JP2003115128A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion of an outer peripheral part by improving adhesion between a film including an optical recording layer 2 and a substrate 1 in an optical recording medium where the optical recording layer 2 and an optical transmission protective layer 4 are sequentially formed on the disk substrate 1. SOLUTION: On the disk substrate 1 of a radius 60 mm, a data area having a groove 11 is formed in a radius range of 24 to 58 mm and, around its outer periphery, a groove 11a is additionally formed intermittently in a radius range of 58 to 59.5 mm (groove adding area) is formed. In a film forming area (area including optical recording layer 2), a film is formed in a radius range of 18 mm to 58.8 mm, and a light transmissive protective layer 4 is formed on the film forming area in a radius range of 12 to 60 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium in which an optical recording layer and a light transmission protective layer are sequentially formed on a disk-shaped substrate.

[0002]

2. Description of the Related Art As a practical example of a rewritable optical disc using a phase change recording material in a conventional optical recording medium, a so-called DVD-RAM is commercially available, and the linear velocity is 6
m / sec, bit length 0.41 μm / sec, track pitch 0.74 μm, laser wavelength of about 650 nm, data transfer rate 11 Mbps, and recording capacity 2.6 GB are realized.

In order to realize a large capacity and a high transfer rate that exceed this, it is effective to reduce the spot size of the recording laser and increase the recording linear velocity. Here, specific methods for reducing the spot size of the recording laser include a method of shortening the laser wavelength and a method of increasing the numerical aperture of the objective lens.

In particular, if both the method of shortening the laser wavelength and the method of increasing the numerical aperture of the objective lens are used together, the spot size can be made smaller than the case where each is used alone. For example, a blue-violet laser having a wavelength near 400 nm is used as a light source, and the numerical aperture N of the objective lens is
The use of an objective lens having A of 0.85 enables theoretically higher density recording.

As described above, in order to increase the recording density, N.
A. It is essential to increase / λ. In this case, for example, in order to achieve a storage capacity of 8 GB, at least N.M. A. Is 0.7 or more and the laser wavelength λ is 0.68.
It is necessary to make it less than μm. Considering that the present red laser is applicable to the blue laser which is expected to be widely used in the future, it is considered appropriate to set the light transmission layer to 10 to 177 μm.

Generally, a disc skew margin DSM
Θ, the light source wavelength λ of the recording / reproducing optical pickup, and the numerical aperture N. A. , And the light transmission protective layer thickness t of the disk
Has a correlation with, and its playability has been sufficiently demonstrated in practice. The relationship between these parameters and DSM [Theta] based on the example of a compact disc (CD) is shown in Japanese Patent Laid-Open No. 3-225650. According to ^{this, -84.115 (λ / N.A. 3} / t) ≦ DSMΘ
It may be ≦ 84.115 (λ / NA. ³ / t).

Here, considering the concrete limit value of DSMΘ in the case of actually mass-producing disks, 0.4 ° is appropriate. This is because, in consideration of mass production, if the size is made smaller than this, the yield will decrease and the cost will increase. For existing optical recording media, the CD is 0.6
And 0.4 for DVDs. Therefore, DSMΘ =
The laser wavelength is shortened to 0.4 °, and the high N.V. A. Calculating how much the thickness of the light transmission protective layer should be set according to the optimization, first, assuming that λ = 0.65 μm, N. A. Is 0.7
8 or more is required. In the future, the wavelength will be shortened and λ =
When it is 0.4 μm, t = 177 μm. The lower limit of the thickness of the light transmission protective layer is determined by the protection function of the light transmission protection layer that protects the optical recording layer, and is preferably 10 μm or more in consideration of the reliability and the influence of the second group lens collision.

In the conventional optical recording medium, a dielectric film is formed on a substrate, and then a recording film, a dielectric film, and a metal film such as Al which is a reflective film are formed. It is composed of a membrane. These are sequentially formed by a film forming apparatus having a continuous film forming chamber.

However, in the higher density optical recording medium as described above, a metal film such as an Al alloy or an Ag alloy, which is a reflective film, is first formed, which is different from the above-described normal film formation sequence.
Then, a dielectric film, a recording film, and a dielectric film are formed (reverse film formation).

