JP2002296611A - Liquid crystal display device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appropriate composition of liquid crystal materials for a display device using lateral electric field generated between electrodes to drive as well as a liquid crystal display device and electronic equipment of high definition prevented disclination by using this composition. SOLUTION: In the liquid crystal display device including a liquid crystal layer placed between a pair of substrates opposed to each other and pixel electrodes connected to plural data signal lines and scan lines arranged in matrix on at least one of the substrates with switching elements, one of the data signal lines or scan lines are curved in one direction to make the treatment solution for washing or etching gush out to the same direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a structure of a liquid crystal material for improving the aperture ratio of the liquid crystal display device to realize high definition.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device is mainly used as a liquid crystal light valve used as a light modulation device in a projection type liquid crystal display device such as a liquid crystal projector. There is a strong demand for finer, smaller, and wider viewing angles. In recent years, as one of means for increasing the viewing angle of a liquid crystal display device, an in-plane horizontal electric field is generated on a substrate, and the horizontal electric field rotates liquid crystal molecules in a plane parallel to the substrate. In-plane switching (IPS) technology having an optical switching function has been put to practical use. In recent years, I
Fringe-Field Switching (hereinafter abbreviated as FFS) technology, which is an improved version of PS technology, is called "High-Transmittance, Wide-Viewin".
g-Angle Nematic Liquid Crystal Display Controlled
by Fringe-Field Switching ", SHLee et al., ASIA D
ISPLAY 98, p.371-374, "A High Quality AM-LCD using
Fringe-Field Switching Technology ", SHLee et a
l., IDW'99, p.191-194.

FIG. 7 is a diagram showing the difference between the concept of the IPS system and the concept of the FFS system. FIG.
(B) shows the FFS method. The liquid crystal molecules 202 between the pair of substrates 200 and 201
However, when the cell gap is d, the electrode width is w, and the distance between the electrodes is L, the relationship between these dimensions is L / d in the IPS system.
> 1 and L / w> 1, whereas in the FFS method, L
/ D <1 and L / w <1, or L / d = 0 and L / w
= 0. That is, while the distance between the electrodes is larger than the cell gap and the electrode width in the IPS system, the distance between the electrodes is smaller than the cell gap and the electrode width in the FFS system (the electrode 203 and the electrode in the IPS system in FIG. 2
04 is sufficiently close), or the distance between the electrodes is 0, in other words, as shown in FIG. 7B, the other electrode 203 is placed above the one electrode 204 (negative pole) via the insulating layer 205. An electrode configuration in which (+ poles) are stacked is adopted.

The direction of the electric field generated by the difference in the electrode configuration slightly changes. The direction of the electric field in the IPS system is the direction in which the electrodes are opposed (Y direction in the figure). In the electrode structure, the electrodes 203, 20
4 have a strong electric field component not only in the lateral direction (Y direction in the figure) but also in the direction perpendicular to the substrate surface (Z direction in the figure) especially near the edge of the electrode 203. As a result, in the IPS mode, the liquid crystal molecules 202 positioned between the electrodes 203 and 204 are driven, but the liquid crystal molecules positioned above the electrodes are hardly driven, but in the FFS mode, the liquid crystal molecules positioned between the electrodes 203 and 204 are driven. Molecules, of course,
The liquid crystal molecules 202 located above the electrodes 203 are also driven. Therefore, in the FFS method, an electrode is formed of indium tin oxide (hereinafter, Idium tin oxide).
If a transparent conductive film (such as TO) is used, the electrode portion can also contribute to the display, and the IPS under the same conditions can be used.
There is an advantage that the aperture ratio can be increased as compared with the liquid crystal display device of the system.

