JP2006026967A - Molding machine, molding method and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a thin cover layer by a molding method without using a film. <P>SOLUTION: A molding material is injected in a cavity 206 from a resin injection port 208. A stamper 205 is held in the vicinity of its outermost periphery by an outer peripheral ring 202. Temperature regulators 204 and 211 are provided for the purpose of regulating the temperature of a mold and and a fixed heater part 203 is provided between the stamper 205 and a fixed mirror mold 201 while a movable heater part 210 is provided between the cavity 206 and a movable mirror mold 212. A resin is injected in a stage that a ceramic heater is turned ON to heat the surface of the cavity 206 to a desired temperature and the ceramic heater is turned OFF to cool the surface of the cavity 206 to a predetermined temperature. The ON-OFF timing of the ceramic heater is set in connection with the movement of the molding machine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molding apparatus, a molding method, and an optical disc applicable to the molding of a disc substrate of an optical disc.

  In recent years, a disk-shaped recording medium (hereinafter abbreviated as an optical disk as appropriate) such as a CD (Compact Disc) and a DVD (Digital Versatile Disc) that performs recording / reproduction using a laser beam is already widely used. As a next-generation optical disc, a high-density disc (Blu-ray-Disc, hereinafter abbreviated as BD disc as appropriate) has been proposed for recording / reproducing with a 12 cm size disc using a blue-violet laser.

  In the BD standard, in order to reduce the beam spot diameter, the light source wavelength is set to 405 nm and the numerical aperture (Numerical Aperture: hereinafter abbreviated as NA) of the objective lens is increased to 0.85. As a result of the high NA, the angle error (referred to as tilt margin) allowed for the tilt from 90 ° of the angle formed by the disk surface and the optical axis of the laser beam is reduced.

  Even in the BD disc, the read-only type has a small recording capacity, and in order to obtain the same recording capacity as the rewritable type, it has been proposed that the disc has a multilayer structure, for example, a two-layer structure.

  A two-layer disc has a signal film on a signal surface of a substrate made of polycarbonate resin (hereinafter abbreviated as PC as appropriate), and then has a signal surface. A semi-transparent reflection film is formed on the signal surface. Transparent adhesive that cures with UV so that the signal surface faces the laminated part (hereinafter abbreviated as a cover layer as appropriate) made of, for example, an optically transparent film of 0.1 t or less, etc. It can be obtained by gluing.

  The intermediate layer interposed between the reflective film and the semi-transmissive reflective film is a single objective lens. When the laminated reflective film and the semi-transmissive reflective film are reproduced by changing the focal position of the laser beam, The total thickness needs to be within an allowable thickness error, and the total thickness of the substrate including the intermediate layer needs to be a layer having a uniform thickness of 70 to 100 μm for the performance of the objective lens.

  As described in, for example, Patent Document 1 below, a disk substrate used in an optical disk is formed by injection molding a heat-melted resin material (PC or the like) with an injection molding machine having a mold device. An uneven pattern is transferred and created.

JP 11-48291 A

  Recently, not only a multi-layer disc but also a single-layer structure, BD discs have been developed by various companies, and a BD disc having a track pitch narrowed to 1/4 or less of a CD has been proposed. In order to transfer a fine uneven signal, it is necessary to mold the substrate at a mold temperature close to the thermal deformation temperature of the resin. For example, when a PC having a glass transition point of 143 ° C. and a weighted deflection temperature of 128 ° C. is used as a molding material, the mold temperature must be raised to 130 ° C. to 140 ° C. to mold the substrate.

  However, in molding with a high temperature mold that exceeds the weight deflection temperature of the resin, in addition to the orientation stress strain at the time of injection, when the disk is taken out of the mold, the substrate is deformed by the ejector, release air, or mechanical stress of vacuum adsorption. As a matter of course, it is necessary to lengthen the cooling time of the resin. Therefore, the molding cycle is long, the productivity is remarkably inferior to that of CD, and the production cost is increased. In addition, such a molding method using a high-temperature mold deteriorates the warping characteristics such as tilt of the molded substrate, and a tilt margin is small in a substrate with a high NA objective lens, which is one of the characteristics of a BD disc. It becomes a molding method that contradicts.

  On the other hand, the compression method, which is a substrate molding method in which molding is performed by heating and pressure press, was used as an extension of the LP record board manufacturing method in the early stage of optical disc development such as CD and LD (Laser Disc). For the compression method, polyvinyl chloride resin having low heat resistance was used as a material because of the repeated relationship between steam and water and heating and cooling. However, as the heat-resistant PC material becomes mainstream, the compression method is not used because the productivity is inferior as an optical disc production method. At present, in the thermoplastic molding, multi-stage molding, etc. Is used for the production of IC cards.

  On the other hand, the compression method is used in the disk molding using the low melting point glass having a glass transition point of 215 ° C. recently proposed by the present inventors. However, in order to transfer a fine uneven signal in a short time. The mold temperature needs to be close to 400 ° C. In a high temperature atmosphere of around 400 ° C at all times, oxidation deterioration of the Ni (nickel) stamper occurs and the signal deteriorates. Therefore, molding in a nitrogen atmosphere is necessary. In addition, oxidative corrosion of the mold part outside the cavity cannot be avoided.

  FIG. 9 is data showing an increase in noise in a low frequency region due to oxidation degradation of the Ni stamper. That is, after performing normal disk molding at a mold temperature of 135 ° C, the stamper is left to cool in an air atmosphere of 400 ° C for 4 hours, and then the disk is molded at a mold temperature of 135 ° C, which is the same molding condition as before. And the presence or absence of noise increase was examined. The characteristics 41 of the disk exposed to a high temperature atmosphere have increased noise in the low frequency region as compared with the characteristics 42 of the disk not exposed to a high temperature atmosphere. If the die member is not dealt with by TiN coating, etc., even if a stainless steel mold material is used, rust due to oxidation will occur in the parts that come into contact with air, causing problems in continuous molding due to poor sliding. .

