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United States Patent (19) ESSSÉÉ United States Patent (19) 11 Patent Number: 4,469,452 Sharpless et al. 45) Date of Patent: Sep. 4, 1984 54 NDCATOR SYSTEMAND MEANS FOR 3,946,611 3/1976 Larsson ............................... 374/106 RREVERSIBLY RECORDING A 3,946,612 3/1976 Sagi et al. ........................... 374/106 TEMPERATURE LIMIT 3,974,317 8/1976 Sharpless ... ... 252/299.7 3,996,007 12/1976 Fanc et al. .......................... 6/206 (75) Inventors: Edward N. Sharpless, Somerville; 4,042,336 8/1977 Larsson ............................... 374/106 Joseph Lichtenstein, Colonia, both of 4,066,567 1/978 Labes .......... ... 252/299.7 4,137,049 1/1979 Couch et al. ........................ 116/206 4,154,106 5/1979 Inoue et al. ......................... 374/106 73) Assignee: Whitman Medical Corporation, 4,232,552 11/1980 Hof et al. ............................ 374/106 Clark, N.J. 4,285,697 8/1981 Neary .......... ... 252A408.1 (21) Appl. No.: 368,379 4,299,727 1/1981 Hof et al. ............................ 374/106 22 Filed: Apr. 14, 1982 FOREIGN PATENT DOCUMENTS 59566 4/1978 U.S.S.R. ........................... 252/299.7 51 Int. Cl. ....................... C09K 3/34; G01N 21/06; 703560 12A1979 U.S.S.R. ........................... 252/299.7 31/22; CO1K 3/00; C01K 11/16 52 U.S. C. .................................... 374/160; 116/206; OTHER PUBLICATIONS 116/207; 116/216; 116/217; 116/219; "Use of Liquid Crystals as Vapor Detectors', Mol. 252/299.5; 252/229.7; 252/408.1; 252/962; Cryst. Liq. Cryst., vol. 27, E. J. Posiomek, et al. 374/102; 374/106,374/141; 374/161; 374/162; 436/2 Primary Examiner-Teddy S. Gron (58) Field of Search ............... 374/102, 106, 141, 160, Attorney, Agent, or Firm-Holman & Stern 374/161, 162; 252/299.5, 299.7, 408.1, 962; 57 ABSTRACT 116/206, 207,216, 217, 219; 436/2 System and means for irreversibly recording the inci 56) References Cited dence of a predetermined temperature comprising a U.S. PATENT DOCUMENTS cholesteric liquid cyrstal system and an activator mate 2,216,127 10/1940 McNaught .......................... 374/106 rial capable of interacting with the liquid crystal system 2,261,473 1/1941 Jennings ........ ... 374/106 to induce a unique irreversible change in the optical 2,716,065 8/1955 Beckett et al. ... 374/106 properties thereof sustantially at the predetermined 3,055,759 9/1962 Busby et al. ...... ... 374/106 temperature. The system preferably includes means for 3,118,774 A1964 Davidson et al. ... 374/106 separating the liquid crystal system and activator at 3,409,404 11/1968 Fergason ........... ... 252/299.7 3,529,156 9/1970 Fergason et al. ..., 252/299,7 temperatures below the activation temperature of the 3,576,761 4/1971 Davis ................ ... 252/299.7 activator. 3,665,770 5/1972 Sagi et al. ... 374/106 3,885,982 5/1975 Fergason .......................... 252/299.5 19 Claims, 9 Drawing Figures n AYYYYYYYAAAAYAAl ZZZYZZYZZZZY awada aayawa A1AAAAAAAAAWA7 YAAAAAAAYAAA1474. AAFA E.R. NZ ; w 22222222222222227 277,273.72 NNNNNNNNNNNN 7 NNNNNNYYYXYY 23S SM 8 ESSSÉÉseeseS2 O 8 4,469,452 2 ten and an activator material capable of interacting NEDICATOR SYSTEM AND MEANS FOR with the liquid crystal system to induce a unique irre RREVERSIBLY RECORDING ATEMPERATURE versible change in the optical properties thereof sub LIMIT stantially at the predetermined temperature. Preferred liquid crystal systems are those which display visible BACKGROUND OF THE INVENTION colors as a result of scattering impingent white light Cholesteric liquid crystalline indicator compositions from the cholesteric substances and which irreversibly are well-known in the art as optical indicators of tran lose this property on interaction with the activator sient environmental conditions. These compositions material, and become colorless; the loss of this property typically depend for their effect on a change in optical 10 broadly coincides with the destruction of the liquid properties in response to a change in environmental crystalline properties of the cholesteric phase by the conditions, such as a shift from color-exhibiting to col activator material and irreversible transition of the cho oriess in response to a change in temperature. lesteric liquid crystal system into the true liquid or iso Several difficulties have been encountered in the use tropic phase. The phase transition and consequent of cholesteric substances as thermometric compositions, 15 change in optical properties usually, but not always, primarily owing to the rapid reversibility of the changes occur at substantially the same temperature. in optical properties. In many applications, it is highly The temperature at which the activator is activated desirable to have a permanent record that a predeter to interact with the liquid crystal system is