Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2002-01-09
2004-04-06
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031280, C347S100000
Reexamination Certificate
active
06716279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cyan ink composition and a magenta ink composition each possessing excellent lightfastness.
2. Background Art
Ink jet recording printers are becoming widely spread in recent years. Ink jet recording is a printing method wherein droplets of an ink composition are ejected and deposited on recording media, such as paper, to perform printing. The feature of the ink jet recording is that images having a combination of high resolution with high quality can be printed at a high speed by means of a relatively inexpensive apparatus. In particular, color ink jet recording apparatuses can improve image quality, can also be utilized as an output device for photographs, and have also become used, for example, as digital printing machines, plotters, and CAD output devices. The images printed by ink jet recording printers, which have become widely utilized in this way, are considered utilizable in various forms. In particular, for example, photograph-like prints are considered to be placed for display in a place exposed to light emitted from a fluorescent lamp or direct sunlight, for example, in the open for a long period of time. Therefore, lightfastness is a very important property requirement to be satisfied by records produced by ink jet recording.
In recent years, inks using a pigment as a colorant have become used for improving the lightfastness of records produced by ink jet recording. In the case of color images yielded by pigment-based ink compositions, fading of images can be suppressed even when exposed to light emitted from a fluorescent lamp or direct sunlight, for example, in the open for a long period of time. Even in such a case, however, in some cases, the hue of the image undergoes a change, and, consequently, the whole image becomes yellowish. For this reason, an ink composition has been desired that can yield images which are less likely to be deteriorated even after storage for a long period of time, that is, possesses excellent lightfastness.
SUMMARY OF THE INVENTION
The present inventors have now found that, in a cyan ink composition, a yellow colorant having a specific fading rate added in addition to a general cyan colorant can suppress a change in hue of printed ink and, consequently, can improve lightfastness of the yielded images. The present inventors have also found that the improvement in lightfastness of images can also be achieved in the same manner in the case of a magenta ink composition. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide an ink composition which can realize images possessing excellent lightfastness.
Thus, according to one aspect of the present invention, there is provided a cyan ink composition comprising, as colorants, a cyan colorant selected from the group consisting of C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, and a mixture of said cyan colorants, and a yellow colorant having a higher fading rate than the cyan colorant.
According to another aspect of the present invention, there is provided a magenta ink composition comprising, as colorants, a magenta colorant selected from the group consisting of C.I. Pigment Red 122, C.I. Pigment Red 202, C. I. Pigment Red 209, and mixtures of said magenta colorants, and a yellow colorant having a higher fading rate than the magenta colorant.
According to a further aspect of the present invention, there is provided an ink set comprising a yellow ink composition, a magenta ink composition, and a cyan ink composition, the cyan ink composition being the cyan ink composition according to the present invention, the magenta ink composition being the magenta ink composition according to the present invention.
In the ink compositions according to the present invention, in addition to a colorant commonly added to ink compositions (that is, a cyan colorant or a magenta colorant), a yellow colorant having a higher fading rate than the cyan colorant or magenta colorant is added as the colorant in the ink compositions. It should be noted that the cyan colorant or the magenta colorant contained as the colorant component in the ink composition, when exposed to outdoor or other environment after image formation, gradually undergoes a change in hue and becomes yellowish. On the other hand, the yellow colorant used in the ink compositions according to the present invention, when exposed to outdoor or other environment after image formation, is faded to render the yellowness of the colorant component low as a whole. Therefore, for example, when an image is formed using a cyan ink composition containing a cyan colorant and a yellow colorant followed by exposure of the image to outdoor or other environment, the cyan colorant contained in the ink composition yellows with the elapse of time while the yellowness of the yellow colorant is lowered. Consequently, it is considered that the recorded image can hold the original hue of the cyan ink composition and can form images possessing excellent lightfastness. The same is applied with respect to the magenta ink composition. The use of a cyan ink composition and a magenta ink composition, which have adopted the above constitution, in an ink set can produce images having better lightfastness. Further, when the yellow colorant to be used in ink compositions respectively containing a cyan colorant and a magenta colorant is properly selected while taking into consideration the difference in fading rate between the cyan colorant and the magenta colorant, the lightfastness of images can be further improved.
DETAILED DESCRIPTION OF THE INVENTION
Ink Compositions
The ink compositions according to the present invention may be used in recording methods using ink compositions. Recording methods using ink compositions include, for example, an ink jet recording method, a recording method using writing utensils, such as pens, and other various printing methods. Preferably, the ink compositions according to the present invention are used in an ink jet recording method.
Cyan Ink Composition
The cyan ink composition according to the present invention basically comprises, as colorants, a cyan colorant and a yellow colorant having a higher fading rate than the cyan colorant. Here the cyan colorant is selected from the group consisting of C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, and a mixture of the cyan colorants.
In the present invention, the “fading rate” refers to a rate at which, when a record with ink coated thereon is exposed to light emitted from a fluorescent lamp or direct sunlight, for example, in the open for a long period of time, the OD value (optical density) of the ink is lowered as compared with that before the exposure. In general, the fading rate can be defined by the following equation through the application of a predetermined acceleration test.
Fading rate=100×{(OD value before acceleration test)−(OD value after acceleration test)}/OD value before acceleration test
“Yellow colorant having a higher fading rate” refers to a yellow colorant which is more likely to fade than the cyan colorant according to the present invention.
Specifically, “that the fading rate of the yellow colorant is higher than the fading rate of the cyan colorant” means that, preferably, the fading rate value of the yellow colorant in a predetermined acceleration test for a predetermined period of time (for example, 200 hr) is three times or higher than the fading rate value of the cyan colorant, more preferably the fading rate value of the yellow colorant is 5 times or higher than the fading rate value of the cyan colorant.
Alternatively, “that the fading rate of the yellow colorant is higher than the fading rate of the cyan colorant” means that, when a print with a colorant coated thereon is placed under such environmental conditions as to cause fading, preferably under predetermined acceleration test conditions, the fading time, of the yellow colorant, defined as the time necessary for the OD value o
Klemanski Helene
Ladas & Parry
Seiko Epson Corporation
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