For example, as shown in FIG. 2, an optical disc (optical recording medium) 10 has an optical recording layer 2 made of a recording thin film formed on a disc substrate (supporting substrate) 1, and an adhesive layer 3 interposed therebetween. And a light transmission protection layer 4 is formed. The optical recording layer 2 includes a reflective layer 5, a first dielectric layer 6a, a recording layer 7,
It is composed of the second dielectric 6b. The arrow L _{1 in the} figure indicates the irradiation direction of the laser light.

When the disk is made of a single plate, the substrate is
Since a certain degree of rigidity is required, it is desirable that the thickness be 0.6 mm or more. Similarly, in the case of a structure in which two sheets are stuck together, it is preferable that the length is half that of 0.3 mm or more. Further, in consideration of diversion of manufacturing equipment such as CD, the substrate thickness is generally about 1.2 mm.

The polycarbonate resin and the polyolefin resin used for the disk substrate 1 have heat resistance during melt molding, are easy to mold, and have little deterioration.
Since it has excellent mechanical properties, it is useful as a substrate for optical recording media.

[0013]

By the way, in an optical disc, a groove usually called a groove for recording / reproducing,
Short grooves called embossed pits are formed and these give address information and tracking signals. Therefore, these groove shapes are generally formed only in the data area portion for recording / reproducing a signal, as shown in FIG.

In FIG. 8, the same parts as in FIG. 2 are shown with the same reference numerals, and 11 is a groove (or pit) formed on the surface of the disk substrate 1.

The optical recording layer 2 including the recording film is formed by sputtering or the like. At this time, the film is formed by masking the outer circumference or the inner circumference in order to prevent the film from being attached to the end surface of the substrate. When masking is performed in this way, the film thickness becomes unstable in a certain range from the mask edge (the range depends on the mask shape and film forming conditions).

Therefore, in anticipation of this region of unstable film thickness, the outer peripheral mask is arranged outside the outer peripheral area of the data area, and the inner peripheral mask is arranged smaller than the inner peripheral area of the data area. To be done.

Therefore, in the present situation, when the film forming area is viewed, the mirror portion 12 having no group can be formed outside the data area (inside in the case of the inner circumference). In the optical disc having such a structure, when the reverse film formation is used, there is a problem that corrosion which is not seen in the normal film formation occurs in the outer peripheral portion.

This is considered to be caused by the poor adhesion between the substrate 1 and the reflective layer formed on the disk substrate 1 by the reverse film formation.

The present invention has been made in view of the above points, and an object thereof is to provide an optical recording medium in which the adhesion between a film including an optical recording layer and a substrate is improved to prevent corrosion.

[0020]

An optical recording medium of the present invention for solving the above-mentioned problems is an optical recording medium in which an optical recording layer and a light transmission protective layer are sequentially formed on a disk-shaped substrate, wherein the substrate A film including at least a laser-readable recording layer is formed thereon, and a light transmission protective layer is formed on the film including the recording layer via an adhesive layer. It is characterized in that a mirror portion does not exist in a portion facing the outer peripheral portion of the film forming area.

Further, a groove or a pit is formed in a portion of the substrate facing the outer peripheral portion of the film forming area of the film including the recording layer.

Further, the substrate is characterized by being formed of a polycarbonate or a polyolefin resin.

The recording layer on the substrate has at least a reflective layer, and the reflective layer is made of an Ag alloy.

The adhesive layer is characterized by being made of an ultraviolet curable resin or an adhesive sheet.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION An optical recording medium to which the present invention is applied will be described below in detail with reference to the drawings.

FIG. 1 shows the relationship between the data area and the film formation area in the optical recording medium of the present invention. The same parts as those in FIG. 8 are designated by the same reference numerals.

In FIG. 1, a disk substrate 1 having a radius of 60 mm has a data area having a groove 11 with a radius of 24.
It is formed in the range of up to 58 mm, and in addition to this, the groove 11a continues on the outer periphery thereof and has a radius of 58 to 59.5 m.
It is formed in the range of m (groove addition area).

