Pyroelectric photoconductive elements and method of charging same

Claim 2

An electrophotographic recording element comprising; a substrate of electrically conductive material, and a layer of photoconductive, pyroelectric material comprising a composite of similar crystalline elemental bodies, said layer being in electrical contact with said substrate, and said elemental bodies of said material being similarly oriented with respect to their crystal axes to produce electrostatic charges of the same polarity on an exposed surface of said recording element when the temperature of said layer is changed.

Claim 3

An electrophotographic recording element as described in claim 1, wherein said material is a compound selected from the group consisting of single-crystal ZnO, CdS, CdSe, and SbSI, and said layer comprises one or more elemental bodies of said compound.

Claim 4

An electrophotographic recording element as described in claim 3, wherein each of said elemental bodies has a c-axis, and said c-axes extend in the same direction and are substantially perpendicular to said surface of said layer.

Claim 5

An electrophotographic recording element as described in claim 1, wherein said material is single-crystal ZnO, said layer comprises a plurality of wafers of said single-crystal ZnO, and each of said wafers has a c-axis extending outwardly from said exposed surface and said layer.

Claim 6

An electrophotographic recording element as described in claim 1, wherein said material is single-crystal zinc oxide, said layer comprises one or more bodies of said single-crystal zinc oxide, and each of said bodies has a c-axis pointing toward said substrate.

Claim 7

An electrophotographic recording element as described in claim 4, wherein each of said wafers has a thickness of at least 0.5 mm, a large surface with an area of at least 2.5 mm2, and a resistivity of at least 109ohm-cm in the dark.

Claim 8

In an electrophotographic method of the type wherein a photoconductive layer of a recording element is sequentially electrostatically charged, selectively discharged with a light image to provide an electrostatic latent image, and said latent image is developed with an electroscopic toner to provide a visible image on said layer, the improvement of charging said recording element comprising the steps of: providing said photoconductive layer in the form of one or more similar crystalline elemental bodies of a photoconductive, pyroelectric material on an electrically conductive substrate, each of said elemental bodies being similarly oriented with respect to their crystal axes to produce electrostatic charges of opposite polarity on the opposite large surfaces, respectively, of said layer when the temperature of said layer is changed, and changing the temperature of said layer to produce said electrostatic charges, whereby to charge said layer.

Claim 9

In an electrophotographic method of the type wherein a photoconductive layer of a recording element is sequentially electrostatically charged, selectively discharged with a light image to provide an electrostatic latent image, and said latent image is developed with an electroscopic toner to provide a visible image on said layer, the improvement of charging said recording element comprising the steps of: providing said photoconductive layer in the form of one or more similar crystalline elemental bodies of a photoconductive, pyroelectric material on an electrically conductive substrate, each of said elemental bodies being similarly oriented with respect to their crystal axes to produce electrostatic charges of opposite polarity on the opposite large surfaces, respectively, of said layer when the temperature of said layer is changed, and changing the temperature of said layer to produce said electrostatic charges, whereby to charge said layer.

Claim 10

In aN electrophotographic method of the type described in claim 7, wherein the step of changing the temperature of said layer to produce said electrostatic charges comprises raising the temperature of said layer between 5*C and 30*C.

Claim 11

In an electrophotographic method of the type described in claim 7, wherein the step of changing the temperature of said layer to produce said electrostatic charges comprises lowering the temperature of said layer between 5*C and 30*C.

Claim 12

In an electrophotographic method of the type described in claim 7, wherein the step of providing said photoconductive layer comprises providing a layer of one or more wafers of single-crystal, photoconductive zinc oxide on an electrically conductive substrate, each of said wafers of zinc oxide having a c-axis that is pointing in the same direction and oriented substantially perpendicularly to opposite large surfaces of said layer, and the step of changing the temperature of said layer comprises heating or cooling said layer at least about 5*C.