JPS5811431B2 - optically active ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a liquid crystal display device with twisted liquid crystal alignment (so-called Twisted Nematic Di'5play).
The present invention relates to an optically active compound used for improving liquid crystal compositions having positive dielectric anisotropy used in liquid crystal compositions (hereinafter abbreviated as TND).

More specifically, the present invention relates to an optically active compound used in a TND liquid crystal composition containing an optically active substance, which facilitates the creation of a TND panel with a uniform appearance and which does not produce the striped pattern that normally occurs in TND panels.

The striped pattern that occurs on TND panels impairs the appearance and visibility of the liquid crystal display element, and significantly reduces the market value of the display device. One of the causes of this is that the liquid crystal is When the twisting direction is not constant on the left and right sides, the area where the twisting direction is reversed (usually called &verse Twist)
Domain (hereinafter abbreviated as RTD)
It is known that this is because it is generated.

It is known that a small amount of cholesteric compound is added as a method of controlling the twisting in one direction and preventing the generation of RTD.

The cholesteric compound is cholesteryl nonaate (Electronic Letters).
nics Letters), 9, P 130-1 (1
973)), cholesteryl chloride (ibid., 10,
P118-20, (1974)) and the like are known.

However, as is generally known, these cholesterol derivatives are chemically and optically relatively unstable substances, so their addition has an adverse effect on the service life of the TND panel.

Therefore, there is a need for a compound that is chemically and photochemically stable and that can achieve the same purpose. It has been reported that the production of RTD can be suppressed by using the compound (1) of the formula.

Although compound (1) is not a liquid crystal substance itself, by adding it to cyanobiphenyl liquid crystal having a structure similar to compound (1), due to the optical activity of compound (1),
It is thought that the twisting direction of the liquid crystal is also restricted to only one of the left and right directions.

However, compound (1) requires a long synthetic route and is not easy to manufacture.

According to JP-A-49-95882, compound (1) is synthesized by the following route.

(Examples 2 and 23) The present inventors have searched for a compound that achieves the same purpose and is an optically active compound that can be produced more easily and has excellent chemical and optical stability. , it has been found that a novel compound represented by the following formula (■) is suitable.

Compound (II) can be prepared by the following route, which is a combination of three reactions.

The main raw material (-) active alcohol is the only optically active primary alcohol that is easily available in Japan.

Other main raw materials are commercially available p-hydroxybenzoic acid and p-dianophenol.

Compound (■) is a colorless needle-like crystal with a melting point of 88-89°C.
The specific power in chloroform solution is [α]2δ=+6.
It is 1°.

Furthermore, as shown in the ultraviolet absorption spectrum of Fig. 1, the compound (I
I) has no absorption in the wavelength range of 300 μm or more.

Therefore, since the light transmitted through the glass plate of the liquid crystal cell is not absorbed, there is no possibility of photochemical reaction during use.

Compound (II) was found to exhibit excellent RTD elimination effects when used in all known compound types of TND liquid crystals.

Typical liquid crystals are shown below by group, but the invention is not limited to these.

(1) p-alkyloxybenzylidene-p'-cyanoaniline and/or p-alkylbenzylidene-p'-cyanoaniline and/or p-alkylbenzylidene-
A Schiff compound-based TND liquid crystal composition obtained by dissolving p'-cyanoaniline and/or p-cyanobenzylidene-p'-alkylaniline.

(2) A liquid crystal composition for TND obtained by dissolving alkylbenzoic acid p-cyanophenyl ester and/or alkyloxybenzoic acid p-cyanophenyl ester in a Schiff compound liquid crystal consisting of p-alkyloxybenzylidene-p-alkylanilines. thing.

(3) A liquid crystal composition for TND which is p-alkyloxybenzylidene-p'-cyanoaniline, p-alkylbenzylidene-p'-cyanoaniline, and a mixture thereof.

(4) A mixed liquid crystal composition consisting of p-alkyl-p'-cyanobiphenyl and p-alkyloxy-p'-cyanobiphenyl, and p-alkyl-p'-cyanoterphenyl and/or p- T added with cyanophenol ester of alkyl-pl-biphenylcarboxylic acid
Liquid crystal composition for ND.

(5) A liquid crystal composition for TND comprising a cyanophenol ester of alkylbenzoic acid and a cyanophenyl ester of alkyloxybenzoic acid.

(6) A liquid crystal composition for TND obtained by adding cyanphenol ester of alkyloxybenzoic acid to p-alkyl-p'-alkyloxyazoxybenzene.

