JP2741675B2 - Ferroelectric liquid crystal composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ferroelectric liquid crystal composition containing two or more liquid crystal substances.

[Related Art] Liquid crystal display elements are widely used for various digital displays such as personal computers, calculators, and watches.

Conventionally, the liquid crystal material used in these liquid crystal display devices is a ferroelectric material that has bistability and high-speed response instead of a nematic low-molecular liquid crystal compound that requires a low electric field response speed and a low pixel density. Low molecular weight liquid crystal compounds have been proposed (JP-A-56-107216, U.S. Pat. No. 4,367,924).

However, the ferroelectric low-molecular liquid crystal compound proposed heretofore needs to be used with the cell thickness smaller than the helical pitch of the ferroelectric low-molecular liquid crystal compound, that is, several microns in order to exhibit its performance. There is. For this reason,
There is a disadvantage that it is difficult to make a large screen.

As a method for solving this problem, a ferroelectric polymer liquid crystal compound having good orientation and film forming properties has been developed (Japanese Patent Laid-Open No.
-99204, JP-A-63-264629, etc.). However, the ferroelectric polymer liquid crystal compound has a drawback that, although a good alignment film can be obtained, the electric field response speed is slower and the manufacturing cost is higher than that of the low-molecular ferroelectric liquid crystal.

Therefore, in order to maintain good orientation and improve the electric field response speed, the optically active high-molecular liquid crystal compound with asymmetric carbon and the low-molecular liquid crystal having an asymmetric carbon in which the twist directions of the helical pitch are opposite to each other. And a chiral smectic liquid crystal composition comprising the compound
No. 289090).

However, this liquid crystal composition requires that the content of the polymer liquid crystal be kept low in order to achieve high-speed response. In addition, when the pitch length is adjusted, the liquid crystal compound and a plurality of low-molecular liquid crystal compounds are spiraled. It is necessary to consider the direction of the twist and the pitch length, so that it is difficult to select the composition ratio.

[Problems to be Solved by the Invention] Under such circumstances, the present invention is to provide a large screen with a high response speed, easy adjustment of the helical pitch length, etc., excellent film forming properties and orientation. The purpose of the present invention is to provide an inexpensive liquid crystal composition that can be used.

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that one or more ferroelectric low-molecular liquid crystals exhibiting right-handed helix and one or more The purpose was achieved by mixing a ferroelectric low-molecular liquid crystal compound consisting of a mixture with a ferroelectric low-molecular liquid crystal exhibiting a left-handed helix, and a liquid crystal polymer containing no asymmetric carbon. The inventors have found that the helical pitch length originally possessed by molecular liquid crystals can be increased, and based on this finding, have completed the present invention.

That is, the present invention provides a ferroelectric low-molecular liquid crystal compound comprising a mixture of one or more ferroelectric low-molecular liquid crystals exhibiting right-handed spiral and one or more ferroelectric low-molecular liquid crystals exhibiting left-hand spiral. And a ferroelectric liquid crystal composition containing a liquid crystal polymer containing no asymmetric carbon.

 Hereinafter, the present invention will be described in detail.

Examples of the ferroelectric liquid crystal compound used in the present invention include Schiff base ferroelectric low molecular liquid crystal compounds, azo and azoxy ferroelectric low molecular liquid crystal compounds, biphenyl and aromatics ester ferroelectric low molecular liquid crystals. Compounds: Non-Schiff base ferroelectric low-molecular liquid crystal compounds using a primary or secondary alcohol as an asymmetric source; ferroelectric low-molecular liquid crystal compounds into which ring substituents such as halogen and cyano groups are introduced; A ferroelectric low-molecular liquid crystal compound, a ferroelectric low-molecular liquid crystal compound using a lactic acid derivative or an amino acid derivative as an asymmetric source, and a ferroelectric low-molecular liquid crystal compound in which a halogen or a cyano group is directly bonded to an asymmetric carbon are listed.

