U.S. patent application number 09/771053 was filed with the patent office on 2001-08-23 for writing instrument.
This patent application is currently assigned to Mitsubishi Pencil Kabushiki Kaisha. Invention is credited to Koyama, Takao.
Application Number | 20010016142 09/771053 |
Document ID | / |
Family ID | 18553458 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016142 |
Kind Code |
A1 |
Koyama, Takao |
August 23, 2001 |
Writing instrument
Abstract
Provided is a free ink type writing instrument having an ink
tank part for storing an ink, in which an amount of the ink can
visually be observed. The free ink type writing instrument is
characterized by that the whole or a part of an internal surface
part in contact with the ink in the ink tank part has a smaller
critical surface tension than a surface tension of the ink, and a
contact angle between the ink and the whole or a part of the
internal surface part in contact with the ink in the ink tank part
is 30.degree. or more at a temperature of 25.degree. C.
Inventors: |
Koyama, Takao;
(Ashikaga-shi, JP) |
Correspondence
Address: |
DARBY & DARBY P. C.
805 Third Avenue
New York
NY
10022
US
|
Assignee: |
Mitsubishi Pencil Kabushiki
Kaisha
|
Family ID: |
18553458 |
Appl. No.: |
09/771053 |
Filed: |
January 26, 2001 |
Current U.S.
Class: |
401/222 ;
401/192; 401/194 |
Current CPC
Class: |
B43K 5/02 20130101; B43K
5/005 20130101; B43K 7/005 20130101; C09D 11/16 20130101; B43K 7/01
20130101; B43K 8/003 20130101; B43K 8/03 20130101 |
Class at
Publication: |
401/222 ;
401/192; 401/194 |
International
Class: |
B43K 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2000 |
JP |
2000-27962 |
Claims
What is claimed is:
1. A free ink type writing instrument of having an ink tank part
for storing an ink, wherein the whole or a part of an internal
surface part in contact with the ink in the ink tank part has a
smaller critical surface tension than a surface tension of the ink,
and a contact angle between the ink and the whole or a part of the
internal surface part in contact with the ink in the ink tank part
is 30.degree. or more at a temperature of 25.degree. C.
2. The writing instrument as described in claim 1, wherein the
whole of the member of the ink tank part or the whole or a part of
the internal surface part of the ink tank part comprises
polymethylpentene.
3. The writing instrument as described in claim 1 or 2, wherein the
ink has a surface tension of 50 mN/m or less at a temperature of
25.degree., and a contact angle between the ink and the internal
surface part in contact with the ink in the ink tank part is
30.degree. to 90.degree. at a temperature of 25.degree. C.
4. The writing instrument as described in any of claims 1 to 3,
wherein the ink has a viscosity of 1000 mPa's or less at a
temperature of 25.degree..
5. The writing instrument as described in any of claims 1 to 4,
wherein a principal solvent of the ink comprises an organic
solvent.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a free ink type writing
instrument in which an ink stored in an ink tank is fed directly to
a pen tip or a writing instrument provided with an ink tank of a
cartridge type for storing an ink, wherein visibility of an amount
of the ink is excellent.
[0003] 2. Description of the Related Art
[0004] In general, it can be given as one of the characteristics of
a free ink type writing instrument that an amount of the ink can be
observed (visibility). That is, in a free ink type writing
instrument, an ink is filled in an ink tank which is a holder part,
and the ink freely moves in the ink tank; and when the pen tip is
turned downward, the amount of the ink can visually be confirmed
through a visible part of the holder part.
[0005] At present, polypropylene which is excellent in transparency
and solvent resistance and which has a good moldability is used for
a holder part for a free ink type writing instrument since the
visibility can be secured.
[0006] In the present situation, however, only a free ink type
writing instrument using a water-based ink having a fluorescent
color or a bright color such as a pen for underlining makes it
possible to visually confirm relatively easily an amount of the
ink, while there involved is a problem that when used are a
water-based ink having a dark color such as black and blue and an
oil-based ink containing an organic solvent as a main solvent, a
free ink type writing instrument does not have sufficiently high
visibility of the amount of the ink yet and has not reached a
practical use level.
[0007] It has so far been known to provide a rib on an internal
surface of an ink tank part to elevate visibility in order to solve
these problems, but the effect thereof has not yet been
satisfactory.
[0008] Further, there have so far been tried various devices such
as using a fluororesin for an ink tank material, treating with
fluorine or silicone oils in order to provide an internal surface
with a low surface energy state (Japanese Patent Publication No.
