JP3993263B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that displays an image or the like, and relates to a liquid crystal display device that can ensure an appropriate capacity and ensure an accurate operation of a thin film transistor and has a high aperture ratio.
[0002]
[Prior art]
Liquid crystal display devices are widely used as display devices that can be reduced in weight, size, and thickness. Among them, twisted nematic mode (TN mode) active matrix liquid crystal display devices have low driving voltage and low power consumption. In addition, it is widely known as a display device with high contrast and high image quality.
[0003]
This type of general TN-mode liquid crystal display element is formed by opposing two glass substrates having a polarizing plate, a transparent electrode, and an alignment film with an interval such that the alignment directions of the alignment films are different from each other by 90 °. The nematic liquid crystal is arranged so as to be twisted by 90 ° between them.
[0004]
However, in recent years, in this type of TN mode liquid crystal display element, the viewing angle dependency has become a problem. FIG. 7 shows a general viewing angle dependency of a TN mode liquid crystal display element, and a hatched portion in FIG. 7 indicates a range where the contrast (CR) is 10 or more. According to FIG. 7, it is clear that the TN mode liquid crystal display element has good visibility from the left and right directions, but extremely low visibility from the vertical direction, particularly from the upper direction.
[0005]
Therefore, the present applicant has previously filed a patent application in Japanese Patent Application No. 7-306276 for a liquid crystal display element having a structure capable of solving such problems.
According to the technologies according to these patent applications, two types of linear electrodes having different poles are provided only on the lower substrate 11 shown in FIG. 8 instead of providing the electrodes for driving the liquid crystal on the upper and lower substrates sandwiching the liquid crystal. .., 13... Are separated from each other, and no electrode is provided on the upper substrate 10 as shown in FIG. 9, and in the direction of the transverse electric field generated between the two linear electrodes 12 and 13 by application of voltage. The liquid crystal molecules 36... Can be aligned along.
[0006]
More specifically, the linear electrodes 12 are connected at the base line portion 14 to form a comb-blade electrode 16, and the linear electrodes 13 are connected at the base line portion 15 to form a comb-blade electrode 17 Then, the linear electrodes 12 and 13 of the comb-shaped electrodes 16 and 17 are alternately arranged adjacent to each other so as not to contact each other, and the power source 18 and the switching element 19 are connected to the base line portions 14 and 15. Composed.
Further, as shown in FIG. 10A, an alignment film is formed on the liquid crystal side surface of the upper substrate 10 and subjected to an alignment treatment so that the liquid crystal molecules 36 are aligned in the β direction. An alignment film is formed on the surface of the liquid crystal side of the substrate, and an alignment process is performed so that the liquid crystal molecules 36 are aligned in the γ direction parallel to the β direction. The substrate 10 is aligned in the β direction of FIG. A polarizing plate having a polarization direction is laminated on the substrate 11 and a polarizing plate having a polarization direction in the α direction is laminated thereon.
[0007]
According to the above configuration, the liquid crystal molecules 36... Are uniformly distributed in the same direction as shown in FIGS. 10 (a) and 10 (b) when no voltage is applied between the linear electrodes 12 and 13. Orient. The light beam that has passed through the lower substrate 11 in this state is polarized in the α direction by the polarizing plate, passes through the liquid crystal molecule 36 as it is, and reaches the polarizing plate in the different polarization direction β of the upper substrate 10. Therefore, since the light is blocked by the polarizing plate and the light beam does not pass through the liquid crystal display element, the liquid crystal display element is in a dark state.
Next, when a voltage is applied between the linear electrodes 12 and 13, among the liquid crystal molecules, the orientation direction of the liquid crystal molecules 36 that are closer to the lower substrate 11 is converted to be perpendicular to the longitudinal direction of the linear electrode 12. The That is, the electric field lines perpendicular to the longitudinal direction are generated by the transverse electric field generated by the linear electrodes 12 and 13, and the longitudinal direction is directed in the γ direction by the alignment film formed on the lower substrate 11. As shown in FIG. 11A, the liquid crystal molecules 36 that have been aligned are converted into the α direction perpendicular to the γ direction by the electric field regulating force stronger than that of the alignment film.
