JPS5949270B2 - Nematic liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel nematic liquid crystal composition that exhibits new electro-optic effects at low temperatures.

Some compounds exhibiting a nematic liquid crystal phase exhibit a so-called new electro-optic effect, in which a reversible change between an opaque and transparent state occurs when an electric field is applied or removed. It can be used as a material for various electro-optical devices such as display devices, optical shutters, and optical modulators. By the way, in order to use liquid crystal compounds as materials for these devices, it is strongly desired that the temperature range of the nematic liquid crystal phase of the substance be at room temperature. The temperature range of the phase is high, above room temperature, and there are very few that exhibit a room temperature range. Conventionally, a method of mixing two or more liquid crystal compounds has been used in order to obtain a substance exhibiting a liquid crystal phase in a low temperature range, but a satisfactory product has not yet been obtained.

In addition, liquid crystal compositions containing azomethine compounds and azoxy compounds have been proposed as liquid crystal compositions that exhibit a nematic liquid crystal phase at relatively low temperatures, but these liquid crystal compositions exhibit a pale yellow color due to the groups in these compounds. Because they have a yellow to yellow coloring, they have the disadvantage that when a voltage is applied to make them opaque, the contrast between transparent and opaque is poor compared to white liquid crystal materials. Because it is unstable, it also has the disadvantage of being easily degraded by light.

The present inventors have continued their intensive research to develop a chemically stable substance that overcomes these drawbacks and exhibits a nematic liquid crystal phase at low temperatures. A new type of stable white nematic liquid crystal composition in which the liquid crystal temperature range is significantly reduced by mixing a 4'-n-alkoxyphenyl ester compound with an aromatic carboxylic acid ester or carbonate ester exhibiting a nematic liquid crystal phase. It was discovered that the sensitivity can be improved by adding a certain hydroxyl compound to the hydroxyl compound, and based on this knowledge, the present invention was completed.

That is, according to the present invention, (a) the general formula (wherein -R, is an n-alkyl group having 4 to 10 carbon atoms; (b) at least one compound selected from ester compounds represented by the general formula (wherein R3 is an n-alkyl group or n-alkoxy group having 3 to 6 carbon atoms); , R4 means an n-alkyl group or n-alkoxy group having 4 to 10 carbon atoms) or the general formula (wherein R5 is an n-alkyl group having 4 to 6 carbon atoms, R6 is 1 n-alkyl group or n-alkoxy group having ~8 carbon atoms) and (c) water, ethylene glycol, propylene glycol, and benzyl. at least one selected from alcohol
A nematic liquid crystal composition is provided, characterized in that it consists of a hydroxyl compound of various types.

The nematic liquid crystal composition of the present invention exhibits an extremely low nematic liquid crystal phase temperature compared to conventional compositions, and has the great advantage of not crystallizing at room temperature. Transparent because it is
It has various advantages such as clear contrast between opacity and chemical stability because the compound that makes up the nematic liquid crystal is an aromatic carboxylic acid ester or carbonate ester, and is a material for various electro-optical devices. It can be used advantageously as

As for the compound represented by the general formula (I) used in the nematic liquid crystal composition of the present invention, R1 in the formula is 4
n-alkyl group with ~10 carbon atoms, R2 is ~4
It is necessary to use ester compounds, meaning n-alkyl groups with 8 carbon atoms.

Anything other than this is inappropriate because the nematic liquid crystal temperature range is not around room temperature. The ester compound represented by the general formula (I) can be synthesized, for example, by the production method disclosed in JP-A-48-62733. That is, n-alkoxybenzoyl chloride and 2
-chloro-4-alkoxyphenol, ketones,
It can be obtained by dehydrochlorination reaction in an organic solvent such as aromatic hydrocarbons or chlorinated hydrocarbons. Specific examples of the compound represented by the general formula (1) include the compounds shown in Table 1. All of these compounds have a nematic liquid crystal temperature range around room temperature, but the nematic liquid crystal temperature range is based on the general formula (■) or the general formula (
By mixing with the compound represented by (2), it is possible to further lower the temperature to room temperature.

