JPH11232701A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-layer optical disk capable of performing recording/ reproducing in an existing optical disk device. SOLUTION: An optical disk 32 is made to have a thickness of about 1.8 mm as a whole by sticking the backsides of a CD layer 34 having a thickness of about 1.2 mm and a high-density layer 36 having a thickness of about 0.6 mm to each other. In the center of the CD layer 34, a center hole 44 having a diameter of 15 mm is formed. In the center of the high-density layer 36, a center hole 52 having a large diameter is formed. Disk clamping is performed in the part of the CD layer 34 having a thickness of about 1.2 mm in the center hole 52 of the high-density layer 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk (read-only disk or recordable disk) having two disk layers, which can be reproduced or recorded by an existing optical disk device.

[0002]

2. Description of the Related Art As an optical disk having two disk layers, for example, an optical disk having a sectional structure shown in FIG. 2 has been proposed. The optical disk 10 has two disk layers 12, 1
4 are bonded together. Disk layer 12 (C
The D layer) has a thickness of 0.6 mm, and a reflective recording film 18 for recording or recording information in a CD format is formed on the back side of the transparent substrate 16. The disk layer 14 (high-density layer) has a thickness of 0.6 mm, and a semi-reflective recording film 22 that records or records information in a predetermined high-density recording format (for example, DVD format) is formed on the back side of the transparent substrate 20. Is formed. The two disk layers 12, 14 are integrated by laminating the front surface 12a of the CD layer 12 and the rear surface 14a of the high-density layer 14, and have an overall thickness of 1.2 mm.

When the optical disk 10 is set in a reproducing apparatus or recording apparatus conforming to the CD standard, a laser beam 24 having a wavelength of 780 nm emitted from an optical pickup is used for the objective lens 2.
6, the beam passes through the semi-reflective recording film 22 of the high-density layer 14, forms a beam spot on the reflective recording film 18 of the CD layer 12, and a recording signal is detected from the reflective recording film 18 or the reflective recording film The signal is recorded at 18. When the optical disk 10 is set in a reproducing device or a recording device conforming to a high-density disk standard (for example, DVD standard), a short wavelength (635 to 650 n in the case of DVD) emitted from an optical pickup is used.
m) is converged by the objective lens 30 to form a beam spot on the semi-reflective recording film 22 and a recording signal is detected from the semi-reflective recording film 22 or the semi-reflective recording film 22
Is recorded.

[0004]

According to the optical disc 10 having the structure shown in FIG. 2, when the CD layer 12 is reproduced or recorded, the laser beam 24 is attenuated when transmitting through the semi-reflective recording film 22, so that the reproduction is performed. Depending on the type of the device or the recording device, reproduction or recording may be difficult due to insufficient light quantity.

An object of the present invention is to provide an optical disk having two disk layers capable of reliably performing reproduction or recording with an existing optical disk device by solving the problems in the conventional technology. .

[0006]

According to the optical disk of the present invention, two disk layers each having a recording film are integrally formed by abutting the back surfaces thereof, and a center hole for clamping is formed at the center. The thickness of the portion on the inner peripheral side of the information recording area of both disc layers is formed to be approximately the thickness of one of the disc layers in the information recording area. According to this optical disk, since the two disk layers are integrally formed by abutting their back surfaces, reproduction or recording of each disk layer is performed by irradiating a light beam from the front surface thereof. Therefore, when reproducing or recording on one disk layer, the light beam does not pass through the other recording film, so that the attenuation is small, and the reproduction or recording can be reliably performed by the existing reproducing apparatus or recording apparatus. In this case, since the two disk layers need to be formed to the required thicknesses respectively, the overall thickness is increased. However, the information recording areas of both disk layers are also determined by the thickness of the inner peripheral portion. By forming the recording area to have a thickness of about one disk layer in the recording area, it can be clamped by an existing reproducing apparatus or recording apparatus.

The disk of the present invention is constituted by, for example, forming a disk layer of each layer on a transparent substrate, forming a recording film thereon, and covering it with a protective film, and bonding and integrating the two disk layers by abutting their back surfaces together. Can be configured. As a structure for forming the thickness of the portion on the inner circumference side of the information recording area of both disk layers to be approximately the thickness of one of the disk layers in the information recording area, the inner circumference side is formed on one disk layer. (The center hole of the other disk layer is formed large.) In addition, the inner peripheral portions of both disk layers are formed thinly, and they are laminated to form a thickness of approximately one layer. You can also.

