JP2000129187A - Aqueous pigment ink for marking pen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous pigment ink for marking pen, good at discharging property, giving opacifying white or pastel color handwriting and easily redispersible by agitation in precipitation after a lapse of time. SOLUTION: This aqueous pigment ink for marking pen is obtained by including at least a titanium oxide having 10-25 g/100 g oil absorption, a titanium oxide having 30-45 g/100 g oil absorption a dispersant and water and is having 5-100 mPa.s viscosity (25 deg.C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink suitable for a marking pen using a nib having an ink flow passage by capillary action. More specifically, the present invention relates to a water-based pigment ink for a marking pen which is easy to redisperse by stirring even if the pigment sediments over time and gives a white or pastel-colored handwriting with high hiding power.

[0002]

2. Description of the Related Art Conventionally, aqueous pigment inks mainly use titanium oxide, which is a white inorganic pigment having a large refractive index, as a concealing agent for imparting opacity to the ink coating film. An aqueous pigment ink using this titanium oxide or a pigment in which titanium oxide and a chromatic pigment are used as a colorant is a white or pastel-colored ink coating film (handwriting, coating mark) capable of concealing an undercoat and overcoating. And the like. The same applies hereinafter.)

However, in an aqueous pigment ink using titanium oxide, titanium oxide having a large specific gravity tends to settle over time. And finally, there was a problem that it was deposited on the bottom of the ink storage chamber to form a hard cake. By the way, a hard cake refers to a sediment that has a high sedimentation hardness and is not easily redispersed. Therefore, various studies have been made to prevent the precipitation of titanium oxide. For example, a method of dispersing titanium oxide into fine particles using various dispersers such as a ball mill and a sand grinder, and preventing sedimentation by Brownian motion of the titanium oxide fine particles in the ink,
A method has been proposed in which a dispersant is adsorbed on the surface of titanium oxide by using a dispersant such as various surfactants and water-soluble resins, and the dispersion is stabilized by steric hindrance repulsion. Specific examples are as follows. Japanese Patent Publication 55-35434
Japanese Patent Laid-Open Publication No. H11-146,086 discloses a method in which a polymer mainly containing an alkyl ester of acrylic acid or methacrylic acid having both a hydrophilic portion and a lipophilic portion is used as a dispersant for a pigment.
In addition, Japanese Patent Publication No. 49433/1994 describes a method in which a hydrophilic fine powder of silicon dioxide and a silicone-based surfactant or a fluorine-based surfactant are used in combination to form a pigment dispersant. In addition, a method of preventing sedimentation of titanium oxide by reducing the movement of a pigment by increasing the viscosity of ink has been attempted.

[0004]

When an aqueous pigment ink using titanium oxide is used by filling it into a marking pen, it is necessary to design in consideration of the sedimentation phenomenon of titanium oxide. For example, a stirrer such as a metal ball is built in an ink storage chamber, and a stirrer is shaken up and down during use to generate a stirrer force to re-disperse precipitated titanium oxide before use. This allows
The pigment concentration in the ink can be made uniform, and a handwriting with a uniform concentration can be obtained.

[0005] However, the above-mentioned water-based pigment inks which have attempted to prevent sedimentation by refining titanium oxide and using a dispersant have good initial dispersibility, but only slow down the sedimentation speed and have a long-term aging effect. Thus, there is a problem that the titanium oxide deposited on the bottom of the ink storage chamber forms a hard cake that cannot be redispersed. The formation of a hard cake in the marking pen significantly reduces the stirring effect due to the resistance of the cake, and the initial hiding power is lost due to the decrease in the pigment concentration in the ink. In addition, the water-based pigment ink whose viscosity is increased with a water-soluble polymer or the like to prevent sedimentation is difficult to discharge ink from the pen tip where fibers are bundled or the extruded pen tip by plastic extrusion molding. There is a problem that it is not suitable for a marking pen using a pen tip having the same.

