JPH11328753A - Production of disk recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a medium at a low cost by applying a UV-curing resin with a roll on both or one of two substrates having an information recording part on one surface, irradiating the UV-curing resin with UV rays and then laminating the two substrates. SOLUTION: A cation polymerizable UV-curing resin 3 as an adhesive is applied with a coating roll 4 on optical disk substrates 1, 2, and the UV-curing resin 3 applied on optical disk substrates 1, 2 is irradiated by an UV-irradiating device 5. Then the two optical disk substrates 1, 2 are temporarily laminated, the optical disk 7 as a laminated body is pressed by a press 6, and the UV- curing resin 3 is hardened. The distance between the rotation axis 41 of the coating roll 4 and the coating face of the optical disk substrates 1, 2 is controlled to const. The relative speed of the rotation axis 41 of the coating roll to the coating face is controlled to const. Further, the thickness of the UV- curing resin 3 deposited on the coating roll 4 is controlled to const by a blade or the like.

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 a disc-shaped recording medium such as a digital video disc (DVD) having at least one of two optical disc substrates having an information recording portion bonded together. In particular, the present invention relates to a method for bonding substrates using a cationically polymerizable ultraviolet curable resin as an adhesive.

[0002]

2. Description of the Related Art With the advent of the multimedia age, optical disks have rapidly become widespread as recording media for large-capacity data such as images, sounds, and information. The optical disc has a single-plate type in which an information recording layer is formed on a substrate such as polycarbonate resin or glass, and two single-plate-type discs for the purpose of increasing the recording capacity, and information recording layers are provided on both sides. There is a bonding structure type. However, in recent years, the demand for higher density of the recording medium has become more and more strong, and the bonding type of the optical disk has become mainstream, including the case where the transparent substrate is bonded.

[0003] For bonding optical disks, hot-melt adhesives or ultraviolet-curable adhesives are used, and spin-coating, roll-coating, screen-printing, and the like are used for applying these adhesives. Have been.

However, in the case of a hot-melt type adhesive, there is a problem that the adhesive is thermoplastic and thus has poor heat resistance, and the optical disk is easily deformed or peeled off by heat.
Further, there is a high possibility that a defect occurs in the optical disk or a warp of the optical disk is caused by heat at the time of applying the adhesive.

[0005] Further, as a prior art of a method of manufacturing an optical disk using an ultraviolet curable adhesive, Japanese Patent Application Laid-Open No. 9-692 discloses a method.
As disclosed in Japanese Patent Publication No. 39, a first step of forming a recording layer or a reflective film on a recording region of a pair of substrates, and a film forming surface side of at least one of the pair of substrates, After applying an ultraviolet-curable adhesive containing a cationic polymerizable material as a main component, a second step of irradiating ultraviolet rays and the film-forming surfaces of the pair of substrates are opposed to sandwich the ultraviolet-curable adhesive. There is a manufacturing method comprising a third step of overlapping and pressurizing to cure the adhesive as described above. In order to prevent the adhesive applied at the time of pressing from protruding from the outer periphery of the substrate, the adhesive is often applied by pattern printing using a screen printing method so as to have a smaller diameter than the outer periphery of the substrate.

However, when the pattern is applied by the screen printing method, since the substrate and the screen gauze come into contact with each other, the silk gauze breaks mainly at the outer peripheral portion of the substrate, resulting in a production loss due to poor coating. is there.

[0007] As a method of solving the trouble caused by the breakage of the gauze, a method of detecting the breakage of the gauze using a sensor or the like is conceivable. As another method, it is conceivable to change the gauze before the screen gauze breaks, but it is difficult to determine the gauze replacement time because the number of applications until the gauze breaks depends on the squeegee pressing force and the substrate outer peripheral burr etc. The running cost of the gauze can be increased due to the early replacement beyond necessity. Furthermore, a method of changing the material of the gauze to metal or the like to make it difficult to break the gauze may be considered, but as an adverse effect of increasing the rigidity of the gauze, there is a possibility that the optical disc is damaged when the gauze comes into contact with the optical disc and becomes a defective product. . We believe that it is difficult to avoid the production failure and increase the cost at the same time in any gauze breakage measures.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to stably produce a disc-shaped recording medium having a laminated structure excellent in reliability and durability at low cost. It is to provide a way to do it.

