JPH0222381A - liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide a liquid crystal composition containing five specific kinds of compounds, having short rise time, quick response and broad nematic liquid crystal temperature range and useful for electro-optical element for TV, computer terminal, word-processor, etc. CONSTITUTION:The objective composition contains the compounds of formulas I-V (R1 and R5 are 1-10C alkenyl; R2-R4 and R6-R8 are 1-10C alkyl). Preferably the content of the compound of formula I is 1-70wt.% and that of the compounds of the formulas II-V are 1-50wt.% each.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal composition useful for use in electro-optical elements.

[Conventional technology]

Conventional electro-optical elements using twisted nematic mode (hereinafter abbreviated as TN mode in the text) sandwich nematic liquid crystal having positive dielectric anisotropy between two opposing electrode substrates, and align 9 defined by processing
It has a helical structure twisted by 0°, and a polarizing plate is placed on the outside of the picture electrode base.

FIG. 4 shows the results of measuring the electro-optic characteristics of an electro-optic element using the conventional TN mode.

However, in recent years, the requirements for the electro-optical characteristics of electro-optical elements, especially the time-division drive characteristics, have become stricter, and the conventional T
In the N mode, a state has been reached where the required characteristics cannot be satisfied.

Therefore, by adding an optically active substance to the nematic liquid crystal, the time-division drive characteristics are improved by a mode (hereinafter abbreviated as STN mode) that has a larger twisted helical structure in the thickness direction of the element than before. The technique is disclosed in, for example, Japanese Patent Laid-Open No. 60-50511.

Furthermore, the new twisted nematic mode (hereinafter abbreviated as NTN mode in the main text) eliminates the discoloration of the appearance of electro-optic elements that is characteristic of the STN mode, and as in Japanese Patent Application No. 121701/1989, a pair of polarized light By providing at least one layer of optically anisotropic material between the plates, it is possible to display white on a black background or black on a white background.

The advantage of these STN and NTN modes over the conventional TN mode is that because the threshold characteristics of the electro-optical characteristics are steep, it is possible to increase the display capacity by time-division driving.

[Problems to be Solved by the Invention] However, with conventional electro-optical elements using STN and NTN modes, sufficient response speed cannot be obtained.
In the case of the N mode, the response speed is 340 m5 including the rising response and the falling response, and the response is too slow for displaying moving images on a TV or the like, causing images to flow.

On the other hand, the number of divisions is 20 when the transmittance of this element is 50% when it is on.
Although a display contrast of 1:14 can be obtained by time-divisional driving of 0, this is still insufficient for displaying television images.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a liquid crystal composition that is effective in obtaining an electro-optical element with excellent electro-optic properties and has excellent steepness and high-speed response.

[Means for Solving the Problems] Based on the above object, the present invention provides a liquid crystal composition that satisfies the above conditions.

general formula %formula% 0 alkenyl group 0 alkyl groups 0 0 0 alkenyl group 0 alkyl groups N R8 is an alkyl group of 1 to 10 It is characterized by being expressed as.

[Implementation Example 1] Hereinafter, the present invention will be described in detail based on examples.

The characteristics of the liquid crystal composition were measured as follows. 1st
The measurement system for electro-optical properties is shown in the figure.Measurement cell 4 has a transparent electrode attached to one side of a glass substrate by vapor deposition or sputtering, and then that surface is covered with an organic thin film and subjected to an alignment treatment. It is made by sandwiching a nylon film frame and fixing two glass substrates facing each other so as to have the desired thickness, and sandwiching them between two mutually orthogonal polarizing plates. This is TN and STN
mode cell. On the other hand, an NTN mode cell further includes at least one optically anisotropic material between polarizing plates. In the text, the distance between the glass substrates (ie, the thickness of the liquid crystal layer) is abbreviated as cell thickness. The light beam emitted from the white light source 1 passes through the lens system 3 and enters the cell 4 in a vertical direction, and the intensity of the transmitted light is measured by a detector provided at the rear. At this time, an alternating rectangular voltage having a frequency of 1 kilohertz and having an arbitrary effective value voltage is applied to the cell 4 by the driving circuit 5. Figure 2.3 shows the voltage-transmittance curve of a liquid crystal cell measured using the measurement system shown in Figure 1. Moreover, FIG. 3 shows the measurement results when using the STN mode. In the figure, the transmittance is expressed as 100%, which is the amount of light transmitted through two polarizing plates bonded together with their polarization axes aligned.In this voltage-transmittance curve, the transmittance T0 at the darkest time and the transmittance T0 at the brightest time are expressed as 100%. Transmittance T
lo. Then T1°. 〜T, from the darkest side, To, T IO, T 20''' T 90, T (.

. As the voltage is gradually increased, the voltage when the transmittance is T1° is the optical threshold voltage vth, and as the voltage is further increased, the transmittance is T. The voltage at the time of is defined as the optical saturation voltage Vsat. At this time, the rise (that is, the steepness) of the voltage-transmittance curve near the optical threshold voltage is determined by the following formula β.

The response speed is measured at an applied voltage such that the rising response time (expressed as Ton) and the falling response time (expressed as Toff) are approximately equal.

Average value T of n and Toff (=Ton+Toff/2)
Shown in milliseconds.

