WO1998020004A1 - 2-(4-alkylphenyl)-5-alkylthiadiazoles - Google Patents

Abstract

Liquid-crystal compounds which are usable as the basic substance of ferroelectric liquid crystal compositions, have a low viscosity, and exhibit a liquid crystal phase in a low-temperature region; and ferroelectric liquid crystal compositions containing them. The compounds are 2-(4-alkylphenyl)-5-alkylthiadiazoles represented by general formula (1) wherein Ra is C5-C15 alkyl; and Rb is C5-C15 alkyl.

Description

 Specification

 2- (4-Alkylphenyl) -1-5-alkyl-thiadiazole compounds

 The present invention relates to a liquid crystal compound that can be suitably used for a ferroelectric liquid crystal display device. Background art

 At present, liquid crystal display devices have been widely used. Among them, a TN (twisted nematic) display element is most widely used as a low-quality display element. This TN type display element has many advantages such as low driving voltage and low power consumption. The power response speed is remarkably inferior to light emitting type display elements such as a cathode ray tube, an electronic luminescence and a plasma display. A new type of TN display element with a twist angle of 180 ° to 270 °, the so-called STN display element, has been developed, and the display capacity has increased dramatically, but the response speed is still limited . In recent years, display devices in which each pixel of a TN display device has a switch device have appeared on the market. Many of these devices are called thin film transistor devices (TFT devices), and have high density, large capacity and full color. The future of the liquid crystal device is expected. However, since semiconductor technology is used in the manufacture of TFT elements, the screen size is limited to more than twenty inches, and the time division capability is also said to be limited to about 1,000 lines. Production costs are also problematic.

 The ferroelectric liquid crystal display device, which is the subject of the present invention, has the potential of realizing both a large screen of more than twenty and a few inches and a reduction in production cost, which the TFT device cannot realize. (Clark et al., Applied Physics Letter (Applied Phys. 1 ett.,) 36, 899 (1980)). This display method uses a chiral smectic phase such as a chiral smectic C phase (hereinafter abbreviated as Sc * phase) that exhibits strong dielectric properties, and is called a surface stabilized ferroelectric liquid crystal display (SS FLC). It is being commercialized by home appliance manufacturers and material manufacturers, and its characteristics are being improved and commercialized.

The reason is that the ferroelectric liquid crystal element has the following features in principle. 1. High-speed response, 2. Memory—

 3. Wide viewing angle,

These features suggest the potential of SSFLC for high-capacity display, making SSFLC very attractive.

 However, as research progressed, problems that had to be solved were identified. Among these problems, stable expression of memory is the first issue. The difficulty in stably expressing memory is due to the non-uniform smectic layer structure (for example, twisted arrangement and chevron structure) and the generation of an internal reverse electric field, which is considered to be caused by the magnitude of spontaneous polarization. It is considered.

 As one of means for achieving stable memory properties, a ferroelectric liquid crystal composition having a negative dielectric anisotropy (Δε <0, Δε represents dielectric anisotropy) is used. (Le Paris et al., Paris Liquid 'Crystal' Conference, p. 217 (1989)). This method is called the AC stabilizing effect.

 Liquid crystal molecules with negative ε in a cell subjected to homogenous alignment treatment tend to be oriented parallel to the glass substrate (the major axis of the molecule is perpendicular to the direction of the electric field) when an electric field is applied. . When a low-frequency electric field is applied, the spontaneous polarization responds to the electric field, and when the direction of the electric field is reversed, the liquid crystal molecules move accordingly to the other stable state, and the substrate remains as it is due to the effect of Δε. In parallel with When a high-frequency electric field is applied, the spontaneous polarization cannot follow the reversal of the electric field, and only Δε is effective. Even if the direction of the electric field is reversed, the liquid crystal molecules do not move and remain parallel to the substrate. Become. This is the mechanism of developing memory properties using the AC stabilization effect. Thereby, a high contrast is obtained. This example has been reported by Jyuari et al. (S ID '85 Digest p. 128 (1989)).

It is known that a ferroelectric liquid crystal material having a negative dielectric anisotropy has another unique property. That is, the memory reversible pulse width has a minimum value (Vmin) with respect to the applied voltage. Using this property, crosstalk A high-contrast display element with no defects has been realized (Future Electronics, Vol. 122, p. 63 (1991)).

