JPH1068973A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain high numerical aperture even when a picture element pitch is reduced and to realize bright high-definition picture display by arranging a common electrode electrically connecting a retaining capacitor between two scanning lines being an odd numbered line and a next even numbered line or an even numbered line and a next odd numbered line. SOLUTION: The common electrode 10 electrically connecting the retaining capacitor is arranged by one per two scanning lines. Namely, the electrode 10 is arranged between two scanning lines Y1 and Y2 being the odd numbered line and the next even numbered line. It is possible to shift the electrode 10 by one line and arrange it between two scanning line Y2 and Y3 being the even numbered line and the next odd numbered line. The retaining capacitor 4 and 5 are formed on the same electrode wiring so as to reduce occupied area. By such constitution, while generating the sufficient retaining capacitor for the picture element, the number of the common electrodes is reduced to half the number in the conventional device, and the number of the source electrode connection parts of signal conductors X1 and X2 and TFTs 1 to 3 is also reduced to half, and the high numerical aperture is maintained even when the picture element pitch is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a liquid crystal display device using a TFT.

[0002]

2. Description of the Related Art As an example of a conventional liquid crystal display device using a TFT, there is "Japan Display 89 Digest p418-421 Matsueda et al.". FIG. 2 is an example of a circuit diagram of a liquid crystal display device using a TFT. X1 and X2 are signal lines, Y1, Y2, Y3, and Y4 are scanning lines. The TFT 11 is located at the intersection of the signal line X1 and the scanning lines Y1, Y2, and Y3.
There are 12 and 13. These TFTs 11, 12, and 13 are turned on and off according to the timing of a selection pulse given to the scanning lines Y1, Y2, and Y3. An image signal applied to the signal line X1 is transmitted through the TFTs 11, 12, and 13 to the liquid crystal capacitors 17, 18, 19 and the storage capacitors 14, 15,
16 is written.

FIG. 3 is an example of a plan view of a pixel portion of a liquid crystal display device. The TFT 2 is located at the intersection of the signal line 21 and the scanning line 22.
4 are arranged. The semiconductor thin film 23 forms the source / drain of the TFT 24 and the channel. 25 is a TFT 24
Reference numeral 26 denotes a contact hole connecting the source portion of the TFT 24 and the signal line 21, and reference numeral 26 denotes a contact hole connecting the drain portion of the TFT 24 and the pixel electrode 29. A storage capacitor 28 is formed between the drain of the TFT 24 and the common electrode 27. In the case of a transmissive display device, the portion indicated by the opening 30 is an area effective for image display.

[0004]

However, the above-mentioned prior art has the following problems.

Generally, in order to obtain a high-definition image, it is necessary to increase the density of pixels. However, as the pixel pitch decreases, the capacity of the liquid crystal decreases, and a sufficient storage capacity is required to maintain high image quality. You have to make it. Further, there is a manufacturing limit in reducing the size of the TFT. Therefore,
When the pixel pitch decreases, the ratio of the region occupied by the storage capacitor and the TFT increases, and the ratio of the region effective for image display, that is, the aperture ratio decreases. The decrease in the aperture ratio not only darkens the screen but also causes a problem that the pattern of the light-shielding layer stands out as if the screen is covered with a thick lattice, resulting in a significant decrease in image quality.

The liquid crystal display device of the present invention solves such a problem, and an object thereof is to realize a liquid crystal display device which can maintain a high aperture ratio even if the pixel pitch is reduced. .

[0007]

According to the liquid crystal display device of the present invention, each pixel electrode is provided with a storage capacitor, and a common electrode for electrically connecting the storage capacitor is scanned in an odd-numbered row and an even-numbered row next thereto. It is characterized by being arranged between two lines or between two even-numbered scanning lines and odd-numbered scanning lines.

