JP2019077749A - Ink composition for memorization pen - Google Patents

Abstract

To provide an ink composition for memorization pen which is used for so-called memorization pen set formed of a combination of a marking pen and a semi-transparent sheet, and which prevents recognition of characters even when a marked portion is covered with a semi-transparent sheet, and prevents infiltration of the ink into a rear face of a paper face even when an object to be written is thin paper like a dictionary.SOLUTION: The ink composition for memorization pen contains at least resin particles each having a glass transition temperature (Tg) of 45°C or lower, and has surface tension of ink of 38 mN/m or more.SELECTED DRAWING: None

Description

  The present invention relates to an ink composition for a dark pen, which is used for a so-called dark pen set or the like, which is a combination of a marking pen (dark pen) and a translucent colored sheet.

  Conventionally, a so-called memorizing pen set consisting of a combination of a marking pen and a translucent colored sheet is well known as a standard writing instrument.

  In this memorizing pen set, for example, a memorizing task at the time of learning is performed by making a printed part etc. not visible by superposing a translucent colored sheet consisting of a specific color on the part printed or written by a marking pen. (See, for example, Patent Document 1).

  However, there are problems with such a memorizing pen set in several respects. As typical ones, it becomes difficult to see the marked characters, etc., the characters can be recognized even if the marking portion is covered with a translucent colored sheet, and the object to be written is a thin paper such as a dictionary. In some cases, the ink may penetrate to the back side of the sheet.

Japanese Patent Application Laid-Open No. 57-37389

  SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems and the like in the prior art, and is an ink composition for dark pen used in a so-called dark pen set or the like comprising a combination of a marking pen and a translucent colored sheet. It is easy to see the marked characters etc. In addition, even if the marking portion is covered with a translucent colored sheet, the characters can not be recognized, and even if the object to be written is thin paper such as a dictionary, An object of the present invention is to provide an ink composition for a dark pen which does not allow the ink to penetrate to the back side of the paper surface.

  The present inventors have conducted intensive studies in view of the above-described conventional problems and the like, and as a result, they contain resin particles having a glass transition temperature (Tg) of at least a specific temperature, and make the surface tension of the ink a specific value or more. As a result, the present inventors have found that the above-mentioned ink composition for dark pens can be obtained, and have completed the present invention.

That is, the ink composition for dark pens of the present invention is characterized by containing resin particles having a glass transition temperature (Tg) of 45 ° C. or less at least and the surface tension of the ink is 38 mN / m or more.
The resin particles are preferably colored resin particles.
The average particle size of the resin particles is preferably 20 to 300 nm.

  According to the present invention, in the ink composition for dark pens used for a so-called dark pen set etc. consisting of a combination of a marking pen and a translucent colored sheet, it is easy to see marked characters etc., and the marking portion is translucent. Even if it is covered with a colored sheet, characters can not be recognized, and even when the target to be written is a thin paper such as a dictionary, the ink composition for a dark pen does not penetrate the back of the paper surface. Provided.

Hereinafter, embodiments of the present invention will be described in detail.
The ink composition for dark pens of the present invention is characterized in that it contains at least a resin particle having a glass transition temperature (Tg) of 45 ° C. or less, and the surface tension of the ink is 38 mN / m or more.

The resin particles used in the present invention have a glass transition temperature (Tg) of 45 ° C. or less. For example, hollow resin particles having voids inside the particles, solid resin particles having no voids inside the particles, colored resin particles Etc.
The material of these resin particles is not particularly limited as long as the glass transition temperature (Tg) is 45 ° C. or lower, and hollow resin particles and solid resin particles are, for example, polyethylene, polypropylene, polyvinyl chloride, Homopolymers such as polyvinylidene chloride, polyvinyl acetate, polystyrene, polymethyl methacrylate, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, polyurethane, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer A copolymer in which two or more types of monomers such as a styrene-butadiene copolymer are coexistent, and solid resin particles such as modified products thereof can be used.