[0005]

If the FFS system having the above configuration is adopted, the liquid crystal on the electrodes can be driven.
The aperture ratio can be increased as compared with the S type, a bright image can be obtained, and the display can be made high definition. However, even with the FFS method capable of increasing the aperture ratio, if the size of the pixel is further reduced to achieve higher definition, the arrangement of liquid crystal molecules at the center of the pixel electrode or between the pixel electrodes is disturbed (disclination). There was a problem that it could not be ignored. Disclination in a liquid crystal display device driven by a lateral electric field is caused by a limited range in which an electric field generated between a pixel electrode and a common electrode can act on liquid crystal, and this disclination is reduced. For this reason, there are methods such as optimizing the design of the pixel electrode, but there is a limit to reducing disclination while maintaining a high aperture ratio, and it is possible to drive even a weak electric field at a position away from the electrode. There has been a demand for the development of a liquid crystal display device having a possible liquid crystal material. However, although research on a liquid crystal material suitable for a liquid crystal display device of a vertical electric field type (TN mode or the like) generally used in the past has been made, a liquid crystal display device driven by a horizontal electric field such as the IPS mode or the FFS mode has been studied. There have been few studies on suitable liquid crystal materials to date.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a characteristic of a liquid crystal material suitable for a liquid crystal display device which performs display by driving a liquid crystal by a lateral electric field generated between electrodes. It is another object of the present invention to provide a liquid crystal display device in which the use of this liquid crystal material prevents disclination and enables high definition. Another object of the present invention is to provide an electronic device having a liquid crystal display device capable of high definition display in a display portion.

[0007]

Means for Solving the Problems To solve the above problems, the present inventor has proposed a method of optimizing the behavior of liquid crystal molecules when the liquid crystal molecules constituting the liquid crystal layer are driven by a lateral electric field. However, by using a drivable liquid crystal material and ensuring that the liquid crystal molecules far from the position where the electric field is generated can be driven, it was thought that disclination, which is a disorder in the arrangement of the liquid crystal molecules, could be prevented. The present inventor has conducted intensive studies on the characteristics of the liquid crystal material, and as a result, by appropriately setting the elastic constant of the liquid crystal material, it is possible to optimize the behavior of liquid crystal molecules driven by a lateral electric field. Therefore, a liquid crystal material that can be driven by a weak electric field can be used. By using a liquid crystal material that can be driven by this weak electric field, disclination in a liquid crystal display device in which liquid crystal is driven by a lateral electric field can be obtained. It has been found that high definition of a liquid crystal display device can be realized by preventing the problem.

That is, in the liquid crystal display device of the present invention, liquid crystal is sandwiched between a pair of substrates facing each other, and at least one of the pair of substrates has a common electrode and a pixel electrode;
The liquid crystal is a liquid crystal display device driven by a lateral electric field generated between a common electrode and a pixel electrode, and the elastic constants K11, K22, and K33 of the liquid crystal material constituting the liquid crystal are K3
3 / K11 ≧ 1.5 and 1.1 ≦ (K33 / K22−
K33 / K11) ≦ 2.7. Here, K11 is the elastic constant in the spray mode, K22 is the elastic constant in the twist mode, and K33 is the elastic constant in the bend mode.

The behavior of liquid crystal molecules in response to an external electric field is generally given by elastic constants K11, K22, and K33 for respective strains of spray mode (spread), twist mode (twist), and bend mode (bend).
In particular, the elastic constant ratios K33 / K11 and K33 / K22 are
It is a parameter that affects the steepness of the rise. The liquid crystal according to the present invention can be driven even by a weak electric field at a position away from the electrodes by optimizing the elastic constant ratio for a liquid crystal display device driven by a lateral electric field. Specifically, by setting the elastic constant ratios K33 / K11 and K33 / K22 of the liquid crystal material so as to satisfy the above relational expression, a liquid crystal that can be driven by a weak electric field when driven by a lateral electric field is configured. As a result, in the liquid crystal display device including the liquid crystal, the range in which the electric field acts can be widened, and disclination between the central portion of the pixel electrode and between the electrodes can be prevented.
The numerical range in the relational expression of the elastic constant ratio in the present inventor has been derived by a simulation performed by the present inventor, and the reason that the numerical range is optimal will be described later in detail.

Next, in the liquid crystal display device of the present invention,
The elastic constant of the liquid crystal material constituting the liquid crystal is 1.7 ≦
It is preferable to satisfy the relational expression of (K33 / K22-K33 / K11) ≦ 2.7. According to the configuration of the present invention, the behavior of the liquid crystal material when driven by the lateral electric field can be further optimized, so that disclination in the liquid crystal display device can be more effectively prevented and the liquid crystal display device can be improved. And the liquid crystal display device with higher definition can be realized.

