JP3481074B2 - Liquid crystal display device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates are those which relate to the liquid crystal display element used in the display for performing such image display and OA equipment information display of the AV equipment.

[0002]

2. Description of the Related Art At present, a liquid crystal display element for displaying an image using a liquid crystal is an audio image (A) for a viewfinder of a video camera, a pocket TV or a high definition projection TV.
V) Video display of devices and OA for personal computers, word processors, etc.
It has been widely used as a display for displaying information of devices, etc., and its development and commercialization have been actively carried out.

In particular, an active matrix type liquid crystal display element using a thin film transistor (TFT) as a switching element has a great feature that a high contrast is maintained even when displaying a large capacity, and in recent years, the demand for the market is extremely high. The development and commercialization of these liquid crystal display elements are being actively pursued as the favorite of liquid crystal display devices in full-color displays for laptop computers and notebook computers, and large-scale, large-capacity full-color displays for engineering workstations.

In such an active matrix type liquid crystal display device, there is a TN (Twisted Nematic) system as a liquid crystal display mode which is widely used. This T
In the N method, a liquid crystal panel having a structure in which liquid crystal molecules of a liquid crystal layer sandwiched between substrates having electrodes are twisted 90 ° between electrode substrates is sandwiched by two polarizing plates. In this TN type liquid crystal display element, the two polarizing plates have their polarizing axis directions orthogonal to each other, and the polarizing axis of one of the polarizing plates is parallel to the major axis direction of liquid crystal molecules in contact with one substrate. It is arranged to be vertical.

When no voltage is applied, white display is performed, but when a voltage is applied between two substrates, that is, in the direction perpendicular to the liquid crystal panel, the light transmittance gradually decreases and black display occurs. . Such display characteristics are obtained because when a voltage is applied to the liquid crystal panel, the liquid crystal molecules between the two substrates tend to be aligned in the direction of the electric field while untwisting the twisted structure. This is because the polarization state changes and the light transmittance is modulated.

However, even in the same molecular arrangement state, the polarization state of the transmitted light changes depending on the incident direction of the light incident on the liquid crystal panel, so that the light transmittance varies depending on the incident direction. That is, the display characteristics of the liquid crystal panel have a viewing angle dependency. The viewing angle dependence of this liquid crystal panel causes an inversion phenomenon of the brightness when the viewpoint is tilted obliquely with respect to the main viewing angle direction (the long axis direction of the liquid crystal molecules in the intermediate layer of the liquid crystal layer), which is an important problem for the image quality of the liquid crystal panel. It is a point.

In order to solve this problem, various methods have been proposed and developed so far. Among them, as a method that has received special attention in recent years, instead of applying a vertical electric field to the glass substrate as in the TN method, the direction of the electric field applied to the liquid crystal is set substantially parallel to the glass substrate, IPS (In-Plane Switchin) that controls the alignment direction of liquid crystal molecules on a plane parallel to the glass substrate.
g) method, which has been proposed, for example, in Japanese Examined Patent Publication No. 63-21907 or Japanese Unexamined Patent Publication No. 6-160878.

FIG. 6 is a perspective view showing the basic structure of a general IPS type liquid crystal display element. In FIG. 6, 1
Is a first glass substrate, 2 is a scanning electrode, 3 is a common electrode formed in the same layer as the scanning electrode 2 at the same time when the scanning electrode 2 is formed, and 4 is an insulating layer, which is generally a laminated structure containing SiNx or SiNx. Is often used in. 5 is a signal electrode,
6 is a pixel electrode formed at the same time as the signal electrode 5, and 7 is a switching element portion, and a-Si is mainly used as a semiconductor layer. Reference numeral 8 denotes a liquid crystal layer, and 9 denotes a second glass substrate which faces the liquid crystal layer.

In the present IPS system, the liquid crystal molecules of the liquid crystal layer 8 are composed of the common electrode voltage applied to the common electrode 3 and the pixel voltage supplied from the signal electrode 5 to the pixel electrode 6 via the switching element section 7. In between, it is controlled by the electric field generated substantially parallel to the first glass substrate 1.

[0010]

However, the conventional IPS type liquid crystal display device as described above has the following problems.

First, the presence of the insulating layer 4 on the common electrode 3 causes a decrease in the electric field strength with respect to the liquid crystal layer 8, which requires an increase in the drive voltage for sufficiently driving the liquid crystal layer 8. That is the problem.

