JPH08334785A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display element having simple constitution, a high yield rate and a wide visual field angle. CONSTITUTION: Pixel electrodes are formed on a TFT substrate and first counter electrodes 31A and second counter electrodes 31B are formed on a counter substrate 12. Control capacitors CX formed on the outer side of a display region are connected to one of the second counter electrodes 31B. Driving voltage is dropped by the control capacitors CX and is impressed on the liquid crystals between the second counter electrodes 31B and the pixel electrodes. The driving voltage is impressed nearly as it is on the liquid crystals between the first counter electrodes 31A and the pixel electrodes. Then, the domains different in orientation states are formed within respective pixels and the visual field angle is widened.

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 having a wide viewing angle.

[0002]

2. Description of the Related Art Liquid crystal display devices can be made thin and lightweight and are used as display devices for various electronic devices.
However, the liquid crystal display element has a drawback that the viewing angle is narrower than that of a CRT or the like, and that the viewing angle dependency during halftone display is remarkable. For example, in a TN liquid crystal display element configured by sandwiching a TN (twisted nematic) liquid crystal cell between a pair of polarizing plates, it has a practically sufficient viewing angle in black and white binary display, but has a viewing angle in multi-gradation display. It has the drawback of being small (narrow).

As a method of widening the viewing angle, each pixel electrode on a substrate on which a TFT is formed is divided into a plurality of sub-pixel electrodes, and a control capacitor electrode facing the sub-pixel electrode is arranged so that the liquid crystal capacitance is increased. A method of connecting a control capacitor for voltage drop in series has been proposed. In this method, the voltage applied to the liquid crystal is made different for each sub-pixel electrode,
Regions having different alignment states can be formed in each pixel region, and the viewing angle can be widened.

FIGS. 10 and 11 show the applied voltage (V) of a normal pixel (pixel without a control capacitor), a voltage drop pixel (a pixel with a control capacitor), and a voltage drop pixel formed by the above method and transmission. The relationship with the rate (T) is shown. FIG. 10 shows V- when the liquid crystal display device is viewed from the front.
11 shows the T characteristic, and FIG. 11 shows the VT characteristic when the liquid crystal display device is viewed from 50 ° downward. The solid line is the normal pixel V-
The T characteristic is shown, the broken line shows the VT characteristic of the voltage drop pixel connected to the control capacitor, and the alternate long and short dash line shows the VT characteristic of the entire pixel.

As shown in FIG. 10, when the liquid crystal display device is viewed from the front, the VT characteristic of a normal pixel shows a monotonically decreasing function in which the transmittance decreases as the applied voltage V increases, and the control capacitance is reduced. The connected voltage drop pixels exhibit a similar monotonic decreasing function at a voltage higher than the applied voltage of the normal pixel. The display characteristic when the pixel is divided into a plurality of pixels is determined by the area average of the display characteristics of the divided pixels, and is monotonically decreased as shown by the alternate long and short dash line between the VT characteristic of the normal pixel and the VT characteristic of the voltage drop pixel. The function has a display characteristic of one pixel. Therefore, when the liquid crystal display element is viewed from the front, no grayscale inversion occurs.

Further, as shown in FIG. 11, when the liquid crystal display device is viewed from a downward direction of 50 °, the VT characteristics of the normal pixel and the voltage drop pixel are shown in FIG. Shows a bump characteristic that fluctuates up and down.
Showing the bump characteristic means that the gradation is inverted between adjacent gradations. However, since the VT characteristics of the normal pixel and the voltage drop pixel are averaged, the respective bumps are canceled out, and the VT characteristics of each pixel become a monotonically decreasing function as shown by the alternate long and short dash line, and the grayscale inversion occurs. Is prevented.

