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
• • 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
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/26—Moulds
  • B29C45/263—Moulds with mould wall parts provided with fine grooves or impressions, e.g. for record 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
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/38—Cutting-off equipment for sprues or ingates
• • 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
• • 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
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
  • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
  • G11B7/2533—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2033/00—Use of polymers of unsaturated acids or derivatives thereof as moulding material
  • B29K2033/04—Polymers of esters
  • B29K2033/12—Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
• • 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
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
  • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
  • G11B7/2533—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins
  • G11B7/2534—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins polycarbonates [PC]
• • 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
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
  • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
  • G11B7/2585—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on aluminium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/21—Circular sheet or circular blank

Definitions

• the invention relates to a molding tool for the production of information carrier disc blanks made of polymethacrylate plastic by means of injection molding or injection molding, a method for producing the information carrier disc blanks, and the blanks and DVDs produced therefrom.
• DE 36 13 334 C2 describes an injection mold for the injection molding of information carrier plates made of polycarbonate or polymethyl methacrylate, in particular compact discs, from two halves, one half of which has a polished insert made of zirconium oxide or silicon nitride in the area of the mold cavity. This measure prevents disturbing influences such as dirt build-up or the precipitation of moisture.
• DE 196 25 717 A1 describes a method for separating the sprue from an injection molded part, in particular from an information carrier disc, the sprue being separated off outside the tool by means of a laser.
• the sprue can be removed particularly dust-free.
• the position of the disk-shaped sprue can be chosen freely. When arranged in the middle area, there is advantageously no burr on the surface of the pane.
• the precise cutting edge of the laser further enables the injection gap between the sprue and the molded part to be enlarged.
• EP-A 551 869 A1 describes a method and an injection molding machine for the production of information carrier disks from thermoplastic material, for example polycarbonate.
• the plastic is first injected into the mold injected and then moved a movable cylinder into the center of the injection molded part, so that a sprue piece, which is only connected to the disc by a thin edge and is then easily removable, is formed.
• US Pat. No. 5,330,693 also describes a method and an injection molding machine for producing information carrier disks from thermoplastic material. It is important that a sufficient gap remains in the range of 0.2-0.9 mm, preferably 0.75-0.85 mm, between the sprue and the washer, so that the filling of the mold is ensured in its entire extent.
• DE 38 39 536 A1 describes an injection molding device for information storage disks, in which the ejector device contains a compressed gas channel.
• Polycarbonate and polymethyl methacrylate are mentioned as injection molding materials.
• the problem of possible form contamination by particle dust when using polymethyl methacrylate is not mentioned.
• the dimensions of the spray gap or the cutting gap are not included.
• Information carrier disks made of plastic are nowadays mainly made of polycarbonate using injection molding or injection molding processes.
• a general problem here is the relatively high tendency to birefringence, which can occur particularly easily in the case of polycarbonate if processing is not optimal, in particular in the case of thin layer thicknesses.
• birefringence When reading the information from the information carrier discs - z.
• compact disks (CD), mini disks (MD) or digital versatile disks (DVD) leads to undesirable disturbances and, in the worst case, to rejects.
• Polymethacrylate plastics that is to say plastics composed predominantly of methyl methacrylate, have a lower tendency to develop birefringence, so that the use of polymethacrylate plastics instead of polycarbonate is an interesting alternative.
• polymethacrylate has the further advantage of higher image accuracy and surface hardness compared to polycarbonate.
• the disadvantage is greater brittleness. This creates problems when separating the sprue parts, since particle dust is increasingly generated and can get into the tool or onto the information carrier disks themselves. Such particles can contaminate the injection mold or the die or, in the worst case, even render it unusable.
• Particle dust on the information carrier disks can lead to problems in subsequent processing steps, in particular during the metallization of the information-carrying side with an aluminum layer. This particle dust leads to increased rejects and an unsealed aluminum surface. It was seen as the task of a tool for the injection molding or injection molding of information carrier disk blanks made of polymethacrylate. To provide plastic that enables information carrier disc blanks to be obtained with high image accuracy and shear off the sprue in the tool to such an extent that it can be easily removed after the blank has been removed. In the event of separation, particle formation in particular by tearing out at the separation point should be avoided.
