JP2001287493A - Writing instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct liquid feed type writing instrument capable of visually recognizing a residue of an ink liquid. SOLUTION: The direct liquid feed type writing instrument A stores a raw ink. In this case, a critical surface tension of an entire or a partial inner wall surface of an ink tank 10 contacted with an ink 11 is smaller than a surface tension of the ink 11, and an contact angle of an overall or a partial inner wall surface of the tank 10 contacted with the ink 11 to the ink 11 is 30 deg. or more at 25 deg.C. Thus, since visibility of the ink residue and continuity of its visible effect are excellent and it is not necessary to surface treat or the like, a complicated following step is not required, and its manufacturing cost is low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writing instrument of a direct liquid type for directly supplying raw ink in an ink tank to a pen tip or a writing instrument having a cartridge type ink tank for storing ink. The present invention relates to a writing instrument excellent in visibility of the remaining amount of liquid.

[0002]

2. Description of the Related Art Generally, one of the features of a direct liquid type writing instrument is that the remaining ink amount can be confirmed (visibility).
That is, in a direct liquid writing instrument, the ink is filled in the ink tank portion serving as the shaft portion, and the ink moves freely in the ink tank portion, and when the pen tip is directed downward, the remaining ink amount is used as the shaft portion. Can be confirmed by the visual recognition section. At present, a shaft portion used in a direct liquid type writing instrument is made of polypropylene or the like which is excellent in transparency and solvent resistance and has good moldability so as to ensure visibility.

However, at present, the remaining amount of ink can be visually recognized only with a direct liquid type writing instrument using a fluorescent or bright aqueous ink such as an underline pen. When a dark aqueous ink or an oil-based ink in which an organic solvent is the main solvent is used, there is a problem that the visibility of the remaining amount of the ink is not yet sufficient and has not reached the practical range.

[0004] In order to solve these problems, there has been known a method in which a rib is provided on an inner wall surface of an ink tank to improve visibility, but the effect is still not sufficient. It is. In addition, a fluorine resin is used for the ink tank member, or a fluorine or silicone oil treatment or the like is used to reduce the inner wall surface to a low surface energy state (Japanese Patent Publication No. 38-20).
913), and furthermore, a combination of the above-mentioned rib and silicone oil treatment (Japanese Patent Application Laid-Open No. 11-216987).

[0005] However, in those disclosed in these publications, it takes time until the ink is repelled from the inner wall surface of the ink tank and slides down (liquid exhaustion), and the visual recognition effect is insufficient or the member is transparent. A solution that is still satisfactory, such as insufficient durability, insufficient sustainability of the effect, poor moldability, and cost issues due to complicated processes. Has not been proposed yet.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems and the current state of the prior art, and is intended to solve the problem. The present invention is excellent in ink visibility and excellent in sustainability of the visual effect. It is intended to provide a writing instrument.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems of the prior art, and as a result, have found that the critical surface tension of all or a part of the inner wall surface in contact with the ink in the ink tank. By specifying the contact angle between the ink and the inner wall surface of the ink tank in contact with the ink,
The present inventors have found that a writing instrument for the above purpose can be obtained, and have completed the present invention. That is, the present invention includes the following (1) to (5). (1) In a direct liquid writing implement having an ink tank for storing ink, the critical surface tension of all or a part of the inner wall surface of the ink tank in contact with the ink is smaller than the surface tension of the ink, and the ink in contact with the ink. A writing implement wherein the contact angle between the ink and all or part of the inner wall of the tank is 30 ° or more at a temperature of 25 ° C. (2) The writing implement as described in (1) above, wherein all or a part of the inner wall portion of the ink tank portion is made of polymethylpentene. (3) The surface tension of the ink is 50 mN at a temperature of 25 ° C.
/ M or less, and the contact angle between the ink and the inner wall surface of the ink tank in contact with the ink is 30 ° to 9 ° C at a temperature of 25 ° C.
The writing implement according to the above (1) or (2), which is 0 °. (4) The viscosity of the ink is 1000 m at a temperature of 25 ° C.
The writing instrument according to any one of the above (1) to (3), which has a Pa · s or less. (5) The above (1) to (1) wherein the main solvent of the ink is an organic solvent.
The writing implement according to any one of (4).

