JP2909266B2 - Liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a pixel of a liquid crystal display device in which a pixel is divided into a plurality of sub-pixels and which can perform multi-tone display.

[0002]

2. Description of the Related Art As a prior art of this kind, U.S. Pat. No. 4,840,460 (Japanese Unexamined Patent Publication No. 2-12 / 1990 "Pixels of a liquid crystal display device and a method of realizing gray scale of pixels in a liquid crystal display device") is known. . That is, as shown in FIG. 1, one pixel region of the liquid crystal display panel is cut out perpendicularly to the panel, and a control capacitor electrode 2 is formed on the inner surface of a transparent substrate 1 such as glass. An insulating film 3 is formed over the entire surface of the transparent substrate 1. The insulating film 3 on the 4 or the like divided towards subpixel electrodes 4 ₁ to 4 ₄ shape is formed. A transparent substrate 5 made of glass or the like provided to face these sub-pixel electrodes at an interval.
A common electrode 6 is formed on the inner surface of the substrate, and a liquid crystal 7 is sealed between the common electrode 6 and the sub-pixel electrode 4 _i (i = 1 to 4). The control capacitor electrode 2, the sub-pixel electrode _4i, and the common electrode 6 are transparent electrodes made of ITO or the like. Thus one pixel to correspond to the subpixel electrodes 41 _{to 4,} is divided into four sub-pixels F ₁ to F _4. As shown in FIG. 2, an insulating film 3 is provided between each sub-pixel electrode 4 _i and the control capacitor electrode 2.
The controlled capacitor C _ci which a dielectric is formed, and also the liquid crystal capacitor C _LCi that the dielectric is formed the liquid crystal 7 between the sub-pixel electrode 4 _i and the common electrode 6. FIG. 3 shows an electrical equivalent circuit of the pixel in FIG. When the codes C _ci and C _LCi are used to represent the capacitance, each sub-pixel electrode 4 of the control capacitor electrode 2 is set so that C _C1 > C _C2 > C _C3 > C _C4 (1).
_The area overlapping with _i has been adjusted.

The control capacitor electrode 2 is adjacent to the pixel shown in FIG.
Thin film transistor formed on transparent substrate 1
(TFT) 8 is connected to the drain electrode D (FIG.
2). There is no space between the control capacitor electrode 2 and the common electrode 6.
Constant voltage V_aIs supplied through the TFT 8. TFT8
Is controlled to be on, each sub-pixel F_iPower supply at
Pressure V_aIs the control capacitor C_CiVoltage V_CiAnd liquid crystal con
Densa C_LCiVoltage V _LCiAnd the partial pressure. V_LCi
Is

[0004]

(Equation 1) It is expressed as By setting the capacitance of each control capacitor C _Ci as in equation (1), each liquid crystal capacitor C _LCi
Voltage across V _LCi of being set to _{V LC1> V LC2> V LC3} > V LC4 (3).

[0005] The liquid crystal of the voltage light transmittance is saturated V _U, when the threshold voltage is V _L, the magnitude of the voltage V _a to be supplied to the pixel as shown in FIG. 4, the liquid crystal capacitor C
Voltage across V _LCi of _LCi is present if the following. (a) When V _LCi = 0 for all i = 1 to 4. At this time, a V _a = 0. _{(b) V LC1 = V U} , if the V _LC2 = V _L. V _LC3 , V
_LC4 is below _VL . It represents a supply voltage V _a when this V _{a1. (c) V LC2 = V U} , if the V _LC3 = V _L. It represents a supply voltage V _a when this V _{a2. (d) V LC3 = V U} , if the V _LC4 = V _L. V _a at this time
_Is represented by Va3. (e) When V _LC4 = V _U. Representing the V _a at this time in the V _a4.

The supply voltage _Vai is such that _Va1 > _Va2 > _Va3 > _Va4 > 0 (4). Multi-gradation display is performed by changing the magnitude of the supply voltage V _a.

[0007]

In THE INVENTION Problem to be Solved] prior art, in the sub-pixel F _i, when the voltage V _a to be supplied to the pixels of the V _ai, voltage across V _LCi of the liquid crystal capacitor C _LCi LCD light transmission is saturated It is set equal to the voltage V _U. That is,

[0008]

(Equation 2) The area of each control capacitor C _Ci that overlaps with the sub-pixel electrode 4 _i is set so that the capacitance satisfies the expression (5). (Five)
As can be seen from the equation, the liquid crystal capacitor V of the sub-pixel 4 _{i
In order} to make the voltage applied to _LCi very small, the capacitance of the corresponding control capacitor C _Ci must be reduced. That is, it is necessary to reduce the area of the control capacitor electrode 2 overlapping the sub-pixel electrode 4 _i . However, the smaller the overlap area (in the above example, C _C4
Smallest) is the overlapping area of the error of the capacitance value C _Ci by variations in the area overlapping the subpixel electrodes ₄₁ to ₄ due to misalignment of the patterns of the control capacitor electrode 2 is increased. The liquid crystal capacitor voltage V _LCi is the light transmission saturation voltage V _U
, The error in multi-tone display becomes large, and the display quality is remarkably deteriorated.

