JP2000113515A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium of a stuck type which is little in camber. SOLUTION: This optical information recording medium is provided with a first substrate 1 having a first information area 2 where first information is recorded on one side, a second substrate 4 which has a pseudo information area 5 where pseudo information is recorded on one side and which has the same material and nearly the same size as those of the first substrate 1 and an adhesive layer 6 by which the first and the second substrate 1, 4 are stuck together. The inner and the outer diameters of the first information area 2 are nearly the same as those of the pseudo information area 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium comprising two substrates bonded together.

[0002]

2. Description of the Related Art In recent years, various disc-shaped optical information recording media have been put to practical use. As playback-only ones, compact disks (Compact Disks: CDs), video disks and the like are widely used. Among them, CD-DA (Compact Disk-Digital Aud)
io) and CDs based on the CD format as software applications for computers and game consoles
-ROM (Compact Disk-Read Only Memory) forms a large market. MPEG (Moving Picture E)
With the development of image compression technology such as xpert Group), video CDs that can record a one-hour moving image on a single CD are also on the market.

Further, DVD (Digital Versat) is used as a next-generation medium such as CD-DA, CD-ROM, and video CD.
ile Disk). The DVD is a large-capacity optical disk suitable for recording data having a large amount of information such as a digitalized video signal. DVDs employ some new technologies to increase the recording density of optical discs in order to secure a large capacity. For example, the thickness of the substrate may be .0.
6mm, two substrates are bonded together and the thickness is 1.2mm
Of the optical disk. DVD includes
A single-layer DVD in which information is recorded on only one substrate,
There is a multilayer DVD in which information is recorded on both substrates.

[0004] The structure of a typical DVD will be described below.
FIG. 5 is a schematic diagram showing a cross-sectional structure of a conventional single-layer DVD, DVD-5. In the figure, 101 is a first substrate, 102 is a reflective film, 103 is a second substrate, 104 is an adhesive layer, and 105 is a pickup. First substrate 101
An information area in which information is recorded as a pit row is formed on one side of the optical disk, and is covered with a reflective film 102. The pit row is formed by being modulated by data to be recorded. The first substrate 101 is bonded via an adhesive layer 104 to a second substrate 103 which is a dummy substrate on which no pit row is formed. The information recorded in the information area is reproduced by the pickup 105.

FIG. 6 shows a DVD which is a conventional multilayer DVD.
It is a schematic diagram for showing the cross-sectional structure of -10. In the figure, the same parts as those in FIG.
A first information area in which information is recorded as a pit row is formed on one surface of the first substrate 101, and is covered with a reflective film 102. The same applies to the second substrate 103. A second information area in which information is recorded as a pit row is formed on one surface of the second substrate 103, and the second information area is covered with the reflective film 102. The first substrate 101 and the second substrate 103 are attached to each other with the readout surface facing outside through an adhesive layer 104. DVD-10 is pickup 105
, Or the optical disk is turned over so that the pickup 105 reproduces both sides from one direction.

In the future, when it is necessary to increase the recording density of an optical disk compared to a DVD, it is expected that the pit shape will be further reduced and the track pitch will be further reduced. In order to reproduce an optical disk having such small pits and a narrow track pitch, the diameter of the light spot is proportional to λ / NA (where λ is the wavelength of the reproduction laser beam and NA is the numerical aperture of the objective lens). It is necessary to perform reproduction by a reproducing apparatus equipped with an optical pickup using a laser beam having a wavelength and an objective lens having a high NA (Numerical Aperture). Since the coma caused by the tilt (warp) of the disc and the tilt of the optical axis of the pickup is proportional to λ / NA3, the warpage of the disc and the adjustment of the pickup must be strictly controlled if the substrate thicknesses are equal. In order to facilitate the adjustment of the disc tilt and the optical pickup, the thickness of one substrate is 0.6 m, which is the thickness of the DVD.
It seems to be thinner than m.

When the thickness of the substrate is reduced, it is considered that the substrate is likely to be warped. In order to suppress the warpage of a thin substrate, the conditions for forming the substrate, the conditions for storing the formed substrate, and the conditions for laminating the substrates must be strictly controlled.However, it is not possible to completely eliminate the warpage of the substrate itself. It is considered possible.

