JP5500537B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

The present invention relates to fringe field switching (FF).
S ". In particular, the present invention relates to an FFS mode liquid crystal display device in which a short circuit between a signal line and a common electrode (hereinafter also referred to as a lower electrode) is suppressed.

As a lateral electric field type liquid crystal display device, an FFS mode liquid crystal display device having a pair of electrodes including a pixel electrode and a common electrode on only one substrate is known. In this FFS mode liquid crystal display device, a pixel electrode and a common electrode for applying an electric field to a liquid crystal layer are arranged in different layers through an insulating film, respectively, have a wide viewing angle, a high contrast, and a low It has a feature that it can be driven by voltage and can display bright because of its higher transmittance. In addition, since the FFS mode liquid crystal display device has a large overlapping area between the pixel electrode and the common electrode in a plan view, a larger storage capacity is generated as a secondary effect, and there is no need to separately provide an auxiliary capacity electrode. Also exist.

However, it has been conventionally manufactured by a vacuum evaporation method, a physical vapor deposition method such as sputtering, or a metal organic chemical vapor deposition method by thermal decomposition. In such an FFS mode liquid crystal display device, the signal line is a common wiring. A step due to the stacking occurred at the position intersecting with the thickness, and the film thickness of the side surface region of the step became thin, so that the withstand voltage was easily lowered, and a disconnection failure or a short-circuit failure was occasionally observed. In the conventional FFS mode liquid crystal display device, the surface of the common wiring is covered with a lower electrode, the surface of the lower electrode is covered with a gate insulating film, and a signal line is formed on the surface of the gate insulating film, Further, a thin film transistor TFT (Thin Film Transistor) as a switching element is formed in the vicinity of the intersection of the scanning line and the signal line. Therefore, at the time of manufacture, for example, an amorphous silicon (a-Si) layer and n are formed on the entire surface of the gate insulating film.
After forming the ⁺ a-Si layer, the semiconductor layer for forming the TFT is patterned by a photolithography method. At this time, there is a washing step with pure water before patterning by applying a photolithography against a-Si layer and n ^{+ a-Si} layer, pure water and n ⁺ a
Since static electricity is generated between the n ⁺ a-Si layer and the common electrode, static electricity is generated between the n ⁺ a-Si layer and the lower electrode. Insulation breakdown may occur in the insulating film.

When a metal film is formed on a fine step formed on a semiconductor substrate, the ratio of the film thickness between the side surface region of the step and the flat part around the step is called step coverage, and at the flat part around the step. Step coverage is B, where A is the thickness of the film and B is the thickness of the side surface of the step.
/ A. The coverage is better as this value is larger than 1, and the coverage is worse as it is smaller than 1. If the film thickness of the side surface region of the step is small compared to the film thickness in the flat part around the step, the coverage is poor, and fine holes and cracks are likely to occur in the side surface region of the step.

In this state, if the signal line, the source electrode, the drain electrode, and the like are patterned after forming the source layer on the surface of the first insulating film, the source layer enters the location where the gate insulating film is destroyed. And the lower electrode may be short-circuited and appear as a line defect. The cause of this phenomenon is that the step formed by the common wiring and the lower electrode is large, and the step coverage of the gate insulating film covering the common wiring and the lower electrode is poor. This is because the thickness of the gate insulating film covering the side surfaces of the gate electrode becomes thin. The reason why the step formed by the common wiring and the lower electrode becomes large is as follows.
(1) In order to improve the aperture ratio and improve the display image quality by arranging the common wiring close to one side of the scanning line adjacent to the area where the common wiring is disposed,
(2) In order to reduce the contact resistance between the common wiring and the lower electrode, it is necessary to maximize the contact area between the common wiring and the lower electrode.
This is because the side surface is formed at the same position as the side surface of the common wiring so that the lower electrode does not protrude from the scanning line side.