[0006]

According to the present invention, the oil absorption is 10%.
~ 25 (g / 100g) titanium oxide and oil absorption of 30
At least 45 g / 100 g of titanium oxide, a dispersant, and water, and have a viscosity of 5 to 100 mPa · s (2
(5 ° C.).

The details will be described below. It is necessary to use titanium oxide having an oil absorption of 10 to 25 (g / 100 g) and titanium oxide having an oil absorption of 30 to 45 (g / 100 g) in combination. Titanium oxide is usually surface-treated with silica and / or alumina to improve its dispersibility and light resistance, and the surface properties change depending on the surface treatment conditions. For example, when the surface of titanium oxide is made porous by surface treatment, the specific surface area increases, and the oil absorption increases. By the way, the amount of oil absorption means that 2 grams of titanium oxide is placed on a glass plate, oil is dropped in small portions, and then mixed well with a metal spatula. Is the amount (gram) of the amount of oil added to the boiled linse until it has the equivalent of 100 g of titanium oxide. Oil absorption of 10 to 25 (g / 100
The titanium oxide of g) is used as a main colorant and a masking agent, and various types of titanium oxide such as rutile type and anatase type can be used. Specifically, Tytone S
R-1 (oil absorption 19 to 21 (g / 100 g)),
650 (oil absorption 20 to 22 (g / 100 g)), R-
3 L (oil absorption 21 to 24 (g / 100 g)), R-5
N (19 to 21 (g / 100 g)) (manufactured by Sakai Chemical Industry Co., Ltd.), Taipaque R-580 (oil absorption 19 (g / 100 g))
100 g)) and R-550 (oil absorption 23 (g / 100
g)) and R-930 (oil absorption 19 (g / 100
g)), A-100 (oil absorption 22 g / 100 g)),
A-220 (oil absorption 21 (g / 100g)), CR
-58 (oil absorption 19 (g / 100 g)) (all manufactured by Ishihara Sangyo Co., Ltd.), Kronos KR-310 (oil absorption 17 to 2)
2 (g / 100 g)) and KR-380 (oil absorption 19 to
24 (g / 100 g)) and KR-480 (oil absorption 19
-24 (g / 100g)) (Titanium Industry Co., Ltd.)
Manufactured), Thai Pure R-900 (oil absorption 14 (g / 100
g)) and R-902 (oil absorption 17 (g / 100 g))
(Above, manufactured by Dupont Japan Limited), Titanics JR-300 (oil absorption 18 (g / 100
g)) and the same JR-301 (oil absorption 18 g / 100)
g)), the same JR-600A (oil absorption 18 g / 100)
g)) and JR-701 (oil absorption 20 (g / 100
g)) (both manufactured by Teica Co., Ltd.).

[0008] Titanium oxide having an oil absorption of 30 to 45 (g / 100 g) is used for preventing hard cake formation because of its porous surface. Specifically, Titanics JR-800 (oil absorption 30 (g / 10
0 g)) and JR-801 (oil absorption 40 (g / 100
g)) (The above are manufactured by Teika Co., Ltd.), Thai Pure R-93
1 (oil absorption 32 (g / 100 g)) and R-933 (oil absorption 36 (g / 100 g)) (all manufactured by DuPont Japan Limited).

The oil absorption is 10 to 25 (g / 100
g) of titanium oxide and an oil absorption of 30 to 45 (g / 100
The titanium oxide of g) can be suitably used as an aqueous pigment ink for a marking pen by using both together. When only a titanium oxide having an oil absorption of 10 to 25 (g / 100 g) is used as a coloring agent, a hard cake is easily formed over time, and only a titanium oxide having an oil absorption of 30 to 45 (g / 100 g) is colored. When the agent is used, if the amount used is increased in order to obtain a preferable hiding power, the dischargeability tends to deteriorate. The combined use amount of the two types of titanium oxide is preferably 2 to 40% by weight based on the total amount of the aqueous pigment ink. The content is preferably 2% by weight or more from the viewpoint of suitably maintaining the hiding power of the ink coating film, and is preferably 40% by weight or less from the viewpoint of maintaining the dischargeability for a marking pen. The ratio (% by weight) between titanium oxide having an oil absorption of 10 to 25 (g / 100 g) and titanium oxide having an oil absorption of 30 to 45 (g / 100 g) is 50:50 to 80:20. Is preferred.