Sho 38-20913) and using the rib described above in combination with
silicone oil treatment (Japanese Patent Application Laid-Open No.
Hei 11-216987).
[0009] However, in such devices as described in these publications,
it takes time until an ink is repelled and slides down (clear
draining) from an internal surface of an ink tank, and the effect
on visibility thereof is unsatisfactory; a tank material does not
have sufficient transparency, so that the effect thereof is not
sufficiently persistent; and moldability of the material is
inferior to require complicated steps, so that there involved is a
problem in terms of a cost. Thus, the existing state is that
satisfactory solutions have not yet been proposed.
[0010] In light of the problems and the status quo of the
conventional techniques described above, the present invention
intends to solve the problems, and an object thereof is to provide
a writing instrument which is excellent in visibility of an ink and
has excellent persistency of the effect thereof.
SUMMARY OF THE INVENTION
[0011] Intensive researches conducted by the present inventors in
order to solve the problems on the conventional techniques
described above have resulted in finding that a writing instrument
which meets the object described above can be obtained by
specifying a critical surface tension of the whole or a part of an
internal surface part in contact with an ink in an ink tank part
and a contact angle between the ink and the whole or a part of the
internal surface part in the ink tank part. Thus, the present
invention has been completed.
[0012] That is, the present invention comprises the following items
(1) to (5). (1) A free ink type writing instrument having an ink
tank part for storing an ink, wherein the whole or a part of an
internal surface part in contact with the ink in the ink tank part
has a smaller critical surface tension than a surface tension of
the ink, and a contact angle between the ink and the whole or a
part of the internal surface part in contact with the ink in the
ink tank part is 30.degree. or more at a temperature of 25.degree.
C. (2) The writing instrument as described in the above item (1),
wherein the whole of the member of the ink tank part or the whole
or a part of the internal surface part of the ink tank part
comprises polymethylpentene. (3) The writing instrument as
described in the above item (1) or (2), wherein the ink has a
surface tension of 50 mN/m or less at a temperature of 25.degree.,
and a contact angle between the ink and the internal surface part
in contact with the ink in the ink tank part is 30.degree. to
90.degree. at a temperature of 25.degree. C. (4) The writing
instrument as described in any of the above items (1) to (3),
wherein the ink has a viscosity of 1000 mPa's or less at a
temperature of 25.degree.. (5) The writing instrument as described
in any of the above items (1) to (4), wherein a principal solvent
of the ink comprises an organic solvent.
[0013] In the present invention, a "free ink type writing
instrument" means a writing instrument which has an ink tank for
directly storing an ink without absorbing in a sliver and in which
installed is an ink reservoir (collector member) for temporarily
reserving the ink pressed out from the ink tank when the air
contained in the ink tank is expanded by a rise in the temperature
so as to prevent the ink from blobbing from the pen tip or the air
hole.
[0014] The "critical surface tension" specified in the present
invention means a critical surface tension .gamma..sub.c
represented by a value of .gamma. corresponding to cos .theta.=1 on
a straight line obtained by measuring contact angles .theta. of
liquids on the surface of a solid which is hardly wet to water and
plotting (Zisman plot) values of cos .theta. against surface
tensions .gamma. of the liquids.
[0015] According to the present invention, provided is a writing
instrument which is excellent in visibility of an ink and
persistency of the effect thereof and which is prevented from being
subjected to surface treatment of the whole or a part of the ink
tank and therefore can be produced at a low cost without
complicated after-steps.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross section showing one example of specific
embodiments in which the writing instrument of the present
invention is applied to a marking pen.
[0017] FIGS. 2 (a) and (b) are cross sections and partial cross
sections showing one example of specific embodiments in which the
writing instrument of the present is applied to a ball point
pen.
[0018] FIG. 3 is a cross section showing one example of specific
embodiments in which the writing instrument of the present
invention is applied to a marking pen equipped with an ink tank of
a cartridge type.
[0019] FIGS. 4 (a) and (b) are cross sections and partial cross
sections showing other examples of specific embodiments in which
the writing instrument of the present is applied to a marking
pen.
[0020] FIGS. 5 (a), (b) and (c) are schematic explanatory drawings
each showing in order the writing instruments used in Examples 1, 2
and Examples 3, 4, Comparative Example 1 respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The embodiments of the present invention shall be explained
below in detail.
[0022] The writing instrument of the present invention is
characterized by a free ink type writing instrument having an ink
tank part for storing an ink, wherein the whole or a part of an
internal surface part in contact with the ink in the ink tank part
has a smaller critical surface tension than a surface tension of
the ink, and a contact angle between the ink and the whole or a
part of the internal surface part in contact with the ink in the
ink tank part is 30.degree. or more at a temperature of 25.degree.
