Patent ID: 6255043
Filing Date: 2001-07-03
Classification: G03B,G03C,Y10S

Abstract:
A method of linear metrology for continuous web or sheet elements comprising providing a preformed biaxially oriented polyolefin sheet, providing a base paper, applying a bonding agent onto the top of said base paper and simultaneously applying said biaxially oriented sheet to said bonding agent to join said microvoided sheet to the top of said base paper, providing a back sheet of biaxially oriented polymer sheet bearing indicia wherein said indicia are machine readable and not visible to the human eye under natural or artificial daylight illuminance, laminating said back sheet to the back of said base paper with bonding agent such that the indicia are adjacent said base paper, providing a means to detect said machine readable indicia, providing a means to collect information about the detection of said machine readable indicia, and providing a means to store and process the said collected information and wherein the machine readable indicia is a substantially transparent magnetic recording layer containing magnetic particles in a binder said magnetic particles have a specific surface area of at least 30 g/m.sup.2, said magnetic recording layer having a dried thickness of less than about 1.5 .mu.m and increases the optical density of the photographic element by less than 0.2 optical density units across the visible portion of the spectrum from 4000 .ANG. to 7000 .ANG..