The dispersant improves the dispersibility of titanium oxide and a chromatic pigment described later. It is possible to select and use a known water-soluble resin or various surfactants according to the type of the pigment to be used. it can. As the water-soluble resin, acrylic acid, methacrylic acid, maleic acid, unsaturated carboxylic acid such as itaconic acid or its alkyl ester, styrene,
Acrylonitrile, a synthetic polymer selected and polymerized from a monomer group such as vinyl acetate, or a synthetic polymer selected and copolymerized from two or more kinds of the monomer group, in the form of an alkali metal salt, an ammonium salt or an amine salt. And the like to be used. As various surfactants, as anionic surfactants, Demol EP, Homogenol L-18, Poise 520, and Poise 530 (Kao Corporation)
Polycarboxylic acid type surfactants such as
(Manufactured by Kao Corporation) and the like, and naphthalene sulfonic acid formalin condensate type surfactants, and as nonionic surfactants, Surfynol TG, 104E (above,
Acetylene glycol-type activators such as Nissin Chemical Industry Co., Ltd.) and Pegnol O-6 (Toho Chemical Industry Co., Ltd.)
Polyoxyethylene alkyl ether surfactants such as Neugen ET (Daiichi Kogyo Seiyaku Co., Ltd.), Nonal 210 and 212 (all of which are manufactured by Toho Chemical Industry Co., Ltd.)
And polyoxyethylene alkylphenyl ether type surfactants. These dispersants are
They can be used alone or in combination. Its usage is
It is preferable to add 1 to 20% by weight based on the total amount of the aqueous pigment ink. 1% by weight in order to keep the dispersibility of the pigment suitable
The above is preferred, and the content is preferably 20% by weight or less from the viewpoint of maintaining the fluidity of the ink suitably.

Water is used as a main solvent, and its amount is preferably 20 to 60% by weight based on the total amount of the aqueous pigment ink.

In addition to the above essential components, various additives used in aqueous pigment inks can be appropriately selected and used as needed. For example, the resin particles reduce the average specific gravity of the solid content in the ink and prevent the sedimentation of titanium oxide. Examples of the material of the resin particles include polyethylene, polypropylene, vinyl chloride, polymethacrylate, benzoguanamine, nylon, styrene-acryl copolymer, styrene-acrylonitrile copolymer, and the like.The shape is spherical, irregular, or hollow. And the like. Further, resin particles colored with a dye or the like can be used, and this also serves as a chromatic pigment. Commercially available resin particles include Eposter S (melamine-formaldehyde condensate, Nippon Shokubai Chemical Industry Co., Ltd.)
Nylon SP500 (Nylon, Toray Industries, Inc.)
LX407BP (styrene-butadiene copolymer), LX407BP6 (styrene-butadiene) (all manufactured by Zeon Corporation), Lumicoll NKW-210
9, NKW-75 (styrene-acrylonitrile copolymer, manufactured by Japan Fluorescence Co., Ltd.). Examples of hollow resin particles include MH5055 (styrene-butadiene copolymer, manufactured by Zeon Corporation), SX863 (A),
SX864 (B), SX865 (B) (above, styrene-acrylic copolymer, manufactured by Nippon Synthetic Rubber Co., Ltd.), Rope Lake OP-62, OP-84J, HP-91 (above, acrylic-styrene copolymer) Combined, Rohm and Haas Japan Co., Ltd.), Chemipearl W100, W
200, W300, W400, W500, WF
640, W308, W700, W950 (or more,
Polyolefin, manufactured by Mitsui Petrochemical Industry Co., Ltd.). As resin particles colored with a dye or the like, SW
-11 (red / orange, color tone, same hereafter), SW-
12 (green), SW-13 (red), SW-14
(Orange), SW-15 (lemon / yellow), SW
-16 (orange / yellow), SW-17 (pink), SW-27 (rose), SW-37 (rubin),
SW-47 (violet), SW-18 (blue)
(The above are manufactured by Shinloich Co., Ltd.), Lumicoll NKW-2
101 (red orange), NKW-2102 (green), NKW-2103 (red), NKW-2
104 (orange), NKW-2108 (blue),
NKW-2117 (pink), NKW-2127
(Rose), NKW-2137 (Rubin), NKW
-2167 (Violet) (the above, styrene-acrylonitrile copolymer, manufactured by Nippon Fluorescent Chemical Co., Ltd.). The above resin particles can be used alone or in combination of two or more.