Film-forming area (area including optical recording layer 2)
Is formed in a radius range of 18 mm to 58.8 mm. The light transmission protective layer 4 has a radius of 12 to 60 on the film formation area.
It is formed in the range of mm.

It is desirable that the groove area exists inside the inner circumference data area. However, since the light transmission protection layer 4 covers the inner circumference film formation area sufficiently to the inner side, It does not matter if there is no groove area inside the area (it does not matter if there is a mirror part on the inner circumference).

On the other hand, the outer peripheral portion of the data area may be used up to the limit of the substrate (also the light transmission protective layer), and therefore the groove 11a needs to be formed in the outer peripheral portion of the data area.

However, the groove 1 outside this data area
1a may be formed in a shape such as a pit as long as the adhesion is improved. Further, it is sufficient that the film forming area is secured for the groove area, and the groove area may extend to the outer peripheral edge of the substrate.

The film forming area in FIG. 1 is formed by a film forming apparatus as shown in FIG. 7, for example. In FIG. 7, a target for forming a reflective film is arranged in the first chamber Ch1 and DC is used as a power source. Second
A target for forming a dielectric film is arranged in the chamber Ch2, and RF is used as a power source.

A target for a recording film is arranged in the third chamber Ch3, and DC with a chopper function is used. A target for forming a dielectric film is arranged in the fourth chamber Ch4, and RF is used as a power source. A target for forming a dielectric film is arranged in the fifth chamber Ch5, and RF is used as a power source.
Is used.

However, the configuration of these chambers depends on the configuration of the film as described in FIGS. 3 to 6 below. 3 to 6, the same parts as those in FIG. 2 are designated by the same reference numerals.

FIG. 3 shows an example in which a layer 21 made of a metal or a semi-metal is provided in contact with one (or both) of the surfaces of the recording layer 7, whereby the functions of the reflection layer, the heat sink layer, etc. Can have

Alternatively, as shown in FIG. 4, the first dielectric layer 16a and the second dielectric layer 16a are formed on one or both surfaces of the recording film 7.
Layer 2 made of metal or semi-metal like the dielectric layer 16b of
1a and 21b may be arranged in multiple layers. In this case, by controlling the film thickness, it becomes possible to control the optical characteristics such as reflectance and absorptance, and the film structure can be easily designed.

Further, as shown in FIG. 5, the optical disk 10 of FIG.
It is possible to increase the capacity by sticking together or by adopting a structure in which the optical recording layer 2 is formed on both surfaces of the substrate.

The order of film formation in the above-mentioned optical disc is the reverse of the conventional one, as shown in FIG. 2, on the disc substrate 1 on the reflective layer 5, the first dielectric layer 6a, the recording layer 7, and the second dielectric layer. 6b is formed in this order, a thin light transmission protection layer 4 is provided, and recording and reproduction are performed from the side opposite to the disk substrate.

As a result, by performing recording / reproduction from the thin light transmission protection layer side, the numerical aperture of the objective lens can be increased and a high recording density can be realized while ensuring the skew margin.

As shown in FIG. 1, the optical recording layer 2 has a film formation area outer diameter smaller than the substrate outer diameter and a film formation area inner diameter larger than the substrate inner diameter. Moreover, the outer diameters of the light transmission protective layer 4 and the adhesive layer are larger than the outer diameter of the film formation area and smaller than the outer diameter of the substrate, and the inner diameters of the light transmission protection layer 4 and the adhesive layer are the inner diameter of the film formation area. Smaller than and larger than the inner diameter of the substrate.

In the optical disc having the above-mentioned structure, as the material used for the disc substrate (supporting substrate) 1, a plastic material such as a polycarbonate resin, a polyolefin resin, an acrylic resin is excellent in terms of cost, but glass. Can also be used.

The injection molding method (injection method) or the photopolymer (2P method) using an ultraviolet curable resin is used for the production.
Can be used. Other than this, any method may be used as long as it has a desired shape (for example, a disk shape with a thickness of 1.1 mm and a diameter of 120 mm) and an optically sufficient smoothness of the substrate surface.

