The recording layer of a CD is located just beneath the labeling side. On a DVD, the recording layer is in the center of the disc. In theory, solvents from a solvent-based marker will not penetrate to the center of a DVD through the polycarbonate layer on both sides of the disc. Consequently, the data and metal layers in the center, in theory, should not come in contact with any harmful solvents.
Many vendors sell CD-safe markers, and they vary in ink solution. For risk-free labeling of any disc, it is best to mark the clear inner hub or the so-called mirror band of the disc, where there are no data see Figure Flexing bending the disc by any means, such as removing it from a jewel case or sitting on it, may harm the disc by causing stresses.
The disc should be stored in its case and placed vertically, like a book, on a shelf. Long-term horizontal storage, particularly in a heated environment, can cause the disc to become permanently bowed. While the data may still be intact, the disc may not operate properly in the drive or permit the laser to follow the track. The maximum degree of flex bend or number of times a disc can be flexed before it incurs damage is not known.
To minimize the risk of damage, it is better to avoid flexing discs. Adhesive labels should not be applied to optical discs destined for long-term storage more than five years.
The label could delaminate over time and interfere with disc drive operation. The adhesive in some earlier labels has also been known to react with the lacquer surface. Any attempts to peel the label off could cause damage to the lacquer and metal layers in CDs.
DVDs are different; peeling a label off a DVD would not have the same adverse affect because the metal layer is not near the surface. Still, removing a label, or any portion thereof, from the surface of a disc can cause an imbalance in the spin of the disc in the disc drive, making the disc unreadable. DVDs are more susceptible to reading problems from minor imbalances than are CDs. To ensure the long-term availability of information on a disc that already has an adhesive label, the information on the disc should be copied to, and stored on, a disc without such a label.
Adhesive labels may be well suited for short-term disc usage less than five years , and can even add a layer of protection from scratches and other potentially harmful contact.
On the other hand, such labels are vulnerable to adverse environmental conditions: they can dry out or absorb moisture, and they can be affected by heat or cold even more than the disc itself.
Such conditions may cause the label to delaminate. Disc manufacturers advise against using adhesive labels because they can create unbalanced disc spin, resulting in premature wear of the drive. If a label is used, it should be manufactured for use on CDs or DVDs, and an appropriate disc label applicator tool should be used to affix the label.
The label applicator tool should center the label on the disc so as to maintain the disc balance as much as possible.
Inkjet printing and thermal transfer printing are commonly used for labeling the surfaces of CD-R discs. Each involves a different technology to place inks on the printing surface of the disc; few inkjet-printable and thermal printable CD-Rs are interchangeable.
The printable area on a DVD disc depends on whether the disc is single- or double-sided. Because ink affects the flatness and balance of a disc, full surface printing may not be the best choice since the ink may not be uniformly distributed over the disc surface.
Nonetheless, if you choose to print labels on your discs, full surface printing is better than partial surface printing. The pits are produced on the label side without having a printable surface , creating a mirrored, holograph-like pattern on the metal layer that becomes the label.
Because no ink is used, the flatness and balance of the disc are not compromised. If a DVD disc has data on both sides double-sided , neither printing nor pit art may be used in the data area of the disc. Only the area of the mirror band and the area between the mirror band and center hole may be printed on or marked.
Thermal Printing In thermal transfer printers, a print head that contains resistive elements in a linear array heats ink-coated films ribbons. The ink is heated, causing it to melt and adhere to the printing surface. Specially formulated materials are used for the printable surface of the disc to enhance ink transfer efficiency and adhesion. Only specially designed thermal printers-not thermal printers designed to print on paper-can be used to print directly on the surface of thermal printable CD-R discs.
Inkjet Printing In inkjet printers, inks are sprayed, via droplets of an ink solution, onto a specially designed printable surface material on the disc.
This surface is designed to hold the ink droplets in place while absorbing the liquid components of the ink. Perhaps just as striking, iTunes sales became a musical powerhouse for Apple, engorging its coffers and changing the way people purchased music — for those who still did pay for it.
In , iTunes outpaced CD sales in two major physical stores for the first time. But the modest victory would be short-lived. The first major on-demand service, Spotify, came eight years later, and together, the two companies helped rewrite the music playbook. In , streaming revenue eclipsed CD sales for the first time, and did the same for digital downloads in Yet, as the physical CD readies to slide into its saddle and ride into the sunset, the music industry is still in relative disarray.
Spotify, the biggest on-demand streamer by leaps and bounds, has yet to turn a profit 10 years on. Will streaming ever become a profitable vessel for the industry at large, or is the Napster wound simply too deep to heal?
And just what happens if streaming services never make money? Instead, we can only bid adieu to the once-mighty CD. Goodbye, old friend. The higher quality recordings become ever crisper and clearer, with each instrumental part emerging from a murky swamp of sound.
But for me, appreciating the difference was reliant on a degree of concentration. Have them on in the background and I might not notice any change between the studio masters and the nastiest compressed MP3.
It takes me away, rather than draws me in. And the truth is, I find the impressionistic sound of an MP3 just as effective at providing this emotional hit as the photographic realism of a studio master recording. Could I tell the difference? It depended on the recording. The difference was subtle to my ears. But listening to different tracks the quality gap became more pronounced. Moving again from low-res to a studio master recording of Overture from West Side Story, a myriad of instruments improved in clarity and depth of tone.
The more layers and instrumentation the starker the difference when we moved from low- to high-res digital files. Three discs sizes - 12, 20 and 30 cm - were developed. It contained up to 5 minutes of analogue video like LaserDisc plus up to 20 minutes of CD digital audio, which could be played on any CD player.
The 12 cm discs were yellow; to distinguish them from the silver audio CDs. Philips intended these discs to be an ideal carrier for video clips. CD-i, the interactive CD. Launched in , the CD-i combined CD sound with video, text, animation and interactivity. It was expected to have a great future in areas like learning and entertainment, and Philips launched more than 30 titles when the system was introduced, while by the end of at least 50 titles were available in the USA.
Like a standard CD, a CD-i disc had a capacity of MB, allowing the storage of around 7, photos, 72 minutes of animation or 19 hours of speech. Or any combination of these, as the CD-i titles showed. Picture quality was also excellent, thanks to digital video with more than 16 million colors.
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