 As described above, a ferroelectric liquid crystal material having a negative dielectric anisotropy can be applied to a display element utilizing the AC stabilizing effect and r-Vmin.

 Many properties are required for a ferroelectric liquid crystal material using a negative △ to be actually used, but at present, a single compound cannot meet the demand. It is provided in the form of a mixture.

 The ferroelectric liquid crystal composition can be composed of a ferroelectric liquid crystal compound alone, a non-chiral smectic smectic phase such as C, F, G, H, and I (hereinafter referred to as Sc, etc.). A compound or composition that exhibits the following formula is used as a basic substance, and one or more ferroelectric liquid crystal compounds or non-liquid crystal optically active compounds are mixed with the compound or composition to form a ferroelectric liquid crystal phase as a whole. There is a method of making a composition. By the way, many liquid crystal compounds containing a thiadiazole ring are already known. For example, J. Prakt. Chemie., Vol. 322, pp. 933 (1980)), DD2 4 7 2 2 1 A1, and DD2 7 6 9 4 A1 Is disclosed in

 In J. Prakt. Chemie., The following compounds are disclosed as compounds exhibiting the Sc phase.

Compositions using these compounds are disclosed, for example, in W088 / 809. As a liquid crystal compound having a thiadiazole ring, there are disclosed in Japanese Patent Application Laid-Open Nos. 2-275688 and 2-28069. Further, the present inventors have already applied for a liquid crystal composition using thiadiabule (Japanese Patent Application Laid-Open No. 7-70564). These compounds are shown below.

Thus, it has been known that the liquid crystal compound having a thiadiabule ring can be suitably used for a ferroelectric liquid crystal. However, compounds having three or more ring structures in the molecule, for example, the following compounds are expected to have high viscosity, and the temperature range in which the Sc phase is exhibited is also high.

Disclosure of the invention

That is, an object of the present invention is to provide a liquid crystal compound having a low viscosity and a low temperature range in which an Sc phase is exhibited, and which can be suitably used for a ferroelectric liquid crystal. Therefore, the present inventors have searched for a liquid crystal compound having a thiadiazole ring having a two-ring structure.

As described in the Background Art section, it has already been reported that a compound having the above structure has an Sc phase appearing in a temperature region slightly higher than room temperature, and can be suitably used in a ferroelectric liquid crystal composition. . However, a compound in which the alkoxy group at the left end in the above structural formula is substituted with a corresponding alkyl group has been used as a liquid crystal.

Tightened paper (Rule 91) Because, in the above-mentioned literature, J. Prakt. Chemie., Vol. 322, p. 933 (1980), the following compounds only show a melting point and no liquid crystal phase. Furthermore, this document does not discuss other compounds having different alkyl group chain lengths.

As described above, the present inventors have conducted various searches focusing on structures that have not been considered to be usable in ferroelectric liquid crystal compositions, and as a result, have arrived at the compounds of the present invention. That is, the present invention

General formula (1)

(In the formula, Ra represents an alkyl group having 5 to 15 carbon atoms, and Rb represents an alkyl group having 5 to 15 carbon atoms.)

 In the compounds of the present invention, it is considered that when the carbon number of each of Ra and Rb is less than 5 or more than 15, the Sc phase is not expressed. Preferred carbon numbers of Ra and Rb are those whose sum is in the range of 11 to 25.

As already mentioned, the general formula similar structure as in (1), long and is ₍₂ ^ 1 ₅ Deari, although compound R b is a C ₇ H ₁₅ is known, liquid crystal phase However, the present inventors have scrutinized the alkyl chain length and found a compound that can be suitably used for ferroelectric liquid crystals by selecting the alkyl chain length in the claims of the present application.

Further, a compound represented by the general formula (1), and a compound having an alkoxy group at the left end corresponding thereto, response is synonymous with viscous is the main object of the present invention ^{^:} A comparison was made by the time . As will be described in detail in Examples below, the ferroelectric liquid crystal composition containing 50% of the compound of the present invention has a response speed shorter than that of the liquid crystal composition containing 50% of the comparative compound by about 30% or more. I have. This indicates the superiority of the compound of the present invention.

Five

Corrected form (Rule 91) Among the compounds represented by the general formula (1), the following compounds can be particularly preferably used.