In the present invention, the "direct liquid writing implement" has an ink tank portion for directly storing ink without absorbing it into batting or the like, and air in the ink tank portion expands due to a rise in temperature or the like. In this case, it is a writing implement provided with an ink reservoir (collector member) for temporarily retaining ink pushed out from the ink tank portion so as not to drool from a pen tip or an air hole. The “critical surface tension” defined in the present invention means that a contact angle θ of a liquid is measured on a solid surface that is hardly wetted by water, and cos θ is plotted against the surface tension γ of the liquid (Jisman plot). A straight line is obtained, and this straight line takes a value of cos θ = 1.
Is referred to as the critical surface tension γ _c .

[0009]

Embodiments of the present invention will be described below in detail. The writing implement of the present invention is a direct liquid writing implement having an ink tank for storing ink, wherein the critical surface tension of all or a part of the inner wall portion of the ink tank in contact with the ink is smaller than the surface tension of the ink, and The contact angle between the ink and all or a part of the inner wall surface of the ink tank portion in contact with the ink is 30 ° or more at a temperature of 25 ° C.

In the writing implement of the present invention, in order to improve the visibility of the remaining amount of ink, the ink is set to have a surface tension (γ _c ) higher than the critical surface tension (γ _c ) of the entire ink tank member or the entire inner wall surface or a part of the inner wall surface. Largely adjusted surface tension [γ (γ _c
<Γ)], and the contact angle between the ink and all or a part of the inner wall surface of the ink tank in the present invention is 30 ° or more at a temperature of 25 ° C. In the present invention, when the ink used is γ _c > γ, and the contact angle between the ink and all or a part of the inner wall surface of the ink tank and the ink is less than 30 ° at a temperature of 25 ° C., the effect of the present invention is obtained. It is not preferable because the visibility cannot be improved and the persistence of the visual effect cannot be maintained.

In the writing instrument of the present invention, the member of the ink tank has visible light transmissivity (transparency), and the contact angle between the ink and all or a part of the inner wall surface of the ink tank at a temperature of 25 ° C. 30 ° or more, preferably 30 °
As long as it is a member that is up to 90 °, it is not particularly limited, and examples thereof include transparent injection-moldable thermoplastics, and specifically, polypropylene, polyethylene, polyethylene terephthalate, polystyrene, and the like. Polyetherimide, polycarbonate, polysulfone, acrylonitrile-styrene copolymer,
Examples include butadiene-styrene-methyl methacrylate terpolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl alcohol copolymer, polymethylpentene, polyethersulfone, and the like.

In the writing instrument of the present invention, the ink to be filled in the ink tank is adjusted to be larger than the critical surface tension (γ _c ) of the entire member or the entire inner wall or a part of the inner wall of the ink tank used. Surface tension [γ (γ _c <
γ)] is not particularly limited as long as it has the ink, for example, a colorant comprising a dye and / or a pigment,
Resin, dispersant, surfactant, other additives for writing implements, etc. are usually dissolved and dispersed in water (purified water, ion-exchanged water, etc.) or a liquid obtained by mixing one or more of organic solvents. Water-based inks, oil-based inks, and the like used for writing instruments can be used.

Examples of the organic solvent include 1-methoxy-2-propanol, 1-ethoxy-2-propanol, benzyl alcohol, ethanol, ethylene glycol, carbitol, cellosolve, glycerin, diethylene glycol stearate, propylene glycol,
Examples include propylene glycol monomethyl ether, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butyl alcohol and the like. As other additives for writing instruments, for example, conventionally known additives such as a pH adjuster, a preservative, and a rust inhibitor can be appropriately added. The present invention is effective regardless of whether it is an aqueous or oil-based ink, but is particularly effective for an oil-based ink having a small surface tension in which the main solvent is an organic solvent.

