JPH11328755A - Production of information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing an information recording medium capable of stationarily assuring an adhesive layer of a uniform thickness and suppressing warpage and deformation under a wet heat environment. SOLUTION: This process for production of the information recording medium (optical disk) 15 consists in laminating a first information recording substrate (first disk substrate) 19a and a second information recording substrate (second disk substrate) 19b with an adhesive layer 20. At this time, a half-curing tacky adhesive sheet 10 having a solvent insoluble component within a range of >=30 to <80 wt.% is prepd. for the adhesive layer 20 described above. This half- curing tacky adhesive sheet 10 is interposed between the first disk substrate 19a and the second disk substrate 19b and thereafter, the solvent insoluble component is regulated to >=80 wt.% by advancing curing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an information recording medium capable of recording information magneto-optically or in a phase-change manner and reading the recorded information.

[0002]

2. Description of the Related Art Among information recording media, an optical recording medium is particularly capable of recording information by irradiating a laser beam and reading the recorded information. As such an optical recording medium, for example, there is an optical recording medium (optical disk) 1 shown in FIG. The optical disk 1 includes first and second disk substrates 5a and 5b, and an adhesive layer 6. In the first disk substrate 5a, an information layer 3a having a fine unevenness information surface 8a is formed on the surface of the first substrate 2a,
In the state along the fine unevenness information surface 8a of the information layer 3a,
It is configured by forming a translucent layer 4a. The second disk substrate 5b has a fine unevenness information surface 8 on the surface of the second substrate 2b.
The information layer 3b having the “b” is formed, and the reflection layer 4b is formed along the fine unevenness information surface 8b of the information layer 3b. The adhesive layer 6 bonds the first and second disk substrates 5a and 5b, and the bonding mode is such that the translucent layer 4a of the first disk substrate 5a and the reflective layer 4b of the second disk substrate 5b are bonded. They face each other via the agent layer 6. In addition, the external shape of the optical disk 1 is generally a disk shape. In the figure, reference numeral 7 denotes a hole formed substantially at the center of the optical disc 1.

[0003] The optical disk 1 is conventionally manufactured by the following method. That is, first, the substrate 2
a and 2b are produced by a method such as injection molding, and then the information layers 3a and 3b are formed on the surface by sputtering or the like, and the semi-transparent layer 4a or the reflection layer 4 is further formed on the surface.
The first and second disk substrates 5a and 5b are manufactured by forming the substrate b by a spin coating method or the like. Next, an adhesive is applied to the surface of the first or second disk substrate 5a, 5b by spin coating, screen printing, or the like to form an adhesive layer 6, and the first Alternatively, the optical disk 1 is manufactured by bonding the second optical disk substrates 5a and 5b. As the adhesive, a reactive adhesive such as a photocurable adhesive or a thermosetting adhesive, a hot melt adhesive, or the like has been used.

[0004]

However, the substrate 2
Since a and 2b are formed by injection molding, the substrate 2
Distortion, bending, and uneven thickness occur in a and 2b. Due to the presence of such distortion, when the adhesive is applied by the spin coating method or the like, the thickness of the adhesive layer 6 becomes uneven, and the thickness of the adhesive layer 6 is constantly maintained in a uniform state. There is a problem that can not be. Further, even if the optical disk 1 is manufactured by bonding the first or second disk substrates 5a and 5b by heating and pressurizing, the thickness of the adhesive layer 6 may be non-uniform. Warpage deformation occurs and becomes an obstacle factor for recording or reading (reproducing) information.

The first and second disk substrates 5a,
Since the fine unevenness information surfaces 8a and 8b are formed on 5b, air bubbles are apt to be mixed into the adhesive layer at the time of bonding, which may be a trouble factor for recording or reading (reproducing) information. There is.

The present invention has been made in view of such circumstances, and can constantly secure an adhesive layer having a uniform thickness.
It is an object of the present invention to provide a method for manufacturing an information recording medium capable of suppressing warpage under a moist heat environment.

