Black ink composition and writing instrument

Abstract

To provide an oil-based black ink composition of higher quality, which suppresses bleeding of a dye other than black from handwriting.SOLUTION: Provided is a black ink composition containing a black dye as a main colorant, comprising: an organic solvent comprising a glycol ether-based solvent or an alcoholic solvent; a black dye soluble in the organic solvent; a second dye which is a dye other than black, is soluble in the organic solvent, and has a polarity index of 5.0 or more; and a resin soluble in the organic solvent. Examples of the black dye include a nigrosine dye such as C.I. Solvent Black 7. Examples of the second dye include a yellow dye such as C.I. Acid Yellow 42.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a black ink composition containing a black dye as a main colorant, and a writing instrument equipped with the black ink composition. The black ink composition of the present invention is one in which bleeding of colorants other than the main colorant from handwriting is suppressed. [Background technology]

[0002] As a black ink used in marking pens and the like, there is an oil-based alcohol-based black ink (for example, Patent Documents 1 and 2). For example, an oil-based black ink containing a glycol ether-based or alcohol-based organic solvent, a black dye such as a nigrosine dye, and a resin is known.

[0003] The oil-based black ink may contain colorants other than black for various purposes. For example, the oil-based black ink described in Patent Document 1 contains a red dye, a blue dye, and a yellow dye of a specific structure in addition to a nigrosine dye (black dye). This is said to provide an oil-based black ink with excellent writing density and stability over time. In addition, since the nigrosine dye alone produces a bluish black color, an oil-based black ink is also known that contains a yellow dye, which is a complementary color, to produce a blacker writing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-158425 [Patent Document 2] JP 2006-56946 A Summary of the Invention [Problem to be solved by the invention]

[0005] The inventor has investigated in detail an oil-based black ink supplemented with dyes other than black dyes. In the process, it was noticed that for some writing objects, a phenomenon occurs in which dyes other than black dyes seep out of the handwriting over time (long periods in months or years). This phenomenon occurred frequently, especially when the writing object was a vinyl chloride product, a sticker or cloth with an adhesive, a surface-treated cloth, etc. Although this phenomenon is not a problem with the black color of the handwriting itself, it presented a problem in providing a higher-quality oil-based black ink. Therefore, an object of the present invention is to provide a higher-quality oil-based black ink composition in which the seepage of dyes other than black dyes from the handwriting is suppressed, and a writing instrument equipped with the oil-based black ink composition.

Means for Solving the Problems

[0006] The inventor considered that the cause of the above phenomenon lies in the polarity of dyes other than black dyes, and conducted studies to solve the above problems. As a result, it was found that the above problems can be solved by selecting a dye other than a black dye having a polarity index of a specific value or more, which will be described later.

[0007] One aspect of the present invention is a black ink composition containing a black dye as a main colorant, an organic solvent composed of a glycol ether-based solvent or an alcohol-based solvent, a black dye soluble in the organic solvent, and a dye other than black, which is soluble in the organic solvent and has the following formula (1): (Number of polar atoms) × 10 / (Number of carbon atoms) ··· (1) (In the formula, the number of polar atoms refers to the number of oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, and halogen atoms) and a second dye having a polarity index represented by the formula of 5.0 or more, and a resin soluble in the organic solvent.

[0008] This aspect relates to a black ink composition containing a black dye as a main coloring agent. The black ink composition of this aspect contains an organic solvent composed of a glycol ether solvent or an alcohol solvent, a black dye soluble in the organic solvent, a second dye other than black, and a resin. And in this aspect, the polarity index of the second dye is 5.0 or more. According to the black ink composition of this aspect, even if the writing object is a vinyl chloride product or the like, the bleeding of the second dye from the handwriting is suppressed, and the black handwriting is maintained clearly over a long period of time.

[0009] Here, the "polarity index" is a value defined by the above formula (1), which is a value obtained by multiplying the number of polar atoms by 10 and dividing this by the number of carbon atoms. Polar atoms refer to oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, and halogen atoms (in particular, chlorine atoms, bromine atoms, and iodine atoms). Regarding the above polarity index, for example, it is also described in JP-A-2003-268280 (normalized polarity index).

[0010] Preferably, the black dye is C.I. Solvent Black 7.

[0011] Preferably, the second dye is a yellow dye.

[0012] Preferably, the yellow dye is C.I. Acid Yellow 42.

[0013] Preferably, the glycol ether solvent is mainly composed of at least one selected from the group consisting of propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and ethylene glycol monobutyl ether.

