Construction for transparency film for plain paper copiers

DETAILED DESCRIPTION Referring now to FIGS.
1, 2, 3, and 4, the transparency film of the present invention comprises: (1) a film sheet base 10, made of a flexible, transparent, heat resistant, polymeric material, (2) an image receiving layer 12 coated upon one major surface of said film sheet base, (3) a layer of non-migratory electrically conductive material 14 coated upon the second major surface of the film sheet base, (4) an optional protective coating layer 16, overcoated upon the layer in (3), the protective coating layer being formed of a resin having lower electrical conductivity than the material of layer 14.
In addition, the film sheet base 10 may have a primer coating 18 for either the image receiving layer 12 or for the layer of conductive material 14, or for both layers.
(See FIGS.
3 and 4).
The film sheet base 10 must have the proper degree of transparency for use in overhead projection, i.
e.
, it must be transparent to visible light.
It must have sufficient heat resistance to withstand a temperature of 150.
degree.
C.
Suitable materials include polyester, cellulose triacetate, polyimide, polycarbonate, and polysulfone.
The preferred material is oriented polyethylene terephthalate film.
The thickness of the film may range from about 0.
001 to about 0.
010 inch.
The preferred thickness is about 0.
003 to about 0.
004 inch.
The image receiving layer 12 is essentially a transparent polymer coated upon the primed or unprimed film sheet base 10.
Like the film sheet base, the image receiving layer 12 must be transparent to visible light.
The image receiving layer 12 preferably contains a roughening agent to provide roughness to aid in sliding one sheet of finished film off the top of a stack of similar sheets.
Increased surface area provided by the roughening agent also allows liquid toner to dry rapidly enough to avoid flowing out of the desired pattern, thus providing sharp images.
It also results in improved toner adhesion.
Suitable materials for the image receiving layer 12 include polymethyl methacrylates, polyesters, cellulosics, polyvinyl acetates, polyvinyl chlorides, vinyl chloride/vinyl acetate copolymers, acrylonitrile-butadienestyrene terpolymers, polyvinylidene chlorides, polyurethanes, polymethacrylates, substituted polystyrenes, and other thermoplastic or cross-linked resins