Polyvinyl chloride film local isometric heat treatment for hidden 3D printing on polymer packaging

Abstract

A method of 3D embossed printing is proposed where both point and line images can be printed on rigid polyvinyl chloride (PVC) shrink films without any consumables, such as paints, primers, dampening solutions, or washes. Embossed lettering and symbols on packaging are intended for people with poor vision, but capable of tactile marking recognition and reading Braille. This 3D printing is based on reversible deformation and stress relaxation in anisotropic glassy polymers by local isometric heat treatment of thermoplastic films under pressure. Films can be protected from counterfeiting by hidden markings due to time separation of information recording onto the film and displaying this information for visual or tactile reading. The results quantify the rate of internal stress relaxation in PVC shrink films at various stages of 3D printing, including tactile sign formation conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43046.

Macro‐mechanism of polyvinyl chloride shrink sleeves embossed marking

“…9 Moreover, heating mechanically unconstrained film for the relief to appear resulted in warped and unsightly embossed imprint. To maintain planarity of prints or their cylindrical shape, corresponding to the shape of the packaging, which is particularly important for labels, heat shrinking is proposed to be carried out directly on the product or the rigid material substrate.…”

“…Previous studies showed that shrinking of PVC glassy polymer films, heated to glass transition temperature and 20-30 8C above the glass transition temperature, leads to a two-stage compressive stresses increase. 10 The first stress rise is due to shrinkage and stress relaxation during cooling of stressed films in manufacturing. The second stage is a result of stressed films cooling under isometric conditions.…”

“…In a pilot study, optimal modes of tactile films marking with different thicknesses and anisotropy of internal stress and shrinkage were established. 9 However, the mechanisms of the relief formation during films shrinkage and the cause of the one-sided relief direction toward the heat source during local thermomechanical polymer treatment remain unclear.…”

“…The ratio of the stresses arising in the label in two successive stages is 3:1, and their total level can reach significant 2-3 MPa values. 10 Stress relaxation and contraction in so-called interval polymer films 9 has a number of characteristics, allowing using their production technology as one of the new methods for relief marking and 3D printing. Interval materials with controlled structure and stress heterogeneity can be obtained by local heat treatment of fixed shrink films.…”

“…Series of tests were conducted using the samples placed on the rods with different gap values of 2,3,4,5,6,7,10,12,15,20,25,30, and 35 mm. Samples installed on the test bed were heated by hot air up to 100 8C for 400-500 s with an average heating rate of 0.15 8C/s to shrink the gap and for the relief to emerge.…”