JPS63196685A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To prepare a large capacity liq. crystal device which is high in the response speed, operable at a low drive voltage and over a wide temp. range, and has excellent time-division characteristics, by sealing a particular liq. crystal compsn. as a liq. crystal compsn. for sealing into a new TN liq. crystal device. CONSTITUTION:A liq. crystal compsn. to be used as a liq. crystal compsn. to be sealed in a new TN liq. crystal device is a nematic liq. crystal compsn. comprising 5-30wt.% liq. crystal compsn. of formula I (wherein R is n-alkyl, a group of formula II is phenyl, and a group of formula III is pyrimidyl), 5-25wt.% liq. crystal compd. of formula IV (wherein R is n-alkyl, a group of formula V is trans-cyclohexyl, and R' is CN or F), 5-20wt.% liq. crystal compd. of formula VI (wherein R is n-alkyl and R' is n-alkyl, CN, or F), and 5-20wt.% liq. crystal compd. of formula VIII (wherein R is n-alkyl) and further an optically active substance in such an amt. as will provide a ratio of a liq. crystal layer thickness d (mum) to liq. crystal intrinsic pitch P (mum) (d/P) of 0.5-1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal device, and particularly to the implementation of a large liquid crystal display device or an electro-optical shutter used in word processors, personal computers, and the like.

[Summary of the invention]

In the present invention, nematic liquid crystal compositions having positive dielectric anisotropy are arranged in a pair of upper and lower transparent 1! A spiral structure is formed between the scratched substrates and twisted in the range of 180° to 270° in the thickness direction, and the transmission axis or absorption axis of a pair of polarizers is provided across the spiral structure. are arranged at an angle of 45° ±30° or 135° ±30°, respectively, with respect to the liquid crystal molecule alignment direction near the interface of the liquid crystal molecules, and the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy of the liquid crystal In a liquid crystal device (hereinafter referred to as a NewTN type liquid crystal device) that applies the electric field controlled birefringence effect and is configured such that the product Δn-d of 〇 falls within the range of 0.5 to 1.2, As the liquid crystal composition sealed inside, the general formula F
-Q-Q-9-R (R is n-alkyl group.

O is phenyl L E> is pyrimidyl group) and trans chlorohexyl group) At least 5 to 25% by weight of a liquid crystal compound of the general formula R-■-■-0-
R' (R is n-alkyl group, R' is n-alkyl group, C
At least 5 to 5 liquid crystal compounds represented by (N group, F group)
20% by weight.

Contains at least 5 to 20 weight percent of a liquid crystal compound represented by the general formula R-[phase]-(CN (R is an n-alkyl group), and has a thickness d (μm) of the liquid crystal layer and a specific pitch P of the liquid crystal. (μm), the value of the ratio d/P is 0.5 to 1.
By using a liquid crystal composition containing an optically active substance so that the optical rotation is within the range of It was made so that it could be done.

Furthermore, in the liquid crystal composition, the general formula R-O-C=C-O-R' (R is n-alkyl group.

By using a liquid crystal composition of at least 5 to 30 percent by weight liquid crystal compound represented by n-furkylcyclohexyl group (R' is n-alkyl group, n-alkoxy group), operation can be achieved with high speed response. This makes it possible to provide a large-capacity liquid crystal device.

[Conventional technology]

In recent years, with the increase in the amount of displayed information, so-called dot matrix liquid crystal display devices with electrodes arranged in an X-Y matrix have become popular.
It is gaining attention as a thin, lightweight, and compact display terminal.

A twisted nematic type liquid crystal display device (hereinafter referred to as a 90° TN type liquid crystal display) having a 90° helical structure as shown in Figure 2 has a change in light transmittance (reflectance) with respect to the voltage applied to the liquid crystal molecules. Because it is not steep, it has serious drawbacks as a large display terminal device, such as poor time division drive characteristics, poor display contrast, and narrow viewing angle due to crosstalk, and is not widely accepted in the market. It has not yet reached the point where it can be done.

Analysis from elastic logic shows that for a nematic liquid crystal composition with positive dielectric anisotropy to be sealed in a liquid crystal panel, the elastic constant of spray is 1, the elastic constant of bend is 1,
It is known that when a liquid crystal with a small ratio K + /K 3 is used, the change in light transmittance (reflectance) with respect to the voltage applied to liquid crystal molecules becomes steep. It is difficult to develop materials, and no sufficient results have been obtained so far.

Recently, as shown in Fig. 1, a nematic liquid crystal composition (6) having positive dielectric anisotropy is connected to a pair of transparent electrodes facing each other so as to have a large helical structure of 180° to 270°. A pair of polarizing plates (la) are sandwiched between substrates (2a) and (2b) and are provided with this spiral structure in between.

The transmission axis (8a), (8b) or absorption axis of (1b) is 45° ±30° with respect to the liquid crystal molecule alignment direction near the interface of the liquid crystal alignment films (4a) and (4b), respectively.
Alternatively, it is arranged at an angle of 135° ±30°, and the product of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy An of the liquid crystal, Δn-d, is 0.5 to 1.2 μm. Electric field controlled birefringence effect (R, A, 5oref) with various panel structures
and M.