Secondly, there is a problem that a difference in polarizability is caused due to the asymmetry of the configuration of the insulating layer 4 on the side of the liquid crystal layer 8 on the pixel electrode 6 side and on the side of the common electrode 3, and a burning phenomenon is likely to occur. This burn-in phenomenon is a phenomenon peculiar to a liquid crystal panel in which, when a fixed pattern is continuously displayed on the liquid crystal panel for a certain period of time, the previous display pattern remains for a certain period of time even after the display pattern is changed.

The present invention solves the above-mentioned problems of the prior art. For a display image by a lateral electric field driving method, it is possible to widen the field of view and obtain good multi-tone display, and improve the display quality. the liquid crystal display element that can
To provide.

[0014]

In order to solve the above problems SUMMARY OF THE INVENTION The liquid crystal display element of the invention conventionally necessary to obtain a wide viewing angle characteristic in the display image when using horizontal electric field display method It is characterized by suppressing the increase in the drive voltage that has been present and the burning phenomenon that is likely to occur because of this.

As described above, with respect to the display image by the horizontal electric field driving method, it is possible to widen the field of view and obtain good multi-gradation display, and to improve the display quality.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display element according to claim 1 of the present invention comprises a plurality of scanning electrode wirings and signal electrode wirings arranged in a matrix on the main plane of a first glass substrate, a picture element electrode wires arranged corresponding to intersections of the scanning electrode lines and the signal electrode lines, a switching element electrically connected between the scan electrode lines and the signal electrode lines and the pixel electrode wiring, the pixel electrode the wiring
An electric field almost parallel to the main plane of the first glass substrate is provided between
The second glass substrate and the first glass substrate on which the common electrode wiring that is configured to generate and the alignment film layer that controls the alignment direction of the liquid crystal molecules are formed and the alignment film layer is formed on the surface are formed. a liquid crystal layer sandwiched, wherein the scanning electrode lines and the signal to drive control the switching element by the driving signal to the electrode wiring, Ri by the fact of generating electric field substantially parallel to the main plane of the pre-Symbol first glass substrate A liquid crystal display element for controlling optical characteristics by the liquid crystal layer, wherein the pixel electrode wiring and the common electrode wiring are arranged so as to be in contact with the alignment film layer, and the common electrode wiring is Mainly made of aluminum
And the first common electrode wiring
Formed on the same layer as the pixel electrode wiring by being electrically short-circuited with the wiring.
Second common electrode wiring. Claim 2
The liquid crystal display element of the above is mounted on the main plane of the first glass substrate as a mask.
A plurality of scan electrode wirings and signals arranged in a trick pattern.
Of the signal electrode wiring and the scanning electrode wiring and the signal electrode wiring
Pixel electrode wiring arranged corresponding to each intersection and
Between inspection electrode wiring, signal electrode wiring, and pixel electrode wiring
A switching element electrically connected to the pixel electrode
Almost parallel to the main plane of the first glass substrate between the wiring
Common electrode wiring configured to generate a strong electric field and a liquid crystal
An alignment layer that controls the direction of molecules is formed and
A second glass substrate having an alignment film layer formed thereon and the first glass substrate.
The liquid crystal layer is sandwiched between the lath substrate and the scanning electrode wiring and
The switching element according to the drive signal to the signal electrode wiring
Is controlled so that it is substantially parallel to the main plane of the first glass substrate.
By generating a parallel electric field, the liquid crystal layer produces
A liquid crystal display device for controlling optical characteristics, comprising:
The pole wiring is made of a metal layer whose main component is aluminum.
The pixel electrode wiring and the common electrode wiring on the same plane.
The pixel electrode wiring and the common electrode
Before the line is formed on the main plane of the first glass substrate
The scanning electrode wiring, the signal electrode wiring, and the switching
Formed on the insulating layer formed to cover the element
The configuration. The liquid crystal display element according to claim 3 is
2. The liquid crystal display element according to 2, wherein a pixel electrode wiring and an electrode
The wiring was formed so as to be in contact with the alignment film layer.
The configuration. The liquid crystal display device according to claim 4 is
2. The liquid crystal display element according to 2 or 3, wherein the pixel electrode is
Electrically short circuit between the first pixel electrode and the first pixel electrode
Second pixel formed on the same plane as the common electrode wiring
It is composed of electrodes. The liquid crystal display element according to claim 5,
The liquid crystal display element according to claim 4, further comprising:
Between the pixel electrode of 1 and the additional capacitance electrode electrically short-circuited
Thus, the additional capacitance is formed. Claim 6
The liquid crystal display element is the liquid crystal display element according to claim 5.
At the same time when forming the first pixel electrode,
Is formed .

