JP2685737B2 - Optical disc recording medium, mounting method thereof, and optical disc device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc recording medium, and more particularly to a structure of an optical disc recording medium suitable for a magnetic chuck system of a recording / reproducing apparatus. 2. Description of the Related Art Conventionally, when a recording medium of an optical disk, that is, a disk is mounted on a spindle of a recording and / or reproducing apparatus, as shown in FIG. 1, a disk composed of two substrates 1 and 1 '. Was supported on the receiving surface of the spindle 2 by pressing it from above onto the spindle 2 with the fixing mechanism 3 (so-called mechanical clamp). All of the currently marketed compact discs and optical video discs are of this type. However, when attempting to reduce the size and weight of the device, the fixing mechanism 3 becomes a problem. That is, since the fixing mechanism 3 attaches and detaches the disk, it is necessary to move upward from the position of FIG. 1, and it is necessary to increase the thickness of the device by the thickness of the fixing mechanism 3 and upward movement. On the other hand, FIG. 2 is a basic configuration diagram of a means for solving this drawback. The structure of one of the examples is described in detail, for example, in Japanese Utility Model Publication No. 59-138030. This is the substrate 1,1 '
A metal piece 5 or a magnetic material is adhered to the outside of the center of the disk constituted by the above, and the disk is attracted to the spindle by utilizing the attraction force with the magnetic material 4 provided on the spindle 2 (so-called. As compared with the magnetic clamp shown in FIG. 1, the fixing mechanism 3 is not necessary, and the feature of the apparatus is that the thickness of the device can be reduced accordingly. However, when this is actually performed, there is a problem that a large retardation occurs due to a change in ambient temperature of the disk. This retardation is generated as a result of strain stress occurring in the substrate due to the difference between the coefficient of thermal expansion of the substrates 1 and 1'and the coefficient of thermal expansion of the bonded metal piece 5 or magnetic material, and the so-called photoelastic effect. Is. This retardation disturbs the polarization state of the recording / reproducing light of the optical disc, and causes deterioration of the recording / reproducing characteristics. For this reason, the allowable value of retardation given to the disc is the compact disc (CD) currently on the market.
70nm for optical video discs, so-called DRAW (Direct Lead After) used for image files, etc.
It is said that the Write type optical disc has a thickness of 40 nm, and the magneto-optical disc that detects a slight rotation angle of polarized light (up to 0.35 °) has a thickness of 10 nm. With respect to this allowable value, a disk having the shape shown in FIG. 2 was prepared, and the retardation generated when the temperature was changed by 40 ° C. was measured, and FIG. 3 is shown. The disc has a radius of 65 mm, and the recording / reproducing area has a radius of 30 to 60 mm. The plastic material of the substrate is a polycarbonate resin. a is a Sumitomo Bakelite Sumiglass FMG-1H with a thickness of 0.8 mm
3 and b are Wallmax P9 of 0.8mm thick Sumitomo Metal Mining
The inner and outer diameters are φ15 and φ33 mm, respectively. All of them are so-called plastic magnets in which a magnetic material is dispersed in plastic, and have a coefficient of thermal expansion much closer to that of plastic than ordinary metal pieces and magnetic material alone.
Further, c is the case of a small diameter ring of iron having a thickness of 0.1 mm. The inner and outer diameters are φ15 and φ20. Here, the physical constants involved in the generation of retardation are the photoelastic constant of polycarbonate resin of 5.5 × 10 ⁻⁴ mm ² / kg and the coefficient of thermal expansion of 6.8.
