MXPA00005955A - Optical recording medium and disc cartridge - Google Patents

Abstract

An optical recording medium is provided which has a substrate and a signal recording layer provided on the substrate and in which an information signal is recorded in the form of microscopic pits. A light beam is focused on the signal recording layer and some change of the light beam carried by a return light from the signal recording layer is detected to read the information signal recorded on the signal recording layer. The optical recording medium has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm. An information signal recording area extends outwardly from a radial position of 12.5 mm or less from the center of the medium. The ratio in area between the information signal recording area and non-signal recording area is 3.4 or more. The storage capacity of this medium is 2 gigabytes or more. The optical recording medium has formed at the center thereof a center hole around which an annular table-abutment convexing to one side of the medium is formed. A magnetic-clamping hub is installed in the center hole and thus the medium is magnetically clamped to a rotation driving mechanism of an optical recording and/or reproducing apparatus. The compactness and high density of recording of the optical recording medium will contribute greatly to a further compact structure of a recording and/or reproducing apparatus in which the medium is to be used.

Description

RECORD MEDIA OPTIC AND PE DISC CARTRIDGE RELATED APPLICATION DATA The present application claims priority of Japanese Patent Application No. Pll -176029, the description of which is fully incorporated herein by reference. BACKGROUND OF THE INVENTION The present invention relates to an optical recording means that includes a substrate and a signal recording layer that is provided on the substrate and wherein an information signal recorded in the signal recording layer, is reproduced optically or upon detection a change of the reflected light that focuses on the signal recording layer, and a disk cartridge circumscribing the optical recording medium. As one of conventional recording means for audio and video information, optical discs of which recorded information is read using a beam of light or to which information is written using a light beam, are widely employed. Since this optical disk is formed of a simple plate-like substrate, it can be easily handled and has a greater storage capacity than other recording media such as magnetic tapes, etc. Therefore, optical discs are widely used as means to record audio and video information, computer-processed data, etc. Information processing units such as computers have been designed increasingly compact with an increasingly smaller internal installation space for a recording and / or reproducing apparatus using optical recording media such as an optical disc or the like. That is, there is demand for a smaller design of that recording and / or reproducing apparatus. There are various types of portable recording and / or reproduction apparatus for recording and / or reproducing audio and video information. For a superior portable capacity, it is also demanded that the apparatuses be of a more compact design. For this smaller reproduction and / or registration apparatus, a recording medium used in the apparatus should be correspondingly smaller, while having a greater storage capacity. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel optical recording medium of smaller design while having a higher storage capacity and a disk cartridge in which an optical recording medium is circumscribed.

Another object of the present invention is to provide an optical recording medium having a greater storage capacity while contributing to a more compact design of a recording or recording and / or reproducing apparatus, wherein the optical recording means is employed, and a disk cartridge circumscribing the optical recording medium. A further objective of the present invention is to provide an optical recording medium of smaller design and positively mounted in a rotary movement means to be rotatable together with the rotary movement mechanism and a disk cartridge circumscribing the recording medium optical. In one embodiment, an optical recording medium according to the present invention includes a substrate and a signal recording layer that is provided in the substrate, an information signal is recorded in the signal recording layer. The optical recording medium has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm. An information signal registration area extends outward from a radial position of 12.5 mm or less from the center of the medium. A ratio between the information signal registration area and an area without registration is 3.4 or more. A storage capacity is at least 2 GB (Gigabytes) or more.

The above optical recording medium has at its center a central hole around which a convex annular plate confinement is formed on one side of the medium and where a clamping plate or cube is fixed. In a modality, an optical recording medium according to the present invention includes a substrate and a signal recording layer that is provided on the substrate, wherein an information signal recorded in the signal recording layer is reproduced upon detecting a change in the reflected light focused on the signal recording layer. The optical recording medium has a diameter of more than 38 mm and less than 52 mm and a thickness of 0.4 to 0.7 mm. An area of the information signal register extends outward from a radial position of 12.5 mm or less from the center of the medium. A storage capacity is at least 1 GB or more. The above optical recording medium has at its center a central hole around which an annular plate confinement is formed which is convex to one side of the medium and where a clamping plate or cube is fixed. In one embodiment, an optical recording medium according to the present invention has an annular plate confinement for placing on a disk plate of a rotary movement mechanism, and a hub that is attracted by a magnet disposed on the disk plate , with which the medium can be rotated together with the disc plate. In one embodiment, an optical recording medium according to the present invention is a read-only optical recording medium. It includes a substrate formed to a thickness of 0.4 to 0.6 mm when injecting resin into a mold prepared by a punch that has there formed a pattern of pitting where the log trail pitch and the smallest pit length are approximately 1.4 times larger than those in a first optical recording medium, with a storage capacity of at least 2 GB including a substrate, and a signal recording layer that is provided in the substrate, and wherein the information signal recorded in the Signal recording layer is reproduced upon detecting a change in reflected light that focuses on the signal registration layer; and a sheet transparent to light which is 0.05 to 0.1 mm thick and having on one side a pitting pattern formed by a punching pattern die, where a signal recording layer is formed. In the optical recording medium, the substrate and the sheet are joined together with their respective pitting sides in a face-to-face relationship through a light-transparent layer of 20 to 35 μm. The first optical recording medium has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm, a defined information signal recording area extends outward from a radial position of 12.5 mm or less from the center of the medium , a diametral length ratio of 3.4 or more between the information signal registration area and an area without registration, and a storage capacity of at least 2 GB. It has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm. A registered signal area of defined information extends outward from a radial position of 12.5 mm or less from the center of the medium. A storage capacity is half or less than that of the first optical disk recording medium. In one embodiment, the optical recording medium is read-only type. It has a diameter of more than 38 mm and less than 52 mm and a thickness of 0.4 to 0.7 mm. An information signal recording area extends outward from a radial position of 12.5 or less from the center of the medium. In one embodiment, a disc cartridge according to the present invention comprises an optical disc including a substrate; a signal recording layer that is provided on the substrate and wherein an information signal recorded in the signal recording layer is reproduced upon detection of a change in the reflected light that is focused on the signal recording layer, the disc optical has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm, a defined information signal recording area extends outward from a radial position of 12.5 mm or less from the center of the optical disc, a ratio of 3.4 or more between the information signal registration area and a non-signal registration area and a storage capacity of at least 2 GB or more; and a rectangular cartridge in which the optical disk is circumscribed. In the disk cartridge, an opening for writing and / or reading access is formed on a side to which an optical pit, for focusing a beam of light on at least the optical disk is opposed through which a portion extending radially the optical disc is exposed, and a central opening is also formed through which a central hole formed at the center of the optical disc is exposed. The write and / or read access opening is formed offset to one side of the midpoint of the front side of the cartridge. In one embodiment, a disk cartridge according to the present invention circumscribes an optical disk including a substrate and a signal recording layer that is provided on the substrate, and wherein an information signal recorded in the recording layer of signal is reproduced upon detection of a change in reflected light that is focused on the signal recording layer. In one embodiment, a disc cartridge has a diameter of more than 38 mm and less than 52 mm and a thickness of 0.4 to 0.7 mm. An information signal registration area extends outward from a radial position of 12.5 mm or less from the center of the medium. Its storage capacity is at least 1 GB. A disk cartridge according to the present invention circumscribing the aforementioned read only optical disk has a read access opening which is formed only in a lower half. These objects and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a first optical disk according to the present invention showing its upper side. Figure 2 is a perspective view of the optical disk of Figure 1, showing its rear side. Figure 3 is a sectional view of the optical disk of Figure 1.

Figure 4 is a sectional view of the optical disk of Figure 1, placed in the rotary movement mechanism of a disk reproduction and / or recording apparatus. Figure 5 is a sectional view of the optical disk of Figure 1, showing the signal registration layer. Figure 6 schematically illustrates the reading of information signal recorded on the optical disc of Figure 1. Figure 7 is a sectional view of a second optical disk according to the present invention. Figure 8 is an enlarged sectional view of a third optical disk according to the present invention, this optical disk is read-only type. Figure 9 schematically illustrates the process of making a sheet from which the read-only optical disk is produced. Figure 10 is a sectional view of the read-only optical disk showing how the substrate and the sheet are joined together. Figure 11 is a sectional view of a read-only optical disk embodiment according to the present invention. - Figure 12 is a perspective view of a first disk cartridge in which the first optical disk is circumscribed. Figure 13 is a perspective view of the first disk cartridge showing its rear side. Figure 14 is a perspective view of a second disk cartridge circumscribing the second optical disk. Figure 15 is a perspective view of the second disk cartridge showing its rear side. Figure 16 is a plan view of an adapter used to allow the second disk cartridge to have the same dimensions as the first disk cartridge. Figure 17 is a sectional view of the adapter of Figure 16. Figure 18 is a plan view of the second disk cartridge fitted in the adapter. Figure 19 is a perspective view of an optical recording and / or reproducing apparatus wherein the optical disk according to the present invention is used. DETAILED DESCRIPTION OF THE MODALITIES CURRENTLY PREFERRED With reference to Figures 1, 2 and 3, a first optical disc according to the present invention is schematically illustrated. The optical disk is generally indicated with a reference 1. As illustrated, the optical disk 1 includes a substrate 2 made of glass or a light-transparent synthetic resin such as polycarbonate resin of 65 mm or less in diameter and 0.4 to 0.7 mm thick and having a signal registration layer formed on one side thereof. More specifically, the optical disc 1 consists of the substrate 2 made of polycarbonate resin, so that it has a diameter Rx of 64 mm and a thickness D¿ of 0.6 mm as illustrated in Figure 3. The substrate 2 has there formed at the center a central hole 3 having a diameter R2 of 8 mm. The substrate 2 has formed around the central hole 3, a convex annular plate confinement 4 on one side of the substrate 2. The plate confinement 4 is to be placed on a disk plate of a rotary movement mechanism on a reproduction apparatus and / or optical register in which the optical disk 1 is adjusted or placed. The plate confinement 4 has an outer diameter R3 of 14 mm, and is convex approximately D2 equal to the thickness D? of the substrate 2 from one side of the latter.

