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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D17/00—Producing carriers of records containing fine grooves or impressions, e.g. disc records for needle playback, cylinder records; Producing record discs from master stencils
  • B29D17/005—Producing optically read record carriers, e.g. optical discs

Definitions

• the invention relates to a method of copying a relief structure from the external surface of a first cylindrical drum to the external surface of a second cylindrical drum.
• the first cylindrical drum is rolled over a major surface of a (planar) flexible sheet of embossable material so as to endow that surface with a relief pattern (which will be a negative of the relief pattern on the outside surface of the first drum).
• the sheet can then be cut to size, wrapped around the external surface of the second cylindrical drum in such a manner that the relief pattern on the sheet faces outward, and affixed to the drum using, for example, an adhesive, clips, screws, etc.
• the material of the sheet is such that it can be hardened (e.g. thermally or using actinic radiation) after it has been embossed, then the second drum may thus be provided with a durable relief surface.
• the known method has a number of disadvantages.
• a certain amount of distortion of the transferred relief pattern due to bending and stretching
• the two adjoining ends of the sheet must be fused seamlessly, which is extremely difficult.
• the cylindrical surface of the second drum around which the (thin) embossed sheet is wrapped must be exceptionally smooth, since any surfacial roughness will otherwise protrude through to the embossed surface of the sheet.
• the new method should not incur joining and seaming problems in the transferred relief pattern.
• the said method should be less sensitive to the presence of surfacial roughness on the surface of the drum onto which the relief pattern is copied.
• Steps (a) and (f) should preferably be performed in such a way that the cylindrical axes of the sleeve and the relevant drum at least substantially coincide, thereby resulting in a gap of substantially uniform radial width. However, this is not essential to the successful operation of the inventive method.
• a particular embodiment of the method according to the invention is characterized in that the average depth of the relief structure lies in the range 50-250 nra, and that the average spacing of the relief structure lies in the range 250-5000 nm.
• depth refers to the height-difference between upper and lower parts of the surfacial relief pattern
• spacing refers to the shortest in-plane separation of neighbouring upper or lower parts of the pattern.
• An example of such an embodiment is in the copying of stampers for producing optical registration tape, in which digital data are represented by series of elongated surfacial bumps or pits which generally have a depth of about 130 nm, a width of about 500 nm and an average length of the order of about 1500 nm.
• the depth of the relief structure is zero, i.e. the external cylindrical surface of the first drum is (optically) smooth.
• Such an embodiment of the inventive method is useful for copying blank master drums, i.e. the precision-machined, optically smooth cylinders on which a hardened, cross- linked photoresist relief structure can later be provided. This is an attractive possibility, since it removes the need to individually machine such blank drums at high cost, and instead allows relatively rough drums (second drums) to be provided with a smoothing surface layer of hardened resin, to meet optical smoothness levels.
• At least one of the first and second hardenable liquid resins is photo-hardenable, and the cylindrical sleeve is transparent to the employed hardening radiation (typically ultra-violet light).
• suitable UV-curable resins in this category include, for example, tripropyleneglycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA), N-vinyl-2- pyrrolidone (NVP), 1,6-hexanediol diacrylate (HDD A) and their mixtures, with the optional presence of ⁇ . ⁇ -dimethoxy- ⁇ -phenylacetophenone (DMPA) as a photoinitiator.
• TPGDA tripropyleneglycol diacrylate
• TMPTA trimethylolpropane triacrylate
• NDP N-vinyl-2- pyrrolidone
• HDD A 1,6-hexanediol diacrylate
• DMPA 1,6-hexanediol
• a suitable sleeve material in this case is quartz.
• a particularly neat contraction of the embossed, hardened resin from the embossing surface is obtained if the source of curing radiation is approximately circumferential and co-axial with the sleeve, and is scanned (swept) along the sleeve in a direction parallel to its cylindrical axis.
• An alternative embodiment of the method according to the invention is characterized in that at least one of the first and second hardenable resins is thermally hardenable.