Next, in the liquid crystal display device of the present invention,
The driving voltage of the liquid crystal can be 5 V or less. According to the configuration of the present invention, since the liquid crystal that can be driven by a weak electric field is provided, the liquid crystal can be driven even when the electric field generated by the pixel electrode and the common electrode is weakened. The driving voltage of the liquid crystal display device for causing this to be reduced can be reduced to 5 V or less. Therefore, low power consumption of the liquid crystal display device can be realized. Also,
According to the configuration of the present invention, the degree of alignment of the liquid crystal is saturated even by an electric field generated by a driving voltage of 5 V or less. Therefore, even if the electric field acting on the liquid crystal changes due to the fluctuation of the driving voltage to the electrodes. , Since the degree of orientation of the liquid crystal does not change,
It is possible to realize a liquid crystal display device having uniform brightness without causing unevenness in display brightness.

Next, in the liquid crystal display device of the present invention,
An electrode arrangement of a fringe field switching system is adopted for at least one of the pair of substrates, and a substrate having a fringe field switching electrode arrangement is provided above a common electrode and a part of the common electrode. It is preferable that the pixel electrode be provided with a pixel electrode formed with an insulating layer interposed therebetween. The electrode arrangement of the fringe field switching (FFS) method in the configuration of the present invention means that the cell gap is d, the electrode width is w, and the distance between the electrodes is L, where L / d <1 and L / w <1. That is, a configuration in which the inter-electrode distance is smaller than the cell gap and the inter-electrode distance is smaller than the electrode width, or L / d = 0 and L / w =
0 (l = 0), that is, a configuration in which a pixel electrode is formed above a part of a common electrode via an insulating layer. In particular, when the latter configuration is adopted, the area of the common electrode can be increased (for example, the common electrode is formed solid), and the following advantages are obtained.

When the pixel electrode on the substrate having the FFS type electrode arrangement is formed of a transparent conductive film and the common electrode is formed of a metal film, the common electrode functions not only as an electrode but also as a reflection layer. Therefore, if both the pixel electrode and the common electrode on the other substrate are formed of a transparent conductive film, a reflection type liquid crystal display device can be realized without adding another reflection layer or an external reflection plate.

Further, if particles such as beads for scattering light are added to the insulating layer interposed between the pixel electrode and the common electrode, or if irregularities are formed on the surface, this insulating layer may It also functions as a scattering layer. According to this configuration, it is possible to realize a reflective liquid crystal display device that is uniformly bright over the entire surface without newly adding a light scattering layer.

The driving method of the liquid crystal of the liquid crystal display device of the present invention includes an in-plane switching (IPS) method,
Although any of the FFS methods may be used, it is more preferable to use the FFS method. If the FFS method is adopted, the liquid crystal molecules located above the pixel electrodes are also driven as described above, so that the electrodes can be made to contribute to display by forming the electrodes with transparent electrodes, and the same conditions can be applied. Since the aperture ratio can be increased as compared with the IPS system, a brighter display can be obtained.

Next, in the liquid crystal display device of the present invention,
It is preferable that the pixel electrode has a width of 5 μm or less. According to the configuration of the present invention, the electric field from the edge of the pixel electrode can be applied to the liquid crystal located at the center of the pixel electrode. Since the liquid crystal can be reliably driven even in the central portion of the electrode where it is difficult to operate, a liquid crystal display device having uniform brightness over the entire surface can be realized.

Next, an electronic apparatus according to the present invention is characterized in that the liquid crystal display device described above is provided in a display unit. According to the configuration of the present invention, it is possible to realize an electronic device including a higher definition liquid crystal display unit.

[0018]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

(Liquid Crystal Display Device) The liquid crystal display device of this embodiment is an example of a transmission type TFT color liquid crystal display device. FIG. 1 is a plan view showing the structure of a lower substrate, and FIG. −
FIG. 3 is a partial cross-sectional view along the line A. In the present embodiment, an FFS type electrode configuration is employed for the lower substrate. In all of the following drawings, the thickness of each component, the ratio of dimensions, and the like are appropriately changed in order to make the drawings easy to see.

