JP3431612B2 - Optical disc, optical disc apparatus suitable for the optical disc, and information recording / reproducing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc capable of recording high-density information, an optical disc device suitable for the optical disc, and an information recording / reproducing method, and is particularly not susceptible to warpage that occurs when the cover layer is cured. The present invention relates to an optical disc, an optical disc device suitable for the optical disc, and an information recording / reproducing method.

[0002]

2. Description of the Related Art Currently, a system for reproducing information from a disk-shaped medium (optical disk) in which information such as video (moving image) and music is recorded has been developed and widely used for the purpose of reproducing movie software, karaoke software, etc. There is.

As the optical disc, for example, LD (laser disc), video CD (video compact disc) or DVD (digital versatile disc) is used.
Etc. are known. Recently, write once (write once) type discs (CD-R, DVD-ROM) and rewritable type discs (CD-RW, DVD-RAM) that can be used as an external storage device of a computer have been put into practical use. Has been done.

In many cases, in the above-mentioned optical disc, the contents of recorded information are recorded on the surface opposite to the information signal reading surface (recording surface) which is the side irradiated with the reproducing (recording) laser beam. The title and the like shown are added by printing (or attaching a label or the like). On the other hand, CD-
Since an optical disc capable of recording information, represented by an RW disc or a DVD-RAM disc, allows a user to freely record data, the disc surface (non-recording face) naturally has information. Although the print or the like indicating the contents of No. 1 is not added, the user can write a keyword indicating the contents of the information, a code or symbol for identification, or attach a sticker or the like.

In response to the demand for higher density recording in the market, it has been proposed to shorten the wavelength of the laser beam used, increase the numerical aperture (hereinafter referred to as NA) of the objective lens, and further increase the recording density. .

For example, considering an optical disc having a high recording density that can record or reproduce information by irradiating a laser beam having a wavelength of 400 nm, for example, using an objective lens having an NA (aperture ratio) of about 0.8. The distance between the surface on the side irradiated with the laser beam and the recording film, that is, the thickness of the cover layer is about 0.1 mm as shown in FIG.
Even in the optical disc 1 having a high recording density shown in FIG. 8, polycarbonate (PC) is used as the material of the substrate 2, and the inner diameter is 15 mm, the outer diameter is 120 mm, and the thickness is the same as in the DVD (CD) standard optical disc. Is 1.2 mm, the thickness of the substrate 2 is
It becomes 1.2-0.1 = 1.1 mm.

[0007]

By the way, the thickness is 1.
One surface 4 of 1 mm base material 2 (usually, pit rows are integrally formed, and the reflection film 3 is deposited to a predetermined thickness)
Then, as a cover layer 7, a polycarbonate sheet 6 having a thickness of 75 μm is adhered by an adhesive layer 5 made of a photocurable resin having a thickness of 25 μm, and when the adhesive layer 5 is cured,
The cover layer 7 is warped.

Since the degree of this warpage is comparable to the distance between the objective lens and the optical disc having an NA of about 0.8, when the optical disc has surface deviation (usually always occurs). There is a problem that the cover layer 7 of the optical disc 1 and the objective lens 9 come into contact with each other.

This causes vibration or shock when reproducing information from the optical disc 1 or recording information on the optical disc 1, which makes it difficult to reproduce good signals and record information. .

Further, like the currently used CD or DVD type optical disc 1, the contents of the information recorded on the optical disc 1 are provided on the side opposite to the cover layer 7 (the side to which the polycarbonate sheet 6 is adhered). Even if the print 8 shown is applied, the above-mentioned warpage is not reduced.

In Japanese Patent Laid-Open No. 4-125827, a protective film having a laminated structure of transparent substrate / recording film layer / reflective film layer is formed by using the same resin as the protective film applied on the reflective film layer. A write-once type optical disc compatible with a compact disc or a compact disc-ROM, which is characterized in that a resin film is formed on a transparent substrate on the opposite side, is disclosed. The cover layer is not assumed, and the side on which the laser beam is incident is the transparent substrate side (the present invention is the cover layer side).
Different from the present invention.

An object of the present invention is to provide an optical disc having a cover layer made of a photocurable resin capable of suppressing warpage, an optical disc device suitable for the optical disc, and an information recording / reproducing method.

[0013]

The present invention has been made in order to achieve the above-mentioned object, and includes a resin substrate and a reflection layer or a reflection layer and a recording layer formed on one surface of the resin substrate. , A first resin layer capable of transmitting light of a predetermined wavelength and covering the reflection layer or the reflection layer and the recording layer, and provided on the other surface different from the one surface of the resin substrate, The content of information recorded on the reflective layer or the reflective layer and the recording layer can be displayed, and a stress that balances the stress generated between the first resin layer and the resin substrate can be applied to the resin substrate. And a second resin layer that can be provided to the optical disc.

Further, according to the present invention, a laser element for emitting light of a predetermined wavelength, an objective lens having a numerical aperture of about 0.85, and a resin substrate and one of the resin substrate with the objective lens interposed. The reflecting layer or the reflecting layer and the recording layer formed on the surface, the first resin layer which can transmit light of a predetermined wavelength and covers the reflecting layer or the reflecting layer and the recording layer, and one surface of the resin substrate. A stress that is provided on the other one of the different surfaces and that can display the content of information recorded in the reflective layer or the reflective layer and the recording layer, and that is balanced with the stress generated between the first resin layer and the resin substrate. A second resin layer that can be provided between the optical disk and a resin substrate, and the light obtained by condensing the light from the laser element is received and photoelectrically converted, whereby A photo device that obtains an output corresponding to the recorded information. It is to provide an optical disk apparatus characterized by comprising: a protector, a.

