JP4806920B2 - Ballpoint pen ink - Google Patents

Description

  The present invention accommodates a ballpoint pen that has a ballpoint pen tip that rotatably holds a ball that transfers ink onto a writing surface such as paper as a writing member, partially protruding from the tip of the opening of the ball holder. The present invention relates to a ballpoint pen ink. More specifically, the present invention relates to a ballpoint pen ink that provides a ballpoint pen with a very light and smooth writing feel with little ink sticking to the outer surface of the ball holder of the ballpoint pen tip.

  When the viscosity of the ink used for the ballpoint pen is low, the capillary action works at the contact point between the tip of the ballpoint pen and the paper to form a handwriting by sucking out the ink, so that the ink at the nib is quickly absorbed by the paper surface. . As a result, surplus ink is hardly generated, and ink does not easily adhere to the outer surface of the ball holder of the chip. Therefore, there is an advantage that writing can be performed with light writing without adding too much writing pressure. However, since the ink has a low viscosity, the resistance to rotation of the ball is small, but the ink film formed between the ball and the seat is easily moved by the force, and the ball and the seat are easily hit directly. , The rotation of the ball is momentarily obstructed, and the crisp feel when writing is transmitted to the hand, resulting in a smooth writing feel. In order to overcome such drawbacks, an attempt has been made to add a lubricant to the ink to obtain a smooth writing feel (see Patent Document 1).

  On the other hand, when the viscosity of the ink is increased by adding a material that imparts viscosity, and the ink film pressure formed between the ball and the seat is increased, the harsh feel is eliminated. However, although the writing quality is smooth, the fluidity of the ink is low, so that the rotational resistance of the ball during writing increases and the writing quality becomes heavy. Further, there is a problem that ink is easily deposited on the ball due to the viscosity, and the “bottom” phenomenon occurs in which the deposited ink falls on the paper surface and the writing line spreads locally. In order to overcome such drawbacks, an attempt was made to obtain a smooth writing feeling by adding a lubricant to the ink, but a smooth writing feeling was obtained due to the high viscosity of the ink. The light writing taste of the thing was not obtained.

In addition, the ink viscosity property is made pseudoplastic by adding a shear thinning agent for the purpose of achieving both ink adhesion to the outer surface of the ball holder, prevention of stickiness, and light and smooth writing. Attempts have also been made to lower the viscosity by high shear force due to the rotation of the ball and to cause the ink to flow and be ejected (see Patent Documents 2 and 3).
JP 2003-192972 (41st line from the top of the left column on page 2 to 12th line from the top of the right column on page 2) JP-A-2003-105245 (the 36th line from the upper right column on page 2 to the 23rd line from the upper right column on page 3) Japanese Patent Laid-Open No. 6-313144 (the 36th line from the upper left column on page 3 to the third line from the upper right column on page 3)

In the invention described in Patent Document 1, in order to obtain sufficient smoothness, it is necessary to put a large amount of lubricant in the ink, and if a large amount of lubricant is added, the affinity between the ink and the metal material is increased. In addition, the wettability to the outer surface of the ball holder is increased, and there is a problem that the ink crawls up to the outer surface of the ball holder and the pen tip becomes dirty. For this reason, the amount of lubricant added is limited, and it has been impossible to achieve both the prevention of ink adhesion to the outer surface of the ball holder, the prevention of blistering, and the light and smooth writing taste.
When shear thinning is applied to ink as described in Patent Document 2 and Patent Document 3, the viscosity decreases due to the shearing force caused by the rotation of the ball during writing. In addition, you can write with light writing without adding too much pressure. In the end, however, the ink film formed between the ball and the seat is also forced during writing, so the film pressure becomes thin, the ball and the seat hit directly, and as a result a sufficiently smooth writing taste It was not obtained.
As described above, the conventional technology has not yet satisfied all of light and smooth writing feeling, prevention of handwriting blur, and prevention of ink adhesion to the outer surface of the ball holder.
SUMMARY OF THE INVENTION An object of the present invention is to provide a ballpoint pen ink that has a very light and smooth writing feel as well as a ballpoint pen ink that causes less ink to adhere to the outer surface of the ball holder and that does not generate mottling.

