JP2008276108A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain higher luminance, narrower frame, etc. of a liquid crystal display device. <P>SOLUTION: The liquid crystal display device includes a lower substrate 1, an upper substrate opposite to the lower substrate 1 and a liquid crystal layer provided between the lower substrate 1 and the upper substrate. The lower substrate 1 has: a plurality of wirings 4, 5, 6 having layer structure of three or more layers of data wiring and gate wiring sectioning a unit pixel area 12; a first insulating film 7 which coats the first wiring 4, a second insulating film 8 which coats the second wiring 5 formed on the first insulating film 7, a third insulating film 9 which coats the third wiring 6 formed on the second insulating film 8 among the plurality of wirings, an upper layer transparent electrode 10; and a lower layer transparent electrode 11 forming storage capacitor in the unit pixel area, forms the third wiring 6 in the same layer as the lower layer transparent electrode 11 and forms the storage capacitor by interposing the third insulating film 9 between the upper layer transparent electrode 10 and the lower layer transparent electrode 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device in which a storage capacitor is formed using two layers of transparent electrodes.

  In recent years, demands for liquid crystal display devices for mobile use such as high color reproduction, high brightness, thinning, and narrow frame have become very strong. There are various types of operation modes of the liquid crystal display device, and one of them is an IPS (in-plane switching) mode. The IPS mode is an operation mode in which liquid crystal molecules are switched by a horizontal electric field in a plane parallel to the substrate surface.

  Recently, an FFS (fringe field switching) mode in which liquid crystal molecules are switched using a lateral electric field parallel to the substrate surface as in the IPS mode has been developed. In an FFS mode liquid crystal display device, a fringe field is formed by making a gap (gap) between a pixel electrode and a common electrode narrower than a gap (cell gap) between two substrates constituting a liquid crystal panel. ing.

  As a technique related to this type of liquid crystal display device, for example, techniques described in Patent Documents 1 and 2 below are known.

Japanese Patent No. 3498163 JP 2005-107535 A

  In a normal multilayer wiring process, a process such as an insulating film and a metal wiring is repeated many times to form a multilayer wiring, which makes the patterning process very complicated and becomes a big problem. In the liquid crystal display device of IPS mode or FFS mode, a pixel electrode, a common electrode, a gate wiring, a data wiring, a thin film transistor (hereinafter also referred to as “TFT”), etc. are formed on a common (same) substrate, Further, an electronic circuit including a pixel driving circuit and various wirings is formed outside (around) the display area, so that the structure becomes very complicated. For this reason, it has been difficult to meet demands for higher brightness and narrower frames.

  The liquid crystal display device according to the present invention includes a first substrate, a second substrate facing the first substrate, a liquid crystal layer provided between the first substrate and the second substrate, The first substrate covers a plurality of wirings having a layer structure of three or more layers including a data wiring and a gate wiring that define a unit pixel region, and covers the first wiring among the plurality of wirings. A first insulating film; a second insulating film covering the second wiring formed on the first insulating film; and a third wiring formed on the second insulating film. A third insulating film; an upper transparent electrode and a lower transparent electrode that form a storage capacitor in the unit pixel region; and the third wiring is formed in the same layer as the lower transparent electrode, and the upper transparent Forming the storage capacitor by interposing the third insulating film between the electrode and the lower transparent electrode; And it is characterized in Rukoto.

  In the liquid crystal display device according to the present invention, by forming a storage capacitor using upper and lower transparent electrodes, light transmittance is increased as compared with the case of using a non-transparent electrode. Further, by adopting a multilayer wiring of three or more layers including the data wiring and the gate wiring, it is possible to reduce the wiring area around the display area. Further, the third wiring is formed in the same layer as the lower transparent electrode, and the third wiring is covered with a third insulating film that forms a storage capacitor, thereby suppressing a decrease in light transmittance due to the multilayer wiring. And the process can be greatly reduced.

  According to the present invention, it is possible to achieve high brightness, narrow frame, and the like by improving the transmittance of the liquid crystal display device and reducing the wiring area.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic sectional view showing a basic configuration of a liquid crystal display device to which the present invention is applied. In the illustrated liquid crystal display device, a liquid crystal panel is configured using a lower substrate 1 serving as a first substrate, an upper substrate 2 serving as a second substrate, and a liquid crystal layer 3 composed of a plurality of liquid crystal molecules. . The lower substrate 1 and the upper substrate 2 are arranged to face each other with a predetermined gap (cell gap).

