JP4874625B2 - Discoloring ink composition, discoloring writing instrument incorporating the same, and writing instrument set - Google Patents

Description

  The present invention relates to a color-changing ink composition, a color-changing writing instrument incorporating the same, and a writing instrument set. More specifically, the present invention relates to a color-changing ink composition capable of forming a handwriting that can be discolored or decolored by application of a color-changing liquid, a color-changing writing instrument incorporating the same, and a writing tool set.

Conventionally, a discolorable ink composition using an acid such as acetic acid or phosphoric acid has been disclosed in order to improve the color developability of the dye when a dye that is discolored or decolored with a reducing agent is used as a colorant. (For example, refer to Patent Documents 1 and 2).
The handwriting formed by the writing instrument incorporating the ink composition can be discolored or decolored by applying a color changing liquid on the handwriting, but depending on the material (pH) of the paper forming the handwriting. It is difficult to obtain a desired handwriting density, or it is difficult to maintain the initial color tone due to discoloration before applying the color changing liquid.
In particular, when a specific green base dye is used, a clear handwriting is obtained on a neutral paper surface, but by adding an acid to the ink composition, it is obtained when writing on an acidic or alkaline paper surface. There was a remarkable phenomenon that the density of the handwriting to be obtained was thin or the handwriting density was decreased with time.
Japanese Patent Publication No.54-22345 JP 2004-256706 A

  In the present invention, even in an ink using a specific green base dye, the handwriting before applying the color-changing liquid is not discolored by the pH of the paper, and the handwriting having a good color density can be maintained permanently. Disclosed are a discolorable ink composition, a discolorable writing instrument incorporating the same, and a writing instrument set.

The present invention relates to C.I. I. Discoloration of pH 3-5 comprising at least Basic Green 1, a weakly volatile weak acid selected from carboxylic acid, phosphoric acid, phosphorous acid, and carbonic acid, an alkaline substance selected from phosphate and carbonate , and water The ink composition is a requirement.
Furthermore, it is a requirement that a color-changing writing instrument incorporating the color-changing ink composition, or a color-changing applicator containing a color-changing liquid at the rear end of the writing instrument.
Furthermore, a writing instrument set including the color-changing writing instrument and a color-changing application tool containing a color-changing liquid is a requirement.

  According to the present invention, by adding an alkaline substance together with a hardly volatile weak acid to an ink composition, a handwriting with a clear concentration can be obtained from the beginning of writing without being affected by the pH of the paper. Color changeable ink composition excellent in practicality that can be held by the color change solution and can be discolored or decolored by applying the color change liquid onto the handwriting, and the color changeable writing instrument incorporating the same, and It is possible to provide a writing instrument set including a color changing applicator containing a liquid.

In the discolorable ink of the present invention, C.I. I. Basic Green 1 is used alone, methine dyes, trimethylmethane dyes, diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, cyanine dyes, azo dyes, anthraquinone dyes, cyanine dyes, etc. It is also possible to use a dye that changes color or decolors with a reducing agent.
In addition to the decolorizable dye, a dye or pigment that is hardly discolored by a reducing agent may be used in combination. By using these in combination, the handwriting in which the color tone of the dye is mixed is visually recognized at the time of writing, and by attaching a color changing liquid to the handwriting, one of the dyes is discolored or decolored to visually recognize the handwriting of a different color tone. A possible configuration can also be adopted.
C. above. I. Basic Green 1 is used in the range of 0.1 to 10% by weight, preferably 0.3 to 5% by weight in the ink composition.
Moreover, when other colorants are used in combination, the colorant can be used in the range of 0.1 to 15% by weight, preferably 0.3 to 10% by weight in the ink composition.

