JPH08315413A - Optical disk and disk driving device - Google Patents

Abstract

PURPOSE: To make both recording layers possible to well execute recording and reproducing of information by providing an optical disk with a polarizing layer between its first recording layer and second recording layer. CONSTITUTION: The optical disk 8 is formed by successively laminating, from below to above, that is, in the incident direction of rays, a first base material 2, a first recording layer 9, an intermediate layer 10, a dichroic polarizing plate 11 which is the polarizing layer, a second base material 12, a second recording layer 13 and protective layer 6. Accordingly, the generation of the reflected light from the second recording layer 13 as a noise in the reflected light of the first reflection layer is prevented because the rays for scanning the first recording layer 9 do not arrive at the second recording layer 13 if the rays are polarized in the direction where the rays do not transmit the polarizing layer 11 by providing the optical disk with the polarizing layer 11 between the first recording layer 9 and the second recording layer 13. The focus is thereby well locked at the first recording layer 9 and the good execution of the recording and reproducing of the information is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a disk drive device.

[0002]

2. Description of the Related Art At present, an optical disc on which information is reproduced by a light beam is realized as a CD (Compact Disk), and an optical disc on which information is recorded by a light beam is also called an MO (Magneto Optical Disk). Has been realized. Although such an optical disc realizes a large capacity and a high density of recorded information, it has been proposed that the optical disc has a multi-layer structure in order to realize a further large capacity and a high density. There is.

A conventional example of such an optical disc will be described below with reference to FIG. It should be noted that the description will be given here on the assumption that the light beam for reproducing information is emitted from the lower side to the upper side.

In this optical disc 1, the first base material 2, the first reflection layer 3, the second base material 4, the second reflection layer 5, and the protective layer 6 are arranged from the lower side to the upper side, which is the direction of incidence of light rays. They are stacked in order. The first base material 2, the second base material 4, and the protective layer 6 are made of a transparent resin, and the first reflective layer 3
Is a semi-transparent dielectric film, and the second reflective layer 5 is
It consists of a total reflection metal film. Concavities and convexities corresponding to information are formed on the upper surfaces of the first and second base materials 2 and 4, and the first and second reflective layers 3 and 5 are formed in accordance with the concavities and convexities. The information reproduced by the light beam is fixedly recorded.

Like the existing CD, the optical disc 1 having such a structure has information fixedly recorded at the time of its production,
This information is reproduced by the light beam. At this time, since separate information is recorded on the first reflective layer 3 and the second reflective layer 5, the first and second reflective layers can be adjusted by adjusting the position of the focal point of the light beam emitted from below. The information recorded in layers 3 and 5 is reproduced individually.

An example of a method for producing such an optical disc 1 will be described below. First, the first base material 2 is manufactured by resin molding using a stamper (not shown) in which irregularities corresponding to information are formed in advance, and the first reflection layer 3 is formed on the upper surface of the first base material 2 by a dielectric material. Is formed by sputtering.
Next, the resin is poured on the surface of the first reflective layer 3 to form the second base material 4 by the stamper, and the second reflective layer 5 is formed on the upper surface by sputtering metal. Finally, the protective layer 6 is formed by resin molding, whereby the optical disc 1 is produced.

A disk drive device (not shown) for reading information from the first and second reflective layers 3 and 5 of the optical disk 1 as described above adjusts the position of the objective lens 7 to adjust the position of the first and second reflective layers 3. , 5 to lock the focus. In the optical disc 1 as described above, it is usually considered that the first reflective layer 3 is mainly used and the second reflective layer 5 is used auxiliary.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Has the same function as the existing CD, but since the information is recorded on each of the first and second reflective layers 3 and 5, the recording capacity of the information can be doubled.

When reading information from the first and second reflection layers 3 and 5 of the optical disc 1 as described above, the focus position is changed by adjusting the position of the objective lens 7 as described above. The focus may be locked on the first and second reflective layers 3 and 5. Further, since the light beam reading the first reflective layer 3 reaches the second reflective layer 5, the reflected light of the second reflective layer 5 is generated as noise in the reflected light of the first reflective layer 3.

In order to prevent such a situation, it has been proposed to form the second base material 4 to a thickness of 40 (μm) and separate the first and second reflection layers 3 and 5 from each other. In this case, it is difficult to improve the productivity because the second base material 4 needs to be manufactured by pouring resin or the like.