[0007]

In the above method, the control capacitor electrode must be formed in the process of forming the TFT, which complicates the manufacturing process and easily causes defects in the TFT. Moreover, since a large number of pixel electrodes are divided, defects in the pixel electrodes are likely to occur. Therefore, T
There is a drawback that the yield of the FT substrate, and eventually the liquid crystal display device, is reduced. Further, since the control capacitor electrode is formed in the display area (area where the pixel matrix is formed), there is a drawback that the display becomes dark due to absorption and scattering of light by the control capacitor electrode.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device having a high yield rate, high display image quality, and a wide viewing angle.

[0009]

In order to achieve the above object, the liquid crystal display element of the present invention is provided with an active element and a first electrode to which a signal voltage is applied via the active element which is turned on. A first substrate, a second substrate arranged to face the first substrate, and a pixel region on a surface of the second substrate facing the first substrate. A second electrode and a third electrode facing the first electrode, an impedance element formed outside the display region and connected to the second electrode, and connected to the impedance element and the third electrode Electrode terminal,
A liquid crystal sealed between the first and second substrates,
The driving voltage applied between the electrode terminal and the first electrode is stepped down by the impedance element, the liquid crystal between the second electrode and the first electrode, and the third electrode. And different voltages are applied to the liquid crystal between the first electrode and the first electrode. The impedance element is
For example, the cloth material is made of a resin containing a conductive material.

[0010]

According to the structure of the liquid crystal display element of the present invention, the second
The alignment state of the liquid crystal between the electrode and the first electrode is different from the alignment state between the third electrode and the first electrode. Therefore, it is possible to improve the comprehensive viewing angle characteristic of each pixel and expand the viewing angle. Moreover, since the impedance element is formed outside the display area (area in which the matrix of pixels is formed), the display image is not adversely affected. Further, by forming the impedance element with the cloth material, the viewing angle can be widened without using an additional configuration.

[0011]

Embodiments of the present invention will be described below with reference to the drawings by taking a TFT liquid crystal display device as an example. (First Embodiment) FIG. 1 shows a sectional structure of a TFT liquid crystal display element according to the first embodiment, FIG. 2 shows a plane structure of a TFT substrate, and FIG. 3 shows a plane structure of a counter substrate.

As shown in FIG. 1, this liquid crystal display device is
A pair of transparent substrates 11 and 1 joined by a sealing material SC
2 and a TN sealed between the pair of transparent substrates 11 and 12
A liquid crystal cell 16 including a (twisted nematic) liquid crystal 13 and polarizing plates 14 and 15 arranged with the liquid crystal cell 16 interposed therebetween.

The transparent substrates 11 and 12 are made of glass, resin film or the like. As shown in FIGS. 1 and 2, TFTs (thin film transistors) 21 as active elements and transparent electrodes (pixel electrodes) 22 are arranged in a matrix on a lower transparent substrate (hereinafter referred to as a TFT substrate) 11, An alignment film 23 is arranged on these.

The source electrode of each TFT 21 is connected to the corresponding pixel electrode 22, the gate electrode of each row TFT 21 is connected to the corresponding gate line GL, and a gate pulse is applied from an external gate driver via the gate line terminal 42. To be done. The drain electrodes of the TFTs 21 in each column are connected to the corresponding data lines DL, and a signal voltage (writing voltage) corresponding to the display gradation is supplied from the external data driver via the data line terminals 41. The pixel electrode 22 is formed of ITO (oxide of indium and tin) or the like, and is turned on by applying a gate pulse.
A signal voltage is applied from the data line terminal 41 connected to the data line DL via 21.

As shown in FIG. 3, on the other transparent substrate (hereinafter referred to as a counter substrate) 12, one stripe-shaped transparent electrode (first counter electrode) is formed in a region (entire pixel region) facing the pixel electrode 22. ) 31A and the other stripe-shaped transparent electrode (second counter electrode) 31B. The first counter electrode 31A and the second counter electrode 31B are made of ITO or the like, and are arranged so as to face the plurality of pixel electrodes 22, respectively.

