Precautions for pre-press design
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The pre-printing design of the optical disc is an important part of the optical disc printing process. Due to the special shape of the optical disc and only a part of the disc surface of the optical disc belongs to the printable area (as shown in the following figure), the pre-press design of the optical disc is special. In actual work, it is often the case that the artwork or film delivered by the customer does not meet the requirements for the printing of the disc, resulting in delays in production, increased scrap rate, and increased printing costs. Therefore, following the correct "prepress design and production guide", the art design manuscript that meets the requirements for CD printing is produced, which has been half successful for CD printing. This article will discuss the main points that should be noted in the design and production of pre-printed discs.
1, standard digital files
(1) Make sure that the image files, screen fonts, print fonts, and layout files are complete.
(2) All documents that need to be output must have color proofs.
(3) When the customer submits the output file to the printing house, the contents of the order of the output file should be printed out.
(4) According to the requirements, put the various elements of the artwork and the registration mark in the correct position.
(5) - Must be in accordance with the "Guide", cited in the center of the CD. The position of the disc stack and the printed outer edge is correctly set.
(6) For digital files, the image file format is recommended to be EPS or PostScript fonts.
2. working environment
Reasonable control of temperature, humidity and cleanliness of the working environment not only reduces the printing of dirty spots, but also reduces the generation of printing static electricity, especially in waterless offset printing. In order to ensure the quality of the disc, the general disc manufacturer specifies that the indoor temperature of the printing workshop is 24 °C ± 3 °C, the relative humidity is about 50%, and the air cleanliness is 100,000. Enterprises that have passed the international quality standard system certification will also regularly record temperature, humidity and cleanliness.
3. Playing white
In recent years, domestic powerful optical disc manufacturers have launched a combination of screen printing and waterless offset printing equipment, first using screen printing to make a white background, then four-color offset printing and UV curing are completed on a printing machine. , thus playing the respective advantages of screen printing and offset printing. At present, most of the optical disc printing equipment using the waterless offset printing process must first use screen printing to make a white background, such as Taiwan's Henderson, Crown Printing. An offset press produced by a supplier of optical disc printing equipment such as Lei Ming. In addition, the white background also has a covering effect on some defects in the production process. At present, the printing of DVD-type optical discs basically uses waterless offset printing. Since the ink layer is thin, in order to improve the adhesion of the surface of the optical disc to the ink, the white ink dedicated to the field before printing is also used to make a white background.
Two common problems and solutions
In the process of printing a disc, technicians often encounter various problems, and several common problems are listed below.
1. Printing static problem
The material of the disc is PC material, which is easy to generate static electricity during the printing process, and this phenomenon is very common in screen printing. In the screen printing process, due to the reciprocating motion of the squeegee, the mesh cloth and the optical disc are rubbed. In addition, the relative frictional movement of the squeegee and the optical disc also generates a large amount of static electricity, which eventually causes a sparking phenomenon, leaving black on the surface of the optical disc. point.
In response to this problem, the solutions of Guangdong Weiya and Zhaoqing Guosheng are very effective in removing static electricity. According to Mr. Fan Yichang of Weiya, Guangdong, under the premise that the temperature and humidity of the printing workshop are relatively constant, the static electricity can be effectively solved by removing the static electricity device such as a conductive brush. In addition, in the interview, the reporter learned that controlling the temperature and humidity of the turnover zone, adding a humidification system in the printing workshop or modifying the printing machine to remove the bar is also a good solution to this problem.
2. Disc warping problem
In fact, the printing pressure is not well adjusted, the ink selection is improper, the curing time and the curing temperature are not correct, which not only affects the printing quality of the optical disc, causes the warpage of the optical disc, and even destroys the information of the optical disc itself. In response to this phenomenon, Mr. Gong Yi, the workshop director of Guangdong Xinfeishi Laser Technology Co., Ltd., did the following analysis.
The material of the disc is made of PC material. If the printing pressure is too large, the PC material will be deformed. Some tiny distortions are invisible to the naked eye, but they change the digital information stored inside the disc. In particular, a DVD-type optical disc is formed by bonding two sheets with an adhesive, and when the printing pressure is too large, misalignment deformation occurs, which affects the quality of the optical disc.
If the ink is not properly selected, the shrinkage of the disc during the curing of the uV is too large, which may cause the disc to warp. The problem of disc quality caused by ink shrinkage has always been a concern of the industry, because once the disc shrinks excessively, it will not only affect the flatness of the disc, but also cause the professional equipment to be unable to focus when reading data. Therefore, it is required that the ink does not shrink or shrink to a small extent during the UV curing process, that is, achieves "low shrinkage. In screen printing,
Since the printing ink layer is relatively thick, the shrinkage phenomenon is also severe. Similarly, if the ink cures for too long and the ink cure temperature is too high, the disc will be deformed.
For the problem of warpage of the disc caused by excessive printing pressure on the offset press, Mr. Chen Deshan's suggestion is to make appropriate adjustments to the printing pressure of the offset press before the official printing of the disc. In the first step, before the ink roller is not inked, the roller is pressed and operated for about half an hour, and then the ink on the ink roller is evenly mixed and then dropped to the ink roller to maintain a uniform ink on the printing plate. The second step is to test and debug to determine a better printing pressure. Note that in order to maintain the amount of ink transferred on the disc, the printing pressure should be appropriately increased during debugging. The third step is to debug the printing speed.
3. Proof of lack of standards
in · Production. Optical disc printing companies generally provide prints to customers for their signature confirmation. In the interview, some respondents reported that the process of confirming the sample with the customer is very cumbersome and time consuming. Because there is no objective standard, the phenomenon of smashing occurs. It is understood that in actual production, the original materials delivered by customers are in various forms. Some customers provide samples, some provide film, and some provide electronic documents. Mr. Fan Weichang of Guangdong Weiya said: "Our special customers, such as Canon, Dell, Epson, etc., they are more concerned about the color of the finished CD-ROM (Dell's black, Epson's green), which symbolizes the company's own The image is part of the overall promotion, so they will provide the standard color and attach a square color to the sample as a comment, the color of the finished product must be within its established range of floats." Faced with this complicated status quo, CD manufacturers can only make appropriate adjustments according to their production habits in accordance with the customer's manuscript, until the customer is satisfied.
4. Mixed phenomenon
The mixing phenomenon mentioned here means that different types of optical discs will be mixed together after printing is completed or the A side and the B side of one type of optical disc are confused. This phenomenon occurs in the production of optical disc printing, which affects the production efficiency of optical discs and greatly increases the scrap rate. Of course, by detecting the disc ID code by a dedicated detecting device, the problem of the disc can be effectively solved. However, if we want to solve this problem fundamentally, the proposal of Mr. He Hongguang, the printing process engineer of Zhaoqing Guosheng Laser Technology Co., Ltd., is to standardize the operation behavior of the employees and the placement of materials to ensure the accuracy and reliability of the testing instruments. In the production process, only one type of disc is placed on one machine during printing. In addition, Mr. He also mentioned that if the trial printing disc is mixed in the finished product, the trial printing disc will be directly scrapped.
A high-quality CD-ROM printing product, from the experience of the operators, and the management of the production process. The bit of experience recorded in the interview above is just a drop in the sea of CD printing technology. There are still many things that we need to continue learning and learn from each other.