In general, an ink composition containing titanium oxide has the problem that it has a high specific gravity and therefore settles down and separates with the passage of time. Accordingly, a means in which the ink composition is sufficiently stirred again before use and then used or a means in which the ink composition is provided with a shear thinning property to inhibit titanium oxide from settling down has so far been taken.
It has so far been known as the above means for providing an ink composition with a shear thinning property to add a thickener and a gelatinizing agent thereto. Materials having various chemical structures have so far been investigated for the above additives. However, it is the existing situation that materials investigated for ink compositions (so-called oil-based ink compositions) comprising organic solvents as principal components are few as compared with materials added to ink compositions (so-called water-based ink compositions) comprising water as a principal component.
Known as a thickener and a gelatinizing agent which are added to oil-based ink compositions are, for example, montmorillonite base clay minerals, fluorinated phlogopite, dextrin fatty acid esters, fatty acid amides and aluminum 2-ethylhexanoate.
Addition of the above materials to the intended ink compositions has made it possible to inhibit to the utmost a hard cake from being formed by settling of titanium oxide up to about 2 months. However, there has been the problem that when stored over a long period of 2 months or longer, a settling layer is gradually formed at the bottom of the ink. Further, a gel structure has strongly been formed in the whole part or a part of the ink compositions with the passage of standing time, and reduction in fluidity and a leveling property of the ink compositions following reduction in a shear thinning property has been brought about. On the other hand, considering that the ink composition is provided to the market in the form of a product, it is a matter of course that the quality is required to be maintained over a longer period than 2 months. Accordingly, a coating fluid in which a quality is maintained over a longer period is desired to be provided.
A material which is an additive investigated in the present invention and which comprises an N-acylamino acid derivative whose fundamental frame is at least one selected from N-acylamino acid amides and N-acylamino acid esters is also known as an oil gelatinizing agent (refer to, for example, patent document 1). Known as an ink composition containing an additive having such characteristic are, for example, one in which 0.5% by weight of N-lauroyl-L-glutamic acid-α,γ-di-n-butylamide is added (refer to, for example, patent documents 2 and 3), one in which 5% by weight of N-lauroyl-L-glutamic acid-α,γ-di-n-butylamide is added (refer to, for example, patent document 4) and one in which 1 to 10% by weight thereof is added (refer to, for example, patent document 5).
As described in patent document 1 described above, however, these additives are scarcely soluble in organic solvents, and therefore a specific means in which inorganic metal salts are allowed to coexist as a solubilizing agent is required. Further, it is known that these additives have a strong oil coagulant function and form a three-dimensional network in a state of enclosing oil in an individual net, so that gel which is short of fluidity is formed.
Further, as described in patent documents 2 and 3 described above, marked reduction in the fluidity is not observed in an ink composition containing 0.5% by weight of the gelatinizing agent because of a small content of the gelatinizing agent, and the writing characteristic is good. However, there has been the problem that titanium oxide can not be inhibited from settling down over a long period of 2 months or more to cause settling and separation as time passes. In an ink composition in which 5% by weight or more of the gelatinizing agent is added, a net work structure of gel is sufficiently formed because of a large amount of the gelatinizing agent, and titanium oxide can be inhibited from settling down over a long period of 2 months or more. However, fluidity of the ink composition is a little short due to the strong net work structure of the gel, and the gel becomes further firm as time passes, so that observed is the problem that reduction in fluidity and a leveling property of the ink composition is brought about to a large extent.
On the other hand, also in the ink composition in which the gelatinizing agent is suitably added, as described in patent document 5 described above, in a range of 1 to 10% by weight, particularly in a range of 1% by weight or more and less than 5% by weight, brought about to not small extent is either of the problems that settling of titanium oxide is caused when time of 2 months or longer passes or that the gel becomes firm to cause reduction in fluidity and a leveling property of the ink composition, and it is the existing situation that both problems (first problem) do not result in being solved at the same time.
Further, it has so far been known that an organic solvent having a relatively high volatility is used for a coating fluid in a fluid applicator such as a writing instrument, a correction device, an adhesive and a toilet tool for the purpose of quickly drying the coating fluid when it is coated. However, organic solvents used for paint markers and correction devices have a high volatilizing rate, and therefore caps have to be put thereon in non-use to prevent the coating fluids from drying. Accordingly, involved therein are the problems (second problem) that a labor for removing the caps in every use is required and that if the caps are neglected to be put on after use, the coating fluids are dried and solidified for a short time, so that the applicators can not be used.
On the other hand, known are a lot of correction devices of a ballpoint pen type equipped with a means in which a ball made of metal is pressed against a point aperture part, for example, by a pressing means such as a spring to seal it (refer to, for example, patent documents 6 and 7 filed by the present applicant).
