JPH0896415A - Optical information recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] An optical information recording medium having a small tilt and good tilt characteristics even when the thickness of the protective coating layer is large and the step of the substrate is large. The purpose is to provide. [Structure] At least one of them has a recording film on which information is reproduced by a light beam and a protective coat layer having a thickness unevenness of 50 μm or more, and has an outer diameter of 80 to 90 mm.
Two recording substrates, and their outer diameters 120 to 1
Two recording substrates of 30 mm each having a compression elastic modulus of 1 kg / cm ² or more and 60 kg / cm ² or less, and a double-sided adhesive sheet of 4 kg / cm ² or more 60 kg / cm ²
An optical information recording medium is constructed by laminating the entire surface with the following double-sided adhesive sheet.

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 having a structure in which a plurality of discs are bonded together and a manufacturing method thereof.

[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 the case of a large-capacity optical disc having an outer diameter of φ300 or more, it is common to use such a bonded state. On the other hand, for discs with small outer diameters such as φ130, φ120, and φ86, read-only music CDs
It is often used in the state of a single plate such as a CD or a 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.

As the pasting structure, only the inner and outer circumferential portions of the disc are pasted together via a spacer so that the middle circumferential portions where the recording layers are laminated are not in contact with each other, and two discs. 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 a read-only optical video disk and the above-mentioned magneto-optical disk. Conventionally, Japanese Unexamined Patent Publication (Kokai) No. 4-16 has been used for bonding disks of this structure.
As shown in Japanese Patent No. 8635, a solvent type adhesive or the like is used. A method using a hot melt adhesive has been proposed as a simple method for improving the erosion and curing strain of the disk substrate, the reflection surface, or the recording surface that occurs when using this type of adhesive (Japanese Patent Publication No. 63-63). -6
7258), is widely used.

However, in the method using the hot melt adhesive, heat is applied to the disk substrate which is mainly made of resin, and there is a concern that the substrate may be deformed. Therefore, a bonding method using a double-sided adhesive (Japanese Patent Laid-Open No. 1-276447) has been devised as a bonding method that does not adversely affect the substrate and the recording film and does not use heat, and the mechanical characteristics of the disk have been improved. .

However, in recent years, with the progress of high-density recording on disks, the specifications of tilt characteristics required for optical disk media have become extremely severe. 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, the above-mentioned λ is, for example, from 830 nm to 690 nm.
If it is reduced to nm, the tilt angle allowed for the disc,
That is, the tilt becomes small. 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 0.6 mm, which is a half, 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 as they are, as described above.

[0009]

Conventionally, in order to bond the above-mentioned thin disk substrates to each other, a double-sided pressure-sensitive adhesive having good characteristics on a 1.2 mm substrate (for example, a silicone pressure-sensitive adhesive of 10 μm on both sides of a PET substrate). Was used as it was. However, in the case of a disc having a structure in which a protective coating layer such as a UV coat is formed on the recording film laminated on the substrate, in particular, due to the uneven thickness caused by laminating the protective coat layer, the film formation / protective coating is performed. In the case of a disc in which the difference between the maximum thickness and the minimum thickness of the entire disc after that exceeds 50 μm, the disc substrate after bonding is deformed and the tilt characteristic is deteriorated.

Also, when the step difference of the disc substrate itself exceeds 40 μm, the tilt characteristic is similarly deteriorated. The present invention has been made in view of such circumstances, and the optical information recording having a small tilt and a good tilt characteristic even when the thickness unevenness of the protective coat layer is large and the step of the substrate is large. An object is to provide a medium and a method for manufacturing the medium.

[0011]

In order to solve the above-mentioned problems, according to the present invention, firstly, at least one of them has a recording film on which information is reproduced by a light beam and a thickness unevenness of 50 μm or more. A protective coating layer is laminated and its outer diameter is 8
An optical information recording medium, characterized in that two recording substrates of 0 to 90 mm are laminated on each other with a double-sided adhesive sheet having a compression elastic modulus of 1 kg / cm ² or more and 60 kg / cm ² or less. Is.

Secondly, a recording film for reproducing information by a light beam and a protective coat layer having a thickness unevenness of 50 μm or more are laminated on at least one of them, and the outer diameter 120 thereof is provided.
An optical information recording medium characterized in that two recording substrates of 130 mm to 130 mm are adhered to each other with a double-sided adhesive sheet having a compression elastic modulus of 4 kg / cm ² or more and 60 kg / cm ² or less. is there.

