JP3206666B2 - Liquid crystal matrix display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel, and more particularly to a liquid crystal panel suitable for making the brightness of pixels for displaying an image uniform.

[0002]

2. Description of the Related Art As flat displays, MOS,
Three-terminal element such as TFT (thin film transistor) and MI
2. Description of the Related Art A liquid crystal active matrix display device that displays an image by laminating a liquid crystal with a two-terminal element such as M (Metal-Insurator-Metal) is known.

FIG. 2 shows a conventional example of a liquid crystal active matrix display device driven by a conventional three-terminal element. The device is a liquid crystal panel 1 composed of TFT2, liquid crystal pixel 3, common terminal 4, scanning line 5, and signal line 6.
, A signal drive circuit 7 and a scan drive circuit 8.

The liquid crystal panel 1 has n scanning lines 5 and m signal lines 6, and has a structure in which n × m liquid crystal pixels are arranged in a matrix as a whole.

FIG. 3 shows an equivalent circuit of the liquid crystal panel 1. FIG. 3A shows an equivalent circuit of a pixel at an arbitrary position on the liquid crystal panel 1. The circuit includes signal lines 10 and 11, scanning lines 9, TFTs 12, liquid crystal pixels 13, common terminals 14, liquid crystal pixels 13, and parasitic capacitances 15 and 16. The parasitic capacitances 15 and 16 are connected to the liquid crystal pixel 13 and the signal line 1.
This is the parasitic capacitance with 0 and 11.

FIG. 3B shows an equivalent circuit of a pixel at the right corner of one pixel of the liquid crystal panel. FIG.
The same parts as those shown in FIG. FIG.
In the circuit shown in FIG. 3B, since there is no signal line on the right side of the liquid crystal pixel 13, there is no parasitic capacitance 15 as shown in FIG.

[0007]

The liquid crystal panel 1 according to the prior art has the following problems. As shown in FIGS. 3A and 3B, the configuration of the parasitic capacitance connected to the liquid crystal pixel 13 differs depending on the location of the liquid crystal panel 1. For this reason, in FIG. 3A, the liquid crystal pixel 13 is
3B receives interference from both the signal lines 10 and 11 via the line 15 and FIG.
And only the signal line 10 receives interference. The above-mentioned interference means that the voltage of the liquid crystal pixel 13 fluctuates due to the fluctuation of the voltage of the signal line 10 or 11 through the parasitic capacitance when the TFT 12 is in an off state (non-conduction state). The amount of voltage fluctuation at this time depends on the value of the parasitic capacitance, the capacitance value of the liquid crystal pixel, and the value of a storage capacitor (not shown) connected in parallel with the liquid crystal pixel.

As a result, in the conventional liquid crystal panel, the amount of interference received from the signal line depends on the location of the panel,
That is, since the fluctuation amount of the voltage of the liquid crystal pixel is different, the brightness in the panel surface varies, and good display cannot be performed. In particular, there is a problem that brightness non-uniformity becomes remarkable when halftone display is performed.

In this case, the ratio of the parasitic capacitance between the pixel electrode 13 and the signal line in FIGS. 3A and 3B is 2 when the values of the parasitic capacitances 15 and 16 are substantially the same. Therefore, in order to reduce the variation in brightness on the panel surface and realize a high quality display as compared with the related art, the ratio of the parasitic capacitance between the pixel electrode 13 and the signal line needs to be 2 or less.

An object of the present invention is to reduce the variation in the ratio of the parasitic capacitance between a pixel electrode for displaying an image and a signal line within a panel plane by two.
An object of the present invention is to provide a liquid crystal panel capable of making the brightness of a displayed image uniform even in a halftone display.

[0011]

In a liquid crystal matrix panel in which a plurality of pixels are arranged in a matrix, all pixel electrodes for displaying an image are sandwiched between signal lines to which a signal voltage for displaying an image is applied. Configuration.