For example, in the optical disk disclosed in Japanese Unexamined Patent Publication No. 6-36343, an opening groove is formed in the center of the track of the first recording layer, and the wavelength of the light beam is switched in two steps.
That is, since the spot diameter is large for a long wavelength light beam, information is recorded on both sides of the opening groove of the first recording layer.
Since the spot diameter of a light beam having a short wavelength is small, the spot diameter is passed through the opening groove of the first recording layer to record information on the second recording layer.

However, in practice, it is difficult to change the wavelength of the laser light source, so it is necessary to prepare two laser light sources having different wavelengths. Further, the current short-wavelength laser light source is not sufficient in output and durability, so that the above-mentioned optical disc is not practical. Further, since the information is recorded on the first recording layer with a large spot diameter, the recording density of the information is reduced and the expansion of the recording capacity is hindered.

[0013]

According to another aspect of the present invention, there is provided an optical disc in which a first recording layer and a second recording layer are sequentially laminated in a light beam incident direction for recording and / or reproducing information. In an optical disc in which at least one of recording and reproducing of information is performed by a light beam in each of these recording layers, a polarizing layer is formed between the first recording layer and the second recording layer.

The optical disc of the second aspect of the present invention is the optical disc of the first aspect of the invention, in which the polarization directions of the polarizing layers are concentrically located.

An optical disk according to a third aspect of the present invention is the optical disk according to the first aspect of the present invention, in which the polarization direction of the polarizing layer is radial.

According to a fourth aspect of the present invention, there is provided a disk drive device in which at least one of recording and reproduction of information on the optical disk is performed by a light beam, and a light beam polarization means for linearly polarizing the light beam is provided.

A disk drive apparatus according to a fifth aspect of the present invention is the disk drive apparatus according to the fourth aspect,
The direction switching means is provided for switching the polarization direction of the light beam to one of the direction parallel to the radius of the optical disc and the direction orthogonal thereto.

[0018]

In the optical disc of the first aspect of the present invention, since the polarizing layer is located between the first recording layer and the second recording layer, the light beam scanning the first recording layer is orthogonal to the polarization direction of the polarizing layer. When deflected in the direction, this light ray reaches the first recording layer but does not reach the second recording layer.

In the optical disc of the second aspect of the present invention, since the polarization directions of the polarization layers are concentric, the polarization direction of the polarization layer with respect to the light rays does not change even when the optical disc rotates.

In the optical disc of the third aspect of the present invention, since the polarization direction of the polarization layer is located radially, the polarization direction of the polarization layer with respect to the light beam does not change even if the optical disc rotates.

In the disk drive device according to the fourth aspect of the present invention, since the light beam polarizing means linearly polarizes the light beam, there is a polarizing layer between the first recording layer and the second recording layer of the optical disc,
If the polarization direction of this polarizing layer is orthogonal to the polarization direction of light rays,
This ray reaches the first recording layer but does not reach the second recording layer.

In the disk drive device according to the fifth aspect of the invention, the direction switching means switches the polarization direction of the light beam to one of the direction parallel to the radius of the optical disk and the direction perpendicular thereto.
If the polarizing layer exists between the first recording layer and the second recording layer of the optical disc, the state where the light beam reaches the second recording layer and the state where it does not reach the second recording layer are switched.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The optical disk 8 shown in this embodiment is
With respect to the above, the same portions as those of the optical disc 1 described above as a conventional example utilize the same names and reference numerals, and detailed description thereof will be omitted.

First, the optical disc 8 of the present embodiment is similar to the optical disc 1 described above as a conventional example in that the first base material 2, the first recording layer 9, and the first base material 2 are directed upward from below, which is the incident direction of light rays. The intermediate layer 10, the dichroic polarizing plate 11 serving as a polarizing layer, the second base material 12, the second recording layer 13, and the protective layer 6,
They are stacked in order.

The first and second recording layers 9 and 13 are made of, for example, a phase change type metal, and both recording and reproducing of information are performed by light rays. As shown in FIG. 2 (a), the dichroic polarizing plate 11 has concentric polarization directions, and as shown in FIGS. 3 and 4, light rays having orthogonal polarization directions are totally reflected. Light rays with parallel polarization directions are transmitted.

