HK1132082B - Optical information recording medium and a manufacturing method thereof - Google Patents

Abstract

The invention provides an optical information recording medium and a manufacturing method thereof. The optical information recording medium comprises at least an optical reflective layer and a protective layer formed on a substrate in that order, avoids abnormal electrical discharge as forming the protective layer using sputtering method, prevents the protective layer at the interface with the substrate from peeling, and thus is devoid of the defects caused by the abnormal electrical discharge. The invention subjects to an optical information recording medium having a disc substrate wherein one of the main surfaces has spiral-shaped groove formed thereon. The optical information recording medium comprises, an optical reflective layer reflecting laser light, an optical recording layer containing a photoabsorptton material which absorbs the laser light, a protective layer having an inorganic material, and an optical transparency layer, formed in that order on said main surface. The protective layer is a layer formed by the sputtering method. The function of avoiding abnormal electrical discharge and peeling of the protective layer is accomplished by setting an area of the protective layer wider than an area of the reflective layer, but narrower than an area of the optical transparency layer.

Description

Optical information recording medium and method for manufacturing the same

Technical Field

The present invention relates to an optical information recording medium and a method for manufacturing the same, and more particularly, to an optical information recording medium having a protective layer and a method for manufacturing an optical information recording medium using a sputtering method.

Background

In recent years, optical information recording media have been required to record high-definition image data, and therefore, they are required to have high information recording density. Therefore, a recordable optical information recording medium, such as a blu-ray disc (hereinafter abbreviated as "BD-R"), using a short wavelength laser beam having a wavelength of about 360 to 450nm (e.g., about 405 nm) on the short wavelength side has been proposed. The optical information recording medium uses an organic dye compound such as an azo dye or a cyanine dye in its optical recording layer, and the organic dye compound is decomposed or degenerated by absorption of laser light to obtain a change in optical characteristics at the recording/reproducing wavelength of the laser light as a modulation degree, thereby enabling recording and reproduction.

In such an optical information recording medium, a light reflection layer and an optical recording layer are formed in this order by being stacked on a resin substrate having a guide groove (also referred to as a pregroove, hereinafter simply referred to as a "groove") formed on a surface on a light incident side, and a light transmission layer made of a light transmitting resin is provided on the optical recording layer, and the light transmission layer is formed to have the same diameter and thickness as those of CD-R or DVD ± R. In order to protect the optical recording layer, a protective layer made of a light-transmitting inorganic material is provided between the optical recording layer and the light-transmitting layer.

The BD-R having the optical recording layer of the organic dye is produced by forming a light reflecting film on the surface of the resin substrate on which the grooves are formed by a sputtering method in vacuum, taking the film out of the atmosphere once, forming the organic dye by a spin coating method, forming a protective film by a sputtering method in vacuum again, and finally attaching a light transmitting sheet to the film to form the BD-R. When the optical recording layer is made of an inorganic material, the light reflecting layer, the optical recording layer, and the protective layer can be laminated without taking out the layers into the atmosphere by a method of carrying the layers in a vacuum and continuously sputtering the layers.

As shown in fig. 5, for example, in a sputtering apparatus used for forming a film of a light reflective layer or the like, a substrate holder 2 and a target holder 6 for an optical information recording medium are used, and a substrate 1 as an information recording medium to be processed is disposed so as to face a target 5 of gold, aluminum or the like, and when forming a film by a high-frequency sputtering method, an insulating resin material is used for the substrate holder 2 and the target holder 6 so as not to be conductive to the substrate or the target to be sputtered.

In order to shield the substrate 1 for an optical information recording medium from the film formation side, the inner mask 3 and the outer mask 4 are disposed at the center and the outer periphery of the substrate 1, and a metal member or an alloy member is generally used as a mask material.

Fig. 6 shows another example of the substrate support, and generally the same inner mask 3 and outer mask 4 are used.

The optical information recording medium is not limited to the BD-R described above, and may be used for other optical information recording media.

