Multilayered dispersed thermochromic liquid crystal

• US 5,805,245 A
• Filed: 09/29/1997
• Issued: 09/08/1998
• Est. Priority Date: 09/19/1995
• Status: Expired due to Term

• Current Assignee: LCR Hallcrest LLC (Ashland Global Holdings, Inc.)
• Original Assignee: Davis Liquid Crystals, Inc.
• Inventors: Davis, Frederick
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/939,264
• Time in Patent Office: 344 Days
• Field of Search: 359/43, 359/52, 359/51, 359/103, 359/241, 359/242, 359/288, 359/289, 349/20, 349/86, 349/89, 349/182, 349/185, 349/186, 345/106
• US Class Current: 349/20
• CPC Class Codes: B41M 5/282 using thermochromic compounds
• CPC Class Codes: G02F 1/132 Thermal activation of liquid crystals exhibiting a thermo-optic effect

Abstract

A multilayered thermochromic display system is provided, wherein a thermochromic substance is applied to inert films in stacked layers with a non-invasive barrier between each layer of thermochromic substance. The thermochromic substance in each layer responds in a different temperature range so that as the temperature changes, the display exhibits repeated sequences of colors. The use of multiple layers with different temperature sensitivities enables the use of the displays over a broad range of temperatures.

Claims

1. A stacked thermochromic display system comprising a substrate and a stack of at least two thermochromic displays wherein each display comprises:

(i) a thermochromic film layer; and

(ii) a transparent barrier overlaying the thermochromic film layer;

wherein the displays are stacked upon each other defining upper displays and lower displays, and;

(iii) wherein the thermochromic film layer of each display is selected to have different temperature sensitivity ranges with the proviso that the transparent barriers are not configured in such a manner as to permit visual observation of the stacked nature of the displays.

2. A stacked display system of claim 1 wherein the displays are generally planar.

3. A stacked display system of claim 1 wherein the thermochromic film layer comprises a thermochromic liquid crystal.

4. A stacked display system of claim 3 wherein the liquid crystal is a nematic liquid crystal.

5. A stacked display system of claim 3 wherein the liquid crystal is a cholesteric liquid crystal.

6. A stacked display system of claim 3 wherein the liquid crystals are dispersed in a water based emulsion.

7. A stacked display system of claim 3 wherein the liquid crystals are microencapsulated.

8. A stacked display system of claim 3 wherein the liquid crystals are mixed with a film-forming polymer.

9. A stacked display system of claim 1 wherein the thermochromic film layer comprises a thermochromic substance selected from the group consisting of anthraquinone functional dyes, 3d metal compounds, samarium sulfide compounds, di-β

-naphthospiropyran, poly(xylylviologen dibromide) and urethane-substituted ETCD polydiacetylene.

10. A stacked display system of claim 1 wherein the barrier of a lower display forms the support of an upper display.

11. A stacked display system of claim 1 wherein the displays are selected to display color at temperature ranges between 0°

to 100°

C.

12. A stacked display system of claim 1 wherein the substrate is opaque.

13. A stacked display system of claim 1 wherein the substrate is black.

14. A stacked display system of claim 1 wherein the thermochromic film layer is a liquid crystal ink comprising an emulsion and the thermochromic liquid crystals.

15. A stacked display system of claim 14 wherein the emulsion is a film-forming polymer and water emulsion.

16. A stacked display system of claim 15 wherein the ink comprises a wetting agent.

17. A stacked display system of claim 15 wherein the ink comprises a thickening agent.

18. A stacked display system of claim 1 wherein the barrier is a water-based acrylic copolymer.

19. A stacked display system of claim 1 wherein the substrate is an opaque water-based acrylic copolymer.