[0007]

In order to achieve the above object, the present invention provides a method for manufacturing an information recording medium, comprising the steps of laminating a first information recording substrate and a second information recording substrate via an adhesive layer. A method for producing an information recording medium, comprising:
A semi-cured pressure-sensitive adhesive sheet having a solvent insoluble content in the range of 30% by weight or more and less than 80% by weight is prepared, and the semi-cured pressure-sensitive adhesive sheet is interposed between the first information recording substrate and the second information recording substrate. After curing, the solvent insoluble content was reduced to 80% by weight.
The above configuration is adopted.

That is, the present inventors have conducted a series of studies in order to obtain an information recording medium in which warpage deformation is suppressed and information recording and reading (reproduction) are not hindered. In the course of this process, he imagined that the cause of the warp deformation of the information recording medium might be in the adhesive layer, and continued his research focusing on the adhesive layer. As a result, the warp deformation is caused by the unevenness of the thickness of the adhesive layer, and a series of further studies were conducted for the purpose of correcting the unevenness of the thickness. As a result, as a pressure-sensitive adhesive sheet used for forming the adhesive layer, using a semi-cured pressure-sensitive adhesive sheet in which the solvent-insoluble content is set to a specific range,
After the semi-cured pressure-sensitive adhesive sheet is interposed between the first information recording medium and the second information recording medium, the curing is advanced to achieve the intended purpose if the solvent-insoluble content is 80% by weight or more. We found what we could do and arrived at this invention.

[0009]

Next, an embodiment of the present invention will be described in detail.

The semi-cured pressure-sensitive adhesive sheet used in the method for producing an information recording medium according to the present invention is a sheet in which the adhesive is in a semi-cured state. Normally, the semi-cured pressure-sensitive adhesive sheet is formed into a semi-cured pressure-sensitive adhesive sheet body by temporarily attaching a separator to the adhesive surface in consideration of handleability. As an example of this type of semi-cured pressure-sensitive adhesive sheet body, as shown in FIG. 1, a semi-cured pressure-sensitive adhesive sheet 10 in which a first separator 11a and a second separator 11b are temporarily attached to both surfaces is cited. Although the shape is not particularly limited, the shape is a disk shape (doughnut shape) having a hole formed at substantially the center in accordance with the shape of the information recording substrate (not shown).

As a material for forming the semi-cured pressure-sensitive adhesive sheet 10 constituting the semi-cured pressure-sensitive adhesive sheet body 12, any material capable of setting the solvent-insoluble content of the semi-cured pressure-sensitive adhesive sheet 10 to a specific range is used. There is no particular limitation, and various pressure-sensitive adhesive compositions are used. Among them, a pressure-sensitive adhesive composition containing isooctyl acrylate and acrylic acid as main components and containing a photopolymerization initiator and an internal crosslinking agent (for example, trimethylolpropane triacrylate) is preferable. This pressure-sensitive adhesive composition is prepared, for example, as follows. That is, first, isooctyl acrylate,
After dispersing the acrylic acid and the photopolymerization initiator, it is irradiated with ultraviolet rays to obtain a viscous substance. And it can be prepared by adding an internal crosslinking agent to this viscous material.

The first and second separators 11a and 11b constituting the semi-cured pressure-sensitive adhesive sheet 12 are not particularly limited, but include polymer films such as polyethylene terephthalate (PET), polyester, and polypropylene; Paper or the like is used. Separator 11a,
11b may be the same material or different materials. The surfaces of the separators 11a and 11b may be subjected to a release treatment.

The semi-cured pressure-sensitive adhesive sheet 12 is formed, for example, by applying a pressure-sensitive adhesive composition to one surface of a first separator 11a and bonding a second separator 11b to the applied surface. It can be obtained by pre-curing by ultraviolet irradiation or the like to form a semi-cured pressure-sensitive adhesive sheet 10.

