The chosen method of printing CDs is controlled by some key factors. These are as follows:
- How many CDs do you need to print?
- What is the intended use of the final product?
- Is the budget limited for the project?
- What work is intended for disks? Photographic images or color blocks?
Once these factors are considered, you can decide which CD printing process is best for your particular project.
Let's take a look at each of the processes in turn, their pros and cons.
Digital CD Printing
This method of printing CDs uses a printer that uses the same process as an inkjet printer that many home users are familiar with. In fact, many home printers can be equipped with a CD tray for use with prefabricated CDRs with a printed surface. Professional CD printing is most likely to use an inkjet printer specifically designed for CD printing. These printers have an automatic loading mechanism that allows you to automatically print up to 200 CDs. The printer automatically loads non-printable discs and unloads finished discs onto separate spindles.
Digital CD printing using one of these printers is slow, but there are no fixed installation costs. This is normal if the number of orders for disks is less than 100 or 200, if a fixed period is not set for the order.
This type of printing is capable of creating highly professional compact discs, since an inkjet printer can print with very high resolution. The printed surface needs to be protected, and a layer with a clear varnish must be applied to the discs in order to prevent moisture from entering the ink through processing or exposure to wet media. This need greatly increases the overall project time. There are printing discs that have a special shape, which become waterproof after printing, but they are more expensive than regular printing discs, and therefore the decision should be made depending on the urgency of the project; additional costs for waterproof discs or extra time for applying a layer of clear varnish?
CD printing
CD Screen printing is ideal for art projects that include solid areas of color. Screen printing is done using a rotating bed machine, which has 5 separate stations, where a different color of ink can be applied. CDs can have a base color that is applied first over the entire area of the disc, which means that the design of the printed CD on the screen can consist of a maximum of 6 different colors.
The ink used during the printing process on the CD screen is sensitive to ultraviolet radiation, and as each color is applied to the station, the disc moves under the UV lamp as it rotates around the next station. The UV lamp cures the ink, and it only requires a moment of exposure.
As the name of the process assumes that screen printing is applied using very thin mesh screens. In the design of works there is a separate screen for each color. To create a screen, a film is created in which there are areas where the ink is not applied to the disc, blacked out. The new screen is initially covered with thermal emulsion. The film and the screen are aligned one above the other using guide marks and placed in the exposure unit. When the screen is exposed to hot, bright light, the area of thermal emulsion that is not protected by the dark area on the film is cured. The screen is then washed with a water spray, and the areas of the uncured emulsion are rinsed to reveal the mesh.
Then the screen is fixed at its station. After all the screens have been prepared in this way, printing can begin. CDs are loaded onto the machine using an automated robotic system. They are placed in a roller that holds the disc tightly. At each station, ink is added on top of the mesh screen, and a rubber scraper blade extends from above, pressing the mesh down onto the surface of the disk and causing the ink to penetrate through the holes of the thin mesh and onto the surface of the disk. The ink drawing drawing takes about a second, and each station simultaneously applies ink to the disk as soon as the first 5 disks are fed into the system. This speed means that the screen printing machine can print more than 3,500 discs per hour, so large orders can be completed quickly.
However, there are significant fixed installation costs due to the requirements for screens and films. They can be reduced by limiting the art to fewer colors, and monochrome printing on a silver disc is the most cost-effective printing. Baseline costs mean that this CD printing process is truly viable for orders from more than 100 discs.
The printing process on the CD screen is capable of producing truly amazing CD printing with very high resolution thanks to the use of extremely thin mesh screens. However, it is not ideal for printing photographic images due to the presence of gradients of the color of sulfur in these images. What makes screen printing a truly unique process is the presence of fluorescent and metallic inks that can really add a WOW factor to your CD printout.
Lithographic (offset) printing CDs
This printing process is very different from screen printing, and the two presses are configured differently. The lithographic process takes advantage of the fact that ink and water do not mix, like oil and water.
The cover image is printed on a lithographic plate for printing CDs using a laser. The surface of the printing form is rough in texture and pre-coated with a thermally reactive emulsion.
The printing plates are processed using chemicals so that the exposed surface of the thermal emulsion can be removed from the printing plate. After the printing plate has been prepared, the area containing the cover image is made inks sensitive and water-repellent. Areas that should not be printed on a CD printing plate are designed to attract water, but not ink. Then the printing plates are collected on a rotating cylinder on a lithographic printer.
When the printing plate passes through each rotation, it passes through a set of rollers that apply water to the plate, water is attached to a rough surface, where ink is not applied to the disc.
Then the printing plate passes through the rollers as the ink is added. Ink is attracted to the smooth areas of the printing form. The cylinder, wrapped in a rubber blanket, then rolls over the plate and picks up the ink. The image of the CD cover is then transferred from the rubber blanket to a CD that is held securely in the metal roller. Again, this process happens very quickly, so that many parts of the process occur simultaneously, and many discs are printed together.
Used ink is sensitive to ultraviolet radiation, as when working with screen printing, when the disks are exposed to ultraviolet radiation, they immediately cure.
Lithographic printing is ideal for printing photographic images, as it copes very well with areas of the gradient color of sulfur. However, this is not so good for large areas of solid color, as there may be a mismatch between ink coverage, which can lead to "spotted" printing on a CD.
As with CD printing, lithographic printing has a fixed installation cost, regardless of how many colors are involved in printing. It becomes economically viable for runs of 100 discs or more, and the more a disc is printed, the lower the unit cost.
CD Print Verification
It is very important to provide your supplier with a high resolution image as much as possible. The better the image quality, the better the quality of the final product. Make sure that you check that all images, especially photographic ones, are in their original format. It is not enough to transfer an image with a resolution of 1024 dpi to a template file created with a resolution of 300 dpi. The original image will not print well and you will be disappointed with the result.
Make sure that dark photographic images print well by running test prints before you test run. If the image is to be printed on the screen, then providing the supplier with a pantone reference code for each of the colors in this area ensures that the print will be displayed exactly as you expect. If you already have a printed disc and are looking for a re-start, ask your supplier about color matching. Most suppliers will provide this service, and this will give you peace of mind that the final product will remain in accordance with previous projects.
Summary
To summarize the above information depending on the intended end use of your CDs:
- If you only need a short disc with less than 100 discs, digital printing will be the most economical way to print CDs. Of course, there is no compromise with print quality, but there are no fixed installation costs.
- If your image will be printed based on a photo, then lithographic printing is the way to go.
- If your image consists of 1 or more solid color areas, then screen printing is a way to print a CD to select a sharp result. Fluorescent and metal covers also require screen printing.
