(US4755012-A)      An absorption filter able to control transmission of rays contains at least 1 anthraquinone (1), where each R is independently Ph or naphthyl opt. at least monosubstd. by alkyl, alkoxy, phenoxy or OH; rings 1 and 2 are opt. at least monosubstd. by lower alkyl or halogen.    R is pref. Ph at least monosubstd. by alkyl or alkoxy. Cpd. (1) is e.g. 1,4,5,8-tetra(4'-ethoxyphenylamino) anthraquinone. The filter has a sharp cut off on the short wave side in the region of 800-900nm.    USE/ADVANTAGE -   For heat retention in agricultural fields, in electronics, for sunglasses. The cpd. is very effective. (9pp)    (JP93064764-B)      Near infrared ray absorbing filter uses anthraquinone cpd. of formula (I) as light absorbing agent for regulating the transmission of light. (A1-A4 are each phenyl or naphthyl gp. which may be substd. by one or more gps. selected from alkyl, alkoxy, phenoxy and hydroxy gps). Anthraquinone cpd. of formula (I) has absorptionn max. at 750-800 nm. and ear 400 nm. and strongly absorbs light from the visible to the near infrared region of 800-900 nm.    USE -   As a sharp-cut filter for infrared rat sensor in electronic industry, agricultural film for heating or the acceleration of growth, sunglasses, protective glasses etc.    (JP95042412-B2)      Radiation-absorbing anthraquinone cpds. of formula (I) are new. A1, A2, A3 and A4 independently=phenyl or naphthyl unsubstd. or substd. with at least one of alkyl, alkoxy, phenoxy or hydroxy. A and B rings are unsubstd. or substd. with at least one lower alkyl or a halogen.    Specifically A1, A2, A3 and A4 independently=phenol substd. with at least one alkyl or alkoxy. (I) is prepd. by reacting a 1,4,5,8-tetrachloroanthraquinone (II) or 1,5-dichloro-4,8- dinitroanthraquinone unsubstd. or substd. with a lower alkyl or a halogen with an aniline (pref. p-toluidine (III) or p-phenetidine) or a naphthylamine cpd. in the presence of an inert solvent, e.g. sulpholane, at pref. 150-200 deg.C, the reaction being completed in from several to 20 hours. Also claimed are: (i) a filter contg. at least one of (A) 1,4,5,8-tetra(4'-methyl-phenylamino) anthraquinone, (B) 1,4,5,8-tetra(4'-ethoxyphenylamino) anthraquinone or (C) 1,4,5,8-tetra(4'-n-butylphenylamino) anthraquinone, or partic. contg. only (A) or (B); (ii) the blending of (I) with a thermoplastic resin followed by injection moulding or with a thermosetting resin followed by moulding or coating then curing; and (iii) the forming of (I) into an ink or lacquer which is printed or coated on a transparent substrate.    USE -   (I) is used (claimed) as a sharp cut radiation filter in the range from visible to (partic. claimed) near infra red which may be used in e.g. intensive cultivation, electronic sensors, eye protection or energy saving in buildings.