That is, the present invention contains at least a copolymer of a styrene monomer and a monomer having a carboxylic acid group in the molecule, and N-acyl taurine, and the N-acyl taurine is 5% by weight or more based on the total amount of the ink. The gist of the ink is about 60% by weight or less of a ballpoint pen.

The reason why the present invention is an oil-based ink for ball-point pens having very good writing taste and less sticking of chips and voids is presumed as follows. That is, a copolymer of a styrene monomer and a hydrophilic monomer having a carboxylic acid group in the molecule exists in a form in which the polymer chain is expanded in the ink. It is attracted by.
Further, the hydrogen of the carboxylic acid group, which is more hydrophilic, forms a hydrogen bond with the nitrogen of N-acyl taurine that is dissolved in the ink. In addition, N-acyl taurine also contains nitrogen and carboxylic acid groups in the molecule, so they interact electrostatically with each other to form a gradual network structure in the ink, resulting in an extremely high viscosity. It is presumed that the yarn length becomes longer without causing it to occur.
As described above, the thread length is increased by the interaction between these polymer chains or between the polymer chain and the lubricant, so that the ink is applied to the paper surface while maintaining a smooth writing feeling by adding a large amount of the lubricant. It becomes easy to be transferred, and ink that could not be transferred is easily collected in the ball house. As a result, it is possible to suppress the adhesion of ink to the outer surface of the ball holder and the occurrence of voids.

In addition, when a copolymer having a molecular weight of 1000 to 20000 and an acid value of 40 to 260 is used as a copolymer of a styrene monomer and a hydrophilic monomer having a carboxylic acid group in the molecule, an ink with particularly little chip adhesion is obtained. be able to. This is because the use of a copolymer of a styrene monomer within the above range and a hydrophilic monomer having a carboxylic acid group in the molecule allows the ink to have an appropriate stringiness, and further N-acyl taurine and solvent. It is presumed that the balance of mutual affinity with can be kept good.

