Radiation imagery chemistry: process – composition – or product th – Erasable imaging
Patent
1987-09-08
1989-12-12
Michl, Paul R.
Radiation imagery chemistry: process, composition, or product th
Erasable imaging
430338, 430341, 430346, 430495, 430962, G03C 172, G03C 516
Patent
active
048867179
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a photochromic material capable of reversibly controlling the recording and erasing of information in the form of letters, figures or the like by light irradiation, a photochromic device utilizing the same, and a method for recording and erasing information.
BACKGROUND ART
Among typical examples of known photochromic materials is silver halogenide. Silver halogenide heretofore used, e.g., for producing photochromic lenses in sunglasses discolors due to thermal vibration at ambient temperature on discontinuation of light irradiation, thus lacking a long-term stability in principle.
Also attempts have been made to use viologens as photochromic materials. In this case, the color development of univalent cation radical produced by reduction is utilized. However, with the progress of dimerization by the high reactivity of the color former itself, discoloration proceeds within hours while consuming viologen. Accordingly viologen also finds no use, in principle, as a material able to withstand a longterm use or repeated use.
DISCLOSURE OF THE INVENTION
In view of the state of the art as described above, the present inventors conducted various lines of research and found the following. Tris(2,2'-bipyridyl)rhodium (III) complex ions (hereinafter referred to as "Rh(bpy) .sub.3.sup.3+ ") or like organic metal complex ions intercalated between the montmorillonite layers when in a photo-excited state accepts electrons from the reducing agent, causing the resulting reductant to stably continue the color development after stoppage of light irradiation. Subsequently the oxidation of the reductant by proper means recovers the original state of Rh(bpy).sub.3.sup.3+ or the like to achieve decoloration.
The present invention provides the following photochromic material, photochromic device and method for recording and erasing information using the photochromic material or device.
(1) A photochromic material comprising a thin film of montmorillonite intercalation compound which has as a guest organic metal complex ions exhibiting a property of accepting electrons in a photo-excited state.
(2) A photochromic device comprising; guest organic metal complex ions exhibiting an electron-accepting property in a photo-excited state, and
(3) A method for recording and erasing information, comprising the steps of forming a thin film of montmorillonite intercalation compound containing as a guest organic metal complex ions having an electronaccepting property in a photo-excited state over a transparent layer of polycrystalline n-type semiconductor, irradiating with light the thin film in contact with an electrolyte containing an electron-donative reducing agent to develop color on the irradiated site of the film and applying a bias voltage to the film being exposed to light to remove the color of the site due to the photosensitizing electrolytic action.
Examples of organic metal complex ions exhibiting an electron-accepting property in a photo-excited state include six-coordinate octahedral rhodium (III) complex ions having bidentate ligands, more specific examples being Rh(phen).sub.3.sup.3+ having 1,10-phenanthrolines as ligands as well as said Rh(bpy).sub.3.sup.3+.
Rh(bpy).sub.3.sup.3+ or like rhodium (III) complex ions to be used in the present invention have the advantages of (a) being brought into active photo-excited state, (b) giving a reductant which is stable and free of consumption by side reaction, (c) being able to regain the original state on oxidation, (d) being able to form a significantly stable intercalation compound in combination with montmorillonite due to intercalation by ion exchange with the result that the Rh(bpy).sub.3.sup.3+ or like rhodium (III) complex ions are unlikely to be released even in water, and (e) producing a reductant which alone has a light-absorbing band at the visible zone. Therefore, the complex ions to be used in the present invention can be said to have properties suitable for producing an opticalmemory material which requires reversibil
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Jinno Masafumi
Kake Ichiro
Masumoto Tsuyoshi
Nishina Yuichiro
Buscher Mark R.
Michl Paul R.
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