GB2404277A

GB2404277A - Anti-scratch system for an optically read disc

Info

Publication number: GB2404277A
Application number: GB0317284A
Authority: GB
Inventors: Rashed Mahmood Aslam
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-07-24
Filing date: 2003-07-24
Publication date: 2005-01-26
Also published as: GB0317284D0

Abstract

A 'remove and replace' anti-scratch system designed to protect the underside of an optically read disc 13 from defects, such as scratches and stains, whilst maintaining disc readability and/or writability. This system involves a temporary underside surface 12 applied to the underside of an optically read disc, which is intended to remain in this position during both disc function and disc storage. The temporary surface has such properties that prevent defects acquired by it from being transmitted to the permanent polycarbonate layer of the disc. The material is also such that allows passage of the laser beam reading or writing data to the disc, maintaining the discs read/write compatibility. Once the temporary underside surface acquires defects that compromise the discs functionability the temporary underside surface is removed and replaced by a new, clean surface restoring disc function. Also a multi layer system is shown where a stack of protective layers are secured to the optical disc, when the surface of the first protective layer is damaged it can be peeled away exposing the surface of the next protective layer.

Description

ANTI-SCRATCH SYSTEM FOR AN OPTICALLY READ DISC

This invention relates to a method for protecting the reading surface (the underside or polycarbonate layer) of an optically read disc e.g. a compact disc (CD).

Compact discs have become a very common means of storing information in a digital format. Data that can be stored on a compact disc includes music, computer data, videos and games. CD technology has evolved since its introduction. The development of CD-R, CD-RW and desktop CD writers have caused an explosion in popularity of home CD recording. The scale of importance of CD technology in peoples lives have made CD preservation ever more important.

Compact discs are typically 12cm in diameter with a thickness of 1.2mm. The thickness can be tolerated (i.e. changed with maintenance of disc readability) by up to an increase of 0.3mm and a decrease of 0. lmm. A centre hole with a diameter of 1 5mm allows the CD to be fixed to a playing device. A CD consists of a number of layers. Starting from the underside (read side) of the disc the first layer is the polycarbonate layer. This is a clear, translucent layer with pits moulded into its upper surface. The upper surface of the polycarbonate layer is coated with aluminium, which is often referred to as the reflective layer. A lacquer coating, onto which the disc label is often printed, protects the reflective layer. The pits, which are seen as bumps on the underside of the disc, are arranged into a single spiral track. The pits are microscopic and thus cannot be seen by the naked eye. Each pit is approximately 0.5 microns wide, 0.15 microns deep and is separated from adjacent tracks by 0.6 m1crons.

A laser beam in the range of 770 to 830nm follows the track, which starts from the central aspect of the CD and spirals outwards. The laser focuses on the pits through the clear polycarbonate layer. Retrieval of stored data on a CD is based on the principle of light reflection. When the laser beam is incident on the reflective layer, between the bumps, the light is reflected back to its region of origin and detected by a photo detector. Light incident on the bumps is reflected in a different direction and thus not detected by the photo detector. In this way a code consisting of 0's and 1's can be created and interpretated e.g. by a computer to provide meaningful data.

Data, in the form of pits, can be stored on a CD during the manufacture process where a template of the required data is used for injection moulding. This process is relatively efficient method for mounting CD data and tends to be used for industrial manufacture of pre-recorded CD's. Data can also be mounted onto CDR discs using CD writers. These are devices that use the heat generated by a laser to form the pits in the reflective layer of a CD-R (a process often referred to as 'burning'). CD writers have become very popular for home and business use.

In order for a CD playing device to optimally retrieve the information stored on a CD the polycarbonate layer of the disc should be clean and void of any surface defects such as scratches. Any such defects would cause the laser beam to become distorted resulting in data loss. It is thus important to maintain such surfaces of optically read discs as much as possible. CD's can currently be protected using CD storage devices such as cases and sleeves. However these do not completely eliminate the threat of scratches being acquired, since the underside surface of the disc remains exposed to the environment between disc transfer, from storage to a playing device, and whilst being used in a playing device.

An object of this invention is to provide a protective system for the underside of an optically read disc (e.g. a CD or DVD) to prevent it from acquiring defects, even when it is being used in a playback device.

Accordingly, this invention provides an anti-scratch system for the underside of an optically read disc (e.g. a CD and DVD), which includes a removable surface applied to the underside of the disc. This temporary surface can be removed and replaced by a new, clean surface once the old surface is damaged with defects such as scratches and stains. The temporary surface is in contact with the underside of the disc and remains so during both data retrieval in a playback device and disc storage. The temporary surface is made from a suitable material, and has a sufficient thickness, to prevent defects that it acquires being transmitted to the permanent polycarbonate underside layer of the disc. The temporary layer is made from a material that also allows the passage of the laser beam reading the disc (or writing information onto it, in the case of a writer/re-writer device), giving uninterrupted disc readability (and writability, in the case of a recordable and re- recordable optical disc).

Two preferred embodiments of the invention (examples I and 2) will now be described with reference to the accompanying drawing in which:

Example 1.

FIGURE I shows a cross sectional view of a CD protected by the antiscratch system, according to a preferred embodiment of the present invention.

FIGURE 2 shows a top view of a CD protected by the anti-scratch system according to a preferred embodiment of a present invention.

FIGURE 3 shows a top view of a CD protected by the anti-scratch system with the top temporary layer partially peeled off, according to a preferred embodiment of the present invention.

Example 2

FIGURE 4 shows a side view of a CD and a temporary underside surface, which is to protect the underside surface of the CD, according to a preferred embodiment of the present invention.