Although the thickness of the disk substrate 1 is not particularly limited, it is preferably 0.3 mm or more and 1.3 mm or less. If the thickness of the substrate is less than 0.3 mm, the strength of the disc may be reduced and the disc may be easily warped. Conversely, 1.3 mm
If it is thicker, the thickness of the disc will be 1.2mm for CD and DVD.
Since it becomes thicker, it may not be possible to share the same disc tray when commercializing a drive device corresponding to all of them.

Further, since the laser for recording / reproducing enters from the light transmission protection layer 4 side, the material of the disk substrate 1 may be a non-transparent material such as metal.

Further, an uneven groove track may be formed on the surface of the disk substrate 1 on which the optical recording layer 2 is formed. Using this groove as a guide, the laser beam can move to any position on the disk. The groove shape is spiral,
Various shapes such as concentric circles and pit rows can be applied.

The light transmission protection layer 4 is preferably made of a material that does not have the ability to absorb the wavelength of the laser for recording / reproducing, and specifically, the material having a transmittance of 90% or more. In addition, the thickness of the light transmission protective layer 4 is preferably 0.3 mm or less. In particular, by setting the thickness to 3 μm to 177 μm and combining it with a high numerical aperture NA (for example, 0.85), it is possible to realize high density recording that has never been achieved. For example, the material used as the transmission layer material includes
Examples include polycarbonate resin and polyolefin resin.

Then, these polycarbonate resins are put into an extrusion device, melted by a heater and extruded into a sheet, formed into a sheet by using a plurality of cooling rolls, and cut into a shape matched to the shape of the substrate.

Further, in order to prevent dust from adhering to the surface of the light transmission protective layer 4 or scratches,
You may further form the protective film which consists of organic type or inorganic type material. Also in this case, it is desirable to use a material having almost no absorptivity with respect to the wavelength of the laser for recording and reproducing.

The following two methods can be roughly classified as a method of manufacturing an optical disk for recording and reproducing from the side of the light transmission protection layer 4 described above. The first method is a method in which a multilayer film is laminated on the disk substrate 1 in which the guide groove is formed, and finally the smooth light transmission protective layer 4 is formed. The method for forming the light transmission protective layer 4 is, for example, 100 μm in thickness.
Optically sufficiently smooth light-transmitting sheet (film) made of the following polycarbonate, polyolefin resin, etc.
It is possible to use a method of bonding with a UV-curable resin as an adhesive by irradiation with ultraviolet rays, or a method of bonding with a sheet having an adhesive function.

The second method is a method in which a multilayer film is laminated on the light transmission protection layer 4 in which the guide groove is formed, and finally the smooth disk substrate 1 is formed. For example, as a method of forming a groove track of unevenness in the light transmission protective layer 4 having a thickness of 100 μm or less, an injection molding (injection) method, a photopolymer method (2P method), a method of transferring unevenness by pressure bonding / pressurization, etc. Can be used.

However, the step of forming irregularities or the step of forming a multilayer film on the light transmission protective layer 4 is not always easy, so that the first method is advantageous when mass production is considered. is there.

In the optical disc having each of the above-mentioned configurations, the recording material layer is formed of a phase change material which causes a reversible phase change between an amorphous state and a crystalline state.

For example, Te, Se, Ge-Sb
-Te, Ge-Te, Sb-Te, In-Sb-Te,
Ag-In-Sb-Te, Au-In-Sb-Te, G
e-Sb-Te-Pd, Ge-Sb-Te-Se, In
-Sb-Se, Bi-Te, Bi-Se, Sb-Se,
Ge-Sb-Te-Bi, Ge-Sb-Te-Co, G
Examples thereof include systems containing e-Sb-Te-Au, and systems in which gas additives such as nitrogen and oxygen are introduced into these systems.

In particular, a material having a crystallization rate at which crystallization is impossible with the laser and the linear velocity used is preferable, and among these, a material having an Sb-Te system as a main component is particularly preferable. , Sb / Te ratio of 2.6 or less is preferable. It is also preferable to add any element such as Se or Pd, or Ge or In, nitrogen or oxygen.

