U.S. patent application number 09/750455 was filed with the patent office on 2002-07-04 for coating for optical information disks.
Invention is credited to Upper, Brandon L..
Application Number | 20020086962 09/750455 |
Document ID | / |
Family ID | 25017933 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020086962 |
Kind Code |
A1 |
Upper, Brandon L. |
July 4, 2002 |
COATING FOR OPTICAL INFORMATION DISKS
Abstract
A transparent coating is used on an optical information disk.
The optical information disk is an injection-molded piece of clear
poly-carbonate plastic and is impressed with microscopic bumps
which are arranged as a single, continuous, extremely long spiral
track of data. A thin, reflective aluminum layer is sputtered onto
the optical information disc so that the thin, reflective aluminum
layer covers the bumps. A thin acrylic layer is sprayed over the
thin, reflective aluminum layer in order to protect it. The
transparent coating is a composite material which is made of silica
as the discontinuous phase and of a
polytetrafluoro-ethylene-derived organic polymer as the continuous
phase which leads to a fluorine-containing silica-based product.
The transparent coating is applied by spin or dip from specific
solutions at room temperature followed by a mild and short heat
treatment.
Inventors: |
Upper, Brandon L.; (Redondo
Beach, CA) |
Correspondence
Address: |
W. Edward Johansen
11661 San Vicente Boulevard
Los Angeles
CA
90049
US
|
Family ID: |
25017933 |
Appl. No.: |
09/750455 |
Filed: |
December 28, 2000 |
Current U.S.
Class: |
526/242 ;
428/64.4; G9B/7.159; G9B/7.182 |
Current CPC
Class: |
Y10T 428/21 20150115;
G11B 7/252 20130101; G11B 7/2585 20130101; G11B 7/2542 20130101;
G11B 7/2534 20130101 |
Class at
Publication: |
526/242 ;
428/64.4 |
International
Class: |
B32B 003/02; C08F
012/20; C08F 014/18; C08F 114/18; C08F 214/18 |
Claims
What is claimed is:
1. A transparent coating for use on an optical information disk
which is an injection-molded piece of clear polycarbonate plastic
and which is impressed with microscopic bumps which are arranged as
a single, continuous, extremely long spiral track of data with a
thin, reflective aluminum layer being sputtered onto the optical
information disc so that the thin, reflective aluminum layer covers
the bumps and with a thin acrylic layer being sprayed over the
thin, reflective aluminum layer in order to protect it, said
transparent coating comprising a composite material which is made
of silica as the discontinuous phase and of a
polytetrafluoro-ethylene-derived organic polymer as the continuous
phase which leads to a fluorine-containing silica-based product and
which is applied by spin or dip from specific solutions at room
temperature followed by a mild and short heat treatment.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a liquid composition which forms a
transparent coating on the optical surface of an optical
information disk in order to protect the optical surface of the
optical information disk from being scratched.
[0002] In their article, entitled "Scratch-resistant single-layer
antireflective coating by a low-temperature sol-gel route,"
published in the Proceedings of SPIE, Volume 1758, pages 135-149,
Sol-Gel Optics II, edited by John D. Mackenzie in December 1992,
Herve G. Floch and Phillippe F. Belleville stated that a
quarter-wave-thick narrow-bandwidth antireflective coating has been
developed for use on plastic substrates by a sol-gel route. This
coating has revealed pronounced scratch-resistance and
climatic-resistance under adverse conditions. The single-layer
coating consists basically of a composite material made of silica
as the discontinuous phase and of a polytetrafluoro-ethylene-deriv-
ed (Teflon.TM.) organic polymer as the continuous phase. This leads
to a fluorine-containing silica-based product so-called
Fluosil-coating. The coating is applied by spin or dip from
specific solutions at room temperature followed by a mild and short
heat treatment. In addition to remarkable abrasion and
environmental resistance properties, such coatings have displayed
excellent laser-induced damage threshold levels surpassing uncoated
substrates. Such a product has opened new perspectives concerning
architectural optical thin-films and ophthalmic lenses.
