Process for producing charge retention medium

A process for producing a charge retention medium, which comprises

• a step of applying a coating composition containing a fluorinated copolymer (A) having repeating units based on tetrafluoroethylene and repeating units based on ethylene, and an organic solvent (C), to a substrate to form a coating film
• and the following steps (I), (II), (IV) and (V) in this order:
• (I) a step of dissolving the fluorinated copolymer (A) in the organic solvent (C) at a temperature of at least the dissolution temperature at which the fluorinated copolymer (A) is dissolved in the organic solvent (C) and at most the melting point of the fluorinated copolymer (A) to obtain a fluorinated copolymer solution;
• (II) a step of cooling the fluorinated copolymer solution to a temperature of less than the dissolution temperature to obtain the coating composition having microparticles of the fluorinated copolymer (A) dispersed in the organic solvent (C);
• (IV) a step of applying the coating composition to the substrate to form a wet film;
• and
• (V) a step of preliminarily drying the wet film at a temperature of at least 50° C. and less than 150° C., followed by baking at from 230 to 350° C. to form the coating film,
• wherein the organic solvent (C) is selected from the group consisting of:
• Methyl ethyl ketone,
• 2-Pentanone,
• Methyl isopropyl ketone,
• 2-Hexanone,
• Methyl isobutyl ketone,
• Pinacolin,
• 2-Heptanone,
• 4-Heptanone,
• Diisopropyl ketone,
• Isoamyl methyl ketone,
• 2-Octanone,
• 2-Nonanone,
• Diisobutyl ketone,
• 2-Decanone,
• 2-Methylcyclohexanone,
• 3-Methylcyclohexanone,
• 4-Ethylcyclohexanone,
• 2,6-Dimethylcyclohexanone,
• 3,3,5-Trimethylcyclohexanone,
• 4-tert-butylcyclohexanone,
• Cycloheptanone,
• Isophorone,
• (-)-Fenchone,
• Ethyl formate,
• Propyl formate,
• Isopropyl fortmate,
• Butyl formate,
• Isobutyl formate,
• sec-Butyl formate,
• t-Butyl formate,
• Amyl formate,
• Isoamyl formate,
• Hexyl formate,
• Cyclohexyl formate,
• Heptyl formate,
• Octyl formate,
• 2-Ethylhexyl formate,
• Nonyl formate,
• Methyl acetate,
• Propyl acetate,
• Isopropyl acetate,
• Isobutyl acetate,
• sec-Butyl acetate,
• t-Butyl acetate,
• Amyl acetate,
• Isoamyl acetate,
• Hexyl acetate,
• Cyclohexyl acetate,
• Heptyl acetate,
• Octyl acetate,
• 2-Ethylhexyl acetate,
• 2,2,2-Trifluoroethyl acetate,
• 2,2,3,3-Tetrafluoropropyl acetate,
• 2,2,3,3,3-Pentafluoropropyl acetate,
• 1,1,1,3,3,3-Hexafluoro-2-propyl acetate,
• 2,2-Bis(trifluoromethyl)propyl acetate,
• 2,2,3,3,4,4,4-Heptafluorobutyl acetate,
• 2,2,3,4,4,4-Hexafluorobutyl acetate,
• 2,2,3,3,4,4,5,5,5-Nonafluoropentyl acetate,
• 2,2,3,3,4,4,5,5-Octafluoropentyl acetate,
• 3,3,4,4,5,5,6,6,6-Nonafluorohexyl acetate,
• 4,4,5,5,6,6,7,7,7-Nonafluoroheptyl acetate,
• 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl acetate,
• 7,7,8,8,8-Pentafluorooctyl acetate,
• 3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluoro-octyl acetate,
• Methyl propionate,
• Ethyl propionate,
• Propyl propionate,
• Isopropyl propionate,
• Butyl propionate,
• Isobutyl propionate,
• sec-Butyl propionate,
• t-Butyl propionate,
• Amyl propionate,
• Isoamyl propionate,
• Hexyl propionate,
• Cyclohexyl propionate,
• Heptyl propionate,
• Methyl butyrate,
• Ethyl butyrate,
• Propyl butyrate,
• Isopropyl butyrate,
• Butyl butyrate,
• Isobutyl butyrate,
• sec-Butyl butyrate,
• t-Butyl butyrate,
• Amyl butyrate,
• Isoamyl butyrate,
• Hexyl butyrate,
• Cyclohexyl butyrate,
• Methyl isobutyrate,
• Ethyl isobutyrate,
• Propyl isobutyrate,
• Isopropyl isobutyrate,
• Butyl isobutyrate,
• Isobutyl isobutyrate,
• sec-Butyl isobutyrate,
• t-Butyl isobutyrate,
• Amyl isobutyrate,
• Isoamyl isobutyrate,
• Hexyl isobutyrate,
• Cyclohexyl isobutyrate,
• Methyl valerate,
• Ethyl valerate,
• Propyl valerate,
• Isopropyl valerate,
• Butyl valerate,
• Isobutyl valerate,
• see-Butyl valerate,