 2-(4-pentylphenyl) 1-5-pentyl + 3 4-1 2-(4-pentylphenyl)-5-hexyl 1, 3 4-1-Cr 19 Sx 22.0 Iso

 2-(4-pentylphenyl) 1 5-3 4 thiadiazole 2-(4-pentylphenyl) 5 1-year-old tylyl 1 3 4 thiadiazole

Cr 34 Sc 42.1 Iso

2- (4-pentylphenyl) 5-nonyl-1,3,4-thiadiazole Cr 36 (S3 21 S2 25) Sc 49.2 Iso

 2- (4-pentylphenyl) -1-5-decyl-1,3,4-thiadiazole

Cr 47 (Sx 33.2) Sc 50.9 Iso

2- (4-Pentylphenyl) -1-5-decyl-1,3-, 4-thiadiazole

Cr 49 (S3 43.0 S2 44.2) Sc 54.3 Iso

2- (4-pentylphenyl) 1 5-1 Dodecyl 1 3 4 1 2- (4-hexylphenyl) 1-5 1-pentyl 1 1 3 4 1 2- (4-hexylphenyl) 1 5 1-hexyl-1 3 4-ole 2--(4-hexylphenyl) 1-1-heptyl-1 3 4-1

Cr 28 Sc 42.1 Iso

2- (4-hexylphenyl) -1-5-octyl-1,3,4-thiadiazole

Cr 33 Sc 45.3 Iso

2- (4-hexylphenyl) -5-nonyl-1,3,4-thiadiazole

Cr 30 (Sx 18) Sc 35.9 Iso

2-(4-Hexylphenyl)-5-decyl 3, 4-thiadiabour Cr 48 (S3 32.2 S2 36.3) Sc 52.3 Iso

2-(4-Hexylphenyl) 1 -5-Dindecyl-1,3,4-thiadiazole 2-(4 -Hexylphenyl)-5-Dodecyl -1,3 4 -R 2-(4 -Heptylphenyl) 1 5- Pencil 1, 3 4 Boolean 2-(4 heptyl) 1 5 1 hexil i, 3 4 sol Cr 28 (Sc 21.5) SA 42.5 Iso

 (4-Heptylphenyl) 1-Heptyl-1,3,4-thiadiazole Cr 33 (S 11) Sc 46.3 SA 50.7 Iso

 (4-1 heptyl)-5-octyl-1, 3, 4 thiaiabul Cr 38 (Sx218 Sx 18.5) Sc 52.1 SA 53.1 Iso

― (4-heptylphenyl) — 5-nonyl— 1,3,4-le Cr 38 (Sx234.2 Sx 37.2) Sc 58.4 Iso

 (4-Heptyl) — 5-decyl 3,4-le Cr 50 (Sx 43.7) Sc 58.5 Iso

 (4-1 heptyl) — 5—Pindecyl 1,3,4

(4-1 heptylphenyl) 3, 4-1-(4-year-old octylphenyl) Pentyl-1 3, 4-1 Cr 38 SA 39.2 [so

 (4-octylphenyl) 5-hexyl-1,3,4-thiadiazol Cr 40 Sc 44.5 Iso

 (4 years old octylphenyl) Heptyl-1,3,4-thiadiazole Cr 38 SC 44.6 SA 51.3 Iso

1- (4-octylphenyl) 1-5-octyl 1,3,4-thiadiazole Cr 34.0 (Sx 25) Sc 54.2 Iso

 (4 one-year-old tyl phenyl) 1 5-nonyl-1,3,4-thiadiabour Cr 33 Sx 40.3 Sc 59.1 Iso

One (41-year-old octylphenol) One 5—decyl-1,3 4—thiaziazole Cr 52 (Sx 47.5) Sc 60.2 Iso

1- (4-octylphenyl) 1- 5-decdecyl-13,4-thiadiazole Cr 47 SF 55.2 Sc 62.6 [so

-(4-octylphenyl) 1 5-dodecyl 1, 3, 3, 4-yl-(4-nonylphenyl) 1 5-pentyl 1, 3, 3, 4- Cr 33 (Sc 22.0) SA 43.7 iso

One (4-nonylphenyl) One 5-hexyl-1,3,4-thiadiazole (4-Nonylphenyl) — 5-heptyl-3,4-thiadiazole Cr 45 (Sx233.0 Sx 34.9 Sc 44.0) SA 57.1 Iso