For example, patent document 1 describes a reproduction-only optical disc in which a light reflection layer and a protective layer are provided on a disc-shaped synthetic resin substrate provided with concave-convex information, wherein when the light reflection layer is provided by sputtering, an inner peripheral edge portion and an outer peripheral edge portion of the substrate are covered with a mask.

Patent document 2 describes that, in an optical information recording medium in which at least a dye recording layer containing a dye material, a reflective layer containing a metal, and a protective layer are formed in this order on a light transmissive substrate, the reflective layer is formed by covering the recording layer with the reflective layer by a method such as sputtering.

Patent document 3 describes that in a two-layer type optical information recording medium having a recording layer containing an organic dye, a light reflecting layer is not in contact with a protective layer containing a sulfur element, and that the protective layer is formed by a sputtering method.

[ patent document 1] Japanese patent laid-open No. Hei 4-14634

[ patent document 2] Japanese patent laid-open No. Hei 11-134714

[ patent document 3] Japanese patent laid-open No. 2005-267670

In both of the optical information recording media described in patent documents 1 and 2, the sputtering method is used only in the step of forming the light reflecting layer, and the protective layer is formed by spin-coating an ultraviolet curable resin on the light reflecting layer, and therefore there is no problem. However, in the BD-R manufacturing process described above, when the protective layer is formed again by the sputtering method after the light reflective layer and the optical recording layer are formed, if the inner mask and the outer mask are in contact with the formed metallic light reflective layer, conduction may occur and abnormal discharge may occur. In this case, the following problems arise: the outer peripheral end surface of the light reflection layer is formed in a zigzag shape, or a lightning-like discharge trace extending from the outer peripheral end of the light reflection film to the inner peripheral side is generated in some cases.

In the optical information recording medium described in patent document 3, although various forms of the protective layer are exemplified, no specific masking method is described. Meanwhile, there is no description about such problems.

Disclosure of Invention

The present invention has an object to provide an optical information recording medium which has a protective layer on an upper layer of a light reflection layer formed on a substrate, solves the above-mentioned problems in forming the protective layer by a sputtering method, prevents the occurrence of abnormal discharge, and is free from defects, and a method for manufacturing the same.

As a result of diligent research directed toward achieving the above object, the present inventors have found that the above problems can be solved by forming a protective layer by a sputtering method using a mask which can avoid contact with a light reflective layer formed already and making the region of the protective layer wider than the region where the light reflective layer is provided.

However, although the generation of abnormal discharge can be prevented by making the area of the protective layer wider than that of the light reflecting layer, in this case, the protective layer is in direct contact with the substrate, and the adhesion between the protective layer made of an inorganic material and the resin substrate is poor, so that there is a problem that the protective layer is easily peeled off from the interface.

Therefore, the present inventors have further studied and found that the above-described problems of both abnormal discharge and peeling can be solved by providing a region where the protective layer is provided wider than a region where the light reflective layer is provided, and providing a light transmissive layer so as to cover the protective layer and provide a portion in close contact with a part of the substrate.

The present invention has been completed based on these findings, and the contents thereof are as follows.

[1] An optical information recording medium provided with at least a substrate, a light reflection layer provided on one of main surfaces of the substrate, an optical recording layer provided on an upper surface of the light reflection layer, a protective layer provided on an upper surface of the optical recording layer, and a light transmission layer provided on an upper surface of the protective layer, the optical information recording medium characterized in that:

the protective layer is a layer formed by a sputtering method, and an area where the protective layer is provided wider than an area where the light reflection layer is provided, and directly or indirectly covers an end portion of the light reflection layer.

[2] The optical information recording medium according to [1], characterized in that: the light-transmitting layer covers the protective layer and is continuously provided up to the outer peripheral end of the substrate.

[3] The optical information recording medium according to [1], characterized in that: the light-transmitting layer is continuously provided so as to exceed the outer peripheral end of the substrate, and is provided so as to cover an edge portion of the outer peripheral end.