Therefore, when a voltage is applied between the linear electrodes 12 and 13, 90 ° twist orientation is achieved as shown in FIGS. 11 (a) and 11 (b). In this state, the polarized light beam transmitted through the lower substrate 11 and polarized in the α direction is converted by the twisted liquid crystal 36, and a polarizing plate having a β direction different from the α direction is provided. The upper substrate 10 can be transmitted, and the liquid crystal display element is in a bright state.
[0008]
By the way, the structure assumed when the structure of the liquid crystal display device provided with the linear electrodes 12 and 13 of the said structure is applied to an actual active matrix liquid crystal drive circuit is shown in FIG. 12 and FIG.
The structure shown in FIGS. 12 and 13 shows only a portion corresponding to one pixel. In the structure of this example, a gate electrode 21 made of a conductive layer and a first linear shape on a transparent substrate 20 such as a glass substrate. Electrodes 22 and 22 are spaced apart and formed in parallel, and a gate insulating layer 24 is formed so as to cover them, and a semiconductor film 26 is sandwiched between the one side and the other side on the gate insulating layer 24 on the gate electrode 21. A thin film transistor T is formed by providing a source electrode 27 and a drain electrode 28, and a second linear electrode 29 made of a conductive layer is formed on the gate insulating film 24 above the middle of the first linear electrodes 22 and 22. Is provided.
[0009]
12 shows the planar structure of the electrodes, the gate wirings 30... And the signal wirings 31... Assembled in a matrix are formed on the transparent substrate 20, and the gate wirings 30. Each rectangular region surrounded by the signal wirings 31 is a pixel, and a gate electrode 21 formed of a part of the gate wiring 30 is formed at a corner of the pixel region. A drain electrode 28 on the gate electrode 21 is formed. The second linear electrode 29 is connected in parallel to the signal wiring 31 via the capacitive electrode portion 33, and the second linear electrode 29 is parallel to the second linear electrode 29 so as to sandwich both sides of the second linear electrode 29. One linear electrode 22, 22 is arranged in a plane.
[0010]
The first linear electrodes 22, 22 are connected by a connection wiring 34 provided in the pixel region in parallel to the gate wiring 30 at the end near the gate wiring 30, and the gate wiring 30 at the other end. Are connected by a common electrode 35 provided in parallel. The common electrode 35 is provided in parallel to the gate wiring 30 over a large number of pixel regions, and is used to apply a common potential to the linear electrodes 22 and 22 provided for each pixel region. is there. Further, one end side of the second linear electrode 29 extends to above the common electrode 35, and a capacitive electrode portion 36 located on the common electrode 35 in the pixel region is provided at the tip of the second linear electrode 29. ′ Is formed, and the capacitive electrode portion 33 on the other end side of the second linear electrode 29 is positioned on the connection wiring 34. These capacitor electrode portions 33 and 36 constitute a capacitor by sandwiching the insulating layer 24 between the connection wiring 34 and the common electrode 35 located below them, and stabilize the operation of the thin film transistor T when driving the liquid crystal. It is for making it.
[0011]
In the structure of the example shown in FIGS. 12 and 13, a horizontal electric field can be applied so as to form electric lines of force in the direction indicated by the arrow a in FIG. As shown in FIG. Accordingly, display non-display can be switched by controlling the orientation of the liquid crystal as in the case described above with reference to FIGS.
[0012]
[Problems to be solved by the invention]
However, the liquid crystal display device having the above-described structure has an advantage that a viewing angle is wide when a practical display device is assumed by designing a circuit for actually driving the liquid crystal. The problem is that the aperture ratio tends to be small.
That is, in the structure shown in FIG. 12 and FIG. 13, in order to stabilize the driving of the thin film transistor T, a capacitor formed by sandwiching the insulating layer 24 between the capacitor electrode portion 33 and the connection wiring 34, and a capacitor electrode portion 36 ′ And the common electrode 35, it is necessary to secure a certain amount of capacitance formed by sandwiching the insulating layer 24. Therefore, instead of the shape shown in FIG. It is necessary to form the widths 35 and 36 'larger than the size shown in FIG. When such a structure is employed, the areas of the common electrode 33, the connection wiring 34, the common electrode 35, and the capacitor electrode portion 36 ′ occupying the pixel region are increased, which causes a problem that the aperture ratio tends to decrease. It was.
Here, the problem that the aperture ratio is small can be compensated by adjusting the brightness of the backlight provided in the liquid crystal display device.
However, since this improvement measure is premised on sacrificing power consumption, there is a problem that the power consumption of the liquid crystal display device cannot be reduced.