  A mold with a mold temperature of 100 ° C or less, or a mold that does not require mold temperature control with a heating medium, and is not limited to a single-layer disk substrate, and has fine irregularities with a track pitch narrowed to 1/4 or less of CD. If signal transfer can be ensured, even in the formation of a high-density optical disc, a long cooling time is not required as in a conventional high-temperature mold, and the productivity of the molding cycle is comparable to that of a CD. Further, the warping characteristics such as tilt of the molded substrate can be improved to the same level as or more than CD.

  In a multi-layered disc, an optically transparent substrate having a thickness of 0.1 mm or less to which a fine uneven signal is transferred can be prepared by an injection molding method and bonded to a normal substrate. Not only can production equipment be used, but material costs and processes can be reduced as compared with a method in which a concavo-convex signal is transferred to a film manufactured by a casting method (hereinafter referred to as a cast film as appropriate) and punched. In addition, there is no need to dispose of the punched film waste, saving resources.

  For this reason, for BD discs and the like, various manufacturers have studied the formation of optically transparent 0.1 mm-thick substrates onto which fine unevenness signals have been transferred by injection molding. Only a substrate with a thickness of 3 mm can be obtained.

  For example, when a PC having a glass transition point of 143 ° C. is used as a material in forming an optical disk substrate, the resin heated and melted at 330 ° C. to 370 ° C. in a cylinder is 130 ° C. to 140 ° C. It passes through the sprue and gate in the mold whose temperature is adjusted to a constant temperature of C, and is filled in the cavity. At the time of filling, the molten resin is cooled at a portion in contact with the mold surface or the stamper, solidification starts, and a skin layer is formed. The skin layer is a portion that solidifies and does not flow. Thus, depending on the molding conditions, for example, a skin layer having a thickness of about 0.1 mm is formed on one side. Therefore, even if the mold, the resin temperature, or the injection pressure is increased, the disk substrate having a thickness of 0.3 mm Molding was the limit.

  Resin that has started to solidify on the mold surface hardly flows, and when molding a disk substrate with a thickness of 0.3 mm or more, new molten resin (that is, the core layer) from the flow tip is successively put into the cavity. It is supplied in a broad manner, reaches the outer diameter of the disk, and a desired substrate can be obtained. However, in forming a 0.1 mm thick disk substrate, there is no core layer, so even if the mold temperature is raised near the glass transition point of the resin, it solidifies immediately after passing through the gate, resulting in optical characteristics. Further, a disk substrate having a thickness of 0.1 mm cannot be obtained while maintaining the substrate deformation. Therefore, in the prior art, only a disk having a thickness of about 0.3 mm can be obtained.

  On the other hand, in the formation of a diaphragm such as a speaker cone that does not require optical characteristics, a 0.1 mm thick molding has been put into practical use. In this molding, the resin is filled at an injection speed of 1000 mm / sec or higher. The resin at this time has high fluidity unlike the resin for disk molding, has a very large molecular orientation in the resin flow direction, and burr is produced on the outer periphery of the product to ensure a uniform thickness.

The speaker diaphragm is made to function as a diaphragm by increasing the injection speed, giving the resin molecular orientation and providing rigidity, but in the formation of optical disks, the resin is optically Since it is an absolute condition that it is transparent and has little birefringence, it is premised on molding with as little molecular orientation as possible. Therefore, even at a high injection speed, molding at 300 mm / sec is the limit.

  As described above, since an optically transparent 0.1 mm thick substrate has not been obtained as an optical disk substrate by injection molding, currently, a casting film having a thickness of 0.1 mm or less or a melt extrusion method is used. The manufactured film (hereinafter, appropriately referred to as an extruded film) is punched into a desired disc shape. In the case of a single-layer disc, a 1.1 mm thick disc substrate and film are bonded with a transparent adhesive sheet or UV resin, or UV resin is applied by spin coating, and the cover layer on the surface layer is irradiated with UV. Then, a method of curing and bonding was taken.

  For multi-layer discs, it is common to directly transfer the concavo-convex signal onto the film, or laminate and transfer with UV resin, etc., and then deposit and laminate the transflective film by sputtering, etc. Is. Alternatively, the UV resin is rotationally stretched by spin coating, applied to a thickness of 100 μm on the disk substrate, and the signals are transferred to the substrate for bonding.

  However, optically transparent films and transparent adhesive sheets with excellent thickness accuracy are expensive due to their production method. Also, when UV resin is applied thickly by spin coating, if there is a center hole on the surface to be applied, the problem is that the UV resin wraps around the center hole and the center hole becomes smaller, which is a basic problem of the production method by rotational stretching. In order to avoid this, it is general to apply the UV resin to a position away from the position of the center hole, and then rotate and stretch.

  When making a disk having a multilayer structure of two or more layers, the unevenness information is directly transferred onto an optically transparent film, or the unevenness information of the UV layer is transferred onto the film by the 2P method, and a recording film is formed. After film formation, lamination is performed by pasting together by the method described above. Alternatively, in the method using spin coating of the UV resin, it is necessary to overlap the uneven signal with the UV resin between the stamper and the disk substrate, and after forming the reflective film thereon, it is necessary to further laminate a 100 μm UV layer. There is also a drawback that uneven thickness is likely to occur. In addition, in order to prevent it from going around the back side of the resin stamper and the disk reading surface near the center hole, it is applied in a donut shape at a position away from the center hole. There are also disadvantages that are not.

  When a film is used on a 0.1 mm thick substrate that is a cover layer for a BD disc, etc., and UV resin or adhesive sheet is used as an adhesive layer with the substrate, the optical properties such as birefringence of the film and the extruded film Due to problems such as minute irregularities on the surface, the properties cannot be satisfied except by a casting method in which a polymer is dissolved in a solvent. However, the cast film is not only very expensive, but the film handling problem during the manufacturing process, the dust trapped during the transportation process, and the foreign material attached to the film due to static electricity due to the thin adhesive layer There is a drawback that protrusions caused by being sandwiched between them expand as defects larger than the actual size.

  Therefore, an object of the present invention is to control the temperature of the mold stamper and the surface part on the cavity side, and can form a disk substrate with less thermal stress and molecular orientation distortion and excellent in transferability. Another object is to provide a molding method and an optical disc.

