JP2002235085A - Cholesteric liquid crystal and recording display material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cholesteric liquid crystal compound capable of achieving a recording in rewritable specific colors or a full color recording by using a low molecular weight compound. SOLUTION: The cholesteric liquid crystal contains an ultrastructural material having at least one group capable of forming intermolecular hydrogen bond and having a steroid skeleton-containing group and a 3-20C alkylene group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cholesteric liquid crystal containing a superstructure material and a rewritable thermosensitive specific color or full color recording / display material.

[0002]

2. Description of the Related Art A color photograph and a color copy are known as recording materials capable of recording full color and not rewriting. Non-full-color rewritable recording materials include thermosensitive recording materials containing long-chain alkyl carboxylic acid derivatives such as behenic acid, optical recording materials using photochromic compounds such as spiropyran derivatives, and other memories such as magnetism and magneto-optics. Materials are known.

Conventional recording materials have not achieved both full color and rewritable characteristics. Certainly, some display materials change their display, such as televisions and liquid crystal displays, and there are full-color ones, but they can be used as a thin card that fits in a wallet or display images stably forever without a power supply It could not be used as a substitute for recording material.

In recent years, full-color recording which can be rewritten by a new method using a liquid crystal compound has been achieved (Japanese Patent Laid-Open No. Hei 1 (1994)).
No. 1-24027, Japanese Patent No. 2946042,
JP-A-2000-7613).

However, since the liquid crystal compound used in the above publication has a relatively large molecular weight of 1000 or more, a liquid crystal substance capable of stably fixing various colors using a compound having a small molecular weight has been desired.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a cholesteric liquid crystal and a recording / display material which use a low molecular weight compound to achieve rewritable specific color recording or full color recording. The purpose is to:

[0007]

That is, the present invention provides a superstructure material having at least one group capable of intermolecular hydrogen bonding, a group having a steroid skeleton, and an alkylene group having 3 to 20 carbon atoms. A cholesteric liquid crystal characterized by containing the cholesteric liquid crystal, and a recording display material characterized by including the cholesteric liquid crystal.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The cholesteric liquid crystal of the present invention
It contains at least one group capable of intermolecular hydrogen bonding, a group having a steroid skeleton, and a superstructure substance having an alkylene group having 3 to 20 carbon atoms.

In the present invention, a superstructure substance is a compound of a type having a supramolecular structure, that is, a structure having a geometrical order due to weak force interaction between molecules, specifically, a hydrogen bond. It is a substance that forms an aggregate with self-organization (self-organization, self-assembly).

The group capable of forming an intermolecular hydrogen bond is not particularly limited. Examples thereof include a carboxyl group, a hydroxyl group, an amide group, an amino group, an imino group, a nitrile group, and a nitrogen-containing heterocyclic group such as a pyridyl group. , An imidazolyl group, an aminopyridyl group, a uracil group and the like.

The intermolecular hydrogen bond formed is not particularly limited, but is a heterocyclic group having nitrogen such as carboxyl groups, hydroxyl groups, amide groups, carboxyl group and pyridyl group, and hydroxyl group and pyridyl group. And a nitrogen-containing heterocyclic group such as a group, a carboxyl group and a nitrile group, and an intermolecular hydrogen bond formed by a diaminopyridyl group and a uracil group.

Examples of the group having a steroid skeleton include, but are not limited to, a cholesterol residue obtained by removing a hydroxyl group bonded thereto from cholesterol, a dihydrocholesterol residue obtained by removing a hydroxyl group bonded thereto from dihydrocholesterol, Cholic acid residue obtained by removing the hydroxyl group bonded to cholic acid,
β-sitosterol residue obtained by removing the hydroxyl group bonded thereto from β-sitosterol, α-spinasterol residue obtained by removing the hydroxyl group bonded thereto from α-spinasterol, and the like. A cholesterol residue and a dihydrocholesterol residue are preferable because they can give a color.

The alkylene group has 3 to 20 carbon atoms,
Preferably it is 3-11. When the carbon number exceeds 20,
Viscosity in the superstructure liquid crystal state may increase and the response to temperature change may be delayed. If the number of carbon atoms is less than 3, it is difficult to fix the cholesteric reflection color by rapid cooling from the superstructure liquid crystal state. Absent.

