Innovation - Self Seal

Using HARMAN advanced multilayer coating technology, we have devised an ink jet receiving medium that provides most of the advantages of lamination without the cost of an extra stage. We call it our self-seal technology.


Self Seal

Prints on most commercially available inkjet materials are relatively poorly robust to handling and scratching, and are also susceptible to staining. It is possible to improve the robustness of printed images by lamination or encapsulation using a transparent laminate that acts as a physical protection for the image and completely seals it from ingress of water. Highly glossy and robust prints may be produced by suitable choice of the laminating sheets, but this is an expensive process because of the additional materials required together with extra handling and equipment. 

The self-seal ink jet material comprises two essential imaging layers: a lower "pumping" layer that is similar to the receiving layer in many conventional ink jet printing materials and is designed to take up the fluid components of the ink; and an upper "sealing" layer that is porous, being formed from small particles of a thermoplastic polymer together with a binder. The material may be printed just like any other ink jet medium, and the porous construction means it is quickly dry to the touch.

However after printing the thermoplastic polymer in the upper layer may be softened or (partially) melted by application of heat. The particles fuse to form a continuous protective film on the surface, resistant to staining and handling. Further, by heating in contact with a smooth-surfaced roller it is possible to obtain high gloss, and it is also possible to pattern the surface or apply a security mark. Another security feature is that once sealed, the surface will no longer receive ink and thus the print cannot be altered.

Self-seal material before and after printing and sealing

The Scanning Electron Microscope pictures above show the surface of a self-seal material before and after printing and sealing. Before printing the particles forming the upper sealing layer are clearly visible; they are around 10 - 20 microns (µm) in size. After sealing there is a smooth glossy surface that is resistant to handling. 

Cross section through printed and sealed material

 

 

 

 

 

 


The accompanying image is a microscopic view of a cross-section through the printed and sealed material. It is clearly seen that the colorant is retained within the upper sealing layer, the lower pumping layer and supporting substrate are also shown.

Prototype system

 

 

 

 

 

 


Finally a view of a prototype system comprising a roll-fed ink jet printer (left) feeding printed material into a sealing unit (right) that incorporates a heated roller in contact with the top surface of the material to seal the surface layer. Ultimately, a single machine will print, dry, and seal.

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Innovation - Inks

At HARMAN technology Ltd we are applying the technology we have learnt in decades of experience in the photographic field in other areas.

Aqueous Ink Jet Inks for Outdoor Use


In addition to coated ink jet media, HARMAN technology Ltd also has experience of developing ink jet inks for specialist uses. For instance, there is interest in employing ink jet printing methods in large and very large format applications for uses such as banners, signage, displays, posters, and billboards. For applications where the print may be exposed to the elements in outdoor usage it is common to use a hydrophobic, durable substrate such as  vinyl (PVC), but the water-based inks generally preferred in ink jet printing do not print well (or at all) on such substrates, either because the ink does not adequately wet the substrate during printing resulting in a poor quality print, or because the ink does not adhere well and is insufficiently robust to handling damage.

Thus it is common either to use an ink-receiving coating on the substrate, or to employ solvent-based or UV cured inks that will print successfully on the uncoated substrate.

However by careful choice of the various components that make up the ink we have designed a water-based ink jet ink formulation that will print successfully on such substrates. The picture below shows a test chart being printed on an uncoated vinyl substrate using an experimental water-based ink.

Printing with a water based ink on an uncoated vinyl substrate

 

 

 

 

 

 

 

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  • About Us - HARMAN technology Limited
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