In order to solve the above-described problem, a first aspect of the present invention is a molding apparatus that molds a substrate on which a concavo-convex pattern of a stamper is transferred by injecting molten resin into a cavity.
A movable side mirror mold and a fixed side mirror mold, which are separable and have mutually facing surfaces, and
Temperature control means for controlling the temperature of the movable side mirror mold and the fixed side mirror mold;
A movable side heater part and a fixed side heater part attached to respective surfaces of the movable side mirror mold and the fixed side mirror mold facing each other;
A stamper fixed to one surface of the movable heater portion and the fixed heater portion,
The movable side heater part and the fixed side heater part have a configuration in which a heating element is sandwiched between first and second members made of non-conductive ceramic,
One of the first and second members has a surface in contact with the movable-side mirror mold and the fixed-side mirror mold;
The molding apparatus is characterized in that the other member of the first and second members has a surface in contact with the cavity or stamper.

According to a second aspect of the present invention, in a molding method for molding a substrate on which a concavo-convex pattern of a stamper is transferred by injecting molten resin into a cavity,
Controlling the temperature of the movable-side mirror mold and the fixed-side mirror mold, which are detachable and have mutually facing surfaces, to a constant temperature not lower than 50 ° C. and not higher than the thermal deformation temperature of the molding material;
A step of turning on the movable side heater part and the fixed side heater part attached to the respective opposing surfaces of the movable side mirror mold and the fixed side mirror mold;
A step of injecting resin in a state where the temperature of the surface constituting the cavity is heated above the glass transition point;
And a step of turning off the movable heater portion and the fixed heater portion.

A third aspect of the present invention is an optical disc having a disc substrate created by an injection molding method.
A first substrate in which the thickness of the first region around the central hole is smaller than the second region on the outer peripheral side of the first region;
A second substrate in which the thickness of the third region around the central hole is larger than the thickness of the fourth region on the outer peripheral side of the third region;
An information layer formed at the boundary between the opposing surfaces of the second region and the fourth region;
This is an optical disc having a constant thickness obtained by bonding the first and second substrates with the information layer interposed therebetween.

  By providing a ceramic heater in the mold apparatus and selectively heating only the cavity surface to an arbitrary temperature with the ceramic heater, a substrate having excellent transferability can be obtained by eliminating thermal stress and molecular orientation distortion during molding. By heating the cavity surface above the glass transition point of the molding material, it is possible to mold a 0.1 mm-thick substrate to which a fine uneven signal is transferred.

  A 0.1mm thick substrate with transferred signals is obtained by injection molding, eliminating the need for punching and punching discs from cast film and extruded film, resulting in waste of material costs and lower costs than film. Conventional manufacturing equipment can be used.

  In the present invention, the entire mold does not need to be set to 400 ° C. because of local heating of the ceramic heater portion, and corrosion does not occur. 6) In the molding of a glass substrate embossed with a signal, even if it is a low-melting glass, a fine uneven signal transfer cannot be obtained unless the entire mold including the stamper is brought to a temperature close to 400 ° C. For this reason, signal degradation and mold corrosion due to oxidative degradation have occurred, but the entire mold does not need to be brought to 400 ° C. due to local heating of the ceramic heater portion and does not corrode.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a high-density optical disc, for example, a read-only optical disc according to an embodiment of the present invention. In FIG. 1A, an enlarged cross-sectional view of a portion C near the center hole of the disk is FIG. 1B. In FIG. 1A, reference numeral 1 indicates a clamp part on the inner periphery side of the disk, reference numeral 2 indicates an inner periphery part, and reference numeral 3 indicates an outer periphery part.

  As shown in FIG. 1B, an information layer, for example, a reflective film 15 is formed on a substrate 16 formed by normal injection molding. Reference numeral 12 indicates a 0.1 mm thick cover layer formed using a mold apparatus according to an embodiment of the present invention. Fine unevenness is transferred to the cover layer 12, and a semi-transmissive reflective film 13 is formed. Opposing surfaces of the reflective film 15 and the semi-transmissive reflective film 13 are bonded together via the intermediate layer 15. In the cover layer 12, the inner peripheral portion 2 and the outer peripheral portion 3 have a thickness of 0.1 mm, and the clan portion 1 around the center hole has a larger thickness. For example, the clamp portion is 0.3 to 0.8 mm thick. The entire disc is 1.2 mm thick. By thickening the area around the center hole, the disk substrate can be handled easily, for example, when the disk is manufactured, for example, when the disk is taken out after molding, the clamp portion 1 can be vacuum-sucked.

  FIG. 2A is a cross-sectional view of a mold apparatus according to an embodiment of the present invention. FIG. 2B is a partially enlarged cross-sectional view of a portion D in FIG. 2A. The mold apparatus includes a fixed mold part 213 and a movable mold part 214 that is moved toward and away from the fixed mold part 213. A closed space constituted by the fixed-side mold part 213, the movable-side mold part 214, and the outer peripheral ring 202 attached to the fixed-side mold part 213 is defined as a cavity 206 filled with a molding material. By closing the outer peripheral portion of the cavity 206 by the outer peripheral ring 202, the outer periphery of the substrate to be molded is defined.

  The fixed-side mold part 213 includes a fixed-side mirror mold 201, a fixed-side heater part 203 attached to the surface of the fixed-side mirror mold 201 on the cavity 206 side, and a stamper attached to the surface of the fixed-side heater part 203. 205. A sprue 207 for supplying a molding material from the resin injection port 208 into the cavity 206 is provided at the center of the fixed-side mold part 213.

  The stamper 205 is a master for molding a disk substrate, and a fine uneven pattern for transferring to the substrate is formed on the surface on the cavity 206 side. The stamper 205 is fixed to the fixed-side mirror 210 by being fitted and fixed to a mold with an inner diameter (not shown) as a guide and sucking the vicinity of the inner diameter and the vicinity of the outer shape in a vacuum.

  The movable side mold part 214 includes a movable side mirror mold 212, and a gate cut punch 209 is provided at the center of the movable side mold part 214.

