Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-08-29
2003-10-14
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031640, C106S031650
Reexamination Certificate
active
06632273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to color W/O emulsion ink for stencil printing, and more particularly to color stencil printing W/O emulsion ink which is excellent in weather resistance of color.
2. Description of the Related Art
The stencil printing is advantageous over other printing systems such as offset printing, gravure printing, letterpress printing and the like in that it permits to easily make prints without a skilled operator and complicated cleaning after printing is not necessary.
From the advent of the thermal stencil making system using a thermal head, image processing in the stencil printing has come to be digitized, whereby it has become feasible to easily obtain high quality printings in a short time, which makes it feasible to use the stencil printer as an information processing terminal.
Further, in the thermal stencil making system using a thermal head, perforations can be more regular in size and accordingly the amount of ink transferred to the printing paper can be more accurately controlled than in the conventional stencil making system in which infrared rays or xenon flash is employed to perforate the stencil material. Thus by using the thermal stencil making system, probability of generation of offset and/or spread of ink is reduced and the quality of printings is greatly improved.
As the stencil printing ink, W/O emulsion ink is generally used. There have been proposed various color inks, for instance, in Japanese Unexamined Patent Publication Nos. 6(1994)-172693, 7(1995)-150091, 9(1997)-227818 and 2000-53903. In color ink for stencil printing, pigment and dye can be used as the coloring agent. However since dye is generally poor in weather resistance, pigment has been generally employed.
Recently, there has been an increasing demand for inks of various colors, e.g., a color between red and orange, slightly reddish purple and the like. An ink of a specific color can be basically produced by one kind of pigment provided that a pigment of the specific color exists. However since when each color is produced by one pigment, the number of pigments to be managed by the factory becomes too large and since a pigment of a special color is ordered in a small amount and accordingly is expensive, the kinds of pigments to be handled by the factory are generally limited and inks of colors which do not conform to the colors of the regular pigments (those regularly stocked in the factory) are generally produced by mixing the regular pigments. That is, inks of various colors are produced by mixing the regular chromatic pigments and fine color adjustment is effected by adding a fine amount of a chromatic pigment (generally smaller than 1% by weight of the total weight of the ink).
However, there has been a problem that since containing a plurality of components different in nature, e.g., oil, water and surface active agent, the W/O emulsion ink is apt to discolor, which makes vain the fine color adjustment. Accordingly, conventionally, the color W/O emulsion ink for stencil printing have generally contained each chromatic pigment in an amount not smaller than 1%by weight. This limits fine color adjustment.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a color W/O emulsion ink for stencil printing which produces a finely adjusted color and the color development performance of which is constant.
Another object of the present invention is to provide a color W/O emulsion ink for stencil printing which produces a finely adjusted color and at the same time does not change with time in its hue, chroma and brightness.
In accordance with the present invention there is provided a color W/O emulsion ink for stencil printing including a plurality of kinds of chromatic pigments different from each other in hue, the total amount of the chromatic pigments being not smaller than 1% by weight and not larger than 10% by weight of the total weight of the ink, wherein the improvement comprises that
the content of at least one of the chromatic pigments is smaller than 1% by weight and at least one of the chromatic pigments the content of which is smaller than 1% by weight is a specific pigment selected from the group consisting of anthraquinone series pigments, perinone.perylene series pigments, phthalocyanine series pigments, dioxazine series pigments, quinacridone series pigments and isoindolinone series pigments.
The “hue” as used here means one of ten colors when color are divided into ten, i.e., yellow, green yellow, green, blue green, blue, purple blue, purple, red purple, red and yellow red.
When a plurality of pigments are contained in the ink in an amount smaller than 1% by weight, it is preferred that all the pigments be the specific pigments.
It is preferred that the content of the oil phase be 15 to 50% by weight and the content of the water phase is 50 to 85% by weight.
It is preferred that at least one of the chromatic pigments the content of which is smaller than 1% by weight satisfies the following formula and all of the chromatic pigments which satisfy the formula and whose contents are smaller than 1% by weight be the specific pigments
0.01≦(
PS
)
2
/PT≦
0.1
wherein PS represents the weight of the chromatic pigment in terms of % by weight to the total weight of the ink and PT represents the total weight of the chromatic pigments included in the ink in terms of % by weight to the total weight of the ink.
In the emulsion ink of stencil printing of the present invention, the chromatic pigment the content of which is smaller than 1% by weight contributes to fine color adjustment and a finer color can be obtained. At the same time, since anthraquinone series pigments, perinone.perylene series pigments, phthalocyanine series pigments, dioxazine series pigments, quinacridone series pigments and isoindolinone series pigments are excellent in weather resistance in a W/O emulsion ink, and are less apt to discolor, the emulsion ink containing therein such a chromatic pigment is stable in its hue, chroma, brightness and color development performance even after long storage or storage at a high temperature.
That is, when the chromatic pigment the content of which is smaller than 1% by weight is an organic pigment such as soluble azoic pigments, insoluble azoic pigments, basic and acidic lake pigments and the like, the pigment is discolored by the other components of the ink such as oil, water and surface active agent and the color development performance of the ink, e.g., hue and chroma, varies. At the same time, when the chromatic pigment the content of which is smaller than 1% by weight is inorganic pigment which is poor in color power and sharpness, it is difficult to use the chromatic pigment to adjust the color of the ink.
When all the pigments contained in the ink in an amount smaller than 1% by weight are the specific pigments, the emulsion ink can be more stable in hue, chroma and brightness against aging.
When at least one of the chromatic pigments the content of which is smaller than 1% by weight satisfies the following formula and all of the chromatic pigments which satisfy the formula and whose contents are smaller than 1% by weight are the specific pigments
0.01≦(
PS
)
2
/PT≦
0.1
wherein PS represents the weight of the chromatic pigment in terms of % by weight to the total weight of the ink and PT represents the total weight of the chromatic pigments included in the ink in terms of % by weight to the total weight of the ink, the emulsion ink can be further more stable in hue, chroma and brightness against aging.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail with reference to embodiments, hereinbelow.
As described above, the color W/O emulsion ink for stencil printing in accordance with the present invention includes
a plurality of kinds of chromatic pigments different from each other in hue, the total amount of the chromatic pigments being not smaller than 1% by weight and not
Hayashi Yoshihiro
Yonekawa Hirotoshi
Klemanski Helene
Nixon & Peabody LLP
Riso Kagaku Corporation
Studebaker Donald R.
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