Thirdly, at least one of them has a recording film on which information is reproduced by a light beam, and has an outer diameter of 80 to 90 mm with a step of 40 μm or more in the thickness direction.
It is intended to provide an optical information recording medium characterized in that the ^two recording substrates are bonded together by a double-sided adhesive sheet having a compression elastic modulus of 1 kg / cm ² or more and 45 kg / cm ² or less.

Fourthly, at least one of them has a recording film on which information is reproduced by a light beam, and two recording substrates having an outer diameter of 120 to 130 mm and having a step of 40 μm or more in the thickness direction. The present invention provides an optical information recording medium, which is obtained by laminating the entire surface with a double-sided pressure-sensitive adhesive sheet having a compression elastic modulus of 4 kg / cm ² or more and 45 kg / cm ² or less.

Fifth, at least one of them is laminated with a recording film on which information is reproduced by a light beam and a protective coat layer having a thickness unevenness of 50 μm or more, and having an outer diameter of 80.
The compression elastic modulus between two recording substrates of 90 to 90 mm is 1
When sticking with a double-sided pressure-sensitive adhesive sheet of not less than kg / cm ^{2 and not} more than 60 kg / cm ² , vacuum pressure 1
The present invention provides a method for manufacturing an optical information recording medium, characterized in that the method is performed by a vacuum press having a pressure of 40 Pa or less and a pressure of 1,000,000 Pa or less.

Sixth, at least one of them is laminated with a recording film on which information is reproduced by a light beam and a protective coat layer having a thickness unevenness of 50 μm or more, and having an outer diameter 120.
When two recording substrates of 130 mm to 130 mm are attached to each other with a double-sided pressure-sensitive adhesive sheet having a compression elastic modulus of 4 kg / cm ² or more and 60 kg / cm ² or less, the attachment is performed under a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less. The present invention provides a method for manufacturing an optical information recording medium, which is characterized in that it is performed by a vacuum press.

Seventh, at least one of them is laminated with a recording film for reproducing information by a light beam, and has an outer diameter of 80 to 90 mm with a step of 40 μm or more in the thickness direction.
When laminating ^two recording substrates to each other with a double-sided pressure-sensitive adhesive sheet having a compressive elastic modulus of 1 kg / cm ² or more and 45 kg / cm ² or less, the bonding is performed by a vacuum press with a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less. The present invention provides a method for manufacturing an optical information recording medium, which is characterized in that

Eighth, two recording substrates each having an outer diameter of 120 to 130 mm having at least one recording film on which information is reproduced by a light beam and having a step of 40 μm or more in the thickness direction. When a double-sided pressure-sensitive adhesive sheet having a compressive elastic modulus of 4 kg / cm ² or more and 45 kg / cm ² or less is bonded over the entire surface, the bonding is performed by a vacuum press with a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less. A method for manufacturing an optical information recording medium is provided.

[0019]

According to the present invention, at least one of the recording substrates has a recording film on which information is reproduced by a light beam and a protective coating layer having a thickness unevenness of 50 μm or more. When the outer diameter is 80 to 90 mm, a double-sided pressure-sensitive adhesive sheet having a compression elastic modulus of 1 kg / cm ² or more and 60 kg / cm ² or less is used, and the outer diameter thereof is 120 to 13
When 0 mm, the compressive elastic modulus is 4 kg / cm ² or more 60
Since the double-sided pressure-sensitive adhesive tape having a sufficiently low elastic modulus of kg / cm ² or less is used for the bonding, the deformation of the substrate can be suppressed even when the protective coating layer having such a large thickness unevenness is used, and the tilt characteristics can be improved. Can be good. Further, at least one of them has a recording film on which information is reproduced by a light beam is laminated, and two recording substrates having a step difference of 40 μm or more in the thickness direction have an outer diameter of 80 to 9
When 0 mm, the compressive elastic modulus is 1 kg / cm ² or more 45
A double-sided pressure-sensitive adhesive sheet of not more than kg / cm ² is used, and when the outer diameter is 120 to 130 mm, the compression elastic modulus is 4 kg /
Since the double-sided pressure-sensitive adhesive tape having a sufficiently low elastic modulus of not less than cm ^{2 and not} more than 45 kg / cm ² is used for bonding, the deformation of the substrate can be suppressed even when a substrate having such a large step is used, and the tilt characteristic Can be good.

Also, good bonding can be achieved by bonding the two substrates with a vacuum press having a vacuum pressure of 140 Pa or less and a press pressure of 600,000 Pa or less.

