Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
  • B29C43/32—Component parts, details or accessories; Auxiliary operations
  • B29C43/34—Feeding the material to the mould or the compression means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C31/00—Handling, e.g. feeding of the material to be shaped, storage of plastics material before moulding; Automation, i.e. automated handling lines in plastics processing plants, e.g. using manipulators or robots
  • B29C31/04—Feeding of the material to be moulded, e.g. into a mould cavity
  • B29C31/042—Feeding of the material to be moulded, e.g. into a mould cavity using dispensing heads, e.g. extruders, placed over or apart from the moulds
  • B29C31/044—Feeding of the material to be moulded, e.g. into a mould cavity using dispensing heads, e.g. extruders, placed over or apart from the moulds with moving heads for distributing liquid or viscous material into the moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0888—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using transparant moulds
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2017/00—Carriers for sound or information
  • B29L2017/001—Carriers of records containing fine grooves or impressions, e.g. disc records for needle playback, cylinder records
  • B29L2017/003—Records or discs
  • B29L2017/005—CD''s, DVD''s

Definitions

• the present invention relates generally to record media useful in optical writing and reading of high—density information, and more particularly to improved fabrication methods for optical disks.
• optical disk technology employs disk elements with spiral or concentric tracks of minute, optically detectable marks (usually on the order of 1 v.m or less in size).
• One real—time mode of recording (writing) such marks is by scanning tracks on the disk with an equivalently small beam of radiation (e.g., from a laser), which is modulated "off” or “on” according to an electrical signal representative of the information to be written.
• Information is recovered (read) by scanning the tracks with a larger, but still very tightly focused, radiation (e.g., light) spot.
• the recovered information is in the form of a fluctuating electrical signal obtained from a photodetector that senses the read—out light reflected from the recorded disk.
• Fig. 1 is a cross—sectional view of a portion of a typical prior—art optical write—and—read recording disk assembly 10.
• Each disk assembly has a transparent substrate 12 coated on one side with a primer layer 14 and a featured (i.e., having a pattern of depressions and/or protuberances) molded sub—layer 16. The ridges and grooves of this sublayer define the tracks along which the information is recorded.
• a thin, reflective metal mirror coating 18 is applied to molded sub—layer 16 so that information may be optically recorded onto, and read from, the disk assembly.
• the mirror coating is in turn coated with a protective layer 20.
• optical systems of high numerical aperture are used to focus light to small spots.
• the optical disk assembly support surface underlying the record layer e.g., the metal coating
• the optical disk assembly support surface underlying the record layer e.g., the metal coating
• One approach to achieving requisite smoothness and flatness has been to start with a disk substrate and then apply thereto a surface—smoothing sub—layer by a known photopolymerization process, in which a liquid composition of acrylate monomers (esters of acrylic acid) is polymerized on a featured mold by exposure to ultraviolet radiation.
• Figs. 2a to 2d illustrate steps in that prior-art process. A few milliliters of the liquid composition (22 in Fig.
• a metal master mold 24 are applied to the center of a metal master mold 24.
• a transparent substrate 12' is placed on the mold such that the space between the master mold and the substrate is filled by a layer of liquid composition 22.
• This layer is exposed to ultraviolet radiation (Fig. 2c) to polymerize the composition and form sub—layer 16'.
• the polymerized composition does not adhere to the mold but does adhere to the substrate; and after the exposure, the substrate and the cured sub—layer adhered thereto are removed from the master mold, as shown in Fig. 2d.
• a reflective metal mirror coating 18 and protective layer 20 (Fig. 1) can then be applied to the sub—layer to complete the disk assembly.
• the acrylic composition is centrally deposited on the surface of the master mold, and is spread over the master mold when a substrate is pressed against the composition.
• the flexible substrate may be spherosymmetrically vaulted before being pressed against the composition, whereby the composition is rolled out over the master mold surface while the vaulted substrate is deformed to a planar configuration. The liquid is then cured, and the substrate and attached cured acrylic composition are removed from the master mold.
• the above-noted molding technique may be effective to inhibit air entrapment in the composition, but it requires that the substrate be flexible. It has, however, been discovered that rigid disks (made of, for example, aluminum) provide superior characteristics when used as substrates for optical disk assemblies. For example, see commonly assigned U.S. Patent No. 4,619,804. Preforming the substrate into a spherosymmetrically vaulted form is inappropriate for substrates of rigid material, and other means for inhibiting air entrapment are required.
• the method of the present invention entails making an optical write—and—read recording disk medium by applying a thin uniform layer of fluid composition between predetermined inside and outside diameters of a substantially flat annular disk substrate.
• a circle of the composition is injected into a gap established between a surface of the disk substrate and an opposed surface of a master mold.
• the circle is applied at a radius such that the surface area of the disk substrate between the predetermined inside diameter and the radius is approximately equal to the surface area of the disk substrate between the radius and the predetermined outside diameter.
• the gap between the substrate and the mold is closed such that the fluid composition spreads radially both inwardly and outwardly from the circle to at least the predetermined inside and outside diameters while allowing air ahead of the advancing composition to escape. Because the inwardly and outwardly directed radial spreading distances are significantly smaller than the overall disk radius, the possibility of trapping air is substantially reduced in comparison to the previously described prior-art .technique.
• a uniform annular circle of the photopolymer composition is metered --- between the closely spaced, parallel surfaces of the master mold and the substrate through a long, slender nozzle such that the composition wets both the surface of the master mold and the surface of the substrate, forming a column of the fluid composition between them.
• the nozzle is withdrawn and the master mold and substrate are pressed together to establish a uniform and defect-free film.
