Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-08-02
2003-10-14
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031600, C106S031640
Reexamination Certificate
active
06632272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to light color W/O emulsion ink for stencil printing, and more particularly to light color stencil printing W/O emulsion ink which is excellent in weather resistance and is not affected by whiteness or color of the printing paper.
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.
Recently, there has been an increasing demand for inks of various colors, e.g., light color inks such as of light blue, slightly purplish light red and the like. As the stencil printing ink, W/O emulsion ink is generally used. Though 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, there has been made no specific proposal on light color ink for stencil printing.
Recently, an increasing number of users have come to use printing papers which are low in whiteness since they are manufactured without use of bleaching agent in order to suppress environmental pollution, or color printing papers, for instance, in order to enhance the advertising effect.
There has been a problem that light color ink is apt to be affected by the whiteness or color of the printing paper and accordingly it is difficult to obtain an expected color when a light color ink is transferred to a low whiteness printing paper or a color printing paper. Further, in the case of a light color ink which is small in the chromatic pigment content, change with time of the pigments largely affects the color of the ink and the color of the ink is apt to change.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide light color stencil printing emulsion ink which produces the same color irrespective of the kind or the color of the printing paper and the color development performance of which is stable against time.
In accordance with the present invention, there is provided a light color W/O emulsion ink for stencil printing, characterized by
containing therein chromatic pigment in an amount not smaller than 0.1% and smaller than 1% by weight of the total weight of the ink and white pigment in an amount not smaller than 7% and not larger than 20% by weight of the total weight of the ink.
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 the white pigment be titanium oxide.
It is preferred that the chromatic pigment be at least one of a 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.
When two or more chromatic pigments are contained, it is preferred that the chromatic pigments be different from each other in hue. The “hue” as used here means 10 colors, i.e., yellow, green yellow, green, blue green, blue, purple blue, purple, red purple, red and yellow red. When two or more chromatic pigments are contained, they may be either of the same series or of the different series.
The light color W/O emulsion ink for stencil printing of this embodiment is especially suitable for printing on a low whiteness printing paper or a color printing paper.
The light color W/O emulsion ink for stencil printing produces the same color irrespective of the kind or the color of the printing paper. It may be considered that this is because the color of the printing paper is covered with the opaque white pigment. When printing with the emulsion ink of this invention, a color image of a desired hue, a desired chroma and a desired brightness can be obtained even if printing is made on a low whiteness printing paper which is not higher than 70 (especially 60) in Hunter whiteness or a color printing paper such as of red, blue or yellow.
When titanium oxide which is excellent in whiteness, hiding power, coloring power and weather resistance, is employed as the white pigment, the aforesaid effect is further enhanced.
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.
By producing an ink selecting two or more chromatic pigments of different colors from the aforesaid group, an ink which can produce light and finer hue and is very stable in color development performance (free from discoloring) can be obtained.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail with reference to embodiments, hereinbelow.
The light color W/O emulsion ink for stencil printing in accordance with the present invention is characterized by containing therein chromatic pigment in an amount not smaller than 0.1% and smaller than 1% by weight of the total weight of the ink and white pigment in an amount not smaller than 7% and not larger than 20% by weight of the total weight of the ink.
As described above, the light color W/O emulsion ink for stencil printing of the present invention produces the same color irrespective of the kind or the color of the printing paper. It may be considered that this is because the opaque white pigment hides the color of the printing paper and acts as the ground, whereby the same color as that obtained when the ink is transferred to a high whiteness printing paper is obtained. When the content of the white pigment is smaller than 7% by weight, whiteness, hiding power and the like of the white pigment becomes insufficient. To the contrast, when the content of the white pigment is larger than 20% by weight, adjustment of viscosity of ink and maintenance of stability against storage become difficult. From these viewpoints, it is especially preferred that the content of white pigment is in the range of 10% by weight to 20% by weight.
Titanium oxide, zinc sulfide, lithopone, zinc white, white lead and the like may be employed as the white pigment. Among those, titanium oxide is preferred because of its excellent whiteness, hiding power, coloring power and weather resistance. The titanium oxide may be any titanium oxide known as pigment and preferably is 0.1 to 0.5 &mgr;m in primary particle size. Among various titanium oxides, titanium oxides of rutile structure are especially excellent in hiding power and weather resistance and are preferred. The white pigment may be contained in either of the oil phase and the water phase. However, since the oil phase penetrates the printing paper more rapidly than the water phase, the white pigment is apt to cover the chromatic pigment to hide it if the white pigment
Hayashi Yoshihiro
Yonekawa Hirotoshi
Klemanski Helene
Nixon & Peabody LLP
Riso Kagaku Corporation
Studebaker Donald R.
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