[0013]
The present invention has been made in view of the above circumstances, and has a large aperture ratio while realizing stable driving of a thin film transistor while maintaining high viewing angle characteristics in a configuration in which liquid crystal is driven by a lateral electric field along the substrate surface. An object of the present invention is to provide a liquid crystal display device that can be used.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a liquid crystal disposed between a pair of substrates, and a plurality of pixel electrodes on the one substrate and the liquid crystal in cooperation with each of the plurality of pixel electrodes. A common electrode for applying an electric field in a direction along the plane is formed so as to form a plurality of pixel regions, and the common electrode is overlapped with the pixel electrode so as to form a capacitance in cooperation with the pixel electrode. It is made to have.
In the present invention, the pixel electrode is provided inside each of the plurality of pixel regions, the common electrode that defines each of the pixel regions is opposed to the pixel electrode, and the capacitance forming electrode portion is provided. It is provided inside the common electrode.
Since the electric field can be applied in the direction along the substrate surface by the common electrode and the pixel electrode provided on the substrate, the alignment of the liquid crystal can be controlled by applying or not applying the electric field, thereby switching display non-display. it can. Since the capacitance forming electrode portion is provided on the common electrode, the capacitance can be formed in cooperation with the pixel electrode.
[0015]
Further, according to the present invention, each electrode in the overlapping portion of the pixel electrode and the capacitance forming electrode portion is formed in a strip shape, and the width of the pixel electrode in the overlapping portion is larger than the width of the capacitance forming electrode portion. It is characterized by that.
Since the capacitance forming electrode portion is hidden by the pixel electrode because the width of the pixel electrode in the overlapped portion is larger than the width of the capacitance forming electrode portion, the aperture ratio may decrease due to the provision of the capacitance forming electrode portion. In other words, the effect of providing the capacitance forming electrode portion does not affect the liquid crystal.
[0016]
Furthermore, the present invention is characterized in that the common electrode is provided on the one substrate, and the pixel electrode is provided above the common electrode.
With this configuration, the pixel electrode can be provided close to the liquid crystal, and the effective voltage effective for driving the liquid crystal can be increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of the present invention will be described with reference to the drawings.
1 and 2 show the main part of the liquid crystal display device according to the present invention. In the drawing of FIG. 2, the upper substrate 40 and the lower substrate 41 have a predetermined gap (cell gap) between each other. The liquid crystal layer 42 is provided between the substrates 40 and 41, and the polarizing plates 43 and 44 are disposed on the outer surface side of the substrates 40 and 41.
These substrates 40 and 41 are made of a transparent substrate such as glass. However, in the actual configuration, the peripheral portions of the substrates 40 and 41 are surrounded by a sealing material (not shown) and are surrounded by the substrates 40 and 41 and the sealing material. A liquid crystal layer 42 is formed by storing liquid crystal in a space, and a liquid crystal cell 45 is configured by combining the substrates 40 and 41, the liquid crystal layer 42, and the polarizing plates 43 and 44.
[0018]
In the structure of this example, a plurality of gate wirings 50 and signal wirings 51 are formed in a matrix on the transparent substrate 41, and the region surrounded by the gate wirings 50... And signal wirings 51. The common electrodes 53 and 53 and the pixel electrode 54 are arranged in parallel to each other.
More specifically, a plurality of gate lines 50 are formed on the substrate 41 in parallel with each other at a predetermined interval, and the common lines are formed on the substrate 41 along the gate lines 50 on the same plane as the gate lines 50. 56 are juxtaposed, and common electrodes 53 and 53 comprising two linear electrodes extend from the common wiring 56 at right angles to each region surrounded by the gate wiring 50... And the signal wiring 51. The tip ends of these two common electrodes 53 and 53 are connected by a connection wiring 57 in the vicinity of the other adjacent gate wiring 50, and the common wiring 56 and the connection wiring 57 are arranged in the middle of the two common electrodes 53 and 53. A band-shaped capacitance forming electrode portion 55 connected to the electrode is provided.
In the entire liquid crystal cell 45, as many gate wirings 50 and signal wirings 51 as necessary for the liquid crystal display device are arranged, and common electrodes 53 and 53 are provided so as to partition both sides of the region partitioned by these. However, FIG. 1 shows only a planar structure of a portion corresponding to two adjacent gate lines 50 and signal lines 51. Therefore, in other words, a plurality of pixel electrodes 54 and a plurality of common electrodes 53 are provided on the substrate 41 so as to define a plurality of pixel regions 59.
