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Silkscreen Printing of Lustre Pigments

COLOR AND LUSTRE EFFECT:

In general the type of lustre achieved is a function of particle size. The smaller particle sizes will impart a sheen or satin appearance. The larger particle sizes will impart glitter. Effects ranging between the extremes are achievable by combining particle sizes to achieve the desired optics. Since each particle operates as a prism (refractive) and some particles are transparent, in addition to the product selection, substrate color can be used to achieve startling visual appearances.

FORMULATIONS:

Any item which interferes with the passage of light through the ink film to the pigment particle will be detrimental to the desired lustre. Accordingly the ink vehicle should be water white. Opacifing agents such as TiO2 and non transparent pigments should be avoided. Transparent dyes and pigments have been used successfully. Other additives should be minimized if possible.

Pigment loading has successfully been run at a maximum 25% based on the binder. Since the particles impart color based on the principle of light refraction as opposed to absorption, they are ideally suited to UV cure and E-beam cure. Materials are compatible with both water and solvent based systems.

INK PREPARATION:

Care must be taken not to break the pigment particles, during ink preparation. Accordingly, Ball Mills, three roll mills, shot mills and bead mills should not be used. Mild agitation using a low shear (impeller) mixer should be used. To insure good wetout of the pigment by this ink vehicle, sufficient time should be allotted between ink preparation and press use to allow for proper binder wetting. Eight hours is considered sufficient. Unlike inks containing conventional metallic pigments, press run inks may be securely closed and reused for an indefinite period of time with no detrimental affect on color or lustre.

SCREEN SIZE:

Consult your screen supplier and our pigment Data Sheets to determine actual screen opening size for various nominal mesh sizes. These figures will vary depending on thickness and type of filament used to construct your screen. Consult your pigment technical data sheet to determine the maximum sized particle. The minimum screen size opening should be at least 1-1/2 times the size of the largest particle, to avoid clogging of the screens.

Screen Mesh/in. Particle Size (Microns) Effect
300 15 Very Fine Lustre
250 30 Fine Lustre
200 50 Lustrous
158 65 Bright
140 80 Sparkle
125 100 Bright Sparkle
110 120 Glimmer