JP2018001755A - Ball point pen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of seat wear due to writing not only in the initial stage but also after a long period of time by effectively suppressing the loss of tungsten carbide particles from the ball surface while maintaining the dispersed state of titanium oxide. Provides a water-based ballpoint pen that can maintain excellent writing performance for a long period of time. SOLUTION: This is a ballpoint pen containing a water-based ink composition using a cemented carbide ball containing tungsten carbide as a main component at the writing tip, and the average particle size of the tungsten carbide is 0.5 μm or less. , The ballpoint pen in which the aqueous ink composition comprises titanium oxide and succinoglycan having an isoelectric point in the pH range of 6-8. [Selection diagram] None

Description

  The present invention relates to a ballpoint pen. Furthermore, the present invention relates to a water-based ballpoint pen using a cemented carbide ball.

Conventionally, balls mainly used for the writing tip of a ballpoint pen have been mainly composed of silicon carbide, zirconia oxide, tungsten carbide, etc., but because tungsten carbide is inexpensive and high writing performance is obtained, Cemented carbide balls containing a metal binder such as cobalt or nickel as the main component are widely used.
When the cemented carbide ball is applied to a water-based ballpoint pen, the binding material and tungsten carbide particles cause elution and dropping over time, and the ball surface becomes uneven, so by writing over a long distance in this state, The ball seat may be worn out and the handwriting may be faded.

Therefore, as a method for solving the above-mentioned problems, a technique of attaching fine particles of silica or boron nitride to the ball surface has been disclosed (see, for example, Patent Document 1).
The ball using the above technique fills the irregularities of the ball surface with the fine particles and increases the surface area of the ball, thereby reducing the contact area with the ball holder and reducing friction with the ball seat. However, since a special process is required for the ball, the processing cost is greatly increased. Further, when titanium oxide is used as a colorant component, it is difficult to obtain an effect.
Titanium oxide has a large specific gravity, so it has poor dispersion stability in ink, and is liable to cause sedimentation even in a stationary state. For this reason, when the ballpoint pen is stored in a state where the penpoint is downward, the proportion near the penpoint increases over time, and when writing in this state, tungsten carbide particles are removed from the ball surface by the polishing action of titanium oxide. Since it is easy to be lost, the ball seat is worn by writing, resulting in problems such as an increase in writing quality and faint writing.

JP 2005-186472 A

  Even when titanium oxide is used as a colorant component in a water-based ballpoint pen using a cemented carbide ball, the present invention maintains the dispersed state of titanium oxide and effectively eliminates tungsten carbide particles from the ball surface. Therefore, the occurrence of seat wear due to writing can be suppressed not only in the initial stage but also after a long period of time, so that an aqueous ballpoint pen that can maintain excellent writing performance over a long period of time is provided.

The present invention is a ballpoint pen incorporating a water-based ink composition using a cemented carbide ball mainly composed of tungsten carbide at the tip of writing, and the average particle diameter of the tungsten carbide is 0.5 μm or less. The water-based ink composition requires a ballpoint pen that contains titanium oxide and succinoglycan having an isoelectric point in the range of pH 6-8.
Furthermore, a ballpoint pen incorporating a water-based ink composition using a cemented carbide ball mainly composed of tungsten carbide at the writing tip, wherein the average particle diameter of the tungsten carbide is 0.5 μm or less, The water-based ink composition requires a ballpoint pen containing titanium oxide and succinoglycan having a surface treatment amount of 5% or more by weight, and the oil absorption amount of the titanium oxide is 25 g / 100 g or more.
Further, it is required that the cemented carbide ball has a bending strength of 200 MPa or more, the cemented carbide ball contains vanadium carbide, and the cemented carbide ball does not contain aluminum and iron.
Further, the titanium oxide is added in the range of 1 to 20% by weight in the total amount of the water-based ink composition, and the titanium oxide has a particle diameter (d50) in the range of 0.1 to 0.6 μm. Is a requirement.
Furthermore, it is required that the pH of the water-based ink composition is in the range of 6 to 8, and the surface tension of the water-based ink composition is in the range of 25 to 45 mN / m.