× 10 ^-5 / deg, Young's modulus 240 kg f / mm ^2, also Sumigarasu FMG-1H3 and × respectively thermal expansion rate 2.46 ^{Wallmax P9 10 -5 /deg,3.0×10 -5 / deg} ,
And Young's modulus are 2100 kg f / mm ² , 1170 kg f
/ Mm ² . The coefficient of thermal expansion of iron is 1.2 × 10 ^-5 / deg
The Young's modulus is 20000 kgf / mm ² . Thus, even if a plastic magnet is used, retardation of several hundreds of nm occurs, and it cannot be used for a CD or an optical video disc having the largest allowable value. You cannot use metal pieces or ferromagnetic materials that have a smaller coefficient of thermal expansion than plastic magnets. Even if the substrate material is changed to an epoxy resin, the physical constants are almost the same as those of the polycarbonate resin, so the situation is the same. Substrate material is PMMA
In this case, since the photoelastic constant of PMMA is about 1/10 of that of polycarbonate resin, it is considerably neglected, but it is still unusable for a magneto-optical disk. FIG. 4 is a calculated value of retardation generated when the resin having a coefficient of thermal expansion different from that of epoxy by only 0.3 × 10 ⁻⁵ / deg is bonded as 5 in FIG. Even in this case, the retardation is a permissible value for the magneto-optical disk (<10 nm).
Is over. As described above, it has been proved that it is not practical to bond the metal piece or the magnetic material to the substrate. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk recording medium which eliminates the above-mentioned drawbacks of the prior art, enables magnetic clamping suitable for thinning the apparatus, and does not cause retardation. To provide. In order to solve the above problems, according to the present invention, in an optical disk recording medium on which information is optically recorded, a substrate having a holding portion and a recording film,
It is characterized in that it has a metal piece or a magnetic body held by a holding portion and adsorbed by a spindle, and the holding portion has substantially the same coefficient of thermal expansion as that of the substrate. As described above, the reason why large retardation occurs in the magnetic clamping disk is that the metal piece or magnetic material having a different coefficient of thermal expansion from the substrate is fixed to the substrate by adhesion. . Therefore, keep a metal piece or magnetic material.
I decided to hold it on the board through the holding part, but this time I will hold it
Part becomes the source of retardation. Follow
Then , if the thermal expansion coefficients of the holding portions are made substantially the same, the occurrence of retardation should be prevented. As another method, if the metal piece or the magnetic material is not fixed to the substrate, that is, if it can be attached to the substrate in a state of being separated from the substrate, the occurrence of retardation should be prevented. This metal piece or magnetic body is used to attract the disk to the spindle by the magnet installed on the spindle. Therefore, when the metal piece or magnetic body is attracted by the magnet, the substrate is also attracted at the same time. It should be
It is not necessary to fix it to the substrate by adhesion or the like. Embodiments of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. (Embodiment 1) FIGS. 5 and 6 are sectional views of a first embodiment of the present invention. Reference numerals 1 and 1'in FIG. 5 denote optical disk substrates made of a plastic such as polycarbonate resin, epoxy resin or PMMA. What is shown is a so-called contact bonding type disc.
There is a recording film between 1 '. Reference numeral 7 is an annular metal piece or magnetic material, which is attached to the substrate in a state where it is separated from the substrate by the annular L-shaped members 6 and 6'bonded to the substrate. As the metal piece or magnetic material, Fe, Ni,
And the like, and plastic magnets such as the above-mentioned Sumiglass FMG-1H3 and Wellmax P9 are used. FIG. 6 is a bottom view of FIG. FIG.
A schematic cross-sectional view of the medium of the present embodiment where it is adsorbed to the spindle of the recording / reproducing apparatus is shown. An annular metal piece or magnetic body 7 is pulled by a magnet 4 attached to the spindle 2. This attractive force is transmitted to the substrate 1'by the annular L-shaped members 6 and 6 ', and the substrate is attracted to the spindle. In the present embodiment, the contact bonding type disc is described, but the air sandwich type disc and the CD are used.
It is clear that the same effect can be obtained with a disk made of a single substrate as described above. Further, in this embodiment, the metal piece or the magnetic body 7 and the annular L-shaped members 6 and 6'are provided on only one side, but in the case of an optical disk using both sides, the same one may be provided on the opposite side. Further, in the present embodiment, the annular L
Although the character-shaped members 6 and 6'are provided on the inside and the outside of the metal piece or the magnetic body 7, only one of them can achieve the purpose and need not be annular. That is, a plurality of L-shaped members may be circumferentially arranged so as to support the annular metal piece or the magnetic body. The L-shaped members 6 and 6 ′ preferably have the same coefficient of thermal expansion as the substrate, and most preferably are formed of the same material as the substrate. It can be suppressed only by the amount of distortion (1 to 2 nm). (Second Embodiment) FIG. 8 shows a second embodiment of the present invention. In this embodiment, an annular metal piece or magnetic body 7 is attached to the substrate 1'in a so-called bag-like shape by a U-shaped member 8. This is a shape that prevents the metal piece or the magnetic body 7 from coming off due to the deformation of the L-shaped member in the first embodiment, and the other points are the same as in the first embodiment. (Embodiment 3) FIG. 9 shows a third embodiment of the present invention. In this case, the optical disk recording medium has a hollow so-called air sandwich structure. That is, recording film 1
Two substrates 10 and 10 'on which 2 and 12' are deposited
Are bonded with ring-shaped spacers 11 and 13 with the recording films 12 and 12 'inside. in this case,
The annular metal piece or magnetic body 7 can be placed in the hollow portion of the air sandwich structure as shown in FIG. (Fourth Embodiment) FIG. 10 shows a fourth embodiment of the present invention, which is essentially equivalent to the third embodiment. Since the annular spacer 14 is further provided on the outer side of the annular metal piece or the magnetic body, the medium strength is superior to that of the third embodiment. (Fifth Embodiment) FIGS. 11 and 12 show a fifth embodiment of the present invention. In this case, a plurality of small holes penetrating the inside of the optical disk recording medium composed of the substrates 1 and 1'is formed, and rivet-shaped metal pieces or magnetic bodies 9, 9'as shown in FIG. It is inserted.
When the rivet-shaped members 9 and 9'are attracted by the magnet provided on the spindle, the heads of the rivet-shaped members 9 and 9'attract the substrates 1 and 1 '. FIG. 12 is a plan view of FIG. 11 seen from above, in which four rivet-shaped members are arranged. The embodiments of the present invention have been described above.
When the optical disk recording medium of the above-mentioned embodiment is attracted to the spindle and the recording or reproducing process is completed and then the optical disk recording medium is removed from the spindle, the above description refers to the attraction force between the magnet and the metal piece or the magnetic body. There is no other way but to forcibly peel it off. For example, in the first embodiment, the L-shaped member 1
A considerable amount of force is applied to 2 and anxiety remains in terms of strength. FIG.
And FIG. 14 is a block diagram of an embodiment for solving this point. In this embodiment, the permanent magnet attached to the spindle of the above-described embodiment is an electromagnet, and an electric current is passed only when the optical disk recording medium is attracted to the spindle 2 to perform a magnet action. In this way, when the optical disk recording medium is removed from the spindle, it can be removed without applying force. In FIG. 13, reference numeral 21 denotes a core material having a high magnetic permeability, and it is preferable to use a rare earth element such as Sm-Co in order to produce a compact and strong force. Reference numeral 20 is a coil spread around the core material 21.
