CTP plate has become the key to CTP system

Keywords: CTP Plate Light Sources When it comes to investing in CTP, CTP plates and plate-making systems are equally important. However, can violet diodes be used for traditional platemaking? Which plate is suitable for which light source? Drupa 2000 is still a confusing issue after the show. Thermal plates can be divided into rinse-type plates and cross-linked plates, while rinse-free plates are classified into ablated plates and polymeric phase-change plates. Purple lasers have become important laser sources as well as argon ion lasers, helium neon lasers, Nd:YAG lasers, and red-diode and infrared diodes.
Since Drupa 2000, the inner drum laser plate-making system equipped with violet laser light source has become an important topic for discussion in the industry, and manufacturers are trying hard to obtain a more important position in the thermal plate-making system market. Therefore, finding an applicable CTP plate becomes an important task.
1. Can a violet laser light source be used in traditional platemaking violet laser light sources for traditional platemaking? People are very concerned about whether this near ideal combination is feasible. However, the answer is almost negative. The main reason is that the sensitivity of traditional printing plates is too low. At the same time, there are too few studies in this area.
Many people have tried to compare the CTP plate with a traditional plate made of film. However, the CTP plate-making light source and the traditional plate-making light source are completely different. Because the CTP light source is an electromagnetic wave, its wavelength (the length between two adjacent peaks) is measured in nanometers (nm) (1 nm = 10-9 m). Figure 1 shows the relationship between the spectral characteristics of various light sources and the output energy. The horizontal axis represents various light sources at different wavelengths: Short-wavelength ultraviolet light with a wavelength range below 400 nm (which is a bright-room plate-making light source and is used as a traditional plate-making light source) Visible light with a wavelength between 400nm and 700nm (which is a darkroom plate-making light source) and infrared light with a wavelength range of 700nm - 1mm (also a bright-room plate-making light source). In the figure, the vertical axis represents the output energy of various light sources, the output energy of the violet laser light source is approximately 5 mW, the output energy of the infrared laser diode light source is approximately 1 W, and the output energy of the thermal Nd:YAG laser and the infrared laser exceeds 10 W.

He-Ne laser and red-laser light sources are rarely used in CTP platemaking systems, but are more often used as film exposure light sources. Argon ion and infrared laser light sources are generally not used in CTP platemaking systems. The violet laser light source and the dual-frequency Nd:YAG laser light source with a wavelength of 532 nm belong to the visible light region and are usually used as a CTP plate making light source. The infrared light source and the Nd:YAG laser light source with a wavelength of 1064 nm belong to the invisible light region, and are often used as a CTP heat-sensitive platemaking light source. The 532nm short-wavelength laser is twice the frequency of the 1064nm wavelength laser. It is often referred to as a "df" dual-frequency laser and belongs to the visible region light source. The 1064nm wavelength Nd:YAG thermal laser source has a high definition for thermal imaging. However, as a plate-making light source, it still suffers a great impact from the violet laser light source.
As we all know, the higher the output energy of the light source, the shorter its working life. Therefore, the new violet laser source will have a longer life and lower cost. Some relevant investigation reports provide reference data for the relationship between the cost and life of the plate-making light source: The 532nm wavelength Nd:YAG laser source is priced at 55,000 Deutschmarks, the working life is 5000 hours, and the 1064nm wavelength laser source is priced at 70,000. Deutschmark Mark; violet laser light source with a full set of optical accessories is currently priced at approximately 15,500 deutsche marks at a substantial price reduction. The earliest used violet laser light source has a working life of 5,000 hours and will gradually exceed 10,000 hours. At the same time, we must distinguish the life of the laser light source from its true working life (referring to the time used in actual plate making). For instance, the manufacturer of the Xpose plate making system believes that the service life of the infrared laser light source used in the system can reach 30,000 to 50,000 hours, because the light source is turned on but not working when the thermal response threshold of the plate is below, only It was only working when the plate was exposed. The light source was priced at only 1100 deutsche marks. They claim that the cost of up to 32, 48, or even 64 infrared laser light sources in their outdated laser platemaking system is about the same as the cost of a high-cost laser light source used in an in-drum laser platemaking system. Even if all laser sources are replaced, the cost is almost the same. However, in a similar technology using the Heidelberg Speedmaster DI-46 laser platemaking system, all 64 laser light sources had only four light sources replaced in four years up to 10,000 hours of work time.
Second, the plate and the light source match the relationship between the exposure of the printing plate and the exposure of the film in photography is the same. Whether it is a natural light source or an artificial light source, the spectral (color) sensitivity of the film should correspond to that of the light source. Similarly, the plate should correspond to the emission spectral characteristics of the laser light source. The sensitivity of the film was measured using ASA and DIN values. Increasing the ASA value (eg, from 100 to 200) or increasing the DIN value by 3 (eg, from 18 to 21) will double the film sensitivity, affecting the camera's shutter speed and aperture aperture size. If the sensitivity of the film is doubled, the shutter opening and closing speed can be faster (for example, from 1/125 seconds to 1/250 seconds) or the aperture aperture can be turned down one step (for example, from 5.6 to 8).
In the plate-making exposure, the aperture aperture problem no longer exists, and the sensitivity of the plate depends only on the exposure time and the intensity of the light source. In order to obtain a higher plate-making quantity per hour, a high-sensitivity plate and a high-power laser light source are required, and a rotating drum in an inner drum system scanner or an outer drum system can rotate at a high speed.
Table 1 shows the average sensitivity of various printing plates. The silver salt plate has a high sensitivity. In the Agfa Galileo Vs and VXT platemaking systems equipped with a violet laser source, the scanner is at 37500 r/min or 55000 r/min. Under high-speed rotation, 17 to 22 plates can be produced per hour. In the Galileo Thermal and Thermal S platemaking systems using 1064nm wavelength Nd:YAG lasers, the scanner rotation speed is 16000r/min or 24000r/min. For the lower sensitivity thermal plate making, only 8 to 8 per hour can be achieved. 12 plates of plate making.
Table 1 Average Sensitivity of Traditional Plates or CTP Plates

