Optical information recording disc and apparatus for driving the disc

Abstract: An optical information recording disc having at least one substrate (1) for recording/reproducing an information through an optical unit is disclosed in which a spindle hole (50) through which a spindle (11) provided in a disc drive system is formed in a central portion of the substrate (1). An engagement member (4; 31; 33; 35; 36; 38) engageable with a disc engagement member (14; 21, 21a; 32; 34; 37; 39) integrally formed with the spindle (11) is formed around the central portion. In addition an associated disc drive apparatus is disclosed in which the disc engagement member is formed in a spindle (11).

Description: The present invention relates to an optical information recording disc having at least one substrate on which information is recorded/reproduced by optical means and which substrate comprises a spindle hole, at a central portion thereof, and an engagement means, at an outer peripheral portion of the spindle hole. The invention also relates to a disc drive apparatus having a spindle for drivingly rotating an optical information recording disc, said apparatus comprising a disc engagement means at said spindle Such an optical information recording disc and such a disc driving apparatus are described in Patent Abstracts of Japan, Vol. 9, No. 127 (P-360), [1850] relating to JP-A-60-10450. This publication relates to the provision of an engagement device for transmitting a power of a spindle provided within a disc driving apparatus to an optical information recording disc. Two kinds of clamping systems for optical information recording discs are known, i.e. a mechanical clamp system and a magnetic clamp system. In the mechanical clamp system, as shown in Fig. 20, a clamp member 42 is disposed in confronted relation to a spindle 41, and an optical information recording disc 43 is loaded on the spindle 41. Thereafter, the clamp member 42 is lowered to press the optical disc 43 by a spring force of a spring 44. On the other hand, in the magnetic clamp system, as shown in Fig. 21, a magnet 46 is embedded in a turntable 45 formed integrally with a spindle 41, and magnetic members 47 are disposed close to a central portion of an optical information recording disc 43, so that the optical disc 43 is clamped by a magnetic attraction force between the magnet 46 and the magnetic members 47. In the mechanical clamp system of the conventionally well known clamp systems, it is necessary to provide the clamp member 42 and a member for driving the clamp member. As a result, the disc drive mechanism becomes expensive. Also, since it is necessary to provide a large space for the arrangement of the clamp member 42 and the like, the disc driving device is enlarged in size. The magnet clamp system does not suffer from the above-described disadvantages. However, in the magnetic clamp system since the optical information recording disc 4 is clamped only by the magnetic attraction force between the magnet 46 and the magnetic member 47 and the friction between the turntable 45 and the magnetic members 47, the clamp force is relatively weak. As a result, when the spindle 41 is started to be operated at a high speed or when the optical disc 43 lacks dynamic balance and is drivingly rotated at a high speed, an undesired slippage occurs between the optical disc 43 and the turntable 45, so that a rotation jitter is increased to cause a recording/reproducing error or to cause a data transfer speed to be lowered. The above-mentioned JP-A-60-10450 discloses an engagement device for engaging an optical recording disc on a disc driving apparatus in which, as in the magnetic clamp system, a magnet is embedded in the spindle of a turntable, while the optical disc has a hub made out of a magnetizable material, so that the disc is attracted by the spindle and a central portion of the spindle fits into the spindle hole of the hub. Further, the spindle is provided with a projecting part that fits in a hole that is provided in the hub, at a peripheral portion thereof. This means that an accurate positioning of the hole with respect to the projection is required when the disc is placed onto the spindle. Accordingly, in the technical field of the optical information recording disc and the disc driving apparatus, it has been one of the most important tasks to solve the above-described technical disadvantages. In order to overcome the above-noted defects, an object of the present invention is to provide a compact disc driving apparatus for drivingly rotating an optical information recording disc at a high speed, and to provide an optical information recording disc applicable to the driving apparatus. In order to attain the object, the optical information recording disc according to the invention is