JPS6348077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device for, for example, television reception.

Background Art and its Problems For example, it has been proposed to display television images using a liquid crystal.

In FIG _. 1, 1 is an input terminal to which a television video signal is supplied, and the signal from this input terminal ₁ is vertically (Y
axial) direction lines L ₁ , L ₂ ...Lm. 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, and clock signals Φ _1H and Φ 2H of m times the horizontal frequency are supplied to this shift register 2, and clock signals Φ _1H and Φ _2H from each output terminal of this shift register _{2 are} supplied. Drive pulse signals φ _{H1 ,} φ _{H2 ,} . Note that the shift register 2 is supplied with a low potential (V _SS ) and a high potential (V _DD ), and drive pulses of these two potentials are formed.

In addition, switching elements M ₁₁ and M ₂₁ each consisting of, for example, an N-channel FET are installed in each line L ₁ to Lm.
...M _o1 , M ₁₂ , M ₂₂ ... M _o2 ... M _1n , M _2n ... M _on are connected at one end. Note that n is a number corresponding to the number of horizontal scanning lines. The other ends of the switching elements M ₁₁ to _{M on} are connected to the target terminal 3 through liquid crystal cells C ₁₁ , C ₂₁ . . . C _on , respectively.

Further, an n-stage shift register 4 is provided, and horizontal frequency clock signals Φ ₁ v, Φ ₂ v are supplied to this shift register 4, and clock signals Φ ₁ v, Φ ₂ from each output terminal of this shift register 4 are supplied. Drive pulse signals φv ₁ , φv ₂ ...φv _o sequentially scanned by v
However, each row of switching elements M ₁₁ to M _on in the X-axis direction (M ₁₁ to M _1n ), (M ₂₁ to M _2n )...(M _o1 to M _on )
are supplied to each control terminal respectively. Note that shift register 4 also has the same function as shift register 2.
V _SS and V _DD are supplied.

That is, in this circuit, shift registers 2 and 4 are supplied with clock signals Φ _1H , Φ _2H , Φ ₁ vφ ₂ v as shown in FIGS. 2A and 2B. The shift register 2 outputs φ _H1 to φ _Hn for each pixel period as shown in FIG. 2C, and the shift register 4 outputs φv ₁ to φv for each horizontal period as shown in FIG. 2D. _o is output. Furthermore, the input terminal 1 is supplied with a signal as shown in FIG. 2E.

When φv ₁ and φ _H1 are being output, switching elements M ₁ and M ₁₁ to _{M 1n} are turned on, and the current path of input terminal 1 → M ₁ → L ₁ → M ₁₁ → C ₁₁ → target terminal 3 is turned on. is formed, and the potential difference between the signal supplied to the input terminal 1 and the target terminal 3 is supplied to the liquid crystal cell _C11 . Therefore, the charge corresponding to the potential difference due to the signal of the first pixel is sampled and held in the capacitance of this cell _C11 . The light transmittance of the liquid crystal changes depending on the amount of charge. The same thing is done sequentially for cells C ₁₂ to _{C on} , and when the next field signal is supplied, each cell
The amount of charge of C ₁₁ to _{C on} is rewritten.

In this way, the light transmittance of the liquid crystal cells C ₁₁ to C _on is changed corresponding to each pixel of the video signal, and this is sequentially repeated to display a television image.

By the way, when displaying with a liquid crystal, AC drive is generally used to improve its reliability and lifespan. For example, when displaying a television image, a signal obtained by inverting a video signal is supplied to the input terminal 1 for each field or frame. That is, the input terminal 1 is supplied with a signal that is inverted for each field or frame as shown in FIG. 2E.

By the way, in the above-mentioned device, for example, one transmission type liquid crystal cell C is constructed as follows. In FIG. 3, A shows a plan view, and B shows a sectional view taken along line A-A. In the figure, reference numeral 20 denotes a glass substrate, on which a gate line 21 made of a transparent electrode is provided, and a Si _SS layer 22 is provided on the gate line 21 and on the entire surface of the glass substrate 20. Also, on the overhanging part 21' of the gate line 21,
Amorphous silicon layer 2 with SiO ₂ layer 22 in between
3 is provided, and a vertical signal line 24 made of metal such as aluminum is provided on the left side of this silicon layer 23, which corresponds to the above-mentioned lines _L1 to _Ln . Further, a pixel electrode 26 made of a transparent electrode is provided on the right side of the silicon layer 23 with a metal layer 25 interposed therebetween.
SiO ₂ is deposited on this silicon layer 23 to pixel electrode 26.
A layer 27 is provided. A liquid crystal 28 is provided on this SiO ₂ layer 27, and a target electrode 29 made of a transparent electrode and a protective glass 30 are provided thereon.