  According to the present invention, the dispersion state of titanium oxide in the ink can be maintained over a long period of time, and the loss of tungsten carbide particles from the ball surface due to long-term aging or writing can be suppressed. Later, the occurrence of seat wear due to writing can be effectively suppressed, and a pastel-colored titanium oxide-containing carbide ballpoint pen that can maintain excellent writing performance with a smooth writing feeling over a long period of time can be provided.

  The ballpoint pen of the present invention is a water-based ballpoint pen that includes a cemented carbide ball mainly composed of tungsten carbide at the writing tip and contains a water-based ink composition containing titanium oxide and succinoglycan.

The water-based ink composition will be described below.
The titanium oxide is used as a white colorant having a high hiding power. In the present invention, one having an isoelectric point in the range of pH 6 to 8 is used. Titanium oxide having an isoelectric point in the above range has high dispersion stability in an aqueous medium, so that it is difficult for sedimentation to occur, and its performance can be maintained over a long period of time.
In order to adjust the isoelectric point within the above range, the titanium oxide can be surface-treated with alumina, silica or the like. Furthermore, by performing the surface treatment, it is possible to improve the weather resistance as well as adjusting the isoelectric point.
In the present invention, the isoelectric point means the hydrogen ion concentration (pH) of the solution at which the electric double layer potential of titanium oxide (the surface-treated one includes alumina and silica) becomes zero.

  Examples of isoelectric points in commercially available titanium oxide include TITANIX JRNC (isoelectric point pH 6.9), JR 701 (isoelectric point pH 7.0), JR 600A (isoelectric point pH 7.4), JR 603 (etc.) Electric point pH 7.6), and JR 602 (isoelectric point pH 8.0) [manufactured by Teika Co., Ltd.].

Since the titanium oxide exhibits particularly high dispersibility when used in a range where its isoelectric point is close to the pH of the ink, it is preferable to adjust the pH of the aqueous ink composition to a range of 6-8. Furthermore, when the pH of the ink is close to the isoelectric point of titanium oxide, the succinoglycan used in combination also functions as an aggregating agent, and titanium oxide can be stably maintained for a long time in an appropriate aggregated state. Even in the course of time, the dispersion state can be maintained without strongly agglomerating and settling.
The pH of the ink can be adjusted by preparing an aqueous ink composition containing titanium oxide and adding an acidic substance or an alkaline substance.

In addition, when titanium oxide having a surface treatment amount of 5% by weight or more is used in place of titanium oxide having an isoelectric point, it has excellent dispersibility and has a buffering effect during ink ejection. Since the seat wear at the time of writing can be suppressed by expressing, the writing feeling which maintained higher lubricity can be obtained over a long period of time. In particular, when the surface treatment amount is 10% by weight or more, its own cushioning property becomes higher, and the effect of suppressing the loss of tungsten carbide particles from the ball surface becomes higher.
Specific examples of the inorganic oxide include silica, alumina, zirconia, and zinc oxide. By coating with these, the dispersion stability of titanium oxide can be maintained satisfactorily, so that aggregation and sedimentation after a long period of time can be suppressed, and the occurrence of seat wear can be more effectively suppressed.
Furthermore, an organic material can also be used as the surface treatment agent containing the inorganic oxide.
Here, the surface treatment amount represents the weight percent of the surface treatment agent (inorganic oxide and additive used if necessary) attached to 100 weight percent of titanium oxide after the surface treatment.

  In a commercially available titanium oxide, as an example of the surface treatment amount with an inorganic oxide, for example, Titanics JR-707 (12% by weight) [manufactured by Teika Co., Ltd.], Tyco R-780-2 (20% by weight) [Above, manufactured by Ishihara Sangyo Co., Ltd.], Ti-Pure TS-6300 (18% by weight) [above, manufactured by DuPont] and the like.

Furthermore, the titanium oxide preferably has an oil absorption of 25 g / 100 g or more. By setting the oil absorption amount to 25 g or more, the surface area of the titanium oxide can be sufficiently increased and the buffering effect can be increased, so that the seat wear is less and writing with high lubricity becomes possible. In addition, the said oil absorption is a value obtained by measuring by the method according to JISK-5101.
Examples of commercially available titanium oxide include Type R-780-2 (40 g / 100 g), CR-85 (30 g / 100 g) [manufactured by Ishihara Sangyo Co., Ltd.], Ti-Pure TS-6300 (37 g / 100 g) [manufactured by DuPont] and the like.