[0014] Preferably, the alcohol solvent is mainly composed of an aliphatic alcohol having 1 to 4 carbon atoms.

[0015] Another aspect of the present invention is a writing instrument characterized by including the above black ink composition.

[0016] According to the writing instrument of this aspect, even if the object to be written on is a vinyl chloride product or the like, the bleeding of the second dye from the handwriting is suppressed, and the black handwriting is maintained clearly over a long period of time.

Effect of the Invention

[0017] According to the present invention, there are provided an oil-based black ink and a writing instrument in which the bleeding of the second dye from the handwriting is suppressed and the black handwriting is maintained clearly over a long period of time.

Modes for Carrying Out the Invention

[0018] The black ink composition of the present invention contains a black dye as a main colorant, and additionally contains a dye other than black (second dye). The writing instrument of the present invention is provided with the black ink composition.

[0019] The black dye is not particularly limited as long as it is soluble in an organic solvent described later, but nigrosine dyes, particularly C.I. Solvent Black 7, are preferably used.

[0020] The second dye in the present invention is a dye other than black, is soluble in an organic solvent described later, and has a polarity index of 5.0 or more as defined by the above formula (1). The polarity index of the second dye may be 5.5 or more, 6.0 or more. Examples of the second dye having a polarity index of 5.0 or more include C.I. Solvent Blue 38 (C 32 H 12 CuN8O6S2·2Na; polarity index 5.0), C.I. Solvent Red 218 (C 14 H9N3O4; polarity index 5.0), C.I. Acid Yellow 42 (C 32 H 24 N8Na2O8S2, polarity index: 5.6), C.I. Solvent Green 7 (C 16 H7Na3O 10 S3; polarity index 8.1).

[0021] Regarding the calculation of the polarity index, for example, C.I. Acid Yellow 42 (C 32 H 24Since (N8Na2O8S2) has 18 polar atoms (N, O, S) and 32 carbon atoms, its polarity index is calculated as 18×10 / 32 = 5.6.

[0022] In a preferred embodiment, the second dye is a yellow dye such as C.I. Acid Yellow 42.

[0023] Although the content ratio of the dyes (black dye + second dye) in the black ink composition is not particularly limited, it is usually about 0.5 to 15.0% by weight, preferably about 2.0 to 12.0% by weight. If the content ratio of the dyes is excessive, the viscosity of the ink composition may increase, causing poor writing performance. If the content ratio of the dyes is too small, there may be insufficient density (insufficient visibility) or insufficient color development of the handwriting.

[0024] As for the weight ratio of the black dye and the second dye contained in the black ink composition, for example, with respect to 100 parts by weight of the black dye, the second dye is about 1.0 to 50.0 parts by weight, preferably about 2.0 to 30.0 parts by weight.

[0025] The black ink composition of the present invention contains an organic solvent composed of a glycol ether solvent or an alcohol solvent. Examples of the glycol ether solvent include those mainly composed of propylene glycol monomethyl ether or dipropylene glycol monomethyl ether. Examples of the alcohol solvent include those mainly composed of C1-C4 aliphatic alcohols. Here, the "main component" means the main component, for example, the content ratio in the organic solvent is 50% by weight or more. Although the content ratio of the organic solvent in the black ink composition is not particularly limited, it is usually about 45.0 to 96.0% by weight, preferably about 58.0 to 93.0% by weight.

[0026] The black ink composition of the present invention contains a resin soluble in the above organic solvent. Examples of the resin include ketone resin; phenolic resins such as alkylphenol resin and rosin-modified phenol resin; xylene resins such as alkylphenol-modified xylene resin and rosin-modified xylene resin; styrene-organic acid copolymers such as styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, and styrene-polyacrylate copolymer. The content ratio of the resin in the black ink composition is not particularly limited, but is usually about 3.0 to 30.0% by weight, preferably about 5.0 to 25.0% by weight.

[0027] In the black ink composition of the present invention, components other than the above may be contained as long as the performance is not impaired. Examples of such components include viscosity modifiers, dye solubilizers, anti-drying agents, surface tension modifiers, and the like.

Examples

[0028] 1. Preparation of black ink composition Various black ink compositions were prepared with the formulations shown in Table 1 (unit: parts by weight). Specifically, hydrogenated rosin resin (resin) was added to propylene glycol monomethyl ether (organic solvent), and stirred at 40°C for 1 to 1.5 hours to dissolve the resin. After confirming dissolution, nigrosine dye (C.I. Solvent Black 7; primary dye, main colorant) and various dyes (secondary dyes) below were added, and further stirred at 40°C for 2 hours. After confirming that the dyes had dissolved, a black ink composition was obtained.

