JP4426378B2 - Reversible thermochromic water-based ink composition for ballpoint pen and ballpoint pen using the same - Google Patents

Description

  The present invention relates to a reversible thermochromic water-based ink composition for ballpoint pens and a ballpoint pen using the same.

Conventionally, a reversible thermochromic water-based ink capable of obtaining a handwriting whose color changes with a temperature change and a ballpoint pen filled with the ink have been disclosed (for example, see Patent Documents 1 and 2).
Although the handwriting formed by the ballpoint pen can be discolored by rubbing with a friction body such as an eraser, elastomer, plastic foam, etc., in order to provide the fixing property that the handwriting can withstand rubbing, it is patented in ink. It is necessary to add a resin emulsion as disclosed in Document 1.
However, the resin contained in the resin emulsion has a specific gravity exceeding 1, and lacks stability in the ink, so that it settles with time and cannot exhibit the desired performance.
In addition, it is conceivable to increase the ink viscosity to prevent the resin from settling, but problems such as faint writing due to the high viscosity are likely to occur.
Patent Document 2 discloses that a specific gravity of an ink is adjusted by adding a halogen compound having a large specific gravity to prevent sedimentation of the resin. However, the halogen compound should not be used from the viewpoint of safety. In addition, since it may interfere with the color changing function of the reversible thermochromic microcapsule pigment, it is not practical.
JP 2003-206432 A JP-A-9-124993

  The present invention relates to a reversible thermochromic water-based ink composition for ballpoint pens that satisfies the scratch resistance of handwriting that changes color by rubbing with a friction body and that can permanently exhibit a thermochromic function, and a ballpoint pen using the same. It is something to be offered.

（式中、Ｒは炭素数４以上のアルキル基又はアルケニル基を示す。）
更には、前記樹脂がポリオレフィン樹脂であること、前記樹脂の平均粒子径が０．３μｍ以下であること等を要件とする。
更には、前記ボールペン用可逆熱変色性水性インキ組成物を収容してなるボールペンを要件とする。 The present invention is represented by the following general formula (1) as a reaction medium for determining the occurrence temperature of (i) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) the color reaction of the both. Color memory retention type reversible heat that reversibly memorizes and retains a colored state or a decolored state having an average particle diameter of 0.5 to 5 μm including a reversible thermochromic composition comprising an ester compound. A reversible thermochromic aqueous ink composition for ballpoint pens comprising a color-changing microcapsule pigment, water, a water-soluble organic solvent, a shear thinning agent, and an emulsion of a resin having a specific gravity of less than 1 is a requirement.

(In the formula, R represents an alkyl group or alkenyl group having 4 or more carbon atoms.)
Furthermore, the resin that is a polyolefin resin, the average particle diameter of the resin is a requirement such as this is 0.3μm or less.
Furthermore, a ballpoint pen containing the reversible thermochromic water-based ink composition for ballpoint pens is a requirement.

  In the present invention, when the handwriting formed on the writing surface is discolored by the frictional heat of the friction body, the sticking property that the handwriting does not peel off due to the frictional body rubbing and the thermochromic function are expressed permanently. A reversible thermochromic water-based ink composition for ballpoint pens and a ballpoint pen using the same can be provided.