It is necessary that the semi-cured pressure-sensitive adhesive sheet 10 has a solvent insoluble content set in a range of 30% by weight or more and less than 80% by weight. Especially, it is preferable that it is set to 50 to 70% by weight. That is, the solvent insoluble content is 30
When the content is less than 10% by weight, the semi-cured pressure-sensitive adhesive sheet 10 does not extend uniformly between the pair of information recording substrates at the time of heating, pressing, and heating / pressing, and the thickness of the adhesive layer can be made uniform. This is because it is difficult, and when the semi-cured pressure-sensitive adhesive sheet body 12 is punched into a disk shape, the workability deteriorates. Conversely, 80% by weight
With the above, the gap formed by the unevenness of the fine unevenness information surface of the information recording substrate cannot be filled, and the adhesiveness is deteriorated, which causes the inclusion of microbubbles.

The solvent-insoluble content is determined as follows. That is, a sample is first cut out to a predetermined size, and this is immersed in a solvent such as ethyl acetate. Then
After taking out the sample and drying it under predetermined conditions, the weight of the sample is weighed. Then, it is obtained according to the following equation (1).

[0016]

(Equation 1)

The thickness of the semi-cured pressure-sensitive adhesive sheet 10 is preferably in the range of 1 to 100 μm, particularly preferably in the range of 10 to 100 μm. That is, if the thickness is too large, the soft semi-cured pressure-sensitive adhesive sheet 10 may deteriorate the dimensional accuracy (thickness accuracy) of the information recording medium as the final product,
On the other hand, if the thickness is too small, the gap due to the unevenness of the fine unevenness information surface may not be sufficiently filled, which may cause a problem in recording or reading (reproducing) information.

Regarding the method for producing the information recording medium of the present invention,
The optical disk 15 having the structure shown in FIGS. 2 and 3 will be specifically described as an example. The structure of the optical disk 15 is as follows.
It looks like this: That is, the optical disk 15
Is a disk-shaped (doughnut-shaped) first and second disk substrate 1 corresponding to the first and second information recording substrates.
9a and 19b are bonded via an adhesive layer 20. More specifically, the first disk substrate 1
9a, an information layer 17a having a fine unevenness information surface 22a is formed on one surface of a first substrate 16a.
a of the semi-transparent layer 18 along the fine unevenness information surface 22a of FIG.
a is formed. In the second disk substrate 19b, an information layer 17b having a fine uneven information surface 22b is formed on one surface of the second substrate 16b, and a reflective layer 18b is formed along the fine uneven information surface 22b of the information layer 17b. Have been. The adhesive layer 20 is formed on both disc substrates 19a and 19b.
Are adhered as shown. 2 and 3, reference numeral 21 denotes a hole formed substantially at the center of the optical disk 15.

The optical disk 15 having such a structure is manufactured, for example, as follows. That is, the first disk substrate 19a and the second disk substrate 19b are manufactured in the same manner as in the related art. Specifically, the substrates 16a, 16
b is prepared by a method such as injection molding, and the information layers 17a and 17b are formed on the surface by sputtering or the like.
The fine uneven information surfaces 22a, 2 of the information layers 17a, 17b
2b along with the translucent layer 18a or the reflective layer 18b.
Is formed by a spin coating method or the like to produce two first and second disk substrates 5a and 5b.

The substrates 16a, 16b, the information layers 17a,
The material for forming the layer 17b, the translucent layer 18a or the reflective layer 18b is not particularly limited, and a conventionally known material can be appropriately used. For example, the substrate 1
It is preferable to use a polycarbonate transparent substrate or the like as 6a and 16b.

Next, as shown in FIG. 4, the first separator 11a of the semi-cured pressure-sensitive adhesive sheet 12 (see FIG. 1)
Pressure-sensitive adhesive sheet 10 exposed by peeling off
Is laminated on the semi-transparent layer 18a of the first disk substrate 19a and integrated. At this time, the semi-cured pressure-sensitive adhesive sheet 10 has a solvent insoluble content of 30% by weight or more and less than 80% by weight, and is moderately soft.
The gap 23a formed by the above can be filled.