[0009]

In order to solve the above-mentioned problems, a method of manufacturing a disk-shaped recording medium according to the present invention is directed to a method of manufacturing a disk-shaped recording medium in which at least one of two substrates having an information recording section is bonded. In the production method, a method for producing a disc-shaped recording medium, comprising applying an ultraviolet-curable resin to both or one of the substrates by a roll, irradiating the resin with ultraviolet rays, and bonding the two substrates together. Become.

[0010] In the above, it is preferable to apply the ultraviolet curable resin so that the resin has a coating thickness distribution.

Further, in the above, it is preferable that the interval of the ultraviolet curable resin coating thickness distribution is 0.1 to 5 mm and the thickness change is 20% or more of the average coating thickness.

Further, in the above, it is preferable that the ultraviolet curing resin is applied in a donut shape having an inner diameter larger than the inner diameter of the substrate and an outer diameter smaller than the outer diameter of the substrate.

[0013] In the above, in one roll,
It is preferable that an ultraviolet curable resin is simultaneously applied to both of the two substrates to be bonded.

Further, in the above, it is preferable that the viscosity of the ultraviolet curable resin is 1,000 to 20,000 centipoise.

[0015] In the above, it is preferable to apply the ultraviolet curable resin so that the resin has an average coating thickness of 10 to 60 µm.

In the above, it is preferable that the disk-shaped recording medium is an optical disk.

In the above, it is preferable that the ultraviolet curable resin is a cationically polymerizable ultraviolet curable resin.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The present invention relates to a method for manufacturing a disc-shaped recording medium, but the description will be given of an example in which a cationically polymerizable ultraviolet curable resin is used in an optical disc.

Although a radical polymerizable ultraviolet curable resin can be used, it is necessary to irradiate ultraviolet rays after two optical disc substrates are superimposed. The amount of UV does not reach the UV curable adhesive and it takes time to cure. Furthermore, since curing is hindered by oxygen, if a bubble is sandwiched during bonding, it becomes difficult to cure and the adhesive strength becomes insufficient. Therefore, a cationically polymerizable ultraviolet curable resin is preferred.

FIG. 1 is a schematic diagram of an optical disk laminating method, FIGS. 2 and 3 are diagrams of a pattern of application of a cationically polymerizable ultraviolet curable resin to an optical disk substrate in a laminating step, FIG. 4 is a schematic diagram of a coating roll, and FIG. FIG. 3 is a sectional view of an optical disk having a bonding structure.

FIG. 1 shows an example of a method for bonding optical disks according to the present invention. (A) a step of supplying the optical disk substrates 1 and 2 manufactured in the preceding step, (B) a step of applying a cationically polymerizable ultraviolet curable resin 3 as an adhesive by a roll 4, and (C) an optical disk by an ultraviolet irradiation device 5. A step of irradiating the cationically polymerizable UV-curable resin 3 applied to the substrates 1 and 2 with ultraviolet light, a step of (D) a step of temporarily bonding two optical disk substrates, and a step of (E) a set of temporarily bonded optical disks 7. Is pressed by the press board 6 and then the resin is cured.

In the step (B), the cationically polymerizable UV-curable resin 3 attached to the rotating roll 4 comes into contact with the optical disk substrates 1 and 2, and the UV-curable resin 3 is coated on the information recording layer of the substrates 1 and 2. It only has to be applied to the side. Therefore, each of the methods of moving the substrates 1 and 2 with respect to the fixed rotating shaft 41, moving the rotating shaft 41 with respect to the fixed substrates 1 and 2, and moving both the rotating shaft 41 and the substrates 1 and 2 Can be adopted.

The average coating thickness of the ultraviolet curable resin 3 is restricted by the thickness standard of the optical disk 7 after bonding, but is not particularly limited. However, in order to obtain a sufficient bonding strength, it is preferable that the sum of the average coating thicknesses of the two substrates to be bonded, that is, the bonding layer thickness of the bonded optical disk 7 is 10 to 60 μm.

The rotation shaft 41 of the roll 4 and the substrates 1, 2
It is desirable that the distance of the application surface be constant and that the relative speed of the rotating shaft 41 to the application surface be constant. Further, the ultraviolet curable resin 3 adhered to the roll 4 by a blade or the like.
Is desirably adjusted to a constant thickness.