[4] A method of manufacturing an optical information recording medium according to any one of the above [1] to [3], the method comprising: an inner peripheral end of the outer mask used for forming the protective layer by sputtering is positioned on an outer peripheral side of a position corresponding to an outer peripheral end of the light reflecting layer providing region.

[5] A method of manufacturing an optical information recording medium according to any one of the above [1] to [3], the method comprising: the outer peripheral end of the inner mask used for forming the protective layer by sputtering is located on the inner peripheral side of a position corresponding to the inner peripheral end of the light reflecting layer providing region.

[6] A method of manufacturing an optical information recording medium according to any one of the above [1] to [3], the method comprising: an inner peripheral end portion of an outer mask used for forming the protective layer by a sputtering method is located at a position corresponding to an outer peripheral end of the light reflection layer installation region, and a thickness of the mask in the vicinity of an inner terminal end portion is continuously or stepwise increased as it is farther from the position corresponding to the outer peripheral end of the light reflection layer.

[ Effect of the invention ]

In the present invention, when the protective layer is formed by the sputtering method, the area of the protective layer is formed to be wider than the area of the light reflecting layer formed, so that the contact between the inner mask and the outer mask and the light reflecting layer can be prevented, and abnormal discharge is not generated.

Drawings

FIG. 1 is a partially enlarged sectional view showing an internal structure of an optical information recording medium of the present invention.

FIGS. 2(A) to (C) are schematic views showing the outer peripheral edge of the optical information recording medium of the present invention.

FIG. 3 is a schematic view showing one mode of an outer mask used in the present invention.

FIG. 4 is a schematic view showing another embodiment of an outer mask used in the present invention.

Fig. 5 is a schematic diagram showing an example of the sputtering apparatus.

Fig. 6 is a schematic view showing another example of the substrate support.

[ description of symbols ]

1 substrate

2 substrate support

3 inner mask

4 outer mask

5 target

6 target pressing plate

10 optical information recording medium

11 substrate

12 groove

13 light reflecting layer

14 optical recording layer

15 protective layer

16 adhesive layer

17 light-transmitting layer

Detailed Description

The optical information recording medium of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an optical information recording medium of the present invention, in which a spiral groove 12 is formed in one main surface of an annular substrate 11 having a thickness of about 1.1 mm. On the principal surface of the substrate 11 on which the spiral groove 12 is formed, a light reflecting layer 13 that reflects laser light, a light recording layer 14 containing a light absorbing substance composed of, for example, an organic dye that absorbs laser light, a protective layer 15 made of an inorganic material, an adhesive layer 16 provided as needed, and a light transmitting layer 17 having a thickness of about 0.1mm are sequentially provided in layers.

In the present invention, the protective layer 15 is a layer formed by a sputtering method, and the region provided with the protective layer is formed to be wider so as to cover the side surface on the inner peripheral side and the side surface on the outer peripheral side of the region provided with the light reflecting layer 13. The light-transmitting layer 17 is formed to be wider than the region where the protective layer 15 is provided, and covers the side surface on the inner periphery side and the side surface on the outer periphery side of the protective layer 15. In this way, the protective layer 15 is formed to be slightly narrower than the region of the light-transmitting layer formed above it. In particular, the outer peripheral end of light-transmitting layer 17 is preferably formed in close contact with the outer peripheral end face or the edge of the outer peripheral side face of substrate 11. By being constituted in this manner, the protective layer 15 can be prevented from peeling off from the interface of the substrate 11.

Even when light-transmitting layer 17 is in the form of a sheet, the outer peripheral end of light-transmitting layer 17 is attached to the outer peripheral end of substrate 11, and therefore substantially the same effect can be obtained.

Fig. 2(a), (B) and (C) are schematic diagrams showing the results of confirming the cross section of the outer peripheral end of the optical information recording medium 10 with a microscope in order to clarify the configuration of the present invention.

