ISO 18938:2014
(Main)Imaging materials — Optical discs — Care and handling for extended storage
Imaging materials — Optical discs — Care and handling for extended storage
ISO 18938:2014 establishes general principles for the care and handling of digital optical discs during use. It addresses the issues of physical integrity of the medium necessary to preserve access to the recorded data (information). ISO 18938:2014 includes recommendations for handling procedures to maximize the effective life of optical discs. The following are within the scope of ISO 18938:2014: use and handling environments, including pollutants, temperature and humidity and light exposure; contamination concerns; inspection; cleaning and maintenance, including cleaning methods and frequency; transportation; disasters, including water, fire, construction and post-disaster procedures; staff training.
Matériaux pour l'image — Disques optiques — Précautions et manipulation pour stockage étendu
Upodobitveni materiali - Optične plošče - Nega in ravnanje za dolgo shranjevanje
Ta mednarodni standard določa splošna načela za nego in ravnanje z digitalnimi optičnimi ploščami med uporabo. Obravnava vprašanja fizične celovitosti medija, potrebne za ohranitev dostopa do zabeleženih podatkov (informacij). Ta mednarodni standard vključuje priporočila za postopke ravnanja za čim večji izkoristek učinkovite življenjske dobe optičnih plošč. Nepravilne tehnike in metode za ravnanje, pakiranje ter prevažanje pogosto fizično poškodujejo plošče in vsebine, zabeležene na njih. Za podaljšanje življenjske dobe optičnih plošč je potrebna opredelitev ustreznih metod za ravnanje ter dobro razvitih in izvajanih programov za usposabljanje.
Za namene tega mednarodnega standarda izraz »optična plošča« zajema družine kompaktnih plošč (CD), digitalnih večstranskih plošč (DVD), visokoločljivostnih digitalnih večstranskih plošč(HD DVD) in plošč Blu-ray (BD)1) ter katere koli hibride teh družin. Izraz »optična plošča« zajema tudi vsak tip plošče v družini, vključno s tehnologijo oblikovanja z vbrizganjem [bralni pomnilnik (ROM)] in tehnologijo z barvnim slojem [zapisljivi (R)] ter fazno spremenljivo tehnologijo [prepisljivi (RW, RE), bralno-pisalni pomnilnik (RAM) in zapisljivi (BD-R)]. Čeprav se nekatera priporočila iz tega mednarodnega standarda (npr. priporočila za usposabljanje osebja) uporabljajo posebej za obsežno ali dolgoročno uporabo, so osnove vseh priporočil v tem mednarodnem standardu namenjene uporabi v okoliščinah, v katerih je želeni rezultat dolgoročna uporaba medija, in sicer arhivska, poslovna ali osebna.
Ta mednarodni standard ne obravnava magnetno-optičnih (MO) plošč, laserskih plošč (LD) ali steklenih plošč. V času pisanja ni mednarodnih standardov za plošče HD DVD in Blu-Ray. Vseeno velja, da se lahko priporočila v tem mednarodnem standardu za nego in ravnanje enakovredno uporabljajo tudi zanje. Priznava se, da posamezni uporabnik morda ne more izpolniti nekaterih zahtev.
Naslednje spada na področje uporabe tega mednarodnega standarda:
– okolja za uporabo in ravnanje, vključno z onesnaževali, temperaturo in vlažnostjo ter izpostavljenostjo svetlobi;
– vprašanja v zvezi z onesnaženostjo;
– inšpekcijski pregled;
– čiščenje in vzdrževanje, vključno s čistilnimi metodami in pogostostjo;
– prevoz;
– katastrofe, vključno z vodo, ognjem, gradnjo in postopki po katastrofi;
– usposabljanje osebja.
Kakovost podatkov, zapisanih na plošči, je zunaj področja uporabe tega mednarodnega standarda. Vendar je visokokakovosten rezultat snemalne faze pomemben za dolgo življenjsko dobo informacij. Priporoča se izvedba strogega programa preskušanja celovitosti podatkov, saj to tvori obvezen del vsega digitalnega dolgoročnega shranjevanja. Poleg tega se pri hranjenju digitalnih informacij za arhivske namene priporoča uporaba strategije z več kopijami/več lokacijami.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2014
1DGRPHãþD
SIST ISO 18938:2011
8SRGRELWYHQLPDWHULDOL2SWLþQHSORãþH1HJDLQUDYQDQMH]DGROJRVKUDQMHYDQMH
Imaging materials - Optical discs - Care and handling for extended storage
Matériaux pour l'image - Disques optiques - Précautions et manipulation pour stockage
étendu
Ta slovenski standard je istoveten z: ISO 18938:2014
ICS:
35.220.30 2SWLþQHVKUDQMHYDOQH Optical storage devices
QDSUDYH
37.040.99 Drugi standardi v zvezi s Other standards related to
fotografijo photography
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL ISO
STANDARD 18938
Second edition
2014-09-15
Imaging materials — Optical discs
— Care and handling for extended
storage
Matériaux pour l’image — Disques optiques — Précautions et
manipulation pour stockage étendu
Reference number
©
ISO 2014
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2014 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Composition of optical discs . 6
4.1 General . 6
4.2 Polycarbonate substrate (plastic) layer . 6
4.3 Data layer . 6
4.4 Reflective layer . 7
4.5 Protective layers . 7
4.6 Adhesive layers . 7
4.7 Additional layers. 8
5 Failure mechanisms . 8
5.1 General . 8
5.2 Physical stress. 8
5.3 Layer sensitivity . 8
5.4 Scratches . 9
5.5 Effects of disc play . 9
6 Handling techniques .10
6.1 General .10
6.2 Flexing .10
6.3 Contamination .10
6.4 Disc enclosures .10
7 Identification .11
7.1 Basic concepts .11
7.2 Adhesive labels .11
7.3 Printing on optical discs .11
7.4 Thermal printing .12
7.5 Inkjet printable surface .12
7.6 Silk screening .12
7.7 Marking .12
8 Contamination .12
8.1 Fingerprints, smudges, dirt, dust .12
8.2 Moisture .12
8.3 Organic solvents .13
8.4 Gaseous impurities .13
8.5 Consumables .13
9 Use environment .13
9.1 General .13
9.2 Temperature and humidity .13
9.3 Water avoidance .14
9.4 Air quality .14
9.5 Light exposure .14
9.6 Acclimatization .15
9.7 Vibrations .15
10 Transportation and shipping .15
10.1 Enclosures .15
10.2 Cartons .15
10.3 Exposure .16
10.4 Security .16
10.5 External fields .16
10.6 Biological irradiation .16
11 Inspection .16
11.1 General requirements .16
11.2 Error rate monitoring .17
12 Cleaning and maintenance .17
12.1 General .17
12.2 Solvents and cleaning compounds .17
12.3 Cleaning methods .17
13 Disasters .18
13.1 General .18
13.2 Water .18
13.3 Fire . .18
13.4 Dry debris .18
13.5 Impact from disasters .19
13.6 Repair .19
14 Disaster response .19
14.1 General .19
14.2 Wet discs .19
14.3 Dry discs .19
15 Staff training .19
15.1 General .19
15.2 Purpose .20
15.3 Training paths .20
15.4 Schedule for training .20
15.5 Update of training .20
15.6 Content of training .20
16 Minimum handling requirements checklist .21
16.1 General .21
16.2 Do list .21
16.3 Not-to-do list .21
Annex A (informative) Disc structure .23
Bibliography .25
iv © ISO 2014 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18938:2008), which has been technically
revised.
