US 2012/0107528 A1
US 2012/0107529 A1
US 2012/0107532 A1
Transparent ink-jet recording films, compositions, and methods
Carestream Health, Inc.
In recent months, Carestream Health (formerly Eastman Kodak’s Health Group) has been particularly active in the field of high quality coatings for transparent film that are designed to give excellent resolution and to accommodate a wide range of optical densities, so making them suitable for medical imaging purposes. These three patents address the problem of detection of transparent media in printers such as the Epson Model 4900, that rely on optical detection of media in order to determine the area printed. As these printers are designed to produce borderless images, they use optical sensors to detect the location of the leading edge of the media sheet, relying on reflection from a white or opaque paper. The solution presented is to incorporate a small amount of a white or reflective pigment particulate material either in a back coating or in one or more layers of the front recording surface.
As previously described, the substrate is a polyester film such as PET and may be blue-tinted. It is coated on one side with a primer or under layer on top of which one or more polyvinyl alcoholbased ink receiving layers is deposited. These coatings may also contain the inorganic pigment boehmite alumina along with nitric acid as a deflocculant. The reverse side of the film is also coated.
Titanium dioxide is initially chosen as a suitable pigment. However, as incorporation of a titanium dioxide pigment in the image receiving layer causes flocculation of the boehmite alumina while a primer layer containing titanium dioxide is not detectable by a printer, the pigment must be incorporated in the reverse side coating. The pigment has a particle size of less than 40 nm and is incorporated into a gelatine coating at a dry loading of around 0.1 gsm within a coating weight up to about 2 gsm and must give rise to a level of haze of less than 53% with a minimum optical density of 0.25. Alternatively, rice starch, zirconium dioxide or zinc oxide pigments may be used. While these pigments can be incorporated in the gelatine-based reverse side coating it is also possible to incorporate them within the front side coatings and the level of haze exhibited is less than 41%.
Further improvements in performance may be achieved when the reverse side coating is a cross-linkable hydroxyl group-containing polymer such as polyvinyl alcohol rather than gelatine. In this case, as is shown in the table, detection using an Epson Model 4900 is achieved for media exhibiting a haze value of less than 28%.
Dr Clare Conboy