CN102093377A - Chiral compound and liquid crystal composition containing the same - Google Patents

Abstract

The invention provides a chiral compound which has a structure shown in a formula or a formula (II):

wherein R is₁、R₂Independently selected from hydrogen, hydroxyl, halogen, amino, nitro, nitrile and C_1-10Alkyl radical, C_1-10Alkoxy, aryl, heteroaryl, cycloalkyl, or heterocyclyl. The invention also provides a liquid crystal composition containing the chiral compound.

Description

Chiral compound and liquid crystal composition containing the same

technical field

The present invention relates to a chiral compound, and in particular to a light-responsive chiral compound with high helical twisting force and a liquid crystal composition containing the compound.

Background technique

Cholesteric liquid crystal display has the characteristics of reflecting external light source without backlight and polarizer, so it can save energy compared with general display mode, and the spontaneous reflection light characteristic can reflect light of different wavelengths, so no color filter is required Chips can meet the needs of color displays.

Cholesteric liquid crystal material (Cholesteric liquid crystal) can also be called chiral nematic liquid crystal material, which is composed of pure nematic liquid crystal and special chiral dopant, originally showing a nematic arrangement The liquid crystal material is affected by chiral additives, which produces a stronger twist than TN (twisted nematic, twisted nematic) or STN (super twisted nematic, super twisted nematic liquid crystal).

The helical pitch p of the cholesteric liquid crystal material is determined by the concentration (concentration, C) of the chiral additive and its helical twisting power (HTP), which has the following relationship:

p=1/(HTP·C).

Since the wavelength reflected by the cholesteric liquid crystal is determined by the helical pitch, the helical pitch of the formulation is controlled by the helical torsion force and concentration of the chiral additive used in the formulation. Therefore, under a specific pitch requirement, the higher the helix twisting force (HTP), the lower the concentration of chiral molecules that need to be added. If the liquid crystal matrix (multilayer nematic liquid crystal) has poor solubility for the optically active liquid crystal molecules, the control of the liquid crystal composition will be limited.

The production of optically-written cholesteric liquid crystal displays requires the use of light-responsive chiral compounds with high helical torsion force, so that they can change the configuration of molecules in the liquid crystal due to light irradiation, and then produce helical torsion force (HTP) changes. Change the pitch (p) of the cholesteric liquid crystal to change the color of different reflected light. However, if the chiral compound itself has a color (such as an orange-red azo molecule), adding it to the nematic liquid crystal matrix will interfere with the color of reflected light, and it is not suitable for optically writing cholesteric liquid crystal formulations.

Therefore, light-responsive chiral compounds must have high helical twisting force, good solubility with liquid crystal formulations, and colorless properties before they can be added to liquid crystal formulations to achieve the effect of optically writing colors. On the other hand, the obtained liquid crystal composition should have characteristics such as high color purity and stable temperature dependence.

Contents of the invention

The object of the present invention is to provide a chiral compound suitable for optical writing type cholesteric liquid crystal formulation.

The present invention provides a chiral compound having a structure such as formula (I) or formula (II):

Wherein R ₁ and R ₂ are independently selected from hydrogen, hydroxyl, halogen, amino, nitro, nitrile, C _1-10 alkyl, C _1-10 alkoxy, aryl, heteroaryl, ring Alkyl, or heterocyclic.

The present invention also provides a liquid crystal composition, comprising: 100 parts by weight of a liquid crystal host; and 3-20 parts by weight of the aforementioned chiral compound.

The advantage of the present invention is that: the chiral compound of the present invention has a single light-responsive functional group, so the half-maximum width (Δλ) of the cholesteric liquid crystal formula prepared by it is relatively small, so it presents better color purity ;With high helical torsion force (HTP>30μm ^-1 ), adding a small amount to nematic liquid crystal can produce cholesteric liquid crystal phase; good solubility with liquid crystal formula and colorless; the reflection of the obtained cholesteric liquid crystal formula The temperature dependence of the wavelength is low (the absolute value of dλ/dT is less than 1), and it has relatively stable display quality.