C.
[0023] In the writing instrument of the present invention, used in
order to elevate visibility of an amount of the ink is an ink
having a surface tension (.gamma.) which is controlled to be larger
than a critical surface tension (.gamma..sub.c)
[.gamma..sub.c<.gamma.] of the whole of the member of the ink
tank part, or the whole or a part of the internal surface part of
the tank part, and a contact angle between the ink and the whole or
a part of the internal surface part in the ink tank part in the
present invention is set to 30.degree. or more at a temperature of
25.degree. C.
[0024] In the present invention, if an ink used has a surface
tension of .gamma..sub.c>.gamma. and the contact angle between
the ink and the whole or a part of the internal surface part in the
ink tank part is less than 30.degree. at a temperature of
25.degree. C., improvement in the visibility and the persistency of
the effect thereof which are the effects of the present invention
can not be maintained, and therefore they are not preferred.
[0025] In the writing instrument of the present invention, the
member of the ink tank part shall not specifically be restricted as
long as it is a member which has transmittance (transparency) of
visible rays and in which a contact angle between the ink and the
whole or a part of the internal surface part in the ink tank part
becomes 30.degree. or more, preferably 30 to 90.degree. at a
temperature of 25.degree. C. It includes, for example,
thermoplastic plastics having transparency and capable of being
injection-molded. To be specific, given as the examples thereof are
polypropylene, polyethylene, polyethylene terephthalate,
polystyrene, polyetherimide, polycarbonate, polysulfone,
acrylonitrile-styrene copolymers, butadiene-styrene-methyl
methacrylate terpolymers, ethylene-vinyl chloride copolymers,
ethylene-vinyl alcohol copolymers, polymethylpentene and
polyethersulfone.
[0026] In the writing instrument of the present invention, the ink
to be filled in the ink tank shall not specifically be restricted
as long as it has a surface tension (.gamma.) which is controlled
to be larger than a critical surface tension (.gamma..sub.c)
[.gamma..sub.c<.gamma.] of the whole of the member of the ink
tank part, or the whole or a part of the internal surface part of
the tank part. Capable of being used are, for example, water-based
inks or oil-based inks used for conventional writing instruments,
which are prepared by dissolving or dispersing colorants comprising
a dye and/or a pigment, resins, dispersants, surfactants and other
additives for a writing instrument in water (purified water and
ion-exchanged water) or a liquid obtained by mixing at least one of
organic solvents.
[0027] The organic solvents include, for example,
1-methoxy-2-propanol, 1-ethoxy-2-propanol, benzyl alcohol, ethanol,
ethylene glycol, carbitol, cellosolve, glycerin, diethylene glycol
stearate, propylene glycol, propylene glycol monomethyl ether,
1-propanol, 2-propanol, 1-butanol, 2-butanol and t-butyl
alcohol.
[0028] Additives which have so far been known such as a pH
controlling agent, a preservative and a rust preventive can
suitably be added as the other additives for a writing
instrument.
[0029] The present invention is effective in both of water-based
and oil-based inks, but particularly effective in an oil-based ink
containing a principal solvent comprising an organic solvent and
having a small surface tension.
[0030] The ink has a viscosity of 1000 mPa's or less, preferably
100 mPa's or less and more preferably 10 mPa's or less at
25.degree. C.
[0031] If the ink has a viscosity exceeding 1000 mPa's, it is hard
for the ink to move in the ink tank, and time which is required
until the ink is repelled and slides down is elongated and deviated
from a practical range. Thus, it becomes difficult to observe the
amount of the ink, and therefore such a viscosity is not
preferred.
[0032] In the writing instrument of the present invention, among
the thermoplastic resins described above, polymethylpenetene which
has such excellent transparency that a transmission factor of
visible rays is 90% or more and which has a small critical surface
tension (.gamma..sub.c) and good moldability is used for the whole
of the ink tank member or the whole or a part of the internal
surface of the tank.
[0033] Use of polymethylpenetene having a small critical surface
tension (.gamma..sub.c) expands a range of a surface tension of an
ink capable of being used and makes it easy to prepare various
kinds of inks. Further, if a surface tension of the ink is
controlled preferably to 24 mN/m or more, a contact angle between
the ink and the whole or a part of the internal surface part in the
ink tank part is controlled to 30.degree. or more at a temperature
of 25.degree. C., and this makes it possible to readily
mass-produce an ink tank part having excellent visibility of an
amount of the ink by conventional plastic molding without carrying
out after-processing such as surface treatment and providing a rib
on the internal surface of the ink tank and therefore is
preferred.