[0003] It is known that the surfaces of solid substrates that have
been subjected to treatments or machining to provide a polish,
gloss, or another surface aspect, as required by technical or
decorative requirements, must be protected by suitable coatings to
prevent any alteration of the surface condition. Such protection is
more necessary when the surface is more fragile or subject to the
risks of alteration or degradation as in the case of, for example,
glass, ceramics, and organic polymeric materials which may be
scratched or opacified from the effects of friction, abrasion, or
even shock.
[0004] U.S. Pat. No. 6,077,583 teaches a transparent protective
cover for the play-side of an optical disk which is made of
polycarbon film. The protective cover is annular in shape and is
appropriately sized to fit the various disc formats. There is
provided an inner crevice or groove that fits the inner molding of
a disc allowing for greater structural integrity and which assists
in the placement of the protector on the disc. The device is
attached to the disc using several clips that are located around
the perimeter.
[0005] U.S. Pat. No. 4,983,437 teaches a thin, flat, polymer,
scratch resistant, user applied disc protector with self-adhesive
backing which affixes to the top of an optical information disc to
help eliminate possible damage from impact which would render the
disc in a semi-unplayable or unplayable condition. This extra layer
of user applied protection is prefabricated to proper size to
adhesively secure to various optical mediums with a self-adhesive
layer by an application method of installation on the top,
protective side of the disc. Adhesive allows for permanent
placement on the disc for convenience without hindering operation
of the disc and without hindering readability of the context of the
information lettering. This disc protector can include a removable
peel-away backing.
[0006] U.S. Pat. No. 5,757,765 teaches a protection structure which
is adapted for protecting a disc includes a film mounted on an
underside of the disc for covering a data reading region of the
disc. The film includes an inner rim portion abutting on an inner
annular portion of the disc, and an outer rim portion abutting on
an outer annular portion of the disc. A plurality of ribs each a
extend radially and inwardly from the inner rim portion of the film
and each abut on the inner annular portion of the disc, and a
plurality of recesses are each defined between adjacent two of the
ribs. An annular adhesive sheet forms an adhesive surface which can
be adhered on each of the ribs and can be adhered on the inner
annular portion of the disc via each of the recesses, thereby
securing each of the ribs on the inner annular portion of the
disc.
[0007] U.S. Pat. No. 5,743,965 teaches a disk coating system for
forming a coating on a disk such as an optical information disk
which transfers disks to and from a pair of spinners with first and
second disk transfer mechanisms. The coating system further has an
intermittently rotating turntable, an apparatus for supplying a
coating material to each disk on the turntable at a predetermined
position, and a system for curing a coating layer on each disk. The
spinners for removing an excess amount of the coating material are
placed between the turntable and the curing system. The first
transfer mechanism is for transferring disks from the turntable to
the spinners, and the second transfer mechanism is for transferring
disks from the spinners to the curing system. The two spinners are
substantially equidistant from a predetermined disk position on the
turntable. The first transfer mechanism has two arms extending in
two directions diverging from a pivot at a predetermined angle.
With both arms, this transfer mechanism can transfer disks from the
predetermined disk position on the turntable alternately to the
first and second spinners at a high speed.
[0008] U.S. Pat. No. 4,736,966 teaches an optical data storage
medium, such as a data card with a strip of optical data storage
material, which has peelable transparent protective layers adhered
above the storage material. When a protective layer becomes too
scratched to read or write through, it may be removed by peeling.
More than one layer may be adhered successively above one another,
and removed one by one as they become scratched. The peelable
protective layers are preferably adhesive tapes made of Aclar,
Mylar, polyester, or other hard-to-tear polymers with pressure
sensitive adhesive. One or more of the layers, and an underlayer
between substrate or card base and the storage material may be a
water barrier material such as a polytrichlorofluoroethylene.