The hardly volatile weak acids (including non-volatile ones) are added to improve the color developability of the colorant (CI Basic Green 1 and other basic dyes) in the ink. For example, carboxylic acids such as malic acid and oxalic acid, phosphoric acid, phosphorous acid, carbonic acid and the like can be applied.
In particular, among the hardly volatile weak acids, carboxylic acids are preferably used, and specific examples include malic acid, oxalic acid, succinic acid, citric acid, tartaric acid, malonic acid, glycolic acid, and gluconic acid.
The hardly volatile weak acid is used in the ink composition in an amount of 0.1 to 15% by weight, preferably 0.5 to 10% by weight.
If the amount is less than 0.1% by weight, it is difficult to sufficiently obtain the coloring property of the dye on the paper surface. Further, it is possible to add more than 15% by weight, but if the amount is less than 15% by weight, sufficient coloring effect of the dye is obtained. Therefore, no additional amount is required.

The alkaline substance is used to adjust the pH of the ink after addition of a weak acid to a desired range, and suppresses discoloration (fading) of the handwriting over time, and particularly those that exhibit weak alkalinity are preferably used. It is done. Examples of the alkaline substance include phosphates such as disodium hydrogen phosphate and trisodium phosphate, carbonates such as sodium carbonate and sodium hydrogen carbonate, alkanolamines such as ammonia and triethanolamine, sodium hydroxide, water Examples thereof include hydroxides such as potassium oxide.
In particular, among the alkaline substances, phosphate is preferably used for showing a high discoloration suppressing effect. Specific examples include disodium hydrogen phosphate, trisodium phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, calcium hydrogen phosphate, calcium phosphite, ammonium hydrogen phosphate, and ammonium phosphite.
The alkaline substance is used in the range of 0.1 to 5% by weight, preferably 0.3 to 3% by weight in the ink composition.
If it is less than 0.1% by weight, it is difficult to suppress changes in the color density of the handwriting on the paper surface, and it is possible to add more than 5% by weight, but sufficient effects are obtained at less than 5% by weight. No additional amount is required.

  In order to improve the color developability of the dye in the ink, it is necessary to set the pH of the ink to 6 or less, that is, in the range of 1 to 6. In particular, it is preferable to adjust the pH of the ink in the range of 3 to 5 because the ink stability and the effect of suppressing discoloration of the handwriting due to the pH of the writing paper surface can be easily obtained.

As a solvent used for the ink, water and, if necessary, a water-soluble organic solvent are used.
Examples of the water-soluble organic solvent include ethanol, propanol, butanol, glycerin, sorbitol, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and 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 and the like are used.

  In addition, as long as it does not affect the color development and decoloration of the dye, if necessary, such as anticorrosive agent, antiseptic agent such as carboxylic acid or antifungal agent, surfactant, wetting agent, antifoaming agent such as methylpolysiloxane, etc. An acrylic resin, a styrene maleic acid copolymer resin, polyvinyl pyrrolidone, polyvinyl alcohol, dextrin, etc. can also be used in order to use an additive, or to fix to a paper surface or impart viscosity.

In addition, when the ink is put into a ballpoint pen for practical use, by adding a shear thinning agent, the ink can be prevented from leaking from the gap between the ball and the tip when not in use, or the tip can be turned upward. It is possible to prevent the ink from flowing backward when left.
The viscosity of the ink composition to which the shear thinning agent was added was 200 to 3000 mPa · s at a shear rate of 3.84S ⁻¹ by an E-type rotational viscometer at 20 ° C. It is preferable that the viscosity 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 a gelling ability extracted from seaweeds such as glucomannan, agar and carrageenan, polymers having a molecular weight of 100,000 to 150,000 mainly composed of derivatives thereof, hydroxyethyl cellulose, alginic acid alkyl esters, and 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 , Polyoxyethylene alkyl ether / polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, fatty acid amide and other nonionic surfactants having an HLB value of 8 to 12, salts of dialkyl or dialkenylsulfosuccinic acid, N-alkyl Examples thereof include a mixture of -2-pyrrolidone and an anionic surfactant, and a mixture of polyvinyl alcohol and an acrylic resin.