  A fixed-side temperature adjustment groove 204 and a movable-side temperature adjustment groove 211 are provided in the fixed-side mirror mold 201 and the movable-side mirror mold 212, respectively, for the purpose of adjusting the mold temperature.

  In one embodiment, a fixed heater 203 is provided between the stamper 205 and the fixed mirror mold 201, and a movable heater 210 is provided between the cavity 206 and the movable mirror 212. A ceramic heater is mounted on a portion corresponding to the cavity 206 surface of a conventional mold apparatus, and a mold is used to adjust the mold to, for example, 50 ° by using a liquid medium such as pressurized hot water or oil. It is always kept at a constant temperature that is C or more and below the heat distortion temperature of the molding material.

  Further, the resin is injected when the ceramic heater is turned on and the surface of the cavity 206 is heated to a desired temperature, and the heater is turned off and cooled to a predetermined temperature. The ceramic heater is turned on and off in conjunction with the molding apparatus. At the time of cooling, the ceramic member side in contact with the mold main body has poor thermal conductivity, and it takes time to cool down due to heat storage, so cooling is performed with a liquid medium circulating in the mold apparatus, and the surface temperature of the cavity 206 is reduced. Reduce cooling time.

  In a conventional mold apparatus, for example, using a PC having a glass transition point of 143 ° C., a fine uneven signal is used to manufacture a BD disc having a track pitch of 0.5 μm or less and a groove depth of 60 nm or more. In order to transfer, it was necessary to heat the entire mold to a high temperature of 130 to 150 ° C. Therefore, the cooling time required more than 10 seconds.

  However, in the mold apparatus according to an embodiment of the present invention, when the ceramic heater is turned on in a state where the temperature of the entire mold is adjusted to a temperature of 100 ° C. or less, for example, 60 ° C., heating is performed at 200 V for 3.3 seconds. About, the temperature of the surface forming the cavity including the surface of the stamper 205 is raised to 300 ° C., which is substantially the same as the resin melting temperature in the molding machine cylinder. Since it is local heating, it is possible to transfer a fine uneven signal without heating the entire mold to a high temperature.

  FIG. 3 shows the state in which the fixed heater unit 203 and the movable heater unit 210 are cut in almost half. The fixed heater 203 includes a disk-shaped ceramic pedestal member 31 in contact with the cavity surface of the fixed-side mirror mold 201, a disk-shaped print heater 32 as a heating element, and a disk-shaped ceramic surface layer member. 33 in this order. The base member 31, the print heater 32, and the surface layer member 33 are disk-shaped. A stamper 205 is stacked on the surface layer member 33.

  Similar to the fixed heater 203, the movable heater 210 has a three-layer structure in which a print heater 35 as a heating element is sandwiched between a disk-shaped ceramic surface layer member 34 and a pedestal member 36. A base member 36 is attached to the cavity-side surface of the movable-side mirror mold 212. The fixed heater section 203 and the movable heater section 210 have a diameter (for example, a diameter of 120 mm) that is substantially equal to the stamper 205. By injecting resin into the cavity 206, a disk substrate 37 (corresponding to a cover layer) onto which the concave / convex pattern of the stamper 205 has been transferred is formed.

  In the above-described ceramic heater, for example, the surface layer member 33 and the surface layer member 34 are made of a material having excellent thermal conductivity such as aluminum nitride, and the base member 31 and the base member 36 are made of a material having poor thermal conductivity such as silicon nitride. used. The aluminum nitride used as the surface layer member 33 and the surface layer member 34 has a thermal conductivity of 150 (RT) (W / m · K) or more, with a heat radiating surface mirror-wrapped. The surface roughness of the heat radiation surface of the surface layer member 33 and the surface layer member 34 that is mirror-wrapped is equal to that of STAVAX, which is a SUS-based material generally used for mold mirror surfaces. It has the surface property.

When the base member 31 and the base member 36 that are heat insulating layers are made of the same material as the surface layer member, a material having poor thermal conductivity or a different material having a coefficient of linear expansion close to that of the surface layer member and poor thermal conductivity is used. used. Aluminum nitride as an example of the same material, thermal conductivity 90 (RT) (W / m · K)
The following are used: Of the different materials, silicon nitride or silicon carbide is preferable. Since materials having poor thermal conductivity are used as the base member 31 and the base member 36, when the heater is heated with the same power, the amount of heating the base member 31 and the base member 36 is small, and the ceramic has good thermal conductivity. More heat is dissipated than on the surface side, which is more efficient.

  FIG. 4 shows an example of the configuration of the print heaters 32 and 35. Reference numeral 41 indicates a print heater, and reference numeral 42 indicates a terminal. In order to heat the surface of the heater pattern to a uniform temperature, it is preferable to increase the linear density of the heater toward the outer peripheral region. For the purpose of making the in-plane temperature distribution uniform, the pattern shape is not limited to the concentric shape, but may be divided into a spiral shape or a plurality of sector shapes as shown in FIG. The reason why the heating element constituting one surface is divided into a plurality of parts is to distribute the current load when energized individually.

  As the heater material, a material obtained by firing a platinum simple substance or an alloy thereof after pattern printing is used, but other materials may be used. Since the print heaters 32 and 35 have a certain thickness, a groove is formed on one side of the pair of ceramics sandwiching the print heaters 32 and 35, and the pattern of the print heaters 32 and 35 is filled in the groove. By doing so, it is possible to secure the vertical parallelism of the pair of ceramics.

  FIG. 5 shows the configuration of an injection molding machine equipped with a mold apparatus. As shown in FIG. 5A, the injection molding machine kneads the heating cylinder 510 filled with the molding material, the hopper 511 for charging the molding material into the heating cylinder 510, and the molding material filled in the heating cylinder 510. A screw 514 that is melted and injected into the mold apparatus, a hydraulic motor 512 and a hydraulic cylinder 513 that drive the screw 514, a mold clamping cylinder 515 that clamps the mold, and one end of the heating cylinder 510 are provided to the mold apparatus. A nozzle 516 serving as an injection port, a fixed-side mold 517 and a movable-side mold 518, a fixed-side die plate 519, and a movable-side die plate 520 are provided.

  FIG. 5B is a plan view of the injection molding machine shown in FIG. 5A. Reference numerals 521 to 523 denote temperature controllers, which are connected to an injection molding machine via a temperature control pipe hose 524. The temperature controller 521 is a movable temperature controller, the temperature controller 522 is a fixed temperature controller, and the temperature controller 523 is a sprue temperature controller. The operation panel 525 controls the operation of the injection molding machine.

  According to one embodiment of the present invention, the following effects can be obtained. A ceramic heater is provided in the mold apparatus, and only the surface of the cavity 206 is selectively heated to an arbitrary temperature with the ceramic heater, thereby eliminating a thermal stress and a molecular orientation distortion at the time of molding and obtaining a substrate having excellent transferability. It is also possible to mold an optically transparent 0.1 mm thick substrate to which a fine uneven signal is transferred.

  Further, in the glass substrate molding, similarly, by providing the above-described ceramic heater in the mold apparatus, it is possible to transfer a fine uneven signal without bringing the entire mold apparatus to a high temperature close to 400 ° C.

  FIG. 6 shows a mold apparatus according to another embodiment of the present invention. Another embodiment is a combination structure of a ceramic heater and a heating press. The press molding apparatus includes a mold including a ceramic heater having a structure that moves up and down.

  The upper heating platen 602 is fixed to the upper fixed platen indicated by reference numeral 601. A ceramic heater 603 and an upper stamper 604 are stacked on the upper heating plate 602 and fixed by an outer peripheral ring 605.

  A lower heating plate 610 is attached to the lower fixing plate 611, and a guide pin 607 is erected with respect to the lower heating plate 610. A ceramic heater 609, a stamper 608, and a glass or plastic disk 606 are laminated in order so that the center hole is passed through the guide pin 607.

  Each structure of the ceramic heaters 603 and 609 is the same as the ceramic heater in the above-described embodiment. The upper heating platen 602 and the lower heating platen 610 are always heated at a constant temperature by the hot platen heater of the press machine, and only the vicinity constituting the cavity is selectively heated by the ceramic heaters 603 and 609. Reference numeral 612 indicates a hydraulic ram.

  For example, in forming a low melting point glass having a glass transition point of 285 ° C., in order to transfer a fine signal, the entire mold is set to 350 ° C. in order to keep the surface temperature of the stamper and the cavity around 350 ° C. It is necessary to do more. However, if the mold, the in-mold sliding parts, the sealing material, etc. are heated to a temperature of around 350 ° C., even SUS mold materials will not function with rust, and there will be no material that can be sealed at high temperatures. Even if the disk can be formed, the stamper also oxidizes and deteriorates as shown in FIG. 9 to increase disk noise.

  For this reason, the heating temperature of the molding machine main body shown in FIG. 6 is constantly lowered to 100 to 200 ° C. with the upper and lower heating plates, and is partially heated to a molding temperature of, for example, 370 ° C. in a short time with a ceramic heater. Since the entire mold apparatus is not heated and the heating time is short, oxidation deterioration and corrosion do not occur, and conventional mold parts and sealants can be used.

  Moreover, the entire apparatus is heated by radiant heat and heat radiation from the heat platen outside the mold apparatus, as seen in the conventional case where the entire mold apparatus is heated, and the upper and lower plates are parallel due to oxidative degradation and heat. There is no hindrance to handling due to heat when moving in or out of work.

  FIG. 7 shows an example of the time change of the surface temperature of the nickel stamper when the ceramic heater of the mold apparatus according to one embodiment of the present invention is turned on and off. The characteristics of FIG. 7 were obtained as a result of measurement in an open state where the molding apparatus of FIG. 6 was fixed to the upper heating plate 602 and the lower heating plate 610 and the heating plate was not heated or cooling water was not flowed into the mold. It is data. FIG. 8 is also an actual injection mold of the following embodiment, and the temperature of the entire mold is adjusted to 80 ° C., and the temperature of the heater is specified at a constant temperature when the ceramic heater is fixed on the mold. Therefore, the cooling efficiency of the ceramic heater is high.

  Ceramic heater: The surface layer member 33 and the surface layer member 34 are made of mirror-finished aluminum nitride having a thermal conductivity of 200 W and a thickness of 4.0 mm, and the base member 31 and the base member 36 have a thermal conductivity of 90 W and a thickness. Is made of aluminum nitride having a thickness of 3.0 mm, and a platinum-based heating element patterned so that the heater surface has a uniform temperature as shown in FIG. 4 is provided between the surface layer member and the base member. , Using heaters with a structure where each is bonded with ceramic or glass adhesive. As another example, a heater having a thermal conductivity of 40 W (silicon nitride) for the base member 31 and the base member 36 is used.

A compression molding apparatus will be described.
Molding machine: 300KN hydraulic automatic press (Watanabe Machine Mfg. Co., Ltd.)
As shown in FIG. 6, an apparatus in which upper and lower heating plates 602 and 610 and upper and lower cooling heating plates 601 and 611 are attached to a press machine body 600 and a lower body 600 integrated with a hydraulic ram 612 is driven up and down.
A normal commercially available heater (not shown) is incorporated in the upper heating plate 602 and the lower heating plate 610 and maintained at a constant temperature around 80 ° C.
In order to prevent the heat from the upper and lower heating plates 602 and 610 from causing squeezing such as parallelism and surface accuracy of the molding machine main body 600, cooling plates 601 and 611 are respectively provided. Cooling water around 0 ° C always flows to keep the molding machine body at a constant temperature.

Mold: As shown in FIG. 6, the mold structure does not use a cooling medium, and an upper ceramic heater 603 and an upper stamper 604 are sequentially fixed to the upper heating platen 602.
Similarly, a lower ceramic heater 609 and a lower stamper 608 are fixed to the lower heating plate 610.
The upper and lower ceramic heaters and the stamper are guided by the lower guide pins 607, and the upper and lower stampers and the ceramic heaters are fitted by the guide pins 607 when the press is raised.
The upper and lower stampers 604 and 608 are each sucked and fixed by a vacuum mechanism (not shown) in the vicinity of the inner and outer diameters.
The outer peripheral ring 605 defines the outer diameter of the disc during pressure molding, and the thickness of the disc is defined by the upper and lower mold bodies 613.