Examples of Schiff base ferroelectric low-molecular liquid crystal compounds include, for example, Compounds such as amyl alcohol as an asymmetric source, Schiff base compounds having introduced a hydroxyl group such as, Schiff base compounds using a secondary alcohol such as an asymmetric source, And a compound in which a cyano group is directly bonded to an asymmetric carbon.

As azo and azoxy ferroelectric low-molecular liquid crystal compounds, for example, Etc. are fried.

Examples of biphenyl and aromatics ester-based ferroelectric low-molecular liquid crystal compounds include, for example, Bicyclic compounds such as And other polycyclic compounds.

Non-Schiff base ferroelectric low-molecular liquid crystal compounds having a primary or secondary alcohol as an asymmetric source include, for example, Etc. are fried.

Halogen, ferroelectric low molecular weight liquid crystal compound having introduced a ring substituent such as a cyano group, for example, Etc. are fried.

As a ferroelectric low-molecular liquid crystal compound having a heterocyclic ring,
For example, Etc. are fried.

As a ferroelectric low-molecular liquid crystal compound having a lactic acid derivative as an asymmetric source, for example, Etc. are fried.

As a ferroelectric low-molecular liquid crystal compound having an amino acid derivative as an asymmetric source, for example, Etc. are fried.

As a ferroelectric low-molecular liquid crystal compound in which a halogen or a cyano group is directly bonded to an asymmetric carbon, for example, Etc. are fried.

In addition to the above compounds, for example, And so on.

The compound is a typical ferroelectric low-molecular liquid crystal compound, and the ferroelectric low-molecular liquid crystal compound of the present invention is not limited to these structural formulas.

As the ferroelectric low-molecular liquid crystal compound in the present invention,
Among the above ferroelectric low-molecular liquid crystals, a mixture of one or more ferroelectric low-molecular liquid crystals exhibiting a right-handed helix and one or more ferroelectric low-molecular liquid crystals exhibiting a left-hand helix, that is, A mixture of ferroelectric low-molecular liquid crystals whose directions of rotation are opposite to each other is used. The use of a mixture of ferroelectric low-molecular liquid crystals having the twist directions of these opposite helical directions allows easy adjustment to an arbitrary helical length.

Examples of the liquid crystal polymer containing no asymmetric carbon used in the present invention include a nematic liquid crystal polymer having no helical structure and a smectic liquid crystal polymer.

Examples of the nematic liquid crystal polymer include a polyacrylate-based nematic liquid crystal polymer, a polymethacrylate-based nematic liquid crystal polymer, and a polysiloxane-based nematic liquid crystal polymer.

As the repeating unit of the polyacrylate-based nematic liquid crystal polymer, for example, And so on.

As the repeating unit of the polymethacrylate-based nematic liquid crystal polymer, for example, And so on.

As the repeating unit of the polysiloxane-based nematic liquid crystal polymer, for example, And so on.

In addition, the repeating unit of the above nematic liquid crystal polymer is a biphenyl skeleton in which the skeleton of the mesogen portion may have a halogen group such as fluorine or a chlorine group, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, and a phenyl-
4-phenylbenzoate skeleton may be replaced by a benzene ring in the skeleton may be replaced by a pyrimidine ring, a pyridine ring, a pyridazine ring, a cyclohexane ring, a dioxoborinane ring, etc., the terminal group of which is linear or branched It may be replaced by an alkyl group, a haloalkyl group, a cyano group, or the like, and the spacer has a methylene chain length of 1 to 1.
6 may be changed.

Examples of the smectic liquid crystal polymer include, for example, a polyacrylate smectic liquid crystal polymer, a polymethacrylate smectic liquid crystal polymer, a polyoxirane smectic liquid crystal polymer, a polysiloxane smectic liquid crystal polymer, a polyester smectic liquid crystal polymer, and the like. Be raised.

As the repeating unit of the polyacrylate-based smectic liquid crystal polymer, for example, And so on.

As the repeating unit of the polymethacrylate smectic liquid crystal polymer, for example, And so on.

As the repeating unit of the polyoxirane-based smectic liquid crystal polymer, for example, And so on.