[0034] If the ink has a surface tension of less than 24 mN/m, the
internal surface of the ink tank part has to comprise a fluororesin
or has to be subjected to fluorine or silicone treatment in the
case of a free ink type writing instrument. A fluororesin has
problems on moldability, transparency and a cost, and fluorine or
silicone treatment have problems on persistency of the effect, a
treating step and a cost. Even if these devices work out well,
since capillary force between fins of a collector member in a
temporary reserving part is prescribed by a clearance between the
fins and a surface tension of the ink, the capillary force between
the fins is reduced when the surface tension of the ink is small,
so that the ink can not be reserved. Accordingly, if the ink has a
surface tension of less than 24 mN/m, the clearance has to be
reduced, but this is difficult in relation to a problem of
moldability and a temporary reserving volume.
[0035] Further, when the ink tank member is made of, for example,
polypropylene, visibility of an amount of the ink which is the
effect of the present invention, is not usually revealed if the ink
does not have a surface tension of 30 mN/m or more.
[0036] In the present invention, the ink has preferably a surface
tension of 50 mN/m or less, more preferably 24 to 50 mN/m at a
temperature of 25.degree. C., and a contact angle between the ink
and the whole or a part of the internal surface part in the ink
tank part is preferably 30.degree. to 90.degree. at a temperature
of 25.degree. C.
[0037] If the ink has a surface tension exceeding 50 mN/m, and the
contact angle between the ink and the internal surface part in the
ink tank part exceeds 90.degree., the ink stays in the state that
it sticks to the internal surface part in the ink tank part because
of a large surface tension of the ink itself and difficulty in
wetting of the ink onto the internal surface part in the ink tank
part, which results in bringing about the problem that the ink is
inhibited from moving in the ink tank part.
[0038] As described above, the structure of the writing instrument
in the present invention shall not specifically be restricted as
long as in the free ink type writing instrument having an ink tank
for storing an ink, the whole or a part of the internal surface
part in contact with the ink in the ink tank part has a smaller
critical surface tension than a surface tension of the ink, and a
contact angle between the ink and the whole or a part of the
internal surface part in contact with the ink in the ink tank part
is 30.degree. or more at a temperature of 25.degree. C. Various
structures of free ink type writing instruments which have so far
been used can be applied thereto. The embodiments of the writing
instruments showing the specific structures of the present
invention shall further be explained below with reference to the
drawings.
[0039] FIG. 1 is a cross section showing one example of specific
embodiments in which the free ink type writing instrument of the
present invention is applied to a marking pen.
[0040] In the free ink type writing instrument A of the present
embodiment, an ink 11 is, as shown in FIG. 1, filled in an ink tank
part 10 which is a holder part. In the present embodiment, the
whole of the member in the ink tank part 10 is composed of
polymethylpentene having excellent transparency.
[0041] A numeral 12 in FIG. 1 is a collector member; a numeral 13
is a holder member; a numeral 14 is a feeder; and a numeral 15 is a
pen feeder which is a pen tip. The ink 11 is derived from the ink
tank 10 into the pen tip 15 via the feeder 14 having an ink passage
which is disposed in a central hole 12a of the collector part
12.
[0042] In the writing instrument A of the present embodiment, the
whole of the internal surface part in contact with the ink 11 in
the ink tank part 10 has a smaller critical surface tension than a
surface tension of the ink 11, and a contact angle between the ink
11 and the whole of the internal surface part in contact with the
ink 11 in the ink tank part 10 is set to 30.degree. or more,
preferably 30 to 90.degree. at a temperature of 25.degree. C.
Further, a surface tension of the ink is set to 50 mN/m or less,
preferably 24 to 50 mN/m at a temperature of 25.degree. C. This
allows the ink 11 to be repelled from the internal surface of the
ink tank and to slide down (clear draining) for a short time and
causes visibility of an amount of the ink to be very excellent.
[0043] In this writing instrument A, only charging the ink tank 10
having the characteristics described above with the ink having the
characteristics described above provides a free ink type writing
instrument which is excellent in visibility of an amount of the
ink. The intended free ink type writing instrument can be produced
without passing through a conventional step for forming a rib shape
in an ink tank part for the purpose of improving visibility of an
amount of the ink, and therefore a free ink type writing instrument
which is excellent in terms of productivity and a cost can be
provided.