In the optical information recording medium of the present invention, as shown in fig. 2(a), the light-transmitting layer 17 is preferably provided continuously to the outer peripheral edge of the disk-shaped substrate 11 of the optical information recording medium 10. According to the optical information recording medium 10, the protective layer 15 covers the end surfaces of the light reflection layer 13 and the optical recording layer 14, and the light transmission layer 17 is continuously provided to the outer peripheral end of the substrate 11 while covering the protective layer 15, so that discharge at the time of forming the protective layer 15 can be prevented. Also, peeling of the protective layer 15 can be effectively prevented. The light-transmitting layer 17 in this embodiment is formed of a sheet-like resin. Here, the adhesive layer 16 for bonding the light-transmitting layer 17 to the upper surface of the protective layer 15 is not shown.

In the embodiment shown in fig. 2(B), the same applies to the case where the protective layer 15 covers the end surfaces of the light reflecting layer 13 and the optical recording layer 14, and the difference from fig. 2(a) is that the outer peripheral end of the protective layer 15 is formed up to the outer peripheral end of the substrate 11. Further, the following is shown: the light-transmitting layer 17 is formed to protrude beyond the outer peripheral end of the protective layer 15 to the edge of the outer peripheral side surface of the substrate 11.

The embodiment shown in fig. 2(C) differs from the embodiment described above in that the optical recording layer 14 is formed to extend to the outer peripheral end of the substrate 11 so as to cover the end face of the optical reflection layer 13. The protective layer 15 is formed to cover the upper surface of the optical recording layer 14, and the light-transmitting layer 17 is formed in the same manner as in fig. 2 (B). In addition, although the position of the outer peripheral edge of the optical recording layer 14 in this embodiment extends to the outer peripheral edge of the substrate 11, the difference in the formation pattern is controlled by the rotation speed and time of spin coating.

By adopting the configuration of fig. 2(B) or 2(C), even when the protective layer 15 is provided up to the outer peripheral end of the substrate 11, peeling can be prevented, and also discharge at the time of forming the protective layer 15 by sputtering can be prevented. The light-transmitting layer 17 in these embodiments is formed by spin-coating a liquid resin while adjusting the number of rotations and time.

The layers constituting the optical information recording medium 11 of the present invention will be described in detail below.

(substrate)

In the present invention, the substrate 11 may be made of any of various materials that are conventionally used as a substrate material. Specific examples thereof include: acrylic resins such as polycarbonate and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, amorphous polyolefins, polyester resins, metals such as aluminum, glass, and the like, and these may be used in combination as necessary. Among these materials, thermoplastic resins are preferable, and polycarbonate is particularly preferable, from the viewpoints of moldability, moisture resistance, dimensional stability, and low cost.

When these resins are used, it is preferable that the substrate 11 is formed into a specific shape by a method such as injection molding, for example, into a ring shape in the case of an optical disc. The thickness of the substrate 11 is preferably set to be in the range of 0.9 to 1.1 mm. Further, the present invention is not limited to this, and for example, an ultraviolet curable resin may be used by applying it to a base and curing the coating film.

In the present invention, it is preferable that the spiral groove 12 is formed simultaneously with the injection molding of the substrate 11 by disposing a template called a stamper, which is formed by performing spiral convex microfabrication having a reverse pattern to the groove 12 on one main surface, in a mold used for the injection molding of the substrate 11.

(light reflecting layer)

The light reflecting layer 13 of the present invention reflects laser light for recording and/or reproducing data, and is a layer provided between the substrate 11 and the optical recording layer 14 in order to provide a function of improving the reflectance with respect to the laser light and improving the recording and reproducing characteristics, and is formed on the surface of the substrate 11 on which the grooves 12 are formed, for example, by a vapor deposition method, an ion plating method, a sputtering method, or the like. Among them, the sputtering method is particularly preferable in view of mass productivity and cost.

The material constituting the light reflecting layer 13 may be any material that is preferably used for a light reflecting film of a general optical disk, and a metal film of Au, Al, Ag, Cu, Pd, or the like, an alloy film of these metals, or an alloy film obtained by adding a trace component to these metals is preferably used.