As a method for solving such a problem, the following Patent Document 1 discloses a semiconductor device that can secure a sufficient dielectric breakdown strength against static electricity or the like by doubling an insulating film. Yes. In the semiconductor device disclosed in Patent Document 1 below, the insulating film has a two-layer structure of a first insulating film made of a silicon oxide film or a silicon nitride film and a second insulating film made of a heat-resistant organic material. Yes. Since the second insulating film is formed by applying a liquid material having increased viscosity, the shoulder does not sag and becomes a precipice, and the shape of the film end is relaxed to form a gentle slope (taper). Therefore, the film thickness of the insulating film can be increased compared to the conventional case,
It is said that sufficient dielectric breakdown strength against static electricity can be secured.

Japanese Patent Laid-Open No. 06-112333

However, in the method of obtaining a sufficient film thickness by making the end portion of the insulating film like the semiconductor device disclosed in Patent Document 1 into a slope shape, the insulating film formed on the upper side of the end portion of the lower electrode is Although the step coverage is improved by making the edge part into a slope, the film thickness is still thinner than the flat part, and it is not enough to form a sufficient thickness over the entire insulating film Have difficulty. Therefore, even in the semiconductor device disclosed in Patent Document 1, the thickness formed above the sloped end of the lower electrode by the electric field generated between the static electricity generated during cleaning and the lower electrode. May be locally electrostatically broken in thin areas.

As a result of various studies to solve the problems of the prior art as described above, the present inventors have extended a lower electrode formed on the common wiring that is the starting point of the occurrence of sparks to form a plurality of steps. As a result, it was found that the insufficient film thickness formation at the edge portion can be eliminated during the CVD film formation of the first insulating film, and the present invention has been completed. That is, an object of the present invention is to provide a highly reliable FFS mode liquid crystal display device that suppresses short-circuiting between a lower electrode and a signal line and reduces the occurrence of line defects.

Another object of the present invention is to provide a method for manufacturing an FFS mode liquid crystal display device capable of achieving the effects of the present invention.

In order to achieve the above object, a liquid crystal display device according to the present invention includes a plurality of scanning lines and common wirings provided in parallel on one of a pair of substrates sandwiching a liquid crystal layer, and the scanning lines. ,
A first insulating film covering the common wiring and the one substrate; a plurality of signal lines provided on the first insulating film in a direction crossing the scanning line and the common wiring; and the scanning A thin film transistor provided near an intersection of a line and the signal line, a lower electrode formed under the first insulating film and connected to the common wiring, the thin film transistor, the signal line, A second insulating film formed on a surface of the first insulating film, and an upper electrode having a slit formed on the second insulating film so as to overlap the lower electrode in a plan view. A liquid crystal display device having a display area in which the liquid crystal layer is driven by an electric field generated between the lower electrode and the upper electrode, and a non-display area formed outside the display area. , The common layout The lower electrode covers the common line so that a plurality of steps are formed on the side surface of the common line. It is characterized by.

The liquid crystal display device according to the present invention includes a plurality of scanning lines and common wirings provided in parallel on one of a pair of substrates sandwiching a liquid crystal layer, and the scanning lines, common wirings, and exposed. A first insulating film covering the first substrate, a plurality of signal lines provided on the first insulating film in a direction intersecting the scanning lines and the common wiring, and the scanning lines and the signal lines Thin film transistor TFT (Thin Film Transistor) provided in the vicinity of the intersection of each of the plurality of scanning lines and signal lines, and is formed under the first insulating film and the common wiring A lower electrode made of a transparent conductive material connected to the thin film transistor, the thin film transistor and its electrode, the signal line, the second insulating film formed on the exposed surface of the first insulating film, Front in plan view on the second insulating film Is formed so as to overlap with the lower electrode, and a, an upper electrode made of a transparent conductive material having a plurality of slits that are disposed in parallel to each other. Thereby, the liquid crystal display device of the present invention operates as an FFS mode liquid crystal display device. Here, the lower electrode operates as a common electrode, and the upper electrode operates as a pixel electrode.

