A method of recording with an inkjet printer, which is one of typical methods among a variety of color recording methods, performs recording by forming ink droplets and making the droplets adhere to a variety of record receiving materials (such as paper, a film, or fabric). In this method, the recording head and the record receiving material are not brought into direct contact with each other. The method therefore has advantages that the method generates little noise and is quiet and that miniaturization and speeding up of inkjet printers can be readily achieved. Accordingly, the method has been rapidly being spread in recent years and is expected to be further popularized in the future.
The recent development of inkjet technologies has remarkably accelerated the printing speed in inkjet printing, and inkjet recording has been proposed to be used in commercial printing or at offices. In such cases, the printing media are generally plain paper having no ink-receiving layer, which has problems in hue, light resistance, and water resistance in many cases, compared to inkjet exclusive paper having an ink-receiving layer, and has been therefore highly desired to be improved.
A black ink is an important ink that is used in both mono-color and full-color images. However, there are many technical barriers in the development of a colorant having neutral hue in both a deep-color region and a light-color region, a high color density, and also excellent fastness properties, and inks showing sufficient performance have been hardly provided in spite of active research and development. Accordingly, a black ink is generally prepared by mixing a plurality of various colorants. An ink prepared by mixing a plurality of colorants is, however, prone to cause problems, such as a change in hue depending on the record receiving material and an increase in discoloration due to light and water, compared to an ink prepared from a single colorant.
The “discoloration” is, in general, known to be capable of being evaluated separately as two different indices. One index is “fade in color”, which is evaluated as a change in print density. The other index is “change in color”, which is evaluated as a change (ΔE) in hue. In these indices, the latter, “change in color”, is notably observed in an ink prepared from a plurality of colorants and is observed even by visual inspection as a significant degradation in a recorded image. It is therefore highly demanded to reduce such a change in color.
For example, PTL 1 proposes a black ink containing a black dye and further another dye for adjusting the color, but a product sufficiently meeting the requirements of the marketplace has not been provided yet.
In addition, the dyes represented by Formula (1) described in the present specification are disclosed in PTLs 2 to 5. These dyes, however, have not sufficiently solved the above-described problems in light resistance and water resistance.
USPTO Backgrounds
USPTO Backgrounds