Further, since the sub-pixel electrode _4i is formed by simply dividing the pixel electrode in the row direction and the column direction, a state in which only one sub-pixel is on and a state in which a plurality of sub-pixels are on In this state, the center of the ON area was different, and the quality of the displayed image was not good. A first object of the present invention is to provide a liquid crystal display element in which the deterioration of the multi-gradation display quality due to the influence of manufacturing variations of the control capacitor is small.

A second object of the present invention is to provide a liquid crystal display device having excellent image display quality even when the ON region of a pixel is increased or decreased without moving the center thereof.

[0011]

According to a first aspect of the present invention, a plurality of separated sub-pixel electrodes constituting each pixel are opposed to a common electrode on a second substrate with a liquid crystal interposed therebetween. A control capacitor electrode is disposed on the first substrate and forms a liquid crystal capacitor therebetween, and a control capacitor electrode facing at least one of the sub-pixel electrodes via a first insulating film is provided between the first substrate and the sub-pixel electrode. Thereby forming a control capacitor connected in series with the liquid crystal capacitor formed between the at least one sub-pixel electrode and the common electrode, and having a drive voltage between the control capacitor electrode and the common electrode. In the liquid crystal display element having a pixel configured to be supplied with, an additional capacitor electrode is formed so as to face the at least one sub-pixel electrode with a second insulating film interposed therebetween. Forming a equivalently parallel additional capacitor to the liquid crystal capacitor me.

According to the second aspect of the present invention, a plurality of separated sub-pixel electrodes constituting each pixel are arranged on the first substrate, facing the common electrode on the second substrate with the liquid crystal interposed therebetween. A liquid crystal capacitor is formed therebetween, and a control capacitor electrode opposed to at least one of the sub-pixel electrodes via the first insulating film is provided between the first substrate and the sub-pixel electrode. At least one subpixel electrode forms a control capacitor connected in series to a liquid crystal capacitor formed between the common electrode and the common electrode, and a driving voltage is supplied between the control capacitor electrode and the common electrode. In the liquid crystal display device having the constituted pixels, according to the present invention, the plurality of sub-pixel electrodes define a central sub-pixel region and at least one loop-shaped sub-pixel region surrounding the periphery substantially concentrically. It is formed in.

[0013]

According to the first aspect of the present invention, since the additional capacitor is equivalently connected in parallel to the liquid crystal capacitor connected in series with the control capacitor, either the control capacitor electrode or the additional capacitor electrode is connected. Even if the area is changed, the capacitance division voltage applied to the liquid crystal constituting the liquid crystal capacitor can be controlled, and the degree of freedom in designing the pixel increases accordingly.

According to the second aspect of the present invention, since the sub-pixels constituting each pixel are arranged concentrically with each other, even if the display state of the sub-pixel is changed, the center of the ON region is substantially at the center of the pixel. To improve the quality of the displayed image.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in FIG. 5 in which one pixel region is cut out, and portions corresponding to those in FIG.
A duplicate description is omitted. In this embodiment, the control capacitor electrode 2 overlaps the entire length of the cross gap Ga between the sub-pixel electrodes, and in this example, the four corners of the substantially rectangular pixel region are each removed in a thick cross shape by removing a predetermined size. It is formed of ITO. Therefore, in the gap between the sub-pixel electrodes, the liquid crystal is driven by the voltage applied to the control capacitor electrode 2. According to a first aspect of the present invention,
The additional capacitor electrode 12 and the sub-pixel electrode 4 _i (i = 1 to
4), an additional capacitor C _Si having the insulating film 11 as a dielectric is formed as shown in FIG. That is, the additional capacitor electrode 12 through an insulating film 11 such as silicon nitride (SiN _x) on the sub-pixel electrode ₄₁ to ₄ which are separated from each other by crisscross gap Ga is, U aluminum in this example
It is formed in a character shape. U-shaped additional capacitor electrode 12 is formed so as to sequentially pass through these subpixel electrodes ₄₁ to ₄ above. Further, the additional capacitor electrodes 12 of the respective pixels in each row are sequentially connected by wiring (not shown),
A constant potential is applied when the liquid crystal display element operates.

