JP2002212486A - Pigment ink composition for ball point pen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil based ink composition for ball point pens which solves the problem of the flooding of writing with time and uses a pigment having high writing fastness and, at the same time, has writing stability without the disabling of writing and the blurring of writing. SOLUTION: The ink composition for ball point pens comprises a pigment, a pigment derivative, and an organic solvent and, in addition, fine particles of a quanamine based or melamine based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment ink composition for a ballpoint pen using a metal nib. More specifically, the present invention relates to a pigment ink composition for a ball-point pen having a clear and dark handwriting without color separation of a handwriting due to permeation of the pigment derivative over time and blurring.

[0002]

2. Description of the Related Art Heretofore, as an oil-based ink composition for a ballpoint pen, an ink composition containing an oil-soluble dye, an oil-soluble resin, an organic solvent, and the like has been widely put to practical use. This oil-based ink for ballpoint pens is easy to check the remaining amount of ink, has good dryness of the pen tip and can be written without fray even if left for a long time without capping. It has various features, such as keeping hands and paper clean even after rubbing handwriting immediately. But,
In such an ink composition, since the coloring agent is a dye, light resistance and weather resistance are inevitably inferior, and there is a disadvantage that writing of a document or the like premised on long-term storage causes a problem such as disappearance of handwriting color. there were.

Various oil-based ballpoint pens using a coloring agent as a pigment have been known to solve such a problem. However, dye inks contain 20 to 40% by weight of a dye and have a sufficient handwriting density. When the pigment content is increased by using a pigment as the colorant, if the pigment content is increased, the fluidity of the ink will be lost, and the ink will not be discharged from the pen tip. Only the concentration is low. In order to thicken the handwriting, it is sufficient to increase the ejection amount of the ink, but usually the solvent of the ink uses a so-called non-volatile / volatile solvent which has a high boiling point and a low vapor pressure to maintain the drying resistance of the pen tip. Therefore, if the ink discharge is increased, the ink solvent does not permeate the paper, and rubbing the handwriting after writing may cause stains on hands and paper.

[0004] It is a known technique to improve the rheological performance such as the dispersibility, the concentration, and the fluidity of a pigment by using a pigment derivative, and it is necessary to disperse the ink using the pigment and the pigment derivative acting on the pigment surface. By doing so, the fluidity and dispersibility of the pigment, especially at high concentrations, are improved and the ink has stable handwriting with a dark color, and it is possible to obtain clear handwriting without changing the ink ejection amount. Although possible, pigment derivatives have a characteristic color similar in structure to that of the pigment from which they are derived.
In the case of ink for writing instruments, in the case of pigment inks using aqueous or xylene-cellosolve-based, ether-based, alcohol-based, or hydrocarbon-based volatile solvents, the solvent dries immediately after writing, so fixing in the ink A handwriting in which the handwriting is dried in a short time is obtained by the resin for use, and the pigment derivative is fixed in the handwriting, but in the case of an ink using a non-volatile solvent such as an oil-based ballpoint pen, the non-volatile solvent is The ink does not evaporate and only penetrates into the paper to create apparently dry handwriting, so over time, the ink penetrates deeply into the fiber of the paper and spreads over a wide area, and at the same time has excellent permeability A color separation phenomenon in which the pigment derivative develops over time on the back side of the paper and around the handwriting, and a color tone different from the original pigment color appears like a blur on the back side of the paper and around the handwriting Derivatives are difficult to produce especially from pigments, and are a very serious problem in black handwriting or toning based handwriting using two or more pigments, which are often dispersed with derivatives derived from another type of pigment. Was.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of color separation over time of a pigment oil-based ballpoint pen ink having a high handwriting density by using a pigment derivative. An object of the present invention is to provide an oil-based ink composition for ballpoint pens, which uses highly pigmentable pigments and has excellent writing stability without writing failure or handwriting blur.

[0006]

That is, the present invention provides a ballpoint pen pigment ink composition comprising at least a pigment, a pigment derivative and an organic solvent. I do.