As the carboxylic acid ester compound represented by the general formula (■), R3 in the formula is an n-alkyl group or n-alkoxy group having 3 to 6 carbon atoms, and R4 is 4 to 1
It is necessary to use what is meant by n-alkyl or n-alkoxy groups with 0 carbon atoms.

When other compounds are added to the ester compound of general formula (1), it becomes difficult to lower the nematic liquid crystal temperature range to around room temperature. Specific examples of the compound of the general formula (■) include the compounds shown in Table 2. In addition, regarding R3 and R4, in the case of n-alkyl group and n-alkoxy group having the same carbon atom,
Since the nematic liquid crystal temperature range is almost similar, the following can also be used.

4-n-propyloxybenzoic acid-4'-n-hexyl phenyl ester, 4-n-propyloxybenzoic acid 4'
-n-Tesylphenyl ester, 4-n-propyloxybenzoic acid-42-n-octylphenyl ester, 4
-n-butyloxybenzoic acid-4'-n-hexyl phenyl ester, 4-n-butyloxybenzoic acid-4'-n
-hexyloxyphenyl ester, 4-n-butyloxybenzoic acid 45-n-decylphenyl ester, 4-
n-Amyloxybenzoic acid-4'-n-hexyloxybenzoic acid ester, 4-n-amyloxybenzoic acid 4'-n-hexyloxybenzoic acid ester
2-n-n-butylphenyl ester, 4-n-amyloxybenzoic acid-4'-n-hexyl phenyl ester, 4-n-amylbenzoic acid-4''-n-decylphenyl ester, 4-n -Hexylbenzoic acid-4'-n-butyloxyphenyl ester and other carbonate ester compounds represented by the general formula (■) include n-alkyl in which R5 has 4 to 6 carbon atoms. group, R6 is 1-
It is necessary to use what is meant by n-alkyl or n-alkoxy groups with 8 carbon atoms.

When other compounds are added to the ester compound of general formula (1), it becomes difficult to achieve the purpose of lowering the nematic liquid crystal temperature range to around room temperature. Specific examples of such carbonate ester compounds are shown in Table 3.

Also, other carbonate esters, such as n-amyl-4
-(42-methylphenoxycarbonyl)phenyl carbonate, n-hexyl-4-(42-ethylphenoxycarbonyl)phenyl carbonate, n-butyl-4
-(4'-heptyloxyphenylcarbonyl)phenyl carbonate and the like can also be used.

In the nematic liquid crystal composition of the present invention, general formula (1)
The amount of the ester compound represented by formula (■) or (■) to be used is preferably selected within the range of 10 to 90 mol%. .

The nematic liquid crystal composition of the present invention can be produced by heating the two liquid crystal components to a temperature above the melting point (liquid crystal/isotropic liquid transition point) to uniformly mix them, and then cooling and solidifying them. - Nematic liquid crystal exhibits a phase transition of a monoisotropic liquid, and within the temperature range of the nematic liquid crystal phase, the composition exhibits a pale milky white color; however, when incorporated into a display element, the composition exhibits a liquid crystal phase transition. Because the layer is so thin, it is almost colorless and transparent, and when a voltage is applied, the colorless and transparent liquid crystal becomes cloudy and opaque, exhibiting a new electro-optical effect.

Regarding the new electro-optical effect of the liquid crystal composition of the present invention, when applying a DC voltage, it generally becomes slightly opaque at a voltage of 10 volts, becomes cloudy clearly at a voltage of 20 volts, and becomes cloudy at around 45 volts. The white turbidity is saturated with voltage. If a DC voltage is applied for a long time, the life of the nematic liquid crystal composition will be shortened due to electrolysis.
There is a time. On the other hand, when applying an AC voltage, unlike the case of a DC voltage, it generally does not become opaque unless a high voltage of about 100 volts is applied, and the response tends to be poor. (a) compound and (b
) in the composition with the compound (c) water, ethylene glycol,
Significant improvements can be made by adding at least one hydroxyl compound selected from propylene glycol and benzyl alcohol.

Even if these hydroxyl compounds contain impurities to the extent found in commonly available commercial products, this will hardly affect the effect on the composition of the present invention, so the commercial products can be used as is. can be used.

