Reversible thermochromic and photochromic ink pens and markers

Abstract

Reversible thermochromic and photochromic ink compositions and markers, pens or writing instruments that use them are herein disclosed.

We claim: 
     
         1 . A reversible thermochromic composition, said reversible thermochromic ink composition comprising,
 a reversible thermochromic pigment in an amount from 1% to 50% by weight of the ink, the reversible thermochromic pigment being susceptible to a temperature-modulated change of color between a first state and a second state along a hysteresis loop;   a non-thermochromic colorant of a different color from the reversible thermochromic pigment when the reversible thermochromic colorant is in a colored state, such that the non-thermochromic colorant and the reversible thermochromic pigment together present a first color when the reversible thermochromic pigment is in the first state and together present a second color when the reversible thermochromic pigment is in the second state; and   a vehicle forming the balance of the composition.   
     
     
         2 . The composition of  claim 1 , wherein the first state is a colored state and the second state is substantially clear. 
     
     
         3 . The composition of  claim 1  where in the composition is formulated for use in a ball point pen. 
     
     
         4 . The composition of  claim 1  wherein the composition is formulated for use in a gel pen. 
     
     
         5 . The composition of  claim 1  wherein the composition is formulated for use in a marker. 
     
     
         6 . The composition of  claim 1  wherein the composition is formulated for use in a paint. 
     
     
         7 . The composition of  claim 1  wherein the composition is formulated for use in a crayon. 
     
     
         8 . The composition of  claim 1  wherein the thermochromic pigment is formulated to have a hysteresis window extending across a range greater than 60° C. 
     
     
         9 . The composition of  claim 1  wherein the thermochromic pigment is formulated to have a hysteresis window extending across a range greater than 80° C. 
     
     
         10 . The composition of  claim 1  wherein the ink is formulated to change color in consequence of heating from black to a color other than black. 
     
     
         11 . The composition of  claim 1  wherein the ink is formulated to change color in consequence of heating from one color to a different color. 
     
     
         12 . In a ball-point pen or marker, the improvement comprising the composition of  claim 1  used as an ink 
     
     
         13 . In a ball-point pen or marker, the improvement comprising the composition of  claim 11  used as an ink 
     
     
         14 . The composition of  claim 1  wherein the non-thermochromic colorant is a microencapsulated photochromic dye. 
     
     
         15 . A method of using the composition of  claim 1 , wherein the composition is applied by a writing instrument to paper, clothing, cardboard or other surfaces and then subjected to a color change by the action of temperature change. 
     
     
         16 . A method of reversibly highlighting using the composition of  claim 1 , comprising applying the ink to a surface at a first temperature; and
 changing the temperature of said surface to a second temperature whereby said ink becomes colorless.