Pressure sensitive recording sheet

Claim 2

A pressure sensitive recording sheet adapted for imaging under the pressure of a typewriter key or other writing instrument comprising at least a pair of fiber plies disposed with one in front of and normally masking the other, said one fiber ply being composed of polyolefin fibers having a surface area exceeding 1 m 2 per gm with the relatively large surface area of the fibers in said one ply resulting in light-scattering interfaces rendering said one ply opaque, said polyolefin fibers also being sufficiently flexible to compact under the pressure of a writing instrument with destruction of these light-scattering interfaces, said one ply becoming relatively transparent when subjected to the localized pressure of a writing instrument in the region where pressure is applied by reason of compaction of said fibers in said region, said other of said fiber plies being composed of wood fibers, and a colored medium distributed in said other ply normally obscured by the opacity of said one ply but made distinct by instrument pressure by reason of the relative transparency of said region produced by fiber compaction.

Claim 3

The pressure sensitive recording sheet of claim 1, which further comprises a third ply of cellulosic fibers disposed in front of said one ply, said third ply having a basis weight not exceeding about 20 gms per m 2 .

Claim 4

The recording sheet of claim 1, wherein colored medium is distributed in said other ply.

Claim 5

The pressure sensitive recording sheet of claim 2, wherein said colored medium is distributed in said other ply.

Claim 6

The pressure sensitive recording sheet of claim 1, wherein said one ply forms the face of the recording sheet.

Claim 7

The pressure sensitive recording sheet of claim 1, wherein said one ply forms a face of the recording sheet, and wherein the sheet has been surface sized with retention in the sheet of from 0.01 to 5 gms per m 2 of sizing material.

Claim 8

A pressure sensitive recording sheet adapted for imaging under the pressure of a typewriter key or other writing instrument, said sheet having a basis weight within the range of about 20 to 60 gms per m 2 , said sheet being a composite of an opaque face ply of polyolefin fibers and a back ply of wood pulp fibers coextensive with and adhered to the face ply, the polyolefin fibers in said face ply having a surface area exceeding 1 m 2 per gm with the relatively large surface area of the fibers in said face ply resulting in light-scattering interfaces rendering said face ply opaque, said polyolefin fibers also being sufficiently flexible to compact under the pressure of a writing instrument with destruction of light-scattering interfaces, said face ply becoming relatively transparent when subjected to the localized pressure of a writing instrument in the region where pressure is applied by reason of compaction of said fibers in said region, said face ply having a basis weight ranging from about 1/3 to 2/3 of the basis weight of the recording sheet, and a colored medium distributed in said back ply normally obscured by the opacity of said face ply but made distinct by instrument pressure by reason of the relative transparency produced in said region.

Claim 9

A pressure sensitive recording sheet adapted for imaging under the pressure of a typewriter key or other writing instrument, said sheet having a basis weight within the range of about 20 to 60 gms per m 2 , said sheet being a composite of an opaque face ply of polyolefin fibers and a back ply of wood pulp fibers coextensive with and adhered to the face ply, the polyolefin fibers in said face ply having a surface area exceeding 1 m 2 per gm with the relatively large surface area of the fibers in said face ply resulting in light-scattering interfaces rendering said face ply opaque, said polyolefin fibers also being sufficiently flexible to compact under the pressure of a writing instrument with destruction of light-scattering interfaces, said face ply becoming relatively transparent when subjected to the localized pressure of a writing instrument in the region where pressure is applied by reason of compaction of said fibers in said region, said face ply having a basis weight ranging from about 1/3 to 2/3 of the basis weight of the recording sheet, and a colored medium distributed in said back ply normally obscured by the opacity of said face ply but made distinct by instrument pressure by reason of the relative transparency produced in said region.

Claim 10

The recording sheet of claim 7, wherein the polyolefin is polyethylene.

Claim 11

A pressure sensitive recording sheet adapted for imaging under the pressure of a typewriter key or other writing instrument comprising a mat of polyolefin fibers where the fibers in said mat have a surface area exceeding 1 m 2 per gm with the relatively large surface area of the fibers in said mat resulting in light-scattering interfaces rendering said mat opaque, said polyolefin fibers also being sufficiently flexible to compact under the pressure of a writing instrument with destruction of the light-scattering interfaces, said mat becoming relatively transparent when subjected to the localized pressure of a writing instrument in the region where pressure is applied by reason of compaction of said fibers in said region, and a colored medium distributed in said recording sheet behind said mat and normally masked by the opacity of said mat but made distinct by instrument pressure by reason of the relative transparency of said region produced by fiber compaction.

Claim 12

A pressure sensitive recording sheet adapted for imaging under the pressure of a typewriter key or other writing instrument comprising a mat of polyolefin fibers where the fibers in said mat have a surface area exceeding 1 m 2 per gm with the relatively large surface area of the fibers in said mat resulting in light-scattering interfaces rendering said mat opaque, said polyolefin fibers also being sufficiently flexible to compact under the pressure of a writing instrument with destruction of the light-scattering interfaces, said mat becoming relatively transparent when subjected to the localized pressure of a writing instrument in the region where pressure is applied by reason of compaction of said fibers in said region, and a colored medium distributed in said recording sheet behind said mat and normally masked by the opacity of said mat but made distinct by instrument pressure by reason of the relative transparency of said region produced by fiber compaction.