It is important for the above-mentioned lamination to eliminate the inclusion of air bubbles, and usually, lamination with a hand roller, a rubber roller, a press, etc., lamination under reduced pressure, lamination under pressure, etc. are performed. Especially, it is preferable to carry out by a rubber roller (for example, pressure bonding of 1 to 10 kg / cm ² at 40 to 80 ° C.).

Subsequently, the second separator 11b is peeled off from the integrated body to expose the semi-cured pressure-sensitive adhesive sheet 10 as shown in FIG. Reflective layer 18 of second disk substrate 19b
b and the disk substrates 19a and 19b are bonded together. This bonding can be performed by various methods in the same manner as described above, but the heating autoclave (for example,
40 to 80 ° C, pressure bonding of 1 to ²⁰ kg / cm ² ),
Alternatively, a vacuum press (for example, 1 to 20 torr, 1
(100 kg / cm ² pressure bonding). In this case, since the semi-cured pressure-sensitive adhesive sheet 10 has a solvent insoluble content of 30% by weight or more and less than 80% by weight and has appropriate rigidity and softness, the semi-cured pressure-sensitive adhesive sheet 10 extends evenly between the disk substrates 19a and 19b. A gap 23 formed by the fine unevenness information surface 22b becomes a layer having a substantially uniform thickness.
b can be filled.

Next, as shown in FIG. 6, the semi-cured pressure-sensitive adhesive sheet 10 interposed between the first disk substrate 19a and the second disk substrate 19b is exposed and cured by ultraviolet irradiation 25, and the like. The curing is advanced to form an adhesive layer 20 having a solvent insoluble content of 80% by weight or more. The preferred range of the solvent-insoluble content of the adhesive layer 20 is 8
5 to 99% by weight. Solvent insoluble content after complete curing is 80
If the amount is less than the weight%, the amount of change in radial tilt in a wet heat environment becomes too large, and information is recorded or read (reproduced).
This is because many defects occur. Note that the radial tilt change amount means a warp angle in a central axis direction (radial direction) when the optical disk 15 is held horizontally, and the optical disk 15 is rotated at a predetermined number of rotations, and a laser beam is irradiated onto the disk. And the value measured from the shake of the optical disk 15 due to the reflection angle.

According to the above manufacturing method, the first disk substrate 19a and the second disk substrate 19b are bonded by the semi-cured pressure-sensitive adhesive sheet 10 in which the solvent-insoluble content is within a specific range. It is possible to obtain the optical disk 15 in which the number 20 can be constantly secured and the warpage of the optical disk 15 is suppressed in a moist heat environment. Also, the fine unevenness information surface 22
The gaps 23a and 23b formed by the holes a and 22b can be filled, so that air bubbles can be obtained. Therefore, the obtained optical disk 15 has both adhesion and wet heat resistance, and can record and read (reproduce) information satisfactorily.

In the above-mentioned optical disc 1, the first and second disc substrates 19a and 19b both have the information layers 17a and 17b formed thereon.
The present invention is not limited to this. For example, instead of the second disk substrate 19b, a single-layer or multi-layer resin substrate without the information layer 17b may be used.

Next, examples will be described together with comparative examples.

[0028]

Embodiment 1 First, an information layer is formed on one surface of a disk-shaped substrate by sputtering, and a semi-transparent layer is formed by spin coating along the fine unevenness information surface of the information layer. A disk substrate was manufactured. Similarly, on one surface of a disc-shaped substrate, an information layer was formed by sputtering, and a reflection layer was formed by a spin coating method along the fine unevenness information surface of the information layer, thereby producing a first disk substrate. .