Reversible thermal discoloration microcapsule pigment of the color memory retention type, shows a large hysteresis characteristic, i.e., the shape of the curve obtained by plotting the change in color density due to a temperature change, is raised from the low temperature side than the color change temperature range the temperature Contrary to the case where the color is changed, the color changes by following a greatly different path from the case where the color is lowered from the color change temperature range, and the color development state in the low temperature range below the complete color development temperature (t ₁ ) or the complete color erasure temperature The decolorization state in a high temperature range of (t ₄ ) or higher is a heat decoloring type that can store and retain colors in a specific temperature range [temperature range between t _{2 and} t ₃ (substantially two-phase holding temperature range)]. it is a microcapsule pigment (see Figure 1).
In addition, as the heat-erasable microcapsule pigment capable of storing and retaining colors, an ester compound represented by the general formula (1) is used as the component (c) previously filed by the present applicant, and a color density-temperature curve. you discoloration indicates a broad hysteresis width (40 to 70 ° C.) with respect.
In order to allow only one of the states before and after the color change to exist in the normal temperature range, the hysteresis width is 40 to 70 ° C., preferably 50 to 70 ° C., more preferably 60 to 70 ° C. The color temperature (t ₄ ) is 45 ° C. or higher, preferably 50 ° C. or higher, and the color development start temperature (t ₂ ) is 0 ° C. or lower, preferably −5 ° C. or lower.
The ester compound is an ester compound composed of an alcohol compound having two aromatic rings in the molecule and a saturated or unsaturated fatty acid having 4 or more carbon atoms.
R in the formula represents an alkyl group or alkenyl group having 4 or more carbon atoms, preferably an alkyl group having 6 to 20 carbon atoms, more preferably an alkyl group having 8 to 18 carbon atoms.
Specific examples of the compound include butanoic acid-4-benzyloxyphenylethyl, pentanoic acid-4-benzyloxyphenylethyl, hexanoic acid-4-benzyloxyphenylethyl, heptanoic acid-4-benzyloxyphenylethyl, and octanoic acid. -4-benzyloxyphenylethyl, nonanoic acid-4-benzyloxyphenylethyl, decanoic acid-4-benzyloxyphenylethyl, undecanoic acid-4-benzyloxyphenylethyl, dodecanoic acid-4-benzyloxyphenylethyl, tridecanoic acid -4-benzyloxyphenylethyl, tetradecanoic acid-4-benzyloxyphenylethyl, pentadecanoic acid-4-benzyloxyphenylethyl, hexadecanoic acid-4-benzyloxyphenylethyl, heptadecanoic acid-4-benzylo Cyphenylethyl, octadecanoic acid-4-benzyloxyphenylethyl, nonadecanoic acid-4-benzyloxyphenylethyl, eicosanoic acid-4-benzyloxyphenylethyl, tricosanoic acid-4-benzyloxyphenylethyl, tetracosanoic acid-4-benzyl Oxyphenylethyl, pentacosanoic acid-4-benzyloxyphenylethyl, hexacosanoic acid-4-benzyloxyphenylethyl, heptacosanoic acid-4-benzyloxyphenylethyl, octacosanoic acid-4-benzyloxyphenylethyl, nonacosanoic acid-4-benzyl Examples thereof include oxyphenyl ethyl, triacontanoic acid-4-benzyloxyphenylethyl, and hentriacontanoic acid-4-benzyloxyphenylethyl.

  Here, the reversible thermochromic microcapsule pigment or the ink is blended with a colorant such as a non-thermochromic dye or pigment to change the color from color (1) to color (2). It can also be set as the structure which exhibits.

The microcapsule pigment may have a circular cross section or a non-circular cross section.
The average particle size of the microcapsule pigment is 0.5 to 5.0 μm, preferably 1 to 4 μm, and more preferably 1 to 3 μm.
When the average particle diameter exceeds 5.0 μm, the ink outflow property is lowered and the fixing property to the writing surface is liable to be lowered. On the other hand, when the average particle size is less than 0.5 μm, it is difficult to exhibit high density color development.
In addition, when the ratio of the reversible thermochromic composition to the wall film increases, the wall film becomes too thin, causing a decrease in resistance to pressure and heat, and conversely, the ratio of the wall film to the reversible thermochromic composition. When the value is increased, a decrease in color density and sharpness during color development is unavoidable, and therefore, reversible thermochromic composition / wall film = 6/1 to 1/1 (weight ratio) is preferable.

The reversible thermochromic microcapsule pigment can be blended in an amount of 2 to 50% by weight, preferably 3 to 40% by weight, more preferably 4 to 30% by weight, based on the total amount of the ink composition.
If it is less than 2% by weight, the color density is insufficient, and if it exceeds 50% by weight, the ink outflow is reduced and the writing property is impaired.

  For the microencapsulation of the reversible thermochromic composition, known means such as an interfacial polymerization method, an interfacial polycondensation method, an in situ polymerization method, and a coacervate method can be applied, but the particle size range satisfying the above-described requirements of the present invention. In order to obtain a microcapsule pigment having a non-circular cross-sectional shape, it is effective to apply an interfacial polymerization method or an interfacial polycondensation method that hardly causes aggregation or coalescence.

As the solvent used for the ink, water and a water-soluble organic solvent are used.
Examples of the water-soluble organic solvent include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, and ethylene glycol monomethyl. Ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, N-methyl-2- Pyrrolidone, or the like is used.

As the emulsion of resin having a specific gravity of less than 1 applied to the present invention, an emulsion of polyolefin resin having a specific gravity of less than 1 is preferably used.
The resin can impart adhesion to the handwriting and can improve the storage stability of the ink, and also satisfies the writing property (cap-off property) after leaving the writing tip in the air.
This is due to the fact that the resin emulsion forms a film as the water evaporates from the tip of the writing, and the film is destroyed and ink flows out during writing.
If a resin emulsion having a specific gravity exceeding 1 is used, it becomes difficult to satisfy the storage stability of the ink. This is because the resin and the microcapsule pigment are easily aggregated and settled, and the resin ejected from the writing tip is reduced and it becomes difficult to show the fixing property, and the ejected capsule pigment is also reduced. Color density also decreases.
The average particle size of the resin is preferably 0.3 μm or less. This is because the visible light transmittance is high, so that it is difficult to inhibit the clear color tone exhibited by the microcapsule pigment in the handwriting.