Incidentally, the intermediate layer 10 and the second base material 12
Although the film thicknesses of and are about 5 (μm), since the plate thickness of the dichroic polarizing plate 11 is 30 (μm), the first and second recording layers 9 and 13 are 40 (μm) as in the conventional case. Have been separated from.

Then, the disk drive device 14 of this embodiment
Has a laser light source 15 as shown in FIG.
A Pockels cell 16 and a half mirror 17, which are light beam polarization means, are arranged in the emission optical path of the laser light source 15. An objective lens 18 is movably supported in the optical axis direction on the reflection optical path of the half mirror 17, and a turntable (not shown) for supporting the optical disk 8 is provided at a position facing the objective lens 18. ing. A beam splitter 19 is arranged in the transmission optical path of the half mirror 17, and two photodiodes 20, 21 are arranged one by one in the spectral direction of the beam splitter 19.

The Pockels cell 16 can linearly polarize the light beam emitted from the laser light source 15, and can switch the polarization direction to a right angle. For this reason, since the linearly polarized light of the light beam applied to the optical disk 8 is switched to one of the direction parallel to the radius of the optical disk 8 and the direction perpendicular thereto, the direction switching means is realized here.

In such a structure, in this embodiment,
The optical disk 8 and the disk drive device 14 are realized as mutually exclusive devices, and the disk drive device 14 records and reproduces information on the optical disk 8. At this time, in the disk drive device 14, the light beam emitted by the laser light source 15 is linearly polarized by the Pockels cell 16, and the polarization direction is made perpendicular to the first and second recording layers 9 and 13 of the optical disk 8. Switch.

More specifically, when recording or reproducing information on the first recording layer 9 of the optical disk 8, the disk drive device 14 uses the Pockels cell 16 to change the polarization direction of the light beam to the dichroic polarizing plate 11 of the optical disk 8. Make it orthogonal to the polarization direction. Then, since the light beam of the disk drive device 14 does not pass through the dichroic polarizing plate 11 of the optical disk 8, the light beam for reproducing the first recording layer 9 does not cause the reflected light of the second recording layer 13 as noise. Since the focus of the light beam is not locked to the second recording layer 13,
The first recording layer 9 can be reliably focused.

When recording or reproducing information on the second recording layer 13, the polarization direction of the light beam is switched to be parallel to the polarization direction of the dichroic polarizing plate 11. Then, the light beam of the disk drive device 14 is transmitted through the dichroic polarizing plate 11 of the optical disk 8, so that information can be recorded or reproduced on the second recording layer 13.

In this case, the reflected light of the first recording layer 9 is generated as noise in the light beam reproducing the second recording layer 13 as in the conventional case, but as described above, the first recording layer 9 is mainly used. If the second recording layer 13 is used as the auxiliary recording area and the second recording layer 13 is used as the auxiliary recording area, it is useful that the first recording layer 9 alone can scan well. Moreover, if the focus of the light beam can be reliably locked on the first recording layer 9 as described above, the focus is set on the basis of this position.
Since it is easy to move to the first and second recording layers 9,
It is possible to satisfactorily lock the focus on both of them.

Moreover, since the plate thickness of the dichroic polarizing plate 11 provided between the first and second recording layers 9 and 13 is 30 (μm), the film thickness of the intermediate layer 10 and the second base material 12 is 5 (μm) is sufficient, and since it can be formed by a thin film technique such as spin coating or sputtering, it has good productivity.

When manufacturing such an optical disk 8, on the surface of the first recording layer 9 formed in the same manner as the conventional one,
An ultraviolet curable 2P resin is applied by spin coating to a film thickness of 5 (μm), a dichroic polarizing plate 11 is placed thereon, and ultraviolet rays are irradiated to cure the 2P resin to form the intermediate layer 10. At the same time, the dichroic polarizing plate 11 is adhered to the intermediate layer 10. The surface of the dichroic polarizing plate 11 is coated with 2P resin by spin coating to a film thickness of 5 (μm), the stamper is pressure-bonded thereto, and the second base material 12 is formed by irradiating ultraviolet rays. Similarly to the above, the second recording layer 13 and the protective layer 6 are formed.