[0021]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing an example of an optical information recording medium (optical disk) according to the present invention. In the figure, reference numerals 1 and 1'indicate
A continuous laser guiding groove is formed in advance, the adjacent track pitch is 1.2 μm or less, and the substrate thickness is 0.6 m.
m is a thin disk substrate for high density recording. The thin disk substrate has an outer diameter of 80 to 90 mm or 120 to 130
It is made of a resin of mm, and is made of, for example, acrylic or polycarbonate processed into the above shape by injection molding or the like. A recording film (eg, phase change type, alloy type film, etc.) or a reflective film (eg, Al, Au, etc.) 2,
2'is formed by vapor deposition or the like. Reference numerals 3, 3 '
Is a protective coat film (UV coat resin or the like) for protecting the recording film or the reflection film.

Conventionally, these discs have been pasted together with a relatively hard double-sided pressure-sensitive adhesive sheet, for example, a pressure-sensitive adhesive sheet having a structure in which a 10 μm silicone pressure-sensitive adhesive is laminated on both sides of a PET base material. If the difference between the maximum and minimum thicknesses of the entire disc in which these layers are stacked becomes large to some extent due to unevenness of the film thickness when coated with ‘
The thin substrate is deformed at the time of bonding, and the tilt characteristic is deteriorated. For example, for two samples with the above-mentioned conventional double-sided pressure-sensitive adhesive sheet, two discs having uneven thickness of the protective coat are bonded at 80 ° C. 90% RH × 2000H
FIG. 2 shows the relationship between the thickness unevenness and the disc tilt after the environmental test when the environmental test is performed. According to this, when the thickness unevenness of the protective coat exceeds 50 μm,
It can be seen that the disc tilt after the environmental test exceeds 5 mred which is the tilt allowable value of the high density recording optical disc.

In this embodiment, a double-sided pressure-sensitive adhesive sheet having a small compression elastic modulus is used for the adhesive 4 portion, so that 50
Even when disks having a protective coat thickness unevenness of μm or more are bonded together, the pressure-sensitive adhesive sheet portion absorbs the thickness unevenness so that good tilt characteristics can be maintained.

The compression elastic modulus of the double-sided adhesive sheet 4 is 4 k when the outer diameter of the disk substrates 1 and 1'is 120 to 130 mm.
It must be g / cm ² or more and 60 kg / cm ² or less. If the outer diameter of the disk is 80 to 90 mm, 1k
The range must be g / cm ² or more and 60 kg / cm ² or less.

In order to achieve the above-mentioned compression modulus, the pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet based on a foamed material such as urethane or polyethylene, polyester, polyethylene or P.
A pressure-sensitive adhesive sheet in which an acrylic or silicone pressure-sensitive adhesive having a thickness of at least 25 μm is laminated on both surfaces of a film base material such as ET is used.

Next, the method for laminating the optical information recording media in this embodiment will be described. As shown in FIG. 3, the double-sided pressure-sensitive adhesive sheet 4 used for pasting has the pressure-sensitive adhesive layer surfaces on both sides covered with the separators 5 and 5 ′, and the pressure-sensitive adhesive surface is protected until the time of use,
In order to simplify the bonding, it is processed into a ring-shaped sheet having the same inner and outer diameters as the bonded substrate.

Bonding of the two disk substrates with the double-sided adhesive sheet 4 can be carried out by using a means such as a laminator or a press, but as in the present invention, a high-density disk that requires high-precision bonding. In particular, the bonding method using a vacuum press is most suitable because it can prevent bubbles and bonding unevenness from remaining on the bonding surface.

FIG. 4 shows an example of the vacuum pressing apparatus used in this embodiment. The first disk substrate 1 on which the recording film 2 and the protective coat film 3 are sequentially laminated and one of the pressure-sensitive adhesive sheets shown in FIG.
As shown in (a) of (a), it is fixed to the laminating device 6, and these are laminated with a certain gap maintained.
Then, by using hydraulic pressure, air pressure, etc., press pressure sufficient to eliminate the gap is applied.

The pressing pressure at this time may be a pressure sufficient to release the gap, and considering the influence on the disk substrate, it is 1,000,000 Pa or less, preferably 600,000 P.
It is preferably a or less.

At this time, the inside of the apparatus is maintained in a vacuum state by drawing a vacuum from the exhaust port 7 in the direction of the arrow. According to our research, the effect of such a vacuum press appears from a vacuum pressure of about several thousand Pa, and the unevenness of bonding can not be visually observed, but when considering the environment resistance and long-term reliability, 140 Pa The following is preferable.

In this way, the bonding of the double-sided pressure-sensitive adhesive sheet and the first disk 1 is completed within a pressing time of several seconds. After that, the other separator 5'of the pressure-sensitive adhesive sheet shown in FIG. 3 is peeled off, and similarly, as shown in FIG. 4 (b), it is attached to the second disk substrate 1 '.

