JPH0723471B2 - Cholesteric liquid crystal composition - Google Patents

Description

The present invention relates to the use of hydroxyethyl cellulose as a liquid crystal component. The present invention more particularly relates to the use of hydroxyethyl cellulose as a lyotropic cholesteric liquid crystal component.

[Conventional technology]

Liquid crystals are classified into smectic type, nematic type and cholesteric type according to the arrangement structure of molecules, and it is well known that liquid type lyotropic liquid crystals and melt type thermotropic liquid crystals are present in each type.

Further, it can be classified into low molecular weight liquid crystals and high molecular weight liquid crystals depending on the size of molecules forming the liquid crystals.

It has been announced that a high molecular weight cellulose derivative also forms a liquid crystal, and there are many reports regarding which of the above-mentioned types it belongs to.

Since cellulose acetate, cellulose nitrate, cellulose vinegar / butyrate, ethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose and the like produced as industrial products also form liquid crystals, production of strong fibers by liquid crystal spinning (JP-A-52-96230, Studies such as the use as a liquid crystal display device (Japanese Patent Laid-Open No. Sho 55-9655) have been widely conducted.

Among the above cellulose derivatives, hydroxypropyl cellulose (HPC) forms a cholesteric liquid crystal, and its concentrated solution selectively reflects visible light, and it is colorless transparent-purple depending on the conditions under which it is placed, for example, temperature. -Green-
It reversibly develops color in the range of yellow-red-colorless and transparent. It has been reported that the HPC melt also exhibits the above-mentioned color at high temperatures.

It is fully expected that such a phenomenon that the color change changes depending on the external conditions is used for the liquid crystal display device.

[Problems to be solved by the invention]

Although the use of HPC for liquid crystal display devices is considered to be promising,
PCs are difficult to manufacture, so the price is expensive. Cellulose derivatives with a fresh cholesteric color such as HPC include acetoxypropyl cellulose, 2-hydroxy-3-methoxypropyl cellulose, 2-hydroxy-3-vinylpropyl cellulose, etc. It is not practical because it requires the use of special reagents.

The present invention, in order to solve the problems of the conventional techniques as described above, a technique that has already been industrially widely used, based on those that have been industrially produced in large quantities, cellulose exhibiting a cholesteric color. It is intended to provide a derivative liquid crystal.

[Means for solving problems]

Among the various cellulose derivatives, the present inventor has focused on hydroxyethyl cellulose (HEC), and as a result, has newly found the fact that a specific HEC is effective in solving the above-mentioned problems. This HEC of this invention
Is characterized in that the molar substitution degree of hydroxyethyl group per anhydrous glucose unit of cellulose molecule (hereinafter abbreviated as MS as widely used in this technical field) is 6 or more.

The MS value of this hydroxyethyl group was obtained from the number of moles of ethylene oxide added to each anhydrous glucose unit of the cellulose molecule by the Morgan method which is a conventional method. Furthermore, the HEC of the present invention has a concentration of 0.3-7d when measured in an aqueous solution.
It was confirmed to have an intrinsic viscosity number within the l / g range. The intrinsic viscosity number of HEC was also determined from the result of viscosity measurement in an aqueous solution at 25 ° C according to a conventional method.

When the MS is less than 6, liquid crystals are formed, but it is difficult to obtain a liquid crystal having a bright color, which is the object of the present invention. If the intrinsic viscosity number is lower than the above range, purification in the HEC manufacturing process becomes difficult, and the intrinsic viscosity number exceeds this range.
With HEC, it is not possible to prepare high-concentration solutions, and liquid crystals cannot be obtained.

The HEC used in the present invention can be obtained by repeating the reaction of a cellulosic material and ethylene oxide (EO) in the presence of an alkali in a suitable organic solvent according to a known HEC production method.

The HEC used in the present invention, as a result of having an MS of 6 or more as described above, and also influences the intrinsic viscosity number, not only water but also methanol, pyridine, dimethylsulfoxide, dimethylformamide, ethylene glycol, low molecular weight It is also soluble in polyethylene glycol.

