JPS5950713B2 - liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a liquid crystal composition having a wide liquid crystal temperature range, and more specifically, the present invention provides a liquid crystal composition having a wide liquid crystal temperature range. The object of the present invention is to provide a liquid crystal composition with improved properties, and further to provide a liquid crystal composition that can be used in a matrix drive.

Nematic liquid crystals are classified into the following two types depending on their dielectric properties.

One is an Nn-type crystal with negative dielectric anisotropy in which the direction of the electric dipole moment is perpendicular to the long axis of the molecule, and the other is an Nn-type crystal with the direction of the electric dipole moment parallel to the long axis of the molecule. It is an Np type liquid crystal with positive dielectric anisotropy. Development of Np-type liquid crystals was delayed because they did not exhibit dynamic scattering, but in 1971, Hoffmann-La Rocheille's M-Sch
adt, and published by W-Helfrich, (
Applied Physics Letters3U3(
4), 12731971) began to attract attention due to the twisted nematic method (T-N method). This TN type cell manufacturing method is described in the above-mentioned document and Japanese Patent Application Laid-open No.
11737, but briefly, a liquid crystal material is sandwiched between two electrodes, one of which is transparent, via a spacer, and the electrode surface is treated to orient the liquid crystal. , and the cell has a structure in which the molecular axes of the liquid crystals oriented on the electrode surface are oriented at right angles to each other, and display is possible using a polarizing plate, and the liquid crystal molecules have their molecular axes aligned with the electrode surface. 90 parallel to the plane from one side to the other
It has a 0 spiral structure. Of course, the direction of the orientation treatment can be changed. On the other hand, Nn type liquid crystal was developed in 1968 by R
Since it was applied to a panel-type display device using the dynamic scattering mode by Heilmeie of C-A., research and development has progressed rapidly and it has been put to practical use in watches, desktop calculators, etc.

In recent years, the application of any liquid crystal as a display element has been remarkable, and various types of displays such as alphanumeric displays and matrix displays have been devised. When creating an alphanumeric display, there are two methods available due to lead wire issues: static drive method and dynamic drive method. It is well known that the dynamic drive method is more advantageous when the number of displayed characters is large.
However, currently known liquid crystals have various problems, and the dynamic drive method cannot yet be fully adopted. One drawback is that the power supply voltage must be changed depending on the temperature. A detailed explanation will be given below with reference to the drawings. The dynamic drive is in principle exactly the same as the matrix drive shown in FIG.

Generally, in a liquid crystal cell, a voltage is applied as shown in FIG. 1 in order to prevent crosstalk. The black circles indicate the voltage V at selected points, and the white circles indicate half-selected points or non-selected points, where the voltage -■ is biased. V is determined so that the black circle portions are scattered and the white circle portions are not scattered. Figure 2 shows the relationship between voltage and light scattering intensity.

If you can use a voltage V that is sufficiently larger than the voltage value ■s when the scattering intensity is saturated, there will not be much of a problem with contrast, but as mentioned above, crosstalk will occur, so
There is an upper limit voltage Vb that is limited from this point. Also, it is necessary to obtain a certain scattering intensity, and for that purpose the lower limit voltage ■a
is necessary. That is, when performing matrix drive using a liquid crystal cell, the power supply voltage V is designed3 so that it satisfies ■a≦V≦Vb, but this Vb - ■a (hereinafter referred to as voltage margin) is O. ．． It is very small, about 1 to 0.2 square meters, and the circuit design is complicated and expensive. In addition, there is the difficulty that the voltage margin varies greatly depending on temperature. Temperature and voltage margins within the so-called mesomorphic range (M.R.) between the transition temperature TN from a crystalline or smectate phase to a nematic phase and the transition temperature T1 from a nematic phase to an isotropic liquid. The relationship is shown in Figure 3a, and a typical example of a normal nematic liquid crystal is shown in Figure 3b.
Shown below. In FIG. 43a, when the driving temperature range of the liquid crystal cell is T1 to T2, the larger the shaded area S in the figure, the better the liquid crystal composition. If the lower limit voltage Va at T1 is larger than the upper limit voltage Vb at T2 as shown in FIG. 3b, the above S
There are no parts corresponding to the driving temperature range T1 to T2.
If priority is given to this, the circuit must be designed so that the voltage changes depending on the temperature. Furthermore, if the voltage is kept constant, the operating temperature range of a device using the cell must be limited, and therefore the product distribution area is limited, which is extremely disadvantageous in terms of cost and product sales. Based on the above considerations, we found that M-R was sufficiently large for T1 and T2.
- It was found that a liquid crystal material with (TN, T1) gives a sufficiently large S.

However, among the currently known nematic liquid crystal materials, N
There are several types of n-type liquid crystals that have a relatively wide M-R, but none of the np-type liquid crystals have a relatively wide M-R.
From a practical point of view, it cannot be said to be very preferable and is insufficient.

Based on this background, various studies were conducted, and as a result, a liquid crystal composition that fully satisfies the above-mentioned performance was successfully obtained.

The present invention provides a liquid crystal composition that has sufficiently excellent electrical performance and temperature characteristics, has a wide liquid crystal temperature range (MR), and has positive dielectric anisotropy. The present invention provides a liquid crystal composition that can be applied.

The liquid crystal composition of the present invention comprises at least one biphenyl-based N, type liquid crystal substance represented by the general formula (1) and a carboxylic acid ester-based N, type represented by the general formula (2), as shown below.
composed mainly of at least one type of liquid crystal material (where R is an alkyl group or an alkoxy group) (however, R
(1, R2 is an alkyl group, an alkoxy group, or an acyloxy group) The present invention is characterized by a liquid crystal composition comprising a liquid crystal substance represented by general formula (1) and a liquid crystal substance represented by general formula (2). However, M-R is sufficiently wide from the low temperature side to the high temperature side, and the operating temperature range of the liquid crystal cell (for example, 0°C to
The point is that it was found that there is almost no change in electrical performance in 5'C).

