Data storage medium comprising colloidal metal and preparation process thereof
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 holgraphic 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 1 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.