  The lower substrate 1 and the upper substrate 2 are each made of a transparent substrate (for example, a glass substrate). On the outer surface (lower surface) of the lower substrate 1 and the outer surface (upper surface) of the upper substrate 2, polarizing plates (not shown) are provided in close contact with each other by adhesion or the like. Further, if the liquid crystal display device displays an image by transmitting light from a backlight light source (not shown), the backlight light source for transmissive display is located at a position facing the outer surface of the lower substrate 1. Provided.

  The liquid crystal layer 3 is configured using, for example, nematic liquid crystal. The liquid crystal layer 3 is provided between the lower substrate 1 and the upper substrate 2 (opposed portion) so as to be sandwiched between the lower substrate 1 and the upper substrate 2. In the embodiment of the present invention, an application example to a liquid crystal display device in a horizontal electric field mode (IPS mode, FFS mode, etc.) will be described. However, the present invention is not limited to this, and a storage capacitor is formed between transparent electrodes. Any other operation mode (for example, twisted nematic mode, electric field control birefringence mode, vertical alignment mode, etc.) can be applied.

(First embodiment)
FIG. 2 is a plan view (A) and a sectional view (B) showing the configuration of the lower substrate 1 as the configuration of the liquid crystal display device according to the first embodiment of the present invention. In FIGS. 2A and 2B, the relationship between the scale and the position does not correspond accurately.

  As shown in the drawing, on the lower substrate 1, a gate wiring 4 serving as a first wiring, a data wiring 5 serving as a second wiring, an additional wiring 6 serving as a third wiring, and a first insulating film The interlayer insulating film 7 to be the second insulating film, the interlayer insulating film 9 to be the third insulating film, the pixel electrode 10 to be the upper transparent electrode, and the common to be the lower transparent electrode An electrode 11 is formed.

  Here, in the “upper transparent electrode and lower transparent electrode”, “upper layer” means a layer on the lower substrate 1 that is closer to the liquid crystal layer 3, and “lower layer” is farther from the liquid crystal layer 3 on the lower substrate 1. The side layer.

  A plurality of gate lines 4 and data lines 5 are formed. The gate wiring 4 is formed in parallel with the x direction, and the data wiring 5 is formed in parallel with the y direction perpendicular to the x direction. As a result, the gate wiring 4 and the data wiring 5 form a matrix arrangement that intersects (orthogonally) each other. The gate line 4 and the data line 5 define a unit pixel region 12. Specifically, an area surrounded by two data wirings 5 adjacent in the x direction and two gate wirings 4 adjacent in the y direction is partitioned as one unit pixel area 12. In FIG. 2A, only two gate wirings 4 and two data wirings 5 are shown for simplification of the drawing.

  The unit pixel region 12 includes a pixel electrode 10, a common electrode 11, and a TFT (not shown) in addition to the gate wiring 4 and the data wiring 5 that partition the unit pixel region 12. The TFT is provided at the intersection of the gate line 4 and the data line 5. The TFT functions as a switching element (driving element) for selectively driving the pixels in the display region of the liquid crystal display device (liquid crystal panel). Due to the configuration of the pixel circuit, the gate electrode of the TFT is electrically connected to the data line 5, the source electrode of the TFT is electrically connected to the data line 5, and the drain electrode of the TFT is electrically connected to the pixel electrode 10. The

  The gate wiring 4 is a first-layer wiring on the lower substrate 1. The gate wiring 4 is formed on the upper surface of the lower substrate 1. The data wiring 5 is a second-layer wiring on the lower substrate 1. The data wiring 5 is formed on the upper surface of the interlayer insulating film 7 on the lower substrate 1. The additional wiring 6 is a third-layer wiring on the lower substrate 1. The additional wiring 6 is formed on the upper surface of the interlayer insulating film 8 on the lower substrate 1.

  Further, the gate line 4 is formed in a state crossing the display area in the x direction, and the data line 5 is formed in a state crossing the display area in the y direction. The additional wiring 6 is disposed outside the unit pixel region 12. More specifically, the additional wiring 6 is formed in a plurality of arrays along the y direction on the frame portion outside (around) the display area. On the lower substrate 1, the outside of the display area is an area for forming an electronic circuit including a pixel driving circuit and various wirings, and an additional wiring 6 is formed as a part or wiring of the pixel driving circuit in the electronic circuit forming area. ing.

  Each of the gate wiring 4, the data wiring 5, and the additional wiring 6 is selected from, for example, aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten (W), tantalum (Ta), and chromium (Cr). It is formed by one or more kinds of metals (including alloys) or metal compounds (for example, MoSi, AlSi, etc.) or a laminated layer thereof. The gate wiring 4, the data wiring 5 and the additional wiring 6 may be formed of the same material or different materials.

