JP3230754B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-division driven field effect type liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device is widely used as a display device for office equipment and the like, and is required to have a large display screen, a large number of pixels and a high display quality.
For such display devices as office equipment, liquid crystal display devices having a simple matrix structure that can simplify the element structure and the drive device are widely used.

In this liquid crystal display element having a simple matrix structure, the signal electrode and the scanning electrode intersect one substrate on which signal electrodes are formed in a stripe shape and the other substrate on which scanning electrodes are formed in a stripe shape. As described above, a liquid crystal cell is formed by interposing a twist-oriented liquid crystal material between the one substrate and the other substrate, and a pair of polarizing plates is disposed outside the liquid crystal cell. And
By supplying a scanning signal to the scanning electrode and supplying a data signal to the signal electrode in synchronization with the scanning signal, the lighting state of any pixel where the scanning electrode and the signal electrode intersect is controlled.

In such a time-division driving method, when the number of time-division is increased, the difference between the voltages applied to the illuminated pixels and the non-illuminated pixels, that is, the operating margin is reduced, the contrast is reduced, and the viewing angle is narrow. Become. Therefore, the conventional TN
In the liquid crystal display device of the type, since the abruptness of the luminance change with respect to the applied voltage is inferior, it is limited to take a time division number of about 1/60 duty, and a large number of pixels and a high quality and large display device are obtained. I couldn't do that.

[0005] In order to improve such abruptness, STN-type liquid crystal display elements and SBE-type liquid crystal display elements in which the twist angle is increased have been proposed and put to practical use.
These liquid crystal display elements improve the agility by setting the twist angle to 180 ° to 270 °,
The time division number can be taken up to about 200 duty. As a result, in the case of a 640 × 400 dot liquid crystal display element, the signal electrode is divided into two parts, the display screen is divided into upper and lower parts, and each pixel is driven at a duty of 1/200.

[0006]

In the above-mentioned liquid crystal display element, the signal electrode is divided into two parts in the upper and lower parts at the center. Therefore, the pixel in the central part where the scanning electrode and the signal electrode adjacent to the divided part are opposed to each other. Is dependent on the positioning accuracy of the opposing substrate, and the positioning error cannot be eliminated.
Since lines for dividing the screen appear, and the signal electrodes are divided into upper and lower parts, driving circuits for supplying data signals to the signal electrodes are required twice as many as the number of signal electrodes, and A scan electrode drive circuit that supplies a scan signal to the scan electrode requires complicated signal processing to scan the scan electrodes in two groups, resulting in a complicated drive circuit and a large number of electronic circuit elements. As a result, the display device becomes large and expensive.

In addition, the above-mentioned liquid crystal display element is required to have stable operation and reliability when operated for a long time. This stability and reliability are considered to be due to the influence of ionic impurities contained in the liquid crystal material.
However, since it is difficult to completely remove ionic impurities in the liquid crystal material, there has been a problem that the operation becomes unstable and the reliability of long-time operation is lacking.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object the purpose of having high contrast, excellent agility of luminance change, and high-speed response, enabling high time-division driving, and stabilizing for a long time. It is an object of the present invention to provide a liquid crystal display device which operates by using a liquid crystal display.

[0009]

[Means for Solving the Problems] of claim 1 invention comprises a pair of substrates facing each other, the opposing electrodes cross each other are formed on the opposed inner surfaces of the pair of substrates, the one <br /> with a liquid crystal material having interposed positive dielectric anisotropy which is twist-aligned by the inter-alignment film formed on the pair of substrates, and a pair of polarizing plates disposed to sandwich the pair of substrates In the liquid crystal display device, the liquid crystal material includes a bent elastic constant K33.
Constant ratio K expressed as the ratio of the splay elastic constant K11
A liquid crystal having a value of 33 / K11 of 1.75 or more and a dielectric constant ratio Δε / ε⊥ of 2 or less, which is a ratio of a dielectric anisotropy Δε and a dielectric constant ε⊥ in a direction orthogonal to the liquid crystal molecular axis. , the pretilt angle of the liquid crystal molecules prior Sharing, ABS direction juxtamembrane of 6 ° or more, and wherein said being twisted at about 230 ° to 250 ° angle between one <br/> pair of substrates .