The invention is described in detail below.
As the colorant, all oil-based and water-based dyes and pigments conventionally used in ballpoint pen inks can be used.
Examples of oil-based dyes include SPILON BLACK GMH SPECIAL, SPILON RED C-GH, SPILON RED C-BH, SPILON BLUE C-RH, SPILON BLUE BPNH, SPILON YELLOW C-2GH, SPILON VIOLET C-RH, S. P. T.A. ORANGE6, S. P. T.A. Eisenspiron colors such as BLUE111 (manufactured by Hodogaya Chemical Co., Ltd.), Eisen SOT dye, ORIENT SPRIT BLACK AB, VALIFAST BLACK 3804, VALIFAST RED 1320, VALIFAST RED 1360, VALIFAST ORANGE 1601, VAL VALIFAST BLUE 1601, VALIFAST BLUE 1603, VALIFAST BLUE 1621, VALIFAST BLUE 2601, VALIFAST YELLOW 1110, VALIFAST YELLOW 3104, VALIFAST YELLOW 3105, VALIFAST INDUSTRY Varifast color, orient oil color, rhodamine B base, solder red 3R, methyl violet 2B base, Victoria blue F4R, nigrosine base LK, etc., neo super blue C-555 (Chuo Synthetic Chemical Co., Ltd.) Conventionally known general materials such as manufactured) can be used. Examples of water-based dyes include acid dyes, direct dyes, basic dyes, and the like, and specific examples include Japan Fast Black D Conch (CI Direct Black 17), Water Black 100L (same 19), Water Black L-200 (same 19), Direct Fast Black B (same 22), Direct Fast Black AB (same 32), Direct Deep Black EX (same 38), Direct Fast Black Conk (same 51), Kayara Spragley VGN (71), Caillas Direct Brilliant Yellow G (CI Direct Yellow 4), Direct Fast Yellow 5GL (26), Eisen Primula Yellow GCLH (44), Direct Fast Yellow R (50), Eisen Direct fast red H (CI Direct Red 1), Nippon Fast Scarlet GSX (same 4), Direct Fast Scarlet 4BS (same 23), Eisen Direct Rhodulin BH (same 31), Direct Scarlet B (same 37), Kayak Direct Scarlet 3B (39), Eisen Primula Pink 2BLH (75), Sumilite Red F3B (80), Eisen Primula Red 4BH (81), Kayaras Spralbin BL (83), Kayaras Light Red F5G ( 225), Cayalas Light Red F5B (226), Cayalas Light Rose FR (227), Direct Sky Blue 6B (CI Direct Blue 1), Direct Sky Blue 5B (15), Sumilite Splash Blue BRR Conch (71) Ibogen Turquoise Blue S (86), Water Blue # 3 (86), Kayara Star Coyze Blue GL (86), Kayala Supra Blue FF2GL (106), Kayara Splatter Turquoise Blue FBL (199), etc. Direct dyes, Acid Blue Black 10B (CI Acid Black 1), Nigrosine (2), Suminol Milling Black 8BX (24), Kayanol Milling Black VLG (26), Suminol Fast Black BR Conch (31), Mitsui Nylon Black GL (52), Eisen Opal Black WH Extra Conk (52), Sumilan Black WA (52), Ranil Black BG Extra Conk (107), Kayanol Milling Black TLB (109) Sumino Milling Black B (the 109), Kaya Nord milling black TLR (the 110), Aizen Opal black New Conc (the 119), Water Black 187-L (the 154), mosquito yak Acid Brilliant Flavin FF (C. I. Acid Yellow 7: 1), Kayasil Yellow GG (17), Xylene Light Yellow 2G 140% (17), Suminol Leveling Yellow NR (19), Daiwa Tarrazine (23), Kayaktor Torazin (23) , Suminol Fast Yellow R (25), Diacid Light Yellow 2GP (29), Suminoll Milling O O (38), Suminol Milling MR MR (42), Water Yellow # 6 (42), Kayanol Yellow NFG (49), Suminol Milling Yellow 3G (72), Suminol Fast Yellow G (61), Suminol Milling Yellow G (78), Kayanol Yellow N5G (110), Suminol Milling Yellow 4G 200% (same 141), Kayanor Yellow NG (same 135), Kayano Lumiling Yellow 5 GW (127), Kayanol Milling 6 GW (142), Sumitomo Fast Scarlet A (CI Acid Red 8), Kayak Silk Scarlet (9), Solar Rubin Extra (14), Daiwa New Coxin (18), Eisenbonso RH (26), Daiwa Red No. 2 (27), Suminol Leveling Brilliant Red S3B (35), Kayasil Rubinol 3GS (37), Eisen Erythrosin ( 51), kayak acid rhodamine FB (52), Suminol leveling rubinol 3GP (57), diacid alizarin rubinol F3G 200% (82), Eiseneosin GH (87), water pink # 2 (same) 92), Eisen Acid Phloxin PB 92), Rose Bengal (94), Cyanol Milling Scarlet FGW (111), Cyanol Milling Lubin 3BW (129), Sinoall Milling Brilliant Red 3BN Conch (131), Suminol Milling Brilliant Red BS ( 138), Eisen Opal Pink BH (186), Suminoll Milling Brilliant Red B Conch (249), Kayaku Acid Brilliant Red 3BL (254), Kayaku Acid Brilliant Red Brilliant Red BL (265), Kayanol Milling Red GW (276), Mitsui Acid Violet 6BN (CI Acid Violet 