A magnetic clamping hub 5 is provided to the center of the substrate 2 to close the central hole 3. The hub 5 is formed of a thin plate of a magnetic metal such as iron. As illustrated in Figure 3, the hub 5 consists of a depressed portion 6 formed at its center for coupling into the central hole 3, and a flange portion 7 formed around the depressed portion 6 for fixing to the substrate 2. The portion depressed 6 in this way has the shape of a cylinder with a bottom. The depressed portion 6 has formed there in its center, a screw hole 8 in which a spindle of the rotary movement mechanism is coupled. The screw hole 8 has a diameter R4 of 2.0 mm. The butt confinement of plate 4 is concave as indicated by a reference 9 in its convex direction. As illustrated in Figure 3, the hub 5 is secured to the substrate 2 with the depressed portion 6 engaged in the central hole 3 of the substrate 2 and the flange portion 7 engaged in the concavity 9 of the substrate 2. The hub 5 is fixed in the flange portion 7 in the concavity 9 with an adhesive. Also as seen in Figure 3, the hub 5 is fixed to the substrate 2 in such a way that the lower surface 6a of the depressed portion 6 positioned on the side of the butt confinement of the plate 4 does not project from the lower surface 4a of confinement to plate stop 4.

That is, the height of the hub 5 from the bottom surface 6a of the depressed portion 6 to the flange portion 7 is designed to be smaller than the thickness of the butt confinement of the plate 4 of the substrate 2. As described above, the optical disk 1 includes the substrate 2 that is provided with the plate stop confinement 4 and the hub 5 is fitted into a rotary movement mechanism 11 of an optical recording and / or recording apparatus as illustrated in Figure 4. The mechanism of Rotary displacement 11 consists of a spindle motor 12, a spindle 13 displaced by the motor 12 and a disk plate 14 fixed at one end of the spindle 13 rotatably with the spindle 13. The disk plate 14 has a disk stopper confinement 15 formed on its outer circumference and a concavity 16 formed within the disk stop confinement 15 where an annular magnet 17 is fixed. The magnet 17 is clamped to be flush with an upper surface 15a of the disk stop 15 or not projecting from the confining surface to disk stop 15a. The optical disk 1 is adjusted in the disk plate 14 by placing the plate stop confinement 4 in the disk stop confinement 15, with the spindle 13 engaged within the spindle hole 8 of the hub 5. The hub 5 of the disk optical 1 is attracted by the magnet 17 and is thus securely held in the disk plate 14. In this way, the optical disk 1 can be rotated together with the disk plate 14. The spindle 13 is formed to have a generally same as the spindle hole 8, such that the center of rotation of the optical disk 1 can coincide with the axis of the spindle shaft 13 for correct adjustment of the optical disk 1 in the disk plate 14. As mentioned above with Referring to Figure 3, the hub 5 is fixed to the substrate 2, such that a lower surface 6a of the depressed portion 6 positioned on the side of the butt confinement of the plate 4, will not project from the lower upper 4a of the confinement to top of plat or 4. Therefore, when the optical disc 1 is adjusted in the disk plate 14, it will be in the vicinity of, but not in contact with the magnet 17. Since the hub 5 is placed in the vicinity of the magnet 17, the optical disk 1 is attracted to the disk plate 14 by a large attractive magnetic force, and thus can be rotated together with the disk plate 14. When the optical disk 1 is adjusted in the disk plate 14, the hub 5 it will not be in contact with the magnet 17, in such a way that excessive attractive force will not act in the hub 5 and therefore the optical disc 1 can be easily adjusted on or removed from the disk plate 14.

Since the hub 5 is attached to the substrate 2, so that the depressed portion 6 thereof is placed on the side of the plate stop 4, the spindle 13 can be engaged in the spindle hole 8 of the hub 5 in a sufficient amount and even if the projection of the disk plate 14 is small. For example, the spindle 13 is provided with a tapering end portion 8a as illustrated in Figure 4, a height can be formed such that it does not project from the optical disk 1 and can center the latter. By forming the spindle 13 to a limited length or height, the rotary movement mechanism 11 can be designed to have a limited height and therefore a recording and / or reproducing apparatus using the low rotation displacement mechanism 11 can be designed thinner . The magneto used in the rotary movement mechanism with conventional magnetic fastening has a BHmax resistance of approximately 30 MG oersteds. In this embodiment, the optical disk 1 includes the substrate 2 made of polycarbonate resin to have the diameter Rx of 64 mm and thickness Dx of 0.6 mm. In order to prevent the optical disc 1 magnetically attached to the disc plate 14 from being easily separated from the disc plate 14 even when the latter is applied with a shock, an attractive magnetic force of approximately 120 g is required. With this attraction, the optical disk 1 can be rotated together with the disk plate 14 even at a rotational speed of 4,000 rpm or more. To obtain this magnetic attracting force using the magnet used in the conventional rotation displacement mechanism, the hub 5 should have a surface of approximately 8 mm in diameter to be attracted by the magnet. Also, to retain the optical disk 1 with the diameter Rx of 64 mm horizontally in the disk plate 14, the butt confinement surface of the annular plate 4a around the hub 5 should be approximately 2.6 mm in width. However, it is difficult due to the molding technique to make the butt confinement of convex plate 4 on one side of the substrate 2 and a high flatness on its entire lower surface 4a at all corners. More specifically, an approximate 0.2 mm range at both ends of the plate stop confinement 4 can not be counted as the plate stop confinement surface 4a. Taking these factors into consideration, the butt confinement of plate 4 should be formed to a diameter of at least about 14 mm in case the hub 5 with a diameter of about 8 mm, which will be attracted by the magnet 17, is placed at the center of the confinement to the top of the plate 4 and inside the lower part or confinement surface to the top of the plate 4a with a diameter of approximately 2.6 mm. As described above, the optical disk 1 has formed at its center the butt confinement of convex plate 4 on one side of the substrate 2 and where the hub 5 is to be fixed. In addition, the optical disk 1 has a signal registration layer 21 formed on the other side of the substrate 2 as illustrated in Figure 5, for example. The signal recording layer 21 consists of a recording layer 22, auxiliary recording layer 23, non-magnetic layer 24 and perpendicular magnetic layer 25 stacked in this order on the substrate 2. The recording layer 22 is formed of a film of a material such as GdFeCo alloy, which has a magnetic axis parallel to the layer surface at room temperature and which will be magnetized in a direction perpendicular to the layer surface at a temperature approximating a read temperature that is reached, when heated with a focused light beam for reading an information signal recorded on the optical disc 1. The auxiliary recording layer 23 is provided to improve the reading resolution and thus the reading characteristic and is formed from a film of a material, such as GdFe alloy that has a Curie temperature approximate to the reading temperature that is reached when it is heated with a beam of reading light, which has a magnetic axis parallel to the layer surface before it is heated to the Curie temperature, and lose the magnetic axis parallel to the layer surface after it is heated to a temperature above the Curie temperature. More particularly, at a temperature lower than the Curie temperature, the recording layer 22 has a switched connection with the auxiliary recording layer 23 and thus has an intraplastic magnetized state, wherein the magnetization direction is parallel to the cap. On the other hand, at a temperature higher than the Curie temperature, the auxiliary recording layer 23 loses the magnetization direction and in this way the recording layer 22 has a magnetostatic connection with the perpendicular magnetic layer 25 and is magnetized perpendicularly in the direction The magnetic layer of the magnetic recording layer 25. The non-magnetic layer 24 is provided to reduce the influence of the recording layer 22 on the magnetic recording layer 25, when the information signal is written in the magnetic recording layer 25. form of a film AlN or SiN for example. The magnetic record layer 25 is an amorphous ferromagnetic layer of which the magnetic easy axis is perpendicular to the layer surface. It is formed of a film of an amorphous ferromagnetic material having a high coercive force at room temperature and a Curie point of approximately 200 ° C such as a TbFeCo alloy or a TbFeCo alloy to which an element of the fourth group such as Cr, it is added in a very small amount. The signal registration layer 21 constructed as described above has a reflective metal layer 26 formed thereon. The reflective metal layer 26 is made of a non-magnetic metal of high reflectivity, to reflect 70% or more of the incident light beam on the optical disk 1. This material should preferably be a good thermal conductor such as Al, Au, Ag or similar. The reflecting metal layer 26 is protected by a protective layer 27 of a photocuring resin or the like which is formed in the reflecting metal layer 26. To write an information signal in the signal recording layer 21 of the optical disk 1 constructed as mentioned above, irradiated pulse magnetic modulation is used, wherein a light beam is pressed for each register data clock to modulate the magnetic field of recording according to the registration data. This technology allows a higher recording density than the intensity modulation of light conventionally used. More specifically, with the irradiated magnetic pulse modulation, pitting having the same shape as a beam spot focused by a target lens on the signal recording layer 21, is written to overlap one on the other in the magnetic recording layer. 25, whereby an information signal can be recorded beyond an optical limit, depending on a light point distribution (? / NA) determined from a relation between a wavelength? of a beam of light generated in the intensity modulation of light and a numerical aperture NA of objective lens by which the light beam is focused on the signal recording layer. To write an information signal using irradiated magnetic pulse modulation, a light beam of 380 to 420 nm or 630 to 670 nm with wavelength? Is used. An objective lens having a numerical aperture NA of 0.5 to 0.7 is used to focus the light beam on the signal recording layer. Recording or recording tracks with a step of 0.3 to 0.55 μm are formed to write the information signal on them and with a step length of 0.1 to 0.22 μm / bit. When the numerical aperture NA of the objective lens is 0.6 and the working distance between the objective lens and the optical disk 1 is 1.1 mm, a beam of light emitted from a semiconductor laser and formed to be a parallel incident light on the objective lens, It has a diameter of 3 mm. In this case, the objective lens on which the parallel light of 3 mm in diameter strikes, should have a diameter of 4 mm. In this way, a lens coil that supports the objective lens has to be 5 mm or more in diameter. To control the focus and tracking of the laser beam exiting the objective lens supported by the lens coil and scanning the signal registration area of the optical disk 1, the lens coil is installed in a biaxial actuator that moves to move the lens target in a focusing direction parallel to the optical axis of the objective lens and in a tracking direction perpendicular to the optical axis. Therefore, an approximate space of 1.5 mm for part installation, has to be provided outside the lens coil. The optical disk 1 has a plate 4 connection of 14 mm approximate in diameter provided at its center. The recording and / or reproducing apparatus has disposed the disk plate 14 which in general has the same size as the plate connection 4 and where the plate connection 4 is to be mounted. When the optical disk 1 constructed as mentioned previously explored with a beam of light emitted from an optical pickup unit using the objective lens of 4 mm in diameter, the center of the light beam can be moved to a radial position of 11 mm near the access area on the optical disc 1 That is, the light beam can not be irradiated to an interior area having a diameter R5 of 22 mm. Therefore, optical disk 1 has an information signal registration area defined outside, of the inner area jon the diameter R5 of 22 mm. To ensure an accurate optical reading by a light beam of an information signal recorded as a magneto-optical signal in the information signal recording area, a birefringence by the substrate 2 has to be 30 nm or less to reciprocate the beam of light. Therefore, the information signal recording area is defined outside the inner area having the diameter R5 of 22 mm and wherein the birefringence of the light beam indicated on the substrate 2 is ensured less than 30 nm to reciprocate. As illustrated in Figure 3, the optical disk 1 has a signal registration area extending outward from a radial position of 12.5 mm or less from the center of the optical disk 1, ie from a diametral position R6 of 25 mm or less, to positively write a maximum amount of an information signal on the optical disk 1 and also positively reading a recorded information signal from the optical disk 1. More specifically, the optical disk 1 has defined an audio and video information signal recording area, of which the inner diameter R6 is 24.5 mm and outer diameter R7 is 61 mm. Furthermore, in the optical disk 1, an area in which the control signals etc., which are used to write information signal to and read from the optical disk 1, are recorded inside the signal recording area and are recorded outside the area. signal recording, an area where control signals, etc., which are indicative of the end of the signal recording area, are recorded. In optical disk 1 constructed as before, the ratio between the information signal recording area and the signal recording areas without information, is 3.4 or more. If pulse irradiated magnetic modulation is adopted with the optical disc 1 according to the present invention, use of a light beam of 400 nm in wavelength?, Allows registering 4 gigabytes or more of an information signal, while the Use of a 660 nm light beam with wavelength?, allows to record 2 gigabytes or more of an information signal. Since it is possible to record 2 gigabytes or more of an information signal on optical disc 1, conventionally proposed signal compression technology can be used to record many images. For example, the JPEG standard can be used to record 200 or more still images, and the audio coding technique included in the MPEG2 standard can be used to record an MPEG2 movie (8 Mbps transfer rate) for more than 30 minutes together with sound. To read a recorded information signal on the optical disc 1 using irradiated magnetic pulse modulation, as described above, a light beam L11 is irradiated in the optical disc 1 through the substrate 2, as illustrated in the Figure 6. When the light beam Lx is irradiated to the optical disk 1, a portion of the recording layer 22 formed of a GdFeCo alloy film in which the light beam Lx is focused, is heated to a temperature higher than the predetermined temperature . A portion of the auxiliary recording layer 23 formed of the GdFe alloy film in which the light beam Lx is focused, is heated to a temperature higher than the Curie temperature and loses the magnetization direction. As a result, the heated portion of the recording layer 22 has a magnetostatic connection with the magnetic recording layer 25 and is magnetized perpendicularly in the magnetized direction of the magnetic recording layer 25 as illustrated in Figure 6A. The surrounding part of the perpendicularly magnetized portion of the magnetic record layer 25 maintains an intraplastic magnetized state wherein the magnetic axis is parallel to the layer surface to function as a mask 29, where Kerr effect will not be carried out while that the perpendicularly magnetized portion functions as an aperture 30 for the incident light beam Lx on the magnetic recording layer 25 as illustrated in Figure 6B. In this way, since only the portion of the recording layer 22 in which the light beam Lx is focused is magnetized perpendicularly to the magnetized direction of the magnetic recording layer 25, it is possible to read, with high resolution, a signal of recorded information in the form of microscopic pits 32 in the registration tracks 31 formed with a small passage in the optical disk 1. In this embodiment, the first optical disk 1 has the diameter Rx of 64 mm and the thickness Dx of 0.6 mm . However, the present invention is not limited to these dimensions but the diameter R? It can be increased up to 65 mm. The diameter Rx can be 65 mm or less, provided that the intended storage capacity is achieved. Also, the thickness D? of the optical disk 1 can be appropriately selected from a range of 0.4 to 0.7 mm depending on the wavelength of the light beam used to describe and / or read the information signal. In addition to the first optical disc 1 as previously described, the present invention also provides another embodiment of an optical disc.