The viscosity of the ink at 25 ° C. is 1
000 mPa · s or less, preferably 100 mPa · s
Or less, more preferably 10 mPa · s or less. If the viscosity of the ink exceeds 1000 mPa · s, the movement in the ink tank becomes poor, it takes a long time before the ink is repelled, it deviates from a practical range, and it is difficult to confirm the remaining amount of the ink. Absent.

In the writing instrument according to the present invention, preferably, all or all of the inner wall surface of the ink tank has a visible light transmittance of 9 among the above-mentioned thermoplastics.
It is desirable to use polymethylpentene which is excellent in transparency of 0% or more, has a small critical surface tension (γ _c ), and has good moldability. When polymethylpentene having a small critical surface tension (γ _c ) is used, the range of the surface tension of the ink that can be used is widened, and a wide variety of ink types can be easily prepared. The surface tension of the ink is preferably 24 mN / m.
When adjusted as described above, the contact angle between the entire or a part of the inner wall surface of the ink tank and the ink becomes 30 ° at a temperature of 25 ° C.
As described above, it is desirable that the ink tank portion having excellent visibility of the remaining ink amount can be easily mass-produced by ordinary plastic molding without post-processing such as surface treatment and providing ribs or the like on the inner wall of the tank.

When the surface tension of the ink is less than 24 mN / m, in the case of a direct liquid type writing instrument, the inner surface of the ink tank needs to be treated with fluorine resin or fluorine or silicone. Has problems in moldability, transparency and cost, and fluorine and silicone treatments have problems in sustainability of the effect, processing steps and cost. Even if these measures are successfully performed, the capillary force between the wings of the collector member of the temporary storage part is defined by the dimension between the wings and the surface tension of the ink. When the ink becomes too small to store the ink, and the surface tension of the ink is less than 24 mN / m, the blade width must be reduced. However, this becomes difficult due to the problem of moldability and the temporary storage volume. In addition, for example, when the ink tank member is made of polypropylene, the effect of the present invention, such as the visibility of the remaining ink amount, usually does not appear unless the surface tension of the ink is 30 mN / m or more.

In the present invention, more preferably, the ink has a surface tension of 50 mN / m or less at a temperature of 25.degree. C., preferably 24 to 50 mN / m, and the inner wall of all or a part of the ink tank and the ink. Contact angle is temperature 25
It is desirably 30 ° to 90 ° in ° C. If the surface tension of the ink exceeds 50 mN / m and the contact angle with the inner wall of the ink tank exceeds 90 °, the large surface tension of the ink itself and the difficulty of wetting the ink on the inner wall of the ink tank may occur. The ink becomes clinging to the inner wall surface of the ink tank, which causes a problem that the movement of the ink in the ink tank is suppressed.

As described above, in the structure of the writing instrument according to the present invention, in a direct liquid type writing instrument having an ink tank for storing ink, the critical surface tension of all or a part of the inner wall surface of the ink tank in contact with the ink is determined. It is not particularly limited as long as the contact angle between the ink and the inner wall portion of the ink tank portion that is in contact with the ink and all or a part of the inner wall surface portion of the ink is 30 ° or more at a temperature of 25 ° C. Various structures of conventionally used direct liquid writing instruments can be applied. Hereinafter, a form of a writing instrument showing a specific structure of the present invention will be further described with reference to the drawings.

FIG. 1 is a sectional view showing an example of a specific embodiment in which the direct liquid type writing instrument of the present invention is applied to a marking pen. As shown in FIG. 1, the direct liquid writing implement A of this embodiment has an ink tank 10 filled with ink 11 serving as a shaft. In the present embodiment, the entire member of the ink tank unit 10 is made of polymethylpentene having excellent transparency. In FIG. 1, 12 is a collector member, 13 is a holder member, 14 is a relay core, and 15 is a pen core as a pen tip. In addition, the lead-out of the ink 11 from the ink tank 10 to the pen tip 15 is performed by the collector member 1.
This is performed by leading the ink from the ink tank 10 to the pen tip 15 via a relay core 14 provided with an ink flow path provided in the center hole 12a of the second ink jet printer.