According to a second aspect of the present invention, a pair of substrates arranged opposite to each other, electrodes formed on inner surfaces of the pair of substrates opposite to each other and intersecting each other, and an alignment film formed on the pair of substrates are provided. A liquid crystal display device having a liquid crystal material having a positive dielectric anisotropy that is twist-aligned with a pair of substrates, and a pair of polarizing plates disposed with a pair of substrates interposed therebetween. The value of the dielectric constant ratio Δε / ε⊥, which is the ratio of the property Δε to the dielectric constant ε⊥ in the direction orthogonal to the liquid crystal molecular axis, is 2 or less, the value of the dielectric constant ε⊥ is smaller than 4, and the average dielectric constant is

The liquid crystal display device is characterized in that it is composed of a liquid crystal having a value of 6 or less and is twisted at an angle of about 230 ° to 250 ° between a pair of substrates.

[0011]

According to the first aspect of the present invention, the twist angle of the liquid crystal material is increased to about 230 ° to 250 °, and the elasticity of the vent is determined.
Elasticity constant expressed by the ratio of number K33 to spray elastic constant K11
The value of the number ratio K33 / K11 is as large as 1.75 or more, and the value of the dielectric constant ratio Δε / ε⊥, which is the ratio of the dielectric anisotropy Δε to the dielectric constant ε⊥ in the direction orthogonal to the liquid crystal molecular axis, is 2 it is possible to obtain rapid Shun threshold characteristics by reducing or less,
By increasing the pretilt angle of the liquid crystal molecules located in the vicinity of the alignment film of the liquid crystal layer interposed between the alignment films to 6 ° or more, the d / p margin (that is, the liquid crystal material is aligned at a constant twist angle, orientation is stabilized becomes larger region) of certain operations upon application, thereby high contrast and excellent rapid Shun and fast response of the brightness change can be obtained, division driving is possible when high.

According to the second aspect of the present invention, the dielectric anisotropy Δε
The dielectric constant ratio Δε / ε⊥, which is the ratio of the dielectric constant and the dielectric constant ε⊥ in the direction perpendicular to the liquid crystal molecular axis, is reduced to 2 or less to improve the response characteristics and the average dielectric constant.

Since the value of 外 is set to 6 or less and the value of the dielectric constant ε⊥ is set to 4 or less, it becomes difficult to take in the ionic impurities adsorbed at the interface of the alignment film into the liquid crystal material again. The amount of mobile ions inside is reduced, and operation stability and reliability when operated for a long time can be improved.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 1, reference numeral 1 denotes a lower substrate made of a glass plate or an isotropic plastic plate. On the upper surface of the lower substrate 1, a plurality of first electrodes 2 made of a stripe-shaped transparent conductive film extending in the front-to-back direction of the drawing are shown.
Is formed, and an alignment film 3 is formed so as to cover the first electrode 2. The alignment film 3 is subjected to an alignment process. The upper substrate 4 opposed to the lower substrate 1 is formed of a glass plate or an isotropic plastic plate, and a lower surface facing the lower substrate 1 is formed on a paper surface so as to be orthogonal to the first electrode 2. A plurality of second electrodes 5 made of a stripe-shaped transparent conductive film extending in the left-right direction are formed, and an alignment film 6 is formed so as to cover the second electrodes 5. The alignment film 6 is subjected to an alignment process. ing. The upper substrate 4 and the lower substrate 1 face each other on the surfaces on which the electrodes 2 and 5 are formed, are joined by a sealing material 7 with a gap of 4 μm to 9 μm, and a liquid crystal material 8 is provided between these substrates 1 and 4. Is enclosed. Polarizing plates 9 and 10 are arranged outside the upper and lower substrates 1 and 4 joined by the sealing material 7.

The alignment films 3 and 6 are formed of a high tilt alignment film made of polyimide or the like which gives a liquid crystal molecule adjacent to the alignment films 3 and 6 of the liquid crystal material 8 a pretilt angle of about 6 ° or more in an initial alignment state. As shown in FIG.
0 with respect to a horizontal line h parallel to the upper and lower edges of the lower substrate 1
The rubbing process is performed in the upward direction where the alignment direction 3a of the alignment film 3 crosses counterclockwise at an angle of about 30 °, and the alignment direction 6a of the alignment film 6 of the upper substrate 4 is rotated by about 30 ° clockwise. It is rubbed in the downward right direction that intersects with. For the alignment films 3 and 6, an alignment material having a large polar force component γ _p value of the surface energy is used in order to make mobile ions in the liquid crystal material 8 easily adsorb. The value of the polar force component γ _p of the surface energy is desirably greater than 40 dyn / cm. In this embodiment, for example, an alignment film having a polar force component of the surface energy of 42.1 dyn / cm is used. .