The liquid crystal display device of the present embodiment has an upper substrate,
The liquid crystal is sandwiched between a pair of lower substrates.
As shown in FIG. 1, the configuration of the lower substrate 1 is a matrix such that a plurality of data lines 3 extending in the vertical direction in the figure and a plurality of gate lines 3 extending in the horizontal direction in the figure cross each other. Is provided. In the lower left part of each pixel in the figure, a gate line 3 branches toward the inside of the pixel, and a part extending along the gate line 3 becomes a gate electrode 4, and a thin film transistor 5 for pixel switching (Thin Film Transistor,
(Hereinafter abbreviated as TFT). Further, a comb-shaped pixel electrode 6 having a plurality of (ten in FIG. 1) electrode fingers 6a extending in the vertical direction in the figure is provided, and a portion connecting the electrode fingers 6a of the pixel electrode 6 is provided. It overlaps the gate electrode 4 in a plane.

According to the sectional structure shown in FIG. 2, a liquid crystal 22 is sandwiched between the lower substrate 1 and the upper substrate 7. The lower substrate 1 has a configuration in which a common electrode 14 which is formed of a transparent conductive film such as ITO and functions as an electrode is formed on a substrate 13 made of glass or the like, and an insulating layer 15 made of a light transmitting material is formed on the common electrode 14. Is formed, and a pixel electrode 6 made of a transparent conductive film such as ITO is formed on the insulating layer 15. Then, an alignment film 16 on which vertical alignment processing is performed is formed on the entire surface of the substrate so as to cover the pixel electrode 6. As a material of the alignment film 16, polyimide, a surfactant, a coupling agent, a metal complex, or the like can be used. Further, an alignment film including a metal film and a monomolecular film formed on the surface of the metal film by a sulfur compound molecule having a linear structure can also be used. The rubbing process may or may not be performed.

On the other hand, as shown in FIG. 2, for example, R (red), G
A color filter 18 having a colored layer of each color (green) and B (blue) and a light-shielding layer (black matrix) is formed. The color filter 18 is used to flatten unevenness formed by the color filter. A flattening film 19 is formed. Then, an alignment film 21 is formed on the entire surface of the substrate so as to cover the flattening film 19. The same material as that of the lower substrate 1 can be used as the material of the alignment film 21.

In the present embodiment, since the lateral electric field is used for driving the liquid crystal, the viewing angle can be widened, and defects such as light leakage do not occur. Further, in the case of the present embodiment, the liquid crystal on the pixel electrode 6 can be driven because the FFS type electrode configuration is adopted even for the substrate in the same lateral electric field mode, and the portion of the pixel electrode 6 is also displayed. Since it can contribute, the aperture ratio can be improved as compared with the case where the IPS method is used. Also, F
In the FS method, when a stacked structure is used as in the present embodiment, the common electrode 14 can be formed in a solid state, so that the common electrode 14 can be formed very easily. Furthermore, if the common electrode 14 is formed of a metal film having high reflectivity such as aluminum or silver, the common electrode 1
Since 4 can be used as a reflection layer, a reflection-type liquid crystal display device can be realized extremely rationally by utilizing the features of the FFS system.

In this embodiment, the common electrode 14 of the lower substrate 1
The liquid crystal 22 is driven by a horizontal electric field generated at the pixel electrode 6 and has an elastic constant of K33 / K11 ≧ 1.5 and 1.1 ≦ (K33 / K
22−K33 / K11) ≦ 2.7. With this configuration, the liquid crystal 22 can be driven even at a low voltage, and the liquid crystal 22 located above the pixel electrode 6 where the applied electric field is relatively weak can be driven reliably. Therefore, the liquid crystal display device of the present embodiment can obtain a uniform transmittance over the entire surface of the pixel, and can obtain a uniform and bright display.

Further, the above elastic constant is calculated as K33 / K11
≧ 1.5 and 1.7 ≦ (K33 / K22-K33 / K
11) If it is set so as to satisfy the relational expression of 2.7, the liquid crystal distant from the position where the electric field is generated can be driven more reliably, so that the alignment state of the liquid crystal can be uniformed over the entire surface of the pixel. Therefore, a more uniform and bright display can be obtained.

(Electronic Apparatus) As an example of an electronic apparatus using the liquid crystal display device according to the present invention, a configuration of a projection display apparatus will be described with reference to FIG.

In FIG. 5, a projection type display device 1100 is shown.
FIG. 1 shows a schematic configuration diagram of an optical system of a projection type liquid crystal display device using three liquid crystal display devices of the present invention prepared as RGB liquid crystal display devices 962R, 962G, and 962B, respectively.

