阅读说明：本技术 液晶材料、薄膜、薄膜的制备方法及液晶写字板 (Liquid crystal material, film, preparation method of film and liquid crystal writing board ) 是由 张慧敏 苗宗成 于 2020-06-12 设计创作，主要内容包括：本发明适用于液晶材料技术领域,提供了一种液晶材料、薄膜、薄膜的制备方法及液晶写字板,该液晶材料包括N*相液晶、可聚合单体、紫外光引发剂和玻璃微珠；所述可聚合单体包括紫外非液晶性可聚合单体和紫外液晶性可聚合单体；所述N*相液晶、所述紫外非液晶性可聚合单体和所述紫外液晶性可聚合单体的质量比为(40~85):(5~50):(3~20)；所述紫外光引发剂的质量为所述可聚合单体质量的0.3%~12%；所述玻璃微珠的质量为所述液晶材料质量的0.3%~1%；所述N*相液晶为具有温致手性翻转特性的正性N*相液晶,含有该液晶材料的薄膜在外界压力刺激时入射光反射率较大,其可用作为液晶写字板,以提高书写字迹清晰度。(The invention is suitable for the technical field of liquid crystal materials, and provides a liquid crystal material, a film, a preparation method of the film and a liquid crystal writing board, wherein the liquid crystal material comprises N-phase liquid crystal, a polymerizable monomer, an ultraviolet light initiator and glass beads; the polymerizable monomer comprises an ultraviolet non-liquid crystal polymerizable monomer and an ultraviolet liquid crystal polymerizable monomer; the mass ratio of the N-phase liquid crystal to the ultraviolet non-liquid crystal polymerizable monomer to the ultraviolet liquid crystal polymerizable monomer is (40-85): 5-50): 3-20; the mass of the ultraviolet initiator is 0.3-12% of that of the polymerizable monomer; the mass of the glass beads is 0.3% -1% of that of the liquid crystal material; the N-phase liquid crystal is positive N-phase liquid crystal with temperature-induced chiral turning characteristics, and a film containing the liquid crystal material has high incident light reflectivity when being stimulated by external pressure, and can be used as a liquid crystal writing board to improve the definition of written characters.)

1. The liquid crystal material is characterized by comprising N-phase liquid crystal, a polymerizable monomer, an ultraviolet light initiator and glass beads; the N-phase liquid crystal is a positive N-phase liquid crystal with a temperature-induced chiral inversion characteristic; the polymerizable monomer comprises an ultraviolet non-liquid crystal polymerizable monomer and an ultraviolet liquid crystal polymerizable monomer; the mass ratio of the N-phase liquid crystal to the ultraviolet non-liquid crystal polymerizable monomer to the ultraviolet liquid crystal polymerizable monomer is (40-85): 5-50): 3-20; the mass of the ultraviolet initiator is 0.3-12% of that of the polymerizable monomer; the mass of the glass beads is 0.3-1% of the mass of the liquid crystal material.

2. The liquid crystal material of claim 1, wherein the non-liquid crystal ultraviolet polymerizable monomer is one or more of an unsaturated polyester, an acrylate monomer, a polyenethiol monomer, and a vinyl ether monomer.

3. The liquid crystal material according to claim 1, wherein the ultraviolet liquid crystal polymerizable monomer is a positive ultraviolet liquid crystal polymerizable monomer.

4. The liquid crystal material of claim 1, wherein the uv initiator is one or more of benzophenone, benzoin dimethyl ether, chlorothianthrone, 2, 4-diethylthianthrone, isopropylthianthrone, 2-hydroxy-2, 2-methyl-1-phenylacetone.

5. The liquid crystal material of claim 1, wherein the N-phase liquid crystal comprises a compound that changes in molecular conformation upon heating, or a compound that has a single or multiple chiral compounds with different chiral motifs that undergo chiral collisions upon heating.

6. A film comprising the liquid crystal material according to any one of claims 1 to 5.

7. The preparation method of the film is characterized by comprising the following steps:

heating a liquid crystal material according to any one of claims 1 to 5 to a liquid state to obtain a liquid mixture;

and placing the liquid mixture between two groups of polyester films with indium tin oxide plated on the inner sides, and performing step-by-step ultraviolet irradiation to obtain the film.

8. The method of claim 7, wherein the film has a reflectance of incident light having a wavelength of 550nm of greater than 85%.