In order to make the above-mentioned and other objects, features and advantages of the present invention more comprehensible, the preferred embodiments are specifically listed below, together with the accompanying drawings, and are described in detail as follows:

Description of drawings

Fig. 1 shows the liquid crystal formula that embodiment 1 and comparative example 1 make are at the peak full width at half maximum of different wavelengths;

Fig. 2 shows the relationship figure of the reflection wavelength and temperature of the liquid crystal formula that comparative example 2 makes;

FIG. 3 shows the relationship between reflection wavelength and temperature of the liquid crystal formulation prepared in Example 1.

Detailed ways

The production of optically writeable cholesteric liquid crystal displays requires the use of light-responsive chiral compounds with high helical twisting force. This light-responsive chiral compound cannot have color, or it will interfere with the wavelength of reflected light. In order to meet the above requirements, the present invention uses asymmetric 1,4:3,6-dianhydromannitol (isomannide) and isosorbide (isosorbide) chiral molecules to do derivation (as shown below), this structure has a good Adding a small amount of HTP (Helical Twisting Power) to the nematic liquid crystal can produce a cholesteric liquid crystal phase, and acrylic functional groups are added to the structure to achieve the effect of photoresponse.

The chiral compound of the present invention has a structure such as formula (I) or formula (II):

Wherein R ₁ and R ₂ are independently selected from hydrogen, hydroxyl, halogen, amino, nitro, nitrile, C _1-10 alkyl, C _1-10 alkoxy, aryl, heteroaryl, ring Alkyl, or heterocyclic. Among them, C _1-10 alkyl and C _1-10 alkoxy may be linear or branched. In one embodiment, R ₁ and R ₂ are independently selected from hydrogen, C _1-10 alkyl, or C _1-10 alkoxy. In another embodiment, both R ₁ and R ₂ are alkoxy.

In the above, "aryl (aryl)" represents a monocyclic or polycyclic hydrocarbon aromatic ring, such as: phenyl, tolyl, naphthyl, tetrahydronaphthyl, biphenyl , Phenanthryl (phenanthryl), anthracyl (anthracyl) and so on.

"Heteroaryl" represents an aromatic group substituted by one or more heteroatoms (such as nitrogen, oxygen, sulfur) in the structure, such as pyridyl (pyridyl), furyl (furyl), thienyl (thienyl), imidazolyl, etc.

"Cycloalkyl" represents a non-aromatic hydrocarbon monocyclic or polycyclic ring, which may contain 3 to 12 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl , Bicyclo[2.2.1]octyl, etc.

"Heterocyclic" represents a cycloalkyl group substituted by one or more heteroatoms (such as nitrogen, oxygen, sulfur) in the structure, such as 1,3-dioxolane (1,3-dioxolane), pyrrole Alkyl (pyrrolidinyl), pyrazolinyl (pyrazolinyl), piperidinyl (piperidinyl), piperazinyl (piperazinyl), tetrahydrofuryl (tetrahydrofuryl), etc.

In addition, one or more hydrogen atoms on the above-mentioned aryl, heteroaryl, cycloalkyl, or heterocyclic groups may be further substituted by halogen, hydroxyl, amine, or other functional groups.

From the formulas (I) and (II), it can be seen that the chiral compound of the present invention is an asymmetric 1,4:3,6-dianhydromannitol and isosorbide (isomannide/isosorbide) chiral compound, and has a light Response (photosensitive) functional groups. Compared with known compounds having two photoresponsive functional groups (as disclosed in US6589445), the chiral compound with a single photoresponsive group can improve the color purity of cholesteric liquid crystals.

The chiral compound of formula (I) can be obtained from 1,4:3,6-dianhydromannitol (isomannide) through a two-step esterification reaction, and its reaction formula is as follows (R ₁ , R ₂ are as defined above, X stands for -OH or -Cl):

Similarly, the chiral compound of formula (II) can be obtained from isosorbide (isosorbide) through a two-step esterification reaction, and its reaction formula is as follows (R ₁ and R ₂ are as defined above, X represents -OH or -Cl ):

The first esterification reaction can generally be performed at 0° C. to room temperature for about 4 hours, and the second esterification reaction can generally be performed at about 80° C. for about 20 hours. For the detailed steps of esterification, please refer to the description of the following examples.