Further, according to the present invention, light is generated by using a laser element which emits light having a predetermined wavelength, and the numerical aperture is 0.8.
Light of a predetermined wavelength can be transmitted through the resin substrate and the reflection layer or the reflection layer and the recording layer formed on one surface of the resin substrate to the light generated by the laser element by the objective lens of around 5 First covering the reflecting layer or the reflecting layer and the recording layer
Of the first resin, which is provided on the other surface of the resin substrate different from the one surface of the resin substrate and is capable of displaying the content of information recorded in the reflection layer or the reflection layer and the recording layer. The stress, which is balanced between the stress generated between the layer and the resin substrate, is condensed onto an optical disc having a second resin layer capable of providing between the resin substrate and the condensed light, and the condensed light is reflected by the optical disc. It is intended to provide an information reproducing method characterized in that an output corresponding to information recorded on the optical disc is obtained by receiving light by a photodetector and photoelectrically converting it.

Still further, according to the present invention, light is generated by using a laser element that emits light having a predetermined wavelength, and an objective lens having a numerical aperture of about 0.85 is used. By changing the light intensity according to the information to be recorded, the resin substrate, the reflection layer formed on one surface of the resin substrate or the reflection layer and the recording layer, and the light of a predetermined wavelength can be transmitted, and the reflection layer Alternatively, the first resin layer covering the reflective layer and the recording layer and the other surface different from the one surface of the resin substrate may be provided to display the content of the information recorded in the reflective layer or the reflective layer and the recording layer. The light is focused on an optical disk having a second resin layer which can be displayed and which can provide a stress that balances the stress generated between the first resin layer and the resin substrate, Information recording characterized by recording information on an optical disc It is intended to provide the law.

Furthermore, according to the present invention, a resin substrate, a reflection layer formed on at least one surface of the resin substrate or a reflection layer and a recording layer can transmit light of a predetermined wavelength,
Information recorded on the reflective layer or the reflective layer or the recording layer and the first resin layer covering the reflective layer and the recording layer and the other surface different from the one surface of the resin substrate. And an optical disc having a second resin layer capable of providing stress between the resin substrate and the stress that occurs between the first resin layer and the resin substrate, and a predetermined wavelength. Laser element that emits
An objective lens of about 5 and a lens holding mechanism for positioning the objective lens at a predetermined relative position with respect to the reflection layer or the recording layer of the optical disc, and the light of the predetermined wavelength from the laser element. The direction and the amount of movement of the objective lens can be calculated by receiving and photoelectrically converting the reflected light reflected by the reflection layer of the optical disc and an arbitrary number of optical elements that guide the objective lens. In the optical disc device, an arbitrary number of photodetectors that output a variation amount are provided, and the lens holding mechanism includes the laser element provided with a predetermined focusing property by the action of the objective lens. A distance of less than 1 mm from the surface of the first resin layer of the optical disc so that light from the optical disc can be condensed on the reflection layer or the recording layer of the optical disc. While facing each other, the objective lens guides toward the optical element so that the photodetector can receive the light reflected by the reflective layer or the recording layer of the optical disc at the time of reproducing the information, and at the time of recording the information. The present invention provides an optical disc device and an information recording / reproducing method, characterized in that the light from the laser element transmitted by the optical element is focused on the recording layer.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of a reproducing optical disk which is an embodiment of the present invention and which has a high recording density.

The optical disc 10 shown in FIG. 1 has an outer diameter of 12
0 mm, inner diameter 15 mm, thickness 1.2 mm ± 0.
The size is 03 mm, which is the same as that of the optical discs of the CD standard and the DVD standard which have already been popular.

The optical disk 10 has a resin substrate 11 having a predetermined thickness, for example, a thickness of about 1.0 mm.
A row of pits (pre-pits) is provided on one surface of the resin substrate 11.
12 is formed in advance.

The pit array 12 is made of, for example, a thin film of aluminum having a thickness of 70 nm, and is covered with a reflective film 13 that covers substantially the entire surface of the pit array 12 and the resin substrate 11.

A surface cover 15 is adhered to the reflective film 13 via an adhesive layer 14 which is a photo-curable (ultraviolet curable) adhesive provided so as to cover the entire surface of the reflective film 13. Therefore, the cover layer 16 is defined by the adhesive layer 14 and the surface cover 15.

The total thickness of the surface cover 15 and the adhesive layer 14 is about 0.1 mm.
Has a thickness of, for example, 0.075 mm (75 μm),
The thickness of the adhesive layer 14 is 0.025 mm (25 μm), which is thinner than ½ of the thickness of the cover layer 16. The surface cover 15 is made of polycarbonate (PC), for example.

The pit row 12 and the reflection film 13 of the resin substrate 11
A second reflective film, which is a thin film of, for example, aluminum and has a thickness substantially equal to that of the reflective film 13, and acts similarly to the reflective film 13 on the surface opposite to the side where the 17 are formed.

The second reflective film 17 is a photocurable (ultraviolet curable) adhesive having a composition substantially equal to that of the adhesive layer 14 used for bonding the surface cover 15 and the reflective film 13. A labeled resin layer 20 in which a label 19 having a thickness substantially equal to that of the surface cover 15 and having a content of information stored in advance as the pit row 12 is preliminarily printed through a certain second adhesive layer 18. Is attached. The warp prevention back cover 21 is defined by the second adhesive layer 18 and the labeled resin layer 20. Also,
In this example, the thickness of the labeled resin layer 20 is about 0.
At 075 mm (75 μm), the thickness of the second adhesive layer 18 is 0.025 mm (25 μm), which is thinner than ½ of the thickness of the labeled resin layer 20. The total thickness of the adhesive layer 18 and the adhesive layer 18 is about 0.1 mm. Further, the labeled resin layer 20 includes
Preferably, for example, polycarbonate having the same composition as the surface cover 15 is used.