 (4-Nonylphenyl) 1-5-year-old 1,3,4-thiadiazol Cr 39 Sx 43.3 Sc 56.2 SA 59.0 Iso

 2- (4-nonylphenyl) -1-5-nonyl-1,3,4-thiadiazol

 Cr 45 Sx 50.1 Sc 63.2 Iso

 (4-nonylphenyl) -1-5-decyl-1,3,4-thiadiazole Cr 45 Sx 55.9 Sc 64.1 Iso

 2 (4-nonylphenyl) -1-5-decdecyl-1,3,4-thiadiabul 2 (4-nonylphenyl) 5-dodecyl-1,3 4-thiadiazole 2 (4-decylphenyl) 5-pentyl-1-1,3,4-thiadiazole 2 (4-decylphenyl) 5-hexyl-1,3-thiadiazole 2 (4-decylphenyl) 5-heptyl-1,3-thiadiazole

Cr 49 (SB 42.0) SA 57.1 Iso

 2 (4-decylphenyl) -1 5-octyl-1,3,4-thiadiazole 2 (4-decylphenyl) -1-5-nonyl-1,3,4-yl 2 (4-decylphenyl) 1,5-decyl-1,3,4— Cole 2 (4-decylphenyl) — 5-Pindecyl 1,3,4-thiaazole Cr 44 SF 64.3 SC 66.1 Iso

 2 (4-decylphenyl) — 5-dodecyl-1,3,4-thiadiazole 2 (4-unddecylphenyl) -1-5-pentyl-1,3,4-thiadiazole 2 (4, decylphenyl) ) —5—Hexyl-1 3,4-thiadiazol 2 (4 ゥ decylphenyl) —5—Heptyl-1 3,4—thiadiazol 2 (4 ゥ decylphenyl) 1-5-octyl 1,3,4-thiadiazol 2 (4,1-decylphenyl) — 5-nonyl-1,3,4l 2 (4,1decylphenyl) -1,5-decyl-1,3,4,2,1 (4 —Pindecylphenyl) 1-5—Pindecyl—1,3,4-thiadiazol

2 — (4-Undecylphenyl) 1 5 — Dodecyl 3, 4 — Thiazyl ― 98/2000

2- (4-dodecylphenyl) -1-5-pentyl-1,3,4-thiadiazole 2- (4-dodecylphenyl) —5-hexyl-1,3,4-thiadiazole 2- (4-dodecylphenyl) — 5—Heptyl-1,3,4-thiadiazol 2— (4—dodecylphenyl) —5-octyloxy and 3,4—thiadiazole 2— (4—dodecylphenyl) —5-nonyl-1,3,4-thiadiabour 2 — (4—dodecylphenyl) — 5—decyl-1,3,4-thiadiaburu 2— (4-dodecylphenyl) — 5-—decdecyl-1,3,4-thiadiazole 2— (4—dodecylphenyl) — 5— Dodecyl-1,3,4-thiadiazol—The compound of the present invention represented by the general formula (1) can be suitably produced by the following route.

 RbCOCl

That is, the 4-alkylbenzoic acid (a) is converted to a lower ester (eg, ethyl ester).

(b)), then react with hydrazine hydrate to form hydrazide (c). Then, in a basic solvent, react with alkanoic acid chloride to obtain dihydrazide (d). In this case, pyridine, triethylamine and the like can be suitably used as the basic solvent. The desired compound (1) can be obtained by reacting the dihydrazide (d) with a phosphorylation reagent. In this case, as the oxidizing reagent, io alone, a mouth reagent, and the like can be suitably used.

BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a diagram showing response times of the compositions of Examples and Comparative Examples.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. Various measurements in the examples were performed by the following methods.

The phase transition temperature was measured by placing the sample on a slide glass, placing the sample covered with a cover glass on a hot plate, and raising the temperature at 1 ° 0 min under a polarizing microscope. The melting point was measured by differential scanning calorimetry (DSC) at a temperature of 1 ° CZmin.

