Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-04-25
2001-09-04
Goodrow, John (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
06284422
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to Japanese Patent Applications Nos. HEI 11(1999)-134567 and HEI 11(1999)-307358, filed on May 14, 1999 and Oct. 28, 1999 whose priorities are claimed under 35 USC §119, the disclosures of which are incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for developing electrostatic latent images and an image-forming apparatus, more particularly, a toner for developing electrostatic latent images which is used in an image-forming apparatus such as a copying machine and an apparatus for forming images using the toner.
2. Description of Related Art
Highly charge-receptive toners have been proposed (for example, Japanese Unexamined Patent Publication No. HEI 5(1993)-72805) which exhibit a good triboelectrification property and are not liable to form blurs in print and spots in non-printed part, not only in developing apparatuses used by a two-component developing method which is a dry development method but also in developing apparatuses used by a one-component developing method in which toners are not in frequent contact with charge donor materials and in developing apparatus in which charge donor materials have a poor charge donating efficiency.
The toner of the above-mentioned publication is comprised of a polyester resin, a colorant and an electric charge controlling agent. As the polyester resin, used is one having an acid value not greater than 15 mgKOH/g, and as the electric charge controlling agent, used is a chromium complex compound represented by the following formula:
(wherein X is Cl, Br, SO
2
NH
2
, SO
2
CH
3
or SO
2
C
2
H
5
, and A
+
is a C
8-16
straight-chain alkylammonium or a C
8-16
branched alkylammonium in which the alkyl moiety is optionally interrupted by an oxygen atom.
The reason why the acid value of the polyester resin in the above toner is 15 mgKOH/g or less is that, if the acid value is over 15 mgKOH/g, free carboxyl groups contained in the polyester resin, which have electron receptivity, improve negative electrification of the toner itself, while chelated rings of a chromium complex compound become liable to decompose. Therefore, the chromium complex compound is prevented from displaying its function as an electric charge controlling agent sufficiently. Especially, if the acid value exceeds 25 mgKOH/g, time constant until the charged triboelectrified amount of the toner reaches its saturation becomes large, and therefore, sufficient triboelectrification is difficult to obtain in the developing apparatus.
On the other hand, if the acid value is 10 mgKOH/g or below, the chromium complex compound is not decomposed at chelate rings due to the effect of carboxyl groups, which brings extremely good electrification characteristics by synergism with readiness to negative electrification that the polyester resin has.
However, if the acid value of the polyester resin is 15 mgKOH/g or below, excellent negative electrification and offset-resistant properties intrinsic to the polyester resin are restricted. A problem lies in that the polyester resin cannot exhibit its excellent properties fully.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a toner for developing electrostatic latent images comprising a polyester resin and an electric charge controlling agent containing a chromium complex compound, wherein the polyester resin has an acid value Z of 15 to 30 mgKOH/g (15<Z≦30) and a hydroxyl value Y of 4 to 17 mgKOH/g (4≦Y≦17).
In other words, the inventors of the present invention have made intensive studies for a toner for developing electrostatic latent images which has sufficient electrification characteristics and does not bring about problems such as blushing, toner scattering and the like while maintaining the property of being negatively electrified and the property of exhibiting offset-resistance at fixation intrinsic to the polyester resin. As a result, we have found that the acid value and hydroxyl value of the polyester resin contained in the toner for developing electrostatic latent images have a close relation with the electrification characteristics, especially in a high-temperature high-humidity environment, that the electrification characteristics are stabilized by including a positive charge controlling agent in the toner, and that admixture of a specific fluidizing agent on the surface of the toner provides still better effect (prevention of reduction in image density when copying a low-density manuscript), finally to achieve the present invention.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The toner for developing electrostatic latent images of the present invention mainly contains a polyester resin and an electric charge controlling agent comprised of a chromium complex compound.
The polyester resin used in the toner of the present invention is a polymer combined by ester bonding through polycondensation of a polybasic acid and a polyhydric alcohol. The polymer may be saturated or unsaturated. The kind of the polyester resin is not particularly limited, and examples thereof include various polymers such as unsaturated polyester resins, alkyd resins, polyethylene terephthalates, polybutylene terephthalates, polyarylates and the like, among which unsaturated polyesters are preferred.
The kind of the polybasic acid forming the polyester resin is not particularly limited, and examples thereof include maleic acid, maleic anhydride, fumaric acid, citraconic acid, citraconic anhydride, itaconic acid, mesaconic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, tetrabromophthalic acid, tetrabromophthalic anhydride, tetrachlorophthalic acid, tetrachlorophthalic anhydride, HET (chloroendic) acid, HET anhydride, endomethylene tetrahydrophthalic acid, endomethylene tetrahydrophthalic anhydride, trimellitic acid, trimellitic anhydride, pyromcllitic acid, pyromellitic anhydride and the like.
The kind of the polyhydroxy alcohol is not particularly limited, and examples thereof include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,3-butylene glycol, 1,6-hexanediol, 1,5-pentanediol, 1,6-pentanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, bisphenol dihydroxypropyl ether, glycol, glycerol and the like.
The polyester polymer may contain one or two or more of the above-mentioned polybasic acids and one or two or more of the above-mentioned polyhydroxy alcohols.
In the present invention, the polyester resin has an acid value Z of 15 to 30 mgKOH/g (15<Z≦30)and a hydroxyl value Y of 4 to 17 mgKOH/g (4≦Y≦17). Here, the acid value means the number of carboxyl residues at the end of the polyester resin, and the hydroxyl value means the number of hydroxyl residues at the end of the polyester resin. The acid value can be raised by increasing the use ratio of the polybasic acid (e.g., trimellitic acid) with respect to a dibasic acid in the polyester resin. The hydroxyl value can be decreased by reducing end groups of the alcoholic component. For example, the acid value can be raised by adding about 1 to 5 % of trimellitic anhydride as well as about 1 to 5% of maleic anhydride. The hydroxyl value can be adjusted within the above-mentioned ra
Murakami Toshihiko
Nagahama Hitoshi
Saito Junichi
Sumida Katsuaki
Goodrow John
Nixon & Vanderhye
Sharp Kabushiki Kaisha
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