Inkjet ink

Abstract

There is provided an inkjet ink comprising a photo-acid generating agent which is capable of generating an acid as it is irradiated with light, a color component, and an acid-polymerizable compound which can be polymerized in the presence of an acid, wherein at least 40% of the acid-polymerizable solvent is a vinyl ether compound represented by the following general formula (1):R13—R14—(R13)p  (1)(Wherein R13(s) is a group selected from the group consisting of a vinyl ether group, a group having a vinyl ether skeleton, an alkoxy group, substituted hydroxyl group and hydroxyl group wherein at least one of R13(s) is vinyl ether group or a group having a vinyl ether skeleton, R14 is a group comprising a substituted or unsubstituted cyclic skeleton and having a valence of (p+1), and p is a positive integer including zero).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional patent application of U.S. Ser. No. 10 / 969,204 filed Oct. 20, 2004, claiming priority to Japanese Patent Application No. 2003-367804, filed Oct. 28, 2003; and No. 2004-252466, filed Aug. 31, 2004, all of which are incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to an inkjet ink. [0004] 2. Description of the Related Art [0005] In a situation where a fairly large number of copies of printed matter are required such as in the cases of local advertisement bill, enterprise handout and a postern of large scale, a printing machine utilizing a form plate has been conventionally employed for meeting such requirements. In recent years however, an on-demand printer which is capable of quickly coping with the diversification of needs and of minimizing stocks has been increasingly utilized in place of the aforementioned conventional printing machine...

AI Technical Summary

Benefits of technology

"The present invention provides an inkjet ink that does not require an organic solvent and an exposure system of large scale for obtaining printed matters of high quality. The ink includes a photo-acid generating agent, a color component, and an acid-polymerizable compound that can be polymerized in the presence of an acid. The ink also contains a compound represented by the following general formula (1), which acts as an acid-polymerizable solvent: \nR13—R14—(R13)p \nThe invention also provides an inkjet ink that does not require an epoxy compound and / or an oxetane compound with high solubility, but still has good viscosity and stability. The ink can be used for inkjet printing without compromising the quality of the printed matter."

Problems solved by technology

This technique of employing a solvent type ink or a solvent type liquid toner is however accompanied with the problem that the organic solvent volatilizes to such an extent that cannot be disregarded when the printing is repeated a certain number of times. Therefore, when this technique is employed, a problem of environmental contamination due to this volatilized organic solvent will be raised, thus necessitating the provision of an exhaust gas processing installation or a solvent recovery system.

Therefore, the ink to be employed in the inkjet printer is required to be sufficiently high in the concentration of solvent, so that even with this technique, it is essentially difficult to overcome the problem of environmental contamination associated with the employment of the organic solvent.

For example, if the surface of printing mater is permeable, bleeding is more likely to occur, and if the surface of printing mater is impermeable, it will become difficult to fix printed images.

Moreover, since it will take a certain period of time in order to dry completely an ink layer that has been formed on the surface of printing matter, when an image is formed relatively thick on a large surface of printing matter, the image is more likely to collapse due to the fluidity of ink.

Moreover, when the solvent type ink is employed, there is high possibility that the printed surface is deteriorated in the drying process of the ink layer.

Thus, according to the aforementioned conventional techniques, it is not necessarily easy to obtain a printer matter with high qualities.

However, this photosensitive ink includes a large amount of carcinogenic radical-generating agents such as a radical generating agent and still more, a volatile acrylic acid derivative to be employed as a radical polymeric monomer is highly stimulating to skin and badly smelling.

Further, the radical polymerization is considerably obstructed by the presence of oxygen in air atmosphere and additionally, the light for exposure will be lost due to the absorption of light by the pigment included in the ink.

As a result, underexposure may occur at a deep region of ink layer, so that the conventional radical polymeric ink is poor in sensitivity to light.

However, since the conventional ink of this type contains a solvent, the problem of the release of the solvent into environment cannot be overcome.

Moreover, a cured layer is more likely to be further hardened, thus giving rise to the problem of clogging of the delivery head since this hardened layer is insoluble.

The composition which has been found capable of performing the inkjet delivery mainly comprises vinyl ether and bisphenol A type epoxy, and hence there is still a serious problem associated with the release of these compounds to the environment.

Since this ink also contains, as an essential component, a specific kind of vinyl ether compound which is high in volatility, there is the same problem as described above.

Further, ordinary vinyl ether compounds are accompanied with the problem that when it is employed in combination with pigment, they become poor in polymerizability.

The vinyl ethers disclosed are accompanied with various problems that they are poor in polymerizability, that the skeleton of bisphenol A exhibits its specific carcinogenic property, and that since the vinyl ethers are employed in combination with an alicyclic epoxy which is high in solubility and dark-reactivity, they are poor in shelf life and a printed matter to be obtained is not sufficiently resistive to a solvent.

In particular, when the printing surface is constituted by an absorptive medium, there will be raised the problem that the conventional acrylic photo-curable inkjet ink cannot be easily cured in the interior of the absorptive printing surface.

Incidentally, the conventional photo-cation-cure type inkjet ink is accompanied with the problem that the viscosity thereof can be greatly fluctuated.

The reason for this can be attributed to the fact that once an acid generates due to changes with time of ink, the acid cannot be easily deactivated, thus giving rise to a great magnitude of dark reaction of ink.

In the case of inkjet ink, when the viscosity thereof is caused to change, it will lead to the disturbance of the ejecting shape of ink, to poor reproducibility of printing, and in the worst case, to a critical condition such as defective delivery of ink and clogging of ink.

Therefore, this problem is very serious.

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