On the other hand, a semi-cured pressure-sensitive adhesive sheet was prepared as follows. That is, first, 2 parts by weight of Isogacure 184 (manufactured by Ciba Kaigie Co., Ltd.) as a photopolymerization initiator is mixed with 100 parts by weight of a monomer mixture composed of 90 parts by weight of isooctyl acrylate and 10 parts by weight of acrylic acid, and then sufficiently mixed. Replace with nitrogen and use a high pressure mercury lamp for about 10
Ultraviolet irradiation of 0 mJ / cm ² was performed. To the obtained viscous material, 1 part by weight of trimethylolpropane triacrylate was added as an internal crosslinking agent, and this was applied on a separator (second separator) to a thickness of 50 μm. Furthermore, in order to eliminate polymerization inhibition caused by oxygen, PET
A separator (first separator) was attached. Thereafter, ultraviolet irradiation at 800 mJ / cm ² was performed with a high-pressure mercury lamp to produce a semi-cured pressure-sensitive adhesive sheet having a sheet-shaped pressure-sensitive adhesive layer (semi-cured pressure-sensitive adhesive sheet) formed thereon.
The pressure-sensitive adhesive layer of this sheet has a thickness of 50 ± 5 μm.
The solvent insoluble content measured by the following method was 60% by weight. Next, the semi-cured pressure-sensitive adhesive sheet body was punched and formed into a disk shape, and then the first separator was peeled off, and pressed against the first disk substrate at 4 kg / cm ² using a silicone rubber roll at 60 ° C. Then, after peeling off the second separator, the pressure-sensitive adhesive layer provided on the first disk substrate and the second disk substrate are vacuum-pressed (10 t).
orr, 50 kg / cm ² ). Thereafter, ultraviolet light of 1400 mJ / cm ² was irradiated from the lower surface of the first disk substrate to be exposed and cured (see FIG. 6), thereby producing a target optical disk. At this time, the solvent-insoluble content measured by the following method was 95% by weight.

The optical disc obtained in this manner was visually inspected for warpage and distortion to examine the presence or absence of bubble generation and shape change. As a result, no bubble was generated, and no change in shape or distortion was observed. . The radial tilt variation measured by the following method was 0.10 °, which was a very good result.

[Solvent Insoluble Content] A sample of about 0.1 g is cut out and immersed in ethyl acetate at room temperature for 5 days. After immersion, the sample is pulled up with tweezers, transferred to an aluminum cup, dried at 130 ° C. for 2 hours, and then weighed. And it calculated according to said Formula (1).

[Radial tilt amount] 80 ° C. × 85% RH
The optical disc was kept horizontal for 100 hours under the wet heat environment. Then, the optical disk was rotated at a rotation speed of 100 rpm, the laser light was irradiated on the optical disk, and the amount of radial tilt change was measured from the deflection of the optical disk due to the reflected light. If the amount of change in the radial tilt is 0.5 ° or less, it can be said that the heat and humidity resistance is excellent, and a good result is obtained.

[0033]

Example 2 When producing a semi-cured pressure-sensitive adhesive sheet, the irradiation amount of ultraviolet rays was set to 700 mJ / cm ² and the solvent-insoluble content was set to 50.
An optical disc was produced in the same manner as in Example 1 except that the content was changed to% by weight.

[0034]

Example 3 When producing a semi-cured pressure-sensitive adhesive sheet, the irradiation amount of ultraviolet rays was 900 mJ / cm ² , and the solvent-insoluble content was 70%.
An optical disc was produced in the same manner as in Example 1 except that the content was changed to% by weight.

[0035]

Example 4 In the same manner as in Example 1, the first disk substrate and the second disk substrate were bonded via a pressure-sensitive adhesive layer. Then, from the lower surface of the first disk substrate, ultraviolet rays 1
Irradiation at 200 mJ / cm ² was performed to cure by exposure (see FIG. 6) to obtain a target optical disc. At this time, the solvent-insoluble content was 85% by weight.

[0036]

Example 5 In the same manner as in Example 1, the first disk substrate and the second disk substrate were bonded via a pressure-sensitive adhesive layer. Then, from the lower surface of the first disk substrate, ultraviolet rays 1
Irradiation was carried out at 600 mJ / cm ² to cure by exposure (see FIG. 6) to obtain a target optical disc. At this time, the solvent-insoluble content was 99% by weight.