A light source device 920 and a uniform illumination optical system 923 are employed in the optical system of the projection type display device of this embodiment. Then, the projection display apparatus uses the uniform illumination optical system 9.
A color separation optical system 92 as a color separation unit that separates a light beam W emitted from 23 into red (R), green (G), and blue (B).
4, three light valves 925R, 925G, and 925B as modulation means for modulating the color light beams R, G, and B;
A color synthesizing prism 910 as a color synthesizing means for re-synthesizing the modulated color luminous flux, and a projection surface 10
A projection lens unit 906 is provided as projection means for performing enlarged projection on the surface of the projection lens 0. Further, a light guide system 927 for guiding the blue light flux B to the corresponding light valve 925B is provided.

The uniform illumination optical system 923 includes two lens plates 921 and 922 and a reflection mirror 931. The two lens plates 921 and 922 are arranged so that the reflection mirror 931 is interposed therebetween. Uniform illumination optical system 923
The two lens plates 921 and 922 each include a plurality of rectangular lenses arranged in a matrix. The light beam emitted from the light source device 920 is transmitted to the first lens plate 92.
The light is split into a plurality of partial light beams by one rectangular lens.
Then, these partial light beams are divided into three light valves 925R and 925R by the rectangular lens of the second lens plate 922.
Superimposed around 5G and 925B. Therefore, by using the uniform illumination optical system 923, even when the light source device 920 has an uneven illuminance distribution in the cross section of the emitted light beam, the three light valves 925R, 925G, and 925B are used.
Can be illuminated with uniform illumination light.

Each color separation optical system 924 includes a blue-green reflecting dichroic mirror 941, a green reflecting dichroic mirror 942, and a reflecting mirror 943. First, in the blue-green reflecting dichroic mirror 941, the blue light beam B and the green light beam G included in the light beam W are reflected at right angles, and head toward the green reflecting dichroic mirror 942. The red light beam R passes through the mirror 941, is reflected at a right angle by the rear reflection mirror 943, and is emitted from the emission unit 944 of the red light beam R to the prism unit 910 side. Next, in the green reflection dichroic mirror 942, only the green light flux G among the blue and green light fluxes B and G reflected by the blue-green reflection dichroic mirror 941 is reflected at a right angle, and the color is emitted from the emission part 945 of the green light flux G. The light is emitted to the side of the combining optical system. The blue light flux B that has passed through the green reflection dichroic mirror 942 is emitted from the emission section 946 of the blue light flux B to the light guide system 927 side. In this example,
From the light emitting portion of the light beam W of the uniform illumination optical element, the light emitting portions 944, 945, and 94 of the respective color light beams in the color separation optical system 924.
6 are set to be approximately equal.

The red and green luminous flux R of the color separation optical system 924
Condensing lenses 951 and 952 are arranged on the emission sides of the G emission sections 944 and 945, respectively. Therefore,
The red and green luminous fluxes R and G emitted from the respective emission sections are incident on these condenser lenses 951 and 952 and are parallelized.
The red and green light fluxes R and G thus collimated enter the light valves 925R and 925G and are modulated, and image information corresponding to each color light is added. That is, the switching of these liquid crystal devices is controlled by driving means (not shown) according to image information.
The modulation of each color light passing therethrough is performed. On the other hand, the blue light flux B is transmitted through the light guide system 927 to the corresponding light valve 9.
25B, where it is similarly modulated according to image information. In addition, the light valve 925R of this example,
925G and 925B further include an entrance-side polarization unit 960R, 960G and 960B, and an exit-side polarization unit 96, respectively.
This is a liquid crystal light valve including 1R, 961G, 961B, and liquid crystal devices 962R, 962G, 962B disposed therebetween.

The light guide system 927 is a light emitting section 94 for the blue light flux B.
No. 6, a condenser lens 954 disposed on the exit side, an incident-side reflection mirror 971, an exit-side reflection mirror 972, an intermediate lens 973 disposed between these reflection mirrors, and a front side of the light valve 925B. And a condenser lens 953. The blue light flux B emitted from the condenser lens 946 is transmitted through the light guide system 927 to the liquid crystal device 962B.
And modulated. The optical path length of each color beam, that is,
Each liquid crystal device 962R, 962G, 9
The distance to 62B is the longest for the blue luminous flux B, and therefore the loss of light quantity of the blue luminous flux is the largest. However, by interposing the light guide system 927, the loss of light amount can be suppressed.