Thus, the optical disc 10 shown in FIG.
Is an adhesive layer made of an adhesive having the same composition as the reflective film and the second reflective films 13 and 17 on the front and back surfaces of the resin substrate 11, that is, the surface on which the pit rows 12 are formed and the surface on the opposite side thereof, respectively. And the second adhesive layers 14 and 18 are provided, and the labeled resin layer 20 and the surface cover 15 having approximately the same thickness are adhered to each other, so that the shrinkage or the shrinkage is mainly dependent on a change in time or environment. Since the mutual internal stresses of the adhesive layer and the second adhesive layers 14 and 18 in which the degree of extension changes are controlled to be substantially equal to each other, the surface cover 15 is prevented from being largely warped due to the influence of the adhesive layer 14 upon curing. To be done.

Further, the labeled resin layer 20 allows the user to understand the content of the information recorded on the optical disk 10 at a glance. The labeled resin layer 2
The label 19 pre-printed on 0 is shown in FIG.
It may be provided on the (inner surface of the disk 10) side that is in contact with the second adhesive layer 18, as indicated by '.

By the way, since the adhesive layer 14 is the main cause of the stress in the optical disk 10, the labeled resin layer 20 and the surface cover 15 provided on the pit row 12 side.
Does not necessarily have to be polycarbonate having exactly the same composition, and the thickness and the material can be appropriately changed in consideration of printability (printing characteristics) when printing the label 19. The label 19 does not necessarily have to be a character or the like, and may be a figure, a symbol, or simply colored.

FIG. 2 is a schematic sectional view showing an example of a writable optical disc which is the optical disc shown in FIG.

The optical disk 70 shown in FIG. 2 has an outer diameter of 12
0 mm, inner diameter 15 mm, thickness 1.2 mm ± 0.
The size is 03 mm, which is the same as that of the optical discs of the CD standard and the DVD standard which have already been popular.

The optical disc 70 has a resin substrate 21 having a predetermined thickness, for example, a thickness of about 1.0 mm.
On one surface of the resin substrate 21, a signal train including prepits and a groove 22 are formed in advance.

Groove 22 and signal train consisting of pre-pits
Is a thin film of aluminum having a predetermined thickness, and includes a signal train formed of prepits, the groove 22 and the resin substrate 21.
Is covered with a reflective film 13 that covers substantially the entire surface of the.

On the reflective film 13, a recording film 24 is formed with a predetermined thickness so as to cover the entire surface of the reflective film 13. The recording film 24 is, for example, a GeSbTe alloy and is covered with a dielectric protective film 25 having a predetermined thickness.

A surface cover 15 is adhered to the entire surface of the dielectric protective film 25 by an adhesive layer 14 which is a photo-curable (ultraviolet curable) adhesive. Therefore, the cover layer 16 is defined by the adhesive layer 14 and the surface cover 15.

The total thickness of the surface cover 15 and the adhesive layer 14 is about 0.1 mm.
Has a thickness of 0.075 mm (75 μm), for example.
The surface cover 15 is made of polycarbonate, for example.

A thin film of aluminum, for example, is formed on the surface of the resin substrate 21 on the side opposite to the side on which the signal train consisting of prepits, the groove 22 and the reflection film 13 are provided, and is substantially equal to the reflection film 13. Given the thickness, the reflective film 13
A second reflective film 17 that operates in the same manner as is formed.

The second reflective film 17 is a photo-curable (ultraviolet curable) adhesive having a composition substantially equal to that of the adhesive layer 14 used for bonding the surface cover 15 and the reflective film 13. A resin with a display surface on which a display surface 29 is formed which has a thickness approximately equal to that of the surface cover 15 and which can display the content of information recorded on the optical disc 70 through a certain second adhesive layer 18. A layer 30 is attached. The second adhesive layer 18 and the resin layer 30 with a display surface define a warp prevention back cover 31.

Further, in this example, the resin layer 30 with a display surface is used.
Is approximately 0.075 mm (75 μm), and the total thickness of the resin layer 30 with a display surface and the second adhesive layer 18 is approximately 0.1 mm. Further, for the resin layer 30 with a display surface, preferably, for example, polycarbonate having the same composition as the surface cover 15 is used.

Thus, the optical disc 70 shown in FIG.
On the front and back surfaces of the resin substrate 21, that is, the surface on which the groove 22 is formed and the surface on the opposite side, respectively, an adhesive layer made of an adhesive having the same composition as the reflective film and the second reflective films 13 and 17, Since the second adhesive layers 14 and 18 are provided and the resin layer 30 with a display surface and the surface cover 15 having substantially the same thickness are adhered to each other, the shrinkage and the shrinkage mainly depend on a change in time or environment. Since the mutual internal stresses of the adhesive layer and the second adhesive layers 14 and 18 in which the degree of extension changes are controlled to be substantially equal to each other, the surface cover 15 is prevented from being largely warped due to the influence of the adhesive layer 14 upon curing. To be done.

Further, since the user can record (display) the content of the information recorded on the optical disc 70 by the user, the resin layer 30 with the display surface shows the content recorded on the optical disc 70 by the user. The contents of the information recorded on the optical disk 70 can be understood at a glance by grasping and writing a display showing the contents with a pencil, a felt-tip pen, or the like.

