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The term comes from Swedish "lack" for lacquer and Latin "novo" for new, since these materials were envisioned to replace natural lacquers such as copal resin. Typically novolaks are prepared by the condensation of phenol or a mixture of p- and m-cresol with formaldehyde (as formalin). The reaction is acid catalyzed.
One very common positive photoresist used with the I, G and H-lines from a mercury-vapor lamp is based on a mixture of diazonaphthoquinone (DNQ) and novolac resin (a phenol formaldehyde resin). DNQ inhibits the dissolution of the novolac resin, but upon exposure to light, the dissolution rate increases even beyond that of pure novolac.
Positive photoresists are composed of a novolac resin, ethyl lactate solvent, and Diazonaphthaquinone (DQ) as the photoactive compound. [9] Positive photoresist reacts with light to cause the polymer to break down and become soluble in a developer solution. Positive resist has better resistance to etchant than negative photoresist.
In this way, DNQ has become an important reagent in photoresist technology in the semiconductor industry. [1] Diazonaphthoquinone sulfonic acid esters are components of common photoresist materials. Such photoresists are used in the manufacture of semiconductors. [2] [3] [4] In this application DNQs are mixed with Novolac resin, a type of ...
The Ischemic Optic Neuropathy Decompression Trial [60] [61] observed that while spontaneous visual function deterioration occurred in 12% of 125 control eyes, the condition worsened in 24% of 119 eyes that underwent decompressive surgery. [62] The application of corticosteroids in NAION treatment remains a topic of debate. [63] [64]
Nerve compression syndrome, or compression neuropathy, or nerve entrapment syndrome, is a medical condition caused by chronic, direct pressure on a peripheral nerve. [1] It is known colloquially as a trapped nerve , though this may also refer to nerve root compression (by a herniated disc , for example).
Phenol-formaldehyde resins, as a group, are formed by a step-growth polymerization reaction that can be either acid- or base-catalysed.Since formaldehyde exists predominantly in solution as a dynamic equilibrium of methylene glycol oligomers, the concentration of the reactive form of formaldehyde depends on temperature and pH.
Neuropathy, ataxia, and retinitis pigmentosa, also known as NARP syndrome, is a rare disease with mitochondrial inheritance that causes a variety of signs and symptoms chiefly affecting the nervous system [1] Beginning in childhood or early adulthood, most people with NARP experience numbness, tingling, or pain in the arms and legs (sensory neuropathy); muscle weakness; and problems with ...