• the invention further relates to a method for producing an information carrier disc blank made of polymethacrylate plastic, and the new information carrier disc blank and DVDs produced therefrom.
• the invention is exemplified by the following figures.
• the molded part (2) is shown as a lower part.
• the sprue (5) or the cavity therefor is designed according to claim 2.
• the molding tool is, in a manner known per se, part of an injection molding or injection stamping machine for the production of information carrier disc blanks.
• the plasticized plastic is injected through a nozzle (3) under high pressure, e.g. B. 10 7 to 10 8 Pa (100 - 1000 bar), injected into the mold, the injection mold.
• the matrix (8) forms the information data (pits) on the disk.
• the cooled information carrier blank can be removed from the mold after opening by removing or opening one of the two mold parts z. B. removed with the help of a robot arm and then processed further.
• the mold In the case of injection molding, the mold is initially still slightly open, approximately 0.5-0.7 mm, when a defined amount of plastic is injected. The mold is then closed by increasing the closing forces. The cooled information carrier disc can then be removed as in injection molding.
• the injection molding process usually leads to improved image accuracy compared to the injection molding process.
• Easy-flowing polymethacrylate molding compositions which are suitable for the production of information carrier disks are also known. They consist for the most part, usually at least 80 or 90, in particular at least 94% by weight of polymerized methyl methacrylate and optionally further (meth) acrylate compounds such as B. methyl acrylate.
• the Vicat standard temperature according to ISO 306 B50 can e.g. B. in Range from 85 to 110 ° C, in particular 100 - 110 ° C.
• the melt flow index MFI according to ISO 1133 (230 ° C / 3.8 kg) can be characterized with 5.0 to 30, preferably 5.5 to 6.5 ml / 10 min.
• Preferred, in particular for the production of DVDs is a polymethacrylate molding compound granulate
• the material composition itself causes a lower tendency to birefringence, especially compared to polycarbonate.
• the good flowability favors good processability.
• a high thermal resistance prevents decomposition during processing.
• Adherence to the modulus of elasticity is particularly advantageous for DVDs that are only 0.6 mm thin. Since it is a granulate, the fine fraction content is still important. In the presence of particles of different sizes, in particular smaller particles, there is a risk of inhomogeneities in the melting behavior of the polymethacrylate molding composition and resulting disruptions to the process and of a reduced yield optical defects on the finished part. Experience has shown that there are no problems with a fine fraction of the granules of less than 0.5% by weight (1.6 mm mesh size).
• Molding compounds offered for injection molding usually always contain mold release agents, e.g. B. stearic acid, palmitic acid, cetyl alcohol, stearyl alcohol, oleic acid amide or technical mixtures of said compounds. It has now been shown that it is in continuous operation, z. B. after several hours, a separation of mold release agent contained in the polymethacrylate molding compound granules as fine droplets at the edge of the mold parts (1, 2) of the mold can occur. When opening the mold, the droplets can either get onto the die or the blank itself. Both are of course undesirable, especially in the production of DVDs with extremely fine data structures, since it immediately leads to deterioration of the die or to rejects.
• mold release agents e.g. B. stearic acid, palmitic acid, cetyl alcohol, stearyl alcohol, oleic acid amide or technical mixtures of said compounds. It has now been shown that it is in continuous operation, z. B. after several hours, a separation of mold release agent contained
• this problem can be solved by using a polymethacrylate molding compound granulate with at most 0.05% by weight or preferably without any mold release agent. It was not foreseeable that, despite the inevitably somewhat less detachability of the blank from the mold, a practically unchanged good image accuracy is retained.
• the invention is based on the knowledge that, in order to avoid undesirable particle dust, both the position and the dimensions of the gate (6), which are characterized by the so-called spray gap (SP), and the conditions when the sprue (5) is sheared off by the impact cylinder ( 9), which are characterized by a cutting gap (SN), must be given special attention.
• SP spray gap
• SN cutting gap
• the spray gap (SP) corresponds to the height of the gate (6).
• the cutting gap (SN) results from the material tolerance between the push cylinder (9) and the information carrier blank (11) and corresponds to the distance between the inner edge of the information carrier blank (11) and the outer edge of the push cylinder (9) during the shearing process.
