Within reverse-printed solvent-based rotogravure packaging structures, the DIC common ink dye is predissolved at 20–25 °C in an ethyl acetate/MEK/isopropanol co-solvent before letdown into a nitrocellulose/polyurethane binder. The recommended dye solids on total wet ink fall between 2.5 wt% and 5.5 wt%; addition above 6.0 wt% causes dye crystallization during long-run solvent evaporation because the ethyl acetate fraction drops below 12 wt% in the ink pan. A 9-station or 10-station Cerutti or Bobst gravure line running at 280–450 m/min requires pan viscosity of 16–22 s DIN 53211/4 mm at 25 °C; lower viscosity produces pinholing on 35 µm low-density polyethylene, while higher viscosity increases drag-out and reduces transfer efficiency to the chrome-plated cylinder. Filtration through 5 µm absolute polypropylene bags is required before the closed ink pan is filled; undissolved dye particle counts above 120 per 100 mL measured by laser particle sensor cause visible streaks in the halftone wedge and force line stoppage.

For food packaging, the print is normally laminated or extrusion-coated so the dye is not in direct food contact, but EU Regulation 10/2011 migration assumptions still apply to the printed outer web. Total migration is verified using 10 days at 40 °C in 3% acetic acid, 10% ethanol, and isooctane as specified in Commission Regulation 10/2011 Article 14; the specific dye must not exceed any assigned specific migration limit. US structures are evaluated under FDA 21 CFR 175.300 resinous and polymeric coatings and FDA 21 CFR 176.170 components of paper and paperboard in contact with aqueous and fatty foods. REACH Annex XVII restriction entries for azocolourants require confirmation that reductive cleavage amines are below 30 ppm in the final printed film when the dye contains azo moieties. Chinese GB 9683 composite laminated food packaging mark, the print remains within its scope when export laminates are specified.

Typical end products are retort pouches, snack food wrappers, shrink-sleeve labels, and lidding film. The dye’s resistance to heat-seal jaw temperatures of 120–160 °C is confirmed by a 30-minute dry-heat test at 150 °C; ΔE measured under ISO 11664-4 CIELAB should remain below 1.5 on a white opacity chart. At gravure cylinder engraving, cell depth of 28–38 µm and screen ruling of 70–90 lines/cm are used for solid dye-containing inks; for vignette tones, cell depth is reduced to 8–15 µm with a doctor blade angle of 60–65°. The ink must remain re-soluble on the cylinder at ambient humidity of 45–65% RH; below 40% RH, ethyl acetate loss accelerates and cyan clean-up time exceeds 6 min. In production, the dye solution is not ground but is added at the letdown stage after nitrocellulose dispersion to avoid shear-induced dye crystallization.

What Limits Dye Load in High-Speed Flexographic Printing on Polyolefin Shrink Film?

Dye addition in flexographic shrink-sleeve inks is constrained by plate swell rather than tinctorial strength. In a solvent-borne flexo formula based on polyvinyl butyral and alcohol-soluble polyamide, the DIC dye is introduced at 1.2–3.0 wt% of total wet ink. At 3.5 wt%, photopolymer plate Shore A hardness drops from 68 to 61 after 8 hours of continuous impression because residual ketone carrier in the dye concentrate migrates into the photopolymer plate. Printers running Mark Andy or OMET presses at 150–250 m/min observe dot bridging when plate swell exceeds 4% linear expansion, measured according to ASTM D471-16 test method. The ink is diluted to printing viscosity of 20–27 s Zahn cup #2 at 25 °C, using a blend of n-propanol, propylene glycol monomethyl ether, and ethoxypropanol; the dye concentrate should contain no more than 15 wt% methyl ethyl ketone if plate swell is to remain below the threshold.

Anilox cell volume is set between 3.2 cm³/m² and 4.8 cm³/m²; banded anilox rolls with line screens from 800–1000 lpi are preferred for dye-based process colours because lower cell volume reduces pinholes on corona-treated polyethylene terephthalate glycol film at 38–42 dyn/cm surface tension. Chambered doctor blade pressure of 0.8–1.2 bar is specified; higher pressure accelerates blade wear and introduces metallic fines that can complex with the dye and shift hue. End-use shrink sleeves for PET bottles require the dye to withstand steam tunnel shrink conditions of 80–95 °C for 8–15 s without hue shift; a dye with weak thermal stability will show ΔE above 2.5 when tested under ISO 11664-4. Drying air temperature is held at 60–70 °C; above 75 °C, substrate deformation on 50 µm PVC and PETG film creates registration error and ink blocking on rewind.