In the writing implement A of the present embodiment, the critical surface tension of the entire inner wall surface of the ink tank portion 10 in contact with the ink 11 is smaller than the surface tension of the ink 11 and the inner surface of the entire ink tank portion 10 in contact with the ink 11. The contact angle of the ink 11 is 30 ° or more at a temperature of 25 ° C, preferably 3 °.
0 ° to 90 °, and the surface tension of the ink is 50 mN / m or less at a temperature of 25 ° C., more preferably 24 to 50 m
N / m is set, so that the ink 11 is repelled from the surface of the inner wall surface of the ink tank, the ink slides down (ink runs out) in a short time, and the visibility of the remaining ink amount is extremely excellent. . In the writing implement A, a direct liquid writing implement having excellent visibility of the remaining ink amount can be obtained by merely filling the ink tank section 10 having the above-described characteristics with the ink having the above-described characteristics. Since the target direct liquid writing instrument can be manufactured without going through the steps of forming a rib shape on the ink kunk part to improve visibility,
A direct liquid writing instrument excellent in productivity and cost can be provided.

FIGS. 2 (a) and 2 (b) are explanatory views showing a specific form when a direct liquid writing instrument is applied to a ballpoint pen. In the direct liquid writing implement B of the present embodiment, the ink 21 is filled in an ink tank section 20 having a viewing section 20a, and the members of the ink tank section 20 are entirely made of polymethylpentene having excellent transparency. ing. The critical surface tension of the entire inner wall surface of the ink tank 20 in contact with the ink 21 is smaller than the surface tension of the ink 21, and the contact angle between the inner wall of the entire ink tank 20 in contact with the ink 21 and the ink is 25 ° C. To 30 ° or more, preferably 30 ° to 90 °, and the surface tension of the ink was 50 mN / m or less at a temperature of 25 ° C, more preferably 24 mN / m or less.
It is set to ５０50 mN / m.

Ink tank 20 other than the above-mentioned viewing portion 20a
Is coated with a coating film, a metal deposition film, or the like, to form an invisible opaque portion. In FIG. 2, reference numeral 22 denotes a collector member, reference numeral 23 denotes a holder member, reference numeral 24 denotes a relay core composed of an induction core 24a and a central core 24b, and reference numeral 25 denotes a pen tip formed of a ballpoint pen tip. In addition, the ink 21 from the ink tank section 20 to the pen tip 25
Is derived from the ink tank section 20 to the pen tip 25 via a relay core 24 having an ink flow path provided in a central hole 22a of the collector member 22 and having a medium core 24b. Will be

In the direct liquid writing implement B of the present embodiment, a visual recognition part 20a (a visual recognition part of the same structure is formed on the opposite back side) is formed in a part of the ink tank 20. Even if the portion (transparent window) 20a is a part of the ink tank portion 20, the relationship between the critical surface tension and the surface tension of the ink and the contact angle between the ink and the part of the inner wall portion which is the visible portion of the ink tank portion are determined. According to the relationship, the ink is not left on the surface of the viewing portion 20a, the ink is repelled from the surface of the inner wall surface of the ink tank, the ink runs out in a short time, and the visibility of the remaining ink amount is extremely excellent. In particular, in the case where the visual recognition part is formed in a part of the ink tank, a conventional direct liquid type writing instrument filled with a dark color ink component such as black or blue has a rib shape or the like. Even with an ink tank, the ink drainability was poor, and there was still a problem in its visibility. However, in the writing implement of the present embodiment, a direct liquid type filled with a dark color ink such as black or blue is used. Even in a writing instrument, the ink runs out in a short time without leaving an ink component on the surface of the viewing portion 20a, and the visibility of the remaining ink amount is extremely excellent.