By the above-mentioned bonding method, an optical disk can be obtained in which bubbles are not left between the two disks and the double-sided adhesive sheet and there is no uneven bonding. At that time, if the protective coating layer laminated on each disk has a thickness unevenness of more than 50 μm and the adhesive sheet 4 does not have the ability to absorb it, a thin disk substrate of 0.6 mm thickness will have a force of vacuum pressing. Will cause deformation. At this time, by selecting the material so that the compression elastic modulus of the double-sided pressure-sensitive adhesive sheet is within the above range, there is no deformation of the substrate or uneven bonding,
A highly reliable optical disc can be obtained.

Next, the result of confirming the effect of the optical disk according to the present embodiment will be described. An optical disc having the structure of FIG. 1 and an outer diameter of 90 mm, in which only the compression elastic modulus of the adhesive sheet 4 was changed, was 80 ° C. · 9.
FIG. 5 shows the relationship between the compression elastic modulus and the tilt after the environmental test when the environmental test of 0% RH × 2000H was performed. As is clear from the figure, in order to keep the disc tilt within 5 mrad, which is the permissible amount for high density recording discs, the compression elastic modulus of the adhesive sheet is 1 kg / cm ² or more.
It must be in the range of 0 kg / cm ² or less. At this time, the lower limit value is a value at which the compression elastic modulus is too small to maintain the shape as a disk, and it becomes a small value by using a disk structure in which a reinforcing plate is sandwiched between two disks. Can be shifted. For example, 1.
0.5k when sandwiching a 2mm thick acrylic reinforcing plate
It is g / cm ² .

Although not shown, even if the disc has an outer diameter of 90 mm, the same relationship as in FIG. 5 can be obtained if the disc has an outer diameter of 80 to 90 mm, and the tilt after the environmental test is 5 mr.
The compression modulus of the pressure-sensitive adhesive sheet must be 1 to be below ad.
It should be in the range of 60 kg / cm ² .

Next, the disk having the structure of FIG. 1 has an outer diameter of 130 m.
m optical disc in which only the compression elastic modulus of the adhesive sheet 4 is changed, 80 ° C./90% RH × 2000H
FIG. 6 shows the relationship between the compression elastic modulus and the tilt after the environmental test when the environmental test of No. 2 was performed. With this outer diameter, the disc tilt is 5 m, which is the allowable amount of the high-density recording disc.
In order to keep the pressure below rad, the compression modulus of the pressure-sensitive adhesive sheet must be in the range of 4 kg / cm ² or more and 60 kg / cm ² or less. It is known that the lower limit value at this time also shifts to a smaller value by adopting a disc structure in which a reinforcing plate is sandwiched between two discs. For example, when sandwiching a 1.2 mm thick acrylic reinforcing plate, 2
It is kg / cm ² .

Although not shown, even if the disc has an outer diameter of 130 mm, if the disc has an outer diameter of 120 to 130 mm, the same correlation as that shown in FIG. 6 can be obtained, and the tilt after the environmental test becomes 5 mrad or less. The compression elastic modulus of the adhesive sheet needs to be in the range of 4 to 60 kg / cm ² .

Next, the result of actual comparison between the optical disk of this embodiment and the conventional optical disk will be described. An optical disc A having an outer diameter of 86 mm and a compression elastic modulus of the pressure sensitive adhesive sheet 4 of 50 kg / cm ² which is within the scope of the present invention having the structure of FIG. 1, and a compression elastic modulus of the pressure sensitive adhesive sheet 4 having the same structure as the optical disk A. An optical disk B having a rate of 550 kg / cm ² and outside the range of the present invention was prepared. FIG. 7 shows changes in tilt when these optical disks were subjected to an environmental test at 80 ° C. and 90% RH × 2000H. According to this, it is confirmed that the tilt of the disk B increases beyond 5 mrad, whereas the disk A maintains a low value of 5 mrad or less even after 2000 hours. Although not shown, the bit error rate (BE.
R. ), The disc B is 10 ⁻³ after the environmental test.
It is confirmed that the disk A keeps a good value of 10 ⁻⁵ without any change from the initial value, while it has a considerably bad value.

Next, an outer diameter of 130 mm having the structure of FIG.
The disc has a compression elastic modulus of 50 kg /
cm ² , which is within the range of the present invention, and the compression elastic modulus of the pressure-sensitive adhesive sheet 4 having the same structure as that of the optical disk C of 5
An optical disc D which is out of the range of the present invention at 50 kg / cm ^2.
And created. These optical discs are at 80 ° C and 90% R
FIG. 8 shows the change in tilt when subjected to the H × 2000H environmental test. According to this, the tilt of the disc D is 5
It is confirmed that the disk C becomes large beyond mrad, whereas the disk C stably maintains a low value of 5 mrad or less even after 2000 hours. Although not shown,
Also at this time B. E. R. Ask for disk D
Then, it was confirmed that the disk C maintained a good value of 10 ^-5 units without change from the initial value, whereas the value after the environmental test was 10 ^-3 units, which was a considerably bad value.

