JP3593391B2 - Active matrix type liquid crystal display - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an active matrix liquid crystal display device in which a liquid crystal composition is held between an active matrix substrate having a thin film transistor (hereinafter abbreviated as TFT) arranged in a matrix as a driving element and a counter substrate. About.
[0002]
[Prior art]
2. Description of the Related Art In recent years, liquid crystal display devices that achieve high performance and high definition while having high density and large capacity have been put to practical use.
[0003]
Among these liquid crystal display devices, TFTs have been conventionally used because there is no crosstalk between adjacent pixels, a high contrast display can be obtained, a transmissive display is possible, and a large area can be easily achieved. An active matrix type liquid crystal display device provided with as a control element is often used.
[0004]
And, among active matrix substrates used for liquid crystal display devices, the storage capacitor line is formed of the same material as the scanning line and the gate electrode, and the pattern is formed together in the same forming step. The structure is similar to that of the first conventional example shown in FIG.
[0005]
That is, on the insulating substrate of the active matrix substrate 1, pixel electrodes 6 connected to the source electrodes 4a of the TFTs 4 provided at intersections of the scanning lines 2 and the signal lines 3 are formed in a matrix pattern. A storage capacitor line 7 made of a light-shielding member, which is patterned in the same step as the scanning line 2, is formed in a pattern below, and an auxiliary capacitor is formed between the storage capacitor line 7 and the pixel electrode 6 via a gate insulating film. I have.
[0006]
However, in such an active matrix substrate 1, the storage capacitance line 7 is formed so as to cross substantially the center of the pixel electrode 6, and the storage capacitance line 7 increases the light shielding area in the pixel electrode 6. For this reason, the aperture ratio has been reduced. Therefore, when such an active matrix substrate is used in a liquid crystal display device, the brightness of the displayed screen is reduced, and in order to obtain the required brightness, the amount of light of the backlight must be increased. There has been a problem that power consumption is increased and energy saving of the device is hindered.
[0007]
For this reason, instead of providing a storage capacitance line independent of the scanning line, a part of the scanning line 8 is made to function as a storage capacitance line as in the second conventional example shown in FIG. An active matrix substrate 11 has been developed in which an auxiliary capacitance is formed at a portion 10 where the scanning line 8 and the pixel electrode 9 overlap.
[0008]
[Problems to be solved by the invention]
Conventionally, in a transmissive liquid crystal display device using an active matrix substrate using a TFT as a driving element, a storage capacitor line is provided at a position which is independent of a scanning line and crosses substantially the center of a pixel electrode, and is provided with a pixel electrode. A storage capacitor is formed at the overlapping portion, or a part of the scanning line is used as a storage capacitor line, and a storage capacitor is formed at the overlapping portion of the pixel electrode and the scanning line.
[0009]
For this reason, in the former, the light transmission area in the pixel electrode is reduced, and thus the aperture ratio of the liquid crystal display device is reduced, the required screen luminance cannot be obtained, and the light amount of the backlight must be increased. However, there has been a problem that energy saving is hindered.
[0010]
On the other hand, in the latter, since a part of the scanning line also serves as the storage capacitance line, the storage capacitance line crossing the pixel electrode can be eliminated, and the aperture ratio of the active matrix substrate can be improved, but the auxiliary capacitance is not increased. Since the pixel electrode is formed at the overlapping portion with the scanning line at the edge of the pixel electrode, if the pattern of the scanning line and the pixel electrode is misaligned during manufacturing, the overlapping area between the pixel electrode and the scanning line varies. As a result, the size of the storage capacity has changed greatly.
[0011]
That is, for example, when the pixel electrode 9 is displaced from the scanning line 8 in the direction of the arrow s as shown in FIG. 6, the overlapping portion 10 of the scanning line 8 and the pixel electrode 9 is reduced as compared with FIG. In proportion, the storage capacity also becomes smaller than that in the case shown in FIG. 5, causing a display defect such as shot unevenness or burn-in, resulting in a problem of deteriorating the display quality.
[0012]
Furthermore, in a large-area liquid crystal display device, when one screen is divided into a plurality of blocks, and exposure and etching are performed for each block to form a pattern of a storage capacitor line or a pixel electrode, a scanning line for each block and The value of the storage capacitance fluctuates from block to block due to a shift in the pattern of the pixel electrodes, and a display defect occurs due to burn-in or shot unevenness in each block, and a shot block is visually recognized and display quality is degraded.
[0013]
In view of the above, the present invention has been made to solve the above-described problems. In an active matrix substrate using a TFT as a driving element, a conventional backlight is provided by stabilizing an auxiliary capacitor and improving screen brightness without causing a decrease in aperture ratio. It is an object of the present invention to provide an active matrix type liquid crystal display device having high display quality, while saving energy required for the device and preventing display defects.