The colored resin particles that can be used have a glass transition temperature (Tg) of 45 ° C. or less, and are not particularly limited as long as they are composed of colored resin particles, and, for example, 1) in resin particles Colored resin particles in which a coloring agent comprising a pigment such as carbon black, an inorganic pigment such as titanium oxide, an organic pigment such as a phthalocyanine pigment, or an azo pigment is dispersed, 2) a coloring agent wherein the surface of the resin particle comprises the above pigment And colored resin particles in which a coloring agent composed of a dye such as a direct dye, an acid dye, a basic dye, a food dye, or a fluorescent dye is dyed on the resin particle.
These hollow resin particles, solid resin particles, and colored resin particles may be an aqueous dispersion or an organic solvent dispersion dispersed in water or an organic solvent.
Moreover, when the glass transition temperature (Tg) of these resin particles exceeds 45 ° C. (45 ° C.), film formation of the particles becomes difficult and the effect of the present invention can not be exhibited. The lower limit of the glass transition temperature (Tg) may be −100 ° C. or higher.
In the present invention, the glass transition temperature (Tg) is a differential scanning calorimeter (DSC) manufactured by Rigaku Corporation at a heating rate of 10 ° C./min, and the temperature is raised from -150 ° C. to + 150 ° C. The heat quantity was measured, and the obtained endothermic curve was differentiated to obtain an inflection point, and this inflection point was judged as Tg.

  As preferable resin particles, 1) resin particles composed of at least an acrylic or methacrylic acid and an ester monomer of a C 2-18 linear or cyclic alcohol, from the viewpoint of further exhibiting the effects of the present invention, 2) A colored resin composed of the resin particle of the above 1), that is, at least an ester monomer of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms, and a basic dye or an oil-soluble dye Particles are desirable.

An ester monomer of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms, which can be used, is a skeleton monomer, and is a linear or 2 to 18 carbon atoms with acrylic acid or methacrylic acid. It is an ester with a cyclic alcohol, and specifically, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, T-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Such as palmityl acid, stearyl (meth) acrylate and behenyl (meth) acrylate Even without can be suitably represents one. In addition, the description of said "(meth) acrylic acid" represents "acrylic acid and / or methacrylic acid."
Particularly preferably, the use of n-butyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate and dicyclopentanyl (meth) acrylate which further enhances the effect of the present invention is desirable.

Examples of basic dyes that can be used when forming colored resin particles include di- and triarylmethane dyes; quinone dyes such as azine dyes (including nigrosine), oxazine dyes and thiazine dyes; xanthene dyes Triazole azo dyes; thiazole azo dyes; benzothiazole azo dyes; azo dyes; methine dyes such as polymethines, azomethines and azamethines; anthraquinone dyes; at least basic dyes such as phthalocyanine dyes One is mentioned, preferably a water-soluble basic dye is desirable.
Specific basic dyes that can be used include C.I. I. Basic yellow (-1, -2, -9, -40, -80, etc.), C.I. I. Basic orange (-1, -2, -7, -34, etc.), C.I. I. Basic red (-1, -1: 1, -2, -3, -53, etc.), C.I. I. Basic violet (-1, -2, -3, -39, etc.), C.I. I. Basic Blue (-1, -2, -5, -7, -88, etc.), C.I. I. Basic green (-1, -4, -6, -10, etc.), C.I. I. Basic brown (-1, -2, -4, -15 etc.), C.I. I. Each No. described in COLOR INDEX such as basic black (-1, -2, -7, -8 etc.). The dye of each color of is mentioned.
In addition, these commercially available products can also be used, and yellow basic dyes such as AIZEN CATHILON YELLOW GPLH (trade names of Hodogaya Chemical Industry Co., Ltd.) and red basic dyes such as AIZEN CATHILON RED BLH and AIZEN CATHILON RED RH and others (trade names of Hodogaya Chemical Industry Co., Ltd.), Diacryl Supra Brilliant Red 2 G and others (trade names of Mitsubishi Chemical Co., Ltd.), Sumicacryl Red B (trade names of Sumitomo Chemical Co., Ltd.), blue basic dyes, etc. In the case of green basic dyes such as AIZEN CATHILON TURQ UOISE BLUE LH (trade name of Hodogaya Chemical Industry Co., Ltd.), etc., and in the case of brown basic dyes such as Diacryl Supra Brilliant Green 2GL (trade name of Mitsubishi Chemical Co., Ltd.) Janus Brown R (Nippon Chemical Co., Ltd. under the trade name), AIZEN CATHILON BROWN GH (Hodogaya Chemical Co., Ltd. under the trade name), and the like.

