| 摘要 |
<p>To enable detecting a toner density of a liquid developer with a high degree of precision, it is sought to reduce air dissolved in the liquid developer and to diminish air bubbles caused therein by such dissolved air, the liquid developer being passed to flow through an area where its toner density is detected with the aid of ultrasonic waves. To this end, a deaerator 20 and a density detector 30 are provided in a liquid developer circulating path 10 through which the liquid developer in a main tank 3 is circulated, wherein the deaerator 20 includes a bundle 28 of hollow fibers each forming a hollow fiber membrane 29 whose inside 29b is depressurized and over whose outer peripheral surface the liquid developer is forced to flow under pressure, thereby sufficiently removing dissolved air in the liquid developer, and a toner density of the liquid developer is detected when the liquid developer of which dissolved air is sufficiently removed is passed through the density detector 30 utilizing ultrasonic waves, making it possible to detect the toner density with a high degree of precision.</p> |
