JP3471737B2 - Active matrix type liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active matrix type liquid crystal display device, which is a horizontal field type and adopts a chevron-like electrode structure, permitting to decrease discrimination near the apex of a chevron-like electrode. SOLUTION: To decrease discrimination areas which have conventionally occurred in the neighborhood of the apexes of the chevron-like electrodes, a transparent common auxiliary electrode 32 and a pixel auxiliary electrode 47 are formed so as to connect the apex parts of the chevrons of the common electrode 22 and the pixel electrode 27, and thus, it has become possible to decrease the discrimination and increase the opening ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly to in-plane switching (IPS: In-Plane-Switchin).
g) Type of liquid crystal display device structure.

[0002]

2. Description of the Related Art In-plane switching (IPS: I)
A display panel of an n-Plane-Switching type liquid crystal display device holds liquid crystals at a predetermined interval between a pair of transparent substrates, and applies an electric field that is effectively parallel to the substrates to display liquid crystal molecules. It has the feature that a wide viewing angle can be achieved by rotating in the plane of the substrate and in the horizontal direction. Here, the electric field effectively parallel to the substrate can be generated by arranging the pixel electrode and the common electrode on one side of the transparent substrate holding the liquid crystal in a comb-like shape with a predetermined gap. Therefore, in the IPS type LCD, the display display is always viewed only from the minor axis direction of the liquid crystal molecules, which has an advantage that the viewing angle is very wide.

As described above, the IPS type LCD has an advantage that the viewing angle is very wide, while it is colored yellow or blue when the screen is tilted from the longitudinal direction of the comb-shaped electrodes. It also has drawbacks. To solve this problem, Japanese Patent Laid-Open No. 10-148826 proposes a dogleg-shaped electrode structure (multi-domain structure).

This electrode structure is shown in FIG. As shown in FIG. 4A, the common electrode 122 is composed of a V-shaped electrode portion and an electrode portion that traverses the pixel central portion and the periphery, and the regions above and below the electrode portion traversing the pixel central portion. When a voltage is applied to the liquid crystal, the liquid crystals corresponding to the above are colored yellow and blue, respectively, when the screen is tilted from the longitudinal direction of the V-shaped electrode, so that they compensate each other for the color change with respect to the viewing angle. You can get no image.

[0005]

[Patent Document 1] Japanese Patent Application Laid-Open No. 10-1488
When the common electrode that crosses the central portion of the pixel, which causes the reduction of the light transmittance, is removed from the doglegged electrode structure shown in Japanese Patent Laid-Open No. 26, the electrode structure as shown in FIG. When a voltage is applied, the electric field concentrates on the apex of the V-shape of the pixel electrode 227, and the force for rotating the liquid crystal is applied to both the right rotation and the left rotation in the plane parallel to the substrate, so that the liquid crystal cannot rotate and the disc It will cause a reinnation. Further, when the pixel electrode 227 and the common electrode 222 are formed by using a mask pattern formed by divided exposure, the pixel electrodes 227 and the common electrode 222 are deviated from the directions facing each other, and the liquid crystal 218 is deviated from the normal orientation direction, resulting in disclination. The position and area change subtly, and along the dividing exposure part boundary line,
Linear display unevenness occurs on the screen. Further, in the left and right regions centering on the apex of the dogleg of the common electrode 222, the driving directions of the liquid crystal 218 are opposite, so that the liquid crystal 21
The liquid crystal orientation changes abruptly depending on the position of 8, resulting in a very sensitive configuration.

To alleviate the above problem, the electrode structure of Japanese Patent Laid-Open No. 10-148826 as shown in FIG. 4 (a) is adopted. Light is blocked by connecting the apexes of a dogleg. If a common wiring is provided in the center of the pixel, the light transmittance will be reduced from 8% to 3 to 5%.

