JP4448635B2 - Substrate for liquid crystal display device and liquid crystal display device including the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate for a liquid crystal display device constituting a display device such as an information device and a liquid crystal display device including the same.
[0002]
[Prior art]
Liquid crystal display devices are roughly classified into a reflection type that displays incident light reflected by a pixel electrode (reflection electrode) and a transmission type that has a light source on the back surface and transmits light incident from the light source. Is done. FIG. 6 shows the configuration of the pixel region of the TFT substrate 101 constituting the conventional reflective liquid crystal display device. As shown in FIG. 6, the TFT substrate 101 includes a plurality of gate bus lines 105 formed on a glass substrate and extending in the horizontal direction in the drawing, and a plurality of gate bus lines 105 extending in the vertical direction in the drawing and intersecting the gate bus lines 105. And a drain bus line 106. A TFT 114 is formed in the vicinity of the intersection between the gate bus line 105 and the drain bus line 106.
[0003]
The drain electrode 116 of the TFT 114 is drawn from the drain bus line 106, and its end is an operating semiconductor layer (not shown) formed on the gate bus line 105 and one end of a channel protective film 118 formed thereon. It is formed so as to be located on the side. On the other hand, the source electrode 120 is formed so as to be positioned on the other end side on the operating semiconductor layer and the channel protective film 118. In such a configuration, the gate bus line 105 immediately below the channel protective film 118 functions as the gate electrode of the TFT 114. In addition, a pixel region is defined by the gate bus line 105 and the drain bus line 106. Each pixel region has a size of about 100 μm × 300 μm.
[0004]
A storage capacitor bus line 122 extending substantially in parallel with the gate bus line 105 is formed in the same layer as the gate bus line 105 at substantially the center of the pixel region. A storage capacitor electrode (intermediate electrode) 124 is formed on the storage capacitor bus line 122 in the same layer as the drain bus line 106 for each pixel region. In each pixel region, a pixel electrode 110 made of a metal having a high reflectance such as aluminum (Al) is formed.
[0005]
FIG. 7 is a cross-sectional view showing the configuration of the TFT substrate 101 cut along line AA in FIG. As shown in FIG. 7, a gate insulating film 104 is formed on the entire surface of the glass substrate 102. A drain bus line 106 is formed on the gate insulating film 104. An overcoat layer (resin insulating layer) 108 made of polyimide resin or the like and having a thickness of about 2 μm is formed on the drain bus line 106 and the gate insulating film 104. A plurality of irregularities are formed on the surface of the overcoat layer 108 by ultraviolet (UV) irradiation or exposure using an exposure mask in which a half exposure region weaker than a normal exposure amount is distributed. Each unevenness has a width of 10 μm or less, which is sufficiently smaller than the width of the pixel region, and a height of about 0.5 μm.
[0006]
A pixel electrode 110 is formed on the overcoat layer 108. Concavities and convexities corresponding to the concavities and convexities on the surface of the lower overcoat layer 108 are formed on the surface of the pixel electrode 110. The pixel electrode 110 has improved light scattering characteristics due to a plurality of projections and depressions formed on the surface, and external light incident on the pixel electrode 110 is scattered in each direction.
[0007]
On the other hand, FIG. 8 is a diagram showing a configuration of a TFT substrate 101 ′ constituting a conventional general transmissive liquid crystal display device, and shows a cross section corresponding to FIG. As shown in FIG. 8, a protective film 112 having a thickness of about 0.4 μm is formed on the transmissive TFT substrate 101 ′ instead of the overcoat layer having a thickness of about 2 μm. Further, the pixel electrode 110 ′ is made of transparent ITO (Indium Tin Oxide) or the like in order to transmit light emitted from a backlight unit (not shown) disposed on the back surface (lower side in the drawing). .
[0008]
By the way, a light shielding film is formed on a counter substrate (not shown) arranged to face the TFT substrates 101 and 101 ′ so as to shield light from areas other than the pixel electrode 110 and 110 ′ formation regions. Therefore, in order to increase the ratio (reflectance) between the intensity of incident light and the intensity of reflected light reflected by the pixel electrode 110 with respect to the incident light, the luminance of the reflective liquid crystal display device can be increased. Need to be larger. Similarly, in order to increase the luminance of the transmissive liquid crystal display device by increasing the ratio (transmittance) between the intensity of incident light and the intensity of the transmitted light that transmits the incident light through the TFT substrate 101, 101 ′ and the counter substrate. It is necessary to increase the area of the pixel electrode 110 ′.