  The titanium oxide preferably has a particle diameter (laser diffraction method, d50 value based on volume) of 0.1 to 0.6 μm, more preferably 0.15 to 0.55 μm. In the above range, aggregation in the ink hardly occurs, and the effect of the present invention can be enhanced because the action of polishing the ball during ink ejection is small.

Furthermore, a general colorant can be added for ink toning.
As the general colorant, all dyes and pigments that can be dissolved or dispersed in an aqueous medium can be used, and specific examples thereof are illustrated below.
As the dye, an acid dye, a basic dye, a direct dye, or the like can be used.
Examples of the acid dye include New Coxin (CI. 16255), Tartrazine (CI. 19140), Acid Blue Black 10B (CI. 20470), Guinea Green (CI. 42085), Brilliant Blue FCF. (CI.42090), Acid Violet 6B (C.I.42640), Soluble Blue (C.I.42755), Naphthalene Green (C.I.44025), Eosin (C.I.45380), Phloxin (C.I. 45410), erythrosine (C.I. 45430), nigrosine (C.I. 50420), acid flavin (C.I. 56205) and the like are used.
Examples of basic dyes include chrysoidine (C.I. 11270), methyl violet FN (C.I. 42535), crystal violet (C.I. 42555), malachite green (C.I. 42000), Victoria blue FB ( CI 44045), rhodamine B (C.I. 45170), acridine orange NS (C.I. 46005), methylene blue B (C.I. 52015) and the like are used.
As direct dyes, Congo Red (C.I. 22120), Direct Sky Blue 5B (C.I. 24400), Violet BB (C.I. 27905), Direct Deep Black EX (C.I. 30235), Kaya Las Black G Conch (C.I. 35225), Direct Fast Black G (C.I. 35255), Phthalocyanine Blue (C.I. 74180) and the like are used.

Examples of the pigment include inorganic pigments such as carbon black and ultramarine blue, and organic pigments such as copper phthalocyanine blue and benzidine yellow, as well as water-dispersed pigments that are finely and stably dispersed in an aqueous medium in advance using a surfactant or the like. For example, C.I. I. Pigment Blue 15: 3B [Product Name: S.P. S. Blue GLL, pigment content 22%, manufactured by Sanyo Color Co., Ltd.], C.I. I. Pigment Red 146 [Product Name: S.P. S. Pink FBL, pigment content 21.5%, manufactured by Sanyo Dye Co., Ltd.], C.I. I. Pigment Yellow 81 [Product name: TC Yellow FG, pigment content about 30%, manufactured by Dainichi Seika Kogyo Co., Ltd.], C.I. I. Pigment Red220 / 166 [Product name: TC Red FG, pigment content: about 35%, manufactured by Dainichi Seika Kogyo Co., Ltd.].
As the fluorescent pigment, a fluorescent pigment in the form of fine particles of a synthetic resin in which various fluorescent dyes are formed into a solid solution in a resin matrix can be used.
Other examples include pearl pigments, gold and silver metallic pigments, luminous pigments, metal powders such as aluminum, and thermochromic compositions, photochromic compositions, capsule pigments directly or microencapsulated with fragrances, etc. it can.

The colorant can be used by appropriately mixing titanium oxide alone or two or more kinds including a general colorant, and is used in the range of 1 to 20% by weight, preferably 2 to 15% by weight in the ink composition.
With titanium oxide alone, by setting the content to 1 to 20% by weight in the ink composition, writing can be performed without excessively polishing the ball, and an excellent color tone can be formed.

The succinoglycan is an organic acid-modified heteropolysaccharide composed of glucose and galactose as constituent monosaccharides and having an average molecular weight of about 1 to 8 million.
Succinoglycan has higher thixotropy than other shear thinning agents and a large viscosity difference in a stationary state, and therefore has a high pigment retention in a stationary state. Therefore, a dispersed state can be maintained even with a titanium oxide having a large specific gravity. In particular, when used in combination with titanium oxide having an isoelectric point in the range of pH 6 to 8, not only in the initial stage but also after a long period of time, the dispersion state of titanium oxide can be maintained. Good ink stability can be maintained without occurring. Therefore, it is possible to suppress an increase in the titanium oxide concentration in the ink near the nib depending on the storage state, and thus it is possible to prevent seat wear due to writing.