[0008] The two disk layers include, for example, a relatively thick disk layer on which information is recorded or recorded at a relatively low recording density and a relative disk layer on which information is recorded or recorded at a relatively high recording density. It can be constituted by a thin disk layer. In this case, a portion on the inner peripheral side of the information recording area of both disc layers can be constituted only by a thicker disk layer, and a center hole for clamping can be formed in the inner peripheral portion.

More specifically, the optical disk of the present invention has a CD layer having a thickness of 1.2 mm according to the CD standard and a high-density recording layer having a recording density higher than the normal CD standard and a thickness smaller than 1.2 mm. The layers are integrally formed with their backs facing each other, the center hole diameter of the CD layer is formed to be 15 mm, and the diameter of the center hole of the high-density layer is larger and higher than the outer diameter of the clamping area of the CD standard. It can be configured as an optical disk formed smaller than the inner diameter of the information recording area of the density layer. The high-density layer can be a high-density layer according to, for example, the DVD standard, the double-density CD standard, the super audio CD standard, and the like. The recording film in the high-density layer may have a plurality of layers (for example, two layers).

[0010]

(Embodiment 1) An embodiment of an optical disk according to the present invention will be described. Here, one disk layer is constituted by a CD layer as a relatively thick disk on which information can be recorded or recorded at a relatively low recording density, and another disk layer is constituted by a relatively high recording density. A case where a relatively thin disk on which information is recorded or recordable is constituted by a high-density layer such as a DVD will be described. 1A and 1B show the configuration, in which FIG. 1A is a plan view (shown in a half-split state), FIG. 1B is a sectional view passing through the center axis of the disk, and FIG. 1C is a part of the sectional view of FIG. It is an enlarged view.

The optical disk 32 has a diameter of 120 mm.
It is composed of a CD layer 34 and a high density layer 36. CD layer 3
Reference numeral 4 denotes a structure in which a recording film 40 (reflection film) is formed on one surface of a transparent substrate 38 such as polycarbonate and is covered with a protective film 42, and the overall thickness is 1.2 mm. A center hole 44 having a diameter of 15 mm is formed at the center of the CD layer 34. A signal is recorded or recordable on the recording film 40 in accordance with the CD standard.

The high-density layer 36 is formed by forming a recording film 48 (reflection film) on one surface of a transparent substrate 46 made of polycarbonate or the like, and covering the same with a protective film 50. The overall thickness is 0.6 mm. ing. A center hole 52 is formed at the center of the high-density layer 36. The diameter of the center hole 52 is larger than the outer diameter of the clamping area 54 of the CD layer (the area having the inner diameter (maximum) of 26 mm and the outer diameter (minimum) of 33 mm) and the information recording area 56 (reproduction) of the high-density layer 36. In the case of a dedicated disk, the innermost circumference is formed smaller than the inner diameter of an area starting from the lead-in area, and in the case of a recordable disk, the innermost circumference is formed smaller than the inner diameter of the area starting with the utility area such as PCA or PMA. The recording film 48 has a predetermined high density standard (for example, D
The signal is recorded or recordable according to the VD standard). The CD layer 34 and the high-density layer 36 are integrated by bonding their back surfaces (bonding surface 57) together and bonding them with an adhesive to form the optical disc 32 having a total thickness of 1.8 mm.

FIG. 3 shows a state during reproduction or recording of the CD layer 34 of the optical disk 32 shown in FIG. A turntable 60 and a center spindle 62 are fixedly formed on the top of a rotating shaft 58 of a spindle motor of a normal reproducing apparatus or recording apparatus of the CD standard. The optical disk 32 is a CD
The center spindle 62 is inserted into the center hole 44 with the layer 34 facing down, and the front surface 34 a of the CD layer 34 is placed and supported on the turntable 60. The clamper 64 is formed to have a smaller diameter than the center hole 52 of the high-density layer 36,
The CD layer 34 is sandwiched and supported between the turntable 60 and the turntable 60.

The laser beam 66 has a wavelength of 780 nm, is emitted upward from the lower surface of the optical disk 32, is converged by an objective lens 68 having a numerical aperture of 0.4 to 0.5, and
The light is incident from the front surface 34 a side of the layer 34 and forms a beam spot on the recording film 40. By driving the spindle motor to rotate the optical disk 32, a signal is read from the recording film 40 or a signal is written to the recording film 40.

FIG. 4 shows a state at the time of reproduction or recording of the high-density layer 36 of the optical disk 32 of FIG. A turntable 72 and a center spindle 74 are fixedly formed on the top of a rotating shaft 70 of a spindle motor of a normal reproducing apparatus or recording apparatus of a predetermined high density standard. The optical disc 32 is inserted with a center spindle 74 into the center hole 44 with the high-density layer 36 facing downward, and the back surface 34b of the CD layer 34 is inserted.
Are placed and supported on the turntable 72. The turntable 72 has a smaller diameter than the center hole 52 of the high-density layer 36. The clamper 76 is in close contact with the front surface 34a of the CD layer 34, and supports the CD layer 34 with the turntable 72 therebetween.