• Suitable resins in this category include the epoxide-amines, a particular example being UHU+ (a two-component glue manufactured by UHU GmbH, Buhl, Germany).
• the sleeve in this case may, for example, be comprised of metal.
• An advantageous embodiment of the method according to the invention is characterized in that the width of the first and second gaps (in the radial direction) lies in the range 10-500 ⁇ m.
• the term "width" as here employed is intended to refer to the closest radial separation of features on the internal surface of the sleeve and the external surface of the drum.
• Substantially smaller gap-sizes result in an extremely thin resin layer, with its attendant susceptibility to breaches and its decreased ability to mask surface roughness.
• an overly large gap will result in an unnecessarily thick resin layer (at least in the case of an optical stamper), which tends to retard the resin-hardening process.
• an overly thick resin layer is more susceptible to internal stress, which may lead to crackling effects.
• the inventors have observed that, upon hardening in steps (c) and (h), the resin tends to contract by approximately 10-20% (in volume). In most cases, this is sufficient to allow straightforward removal of the drum from the surrounding sleeve (by coaxial displacement), at least for relatively shallow relief patterns (i.e. patterns having a small depth), such as in the case of relief patterns for optical registration purposes.
• An advantageous embodiment of the method according to the invention is characterized in that, before filling a gap with resin as in steps (b) and (g), the gap is temporarily caused to narrow by heating at least one of the cylindrical surfaces delimiting it.
• the coefficient of thermal expansion of the material of the sleeve e.g. quartz
• a drum e.g. copper-nickel
• step (e) serves to prevent the second liquid resin administered in step (g) from permanently adhering to the hardened first resin layer resulting from step (c).
• Such passivation can, for example, be carried out using the following procedure: subjecting the hardened first resin layer to an ultra-violet ozone cleaning (— 10 minutes) or a corona discharge (- 30 seconds); introducing the hardened resin layer into a vacuum chamber, together with an open vessel of a liquid passivating agent such as octadecyl triethoxysilane or octadecyl trichlorosilane; evacuating the chamber, so as to cause the passivating agent to evaporate and form a vapour atmosphere around the hardened resin layer; leaving the hardened resin layer for several hours in this atmosphere, before removing it from the vacuum chamber.
• a liquid passivating agent such as octadecyl triethoxysilane or octadecyl trichlorosilane
• the method according to the invention may also, for example, be used in the duplication (manufacture) of spiral groove bearings.
• Another possible application is in the copying of optical tracking markings between the axles of precision lathes; such markings can be used, in combination with a laser tracking device connected to an actuator, to finely translate the lathe axis back and forth along its cylindrical axis according to a desired pattern, thereby allowing the lathe to cut complex forms which are not circularly symmetric.
• the method according to the invention as hereabove described can be performed in two distinct phases, which respectively comprise steps (a) to (d) and steps (g) to (i). These phases are the subjects of Claims 8 and 9, respectively.
• Figure 1 renders a perspective view of a drum-shaped stamper for use in the manufacture (embossing) of optical registration tape;
• Figure 2 illustrates step (a) of the method according to the invention, whereby the subject of Figure 1 is being inserted into a transparent cylindrical sleeve;
• Figure 3 shows the subject of Figure 2, after complete coaxial insertion of the stamper into the sleeve
• Figure 4 shows the sleeve after enaction of step (d) of the method according to the invention
• Figure 5 illustrates step (f) of the method according to the invention, whereby a blank drum is being inserted into the subject of Figure 4;
• Figure 6 shows the drum after enaction of step (i) of the method according to the invention, the surface of which drum has now been provided with a relief pattern.
• FIGS. 1-6 depict various aspects of a particular embodiment of the method according to the invention. Corresponding features in the various Figures are denoted by the same reference numerals.
• Figure 1 renders a perspective view of a drum-shaped stamper 1 (first cylindrical drum) for use in optical tape manufacture.
• the drum 1 has a cylindrical axis 3 and a cylindrical surface 5 (external surface).