referred to mined temperature on other environmental condition herein as the "activation temperature”. The activator has occurred, for example in the storage of food or 20 and liquid crystal system are selected for amounts and sensitive biological materials. Many cholesteric sub characteristics so that the activator is effectively inter stances, however, provide only fleeting records of fluc soluble with the liquid crystal system substantially at tuating environmental conditions, rapidly changing the predetermined temperature; the term “effectively color or gaining or losing color in response to stimulus. intersoluble' is defined to mean that (a) the activator is While methods have been devised to prolong these 25 sufficiently soluble in the liquid crystal system at or near optical changes in some liquid crystal systems, the re the activation temperature to rapidly interact therewith, cord of the occurrence of a predetermined condition and (b) interaction of the activator and liquid crystal generally is still too evanescent to be useful in applica system induces a unique irreversible change in the liquid tions where regular monitoring is not feasible. crystal optical properties substantially at the predeter It is accordingly an object of this invention to provide 30 a method and means for irreversibly recording an envi mined temperature. ronmental event. The invention further comprises a method for provid It is another object of this invention to provide a ing a permanent visual record of the incidence of a method and means for making a permanent visual re predetermined temperature wherein an activator mate cord of the occurrence of a predetermined temperature. 35 rial effectively intersoluble with a cholesteric liquid It is a further object of this invention to provide an crystal system is combined with the cholesteric liquid indicator system for selectively indicating the occur crystal system so that the optical properties thereof are rence of a predetermined temperature over a wide uniquely and irreversibly changed substantially at the range of temperatures. predetermined temperature. It is yet another object of this invention to provide a The activator comprises both reactive materials, rapid and permanent indication of the occurrence of a which chemically combine with the liquid crystal mate predetermined temperature which is readily apparent to rial to alter its optical properties, and passive activator the naked eye. materials, which physically affect the molecular config It is also an object of this invention to provide a sys uration of the liquid crystal system to alter its optical tem and method for irreversibly recording the occur 45 properties; while the passive activator materials gener rence of a predetermined maximum temperature. ally need to be highly intersoluble with the liquid crys Other objects and advantages of the invention will be tal system to effect the desired change in optical proper readily apparent to those skilled in the art. ties, the reactive activator materials usually need only to be partly soluble to achieve the same result. Activa BRIEF DESCRIPTION OF THE DRAWINGS 50 tors are selected for the capacity of rapidly interacting FIGS. 1-3 are alternate schematic embodiments of with the liquid crystal system within the context of the the indicator system of the invention; indicator system at the activation temperature, while FIG. 4 is a top view of one embodiment of the indica being inactive, or inactivatable, at other temperatures, tor means of the invention; usually temperatures below the activation temperature. FIG. 5 is a side view of the indicator means of FIG. 55 Thus, a solid material having a melting point substan 4; tially coinciding with the activation temperature may FIG. 6 is a side view of an alternate embodiment of be directly admixed with the liquid crystal system, or the indicator means of FIG. 4; the indicator system may include barrier means for FIG. 7 is a top view of the indicator means of FIG. 6; separating the activator material from the liquid crystal FIG. 8 is a top view of the indicator means of FIG. 4 60 below the activation temperature of the activator. The folded along the line 13; and activation temperature in this instance will be the tem FIG. 9 is a side view of the indicator means of FIG. perature at which the activator permeates the barrier 7, folded along the line 13a. means to interact with the liquid crystal system, owing to a change in either physical or chemical characteris SUMMARY OF THE INVENTION 65 tics of the activator at the activation temperature. The invention provides an indicator system for irre The invention further includes indicator means for versibly recording the incidence of a predetermined permanently recording a predetermined temperature, temperature
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