In the liquid crystal display device of the present invention, the lower electrode is formed so as to cover the common wiring so that a step is formed on the side surface of the common wiring, and a plurality of steps are formed by the common wiring and the lower electrode. I am doing so. With such a configuration, even if the surface is covered with the first insulating film, the individual steps are small, so that the thickness of the first insulating film is suppressed from being reduced. It is possible to suppress dielectric breakdown of the insulating film 1 due to static electricity during a manufacturing process such as cleaning. Therefore, according to the liquid crystal display device of the present invention, since a short circuit between the signal line and the common wiring is suppressed, a liquid crystal display device with few line defects can be provided.

In the liquid crystal display device of the present invention, the lower electrode also covers the surface of the common wiring between the lower electrodes. Usually, the lower electrode only needs to be formed in each region divided by the plurality of scanning lines and signal lines. However, if the surface of the common wiring between the lower electrodes is also covered, it intersects with the common wiring. Since no step is generated in the first insulating film on both sides of the signal line at the portion where the signal line is formed, it is possible to further suppress the dielectric breakdown of the first insulating film due to static electricity during cleaning.

In the liquid crystal display device of the present invention, the common wiring is disposed close to one side of the scanning line adjacent to the pixel region where the common wiring is disposed. By adopting such a configuration, the common wiring is not located in the center of one pixel, so that the aperture ratio can be increased, and one pixel is divided into two regions by the common wiring. Display quality is improved.

In the liquid crystal display device of the present invention, the width of the step portion of the lower electrode is preferably 2.25 μm or more from the side surface of the common wiring.

The thickness of the scanning line and the common wiring is about 0.2 μm, the thickness of the lower electrode is about 0.1 μm, and the thickness of the first insulating film, which is also called a gate insulating film, is generally 0.4 μm. Degree. Therefore, by setting the width of the step portion of the lower electrode to 2.25 μm or more from the side surface of the common wiring, the first electrode layer formed on the upper layer of the lower electrode can be taken into consideration even if the line width of the signal line and the pattern deviation are taken into consideration. The thickness of the insulating film 1 can be set to a thickness that can sufficiently suppress dielectric breakdown due to static electricity even on the side surface of the stepped portion. Therefore, according to the liquid crystal display device of the present invention, a short circuit between the signal line and the common wiring can be further suppressed, and a liquid crystal display device with fewer line defects can be provided. If the width of the step of the lower electrode is less than 2.25 μm, it is not preferable because the number of short circuits between the lower electrode and the signal line increases.

In the liquid crystal display device of the present invention, it is preferable that the step portion of the lower electrode is formed only in the vicinity of a position where the common line and the signal line intersect.

Since the present invention aims to prevent a short circuit between the lower electrode and the signal line, it is sufficient to form a step portion of the lower electrode only at a portion where the common wiring and the signal line intersect. Therefore, according to the liquid crystal display device of the present invention, it is possible to provide a liquid crystal display device in which the occurrence of line defects is suppressed, the aperture ratio is large, and the display image quality is good.

In the liquid crystal display device of the present invention, the step coverage of the first insulating film is
When the thickness of the insulating film formed on the flat portion on the lower electrode is A and the thickness of the insulating film formed on the side surface of the step of the lower electrode is B,
B / A ≧ 1
It is preferable to be formed so as to satisfy the relationship.

If the step coverage of the first insulating film satisfies the relationship of B / A ≧ 1, the film thickness of the side surface region of the step is sufficiently thick compared with the film thickness of the flat portion around the step, and the coverage is high. It can be judged that it is good, and a sufficient withstand voltage can be applied to the first insulating film. Therefore, according to the liquid crystal display device of the present invention, since the dielectric strength of the first insulating film can be increased, a short circuit between the signal line and the common wiring can be further suppressed, and the line defect can be further reduced. A liquid crystal display device with less generation can be provided. When the step coverage is in the relationship of B / A <1, the film thickness of the side surface area of the step is smaller than the film thickness in the flat part around the step, and fine holes and cracks are generated in the side surface area of the step. This is not preferable because the number of short circuits between the lower electrode and the signal line increases.

