Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Patent
1993-04-02
1995-01-03
Martin, Roland
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
G03G 9097
Patent
active
053785711
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to the use of special aryl and aralkyl sulfide, sulfoxide or sulfone compounds as charge regulators in electrophotographic toners and developers and as charge regulators in powders and powder coatings for surface coating. The compounds according to the invention have particularly high and constant charge regulating effects and are distinguished by the simplicity of the synthesis units and the preparation process. In addition, these compounds have very good thermal stabilities and dispersing properties.
In electrophotographic recording processes a "latent charge image" is produced on a photoconductor. This is effected, for example by charging a photoconductor by means of a corona discharge and subsequent image-wise exposure of the electrostatically charged surface of the photoconductor, drainage of the charge to the earthed substrate at the exposed areas being effected by the exposure. The "latent charge image" produced in this way is then developed by applying a toner. In a subsequent step, the toner is transferred from the photoconductor to, for example, paper, textiles, foils or plastic and fixed, for example by means of pressure, radiation, heat or solvent action. The photoconductor used is then cleaned and is available for a fresh recording operation.
The optimization of toners is described in numerous patents and, inter alia, the influence of the toner binder (variation of resin/resin components or wax/wax components), the influence of carriers (in the case of two-component developers) and magnetic pigments (in the case of one-component developers) are studied.
A criterion for the toner quality is its specific charge q/m (charge per unit mass). In addition to the sign and level of the electrostatic charge, in particular the rapid achievement of the desired charge level and the constancy of said charge over a prolonged activation period is a decisive quality criterion. In practice, this is of central importance inasmuch as the toner can be exposed to a considerable activation time in the developer mixture before it is transferred to the photoconductor since it sometimes remains in the developer mixture over a period extending from the preparation up to several thousand copies. In addition, the insensitivity of the toner to climatic influences, such as temperature and atmospheric humidity, is a further important suitability criterion.
Both positively and negatively chargeable toners are used in copiers and laser printers, depending on the process and equipment type.
So-called charge regulators (also termed charge controllers) are frequently added in order to obtain electrophotographic toners or developers which have either positive or negative charging. In addition to the sign of the charge regulation, the extent of the regulating effect is important since a greater effectiveness permits the use of a smaller amount. Since toner binders as a rule show high dependence of the charge on the activating time, the purpose of a charge regulator is, on the one hand, to adjust the sign and level of the toner charge and, on the other hand, to counteract the charging drift of the toner binder and to ensure constancy of toner charging.
Charge regulators which are not able to prevent the toner or developer exhibiting a high charge drift when used over a prolonged period (ageing), which can even cause the toner or developer to undergo charge reversal, are therefore unsuitable in practice. Full-color copiers and laser printers operate on the principle of trichromatism, which makes precise color shade matching of the three primary colors (yellow, cyan and magenta) necessary.
Extremely small shifts in color shade, even in only one of the three primary colors, necessarily demands a shift in color shade of the other two colors to enable full-color copies or prints true to the original to be produced even under these conditions.
Because of this requisite precise matching of the coloristics of the individual colorants with respect to one another in color toners, charge regulators wh
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patent: 4377629 (1983-03-01), Tarumi et al.
patent: 4480021 (1984-10-01), Lu et al.
patent: 4795690 (1989-01-01), Shindo et al.
patent: 5238768 (1993-08-01), Ong
patent: 5250381 (1993-10-01), Ciccarelli et al.
Macholdt Hans-Tobias
Nagl Gert
Hoechst Aktiengesellschaft
Martin Roland
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