The prepared chiral compound is a white solid, has good solubility in the nematic liquid crystal formula, and is colorless after dissolving, so it will not interfere with the color of reflected light. In addition, the chiral compound of the present invention generally has a high helical torsional force (HTP) greater than 30 μm ^-1 , and in a preferred embodiment, the helical torsional force (HTP) can reach 60 μm ^-1 . Therefore, only a small amount of chiral compound needs to be added to the liquid crystal composition, which can avoid adverse effects on the liquid crystal phase behavior and photoelectric properties of the liquid crystal composition due to excessive addition.

Liquid crystal composition of the present invention comprises:

(a) 100 parts by weight of a liquid crystal host; and

(b) 3-20 parts by weight of the chiral compound of formula (I) or formula (II); preferably about 5-15 parts by weight.

The chiral compound of the present invention can be used as a photoresponsive chiral additive and added to nematic liquid crystals, smectic liquid crystals, or discotic liquid crystals. Preferably, it can be added to form a cholesteric liquid crystal formula in a nematic liquid crystal, as an application of an optical writing type cholesteric liquid crystal display.

The liquid crystal host used may or may not contain polymerizable groups. In addition, the liquid crystal composition of the present invention may also add polymerizable monomers, polymerization initiators, binder resins, solvents, surfactants, tackifiers, ultraviolet light absorbers, or other chiral additive. For specific examples of liquid crystal hosts and other components, please refer to US 6589445.

The light-responsive chiral compound of the present invention can change the configuration of the molecule due to light irradiation, and then produce a change in the helical torsion force (HTP), so that the pitch (p) of the cholesteric liquid crystal can be changed to achieve different colors of reflected light. According to the length of illumination time, the liquid crystal composition of the present invention can produce a wavelength shift ranging from 50 to 250 nm, so as to display red (R), green (G), blue (B) in the range of visible light (380 nm-800 nm). ) and other specific reflection wavelengths. The light source used for illumination is preferably ultraviolet light, because it has higher energy and can shorten the time required for molecular configuration change.

Compared with known compounds having two photoresponsive functional groups, the cholesteric liquid crystal formulation prepared by the chiral compound with a single photoresponsive functional group of the present invention has a smaller peak half-width (Δλ), and therefore presents a relatively Excellent color purity. In addition, the obtained cholesteric liquid crystal formulation has low temperature dependence of reflection wavelength (the absolute value of dλ/dT is less than 1), and has relatively stable display quality.

The liquid crystal composition of the present invention can also form a mixed solution with high molecular monomers, and polymerize the high molecular monomers by means of heat or light, and phase separation occurs as the solubility between the monomers and liquid crystals decreases during the polymerization process, so that the liquid crystals are slightly The droplet form is evenly dispersed in the polymer to become a polymer dispersed cholesteric liquid crystal (PDChLC).

In summary, the chiral compound of the present invention at least provides the following advantages:

1. Possess high helical torsion force (HTP>30μm ^-1 ).

2. Good solubility with liquid crystal formula and colorless itself.

3. The prepared cholesteric liquid crystal formula has high color purity.

4. It has stable temperature dependence (the absolute value of dλ/dT is less than 1).

Through the chiral compound of the present invention, an optical writing cholesteric liquid crystal display with high color purity and stable display quality can be obtained for various wide applications, such as electronic labels, e-books, smart cards, flat-panel displays, large-scale Advertising billboards, and handwriting computers, etc.

The liquid crystal composition of the present invention can also be used for making other types of display devices, such as twisted nematic (TN) displays, super twisted nematic (STN) displays, color super twisted nematic (CSTN) displays and thin film transistor type displays. (TFT) display. In addition, the liquid crystal composition of the present invention can also be used to make reflective polarizers, cholesteric reflective polarizers, reflectors, optical compensation films, retardation films, color filters, photochromic coatings or liquid crystal dyes wait.