In the liquid crystal display device of the present invention, it is preferable that a dummy pixel is formed in the non-display area, and a step portion of the lower electrode is formed in the dummy pixel.

The dummy pixel area is an area formed in an area adjacent to the display area and does not contribute to actual display. However, since the dummy pixels are formed, the film thickness of each layer of the display area can be made the same as the film thickness of each layer of the dummy pixels, so that the display image quality of the pixels in the periphery of the display area is not displayed. It is less likely to be adversely affected by being adjacent to a region. In addition, since the dummy pixel is formed around the display area, it can absorb external stress such as static electricity, so that the occurrence of a defect in the pixel in the display area can be suppressed. Therefore, according to the liquid crystal display device of the present invention, it is possible to suppress a short circuit between the signal line and the common line even in the dummy pixel. Therefore, when the dummy pixel functions normally, A highly reliable liquid crystal display device in which defects are suppressed can be provided.

Furthermore, the manufacturing method of the liquid crystal display device of the present invention is characterized by including the following steps (1) to (9).
(1) A step of patterning a plurality of scanning lines having a gate electrode portion and a plurality of common wirings in parallel with each other by covering and etching the conductive layer over the entire surface of the transparent substrate;
(2) The transparent conductive layer is covered over the entire surface of the substrate obtained in the step (1), and the surface of the common wiring between the lower electrodes is covered at a position corresponding to each pixel, and the common Patterning the lower electrode so as to extend beyond the side of the wiring;
(3) A step of covering the first insulating film over the entire surface of the substrate obtained in the step (2),
(4) A step of patterning the semiconductor layer at a position corresponding to the gate electrode portion by covering and etching the semiconductor layer over the entire surface of the first insulating film,
(5) By covering and etching the conductive layer over the entire substrate surface obtained in the step (4), a signal line is provided for each pixel in a direction intersecting the scanning line and the common wiring. Patterning a drain electrode and a source electrode electrically connected to the signal line;
(6) A step of coating the second insulating film over the entire surface of the substrate obtained in the step (5),
(7) forming a contact hole in the second insulating film located on the drain electrode of each pixel;
(8) The upper electrode having a plurality of slits in each pixel is patterned by covering and etching the transparent conductive layer over the entire surface of the substrate obtained in the step (7), and the upper electrode. Electrically connecting the drain electrode and the drain electrode,
(9) A step in which the substrate obtained in the step (8) and the color filter substrate are opposed to each other, and liquid crystal is sealed between the substrates.

According to the method for manufacturing a liquid crystal display device of the present invention, it is possible to manufacture the FFS mode liquid crystal display device of the present invention that exhibits the above effects.

It is a top view of the liquid crystal display device of the FFS mode of embodiment. FIG. 3 is a schematic plan view of two pixels on the array substrate side of the FFS mode liquid crystal display device of the embodiment. It is a schematic sectional drawing in alignment with the III-III line of FIG. 4A to 4F are cross-sectional views of a portion corresponding to the line III-III in FIG. 1, which sequentially shows the manufacturing process for one pixel of the embodiment. FIG. 5A to FIG. 5C are cross-sectional views subsequent to FIG. 4 that sequentially show the manufacturing process for one pixel of the embodiment. 6A is an enlarged plan view that passes through the signal line of the VIA portion of FIG. 2, and FIG. 6B is a cross-sectional view taken along the line VIB-VIB of FIG. 6A. FIG. 7A is a cross-sectional view corresponding to FIG. 6B of the conventional example, and FIG. 7B is a cross-sectional view showing a spark state. 8A is a plan view corresponding to FIG. 6A showing a short-circuit state of a conventional example, and FIG. 8B is a cross-sectional view taken along line VIIIB-VIIIB of FIG. 8A.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies an FFS mode liquid crystal display device as a liquid crystal display device for embodying the technical idea of the present invention, and the present invention is specified as the FFS mode liquid crystal display device. And is equally applicable to other embodiments within the scope of the claims. In each drawing used for the description in this specification, each layer and each member are displayed in different scales so that each layer and each member can be recognized on the drawing. However, it is not necessarily displayed in proportion to the actual dimensions.