9. A liquid crystal tablet, characterized in that it comprises a film according to claim 6 or 8.

Technical Field

The invention belongs to the technical field of liquid crystal materials, and particularly relates to a liquid crystal material, a film, a preparation method of the film and a liquid crystal writing board.

Background

The optical energy liquid crystal writing board prepared based on the N-phase liquid crystal/high polymer material film has the advantages of being capable of repeatedly erasing and writing information, capable of memorizing information, light, energy-saving and the like. In addition, the optical energy liquid crystal writing board can avoid dust suction, and the optical energy liquid crystal writing board can be used as a children drawing board, and can also avoid hidden dangers such as messy coating, messy writing, gnawing and eating by mistake, electronic radiation and the like. Therefore, the development of liquid crystal display materials which can be used as optical energy liquid crystal writing boards is an objective requirement for the healthy life of people and is a necessary trend of market development.

When the pitch (P) of the cholesteric liquid crystal is short, the plane texture and the focal conic texture can be stably maintained under the action of no external field, so that the cholesteric liquid crystal has a bistable characteristic. The N-phase liquid crystal/polymer material film enables the N-phase liquid crystal in the polymer matrix to realize the conversion from the focal conic texture to the plane texture through surface shearing force, and then the conversion from the plane texture to the focal conic texture is realized by using an electric field.

The color of the N-phase liquid crystal/polymer film is mainly determined by the reflection wavelength of the film controlled by the pitch (P) of the N-phase liquid crystal when the N-phase liquid crystal/polymer film is stimulated by external pressure, and if the product of the average refractive index N and the pitch P of the cholesteric liquid crystal is 400< np <700nm, the cholesteric liquid crystal in the plane texture has obvious color; the N-phase liquid crystal has the characteristic of selective reflection of incident light incident along the spiral axis direction. N-phase liquid crystals with a left-handed helical structure allow right-handed circularly polarized light to pass through while reflecting left-handed circularly polarized light and vice versa. The wavelength λ of the reflected incident light is nP, and the wave width Δ λ is Δ nP, where n and Δ n are the average refractive index and birefringence of the liquid crystal material, respectively, and both left-handed and right-handed circularly polarized light is transmitted outside the reflected wave width. For incident light having a wavelength satisfying the formula λ ═ nP, when the light is incident on the N × phase liquid crystal having planar orientation, two kinds of circularly polarized light are generated, and only the circularly polarized light having the same spiral direction as that of the N × phase liquid crystal is reflected, so that the reflectance is about 50% for incident light having a wavelength at which Bragg reflection occurs.

In addition, the existing liquid crystal writing board only has the upper layer which is made of transparent polyethylene terephthalate (PET) film with Indium Tin Oxide (ITO) plated on one side, and the bottom of the existing liquid crystal writing board is made of a non-transparent black film of PET with ITO plated on one side, so that the problems of low incident light reflectivity and unclear writing are solved.

Disclosure of Invention

An object of an embodiment of the present invention is to provide a liquid crystal material, which is intended to solve the problems set forth in the background art.

The embodiment of the invention is realized in such a way that the liquid crystal material comprises N-phase liquid crystal, a photopolymerizable monomer, an ultraviolet initiator and glass beads; the light polymerizable monomer comprises an ultraviolet non-liquid crystal polymerizable monomer and an ultraviolet liquid crystal polymerizable monomer; the mass ratio of the N-phase liquid crystal to the ultraviolet non-liquid crystal polymerizable monomer to the ultraviolet liquid crystal polymerizable monomer is (40-85): 5-50): 3-20; the mass of the ultraviolet light initiator is 0.3-12% of that of the polymerizable monomer; the mass of the glass beads is 0.3-1% of that of the liquid crystal material; the N-phase liquid crystal is positive N-phase liquid crystal with temperature-induced chiral inversion characteristics.

The N-phase liquid crystal has the characteristic of chiral inversion along with the change of temperature, and the dielectric anisotropy of the N-phase liquid crystal is a positive value (delta > 0). The N-phase liquid crystal system needs to contain a temperature-induced chiral reversal compound, which can be selected from molecules that undergo chiral reversal upon heating due to molecular conformation or chirality between different chiral compounds and different chiral motifs (or chiral centers) of a single chiral compound.

As a preferable mode of the embodiment of the present invention, the ultraviolet non-liquid crystal polymerizable monomer is one or more of an unsaturated polyester, an acrylate monomer, a polyene thiol system monomer, and a vinyl ether monomer.