The liquid crystal material 8 sealed between the alignment films 3 and 6 is such that the liquid crystal molecules are aligned in the alignment processing direction 3a of the upper substrate 1.
From the liquid crystal layer thickness d of the liquid crystal layer anisotropy Δn and the liquid crystal layer thickness d. value
It is set in the range of 0.75 to 0.90. This liquid crystal material 8
Is to mix a large number of liquid crystal compounds having a large elastic constant ratio K33 / K11 represented by the ratio between the vent elastic constant K33 and the splay elastic constant K11, to reduce the amount of the liquid crystal compound having a cyano group, and to reduce ester bond and hetero bond. It is a liquid crystal composition formed so as not to contain a cyclic compound, and has a value of an elastic constant ratio K33 / K11 expressed by a ratio of a bent elastic constant K33 to a spray elastic constant K11 of 1.75.
That's all. The liquid crystal material 8 has a dielectric constant ratio Δε / ε⊥ of 2 or less, which is a ratio of the dielectric anisotropy Δε and the dielectric constant (perpendicular component of the dielectric constant) ε⊥ in a direction orthogonal to the liquid crystal molecular axis. And d / p is 0.5. Further, the liquid crystal material 8
In order to make it difficult for the ionic impurities (mobile ions) adsorbed on the alignment films 3 and 6 to be taken into the liquid crystal material 8 again, the vertical component ε⊥ of the dielectric constant is as small as 4 or less, and the average dielectric constant is

[Outside 2] Is as small as 6 or less.

On the other hand, as shown in FIG. 2, the polarizing plates 9 and 10 have a polarizing axis (transmission axis) of the polarizing plate 10 with respect to an alignment processing direction 6a of the alignment film 6 provided on the upper substrate 4. )
10a is oriented in a direction rotated by an angle A in a counterclockwise direction, and the polarization axis (transmission axis) 9a of the polarizing plate 9 is oriented in a direction rotated by an angle B in a counterclockwise direction. That is, the upper substrate 4
The angle A of the polarization axis (transmission axis) 10a of the polarizing plate 10 with respect to the alignment processing direction 6a of the alignment film 6 provided in the above is set in the range of 30 ° to 60 °, and the polarization axis (transmission axis) of the polarizing plate 9 is set.
The angle B of 9a is set in the range of 95 ° to 120 °. Note that this liquid crystal display device is in the yellow mode in which the background color is light yellow. In this liquid crystal display device, it is particularly preferable that the angle A is 50 ° and the angle B is 100 ° as shown in FIG.

The liquid crystal display device shown in FIGS. 3 and 4 is in a B / W mode in which the display color is black and white, and is transmitted between the upper substrate 4 and the upper polarizer 10 to prevent the display screen from being colored. A phase plate 12 for performing light color correction is provided. In this liquid crystal display device, particularly, as shown in FIG.
It is desirable that the angle B is 0 ° and the angle B is 105 °. The phase plate 12 has a phase difference of 500 nm to 600 nm, and its optical axis (slow axis) 12 a
They are arranged in a direction intersecting at an angle C counterclockwise with reference to a. That is, the angle C of the optical axis (slow axis) 12a with respect to the alignment processing direction 6a is set in the range of 55 ° to 90 °, and it is particularly preferable that the angle is about 80 °.

