Second, waterless offset
In the past two years, mainland CD manufacturers have begun to introduce offset printing equipment on a large scale, which greatly replaces the potential of screen printing. According to incomplete statistics, Henderson and Guan Wei, two companies that produce offset printing equipment in Taiwan Province, sold more than 200 offset printing equipment in the mainland in 2004. The vast majority of waterless offset printing used in CD printing is carried out using the "four-color dry" method, which is mainly affected by the Japanese DIC offset printing press, because it uses a silicone-coated waterless version, using special UV ink (based on D, C inks), the printer has a strict temperature and humidity control system.
Offset printing on discs began around 1997. In fact, printing on optical disks (plastic materials) is very different from printing on paper. Therefore, offset printing currently used for optical disks is waterless offset printing, as shown in FIG. 4.
If color separation negatives and positives are used, negative and positive patterns are used for non-watermarked versions. At present, the non-watermark version used by the company is a TORAY negative type watermarkless version.
1. CD-free waterless printing features
CD-ROM waterless offset printing mainly has the following advantages.
(1) Bright colors, crispness, and consistency. As waterless offset printing plate production is more standardized, the degree of automation of the printing press is higher than screen printing. In large batch production, as long as the temperature and humidity are properly controlled, the consistency of the product can easily meet the requirements.
(2) The printing accuracy is high, and the dot gain is small, and the original design concept can be reproduced well. The number of screens for offset printing is generally 1,75 lines per inch, and the reproduction range of the screens is from 2% to 97%. The dot layering is particularly strong.
(3) The printing ink layer is thin, only 2-3 U m, its flatness is particularly good, ink shrinkage will not cause the warpage of the disc, especially suitable for DVD printing.
(4) The production of the waterless version is simple, the production preparation cycle is short, and the equipment operation is relatively simple, especially suitable for mass production.
In view of the above advantages, ASLJS, Samsung and other companies prefer to use this type of printing method for the production of optical discs.
The disadvantages are mainly the following aspects.
(1) The requirements for the printing operation environment are relatively high. The temperature at the printing site is required to be 20-25 C, and the relative humidity is 50%-60%. If the temperature is too low, the viscosity of the ink will increase, and failures such as uneven ink transfer will occur during production. If the temperature is too high, the ink will become thin, the printing dots will increase, the ink layer will become thin, and the color saturation will occur. Can not reach the requirements of the sample.
(2) The appearance quality of printed products is not easy to control. Because the viscosity of DIC ink is relatively large, it is easy to adhere dirt on the ink roller, printing plate, and blanket, and then transfer it to the disc, causing quality defects.
(3) When printing, it is necessary to adjust the color to meet the color requirements of the product through the test machine plate. Therefore, the production of the test machine plate is particularly large, which objectively affects the production efficiency and increases the production cost.
(4) The investment in equipment is relatively large. The price of the non-watermark version is much higher than that of the screen version. Silicone on the surface is easily worn out, repairing is relatively difficult, and scratching cannot be reused.
The waterless offset printing process mainly has no watermark version brush and blanket. The process flow is shown in Figure 5.
(to be continued)