The material of the roll 4 is not particularly limited.
Considering the substrate damage when the roll 4 comes into contact with the substrates 1 and 2, rubber is more preferable than metal. However, it is necessary to select a rubber having excellent chemical resistance to the composition of the cationically polymerizable UV-curable resin 3.

In the step (D), when two optical disk substrates are temporarily bonded in the air, air bubbles are frequently inserted. When relatively large bubbles are locally present in the adhesive layer of the bonded optical disk 7, not only the adhesive strength in that region is significantly reduced compared to other regions, but also the density difference of the optical disk 7 caused by the bubbles. ,
At the time of high-speed rotation of recording / reproducing, a problem such as an increase in surface deflection of the optical disk 7 occurs. Therefore, it is preferable to apply the cationically polymerizable UV-curable resin 3 so as to form an application thickness distribution as shown in FIG.

FIG. 2 shows that the ultraviolet curable resin 3 is lightly coated 31 on the entire surface of the optical disk substrate, and the black circles 32 in the figure which are present at regular intervals are thickly coated.

In this case, the interval between the thickly painted black circles 32 is 0.
1-5 mm, and the adjacent lightly-coated portion 31 and thickly-coated portion 32
Is preferably 20% or more of the average coating thickness.

When the two optical disc substrates having such a coating thickness distribution are temporarily bonded to each other, no large air bubbles exist in the adhesive layer of the bonded optical disk 7, and the fine air bubbles are substantially uniform. Will be distributed. Although the adhesive strength is slightly inferior to the case where no air bubbles are present in the adhesive layer, a uniform adhesive strength can be obtained over the entire surface of the optical disc 7. Further, since the density distribution of the optical disk 7 becomes uniform, it is possible to suppress the surface runout during high-speed rotation.

In order to form the coating thickness distribution shown in FIG. 2, fine irregularities may be regularly provided on the surface of the coating roll 4 in a mesh form. The optimum shape, depth, and spacing of the irregularities are greatly affected by the viscosity of the ultraviolet curable resin 3 to be applied, but when the viscosity is about 10,000 centipoise,
It is desirable to provide irregularities with a depth of about 70 μm on the roll surface at intervals of up to 260 μm.

In the step (E), if the cationically polymerizable UV-curable resin 3 is applied to the entire surface of the optical disk substrates 1 and 2, when the temporary bonded disk is pressed by the press platen 6, the UV-curable resin 3 adheres. It protrudes to the outer periphery of the combined optical disk 7. If the amount of the UV curable resin 3 protruding is large, not only the appearance of the optical disk 7 is impaired, but also trouble may occur during the transportation of the production line. Requires a post-processing step.

Therefore, as shown in FIG. 3, it is preferable to apply the ultraviolet curable resin 3 in a donut shape having an inner diameter larger than the inner diameter 14 and an outer diameter smaller than the outer diameter 15 of the optical disk substrate 1. Furthermore, it is desirable that the donut-shaped application region be such that the inner and outer diameters of the adhesive layer coincide with the inner and outer diameters of the optical disk 7 when the pressing is completed. As a result, the UV curable resin 3 can be prevented from protruding.

In order to obtain the coating area shown in FIG. 3, as shown in FIG. 4, the ultraviolet curable resin 3 is adhered only to the donut-shaped area 42 on the surface of the coating roll 4 which is the same as the coating pattern. The application may be performed while the speed and the relative speed of the rotating shaft 41 to the substrate application surface are equal and synchronized.

When the two optical disc substrates 1 and 2 are bonded to each other after the step (C), if at least one of the substrates 1 and 2 is coated with the cationically polymerizable ultraviolet curable resin 3 as an adhesive, It is possible to bond two substrates. However, ultraviolet rays are applied after the boundary surface between the substrates 1 and 2 and the ultraviolet-curable resin 3 are formed to perform temporary bonding, and ultraviolet rays are applied to the ultraviolet-curable resin 3 applied to one of the substrates 1, In the case where the boundary surface between the other substrate 2 and the ultraviolet curable resin 3 is formed at the time of the temporary bonding, there is a difference in the formation state of the interface. Therefore, to stabilize the quality of the bonded optical disk 7,
It is preferable to apply the ultraviolet curing resin 3 to both substrates 1 and 2. In this case, productivity can be improved by using one roll as shown in FIG. 4 and simultaneously applying the ultraviolet curing resin 3 to both substrates 1 and 2 to be bonded.