Now with reference to Figure 7, a second optical disk according to the present invention is schematically illustrated. The optical disk is generally indicated with a reference 41. This optical disk 41 can be used in an optical recording and / or recording apparatus wherein the above-mentioned optical disk 1 can also be used. The optical disk 41 has the same construction as the optical disk 1 except for its outer diameter. Therefore, the same or similar elements as those of the optical disc 1 are indicated with the same or similar references and will not be described further. The optical disk 41 is formed to have a diameter greater than 38 mm or less than 52 mm and a thickness of 0.4 mm to 0.7 mm. More specifically, the optical disk 41 has a diameter RX1 of 50 mm, as illustrated in the Figure 7. The optical disc 41 comprises a substrate 42 formed of glass or a light-transparent polycarbonate resin having a signal registration layer formed on one side. The substrate 42 of the optical disk 41 is formed of a polycarbonate resin to have the diameter R1X of 50 mm and a thickness of D1X of 0.6 mm, as illustrated in Figure 7. The substrate 42 has a central hole formed at its center 3. having a diameter R2 of 8 mm as the optical disk 1. The substrate 42 has formed around the central hole 3, a butt confinement of annular plate 4 convex to one side of the substrate 42. It is provided to the center of the substrate 42, a magnetic clamping hub 5 for closing the central hole 3 as in the optical disk 1. As illustrated, the hub 5 consists of a depressed portion 6 formed at its center. The depressed portion 6 has therein formed in the center, a screw hole 8 in which it engages a spindle of a rotation displacement mechanism. The screw hole 8 has a diameter R4 of 2.0 mm. As in the optical disk 1, the hub 5 engages the depressed portion 6 in the central hole 6 of the substrate 2, and the butt confinement of the plate 4 is concave as indicated by a reference 9 in its convex direction. The hub 5 has a flange 7 formed around the depressed portion 6 and which is to be engaged in the concavity 9 of the substrate 42. The substrate 42 has provided on its side, opposite to where the confinement to plate stop 4 is formed, a signal recording layer 21 which is similar to that on the optical disk 1. To write an audio and video information signal in the signal recording layer 21 of the optical disk 41, constructed as mentioned above, magnetic modulation irradiated by pulse, wherein a light beam is pressed for each register data clock to modulate the magnetic field of recording according to the registration data, it is adopted as with optical disk 1. As in optical disk 1, the optical disc 41 has the plate connection 4 which is provided at its center as mentioned above. The recording and / or reproducing apparatus, which is compatible with both optical discs 1 and 41, has there arranged a disc plate 14 with the same overall size as the plate connection 4, and wherein the plate connection 4 going to ride In this way, the optical pickup unit compatible with the optical disc 1 will be used with the optical disc 42. Therefore, similarly to the optical disc 1, the optical disc 41 will have therein formed an information signal recording area that will be extends outward from the inner diameter R5 of at least 22 mm. That is, the optical disk 41 has a signal registration area that extends outward from a radial position of 12.5 mm or less from the center of the optical disk 41, ie from a diametral position R6 of 25 mm or less, as illustrated in Figure 7 to positively describe a maximum amount of information signal. More specifically, the optical disk 41 has an audio and video information signal recording area defined of which the inner diameter of R6 is 24.5 mm and the outer diameter R17 is 46.5 mm. further, an area in which control signals, etc., which are used to write and read information signals from the optical disk 1, is recorded and out of the area in the optical disc 41, within the signal registration area, is formed. signal recording an area where control signals, etc., which are indicative of the end of the signal recording area, are recorded. If the pulse-irradiated magnetic modulation is adopted with the optical disk 41 according to the present invention, the use of a light beam of 400 nm in wavelength?, Allows registering 2 gigabytes or more of an information signal, while than the use of a light beam of 660 nm with wavelength? allows to record a gigabyte or more of information signal. In order to read a recorded information signal on the optical disk 41 using the pulse irradiated magnetic modulation as described above, the same method is adopted as that for reading an information signal recorded on the optical disk 1. In the second embodiment, the second optical disk 41 has the diameter RX1 of 50 mm and the thickness of DX1 of 0.6 mm. To ensure an intended storage capacity of the optical disc 41 however, the diameter RX1 can be appropriately selected from a range of 38 to 52 mm, while the thickness D1X can appropriately be selected from a range of 0.4 to 0.7 mm, depending on the length of a beam of light used to write and / or read an information signal. Previously, the first and second optical discs 1 and 41 according to the present invention have been described. Each of the optical discs 1 and 41 has a single signal recording layer in each of the substrates 2 and 42. However, in the case in which the optical discs 1 and 41 are read-only optical discs, they can be formed two or more signal recording layers in each of the substrates 2 and 42. Now with reference to Figure 8, a third optical disk is shown schematically, which is a read-only optical disk with two layers of signal recording. The optical disk is generally indicated with a reference 111. The optical disk 111 is formed to have the same size as the first optical disk 1. Its diameter is 65 mm or less and its thickness is in the range of 0.4 to 0.7 mm. Similar to optical disk 1, optical disk 111 can have a diameter of up to 65 mm. It can have a diameter of 65 mm or less depending on an intended storage capacity. Also, the optical disk 111 is formed to have an appropriately selected thickness of a range of 0.4 to 0.7 mm according to the wavelength of a light beam used to read an information signal that is recorded on the optical disk 111. As illustrated in Figure 8, the third optical disc 111 comprises a substrate 112 formed of a light-transparent synthetic resin such as polycarbonate. The substrate 112 is formed to have a diameter 65 mm or less and a thickness D21 in the range of 0.4 to 0.7 mm. It has preformed on one side, a pitting pattern 113 which is a pattern of very small convexities and concavities. That is, the substrate 112 is formed by injecting a molten polycarbonate into a mold where a die is placed having a pattern of convexities and concavities corresponding to the concavities and convexities respectively in the pit pattern 113. As illustrated in FIG. Figure 8, the substrate 112 has a first signal registration layer 114 formed on the pit pattern 113 on one side, where the pit pattern 113 is formed. The first signal recording layer 114 is formed of a translucent silicone film such as Si3N4, SiO2 or the like, which allows a predetermined amount of an irradiated beam of light to pass through the substrate 112 while reflecting a predetermined amount of the beam of light. light The first signal recording layer 114 consists of more than one silicone film of Si3N4, SiQ2 or the like stacked one on top of another at a thickness D22 of 100 to 500 nm. Silicone films of Si3N4, SiO2 or the like are produced by vacuum deposition 0 electrodeposition. In this read-only optical disk 111, the pit pattern 113 formed on the substrate 112 is formed with an approximate track pitch 1.4 times larger than that of the registration tracks formed on the optical discs 1 and 41. the minimum length of pitting included in the pitting pattern 113 is approximately 1.4 times larger than that in the optical discs 1 and 41. That is, in the read-only optical disc 111, the track pitch of the registration tracks is 0.4 to 0.77 μm and the pit length is 0.14 to 0.31 μm / bit. Therefore, the registration tracks can be formed by injection molding a synthetic resin. When forming sizes for discs 1 and 41 respectively, the die prepared with the aforementioned track pitch and shorter pit length will provide a pit pattern that is half that recorded on optical discs 1 and 41. pitting pattern will result in a storage capacity of the substrate 112 that is also half that of the disks 1 and 41. Therefore, when the considered die is used to form the optical disc 111 in a size corresponding to that of the discs 1 and 41, the amount of information recorded in this optical disc 111 will be half of the recordable on the optical discs 1 and 41. On the optical disc 111, the substrate 112 has a central hole 3 formed at its center, as in the optical discs 1 and 41. The substrate 112 has formed around the central hole 3 and in a side thereof, opposite the side on which the signal registration layer 114 is formed, an annular disc stopper confinement 4 which is convex away from the signal registration layer 114. Further, a magnetic holding hub 5 provides the center of the substrate 112 for closing the central hole 3 as in the optical discs 1 and 41. To the first signal registration layer 114 on the substrate 112 of the optical disc 111, a sheet 116 formed sufficiently thinner is attached than the substrate 112 and having preformed on one side, a pit pattern 115 which is a pattern of very small concavities and convexities corresponding to information signals. There is provided between the first signal recording layer 114 and the sheet 116, a light transparent layer 117 made of a light-curable ultraviolet light-curable synthetic resin. The sheet 116 is formed from a synthetic resin transparent to light, such as polycarbonate at a thickness D23 of 0.05 to 01 mm. The pitting pattern 115 formed on one side of the sheet 116 is formed by thermally stamping a pattern formed in a die and consisting of corresponding convexities and concavities in the concavities and convexities respectively of the pit pattern 115. As illustrated in the Figure 8, a second signal registration layer 118 is formed on the pit pattern 115. To reflect with high efficiency towards an optical pickup unit positioned opposite the substrate 112, a light beam focused through the first recording layer of signal 114 and a light transparent layer 117, the second signal recording layer 118 is formed from a film of a highly reflective metal such as aluminum (Al), gold (Au) or silver (Ag). The sheet 116 having the pin pattern 115 and the second signal recording layer 118 formed therein, is produced through a process as illustrated in Fig. 9. To form the sheet 116, a polycarbonate screen 121 is fed to a die-cutting or replication post wherein the die 122 and the pressure roller 124 are provided. The die 122 has formed on it a pattern 123 of concavities and convexities, corresponding to the concavities and convexities respectively of the intended pitting pattern 115. The pressure roll 124 is provided with a heating means. The polycarbonate web 121 is passed between the die 122 and the pressure roller 124, while being heated and pressed. In this way, the polycarbonate web 121 has the pit pattern 123 punched thereon, and is further fed to a pickup roller 121a. Before the polycarbonate web is collected on the roller 121a, it is moved to an electrodeposition post where the second signal recording layer 118 is formed in a portion of the web 121_ in which the pin pattern has been punched. In addition, the polycarbonate web 122 is moved to a die-cut post where the weft portion in which the second signal registration layer 118 is formed is punched to a size for connection to the substrate 112, thereby forming the sheet 116. The web 122 is wound on a pickup roller 121a. The pattern of pitting 123 formed in the die 122 is formed in the registration tracks whose pitch is approximately 1.4 times larger than that of the registration tracks formed in the optical disks 1 and 41. The minimum length of the pits that constitute the pitting pattern 115 is also approximately 1.4 times larger than the optical discs 1 and 41. When the die 122 for this track pitch and minimum pit length is formed at sizes corresponding to those of the optical discs 1 and 41, respectively, will have a pitting pattern that is half of those of the pit patterns formed on the optical discs 1 and 41, and whose storage capacity is also half of the optical discs 1 and 41. When the blade 116 formed by the die 122 is formed at sizes corresponding to those of the optical discs 1 and 41, respectively, the amount of information recorded on the sheet 116 will be half of those of the optical discs 1 and 41. The sheet 116 thus formed it joins the substrate 112 with the second and first signal recording layers 118 and 114 positioned front-to-front. As mentioned above, a curable resin with ultraviolet light is used as the light-transparent layer 117 between the sheet 116 and the substrate 112. To join the sheet 116 to the substrate 112, they center between each other and the first and second layers of the substrate 112. signal register 114 and 118 are placed in a front-to-front relationship with a D24 space of 20 to 35 μm between them. For this purpose, an attachment 125, for example, is inserted into a central hole 116a formed in the center of the sheet 116 and a central hole 3 in the substrate 112 as illustrated in Figure 10 to center the sheet 116 and the substrate 112 between yes and provide the 35 μm space 20 between the first and second signal registration layers 114 and 118. Then, an ultraviolet curable resin, for example is injected between the substrate 112 and the sheet 116, to form the transparent layer a light 117. With the substrate 112 and blade 116 rotated, the ultraviolet curable resin injected between the substrate 112 and the sheet 116 is dispersed to a uniform thickness. Subsequently, ultraviolet rays are irradiated through the substrate 112, to harden the ultraviolet curable resin to bond the substrate 112 and the sheet 116 together. Next, the hub 5 is installed on the substrate 112 to cover the central hole 3 in the substrate 112, to terminate the optical disk 111. As mentioned above, the substrate 112 and the sheet 116 are joined together with the space 20. at 35 μm between them and the ultraviolet curable resin, for example that is injected into the space to form the light-transparent layer 117, which will thus have a thickness D24 of 20 to 35 μm. When a light beam of 380 to 420 mm in wavelength?, Or a light beam of 630 to 670 nm in wavelength?, Focuses on the first or second signal registration layers 114 or 118 through an objective lens that has a numerical aperture (NA) of 0.5 to 0.7, the focal depth will be +. 1 μm. Since the transparent light layer 117 has the thickness D24 of 20 to 35 μm, an information signal recorded in the first or second signal recording layers 114 or 118 can be read precisely by a common light beam L2 and objective lens 131, independently without mutually affecting each other and without being influenced by a spherical aberration of objective lens 131. To read an information signal from the first or second recording layers 114 or 118, the position of the objective lens 131 is controlled so that the beam of light L2 is focused on the first or second signal registration layers 114 or 118, as illustrated in Figure 8. The objective lens position 131 is controlled using for example control signals indicative of the first and / or second layer of signal register 114 and / or 118 and registers in control signal recording areas for the first or second signal registration layers 114 and / or 118. In the third optical disk 111 mentioned above d In accordance with the third embodiment, an information signal may be recorded in each of the first and second signal registration layers 114 and 115 in an amount that is half of the recordable one in the optical disk 1. Therefore, the disk optical 111 has a total storage capacity equivalent to that of optical disk 1. As previously, the read-only optical disk 111 is constructed such that an information signal is read from the first and second signal recording layers 114. and 118, by irradiating light beams through the substrate 112 to the respective signal recording layers 114 and 118. However, by forming the second signal registration layer 118 from a translucent material, which will allow a predetermined amount of light to pass through while which reflects a predetermined amount of the light beam, it is also possible to read information from the first and second signal recording layers 114 and 118, by irradiating a light beam through the sheet 116. Furthermore, in the optical disk of only 111 reading, a second sheet 126 may be attached to the sheet 116 (ie the first sheet) with a second light-transparent layer 127, which is made of a light-curable ultraviolet curable material, or the like placed between them as is illustrated in Figure 11. In this case, the signal registration layer 118 formed at least on the first sheet 116, is formed as a translucent layer that will allow a predetermined amount of a beam of light to pass through while that reflects a predetermined amount of light beam. The aforementioned read-only multilayer optical disk can be formed to the size of the second optical disk according to the present invention, that is, the optical disk 41. Also in this case, since each of the recording layers of signal is able to record one half of the amount of information that is recorded on the optical disc 41, the two layers of signal recording can record a total amount of information, equivalent to register on the first optical disk according to the present invention, that is to say the optical disk 1. The constructed optical disks 1 and 41 which have been described above record an information signal with an extremely high density. Therefore, any dust or small scratch on the optical discs will make it impossible to accurately write or read an information signal. In this way, to avoid the above inconvenience, each of the optical discs 1 and 41 according to the present invention is circumscribed in a cartridge. Like a disc cartridge, it is circumscribed in a recording and / or reproduction apparatus, or stored circumscribed in the cartridge. Now with reference to Figures 12 to 19, disc cartridges according to the present invention are illustrated. The disc cartridge is generally indicated with a reference 51 as illustrated in Figures 12 and 13.