15), Mitsui Acid Violet BN (17), Sumitomo Patent Pure Blue VX (CI Acid Blue) 1), Water Blue # 106 (same 1), Patent Blue AF (same 7), Water Blue # 9 (same 9), Daiwa Blue 1 (same 9), Spranol Blue B (same 15), Orient Solve Blue OBC (22), Suminol Leveling Blue 4GL (23), Mitsui Nylon Fast Blue G (25), Kayasil Blue AGG (40), Kayasil Blue BR (41), Mitsui Alizarin Saphirol SE (43) , Suminol Leveling Sky Blue R Extra Conk (62), Mitsui Nylon Fast Sky Blue B (78), Sumitomo Brilliant Indocyanine 6Bh / c (83), Sandlancyanine N-6B 350% (90), Water Blue # 115 (90), Orient Soluble Blue OBB The same 93), Sumitomo brilliant blue 5G (the 103), Kaya Nord milling Ultra Sky SE (the 112), Kaya Nord milling cyanine 5R (the 113), Aizen Opal Blue 2GLH (the 158), Daiwa Guinea green B (C. I. Acid Green 3), Acid Brilliant Milling Green B (same 9), Daiwa Green # 70 (same 16), Cyanol Cyanine Green G (same 25), Suminol Milling Green G (same 27), etc. Ron Yellow 3GLH (CI Basic Yellow 11), Eisen Cachiron Brilliant Yellow 5GLH (13), Sumiacryl Yellow E-3RD (15), Maxilon Yellow 2RL (19), Astrazone Yellow 7GLL (same) 21), Kayacrill Golden Yellow GL-ED (same 28), Astrazone Yellow 5GL (same 51), Eisen Cachiron Orange GLH (CI Basic Orange 21), Eisen Katyron Brown 3GLH (same 30), Rhodamine 6 GCP (C.I. Sick Red 1), Eisen Astra Phloxin (12), Sumiacryl Brilliant Red E-2B (15), Astrazone Red GTL (18), Eisen Cathlon Brilliant Pink BGH (27), Maxilon Red GRL ( 46), Eisenmethyl Violet (CI Basic Violet 1), Eisen Crystal Violet (Same 3), Eisen Rhodamine B (Same 10), Astrazone Blue G (CI Basic Blue 1), Astrazone Blue BG (same 3), Methylene blue (same 9), Maxilon blue GRL (same 41), Eisen Cachiron blue BRLH (same 54), Eisen diamond green GH (CI basic green 1), Eisen malachite green (same) 4) Bismarckbrow G include basic dye (C.I. Basic Brown 1) and the like. These must be soluble in at least one of the solvents in the ink.
Specific examples of pigments include ocher, barium yellow, ultramarine, bitumen, cadmium red, barium sulfate, titanium oxide, petal, black iron oxide, yellow iron oxide, red iron oxide, furnace black, contact black, thermal black, Carbon black such as acetylene black, inorganic pigments such as cobalt blue, titanium yellow, turquoise and molybdate orange, azo pigments, nitroso pigments, nitro pigments, basic dye pigments, acid dye pigments, building dyes Dye-based pigments, mordant dye-based pigments, and natural dye-based pigments, C.I. I. PIGMENT RED2, 3, 5, 17, 17, 38, 41, 48: 2, 48: 3, 49, 50: 1, 53: 1, 57: 1, 58: 2, 60, 63: 1, 63: 2, 64: 1, 88, 112, 122, 123, 144, 146, 149, 166, 168, 170, 176, 177, 178, 179, 180, 185, 190, 194, 206, 207, 209, 216, 245, C.I. I. PIGMENTORAGE 5, 10, 13, 16, 36, 40, 43, C.I. I. PIGMENT VIOLET 19, 23, 31, 33, 36, 38, 50, C.I. I. PIGMENTBLUE 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 5, 16, 17, 17, 22, 25, 60, 66, C . I. PIGMENT BROWN 25, 26, C.I. I. PIGMENT YELLOW 1, 3, 12, 13, 24, 93, 94, 95, 97, 99, 108, 109, 110, 117, 120, 139, 153, 166, 167, 173C. I. Examples thereof include organic pigments such as PIGMENTGREEN 7, 10, and 36, metal powder pigments such as aluminum powder, gold powder, silver powder, copper powder, tin powder, and brass powder, fluorescent pigments, and mica-based pigments.
The amount of these colorants to be used is preferably 1% by weight or more and 40% by weight or less based on the total ink composition, and 3 to 20% by weight is more preferable for obtaining sufficient handwriting fastness. When the amount used is less than 1% by weight, the handwriting is too thin, and the amount of the colorant remaining on the paper surface when the light resistance test or the solvent resistance test is performed becomes small and the handwriting becomes difficult to read. When the amount is more than 40% by weight, writing becomes difficult due to insufficient dissolution at the time of blending or inability to write due to clogging due to sedimentation over time, or an increase in the solid content in the ink. These colorants may be used alone or in combination of two or more.

