How to Use Pearlescent Pigment in Printing?

Pearlescent pigments are composed of mica flakes coated with metal oxides, which produce a pearl-like luster. These pigments appear as transparent, flat powder particles, characterized by larger diameters, smooth surfaces, and high refractive indices (average effective refractive index of 2.5, with iron series products reaching up to 3.0). They are non-toxic, odorless, acid/alkali-resistant, non-combustible, non-conductive, and arc-resistant, with high heat resistance (up to 900°C) and excellent weather resistance.

I. Primary Applications

With the advancement of pearlescent pigments, their applications have expanded significantly. They are used in:

• Automotive and bicycle coatings
• Decorative architectural coatings
• Pearlescent inks, leather, plastics, cosmetics
• Papermaking, dyeing, printing, handicrafts, rubber, ceramics, and more.

Printing Inks:
Pearlescent pigments are widely used in various printing inks to add elegant pearl luster to paper, cardboard, wallpaper, plastics, and textiles. Available in different particle sizes, they can be selected based on printing methods. Pearlescent pigments may be used alone or combined with transparent pigments/dyes to create diverse high-end packaging and printing products.

II. Main Product Series

1. Silver-White Series:
   • Produced by varying titanium dioxide (TiO₂) types, coating rates, and particle sizes.
   • Larger particles exhibit metallic shimmer, while smaller particles offer silk-like softness.
   • For weather resistance, use rutile-type TiO₂-coated mica.
2. Iridescent Series:
   • Displays rainbow-like colors via light interference.
   • Color shifts with TiO₂ layer thickness, creating distinct reflected/transmitted light effects.
3. Colored Series:
   • Mica coated with TiO₂ and additional transparent pigments, combining pearl luster with vibrant hues.
4. Mica-Iron Series:
   • Mica coated with iron oxide, producing bronze, red-brown, wine-red, purple-red, and red-green interference colors with metallic sheen.
5. Metallic Series:
   • Mica coated with TiO₂ and iron oxide, blending pearl luster with iron oxide’s chromatic effects.

III. Applications in Printing Inks

Pearlescent pigments enhance substrates like paper, plastic films, and textiles with pearl luster. Key considerations:

1. Pigment Selection:
   • Opt for transparent dyes/pigments to maximize pearlescent effects.
   • Avoid opaque additives that scatter light.
2. Gravure Printing Example:
   • Pre-wet pigments with solvent/ink for optimal dispersion.
3. Printing Methods:
   • Adjust parameters for gravure, flexographic, screen, or hot stamping printing:
     • Screen mesh: 100–250目 for larger particles.
     • Gravure line count: 75–100 lines.
   • Post-printing processes (e.g., calendering, embossing) enhance luster.
4. Applications:
   • Packaging containers, gift wraps, book covers, calendars, business cards, wallpapers, textiles, etc.

IV. Common Issues & Solutions

A. Weak Pearlescent Effect

• Causes: Opaque additives, improper pigment dosage, mismatched screen/particle size, poor ink transparency.
• Solutions: Use transparent media, adjust pigment ratio, optimize screen parameters, ensure dispersion.

B. Pinholes/Bubbles

• Causes: Moisture, poor dispersion, dust contamination, incompatible solvents.
• Solutions: Filter ink, replace solvents, improve workshop cleanliness.

C. Vertical Streaks

• Causes: Incorrect viscosity, improper speed/pressure, damaged doctor blade.
• Solutions: Adjust viscosity, recalibrate press settings, replace blades.

V. Usage Precautions

1. Pair with transparent dyes/pigments; avoid opaque pigments.
2. Avoid high-shear mixing to prevent particle damage.
3. Stir settled pigments before use.
4. Do not blend iridescent series (risk of color cancellation).
5. Pre-wet pigments for uniform dispersion.