JPH01220280A - Optical disk - Google Patents

Abstract

PURPOSE:To shorten the start-up time of an optical disk and to accelerate the operation of a system by increasing a friction coefficient in a clamping area by extending a part of a center hub to the clamping area. CONSTITUTION:Each center hub 3 is constituted of a main body part 3a and a flange part 3b extended in a circumferential direction at the outer peripheral part of the main body part, and those main body part 3a and flange part 3b are formed integrally with the same material. The flange part 3b is formed in the clamping area brought into contact with the upper surface of a placing par 5b on a turntable 5, and SUS440C or polycarbonate is used as the material. The static friction coefficient of the SUS440C and the polycarbonate is larger that of glass, which provides around a double friction coefficient, and slippage can be suppressed by the increase of the friction coefficient. In such a way, it is possible to shorten the startup time and the stopping time of the optical disk, and to accelerate the operation of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc on which information can be optically recorded, reproduced, or erased.

[Conventional technology]

2. Description of the Related Art In recent years, so-called optical discs have been developed in which recording, reproduction, or erasing is performed on a disc-shaped recording medium using an optical head using a laser or the like.

These optical disks have a medium on which information can be recorded, reproduced, and erased on a substrate such as glass, plastic, or metal, and recording areas are provided in a concentric or spiral manner.

Here, normally when the disk is rotated by a motor etc.
Mechanical errors cause the disk to run out, making it impossible to accurately track tracks when recording, reproducing, or erasing using light irradiated from an optical head. This is also due to the fact that the intervals between the spiral or concentric recording areas (tracks) are extremely small, approximately 1 to 2 μm. Therefore, in a drive system that drives an optical disk, the optical head uses some method to detect the amount of deviation of the light beam spot from the track, and uses this output value to adjust the position of the light spot used for recording, playback, and erasing to ensure accuracy. It is common to have a servo system that can follow the track section.

However, the capabilities of this servo system are not perfect and have limits, so it is extremely important to manage the amount of center runout within limits to produce optical disks.

For this reason, a disk having a structure as shown in FIG. 6 has been proposed as an example.

That is, the center hubs 13, 13 are located at the center of the optical disc 12 to which the optical disc substrates 11, 11 are integrally joined.
14a, which is the center of rotation of the motor 14, is fitted into the center through hole of each center hub 13 to serve as a reference for the center of rotation. The center hub 13 is made of a ferromagnetic material such as iron, and is attracted by a magnet 16 disposed in the recess 15a of the turntable 15.

The above-mentioned center hub 13 is provided so that when the optical disk 12 is rotated, the center of the track on which information is recorded, reproduced, and erased forms part of the center of the center hub 13 .

By providing the center hub 13 in this manner, it becomes possible to extremely reduce dimensional errors such as eccentricity that occur during the manufacturing process of the optical disc 12. In addition, the center hub 13
is fitted into the recess 15a of the turntable 15, the mounting portion 15b of the turntable 15 supports the optical disk 12 by bringing its upper surface into contact with the clamp area 17 of the optical disk 12. Surface runout will be considerably suppressed.

Now, in such an optical disk device, one of the generally required performances is to shorten the startup time and stop time, which are the time it takes for the optical disk 12 to reach a steady rotation state from a stationary state. . This is useful when optical discs are used frequently, or for so-called jukebox-type devices that store many optical discs and automatically select and load one of them to record, play, and erase information. This is especially important.

[Problem that the invention seeks to solve]

However, when the rotational speed of the turntable 15 is suddenly increased, for example in order to shorten the start-up time, the inertia force that tries to maintain the stationary state of the optical disc 12 causes slippage in the clamp area 17, causing the turntable to slip. This results in a situation where the 15 is idle.

In particular, when the above-mentioned optical disk is made of a glass substrate, its weight is approximately twice as much as that of an optical disk made of plastic, and therefore, approximately two to three times as much torque is required at the time of starting rotation. However, in the case of glass, the coefficient of friction on the surface is smaller than that of plastic. For example, in the case of glass-metal, the static friction coefficient of the contact surface is about 0.1 to 0.2, which is only about half the coefficient of static friction of plastic-metal, which is 0.3 to 0.5. . Therefore, in an optical disk made of a glass substrate, unless the starting time is several times longer than that of an optical disk made of plastic and the rotational speed is gradually increased, slippage will occur in the clamp area 17 as described above.

For this reason, the start-up time cannot be shortened, resulting in a problem that speeding up the operation of the system is hindered.

[Means for solving problems]

In order to solve the above problems, an optical disc according to the present invention has a center hub that is attracted to a magnet arranged in a recess of a turntable, and a center hub that contacts the upper surface of a mounting part formed around the recess. and a clamp area, the center hub is attracted to the magnet, and the clamp area is the! ! In an optical disc that records, reproduces, or erases information by being rotated by the rotation of a turntable while in contact with the upper surface of the mounting part, a part of the center hub is extended to the clamp area, and a part of the center hub is extended to the clamp area. It is characterized by a large friction coefficient.

