JP2006152186A - Erasable ink composition and method for erasing recorded image and writing utensil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an erasable ink composition having excellent coloring stability in ink, well carrying out recording at a high density and optionally erasing a recorded image after recording and having good stability with time after erasing. <P>SOLUTION: The erasable ink composition contains at least an electron-donative coloring compound and an electron-accepting compound and is obtained by dispersing coloring droplets which are liquid or pasty at normal temperature in a solvent. A method for erasing the recorded image and a writing utensil filled with the ink composition are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an erasable ink composition and the like. More specifically, it is filled in a writing instrument and the like, has excellent coloration stability in ink, and can arbitrarily erase a recorded image recorded. The present invention relates to an erasable ink composition capable of stably maintaining an image.

  As a conventional erasable ink, various writing inks using an electron donating color developing compound and an electron accepting compound (developer) represented by leuco dyes have been proposed. For example, there is an ink using an organic solvent as a main solvent as disclosed in Japanese Patent No. 2511838. However, since these inks use alcohol as the main solvent, they have the drawback of causing blurring and back-throwing when written on paper, and are not suitable for writing on paper.

  On the other hand, in order to solve these problems, an ink using water as a main solvent has been proposed. For example, there is a method in which a leuco dye reacts with a developer and develops a pigment as it is and disperses it in an aqueous solvent, as disclosed in JP-A-9-165537, JP-A-10-77437, Japanese Patent Laid-Open No. 10-287081 has been reported. However, since these pigmented leuco dyes are in direct contact with water, they tend to cause problems such as pigment swelling and / or poor coloration (decoloration) in the ink, and inks containing water as the main solvent are sufficient. There was a drawback that it was not possible to obtain a stable coloration.

  JP-A-2001-220530 discloses a method in which a leuco dye that has developed a color by reacting with a developer is fixed with a binder component such as a resin to form a pigment and is dispersed in an aqueous solvent. JP-A-2001-247807, JP-A-2001-271101, JP-A-2001-279144, JP-A-3359018, JP-A-2001-311024, JP-A-2001-342415, etc. have been reported. However, also in this case, since water is in direct contact with the pigment fixed by the binder component without causing interface separation, the swelling of the pigment in the ink and / or poor coloration (decoloration), etc. over time. Insufficient coloration stability was not obtained with an ink containing water as a main solvent. Further, in the above configuration, since components other than the coloring component such as a resin are included in the pigment, the existence ratio of the coloring component is naturally lowered, and there is a disadvantage that a sufficient pigment concentration cannot be obtained.

  Further, there is a method in which a leuco dye and a developer are dyed on resin fine particles and the like and dispersed in an aqueous solvent. Japanese Patent Laid-Open Nos. 2002-294104, 3520275, 2003-73593 Japanese Patent Laid-Open No. 2003-246944 has been proposed. However, in this method, there is a limit to the dyeing of the leuco dye to the resin fine particles, so the pigment concentration cannot be further increased as compared with the case where the coloring component itself is a pigment, and as a recording ink such as a writing instrument. It was difficult to obtain a suitable handwriting density.

By the way, Japanese Patent Application Laid-Open No. 5-9421 is characterized in that a core material made by dissolving or dispersing a coloring material in a first solvent is emulsified in a second solvent that is not compatible with the core material. Ink jet printer inks have been proposed, and leuco dyes, which are a kind of electron-donating color-forming compounds, are described as examples of the coloring material.
However, the leuco dye is only given as an example of a colorant, and the coloration stability of the colorant droplets that are in a colored state due to the reaction between the electron donating colorant compound and the electron acceptor compound is stable. However, it does not solve the problem with respect to the recording property and the erasability after recording, and there is no description of the solution.
Further, as a heat-sensitive color-forming stencil printing emulsion ink, JP-A-6-320859 discloses a water-in-oil emulsion ink composed of an oil layer and an aqueous phase. Proposed are those characterized in that the colorants are contained simultaneously or separately. However, this technique is one in which the leuco dye changes from colorless to colored by heating after recording the decolored leuco dye in the ink. It does not solve the problems of color stability and erasability after recording of colored droplets that are in a colored state due to the reaction of the electron-accepting compound and there is no description of the means for explaining it. It was a thing.
Japanese Patent No. 2511838 JP-A-9-165537 JP-A-10-77437 Japanese Patent Laid-Open No. 10-287081 JP 2001-220530 A JP 2001-247807 A JP 2001-271011 A JP 2001-279144 A Japanese Patent No. 3359018 JP 2001-311024 A JP 2001-342415 A JP 2002-294104 A Japanese Patent No. 3520275 JP 2003-73593 A JP 2003-246944 A JP-A-5-9421 JP-A-6-320859

  The present invention is excellent in color stability in ink when used for writing instruments, etc., can be recorded well at high density, and can be arbitrarily erased after recording, An object of the present invention is to provide an erasable ink composition having good stability over time after erasure, and as a means for solving such a problem, an erasable ink composition and a recorded image erasing method As well as writing instruments.

