JPS62149789A - Liquid crystals display element - Google Patents

Abstract

PURPOSE:To obtain a field-effect liq. crystal displays element having excellent time division drive characteristics, by enclosing, in a torsionally oriented state, a nematic liq. crystal compsn. to which a particular liq. crystal material has been added between transmittable electrode substrates. CONSTITUTION:A nematic liq. crystal compsn. to which 10-50wt% liq. crystal material of formula I (wherein R is a compd. of formula II, wherein n is an integer of 2-7) is enclosed between transmittable electrode substrates in such a state that the liq. crystal compsn. is oriented at a torsional angle of 160-230 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a field-effect liquid crystal display element having high time-division driving characteristics.

[Conventional technology] Twisted nematic (TN) type liquid crystal display elements, which are one type of field-effect liquid crystal display devices, are driven at low voltage, consume low power, and are not self-luminous, so they can be used in bright surroundings. Since 1975, it has maintained an advantageous position as a display device, and has been gaining popularity in recent years. Calculators, watches, etc. are now mostly replaced by liquid crystal displays.

On the other hand, as the field of use of liquid crystal displays and related research and development progress, there has been a growing demand for liquid crystal display elements for use in large screens, particularly in the information field. For this reason, improvements in liquid crystal materials and research on liquid crystal interfaces have been carried out, and
A four-line (1/32 duty drive) liquid crystal display element has been put into practical use, and has therefore come to be used in simple word processors, typewriters, and the like. Recently, there has been a growing demand for larger screens for information displays, and we have entered an era in which displays for hand belt personal computers, desktop computers, etc. are being put to practical use.

However, the 8-line (1/64 duty drive) or 12-line (1/100 duty drive) liquid crystal display elements used in these displays are driven in high time divisions, so they cannot be displayed at these duty ratios. There is a problem in that the on/off ratio (contrast) between the segments and the non-displayed segments inevitably becomes small, resulting in a decrease in display quality. For this reason, improvements in liquid crystal materials, liquid crystal interfaces, etc. have continued to be made, but all of these improvements have remained small, and there has been a limit to the improvement in display quality of liquid crystal displays.

To improve this problem, the twist angle of the helical structure of the liquid crystal molecules of the nematic liquid crystal sealed between the pair of upper and lower electrode substrates arranged opposite to each other is set to 160 degrees or more, and the helical structure of the liquid crystal molecules is The present inventors have proposed a liquid crystal display element in which a pair of polarizing plates are arranged at a certain angle with respect to the alignment direction of liquid crystal molecules (Japanese Patent Application Laid-Open No. 60-1973).
-50511).

With such a configuration, compared to the normally used liquid crystal display element with a 90-degree twisted structure, the falling characteristic due to the voltage transmittance becomes steeper, and the time division characteristic is dramatically improved.
1/100 duty drive or 1/200 duty yA
It is now possible to display up to RIH.

[Problem that the invention seeks to solve]

In the conventional example described above, the 90 degree twisted structure of liquid crystal molecules,
When liquid crystal display elements having a twisted structure of 160 degrees or more, for example, 180 degrees, are compared in terms of characteristics, for example, the angle dependence of voltage-transmittance characteristics, 180 degrees as shown in FIG.
A liquid crystal display element having a twisted structure is shown in FIG.
Compared to a liquid crystal display element having a 0 degree twist structure, the falling characteristics due to the voltage transmittance are sharper, and the characteristics are clearly improved. Note that in these figures, θn~05G indicates a viewing angle of 0 degrees to 50 degrees in the viewer's direction. In this way, a liquid crystal display element having a 180-degree twisted structure has a steep falling characteristic of the JL pressure, so the voltage difference between the on state and the off state during time-division driving is extremely high. Time division driving becomes possible.

By setting the twist angle in the range of 160 degrees to 230 degrees in this way, the fall characteristics are improved, but even when using various liquid crystals, the fall characteristics (r% (referred to as "sexuality") is greatly improved.

However, in a liquid crystal display element configured in this way, the relationship between the γ characteristics when the liquid crystal material has a twist angle of 90 degrees and the γ characteristics when the twist angle is between 160 degrees and 230 degrees does not show the same tendency, and generally A phenomenon has emerged in which the conventional wisdom (90 degree twist angle) that the smaller the ratio of elastic modulus (Kss/Kst) is, the better the material with good γ properties is.

An object of the present invention is to provide a liquid crystal display element in which the one-time division characteristics can be further improved in a liquid crystal display element in which the liquid crystal molecules have a twist angle of 160 degrees to 230 degrees.