The chromatic pigment is used as a colorant for ink. Specifically, inorganic pigments such as red iron oxide, ultramarine blue, navy blue, cobalt blue, titanium yellow, turquoise, and molybdate orange; I. Pigment Red 2, 3, 5, 17, 22, 22, 38, 4
1, 48: 2, 48: 3, 49, 50: 1, 53: 1, 57: 1, 58: 2, 60, 63:
1, 63: 2: 64: 1, 88, 112, 1
22, 123, 144, 146, 149, 1
66, 168, 170, 176, 177, 1
78, 179, 180, 185, 190, 1
94, 206, 207, 209, 216, 2
45, C.I. I. Pigment Orange 5, 10, 10
3, same 16, same 36, same 40, same 43, C.I. I. Pigment Violet 19, 23, 31, 33, 3
6, 38, 50, C.I. I. Pigment Blue 2, 15, 15: 1, 15: 2, 15: 3, 15:
4, 15: 5, 15: 8, 16, 17, 17, 2
2, 25, 60, 66, C.I. I. Pigment Brown 25 and 26, C.I. I. Pigment Yellow 1, 3, 12, 13, 24, 74, 83, 9
3, 94, 95, 97, 98, 99, 10
8, 109, 110, 117, 120, 13
9, 153, 166, 167, 173, C.I.
I. Pigment Green 5, 7, 10, and 36, as well as fluorescent pigments and mica pigments.

An aqueous ink composition base of a dispersed pigment obtained by dispersing a pigment in an aqueous medium can also be used. Specifically, Fuji. SP series,
Sanyo Dyeing Co., Ltd. Emacol series, Sandye
Series, MicroPi manufactured by Orient Chemical Industry Co., Ltd.
gmo series, MicroJet series, and Ryo. Fast series, EM Colo
Dispersion of inorganic or organic pigments such as r series, and dispersion of fluorescent pigments such as NKW series manufactured by Nippon Fluorescent Chemical Co., Ltd., Cosmo Color Series manufactured by Toyo Soda Co., Ltd., and Shinroihi Color Base Series manufactured by Shinloich Co., Ltd. No. These can be used alone or in combination. The amount of the chromatic pigment used is 1 to the total amount of the aqueous pigment ink.
It is preferable to add 40% by weight. The content is preferably 1% by weight or more from the viewpoint of suitably maintaining the concentration of the ink, and is preferably 40% by weight or less from the viewpoint of suitably maintaining the fluidity of the ink.

In addition, a water-soluble organic solvent can be used for the purpose of preventing the ink from drying at the pen tip and preventing the ink from freezing at a low temperature. Specifically, ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol, thiodiethylene glycol, water-soluble organic solvents such as glycerin, ethylene glycol monophenyl ether, glycol ether solvents such as propylene glycol lower alkyl ether, and ethyl acetate, Examples include ester solvents such as ethyl lactate.