[0019]
Then, an insulating layer 58 is formed on the substrate 41 so as to cover them, and each signal wiring 51 is formed on the insulating layer 58 so as to form a matrix shape orthogonal to the respective gate wirings 50 in plan view. The gate electrode 60 is a portion in the vicinity of the intersection with the signal wiring 51. On the insulating layer 58 on the gate electrode 60, the source electrode 62 and the drain electrode in a state where the semiconductor film 61 is sandwiched from one side to the other side. 63 is provided to constitute a thin film transistor (switching element) T. Further, the pixel electrode 54 is disposed on the insulating layer 58 on the capacitor forming electrode portion 55, and the capacitor is configured by sandwiching the insulating layer 58 between the pixel electrode 54 and the capacitor forming electrode portion 55.
[0020]
Next, the source electrode 62 is connected to the source wiring 51, and the drain electrode 63 is connected to a capacitance electrode 64 provided on the insulating layer 58 on the connection wiring 57. A pixel electrode 54 extends from the central portion of the pixel electrode 54 in parallel with the common electrode 53, and the tip end side of the pixel electrode 54 is connected to a capacitor electrode 65 formed on the insulating layer 58 on the common wiring 56. Is covered with a covering layer 66 as shown in FIG.
In this example, the common wiring 56 is formed thinner than the connection wiring 57, the pixel electrode 54 is formed thinner than the common wiring 56, and the common electrode 53 is formed slightly narrower than the pixel electrode 54, thereby forming a capacitor. The electrode portion 55 is formed slightly thinner than the pixel electrode 54.
The common electrodes 53 and 54 used in this example may be formed of either a light-shielding metal electrode or a transparent electrode. However, when adopting a normally black type display mode described later, ITO (indium A transparent electrode made of tin oxide) is preferable.
[0021]
Further, in the liquid crystal display device of this example, alignment films (not shown) are provided on the liquid crystal layer 42 side of the lower substrate 41 and the liquid crystal layer 42 side of the upper substrate 40, respectively. Orientation treatment is performed in a direction substantially parallel to the length direction of 53.
That is, the liquid crystal molecules of the liquid crystal layer 42 existing between the substrates 40 and 41 are in a state in which their major axes are parallel to the length direction of the common electrode 53 in a state where no electric field is applied. It is designed to be homogenous.
[0022]
In the structure of this example, the direction of the polarization axis of the upper polarizing plate 43 is directed in the direction parallel to the length direction of the common electrode 53 (the direction of arrow E in FIG. 1), and the polarization axis of the lower polarizing plate 44 The direction is directed in the direction perpendicular to the length direction of the common electrode 53 (the direction of arrow F in FIG. 1). 2 is a black matrix. The black matrix 67 covers a portion of the thin film transistor T that does not contribute to display, a portion of the gate wiring 50, a portion of the signal wiring 51, and the like.
In addition, in the structure of the liquid crystal display device shown in FIGS. 1 and 2, the color filter necessary for color display is omitted, but the color filter on the substrate 40 side when the structure for performing color display is used. Of course, each color region of the color filter red (R), green (G), and blue (B) is arranged for each pixel region 59 on the opposite substrate 41 side.
[0023]
In the structure according to the present invention, display is not displayed by switching whether or not to apply a voltage between the common electrodes 53 and 53 and the pixel electrode 54 in the desired pixel region 59 by the operation of the thin film transistor T which is a switching element. Can be used.
That is, by operating the thin film transistor T and applying a voltage between the common electrodes 53 and 53 provided in the pixel region 59 at a desired position and the pixel electrode 54, the substrate surface direction (lateral direction) in FIG. An electric field can be applied to the liquid crystal, whereby the liquid crystal molecules can be twisted by 90 ° between the upper and lower substrates (bright state) as in the case shown in FIG. Further, by not applying a voltage between the common electrodes 53 and 53 and the pixel electrode 54, the alignment treatment direction of the alignment film (β direction and γ direction) is the same as in the case shown in FIG. It can be in a state (dark state) that is homogeneously oriented in the same direction.