Therefore, in order to reduce the warpage of the optical disk after the two substrates are bonded, the amount of the warpage generated on each substrate before the bonding is made equal, and the absolute amount of the warp is made as small as possible. Further, by making the conditions such as the position where the warp occurs and the like as much as possible, and bonding the two substrates in the same state, the warpage of the substrates is offset and the warp after the bonding is eliminated. Is considered appropriate.

[0009]

SUMMARY OF THE INVENTION However, DVD
In the case of manufacturing an optical information recording medium in which an information area is formed only on one substrate, such as -5, the first substrate 10 having an information area in which information is formed as a row of minute pits
The flow of the resin at the time of molding 1 differs from the flow of the resin at the time of molding the second substrate 103 having no pit array on the surface. Therefore, the residual stress in the substrate generated at the time of molding differs for each substrate, and the amount of warpage generated at each substrate after molding and the position at which the warpage occurs differ.

On the other hand, in an optical information recording medium such as DVD-10 in which two substrates each having an information area are bonded together, the amount of data recorded in the information area of each substrate is often different. Exists, in this case, the first substrate 1
01 of the first information area and the second substrate 103
Is different from the end position of the second information area. When producing such an optical information recording medium, the first substrate 1
01 and the flow of the resin at the time of molding the second substrate 103 are different. Therefore, the residual stress in each substrate is different, and the amount of warpage of the molded substrate and the position where the warp occurs are different.

When two substrates having different warpages are bonded as described above, even if the two substrates can be mechanically corrected at the time of bonding and the warpage can be suppressed, the warpage does not occur over time. This causes a problem that the reproduced signal deteriorates, and if it is severe, the reproduction becomes impossible. An object of the present invention is to provide a bonded optical information recording medium having a small amount of warpage by solving the above problems.

[0012]

According to a first aspect of the present invention, there is provided an optical information recording medium having a first information area in which first information is recorded on one side. A first substrate, a second substrate having a pseudo information area in which pseudo information is recorded on one surface and having the same material and substantially the same dimensions as the first substrate, the first substrate and the second substrate 2
And an inner layer and an outer diameter of the first information area and an inner diameter and an outer diameter of the pseudo information area are substantially the same.

[0013] According to a second aspect of the present invention, in the optical information recording medium, a first substrate having a first information area in which first information is recorded on one side, and a second information is recorded on one side. A second information area and a pseudo information area in which pseudo information is recorded following the end position of the second information area, the second information area having the same material and substantially the same size as the first substrate.
And an adhesive layer for bonding the first substrate and the second substrate, wherein an inner diameter of the first information area and an inner diameter of the second information area are substantially the same, The outer diameter of the first information area is substantially the same as the outer diameter of the pseudo information area.

According to a third aspect of the present invention, in the optical information recording medium according to the first aspect, the first information area is covered with a first reflective film, and the pseudo information area is a second reflective film. The first reflection film and the second reflection film are made of the same material and have substantially the same thickness, and the inner diameter and the outer diameter of the region where the first reflection film is formed and the second reflection film Wherein the inner diameter and the outer diameter of the region where the reflective film is formed are substantially the same.

According to a fourth aspect of the present invention, in the optical information recording medium according to the second aspect, the first information area is covered with a first reflective film, and the second information area and the pseudo information are recorded. The region is covered with a second reflective film, the first reflective film and the second reflective film are of the same material and substantially the same thickness, and the inner diameter of the region where the first reflective film is formed And the outer diameter and the inner diameter and the outer diameter of the region where the second reflective film is formed are substantially the same.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a cross-sectional structure of a first embodiment of the optical information recording medium of the present invention.
In the figure, 1 is a first substrate, 2 is a first information area, 3 is a first information area.
4 is a second substrate, 5 is a pseudo information area, and 6 is an adhesive layer.

The first substrate 1 is a resin substrate made of polycarbonate resin, for example, having an outer diameter of 80 mm, an inner diameter of 10 mm, and a thickness of 0.3 mm. On one surface of the first substrate 1, a first information area 2 in which information is recorded as a pit row is formed. In the first information area 2, for example, a pit row having a depth of about 80 nm, a shortest pit length of 0.3 μm, a longest pit length of 1.4 μm, and a track pitch of 0.5 μm is recorded. In this embodiment, the first information area 2
Is formed in a range of 40 mm to 77 mm in diameter.

The first information area 2 is covered with a first reflection film 3. In this embodiment, the first reflection film 3 has a diameter of 3 mm.
It is formed in a range of 8 mm to 79 mm, is made of an aluminum thin film, and has a thickness of about 80 nm.

