Temperature indicating devices
First Claim
1. A temperature indicating device comprising a series of liquid crystal cells each being free of cholesteryl compounds and containing (1) a cyanobiphenyl compound having the formula ##STR8## where Rc is (+)-2-methylbutyl, (2) a nematic liquid crystal material which is liquid crystalline at room temperature (20°
- C.) including a compound of the formula ##STR9## where Rc is (±
)-2-methyl butyl and (3) a liquid crystal material having a clearing point above 100°
C., said cyanobiphenyl compounds being present in different concentrations in different cells whereby said cyanobiphenyl compounds selectively reflect light of the same color in the grandjean state at temperatures below their respective temperature clearing points, but have different clearing points varying stepwise from cell-to-cell to indicate temperature by iridescence of the cells, each cell undergoing, on cooling from the isotropic liquid state, the transition isotropic liquid state to focal conic state, without reverting immediately to the grandjean state.
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Accused Products
Abstract
A temperature indicating device comprising a series of liquid crystal cells each of which contains a liquid crystal material having a different composition, the composition varying from cell-to-cell, and each of which cells exhibits the grandjean state whereby temperature is indicated by iridescence of the cells, the cells being such that the liquid crystal material in each has a clearing point at a different selected temperature in a series of temperature in a temperature range of interest and that each of the cells is such that its liquid crystal material does not revert immediately to the grandjean state on cooling from the isotropic liquid state wherein the improvement comprises the cells having a construction such that the liquid crystal material of each cell undergoes, on cooling from the isotropic liquid state, the transition isotropic liquid state to focal conic state, without reverting immediately to the grandjean state.
45 Citations
8 Claims
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1. A temperature indicating device comprising a series of liquid crystal cells each being free of cholesteryl compounds and containing (1) a cyanobiphenyl compound having the formula ##STR8## where Rc is (+)-2-methylbutyl, (2) a nematic liquid crystal material which is liquid crystalline at room temperature (20°
- C.) including a compound of the formula ##STR9## where Rc is (±
)-2-methyl butyl and (3) a liquid crystal material having a clearing point above 100°
C., said cyanobiphenyl compounds being present in different concentrations in different cells whereby said cyanobiphenyl compounds selectively reflect light of the same color in the grandjean state at temperatures below their respective temperature clearing points, but have different clearing points varying stepwise from cell-to-cell to indicate temperature by iridescence of the cells, each cell undergoing, on cooling from the isotropic liquid state, the transition isotropic liquid state to focal conic state, without reverting immediately to the grandjean state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- C.) including a compound of the formula ##STR9## where Rc is (±
Specification