The disk cartridge 51 circumscribes the optical disc 1 previously described. It consists of upper and lower halves 52 and 53 confined abutting each other to form a cartridge 54 where the optical disk 1 is circumscribed. The cartridge 54 is constituted to have a rectangular shape of which a first side has a length x of 52 to 70 mm and a second side has a length W2 of 52 to 75 mm, perpendicular to the first side. Therefore, the optical disk 1 of 65 mm or less in diameter can be rotationally circumscribed in the cartridge 54. The lengths x and W2 of the first and second sides of the cartridge 54, are appropriately chosen from the ranges 52 to 70 mm and 52 to 75 mm, respectively, according to the size of the optical disc 1 circumscribed in the cartridge 54. The cartridge 54 has a thickness D3 selected from a range of 3 to 6 mm according to the thickness of the optical disc 1 circumscribed therein. . That is, the cartridge 54 is formed according to the size of the optical disc 1 to have a rectangular shape with minimum length, width and thickness necessary to circumscribe the optical disc 1. In effect, the disc cartridge 51 shown in FIGS. and 13 comprises the cartridge 54 with the first side having a length Wx of 68 mm, the second side having the length W2 of 72 mm and the thickness D3 of 5 mm, since the optical disk 1 circumscribed there has a diameter Rx of 64 mm and a Dx thickness of 0.6 mm.