[0008]

According to the above configuration of the present invention, the number of common electrodes for electrically connecting the storage capacitors is reduced to half that of the conventional one while the sufficient storage capacitance is formed in each pixel, and the signal line and the source of the TFT are formed. The number of electrode connections can also be halved from the conventional one.
Therefore, a high aperture ratio can be maintained even if the pixel pitch decreases.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment will be described below with reference to the drawings. FIG. 1 is an example of a circuit diagram of a liquid crystal display device of the present invention. X1 and X2 are signal lines, and Y1, Y2, Y3 and Y4 are scanning lines. TFTs 1, 2, and 3 are disposed at intersections of the signal line X1 and the scanning lines Y1, Y2, and Y3, respectively. These TFTs 1, 2, and 3 are turned on and off according to the timing of a selection pulse applied to the scanning lines Y1, Y2, and Y3.
The image signal given to the signal line X1 is a signal
The data is written to the liquid crystal capacitors 7, 8, 9 and the storage capacitors 4, 5, 6 via 1, 2, and 3. In the present invention, the common electrode 10 for electrically connecting the storage capacitors is arranged at a ratio of one to two scanning lines. For example, since the storage capacitors 4 and 5 are formed on the same electrode wiring, a sufficient capacity can be built up in a smaller occupied area as compared with the case where they are formed on separate electrode wirings as in the related art. Also, since two TFTs for the upper and lower two pixels are arranged side by side, two TFTs
The connection between the source and the signal line can be shared. For example, TFT
Only one connection is required between the signal lines 2 and 3 and the signal line X1. Therefore, the area occupied by the TFT is reduced.

In FIG. 1, the common electrode 10 is arranged between the two scanning lines in the odd-numbered row and the next even-numbered row. Line 2
It is also possible to arrange them between the scanning lines.

FIG. 4 is an example of a plan view of a pixel portion of a liquid crystal display device. The TFT 3 is located at the intersection of the signal line 31 and the scanning line 32.
4 are arranged. The semiconductor thin film 33 forms a source / drain and a channel portion of the TFT. Reference numeral 35 denotes a contact hole for connecting the signal lines 31 to the source portions of the TFTs for the upper and lower two pixels. Reference numeral 36 denotes a contact hole for connecting the drain portion of the TFT 34 and the pixel electrode 39. A storage capacitor 38 is formed between the drain of the TFT 34 and the common electrode 37. On the common electrode 37, storage capacitors of two pixels located on both sides of this electrode are arranged. In the case of a transmissive display device, the portion indicated by the opening 40 is a distribution effective for image display. Since the area other than the opening 40 deteriorates the image quality, the area is usually covered with a light shielding layer so that light does not pass therethrough.

In this embodiment, since the common electrode 37 is disposed in a region between the pixel electrodes which is not necessary for displaying an image,
A high aperture ratio can be obtained. Opening 4 in FIG.
The area of 0 is about 30% larger than that of the opening 30 in FIG. That is, the screen can be made 30% brighter while producing the same element at the same pixel pitch, and since the shape of the opening changes from a horizontally long rectangle to a square, the lattice of the light shielding portion becomes less noticeable, and the image quality is dramatically improved. . Further, when an inclined wiring pattern is used together, the shape of the opening can be made closer to an ideal circular shape.

Another feature of the present invention is that the driving system has a high degree of freedom. As is well known, NT
SC and HDTV signals consist of two interlaced fields. When these signals are displayed on a liquid crystal display device, a driving method is often used in which two scanning lines are paired and selected at the same timing, the same data is written, and the combination of the scanning lines to be paired is changed for each field. This method is a practical method that does not require a complicated peripheral circuit such as a memory, improves the response of pixels in the case of a moving image, and can prevent flicker. However, in the structure of the conventional liquid crystal display device as shown in FIG. 3, the pixel electrode and the previous scanning line are adjacent to each other. There has been a problem that the voltage differs between the two scanning lines, and the brightness differs for each scanning line on the screen. On the other hand, in the liquid crystal display device of the present invention shown in FIG. 4, since the pixel electrode and the preceding scanning line are not adjacent to each other, even if this driving method is used, a uniform screen can be obtained without such a problem. Of course, normal sequential scanning is also possible, and the driving method can be changed according to the purpose.

When three primary color filters of R (red), G (green), and B (blue) are used, the above-described driving method for simultaneously selecting two scanning lines employs a vertical stripe color filter arrangement. There is a need to. Of course, in a normal progressive scanning driving method, a mosaic type or triangle type color filter arrangement can be used.