[Means for solving problems]

The present invention solves the above-mentioned problems by adding a nematic liquid crystal composition between transparent electrode substrates at an angle of 160 w to 230 degrees and a twisted alignment liquid crystal material in an amount of 10 to 50 wt. .

[Effect]

In the present invention, by adding a liquid crystal material represented by the general formula R%CN (R=CnHzn+l: n=2 to 7), the fall characteristic becomes even steeper.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Normally, at a twist angle of 90 degrees, it has been said that the liquid crystal material with the best γ characteristics is a liquid crystal material containing a pyrimidine system with a small ratio of 1 elastic modulus ('3, 4, . . .). - For example, as shown in Figure 1, at a twist angle of 90 degrees, the ratio of elastic modulus (K83/
,, ) becomes smaller, this tendency becomes more apparent. 10° In the same figure, the meaning of 'ao%-2o% on the vertical axis is the γ characteristic (voltage fall characteristic), which is the ratio of the voltage between the transmittance of 80 degrees and the transmittance of 20% at a viewing angle of 10 degrees. It shows. On the other hand, in the case of a torsion angle of 180 degrees, as shown in Figure 2, pyrimidine material A with a smaller elastic modulus ratio (I(ssAr, 1.) has a lower γ property than PCH material B. In this way, when the twist angle is from 160 degrees to 230 degrees, the previous thinking does not hold, and PCH material B shows good γ characteristics.Next, when the twist angle is from 160 degrees to 230 degrees,
At a twist angle of 0 degrees, for example at a twist angle of 180 degrees,
As a result of measuring and comparing the γ characteristics of various materials, such as pyrimidine materials indicated by ○, PCH materials indicated by X, and biphenyl materials indicated by Δ, using a meter at a viewing angle of 10 degrees, It has become clear that the PCH-based material indicated by the X mark has the best γ characteristics.

Hereinafter, the present invention will be explained in detail by giving specific examples.

(XcN (R=CnHzH+tyn=2~7
) is listed in Table 1, along with data showing each liquid crystal material, showing how the time division characteristics are improved by adding 10 to 50 wt% of . The liquid crystal interface used to evaluate these liquid crystal materials uses an alignment film formed by rubbing the surface of a d-photosensitive electrode substrate on which electrodes are formed.

7''X'2/'
It is added in a range of 0.6 wt%.

As is clear from Table 1 above, in Specific Examples 1, 2 and 3, the general formula R-■@-CN (R= C1H2n+t : n=
By adding the PCH-based liquid crystal materials represented by 2 to 7), γ8o%-2
8% was significantly improved, and it was possible to improve the 1 time division characteristic.

〔Effect of the invention〕

As explained above, according to the present invention, a nematic liquid crystal composition is twisted and oriented in a range of 160 degrees to 230 degrees between transparent electrode substrates, and the nematic liquid crystal composition is oriented with the general formula R.
−■()−CN (R= C1H2n+t :n=
By adding the liquid crystal materials shown in 2 to 7) in a range of 10 to 50 wt%, the γ characteristics are significantly improved, making it possible to obtain an extremely excellent liquid crystal display element with excellent high time division characteristics. have an effect.

[Brief Description of the Drawings] Figure 1 is a diagram showing the relationship between the ratio of elastic modulus at a 90 degree twist angle and γ characteristics of pyrimidine liquid crystal material A and PCH liquid crystal material B, and Figure 2 is a diagram showing the relationship between the γ characteristics of pyrimidine liquid crystal material A and PCH liquid crystal material B. A diagram showing the relationship between the ratio of elastic modulus and the γ characteristic at a 180 degree twist angle of A and PCH liquid crystal material B, and FIG. 3 is a diagram showing the relationship between the voltage and the γ characteristic at a 180 degree twist angle of various liquid crystal materials. , FIG. 4 is a characteristic diagram showing the angle dependence of voltage-transmittance characteristics of a liquid crystal display element having a 180 degree twisted structure,
FIG. 5 is a characteristic diagram showing the angle dependence of voltage-transmittance characteristics of a liquid crystal display element having a 90 degree twisted structure. Figure 1 (■ to K3y) Figure 2 (II to 3V) Figure 5 1.0 1.5 2.0 2
．． 5 3.0 voltage (Y'mS) faction wi
cap article i

Claims (1)

[Claims] A nematic liquid crystal composition is twisted and oriented within a range of 160 degrees to 230 degrees and sealed between transparent electrode substrates, and the liquid crystal composition has a general formula ▲ mathematical formula, chemical formula, table, etc. ▼ A liquid crystal display element characterized by adding a liquid crystal material represented by (R=CnH_2n+1; n=2 to 7) in a range of 10 to 50 wt%.