The cartridge 54 has formed in the upper half 52 a writing access opening 55, through which a radially extending part of the optical disc 1 therein circumscribed is exposed. The write access opening 55 is provided to allow a magnetic head applying an external field of a recording and / or reproducing apparatus to approach the optical disk 1 to write an information signal in the latter. The writing access opening 55 is formed to a rectangular structure extending from near the center of the cartridge 54 to near a shorter front side of the cartridge 54. The write access opening 55 is located with its longitudinal axis passing through the center of the optical disc 1 and a mid point Px of the width of the front side of the cartridge 54. Also, the lower half 54 of the cartridge 54 has therein formed a read / write access opening 56, through which exposes a radially extending part of the optical disk 1 therein circumscribed, and which allows an optical collection unit of a recording and / or reproducing apparatus approaches the optical disk 1 to write and read an information signal to and from it, and a central opening 57 through which the plate stop confinement 4 which is provided to the center of the optical disc 1 is exposed. The central opening 57 is formed at the center of the lower half 53 and the read / write access opening 56 is contiguously formed to the central opening 57 to have a rectangular shape extending near the front side of the cartridge 54. As is illustrated in Figure-13, the read / write access opening 56 has a midpoint P2 of its width offset from the midpoint Px of the front side width of the cartridge 54 -to one of the sides of the cartridge 54. Due at this deviation of the read / write access opening 56 from the center of the cartridge 54, the main body of the optical pickup unit can be displaced from the centerline of the optical disc 1, with the optical axis of the objective lens placed in the centerline of the optical disc 1, such that the recording and / or reproducing apparatus compatible with the disc cartridge 51 can be designed more compactly. The cartridge 54 is provided with a shutter member 58 for opening and closing the write access opening 55, the read / write access opening 56 and the central opening 57 at the same time. The sealing member 58 is made by punching and bending a thin metal sheet. It consists of a first sealing portion 59 for opening and closing the writing access opening 55, second sealing member 60 for opening and closing the read / write access opening 56 and the central opening 57 and a joint or link 61 for connecting the bases of the first and second shutter portions 59 and 60. The sealing member 58 is formed to have a generally C-shaped cross section. The joint 61 has first and second projecting sliding guides 62 and 63 coupled on the front side of the cartridge 54. As illustrated in Figure 12, the first portion The shutter 59 is formed to have a rectangular structure with sufficient dimensions to close the writing access opening 55. As illustrated in Figure 13, the second plug portion 60 extends from the joint 61, while deviating laterally in relation to the first obturator portion 59 to close both the read / write access opening 56 formed outside the center of the cartridge 54, and the central opening 57 formed in the center of the cartridge 54. , the second obturator portion 60 is bent to close the central opening 57 which is positioned outside the longitudinal axis of the read / write access opening 56. The obturator member 58 is engaged on the cartridge 54 with the first obturator portion 59 positioned on the writing access opening 55 and the second sealing portion 60 placed on the read / write access opening 56 and the central opening 57. At this point, the first and second sliding guides 62 and 63 of the sealing member 58, are coupled on the front side of the cartridge 54 with guide pieces (not shown) engaged in sliding guide recesses respectively formed in the cartridge 54. The sealing member 58 -of As installed in the cartridge 54, it can be prevented from sliding on the cartridge 54, and can be moved on the front surface of the cartridge in the directions of the arrows A and B in Figures 12 and 13, to open and close the opening of the cartridge. write access 55, read / write access opening 56 and central opening 57, simultaneously. There is provided within the cartridge 54, a locking member (not shown) that engages the shutter member 58 moved to a position where it - closes the write access opening 55, the read / write access opening 56 and the opening central 57, to thereby maintain the sealing member 58 in that position. When the sealing member 58 is in the closed position, the locking member engages with a locking piece provided in the first sliding guide 62 to maintain the sealing member 58 in the closed position. When the disc cartridge 51- is ejected from a recording and / or reproducing apparatus, the sealing member 58 is held by a shutter retention member and moves relative to the cartridge 54 to a position where it closes the access opening of the cartridge 54. read / write 56 and the central opening 57. Therefore the disc cartridge 51 does not require force means such as a spring to move the sealing member 58 to the closed position. The second obturator portion 60 formed sufficiently long to close the read / write access opening 56 and the central opening 57, has its free end supported by a fixed moving guide part 60a on the lower surface of the cartridge 54 as illustrated in FIG. Figure 13. In this way, the second plug portion 60 is prevented from floating from the bottom surface of the cartridge 54 and can positively close the central opening 57. The cartridge 54 has on its front side a coupling recess 64, in wherein a shutter release member that is provided in a recording and / or reproducing apparatus engages when the disc cartridge 51 is adjusted in the recording and / or reproducing apparatus. The coupling recess 64 opens at one end where the disc cartridge 51 is first inserted into the recording and / or reproducing apparatus. When the disk cartridge 51 thus constructed, is inserted into a recording and / or reproducing apparatus first on a side in which the coupling recess 64 is open, ie in the direction of the arrow E in Figures 12 and 13, the shutter release member of the recording and / or reproducing apparatus enters the coupling recess 64 and presses to move the locking member, thereby detaching the latter from the locking part of the sealing member 58. According to the cartridge disc 51 is further inserted into the recording and / or reproducing apparatus after the interlocking piece detaches from the interlocking member, the cartridge 54 moves while the sealing member 58 is restricted from movement by the obturator release member , such that the write access opening 55, the read / write access opening 56 and the central opening 57 are opened. In this way, the disc cartridge 51 is adjusted in place in the recording and / or reproducing apparatus. As illustrated in Figure 13, the cartridge 54 has formed on its lower surface first and second positioning holes 65 and 66 for receiving positioning pin provided in the recording and / or reproducing apparatus. The positioning holes 65 and 66 are formed at positions at the front corners respectively of the cartridge 54, where the holes 65 and 66 are not opposed to the optical disc 1 circumscribed in the cartridge 54.

The first disk cartridge 51 constructed as described above, is formed to have a size sufficient to circumscribe the optical disk 1 with a small diameter. The read / write access opening 56 is formed closer to one side of the cartridge 54. Therefore, together with the compact design of the disc cartridge 51, the recording and / or reproducing apparatus wherein the disc cartridge 51 it is going to be used, it can be designed correspondingly compact. Now with reference to Figures 14 and 15, there is illustrated a second disk cartridge according to the present invention, designed to circumscribe the second optical disk according to the present invention, i.e. the optical disk 41. The disk cartridge generally it is indicated with a reference 71. Similar to the first disk cartridge, i.e. the disk cartridge 51 previously described, the disk cartridge 71 consists of an upper half 72 and a lower half 73 confined abutting each other to form a cartridge 74 in where the disk cartridge 41 is to be circumscribed. The cartridge 74 is formed to have a rectangular structure of which a first side has a length x of 41 to 57 mm and a second side has a length Vj? from 41 to 62 mm, perpendicular to the first side. Therefore, the optical disk 41 of more than 38 mm and 52 mm or less in diameter can be rotationally circumscribed in the cartridge 74. The lengths Wx and 2 of the first and second sides of the cartridge 74 are appropriately chosen from ranges 41 to 57 mm and 41 to 62 mm, respectively, according to the size of the optical disc 1 circumscribed in the cartridge 54. The cartridge 54 has a thickness D4 selected from a range of 3 to 6 mm according to the thickness of the optical disc 41 that is circumscribed there. This is the cartridge 74 is formed according to the size of the optical disk 41 so that it has the rectangular shape with minimum length, width and thickness necessary to circumscribe the optical disk 41. In effect, the disk cartridge 71 shown in Figures 14 and 15, comprises the cartridge 74 with a first side having a length 3 of 54 mm, a second side having a length of 4 of 57 mm and a thickness D4 of 5 mm, since the optical disk 41 to be circumscribed there, has a diameter Rl? of 50 mm and a thickness of D of 0.6 mm. As in the disc cartridge 51, the cartridge 74 has formed in the upper half 72, a writing access opening 75 through which a radially extending part of the optical disk 41 circumscribed therein is exposed. Also, the lower half 73 of the cartridge 74 has a read / write access opening 76 through which a radially extending part of the optical disc 41 circumscribed therein is exposed and allows an optical pick-up unit of a recording and / or reproducing apparatus approaches the optical disc 41 for writing and reading an information signal a and the latter, and a central opening 77 through which the plate stop 4 confinement that is provided in the center of the optical disc 41, is exposed. Similarly to the read / write access opening in the disk cartridge 51, the read / write access opening 76 has a midpoint P4 of its width offset from the midpoint P3 of the front side width of the cartridge 74 towards a from the sides of the cartridge 74, as illustrated in Figure 15. The cartridge 74 is provided with a shutter member 78 for opening and closing the write access opening 75, the read / write access opening 76 and the central opening 77, at the same time. The sealing member 78 is dimensioned differently from the sealing member of the disc cartridge 51 but similarly constructed to the latter. In such a way that elements equal or similar to those of the sealing member of the disc cartridge 51, are indicated with the same reference numerals used for the latter and will not be described in greater detail.

