In recent years, since ink-jet recording systems are capable of easily forming images at low cost, they have been applied to various printing fields such as photography, various types of printing, and special printing such as marking or color filters.
Ink-jet inks employed in such ink-jet recording systems include a plurality of inks such as an aqueous ink employing water as a main solvent, an oil ink employing non-volatile solvents as a main solvent, a solvent ink employing volatile solvents as a main solvent, a hot-melt ink enabling printing via thermally melting an ink which is solid at room temperature, or an actinic radiation curable ink which is cured by exposure to actinic radiation such as light after printing, and each of the above inks is appropriately employed in response to its use.
On the other hand, recording media prepared via employing polyvinyl chloride are widely employed to prepare various products such as outdoor bulletin boards which are required to be weather resistant over a long period of time, or printed matter which is required for close contact with a curved surface. There is a plurality of methods to achieve printing onto soft polyvinyl chloride. Of these, an ink-jet recording method is available which does not require plate preparation, shortens the time for a finished print, and is suitable for production of small quantities, but of many types.
When ink-jet recording is applied to soft polyvinyl chloride, a solvent ink, incorporating a major amount of cyclohexanone, has been employed as an ink-jet ink. For example, a cyclohexanone incorporating ink is disclosed (refer to Patent Document 1). Cyclohexanone results in high dissolving capability to soft polyvinyl chloride and pigments in an ink-jet ink enter into soft polyvinyl chloride, resulting in desired abrasion resistance and glossiness. However, cyclohexanone is specified as the Second Class Organic Solvent in Japan, and not only results in concerns of safety but also results in a problem in which during handling of an ink-jet ink incorporating cyclohexanone, a localized exhaust system is required.
Contrary to this, solvent inks which do not feature incorporation of cyclohexanone have been developed and marketed. Instead of cyclohexanone as a solvent to dissolve polyvinyl chloride with the inherent problems as above, solvent inks which incorporate solvents such as amide are disclosed (refer to Patent Documents 2 and 3). Even though such ink-jet inks are employed, it is not possible to completely eliminate unpleasant odor during printing since the major ink component is composed of organic solvents. In addition, it is hard to state that the present ink-jet ink provides sufficient characteristics such as personal safety, no unpleasant odor, and appropriateness when printed onto polyvinyl chloride. Further, the solvent inks, disclosed in above Patent Documents 2 and 3, are appropriate to some extent aptitude to record onto polyvinyl chloride, but when printed onto media employing paper as a substrate, problems result in which colorants easily bleed through to the reverse side and density is insufficient.
(Patent Document 1) Japanese Translation of PCT International Application Publication No. 2002-526631
(Patent Document 2) Unexamined Japanese Patent Application Publication No. (hereinafter, referred to as JP-A) 2005-15672
(Patent Document 3) JP A 2005-60716