The Basics
Every ink is built from four raw materials:
- Pigment (or dye) — provides the colour
- Resin — disperses the pigment and provides adhesion to the substrate
- Solvent — thins the ink and controls drying rate and viscosity
- Additives — impart special properties
Pigments are coloured particles that stay undissolved in the vehicle (dyes dissolve). How much pigment is used, which vehicle carries it, and how well it's dispersed together decide the ink's hue, strength, and — crucially — its transparency or opacity.
The Landscape
Printing inks fall into three broad groups:
- Liquid ink — solvent- or water-based gravure and flexographic inks
- Paste ink — offset (sheetfed, heatset, coldset), screen printing, metal decoration
- Energy-curing (UV) inks — flexo, offset and screen
For solvent-based packaging ink specifically, the print is done one of two ways: reverse printing or surface printing.
Which Side of the Film
Reverse printing — ink is applied to a transparent film (polyester, BOPP, nylon, PVdC-coated films) and then laminated to another film, so the ink ends up sandwiched between layers. Used for snacks, biscuits, wheat flour, detergent powder, soap and shampoo packs.
Surface printing — ink is applied to the top surface of the substrate (natural or white LDPE, pearlised BOPP, metallised polyester/BOPP, aluminium foil, CPP, paper and board). Because it's exposed, the ink needs good gloss, rub, crinkle and scratch resistance. Used for milk, butter, oil, ghee, cold drinks and detergent powder packs.
Intaglio
Gravure transfers ink directly from cylinder to substrate. The image is etched into the surface of a metal cylinder as tiny wells; excess ink is scraped off the surface by a stainless-steel doctor blade; and as the substrate passes between the engraved cylinder and the impression roller, ink lifts from the wells onto the substrate, then dries at 50–90°C.
Relief
In flexo, ink is applied to the substrate via a compressible plate. The amount of ink is metered by an anilox roller, fed from an ink tank through a pumping and filtration system, with a chambered doctor blade controlling the film. It's the workhorse process for flexible packaging.
Resin Selection
The resin system is chosen around the substrate, whether the job is laminated, and which print method is used. A representative slice:
|
Resin System |
Market Term |
Printing |
Laminated |
Substrate |
|
Vinyl/EVA |
Vinyl |
Reverse |
Yes |
Polyester |
|
Vinyl/PU |
PU |
Reverse |
Yes |
Polyester, BOPP, Nylon |
|
Polyamide/Ketonic |
Polyamide |
Surface |
No |
LDPE, BOPP |
|
Polyamide/Epoxy |
2-pack ink |
Surface |
No |
LDPE |
|
NC/Polyamide |
Label wrap |
Surface |
No |
Pearlised BOPP, BOPP |
|
NC/Acrylic |
Shrink wrap |
Reverse |
No |
PVC |
|
NC/MF |
Paper & foil ink |
Surface |
No |
Paper, aluminium foil |
|
EVA / CPP blend |
PP extrusion ink |
Reverse |
Yes |
BOPP |
|
NC/PU |
Lamination & surface |
Reverse / surface |
Yes / No |
Polyester, BOPP |
|
Polyamide/Phenolic |
Deep-freeze ink |
Surface |
No |
LDPE |
For Lamination
- Polyurethane (PU) — excellent printability and resolubility, very good adhesion on most substrates, runs well at high speed, very good lamination bond strength, extremely low solvent retention, and suitable for boil and retort applications.
- Vinyl — for polyester film (BOPP with an additive); very good printability and resolubility, very low solvent retention, but lower bond strength than PU.
- NC-Acrylic — for shrinkable PVC and PET films; excellent shrink properties; non-laminating; used for labels on beer, juice, mineral water, detergents and shampoos.
- BOPP extrusion ink — for BOPP followed by PP extrusion with woven fabric; for rice, wheat, fertiliser and pet-food bags where the laminate needs high strength.
Exposed Ink
- General-purpose (PA-ketonic) — for treated PE, CPP, BOPP or metallised films where heat resistance isn't needed; carry bags, toffee and gift wrappers.
- Oil & fat resistant (PA-epoxy, 2-pack) — for oil packaging, usually with a two-pack overprint varnish.
- De-freeze (NC-polyamide) — for pearlised BOPP, BOPP, CPP and LDPE films used in frozen packs.
- Heat resistant (NC-MF) — toluene- and MEK-free, for paper and aluminium foil.
- Common surface + reverse (NC-PU) — toluene- and MEK-free; used directly for reverse printing, or with a slip additive for surface printing; excellent bond strength and heat/scuff/crinkle resistance.
The Portfolio
Following the integration of the Heubach and Clariant pigment ranges, Sudarshan's ink portfolio now spans several brands:
|
Brand |
Position |
|
Sudaperm |
High-performance pigments — excellent light/weather fastness, high heat stability |
|
Sudafast |
Versatile performance pigments — strength and fastness at good value |
|
Sudacolor |
Traditional colours for lower-end applications; a major ink range |
|
Hostaperm |
Premium organic pigments — excellent weather and light fastness for high-end use |
|
Novaperm |
Organic pigments with above-average fastness |
|
Permanent |
High tinctorial strength with moderate-to-good all-round fastness |
|
Heuco |
High-quality organic pigments for printing ink |
Within each CI pigment number (PY 12/13/14/17/83/180, PO 13, PR 53:1/48:1/48:2/48:3/57:1/146/122, PB 15:3/15:4, PV 3/23/27, PG 7) the portfolio offers opaque, semi-transparent and transparent grades tuned for the main ink systems — Vinyl, Polyamide, PU, CPP and NC/PU — so a formulator can match shade, transparency, rheology and fastness to the job.