An electrical equivalent circuit of the pixel shown in FIG. 5 is represented as shown in FIG. That is, since the additional capacitor C _Si is held at a constant potential by a wiring (not shown), it is equivalently connected in parallel with the liquid crystal capacitor C _LCi . Driving voltage V _a applied between the control capacitor electrode 2 and the common electrode 6 and the control capacitor capacitance C _Ci, combined capacitance of the liquid crystal capacitance C _LCi and the additional capacitance C _Si C
_The voltage V _{LCi divided} by _LCi + C _Si and applied to the liquid crystal capacitor C _LCi is

[0017]

(Equation 3) Is represented by In the prior art, the liquid crystal capacitor voltage V _LCi is set only by adjusting the control capacitor capacitance C _Ci , but in the present invention, the adjustment of the additional capacitance C _Si is also used. For example, the voltage V _LC4 across the capacitor C _LC4 is V
When the smallest set in _LC1 ~V _LC4, C _S4 with the C _C4 is small is set larger, thereby
In the equation (6), the value of C _C4 / (C _LC4 + C _S4 + C _C4 ) is i = 1 to
3 is set to be the smallest. When the additional capacitor C _Si is used together in this way, the control capacitor capacitance C _Ci is not made so small as in the conventional case, and the effect of the manufacturing variation is kept to a small extent. Even if the position of the additional capacitor electrode 12 is displaced due to manufacturing variations, it is desirable to minimize the manufacturing variation of the capacitance value so that the area overlapping each subpixel electrode 4 _i does not change much.

Since the thick cross-shaped control capacitor electrode 2 overlaps the gaps between the sub-pixel electrodes, the liquid crystal on these gaps includes the control capacitor electrode 2 and the common electrode 6
Voltage V _a applied and the insulating film 3 and 11 between the liquid crystal 7
Is divided by the, by the magnitude of the voltage V _a, the liquid crystal portion to control the state of light transmission or light blocking, so as to contribute to the multi-gradation display as well as the sub-pixel electrode. Thereby, the aperture ratio of the pixel is improved.

The control capacitor C_C1~ C_C4Of which
Sub-pixel electrode 4 forming the maximum capacitance₁Liquid crystal in the area
A large voltage will be applied. The power supplied to the pixel
Pressure V _aWhen the constant is
The control capacitor electrode 2 is connected to the sub-pixel electrode 4₁All of
The sub-pixel electrode 4 may be formed so as to face and overlap the surface.
₁And the control capacitor electrode 2 can be electrically connected.
it can. The embodiment described below corresponds to this case, and the control
Sa C_C1Is equivalent to infinite capacity. In that case
Is the control capacitor electrode 2 and the sub-pixel electrode 4₁Overlap with
It may be arbitrary and may not have overlap.Design of voltage versus transmittance characteristics Sub-pixel F₁~ F_FourThe voltage versus transmittance characteristics of
Capacitor capacity C_SiAnd control capacitor capacitance C_CiAnd by
To control the transmittance characteristics of the entire pixel
The degree of freedom to obtain various favorable characteristics.
Wear. (A) Sub-pixel F₁~ F_FourOf the voltage as shown in FIG.
By setting an interval in the direction of the axis, the total pixel
The matching characteristic can be made stepwise as shown in FIG. (B) Sub-pixel F₁~ F_FourThe characteristics of
Pixel F_iVoltage V at which the light transmittance of the sample becomes 90%_a
And sub-pixel F_{i + 1}Applied when the light transmittance of the
Pressure V_aAnd the sub-pixel F₁~ F_FourThe characteristics of
If set, the overall characteristics of the pixel will be straightforward as shown in FIG.
It becomes linear, and its inclination is gentler than when it is not divided into sub-pixels.
It can be done. In this way, each sub-pixel
F_iThe deviation of the transmittance from the straight line in FIG.
Resulting in less compression in the overall properties of 9B
Characteristic and the linearity is improved. Also the total of pixels
The linear region of the characteristics is also wider than the individual characteristics in FIG.
It becomes. For this reason, the liquid crystal display element normally displays video signals.
When used as a detector, adjust the applied voltage value to compensate for linearity.
Correction so-called γ (gamma) correction becomes unnecessary. Also voltage vs.
Performs video display, etc., because the transmittance characteristics are moderate.
When the output deviation of the drive IC that supplies the signal to the source bus
Margin can be increased. As shown in FIG.
When the voltage versus transmittance characteristics of each sub-pixel are set in
The voltage at which the transmittance of the pixel is saturated as shown in FIG.
8 lower than in case of B, lower voltage driving is possible
Becomes (C) Essential features of TN type liquid crystal display devices for color display
Pixel for each color of R, G, B based on optical rotation dispersion
The voltage-transmittance characteristics of
According to the present invention, the voltage of the pixel
Since the degree of freedom in designing the transmittance characteristics has increased, the desired characteristics can be set.
It is easy to measure each color, as shown in FIG.
It can be corrected to the same characteristics. In this correction, the pixel is a sub-pixel
Control capacitor capacitance C_CAnd with
Capacity C_SAnd the liquid crystal capacitor voltage V_LC= V_aC
_C/ (C_LC+ C_S+ C_C) Can be adjusted for each color,
The same correction as described above is possible.

