Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-11-23
2002-04-30
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031270, C106S031430, C106S031360, C106S031580
Reexamination Certificate
active
06379441
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cyan ink composition capable of realizing images having excellent lightfastness and an ink set capable of realizing color images having excellent lightfastness.
2. Background Art
Ink jet recording is a recording method wherein a recording liquid is ejected, through fine nozzles provided in a recording head, by vibration utilizing a piezoelectric element, action of heat energy or the like to perform recording. This recording method has advantages including quietness during recording and formation of high-resolution images at a high speed and low running cost by virtue of use of a high-density head. This has led to utilization of the ink jet recording in various recording fields, such as printers for personal computers, video printers, and printers for graphics.
In the formation of color images, at least three colors of magenta ink, yellow ink, and cyan ink are generally used. In particular, in ink jet recording, these three colors and, if necessary, four colors of these three colors and additionally black ink are provided, and the ejection of each ink is controlled by an electric signal to adjust the mixing ratio of the colors, thereby performing multi-color rendering. For example, red is produced by magenta ink and yellow ink. A variation in ejection ratio of the magenta ink and the yellow ink can create a change in mixing ratio of colors to render subtle gradation of red. Likewise, blue is rendered by color mixing of cyan ink and magenta ink, and green is rendered by color mixing of yellow ink and cyan ink. Further, a method has also been proposed wherein a light color ink having lower color density is used in addition to these three or four colors to improve color gradation, thereby further enhancing color rendering.
Inks used in the ink jet recording are required to have properties, for example, such that the values of properties, such as viscosity and surface tension, are proper, the optical density is high, vivid color tones and images can be provided, images having excellent fastness properties, such as excellent waterfastness and lightfastness can be produced, the storage stability is excellent, nozzles are less likely to be clogged, a bad smell is less likely to be emitted, and the safety in terms of hazard associated with fire fighting is high. Most of these requirements are satisfied by water-base inks prepared by dissolving a water-soluble dye in water or a mixed solution composed of water and a water-soluble organic solvent, and inks having various hues may be prepared from dyes having various hues.
Dyes, however, are known to be deteriorated by ultraviolet light in the sunlight and consequently to cause color change and fading. Therefore, various dyes, additives and the like have been studied in order to improve the lightfastness.
In the case of ink jet recording, the ejected ink penetrates into a recording medium, while the dye is merely adsorbed onto the recording medium. Thus, unlike silver salt photography and heat fusing methods, the dye is not protected by a binder, a cover film or the like. Therefore, recorded images (that is, dyes) are exposed directly to light, such as sunlight and light from fluorescent lamps, and, at the same time, are always exposed to oxygen, water, gases and the like contained in the air.
Methods for improving the lightfastness have been proposed such as a method wherein dyes, with specific structures, possessing excellent lightfastness are used, and a method wherein ultraviolet absorbers and light stabilizers are added to the ink to prevent color change and fading of dyes. Further, Japanese Patent Laid-Open No. 106971/1987 proposes, for example, a method wherein an ultraviolet absorber and an antioxidant are added to the ink to improve the lightfastness. However, some dyes possessing excellent fastness to ultraviolet light have undergone color change and fading under actual environment containing visible light. Further, some dyes possessing excellent lightfastness under environment containing the visible region have undergone color change and fading upon color mixing with other dyes. Further, it was found that although the proposed additives have the effect of preventing color change and fading of dyes caused by ultraviolet light, the effect is unsatisfactory under actual environment containing visible light.
Japanese Patent Publication No. 53436/1994 proposes a method for protecting dyes wherein a PET (polyethylene terephthalate) film containing an ultraviolet absorber and the like is laminated onto recorded images. The lamination, however, often sacrifices the sharpness of images and necessitates the provision of the additional step of lamination after printing, that is, lacks in simpleness, and thus is not a useful method. The lamination is effective in preventing color change and fading of the dye caused by ultraviolet light. However, it was found that this effect is unsatisfactory under actual environment containing visible light.
The deterioration in images caused by visible light is believed to be attributable to color change and fading of dyes caused by visible light. More specifically, the deterioration is considered to be attributable to deterioration or decomposition of dyes by photo-oxidation or photo-reduction. In particular, oxygen molecules in the air are converted to singlet oxygen (
1
O
2
) due to interaction between oxygen molecules and dye molecules, and the singlet oxygen often attacks the dye molecules and deteriorates and decomposes them. Specifically, some dyes per se function as a sensitizer of the singlet oxygen in the presence of light and oxygen. This leads to the formation of singlet oxygen which oxidizes the dyes per se. That is, the dyes are deteriorated by autosensitization. Further, in the case of ink jet recording wherein inks having different hues are ejected at an adjusted ejection ratio (that is, color mixing ratio) to perform multi-color rendering, it is considered that some dyes function as a sensitizer of singlet oxygen, i.e., as a catalyst, and the resultant singlet oxygen is reacted with contiguous or mixed other dye to cause color change and fading of the dye, that is, to accelerate the deterioration and decomposition of the dye.
Copper phthalocyanine dyes are generally used as the colorant of the cyan ink from the viewpoint of lightfastness, vividness and the like. The present inventors have confirmed that the copper phthalocyanine dyes function as a sensitizer of singlet oxygen. They have further found such a tendency that some colorants, especially magenta dyes, are likely to be deteriorated by the singlet oxygen, resulting in significant color change and fading at a portion where the cyan ink is contiguous with or mixed with other color, particularly magenta ink.
Magenta dyes, which are likely to cause color change and fading by attack of the singlet oxygen, are particularly azo dyes. On the other hand, many azo dyes possess excellent vividness and lightfastness. That is, single-color images of magenta ink possess excellent lightfastness, but on the other hand, the color change and fading at a portion of a mixed color of the magenta ink and the ink containing a copper phthalocyanine dye are significant. Consequently, the lightfastness of the color image is poor as a whole.
So far as the present inventors know, copper phthalocyanine dyes, which do not accelerate the photodeterioration of magenta dyes and are excellent in both vividness and lightfastness, have not been found, and, in addition, colorants, particularly magenta dyes, which do not cause photodeterioration at a portion of a mixed color of the colorant and the copper phthalocyanine dye and are excellent in both vividness and lightfastness, have also not been found.
SUMMARY OF THE INVENTION
According to the first aspect of the present invention, a cyan ink composition containing a copper phthalocyanine dye is provided which can realize images much less susceptible to color change and fading upon exposure to visible light at a portion of a mi
Ito Jun
Kanaya Miharu
Klemanski Helene
Ladas & Parry
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