Examples of the water-soluble viscosity modifier include natural or semi-synthetic water-soluble polymers such as gum arabic, tragacanth, guar gum, xanthan gum, dextran, processed starch, carboxymethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose, and polyvinyl alcohol. And synthetic water-soluble polymers such as polyvinylpyrrolidone, polyacrylic acid, and polyethylene oxide.

In addition, handwriting drying accelerators such as ethyl alcohol and isopropyl alcohol, rust inhibitors such as benzotriazole and ethylenediaminetetraacetate, urea,
Wetting agents such as ethylene urea, preservatives such as benzothiazoline and omazine, antifoaming agents such as silicone surfactants, leveling agents such as fluorine surfactants, acids and alkalis Various additives such as a pH adjuster can be appropriately selected and used.

The aqueous pigment ink for a marking pen of the present invention needs to have a viscosity of 5 to 100 mPa · s (25 ° C.). This is because the ink for marking pens is excellent in ease of writing, has good ink ejection, and secures sufficient handwriting density. Ink viscosity is 5mPa
If it is lower than s, the amount of solid content such as titanium oxide is limited, so that sufficient handwriting density cannot be secured. On the other hand, when the ink viscosity is higher than 100 mPa · s, the ink ejection property from a pen tip that bundles fibers or a pen tip by plastic extrusion molding is poor, and is not suitable for a marking pen.

In producing the aqueous pigment ink for a marking pen of the present invention, various conventionally known methods can be employed. For example, the above components are blended, and this is stirred and mixed by a stirrer such as a turbo mixer, a Henschel mixer, a homomixer, or a ball mill, an attritor,
It can be easily obtained by uniformly mixing and dispersing with a disperser such as a sand grinder, a speed line mill, and a three-roll mill.

[0020]

In general, it is said that titanium oxide, which is a polar substance, has a high affinity for a highly polar solvent such as water and has good dispersion stability when used in an aqueous pigment ink. However, when used as a low-viscosity aqueous pigment ink for marking pens, titanium oxide has a high sedimentation speed due to its large specific gravity, and accumulates at the bottom of the ink storage chamber over a long period of time. As a result, there is a problem that the titanium oxide is densely deposited and forms a hard cake which cannot be redispersed without strong mechanical force. Therefore, in order to prevent hardening of titanium oxide, it is necessary to form a bulky and weak network structure between the titanium oxide particles. Normally, titanium oxide having an oil absorption of 10 to 25 (g / 100 g) used as a coloring agent and a hiding agent of an aqueous pigment ink has a small specific surface area due to its surface properties. The titanium oxide particles are less likely to be adsorbed by the dispersant, and the titanium oxide particles are strongly aggregated, so that a hard cake is easily generated. On the other hand, the oil absorption amount is 30 to 45 (g / 100
The titanium oxide of g) has a porous surface property and a large specific surface area, and thus is easily adsorbed to a dispersant. The dispersion of titanium oxide and the dispersant has a large bulk and has an effect of stably dispersing in water. However, when this titanium oxide is used as a coloring agent in an aqueous pigment ink for a marking pen,
When the amount used is increased to obtain a preferable hiding power, there is a problem that the viscosity increases and the ink ejection property deteriorates. Therefore, in order to obtain a water-based pigment ink that is preferable for a marking pen, it is necessary to use two types of titanium oxides having different oil absorption amounts. Oil absorption 30 to 4
A dispersion formed by 5 (g / 100 g) titanium oxide;
A bulky and weak network structure is formed between the dispersion and the dispersion formed by titanium oxide having an oil absorption of 10 to 25 (g / 100 g). Thus, it is considered that the titanium oxide becomes a soft cake that can be easily redispersed by simple stirring without forming a hard cake even if it settles over a long period of time. Further, even if the amount used is increased to obtain a hiding power, the viscosity is low, and good handwriting can be obtained. Further, it is presumed that the addition of the resin particles has an effect of increasing the effect of forming the soft cake.