Further, in the present invention, since it relates to the prevention of abnormal discharge at the time of reverse film formation by the apparatus, not only the phase change material but also Tb-Fe system, Te-FeCo system, Gd-Fe system.
-Based, Gd-FeCo-based magneto-optical recording materials, Al alloys and A
The same effect can be easily expected in a ROM or the like using a g-alloy as a reflective film, and thus the present invention is not limited to the phase change recording material.

The present phase change recording medium is characterized in that it is composed of a phase change recording film having a crystallization rate at which crystallization becomes impossible at the laser and linear velocity used. It is possible to perform an operation of recording and reproducing by creating an amorphous state and utilizing an optical change such as reflectance due to this state change.
In general, after film formation, a low wavelength, high power laser is used to give sufficient crystallization time to once perform crystallization (generally referred to as initialization).

The recording layer 7 may be composed of two or more continuous layers (different in material, composition or complex refractive index) as shown in FIG.

The reflective layer 5 made of metal or semimetal is
For example, in the case of considering the function as reflection, it has a reflectivity for the wavelength of the recording / reproducing laser and has a thermal conductivity of 0.
0004 [J / (cm · K · s)] to 4.5 [J / (c
m · K · s)], a metal element, a metalloid element, and a compound or mixture thereof.

As a specific example, Al, Ag, A
u, Ni, Cr, Ti, Pd, Co, Si, Ta, W,
Examples include simple substances such as Mo and Ge, or alloys containing these as the main components. Among these, especially Al-based,
Ag-based, Au-based, Si-based, and Ge-based materials are preferable in terms of practicality. As the alloy, for example, Al-Ti, Al-
Cr, Al-Co, Al-Mg-Si, Ag-Pd-C
u, Ag-Pd-Ti, Si-B and the like.

These materials are set in consideration of optical characteristics and thermal characteristics. Generally, when the thickness of the material is set to a thickness at which light is not transmitted (for example, 50 nm or more), the reflectance becomes high and heat easily escapes. Especially Al-based and Ag
The system material is suitable because it has a high reflectance even in a single wavelength region (for example, 80% or more when λ = 400 nm). Further, as shown in FIG. 6, the layer (reflection layer) made of metal or metalloid may be a two-layer film of the first reflection layer 15a and the second reflection layer 15b. Further, it is also possible to have a multilayer structure of two or more layers. This facilitates optical design and balances with thermal characteristics.

As a material used for the dielectric layers 6a and 6b, a material having no absorption ability with respect to the wavelength of the recording / reproducing laser is desirable, and specifically, a material having an extinction coefficient k of 0.3 or less. Is preferred. As such a material, for example, Z
nS-SiO ₂ mixture (about particular molar ratio of 4: 1) can be mentioned. However, other than the ZnS—SiO ₂ mixture, any material conventionally used for optical recording media can be applied to the dielectric layer.

For example, Al, Si, Ta, Ti, Zr,
Gold such as Nb, Mg, B, Zn, Pb, Ca, La, Ge
Nitrides, oxides, carbides, metals of elements such as metals and metalloids
From fluoride, sulfide, oxynitride, nitrocarbide, oxycarbide, etc.
It is possible to use a layer consisting of
come. Specifically, AIN_x(0.5 ≦ x ≦ 1), especially
AIN, Al₂O_3-x(0 ≦ x ≦ 1), especially Al₂O₃, S
i₃N_4-x(0 ≦ x ≦ 1), especially Si₃N_Four, SiO_x(1
≦ x ≦ 2), especially SiO₂, SiO, MgO, Y ₂O₃，
MgAl₂O_Four, TiO_x(1 ≦ x ≦ 2), especially TiO₂，
BaTiO₃, StTiO₃, Ta₂O_5-x(0 ≦ x ≦
1), especially Ta₂O_Five, GeO_x(1 ≦ x ≦ 2), Si
C, ZnS, PbS, Ge-N, Ge-NO, Si-
NO, CaF₂, LaF, MgF₂, NaF, ThF_Four
Etc. can be mentioned. Layer consisting of these and this
A layer containing them as a main component is applicable. Or these
A mixture of, for example, AlN-SiO₂A layer consisting of a dielectric
It can also be a layer.