Therefore, in this device, when a signal is supplied to the signal line 24 and the gate line 21 becomes high potential, the signal supplied to the signal line 24 is supplied to the metal layer 25 through the silicon layer 23, and the signal is connected to the metal layer 25. It is stored in the capacitive component formed between the line 24 and the line 24. This stored signal is then supplied to the pixel electrode 26, and the light transmittance of the liquid crystal 28 is changed according to the potential difference with the target electrode 29.

However, in this case, the signal line 24 and the metal layer 25
A coupling capacitance is formed between the two, and crosstalk of signals in the Y-axis direction occurs through this coupling capacitance.
In other words, when figure A appears in Fig. 4,
When a signal is supplied to the corresponding line Ls~Lt in the Y-axis direction, the signal is also supplied to other liquid crystal cells ( _C1S ~ _CoS )~( _C1t ~ _Cot ) in the Y-axis direction through the coupling capacitance. , crosstalk occurs in the Y-axis direction. Additionally, the amount of crosstalk reduces the storage capacity of the cell, C _M ,
If the coupling capacitance is C _S , it corresponds to the value of C _S /C _M + C _S , and if the pixel area is reduced here,
While the storage capacity C _M becomes smaller, the coupling capacitance C _S
is approximately constant, so crosstalk becomes large.

Furthermore, when AC driving is performed as described above, a signal of opposite polarity is supplied every field or frame, so this signal of opposite polarity jumps to each liquid crystal cell through the coupling capacitance C _S mentioned above. ,
Particularly in the lower part of the screen where it takes a long time to rewrite the signal, shading occurs in which the entire image becomes darker. Similar to the above-mentioned crosstalk, this shading becomes a problem when the pixel area is reduced.

Furthermore, crosstalk and shading are also caused by leakage from the switching elements M ₁₁ to M _on .

Therefore, the inventor of the present application previously proposed the following method for preventing such crosstalk and shading.

In the apparatus shown in FIG. 1, signals as shown in FIG. 5 are supplied to the input terminal 1. That is, for example, in an odd field, a signal that is inverted every horizontal period as shown in FIG. 5A is supplied, and in an even field, as shown in FIG. is supplied.

As a result, the signal that entered the non-selected pixel in the previous horizontal period is canceled by the signal of the opposite polarity that enters the next horizontal period. In other words, for example, when figure A as shown in Figure 4 is displayed, the amount of crosstalk during one field period is expressed as follows: where the time of one field is Tv (=1/60sec) and the time of one horizontal period is _TH. , However, v _S is the potential of the background video signal.
V _W and the potential of the figure as V _B , v _S = V _W - V _B n is the number of horizontal scanning lines in the figure part, and if n is an even number and v _S is constant, the above-mentioned crosstalk will be 0. . Also, even if n is an odd number, the value is T _H v _S /T _V・C _S /C _M +C _S , which is 1 more than the conventional case of nT _H v _S /T _V・C _S /C _M +C _S. /n.

Furthermore, since each field has an opposite phase, each pixel is driven by alternating current driving.

Similarly, the effects of shading and leakage of switching elements are also eliminated.

Crosstalk and shading can thus be prevented in this device.

However, in this case, if we pay attention to two liquid crystal cells lined up in the vertical direction, each pixel electrode 26
Since potentials having opposite phases are accumulated in a and 26b, the electric field formed by the two electrodes has equipotential lines as shown in FIG. For this reason, the liquid crystal between pixels in the vertical direction is no longer modulated due to potential cancellation between the upper and lower pixels.
The display area becomes smaller and the image quality deteriorates.

OBJECTS OF THE INVENTION In view of these points, the present invention prevents crosstalk and shading, and removes non-modulated portions between pixels in the vertical direction.

