Buskro Marketing Memo 

October 2018. Pickering Canada

Buskro offers a full suite of ink formulations with its family of inkjet printing technologies to optimize the print results on the widest range of substrates. Buskro ink formulations include UV-curable, solvent, and water-based inks, each designed to produce the best results on particular substrates and operating conditions. As the inkjet specialists, Buskro takes great pride in its extensive knowledge and experience gained over the years with varying ink formulations and has prepared a guide to assist with the selection of its inks.

UV Curable Inks

UV curable inks are a liquid ink formulation consisting of monomers, oligomers and a small percentage of photo-initiators, which when exposed to high-intensity ultraviolet light, initiates a photochemical reaction that cures (harden) and causes the ink to adhere to most printing substrates. Buskro offers a variety of UV curable inks (Renoir, Renoir-LED, Bosch) that cure both with mercury vapor lamp (“D” type) and/or LED curing light source, although most applications today employ LED curing for its efficiency and convenience. Although UV-curable inks are versatile and are often touted as being compatible with virtually all printing substrates, it is important to note that the performance of such inks are dependent on both the i) intensity of the UV light source and ii) the surface tension of the material.

UV light Intensity

UV light intensity, or more importantly the amount of ink exposure to such light, determines the level of cure of the printed image. An insufficient amount of exposure results in a “wet” or partially cured image that may be susceptible to abrasion. It should be noted that the curing process occurs from the surface inwards and continues for some period (>1 hour) after exposure. Printed images which may appear to be insufficiently cured immediately after UV light exposure when exposed to aggressive scratching and/or abrasive mechanical elements, often are deemed to be acceptable by the time the printed material is handled for packaging. In cases where the printing application requires high-speed and/or high density (High DPI) images, it may be necessary to augment the exposure period by adding a second curing lamp to ensure full cure of the printed image with an acceptable scratch-resistance. Buskro currently offers LED curing lamps operating in the 395 nm wavelength range with an intensity of 16 w/cm2, sufficient for most applications.

Surface Tension

Material surface tension is measured and expressed in Dyne/cm. The general rule for the optimal application of UV inks onto materials is that the material’s dyne level exceed the ink’s dyne level by at least 10 dyne/cm. A material’s surface tension is a function of its coating properties and the amount of time after producing it, which is to say that the material’s dyne level will often decrease over time. Thus, a material that exhibits good adhesion shortly after its manufacture may produce poor results a number of days afterwards. If there is an imbalance between the ink and the printed material’s surface tension, the adjacent ink drops deposited on the material may not flow freely and join giving the appearance of poor, “scratchy” print (lines in the printed image) in the best case, or easily removable through abrasive contact, in the worst case. Glossy printed materials including some plastic cards, UV coated, and aqueous-coated stocks are most susceptible to the aforementioned problems.

Buskro UV-curable inks and their associated dyne levels include Renoir (24-28 dyne/cm) and Bosch (21-25 dyne/cm). Where a printing application requires a material with a challenging surface tension, a positive outcome may be achieved with the application of inline surface treatment prior to the printing process delivered by corona, plasma, or heat devices which act to increase surface tension.

Recommendation: 

If there is any concern over the material’s surface tension, the required high print density and speed, or any other factor which may adversely affect the printing result, please send such materials to Buskro for testing and sample production so that Buskro may advise prior to any printing equipment purchase.

Things to Remember:

  1. Surface tension of glossy products may be insufficient, resulting in poor print and/or adhesion;
  2. Surface tension may adversely decrease over time;
  3. The curing lamp may not provide sufficient UV light exposure to fully cure images requiring high-speed and/or high DPI print;
  4. Printed images will continue to cure over time and such cure occurs from the surface inwards;
  5. Optimal surface tension range for the material is around 38-50 dynes/cm, but should not be higher than 54-60 dynes/cm;
  6. Surface treatment devices such as corona, plasma, or heat act to increase dyne levels and may be used to optimize surface tension prior to printing.

Water-based Inks

Water-based inks are a liquid ink formulation consisting of dyes or pigments suspended in water acting as the solvent. Buskro offers a variety of water-based inks for the Atom, Atlas, Quantum, and Apollo print systems as follows:

  • Apollo Versatile Black TIJ2.5 HP ink cartridge
  • Atlas/Atom Legar dye-based aqueous
  • Atlas/Atom Chardin dye-based aqueous
  • Atlas/ Atom Forain pigmented-based aqueous
  • Quantum Seurat pigmented-based aqueous

Water-based inks are ideal for porous and some coated stocks where material porosity properties permit rapid ink penetration in combination with an evaporative effect sufficient to permit these inks to be dry-to-the-touch when first handled/touched. Water evaporation is necessary to set the ink which can take place either at room temperature or with the assistance of heat. The rate of evaporation depends on the properties of the water-based ink used, the nature of the substrate, and the amount of ink applied. There are a number of factors which affect the performance and reliability of water-based inkjet printers, the appearance of the printed image, and the achievable production rates as follows:

Production Rate

As previously mentioned, ink setting properties are dependent on both the penetrative characteristics of the material combined with the evaporative characteristics of the ink which directly correlates to the maximum production rate achievable. As solvents go, water exhibits a relatively low evaporation rate which often necessitates the addition of a heat source especially when glossy and coated stocks limit the ink’s penetrative abilities.

