JP2003057670A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve optical efficiency. SOLUTION: Pixel electrodes PX and opposing electrodes CT, which are used to generate electric field between the electrodes PX, are provided in the pixel regions of the liquid crystal side located on the other substrate of substrates SUB that are oppositely arranged through liquid crystals. The electrodes PX and CT are respectively made up with a plurality of electrodes which are alternatively arranged and extended in one direction and crossed with respect to the direction in a belt shape. Among these electrodes, electrodes having wider widths are provided. The separation width between the electrode whose width is set wider and an adjacent electrode is set larger than the separation width of the other adjacent electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a so-called lateral electric field type liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device called a horizontal electric field type is
A counter electrode for generating an electric field between a pixel electrode and the pixel electrode is provided in each pixel region on the liquid crystal side of one of the pair of substrates arranged to face each other with the liquid crystal interposed therebetween. The parallel components are configured to control the light transmittance of the liquid crystal. The pixel electrode and the counter electrode are each composed of, for example, a plurality of strip-shaped electrodes that extend in one direction and are alternately arranged in a direction intersecting the direction.

In order to control the light transmittance of the liquid crystal with a small driving voltage, it is preferable to reduce the distance between the pixel electrode and the counter electrode. From this fact, each pixel electrode is adjacent to the pixel electrode. The separation distances from the counter electrode were set to be equal.

In this case, a so-called V-T (driving voltage applied between the pixel electrode and the counter electrode-transmittance) curve is prepared on the assumption that the pixel electrode and the counter electrode have the same width. Since the VT curve has a maximum point, what distance should be set between the electrodes in order to maximize the transmittance, or how much the drive voltage between the pixel electrode and the counter electrode should be set. I was deciding what to do. That is, by doing so, even if the same drive voltage is applied, it is possible to achieve a display with the best light efficiency.

[0005]

However, in the liquid crystal display device having such a structure, in order to solve a certain disadvantage in recent years, for example, the width of a specific counter electrode is changed to the width of other electrodes. It has become known that the structure is thicker than that.

Therefore, a counter electrode having a large width is arranged on one side of the pixel electrode and a counter electrode having a normal width is arranged on the other side. The pixel electrode and the counter electrode having a large width are arranged. The lines of electric force between the pixel electrode and the counter electrode having a normal width are increased. In other words, this means that the electric field between the pixel electrode and the counter electrode on one side becomes larger than the electric field between the pixel electrode and the counter electrode on the other side.

Therefore, it is equivalent to that the voltage between the pixel electrode and the counter electrode is high in this region, and since it is driven at a portion deviated from the maximum point of the VT curve, a predetermined transmission is performed. Therefore, the efficiency cannot be obtained and the light efficiency is lost. The present invention has been made under such circumstances, and an object thereof is to provide a liquid crystal display device having improved light efficiency.

[0008]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows. Means 1. The liquid crystal display device according to the present invention is provided with, for example, a pixel electrode on one side of each of the substrates opposed to each other with the liquid crystal interposed therebetween, and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode. The pixel electrode and the counter electrode each include a plurality of strip-shaped electrodes that extend in one direction and are alternately arranged in a direction intersecting with the direction, and are set wider than the other electrodes among these electrodes. Equipped with electrodes,
The width of the gap between the electrode and the electrode adjacent to the wide electrode is set to be larger than the gap between the adjacent electrodes.

Means 2. A liquid crystal display device according to the present invention includes, for example, a switching element that is operated by a scanning signal from a gate signal line in a pixel region on the liquid crystal side of one of the substrates that are arranged to face each other via a liquid crystal, and the switching element A pixel electrode to which a video signal is supplied from the drain signal line via the pixel electrode and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode, and the pixel electrode and the counter electrode extend in one direction. The counter electrode includes a plurality of strip-shaped electrodes that are alternately arranged in a direction intersecting with the direction, and includes a counter electrode that overlaps the drain signal line among the plurality of counter electrodes via an insulating film. The width of the counter electrode is wider than that of the other electrode, and the gap between the counter electrode and the adjacent electrode overlapped with the drain signal line is set to be larger than the gap between other adjacent electrodes. And it is characterized in that they are.