Further, as shown in the enlarged plan view of FIG. 4B, the liquid crystal 1 oriented parallel to the data lines when no voltage is applied.
18 denotes the pixel electrode 12 when a voltage is applied between the electrodes.
7 and the common electrode 122 uniformly change their directions to face each other, but as shown in FIG. 4A, a region Y facing each other in the vicinity of the apex of the dogleg and the electrode crossing the pixel periphery. , The pixel electrode 127 and the common electrode 12
The two pixel electrodes 127 or the same common electrode 122 do not face each other and sandwich the region Y at an acute angle, and the electric field applied to the liquid crystal in the region Y is a desired electric field. Instead, the liquid crystal becomes the pixel electrode 127.
Further, the common electrodes 122 do not face each other but face a halfway direction, and disclination occurs in the region Y.

Further, in the case of forming a square-shaped electrode as shown in FIG. 2A, the exposure range of the exposure device is usually limited in the exposure for a large monitor, and therefore the exposure for forming the electrode pattern is not performed. The division exposure method is used. For this reason,
Disclination does not appear in an arbitrary part, and due to the exposure deviation of the exposure device, the display image quality becomes uneven evenly in the boundary part for divided exposure, that is, in the straight part connecting the apexes of the doglegs. As a result, a line appears in the divided exposure part, resulting in a defective screen. As shown in the enlarged plan view of the common electrode 222 and the pixel electrode 227 in the vicinity of the V-shaped apex of FIG. 5B, the cause of the screen defect is a pattern shift (about 1 μm) at the divided portion. Occur. When divided exposure is performed accurately,
The electrode pattern is formed as shown in (a), and disclination occurs vertically symmetrically in the vicinity of the dog-leg apex of the pixel electrode 227 substantially toward the paper surface. On the other hand, as shown in FIG. 5B, when the overlay misalignment of the divided exposure occurs downward toward the paper surface, the electric field strength depends on the inter-electrode distance, and the pattern overlay shift changes the electrode interval. So
The electric field is applied unevenly only in the overlapped portion, and in particular, the disclination moves in the electric field region with respect to the portion where the electrode spacing of the common electrode 227 is widened from the apex of the dogleg of the pixel electrode 227 where the electric field is concentrated. The phenomenon that occurs is seen, and linear unevenness occurs on the display screen.

An object of the present invention is to reduce the disclination near the apex of a dogleg-shaped electrode in an active matrix type liquid crystal display device having a lateral electric field type dogleg-shaped electrode structure. An object is to provide an active matrix type liquid crystal display device.

[0010]

An active matrix type liquid crystal display device of the present invention includes a common wiring and a source / drain wiring provided on a first substrate, and the common wiring provided on the first substrate. And a TFT-side insulating film that covers the source / drain wiring and an alignment film thereon
A T substrate, a color layer provided on the second substrate, and the second substrate.
A color filter substrate having a color filter-side insulating film on the substrate and covering the color layer and an alignment film on the color filter substrate; and a liquid crystal sandwiched between the TFT substrate and the color filter substrate. line and the source and drain lines has a respective common electrode and the pixel electrode exhibits at least one carbonochloridate the shape running parallel schematically regular intervals, the voltage between the common electrode and the pixel electrode Is applied to generate an electric field to rotate the liquid crystal in a plane substantially parallel to the surface of the first substrate, wherein the common electrode and the pixel electrode are Is provided in a direction parallel to the electric field at the apex of the letter, and is connected to the common electrode and the pixel electrode, respectively.
The basic structure is a structure having a common auxiliary electrode and a pixel auxiliary electrode, which are provided in different layers from the pixel electrode . The active matrix type liquid crystal display device of the present invention has the following application forms.

First, the pixel electrode is located in the TFT-side insulating film and is located closer to the liquid crystal than the common electrode is.
The common auxiliary electrode and the pixel auxiliary electrode pass through the first opening and the second opening, respectively, which are provided by opening the TFT-side insulating film on the common electrode and the pixel electrode, respectively. It is connected to the pixel electrode.

