Compositions – Light transmission modifying compositions – Modification caused by energy other than light
Patent
1992-11-12
1994-06-14
Lovering, Richard D.
Compositions
Light transmission modifying compositions
Modification caused by energy other than light
2041577, 252586, 252588, 252589, 252600, 430 78, G02B 523, G02F 100
Patent
active
053207840
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a crystal comprising an indolinospirobenzopyran derivative and its ring opened isomer, a process for producing the same and a piezochromic material comprising said crystal.
BACKGROUND ART
The organic compounds undergoing a reversible change of color on exposure to photic or thermal energy which are typical and best known are spiropyran derivatives and G. H. Brown: Photochromism (John Wiley & Sons, Inc., 1971), for one, can be consulted for a specific listing of such derivatives and their physical properties. However, when an attempt is made to exploit the hitherto-known spiropyran derivatives commercially in recording materials, they are found to have serious disadvantages. Thus, because the meta-stable species (ring opened isomers) are lacking in thermal stability in solutions as well as in polymeric binders, they tend to promptly revert to the ground state or fade out so that the chromic response at a necessary level cannot be sustained for a sufficient duration.
Meanwhile, as piezochromic compounds, there are known, inter alia, 9-(p-nitrophenylphenylmethylene)xanthene [J. Am. Chem. Soc., 79, 6020 (1957)], diflavine [J. Am. Chem. Soc., 80, 6312 (1958)], dehydrodianthrone [Chem. Ber., 100, 280 (1967), hexaphenylbiimidazolyl (Bull. Chem. Soc. Japan, 38, 685 (1965); ibid. 38, 2202 (1965); ibid, 43, 429 (1970)], tetraphenylvinyl dimer [Bull. Chem. Soc. Japan, 43, 1431 (1970)], phthalocyanine-cobalt complex [Journal of Synthetic Organic Chemistry, Japan, 30, 521 (1972)] and hydroxycarboxylic acid derivatives [Japanese Kokai Patent Publication No. 132857/1988], as well as spiropyranthiopyrans [Japanese Kokai Patent Publication No. 46079/1977] and spirobenzopyranoxadiazoline derivatives [Japanese Kokai Patent Publication No. 42880/1977], both of which are commonly referred to briefly as spiropyrans. However, many of these known compounds have several problems that must be overcome, viz. some require a substantial pressure for coloration or have only a low contrast of color between the colorless state and the colored state, while others are too labile, as very compounds, to be utilized as industrial materials and still others involve a complicated route for synthesis.
It is an object of the present invention to provide a piezochromic compound which insures a sufficient color density in a stable manner.
It is a further object of the invention to provide a piezochromic compound which can be intensely colored with a relatively low pressure to give a large contrast of color between the colored and colorless states and is superior in thermal stability.
It is a still further object of the invention to provide an expedient process for synthesizing such a piezochromic compound.
DISCLOSURE OF THE INVENTION
The inventor of the present invention explored in earnest for a spiropyran derivative free from the aforementioned disadvantages and insuring a stable or fatigueless piezochromic response and succeeded in isolating such a color-fast spiropyran derivative in the crystalline form. The inventor further found that this crystal changes color on application of a relatively small pressure and ultimately perfected the present invention.
The present invention relates to a crystal comprising an indolinospirobenzothiopyran compound of the following general formula and its ring opened isomer, a process for producing the same, and a piezochromic material comprising said crystal. ##STR2## wherein R.sup.1 means an alkyl group of 1 to 20 carbon atoms, an aralkyl group, a methacryloxymethyl group or a methacryloxyethyl group. R.sup.2, R.sup.3, R.sup.4 and R.sup.5 may be the same or different and each means a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an aryl group, an aralkyl group, an alkoxy group of 1 to 5 carbon atoms, a halogen atom, a cyano group or a nitro group. R.sup.6 and R.sup.7 may be the same or different and each means a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an aryl group, an aralkyl group, a halogen atom, a cyano group or a nitro group. R.s
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patent: 4139274 (1979-02-01), Yamashita et al.
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Lovering Richard D.
Otsuka Kagaku Kabushiki Kaisha
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