As the repeating unit of the polysiloxane-based smectic liquid crystal polymer, for example, And so on.

As the repeating unit of the polyester-based smectic liquid crystal polymer, for example, And so on.

In the repeating unit of the smectic liquid crystal polymer, the skeleton of the mesogen portion may be replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, a phenyl-4-phenylbenzoate skeleton, and the like. May be replaced with a pyrimidine ring, a pyridine ring, a pyridazine ring, a cyclohexane ring, a dioxoborinane ring, or the like, and may have a halogen group such as fluorine or a chlorine group, and the terminal group may be a linear or It may be replaced by a branched alkyl group, a haloalkyl group, a cyano group, or the like, and the length of the spacer may vary within a range of 1 to 30 methylene chains.

The degree of polymerization of a liquid crystal polymer containing no asymmetric carbon is usually 2
It is in the range of ~ 2000.

These liquid crystal polymers containing no asymmetric carbon can be produced by a known method.

These liquid crystal polymers containing no asymmetric carbon may be used alone or as a mixture of two or more.
When two or more types are used in combination, for example, nematic liquid crystal polymers may be mixed, smectic liquid crystal polymers may be mixed, or nematic liquid crystal polymers and smectic liquid crystal polymers may be mixed. Good.

By mixing the ferroelectric low-molecular compound with the liquid crystal polymer containing no asymmetric carbon, the film-forming property is improved and the helical pitch length originally possessed by the ferroelectric low-molecular liquid crystal compound is increased. . In addition, a liquid crystal composition having an electric field response speed almost equal to that of a ferroelectric low-molecular liquid crystal compound in which a liquid crystal polymer is not mixed and having excellent switching characteristics can be provided.

In order to obtain a ferroelectric liquid crystal composition having a wide temperature range of chiral smectic C phase, as a liquid crystal polymer containing no asymmetric carbon, a smectic liquid crystal polymer, preferably a liquid crystal polymer having a smectic C phase, Preferably, a liquid crystal polymer having a wide smectic C phase temperature range is used.

The mixing ratio of the liquid crystal polymer containing no asymmetric carbon to the ferroelectric low molecular weight liquid crystal compound is usually in the range of 2 to 90% by weight, preferably 5 to 50% by weight. When the mixing ratio of the liquid crystal polymer containing no asymmetric carbon is 2% by weight or less, the above effect is hardly obtained, and when the mixing ratio is 90% by weight or more, the electric field response speed is undesirably reduced.

The ferroelectric liquid crystal composition of the present invention can further increase the electric field response speed by adding a viscosity reducing agent,
The strength can also be increased by adding an adhesive. The viscosity reducing agent refers to a non-chiral substance having no twisted structure or spontaneous polarization, and examples thereof include compounds of the following formula.

(Where R ₁ and R ₂ are linear or branched C ₁ to C 12
Wherein R ₁ and R ₂ may be the same or different. As the adhesive, an epoxy adhesive, an acrylic adhesive, an unsaturated polyester adhesive, a polyurethane adhesive, a hot melt adhesive, an elastomer adhesive, or the like can be used.

Note that the ferroelectric liquid crystal composition of the present invention may optionally contain other polymers, stabilizers, plasticizers, and other substances.

[Examples] Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Production Example 1 Production of liquid crystal polymer having repeating unit of formula (B) 30 mmol of 4- (9-decenyloxy) benzoic acid (8.
3g) and thionyl chloride 60mmol 7.4g toluene 50ml
After the solution was stirred at 80 ° C. for 3 hours, it was concentrated under reduced pressure to obtain an acid chloride. Hexyl 4-hydroxybenzoate 25
Mmol (5.6 g) and 5 ml of triethylamine in 50 ml of THF
A solution of acid chloride in 5 ml of THF was added dropwise to the solution,
Stirred for hours. After the reaction solution was concentrated, water was added thereto, and the mixture was extracted with ether. After the extract is dried and concentrated, it is purified by column chromatography to obtain 11.3 g of a monomer precursor (94% yield).
I got

