Patent GB-653396-A (GB)
Title: Improvements in or relating to articles having spaced markings on surfaces thereof, such as optical gratings or sound records
IPC: G02B5/18
Filed: 1947-09-26
Abstract: The surface of an article having spaced markings, e.g. an optical grating or sound record, is formed of the copolymerization product of an unsaturated alkyd resin and a material copolymerizable therewith. Examples of copolymerizable materials are compounds containing a CH2 = C< group, e.g. styrene and substituted styrenes, vinyl naphthalene, vinyl cyclohexane, vinyl furane, vinyl dibenzofuran, divinyl benzene, ethyl vinyl ether, diallyl, dimethyallyl and methallyl ethyl ethers, divinyl ketone, methyl vinyl and methyl allyl ketones, methylene methyl malonate and the allyl, methallyl, crotyl, chloroallyl, cinnamyl, vinyl, methyl vinyl, a -phenyllalyl and propargyl esters of acids such as acetic, propionic, butyric, valeric, caproic, acrylic, alkacrylic, crotonic, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, maleic, fumaric, citraconic, mesaconic, itaconic, acetylene dicarboxylic, aconitic, benzoic, toluic, phenylacetic, phthalic, terephthalic and benzoylphthalic; and methyl, ethyl, propyl, butyl and isobutyl esters of unsaturated acids.  The unsaturated alkyd resin may be prepared from any polyhydric alcohol and a ,b -unsaturated polycarboxylic acid or anhydride.  This may be modified by replacing part of the acid with a saturated aliphatic, cycloaliphatic or an aromatic polycarboxylic acid.  The alkyd resin may also incorporate one or more saturated or unsaturated monohydric alcohols and/or one or more saturated or unsaturated monocarboxylic acids so that inter-esterification occurs. Polymerization is effected, preferably in the presence of a catalyst, e.g. an organic peroxide, cobalt linoleate or naphthenate, p-toluene sulphonic acid, aluminium chloride, stannic chloride and boron trifluoride, at temperatures generally from 40-200 DEG  C., and actinic light may be used.  The viscosity of the mixture may be reduced by heating with an esterification catalyst, e.g. p-toluene sulphonic acid. The induction period may be reduced by bodying at a temperature of about 70-130 DEG  C.  An inhibitor may be used in the polymerization, examples being hydroquinone, benzaldehyde, ascorbic acid, resorcinol, tannin, sym. - di - (beta - naphthyl) - p - phenylene diamine, phenolic resins and sulphur compounds.  These may be added before or during the preparation of the alkyd resin or before or after bodying.  The mixture is poured on to a master article in a mould when separation may be facilitated by use of a lubricant, e.g. zinc stearate or a silicone resin; or it is interposed between the master article and a substrate to which it adheres and which itself may comprise the same polymerization product which may contain reinforcing fillers, e.g. wood flour, or be used as the bond in a laminate (see Group VIII).  The substrate may also be made of materials such as glass, metal and polymethyl methacrylate. The surface itself may be lined or recorded on directly, and may be coated with a nitrocellulose solution or given a reflecting surface by spluttering on a thin layer of metal, e.g. aluminium.  The compositions may contain dyes, pigments, natural resins, e.g. shellac, nylon, polyvinyl acetal, urea-formaldehyde resins, aminotriazine-aldehyde resins, nitrocellulose and plasticizers, e.g. tricresyl phosphate and dibutyl and dioctyl phthalates and sebacates.