In the above description, the case where a pixel is divided into four sub-pixels has been described. However, it is apparent that the pixel can be generally divided into n (an integer of 2 or more). According to the second aspect of the present invention, a plurality of subpixel regions obtained by dividing each pixel are arranged concentrically with each other. For example, as shown in FIG. 11 by attaching the same reference numerals to those corresponding to FIG. 5, the ITO pixel electrode is concentric with _two square loop-shaped sub-pixel electrodes 4 _{1 and} 4 ₂ by a square loop-shaped gap Ga. Has been split. Center sub-pixel electrodes 4 ₁ rectangular window W is formed. The control capacitor electrode 2, as shown in FIG. 12, the sub-pixel electrodes 4 ₁
Substantially does not overlap the half area hole 2a is formed as the sub-pixel electrodes 4 ₁ except that hole _2a, 4 ₂ and rectangular window W of
And is formed of ITO over almost the entire area of the pixel so as to oppose each other via the insulating film 3. In this example, the central window W
Region of the control capacitor electrode 2 which is electrically exposed through the insulating film 3 in defining a subpixel area F _1. Accordingly, when gradually increasing the drive voltage Va applied between the control capacitor electrode 2 and the common electrode 6, the first sub-pixel region F ₁ of the central window W is turned on, then the sub-pixel electrodes 4 ₁ provisions subpixel region F ₂ is additionally turned on, the last subpixel electrodes 4 ₂ sub-pixel region F ₃ is additionally on defining the. Even if the ON area increases or decreases in this way, the center position of the ON area is fixed at substantially the center of the pixel, and therefore, according to the liquid crystal display device having such a configuration, an image that is easy to see for human eyes can be obtained. It was confirmed by experiments that the display was possible and that the display quality of the image was better than when the pixel electrode was divided in the row direction and the column direction as shown in FIG. Other Embodiments A plan view of an embodiment according to a combination of the first and second aspects of the present invention in which each pixel is composed of two sub-pixels and a first sub-pixel electrode is connected to a control capacitor electrode, A-
13, 14, and 15 are sectional views of A and BB.
The same reference numerals are given to portions corresponding to FIG. 5 and FIG. The light shielding layer 13 is formed on the transparent substrate 1 in an island shape. The light shielding layer 13 prevents light from entering the TFT. Silicon oxide (Si) is formed on the transparent substrate 1 and the light shielding layer 13.
An insulating film 14 such as O ₂ ) is formed, and a control capacitor electrode 2 having a loop shape is formed thereon by ITO or the like. An insulating film 15 such as silicon oxide is formed on the control capacitor electrode 2 and the insulating film 14, and a source bus 21, a source electrode 21a, a drain electrode 22, and sub-pixel electrodes 4 ₁ and 4 ₂ are formed thereon by using ITO or the like. Is done. Subpixel electrodes 4 ₁ in the contact hole 15H formed in the insulating film 15 on the control capacitor electrode 2 is formed in contact with the control capacitor electrode 2 is in a conductive state with each other. The drain electrode 22 of the sub-pixel electrodes 4 ₁ TFT8
And are connected to each other. A semiconductor layer 23 such as amorphous silicon is formed over the source electrode 21a and the drain electrode 22. Silicon nitride (SiN) is formed over the semiconductor layer 23 and the sub-pixel electrodes 4 ₁ and 4 _2.
x ), etc., and a gate bus 25 and a gate electrode 25 made of, for example, aluminum are formed thereon.
a, the additional capacitor electrode 12 is formed at the same time.

As described above, the TFT 8, the sub-pixel electrode 4 ₁ ,
4 ₂ such as a transparent substrate 1 formed is is arranged opposite to the transparent substrate 5 which common electrode 6 is formed on the inner surface, the liquid crystal 7 is sealed between the substrates. At the intersection of the source bus 21 and the gate bus 25 and at the intersection of the source bus 21 and the additional capacitor electrode 12, island-shaped semiconductor layers 23a and 23b are formed by being stacked below the gate insulating film 24 to improve the insulation. ing. The TFT 8 is formed near the intersection of the gate bus 25 and the source bus 21. In a region surrounded by the right and left source bus 21 and the upper and lower gate bus 25 and the sub-pixel electrodes 4 ₁ small-area subpixel electrodes 4 ₂ large area is formed. The control capacitor electrode 2 is formed in a loop shape overlaps with the peripheral portion surrounds the peripheral edge of the subpixel electrodes 4 _2. The sub-pixel electrodes 4 ₁ and the control capacitor electrode 2 are electrically connected to each other by a contact hole 15H as already mentioned.