  The above-mentioned ceramic heater is fixed to the upper and lower heating plates 602 and 610 which are not temperature-controlled as shown in FIG. 6, and a voltage of 220 V is applied for 3.0 seconds by a controller (not shown), and the clamped vacuum is 0 to the fixed heater portion. The characteristic shown in FIG. 7 is the temperature of a K-type thermocouple on a nickel stamper with a thickness of 4 mm. That is, FIG. 7 shows a temperature rising / cooling curve of the nickel stamper in the atmosphere. In FIG. 7, t1 is a period during which the ceramic heater is turned on, and t2 is a period during which the ceramic heater is turned off. In a period t3 before and after the time when the surface temperature of the stamper reaches the maximum value, the resin or glass disk is pressurized and compressed in the cavity.

  Reference numeral 71 indicates a change in temperature of the stamper when a heater having a conductivity of 90 W (aluminum nitride) is used for the base member 31 and the base member 36, and reference numeral 72 indicates a conductivity of 40 W for the base member 31 and the base member 36. The temperature change of a stamper at the time of using the heater of (silicon nitride) is shown.

  Similarly, FIG. 8 shows the temperature change of the stamper using a heater whose conductivity is 90 W (aluminum nitride) as the base member 36 in the case of an injection mold controlled at a constant temperature of 80 ° C., and the ceramic heater is turned on. The surface temperature of the stamper 205 at that time depends on the heater capacity and the energization amount. For example, when heated at 220 V for t1 (= 3.3) seconds, the temperature rises from 80 ° C, which is the same temperature as the mold, to near 360 ° C. When the heater is turned off, the surface temperature of the stamper 205 is rapidly cooled by cooling with the circulating liquid medium in the mold and heat radiation to the atmosphere, and the original mold temperature control temperature is 80 ° in about 10 seconds. Return near C.

  In this way, when the ceramic heater is turned on with the temperature of the entire mold adjusted to a temperature of 100 ° C. or lower, the surface temperature of the stamper 205 is melted by the resin in the molding machine cylinder at 200 V or higher for about 3 seconds. The temperature can be raised to about 300 ° C, which is almost the same as or higher than the temperature, and when the heater power is turned off, it can be cooled rapidly, and the entire mold is not heated to a high temperature at all times. It is possible to transfer the signal.

  Compared with reference numeral 71 and reference numeral 72 in FIG. 7, the thermal conductivity of silicon nitride of the pedestal member is 35 W as compared with aluminum nitride 90 W, and has a heat storage property, and the cooling characteristics after the heater is turned off compared to aluminum nitride. I know it ’s bad. Although the cooling characteristics are poor, the input power is small, and there is an advantage that cooling strain can be removed by annealing in the mold without being rapidly cooled in compression molding of glass or the like.

  The characteristics for several examples of fine ceramics are shown in Tables 1 and 2 below. This table shows that aluminum nitride has a high thermal conductivity.

  Examples relating to molding of 1.1 mm thick substrates by injection molding are described below.

  Mold: A mold structure having a structure shown in FIG. 2 using a cooling medium such as water as a cooling medium, and the entire mold is always maintained at a constant temperature around 80 ° C. by the temperature control groove 204 and the temperature control groove 211. The fixed heater section 203 is fixed to the surface of the mold body, and the nickel stamper 205 is vacuum fixed on the fixed heater section 203.

  Molding machine: A disk-type injection compression molding machine (MO40H manufactured by Nissei Plastic Industry) with a maximum clamping pressure of 40 tons is used.

Resin: ST3000 (Teijin Kasei: Tg point 143 ° C) or AD5503S (Teijin Kasei: Tg point 145 ° C) However, no resin is injected during measurement.
Resin melting temperature: 350 ° C
Cooling time: 14 sec

Heater: A heater similar to that for obtaining the characteristic 101 shown in FIG. 8 is used.
Mold apparatus: The mold apparatus shown in FIG. 2 is used. A pair of ceramic heaters are fixed to the fixed mold part 213 and the movable mold part 214, and a stamper 205 is fixed to the fixed side. The die body cools the surfaces of the stamper 205 and the cavity 206 to a constant temperature of 80 ° C. or less by supplying the coolant passing through the chiller to the die body through the temperature control groove.

  The heat conductivity of aluminum nitride of the surface layer member 33 and the surface layer member 34 is 200 W, and the heaters whose heat conductivity of aluminum nitride of the pedestal member 31 and the pedestal member 36 is 90 W are used, 220 V, and the energization time is 3.3 seconds. As shown in FIG. 8, the surface temperature of the stamper 205 increased from 80 ° C. to 360 ° C. When the surface temperature of the stamper 205 2 to 4 seconds after energization was 260 ° C. or higher, which is higher than the glass transition point of the resin, the resin was filled in the mold to obtain a disk substrate.

The molding process of the substrate injection molding is as follows.
A delay timer is activated by a cooling completion signal or a mold opening signal from the molding machine, and the ceramic heater is turned on at an arbitrary time between the mold opening → substrate removal → mold closing and heating of the cavity 206 and the stamper 205 surface is started. .

  Since it takes about 1.5 to 3.0 seconds from mold opening → disk removal → mold closing → injection start, the surface temperature is raised to 260 ° C. or higher, preferably 300 ° C. or higher during that time.

  Next, the injection speed of PC (ST3000) heated to around 350 ° C. (nozzle temperature is 300 to 365 ° C.) in the molding machine cylinder is gradually reduced to 200 mm / sec to 50 mm / sec, and cavity 206 The molten resin is injected into the inside. At this time, a mold opening injection compression molding method was used in which the mold was opened 0.2 to 0.3 mm before injection and the mold was tightened while the resin was injected. The purpose of this molding method is to widen the gate only when it is filled in order to prevent the molten resin injected when the gate in the mold remains 0.2 to 0.3 mm from passing through the gate.