[0009] U.S. Pat. No. 5,518,788 teaches an optical recording disk
which has an anti-static hard coat layer provided on at least one
surface of the disk. The hard coat layer includes a fluorinated
ionic salt. A polymer includes a plurality of pendant fluorinated
groups and optionally a nonionic fluorinated surfactant. The
polymer comprising a plurality of pendant fluorinated groups is
preferably a copolymer derived from monomers comprising a
nonfluorinated vinyl monomer; and a vinyl monomer comprising a
fluorinated group.
[0010] U.S. Pat. No. 5,935,673 teaches an optical disk which has a
surface which is coated with a removable layer of a material that
does not significantly alter the optical properties of the disc in
order to protect the optical surface of optical information disk
such as an optical information disk or a digital versatile disk.
Whenever the coating layer may have become damaged, it is removed
and replaced with a new layer.
[0011] U.S. Pat. No. 5,744,243 teaches a composition which produces
durable coatings and a process for preparing a single-layer broad
band antireflective coating on solid substrates, such as glass,
ceramics, metals, and organic polymeric materials. The coating
composition consists, in combination, acid catalyzed hydrolysis and
condensation products of water-silane monomer mixture and a film
forming amount of a polymer having functional groups selected from
amino, hydroxy and carboxy, hydroxy and amino, amino and carboxy,
and amino, hydroxy and carboxy. The process includes the steps of
applying the aforesaid coating composition (or an acid catalyzed
sol-gel coating composition) substantially free of preformed oxide
sol and water soluble metal salt to the surface of a solid
substrate, curing the applied coating, and treating the cured
coating with an aqueous electrolyte solution for a time sufficient
to produce a coating having graded porosity which is antireflective
over a broad band of the visible spectrum.
[0012] U.S. Pat. No. 5,120,811 teaches a 1 to 8 micron
organic/inorganic (epoxy/glass) wear surface coating over a clear,
protective layer provides excellent stain and gloss protection. An
acid hydrolyzed silicate is combined with an acid hydrolyzed
silicone coupling agent; an epoxy monomer; a photoinitiator and
silicon oil surfactant to produce a coating composition which is
dried to remove alcohol/water solvent and U.V. cured.
[0013] U.S. Pat. No. 4,808,291 teaches apparatus for coating
optical information disks which includes a rotating table which is
loaded with removable carriers, each of which holds a substrate to
be coated. The carriers are advanced to a loading position and are
pushed from the table thereat into a hollow cylinder. Each carrier
has a pair of O-rings on its periphery which are squeezed against
the inside surface of the cylinder to effect a double seal. Each
carrier pushes the carrier ahead of it up through the cylinder in a
train like fashion. Along the cylinder there are vacuum stations
which act to pump down and degas the substrates. Apertures are
provided in the vacuum stations and these apertures are formed to
permit the O-rings to expand as the carriers pass by the apertures
without causing the O-rings to be cut or scored. Within a vacuum
chamber there is included a vapor trap which helps remove water
vapor from the substrates during the degassing operation.
[0014] U.S. Pat. No. 5,571,041 teaches a method which repairs and
refinishes an audio and video optical information disk having a
scratch or a plurality of scratches on a plastic cover bottom side
of the disk. The scratch interfering with a laser beam reading
digital information upwardly through the bottom side of the disk.
The top-side of the disk having a thin film layer of the recorded
digital information secured thereon. The interference by the
scratch causing an unwelcome "skip" during the play of the disk
thereby lending its playing qualities unacceptable. The method of
repair includes first inspecting the disk to determine the depth of
the scratch. If the scratch is deep, a heavy cut, medium cut and
fine cut cleaner may be used. The top-side of the disk is then
placed against the soft covered wheel and secured thereto. As the
disk is spun at low rpm, the heavy cut cleaner is applied evenly
across the surface of the bottom side of the disk using a clean
cotton cloth or cotton pad. This step is repeated at higher rpm
using a medium cut cleaner and then a fine cut cleaner is used. A
clear plastic cleaner and a clear plastic polish are then applied
using a cotton pad. The disk is then finally inspected for any
remaining scratches. To further enhance the repair of the disk and
extend the playing life of the disk, a clear plastic cover is
applied to the top side of the disk to protect the recorded data
thereon from permanent damage.
[0015] U.S. Pat. No. 5,791,467 teaches a protective cover for an
optical disk, such as an optical information disk, which includes a
flexible and transparent base portion for covering one side of the
optical disk. A first retaining portion is affixed to the top of
the base portion so as to define a pocket for snugly receiving and
frictionally retaining a portion of an optical disk. A second
retaining portion is affixed to the top of the base portion at a
distance from the first retaining portion. The second retaining
portion defines another pocket for receiving and retaining another
portion of the optical disk. Since the cover is transparent and
snugly receives the optical disk, digitally encoded data may be
readily obtained from the optical disk with conventional equipment,
like an optical information disk player, while the cover is
positioned over the disk.
[0016] U.S. Pat. No. 5,922,430 teaches an optical information disk
protector for an optical data storage disk which includes a thin,
transparent sheet having an inside diameter being larger than an
inner hole of the disk and the sheet extending within and being
bounded by a main region for placement against a first side of the
disk, and approximately 24 circumferentially spaced support
portions extending radially outwardly from the main region to a
distance being greater than a thickness of the disk beyond the disk
outside diameter. Each support portion has a bridge width being not
greater than 2 percent of the disk outside diameter within a bridge
region that is concentric with the inside diameter and extends from
the disk outside diameter radially outwardly a distance
corresponding to the disk thickness. A retainer holds the support
portions folded against a second side of the disk when the main
region of the sheet is placed against the first side of the disk,
the inside diameter of the sheet being maintained concentric with
the disk outside diameter by the bridge portions engaging outside
edge portions of the disk, the retainer being a thin, sheet having
an inside diameter larger than the inner hole of the disk, the
sheet being smaller than the disk and having adhesive applied to
one side for contacting the support portions.
[0017] U.S. Pat. No. 5,910,932 teaches an optical disc system which
uses a rewritable optical disc with a light-transmitting cover and
an objective lens for bundling or focusing a light beam on a
recording layer of the optical disc in order to perform recording
and/or reproducing of information. The recording layer is formed of
a phase-change material. The thickness of the light-transmitting
cover falls within the range of 0.05 mm to 0.6 mm, the numerical
aperture (NA) of the objective lens is set to fall within the range
of 0.55 to 1.10, and the wavelength of the light beam is selected
to be between 100 nm to 780 nm.
[0018] U.S. Pat. No. 4,485,130 teaches a basic liquid composition
which includes, in solution in at least one organic solvent, with
or without water, from 10 to 40% of a hard-enable organosilicic
compound resulting from a first hydrolysis reaction achieved at a
temperature lower than 50.degree. C. in the presence of a
carboxylic acid and water on at least one R'Si(OR)4 alkoxysilane
with n=1 or 2, in association or without association with at least
one Si(OR")4-alkoxysilane, then, a second hydrolysis at a
temperature lower than 40.degree. C. after removal of the formed
volatile solvents and addition of a less volatile solvent and at
least one R"'Si(OR1)3-alkoxysilane, said reaction being followed
with the setting of the pH to between 3.5 and 5.5 by an organic
base. It is known that solid surfaces that have been submitted to
sometimes very extensive treatments or machinings to confer upon
them polish, gloss or any other aspect as required by technical or
merely decorative requirements or needs, must be protected by
suitable coatings to prevent any risks of alteration of the
conditions thereof. Such protection is the more necessary the more
fragile the surface considered or when the latter is particularly
subjected due to its very nature to such risks of alteration or
degradation as in the case of for example glass or glass
substitutes which are scratchable or opacifiable from the effect of
friction, abrasion, or even shocks. Such scratching hazards are met
moreover also in the case of other products such as plastic
materials, ceramics, porcelain, earthenwares, stonewares, machined
or polished metals, and the like. A number of coatings have already
been proposed to prevent or resist such surface degradation;
however, such coatings generally present among others at least one
of the following deficiencies: insufficient adherence to carrier;
insufficiently high scratching and/or abrasion strength; short
transparency longevity; short hardness longevity; poor cracking
strength; loss of protective efficiency under the effect of water
or moist atmospheres. Furthermore, the solutions from which such
coatings are prepared have not sufficient stability in the course
of time to permit durable storage. Their degradation with time is
actually detrimental to the physical properties of the coatings to
be realized.