Introduction
In addition to storage conditions, the proper care and handling of optical discs is also vital to prolonged
disc life. This is becoming increasingly important as optical discs are widely used for the recording and
storage of information. This International Standard gives guidelines for their recommended care and
handling and will be beneficial for all digital optical discs, regardless of their inherent stability.
NOTE It is recognized that both “optical discs” and “optical disks” are acceptable spellings. In this International
Standard, the former spelling is used.
Probably no form of data storage has been accepted and adopted as rapidly as the optical disc. It has
become the medium of choice for numerous applications with ever increasing use for the recording and
storage of information. Information is recorded in digital format that not only provides high storage
density, but also allows duplication without information loss, ease of data manipulation and facilitates
transmission. It is of tremendous benefit for audio usage since it permits uninterrupted playback for
long periods of time. Information in a disc format can be accessed very quickly, unlike that in a roll
format such as magnetic tape, which requires longer search time.
While the advantages are many, as with other media, there are nevertheless concerns about the life
expectancy of recorded information on optical discs. This depends upon three independent components,
namely the permanence of the disc itself, the disc drive and the software. Obsolescence of the disc drive
and software, lack of playback device or inoperability of the playback device are all serious uncertainties.
Another important issue is the quality of the initial data recorded onto the disc, which needs to be
as high as possible. In addition, the very popularity of recordable optical discs has led to their wide
availability, and wide variability in the quality of discs for long term preservation of information. Many
discs may not be of sufficient quality for long term use.
The finite life of optical discs is well recognized and one approach to addressing this issue is by
periodically transferring or reformatting the information. In addition, the ability to play back a disc in
the future depends on the existence of functional playback equipment. As newer formats and equipment
become popular, equipment manufacturers will probably discontinue production and support of the
older, superseded equipment. Eventually, usable equipment to play obsolete optical disc formats will
become difficult to find. Before this occurs, it is advisable that a migration plan be in place. However, these
issues are outside the scope of this International Standard, which is only concerned with the stability of
the optical disc itself. A primary objective of those involved with the preservation of information on this
media is to ensure that the disc is not the weak link among the necessary components. To support this
objective, it is advisable that steps be taken to maximize the optical disc’s potential to be more stable
than either the hardware or the software.
As with paper records, photographic film and magnetic tape, optical discs are subject to both damage
and decay. They have a finite life. Predictions of the life expectancy of optical discs have involved
extrapolations of property retention after high temperature and humidity incubations back to practical
conditions. These extrapolations follow mathematical treatments that were developed for simpler
chemical reactions, and therefore the results need to be interpreted with some caution. Predictions cover
a very wide range, from 25 years to over 250 years, which vary with the manufacturer and the disc type.
Their effective life can be increased or decreased significantly depending upon the conditions under
which they are stored. Storage recommendations for optical discs are given in ISO 18925. Following
these recommendations promotes the physical integrity of the media and increases their effective life.
vi © ISO 2014 – All rights reserved
INTERNATIONAL STANDARD ISO 18938:2014(E)
Imaging materials — Optical discs — Care and handling for
extended storage
1 Scope
This International Standard establishes general principles for the care and handling of digital optical
discs during use. It addresses the issues of physical integrity of the medium necessary to preserve access
to the recorded data (information). This International Standard includes recommendations for handling
procedures to maximize the effective life of optical discs. Faulty handling, packing and transporting
techniques and methods often cause physical damage to the discs and to the content recorded thereon.
Extending the longevity of optical discs requires the identification of appropriate handling methods, as
well as well-developed and implemented training programs.
For the purposes of this International Standard, the term “optical disc” includes the families of compact
disc (CD), digital versatile disc (DVD), high definition digital versatile disc (HD DVD) and Blu-ray disc
1)
(BD) , and any hybrids of these families. The term “optical disc” also includes each type of disc within
a family, including injection moulded [read-only memory (ROM)], dye-layer [recordable (R)] and phase
change [rewritable (RW, RE), random access memory (RAM), and recordable (BD-R)] technologies.
While some of the recommendations in this International Standard (e.g. those for staff training) apply
specifically to large-scale or long term usage, the basics of all recommendations in this International
Standard are intended to be applied in circumstances where the desired result is long-term usage of the
medium whether archival, commercial or personal.
This International Standard does not cover magneto-optical (MO) discs, laser discs (LD) or glass discs.
At the time of writing, International Standards do not exist for HD DVD and Blu-ray discs. Nonetheless,
it is believed that the recommendations in this International Standard for care and handling can equally
apply to them. It is recognized that some of these requirements are not necessarily possible for the
individual user to achieve.
The following are within the scope of this International Standard:
— use and handling environments, including pollutants, temperature and humidity and light exposure;
— contamination concerns;
— inspection;
— cleaning and maintenance, including cleaning methods and frequency;
— transportation;
— disasters, including water, fire, construction and post-disaster procedures;
— staff training.
The quality of the data written on the disc is outside the scope of this International Standard. However,
a high quality result of the recording phase is important to the longevity of information. It is advisable
that a rigorous program of data integrity testing be implemented, as this forms an obligatory part of
all digital long-term storage. In addition, when keeping digital information for archival purposes, it is
advisable that a multiple copy/multiple location strategy be in place.
TM TM
1) Blu-ray Disc and Blu-ray are trademarks of Blue-ray Disc Association, and Blu-ray Disc and HD DVD are
examples of suitable products available commercially. This information is given for the convenience of users of this
International Standard and does not constitute an endorsement by ISO of these products.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 14644-1, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness
by particle concentration
ISO 18925, Imaging materials — Optical disc media — Storage practices
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acclimatization staging
process of conditioning material from one set of temperature-moisture conditions to another
3.2
balance
precision vertical position of the disc as it spins
3.3
blister
localized delamination that looks like a bubble
3.4
Blu-ray Disc
BD
optical disc having a cover layer around 0,1 mm thick and a substrate around 1,1 mm thick on which
data is read or recorded by an OPU using 405 nm laser diode and NA = 0,85 lens
3.4.1
Blu-ray Disc Read Only Memory
BD-ROM
optical disc to which information is transferred during manufacture to moulded areas in the Blu-ray
disc format and can be read multiple times by an optical beam
3.4.2
Blu-ray Disc Recordable
BD-R
recordable optical disc in which information can be recorded once to areas in the Blu-ray disc format
and read many times
3.4.3
Blu-ray Disc Rewritable
BD-RE
recordable optical disc in which information can be recorded to areas in the Blu-ray disc format and can
be erased, rerecorded and read many times
3.5
carton
box outer container that can hold one or more individual units and can be a fabrication of paper, card
stock or plastic
2 © ISO 2014 – All rights reserved
3.6
compact disc
CD
optical disc in which the information layer is located near one surface of a substrate and the data can be
read by an optical beam with a wave length of 780 nm
Note 1 to entry: Described in IEC 60908.
3.6.1
CD read only memory
CD-ROM
optical disc to which information is transferred during manufacture to moulded areas in the compact
disc format and can be read multiple times by an optical beam
Note 1 to entry: Described in ISO/IEC 10149.
3.6.2
CD Recordable
CD-R
recordable optical disc in which information can be recorded once to areas in the compact disc format
and read many times
3.6.3
CD Rewritable
CD-RW
rewritable optical disc in which information can be recorded to areas in the compact disc format and
can be erased, rerecorded and read many times
3.7
conditioning
exposure of a material to air at a given relative humidity and temperature until equilibrium is reached
3.8
container
box, can or carton used for storage and shipping of recording materials
EXAMPLE The box into which a reel, cassette, cartridge or shell is placed.
3.9
delamination
separation of a laminate into its constituent layers
3.10
digital versatile disc
DVD
optical disc in which one or more information layers are located between two substrates and the data
can be read by an optical beam with a wave length of 650 nm
Note 1 to entry: Formerly called digital video disc.
3.10.1
DVD read only memory
DVD-ROM
optical disc in which information is transferred during manufacture to certain areas in the DVD format
and can be read multiple times by an optical beam
Note 1 to entry: Described in ISO/IEC 16448 and ISO/IEC 16449.
3.10.2
DVD Recordable
DVD-R, +R
recordable optical disc in which information can be recorded once to areas in the DVD format and read
many times
Note 1 to entry: Described in ISO/IEC 23912, ISO/IEC 17344 and ISO/IEC 25434.
3.10.3
DVD Rewritable
DVD-RAM, DVD-RW, +RW
DVD optical discs that can be written, read and overwritten many times using phase change technology
Note 1 to entry: Described in ISO/IEC 17592, ISO/IEC 17341 and ISO/IEC 26925.
3.11
enclosure
case, cartridge, folder, envelope, sleeve or clam shell that is intended for physical protection against
mechanical damage
3.12
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having permanent value
3.13
high definition digital versatile disc
HD DVD
optical disc in which one or more information layers are located between two substrates and the data
can be read by an optical beam with a wave length of 405 nm
Note 1 to entry: Sometimes called high density digital versatile disc.
3.13.1
HD DVD read only memory
HD DVD-ROM
optical disc in which information is transferred during manufacture to certain areas in the HD DVD
format and can be read multiple times by an optical beam
3.13.2
HD DVD recordable
HD DVD-R
recordable optical disc in which information can be recorded once to areas in the HD DVD format and
read many times
3.13.3
HD DVD rewritable
HD DVD-RW
HDDVD optical discs that can be written, read and overwritten many times using phase change
technology
3.14
information
data recorded using the system
3.15
insulated record container
storage box designed to provide an environmental buffer against temperature and humidity fluctuations
4 © ISO 2014 – All rights reserved
3.16
jewel case
plastic enclosure featuring a hinged lid and one or more trays, each containing a hub clamp to secure
and protect the disc surface
3.17
keep case
case designed for DVD discs slightly larger than a jewel case
3.18
macroenvironment
atmospheric conditions in a large area in which records are kept
Note 1 to entry: Atmospheric conditions are temperature, relative humidity and pollutants.
3.19
medium
material on which information is recorded
3.20
microenvironment
atmospheric conditions inside a storage enclosure in which records are kept
Note 1 to entry: Atmospheric conditions are temperature, relative humidity and pollutants.
3.21
optical disc
disc that will accept and retain information from light modulation changes in a recording or reflective
layer that can be read with an optical beam
3.22
optical disc cartridge
ODC
optical disc enclosure required for the operation of the disc
3.23
recording layer
layer of an optical disc on which data is written either during manufacture or in use
3.24
relative humidity
RH
ratio, defined as a percentage, of the existing partial vapour pressure of water to the vapour pressure
at saturation
Note 1 to entry: It is usually, but not always, equal to the percentage of the amount of moisture in the air to that
at saturation.
3.25
replicated disc
disc made by an injection moulding process where the land and pits that make up the data are physically
pressed into the polycarbonate
3.26
retrievability
ability to access information as recorded
3.27
slimline case
slimmer version of the jewel case
3.28
snapper case
alternative to the keep case with a cardboard cover
3.29
storage environment
conditions for storing materials
Note 1 to entry: The conditions are temperature, relative humidity, cleanliness of facilities and atmospheric
pollutants.
3.30
storage housing
physical structure supporting materials and their enclosures
Note 1 to entry: It can consist of drawers, racks, shelves or cabinets.
3.31
substrate
layer which may be transparent or not, provided for the mechanical support of the recording layer
3.32
system
combination of media, hardware, software and documentation necessary for recording and/or retrieving
information
3.33
WORM disc
optical disc in which the data in specified areas can be written only once and read multiple times by an
optical beam
4 Composition of optical discs
4.1 General
Optical discs are composed of a series of layers made of different materials assembled like a sandwich.
Typically, these layers include the polycarbonate substrate (plastic) layer(s), the data layer(s), the metal
layers(s) or reflective layer, the metal protective layers, the adhesive layer and an optional extra layer
for labelling or added protection. These layers are listed in Annex A.
4.2 Polycarbonate substrate (plastic) layer
The polycarbonate substrate makes up most of the disc. The polycarbonate is typically clear, but may be
coloured for appearance or to prevent copyright infringement. The laser beam of a disc drive travels
through this substrate for CD, DVD and HD DVD and through the cover layer for BD. The substrate
provides the layer depth necessary to maintain laser focus for CD, DVD and HD DVD. The substrate also
gives the disc enough strength to remain flat for CD, DVD, HD DVD and BD.
A CD is one continuous 1,2 mm thick polycarbonate layer. Both DVDs and HD DVDs are made up of two
0,6 mm thick polycarbonate layers bonded together. BDs are made up of 1,1 mm thickness polycarbonate
layer and 0,1 mm thickness cover layer. CDs and BDs are read from one side only. DVDs and HD DVDs are
read from one or both sides.
4.3 Data layer
As its name implies, the data layer of optical discs is the layer that contains the encoded data. The
encoded data appear as marks or pits that either transmit or alter light from the laser beam back to
the laser photosensor by way of the metal reflective layer. Write-once (–R, +R) discs use organic dye
material or phase change materials, whereas rewritable (–RW, +RW, –RAM, –RE) discs use phase change
6 © ISO 2014 – All rights reserved
materials as the layer(s) for holding record data written by a disc drive. ROM discs do not use a separate
layer, but the data has been pressed in the form of pits from injection moulding on the inner surface of
the polycarbonate substrate during the disc manufacturing process.
4.4 Reflective layer
The metal layer in optical discs reflects the laser beam back to the laser photodiode in the optical pickup
unit (OPU). Three main types of reflective metals typically are used for this layer:
a) aluminium or aluminium alloy,
b) gold, and
c) silver or silver alloy.
In “dual-layer” DVDs, silicon is sometimes used as one of the semi-reflective layers. Some discs use a
copper alloy for the purposes of appearance.
Aluminium is used in ROM, RW and RAM discs. Silver, silver alloy or gold are used in R discs, since
aluminium is too active to use with dye. Aluminium is also prone to corrosion when exposed to moisture
or other pollutants that penetrate into the disc. Oxidation of the aluminium diminishes its reflectivity,
eventually making the disc unreadable by the laser. This is sometimes referred to as disc “rot”.
Silver can lose reflectivity due to corrosion on exposure to pollutants such as sulfur dioxide. Silver alloys
are designed to inhibit corrosion.
In “dual-layer” DVDs, the outer reflective layer (silicon, gold, silver or silver alloy) is only semi-reflective,
i.e. it reflects back some of the laser beam and allows some of it to pass through to the fully reflective
layer and then reflect back.
To summarize, the relative properties of the three main types of reflective metals are as follows:
— Cost: aluminium < silver < silver alloy < gold;
— Stability: aluminium < silver or silver alloy < gold.
4.5 Protective layers
A very thin lacquer layer is applied to the label side of CDs to protect the metal from exposure to the
environment. Without this protective layer, the aluminium will oxidize within several days. The layer
also gives some limited protection from writing on or labelling the disc. Some solvents used in markers
(e.g. xylene, toluene) can also affect lacquer coatings and expose or react with the metal. Once the metal
is damaged, the laser cannot read data in the damaged areas. DVDs have no such protective lacquer
coating, due to the reflective layer location in the middle of the disc.
Sometimes a manufacturer will add an additional layer designed specifically to provide more resistance
to fingerprints and scratches on the label side of CDs.
Protective layers also are available to place on the laser reading side of the disc. These are specifically
designed for protection against scratches and other surface damage.
4.6 Adhesive layers
The discs of all DVD formats are formed by bonding two 0,6 mm discs together. Disc durability and
reliability require excellent bonding. The bonding methods include hot-melt bonding and ultraviolet
(UV) bonding. The bonding layer needs to be optically transparent for some dual-layer DVDs.
The DVD bonding process mainly uses the following three methods:
— the spinning method, using a radical UV resin;
— the screen printing method, using a cationic UV resin;
— the sheet method, using a double-sided adhesive sheet.
It is essential that the adhesive layer be uniform within close tolerances, that it does not introduce tilt
out of the range of the DVD specification, that no defects such as bubbles occur and that it is optically
transparent in dual layer DVDs.
4.7 Additional layers
An optional layer may also be added to optical discs to provide a writable, printable or coloured surface.
Such surfaces include thermal-printable, inkjet-printable and silkscreen-printable surfaces. These
layers are applied over the lacquer layer on CDs, or over the polycarbonate substrate on other single-
sided discs.
5 Failure mechanisms
5.1 General
Optical disc performance depends on the performance of the disc drive and the characteristics of the
disc itself. This clause only discusses failure mechanisms due to the disc.
5.2 Physical stress
Optical discs are typically handled directly by users. They are subject to a variety of physical stresses,
including mechanical impact and thermal shock. Mechanical impact can result in scratching, fracturing,
breakage, warpage or delamination. Thermal shock is a rapid temperature change that can cause
differential expansion or contraction resulting in warpage or delamination. Warping can be a temporary
condition that returns to normal, but severe warping or repetitive warping can cause delamination and
permanent damage.
5.3 Layer sensitivity
5.3.1 General
Proper care and handling of optical discs requires knowledge of the sensitivities of the various layers
which make up optical discs. Various types of defects can be encountered because of the complex
structure of these materials. Optical discs are laminates of very dissimilar layers and each layer can
cause malfunctions. It is essential that the disc does not undergo any delamination. The primary layers
and their susceptibilities to failure or damage sensitivities are as described in 5.3.2 to 5.3.6 below.
5.3.2 Polycarbonate substrate
The laser beam of CD, DVD and HD DVD system transmits to its focus point and back to the reading sensor
through the polycarbonate substrate. Eccentricity, manufacturing flaws, off-centring, lack of flatness or
balance creates tracking and/or reading problems. This may be caused by physical stress, exposure
to high or rapidly changing temperatures,
...
INTERNATIONAL ISO
STANDARD 18938
Second edition
2014-09-15
Imaging materials — Optical discs
— Care and handling for extended
storage
Matériaux pour l’image — Disques optiques — Précautions et
manipulation pour stockage étendu
Reference number
©
ISO 2014
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2014 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Composition of optical discs . 6
4.1 General . 6
4.2 Polycarbonate substrate (plastic) layer . 6
4.3 Data layer . 6
4.4 Reflective layer . 7
4.5 Protective layers . 7
4.6 Adhesive layers . 7
4.7 Additional layers. 8
5 Failure mechanisms . 8
5.1 General . 8
5.2 Physical stress. 8
5.3 Layer sensitivity . 8
5.4 Scratches . 9
5.5 Effects of disc play . 9
6 Handling techniques .10
6.1 General .10
6.2 Flexing .10
6.3 Contamination .10
6.4 Disc enclosures .10
7 Identification .11
7.1 Basic concepts .11
7.2 Adhesive labels .11
7.3 Printing on optical discs .11
7.4 Thermal printing .12
7.5 Inkjet printable surface .12
7.6 Silk screening .12
7.7 Marking .12
8 Contamination .12
8.1 Fingerprints, smudges, dirt, dust .12
8.2 Moisture .12
8.3 Organic solvents .13
8.4 Gaseous impurities .13
8.5 Consumables .13
9 Use environment .13
9.1 General .13
9.2 Temperature and humidity .13
9.3 Water avoidance .14
9.4 Air quality .14
9.5 Light exposure .14
9.6 Acclimatization .15
9.7 Vibrations .15
10 Transportation and shipping .15
10.1 Enclosures .15
10.2 Cartons .15
10.3 Exposure .16
10.4 Security .16
10.5 External fields .16
10.6 Biological irradiation .16
11 Inspection .16
11.1 General requirements .16
11.2 Error rate monitoring .17
12 Cleaning and maintenance .17
12.1 General .17
12.2 Solvents and cleaning compounds .17
12.3 Cleaning methods .17
13 Disasters .18
13.1 General .18
13.2 Water .18
13.3 Fire . .18
13.4 Dry debris .18
13.5 Impact from disasters .19
13.6 Repair .19
14 Disaster response .19
14.1 General .19
14.2 Wet discs .19
14.3 Dry discs .19
15 Staff training .19
15.1 General .19
15.2 Purpose .20
15.3 Training paths .20
15.4 Schedule for training .20
15.5 Update of training .20
15.6 Content of training .20
16 Minimum handling requirements checklist .21
16.1 General .21
16.2 Do list .21
16.3 Not-to-do list .21
Annex A (informative) Disc structure .23
Bibliography .25
iv © ISO 2014 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18938:2008), which has been technically
revised.
Introduction
In addition to storage conditions, the proper care and handling of optical discs is also vital to prolonged
disc life. This is becoming increasingly important as optical discs are widely used for the recording and
storage of information. This International Standard gives guidelines for their recommended care and
handling and will be beneficial for all digital optical discs, regardless of their inherent stability.
NOTE It is recognized that both “optical discs” and “optical disks” are acceptable spellings. In this International
Standard, the former spelling is used.
Probably no form of data storage has been accepted and adopted as rapidly as the optical disc. It has
become the medium of choice for numerous applications with ever increasing use for the recording and
storage of information. Information is recorded in digital format that not only provides high storage
density, but also allows duplication without information loss, ease of data manipulation and facilitates
transmission. It is of tremendous benefit for audio usage since it permits uninterrupted playback for
long periods of time. Information in a disc format can be accessed very quickly, unlike that in a roll
format such as magnetic tape, which requires longer search time.
While the advantages are many, as with other media, there are nevertheless concerns about the life
expectancy of recorded information on optical discs. This depends upon three independent components,
namely the permanence of the disc itself, the disc drive and the software. Obsolescence of the disc drive
and software, lack of playback device or inoperability of the playback device are all serious uncertainties.