(optical recording layer)

The optical recording layer 14 preferably contains a light-absorbing substance composed of an organic dye that absorbs laser light. Among them, a dye-based optical recording layer in which data is recorded by forming recording pits by laser irradiation is preferable. The organic dye is preferably a phthalocyanine dye, a cyanine dye, an azo dye, or the like, and for example, an azo dye represented by chemical formula 1 or a cyanine dye represented by chemical formula 2 is preferably dissolved in a solvent such as TFP (TetraFluoroPropanol) together with a binder or the like to prepare a coating liquid. Next, the coating liquid is applied through the light reflecting layer by a spin coating method, a screen printing method, or the like to form a coating film, and then dried at a temperature of, for example, 80 ℃ for about 30 minutes to form the light recording layer 14.

[ solution 1]

(wherein A and A' represent the same or different heterocyclic rings each containing one or more hetero atoms selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom and a tellurium atom₂₁To R₂₄Each independently represents a hydrogen atom or a substituent. Y is₂₁、Y₂₂Represent heteroatoms selected from the group 16 elements of the periodic Table of the elements, which are identical to or different from one another. )

[ solution 2]

(wherein phi. is⁺And φ represents an indolenine ring residue, a benzindole ring residue or a dibenzoindolenine ring residue, respectively, and L represents a linking group for forming a mono-or dicarbonyl cyanine pigment. X^-Represents an anion, and m is an integer of 0 or 1. )

(protective layer)

In the present invention, the protective layer 15 is formed between the optical recording layer 14 and a light transmitting layer 17 described later in order to adjust recording characteristics or the like, improve adhesiveness, protect the optical recording layer 14, or the like, and is formed of SiO on the optical recording layer 14 by sputtering₂、ZnS-SiO₂、Nb₂O₅-Al₂O₃And the like.

In the present invention, the light reflecting layer 13 including the metal film or the alloy film is formed in order to form the protective layer 15. Therefore, at least one of the inner mask 3 and the outer mask 4 used in sputtering must be a mask that does not contact the light reflecting layer 13 that has been formed.

A specific example of the mask used will be described below.

The mask of example 1 is formed as follows: the shielding areas of the outer mask 4 and the inner mask 3 used when the protective layer 15 is formed are larger than those of the outer mask 4 and the inner mask 3 used when the light reflecting layer 13 is formed.

In other words, the outer mask 4 used for forming the protective layer 15 has an inner peripheral end portion located on the outer peripheral side of the position corresponding to the outer peripheral end portion of the reflective layer region formed, and the inner mask used for forming the protective layer 15 has an outer peripheral end portion located on the inner peripheral side of the position corresponding to the inner peripheral end portion of the reflective layer region formed.

For example, when the light reflecting layer 13 is formed by using the outer mask 4 having an inner peripheral diameter of 118.0mm and the inner mask 3 having an outer peripheral diameter of 34.0mm, the light reflecting layer can be effectively prevented from contacting the light reflecting film by providing a diameter difference of 1mm with respect to the inner periphery of the outer mask 4 used for forming the light reflecting layer 13 and the inner periphery of the outer mask 4 used for forming the protective layer 15, and setting the shielding region to a range of 119.0mm or more from the center. Fig. 3 shows an example of the outer mask 4. When the inner peripheral diameter of the outer mask 4 is 118.5mm, the light reflecting film 13 may be brought into contact with the film deposited on the mask or the substrate or the device may be formed with the reflecting layer slightly displaced due to misalignment of the substrate or the device.

Similarly to the inner mask 3 used for forming the protective layer 15, the outer periphery thereof is set to have a diameter difference of 1mm from the outer periphery of the inner mask 3 used for forming the light reflective layer 13, and the outer periphery thereof is set to 33.0mm, whereby contact with the light reflective film 13 can be effectively avoided.