In such an embodiment, the value of the dielectric constant ratio Δε / ε⊥ of the liquid crystal material 8 is reduced to 2 or less.
Since the difference in the absolute value of ε‖−ε⊥ becomes small and the dielectric constant of the liquid crystal layer changes little even when the orientation state of the liquid crystal molecules changes when an electric field is applied, the effective voltage applied to this liquid crystal layer is small. The change in the electric field strength is small, and the sharpness of the change in luminance is extremely improved. That is, as shown in FIG. 5, the value of the agility γ of the liquid crystal display device depends on the elastic constant ratio K33 of the liquid crystal materials 9 and 17.
The larger the value of / K11 and the smaller the value of the dielectric constant ratio Δε / ε⊥, the closer to 1.0, the better the agility. In particular, when the value of the dielectric constant ratio Δε / ε⊥ is as small as 2 or less, the sharpness becomes extremely good. In this case, when the value of the dielectric constant ratio Δε / ε⊥ of the liquid crystal material 8 is reduced to 2 or less, the d / p margin (when the liquid crystal having the natural pitch p is sealed between the upper and lower substrates at the substrate interval d, The molecules are twist-oriented at a predetermined twist angle, for example, 240 °, and the range of the substrate interval d for obtaining uniform twist orientation without unevenness even when a voltage is applied becomes narrower.
Although the upper limit of the d / p margin becomes small as shown in FIG. 6 and a stable twist alignment cannot be obtained, in this embodiment, the pretilt angle of the liquid crystal molecules is 6 ° or more, preferably 8 ° or more. As a result, as shown in FIG.
The margin can be increased and the twist angle is 240
The d / p margin becomes sufficiently large even if it is increased to °, and a stable alignment state can be obtained. For this reason, in this embodiment, the abruptness of the luminance change with respect to the applied voltage of the liquid crystal display device is improved, the response speed is increased, high time division driving at 1/400 duty is possible, and the contrast is also high. In addition, a uniform and stable twist orientation can be obtained over the entire display screen.

In this embodiment, since the polar force component γ _p of the surface energy of the alignment films 3 and 6 is increased to 40 dyn / cm or more, mobile ions in the liquid crystal material 8 are adsorbed on the alignment films 3 and 6. And the average dielectric constant of the liquid crystal material 8

Since the value of ## EQU2 ## is as small as 6 or less, it becomes difficult for impurity ions to be taken into the liquid crystal material 8, and the stability and reliability of operation as a liquid crystal display element are improved. Further, in the liquid crystal material 8 of this embodiment, the value of the vertical component ε⊥ of the dielectric constant is smaller than 4. As described above, the liquid crystal material 8 having a small value of the vertical component ε 誘 電 of the dielectric constant does not take in the ionic impurities adsorbed on the alignment film into the liquid crystal again, so that the amount of mobile ions in the liquid crystal material decreases. In addition, the stability and reliability of the liquid crystal display device for long-term operation are improved. Further, when the value of ε⊥ of the liquid crystal material 8 is small, the value of ε‖ of the liquid crystal composition for making the value of the dielectric anisotropy Δε of the liquid crystal composition given by ε‖−ε⊥ positive is reduced. The average dielectric constant of the liquid crystal composition can be

The average dielectric constant also becomes smaller

Since the liquid crystal composition having a small size is difficult to take in impurity ions, the amount of mobile ions in the liquid crystal material 8 is reduced, and as a result, the reliability is improved.

Further, when viewed from the electro-optical characteristics,
Average permittivity

The liquid crystal material 8 with a small value of
5 and the liquid crystal material 8 interposed therebetween, the capacitance of the equivalent capacitor of each pixel is reduced, and the charge charged between these electrodes 2 and 5 is quickly performed. As a result, The afterimage phenomenon appearing on the display screen can be reduced. Further, since the capacitance of each pixel is reduced, the driving capability of the driving circuit for supplying a signal to each pixel can be reduced, so that the configuration of the driving circuit is simplified and downsized.

The amount of mobile ions in the liquid crystal material 8 corresponds to the voltage holding ratio. As shown in FIG. 9, the voltage holding ratio is set between the electrodes 2 and 5 facing each other across the liquid crystal material 8.
When the voltage V is applied for the time t ₁ (60 μs) and the circuit is left open for the remaining time t ₂ , and when this is repeated at a cycle of 30 Hz, the value is a value representing the rate at which the effective value of the electrode-to-electrode voltage ν changes. 9, an area surrounded by a solid line representing the reference potential G and the interelectrode voltage ν is defined as 2 representing the reference potential G and an ideal voltage waveform.
It is the value divided by the area enclosed by the dotted line. FIG. 8 shows the results of measuring the voltage holding ratio using various liquid crystal materials 8 having different vertical components ε⊥ of the dielectric constant. As is clear from FIG. 8, the smaller the value of the vertical component of the dielectric constant is, the higher the voltage holding ratio is. When the value of the vertical component of the dielectric constant is smaller than 4, the voltage holding ratio exceeds 80%. ing. Therefore, by using the liquid crystal material 8 having a voltage holding ratio of more than 80%, it is possible to obtain a liquid crystal display device having extremely good operation stability and reliability as described above. Therefore, the relationship between the voltage holding ratio and the value of the vertical component ε⊥ of the dielectric constant can be applied to the evaluation value of the reliability of the liquid crystal display device. That is, the stability and reliability of the operation of the liquid crystal display device can be easily evaluated only by measuring the voltage holding ratio, which is an electrical characteristic of the liquid crystal display device.

