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Matte surfaces
December 9, 2007
Continuing with the subject of surface haze, we have the figure showing the impact of surface roughness to the affect of haze where the line separating no effect and an affect is shown as the Rayleigh Model for a wavelength of 550 nm, which is red light. Here the wavelength (lamda) is divided by 8sin(angle) which is where the approximate 1/6 of the wavelength of light rule of thumb comes from. Now if we want to make a low surface haze, we want a smooth surface, but if we want a hazy surface (matte surface) this allows us to estimate the size of the bumps we need to put in the film surface to make it hazy.
In general, matte films are produced by coextruding a thin layer onto a substrate where the outer skin is filled with mineral particles or by using an incompatible blend of polymers. In this case, the viscosity ratio of the various polymers can be used to control the particle diameter. Generally, for oriented PP films (OPP), the surface layer is a blend of PP, HDPE and perhaps copolymer PP. There are many patents for the matte-film blends, and it is hard to decipher what the real blends are, but generally they are three polymers as described here.
Posted by Eldridge M. Mount on December 9, 2007 | Comments (8)
In response to: Matte surfaces
Juan Carlos Michel commented:
Why is it too difficult to print rotogravure designs in matte pet, and why does matte pet have two sides with matte finish? Ive tried printing on Mitsubishi MOTR, and it's too hard.
In response to: Matte surfaces
Eldridge commented:
I would suspect that printing on a matte surface with gravure roll would be difficult because the wetting of the ink to the surface would be more difficult, due to trapped air in the matte surface behind the ink, and this may prevent the suction needed to pull the ink from the cells making the ink transfer more difficult. I.e. it is easier to pull the ink off the matte surface than from the gravure cell. You might be able to lower the surface tension of the ink to make it easier to pull from the cell. As to the double sided matte PET, it is likely that the PET film is a single layer product and not coextruded and that the matte technology is "in" the film as opposed to being "at" the surface as would be the case with a coextruded product which would allow a differential surface. Ask your supplier if the film is coex and if so for a one side matte film.
In response to: Matte surfaces
Nir Dvir commented:
Matte surface can be achieved by PET either through the film itself (matte production) or through a matte coating on a clear film. Using the second method allows you to purchase a film that is topcoated to the right level of matte you wish to achieve but also coated for your right ink/printing-system combination. I could help you finding the right solution. Nir Dvir nir@hanitacoatings.com
In response to: Matte surfaces
Frederick Liu commented:
We are laminating PET film to Nylon fabric using an alipatic PU film adhesive. We get condensed water vapor on the film which degrades our bond. I assume that the moisture is coming from the adhesive film or from the nylon fabric. Ambient dew point is around 0 deg F. Laminating temperature is 375 deg F. Has anyone overcome this problem?