How to use pearlescent ink
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Pearlescent pigments have excellent dispersing power. It is generally necessary to mix with a low viscosity printing ink with a slight agitation. Since the pearlescent ink is a layered structure, the pearlescent pigment can only be slightly stirred when mixed with the ink to avoid breakage of the pearlescent pigment. Avoid rude mechanical agitation and dispersion, for example: using a three-roller, a high-speed mixer, or a ball/bead mill, the pigment will be damaged and lose its luster. In general, pearlescent pigments are uniformly added to the printing ink in the final procedure of ink production. When using a dispersing machine and a high-speed mixer, the mixing time of each batch must be kept constant and shortest, so as to avoid chromatic aberration in each batch of products. In the case of manufacturing high-viscosity printing inks, if the offset printing has to use a three-roller, the gap between the rollers must be as large as possible, and the stirring should be completed in the shortest possible time to avoid the loss of gloss due to the breakage of the pigment.
Note: Transparent binders must be used as much as possible to avoid the use of opaque and light-scattering additives.
Pearlescent pigments help to create a colorful visual experience due to the transparency of light and the light scattering properties. For some special requirements, the color tone can be copied as long as it is formulated according to the recipe parameters.
The pearlescent pigments currently on the market generally consist of mica-titanium dioxide and/or iron oxide. It is non-toxic, chemically stable and environmentally friendly, and can be used for food packaging and meets national standards. Note: Simply emphasize the removal of excess ink, the cleaning of the plate or ink delivery system, the recycling of printed matter and the removal of accumulated printed waste.
The application and role of pearlescent pigments in various printing fields:
Pearlescent pigments for screen printing
Through my understanding of screen printing, I feel that pearlescent pigments are still the most suitable for screen printing. It can choose mesh screens with suitable mesh sizes for pearlescent pigments of different sizes. The mesh should be 1.5 to the maximum particle size of the pigment. 2.5 times. Depending on the printing work, screen type pearlescent pigments, substrates, and ink binders must be used for matching.
1. How to use pearlescent pigments in printing inks
Pearlescent pigments can be applied to all screen ink systems, but are best used only with clear ink binders. The well-dispersed transparent colorant can improve the coloring effect in an amount not exceeding 3% of the finished ink.
In order to better mix the pigment with the ink, it is preferred to pre-wet the powdered pigment with the ink solvent. For example, a diluent. Then mixed into the ink to improve the dispersibility of the pigment. Avoid ink dust and ink viscosity changes.
2. pearlescent pigment in the printing process
Before using the pearlescent pigmentary screen ink for ink printing, the most suitable screen material should be selected. Basically, various pearlescent pigments can be used for screen printing. When the pearlescent pigment particles are less than 15, 400 mesh/inch can be used. Number; the number of the screen between 5-25 can be up to 355 mesh / inch, that is, 140; when the particle is between 10 and 60, the screen number can be 156 mesh / inch, that is, 61; particles to 200 The screen number can be up to 54 mesh/inch, which is No. 21.
In screen printing, ink drying parameters need to be strictly controlled due to the relatively thick layer on the substrate. Since the special form of the pearlescent pigment causes the solvent attached to the surface thereof to have a large viscosity, the drying conditions need to be adjusted to extend the drying time; or the drying (curing) temperature is slightly increased to achieve a particularly required curing strength. For example, when using pearlescent pigments in color wet/wet printing, use inter-stack drying to avoid printing the printed color onto the back plates. Pearlescent pigments have so far been used as spot colors after color printing. Or used in some other industries.
Pearlescent pigments and substrates
In screen printing, pearlescent pigments are available in many directions, but are most commonly used on textiles.
Screen printing of textiles today mostly uses water-based inks. Pearlescent pigments are excellent in water resistance, alcohol resistance, heat curing, solvent resistance, water wash resistance, anti-sweat, chemical dry cleaning and other characteristics, especially suitable for this application. Secondly, pearlescent pigments can be used in paper, paperboard, plastic film, etc. to obtain satisfactory results.