[0014]
[Means for Solving the Problems]
According to an aspect of the present invention, there is provided an active matrix substrate having pixel electrodes arranged in a matrix, a counter substrate having a counter electrode opposed to the active matrix substrate, and the active matrix substrate. and in Akti I blanking matrix type liquid crystal display device comprising a liquid crystal composition sealed between the counter substrate, the active matrix substrate is formed on a transparent insulating substrate, a gate electrode above a gate insulating film A plurality of thin-film transistors arranged in a matrix and having a source electrode and a drain electrode sandwiching the active region, formed on the insulating substrate, and supplying a scanning signal to the gate electrode. And a plurality of signals for supplying a video signal to the drain electrode. A line at the insulating substrate, a storage capacitor line which is connected to the previous scan line holds the following thin-wire gap 10 [mu] m, it will be connected to the source electrode, one side, the thin wires And a matrix-shaped pixel electrode located in the gap between the pixels.
[0015]
According to a second aspect of the present invention, in the active matrix type liquid crystal display device according to the first aspect, the width of the scanning line is set to 10 μm or less .
[0016]
The invention described in claim 3, the active matrix type liquid crystal display device according to claim 1, by dividing one screen into a plurality of blocks, the exposure for each block, and producing etched.
[0018]
[Action]
According to the present invention, the scanning line is processed into a fine line, and the storage capacitor line is close to the preceding scanning line so as to have a fine line gap, while the preceding scanning line and the storage capacitance line are partially connected. As a result, the area of the pixel electrode is increased, the aperture ratio of the active matrix substrate and thus the screen brightness are improved, the power required for the backlight is reduced, and the thinning of the scanning line causes disconnection of the scanning line. However, since the signal is electrically bypassed to the storage capacitor line side and is conducted, the signal transmission function is not impaired.
[0019]
Further, according to the present invention, by forming the pixel electrode so that one side thereof is located in a fine line gap between the scanning line and the storage capacitor line, the pattern of the scanning line and the storage capacitor line and the pattern of the pixel electrode are overlapped. Even if the alignment is misaligned, the misalignment can be compensated for by the fine line-shaped gap, so that the required storage capacity is always at a required constant value, preventing display defects due to image sticking and uneven shots, and improving display quality. It is intended.
[0020]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Reference numeral 20 denotes an active matrix type liquid crystal display device, which is a nematic type liquid crystal composition between an active matrix substrate 22 using a TFT 21 as a driving element and a counter substrate 23 via alignment films 24 and 26 made of polyimide. The liquid crystal 27 is held and has polarizing plates 53 and 54.
[0021]
Here, the active matrix substrate 22 is formed by forming thallium (Ta), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), aluminum (Al), copper on an insulating substrate 28 made of transparent glass. It is composed of a single layer film or a laminated film made of a metal material such as (Cu) or an alloy thereof, supplies a scanning signal and partially projects as a gate electrode 31. The scanning line 30 of the stage and the storage line 13 of the (N + 1) th stage connected to the scanning line 30 at the connection portion 13a are separated from the scanning line 30 by a fine line-shaped gap 12 having a width of 5 μm. Have been.
[0022]
These are covered with a gate insulating film 32 made of silicon oxide (SiOx). Above the gate electrode 31 via the gate insulating film 32, i-type hydrogenated amorphous silicon (hereinafter referred to as i-type a -Si: H), a protective insulating film 35 made of silicon nitride (SiNx), and n-type amorphous silicon (hereinafter referred to as n-type a-Si) for obtaining a good ohmic contact. The ohmic film 40 is patterned to form a TFT 21 having a source region (B) and a drain region (C) sandwiching the channel region (A).
[0023]
Further, a pixel electrode 43 made of indium tin oxide (hereinafter, referred to as ITO) is pattern-formed on the gate insulating film 32, and an end 43 a of the pixel electrode 43 on the side of the storage capacitor line 13 is connected to the storage capacitor line 13. The pattern is formed so as to be approximately 2 μm larger than the end 13 b of the storage capacitor line 13 so as to be located substantially at the center of the gap 12 between the scanning lines 30. Then, a storage capacitor is formed by a portion where the storage capacitor line 13 and the pixel electrode 43 overlap.
[0024]
Furthermore, a single-layer film made of a metal material such as thallium (Ta), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), aluminum (Al), copper (Cu), or an alloy thereof, A source electrode 37 connected to the pixel electrode 43, a signal line 38, and a drain electrode 39 branched from the signal line 38 are formed by patterning.
[0025]
These upper surfaces are covered with an insulating protective film 41 made of silicon nitride (SiNx).
[0026]
On the other hand, the counter substrate 23 is made of chromium (Cr), which is a light-shielding material, on an insulating substrate 46 made of transparent glass, and has a red (R), green (G), and blue (B) coloring layer in each region. It has a black matrix 47 and a counter electrode 48 made of ITO.