[0022] Since the control capacitor electrode 2 connected to the sub-pixel electrode 4 ₁ is arranged concentrically surrounding the subpixel electrode 4 _2, the voltage V _a in through TFT8 in driving the liquid crystal display device is given sometimes first sub-pixel (including sub-pixels 4 ₁ region) 4 ₂ area of the control capacitor electrode 2 surrounding the oN (light transmission), and even more subpixels 4 ₂ regions when a voltage V _a higher predetermined value than Turns on. When the display area of the pixels is concentrically controlled as described above, the display quality is better than when the sub-pixels are arranged vertically and horizontally as shown in FIG.

The additional capacitor electrode 12 is a gate insulating film 2
4 through the sub-pixel electrode 4_TwoIs formed on. Additional
The capacitor electrode 12 has an H shape in this embodiment.
The horizontal portion 12C is located substantially at the center of the control capacitor electrode 2.
It extends horizontally and has vertical portions 12 at each end.
A and 12B are provided. The vertical parts 12A, 12B
It extends so as to overlap with the side edge of the control capacitor electrode 2. water
The flat part 12C is extended at both ends to extend the gate bus 25.
Connected to the additional capacitor electrode 12 of the pixel adjacent in the direction
ing. During operation of the liquid crystal display element,
The additional capacitor electrode 12 is fixed at the extension end of the horizontal portion 12C.
Constant current by applying a DC voltage of
Is held in place. The control capacitor electrode 2 is a sub-pixel electrode
4₁, 4 _TwoIt is arranged so as to overlap with the gap Ga between them.

[0024] While control capacitor C _C2 is formed between the control capacitor electrode 2 and the subpixel electrode 4 _2, since the control capacitor electrode 2 and the subpixel electrode 4 ₁ is electrically shorted, the control capacitor C _C1 is not formed (or C
It can be seen that _C1 is formed but both ends are short-circuited). Additional capacitor electrode 12 and sub-pixel electrode 4 ₂
, An additional capacitance C _S2 is formed. In this example, direct additional capacitance C _S1 without formation, the control capacitor electrode 2 (connected with the sub-pixel electrode 4 ₁₎ instead and the additional capacitor electrode between the subpixel electrodes 4 ₁ and the additional capacitor electrode 12 12 is formed. Subpixel electrodes 4 ₁ and the common electrode 6
Common electrode 6 crystal capacitor C _LC1A is the control capacitor electrode 2 which faces the gap Ga between the subpixel electrodes between the
Between the liquid crystal capacitor C _LC1b and the sub-pixel electrode 4 ₂
The liquid crystal capacitor _CLC2 is formed between the common electrode 6 and the common electrode 6. Accordingly, the electrical equivalent circuit of the pixel in the embodiment of FIGS. 13, 14 and 15 is as shown in FIG.

In the example of FIG. 13, the control capacitor electrode 2 is dimensioned to be overlaid with the peripheral edge portion of the subpixel electrode 4 ₂ is approximately 12 [mu] m, if the conventional example to not mix constituting the additional capacity as this overlapping The required size must be extremely small, for example, about 1.5 μm, and a manufacturing margin for a pattern shift cannot be obtained. As can be seen from FIG. 13, the vertical portions 12A and 12B of the additional capacitor electrode 12 are formed.
Since overlaps the side edges of the control capacitor 2 in the middle in the width direction, with respect to the positional deviation of the vertical and lateral directions manufacture of additional capacitor electrode 12, the area and the control capacitor overlapping the subpixel electrode 4 ₂ area overlapping with the electrode 2 (connected subpixel electrodes 4 ₁ and) does both little change. Therefore, the additional capacitor capacities C _S1 and C _S2 are kept substantially constant with respect to manufacturing variations due to pattern shifts and the like. The additional capacitors C _S1 and C _S2 function as storage capacitors for holding signal charges, and contribute to improvement of display stability in high-temperature operation where leakage current increases.

