It can be used in various printing systems as intaglio printing, offset printing, screen pritning, surface printing and etc. Such can make packing cards, name cards, decoration, wallpaper, yew paper, greeting cards, tobacco and wine packaging, etc.
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1. Paper printing techniques are primarily divided into 4 types. All of them have their own sets of advantages. They are:
I. Surface Printing —In surface printing, impregnated metal rollers with a rubber pattern are used. These are mounted on a single machine. Add the pearl powder to the ink and ink is applied to the surface roller. The pearl pigments ink lays in the rubber pattern or hills sitting above the surface of the roller, then ink is pressed on to the paper by the roller.
II. Gravure Printing —Individual roller is used for printing a single color. Large, full-size gravure-printing machines can hold as much as 12 cylinders, capable of creating the whole pattern. The paper roll under application moves to one copper cylinder. Thereafter, a back roller picks the pearlescent pigments and pushes it against an engraved roller. A steel doctor blade pushes against the engraved cylinder, assisting in forcing pearl pigment of ink into the etched detail. For enabling the wallpaper to pick up the pearlescent pigment ink in the valleys, a rubber roller is used. It presses the paper against the cylinder. In the last step, rollers carry the paper away from the cylinder and put it into a dryer.
III. Silk Screen Printing — A pattern to be imprinted on a wallpaper using silk screen printing requires an individual stencil for each color present in the pattern. Stencils of different colors are used from silk mesh screen using a photographic process. First, a photographic negative is made according to the pattern to be imprinted.
This is followed by attachment of a silk screen stretched over a magnesium or wooden frame. The screen is then coated with a light-sensitive emulsion or ink with the effect powder, followed by placing the photographic negative on top of the screen. When the bright light falls on the screen, the emulsion hardens in regions not covered by the photographic negative. It results in the formation of a stencil. In order to better mix the effect pigment with the ink, it is preferred to pre-wet the powdered pearl pigment with the ink solvent. For example, a diluent, then mixed into the pearl pigment ink to improve the dispersibility of the pearl pigment. Avoid ink dust and ink viscosity changes.
Each screen is placed carefully with a block, guides, etc. This ensures that the pattern is aligned in a regular fashion all over the wallpaper without any breaks or interruptions. Though there is an endless number of colors that can be used in silk screen printing, high costs limit paper suppliers and manufacturers to use only a few colors.
IV. Rotary Printing — Rotary printing combines mechanics of gravure painting with the precision of photographically produced stencils. It starts with wrapping mesh stencils around hollow tubes mounted within a machine. For imparting color, the ink with pearl pigments flows continuously through film-wrapped tubes onto the paper. This technique is preferred for its speed, which is about 80 yards of paper per minute.
2.1)Before printing with pearl pigment screen ink, the most suitable screen material should be selected.Basically, various particles of pearl pigment can be used for screen printing.
①Use 400 mesh/inch when the bead size is less than 15 mesh/inch effect pigment.
② Mesh size up to 355 mesh/inch for particles of effect pigment between 5-25;
③ When the particles of effect pigment are between 10 and 60, the screen size can be up to 156 mesh/inch;
④ Up to 200 mesh size of effect pigments are up to 54 mesh/inch.
2)The particle size of pearlescent powder also has a great relationship with the engraving depth of printing mesh roll. If the engraving depth is not enough, the pearlescent powder is difficult to transfer to the paper base, and will only transfer the ink, leaving the pearlescent powder in the mesh roll and ink tank, can not achieve the ideal pearlescent effect.
3)Screen printing:Pearlescent pigment ink should be depending on the size of pearlescent pigment choose screen, to ensure its printing suitability, generally screen mesh size than the largest pearlescent pigment particle size of one times, is conducive to the transfer of ink.
4)In order to make pearl pigment and ink better mix, it is best to powder pearl pigment with ink solvent pre-wetting.Such as diluents, then mixed with ink to improve the dispersion of pearl pigment.Avoid floating ink and ink viscosity changes.
5)In gravure printing, the pearlescent pigment ink of the silver-white column must be matched with a color with a higher hue purity to obtain a sufficient payment effect and avoid the loss of the pearlescent effect. The visual effect of pearlescence on the lighter base ink is relatively poor, especially the use of white-colored colors. In comparison, the silver-white series pearl pigment is more effective on darker inks.
Chameleon series pearlescent pigment inks are best to choose a light background color. The darker the color, the only the reflected light can be seen and the two-color effect cannot be observed. If you need to use a chameleon pearl pigment on a dark base, it is best to have the same hue and high transparency. The pearl pigment of interference color of two different hues cannot be mixed, which will reduce the effect of two colors.
3.Advantage :
① Special paper has white and smooth surface, thick and consistent, compact texture, no powder and hair, and uniform ink absorption, small elastic function, toughness, folding not easy to fracture and other functions.
② There are many kinds of special paper, most of them have good absorbability and strong penetration.
③ Special types of paper will be very different due to the different printing technology, and will play a special role in different situations, and the scope of application is more extensive.