[0021]

The present invention will be described below in more detail with reference to examples.
The ink viscosity in the examples was measured at 25 ° C. using a B-type viscometer (No. 1 rotor manufactured by Tokyo Keiki Seisakusho).
Was measured under the following conditions. Example 1 Titanics JR-300 (titanium oxide, oil absorption 18 (g / 100 g), manufactured by Teika Co., Ltd.) 29.0 parts by weight Titanics JR-800 (titanium oxide, oil absorption 30 (g / 100 g)) 10.0 parts by weight SR-131 (water-soluble acrylic resin, solid content 25% by weight, manufactured by Ryo Kagaku Kogyo Co., Ltd.) 25.0 parts by weight Proxel GXL (preservative, Zeneca Corporation) )) 0.3 parts by weight Ethylene glycol (anti-drying agent) 5.0 parts by weight Water 30.7 parts by weight The above components are mixed and dispersed for 24 hours by a ball mill to obtain a viscosity of 42.5 mPa · s. Thus, a water-based pigment white ink for a marking pen was obtained.

Example 2 Titanics JR-300 (described above) 24.2 parts by weight Titanics JR-800 (described above) 10.0 parts by weight SR-131 (described above) 25.0 parts by weight Proxel GXL (described above) 3 parts by weight SX865 (B) (hollow resin particles, solid content: 40% by weight, manufactured by Nippon Synthetic Rubber Co., Ltd.) 12.0 parts by weight Ethylene glycol (described above) 5.0 parts by weight Water 23.5 parts by weight Each of the above The components were mixed and subjected to a dispersion treatment by a ball mill for 24 hours to obtain an aqueous pigment white ink for a marking pen having a viscosity of 45.2 mPa · s.

Example 3 Titanics JR-300 (described above) 24.2 parts by weight Titanics JR-800 (described above) 10.0 parts by weight SR-131 (described above) 25.0 parts by weight Proxel GXL (described above) 3 parts by weight FUJI SP GREEN 7051 (aqueous dispersion composition of CI Pigment Green 7, pigment content 31% by weight, manufactured by Fuji Dye Co., Ltd.) 15.5 parts by weight Ethylene glycol (described above) 5.0 parts by weight Water 20.0 parts by weight The above components were mixed and subjected to a dispersion treatment for 24 hours by a ball mill to obtain a pastel-based aqueous pigment green ink for a marking pen having a viscosity of 35.8 mPa · s.

Example 4 Titanics JR-300 (described above) 29.0 parts by weight Titanics JR-801 (titanium oxide, oil absorption 40 (g / 100 g), manufactured by Teica Corporation) 10.0 parts by weight SR -131 (described above) 25.0 parts by weight Proxel GXL (described above) 0.3 parts by weight Ethylene glycol (described above) 5.0 parts by weight Water 30.7 parts by weight The above components are mixed and dispersed by a ball mill for 24 hours. Was carried out to obtain an aqueous pigment white ink for a marking pen having a viscosity of 48.2 mPa · s.

Example 5 Taipaque A-100 (titanium oxide, oil absorption 22 (g / 100 g), manufactured by Ishihara Sangyo Co., Ltd.) 20.2 parts by weight Titanics JR-800 (described above) 8.3 parts by weight Jonkrill 61J (ammonium salt of styrene / acrylic acid copolymer, solid content 30.5% by weight, manufactured by Johnson Polymer Co., Ltd.) 20.8 parts by weight Proxel GXL (described above) 0.3 part by weight NKW-2102 (colored resin particles) 12.9 parts by weight Ethylene glycol (described above) 4.2 parts by weight Water 33.3 parts by weight The above components were mixed and dispersed by a ball mill for 24 hours. To obtain a pastel-like aqueous pigment green ink for a marking pen having a viscosity of 8.5 mPa · s.