The oil-soluble dyes which can be used include monoazo, disazo, metal complex type monoazo, anthraquinone, phthalocyanine, triarylmethane and the like which are generally commercially available. In addition, a salt forming type oil-soluble dye in which a functional group such as an acid / basic dye is substituted with a hydrophobic group can also be used.
As a yellow series, C.I. I. Solvent Yellow 16, 29, 30, 56, 79, 82, 114, 116; I. Solvent orange 67; as red, C.I. I. Solvent red 1, 8, 25, 27, 49, 122, 127, 132, 146, 218; I. Solvent Blue 5, 36, 38, 44, 63, 70, 83, 105, 111; as black, C.I. I. Solvent Black 3, 7, 27, 29;
Specific examples of commercially available oil-soluble dyes include blue dye SBN blue 701 (made by Hodogaya Chemical Industry Co., Ltd.), blue dye SPT Blue 26 (made by Hodogaya Chemical Industry Co., Ltd.), red dye Savinyl Pink 6BLS (made by Clariant Chemicals Inc.) Etc. can be mentioned.

  The preferred resin particles of the above 1) to be used are, for example, ammonium persulfate, potassium persulfate, peroxide in a mixed monomer containing the above-mentioned acrylic acid or methacrylic acid and an ester monomer of C2-18 linear or cyclic alcohol. Producing an aqueous dispersion of resin particles by emulsion polymerization using hydrogen etc. as a polymerization initiator, a polymerization initiator further using a reducing agent in combination, and, if necessary, a polymerizable surfactant. In the case of the preferred colored resin particles of the above 2), for example, a basic dye or an oil-soluble dye is dissolved in the above mixed monomer, and ammonium persulfate, potassium persulfate, hydrogen peroxide or the like is used as a polymerization initiator In addition, a coloring agent may be used as a polymerization initiator in which a reducing agent is further used in combination, and further, when necessary, emulsion polymerization is performed using a polymerizable surfactant. It is possible to produce an aqueous dispersion of particles. Although the above-mentioned dyeing was carried out simultaneously with the polymerization, the dyeing may be carried out by dissolving a basic dye or an oil-soluble dye after the polymerization.

  At the time of the above-mentioned emulsion polymerization, other hydrophobic vinyl monomers may be mixed and emulsion polymerization may be performed as long as the effects of the present invention are not impaired. Examples of hydrophobic vinyl monomers that can be used include styrenes and styrenes such as methylstyrene, and also have reactive crosslinking groups such as epoxy groups, hydroxymethylamide groups and isocyanate groups in emulsion polymerization. A monomer or a polyfunctional monomer having two or more vinyl groups may be blended and crosslinked.

  When used as colored resin fine particles, the content of the above-mentioned basic dye or oil-soluble dye is preferably 0 with respect to the total amount of monomers, from the viewpoint of the function as a coloring material such as color developability, weatherability and stability. It is desirable that the amount be 2 to 50% by mass, and more preferably 0.5 to 10% by mass.

  The polymerizable surfactant which can be used according to the need is not particularly limited as long as it is a polymerizable surfactant generally used for the above-mentioned emulsion polymerization, but as the polymerizable surfactant, for example, an anionic Or a nonionic polymerizable surfactant, Adeka Resoap NE-10, NE-20, NE-30, NE-40, SE-40N, manufactured by Adeka Co., Ltd., Kao Co., Ltd. Latemul S-180, S-180A, S-120A, and Eleminol JS-20 manufactured by Sanyo Chemical Industries, Ltd., and the like. The amount of these polymerizable surfactants used is desirably 0 to 50% by mass, preferably 0.1 to 50% by mass, based on the total amount of the monomers.

The above-described preferred embodiment, specifically, by emulsion polymerization of a mixed monomer containing at least 40% by mass of the carboxyl group-containing vinyl monomer of the component (A) and 20% by mass or more of the ester monomer of the component (B) In addition, the basic dye or the oil-soluble dye is dissolved in the mixed monomer as described above, and then emulsion polymerization is performed, or at least after the polymerization of the components (A) and (B), the basic dye or By dissolving and staining the oil-soluble dye, a dispersion liquid of resin fine particles and colored resin fine particles in which 20 to 50% by mass of colored resin fine particles as resin solid content is dispersed in water is obtained.
The obtained resin fine particles and colored resin fine particles have a glass transition temperature (Tg) of 45 ° C. or less, are hard to sink in a solvent such as water, and are excellent in line-drying (fast-drying) and line-forming properties A high contact angle (75 ° to the paper surface), a high surface tension, and in the case of colored resin fine particles, color selection close to infinity by selecting each color such as the above-mentioned basic dye or oil-soluble dye to be used It also has the advantages of being able to do pinpoint toning. Therefore, as resin particles of the ink composition for dark pen, the colored resin fine particles are useful as a coloring material.