By adding a shear thinning agent to the ink, ink leakage from the gap between the ball and the tip can be prevented when the ballpoint pen for filling the ink is not used, or the writing tip can be directed upward (upright state). Ink backflow can be prevented when left untreated.
In addition, the viscosity of the ink composition to which the shear thinning agent is added shows an ink viscosity of 200 to 3000 mPa · s at a shear rate of 3.84S ⁻¹ by an E-type rotational viscometer at 20 ° C., and It is preferable that the shear thinning index is 0.1 to 0.6.
The shear thinning index (n) is expressed by an empirical formula T = Kj ⁿ (K is a non-Newtonian viscosity coefficient) obtained from rheological measurement by a viscometer such as a shear stress value (T) and a shear rate value (j). It is a value calculated by fitting.

  Examples of the shear thinning agent include xanthan gum, welan gum, succinoglycan (average molecular weight of about 1 to 8 million) whose constituent monosaccharide is an organic acid-modified heteropolysaccharide of glucose and galactose, alka gum, guar gum, locust bean gum and A gel having the ability to be extracted from seaweeds such as glucomannan, agar, carrageenan, etc., polymers having a molecular weight of 100,000 to 150,000 mainly composed of derivatives thereof, hydroxyethyl cellulose, alginic acid alkyl esters, alkyl esters of methacrylic acid Viscous polysaccharides, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, crosslinkable acrylic acid polymer, inorganic fine particles, polyglycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol fatty acid ester Nonionics having an HLB value of 8 to 12 such as polyoxyethylene castor oil, polyoxyethylene lanolin, lanolin alcohol, beeswax derivative, polyoxyethylene alkyl ether / polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, fatty acid amide, etc. Examples of the surfactant include dialkyl or dialkenylsulfosuccinic acid salts, a mixture of N-alkyl-2-pyrrolidone and an anionic surfactant, and a mixture of polyvinyl alcohol and an acrylic resin.

  Furthermore, higher fatty acids such as oleic acid, nonionic surfactants having a long chain alkyl group, polyether-modified silicone oil, thiophosphite tri (alkoxycarbonylmethyl ester) and thiophosphite tri (alkoxycarbonylethyl ester) Thiophosphorous acid triester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphoric acid monoester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphoric acid diester, or metal salt or ammonium salt thereof It is preferable to add a lubricant such as an amine salt or an alkanolamine salt to impart an effect of preventing wear of the ball seat.

  In addition, pH adjusters such as inorganic salts such as sodium carbonate, sodium phosphate and sodium acetate, organic basic compounds such as water-soluble amine compounds, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium night as necessary Rust prevention agent such as light, saponin, coal acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetra Preservatives or fungicides such as chloro-4- (methylsulfonyl) pyridine, urea, nonionic surfactants, reduced or non-reduced starch hydrolysates, oligosaccharides such as trehalose, sucrose, cyclodextrin, glucose, dextrin , Sorbit, N'nitto, wetting agents such as pyrophosphate sodium, defoamers, may be used a dispersing agent, a fluorine based surfactant to improve ink permeability and nonionic surfactants.

The ink composition is practically used by filling a ballpoint pen with a tip attached to the writing tip.
The structure and shape of the ballpoint pen itself are not particularly limited, but it has an ink containing tube filled with an ink composition in a shaft cylinder, and the ink containing tube communicates with a chip with a ball attached to the tip. Furthermore, a ballpoint pen having a structure in which a liquid stopper for preventing backflow is in close contact with the end face of the ink is suitable.

The ballpoint pen tip will be described in more detail. A tip formed by holding a ball in a ball holding portion obtained by pressing and deforming the vicinity of the tip of a metal pipe inward from the outer surface, or a metal material is cut by a drill or the like A chip formed by holding the ball in the ball holding part formed by the above, a chip provided with a resin ball receiving seat inside a metal or plastic chip, or a ball held by the chip is moved forward by a spring body Energized items can be applied.
Moreover, the said ball | bowl can use the thing about 0.3-3 mm diameters, such as a cemented carbide alloy, stainless steel, a ruby, a ceramic, resin, rubber | gum.
In addition, the ball-point pen which fills the ink of this invention contains what provided the rolling mechanism, such as a roller, in the writing front-end | tip part, which forms a handwriting by the same rolling operation as a ball | bowl.