• t-Butyl valerate,
• Amyl valerate,
• Isoamyl valerate,
• Methyl isovalerate,
• Ethyl isovalerate,
• Propyl isovalerate,
• Isopropyl isovalerate,
• Butyl isovalerate,
• Isobutyl isovalerate,
• sec-Butyl isovalerate,
• t-Butyl isovalerate,
• Amyl isovalerate,
• Isoamyl isovalerate,
• Methyl hexanoate,
• Ethyl hexanoate,
• Propyl hexanoate,
• Isopropyl hexanoate,
• Butyl hexanoate,
• Isobutyl hexanoate,
• sec-Butyl hexanoate,
• t-Butyl hexanoate,
• Methyl heptanoate,
• Ethyl heptanoate,
• Propyl heptanoate,
• Isopropyl heptanoate,
• Methyl octanoate,
• Ethyl octanoate,
• Methyl nonanoate,
• Methyl cyclohexanecarboxylate,
• Ethyl cyclohexanecarboxylate,
• Propyl cyclohexanecarboxylate,
• Isopropyl cyclohexanecarboxylate,
• 2,2,2-Trifluoroethyl cyclohexane- carboxylate,
• Bis(2,2,2-trifluoroethyl) succinate,
• Bis(2,2,2-trifluoroethyl) glutarate,
• Bis(2,2,2-trifluoroethyl) adipate,
• Methyl trifluoroacetate,
• Ethyl trifluoroacetate,
• Propyl trifluoroacetate,
• Isopropyl trifluoroacetate,
• Butyl trifluoroacetate,
• Isobutyl trifluoroacetate,
• sec-Butyl trifluoroacetate,
• t-Butyl trifluoroacetate,
• Amyl trifluoroacetate,
• Isoamyl trifluoroacetate,
• Hexyl trifluoracetate,
• Cyclohexyl trifluoroacetate,
• Heptyl trifluoroacetate,
• Octyl trifluoroacetate,
• 2-Ethylhexyl trifluoroacetate,
• Methyl difluoroacetate,
• Ethyl difluoroacetate,
• Methyl perfluoropropionate,
• Ethyl perfluoropropionate,
• Methyl perfluorobutanoate,
• Ethyl perfluorobutanoate,
• Methyl perfluoropentanoate,
• Ethyl perfluoropentanoate,
• Methyl 2,2,3,3,4,4,5,5-octafluoro- pentanoate,
• Ethyl 2,2,3,3,4,4,5,5-octafluoro pentanoate,
• Methyl perfluoroheptanoate,
• Ethyl perfluoroheptanoate,
• Methyl 2,2,3,3,4,4,5,5,6,6,7,7- dodecafluoroheptanoate,
• Ethyl 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanoate,
• Methyl 2-trifluoromethyl-3,3,3-trifluoropropionate,
• Ethyl 2-trifluoromrthyl-3,3,3-trifluoropropionate,
• 2-Ethoxyethyl acetate,
• 2-Propoxyethyl acetate,
• 2-Butoxyethyl acetate,
• 2-Pentyloxyethyl acetate,
• 2-Hexyloxyethyl acetate,
• 1-Methoxy-2-acetoxypropane,
• 1-Ethoxy-2-acetoxypropane,
• 1-Propoxy-2-acetoxypropane,
• 1-Butoxy-2-acetoxypropane,
• 1-Pentyloxy-2-acetoxypropane,
• 3-Methoxybutyl acetate,
• 3-Ethoxybutyl acetate,
• 3-Propoxybutyl acetate,
• 3-Butoxybutyl acetate,
• 3-Methoxy-3-methylbutyl acetate,
• 3-Ethoxy-3-methylbutyl acetate,
• 3-Propoxy-3-methylbutyl acetate,
• 4-Methoxybutyl acetate,
• 4-Ethoxybutyl acetate,
• 4-Propoxybutyl acetate,
• 4-Butoxybutyl acetate,
• 2-(Perfluoropropyloxy)-2,3,3,3- tetrafluoropropyl acetate,
• Dimethyl carbonate,
• Ethylmethyl carbonate,
• Diethyl carbonate,
• Dibutyl carbonate,
• Dibutyl carbonate,
• Bis(2,2,2-trifluoroethyl) carbonate,
• Bis(2,2,3,3-tetrafluoropropyl) carbonate,
• Tetrahydrofuran,
• Butyronitrile,
• Isobutyronitrile,
• Valeronitrile,
• Isovaleronitrile,
• Capronitrile,
• Isocapronitrile,
• Heptanenitrile,
• Octanenitrile,
• Nonanenitrile,
• Decanenitrile,
• 5-(Perfluorobutyl)bicyclo[2,2,1]-2-heptene,
• 5-(Perfluorohexyl)bicyclo[2,2,1]-2- heptene,
• 5-(Perfluorobutyl)bicyclo[2,2,1]heptane,
• 5-(Perfluorohexyl)bicyclo[2,2,1]heptane,
• HFC-c447ef(1,1,2,2,3,3,4- heptafluorocyclopentane),
• 1,1,1,2,3,3-Hexafluoro-4-(1,1,2,3,3,3- hexafluoropropoxy)pentane,
• 2,2,3,4,4,4-Hexafluoro-1-butanol,
• 2,2,3,3,4,4,5,5-Octafluoro-1-pentanol,
• 2,2-Bis(trifluoromethyl)-1-propanol,
• 3,3,4,4,5,5,6,6,6-Nonafluoro-1-hexanol,
• 2,3,3,3-Tetrafluoro-2-(perfluoropropyl- oxy)-1-propanol,
• 4,4,5,5,6,6,7,7,7-Nonafluoro-1-heptanol,
• 3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluoro-1-octanol,
• 7,7,8,8,8-Pentafluoro-1-octanol,
• 4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluoro-1-nonanol,
• 7,8,8,8-Tetrafluoro-7-(trifluoromethyl)-1-octanol,
• 2,3,3,3-Tetrafluoro-2-(1,1,2,3,3,3-hexa-fluoro-2-(perfluoropropyloxy)propyloxy)-1-propanol,
• Cyclopentanone, and
• Dioxane.