characterized in that said engagement means includes a gear. Further, the disc drive apparatus according to the invention is characterized in that said disc engagement means includes a gear formed on an optical disc loading surface of a turntable formed integrally with said spindle. As described above, when the optical information recording disc and the spindle are engaged with each other through mechanical engagement means, there is no slippage therebetween even during the application of a large torque. It is, therefore, possible to start the rotation of the optical information recording disc at a high speed or rapidly and to drivingly rotate the disc at a high speed. Thus, it is possible to increase the data transfer speed and to reduce errors in recording/reproducing the information. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is a perspective view showing an optical information recording disc according to a first embodiment of the invention; Fig. 2 is a cross-sectional view showing the disc shown in Fig. 1; Fig. 3 is a perspective view showing a disc drive system for the disc shown in Fig. 1; Fig. 4 is a sectional view showing an engagement between the disc and the disc drive system according to the first embodiment; Fig. 5 is a sectional view showing a disc drive system according to a second embodiment of the invention; Fig. 6 is a bottom view of the disc drive system shown in Fig. 5; Fig. 7 is a sectional view showing the engagement between the disc and the disc drive system according to the second embodiment; Figs. 8 and 9 are plan views showing disc drive systems according to a third embodiment of the invention; Fig. 10 is a sectional view showing an engagement between the disc and the disc drive system according to the third embodiment; Fig. 11 is a plan view showing an optical information recording disc in accordance with a fourth embodiment; Fig. 12 is a plan view of a disc drive system for the optical disc according to the fourth embodiment; Fig. 13 is a plan view showing an optical information recording disc according to a fifth embodiment; Fig. 14 is a plan view showing a disc drive system for the optical disc according to the fifth embodiment; Fig. 15 is a sectional view of an optical information recording disc according to a sixth embodiment; Fig. 16 is a plan view of the optical disc according to the sixth embodiment; Fig. 17 is a sectional view of an engagement between the disc and the disc drive system according to the sixth embodiment; Fig. 18 is a plan view showing an optical information recording disc according to a seventh embodiment of the invention; Fig. 19 is a sectional view of a disc drive system for the optical disc shown in Fig. 18; Fig. 20 is a sectional view showing a conventional optical disc; and Fig. 21 is a sectional view showing another conventional optical disc. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described by way of unlimited examples with reference to the accompanying drawings. An optical information recording disc according to a first embodiment of the invention will now be described with reference to Figs. 1 and 2. Fig. 1 is a perspective view showing the optical information recording disc according to the invention, and Fig. 2 is a cross-sectional view of the disc. As shown in Figs. 1 and 2, a pair of substrates 1 are bonded to each other through an inner circumferential spacer 2 and an outer circumferential spacer 3. A hub 5 is provided integrally with a crown gear 4 in a central portion of the disc assembly. The pair of substrates 1 are made of transparent ceramic such as glass or transparent resinous material such as polycarbonate (PC), polymethylmethacrylate (PMMA), polymethylpentene, and epoxy and are provided at their center with center holes 6. In an inner surface of each substrate 1, there are formed signal patterns 7 such as guide grooves for optical spots and signal-modulated prepits arrangement. A recording film or reflecting film 8 is formed on the signal pattern 7. A suitable method is selected for forming the signal pattern 7 in accordance with a kind of material of the substrates 1. For example, in the case where the substrates 1 are formed of thermoplastic resin such as PC, PMMA and polymethylpentane, a so-called injection-molding method including a step of injecting a molten material for the substrates into an injection molding dies to integrally form the substrates 1 and the signal patterns 7 is preferable. With respect to this substrate material, a so-called compression molding method or injection-compression molding method in which, after the molten material has been injected into the injection molding dies, a pressure is applied thereto, may be used. These methods are known in the art. In the case where the substrates 1 are made of ceramic such as glass or