An FFS mode liquid crystal display device 10 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the liquid crystal display device 10 according to the present embodiment includes an array substrate AR and a color filter substrate CF, a sealing material 25 for bonding the substrates AR and CF, and an array substrate A.
Liquid crystal (not shown) in the region surrounded by R, color filter substrate CF and sealing material 25
Is a liquid crystal display device in which the liquid crystal injection port 27 is injected from the liquid crystal injection port 27 and the liquid crystal injection port 27 is sealed with a sealing material 28. In the liquid crystal display device 10, a region surrounded by the sealing material 25 forms a display region 26, and a region provided around the display region 26 where an image is not recognized is a non-display region 29 of the liquid crystal display device 10. It becomes.

The array substrate AR is obtained by forming various wirings for driving liquid crystal on the surface of a rectangular first transparent substrate 11 made of glass or the like. The array substrate AR is longer in the longitudinal direction than the color filter substrate CF, and an extended portion 11a extending to the outside when the substrates AR and CF are bonded together is formed. The extension portion 11a is provided with a driver Dr made of an IC chip or an LSI that outputs a drive signal.

In the array substrate AR of the FFS mode liquid crystal display device 10 of this embodiment, the plurality of scanning lines 12 and the plurality of common wirings 13 are parallel to each other over the entire surface of the transparent substrate 11 by photolithography or etching. (See FIGS. 2 and 4A). In the liquid crystal display device 10 according to the present invention, the common wiring 13 is arranged close to one side of the scanning line 12 in order to improve the aperture ratio and display image quality.

Next, I over the entire surface of the transparent substrate 11 on which the scanning lines 12 and the common wirings 13 are formed.
A transparent conductive layer made of TO (Indium Thin Oxide) or IZO (Indium Zink Oxide) or the like is covered, and the lower electrode 14 is formed by the same photolithography method or the like. At this time, as shown in FIGS. 4B, 6A, and 6B, the lower electrode 14 also covers the surface of the common wiring 13 between the pixels and the common wiring 13 so that a plurality of steps 14a are formed over the width X. Cover the surface of the. Here, a part of the lower electrode 14 is extended to a position covering the scanning line 12 of the adjacent pixel at a position where it overlaps the signal line 17 in plan view.

After forming the lower electrode 14 in this manner, the entire surface is covered with a first first insulating film 15 made of a silicon nitride layer (see FIG. 4C). At this time, the first insulating film 15 is formed of the lower electrode 1.
Since the film is formed on the plurality of steps 14a formed on the first insulating film 15, the first insulating film 15 also has a plurality of steps.

Next, after covering the entire surface of the first insulating film 15 with the a-Si layer 16 a and the n ⁺ a-Si layer 16 b, the a-Si layer 16 a and the n ⁺ a-Si layer 16 b are similarly formed on the TFT formation region by a photolithography method or the like.
The semiconductor layer 16 composed of the Si layer 16a and the n ⁺ a-Si layer 16b is formed (FIGS. 4D and 4).
E). The region of the scanning line 12 at the position where the semiconductor layer 16 is formed forms the gate electrode G of the TFT.

Next, a conductive layer is coated over the entire surface of the transparent substrate 11 on which the semiconductor layer 16 is formed,
Similarly, the signal line 17 and the drain electrode D are formed by a photolithography method or the like (
(See FIG. 5A). Both the source electrode S portion and the drain electrode D portion of the signal line 17 partially overlap the surface of the semiconductor layer 16.