Next, a specific example of this embodiment will be described. 1 to 4 using the liquid crystal A having the physical properties shown in Table 1.
Table 2 shows the configuration of the element and the electro-optical characteristics at a measurement temperature of 25 ° C. when observed from the normal direction of the liquid crystal display element in Examples in which the liquid crystal display device shown in FIG.
It was shown to.

[Table 1]

[Table 2] Here, the liquid crystal display device shown in FIGS.
In this case, the angle A of the polarizing axis 10a of the polarizing plate 10 and the angle B of the polarizing axis 9a of the polarizing plate 9 are 50 ° and 100 °, respectively. The liquid crystal display device shown in FIG. 3 and FIG.
Mode, and the phase difference Re of the phase plate 12 is 600
nm, the angle A of the polarizing axis 10a of the polarizing plate 10, the angle B of the polarizing axis 9a of the polarizing plate 9, and the angle c of the optical axis 12a of the phase plate 12 are 40 °, 105 °, and 80 °, respectively.
Vth is an operating voltage at which the maximum value of contrast is obtained.

As apparent from Table 2, Examples 1 and 2
Has a twist angle of 240 °, a dielectric constant ratio Δε / ε⊥ of 2 or less, and a pretilt angle of 8 or more, so that a steep luminance characteristic can be obtained and the response time is 320 msec.
It can be driven with a duty of 1/400, as fast as 50 msec. In addition, in the third and fourth embodiments, in addition to the conditions of the first and second embodiments, since the phase plate 12 for correcting the display color is provided, the response time is fast, and the driving can be performed at 1/400 duty. The contrast is as high as 36 and 22. In this case, the contrast is the elastic constant ratio K33 / K1.
It increases as 1 increases. That is, if the elastic constant ratio K33 / K11 is 1.75 or less, it becomes about 10, and
When the elastic constant ratio K33 / K11 is 1.75 or more, it becomes extremely high at about 63. Therefore, to increase the contrast, the value of the elastic constant ratio K33 / K11 is preferably 1.75 or more. Further, in Examples 1 to 4, the average dielectric constant was

When the ratio is less than 6, impurity ions are hardly taken in, so that the alignment unevenness does not occur in the liquid crystal material 8 and the operation is stable.

As described above, according to this embodiment, the twist angle is 240 °, the pretilt angle is 6 ° or more, and the dielectric constant ratio Δ
The value of ε / ε⊥ is 2 or less, the value of permittivity ε⊥ is less than 4, and the average permittivity is

Since 外 is set to 6 or less, rapid luminance characteristics can be obtained, the response speed is high, and a high contrast can be obtained even when driven at 1/400 duty.

Further, the alignment films 3 and 6 are high tilt alignment film materials that give liquid crystal molecules a pretilt angle of 6 ° or more, preferably 8 ° or more, and have a surface energy of 40 dyn / c.
m or more, a 240 ° twist alignment can be stably obtained, mobile ions in the liquid crystal material 8 can be adsorbed, and the average dielectric constant of the liquid crystal material 8

Since the value of 外 is set to 6 or less, it is difficult to take in impurity ions into the liquid crystal material 8, it is possible to prevent the occurrence of alignment unevenness, and the operation stability and reliability of the liquid crystal display element for long-time driving are improved. Get higher.

Further, the average dielectric constant

Since the value of ## EQU1 ## is reduced, the electric capacity of each pixel is reduced to prevent an afterimage phenomenon of an image, and a driving circuit having a small driving ability can be used.