[0024]
Therefore, the alignment control of the liquid crystal molecules can be performed as described above. By introducing the light beam from the backlight provided on the lower side of the substrate 41, the light beam of the backlight is darkened by the alignment control state of the liquid crystal molecule. Can be switched to the bright state. In this example, the display form is black in the state where the alignment control of the liquid crystal molecules is not performed, and is in the bright state in the state where the alignment control of the liquid crystal molecules is performed. Therefore, the display form is referred to as normally black.
[0025]
Next, the capacitance electrodes 64 and 65 are provided, and the common wiring 56 and the connection wiring 57 are provided so as to be opposed to each other through the insulating layer 58, whereby a capacitance can be formed between them. Thus, part of the parasitic capacitance generated in the liquid crystal display device can be canceled, and the thin film transistor T can be stably operated. Further, in the structure of this example, a capacitance forming electrode portion 55 is provided below the pixel electrode 54 via the insulating layer 58, and a capacitance is also formed in these portions. Therefore, the structure shown in FIG. 1 can reduce the width of the capacitor electrode 65 in the case where the same capacity is secured as compared with the structure shown in FIG. Therefore, the area of the pixel region 59 can be increased by reducing the width of the capacitor electrode 65, and the aperture ratio can be made larger than the structure shown in FIG.
[0026]
Further, if the parasitic capacitance is reduced by adopting the above structure, a certain amount of capacitance can be secured in the overlap portion, so that the widths of the common electrode 53 and the pixel electrode 54 may be reduced. As a result, the aperture ratio can be improved by reducing the width of the pixel electrode 54. Therefore, a dark state and a bright state can be switched depending on the alignment state of the liquid crystal, and a liquid crystal display device having a small viewing angle dependency and a high aperture ratio can be provided.
[0027]
In addition, when the common electrodes 53 and 53, the pixel electrode 54, the capacitor forming electrode portion 55, and the capacitor electrodes 64 and 65 are formed of a transparent electrode film to form a normally black display mode, a voltage is applied to the pixel electrode 54. The liquid crystal molecules on the common electrodes 53 and 54 rise up in the same manner as in the case shown in FIG. 9, but this portion is also in a bright state that allows the light from the backlight to pass to some extent, so the common electrode 53 and the pixel electrode 54 The portion above the upper portion also contributes to the display, whereby the aperture ratio of the liquid crystal display element can be increased.
Furthermore, since the display is in a dark state when no voltage is applied to the pixel electrode 54, the liquid crystal state on the common electrode 53 and the pixel electrode 54 does not particularly adversely affect the dark state display.
Next, in the present embodiment, the pixel electrode 54 is located at the center of the pixel region 59 because the pixel electrode 54 is provided on the inner side of the pixel region 59 so that it is less affected by the electric field of the gate wiring 50 and the signal wiring 51. Placed in the department.
Further, the present embodiment is characterized in that common electrodes 53 and 53 are provided on the substrate 41, and the pixel electrode 54 is provided above the common electrodes 53 and 53.
With this configuration, the pixel electrode can be provided close to the liquid crystal, and the effective voltage that works effectively when the liquid crystal is driven can be increased.
[0028]
FIG. 3 shows another embodiment of the liquid crystal display device according to the present invention. In this embodiment, a pixel electrode 70 is provided on an insulating layer 58 on each common electrode 53, and these pixel electrodes 70 are provided as drain electrodes. 63, a common electrode 71 is provided in place of the capacitance forming electrode portion 55 of the previous form, and no electrode is provided on the insulating layer 58 on the common electrode 71. The other structure is the same as the structure of the previous embodiment, and the same parts are denoted by the same reference numerals and description thereof is omitted.
In this example, an electric field is generated between the pixel electrodes 70 and 70 and the common electrode 71, and the alignment of the liquid crystal can be controlled in the same manner as the structure of the previous embodiment. In the structure of this example, since the common electrode 53 also serves as a capacitance forming electrode portion, a capacitance can be formed between the pixel electrode 70 and the common electrode 53.
[0029]
Next, FIG. 4 shows another embodiment of the liquid crystal display device according to the present invention. In this embodiment, the pixel electrode 54 ′ is disposed obliquely with respect to the common electrode 53, and the capacitor is disposed under the pixel electrode 54 ′. It is characterized in that the formation electrode portion 55 ′ is arranged in parallel with the pixel electrode 54 ′. That is, the pixel region 59 is divided into two substantially triangular regions by the pixel electrode 54 ′. Further, since the pixel electrode 54 ′ is inclined with respect to the common electrodes 53, 53, a narrow space portion 72 is formed at a portion where the common electrodes 53, 53 and the pixel electrode 54 ′ approach each other.
