JPS6158386A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To display a good static picture for a long time without strains of an image not using the specific scan by regulating a signal and resetting an electric load after the signal taken out of a liquid crystal cell is returned to the same liquid crystal cell. CONSTITUTION:An input terminal 1 is connected with switching component M1-Mm through a switching component MB and a common display side of connecting point N of a common/static display switch MA. The connecting point between the component MB and M1-Mm is connected with an amplifier 12 through a switching component MA and connected with a condenser 13 and a turn circuit 14 by the output of the amplifier 12. The output of the circuit 14 is regulated by a regulating circuit 15 to connect with a static display side connecting point S of a switch 11. Further, switching components MR1-Mm is connected with each signal line L1-Lm and a target terminal 3 is connected with M1-Rm to display a good static picture for a long time without strains of the image.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to /ff? The present invention relates to a liquid crystal display device for displaying still images.

[Conventional technology]

For example, it has been proposed to display a 1thl image on a television using a liquid crystal.

In FIG. 8, (11 is an input a111 to which a television video signal is supplied, and the signal from this input terminal (11) is vertically (Y It is supplied to lines LL, L2 . . . Lm in the axial direction.

Note that m is a number corresponding to the number of pixels in the horizontal (X-axis) direction. Furthermore, a clock signal Φ□H1''2N with m times the horizontal frequency is supplied to an m-stage shift register (2 rows are provided, this shift register 12), and this shift register (2
) ☆1; Clock signal from 1 child ΦIHT Φ
Pixel switch signal φH1, which is sequentially scanned by 2H.
φH2...φHTn are supplied to each control terminal of the switching elements M1 to Mm. Note that the shift register (2) is supplied with a low potential (V ss ) and a high potential (Voo), and drive pulses of these two potentials are formed.

In addition, each line L1 to Lm has a switching element M111M21, for example, an N-channel FET.
・Mn11M129M22...Mn7. ...M i
n r M 2. ．． 1...One end of Mnm is connected. Note that n is a number corresponding to the number of horizontal scanning lines. The other ends of the switching cables MLI to Mnm are connected to target terminals (
3).

Further, a 0-stage shift register (4) is provided, and this shift register (4) receives a horizontal frequency clock signal ΦIV.
r Φ2V is supplied, and l! by the clock signals Φ□V and Φ2v from each output terminal of this shift register (4). Scanning line switch signal φV1+φ scanned sequentially
v2...φvn is the gate line G1 in the horizontal (X-axis) direction
．． -02...Switching element M through On
Each row in the X-axis direction of 11 to Mnm<Mtt to M1m),
(M21 to M21)... (Mn1 to Mnm) are respectively supplied to control terminals. Note that the shift register (4) also has VSS and V as in the shift register (2).
DD is supplied.

That is, in this circuit, a shift register (2).

(4) As shown in FIG. 9A and B, the lock signal ΦI
HI Φ2H1ΦtV+Φ2v is supplied. The shift register (2) outputs φH1 to φho for each pixel period as shown in FIG. 9C, and the shift register (4) outputs φv4 for each horizontal period as shown in FIG. 9. ~φvn is output. Furthermore, input terminal (1)
is supplied with a signal as shown in FIG. 9E.

When φVl+ φH is being output, switching elements M1 and M11 to M1□ are turned on, and input terminal (1) = M 1 = L 1 - M u = C11→
A current path for the target terminal (3) is formed and the liquid crystal cell C
The potential difference between the signal supplied to the input terminal (II) and the target terminal (3) is supplied to u. Therefore, this cell C1
A charge corresponding to the potential difference due to the signal of the first pixel is applied to the sample water in the capacity of 1. The light transmittance of the liquid crystal changes depending on the amount of charge. The same process is performed sequentially for cells Ct2 to Cnm, and when the next field signal is supplied, each cell C1l to Cnm is
The amount of charge in nm is rewritten.

In this way, the light transmittance of the liquid crystal cells C1l to Cnm is changed corresponding to each pixel of the video signal, and this is sequentially repeated until the TV lI! A tI image is displayed.

By the way, when displaying with a liquid crystal, AC drive is generally used to improve its reliability and lifespan. For example, when displaying television images, a signal obtained by inverting the video signal for each field or frame is input to the input terminal (1).
supply to. In other words, the input terminal (1) has the 91st gl.
As shown in E, an inverted signal is supplied for each field or frame.

By the way, in the above-mentioned apparatus, there is a demand for displaying an arbitrary television image as a still image. In that case, conventionally, for example, a memory for one field or one frame is provided, a desired image is stored in this memory, this is repeatedly stored, and the phase of the read signal is inverted for each field. 'ζ It is proposed to feed the above-mentioned input terminal (11).

However, the memory for one field or one frame as described above is itself large and quadrivalent.
It is difficult to apply it to general consumer equipment.