  Further, when the ink is incorporated in a ballpoint pen for practical use, a higher fatty acid such as oleic acid, a nonionic surfactant having a long chain alkyl group, a polyether-modified silicone oil, a thiophosphorous acid tri (alkoxycarbonylmethyl ester) And thiophosphite triesters such as thiophosphite triester (alkoxycarbonylethyl ester), polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphate monoester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether It is preferable to add a lubricant such as phosphoric acid diesters or their metal salts, ammonium salts, amine salts, alkanolamine salts, etc. to give the ball seat wear-preventing effect.

The color-changing ink composition is practically used by filling a marking pen or a ballpoint pen with a tip attached to a writing tip.
When filling the marking pen, the structure and shape of the marking pen itself are not particularly limited. For example, a marking pen tip such as a fiber tip, a felt tip, or a plastic tip is attached to the writing tip and the inside of the shaft tube. A structure in which ink is impregnated into a stored fiber bundle and ink is supplied to the writing tip, ink is stored directly in the shaft cylinder, and ink flow adjustment member or fiber bundle made up of fiber bundle A marking pen with a structure that supplies a predetermined amount of ink to the writing tip through an adjustment member, a structure that stores ink directly inside the shaft cylinder, and supplies a predetermined amount of ink to the writing tip by a valve mechanism, etc. Can be mentioned.
When filling the ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited.For example, the ink occlusion body composed of a bundle of fibers accommodated in the shaft tube is impregnated with ink, and the writing tip portion attached with the ballpoint pen tip is used. A structure for supplying ink, a structure in which ink is directly stored in the shaft cylinder, and a predetermined amount of ink is supplied to the writing tip portion via an ink flow rate adjusting member composed of a comb groove-shaped ink flow rate adjusting member or a fiber bundle, An example is a ballpoint pen that has an ink containing tube filled with ink in the shaft cylinder, the ink containing tube communicates with a ballpoint pen tip, and a liquid stopper for preventing backflow is provided on the end face of the ink. it can.

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 balls can apply about 0.1-3 mm diameter things, such as a cemented carbide alloy, stainless steel, a ruby, a ceramic, resin, rubber | gum.
In addition, the writing instrument filled with the ink of the present invention includes those provided with a rolling mechanism such as a roller at the tip of the writing for forming a handwriting by the same rolling operation as that of the ball.

As the ink containing tube (shaft cylinder) for containing ink, for example, a transparent molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, nylon, or polycarbonate is preferably used.
The transparency of the ink containing tube includes colored translucent, translucent, and colored translucent, and the ink color, ink remaining amount, and the like can be confirmed.
A writing instrument can be constructed by connecting a chip to the ink storage tube directly or via a connecting member to form a refill and storing the refill in a shaft tube. By making the shaft cylinder accommodating the refill transparent (including colored transparent, translucent, and colored translucent), the ink color, remaining ink amount, and the like in the refill can be confirmed.
Further, the writing instrument can be configured by directly filling the shaft cylinder itself with the tip attached to the tip with ink.

The back end of the ink stored in the ink storage tube or the shaft tube may be filled with an ink backflow prevention body.
The ink backflow preventer comprises a non-volatile liquid and / 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, A polyether modified silicone oil, a fatty acid modified silicone oil, etc. are mentioned, 1 type, or 2 or more types can also be used together.

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 and the solid ink backflow prevention body can be used in combination.

A reducing agent is added to the color changing liquid used for changing or erasing the color changing ink.
Specific examples of the reducing agent include sodium sulfite, potassium sulfite, lithium sulfite, calcium sulfite, ammonium sulfite, zinc sulfite, sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, sodium hypochlorite, tin chloride, hydrosal A phyto etc. can be illustrated and sodium sulfite is used suitably from a viewpoint of discoloration or decoloring performance.
Moreover, an organic solvent and various additives can be mix | blended with the said discoloration liquid as needed, for example, erasability can be improved when alkanolamines, such as a triethanolamine, are added.

