Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
  • G11B7/263—Preparing and using a stamper, e.g. pressing or injection molding substrates
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
  • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
  • G06K19/06009—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code with optically detectable marking
  • G06K19/06046—Constructional details
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
  • G11B7/003—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with webs, filaments or wires, e.g. belts, spooled tapes or films of quasi-infinite extent

Definitions

• the invention relates to a method of manufacturing a read-only optical registration medium in the form of a flexible tape.
• the invention also relates to a read-only optical registration medium in the form of a flexible tape having a layered structure.
• the invention further relates to a cassette comprising a housing which contains such an optical registration tape in combination with two spools, the tape being partially wound around one of the spools and being connected to the other spool.
• recorded binary data can be read by scanning a focused light beam along a reflective registration surface of the medium.
• Each data bit in this registration surface is represented by a localised region having specific reflection characteristics, which are mutually different for data bits representing a " 1 " and those representing a "0".
• data bits are represented by a series of pits in an otherwise smooth registration surface. The depth of these pits is chosen to have a value ⁇ /4n, whereby the scanning light beam is assumed to be polarised and to have a monochromatic wavelength ⁇ (in air), and the registration surface is assumed to be overlaid by a protective film of refractive index n.
• phase-shift can in turn be detected on the basis of interference effects. In this manner, it is possible to optically "read" the topography of the registration surface, and thus also the binary bit-streams to which that topography corresponds.
• a method as stated in the opening paragraph is known from German Patent Application DE 35 20 111, in which a screen printing procedure is used to create small pigmented domains on a reflective registration surface of a tape.
• the reflection coefficient of these domains differs significantly from that of the surrounding un-pigmented surface, so that stored data on the tape can be optically read by monitoring the intensity of the scanning light beam after its reflection from the registration surface.
• a layer of such material on a tape-like substrate can be inscribed using a focused laser beam whose intensity is modulated in accordance with a given binary bit-stream.
• information can be retrieved from the phase-change layer by monitoring the intensity of a light beam reflected therefrom.
• the smallest pigmented domains which can be produced using a screen printing procedure have a typical diameter of the order of 20-50 ⁇ m.
• the width of the pits on a Compact Disc is of the order of l ⁇ m. It is therefore evident that the storage density of such pigmented tape falls very short of the levels achievable with disc media.
• the very nature of the reading procedure regularly exposes the pigmented domains to intense laser light, with the attendant long-term risk of pigment fading and associated increase in noise levels;
• phase-change materials In the case of the second medium, an inherent disadvantage of phase-change materials is that they must be inscribed in real time, i.e. the speed at which they are inscribed is of the same order of magnitude as their play-back speed. This is due to the fact that the localised phase-changed domains must be written on a one-by-one basis, using a focused laser beam.
• An additional disadvantage is the inherent statistical risk of a spontaneous reverse phase-change in some domains. Though this risk is relatively small, it can nevertheless lead to increased noise levels in the long run;
• a drawback of the third medium is that the pits produced by laser ablation are rather ill-defined, with an irregular depth and raised rim walls.
• the material removed to create the pits in the first place can precipitate as unwanted debris somewhere else on the medium.
• the ablative medium must be inscribed in real time, which is tedious (and costly).
• a method should circumvent the problems cited hereabove.
• the new method should allow fast inscription of the said registration layer.
• the inventive method exploits a surprising discovery, as will now be elucidated.
• an optical registration tape is preferably optically smooth on the side from which its registration surface is read.
• the stamper itself may, for example, take the form of a (hard) drum whose cylindrical surface contains microscopic bumps arranged along a helical path, the width of this path being equal to the width of the tape. If such a stamper is rolled along the tape's registration layer, in such a manner that the region of contact between the drum and the tape translates along the said helical path, then the registration layer will be inscribed with pits corresponding to the said bumps.
• the stamper takes the form of a (hard) tape having a master side which is provided with a longitudinal array of microscopic bumps. If such a stamper tape is wound from one spool to another, and its master surface is thereby rolled at some point against the registration layer of the optical tape, which is concurrently being wound between two different spools at the same speed and in the same direction, then the registration layer will be endowed with pits corresponding to the bumps on the master surface.
• the flexible substrate employed in the inventive method may be roughened by the presence of fillers therein (e.g. microscopic silica or alumina particles), or by the application of a backing layer thereupon.
• a suitable substrate material in the first category is LUMIRROR (Toray Industries, Inc.), which is a transparent PET foil having a thickness of approximately 8 ⁇ m and containing fillers with a diameter of the order of 400 nm.
• a suitable substrate material in the second category is a PET foil which has been coated on one side with a binder (e.g. a resin) containing dispersed particles of carbon black, chromium trioxide or calcium carbonate (ideally having a diameter in the range 50-300 nm); the thickness of such a rough backing layer need only be of the order of 1 ⁇ .
• the embossable registration layer is chosen to comprise a photocurable organic polymeric material, and, during the embossing step (c), the interface of the registration layer with the stamper is exposed to curing actinic radiation.
• a suitable material in this category is SURPHEX (Du Pont), which is a dry UV-curable material available in the form of thin sheets of standard thickness (in the micron range). Such sheets can be laminated directly to a substrate foil, e.g. by heating and rolling.
• a dry photocurable resin e.g. an acrylic ester
• the embossable registration layer is chosen to comprise a thermoplastic which, in the embossing step (c), is first thermally softened, and is then allowed to cool and harden after being impressed upon by the stamper.
• the employed thermoplastic should have a lower softening temperature than the substrate material; in this manner, the registration layer can be softened without untoward softening of the substrate (with the attendant risk of decreasing the substrate's roughness).
• suitable thermoplastics for this purpose are polyvinyl chloride and polypropene.
• the registration layer is chemically softened prior to embossing, by applying a chemical solvent to its exposed surface.
• Candidate solvents for this purpose include, for example, acetone and isopropanol, as well as various chloroalkane solutions, ethers and esters, the exact choice depending on the particular material employed in the registration layer.
• the softened registration layer is hardened by removing the employed solvent therefrom. This can be achieved, for example, by heating the registration layer.
• the registration layer will generally have a thickness of the order of 1-10 ⁇ m, though a thicker or thinner registration layer is also compatible with the inventive method.
• the protective film provided in step (d) of the inventive method may be either inorganic or organic. Suitable inorganic materials such as SiO 2 , TiO 2 , A1N, Si 3 N 4 , etc. , can be provided by reactive sputter deposition or evaporation, for example. On the other hand, suitable organic materials such as polyurethane or polyacrylate resins can be provided using roller coating, or a spraying or brushing procedure, for example.
• the protective film will typically be of the order of 2-10 ⁇ m thick in the case of an organic film, and 20-500 nm thick in the case of an inorganic film, but may also be thicker, if so desired.
• the exposed surface of the protective film is preferably optically smooth.
• the term "optically smooth" is intended to indicate an RMS surfacial roughness which is at most 50 nm, preferably not in excess of 20 nm, and ideally no more than 5 nm. Such a finish is generally achieved automatically, as a result of surface-tension effects in the protective film during its formation.
• a particular embodiment of the method according to the invention is characterised in that, between steps (c) and (d), a metallic reflection layer is deposited on the embossed surface of the registration layer.
• a metallic reflection layer may comprise a pure metal or an alloy, and may be provided using sputter deposition, vapour deposition or laser ablation deposition, for example. Exemplary materials for this purpose include aluminium, gold, copper, silver, and their alloys. Use of such a reflection layer ensures that, when the registration side of the medium is scanned with a focused light beam, enough light intensity is reflected to yield an acceptable output signal level.
• An alternative embodiment of the inventive method is characterised in that at least one dye is added to the registration layer and/or the protective film, so as to achieve a substantial difference between the refractive indices of the registration layer and the protective film (at the wavelength of the reading light beam). In this manner, it is possible to increase the reflection coefficient at the interface between the protective film and the registration layer (for light incident through the protective film). In particular, for a sufficient difference in refractive index, Total Internal Reflection can be induced at this interface, with a relatively small associated Brewster angle in the protective film.
• n n + ik
• n the real refractive index
• k the abso ⁇ tion coefficient.
• the difference between the values of ⁇ for the registration layer and the protective film may lie in either the real or imaginary part of ⁇ , or both.
• the value of k for that dye should preferably be relatively small, so as to avoid untoward abso ⁇ tion of the incoming and reflected light beam.
• suitable dyes include pyrylium-4,4'-cyanine and butyl-benzo-indo-carbocyanine.
• These dyes have respective n- values of 3.270 and 3.050, and respective k-values of 0.570 and 0.058 (all values at a wavelength of 780 nm).
• use can be made of, for example, a squarylium dye.
• various other layers may be applied between those provided in steps (a), (b), (c) and (d) of the inventive method. For example:
• An adhesive layer or adhesion-promoting layer may de disposed between the substrate and the registration layer;
• a dielectric layer may be applied between the registration layer and the protective film
• a rough backing layer may be applied to the side of the substrate remote from the registration layer. This list is given by way of example only, and is not exhaustive.
• the method according to the invention can be employed to manufacture a novel read-only optical registration tape with excellent properties.
• a novel read-only optical registration tape is characterised in that it has a layered structure which successively comprises: A substrate; A registration layer;
• a reflective registration surface in which binary data are represented by localised level-variations
• the "reflective registration surface” referred to hereabove may be inte ⁇ reted as being one of the following:
• a metallic reflection layer applied to the side of the inscribed registration layer remote from the substrate;
• the interface of the inscribed registration layer and the protective film if use has been made of a dye to enhance the reflection coefficient at this interface.