The second counter electrode 31B is connected to one end of the control capacitor CX outside the display area (pixel forming area) indicated by the broken line. The other end of the control capacitor CX is the first counter electrode 3
It is connected to 1 A and is connected to an electrode terminal 37 to which a common voltage (common voltage) is supplied. The control capacitance CX is, for example, as shown in the cross section in FIG. 4, the second counter electrode 31B.
And the ITO film constituting the first counter electrode 31A are formed by arranging the dielectric film and the ITO film constituting the first counter electrode 31A so as to face each other.

A black mask 32 having a light-shielding property is arranged in a portion facing the TFT 21 on the counter substrate 12 and a portion facing the portion between the pixel electrodes 22. In addition, in each pixel region on the first counter electrode 31A and the second counter electrode 31B, the color filters 33 (33R, 33R,
33G, 33B) are arranged. Color filter 3
3 (33R, 33G, 33B), the overcoat layer (protective layer) 34 is disposed.

An alignment film 36 made of polyimide or the like is formed on the overcoat layer 34. The lower alignment film 23 in FIG. 1 is subjected to alignment treatment such as rubbing in the direction indicated by the broken line in FIG. 5 (0 ° direction), and the upper alignment film 3 is formed.
6 is subjected to the alignment treatment in the direction indicated by the solid line in FIG. 5 (direction of 90 °).

The liquid crystal 13 is composed of a nematic liquid crystal to which a chiral agent is added, and the lower substrate 11 is subjected to an alignment treatment.
From the top to the upper substrate 12 in the clockwise direction by 90 ° (0 ° ~
-90 °) Twisted and oriented.

As shown in FIG. 5, the lower (light incident side) polarizing plate 14 has its transmission axis perpendicular (90 °) to the direction of the alignment treatment applied to the lower alignment film 23. The polarizing plate 15 on the upper side (light emission side) is set so that its transmission axis is perpendicular to the transmission axis of the lower polarizing plate 14.

Each pixel of the liquid crystal display element having such a structure has a first counter electrode 31A as shown in an enlarged view in FIG.
Is divided into a normal pixel A1 in which is arranged and a voltage drop pixel A2 in which the second counter electrode 31B is arranged.

Liquid crystal capacitance of the normal pixel A1 (first liquid crystal capacitance)
CLC1 and liquid crystal capacitance of voltage drop pixel A2 (second liquid crystal capacitance)
Is CCL2 and the drive voltage applied between the electrode terminal 37 and the data line terminal 41 is V0, the equivalent circuit of each pixel is as shown in FIG. The color filter 3
3, the voltage applied to the overcoat layer 34 and the alignment films 36 and 23 is the same between the normal pixel A1 and the voltage drop pixel A2, and is small, so it is ignored.

As shown in FIG. 7, the liquid crystal 1 of the normal pixel A1
The voltage VLC1 applied to 3 has a value substantially equal to the drive voltage V0. Further, the voltage VLC2 applied to the liquid crystal 13 of the normal pixel A2 has a value represented by the formula 1.

[0024]

[Formula 1] VLC2 = V0 × (CX / (CX + CLC2)) That is, the voltage VLC2 applied to the second liquid crystal capacitance CLC2 is a voltage obtained by stepping down the drive voltage V0 by the control capacitance CX.

Since the voltage VLC1 (≈V0) applied to the liquid crystal 13 of the normal pixel A1 and the voltage VLC2 applied to the liquid crystal 13 of the voltage drop pixel A2 are different from each other, the alignment state of the liquid crystal 13 of the normal pixel A1 is different. And the alignment state of the liquid crystal 13 of the voltage drop pixel A2 is different. Therefore, the optical characteristics of the liquid crystal 13 of the normal pixel A1 and the optical characteristics of the liquid crystal 13 of the voltage drop pixel A2 are averaged according to the area ratio, and the viewing angle of one pixel is widened.

The voltage VLC2 can be arbitrarily changed and adjusted by changing the size of the control capacitor CX. That is, the voltage VLC2 can be arbitrarily changed and adjusted by changing the material or size of the control capacitor CX shown in FIG. Therefore, the conditions for obtaining the optimum voltage VLC2 are found by experiments, and the control capacitance CX is calculated according to this condition.
To form.