SUMMARY OF THE INVENTION The present invention provides display liquid crystal cells arranged in a matrix, a plurality of signal lines provided in parallel between each column of the liquid crystal cells, and these signal lines connected every other column. , are second connection points, and display signals of opposite polarity are supplied to these connection points, and the liquid crystal cells are connected to one side or the other side of the signal lines on both sides for each row via selection elements. A liquid crystal display device in which crosstalk and shading are prevented, and the display signal supplied to the connection point is inverted each time each row is selected.
In addition, non-modulated portions between pixels in the vertical direction can be removed.

Embodiment In FIG. 7, the signal from the input terminal 1 is supplied to the signal inversion circuit 5 and inverted, and this inverted signal is supplied to one fixed contact of the switch 6 and the other fixed contact of the switch 7. At the same time, the original signal from input terminal 1 is supplied to the other fixed contact of switch 6 and to one fixed contact of switch 7. The switches 6 and 7 are switched every horizontal period in relation to, for example, a clock signal _φ2V .

The signals from the switches 6 and 7 are transmitted to every other switching element M ₁ , M _{3 .} . . and M ₂ , M _{4 ,} respectively.
...via every other vertical signal line L ₁ , L ₃
…and supplied to L ₂ , L ₄ ….

Furthermore, itching elements (M ₁₁ , M ₁₂ ...), (M ₃₁ , M ₃₂ ...) ... and (M ₂₁ , M ₂₂ ...), (M ₄₁ , M ₄₂ ...) ... which constitute every other horizontal scanning line are connected to the left vertical signal lines L ₁ , L _{2 .} . . and the right vertical signal lines L ₂ , L ₃ .

Therefore, in this device, positive signals are supplied to the lines L ₁ , L _{3 .} . . in one horizontal period, and the lines L ₂ , L 3 .
A negative signal is supplied to L ₄ ..., and this is reversed in the next horizontal period, so that the signal supplied from line L ₁ to liquid crystal cell C ₁₁ in one horizontal period and the line L in the next horizontal period are Both the signals supplied from _C2 to the liquid crystal cell _C21 become positive in-phase signals.

This eliminates the above-mentioned non-modulated portion of the liquid crystal between vertical pixels.

Also, each vertical signal line L ₁ , L _{2 .} . . is supplied with an inverted signal every horizontal period, so that
No crosstalk or shading occurs.

Furthermore, the signal supplied to the input terminal 1 is inverted every vertical period, and AC driving is performed in each liquid crystal cell.

In addition, in the above-mentioned device, the signal of the liquid crystal cell is inverted between pixels in the horizontal direction, and a non-modulated part occurs between the pixels, but this part was originally not displayed due to the influence of the vertical signal lines L ₁ , L ₂ , etc. Therefore, even if there is a non-modulated part in this part, it is not a substantial problem. Especially in a transmission type device, this is a part where light does not originally pass through due to the metal signal line.

Furthermore, in the above-described apparatus, the signals are shifted by one pixel between the odd-numbered horizontal scanning lines and the even-numbered horizontal scanning lines. Therefore, as shown in FIG. 8, the timing of generation of horizontal drive pulses φ _H1 , φ _{H2 .} . . is advanced by one clock between odd-numbered horizontal scanning periods and even-numbered horizontal scanning periods. Alternatively, as shown in FIG. 9, a delay circuit 8 for one pixel period is provided, and the switch 8
The signal may be delayed by one pixel period for each horizontal period.

Note that this device can be applied to a liquid crystal display device using an active matrix using TFTs such as amorphous silicon, polysilicon, and silicon-on-sapphire.

Effects of the Invention According to the present invention, it was possible to prevent crosstalk and shading, and to remove non-modulated portions between pixels in the vertical direction.

[Brief explanation of drawings]

1 to 6 are diagrams for explaining a liquid crystal display device, FIG. 7 is a configuration diagram of an example of the present invention, and FIGS. 8 and 9 are diagrams for explaining the same. 1 is an input terminal, 2 is a shift register, 5 is a signal inversion circuit, M is a switching element, C is a liquid crystal cell, and L is a vertical signal line.

Claims (1)

[Claims] 1 Display liquid crystal cells are provided in a matrix,
A plurality of signal lines are provided in parallel between each column of the liquid crystal cells, and every other signal line is connected to serve as a first and second connection point, and wires of opposite polarity are connected to these connection points. While the display signal is supplied, the liquid crystal cells are alternately connected to one side or the other side of the signal lines on both sides for each row via selection elements, and are supplied to the connection point for each selection of each row. A liquid crystal display device in which the above-mentioned display signal is inverted.