Newspaper and Purple Laser CTP Technology

Since the drupa printing trade show in Germany in 1995, the computer-to-plate (CTP) technology was launched. In a short time of more than ten years, the CTP system has been rapidly popularized in the world. Now, the application of the CTP system in developed countries and regions such as the United States, Western Europe, and Japan has accounted for more than 50% of all printing plate making processes, and some places have reached 60% to 70%. By the end of 2005, more than 400 CTP systems have been put into use in China, mainly in the Yangtze River Delta, the Pearl River Delta, and municipalities directly under the central government, as well as in inland capital cities. The development space is very large.

First, the violet laser CTP - after the laser direct plate making star

1. Purple laser development and CTP platesetter In 1996, Nichia Corporation of Japan developed a 400-410nm InGaM crystal violet laser diode, which was originally developed to further increase the storage capacity of DVD discs. Due to its shorter wavelength, the light is focused. The smaller the size, the same size of the disc is 40 times more than ordinary CD, 6 to 7 times the average home DVD disc, but the laser power applied to the DVD is very small. With the continuous expansion of laser power, purple laser diodes with a lifetime of more than 3,000 hours in 1999 were introduced. In May 2000, the CTP platemaking system began to use a violet laser, initially only 5 mW, and it was only able to expose the silver salt CTP plate. In 2001, when a plate-making machine used a 15 mW violet laser, it was possible to expose high-sensitivity photopolymer plates, but the platemaking speed was slow. In 2002, the 30 mW violet laser diode appeared and was applied to the CTP platemaking system. At this time, it has been able to rapidly make plates and the advantages of the violet laser CTP plate making system have appeared. In drupa2004, the violet laser CTP has become a big show. Agfa, Fuji, Heidelberg, Esko-Graphic, Escher-Grad, ECRM, Highwater, Krause and other companies have introduced violet laser CTP devices with power of 30 to 60 mW. After 2005, with the advent of 60 mW, 100 mW or even higher power lasers, violet laser CTP technology is even more powerful. Especially for newspapers with high requirements for plate speed and quality stability, the violet laser CTP plate making system is favored. On the other hand, the increase in the power of the platesetter will reduce the reliance on high-sensitivity CTP plates, making it possible to mass-produce medium-sensitivity violet laser CTP plates. This has also become a strong backing for the rapid promotion of violet laser CTP technology. China's surge in the installed capacity of the violet laser CTP platesetter in the newspaper industry last year also fully demonstrated that the violet laser CTP is a rising star in laser direct plate making.

2. Features of violet laser CTP technology (1) Brighter operating environment (2) Small laser spot, high resolution (3) Small size, easy maintenance and replacement (4) Fast speed (5) Stable quality (6) Long service life

Second, violet laser CTP equipment
1. Equipment characteristics

Because of the small size of the laser, the violet laser CTP device usually uses an internal drum imaging structure. It is a drum that supports the printing plate, and the printing plate is fixed at a fixed position on the inner contour. During exposure, the acousto-optic modulator modulates the continuous laser beam generated by the laser light source based on the light and dark features of the image information in the computer. The modulated laser beam is first irradiated to the rotating mirror. As the mirror rotates, the laser beam is refracted onto the roller to form an exposure image. Adjust the focus can change the diameter of the laser beam, so as to get different degrees of resolution; adjust the speed of the mirror, you can adjust the exposure time. The advantages of this plate making method are:

(1) Scan faster. Because the violet laser is a short-wavelength laser with a wavelength of 400-410 nm, and the shorter the wavelength, the higher the energy is. Therefore, the violet laser has a higher imaging speed than other common CTP light sources such as a green laser and a red laser. The scanning speed of the violet laser can reach 55,000 lines/minute, which is equivalent to a 2400 dpi resolution to complete a split-screen scan in 1 minute and 46 seconds.

(2) Higher accuracy. The shorter wavelength light also has another characteristic, namely the laser light spot will be finer, and can scan more fine 250 lpi (1% to 98%) dot.

(3) Close to bright room operation. The violet laser plate-making system can be operated under a yellow safety light, providing the operator with a brighter working environment and making the operation more convenient.

(4) Longer life. The violet laser life of the current violet laser platemaking machine can already reach about 5 000 h. Since its working principle is start-up, it only needs to be exposed when the laser is started, usually in the closed state, without preheating stability that can produce a stable laser value, so the overall service life is longer, generally 4.5 to 5 Year (related to workload).

(5) The price is cheaper. Since the violet laser is also widely used in other work, such as making DVD discs, automobile manufacturing, etc., it has a lower price. In addition, single beam laser heads can also be used, making the violet laser CTP platemaking equipment relatively inexpensive.

(6) Others. Such as the upper and lower version is convenient, can support a variety of punching specifications and so on.

2. Domestic and foreign equipment manufacturers and brands Since the introduction of the purple laser in the CTP plate-making system in May 2000, more than 20 plate-making machine manufacturers worldwide have sold violet laser CTP platesetters to the market. At present, violet laser CTP devices commonly use violet laser diodes with power of 30 to 60 mW and a wavelength of 405 to 410 nm. Since drupa2004, models have higher precision and more types.
Table 1 lists the products and performance of the main manufacturers of violet laser CTP equipment.