According to this embodiment, since the control capacitor CX is formed on the counter substrate 12, it is possible to prevent the TFT from being destroyed in the manufacturing process and to improve the manufacturing yield of the liquid crystal display device. Further, since the control capacitance CX is formed outside the display area, it does not adversely affect the display image.

(Second Embodiment) In the first embodiment, the control capacitor CX is formed on the counter substrate 12, but the impedance for voltage drop is formed by the cross material connecting the TFT substrate 11 and the counter substrate 12. You may. The second embodiment according to this method will be described below.

FIG. 8 shows the structure of the electrodes on the counter substrate 12 of the second embodiment, and FIG. 9 is an external perspective view of the liquid crystal display element. As shown in FIG. 8, the first counter electrode 31A includes the counter substrate 1
The second end is connected to the cross electrode terminal 37A. Similarly, the second counter electrode 31B is connected to the cross electrode terminal 37B at the end of the counter substrate 12.

As shown in FIG. 9, the cross electrode terminal 37A is connected to one end of a cross material 39A provided outside (or inside) the seal material SC, and the other end of the cross material 39 is on the TFT substrate 11. Is connected to the common electrode terminal 40 formed on. The cross electrode terminal 37B is connected to one end of a cross material 39B provided adjacent to the cross material 39A, and the other end of the cross material 39B is connected to the common electrode terminal 4A.
Connected to 0. The cloth members 39A and 39B are made of a conductive resin made of a resin containing conductive particles such as gold micropearls, and have different resistance values and capacitances (parasitic capacitances).

In the liquid crystal display device having such a structure,
By applying the drive voltage V0 between the common electrode terminal 40 and the data line terminal 41, the liquid crystal 1 of the normal pixel A1 can be obtained.
The driving voltage V0 is applied to the liquid crystal 3 of the voltage drop pixel A2 by being stepped down by the cloth material 39A.
Is stepped down by the cross material 39B and applied. Therefore, by making the impedances of the cross members 39A and 39B different, the voltage applied to the liquid crystal 13 of the normal pixel A1 and the voltage applied to the liquid crystal 13 of the voltage drop pixel A2 can be made different. Therefore, as in the first embodiment, the alignment state of the liquid crystal 13 can be made different between the normal pixel A1 and the voltage drop pixel A2 to widen the viewing angle.

According to this embodiment, similarly to the first embodiment, it is possible to prevent the TFT from being destroyed during the manufacturing process.
The manufacturing yield of the liquid crystal display device can be improved. Further, since the impedance element is formed by using the cross members 39A and 39B, it is not necessary to provide a special structure for the voltage drop.

The amount of voltage drop in the cloth members 39A and 39B can be adjusted by changing the material and size of the resin forming the cloth members 39A and 39B, or the content of the gold micropearl mixed therein. Therefore, the configurations of the cross members 39A and 39B can be arbitrarily adjusted so that the desired viewing angle can be obtained.

In the present embodiment, the cloth material 39A and the cloth material 39B are each formed at one location outside the sealing material SC, but the cloth material may be arranged at a plurality of locations.

In order to effectively use the drive voltage V0, it is desirable to use one of the cross members 39A and 39B, for example, the cross member 39A as a conductor to reduce the impedance.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, according to the above embodiment, the pixel is divided into two, but the pixel may be divided into three or more.

Further, although the present invention is applied to the color liquid crystal display device using the color filter in the above-mentioned embodiment, it is also applicable to the liquid crystal display device for monochrome gradation display.

The direction of the alignment treatment applied to the upper and lower alignment films 23 and 36 and the arrangement of the transmission axes of the polarizing plates 14 and 15 are not limited to those in the above embodiments, and can be arbitrarily changed. For example, the transmission axis of the polarizing plate 14 on the light incident side may be parallel to the alignment treatment of the lower alignment film 23. Further, the transmission axis of the polarizing plate 15 on the light emitting side may be parallel to the transmission axis of the lower polarizing plate 14.