The cartridge 74 of the disk cartridge 71 has formed on its front side, a coupling recess 84 in which a shutter release member, which is provided in a recording and / or reproducing apparatus, engages when the disc cartridge 71 is adjusted in the recording and / or reproducing apparatus. The coupling recess 84 is open at one end in which the disc cartridge 71 is first inserted into the recording and / or reproducing apparatus. When the disc cartridge 71 constructed in this way is inserted into a recording and / or reproducing apparatus first on a side in which the coupling recess 84 is open, the obturator release member (not shown) of the recording apparatus and / or reproduction enters the coupling recess 84 and presses to move the locking member (not shown), thereby detaching the latter from the interlocking piece (not shown) of the sealing member 78. As the disc cartridge 71 is additionally inserts into the recording and / or reproducing apparatus, after the interlocking member of the locking member is detached, the cartridge 74 moves while the sealing member 78 is constrained by the obturator release member against movement, such that the write access opening 75, the read / write access opening 76 and the central opening 77 are opened. In this way, the disk cartridge 71 is adjusted in place in the recording and / or reproducing apparatus. As illustrated in Figure 15, the cartridge 74 has formed on its lower surface first and second positioning holes 85 and 86, wherein locating pins provided in the recording and / or reproducing apparatus, are engaged when the cartridge Disk 71 is set in the recording and / or playback apparatus. The location holes 85 and 86 are formed at positions at the front corners, respectively of the cartridge 74 in which the holes 85 and 86 are not opposed to the optical disc 41 circumscribed in the cartridge 74. The disc cartridge 71 is designed for small that the disk cartridge 51, since it is used to circumscribe the optical disk 41 smaller than the optical disk 1. However, since the optical discs 1 and 41 are identical to each other in the method of connecting each of them to the The rotary movement mechanism of a recording and / or reproducing apparatus and the method of writing and reading an information signal to and from the signal recording layers, is convenient for both disk cartridges 51 and 71 to be commonly usable in the recording and / or reproducing apparatus that is compatible with at least the disk cartridge 51.