The speed of rotation of the scanner can no longer be increased without using other special methods. However, the imaging process of each pixel on the plate requires a certain amount of time, and this problem can only be solved by using a more energy (and more expensive) laser light source. In the fast CTP platemaking system, the rotational speed of the outer drum platemaking system can only reach 1000 r/min, which is too slow. Therefore, it is necessary to use multiple laser light sources to make plates or split the laser beam into several beams, so as to obtain higher laser platemaking efficiency.
Third, the current status of CTP plates Table 2 (slightly) lists the current CTP plates that are currently in use. The plates exposed in the visible spectrum and in safe light (yellow light for violet laser light sources) can be classified into high-sensitivity silver salt plates and polymer plates. All thermal plates are light exposure plates. Thermal plates are divided into wash-type thermal plates and cross-linked plates, which are the same as traditional negative plates and positive plates. The Dtp830 thermal plate from Kodak Polychrom Graphics was exposed to 140°C in a special preheater to ensure adequate cross-linking of the polymer. In non-flushing thermal plates, whether the polymer is ablated or phase change determines the type of thermal plate.
In the case of water offset printing, the polymer on the ablation type printing plate is composed of a hydrophilic layer, and in the dry offset printing, the polymer on the printing plate is composed of an ink repellent layer. Underneath this layer is a layer of ink, which ablates the upper polymer material and allows the ink to contact the underlying ink-receptive layer that represents the image portion. Agfa's Mistral plate used in the Calileo Talant system is a method of ablation of non-image parts, and the ablation must be removed, which is extremely simple in the outer drum laser platemaking system. A special vacuum system must be used to remove the ablated material in the inner drum type Calileo Talant laser platemaking system.
People are very interested in polymerizing phase change printing plates. Although such printing plates are relatively expensive and the cost of printing plates is approximately double that of traditional printing plates, manufacturers are still focusing their attention on process-free printing plates and pricing their prices. Less than twice the price of traditional plates.
IV. Characteristics of the violet laser light source and the infrared laser light source The violet laser light source is suitable for the inner drum type or platform type laser plate making system, but it does not mean that it can replace the outer drum type laser plate making system equipped with an infrared laser light source. The following are the characteristics of the violet laser light source, the infrared laser light source, and the corresponding laser platemaking system.
Internal drum and flatbed laser platemaking system with violet laser source:
· The stability of the printing plate during the plate making process;
Single light source can ensure higher plate-making precision;
Long lamp life, no maintenance;
·Using a single optical component, beam focusing degree is good;
· Using a single data channel, the electronic control signal is not easy to lose;
· Puncture on inner drum or flatbed laser platemakers, the operation is very simple;
· The eight-plate version takes only about 2 minutes;
• Agfa Lithostar Uitra LAP-V Silver Salt plate can be used.
Outer drum laser platemaking system with infrared laser source:
• No need for expensive optical systems to position the light source on the plate;
· Multi-beam laser plate making for high productivity with slow rotation of the drum;
· Can replace single light source, reduce the cost of replacement;
Long lamp life, no maintenance;
· Even if individual light sources are damaged, the entire system will work as usual;
Real light room operation
· The same technology as CTPress;
· Can use plates produced by all plate manufacturers;
New and higher-sensitivity plates increase plate-making productivity;
· Printing plate printing plate after the printing rate of up to 1 million India;
·Manual operation using the same chemical treatment as traditional printing plates