General Information for Printing with UV-Inks

Technical Requirements for Printing with UV-Inks  

  • There are only rollers made out of EPDM suitable for printing with UV-Inks (this material will be destroyed by mineral oil). When change between conventional and UV printing is planned,      special working material is available (Nitrile rubber).
  • EPDM-printing blankets are suitable for pure printing with UV-inks. Nitrile rubber blankets are suited for change between printing methods.  

  • Positive and negative plates are appropriate for printing with UV- and conventional inks, these plates should be baked before use. The plate supplier will make recommendations for most suitable types.  

  • UV-radiators must be equipped with sufficient power. Depending on the type of radiation lamp there will be ozone suction device necessary.  
  • Depending on the pigments used, UV-inks often tend to a thixotropic behaviour (“not flowing”) in the inks duct, therefore steering device is recommended.
  • To reduce ink mist suction device on the printing machine is recommended.    

 

UV-Inks  

UV-binding agents are acrylates of different viscosity.

UV-Inks are not mixable with printing inks based on a conventional binding agent combination.  

For suited washing agents like alcohol, ester, ketone ask your suppliers of washing agents of recommendation.  

For handling of UV-inks and UV-washing agents it is recommended to comply with the prevailing safety regulations.  

The prevailing safety regulations can be gathered from the information sheets of the suppliers (Material Safety Data Sheet)    

 

Instructions for Use  

  • Inking unit must be properly cleaned from conventional inks. Residues of washing agents on the inking rollers cause drying- and scumming problems.
  • Before in feeding UV-inks we recommend to wet rollers with a small amount of UV-thinner Z914 to achieve deep inking. Using to much thinner can cause scumming problems.
  • Supply least amount of fountain solution possible, because UV-Inks are more water sensitive than conventional inks.
  • We recommend 3 % fountain solution Waterfit Z450 and 3 – 8 % IPA to reduce the surface tension. Avoid residues of washing agent in the fountain solution, this could cause damping, scumming and drying problems. The fountain solution must be renewed when these problems appear.    

 

Storage of UV-Inks  

  • Close ink tins accurately after taking out some ink and protect packaging from the influence of daylight.  
  • Store in a cool and dark place  
  • Storage stability in the original, unopened container: 6 months at 20° C  

 

Printing Additives  

  • UV-Thinner Z914 To reduce viscosity when inks are too stiff  
  • UV-Accelerator  Z967 Addition of 2 – 5 % to accelerate curing of the ink  
  • UV-Transparent White 7P164 Adding up to 90 % to lighten up the UV-Ink  
  • UV-Opaque White Z220  
  • UV-Varnish Z440  

UV-Inks normally are mixable among each other      

 

Problems during the printing process

Sources of problems and there possible solutions  

Scumming  

  • Unsuited plates

  • The proportion of alcohol in the fountain solution is too high

  • Unsuited washing agent

  • Residues of washing agents in the ink unit, on the damping roller or in the fountain solution.

  • Swelled plate ink rollers (control transport!)

  • Badly dispersed printing additives

  • Too much thinner added to the ink

  • Oxidised printing plate

 

Smearing/Smudging  

  • Insufficient amount of fountain solution

  • Swelled ink rollers (control transport!)

  • Residues of conventional offset printing inks or washing agent in the inking unit.    

 

Drying problems

  • Insufficient performance of the UV-lamps

Possible source of problems:

  • Connection value of the UV-Drier is not optimized

  • Unsuited lamps

  • Too powerful cooling of the lamps (lamps do not reach maximum intensity of radiation resp. efficiency)

  • Dirty reflectors or eventually existing clear-view screens

  • Too wide distance of the lamps (more than 6 – 8 cm) to the print.

  • Dirty lamps caused by – for example – burned in powder

  • When lamps are cooled by water, examine coolant for pureness, perhaps a change of water is necessary. Use distilled water.

  • Control hours of operation of the lamp (aging), consult the lamp supplier.  

 

  • The proportion of ink thinner or varnish to the ink is too high (addition of UV-Accelerator  1167 recommended)

  • Residues of washing agent in the ink

  • The proportion of water in the ink is too high    

 

Piling up on the following printing blanket and/or on the back pressure during continuous stationery printing after UV-Drying (inter-unit drying)  

  • Unsatisfying drying properties

  • Web temperatures are too high after the inter-deck drying unit (web cooling recommended)    

 

Picking  

  • Ink consistency too stiff (addition of  2 – 5 % UV-Thinner Z914)

  • Unsuited rubber blanket (it strips off and becomes sticky – formation of reliefs)  

Mottled impression  

  • Ink consistency too stiff

  • Embedded fountain solution in the ink

  • Mostly paper problem (different setting)  

 

Roller Marks  

  • Control make ready of plate ink/damper rollers. Adjustment of ink to damp-roller.

  • Too much ink  

 

Ink Misting  

  • Ink consistency too stiff (Addition of 2 – 5 % UV-Thinner Z914).

  • Cover of inking unit rollers is too aged and porous.

  • Unsuited inking rollers (cooled distributor rollers and roller material with increased shore hardness have a positive effect)

  • Control transport of the ink through the rollers.  

 

Ink Splashing  

Too much fountain solution emulsified in the ink.

Remedies:

  • Reducing the amount of fountain solution

  • Cooling of the damping unit

  • Using of suited fountain solution additive  

 

Build-up on the Rubber Blankets  

  • Ink consistency too stiff (addition of UV-thinner)

  • Poor ink trapping (check printing pressure adjustment)

  • Unsuited printing blanket (formation of reliefs)

  • Too much fountain solution additive