A solution of 10 mmol (4.8 g) of the monomer precursor and 15 mmol (2.6 g) of m-chloroperbenzoic acid in 50 ml of methylene chloride was purged with argon, and then stirred at room temperature for 5 hours. The reaction solution was washed with an aqueous potassium carbonate solution and water, dried and filtered.
After the filtrate was replaced with argon, 0.5 mmol of stannic chloride was added and reacted at room temperature for 4 days. After concentrating the reaction mixture, purify it by column chromatography to obtain the desired polymer.
3.5 g (yield 71%, Mn = 1600, TCl: 62 ° C., SA-SC * transition temperature: 30 ° C., Tm: 1 ° C.) were obtained.

Example 1 Ferroelectric low-molecular liquid crystal compound having a helix of right-handed spiral (45% by weight in the following formula (E)) and a ferroelectric low-molecular liquid crystal compound having a left-handed spiral in a left-handed twist ((F) A mixture of 55% by weight (having an extremely long (20 μm or more) helical pitch length) and a smectic liquid crystal polymer (Mwt = 1600, repeating unit of the following formula (B)) was mixed. A composition exhibiting a chiral smectic C phase at 20% by weight or more of the dielectric low-molecular liquid crystal compound was obtained. When the response time of this composition to an electric field was examined, it was almost the same as the response time of the ferroelectric low-molecular liquid crystal compound when the composition of the ferroelectric low-molecular liquid crystal compound was 50% by weight or more.

In addition, a composition in which the helical pitch is too long to be measured even when the mixing ratio of the ferroelectric low-molecular liquid crystal compound is changed in the range of 20 to 90% by weight, and which contains 70% by weight of the ferroelectric low-molecular liquid crystal compound Had a spontaneous polarization value of 3.6 nC / cm ² . This composition is injected in an isotropic phase into a cell with a cell gap of 50 μm (substrate subjected to parallel alignment treatment and provided with an ITO transparent electrode), slowly cooled down to the S _m C ^X phase, and the alignment state is observed with a polarizing microscope. As a result, it was confirmed that a better monodomain was formed as compared with the case where only the low-molecular liquid crystal compound was used.

30 wt% of the polymer liquid crystal shown in Table 1 of the following in place of the liquid crystal polymer used in Examples 2-5 Example 1, compositions were added to the low molecular weight liquid crystal of Example 1, all S _m C It was confirmed that it showed an ^X phase and had an extremely long spiral pitch. Table 1 shows spontaneous polarization values and response times of these compositions.

The electric field response time was measured using a 20 × 10 mm ITO substrate 2
The polymer is sandwiched between the sheets, the thickness is adjusted to 25 μm with a spacer, and an AC electric field E = 2 × 10 ⁶ V / m is applied, and the response time of the change in the amount of transmitted light (0 → 90%) is measured. It was done by doing.

[Effects of the Invention] According to the configuration of the present invention described above, spontaneous polarization is large, helical pitch is relatively large, response speed to an electric field is fast, switching characteristics are good, and film formability and orientation are excellent. A ferroelectric liquid crystal composition is obtained. Therefore, a large screen can be obtained. Further, the pitch length can be easily adjusted because a mixture of ferroelectric low-molecular liquid crystal compounds whose helix directions are opposite to each other is used as the ferroelectric low-molecular liquid crystal compound.

The ferroelectric liquid crystal composition of the present invention includes various elements such as display elements such as watches and calculators, electro-optical shutters, electro-optical diaphragms, optical communication optical path switching switches, optical modulators, liquid crystal printer heads, memories, and variable focal length lenses. The present invention can be used in the field of optoelectronics such as electro-optical devices.

Claims (1)

(57) [Claims] 1. A ferroelectric low-molecular liquid crystal compound comprising a mixture of at least one ferroelectric low-molecular liquid crystal exhibiting right-handed spiral and at least one ferroelectric low-molecular liquid crystal exhibiting left-handed spiral. A ferroelectric liquid crystal composition containing a liquid crystal polymer containing no asymmetric carbon.