Ink Smear

The residual ink pigments which form the printed image and settle on the surface of a material requires that sufficient evaporation has taken place to set and bind these ink pigments to each other and to the substrate. In the absence of such ink setting, the ink can smear under the application of physical touch especially for highly glossy stocks. Legar and Seurat inks are designed to have superior setting characteristics when exposed to heat.

Wettability

The water-based inks, employed for both the Quantum and Atom print technologies, offer some flow resistance when first introduced into a dry or evacuated print head until the ink fully saturates and wets the internal ink path from the bottle to the orifices. This effect prevents and restricts ink flow into some of the jetting orifices resulting in missing jets until full wetting is achieved. Some time and patience (@1 hour) will be necessary to fully recover all the jets of a printer when ink is first introduced into the printer.

Ink Drying and clogging

Water-based inks set on a material when the solvent (water) has evaporated sufficiently such that only the pigment remains on the material’s surface. During extended periods of printer inactivity, localized surface evaporation on the orifice plate resulting in clogged jets will occur to varying degrees depending on capping practices, the frequency of maintenance regimens, and environmental influences such as air humidity and temperature. Applying liquid ink or a flushing agent to the orifice plate will facilitate jet recovery. In extreme cases, a print head may require the rigorous application of a flushing regimen conducted by Buskro LTD at its factory.

Recommendation:

If there is any concern over the production rate capabilities on coated stocks, smear resistance, or any other factor which may adversely affect the printing result, please send such materials to Buskro for testing and sample production so that Buskro may advise prior to any printing equipment purchase.

Things to Remember:

  1. Coated stocks will generally adversely affect the production rate by limiting ink penetration and increasing the amount time required for evaporation and setting;
  2. Higher DPI print requirements will generally adversely affect the production rate by increasing the amount of ink that requires evaporation and setting;
  3. Application of a heat source may increase production rates and smear-resistance by reducing the ink setting time and improving evaporation rates;
  4. Jet-clogging may occur over extended periods of printer inactivity. Applying liquid ink or a flushing agent to the orifice plate will facilitate jet recovery;
  5. Opacity and appearance of the printed image is directly related to the amount and distribution of the ink penetration into the substrate.

Solvent Inks

Solvent inks are a liquid ink formulation consisting of dyes or pigments similar to water-based inks with the difference being the use of more aggressive solvents which evaporate and set at a far greater rate than water. Buskro offers a variety of solvent inks for the Atlas, Atom, and Apollo print systems some of which are as follows:

  • Atlas/Atom Monet
  • Atlas/Atom Cezanne

Apollo HP2580 Solvent inks are designed for the more challenging surfaces presented by most coated stocks where limited material porosity exists. Solvent evaporation is necessary to set the ink which can take place either at room temperature or with the assistance of heat. The rate of evaporation depends on the properties of the solvent used in the ink, the nature of the substrate, and the amount of ink deposited. A number of factors exist which affect the performance and reliability of solvent-based inkjet printers, the appearance of the printed image, and the achievable production rates as follows:

Production Rate

As previously indicated ink setting properties are dependent on both the penetrative characteristics of the material combined with the evaporative characteristics of the ink which directly correlates to the maximum production rate achievable. Solvents generally exhibit a faster rate of evaporation than water. This rate depends on the type of solvent used and often is enhanced and improved by the addition of a heat source. Ink Smear. The residual ink pigments which form the printed image and settle on the surface of a material requires that sufficient evaporation has taken place to set and bind these ink pigments to each other and to the substrate. In the absence of such ink setting, the ink can smear under the application of physical touch especially for highly glossy stocks. Monet and especially Cezanne are designed to set at a much quicker rate than water.

Ink Drying and clogging

Solvent inks set on a material when the solvent has evaporated sufficiently such that only the pigment remains on the material’s surface. Buskro solvent inks for the Atom and Atlas print technologies include Monet, a compromise formulation offering moderate drying capabilities superior than water as well as Cezanne, and aggressive formulation with very rapid drying capabilities. During periods of printer inactivity, about 20-30 minutes for Monet and 1-2 minutes for Cezanne, localized surface evaporation on the orifice plate may result in clogged jets will occur to varying degrees depending on the environmental influences such as air humidity and temperature. Applying a purging regimen and/or liquid ink or a flushing agent to the orifice plate will facilitate jet recovery. In extreme cases, a print head may require the rigorous application of a flushing regimen conducted by Buskro LTD at its factory.

Recommendation:

If there is any concern over the production rate capabilities on coated stocks, smear resistance, or any other factor which may adversely affect the printing result, please send such materials to Buskro for testing and sample production so that Buskro may advise prior to any printing equipment purchase.

Things to Remember:

  1. Monet ink is a compromise formulation designed to offer moderate drying capabilities over water-based inks and may be used on most coated stocks. It generally produces a “lighter” print than a water-based ink on porous stocks;
  2. Cezanne ink is a fast-acting, more demanding ink formulation designed for the most challenging of glossy substrates. It works best when in constant use and may exhibit missing/misfiring jets in as little as 5 seconds of inactivity;
  3. Higher DPI print requirements will generally adversely affect the production rate by increasing the amount of ink that requires evaporation and setting;
  4. Application of a heat source may increase production rates and smear-resistance by reducing the ink setting time and improving evaporation rates;
  5. Jet-clogging may occur over periods of printer inactivity. Applying liquid ink or a flushing agent to the orifice plate will facilitate jet recovery;
  6. Opacity and appearance of the printed image is directly related to the amount of the ink and penetration into the substrate.