thermosetting resin such as epoxy, a so-called 2P method (photopolymerization method) is suitable in which a photopolymerizable resin is spread between the substrate 1 and a stamper (die) having a reversed or negative pattern for a desired signal pattern to transfer the reversed pattern of the stamper to the substrate. Also, in case of the thermosetting resin such as epoxy, it is possible to employ a so-called injection molding method in which substrate material kept under the molten condition is statically poured into the mold to integrally form the substrate 1 and the signal pattern 7 together. A recording film or layer 8 may be made of a desired heat mode material in accordance with a kind of the optical information recording disc. For example, in case of the rewritable type optical information recording disc, the recording film 8 is formed of low melting point alloy typically such as tellurium-selenium alloy, or organic dye material such as cyanine or phthalocyanine system organic dye. Also, in case of the erasable optical information recording disc, the recording film is formed of magnet optical recording material typically such as amorphous alloy composed mainly of terbium, iron and cobalt or phase-changeable recording material typically such as amorphous alloy made mainly of indium and selenium. In the case where the optical information recording disc is of the read-only type, a reflecting film or layer is deposited instead of the recording film. For example, the reflecting film may be made of aluminum. These recording films or reflecting films 8 may be formed by conventional thin film deposition methods such as sputtering, vacuum-evaporation, ion-plating, plasma deposition, non-electrolyte plating or the like. The inner and outer circumferential spacers 2 and 3 are made of metallic or resinous material and are in the form of rings having desired inner and outer diameters. The inner and outer circumferential spacers 2 and 3 are bonded to the inner surfaces of the substrates 1 through adhesives 9. It is possible to use desired conventional adhesives as the adhesives 9. However, it is preferable to use photopolymerizable adhesives or hot-melt adhesives. The hub 5 is constituted by a base portion 5a having such an outer diameter that the base portion 5a can be inserted into the center hole 6 of the substrate 1 and a height that is substantially equal to a thickness of the substrate 1, and a flanged portion 5b having an outer diameter that is larger than the diameter of the center hole 6 and a thickness that is substantially half the thickness of the inner and outer circumferential spacers 2 and 3. A spindle hole 5c is formed through the central portion of the hub 5. The hub 5 is made of wear-resistant and magnetic metal. The hub 5 may be made of magnetic material such as soft iron, ferrite or martensite system stainless steel. It is more preferable to use stainless steel SUS 430 under JIS standards, which has rust-proof or anticorrosive property and is available in the market relatively cheaply. The base portion 5a is inserted into the center hole 6 from the inside of the substrate 1. The outer surface of the base portion 5a and the inner circumferential surface of the center hole 6 are bonded to each other, and the upper surface of the flanged portion 5b and the inner surface of the substrate 1 are bonded to each other by means of adhesives 9, thereby setting the hub 5 onto the central portion of the substrate 1. The adhesives may be the same as those used to bond the substrate 1 with the spacers 2 and 3. The crown gear 4 is formed coaxially with the spindle hole 5c on an outer surface of the base 5a of the hub 5. The crown gear 4 may be integrally formed with the hub 5 or otherwise may be formed separately from the hub 5 and then bonded to the hub 5 with the adhesives or the like. In the case where the crown gear 4 is formed separately, it may be made of resin. In order to reduce a slippage between the crown gear 4 and an associated crown gear formed on a turntable of the disc driving apparatus to be engaged therebetween during a period from a moment when the crown gear 4 comes into contact with the associated crown gear to a moment when the engagement therebetween has been completed, it is preferable to increase the number of the teeth of the crown gears as much as possible. Also, since the crown gear 5 is not engaged with a pinion for the power transmission, there is no slippage after the completion of the engagement. Therefore, the tooth configuration is not limited to an involute gear tooth or a cycloid gear tooth but may be modified to a rectangular, triangular and mountain-like configuration or the like. A disc driving apparatus for drivingly rotating an optical information recording disc in accordance with the first embodiment and a method