[0012]

By arranging all the pixel electrodes for displaying an image between the signal lines, the variation in the ratio of the parasitic capacitance between the pixel electrode for displaying the image and the signal line can be reduced to 2 or less.

As a result, the influence of the signal voltage applied to the signal line can be reduced as compared with the related art. As a result, unevenness in brightness, which is a problem of the related art, can be reduced over all display pixels, and high-quality display can be performed.

[0014]

FIG. 1 shows a configuration example of a liquid crystal matrix panel according to the present invention. FIG. 1A is a plan view showing a configuration of one pixel of a liquid crystal matrix panel. 20, 21
Is a signal line, 22 and 23 are scanning lines, 24 is a pixel electrode, 25
Is a TFT. The TFT 25 includes a source electrode 25a, a gate electrode 25b, and a drain electrode 25c.

FIG. 1B schematically shows a cross-sectional view of FIG. 1A. Reference numeral 26 denotes a circuit board on which a TFT or the like is formed. The circuit board 50 may be a transparent substrate such as glass, for example, and is not particularly limited. The TFT 26 may be a semiconductor such as a-Si (amorphous silicon) or p-Si (polycrystalline silicon), or a single-crystal MOS, and is not particularly limited. The same parts as those in FIG. 1A are denoted by the same reference numerals.

The configuration shown in FIG. 1 is applied to all pixels of a liquid crystal matrix panel. At this time, if the spaces 11 and 12 between the pixel electrode 24 and the signal line 20 and between the signal line 21 and the signal line 21 are made the same, the parasitic capacitance between the pixel and the left and right signal lines 20 and 21 can be made the same. good.

At this time, the pixel electrode 24 and the signal lines 20 and 21
The spaces l1 and l2 do not necessarily have to be the same as long as the parasitic capacitance between them can be made substantially equal.

FIG. 4 shows another embodiment of one pixel. FIG.
The same reference numerals are given to the same parts. The difference from FIG. 3 is that the arrangement state of the TFT 25 is different. This pixel configuration is applied to all pixels of the liquid crystal matrix panel.

Although not shown in the drawings, a modification of the pixel can be considered depending on the shape of the pixel electrode 24 and the shape and arrangement of the TFT 25, but it is sufficient if all the pixel electrodes are sandwiched between the signal lines. The configuration of the pixel is not limited. Note that the pixel configuration shown in FIG. 3 and FIG.
Applies only to the part that displays the image.

FIG. 5 shows an example of the configuration of a liquid crystal matrix display device using the pixels shown in FIGS. 3 and 4.
26 is a liquid crystal matrix panel, 26a, 26b, 26
d, 26e, 26f are signal lines, 26c is a scanning line, 27,
28 is a signal circuit and 29 is a scanning circuit.

The signal lines are led out to the signal circuit 27 by connecting i signals UD1 to UDi to the signal circuit 27 and LD to the signal circuit 28.
1 to LDi. Thus, the liquid crystal matrix panel 26 is composed of 2 × i × n pixels, and an image is displayed on the pixels. 26d is a dummy signal line, which is electrically connected to the signal line 26b.

This dummy line may be connected to the signal line 26f, and the connection method is not particularly limited. Also, as shown in the drawing, in addition to driving the dummy line by connecting to another signal line in the liquid crystal matrix panel 26, whether the dummy line is drawn out of the liquid crystal matrix panel 26 and connected to the output terminal of the signal circuit 27 Alternatively, a driving circuit may be provided independently of the signal circuit for driving, and the wiring method and the driving method are not particularly limited.

FIG. 6 shows another configuration example of the liquid crystal matrix display device. 30 is a signal circuit, 31 is a scanning circuit, 32 is a liquid crystal matrix panel, 33 is a signal line, 34 is a scanning line,
5 is a dummy line. As shown, the dummy line 35
May be driven by a method similar to that described in the embodiment of FIG. 5 in addition to the connection to the signal line at the right corner, and the connection method, the driving method, and the driving conditions are not particularly limited.