J, Rafuse, J, Appl, Phys, 43°2
029 (1972)) has been proposed, and it has been confirmed that the display characteristics significantly exceed those of the conventional 90" TN type liquid crystal display.
There are great expectations for its application as a large-capacity liquid crystal display device in the future.

[Problem that the invention seeks to solve]

However, in the case of New TN type liquid crystal display devices, because the alignment direction of liquid crystal molecules and the transmission axis (absorption axis) of the polarizing plate are significantly misaligned, the hue changes due to tolerances or temperature changes in the thickness of the liquid crystal panel. is extremely large, and the change in hue with respect to temperature is particularly remarkable.

In order to suppress the hue change due to temperature change, N-1 of the nematic liquid crystal composition having positive dielectric anisotropy sealed inside the New TN type liquid crystal display device is used.
A method has been devised to minimize the temperature change in the refractive anisotropy Δn of a liquid crystal composition by increasing the (nematic-isotropic) transition temperature. As shown in , the liquid crystal compound with the general formula (% formula %) and the general formula R-e-0-:Q-R' (R, R' are n-7JL'
liquid crystal compound represented by the general formula R-8-0-0-R' (R is an n-alkyl group, R'
However, as shown in Table 2, the dark value voltage of the liquid crystal display device becomes high, and the driving voltage 0 had the disadvantage of high
v in the table indicates N when using the liquid crystal composition shown in Table 1.
ew The voltage required to operate a TN type liquid crystal display device at 25° C. with optimum contrast is described.

In addition, a nematic liquid crystal composition with such a composition has a high viscosity and cannot have a large refractive anisotropy, resulting in a slow response speed.
For N-type liquid crystal display devices, the helical angle of liquid crystal molecules is 180°.
270° and 90° are two to three times larger than TN type liquid crystal display devices, and especially the falling response speed (ton
) was slow, and when combined with the start-up response speed (tons), it was 600 to 800 asec at 25°C.

Therefore, the present invention has been made to solve the above-mentioned problems, and its purpose is to solve the problems described above.
An object of the present invention is to realize a high-contrast liquid crystal device with a low driving voltage, a fast response speed, and a high contrast while minimizing changes in hue of a display surface due to changes in ambient temperature.

(Table 1: Table showing conventional liquid crystal compositions; Table 2: Table showing electro-optical properties and physical properties of conventional compositions) [Means for solving the problems] Solving the problems described so far In order to achieve this, it is necessary to optimally design the nematic liquid crystal composition sealed in the New TN type liquid crystal device and impart the following characteristics.

+11 In order to minimize the change in hue of the display surface due to changes in ambient temperature, use a nematic liquid crystal composition with as high an N-1 transition point as possible. N- at least 80℃ or higher
It is required to have one transition point.

(2) In order to keep the driving voltage low, the nematic liquid crystal composition must have a small elastic constant and a positive dielectric anisotropy with a large dielectric force.

(3) In order to speed up the response speed, the nematic liquid crystal composition must have as low a viscosity as possible and a large refractive index anisotropy Δn. If Δn is large, it is the most suitable liquid crystal layer for the New TN type liquid crystal device. The thickness d (μm) becomes smaller, and as a result, the response speed can be increased.

However, with conventionally known liquid crystal compositions,
There is no such thing that can satisfy these requirements, and as a result of our earnest efforts, the inventors of the present invention found that at least 5 to 30% by weight of a liquid crystal compound represented by the general formula F-OOE)-R, At least 5 to 25 weight percent of a liquid crystal compound represented by the general formula R-Goo-
R' contains at least 5 to 20 percent by weight, and the ratio d/P of the thickness d (μm) of the liquid crystal layer to the inherent pitch P (μ111) of the liquid crystal is 0.5 to 1.0. If a nematic liquid crystal composition containing an optically active substance within the range of discovered.

Furthermore, by adding at least 5 to 30 weight percent of a liquid crystal compound represented by the formula -i R-O-C; C-0-R' to the above-mentioned liquid crystal composition, a liquid crystal device capable of faster response can be realized. I found out what I can do.

〔Example〕

Table 3 is a table showing the composition of the nematic liquid crystal used as an example. The basic structure of the New TN type liquid crystal device used is shown in Figure 1, and specifically,
The helical angle (5) of the liquid crystal molecules is 200', and the liquid crystal alignment film (
4a), (4b), molecular arrangement direction near the interface (
7a), (7b) and polarizing plates (la), (lb)
The angle to be tested with the transmission axes (8a) and (8b) is 45°
And so. The thickness of the liquid crystal layer is set so that the product Δn-d of the refractive index anisotropy Δn and the thickness d of the liquid crystal layer is 0.95, and the thickness d of the liquid crystal layer, the characteristic of the liquid crystal composition, and the Sochi P ( μm)
Merck's optically active substance S-811 was added so that the ratio d/P was 0.65.