The average particle diameter of the resin particle of the said preferable aspect and the resin particle containing colored resin microparticles | fine-particles are
From the point of coloring property and dispersion stability, the thing of 20-300 nm is desirable.
More preferably, 40 to 150 nm, particularly preferably 60 to 110 nm are desirable.
In addition, the "average particle diameter" prescribed | regulated by this invention is the value of D50 measured with the particle size distribution measuring apparatus [FPAR1000 (made by Otsuka Electronics)].

When the colored resin particles are used alone as a coloring material, the content of these resin particles may be determined according to the purpose, for example, when used together as a non-colored resin particle and as a colored resin particle to be a coloring material. fluctuate. For example, when it is difficult to sink resin particles in a solvent such as water, and used for line-drying (quick-drying), line-forming, high contact angle (75 ° to paper), high surface tension, etc. When used as colored resin particles, each has an appropriate content but is not uniform.
Specifically, from the viewpoint of achieving the effects of the present invention at a high level, when used as resin particles without coloring, 5 to 30% by mass is preferable with respect to the total amount of the ink composition. When using independently, 5-30 mass% is desirable with respect to the ink composition whole quantity.

When the resin particles having a glass transition temperature (Tg) of 45 ° C. or less are not used as colored resin particles in the ink composition for dark pen of the present invention, it is preferable to contain a coloring material.
Examples of colorants that can be used include pigments and / or water-soluble dyes conventionally used in dark pen ink compositions. As the pigment, any of inorganic and organic pigments can be used.
As an inorganic type pigment, carbon black, titanium oxide, metal powder etc. are mentioned, for example. Examples of organic pigments include: azo lake, insoluble azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perinone pigment, anthraquinone pigment, quinacridone pigment, dye lake, nitro pigment, nitroso pigment and the like.
As the water-soluble dye, any of direct dyes, acid dyes, food dyes and basic dyes can be used.
These coloring materials may be used alone or in combination of two or more kinds together with the resin particles and used in an amount of 0.05 to 30% by mass with respect to the total amount of the ink composition.

  In the ink composition for memorizing pens of the present invention, water which is a solvent (tap water, purified water, distilled water, ion-exchange water, pure water) as the remainder in addition to resin particles having a glass transition temperature (Tg) of 45 ° C. or less In addition to the above, each component usually used, for example, a water-soluble organic solvent, a moisturizer, an antiseptic or antifungal agent, a pH adjuster, etc. can be contained in an appropriate amount as long as the effect of the present invention is not impaired. .

As a water-soluble organic solvent that can be used, for example, ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butane Diol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl 1,3 Alkylene glycols such as butanediol, 2-methylpentane-2,4-diol, 3-methylpentane-1,3,5 triol, 1,2,3-hexanetriol, and polyalkylene glycols such as polyethylene glycol and polypropylene glycol , Glycerol, jig Lower alkyl ethers of glycerol such as glycerol, triglycerol etc., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, N-methyl-2-pyrrolidone And at least one of 1,3-dimethyl-2-imidazolidinone and the like.
Besides, for example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, benzyl alcohol, etc., dimethylformamide, Water-soluble solvents such as amides such as diethylacetamide and ketones such as acetone can also be mixed.
The content of the water-soluble organic solvent is preferably 0.1 to 10.0% by mass with respect to the total amount of the ink composition.

In order to further improve the drying resistance, the bleeding resistance and the like, it is preferable that the ink composition for dark pen of the present invention contain a moisturizing agent.
As a moisturizer, maltitol, reducing sugar containing maltitol as a main component, sorbitol, reducing sugar containing sorbitol as a main component, reducing oligosaccharide, reducing maltooligo from the viewpoint of non-toxicity, solubility in water and water retention property Sugar, reduced starch degradation product, reduced dextrin, reduced maltodextrin, alpha-cyclodextrin, beta-cyclodextrin and maltosyl cyclodextrin, pentaerythritol, trimethylol ethane, trimethylol propane, preferably one or more selected from .
These have a function to improve the writing taste and the drying resistance without changing the ink viscosity and pH with time. In addition, since it does not affect the anionic or cationic substance, there is an advantage that the coloring material can be arbitrarily selected from colored resin particles, dyes and pigments.
The content of the humectant is preferably 20% by mass or less, more preferably 0.1 to 10.0% by mass, with respect to the total amount of the ink composition.