  Further, a general-purpose shear thinning agent can be used in combination, for example, xanthan gum, welan gum, guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alkyl alginate, alkyl ester of methacrylic acid as a main component. 100,000 to 150,000 polymers, glucomannan, carbohydrates having gelling ability extracted from seaweed such as agar and carrageenin, benzylidene sorbitol and benzylidene xylitol or their derivatives, crosslinkable acrylic acid polymer, inorganic fine particles, HLB Nonionic surfactants having a value of 8 to 12 and metal salts and amine salts of dialkylsulfosuccinic acid can be exemplified. Further, N-alkyl-2-pyrrolidone and an anionic surfactant are used in combination in the ink composition. Can also be added.

If necessary, a water-soluble organic solvent compatible with water can be used. Specifically, ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol mono Examples include ethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.
In addition, the said water-soluble organic solvent can be used 1 type or in combination of 2 or more types, and is used in 2-40 weight%, Preferably it is 5-30 weight%.

  Furthermore, a water-soluble resin can be added in order to impart adhesion and viscosity to the paper surface. Examples of the water-soluble resin include alkyd resins, acrylic resins, styrene maleic acid copolymers, cellulose derivatives, polyvinyl pyrrolidone, polyvinyl alcohol, and dextrin. The water-soluble resin can be used alone or in combination of two or more, and is used in the range of 1 to 30% by weight in the ink composition.

In addition, if necessary, pH adjusters such as inorganic salts such as sodium carbonate, sodium phosphate and sodium acetate, organic basic compounds such as water-soluble amine compounds, rust preventives such as benzotriazole, tolyltriazole and saponin , Carboxylic acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetrachloro-4- (methylsulfonyl) Preservatives or antifungal agents such as pyridine, urea, sorbit, mannitol, sucrose, glucose, reduced starch hydrolysates, wetting agents such as sodium pyrophosphate, antifoaming agents, fluorine-based interfaces that improve ink permeability An activator or a nonionic surfactant may be used.
Further, a lubricant can be added, such as metal soap, polyalkylene glycol fatty acid ester, ethylene oxide addition type cationic surfactant, phosphate ester type surfactant, N-acyl amino acid type surfactant, dicarboxylic acid type surfactant. , Β-alanine type surfactant, 2,5-dimercapto-1,3,4-thiadiazole and its salts and oligomers, 3-amino-5-mercapto-1,2,4-triazole, thiocarbamate, dimethyl A dithiocarbamate, α-lipoic acid, a condensate of N-acyl-L-glutamic acid and L-lysine, a salt thereof, or the like is used.
Ascorbic acid, erythorbic acid, α-tocopherol, catechins, synthetic polyphenol, kojic acid, alkylhydroxylamine, oxime derivative, α-glucosylrutin, α-lipoic acid, phosphonate, phosphinate, sulfite, sulfoxylate It is also possible to chemically remove bubbles by adding dithionite, thiosulfate, thiourea dioxide or the like.
Further, oligomers of N-vinyl-2-pyrrolidone, oligomers of N-vinyl-2-piperidone, N-vinyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, ε-caprolactam, N-vinyl-ε-caprolactam By adding a thickening inhibitor such as an oligomer, it is possible to enhance the function in the intruding form.

The water-based ink composition composed of the above materials preferably has a surface tension in the range of 25 to 45 mN / m, more preferably 30 to 43 mN / m.
When the surface tension is in the above range, a stable ink ejection property is exhibited without causing handwriting blurring or back-through phenomenon at the time of writing, so that a uniform handwriting (density or width) is easily obtained.