• the spray gap (SP) is too large, the problem arises that when the sprue (5) is sheared off, a large amount of material is virtually torn out and particle dust can thus arise to an increased extent. If it is too small, the problem arises that the mold may be insufficiently filled. If the cutting gap (SN) is too small, the impact cylinder (9) may "seize” and the material may be twisted. If the cutting gap (SN) is too large, the impact cylinder (9) will be guided inaccurately. The material If more is broken out than sheared in the area of the gate, undesirable particles are increasingly formed.
• the invention teaches that the spray gap (SP) between the gate (6) of the sprue (5), which must be positioned in the middle, and the information carrier blank (11) is less than 0.3 mm, preferably at DVD production must be 0.15 to 0.25 mm, and that at the same time the cutting gap (SN) between the edge of the push cylinder (9) and the information carrier blank (11) is less than 0.2 mm, preferably 0.02 to 0.12 mm.
• polymethacrylate plastic for the information carrier blank (11) without tearing or particle dust to a disruptive extent when removing the sprue (5).
• the polymethacrylate plastic is melted in the z. B. 240-320, preferably 260-300 ° C, via a nozzle (3) under high pressure, for. B. 10 7 to 10 8 Pa (100 - 1000 bar), injected through the sprue bushing (4) into the tool.
• the polymethacrylate plastic is distributed over the sprue bushing (4) into the sprue (5) and over the gate (6) into the cavity for the information carrier blank into the information of the die (8) and solidifies in the mold at a temperature from approx. 40 - 80 ° C.
• the finished blank information carrier disc (11) can be removed after opening the tool.
• ECMA 267 specifies four DVD types - (Read Only Disks) - with storage capacities from 4, 7 to 17.0 gigabytes.
• ECMA 268 specifies DVDs with a diameter of 80 mm. It is currently assumed that the ECMA specifications will be adopted in ISO / IEC JTC1 standards.
• the new information disc blank made of polymethacrylate plastic has a roughening in the center of the hole from the removal of the cut, which can be felt and seen (if necessary with the aid of a magnifying glass or the like). It is characterized by an extraordinarily high mapping accuracy of the data structures (pits). It has practically no significant birefringence, which is particularly advantageous for thin DVDs with high data densities.
• Blank information carrier disks made of polymethacrylate plastic generally have birefringence differences of less than 50 nm, preferably 15-30 nm, in particular 5-15 nm, the birefringence difference in the course of the radius from inside to outside by no more than +/- (plus / minus) 40%, preferably not more than +/- 30%, particularly preferably not more than +/- 20% fluctuates.
• the so-called jitter value which describes the fluctuation in the form of the standard deviations of the pit lengths from the standard value, serves as a measure of the image accuracy of the pit structures.
• the ECMA 267 stipulates jitter values of less than 8% under point 13.4J. With the method according to the invention, this value can be maintained for DVDs.
• DVDs Digital Versatile Disks manufactured according to the invention are characterized by a jitter value of the displayed data according to the ECMA standard 267, 13.4.1 of less than 8.0% and can, at the same time, preferably, a signal asymmetry according to the ECMA -Norm 267, 13.2, of less than 15%.
• the flatness of the DVD is described by measuring the radial and the tangential angle tilt.
• the angular tilt can be determined as a deviation from a reference plane in both the radial and tangential planes.
• the ECMA 267 describes a permissible radial tilt of at most +/- 0.8 ° and a permissible tangential tilt of at most +/- 0.3 °. Too high a tilt causes problems when focusing the laser beam onto the smallest information unit (pits) due to the shift of the information level from the reference level - especially with a DVD with several information levels - and thus problems with reading out information on the different information levels of a DVD.
• the method according to the invention makes it possible to produce DVDs which have a radial tilt (radial angular tilt) of not more than +/- 0.8 °, preferably not more than +/- 0.7 ° and a tangential tilt (tangential angular tilt) of not more than ⁇ 0.3 °, preferably not more than +/- 0.2 °.
• the blank information carrier disc is intended as an essential component of finished CDs, DVDs or MDs.
• the further processing of the information carrier blank z. B. to a finished CD, DVD, MD or other disk is done in a conventional manner.
• the information-carrying side is metallized, e.g. B. by metallizing with aluminum (Sputtem).
• a layer of lacquer is applied for protection, which can still be printed.
• DVDs are made from two blank information carrier disks that are connected with an adhesive layer.
