Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-07-03
2004-06-15
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031900, C106S031650, C106S415000, C106S472000, C106S403000
Reexamination Certificate
active
06749676
ABSTRACT:
TECHNICAL FIELD
This invention relates to erasable inks, and more particularly to erasable inks for use in writing instruments.
BACKGROUND
Some writing instruments, e.g., pens and markers, include erasable inks which allow markings formed with the ink to be erased. It is desirable that such inks be easily erased using a conventional eraser, that erasure be substantially complete, and that it be possible to erase the marking both immediately after the marking is made and after a period of time has elapsed. It is also desirable that erasable inks provide good writing performance when compared with non-erasable inks.
SUMMARY
This invention provides erasable inks that provide good writing performance when used in writing instruments.
In accordance with one aspect of the invention, an erasable ink for use in a writing instrument comprises a solvent and a pigment having a flake-like morphology. The pigment is dispersed in the solvent, and the ink is substantially free of colorants other than the pigment.
In accordance with another aspect of the invention, an erasable ink for use in a writing instrument comprises a solvent and a flake-like pigment. The pigment has an average diameter from about 1 micron to about 25 microns, and is dispersed in the solvent.
In accordance with another aspect of the invention, an erasable ink for use in a writing instrument comprises a solvent and a flake-like pigment. The pigment has an average thickness of less than about 1 micron, and is dispersed in the solvent.
In accordance with an additional aspect of the invention, a method of forming an erasable marking on a paper substrate comprises making a marking on the substrate with a writing instrument containing an erasable ink. The erasable ink comprises a solvent and a pigment having a flake-like morphology. The pigment is dispersed in the solvent, and the ink is substantially free of colorants other than the pigment.
In accordance with yet another aspect according to the invention, a method of forming an erasable marking on a paper substrate comprises making a marking on the substrate with a writing instrument containing an erasable ink. The erasable ink comprises a solvent and a flake-like pigment. The pigment has an average diameter from about 1 micron to about 25 microns, and is dispersed in the solvent.
In accordance with another aspect according to the invention, a method of forming an erasable marking on a paper substrate comprises making a marking on the substrate with a writing instrument containing an erasable ink. The erasable ink comprises a solvent and a flake-like pigment. The pigment has an average thickness of less than about 1 micron, and is dispersed in the solvent.
In accordance with yet another aspect according to the invention, a writing instrument comprises a reservoir containing an erasable ink. The erasable ink comprises a solvent and a pigment having a flake-like morphology. The pigment is dispersed in the solvent, and the ink is substantially free of colorants other than the pigment.
In accordance with another aspect according to the invention, a writing instrument comprises a reservoir containing an erasable ink. The erasable ink comprises a solvent and a flake-like pigment. The pigment has an average diameter from about 1 micron to about 25 microns, and is dispersed in the solvent.
In accordance with another aspect according to the invention, a writing instrument comprises a reservoir containing an erasable ink. The erasable ink comprises a solvent and a flake-like pigment. The pigment has an average thickness of less than about 1 micron, and is dispersed in the solvent.
These and other features, aspects, and advantages of the invention will become better understood with regard to the following description and appended claims.
DETAILED DESCRIPTION
This invention provides erasable inks for use in writing instruments. Erasability can be obtained by using pigments having a flake-like morphology as the primary colorant in the ink. In preferred inks, such pigments are the only colorant in the ink, i.e., the ink is substantially free of dyes, and of pigments having a non-flake-like morphology, as these colorants will tend to interfere with erasability.
Some preferred inks are also shear-thinning, i.e., the inks are non-Newtonian liquids that exhibit shear-thinning flow behavior when subjected to shear. Preferred shear-thinning inks of the invention become thin, readily flowable liquids having a viscosity of no greater than about 1000 mPa sec at shear rates greater than about 100 sec
−1
.
In one aspect, the invention features an erasable ink for use in a writing instrument including a solvent, and, dispersed in the solvent as a colorant, a pigment having a flake-like morphology, the ink being substantially free of other colorants.
Implementations of this aspect of the invention may include one or more of the following features. The pigment is a pearlescent pigment. The pigment is selected from the group consisting of mica flake pigments, graphites, and metal flake pigments. The pigment has a radius of gyration of at least about 0.5 micron. The ink exhibits an erasability of at least 80%. The solvent includes an aqueous solvent system. The ink is shear-thinning. The ink has a shear-thinning index of between about 0.01 and about 0.8.
In another aspect, the invention features an erasable ink for use in a writing instrument, including a solvent and, dispersed in the solvent as a colorant, a pigment having a radius of gyration of at least about 0.5 micron.
Implementations of this aspect of the invention may include one or more of the following features. The pigment is a pearlescent pigment. The pigment is selected from the group consisting of mica flake pigments, graphites, and metal flake pigments. The ink exhibits an erasability of at least 80%. The solvent includes an aqueous solvent system. The ink is shear-thinning. The ink has a shear-thinning index of between about 0.01 and about 0.8.
In a further aspect, the invention features an erasable ink for use in a writing instrument, including a solvent and, dispersed in the solvent as a colorant, a pigment having an aspect ratio of from about 1 to about 8.
Implementations of this aspect of the invention may include one or more of the following features. The pigment is a pearlescent pigment. The pigment is selected from the group consisting of mica flake pigments, graphites, and metal flake pigments. The pigment has a radius of gyration of at least about 0.5 micron. The ink exhibits an erasability of at least 80%. The solvent includes an aqueous solvent system. The ink is shear-thinning. The ink has a shear-thinning index of between about 0.01 and about 0.8.
When used in a writing instrument, preferred inks exhibit even laydown and good line intensity, e.g., a line intensity greater than about 25 percent, more preferably greater than about 30 percent, good line uniformity, and good writing performance.
As used herein, the term “laydown” refers to the amount of ink that is deposited on a substrate when making a marking of a particular length. Typical laydown for the preferred pearlescent inks is between about 0.1 mg/m and about 15.0 mg/m; preferably, between about 1.0 mg/m and about 12.0 mg/m; and most preferably, between about 5.0 mg/m and about 10.0 mg/m.
As used herein, the term “even laydown” refers to the morphology of the ink when it is applied to a substrate to create a continuous marking and is characterized by minimal skipping, i.e., few voids within the written line, and uniform thickness, i.e., the width of the written line is approximately constant along the length of the line.
As used herein, the term “line intensity” refers to the intensity of a marking made on a substrate such as paper. The intensity of a marking can be measured as the average gray value of the detected tracings (black=0; white=255). The percent intensity of the writing with an average gray value of z is then calculated as: % Intensity=(1−[z/255]) multiplied by 100. Alternatively, the intensity of a marking can b
Czubarow Pawel
Spencer Jean L.
Bell Mark L.
Berol Corporation
Faison Veronica F.
Marshall & Gerstein & Borun LLP
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