  At the end of injection, the ceramic heater is turned off, the cooling is performed for 14 seconds, and the convex clamp part is vacuum-sucked at a temperature of 80 ° C., and the signal part is 0.1 mm thick and the clamp part is 0.3 to 0.8 mm thick disk substrate Was taken out.

  An example of molding a glass disk by a compression molding method using low melting point glass according to another embodiment of the present invention is as follows.

Mold apparatus: A mold apparatus having the structure shown in FIG. 6 is used.
Heater: The surface layer member 33 and the surface layer member 34 are made of aluminum nitride FAN-200 having a diameter of 75 mm, a thickness of 3.0 mm, and a thermal conductivity of 200 W. The pedestal member 31 and the pedestal member 36 have a diameter of 100 mm, a thickness of 4.0 mm, and are made of SN-55, which is silicon nitride having a thermal conductivity of 35 W. A structure in which a platinum heating element is sandwiched between aluminum nitride and silicon nitride is used.
Low melting point glass disk: A low melting point glass having a glass transition point of 285 ° C., a bending point of 310 ° C. and a refractive index of nd≈1.50, K-PG325 (manufactured by Sumita Optical Glass) is used.

  In the upper heating plate 602 and the lower heating plate 610 in FIG. 6, the ceramic heater 603 and the ceramic heater 609 that are divided by the upper and lower outer peripheral rings 605 constituting the cavity are divided into upper and lower parts, similarly to the injection mold. As shown in FIG. 3, the surface layer member 33 and the surface layer member 34 are made of aluminum nitride, and the pedestal member 31 and the pedestal member 36 are made of 4.0 mm thick silicon nitride having a thermal conductivity of 40 W, and a platinum-based heating element is patterned between them. The heater 32 that has been tempered and bonded with a ceramic adhesive is attached to the upper heating plate 602 and the lower heating plate 610 of the compression molding machine shown in FIG. The upper heating plate 602 and the lower heating plate 610 are heated and held at a constant temperature below the heat deformation temperature of the molding material by an ordinary cartridge heater or the like.

The process of molding a glass disk by the compression molding method is as follows.
A glass disk made of the low-melting glass and having an inner and outer shape close to a desired shape and slightly thicker than the desired thickness (within 100 μm) and having a matte finish on both sides Ra = 10 μm is prepared.

  The upper heating plate 602 and the lower heating plate 610 are constantly heated and held at around 150 ° C. below the glass transition point, and the upper and lower parallel plates 611 and 611 are not out of alignment by heat from the heating plate. Thus, the whole is always cooled to near normal temperature with a circulating refrigerant.

  The center guide pin 607 in the mold is inserted into the low melting glass disc 606 and the guide is inserted. At this time, it is desirable that the glass disk is preliminarily heated in advance in a separate drying furnace or the like at a temperature equal to or lower than the mold temperature, for example, 120 ° C. This is to prevent the glass disk from cracking due to internal and external thermal expansion distortion and to shorten the preheating time when glass at room temperature is inserted into the high temperature mold.

  The hydraulic ram 612 is raised and stopped at a position of 0.5 to 1.0 mm where the upper and lower molds come into contact, and the glass disk 606 is brought to a uniform temperature of about 150 ° C. while flowing nitrogen gas into the cavity. Hold.

  From the controller, the ceramic heater 603 and the ceramic heater 609 are energized at 160 V for 20 seconds to fix and keep the surface temperature of the stamper at a temperature of 300 ° C., thereby sufficiently preheating and softening the glass disk. Furthermore, it supplies with electricity at 200V for 6 second, and makes the surface temperature of a stamper 380 degreeC.

  The hydraulic ram 612 is further raised, the supply of nitrogen gas is stopped immediately before the mold is closed, and the inside of the cavity is evacuated.

  When the mold is clamped at a pressure of 20 to 30 KN, the heater energization is turned off, the pressurization is performed for 2 seconds, and the pressure is stopped as it is, so that the pressure gradually decreases due to the creep phenomenon and the stress in the mold is relieved.

  The pressure at the time of performing signal transfer on the substrate does not need to melt the entire glass substrate in the mold, and may be such that the surface layer of the glass substrate is melted.

  Thereafter, when the mold temperature is close to 150 ° C., the hydraulic ram 612 is lowered and the disk is removed from the mold.

  When a ceramic member such as silicon nitride having poor thermal conductivity is used as the pedestal member, the cooling curve after turning off the current is removed, so that glass substrate molding has the effect of annealing the thermal strain inside the glass. When the pedestal member has a thermal conductivity of 150 W or more, the base member is rapidly cooled, and the substrate is easily cracked when taken out.

  One embodiment and other embodiments of the present invention described above have the following effects.

  1) Lower the resin flow resistance in the mold by raising the stamper or cavity surface temperature in the mold to an arbitrary temperature within the mold melting temperature of the molding machine above the glass transition point of the molding resin before resin injection. By filling and solidifying the resin, it is possible to avoid solidification while increasing the flow viscosity (resistance) with conventional temperature control of a constant mold temperature, and extremely reduce optical distortion due to molecular orientation and skew due to thermal stress. it can.

  2) By turning off the heater after resin injection, the mold temperature can be taken out at a temperature lower than the heat deformation temperature, and a substrate with less warping deformation such as skew, which was impossible with a mold with temperature control at a constant temperature, is injection molded. It became possible.

  3) A 0.1mm thick substrate to which the signal is transferred is obtained by injection molding, eliminating the need for the disc punching process and punching from the cast film and extrusion film found on BD discs. A conventional manufacturing apparatus such as a DVD can be used at low cost.

  4) Even with BD discs, when creating discs with a multi-layered structure such as a two-layer ROM, the film is used by directly forming a 0.1 mm thick substrate with signals on the film by hot pressing or indirectly by the 2P method and punching it into a disc. Many processes such as having to be used can be omitted, and the process can be simplified.