In the display device shown in FIGS. 5 and 6, the voltage waveform of the signal voltage applied to the signal line is not particularly limited, but a driving method capable of reducing the voltage fluctuation of the pixel is convenient. For example, in FIG. 5, the polarity of the signal voltage applied to each of the signal lines extending upward and downward is set to the opposite polarity of positive and negative. In FIG. 6,
Variations in the voltage applied to the pixel can also be reduced by reversing the polarity of the signal voltage applied to the odd and even signal lines, or if the polarity is the same, by adjusting the voltage level of the signal voltage.

Further, in the display device shown in FIGS. 5 and 6, the polarity of the signal voltage is sequentially reversed to coincide with the timing of sequentially scanning the scanning lines 1 to n, so that the voltage is applied to the pixels. Voltage fluctuation can be reduced, and uneven brightness can be prevented.

FIGS. 7 and 8 show modified examples of the present invention. FIG.
Shows an embodiment of a liquid crystal matrix panel, and includes a signal line 36, a scanning line 37, a light shielding film 38, and a TFT.
39.

Although the liquid crystal matrix panel is composed of i signal lines and n scanning lines, the i-th pixel is not a display pixel because it is covered by the light shielding film 38. Therefore, the i-th signal line becomes a dummy line, and as a result, the number of pixels for displaying an image is (i−1) × n pixels.

FIG. 8 is a schematic sectional view of the liquid crystal matrix panel near the dummy line shown in FIG. This sectional view is a diagram for explaining the basic configuration of a liquid crystal matrix panel according to the present invention, and omits TFTs, liquid crystal alignment films, and the like.

46 is a transparent substrate, 38 is a light-shielding film, 45 is a light-shielding film for blocking leak light other than pixel electrodes, 47 is a transparent (or opaque) substrate, 39 and 40 are i-th pixel electrodes and signal lines, 41 Reference numerals 42 and 42 denote an (i-1) th pixel electrode and a signal line, 43 denotes an (i-2) th pixel electrode, and 48 denotes a backlight. The i-th pixel electrode 39 and
The light shielding film 45 may be omitted.

The light-shielding film 38 has an effect of blocking light passing through the i-th pixel electrode. Note that the light-shielding film 38 may be provided on the substrate 47, and the installation place is not particularly limited. Further, a reflective display in which the backlight is omitted may be used.

As in the embodiment shown in FIG. 7, the object of the present invention can be achieved by adopting a structure in which at least a pixel for displaying an image has a pixel electrode sandwiched between signal lines.

As described above, the brightness can be made uniform by making the parasitic capacitance at least between the pixel electrode of the pixel displaying an image and the signal line substantially the same.

When the parasitic capacitance between the pixel electrode and the signal lines located on the left and right of the pixel electrode is not the same, the object of the present invention can be achieved by reducing the ratio of the parasitic capacitance between the two to 3 or less. Can be achieved.

Although not shown, when the parasitic capacitance is not uniform, the object of the present invention can be achieved by adjusting the voltage level of the signal voltage for each signal line.

[0035]

According to the present invention, when an image is displayed on a liquid crystal matrix panel, the brightness and contrast ratio of all display pixels can be made uniform, so that a display device with high display quality can be realized. Even in the case of the halftone display, since the brightness of the entire display area can be made uniform, it is possible to make the apparatus particularly suitable for full-color display.

[Brief description of the drawings]

FIG. 1 shows one of pixels of a liquid crystal matrix panel according to the present invention.
It is a figure showing an example.

FIG. 2 is a diagram illustrating a configuration example of a conventional liquid crystal matrix display device.

FIG. 3 is a diagram showing a configuration example of one pixel of a conventional liquid crystal matrix panel.

FIG. 4 is a diagram showing another embodiment of the pixel of the liquid crystal matrix panel according to the present invention.

FIG. 5 is a view showing one embodiment of a liquid crystal matrix display device according to the present invention.

