What type of ink is best for CI flexo presses?

Water-based or solvent-based inks are commonly used for CI (Central Impression) flexographic presses due to their compatibility with high-speed, multi-color printing on flexible packaging films. Water-based inks are ideal for eco-friendly and food-safe applications, while solvent-based inks offer excellent adhesion on untreated plastic films.

When should UV flexo ink be used instead of water-based or solvent-based ink?

UV flexo ink is best suited for label printing and applications requiring high precision, fast curing, and special finishing effects. It is ideal for inline flexo presses where instant drying, fine detail, and value-added processes like cold foil or die-cutting are required.

What type of ink is used in flexography?

Date: Jul 28 2025 From: Star Color Views:

Flexographic printing (Flexographic Printing) has been widely used in the printing of various materials such as food packaging, labels, self-adhesive materials, paper bags, plastic films, and non-woven fabrics due to its advantages of flexibility, high speed, and environmental protection. With increasingly strict environmental regulations and the continuous enrichment of printing substrates, the types of inks used in flexography have also shown a diversified development trend.
Starting from the characteristics of the flexographic printing process, this article will systematically analyze the technical parameters of three mainstream flexographic inks (water-based, solvent-based, and UV inks), and analyze the adaptability of various inks in combination with flexographic equipment types (CI central impression type, stack type, Inline online type, Hybrid type), helping us make the best choices in different application scenarios.

I. Overview of Flexographic Printing Process and Equipment Types

Flexography is an indirect printing method that transfers ink to a flexible printing plate through anilox rollers and then prints it on the surface of the substrate. Its key characteristics are:

Use of flexible plates (mostly resin or rubber)
Low ink viscosity, suitable for high-speed printing
Adaptable to various materials, such as paper, plastic films, aluminum foil, etc.

Common flexographic equipment structures are as follows:

Equipment Type	Structural Characteristics	Application Scenarios
CI Central Impression Type (Satellite Type)	All colors revolve around the central impression cylinder, with high registration accuracy	High-speed printing of flexible packaging, BOPP, PE, PET films
Stack Type	Each color has an independent unit, arranged vertically stacked or linearly	Packaging paper bags, non-woven fabrics, fruit bags, medium and low-speed multi-material printing
Inline Type	Printing units integrated with die-cutting, glazing and other entire lines, arranged in a straight line	Labels, self-adhesives, medical stickers, bill types
Hybrid Type	Integrates multiple printing methods such as water-based and UV	Personalized labels, high-end packaging, functional coatings

II. Analysis of Common Flexographic Ink Types and Technical Parameters

1. Water-Based Flexographic Ink

With water as the main solvent, it is environmentally friendly and safe, widely used in food packaging, daily chemical packaging, paper products, etc.

Technical Parameters	Range/Characteristics
Viscosity (25℃, No.4 cup)	25–45 seconds (adjust according to printing speed)
pH Value	8.0–9.5, requiring dynamic monitoring and adjustment
Drying Method	Hot air, IR drying (high requirements for equipment drying section)
Surface Tension	30–35 dyn/cm, suitable for polar materials
VOC Emission	<5%, environmentally friendly, meeting FDA and REACH standards
Adhesion	Corona treatment or primer needed for non-polar plastic films

Advantages:

Low odor, low migration, suitable for food-grade applications
Safe to operate, no flammable risks
Mainstream in environmental protection trends, suitable for replacing solvent-based inks

Application Range: Paper packaging, non-woven fabrics, food packaging paper, PE coated paper, BOPP films, fast food bags, shopping bags, etc.

2. Solvent-Based Flexographic Ink

With organic solvents such as alcohols and esters as carriers, it volatilizes quickly and has strong adhesion, suitable for non-polar materials and high-speed printing.

Technical Parameters	Range/Characteristics
Viscosity	20–40 seconds, strong fluidity
Drying Speed	Fast, suitable for CI high-speed printing
Adhesion	Excellent, suitable for BOPP, PET, PE and other films
VOC Emission	High (60–80%), requiring exhaust systems
pH Control	Not needed, system stability is high

Advantages:

Strong adhesion, no need for corona or treatment layer
Fast drying speed, suitable for mass high-speed production

Disadvantages:

Safety hazards (flammable and explosive)
High VOC emissions, subject to many environmental regulations

Application Range: Frozen food packaging films, composite bags, condiment films, etc.

3. UV Flexographic Ink

Curing reaction is initiated by ultraviolet irradiation, no volatilization, and instant drying.

Technical Parameters	Range/Characteristics
Viscosity	High (1000–2500 cps), requiring special ink fountain and anilox roller
Drying Method	UV lamp or UV LED, instant curing
Adhesion	Strong, applicable to various coated substrates
Environmental Friendliness	Zero VOC, no solvent volatilization
Storage Stability	High, not affected by pH or ambient temperature

Advantages:

Dries immediately after printing, saving space
High precision, suitable for small characters and fine patterns
Can realize online cold stamping, die-cutting, varnishing and other processes

Disadvantages:

High investment cost (UV lamp, cooling system)
Photoinitiator components need strict control to prevent migration

Application Range: Cosmetic labels, wine labels, pharmaceutical packaging, self-adhesives, metal foil packaging.

III. Adaptability Analysis of Inks and Flexographic Equipment

Flexographic Equipment Type	Recommended Ink Type	Typical Applications
CI Central Impression Type (Satellite Type)	Water-based / solvent-based flexographic ink	Plastic film packaging, food bags, composite films
Stack Type Flexographic Press	Water-based flexographic ink	Paper bags, non-woven packaging, toilet paper bags
Inline Online Flexographic Press	UV flexographic ink	Labels, self-adhesives, e-commerce barcodes, drug stickers
Hybrid Type Flexographic Press	Combination of water-based and UV inks	High-end packaging, functional films, metallized labels

Selection Suggestions:

For paper substrates → Prefer water-based inks
For non-polar film substrates → If corona treatment is perfect, water-based inks can be used; otherwise, choose solvent-based or UV inks
For online processes and fine patterns → Prefer UV inks with Inline or Hybrid equipment
Focus on food safety and environmental certifications → First choose low-migration water-based inks, combined with CI equipment and hot air drying systems

IV. Comprehensive Comparison Table of Three Types of Inks

Attribute	Water-Based Flexo Ink	Solvent-Based Flexo Ink	UV Flexo Ink
Environmental Friendliness	★★★★★ (Low VOC)	★★ (High VOC)	★★★★ (Zero VOC, but contains photoinitiators)
Drying Method	Hot air/IR	Volatilization	UV curing
Equipment Requirements	Drying system, pH control	Exhaust system, explosion-proof	UV lamp, cooling system
Adhesion	Medium (needs treatment)	Strong	Very strong
Cost	Medium	Low raw material cost, but high safety cost	Expensive ink, high equipment investment
Adaptability to Printing Speed	Medium to high speed	High speed	Medium to high speed
Application Scenarios	Food packaging, environmental protection paper bags	Composite films, frozen packaging	High-end labels, cosmetic packaging

Conclusion

As one of the main technologies in the field of sustainable packaging, flexographic printing is undergoing an accelerated transformation from solvent-based to water-based and UV inks. The correct selection of the combination of inks and flexographic equipment not only affects printing quality and production efficiency but also relates to brand image and regulatory compliance.