Imperial Chemical Industries Limited

Andrew Alec Clifton

Alan James Butters

Jeffrey Michael Howell

Julie C Double

An article for receiving an image by thermal transfer printing includes an image-receiving surface of plastics material coated with a layer of dye-receptive material capable of accepting an image by means of a dye thermal transfer process, wherein the glass transition temperature (Tg) of the dye receptive material is at least 50&#xb0; C. lower than the softening point of the plastics material of the image-receiving surface. By having a difference between the softening point of the plastics material article surface and the Tg of the material coated thereon of at least 50&#xb0; C. it is possible to achieve printing in a single step transfer process of high density images without distortion of the plastics material. The invention can be used with three-dimensional articles possibly having compound curves, including casings for mobile telephones made of polymers such as polycarbonate.

Thermal transfer printing

A thermal transfer medium for use in mass transfer printing comprises a substrate bearing on at least part of one surface thereof a coating of an overlay material comprising polyester having a glass transition greater than 50&#xb0; C. (preferably at least 75&#xb0; C.) and a molecular weight in the range 6,000 to 10,000. The overlay material combines good transfer characteristics, barrier properties and durability and is highly transparent.

Thermally-transferable polyester image-protecting layer

A receiver medium for digital imaging comprises a substrate having a dye-receiving surface bearing a coating comprising a highly branched functionalised polymer of generally globular form, e.g. a dendrimer, dispersed in a host polymer. Functional groups at or near the surface of the branched polymer, may interact with and bind dye molecules having complementary functional groups, eg dyes as disclosed in WO 96/34766, e.g. by acid-base interaction, thus having the effect of chemically fixing the dye within the coating on the receiver medium. Because dye molecules can be chemically bound to the branched polymer in the receiver sheet, it is possible to use host polymer materials of lower Tg than generally required in the prior art, with the host polymer typically having a Tg of less that 50&#xb0; C. This means that dye molecules can have significantly increased diffusivity through the coating, prior to interaction, resulting in a more even distribution of dye through the coating than has been possible hitherto. The invention also covers a method of making the receiver medium, a method of printing, and a receiver medium/dye combination.

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Ipswich, United Kingdom

Andrew Alec Clifton