Means 3. A liquid crystal display device according to the present invention includes, for example, a switching element that is operated by a scanning signal from a gate signal line in a pixel region on the liquid crystal side of one of the substrates that are arranged to face each other via a liquid crystal, and the switching element A pixel electrode to which a video signal is supplied from the drain signal line via the pixel electrode and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode, and the pixel electrode and the counter electrode extend in one direction. The plurality of pixel electrodes, which are alternately arranged in a direction intersecting with the direction, each of the plurality of pixel electrodes, the pixel electrode electrically connected to the switching element is formed wider than the other electrodes. Further, a separation width between the pixel electrode electrically connected to the switching element and an electrode adjacent to the pixel electrode is set to be larger than a separation width of other electrodes. It is intended.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a liquid crystal display device according to the present invention will be described below with reference to the drawings. Example 1. << Equivalent Circuit >> FIG. 2 is an equivalent circuit diagram showing an embodiment of the liquid crystal display device according to the present invention. Although this figure is an equivalent circuit diagram, it is drawn corresponding to the actual geometrical arrangement.

In FIG. 2, there is a pair of transparent substrates SUB1 and SUB2 arranged to face each other with a liquid crystal interposed therebetween, and the liquid crystal is enclosed by a sealing material SL which also fixes one transparent substrate SUB1 to the other transparent substrate SUB2. ing.

On the liquid crystal side surface of the one transparent substrate SUB1 surrounded by the seal material SL, the gate signal lines GL extending in the x direction and juxtaposed in the y direction and the y direction extending in the y direction. A drain signal line DL is formed side by side in the direction.

Each gate signal line GL and each drain signal line D
The region surrounded by L and L constitutes a pixel region, and the matrix-shaped aggregate of these pixel regions is the liquid crystal display unit A.
It constitutes R.

Further, a common counter voltage signal line CL running in each pixel area is formed in each of the pixel areas arranged in parallel in the x direction. The counter voltage signal line CL serves as a signal line for supplying a reference voltage for a video signal to a counter electrode CT described later in each pixel region.

Further, one end of each of the counter voltage signal lines CL is commonly connected to a counter voltage terminal CTM formed outside the sealing material SL, and the counter voltage terminal C is formed.
The voltage is supplied from TM.

In each pixel region, a thin film transistor TFT which is operated by a scanning signal from a gate signal line GL on one side thereof and a pixel electrode to which a video signal from the drain signal line DL on one side is supplied via the thin film transistor TFT. PX is formed.

The pixel electrode PX generates an electric field between the counter voltage signal line CL and the counter electrode CT connected thereto, and the electric field controls the light transmittance of the liquid crystal.

One end of each of the gate signal lines GL extends beyond the seal material SL, and the extended end constitutes a terminal to which an output terminal of the vertical scanning drive circuit V is connected. . Further, a signal from a printed circuit board arranged outside the transparent substrate SUB1 is input to the input terminal of the vertical scanning drive circuit V.

The vertical scanning drive circuit V comprises a plurality of semiconductor devices, and a plurality of gate signal lines adjacent to each other are grouped, and one semiconductor device is assigned to each of these groups.

Similarly, one end of each of the drain signal lines DL extends beyond the sealing material SL, and the extended end constitutes a terminal to which the output terminal of the video signal driving circuit He is connected. Has become. Further, the input terminal of the video signal drive circuit He is adapted to receive a signal from a printed circuit board arranged outside the transparent substrate SUB1.

The video signal driving circuit He is also composed of a plurality of semiconductor devices, and a plurality of drain signal lines DL adjacent to each other are grouped, and one semiconductor device is applied to each of these groups. There is.

One of the gate signal lines GL is sequentially selected by a scanning signal from the vertical scanning circuit V. Further, a video signal is supplied to each of the drain signal lines DL by a video signal drive circuit He at the timing of selecting the gate signal line GL.

<< Pixel Structure >> FIG. 1 is a plan view showing an embodiment of the structure of the pixel region, and shows the structure shown in the circle in FIG. A cross section taken along the line III-III in FIG. 1 is shown in FIG. In FIG. 1, first, on the surface of the transparent substrate SUB1 on the liquid crystal side, a pair of gate signal lines GL extending in the x direction and juxtaposed in the y direction are formed. These gate signal lines GL surround a rectangular area together with a pair of drain signal lines DL described later, and this area is configured as a pixel area.

An insulating film GI made of, for example, SiN is formed on the surface of the transparent substrate SUB1 on which the gate signal lines GL have been formed as described above so as to cover the gate signal lines GL as well. The insulating film GI functions as an interlayer insulating film for the gate signal line GL in the formation region of the drain signal line DL described later, and functions as a gate insulation film in the formation region of the thin film transistor TFT described later.
It has a function as a dielectric film in a formation region of a capacitive element Cstg described later.

On the surface of this insulating film GI,
A semiconductor layer AS made of, for example, amorphous Si is formed so as to overlap a part of the gate signal line GL. This semiconductor layer AS is a thin film transistor TFT.
In addition, by forming the drain electrode SD1 and the source electrode SD2 on the upper surface thereof, it is possible to configure the MIS transistor having the inverted stagger structure in which a part of the gate signal line GL is used as the gate electrode.

Here, the drain electrode SD1 and the source electrode SD2 are formed at the same time when the drain signal line DL is formed. That is, the drain signal line DL extending in the y direction and arranged in parallel in the x direction is formed, and a part of the drain signal line DL extends to the upper surface of the semiconductor layer AS to form the drain electrode SD1. A source electrode SD2 is formed apart from the electrode SD1 by the channel length of the thin film transistor TFT.

The source electrode SD2 extends from the surface of the semiconductor layer AS toward the pixel region side, and the extending portion extends, for example, in the (+) y direction in the figure, and then in the (+) x direction. The pixel electrode PX is formed as a “U” -shaped pattern such as in the (−) y direction.

The pixel electrode PX in this case is formed as two pixel electrodes (pixel electrode group) extending in the y direction and arranged in parallel in the x direction in the pixel region. The width of each of these pixel electrodes PX is set to w.

The pixel electrode PX is made of the same material as the drain signal line DL as described above. However, the present invention is not limited to this, and the drain signal line DL may be made of a different material. In this case, there is no choice but to form the drain signal line DL in a step different from the step of forming the drain signal line DL.
(Indium Tin Oxide) or the like can be used for the translucent material, and the aperture ratio of the pixel can be improved.

Incidentally, the semiconductor layer AS and the drain electrode SD1
A thin layer doped with a high concentration of impurities is formed at the interface with the source electrode SD2, and this layer functions as a contact layer.

This contact layer is, for example, the semiconductor layer A.
When S is formed, a high-concentration impurity layer is already formed on the surface thereof, and the drain electrode SD1 formed on the upper surface of the impurity layer is formed.
And the impurity layer exposed from the pattern of the source electrode SD2 as a mask may be etched.

As described above, the transparent substrate SUB1 on which the thin film transistor TFT, the drain signal line DL, the drain electrode SD1 and the source electrode SD2 are formed has a protective film PSV1 made of, for example, SiN, and an organic material layer on the upper surface thereof. A protective film PSV2 is formed.

The protective films PSV1 and PSV2 are intended to prevent direct contact with the liquid crystal of the thin film transistor TFT to prevent characteristic deterioration of the thin film transistor TFT, and the protective film PSV2 made of an organic material layer is used. The reason is to lower the dielectric constant of the entire protective film.

A counter electrode CT is formed on the upper surface of the protective film PSV2. The counter electrode CT extends at least in the center of the pixel region in the y direction in the drawing and has a width w, and the counter electrode CT overlaps with the drain signal line DL arranged on both sides of the pixel region and the drain. The counter electrode CT is composed of an electrode group having a width W (> w) wider than the signal line DL.

The reason why the width of the counter electrode CT overlapping the drain signal line DL is larger than that of the drain signal line DL is that the electric field from the drain signal line DL is above the counter electrode. This is to facilitate termination to CT and prevent termination to the pixel electrode PX.
This is because if the electric field ends in the pixel electrode PX, it becomes noise.

In this case, the counter electrode CT (whose width is w) running in the center of the pixel region and the pixel electrodes PX on both sides of the counter electrode CT are separated from each other by a distance d, and also overlap the drain signal line DL. The counter electrode CT (its width is W) and the pixel electrodes PX on both sides of the counter electrode CT are separated by a distance D (> d).

That is, the counter electrode CT superposed on the drain signal line DL has a width wider than that of the other electrodes, so that the counter electrode CT is formed.
The distance between the pixel electrode PX and the adjacent pixel electrode PX is set larger than the distance between the other adjacent electrodes.