The second substrate 4 is made of the same material as the first substrate 1 and is made of polycarbonate resin.
m, a resin substrate having an inner diameter of 10 mm and a thickness of 0.3 mm.

On one surface of the second substrate 4, there is formed a pseudo information area 5 composed of a dummy pit row (not necessarily meaningful information). In the pseudo information area 5, the first
A dummy pit row is recorded with the same specifications as the information area of No. 5, that is, a depth of about 80 nm, a shortest pit length of 0.3 μm, a longest pit length of 1.4 μm, and a track pitch of 0.5 μm. The pseudo information area 5 is formed at the same diameter position as the first information area 2, that is, in the range of 40 mm to 77 mm in diameter.

The first substrate 1 and the second substrate 4 are bonded together by an adhesive layer 6 made of an ultraviolet curable resin or the like so that the first information region 2 and the pseudo information region 5 face each other.

It is considered that the main cause of the warpage in the optical information recording medium in which the two substrates are bonded to each other is the warpage generated in each substrate. However, when a reflective film is formed on a substrate having the same amount of warpage and when the reflective film is not formed, the respective stresses are different, and the amount of warpage and the amount of warpage are different between the substrate on which the reflective film is formed and the substrate without the reflective film. It is considered that the position where the occurrence occurs is different. Therefore, although not shown, the pseudo information area 5 may be configured to be covered with the second reflection film. In this case, it is preferable that the second reflective film has the same material, thickness, and inner and outer diameters of a region where the second reflective film is formed as the first reflective film 3.

FIG. 2 shows an optical information recording medium having a pseudo information area formed on a second substrate according to the first embodiment of the present invention and a conventional optical information recording medium having no pseudo information area formed on a second substrate. FIG. 4 is a characteristic diagram comparing the amounts of warpage (radial tilt) in the vertical direction. (1) The pseudo information area 5 in the second substrate 4
The optical information recording medium on which (2) is formed has a pseudo information area 5 formed on the second substrate 4 and further represents the amount of warpage in the vertical direction of the optical information recording medium on which the second reflection film is formed. I have.
As a comparative example, (3) represents the amount of warpage in the vertical direction of the optical information recording medium in which neither the pseudo information area 5 nor the second reflection film was formed on the second substrate 4. These values are average values of 30 types of optical information recording media.

As shown in FIG. 2, as the number of elapsed days increases, (3) the warp in the vertical direction of the optical information recording medium in which neither the pseudo information area 5 nor the second reflection film is formed on the second substrate 4. The amount increased, and after 30 days, increased to 0.39 degree, which was about twice the initial value. On the other hand, the optical information recording medium having the pseudo information area 5 formed on the second substrate 4 of (1) and the pseudo information area 5 formed on the second substrate 4 of (2),
Further, the amount of warpage in the vertical direction of the optical information recording medium on which the second reflective film was formed was 0.30 degree even after 30 days.
Within the value.

As described above, the optical information recording medium of the present embodiment has the first information area on the second substrate 4 having the same inner and outer diameters as the inner and outer diameters of the first information area 2. A pseudo information area 5 in which a pit row having the same specifications as the pit row formed in No. 2 is recorded is provided. Therefore, the flow of the resin during the molding of the first substrate 1 and the second substrate 4 becomes substantially the same, and the residual stresses of the two substrates also become substantially the same, so that the first substrate 1 and the second substrate 4 are formed. The warpage amount and the position where the warp occurs are almost the same.

By bonding the first substrate 1 and the second substrate 4 having substantially the same amount of warpage and the same warpage, the warpage of the two substrates can be canceled out. The amount of warpage of the optical information recording medium after bonding is small and the change with time is small.

FIG. 3 is a schematic view showing a sectional structure of a second embodiment of the optical information recording medium of the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. 7 is the second
The information area 8 is a second reflection film. First substrate 1
Is made of a polycarbonate resin, for example, having an outer diameter of 80.
mm, an inner diameter of 10 mm, and a thickness of 0.3 mm.

On one surface of the first substrate 1, a first information area 2 in which information is recorded as a pit row is formed. For example, the first information area 2 has a depth of about 80 nm,
A pit row is recorded with a shortest pit length of 0.3 μm, a longest pit length of 1.4 μm, and a track pitch of 0.5 μm.
In the present embodiment, the first information area 2 is formed in a range from a diameter of 40 mm to a diameter of 77 mm.