  The solvent used as the main medium of the ink can be used without particular limitation as long as it is conventionally used for ink for ballpoint pens, and water, glycol ethers, glycols, and alcohols are preferable. For example, ethanol, 1-propanol, 2-propanol, butyl alcohol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycerin, Ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, phenyl cellosolve, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether , Tripropylene glycol Over mono-butyl ether, 2-pyrrolidone, can be mentioned triethanolamine. These solvents can be used alone or in combination, and the amount used is preferably 10% by weight or more and 80% by weight or less based on the total amount of the ink.

N-acyl taurine is for imparting lubricity to the ink. For example, N-oleoyl tauric acid, N-lauroyl tauric acid, N-myristoyl tauric acid, N-palmitoyl tauric acid and the like can be mentioned. It is done. These lubricants may be added unneutralized or neutralized, and the state of addition is appropriately selected depending on the miscibility with the solvent used in the ink. These are preferably added in an amount of 5 to 60% by weight based on the total amount of ink. When the amount is less than 5% by weight, sufficient lubricity cannot be obtained, so that a light and smooth writing taste cannot be obtained sufficiently, and when more than 60% by weight of a lubricant is added, blurring of handwriting occurs.

Organic and inorganic thickeners that are generally used for the purpose of imparting shear thinning to the ink can be used. Specific examples include water-soluble polysaccharides, polyvinyl alcohol, fatty acid amides, long-chain fatty acid ester polymers, polyethylene oxide, polyvinyl pyrrolidone, silica, seed polysaccharides, microbial thickeners, seaweed polysaccharides, and the like. Of these, water-soluble polysaccharides are preferred because they impart shear thinning to the ink with a small addition amount, and they must be soluble in one of the above organic solvents. Examples of the cellulose derivative include hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, and ethyl cellulose. Among these, hydroxypropyl cellulose having favorable solubility characteristics and viscosity characteristics is preferable. These thickeners can be used alone or in combination of two or more.
In addition, in order to suppress ink leakage and obtain a light writing at the same time, the amount of water-soluble polysaccharide used should be 0.02 wt% or more and 2.0 wt% or less with respect to the total ink composition, and at that time It is preferable to adjust the ink viscosity to 600 mPa · s or more and 10,000 mPa · s or less. (Measurement conditions: shear rate 2 / s, measurement temperature: 25 ° C.)
It should be noted that the shear thinning index is 0.3 or more and 0 for the purpose of making the writing quality lighter by preventing the ink from leaking out when the pen tip is left face down and making the viscosity decrease during writing an optimum value. .9 or less is preferable.