Since the adhesive layer 14 is the main cause of the stress in the optical disk 70, the resin layer 30 with the display surface, the signal train including the prepits, and the surface cover 15 provided on the groove 22 side are not necessarily required. It is not necessary that the polycarbonates have exactly the same composition, and the thickness and the material can be appropriately changed in consideration of easiness of formation (printing characteristics) when forming the display surface 29. The display surface 2
When 9 is processed into an opaque rough surface, writing and erasing with a pencil or the like is possible.

FIG. 3 is a schematic block diagram showing an example of an optical disc device (information recording / reproducing device) capable of writing information on the optical disc shown in FIGS. 1 and 2 or reproducing information from the optical disc shown in FIG. is there.

The optical disk device 101 shown in FIG. 3 focuses a laser beam L having a predetermined wavelength, for example 400 nm, on a predetermined position of the optical disk 10 (70) having a high recording density, that is, on the pit row 12 or the groove 22. It has an objective lens 131. The objective lens 131
Is a compound lens in which first and second lenses 131a and 131b to which a predetermined focusing power is applied are laminated. In addition, the first and second lenses 131a and 131b
The numerical aperture NA (which is the same as the numerical aperture of a single lens) NA of the objective lens 131 provided by the above is 0.8 considering that the thickness of the surface cover 15 is 0.1 mm.
To 0.9.

The objective lens 131 includes a folding mirror 1
A laser beam L having a wavelength of 400 nm is emitted from the semiconductor laser (laser element) 133 by 32.

A collimating lens 13 for collimating the laser beam L emitted from the laser element 133 is provided at a position where the laser beam L can be incident on the folding mirror 132.
4. Diffraction grating (grating) 135 for giving a predetermined diffraction component to the laser beam L, optical disk 10 (70)
Λ / which gives a predetermined characteristic to the laser beam L directed to
2 plates (HWP) 136, a polarization beam splitter 137 for separating a laser beam L directed from the laser element 133 toward the optical disc 10 (70) and a reflected laser beam L ′ reflected by the reflection film 13 of the optical disc 10 (70), an optical disc The beam expander 138, which is a combination of an arbitrary number of optical elements for increasing the diameter of the laser beam L directed to the optical disc 10 (70), the laser beam L directed to the optical disc 10 (70), and the reflected laser beam L'reflected. Λ / 4 plate (QWP) 139 for matching the isolation with the dichroic mirror 140
Etc. (shown in plan in FIG. 3) are provided in order.

In the direction in which a part of the laser beam L toward the optical disk 10 (70) is reflected by the surface of the polarization beam splitter 137 on the side of the laser element 133, the reflected part of the laser beam is received and photoelectrically converted. A photodetector 141 for converting and monitoring the light intensity of the laser beam L emitted from the laser element 133 is provided.
The photodetector 141 is configured so that a part of the laser beam reflected again by the cover glass (not shown) on the light receiving surface of the photodetector 141 does not enter the laser element 133 or the reproducing photodetector 144 described below. Laser element 133 to optical disc 10
It is arranged in a state of being inclined at an arbitrary angle with respect to the principal ray of the laser beam L directed to (70).

In the direction in which the reflected laser beam L ′ separated by the polarization beam splitter 137 is guided, the focusing lens 1 which gives the reflected laser beam L ′ a predetermined focusing property.
42, laser beam L directed to the optical disk 10 (70)
A hologram plate (HOE) 143 for giving a predetermined image forming pattern to the reflected laser beam by utilizing the diffraction characteristics given to the reflection laser beam by the diffraction grating 135, and a reflected laser beam having a predetermined image forming pattern given by the hologram plate 143. L'is received and photoelectrically converted, and the optical disc 1
While playing back the information recorded in 0 (70),
Pit row 12 provided on the optical disc 10 (70)
A photodetector 144 for generating a servo signal for setting the relative positional relationship between the (reflection film 13) or the groove 22 (recording layer 24) and the objective lens 131 within a predetermined condition is provided.

In the optical disc device 101 shown in FIG. 3, the laser beam L emitted from the laser element 133 is used.
The light intensity of the laser beam L from the APC circuit 152 is based on the light intensity detected by the photodetector 141.
Is controlled by being fed back to the laser drive circuit 151 for the fluctuation of the light intensity of the.

When the information to be recorded is input to the laser drive circuit 151, a recording signal for modulating the light intensity of the recording laser beam output from the laser element 133 according to the information to be recorded. The generator 153 is connected.

The photodetector 144 is the optical disc 1
It is reflected by the recording surface of 0 (70) and the cross section is converted into substantially parallel by the objective lens 131, and the dichroic mirror 1
40, the QWP 139, the beam expander 138, the polarization beam splitter 137, the condenser lens 142, and the hologram plate 143, receives the reflected laser beam L ′ sequentially transmitted, photoelectrically converts the reflected laser beam L ′, and outputs it to the amplifier 154 connected to the subsequent stage. , And outputs a signal according to the light intensity and pattern of the received reflected laser beam L ′. The signal photoelectrically converted by the photodetector 144 and amplified to a predetermined level by the amplifier 154 is output to a focus error detection circuit, a track error detection circuit (not shown), a buffer memory (not shown) that holds reproduction data, and the like.

The objective lens 131 is arranged in a predetermined direction and size in a focus control coil and a track control coil (not shown) based on the focus error amount and the track error amount output from the focus error detection circuit and the track error detection circuit (not shown). When the drive current is supplied to the optical disc 10 (70), the optical disc 10 (70) is focus-locked with respect to the pit row 12 or the groove 22, and the center of the pit row 12 or the groove 22 can be traced. The positional relationship with is controlled.

By the way, the optical disk device 1 shown in FIG.
In 01, the numerical aperture NA of the objective lens 131 is 0.8 to
Since it is 0.9, the quality of the reproduced signal is
It is very sensitive to the warp of (70). Further, the distance between the objective lens 131 and the optical disc 10 (70) is also 1 mm or less in the steady state, and the optical disc 10 (7
0) is also susceptible to surface wobbling when it is rotated.