For example, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon is used as the ink storage tube that stores the ink composition.
Furthermore, by using a transparent, colored transparent, or translucent molded body as the ink containing tube, the ink color, the remaining amount of ink, and the like can be confirmed.
In addition to directly connecting the chip to the ink storage tube, the ink storage tube and the chip may be connected via a connecting member.
The ink storage tube may be a refill type in which the refill is accommodated in the shaft cylinder, or the shaft cylinder itself having a tip mounted on the tip is used as an ink container to directly fill the shaft cylinder with ink. May be.

The back end of the ink composition accommodated in the ink accommodating tube may be filled with an ink backflow prevention body.
The ink backflow prevention body composition is composed of a non-volatile liquid or a hardly volatile liquid.
Specifically, petroleum jelly, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, Examples thereof include polyether-modified silicone oil and fatty acid-modified silicone oil, and one or more can be used in combination.

It is preferable to add a gelling agent to the nonvolatile liquid and / or the hardly volatile liquid to increase the viscosity to a suitable viscosity. The surface of the silica is hydrophobized, the surface is methylated fine particle silica, and aluminum silicate. , Swellable mica, hydrophobic thickeners such as bentonite and montmorillonite, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, zinc stearate, tribenzylidene sorbitol, fatty acid amide, amide modified Examples include dextrin compounds such as polyethylene wax, hydrogenated castor oil, fatty acid dextrin, and cellulose compounds.
Furthermore, the liquid ink backflow prevention body composition and a solid ink backflow prevention body composition can be used in combination.

The handwriting formed by the ballpoint pen containing the ink composition can be discolored by rubbing with a friction body.
The friction body may be a plastic molded body, metal, cloth, paper, finger, etc., but an elastic body such as an arbitrary shape of eraser, elastomer, plastic foam, etc. is rich in elasticity and easy to use.
The elastic body can be put to practical use by being attached to the top of the cap, or attached to the rear part of the barrel or the tail plug.
Moreover, a ball-point pen main body, for example, the rear part of a shaft cylinder, a tail plug, and a part of cap (for example, the top part of a cap) can also be functioned as a friction body.

The following table shows the ink compositions of Examples and Comparative Examples. The numbers in the table are parts by weight.

The contents of the raw materials in the table are described below according to the note numbers.
1 Capsule pigment (T ₁ : 8 ° C., t ₂ : 13 ° C., t ₃ : 34 ° C., t ₄ : 40 ° C., color change from blue to colorless, average particle diameter) : 2.5 μm, temperature-sensitive color-change color memory composition / wall film = 2.6 / 1.0) slurry (solid content 65%)
Capsules pigments containing two thermochromic coloring color-memory composition _{(t 1: -10 ℃, t} 2: 3 ℃, t 3: 34 ℃, t 4: 44 ℃, a color change from pink colorless, average (Particle size: 3.0 μm, temperature-sensitive color-changing color memory composition / wall film = 3.0 / 1.0) slurry (solid content 65%)
3 Capsule pigment encapsulating a temperature-sensitive color-change color memory composition (t ₁ : -14 ° C, t ₂ : -6 ° C, t ₃ : 48 ° C, t ₄ : 62 ° C, color change from black to colorless, average (Particle size: 2.5 μm, temperature-sensitive color-changing color memory composition / wall film = 2.5 / 1.0) slurry (solid content 65%)
4 Product name: Phloxin, C.I. I. Acid Red92, C.I. I. 45410
5 Sanyo Dye Co., Ltd., trade name: Sundye Super YELLOW-GN, solid content 30%
6 Sanki Co., Ltd., trade name: Leozan, organic acid-modified heteropolysaccharide whose constituent monosaccharide is glucose and galactose 7 Sanki Co., Ltd., trade name: Kelzan ST
8 Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prisurf AL, polyoxyethylene distyrenated phenyl ether phosphate monoester and diester mixture 9 Avicia Co., Ltd. trade name: Proxel XL-2, 1, 2-Benzthiazoline-3-one 10 manufactured by San Nopco Co., Ltd., trade name: SN deformer 013B
11 Made by Mitsui Petrochemical Co., Ltd., trade name: Chemipearl S-120, polyolefin resin emulsion, resin specific gravity 0.95, particle size less than 0.1 μm, solid content 27%
12 manufactured by Johnson Polymer Co., Ltd., trade name: John wax 26, polyethylene wax emulsion, resin specific gravity less than 0.998 (20 ° C.), particle size 0.069 μm, solid content 25%
13: Sumitomo Seika Co., Ltd., trade name: Xyxen A, polyolefin resin emulsion, resin specific gravity less than 0.984 (20 ° C.), particle size less than 0.2 μm, solid content 25%
14 manufactured by Johnson Polymer Co., Ltd., trade name: Jonkrill 74J, styrene-acrylic copolymer resin emulsion, resin specific gravity 1 to 1.04, particle size 0.08 μm, solid content 45%
15 Product name: Chemipearl A-100, polyolefin resin emulsion, resin specific gravity 0.87, particle diameter 5 μm, solid content 40%, manufactured by Mitsui Petrochemical Co., Ltd.
16 Capsule pigment (T ₁ : 11 ° C., t ₂ : 15 ° C., t ₃ : 34 ° C., t ₄ : 40 ° C., color change from blue to colorless, average particle diameter) : 5.5 μm, temperature-sensitive color-changing color memory composition / wall film = 2.6 / 1.0) (solid content 65%)