A copolymer of a styrene monomer and a hydrophilic monomer having a carboxylic acid group in the molecule is used as a stringiness imparting agent, and examples thereof include SMA1000, SMA2000, SMA3000, SMA EF30, SMA EF40, and SMA1440. , SMA17352, SMA2625, SMA3840 (manufactured by Kawa Crude Chemical Co., Ltd.), etc. Examples thereof include styrene-acrylic acid resins such as John Crill 682, John Crill 683, and John Crill 690 (manufactured by Johnson Polymer Co., Ltd.). These may be used alone or in combination of two or more of the same copolymers having different physical properties such as molecular weight and acid value. In some cases, it may be neutralized and added to the ink in the form of a salt. The state to be added is appropriately selected depending on the solubility in the solvent used in the ink.
The amount used is preferably 0.01 to 10 parts by weight based on the total ink composition. If the amount is less than 0.01 parts by weight, the desired spinnability cannot be obtained, and if it exceeds 10 parts by weight, the amount of solids in the ink composition increases, so the viscosity of the ink becomes too high, resulting in a writing feel. It has an adverse effect and places great constraints on other formulations.
It is preferable to adjust the string length of the ink to 20 mm or more and 400 mm or less (measurement method: when a 7 mm diameter regular cylinder glass rod is immersed 5 mm vertically in the ink and pulled up at a constant speed in the vertical direction at 50 mm / sec. (Measurement temperature: 25 ° C.) When the string length is less than 20 mm, the ink drops and the tip sticks more, and the string length is too long. When the length is longer than 400 mm, the spinnability becomes too strong, and the “whiskering” occurs in which the ink is not cut as it is in a state where the thread is pulled and adheres to the paper surface in a beard shape.

  Other anticorrosive agents such as benzotriazole, metal salt and phosphate ester compounds, antiseptics such as isothiazolone and oxazolidine compounds, antifoaming agents, anti-scratch agents, natural resins, synthetic resins, Dispersants such as anions, cations, nonions, amphoteric surfactants, wetting agents such as glycerin, sorbitan, polysaccharides, urea, ethyleneurea or their derivatives, acetylene glycol, acetylene alcohol and silicon surfactants It is also possible to use a conventional well-known additive for ink such as leveling property imparting agents and antifreezing agents.

  In producing the oil-based ink of the present invention, various conventionally known methods can be employed. For example, when a dye is used as the colorant, the solid raw material and the solvent are placed in a stirrer such as a homomixer and stirred and dissolved, and then the dye and the remaining components are added and further mixed and stirred. At this time, it may be heated depending on circumstances. Also when a pigment is used as the colorant, it can be obtained by a conventionally known method. As an example of the production example, a pigment, a solvent, and a dispersant are mixed, stirred uniformly with a propeller stirrer or the like, and then dispersed with a disperser. A dispersing machine such as a roll mill, a ball mill, a sand mill, a bead mill, or a homogenizer is appropriately selected depending on the amount of solvent of the ink and the pigment concentration. The dispersed pigment is further added with the remaining components, for example, a viscosity adjusting resin, a solvent, a lubricant, a water-soluble polysaccharide, and the like, and mixed by stirring to obtain a ballpoint ink composition. Further, the mixed ink may be further dispersed by a disperser depending on the case, or the obtained ink may be filtered or centrifuged to remove coarse particles and insoluble components.

(Example 1 )
Neo Super Blue C-555 (oil-based dye, manufactured by Chuo Synthetic Chemical Co., Ltd.) 8.0 parts OIL BLUE 613 (oil-based dye, manufactured by Orient Chemical Co., Ltd.) 3.0 parts SPILON RED C-GH 1.0 part benzyl alcohol 20.0 parts phenyl cellosolve 44.8 parts Crucell H ( hydroxypropyl cellulose, manufactured by Sanki Co., Ltd. ) 0.2 parts Jonkrill 586 (styrene-acrylic acid copolymer, molecular weight 4600, acid value 108, Johnson polymer ( Co., Ltd.) 2.0 parts oleoyl tauric acid 21.0 parts
Among the above components, Crucelle H and Jonkrill 586 were dissolved in benzyl alcohol and phenyl cellosolve while being heated and dissolved until they were uniformly dissolved with a propeller stirrer. Next, Neo Super Blue C-555, OIL BLUE 613 and SPILON RED C-GH were mixed and stirred for another 2 hours, and oleoyl tauric acid was added thereto and stirred for 1 hour to obtain a blue ballpoint pen ink.