In order to solve the above-mentioned problems, the present invention provides an erasable ink composition obtained by dispersing liquid or paste-like colored liquid droplets at room temperature in a solvent. An ink composition, a recorded image erasing method and a writing instrument were completed.
That is, the present invention
“1. An erasable ink composition obtained by dispersing liquid or pasty color-forming droplets in a solvent at room temperature containing at least an electron-donating color-forming compound and an electron-accepting compound.
2. 2. The erasable water-based ink composition according to item 1, wherein the color developing droplets are emulsified and dispersed in an aqueous medium.
3. 3. The erasable ink composition according to item 1 or 2, comprising an acid substance that is liquid or pasty at room temperature as an electron-accepting compound.
4). Item 4. The erasable ink composition according to any one of Items 1 to 3, comprising a polyoxyethylene alkyl ether phosphate as an electron-accepting compound.
5. After performing color recording using the erasable ink composition according to any one of items 1 to 4, the recording is performed with an erasing liquid containing at least an alcohol and a solid erasing agent at room temperature. A method for erasing a color recording image, which erases an image.
6). A writing instrument capable of erasing handwriting, which is filled with the ink composition according to any one of Items 1 to 4. ".

  According to the ink composition and the like, when used in a writing instrument or the like, it has excellent color stability in the ink, the color state is less likely to deteriorate over time before recording, and is recorded well at a high concentration. The recording image can be arbitrarily erased after recording and has excellent effects of obtaining an erasable ink composition having good stability over time after erasure. It is.

As an ink composition for a writing instrument or the like, a water-based ink that is less likely to cause bleeding or back-through when writing on paper is suitably required.
For applications such as stamp inks, water-based inks that can be designed to have a relatively low ink viscosity and are less likely to cause bleeding and back-through when printed on paper are suitable.
On the other hand, as an erasable ink composition, as its color developing / coloring (coloring) component, an electron donating color developing compound represented by a leuco dye and an electron generally called a developer. A coloring material containing at least an accepting compound is used, and the electron-donating color-forming compound and the electron-accepting compound react to develop color (color development), and the third component inhibits the reaction. The color is to be erased.
Therefore, the reaction between the electron-donating color-forming compound and the electron-accepting compound is hindered by the presence of a polar substance as the third component used in erasing inks and the like.
By the way, when an aqueous medium is used as the solvent of the ink composition, the reaction is hindered by the coexistence of water, which is a kind of polar solvent similar to the third component used as the erasing material, and is exhibited before recording. The color state tends to be deteriorated with time, and there are many unstable ones, and there is a big problem in stably maintaining the color state in the ink.
As a countermeasure for this, there are some pigments obtained by fixing a coloring component or the like with a binder component such as a resin as described above, but the pigmented one has not only a problem of its concentration, but also the pigment surface and water. However, if the surface reactivity is suppressed to suppress the influence of the polar solvent, there is a problem that the erasability after recording is deteriorated.

  Therefore, the basic configuration of the present invention is to form a liquid or paste-like colored droplet at room temperature containing at least an electron-donating coloring compound and an electron-accepting compound as a coloring component, and as an ink composition, The droplets are dispersed in a solvent. If desired, additional components such as a solvent and a resin can be added to the droplets.

  Many of the color developing components that are preferably used at the present time are oil-soluble, and for the above reasons, the system as the entire ink composition is preferably a water-based ink. It is also possible to form an aqueous droplet and disperse it in an oily medium.

  In the present invention, the color developing component affected by the color developability by the reaction with the solvent or the substance coexisting with the solvent is dispersed and held as droplets in the solvent. The activated surface takes the form of droplets that can hold the color developable component in a state isolated from the solvent, thereby avoiding contact with the color inhibiting substance and reducing the color developed state over time before recording. Can be prevented.

The following describes the erasable water-based ink composition obtained by emulsifying and dispersing colored droplets in an aqueous medium in the present invention.
Here, a technique of emulsifying and dispersing the colored droplets in an aqueous medium is used. According to the emulsification / dispersion technique, water can be used as a solvent, so that the above-mentioned demand is satisfied.
In addition, in the present invention, in order to retain in the ink (aqueous medium) the color developable component that is inherently affected by the color developability by coexistence with the polar substance, it is emulsified and dispersed as droplets. As a result, it is possible to take a droplet structure that can retain the color developable component containing the component that has already been stably colored in the ink in a state of being separated from the solvent (aqueous medium), and polar substances such as water Can be prevented, the coloration state before recording can be prevented from decreasing with time, and recording can be performed with a high density as a stable ink.