The interlayer insulating film 7 is formed on the lower substrate 1 so as to cover the gate wiring 4. The interlayer insulating film 8 is formed on the interlayer insulating film 7 so as to cover the data wiring 5. The interlayer insulating film 9 is formed on the interlayer insulating film 8 so as to cover the additional wiring 6 and the common electrode 11. The interlayer insulating film 7, the interlayer insulating film 8, and the interlayer insulating film 9 are each formed of a light-transmitting organic insulating film or inorganic insulating film. As the organic insulating film, for example, an acrylic or novolac organic film can be used. As the inorganic insulating film, for example, an inorganic film such as silicon oxide (SiO ₂ ) or silicon nitride (SiN) can be used.

  On the lower substrate 1, the interlayer insulating film 7 is formed as a first insulating film, the interlayer insulating film 8 is formed as a second insulating film, and the interlayer insulating film 9 is formed as a third insulating film. On the other hand, the gate wiring 4 is formed as a first layer conductor, the data wiring 5 is formed as a second layer conductor, the additional wiring 6 and the common electrode 11 are formed as a third layer conductor. Therefore, the additional wiring 6 and the common electrode 11 are formed in the same layer in the stacking direction. “Formed in the same layer” described here means that it is formed between two insulating films adjacent to each other in the stacking direction (in this embodiment, the interlayer insulating film 8 and the interlayer insulating film 9).

  The pixel electrode 10 is formed for each unit pixel region 12. The pixel electrode 10 is covered with an alignment film (not shown) formed on the interlayer insulating film 9. The common electrode 11 is an electrode common to each unit pixel region 12 and has a plate shape (solid structure) in the entire display region except for a contact hole portion CH for electrically connecting the pixel electrode 10 to the TFT. ). Each of the pixel electrode 10 and the common electrode 11 is made of a transparent electrode material such as ITO (Indium Tin Oxide), and forms a storage capacitor in the unit pixel region 12. In the unit pixel region 12, the storage capacitor is configured such that two transparent electrodes composed of the pixel electrode 10 and the common electrode 11 are arranged in an opposing state (overlapping state), and an interlayer insulation is provided between the two transparent electrodes. It is formed by disposing the film 9 therebetween.

Therefore, the interlayer insulating film 9 becomes an insulating film that forms a storage capacitor between the pixel electrode 10 and the common electrode 11 in the unit pixel region 12. In addition, when the additional wiring 6 serving as the third-layer conductor is processed by a thin line process in a dry process, the damage to the film increases if the lower layer film is a relatively soft organic film. For this reason, when the additional wiring 6 is formed by a dry process, it is preferable to use an inorganic insulating film (SiO ₂ , SiN, etc.) as the interlayer insulating film 8, and further, an SOG (Spin on Grass) film having excellent flatness is used. It is desirable to use it. Similarly, when the data wiring 5 is formed by a dry process, it is preferable to use an inorganic insulating film as the interlayer insulating film 7.

Further, when the additional wiring 6 is formed of a metal wiring, the interlayer insulating film 9 functions as a corrosion preventing film for preventing the corrosion of the metal wiring by covering the additional wiring 6 with the interlayer insulating film 9. In this case, either an inorganic insulating film or an organic insulating film may be used as the interlayer insulating film 9, but in the case of a liquid crystal display device operating in the FFS mode, the film thickness of the interlayer insulating film 9 is accurately controlled ( Therefore, it is desirable to form with an inorganic insulating film (SiO ₂ , SiN, etc.).

  In the liquid crystal display device having the above configuration, since the storage capacitor is formed using the two layers of transparent electrodes including the pixel electrode 10 and the common electrode 11, the storage capacitor is formed using a non-transparent electrode made of metal or the like. Compared with the case where it does, the transmittance | permeability of the light in the unit pixel area | region 12 goes up. For this reason, the brightness of the liquid crystal display device can be increased. Further, since the common electrode 11 is formed in a plate shape (solid shape) on the entire display region on the lower substrate 1, and the pixel electrode 10 is formed on the upper layer via the interlayer insulating film 9, the unit electrode region 12 A wider range of liquid crystal molecules can be operated. For this reason, further increase in luminance can be expected by improving the aperture ratio.