FIG. 13, as it is the control capacitor electrode 2 so as to surround the sub-pixel electrode 4 ₂ is formed in FIGS. 14 and 15, shown, in simplified form, in FIG 17 corresponds to FIG. 13, The control capacitor electrode 2 is arranged in the center in an island shape, and the sub-pixel electrode 4 ₂ is overlapped with and surrounds the periphery thereof.
May be formed. In this case, as the applied voltage Va is increased, the central sub-pixel region is turned on, and then the outer sub-pixel region is also turned on.

Further, as shown only in the cross section in FIG. 18, the source electrode 21a and the drain electrode 22 of the TFT 8 in the embodiment of FIGS. 13, 14 and 15 are formed in the same layer as the control capacitor electrode 2, and it is also possible to form the electrodes 4 ₁ and the control capacitor electrode 2 in the integral structure continuously. 13, although the additional capacitor electrode 12 on the sub-pixel electrode 4 ₂ is provided in the embodiment of FIGS. 14 and 15, 19
Alternatively, as shown in FIG. 20, it may be provided on the same surface as the control capacitor electrode 2 under the sub-pixel electrodes 4 ₁ and 4 ₂ . That is, in the embodiment shown in FIGS. 19 and 20, a part of the rectangular loop-shaped control capacitor electrode 2 in FIG. 13 is removed to form the passage 2A, and the passage 2A is formed in the horizontal direction of the modified H-shaped additional capacitor electrode 12. The vertical portion 12A and the vertical portion 12B of the H-shaped electrode 12 are disposed outside and inside the rectangular loop-shaped electrode 2, respectively. The sub-pixel electrode in this embodiment 4 ₁ its side edges the control capacitor electrode 2
Extends parallel along substantially the entire length of the formed so as to overlap the side edges and the additional capacitor electrode 12, and at an approximately rectangular subpixel electrode 4 _second long sides and spacing Ga. Both ends of the vertical portion 12A of the H-shaped additional capacitor electrode 12 are extended and connected to the vertical portions 12A of the additional capacitor electrodes of vertically adjacent pixels, respectively, and the additional capacitor electrode 12 is kept at a constant potential during operation of the liquid crystal display element. Is done.
The connection equivalent circuit of each capacitor in this embodiment is completely the same as that shown in FIG.

In each of the above-described embodiments, the additional capacitors C are provided for all the sub-pixel electrodes 4 ₁ , 4 ₂ ,.
_Although the case where _S1 , _Cs2 ,... _Are provided is shown, an additional capacitor may not be connected to at least one sub-pixel electrode in some cases. For example, in the embodiments shown in FIGS. 13, 14 and 15, the embodiment in which the additional capacitor C _S1 is omitted is simplified and shown in FIGS. 21, 22 and 23. Additional capacitor electrode 12 in this embodiment is formed simultaneously with substantially rectangular sub-pixel electrode 4 _{and second} one side edge parallel to the same material as the gate bus 25 so as to overlap through the gate insulating film 24 (e.g. aluminum) ing. Sub-pixel electrode 4 ₁
Is the insulating film 1 in the same manner as in the embodiment of FIG. 13, FIG. 14 and FIG.
5 is connected to the control capacitor electrode 2 through a contact hole 15H. The control capacitor electrode 2 does not overlap with the additional capacitor electrode 12,
Therefore, the sub-pixel electrodes 4 ₁ additional capacitor not connected in this embodiment. The electrical equivalent circuit of the pixel in this embodiment is the same as that in FIG. 16 from which the additional capacitor C _S1 is removed.

Similarly, in the embodiment shown in FIGS. 19 and 20, the embodiment in which the additional capacitor C _S1 is removed is simplified and shown in FIGS. 24, 25 and 26. In this embodiment, the additional capacitor electrode 12 is a control capacitor electrode 2 made of ITO.
The same surface to be formed at the same time, is extended in the same direction as the source bus 21 so as to overlap with the sub-pixel electrode 4 _2. Subpixel electrodes 4 ₁ do not overlap each other and in that although additional capacitor electrode 12 is connected to the control capacitor electrode 2 through the contact hole 15H formed in the insulating film 15. Therefore additional capacitor is not connected to the subpixel electrodes 4 _1, electrical equivalent circuit of a pixel is the same as removing the additional capacitor C _S1 in FIG.

As described above, the effect of the additional capacitor according to the principle of the first aspect of the present invention is that the degree of freedom in designing a control capacitor for the sub-pixel electrode to which the additional capacitor is connected is increased. Therefore, FIG. 21, FIG. 22 and FIG.
24, 25 and 26, the principle of the present invention cannot be applied to the sub-pixel electrode to which the control capacitor is not connected in series.
It is not necessary to provide an additional capacitor. However, by connecting the additional capacitor, the capacity of the liquid crystal capacitor is increased, and a larger amount of electric charge can be accumulated. Therefore, as is well known, the effect of delaying the voltage drop against the increase in the leak current at a high temperature can be obtained.