FIG. 3 is an explanatory diagram for explaining a specific form of a writing instrument (marking pen) having a cartridge type ink tank portion. As shown in FIG. 3, the cartridge-type writing instrument C of this embodiment includes a cartridge-type ink tank section 30, a writing instrument body 40, and a cap body 50. Cartridge type ink tank unit 30
Is entirely made of polymethylpentene, and has an ink 31 and a seal ball 32 in an ink tank portion 30. Further, the writing instrument main body 40 has a front shaft 41 and a rear shaft 42, and a collector member 43,
Holder member 44, relay lead 45, pen lead 4 serving as a pen tip
6 is provided. The rear shaft 42 includes a rear end cylindrical portion 47, a seal receiving portion 48, and a cylindrical protrusion 49 integrated with the front shaft 41. The front shaft 41, the rear end cylindrical portion 47, and the rear shaft 42 are all made of polycarbonate. The ink 31 is drawn out from the cartridge type ink tank unit 30 to the pen tip 46 from the cartridge type ink tank unit 30 via a relay core 45 provided with an ink flow path provided in the center hole 43a of the collector member 43. This is performed by leading to the pen core 46.

The writing implement C of the present embodiment has a
The critical surface tension of the inner wall portion of the entire ink tank portion 30 of the cartridge type is smaller than the surface tension of the ink 31, and the contact angle between the inner wall portion of the entire ink tank portion 30 in contact with the ink 31 and the ink is 30 ° at a temperature of 25 ° C. As described above, the surface tension of the ink is preferably 30 ° to 90 °, and the surface tension of the ink is 50 mN / m or less at a temperature of 25 ° C, more preferably 24 mN / m.
５０50 mN / m, so that the ink 3
No. 1 is repelled from the inner wall surface of the ink tank, runs out of ink in a short time, and is extremely excellent in visibility of the remaining amount of ink. In the case of the writing implement C of the present embodiment, the visual recognition of the ink remaining amount in the cartridge type ink tank unit 30 is mainly performed by using the transparent rear shaft 4 of the writing implement main body 40.
2 can be visually recognized.

FIGS. 4A and 4B show another example of a specific embodiment in which the direct liquid writing instrument of the present invention is applied to a marking pen. In addition, the same thing as the writing implement A of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The writing implement D of the present embodiment has a configuration in which the members of the ink tank unit 10 are made of polypropylene having transparency, and is transparent so as to be in contact with the inner peripheral surface of the ink tank unit 10 and the rear end surface of the collector member 12. At the point where the cylindrical transparent body 16 made of excellent polymethylpentene is inserted, the surface of the ink tank 10 other than the visible part (transparent window) 10a of the ink tank 10 is coated with a coating film or metal. 1 is different from the above-described writing implement A of FIG. 1 which has an ink tank portion entirely made of polymethylpentene having excellent transparency in that a coated film such as a film is applied to form an invisible opaque portion. It is.

In the writing implement D of the present embodiment, the critical surface tension of the inner wall surface of the transparent body 16 provided in a part of the ink tank 10 in contact with the ink 11 is smaller than the surface tension of the ink 11, and The contact angle between the inner wall surface of the transparent body 16 and the ink 11 that is in contact with the ink 11 is 30 ° or more at a temperature of 25 ° C.
Preferably, the surface tension of the ink is set at 30 ° to 90 °, and the surface tension of the ink is set to 50 mN / m or less at a temperature of 25 ° C., more preferably 24 to 50 mN / m. The ink is repelled, runs out of ink in a short time, and the visibility of the remaining ink amount is extremely excellent. In the case of the writing implement D of the present embodiment, the remaining ink amount, which is the final part of the ink consumption in the ink tank section 10, is visually recognized through the viewing section 10a of the writing implement main body 10.

The direct liquid type writing implement of the present invention is not limited to the marking pens and ball pens of the forms A, B and D, but may also be applied to brush pens, fountain pens, felt-tip pens and the like. Examples of the writing implement having the cartridge type ink tank section of the form C include, for example,
Felt-tip pen with cartridge-type ink tank,
The present invention can be applied to a ballpoint pen, a fountain pen, and the like, and further can be applied to an applicator in which the pen tip is replaced with a coating material and the ink is replaced with a cosmetic liquid such as a nail polish or a liquid drug having a pharmacological effect. Further, although polymethylpentene is used in the above embodiments A to D, it may be one using polypropylene, polyethylene, polyethylene terephthalate, polycarbonate or the like as described above.