[0029] <Secondary dye> · Experimental Example 1: VALIFAST BLUE 1605 (Solvent Blue 38 (C 32 H 12 CuN8O6S2·2Na); polarity index 5.0) · Experimental Example 2: VALIFAST PINK 2310 (Solvent Red 218 (C 14 H9N3O4); polarity index 5.0) · Experimental Example 3: VALIFAST YELLOW 1151 (Acid Yellow 42 (C 32 H 24 N8Na2O8S2); Polarity Index 5.6) · Experimental Example 4: VALIFAST YELLOW 1171 (Acid Yellow 42 (C 32 H 24 N8Na2O8S2; Polarity Index 5.6) · Experimental Example 5: AL YELLOW 2307 (Acid Yellow 42 (C 32 H 24 N8Na2O8S2); Polarity Index 5.6) · Experimental Example 6: Pyronine (Solvent Green 7 (C 16 H7Na3O 10 S3); Polarity Index 8.1) · Experimental Example 7: OIL BLUE 8BN (Solvent Blue 5 (C 33 H 41 N3O); Polarity Index 1.2) · Experimental Example 8: OIL YELLOW 129 (Solvent Yellow 29 (C 44 H 52 N4O2); Polarity Index 1.4) · Experimental Example 9: OIL PINK 330 (Solvent Red 49 (C 28 H 30 N2O3); Polarity Index 1.8) · Experimental Example 10: VALIFAST RED 1364 (Basic Red 1:1 (C 27 H 29 ClN2O3); Polarity Index 2.2) · Experimental Example 11: AL YELLOW GSE (Basic Yellow 51 (C 20 H 25 N3O4S); Polarity Index 4.0) · Experimental Example 12: AL RED 2311G (Basic Red 1 (C 28 H 31 ClN2O3) + Acid Yellow 61 (C 24 H 20 Cl2N5NaO6S2); Polarity Index 4.0) · Experimental Example 13: OIL RED 52S (Acid Red 52 (C 27 H29 N2NaO7S2); Polarity index 4.1)

[0030] Each black ink composition was filled into the core of a marker pen equipped with a chip made of a fiber bundle to produce a writing instrument.

[0031] Using each writing instrument, characters were written on overshoes made of vinyl chloride, a seal with a polypropylene (PP) film, and an ironing cloth (cloth with an adhesive). After writing, they were stored in a thermostat at 50 °C for one month, and the bleeding of inks other than black from the handwriting was evaluated. Those with no change in the black handwriting were designated as "A", and those with some bleeding of the color of the second dye from the black handwriting were designated as "B". The results are shown in Table 1.

[0032]

Table 1

[0033] As shown in Table 1, in Experimental Examples 1 to 6 using a second dye with a polarity index of 5.0 or more, all evaluations were "A", no bleeding of the second dye occurred, and the handwriting was maintained clearly. On the other hand, in Experimental Examples 7 to 13 using a second dye with a polarity index of 4.1 or less, the color of the second dye bled from the handwriting, resulting in blurred handwriting. From the above, it was shown that by using a second dye with a polarity index of 5.0 or more, the handwriting of the black ink containing nigrosine dye can be kept clear for a long period.

Claims

1. A black ink composition containing a black dye as a main colorant, an organic solvent composed of a glycol ether-based solvent, a black dye soluble in the organic solvent, a dye other than black, soluble in the organic solvent, and having the following formula (1): (Number of polar atoms) × 10 / (Number of carbon atoms) ··· (1) (In the formula, the number of polar atoms refers to the number of oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, and halogen atoms) a second dye having a polarity index represented by the formula of 5.0 or more, a resin soluble in the organic solvent, and comprising, wherein the black dye is C.I. Solvent Black 7, the glycol ether-based solvent is mainly composed of at least one selected from the group consisting of propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and ethylene glycol monobutyl ether. A black ink composition characterized by this.

2. The black ink composition according to Claim 1, wherein the glycol ether-based solvent is mainly composed of propylene glycol monomethyl ether.

3. The black ink composition according to Claim 1, wherein the resin is a hydrogenated rosin resin.

4. The black ink composition according to Claim 2, wherein the resin is a hydrogenated rosin resin.

5. The black ink composition according to any one of Claims 1 to 4, wherein the second dye is a yellow dye.

6. The black ink composition according to Claim 5, wherein the yellow dye is C.I. Acid Yellow 42.

7. A writing instrument comprising the black ink composition according to any one of Claims 1 to 6.

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