JPH0196287A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain an inexpensive dynamic scattering mode (DSM) type liquid crystal composition having low current consumption and high speed of response, by blending a liquid crystal compound having negative dielectric anisotropy with a specific amount of n-tetradecane. CONSTITUTION:The aimed composition obtained by blending (A) a liquid crystal compound having negative anisotropy of a higher dielectric constant in the minor axis direction of liquid crystal molecules than that in the major axis direction with (B) n-tetradecane in an amount of 10-17pts.vol. (preferably 13-17pts.vol.) based on 100pts.vol. total composition. Furthermore, an electrolytic compound, dichroic dye, etc., as necessary, may be further blended. When the above-mentioned composition is especially applied to a large-sized liquid crystal panel, cost down is extremely great.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal composition, and more particularly to a liquid crystal composition that is inexpensive while maintaining liquid crystal characteristics.

[Prior Art] There are various types of liquid crystal display systems, but currently TN (Twist Nem.
atiC) method is often used. When this TN method is used, its characteristics greatly depend on the cell gap, so highly accurate gap control is required. Therefore, it is difficult to use the TN method in curved display elements or large display elements for which gap control is difficult.

Therefore, there is a DSM method as a display method that can be applied to such a device with poor gap accuracy. And this O8M
The liquid crystal composition used in the DSM method is one in which a dynamic scattering mode occurs when the liquid crystal composition is sandwiched between transparent electrodes and a constant voltage is applied. 1lli product composition is used (Japanese Unexamined Patent Publication No. 60-213929)
.

[Problems to be solved by the invention] When this DSM type liquid crystal composition is applied to a large-sized display element, the area is large and the cell gap is often made large to reduce display unevenness due to gap non-uniformity. .

Therefore, since this display element uses a large amount of an SM type liquid crystal composition, the proportion of liquid crystal in the cost becomes very large.

As a solution to this problem, it may be possible to reduce the amount of liquid crystal used by adding inexpensive additives to the liquid crystal, but this generally involves deterioration of characteristics such as an increase in power consumption.

The present invention solves the above-mentioned problems, and aims to provide a DSM type liquid crystal composition containing an inexpensive additive that does not deteriorate the properties of the liquid crystal.

[Means for Solving the Problems] The liquid crystal composition and acid compound of the present invention are liquid crystal compounds having negative dielectric anisotropy in which the dielectric constant in the minor axis direction of the liquid crystal molecules is larger than the dielectric constant in the major axis direction. DSM (Dynamic 3cat)
(tering 1ylode) type liquid crystal composition, when the liquid crystal composition is 100 parts by volume, 10 to 17
It is characterized by containing n-tetradecane (hereinafter simply referred to as tetradecane).

The liquid crystal compound may be one having negative dielectric anisotropy and producing a dynamic scattering mode upon application of a constant voltage, and various compounds may be selected and used depending on the purpose, use, etc. Further, the present liquid crystal composition may contain one type of liquid crystal compound, or may be a mixed liquid crystal of two or more types.

Usually, a mixed liquid crystal is used from the viewpoint of practical liquid crystal properties. Further, if the addition ratio of tetradecane is less than 10% by volume, the extinction current increases, and if it exceeds 17% by volume, the additive and the liquid crystal will separate and become non-uniform.

Furthermore, various additives for improving the practical properties of liquid crystals, such as electrolyte compounds and dichroic dyes, can be blended into the liquid crystal composition depending on the purpose and use.

[Example] The present invention will be explained below with reference to Examples.

(1) Production of liquid crystal cell; Nematic liquid crystal with negative dielectric anisotropy (rZL manufactured by Merck & Co.)
r-1623J) and tetradecane (special grade reagent).
A predetermined liquid crystal composition was prepared by mixing in various proportions (O14, A, 10.13.17% by volume) as shown in the figure. Note that the volume % herein refers to the volume % of tetradecane added when the liquid crystal composition is 100 volume % (hereinafter simply referred to as %).

).

Furthermore, if it is added in an amount exceeding 17%, the additive and the liquid crystal will separate and will not be uniform.

Next, a pair of glass substrates, a transparent electrode formed on the glass substrate, a liquid crystal alignment film formed on the transparent electrode,
A cell before liquid crystal injection, consisting of a spacer placed between the glass substrates and a peripheral sealing member, was fabricated by a conventional method. Note that this glass substrate is 30×50111ffl, and its cell gear is 20 μm. Thereafter, each of the above liquid crystal compositions was injected by a vacuum injection method to produce a liquid crystal cell.