Further, the common auxiliary electrode and the pixel auxiliary electrode are provided by extending the surface of the TFT-side insulating film in parallel with the electric field and in a protruding direction of a dogleg.
The common auxiliary electrode and the pixel auxiliary electrode are provided to partially overlap the pixel electrode and the common electrode, respectively.

Further, the common electrode has a V-shaped blank pattern in a region not sandwiched by the pixel electrodes.

The common electrode is provided so as to connect the dogleg ends of the common electrode sandwiched by the pixel electrodes in a direction parallel to the electric field.

Finally, both the common auxiliary electrode and the pixel auxiliary electrode are made of transparent conductive films.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an active matrix type liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIG. Here, FIG. 1A is a plan view of the TFT substrate viewed from the liquid crystal side, and FIG.
The TFT substrate, the liquid crystal, and the CF (color filter) on a plane that passes through the cutting line AA ′ in (a) and is orthogonal to the TFT substrate.
It is sectional drawing when a board | substrate is cut. The active matrix type liquid crystal display device of the present embodiment is a horizontal electric field type liquid crystal display device, and since the configuration is the same as the diagram used in the description of the related art, a detailed description is omitted here and a configuration different from the conventional one is used. The explanation will focus on. It should be noted that the same elements as the conventional ones have the numbers obtained by removing 1 from the numbers in the hundreds of the conventional illustrated numbers.

As shown in FIG. 1A, the feature of this embodiment is that the common auxiliary electrode 32 and the pixel auxiliary electrode 37 are provided at the tops of the dog-legged common electrode 22 and the pixel electrode 27, respectively. Are connected to the common electrode 22 and the pixel electrode 27, respectively, and further extend in the protruding direction of the dogleg, and the ends thereof are respectively formed by the pixel electrode 27 and the common electrode 2.
It is formed so as to overlap 2.

Next, a manufacturing method for forming the common auxiliary electrode 32 and the pixel auxiliary electrode 37 will be described mainly with reference to FIG.

The plane size is 360 × 465 and the thickness is 0.
First, the gate wiring 2 and the common electrode 22 are formed on the first transparent substrate 1 made of a glass substrate of 7 (unit mm). The gate line 2 and the common electrode 22 are the first transparent substrate 1
It is formed by forming a 200 nm Cr film with a sputtering apparatus on the above, applying a positive resist film, and performing exposure, development, and etching.

Next, the first insulating film 3, 100 having a thickness of 200 nm is formed.
nm a-Si (amorphous silicon) layer is formed,
The a-Si layer is patterned to form the a-Si region 6. Then, a metal such as Cr having a film thickness of 200 nm is deposited on the first insulating film 3 so as to cover the a-Si region 6, and is patterned to be an SD electrode (a source / drain electrode; hereinafter referred to as SD). 7, the pixel electrode 27 and the data line 37 which are formed at the same time as the SD electrode 7 are formed. Then, the a-Si region 6 is formed using the SD electrode 7 as a mask.
Is partially etched from its surface to form a TFT channel portion. Here, the common electrode 22 and the pixel electrode 27
Are formed in a dogleg shape and are formed in parallel with each other, as shown in FIG.

Next, the first insulating film 3 is covered so as to cover the SD electrode 7 and the like.
A protective film 8 made of, for example, a silicon nitride film (SiNx)
Then, contact holes 9 are formed by opening predetermined regions of the protective film 8 and the first insulating film 3. At this time, the contact hole 9 is opened at the top of the dog-leg of the common electrode 22 and the pixel electrode 27.

Next, an ITO film is formed to a thickness of 50 nm on the protective film 8 having the contact holes 9 formed therein, and patterned to form a common auxiliary electrode 32 and a pixel auxiliary electrode 37. The TFT substrate 40 is obtained by forming the polarizing plate 10 on the other surface of the first transparent substrate 1.