• the "localised level variations” may, for example, be achieved by endowing the registration layer with a pattern of pits or bumps.
• a " 1 " may be represented by a pit
• a "0" may be represented by a level (i.e. unpitted) portion of the surface S in which the pits are made, the length of such a pit or level portion being an integral multiple of some basic unit representing a single bit.
• Both the surface S and the bottom of each pit are reflective, and reading of the registration surface can be achieved on the basis of the phase-difference between a (polarised) light beam reflected from the surface S and one reflected from the bottom of a pit.
• the magnitude of the level differences in the registration surface is preferably ⁇ /4n, for (polarised) light of wavelength ⁇ and a protective film of real refractive index n.
• the invention also relates to a cassette comprising a housing which contains two spools and the inventive read-only optical registration tape, the tape being partially wound around (at least) one of the spools and being connected to the other spool.
• the tape passes from one spool to another via guiding means which serve to position the tape behind an aperture in the housing in such a manner as to allow in situ optical access through the aperture to the registration surface of the tape.
• guiding means are not strictly necessary: if so desired, the tape can be looped out of the cassette housing and can be read ex situ.
• Figure 1 renders a cross-sectional view of a flexible substrate in the form of a tape, on which an embossable registration layer has been provided;
• Figure 2 shows the subject of Figure 1 subsequent to the performance of an embossing step thereupon, resulting in the formation of a pattern of low and high surfacial regions in the registration layer;
• Figure 3 depicts the subject of Figure 2 subsequent to the provision of a metallic reflection layer on the embossed registration layer;
• Figure 4 shows the subject of Figure 3 subsequent to the provision of a protective film over the metallic reflection layer, thereby creating an optical registration tape in accordance with the invention;
• Figure 5 depicts manufacturing apparatus for enacting a particular embodiment of the inventive method
• Figure 6 shows a cassette in accordance with the invention.
• Figures 1-4 depict various stages of a particular embodiment of the method according to the invention, and also of a particular embodiment of the inventive optical registration tape. Corresponding features in the various Figures are denoted by the same reference symbols.
• Figure 1 renders a cross-sectional view of part of a flexible substrate 1 in the form of a tape.
• the substrate 1 has two major surfaces la, lb, and is approximately 8 ⁇ m thick. It contains embedded microscopic fillers (not depicted), whose presence causes the surfaces la, lb to demonstrate an RMS roughness of the order of 10-20 nm.
• An example of a suitable such substrate 1 is a transparent PET foil in which silica particles having a diameter of the order of 400 nm have been dispersed.
• Such a substrate 1 is commercially marketed under the brand name LUMIRROR (type N997) by Toray Industries, Inc.
• An embossable registration layer 3 has been provided on the surface lb of the substrate 1.
• This layer 3 has a thickness of the order of 10 ⁇ m, and comprises, for example, a dry photocurable resin.
• the employed resin is SURPHEX P-6 (marketed by Du Pont), which is available in sheet form at a thickness of 6 ⁇ m, and was directly laminated onto the substrate 1 at a temperature of 120 °C and a rolling pressure of 250 kPa.
• the layer 3 presents a surface S remote from the substrate 1.
• the layer 3 has been embossed under pressure with the aid of a stamper (not depicted), in accordance with the inventive method.
• this has entailed the creation of shallow pits 5 in the surface S.
• the pits 5 have a depth of approximately 150 nm, a width (pe ⁇ endicular to the plane of the drawing) of approximately 0.5 ⁇ m, and variable length.
• a suitable embossing procedure is described in Embodiment 2 herebelow.
• the embossed surface of the layer 3 has been coated with a thin metallic reflection layer 7.
• the layer 7 is comprised of Al, has a thickness of 100 nm, and has been deposited using Vacuum Vapour Deposition. Because it hugs the contours of the original embossed surface of the registration layer 3, the layer reflection 7 demonstrates a series of sha ⁇ ly defined pits 5' in an otherwise smooth exposed surface.
• Figure 4 shows the subject of Figure 3 after the provision thereupon of a protective film 9.
• the material of the film 9 is, in this case, a polyacrylate resin, and has been roll-coated onto the reflection layer 7 to a thickness of approximately 5 ⁇ m.
• the exposed surface 11 of the film 9 is optically smooth, with an RMS roughness of 5 nm. This finish is naturally achieved as a result of surface tension effects in the film 9 during its formation on the underlying reflection layer 7.
• Figure 5 depicts manufacturing apparatus for enacting a particular embodiment of the inventive method.