Pearlescent pigments and post-press processing
Post-press processing of products screen printed with pearlescent pigments does not adversely affect the pearlescent effect.
Post-press processing such as cold, heat sealing, and compounding can be processed as usual.
Generally, the pearlescent pigment has good scratch resistance, insulation, and acid and alkali resistance. The effect of pearlescent pigment printing can be significantly increased by calendering, just as it is applied to the gloss printing cloth obtained by textile printing. Due to the excellent chemical resistance of pearlescent pigments, other methods can be used, such as water washing, stone washing or alkaline burning of denim. Another interesting method known in the textile industry is the burnt flower. Due to the chemical resistance of the pearlescent pigment, the pattern printed on the fabric is retained by the acidic reaction to form a unique printing effect.
Selection of pearlescent pigments
The use of iridescent interference color can achieve the effect of being beautiful and anti-counterfeiting.
Pearlescent pigments with different particle sizes; if large-grain pearlescent pigments are used, it is best to use small-grain pigments at the same time, so that the glittering luster can be obtained without passing through the bottom; when used together, the ratio is about large particle pigments; Particulate pigment = 1:3 or 1:4.
Note: When mixing iridescent interference pearlescent pigments with different particles, only the series of glossy varieties, such as Ir, can be used. 249 with Ir. 201, etc., otherwise it will lose the interference color pearl effect.
Pearlescent pigments can exhibit richer color when mixed with different color inks.
Screen selection
Single-filament screen is more suitable for pearl printing, because it is not easy to block the net; use the screen with thickness T; choose the appropriate mesh size to avoid blocking the net; usually the mesh size should be the maximum pigment size of 1.5~ 2.5 times. Below we give the corresponding screen selection according to the Iriodin pearlescent pigment of Merck in Germany.
Selection requirements for connecting materials
As colorless and transparent as possible, otherwise it will lose the luster of pearl; it has good wettability and bonding with the substrate; it has good bonding with pearlescent pigment; it has good abrasion resistance.
Preparation of ink
According to different printing materials and gloss requirements, the pearlescent pigment concentration is between 8~15%:
First, pre-wetting: very critical, related to the dispersion of pearl powder and test performance, must be strictly in accordance with the following procedures:
1. Prepare a suitable solvent
2. Measure the solvent which accounts for about 30% of the weight of the pearl powder, add it into the pearl powder, and stir slowly. The process is: there is no effect when the city is stirred, the stirring resistance is gradually increased, and the pearl powder is formed into small balls. The color becomes darker; continue to stir, the small ball breaks into smaller particles, and the stirring resistance is obviously reduced, and the stirring becomes easy; finally, the pearl powder becomes a granular mixture of uniform size, and the color is dark and the pearl powder is stirred. Allow to stand for 20~30 minutes; mix the above mixture with the binder and mix well. Note: Avoid using a large-shear dispersing device such as a three-roll mill. For dry adjustment, it is necessary to select a suitable drying temperature depending on the thickness of the ink layer and the printing speed.
Pearlescent pigments for flexographic printing
Flexographic inks are classified into low viscosity liquids. Available in solvent, water and photocuring (UV). Pearlescent pigments can be used for all three inks. However, you should choose a highly transparent binder to configure the ink to avoid loss of pearlescent effect.
When the color ink is disposed, only the dispersibility is good, and the transparent color material can be mixed with the pearl pigment, and generally does not exceed 20% of the weight of the pearl pigment. Too much hue will affect the pearl effect. Because pearlescent pigments have unique optical interference functions only in the well-lit ink layer, and excessive colored pigments cause a large amount of light to be scattered and lost.
Pre-wetting: In order to optimize the pearlescent pigment in the ink, it is recommended to pre-wet the pigment with an ink solvent (such as water, alcohol, and diluent) equivalent to 30% by weight, and then mix the ink. This procedure avoids the occurrence of floating dust and viscosity changes of the finished ink when the ink is manufactured, so that the pearlescent pigment and the ink are optimally mixed.