Another important issue is the quality of the initial data recorded onto the disc, which needs to be
as high as possible. In addition, the very popularity of recordable optical discs has led to their wide
availability, and wide variability in the quality of discs for long term preservation of information. Many
discs may not be of sufficient quality for long term use.
The finite life of optical discs is well recognized and one approach to addressing this issue is by
periodically transferring or reformatting the information. In addition, the ability to play back a disc in
the future depends on the existence of functional playback equipment. As newer formats and equipment
become popular, equipment manufacturers will probably discontinue production and support of the
older, superseded equipment. Eventually, usable equipment to play obsolete optical disc formats will
become difficult to find. Before this occurs, it is advisable that a migration plan be in place. However, these
issues are outside the scope of this International Standard, which is only concerned with the stability of
the optical disc itself. A primary objective of those involved with the preservation of information on this
media is to ensure that the disc is not the weak link among the necessary components. To support this
objective, it is advisable that steps be taken to maximize the optical disc’s potential to be more stable
than either the hardware or the software.
As with paper records, photographic film and magnetic tape, optical discs are subject to both damage
and decay. They have a finite life. Predictions of the life expectancy of optical discs have involved
extrapolations of property retention after high temperature and humidity incubations back to practical
conditions. These extrapolations follow mathematical treatments that were developed for simpler
chemical reactions, and therefore the results need to be interpreted with some caution. Predictions cover
a very wide range, from 25 years to over 250 years, which vary with the manufacturer and the disc type.
Their effective life can be increased or decreased significantly depending upon the conditions under
which they are stored. Storage recommendations for optical discs are given in ISO 18925. Following
these recommendations promotes the physical integrity of the media and increases their effective life.
vi © ISO 2014 – All rights reserved
INTERNATIONAL STANDARD ISO 18938:2014(E)
Imaging materials — Optical discs — Care and handling for
extended storage
1 Scope
This International Standard establishes general principles for the care and handling of digital optical
discs during use. It addresses the issues of physical integrity of the medium necessary to preserve access
to the recorded data (information). This International Standard includes recommendations for handling
procedures to maximize the effective life of optical discs. Faulty handling, packing and transporting
techniques and methods often cause physical damage to the discs and to the content recorded thereon.
Extending the longevity of optical discs requires the identification of appropriate handling methods, as
well as well-developed and implemented training programs.
For the purposes of this International Standard, the term “optical disc” includes the families of compact
disc (CD), digital versatile disc (DVD), high definition digital versatile disc (HD DVD) and Blu-ray disc
1)
(BD) , and any hybrids of these families. The term “optical disc” also includes each type of disc within
a family, including injection moulded [read-only memory (ROM)], dye-layer [recordable (R)] and phase
change [rewritable (RW, RE), random access memory (RAM), and recordable (BD-R)] technologies.
While some of the recommendations in this International Standard (e.g. those for staff training) apply
specifically to large-scale or long term usage, the basics of all recommendations in this International
Standard are intended to be applied in circumstances where the desired result is long-term usage of the
medium whether archival, commercial or personal.
This International Standard does not cover magneto-optical (MO) discs, laser discs (LD) or glass discs.
At the time of writing, International Standards do not exist for HD DVD and Blu-ray discs. Nonetheless,
it is believed that the recommendations in this International Standard for care and handling can equally
apply to them. It is recognized that some of these requirements are not necessarily possible for the
individual user to achieve.
The following are within the scope of this International Standard:
— use and handling environments, including pollutants, temperature and humidity and light exposure;
— contamination concerns;
— inspection;
— cleaning and maintenance, including cleaning methods and frequency;
— transportation;
— disasters, including water, fire, construction and post-disaster procedures;
— staff training.
The quality of the data written on the disc is outside the scope of this International Standard. However,
a high quality result of the recording phase is important to the longevity of information. It is advisable
that a rigorous program of data integrity testing be implemented, as this forms an obligatory part of
all digital long-term storage. In addition, when keeping digital information for archival purposes, it is
advisable that a multiple copy/multiple location strategy be in place.
TM TM
1) Blu-ray Disc and Blu-ray are trademarks of Blue-ray Disc Association, and Blu-ray Disc and HD DVD are
examples of suitable products available commercially. This information is given for the convenience of users of this
International Standard and does not constitute an endorsement by ISO of these products.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 14644-1, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness
by particle concentration
ISO 18925, Imaging materials — Optical disc media — Storage practices
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acclimatization staging
process of conditioning material from one set of temperature-moisture conditions to another
3.2
balance
precision vertical position of the disc as it spins
3.3
blister
localized delamination that looks like a bubble
3.4
Blu-ray Disc
BD
optical disc having a cover layer around 0,1 mm thick and a substrate around 1,1 mm thick on which
data is read or recorded by an OPU using 405 nm laser diode and NA = 0,85 lens
3.4.1
Blu-ray Disc Read Only Memory
BD-ROM
optical disc to which information is transferred during manufacture to moulded areas in the Blu-ray
disc format and can be read multiple times by an optical beam
3.4.2
Blu-ray Disc Recordable
BD-R
recordable optical disc in which information can be recorded once to areas in the Blu-ray disc format
and read many times
3.4.3
Blu-ray Disc Rewritable
BD-RE
recordable optical disc in which information can be recorded to areas in the Blu-ray disc format and can
be erased, rerecorded and read many times
3.5
carton
box outer container that can hold one or more individual units and can be a fabrication of paper, card
stock or plastic
2 © ISO 2014 – All rights reserved
3.6
compact disc
CD
optical disc in which the information layer is located near one surface of a substrate and the data can be
read by an optical beam with a wave length of 780 nm
Note 1 to entry: Described in IEC 60908.
3.6.1
CD read only memory
CD-ROM
optical disc to which information is transferred during manufacture to moulded areas in the compact
disc format and can be read multiple times by an optical beam
Note 1 to entry: Described in ISO/IEC 10149.