In response to this, for example, as disclosed in Japanese Patent Laid-Open No. 58-107782, it has been proposed to utilize the memory function of the liquid crystal cell C to display still images. That is, in this device, in a liquid crystal video display drive circuit having a first sample bold circuit that supplies a video signal whose polarity is inverted for each screen to a plurality of pixels in time series, the video signal is inverted and the polarity is inverted. an inverting means for supplying the sample and hold circuit to the sample and hold circuit of the plurality of ii! Switching to supply the video signal from the second sample bold circuit and the external 61ii element or the video signal from the second sample and hold circuit to the inverting means without reading out the video signal from the element II in time series. A liquid crystal video display driving circuit having means.

However, in the case of this device, as described in the publication, the image shifts by one pixel in the scanning direction each time one field is displayed. For this reason, measures such as reversing the scanning direction for each field are taken, but switching the scanning direction in this way requires a large-scale circuit, and the scanning direction is shifted by one pixel alternately for each field. Since the state remains, there is a possibility that this may result in flicker or the like.

Also, since the signal from the liquid crystal cell C is extracted, this signal is returned to the liquid crystal cell C, and this process is repeated to display a still image, if there is any distortion in the signal transmission characteristics during this time, this distortion will occur. This accumulates and the image quality deteriorates significantly in a short period of time. For this purpose, it has been shown that the gain of the inverting means should be set to d, but it is impossible to make such adjustments completely, and it is impossible to display a still image in an orthogonal manner for a long period of time. It is extremely difficult 1'-1t.

Furthermore, if there is residual electricity in the stray capacitance of the signal line when extracting the signal from the liquid crystal cell C, the signal will also deteriorate, making it impossible to display still images for a long time. I end up.

[Problem that the invention seeks to solve]

Conventional devices were constructed as described above. For this reason, conventional devices have problems such as complicated configurations and extremely poor image quality when displaying still images for a long time.

[Means for solving problems]

In the present invention, the number of column lines Ll is equal to the number of horizontal pixels.

L2 . . . Lm are horizontal switch elements M1, . M2...supplies the video signal via Mm, and connects the row lines G, G of the number equal to the number of horizontal scanning lines.
2... Gn is supplied with a scanning line switch signal sequentially formed by horizontal scanning clocks, and a pixel switch element M11 is driven on by the scanning line switch signal at each intersection of each column line and row line. ．． M12...Mn
m, and the video signal supplied to the column line through these pixel switch elements is supplied to liquid crystal display cells Cu, C12...Cnm4, each of which constitutes one pixel. , a first switch element MA that is turned on in the first half of the pixel switch signal is connected to the signal path (1) that commonly supplies the video signal to the horizontal switch elements, and the on period of this first switch element is controlled. The video signal stored in the liquid crystal cell is taken out via the pixel switch element and the horizontal switch element, and this taken out signal is inverted (1
4) and normalization for each predetermined level range (15) L,
This inverted and IF normalized signal is supplied to the signal path via the second switch element MB which is turned on in the latter half of the pixel switch signal, and the horizontal block of the video signal is supplied to each column line. This is a liquid crystal display device characterized in that a reset voltage (3) is supplied through third switching elements MR□, MR2, . . . MRll, which are turned on every ranking period.

[Effect]

According to this device, the signal taken out from the liquid crystal cell C is returned to the same liquid crystal cell C. There is no image shift, etc., no special scanning is required, and the drive circuit etc. is the same as the conventional one. can be used as is.

In addition, since the signal is normalized and the signal line potential is reset, the image quality will not deteriorate due to these steps.
Good still image display can be performed for a long time.

〔Example〕

In Figure 1, the manual terminal (1) always displays iln / /
j71 It is connected to the switching elements M1 to Mrn through the normal display side contact N of the still image display changeover switch (11) and the switching element MB. Also, switching element M
The connection midpoint between B and switching elements M1 to Mm is connected to an amplifier (12) via switching element M, and a capacitor (13) is connected to the output terminal of this amplifier (12), and this output terminal is inverted. It is connected to a normalizer (15) through circuit M& (14). The output terminal of this normalization circuit (15) is the changeover switch (1
It is connected to the still image table unexpected contact point S of 1). Furthermore, each of the signal lines L1 to Lm has a switching element MR□,
MR2 .

In this device, switching elements MA, MB
Switch signals φA and φB as shown in C and D are supplied to the gate terminals of pixel switch signals φH□ and φH2 as shown in A and B in FIG. 2, respectively. Note that for the following pixel switch signals φH3, . . . , φB is formed into a similar switch signal φ.

As a result, for example, the signal of the corresponding liquid crystal cell C is taken out in the first half of the pixel switch signal φH□, this signal is accumulated on the capacitor (13) through the amplifier (12), and the inverting circuit (14) and the normalizing circuit ( 15), it is written into the same liquid crystal cell C in the latter half of the pixel switch signal φH.

Set the potential of the signal from cell C to 11 with -3, and
If the capacitance of the capacitor (13) is 05, then the amplifier (1
If the capacitance of 2) is CP, the potential of the hot side of the capacitor (13) is v', and the gain is -A, then the output potential of this inverting circuit (14) is vI+, , = , . By setting the value of -A to , the same inverted signal is rewritten to the liquid crystal cell C, and a still image is displayed by AC drive.