The structure of the cemented carbide ball and ballpoint pen will be described below.
The structure of the tip of the writing pen (tip) of the ballpoint pen has conventionally used a general-purpose mechanism. For example, the ball is held by a ball holding portion in which the vicinity of the tip of a metal pipe is pressed and deformed inward from the outer surface. Or a chip formed by holding a ball in a ball holding part formed by cutting a metal material with a drill or the like, or a chip formed by cutting a metal pipe or metal material A ball or the like that is urged forward by a spring body can be applied.

The cemented carbide ball is made of tungsten carbide (tungsten carbide), which is chemically stable and high in hardness, and uses a metal such as cobalt, nickel, aluminum, or iron as a binder, and is sintered. A ball formed by a method.
In the ball having the above structure, since the binder such as cobalt and nickel is easily eluted in the water-based ink, the tungsten carbide is dropped by the elution of the binder and the ball surface becomes rough. The ball is polished with ink (titanium oxide) ejected at the time of writing, tungsten carbide is lost, and the surface of the ball becomes rough.
As a result, if the ball rotates while being in contact with the ball seat, the wear of the seat becomes severe, so that the smooth writing feeling is impaired and the clearance (clearance) between the ball in the axial direction and the ball holding portion increases. Problems such as increased ink outflow and thicker handwriting, and blurring and line skipping are likely to occur.
Therefore, in the present invention, by setting the average particle diameter of the tungsten carbide to 0.5 μm or less, the particles constituting the ball surface can be arranged densely, so that the loss due to polishing is less likely to occur, and even when the loss is large. Since the separation with particles is eliminated, the surface of the ball is hardly roughened.
In addition, since vanadium carbide is contained in the cemented carbide ball, the average particle diameter of tungsten carbide can be easily controlled to 0.5 μm or less, which is particularly useful.

  Further, by setting the bending strength of the cemented carbide ball to 200 MPa or more, it becomes a ball having a strength suitable for a titanium oxide-containing ballpoint pen, so that the loss of tungsten carbide can be suppressed even when polishing with titanium oxide. The bending strength is a value obtained by performing a test piece made of a sintered body having the same composition in accordance with the three-point bending test of JIS R1601.

Of the materials constituting the cemented carbide balls, aluminum and iron are easily oxidized because of their high ionization tendency, and depending on the type of ink, ball corrosion resulting from this may occur. Therefore, for the water-based ink having this configuration, it is preferable to use a hard ball that does not contain aluminum and iron.
The balls having a diameter in the range of 0.1 mm to 2.0 mm are preferably used. In particular, when the ball diameter is a small diameter of 0.5 mm or less, the number of rotations of the ball with respect to the writing distance increases, and seat wear is likely to occur. Therefore, the configuration of the present invention works more favorably. Therefore, the configuration of the present invention works more advantageously as the ball diameter becomes smaller, such as 0.5 mm, 0.4 mm, 0.38 mm, 0.35 mm, 0.3 mm, 0.28 mm, and 0.25 mm.

  By combining the cemented carbide ball having the above-described structure with the water-based ink composition described above, the occurrence of seat wear due to writing can be suppressed not only in the initial stage but also after a long period of time. It becomes a titanium oxide-containing ballpoint pen that can maintain excellent writing performance over a long period of time.

The shaft cylinder to which the writing tip is connected directly or via a connecting member is a form capable of directly containing a water-based ink composition, but impregnated with an impregnating material (filled) depending on the viscosity. Can also be accommodated.
As the shaft cylinder, for example, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or the like is preferably used in terms of low ink evaporation and productivity, but a metal processed body can also be used. It is. Further, by using a transparent, colored transparent, or translucent molded body, the resin shaft can confirm the ink color, the remaining amount of ink, and the like.
When the ink composition accommodated in the shaft cylinder has a low viscosity, a method of mounting an ink holding member on the front of the shaft cylinder and storing the ink composition directly in the shaft cylinder, porous body or fiber processing It is also possible to use a method in which the ink composition is impregnated in a body and accommodated.
In addition, the said shaft cylinder may accommodate this refill in an outer shaft as a form of the refill for ball-point pens.