Here, the case of the present embodiment and the case of the conventional example will be described with reference to FIGS. In the step shown in FIG. 4F, there is a step of cleaning with pure water WT after forming the semiconductor layer 16b. In the conventional example, the first insulating film 15 on the common wiring 13 is formed of the lower electrode 14 as shown in FIG. 7A.
Has the edge portion E, and the first insulating film 15 is formed on the edge portion E. Therefore, the edge portion E is formed on the edge portion E as compared with the thickness A ′ of the flat portion of the first insulating film 15. The thickness B ′ of the first insulating film is reduced, and the step coverage (B ′ / A ′) is deteriorated.

At this time, as shown in FIG. 7B, the semiconductor layer 16 is also formed on the surface of the first insulating film 15 on the common wiring 13 and cleaned in this state. Therefore, during cleaning with pure water WT,
Static electricity generated by friction between the pure water WT and the n ⁺ a-Si layer 16b is connected to the lower electrode 14 formed on the common wiring 13 via the n ⁺ a-Si layer 16b and the a-Si layer 16a. A spark 22 is generated between them, and the first insulating film 15 formed thinly on the lower electrode 14 is destroyed and scratches 23
Will be formed (see FIG. 8B). Then, the process proceeds to the step shown in FIG. 4F with the scratch 23 left on the first insulating film 15, and when the signal line 17 is formed on the upper layer of the first insulating film 15, the source layer becomes the first layer when the source layer is formed. In this case, the signal line 17 and the lower electrode 14 are short-circuited, resulting in a defective line defect.

Therefore, in this embodiment, as shown in FIGS. 6A and 6B, the lower electrode 14 is connected to the common wiring 13.
A plurality of steps 14a are formed over the width X so as to cover. Then, by forming the first insulating film 15 so as to cover the step 14a, the thickness A of the flat portion and the thickness B of the step 14a of the first insulating film 15 are substantially the same. Formed. Therefore, the step coverage (B / A) of the first insulating film 15 in the step portion is improved, that is, the first insulating film 15 is formed thicker than that of the conventional example, so that the dielectric strength against static electricity is increased. The first insulating film 15 is prevented from being broken by static electricity generated during cleaning with pure water WT, and as a result, the short circuit 24 between the lower electrode 14 and the signal line 17 can be suppressed. become.

In the present embodiment, a part of the lower electrode 14 is extended to a position that covers the scanning line 12 of the adjacent pixel at a position that overlaps the signal line 17 in plan view.
The effect generated between the signal line 17 and the scanning line 12 can be expected between the signal line 17 and the scanning line 12. Therefore, in the present embodiment, the effect is formed between the signal line 17 and the scanning line 12. It is possible to suppress short circuits that may occur.

Next, in order to complete the liquid crystal display device 10 of the present embodiment, the second insulating film 18 made of a silicon nitride layer is coated on the entire surface of the substrate, and then the second position corresponding to the drain electrode D is applied.
A contact hole 19 is formed in the insulating film 18 to expose a part of the drain electrode D (see FIG. 5B). Further, a transparent conductive layer made of ITO or the like is coated over the entire surface, and the scanning line 1 is formed so that the pattern shown in FIG.
2 and an upper electrode 21 having a plurality of slits 20 parallel to each other are formed on the second insulating film 18 in a region surrounded by the signal lines 17 (see FIG. 5C). The slit 20 is for generating a fringe field effect. Since the upper electrode 21 is electrically connected to the drain electrode D through the contact hole 19, it functions as a pixel electrode.

Next, an array substrate AR is completed by forming a predetermined alignment film (not shown) over the entire surface. The array substrate AR manufactured in this way and the separately manufactured color filter substrate are opposed to each other, and the periphery is bonded with a sealing material 25, and liquid crystal is sealed in a space formed between the two substrates. The FFS mode liquid crystal display device 10 is obtained. Although detailed description of the color filter substrate CF is omitted, a color filter layer, an overcoat layer, and an alignment film are respectively laminated on the surface of a transparent substrate such as glass, and a common electrode is not provided. The TN (Twisted Nematic) type liquid crystal display device has substantially the same configuration.

