The turn of the century was a period of rapid rise and development of CTP technology in the printing industry. Especially between 1995 and 2000, direct-to-plate-making machines suitable for sensitization by various laser light sources appeared one after another. Once the plate problem of the development of CTP technology was solved, the world number of CTP systems adopted in the scope has increased dramatically. The number originally expected to reach 5,000 sets by 2000 has now been achieved and exceeded. However, the development speed of CTP in our country is still very slow. There may be many reasons for this, mainly the following two points.
First, the electronic separation and phototypesetting plate making processes that have been formed over many years have become very mature and can produce excellent products; second, there are many types of CTP equipment and plates, making it difficult for people to distinguish which equipment and plates are more suitable for the moment. Future development and large investments make people have a waiting mentality, and this process of analysis and identification is necessary.
Adopting a CTP system does require certain conditions. From the perspective of business operators, the following considerations should be taken: First, whether the company has a large amount of plate making workload. Today's better CTP plate making equipment has a very fast publishing speed. How to ensure the live source? Adequacy is a big problem; secondly, the number of films and plates used by the enterprise should be relatively large, so the extent of saving film and time will be relatively large. If there are more short-run jobs, the CTP system will have more advantages. On the contrary, if most of the prints are more than 100,000 copies, the advantages of CTP equipment will not be obvious. Thirdly, the CTP system still needs the support of other hardware. For example, if digital proofing equipment is used to replace traditional proofing equipment, there should be a certain number of single proofing equipment. Sheet paper multi-color offset printing machine or offset printing rotary printing machine above half, etc. These conditions are not difficult for domestic newspapers and printing plants with advanced equipment. As long as an initial investment is spent, it is still easy to implement the CTP system. However, users are more concerned about the selection and stable supply of CTP plates. With CTP plates of stable quality and acceptable price, the development of CTP technology applications will have a reliable foundation. This article discusses some views on the development of existing CTP plates.
The adaptability of the photosensitive layer of CTP plate to the laser spectrum wavelength range
The emergence of a new technology is often the continuation and development of the old process, and eventually it mutates and completely replaces the original technology. The same is true for CTP plates. Initially, most laser light sources were in the visible to infrared range, and it was difficult for the photosensitive layer of the PS plate to move from the ultraviolet region to the long-wavelength region. Therefore, the earliest applied CTP plate was a double-layer composite version. It is to coat the existing PS plate photosensitive layer with a silver salt photosensitive layer, so that the resulting printing plate can be easily scanned by a general laser light source. After the silver salt development process, an ultraviolet light source is applied to expose the underlying resin photosensitive layer. , and the printing plate is obtained after redevelopment. Although this method can achieve the purpose of laser plate making, its two exposures and two developments do not show the advantages of laser plate making. On the surface, this method seems to remove the film, but it only removes the silver salt photosensitive layer. It is added to the coating of the original PS plate, so this method is the initial transition stage of CTP plate.
The biggest difference between the photosensitivity mechanism of the CTP system and that of the PS plate is that the PS plate is exposed using an ultraviolet point light source. In addition to direct irradiation, there is also scattered and refracted light during printing. The loss of light energy is very large, while the laser plate making system Most laser light sources are monochromatic light, generally choosing one wavelength or a range of wavelengths. This is where laser platemaking equipment is advanced. With the development of science and technology and the improvement of lasers, we have more and more choices for CTP systems. The spectral region of the current laser light source can range from 350nm to 1200nm, which means from the ultraviolet light region to the visible light There are corresponding laser equipment available in the region (blue-violet light to red light), all the way to the infrared spectrum region, which also makes the choice of laser plates more extensive. Considering the operating environment, in the photographic plate making and electronic stage, people have been working in darkrooms for a long time. People are very willing to use the development of CTP technology to obtain a new environment of white light or yellow light, such as ultraviolet laser plate making machine, violet laser plate making machine and far infrared plate making machine. Laser plate making machines have greater development advantages. Therefore, photopolymer printing plates and thermal printing plates were welcomed as soon as they came out. Especially at the Drupa 2000 exhibition, the ultraviolet laser plate making equipment on display aroused great interest among professionals. From this, we can see that the use of The traditional PS version is expected to achieve the purpose of laser plate making. For example, Purup-Eskofot's Dicon high-speed ultraviolet laser equipment uses a mercury lamp source, which emits light in the ultraviolet and blue-violet light regions. Its equipment can decompose ultraviolet light into multiple beams of light, and then passes through optical fibers. Passed to the printing plate, this is not much different from the conventional PS plate exposure range. To apply this system, you only need to add an ultraviolet CTP plate making machine to the traditional printing plate process. The technical content of the CTP system is completed with almost no major changes in the process method.
High resolution and low power exposure function of CTP plate
Producing fine color prints requires high plate materials, which must have the characteristics of high sensitivity, high resolution, strong dot reduction, and good printing performance. To achieve high resolution, the plate is required to have high contrast properties, and the degree of mutation before and after exposure must be obvious, so that it is easy to produce a good printing plate. The laser system can concentrate the light energy on a specific wavelength and output it in parallel light, which provides good conditions for exposure. And because the output resolution of the plate making machine is greater than 2000dpi, it is not difficult to achieve it, and the CTP plate currently used Whether it is a heat-sensitive plate, a silver salt diffusion plate, a silver salt emulsion and polymer composite plate or a photopolymerized resin plate, they all have good resolution performance and can reach printing lines of 60 lines/cm, 75 lines/cm or even higher. Counting won't be a big problem. Among them, thermal plate imaging technology is more attractive. It absorbs infrared light and converts it into heat energy, causing the photosensitive layer to change. The layout will not change before reaching a certain temperature. When it reaches a certain temperature, the photosensitive layer will be sensitized or ablated in an instant, and the contrast effect will be more prominent. The edge effect of the dots will be very small, unlike ordinary PS. During the printing process, the dots are deformed due to improper vacuuming or the intrusion of scattered light.
The use of CTP system can effectively increase the speed of plate making. Now many laser direct plate making machines can output 20 to 30 folio plates per hour. This requires faster sensitization of the photosensitive layer and the use of light energy for exposure. It should be relatively low to achieve a high-sensitivity effect. Judging from the current sensitivity of CTP, it has been greatly improved.
Huida Print-All Technology company is an advanced and professional manufacturer of producing printing plates, mainly sales CTP, CTCP, and PS plates as well as offering ODM/OEMs, especially for the offset. For more information, please click the official website link here: https://www.huidaoffsetplate.com/.