The liquid crystal composition has excellent properties in addition to those mentioned above.For example, due to its chemical structure, it has excellent heat resistance, acid resistance, alkali resistance, light resistance, weather resistance, and electrochemical reaction. When layered, it is colorless and transparent, with good contrast, and N
Since it is a mixture of p-type liquid crystals, it has all the performance required from a practical standpoint, such as good response. The liquid crystal composition of the present invention can be mixed as desired depending on the desired performance, but it is better to have more biphenyl-based Np type liquid crystal in order to improve the electrical properties. Regarding this point, it is better to have a larger amount of carboxylic acid ester liquid crystal, and all of the liquid crystal compositions have a higher upper limit voltage Vb at the upper operating temperature T2 than the lower limit voltage Va at the lower operating temperature T of the liquid crystal cell. It is self-contained. Further, R is an alkyl group or an alkoxy group having 1 to 10 carbon atoms, R1,
R2 is preferably an alkyl group, an alkoxy group or an acyloxy group having 1 to 10 carbon atoms. Furthermore, biphenyl N
P-type liquid crystal is 10% to 99%, preferably 30% to 95%
Particularly preferably 50% to 90%, and carboxylic acid ester Np type liquid crystal preferably 1% to 90%, preferably 5% to 70%.
J is particularly preferably 10% to 50%, and in addition to this, 1
For example, 02N be? A liquid crystal composition containing a substance exhibiting positive dielectric anisotropy, such as Σ卜一〈心》-CN, can also be used in the present invention.

Furthermore, the M-R of the composition is preferably 20° C. above and 10° C. below the operating temperature range T1 to T2 of the liquid crystal cell, preferably 30° C. above and 15° C. below. Particularly preferably, the upper part is 40°C wider and the lower part is 20°C wider. For example, when the liquid crystal composition of the present invention is used in an electronic desktop calculator, -
A liquid crystal composition having an MR of 10°C to 60°C or higher is preferred, preferably -15°C to 70°C, particularly preferably -20°C.
It is preferable that the composition has an MR of 80° C. to 80° C. or higher.

Specific examples of the liquid crystal substance represented by the general formula (1) that can be preferably used in the present invention are as shown in the table below.

R-ku》》》《《O,》CN-based compounds and similarly preferred liquid crystals represented by the general formula (2) are as shown in the table below.

-? The liquid crystal used in the present invention is not limited to these compounds, but may be any liquid crystal composition that exhibits positive dielectric properties alone or in combination, as long as it satisfies the purpose of the present invention. It is something that undermines everything.

Examples are shown below.

Example 1 A case where a mixed biphenyl liquid crystal (abbreviated as liquid crystal M) containing 2.3 parts by weight of A2.3 and 2 parts by weight of A4. Fig. 4 shows the change in MR of .

As is clear, a liquid crystal composition having a wide range of MR was obtained.

Furthermore, almost the same results were obtained even when the mixing ratio of A2 and A4 was changed and the mixing ratio of C4 and E2 was changed. Example 2 Similar results were obtained in Example 1 using biphenyl liquid crystals as shown in the table below.

Example 3 In Example 1, even when carboxylic acid esters as shown in the table below were used, completely similar results were obtained.

Example 4 Merck &Co.'s biphenyl mixed liquid crystal E3 (trade name) (abbreviated as liquid crystal P) consisting of a liquid crystal in which R in general formula (1) is an alkyl group and a liquid crystal in which an alkoxy group is used.
FIG. 5 shows a phase diagram of a mixed liquid composition of E2=2:1:2 with a carboxylic acid ester mixed liquid crystal (abbreviated as liquid crystal Q) with respect to MR.

As is clear from the figure, the M-R is wide and is an excellent liquid crystal composition.

Example 5 A2:A4:C4:E2=4.2:2.8:1.5:1
．． A mixed composition having a composition ratio of 5 (M-R: -30~
82°C) to make a TN type liquid crystal cell with the above structure,
When the dynamic drive was performed, the temperature reached 0.0, which is within the practical temperature range. ℃~40℃, sufficient driving was possible without changing the voltage.

Furthermore, when the cell was continuously left at -15° C. and 60° C. and its reliability against temperature was examined, no change in performance was observed even after 4 months or more, and the initial good state was maintained. Example 6 When the liquid crystal cell prepared in Example 5 was continuously energized at AC5■, there was no change from the initial state even after half a year, and sufficient reliability was confirmed in terms of life.

It is understood from the above Examples that the liquid crystal composition of the present invention is particularly excellent. The liquid crystal composition of the present invention can be used in a variety of ways like conventional liquid crystal materials, but it is particularly expected to be applied to display elements that utilize electro-optic effects, and can be used for watches, desktop electronic meters, and other alphanumeric displays. Yes, but above all, dynamic drive (
It is suitable for displays with a large number of digits, and is particularly effective for desk-top computers with four or more digits, wall-mounted televisions, flat display devices, etc.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing the electrode configuration of a matrix drive.

Claims (1)

[Scope of Claims] 1. At least one type of biphenyl liquid crystal represented by the general formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and a carboxylic acid ester liquid crystal represented by the general formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A liquid crystal composition comprising at least one type of liquid crystal composition. (In the general formula, R represents an alkyl group or an alkoxy group. R_1 and R_2 represent an alkyl group, an alkoxy group, or an acyloxy group. However, when R is an alkyl group, R_1 does not become an alkyl group or an alkoxy group. do not have.)