According to the FFS mode liquid crystal display device of the embodiment manufactured as described above, the first insulating film with good step coverage is formed on the surface of the lower electrode, so that the first insulating film is destroyed by static electricity. As a result, a short circuit between the lower electrode and the signal line can be suppressed, and a highly reliable liquid crystal display device can be provided.

In the present embodiment, the step of the lower electrode is shown as being formed on the entire surface along the common wiring, but only in a place where a short circuit is likely to occur, for example, near the position where the common wiring and the signal line intersect. May be formed only. By doing so, the purpose of preventing a short circuit between the lower electrode and the signal line can be achieved, and an FFS mode liquid crystal display device with good display image quality can be provided.

Note that the width X of the plurality of steps of the lower electrode is preferably 2.25 μm or more so that the first insulating film can be formed with a sufficient thickness. The thickness of the lower electrode is about 0.1 μm, but the thickness of the first insulating film called a gate insulating film usually needs to be about 0.4 μm. By setting the width X of the plurality of steps of the lower electrode to 2.25 μm or more, the first insulating film formed on the upper layer of the lower electrode can be taken into consideration even if variations in the line width of the signal line and pattern deviation are taken into consideration. It is possible to make the thickness such that the dielectric breakdown due to static electricity can be sufficiently suppressed even on the side surface of the stepped portion. If the width X of the plurality of steps of the lower electrode is less than 2.25 μm, short circuit between the lower electrode and the signal line increases, which is not preferable.

In addition, the measurement location of the film thickness A of the flat portion of the first insulating film used for calculating the value of step coverage (B / A) in the present embodiment is the flat portion center at the top of the step or the flat portion around the step. It is desirable that the measurement area of the film thickness B in the side region is the thinnest part of the corresponding stepped portion, thereby accurately calculating the step coverage (B / A) value. it can.

In addition, the value of step coverage (B / A), which is the ratio between the film thickness A of the flat portion of the first insulating film and the film thickness B of the side region in this embodiment, is preferably 1 or more. . By doing so, the film thickness B of the side surface region is sufficiently thicker than the film thickness A of the flat portion, and the material material for forming the film also remains in the side surface region of the stepped portion. It is possible to form a stable metal film or insulating film without generating any holes or cracks. In this way, since a sufficient withstand voltage can be applied to the first insulating film, the dielectric strength of the first insulating film can be increased, and a short circuit between the signal line and the common wiring is possible. Therefore, it is possible to provide a liquid crystal display device with fewer line defects. If the value of step coverage (B / A) is less than 1, the material substance for forming the film also in the side surface region of the stepped portion, the film thickness B of the side surface region is thinner than the film thickness A of the flat portion. Is not sufficiently retained, and fine holes and cracks are generated, which is not preferable because a short circuit between the lower electrode and the signal line increases.

In addition, dummy pixels are formed in the non-display area 29 of the liquid crystal display device in the present embodiment,
The step portion of the lower electrode may be formed in this dummy pixel. Since the dummy pixels are also preferentially destroyed by static electricity and have a function to prevent the influence of static electricity on the pixels in the display area, if the dummy pixels are functioning normally, the pixels in the display area Since the influence of static electricity can be prevented, a more reliable liquid crystal display device can be provided.