[0030]
In the structure of this embodiment, since the narrow gap portion 72 is provided between the common electrodes 53 and 53 and the pixel electrode 54 ′, the common electrode 53 and the pixel electrode 54 ′ are generated in the narrow gap portion 72. The electric field to be generated is stronger than the other portions, and as a result that the liquid crystal can be driven strongly with a high voltage, the liquid crystal can be made to respond at high speed. Therefore, the liquid crystal in the region where the common electrodes 53, 54 ', 53 are provided can be made to respond at high speed without increasing the number of linear electrodes and without decreasing the aperture ratio. Further, by adopting the above structure, it is possible to increase the response speed as the brightness increases in the halftone display area, in other words, when the applied voltage is small.
This is because, in the display in the halftone display area, the human being is more sensitive to the response speed as it is brighter than dark, so by adopting the above structure, the response speed is improved in the bright display area of the halftone display area that is easy for humans to recognize. It means that you can speed up. In addition, since the ratio of humans who feel flicker (flicker) tends to be the same as in the case of halftone display, the use of the above structure can make flicker inconspicuous during halftone display.
[0031]
【Example】
Example 1
A thin film transistor type liquid crystal display device having a circuit having the structure shown in FIG. 1 was manufactured.
Using two transparent glass substrates, a thin film transistor circuit having the common electrode shown in FIG. 1 is formed on one of these substrates, an alignment film is formed thereon, and an alignment film is also formed on the other substrate. Each alignment film is subjected to alignment treatment for liquid crystal alignment by rubbing treatment, and two transparent substrates are arranged in a gap between the substrates with gap-forming beads arranged at predetermined intervals. Was bonded with a sealing material, and a polarizing plate was arranged outside the substrate to assemble a liquid crystal cell. In the above structure, each alignment film was subjected to an alignment treatment by rubbing a rubbing roll in a direction orthogonal to the length direction of the common electrode.
[0032]
In order to manufacture this device, a large number of gate wirings having a width of 10 μm and made of Cr were formed on a transparent substrate at intervals of 129 μm, and a common wiring made of Cr having a width of 16 μm was formed adjacent to each of the gate wirings. In this common wiring, a common electrode having a width of 6 μm is formed in a direction perpendicular to the common wiring so as to extend to both corners of each pixel region, and a Cr capacitor having a width of 3 μm is formed in the common wiring in the center of each pixel region. A forming electrode portion was formed.
[0033]
Next, cover them with SiN _x A pixel electrode made of Cr having a width of 4 μm was formed on the insulating layer made of the above and parallel to the common electrode at the center of the common electrode on both sides of each pixel region.
In addition, a thin film transistor having a structure in which a semiconductor film made of a-Si is sandwiched between a gate electrode and a source electrode is formed in the vicinity of a portion where a gate wiring and a signal wiring intersect, and these are covered with a covering layer, and further a polyimide-based orientation A film was formed, and an alignment treatment with a rubbing roll was performed to form a transistor array substrate.
[0034]
On the other hand, for comparison, a thin film transistor liquid crystal display device having a circuit having the structure shown in FIG.
As a result of measuring the aperture ratio for each liquid crystal display device formed as described above, the aperture ratio of 38% in the structure shown in FIG. 14 is 40.1% in the structure shown in FIG. It became clear that improved.
[0035]
(Example 2)
The basic structure is the same as that of the first embodiment, and a pixel electrode having a width of 3 μm made of chromium and inclined at an angle of 8.2 ° with respect to the common electrode formed on the substrate is connected to the drain electrode. Thus, a liquid crystal display device formed on the insulating layer was manufactured.
Next, for comparison, a liquid crystal cell having a structure in which linear electrodes are arranged in parallel to the linear electrodes as shown in FIG. 14 instead of the linear electrode structure shown in FIG. 4 is prepared as a comparative liquid crystal cell. However, the aperture ratio was improved in the structure shown in FIG. 4 than in the structure shown in FIG.