for driving the disc in the disc driving apparatus will be explained with reference to Figs. 3 and 4. As shown in Fig. 3, a disc driving system is built in the disc driving apparatus. The disc driving system is composed of a spindle 11 connected to a disc drive motor (not shown) and a turntable 12 fixedly secured near an end portion of the spindle 11. The spindle 11 has such an outer diameter that the spindle 11 may be fitted by a certain pressure into the spindle hole 5c formed in the hub 5. The distal end portion of the spindle 11 is chanfered at 11a for easy insertion of the spindle into the spindle hole 5c. The turntable 12 is disposed somewhat below the top end of the spindle 11, and have the outer diameter D1 substantially the same as an outer diameter D2 of the base portion 5a of the hub 5. A disc receiver 13 is projected somewhat inside of an outer circumference of an upper surface of the turntable 12. The upper surface of the disc receiver 13 is located just below a lower edge of the chanfered portion 11a formed at the distal end portion of the spindle 11. A crown gear 14 for engagement with the crown gear 4 is formed in confronted relation of the crown gear 4 on the upper surface of the turntable 12. As a matter of course, the crown gear 14 is formed coaxially with the spindle 11. A magnet 15 is mounted along the outer circumference of the disc receiver 13 formed on the upper surface of the turntable 12. When the optical information recording disc in accordance with the first embodiment is loaded in the disc driving apparatus provided with the above-described disc drive system, first of all, the disc is moved toward the turntable 12 by the gravitational force and a magnetic force applied between the hub 5 and the magnet 15 provided in the turntable 12. As a result, the distal end portion of the spindle 11 is inserted into the spindle hole 5c formed in the hub 5. Under such a condition, assuming that grooves 4a between the teeth of the crown gear 4 formed in the hub 5 are completely in alignment with teeth 14b of the crown gear 14 formed in the turntable 12, and the teeth 4b of the crown gear 4 be completely in alignment with grooves 14a between the teeth of the crown gear 14, as shown in Fig. 4, the engagement between the two crown gears 4 and 14 are completed immediately after the insertion of the spindle 11 into the spindle hole 5c. Accordingly, it is possible to drive the optical disc by rotating the spindle 11. On the other hand, if the grooves 4a between the teeth of the crown gears 4 are out of alignment with the teeth 14b of the crown gear 14, at the stage when the distal end portion of the spindle 11 has been inserted into the spindle hole 5c, the two crown gears 4 and 14 are in abutment with each other at their peak portions. In this case as the spindle 11 is rotated, slippages are generated between the peak portions of the crown gears 4 and 14. At a moment when the grooves 4a between the teeth 4b of the crown gear 4 are in alignment with the teeth 14b of the crown gear 14, the engagement between the two crown gears 4 and 14 is completed. In the first embodiment for the optical information recording disc and the disc driving apparatus, since the rotational force of the spindle 11 is transmitted to the disc through the mechanical engagement between the crown gears 4 and 14, even if the spindle 11 is started at a high speed or the disc that is somewhat defective in dynamic balance is drivingly rotated at a high speed, there is not a fear that substantial slippage between the spindle 11 and the optical disc would occur. Accordingly, it is possible to provide an optical information recording system in which a data transmission speed is high and an error in recording/reproducing due to a jitter in rotation is suppressed. A second embodiment of the invention will now be described with reference to Figs. 5 through 7. The second embodiment is characterized in that an engagement pin is provided in the disc drive system of the disc driving apparatus. The optical information recording disc used in this embodiment is the same as that used in the first embodiment. Fig. 5 is a sectional view showing a drive system in the disc driving apparatus in accordance with the second embodiment. Fig. 6 is a bottom view showing the drive system, and Fig. 7 is a sectional view showing the apparatus in the operating condition. In Figs. 5 to 7, reference numeral 21 denotes an engagement pin, numeral 22 denotes a spring member and numeral 23 denotes a through-hole. In the second embodiment, the same reference numerals are used to indicate the like components or members shown in Figs. 1 through 4. The engagement pin 21 is formed in such a size and a configuration that the pin 21 is insertable into a groove 4a between teeth 4b of the crown gear 4 provided