When the ink composition is directly filled in the shaft cylinder, an ink backflow preventer (liquid stopper) can be disposed at the rear end of the ink.
As the ink backflow preventer, either liquid or solid can be used, and examples of the liquid ink backflow preventer include non-volatile media such as polybutene, α-olefin co-oligomer, silicone oil, and refined mineral oil. If desired, silica, aluminum silicate, swellable mica, fatty acid amide and the like can be added to the medium. Moreover, a resin molding is mentioned as a solid ink backflow prevention body. The liquid and solid ink backflow preventers can be used in combination.

The ballpoint pen using the shaft tube can be applied to either a cap type or a retractable type. The retractable ballpoint pen is stored in the outer shaft with the writing tip provided on the ballpoint pen refill exposed to the outside air, and the writing tip protrudes from the opening of the outer shaft by the operation of the retracting mechanism. Anything can be used.
Examples of the operation method of the retracting mechanism include a knock type, a rotary type, and a slide type.
The knock type has a knock portion on the outer shaft rear end portion or the outer shaft side surface, and by pressing the knock portion, the writing pen tip portion of the ballpoint pen refill is caused to protrude or retract from the outer shaft front end opening portion, or on the outer shaft. By pressing the provided clip portion, a configuration in which the writing tip portion of the ballpoint pen refill is projected and retracted from the outer shaft front end opening portion can be exemplified.
The rotary type has a rotating part at the rear part of the outer shaft, and can be exemplified by a configuration in which the writing tip part of the ballpoint pen refill is projected and retracted from the outer shaft front end opening by turning the rotating part.
The slide type has a slide portion on the side surface of the shaft cylinder, and a configuration in which the writing tip portion of the ballpoint pen refill is projected and retracted from the front end opening portion of the outer shaft by operating the slide portion, or a clip portion provided on the outer shaft is provided. By sliding, the structure which makes the writing tip part of a ball-point pen refill appear and disappear from the outer-axis front-end opening part can be illustrated.
The retractable ballpoint pen may be a composite retractable ballpoint pen (refill exchange type) in which a plurality of ballpoint pen refills are accommodated in an outer shaft.

Examples will be described below, but the present invention is not limited to these examples.
The following table shows the ball physical properties of the ballpoint pens of Examples and Comparative Examples and the composition of the water-based ink. In addition, the numerical value of the ink composition in a table | surface shows a weight part. The surface tension was measured using a surface tension meter (C3VP-A3) manufactured by Kyowa Interface Science. The particle diameter of titanium oxide is a dynamic light scattering type particle size distribution analyzer LB-500 manufactured by Horiba, Ltd., and the median diameter (d50) is the particle diameter. The average particle diameter of tungsten carbide is The average value of the 50 longest diameters selected at random by observing an image with an electron microscope Miniscope TM3030 manufactured by Hitachi, Ltd. at a magnification of 3000 times.

The contents of the raw materials in the table will be described along the note numbers.
(1) Product name: Titanics JR-701 (isoelectric point: 7.0, particle size: 0.27 μm), manufactured by Teika Co., Ltd.
(2) Product name: Titanics JR-805 manufactured by Teika Co., Ltd. (isoelectric point: 6.0, particle size: 0.29 μm)
(3) Product name: Titanics JR-707 (isoelectric point: 6.0, particle size: 0.25 μm), manufactured by Teika Co., Ltd.
(4) Ishihara Sangyo Co., Ltd., trade name: Taipei R-780 (isoelectric point: 5.6, particle size: 0.24 μm)
(5) DuPont's product name: Ti-Pure TS-6300 (Silica surface treatment amount: 18% by weight, oil absorption amount 37 g / 100 g, particle size: 0.53 μm)
(6) Ishihara Sangyo Co., Ltd., trade name: Taipei R-780-2 (silica surface treatment amount: 20 wt%, oil absorption 40 g / 100 g, particle size: 0.24 μm)
(7) Teika Co., Ltd., trade name: Titanics JR-707 (alumina, silica, zinc oxide surface treatment amount: 12% by weight, oil absorption 22 g / 100 g, particle size: 0.25 μm)
(8) Ishihara Sangyo Co., Ltd., trade name: Taipei PF-739 (zirconia surface treatment amount: 3% by weight, oil absorption 14 g / 100 g, particle size: 0.25 μm)
(9) Hodogaya Chemical Industry Co., Ltd., trade name: Phloxine (10) Big Chemie Japan Co., Ltd., trade name: DISPER BYK-191
(11) Product name: DISPER BYK-2015, manufactured by Big Chemie Japan Co., Ltd.
(12) Rohm and Haas Co., Ltd., trade name: Ropeke Ultra E (solid content 30%)
(13) Product name: Prisurf AL, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
(14) Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prisurf A208B
(15) Product name: Proxel XL-2, manufactured by Lonza Japan