In the present invention, liquid or paste-like colored droplets are used as so-called coloring components at room temperature. Compared to conventional pigment-based ones, the stability in ink is extremely excellent while maintaining the erasability of the recorded image at a certain level.
In other words, pigment-based materials are those in which a color-forming component consisting of an electron-donating color-forming compound and an electron-accepting compound is physically fixed with a resin or the like. Although the color reaction of the dye has a large effect on color development and decoloration, the surface of the ink is in direct contact with the solvent, and electron donating color-forming compounds such as leuco dyes are susceptible to color inhibition and prevent it. Therefore, when a protective layer is provided, there is a difficult problem that the erasability of the recorded image after recording deteriorates. In the case of the present invention, at least the electron donating property of the color developing component as a droplet. Since the color developable compound is dissolved or dispersed in the droplet and is not in direct contact with the ink solvent as described above, the occurrence of the problem is small.

  The color-forming droplets are liquid or paste-like droplets at room temperature containing at least an electron-donating color-forming compound and an electron-accepting compound. At that time, when an electron-accepting compound that is liquid or pasty at room temperature is used, the electron-accepting compound itself can be used as a solvent for droplets, and an electron-donating color-forming compound can be dissolved or dispersed therein. In that case, the electron-donating color-forming compound and the electron-accepting compound are in direct contact in a solid and liquid state, and in the ink, the electron-donating color-forming compound is encased in the electron-accepting compound. Since the ink solvent is protected from the ink solvent, the coloration state hardly deteriorates with time before recording, and good recording can be performed at a high density.

  Furthermore, the droplet structure is easy to penetrate and fix near the surface during recording when the colorable droplet has an appropriate viscosity, so that the recording density is high and clear recording is possible. Furthermore, since the erasing liquid and the color developing component can be brought into direct contact with each other during the subsequent erasing, unlike the pigment system, the erasability is excellent and the erasing stability is excellent.

  As described above, the color-forming droplets are composed of at least an electron-donating color-forming compound and an electron-accepting compound, and additional components such as a solvent and a resin that are blended as desired. At this time, when an electron-accepting compound that is liquid or pasty at room temperature is used, a colorant in a droplet state can be formed using only the electron-donating color-forming compound and the electron-accepting compound that are the minimum constituent elements.

Here, the phosphoric acid ester compound is often liquid or pasty at room temperature, and is a kind of electron-accepting compound.
Examples of the phosphoric acid ester compound include phosphoric acid ester of polyoxyethylene alkyl ether and phosphoric acid ester of polyoxyethylene alkyl allyl ether, and phosphoric acid ester of polyoxyethylene alkyl ether is most suitable.

Furthermore, a liquid or paste-like electron-accepting compound may be additionally blended with the above-described configuration at another normal temperature to form droplets with better color developability.
In addition, a colorable droplet can be obtained by using a liquid or pasty electron-accepting compound that is liquid or paste at room temperature as the electron-donating color-forming compound and the electron-accepting compound that are not easily solid or droplets at room temperature.
Specifically, a leuco dye (solid electron-donating color-forming compound) and isoamyl gallate (developer: solid-state electron-accepting compound) and a phosphate ester compound (developer: liquid or paste-like) In particular, the coloration stability in the ink and the coloration stability of the recorded image are more preferable.

  When a phosphate ester compound is blended in a pigment-based ink containing an electron-donating color-forming compound and an electron-accepting compound as in the past, the pigment softens or swells, so that it is stable as a pigment. Cannot exist. Therefore, when a liquid or pasty substance such as a phosphoric ester compound is desired, a wide variety of materials can be used with the colorable droplet structure as in the present invention.

Further, when the colorant coloring material is a pigment (solid state), there is a tendency that the pigment swells and disappears when water enters the pigment. Once the coloration complex between the electron-donating color-forming compound and the electron-accepting compound is destroyed, it is a solid and has low reactivity, making it difficult to recolor, and once it has been inhibited from color development. It is difficult to increase its concentration again. On the other hand, when the coloring material is a liquid droplet (solution state), since it is a liquid, the coloration reactivity between the electron-donating color-forming compound and the electron-accepting compound is high. Even if water enters, if the electron-accepting compound (acid) concentration in the droplet is kept above a certain level, it is considered that the coloration can be maintained due to its high reactivity.
At this time, if a liquid electron-accepting compound is used as the developer at room temperature, it is possible to obtain liquid droplets with a high acid concentration. The

  As the electron-donating color-forming compound used in the present invention, leuco dyes that are generally used electron-donating color-forming compounds can be used, and these can be used alone or in combination of two or more. Can do.

