potential (V _SSY ).
And a high potential (V _DDY ) is supplied.

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 Φ ₁ V and φ ₂ V shown in FIG. 4B are input, and the drive pulses shown in FIG. 4D are output from the shift registers 4 and 5. 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 ₁ m are turned on, and the loop of input terminal 1 → M ₁ → L ₁ → M ₁₁ → C ₁₁ → common potential 3 There the liquid crystal cell C ₁₁ is formed, the potential difference between the input terminal 1 and the common potential 3 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 up to C _{11 to} Cnm, and the light transmittance of each liquid crystal cell is changed by the charge amount to change the first field and the second field. A 1-frame television image is displayed with the writing of fields.

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} Mnm are unipolar switches such as N-channel transistors, the polarity of the charges applied to the liquid crystal cell causes a difference in the written state and the held state of the charges. 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 flicker 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 panel in which cell rows are alternately arranged in the column direction, and first (odd number) liquid crystal cell rows and second (even number) liquid crystal cell rows are alternately arranged in the row direction. In a liquid crystal display device that is driven 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 first row selection timing Based on the signal (φ1V), the first
(Odd row) liquid crystal cell rows are selected in the arrangement order along the column direction, and in the other (second) field, based on a timing signal (φ1V) having a phase opposite to that of the first row selection signal, For each blanking period between the scanning periods of each row, the first
First row selecting means (4, M11, M12 ...) for selecting (odd row) liquid crystal cell rows in the arrangement order along the column direction, and second row selection in the one (first) field. Based on the timing signal (φ2V), the second (even row) liquid crystal cell row is selected in the arrangement order along the column direction every retrace line period during the scanning period of each row, and the other (first row) is selected. In the field 2), based on the timing signal (φ2V) having a phase opposite to that of the second row selection signal, the second (even row) liquid crystal cell row is arranged along the column direction every scanning period. Second row selection means (5, M21, M22)
...), and a column selection unit that selects the liquid crystal cell columns of each column in the arrangement order along the row direction during the scanning period and simultaneously selects the liquid crystal cell columns of each column during the blanking period ( 2, 9, θ1,
.theta.2 ... .theta.n, M1, M2 ... Mm), and in the blanking period, the predetermined DC potential (17) having one (positive) polarity with respect to the reference potential is applied to the second (even column) liquid crystal cell. Output to a column, and in the scanning period, a video signal (1) having the other (negative) polarity with respect to the reference potential.
6) is output to the second (even column) liquid crystal cell column
Switch (8) and the other (negative) with respect to the reference potential in the blanking period.
The predetermined DC potential (7) having a polarity of
It outputs to the liquid crystal cell row of (odd row), and in the scanning period,
A second switch (18) for outputting the video signal (6) having the one (positive) polarity with respect to the reference potential to the first (odd row) liquid crystal cell row, To do.

〔Example〕

An embodiment of the present invention will be described below by using a constant DC level for potentials other than video signals.

In the present invention, the input terminals 1 and 21 in FIG.
Video signals 6 and 16 and potentials other than the corresponding video signals 7,
17 is switched and supplied, and a potential other than the above video signal is applied to the liquid crystal cell connected to the skipped scanning line. FIGS. 1 and 2 show an embodiment of the present invention. As
A method of writing a potential other than the above video signal within the horizontal blanking period of the video signal of the television is shown. First
In the figure, when φs is at the “H” level due to the input switching signal φs at the input terminals 1 and 21 (during the horizontal blanking period)
Is when the potentials 7 and 17 other than the video signal are connected to the input terminals 1 and 21 and φs is at the “L” level (during the horizontal scanning period).
Is added with input switching circuits 8 and 18 for controlling the video signals 6 and 16 to be connected, and at the same time, switches M ₁ ... Mn
So that it can be turned on all the way from the outside.
₁ θ ₂ ... Adds θn. The input switching signal φs is applied to the all-on terminal 9. When each signal is input to such a circuit structure at the timing shown in FIG. 2, the input terminal 1 has a waveform in which the video signal 6 shown in FIG. 8 and the potential 17 other than the video signal are switched.

In the first field, φ ₁ V is the shift register 4
Are input to φV ₁ , φV ₃ ...... are input to input terminals 1,21 and video signals 6,1
A drive pulse is generated when 6 is input, and the display liquid crystal cells C ₁₁ , C ₁₃ , C ₁₅ , C ₁₇ , ... connected to the odd-numbered vertical lines and connected to the odd-numbered horizontal lines. C ₃₁ ,
The video signal 6 of positive polarity is sequentially written in C ₃₃ , and the liquid crystal cells for display which are connected to the even-numbered vertical lines and connected to the odd-numbered horizontal lines have C ₁₂ , C ₁₄ ...
The negative video signal 16 is sequentially written. At this time, during each horizontal blanking period, no drive pulse is generated from the shift register 4 and the shift register 5 receiving φ ₂ V outputs φ.
V ₂ , φV ₄ ……, but input terminals 1 and 21 have potentials other than video signals 7,1
A drive pulse is generated when 7 is input, and liquid crystal cells C ₂₁ and C ₂₃ for display connected to odd-numbered vertical lines and even-numbered horizontal lines are not negative polarity video signals. 7 are sequentially written, and the potentials 17 other than the positive polarity video signal are sequentially written to the display liquid crystal cells C ₂₂ , C _24, ... Which are connected to the even-numbered vertical lines and are connected to the even-numbered horizontal lines. Be done.