As the cationically polymerizable ultraviolet-curable resin 3 used in the present invention, an aromatic diazonium salt, an aromatic halonium salt, an aromatic sulfonium salt, which contains an epoxy resin and an epoxy diluent as main components and generates a Lewis acid by light, etc. There is an epoxy ring-opening polymerization type resin which uses as a photopolymerization initiator. However, since it is applied by a roll, the ultraviolet curable resin 3
Recommends a viscosity of 1000 to 20,000 centipoise, preferably 3000 to 15,000 centipoise.

Next, the configuration of an optical disk formed by the bonding method of the present invention will be described with reference to FIG.

The structure of the optical disk substrate 1 or 2 to be bonded is not particularly limited. For example, information recording is performed by providing a dielectric layer, a recording layer, a dielectric layer, and a reflective cooling layer on the transparent substrates 11 and 21. It is possible to adopt a configuration in which the portions 12 and 22 are formed, and the organic resin protective layers 13 and 23 are further laminated thereon. Note that at least one of the two substrates to be bonded is a substrate having an information recording unit.

As the transparent substrates 11 and 21, it is preferable to use a material through which laser light for recording and reproducing is transmitted from the substrate side.
Organic polymer resins such as C) and polymethyl methacrylate (PMMA) and glass can be used.

The dielectric layer serves to prevent the transparent substrate and the recording layer from being deformed by the heat generated by recording and to prevent the recording / erasing / reproducing characteristics from deteriorating, and to provide the recording layer with wet heat resistance and oxidation resistance. . As such a dielectric layer, Zn
S, SiO ₂ , Ta ₂ O ₅ , ITO, ZrC, TiC, M
An inorganic film such as gF ₂ or a mixed film thereof can be used. In particular, a mixed film of ZnS and SiO ₂ and a mixed film of ZnS and MgF ₂ are excellent in moist heat resistance, and furthermore, are preferable because deterioration of the recording layer at the time of recording / erasing / reproduction is suppressed.

As a recording layer, a Ge—Sb—Te thin film, an M—Ge—Sb—Te thin film, and M is Pd, Cu, A
metal elements such as g, Tl, and Co; and In-Sb-Te-based thin films. In particular, Ge-Sb-Te thin film, Pd
-Ge-Sb-Te thin film, Pd-Ge-Sb-Te-
The Nb-based thin film is preferable because it hardly deteriorates even when recording / erasing / reproducing is repeated and has excellent thermal stability.

As the reflective cooling layer, a mixture of a metal or a metal oxide, a metal nitride, a metal carbide and the like, for example, a metal such as Zr, Cr, Ta, Mo, Si, Al, Au or an alloy thereof, or a mixture thereof. Zr oxide, Si oxide,
What mixed Si nitride, Al oxide, etc. can be used. In particular, Al, Au, Ta and alloys thereof are preferable because the film can be easily formed.

As a method for forming the dielectric layer, the recording layer, and the reflection cooling layer on the substrate, a method for forming a thin film in a vacuum, for example, a vacuum deposition method, an ion plating method, a sputtering method, or the like can be used. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled.

As the organic resin protective layers 13 and 23, an actinic curable resin composition containing a polymerizable monomer or oligomer as a main component, a thermosetting resin composition, or the like can be used. The curing of the organic resin protective layer composition is performed by applying the composition onto a recording layer formed on a substrate, and then irradiating an actinic ray, that is, an ultraviolet ray, an electron beam, or an active energy ray such as a gamma ray, or heating. Do it.

Various methods such as a spin coating method, a roll coating method, and a spray coating method can be used for applying the protective layers 13 and 23. The thickness of the organic resin protective layer is not particularly limited, but is preferably 0.5 to 30 μm.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for producing a disk-shaped recording medium according to the present invention will be described below in detail. However, the present invention is not limited to the following examples.

On a polycarbonate substrate having an outer diameter of 120 mm, an inner diameter of 15 mm, and a thickness of 0.6 mm on which a guide groove is formed by injection compression molding, a recording layer and other information recording portions are entirely formed except for an inner peripheral portion and an outer peripheral portion by a sputtering method. Was formed, and two optical disk substrates each having an organic protective film formed on an information recording portion by a spin coating method were used for bonding.

As a cationically polymerizable UV-curable resin, Sony Chemical Corporation UV-curable adhesive “SK-700” is used.
0 "(viscosity of about 12,000 centipoise), and a two-roll type flexographic printing machine was used for coating.