  5) For example, in a BD two-layer structure using a 0.1 mm thick substrate, the handling by the adsorption type between production process steps using a film causes the deformation of the 0.1 mm thick disk without deformation or stacking. However, when using an injection molded substrate, the thickness of the clamp part at the center used for handling is increased, and the first layer is reduced by a corresponding amount to give a total thickness of 1.2 mm. It is possible to improve the handling of the production process by making the signal part 0.1 mm thick and the clamp part thick.

  6) In the molding of a glass substrate embossed with a signal, even if it is a low-melting glass, a fine uneven signal transfer cannot be obtained unless the entire mold including the stamper is brought to a temperature close to 400 ° C. For this reason, signal degradation and mold corrosion due to oxidative degradation have occurred, but the entire mold does not need to be brought to 400 ° C. due to local heating of the ceramic heater portion and does not corrode.

  7) By using a ceramic heater at the cavity part in the mold, it is possible to partially raise the temperature separately from the whole mold temperature. The molded product is obtained.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible. For example, the present invention can be applied to a rewritable optical disk or a write-once optical disk in addition to a read-only optical disk. In that case, not a pit but a groove is formed as the fine uneven pattern. Moreover, the numerical value quoted in the above-mentioned embodiment is only an example, and you may use a numerical value different from this as needed.

1 is a perspective view and a partially enlarged sectional view showing a two-layer structure disk to which the present invention can be applied. It is sectional drawing of the external heating medium combined use mold apparatus by one Embodiment of this invention. It is a perspective view which shows the ceramic heater structure and positional relationship in one Embodiment of this invention. It is a basic diagram which shows the pattern of the print heater of the ceramic heater in one Embodiment of this invention. It is the schematic diagram and top view of an injection molding machine which mount the die apparatus by one Embodiment of this invention. It is sectional drawing of other embodiment which applied this invention to the pressurization / heating press. It is a graph which shows an example of a temperature rising curve and a cooling curve in the air | atmosphere of Ni stamper in one Embodiment of this invention. It is a graph which shows the other example of a temperature rising curve and a cooling curve in the air | atmosphere of the Ni stamper in one Embodiment of this invention. It is a graph for demonstrating that oxidation deterioration arises in a Ni stamper, and the noise of the low frequency range of a disk generate | occur | produces.

Explanation of symbols

31, 36 ... Base member 32, 35 ... Print heater 33, 34 ... Surface layer member 203 ... Fixed heater unit 205 ... Stamper 206 ... Cavity 210 ... Movable heater unit 603, 609 ... Ceramic heater

Claims (13)

In a molding apparatus that molds a substrate on which a concavo-convex pattern of a stamper is transferred by injecting molten resin into a cavity,
A movable side mirror mold and a fixed side mirror mold, which are separable and have mutually facing surfaces, and
Temperature control means for controlling the temperature of the movable side mirror mold and the fixed side mirror mold,
A movable side heater part and a fixed side heater part attached to the respective opposing surfaces of the movable side mirror mold and the fixed side mirror mold;
A stamper fixed to one surface of the movable heater portion and the fixed heater portion,
The movable heater portion and the fixed heater portion are configured such that a heating element is sandwiched between first and second members made of non-conductive ceramic,
One of the first and second members has a surface that comes into contact with the movable mirror mold and the fixed mirror mold,
A molding apparatus, wherein the other member of the first and second members has a surface in contact with the cavity or the stamper. In claim 1,
A molding apparatus, wherein the cavity surface portion is heated separately from the mold body temperature by turning on and off energization of the heating element. The molding apparatus according to claim 1, wherein a surface of the other member contacting the cavity or the stamper is mirror-finished. The molding apparatus according to claim 3, wherein the mirror finish has a surface roughness of Ra 0.1 μm or less. The molding apparatus according to claim 1, wherein the thermal conductivity of the one member is lower than the thermal conductivity of the other member. In claim 5,
The one member is a member having a thermal conductivity of 90 (RT) (W / m · k) or less and a poor thermal conductivity,
The molding apparatus according to claim 1, wherein the other member is a member having a thermal conductivity of 150 (RT) (W / m · k) or more and excellent in thermal conductivity. In claim 5,
The molding apparatus characterized in that the one member is silicon nitride and the other member is aluminum nitride. In claim 1,
The heating element is divided into a plurality of heating elements constituting one surface,
A molding apparatus, wherein a groove is formed in one of the first and second members, and the heating element is disposed in the groove. In the molding method of injecting molten resin into the cavity and molding the substrate on which the uneven pattern of the stamper is transferred,
Controlling the temperature of the movable-side mirror mold and the fixed-side mirror mold, which are detachable and have mutually facing surfaces, to a constant temperature not lower than 50 ° C. and not higher than the thermal deformation temperature of the molding material;
A step of turning on the movable side heater part and the fixed side heater part attached to the opposing surfaces of the movable side mirror mold and the fixed side mirror mold; and
A step of injecting resin in a state where the temperature of the surface constituting the cavity is heated above the glass transition point;
A molding method comprising a step of turning off the movable heater portion and the fixed heater portion. In claim 9,
The command to turn on and off the movable heater section and the fixed heater section is synchronized with the operation signal of the mold apparatus,
From the mold opening command to the disk removal → mold closing → resin injection filling, the movable heater section and the fixed heater section are turned on,
The molding method characterized in that the movable heater section and the fixed heater section are turned off from the cooling start command to the end of cooling. In an optical disc having a disc substrate created by an injection molding method,
A first substrate in which the thickness of the first region around the central hole is smaller than the second region on the outer peripheral side of the first region;
A second substrate in which the thickness of the third region around the center hole is larger than the thickness of the fourth region on the outer peripheral side of the third region;
An information layer formed at a boundary between opposing surfaces of the second region and the fourth region;
An optical disc having a constant thickness obtained by bonding the first and second substrates with the information layer interposed therebetween. In claim 11,
An optical disc in which the thickness of the third region is 0.3 to 0.8 mm, the thickness of the fourth region is 0.1 mm, and the thickness of the optical disc is 1.2 mm. In claim 11,
An optical disc having two or more information layers.

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