FIG. 5 is an example of a sectional view of the liquid crystal display device corresponding to FIGS. 4 and 3. In general, a liquid crystal display device using a TFT includes a liquid crystal 43 sandwiched between two insulating substrates, that is, a TFT substrate 41 and a counter substrate 42. On the TFT base 41, an element including a TFT section 44 and a storage capacitor section 45 is arranged. The configuration of the TFT as shown in this figure is called a coplanar type, and the source part 47, the drain part 49,
The channel section 48 is made of the same semiconductor thin film. Since impurities are implanted into the source portion 47 and the drain portion 49 from above the gate insulating film 50 using the gate electrode 46 as a mask,
It becomes a self-aligned TFT. Gate electrode 4
The MOS capacitance between the common electrode 51 and the drain 49 made of the same film as 6 is used as a storage capacitance. There are two methods for forming the MOS capacitor. One is a method in which an impurity is previously implanted into the semiconductor thin film in this portion before forming the source / drain. In this case, the potential of the common electrode 51 can be arbitrarily selected. The other is a method in which impurities are not particularly implanted. In this case, the semiconductor thin film under the common electrode 51
Therefore, in order to use the MOS capacitor as a MOS capacitor, it is necessary to apply a bias to the common electrode 51 so as to form an inversion layer in the channel portion. Signal line 53 and pixel electrode 52
Are respectively connected to the source part 47 and the drain part 49 of the TFT via contact holes. In the configuration shown in the figure, a storage capacitor is formed between the pixel electrode 52 and the common electrode 51 via the interlayer insulating film 54. In general, a dense and low-defect film such as a thermal oxide film is used for the gate insulating film,
The film thickness is reduced to obtain good FT transfer characteristics. For this reason, the above-mentioned MOS capacitor can produce many times the capacity using the interlayer insulating film and has few defects. In this figure, when the contact hole between the drain part 49 of the TFT and the pixel electrode 52 is arranged on the right side of the common electrode 51, only the MOS capacitance becomes the storage capacitance.

The passivation film 55 has a function of protecting the thin film element portion and a function of cutting a DC voltage applied to the liquid crystal. The light shielding layer 56 provided on the counter substrate 42 is
There is a function of suppressing the light leakage current of the FT and a function of obtaining a high-quality image having a large contrast ratio by covering a portion that is not effective for pixel display. The opening 58 is an area effective for displaying an image. The counter electrode 57 made of a transparent conductive film covers the entire surface in contact with the liquid crystal, and the liquid crystal 43 is driven by an electric field between the pixel electrode 52 and the counter electrode 57. When used as a transmissive display device, the pixel electrode 52 is formed of a transparent conductive film. When used as a reflective display device, the pixel electrode 52 is formed of a metal thin film.

FIG. 6 is a second example of a plan view of a pixel portion of the liquid crystal display device. At the intersection of the signal line 61 and the scanning line 62, T
FT is arranged. In this figure, the source 65 and drain 66 of the TFT and the channel 64 are formed of different thin films. On the common electrode 67, storage capacitors 68 of two pixels located on both sides of this electrode are arranged. Both the drain 66 of the TFT and the storage capacitor 68 are connected to the pixel electrode 69. In the case of a transmissive display device, the opening 70
The portion indicated by is an area effective for image display. Opening 70
Since areas other than the above deteriorate image quality, they are usually covered with a light shielding layer so that light does not pass therethrough.

FIG. 7 is an example of a sectional view of the liquid crystal display device corresponding to FIG. The liquid crystal display device of this embodiment is also formed by sandwiching a liquid crystal 73 between two insulating substrates, that is, a TFT substrate 71 and a counter substrate 72. TFT on the TFT substrate 71
An element including a portion 74 and a storage capacitor portion 75 is arranged.
The configuration of the TFT as shown in this figure is called an inverted staggered type, in which a gate electrode 76, a gate insulating film 80, a semiconductor thin film 78 forming a channel, and an impurity semiconductor thin film 88 forming source / drain portions are sequentially deposited. It has a structure.
A source electrode 77 and a drain electrode 79 are formed on the impurity semiconductor thin film 88. The source electrode 77 is a branch of a signal line, and the drain electrode 79 is connected to the pixel electrode. As another structure of the TFT, there is a so-called staggered type in which the TFT of this figure is turned upside down. The storage capacitor 75 has the same structure as the drain of the TFT, is arranged on the common electrode 81, and is connected to the pixel electrode 82.
As another configuration, a storage capacitor can be formed by overlapping the pixel electrode 82 on the common electrode 81 with the gate insulating film 80 interposed therebetween. The passivation film 84 has a function of protecting the thin film element portion and a function of cutting a DC voltage applied to the liquid crystal. The light-shielding layer 86 provided on the counter substrate 72 has a function of suppressing a light leak current of the TFT and a function of obtaining a high-quality image having a large contrast ratio by covering a portion that is not effective for image display. The opening 77 is an area effective for displaying an image. The opposing electrode 86 made of a transparent conductive film covers the entire surface in contact with the liquid crystal, and the liquid crystal 73 is driven by an electric field between the pixel electrode 82 and the opposing electrode 86.

