Pearlescent ink use (3)

Pearlescent pigments in gravure printing

Pearlescent pigments can be used for both corroded and engraved plates. Tests have shown that roller type printing plates using a de-tapered ink injecting hole with an ink opening angle of about 120 degrees have the best effect. When the pigment particle size is large (average particle size is greater than 25), it is recommended to use an etching roller, because its special hole allows a lot of ink to pass through, and gives active support to the pearlescent effect of pearlescent pigment printing.

The parameters of the plate cylinder must match with the pigment particle size. It is recommended to prepare the plate cylinder with reference to the data in the table.

In addition, common solvent-based inks are suitable for printing rollers with an opening angle of 120 degrees in the cell, and water-based inks are suitable for printing rollers with an opening angle of 140 degrees.

For corrosion-type printing plates, the wall-to-wall ratio is preferably 10:1 or higher and not lower than 6:1.

The printing effect depends on how much the ink is delivered to the substrate. The thickness of the ink layer leads to a more pronounced pearlescent effect. It is therefore recommended that solvent inks use approximately 50 ink holes deep.

The best printing effect can be obtained by adjusting the printing speed. It is desirable to have a brief casting process after transfer of the ink to the paper, which has kept the pearlescent pigments in optimal parallel alignment with the surface of the substrate.

Pearlescent pigments and substrates and postpress

There are many types of substrates that can be used, from PVC in the wallpaper industry to coated paper, cardboard or heavy paper in the packaging and labeling industry, kraft paperboard, paper towels, plastic films, and fabrics.

The choice of substrate has a great influence on the printing effect. The substrate with a smooth, flat surface has the best pearlescent effect.

Pearlescent pigments used in offset printing

Pearlescent pigments in printing inks

The ordinary offset ink is a high viscosity ink, which makes it difficult to disperse the coarse pearlescent pigments. Therefore, it is best to use a specially developed pearl offset ink. Relative to traditional offset inks, the viscosity of pearlescent ink should be slightly lower.

For pearl offset printing, the viscosity of the ink needs to be adjusted according to the printing conditions and the substrate using a release agent or a thickener. To obtain the best printing effect, a special printing rubber skin must be used. Due to the structure of the pearlescent pigment offset printing ink. It is necessary to increase the amount of ink supply. It is also possible to print a continuously adjusted pearlescent effect by screening, but it is important that the pigment particles match the number of screens. Tests have shown that pearlescent pigments with particles between 5 and 25 can be used for screening in the field and 60 lines/cm, and denser screen lines may reduce the pearlescent effect.

Before formal printing begins, the ink supply system of the press must be fully inked. The initial prints should be over-inked. The initial pearl ink supply should be 3 to 4 times that of the normal four-color ink. Note that the initial ink supply should meet the above requirements before the official printing. (You can take more prints than printing paper).

Once the desired pearlescent effect is achieved, the operator should gradually reduce the thickness of the ink in order to achieve a perfect pearlescent printing effect.

All packaging materials and labels can be printed with pearlescent pigment offset inks. The surface of the substrate should be as smooth and flat as possible so that the alignment of the pigments is better. This is extremely important for obtaining the desired pearlescent effect because the ink layer in the offset printing is relatively thin.

Pearlescent pigment offset inks have no adverse effect on post-press processing. Multi-color overprinting or coating, cold, heat sealing, laminating, embossing can be conventionally processed.

Pearlescent pigments have good resistance to rubbing, insulation and acid and alkaline resistance.

Glazing process

Pearlescent pigments for glazing

Pearlescent pigments can be used in glazing processes dispersed in either water or UV varnish. This process is usually performed on an offset glazing unit and a separate off-line coater. Its advantages are:

It can express creative ideas on different substrates. It has rich light-color effects. It has both decorative and anti-scratch functional properties. The safety of pearlescent pigments makes it suitable for food packaging that can be recycled and reused. Pearlescent pigments are semi-transparent, so they can be covered in a variety of background colors to provide more creative ideas for color.

The hiding power of different particle size pearlescent pigments is different, and the user should choose different combinations of substrate design. Fine-grained pigments can express soft and delicate luster like silk satin, but their hiding power is also strong, and it is easy to change the color of the first printed script and it needs attention.

Pearlescent pigments in varnish

Basic formula: <= 30% pearlescent pigment >= 70% ordinary high transparency water or UV top varnish

Pre-wetting: In order to achieve the best effect of pearlescent pigments in use, it is recommended to pre-wet the pigments with a diluent equivalent to 30% of their weight (eg water, alcohol, etc.), and then mix them with a varnish. This procedure avoids the appearance of floating dust and the viscosity change of the finished varnish during operation, so that the pearlescent pigments can be optimally mixed with varnish. Another way is to use the varnish to pre-wet the pigment.

When using waterborne varnish, pay attention to the acidity and alkalinity of the system. If the surface of the pigment is slightly acidic, adjust it with an appropriate alkaline additive.

When mixing the pigment with the varnish, be careful of the mixing evenly and thoroughly. It is best to add the pigment batchwise so that the dispersion is more uniform. Avoid dispersing equipment that uses large shear forces or it will damage the pigment. A suitable defoamer can be added to remove bubbles from the agitation.

appendix:

The following data are some of the famous types of pearlescent pigments and data of the Merck Group.

IriodinÃ’ Pearlets Pearl Ball is a newly developed pigment preparation developed by Merck for liquid inks (flexographic printing, gravure printing and glossing). It is processed from traditional powdered Iriodin pearlescent pigments.

Compared with traditional dry powder pearlescent pigments, Iriodin Pearlets has the following advantages:

§ Easy to operate, dust-free § Accurate metering control, reduced waste § Excellent dispersibility in ink, no wetting § Shortest ink dispensing time § Reduced settling, easy reuse of ink § Better pearl luster effect