[0009]
In order to increase the area of the pixel electrode, it is necessary to bring the ends of the pixel electrodes 110 and 110 ′ closer to the gate bus line 105 and the drain bus line 106 formed around the pixel electrodes 110 and 110 ′. However, when the distance D1 between the pixel electrodes 110 and 110 ′ and both bus lines 105 and 106 is reduced, the capacitance generated between the pixel electrodes 110 and 110 ′ and both bus lines 105 and 106 increases, thereby causing crosstalk. Will occur and display quality will deteriorate.
[0010]
As shown in FIGS. 7 and 8, the overcoat layer 108 formed on the TFT substrate 101 of the reflective liquid crystal display device is compared with the protective film 112 formed on the TFT substrate 101 ′ of the transmissive liquid crystal display device. It is necessary to form irregularities on the surface, and it is not necessary to transmit light, so that it is formed thick. Further, since the coating is formed using a spin coating method or the like, it can be easily formed thicker than the protective film 112 formed using a CVD (Chemical Vapor Deposition) method or the like.
[0011]
As shown in FIGS. 7 and 8, in the TFT substrate 101, the distance in the normal direction of the substrate surface between the pixel electrode 110 and the drain bus line 106 is such that the pixel electrode 110 ′ and the drain bus line of the TFT substrate 101 ′. Since it is longer than the distance in the normal direction of the substrate surface to 106, the distance D1 can be sufficiently wide even if the distance in the substrate surface direction is shortened. By doing so, the interval D2 between the adjacent pixel electrodes 110 becomes narrower than the interval D3 between the adjacent pixel electrodes 110 ′.
[0012]
Although not shown in the drawing, a transmission type liquid crystal display device having a pixel on passivation structure in which an interlayer insulating film (resin insulating layer) is formed on a drain bus line has an interlayer insulating film spin-coated. The coating is formed using a method or the like. Therefore, the interlayer insulating film can be easily formed thick, and the interval between the adjacent pixel electrodes can be made smaller than the interval D3 between the pixel electrodes 110 ′, similarly to the reflective liquid crystal display device shown in FIG.
[0013]
[Problems to be solved by the invention]
When the distance D2 between the adjacent pixel electrodes 110 is narrowed, a short circuit between the adjacent pixel electrodes 110 is likely to occur due to contamination of foreign matters due to a defect in the manufacturing process. As shown in FIG. 6, the short-circuit defect caused by the foreign material 126 is repaired by cutting the cut portions 128 and 128 ′ at the end of the pixel electrode 110 with laser light in the defect repairing process. However, since the distance in the substrate surface direction between the cut portions 128 and 128 ′ and the drain bus line 106 is extremely short, the drain bus line 106 may be cut by mistake when cutting. For this reason, the problem that the manufacturing yield falls and manufacturing cost increases has arisen.
[0014]
An object of the present invention is to provide a substrate for a high-brightness liquid crystal display device with a high manufacturing yield while suppressing manufacturing costs, and a liquid crystal display device including the same.
[0015]
[Means for Solving the Problems]
The object is to provide a plurality of bus lines formed on the substrate so as to cross each other, a pixel region defined by the bus lines, a thin film transistor formed near the crossing position of the bus lines, and the bus lines. A liquid crystal comprising: an insulating layer formed; and a pixel electrode formed in each pixel region on the insulating layer and having a linear cut portion cut from an end portion in the vicinity of the bus line. This is achieved by the display device substrate.
[0016]
In the substrate for a liquid crystal display device according to the present invention, the insulating layer is a resin insulating layer formed of a resin. In the substrate for a liquid crystal display device according to the present invention, the cut portion is formed substantially parallel to the bus line. In the substrate for a liquid crystal display device according to the present invention, the cut portion is formed substantially perpendicular to the bus line.
[0017]
In addition, in the liquid crystal display device having two substrates, at least one of which is transparent, and a liquid crystal sealed between the substrates, the substrate for a liquid crystal display device of the present invention is used as one of the substrates. This is achieved by a liquid crystal display device.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A substrate for a liquid crystal display device according to a first embodiment of the present invention and a liquid crystal display device including the same will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a liquid crystal display device according to the present embodiment. In the liquid crystal display device, a TFT substrate 2 on which a thin film transistor (TFT) or the like is formed and a counter substrate 4 on which a color filter (CF) or the like is formed are bonded to each other, and a liquid crystal is interposed therebetween. It has an enclosed structure. At least one of the substrates 2 and 4 is made of a transparent substrate such as glass.
[0019]
FIG. 2 shows an equivalent circuit of elements formed on the TFT substrate 2 which is a substrate for a liquid crystal display device according to the present embodiment. On the TFT substrate 2, a plurality of gate bus lines 6 extending in the left-right direction in the drawing are formed in parallel to each other, and a plurality of drain bus lines 8 extending substantially perpendicular to them and extending in the vertical direction in the drawing are formed in parallel to each other. . Each region surrounded by the plurality of gate bus lines 6 and drain bus lines 8 is a pixel region. A TFT 10 and a pixel electrode 12 are formed in each pixel region. The drain electrode of each TFT 10 is connected to the adjacent drain bus line 8, the gate electrode is connected to the adjacent gate bus line 6, and the source electrode is connected to the pixel electrode 12. A storage capacitor bus line 14 is formed substantially in the center of each pixel region in parallel with the gate bus line 6. These TFT 10, pixel electrode 12, and each bus line 6, 8, 14 are formed by a photolithography process, and are formed by repeating a series of semiconductor processes of “film formation → resist application → exposure → development → etching → resist stripping”. Is done.
[0020]
Returning to FIG. 1, the TFT substrate 2 which is disposed opposite to the counter substrate 4 by sealing the liquid crystal has a gate drive circuit 16 on which a driver IC for driving the plurality of gate bus lines 6 is mounted, and a plurality of drain buses. A drain driving circuit 18 on which a driver IC for driving the line 8 is mounted is provided. The drive circuits 16 and 18 are configured to output a scanning signal and a data signal to a predetermined gate bus line 6 or drain bus line 8 based on a predetermined signal output from the control circuit 20. A polarizing plate 22 is disposed on the substrate surface opposite to the element formation surface of the TFT substrate 2, and a backlight unit 24 is attached to the surface of the polarizing plate 22 opposite to the TFT substrate 2. On the other hand, a polarizing plate 26 disposed in crossed Nicols with the polarizing plate 22 is attached to the surface opposite to the CF forming surface of the counter substrate 4. These are the configurations of the transmissive liquid crystal display device, and the reflective liquid crystal display device does not have the polarizing plate 22 and the backlight unit 24 and reflects incident external light at the pixel electrode 12. .
[0021]
FIG. 3 shows the configuration of the TFT substrate 2 of the substrate for a liquid crystal display device according to the present embodiment. As shown in FIG. 3, the TFT substrate 2 includes a plurality of gate bus lines 6 and 6 'formed on a glass substrate and extending in the left-right direction in the drawing, and crossing the gate bus lines 6 and 6' in the vertical direction in the drawing. And a plurality of drain bus lines 8 and 8 'extending in the direction. A TFT 10 is formed in the vicinity of the intersection between the gate bus line 6 and the drain bus line 8, and a TFT 10 ′ is formed in the vicinity of the intersection between the gate bus line 6 and the drain bus line 8 ′.
[0022]
The drain electrode 34 of the TFT 10 is drawn out from the drain bus line 8, and an end portion of the TFT 10 is an operating semiconductor layer (not shown) formed of amorphous silicon (a-Si) or the like on the gate bus line 6. The channel protective film 36 is formed so as to be positioned on one end side. On the other hand, the source electrode 38 is formed so as to be positioned on the other end side on the operating semiconductor layer and the channel protective film 36. In such a configuration, the gate bus line 6 immediately below the channel protective film 36 functions as a gate electrode of the TFT 10. A TFT 10 ′ formed adjacent to the right side of the TFT 10 in the drawing has the same configuration as the TFT 10.
[0023]
A plurality of pixel regions are defined by the gate bus lines 6 and 6 'and the drain bus lines 8 and 8'. Each pixel region has a size of about 100 μm × 300 μm. A storage capacitor bus line 14 extending substantially in parallel with the gate bus lines 6 and 6 ′ is formed in the same layer as the gate bus lines 6 and 6 ′ at substantially the center of the pixel region. On the storage capacitor bus line 14, storage capacitor electrodes 28 and 28 'are formed in the same layer as the drain bus lines 8 and 8' for each pixel region.
[0024]
A pixel electrode 12 is formed in the pixel region. For example, the pixel electrode 12 of the reflective liquid crystal display device is formed of a metal having a high reflectance such as Al in order to reflect external light incident from above. The pixel electrode 12 is electrically connected to the source electrode 38 via the contact hole 40, and is electrically connected to the storage capacitor electrode 28 via the contact hole 41. A pixel electrode 12 ′ formed adjacent to the right side of the pixel electrode 12 in the drawing has the same configuration as the pixel electrode 12.
[0025]
The pixel electrode 12 has a linear shape that is cut in substantially parallel to the drain bus line 8 ′ from the upper end of the pixel electrode 12 downward in the drawing at the end along the right drain bus line 8 ′ in the drawing. It has the notch part 30a. Similarly, the pixel electrode 12 is a line cut substantially parallel to the drain bus line 8 from the lower end of the pixel electrode 12 to the upper end along the drain bus line 8 on the left side of the drawing. The cut portion 30b has a shape.
[0026]
Further, the pixel electrode 12 has a linear cut portion 30c cut from the left to the right in parallel with the gate bus line 6 at the end along the upper gate bus line 6 in the drawing. is doing. Further, the pixel electrode 12 has a cut portion that is linearly cut from the right side to the left side at the end portion along the gate bus line 6 ′ in the lower part of the drawing, substantially parallel to the gate bus line 6 ′. 30d. As described above, the pixel electrode 12 has the cut portions 30a to 30d at each end.
[0027]
The cut portions 30a to 30d have end portions 32a to 32d so that the pixel electrode 12 is not separated into a plurality in the pixel region. The end portions 32a to 32d are formed wider than other regions of the cut portions 30a to 30d so that the pixel electrode 12 can be easily cut, and have, for example, a rectangular shape. Although description is omitted, the pixel electrode 12 ′ adjacent to the right side of the pixel electrode 12 in the drawing has the same cut portions 30 a ′ to 30 d ′ as the pixel electrode 12. The cut portions 30a to 30d and 30a ′ to 30d ′ are formed simultaneously with the pixel electrodes 12 and 12 ′ in the photolithography process.
[0028]
Next, a defect repair method for the liquid crystal display device according to the present embodiment will be described with reference to FIG. It is assumed that a short-circuit defect due to the foreign matter 42 has occurred between the pixel electrodes 12 and 12 ′ adjacent in the left-right direction, and the short-circuit defect has been found in advance by lighting display inspection or the like.
[0029]
First, the cutting portion 44 between the end portion 32a of the cut portion 30a of the pixel electrode 12 and the lower end portion of the pixel electrode 12 in the drawing, the end portion 32b ′ of the cut portion 30b ′ of the pixel electrode 12 ′, and the pixel electrode 12 ′. The two portions with the cutting portion 44 ′ between the upper end portion in FIG. Thereby, the pixel electrodes 12 and 12 ′ are electrically separated. Through the above process, the short-circuit defect generated between the pixel electrodes 12 and 12 ′ is repaired.
[0030]
According to the present embodiment, the distance in the substrate surface direction between the cut portions 44, 44 ′ and the drain bus line 8 ′ is such that the cut portions 128, 128 ′ of the conventional TFT substrate 101 shown in FIG. Since it is longer than the distance in the substrate surface direction from the line 106, the drain bus line 8 'is not accidentally cut. Further, since the cut portions 30a to 30d and 30a ′ to 30d ′ are linear, the area of the pixel electrode 12 is not reduced so much. Accordingly, it is possible to realize a high-brightness liquid crystal display device with a high manufacturing yield while suppressing manufacturing costs.
[0031]
Next, a liquid crystal display substrate according to a second embodiment will be described with reference to FIG. FIG. 4 shows the configuration of the liquid crystal display substrate according to the present embodiment. As shown in FIG. 4, the pixel electrode 13 has a plurality of linear cuts cut substantially perpendicularly to the drain bus line 8 ′ at the end along the right drain bus line 8 ′. It has a portion 31a. Similarly, the pixel electrode 13 has a plurality of linear cut portions 31b cut almost perpendicularly to the drain bus line 8 at the end portion along the left drain bus line 8 in the drawing. Yes.
[0032]
Further, the pixel electrode 13 has a plurality of linear cut portions 31c cut almost perpendicular to the gate bus line 6 at the end along the upper gate bus line 6 in the drawing. At the end portion along the lower gate bus line 6 ′, there are a plurality of linear cut portions 31d cut almost perpendicularly to the gate bus line 6 ′. Although description is omitted, the pixel electrode 13 ′ adjacent to the right side of the pixel electrode 13 has the same cut portions 31 a ′ to 31 d ′ as the pixel electrode 13. The cut portions 31a to 31d and 31a ′ to 31d ′ are formed simultaneously with the pixel electrodes 13 and 13 ′ in the photolithography process.
[0033]
Next, a defect repair method for the liquid crystal display device according to the present embodiment will be described with reference to FIG. As in the first embodiment, a short-circuit defect due to the foreign matter 42 occurs between the pixel electrodes 13 and 13 'adjacent in the left-right direction, and the short-circuit defect is discovered in advance by lighting display inspection or the like. Shall.
[0034]
First, the cut portion 45 between the two cut portions 31a of the pixel electrode 13 formed on both sides of the left end of the foreign substance 42 in the drawing, and the pixel electrode 13 ′ formed on both sides of the right end of the foreign substance 42 in the drawing. The two cut portions 45 ′ between the two cut portions 31b ′ are cut with a laser beam. Thereby, the pixel electrodes 13 and 13 ′ are electrically separated. Through the above process, the short-circuit defect occurring between the pixel electrodes 13 and 13 ′ is repaired.
[0035]
According to the present embodiment, the distance in the substrate surface direction between the cut portions 45, 45 ′ and the drain bus line 8 ′ is such that the cut portions 128, 128 ′ of the conventional TFT substrate 101 shown in FIG. Since it is longer than the distance in the substrate surface direction from the line 106, the drain bus line 8 'is not accidentally cut. In addition, since the cut portions 31a to 31d and 31a ′ to 31d ′ are linear, the area of the pixel electrode 12 is not significantly reduced. Accordingly, it is possible to realize a high-brightness liquid crystal display device with a high manufacturing yield while suppressing manufacturing costs.
[0036]
Next, a liquid crystal display substrate according to a third embodiment will be described with reference to FIG. FIG. 5 shows the configuration of the liquid crystal display substrate according to the present embodiment. In addition, the same code | symbol is attached | subjected about the component which has the same function effect | action as the component of the board | substrate for liquid crystal display devices by 1st Embodiment shown in FIG. 3, and the description is abbreviate | omitted. As shown in FIG. 5, the pixel electrode 15 is disposed so as to overlap the gate bus line 6 and the drain bus line 8 when viewed in the direction perpendicular to the substrate surface. That is, each pixel area is not arranged in an area defined by both bus lines 6, 6 ′, 8, and 8 ′, but is shifted from the area toward the upper left in the figure and arranged in a matrix.
[0037]
Next, a defect repair method for the liquid crystal display device according to the present embodiment will be described with reference to FIG. As in the first and second embodiments, a short-circuit defect due to the foreign matter 42 occurs between the pixel electrodes 15 and 15 'adjacent in the left-right direction, and the short-circuit defect is discovered in advance by lighting display inspection or the like. It is assumed that
[0038]
First, the foreign matter 42 that is short-circuited between the pixel electrodes 15 and 15 ′ is cut with a laser beam at the cutting portion 46 between the pixel electrodes 15 and 15 ′. Thereby, the pixel electrodes 15 and 15 ′ are electrically separated. Through the above process, the short-circuit defect generated between the pixel electrodes 15 and 15 ′ is repaired.
[0039]
In the present embodiment, the drain bus line 8 ′ is formed below the pixel electrode 15 ′ and is not disposed between the pixel electrodes 15 and 15 ′. Therefore, the distance in the substrate surface direction between the cut portion 46 and the drain bus line 8 ′ is the substrate surface between the cut portions 128, 128 ′ of the conventional TFT substrate 101 shown in FIG. Since it is longer than the distance in the direction, the drain bus line 8 ′ is not accidentally cut. Accordingly, it is possible to realize a high-brightness liquid crystal display device with a high manufacturing yield while suppressing manufacturing costs.
[0040]
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the CF is formed on the counter substrate. However, the present invention is not limited to this, and the CF may be formed on the TFT substrate.
[0041]
【The invention's effect】
As described above, according to the present invention, a high-brightness liquid crystal display device with low manufacturing cost and high manufacturing yield can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a liquid crystal display substrate according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a substrate for a liquid crystal display device according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a liquid crystal display substrate according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a substrate for a liquid crystal display device according to a third embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of a conventional substrate for a reflective liquid crystal display device.
FIG. 7 is a cross-sectional view showing a configuration of a conventional substrate for a reflective liquid crystal display device.
FIG. 8 is a cross-sectional view showing a configuration of a conventional substrate for a transmissive liquid crystal display device.
[Explanation of symbols]
2 TFT substrate 4 Counter substrate 6 Gate bus line 8 Drain bus line 10 TFT
12, 13, 15 Pixel electrode 14 Storage capacitor bus line 16 Gate bus line drive circuit 18 Drain bus line drive circuit 20 Control circuit 22, 26 Polarizer 24 Backlight unit 28 Storage capacitor electrodes 30a-30d, 31a-31d Cut portion 32a 32d Terminal 34 Drain electrode 36 Channel protective film 38 Source electrode 40, 41 Contact hole 42 Foreign matter 44, 45, 46 Cutting part

Claims (6)

A plurality of gate bus lines and drain bus lines formed to cross each other on the substrate;
A pixel region defined by the gate bus line and the drain bus line;
A thin film transistor formed near the intersection of the gate bus line and the drain bus line;
An insulating layer formed on the gate bus line and the drain bus line;
Formed for each of the pixel regions on the insulating layer, and having a linear notch extending from one end to the vicinity of the other end only at the end along the gate bus line or drain bus line, and in the normal direction of the substrate surface And a pixel electrode that does not overlap the gate bus line and the drain bus line. A substrate for a liquid crystal display device according to claim 1,
The substrate for a liquid crystal display device, wherein the insulating layer is a resin insulating layer formed of a resin. A substrate for a liquid crystal display device according to claim 1 or 2,
The substrate for a liquid crystal display device, wherein the cut portion is formed substantially parallel to the gate bus line or the drain bus line. A plurality of gate bus lines and drain bus lines formed to cross each other on the substrate;
A pixel region defined by the gate bus line and the drain bus line;
A thin film transistor formed near the intersection of the gate bus line and the drain bus line;
An insulating layer formed on the gate bus line and the drain bus line;
A linear notch that is formed for each pixel region on the insulating layer and is cut only at one end along the gate bus line or drain bus line from one end substantially parallel to the gate bus line or drain bus line. And a pixel electrode that is provided at the other end and is cut at the time of short circuit repair, and that does not overlap the gate bus line and the drain bus line when viewed in the normal direction of the substrate surface. A substrate for a liquid crystal display device. A substrate for a liquid crystal display device according to claim 4 ,
The substrate for a liquid crystal display device, wherein the insulating layer is a resin insulating layer formed of a resin. In a liquid crystal display device having two substrates, at least one of which is transparent, and a liquid crystal sealed between the substrates,
A liquid crystal display device according to claim 1, wherein the substrate for a liquid crystal display device according to claim 1 is used on one of the substrates.

Images