As pH adjusters, alkali metal salts of carbonic acid and phosphoric acid such as ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, aminomethylpropanol, sodium tripanate, sodium carbonate and the like, hydroxides of alkali metals such as sodium hydroxide and the like And at least one other.
Phenol, sodium omazine, pentachlorophenol sodium, 1,2-benzisothiazolin 3-one, 2,3,5,6-tetrachloro-4 (methylphonyl) pyridine, benzoic acid and sorbin as preservatives or fungicides Examples thereof include at least one of an acid, an alkali metal salt of dehydroacetic acid, and a benzimidazole compound.

The ink composition for dark pen of the present invention contains at least resin particles having a glass transition temperature (Tg) of 45 ° C. or less in the above constitution, and water, other components, etc. are appropriately combined to obtain a homomixer, homogenizer or The ink composition for dark pen can be prepared by removing coarse particles in the ink composition, etc. by filtration or centrifugation, if necessary, by stirring and mixing with a stirrer such as Disper. The surface tension of the ink composition for dark pen needs to be 38 mN / m or more, preferably 40 mN / m or more and 60 mN / m or less, from the viewpoint that the ink composition is easily repelled from the surface. Is desirable.
When the surface tension of the ink composition is less than 38 mN / m, the ink composition is less likely to be repelled from the character surface, and the effects of the present invention can not be exhibited.
In order to set the surface tension of this ink composition for dark pens to 38 mN / m or more, it is preferable to appropriately combine other resin particle types (including colored resin particles) and other components such as the content thereof and a humectant. And the like.

In the present invention, the surface tension (25 ° C.) of the ink refers to a value measured by a surface tension measuring device: CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.

In the present invention, the ink composition for dark pens of the above composition is used as a dark pen (marking pen) by mounting it on a marking pen or the like provided with a pen point such as a fiber core or a porous core, for example. The Rukoto.
The structure of the pen (marking pen) is not particularly limited. For example, the barrel itself is used as an ink container, and a collector structure (ink holding mechanism) in which the above-described ink composition for dark pen is filled in the barrel is used. It may be a direct solution type marking pen or the like.
As a dark pen set or the like using the ink composition for dark pen of the present invention, for example, a translucent colored sheet made of a specific color is marked with a red or green pen using colored resin particles etc. in a portion to be remembered (For example, since it becomes impossible to visually recognize the printed or written part by superimposing on the marked part of the red pen (for example, the green sheet for the red pen and the red sheet for the green pen), for example, It can be used.

  The ink composition for dark pen of the present invention configured as described above contains resin particles having a glass transition temperature (Tg) of 45 ° C. or less at least, and the surface tension of the ink is 38 mN / m or more. Colored resin particles are difficult to sink in solvents such as water, and excellent in line-drying property (fast-drying property) and line-forming property, high contact angle (75 ° on paper), high surface tension (50 mN / m or more) It is easy to see the marked characters, etc. In addition, even if the marking portion is covered with a translucent colored sheet, the characters can not be recognized, and furthermore, the object to be written is a thin paper such as a dictionary. Also in this case, the ink composition for recording pen can be obtained in which the ink does not penetrate the back of the sheet.

  The present invention will next be described in more detail by way of production examples, examples and comparative examples, but the present invention is not limited to the following examples and the like.

Production Examples 1 to 9: Production of water dispersion of resin particles and colored resin fine particles
According to the composition shown in the following Production Examples 1 to 9 and Table 1, dispersions of resin particles and colored resin fine particles were produced.

(Production Example 1)
Attach a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000 ml separatory funnel for monomer charging to a 2 liter flask, set it in a warm water tank, and mix ion exchange water and polymerizability according to the mixture ratio in Table 1 below. A surfactant ("Adekaria soap SE-10N" manufactured by Adeka Corp.) and ammonium persulfate were charged, and the internal temperature was raised to 50 ° C. while introducing nitrogen gas.

On the other hand, a liquid was prepared by mixing mixed monomers consisting of methacrylic cyclohexyl and n-butyl methacrylate in accordance with the proportions shown in Table 1 below.
This prepared solution was added from the above separating funnel into the above flask kept at around 50 ° C. under stirring for 3 hours to carry out emulsion polymerization. Aging was further carried out for 5 hours to complete the polymerization, and an aqueous dispersion of resin fine particles (particle 1) was obtained.

(Production Examples 2 to 6, 9)
At the compounding ratio of each component shown in the following Table 1, it carried out similarly to the said manufacture example 1, and obtained the water dispersion (particles 2-6, 9) of the resin fine particle.