[Function] According to the above configuration, slipping in the clamp area can be suppressed by the increase in the friction coefficient of the clamp area. As a result, even if the rotational speed of the turntable is rapidly increased or decreased, the optical disk almost certainly rotates as the turntable rotates, and a situation where the turntable idles is avoided. This reduces the start-up time, which is the time it takes for the optical disk to reach a steady rotation state from a stationary state, as well as the stop time, which is the time it takes for an optical disk to reach a stationary state from a steady rotation state, resulting in faster system operation. can be achieved.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 3.

As shown in FIG. 1, the optical disc 1 according to the present invention has the following features:
Two disc-shaped optical memory boards 2 and 2 made of glass.
It is made by integrally joining together, and information can be recorded, reproduced, and erased on both the front and back sides. A through hole 2a is formed in the center of each optical memory board 2, and center hubs 3 are respectively attached so as to cover each through hole 2a. Of course, each center hub 3
is provided so that when the optical disc 1 is rotated, the center of the track coincides with the center of the center hub 3 for the track on which information is recorded, reproduced, and erased.

Each center hub 3 is composed of a main body part 3a and a flange part 3b extending in the circumferential direction on the outer periphery of the main body part 3a, and the main body part 3a and the flange part 3b are integrally formed of the same material. ing. The flange portion 3b is formed in a clamp region that contacts the upper surface of the mounting portion 5b of the turntable 5, and its thickness is set to about 0.1 mm. The mounting portion 5b forms a peripheral wall of the recess 5a in the turntable 5 and supports the optical disc 1, and has a flat upper surface.

On the other hand, the main body part 3a is a part that is fitted into the recess 5a, and has a shape corresponding to the recess 5a. A certain gap is maintained with respect to the magnet 6 built in the recess 5a. In addition, the main body part 3a.
Through holes 3C and 3C are coaxially formed in the center of 3a, and when the main body 3a is fitted into the recess 5a, the shaft 7a, which is the center of rotation of the motor 7, is fitted and the center of rotation is aligned. It has become a standard.

Each center hub 3 is made of a ferromagnetic material such as 5O3440C, and its main body 3a has a recess 5a.
When it fits in, it is attracted by the magnet 6 mentioned above. The optical disc 1 is connected to the center hub 3 described above.
With the main body part 3a attracted to the magnet 6 and the collar part 3b in contact with the upper surface of the placement part 5b, the main body part 3a is rotated by the rotation of the turntable 5 to record, reproduce, or record information. It is designed to be erased.

Note that the center hub 3 may be made of plastic such as polycarbonate, for example, and in such a case, as shown in FIG. Alternatively, the metal plate 8 may be buried in the main body portion 3a, or the center hub 3 may be formed of plastic mixed with magnetic powder. The metal plate 8 and the above-mentioned magnetic powder are attracted by a magnet, and the above-mentioned main body portion 3a is attracted by the above-mentioned magnet 6 in the same manner as described above while being fitted into the recess 5a.

Furthermore, the shape of the center hub 3 is not limited to that described above. For example, as shown in FIG. 3, a protruding part 3d facing into the through hole 2a of the optical memory board 2 is formed on each main body part 3a, and an adhesive layer 9 is interposed between these protruding parts 3d and 3a. The hubs 3 may be fixed to each other by adhesive.

According to the above configuration, the flange portion 3b of the center hub 3 is made of the same material as the main body portion 3a, and is 5US440C1 or polycarbonate. 5US440C
And the coefficient of static friction of polycarbonate is greater than that of glass. For example, in the case of glass and metal, the static friction coefficient of the contact surface is about 0.1 to 0.2, whereas in the case of plastic (polycarbonate) and metal, it is 0.
．． It has a size of 3 to 0.5. Therefore, it is possible to obtain a coefficient of friction that is about twice as large, and slippage can be suppressed by an amount corresponding to the increase in the coefficient of friction. As a result, even if the rotational speed of the turntable 5 is rapidly increased, the optical disc 1 will almost certainly rotate as the turntable 5 rotates, and a situation where the turntable 5 will idle is avoided. As a result, the startup time, which is the time it takes for the optical disc 1 to reach a steady rotation state from a resting state, and the stop time, which is the time it takes for the optical disc 1 to go from a steady rotation state to a resting state, can be shortened, and as a result, System operation can be accelerated.

In particular, as a recording medium, for example, TbFeC.

It is suitable for a magneto-optical disk using a rare earth transition metal film such as a GdTbFe type, a GdTbFe type, or a NdDyFeC0 type. In other words, rare earths and transition metals are sensitive to oxygen and moisture and easily oxidize and corrode.
This is because it is most desirable to use a glass substrate with almost no water permeability or oxygen permeability, and in this way,
This is because when a glass substrate is used, it becomes necessary to eliminate the disadvantages caused by the small coefficient of friction of glass.