In the second field, the phases of φ ₁ V and φ ₂ V are opposite to the first field, and the display liquid crystal cell to which the video signal of positive polarity has been input is other than the video signal of negative polarity. The potential of, the display liquid crystal cell to which the potential other than the negative polarity video signal is input, the positive polarity video signal is input, to the display liquid crystal cell to which the negative polarity video signal is input, The potentials other than the positive polarity video signal are sequentially written so that the negative polarity video signal is input to the display liquid crystal cells to which the potentials other than the positive polarity video signal have been input.

The change over time of the light transmittance of the liquid crystal cell in this driving is represented by the display liquid crystal cells C ₁₁ , C ₁₂ , C ₂₁ and C ₂₂ as shown in FIG.

In FIG. 9, the solid line 10 represents the change in light transmittance of the display liquid crystal cell C ₁₁ , the broken line 11 represents C ₁₂ , the one-dot chain line 19 represents C ₂₂ , and the two-dot chain line 20 represents C.
₂₁ shows changes in the light transmittance of each of the ₂₁ 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 using the method of inputting a constant DC potential in the horizontal blanking period by using a constant DC potential as the potential other than the video signal. The memory has two scanning lines, and while reading and storing the video signal of the next scanning line, one line of the previously stored video signal and a constant DC potential are stored for 1/2 horizontal scanning period. Writing method one by one and writing L ₁ , L ₂ ...... L
The same effect can be obtained even when a video signal and a constant DC potential are applied by writing the stored contents corresponding to m in a line sequential manner by turning on the switches M ₁ , M ₂ ... Mm at the same time. .

〔The invention's effect〕

As described above, according to the present invention, by inputting a constant linear potential to an interlaced liquid crystal cell having no video signal and alternately driving it with a 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.

e) In addition to the row direction, the polarity reversal drive can be performed not only in the column direction but also in the column direction. Therefore, even if the flicker caused by the imbalance between the positive polarity and the negative polarity occurs between the inverted units, the row, In both columns, it is difficult to see between pixels so that the display quality is improved in image display.

[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 the driving method of the liquid crystal display device. FIG. 4 is a timing chart of each signal showing the driving method of the 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 change of rate 1,21 …… Input terminals to liquid crystal display device, 2,4,5 …… Shift register, 3 …… Common potential, 6,16 …… Video signal, 7,17…
… Potentials other than video signals (constant DC potential), 8,18… Switching circuit, 9 …… All-on terminals, 10,11,19,20 …… Transmittance of light from liquid crystal cell M is a switching element, C Is a liquid crystal cell and L is a vertical signal line.

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 defective cell row are alternately arranged in a column direction, and a first liquid crystal. A liquid crystal panel in which cell columns and second liquid crystal cell columns are alternately arranged in the row direction is applied to a video signal in which one frame is composed of two fields and a predetermined DC potential other than the video signal. In the liquid crystal display device driven based on the above, 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 field is selected. Then
The first liquid crystal cell rows are selected in the arrangement order along the column direction for each blanking period between the scanning periods of each row based on a timing signal having a phase opposite to that of the first row selection signal. First row selection means, and in the one field, based on a second row selection timing signal, the second liquid crystal cell row is arranged in the column direction in each retrace period between the scanning periods of the respective rows. In the other field, the second liquid crystal cell rows are arranged in the column direction in each scanning period based on a timing signal having a phase opposite to that of the second row selection signal in the other field. Second row selecting means for selecting an array sequence along the row, and liquid crystal cell columns of each column in the array order along the row direction during the scanning period, and the liquid crystal cells of each column during the blanking period. Column selecting means for selecting cell columns at the same time, and in the blanking period, the reference The predetermined DC potential having one polarity with respect to the second potential is output to the second liquid crystal cell column, and the video signal having the other polarity with respect to the reference potential is supplied to the second liquid crystal in the scanning period. A first switch for outputting to a cell row, and, in the blanking period, outputs the predetermined DC potential having the other polarity with respect to a reference potential to the first liquid crystal cell row, and in the scanning period, A second switch for outputting a video signal having one of the polarities with respect to the reference potential to the first liquid crystal cell column, a liquid crystal display device.