  On the lower substrate 1, since the multilayer wiring is formed in a three-layer structure including the gate wiring 4, the data wiring 5 and the additional wiring 6, the additional wiring 6 is not overlapped with the gate wiring 4 or the data wiring 5. As compared with the case where the position is shifted in the substrate surface direction (lateral direction), the wiring area around the display area can be reduced. Therefore, it is possible to narrow the frame of the liquid crystal display device, increase the density of the drive circuit, and improve the aperture ratio. Further, since the additional wiring 6 is formed in the same layer as the common electrode 11 and the additional wiring 6 is covered with the interlayer insulating film 9 that forms a storage capacitor in the unit pixel region 12, the additional wiring 6 is connected to the common electrode 11. Compared with the case of forming in a layer different from 11, the enlargement of the frame and the decrease in light transmittance due to the multilayer wiring can be suppressed, and the manufacturing process can be simplified.

  In the above embodiment, the additional wiring 6 is a third-layer wiring on the lower substrate 1, but the present invention is not limited to this, and the multilayer wiring including the gate wiring 4, the data wiring 5, and the additional wiring 6 is used. May be formed with a layer structure of three or more layers. However, in any case, the additional wiring 6 and the common electrode 11 are formed in the same layer.

(Second Embodiment)
FIG. 3 is a plan view (A) and a cross-sectional view (B) showing the configuration of the lower substrate 1 as the configuration of the liquid crystal display device according to the second embodiment of the present invention. In the second embodiment, the same components as those in the first embodiment will be described with the same reference numerals.

  In the second embodiment of the present invention, in particular, the structure of the pixel electrode 10 is different from that of the first embodiment. That is, in the first embodiment, the pixel electrode 10 is formed in a flat plate shape. In the second embodiment, the pixel electrode 10 is formed in a slit structure. More specifically, a plurality of slits 10A are cut in the pixel electrode 10 in parallel with the y direction, whereby the entire pixel electrode 10 is formed in a comb shape.

  Thus, when the pixel electrode 10 is formed in a slit structure, liquid crystal molecules are switched by a lateral electric field in a plane parallel to the substrate surface without providing ITO or the like on the upper substrate 2 side facing the lower substrate 1. The liquid crystal display device can be operated in a so-called FFS mode. Therefore, it is possible to provide a liquid crystal panel having a wide viewing angle, a narrow frame, and a high transmittance.

  As the slit structure of the pixel electrode 10, the direction of the slit may be parallel to the x direction, and the shape of the slit may be a “<” shape. However, in order to efficiently operate the liquid crystal molecules of the liquid crystal layer 3, it is preferable that the direction of the slit of the pixel electrode 10 is parallel to the data wiring 5 (y direction). In addition, when the slit of the pixel electrode 10 has a “<" shape, the data wiring 5 is preferably formed in a "<" shape so that the direction of the slit is parallel to the data wiring 5. .

(Third embodiment)
FIG. 4 is a cross-sectional view showing the structure of the lower substrate 1 in particular as the structure of the liquid crystal display device according to the third embodiment of the present invention. In the third embodiment, the same components as those in the first embodiment and the second embodiment will be described with the same reference numerals.

  The third embodiment of the present invention is different from the second embodiment in that a plate-like light reflection film 14 is provided in the unit pixel region 12. The light reflecting film 14 is provided in the unit pixel region 12 as a third wiring. The light reflecting film 14 is formed in the same layer as the additional wiring 6 and the common electrode 11. That is, the light reflecting film 14 is formed on the lower substrate 1 as a third layer conductor together with the additional wiring 6 and the common electrode 11.

  The light reflecting film 14 is formed of the same metal as that of the additional wiring 6, and is particularly formed of a metal (including an alloy) having a high reflectance such as aluminum. The light reflecting film 14 is formed on the interlayer insulating film 8 so as to overlap a part of the common electrode 11. For this reason, external light incident from the upper substrate 2 side is reflected by the light reflecting film 14, and light incident from a backlight source (not shown) is transmitted through the portion of the common electrode 11 on which the light reflecting film 14 is not overlapped. To do. As a result, a “semi-transmissive” liquid crystal display device having both transmissive and reflective functions is realized.

  In general, a transparent electrode such as ITO has a slightly higher electrical resistance value than that of a metal. However, if a metal film forming the light reflecting film 14 is overlapped on the common electrode 11 and electrically connected, the metal The resistance of the common electrode 11 can be reduced by using a film as an auxiliary wiring. In particular, the light reflecting film 14 is preferably formed of aluminum in order to achieve both the low resistance of the common electrode 11 and the function as a light reflecting plate.