The CF substrate 50 facing the TFT substrate 40 has a second transparent substrate 51 and a second transparent substrate 51 including a black matrix 61 on one surface of the second transparent substrate 51, a color layer 63, a silicon nitride film (SiNx), and the like. The two insulating films 64, the conductive film 65 on the other surface of the second transparent substrate 51, and the polarizing plate 66 are formed.

The TFT substrate 40 and the CF substrate 50 are obtained by printing an alignment film on the uppermost surface of each of the TFT substrate 40 and the CF substrate 50 thus obtained by a method such as offset printing. Complete.

The alignment films of the TFT substrate 40 and the CF substrate 50 thus obtained are rubbed to form the alignment film 17, and the alignment film molecules are arranged in a predetermined direction, and the cell gap is set so that the two substrates have a predetermined space. The materials are sandwiched and combined, and the liquid crystal 18 is sealed in the space.

The liquid crystal panel thus obtained has a TFT in the alignment direction of the liquid crystal 18 defined by the rubbing method.
The transmission axes of the polarizing plate 10 of the substrate 40 are aligned and the CF
A polarizing plate 66 whose absorption axis is orthogonal to the TFT substrate 40 side is attached to the substrate 50, and light 56 is irradiated from the TFT substrate 40 side to freely give a potential difference between the pixel electrode 27 and the common electrode 22. Thus, full-color display from black display to white display can be performed.

Next, details of the difference between this embodiment and the conventional example will be described. There are two differences from the conventional configuration.

First of all, the ITO film, which has been used in the past to keep the periphery of the first transparent substrate 1 on the side of the TFT substrate 40 electrically connected, is used inside the pixel, and the common electrode 22 and the pixel electrode 27 are formed. It is used as the common auxiliary electrode 32 as the auxiliary electrode and the pixel auxiliary electrode 37. Since the common auxiliary electrode 32 and the pixel auxiliary electrode 37 are used as the auxiliary electrodes of the common electrode 22 and the pixel electrode 27, the electric field is disturbed in the vicinity of the apex of the dog-legged common electrode 22 and the pixel electrode 27. Is corrected by the common auxiliary electrode 32 and the pixel auxiliary electrode 37 to prevent disturbance of the electric field. As a result, it has become possible to drive the area where the conventional electrode structure could not drive the liquid crystal in the normal direction due to disclination (liquid crystal alignment abnormality).

Secondly, in the structure disclosed in Japanese Unexamined Patent Publication No. 10-148826, the common electrode 122 is provided in the center in a direction parallel to the electric field direction. However, in the present embodiment, the dogleg-shaped common electrode is used. 22. Since the common auxiliary electrode 32 and the pixel auxiliary electrode 37 of the transparent conductive film prevent the disturbance of the electric field in the vicinity of the dog-legged top of the pixel electrode 27 and the pixel electrode 27, the common electrode 22 of the present embodiment is provided around the element. The wiring area can be moved to an area where the liquid crystal cannot be driven, and the conventional panel transmittance is 5% or less (the lower wiring portion composed of the common electrode 22 is a Cr film so that light does not pass through).
It could be improved to 8% or more.

When the electrode structure of the present invention is used, the state of liquid crystal driving when the electric field between the electrodes is turned on and off is improved as shown in FIG. That is, conventionally, when a voltage is applied, a region X which cannot be rotated is generated in the liquid crystal near the apex of the dogleg as shown in FIG. 2A, whereas when the electrode structure of the present invention is used. As shown in FIG. 2 (b), in the region X,
It becomes possible to drive the liquid crystal in the regions X1 and X2 other than immediately above the pixel auxiliary electrode 32 (or the common auxiliary 47). As a result, the display range is expanded, the image can be clearly displayed, and the screen also has a higher transmittance and a bright screen can be displayed.