The writing implement of the present invention is constructed as described above. In a direct liquid type writing implement having an ink tank for storing ink, all or a part of the inner wall surface of the ink tank in contact with the ink is provided. Only when the critical surface tension is lower than the surface tension of the ink and the contact angle between the ink and all or a part of the inner wall surface of the ink tank in contact with the ink is 30 ° or more at a temperature of 25 ° C., the ink is used for the first time. The ink is easily repelled from the inner wall surface, runs out of ink in a short time, and has excellent visibility of the remaining ink amount.

[0030]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. 5A, 5B and 5C.
1 is a schematic explanatory view of a writing implement used in Examples 1 and 2 and Examples 3 and 4 and Comparative Example 1, respectively.

Example 1 A marking pen shown in FIGS. 1 and 5 (a) was produced. That is, polymethylpentene (Mitsui Chemicals, Inc.)
Manufactured by TPX RT-18XB).
An ink tank (shaft) molded to an inner diameter of 8 mm and a length of 80 mm was obtained. The critical surface tension obtained by the Disman plot of polymethylpentene is 23.3 mN / m
(25 ° C.). An ink having the following composition was used as the ink to be filled in the ink tank portion. (Parts by weight) Propylene glycol monomethyl ether 79.95 Ketone resin (Hilac 110H, manufactured by Hitachi Chemical Co., Ltd.) 10 Dye (Varifast Black # 1308, manufactured by Orient Chemical Co., Ltd.) 5 Benzyl alcohol 5 Surfactant (KP361, Shin-Etsu Chemical Co., Ltd.) 0.05) The black ink having the above composition was filled so as to fill approximately 30% of the total volume of the ink tank. The physical properties of the ink are as follows. Surface tension: 25 mN / m (25 ° C.) Viscosity: 5 mPa · s (25 ° C.) Contact angle: 32.8 degrees (vs. polymethylpentene; 25)
℃)

Example 2 An ink tank (shaft) was molded using polypropylene (J229E, manufactured by Mitsui Chemicals, Inc.) with the same dimensions as in Example 1, and the outer diameter of the center of the ink tank was adjusted with polymethylpentene. A ring-shaped (cylindrical) transparent body having a size of 8 mm, an inner diameter of 7.5 mm, and a length of 10 mm is inserted in a nested manner [FIG.
(See FIG. 5A and FIG. 5B)], a part of the inner wall surface of the ink tank was made of polymethylpentene (transparent body). The writing implement of the second embodiment is slightly different from the writing implement of FIG. 4A in that a transparent body 16 is provided at a central portion (the portion is a transparent window and serves as a visible portion). An ink having the following composition was used as the ink to be filled in the ink tank portion. (Parts by weight) Propylene glycol monomethyl ether 80 Ketone resin (Hilac 110H, manufactured by Hitachi Chemical Co., Ltd.) 10 Dye (Varifast Black # 1308, manufactured by Orient Chemical Co., Ltd.) 5 Benzyl alcohol 5 Black ink of the above composition is used in all ink tanks. Filling was performed to fill approximately 30% of the volume. The physical properties of the ink are as follows. Surface tension: 27.4 mN / m (25 ° C) Viscosity: 5 mPa · s (25 ° C) Contact angle: 40.0 degrees (vs. polymethylpentene; 25
℃)