(Comparative Example 1)
Water Black # 256L (14% aqueous solution of black dye, Orient Chemical Co., Ltd.)
20.0 parts ethylene glycol 5.0 parts glycerin 6.0 parts diethylene glycol 6.0 parts ion-exchanged water 41.3 parts Crucell M (hydroxypropylcellulose, manufactured by Sanki Co., Ltd.) 0.2 parts sarcosinate OH (oleoyl) Sarcosine (manufactured by Nikko Chemicals Co., Ltd.) 20.0 parts Sodium hydroxide 1.5 parts Among the above components, Crucelle M and water are stirred and dissolved uniformly for 30 minutes to prepare a Crucelle M aqueous solution. Were mixed and stirred for another 2 hours to obtain a black ballpoint pen ink.

(Comparative Example 2)
PERMANENT RED FRR (CI Pigment Red 2, manufactured by Clariant Japan) 15.0 parts Phenylcellosolve 29.5 parts Crucell M (previously described) 0.5 parts Nikkor PBC-34 (POE (20) POP (4) cetyl ether , Manufactured by Nikko Chemicals Co., Ltd.) 5.0 parts Sarcosinate OH (previously described) 50.0 parts Among the above components, the entire amount of Nikkor PBC-34, benzyl alcohol and phenyl cellosolve is heated and stirred at about 70 ° C., and uniformly dissolved. Then, the entire amount of PERMANENT RED FRR was added and mixed uniformly. This was allowed to cool to room temperature and then passed 10 times with a three roll mill to obtain a red paste. Next, all the remaining components were added, heated to about 70 ° C., mixed and stirred with a propeller stirrer until uniform, and stirred for 2 hours until dissolved to obtain a red ballpoint pen ink.

(Comparative Example 3)
PERMANENT RED FRR (CI Pigment Red 2, manufactured by Clariant Japan) 15.0 parts Phenylcellosolve 29.5 parts Crucell M (previously described) 0.5 parts SMA 1440 (styrene-maleic acid copolymer, molecular weight 7000, acid value) 185, manufactured by Kawa Crude Chemical Co., Ltd.) 11.0 parts Sarcosinate OH (previously described) 50.0 parts Among the above components, the entire amount of Nikkor PBC-34, benzyl alcohol, and phenyl cellosolve is heated and stirred at about 70 ° C, and uniform. Then, the entire amount of PERMANENT RED FRR was added and mixed uniformly. This was allowed to cool to room temperature and then passed 10 times with a three roll mill to obtain a red paste. Next, all the remaining components were added, heated to about 70 ° C., mixed and stirred with a propeller stirrer until uniform, and stirred for 2 hours until dissolved to obtain a red ballpoint pen ink.

(Comparative Example 4)
VALIFAST BLUE 1603 (salt-forming dyes of CI DIRECT BLUE 86 and CI BASIC BLUE 7, manufactured by Orient Chemical Co., Ltd.) 11.0 parts SPILON RED C-GH (oil-based dye, Hodogaya Chemical Co., Ltd.) )) 1.0 parts benzyl alcohol 11.54 parts phenyl cellosolve 36.4 parts Crucell H (hydroxypropylcellulose, manufactured by Sanki Co., Ltd.) 0.06 parts Jonkrill 682 (styrene-acrylic acid copolymer, molecular weight) 1700, acid value 238, manufactured by Johnson Polymer Co., Ltd.) 0.4 parts Nikkor BL-4.2 (POE (4.2) lauryl ether, manufactured by Nikko Chemicals Co., Ltd.) 39.6 parts Among the above components, benzyl While heating and dissolving Crucell H and Joncrill 682 in alcohol and phenyl cellsolve It stirred until it melt | dissolved uniformly with the propeller stirrer. Next, VALIFAST BLUE 1603 and SPILON RED C-GH were mixed and further stirred for 2 hours, and then Nikkor BL-4.2 was added thereto and stirred for 1 hour to obtain a blue ballpoint pen ink.