The molecular weight of the superstructure material is preferably 385
９００900, more preferably 500-800. If the molecular weight exceeds 900, the viscosity in the superstructure liquid crystal state may increase and the response to temperature change may be delayed. If the molecular weight is less than 385, the cholesteric reflection color is fixed by a rapid cooling operation from the superstructure liquid crystal state. There is a possibility that the conversion is difficult.

Specific examples of the superstructure substance include the following cholesteryl ester compounds.

[0016]

Embedded image

[0017]

Embedded image (Wherein, Y represents a cholesterol residue obtained by removing a hydroxyl group bonded thereto from cholesterol, and n represents 3 to
Indicates an integer of 20. X represents -OH, -Me, -O
Me, -NO _2, shows -Cl, -Br, -I, and -CN, m is an integer of 0 to 2, in the case of m = 2 may be the same different in substituent group substituents. )

The cholesteryl ester compound can be produced, for example, by the following methods (a) to (d).

[0019]

Embedded image

[0020]

Embedded image

[0021]

Embedded image

[0022]

Embedded image (Wherein, Y represents a cholesterol residue obtained by removing a hydroxyl group bonded thereto from cholesterol, and n represents 3 to
Indicates an integer of 20. )

Specific examples of the cholesteric liquid crystal of the present invention include compounds represented by the above general formulas (1) to (1 "), compounds represented by the above general formulas (2) to (2"), Supramolecular compounds represented by the formula (3) wherein n is an even number, or supramolecular compounds formed by a combination of an even number and an odd number, wherein the same number of carbon atoms may be used alone or the number of carbon atoms may be different. May be combined.
In the latter case, the liquid crystal temperature and the wavelength range that can be fixed can be adjusted by appropriately setting the number of carbon atoms n and the mixing ratio.

Further, a combination of a compound represented by any of the above formulas (1) to (4) and a compound represented by any of the above formulas (5) to (5 ″), A compound represented by any one of 1) to (4) and 4,4′-
Combination with bipyridyl, the above general formula (5)-
Supramolecular compounds formed by a combination of the compound represented by any one of (5 ″) and terephthalic acid can be mentioned. In these cases, the liquid crystal temperature and the fixed The mixing ratio of the two is not particularly limited, but it is preferable to mix the hydrogen donor and the hydrogen acceptor in a molar ratio of 1: 2 to 2: 1.

The liquid crystal of the present invention can reproduce a specific color or a color in the entire visible range (full color) according to the heating temperature.
Further, the color (reflected light) can be fixed, and it can be used as a thermosensitive recording material capable of being fixed to a full color or a specific color.

The recording and display material of the present invention comprises the above liquid crystal and is used in the form of the liquid crystal of the present invention alone or in a mixture. When used as a mixture, examples of the compound to be mixed include a liquid crystal compound such as dicholesteryl ester and cholesterol. Further, additives such as a dye and an antioxidant can be included. In this case, the amount of the liquid crystal of the present invention is 9
It is preferably at least 0% by weight.

As an embodiment of the recording and display material of the present invention, for example, a recording and display material comprising at least one of the above-mentioned liquid crystals sandwiched between two substrates having a transparent portion is exemplified.

The substrate used in the present invention is usually a thin glass plate or the like, but may be a metal plate or a thin film such as a polymer film. In addition, one of the two sheets needs to have transparency so that at least a part of light is transmitted. When light is used for writing or erasing a record as described later, it is desirable that one substrate absorbs the light.

As a method of sandwiching the liquid crystal of the present invention between two substrates, first, the liquid crystal of the present invention or a mixture containing the liquid crystal is heated to a temperature of a molten state or a liquid crystal state, and then cast on one substrate. , Or put another board on it,
There is a method of inserting between two substrates kept in parallel by utilizing a reduced pressure or a capillary phenomenon.

The distance between the substrates is not particularly limited, but is preferably about several μm to 100 μm.

The recording and display material of the present invention can perform recording (writing) and display of recording by heating partially or entirely. For the heating, a thermal head,
All methods such as a heating roll and a laser beam are possible. Heating that requires temperature control to the liquid crystal temperature range can be achieved by controlling the temperature of the thermal head or heating roll, adjusting the intensity or spot diameter of the laser beam, or by heating the entire unit to a certain temperature. This can be achieved by lowering the temperature to the required temperature with a flat metal plate or rubber plate.

On the other hand, in order to fix the coloration of the liquid crystal of the present invention, it is necessary to rapidly cool the liquid crystal to a temperature lower than its glass transition temperature. For example, a method of immersion in the inside or a method of partially contacting the head with the cooled head is employed.