For selective use of the disk cartridges 51 and 71 of different sizes in a common recording and / or reproducing apparatus, it is necessary to provide the apparatus with a cartridge support receiver which can selectively locate each of the disk cartridges 51 and 71 to connect to the rotary movement mechanism. A recording and / or reproducing apparatus for optical discs as recording means comprises an optical pickup unit and magnetic head unit which move on the upper and lower surfaces of the optical disc. Therefore, it is difficult to additionally provide disk cartridge location mechanisms within the scope of the optical pickup unit and the magnetic head unit. In this situation, it should be convenient to be able to with only a minor modification of the recording and / or reproducing apparatus where the disk cartridge 51 is used, to fit the disk cartridge 71 in place in the apparatus in a similar fashion to that to adjust the disc cartridge 51. For this purpose, the present invention also provides an adapter for use with both disc cartridges 51 and 71 commonly in a recording and / or reproducing apparatus. Figures 16 to 18 show the adapter as a whole. The adapter is generally indicated with a reference 91 and has the same size as the disc cartridge 51. As illustrated in Figure 16, the adapter 91 is designed to have a rectangular shape whose outer dimensions are the same as those of the cartridge 54 of the adapter 51. The adapter 91 has a concavity formed at its center for retaining a cartridge 92 for receiving the disc cartridge 71. The concavity 92 is large enough to receive the disc cartridge 71. The adapter 91 is formed in the bottom of the concavity 92, first and second location pins 93 and 94 that engage the first and second locating pin coupling holes 85 and 86 respectively formed in the disk cartridge 71, as illustrated in Figures 16 and 17. In addition, first and second projections 95 and 96 are formed at the bottom of the concavity 92 on a wall of the concavity 92 opposite the wall on which the past is provided. 93 and 94. The first and second projections 95 and 96 are provided to support the lower surface of the disc cartridge 71 and to level the latter in relation to the adapter 91. Furthermore, an opening is formed at the bottom of the concavity 92. 97 through which the read / write access opening 76 and the central opening 77, which is formed in the lower half of the disk cartridge 71 received in the adapter 91, are exposed. In addition, the adapter 91 has on its front surface provided a shutter coupling member 98 which is connected to the shutter member 77 of the disc cartridge 71 fitted on the adapter 91. The shutter coupling member 98 is provided with a coupling projection 99, for engaging in the coupling hole 61a formed in the joint 61 of the sealing member 78. The sealing member 78 is movably installed on the front side of the adapter 91 in the directions of arrows C and D in Figure 16, which is the same as the direction of movement of the shutter member 78. The shutter coupling member 98 is also provided with a coupling piece 100 which will engage a recess for shutter release member coupling 84 formed in the disc cartridge 71 fitted in the cartridge retaining concavity 92. In addition, the adapter 91 has formed on its front side a recess of the shutter release member 101, similar to the recess of the shutter release member 64 formed on the side front of the disc cartridge 51. Furthermore, the adapter 91 has formed on its lower surface first and second locating pin coupling holes 102 and 103 in positions corresponding respectively to the first and second locating pin coupling holes 65 and 66 of the disk cartridge 51. As illustrated in Figure 18, the disc cartridge 71 is received in the adapter 91 in this manner constructed with the coupling projection 99 coupled in the coupling hole 61a of the sealing member 78, the coupling part 100 engages in the coupling recess of the release member of the coupling member. shutter 84 and the first and second location pins 93 and 94 coupled in the first and second coupling holes 85 and 86 respectively. The disk cartridge 71 thus received in the adapter 91 will have the same shape as the disk cartridge 51. That is, it can be handled similarly to the disk cartridge 51. That is, the adapter 91 with the disk cartridge 71 fitted in the concavity cartridge retainer 92 is inserted, first on its side perpendicular to the front side in which the sealing coupling member 98 is installed in a recording and / or reproducing apparatus. As the adapter 91 is further inserted into the recording and / or reproducing apparatus, the obturator release member that is provided in the recording and / or reproducing apparatus enters the engaging recess of the obturator release member 101 to move the sealing plug member 98 in the direction of arrow C in Figure 18. As the sealing coupling member 98 moves in the direction of arrow C in Figure 18, the coupling piece 100 that is provided in the member Shutter Coupling 98 moves in the recess of the plug release member 84 of the disc cartridge 71, in the direction of the arrow C to press and move the locking member provided within the disc cartridge 71. In this way, the locking member is detached from the interlocking piece provided in the sealing member 78. As the adapter 91 is inserted further into the apparatus and reading and / or reproducing after detachment of the locking member from the locking piece, the cartridge 74 moves together with the adapter 91 with the sealing member 78 restraining against movement by the coupling piece 100, such that the opening for write access 75, the read / write access opening 76 and the central opening 77, open. Subsequently, the adapter 91 is adjusted together with the disk cartridge 71 held thereon on a cartridge assembly in the recording and / or reproducing apparatus. The adapter 91 is correctly located in the cartridge assembly, since locating pins provided in the recording and / or reproducing apparatus are engaged in the first and second locating pin coupling holes 102 and 103, respectively. It will be noted that in order to selectively fit the disk cartridges 51 and 71 of different sizes in the recording and / or reproducing apparatus, a cartridge assembly in which each of the disk cartridges 51 and 71 can be retained, can be provided in the device. In this case, the cartridge assembly is provided with locating pins to be engaged in the first and second locating pin coupling holes 65 and 66 in the disc cartridge 51, respectively, and those that are to be engaged in the cartridge. first and second locating pin coupling holes 85 and 86, respectively. To make this possible in selectively adjusting the cartridges, disk 51 and 71 in the recording and / or reproducing apparatus, disk holes 51 are formed larger than the disk cartridge 71, relief holes where the pins of location are to be received in the first and second locating pin coupling holes 85 and 86, respectively in the disk cartridge 71. As previously described, since the disk cartridges 51 and 71 circumscribe the optical discs read / write 1 and 41, respectively, which are capable of recording an information signal, the cartridges 54 and 74, have in their upper half the access openings for writing 55 and 75 through which a magnetic head writes information to the respective exposed optical discs 1 and 41. However, a disk cartridge in which the read only optical disk 111 circumscribes does not have a writing access opening formed in its upper half, while it has formed in its lower half only an access opening for reading, through which the Optical pick-up unit is exposed and a central opening through which a confinement to plate stop is exposed. Therefore, the disk cartridge circumscribing the read-only optical disk may only have one shutter for the read access aperture and the central aperture formed in its lower half. The disk cartridge 51 circumscribing the optical disk 1 and the disk cartridge 71 circumscribing the optical disk 41, are set in a recording and / or reproduction apparatus constructed as will be described below, to write and read the information signal and of the optical discs 1 and 41. As mentioned above, the disc cartridge 71 is adjusted in the adapter 91 and adjusted as it is in the recording and / or reproducing apparatus. Similarly to the disk cartridges 51 and 71, the cartridge in which the read-only optical disk 111 is circumscribed may be adjusted in the recording and / or reproducing apparatus to read the information signal recorded in the optical disk 111. Now with Referring to Figure 19, a recording and / or reproduction apparatus is schematically displayed in which each of the disk cartridges 51 and 71 and the disk cartridge circumscribing the read-only optical disk 111 is usable. The recording and / or reproducing apparatus is generally indicated with a reference 20Q. As illustrated, the disc cartridge 51, the disc cartridge 71 fitted to the adapter 91 or the disc cartridge circumscribing the read-only optical disc 111, fits into the recording and / or reproducing apparatus 200 to write signals of information such as an audio signal, video signal, etc., and reads an information signal recorded on the optical disc. The recording and / or reproducing apparatus 200 comprises a magnetic head unit for applying an external magnetic field to the magneto optical disk when the information signal is written in the latter. As illustrated in Figure 19, the recording and / or reproducing apparatus 200 comprises a housing, a flat, generally rectangular base 201 formed of a metallic material and disposed in the housing, a cartridge holder 202 for holding a disc cartridge . The cartridge holder 202 is pivotally supported on the base 201. The base 201 has therein incorporated a rotation shift mechanism 11, which moves to rotate the optical disk 1 (41 or 111) and an optical pickup unit 203. It is provided in the base 201, a cartridge assembly 205 in which a disc cartridge (not shown) retained in the cartridge holder 202 is adjusted. The cartridge holder 202 is provided with a magnetic head unit 206 which moves in synchrony with the optical pickup unit 204 radially of the optical disk 1. The rotary movement mechanism 11 is constructed as previously described with reference to Figure 4. As is illustrated in Figure 19, the optical pickup unit 204 comprises primarily a semi-conductor laser for emitting a laser beam, an objective lens 131 for focusing the laser beam emitted from the semiconductor laser onto the optical disk 1, a photodetector, for detecting a return light from the optical disc 1 in order to detect an information signal and control signals, etc. The optical pickup unit 204 is held on both sides by a pair of guide arrows 207 installed in parallel with each other at the bottom of the base 201 to radially move the optical disk 1 fitted on the disk platter 14. The objective lens 131 faces the upper surface of the base 201 and the optical disk 1 fitted in the disk plate 14 through an opening 208 formed in the base 201. The optical pick-up unit 204 is guided in the guide arrows 207 by a feed screw ( not shown) displaced by a displacement motor (not shown) fixed at the bottom of the base 201 and thus radially moving the optical disk 1 on the disk plate 14. This is, to write or read an information signal, the optical pickup unit 204 moves radially from the access area to the output area of the optical disc 1. - As also illustrated in Figure 19, the magnetic head unit 206 is connects to the optical pickup unit 204 that writes an information signal to the optical disk 1. That is, the magnetic head unit 206 also moves radially of the optical disk 1 on the disk plate 14 as the optical pickup unit moves 204. The magnetic head unit 206 comprises a magnetic head 210 for applying to the optical dico 1 with an external magnetic field modulated in accordance with an information signal that is written on the optical disc, and a magnetic head support plate 211 which it is provided with a leaf spring which supports the magnetic head 210 at its free end and which can move elastically. The magnetic head unit 206 is linked to the optical pickup unit 204 by an articulation member 213, such that it is located in a position where it will be opposite the optical pickup unit 204 with the optical disk 1 on the platen of disk 14 located between them. As illustrated in Figure 19, the hinge member 213 consists of a coupling piece 215 and an attachment 216 formed by bending one end of the coupling piece 215 perpendicular to the latter and whereby the hinge member 213 is fixed to the optical pick-up unit 204. The articulation member 213 is formed to have an L-shape in general. The articulation member 213 is installed in the optical pickup unit 204 with the fixture 216 fixed to the optical block with fixing screws or the like, such that the free end of the coupling piece 215 projects onto the base 201. The base end of the magnetic head support plate 211 is pivotally held at the ends of the coupling part 215 by means of a pivot (not shown). In this way, the magnetic head support plate 211 is pivotable with respect to the kingpin in directions of the magnetic head 210 supported on the free end of the plate 211, rotated toward and away from the optical disk 1 in the disk plate 14. According to the optical pick-up unit 204 is moved by the feed motor to move radially of the optical disc 1, the magnetic head unit 206 thus coupled with the optical pick-up unit 204 by the hinge member 213, also moves together with the optical pickup unit 204 radially of the optical disc 1. As illustrated in Figure 19, the cartridge holder 202 in which the disc cartridge is inserted and retained, is pivotally installed in the base 201 at a position between the base 201 and the magnetic head unit 206. The cartridge holder 202 has on its opposite sides, provided guided cartridges 221 and 222 for guiding and holding a disc cartridge and also an inlet d and cartridge 223 formed on its front side. A disc cartridge inserted from the cartridge inlet 223 in the cartridge holder 202 is held on opposite sides by cartridge guides 221 and 222 respectively. The recording and / or reproducing apparatus _200 with the rotary movement mechanism 11 constructed as mentioned above, works as will be described below when the disk cartridge 51 circumscribing the optical disk 1 for example fits there: First, to write an information signal to the optical disc 1 or to read an information signal recorded on the optical disc 1, the cartridge holder 202 is pivoted to its upper position when it is spaced from the cartridge assembly 205. At this time, the cartridge inlet 223 of the cartridge holder 202 will be directed onto the apparatus. Then, the cartridge holder 202 in which the disk cartridge is held, is pivoted towards the cartridge assembly 205 and thus the disk cartridge 51 is located in place in the cartridge assembly 205. At this time, the disk optical 1 in the disc cartridge 51 is adjusted in the disc plate 14 of the rotary movement mechanism 11 and held for rotation with the disc plate 14. When it is detected that the disc cartridge fitted in the cartridge assembly 205 circumscribes the optical disk 1 and the writing operation mode is chosen when using a recording or recording button, the spindle motor 12 is moved to rotate advancing and the optical disk 1 is rotated together with the disk plate 14. The unit Optical pickup 204 is put into operation. A beam of light emitted from a light source scans on the signal recording layer 21 of the optical disk from the access to the output, while the magnetic head 210 applies the optical disk 1 with an external magnetic field modulated in accordance with an information signal to write. In this way, a desired information signal is written to the optical disk 1. When the reading operation mode is chosen when using a play button, a light beam emitted from the semiconductor laser of the optical pickup unit 204 is irradiated to the signal recording layer 21 of the optical disk 1, a return light of the signal recording layer 21 of the optical disk 1 is detected by the photodetector of the optical pickup unit 204. In this way, an information signal it is read from the optical disk 1. It will be noted that for reading the information signal, no external magnetic field can be applied to the optical disk 1, i.e. the magnetic head unit 206 is not required in the recording and / or reproducing apparatus. aforementioned 200, the optical pickup unit 204 emits a light beam that allows a high density recording, as previously described. A semiconductor laser that emits a beam of light from 380 to 420 nm in wavelength? or a beam of light from 630 to 670 nm in wavelength?, is used as the laser source. The objective lens 131 has a NA numerical aperture of 0.5 to 0.7 to allow high resolution. The magnetic head 210 is of the high frequency type to allow a high density recording.

In addition to the first disk cartridge 51 circumscribing the first optical disk 1, the second disk cartridge 71 circumscribes the second optical disk 41 or the disk cartridge in which the read-only optical disk 111 is circumscribed, can be used in the apparatus registration and / or reproduction to write or read an information signal in the same way as mentioned above. As described above, since the optical recording medium and the disk cartridge circumscribing the optical recording medium according to the present invention are very compact and capable of recording an information signal with high density, an apparatus can be provided of recording and / or reproduction which is correspondingly compact and can write or read an information signal such as audio and video information for a sufficiently long time. Although modifications and changes may be suggested by those of ordinary skill in the art, it is the intention of the inventors to incorporate within the patent herein guaranteed, all changes and modifications that fall reasonably and adequately within the scope of their contribution to the art.