The first information area 2 is covered with a first reflection film 3. In this embodiment, the first reflection film 3 has a diameter of 3 mm.
It is formed in a range of 8 mm to 79 mm, is made of an aluminum thin film, and has a thickness of about 80 nm.

The second substrate 4 is made of the same material as the first substrate 1 and is made of a polycarbonate resin.
m, a resin substrate having an inner diameter of 10 mm and a thickness of 0.3 mm.

On one surface of the second substrate 4, a second information area 7 in which information is recorded as a pit row is formed from the inner peripheral side. The second information area 7 has a depth of about 80n.
m, shortest pit length 0.3 μm, longest pit length 1.4 μm
m, a pit row is recorded at a track pitch of 0.5 μm. Here, the information recorded in the second information area 7 may be information that is continuous or related to the information recorded in the first information area 2, or may be information that is completely different. There may be.

In this embodiment, the data amount of information recorded in the second information area 7 is smaller than the data amount of information recorded in the first information area 2. For example, the second information area 7 is formed in a range from 40 mm to 60 mm in diameter.

Further, on the second substrate 4 of the optical information recording medium of this embodiment, a pseudo information area 5 composed of a dummy pit row is formed following the second information area 7. The dummy information area 5 has the same specifications as the first information area, that is, a dummy pit row having a depth of about 80 nm, a shortest pit length of 0.3 μm, a longest pit length of 1.4 μm, and a track pitch of 0.5 μm. ing.

The pseudo information area 5 starts following the end position of the second information area 7 and extends to the same diameter position as the end position of the first information area 2. That is, in the present embodiment, the pseudo information area 5 is formed in a range of the diameter of the second substrate 4 from 60 mm to 77 mm.

As described above, on the second substrate 4 of the optical information recording medium of the present embodiment, the second information area 7 is formed in the range of 40 mm to 60 mm in diameter, and the second information area 7 is formed in the range of 60 mm to 77 mm in diameter. An information area 5 is formed. That is,
Like the first substrate 1, the second substrate 4 has a diameter of 60 m.
A pit row having a depth of about 80 nm, a shortest pit length of 0.3 μm, a longest pit length of 1.4 μm, and a track pitch of 0.5 μm is recorded in the range of m to 77 mm.

The second information area 7 and the pseudo information area 5
It is covered with the second reflection film 8. In this embodiment, the second reflective film 8 is formed in a range of 38 mm to 79 mm in diameter, is made of an aluminum thin film, and has a thickness of about 80 nm. Here, since meaningless information is recorded in the pseudo information area 5, only the second information area 7 needs to be covered with the second reflection film 8, but the area where the reflection film is formed may be used. It is considered that the stresses are different between the substrates having different patterns, and the amounts of warpage and the positions where the warpages occur are different between the substrates. Therefore, in order to equalize the cause of the warpage on the first substrate 1 side and the second substrate 4 side, a region having the same inner and outer diameters as the inner and outer diameters of the region where the first reflective film 3 is formed is provided. It is preferable to form the second reflection film 8 on the second surface.

The first substrate 1 and the second substrate 4 are bonded to each other with an adhesive layer made of an ultraviolet curable resin or the like such that the first information region 2 and the second information region 7 (the pseudo information region 5) face each other. 6 are laminated.

FIG. 4 shows a comparison of the warpage between the optical information recording medium having the pseudo information area on the second substrate of the present embodiment and the conventional optical information recording medium having no pseudo information area on the second substrate. FIG. (1) The amount of vertical warpage of the optical information recording medium in which the pseudo information area 5 is formed on the second substrate 4 and the second reflective film 8 is formed so as to cover only the second information area 7; 2) indicates the amount of warpage in the vertical direction of the optical information recording medium in which the pseudo information area 5 is formed on the second substrate 4 and the second reflection film is also formed on the pseudo information area 5.
As a comparative example, (3) shows an optical information recording medium in which the pseudo information area 5 is not formed on the second substrate 4 but is formed as a smooth area, and the second reflective film 8 is formed so as to cover only the second information area 7. In the vertical direction. These values are average values of 30 types of optical information recording media.