The discoloring applicator for storing the discoloring liquid has a simple structure applicator for directly attaching the stored discoloring liquid to the handwriting from the opening, and a cap provided with a liquid absorbing liquid such as a brush in the opening. An example of the applicator has a structure in which the liquid-absorbing liquid impregnates the color-changing liquid in the container in the fitted state, and the liquid-absorbing liquid is brought into contact with the handwriting to apply the color-changing liquid.
Also, it may be an applicator having the structure of a writing instrument, and an ink occlusion composed of a fiber bundle housed in a writing tip with a fiber tip, felt tip, plastic tip, brush tip, etc. attached to the applicator. A structure in which the body is impregnated with the color changing liquid and the color changing liquid is supplied to the writing tip part, the ink is directly stored in the shaft tube, and a liquid flow rate adjusting member composed of a comb groove-like liquid flow rate adjusting member or a fiber bundle is interposed. Marking pen, brush pen, shaft with a structure that supplies a predetermined amount of color-changing liquid to the writing tip, and a structure that supplies the color-changing liquid directly to the writing tip by a valve mechanism A structure that impregnates the color changing liquid into the occlusion body consisting of fiber bundles contained in the cylinder and supplies the color changing liquid to the writing tip with the ball-point pen tip. Liquid consisting of members and fiber bundles A structure for supplying a predetermined amount of the color changing liquid to the writing tip through the flow rate adjusting member, and a housing tube filled with the color changing liquid in the shaft cylinder, the housing pipe communicating with the ballpoint pen tip, and further the color changing A ballpoint pen having a structure in which a liquid stopper for preventing a backflow is disposed at the rear end of the liquid can be exemplified.

The discoloring applicator (ball pen, marking pen, brush pen, etc.) is provided in a part of the discoloring writing instrument containing the discoloring ink, specifically the rear part (so-called double-headed writing instrument structure), and obtained by writing. The written handwriting can be made into a writing instrument excellent in portability that can be discolored or decolored by a single writing instrument.
When the discoloration liquid is housed in an applicator in the form of a writing instrument for practical use, an applicator that can form a handwriting width thicker than the width of the handwriting formed with the color-changing ink efficiently discolors or erases the handwriting. Can be colored.

In addition, a writing instrument set can be obtained by combining the color changing applicator and a color changing writing instrument containing a color changing ink.
The writing instrument set may be composed of a single color-changing writing tool and a color-changing applicator, but a plurality of color-changing writing tools having different color tones and a plurality of color-changing writing tools having different handwriting widths and a color-changing applicator. By using a combined writing instrument set, it is possible to form a writing instrument set that is rich in variations, and has an unexpectedness that can change or erase the handwriting or the pattern.
When the discoloration liquid is housed in a writing instrument-shaped applicator for practical use, an applicator that can form a handwriting width wider than the width of the handwriting formed by the color-changing ballpoint pen can effectively discolor or erase the handwriting. Can be colored.

The ink compositions of Examples and Comparative Examples are shown in the following table. The numerical values of the composition in the table indicate parts by weight.
In addition, this invention is not limited to a following example.

Preparation of color-changing ink Each raw material was mixed in the blending amounts of the above Examples and Comparative Examples, and stirred for 1 hour with a disper at room temperature to obtain a green color-changing ink composition.

Production of color-changing writing instrument A Each of the color-changing ink compositions is directly accommodated in a shaft cylinder, and a chisel-type fiber marking pen tip is attached to the tip of the shaft cylinder via a comb groove-shaped ink flow rate adjusting member. The form of discoloring writing instrument A was obtained.
The discoloring writing instrument is provided with a detachable cap.

The following tests were performed using the color-changing writing instrument A containing the color-changing inks obtained in the respective examples and comparative examples.
Temporal discoloration test Using each color-changing writing instrument A, write on each of acidic paper (pH 5.8) and alkaline paper (pH 9.5), and visually observe the state of the handwriting after left at 25 ° C for 1 hour and 60 days. Was observed. The test results are shown in the following table.