Ink Preparation In Examples and Comparative Examples, components other than the shear thinning agent were added to water, mixed and stirred, then the shear thinning agent was added, and the mixture was stirred at 4000 rpm for 1 hour at 20 ° C with a disper. Each ink was prepared by filtration.

Preparation of Ink Backflow Preventing Body After adding 1.5 parts of fatty acid amide as a thickener to 98.5 parts of polybutene as a base oil, the mixture was kneaded with three rolls to obtain an ink backflow preventing body.

Fabrication of ballpoint pens Four types of 0.4mm diameter balls (WC-Co cemented carbide balls) mainly composed of tungsten carbide, and stainless steel tips that hold each ball (accommodates a ball spring) Is filled with 1 g of the water-based ink compositions of the examples and comparative examples, and the ink backflow prevention body is disposed at the rear end of each ballpoint pen refill. Four types of sample ballpoint pens were prepared for each ink by incorporating them into the shaft (protruding type).
The four types of balls (A to D) include A: an average particle diameter of tungsten carbide of 0.3 μm (containing vanadium carbide), a bending strength of 235 MPa, and B: an average particle diameter of tungsten carbide of 0.4 μm (vanadium). Carbide-containing), bending strength of 215 MPa, C: tungsten carbide having an average particle diameter of 0.5 μm (containing vanadium carbide), bending strength of 230 MPa, D: tungsten carbide having an average particle diameter of 1.0 μm and bending strength of 180 MPa Using.

The following tests were conducted using the sample ballpoint pen.
Written test Each sample ball-point pen that has been confirmed to be writable can be written on JIS P3201 writing paper A with a running tester immediately after production and after standing in a 50 ° C. environment for 90 days. The state of the handwriting when the spiral circle was continuously written was confirmed.
The results of the test are shown in the following table.

The evaluation of the test results is as follows.
Written test ○: Writing was completed with good handwriting.
X: Seat wear was large, and many line jumps were seen in the handwriting, and could not be completely written.

Claims (10)

  A ballpoint pen containing a water-based ink composition in which a cemented carbide ball mainly composed of tungsten carbide is used for a writing tip, wherein the tungsten carbide has an average particle diameter of 0.5 μm or less, and the water-based ink A ballpoint pen wherein the composition comprises titanium oxide and succinoglycan having an isoelectric point in the range of pH 6-8.   A ballpoint pen containing a water-based ink composition in which a cemented carbide ball mainly composed of tungsten carbide is used for a writing tip, wherein the tungsten carbide has an average particle diameter of 0.5 μm or less, and the water-based ink A ballpoint pen wherein the composition contains titanium oxide and succinoglycan having a surface treatment amount of 5% by weight or more with an inorganic oxide.   The ballpoint pen according to claim 2, wherein the titanium oxide has an oil absorption of 25 g / 100 g or more.   The ballpoint pen according to claim 1 or 2, wherein the cemented carbide ball has a bending strength of 200 MPa or more.   The ballpoint pen according to claim 1, wherein the cemented carbide ball contains vanadium carbide.   The ballpoint pen according to claim 1, wherein the cemented carbide ball does not contain aluminum and iron.   The ballpoint pen according to any one of claims 1 to 3, wherein the titanium oxide is added in an amount of 1 to 20% by weight in the total amount of the water-based ink composition.   The ballpoint pen according to any one of claims 1 to 3, wherein the titanium oxide has a particle size (d50) in a range of 0.1 to 0.6 µm.   The ballpoint pen according to claim 1 or 2 whose pH of said water-based ink composition exists in the range of 6-8.   The ballpoint pen according to claim 1, wherein the surface tension of the water-based ink composition is in the range of 25 to 45 mN / m.