As a second effect, it is possible to compensate for the pattern shift that occurs during exposure, which is a problem in actual mass production. In detail, the exposure has a limited exposure range on a large monitor. Therefore, since the exposure is performed in divisions, the disclination does not appear in any part, and due to the mask limit of the exposure device, it is uniformly displayed in the boundary portion for division exposure, that is, the straight line portion connecting the apex of the dogleg. The image quality is uneven. As a result, a line appears on the divided exposure part, resulting in a defective screen (currently about 20% occurs). The cause of the screen defect is caused by the pattern shift (about 1 μm) at the divided portion, and the ITO auxiliary electrode pattern of the present invention is
The wiring having a thickness of 2 μm, which is thicker than the divisional pattern deviation (1 μm), covers the pattern deviation and exhibits the effect of not causing display failure even if the pattern deviation occurs at the exposure division boundary portion.

Further, as a third effect, Cr in the lower layer is
The common electrode made of a film does not transmit light because it is made of a Cr film having a reflectance of 95%. Therefore, the panel (TFT
The transmittance in the state of (substrate + liquid crystal material + CF substrate) is low. Therefore, the common electrode, which was conventionally wired across the central portion of the pixel, is moved from the central portion of the pixel to the peripheral portion of the pixel,
The transmittance could be improved. Also, in the conventional structure, since the disturbance of the electric field is prevented by traversing the common electrode in the central portion of the pixel, the common electrode in the central portion of the pixel cannot be removed. Since the common electrode is formed of a transparent electrode, the light-shielding common electrode can be removed.

Next, a second embodiment of the present invention will be described with reference to FIG. The cross-sectional structure in this embodiment is the first
Since it is the same as the embodiment of FIG. 3, only a plan view of the TFT substrate side is shown in FIG.

As shown in FIG. 3, the features of this embodiment are as follows.
The common auxiliary electrode 82 and the pixel auxiliary electrode 8 are provided on the tops of the dog-legged common electrode 72 and the pixel electrode 77, respectively.
7 is formed so as to extend in the protruding direction of the V-shape, and its ends are formed so as to overlap the pixel electrode 77 and the common electrode 72, respectively.

From the description of the first embodiment, if the V-shaped electrodes have substantially the same area, the transmittance does not change from that of the first embodiment. Therefore, a plurality of V-shaped electrodes are formed as shown in FIG. It may be provided. Therefore, by utilizing this advantage, the present invention can be applied to a configuration in which a large number of dog-legged portions are connected in a single element to form a zigzag line shape and the appearance of dots is highly defined.

[0036]

In the active matrix type liquid crystal display device adopting the lateral electric field type dogleg-shaped electrode structure according to the present invention, the disclination region which has conventionally been generated in the vicinity of the vertex of the dogleg shaped electrode is eliminated. In order to reduce the number, a transparent auxiliary electrode is formed so as to connect the common electrode and the pixel electrode with the apex portions of the doglegs. It is possible to reduce the disclination and increase the aperture ratio. .

[Brief description of drawings]

FIG. 1 is a plan view of a TFT substrate of an active matrix type liquid crystal display device and a cross-sectional view of a liquid crystal panel for explaining a first embodiment of the present invention.

FIG. 2 is an enlarged plan view for explaining an improvement situation of disclination in the first embodiment of the present invention.

FIG. 3 is a plan view of an active matrix type liquid crystal display device for explaining a second embodiment of the present invention.

FIG. 4 is a plan view and an enlarged plan view of a conventional active matrix type liquid crystal display device.

FIG. 5 is an enlarged plan view for explaining display defects due to misalignment of electrode patterns in a conventional active matrix liquid crystal display device.