FIG. 6 is a diagram showing one embodiment of a liquid crystal matrix display device according to the present invention.

FIG. 7 is a view showing one embodiment of a liquid crystal matrix panel according to the present invention.

8 is a schematic diagram of a cross section of the liquid crystal matrix panel near a dummy line shown in FIG. 7;

[Explanation of symbols]

20, 21, 26a, 26b, 26d, 26e, 26
f, 33, 35, 36, 40, 42 ... signal lines, 22, 2
3, 26c, 34, 37 ... scanning lines, 24, 39, 41,
43: pixel electrode, 25: TFT, 26, 32: liquid crystal matrix panel, 27, 28, 30 ... signal circuit, 29, 3
1 ... scanning circuit, 38, 45 ... light shielding film, 46, 47 ... transparent substrate, 50 ... circuit board.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yasuyuki Mishima 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-3-18819 (JP, A) JP-A 64-64 3630 (JP, A) JP-A-2-157826 (JP, A)

Claims (6)

(57) [Claims] A plurality of scanning lines, m signal lines extending in a direction intersecting the plurality of scanning lines, and m signal lines; a liquid crystal panel in which a plurality of thin film transistors corresponding to each of the adjacent husband region sandwiched by the pair s arranged a plurality of pixel electrodes and pixel electrodes, each of the plurality of thin film transistors n-th said adjacent ( Where n is 1 or more
(M-1 or less) signal lines and (n + 1) th signal lines, and the n-th signal is applied to one of the pixel electrodes in response to a signal from one of the plurality of scanning lines. An image is displayed by the pixel electrode by applying a signal voltage of a line, and the m-th of the signal line is formed as a dummy, and is disposed between each of the plurality of pixel electrodes and the pair of signal lines sandwiching the pixel electrode. Wherein the variation in the ratio of the parasitic capacitance occurring in the liquid crystal matrix display device is 2 or less. 2. One of a pair of substrates opposed to each other with a liquid crystal layer interposed therebetween, a plurality of scanning lines, m signal lines extending in a direction intersecting the plurality of scanning lines, and m signal lines. a liquid crystal panel in which a plurality of thin film transistors corresponding to each of the adjacent husband region sandwiched by the pair s arranged a plurality of pixel electrodes and pixel electrodes, each of the plurality of thin film transistors n-th said adjacent ( Where n is 1 or more
(M-1 or less) signal lines and (n + 1) th signal lines, and the n-th signal is applied to one of the pixel electrodes in response to a signal from one of the plurality of scanning lines. An image is displayed by the pixel electrode by applying a signal voltage of a line, and the m-th of the signal line is formed as a dummy, and each of the plurality of pixel electrodes and the pair of adjacent signal lines sandwiching the pixel electrode are formed. A liquid crystal matrix display device, wherein a ratio of a parasitic capacitance generated on one side to a parasitic capacitance generated on the pixel electrode and the other of the pair of signal lines is 3 or less. 3. The m-th signal line is electrically connected to the (m-2) -th signal line of the plurality of signal lines, and the voltage applied to each of the odd-numbered signal lines of the plurality of signal lines is 3. The liquid crystal matrix display device according to claim 1, wherein the liquid crystal matrix display device has a polarity opposite to that of an even-numbered voltage applied to the signal lines. 4. The liquid crystal matrix display device according to claim 1, wherein the m-th signal line is electrically connected to the (m-1) -th signal line of the plurality of signal lines. . 5. The plurality of scanning lines sequentially send the signal to the plurality of thin film transistors for each scanning line, and the polarity of a voltage applied to the signal line is sequentially changed with respect to signal transmission for each scanning line. The liquid crystal matrix display device according to claim 1, wherein the liquid crystal matrix display device is reversed. 6. A pixel electrode connected to the m-th signal line
Is covered with a light shielding film, and (m-1)
6. The liquid crystal matrix display device according to claim 1, wherein a pixel electrode connected to the mth signal line is formed on a side opposite to the mth signal line.