Therefore, the thickness of the cover layer 16 (the thickness of the surface cover 15 and the adhesive layer), which is the distance between the pit row 12 (reflection film 13) or the groove 22 (recording layer 24) and the laser beam L incident side. In the optical disc 10 (70) capable of high density recording, the total thickness of 14) is about 0.1 mm.
The allowable warpage of the optical disk 10 (70) should be 0.3 mm or less with respect to the radius (60 mm) of the optical disk 10, and more preferably 0.1 mm or less in consideration of surface deviation.

In the present invention, the surface cover 15 having a thickness of approximately 0.1 mm is adhered to the resin substrate 11 (21) by the adhesive layer 14 which is a photo-curing resin, so that the pit row 12 is formed.
While covering the information surface provided with the (reflection film 13) or the groove 22 (recording layer 24), the labeled resin layer 20 having the same thickness as the surface cover 15 or the display is provided on the surface opposite to the information surface. The surface-attached resin layer 30 (warp-preventing back cover 21 (31)) is adhered by the second adhesive layer 18 made of an adhesive having substantially the same composition as the adhesive layer 14, so that the front and back surfaces of the resin substrate 11 (21) are covered. Since the internal stress due to the attachment of the cover 15 (providing the cover layer 16) is balanced, and the magnitude of the warpage generated on the front and back of the resin substrate 11 (21) is balanced, the optical disk 10 (70) is
The warp exceeding the limit is prevented from occurring.

FIG. 4 is a schematic diagram for explaining a modified example of the optical disc shown in FIG. The same components as those described above with reference to FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4, an optical disc 1 for reproduction is used.
In FIG. 10, a pit row 12 is formed in advance on one surface of a resin substrate 11 having a thickness of about 1.0 mm, for example. The pit row 12 is made of a thin film of aluminum and is covered with a reflective film 13 that covers substantially the entire surface of the pit row 12 and the resin substrate 11. A surface cover 15 is adhered to the reflective film 13 via an adhesive layer 14 which is a photo-curable (ultraviolet curable) adhesive provided so as to cover the entire surface of the reflective film 13. The cover layer 16 is defined by 15. The surface cover 15
The total thickness of the adhesive layer 14 and the adhesive layer 14 is about 0.1 mm.
Then, the thickness of the surface cover 15 is, for example, 0.075 mm.
(75 μm). The surface cover 15 is made of polycarbonate, for example.

Pit row 12 and reflection film 13 of resin substrate 11
On the surface opposite to the side where the
5 is provided with a composition that is substantially equal to that of the adhesive layer 14 used for bonding the reflective film 13 and the reflective film 13 to each other (photo-curing type).
The surface cover 1 is provided via the second adhesive layer 18 which is an adhesive.
A labeled resin layer 20 having a thickness substantially equal to 5 and having a label 19 indicating the content of information stored in advance as the pit row 12 is pre-printed is attached. The second adhesive layer 18 and the labeled resin layer 20
Defines the warp prevention back cover 121.

In this example, the labeled resin layer 20 is also used.
Is approximately 0.075 mm (75 μm), and the total thickness of the labeled resin layer 20 and the second adhesive layer 18 is approximately 0.1 mm. Further, for the labeled resin layer 20, preferably, for example, polycarbonate having the same composition as that of the surface cover 15 is used.

Thus, the optical disk 110 shown in FIG.
In comparison with the optical disc 10 shown in FIG. 1, the reflection film 13 provided on the resin substrate 11 on the side opposite to the cover layer 16 (the surface cover 15 and the adhesive layer 14) is omitted. That is, the aluminum reflection film 17 provided on the side opposite to the cover layer 16 has good adhesion between aluminum and polycarbonate which is the resin substrate, and the condition is not specified, but the reflection film 13 on the pit row 12 side is protected. It is not always necessary if the resistance can be sufficiently secured by being covered with the film (in this case, the adhesive layer 14) and the factors such as shrinkage and expansion can be reduced, and
It is also possible to omit it, provided that the stress balances are approximately equal.

Thus, the optical disk 11 shown in FIG.
0 indicates the front and back of the resin substrate 11, that is, the surface on which the pit row 12 is formed and the surface on the opposite side,
By providing the reflective film 13, the adhesive layers made of an adhesive having the same composition, and the second adhesive layers 14 and 18, the labeled resin layer 20 and the surface cover 15 having approximately the same thickness are adhered to each other. When the adhesive layer 14 is cured, the mutual internal stresses of the adhesive layer and the second adhesive layers 14 and 18 in which the degree of shrinkage or extension changes mainly depending on changes in time and environment are controlled to be substantially equal. Due to the influence of the surface cover 1
A large warp of 5 is prevented.

FIG. 5 is a schematic view for explaining a modified example of the optical disc shown in FIG. The same components as those previously described with reference to FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. It is a schematic sectional drawing which shows an example of a writable optical disk.

As shown in FIG. 5, the writable optical disc 170 has a resin substrate 21 having a thickness of about 1.0 mm.
On one surface, a signal line consisting of pre-pits and a groove 22 are formed in advance and covered with a reflective film 13 formed of a thin film of aluminum having a predetermined thickness. The recording film 2 is provided on the reflective film 13 so as to cover the entire surface of the reflective film 13.
4 is formed with a predetermined thickness. The recording film 24
Is, for example, a GeSbTe alloy, and is covered with a dielectric protective film 25 having a predetermined thickness.

