Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-09
2003-01-07
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S489000, C524S548000
Reexamination Certificate
active
06503966
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a non-aqueous ball point pen ink and a ball point pen using the ink. Specifically, the present invention relates to a non-aqueous ink provided with pseudoplasticity. The ink is provided by blending a non-Newtonian viscosity imparting agent while applying a cohesive force by blending a thickening agent comprising polyvinyl pyrrolidone with a weight-average molecular weight of about 40,000 to 100,000 to eliminate ink blobbing and scratching. The present also related to a non-aqueous ball point pen using this ink.
BACKGROUND OF THE INVENTION
A conventional non-aqueous ball point pen has been designed by setting an ink viscosity in a range of 10,000 to 30,000 mPa•s at 20° C. to prevent leakage. However, when the viscosity during writing is high in this manner, the ball rotation resistance during writing automatically increases and writing smoothness is very low and fails to be satisfactory. Moreover, a high writing pressure is necessary during writing. In some cases, a load of 500 gf or more is applied to a pen point. The heavy load causes the pen point to be quickly damaged. Furthermore, ball breakage and writing defects frequently occur as a consequence. On the other hand, as disclosed in Japanese Patent Application Laid-Open Nos. 6-313143 (1994), 6-313144 (1994), 7-196972 (1995) and 9-48941 (1997), attempts were carried out to improve the above-described defects by creating inks having a pseudoplasticity viscosity property, where the ink viscosity during writing is low and where the ink viscosity is relatively high when writing is not performed. However, the but the attempts were not sufficient in enhancing the writing smoothness and completely preventing the leakage.
SUMMARY OF THE INVENTION
The present invention provides an ink which realizes a remarkably satisfactory writing smoothness, can be untilized for low pressure writing such as in conjunction with an aqueous ball point pen, forms a fresh drawn line, eliminates blobbing and feathering, and can completely prevent leakage. The present invention further provides a non-aqueous ball point pen in which no ink adheres to an ink reserving tube inner wall and an ink residual amount is clear.
The present invention relates to a non-aqueous ball point pen ink or ink composition in which a colorant, an organic solvent, a non-Newtonian viscosity imparting agent, and a thickening agent comprising only polyvinyl pyrrolidone with a weight-average molecular weight of about 40,000 to 100,000 are contained as main components. A non-Newtonian viscosity index of the ink may be as low as 0.1 and less than 0.4. The viscosity of the ink a shearing speed of 500 sec
−1
may be as low as 1,000 and less than 3,000 mPa•s at 20° C. The viscosity of the ink in the shearing speed of 0.19 sec
−1
may be as low as 40,000 mPa•s at 20° C. and as high as 70,000 mPa•s at 20° C. The non-aqueous ball point pen ink of this invention may contain polyvinyl pyrrolidone with the weight-average molecular weight of about 40,000 to 100,000 in a range of 1 to 3 mass % with respect to a total amount of the ink composition. The non-Newtonian viscosity imparting agent may be a fatty acid amide wax with a melting temperature of 140° C. or more, and the content may be in a range of 2 to 5 mass % with respect to the total amount of the ink composition.
The ink may be directly filled into an ink reserving tube of a ball point pen. The ink reserving tube of the ball point pen may be a polypropylene tube with silicone applied to an inner face.
PREFERRED EMBODIMENTS OF THE INVENTION
Various measures for enhancing a ball point pen stroke have been studied. Above all, it is a known fact that a ball rotation resistance exerts a remarkably large influence on the stroke, and it is also obvious that the ball rotation resistance depends on ink viscosity. Specifically, in order to enhance the stroke, it is a most effective measure to set the ink viscosity during writing to be as low as possible and reduce the ball rotation resistance. However, when the ink viscosity is set to be excessively low, problems such as leakage and blobbing, non-uniform line darkening (“scratching”) and blurring (“feathering”) due to absorption by paper, etc. naturally increase. As described above, the technique of setting pseudoplasticity as an ink viscosity property to solve these problems has been disclosed, but the writing with a remarkably low pressure like an aqueous ball point pen and smooth sroke have not been realized, and a fresh drawn line has not been obtained.
Concretely, in order to enable the writing with the remarkably low pressure like the aqueous ball point pen, realize the smooth stroke and obtain the fresh drawn line, the ink viscosity during writing should preferably be less than 3,000 mPa•s. In the present invention, a non-aqueous ink has been studied based on the prerequisite to invent a non-aqueous ball point pen ink which prevents leakage and blobbing, further scratching, and feathering from occurring, provides a superior touch, obtains a satisfactory drawn line and which causes no leakage. The blobbing means a phenomenon in which surplus ink during writing is accumulated in a pen point.
In the present invention, the viscosity in a shearing speed of 500 sec
−1
may be as low as 1,000 and less than 3,000 mPa•s at 20° C., even though ink outside of this range is still acceptable. This is a viscosity area essential for realizing a remarkably smooth stroke, and obtaining a fresh drawn line like the aqueous ball point pen. With the viscosity less than 1,000 mPa•s, the problem of feathering cannot be effectively prevented. Moreover, no satisfactory oil film can be formed between a ball and a ball seat and the intrinsic smoothness of the non-aqueous ball point pen can be deteriorated. On the other hand, with the viscosity of 3,000 mPa•s or more, it is difficult to obtain a fresh drawn line relative to that obtained by an aqueous ball point pen. Specifically, in order to obtain a satisfactory stroke, the ink viscosity in the shearing speed of 500 sec
−1
should preferably be set substantially to 10,000 mPa•s or less. However, when the viscosity is 3,000 mPa•s or more, a complete transfer type ball point pen, that is, a writing system of transferring the ink to a paper surface only via the ball can be constituted, the penetration to paper is reduced because of the high viscosity and no fresh drawn line can therefore be obtained.
According to experiments by the inventors of the present invention, when the ink viscosity in the shearing speed of 500 sec
−1
is less than 3,000 mPa•s, a writing utensil also utilizing the penetration to the paper surface can be obtained and a very fresh drawn line can be obtained. The ink viscosity described herein is measured in a measurement environment of 20° C. using a rheometer CSL manufactured by British Carrymay, Ltd.
The most important constituting requirement in the present invention lies in that the ink viscosity in the shearing speed of 500 sec
−1
is set as low as 1,000 and less than 3,000 mPa•s at 20° C., a non-Newtonian viscosity index is set as low as 0.1 and less than 0.4, remarkably low, the viscosity in the shearing speed of 0.19 sec
−1
is further set to 40,000 mPa•s (at 20° C.) or more, and the ink is provided with pseudoplasticity. The necessity for setting the ink viscosity during writing to be low has been described above, but in this viscosity area, the leakage and blobbing, further scratching, and feathering could be increased. In order to prevent these defects, the necessity of setting the non-Newtonian viscosity index as low as 0.1 and less than 0.4 and setting the viscosity in the shearing speed of 0.19 sec
−1
to 40,000 mPa•s at 20° C. or more arises. In other words, the above-described defects can be prevented by setting the pseudoplasticity as the ink viscosity property to be strong and setting the ink viscosity to be high during low shearing, that is, when not wr
Fujii Takeshi
Fukasawa Teruaki
Funabashi Kahori
Jagannathan Vasu
Kabushiki Kaisha Pilot
Rader & Fishman & Grauer, PLLC
Shosho Callie E.
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