Table 4 shows the electro-optical properties and material values when a nematic liquid crystal composed of the composition listed in Table 3 is sealed in a New TN type liquid crystal device. has a large positive dielectric anisotropy, a large Δn, and a high N-1 point, 4-fluoro, 4
'-Alkylbiphenylpyrimidine, 4-alkyl-3", 4' with low viscosity and high N-1 point and positive dielectric anisotropy
Difluorophenylcyclohexyclohexane.

Overall, it has a low viscosity, high N-1 point, and excellent compatibility.
It is a liquid crystal compound based on alkyl, 41-alkylphenylcyclohexylcyclohexane, 4-alkyl, 3° fluoro, and 4" cyanophenylcyclohexane, which has extremely large positive dielectric anisotropy and has low viscosity. A composition was made up.

<Table 3 Composition table of nematic liquid crystal composition constructed according to the present invention> Table 3 Composition table of nematic liquid crystal composition constructed according to the present invention> (Table 3 Composition table of nematic liquid crystal composition constructed according to the present invention) Table 3 Composition table of nematic liquid crystal composition constructed according to the present invention (Table 3 Composition table of nematic liquid crystal composition constructed according to the present invention) Table 4 Composition shown in Table 3 Table showing electro-optical characteristics and characteristic values of New TN type liquid crystal display device according to material〉Example 1
By using the liquid crystal composition of ~3 in a New TN type liquid crystal device, the N-1 point is 80°C and the dark value voltage is also 1.3.
We were able to realize a liquid crystal display device that exhibits an extremely low value of ~1.6v. When this liquid crystal display device was operated at 1/100 duty and 1/11 bias, 1O-
With a low operating voltage of 11V, a display with very good control can be obtained, and the response speed is improved to 300 to 400!1 sec (tOn+torf), which is about 172 times faster than that using a conventional nematic liquid crystal composition. was completed.

Furthermore, the New TN type liquid crystal display device filled with the liquid crystal composition of Example 4.5, which is based on the above-mentioned nematic liquid crystal and mixed with a tolan-based liquid crystal compound, has a low threshold voltage and a high N-1 point. While maintaining these favorable characteristics, the response speed was 200 to 250 m5ec, making it possible to realize a liquid crystal display device capable of extremely high-speed response.

〔Effect of the invention〕

As described above, by using the present invention, New TN with excellent contrast, which has little change in hue of the display surface due to changes in ambient temperature, can be driven at low voltage, can respond at high speed,
type liquid crystal device.

[Brief explanation of the drawing]

FIG. 1 is a perspective sectional view showing the configuration of a display device using the present invention. FIG. 2 is a sectional view showing the structure of a 90° TN type liquid crystal display device. la, lb...Polarizing plate 2a, 2b...Transparent glass substrate 3a, 3b...Transparent electrode 4a, 4b...Liquid crystal alignment film 5...Twist angle of liquid crystal 6... Liquid crystals 7a, 7b...Orientation direction 8 of liquid crystal molecules near the alignment film
a, 8b... Transmission axes 21a, 21b of polarizing plates - Polarizing plates 22a, 22b... Transparent glass substrate 23...
Liquid Crystal Molecules Applicant Seiko Electronics Industries Co., Ltd. Agent Patent Attorney Mogami Tsutomu (1 other person)

Claims (2)

[Claims] (1) A nematic liquid crystal composition having positive dielectric anisotropy is sandwiched between a pair of upper and lower transparent electrode substrates arranged opposite each other, and has a helical structure twisted within a range of 180° to 270° in the thickness direction. and the transmission axis or absorption axis of the pair of polarizing plates provided on both sides of this helical structure are 45°±30° and 135°, respectively, with respect to the liquid crystal molecule alignment direction near the interface of the liquid crystal alignment film. The thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn of the liquid crystal layer are arranged at an angle of ±30°.
In a liquid crystal device in which the product Δn・d is within the range of 0.5 to 1.2 μm, the liquid crystal composition sealed in the liquid crystal device includes general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼ (R is At least 5 to 30 liquid crystal compounds represented by n-alkyl group, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼ are phenyl groups, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼ are pyrimidyl groups)
Liquid crystal compound represented by weight percent, general formula ▲ Numerical formula, chemical formula, table, etc. available ▼ (R is n-alkyl group, ▲ mathematical formula, chemical formula, table, etc. available ▼ is transcyclohexyl, R' is CN or F group) at least 5 to 25% by weight of a liquid crystal compound represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (R is n-alkyl group, R' is n-alkyl group, CN group, F group). ~20% by weight, general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (R contains at least 5 to 20% by weight of a liquid crystal compound represented by an n alkyl group, and the thickness d (μm) of the liquid crystal layer, A liquid crystal device characterized in that a liquid crystal composition containing an optically active substance is used so that the ratio d/P to the intrinsic pitch P (μm) of the liquid crystal is in the range of 0.5 to 1.0. (2) The liquid crystal composition sealed in the liquid crystal device includes the general formula ▲ mathematical formula,
There are chemical formulas, tables, etc. ▼ (R is n-alkyl group, n-alkylcyclohexyl group, R' is n-alkyl group, n-alkoxy group) Added at least 5 to 30% by weight of a liquid crystal compound A liquid crystal device according to claim 1, characterized in that: