General overview of CD printing technology
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1 CD printing technology
2 quality control points
2.1 CD printing points 2.2 Selection and testing of CD printing consumables 2.3 Production quality of film 2.4 Working environment 2.5 White background
3 common problems and solutions
3.1 Printing Electrostatic Problems 3.2 Disc Warping Problem 3.3 Proofing Lack of Standard 3.4 Mixing Phenomenon
1 CD printing technology
In the past, most of the color graphics on the disc were done using a screen printing process. However, in recent years, with the continuous development of optical disc technology, the application of DVD disc products has become more and more extensive, and the quality of decorative quality of disc discs is getting higher and higher. In order to cater to this market development trend, while ensuring the playback function of optical disc products and higher sound and painting quality requirements, waterless offset printing (in most cases, screen printing combined with waterless offset printing) has become an emerging optical disc printing technology. .
2 quality control points
CD printing points
Due to the difference in substrates, there are many essential differences between optical disc printing and traditional paper media printing. But in fact, CD printing is not as complicated as traditional paper media printing. As long as you master the quality control activities, you can print products that satisfy customers. Most technicians believe that controlling the following factors is critical to improving the quality of CD-ROM printing, and introduces their own experience for these links.
Selection and testing of optical disc printing consumables
(1) Special UV ink
1UV screen printing ink
The UV screen printing ink for optical disc printing requires high saturation, good transparency, good thixotropy, and fine and uniform ink particles. To ensure that the ink pigment particles pass through the mesh smoothly, the particle size should be 1/ of the mesh. 4 to 1/3. Adobe ink for CD and VCD type disc printing, in addition to the above requirements, should also have good adhesion to PC (polycarbonate) materials. The UV ink used for DVD-type disc printing has a small degree of shrinkage during UV curing; and the ink layer is thin and uniform to minimize the effect on the flatness and high definition of the DVD during UV ink curing.
2UV waterless offset ink
UV water-free offset printing ink for optical disc printing requires high transparency, fine pigment particles, elegant color, strong coloring power, the viscosity of the ink should not be too small, the thixotropy should not be too large, the yield value should not be too high, and the rheology should be good.
In addition to the basic performance requirements of special UV inks, there are many artificial regulations in the printing of optical discs. When processing a single optical disc (such as a printer, digital camera, scanner, etc.), the ink used by the optical disc printing enterprise must meet the international environmental protection requirements, that is, obtain the corresponding green environmental protection certificate, and the product printed with the ink. In order to enter the international market.
(2) UV curing device
The core component of the UV curing device is the UV lamp and reflector cover book printing. The function of the device is to cure the ink on the surface of the disk by the irradiation of the UV lamp. This device is very critical in optical disc printing equipment. The UV-curing device is provided after each color group on the special screen printing machine for the optical disc, and the special offset printing machine for the optical disc is only equipped with a set of UV curing devices after the 4-color printing. The spectral characteristics of the color management UV lamp must match the spectral characteristics of the ink, otherwise it will affect the dryness of the UV ink on the surface of the disc, resulting in quality problems such as ink shedding.
(3) scraper, blanket and tray gasket
The quality of the scraper and the tray gasket plays an important role in whether the screen printing is flat or not. The quality of blankets and tray gaskets is closely related to the quality of waterless offset printing. Because in the waterless offset printing, the graphic is transferred from the printing plate to the blanket, and finally transferred to the printing surface of the optical disc.
(4) Testing equipment
Detection is an indispensable part in high-quality optical disc printing. The general detection content is: detecting the color difference of the printed surface of the optical disc under a standard light source, and checking whether the spectral characteristics of the UV lamp and the UV ink are matched by a UV energy detector. . At present, the commonly used testing equipment in optical disc printing includes standard light source, electronic calculation equation oil adjustment scale, UV energy detector, ID code inspection machine and the like. There are also some professional testing equipment equipped on the printing equipment for online real-time monitoring, such as Papageno, Basler disc detection system, in which Papageno disc detection system is used to check the disc printing surface for defects, Basler disc detection system is used to check the disc. The information surface has the correctness of the defect and the core number.
Film production quality
At present, domestic CD-ROM printing has not introduced CTP (computer-to-plate) technology. Therefore, the pre-press link still uses the traditional plate-making method. If the customer provides electronic paper packaging, the laser will be used to output the film, so the quality of the film will directly affect the final print quality of the disc. Prepress staff should make appropriate adjustments and treatments depending on the printing method used.
The number of screen lines for screen printing is controlled below 133 lines/inch, the reproduction range of dot tone is 10% to 90%, the line width of text and thin lines is not less than 50μm; the number of screen lines for film for waterless offset printing The control is within 200 lines/inch, and the dot tone reproduction range is 2% to 98%.
In order to ensure the quality of the production, some specific requirements have been put forward on the film provided by the customer (for example, screen printing).
1 film requirements are Zhengyang tablets Litong, the film is on.
2 The main pattern of characters or scenery and some non-solid patterns with dark and light colors, the number of screen lines should be controlled at 80-120 lines/inch.
3 The printed graphic must be in the range of 117 mm in outer ring diameter and 20 mm in inner ring diameter.
4 There should be an alignment crosshair on each film, and it must be marked outwards at a distance of 3mm from the outer diameter of the disc (ie 126mm in diameter) with a tolerance of 0.1mm. The alignment line is on the center of the pattern. The lower, left and right positions, the alignment line length is 15mm, and the width is 0.1mm, as shown in Figure 1.
5 Attach the number of the plate number and the printed color (PANTONE color number) or the C, M, Y, and K color marks to the film surface.
working environment
Reasonable control of the working environment temperature, humidity and cleanliness can not only reduce the printing of dirty spots, but also reduce the printing static electricity produced by the printing and packaging city, 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 the temperature, humidity and cleanliness.
Playing white
In recent years, rubber products, domestic strong optical disc manufacturers have launched a combination of screen printing and waterless offset printing equipment, first with screen printing white background, then four-color offset printing and UV curing are in one printing Completed on board, thus taking advantage of 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 white standard and certification. 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, a special white ink is used to make a white background before printing.
3 common problems and solutions
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 and the optical disc are fully 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 on the surface of the optical disc. Leave a black dot.
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, controlling the temperature and humidity supply 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.
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, but also causes the disc to warp and even destroy the information of the disc itself. 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 UV curing process 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, achieve "low shrinkage". In screen printing, since the printing ink layer is relatively thick, the shrinkage phenomenon is also serious. 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 of the offset printing machine, the printing pressure of the offset printing press should be appropriately adjusted before the official printing of the optical disc. In the first step, before the ink roller is not inked, let the roller press the CTP for about half an hour, then beat the ink on the ink roller and then drop the ink roller to keep the 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 for security printing, the printing pressure should be appropriately increased during debugging. The third step is to debug the printing speed.
Proof of lack of standards
In production, optical disc printing companies generally provide prints to customers for their signature confirmation. Some people reflect digital printing, and the process of confirming proofs with customers is very cumbersome and time consuming. Because there is no objective standard, there is a phenomenon that occurs. It is understood that in the actual production of digital printing and post-press processing, the original materials delivered by customers are in various forms. Some customers provide samples, some provide film, and some provide electronic documents. Layout design Faced with this complex situation, CD manufacturers can only make appropriate adjustments according to their production habits in accordance with the customer's draft, until the customer is satisfied.
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 design of the optical disc 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, we should 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, we guarantee that only one machine will be placed on the machine during printing. Put a variety of discs. In addition, if the test disc is mixed in the finished product, the trial disc is directly scrapped.
A high-quality CD-printing product network publishing is inseparable from the experience of the operators and the management's checks on the production process.
