Overview: The Origin and Introduction of CTP Technology

1, what is CTP

In general, CTP contains four meanings:

(1) Computer to plate: Directly from the computer to the plate, that is "offline direct plate." The earliest developments were made by photolithography, all using computer-controlled laser scanning imaging, followed by printing, fixing, and other processes. This technology eliminates the intermediate medium of film, allowing words and images to be directly converted into numbers, reducing the loss of quality and material consumption of intermediate processes. This is usually referred to as CTP.

(2) Computer to press: Directly from the computer to the press, that is "in the machine directly plate." The computer-controlled laser beam outputs the graphic information directly to the printing plate, which is mounted on the platen. This printing plate can only be used once, and it can record graphic information.

(3) Computer To Paper/Print: The computer goes directly to paper or print, ie direct printing technology. Manroland first introduced computer to print: "DICOweb rotary printing machine" DICOweb.

(4) Computer To proof: Computer directly out of proofs, color digital proofing.

2, the working principle of CTP

The CTP 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 bright and dark changes of the laser beam and then become controlled beams. After focusing, several hundred micro lasers directly hit the surface of the printing plate for engraving work. After scanning and engraving, the latent image of the image is 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 shape 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 sharpness 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 breakthrough in the contemporary printing industry.

Third, the history of the development of CTP technology

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) :

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.

US opinion polls: CTP is an unavoidable technology that will replace the photo-taking technology, just as an electric extension is replaced by an imagesetter.

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. At the drupa printing exhibition in 1995, 42 kinds of CTP systems were exhibited. On Drupa 2000, more than 90 direct plate-making systems and material manufacturers from around the world exhibited nearly 100 products. 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.

China uses CTP technology much later than abroad. In April 1998, Yangcheng Evening News, Agfa's flat CTP platesetter and Fang's Optronics Drum CTP were tested in the "New Express" section. China's first film-free CTP computer-to-platemaking system was successfully developed at the Boji Institute of Science and Technology in Shenyang. This is a high-tech achievement that the scientists and technicians have worked hard for more than a year. It fills a gap in China's printing and graphic arts industry.

Then from 2001 to 2003, digital process technology, color control technology, variable data printing technology, and network printing platform technology were all rapidly developed. During the four years, the prepress workflow and CTP technology have matured, and the products are extremely rich. Most of the products have been upgraded. “High performance, high speed” has become a clear sign of the third generation of color digital printing machines. What brings people is "the trouble of choice".

From Drupa's 2004 exposition in May 2004 we can see: Drupa 2004 "Shining Star" JDF control software has come to the fore. JDF is written in XML and built on top of PPF and PJTF. The application of XML language is an important feature of JDF, because the language makes JDF easily combined with the network for unlimited development. Obviously, JDF connects the existing printing production process system with the sales department's database, and thus achieves the goal of full automation throughout the entire process. The publisher's processes can also be automated with JDF. They no longer need to write paper and pen to write annoying orders, and they can track the progress and problems of printing at any time.

After that, from drupa 2004, as well as IPEX 2006 and 2006 China International Printing Exhibition, CTP's development direction will be: First, free processing of plates will become the future direction of development, and second, with the continuous development of purple laser diode technology, Purple laser CTP will gradually replace the thermal CTP, occupying the dominant position in the CTP market.