[0027]
Next, a method for manufacturing the liquid crystal display device 20 will be described. First, the active matrix substrate 22 is formed by sputtering a metal material such as thallium (Ta), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), or aluminum (Al) on an insulating substrate 28 by sputtering. A single-layer film or a stacked film made of the alloy is formed, and the scanning line 30, the gate electrode 31, and the storage capacitor line 13 are patterned by using a photolithography technique of etching using a photoresist (not shown) as a mask. .
[0028]
Next, after a gate insulating film 32, an (i-type a-Si: H) film, and a silicon nitride (SiNx) film are laminated and formed by a plasma CVD method, a negative resist is applied, and insulation is performed using the gate electrode 31 as a mask. Exposure is performed from the back surface of the substrate 28, and a negative resist is patterned to leave an exposed portion. Then, using this negative resist as a mask, a silicon nitride (SiNx) film is shaped in a self-aligned manner with respect to the gate electrode 31 to form a protective insulating film 35. Thus, the protective insulating film 35 is formed to be smaller than the gate electrode 31 by 0 to 3 μm by diffraction of light at the time of back surface exposure.
[0029]
Subsequently, an (n-type a-Si) film is formed on the (i-type a-Si: H) film using a plasma CVD method, and the (i-type a-Si: H) film and the (n-type a-Si: H) film are formed by photolithography. The semiconductor layer 34 and the ohmic layer 40 are patterned by photoetching the n-type a-Si) film.
[0030]
Next, after forming an ITO film by a sputtering method, a resist is applied, a resist is patterned by a photolithography technique, and the ITO film is photo-etched using the resist as a mask to pattern-form the pixel electrode 43.
[0031]
Further, a single layer film or a laminated film made of a metal material such as thallium (Ta), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), aluminum (Al), or an alloy thereof is formed by a sputtering method. After forming a film and patterning the source electrode 37, the signal line 38, and the drain electrode 39 by photolithography, an insulating protective film 41 made of silicon nitride (SiNx) is formed and formed into a predetermined shape by photolithography. The active matrix substrate 22 is formed by patterning.
[0032]
Next, in the counter substrate 23, a chromium (Cr) film is formed on the insulating substrate 46 by a sputtering method, and etched into a predetermined shape by a photolithography technique to form a black matrix 47 in a lattice shape. Then, after a layer in which a pigment is dispersed is applied to the black matrix 47, pattern exposure and development are repeated to form three stripe regions of red, green, and blue on the black matrix 47. The counter substrate 23 is formed by forming the electrode 48 on the entire surface.
[0033]
Subsequently, alignment films 24 and 26 made of low-temperature curing type polyimide are applied by printing on the entire surface of the active matrix substrate 22 and the counter substrate 23 on the pixel electrode 43 side and the counter electrode 48 side. After performing a rubbing process so that the axis becomes 90 °, the two substrates 22 and 23 are assembled to face each other to form a cell, and a nematic liquid crystal 27 is injected into a gap therebetween and sealed. Then, polarizing plates 53 and 54 are attached to the insulating substrates 28 and 46 of the substrates 22 and 23, respectively, to complete the liquid crystal display device 20.
[0034]
With this configuration, the width of the scanning line 30 is patterned to the minimum processing size, and the storage capacitor line 13 is brought close to the scanning line 30 so that the gap 12 between the scanning line 30 and the storage capacitor line 13 becomes the minimum processing size. By forming the pattern, the area of the light transmitting portion of the pixel electrode 43 can be increased, so that the aperture ratio of the active matrix substrate 22 can be improved, and the screen brightness of the liquid crystal display device 20 can be improved. Therefore, the amount of light of the backlight can be reduced, and energy saving of the device can be promoted.
[0035]
In addition, by setting the width of the scanning line 30 to the minimum processing size, even if a disconnection occurs, the scanning line 30 is connected to the storage capacitor line 13 at the connection portion 13a and is electrically conducted, thereby impairing the scanning signal supply function. The yield is not reduced due to the disconnection of the scanning line 30 during manufacturing.
[0036]
Furthermore, at the time of manufacturing, even if the pattern of the pixel electrode 43 superimposed on the storage capacitor line 13 is shifted, the amount of protrusion of the pixel electrode 43 into the gap 12 between the storage capacitor line 13 and the scanning line 30 is actually changed. However, since the area of the overlapping portion of the storage capacitor line 13 and the pixel electrode 43 is the same, the value of the storage capacitor is not changed, and display defects due to shot unevenness and image sticking can be prevented, and a high-quality display image can be prevented. Can be obtained.
[0037]
The present invention is not limited to the above embodiment, and can be modified without departing from the scope of the invention. For example, the material of the gate electrode, the scanning line or the signal line, or the gate insulating film or the insulating protective film Is arbitrary.
