Digital imaging of flexographic plates is a multiple step process, but requires far fewer steps than conventional flexographic platemaking. The process begins with the placement of the plate material on an external drum where it is held in place by vacuum or double stick tape. The process of imaging the plate on the external drum is known as imaging in the round.

Another type of plate that is used for CtFlex is a seamless material that is bonded to a sleeve and is known as computer-to-sleeve. The flexographic sleeve is used when continuous imaging is desired.

A flexographic CTP plate consists of a photopolymer layer topped by a black masking layer. As the imaging drum rotates, a laser head creates the image on the plate by ablating portions of the black masking layer to reveal corresponding areas on the photopolymer layer. Many flexographic platesetters use lasers that operate at 830 nm or 1064 nm wavelengths. Only a light coating of ash is formed from the imaging process, which is removed with a debris extractor built into the system. This is followed by a simple water wash and a short drying period.

Flexographic platesetters require more power than offset thermal units in order for the lasers to ablate unwanted areas of the plate material and provide proper imaging. The plate material must be strong enough to withstand the extremes placed upon it during the printing process, but must also allow the lasers to erode the material easily during the imaging process.

In conventional, flat platemaking, the image can become distorted because of the cupping and distortion that may occur when the plate is mounted to the printing cylinder. Much of the distortion of the image is eliminated with CtFlex because the image is engraved in the round and because additional measures are used during the imaging process to compensate for potential distortion. This results in a printed application of a much higher quality than is possible with conventional flexography.

The primary difference between a conventionally imaged flexographic plate and one that is digitally imaged is the dot size. On a conventional plate, the resulting dot on the plate is larger than the dot on the negative and the top of the dot is flat. On a digitally imaged plate, the dot is the same size as the dot that was imaged; therefore the plate can hold a much smaller dot than a conventional plate, which results in improved print quality. The top of the dots on the digitally imaged plate are rounded, which also a factor in improved print quality.

In traditional flexographic platemaking, the average of the tonal range is between 10% to 85%, so it is common for some areas of highlights and shadows to be lost. CtFlex improves on the tonal range significantly. A tonal range of 3% to 97% is most often achieved. With four-color or hi-fidelity color work, it is possible to achieve much better definition and contrast. The printed image is much closer to continuous tone quality (such as in a photograph) than it is when using conventional flexographic plates.

• CtFlex eliminates film from the workflow, which reduces production time, materials, and labor cost.
  
  
• Storing digital images is easier and more efficient than storing film negatives, which often requires large areas of physical space.
  
  
• Film can get scratched and damaged, even in storage, but digital images will always look consistent, clear, and sharp.
  
  
• Print quality is improved because dot gain, associated with plates imaged from film, is eliminated.
  
  
• Film substrates are affected by temperature and humidity changes. The film may stretch or shrink resulting in registration problems at the press and substandard quality. CTP eliminates these problems because no film is involved.
  
  
• Cupping and distortion of plates is reduced or eliminated because CtFlex plates are imaged in the round.
  
  
• Copy changes are much easier with CTP because changes are made to a digital file, which can be changed easily and can be changed as many times as possible before the plate is imaged.
  
  
• Large quantities of hazardous waste are produced in conventional flexography. The use of film produces byproducts such as silver and developing chemicals that must be handled with care and disposed of properly in accordance with government regulations. Proper disposal can be costly. CTP technology eliminates much of the chemical hazards and waste disposal problems, making it a much safer plating procedure for humans and for the environment.