Computer-to-plate Introduction

Computer-to-plate (CTP) technology appeared in the 1880s. This period is the initial stage of the study of direct plate-making technology. Therefore, during this period, neither the technology nor the quality of the platemaking industry was very mature. In the 1990s, the close cooperation between equipment manufacturers and printing manufacturers accelerated the pace of research and development of this technology, and reached a level of maturity and industrialization during this period. Thus, at the drupa printing exhibition in 1995, 42 kinds of CTP systems were exhibited. This move immediately caused the printing industry to pay close attention to this technology. Between 1995 and 1997, many large-scale printing companies adopted the CTP system to implement the direct plate-making process. However, since the platesetter was still very expensive during this period, the use of the technology in various SMEs was limited. Promotion. During the period from 1997 to 1998, the price of direct plate-making machines drastically decreased, and the plates for direct platemaking began to mature and develop. Therefore, a large number of small- and medium-sized printing factories began to accept and use CTP technology. For the case of the printing factory, the developed machine format includes two pairs of open, eight open, and 16 open. According to statistics, in the United States by 1997, 65% of the large-scale printing companies (employees in more than 100) used CTP technology. According to the survey of the US printing technology authority GATF, from 1995 to 2000, the number of CTP systems installed and expected to be installed worldwide is as follows (including the CTP system used by the newspaper printing industry, including 8 on, off, and on) :

1995 1996 1997 1998 1999 2000
311 721 1686 3100 6200 12150

From this set of data, the speed of application of CTP is growing at a rate that is more than doubled every year. During the three years from 1995 to 1998, the growth rate was as high as 10 times.

The reason why CTP system can be popularized in the user group at such an astonishing speed, besides its good plate-making performance and the elimination of the advantages of film application, the expansion of the application scope of CTP technology is also one of the main reasons. At present, the direct plate-making machine on the market can be suitable for large-format, small-format printing size, single and double-color printing and four-color printing, newspaper printing and commercial printing and other needs. Therefore, it is very flexible to use. Moreover, in recent years, the speed of development and improvement of plates has also been rapid. The sharp decline in the price of CTP equipment within five years has promoted the rise and development of the market. At present, the 8 boot has been reduced from the previous $400,000 to between $150,000-$200,000. The boot model has also been reduced to approximately $400,000.

US opinion polls: CTP is an unavoidable technological revolution that will replace photocopying technology, just as it was when an extension was replaced by an imagesetter five years ago. At the NEXPO98 exhibition organized by the American Press Association in June 1998, a total of 11 companies exhibited their respective CTP systems. However, none of the influential manufacturers introduced new laser imagesetters and related technologies. This fully shows that all manufacturers are no longer hesitant about CTP technology and have entered a practical stage.

Classification of CTP Platesetters Currently, CTP platesetters are generally classified into inner drums, outer drums, flat plates, and curved lines. Among these four types, the most used are the inner drum and the outer drum type; the flat panel type is mainly used for large format plates such as newspapers; and the curved type is rarely used. According to statistics, of the 58 CTP machines provided by 29 manufacturers in 1997, there were 24 internal drums, 16 external drums, 9 flat plates, and 9 curved lines. In these forms, the external drum gradually shows the mainstream trend.

Loading mode According to the degree of automation, the loading mode can be divided into manual and automatic. Manually on the version of the machine is cheap, but generally requires a darkroom operation, so the efficiency is lower; and automatic version of the equipment, work efficiency, but the price is more expensive, generally more expensive than the manual model 100,000 US dollars . Moreover, when the automatic device is in the upper version, it must use a full-size plate with a release paper. There is a layer of light protection film on the surface of the plate, so it can be operated in bright room. In the upper version, it is possible to automatically peel off the protective film on the surface of the printing plate by means of a plate feeder so that the plate material can participate in plate making.

The fixing method of the plate material on the drum includes: full adsorption type and middle adsorption, and two types of clamping are fixed at the end and end. There is no limit to the size of the plate for full adsorption, and the size of the plate for the clip type must be fixed. 30% of CTP equipment with punching device, the general punching process after exposure, this can ensure that the printing plate in the printing press precise positioning, reduce the pre-press preparation time for the printing roller adjustment, improve the printing quality and overprint ,positioning accuracy.

The printing plate used in the printing size CTP machine generally has a special large-format printing plate with a size of 66*84 inches according to the requirements of the printing format and equipment; the large-format printing plate has a size of 55*67 inches; the medium-sized printing plate has a size of 41. Inch, 32 inch, 22 inch three; small format plate, size less than 18 inches. The most used ones are medium format and small format.

The suppliers of major equipment suppliers for CTP equipment are mostly from the United States, as well as companies established by Germany and Japan in the United States. The suppliers of large-format equipment include Agfa, Barco, Creo, Heidelberg, Gerber, ECRM, Optronics, Saiten U.S. Prepress, U.S. Screen, etc.; medium and small format manufacturers include: PrintWare, DuPont, etc. Many. Providing equipment dedicated to newspapers includes Creo, Krause and others.