As is clear from the above, the disc of the present invention can obtain a tilt property which is very good including long-term reliability; a tilt property which does not exceed 5 mrad which is the specification of a high density disc. And it guarantees that good recording / reproducing characteristics can be maintained.

In the above embodiment, the case where the disks having the protective layers with uneven thickness are directly adhered to each other has been described, but this embodiment can be adopted even if they are not necessarily directly adhered. For example, as shown in FIG. 9, a structure in which a reinforcing plate 8 is sandwiched between two discs and the discs are attached may be used.

Further, the recording film to be laminated on the disc of the present invention does not have to be only one layer, and as shown in FIG. 10, the recording films 21 and 22 and the recording films 21 'and 22' and the two recording films are formed. It may be a structure having a recording film or a structure having more recording films.

Next, an embodiment of the second invention will be described. FIG. 11 is a sectional view showing an example of an optical information recording medium (optical disc) according to the present invention. In the figure, reference numeral 10
Reference numerals 1, 101 'are 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 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. Each of these substrates has a step difference of 40 μm or more in the thickness direction. A recording film (for example, phase change, alloy type film, etc.) or a reflective film (for example, Al, Au, etc.) 102, 102 'is formed on each of these by vapor deposition or the like.

The resin disk substrate processed by injection molding or the like may have a step due to the structure of the molding die, or the disk structure may have a step due to some intention.

Conventionally, these discs have been pasted together with a relatively hard double-sided pressure-sensitive adhesive sheet, for example, a pressure-sensitive adhesive sheet having a structure in which a 10 μm silicone pressure-sensitive adhesive is laminated on both sides of a PET substrate. If the step in the depth direction becomes large to some extent, the thin substrate may be deformed during bonding or uneven bonding may occur, and tilt characteristics may deteriorate. For example, two disk substrates having uneven disk thickness due to the unevenness may be used. 80 ° C / 90% RH x on the sample pasted with the conventional double-sided adhesive sheet
FIG. 12 shows the relationship between the level difference and the disc tilt after the environmental test when an environmental test of 2000H is performed.
According to this, when the local disc thickness change due to the step exceeds 40 μm, the disc tilt after the environmental test is
It can be seen that the tilt allowable value of the high density recording optical disk exceeds 5 mrad.

In this embodiment, a double-sided pressure-sensitive adhesive sheet having a small compression elastic modulus is used for the adhesive 104,
Even when disks with a step difference of 40 μm or more are stuck together, the adhesive sheet part absorbs the thickness change,
This is to maintain good tilt characteristics.

The double-sided pressure-sensitive adhesive sheet 104 has a compression modulus of elasticity such that the outer diameters of the disk substrates 101 and 101 'are 120 to 130 m.
In the case of m, it is necessary to be 4 kg / cm ² or more and 45 kg / cm ² or less. Moreover, the outer diameter of the disk is 80 to 90 mm.
In this case, the range must be 1 kg / cm ² or more and 45 kg / cm ² or less.

In order to achieve the above compression elastic modulus, the pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet based on a foamed material such as urethane or polyethylene, polyester, polyethylene or P.
A pressure-sensitive adhesive sheet in which an acrylic or silicone pressure-sensitive adhesive having a thickness of at least 30 μm is laminated on both sides of a film base material such as ET is used.

Next, a method for laminating the optical information recording media in this embodiment will be described. As shown in FIG. 13, the double-sided pressure-sensitive adhesive sheet 104 used for bonding has separators 105, 105 ′ on both surfaces of the pressure-sensitive adhesive layer.
The adhesive surface is protected until it is used, and it is processed into a ring-shaped sheet having the same inner and outer diameters as the bonded substrate for easy bonding.

Bonding of the two disk substrates by the double-sided adhesive sheet 104 can be carried out by using a means such as a laminator, a press, etc., but a high density disk which requires highly accurate bonding as in the present invention. In particular, the bonding method using a vacuum press is most suitable because it can prevent bubbles and bonding unevenness from remaining on the bonding surface.

FIG. 14 shows an example of the vacuum pressing apparatus used in this embodiment. The first disk substrate 101 having the recording film 102 laminated thereon and the adhesive sheet shown in FIG. 13 from which one of the separators 105 has been peeled off are fixed to a bonding device 106 as shown in FIG. , These are stacked with a certain gap maintained. Then, by using hydraulic pressure, air pressure, etc., press pressure sufficient to eliminate the gap is applied.

The pressing pressure at this time may be a pressure sufficient to release the gap, and considering the influence on the disk substrate, it is 1,000,000 Pa or less, preferably 600,000 P.
It is preferably a or less.

At this time, the inside of the apparatus is maintained in a vacuum state by evacuating from the exhaust port 107 in the direction of the arrow.
According to our research, the effect of such vacuum pressing is
Although the vacuum pressure appears from several thousands Pa and the bonding unevenness is not visually observed, it is preferably 140 Pa or less in consideration of the environment resistance and long-term reliability.

In this way, the bonding of the double-sided pressure-sensitive adhesive sheet and the first disc 101 is completed within a pressing time of several seconds. After that, the other separator 105 'of the pressure-sensitive adhesive sheet shown in FIG. 13 is peeled off, and similarly, as shown in FIG. 14 (b), it is bonded to the second disk substrate 101'.

By the above-mentioned bonding method, an optical disk can be obtained in which bubbles are not left between the two disks and the double-sided adhesive sheet and there is no uneven bonding. At that time, if each disc substrate has a step in the thickness direction exceeding 40 μm and the adhesive sheet 104 has no ability to absorb it, the thin disc substrate with a thickness of 0.6 mm is deformed by the force of a vacuum press. Will cause At this time, by selecting the material so that the compression elastic modulus of the double-sided pressure-sensitive adhesive sheet falls within the above range, it is possible to obtain a highly reliable optical disk having neither deformation of the substrate nor uneven bonding.

Next, the result of confirming the effect of the optical disk according to the present embodiment will be described. An optical disc having an outer diameter of 90 mm having the structure of FIG. 11 in which only the compression elastic modulus of the adhesive sheet 104 is changed is 80 ° C.
FIG. 15 shows the relationship between the compressive elastic modulus and the tilt after the environmental test when the environmental test of 90% RH × 2000H is performed. As is clear from the figure, in order to keep the disc tilt within 5 mrad, which is the permissible amount for high-density recording discs, the compression elastic modulus of the adhesive sheet is 1 kg / cm ^2.
It should be in the range of 45 kg / cm ² or less. The lower limit value at this time is a value at which the compression elastic modulus is too small to maintain the shape of the disk, and
It is known that a disc structure in which a reinforcing plate is sandwiched between a number of discs shifts to a smaller value. For example, when a 1.2 mm thick acrylic reinforcing plate is sandwiched, the pressure is 0.5 kg / cm ² .

Although not shown, even if the disc has an outer diameter of 90 mm, the same correlation as that shown in FIG. 15 can be obtained if the disc has an outer diameter of 80 to 90 mm, and the tilt after the environmental test is 5 m.
The compression modulus of the pressure-sensitive adhesive sheet is 1 in order to be rad or less.
It must be in the range of ~ 45 kg / cm ² .

Next, the disk outer diameter 13 of the structure of FIG.
A 0 mm optical disc in which only the compression elastic modulus of the adhesive sheet 104 is changed is 80 ° C./90% RH × 2.
FIG. 16 shows the correlation between the compressive elastic modulus and the tilt after the environmental test when the environmental test of 000H was performed. In the case of this outer diameter, in order to keep the disc tilt within 5 mrad which is an allowable amount of the high-density recording disc, the compression elastic modulus of the adhesive sheet must be in the range of 4 kg / cm ² or more and 45 kg / cm ² or less. I won't. The lower limit value at this time is also 2
It is known that a disc structure in which a reinforcing plate is sandwiched between a number of discs shifts to a smaller value. For example, when sandwiching a 1.2 mm-thick acrylic reinforcing plate, it is 2 kg / cm ² .

Although not shown, even if the disc has an outer diameter of 130 mm, if the disc has an outer diameter of 120 to 130 mm, the same correlation as that shown in FIG. 16 is obtained, and the tilt after the environmental test is 5 mrad or less. The compression modulus of the pressure-sensitive adhesive sheet needs to be in the range of 4 to 45 kg / cm ² .

Next, the result of actual comparison between the optical disk of this embodiment and the conventional optical disk will be described. An optical disc E having an outer diameter of 86 mm and a compression elastic modulus of the pressure-sensitive adhesive sheet 104 of 30 kg / cm ² is within the range of the present invention having the structure of FIG. 11, and a compression of the pressure-sensitive adhesive sheet 104 having the same structure as the optical disk E. Elastic modulus is 550 kg /
cm ² and an optical disk F which is out of the scope of the present invention were prepared. These optical discs are stored at 80 ° C / 90% RH × 200
The change in tilt when subjected to the 0H environmental test is shown in FIG. According to this, the tilt of the disc F is 5 mrad.
The size of the disk E is 2
It is confirmed that a low value of 5 mrad or less is stably maintained even after 000 hours. Although not shown, if the bit error rate (B.E.R.) at which the signal of the disk is actually read and written at this time is obtained, the disk F has a considerably bad value of 10 ⁻³ after the environmental test. On the other hand, it was confirmed that the disk E keeps a good value of 10 ⁻⁵ units without changing from the initial value.

Next, with the disk having the outer diameter of 130 mm having the structure of FIG. 11, the compression elastic modulus of the adhesive sheet 104 is 30 kg /
cm ² and an optical disk G within the range of the present invention, and an optical disk H having the same structure but having a compression elastic modulus of the adhesive sheet 104 of 550 kg / cm ² and outside the range of the present invention were prepared. These are 80 ℃, 90% RH × 20
FIG. 18 shows changes in tilt when subjected to the 00H environmental test.
Shown in. According to this, the tilt of the disc H is 5 mra.
It is confirmed that the disk G grows larger than d, whereas the disk G stably maintains a low value of 5 mrad or less even after 2000 hours have passed. Although not shown, B. E. R. It was confirmed that while the disk H had a considerably bad value of 10 ⁻³ after the environmental test, the disk G kept a good value of 10 ⁻⁵ without changing from the initial value. It was

As is clear from the above, the disc of the present invention can obtain a tilt property which is very good including long-term reliability; the tilt property does not exceed 5 mrad which is the specification of the high density disc. And it guarantees that good recording / reproducing characteristics can be maintained.

Although the above embodiment has described the case where the discs having the steps are directly attached to each other, the present embodiment can be adopted even if the discs are not necessarily attached directly to each other. 2 as shown
The structure may be such that the reinforcing plate 108 is sandwiched between the discs and the discs are attached.

The recording film to be laminated on the disc of the present invention does not have to be only one layer, and as shown in FIG. 20, recording films 121 and 122, and recording films of two layers 121 'and 122'. It may be a structure having a recording film or a structure having more recording films. Further, as shown in FIG. 21, a structure may be adopted in which a protective layer 130 is formed on the recording film or the like.

[0064]

As described above, according to the present invention, the thickness unevenness of the protective coat is 50 μm or more, or the level difference of the substrate is 4 or more.
Provided is an optical information recording medium having a small deformation of the substrate and good tilt characteristics even in an optical disc having a thickness of 0 μm or more, and a manufacturing method thereof.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the relationship between unevenness of protective coat thickness and tilt after an environmental test in the information recording medium shown in FIG.

FIG. 3 is a cross-sectional view showing a double-sided pressure-sensitive adhesive sheet used for bonding substrates.

FIG. 4 is a diagram for explaining a substrate bonding method according to the present invention.

5 is a diagram showing the relationship between the compression elastic modulus of an adhesive sheet and the tilt after an environmental test in an information recording medium having a disc diameter of 90 mm having the structure shown in FIG.

FIG. 6 is a diagram showing the relationship between the compression elastic modulus of an adhesive sheet and the tilt after an environmental test in an information recording medium having a disk diameter of 130 mm having the structure shown in FIG.

7 is a diagram showing the relationship between the environmental test time and the tilt after the environmental test when the compression elastic modulus of the adhesive sheet is changed in the information recording medium having the disc diameter of 90 mm having the structure shown in FIG.

8 is a diagram showing the relationship between the environmental test time and the tilt after the environmental test when the compression elastic modulus of the adhesive sheet is changed in the information recording medium having the disk diameter of 130 mm having the structure shown in FIG.

9 is a sectional view showing a modified example of the information recording medium of FIG.

10 is a cross-sectional view showing another modified example of the information recording medium of FIG.

FIG. 11 is a sectional view showing an information recording medium according to another embodiment of the present invention.

12 is a diagram showing the relationship between the level difference of the disc substrate and the tilt after the environmental test in the information recording medium shown in FIG.

FIG. 13 is a cross-sectional view showing a double-sided pressure-sensitive adhesive sheet used for bonding substrates.

FIG. 14 is a diagram for explaining a substrate bonding method according to the present invention.

15 is a diagram showing the relationship between the compression elastic modulus of an adhesive sheet and the tilt after an environmental test in an information recording medium having a disc diameter of 90 mm having the structure shown in FIG.

16 is a disk diameter of 130 mm of the structure shown in FIG.
6 is a diagram showing the relationship between the compression elastic modulus of the pressure-sensitive adhesive sheet and the tilt after the environmental test in the information recording medium of FIG.