Example 3 A marking pen shown in FIGS. 1 and 5 (c) was produced. Using a polypropylene (J229E, manufactured by Mitsui Chemicals, Inc.), an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 80 mm were molded to obtain an ink tank shaft. Disman of polypropylene
The critical surface tension obtained from the plot is 29 mN / m
(25 ° C.). An ink having the following composition was used as the ink to be filled in the ink tank portion. (Parts by weight) Diethylene glycol monomethyl ether 60 Ketone resin (Hilac 110H, manufactured by Hitachi Chemical Co., Ltd.) 10 Dye (SBN blue 701, manufactured by Hodogaya Chemical Co., Ltd.) 5 Diethylene glycol monoethyl ethyl ether 20 Propylene glycol monomethyl ether 5 The ink tank was filled so as to fill about 30% of the total volume of the ink tank. The physical properties of the ink are as follows. Surface tension: 33.6 mN / m (25 ° C) Viscosity: 7.8 mPa · S (25 ° C) Contact angle: 36 degrees (vs. polypropylene; 25 ° C)

Example 4 A marking pen shown in FIGS. 1 and 5 (c) was produced. Polypropylene (J229E, manufactured by Mitsui Chemicals, Inc.)
Was used to form an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 80 mm to obtain an ink tank shaft. The critical surface tension obtained by the Zisman plot of polypropylene is 29 mN /
m (25 ° C.). An ink having the following composition was used as the ink to be filled in the ink tank portion. (Parts by weight) Ethylene glycol monomethyl ether 50 Ketone resin (Hilac 110H, manufactured by Hitachi Chemical Co., Ltd.) 15 Dye (SBN blue 701, manufactured by Hodogaya Chemical Co., Ltd.) 5 Ethylene glycol monophenyl ether 20 Propylene glycol monomethyl ether 10 Blue obtained The ink was filled so as to fill approximately 30% of the total volume of the ink tank. The physical properties of the ink are as follows. Surface tension: 33 mN / m (25 ° C) Viscosity: 7.2 mPa · S (25 ° C) Contact angle: 35 ((to polypropylene; 25 ° C)

Example 5 A marking pen shown in FIG. 1 was produced. Using polyethylene (Mitsui Chemicals, high density polyethylene)
It was molded into an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 80 mm to obtain an ink tank shaft. The critical surface tension selected by the Zisman plot for polyethylene is 30 mN / m (25 mN / m).
° C). An ink having the following composition was used as the ink to be filled in the ink tank portion. (Parts by weight) Diethylene glycol monomethyl ether 50 Ketone resin (Hilac 110H, manufactured by Hitachi Chemical Co., Ltd.) 15 Dye (SBN blue 701, manufactured by Hodogaya Chemical Co., Ltd.) 5 Diethylene glycol monophenyl ether 20 Propylene glycol monomethyl ether 10 The obtained blue ink is used as an ink. The tank was filled to about 30% of the total volume of the tank. The physical properties of the ink are as follows. Surface tension: 33.7 mN / m (25 ° C) Viscosity: 10.8 mPa · S (25 ° C) Contact angle: 37 degrees (vs. polyethylene; 25 ° C)

Comparative Example 1 The same ink tank produced in Example 3 was used as an ink tank part (see FIGS. 1 and 5 (c)). The critical surface tension according to the Zisman plot of polypropylene is
It was about 29 mN / m (25 ° C.). The ink was the same as in Example 1 [Surface tension: 25 mN / m (25 ° C.),
Viscosity: 5 mPa · S (25 ° C.), contact angle: 20.0 degrees (vs. polypropylene; 25 ° C.)].

Examples 1 to 5 and Comparative Example 1 obtained above
The writing implement (sample) was evaluated for the visibility of the remaining ink amount by the following method. The evaluation results are shown in Table 1 below.

(Evaluation Method of Visibility) Evaluation of the visibility of the remaining amount of ink is performed until each ink-filled sample is lightly shaken up and down, and then the ink is repelled from the inner wall surface of the ink tank until the remaining amount of ink can be visually recognized. Was measured and evaluated. Therefore, the shorter the time, the better the visibility. The evaluation results are shown in Table 1 below.