EU Regulation 10/2011 applies when the shrink-sleeve outer print is removed before food contact; if the print remains on the container after shrink application, the dried ink layer is considered as a set-off or direct food-contact article under Article 7 and must be tested with compound-specific migration limits where applicable. Heavy-metal content is controlled under EN 71-3 migration method for toy-related packaging, with soluble lead below 2.0 µg/g, cadmium below 0.3 µg/g, and chromium VI below 0.2 µg/g as voluntary supply-chain limits. The ink should not be used with aromatic isocyanate crosslinkers in polyurethane flexo systems because dye amine groups react within the pot life window of 4 h, increasing viscosity by more than 15% and producing print mottle.

Sheetfed lithographic paste inks use the DIC dye primarily as a shading component in deep black series rather than as the main colourant, because dye-based offset inks exhibit poorer water resistance when compared with pigment blue 15.3 or carbon black. In a mineral oil/linseed alkyd vehicle with a tack of 9–12 under ISO 12634, dye loading is held between 0.3 wt% and 1.5 wt% for shade correction; addition above 2.0 wt% causes the wet ink to emulsify more than 35% fountain solution within 90 s on a lithotronic emulsification tester, leading to tinting in non-image areas. The dye concentrate is dissolved into the alkyd vehicle at 60–70 °C while mixing at 800–1200 rpm; no bead milling is required because the dye is fully soluble in the oleoresinous matrix. The finished ink should be aged for 24 h before drawdown evaluation because dye solubility in the vehicle reaches equilibrium slowly.

On press, plate temperature is maintained at 24–28 °C, fountain solution pH at 4.8–5.5, and isopropyl alcohol concentration at 6–10%. Conductivity of the fountain solution at 1200–1600 µS/cm prevents excessive dye extraction into the water phase; dye bleed is monitored by placing a drip of fountain solution on coated paper for 3 min and measuring stain density. A density increase below 0.02 over the paper blank is acceptable; higher readings indicate fountain solution emulsification and require reformulation of the wetting agent. End products are commercial catalogues, magazine covers, and art reproductions controlled under ISO 12647-2 process control and ISO 2846-1 colour reference. The dye-containing ink is not recommended for moist packaging applications because residual water-soluble dye can stain adjacent pages or offset onto unprinted surfaces during storage.

Aqueous writing ink rheology is bound by dye solubility, not pigment dispersion

In water-based rollerball and writing inks, the DIC dye is dissolved at 8–18 wt% into a humectant matrix of glycerol, diethylene glycol, and triethanolamine; the formulation has no dispersed pigment phase, so its Brookfield viscosity at 25 °C, spindle 4, 20 rpm, remains between 4500 mPa·s and 11000 mPa·s depending on the selected resin. Dye precipitation occurs if the water content exceeds 65 wt% and the pH drifts below 5.0, creating visible sediment within 72 h at 40 °C accelerated storage. The finished ink must pass centrifuge stability for 30 min at 3000 rpm with sediment below 0.5 vol%; this test is run on every batch because dye crystal agglomeration can occur in the presence of residual sodium sulfate above 50 ppm. No high-shear pigment dispersion step is required, but the dissolution vessel is blanketed with nitrogen if the dye contains oxidizable amine groups.

Filling lines for rollerball reservoirs use 0.45 µm absolute membrane cartridges after the dye dissolution vessel; unfiltered dye leads to feed blockage at the 0.18–0.25 mm tungsten carbide ball seat. Batch-to-batch dye colour strength is controlled by spectrophotometric absorbance at λmax with a tolerance of ±2% against a retained standard; dye lots that fall outside this range are adjusted by changing the humectant ratio rather than the dye-loading step to preserve viscosity. End products include rollerball pens and fibre-tipped writing instruments covered by ISO 12757-1:2017 for general-use ballpoint pens and refills. Toy-grade marker versions must comply with EN 71-3 migration limits for heavy metals and with REACH Annex XVII entry 51 phthalates if plasticized components are present; the dye itself is screened through OECD 404 dermal irritation data and must not contain EU CMR category 1A or 1B substances above 0.1 wt%. For archival writing, lightfastness is evaluated under ISO 11798 using blue wool scale 5 at 48 h Xenon arc; formulations based solely on dye commonly show lower lightfastness than pigmented inks, which limits their use in permanent records.

Thermal inkjet printhead conditions impose a maximum salt content of 100 ppm for dye-based inks formulated with the DIC product, measured as sodium chloride equivalent by ion chromatography. The dye is purified by reverse osmosis and ion-exchange after synthesis; residual chloride above 150 ppm accelerates kogation on the heater resistor and causes drop volume to fall below 85% of the nominal value within 500 million pulses. In a piezo printhead, the ink viscosity is adjusted to 2.8–3.5 mPa·s at 40 °C and surface tension to 28–32 mN/m with 2-pyrrolidone and 1,5-pentanediol as co-solvents; dye loading falls between 0.8 wt% and 2.2 wt% because optical density reaches practical saturation by 2.5 wt% on plain paper. Membrane filtration through 0.1 µm PVDF is mandatory, followed by vacuum degassing to dissolved oxygen below 5% saturation; dissolved oxygen above 7% shortens dye stability at 60 °C storage from 8 weeks to 2 weeks.