As the printing plate, "AFP, K-11" manufactured by Asahi Kasei Kogyo Co., Ltd., whose material is butadiene rubber, was used. The plate shape is 200 mesh (127 μm intervals), halftone dot density 20%, halftone dot depth 70 μm, and triangular groove.

First, an adhesive was applied to a donut-shaped region having an inner diameter of 17 mm and an outer diameter of 118 mm for each of the optical disk substrates to be bonded. Average coating thickness is 20μm
It was adjusted to be.

Next, two optical disk substrates to which the adhesive was applied were temporarily bonded in the air, pressed for 10 seconds, and left until the adhesive was cured.

The laminated optical disk manufactured as described above was subjected to 85 ° C., 90% R.D. H. When a durability test was performed in an environment, mechanical characteristic values such as a warp angle and a plane runout acceleration, which are regarded as important in the bonded optical disk, were set to target values (warp angle: 6 mrad, axial acceleration: 8 m / s ² ) was cleared. In the measurement, an optical disk was rotated at 3000 rpm, and a measuring device capable of obtaining various mechanical characteristic values by data processing from a displacement amount of an optical pickup equipped with a capacitance type displacement sensor in a focusing and tracking state was used. .

[0052]

According to the method for manufacturing a disk-shaped recording medium of the present invention, not only can the problem of breakage of the gauze occurring when the ultraviolet curable resin is applied by the screen printing method be avoided, but also a high-quality recording medium can be manufactured at low cost. Therefore, it can be manufactured stably.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a method of bonding optical disks.

FIG. 2 is an application pattern diagram of a cationically polymerizable ultraviolet curable resin.

FIG. 3 is an application pattern diagram of a cationically polymerizable ultraviolet curable resin.

FIG. 4 is a schematic view of a coating roll.

5 is a schematic cross-sectional view of the coating roll of FIG.

FIG. 6 is a sectional view of an optical disk having a laminated structure.

[Explanation of symbols]

 1, 2 ... optical disk substrate 11, 21 ... transparent substrate 12, 22 ... information recording layer 13, 23 ... organic resin protective layer 14 ... transparent substrate inner diameter 15 ... transparent substrate outer diameter 3 ... cationically polymerizable ultraviolet curable resin 3 4 ... coating Roll 41: Coating roll rotation axis 42: Coating roll surface resin adhesion area 5: UV irradiation device 6: Press plate 7: Laminated optical disk

Claims (9)

[Claims] In a method of manufacturing a disc-shaped recording medium in which two substrates each having an information recording portion on at least one side are bonded, an ultraviolet curable resin is applied to both or one of the substrates by a roll, and the resin is applied to the resin. A method for manufacturing a disc-shaped recording medium, comprising: irradiating an ultraviolet ray and bonding the two substrates together. 2. The method for manufacturing a disk-shaped recording medium according to claim 1, wherein said resin is applied so that said ultraviolet-curable resin has an applied thickness distribution. 3. The production of a disc-shaped recording medium according to claim 1, wherein the interval of the ultraviolet curable resin coating thickness distribution is 0.1 to 5 mm, and the thickness change is 20% or more of the average coating thickness. Method. 4. The disk-shaped recording medium according to claim 1, wherein the ultraviolet curable resin is applied in a donut shape having an inner diameter larger than the inner diameter of the substrate and an outer diameter smaller than the outer diameter. Production method. 5. The method for manufacturing a disc-shaped recording medium according to claim 1, wherein the ultraviolet curable resin is simultaneously applied to both of the two substrates to be bonded with one roll. 6. The ultraviolet curable resin has a viscosity of 1,000 to 1,000.
6. The method according to claim 1, wherein the weight is 20,000 centipoise.
The method for producing a disk-shaped recording medium according to any one of the above. 7. An ultraviolet-curable resin having an average coating thickness of 10
The method for producing a disc-shaped recording medium according to any one of claims 1 to 6, wherein the resin is applied so as to have a thickness of up to 60 m. 8. The method for manufacturing a disk-shaped recording medium according to claim 1, wherein said disk-shaped recording medium is an optical disk. 9. The method for producing a disk-shaped recording medium according to claim 1, wherein said ultraviolet-curable resin is a cationically polymerizable ultraviolet-curable resin.