In example 2, the inner peripheral end of the outer mask 4 or the outer peripheral end of the inner mask 3 is provided with a portion in which the thickness of each mask is reduced so that the peripheral end of the mask 3 or 4 on the substrate side is chamfered into a slanted or stepped shape. By forming the light reflecting film 13 in such a shape, the protective layer 15 can be formed without contacting the masks 3 and 4. Meanwhile, the abnormal discharge can be prevented.

Fig. 4 shows an example of the outer mask 4. As shown in the figure, the inner peripheral diameter of the outer mask 4 is 118.0mm as in the above example, and the inner peripheral end of the outer mask 4 is located at a position corresponding to the outer peripheral end of the light reflecting layer formed. The mask 4 is provided so that the thickness thereof increases obliquely toward the outer periphery at the inner peripheral end portion side thereof, and the space formed by the inclined portion effectively avoids contact with the light reflecting film 13 formed.

Similarly, in the case of the inner mask 3, contact with the light reflection film 13 can be effectively avoided even if the outer peripheral end is provided with a step or an inclination toward the central portion.

In fig. 4, the masks 3 and 4 used for forming the protective layer 15 are shown as having an inclination on the peripheral end side in contact with the substrate side, but in the present invention, the substrate side thickness of the masks may be increased as being away from the region where the light reflective layer is formed so that the masks 3 and 4 used do not contact the formed light reflective layer 13.

(adhesive layer)

In the present invention, the adhesive layer 16 is an arbitrary layer formed to improve adhesion between the protective layer 15 and the sheet-like transparent layer 17 described below.

Such an adhesive layer 16 is preferably a disc-shaped optical information recording medium having a thickness of about 1.2mm, which is obtained by applying a transparent reactive curing resin other than an epoxy resin or an ultraviolet-curable transparent resin as a main component onto the protective layer 15 and/or the lower surface of a sheet-shaped light transmitting layer 17 having a thickness of about 0.1mm, which will be described later, by a spin coating method, a screen printing method, or the like, and then bonding the protective layer 15 of the substrate 11 and the sheet-shaped light transmitting layer 17 by the adhesive layer 16.

(light transmitting layer)

In the present invention, the light-transmitting layer 17 preferably contains a transparent resin. More specifically, it is preferable to form the light-transmitting layer 17 by using a sheet made of a resin having good light-transmitting properties such as a polycarbonate resin and an acrylic resin, or by applying these resins by a spin coating method.

As described in fig. 2(a) to (C), the light-transmitting layer 17 is formed to be wider than the region where the protective layer 15 made of an inorganic material is formed, and thus, the protective layer 15 made of an inorganic material can be prevented from being peeled off at the interface of the substrate 11.

In particular, the light-transmitting layer 17 is preferably provided continuously up to the outer peripheral edge of the optical information recording medium, whereby deterioration under a high-temperature and high-humidity environment can be effectively prevented.

The thickness of the light-transmitting layer 17 is generally preferably 0.1mm, because it is generally configured to record data in the optical recording layer 14 and/or read data from the optical recording layer 14 by irradiating laser light having a wavelength of about 400nm to 420 nm.

[ examples ]

The present invention will be further specifically described below based on the manufacturing method of the embodiment shown in fig. 2 (C).

< production of substrate >

A resist film is formed by applying a resist (photosensitizer) to a glass master in a predetermined thickness by a spin coating method, and after exposure is performed to a predetermined exposure width dimension by a laser beam from a dicing device, a developing solution is dropped on the obtained glass master to perform a development treatment, thereby forming a concave-convex resist pattern corresponding to the grooves 12 of the substrate 11 of the disk-shaped optical information recording medium.

Next, nickel is deposited on the glass master by plating, and the glass master is peeled off to modify the outer shape into a disk shape, thereby obtaining a stamper.

Then, the stamper was set in a cavity of an injection molding apparatus, and a polycarbonate resin was injected into the cavity to obtain a substrate 11 having a major surface with a spiral groove 12 and a major diameter of 120 mm.