[0044] FIGS. 2 (a) and (b) are explanatory drawings showing a
specific embodiment in which the free ink type writing instrument
is applied to a ball point pen.
[0045] In the free ink type writing instrument B of the present
embodiment, an ink 21 is filled in an ink tank part 20 having a
visible part 20a and, the whole of a member of the ink tank part 20
is composed of polymethylpentene having excellent transparency. The
whole of an internal surface part in contact with the ink 21 in the
ink tank part 20 has a smaller critical surface tension than a
surface tension of the ink 21, and a contact angle between the ink
21 and the whole of the internal surface part in contact with the
ink 21 in the ink tank part 20 is set to 30.degree. or more,
preferably 30 to 90.degree. at a temperature of 25.degree. C.
Further, a surface tension of the ink is set to 50 mN/m or less,
preferably 24 to 50 mN/m at a temperature of 25.degree. C.
[0046] A coating film such as a coated film and a metal-deposited
film is provided on a surface part of the ink tank 20 excluding the
visible part 20a described above to form an opaque part from which
the ink is invisible.
[0047] A numeral 22 in FIG. 2 is a collector member; a numeral 23
is a holder member; a numeral 24 is an ink feeder comprising a
guiding feeder 24a and a center feeder 24b; and a numeral 25 is a
pen tip comprising a ball point pen tip. The ink 21 is derived from
the ink tank 20 into the pen tip 25 via the feeder 24 which
comprises the guiding feeder 24a and the center feeder 24b and has
an ink passage and which is disposed in a central hole 22a of the
collector part 22.
[0048] In the writing instrument B of the present embodiment, a
visible part 20a (another visible part having the same structure on
a back face side which is a reverse side) is formed on a part of
the ink tank 20. Even if this visible part 20a (transparent window)
is a part of the ink tank 20, the relation of the critical surface
tension described above to a surface tension of the ink and the
relation of the contact angle between the ink and a part of an
internal surface part which is the visible part of the ink tank do
not allow the ink to remain on a surface of the visible part 20a
and cause the ink to be repelled from the internal surface of the
ink tank and to slide down for a short time. Accordingly, obtained
is the writing instrument which is very excellent in visibility of
an amount of the ink.
[0049] In particular, when a visible part is formed in a part of an
ink tank, the ink-repelling property thereof is inferior even if
the ink tank is provided with a rib shape in a conventional free
ink type writing instrument filled with an ink having a dark color
such as black and blue, and the visibility thereof is still
problematic. In the writing instrument of the present invention,
however, ink components do not remain on the surface of the visible
part 20a even in the free ink type writing instrument filled with
an ink having a dark color such as black and blue, and the ink is
repelled for a short time. Accordingly, obtained is the writing
instrument which is very excellent in visibility of an amount of
the ink.
[0050] FIG. 3 is an explanatory drawing for explaining a specific
embodiment of a writing instrument (marking pen) equipped with an
ink tank of a cartridge type.
[0051] As shown in FIG. 3, the cartridge type writing instrument C
of the present embodiment is composed of an ink tank 30 of a
cartridge type, a writing instrument main body 40 and a cap body
50.
[0052] The whole of the ink tank 30 of a cartridge type is composed
of polymethylpentene, and an ink 31 and a sealing ball 32 are
present in the ink tank 30.
[0053] The writing instrument main body 40 has a front holder 41
and a rear holder 42, and the front holder 41 is provided therein
with a collector member 43, a holder member 44, a feeder 45 and a
pen feeder 46 which is a pen tip. The rear holder 42 is provided
therein with a cylinder part 47 to be integrated with the front
holder 41, a seal-receiving part 48 and a cylindrical projection
49. All of the front holder 41, the cylinder part 47 and the rear
holder 42 are composed of polycarbonate.
[0054] The ink 31 is derived from the ink tank 30 of a cartridge
type into the pen feeder 46 via the feeder 45 having an ink passage
which is disposed in a central hole 43a of the collector part
43.
[0055] In the writing instrument C of the present embodiment, the
whole of an internal surface part in contact with the ink in the
ink tank 30 of a cartridge type has a smaller critical surface
tension than a surface tension of the ink 31, and a contact angle
between the ink and the whole of the internal surface part in
contact with the ink 31 in the ink tank part 30 is set to
30.degree. or more, preferably 30 to 90.degree. at a temperature of
25.degree. C. Further, a surface tension of the ink is set to 50
mN/m or less, preferably 24 to 50 mN/m at a temperature of
25.degree. C. This allows the ink 31 to be repelled from the
internal surface of the ink tank and to slide down for a short time
and causes visibility of an amount of the ink to be very excellent.