[0038]
The width of the scanning line and the width of the gap between the scanning line and the storage capacitor line are also arbitrary. However, in order to improve the aperture ratio, it is desirable that the processing be thin, and more preferably 10 μm or less.
[0039]
However, for the width of the gap between the scanning line and the storage capacitor line, it is necessary to further consider the overlay accuracy of the pattern of the storage capacitor line and the scan line and the pixel electrode pattern. For example, the overlay accuracy of both patterns is a μm If the width of the gap is set so as to maintain at least 2a (μm), the displacement at the time of pattern formation can be surely compensated, and the variation of the storage capacitance can be more reliably prevented.
[0040]
Further, the shape of the storage capacitor line is also arbitrary as long as it is close to the scanning line so as to maintain a fine line-shaped gap. For example, as in another modification shown in FIG. Alternatively, the storage capacitor line 60 that is brought into close proximity may be formed in a π-shaped pattern instead of a linear shape, and may be connected to the scanning line 57 at the connection portion 60a.
[0041]
When formed in this manner, the storage capacitor line 60 can also serve as a part of a light shield, and light is also transmitted to the hatched area (D) of the pixel electrode 61. Can be further improved.
[0042]
The method of manufacturing the active matrix substrate is also arbitrary. For example, in the case of a large area liquid crystal display device, one screen is divided into a plurality of blocks, and exposure and etching are performed for each block, and a storage capacitor line or a pixel electrode is formed. Etc. may be patterned. Even in such a manufacturing method, since the value of the storage capacity does not vary from block to block as in the related art, even when the halftone display is performed, the shot block due to burn-in or block unevenness of each block is not visually recognized. And display quality can be improved.
[0043]
【The invention's effect】
As described above, according to the present invention, the area of the light transmitting portion of the pixel electrode can be enlarged by patterning the scanning line and the gap between the scanning line and the storage capacitor line in a fine line shape, and Since the aperture ratio and thus the screen brightness of the liquid crystal display device can be improved, energy saving can be promoted by reducing the amount of light of the backlight.
[0044]
Moreover, even if the scanning line is thinned and a disconnection occurs, a part of the scanning signal is connected to the storage capacitance line and the scanning signal is bypassed to the storage capacitance line, so that the signal transmission function is not impaired. The yield is not reduced.
[0045]
Further, even if the pattern of the storage capacitor line and the pattern of the pixel electrode superimposed thereon are shifted during manufacturing, the shift is compensated by the gap, and the area of the overlapping portion between the storage capacitor line and the pixel electrode is always constant. Since the shot blocks are held, it is possible to prevent a display defect due to shot unevenness or burn-in and visual recognition of a shot block, and to obtain a high-quality display image.
[Brief description of the drawings]
FIG. 1 is a partially schematic explanatory view of an active matrix substrate according to an embodiment of the present invention as viewed from above.
FIG. 2 is a schematic cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention at a position corresponding to the line AB and the line BC in FIG.
FIG. 3 is a partially schematic explanatory view of an active matrix substrate of another modified example of the present invention as viewed from above.
FIG. 4 is a partial schematic explanatory view of a first conventional active matrix substrate as viewed from above.
FIG. 5 is a partial schematic explanatory view of a second conventional active matrix substrate viewed from above.
FIG. 6 is a partial schematic explanatory view of a case where a pattern of a storage capacitor electrode and a pattern of a pixel electrode of a second conventional active matrix substrate are displaced, as viewed from above.
[Explanation of symbols]
12 gap 13 storage capacitance line 20 liquid crystal display device 21 TFT
22 Active matrix substrate 30 Scanning line 43 Pixel electrode

Claims (3)

An active matrix substrate having pixel electrodes arranged in a matrix, a counter substrate facing the active matrix substrate and having a counter electrode, and a liquid crystal composition sealed between the active matrix substrate and the counter substrate are provided. in Akti I blanking matrix type liquid crystal display device which,
The active matrix substrate,
An active region formed on a transparent insulating substrate and provided above the gate electrode with a gate insulating film interposed therebetween, and a plurality of thin film transistors having a source electrode and a drain electrode sandwiching the active region and arranged in a matrix;
A plurality of fine scanning lines formed on the insulating substrate and supplying a scanning signal to the gate electrode;
A plurality of signal lines for supplying a video signal to the drain electrode,
The insulated by the substrate, the storage capacitor line which is connected to the previous scan line holds the following thin-wire gap 10 [mu] m,
An active matrix liquid crystal display device, comprising: a matrix-shaped pixel electrode connected to the source electrode and having one side positioned in the fine line gap . Active matrix liquid crystal display device according to claim 1 Symbol mounting and wherein the width of the scanning line is 10μm or less. 2. The active matrix type liquid crystal display device according to claim 1, wherein one screen is divided into a plurality of blocks, and each block is exposed and etched to manufacture .

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