The electron-accepting compound used in the present invention acts as a color developer for the electron-donating color-forming compound, and is preferably a liquid or paste-like compound at room temperature as described above. In particular, acidic substances such as phosphate esters are preferred.
Specific examples include phosphoric acid esters of polyoxyethylene alkyl ether and / or phosphoric acid esters of polyoxyethylene alkyl allyl ether. More specifically, Prisurf A212E, A210G, A207H, AL, A212C, A215C, A208B, A208S, A208N, A208F, DB-01 (above, Daiichi Kogyo Seiyaku Co., Ltd. ), Phosphanol RE-410, PE-510, RE-610, RM-410, RM-510, RM-710, RH-610H, RP-710, RS-410 RS-610, RS-710, RD-510Y, RB-410, RA-600, BH-650, ML-220, LO-529, SC-6103, GB-520 RD-720 (manufactured by Toho Chemical Industry Co., Ltd.).
An acidic substance that is solid or pasty at room temperature can be used as long as the colorable droplets can be made into a liquid or paste at room temperature.
Specifically, Plysurf A217E, A219B, M208F (or more), as polyoxyethylene alkyl ether phosphate ester and / or polyoxyethylene alkyl allyl ether phosphate ester which is solid or pasty at normal temperature Daiichi Kogyo Seiyaku Co., Ltd.), Phosphanol RE-960, RL-210, ML-200 (above, manufactured by Toho Chemical Co., Ltd.), etc., and phosphoric acid of polyoxyethylene alkyl ether Esters are optimal.
In addition, as long as the color-forming droplets can be made into a liquid or paste at room temperature, other electron-accepting compounds can be used in combination or alone as a developer. For example, gallic acid ester-based, hydroxyacetophenone-based, hydroxybenzophenone-based, benzenetriol-based, benzenediol-based, bisphenol-based, triphenol-based compounds, and the like can be given. Among them, gallic acid ester compounds which are electron accepting compounds having a phenolic hydroxyl group are preferable. Specifically, n-propyl gallate, n-butyl gallate, i-amyl gallate, lauryl gallate, cetyl gallate , Myristyl gallate, stearyl gallate, behenyl gallate and the like. These developers can be used alone or in admixture of two or more.

  Moreover, components other than those described above can be arbitrarily used in the color-forming droplets. For example, the viscosity of the droplets present in the ink may be adjusted, or a solvent may be added to obtain a liquid or paste-like form at room temperature. For example, 2-phenoxyethanol, benzyl alcohol, alkylnaphthalene, diallylalkane, Nisseki Hyzol SAS296 (manufactured by Shin Nippon Petrochemical Co., Ltd.) and the like can be mentioned.

 Various resins may be added as a solubilizing agent for compatibilizing the electron-donating color-forming compound and the electron-accepting compound or for improving the solubility thereof. Specifically, an acrylic resin, a styrene resin, a phenol resin, etc. are mentioned. More specifically, examples of the acrylic resin include Dianal BR-50, BR-52, BR-53, BR-60, BR-64, BR-73, BR-75, and BR-. 77, BR-79, BR-80, BR-82, BR-83, BR-85, BR-87, BR-88, BR-90, BR-93, BR- 95, BR-100, BR-101, BR-102, BR-105, BR-106, BR-107, BR-108, BR-112, BR-113, BR- 115, the same BR-116, the same BR-117, the same BR-118 (above, manufactured by Mitsubishi Rayon Co., Ltd.), and the styrene resin, Heimer TB-1000F, the same ST-120 (above, Sanyo Chemical Industries, Ltd.) Manufactured), Picolastic A-5, A-75, D-125, the D-0.99 (or higher, Rika Hercules Co., Ltd.), as the phenol resin, SUMILITERESIN PR-fifty thousand six hundred forty-one, the PR-219 (above, Sumitomo Bakelite Co., Ltd.). Of these, the phenol resin has a phenolic hydroxyl group having a color developing effect, so it does not hinder the color reaction of the electron donating color-forming compound, and is most preferable, and then a styrene resin having no polar group is the color stability. It is preferable because it hardly affects Care must be taken because acrylic resins having polar groups may affect the color stability.

In addition, a desensitizer ordinarily used for improving handwriting erasability may be added. For example, higher alcohols are used as polar organic compounds, and amines are used as basic compounds. Also, a resin having a polar group can be used as a desensitizer. Specific examples include butyral resin. More specifically, ESREC BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-S, BL-SH, BX-10 BX-L, BM-1, BM-2, BM-5, BM-S, BM-SH, BH-3, BH-6, BH-S, BX-1 BX-3, BX-5, KS-10, KS-1, KS-3, KS-5 (above, manufactured by Sekisui Chemical Co., Ltd.). However, the type and amount of addition must be used within a range that does not affect the coloration stability of the colorable droplets.