In the above embodiments, the present invention has been described by taking the TFT liquid crystal display element as an example, but the present invention can also be applied to a liquid crystal display element using an MIM as an active element. Further, it is also applicable to a passive matrix type liquid crystal display element which does not use an active element.

The present invention is not limited to a TN (twisted nematic) liquid crystal display element, but can be similarly applied to an STN liquid crystal display or the like. Further, the present invention is not limited to the transmissive liquid crystal display element, but can be applied to a reflective liquid crystal display element having a reflective film. In this case, the polarizing plate on the reflective film side may be omitted.

[0041]

As described above, according to the present invention, each pixel is divided into a plurality of pixels, and the impedance element is connected in series to the liquid crystal capacitance of one divided pixel. A liquid crystal display device can be manufactured with a high yield rate. Further, by configuring the impedance element using a cloth material, it is possible to realize a liquid crystal display element having a wide viewing angle with a simple configuration without any additional configuration.
Further, since the impedance element is arranged outside the display area, the display image is not adversely affected.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a color TN type liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a TFT substrate.

FIG. 3 is a plan view showing a configuration of electrodes of a counter substrate.

FIG. 4 is a cross-sectional view showing a configuration example of a control capacitor.

FIG. 5 is a diagram showing a direction of alignment treatment.

FIG. 6 is a cross-sectional view showing the structure of one pixel of the liquid crystal display element of the first embodiment according to the present invention.

FIG. 7 is an equivalent circuit diagram of one pixel of the liquid crystal display element of the first embodiment.

FIG. 8 is a plan view showing a structure of electrodes of a counter substrate according to a second embodiment.

FIG. 9 is a perspective view of a liquid crystal display element according to a second embodiment.

FIG. 10 is a VT characteristic diagram when a liquid crystal display device having a conventional structure is viewed from the front.

FIG. 11 is a VT characteristic diagram when a liquid crystal display device having a conventional structure is viewed from a downward direction of 50 °.

[Explanation of symbols]

11 ... TFT substrate, 12 ... counter substrate, 13 ... liquid crystal,
14 ... Polarizing plate, 15 ... Polarizing plate, 16 ... Liquid crystal cell, 2
1 ... TFT, 22 ... Pixel electrode, 23 ... Alignment film, 31
A ... 1st counter electrode, 31B ... 2nd counter electrode, 32
... Black mask, 33 ... Color filter, 34 ...
Overcoat layer, 36 ... Alignment film, 37 ... Electrode terminal,
37A, 37B ... Cross electrode terminals, 39A, 39B ...
Cross material, 40 ... Common electrode terminal, 41 ... Data line terminal, CX ... Control capacitance, SC ... Seal material, GL ... Gate line, DL ... Data line, A1 ...・ Normal pixels,
A2 ・ ・ ・ Voltage drop pixel

Claims (4)

[Claims] 1. An active element, a first substrate on which a first electrode to which a signal voltage is applied via the active element which is turned on is formed, and a first substrate arranged to face the first substrate. A second substrate, a second electrode and a third electrode formed in each pixel region on the surface of the second substrate facing the first substrate, each of which faces the first electrode, and a third electrode. An impedance element formed outside the region and connected to the second electrode, an electrode terminal connected to the impedance element and the third electrode, and sealed between the first and second substrates. And a liquid crystal between the second electrode and the first electrode, the driving voltage applied between the electrode terminal and the first electrode is stepped down by the impedance element. And a liquid crystal between the third electrode and the first electrode, The liquid crystal display element characterized by applying a different voltage. 2. The electrode terminal is formed on the first substrate, and the impedance element is composed of a cross member for connecting the second electrode to the electrode terminal. The liquid crystal display element according to claim 1. 3. The liquid crystal display element according to claim 2, wherein the cloth material is made of a resin containing a conductive material. 4. The liquid crystal according to claim 1, further comprising a second impedance element arranged outside the display area and connecting the third electrode to the electrode terminal. Display element.