Each light valve 925R, 925G, 92
The color light fluxes R, G, and B modulated through 5B are incident on a color combining prism 910, where they are combined. Then, the light combined by the color combining prism 910 is enlarged and projected on the surface of the projection surface 100 at a predetermined position via the projection lens unit 906.
Although not shown, since the liquid crystal device and the polarizing means are formed separately from each other, an air layer is formed between the liquid crystal device and the polarizing means. By sending air such as cool air to the liquid crystal device, a rise in the temperature of the liquid crystal device can be further prevented, and a malfunction due to a rise in the temperature of the liquid crystal device can be prevented.

In the present embodiment described above, the liquid crystal panel used for the transmission type liquid crystal device of the active matrix system has been described for convenience as a liquid crystal driving system. Since the method of driving liquid crystal can be applied without any problem, the image display method is not limited to the above embodiment, and can be applied to both color display and monochrome display, and is not limited to the transmission type. Needless to say, a reflection type, a transflective type or a projection type may be used.

(Other Electronic Apparatus) As another example of an electronic apparatus using the liquid crystal device (electro-optical device) of each of the above-described embodiments, see FIG. 6 for a configuration of a portable electronic apparatus such as a small portable information terminal. I will explain. FIG. 6A is a perspective view illustrating an example of a mobile phone. In FIG. 6A, reference numeral 1000 denotes a mobile phone main body, and reference numeral 1001 denotes a liquid crystal display unit using the above-described liquid crystal display device. FIG.
(B) is a perspective view showing an example of a wristwatch-type electronic device. In FIG. 6B, reference numeral 1100 denotes a watch main body, and reference numeral 1101 denotes a liquid crystal display unit using the above-described liquid crystal display device. FIG. 6C is a perspective view illustrating an example of a portable information processing device such as a word processor, a personal computer, and a PDA (Parsonal Digital Assistant). FIG.
In (c), reference numeral 1200 denotes an information processing device, and reference numeral 1 denotes
Reference numeral 202 denotes an input unit such as a keyboard, reference numeral 1204 denotes an information processing apparatus main body, and reference numeral 1206 denotes a liquid crystal display unit using the above-described liquid crystal display device.

Since the electronic apparatus shown in FIGS. 6A to 6C includes the liquid crystal display using the liquid crystal device of the above embodiment, the liquid crystal can be driven by a weak electric field at a position away from the electrodes. By preventing disclination by adopting an electronic device, it is possible to realize an electronic device having a display unit that supports high definition. Note that the technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventor conducted a simulation for verifying the effects of the present invention. Hereinafter, the results will be described.

(Embodiment 1) In this embodiment, FIGS.
In the liquid crystal display device having the structure shown in (1), the elastic constant ratio of the liquid crystal interposed between the substrates was changed as a parameter, and the change in the transmittance of the liquid crystal display device due to this was derived. As a condition for the simulation, the pixel electrode width w is set to 5
μm, the interval m between pixel electrodes was 5 μm, and the thickness of the insulating film between the pixel electrode and the common electrode was 150 nm. The cell gap d was 3 μm.

First, in the above-mentioned liquid crystal display device, the liquid crystal is oriented in a direction parallel to the substrate surface, and is generally used as a parameter representing the behavior of the liquid crystal material when an electric field is applied, and can be measured. Elastic constant ratio K33 / K
11, K33 / K22 and their difference (K33 / K2
2-K33 / K11) was employed to derive a change in transmittance of the liquid crystal display device by changing these parameters. For K33, K22, and K11, ranges that can be actually synthesized are determined as the physical property values of the liquid crystal. For example, an elastic constant K33 of a certain liquid crystal molecular material can be synthesized only up to twice the elastic constant K11 of another liquid crystal molecular material, or an elastic constant K33 of a certain liquid crystal molecular material is an elastic constant of another liquid crystal molecular material. Liquid crystal materials up to three times the size of K11 can be developed. Therefore, K33 / K11 and K33 / K22 are taken into consideration in consideration of actual materials and dimensionless values.
Was adopted as a parameter. The ratio of these parameters is an optimal parameter when considering the FFS mode liquid crystal mode.