Further, for stability of orientation, the nematic liquid crystal composition of the present invention to which an optically active substance was added was sealed in a cell. The amount of the optically active substance added was determined from the formula below.

Here, C is the optically active substance addition fi [wt%], θ is the torsion angle of the cell [degl, d is the cell thickness [μml, P
indicates the optical power of an optically active substance.

The stability of the nematic liquid crystal phase was shown as high-temperature liquid crystallinity and low-temperature liquid crystallinity when sealed in a cell.

Assuming that the room temperature is 20°C, whether the nematic phase is stable at 50°C, which is 30°C higher than that, is called high-temperature liquid crystallinity, and on the other hand, whether the nematic phase is stable at 10°C, which is 30°C lower than 20°C, is called high temperature liquid crystallinity. It has low temperature liquid crystallinity.

The measurement temperature was 25°C in all cases.

Further, the measurement was carried out using the NTN mode under the conditions that the twist angle of the cell was 210° to the left, and the product Δnd of the cell thickness d and the refractive index anisotropy Δn of the liquid crystal was about 069. Note that the effects of the present invention are not limited to these conditions and modes,
Similar effects can be obtained under other conditions and modes (TN, STN mode, etc.).

(Example-1) The composition and properties of Example-1 according to the present invention are shown in Table 1. However, in this example, the compound (5) has the general formula R? %
CE C-C MiC Beo > Ra (in the formula, R7 and R represent a straight-chain alkyl group having 1 to 10 carbon atoms) (hereinafter abbreviated as BTT in the text) to 10
It is characterized by containing % by weight.

Further, the characteristics of Conventional Example-1 are shown in Table 2.

While the response speed T of Conventional Example-1 is 132 milliseconds, the response speed T of Example-1 is significantly increased to 64 milliseconds.

In addition, the β value, which determines the steepness, is 1.09 in Conventional Example-1.
0, whereas Example-1 has l,076, which is a great improvement.

Regarding the optical threshold voltage, Example-1 was compared to the conventional example.
Although it is a little more concave, it is not a big difference and is well within the allowable range, so it is not a problem at all.

Furthermore, Example-1 has high-temperature liquid crystallinity at 50°C and low-temperature liquid crystallinity at -10°C, is sufficiently stable, and has a sufficiently wide nematic liquid crystal temperature range to be used as a normal display.

As described above, this example has a very fast response speed and excellent steepness, and is a liquid crystal composition useful for electro-optical elements.

(Example-2) Table 1 shows the composition and properties of Example-2 according to the present invention. However, in this example, compound (2) has the general formula R, ()
8 stones) Contains 22.4% by weight of a compound represented by NC3 (in the formula, R2 represents a linear alkyl group having 1 to 10 carbon atoms) and 10% by weight of BTT. shall be.

Further, the characteristics of Conventional Example-1 are shown in Table 2.

While T is 132 milliseconds in Conventional Example-1, T is 60 milliseconds in Example-2, which is a significant increase of 55%.

Furthermore, the β value is 1.090 in Conventional Example-1, while it is 1.077 in Example-2, which is a considerable improvement.

The optical threshold voltage of Example-2 is 1.88V, which is significantly lower than 2.07V of Conventional Example-1.

Furthermore, the nematic liquid crystal temperature range is sufficiently wide and there are no problems.

As described above, this example is a useful liquid crystal composition similar to Example-1, and especially regarding the optical threshold voltage, Example-1
It has been further improved.

Table 1 Table 2 [Effects of the Invention 1 As described above, the liquid crystal composition of the present invention has superior steepness and extremely fast response speed compared to conventional compositions, and also has a nematic liquid crystal temperature range. is sufficiently wide and very useful.

Applications of electro-optical elements using the liquid crystal composition of the present invention include televisions, computer terminals, word processors, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hardware diagram showing a measuring device used in an embodiment of the present product. FIG. 2 is a curve diagram showing the voltage-transmittance change in NTN mode generally obtained using the measuring device shown in FIG. FIG. 3 is a curve diagram showing a change in voltage-transmittance in STN mode, which is generally obtained using the measuring device shown in FIG. FIG. 4 is a curve diagram showing changes in voltage-transmittance in STN mode generally obtained using the measuring device shown in FIG. 1.・Light source, light beam, lens and filter system, cell, light receiving part (photoelectric intensifier tube) Applicant: Seiko Epson Corporation Representative Patent attorney: Kizobe Suzuki (and 1 other person) Satokuni

Claims (1)

[Claims] 1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (4) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (5) Each group represented by (1), (2), (3), (4), (
5) A liquid crystal composition containing at least one component of each of the compounds. However, R_1 is an alkenyl group of 1 to 10 R_2 is an alkyl group of 1 to 10 R_3 is an alkyl group of 1 to 10 R_4 is 1 to 10 R_5 is an alkenyl group of 1 to 10 R_6 is an alkyl group of 1 to 10 R_7 is an alkyl group of 1 to 10 10〃 R_8 indicates 1 to 10〃. 2) The proportion of compound (1) is 1 to 70% by weight (2) 1 to 50 (3) 1 to 50 (4) 1 to 50 (5) 1 to 50 The liquid crystal composition according to item 1, characterized in that: