Thermal print head wafer and method of making the same

Claim 2

A thermal print wafer comprising: a dielectric substrate having first and second opposed planar surfaces, mutually, substantially perpendicular to a third surface thereof; said first, second, and third surfaces being formed to provide one continuous blended area extending completely over said third surface and partly over said first and second surfaces; said blended area having small grooves therein below the surface thereof; said grooves being aligned substantially parallel to an imaginary plane mutually perpendicular to said first, second, and third surfaces; and a plurality of discrete resistive elements secured to said blended area and extending completely across said third surface and partly over said first and second surfaces; said resistive elements being positioned in spaced parallel relationship with one another and having portions filling said grooves.

Claim 3

The wafer as claimed in claim 1 in which said substrate has a constant radius of curvature joining said first and third surfaces and another constant radius of curvature joining said second and third surfaces at said blended area.

Claim 4

The wafer as claimed in claim 2 in which said substrate is continuous at said blended area so as to form a heat sink for said resistive elements.

Claim 5

The wafer as claimed in claim 1 in which said resistive elements are made of semiconductor material.

Claim 6

The wafer as claimed in claim 4 in which said semiconductor material is tin oxide which has a small amount of boric oxide therein to increase the print-to-burnout ratio of the resistive elements.

Claim 7

The wafer as claimed in claim 1 in which said resistive elements are spaced apart a short distance when compared to the width of individual resistive elements so as to increase the print-to-burnout ratio of the resistive elements.

Claim 8

The wafer as claimed in claim 1 further comprising: electrical conductor means for energizing selected ones of said resistive elements; said conductor means being located on said first and second surfaces of said substrate.

Claim 9

A thermal print head comprising: a plurality of print wafers and insulating members alternately arranged in a stacked array with one of said insulating members being positioned between two adjacent print wafers; each said print wafer comprising: a dielectric substrate having first and second opPosed planar surfaces mutually, substantially perpendicular to a third surface thereof; said first, second, and third surfaces being formed to provide one continuous blended area extending completely over said third surface and partly over said first and second surfaces; said blended area having small grooves therein below the surface thereof; said grooves being aligned substantially parallel to an imaginary plane mutually perpendicular to said first, second, and third surfaces; a plurality of discrete resistive elements secured to said blended area and extending completely across said third surface and partly over said first and second surfaces; said resistive elements being positioned in spaced parallel relationship with one another and having portions filling said grooves; and electrical conductor means for energizing selected ones of said resistive elements; said conductor means being located on said first and second surfaces of each said substrate; said third surfaces of said substrates lying substantially in a common plane so that the resistive elements positioned thereon can cooperate with a thermally sensitive record medium to produce a mark on said record medium when a selected resistive element is energized.

Claim 10

A thermal print head comprising: a plurality of print wafers and insulating members alternately arranged in a stacked array with one of said insulating members being positioned between two adjacent print wafers; each said print wafer comprising: a dielectric substrate having first and second opPosed planar surfaces mutually, substantially perpendicular to a third surface thereof; said first, second, and third surfaces being formed to provide one continuous blended area extending completely over said third surface and partly over said first and second surfaces; said blended area having small grooves therein below the surface thereof; said grooves being aligned substantially parallel to an imaginary plane mutually perpendicular to said first, second, and third surfaces; a plurality of discrete resistive elements secured to said blended area and extending completely across said third surface and partly over said first and second surfaces; said resistive elements being positioned in spaced parallel relationship with one another and having portions filling said grooves; and electrical conductor means for energizing selected ones of said resistive elements; said conductor means being located on said first and second surfaces of each said substrate; said third surfaces of said substrates lying substantially in a common plane so that the resistive elements positioned thereon can cooperate with a thermally sensitive record medium to produce a mark on said record medium when a selected resistive element is energized.

Claim 11

A thermal print wafer for thermally marking a thermally responsive record medium which moves in a predetermined direction past said printing wafer comprising: a dielectric substrate having first and second opposed planar surfaces mutually perpendicular to a third surface thereof; said first, second, and third surfaces being formed to provide one continuous blended area extending completely over said third surface and partly over said first and second surfaces; said blended area having small grooves therein below the surface thereof with the grooves being aligned substantially parallel to said predetermined direction; a plurality of discrete resistive elements secured to said blended area and extending completely across said third surface and partly over said first and second surfaces; said resistive elements being positioned in spaced parallel relationship with one another and having portions filling said grooves; and electrical conductor means positioned on said first and second surfaces for energizing selected ones of said resistive elements.

Claim 12

A thermal print wafer for thermally marking a thermally responsive record medium which moves in a predetermined direction past said printing wafer comprising: a dielectric substrate having first and second opposed planar surfaces mutually perpendicular to a third surface thereof; said first, second, and third surfaces being formed to provide one continuous blended area extending completely over said third surface and partly over said first and second surfaces; said blended area having small grooves therein below the surface thereof with the grooves being aligned substantially parallel to said predetermined direction; a plurality of discrete resistive elements secured to said blended area and extending completely across said third surface and partly over said first and second surfaces; said resistive elements being positioned in spaced parallel relationship with one another and having portions filling said grooves; and electrical conductor means positioned on said first and second surfaces for energizing selected ones of said resistive elements.

Claim 15

The method as claimed in claim 10 in which said step (b) forming is accomplished by grinding in the direction of anticipated current flow through the resistor elements to be formed.

Claim 16

The method as claimed in claim 11 in which said step (c) applying semiconductor material is accomplished while exposing said portion of said substrate including the blended area to the atmosphere while heating the remaining portion thereof.

Claim 17

The method as claimed in claim 12 in which said step (c) applying semiconductor material is accomplished by spraying said semiconductor material in liquid form through at least one nozzle located in the atmosphere and directed at said portion which is exposed to the atmosphere.

Claim 18

The method as claimed in claim 13 in which said step (c) applying semiconductor material is effected by spraying in time-spaced pulses with the time between pulses enabling the portion of the substrate exposed to the atmosphere to be reheated by the remaining portion thereof which is heated continuously.

Claim 19

The method as claimed in claim 14 in which the heating of the remaining portion of the substrate is effected by locating the remaining portion of the substrate in a furnace, a portion of the furnace being used for masking the remaining portion of the substrate which does not receive the semiconductor material.

Claim 20

The method as claimed in claim 10 in which said step (d) dividing said semiconductor material into discrete resistor elements is effected by covering said semiconductor material with a slitted U-shaped mask and by spraying abrasive material through the slits in the mask at said semiconductor material.

Claim 21

The method as claimed in claim 10 in which said step (b) forming said first, second, and third surfaces into one continuous blended area comprises: positioning said substrate so that the first and third planar surfaces thereof are perpendicular to a moving planar abrasive surface so that said third surface contacts said abrasive surface; rotating said substrate through an angle of 90* degrees so as to form a precise radius on said first edge; repositioning said substrate so that said first and third planar surfaces thereof are perpendicular to said planar abrasive surface so that said third surface contacts said moving abrasive surface; and rotating said substrate through an angle of 90* so as to form a precise radius on said second edge.