Hereinafter, this will be described in more detail. In the present invention, the pigment is carbon black or insoluble azo pigment, azo lake pigment, condensed azo pigment, diketopyrrolopyrrole pigment,
Conventional organic pigments such as phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, quinophthalone pigments, perinones and perylene pigments Known general pigments can be used. These may be used alone or in combination of two or more. Dispersion with a pigment derivative is particularly suitable for such a toning system, since the same polarity can be imparted to the surfaces of different pigments, so that aggregation and separation between different types of pigments can be efficiently prevented. The use amount of these coloring agents is preferably 1 to 50% by weight based on the total ink composition, and is preferably 15 to 40% by weight in order to obtain a sufficient handwriting density. If the amount used is small, the handwriting will not be stained when rubbed with hand or paper.If the amount of ink ejected, the handwriting will be thin, and if it is large, the followability of the ink from the ballpoint pen will worsen, causing blurring and ink not discharging There is.

[0008] Carbon black can be used as the black pigment. Neutral to alkaline carbon black produced by the furnace method has a large effect of improving coloring power and blackness by providing a polar group with a pigment derivative, and can be used particularly preferably. Examples of the blue pigment include C.I. I. Pigmen
t Blue 2, 9, 15, 15: 1, 15: 2, 1,
5: 3, 15: 4, 15: 6, 16, 17, 28, 2
9, 36, 60, 68, 76 and the like can be used, but the phthalocyanine pigment gives a particularly clear handwriting. From the crystal stability and dispersion stability in the solvent, C.I. I. Pigment
A pigment derivative treatment type of Blue 15: 4 or 15: 6 can be suitably used. Examples of pigments that can produce dark handwriting include C.I. I. Pigment Blue 60 is preferred.
Red pigments include C.I. I. Pigment Red
5, 8, 17, 31, 48: 1, 48: 2, 48: 3,
48: 4, 53: 1, 57: 1, 122, 144, 14
6, 166, 170, 177, 202, 207, 21
1, 213, 254, 255, 264, 270, 272
Etc. can be used. The diketopyrrolopyrrole-based C.I. has good light fastness and the appearance color becomes vivid red when the ink is filled into the refill. I. Pigment Re
d254, 255, 264 are particularly preferred. Yellow pigments include C.I. I. Pigment Yellow
1, 3, 12, 13, 14, 17, 55, 81, 83,
79, 93, 94, 95, 97, 109, 110, 12
0, 128, 138, 147, 151, 154, 16
7, 185, 191 and the like can be used. Green pigments include C.I. I. Pigment Green 7, 36, 37
And the like, but as a green ink, preparing an ink with a toning of a blue pigment and a yellow pigment provides a clearer refill color.

The pigment derivative is a very effective component for stabilizing the dispersion and improving the fluidity of the pigment in a non-aqueous system. The pigment derivative combines a long-chain aliphatic hydrocarbon, aluminum benzoate, and a resin polymer having an affinity for a vehicle with the pigment. There are various types such as those obtained by adding various substituents to the surface of the pigment and imparting polarity. In many cases, such pigment derivatives are adjusted by the manufacturer supplying the pigment with their own know-how in accordance with the properties of the pigment matrix and the vehicle system used. Often a mixture of derivatives is provided. Such a pigment which has been treated with a derivative in advance can also be used. However, such pigments are often designed for general-purpose paints and printing inks, and are sufficiently compatible with special solvent compositions to prevent drying at the pen tip of ballpoint pen ink and resin compositions for handwriting. In order to avoid the problem that the ink does not discharge or that there are coarse particles of poorly dispersed pigment in the ink, the pen tip may become clogged and the ink may not be ejected, or the ball seat of the ball holder may be damaged by the coarse particles. Often does not correspond to the pigment particle size of the pigment, a derivative is prepared in accordance with the desired pigment, or Solsperse 5000, which is commercially available as a pigment derivative alone,
2000, 22000 (Avisia Co., Ltd.) and EFK
A6745, 6750 (EFKA CHEMICALS
B. V. Is preferred.

When a commercially available pigment previously treated with a pigment derivative is not used, the blending amount of the pigment derivative is 1.
0 to 15.0%, preferably 3.0 to 10.0%
It is. If the amount is too small, sufficient dispersibility cannot be obtained, and if it is too large, color separation becomes large.