The content (weight ratio) of the pearlescent pigment is about 15 to 25% of the finished ink.
The ink needs to be thoroughly and carefully stirred before printing to evenly disperse the pigment in the ink without flocculation or precipitation. In long-run printing, use a recirculating ink supply as much as possible to avoid sedimentation.
Suitable ink auxiliaries are generally used to avoid foaming and to prevent pigment precipitation.
If you need to add color toning, it should be based on the naked eye.
Prior to printing, the viscosity of the ink needs to be adjusted based on the substrate, printing speed, and drying conditions. Usually in water-based inks, for smooth paper or plastic film, the suitable viscosity is 40~60 seconds (DIN4 viscosity cup 23 degrees), for coarse kraft paperboard, corrugated cardboard or gray cardboard, low Viscosity inks, such as 25 to 35 seconds (DIN 4 viscosity cup 23 degrees).
It is very important to choose the right photosensitive resin sheet. For pearl printing, I recommend the following varieties: Soli's HOF, PLB, PLS, POF and UVB, BASF's "Nyloflex" FA, FAH and FAR.
There are many types of anilox rolls used in flexographic printing, such as conventional steel anilox rolls and laser-engraved ceramic anilox rolls. The choice of the anilox roll is determined by the substrate and the desired thickness of the ink layer. Tests have shown that laser-engraved porcelain rolls work best in pearlescent pigment flexographic printing, especially for aqueous inks. The technical parameters of flexographic printing must be coordinated with the particle size of the pearlescent pigment.
The particle size matching relationship between the anilox roller and the pigment.
The printing effect depends on how much ink is delivered to the substrate. The thick ink layer results in a noticeable gloss effect. Therefore, it is recommended that the solvent based ink use an anilox roller of ink orifices as deep as 50. The best printing results can be obtained by adjusting the printing speed. Preferably, the ink can be temporarily cast after transfer to the substrate to maintain optimal alignment of the pigment with the surface of the substrate.
About the substrate
There are many types of substrates that can be used, including corrugated cardboard, white cardboard, label paper, light and heavy paper, paper towels, kraft paper, and plastic film. The choice of substrate has a great influence on the printing effect. A substrate with a smooth, flat surface achieves the best pearlescent effect.
Postpress processing
Pearlescent pigments have no adverse effects on the finishing of flexographic printing products.
The postpress process can be handled as usual. Cold, heat sealing, embossing, glazing, and film coating can be carried out without special adjustment. Twilight and embossing may increase the pearlescent effect because they have a better pigment arrangement.
There are also pearlescent pigments that are scratch-resistant, insulating, and acid and alkali resistant.
Pearlescent ink for gravure printing
Low viscosity liquid inks are mainly used in gravure printing. Pearlescent pigments can be used for solvent-based or water-based inks, but a more transparent binder should be chosen to avoid loss of pearlescent effect.
In the preparation of color inks, only the dispersibility is good, and the transparent colorant can be mixed with the pearlescent pigment generally not more than 20% by weight of the pearlescent pigment. Too much hue will affect the pearl effect. . Because pearlescent pigments can only have special optical interference functions in a well-lit ink layer. Excessive other colored pigments cause a large amount of light to scatter and lose.
Pre-wetting: We performed nano-scale microscopic observation on the surface of pearlescent pigments, and we found that there are many extremely fine capillary structures distributed. This results in a relatively large surface energy. In order to achieve the best performance of the pearlescent pigment in the ink, it is recommended to pre-wet the pigment with an ink solvent (such as water, alcohol, and diluent) equivalent to 30% by weight, and then mix the ink. This procedure avoids the occurrence of floating dust and viscosity changes of the finished ink when the ink is manufactured, so that the pearlescent pigment and the ink are optimally mixed.