The surface cover 15 is adhered to the entire surface of the dielectric protective film 25 by the adhesive layer 14 which is a photo-curable (ultraviolet curable) adhesive, and the cover layer 16 is formed by the adhesive layer 14 and the surface cover 15. Is defined. The front cover 1
5 and the adhesive layer 14 have a total thickness of about 0.1 m.
m, the thickness of the surface cover 15 is, for example, 0.075 mm.
(75 μm). The surface cover 15 is made of polycarbonate, for example.

On the surface of the resin substrate 21 opposite to the side where the signal train consisting of pre-pits, the groove 22 and the reflection film 13 are provided, an adhesive layer used for adhering the surface cover 15 and the reflection film 13 to each other. A second adhesive layer 18, which is a photo-curable (ultraviolet-curable) adhesive having a composition substantially equal to that of 14, is defined to have a thickness substantially equal to that of the surface cover 15, and is recorded on the optical disc 70. A resin layer 30 with a display surface on which a display surface 29 capable of displaying the contents of the information is formed is attached. The second adhesive layer 18 and the resin layer 30 with the display surface define a warp prevention back cover 131.

Further, in this example, the resin layer 30 with a display surface is used.
Is approximately 0.075 mm (75 μm), and the total thickness of the resin layer 30 with a display surface and the second adhesive layer 18 is approximately 0.1 mm. Further, for the resin layer 30 with a display surface, preferably, for example, polycarbonate having the same composition as the surface cover 15 is used.

In this way, the optical disk 17 shown in FIG.
0 indicates the front and back surfaces of the resin substrate 21, that is, the surface on which the signal line consisting of the prepits and the groove 22 are formed and the surface on the opposite side thereof, respectively, and the adhesive layer made of an adhesive having the same composition as the reflective film 13 and the second surface. The adhesive layers 14 and 18 are provided to bond the display surface-equipped resin layer 30 and the surface cover 15 of approximately equal thickness to each other, so that the contraction and expansion mainly depend on changes in time and environment. Since the mutual internal stresses of the adhesive layer and the second adhesive layers 14 and 18 of varying degrees are controlled to be substantially equal to each other, the surface cover 15 is prevented from being largely warped due to the influence of the adhesive layer 14 upon curing. .

FIGS. 6 and 7 are schematic views for explaining still another modified example of the reproducing optical disk and the writable optical disk described above with reference to FIGS. 1 and 2, respectively. The same components as those described above with reference to FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 6, an optical disk 2 for reproduction is used.
In FIG. 10, a pit row 12 is formed in advance on one surface of a resin substrate 11 having a thickness of about 1.0 mm, for example. The pit row 12 is made of, for example, a thin film of aluminum, and is covered with a reflective film 13 that covers substantially the entire surface of the pit row 12 and the resin substrate 11.

A cover layer 216, which is a photo-curable (ultraviolet curable) resin, is formed on the reflective film 13 so as to cover the entire surface of the reflective film 13 and is then cured. The thickness of the cover layer 216 is about 0.1.
mm.

On the other hand, on the surface of the resin substrate 11 opposite to the side where the pit rows 12 and the reflective film 13 are provided, the composition substantially equal to that of the cover layer 216 or the magnitude of the internal stress at the time of curing is set. The warp control layer 220 is formed by depositing and curing a photo-curable (ultraviolet curable) resin having a characteristic substantially equal to that of the cover layer 216 to a predetermined thickness. The warp control layer 220 is provided with, for example, by printing or by attaching a label or the like, a character string, a pictogram, a symbol, an identification code, or the like indicating the content of information previously recorded in the pit string 12. It

The above-described warpage control layer 220 may be transparent or opaque in terms of light transmission as long as it does not affect the printing characteristics when printing the label 221 to be printed subsequently, and its thickness is not necessarily covered. It need not be equivalent to layer 216. However, in the warp control layer 220, the magnitude of the internal stress generated when itself is cured can be approximately balanced with the internal stress generated when the cover layer 216 is cured, and the warpage can be canceled on the front and back of the resin substrate 11. Needless to say, is required.

Thus, the optical disk 21 shown in FIG.
0 means that the cover layer 216 has substantially the same composition as the cover layer 216, and the internal stress at the time of curing is set on the front and back surfaces of the resin substrate 11, that is, the surface on which the pit rows 12 are formed and the surface on the opposite side thereof. Since the warp control layer 220 made of a photo-curable resin, which is given a characteristic that is almost equal to that of the cover layer 216, is provided, the degree of contraction or extension mainly depends on changes in time or environment. The changing internal stress generated in the cover layer 216 can be canceled, and the optical disc 210 can be prevented from being largely warped.

A writable optical disc 27 shown in FIG.
0 has a resin substrate 21 having a thickness of about 1.0 mm, and the information surface in which the signal train consisting of prepits and the groove 22 are previously formed on one surface of the resin substrate 21 has a predetermined thickness. Is provided with a reflection film 13 which is a thin film of aluminum. A recording film 24 made of, for example, GeSbTe alloy and provided so as to cover the entire surface of the reflective film 13 is formed to a predetermined thickness on the reflective film 13. The recording film 24
Are covered with a dielectric protective film 25 having a predetermined thickness.

On the entire surface of the dielectric protective film 25, a cover layer 216 is provided, which is formed by curing a photocurable (ultraviolet curable) resin having a predetermined thickness and curing the resin. The cover layer 216 has a thickness of approximately 0.1 mm.

On the surface of the resin substrate 21 on which the signal line consisting of pre-pits, the groove 22 and the reflection film 13 are provided, that is, the surface opposite to the information surface, the composition or curing substantially equal to that of the cover layer 216 is applied. The internal stress at the time is the cover layer 2
A display surface forming portion (warpage control layer) 230, which is a photo-curable (ultraviolet curable) resin having a characteristic substantially equal to 16, is formed. The thickness of the display surface forming portion (warpage control layer) 230 is, for example, 0.1 mm.
Further, the display surface forming unit 230 performs printing capable of writing the content of information recorded on the optical disk 270 (rough surface processing is also possible).
The thickness may be changed depending on the case where the label is applied or a label (sticker) on which information content is printed, for example, synthetic paper is attached. However, the display surface forming unit 23
0 means that the magnitude of the internal stress generated when itself hardens can be almost balanced with the internal stress generated when the cover layer 216 hardens, and it is required that the warp can be canceled on the front and back of the resin substrate 21. Needless to say.

In this way, the optical disc 27 shown in FIG.
0 means that the cover layer 216, which is a photo-curable resin, and the cover layer 216 have the same composition on the front surface and the back surface of the resin substrate 21, that is, on the surface on which the signal line consisting of prepits and the groove 22 are formed and on the surface on the opposite side. Display surface forming portion (warp control layer) 2 made of a photo-curable resin that is substantially equal or has a characteristic that internal stress during curing is almost equal.
Since 30 is provided, it is possible to cancel the internal stress generated in the cover layer 216 whose degree of contraction and expansion mainly changes according to changes in time, environment, etc., and prevent the optical disc 270 from significantly warping.

As described above, the optical disk of the present invention is provided on the surface opposite to the information surface formed so as to be balanced with the internal stress by the cover layer provided on the information surface side which is one surface of the resin substrate. It is provided with a labeled resin layer (or a displayable resin layer). That is, by balancing the internal stress of the cover layer and the internal stress of the resin layer, a cover layer that is thinner than the resin substrate and is bonded to the resin substrate causes a cover layer to be generated on the bonding surface. The warpage caused by the internal stress (contraction stress) that causes the inside of the layers to be canceled by the warpage that occurs when the resin layer formed on the surface opposite to the information surface is cured. The warp of the optical disk is also reduced.

As described above, the front and back surfaces of the resin substrate are formed by substantially the same process so that both surfaces of the optical disk are substantially symmetrical, so that the resin substrate and each layer, particularly the resin layer or An optical disc apparatus using an objective lens with a numerical aperture NA of 0.8 to 0.9 that makes the distance between the optical disc and the objective lens less than 1 mm from the warp of the optical disc caused by internal stress when the photocurable resin is cured. Can be reduced to a level that can be used for. As a result, recording of information having a high recording density using an objective lens having a numerical aperture NA of 0.8 to 0.9 such that the distance between the optical disc and the objective lens is 1 mm or less, and information recorded at that recording density Can be reproduced.

If internal stress is generated between the resin substrate and the cover layer on the information surface side and between the resin substrate and the resin layer on the side opposite to the information surface, the adhesive layer mainly made of an adhesive agent is generated. In the case where it can be seen (the cover layer and the resin layer are thicker than the adhesive layer), the internal stresses are mutually canceled by forming at least two layers of the adhesive in substantially the same process, An optical disc with less warpage can be obtained.

Further, a resin layer (resin layer adhered by an adhesive layer) for canceling internal stress of the cover layer provided on the information surface is provided with a label layer (or a layer for displaying the content of information recorded on the optical disc). By adopting a display surface layer capable of displaying the content of information recorded on the optical disc,
The reproduction optical disc can display the content information of the disc, and the writable disc can display (write) the content of the recorded information. It should be noted that the display surface layer is made of a material that can be written by an erasable writing tool such as a pencil in the case of a rewritable recording / reproducing optical disc that can be repeatedly recorded. This is important for optical discs that can be repeated.

[0082]

As described above, according to the present invention, the cover layer that covers the information surface, which is one surface of the resin substrate of the optical disk, is different from the information surface of the resin substrate on the other surface. In addition, a resin layer with a label function capable of displaying the content of information recorded on the optical disc or writing the content of information recorded on the optical disc is formed on the resin substrate in a process substantially equal to that of the cover layer. By providing the optical disc in a symmetrical or nearly symmetrical configuration, it is possible to cancel the internal stress generated when the cover layer is formed, and it is possible to obtain an optical disc having good mechanical characteristics represented by warpage.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an example of an optical disc according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an example of an optical disc different from the optical disc shown in FIG.

FIG. 3 is a schematic diagram illustrating an example of an optical disc apparatus that records information on the optical disc shown in FIGS. 1 and 2 and reproduces information from the optical disc.

FIG. 4 is a schematic diagram illustrating a modified example of the optical disc shown in FIG.

FIG. 5 is a schematic diagram illustrating a modified example of the optical disc shown in FIG.

FIG. 6 is a schematic diagram illustrating still another modified example of the optical disc shown in FIG.

FIG. 7 is a schematic diagram illustrating still another modified example of the optical disc shown in FIG.

FIG. 8 is a schematic diagram illustrating a factor that causes warpage in an optical disc having an increased recording density.

[Explanation of symbols]

1 ... Pixel, 2 ... opening, 3 ... Inter-field blanking period, 4 ... MTF within Nyquist frequency, 5 ... Folding distortion characteristics, 6 ... Return distortion / high resolution condition, 7 ... Liquid crystal display panel, 8 ... light source, 9 ... Lens system, 10 ... screen, 11 ... Position control unit, 12 ... Write signal to display device substrate.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G11B 7/24 535 G11B 7/24 535G 535K 538 538V 7/12 7/12

Claims (11)

(57) [Claims] 1. A resin substrate, a reflection layer or a reflection layer and a recording layer formed on one surface of the resin substrate, and a light having a predetermined wavelength can be transmitted through the reflection layer or the reflection layer and the recording layer. Is provided on the first resin layer that covers the first resin layer and the other surface of the resin substrate that is different from the one surface, and can display the content of information recorded in the reflective layer or the reflective layer and the recording layer. An optical disk, comprising: a second resin layer capable of providing a stress, which is balanced with a stress generated between the first resin layer and the resin substrate, between the resin substrate and the second resin layer. 2. The substantially same composition or substantially the same internal stress upon curing is provided between each of the first resin layer and the second resin layer and the base material (resin substrate). The optical disc according to claim 1, wherein a photo-curable resin provided with various characteristics is respectively interposed. 3. The first resin layer and the second resin layer each have a structure that is symmetrical or symmetrical to the base material (resin substrate).
The described optical disc. 4. A photo-curable resin having substantially the same composition as the first resin layer and the second resin layer, or a photo-curable resin having a characteristic that internal stresses during curing are substantially equal to each other. 2. The optical disc according to claim 1, wherein the optical disc is a layer formed of a plurality of layers. 5. The first resin layer and the second resin layer each have a configuration symmetrical or symmetrical to the base material (resin substrate).
The described optical disc. 6. The thickness of each of the first resin layer and the second resin layer is approximately 0.1 mm, and the thickness of the base material (resin substrate) is approximately 1 mm. The optical disc according to claim 1, wherein 7. The substantially same composition or substantially the same internal stress at the time of curing is provided between each of the first resin layer and the second resin layer and the base material (resin substrate). Various characteristics are provided, and a photocurable resin having a thickness less than ½ of the thickness of each of the first resin layer and the second resin layer is interposed. Item 6. The optical disk according to item 6. 8. A resin element which emits light of a predetermined wavelength, an objective lens having a numerical aperture of around 0.85, and a resin substrate and one surface of the resin substrate with the objective lens interposed. And the first resin layer that is capable of transmitting light having a predetermined wavelength and covers the reflective layer or the reflective layer and the recording layer, and another surface different from one surface of the resin substrate. The resin substrate, which is provided on one surface and can display the content of information recorded in the reflective layer or the reflective layer and the recording layer, has a stress that balances the stress generated between the first resin layer and the resin substrate. By receiving the light obtained by condensing the light from the laser element and performing photoelectric conversion on the optical disk having a second resin layer that can be provided between
An optical disk device comprising: a photodetector that obtains an output corresponding to information recorded on the optical disk. 9. A light is generated by using a laser element that emits light of a predetermined wavelength, and the light generated by the laser element by an objective lens having a numerical aperture of about 0.85 is transferred to a resin substrate and a resin. A reflective layer or a reflective layer and a recording layer formed on one surface of the substrate, a first resin layer capable of transmitting light of a predetermined wavelength and covering the reflective layer or the reflective layer and the recording layer, and one of the resin substrates. Is provided on the other surface different from the surface of (1) and is capable of displaying the content of information recorded in the reflective layer or the reflective layer and the recording layer, and is generated between the first resin layer and the resin substrate. A second resin layer capable of providing a stress balanced with the stress between the resin substrate and the second resin layer is condensed, and the condensed light is received by the photodetector to receive photoelectric conversion. Is recorded on the optical disc by Information reproducing method characterized by obtaining an output corresponding to have information. 10. Light is generated using a laser element that emits light of a predetermined wavelength, and the light intensity of the light generated by the laser element is recorded using an objective lens having a numerical aperture of about 0.85. Depending on the information to be changed, the resin substrate, the reflective layer or the reflective layer formed on one surface of the resin substrate and the recording layer, the light of a predetermined wavelength can be transmitted, the reflective layer or the reflective layer. The first resin layer covering the recording layer and the other surface different from the one surface of the resin substrate are provided, and the content of information recorded in the reflective layer or the reflective layer and the recording layer can be displayed. Then, a stress that balances the stress generated between the first resin layer and the resin substrate is condensed onto an optical disc having a second resin layer that can provide between the resin substrate and the stress, and information is recorded on the optical disc. An information recording method characterized by recording. 11. A resin substrate, a reflective layer or a reflective layer and a recording layer formed on at least one surface of the resin substrate, and a light having a predetermined wavelength can be transmitted therethrough, and the reflective layer or the reflective layer and the recording layer. A first resin layer for covering the first resin layer and the other surface different from the one surface of the resin substrate, and can display the content of information recorded in the reflective layer or the reflective layer and the recording layer, An optical disc having a second resin layer capable of providing a stress between the first resin layer and the resin substrate, the stress being balanced between the stress generated between the first resin layer and the resin substrate; and a laser element for emitting light of a predetermined wavelength, An objective lens having a numerical aperture of around 0.85, a lens holding mechanism for positioning the objective lens at a predetermined relative position with respect to the reflection layer or recording layer of the optical disc, and the predetermined laser from the laser element. Light of the wavelength A number of optical elements for guiding the objective lens, and photoelectric conversion of the reflected light reflected by the reflective layer of the optical disk to photoelectrically convert the objective lens to move and the amount of change that can be calculated. And an arbitrary number of photodetectors for outputting the optical disc device, wherein the lens holding mechanism controls the objective lens from the laser element provided with a predetermined focusing property by the action of the objective lens. The light is made to face the surface of the first resin layer of the optical disc at a distance of less than 1 mm so that the light can be condensed on the reflection layer or the recording layer of the optical disc, and the objective lens is used to reproduce the information. The light reflected by the reflective layer or recording layer of the optical disc is taken in and guided toward the optical element so that the photodetector can receive the light, During the recording, the optical disk apparatus, and information recording and reproducing method characterized by condensing the light from the laser element that is transmitted by the optical element to the recording layer.