3.6.2
CD Recordable
CD-R
recordable optical disc in which information can be recorded once to areas in the compact disc format
and read many times
3.6.3
CD Rewritable
CD-RW
rewritable optical disc in which information can be recorded to areas in the compact disc format and
can be erased, rerecorded and read many times
3.7
conditioning
exposure of a material to air at a given relative humidity and temperature until equilibrium is reached
3.8
container
box, can or carton used for storage and shipping of recording materials
EXAMPLE The box into which a reel, cassette, cartridge or shell is placed.
3.9
delamination
separation of a laminate into its constituent layers
3.10
digital versatile disc
DVD
optical disc in which one or more information layers are located between two substrates and the data
can be read by an optical beam with a wave length of 650 nm
Note 1 to entry: Formerly called digital video disc.
3.10.1
DVD read only memory
DVD-ROM
optical disc in which information is transferred during manufacture to certain areas in the DVD format
and can be read multiple times by an optical beam
Note 1 to entry: Described in ISO/IEC 16448 and ISO/IEC 16449.
3.10.2
DVD Recordable
DVD-R, +R
recordable optical disc in which information can be recorded once to areas in the DVD format and read
many times
Note 1 to entry: Described in ISO/IEC 23912, ISO/IEC 17344 and ISO/IEC 25434.
3.10.3
DVD Rewritable
DVD-RAM, DVD-RW, +RW
DVD optical discs that can be written, read and overwritten many times using phase change technology
Note 1 to entry: Described in ISO/IEC 17592, ISO/IEC 17341 and ISO/IEC 26925.
3.11
enclosure
case, cartridge, folder, envelope, sleeve or clam shell that is intended for physical protection against
mechanical damage
3.12
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having permanent value
3.13
high definition digital versatile disc
HD DVD
optical disc in which one or more information layers are located between two substrates and the data
can be read by an optical beam with a wave length of 405 nm
Note 1 to entry: Sometimes called high density digital versatile disc.
3.13.1
HD DVD read only memory
HD DVD-ROM
optical disc in which information is transferred during manufacture to certain areas in the HD DVD
format and can be read multiple times by an optical beam
3.13.2
HD DVD recordable
HD DVD-R
recordable optical disc in which information can be recorded once to areas in the HD DVD format and
read many times
3.13.3
HD DVD rewritable
HD DVD-RW
HDDVD optical discs that can be written, read and overwritten many times using phase change
technology
3.14
information
data recorded using the system
3.15
insulated record container
storage box designed to provide an environmental buffer against temperature and humidity fluctuations
4 © ISO 2014 – All rights reserved
3.16
jewel case
plastic enclosure featuring a hinged lid and one or more trays, each containing a hub clamp to secure
and protect the disc surface
3.17
keep case
case designed for DVD discs slightly larger than a jewel case
3.18
macroenvironment
atmospheric conditions in a large area in which records are kept
Note 1 to entry: Atmospheric conditions are temperature, relative humidity and pollutants.
3.19
medium
material on which information is recorded
3.20
microenvironment
atmospheric conditions inside a storage enclosure in which records are kept
Note 1 to entry: Atmospheric conditions are temperature, relative humidity and pollutants.
3.21
optical disc
disc that will accept and retain information from light modulation changes in a recording or reflective
layer that can be read with an optical beam
3.22
optical disc cartridge
ODC
optical disc enclosure required for the operation of the disc
3.23
recording layer
layer of an optical disc on which data is written either during manufacture or in use
3.24
relative humidity
RH
ratio, defined as a percentage, of the existing partial vapour pressure of water to the vapour pressure
at saturation
Note 1 to entry: It is usually, but not always, equal to the percentage of the amount of moisture in the air to that
at saturation.
3.25
replicated disc
disc made by an injection moulding process where the land and pits that make up the data are physically
pressed into the polycarbonate
3.26
retrievability
ability to access information as recorded
3.27
slimline case
slimmer version of the jewel case
3.28
snapper case
alternative to the keep case with a cardboard cover
3.29
storage environment
conditions for storing materials
Note 1 to entry: The conditions are temperature, relative humidity, cleanliness of facilities and atmospheric
pollutants.
3.30
storage housing
physical structure supporting materials and their enclosures
Note 1 to entry: It can consist of drawers, racks, shelves or cabinets.
3.31
substrate
layer which may be transparent or not, provided for the mechanical support of the recording layer
3.32
system
combination of media, hardware, software and documentation necessary for recording and/or retrieving
information
3.33
WORM disc
optical disc in which the data in specified areas can be written only once and read multiple times by an
optical beam
4 Composition of optical discs
4.1 General
Optical discs are composed of a series of layers made of different materials assembled like a sandwich.
Typically, these layers include the polycarbonate substrate (plastic) layer(s), the data layer(s), the metal
layers(s) or reflective layer, the metal protective layers, the adhesive layer and an optional extra layer
for labelling or added protection. These layers are listed in Annex A.
4.2 Polycarbonate substrate (plastic) layer
The polycarbonate substrate makes up most of the disc. The polycarbonate is typically clear, but may be
coloured for appearance or to prevent copyright infringement. The laser beam of a disc drive travels
through this substrate for CD, DVD and HD DVD and through the cover layer for BD. The substrate
provides the layer depth necessary to maintain laser focus for CD, DVD and HD DVD. The substrate also
gives the disc enough strength to remain flat for CD, DVD, HD DVD and BD.
A CD is one continuous 1,2 mm thick polycarbonate layer. Both DVDs and HD DVDs are made up of two
0,6 mm thick polycarbonate layers bonded together. BDs are made up of 1,1 mm thickness polycarbonate
layer and 0,1 mm thickness cover layer. CDs and BDs are read from one side only. DVDs and HD DVDs are
read from one or both sides.