[0039]

[Table 1]

As is evident from the results in Table 1, Examples 1 to 5, which fall within the scope of the present invention, are much more excellent in visibility than Comparative Example 1, which falls outside the scope of the present invention. did. Considering specifically, in Example 1, the critical surface tension (γ _c =
23.3 mN / m; 25 ° C.) is the surface tension of the ink (γ =
25mN / m; 25 ° C), and the contact angle between the inner wall surface and the ink in contact with the ink in the ink tank was 32.8 ° (> 30 °) at a temperature of 25 ° C. 5 is the critical surface tension of the inner wall surface of the ink tank that comes into contact with the ink (γ _c = 23.3, 29, 29.
30 mN / m; 25 ° C.) is the surface tension of the ink (γ = 27.4, 33.6, 33, 33.7 mN / m, respectively; 2)
5 ° C), and the contact angle between the inner wall surface of the ink tank and the ink that contacts the ink is 40.0 °, 36 °, 35 °, and 37 ° (> 30 °) at a temperature of 25 ° C. It can be seen that the visibility is extremely excellent. On the other hand, in Comparative Example 1, the critical surface tension (γ _c = 29 mN / m; 25) of the inner wall surface in contact with the ink in the ink tank was used.
° C) is the surface tension of the ink (γ = 25 mN / m; 25 ° C)
Is larger than 20.0 ° (<25 ° C. at a temperature of 25 ° C.)
30 °), it can be seen that a sufficient visual recognition effect cannot be exhibited.

[0041]

According to the present invention, excellent visibility of the remaining amount of ink and persistence of the visual effect can be obtained, and since no surface treatment or the like is performed, a complicated post-process is not required and the production can be performed at low cost. A writing implement is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a specific embodiment when a writing instrument of the present invention is applied to a marking pen.

FIGS. 2A and 2B are a cross-sectional view and a partial cross-sectional view showing an example of a specific embodiment when the writing implement of the present invention is applied to a ballpoint pen.

FIG. 3 is a cross-sectional view showing an example of a specific form in which the writing instrument of the present invention is applied to a marking pen having a cartridge type ink tank.

FIGS. 4A and 4B are a cross-sectional view and a partial cross-sectional view showing another example of a specific embodiment when the writing instrument of the present invention is applied to a marking pen.

FIGS. 5 (a), (b) and (c) are schematic illustrations of writing instruments used in Examples 1, 2 and 3, 4 and Comparative Example 1, respectively.

[Explanation of symbols]

 A writing implement (marking pen) B writing implement (ball pen) C writing implement (marking pen) D writing implement (marking pen) 10 ink tank unit 10a visual recognition unit 11 ink 12 collector member 12a center hole 13 holder member 14 relay core 15 pen tip 20 ink tank Part 20a Visual recognition part 21 Ink 22 Collector member 22a Center hole 23 Holder member 24 Relay core 24a Induction core 24b Middle core 25 Pen tip 30 Cartridge type ink tank part 31 Ink 32 Seal ball 40 Writing implement main body 41 Front shaft 42 Rear shaft 43 Collector member 43a center hole 44 holder member 45 relay core 46 pen core 47 rear end cylindrical part 48 seal receiving part 49 cylindrical projection 50 cap body

Claims (5)

[Claims] In a direct liquid type writing instrument having an ink tank for storing ink, the critical surface tension of all or a part of the inner wall surface of the ink tank in contact with the ink is smaller than the surface tension of the ink. The contact angle between the ink and all or a part of the inner wall surface of the ink tank in contact with the ink is 30 ° or more at a temperature of 25 ° C. 2. The ink tank part according to claim 1, wherein all or a part of the inner wall part is made of polymethylpentene.
Writing instrument described. 3. The ink according to claim 1, wherein the surface tension of the ink is 50 mN / m or less at a temperature of 25 ° C., and the contact angle between the ink and the inner wall surface of the ink tank in contact with the ink is 3 m at a temperature of 25 ° C.
The writing implement according to claim 1, wherein the writing implement is at an angle of 0 ° to 90 °. 4. The ink has a viscosity of 10 at a temperature of 25 ° C.
The writing instrument according to any one of claims 1 to 3, which has a pressure of 00 mPa · s or less. 5. The writing implement according to claim 1, wherein the main solvent of the ink comprises an organic solvent.