Next, a more specific embodiment of the present invention will be described.

(Embodiment 1) The relationship between the data area and the film formation area in the optical recording medium of this embodiment is as shown in FIG. That is, a disk substrate 1 having a radius of 60 mm has a data area having a groove 11 with a radius of 24 to 5
In addition to this, the groove 11a is continuously formed on the outer periphery thereof in the range of a radius of 58 to 59.5 mm (groove addition area) to form a film forming area (optical recording layer 2).
Area) including a radius of 18 mm to 58.8 mm, and the light transmission protection layer 4 is formed on the deposition area with a radius of 12 mm to 58.8 mm.
It is formed in the range of 60 mm.

A film was formed on the above medium by using the film forming apparatus shown in FIG. DC in the first chamber Ch1
Power is disposed on the target Yes by arranging the Ag alloy, the second chamber Ch2 is arranged RF power, target marked with ZnS-SiO ₂ film. A DC power source is arranged in the third chamber Ch3, and the target is S
A bTe recording film is attached. 4th and 5th chamber C
An RF power source is placed on h4 and Ch5, and the target is Zn.
S-SiO ₂ is attached. Each target is φ200
Is.

The film forming conditions for the single-wafer sputtering machine are as follows.

[Process start vacuum degree 9E-5 mbar] Conditions of each process Ag ... Ar gas 20 sccm, gas pressure 4e-3 mbar
r, PW 3kW, ZnS-SiO 2 ... Ar gas 12s
ccm, gas pressure 3e-3 mbar, PW 4.5k
W, SbTe recording film ... Ar gas 20 sccm, gas pressure 2.5e-3 mbar, PW 0.7 kW The diameter of each target is 200 mm.

Then, a substrate made of polycarbonate having a diameter of 120 mm and a thickness of 1.1 mm was prepared. This substrate has a groove called a concave groove on one surface.
The groove spacing (track pitch) is 0.32 μm.
The data area has a radius of 24-58 mm,
In addition to this, the groove continues on the outer circumference and the radius is 58 ~
It is formed with 59.5 mm.

On the concave side of the substrate, an inner peripheral mask (radius 18
mm), using a peripheral mask (radius 58.8 mm)
In the chamber Ch1, Ag alloy is deposited by DC at a power of 3 kW and 1000 Å. Followed by the second chamber Ch2 in ZnS-SiO ₂ dielectric film is 100Å deposited with 1kW of power at RF. An SbTe-based recording film is formed on the ZnS-SiO ₂ in the third chamber Ch3 by DC at 700 W and 100 Å. Continue to the 4th and 5th chamber Ch
A ZnS-SiO ₂ film of 4 and Ch 5 is formed by RF with a power of 4 kW and a total thickness of 450 Å. Then, it was taken out from the sputtering apparatus, and the light transmission layer made of polycarbonate was bonded onto the ZnS-SiO ₂ via an adhesive. At this time, the total thickness of the adhesive and the polycarbonate sheet was set to 0.1 mm.

(Comparative Example) As shown in FIG. 8, there is no groove shape in the outer peripheral portion of the data area, and the so-called mirror portion 12 is formed.
A film was formed on the disk substrate 1 on which was formed in the same manner as in the above-described embodiment.

Next, in Embodiment 1 and Comparative Example, the progress of corrosion was observed.

The experimental conditions are 80 ° C. and 85% for 500 hours.

As a result, although no difference was observed in the corrosion of the data area, erosive corrosion was observed in the comparative example in the outer peripheral portion.

It is considered that the groove shape addition (11a) at the outer peripheral portion of the data area according to the present invention improves the adhesion between the reflective film (reflective layer 5) and the substrate 1 and prevents the outer peripheral edge corrosion. To be

Such a problem of adhesion was not a problem in the normal forward film formation. It is considered that this was because the adhesion between the substrate and the dielectric film was good, and there was no influence of a stressed material such as a light transmission protective layer (the light transmission protective layer was formed by using a polycarbonate sheet on the inner surface). It is believed that the outer peripheral part is under stress because it is pasted from the part to the outer peripheral part.).