Claims (24)

1. CLAIMS 1. A recording member for optical reading / writing, comprising: a disk having a diameter of 65 mm or less and a thickness between and including 0.4 mm and 0.7 mm, the disk also has a center; and a recording area for an information signal on the disc, the recording area extends outwards 12.5 mm or less from the center of the disc, a diametral length relationship between the recording area and a non-recording area on the disc is 3.4 or more, the recording area has an information signal storage capacity of at least 2 Gigabytes.
2. 2. The recording medium for optical reading / writing according to claim 1, characterized by the recording area further comprises tracks having a pitch between and including 0.3 μm and 0.55 μm to record an information signal represented as pitting in the tracks, the pits have a length between and including 0.1 m / bit and 0.22 μm / bit. The recording medium for optical read / write according to claim 1, characterized by further comprising: a central hole formed at the center of the disk; a butt confinement of an annular plate formed around the central hole and convex to one side of the disk; and a fixed magnetic clamping hub to the butt confinement of annular plate. The recording medium for optical read / write according to claim 3, characterized in that the annular plate stop confinement is convex by 0.4 mm to 0.7 mm and has an outer diameter of approximately 14 mm and an inner diameter of approximately 8 mm. mm. 5. An optical read / write recording medium comprising: a disk having a diameter between 38 mm and 52 mm and a thickness between and including 0.4 mm to 0.7 mm, the disc has a center; and a recording area on the disc extends outwards 12.5 mm or less from the center of the disc, the recording area has an information signal storage capacity of at least 1 Gigabytes The optical read / write recording medium according to claim 5, characterized in that the recording area further comprises tracks having a pitch between and including 0.3 μm and 0.55 μm to record an information signal represented as cavities in the tracks, the cavities have a length between and that includes 0.1 μm / bit and 0.22 m / bit. The optical read / write recording medium according to claim 5, characterized in that it further comprises: a central hole formed at the center of the disk; a butt confinement of annular plate formed around the central hole and convex to one side of the disk; and a fixed magnetic clamping hub to the butt confinement of annular plate. The optical read / write recording medium according to claim 7, characterized in that the plate stop confinement is formed to the same size as that of a second plate stop confinement formed for a second optical recording medium which comprises: a disc having a diameter of 65 mm or less and a thickness between and including 0.4 mm and 0.7 mm, the disc has a center; and a recording area for an information signal on the disc, the recording area extends outward 12.5 mm or less from the center of the disc; a relationship in diametral length between the recording area and a non-recording area on the disc that is 3.4 or more, the recording area has an information signal storage capacity of at least 2 Gigabytes. 9. A read-only optical recording medium simulated to a read / write recording medium, the read / write recording medium has a disk with a diameter of 65 mm or less and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extends outwards 12.5 mm or less from a center of the disc, the recording area has a storage capacity of at least 2 Gigabytes and a ratio in diametral length between the recording area and a non-recording area of the disc that is 3.4 or more, the read-only optical recording medium comprises: a substrate formed to a disc structure having a thickness between and including 0.4 mm and 0.6 mm, when a resin is injected into a mold having a cavity pattern formed in a track of recording in which a smaller cavity length and a recording track pitch are approximately 1.4 larger than a cavity length and a track pitch in the read / write recording medium; a first information recording layer formed in the pattern of cavities in the substrate; a sheet transparent to light between and including 0.05 mm and 0.1 mm in thickness and having on one side a pattern of cavities formed by thermally stamping a die or stamper with cavity pattern; and a second information recording layer formed on the cavity pattern side of the light transparent sheet, wherein the pattern of cavities in the substrate and the pattern of cavities in the light transparent sheet are bonded with a resin transparent between them, the transparent resin between the substrate and the transparent sheet to light has a length between and including 20 μm and 35 μm. 10. A read-only optical recording medium according to claim 9, characterized in that the first information recording layer is translucent for optical reading of an information signal recorded from the substrate side. 11. The read-only optical recording medium according to claim 9, characterized in that it further comprises: a central hole formed at the center of the substrate; a butt confinement of annular plate formed around the central register and convex to one side of the substrate; and a fixed magnetic clamping hub to the butt confinement of annular plate. The read-only optical recording medium according to claim 11, characterized in that the annular plate stop confinement is convex at 0.4 mm to 0.7 mm and has an outer diameter of approximately 14 mm and an inner diameter of approximately 8 mm. mm. 13. A read-only optical recording medium simulated to a read-write recording medium, the read-write recording medium includes a disk having a diameter between 38 mm and 52 mm and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extends outwards 12.5 mm or less from a center of the disc, the recording area has an information signal storage capacity of at least 1 Gigabyte, the optical recording medium read-only comprises: a substrate formed to a disc structure having a thickness between and including 0.4 mm and 0.6 mm, when injecting a resin into a mold having formed a pattern of cavities in a recording track where a length of smaller cavities and a recording track pitch are approximately 1.4 times larger than a length of cavities and a track length in the read-write recording medium; a first information recording layer formed in the cavity pattern of the substrate; a sheet transparent to light between and including 0.05 mm and 0.1 mm in thickness and having a cavity pattern formed therein when thermally stamping a cavity pattern die; and a second information recording layer formed on the cavity pattern side of the light transparent sheet, wherein the pattern of cavities in the substrate and the pattern of cavities in the light transparent sheet are bonded together with a transparent resin between them, the transparent resin between the substrate and the transparent sheet to the light has a length between and including 20 μm and 35 μm. 14. The read-only optical recording medium according to claim 13, characterized in that the first information recording layer is translucent to optically read an information signal recorded from the substrate side. 15. The read-only optical recording medium according to claim 13, characterized in that a central hole formed at the center of the substrate; a butt confinement of annular plate formed around the central hole and convex to one side of the substrate; and a fixed magnetic clamping hub to the butt confinement of annular plate. 16. The read-only optical recording medium according to claim 13, characterized in that the annular plate stop confinement is convex at 0.4 mm to 0.7 mm and has an outer diameter of about 14 mm and an inner diameter of about 8 mm. 17. A disk cartridge wherein a read-write recording medium is circumscribed, the read-write recording medium includes a disk having a diameter of 65 mm or less and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extends outwards 12.5 mm or less from a center of the disc, the recording area has a storage capacity of at least 2 Gigabytes, a ratio in diametral length between the recording area and a disc not recording area that is 3.4 or more, the disc cartridge comprises: a cartridge having a rectangular shape and including a first side with length between and including 52 mm and 70 mm, and a second side perpendicular to the first side, which has a length between and including 52 mm and 75 mm, the cartridge has a thickness between and including 3 mm and 6 mm; and at least one opening formed on one side of the cartridge parallel to the read / write recording medium, the opening is an access opening for writing and reading through which a radially extending portion of the recording medium is exposed to a beam of light from an optical pickup assembly and through which the magnetic gripper is exposed, the aperture is furthermore biased to one side from a midpoint of a front of the cartridge. The disk cartridge according to claim 17, further characterized in that it comprises a shutter member slidably mounted on one side of the cartridge for opening and closing at least the write access opening and the read access opening formed in the cartridge . 19. A disc cartridge having a read-write recording medium is circumscribed there, the read-write recording medium includes a disc having a diameter between 38 mm and 52 mm and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extends outwards 12.5 mm or less from a center of the disc, the recording area has a storage capacity of at least 1 Gigabyte, the disc cartridge comprises: a cartridge that has a rectangular shape and including a first side having a length between and comprising 41 mm and 57 mm, and a second side, perpendicular to the first side having a length between and including 41 mm and 62 mm, the cartridge has a thickness between and including 3 mm and 6 mm; and at least one aperture formed on one side of the cartridge, parallel to the read-write recording medium, the aperture is a write and / or read access aperture through which a radially extending portion of the recording medium. it is exposed to a light beam from an optical pickup and through which the magnetic holding hub is exposed, the aperture is furthermore biased to one side from a midpoint of a front of the cartridge. 20. The disk cartridge according to claim 19, characterized in that it further comprises a sealing member slidably mounted on one side of the cartridge for opening and closing at least the write access opening and the read access opening formed in the cartridge. . 21. A disk cartridge that has a read-only optical recording medium circumscribed therein, the read-only optical recording medium includes a disc having a diameter of 65 mm or less and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extending outwards 12.5 mm or less from a disc center, the recording area has a storage capacity of at least 2 Gigabytes, a ratio in diametral length between the recording area and a non-recording area of the disc is 3.4 or more, the disc cartridge comprises: cartridge of rectangular shape including a first side with a length between and including 52 mm and 70 mm and a second side, perpendicular to the first side having a length between and including 52 mm and 75 mm, the cartridge has a thickness between and that includes 3 mm and 6 mm; and at least one aperture formed on one side of the cartridge parallel to the read-only recording medium, the aperture is a write-and-read access aperture, through which a radially extending portion of the recording medium is exposed to a beam of light from an optical pickup assembly through which the magnetic gripper is exposed, the aperture is furthermore biased to one side from a midpoint of a front of the cartridge. 22. The disc cartridge according to claim 21, characterized in that it further comprises: a sealing member slidably mounted on one side of the cartridge for opening and closing at least the writing access opening and the reading access opening formed in the cartridge. 23. A disk cartridge having a read-only optical recording medium circumscribed therein, the read-only optical recording medium includes a disk having a diameter between 38 mm and 52 mm and a thickness between and including 0.4 mm and 0.7 mm, a recording area on the disc extends outwards 12.5 mm or less from a center of the read-only optical recording medium, the recording area has a storage capacity of at least 1 Gigabyte of an information signal with a pattern of cavities, the disc cartridge comprising: a cartridge of rectangular shape including a first side having a length between and including 41 mm 52 mm and a second side, perpendicular to the first side, having a second length between and which includes 41 mm and 62 mm, the cartridge has a thickness between and including 3 mm and 6 rare; and at least one aperture formed on a side parallel to the read-write recording medium, the aperture is a write and / or read access aperture, through which a radially extending portion of the optical disc is exposed to a beam of light from an optical pickup assembly and through which the magnetic gripper is exposed, the aperture is formed offset one side from a midpoint of a front of the cartridge. 24. The disk cartridge according to claim 23, characterized in that it further comprises a sealing member slidably mounted on one side of the cartridge for opening and closing at least one write access opening and a read access opening formed in the cartridge. . SUMMARY OF THE INVENTION An optical recording medium is provided having a substrate and a signal recording layer that is provided on the substrate and wherein an information signal is recorded in the form of microscopic pits. A light beam is focused on the signal recording layer and some change of the light beam carried by a return light from the signal recording layer is detected to read the information signal recorded in the signal recording layer. The optical recording medium has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm. An information signal recording area extends outward from a radial position of 12.5 mm or less from the center of the medium. The area ratio between the information signal recording area and a non-signal recording area is 3.4 or more. The storage capacity of this medium is 2 Gigabytes or more. The optical recording medium has, at its center, a central hole around which a convex annular plate stop confinement is formed on one side of the medium. A clamping hub by magnetic clamp is installed in the central hole and in this way the medium is magnetically clamped to a rotary movement mechanism of an apparatus of 18375 reproduction and / or optical recording. The compactness and high recording density of the optical recording medium will greatly contribute to a more compact structure of a recording and / or reproduction apparatus in which the medium is to be used. 18375