[0019]

As described above, the liquid crystal display device of the present invention can maintain a high aperture ratio even if the pixel pitch is reduced, so that a high definition and bright image can be displayed. In addition, since the size of the liquid crystal display device can be reduced to realize the same number of pixels, the cost can be reduced. Furthermore, the interlaced moving image signal can be pseudo-displayed in full lines, and a high-resolution moving image can be displayed. For example, high image quality and low cost can be simultaneously realized in a viewfinder of a video camera that requires small size and light weight and low power consumption, and a light valve of a video projector that requires high definition and a high aperture ratio.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a liquid crystal display device of the present invention.

FIG. 2 is a circuit diagram of a conventional liquid crystal display device.

FIG. 3 is a plan view of a pixel portion of a conventional liquid crystal display device.

FIG. 4 is a plan view of a pixel portion of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view of the liquid crystal display device of the present invention.

FIG. 6 is a plan view of a pixel portion of the liquid crystal display device of the present invention.

FIG. 7 is a cross-sectional view of the liquid crystal display device of the present invention.

[Explanation of symbols]

 1, 2, 3, 11, 12, 13. . . TFT 4, 5, 6, 14, 15, 16. . . Storage capacity 7, 8, 9, 17, 18, 19. . . Liquid crystal capacitors 27, 37, 51, 67, 81. . . Common electrode 30, 40, 58, 70, 77. . . Aperture

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[Procedure amendment]

[Submission date] August 18, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Display device

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

The present invention relates to a structure of a display device using a TFT.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

A liquid crystal display device according to the present invention comprises a plurality of signal lines on a substrate, a scanning line intersecting the plurality of signal lines, and a thin film transistor connected to each of the signal lines and the scanning line. And a display device having a pixel electrode and a storage capacitor connected to the thin film transistor, wherein the first pixel is located between a first pixel electrode and a second pixel electrode at a stage next to the first pixel electrode. A first scanning line connected to the electrode and a second scanning line connected to the second pixel electrode are arranged, and the second scanning line is connected to the second pixel electrode with respect to the second pixel electrode. A common electrode serving as one electrode of the storage capacitor is arranged between the third pixel electrode of the stage and the third pixel electrode, and a signal line is sandwiched between the third pixel electrode and the second pixel electrode. The respective storage capacitances of the fourth pixel electrodes adjacent to each other are the third pixel electrode and the fourth pixel electrode. Extend so as to overlap the common electrode formed between the second pixel electrode and the third pixel electrode with an insulating film interposed therebetween. It is characterized by being formed by.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

FIG. 6 is a reference example of a plan view of a pixel portion of a liquid crystal display device. TF is set at the intersection of the signal line 61 and the scanning line 62.
T is arranged. In this figure, the TFT source 6
5 and the drain 66 and the channel 64 are formed of different thin films. On the common electrode 67, storage capacitors 68 of two pixels located on both sides of this electrode are arranged. Pixel electrode 6
9 is connected to both the drain 66 of the TFT and the storage capacitor 68. In the case of a transmissive display device, the portion indicated by the opening 70 is an area effective for image display. Since the area other than the opening 70 deteriorates the image quality, the area is usually covered with a light-shielding layer to prevent light from passing therethrough.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