On the other hand, a lot of ink compositions for marking pens which are prevented from drying up by adding a cap-off performance-improving agent such as lecithin to a coating fluid have so far been known, but if a cap-off performance-improving agent such as lecithin is used for a coating fluid containing titanium oxide which is liable to settle down, coagulating and settling down of titanium oxides themselves caused by breakage of a dispersion system and subsequent separation of the liquid are brought about in a certain case, and therefore it is the existing situation that cap-off performance-improving agents used for ink compositions for writing instruments can not simply be diverted. Further, the present applicants have filed a correction liquid-blended composition characterized by adding at least paraffin waxes as a cap-off performance-improving agent (refer to, for exampled, a patent document 8).
However, in the art described in the patent documents 6 and 7 described above, it is impossible to completely seal a tip part because of contact of metal with metal in which a metal ball is pressed against an aperture part, and the problem (third problem) that a cap is always put on in non-use is not solved.
Further, the art described in the patent document 8 described above is a correction liquid composition having an excellent cap-off performance which has not so far been available. However, if an addition amount of paraffin wax is small, a period in which the cap-off performance can be maintained is about 2 weeks, and on the other hand, a period in which the cap-off performance can be maintained is extended to one month or longer by increasing an addition amount of paraffin wax. In the product, however, a quality has to be maintained for a long period of several months or longer, and therefore it is the existing situation that the product can not help being equipped with a cap even when the art described above is used.
Further, in a gel ink ballpoint pen for correction which is a fluid applicator, a fluid reservoir filled with a correction liquid (fluid) has so far been desired to be so-called refillable because of an environmental problem. In such case, a ball point has to be protected in transporting and storing a refill alone, and a solvent has to be inhibited from being volatilized from the point.
In order to prevent such volatilization, countermeasures such as making parts constituting a fluid reservoir main body of metal or resins and providing a tip point with a seal by a resin coating film have been taken.
Many arts regarding the above fluid reservoir in which a tip point is sealed by a resin coating film have so far been proposed, and known are, for example, a resin coating film formed from a synthetic resin emulsion (refer to, for exampled, patent document 9), a resin coating film formed from a molten thermoplastic resin (refer to, for exampled, patent document 10), a resin coating film formed from a polymer latex (refer to, for exampled, patent document 11), a resin coating film formed from a hot melt resin (refer to, for exampled, patent document 12) and a colored resin coating film (refer to, for exampled, patent document 13).
The seals formed by the resin coating films described in patent documents 9 to 11 and 13 described above prevent solvents having no high volatility and water contained in water-based inks and water-based gel inks having a shear thinning property from vaporizing from tip point parts (writing point parts). In the cases of applicators filled with fluids containing solvents having high volatility such as n-hexane, cyclohexane and methylcyclohexane, the solvents are still insufficiently inhibited from vaporizing even if resin coating films of synthetic resin emulsions and polymer latexes are formed, and therefore involved therein is the problem (fourth problem) that the fluids are liable to be solidified at the sealed parts due to dry-up so that the fluids can not discharge from the tips when long time passes from production through use.
Also, the seal prepared by the resin coating film described in patent document 12 described above is formed by coating a tip point of an applicator filled with a coating liquid having a high viscosity such as a correction liquid, a toilet liquid, an adhesive and a paint with a hot melt resin such as an ethylene-vinyl acetate base resin, a polyester base resin, a polyamide base resin, a polyolefin base resin and a rubber base resin, which are comprehensive resin names, and it shows an art close to that of the present invention. However, careful investigation of the above patent document 12 shows that the examples are not described and that the specific kinds of the solvents and the specific names of the hot melt resins are not described.
In particular, in the cases of applicators filled with fluids containing solvents having high volatility such as n-hexane, cyclohexane and methylcyclohexane, the solvents are still insufficiently inhibited from vaporizing even by resin coating films of ethylene-vinyl acetate base resins and polyamide base resins, and therefore involved therein is, as is the case with the fluid applicator for a water-based ink described above, the problem (fifth problem) that the fluids are liable to be solidified at the sealed parts due to dry-up so that the fluids can not discharge from the tips when long time passes from production through use.
Patent document 1: Japanese Patent Application Laid-Open No. 68102/1977 (examples and others)
Patent document 2: Japanese Patent Application Laid-Open No. 343875/2000 (examples and others)
Patent document 3: Japanese Patent Application Laid-Open No. 343879/2000 (examples and others)
Patent document 4: Japanese Patent Application Laid-Open No. 53034/1997 (examples and others)
Patent document 5: Japanese Patent Application Laid-Open No. 256178/2002 (examples and others)
Patent document 6: Japanese Patent Application Laid-Open No. 58292/1996 (claims, examples and others)
Patent document 7: Japanese Patent Application Laid-Open No. 118896/1996 (claims, examples and others)
Patent document 8: Japanese Patent Application Laid-Open No. 213162/2003 (claims, examples and others)
Patent document 9: Japanese Patent Application Laid-Open No. 96597/1983 (claims and others)
Patent document 10: Japanese Patent Application Laid-Open No. 35294/1986 (claims, examples and others)
Patent document 11: Japanese Patent Application Laid-Open No. 98396/1982 (claims, examples and others)
Patent document 12: Japanese Patent Application Laid-Open No. 222950/1995 (claims, examples and others)
Patent document 13: Utility Model Registration No. 3076019 (claims, examples and others)