The content (weight) of pearlescent pigment is about 15~30% of the finished ink.
The ink needs to be thoroughly and carefully stirred before printing to evenly disperse the pigment in the ink without flocculation or precipitation. In the long printing process, try to use a recirculating ink supply to avoid sedimentation.
It is recommended to use suitable ink additives to avoid foaming and to prevent pigment precipitation.
If you need to add color toning, it should be based on the naked eye.
The viscosity of the ink needs to be adjusted according to the substrate, printing speed and drying conditions before printing. The usual viscosity for solvent-based inks is 14 to 25 seconds (DIN 4 viscosity cup 23 degrees), which is higher for water-based inks (such as decorative paper inks) until 40 seconds (DIN4 viscosity cup 23 shots) Degree)
Pearlescent pigments in gravure printing
Pearlescent pigments can be used on both corroded and engraved plates. Tests have shown that the use of a roller-type printing plate with an ink-receiving opening angle of about 120 degrees is the best. When the pigment has a large particle size (average particle size is greater than 25), it is recommended to use an etching roller, which allows a large amount of ink to pass through it, and actively supports the pearlescent effect of pearlescent pigment printing.
The parameters of the plate cylinder need to match the particle size of the pigment. It is recommended to prepare the plate cylinder with reference to the data in the table.
In addition, ordinary solvent-based inks are suitable for plate rolls with a cell opening angle of 120 degrees, and water-type inks are suitable for plate rolls with a 140 degree opening angle.
For corrosive plates, the mesh wall ratio is preferably 10:1 or higher and not lower than 6:1.
The printing effect is determined by how much ink is delivered to the substrate. The thickness of the ink layer results in a more pronounced pearlescent effect. Therefore, it is recommended that the solvent type ink use an ink hole having a depth of about 50.
The best printing results can be obtained by adjusting the printing speed. It is preferred to have a short casting process after the ink has been transferred to the paper to maintain an optimal parallel alignment of the pearlescent pigment with the surface of the substrate.
Pearlescent pigments and substrates and post-press processing
There are many substrates to choose from, from PVC in the wallpaper industry to coated paper, cardboard or heavy paper, kraft paper, paper towels, plastic film, fabrics, etc. in the packaging and labeling industry.
The choice of substrate has a great influence on the printing effect. A substrate with a smooth, flat surface gives the best pearlescent effect.
Pearlescent pigments used in offset printing
Pearlescent pigment in printing ink
Ordinary offset inks are high viscosity inks that make it difficult to disperse coarsely divided pearlescent pigments. Therefore, it is best to use specially developed pearlescent offset inks. Pearlescent ink viscosity should be slightly lower than traditional offset inks.
For pearl offset printing, it is necessary to adjust the viscosity of the ink according to the printing conditions and the substrate using a debonding agent or a thickener. To obtain the best printing effect, 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 supplied. 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 screen lines. Tests have shown that pearlite pigments with particles in the range of 5 to 25 can be used for screening in the field and 60 lines/cm. The denser mesh number may reduce the pearlescent effect.
Before the official printing begins, the ink supply system of the printing press must be fully inked, and the original printed sheet should be over-inked. The initial amount of pearl ink should be 3 to 4 times that of ordinary four-color ink. Note that the initial ink supply should meet the above requirements before official printing. (You can take more printing papers).
Once the desired pearlescent effect is achieved, the operator should gradually reduce the thickness of the ink to achieve a perfect pearlescent print.
All packaging materials and labels can be printed with pearlescent offset printing inks. The surface of the substrate should be as smooth and flat as possible to better align the pigment orientation. This is extremely important for achieving the desired pearlescent effect because the ink layer in the offset is relatively thin.
Pearlescent pigment offset inks have no adverse effects on postpress processing. Multi-color overprinting or glazing, cold, heat sealing, laminating, and embossing can be processed as usual.
Pearlescent pigments have good rub resistance, insulation and acid and alkali resistance.