[0036]
Next, with respect to each of the obtained liquid crystal display devices, the applied voltage when the light transmittance is maximum is assumed to be 100%, and the transmittance at this time is set to 100%, and 90%, 50%, 10% V (0) ← → V (10) (transmission) when the voltages for the respective transmittances of% and 0% are V (90), V (50), V (10), and V (0), respectively. As a result of measuring the response speed between 0% and 10%, that is, it means that the response speed was measured by applying a voltage such that the transmittance becomes 0% and 10%. (0) ← → V (50) (result of applying the voltage while switching the transmittance to 0% and 50% and measuring the response speed), V (0) ← → V (90), The result of measuring each value of V (0) ← → V (100) is shown in FIG. In FIG. 5, the vertical axis represents the rise time (τ _r ) And fall time (τ _d ).
[0037]
As is clear from the results shown in FIG. 5, the response speed in the dark area (V (0) ← → V (10)) as the display is slower than that in the comparative example structure, but the halftone area (V (0) ← → V (50)) and bright areas (V (0) ← → V (90), V (0) ← → V (100)) must be faster than the comparative structure shown in FIG. Is clear. In particular, in the halftone region (V (0) ← → V (50)), the response time could be shortened to 72 msec while the comparative example structure was 91 msec. Moreover, the response time tends to be shorter as the overall brightness is increased.
[0038]
Next, FIG. 6 shows that the brightness of the liquid crystal display device and CFF (Critical Flicker Freqeqency: the maximum frequency at which a person sees flickering and feels flicker (flicker), that is, flicker is not felt at a frequency higher than CFF. ).
As shown in FIG. 6, the brighter the CFF is. That is, it can be seen that the brighter the human eye is, the faster it can follow the temporal change in luminance. From this, it is considered that the human eye is more sensitive to a temporal change in brightness faster as it is brighter and less sensitive as it is darker.
[0039]
Considering the result shown in FIG. 6 again based on the above consideration, if it has the structure of this embodiment and is a normally black type display mode, the response speed tends to increase as the brightness increases. From the human optical viewpoint, it is clear that it is improved as compared with the comparative example. That is, even if the effect of speed is small as an average speed, it is a more effective improvement for human eyes.
[0040]
Next, FIG. 15 shows a fourth embodiment of the liquid crystal display device according to the present invention. The connection wiring 57 is omitted from the structure shown in FIG. This is an example in which a structure in which 64 is omitted is employed, and the same effect as in the first embodiment can be obtained also in this structure.
16 shows a structure in which two common electrodes 53 are provided at both corners of one pixel area, and one pixel electrode 54 is provided on one common electrode 53. FIG. 17 shows both structures in one pixel area. This is an example in which common electrodes 53 and 53 are provided at the corners, and three pixel electrodes 54 are provided at both corners and the center of one pixel region. In these structures, the same effect as in the first embodiment is provided. Can be obtained.
[0041]
【The invention's effect】
As described above, according to the present invention, since the electric field can be applied in the direction along the substrate surface by the common electrode and the pixel electrode provided on the substrate, the alignment of the liquid crystal is controlled by applying or not applying the electric field. A state and a dark state can be switched, and thereby, display non-display can be switched. In addition, since the capacitance forming electrode portion is provided in the common electrode, the capacitance can be formed in cooperation with the pixel electrode, and the switching element can be stably operated when the application of the lateral electric field is switched by the switching element. it can.
Further, according to the present invention, the liquid crystal is homogeneously aligned while being parallel to the substrate, or the liquid crystal is aligned so as to be twisted between the pair of substrates, so that the long axis of the liquid crystal molecules is always oriented in the direction parallel to the substrate Since the bright state and the dark state are switched by the rotation of the molecules, the long axis of the liquid crystal is not raised, and thus a liquid crystal display device having high viewing angle characteristics can be provided.
Therefore, it is possible to provide a liquid crystal display device having high viewing angle characteristics and stabilizing the operation of the switching element.
[0042]
Next, in the present invention, since the pixel electrode and the capacitance forming electrode portion overlap each other so that the pixel electrode width is larger than the capacitance forming electrode portion, the capacitance forming electrode portion is hidden by the pixel electrode. The aperture ratio is not lowered due to the provision of the capacitance forming electrode portion, and the influence of the provision of the capacitance forming electrode portion can be prevented from affecting the liquid crystal.
Therefore, it is possible to provide a liquid crystal display device having a high aperture ratio, high viewing angle characteristics, and stable operation of the switching element.
