What is thermal CTP technology?

The so-called CTP technology is from the computer to the printing plate (CTPlate), printing machine (CTPress), proofing (CTProof), printing (CTPaper/Print) and ordinary PS version (CTcP). Now the printing industry often said CTP is from the computer to the plate (CTPlate), is the use of computers will be the original picture, text after digital processing, graphic integration, proofreading, direct imaging in the plate, and then after development or post-processing and other post-processing procedures made of printing plates. CTP technology can be divided into light-sensitive CTP technology (visible light, violet laser, ultraviolet light) and thermal CTP technology, the following focus on thermal CTP technology.

First, thermal CTP technology classification

Thermal CTP technology can be divided into the following categories according to the plate:

(1) thermal ablation type; (2) thermal cross-linking plate (preheated, negative type); (3) thermal decomposition plate (without preheating treatment, Yangtu); (4) heat transfer plate; (5) thermal phase change plate material.

Second, thermal CTP technology imaging principle

Thermal CTP is mainly the use of thermal imaging technology, so that the plate absorbs heat to change the state of the material, so as to realize the change in material properties.

(1) thermal ablation type

1. plate composition

The plate consists of silicone oil refusal layer, light and heat conversion layer (light absorption layer), oil wet layer and plate base (Figure 1).

2. Imaging principle

The main role of the photothermal conversion layer is to absorb the light energy emitted by the infrared laser, and the absorbed light energy is effectively converted into thermal energy, so that the temperature of the plate rises to the level of the vaporization temperature. Bright area of the photothermal conversion layer in the role of thermal energy vaporization, the corresponding position of the silicone oil exclusion layer with the photothermal conversion layer in the role of heat vaporization and be removed, so that the oil wet layer below the exposure to become a part of the plate to receive the graphics of the ink; can not see the light of the region of the photothermal conversion layer does not vaporize, the corresponding position of the silicone oil exclusion layer does not change the formation of a blank portion of the printing plate (Figure 2).

3. Version base

The plate base of this type of plate can be either a metal plate base (e.g., aluminum base) or a flexible polymer sheet base (e.g., polyester base), which has a relatively wide range of adaptability. This type of plate can be printed after laser imaging, making it particularly suitable for on-machine direct plate making systems.

Although this type of plate is also a direct plate without post-processing, it produces ablative vapor mist and debris during the imaging process, which requires the necessary effluent treatment measures or else it will contaminate the imaging optics and the environment.

(2) Thermal crosslinking plate (preheated, negative type)

1. Plate composition

Thermally cross-linked plates consist of a thermally sensitive coating and a hydrophilic plate base. The thermal coating generally consists of (alkali) water-soluble film-forming resin (phenolic resin), thermal cross-linking agent, and infrared dye. The hydrophilic plate base can be used with an aluminum plate base identical to that of conventional PS plates (Fig. 3).

2. Imaging principle

The role of infrared dye is to effectively absorb the light energy of infrared laser and convert the absorbed light energy into heat energy, so that the temperature of the thermal coating reaches the reaction temperature of the thermal crosslinking agent; The role of the thermal crosslinking agent is to react with the film-forming resin under the effect of temperature to form a spatial network structure, so that the thermal coating loses its water (alkali) solubility. Due to the role of spatial cross-linking, the bright zone thermal coating under the action of heat cross-linking occurs, the formation of small molecules to macromolecules, from linear molecules to mesh molecules of film resin, insoluble in alkali, and after the development of the layout is still retained as an oil-wetted graphic components. The thermal coating in the non-visible area does not undergo a cross-linking reaction, is alkali-soluble, and dissolves during the development process, exposing the hydrophilic version of the base as a hydrophilic blank part (Figure 4).

3、Pre-heat treatment

In order to further improve the effect of thermal cross-linking, some plates are often preheated after exposure to further deepen the effect of thermal cross-linking (which is also an increase mechanism to improve sensitivity). These plates are called thermally cross-linked plates and require preheating. The graphic areas of thermally cross-linked plates are composed of spatially cross-linked polymer resins, so these plates usually have very high mechanical strength and print resistance, and can typically print hundreds of thousands of prints, which is very advantageous. Suitable for the long run printing market.