Example 6 Thai Pure R-900 (titanium oxide, oil absorption 15 (g / 100 g), manufactured by Dupont Japan Limited) 29.0 parts by weight Titanics JR-800 (described above) 10.0 parts by weight John Krill 62 (Ammonium salt of styrene / α-methylstyrene / acrylic acid copolymer, solid content 34% by weight, manufactured by Johnson Polymer Co., Ltd.) 24.7 parts by weight Poise 530 (Anionic surfactant, Kao Corporation) 0.3 parts by weight Proxel GXL (described above) 0.3 parts by weight PVA203 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd.) 1.5 parts by weight Ethylene glycol (described above) 5.0 parts by weight Water 29.2 parts by weight And a dispersion treatment with a ball mill for 24 hours to obtain an aqueous face for a marking pen having a viscosity of 87.0 mPa · s. A white ink was obtained.

Comparative Example 1 A marking pen having a viscosity of 35.5 mPa · s was prepared in the same manner as in Example 1 except that Titanics JR-300 was added in the same amount as in Example 1, except that Titanics JR-800 was used. An aqueous pigment white ink was obtained.

Comparative Example 2 In Example 6, 1.5 parts by weight of PVA203 was added to 3.0 parts by weight.
A water-based pigment white ink for a marking pen having a viscosity of 133 mPa · s was obtained in the same manner as in Example 6 except that the amount was changed to 27.7 parts by weight and water was changed to 27.7 parts by weight.

Comparative Example 3 In Example 1, the amount of Typeque R-550 (titanium oxide, oil absorption 2
3 (g / 100g) manufactured by Ishihara Sangyo Co., Ltd.)
An aqueous pigment white ink for a marking pen having a viscosity of 34.2 mPa · s was obtained in the same manner as in Example 1.

The aqueous pigment inks for marking pens obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to a hiding power test, a color separation test, a redispersibility test, and a dischargeability test.
Table 1 shows the results.

[0031]

[Table 1]

Hiding power test In accordance with the hiding rate test specified in JIS S6055 (office pigment composition), an aqueous pigment ink was applied to a hiding rate test paper using a 50 μm film applicator and dried, and then SM color was applied. Computer (MODEL, S
M-4, manufactured by Suga Test Instruments Co., Ltd.), and the concealment ratio (unit%) was measured. The larger the value, the higher the hiding power of the pigment.

Redispersibility test The aqueous pigment ink was applied to a marking pen (pigment marker, Pentel Co., Ltd.) using a fiber core nib 8c.
c, filled with a stirring ball (stainless steel ball, 6.4 mm
(Diameter) to make a product. Next, after leaving the pen point upward for three months, the marking pen was moved up and down, and the number of times of shaking until the stirring ball was moved was measured. The smaller the value, the better the redispersibility is evaluated.

Using the product prepared in the redispersibility test described above, a spiral writing was made by hand on fine wood paper, and the handwriting was visually evaluated. Evaluation ：: Good handwriting without blurring was obtained. △: Some blurred ×: Writing not possible

[0035]

As described above in detail, the water-based pigment ink for a marking pen according to the present invention provides a white or pastel-colored handwriting having a good ejection property and a high concealing power, and the pigment is produced over time. It has the feature that re-dispersion by agitation is easy even if it settles.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J039 AD01 AD03 AD05 AD08 AD09 AD10 AD11 AD14 AE03 AE08 BA13 BA23 BA35 BA36 BA37 BA38 BC09 BC13 BC27 BC28 BC66 BC79 BD02 BD03 BE01 BE22 CA06 EA18 EA21 EA44 GA26

Claims (3)

[Claims] An oil absorption of at least 10 to 25 (g / 100 g), a titanium oxide having an oil absorption of 30 to 45 (g / 100 g), a dispersant, and water, and a viscosity of at least 5. A water-based pigment ink for a marking pen having a viscosity of 100 mPa · s (25 ° C.). 2. The aqueous pigment ink for a marking pen according to claim 1, further comprising resin particles. 3. The method according to claim 1, further comprising a chromatic pigment.
Aqueous pigment ink for a marking pen according to claim 1.