An ITO (indium tin oxide) film was used as the transparent electrode, a polyimide film was used as the liquid crystal alignment film, and the alignment treatment was performed by rubbing to achieve homogeneous alignment.

(2) Eliminate V! Measurement of current An AC voltage of 30 V was applied to the liquid crystal cell obtained as described above.
(64H2) was applied, and the relationship between the amount of tetradecane added and the current consumption is shown in FIG.

As this figure shows, as the amount added increases, the current consumption increases, reaching a peak at 4%, and then begins to decrease at 1.
It showed an inflection point at 0% and reached almost saturation at 13%. From the above, when the additive amount was 10 to 17%, the current consumption was almost the same or increased only slightly compared to when no additive was added. In particular, in the case of 13 to 17%, the current consumption was almost the same as in the case of no additive.

(3) Measurement of response speed Next, each of the above liquid crystal cells was measured using the apparatus shown in FIG. 3 under conditions of a measurement temperature of 0 DEG C. and an applied AC voltage of 30 V (641-12). The results are shown in Figure 2. As for the response time, the time at which 90% of the total change in transmittance changed was adopted.

According to this figure, the response speed increases by approximately 7% without increasing the amount of m added, either when a predetermined voltage is applied (solid line in the figure) or when no voltage is applied (dotted line in the figure). Almost saturated.

When the additive amount is 10%, the response speed is 2.4 times when voltage is applied and 2.3 times when no voltage is applied, and when it is 17%, the response speed is 2.2 times when no voltage is applied. 7 times faster.

(4) Measurement of liquid crystal operating temperature range Liquid crystal rZL I-1623 without the above additives
(Ester-cyclohexane mixed liquid crystal, manufactured by Merck)
The temperature range was -10°C to 80°C.

On the other hand, the operating temperature range of an IC liquid crystal composition with 17% tetradecane added is -10°C to 52°C, with an upper limit of about 30°C.
It was still within a practical range.

Note that if the addition ratio is less than the above, the upper limit of the vJ and humidity temperature range is considered to be a large value.

(5) From the summary above, when 10-17% by volume of tetradecane is added,
Although the upper limit of the liquid crystal operating temperature range is lower, it is still within a sufficiently practical range, the current consumption is lower, and the response speed is 2.
．． The speed is about 3 to 2.7 times faster, and the characteristics of liquid crystal are sufficiently maintained. Furthermore, this composition contains up to 17% of additives, which are inexpensive compared to expensive liquid crystals, making it an extremely inexpensive liquid crystal composition.

[Effects of the Invention] The liquid crystal composition of the present invention has a liquid crystal compound having a negative dielectric anisotropy in which the dielectric constant in the short axis direction of the liquid crystal molecules is larger than the dielectric constant in the long axis direction, and the whole silk-acid is added to 100% of the liquid crystal compound. When using a convex part 1
It is characterized by containing 0 to 17 parts of tetradecane.

On the other hand, in conventional liquid crystal compositions, the amount of additives added to improve properties is generally very small. However, in this liquid crystal composition, contrary to common sense, many inexpensive additives are added to the liquid crystal. Even when added in such a large amount, the properties of the liquid crystal can be maintained or improved, and furthermore, the cost of the liquid crystal composition can be significantly reduced. In particular, when this composition is applied to large-sized liquid crystal panels (particularly DSM type liquid crystal compositions are often used for large-sized panels), the cost reduction will be extremely significant.

Furthermore, since the present composition consumes less current and can increase response speed, it is extremely preferable for DSM type liquid crystal compositions, which generally consume more energy than TN type and have a thicker liquid crystal layer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between the amount of tetradecane added and current consumption in Examples. FIG. 2 is a graph showing the relationship between the amount of tetradecane added and the response speed in Examples. FIG. 3 is an explanatory diagram schematically showing the response speed measuring device. Patent applicant: Toyota Motor Corporation Agent
Patent attorney Hiroshi Okawa @l -H4<

Claims (2)

[Claims] (1) D containing a liquid crystal compound with negative dielectric anisotropy in which the dielectric constant in the minor axis direction of liquid crystal molecules is larger than the dielectric constant in the major axis direction
SM (DynaMic Scattering Mod
e) type liquid crystal composition, which contains 10 to 17 parts by volume of n-tetradecane when the liquid crystal composition is 100 parts by volume. (2) The amount of n-tetradecane is 13 to 17 parts by volume when the liquid crystal composition is 100 parts by volume.
The liquid crystal composition described in .