FIG. 7 is an example of a sectional view of the liquid crystal display device corresponding to FIG. The liquid crystal display device of this reference example also has a liquid crystal 73 sandwiched between two insulating substrates, that is, a TFT substrate 71 and a counter substrate 72. TFT on the TFT substrate 71
An element including a portion 74 and a storage capacitor portion 75 is arranged.
The configuration of the TFT as shown in this figure is called an inverted staggered type, in which a gate electrode 76, a gate insulating film 80, a semiconductor thin film 78 forming a channel, and an impurity semiconductor thin film 88 forming source / drain portions are sequentially deposited. It has a structure.
A source electrode 77 and a drain electrode 79 are formed on the impurity semiconductor thin film 88. The source electrode 77 is a branch of a signal line, and the drain electrode 79 is connected to the pixel electrode. As another structure of the TFT, there is a so-called staggered type in which the TFT of this figure is turned upside down. The storage capacitor 75 has the same structure as the drain of the TFT, is arranged on the common electrode 81, and is connected to the pixel electrode 82.
As another configuration, a storage capacitor can be formed by overlapping the pixel electrode 82 on the common electrode 81 with the gate insulating film 80 interposed therebetween. The passivation film 84 has a function of protecting the thin film element portion and a function of cutting a DC voltage applied to the liquid crystal. The light-shielding layer 86 provided on the counter substrate 72 has a function of suppressing a light leak current of the TFT and a function of obtaining a high-quality image having a large contrast ratio by covering a portion that is not effective for image display. The opening 77 is an area effective for displaying an image. The opposing electrode 86 made of a transparent conductive film covers the entire surface in contact with the liquid crystal, and the liquid crystal 73 is driven by an electric field between the pixel electrode 82 and the opposing electrode 86.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

[0019]

As described above, the display device of the present invention has the following features.
The following effects can be obtained. 1) Since a high aperture ratio can be maintained even when the pixel pitch is reduced, a high-definition and bright image can be displayed. In addition, since the size of the liquid crystal display device can be reduced to realize the same number of pixels, the cost can be reduced. 2) The storage capacitor can be formed at the same time as the thin film transistor, and the storage capacitor can be formed by extending the silicon thin film serving as the source / drain region so as to overlap the common electrode of the storage capacitor. This structure does not require an opening to form. Therefore, the thin film transistor and the charge storage capacitor can be formed with a simple structure.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a liquid crystal display device of the present invention.

FIG. 2 is a circuit diagram of a conventional liquid crystal display device.

FIG. 3 is a plan view of a pixel portion of a conventional liquid crystal display device.

FIG. 4 is a plan view of a pixel portion of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view of the liquid crystal display device of the present invention.

FIG. 6 is a plan view of a pixel portion of a liquid crystal display device according to a reference example of the present invention.

FIG. 7 is a cross-sectional view of a liquid crystal display device according to a reference example of the present invention.

[Description of reference numerals] 1, 2, 3, 11, 12, 13. . . TFT 4, 5, 6, 14, 15, 16. . . Storage capacity 7, 8, 9, 17, 18, 19. . . Liquid crystal capacitors 27, 37, 51, 67, 81. . . Common electrode 30, 40, 58, 70, 77. . . Aperture

Claims (4)

[Claims] 1. A thin film transistor (hereinafter abbreviated as TFT) disposed on a first insulating substrate at a plurality of signal lines and scanning lines, at intersections of the signal lines and the scanning lines, and the TFT
And a pixel electrode connected to the second insulating substrate, a counter electrode on the second insulating substrate, and a liquid crystal sandwiched in a space where the first insulating substrate and the second insulating substrate face each other. In the display device, each of the pixel electrodes is provided with a storage capacitor, and a common electrode electrically connecting the storage capacitor is provided between the odd-numbered row and the next even-numbered scanning line or between the even-numbered row and the even-numbered row. A liquid crystal display device, wherein the liquid crystal display device is arranged between the two scanning lines in the next odd-numbered row. 2. A source line connection portion between two even-numbered and next odd-numbered TFTs and the signal line, or an odd-numbered line and a next even-numbered two TFT source portions. 2. The liquid crystal display device according to claim 1, wherein a connection portion between the signal line and the signal line is shared. 3. The common electrode for electrically connecting the storage capacitor covers at least a portion between the pixel electrodes on odd and even rows or between the pixel electrodes on even and odd rows. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is arranged as described above. 4. The method according to claim 1, wherein two adjacent scanning lines are simultaneously selected, and a combination of the two scanning lines is changed between an odd field and an even field.
4. A liquid crystal display device according to claim 2 or claim 3.