As the organic solvent used in the present invention, conventionally known organic solvents for ballpoint pens can be used.
For example, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mononormal Butyl ether, propylene glycol mononormal propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mononormal propyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl Glycol ether solvents such as ether, tripropylene glycol monoethyl ether and tripropylene glycol monobutyl ether; glycol solvents such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, glycerin, and polyethylene glycol; ethyl acetate Ester solvents such as n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, 2-ethylhexyl acetate, isobutyl isobutylate, ethyl lactate and n-butyl lactate; benzyl Alcohols, β-phenylethyl alcohol, α-methylbenzyl alcohol, lauryl alcohol, tridecyl alcohol, isododecyl alcohol, isotridecyl alcohol, etc. Coal-based solvents and the like can be used. In particular, ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, triethylene glycol monophenyl ether, propylene glycol monophenyl ether, dipropylene glycol monophenyl ether, and tripropylene glycol monophenyl ether , Ethylene glycol monobenzyl ether, aromatic glycol ethers such as diethylene glycol monobenzyl ether, benzyl alcohol, α-methylbenzyl alcohol, β
-Aromatic alcohols such as phenylethyl alcohol are preferable because they have good compatibility with various additives and resin components, and the performance of stabilizing the dispersion of the pigment is better than that of a linear solvent. These may be used alone or as a mixture of two or more kinds. The compounding amount is 15 to 90% by weight based on the total amount of the ink.
Preferably it is 35 to 85% by weight.

In the present invention, the fine resin particles are resin compositions capable of maintaining the external shape and hardness at the time of blending in both ink and handwriting. In ink, even fine particles form a film in the process of handwriting drying. Emulsions that cannot maintain their shape in handwriting, resin fine particles of a type that exhibits performance by swelling in latex or solvent, and some acrylic resin fine particles that dissolve in the organic solvent of the ink even when they are fine particles when mixed Is not included. As such resin fine particles, polyolefin-based resin fine particles, fluororesin-based resin fine particles, polyamide-based resin fine particles, silicon-based resin fine particles, melamine-based resin fine particles, benzoguanamine-based resin fine particles, and the like are dissolved and swelled in the solvent of the ballpoint pen ink used. Can be used in a range of combinations that do not. There are various shapes such as spherical, erythrocyte, and crushed irregular shapes, and any of them can be used.However, it has a narrow range of controlled particle size distribution to discharge smoothly from the tip of a ballpoint pen, A spherical shape is preferable because it is necessary not to break between the seats or to damage the ball or the seat. Further, a hollow body or a porous body can also be used. Specifically, Chemipearl W
100, W200, W300, W400, W500, W
F640, W308, W700, W950 (polyolefin-based spherical resin fine particles, manufactured by Mitsui Chemicals, Inc.), Fluon AD133, AD1S, AD145, AD1006
(PTFE resin fine particles), nylon SP500 (made by Nylon, manufactured by Toray Industries, Inc.), Tospearl 105, Tospearl 120, Tospearl 130, Tospearl 145, Tospearl 312 (silicone resin fine particles, manufactured by Toshiba Silicone Co., Ltd.), Eposter MS, Eposter L15 ,
Eposter M30, Eposter GP series (benzoguanamine-based resin fine particles, manufactured by Nippon Shokubai Co., Ltd.), Eposter S, S6, S12 (melamine-based resin fine particles, manufactured by Nippon Shokubai Co., Ltd.) and the like. These exemplified resin fine particles do not dissolve or swell in the organic solvents exemplified above. Polyolefin and polyamide resin fine particles have a melting point of between 100 and 200 ° C, and are softened, deformed, and crushed by dispersion in a roll mill or bead mill that may be subject to a large shear force or heat during dispersion. It is necessary to pay attention to the dispersion process because of the possibility. Fluorine-based or silicone-based resin fine particles have substantially no melting point and excellent mechanical strength, but have high water and oil repellency on the surface and are difficult to disperse. Benzoguanamine-based and melamine-based resin fine particles have high heat resistance, solvent resistance and mechanical strength, so they can be dispersed with a dispersing machine such as a roll mill, ball mill, bead mill, etc. It is particularly preferable because it has a high ability to adsorb derivatives not adsorbed to the pigment and prevent color separation of handwriting. Here, the benzoguanamine resin refers to a benzoguanamine formaldehyde condensate, a benzoguanamine melamine formaldehyde condensate, and the melamine resin refers to a melamine formaldehyde condensate. The average particle diameter of the resin fine particles is 0.05 to 30 μm, preferably 0.1 to 10 μm.
m. If the particle size is too small, the ability to prevent color separation is not sufficient, and if it is too large, ink ejection from a ballpoint pen tip may be adversely affected. The addition amount is preferably 0.1 to 3% based on the total amount of the ink. If the addition amount is small, the effect of preventing color separation is small, and if it is too large, the viscosity of the ink increases and the ink ejection decreases, or the ink does not follow at the time of rapid writing.