[0043]
In the present invention, the common electrode is provided on one substrate, and the pixel electrode is provided above the common electrode, so that the pixel electrode can be provided close to the liquid crystal, which effectively works for driving the liquid crystal. The effective voltage can be increased and low voltage driving can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an electrode arrangement structure of a first embodiment of a liquid crystal display device according to the present invention.
FIG. 2 is a diagram showing a cross-sectional structure of the first example.
FIG. 3 is a diagram showing a cross-sectional structure of a second embodiment of the liquid crystal display device according to the present invention.
FIG. 4 is a diagram showing an electrode arrangement structure of a third embodiment of the liquid crystal display device according to the present invention.
FIG. 5 is a plan view showing the relationship between the applied voltage and the response speed obtained in each of the liquid crystal display devices of the example and the comparative example.
FIG. 6 is a diagram showing a relationship between light intensity and flicker.
FIG. 7 is a diagram showing a general viewing angle dependency of a TN mode liquid crystal display element;
FIG. 8 is a plan view of a substrate provided with linear electrodes described in the specification of a patent application previously filed.
FIG. 9 is a cross-sectional view showing the alignment state of liquid crystal molecules when a voltage is applied to a linear electrode.
FIG. 10A is a diagram showing a dark state liquid crystal array described in the specification previously filed, and FIG. 10B is a side view of FIG. 10A.
11A is a diagram showing a liquid crystal array in a bright state described in the specification of a patent application previously filed, and FIG. 11B is a side view of FIG. 11A.
FIG. 12 illustrates an example of a cross-sectional structure of a liquid crystal display element.
13 is a plan view of the structure shown in FIG.
14 is a plan view showing an arrangement example of linear electrodes having the structure shown in FIG. 13;
FIG. 15 is a diagram showing a fourth embodiment of a liquid crystal display device according to the present invention.
FIG. 16 is a diagram showing a fifth mode of a liquid crystal display device according to the present invention.
FIG. 17 is a diagram showing a sixth embodiment of a liquid crystal display device according to the present invention.
[Explanation of symbols]
40, 41 substrate
42 Liquid crystal layer
43, 44 Polarizing plate
45 Liquid crystal cell
50 Gate wiring
51 Signal wiring
53 Common electrode
54 Pixel electrode
55 Capacitance forming electrode section
56 Common wiring
57 Connection wiring
58 Insulation layer
64, 65 capacitive electrode

Claims (6)

A substrate,
A gate line and a signal line that intersect with each other on the substrate and define a pixel region;
A plurality of common electrodes parallel to the signal wiring in the pixel region, and a parallel pixel electrode to the common electrode in the pixel region, in order to form a capacitor in between these common electrodes and the pixel electrodes, the pixel An electrode is superimposed on at least one of the plurality of common electrodes;
Each electrode in the overlapping portion of the pixel electrode and the capacitance forming electrode portion is formed in a band shape, and the width of the pixel electrode in the overlapping portion is larger than the width of the capacitance forming electrode portion Liquid crystal display device.   The pixel electrode is provided inside each of the plurality of pixel regions, the common electrode that defines each of the pixel regions in opposition to the pixel electrode is provided, and the capacitance forming electrode portion is the common electrode The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided inward of the liquid crystal display.   The liquid crystal display device according to claim 1, wherein the common electrode is provided on the one substrate, and the pixel electrode is provided above the common electrode. The plurality of common electrodes having three linear electrodes including a capacitance forming electrode, wherein the pixel electrode is overlapped with a central electrode of the three linear electrodes including the capacitance forming electrode. Liquid crystal display device. 2. A plurality of common electrodes having three linear electrodes including a capacitance forming electrode, wherein the three common electrodes and the pixel electrode are overlapped with the two common electrodes except for the capacitance forming electrode. Liquid crystal display device. A substrate,
A gate line and a signal line that intersect with each other on the substrate and define a pixel region;
A plurality of common electrodes parallel to the signal wiring in the pixel region, wherein it is the common electrode and electrically connected to the pixel region, and the oblique capacitor forming electrode portions on the signal line,
In the pixel region, it is superimposed on the capacitance forming electrode portions, have a parallel pixel electrode on the capacitor forming electrode portions,
Each electrode in the overlapping portion of the pixel electrode and the capacitance forming electrode portion is formed in a band shape, and the width of the pixel electrode in the overlapping portion is larger than the width of the capacitance forming electrode portion. a liquid crystal display device.

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