Performance requirements for CTP digital printing materials

Digital printing materials require CTP performance, and it is well known that the CTP process can bring many benefits to printing: excellent imaging quality, near-perfect calibration, and fast production turnaround. But its various advantages depend not only on the imaging device, but also on the quality and performance of the CTP plate.

Here we will focus on a few characteristics of the plate and see how they interact with each other to assist the CTP equipment in digital plate making and thus affect the image quality. This applies to all CTP plates, but especially to thermal plates. Thermal plates are now rapidly increasing in use worldwide and are also recognized as the plate of choice for high quality lithography.

Aluminum base requirements

In conventional platemaking, the accurate positioning of the dot on the plate depends to a large extent on the exact position of the plate and the positioning register when using a vacuum unit or a continuous reproduction unit. In any case, this requires the plate to be fairly flat when laid flat, but since the imaging process uses direct contact exposure, the whole process can accept different types of variations in the surface flatness of the plate that are due to the production of conventional plates with aluminum base surface treatments. However, because digital printing plates are exposed by the energy emitted from a focused laser light source, the requirements for the flatness of the digital plate, including the surface finish of the aluminum base, are much more stringent.

In addition, unlike direct imaging, the use of energy-focused imaging means that there are no visible streaks when imaging on the digital plate, as streaks do not appear when anodizing and grinding the aluminum plate.

When applying emulsions to digital plates, they must be smooth, uniform and free of defects. Because of the very small size of the dot produced on the laser platesetter, any dust in the air during web production, no matter how small, that falls on the plate will cause this artifactual image dot. In fact, it also creates an irregular image due to electrostatic speckling, and it is so small that it is invisible even when conventional printing materials are examined with a magnifying glass.

The same uniformity requirements apply to the photopolymer coating of digital plate composites. In general: a conventional printing plate, when exposed to UV light, receives approximately 10,000 times the energy delivered to the coating of a digital plate by the laser system in a platesetter. In other words, in order to accurately meet the physical properties described above, the emulsion coatings of digital printing materials must be very stringent in order to achieve a specific range of spectrally sensitive properties for the synthesized substance (especially the molecular structure in the coating) ) and respond positively to the energy. Plants producing digital printing materials therefore require special and additional chemicals as well as special production workflows.

Operational requirements

CTP plates also require different handling during handling compared to conventional plates. This is because many digital plate imaging uses the edge of the plate as a key reference point to calculate the imaging position. Digital plates have very stringent requirements for edge straightness and uniformity. While this is a minor issue for traditional plates, if the edges of a digital plate are not straight, abnormal or damaged, the plate will not function properly.

The final step in the production of digital plates is to create and maintain a service team that can help printers resolve issues whenever and wherever they arise. This is something that should be considered when evaluating any traditional and digital license plate, but is especially important for digital plates. This is because printers that are typically produced using CTP do so because the customer has a particularly strict time constraint, which means that whenever a problem arises it must be resolved immediately.

When comparing different digital plates or platemaking systems, it is worth noting that the end product is not a stack of plates sent to the pressroom, but rather a printed product produced by trouble-free printing from plates that have been accurately imaged on a printing press. When considering the cost of producing digital printing plates, several important factors that make them more expensive than traditional plates should be considered. One of the most important is the need for high-quality raw materials. Thermal technology is the technology of choice for printers using CTP systems. Thermal plates will give users accurate quality and consistently high quality.