[0017]

[0018]

[0019]

[0020]

[0021] According to these configurations, conventionally, the up drive voltage needed for obtaining a wide viewing angle characteristic in the display image when using horizontal electric field display method, has become liable to occur because the Suppresses the burning phenomenon.

The liquid crystal display element and the method of manufacturing the same according to the embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 and FIG. 2 are a schematic plan view and a schematic sectional view showing a structure of a thin film transistor array substrate in a liquid crystal display element according to a first embodiment. In FIG. 1 and FIG. 2, 101 and 103 respectively indicate a scanning electrode wiring and a first common electrode wiring. In the present embodiment, the scanning electrode wiring 101 and the first common electrode wiring 1 are shown.
In No. 03, a metal thin film containing aluminum as a main component was formed on the same plane, and the shape shown in the drawing was formed by a photolithography method. These scan electrode wirings 10
The metal material used for the first and first common electrode wirings 103 is not particularly limited to aluminum-based metal, and either a single layer film or a multilayer film may be used.

Next, after laminating the anodized layer of the aluminum film and silicon nitride (SiNx) as an insulating film and amorphous silicon as a semiconductor layer,
A part of the anodic oxide layer and the silicon nitride layer on the first common electrode wiring 103 is removed, and then two layers of aluminum / titanium (Al / Ti) are deposited by a sputtering method, and then the signal electrode wiring 1 is formed by dry etching.
02 and the pixel electrode wiring 104 were patterned. At this time, at the same time, the second common electrode wiring 106 was formed so as to mate with the pixel electrode wiring 104 so as to be electrically short-circuited with the first common electrode wiring 103. Reference numeral 105 denotes a thin film transistor element which is a switching element.

In this embodiment, the line width of the pixel electrode wiring 104 and the second common electrode wiring 106 is 5 μm.
Further, the additional capacitance portion 107 is formed in the pixel electrode wiring 104 with the scanning electrode wiring 101. Additional capacitance unit 107
Was formed between the scanning electrode wiring 101 corresponding to one line before and the scanning electrode wiring 101 corresponding to that,
Alternatively, it may be formed between the first common electrode wiring 103 and the first common electrode wiring 103 and is not particularly limited.

Next, the pixel electrode wiring 104 and the second common electrode wiring are provided between the thin film transistor array substrate shown in FIGS. 1 and 2 and the counter substrate formed with the red, green and blue color filters. The operation and characteristics of the liquid crystal display element sandwiching the liquid crystal layer oriented between 5 ° and 15 ° with respect to the longitudinal direction of 106 will be described in detail.

As shown in FIGS. 1 and 2, a signal potential is supplied from the signal electrode wiring 102 to the pixel electrode wiring 104 while the thin film transistor element 105 is on. After that, in a state where the thin film transistor element 105 is deselected (OFF), the potential of the pixel electrode wiring 104 is set to the additional capacitance portion 1 formed between the pixel electrode wiring 104 and the scanning electrode wiring 101 one line before.
07, a horizontal electric field is generated between the second common electrode wiring 106 and the second common electrode wiring 106. Depending on the magnitude of the electric field intensity, the alignment direction of the liquid crystal molecules is deformed in the main plane, and as a result, the polarization state of the incident light changes.

In the structure of this embodiment, the pixel electrode wirings 104 and the second common electrode wirings 106 that interlock with each other are arranged in the same layer and on the surface which is in contact with the liquid crystal layer including the alignment film. Compared with the general configuration in which the common electrode wiring is arranged in the lower layer of the insulating layer, the electric field strength supplied to the liquid crystal layer when the same potential is applied becomes larger,
It becomes possible to operate at a low voltage. FIG. 3 shows the measurement results of the voltage-transmittance characteristic of each liquid crystal display element of the conventional configuration (shown by a broken line) and this embodiment (shown by a solid line). It can be seen that in the liquid crystal display element of the present embodiment, the voltage can be lowered by about 0.5 (V) in the maximum transmittance portion as compared with the conventional configuration.