The evaluation of the test results in the table is as follows.
After standing for 1 hour: Good handwriting is obtained from the initial stage, and no change is seen in the color tone of the handwriting.
Δ: Initial handwriting is thin, but good handwriting is obtained.
X: Handwriting does not color.
After standing for 60 days ○: No change in the color of the handwriting compared to the initial good handwriting.
□: The handwriting is slightly thinner than the good handwriting at the beginning or after standing for 1 hour.
Δ: A fairly thin handwriting can be obtained.
X: The handwriting does not develop color or disappears.

Preparation of color changing solution Sodium sulfite (reducing agent) 10.0 parts Potassium carbonate 1.0 part Phosphate ester surfactant 0.2 part [Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prisurf AL]
Carboxylic acid (preservative) 0.1 part Glycerin 10.0 part Water (ion-exchanged water) 78.7 parts A reducing agent and various additives were added to the solvent and stirred to obtain a color changing liquid.

Preparation of the color change applicator A The color change liquid is directly stored in the shaft tube, and a chisel-type fiber marking pen tip is attached to the tip of the shaft tube through a comb-groove-shaped ink flow rate adjusting member. An applicator A was obtained.
The discoloring applicator is provided with a detachable cap.

Preparation of discoloration applicator B A fiber sizing ink occlusion body in which a polyester sliver is coated with a synthetic resin film is impregnated with the discoloration liquid and accommodated in the shaft cylinder, and a chisel-type fiber marking pen tip is attached to the tip of the shaft cylinder. An applicator B for discoloration in the form of a marking pen was obtained.
The discoloring applicator is provided with a detachable cap.

Preparation of double-headed color-changing writing instrument a The color-changing ink prepared in Example 1 is accommodated in one (large volume portion) of a shaft cylinder having an opening at both ends provided with a partition wall having a volume of 7: 3 inside the shaft cylinder. Then, a chisel-type fiber marking pen tip was attached to the tip of the shaft cylinder through a comb groove-shaped ink flow rate adjusting member.
Next, the discoloration liquid was accommodated in the other (small volume portion), and a chisel-type fiber marking pen tip was attached to the tip of the shaft cylinder via a comb groove-shaped ink flow rate adjusting member to obtain a double-headed discoloring writing instrument a. .
When writing on the paper surface using the writing instrument, a green handwriting was obtained, and when the discoloring solution provided on the other side was applied from the handwriting, the handwriting was decolored.
Since the writing instrument can perform writing and erasing with one writing instrument, it is excellent in portability and convenience.

Preparation of double-headed color-changing writing instrument b The ink prepared in Example 4 is accommodated in one end of a shaft cylinder having an opening on both ends provided with a partition wall having a volume of 5: 5 inside the shaft cylinder, and comb-shaped ink A bullet-type fiber marking pen tip was attached to the tip of the shaft tube through the flow rate adjusting member.
Next, a double-headed color-changing writing instrument that contains a color-changing ink capable of forming a red handwriting separately produced on the other side, and a bullet-type fiber marking pen tip is attached to the tip of the shaft cylinder via a comb groove-shaped ink flow rate adjusting member b was obtained.
When writing on the paper surface using the writing instrument, green and red handwriting was obtained, and when the discoloring liquid was applied from the handwriting using a discoloring applicator, the handwriting was decolored.
Since the writing instrument can form handwriting of different colors with one writing instrument, it is excellent in portability and convenience.

Preparation of writing instrument set 1 The writing instrument set 1 was obtained by combining the double-headed discoloring writing instrument b and the discoloring applicator B.
When writing on the paper surface using the double-headed color-changing writing tool b, green and red handwriting was obtained, and when the color changing liquid was applied from the handwriting using the color changing applicator B, the handwriting was decolored.

Preparation of Writing Instrument Set 2 A writing instrument set 2 was obtained by combining the discoloring writing instrument A containing the discoloring ink of Example 1 and the applicator A for discoloration.
When writing on the paper surface using the color-changing writing tool A, a green handwriting was obtained, and when the color changing liquid was applied from the handwriting using the color changing applicator A, the handwriting was decolored.