[0027]

As described above, according to the present invention, the twist angle of the liquid crystal material is increased to about 230 ° to 250 °,
Expressed as the ratio between the vent elastic constant K33 and the spray elastic constant K11.
The value of elastic constant ratio K33 / K11 is as large as 1.75 or more.
Ku, and a ratio value of the dielectric constant ratio [Delta] [epsilon] / .epsilon..perp is the direction of the dielectric constant .epsilon..perp perpendicular to the dielectric anisotropy [Delta] [epsilon] and the liquid crystal molecular axis is small as 2 or less, more of the liquid crystal molecules near the alignment film by increasing the pre-tilt angle between 6 ° or more, uniformly in a stable twist orientation of the liquid crystal molecules is obtained, thereby it is possible to obtain a <br/> sudden Shun resistance threshold properties, and excellent high contrast As a result, a sharp change in luminance and a high-speed response can be obtained, and high time-division driving can be performed. According to the present invention, the dielectric anisotropy Δε and the dielectric constant ε⊥ in a direction orthogonal to the liquid crystal molecular axis are also provided.
The value of the dielectric constant ratio Δε / ε⊥, which is the ratio of

Since the value of 外 is set to 6 or less and the value of the dielectric constant ε⊥ is made smaller than 4, the amount of mobile ions in the liquid crystal material decreases, and the operation stability and reliability when operated for a long time Can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device of the present invention.

FIG. 2 is a plan view showing an alignment direction of the liquid crystal display device shown in FIG. 1 and an arrangement of upper and lower polarizers in a polarization axis direction.

FIG. 3 is a cross-sectional view of another liquid crystal display device of the present invention.

FIG. 4 is a plan view showing the alignment direction of the liquid crystal display device shown in FIG. 3, the polarization axis directions of upper and lower polarizing plates, and the optical axis direction of a phase plate.

FIG. 5: Elastic constant ratio K33 / K11 and dielectric constant ratio Δε / ε
The figure which shows the relationship of the rapidity with respect to the ratio with (circle).

FIG. 6 shows an elastic constant ratio K33 / K11 and a dielectric constant ratio Δε / ε.
The figure which shows the relationship with the upper limit of d / p margin with respect to the ratio with (circle).

FIG. 7 is a diagram showing a relationship between a twist angle and a d / p margin.

FIG. 8 is a diagram showing a relationship between a dielectric constant and a voltage holding ratio.

FIG. 9 is a diagram showing a definition of a voltage holding ratio.

[Explanation of symbols]

 1, 4 substrate 2, 5 electrode 3, 6 alignment film 8 liquid crystal material 9, 10 polarizing plate

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 G02F 1/1337 G09F 9/35

Claims (2)

(57) [Claims] 1. A pair of substrates disposed to face each other, electrodes formed on inner surfaces of the pair of substrates facing each other and intersecting each other, and interposed between alignment films formed on the pair of substrates. In a liquid crystal display device comprising a twisted liquid crystal material having a positive dielectric anisotropy and a pair of polarizing plates arranged with the pair of substrates interposed therebetween, the liquid crystal material has a bent elastic constant K33 and a spray Elasticity
The value of the elastic constant ratio K33 / K11 expressed by the ratio with the number K11 is
1.75 or more, the value of the relative dielectric constant ratio [Delta] [epsilon] / .epsilon..perp the direction of permittivity .epsilon..perp perpendicular to the dielectric anisotropy [Delta] [epsilon] liquid crystal molecular axis is from 2 or less of the liquid crystal, before Sharing, ABS alignment film A liquid crystal display device, wherein the liquid crystal molecules in the vicinity have a pretilt angle of 6 ° or more and are twisted at an angle of about 230 ° to 250 ° between the pair of substrates. 2. A pair of substrates arranged opposite to each other, electrodes formed on inner surfaces of the pair of substrates opposite to each other and intersecting each other, and interposed between alignment films formed on the pair of substrates. In a liquid crystal display device comprising a liquid crystal material having a twisted orientation and a positive dielectric anisotropy, and a pair of polarizing plates disposed with the pair of substrates interposed therebetween, the liquid crystal material has a dielectric anisotropy Δε. Dielectric constant ε⊥ perpendicular to liquid crystal molecular axis
A liquid crystal having a dielectric constant ratio Δε / ε⊥ of 2 or less, a dielectric constant ε⊥ of less than 4 and an average dielectric constant of 6 or less; A liquid crystal display device having a twist alignment between a pair of substrates at an angle of about 230 ° to 250 °.