[0019] This basic composition is suited for achieving transparent
coatings or varnishes and stable in the course of time to permit
storage thereof without any risks of degradation, on the one hand,
and on the other hand, varnishes which have not any of the
above-mentioned deficiencies, but on the contrary present all the
following main properties, i.e. good adherence to the carrier, good
scratching and/or abrasion strength, good hardness, good
opacification strength longevity, good cracking strength, good
resistance to water and moist atmospheres, and a sufficient
thickness in the hardened varnish. More especially, the object of
this invention is a basic composition for varnishes of the type
comprising an organosiloxane or alkoxysilane hydrolysate.
[0020] U.S. Pat. No. 4,346,131 describes the preparation of a clear
alcohol solution of acid hydrolyzed metal alkoxide which can be
coated on a substrate and dried to produce an optical coating.
[0021] U.S. Pat. No. 4,480,072 teaches a useful means to cross-link
organic and inorganic surfaces and particles. In his article,
entitled SQL-GEL DERIVED DIP COATINGS Helmut Dislich discloses how
mixtures of metal alkoxides may be used to condense mixed metal on
a glass surface such as silicon-titanium, aluminum-magnesium,
cadmium-tin, indium-tin, etc. In his article, entitled ORGANICALLY
MODIFIED SILICATES AS INORGANIC-ORGANIC POLYMERS H. K. Schmidt
describes combinations of linear organic polymer networks with
three dimensional tetrahedron silicon networks using the sol-gel
process, e.g. where combined polymerization of methacrylate and
condensation of Ti(OR).sub.4/Si(OR).sub.4/epoxy-Si(OR).s- ub.3
produce a reinforced system with increased tensile strength and
scratch resistance.
[0022] Japanese Application 86/25,739 teaches antifogging tile
coatings where silica is bonded to polyvinyl alcohol using
hydrolyzed [3-(glycidyloxy)propyl] trimethoxysilane.
[0023] European Patent Application 222,582 teaches an ultraviolet
curable composition with good adhesion to glass comprising epoxy
resin, poly-organosiloxane, aromatic onium salt and acrylate
resin.
[0024] British Patent Application GB 2,177,093 teaches an
ultraviolet curable coating composition which includes
multifunctional glycidyl or cycloaliphatic epoxy oligomer,
hydrolyzed silane coupling agent treated inorganic filler and
photoinitiator for reaction of epoxy groups. Still, in spite of all
the known art and available compositions of matter, a need existed
to provide protective wear surfaces which could be conveniently
produced without adverse environmental effects.
[0025] U.S. Pat. No. 4,753,827 teaches an organoalkoxy-silane/metal
oxide sol-gel composition. The organoalkoxy-silane is of the
general formula Rx Si(OR')4-x wherein R is an organic radical, R'
is a low molecular weight alkyl radical, and x is at least 1 and
less than 4, is partially hydrolyzed in organic solution and
reacted with a titanium or zirconium alkoxide of the general
formula M(OR")4 wherein M is titanium or zirconium and R" is a
lower alkyl radical. The composition is hydrolyzed, dried and
condensed to form an organosiloxane/metal oxide abrasion-resistant
coating on a substrate.
[0026] U.S. Pat. No. 3,004,863 teaches a method which increases the
scratch resistance of glass by applying to the glass surface an
acidic aqueous solution of an organic titanate ester composition
and heating at a temperature sufficient to anneal the glass.
