Organic compounds -- part of the class 532-570 series – Organic compounds – Azo
Reexamination Certificate
2002-08-12
2004-05-18
Powers, Fiona T. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Azo
C534S708000, C534S714000, C106S031500, C106S031520
Reexamination Certificate
active
06737517
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a metal chelated azo dyestuff for inkjet recording, a recording liquid and recording liquid for inkjet containing the dyestuff and an inkjet recording method using the dyestuff. More particularly, the present invention relates to a metal chelated azo dyestuff for inkjet recording which can be preferably used as a black dyestuff in inkjet recording, a recording liquid for inkjet and an inkjet recording method.
BACKGROUND ART
A so-called inkjet recording method which allows droplets of a recording liquid containing water soluble dyestuffs such as direct dye and acidic dye to be ejected from a minute ejection orifice to effect recording has been put to practical use. The recording liquid for use in the inkjet recording method requires that it be able to be ejected over an extended period of time. The recording liquid also requires that it be fixed rapidly on PPC (plain paper COPIA) paper such as electrophotographic paper and fanhold paper (recording paper widely used for general official purposes such as continuous paper for computer, etc.) and give a printed matter having a good print quality, i.e., print having a definite contour free of running. The recording liquid further requires that it exhibit an excellent storage stability as a recording liquid. Accordingly, the solvent which can be used in the recording liquid is remarkably limited.
On the other hand, the dyestuff for recording liquid requires that it has a sufficient solubility in the solvent thus restricted and remain stable even after prolonged storage in the form of recording liquid. The dyestuff for recording liquid also requires that it gives a printed image having a high density and an excellent water resistance and light-fastness. However, it was difficult to meet these many requirements at the same time.
Further, the inkjet recording has been recently required to have adaptability to printing photo-like image, graphic image or the like (hereinafter abbreviated as “photographic image”) which is drastically improved as compared with the conventional inkjet recording. The black recording liquid for use in the printing is required to have further improvement in achromaticity of printed image. Further, unlike the letter printing involving printing with a density of 100%, the photographic image often employs so-called halftone printing involving 80% halftone dot meshing printing or 70% halftone dot meshing printing. In this printed area, the color of printed matter is gray rather than black. Therefore, the delicate hue of dyestuff which is not highlighted in 100% solid printed area, i.e., black printed area becomes highlighted.
In order to numerically express the achromaticity of the halftone area, halftone dot meshing printing is effected with a black ink at an arbitrary print density of from 0% to 100%, e.g., 80% using, e.g., “halftone dot meshing function” of a commercially available graphic software or word processing software. The printed matter thus obtained may be measured for saturation (C* value) by means of a commercial colorimeter. C* is an index indicating the saturation of color of image. In the case of black image, as C* value is closer to zero, it indicates that the color of the image is a pure black or gray having less color hue to advantage. In order to give a satisfactory inkjet recorded image, it is desired that C* value of a halftone dot meshing image printed at a density of 80% which normally looks a dark gray be not greater than 8, preferably not greater than 7.5, more preferably not greater than 7, particularly not greater than 4.
However, it has heretofore been extremely difficult to obtain a pure black free of delicate hue such as greenish, reddish and bluish hues, i.e., achromatic black image over a wide print density range from light to dark color using a single dyestuff. In other words, when an image subjected to halftone dot meshing printing at a density of 80% in the same manner using a single dyestuff which is normally used in inkjet recording is measured for saturation, C* value thus measured is from 10 to 15 or about 20 in the extreme case. Accordingly, a gray image which is not required to have color tone looks bluish, brownish or reddish.
Therefore, in general, a black inkjet recording liquid which contains a plurality of dyestuffs incorporated therein in combination to compensate deviation of color tone is used. However, this black inkjet recording liquid is disadvantageous in that different dyestuff molecules excessively prevent the agglomeration of the other dyestuff particles and catalytic fade causes deterioration of light-fastness.
On the other hand, in order to embody a highly fine and highly sharp image during IJ recording, particularly photographic image printing, a dedicated coated paper, dedicated glossy paper, etc. (hereinafter abbreviated as “dedicated paper”) is used. However, when printed on recording media normally called photographic glossy paper, paper dedicated for inkjet, etc., the dyestuff tends to be acceleratedly decomposed under light due to the action of silicon oxide, aluminum oxide and a waterproofing agent such as polyamine which have been incorporated therein to form a highly fine and highly sharp image. As a result, when the photographically printed image obtained by inkjet recording method is posted indoor or outdoor, it can be easily discolored to disadvantage.
The light-fastness of an image can be numerically expressed as, e.g., discoloration value (&Dgr;E) determined by measuring the image which has been subjected to photo-deterioration acceleration test involving irradiation with, e.g., xenon arc light for degree of image discoloration from the initial value by means of a color difference meter. In order to provide a photographic image formed on dedicated paper by inkjet printing with a sufficient light-fastness, a black image having &Dgr;E value of about 10 or less after 80 hours of irradiation with xenon arc light is required. However, the conventional dyestuffs can difficultly provide 100% solid printed area with the aforementioned desired light-fastness. Further, the conventional dyestuffs show more remarkable image discoloration due to light, often as extremely great as from 20 to 50 as calculated in terms of &Dgr;E value, in a so-called halftone area such as 80% halftone dot meshing-printed area and 70% halftone dot meshing-printed area, which is often used in photographic image printing.
In an attempt to improve the achromaticity and light-fastness of a black image at the same time, various dyestuffs and recording methods have heretofore been proposed. However, a dyestuff has never been developed which meets sufficiently the aforementioned complicating and growing need of the market and can be easily prepared.
In general, a black recording liquid contains a disazo dyestuff, a trisazo dyestuff or a polyazo dyestuff containing more azo groups. These dyestuffs are used to form the aforementioned purer black, i.e., achromatic black image. However, this type of a dyestuff can difficultly meet the recent requirement for strict light-fastness, especially on dedicated paper.
In addition, the aforementioned requirement for achromaticity cannot be attained by the conventional polyazo dyestuffs such as disazo and trisazo dyestuffs. Therefore, it has been often practiced to adjust the color hue to higher achromaticity by using a complementary color or using a plurality of black dyestuffs in combination. As a result, the light-fastness, which is now insufficient, tends to be deteriorated more and more.
On the other hand, in an attempt to embody an sufficiently light-fast image, the application of an existing or novel metal chelated azo dyestuff which is considered excellent in light-fastness has been studied. For example, Japanese Patent Laid-Open No. 1990-75672 discloses that a metal chelated dyestuff is used for inkjet recording and exemplifies metal chelated dyestuffs having the following structures. Although these metal chelated dyestuffs have an improved light-fastness, they tend to have bluish tone
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Powers Fiona T.
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