• the employed stamper 51 has the form of a cylindrical aluminium drum with a diameter of 150 mm and a length of 165 mm, and with a relief pattern of microscopic bumps on its cylindrical surface 51a. The manner in which such bumps can be created is discussed in Embodiment 3 herebelow.
• the drum 51 and roller 53 are arranged with their cylindrical axes parallel to one another, and with their cylindrical surfaces 51a, 53a pressed against opposite sides of an inte ⁇ osed optical registration tape 55, which is as yet unembossed.
• This tape 55 extends substantially pe ⁇ endicular to the said cylindrical axes, in such a manner that its (curable) registration layer is in contact with the relief pattern on the surface 51a.
• the drum 51 is pressed against the roller 53 with a force of 5000 N, resulting is a pressure of the order of 15 N/mm 2 on the tape 55.
• the inte ⁇ osed tape 55 is pulled through between them, and its registration layer is embossed along its length with a series of pits corresponding to the bumps on surface 51a.
• the registration layer on the tape 55a is cured by directing actinic radiation R (e.g. UV radiation) onto that region 55a of the tape 55 which, at any given time, is still in contact with the surface 51a. If so desired, supplementary curing can be subsequently performed using a second beam of actinic radiation R' .
• actinic radiation R e.g. UV radiation
• the tape 55 passes through an on-line deposition chamber 57, where the embossed surface of the tape 55 is provided with a vacuum-evaporated metallic reflection layer.
• the tape 55 is first wound onto a buffer spool A, which can later be transferred into a vacuum chamber; the tape 55 is then unwound from the spool A and metallised on its embossed side.
• the tape 55 is subsequently provided with a protective film on its embossed side. This is here achieved by roller-coating the tape 55 in a roller-coater 59. If required, the freshly coated tape 55 may be subsequently dried using a heat source or air flow H. Alternatively, if the applied resinous liquid is photocurable, then the means H can be regarded as comprising actinic radiation for the purposes of curing the freshly applied film.
• the tape 55 is either wound onto a buffer spool B, or is directly wound into a cassette housing 511. If required, the tape 55 may first be cut to an appropriate (uniform) lateral width (e.g. 8 mm) with the aid of cutting wheels 513.
• an appropriate (uniform) lateral width e.g. 8 mm
• the microscopic bumps on the cylindrical surface 51a of the stamper drum 51 can be created using either a direct or indirect procedure, as will now be explained.
• the cylindrical surface 51a is coated with a layer of photoresist.
• this layer of photoresist is irradiated in accordance with the desired surfacial pattern of bumps, and is subsequently developed and cross-linked.
• the process described in the preceding paragraph is performed on one side of a sheet or ribbon, which is then wound around the drum 51 in such a manner that the bumped side of the sheet or ribbon faces outward and forms the surface 51a.
• Figure 6 depicts a particular embodiment of a cassette 60 in accordance with the invention, comprising a housing 62 which contains two spools 64 and a read-only optical registration tape 66 according to the invention. Also depicted is an aperture 68 in a wall of the housing 62.
• the tape 66 can be wound back and forth from one spool 64 to the other, and is thus arranged that its registration surface faces the aperture 68. In this manner, the reflective registration surface of the tape 66 can be accessed in situ by a light beam entering and leaving the housing 62 through the aperture 68.
• the housing 62 may also contain guide means (not depicted), which serve to maintain a given length of the tape 66 at a constant distance from the aperture 68.
• guide means may, for example, comprise a reference block over which the tape is spanned and which is located behind the aperture 68.
• the guide means referred to hereabove may be omitted from the housing 62, and the tape 66 may be read using a play-back device which loops a given length of the tape 66 out through the aperture 68 and then reads it ex situ, in analogy to a VHS video cassette, for example.
• the aperture 68 is preferably much wider than here depicted, so as to facilitate mechanical access to the tape 66.
• the aperture 68 is preferably located behind a mechanical shutter door (not depicted), so as to protect the tape 66 from dust and scratches.

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• 1996
  • 1996-09-26 WO PCT/IB1996/000995 patent/WO1997014142A1/en not_active Application Discontinuation
  • 1996-09-26 CZ CZ971721A patent/CZ172197A3/cs unknown
  • 1996-09-26 CA CA002207087A patent/CA2207087A1/en not_active Abandoned
  • 1996-09-26 KR KR1019970703889A patent/KR987000645A/ko not_active Application Discontinuation
  • 1996-09-26 CN CN96191474A patent/CN1168190A/zh active Pending
  • 1996-09-26 JP JP9514851A patent/JPH10510940A/ja active Pending
  • 1996-09-26 EP EP96930302A patent/EP0797825A1/de not_active Withdrawn
  • 1996-09-26 PL PL96320640A patent/PL320640A1/xx unknown
  • 1996-09-26 BR BR9606681A patent/BR9606681A/pt not_active Application Discontinuation

Non-Patent Citations (1)

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