  In the present invention, the colorable droplets are dispersed in a solvent to obtain an ink composition. As the solvent, water and an aqueous medium such as a water-soluble solvent are preferable.

  In the ink composition, other components that are usually used according to the intended use can be arbitrarily used. For example, you may add resin etc. which are normally used in order to adjust ink viscosity or to adjust permeability or to improve water resistance. In addition, components such as preservatives, rust preventives, dispersants, lubricants, humectants, pH adjusters, viscosity adjusters, shear thinning agents, surfactants, desensitizers, specific gravity adjusters may be used. it can. However, the type and amount of addition must be within a range that does not affect the coloration stability of the colorable droplets used in the present invention.

As a preservative, 1,2-benzisothiazolin-3-one, sodium benzoate, phenol and the like can be used.
As the dispersant, a commonly used surfactant may act as a desensitizer, so it must be selected with care. Therefore, it is preferable to use a water-soluble resin-based dispersant such as polyvinyl alcohol.
As the humectant, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, glycerin, polyethylene glycol and other polyhydric alcohols, urea, thiourea, ethylene urea, etc. are used alone or in combination of two or more. Can be used in combination.
As a pH adjuster, monoethanolamine, diethanolamine, triathanolamine, N, N-diethanolamine, N, N-dibutylethanolamine, N, N-methyldiethanolamine, sodium hydroxide, potassium carbonate, citric acid, etc. are used. be able to.
As the shear thinning agent, an inorganic, natural polymer, synthetic polymer, high molecular polysaccharide or the like shear thinning agent can be used.
Specific gravity adjusters include sodium molybdate, ammonium molybdate, potassium molybdate, sodium tungstate, potassium tungstate, ammonium paramolybdate, sodium metatungstate, ammonium metatungstate, sodium molybdophosphate, sodium molybdosilicate, tongue Sodium strinate, sodium tungstosilicate, SPT (manufactured by SOMETU) or the like can be used.

The ink composition of the present invention can be used by filling various known writing instruments and stamps.
Further, the ink composition can be produced by a general production method according to the use. When the ink composition of the present invention is used for a writing instrument, it can be suitably used for a fountain pen, a sign pen, a marking pen, a plate pen, a ballpoint pen, and the like.

The ink composition of the present invention is an erasable ink composition. When the ink composition of the present invention is filled in a writing instrument or the like and written, a handwritten, that is, a colored recording image can be obtained. At that time, a solvent such as water in the ink is dried or penetrates and diffuses into the paper surface, and when the colored droplets have an appropriate viscosity, the colored component in the droplets is Since it permeates and fixes near the surface of the paper, a high-density recording image can be obtained.
In addition, as described above, those that inhibit the color developability of the color developability do not coexist, so that a relatively stable recorded image can be maintained even after recording.
On the other hand, the recorded image can be erased arbitrarily with an erasing liquid containing an erasing agent, and the color erasing reaction is extremely smooth, and the temporal stability after erasing is also good. The coloration component is penetrating and fixing near the surface of the paper during recording, and the components that make up the droplet components are more soluble in the erasing liquid solvent, making them more reactive with erasing agents than pigments. This is due to the fact that they are more sensitive to the color-decoloring reaction.

As a method for erasing the ink composition of the present invention, a desensitizing action by a polar compound is used. By applying a polar compound on the recording image, the complex of the electron-donating color-forming compound and the electron-accepting compound in a colored state is destroyed, and the electron-donating color-forming compound such as a leuco dye is chemically colorless. To the state.
A preferred method for erasing a color-recorded image of the present invention is, specifically, erasing an organic compound having a low or medium boiling organic solvent and a polar group after performing color recording using the ink composition. The recorded image is erased with an erasing liquid containing at least an agent.
Examples of the organic solvent having a low boiling point or a medium boiling point include ethanol, isopropyl alcohol, 3-methoxy-3-methylbutanol, methyl ethyl ketone, propylene glycol monomethyl ether, propylene glycol monoethyl ether, methyl lactate, and ethyl lactate.
Examples of the erasing agent for the organic compound having a polar group include higher alcohols, quaternary ammonium salts, and alkylamines. Among these, when considering rewriteability, a polar organic compound that is solid at room temperature is particularly preferable.
When a solid erasing agent is used at room temperature, a solvent such as alcohol volatilizes after erasing, and then the erasing agent becomes a solid and is fixed on the paper surface. Normally, regardless of the type of erasing agent, an excessive amount of erasing agent remains on the paper after erasing the handwriting, but this comes into contact with the colorant coloring material of the writing ink at the time of rewriting. At this time, if the erasing agent is in a solid state, the reactivity with the color material is suppressed to a small value, and thus the handwriting tends to be difficult to disappear. If it is liquid, rewriting tends to be difficult due to its high reactivity. For the above reasons, it is preferable to use a solid erasing agent when rewriting is considered.
Also, a resin having a polar group can be suitably used as an erasing agent for the same reason, and is more preferable from the viewpoint of re-writing property.