• the stroke of the impact cylinder (9) also has an influence on the particle formation on the punched edge and - possibly as a result - on the breaking strength.
• a stroke in the range of 1.5 mm or above is usually selected for the production of information carrier disks from polycarbonate.
• the stroke of the impact cylinder is limited to 0.3 to 1.3 mm, preferably 1.0 to 1.3 mm in CD production and DVD - Production to 0.3-1.0 mm, preferably 0.4 to 0.6 mm, the particle formation at the central punch hole is reduced again. It is assumed that this is related to the fact that when the impact cylinder slides along the gate, even the smallest particles can be torn out and that the longer this path, the more it occurs. Obviously, small particles are created that are no longer visible to the naked eye. This is derived from the fact that mold contaminations are not only not detectable initially, but also no longer occur after several hours of operation if the stroke of the impact cylinder is limited accordingly.
• the position of the gate (6), the spray gap (SP), the cutting gap (SN) and the stroke of the impact cylinder (stroke mm) were in each case tested by installing a different impact cylinder (9) and / or a different sprue bushing ( 4) modified.
• PC polycarbonate molding compound
• PM-1 and PM-2 polymethacrylate molding compounds
• the molding compositions were each injected at a pressure of approximately 500 bar with an initial melting temperature of 290 ° C. and a molding temperature of 60 ° C.
• the cycle time for injection, repressing, cooling time, punching the sprue, opening the mold and removing the DVD was approx. 5s.
• the test was assessed using DVDs, which were taken from the manufacturing process after approx. 5 minutes of driving.
• the punched edge in the center hole (roughening, resulting from the removal of the sprue by means of the push cylinder) of the DVDs obtained was optically assessed using the criteria below. If the gate is on one side, the top edge of the sprue is flush with the top edge of the DVD half side (in contrast to the sprue placed in the middle).
• PC Commercially available, low molecular weight polycarbonate molding compound (provided by the manufacturer as for optical data carriers or designated as suitable for DVD production)
• the assessment of the breaking strength was checked by bending the DVDs by hand.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Manufacturing Optical Record Carriers (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Optical Record Carriers And Manufacture Thereof (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=26048939

Family Applications (1)

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Families Citing this family (9)

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• 1999
  • 1999-09-15 IL IL14131799A patent/IL141317A0/xx unknown
  • 1999-09-15 KR KR1020017003450A patent/KR100542421B1/ko not_active IP Right Cessation
  • 1999-09-15 JP JP2000573897A patent/JP2002526294A/ja active Pending
  • 1999-09-15 YU YU9501A patent/YU9501A/sh unknown
  • 1999-09-15 CZ CZ2001818A patent/CZ2001818A3/cs unknown
  • 1999-09-15 EP EP99948756A patent/EP1656244A1/de not_active Withdrawn
  • 1999-09-15 AU AU61912/99A patent/AU746464B2/en not_active Ceased
  • 1999-09-15 BR BR9913336-9A patent/BR9913336A/pt not_active Application Discontinuation
  • 1999-09-15 NZ NZ510250A patent/NZ510250A/en unknown
  • 1999-09-15 CA CA002344476A patent/CA2344476A1/en not_active Abandoned
  • 1999-09-15 PL PL99346625A patent/PL346625A1/xx unknown
  • 1999-09-15 US US09/805,777 patent/US6555195B1/en not_active Expired - Fee Related
  • 1999-09-15 SK SK315-2001A patent/SK3152001A3/sk unknown
  • 1999-09-15 CN CN99810656A patent/CN1326400A/zh active Pending
  • 1999-09-15 TR TR2001/00777T patent/TR200100777T2/xx unknown
  • 1999-09-15 ID IDW20010650A patent/ID28364A/id unknown
  • 1999-09-15 MX MXPA01002779A patent/MXPA01002779A/es unknown
  • 1999-09-15 WO PCT/EP1999/006822 patent/WO2000016957A1/de not_active Application Discontinuation
  • 1999-12-01 TW TW088116066A patent/TW442372B/zh not_active IP Right Cessation
• 2001
  • 2001-03-09 BG BG105317A patent/BG105317A/xx unknown
• 2002
  • 2002-04-04 HK HK02102514.1A patent/HK1040957A1/zh unknown

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