Since this electromagnet is rotated by the coil 22 together with the spindle 2, the disc 25 is necessary to supply the electric current to the electromagnet. As shown in FIG. 14, the disk 25 is provided with concentric conductors 28 and 29, which are connected by 26 and 27 to a current source. The side of the rotary spindle 2 is connected by ball-shaped members 23 and 24, which are connected to the coil 20 in the spindle. As described at the end of the first embodiment, it is desirable that the metal piece or the magnetic material be held by a member made of a material having a thermal expansion coefficient substantially the same as that of the substrate. In this case, as shown in FIGS. 9 to 11, a holder may be configured by a part of the substrate to hold the metal piece or the magnetic material 7, 9, 9 ′. According to the present invention, a metal piece or a magnetic material can be carried on an optical disk recording medium by a method in which retardation does not occur. The chuck method can be adopted, which is very effective in reducing the thickness of the recording / reproducing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a conventional example. FIG. 2 is a sectional view showing a conventional example. 3 is a graph showing measured values and calculated values of retardation generated on the substrate having the configuration of FIG. FIG. 4 is a graph showing measured values and calculated values of retardation generated on the substrate having the configuration of FIG. FIG. 5 is a sectional view and a front view showing an embodiment of the present invention. FIG. 6 is a sectional view and a front view showing an embodiment of the present invention. FIG. 7 is a sectional view and a front view showing an embodiment of the present invention. FIG. 8 is a sectional view and a front view showing an embodiment of the present invention. FIG. 9 is a sectional view and a front view showing an embodiment of the present invention. FIG. 10 is a sectional view and a front view showing an embodiment of the present invention. FIG. 11 is a sectional view and a front view showing an embodiment of the present invention. FIG. 12 is a sectional view and a front view showing an embodiment of the present invention. FIG. 13 is a sectional view and a partial front view of a spindle suitable for carrying out the present invention. FIG. 14 is a sectional view of a spindle suitable for implementing the present invention and a partial front view thereof. [Explanation of Codes] 1, 1 '... Optical disc substrate, 2 ... Spindle, 6, 6'
... annular L-shaped member, 7 ... annular metal piece or magnetic body, 9,
9 ', 9 "9"' ... Rivet-shaped metal piece or magnetic material.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yoshito Tsunoda               1-280 Higashi Koikebo, Kokubunji-shi, Tokyo                 Central Research Laboratory, Hitachi, Ltd. (72) Inventor Kazuo Shigematsu               1-280 Higashi Koikebo, Kokubunji-shi, Tokyo                 Central Research Laboratory, Hitachi, Ltd. (72) Inventor Anori Kanazawa               Hitachi, 1-88, Ushitora, Ibaraki-shi, Osaka               Maxell, Inc. (72) Inventor Toshinori Sugiyama               Hitachi, 1-88, Ushitora, Ibaraki-shi, Osaka               Maxell, Inc. (72) Inventor Tetsuro Igaki               Hitachi, 1-88, Ushitora, Ibaraki-shi, Osaka               Maxell, Inc.                (56) References Japanese Patent Publication 8-10497 (JP, B2)

Claims (1)

(57) [Claims] In an optical disc recording medium on which information is optically recorded, a substrate provided with a recording film and a protective film adhered to the substrate are provided.
A lifting unit, held in the holding portion, and a metal piece or magnetic is attracted to the spindle, the retaining portion is an optical disk recording medium characterized by having substantially the same thermal expansion coefficient as the substrate. 2. In an optical disc recording medium on which information is optically recorded, a substrate provided with a recording film and a protective film adhered to the substrate are provided.
A lifting unit, held in the holding portion, and a metal piece or magnetic is attracted to the spindle, the retaining portion is an optical disc recording, characterized in that it consists of a material having substantially the same coefficient of thermal expansion between the substrate Medium. 3. The optical disk recording medium according to claim 1 , wherein the metal piece or the magnetic body has an annular shape. 4. For optical disc recording media where information is optically recorded
The substrate with the recording film and the spindle.
It has a metal piece or a magnetic body, and the substrate is
Has a holding part made of a material with a coefficient of thermal expansion that is almost the same as the substrate.
However, the metal piece or magnetic substance should be retained in the retaining part.
An optical disk recording medium characterized by: 5. For optical disc recording media where information is optically recorded
The substrate with the recording film and the spindle.
It has a metal piece or a magnetic body, and the substrate is
The metal piece has a holding portion with a coefficient of thermal expansion almost the same as that of the substrate
Alternatively, the magnetic body is held by the holding portion.
Optical disc recording medium. 6. The optical disk recording medium according to claim 2 , wherein the metal piece or the magnetic body has an annular shape. 7. The optical disk recording medium according to claim 4 , wherein the metal piece or the magnetic body has an annular shape. 8. The optical disk recording medium according to claim 5 , wherein the metal piece or the magnetic body has an annular shape.