However, in this case, it is impossible to completely determine the value of -A in the manner described above. Therefore, the normalization circuit (15)
is provided. The human output characteristics of this normalization circuit (15) are as shown in Figure 3, and by providing this, even if there is some error in the value of -A, the output signal (reproduction) is always (write multiple) can be set to a constant value.

Furthermore, a horizontal blanking signal φHaLK is supplied to the gate terminals of the switching elements MR, MR,11.

Therefore, each signal line L1 to Lm is reset to the target voltage every 1t blanking. Therefore, the signals remaining on each signal line are reset, and the liquid crystal cell C
Unnecessary signals will not be mixed in when extracting the signals.

In this way, still images are displayed, and the above-mentioned device has a very hour wheel configuration, and the signal does not deteriorate even if it is displayed for a long time, so it always maintains a good quality. You can perform still image display.

Furthermore, FIG. 4 shows a case where the number of liquid crystal cells C is tripled to display a color display, and each color (red, red, etc.) is displayed.

A circuit corresponding to the edge (blue) is provided in parallel (R.

G and B suffixes) are simultaneously driven to perform the same operation as described above. In this case, the processing of extracting, inverting, and rewriting the signal from the liquid crystal cell C described above requires processing time because it includes a capacitor, and the above-mentioned configuration lengthens the processing time. Note that this configuration can also be applied when increasing the density of an image in monochromatic display.On the contrary, it can also be applied when using a low-speed circuit that requires a long processing time.

By the way, in the above configuration, the normalization circuit (15R) (1
5G ) (1511) has a short processing time but a large circuit scale. Therefore, as shown in Fig. 5, the signals for three pixels supplied in series are transferred to the switching element MOIB,
Simultaneous with MO2B and MO3B, capacitor (1
61n) (16G) (16B) to the buffer circuit (17Rn (17G) <178), and this signal is supplied to the switching elements MBR, M8G
, M BB to each liquid crystal cell similar to the above, and from each liquid crystal cell to a switching element M AR
, M AG , M AR, Amplifier (12R) (1
2G) (12B), capacitor (13R) (
13G) (13B), inversion circuit (14R)
(14G) and (14B), this signal is serialized to the switching element MOI by +MO2A+M03A, and is supplied to the normalization circuit (15). Note that FIG. 6 shows a time chart of each switching. This also allows the same still image display as described above.

Furthermore, in Figure 7, six pixels are arranged in parallel, ii! In this case, two sets of three circuits each (suffix O,
(denoted with E), and these are driven in parallel. In this case, normalization circuits (150), (151
It can also be made as slow as possible.

Note that this device can be used for active matrix liquid crystal display devices using TPT such as amorphous silicon, polysilicon, silicon on the fire, and Aritsuki half-body.

Furthermore, the above-mentioned shift registers +21, +4) may be provided outside the IG that constitutes the device.

Furthermore, the display can be either dot-sequential or line-sequential.

〔Effect of the invention〕

According to the present invention, since the signal taken out from the liquid crystal cell C is returned to the same liquid crystal cell C, there is no possibility of image shift, etc., and there is no need for special scanning, etc., and the drive circuit etc. Things can be used as is.

In addition, since the signal is normalized and the potential of the signal line is reset, the °C image quality does not deteriorate due to these operations, and it is now possible to perform high-quality still image display over a long period of time. Ta.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of the present invention, FIGS. 2 to 7 are diagrams for explaining the same, and FIGS. 8 and 9 are diagrams for explaining a conventional apparatus. L1~Lm are vertical signal lines, G1~On are gates Lisen, Ml~Mm, Mzt~Mnm, MA, MB. MR1~M1. is a switching element, (14) is an inversion circuit, and (15) is a normalization circuit. Figure 6 Gφp Figure 8 Figure Van Figure 9

Claims (1)

[Claims] Supplying a video signal to a number of column lines equal to the number of horizontal pixels through horizontal switch elements that are turned on by pixel switch signals sequentially formed by a horizontal pixel clock,
A scanning line switch signal that is sequentially formed by a horizontal scanning clock is supplied to the row lines equal to the number of horizontal scanning lines, and a pixel is turned on by the scanning line switch signal at the intersection of each column line and the row line. In a liquid crystal display device that includes switch elements and supplies the video signals supplied to the column lines via these pixel switch elements to liquid crystal display cells each constituting one pixel, the horizontal switch element A first signal path that commonly supplies the video signal is turned on in the first half of the pixel switch signal.
The video signal stored in the liquid crystal display cell is extracted through the pixel switch element and the horizontal switch element during the ON period of the first switch element, and the extracted signal is inverted and The signal is normalized for each predetermined level range, and the inverted and normalized signal is supplied to the signal path via a second switch element that is turned on in the latter half of the pixel switch signal, and is also applied to each column line. A liquid crystal display device characterized in that a reset voltage is supplied through a third switch element that is turned on every horizontal blanking period of the video signal.