Different kinds of ink-receptive coatings can enhance various properties of printing media. Ink-receptive coatings are used to improve the spread of ink droplets and increase the durability of the printed image. In addition, they also grow the ink’s dry time and provide water and UV resistance.
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Fumed silica
A first ink-receptive layer may consist of dye-absorbing particulates such as precipitated silica or synthetic silica. It can also be composed of clay, talc, or kaolin. Other options include colloidal silica, styrene-based plastic pigments, and aluminum oxide.
To assess the effects of fumed silica on inkjet printing performance, this study evaluated the effects of this compound on the properties of existing inkjet prototypes. Previous inkjet prototypes showed excellent image quality but were plagued by long drying times and persistent tackiness. In the present study, fumed silica is used in a pigment-binder combination that improves ink absorption while reducing tackiness.
The ink-receptive coating is composed of 35-43% solids. It is applied over a base coat using any suitable coating apparatus. It may be applied to either side or both sides of the substrate.
Mesoporous silica
Using mesoporous silica in an ink receptive coating can reduce the gamut area of the print and increase sharpness. A mesoporous silica layer consists of large pores that absorb a droplet of ink. These large pores help reduce the lateral spread of the droplet and surface wicking.
Synthetic silicas with a large internal surface area were synthesized in this study using a sol-gel method. The coatings’ properties were characterized by spectroscopy. The layers retained the desired morphological properties even after aluminization.
A cationic additive was added to PVOH-silica coatings. This additive significantly increased the smoothness and strength of the paper. However, the effect of the VAE additive was not as pronounced. The VAE particles were too large to enter silica pores and fill gaps between the particles. Hence, the VAE-based coating had a more uniform surface and greater pore volume than the PVOH-silica coating.
The print quality of inkjet receptive coatings depends on the type of ink used. A dye-based ink provides the highest gamut area, while pigment-based ink gives the sharpest print quality. To assess the effect of ink on the coating, MicroDAT micro drop absorption test equipment is used. MicroDAT can dispense a wide range of liquids with high velocity and tiny droplets.
Swellable alumina
Swellable alumina is a widely used material for ink-receptive coatings. This material allows ink to bond to a substrate without allowing water or other low molecular-weight organic materials to migrate. It also promotes the coalescence of ink components, resulting in less liquid mass and reduced smudging. It is handy for printing on clear containers.
Another essential property of this polymer is its good interaction with water and methacrylic acid. Additionally, it has sufficient hydrophobicity and resists swelling. This property is beneficial in producing ink-receptive coatings with high gloss and fast drying times.
The ink-receptive coating may be used with water-based inks. These types of inks have good wet abrasion resistance. However, swollen things in the presence of water or polar solvents tend to absorb water more quickly. As a result, swollen coatings tend to rub more rapidly, and the resulting image may not be as legible.
Microporous silica
Microporous silica can be used for an ink-receptive coating. It has low viscosity and can be applied directly to the substrate or over an existing ink-receptive layer. This characteristic allows it to be easily used and minimizes coating defects.
Microporous silica is an inorganic substance that is often produced from fumed alumina. Its fractal structure results in channels and voids, which allow liquid to adhere to the surface. The material can also be used to create high-gloss films. Eventually, microporous silica is expected to play a significant role in developing coated glossy media.
Microporous silica can be applied to a paper substrate to create an ink-receptive coating. Typically, it is used as an underlayer to the paper substrate. With its porous structure, the first layer produces a matte surface finish comparable to uncoated matte paper. The second layer, however, creates a glossy or semi-glossy coating.