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to the examples.

Formulation Example 1
Colorable droplet component a
Leuco dye (electron-donating color-forming compound: Note 1) 30.0% by mass
Developer 1 (electron-accepting compound: Note 2) 70.0% by mass
The leuco dye and the developer 1 were heated and melted at 170 ° C. to develop a color, and a paste-like colored droplet component a was obtained at room temperature.
Note 1: Black-15 (manufactured by Yamamoto Kasei Co., Ltd.) was used as the leuco dye.
Note 2: As developer 1, polyoxyethylene alkyl ether phosphate ester (Plysurf A208S, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

Formulation Examples 2-6
The composition of the color-forming droplet component was as shown in Table 1, and liquid or paste-like color-forming droplet components b to f were obtained at room temperature.
In Formulation Example 2, the leuco dye, the developer 1 and the developer 3 were heated and melted at 170 ° C. to develop a color, and a paste-like color droplet component b was obtained at room temperature.
In Formulation Example 3, a paste-like colored droplet component c was obtained at room temperature in the same manner as Formulation Example 1.
In Formulation Example 4, the leuco dye, the developer 1 and the resin were heated and melted at 170 ° C. to develop a color, and a paste-like colored droplet component d was obtained at room temperature.
In Formulation Example 5, after the leuco dye, the developer 1 and the resin were heated and melted at 170 ° C., a solvent was further added and the mixture was heated and melted at 100 ° C. to obtain a color-forming droplet component e which was liquid at room temperature.
Formulation Example 6 is a color developing solution that is liquid at room temperature by adding leuco dye, developer 1, developer 3 and resin, heating and melting at 170 ° C., adding a solvent and heating and melting at 100 ° C. Drop component f was obtained.

注１：Ｂｌａｃｋ−１５（山本化成（株）製）
注２：ポリオキシエチレンアルキルエーテルのリン酸エステル（プライサーフＡ２０８Ｓ 第一工業製薬（株）製）
注３：ポリオキシエチレンアルキルアリルエーテルのリン酸エステル（プライサーフＡL 第一工業製薬（株）製）
注４：没食子酸ｉ−アミル（東京化成工業（株）製）
注５：フェノール樹脂（スミライトレジンＰＲ−２１９ 住友ベークライト（株）製）
注６：日石ハイゾールＳＡＳ２９６（新日本石油化学（株）製）

Note 1: Black-15 (manufactured by Yamamoto Kasei Co., Ltd.)
Note 2: Polyoxyethylene alkyl ether phosphate ester (Plysurf A208S, Daiichi Kogyo Seiyaku Co., Ltd.)
Note 3: Phosphoric acid ester of polyoxyethylene alkyl allyl ether (Plysurf AL, Daiichi Kogyo Seiyaku Co., Ltd.)
Note 4: i-amyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.)
Note 5: Phenol resin (Sumilite Resin PR-219, manufactured by Sumitomo Bakelite Co., Ltd.)
Note 6: Nisseki Hyzol SAS296 (manufactured by Nippon Petrochemical Co., Ltd.)

Example 1
Ion-exchanged water 67.8% by mass
Dispersant (Note 7) 2.0% by mass
Preservative (Note 11) 0.2% by mass
Moisturizer (Note 12) 10.0% by mass
Colorable droplet component a 20.0% by mass
First, a dispersant, preservative, and humectant were added and dissolved in ion exchange water to obtain a base solution. Thereafter, the base liquid was added to the color developable droplet component a, and dispersed with an ultrasonic disperser for 20 minutes to obtain a black emulsified and dispersed aqueous ink composition.
Note 7: Polyvinyl alcohol (PA-05GP manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a dispersant.
Note 11: 1,2-Benzisothiazolin-3-one (Proxel XL-2 (S) manufactured by Avicia Co., Ltd.) was used as a preservative.
Note 12: Glycerin was used as a humectant.

(Examples 2 to 11)
A water-based ink composition was obtained in the same manner as in Example 1 except that the ink composition was as shown in Table 2.