Glazing process
Pearlescent pigment for glazing process
Pearlescent pigments can be dispersed in water or UV-type varnishes for use in glazing processes, typically on offset glazing units and separate off-line coating machines. The advantages are:
Can express ideas on different substrates
Rich in light color performance
Both decorative and anti-scratch functional functions
The safety of pearlescent pigments makes them suitable for food packaging
Can be recycled, more environmentally friendly
Since pearlescent pigments are translucent, they can be applied to a variety of background colors, providing more possibilities for novel color creation.
The opacity of pearlescent pigments with different particle sizes is different, and users should choose different combinations of substrate design. Finer-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 image.
Pearlescent pigment in varnish
Basic formula: <=30% pearlescent pigment
>=70% ordinary high transparency water or UV type varnish
Pre-wetting: In order to achieve the best effect of pearlescent pigments in use, it is recommended to pre-wet the pigment with a diluent (such as water, alcohol, etc.) equivalent to 30% of its weight, and then mix it with the varnish. This procedure avoids the change of viscosity of the floating dust and the finished varnish during operation, so that the pearlescent pigment and the varnish are optimally mixed. Another way is to pre-wet the pigment with a varnish.
Please pay attention to the acidity and alkalinity in the system when using water-based varnish. If the surface of the pigment is slightly acidic, please adjust it with a suitable alkaline additive.
Pay attention to the uniformity and thoroughness of the mixing when mixing the pigment with the varnish. It is preferred to add the pigment in portions so that the dispersion is more uniform. Avoid using large shearing dispersing equipment that would otherwise destroy the pigment. A suitable antifoaming agent can be added to remove the bubbles generated by the agitation.
Appendix:
The following data are some of the types and data of some of the famous Merck Group pearlescent pigments.
IriodinÒ Pearlets is a pigment pre-formulation developed by Merck for liquid inks (flexographic, gravure and glazing), processed from traditional powdered Iriodin pearlescent pigments.
Compared to traditional dry powdered pearlescent pigments, IriodinÒ Pearlets pearl balls have the following advantages:
§ Easy to operate, no dust
§ Accurate metering control and reduced waste
§ Excellent dispersibility in ink without wetting
§ The shortest ink time
§ Reduce precipitation and facilitate ink reuse
§ Better pearl gloss effect
The following abbreviations in the pigment model indicate the ink system for which the Pearlets are suitable:
W water-based ink system
S Solvent-based ink system
UV UV curing ink system
Iriodin® 100 Silver White Pearl Series---Pearl Light
Provides a flawless bright white pearly luster. It can be used alone or in combination with traditional pigments. According to the difference in the particle size of the pearl, it is possible to simulate the gloss which is felt by the silky texture.
Iriodin® 200 Symphony Pearl Series - Light Color
Symphony pearlescent pigments have created a new world of design. Through the cooperation with traditional pigments, the psychedelic effect of the illusion can be obtained from different observation angles.
Iriodin® 300 Golden Pearl Series - Exquisite Golden Light
The Iriodin® gold pearlescent series has a metallic sheen effect, but it is not a metallic pigment. It coats titanium dioxide and iron oxide on a mica substrate to produce a natural gold color.
Iriodin® 500 --- Future metallic luster
The Iriodin® metal pearlescent series is not a metallic pigment. However, the effect of this series can simulate the luster of metallic pigments. This is achieved by coating iron oxide on mica
The Pearlprint Litho range is a pigment pre-formulation developed specifically for offset printing. It is based on conventional Iriodin pigments and has been specially treated on the surface of pigment particles to achieve the following performance optimizations:
1.Easy to disperse in the ink;
2.Good transferability in printing operations;
3.Will not dust, easy to prepare ink
Pearlescent offset inks using the Pearlprint Litho range of pigments have good printability and better gloss.
The collection includes silver white, five iridescent interference colors, two pearlescent gold and pearl bronze.