in the disc. As shown in Fig. 7, the pin 21 is fixed to an end of the spring member 22 in the form of a ring. The engagement pin 21 is inserted from the back side of the turntable 12 into the through hole 23 as shown in Fig. 5, with its distal end being projected beyond the surface of the turntable 12. The spring member 22 is mounted on the turntable 12 by fixing the opposite end thereof by means of the engagement pin 21 to the back surface of the turntable 12. The penetrating hole 23 is formed at a position corresponding to the groove 4a between the teeth 4b of the crown gear 4. In the disc drive system according to the second embodiment, if the engagement pin 21 is out of alignment with the groove 4a between the teeth 4b of the crown gear 4 upon the loading of the disc, as shown in Fig. 7, the engagement pin 21 is retracted back into the through hole 23 with the pin 21 being pressed by the hub 5. Then, as the spindle 11 is rotated, a slippage is generated between the peak portion of the tooth 4b of the crown gear 4 and the engagement pin 21. When the groove 4a between the teeth 4b of the crown gear 4 and the engagement pin 21 are in alignment with each other, the engagement pin 21 is inserted into the groove 4a of the crown gear 4 by the action of the resilient force of the spring member 22, thereby completing the engagement therebetween. The disc drive system according to the second embodiment has the same advantages as those of the first embodiment. In addition, the following advantages may be enjoyed according to the second embodiment. (i) It is possible to dispense with the expensive crown gear, to reduce a cost for the disc drive system. (ii) It is possible to reduce powder due to wear in comparison with the engagement of the two crown gears. (iii) Since the engagement pin 21 is provided to be insertable into the through hole 23, irrespective of whether the groove 4a between the teeth 4b of the crown gear 4 and the engagement pin 21 are in alignment with each other or not, it is possible to rapidly locate in place the disc on a disc receiver 13 of the turntable 12, thereby increase the stability of the disc. A third embodiment of the invention will now be described with reference to Figs. 8 to 10. The embodiment is characterized in that two engagement pins are provided in the drive system for driving an optical information recording disc. The disc used in the first embodiment is used in the third embodiment. Figs. 8 and 9 are plan views showing the disc drive system in accordance with the third embodiment. Fig. 10 is a sectional view showing the apparatus in the operating condition. In Figs. 8 to 10, reference characters 21 and 21a denote engagement pins. The same reference characters as used in Figs. 1 through 7 are used to indicate the like components or members. The engagement pins 21 and 21a are both formed in such a size and a configuration that the pins are insertable into the grooves 4a between the teeth 4b of the crown gear 4 provided in the disc, respectively. As shown in Fig. 10, the pins 21 and 21a are fixed to a spring member 22 in the form of a ring. As shown in Fig. 10, the engagement pins 21 and 21a are inserted into through holes 23 from a back surface of the turntable 12 with distal ends thereof being projected beyond the surface of the turntable 12. As shown in Figs. 8 and 9, the two engagement pins 21 and 21a are arranged so that when one of the engagement pin 21 is located at a position corresponding to the groove 4a between the teeth 4b of the crown gear 4, the other engagement pin 21a is located at a position corresponding to the tooth 4b of the crown gear 4. Namely, if the number of the teeth 4b of the crown gear 4 (or the number of the grooves between the teeth) is an odd number, as shown in Fig. 8, the two engagement pins 21 and 21a are arranged in a symmetrical manner with respect to the spindle 11. Also, if the number of the teeth (or the grooves between the teeth) of the crown gear 4 is an even number, as shown in Fig. 9, one of the engagement pins 21a is arranged at a position offset by half a pitch p of the teeth 4b of the crown gear 4 from the symmetrical position with respect to the spindle 11. In such an arrangement, it is possible to engage one of the engagement pins 21, 21a with the grooves 4a between the teeth 4b of the crown gear 4 only by rotating the turntable 12 by half the pitch p of the teeth 4b of the crown gear 4. As a result, the wear of the engagement pins 21 and 21a and the crown gear 4 may be minimized. Thus, the adverse effect of the wear powder may be negligible. The other engagement pin that is not inserted into the groove 4a between the teeth 4b of the crown gear 4 is retracted into the through hole 23 by the tooth 4b of the crown gear 4 as shown in Fig. 10. The other structure of the