(7) For non-cyano TNDs consisting of phenylbenzoic acid having an alkyl group or alkyloxy group at the p and p' positions and phenyl p-benzoyloxybenzoate having an alkyl group or an alkyloxy group at the p and p' positions liquid crystal composition.

For liquid crystal compositions belonging to each of the above categories, compounds (II
) is added in a weight ratio of 0.1 to 3, the RTD elimination effect becomes extremely noticeable.

It is generally unnecessary to add more than this, and depending on the type of the basic liquid crystal composition, adding too much may cause the liquid crystal display panel to become slightly cloudy, or if left for a long time at low temperatures, the compound ( This results in unfavorable results such as precipitation of II).

The optimum amount of compound (II) to be added varies depending on the thickness of the liquid crystal layer of the TND panel to be manufactured and the surface characteristics of the electrode glass.

If you want to make the liquid crystal layer relatively thick, use a compound (■)
It is best to experimentally determine the amount of addition toward the lower limit of the above range.On the contrary, when manufacturing a TND panel with a relatively thin liquid crystal layer, it is better to experimentally determine the amount toward the upper limit of the above range. .

In addition, the surface characteristics of the electrode glass depend on the manufacturing method of the electrode glass, that is, the type of vapor deposition material, the vapor deposition method, the vapor deposition conditions, the surface treatment method,
Since it varies slightly depending on thermal history and the like, and the relationship between surface properties and liquid crystal orientation has not been theoretically elucidated, it is best to determine the optimum amount of compound (II) to be added experimentally.

However, ordinary TND panels are usually several microns to 20
Since the liquid crystal layer is manufactured to have a thickness on the order of microns, by adding compound (II) in the above concentration range, the RTD erasing effect is remarkable, and the practical purpose can be fully achieved.

EXAMPLES Below, the method for producing the compound of the present invention, examples of liquid crystal compositions containing the compound, and their effects will be explained in more detail with reference to Examples.

Example 1 Production of compound (n) Since the reaction is carried out in three stages, the explanation will be divided into three stages.

1st stage Production of 2-methyl-1-bromobutane Commercially available activated amyl alcohol ((iii) 2-methyl-butanol-
1) Put 70g into a 300U Mitsuro flask and heat at -10°C.
I cooled it down to about 100 ml, and poured 79 g of commercially available phosphorus tribromide into a funnel for 1.5 hours.

Five minutes after the completion of application, the temperature was returned to room temperature, and after further heating at 40°C for 30 minutes, the black part was vacuumed, and the part at 55 to 68°C was taken at 140 mmHg.

This part was treated with calcium chloride and then with anhydrous potassium carbonate powder, and then vacuumed again to 67 to 7
The part at 0°C was taken.

The yield was 60 g, which was 50% of the theoretical value.

2nd stage: Production of P-(,2-methyl-butoxy)benzoic acid In the 11 three-turn flask, 37 g of caustic potassium and 52 ml of water were added.
364 ml of ethanol was added, and 45 g of commercially available p-hydroxybenzoic acid was added and dissolved with stirring.

To this was added 60 g of 2-methyl-1-bromobutane obtained in the first stage reaction, and after heating under reflux for 10 hours, the solvent was distilled off at normal pressure on a hot water bath, and the by-produced ester was further hydrolyzed. 100 ml of a 10% caustic potassium aqueous solution was added and heated under reflux.

Next, acidify with hydrochloric acid, collect the precipitated acid by filtration, dissolve it in benzene 11 by heating, and then return to room temperature.
The precipitated p-hydroxybenzoic acid was removed.

Concentrate the benzene solution to about 200ml, redissolve the precipitated p-(2-methyl-butoxy)benzoic acid in the minimum necessary amount (about 100rrLl) of benzene, and recrystallize it to obtain a solution with a melting point of 110 to 112.5. 15 g of colorless crystals were obtained.

Elemental analysis value compensation value (as C12H16O3) Experimental value C69.2%
69.3% H7.7% 7.7% 0 23.1% Third stage Production of compound (II) p-(2-methylbutoxy)benzoic acid obtained in the second stage9.
After adding 16 g of thionyl chloride to 1 g and heating under reflux for 1 hour, excess thionyl chloride was distilled off under reduced pressure.

16 g of benzene was added to this, and a solution of 6 g of commercially available p-cyanophenol dissolved in 15 rl of pyridine was added, and after heating under reflux for 1 hour, ice was added and cooled.
Add Ilj and 10゛0rrLl of water, transfer to a separating funnel, wash with dilute hydrochloric acid, dilute aqueous soda solution, and saturated saline, distill off the benzene, and recrystallize the remaining solid from ethanol to give 8 g. Colorless crystals of compound (II), ie (d)-p-(2-methyl-butoxy)benzoic acid p'-cyanophenyl ester, were obtained.

