Abstract: In an ink composition, a coloring agent, a color developer, and a decolorization agent are dissolved or dispersed in a solvent. The ink is capable of being colored at 40° C. or less, with the coloring agent reacting with the color developer to form a bonded structure, and also capable of being decolorized when heated to 100° C. or more, with the bonded structure being ruptured to liberate the color developer therefrom, and the liberated color developer being chemically bonded to the decolorization agent. An ink jet printer is provided with a paper feeder for feeding a recording sheet for ink jet printing, a recorder for recording an ink image on the recording sheet fed from the paper feeder using the above-mentioned ink composition, and a paper discharger for discharging the recording sheet from the ink jet printer. By further providing an eraser, the ink image recorded on the recording sheet by the recorder can be erased, thereby achieving recycling of the recording sheet.

Abstract: In an ink composition, a coloring agent, a color developer, and a decolorization agent are dissolved or dispersed in a solvent. The ink is capable of being colored at 40° C. or less, with the coloring agent reacting with the color developer to form a bonded structure, and also capable of being decolorized when heated to 100° C. or more, with the bonded structure being ruptured to liberate the color developer therefrom, and the liberated color developer being chemically bonded to the decolorization agent. An ink jet printer is provided with a paper feeder for feeding a recording sheet for ink jet printing, a recorder for recording an ink image on the recording sheet fed from the paper feeder using the above-mentioned ink composition, and a paper discharger for discharging the recording sheet from the ink jet printer. By further providing an eraser, the ink image recorded on the recording sheet by the recorder can be erased, thereby achieving recycling of the recording sheet.

Abstract: A device for measuring a rate exposed to deleterious materials comprises a heartbeat sensor for sensing heart rates, a deleterious material sensor for sening concentrations of deleterious materials in the air, a memory for storing the conversion values for converting the heart rates into corresponding respiration rates, and an operation unit. The operation unit counts a heart rate based a heartbeat signal received from the heartbeat sensor, calculates a respiration rate corresponding to the heart rate based on a conversion value read out from the memory, and calculates a rate exposed to deleterious material per unit time based on the calculated respiration rate and a signal respresenting a concentration of the deleterious material which signal is received from the deleterious material sensor.