注７：ポリビニルアルコール（ＰＡ−０５ＧＰ 信越化学工業（株）製）
注８：陰イオン性界面活性剤（デモールＮＬ 花王（株）製）
注９：非イオン性界面活性剤（エマルゲン１０９Ｐ 花王（株）製）
注１０：クエン酸一水和物（特級 和光純薬工業（株）製）
注１１：１，２−ベンゾイソチアゾリン−３−オン（プロキセルＸＬ−２（Ｓ） アビシア（株）製）
注１２：グリセリン

Note 7: Polyvinyl alcohol (PA-05GP manufactured by Shin-Etsu Chemical Co., Ltd.)
Note 8: Anionic surfactant (Demol NL Kao Co., Ltd.)
Note 9: Nonionic surfactant (Emulgen 109P manufactured by Kao Corporation)
Note 10: Citric acid monohydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.)
Note 11: 1,2-benzisothiazolin-3-one (Proxel XL-2 (S) manufactured by Avicia Co., Ltd.)
Note 12: Glycerin

Formulation Examples 6-11
The composition of the color developable component was as shown in Table 3, and the color developable components f to k were obtained.
Formulation Example 6 is a color developing solution that is liquid at room temperature by adding leuco dye, developer 1, developer 3 and resin, heating and melting at 170 ° C., adding a solvent and heating and melting at 100 ° C. Drop component f was obtained.
In Formulation Example 7, a paste-like colored droplet component g was obtained at room temperature in the same manner as Formulation Example 4.
In Formulation Example 8, after the leuco dye and the developer 1 were heated and melted at 170 ° C., a solvent was further added and the mixture was heated and melted at 100 ° C. to obtain a color-forming droplet component h that was liquid at room temperature.
In Formulation Example 9, the leuco dye and the developer 4 were heated and melted at 170 ° C. to develop a color, and a solid colorable solid component i was obtained at room temperature.
In Formulation Example 10, the leuco dye, the developer 4 and the resin were heated and melted at 170 ° C. to develop a color, thereby obtaining a colorable solid component j that was solid at room temperature.
Formulation Example 11 was similar to Formulation Example 10 to obtain a colorable solid component k that was solid at room temperature.

注１：Ｂｌａｃｋ−１５（山本化成（株）製）
注２：ポリオキシエチレンアルキルエーテルのリン酸エステル（プライサーフＡ２０８Ｓ 第一工業製薬（株）製）
注４：没食子酸ｉ−アミル（東京化成工業（株）製）
注５：フェノール樹脂（スミライトレジンＰＲ−２１９ 住友ベークライト（株）製）
注６：日石ハイゾールＳＡＳ２９６（新日本石油化学（株）製）
注１３：没食子酸ｎ−プロピル（和光一級 和光純薬工業（株）製）
注１４：スチレン樹脂（ハイマーＳＴ-１２０ 三洋化成工業（株）製）
注１５：アクリル樹脂（ダイヤナールＢＲ-１００ 三菱レイヨン（株）製）

Note 1: Black-15 (manufactured by Yamamoto Kasei Co., Ltd.)
Note 2: Polyoxyethylene alkyl ether phosphate ester (Plysurf A208S, Daiichi Kogyo Seiyaku Co., Ltd.)
Note 4: i-amyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.)
Note 5: Phenol resin (Sumilite Resin PR-219, manufactured by Sumitomo Bakelite Co., Ltd.)
Note 6: Nisseki Hyzol SAS296 (manufactured by Nippon Petrochemical Co., Ltd.)
Note 13: n-propyl gallate (Wako First Grade Wako Pure Chemical Industries, Ltd.)
Note 14: Styrene resin (Hymar ST-120, manufactured by Sanyo Chemical Industries, Ltd.)
Note 15: Acrylic resin (Dianar BR-100, manufactured by Mitsubishi Rayon Co., Ltd.)

(Examples 12 to 15), (Comparative Examples 1 to 3)
The ink composition was as shown in Table 4, and Examples 12 to 15 were similar to Example 1 to obtain water-based ink compositions.
In Comparative Examples 1 to 3, first, a dispersant and preservative were added to ion exchange water and dissolved to obtain a base solution. Then, the colorable solid components i to k were added to the base solution, and a bead mill was used. A black pigment-dispersed aqueous ink composition was obtained by pulverizing and dispersing for 60 minutes.

注７：ポリビニルアルコール（ＰＡ−０５ＧＰ 信越化学工業（株）製）
注８：陰イオン性界面活性剤（デモールＮＬ 花王（株）製）
注９：非イオン性界面活性剤（エマルゲン１０９Ｐ 花王（株）製）
注１０：クエン酸一水和物（特級 和光純薬工業（株）製）
注１１：１，２−ベンゾイソチアゾリン−３−オン（プロキセルＸＬ−２（Ｓ） アビシア（株）製）
注１２：グリセリン
注１６：トリエタノールアミン