[0027] U.S. Pat. No. 3,582,395 teaches a method which increases the
scratch resistance of glass by treating the surface at a
temperature between the strain point and the softening point with
an alkylsilyl titanate to form a protective coating of
silica-titania.
[0028] U.S. Pat. No. 3,986,997 and U.S. Pat. No. 4,027,073 teach an
acidic dispersion of colloidal silica and hydroxylated
silsesquioxane in an alcohol-water medium coated onto substrates
such as acrylic lenses to provide an abrasion-resistant
coating.
[0029] U.S. Pat. No. 4,242,403 teaches multi-layer automotive
glazing units which include transparent substrates with protective
covers and that combine penetration resistant body portions with
abrasion resistant surfaces of a silica-reinforced
organopolysiloxane.
[0030] U.S Pat. No. 4,275,118 teaches a coating composition which
includes an acidic dispersion of colloidal titania, colloidal
silica and hydroxylated silsesquioxane in an alcohol-water medium
which produces a hard, abrasion-resistant coating when cured on a
plastic surface such as polycarbonate.
[0031] U.S. Pat No. 4,390,373 and U.S. Pat. No. 4,442,168 teach a
coating composition which includes an effective abrasion resisting
amount of a colloidal dispersion containing colloidal antimony
oxide and colloidal silica in a water-alcohol solution of the
partial condensate of an organosilanol which upon curing forms an
improved transparent, abrasion-resistant coating.
[0032] U.S. Pat. No. 4,405,679 teaches a coated shaped article of a
polycarbonate type resin of abrasion resistance which includes a
shaped polycarbonate substrate, an undercoat applied and cured on
the substrate, and an overcoat applied and cured on the undercoat
which includes a hydrolyzate of an epoxy-containing silicon
compound, at least one member of the group of hydrolyzates of
organic silicon compounds, colloidal silica and organic titania
compounds, and a curing catalyst.
[0033] U.S. Pat. No. 4,477,499 teaches ultraviolet radiation
resistant silicone resin coatings which have thermo-formability and
shortened required aging achieved by the addition of a Lewis acid
compound to the coating composition.
[0034] U.S. Pat. No. 4,500,669 and U.S. Pat. No. 4,571,365 teach
transparent, abrasion-resistant coating compositions which include
a colloidal dispersion of a water-insoluble dispersant in a
water-alcohol solution of the partial condensate of silanol wherein
the dispersant comprises metals, alloys, salts, oxides and
hydroxides thereof.
[0035] European patent application No. 85110293.9 teaches
carbon-containing monolithic glasses prepared by a sol-gel process
involving a partial condensate of a silanol containing colloidal
metal oxides such as SnO2, B2 O3 and ZnO2.
[0036] U.S. patent application Ser. No. 915,344 teaches solgel
compositions which contain silane and alumina, and abrasion
resistant coatings produced therefrom.
[0037] The inventor incorporates the teachings of the above-cited
patents into this specification.
SUMMARY OF THE INVENTION
[0038] The present invention is generally directed to a transparent
coating which is used on an optical information disk. The optical
information disk is an injection-molded piece of clear
poly-carbonate plastic and is impressed with microscopic bumps
which are arranged as a single, continuous, extremely long spiral
track of data. A thin, reflective aluminum layer is sputtered onto
the optical information disc so that the thin, reflective aluminum
layer covers the bumps. A thin acrylic layer is sprayed over the
thin, reflective aluminum layer in order to protect it.
[0039] In a first separate aspect of the present invention, the
transparent coating is a composite material which is made of silica
as the discontinuous phase and of a
polytetrafluoro-ethylene-derived organic polymer as the continuous
phase which leads to a fluorine-containing silica-based
product.
[0040] In a second separate aspect of the present invention, the
transparent coating is applied by spin or dip from specific
solutions at room temperature followed by a mild and short heat
treatment
[0041] Other aspects and many of the attendant advantages will be
more readily appreciated as the same becomes better understood by
reference to the drawing and the following detailed
description.