The laser beam 78 has a wavelength of 635-650 nm.
(For DVD, Super Audio CD) or 7
At a wavelength of 80 nm (in the case of a double-density CD), the light is emitted upward from the lower surface side of the optical disk 32 and has a numerical aperture of 0.6 to 0.5.
Objective lens 65 (for DVD, super audio CD) or 0.5-0.6 (for double density CD)
The light is converged at 9 and is incident from the front surface 36 a side of the high-density layer 36 to form a beam spot on the recording film 48. By driving the spindle motor to rotate the optical disc 32, a signal is read from the recording film 48 or a signal is written to the recording film 48. In this case, since the high-density layer 36 is located below the upper surface of the turntable 72, a normal disk (a disk having an overall thickness of 1.2 mm and consisting only of the high-density layer) is used. Although the focus point is lower than in the case of reproducing or recording, the working distance of the optical head is generally 1 mm or more, so that recording or reproducing can be performed without any trouble.

(Embodiment 2) In the above embodiment, the center hole 52 of the high-density layer 36 is formed to have a large diameter so that clamping is performed only by the CD layer 34 having a thickness of 1.2 mm. By forming both the layer 34 and the high-density layer 36 on the inner peripheral side of the information recording area thinner,
The plate thickness at the clamp location can be 1.2 mm.
FIG. 5 shows an example of such a configuration. In the optical disk 80 of FIG. 5, the same reference numerals are used for the portions common to FIG. The optical disc 80 has a structure in which the CD layer 34 and the high-density layer 36 are joined together by bonding their back surfaces with an adhesive.

The front surface 34a of the CD layer 34 and the high-density layer 3
6, a circular recess 82 is formed in a central portion 80a of the front surface 36a.
84 are formed, and the thickness of the portion 80a is formed to be about 1.2 mm in total. This thin plate part 80
The diameter a is larger than the outer diameter (minimum 33 mm) of the clamping area of the CD standard and smaller than the inner diameter of the information recording area of both disk layers 34 and 36. At the center of the thin plate portion 80a (the center of the optical disk 80), a center hole 44 for clamping having a diameter of 15 mm is formed on both disk layers 3a.
4, 36 are formed. This optical disk 8
0 indicates both disc layers 3 in the same manner as in FIGS.
4, 36 can be reproduced or recorded.

[Brief description of the drawings]

FIG. 1 is a plan view (shown in a half-split state) showing an embodiment of an optical disk of the present invention, a cross-sectional view passing through the center axis of the disk, and a partially enlarged view of the cross-sectional view.

FIG. 2 is a cross-sectional view of a conventional two-layer optical disk.

FIG. 3 is a cross-sectional view showing a state in which the optical disc of FIG. 1 is reproduced or recorded by a normal reproducing apparatus or recording apparatus of the CD standard.

FIG. 4 is a cross-sectional view showing a state where the optical disc of FIG. 1 is reproduced or recorded by a normal high-density standard reproducing apparatus or recording apparatus.

FIG. 5 is a view showing another embodiment of the optical disc of the present invention, and is a cross-sectional view passing through the center axis of the disc.

[Explanation of symbols]

 32,80 optical disk 34 CD layer (relatively thick disk layer) 36 high density layer (relatively thin disk layer) 44 center hole of CD layer, center hole for clamping 52 center hole of high density layer 54 clamping area 56 Information recording area

Claims (3)

[Claims] 1. Two disk layers each having a recording film formed thereon are integrally formed by abutting the back surfaces thereof, a center hole for clamping is formed at the center, and an information recording area of both disk layers is formed. An optical disc in which the thickness of the inner peripheral portion is formed to be substantially the thickness of one disc layer in the information recording area. 2. A relatively thick disk layer on which information can be recorded or recorded at a relatively low recording density and a relatively thin disk layer on which information can be recorded or recorded at a relatively high recording density. The rear surfaces of these discs are joined together to form an integral part, the part on the inner periphery side of the information recording area of both disc layers is composed only of a thicker disc layer, and a center hole for clamping is formed in the inner periphery part. Optical disc. 3. A CD standard CD layer having a thickness of 1.2 mm,
Recording density is higher than normal CD standard and thickness is 1.2mm
A thinner high-density layer is integrally formed by abutting the back surfaces thereof, and the center hole diameter of the CD layer is formed to be 15 mm. An optical disk formed larger than the inner diameter of the information recording area of the high-density layer.