Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-03-09
2002-09-24
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S107100, C430S108210, C430S109400, C430S126200
Reexamination Certificate
active
06455215
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotographic toner, particularly a magenta toner suitable for forming a color image. This invention also relates to an electrophotographic magenta developer, and an image formation method using the magenta toner or magenta developer.
BACKGROUND OF THE INVENTION
Color development is generally based on a three color synthesis system, such as a subtractive color process, in which at least three layers of electrostatic latent images are formed, developed with at least three different color toners, and superimposed on copying paper to give a full color image as described in U.S. Pat. No. 2,962,374.
Examples of color toners comprising pigments as a colorant include those described in JP-B-49-46951 (the term “JP-B” as used herein means an “examined published Japanese patent application”) and JP-A-52-17023 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). Examples of color toners comprising dyes as a colorant include those disclosed in JP-A-57-130043 and JP-A-57-130044.
Colorants which have been commonly used for a magenta toner for color electrophotography include azo lake pigments, anthraquinone dyes, quinacridone pigments, rhodamine dyes and lake pigments thereof. Of these colorants, rhodamine dyes are suitable as a colorant of a magenta toner because of their broad range of color reproducibility and high coloring power. However, they are disadvantageous for image preservation in that they are apt to migrate to a polyvinyl chloride (PVC) sheet and have poor resistance to light. Azo lake pigments are magenta pigments providing a red tone in a processed color. They have satisfactory reproducibility of a red tone in a processed color, high coloring power and excellent preservability as compared with other magenta pigments. Further, they are unwilling to adhere to a PVC sheet and have excellent light resistance. However, as compared with rhodamine dyes, azo lake pigments have a narrow range of color reproduction and are inferior in reproduction of a blue tone in a processed color. Quinacridone pigments, which are magenta pigments having a blue tone, provide satisfactory reproduction of a blue color in a processed color and also exhibit excellent preservability, and are therefore suitable as a magenta colorant. However, they have poor red color reproducibility in a processed color in nature of their color characteristics.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the above described problems of conventional colorants for magenta toner.
Therefore, an object of the present invention is to provide a magenta toner and a magenta developer for color electrophotography which have good color developability and an adequately broad range of color reproduction and are excellent in resistance against adhesion to a PVC sheet, light resistance, and image preservability, and to provide a full color image forming method using the toner or developer.
Other objects and effects of the present invention will be apparent from the following description.
The present inventors have sought for colorants for a color electrophotographic magenta toner excellent in color developability, color reproducibility, resistance to adhesion to a PVC sheet and light resistance. As a result, they have found that the above object of the invention can be achieved by incorporating (a) a compound classified as C.I. Pigment Red 57:1 and (b) a compound classified as C.I. Pigment Red 81 or C.I. Pigment Red 122 into a toner. The present invention has been completed based on this finding.
The present invention relates to an electrophotographic magenta toner which comprises a binder resin and a colorant comprising (a) 0.5 to 15 parts by weight of C.I. Pigment Red 57:1 and (b) 0.5 to 15 parts by weight of C.I. Pigment Red 81 or C.I. Pigment-Red 122, each per 100 parts by weight of the toner.
The invention also relates to an electrophotographic magenta developer comprising magnetic particles and a magenta toner,
wherein said magnetic particles comprises core particles having thereon a resin coating layer, and
wherein said magenta toner comprises a binder resin and a colorant comprising (a) 0.5 to 15 parts by weight of C.I. Pigment Red 57:1 and (b) 0.5 to 15 parts by weight of C.I. Pigment Red 81 or C.I. Pigment Red 122, each per 100 parts by weight of the toner.
The invention further relates to a method for forming a full color image comprising the steps of:
forming a latent image on a latent image carrier;
developing the latent image using a developer on a developer carrier to form a toner image on the latent image carrier; and
transferring the toner image onto an image-receiving member;
wherein the developing step is conducted by using, as one developer, a magenta toner comprising a binder resin and a colorant comprising (a) 0.5 to 15 parts by weight of C.I. Pigment Red 57:1 and (b) 0.5 to 15 parts by weight of C.I. Pigment Red 81 or C.I. Pigment Red 122, each per 100 parts by weight of the toner.
DETAILED DESCRIPTION OF THE INVENTION
The magenta toner of the invention is characterized by containing (a) C.I. Pigment Red 57:1 and (b) C.I. Pigment Red 81 or C.I. Pigment Red 122 as colorants. The magenta toner containing C.I. Pigment Red 57:1 and C.I. Pigment Red 81 provides a magenta toner image having markedly excellent light resistance. The magenta toner containing C.I. Pigment Red 57:1 and C.I. Pigment Red 122 exhibits improved color reproducibility. Thus, the magenta toners in both embodiments provide a magenta color image having excellent characteristics. These colorants are preferably subjected to flushing-processing prior to use.
The compound classified as C.I. Pigment Red 57:1 has the following structural formula:
The compound classified as C.I. Pigment Red 81 has the following structural formula:
The compound classified as C.I. Pigment Red 122 has the following structural formula:
C.I. Pigment Red 57:1 is used in an amount of 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of the toner. If the content of this colorant is less than 0.5 part, the toner-has weak coloring power, failing to produce sufficient effects as expected. If it exceeds 15 parts, tone deviation is caused to show poor color reproduction. C.I. Pigment Red 81 is used in an amount of 0.5 to 15 parts by weight, preferably 0.5 to 10 parts by weight, still preferably 0.5 to 8 parts by weight, per 100 parts by weight of the toner. C.I. Pigment Red 122 is used in an amount of 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, still preferably 1 to 8 parts by weight, per 100 parts by weight of the toner. If the content of C.I. Pigment Red 81 or C.I. Pigment Red 122 is less than 0.5 part, the toner has weak coloring power, failing to produce sufficient effects as expected. If it exceeds 15 parts, the resistance against adhesion to a PVC sheet and the light resistance are deteriorated.
The mixing ratio of the two kinds of the colorants preferably ranges from 2:8 to 8:2. The total content of the two colorants preferably ranges from 1 to 20 parts by weight, more preferably 2 to 18 parts by weight, per 100 parts by weight of the toner. If the total content of the two colorants is less than 1 part, the toner has weak coloring power. If it exceeds 20 parts, the toner has reduced transparency and deteriorated fixing properties.
The binder resin for use in the magenta toner of the invention is required to ensure low temperature fixing properties, transparency and color developability of the resulting toner. Taking the above into consideration, polyester resins are preferably used as the binder resin. Polyester resins are produced by reacting a polyhydric alcohol and a polybasic carboxylic acid or a reactive acid derivative thereof. Suitable polyhydric alcohols constituting the polyester resin include diols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentylene glycol and cyclohexanedimethanol; hydrogenat
Hashimoto Masaki
Ichimura Masanori
Takano Hiroshi
Take Michio
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Rodee Christopher
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