(Embodiment 2) A normal substrate before film formation shown in FIG. 8 is prepared, and its data area is masked.
Only the outer peripheral portion was exposed, and this was subjected to etching treatment by reverse sputtering with a sputtering device. Reverse sputtering conditions were Ar 20 sccm, 3 mTorr, RFP
It was carried out at W 0.3 kW for 8 minutes.

When the above media was formed into a film in the same manner as in Embodiment 1, the corrosion resistance results were the same as in Embodiment 1.

In the second embodiment, the molded substrate is etched, but there is a problem in productivity. Of course, when productivity is taken into consideration, as a method to obtain the same effect,
Etching outside the data area in the stamper,
Use a method of rubbing with a file.

[0079]

As described above, according to the present invention, the mirror portion is not present at the portion of the substrate facing the outer peripheral portion of the film formation area including the recording layer. In an optical recording medium manufactured by so-called reverse film formation in which a reflective film is first formed, the adhesion between the substrate and the film is improved and corrosion from the outer peripheral portion can be prevented.

In particular, when a groove or pit is formed in a portion of the substrate facing the outer peripheral portion of the film forming area, the vertical area increases, the adhesion is improved by the anchor effect, and corrosion from the outer peripheral portion can be prevented. .

Since the adhesion between the substrate and the reflection film formed thereon is improved in this way, polycarbonate or polyolefin resin, which is considered to have poor adhesion, can be used as the substrate material. The advantages are that it is easy to mold, there is little deterioration, and the cost is reduced.

For the same reason, Ag having poor adhesion is used.
Alloys can be used as the reflective layer, which improves the reflectance properties.

Further, by forming the adhesive layer with an ultraviolet curable resin or an adhesive sheet, the production becomes easy.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of an essential part showing an example of the configuration of an optical disc to which the present invention is applied.

FIG. 3 is a cross-sectional view of main parts showing another example of the configuration of an optical disc to which the present invention is applied.

FIG. 4 is a cross-sectional view of main parts showing another example of the configuration of an optical disc to which the present invention is applied.

FIG. 5 is a sectional view of an essential part showing another example of the configuration of the optical disc to which the present invention is applied.

FIG. 6 is a sectional view of an essential part showing another example of the configuration of the optical disc to which the present invention is applied.

FIG. 7 is a configuration diagram showing an example of a film forming apparatus for manufacturing the optical recording medium of the present invention.

FIG. 8 is a sectional view showing an example of a conventional optical disc.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk substrate, 2 ... Optical recording layer, 3 ... Adhesive layer, 4 ... Light transmission protective layer, 5, 15a, 15b ... Reflective layer, 6a, 6
b, 16a, 16b ... Dielectric layer, 7 ... Recording layer, 10 ... Optical disk, 11, 11a ... Groove, 12 ... Mirror section,
21, 21a, 21b ... Metal or metalloid layer.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) G11B 7/24 G11B 7/24 538F

Claims (5)

[Claims] 1. An optical recording medium in which an optical recording layer and a light transmission protective layer are sequentially formed on a disk-shaped substrate, wherein a film including at least a laser-readable recording layer is formed on the substrate, A light transmission protective layer is formed on the film including the recording layer via an adhesive layer, and a mirror portion does not exist at a portion of the substrate facing the outer peripheral portion of the film formation area of the film including the recording layer. Characteristic optical recording medium. 2. The optical recording according to claim 1, wherein a groove or a pit is formed in a portion of the substrate facing the outer peripheral portion of the film formation area of the film including the recording layer. Medium. 3. The optical recording medium according to claim 1, wherein the substrate is formed of polycarbonate or polyolefin resin. 4. The optical recording medium according to claim 1, wherein the recording layer on the substrate has at least a reflective layer, and the reflective layer is made of an Ag alloy. 5. The optical recording medium according to claim 1, wherein the adhesive layer is made of an ultraviolet curable resin or an adhesive sheet.