4.3 Data layer
As its name implies, the data layer of optical discs is the layer that contains the encoded data. The
encoded data appear as marks or pits that either transmit or alter light from the laser beam back to
the laser photosensor by way of the metal reflective layer. Write-once (–R, +R) discs use organic dye
material or phase change materials, whereas rewritable (–RW, +RW, –RAM, –RE) discs use phase change
6 © ISO 2014 – All rights reserved
materials as the layer(s) for holding record data written by a disc drive. ROM discs do not use a separate
layer, but the data has been pressed in the form of pits from injection moulding on the inner surface of
the polycarbonate substrate during the disc manufacturing process.
4.4 Reflective layer
The metal layer in optical discs reflects the laser beam back to the laser photodiode in the optical pickup
unit (OPU). Three main types of reflective metals typically are used for this layer:
a) aluminium or aluminium alloy,
b) gold, and
c) silver or silver alloy.
In “dual-layer” DVDs, silicon is sometimes used as one of the semi-reflective layers. Some discs use a
copper alloy for the purposes of appearance.
Aluminium is used in ROM, RW and RAM discs. Silver, silver alloy or gold are used in R discs, since
aluminium is too active to use with dye. Aluminium is also prone to corrosion when exposed to moisture
or other pollutants that penetrate into the disc. Oxidation of the aluminium diminishes its reflectivity,
eventually making the disc unreadable by the laser. This is sometimes referred to as disc “rot”.
Silver can lose reflectivity due to corrosion on exposure to pollutants such as sulfur dioxide. Silver alloys
are designed to inhibit corrosion.
In “dual-layer” DVDs, the outer reflective layer (silicon, gold, silver or silver alloy) is only semi-reflective,
i.e. it reflects back some of the laser beam and allows some of it to pass through to the fully reflective
layer and then reflect back.
To summarize, the relative properties of the three main types of reflective metals are as follows:
— Cost: aluminium < silver < silver alloy < gold;
— Stability: aluminium < silver or silver alloy < gold.
4.5 Protective layers
A very thin lacquer layer is applied to the label side of CDs to protect the metal from exposure to the
environment. Without this protective layer, the aluminium will oxidize within several days. The layer
also gives some limited protection from writing on or labelling the disc. Some solvents used in markers
(e.g. xylene, toluene) can also affect lacquer coatings and expose or react with the metal. Once the metal
is damaged, the laser cannot read data in the damaged areas. DVDs have no such protective lacquer
coating, due to the reflective layer location in the middle of the disc.
Sometimes a manufacturer will add an additional layer designed specifically to provide more resistance
to fingerprints and scratches on the label side of CDs.
Protective layers also are available to place on the laser reading side of the disc. These are specifically
designed for protection against scratches and other surface damage.
4.6 Adhesive layers
The discs of all DVD formats are formed by bonding two 0,6 mm discs together. Disc durability and
reliability require excellent bonding. The bonding methods include hot-melt bonding and ultraviolet
(UV) bonding. The bonding layer needs to be optically transparent for some dual-layer DVDs.
The DVD bonding process mainly uses the following three methods:
— the spinning method, using a radical UV resin;
— the screen printing method, using a cationic UV resin;
— the sheet method, using a double-sided adhesive sheet.
It is essential that the adhesive layer be uniform within close tolerances, that it does not introduce tilt
out of the range of the DVD specification, that no defects such as bubbles occur and that it is optically
transparent in dual layer DVDs.
4.7 Additional layers
An optional layer may also be added to optical discs to provide a writable, printable or coloured surface.
Such surfaces include thermal-printable, inkjet-printable and silkscreen-printable surfaces. These
layers are applied over the lacquer layer on CDs, or over the polycarbonate substrate on other single-
sided discs.
5 Failure mechanisms
5.1 General
Optical disc performance depends on the performance of the disc drive and the characteristics of the
disc itself. This clause only discusses failure mechanisms due to the disc.
5.2 Physical stress
Optical discs are typically handled directly by users. They are subject to a variety of physical stresses,
including mechanical impact and thermal shock. Mechanical impact can result in scratching, fracturing,
breakage, warpage or delamination. Thermal shock is a rapid temperature change that can cause
differential expansion or contraction resulting in warpage or delamination. Warping can be a temporary
condition that returns to normal, but severe warping or repetitive warping can cause delamination and
permanent damage.
5.3 Layer sensitivity
5.3.1 General
Proper care and handling of optical discs requires knowledge of the sensitivities of the various layers
which make up optical discs. Various types of defects can be encountered because of the complex
structure of these materials. Optical discs are laminates of very dissimilar layers and each layer can
cause malfunctions. It is essential that the disc does not undergo any delamination. The primary layers
and their susceptibilities to failure or damage sensitivities are as described in 5.3.2 to 5.3.6 below.
5.3.2 Polycarbonate substrate
The laser beam of CD, DVD and HD DVD system transmits to its focus point and back to the reading sensor
through the polycarbonate substrate. Eccentricity, manufacturing flaws, off-centring, lack of flatness or
balance creates tracking and/or reading problems. This may be caused by physical stress, exposure
to high or rapidly changing temperatures, humidity or manufacturing errors. Surface or penetrated
containments can hinder or obstruct the laser beam.
5.3.3 Data layer
In ROM (replicated) discs, the data are moulded into the substrate and the data layer is not a separate
layer as in R, RW, RAM and RE discs. The recording layer in R, RW, RAM and RE discs can be damaged by
light, heat or moisture. The recorded signal therefore can be degraded by unwanted exposure to these
factors or by chemical degradation due to aging. Physical damage that is deep enough to reach the data
layer will also damage the data.
8 © ISO 2014 – All rights reserved
5.3.4 Reflective layer
This layer serves to reflect the modulated optical beam to the receiver. Any change in reflectivity caused
by dents, abrasion or corrosion due to moisture or other contaminant penetration is very detrimental.
Any change in flatness will change the laser beam angular reflection.
5.3.5 Protective (lacquer) layer
This layer exists on the label side and edge of CDs to protect the metal layer. Any removal, abras
...
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