FIGURE 5 shows a top view of a temporary surface, according to a preferred embodiment of the present invention.

Example 1. Reference numbers to the drawings referred to in example 1 relate to figures 1, 2, and 3.

This system involves layers of temporary surfaces (2), (3), (4) mounted onto the underside of a CD ( 1), which are supported in position by their continuation onto the upper (label) side (10) ofthe CD(1). This involves the temporary surfaces (2), (3)7 (4) folding onto the label side (10) of the disc along the outer perimeter of the disc and around the central aperture (11), creating a rim around the outer (5) and inner (6) perimeters ofthe disc. The temporary underside surfaces (2), (3), (4) are preferably mounted during manufacture of the CD(I) and are made from polycarbonate of 0. lmm thickness. The temporary surfaces (2), (3), (4) are moulded into position around the CD(1) to avoid the presence of any joins on the underside of the CD, which would otherwise cause optical distortion. The combined thickness of the CD (1) and the temporary surfaces (2), (3), (4), in contact with the underside of the CD (1), is in a range compatible with disc readability and writability (i.e. a maximum combined thickness of 1.5mm and a minimum of 1. Imm). The outer rim (5) of each layer contains a layer-removal region (7), (8), (9), which consists of two scored parallel lines approximately 1 cm apart. The rim region between the lines is pulled which, induces a tear along the scored lines (8). Further pulling causes the tear lines to propagate to the underside region of the temporary surface aiding the removal of the whole layer. The action of removing the outer most temporary surface layer (4) results In exposure ofthe next temporary layer (3) in the sequence.

A user of a CD incorporating this preferred embodiment of the antiscratch system, described herein, uses the CD as normal with the antiscratch system remaining intact on the CD during its normal function. Once the outer most temporary surface layer (4) has acquired defects that compromise the CD's functionability the user removes the outer most layer (4), as described herein, resulting in the exposure of the next temporary surface (3). Since the new temporary surface (3) has been protected from acquiring defects by the original outer layer (4) it is free from surface defects and restores disc function.

Example 2. Reference numbers to the drawings referred to in example 2 relate to figures 3 and 4.

This system involves a single temporary surface (12) applied to the underside of a CD (13). The CD (13) is modified to accommodate the temporary surface (12) whilst maintaining disc readability and writability. This modification is to the thickness of the CD (13) and involves a reduction in the thickness ofthe CD (13) so that the combined thickness of the CD (13) and temporary underside surface (12) remains in the range that makes the CD (13), read and write compatible. The other dimensions of the CD (13), and temporary surface (12), are the same as a standard CD (i.e. 120mm diameter with a 15mm central aperture). In this particular example the CD (13) has a thickness of 0.7mm and the temporary surface (12), which is made from polycarbonate, has a thickness of 0.5mm. The temporary surface (12) is applied to the underside ofthe CD (13) and is supported in position by an adhesive region (14) around the central aperture (15) ofthe temporary surface. The adhesive region (14) forms a ring, with a diameter of 35mm, around the central aperture (15). When applied, the adhesive region (14) of the temporary surface (12) adheres to the corresponding region ofthe CD (13) (i.e. the polycarbonate region around the central aperture (16) of the CD, which contains no reflective layer). The adhesive properties ofthis region are such that allow firm adhesion of the temporary surface (12) to the CD (13) but which also allow its removal by applying gentle pressure, without leaving any (or minimal) residue. The temporary surface (12) sits tightly next to the polycarbonate layer ofthe CD (13) with there being no gaps between the two and is in parallel with the CD (13) so that the central apertures of both the CD (16) and temporary surface (15) meet in line with no overlap. Applying gentle pressure between the CD (13) and temporary layer (12), enough to overcome the adhesive force keeping the temporary surface (12) in contact with the CD (13), results in removal of the temporary layer ( 12).

The user preferably applies the temporary surface (12) to the underside of the CD (13) and uses the CD as normal thereafter. Once the temporary underside surface (12) acquires defects which compromise disc readability and/or writability the damaged temporary layer is removed by the user and replaced by a new one, which is free from any surface defects, restoring disc function.

Claims

1. An anti-scratch system that remains present during the function of an optically read disc and protects the discs underside (playside) surface, by the presence of a temporary underside surface, whilst maintaining disc readability and/or writability and which can be removed, and replaced by a new temporary surface without causing injury to the underside of the optically read disc.

2. An anti-scratch system claimed in Claim 1 where there are multiple said temporary underside surfaces arranged in layers, where each layer protects the next layer in the sequence from acquiring defects (and thus ultimately protecting the polycarbonate underside of the optical disc) and in which the layers can be removed sequentially to expose the next layer in the sequence.

3. An anti-scratch system claimed in Claim 1 or Claim 2 where the said temporary underside surface is supported by an adhesive element.

4. An anti-scratch system claimed in any preceding claim which involves an optical disc modified to receive a said temporary underside layer, for the purpose of maintaining disc function whilst supporting the anti- scratch system.

5. An anti-scratch system claimed in any preceding claim where the said temporary underside layer is made from a material that allows the passage of a laser reading or writing to an optically read disc and thus maintaining disc functionability.

6. An anti-scratch system claimed in any preceding claim where the said temporary underside layer is made from a suitable material with sufficient thickness to prevent defects acquired by it being transmitted to the polycarbonate underside of the optically read disc which it is intended to protect.

7. An anti-scratch system claimed in any preceding claim where the said temporary underside surface is applied during manufacture of an optically read disc.

8. An anti-scratch system for an optically read disc substantially as herein described and illustrated in the accompanying drawings.