As shown in FIG. 4, as the number of elapsed days increases, the pseudo information area 5 is not formed on the second substrate 4 in (3), but the second reflection film 8 is formed as a smooth area. The amount of warpage in the vertical direction of the optical information recording medium formed so as to cover only the number 7 increases to 0.33 degrees after 30 days. On the other hand, the pseudo information area 5 in the second substrate 4 of (1)
Is formed, and a pseudo information area 5 is formed on the optical information recording medium formed so as to cover the second reflection film 8 only in the second information area 7 and on the second substrate 4 of (2). Area 5
The amount of warpage in the vertical direction of the optical information recording medium having the second reflective film formed thereon is still within 0.30 degrees even after 30 days.

As described above, the optical information recording medium of the present embodiment has a range from the end position of the second information area 7 on the second substrate 4 to the same diameter as the end position of the first information area 2. The pseudo information area 5 is provided, and the first substrate
In the area having the same inner and outer diameter as the inner and outer diameters of the information area 2,
A pit row having the same specifications as the pit row formed in the information area 2 is recorded. Therefore, the flow of the resin during the molding of the first substrate 1 and the second substrate 4 becomes substantially the same, and the residual stresses of the two substrates also become substantially the same.
The amount of warpage of the first substrate 1 and the position of the warpage of the second substrate 4 are substantially the same.

Since the first substrate 1 and the second substrate 4 having substantially the same amount of warpage and the same warpage can be offset from each other, the two substrates can be bonded together. The warpage of the optical information recording medium after the alignment can be reduced.

[0042]

According to the present invention, it is possible to provide a bonded optical information recording medium having a small amount of warpage.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an optical information recording medium according to a first embodiment of the present invention.

FIG. 2 shows a vertical direction between an optical information recording medium having a pseudo information area formed on a second substrate and a conventional optical information recording medium having no pseudo information area formed on a second substrate according to the first embodiment of the present invention; FIG. 4 is a characteristic diagram comparing the amounts of warpage of the two.

FIG. 3 is a schematic view showing a sectional structure of a second embodiment of the optical information recording medium of the present invention.

FIG. 4 shows a vertical direction between an optical information recording medium having a pseudo information area on a second substrate and a conventional optical information recording medium having no pseudo information area on a second substrate according to a second embodiment of the present invention; FIG. 4 is a characteristic diagram comparing the amounts of warpage of the two.

FIG. 5 is a schematic diagram showing a cross-sectional structure of a conventional single-layer DVD, DVD-5.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a conventional multi-layer DVD, DVD-10.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 1st information area 3 1st reflection film 4 2nd board | substrate 5 pseudo information area 6 adhesive layer 7 2nd information area 8 2nd reflection film 101 1st substrate 102 reflection film 103 Second substrate 104 Adhesive layer 105 Pickup

Claims (4)

[Claims] 1. A first substrate having a first information area having first information recorded on one side thereof, and a pseudo information area having pseudo information recorded on one side having the same information as the first substrate. A second substrate having a material and substantially the same dimensions; and an adhesive layer for bonding the first substrate and the second substrate, wherein the inner and outer diameters of the first information area and the pseudo An optical information recording medium, wherein an inner diameter and an outer diameter of an information area are substantially the same. 2. A first substrate having a first information area in which first information is recorded on one side, a second information area in which second information is recorded on one side, and the second information area. A second substrate having a pseudo information area in which pseudo information is recorded subsequent to the end position, and having the same material and substantially the same dimensions as the first substrate; the first substrate and the second substrate An adhesive layer for bonding the substrate to the substrate, wherein the inner diameter of the first information area and the inner diameter of the second information area are substantially the same, and the outer diameter of the first information area and the outer diameter of the pseudo information area An optical information recording medium having a diameter substantially the same. 3. The optical information recording medium according to claim 1, wherein the first information area is covered with a first reflection film, the pseudo information area is covered with a second reflection film, and the first information area is covered with a second reflection film. The reflection film and the second reflection film are made of the same material and have substantially the same thickness, and the inner and outer diameters of the region where the first reflection film is formed and the region where the second reflection film is formed An optical information recording medium, wherein the inner diameter and the outer diameter are substantially the same. 4. The optical information recording medium according to claim 2, wherein said first information area is covered with a first reflection film, and said second information area is covered with a second reflection film.
Are covered with a second reflective film, the first reflective film and the second reflective film are made of the same material and have substantially the same thickness, and the first reflective film An optical information recording medium characterized in that the inner and outer diameters of the area where the second reflective film is formed are substantially the same as the inner and outer diameters of the area where the second reflective film is formed.