Data storage medium comprising colloidal metal and preparation process thereof

Abstract

Disclosed is a photopolymerizable holographic recording medium for data storage that comprises colloidal metal, and which exhibits a threshold for a second stage polymerization which is substantially insensitive to the light used for both forming holograms and interrogating the medium during servo and/or read events. Also disclosed is a method of preparing said photopolymerizable holographic recording medium. Also disclosed is a method for preparing a colloidal without additives in a viscous medium.

1 . A method of preparing a holographic recording medium, said method comprising the steps of:
 a) thermally decomposing an organotransition metal compound in a solution comprising a monomer or oligomer that polymerizes under cationic conditions and a second component, referred to as a “binder”, that is capable of supporting cationic polymerization, thereby forming a dispersion of stable transition metal colloidal nanoparticles in the solution; and   b) adding to the dispersion formed in step a) a compound, referred to as “a first acid generator” which produces acid upon exposure to actinic radiation and a compound, referred to as a “second acid generator” which produces acid when exposed to heat.   
     
     
         2 . The method of  claim 1  additionally adding to the dispersion in step b) a compound, referred to as a “sensitizer”, which sensitizes the first acid generator to produce acid at a particular wavelength of light. 
     
     
         3 . The method of  claim 2  wherein the sensitizer is an aromatic hydrocarbon substituted with at least two alkynyl groups or two alkenyl groups. 
     
     
         4 . A method of preparing a stable transition metal colloid dispersion comprising the step of thermally decomposing an organotransition metal compound in a solution having a viscosity greater than about 10 centipoise. 
     
     
         5 . The method of  claim 4  wherein the organotransition metal compound is an organopalladium (II) compound or an organoplatinum (II) compound. 
     
     
         6 . The method of  claim 4  wherein the organotransition metal compound comprises gold, silver, nickel, cobalt or copper. 
     
     
         7 . The method of  claim 5  wherein organotransition metal compound is thermally decomposed in a solution comprising: 1) a monomer or oligomer that polymerizes under cationic conditions; or a binder that supports cationic polymerization; or 3) a monomer or oligomer that polymerizes under cationic conditions and a binder that supports cationic polymerization. 
     
     
         8 . The method of  claim 7  wherein the binder has a refractive index that differs from the refractive index of polymerized monomer or polymerized oligomer by at least about 0.04. 
     
     
         9 . The method of  claim 8  wherein the monomer is an epoxide monomer. 
     
     
         10 . The method of  claim 9  wherein the solution comprises between about 10 parts binder and about 90 parts monomer (w/w) to between about 10 parts monomer and about 90 parts binder (w/w). 
     
     
         11 . The method of  claim 10  wherein the binder is a poly(methyl phenyl siloxane) and the epoxide monomer is a siloxane comprising two or more cyclohexene oxide groups. 
     
     
         12 . The method of  claim 10  wherein the epoxide monomer is a polyfunctional siloxane comprising three or more cyclohexene oxide groups. 
     
     
         13 . The method of  claim 11  wherein the solution additionally comprises a second monomer which polymerizes under cationic conditions. 
     
     
         14 . The method of  claim 13  wherein the second monomer is a polyfunctional siloxane comprising three or more cyclohexene oxide groups. 
     
     
         15 . The method of  claim 13  wherein the medium additionally comprises a third monomer which undergoes cationic polymerization. 
     
     
         16 . The method of  claim 15  wherein the third monomer is a vinyl ether comprising one or more alkenyl ether groupings. 
     
     
         17 . The method of  claim 15  wherein the third monomer is a propenyl ether comprising one or more propenyl ether groupings. 
     
     
         18 . The method of  claim 11  wherein the epoxide monomer is RSi(R 1 ) 2 OSi(R 2 ) 2 R or R 3 Si(OSi(R 4 ) 2 R 5 ) 3 , wherein:
 each group R is, independently, a monovalent epoxy functional group having 2-10 carbon atoms;   each group R 2  is a monovalent substituted or unsubstituted C 1-12  alkyl, C 1-12  cycloalkyl, aralkyl or aryl group;   each group R 2  is, independently, R 1 , or a monovalent substituted or unsubstituted C 1-12  alkyl, C 1-12  cycloalkyl, aralkyl or aryl group;   R 3  is an OSi(R 4 ) 2 R 5  grouping, or a monovalent substituted or unsubstituted C 1-12  alkyl, C 1-12  cycloalkyl, aralkyl or aryl group;   each group R 4  is, independently, a monovalent substituted or unsubstituted C 1-12  alkyl, C 1-12  cycloalkyl, aralkyl or aryl group; and   each R 5  is, independently, a monovalent epoxy functional group having 2-10 carbon atoms.   
     
     
         19 . The method of  claim 18  wherein the epoxide monomer is RSi(R 1 ) 2 OSi(R 2 ) 2 R and R is 2-(3,4-epoxycyclohexyl)ethyl; each R 1  is a methyl group, and each group R 2  is a methyl group; or the epoxide monomer is R 3 Si(OSi(R 4 ) 2 R 5 ) 3  and R 3  is a methyl group or OSi(R 4 ) 2 R 5 ; each R 4  is a methyl group, and each group R 5  is 2-(3,4-epoxycyclohexyl)ethyl; and wherein the binder is 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane.