JPH0917027A - Optical information recording medium - Google Patents

Abstract

PURPOSE: To suppress the unequal thicknesses of the protective films on recording films or reflection films by restricting the unequal thicknesses of the protective films and adjusting the viscosity of a protective film coating liquid or providing substrates with a specific step difference near their outer peripheries. CONSTITUTION: This optical information recording medium has the substrates 1, 1' having spiral or concentric tracks having an adjacent track pitch of <=1.2μm, an outside diameter of 80 to 90mm and a thickness of <=0.6mm, the recording films or reflection films 2, 2' formed on these substrates and the protective films 3, 3' formed on the recording films or reflection films. The protective films 3, 3' are confined in the difference between the film thickness of the region inner by 5mm from the outer periphery and the film thickness of the other regions to <=10μm. The protective films 3, 3' are formed by applying a UV curing resin soln. on the recording films or the reflection films 2, 2' and the viscosity thereof is confined to <=1500 centipoise. Further, the substrates 1, 1' are provided with the step difference in such a manner that the thickness of the region inner by 2mm from the outer periphery is made thinner by 0.05 to 0.15mm than the thickness of the other regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium used for recording / reproducing with a light beam such as a laser.

[0002]

2. Description of the Related Art Information is reproduced by a light beam such as a laser,
Alternatively, in an optical information recording medium for recording / reproducing, in order to increase the recording capacity, the two mediums may be used in a state of being stuck to each other with the inner side being the inside. In particular, in a large-capacity optical disc having an outer diameter of 300 mm or more, it is common to use such a laminated state. On the other hand, for discs having small outer diameters such as 130 mm, 120 mm, and 86 mm, they are often used in a single plate state such as a reproduction-only music CD or CD-ROM.

However, with the advent of discs such as recordable / reproducible magneto-optical discs which require a large capacity even with a small diameter, it is becoming common to use such a small-diameter disc in a laminated structure.

The bonding structure includes an air sandwich structure in which only the inner and outer peripheral portions of the disks are bonded together via a spacer so that the middle peripheral portions where the recording films are laminated are not in contact with each other. It can be roughly classified into two types, that is, an entire surface adhesion (solid adhesion) structure in which the entire surface is adhered, and it is used properly according to the recording method and the like.

Of these, the latter whole surface adhesive structure is generally used for various kinds of disks such as an optical video disk for reproduction only and the above-mentioned magneto-optical disk (for example, Japanese Patent Publication No. 63-67258). ). In this structure,
Due to the large bonded area, better mechanical properties than the former are obtained.

However, in recent years, with the progress of high-density recording on disks, the specifications of mechanical characteristics, particularly tilt characteristics, required for optical disk media have become extremely strict. As means for achieving high-density recording, it is known to shorten the wavelength λ of the recording laser and increase the numerical aperture NA of the objective lens for narrowing the laser light. However, if the above λ is reduced from 830 nm to 690 nm, for example, the tilt angle allowed for the disc, that is, the tilt is reduced. However, with respect to the size of this tilt margin, an allowable tilt equivalent to 830 nm can be secured even if the substrate thickness is thin and λ is 690 nm. On the other hand, the same applies to NA. Even if the NA is increased from 0.5 to 0.6, the same allowable tilt may be obtained if the substrate thickness is reduced.

Therefore, a thin disk substrate having a substrate thickness reduced from 1.2 mm to 0.8 mm or less has been used as a high density recording substrate. By using this disc, it is possible to achieve high density recording with the tilt specifications unchanged from the above (Japanese Patent Application No. 6-423).
No. 0).

On the other hand, in the case of an optical disk, an overcoat film for protecting a metal film or a recording film, which is apt to corrode, may be laminated and used, especially in a disk used as a single plate such as a CD. As the overcoat film, a UV overcoat is generally used because it has good durability and can be easily laminated. Recently, as the precision and density of optical discs have increased, the UV overcoat protective film may be laminated even on a disc having the above-mentioned entire surface bonding structure in which the film does not come into direct contact with the outside air (US Pat. No. 4,310). , 919).

FIG. 13 shows an example of an optical disk having a conventional UV overcoat film formed thereon. For example, a method in which the recording layer 2 is laminated on a thin disk substrate 1 having a thickness of 0.8 mm or less as described above and the UV overcoat material 13 used for the disk substrate having a thickness of 1.2 mm is used as it is, It was applied under the conditions.

As shown in FIG. 13, at the outermost peripheral edge portion of the disk substrate 1, due to the influence of the surface tension, a slight unevenness of the thickness of the overcoat layer occurs. Due to this thickness unevenness, when two such optical discs are bonded together, distortion occurs in the outer peripheral portion of the disc, and the mechanical characteristics of that portion, particularly the surface run-out acceleration, tend to be greatly deteriorated. The surface wobbling acceleration is an important factor that determines whether or not the optical head can follow the recording film surface when the information written on the disk is read by the drive.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and suppresses the uneven thickness of the protective film on the recording film or the reflective film and increases the surface wobbling acceleration in the vicinity of the outer circumference of the disk. To prevent.

[0012]

According to the first aspect of the present invention, adjacent track pitches are 1.2 μm or less, and the outer diameter is 8 μm.
A substrate having a spiral or concentric track of 0 to 90 mm and a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film. In the optical information recording medium including the above, the protective film is characterized in that the difference between the film thickness in the region from the outer periphery to 5 mm inside and the film thickness in the other region is at least 10 μm or less. An information recording medium is provided.

According to the second aspect of the present invention, optical information having a substrate, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film. In the recording medium, there is provided an optical information recording medium, characterized in that the protective film has a difference of 20% or less between the film thickness in the region from the outer periphery to the inner side of 5 mm and the film thickness in other regions. .

According to a third aspect of the invention, a thickness of 0.6
a substrate having a spiral or concentric track of not more than mm, and a recording film or a reflective film formed on the substrate,
In the optical information recording medium having a protective film formed by applying a UV curable resin solution on the recording film or the reflective film, the viscosity of the UV curable resin solution is 1
There is provided an optical information recording medium characterized by being 500 cps or less.

According to the fourth aspect of the present invention, the adjacent track pitch is 1.2 μm or less and the outer diameter is 80 to 90 m.
m, a substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film. In the optical information recording medium having the above, the substrate is provided with a step so that the thickness of the region from the outer circumference to 2 mm inside is thinner by 0.05 mm to 0.15 mm than the thickness of the other regions. A featured optical information recording medium is provided.

According to the fifth aspect of the present invention, the adjacent track pitch is 1.2 μm or less, the outer diameter is 80 to 90 mm,
A substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and applying a UV curable resin solution on the recording film or the reflective film. In the optical information recording medium having a protective film formed by, the protective film has a difference in thickness between a region of 5 mm inside from the outer periphery and a thickness of other regions of at least 10 μm or less, Also, an optical information recording medium is provided in which the viscosity of the UV curable resin solution is 1500 cps or less.

According to a sixth aspect of the invention, a thickness of 0.6
a substrate having a spiral or concentric track of not more than mm, and a recording film or a reflective film formed on the substrate,
In an optical information recording medium having a protective film formed by applying a UV curable resin solution on the recording film or the reflective film, the protective film has a film thickness in a region from the outer periphery to 5 mm inside, The difference from the film thickness in other regions is 20% or less, and the viscosity of the UV curable resin solution is 150%.
There is provided an optical information recording medium characterized by being 0 cps or less.

According to the seventh aspect of the present invention, the adjacent track pitch is 1.2 μm or less, the outer diameter is 80 to 90 mm,
A substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film. In the optical information recording medium, the protective film has a difference of at least 10 μm or less between the film thickness of the region from the outer periphery to the inner side of 5 mm and the film thickness of the other region, and the substrate is 2 mm from the outer periphery to the inner side. There is provided an optical information recording medium, characterized in that a step is provided so that the thickness of the area (1) is thinner by 0.05 mm to 0.15 mm than the thickness of other areas.

According to the eighth aspect of the present invention, the adjacent track pitch is 1.2 μm or less and the outer diameter is 80 to 90 m.
m, a substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film. In the optical information recording medium having, the protective film has a difference of 20% or less between the film thickness of the region from the outer periphery to the inner side of 5 mm and the film thickness of the other region, and the substrate is
Provided is an optical information recording medium characterized in that a step is provided so that a thickness of a region from the outer periphery to 2 mm inside is thinner by 0.05 mm to 0.15 mm than the thickness of other regions. .

According to a ninth aspect of the present invention, the adjacent track pitch is 1.2 μm or less, the outer diameter is 80 to 90 mm,
A substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and applying a UV curable resin solution on the recording film or the reflective film. In the optical information recording medium having a protective film formed by, the protective film has a difference of at least 10 μm or less between the film thickness of the region from the outer periphery to 5 mm inside and the film thickness of the other region, The viscosity of the UV-curable resin solution is 1500 cps or less, and the substrate has a thickness of 2 mm inside from the outer circumference of 0.05 mm to 0.15 mm thinner than the thickness of other areas. Provided is an optical information recording medium having a step.

According to the tenth aspect of the present invention, the adjacent track pitch is 1.2 μm or less and the outer diameter is 80 to 90 m.
m, a substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and a UV curable resin solution applied on the recording film or the reflective film. In the optical information recording medium having the protective film formed by the above, the protective film has a difference of 20% or less between the film thickness of the region from the outer periphery to 5 mm inside and the film thickness of other regions. The viscosity of the UV curable resin solution is 1500 cps or less, and the thickness of the region from the outer periphery to the inner side of 2 mm of the substrate is 0.05 mm to 0.15 mm thinner than the thickness of other regions. Provided is an optical information recording medium having a step.

[0022]

According to the first aspect of the present invention, in an optical information recording medium using a substrate having an adjacent track pitch of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, the protection thereof is provided. By setting the difference between the film thickness of the region 5 mm from the outer periphery of the film and the film thickness of the other region to 10 μm or less, the unevenness of the overcoat on the recording film or the reflective film is suppressed, and the disc, especially the outer periphery, It is possible to prevent an increase in surface runout acceleration in the vicinity.

Further, according to the second aspect of the present invention, the difference between the film thickness of the region within 5 mm from the outer periphery of the protective film of the optical information recording medium and the film thickness of other regions is 20% or less. By so doing, it is possible to suppress unevenness in the thickness of the overcoat on the recording film or the reflective film, and to prevent an increase in surface wobbling acceleration particularly in the vicinity of the outer periphery of the disc.

According to a third aspect of the invention, a thickness of 0.6
In an optical information recording medium using a substrate of mm or less,
By forming the protective film using a UV curable resin solution having a viscosity of 1500 cps or less, uneven thickness of the overcoat on the recording film or the reflective film is suppressed, and an increase in surface runout acceleration particularly in the vicinity of the outer periphery of the disc is suppressed. Can be prevented.

According to the fourth aspect of the present invention, the adjacent track pitch is 1.2 μm or less and the outer diameter is 80 to 90 m.
In an optical information recording medium using a substrate having a thickness of 0.6 mm or less and a thickness of 0.6 mm or less, the thickness of the region from the outer periphery of the substrate to the inner side of 2 mm is 0.05 mm to 0.1 mm more than other regions.
By providing a step on the substrate so that the thickness is reduced by 5 mm, it is possible to suppress unevenness in the thickness of the overcoat on the recording film or the reflective film, and prevent an increase in surface wobbling acceleration particularly in the vicinity of the outer periphery of the disc.

According to the fifth aspect of the present invention, by combining the features of the first and third aspects of the present invention, it is possible to suppress the thickness unevenness of the overcoat on the recording film or the reflective film, and particularly the disk. It is possible to more effectively prevent an increase in surface runout acceleration near the outer circumference.

According to the sixth aspect of the present invention, by combining the features of the second and third aspects of the present invention, it is possible to suppress the unevenness of the thickness of the overcoat on the recording film or the reflective film, and particularly the disc. It is possible to more effectively prevent an increase in surface runout acceleration near the outer circumference.

According to the seventh aspect of the present invention, by combining the features of the first and fourth aspects of the present invention, it is possible to suppress the thickness unevenness of the overcoat on the recording film or the reflective film, and particularly to disc. It is possible to more effectively prevent an increase in surface runout acceleration near the outer circumference.

According to the eighth aspect of the present invention, by combining the features of the second and fourth aspects of the present invention, it is possible to suppress unevenness in the thickness of the overcoat on the recording film or the reflective film, and particularly for the disk. It is possible to more effectively prevent an increase in surface runout acceleration near the outer circumference.

According to the ninth aspect of the present invention, by combining the features of the first, third and fourth aspects of the present invention, it is possible to suppress the uneven thickness of the overcoat on the recording film or the reflective film. It is possible to more effectively prevent an increase in surface wobbling acceleration in the disk, especially in the vicinity of the outer circumference.

According to the tenth aspect of the present invention, by combining the features of the second, third and fourth aspects of the present invention, uneven thickness of the overcoat on the recording film or the reflective film is suppressed. It is possible to more effectively prevent an increase in surface wobbling acceleration in the disk, especially in the vicinity of the outer circumference.

[0032]

【Example】

Example 1 Hereinafter, a first example of the present invention will be described. FIG. 1 is a sectional view showing an example of an optical information recording medium according to the present invention. In the figure, 1 and 1'denotes thin disk substrates for high-density recording in which continuous laser guiding grooves are formed in advance, the adjacent track pitch is 1.2 μm or less, and the substrate thickness is 0.6 mm. The thin disk substrates 1 and 1'have an outer diameter of 80.
It is made of resin having a length of 90 mm or 120 mm to 130 mm, and is made of, for example, acrylic or polycarbonate processed into the above shape by injection molding or the like. Recording films (for example, magneto-optical, phase change, alloy type films, etc.) or reflective films (for example, Al, Au, etc.) 2, 2 ′ are formed on these substrates 1, 1 ′ by vapor deposition or the like. 3,3 '
Is UV for protecting the recording film or the reflective film 2, 2 '.
It is an overcoat protective film. Reference numeral 4 denotes an adhesive layer for sticking these disks together, and for example, a hot melt adhesive or a double-sided adhesive is used.

The UV overcoats 3 and 3'are usually formed by applying a liquid UV curable resin from the inside of the recording area to the outermost circumference by spin coating on the disk substrate, and applying U
It is cured by irradiation with V light and laminated.

FIG. 2 shows a state in which the disc substrate is mounted on the overcoat coating device. First, the disk substrate is turned table 25 of the overcoat coating device.
UV overcoat agent 2 as shown in FIG.
2 is applied from the overcoat agent application nozzle 23 onto the substrate 21 provided with the recording layer. At this time, the turntable 25 is rotated by the motor 24 at several tens of rpm. It is rotating at the low speed in the direction of the arrow.

FIG. 3 is a diagram showing how the disk substrate is spin-coated. The disk substrate 21 coated with the overcoat agent is subjected to spin coating as shown in FIG. At this time, the turntable 25 is rotated by the motor 24 at several thousand rpm. It is rotating at high speed in the direction of the arrow.

FIG. 4 is a diagram showing how the disk substrate is irradiated with UV. As shown in FIG. 4, UV irradiation is performed on the disk substrate 21 on which the overcoat agent is spin-coated at a high speed to cure the overcoat agent.

Conventionally, the thickness of the UV overcoat layer tends to become thick at the outermost peripheral edge portion of the disc substrate due to the influence of the surface tension, and this thickness unevenness causes the UV outer coat layer to become thicker on the outer peripheral portion of the disc when the discs are bonded together. There was a tendency that distortion occurred and the mechanical properties of that portion, particularly the surface runout acceleration, deteriorated significantly.

However, according to our detailed experiments, UV in the region from the outermost periphery to 5 mm inside and in other regions
It was found that the surface runout acceleration can be suppressed by controlling the difference in the average film thickness of the coat.

FIG. 5 shows the surface runout acceleration at the outermost periphery when a disc having an outer diameter of 86 mm and having a structure as shown in FIG. 1 prepared by varying the UV coating film thickness difference is evaluated at 3600 rpm. It is a graph figure. From FIG. 5, by suppressing the above film thickness difference to 10 μm or less,
It can be seen that the surface runout acceleration can be suppressed within the standard value of 30 m / sec ² .

According to the present invention, the mechanical characteristics required for an optical disk can be satisfied by setting the thickness difference between the protective film near the outer periphery and the inner region thereof to 10 μm or less.

Specific methods for controlling the film thickness difference of the protective film to 10 μm or less include, for example, increasing the rotation speed during spin coating, UV irradiation while rotating the disk at a high rotation speed, and coating. Examples include changing the method itself to screen printing.

The optical disk according to the present invention and the conventional optical disk will be compared below with specific examples. With a disk having an outer diameter of 86 mm having the same structure as in FIG. 1, the UV coat average film thickness of the UV coat portions 3 and 3'excluding the range of 5 mm from the outermost circumference and the maximum film thickness of the outermost circumference of 5 mm range The difference is 7μ
Let A be an optical disc that is m and that conforms to the present invention. On the other hand, an optical disc having the same structure as that of the present invention, except that the thickness difference of 3 and 3'is 25 μm, which does not correspond to the present invention, is designated as B. These surface wobbling accelerations are calculated by disc rotation speed 3600r.
When evaluated by pm, A is 14 m / sec ^{2, which} is within the standard value, whereas B is 83 m / sec ^{2, which} is a large overshoot. At this time, when the byte error rate (B.E.R.) that actually reads and writes the signal of the disk is calculated, the value is 10 ^{−3 in} the disk B, which is a considerably bad value. A shows a good value of 10 ⁻⁵ .

As is clear from the above, the disk of the present invention provides very good surface wobbling acceleration characteristics; characteristics that do not exceed the high density disk specifications of 30 m / sec ² . And it guarantees that good recording / reproducing characteristics can be maintained.

In the above embodiment, the recording film, U
Although the disk having the structure in which the disks having the V overcoat laminated thereon are adhered to each other, the present invention only needs to have a structure in which at least one of the two disks adhered over the entire surface has the above-mentioned overcoat layer. FIG. 6 is a sectional view showing an optical disc having a structure with a cover according to the present invention. For example, the optical information recording medium of the present invention may have a structure in which the recording film / overcoat is not laminated on one of the disks 1 or 1'of FIG. 1 and is used as the protective plate 11 as shown in FIG. I do not care.

Embodiment 2 Next, an embodiment of the second invention will be described. FIG.
It is sectional drawing which shows another example of the optical information recording medium which concerns on this invention. In the figure, 101 and 101 'have continuous grooves for laser guide formed in advance, and adjacent track pitches are 1.
It is a thin disk substrate for high density recording having a thickness of 2 μm or less and a substrate thickness of 0.6 mm. Thin disk substrate has an outer diameter of 80
It is made of resin having a length of 90 mm or 120 mm to 130 mm, and is made of, for example, acrylic or polycarbonate processed into the above shape by injection molding or the like. Each of these has a recording film (eg magneto-optical, phase change, alloy type film, etc.)
Alternatively, reflective films (eg, Al, Au, etc.) 102, 102
′ Is formed by vapor deposition or the like. 103, 103 '
Is a UV overcoat protective film for protecting the recording film or the reflective film, which will be described in detail later. 104
Is an adhesive layer for sticking these disks together, and for example, a hot melt adhesive or a double-sided adhesive is used.

The UV overcoats 103 and 103 'are
Usually, a liquid UV curable resin is applied on the disc substrate by spin coating from the inside of the recording area to the outermost periphery,
By irradiating this with UV light, it is cured and laminated. At this time, in the conventional UV overcoat layer, the overcoat layer tends to be thick due to the influence of surface tension at the outermost peripheral edge portion of the disk substrate. Therefore, when the disks are attached to each other due to the uneven thickness, distortion occurs in the outer peripheral parts of the disks, and the mechanical characteristics of the parts, particularly the surface runout acceleration, tend to be greatly deteriorated.

However, according to the detailed study by the inventors, it was found that the surface runout acceleration can be suppressed by lowering the viscosity of the UV overcoating agent for spin coating at the time of application.

Now, a UV curable resin having a viscosity changed at the time of application is used for the portions 103 and 103 'of the disk having the structure of FIG. Spin coat under the conditions and use the same method as before.
FIG. 8 is a graph showing the surface wobbling acceleration at the outermost circumference when a disk having a V-cured UV overcoat layer laminated thereon was evaluated at 3600 rpm. According to this, it can be seen that the surface runout acceleration can be suppressed within the standard value of 30 m / sec ² by suppressing the viscosity to 1500 cps or less.

This embodiment is based on this result,
By setting the resin viscosity to 1500 cps or less, the mechanical properties required for the optical disk are satisfied.

Hereinafter, the optical disc of the present invention and the conventional optical disc will be compared with reference to specific examples. With the disc having an outer diameter of 86 mm having the structure shown in FIG.
Viscosity of UV resin used for 3'is 1200 cps
Let C be an optical disc that conforms to the present invention. On the other hand, a conventional optical disc having the same structure as this, but using the UV resin having the viscosity of 8000 cps for 103 and 103 ', which does not correspond to the present invention, is designated as D. When these runout acceleration is evaluated by disk rotation speed 3600 rpm, C whereas enter 19 m / sec ² and the standard value, resulting in significantly over a 95 m / sec ^2, D. At this time, if the byte error rate (B.E.R.) at which the signal of the disk is actually read and written is calculated, it is 1 for the disk D.
The disk C shows a good value of 10 ⁻⁵ while the value of 0 ⁻³ is considerably bad.

By the way, it has been confirmed by experiments by the inventors that the thickness unevenness can be improved by increasing the spin rotation speed at the time of coating. For example, also in the case of the disk D, the spin rotation speed of 2500 rpm in the above experiment was confirmed. By increasing the speed to 4200 rpm, the surface acceleration becomes 2
It can be lowered to 8 m / sec ² . However, if the number of revolutions is extremely changed in this way, the average film thickness of the UV overcoat layer also becomes extremely thin, so that the original function of protecting the recording film or the reflective film may be impaired. For example, if the UV curable resin of disk D is 4200 rp
The disk spin-coated with m is E, and disk C is
And E were subjected to an environmental test at 80 ° C. and 90% RH × 2000H. E. FIG. R. Was measured. The result is shown in FIG. FIG. 9 shows the environmental test time and B. E. FIG. R.
It is a graph showing the relationship with. Disk C is 10 ^-5
While the good value of the unit is shown without change, the value of the disk E changes from 10 ⁻⁵ to 10 ⁻³ after the environmental test, which is a considerably bad value.

Taking this into consideration, by setting the coating viscosity of the UV curable resin to at least 1500 cps or less, an appropriate and uniform overcoat layer thickness can be obtained.
The characteristics suitable for the optical disk can be stably obtained.

As is clear from the above, the disk of the present invention provides very good surface wobbling acceleration characteristics; characteristics that do not exceed the high-density disk specification of 30 m / sec ² . Accordingly, good recording / reproducing characteristics including environment resistance can be maintained.

In the above embodiment, the recording film, U
Although a disk having a structure in which disks each having a V overcoat laminated thereon are adhered to each other, the present invention only needs to have a structure in which at least one of the two disks to be entirely adhered has the overcoat layer. As shown in FIG. 6, the structure may be such that one of the disks is not laminated with the film / overcoat and is used as a protective plate.

Embodiment 3 Next, an embodiment of the third invention will be described. FIG. 10 is a sectional view showing still another example of the optical information recording medium according to the present invention. In the figure, 201 and 201 'are high-density recording of the present invention in which continuous laser guiding grooves are formed in advance, the adjacent track pitch is 1.2 μm or less, and the entire substrate thickness excluding the outermost periphery is 0.6 mm. It is a thin disk substrate for. The thin disk substrate is made of a resin having an outer diameter of 80 to 90 mm or 120 to 130 mm, and for example, acrylic or polycarbonate is processed into the above shape by injection molding or the like and used. In the disk substrate of the present invention, in particular, a step is provided on the groove forming surface side of the portion up to 2 mm from the outermost peripheral edge toward the center, and the disk thickness is made thinner by 0.05 to 0.15 mm than the others. have.

Each of these has a recording film (eg, magneto-optical,
Phase change, alloy type film, etc. or reflective film (eg Al, A)
(e.g. u) 202, 202 'are formed by vapor deposition or the like. 203 and 203 'are UV overcoat protective films for protecting the recording film or the reflective film. 20
Reference numeral 4 denotes an adhesive layer for sticking these disks together, and for example, a hot melt adhesive or a double-sided adhesive is used.

The UV overcoats 203 and 203 'are
Usually, a liquid UV curable resin is applied on the disc substrate by spin coating from the inside of the recording area to the outermost periphery,
By irradiating this with UV light, it is cured and laminated. At this time, in the conventional UV overcoat layer, as shown in FIG. 13, the overcoat layer tends to be thick due to the influence of the surface tension at the outermost peripheral edge portion of the disk substrate. Therefore, when the disks are attached to each other due to the uneven thickness, distortion occurs in the outer peripheral parts of the disks, and the mechanical characteristics of the parts, particularly the surface runout acceleration, tend to be greatly deteriorated.

The inventors have considered that the above uneven thickness can be absorbed by reducing the thickness of the outermost circumference of the disk to improve the surface wobbling acceleration. FIG. 11 shows a disc having an outer diameter of 86 mm and having a structure as shown in FIG. 10, and the disc substrate 201, 201 ′ has discs with different step sizes on the outer periphery from the outermost periphery to 2 mm inside.
It is a graph which shows the surface runout acceleration in the outermost circumference when evaluated at 00 rpm. According to this, it is understood that the surface wobbling acceleration can be suppressed within the standard value of 30 m / sec ² by setting the step difference in the range of 0.05 mm or more and 0.15 mm or less.

In this embodiment, based on this result, the step difference is set in the range of 0.05 mm or more and 0.15 mm or less so as to satisfy the mechanical characteristics required for the optical disk.

Hereinafter, the embodiment of this optical disc and the example of the conventional optical disc will be compared by giving concrete examples. With the disc having an outer diameter of 86 mm having the structure of FIG.
An optical disk conforming to the present invention, in which the step difference of the outer peripheral portions of 1,201 ′ is 0.10 mm, is designated as F. On the other hand, a conventional optical disk which does not correspond to the present invention, which has the same structure as this, but uses the above-mentioned disk substrate without steps 201 and 201 'is designated as G. When these surface runout accelerations are evaluated at a disk rotation speed of 3600 rpm, F is 11 m / sec.
^Although it is within the standard value of ² , the G is greatly overrun at 83 m / sec ² . At this time, the byte error rate (BE.
R. ), The disk G shows a very bad value of 10 ⁻³ , whereas the disk F shows a good value of 10 ⁻⁵ .

By the way, in the above embodiment, the length of the step from the outer peripheral edge of the disc was fixed to 2 mm, but according to the detailed study by the inventors, the effect of the invention is sufficiently obtained when the length is less than 2 mm. If it is larger than this, on the contrary, the overall thickness of the outer circumference of the disc tends to be smaller than that of the inner and middle circumferences, and a step may occur in the information recording area. Therefore, it is known that it is optimal to fix it here to 2 mm.

As is clear from the above, the disk of the present invention has very good surface wobbling acceleration characteristics; characteristics that do not exceed the high-density disk specifications of 30 m / sec ² are obtained, and good recording / reproduction is achieved. The characteristics can be maintained.

In the above embodiment, the recording film, U
The disk having the structure in which V-overcoats are laminated and the same-shaped disks are bonded to each other has been described. However, the present invention is only required to have a structure in which at least one of the two disks adhered over the entire surface has the overcoat layer. For example, as shown in FIG. 12, one disc may have a structure with a cover that is used as a protective plate without forming a step, a film, or an overcoat.

[0064]

As described above, according to the present invention, it is possible to suppress the unevenness of the thickness of the protective film on the recording film or the reflective film, and to prevent the increase of the surface wobbling acceleration particularly in the vicinity of the outer periphery of the disc.

Also, with respect to an optical disc having a sandwich structure in which two substrates each provided with a recording film, a reflective film, and a protective film are laminated, it is possible to prevent an increase in surface deviation acceleration. In this way, according to the present invention, an optical recording information medium suitable for high-density recording can be obtained without the mechanical characteristics being extremely deteriorated on the outer periphery thereof.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an optical information recording medium according to the present invention.

FIG. 2 is a diagram showing a state in which a disc substrate is mounted on an overcoat coating device.

FIG. 3 is a diagram showing how a disk substrate is spin-coated.

FIG. 4 is a diagram showing how a disk substrate is irradiated with UV.

FIG. 5 is a graph showing the relationship between the UV coating film thickness and surface wobbling acceleration.

FIG. 6 is a sectional view showing an example of an optical disc having a structure with a cover according to the present invention.

FIG. 7 is a sectional view showing another example of the optical information recording medium according to the present invention.

FIG. 8 is a graph showing the relationship between the viscosity of the UV overcoating agent and the surface wobbling acceleration.

FIG. 9: Environmental test time and B. E. FIG. R. Graph showing the relationship with

FIG. 10 is a sectional view showing still another example of the optical information recording medium according to the present invention.

FIG. 11 is a graph showing the relationship between the size of a step provided 2 mm inside from the outermost periphery of the substrate and the surface runout acceleration.

FIG. 12 is a sectional view showing another example of an optical disc having a structure with a cover according to the present invention.

FIG. 13 is a diagram showing an example of an optical disc having a conventional UV overcoat film formed thereon.

[Explanation of symbols]

1, 1 ', 101, 101', 201, 201 '... Thin disk substrate 2, 2', 102, 102 ', 202, 202' ... Recording film or reflective film 3, 3 ', 103, 103' 203, 203 '... Protective film 4, 104, 204 ... Adhesive layer 13 ... Conventional protective film

Claims (10)

[Claims] 1. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film or a reflection film formed on the substrate. In an optical information recording medium including a film and a protective film formed on the recording film or the reflective film, the protective film has a film thickness in a region from the outer periphery to 5 mm inside and a film thickness in other regions. An optical information recording medium having a difference of at least 10 μm or less. 2. An optical information recording medium having a substrate, a recording film or a reflective film formed on the substrate, and a protective film formed on the recording film or the reflective film, wherein the protective film comprises: An optical information recording medium, characterized in that the difference between the film thickness in the area 5 mm from the outer circumference and the film thickness in other areas is 20% or less. 3. A substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and U on the recording film or the reflective film.
An optical information recording medium having a protective film formed by applying a V-curable resin solution, wherein the UV-curable resin solution has a viscosity of 1500 cps or less. 4. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film formed on the substrate. In an optical information recording medium having a reflective film and a protective film formed on the recording film or the reflective film, in the substrate, the thickness of the region from the outer periphery to 2 mm inside is larger than the thickness of other regions. An optical information recording medium, wherein a step is provided so as to be thinner by 0.05 mm to 0.15 mm. 5. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film or a reflection film formed on the substrate. In an optical information recording medium comprising a film and a protective film formed by applying a UV-curable resin solution on the recording film or the reflective film, the protective film has a region of 5 mm from the outer circumference. The difference between the film thickness and the film thickness in other regions is at least 10 μm or less, and the viscosity of the UV curable resin solution is 150 μm or less.
An optical information recording medium characterized by being 0 cps or less. 6. A substrate having a spiral or concentric track with a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and U on the recording film or the reflective film.
In an optical information recording medium having a protective film formed by applying a V-curable resin solution, the protective film has a film thickness in a region from the outer periphery to 5 mm inside and a film thickness in other regions. An optical information recording medium, wherein the difference is 20% or less, and the viscosity of the UV curable resin solution is 1500 cps or less. 7. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film or a reflection film formed on the substrate. In an optical information recording medium including a film and a protective film formed on the recording film or the reflective film, the protective film has a film thickness in a region from the outer periphery to 5 mm inside and a film thickness in other regions. Is at least 10 μm or less, and the substrate is 2 mm from the outer circumference.
The thickness of the inner region is 0.0 than the thickness of the other regions.
An optical information recording medium, wherein a step is provided so as to be thinned by 5 mm to 0.15 mm. 8. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film formed on the substrate. In an optical information recording medium having a reflective film and a protective film formed on the recording film or the reflective film, the protective film has a film thickness in a region from the outer periphery to 5 mm inside and a film thickness in other regions. Is 20% or less, and the substrate is stepped so that the thickness of the region from the outer circumference to 2 mm inside is 0.05 mm to 0.15 mm thinner than the thickness of the other regions. An optical information recording medium characterized by being present. 9. A substrate having adjoining track pitches of 1.2 μm or less, an outer diameter of 80 to 90 mm, and a thickness of 0.6 mm or less, which are spiral or concentric, and a recording film or a reflection film formed on the substrate. In an optical information recording medium comprising a film and a protective film formed by applying a UV-curable resin solution on the recording film or the reflective film, the protective film has a region of 5 mm from the outer circumference. The difference between the film thickness and the film thickness of other regions is at least 10 μm or less, and the viscosity of the UV curable resin solution is 1500 c.
ps or less, and in the substrate, the thickness of the region from the outer periphery to 2 mm inside is 0.05 m greater than the thickness of other regions.
An optical information recording medium, characterized in that a step is provided so as to be thinned by m to 0.15 mm. 10. The adjacent track pitch is 1.2 μm.
Hereinafter, a substrate having a spiral or concentric track with an outer diameter of 80 to 90 mm and a thickness of 0.6 mm or less, a recording film or a reflective film formed on the substrate, and UV on the recording film or the reflective film. In an optical information recording medium having a protective film formed by applying a curable resin solution, the protective film has a difference between a film thickness in a region from the outer periphery to 5 mm inside and a film thickness in other regions. Is 20% or less, the viscosity of the UV-curable resin solution is 1500 cps or less, and the substrate has a thickness of 2 mm inside from the outer periphery of 0.05 mm to 0 mm more than the thickness of other areas. .15
An optical information recording medium, wherein a step is provided so as to be thinner by mm.