(Production Examples 7 and 8)
Attach a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000 ml separatory funnel for monomer charging to a 2 liter flask, set it in a warm water tank, and mix ion exchange water and polymerizability according to the mixture ratio in Table 1 below. A surfactant ("Adekaria soap SE-10N" manufactured by Adeka Corp.) and ammonium persulfate were charged, and the internal temperature was raised to 50 ° C. while introducing nitrogen gas.
On the other hand, a liquid prepared by mixing a water-soluble dye having the mixing ratio of Table 1 with each mixed monomer consisting of methacrylic cyclohexyl or dicyclopentanyl methacrylate and n-butyl methacrylate according to the mixing ratio of Table 1 below. Prepared.
This prepared solution was added from the above separating funnel into the above flask kept at around 50 ° C. under stirring for 3 hours to carry out emulsion polymerization. Aging was further carried out for 5 hours to complete the polymerization, whereby an aqueous dispersion of colored resin fine particles (particles 7 and 8) was obtained.

  The glass transition temperature (Tg) and average particle diameter of each of the obtained resin particles and colored resin fine particles (particles 1 to 9) were measured using the above-described measurement devices [differential scanning thermal analyzer (DSC), particle size distribution measurement device]. ,It was measured. These measured values are shown in Table 1 below.

Examples 1 to 8 and Comparative Examples 1 to 2 Preparation of Ink Composition for Dark Pen
Using each resin particle produced according to the above-mentioned Production Examples 1 to 9 and the aqueous dispersion (particles 1 to 9) of colored resin fine particles, each dark pen according to the conventional method according to the composition shown in Table 2 below (total amount 100% by mass) An ink composition was prepared.

The surface tension of the ink composition was measured using the above-described measuring device (surface tension measuring device) for each of the obtained ink compositions for dark pen (total amount: 100% by mass).
Further, using each of the ink compositions for recording pens of Examples 1 to 8 and Comparative Examples 1 and 2 obtained above, a recording pen (marking pen) having the following configuration was produced and used for the following evaluation.
Each marking pen ink composition described above is loaded into a marking pen [Mitsubishi Pencil Co., Ltd., trade name: PROPASS Window PUS-102T, pen point, thick: PE resin sintered core, fine: PET fiber core] A pen (marking pen) was produced.
It evaluated about character visibility, character concealability, and strike-through property by each following evaluation method using each obtained dark pen.
The evaluation results and the like of Examples 1 to 8 and Comparative Examples 1 to 2 are shown in Table 2 below.

(Evaluation method of character visibility)
The 12-point characters printed on PPC paper were marked with the above-mentioned memorizing pen and evaluated according to the following evaluation criteria.
Evaluation criteria:
A: The characters are clearly visible.
B: The boundary between the letters and the paper is somewhat unclear.
C: The characters are totally unclear.

(Evaluation method of character hiding property)
In the above samples, a red transparent sheet is covered for Examples 1, 3, 5, 7 and Comparative Example 2, and a green transparent sheet is covered for Examples 2, 4, 6, 8 and Comparative Example 1. About the concealability of the printed character, it evaluated by the following evaluation criteria.
Evaluation criteria:
A: The characters are not visible at all.
B: The outline of the character can be partially recognized.
C: The characters can be read.

(Evaluation method of character strikethrough)
Iwanami Japanese Language Dictionary A 4th edition optional item was marked with the above-mentioned memorizing pen, and the condition from the back side was evaluated by the following evaluation criteria.
Evaluation criteria:
A: No strike-through is observed at all.
B: There is a darkened part.
C: Strike-through is observed, or the color is dark overall.

  In consideration of the above Tables 1 and 2, Examples 1 to 8 falling within the scope of the present invention have an ink surface tension of 38 mN / m or more as compared with Comparative Examples 1 and 2 falling outside the scope of the present invention. It was found that the character was excellent in character hiding ability, and there was no character passing character.

  The ink composition for dark pens used for what is called a dark pen set etc. which consists of a combination of a marking pen and a translucent sheet is obtained.

Claims (3)

  An ink composition for a dark pen, comprising at least a resin particle having a glass transition temperature (Tg) of 45 ° C. or less and a surface tension of the ink of 38 mN / m or more.   The ink composition for dark pens according to claim 1, wherein the resin particles are colored resin particles.   The ink composition for a dark pen according to claim 1 or 2, wherein the resin particles have an average particle size of 20 to 300 nm.