Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-07-07
2001-05-22
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S106100
Reexamination Certificate
active
06235442
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to colored powder, the individual particles of which contain a thermoplastic resin, possibly a magnetically attractable material and fluorescent dye. Powders of this kind are used, inter alia, in electrographic, electrophotographic and magnetographic image-forming processes. These types of powders, hereinafter also referred to as toner powders, are described inter alia in European Patent Application No. 0 350 099. In addition to possible other additives, toner powders according to this European Patent Application contain thermoplastic resins, finely distributed magnetically attractable pigments, such as carbonyl iron, and at least one yellow-fluorescent dye which has a strong fluorescence in the thermoplastic resin. The highly fluorescent yellow dyes are required to provide a color of acceptable brightness and color saturation to the toner powder, despite the very dark, magnetically attractable pigment present therein. In combination with the highly fluorescent yellow dye, other pigments or (fluorescent) dyes may be present to give the toner powder the intended color.
Examples of fluorescent dyes which may be present in the toner powder according to EP 0 350 099 are Rhodamine B (C.I. No. 45170), Basonyl Rot 560 (C.I., Basic Violet 11:1), Astra Phloxine (C.I. No. 48 070), Macrolex Fluorescent Yellow B10GN (C.I. Solvent Yellow 160:1), Thermoplast f-Gelb (C.I. No. 59 075) and Maxilon Brilliant Flavine 10 GFF (C.I. Basic Yellow 40).
In the preparation of toner powders according to the above European Patent Application, wherein magnetic pigment and fluorescent dye or dyes are finely distributed in the resin melt, a phenomenon which repeatedly occurs is that the fluorescence of the fluorescent dyes falls off sharply and finally colored toner powder of inadequate color quality is obtained.
This disadvantage occurs particularly in the preparation of red or magenta toner powder using the dyes of the type C.I. Basic Violet 11:1, such as Basonyl Rot 560, and fluorescence extinction is observed now and then during toner preparation in the case of other fluorescent dyes, such as the yellow-fluorescent dyes referred to in EP 0 350 099.
It has not yet been possible to ascertain the exact incidence of the fluorescence extinction, but it is clear that the effect is produced by the presence of iron ions, for example from the magnetic pigment, and that it is also influenced by the temperature level of the resin melt.
SUMMARY OF THE INVENTION
It has now surprisingly been found that the fluorescence extinction can be counteracted and even prevented by including in the toner powder a compound of a metal of which an ion is diamagnetic. Particular examples of metal of which an ion is diamagnetic include zinc and magnesium. Other metals are calcium, silver, sodium, potassium, barium, aluminium and zirconium.
By including in the resin melt a metal compound as specified above, particularly a salt of such a metal in an effective amount, e.g., about 2 to 15% by weight, during the toner preparation in a finely distributed and preferably in a dissolved condition, fluorescence extinction can be obviated or greatly reduced. Frequently a higher fluorescence can also be achieved than is possible in the case where no metal compound is present and no perceptible fluorescence extinction occurs. The choice of the metal compound, particularly the metal salt which can be used to obtain reduction of fluorescence extinction, does not appear to be critical. Thus, the fluorescence-improving effect has been observed with a considerable variation in salts of metals having a diamagnetic ion.
A particular condition for achieving better fluorescence is that the metal compound, for example, the metal salt, should be present in the resin compound in a dissolved or at least a very finely distributed form. The choice of the metal salt will accordingly be determined primarily by the solubility or its distributability in the thermoplastic resin or mixture of thermoplastic resins from which the toner powder is prepared. Of course, the metal compound (metal salt) must be selected which is colorless or practically colorless, or the color is compatible with the color to be achieved in the final toner powder. The quantity of metal compound required to avoid fluorescence extinction is present in an amount up to 15% by weight, e.g., about 2 to 15% by weight and is dependent, inter alia, on the amount of iron (e.g., iron-containing magnetic material or other iron-containing additive) present in the toner compound, the fineness with which the metal compound is distributed in the toner compound, and whether the toner compound contains substances which are chemically active with respect to the metal compound, for example, by forming a complex therewith. With increasing iron content in the toner compound and/or a less fine distribution of the metal compound, e.g., metal salt, in the toner compound, and/or if the toner compound contains substances which enter into a chemical bond (complexing) with the metal compound, a larger quantity of metal compound is required to obtain the optimum. A substance which complexes or at least can complex with zinc salts, for example, is the yellow dye (Macrolex Fluorescent Yellow 10GN (C.I. Solvent Yellow 160:1), which can be used in combination with Basonyl Rot 560 to give a red toner powder.
Examples of salts of a metal with a diamagnetic ion which can be used according to the present invention include zinc chloride, zinc sulphate, zinc nitrate, zinc iodide, zinc phosphate, zinc acetate, zinc salts of mono or polyvalent carboxylic acids such as zinc octanoate, zinc stearate, zinc palmitate, zinc-2-ethyl hexanoate, zinc malonate, zinc tartrate, zinc adipate; zinc benzoate, zinc naphthoate, and the corresponding magnesium salts. We can also mention calcium octanoate, sodium octanoate, calcium-2-ethyl hexanoate, sodium-2-ethyl hexanoate, silver stearate, silver palmitate, calcium stearate, aluminum palmitate, aluminium-2-ethyl-hexanoate, and barium-2-ethyl hexanoate.
The zinc and magnesium salts, which dissolve or are easily, very finely distributed in the resin compound from which the toner powder is formed, are preferred. Preferred salts for the resins conventionally used in toner powders, such as polyester resins, epoxy resins and phenoxy resins, are zinc and magnesium salts of branched or non-branched aliphatic carboxylic acids, and carboxylic acids particularly having a relatively long hydrocarbon radical containing at least six carbon atoms. The optimum quantity of metal compound, e.g. metal salt, for a specific toner compound of thermoplastic resin, magnetically attractable material and fluorescent dye, can readily be determined experimentally by finely distributing or dissolving different percentages by weight in a test quantity of melted or plasticized thermoplastic resin, in which the required quantities of magnetically attractable material, fluorescent dye and possibly other additives have been included either beforehand or simultaneously, and by determining the fluorescence of the samples in a known manner.
The thermoplastic resin, magnetically attractable material and fluorescent dye contained in toner powders according to the present invention may be the raw materials known for this application.
The thermoplastic resin selected is a resin in which the fluorescent dyes used have the maximum possible fluorescence. Examples of suitable thermoplastic resins are epoxy resins, polyester resins and modified polyester resins which, in their polymer chains, carry groups having a high dipole moment of preferably at least 2 debye, such as amide, anhydride, sulphonyl and/or ureido groups.
Suitable epoxy resins are the relatively low molecular weight epoxy resins such as those available under the trade name Epikote 1001 and 1004 (Shell-Nederland). Also usable are the resins derived from such epoxy resins and obtained by blocking the epoxy groups with a monofunctional reagent such as p-cumylphenol, or largely blocking them with a monofunctional reagent o
Coppenrath Marcella
Everaars Marcel Dialma
Birch & Stewart Kolasch & Birch, LLP
Chapman Mark
Oce--Technologies B.V.
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