DESCRIPTION OF SYMBOLS 10: Liquid crystal display device 11: Transparent substrate 11a: Extension part 12: Scanning line 13: Common wiring 14: Lower electrode 14a: Step 15: 1st insulating film 16: Semiconductor layer 17: Signal line 18: 2nd insulation Film 19: Contact hole 20: Slit 21: Upper electrode 22
: Spark 23: Scratch 24: Short circuit 25: Sealing material 26: Display area 27: Liquid crystal injection port 28: Sealing material 29: Non-display area AR: Array substrate CF: Color filter substrate
D: Drain electrode G: Gate electrode S: Source electrode Dr: Driver E: Edge part

Claims (3)

On one of the pair of substrates sandwiching the liquid crystal layer,
A plurality of scanning lines and a common wiring provided in parallel;
A first insulating film covering the scanning line, the common wiring, and the one substrate;
A plurality of signal lines provided on the first insulating film in a direction crossing the scanning line and the common wiring;
A thin film transistor provided near the intersection of the scanning line and the signal line;
A lower electrode formed under the first insulating film and connected to the common wiring;
A second insulating film formed on a surface of the thin film transistor, the signal line, and the first insulating film;
An upper electrode formed on the second insulating film so as to overlap the lower electrode in plan view, and having a slit;
With
In a liquid crystal display device having a display region in which the liquid crystal layer is driven by an electric field generated between the lower electrode and the upper electrode, and a non-display region formed outside the display region,
The common wiring is disposed close to one side of the scanning line adjacent to the region where the common wiring is disposed,
The lower electrode covers the common wiring so that a plurality of steps are formed on at least one side surface of the common wiring ;
The step portion of the lower electrode has a width from the side surface of the common wiring to the end portion of the lower electrode of 2.25 μm or more,
The step portion of the lower electrode is formed only in the vicinity of the position where the common wiring and the signal line intersect,
A dummy pixel is formed in the non-display area, and a step portion of the lower electrode is formed in the dummy pixel . The step coverage of the first insulating film is
The thickness of the insulating film formed on the flat portion on the lower electrode is A,
When the thickness of the insulating film formed on the side surface of the step of the lower electrode is B,
B / A ≧ 1
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed so as to satisfy the above relationship. (1) A step of patterning a plurality of scanning lines having a gate electrode portion and a plurality of common wirings in parallel with each other by covering and etching the conductive layer over the entire surface of the transparent substrate;
(2) The transparent conductive layer is covered over the entire surface of the substrate obtained in the step (1), and the surface of the common wiring between the lower electrodes is covered at a position corresponding to each pixel, and the common Patterning the lower electrode so as to extend beyond the side of the wiring;
(3) A step of covering the first insulating film over the entire surface of the substrate obtained in the step (2),
(4) A step of patterning the semiconductor layer at a position corresponding to the gate electrode portion by covering and etching the semiconductor layer over the entire surface of the first insulating film,
(5) By covering and etching the conductive layer over the entire substrate surface obtained in the step (4), a signal line is provided for each pixel in a direction intersecting the scanning line and the common wiring. Patterning a drain electrode and a source electrode electrically connected to the signal line;
(6) A step of coating the second insulating film over the entire surface of the substrate obtained in the step (5),
(7) forming a contact hole in the second insulating film located on the drain electrode of each pixel;
(8) The upper electrode having a plurality of slits in each pixel is patterned by covering and etching the transparent conductive layer over the entire surface of the substrate obtained in the step (7), and the upper electrode. Electrically connecting the drain electrode and the drain electrode,
(9) The step of causing the substrate obtained in the step (8) and the color filter substrate to face each other and encapsulating liquid crystal between the substrates,
Including
In the step (2), a step portion that is a portion extending beyond the side surface of the common wiring of the lower electrode is formed only in the vicinity of a position where the common wiring and the signal line intersect, and , The width from the side surface of the common wiring to the end of the lower electrode is 2.25 μm or more,
Furthermore, a display region in which the liquid crystal layer is driven by an electric field generated between the lower electrode and the upper electrode, and a non-display region formed outside the display region are formed,
Dummy pixels are formed in the non-display area;
The method of manufacturing a liquid crystal display device, wherein the step portion of the lower electrode is formed in the dummy pixel.

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