In the case of the writing instrument C of the present embodiment,
the amount of the ink in the ink tank 30 of a cartridge type is
visually confirmed mainly via the rear holder 42 having
transparency in the writing instrument main body.
[0056] FIGS. 4 (a) and (b) are another example of specific
embodiments in which the free ink type writing instrument of the
present invention is applied to a marking pen. The same members as
in the writing instrument A shown in FIG. 1 are shown by the same
symbolss, and therefore explanations thereof shall be omitted.
[0057] The writing instrument D of the present embodiment is
different from the writing instrument A shown in FIG. 1 having the
ink tank part the whole of which is composed of polymethylpentene
having excellent transparency in the following points; a member of
an ink tank part 10 is composed of polypropylene having
transparency; a cylindrical transparent body 16 which is composed
of polymethylpentene having excellent transparency is installed on
an internal circumference of the ink tank part 10 so that it comes
in contact with an end face of a collector member 12; and a coating
film such as a coated film and a metal-deposited film is provided
on a surface part of the ink tank part 10 excluding a visible part
(transparent window) 10a of the ink tank part 10 to form an opaque
part from which the ink is invisible.
[0058] In the writing instrument D of the present embodiment, an
internal surface part of the transparent body 16 that is provided
in a part of the ink tank part 10, which comes to contact with the
ink 11, has a smaller critical surface tension than a surface
tension of the ink 11, and a contact angle between the ink 11 and
the internal surface part of the transparent body 16 in contact
with the ink 11 is set to 30.degree. or more, preferably 30 to
90.degree. at a temperature of 25.degree. C. Further, a surface
tension of the ink is set to 50 mN/m or less, preferably 24 to 50
mN/m at a temperature of 25.degree. C. This allows the ink 11 to be
repelled from the internal surface of the transparent body 16 and
to slide down for a short time and causes visibility of an amount
of the ink to be very excellent. In the case of the writing
instrument D of the present embodiment, the amount of the ink in
the ink tank part 10, which is to be finally consumed, is visually
confirmed via the visible part 10a in the writing instrument body
10.
[0059] The free ink type writing instrument of the present
invention shall not be restricted to the marking pen and the ball
point pen of the embodiments A, B and D described above and can be
applied as well to a brush pen, a fountain pen and a felt tip pen.
The writing instrument of the embodiment C described above which is
provided with the ink tank of a cartridge type can be applied to,
for example, a felt tip pen, a ball point pen and a fountain pen
which are provided with an ink tank of a cartridge type. Further,
it can be applied as well to an applicator prepared by substituting
a coater and a cosmetic liquid such as a manicure liquid or a
liquid drug having a pharmacological effect, for the pen tip and
the ink respectively.
[0060] In the embodiments A to D described above, polymethylpentene
is used, but as described above, polypropylene, polyethylene,
polyethylene terephthalate and polycarbonate may be used.
[0061] The writing instrument of the present invention is
constituted as described above. In the writing instrument of a free
ink type having an ink tank for storing an ink, a critical surface
tension of the whole or a part of the internal surface part in
contact with the ink in the ink tank part is smaller than a surface
tension of the ink, and a contact angle between the ink and the
whole or a part of the internal surface part in contact with the
ink in the ink tank part is set to 30.degree. or more at a
temperature of 25.degree. C., whereby the ink is readily repelled
from the internal surface in the ink tank part and slides down for
a short time, so that it is very excellent in visibility of an
amount of the ink.
EXAMPLES
[0062] Next, the present invention shall be explained in further
details with reference to examples and comparative examples, but
the present invention shall by no means be restricted to the
following examples. FIG. 5 (a), (b) and (c) are schematic
explanatory drawings each showing the writing instruments used in
Examples 1, 2 and Examples 3, 4, Comparative Example 1
respectively.
Example 1
[0063] A marking pen shown in FIG. 1 and FIG. 5 (a) was prepared.
That is, polymethylpentene (TPX RT-18XB, manufactured by Mitsui
Chemicals Inc.) was used and molded to obtain an ink tank part
(holder) having an outer diameter of 10 mm, an inner diameter of 8
mm and a length of 80 mm.
[0064] The critical surface tension of polymethylpentene obtained
by Zisman-plot was 23.3 mN/m (25.degree. C.).
[0065] The ink tank part was charged with an ink having the
following composition.
1 (parts by weight) Propylene glycol monomethyl ether 79.95 Ketone
resin (Hilac 110H, manufactured 10 by Hitachi Chemical Co., Ltd.)