Example 1

 2- (4-octylphenol) 1-5-Heptyl-3,4-thiadiazole Stage 1: Production of 4-octylpenzohydrazide

 To 100 g of 4-octyl benzoate, 100 ml of ethanol was added, 80 g of hydrated hydrazine was added dropwise, and the mixture was heated under reflux for 4 hours. After cooling, the reaction solution was poured into ice water, and the precipitated crystals were collected by filtration and washed with water. The solid was air-dried and recrystallized from ethanol (10 Om1) to obtain 72.9 g of the desired product.

 (m.p.ί 00.1-1 0 1.2 ° C)

 Stage 2: N— (4-octyl benzoyl) -N′—Preparation of butyl dihydrazide 9.0 g of 4-octyl benzohydrazide obtained in stage 1 and 40 ml of pyridine are added, and octanoyl is added. 5.9 g of chloride was added dropwise, and the mixture was heated under reflux for 3 hours. After allowing to cool, the reaction product was poured into water, and the precipitated crystals were collected by filtration and air-dried. The solid was washed with hot ethanol to obtain 10.3 g of the desired product.

 (m.p. 1 13.8-1 15.4 ° C)

 Stage 3:

The second stage obtained in N-(4-Okuchirupenzo) - N '- to Petit total amount and the mouth one Son reagent dihydrazide 1 1. The mixture 2 g of a THF 5 Om 1, _c reaction solution was stirred with heating for 6 hours Was added to water and extracted with toluene. The organic layer was washed with an aqueous solution of sodium hydrogen sulfite, and then washed with neutralized water. After drying the solution, it is concentrated, the residue is purified by column chromatography packed with active alumina, the effluent is concentrated ', and recrystallized using ethanol to obtain the desired 2- (4- 5.9 g of 1,5-heptyl-1,3,4-thiadiazol was obtained.

 Ten

Corrected form (Rule 91) Phase transition point (Cr 38 Sc 44.6 SA 51.3 I so)

Example 2 (composition example)

 Sc compositions (mixtureA) composed of the following six compounds were prepared. <The respective concentrations are 30.2010, 10 and 20.10 wt% in order from the top. The phase transition temperature of this composition A was Cr4SC65SA79N90ISO.

 N.

 <·

' ^c a ^H i7

 N:

 The compound of the present invention (50 wt%) obtained in Example 1 was mixed with the above (m i X t ure

A) A ferroelectric liquid crystal composition (FLC.A) consisting of (45 wt. And optically active compound (Ch ra 1.A) (5 wt.%) Was prepared. It was as follows.

room temperature-S c * 54.4 SA 5 8.9 I so

C h r a 1. A: phase transition point (C r 71.0 N * 80.0 I so)

Comparative Example 1

 2- (4-year-old tylphenyl) -1-5-heptyl-1, 3,4-thiadiazole (compound of Example 1) in place of 2- (4-octyloxyphenyl) -5-pentyl-1 In the same manner as in Example 2 except that, 3,4-th

1 1 Corrected paper (Rule 91) An electrically conductive liquid crystal composition (FLC. B) was prepared. The phase transition temperature of this (FL C. B) was as follows.

room temperature- Sc * 67.3 SA 76.0 I so

Phase transition point (Cr 6 2 Sc 6 9.6 SA 80.7 Iso) Example 3

 Each of the compositions of Example 2 and Comparative Example 1 was sealed in a cell having a thickness of 2 m, and the response time of each was measured. The response time at each measurement temperature was as follows. C These data are shown in FIG.

 Measurement temperature Response time

 (° C), s e c)

 Example Comparative example

 6 2 3 2 0.2

 5 7 3 2 4 6

 5 2 3 2 9 0

 4 9 4 2 4 4

 4 7 3 3 4 0

 4 4 4 3 0 0

 3 9 4 3 5 0

 3 7 3 4 8.0

 3 4 4 4 2 0

 2 5 0 6 1 5 9 1.0

 1 4 4 1 0 0 0

Industrial applicability

 Provided are a liquid crystal compound which can be used as a basic substance of a ferroelectric liquid crystal composition, has a low viscosity and exhibits a liquid crystal phase and has a low temperature range, and a ferroelectric liquid crystal composition containing this compound.

Claims

The scope of the claims

1. a liquid crystal compound represented by the following general formula (1),

(In the formula, Ra represents an alkyl group having 5 to 15 carbon atoms, and Rb represents an alkyl group having 5 to 15 carbon atoms.)

 2. A ferroelectric liquid crystal composition containing at least one compound according to claim 1.