(1) Brightroom operation performance;
(2) The imaging energy threshold is obvious (ie, there is no energy accumulation effect in the imaging process);
(3) High-tech solid infrared laser light source (IR-LD and YAG) with mature technology, but the fatal weakness is very low sensitivity (sensitivity).
Thermal imaging material systems mostly rely on changes in the state of matter to achieve imaging records, such as thermal melting, thermal induced vaporization, thermal induced phase change, thermochemical reaction, etc., requiring that the temperature must be above the temperature of the corresponding state of change. Therefore, the physical stimulus (laser or heating head) must have enough intensity (power) to make all the energy absorbed by the plate contribute to the increase of temperature (approximately adiabatic conditions), so as to achieve sufficient change in state The temperature, otherwise, the absorbed energy will disappear in the heat exchange with the environment, and the temperature of the plate cannot reach a temperature sufficient to change the state of matter.
This is why thermal imaging systems generally have no energy-cumulative effects (→ can achieve bright-room operation) and have significant imaging power thresholds (→clear image edges, high contrast).
On the other hand, the change of state requires relatively high energy, and it is generally difficult to introduce a chain reaction mechanism (ie, the so-called amplification mechanism), so the sensitivity (sensitivity) is relatively low, and the minimum imaging exposure is generally several hundred mJ/ Above cm2, much higher than other imaging material systems; such as: photocrosslinking/light modification (tens of mJ/cm2, photopolymerization (tens of μJ/cm2), silver salt, and electrophotographic system (number μJ/cm2 )and many more.
In order to make up for the shortcomings of the low sensitivity of the thermal imaging system, it is generally necessary to use a high power laser with a W/cm2 level or more in order to achieve the plate making speed required for practical applications, which is not a very favorable choice. Judging from the trend of development, in the field of off-line direct plate making, the infrared thermal imaging system and the ultraviolet photosensitive imaging system will certainly become the focus of competition in the future.