17 is a diagram showing the relationship between the environmental test time and the tilt after the environmental test when the compression elastic modulus of the adhesive sheet is changed in the information recording medium having the disc diameter of 90 mm having the structure shown in FIG.

FIG. 18 is a disk diameter of 130 mm of the structure shown in FIG.
6 is a diagram showing the relationship between the environmental test time and the tilt after the environmental test when the compression elastic modulus of the pressure-sensitive adhesive sheet is changed in the information recording medium of FIG.

19 is a cross-sectional view showing a modified example of the information recording medium of FIG.

20 is a sectional view showing another modification of the information recording medium of FIG.

21 is a sectional view showing still another modification of the information recording medium of FIG.

[Explanation of symbols]

 1, 1 ', 101, 101' ... disk substrate 2, 2 ', 102, 102' ... recording film or reflective film 3, 3 '... protective coating layer 4, 104 ... double-sided adhesive sheet

Claims (8)

[Claims] 1. A recording film, on which information is reproduced by a light beam, and a protective coat layer having a thickness unevenness of 50 μm or more are laminated on at least one of them, and the outer diameter thereof is 80 to 9.
Two recording substrates of 0 mm have a compression elastic modulus of 1 kg /
An optical information recording medium, which is obtained by laminating the entire surface with a double-sided pressure-sensitive adhesive sheet having a cm ² or more and 60 kg / cm ² or less. 2. A recording film, on which information is reproduced by a light beam, and a protective coating layer having a thickness unevenness of 50 μm or more, are laminated on at least one of the sheets, and the outer diameter thereof is 120 to 1
Two recording substrates of 30 mm have a compression elastic modulus of 4 kg.
/ Cm ² or more and 60 kg / cm ² or less, a double-sided pressure-sensitive adhesive sheet, which is laminated on the entire surface to provide an optical information recording medium. 3. A recording film on which information is reproduced by a light beam is laminated on at least one of the sheets, and 40 μm in the thickness direction.
Two recording substrates having an outer diameter of 80 to 90 mm with a step difference of m or more have a compression elastic modulus of 1 kg / cm ² or more and 45 k
An optical information recording medium, which is obtained by laminating the entire surface with a double-sided adhesive sheet of g / cm ² or less. 4. A recording film, on which information is reproduced by a light beam, is laminated on at least one of the sheets, and 40 μm in the thickness direction.
Two recording substrates having an outer diameter of 120 to 130 mm and having a step of m or more have a compression elastic modulus of 4 kg / cm ² or more 45
The optical information recording medium characterized by comprising bonding the entire surface in kg / cm ² or less double-sided pressure-sensitive adhesive sheet. 5. A compressive elastic modulus between two recording substrates having an outer diameter of 80 to 90 mm, wherein a recording film on which information is reproduced by a light beam and a protective coat layer are laminated on at least one of them. Is 1 kg / cm ² or more 60 kg / cm ²
A method for producing an optical information recording medium, characterized in that, when the following double-sided pressure-sensitive adhesive sheets are attached, the attachment is performed with a vacuum press having a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less. 6. A recording film, on which information is reproduced by a light beam, and a protective coat layer are laminated on at least one of them, and two recording substrates each having an outer diameter of 120 to 130 mm have a compression elastic modulus. 4 kg / cm ² or more 60 kg / cm
^When laminating with a double-sided adhesive sheet of ² or less, the laminating is performed under a vacuum pressure of 140 Pa or less and a pressing pressure of 100.
A method for manufacturing an optical information recording medium, characterized in that the method is performed by a vacuum press at 10,000 Pa or less. 7. A recording film, on which information is reproduced by a light beam, is laminated on at least one of the sheets, and 40 μm in the thickness direction.
Two recording substrates having an outer diameter of 80 to 90 mm with a step difference of m or more have a compression elastic modulus of 1 kg / cm ² or more and 45 k
A method for producing an optical information recording medium, characterized in that when laminating the entire surfaces with a double-sided pressure-sensitive adhesive sheet of g / cm ² or less, the laminating is performed with a vacuum press having a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less. 8. A recording film, on which information is reproduced by a light beam, is laminated on at least one of the sheets, and 40 μm in the thickness direction.
Two recording substrates having an outer diameter of 120 to 130 mm and having a step of m or more have a compression elastic modulus of 4 kg / cm ² or more 45
A method for producing an optical information recording medium, characterized in that, when laminating the entire surfaces with a double-sided pressure-sensitive adhesive sheet of kg / cm ² or less, the laminating is performed with a vacuum press having a vacuum pressure of 140 Pa or less and a press pressure of 1,000,000 Pa or less.