• the master mold and the substrate are separated.
• the hardened composition adheres to the substrate, creating a copy of the master.
• the circle of material may be applied to only one of the foregoing surfaces in the form of an annular bead, which is subsequently contacted by the other surface and displaced to establish the desired film.
• Fig. 1 is a fragmental sectional view of an optical disk assembly in accordance with the prior art
• Figs. 2a—2d are a series of fragmental sectional views illustrating a prior—art process for making optical disk assemblies
• Fig. 3 is a perspective sectional view showing one step of a process for making single—sided optical disk assemblies in accordance with the present invention
• Fig. 4 is a perspective sectional view similar to Fig. 3 but showing corresponding steps of a like process for making double—sided optical disk assemblies in accordance with the present invention
• Fig. 5 is an exploded perspective view of apparatus partially shown in Fig. 3.
• Fig. 3 best illustrates the basic features of this invention. Best Mode for Carrying Out the Invention
• the manufacturing method described herein presents a process for making optical disk assemblies by molding a radiation—curable plastic sub—layer onto a metal substrate disk, although other substrate materials may be used.
• this process involves placing a clear glass master mold in spaced alignment with the substrate, injecting a viscous, radiation—curable, fluid composition between the master mold and the substrate disk, spreading the composition uniformly and without defect over the substrate disk, exposing the composition to radiation, and delaminating the master mold from the disk, leaving the sub—layer bonded to the disk.
• Metal and other ' layers may be coated over the sub—layer to complete the disk assembly.
• a master mold 26 consists of a flat glass plate. One surface (the bottom one in Fig.
• a master mold 26 is positioned opposite to a substrate disk 30 such that parallel surfaces of the master mold and the substrate are closely spaced to form a uniform gap.
• a nozzle 32 extends into the gap to deliver a circle 33 of photopolymer between the master mold and the substrate. Details of the nozzle are set forth below with reference to Fig. 5. The circle is formed when the nozzle moves in a circular path within the gap. Of course the nozzle can be held stationary and the master mold and substrate rotated about their common axis.
• the photopolymer wets both the surface 28 of the master mold and the opposing surface of the substrate to form a uniform annular column 33 suspended between the master mold and substrate surfaces due to capillary action. Suspension of the column allows the circle of photopolymer to cling to both surfaces while it is fluid, thus inhibiting any trapping of small air bubbles in the photopolymer between the two surfaces.
• a photopolymer whose viscosity is in the 100-150 cp range, having contact angles with the substrate and master mold of about 25 to 40 , indicate that the column can be reliably established and maintained if the separation between the master mold and substrate surfaces is less than about 0.25 cm. For best results, the ratio of the nozzle tip velocity in centimeters per second to the photopolymer delivery rate in cubic centimeters per second should not exceed about 31 to 1.
• the photopolymer column is formed at a radius such that the surface area between a predetermined inside diameter to which the photopolymer is to be spread and the photopolymer column--is approximately equal to the surface area from the photopolymer column outwardly to an outside diameter to which the photopolymer is to be spread.
• Spacer rings 34 and 36 have been provided at those inside and outside diameters.
• Delivery of the photopolymer along nozzle 32 may be effected by any suitable mechanism.
• the presently preferred method is to provide a syringe driver, not shown, to meter a precise volume of photopolymer at a flow rate synchronized with the angular velocity of the nozzle relative to the master mold and substrate.
• the film is polymerized by exposure to ultraviolet radiation through transparent master mold 26.
• the radiation source may be a mercury—vapor lamp having a wave length of about 330 nm to 450 nm.
• the photopolymer composition is formulated to preferably adhere to substrate 30 and become a highly cross—linked solid replicate of the master mold's surface. Upon separation of the master mold from the substrate, the photopolymer does adhere slightly to the master mold, thereby removing any dirt particles which may be present, leaving the master mold clean for the next molding operation. Thus, the operation is self—cleaning.
• Fig. 3 produces a substrate having one side coated for production of a single—sided optical disk assembly.
• FIG. 4 we have shown a similar operation, but wherein the substrate 30' is being coated on two sides.
• a second master mold 26" is positioned on the side of substrate 30' opposite to master mold 26'. Inner and outer spacers 34" and 36", respectively, are provided on master mold 26".
• a second nozzle 32" extends into the gap between substrate 30' and master mold 26".
• the operation for coating both sides of substrate 30* is quite similar to that of Fig. 3 for coating only one side.
• Photopolymer composition is delivered through both nozzles 32' and 32" simultaneously to form annular columns 33' and 33" of composition on both sides of the substrate. After the composition has been spread by closing the gaps on both sides of the substrate, ultraviolet radiation is passed through both master molds to polymerize the composition on both sides before the molds are removed.
• Fig. 5 shows details of a preferred embodiment of nozzle 32.
• the nozzle has a seamless, thin— all, stainless-steel tube 38 attached, by flexible tube 39, to a photopolymer composition delivery system (not shown).
• Tube 38 is elliptical in -cross section, with its major and minor axes oriented during delivery such that the minor axis is in the direction of the gap width. Formation of a photopolymer composition column is aided by the presence of means for causing the composition stream to part as it leaves the nozzle and for causing a portion of the stream to be directed toward the substrate and another portion to be directed toward the master mold.
• a thin wire 40 across the nozzle tip directs composition exiting from the tip both upwardly and downwardly across the gap between the substrate and the master mold, whereby contact is made with the opposing surfaces thereof to permit capillary action to form the column. Thin wire 40 also allows withdrawal of the nozzle tip from the composition column without causing composition to trail behind the tip.

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• 1986
  • 1986-11-07 EP EP19860907122 patent/EP0245460A1/de active Pending
  • 1986-11-07 WO PCT/US1986/002383 patent/WO1987002934A1/en unknown

Non-Patent Citations (1)

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