Preferably, the ultraviolet non-liquid crystal polymerizable monomer is a mixture of a monomer A, a monomer B, a monomer C and a monomer D; the structural formula of the monomer A is shown as a formula I-1, the structural formula of the monomer B is shown as a formula I-2, the structural formula of the monomer C is shown as a formula I-3, wherein n in the structural formula I-3 is approximately equal to 14-16. The structural formula of the monomer D is shown as formula I-4:

wherein the mass ratio of the monomer A to the monomer B to the monomer C to the monomer D is (40-55): 30-35): 10-15): 5-10.

As another preferable mode of the embodiment of the present invention, the ultraviolet liquid crystal polymerizable monomer is a positive ultraviolet liquid crystal polymerizable monomer. Preferably, the structural formula of the ultraviolet liquid crystal polymerizable monomer is formula II;

the ultraviolet initiator is one or more of benzophenone, benzoin dimethyl ether, chloro-thioxanthone, 2, 4-diethyl thioxanthone, isopropyl thioxanthone and 2-hydroxy-2, 2-methyl-1-phenyl acetone. Preferably, the uv initiator has the formula III:

as another preferred embodiment of the present invention, the N-phase liquid crystal includes a compound whose molecular conformation changes with heating, or a compound in which single or multiple chiral compounds containing different chiral moieties have chiral collisions with heating. Specifically, the N-phase liquid crystal consists of a temperature-induced chiral reversal compound and a nematic liquid crystal; or consists of a temperature-induced chiral reversal compound, nematic liquid crystal and positive cholesteric liquid crystal molecules; or consists of a temperature-induced chiral reversal compound and positive cholesteric liquid crystal molecules.

Preferably, the N-phase liquid crystal comprises a temperature-induced chiral reversal compound and a nematic liquid crystal, wherein the temperature-induced chiral reversal compound has a structural formula of IV-1 or IV-2; the nematic liquid crystal is one of SLC1717 liquid crystal, BHR32200-100 liquid crystal, HPC859300-100 liquid crystal and E8 liquid crystal.

Wherein the mass ratio of the temperature-induced chiral flipping compound to the nematic liquid crystal is (3-6): 70-75); as another preferable aspect of the embodiment of the present invention, the N × phase liquid crystal further includes positive cholesteric liquid crystal molecules; the structural formula of the positive cholesteric liquid crystal molecule is a Compound (CST) of formula IV-3:

wherein Chol is:

CST(m+n＝4，X_chol＝m/4)，m/n＝7/1。

wherein the mass ratio of the compound with the structural formula of IV-3 to the nematic liquid crystal is (2-4): 70-75).

It is another object of the embodiments of the present invention to provide a film, which contains the liquid crystal material.

Another objective of the embodiments of the present invention is to provide a method for preparing a thin film, which includes the following steps:

heating the liquid crystal material to a liquid state to obtain a liquid mixture;

and placing the liquid mixture between two groups of polyester films with indium tin oxide plated on the inner sides, and performing step-by-step ultraviolet irradiation to obtain the film.

Another object of an embodiment of the present invention is to provide a thin film prepared by the above preparation method, wherein the reflectivity of the thin film to incident light with a wavelength of 550nm is greater than 85%.

Another objective of the present invention is to provide a liquid crystal tablet, which includes the above-mentioned film.

Under the ultraviolet irradiation, a liquid crystal polymer network formed by polymerizing ultraviolet liquid crystal polymerizable monomers has the same rotating direction as N-phase liquid crystal at the polymerization temperature; then, a sample of the above system is quenched to a set temperature at which the non-polymerized N-phase liquid crystal will reflect light in the visible region having the same reflection wavelength and a helical pitch opposite to that of the uv polymerization temperature.

According to the liquid crystal material provided by the embodiment of the invention, the N-phase liquid crystal containing the temperature-induced chiral reversal compound and the nematic liquid crystal is used as a raw material, so that the incident light reflectivity of the liquid crystal material can be improved when the liquid crystal material is stimulated by external pressure; the film containing the liquid crystal material is used as a liquid crystal writing board, so that the writing definition can be improved, and the upper substrate and the lower substrate of the liquid crystal writing board can be made of transparent PET films plated with ITO.

Drawings

FIG. 1 is a diagram illustrating the reflection effect of a liquid crystal writing board manufactured by using the films provided in embodiments 1-2 of the present invention when stimulated by external pressure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.