Another embodiment of the recording and display material of the present invention is a dispersion in which the liquid crystal of the present invention or a mixture containing the liquid crystal of the present invention is dispersed in a polymer compound film or another molded product.

The recording and display material of the present invention includes, for example, cards, sheets for overhead projects, labels,
It can be used as a ticket or the like, and if necessary, a protective layer, a back surface layer, and the like may be further provided. For example, in the case of a label, a mount is provided on the back surface of the recording display material via an adhesive layer. In the case of a magnetic ticket, a magnetic recording layer made of a binder and a ferromagnetic powder is provided in place of the mount.

[0035]

EXAMPLES (Example 1) <Synthesis of compound represented by general formula (1) (n = 5, m = 0) and compound represented by general formula (2) (n = 5, m = 0)> According to the above reaction formula (a), a compound represented by the general formula (1) (n = 5, m = 0) and a compound represented by the general formula (2) (n = 5, m = 0) were synthesized.

1.95 g (13 mmol) of methyl 4-hydroxybenzoate, 2.5 g (13 mmol) of 6-bromo-n-hexanoic acid and 3.6 g of potassium carbonate
(26 mmol) was refluxed with heating in 20 ml of acetone for 8 hours. After cooling, 100 ml of water was added, and 5% hydrochloric acid was further added until the solution became acidic. The solution was extracted with a chloroform solvent and purified by silica chromatography to obtain a condensate (3.0 g, 11 mmol).

The condensate (3.0 g, 11 mmol) was mixed with 2.2 g (56 mmol) of sodium hydroxide in water 15.
The mixture was heated at 70 ° C. for 6 hours in 15 ml of tetrahydrofuran, cooled after completion of the reaction, and then acidified with hydrochloric acid.
2.1 g of a precipitated white powder (dicarboxylic acid compound) was obtained.

0.76 g (3 mmol) of dicarboxylic acid compound
l), 1.2 g (3 mmol) of cholesterol and 0.62 g (3 mmol) of dicyclohexylcarbimide are dissolved in 40 ml of methylene chloride, and the mixture is stirred at room temperature for 21 hours with 0.04 g (0.3 mmol) of 4-dimethylaminopyridine as a condensation catalyst. did. Separation and purification by column chromatography were carried out to obtain the compound 0.1 represented by the general formula (1).
45 g and 0.30 g of the compound represented by the general formula (2) were obtained.

(Example 2) <Synthesis of compound (n = 9) represented by general formula (3)> According to the above reaction formula (b), compound (n = 9) represented by general formula (3) was synthesized. did.

2.2 g of 1,9-nonanedicarboxylic acid (1
0 mmol), 3.7 g of cholesterol (10 mmol)
l) and 2.02 g of dicyclohexylcarbimide (1
0 mmol) was dissolved in 80 ml of methylene chloride, and 0.12 g (1 m 2) of 4-dimethylaminopyridine was used as a condensation catalyst.
mol) with the mixture at room temperature for 24 hours. Separation and purification by column chromatography gave 2.3 g of cholesteryl ester.

Example 3 <Synthesis of compound represented by general formula (4) (n = 5, m = 0)> According to the above reaction formula (c), compound represented by general formula (4) (n = 5) 5, m = 0).

10.5 g of 6-bromo-n-hexanoic acid
(52 mmol) and 19.2 g of cholesterol (52 m
mol) and dicyclohexylcarbodiimide 10.8
g (52 mmol) was dissolved in 280 ml of methylene chloride, and 0.6 ml of 4-dimethylaminopyridine was used as a condensation catalyst.
3 g (5.2 mmol) was added, the mixture was stirred at room temperature for 15 hours, recrystallized from ethanol, and cholesteryl ester 18 was added.
g was obtained.

2.8 g of synthesized cholesteryl ester
(5 mmol), 5-hydroxyisophthalic acid dimethyl ester 1.05 g (5 mmol), potassium carbonate 1.
4 g (10 mmol) were heated under reflux in MEK for 27 hours. Purification by silica gel chromatography gave 2.5 g (3.6 mmol) of a condensate.

Heating 2.5 g (3.6 mmol) of the condensate together with 0.43 g (10.8 mmol) of sodium hydroxide in 28 ml of water and 28 ml of tetrahydrofuran for 2 hours at 70 ° C. The obtained white powder was purified by silica gel chromatography to obtain 1.7 g of cholesteryl ester.