drive system according to the third embodiment provides the same effects as those as in the first and second embodiments. A fourth embodiment of the invention will now be described with reference to Figs. 11 and 12. Fig. 11 is a plan view of an optical information recording disc in accordance with the fourth embodiment, and Fig. 12 shows a plan view of a disc drive system applied to the apparatus. As shown in Fig. 11, the disc according to the fourth embodiment is characterized in that a spur gear 31 is provided in a hub 5 as an engagement means with the disc drive system. The other components are the same as those as in the first embodiment. The like components or members are designated by the same reference numerals and the explanation therefor will be omitted. On the other hand, an internal gear 32 that is engageable with the spur gear 31 is provided in the turntable 12 in the disc drive system for drivingly rotating the optical disc, as shown in Fig. 12. The disc and the disc driving apparatus in accordance with the fourth embodiment may ensure the same advantages as those in the first embodiment. In addition, the disc drive systems in accordance with the second and third embodiments may be applied to the optical disc according to the fourth embodiment. A fifth embodiment of the invention will now be described with reference to Figs. 13 and 14. Fig. 13 is a plan view of an optical information recording disc in accordance with the fifth embodiment, and Fig. 14 is a plan view of a disc drive system to which the disc of Fig. 13 is applied. As shown in Fig. 13, the disc according to the fifth embodiment is characterized in that an internal gear 33 is provided as an engagement means with the disc drive system. The other components are the same as those as the disc of the first embodiment. The like components are designated by the same reference characters and the explanation therefor will be omitted. On the other hand, as shown in Fig. 14, a spur gear 34 that is engageable with the internal gear 33 is provided in the disc drive system for drivingly rotating the disc according to the fifth embodiment. The disc and the disc drive apparatus according to the fifth embodiment may ensure the same advantages as those of the first and second embodiments. The disc drive system that has been explained in connection with the second and third embodiments may be applied to the disc according to the fifth embodiment. A sixth embodiment of the invention will now be described with reference to Figs. 15 through 17. Fig. 15 is a sectional view of an optical information recording disc in accordance with the sixth embodiment. Fig. 16 is a plan view thereof. Fig. 17 is a sectional view showing the engagement condition between the optical disc and the drive system according to the sixth embodiment. As shown in Figs 15 and 16, the disc according to the sixth embodiment is characterized in that a plurality of penetrating holes 35 are formed in the hub 5 as an engagement means with the disc drive system. The plurality of holes 35 are equiangularly arranged on a coaxial circle in the circumferential portion of the spindle hole 5c. The number of the through holes 35 may be selected as desired. However, in order to smoothly perform the engagement with engagement pin(s) to be described later, it is preferable to increase the number of the through holes 35 as much as possible. The other components are the same as those of the disc according to the first embodiment. The like components are indicated by the same reference numerals and the explanation therefor will be omitted. The drive system that has been explained in connection with the second and third embodiments may be applied to the disc drive system for drivingly rotating the disc according to the sixth embodiment. Namely, as shown in Fig. 17, the engagement pin 21 is engaged with one of the through holes 35 formed in the hub 5, so that the disc may be drivingly rotated. The disc according to the sixth embodiment has the advantage that it may be made at low cost because an expensive gear may be dispensed with, in addition to the like advantages as those of the first through fifth embodiments. A seventh embodiment of the invention will now be described with reference to Figs. 18 and 19. Fig. 18 is a plan view of a main part of an optical information recording disc in accordance with the seventh embodiment. Fig. 19 is a sectional, side elevational view of a disc drive system for the disc of Fig. 18. As shown in Fig. 18, the disc according to the seventh embodiment is characterized in that a plurality of splines 36 is formed in the circumferential wall of the spindle hole 5c formed in the hub 5 as an engagement means with the drive system. The other components are the same as those as the first embodiment. The like components