End-use test on plain paper per ISO/IEC 24711 evaluates line width, dropout frequency, and optical density; dye-based inks should maintain optical density above 1.0 on standard copy paper without feathering. Printhead reliability is validated through a 1000-page continuous print test on a representative multi-channel head; delamination of the nozzle plate or permanent deflection of the piezoelectric actuator is not acceptable. Divalent cations in make-up water must be below 10 ppm as CaCO₃ to prevent dye aggregation; ethylenediaminetetraacetic acid at 0.05–0.15 wt% is specified as a chelating agent. For indirect food additive use, published data for this specific configuration is limited, so the ink is not recommended for printed napkins or direct food packaging without migration testing under US FDA 21 CFR 176.170; the formulation is classified under REACH Article 31 for safety data sheet obligations, and the dye must be listed in the European Inventory or notified before placement on the EU market.

When inkjet grade dye is reformulated for screen printing, filtration economics shift

Screen printing pastes require much higher viscosity than inkjet or flexo inks; dye loading in a plastisol-free solvent-borne screen ink for pressure-sensitive overlays is 0.8–2.5 wt% because the thicker ink film requires lower chroma to avoid blocking and residual solvent entrapment. The dye is incorporated into a vinyl chloride-vinyl acetate copolymer solution in cyclohexanone/isophorone at 15–25 °C using a slow-speed planetary mixer at 30–60 rpm; high-speed dispersers above 1500 rpm introduce air that becomes trapped during screen stencil snap-off. Printing viscosity is set to 600–1500 mPa·s at 23 °C with Brookfield spindle 5 at 20 rpm; thixotropic additives or fumed silica are minimized because they reduce dye transparency and alter the blue shade in backlit overlays. Filtration shifts from 0.1 µm inkjet-grade membranes to 10 µm screen-grade bags because the higher resin content clogs fine membranes and increases shear.

Mesh count for polycarbonate overlays is 77–90 threads/cm with polyester monofilament; tension is set to 20–24 N/cm, squeegee durometer 70–75 Shore A, angle 60–70°, and pressure 0.3–0.5 MPa. Drying tunnel temperature is held at 55–65 °C for 3–5 min; residual solvent below 50 mg/m² must be confirmed by gas chromatography headspace per ISO 11890-2. End products are membrane switch overlays, nameplates, and point-of-sale graphics; adhesion is evaluated by cross-cut tape pull per ISO 2409, with no more than 5% removal acceptable on polyester or polycarbonate. For PVC overlays, lead and cadmium restrictions under EU 2011/65/EU RoHS Annex II apply: lead below 1000 ppm, cadmium below 100 ppm, and chromium VI below 1000 ppm. If the print is on an external surface of electronic equipment, IEC 62321-5 and IEC 62321-6 methods are used for lead and cadmium respectively; dye formulations containing brominated flame retardants are not permitted due RoHS Annex II PBB/PBDE limits of 1000 ppm.

Water-based marker ink formulations demand high dye solubility at low temperature because nib drying and feed stability are evaluated after storage at -10 °C for 72 h. Dye loading is 2–6 wt%; the formulation uses water, glycerin, propylene glycol, a preservative, and a buffering agent to hold pH at 6.5–7.5. High-shear mixing at 40–50 °C is followed by filtration through 1 µm glass fibre to remove undissolved agglomerates; the dye must not precipitate when the ink is frozen and thawed once per day for 3 cycles. Porous nib assemblies are filled under vacuum with ink viscosity between 3–10 mPa·s for fine-line markers and 30–150 mPa·s for stamp pad inks. Whiteboard markers require the ink to form a dry-wipe film on melamine and enamel boards; the dye must migrate into the hydrophobic binder phase at less than 0.1 mg/m² after 24 h contact to prevent ghosting.

Lightfastness on paper is tested under ISO 105-B02; dye-based marker inks typically reach blue wool scale 3–4, which is acceptable for temporary signage but not for archival documents. Toy-grade formulations comply with EN 71-3 migration limits for heavy metals, and the dye lot must be free of aromatic amines above 30 ppm when azo colourants are present under REACH Annex XVII entry 43. Art material labelling follows ASTM D4236 for chronic health hazards; the finished ink must not contain methanol above 0.5 wt% when sold in EU stationery channels as a precautionary supply-chain limit. The preservative system is selected after challenge testing under ISO 11930; dye components that bind to isothiazolinone preservatives reduce efficacy below the required log reduction of 3 for Pseudomonas aeruginosa within 7 days.

Compliance verification matrix for dye migration, mechanical, and chemical endurance