The solvent used in the present invention may be the above-mentioned one alone or a mixture of two or more kinds.

The concentration of HEC is particularly important for the lyotropic cholesteric liquid crystal of the present invention to exhibit coloration behavior.

Although the HEC solution changes its coloration depending on the temperature change, the low-concentration solution generally develops the color in the low temperature region, and the temperature region showing the color change increases as the concentration increases.

As an example, the following table shows the dependency of HEC with MS7.8 and intrinsic viscosity of 1.4 on the color density and temperature of an ethylene glycol solution.

The coloration state of the lyotropic cholesteric liquid crystal of the present invention varies depending on the concentration, temperature as described above, MS, degree of polymerization, and type of solvent.

The liquid crystal composition of the present invention can be advantageously used for display devices, accessories, toys, stained glass, and the like.

〔Example〕

Examples 1 to 3 Microcrystalline cellulose prepared from wood pulp 37.2 g, caustic soda 12.0 g, water 82.6 g, ter.-butyl alcohol 363.8 g
Was placed in a separable flask and stirred at 15 ° C. for 1 hour. Then 42.6 g EO was added and mixed with stirring for 20 minutes at 15 ° C. Then, it heated at 50 degreeC for 90 minutes, and further heated at 70 degreeC for 80 minutes. Then, after cooling to room temperature, EO was further adjusted to 42.6
g, and heated under the above temperature conditions. This cooling-EO addition-heating was repeated to obtain HEC of desired MS. Total EO
The relationship between the amount added, the number of repetitions and the MS of HEC is shown in Table 1. The HEC thus obtained was prepared by neutralizing caustic soda with acetic acid, and then the dope was diluted with water and desalted by dialysis. Then, it concentrated with the evaporator and regenerated in a large amount of acetone. The precipitate was redissolved in water and regenerated in acetone.

This reprecipitation operation was repeated several times. The precipitate is then washed with 50
It was vacuum dried at ° C.

Each HEC obtained was dissolved in ethylene glycol to prepare a solution having each concentration, and the coloration state at 5 ° C and 25 ° C was observed. The results are summarized in Table 1.

Comparative Examples 1-2 The HEC of MS2 and MS4 were adjusted using microcrystalline cellulose as a raw material by the method described in Examples 1-3. HEC concentration 70, 75, 80, 8
5, 90, 95 wt% HEC to water compositions were conditioned at room temperature (about 25 ° C). With a composition of 80% or more, a homogeneous mixture with water was not obtained, and the solid phase portion and the solution phase portion were mixed, and no coloration was observed even partially. Therefore, adjust the HEC low-concentration aqueous solution, then volatilize the water to obtain an HEC concentration of 80%.
% Or more of the above composition was obtained, but it was a slightly sticky film or lump, and no coloration was observed.

The composition with an HEC concentration of 70,75% also did not develop color.

Examples 4 to 5 HEC was adjusted by using celluloses having different polymerization degrees as raw materials under the same formulation and conditions as in Example 2. Cellulose raw material, HEC obtained
Table 2 shows the MS and intrinsic viscosity of the above. Each HEC was dissolved in ethylene glycol to prepare a solution having each concentration.
The colored state was observed at 5 ° C and 25 ° C. The results are summarized in Table 2.

Examples 6-9 Using the HEC of Example 2, 90 and 9 with each solvent shown in Table 3 was obtained.
Table 3 shows the results of observing the coloration state at 25 ° C by adjusting a 5 wt% solution.

Claims (2)

[Claims] 1. A cholesteric lyotropic liquid crystal composition containing, as a liquid crystal component, hydroxyethyl cellulose having a degree of molar substitution of hydroxyethyl groups per anhydroglucose unit of 6 or more. 2. The cholesteric lyotropic liquid crystal composition according to claim 1, wherein the hydroxyethyl cellulose is dissolved in water, an organic solvent or an aqueous solution of an organic solvent.