[0031]

As described above, the first aspect of the present invention is as follows.
According to an aspect, at least one sub-pixel of the plurality of sub-pixels
F_iIn the conventional control capacitor C_CiWith additional
Capacitor C_SiIs the liquid crystal capacitor C_LCiVoltage V_LCi
Is used to determine the sub-pixel voltage versus transmittance characteristics.
Sex design freedom increases accordingly. Therefore, the control
Capacitance error due to pattern shift etc.
Becomes more problematic, the sub-pixel electrode 4_iSmall overlapping area
It is no longer necessary to use _LCiTo
It can be set with higher accuracy than before. Because of this pixel
Display can be performed more accurately than before.
Position can be improved. By using this additional capacitor together,
It is possible to accurately set the voltage-transmittance characteristics of the sub-pixel.
The linearity of the pixel's overall voltage versus transmittance characteristics
It is easy to improve, and it is conventionally performed for linearity correction.
This eliminates the need for so-called gamma correction. Also for the same reason
-Color caused by optical rotation dispersion in TN type liquid crystal display devices
Correction of voltage-transmittance characteristics between different pixels
it can.

According to the second aspect of the present invention, since each pixel is configured such that a plurality of sub-pixels are arranged concentrically, the display quality of an image can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a pixel configuration in a conventional liquid crystal display element.

FIG. 2 is a diagram showing a capacitance formed between electrodes of FIG. 1;

FIG. 3 is a diagram illustrating an electrical equivalent circuit of the pixel in FIG. 1;

4 is a diagram showing an applied voltage V _a pair of liquid crystal capacitor voltage V _LCi characteristic in the sub-pixel F _{i (i} = 1~4) of FIG.

FIG. 5 is a perspective view showing a pixel configuration in an embodiment according to the first aspect of the present invention.

FIG. 6 is a diagram showing a capacitance formed between each electrode in FIG. 5;

7 is a diagram showing an electrical equivalent circuit of the pixel in FIG.

8A is a diagram illustrating an example of a voltage versus transmittance characteristic of each sub-pixel in FIG. 5, and FIG. 8B is a diagram illustrating a total voltage versus transmittance characteristic of A.

9A is a diagram illustrating another example of the voltage versus transmittance characteristic of each sub-pixel in FIG. 5, and FIG. 9B is a diagram illustrating the total voltage versus transmittance characteristic of A.

FIG. 10A shows R, R in a TN type color liquid crystal display device.
FIG. 3 is a diagram showing general voltage versus transmittance characteristics of each pixel of G and B, where B is R, G, and B in the liquid crystal display device of the present invention.
FIG. 4 is a diagram showing an example of a voltage versus transmittance characteristic of each pixel of FIG.

FIG. 11 is a perspective view showing an embodiment of a pixel configuration according to a second aspect of the present invention.

FIG. 12 is a plan view of a control capacitor electrode in FIG. 11;

FIG. 13 is a plan view showing a main part of another embodiment of the present invention.

FIG. 14 is a sectional view taken along line AA of FIG.

FIG. 15 is a sectional view taken along line BB of FIG.

FIG. 16 is a diagram showing an electrical equivalent circuit of the pixel shown in FIGS. 13, 14, and 15;

FIG. 17 is a simplified plan view showing a modified example corresponding to FIG. 13;

FIG. 18 is a sectional view showing a modification of the embodiment of FIGS. 13, 14 and 15;

FIG. 19 is a plan view showing still another embodiment of the present invention.

FIG. 20 is a sectional view taken along line AA of FIG. 19;

FIG. 21 is a plan view of still another embodiment.

FIG. 22 is a sectional view taken along the line AA in FIG. 21.

23 is a sectional view taken along the line BB in FIG. 21.

FIG. 24 is a plan view of still another embodiment.

25 is a sectional view taken along the line AA in FIG. 24.

26 is a sectional view taken along the line BB in FIG. 24.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-72392 (JP, A) JP-A-2-12 (JP, A) JP-A-2-79026 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G02F 1/136 500 G02F 1/1343

Claims (14)