Production of Ballpoint Pen A 0.7 mm stainless steel ball was used, and a ballpoint pen tip having a difference between the inner diameter of the ball housing and the outer diameter of the ball of about 20 μm and an axially movable distance of about 70 μm was used.
Each ink (colored in advance) was sucked and filled into a polypropylene pipe having an inner diameter of 3.3 mm, and connected to a ballpoint pen tip via a resin holder.
Next, from the rear part of the polypropylene pipe, a polybutene-based ink follower (liquid stopper) having a viscoelasticity is filled, and after the shaft cylinder, cap, cap and tail plug are assembled, the deaeration process is performed by centrifugation. Got a ballpoint pen.
The cap is formed by attaching a silicone resin as a friction body on the top.

Scratch resistance test Using each of the ballpoint pens, a handwriting was formed by writing on a report paper, and after 1 minute, rubbing until a color change occurred with a friction body, and then the color was changed again to check the state of the handwriting.
Cap-off test Remove the cap of each ballpoint pen and leave it for 20 minutes at 60 ℃ RH for 1 week. Then draw 12 circles of 1.5cm in diameter on the report paper in a row. confirmed.
Ink stability test Each ink was accommodated in a glass container and allowed to stand at 50 ° C for 2 weeks, and then the state of the ink was visually observed.
Color Density Test Using each of the ballpoint pens, writing was made on a report sheet, and the color tone of the handwriting was observed.
Writing Test Using a spiral automatic writing tester, writing was performed at a writing load of 100 g, a writing speed of 4 m / min, and a writing angle of 70 °.

The results of each test are shown in the following table.

Scratch resistance test ○: Handwriting that was not changed compared with the initial stage was confirmed.
(Triangle | delta): The smear has arisen in the blank part which has not formed the handwriting compared with the initial stage.
X: Handwriting peels off and cannot be confirmed.
Cap-off test ○: Written within one circle.
Δ: Written within one line.
×: Cannot be written within one line.
Ink stability test ○: Separation is not seen in the ink.
X: Layer separation occurred in the ink.
Color density test ○: The handwriting has a sufficient color density.
X: The handwriting is whitish and the color density looks low.
Written test ○: Good handwriting is obtained.
X: The handwriting is blurred or lined.

It is explanatory drawing which shows the discoloration behavior of a color memory retention type microcapsule pigment.

t ₁ Complete color development temperature of heat-decolorable microcapsule pigment and color memory retention type microcapsule pigment t ₂ Color development start temperature of heat decoloration type microcapsule pigment and color memory retention type microcapsule pigment t ₃ Heat decolorization type microcapsule Decolorization start temperature of pigment and color memory retention type microcapsule pigment t ₄ Complete decolorization temperature of heating decolorization type microcapsule pigment and color memory retention type microcapsule pigment

Claims (4)

(B) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of the both occurs , from an ester compound represented by the following general formula (1) A color memory retention type reversible thermochromic microcapsule that reversibly memorizes and retains a colored state or a decolored state having an average particle diameter of 0.5 to 5 μm encapsulating the reversible thermochromic composition. A reversible thermochromic aqueous ink composition for ballpoint pens comprising a pigment, water, a water-soluble organic solvent, a shear thinning agent, and an emulsion of a resin having a specific gravity of less than 1.

(In the formula, R represents an alkyl group or alkenyl group having 4 or more carbon atoms.)   The reversible thermochromic water-based ink composition for ballpoint pens according to claim 1, wherein the resin is a polyolefin resin.   The reversibly thermochromic water-based ink composition for ballpoint pens according to claim 1 or 2, wherein the resin has an average particle size of 0.3 µm or less. A ballpoint pen containing the reversible thermochromic water-based ink composition for ballpoint pens according to any one of claims 1 to 3.

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