Note 7: Polyvinyl alcohol (PA-05GP manufactured by Shin-Etsu Chemical Co., Ltd.)
Note 8: Anionic surfactant (Demol NL Kao Co., Ltd.)
Note 9: Nonionic surfactant (Emulgen 109P manufactured by Kao Corporation)
Note 10: Citric acid monohydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.)
Note 11: 1,2-benzisothiazolin-3-one (Proxel XL-2 (S) manufactured by Avicia Co., Ltd.)
Note 12: Glycerin Note 16: Triethanolamine

The ink compositions obtained in the above examples and comparative examples were tested by the following test method. The results are shown in Tables 2 and 4.
1. Ink viscosity: After the ink composition was prepared, the viscosity at a shear rate of 384 s ⁻¹ (100 rpm) was measured with a DV-2 + viscometer (Brookfield) using a CPE-42 spindle (at 20 ° C.).
2. Coloration stability: The ink composition was filled into a 30 ml screw tube, put in a capped state at 50 ° C. for 12 weeks, and the color tone of the ink composition was visually confirmed. The evaluation criteria were as follows.
A: No change from the initial stage.
○: Slightly faded from the initial stage.
Δ: Fading from the initial stage.
X: Loss of coloration.
3. Handwriting density: An ink composition is filled into a cartridge for water-based ballpoint pens manufactured by Pilot Corporation (trade name: Multiball (fine characters)), and a refill is made. Using the ballpoint pen, fine paper (OK Moonlight White, It was written on Oji Paper Co., Ltd. (52.3 g / cm ² ). The evaluation criteria were the following three stages.
A: A handwriting that is sufficiently deep to be legible is obtained.
Δ: A thin but readable handwriting was obtained.
X: A handwriting thin enough to be unreadable was obtained.
4). Handwriting erasability: A cotton pad impregnated with erasable ink composed of denatured alcohol (Alcosol P-9, manufactured by Gansu Chemical Industry Co., Ltd.) and laurylamine (Farmin 20D, Kao Co., Ltd.), a solid erasing agent at room temperature. Incorporated into the exterior material of a fluorescent marker (trade name: spot writer) manufactured by Pilot Corporation, the eraser was applied to the handwriting on the fine paper used in handwriting density evaluation, and the erased state was observed. The evaluation criteria were the following three stages.
○: Almost decolored.
Δ: Decoloring was not sufficient.
X: The color was not erased.

From the results of Table 1 and Table 2, the ink compositions of Examples 1 to 15 can be filled in a writing instrument and write well, and the recorded image (handwriting) can be arbitrarily erased after writing, and the time-lapse presentation thereof. It turns out that it is a water-based ink composition excellent also in color stability.
However, although the ink compositions of Examples 12 to 13 had good handwriting density and handwriting erasability, a pH adjustment agent that is not an acid substance was used and a slightly high pH was designed. As a result, the ink for writing instruments was somewhat lacking in stability, and the coloration stability was slightly inferior.
In addition, the ink compositions of Examples 14 to 15 also had good handwriting density and handwriting erasability, but there was some difficulty in the compatibility of the colorable droplet components, and precipitates were formed in the droplets. The ink for writing instruments was somewhat lacking in stability.
In Comparative Examples 1 to 3, since the color developing component is solid (pigment type), the color stability is inferior. In Comparative Example 3 and the like, the color developing component (pigment) is used in the ink. Swelling occurred and could not be written.

(Application example of erase method)
In the above examples and the evaluation method thereof, after performing color recording using a writing instrument filled with the water-based ink composition, the recorded image is erased with an erasing liquid containing at least an alcohol and a solid erasing agent at room temperature. Therefore, good erasability was obtained. Although specific description was omitted, in terms of re-writeability, better results were obtained than when a liquid erasing agent was used at room temperature. Furthermore, when a resin having a polar group or the like was used as an erasing agent, better rewriting performance could be obtained for the reasons described above. In addition, when the composition of only liquid alcohol was used as the erasing liquid, sufficient erasing stability could not be obtained.

Claims (6)

  An erasable ink composition prepared by dispersing liquid or paste-like color-forming droplets in a solvent at room temperature containing at least an electron-donating color-forming compound and an electron-accepting compound.   The erasable water-based ink composition according to claim 1, wherein the color-forming droplets are emulsified and dispersed in an aqueous medium.   The erasable ink composition according to claim 1, comprising an acid substance that is liquid or pasty at room temperature as an electron-accepting compound.   The erasable ink composition according to any one of claims 1 to 3, comprising a phosphoric acid ester of polyoxyethylene alkyl ether as the electron-accepting compound.   After performing color recording using the erasable ink composition according to any one of claims 1 to 4, the recorded image is formed with an erasing liquid containing at least an alcohol and a solid erasing agent at room temperature. A method for erasing a color-coded recorded image. A writing instrument erasable in handwriting, which is filled with the ink composition according to claim 1.