The basic working principle of CTP The CTP direct plate making machine consists of three parts: precise and complex optical system, circuit system, and mechanical system. The single-beam original laser generated by the laser is split into multiple beams (usually 200-500 beams) through multiple optical fibers or a complex high-speed rotating optical splitting beam system. Each beam of light is transmitted through an acousto-optic modulator. The bright and dark features of the image information in the computer modulate the light and dark changes of the laser beam to become controlled light beams. After focusing, several hundred micro lasers are directly shot onto the surface of the printing plate to perform engraving work. After scanning and engraving, latent images are formed on the printing plate. After development, the image information on the computer screen is restored on the plate for direct printing by the offset press. The diameter of each micro laser beam and the light intensity distribution of the beam determine the sharpness and resolution of the latent image formed on the plate. The smaller the beam spot, the closer the light intensity distribution of the beam is to the rectangle (ideal case), the higher the clarity of the latent image. The scanning accuracy depends on the mechanical and electronic control parts of the system. The number of laser microbeams determines the length of the scan time. The greater the number of microbeams, the shorter the time for etching one plate. At present, the beam diameter has been developed to 4.6 micrometers, which is equivalent to the printing accuracy of 600lpi. The number of beams can reach 500. The etching time of a pair of printing plates can be completed in 3 minutes. On the other hand, the higher the output power and the energy density of the plate beam (laser energy per unit area, in joules/cm2), the faster the etching rate. However, too high power also has the negative effect of shortening the working life of the laser and reducing the beam distribution quality.

The source of the platemaking machine includes: gas laser (argon ion laser 488nm, power: about 20mw); solid laser (FD YAG 532nm, 100mw or more); semiconductor laser (LD, infrared semiconductor laser in semiconductor laser has low power, long life advantages .)

The plate making system is a comprehensive multidisciplinary technology industry. It includes precision machinery and optical technology, electronic technology, color digital image technology, computer and software technology, new type plate and material technology, automation technology and network technology. The automatic production system is yet another major technological revolution in the contemporary printing industry.

The development trend of CTP is surging. From the end of 1990-1996, there were more than 300 patent articles published. In 1996, 55.3% of the 100 largest printing companies in the United States used CTP systems, and 28.8% used color short-run digital printing systems. Yangcheng Evening News In April 1998, Agfa's flat CTP platesetter and Fang's Optronics Drum CTP were tested in the "New Express" section. Since 1985, most newspapers and printing factories in mainland China have adopted laser photocopying and offset printing. The next step of technological transformation of these financially powerful newspapers and printing houses is direct plate making, color newspapers, and high-end color printing and packaging printing. Requires scanning of the web to be expanded to the side (740*510), and the printability of the media is from 300,000 to 500,000 impressions.

For newspaper printing, CTP saves manpower, improves quality, and reduces environmental pollution. And refine the optimized process, easy to set up a high degree of automation of the continuous production line. In terms of newspapers, the nationwide national newspaper has a high degree of prepress digitalization and advanced technology and equipment. Compared with foreign newspapers, there is no obvious difference. The domestic newspaper industry is facing fierce competition. The CTP system can save the entire publication stream for 30-50 minutes, so for the publication of evening newspapers in particular, the time for press release can be postponed by 30-50 minutes without changing the printing time. This is important for the news of the day. significance.

CTP system and technology have been taken as a development direction of China's printing and publishing industry, and have been listed in the national "Ninth Five-Year Plan" key scientific and technological projects. It is a typical high-tech, high-growth, high-return technology-intensive industry.

CTP system requirements When using CTP systems, first of all, pay attention to the interface technology with the front-end system, namely: the data exchange technology between the color prepress processing system, and the completion of the data back-end equipment technology. For large-capacity files, data exchange speed and data transmission speed are of utmost importance. Secondly, companies are required to establish a complete set of new electronic document management systems, improve data preservation and retrieval technologies, and then apply color management technologies and RIP technologies. The requirements are also very important. Large-capacity files require RIP's powerful processing capabilities to achieve efficient work efficiency. For the consistency of proofing and output, it is necessary to participate in color management technology. When purchasing CTP, users need to make detailed system argument analysis and make decisions based on their own needs. The new technology system should not be required to match with the old workflow. It should be considered comprehensively: comprehensive benefits, maintenance workload, consumables prices and supply sources; the system must be open, and the technology used may be upgraded.

Performance description of CTP platesetter for newspapers K&F and Krause:
The LaserExpress Direct Plate System is the fastest and most flexible CTP system available, with up to 200 full-sheet (or 200 duplex) plates per hour at a production speed of 1016 dpi, and up to 150 sheets at 1270 dpi. /hour. The print format can take into account all the dimensions of the current newspaper. Automatic plate-up and unloading, auto-removal of plate stocks. After exposure, the developed plate is sent to the K&F plate for punching and bending functions. The available plate material is Agfa's SilverLith SDB silver salt diffusion plate; the photopolymer CTP plate can also be used. material. Both plates are sensitive to the wavelength of 532nm, but there is still a certain distance from the competitive thermal imaging plates under high-speed production conditions.

Krause:
Design Star2000 series CTP platesetter, can be used for thermal plate making mode, the light source includes: visible light, and red