[0013] The resin component used in the oil-based ballpoint pen ink has a viscosity, a rheological property and a spinning property controlling property.
One with handwriting prevention and handwriting solidification / hardening function,
There are various types such as a polymeric pigment dispersant having a pigment dispersing function. Although one resin component often has a plurality of functions and also has an effect of combination, it is desirable to mix the following resin components.

Addition of a high molecular weight pigment dispersant having a pigment dispersing and stabilizing function enhances the wettability of the pigment by interaction with the pigment derivative adsorbed on the pigment, forms steric hindrance, and re-aggregates Can be prevented. There are many types of such dispersants depending on the composition and structure of the polymer portion and the type of polar group. For example, EFKA-
1120, EFKA-1500, EFKA-4008,
EFKA-4009, EFKA-4046, EFKA-
4047, EFKA-4520, EFKA-4010,
EFKA-4050, EFKA-4055, EFKA-
4400, EFKA-4401, EFKA-4403,
EFKA-4510, EFKA-4530, EFKA-
4560, EFKA-5010, EFKA-5044,
EFKA-5054, EFKA-5063, EFKA-
5064, EFKA-5065, EFKA-5066,
EFKA-5071, EFKA-5207 (EFKA
CHEMICALS B. V. Solsperse 13
240, Solsperse 13940, Solsperse 170
00, Solsperse 18000, Solsperse 2000
0, Solsperse 21000, Solsperse 24000
SC, Solsperse 24000GR, Solsperse 26
000, Solsperse 28000, Solsperse 318
45, Solsperse 32000, Solsperse 3250
0, Solsperse 32600, Solsperse 3350
0, Solsperse 34750, Solsperse 3660
0, Solsperse 38500, Solsperse 4100
0, Solsperse 41090 (manufactured by Avicia),
Disperbyk-160, Disperbyk-1
61, Disperbyk-162, Disperby
k-163, Disperbyk-164, Dispe
rbyk-166, Disperbyk-170, Di
sperbyk-130, Disperbyk-10
1, Disperbyk-180, Disperbyk
-182 (manufactured by BYK Japan KK). One or more of these can be appropriately selected from those which dissolve well in the solvent of the ballpoint pen ink. When the polarity of the pigment derivative is basic, the polar group of the polymer type pigment dispersant is acidic, and when the polarity of the pigment derivative is acidic, a pigment dispersant having a basic group is selected. Particularly, Solsperse 20000 and Solsperse 27000 are preferable.

The following resins can be added to prevent show-through and to solidify and harden the handwriting. Acrylic resin, maleic resin, copolymer of styrene and maleic ester, copolymer of styrene and acrylic acid or its ester, urea resin, polyvinyl butyral, polyvinyl acetal, polyamide resin, epoxy resin,
Polyvinyl alkyl ether, coumarone-indene resin, polyterpene, rosin-based resin and its hydrogenated product, ketone resin, polyacrylic acid-polymethacrylic acid copolymer,
Phenol resins and the like can be mentioned, but ketone resins are preferred because of good show-through prevention.

A resin having a viscosity, rheological property, and spinning property controlling property gives a yield value to prevent leakage or dripping of ink from a pen tip, or imparts a shear thinning property to prevent ink from pen tip. Even if a relatively small amount is added, such as stabilizing the discharge regardless of the speed or imparting the spinning property to enhance the ink followability and prevent the ink from running out at the pen tip, the important performance of the ballpoint pen ink is influenced. It is preferable to add polyvinylpyrrolidone, polyethylene oxide, N-vinylacetamide, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose as a resin having such performance.

If necessary, auxiliary agents commonly used in oil-based ink compositions such as preservatives, rust inhibitors, defoamers, lubricants, anti-sagging agents, and surfactants may be added.

For the preparation of the oil-based ink composition for a ballpoint pen, conventionally known methods for producing an ink composition can be applied. An oil-based ink composition for a ballpoint pen can be obtained by appropriately selecting a dispersing mixer such as a roll mill, a ball mill, or a sand mill depending on the ink solvent and the pigment concentration and dispersing the pigment together with other components.