First, (K33 / K22)
−K33 / K11), in order to verify the change in the transmittance of the liquid crystal display device when K33 / K11 is changed, 1.
9, and as shown in Table 1, (K33 / K22-K
33 / K11) was derived when the value was changed in the range of 1.0 to 2.8. Table 1 shows the results of the simulation, and FIG. 3 shows (K33 / K22-K33 / K1
1) shows the transmittance distribution in the vicinity of each pixel electrode when 2.5 and 1.0 are set. Next, K33 / K11
The value of (K33 / K22-K33 / K11) is fixed at 2.5 and the value of K33 / K11 is set to 1.0 to 1 in order to verify the change in transmittance of the liquid crystal display device when .
The transmittance when changed in the range of 9 was derived. Table 2 shows the results of this simulation.

When used as a transmissive liquid crystal display device, the average transmissivity must be 0.6 or more. This means that when the average transmittance is less than 0.6, the ends of the electrode shapes arranged in a wedge shape when viewed in a plan view include:
Since no electric field is generated in the normal direction of the electric field, the orientation of the liquid crystal molecules is disturbed and the transmittance is reduced, resulting in a very dark panel display. When the average transmittance is 0.6, the average transmittance is 0.1.
Some places have a transmittance of less than 6. From these facts, those having an average transmittance of 0.6 or less are remarkably large, so that an average transmittance of 0.6 or more is desired to obtain a bright display. As shown in Table 1, 1.1 ≦
In a liquid crystal display device in which (K33 / K22-K33 / K11) ≦ 2.7, it was confirmed that an average transmittance of 0.6 or more was obtained. Also, 1.7 ≦ (K33 / K
22−K33 / K11) ≦ 2.7, 0.6
It was confirmed that a high average transmittance of 5 or more was obtained.
And (K33 / K22-K33 / K11) = 2.5
Then, it was confirmed that bright display with an average transmittance of 0.7 was possible. Also, as shown in Table 2, K3
When 3 / K11 is 1.5 or more, an average transmittance of 0.65 or more is obtained, but K33 / K11 is 1.5 or more.
If less than (K33 / K22-K33 / K11)
Was in the above range, it was confirmed that only an average transmittance of 0.55 or less was obtained.

FIG. 3 is a graph showing the transmittance distribution in the width direction with one electrode finger as the center. The horizontal axis shows the distance from the center of the electrode finger, and the vertical axis shows the transmittance. . The curve indicated by reference numeral 30 in FIG. 3 is (K33 / K22
−K33 / K11) = 2.5 is a curve showing the transmittance distribution, and the curve denoted by reference numeral 31 is (K33 / K11).
It is a curve which shows the transmittance distribution at the time of setting 22-K33 / K11) = 1.0. As shown in FIG. 3, (K33 / K22-K33 / K11) indicated by reference numeral 30 = 2.
The transmittance distribution of the liquid crystal display device set to 5 is indicated by reference numeral 31 (K33 / K22-K33 / K11) = 1.0.
Compared to the transmittance distribution of the liquid crystal display device, the average transmittance and the transmittance distribution are both excellent. In particular, the drop of the transmittance above the pixel electrode is small, and the excellent transmittance characteristics are obtained. It can be seen that the liquid crystal display device was provided. From the above, the liquid crystal display device according to the present invention is:
It was confirmed that it had excellent characteristics in average transmittance and transmittance distribution.

[0043]

[Table 1]

[0044]

[Table 2]

(Embodiment 2) In this embodiment, in order to verify the effect of defining the pixel electrode width, FIGS.
The change in the transmittance when the pixel electrode width w and the drive voltage were changed in the liquid crystal display device having the configuration shown in FIG. As conditions for the simulation, the distance m between the pixel electrodes was 5 μm, and the thickness of the insulating film between the pixel electrode and the common electrode was 1500 °. Also,
The cell gap d was 3 μm. The elastic constant ratio of the liquid crystal is K33 / K11 = 1.9 and (K33 / K11, respectively).
22-K33 / K11) = 2.5.