Further, it has been found that, as a great effect on the characteristics of the liquid crystal display device having the structure of this embodiment, the resistance to the burning phenomenon can be greatly improved. As described above, the image sticking phenomenon in a liquid crystal display element is a kind of afterimage in which when a fixed pattern such as a window is continuously displayed on a liquid crystal panel for a certain period of time, the previous display pattern remains for a certain period of time even after the display pattern is changed. This is a phenomenon peculiar to liquid crystal panels.

Further, in the liquid crystal display device of the conventional structure and the structure of the present embodiment, after a black window pattern is displayed on a white background for a certain period of time, until the image sticking phenomenon occurs when the entire surface is displayed in halftone. As a result of the evaluation of the time, it was confirmed that the occurrence time was not observed for 5 hours or more in this structure, compared with the occurrence time in the conventional structure of about 30 minutes. Although the degree of occurrence of the above-mentioned baking phenomenon varies depending on the material system such as the liquid crystal material and the alignment film, the baking occurrence time is improved about 5 to 10 times that of the conventional configuration for any material system. I confirmed that I can do it.

In the conventional structure, since the insulating layer is provided on at least one of the pixel electrode and the common electrode, polarization easily occurs at the interface between the insulating layer and the alignment film, so that the burning phenomenon occurs. It will be easier. On the other hand, in the structure of the present invention, since there is no insulating layer on the electrodes, polarization is less likely to occur, and as a result, the baking phenomenon can be greatly improved. (Second Embodiment) Next, the liquid crystal display element of the second embodiment will be described in detail.

4 and 5 are a schematic plan view and a schematic sectional view showing the structure of the thin film transistor array substrate in the liquid crystal display element according to the second embodiment. In FIGS. 4 and 5, reference numeral 101 denotes scanning electrode wirings respectively. In this embodiment, a metal thin film containing aluminum as a main component is formed and a shape as shown in the drawing is formed by a photolithography method. . The metal material used for the scan electrode wiring 101 is not particularly limited to an aluminum-based metal, and either a single layer film or a multilayer film may be used.

Next, aluminum / titanium (Al / Ti) is formed by stacking the anodic oxide layer and silicon nitride (SiNx) of the above aluminum film as an insulating film and amorphous silicon as a semiconductor layer, and depositing them by a sputtering method. After depositing these two layers, the signal electrode wiring 102 and the first pixel electrode wiring 404 were patterned by dry etching. At this time, at the same time, the additional capacitance electrode 407 serving as an additional capacitance was arranged between the scan electrode wiring 101 and the electrode. Reference numeral 105 denotes a thin film transistor element which is a switching element. Then, the planarization layer 408
Is formed on the entire surface, a part of the planarization layer 408 on the first pixel electrode wiring 404 and the additional capacitance electrode 407 is removed, and finally, a metal thin film is formed and patterned to form the second pixel. Electrode wiring 409 and common electrode wiring 403
Were formed to occlude each other. At this time,
The second pixel electrode wiring 409 is configured to electrically short-circuit the additional capacitance electrode 407 and the first pixel electrode wiring 404. Second pixel electrode wiring 409 and common electrode wiring 40
The line width of 3 was 5 μm.

In the configuration of this embodiment, the common electrode wiring 4
03 can be formed on the scan electrode wiring 101,
It is possible to increase the aperture ratio of a region that transmits light in the pixel region, that is, a pixel portion.

Also in the structure of the present embodiment, as in the structure shown in the first embodiment, there is no insulating layer on the electrodes that mesh with each other. It was possible to confirm the same result as in the first embodiment.

[0035]

As described above, according to the present invention, an increase in drive voltage, which was conventionally required to obtain a wide viewing angle characteristic in a display image when using an in-plane switching display system, is generated. It is possible to suppress the burning phenomenon which has become easy.

Therefore, with respect to the display image when the horizontal electric field driving method is used, it is possible to widen the field of view and obtain good multi-gradation display, and to improve the display quality.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of a liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the liquid crystal display element according to the first embodiment.

FIG. 3 is an explanatory diagram of voltage-transmittance characteristics of the liquid crystal display element according to the first embodiment.

FIG. 4 is a plan view showing a configuration of a liquid crystal display element according to Embodiment 2 of the present invention.

FIG. 5 is a sectional view showing the configuration of the liquid crystal display element according to the second embodiment.

FIG. 6 is a cross-sectional view showing a configuration of a conventional horizontal electric field driving type liquid crystal display element.

[Explanation of symbols]

101 Scan electrode wiring 102 signal electrode wiring 103 first common electrode wiring 104 Pixel electrode wiring 105 thin film transistor element 106 Second common electrode wiring 107 Additional capacity section 403 common electrode wiring 404 First pixel electrode wiring 407 Additional capacitance electrode 408 Planarization layer 409 Second pixel electrode wiring

Continuation of front page (56) Reference JP-A-7-181439 (JP, A) JP-A-7-128683 (JP, A) JP-A-10-232411 (JP, A) JP-A-10-186391 (JP , A) JP-A-9-258242 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/1343 G02F 1/1362 G02F 1/1333 G09F 9/30

Claims (6)

(57) [Claims] 1. A plurality of scan electrode wirings and signal electrode wirings arranged in a matrix on a main plane of a first glass substrate, and a plurality of scan electrode wirings and signal electrode wirings arranged corresponding to respective intersections of the scan electrode wirings and the signal electrode wirings. a picture element electrode wirings, and switching elements electrically connected between the scan electrode lines and the signal electrode lines and the pixel electrode wiring, the pixel electrode wiring
And a voltage substantially parallel to the main plane of the first glass substrate.
And a first glass substrate on which a common electrode wiring configured to generate a field and an alignment film layer for controlling the alignment direction of liquid crystal molecules are formed, and the alignment film layer is formed on the surface thereof. a liquid crystal layer sandwiched, wherein the switching element is controlled and driven by a driving signal to the scan electrode lines and the signal electrode lines, to generate a substantially parallel electric field with the previous SL first principal plane of the glass substrate at a yo is, a liquid crystal display device for controlling the optical characteristics of the liquid crystal layer, a common electrode wiring and the pixel electrode wire, constituted by arranging so as to be in contact with the alignment film layer, the common electrode line With aluminum as the main component
Of the common electrode wiring and the first common electrode wiring electrically
A second short circuit which is short-circuited and formed in the same layer as the pixel electrode wiring
A liquid crystal display device, characterized in that the liquid crystal display device is composed of through electrode wiring . 2. A plurality of scan electrode wirings and signal electrode wirings arranged in a matrix and a plurality of scanning electrode wirings and signal electrode wirings arranged in a matrix on the main plane of the first glass substrate and corresponding to respective intersections of the scan electrode wirings and the signal electrode wirings. a picture element electrode wirings, and switching elements electrically connected between the scan electrode lines and the signal electrode lines and the pixel electrode wiring, the pixel electrode wiring
And a voltage substantially parallel to the main plane of the first glass substrate.
And a first glass substrate on which a common electrode wiring configured to generate a field and an alignment film layer for controlling the alignment direction of liquid crystal molecules are formed, and the alignment film layer is formed on the surface thereof. a liquid crystal layer sandwiched, wherein the switching element is controlled and driven by a driving signal to the scan electrode lines and the signal electrode lines, to generate a substantially parallel electric field with the previous SL first principal plane of the glass substrate at a yo is, a liquid crystal display device for controlling the optical characteristics of the liquid crystal layer, the metal layer and the scanning electrode wiring consisting mainly of aluminum
In formed, a common electrode wiring and the pixel electrode wiring, and constituted by arranging on the same plane, the pixel electrode wiring and the common electrode lines, the first moth
In front of the scan electrode wiring formed on the main plane of the lath substrate
The signal electrode wiring and the switching element should be covered.
A liquid crystal display element, which is formed on an insulating layer formed as described above . 3. A pixel electrode wiring and an electrode wiring are provided with an alignment film layer.
The liquid crystal display element according to claim 2, wherein the liquid crystal display element is formed so as to come into contact with the . 4. A pixel electrode comprising: a first pixel electrode;
It is electrically shorted to the pixel electrode of No. 1 and has the same level as the common electrode wiring.
3. A second pixel electrode formed on the surface
Alternatively, the liquid crystal display element according to the item 3. 5. The scan electrode and the first pixel electrode are electrically connected to each other.
An additional capacitance is formed between the short-circuited additional capacitance electrode
The liquid crystal display element according to claim 4 . 6. A first pixel electrode is formed at the same time when it is formed.
The liquid crystal display element according to claim 5, wherein a capacitance electrode is formed.