With respect to the optical discs obtained in this way (Examples 2 to 5), the presence or absence of bubbles and the shape change were examined by visually judging warpage and distortion. Also, there was no shape change or distortion. Also, the radial tilt change amount is small,
Good results.

[0038]

Comparative Example 1 In the same manner as in Example 1, the first disk substrate and the second disk substrate were bonded via a pressure-sensitive adhesive layer. Then, from the lower surface of the first disk substrate, ultraviolet rays 1
Irradiation at 000 mJ / cm ² was performed to cure by exposure (see FIG. 6), and an intended optical disk was obtained. At this time, the solvent-insoluble content was 79% by weight.

The thus obtained optical disk has a radial tilt change amount of 0.
7 °, which hindered recording and reading of information.

[0040]

[Comparative Example 2] When a semi-cured pressure-sensitive adhesive sheet was produced, the irradiation amount of ultraviolet rays was 500 mJ / cm ² , and the solvent-insoluble content was 29.
An optical disc was produced in the same manner as in Example 1 except that the content was changed to% by weight.

In the optical disk obtained in this manner, the thickness of the adhesive layer was not uniform, and the optical disk was distorted, which hindered the recording and reading of information.

[0042]

Comparative Example 3 When producing a semi-cured pressure-sensitive adhesive sheet, the irradiation amount of ultraviolet rays was set to 1000 mJ / cm ² and the solvent-insoluble content was set to 8
An optical disk was produced in the same manner as in Example 1 except that the amount was set to 0% by weight.

The optical disk obtained in this manner includes:
Generation of microbubbles was partially observed.

[0044]

As described above, in the method for manufacturing an information recording medium of the present invention, a semi-cured pressure-sensitive adhesive sheet having a solvent-insoluble content within a specific range is prepared for forming an adhesive layer, and the semi-cured pressure-sensitive adhesive sheet is prepared. After the agent sheet is interposed between the first information recording substrate and the second information recording substrate, the curing is advanced, and the solvent insoluble content is reduced by 8%.
0% by weight or more. For this reason, it is possible to constantly obtain an adhesive layer having a substantially uniform thickness, and it is possible to obtain an information recording medium in which warpage is suppressed in a wet heat environment. In addition, this information recording medium has excellent adhesion,
No air bubbles are mixed. Therefore, the information recording medium obtained by the production method of the present invention has both adhesion and wet heat resistance, and can record and read (reproduce) information satisfactorily.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a semi-cured pressure-sensitive adhesive sheet used in the production method of the present invention.

FIG. 2 is a schematic cross-sectional view showing an optical disc which is an example of an information recording medium obtained by the manufacturing method of the present invention.

FIG. 3 is a plan view of the optical disc.

FIG. 4 is an explanatory diagram for explaining an example of a method of manufacturing the optical disc.

FIG. 5 is an explanatory diagram for explaining an example of a method of manufacturing the optical disc.

FIG. 6 is an explanatory diagram for explaining an example of a method of manufacturing the optical disc.

FIG. 7 is a schematic cross-sectional view for explaining a conventional optical disc.

[Explanation of symbols]

 15 optical disk 19a first disk substrate 19b second disk substrate 20 (10) adhesive layer (semi-cured adhesive sheet)

Claims (1)

[Claims] 1. A method for producing an information recording medium comprising a first information recording substrate and a second information recording substrate laminated via an adhesive layer, wherein the adhesive layer has a solvent-insoluble content of 30%. weight%
A semi-cured pressure-sensitive adhesive sheet having a content of not more than 80% by weight is prepared, and after the semi-cured pressure-sensitive adhesive sheet is interposed between the first information recording substrate and the second information recording substrate, curing is performed. A method for producing an information recording medium, wherein a solvent-insoluble content is 80% by weight or more.