• the surface 5 carries a helical pattern of lanes 7, each lane 7 containing a relief structure 9 running along the length of the lane 7 (only one such relief structure has here been depicted).
• the relief structure 9 comprises a smooth surface 5 which is provided with series of elongated pits representing binary data. All of these pits have the same depth ( » 130 nm) and width ( » 500 nm), but varying lengths (of the order of 1500 nm).
• the bulk of the drum 1 is comprised of brass, with a thin, optically smooth surfacial layer of nickel ( « 0.5 mm thick). This nickel layer is in turn covered by a hardened, cross-linked photoresist layer containing the relief pattern 9.
• the diameter of the drum 1 is 150 mm, its length is 200 mm, and the (in-plane) width of each lane 7 is 8 mm. If the drum 1 is rolled over a sheet of embossable material (as in
• FIG. 2 illustrates the enaction of step (a) of the inventive method.
• the drum 1 is being slid into a cylindrical sleeve 11 so that the axis 3 coincides with the sleeve's cylindrical axis 13.
• the sleeve 11 has a smooth internal surface 15, which is separated from the external surface 5 by a gap 20 (first gap). In this case, the width of the gap 20 is
• FIG. 3 shows the subject of Figure 2, after complete coaxial insertion of the drum 1 into the sleeve 11.
• a first hardenable liquid resin (not depicted) is introduced by capillary action into the gap 20 from a butt-end of the sleeve 11 (step (b)).
• the resin is UV-hardenable.
• the actual hardening (step (c)) can be performed by scanning a circumferential array of UV lamps 22 along the length of the transparent sleeve 11 (in the direction 24).
• the resin in the gap 20 hardens, it adheres to the internal surface 15 of the sleeve 11 , but contracts radially and withdraws from the relief pattern 9 on the external surface 5 of the drum 1. In this way, the inside surface 15 of the sleeve 11 becomes endowed with a helical pattern of lanes 17 having a relief structure 19 which is the negative of the relief structure 9, as shown in Figure 4. Because the resin contracts upon hardening, the drum 1 can be slid out of the sleeve 11 (step (d)) without damaging either of the surfaces 5,15.
• the relief structure 9 may be passivated and/or the internal surface 15 may be subjected to an adhesion-promoting treatment prior to enacting step (a), so as to further promote flawless separation of the drum 1 and sleeve 11 in step (d).
• an adhesion-promoting treatment prior to enacting step (a)
• adhesion can be promoted by subjecting the surface 15 to an ultra-violet ozone cleaning (— 10 minutes) or a corona discharge ( ⁇ 30 seconds).
• step (e) the hardened resin relief structure 19 on the inside surface 15 of the sleeve 11 is now passivated (step (e)), e.g. using the procedure already described hereabove.
• Figure 5 depicts the enaction of step (f) of the inventive method, whereby a drum 21 (second cylindrical drum) is slid coaxially into the sleeve 11 depicted in Figure 4.
• the drum 21 has a cylindrical axis 23 and a smooth cylindrical surface 25 (external surface).
• the diameter of the drum 21 is chosen so as to leave a gap 30 (second gap) between the surfaces 25 and 15.
• the gap 30 has a width of approximately 0.25 mm.
• step (g) a second hardenable liquid resin (not depicted) is introduced by capillary action into the gap 30 from a butt-end of the sleeve 11 (step (g)).
• the second resin is identical to the first resin employed in step (c).
• step (h) can be performed by scanning a circumferential array of UV lamps along the length of the transparent sleeve 11.
• the resin in the gap 30 hardens, it adheres to the external surface 25 of the drum 21 , but contracts radially and withdraws from the relief pattern 19 on the passivated internal surface 15 of the sleeve 11.
• the external surface 25 of the drum 21 becomes endowed with a helical pattern of lanes 27 having a relief structure 29 which is the negative of the relief structure 19, and thus the positive of the relief structure 9. Because the resin contracts upon hardening, the drum 21 can be slid out of the sleeve 11 (step (i)) without damaging either of the surfaces 15,25.
• the external surface 25 may be subjected to an adhesion-promoting treatment prior to enacting step (f), so as to further promote flawless separation of the drum 21 and sleeve 11 in step (i). This may, for example, be achieved by subjecting the surface 25 to an ultra-violet ozone cleaning or a corona discharge.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (1)

Family

ID=8224329

Family Applications (1)

Country Status (3)

Family Cites Families (2)

• 1997
  • 1997-06-26 EP EP97926177A patent/EP0858658A1/en not_active Withdrawn
  • 1997-06-26 WO PCT/IB1997/000794 patent/WO1998009282A1/en not_active Application Discontinuation
  • 1997-06-26 JP JP10511420A patent/JPH11514782A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events