[0019]

Although it is not clear how the oil-based ink composition for a ballpoint pen of the present invention prevents color separation of handwriting, it is presumed as follows. As the pigment derivative, a derivative having the following structure derived from an azo pigment, a phthalocyanine pigment, a polycyclic pigment, or the like is typically used. ^{(1) D-COO - X} + (2) D-SO 3 - X + (3) structure represented by the following (Equation 1). (D: pigment residue, X: H, metal, amine, etc., Y: -C
_{O -, - SO 2 -,} - CH 2 - , etc., R _1, R _2: alkyl, form a ring R ₁ R _2, in R ₁ R _2, etc. form a heterocyclic ring containing N, n: 2,3 Above) The pigment residue (D) of such a pigment derivative is adsorbed on the surface of the pigment having a low polarity with strong affinity, while the resin polymer and various substituents introduced into the pigment derivative have the resin in the vehicle and the resin in the resin. It is considered that having an affinity for the polar group of the above and the polar group of the surfactant prevents the aggregation and structuring of the pigment particles and forms a stable and fluid dispersion system. However, all of the pigment derivatives cannot be adsorbed on the pigment surface, or a free portion separated from the pigment surface by mechanical force during dispersion exists in the solvent. It is considered that the presence of the resin fine particles in the ink prevents the pigment derivative from penetrating beyond the handwriting by burying the resin fine particles in the gaps between the paper fibers on the paper surface. In particular, benzoguanamine-based and melamine-based resin microparticles have a nitrogen-containing cyclic moiety in the structure, and the conjugated double bond is easily bonded to the acidic polar group of the pigment derivative. The effect is great because the color separation of the handwriting can be prevented even by chemical bonding. Further, the benzoguanamine-based resin fine particles can exhibit performance regardless of the polarity of the derivative because the aromatic ring in the structure is adsorbed to the pigment residue of the derivative.

[0020]

(Equation 1)

[0021]

EXAMPLES Examples and comparative examples will be described below. In addition, the notation of the following parts shows weight%. (Example 1) Carbon black # 750 (manufactured by Mitsubishi Chemical Corporation) 25.0 parts Solsperse 12000 (pigment derivative: blue Avisia Co., Ltd.) 2.5 parts Solsperse 20000 (polymer pigment dispersant Avicia Co., Ltd.) 10.0 parts Ethylene glycol monophenyl ether 37.3 parts β-phenylethyl alcohol (I tried using it because it was added) 9.0 parts Eposter MS (benzoguanamine spherical fine particles: average particle diameter 1-3 μm Nippon Shokubai) Industrial Co., Ltd.) 1.0 part Resin SK (ketone resin, manufactured by Huls GmbH (Germany)) 15.0 parts Alcox R-100 (polyethylene oxide manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 part Among the above components Carbon black and Solsperse 1200
The components except for 0 are heated and stirred, and Solsperse 12000
After stirring for 1 hour, carbon black was added, and the mixture was dispersed in a bead mill for 1 hour to obtain a black ink.

(Example 2) C.I. I. Pigment Blue 15: 6 20.0 parts Solsperse 12000 2.0 parts Solsperse 20000 12.0 parts Ethylene glycol monophenyl ether 43.0 parts Tripropylene glycol monobutyl ether 10.5 parts Eposter S (melamine spherical fine particles: average particle diameter of 0. 2.0 parts Resin SK 10.0 parts Luviscol K-90 (polyvinylpyrrolidone, manufactured by BASF (Germany)) 0.5 parts Blue pigment and Solsperse 12000, K-
The components except for 90 are heated and stirred, and Solsperse 1200
After adding 0 and stirring for 0.5 hour, a blue pigment was added, and K-90 was added to a mill base dispersed by a bead mill for 1 hour, followed by heating and stirring to obtain a blue ink.

Example 3 C.I. I. Pigment Red 254 20.0 parts Solsperse 22000 (pigment derivative: yellow, manufactured by Avisia Co., Ltd.) 0.5 parts Disperbyk-160 (polymer pigment dispersant, manufactured by Big Chemie Japan Co., Ltd.) 2.0 parts Propylene glycol monophenyl ether 64 0.5 parts Tospearl 120 (silicone spherical resin fine powder: average particle diameter 2 μm, manufactured by Toshiba Silicone Co., Ltd.) 1.0 part Luviscol K-30 (polyvinylpyrrolidone, manufactured by BASF AG (Germany)) 2.0 parts GE- 191 (N-vinylacetamide, manufactured by Showa Denko KK) 10.0 parts of benzyl alcohol 1% solution GE-191 was separately prepared by stirring as a 1% solution of benzyl alcohol, and the red pigment and GE-19 in each of the above components were prepared.
The components excluding the 1% benzyl alcohol 1% solution were heated and stirred, a red pigment was added, and a GE-191 benzyl alcohol 1% solution was added to a mill base dispersed by a bead mill for 2 hours, followed by heating and stirring to obtain a red ink.