[Comparative Example 1: Chiral Compound 1 with Double Photoresponse Group]

Weigh 4-methoxycinnamic acid (4-Methoxycinnamic acid) (10.7g, 60mmol) into a double-necked bottle, and set up a reflux tube, use the feeding tube to drop _SOCl2 , and react at 50 ° C for about 3 After 2 hours, the excess _SOCl2 was sucked off with a vacuum pump, leaving a pale yellow liquid. On the other hand, isomannide (7.3g, 50mmol) was dissolved in pyridine (20ml) and dichloromethane (50ml), slowly dripped into the upper solution with a feeding tube, and reacted at room temperature for about 20 hours. After the reaction was completed, HCl _{( aq)} and CH ₂ Cl ₂ extraction, the organic layer was taken and dried to obtain a pale yellow oil, which was recrystallized from MeOH to obtain a white solid with a yield of 28.7% (6.7 g, 14.4 mmol). HTP of the product = 45 μm ^-1 .

[Comparative Example 2: Chiral Compound 2 with Double Photoresponse Group]

The synthesis procedure was the same as that of Comparative Example 1, but the isomannide was changed to isosorbide, and the obtained product was a white solid with HTP=45 μm ^-1 .

【Example 1】

Weigh 4-methoxycinnamic acid (4-Methoxycinnamic acid) (10.7g, 60mmol) into a double-necked bottle, and set up a reflux tube, use the feeding tube to drop _SOCl2 , and react at 50 ° C for about 3 After 2 hours, the excess _SOCl2 was sucked off with a vacuum pump, leaving a pale yellow liquid. On the other hand, isosorbide (7.3g, 50mmol) was dissolved in pyridine (20ml) and dichloromethane (50ml), slowly dripped into the upper solution with a feeding tube, and reacted for about 4 hours under ice-cooling _{. )} and CH ₂ Cl ₂ extraction, the organic layer was taken and dried to obtain a light yellow oil, which was first recrystallized with MeOH to obtain unwanted by-products, and then separated by column chromatography to obtain the product with a yield of 33.3% ( 5.1 g, 16.7 mmol).

Weigh 3-(4-methoxy-phenyl)-acrylic acid 6-hydroxy-hexahydro-fluoro[3,2-b]furan-3-yl ester (3-(4-Methoxy-phenyl)-acrylic acid 6-hydroxy-hexahydro-furo[3,2-b]furan-3-ylester) (3.8g, 15mmol) was put into the double-necked bottle, and the reflux tube was set up, and SOCl was _dripped in by using the feeding tube, at 50 After reacting at °C for about 3 hours, the excess _SOCl2 was sucked off with a vacuum pump, leaving a white solid. On the other hand, the white solid (1.5g, 5mmol) obtained in the previous step was dissolved in pyridine (50ml), slowly dripped into the upper liquid with a feeding tube, then added a small amount of 4-dimethylaminopyridine (4-Dimethylaminopyridine), and heated Reaction at 80°C for about 20 hours, after the reaction was completed, extracted with HCl _(aq) and ethyl acetate, the organic layer was taken and dried to obtain a light yellow oil, which was separated by column chromatography to obtain a white solid with a yield of 21 % (0.6 g, 1 mmol). HTP of the product = 60 μm ^-1 .

[Example 2]

The synthesis procedure is the same as in Example 1, but isosorbide is changed to isomannide, and the obtained product is a white solid, HTP=33 μm ^-1 .

【Lighting evaluation results】

0.15 g of the chiral compound of Example 1 was configured in 2.94 g of nematic liquid crystal host BL-087 (Merck) (birefringence index 0.24), and before irradiation with a UV lamp (365nm; ~2mW/cm ² ). The wavelength of cholesteric liquid crystal is 568nm, and it is 782nm after being illuminated for 270 seconds, and the wavelength shift is as high as 214nm.