This product had a melting point of 88.2 to 89°C and a light intensity [α]20=6.2° in a chloroform solution.

The elemental analysis values were as follows.

Calculated value (as C19H19N103) Experimental value C7
3.8% 73.6% H6.2% 6.2% N 4.5% 4.6%0
15.5% Further, its ultraviolet absorption spectrum and infrared absorption spectrum are shown in FIGS. 1 and 2.

Example 2 Effect experiment of compound (II) as a liquid crystal composition (Part 1)
) 4-diano-4'-n-pene 39% (weight... below tylbiphenyl) 4-cyano-4'-n-hep 23% tylphenyl 4-cyano-4'-n-pene 9 % Tyloxybiphenyl 4-cyano-4'-n-hep 85% Tyloxybiphenyl 4-cyano-4'-octyl 12.5% Oxybiphenyl 4-cyano-4'-n-pene 8% Tilterphenyl or higher A liquid crystal mixture having the following composition is prepared and is referred to as liquid crystal composition A.

1 of the compound (■) obtained in Example 1 was added to liquid crystal composition A.
The product with the weight factor added is called liquid crystal composition B.

Sixteen empty liquid crystal cells having a gap of 12±2 μm were prepared.

The electrodes are: - indium oxide rubbed in a certain direction with a cotton cloth - tin oxide rubbed in a certain direction with a cotton cloth - silicon oxide deposited on indium oxide and rubbed in a certain direction with a cotton cloth, and - indium oxide. There are 4 of each type with silicon oxide deposited on top.

Liquid crystal composition B was injected into 8 cells, 2 of each of 4 types of liquid crystal cells.

In both cases, RTD was generated at the beginning of implantation, but this soon resolved itself and uniform orientation was obtained.

RTD, which occurs when the liquid crystal layer is disturbed by applying external force, was also naturally resolved.

Even if the original orientation non-uniformity is very severe, it will completely resolve within an hour at most, and usually within a few minutes.

Heating accelerates this resolution, but in general, no special heating operation is required since the uniform orientation is achieved by its own tendency within the time required for the normal TND panel manufacturing process.

Contrary to the above, all 8 liquid crystal cells in which liquid crystal composition A without compound (II) was injected into two each of four types of liquid crystal cells were R.
TD occurred.

Even if the liquid crystal layer is relatively uniformly aligned (low RTD), if an external force is applied to disturb the liquid crystal layer, the RTD will expand, and once this happens, it is impossible to achieve uniform alignment.

Example 3 Effect experiment of compound (II) (part 2) p-methoxybenzylidene-p'-n -31% butylaniline, -ethoxybenzylidene-p'-n-21% butylaniline p-methoxybenzylidene-p' - A liquid crystal mixture having a composition of n -36% hebutylaniline p-butoxybenzylidene-p'-sia 12-chain noaniline or higher is prepared, and this is designated as liquid crystal composition C.

In addition, 0.5% of the compound (■) obtained in Example 1 was added to this.
The added material is called a liquid crystal composition.

Using 16 liquid crystal cells of four types completely similar to those used in Example 2, liquid crystal composition B in Example 2 was replaced with liquid crystal composition R, and liquid crystal composition A was replaced with liquid crystal composition C. As a result of carrying out the same experiment except for the above, the composition B gave the same results as the composition C, and the composition C gave the same results as the composition A.

In the above examples, only the right-handed compound (II) was described, but if (+) activated amyl alcohol is used as a starting material, a left-handed compound (■) can be obtained, and a left-handed compound (■) can be obtained. II) has the same properties as the right-handed compound (■) except that the decorative properties are reversed, and RT, D
Those skilled in the art can easily infer that it also has the effect of erasing .

Of course, in the left-handed compound (■), the right-handed compound (II)
Align the twist direction uniformly in the opposite direction.

As described above, by using the optically active p-(2-methyl-butoxy)benzoic acid p'-cyanophenyl ester of the present invention, it is possible to improve the disadvantages of conventionally known TND liquid crystals in an extremely economical manner. .

[Brief explanation of drawings]

Figure 1 shows the ultraviolet absorption spectrum of compound (■), and Figure 2 shows the infrared absorption spectrum of compound (II).

Claims (1)

[Claims] 1 Optically active form of p-(2-methyl-butoxy)benzoic acid p'-cyanophenyl ester.