FIG. 4 shows the result of deriving the transmittance of the liquid crystal display device having the above configuration by changing the pixel electrode width w and the driving voltage. The horizontal axis of the graph shown in FIG. 4 indicates the drive voltage (V), and the vertical axis indicates the maximum transmittance. Here, the maximum transmittance indicates the maximum of the average transmittance when the entire surface of the pixel is turned on. From the graph shown in FIG.
Is 4 μm and 5 μm, it was confirmed that a maximum transmittance of 0.8 or more was obtained and the transmittance was saturated at a driving voltage of less than 5 V. Therefore, in the liquid crystal display device according to the present invention, for example, when driving with a driving voltage of 5 V, a stable high transmittance can be obtained even when there is a fluctuation of the driving voltage of about ± 0.5 V. confirmed. On the other hand, when the pixel electrode width w is set to 6 μm and 7 μm, even if the driving voltage is increased to 6 V, 0.55 (w = 6 μm)
m) and 0.4 (w = 7 μm), and the maximum transmittance is not saturated with respect to the driving voltage.
The transmittance tends to increase as the drive voltage increases. This suggests that when the pixel electrode width is set to 6 μm or more, the transmittance varies with the variation of the driving voltage.

[0047]

As described above in detail, in the liquid crystal display device of the present invention, the elastic constant of the liquid crystal sandwiched between the substrates is K33 / K11> 1.5 and 1.1 ≦ (K33 / K
22−K33 / K11) ≦ 2.7, so that the liquid crystal can be driven at a low voltage, and the liquid crystal on the pixel electrode can be driven without fail. In addition, uniform and bright display can be achieved over the entire surface of the pixel by preventing the pixelation. In addition, since the driving range of the liquid crystal can be expanded as described above, a bright display can be obtained by increasing the aperture ratio, and a liquid crystal display device capable of high definition can be provided. Further, according to the invention, by providing the liquid crystal display device corresponding to the above-described high definition in the display portion, it is possible to provide an electronic device including the display portion having excellent visibility.

[Brief description of the drawings]

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

FIG. 2 is a partial cross-sectional view of the liquid crystal display device shown in FIG. 1, taken along line AA.

FIG. 3 is a graph showing a transmittance distribution in a pixel electrode width direction according to an embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a driving voltage and a maximum transmittance according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of an electronic apparatus including the liquid crystal display device according to the present invention.

FIGS. 6A to 6C are diagrams showing another example of the electronic device according to the present invention.

FIG. 7 is a diagram for explaining the principle of a liquid crystal display device in a lateral electric field mode ((a) IPS mode, (b) FFS mode).

[Explanation of symbols]

 1 lower substrate 6 pixel electrode 7 upper substrate 14 common electrode 22 liquid crystal

Continued on the front page F term (reference) 2H088 EA14 EA15 HA03 HA08 HA12 HA13 HA21 HA23 HA24 HA28 JA03 KA08 MA03 MA06 MA18 2H092 GA13 GA14 JA24 NA01 NA04 NA07 PA02 PA07 PA08 PA12 PA13 QA05

Claims (6)

[Claims] 1. A liquid crystal is sandwiched between a pair of substrates facing each other, a common electrode and a pixel electrode are provided on at least one of the pair of substrates, and the liquid crystal is a horizontal electric field generated between the common electrode and the pixel electrode. A liquid crystal display device driven by a liquid crystal display, wherein elastic constants K11 and K2 of a liquid crystal material forming the liquid crystal are
2, K33, K33 / K11 ≧ 1.5 and 1.1 ≦ (K33 / K22
−K33 / K11) ≦ 2.7. Here, K11 is the elastic constant in the spray mode, K22 is the elastic constant in the twist mode, and K33 is the elastic constant in the bend mode. 2. An elastic constant of a liquid crystal material constituting the liquid crystal is 1.7 ≦ (K33 / K22−K33 / K11) ≦
2. The liquid crystal display device according to claim 1, wherein a relational expression of 2.7 is satisfied. 3. The liquid crystal display device according to claim 1, wherein a driving voltage of the liquid crystal is 5 V or less. 4. A fringe field switching type electrode arrangement is adopted for at least one of the pair of substrates, and a substrate having the fringe field switching type electrode arrangement is a common electrode and a common electrode. The liquid crystal display device according to any one of claims 1 to 3, further comprising a pixel electrode formed above a part thereof with an insulating layer interposed therebetween. 5. The liquid crystal display device according to claim 4, wherein the pixel electrode has an electrode width of 5 μm or less. 6. An electronic apparatus comprising the liquid crystal display device according to claim 1. Description: