Graphic & Imaging Print Media FAQ's

Why do I need a coating to print on films?

Plastic films typically have very low surface tension, which means it is difficult to get liquids such as ink, to stick to them. DUNMORE provides special coatings and applications which allow inks of all types to quickly adhere and dry on the surface of the film. Topcoating a film usually provides the longest-lasting, most robust printing surface for ink adhesion.

Is coating the only solution?

No. Depending on the requirements and printing process, films may be either corona or plasma treated at DUNMORE. Sometimes they are also treated this way before they are coated.

What is corona treatment?

Corona treatment is the process of passing a film through a high electric energy field called a "corona." The energy field alters the surface on the film to make it more receptive to ink and other chemicals. Corona treatment is effective for improving dyne-levels on a film but must be used within a short time after treatment for it to it be fully effective.

What is plasma treatment?

Plasma treatment is the process of passing a film through a hot plasma gas, usually but not always, in a vacuum chamber. Plasma treatment provides a print or coating receptive surface for a longer period of time compared to corona treatment due to the type of process and its effect on the surface of the film. Plasma treatment is frequently used as a pre-treatment prior to metallizing films which are naturally resistant to evaporative metal deposition.

Why are there different coatings for different printing processes?

Different processes require different inks. For example Flexo presses print on rolls directly with the inks being designed for that process specifically. Offset inks are designed to work with water/oil offset processes and digital printing processes require toner and electrostatic inks to process properly. Each one of these processes has its own requirements for successful film printing and drying.

Regarding inks, what is the difference between conventional printing processes using solvent, aqueous and UV inks as compared to digital processes?

The differences are primarily between the ink composition and methods used to dry the ink. Inks containing solvents, the "vehicle," evaporate leaving pigment and/or dye on the surface of the coated film. Water based inks use ink emulsions with water being the "vehicle." Since water does not evaporate quickly, it may need additional drying over solvent based inks. UV inks consist of 100% solids and are dried or "cured" instantly when exposed to specific UV light for an optimized duration. Digital laser printing consists of either dry toner or liquid toner. Dry toners are typically fused to the coated film by heat and pressure.

What do you mean by digital printing?

Digital printing does not use conventional imaging plates for printing. Instead the image is formed on an imaging drum and processed directly from the computer image. Each digital image may vary from the preceding image as it is digitally created. This is the true strength of the digital process. Digital printing is suited for small volumes and variable data printing such as ID cards, serial numbers, direct mail components etc. Digital printing can use laser technology, liquid toner inks, inkjet processes, or a combination of several processes.

What is the difference between dry toner and liquid toner?

Liquid toner (primarily used in HP Indigo presses) is an ink in liquid form. It is deposited to the imaging drum and held in place with electric voltages and then transferred to a blanket cylinder and then to the substrate. Dry toner, which is typically referred to as xerography or laser printing, uses a dry ink referred to as toner, which is deposited on the imaging drum with electric voltages. It is then fused with heat and pressure to "melt" the toner to form the image on the substrate. Dry toner is the most common process and is found in most business and home office laser printers.

What is a "master roll"?

A master roll is typically a roll as it is shipped from the film manufacturer. They are usually at least 48" to 60" (1.22 -1.52 m) wide and vary in length due to film thickness. A typical 2 mil (50 micron) polyester master roll is 56" wide and 5000 yards in length. The typical master roll weighs between 800 and 1500 lbs. These rolls can be slit by DUNMORE to your specific width prior to shipment.

What are my minimum quantities to purchase materials from DUNMORE?

Generally, except for trial and development purposes, DUNMORE requires at least one master roll to produce materials cost effectively for its customers.

Why should I purchase coated material when I can coat my own material in house?

Certified material is guaranteed by the manufacturer to perform to expectations. The material has been tested to maintain consistent performance throughout the entire printing process. Even though some plastics may be made of the same material, their properties can vary slightly enough to make a difference in performance. Buying certified material will insure you don't have problems with your run.

Can I used DUN-DIGTIAL™ media on both Indigo and iGen presses?

DUNMORE's new Indigo digital top coat can print successfully on the iGen press. We do however recommend a scale up trial to assure satisfaction. DUNMORE also has specialized coated products specifically designed for the iGen and NexPress printing platforms. Please Contact Us for any laser toner film media applications.

How should I store and handle DUN-DIGITAL™ media?

Above all keep your media in the bag and away from too much moisture at all times. In contrast it is advisable to try to keep the material in a cool and static-neutral environment when ever possible. Prior to loading sheets static eliminators are recommended to reduce bonding of sheets. Treat media like photo paper; protected from the elements as much as possible.

What is RIT Certification?

The Rochester Institute of Technology routinely certifies materials for use on a variety of digital presses. Included in this are the HP Indigo series and Kodak Nexpress. In the HP Certification process, RIT offers one, two and three star performance levels based upon meeting certain print performance requirements. All DUN-DIGITAL™ media offered meet the 3 Star rating which is the highest performance standard in the certification tests. For more information on the test procedures, visit www.printlab.rit.edu