About CD's

Hello all,

I have some questions about Compact Disk (CD).

1- What is the difference between the material of CD-R and CD-RW?
2-What the polycarbonate level of CD for?

Thanks in advance.

Hi Kurdman,

CD-R is a short form of "CD-Recordable", meaning recordable CD. In the past, users could only read the data on a CD-ROM. If users wanted to record data onto a CD, they had to ask assistance from a factory and do so in large quantities. With CD-R however, individuals can save data on a CD and produce a format that is exactly the same as that of a standard CD-ROM. But once made, the recorded sections of a CD cannot be recorded over, and due to different materials used, the colors of CD-R vary between gold, blue and green, unlike the silver of a standard CD-ROM .


CD-RW is short form for "CD- Rewritable", in other words, a rewritable CD. The special feature of CD-RW is that the recorded sections can be cleared and reused for re-recording. Of course, users cannot rewrite the CD-RW to an infinite number of times. Typically, each CD-RW can be rewritten about 1,000 times.

Source: Difference between CD-R and CD-RWs. Major Price Difference? / Nordex Media Blog

I'll do some more research and see if I can find the answer to your second question. :)

-Chuck

I couldn't find anything specific for what your asking, but maybe this would help?

Polycarbonate plastic is a lightweight, high-performance plastic that possesses a unique balance of toughness, dimensional stability, optical clarity, high heat resistance and excellent electrical resistance. Because of these attributes, polycarbonate is used in a wide variety of common products including digital media (e.g. CDs, DVDs), electronic equipment, automobiles, construction glazing, sports safety equipment and medical devices. The durability, shatter-resistance and heat-resistance of polycarbonate also make it an ideal choice for tableware as well as reusable bottles and food storage containers that can be conveniently used in the refrigerator and microwave (APME).

Source: Polycarbonate Plastic and Bisphenol A

-Chuck :)

Oh, I'm sorry. I must have read your question wrong.

I think I found what you want to know! :)

The media for CD-RW has basically the same layers as CD-R media. The reflective layer is, however, a silver-indium-antimony-tellurium (AgInSbTe) alloy, which has in its original state, a polycrystalline structure and reflective properties. When writing the laser beam uses its maximum power (8 - 14 mW)[4] to heat the material to 500–700 °C. This causes liquefaction of the material. In this state, the alloy loses its polycrystalline structure, assumes an amorphous state and lose its reflectivity. The lost reflectivity serves the same function as bumps on a manufactured CDs and the opaque spots on a CD-R which will be read as a "0".[5] The polycrystalline state of the disk forms the trenches, which is read as "1".[5] The scanning signal when reading is created by strong or weak reflection of the laser beam (not unlike the destructive interference of light caused by and used to read "pits" in pressed CD-ROMs). To erase the disc, the write beam heats the amorphous regions with low power to about 200 °C. The alloy is not melted, but returns to the polycrystalline state and is thus again reflective.

I'm glad it helped!

Have a great day,
-Chuck

No problem. :)