4 disc digital printing technology
CD digital printing technology - CD printing machine, can replace traditional printing equipment such as silk screen, pad printing, transfer, etc., without plate making, no coloring, and higher printing quality than traditional methods, simple machine operation, stable performance, one-time imaging, Directly print color patterns, LOGO, and text on the surface of the disc without the need for plate making, filming, and drying. Now the mainstream format of A3/A2 can meet the needs of CD-ROM small and medium-sized disc printing. Due to its free and flexible digital printing output mode, it is widely favored by some small and medium-sized disc manufacturers, eliminating the need for small screen printing cost and slow speed. The complicated process.
Disc screen printing technology
Screen printing can print pictures on the paint layer of the disc, which is strong and scratch resistant, and has good waterproof performance.
The reprint of the picture can be up to eight colors, but it also depends on the ability of the duplicator to print the label. It converts the image into a perforated web, and the ink is attached to the disc through the web, a process similar to wax paper printing.
Screen printing has proven to be the most effective way of disc printing, with 90% of disc printing being screen printed. Screen printing is available in a wide range of applications, from monochrome text and image printing to four-color printing.
The main development of screen printing is to obtain a thinner wire diameter, thereby reducing the ink and film thickness, and the automatic screen coating process can obtain a thinner film thickness and finer dot resolution.
In the field of screen printing of optical discs, the basic coating of white ink is very important, and it is also the basic coating of waterless offset printing. So we tested different formulations of white oil between the two layers using a 140/34 mesh. Using improved white inks in silk screens, we can see that printed discs do not meet specifications quickly before the climate test.
Note: We all use A-class disc printing, the damage rate can be controlled within 0.03%, if there is normal damage, we will unconditionally replace!
5 CD screen printing static elimination
What is static electricity? From an atomic point of view: Any neutral material, such as plastic, paper, etc., is the positively charged nuclei in each atom and the negatively charged electron cloud in the surrounding, when the material passes through the friction After the contacts are separated, the electrons in the insulating material are released to the surface of the material.
Printing, especially in screen printing, often occurs when the web template is ejected from the substrate, and the ink in the pattern portion of the screen is also pulled up and floated from the substrate with the fluffy "spider". When the screen continues to rise, the "spider" drifts on the substrate before and after the wind drifts, making the surface of the substrate dirty and the edges of the pattern not sharp. This phenomenon is very annoying and is not desired to be seen by any printer. This is an electrostatic phenomenon.
What is the static electricity? From an atomic point of view: any neutral material, such as plastic, paper, etc., is the positively charged nucleus in each atom and the negatively charged electron cloud in the surrounding, when the material passes After the frictional contact is separated, the electrons in the insulating material are released to the surface of the material. For example, in the middle school physics, the glass rod is rubbed with silk, and static electricity generated on the glass rod can suck up the paper scraps. The surface of the electron-reduced material is positively charged, and the surface of the material with excess electrons added by electrons is negatively charged. If the material with reduced electrons is supplemented with negative electricity and the material with increased electrons is positively charged, then the positive and negative charges of the two materials are balanced. Then the two materials are neutral.
In optical disc printing, so-called screen printing is a process in which ink is transferred to a substrate by a relative movement of the screen and the squeegee under a certain scraping pressure. The screen (screen) and the squeegee (polyurethane squeegee) are all insulators. In the silk screen, they are relatively scraped and rubbed at the position, especially in low humidity, which will cause static electricity to affect the surface charge of the substrate. Distribution status. In particular, insulating materials, such as PC substrates for optical discs, PET sheets for touch-opening, and PVC for use in name and sign, PP, PE for plastic bottles, etc., are basically insulators, and they are not noticed in screen printing operations. Static electricity will be produced. For example, when the screen printing film switch is decorated with ink, since the PET film base is coated on the surface, a surface of PVC or the like is coated with a self-adhesive film to protect the surface.