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Anatomie de la magnétographie

Abstract : The work presented here is about the magnetographic printing systems designed and manufactured by NIPSON Technology. The medium that is supposed to retain the information one would like to print is a metallic cylinder, called the drum, on which two magnetic layers are grown: a FeNi ferromagnetic underlayer that acts as a “magnetic keeper” and a CoNiP semi-hard ferromagnetic medium. Using writing heads, an assembly of magnetized dots is recorded, thus forming the latent image to be written. This latent image is then revealed with magnetic ink particles that are attracted to regions that exhibit high gradients of stray field. Then the printing process is finalized by transferring the ink onto plain paper, cardboards, etc. Magnetic printing seems, at first glance, to be similar to the hard disk drive technology in the way the writing process works. However, the “read-out” in the former case sets itself apart by the necessity of having a sufficiently strong magnetic force to attract the ink particles, which involves layers that are tens of microns thick. The main objective of the thesis is to provide NIPSON Technology with options as to how to improve the printing speed of their devices from 150 m/min currently up to 600 m/min in the long run. To achieve that, a deeper understanding of the writing and the erasing processes in the magnetic medium is necessary. The task in the thesis is threefold. First, the magnetic field applied on the medium was determined by finite elements modelling both in the writing and the erasure processes. In the meantime, we studied the structural properties of the CoNiP and how they were linked to the magnetic properties of the medium. Then, by analyzing the results obtained in the two previous steps we succeeded in establishing a first model of the magnetic configuration in a single dot written by magnetic printing. On the erasure side, we managed to figure out how the parameters of the printer shape the AC demagnetization process used to erase an old latent image. Furthermore, we examined the possibility of implementing a DC erasure process as an alternative to the AC demagnetization, as well as an incremental alteration of the magnetic medium, so as to get a printing quality at 600 m/min as good as what one has at 150 m/min in the current system.
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Submitted on : Tuesday, June 2, 2020 - 5:07:36 PM
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  • HAL Id : tel-02736065, version 1


Alexandre Dekens. Anatomie de la magnétographie. Physique [physics]. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0300⟩. ⟨tel-02736065⟩



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