(Comparative Example 5)
A blue ballpoint pen ink was obtained in the same manner as in Example 4 except that the amount of oleoyl tauric acid was reduced to 2 parts by weight and phenyl cellsolve was added accordingly.

As mentioned above, the following test was done about the ink composition obtained by the Example and the comparative example. The results are shown in Table 1.
The viscosity was measured with a TV type viscometer TVH-20 manufactured by Toki Sangyo Co., Ltd. Measurement was performed at 2 rpm using one rotor. The measurement temperature was 25 ° C.
For the shear thinning, the viscosity was measured by changing the shear rate under the above conditions, and the measured value was applied to the following equation to calculate the shear thinning index.
σ = kγ ⁿ
σ: shear stress k: viscosity coefficient (constant, Pa · s)
γ: Shear rate (1 / s)
n: Shear thinning index

  The measurement of the string length of the ink was performed as follows in an environment at room temperature of 25 ° C. About 10 g of ink was collected in a 35 ml glass bottle, and a regular cylindrical glass rod having a diameter of 7 mm was immersed in the ink by 5 mm. Then, when the glass rod was pulled up at a constant speed in the vertical direction at 50 mm / second, the length at the time when the ink string was broken was measured and this was defined as the string length.

(Preparation of test ballpoint pen)
0.3 g of the oil-based ballpoint pen ink obtained in the above Examples and Comparative Examples was applied to a writing instrument having the same structure as a commercially available oil-based ballpoint pen (.e-ball, product code BK127, manufactured by Pentel Co., Ltd. (ball diameter φ0.7)). After filling, a centrifugal force was applied with a centrifuge to degas bubbles in the ink, and a test ballpoint pen was produced.

<Ink adherence to ball holder>
Three ball pens for the above test were prepared for each example, and 100 m was written with a spiral writing tester (writing angle 70 °, load 150 g, writing speed 7 cm / sec), and if there was ink adhering to the ball holder, The ink length adhered to the ball holder when 200 m was written again was measured. In addition, the vertical distance from the tip of the opening of the ball holder to the area where ink was adhered was defined as the ink length. The test results were evaluated as average values.

  Both: Three ballpoint pens for the above test were prepared for each example, and 100 m was written with a spiral writing tester (writing angle 70 °, load 150 g, writing speed 7 cm / sec), the nib was wiped off, and 100 m was written again. The number of bots when it occurred on a writing line between 100 m and 200 m was measured. In addition, the ink spread more than the size prescribed | regulated to JISS6039 (medium for ball-point pens) was measured with the edge. The test results were evaluated as average values.

  Written taste: A sensory test by handwriting was conducted with 5 monitors, and the written taste was evaluated as 1 point: heavy or not smooth, 2 points: light and smooth, 3 points: very light and smooth, and the average of 5 people The value was calculated.

  As described above in detail, the ink of the present invention relates to a ball-point pen ink that has a very light and smooth writing taste, and has less ink adhesion to the ball holder outer surface of the ball-point pen chip and less voids.

Claims (2)

It contains at least a copolymer of a styrene monomer and a monomer having a carboxylic acid group in the molecule, and N-acyl taurine, and the N-acyl taurine is 5% by weight or more and 60% by weight or less based on the total amount of the ink. Ballpoint pen ink. 2. The ballpoint pen ink according to claim 1, wherein the copolymer of the styrene monomer and the monomer having a carboxylic acid group in the molecule has a molecular weight of 1,000 to 20,000 and an acid value of 40 to 260. 3.