[Explanation of symbols]

1 first transparent substrate 2, 52, 102 Gate electrode 3 First insulating film 6, 56, 106 a-Si region 7, 57, 107 SD electrode 8 protective film 9 contact holes 10, 66 Polarizer 17 Alignment film 18, 118, 218 liquid crystal 22, 72, 122, 222 common electrode 27, 77, 127, 227 Pixel electrodes 32, 82 common auxiliary electrode 37, 87, 137 data lines 40 TFT substrate 47, 97 pixel auxiliary electrode 50 CF substrate 51 Second transparent substrate 56 light 61 Black Matrix 63 color layers 64 Second insulating film 65 Conductive film

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1343 G02F 1/1362 G02F 1/1337 G02F 1/1333

Claims (7)

(57) [Claims] 1. A common wiring and a source / drain wiring provided on a first substrate, and a TFT on the first substrate which covers the common wiring and the source / drain wiring.
A TFT substrate having a side insulating film and an alignment film thereon,
A color filter substrate having a color layer provided on a second substrate, a color filter side insulating film on the second substrate and covering the color layer, and an alignment film thereon;
A liquid crystal sandwiched between the T substrate and the color filter substrate, wherein the common wiring and the source / drain wirings run in parallel at approximately equal intervals.
The liquid crystal has a common electrode and a pixel electrode each having a V shape , and a voltage is applied between the common electrode and the pixel electrode to generate an electric field so that the liquid crystal is substantially parallel to the surface of the first substrate. An active matrix type liquid crystal display device rotated in a flat plane, wherein the common electrode and the pixel electrode are provided at the apexes of the doglegs in a direction parallel to the electric field, and the common electrode and the pixel electrode are provided, respectively. The common electrode and the pixel electrode are connected to the pixel electrode.
An active matrix type liquid crystal display device comprising a common auxiliary electrode and a pixel auxiliary electrode, which are provided in layers different from the poles . 2. A common wiring and a source / drain wiring provided on a first substrate, and a TFT on the first substrate which covers the common wiring and the source / drain wiring.
A TFT substrate having a side insulating film and an alignment film thereon,
A color filter substrate having a color layer provided on a second substrate, a color filter side insulating film on the second substrate and covering the color layer, and an alignment film thereon;
A T substrate and a liquid crystal sandwiched between the color filter substrates, wherein the common line and the source / drain lines have at least one dogleg shape running in parallel at substantially equal intervals, respectively, and a common electrode and a pixel. An active matrix type having electrodes and rotating the liquid crystal in a plane substantially parallel to the surface of the first substrate by applying a voltage between the common electrode and the pixel electrode to generate an electric field. In the liquid crystal display device, the common electrode and the pixel electrode are made of metal, and are provided in a direction parallel to the electric field at apexes of the V-shape, and are connected to the common electrode and the pixel electrode, respectively. , The common electrode and
The have a respective common auxiliary electrode and the pixel auxiliary electrode provided on the layer different from the pixel electrode, the common auxiliary electrode and
The active matrix type liquid crystal display device , wherein the pixel auxiliary electrodes are both made of a transparent conductive film . 3. The pixel electrode is located in the TFT-side insulating film and is closer to the liquid crystal than the common electrode, and the common auxiliary electrode and the pixel auxiliary electrode are respectively the common electrode and the pixel electrode. 3. The active matrix type liquid crystal display device according to claim 1 or 2, which is connected to the common electrode and the pixel electrode respectively through a first opening and a second opening provided by opening the TFT side insulating film on the substrate. . 4. The common auxiliary electrode and the pixel auxiliary electrode are provided by extending a surface of the TFT-side insulating film in parallel with the electric field and in a direction in which a dogleg is projected. 2. The active matrix liquid crystal display device according to item 2. Wherein said common auxiliary electrode and the pixel auxiliary electrode, an active matrix type liquid crystal display device of some overlapping claim 1 or 2, wherein provided in each of the pixel electrodes and the common electrode. Wherein said common electrode is in a region not sandwiched between the pixel electrode, an active matrix type liquid crystal display device according to claim 1 or 2, wherein presenting the shape of open pattern of dogleg. Wherein said common electrode is an active matrix liquid crystal display of the character end of Ku of the common electrode sandwiched between the pixel electrode and the electric field and the claim 1 or 2 wherein is provided to be engaged in a direction parallel to apparatus.