(57) [Claims] An image is formed on an inner surface of a first substrate of a liquid crystal display panel.
A control capacitor electrode is formed for each element, and over the entire surface of the first substrate on the control capacitor electrode.
A first insulating film is formed on the control capacitor electrode via the first insulating film.
At least one sub-pixel electrode is formed, and a common electrode is formed on the inner surface of the second substrate of the liquid crystal display panel.
Is, the liquid crystal between the first substrate and the second substrate is sealed, between the at least one sub-pixel electrode and the common electrode
A liquid crystal capacitor is formed in the at least one subpixel electrode and the control capacitor.
A liquid crystal display element having a pixel formed with a control capacitor between the electrode and a driving voltage supplied between the control capacitor electrode and the common electrode; An additional capacitor voltage maintained at a constant potential so as to face the electrode via the second insulating film.
A pole is provided, wherein the at least one sub-pixel electrode is
A liquid crystal display device comprising an additional capacitor formed between the additional capacitor electrode . 2. An image forming method according to claim 1 , further comprising:
A control capacitor electrode is formed for each element, and over the entire surface of the first substrate on the control capacitor electrode.
A first insulating film is formed on the control capacitor electrode via the first insulating film.
At least one sub-pixel electrode is formed, and a common electrode is formed on the inner surface of the second substrate of the liquid crystal display panel.
Is, the liquid crystal between the first substrate and the second substrate is sealed, between the at least one sub-pixel electrode and the common electrode
A liquid crystal capacitor is formed in the at least one subpixel electrode and the control capacitor.
A liquid crystal display element having a pixel formed with a control capacitor between the electrode and a driving voltage supplied between the control capacitor electrode and the common electrode; The electrode and the control capacitor electrode are arranged concentrically so that one substantially surrounds the other and overlaps at least on the periphery with the insulating film interposed therebetween, thereby forming an island-like first sub-pixel region and a loop-like substantially surrounding the first sub-pixel region. A second sub-pixel area of the liquid crystal display element. 3. The first sub-pixel region is a part of a region of the control capacitor electrode defined inside the second sub-pixel region, and the sub-pixel electrode substantially surrounds the first sub-pixel region. 3. The liquid crystal display device according to claim 2, wherein the liquid crystal display device is formed in a loop. 4. The first sub-pixel region is the at least one sub-pixel electrode disposed inside the second sub-pixel region, and the control capacitor electrode is a region substantially surrounding the at least one sub-pixel electrode. 3. The liquid crystal display element according to claim 2, comprising: the second sub-pixel region. 5. The image display device according to claim 1, further comprising another sub-pixel electrode separated by a gap from the at least one sub-pixel electrode, and the other sub-pixel electrode and the control capacitor electrode are electrically connected. Item 2. A liquid crystal display device according to item 1. 6. The liquid crystal display element according to claim 5, wherein the control capacitor electrode substantially surrounds a peripheral portion of the at least one sub-pixel electrode and overlaps the peripheral portion. 7. The liquid crystal display device according to claim 5, wherein said at least one subpixel electrode is formed so as to substantially surround a peripheral portion of said control capacitor electrode and to overlap with the peripheral portion. 8. The second insulating film is formed over the at least one sub-pixel electrode over substantially the entire surface of the first substrate, and the additional capacitor electrode is formed thereon. 2. The liquid crystal display device according to 1. 9. The liquid crystal display device according to claim 5, wherein said another sub-pixel electrode is formed integrally with said control capacitor electrode on the same plane. 10. The liquid crystal display device according to claim 1, wherein said second insulating film is also used by said first insulating film, and said control capacitor electrode and said additional capacitor electrode are formed on the same surface. 11. The liquid crystal display device according to claim 5, wherein said another sub-pixel electrode and said control capacitor electrode are connected to each other through a contact hole formed in said first insulating film. 12. The another sub-pixel electrode is formed on the same plane as the at least one sub-pixel electrode and separated from each other by a gap, and the control capacitor electrode has a region overlapping with the gap over substantially the entire length thereof. The liquid crystal display device according to claim 5, comprising: 13. The liquid crystal display according to claim 1, wherein the additional capacitor electrode has an extension connected to the additional capacitor electrode of the pixel adjacent in one of the row arrangement and the column arrangement. element. 14. An inner surface of a first substrate of a liquid crystal display panel.
A control capacitor electrode is formed for each pixel, and extends over the entire surface of the first substrate on the control capacitor electrode.
A first insulating film is formed on the control capacitor electrode via the first insulating film.
At least one sub-pixel electrode is formed, and a common electrode is formed on the inner surface of the second substrate of the liquid crystal display panel.
Is, the liquid crystal between the first substrate and the second substrate is sealed, between the at least one sub-pixel electrode and the common electrode
A liquid crystal capacitor is formed in the at least one subpixel electrode and the control capacitor.
A control capacitor is formed between the control electrode and the common electrode, and a driving voltage is supplied between the control capacitor electrode and the common electrode. The central island-shaped one is substantially surrounded by at least one other, and is arranged concentrically so as to overlap with each other at least on the peripheral edge via the insulating film. A liquid crystal display element, wherein the liquid crystal display element defines a substantially loop-shaped second sub-pixel region.