Dye (Valifast Black #1308, manufactured 5 by Orient Chemical Ind.,
Ltd.) Benzyl alcohol 5 Surfactant (KP361, manufactured by 0.05
Shin-Etsu Chemical Co., Ltd.)
[0066] A black ink having the composition described above was
charged into the ink tank to such an extent that the whole volume
of the tank was filled by about 30%.
[0067] The following ink physical properties were obtained. Surface
tension: 25 mN/m (25.degree. C.) Viscosity: 5 mPa's (25.degree. C.)
Contact angle: 32.8 degree (to polymethylpentene; 25.degree.
C.)
Example 2
[0068] Polypropylene (J229 E manufactured by Mitsui Chemicals Inc.)
was used to mold an ink tank part (holder) having the same
dimension as in Example 1, and telescopically inserted into a
central part of the ink tank was a transparent body prepared by
molding polymethylpentene into a ring shape (cylinder) having an
outer diameter of 8 mm, an inner diameter of 7.5 mm and a length of
10 mm (refer to FIG. 4 (a) and FIG. 5 (b)), and thus a part of an
internal surface of the ink tank part was formed from
polymethylpentene (transparent body). The writing instrument of
Example 2 is a little different from the writing instrument shown
in FIG. 4 (a) in the point that the transparent body 16 is disposed
in the middle part (this part is a transparent window and a visible
part).
[0069] The ink tank part was charged with an ink having the
following composition.
2 (parts by weight) Propylene glycol monomethyl ether 80 Ketone
resin (Hilac 110H, manufactured 10 by Hitachi Chemical Co., Ltd.)
Dye (Valifast Black #1308, manufactured 5 by Orient Chemical Ind.,
Ltd.) Benzyl alcohol 5
[0070] A black ink having the composition described above was
charged into the ink tank to such an extent that the whole volume
of the tank was filled by about 30%.
[0071] The following ink physical properties were obtained. Surface
tension: 27.4 mN/m (25.degree. C.) Viscosity: 5 mPa's (25.degree.
C.) Contact angle: 40.0 degree (to polymethylpentene; 25.degree.
C.)
Example 3
[0072] A marking pen shown in FIG. 1 and FIG. 5 (c) was
prepared.
[0073] Polypropylene (J229E, manufactured by Mitsui Chemicals Inc.)
was used and molded to obtain an ink tank part (holder) having an
outer diameter of 10 mm, an inner diameter of 8 mm and a length of
80 mm.
[0074] The critical surface tension of polypropylene obtained by
Zisman-plot was 29 mN/m (25.degree. C.).
[0075] The ink tank part was charged with an ink having the
following composition.
3 (parts by weight) Diethylene glycol monomethyl ether 60 Ketone
resin (Hilac 110H, manufactured 10 by Hitachi Chemical Co., Ltd.)
Dye (SBN Blue-701, manufactured by 5 Hodogaya Chemical Co., Ltd.)
Diethylene glycol monoethyl ether 20 Propylene glycol monomethyl
ether 5
[0076] A blue ink thus obtained was charged into the ink tank to
such an extent that the whole volume of the tank was filled by
about 30%.
[0077] The following ink physical properties were obtained. Surface
tension: 33.6 mN/m (25.degree. C.) Viscosity: 7.8 mPa's (25.degree.
C.) Contact angle: 36 degree (to polypropylene; 25.degree. C.)
Example 4
[0078] A marking pen shown in FIG. 1 and FIG. 5 (c) was
prepared.
[0079] Polypropylene (J229E, manufactured by Mitsui Chemicals Inc.)
was used and molded to obtain an ink tank part having an outer
diameter of 10 mm, an inner diameter of 8 mm and a length of 80
mm.
[0080] The critical surface tension of polypropylene obtained by
Zisman-plot was 29 mN/m (25.degree. C.).
[0081] The ink tank part was charged with an ink having the
following composition.
4 (parts by weight) Ethylene glycol monomethyl ether 50 Ketone
resin (Hilac 110H, manufactured 15 by Hitachi Chemical Co., Ltd.)
Dye (SBN Blue-701, manufactured by 5 Hodogaya Chemical Co., Ltd.)
Ethylene glycol monophenyl ether 20 Propylene glycol monomethyl
ether 10
[0082] A blue ink thus obtained was charged into the ink tank to
such an extent that the whole volume of the tank was filled by
about 30%.
[0083] The following ink physical properties were obtained. Surface
tension: 33 mN/m (25.degree. C.) Viscosity: 7.2 mPa's (25.degree.
C.) Contact angle: 35 degree (to polypropylene; 25.degree. C.)