(Example 4) C.I. I. Pigment Violet 19 surface pigment derivative treatment grade 30.0 parts Solsperse 24000SC (polymer pigment dispersant manufactured by Avicia Co., Ltd.) 3.0 parts Nylon SP500 (nylon resin particles, particle size 10 to 20 μm, manufactured by Toray Industries, Inc.) 0 parts Propylene glycol monophenyl ether 40.0 parts Benzyl alcohol 10.0 parts Resin SK 10.0 parts Luviscol K-30 5.0 parts Luviscol K-90 1.0 part Red pigment and K- The components excluding 90 were heated and stirred, K-90 was added to a mill base to which a red pigment was added and dispersed by a bead mill for 2 hours, and heated and stirred to obtain a red ink.

(Comparative Example 1) Eposter MS from Example 1
And a black ink was obtained in the same manner as in Example 1 except that 10.0 parts of β-phenylethyl alcohol was used.

(Comparative Example 2) ADVANCE-MSS P02N (amorphous silica spherical fine particles: average particle diameter: 0.2 μm, manufactured by Advance Co., Ltd.) was 2.0 parts as in Example 2 except for Eposter S. To obtain a blue ink.

Comparative Example 3 Tospearl 12 from Example 3
A red ink was obtained in the same manner as in Example 3 except that propylene glycol monophenyl ether was 65.5 parts except for 0.

(Comparative Example 4) I. Pig
A red ink was obtained in the same manner as in Example 4 except that the surface untreated grade was 30.0 parts except for the grade of the pigment treated with the ment Violet 19 surface pigment derivative.

[0029]

Effect of the Invention Preparation of Test Samples: Examples 1-4
Each of the oil-based ink compositions for ball-point pens obtained in Comparative Examples 1 to 4 is a commercially available oil-based ball-point pen (BK100, manufactured by Pentel Co., Ltd.). The nib is a super hard ball as a writing member held by a stainless steel ball holder. A writing instrument having the same structure as described above was filled with 0.3 g to obtain a test sample.

Straight-line writing test: Hand-written 10 lines of 10 cm length are written on writing paper A by hand, and the writing is performed at a temperature of 50 ° C. and a humidity of 30%.
After standing for 72 hours in a constant temperature bath, the handwriting is observed visually and with a microscope of 40 ×. Also observe the show-through from the back side of the paper. Handwriting observation ○: Color separation cannot be confirmed under a microscope of × 40 ×: Color separation cannot be confirmed visually but can be confirmed under a microscope ×: Color separation can be confirmed visually

Writing test: A commercially available spiral writing tester (MO
DEL TS-4C-20, manufactured by Seiki Industry Laboratory), writing speed 7 cm / sec, writing angle 70 °, load 2
At 600 g, write continuously on JIS P3201 writing paper A for 600 m, observe the handwriting, and determine the amount of sinking of the ball. The length of the ball protruding from the tip of the ball holder in a state where the ball before and after writing is pressed against the seat. The difference in height was measured.

Heat aging test: After leaving the sample in a 50 ° C. constant temperature bath for 4 weeks. A writing test was performed in the same manner as above, and handwriting was observed.

[0033]

[Table 1]

As described in detail above, the ink composition for ball-point pens according to the present invention is an ink composition using a pigment derivative, which is stably dispersed, can maintain ink fluidity, and has clear handwriting without color separation. can get.

Claims (3)

[Claims] A ballpoint pen pigment ink composition comprising at least a pigment, a pigment derivative and an organic solvent,
A pigment ink composition for a ball-point pen containing resin fine particles. 2. The ballpoint pen pigment ink composition according to claim 1, wherein the resin fine particles are benzoguanamine-based resin particles. 3. The ballpoint pen pigment ink composition according to claim 1, wherein the resin fine particles are melamine resin particles.