【Color Purity Analysis】

0.50 grams of the chiral molecules of Comparative Example 1 and Example 1 were arranged in 6.81 grams of nematic liquid crystal host BL-087 (Merck) (birefringence 0.24), and UV lamp (365nm; ~2mW/cm ² ) After irradiating light for 0-60 seconds, measure its peak half-maximum width (Δλ), and the results are shown in Table 1 and Figure 1.

Table 1

It can be clearly seen from Table 1 and FIG. 1 that the photoresponsive cholesteric liquid crystal prepared by the chiral molecule in Example 1 has a smaller Δλ and better color purity. This is because the molecule of Example 1 has only one photoresponsive group, and the photoisomerization reaction from trans to cis is simple; the molecule of Comparative Example 1 needs to go through (trans, trans) to (cis, trans) because of two photoresponsive groups. ) or (trans, cis) transition state, and finally to (cis, cis), resulting in a larger Δλ.

【Temperature dependence analysis】

0.40 g of the chiral molecules of Comparative Example 2 and Example 1 were respectively configured in 4.63 g of nematic liquid crystal host BL-087 (Merck). Measure the reflection wavelength of the obtained cholesteric liquid crystal formulation at 0°C to 50°C to obtain the relationship diagrams shown in Figure 2 and Figure 3, and parallel linear regression to obtain slopes (dλ/dT) of -1.05 (compared to Example 2), -0.51 (Example 1). It can be seen that the cholesteric liquid crystal formulation obtained in the present invention is less sensitive to temperature and can have a more stable display quality.

Although the present invention has been disclosed above with several preferred embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make arbitrary changes without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims (20)

1. A chiral compound has a structure such as formula (I) or formula (II): Wherein R ₁ and R ₂ are independently selected from hydrogen, hydroxyl, halogen, amino, nitro, nitrile, C _1-10 alkyl, C _1-10 alkoxy, aryl, heteroaryl, ring Alkyl, or heterocyclic. 2. The chiral compound according to claim 1, which has the structure of formula (I). 3. The chiral compound according to claim 2, wherein R ₁ and R ₂ are independently selected from hydrogen, C _1-10 alkyl, or C _1-10 alkoxy. 4. The chiral compound according to claim 1, which has the structure of formula (II). 5. The chiral compound according to claim 4, wherein R ₁ and R ₂ are independently selected from hydrogen, C _1-10 alkyl, or C _1-10 alkoxy. 6. The chiral compound according to claim 1, which is a white solid. 7. The chiral compound according to claim 1, whose helical twisting force is greater than 30 μm ^-1 . 8. The chiral compound according to claim 1, which has the following structural formula:

9. The chiral compound according to claim 1, which has the following structural formula:

10. A liquid crystal composition comprising: 100 parts by weight of the liquid crystal host; and 3-20 parts by weight of the chiral compound according to claim 1. 11. The liquid crystal composition according to claim 10, wherein the absolute value of the temperature dependence (dλ/dT) of the reflection wavelength is less than 1. 12. The liquid crystal composition according to claim 10, whose reflection wavelength is between 380-800 nm. 13. The liquid crystal composition according to claim 10, wherein the liquid crystal host is a nematic liquid crystal. 14. The liquid crystal composition according to claim 13, which is a liquid crystal formulation as an optical writing type cholesteric liquid crystal display. 15. The liquid crystal composition according to claim 10, wherein the chiral compound has a structure of formula (I). 16. The liquid crystal composition according to claim 15, wherein R ₁ and R ₂ of the chiral compound are independently selected from hydrogen, C _1-10 alkyl, or C _1-10 alkoxy. 17. The liquid crystal composition according to claim 10, wherein the chiral compound has a structure of formula (II). 18. The liquid crystal composition according to claim 17, wherein R ₁ and R ₂ of the chiral compound are independently selected from hydrogen, C _1-10 alkyl, or C _1-10 alkoxy. 19. The liquid crystal composition according to claim 10, wherein the chiral compound has the following structural formula:

20. The liquid crystal composition according to claim 10, wherein the chiral compound has the following structural formula:

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