(Example 4) <Synthesis of compound represented by general formula (5) (n = 5, m = 0)> According to the above reaction formula (d), compound represented by general formula (5) (n = 5, m = 0).

0.038 g of 4-hydroxypyridine (4
mmol), 2.8 g (5 mmol) of cholesteryl 6-bromo-n-hexanoate, 0.7 of potassium carbonate
1 g (5.2 mmol) was heated under reflux in MEK for 25 hours. Purification by silica gel chromatography gave 0.30 g of cholesteryl ester.

Example 5 <A mixture of a compound represented by the general formula (3) (n = 9, m = 0) and a compound represented by the general formula (5) (n = 5, m = 0) ( Preparation of a molar ratio of 1: 1)> The compound represented by the general formula (3) synthesized in Example 2 (n = 9, m = 0)
After dissolving 0.01 mmol and 0.01 mmol of the compound represented by the general formula (5) synthesized in Example 4 (n = 5, m = 0) in 0.5 ml of pyridine and slowly removing the solvent under reduced pressure, Drying under reduced pressure at 80 ° C. for 24 hours gave a white powder.

Example 6 Compounds shown in Table 1 (compounds represented by general formulas (1), (2) and (5): m = 0, compounds represented by general formula (4): m = 0, carboxyl group Was substituted between two glass plates having a thickness of 0.18 mm, and the whole was heated to a liquid crystal temperature and melted to prepare a sample portion having a thickness of 20 μm. Thereafter, when the sample was quickly immersed in ice water, the sample was solidified and the color state shown in Table 1 was fixed as it was. Table 1 shows the liquid crystal temperature range, coloration state, and peak wavelength.

FT-IR measurement of Compound 6 showed that the spectrum of A alone was 3200 c
Although a peak attributable to hydrogen bonding between the same molecules was observed at m ^-1 , the peak disappeared in Compound 6 (mixture of A and B), and a peak attributable to hydrogen bonding due to a carboxyl group and a pyridyl group was 1950 cm. ^-1 and around 2500 cm ^-1 . Also, a change was observed in the carbonyl peak.

[0050]

[Table 1]

[0051]

As described above, according to the present invention, rewritable specific color recording or full color recording can be achieved. In addition, since a low molecular weight compound can be used, the range of materials that can be used for recording and display can be expanded, and furthermore, the temperature range and the wavelength range in which colors can be fixed can be varied.

Therefore, a full-color photograph can be recorded on a card or the like and can be freely rewritten. When used as a sheet for an overhead project,
It is possible to rewrite the color multiple times and use it, which is also effective for solving environmental problems.

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 597072464 Hiroo Matsuda 1966-8 Uenomuro, Tsukuba City, Ibaraki Prefecture (72) Inventor Atsushi Takahashi 4-14-12 Koishikawa, Bunkyo-ku, Tokyo Kyodo Printing Co., Ltd. (72) Invention Nobuyuki Tamaki 1-1, Higashi, Tsukuba, Ibaraki Pref., Ministry of Economy, Trade and Industry, National Institute of Advanced Industrial Science and Technology (72) Inventor: Hiroo Matsuda 1-1, Higashi, Tsukuba, Ibaraki, Japan F-term in the laboratory (reference) 2H111 FB59 HA07 4H027 BA02 BB07 DM01 DM02 DM05

Claims (6)

[Claims] 1. A group having at least one group capable of intermolecular hydrogen bonding, having a steroid skeleton, and having 3 to 20 carbon atoms.
A cholesteric liquid crystal comprising a superstructure material having an alkylene group represented by the formula: 2. The cholesteric liquid crystal according to claim 1, wherein the group capable of intermolecular hydrogen bonding is a carboxyl group, and the carboxyl groups form intermolecular hydrogen bonds. 3. The cholesteric according to claim 1, wherein the group capable of intermolecular hydrogen bonding is a carboxyl group and a heterocyclic group having nitrogen, and forms an intermolecular hydrogen bond between the two. liquid crystal. 4. A recording and display material comprising the cholesteric liquid crystal according to claim 1. 5. The recording and display material according to claim 4, wherein at least the cholesteric liquid crystal is sandwiched between two substrates or thin films having at least one transparent portion. 6. The recording and display material according to claim 4, wherein at least the cholesteric liquid crystal is dispersed in a molded article having a transparent portion.