Production of writing instrument set 3 Color-changing writing instrument A that contains the color-changing ink of Example 4; a color-changing writing instrument that contains a color-changing ink that can form a red handwriting separately produced; and a color-changing applicator B And writing instrument set 3 was obtained.
When writing on the paper surface using each of the writing tools, green and red handwriting was obtained, and when the color changing liquid was applied using the color changing applicator B from the handwriting, the handwriting was decolored.

Preparation of writing instrument set 4 The discolorable ink composition of Example 1 was impregnated into a fiber sizing ink occlusion body in which a polyester sliver was coated with a synthetic resin film, and accommodated in a shaft tube, and a chisel-type fiber was formed at the tip of the shaft tube A writing pen set 4 was obtained by combining the discoloring writing tool B (comprising a detachable cap) in the form of a marking pen with a marking pen tip and the discoloring applicator B.
When writing on the paper surface using the writing tool, a green handwriting was obtained, and when the color changing solution was applied from the handwriting using the color changing applicator B, the handwriting was decolored.

Application example 1
Using the double-headed discoloring writing instrument a, writing was performed so as to cover black characters printed on the paper surface, thereby forming a green handwriting. The black characters were visible through the handwriting.
When a red transparent sheet is placed on the handwriting, the green color of the handwriting and the red color of the sheet are in a complementary color relationship and are visually recognized as black, so that the characters are not visually recognized.
Next, when the red transparent sheet was removed and a discoloration liquid provided on the other hand was applied from the handwriting, the handwriting was erased, so that only black characters were visible again, and a writing instrument suitable for memorization was obtained.

Application example 2
Using the double-headed color-changing writing instrument b of the writing instrument set 1, writing was performed so as to cover the black characters printed on the paper surface, thereby forming a green handwriting. The black characters were visible through the handwriting.
When a red transparent sheet of the same color was placed on the character, the character was visually perceived as black because of the complementary color relationship.
Next, when the red transparent sheet was removed and the color changing solution was applied from the handwriting using the color changing applicator B, the handwriting was discolored, so that a writing tool suitable for memorization was obtained.
In addition, the handwriting formed on the character with the red ink provided on the other side is visible in black due to the complementary color when the green transparent sheet is placed, so that the character is not visible and suitable for memorization. became. The red handwriting could also be erased by the color changing liquid.

Application example 3
Using the color-changing writing instrument A of the writing instrument set 2, writing was performed so as to cover the black characters printed on the paper surface, thereby forming a green handwriting. The black characters were visible through the handwriting.
When a red transparent sheet is placed on the handwriting, the green color of the handwriting and the red color of the sheet are in a complementary color relationship and are visually recognized as black, so that the characters are not visually recognized.
Next, when the red transparent sheet is removed and the color changing liquid is applied from the handwriting using the color changing applicator A, the handwriting is decolored, so that only black characters are visible again, and a writing tool suitable for memorization is obtained. It was.
Further, using the color-changing writing instrument A, letters were written on the paper surface to form a green handwriting.
When a green transparent sheet of the same color was placed on the character, the character was not visible.
Next, the green transparent sheet was removed, and when the color changing liquid was applied onto the handwriting (character) using the color changing applicator A, the handwriting was decolored, so that a writing tool suitable for memorization was obtained.

Claims (4)

C. I. Discoloration of pH 3-5 comprising at least Basic Green 1, a weakly volatile weak acid selected from carboxylic acid, phosphoric acid, phosphorous acid, and carbonic acid, an alkaline substance selected from phosphate and carbonate , and water Ink composition. A discoloring writing instrument comprising the discolorable ink composition according to claim 1. The color-changing writing instrument according to claim 2, comprising a color-changing applicator containing a color-changing liquid at the rear end. A writing instrument set comprising the color-changing writing instrument according to claim 2 and a color-changing applicator containing a color-changing liquid.