Composite comprising a polymer and a blue phase liquid crystal, a method for preparing the composite, and a liquid crystal display device comprising the composite

Patent metadata

Field	Value
Publication number	US-9139776-B2
Application number	US-201314058662-A
Country	US
Kind code	B2
Filing date	Oct 21, 2013
Priority date	Oct 24, 2012
Publication date	Sep 22, 2015
Grant date	Sep 22, 2015

Abstract

The present invention relates to a composite comprising a polymer and a blue phase liquid crystal (BPLC). The polymer is a crosslinked and non-liquid crystalline polymer, the BPLC is dispersed in said polymer, and the ratio of the polymer to the BPLC by weight (W p /W l ) satisfies the relationship: 12:88<W p /W l ≦30:70, wherein the W p is the weight of the polymer, and W l is the weight of the BPLC. The composite exhibits a very wide temperature range of blue phase of the BPLC, and can respond to an electric field at a millisecond level. The composite has an excellent stability, and a lower viscosity, while a wide viewing angle and a low driving voltage can be achieved. The invention also provides a method for preparing the composite, and a LCD device comprising the composite. The method of the present invention is simple and efficient.

First claim

The invention claimed is:

1. A composite comprising a polymer and a blue phase liquid crystal, wherein the polymer is a crosslinked and non-liquid crystalline polymer, the blue phase liquid crystal is dispersed in said polymer, and the ratio of the polymer to the blue phase liquid crystal by weight (W p /W l ) satisfies the following relationship:
12:88 <W p /W l ≦30:70,

wherein the W p is the weight of the polymer, and W l is the weight of the blue phase liquid crystal.

2. The composite according to claim 1 , wherein the ratio of the polymer to the blue phase liquid crystal by weight (W p /W l ) satisfies the following relationship:
15:85 ≦W p /W l ≦25:75.

3. The composite according to claim 2 , wherein the ratio of the polymer to the blue phase liquid crystal by weight (W p /W l ) is 20:80.

4. The composite according to claim 1 , wherein the polymer is derived from monomers comprising at least one photo-polymerizable multifunctional (methyl)acrylate and at least one photo-polymerizable monofunctional (methyl)acrylate.

5. The composite according to claim 4 , wherein
the multifunctional (methyl)acrylate is selected from the group consisting of butanediol diacrylate (BDDA), trimethylolpropane triacrylate (TMPTA), 4-[2-methyl-4-(4-acryloxylpropoxyl)benzoyloxy]phenoxycarbonyl-phenoxylpropyl acrylate and a combination thereof; and
the monofunctional (methyl)acrylate is selected from the group consisting of (2,2,5-trimethyl)hexyl acrylate (TMHA), 2-ethylhexyl acrylate and a combination thereof.

6. The composite according to claim 4 , wherein
the ratio of the total monofunctional (methyl)acrylate to the total multifunctional (methyl)acrylate on a molar basis is 1:1 to 1:9.

7. The composite according to claim 6 , wherein
the ratio of the total monofunctional (methyl)acrylate to the total multifunctional (methyl)acrylate on a molar basis is 1:4.

8. A method for preparing a composite comprising a polymer and a blue phase liquid crystal, including the following steps:
blending a non-liquid crystalline compound having a photopolymerizable functional group with the blue phase liquid crystal at a ratio W c /W l to form a blend, wherein the W c is the weight of the non-liquid crystalline compound, W l is the weight of the blue phase liquid crystal; and the ratio W c /W l satisfies the relationship: 12:88<W c /W l ≦30:70;
adding a photoinitiator into the blend to form a reactive mixture; and
while keeping the blue phase liquid crystal in the reactive mixture in the blue phase, radiating the reactive mixture with a light so that a polymer network is formed through a crosslinking reaction between the non-liquid crystalline compound having a photopolymerizable functional group, and thereby forming a composite comprising the polymer and the blue phase liquid crystal.

9. The method according to claim 8 , wherein
the blue phase liquid crystal exhibits a temperature range of blue phase of more than 5.0° C., and has a viscosity of 34 to 45 mPa·s, a melting point of −20° C. to −15° C., and a clearing point of 68 to 88° C.

10. The method according to claim 8 , wherein
the ratio W c /W l satisfies the relationship: 15:85≦W c /W l ≦25:75.

11. The method according to claim 10 , wherein
the ratio W c /W l is 20:80.

12. The method according to claim 8 , wherein
the non-liquid crystalline compound having a photopolymerizable functional group comprises at least one multifunctional (methyl)acrylate and at least one monofunctional (methyl)acrylate.

13. The method according to claim 12 , wherein
the multifunctional (methyl)acrylate is selected from the group consisting of butanediol diacrylate (BDDA), trimethylolpropane triacrylate (TMPTA), 4-[2-methyl-4-(4-acryloxylpropoxyl)benzoyloxy]phenoxycarbonyl-phenoxylpropyl acrylate and a combination thereof; and
the monofunctional (methyl)acrylate is selected from the group consisting of (2,2,5-trimethyl)hexyl acrylate (TMHA), (2-ethyl)hexyl acrylate, and a combination thereof.

14. The method according to claim 12 , wherein
among the non-liquid crystalline compound having a photopolymerizable functional group, the ratio of the total monofunctional (methyl)acrylate to the total multifunctional (methyl)acrylate on a molar basis is 1:1 to 1:9.

15. The method according to claim 14 , wherein
among the non-liquid crystalline compound having a photopolymerizable functional group, the ratio of the total monofunctional (methyl)acrylate to the total multifunctional (methyl)acrylate on a molar basis is 1:4.

16. The method according to claim 8 , wherein
the amount of the photoinitiator is 0.5% to 1.5% by weight, in relative to the total amount of the non-liquid crystalline compound having a photopolymerizable functional group.

17. The method according to claim 16 , wherein
the photoinitiator is a UV-light initiator and the light for irradiating is a UV-light.

18. A liquid crystal display device, comprising
a pair of substrates wherein at least one of the substrates has an electrode formed thereon; and
the composite according to claim 1 being enclosed and sealed between the pair of substrates.

Assignees

• Boe Technology Group Co Ltd

Inventors

• Yang Huai
• Wang Ling
• He Wanli

Classifications

• C09K19/54

  Additives having no specific mesophase {characterised by their chemical composition} · CPC title

• C09K19/0275 Primary

  Blue phase · CPC title

• C09K2019/546

  creating a polymeric network · CPC title

• C09K19/544

  as dispersing or encapsulating medium around the liquid crystal · CPC title

• C09K19/542 Primary

  Macromolecular compounds · CPC title