KPR, originally known as
Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
Photoresist
A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronic industry.
...
, is a
photosensitive Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicit ...
material used in
photoengraving
Photoengraving is a process that uses a light-sensitive photoresist applied to the surface to be engraved to create a mask that protects some areas during a subsequent operation which etches, dissolves, or otherwise removes some or all of the mat ...
,
Photogravure
Photogravure (in French ''héliogravure'') is a process for printing photographs, also sometimes used for reproductive intaglio printmaking. It is a photo-mechanical process whereby a copper plate is grained (adding a pattern to the plate) and ...
and
photolithography. Once dried, KPR can be dissolved by several solvents. However, after exposure to strong
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
light, it hardens and becomes insoluble by some of these solvents. It is also resistant to
acid,
ferric chloride
Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The col ...
and other chemicals used to etch metals.
The fundamental method of its use was first described in two US Patents, USP 2610120 and USP 2670287,
assigned to the
Eastman Kodak Company
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
of
Rochester, New York
Rochester () is a city in the U.S. state of New York, the seat of Monroe County, and the fourth-most populous in the state after New York City, Buffalo, and Yonkers, with a population of 211,328 at the 2020 United States census. Located in W ...
. These photo-resistant resins are formed from cinnamic acid esters, with the most preferable being polyvinyl cinnamate. While they were developed primarily for photolithography for high-speed print setting for uses such as newspaper printing, their perhaps highest value came from their ability to produce non-conducting layers on top of conducting layers to precise dimensions. This enabled the "printing" of large scale, closely placed conductive and non-conductive pathways to create binary gates. These were semi-conductors or the means to create semiconductors. This technology was utilized heavily by the Shockley 8, at the original Fairchild Semiconductor to produce more and more closely spaced semiconductors for computing. It is ironic that Kodak, the original patent assignee, did not really participate in the economic juggernaut that it created through this lithographic printing technology.
References
Kodak
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