are designated by the same reference characters and the explanation therefor will be omitted. On the other hand, as shown in Fig. 19, the splines 37 which are engageable with splines 36 are formed on the spindle 11 of the disc drive system for drivingly rotating the optical disc according to the seventh embodiment. The optical disc according to the seventh embodiment may be drivingly rotated without slippage between the spindle 11 and the turntable 12, while being engaged with the drive system through the splines 36 and 37. Therefore, the same advantages as the first embodiment may be ensured by the disc and the disc drive system according to the seventh embodiment. In this embodiment, it is possible to use a serration instead of the splines 36 and 37 to ensure the same effects. Although, in the foregoing embodiments, the hub 5 is provided in the central portion of the substrate 1, the arrangement is not limited thereto or thereby, it is possible to modify the arrangement so that the engagement means explained in conjunction with the first through eighth embodiments may be provided directly to the substrate 1. Also, in the foregoing embodiments, the optical information recording disc is of the air-sandwich structure type. However, the invention is not limited thereto but may be applied to conventional disc structures such as a single plate type disc and an intimate cemented structure type disc. As has been described above, according to the present invention, since the disc is mechanically engaged with the disc drive system, there is no slippage therebetween even if a large torque is applied thereto. Therefore, it is possible to increase the starting speed or acceleration of the drive rotation of the spindle and the speed of the drive rotation of the disc. Also, it is possible to reduce the recording/reproducing errors and to increase the speed of data transfer.

Claims: An optical information recording disc having at least one substrate on which information is recorded/reproduced by optical means and which substrate (1) comprises a spindle hole (5c), at a central portion thereof, and an engagement means (4; 31; 33; 35; 36; 38), at an outer peripheral portion of the spindle hole for engaging with a mating engagement means formed on the spindle, characterized in that said engagement means includes a gear (4; 31; 33). The disc according to claim 1, wherein said substrate has a hub made from magnetic material in the central portion thereof, and said spindle hole (5c) and said gear of the substrate are formed in said hub. The disc according to claim 1, wherein said spindle hole (5c) and said gear are formed directly in said substrate. The disc according to claim 1, wherein said gear is a crown gear (4). The disc according to claim 1, wherein said gear is a spur gear (31). The disc according to claim 1, wherein said gear is an internal gear (33). The disc according to claim 1, wherein said gear includes a plurality of equiangularly arranged penetrating holes (35). The disc according to claim 1, wherein said gear includes a number of splines (36) formed in a circumferential wall of said spindle hole. A disc drive apparatus having a spindle for drivingly rotating an optical information recording disc, said apparatus comprising a disc engagement means (14; 21, 21a, 32; 34; 37; 39) at said spindle for engaging with a mating engagement means formed on the disk, characterized in that said disc engagement means includes a gear (14; 21; 21a; 32; 34) formed on an optical disc loading surface of a turntable formed integrally with said spindle. The apparatus according to claim 9, wherein said gear is a crown gear (14). The apparatus according to claim 9, wherein said gear is a spur gear (34). The apparatus according to claim 9, wherein said gear is an internal gear (32). The apparatus according to claim 9, wherein said gear includes at least one projection (21, 21a) projecting from an optical disc loading surface of a turntable (12) formed integrally with said spindle (11) and mounted to be retractable into said turntable (12). The apparatus according to claim 13, wherein said engagement means includes two projections (21, 21a) formed at a position corresponding to a convex portion (4a) of an engagement means of said disc and at another position corresponding to a concave portion (4b) of said engagement means of said disc. The apparatus according to claim 9, wherein said disc engagement means includes a number of splines (37) formed around an end portion of said spindle.

Inventors: KURANE KOREAKI, SAITO AKIRA, SONOBE TAKEO, SUZUKI MASAHIRO, KURANE, KOREAKI, SAITO, AKIRA, SONOBE, TAKEO, SUZUKI, MASAHIRO
Applicants: HITACHI LTD, HITACHI MAXELL, HITACHI MAXELL LTD., HITACHI, LTD.
Application year: 1989
Main classification: G11B17
IPC codes: G11B17, G11B7, G11B23