With such a structure, in the region between the counter electrode CT running in the center of the pixel region and each pixel electrode PX adjacent to the counter electrode CT, the maximum is obtained according to the characteristic based on the VT curve. The width d for achieving the light efficiency can be set, and the characteristics based on the VT curve in the region between the counter electrode CT superimposed on the drain signal line DL and the pixel region electrode PX adjacent to the counter electrode CT. The width D for achieving the maximum light efficiency can be set according to Therefore, the maximum light efficiency can be obtained in the entire pixel area.

Then, each of the counter electrodes CT is integrally formed with a conductive layer made of the same material as that of the counter electrode CT overlapped with the gate signal line GL so that they are electrically connected to each other. Has become.

In other words, for each counter electrode CT, a conductive layer formed over the entire area of the liquid crystal display portion AR is provided with a hole in the portion where the pixel electrode PX is formed and the portions on both sides thereof, which extend in the y direction in the drawing. It is formed by

The counter electrode CT thus constructed is formed so as to overlap the portion of the pixel electrode PX extending in the x direction in the drawing, and the capacitive element Cstg is formed at this overlapping portion. There is. This capacitive element Cstg
Has a function of, for example, accumulating the video signal supplied to the pixel electrode PX for a relatively long time.

Here, the counter electrode CT is made of a non-translucent material (for example, Al, Cr, Mo, T) made of metal.
a, W, Ti, Ni, Cu, etc.), and in order to improve the aperture ratio, for example, ITO, IZO
It may be made of a translucent material such as.

An alignment film (not shown) is formed on the upper surface of the transparent substrate on which the counter electrode CT is thus formed so as to cover the counter electrode CT. This alignment film is a film that directly contacts the liquid crystal, and the rubbing formed on the surface determines the initial alignment direction of the molecules of the liquid crystal.

Example 2. FIG. 4 is a plan view showing another embodiment of the pixel of the liquid crystal display device according to the present invention and corresponds to FIG. A configuration different from that of FIG. 1 is that the width w ′ of the pixel electrode PX on the side connected to the source electrode SD2 of the thin film transistor TFT among the pixel electrodes PX formed to extend in the y direction in the drawing is different. Of the pixel electrode PX formed with a width larger than the width w of the pixel electrode PX of
The distance between the counter electrodes CT on both sides thereof is slightly larger.

This embodiment also has the same concept as that of the first embodiment, and when there is an electrode whose width is wider than that of the other electrode, the distance between the adjacent electrodes is adjusted accordingly. The value is increased and the value is set so as to maximize the light efficiency in that region in accordance with the characteristics of the VT curve.

That is, in the case of the present embodiment based on the configuration of the first embodiment, the counter electrode CT that is arranged so as to overlap the drain signal line DL and the wide pixel electrode PX adjacent to this counter electrode CT.
The separation distance D ′ between the pixel electrode PX and the counter electrode CT is slightly larger than that in the first embodiment (D), and the separation distance d ′ between the pixel electrode PX and the counter electrode on the other side different from the counter electrode CT is It is set to be slightly larger than that in the case of the first embodiment (d).

In this embodiment, each pixel electrode P
The width of the pixel electrode PX of X on the side connected to the source electrode SD2 of the thin film transistor TFT is formed to be larger than the width of the other pixel electrode PX in order to prevent disconnection particularly in this portion. .

Example 3. FIG. 5 is a plan view showing another embodiment of the pixel of the liquid crystal display device according to the present invention and corresponds to FIG. Compared to the case of FIG. 1, the counter electrode CT
Is formed in the same layer as the gate signal line GL, and is otherwise substantially the same in configuration. Note that FIG.
6 is a sectional view taken along line VI-VI of FIG.

That is, for example, the counter voltage signal line CL running in the y direction at the center of the pixel region is formed at the same time as the manufacture of the gate signal line GL, and the counter voltage signal line CL is formed.
A plurality of counter electrodes CT are integrally formed in the.

Each counter electrode CT is, for example, three counter electrodes CT which run in the center of the pixel region in the y direction, and each counter electrode CT which is arranged parallel to the counter electrode CT and adjacent to the drain signal line DL. It consists of

Here, each counter electrode CT arranged adjacent to the drain signal line DL is formed wider than the other counter electrodes CT. This is because the line of electric force from the drain signal line DL is terminated in the wide counter electrode CT and is not terminated in the pixel electrode PX.

The pixel electrode PX is composed of two electrodes as in the case of the first embodiment. The pixel electrodes PX are electrically connected on the counter voltage signal line CL, and are connected to the counter voltage signal line CL at the connection portion. The capacitive element Cstg is formed in the. The separation distance between the counter electrode CT and the pixel electrode PX is set in the same relationship as in the first embodiment.

As described above, since the counter electrode CT adjacent to the drain signal line DL is formed wider than the other electrodes, the counter electrode CT and the pixel electrode PX adjacent thereto are correspondingly formed. The separation distance is slightly larger than the separation distance between other adjacent electrodes.

In each of the above-described embodiments, the number of counter electrodes CT is three and the number of pixel electrodes PX is two, but the number of counter electrodes CT is not limited to this.

In order to avoid the termination of the line of electric force from the drain signal line DL to the pixel electrode PX, when the counter electrode CT is formed so as to overlap or be adjacent to the drain signal line DL, the number of counter electrodes CT is the number of pixels. One more electrode PX is formed. Therefore, it goes without saying that a configuration may be adopted in which the number of counter electrodes and pixel electrodes is increased by providing this relationship.

In each of the above-mentioned embodiments, the counter electrode C is used.
The T is formed so as to overlap or be adjacent to the drain signal line DL, but it is not necessarily limited to this, and needless to say, it is applicable to a configuration in which the pixel electrode is adjacent to the drain signal line DL. .

[0058]

As is apparent from the above description,
According to the liquid crystal display device of the present invention, the light efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a pixel of a liquid crystal display device according to the present invention.

FIG. 2 is an equivalent circuit diagram showing an embodiment of a liquid crystal display device according to the present invention.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

FIG. 5 is a plan view showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

6 is a sectional view taken along line VI-VI in FIG.

[Explanation of symbols]

SUB ... Transparent substrate, GL ... Gate signal line, DL ... Drain signal line, GI ... Insulating film, AS ... Semiconductor layer, TFT ... Thin film transistor, PSV ... Protective film, PX ... Pixel electrode, C
T ... counter electrode, CL ... counter voltage signal line.

Continued front page    (72) Inventor Masahiro Ishii             Hitachi, Ltd. 3300 Hayano, Mobara-shi, Chiba             Factory Display Group F term (reference) 2H092 GA15 JA24 JA45 JB06 JB13                       PA06

Claims (3)

[Claims] 1. A pixel electrode on the liquid crystal side of one of the substrates arranged to face each other with a liquid crystal interposed between the pixel electrode and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode. The counter electrode is composed of a plurality of strip-shaped electrodes that extend in one direction and are alternately arranged in a direction intersecting the direction, and each of the electrodes includes an electrode that is set wider than the other electrodes. A liquid crystal display device, characterized in that a separation width between the electrode set wide and an electrode adjacent thereto is set larger than a separation width between other adjacent electrodes. 2. A switching element operated by a scanning signal from a gate signal line, and a drain signal via the switching element in a pixel area on the liquid crystal side of one of the substrates arranged to face each other with the liquid crystal interposed therebetween. A pixel electrode to which a video signal from a line is supplied, and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode. The pixel electrode and the counter electrode extend in one direction and intersect with each other. A plurality of strip electrodes that are alternately arranged in the direction, and a counter electrode that is overlapped with the drain signal line through an insulating film among the plurality of counter electrodes is provided, and the counter electrode is wider than other electrodes. Is widely formed, and a separation width between the counter electrode and an electrode adjacent to the counter electrode overlapped with the drain signal line is set to be larger than a separation width between other adjacent electrodes. Liquid crystal display device. 3. A switching element operated by a scanning signal from a gate signal line, and a drain signal via the switching element, in a pixel area on the liquid crystal side of one of the substrates arranged to face each other with the liquid crystal interposed therebetween. A pixel electrode to which a video signal from a line is supplied, and a counter electrode for generating an electric field between the pixel electrode and the pixel electrode. The pixel electrode and the counter electrode extend in one direction and intersect with each other. Of the plurality of pixel electrodes, the pixel electrode electrically connected to the switching element is formed wider than the other electrodes, and the switching element and the switching element are arranged alternately. A liquid crystal display device, wherein a separation width between the electrically connected pixel electrode and an electrode adjacent to the pixel electrode is set to be larger than a separation width of other electrodes.