It should be noted that the optical disk 8 of the present embodiment has the structure shown in FIG.
As shown in (a), since the polarization directions of the dichroic polarizing plate 11 are concentrically arranged, the polarization direction of the dichroic polarizing plate 11 with respect to the light beam does not change even if the optical disc 8 is rotationally driven. Therefore, the disk drive device 14 can scan the first and second recording layers 9 and 13 of the rotating optical disk 8 favorably with the deflected light beam, and the intensity of this light beam does not change. Note that the present invention is not limited to the above-described embodiment, and the dichroic polarizing plate 22 whose polarization direction is located in the radial direction functions similarly as shown in FIG. 2 (b).

Further, although the optical disc 8 in which information can be rewritten is illustrated in the present embodiment, the present invention is not limited to the above-mentioned embodiment, and can be applied to a read-only or write-once optical disc. Similarly, in the present embodiment, the disk drive device 14 that both records and reproduces information is illustrated, but
The present invention is not limited to the above embodiment, but can be applied to a reproduction-only or recording-only disk drive device.

[0037]

According to the optical disk of the first aspect of the present invention, since the polarizing layer is formed between the first recording layer and the second recording layer, if the light beam is polarized in a direction that does not pass through this polarizing layer, Since the light beam scanning the first recording layer does not reach the second recording layer, information can be recorded and reproduced well on the first recording layer, and the focus is well locked on the first recording layer. be able to.

In the optical disc of the second aspect of the present invention, since the polarization directions of the polarization layers are concentrically arranged, the polarization direction of the polarization layer with respect to the light rays does not change even if the optical disc rotates, so that information recording or reproduction is performed. Can be performed stably.

In the optical disc of the third aspect of the present invention, since the polarization direction of the polarization layer is radial, the polarization direction of the polarization layer with respect to the light beam does not change even when the optical disc rotates, so that information recording or reproduction is performed. Can be performed stably.

In the disk drive device according to the fourth aspect of the present invention, since the light beam polarizing means for linearly polarizing the light beam is provided, the polarizing layer that does not transmit the light beam is the first recording layer and the second recording layer of the optical disk. If present, the light beam scanning the first recording layer does not reach the second recording layer, so that information can be recorded and reproduced well on the first recording layer, and The focus can be locked well.

In the disk drive device of the fifth aspect of the present invention, by providing the direction switching means for switching the polarization direction of the light beam to one of the direction parallel to the radius of the optical disk and the direction perpendicular thereto, the concentric circles of the optical disk or the radiation. If there is a polarizing layer having a polarization direction parallel to that between the first recording layer and the second recording layer, it is possible to switch the arrival of the light beam to the second recording layer by switching the polarization direction.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an optical disc according to an embodiment of the present invention.

FIG. 2 is a plan view showing a dichroic polarizing plate serving as a polarizing layer.

FIG. 3 is a schematic diagram showing a relationship between polarization directions of a polarizing plate and light rays.

FIG. 4 is a characteristic diagram showing a relationship between a direction of a polarizing plate and a light ray and a transmittance.

FIG. 5 is a side view showing a disk drive device.

FIG. 6 is a vertical sectional front view showing an optical disc of a conventional example.

[Explanation of symbols]

 8 Optical Disc 9 First Recording Layer 11 Polarizing Layer 13 Second Recording Layer 14 Disc Driving Device 16 Light Beam Polarizing Means

Claims (5)

[Claims] 1. A first recording layer and a second recording layer are sequentially laminated in the incident direction of a light beam for performing at least one of recording and reproducing of information, and recording and reproducing of information by each of these recording layers. An optical disc in which at least one of the above is performed by light rays, wherein a polarizing layer is formed between the first recording layer and the second recording layer. 2. The optical disc according to claim 1, wherein the polarization directions of the polarizing layers are concentrically arranged. 3. The optical disk according to claim 1, wherein the polarization direction of the polarizing layer is radial. 4. A disk drive device for performing at least one of recording and reproducing of information on an optical disk by means of a light beam, wherein a light beam polarization means for linearly polarizing the light beam is provided. 5. The disk drive device according to claim 4, further comprising direction switching means for switching the polarization direction of the light beam into one of a direction parallel to the radius of the optical disk and a direction perpendicular thereto.