(Fourth embodiment)
FIG. 5 is a plan view (A) and a sectional view (B) showing the configuration of the lower substrate 1 as the configuration of the liquid crystal display device according to the fourth embodiment of the present invention. In the fourth embodiment, the same components as those in the first embodiment, the second embodiment, and the third embodiment will be described with the same reference numerals.

  The fourth embodiment of the present invention is different from the first embodiment in that a light shielding film 15 is provided in the unit pixel region 12. The light shielding film 15 is provided in the unit pixel region 12 as a third wiring. The light shielding film 15 is formed in the same layer as the additional wiring 6 and the common electrode 11. That is, the light shielding film 15 is formed on the lower substrate 1 as a third layer conductor together with the additional wiring 6 and the common electrode 11.

  The light shielding film 15 is formed of the same metal as that of the additional wiring 6, but is particularly formed of a metal (including an alloy) having a low reflectance such as molybdenum or titanium. The light shielding film 15 is formed adjacent to the common electrode 11 on the interlayer insulating film 8. Further, the light shielding film 15 is arranged in a matrix arrangement in the same manner as the gate wiring 4 and the data wiring 5 by superimposing a plurality of strip-shaped patterns parallel to the x direction and a plurality of strip-shaped patterns parallel to the y direction so as to cross each other. It is formed with. The strip pattern parallel to the x direction of the light shielding film 15 is arranged so as to overlap the gate wiring 4, and the strip pattern parallel to the y direction of the light shielding film 15 is arranged to overlap with the data wiring 5.

  In the liquid crystal display device having the above configuration, light incident from a backlight light source (not shown) is shielded by the light shielding film 15. For this reason, the light shielding film 15 can be used instead of the black matrix. Further, since the light reflected by the data wiring 5 or the like is shielded by the light shielding film 15, the influence of unnecessary reflected light can be reduced and the contrast can be improved.

  In the fourth embodiment, the light shielding film 15 is formed in a matrix arrangement. However, the present invention is not limited to this. For example, the light shielding film 15 may be formed in a stripe arrangement.

It is a schematic sectional drawing which shows the fundamental structure of the liquid crystal display device with which this invention is applied. 1 is a diagram showing a configuration of a lower substrate, in particular, as a configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows especially the structure of a lower substrate as a structure of the liquid crystal display device which concerns on 2nd Embodiment of this invention. It is a figure which shows especially the structure of a lower board | substrate as a structure of the liquid crystal display device which concerns on 3rd Embodiment of this invention. It is a figure which shows especially the structure of a lower substrate as a structure of the liquid crystal display device which concerns on 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lower substrate, 2 ... Upper substrate, 3 ... Liquid crystal layer, 4 ... Gate wiring, 5 ... Data wiring, 6 ... Additional wiring, 7, 8, 9 ... Interlayer insulating film, 10 ... Pixel electrode, 11 ... Common electrode, 12 ... Unit pixel region, 14 ... Light reflecting film, 15 ... Light shielding film

Claims (10)

A first substrate;
A second substrate facing the first substrate;
A liquid crystal layer provided between the first substrate and the second substrate;
The first substrate is
A plurality of wirings having a layer structure of three or more layers including a data wiring and a gate wiring partitioning the unit pixel region;
A first insulating film covering the first wiring among the plurality of wirings;
A second insulating film covering the second wiring formed on the first insulating film;
A third insulating film covering the third wiring formed on the second insulating film;
An upper transparent electrode and a lower transparent electrode that form a storage capacitor in the unit pixel region;
The third wiring is formed in the same layer as the lower transparent electrode, and the storage capacitor is formed by interposing the third insulating film between the upper transparent electrode and the lower transparent electrode. A characteristic liquid crystal display device. The liquid crystal display device according to claim 1, wherein the third wiring is disposed outside the unit pixel region. The liquid crystal display device according to claim 1, wherein the third wiring is arranged in the unit pixel region. The third wiring is made of metal wiring,
The liquid crystal display device according to claim 1, wherein the third insulating film functions as a corrosion preventing film that prevents corrosion of the metal wiring. The liquid crystal display device according to claim 3, wherein the third wiring arranged in the unit pixel region also serves as a light shielding film. The liquid crystal display device according to claim 3, wherein the third wiring arranged in the unit pixel region also serves as a light reflecting film. The liquid crystal display device according to claim 1, wherein the upper transparent electrode is formed in a slit structure. The liquid crystal display device according to claim 1, wherein the third insulating film is made of an inorganic insulating film. The liquid crystal display device according to claim 1, wherein the second insulating film is made of an inorganic insulating film. The liquid crystal display device according to claim 1, wherein the second insulating film is an SOG (Spin on Grass) film.

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