[0042] The features of the present invention which are believed to
be novel are set forth with particularity in the appended
claims.
DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a top plan view of an optical information disk for
use with a transparent coating in accordance with the present
invention.
[0044] FIG. 2 is an elevation view in cross-section (not to scale)
the optical information disk of FIG. 1 with a transparent coating
which is used on an optical information disk.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0045] In his article, entitled "How Compact Disks Work," Marshall
Brain stated that an optical information disk can store up to 74
minutes of music. The total amount of digital data which must be
stored on an optical information disk is 44,100 samples per channel
per second times 2 bytes per sample times 2 channels times 74
minutes times 60 seconds per minute=783,216,000 bytes. In order to
fit more than 783 megabytes onto a disk only 12 centimeters in
diameter requires that the individual bytes be very small. By
examining the physical construction of the optical information disk
one can begin to understand how small they are. An optical
information disk is a fairly simple piece of plastic, about 1.2
millimeters thick.
[0046] Referring to FIG. 1 in conjunction with FIG. 2 an optical
information disk 10 is an injection-molded piece of clear
polycarbonate plastic. During manufacturing, the optical
information disk 10 is impressed with microscopic bumps 11 which
are arranged as a single, continuous, extremely long spiral track
12 of data. Once the optical information disk 10 is formed, a thin,
reflective aluminum layer 13 is sputtered onto the optical
information disc 10 so that the thin, reflective aluminum layer 13
covers the bumps 12. A thin acrylic layer 14 is sprayed over the
thin, reflective aluminum layer in order to protect it. A label 15
is printed onto the thin acrylic layer 14.
[0047] The optical information disk 10 has a single spiral track of
data, circling from the inside of the disk to the outside. The fact
that the spiral track 12 starts at the center means that the
optical information disk 10 can be smaller than 12 centimeters if
desired. There are now plastic baseball cards and business cards
which you can put into an optical information disk player. The
optical information disk-business cards hold about 2 megabytes of
data before the size and shape of the card cuts off the spiral.
What the picture on the right does not even begin to impress upon
one is how incredibly small the data track is--it is approximately
0.5 microns wide, with 1.6 microns separating one track from the
next. And the elongated bumps that make up the track are each 0.5
microns wide, a minimum of 0.83 microns long and 125 nanometers
high. Looking through the polycarbonate layer at the bumps 11, the
bumps 11 look something like "pits." One often reads about "pits"
on an optical information disk 10 instead of bumps 11. The bumps 11
appear as pits on the aluminum side, but on the side which the
laser reads from the pits are bumps 11. The incredibly small
dimensions of the bumps 11 make the spiral track on an optical
information disk 10 extremely long. If one could lift the data
track 12 off the optical information disk 10 and stretch it out
into a straight line, it would be 0.5 microns wide and almost 3.5
miles long. To read something this small one needs an incredibly
precise disc-reading mechanism.
[0048] Referring to FIG. 2 a transparent coating 20 is applied to
the exposed polycarbonate plastic side of the optical information
disk 10. The transparent coating 20 consists of a composite
material. The composite material is made of silica as the
discontinuous phase and of a polytetrafluoro-ethylene-derived
organic polymer as the continuous phase. This leads to a
fluorine-containing silica-based product so-called Fluosil-coating.
The transparent coating 20 is applied by spin or dip from specific
solutions at room temperature followed by a mild and short heat
treatment. In addition to remarkable abrasion and environmental
resistance properties, the coating 20 has displayed excellent
laser-induced damage threshold levels surpassing non-coated optical
information disk 10. The transparent coating 20 on the optical
surface of the optical information disk 10 protects the optical
surface from being scratched.
[0049] From the foregoing it can be seen that a transparent coating
for an optical information disk has been described.
[0050] Accordingly it is intended that the foregoing disclosure and
drawings shall be considered only as an illustration of the
principle of the present invention.
* * * * *