When such hydroxyl compounds are added to the above-mentioned nematic liquid crystal composition, these compounds exhibit a lower resistance value than the liquid crystal, thereby reducing the resistance value of the liquid crystal composition as a whole and bringing about effects such as increased sensitivity. I think that the.

When a small amount of this hydroxyl compound is added to a liquid crystal, for example, it becomes opaque at about 10 volts, becomes clearly cloudy at 20 volts, and becomes saturated at around 45 volts.

Further, the addition of such a hydroxyl compound has the advantage of preventing effects on liquid crystals on the container surface (for example, Nesa glass) and stably producing a new electro-optic effect with a constant voltage. The voltage applied to the nematic liquid crystal composition of the present invention may be either direct current or alternating current, but in the case of alternating current voltage, the relationship with frequency is as follows.

In other words, at a constant temperature, the transmittance is constant in the low frequency range, independent of the frequency, but as the frequency exceeds a certain level, it increases as the frequency increases, and above a certain limit frequency, it is no longer a new electro-optic. The effect will no longer be seen. As the temperature decreases, this limit frequency shifts to a lower frequency side, and as the amount of the hydroxyl group-containing compound added increases, it shifts to a higher frequency side. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 4-n-hexyloxybenzoic acid-21-chloro 4'
-n-hexyloxyphenyl ester 2.367f!
and n-butyl-4-(4'-monoethoxyphenoxycarbonyl) phenyl carbonate (nematic liquid crystal temperature range 53-85°C) 1.

1139 were thoroughly mixed to prepare a mixed liquid crystal composition.

Next, 1.0% by weight of ethylene glycol based on the total amount was added thereto, heated and melted to uniformly disperse it, and then cooled and solidified. Next, this nematic liquid crystal composition was sandwiched between glass plates coated with tin oxide to make a sandwich cell with a liquid crystal layer thickness of 12 μm, and when an AC voltage of 50 Hz was applied to this cell at 20° C., 8 The bolt caused cloudiness.

Example 2 In the same manner as in Example 1, 4-n-butyloxybenzoic acid-2'-chloro-4'-n-octyloxyphenyl ester and 4-n-amylbenzoic acid 4'-n-hexyloxyphenyl ester were prepared. enyl ester (nematic liquid crystal temperature range 41~
A mixed liquid crystal composition (59°C) was prepared.

This one has 1. When propylene glycol of O weight % was added and an AC voltage of 50 Hz was applied in the same manner as in Example 1, clouding occurred at 7 volts.

For comparison, similar measurements were made on a sample without propylene glycol, which became cloudy at 100 volts. Example 3 In the same manner as in Example 1, 4-n-hexyloxybenzoic acid-2'-chloro-4'-n-hexyloxyphenyl ester 1.819, 4-n-butylbenzoic acid-41-
Hexyloxyphenyl ester 1. O39 and n-
Butyl-4-(4'-monoethoxyphenoxycarbonyl)
A composition obtained by mixing and melting 1.049 phenyl carbonate underwent a phase transition from crystal to nematic liquid crystal at 10°C, and from nematic liquid crystal to isotropic liquid at 49.5°C.

Add 1.0% by weight of benzyl alcohol to this,
When an AC voltage of 50 Hz was applied in the same manner as in Example 1, clouding occurred at 8 volts. When no benzyl alcohol was added, it became cloudy at 100 volts.

Claims (1)

[Claims] 1(a) General formula ▲ Numerical formulas, chemical formulas, tables, etc. At least one compound selected from ester compounds represented by (b) general formula ▲ mathematical formula, chemical formula, table, etc. ▼ (in the formula, R_3 is 3 ~ n-alkyl or n-alkoxy group with 6 carbon atoms, R_4 means n-alkyl or n-alkoxy group with 4 to 10 carbon atoms) or general formula ▲ Numerical formula, chemical formula, table etc. ▼ (In the formula, R_5 means an n-alkyl group having 4 to 6 carbon atoms, R_6 means an n-alkyl group or n-alkoxy group having 1 to 8 carbon atoms.) and (c) at least one hydroxy compound selected from water, ethylene glycol, propylene glycol, and benzyl alcohol. Composition.