< formation of light reflecting layer >

On one of the main surfaces of the substrate 11 on which the spiral groove 12 was formed, an outer mask 4 having an inner peripheral diameter of 118.0mm and an inner mask 3 having an outer peripheral diameter of 34.0mm were used by a sputtering apparatus, and an Ag alloy having a composition of "Ag-0.65 Cu-1.0In (wt%)" was used as a target material, and the thickness of the Ag alloy was measured at 10 degrees C^-2Argon gas is made into plasma under about torr (Torr) pressure, Ar is made into plasma⁺Ions impact the target to sputter. In a region of a radius of 17mm to 59mm from the center of the disc, a light reflection layer 14 of a uniform thickness of 100nm was formed.

< formation of optical recording layer >

An optical recording layer 14 having a film thickness of 60nm is formed on the upper surface of the substrate 11 on which the reflective layer 13 is formed in a region of 18mm to 60mm in radius from the center of the disk. Specifically, the azo dye represented by chemical formula 1 or the cyanine dye represented by chemical formula 2 is dissolved in a solvent such as TFP (tetrafluoropropanol) together with a binder or the like to prepare a coating solution. Then, the coating liquid was applied on the light reflective layer by a spin coating method to form a coating film, and then dried at a temperature of 80 ℃ for 30 minutes to form the optical recording layer 14.

< formation of protective layer >

Then, on the substrate on which the optical recording layer 14 was formed, an outer mask 4 having an inner peripheral diameter of 119.0mm and an inner mask 3 having a diameter of 33.0mm were used by a sputtering apparatus at 10^-2Argon gas is made into plasma under the pressure about torr, Ar is made⁺Ion impact ZnS-SiO₂Sputtering is performed. By this sputtering, the protective film 15 having a thickness of 25nm was formed in a region of a radius of 16.5mm to 60mm from the center of the disc. No abnormal discharge is generated during the formation of the protective film 15. As the outer mask 4 for forming the protective layer 15, an outer mask 4 having an inclined portion on the inner peripheral side as shown in fig. 4 is used.

< formation of light-transmitting layer >

Further, on the substrate on which the protective layer 15 was formed, an acrylic resin was applied by a spin coating method in a region which was 9mm to 60mm beyond the radius from the center of the disk, covered the outer periphery and the inner periphery of the protective layer 15, and the outer peripheral side reached the side surface of the substrate 11, and then irradiated with ultraviolet rays to be cured, thereby forming a light-transmitting layer 17 having a thickness of 0.1 mm. By performing these steps, the disk-shaped optical information recording medium 10 having a thickness of about 1.2mm is obtained.

The obtained optical information recording medium 10 had no defects in appearance, and had no abnormalities in electrical characteristics as designed.

Comparative example

An optical information recording medium 10 was obtained in the same manner as in example 1, except that the outer mask 4 having an inner peripheral diameter of 118.0mm and the inner mask 3 having a diameter of 34.0mm were used for the protective layer 15 in example 1. The occurrence of abnormal discharge was observed during the formation of the protective film 15. The obtained optical information recording medium was confirmed to have a sawtooth shape along the peripheral surface at the outermost peripheral portion of the light reflection layer, and to have a poor appearance, deteriorated jitter (jitter), and deteriorated recording sensitivity.

The embodiments of the present invention and the structures and operations described in the embodiments are not limited to the description, and various modifications may be made without departing from the scope of the present invention.

Claims (1)

1. A method for manufacturing an optical information recording medium provided with at least a substrate, a light reflection layer provided on one of main surfaces of the substrate, an optical recording layer provided on an upper surface of the light reflection layer, a protective layer provided on an upper surface of the optical recording layer, and a light transmission layer provided on an upper surface of the protective layer, the method comprising: an inner peripheral end of the outer mask used when the protective layer is formed by sputtering is positioned on an outer peripheral side of a position corresponding to an outer peripheral end of the light reflecting layer providing region, and an outer peripheral end of the inner mask used when the protective layer is formed by sputtering is positioned on an inner peripheral side of a position corresponding to an inner peripheral end of the light reflecting layer providing region.