Patent GB-1494747-A (GB)
Title: Photochromic composition and method
IPC: G03C1/73
Filed: 1974-10-28
Abstract: 1494747 Luminescent compositions ASAHI KASEI KOGYO KK 28 Oct 1974 [29 Oct 1973] 46502/74 Heading C4S [Also in Division C3] A photochromic composition comprises as the sole photochromic substance an aromatic amine having an ionization potential of #7À6 eV, capable of photoionization to generate a coloured cation and an electron by absorption of two light photons and dispersed in a rigid polymer matrix having a polar group in the main or side chain which will increase and stabilize the photoionized state, the amine being selected from those of the formula wherein R, and R 2  are hydrogen, lower alkyl, lower alkoxy, allyl, substituted allyl, phenyl, substituted phenyl, amino and substituted amino, said substituents being selected from amino, lower alkyl and lower alkoxy; R 3  is as defined R 1  and R 2  except that the substituents when on an amino group are selected from allyl and phenyl; and R 4  to R, being as defined for R 1  and R 2 ; or R 3  with R 4  or R 6 , R 4  with R 5 , or R 6  with R 7  form an aromatic ring or a substituted aromatic ring wherein the substituents are as defined for R 1  and R 2 , R 8  to R 11  are selected from hydrogen, lower alkyl, phenyl, substituted phenyl, amino, substituted amino, allyl, and substituted allyl, the substituents being selected from amino lower alkyl and lower alkoxy, and "lower" being up to 12 C atoms, X and Y are selected from 0 to 4 R 1 , R 2 , R 4  to R, groups and halogen and sulphonate groups; and the polymer being thermoplastic with a glass transition temperature # 300‹ K., or a cross-linked polymer having at least one cross link/10<SP>3</SP> repeating units. Numerous amines including anilines, toluidines, and hydrazine are listed. Benzidene or specified benzidine derivatives such as phenylimino compound also exhibit phosphorescence after a time lag. The polymer may be one formed by conventional condensation or addition reactions including free radical condensation reactions effected by thermal or other radiation energy (e.g. light, y-rays, X-rays or high energy electrons or supersonic waves), or by the use of peroxide or azo compounds. Many polymers are listed and included by reference to publications, and detailed examples specifying compositions and formations thereof, excitations, and dimensions of the product, for instance are included. As examples only of the polymers listed are acrylic, styrenic, polyether, polyamide, olefinic and cellulosic polymers and copolymers thereof, polymers cross-linked by light such as polyvinyl alcohol-cinnamic acid ester, polymers incorporating low m.w. azide or diazonium compounds, or wherein vinyl type or vinylidene type polymers are photochemically cross-linked. Examples only of polymers cross-linked by heat and including specified thermosetting resins are phenol, formalin, urea-formalin, melamine-formalin, unsaturated polyester, epoxy and polyester acrylate resins. Polar groups incorporated in the main or side chains are listed. The amine is preferably included in amount 10<SP>-5</SP> to 20% by wt. of the polymer matrix, e.g. 10<SP>-2</SP> to 2% by wt. For phosphorescence, the respective ranges for benzidine or its derivative is 1À2 Î 10<SP>-5</SP> to 25% by wt. (e.g. 1À2Î10<SP>-2</SP> to 2À5% by wt.). Sensitizers of high electron affinity (0À5 to 2À5 eV) such as an aromatic nitro compound or a quinone are listed, additional classes being fluorenone, anthrones and other homologs and analogs of anthrone, and inclusion being in amount 10<SP>-2</SP> to 10 times the wt. of the amine. The amine, with sensitizer if used, can be mixed with the polymer in solution or in the melt or mixed with the monomer before polymerization. The resulting solution may be cast into shape, the amine and sensitizer substituted for the polymer plasticizer, and the system provided as a plate, film, fibre, rod or cylinder. The system may be protected by laminated layer. The intensity of coloration is proportional to the square of the excitation intensity and pulse and steady input excitations are considered. The former may include laser sources using nitrogen gas with 3371 Š emission, ruby at 3471 Š, or Xe or Ar sources, and the latter may include sunlight, ultra-high or -low p Hg or Xe lamps and lasers. Quenching of the T 1  state (Fig. 1, not shown) by oxygen is less for pulse inputs. The compositions may be used as dry recording materials (Fig. 3, not shown), the phosphorescence facilitating checking in ordinary light and the dark room, in data displays, sign boards, advertisements, photoprinting film, photosensitive print making materials, radiation dosimeters and camouflage. P/c colour extinction may be by heat, visible light or infra-red radiation.