Thermographic overcoat layer and thermographic image recording members
View Patent ↗There is described a protective overcoat material comprising from about 40 weight percent to about 85 weight percent of poly(methyl methacrylate) having a Tg above about 100° C., from about 10 weight percent to about 50 weight percent of poly(ethyl methacrylate) having a Tg of from about 52° C. to about 65° C. and about 1 weight percent of a melt flow modifier. Also described are thermal image recording members which include a protective overcoat layer.
1. A thermal image recording member comprising a substrate carrying a layer bearing an image and a protective overcoat layer overlying said image, said protective overcoat layer comprising from about 40% to about 85% by weight of poly(methyl methacrylate having a Tg above about 100° C., from about 10% to about 50% by weight of poly (ethyl methacrylate) having a Tg of from about 52° C. to about 65° C. and about 1% by weight of a melt flow modifier, wherein said melt flow modifier lowers the melt flow index of said poly (methyl methacrylate) and said poly (ethyl methacrylate).
2. The image recording member as defined in claim 1 wherein said substrate comprises an approximately 6 mil thick layer of oriented polypropylene arranged between two approximately 2 mil thick layers of polyethylene.
3. The image recording member as defined in claim 1 wherein said poly(methyl methacrylate) has a Tg of about 104° C.
4. The image recording member as defined in claim 3 wherein said poly(ethyl methacrylate) has a Tg of about 65° C.
5. The image recording member as defined in claim 4 wherein said melt flow modifier is ethylacrylate-2-ethylhexylacrylate copolymer.
6. The image-recording member as defined in claim 1 wherein said protective overcoat layer is from about 1 to about 5 microns in thickness.
7. The image recording member as defined in claim 6 wherein said protective overcoat layer is about 1.6 microns in thickness.
8. The image recording member is defined in claim 1 wherein said protective overcoat layer further includes an ultraviolet light-absorbing material and a light-stabilizing material.
9. A protective overcoat material for an image formed by a thermal imaging method comprising a substrate carrying an overcoat layer comprising from about 40 weight percent to about 85 weight percent of poly(methyl methacrylate) having a Tg above about 100° C., from about 10 weight percent to about 50 weight percent of poly(ethyl methacrylate) having a Tg of from about 52° C. to about 65° C. and about 1 weight percent of a melt flow modifier, wherein said melt flow modifier lowers the melt flow index of said poly (methyl methacrylate) and said poly(ethyl methacrylate).
10. The protective overcoat material as defined in claim 9 wherein said poly(methyl methacrylate) has a Tg of about 104° C.
11. The protective overcoat material as defined in claim 10 wherein said poly(ethyl methacrylate) has a Tg of about 65° C.
12. The protective overcoat material as defined in claim 11 wherein said melt flow modifier is ethylacrylate-2 -ethylhexylacrylate copolymer.
13. The protective overcoat material as defined in claim 9 and further including an ultraviolet light absorbing material and a light stabilizing material.