Imaged articles comprising a substrate having a primed surface

Abstract

The present invention relates to an imaged article comprising a substrate having a primed surface layer. The primed surface layer is comprised of a base polymer having a solubility parameter, molecular weight (Mw) and glass transition temperature within a specified range. The presence of the primer improves the overall image quality by improving at least one property including ink uptake, dot gain, color density and / or ink adhesion. Preferred primer compositions are soluble at least in part in the ink composition resulting in an increase in ink layer thickness that further improves the durability and / or day / night color balance. A variety of substrates may be primed including various sheeting for traffic control signage and commercial graphic films for advertising and promotional displays.

Description

[0001] The present invention relates to an imaged article comprising a substrate having a primed surface layer. The primed surface layer is comprised of a base polymer having a solubility parameter, molecular weight (Mw) and glass transition temperature within a specified range. The presence of the primer improves the overall image quality by improving at least one property including ink uptake, dot gain, color density and / or ink adhesion. Preferred primer compositions are soluble in the ink composition resulting in an increase in ink layer thickness that further improves the day / night color balance and / or durability. A variety of substrates may be primed including various sheeting for traffic control signage and commercial graphic films for advertising and promotional displays.BACKGROUND OF INVENTION[0002] A variety of print methods have been employed for imaging various sheet materials. Commonly employed print methods include gravure, offset, flexographic, lithographic, electrogra...

AI Technical Summary

Benefits of technology

[0094] Objects and advantages of the invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in the examples, as well as other conditions and details, should not be construed to unduly limit the invention. All parts, percentages and ratios herein are by weight unless otherwise specified.

Problems solved by technology

Image defects are typically due to a subsequent recession of the ink contact angle with the substrate.

Accordingly, ink / substrate combinations that result in good image quality when printed with contact methods such as screen printing, often exhibit insufficient wetting when imaged with non-contact printing methods such as ink jet printing.

It is not generally feasible to dilute a screen printing ink to make it suitable for ink jet printing.

The addition of large amounts of low viscosity diluents drastically deteriorates the ink performance and properties, particularly the durability.

Further, the polymers employed in screen printing inks are typically high in molecular weight and exhibit significant elasticity.

One problem, however, with ink jet inks is that ink compositions do not uniformly adhere to all substrates.

Such artificial back lighting results in a washed out appearance of the printed media (e.g. colored graphic).

The Applicant has found that base compositions having such physical properties outside this range typically detract from, rather than improve the overall image quality.

Further, highly polar solvents, such as low molecular weight alcohols and glycols, tend to have too high of a solubility parameter to sufficiently dissolve the primer.

If the ink drops do not spread enough, unfilled background areas will contribute to reduced color density and banding defects (i.e. gaps between the rows of ink drops).

On the other hand, if the ink drops spread too much, loss of resolution and poor edge acuity is evident, and inter-color bleed occurs in the case of multi-color graphics.

However, in the case of poor primer adhesion to the substrate, both the ink and primer are removed from the substrate, rather than merely the ink.

Such primer compositions are typically unreactive with the ink composition.

At too low of a molecular weight, the base polymer of the primer composition does not adequately thicken the ink composition upon dissolution.

At too high of a molecular weight, however, it become increasingly difficult to form a primer composition that is sufficiently low in viscosity such that it can be applied at low coating thicknesses.

le. At a Tg of greater than about 95.degree. C., the primer coating is typically brittle such that the primer coating is susceptible to cracking upon being flexed or crea

Excessive solvent absorption can have a plasticizing effect that substantially decreases the Young's modulus of the substrate (e.g. by as much as 85%) causing the substrate to become too flimsy to be easily applied to the target substrate, such as a billboard backing.

Although the primer composition could be applied to substrates such as paper, upon exposure to rain, paper typically deteriorates and thus is not sufficiently durable for outdoor usage.

However, this construction would also exhibit poor durability.

Other materials that are typically unsuitable for use as the substrate include materials that corrode (e.g. oxidize) or dissolve in the presence of water such as various metals, metallic oxides, and salts.

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