Therefore, according to the optical disc of the present invention, by using the above-mentioned glass substrate as its substrate, it is possible to improve the weather resistance of the optical disc and speed up the system operation.

Note that the height of the recording surface of the optical disc 1 described above is increased by the thickness of the flange 3b of the center hub 3, but in the drive system that drives the optical disc 1, the objective lens is adjusted to a predetermined position in order to adjust the focus direction. Since it is movable in the vertical direction within a range, the thickness of the flange portion 3b is 0.
If it is about 1 mm, it will fall within the movable range of the objective lens, and no problem will arise.

[Embodiment 2] Another embodiment of the present invention will be described based on FIGS. 4 and 5. It should be noted that members having the same functions as those in the first embodiment described above are given the same reference numerals and their explanations will be omitted.

In this embodiment, as shown in FIG. 4, each center hub 3 has a main body portion 3a that fits into the recess 5a of the turntable 5, and a mounting portion 5b of the turntable 5, as in the first embodiment. A locking part 3e having a contacting collar part 3b and a through hole 3c through which the shaft 7a of the motor 7 is inserted, and extending in the circumferential direction from the outer circumferential side of the collar part 3b.
It is equipped with On the other hand, the through hole 2a of each optical memory board 20 is formed to be larger than the diameter of the flange 3b, so that the locking part 3e is locked to the periphery of the through hole 2a in each optical memory board 2. It has become. Each center hub 3 is securely fixed to the optical memory board 2 by its locking portion 3e, but the gap 10 formed between the center hubs 3 is filled with adhesive and the center hub The optical disc 1 may be made more robust by also fixing the discs 3 and 3 together.

By bringing the above-described flanges 3b inside the through holes 2a in the optical memory board 2, each of the flanges 3b can be formed at the same height as the surface of the optical memory board 2. Therefore,
As in the first embodiment, it is possible to prevent the height of the recording surface of the optical memory substrate 2 from increasing by the thickness of the flange portion 3b, and to avoid substantial erosion of the movable range of the objective lens. It becomes possible.

As shown in FIG. 5, by forming a tapered part 3f between the locking part 3e and the flange part 3b in the center hub 3, when the optical disc 1 is placed on the turntable 5, the taper The flange portion 3b of the center hub 3 is guided to the @ placement portion 5b by the portion 3f, making it easier to load the optical disc 1 onto the turntable 5. In this case, the center hub 3 is provided only on one side, but the center hub 3 is not limited to this, and may be provided on each of the optical memory boards 2.

〔Effect of the invention〕

As described above, the optical disc according to the present invention includes a center hub that is attracted to a magnet arranged in a recess of a turntable, and a clamp area that contacts the upper surface of a mounting part formed around the recess. When the center hub is attracted to the magnet and the clamp area is in contact with the top surface of the mounting section, the turntable is rotated to record, reproduce, or erase information. In this optical disc, a part of the center hub is extended to the clamp area to increase the coefficient of friction in the clamp area.

As a result, slippage in the clamp area can be suppressed, and even if the rotation speed of the turntable is rapidly increased, the optical disc will almost certainly rotate as the turntable rotates. Situations such as idling are avoided. Therefore, the start-up time and stop time of the optical disc can be shortened, and as a result, the system operation can be speeded up.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a sectional view showing an optical disc placed on a turntable, FIG. 2 is a sectional view of a center hub,
FIG. 3 is a cross-sectional view of an optical disc having an adhesive layer between protrusions, and FIGS. 4 and 5 show other embodiments. FIG. 4 shows an optical disc placed on a turntable. 5 is a sectional view showing a state in which an optical disc with a tapered center hub is placed on a turntable, and FIG. 6 is a sectional view showing a conventional example, in which an optical disc is turned. It is a sectional view showing a state where it is placed on a table. 1 is an optical disk, 2 is an optical memory board, 2a is a through hole, 3
is the center hub, 3a is the main body, 3b is the flange (clamp area), 3f is the taper portion, 5 is the turntable, 5a is the recessed portion, 5b is the R rest, 6 is the magnet, 7 is the motor, 7a is a shaft, and 8 is a metal plate. Figure 1 1 = ￥ Figure 3 4b' Kanimuro f'- Figure 2

Claims (1)

[Scope of Claims] 1. The turntable has a center hub that is attracted to a magnet arranged in a recessed part, and a clamp area that contacts the upper surface of a mounting part formed around the recessed part, In an optical disc that records, reproduces, or erases information by rotating a turntable with the center hub attracted to the magnet and the clamp area in contact with the upper surface of the mounting section, An optical disc characterized in that a part of the center hub extends into the clamp area to increase the friction coefficient of the clamp area.