PRINTING IMPROVED TACTILE IMAGES USING INTERMEDIATE TRANSFER MEMBER
A method of forming an electrophotographic image having raised information providing a distinct tactile feel. One or more layers of marking particles are formed on an intermediate transfer member using an electrophotographic process responsive to visible image data. A layer of non-marking particles is then formed over the layers of marking particles responsive to tactile image data, wherein a volume average diameter of the non-marking particles is between 150% and 200% of the volume average diameter of the marking particles. The formed layers of marking particles and non-marking particles are then transferred onto a receiver medium so that the non-marking particles are in direct contact with the receiver medium. The transferred layers of non-marking particles and marking particles are then fused onto the receiver medium, wherein the layer of fused non-marking particles has a maximum thickness of at least 20 μm to provide the distinct tactile feel.
1 . A method of forming an electrophotographic image on a receiver medium having raised information providing a distinct tactile feel, comprising:
forming one or more layers of marking particles on a surface of an intermediate transfer member using an electrophotographic process responsive to visible image data,
forming a layer of non-marking particles over the one or more layers of marking particles on the surface of the intermediate transfer member using an electrophotographic process responsive to tactile image data, wherein a volume average diameter of the non-marking particles is at least 150% of a volume average diameter of the marking particles and is no more than 200% of the volume average diameter of the marking particles;
transferring the formed layers of marking particles and non-marking particles from the intermediate transfer member onto the receiver medium so that the non-marking particles are in direct contact with the receiver medium; and
fusing the transferred layers of marking particles and non-marking particles onto the receiver medium, wherein the fused layer of non-marking particles has a maximum thickness of at least 20 μm to provide the distinct tactile feel.
2 . The method of claim 1 wherein the volume average diameter of the marking particles is between 4-9 μm.
3 . The method of claim 1 wherein the layer of non-marking particles has a maximum coverage of at least 2 mg/cm 2 .
4 . The method of claim 1 wherein a surface charge density of the non-marking particles is between 30% and 60% of a surface charge density of the marking particles.
5 . The method of claim 1 wherein the intermediate transfer member includes at least one compliant layer.
6 . The method of claim 5 wherein the compliant layer has a Young's modulus of less than 50 MPa.
7 . The method of claim 5 wherein the intermediate transfer further includes a surface layer disposed over the at least one compliant layer.
8 . The method of claim 7 wherein the surface layer has a Young's modulus that is in the range of 50 MPa to 2000 MPa.
9 . The method of claim 1 wherein the volume average diameter of the non-marking particles is at least 160% of the volume average diameter of the marking particles and is no more than 190% of the volume average diameter of the marking particles.
10 . The method of claim 1 wherein the raised information is used to form Braille characters that can be sensed by visually-impaired persons.