Example 5
[0084] A marking pen shown in FIG. 1 was prepared.
[0085] Polyethylene (high density polyethylene, manufactured by
Mitsui Chemicals Inc.) was used and molded to obtain an ink tank
part having an outer diameter of 10 mm, an inner diameter of 8 mm
and a length of 80 mm.
[0086] The critical surface tension of polyethylene obtained by
Zisman-plot was 30 mN/m (25.degree. C.).
[0087] The ink tank part was charged with an ink having the
following composition.
5 (parts by weight) Diethylene glycol monomethyl ether 50 Ketone
resin (Hilac 110H, manufactured 15 by Hitachi Chemical Co., Ltd.)
Dye (SBN Blue-701, manufactured by 5 Hodogaya Chemical Co., Ltd.)
Diethylene glycol monophenyl ether 20 Propylene glycol monomethyl
ether 10
[0088] A blue ink thus obtained was charged into the ink tank to
such an extent that the whole volume of the tank was filled by
about 30%.
[0089] The following ink physical properties were obtained. Surface
tension: 33.7 mN/m (25.degree. C.) Viscosity: 10.8 mPa's
(25.degree. C.) Contact angle: 37 degree (to polyethylene;
25.degree. C.)
Comparative Example 1
[0090] The ink tank prepared in Example 3 was used for an ink tank
part (refer to FIG. 1 and FIG. 5 (c)).
[0091] The critical surface tension of polypropylene obtained by
Zisman-plot was about 29 mN/m (25.degree. C.).
[0092] Used was the same ink as in Example 1 [surface tension: 25
mN/m (25.degree. C.), viscosity: 5 mPa's (25.degree. C.) and
contact angle: 20.0 degree (to polypropylene; 25.degree. C.)].
[0093] The writing instruments (samples) obtained in Examples 1 to
5 and Comparative Example 1 were used to evaluate visibility of an
amount of the ink by the following method. Evaluation method of
visibility:
[0094] The visibility of the amount of the ink was evaluated by
slightly shaking the respective samples charged with the inks
upward and downward and then determining time consumed until the
amount of the ink can visually be confirmed after the inks are
repelled from the internal surfaces of the ink tanks. Accordingly,
the shorter the time, the better the visibility.
[0095] The evaluation results thereof are shown in the following
Table 1.
6TABLE 1 Evaluation results of visibility Time consumed until
confirming ink amount after ink is repelled Example 1 20 seconds or
shorter Example 2 10 seconds or shorter Example 3 20 seconds or
shorter Example 4 20 seconds or shorter Example 5 20 seconds or
shorter Comparative 300 seconds or longer Example 1
[0096] As apparent from the results shown in table 1 described
above, it has been found that the writing instruments prepared in
Examples 1 to 5 which fall in the scope of the present invention
are very excellent in visibility as compared with that prepare in
Comparative Example 1 which falls outside the scope of the present
invention.
[0097] To give specific considerations, in Example 1, the internal
surface in contact with the ink in the ink tank part has a smaller
critical surface tension (.gamma..sub.c=23.3 mN/m; 25.degree. C.)
than a surface tension (.gamma.=25 mN/m; 25.degree. C.) of the ink,
and the contact angle between the ink and the internal surface in
contact with the ink in the ink tank part is 32.8.degree.
(>30.degree.) at a temperature of 25.degree. C. Similarly in
Examples 2 to 5, the internal surfaces in contact with the inks in
the ink tank parts have smaller critical surface tensions
(.gamma..sub.c=23.3, 29, 29 and 30 mN/m respectively; 25.degree.
C.) than surface tensions (.gamma.=27.4, 33.6, 33 and 33.7 mN/m
respectively; 25.degree. C.) of the inks, and the contact angles
between inks and the internal surfaces in contact with the inks in
the ink tank parts are 40.0.degree., 36.degree., 35.degree. and
37.degree. (>30.degree.) at a temperature of 25.degree. C. Thus,
it can be found that they are very excellent in a visibility.
[0098] In contrast with this, in Comparative Example 1, the
internal surface in contact with the ink in the ink tank part has a
larger critical surface tension (.gamma..sub.c29 mN/m; 25.degree.
C.) than a surface tension (.gamma.=25 mN/m; 25.degree. C.) of the
ink, and the contact angle between the ink and the internal surface
in contact with the ink in the ink tank part is 20.0.degree.
(<30.degree.) at a temperature of 25.degree. C. Accordingly, it
can be found that the sufficiently high visible effect can not be
exhibited.
* * * * *