JPH0991773A - Production of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing an optical recording medium which has excellent mechanical characteristics and is not deteriorated in the characteristics in spite of resting in a high-temp. atmosphere by specifying the range of the modulus of elasticity in compression of elastic sheets to be disposed between a pressing plate and a pair of substrates. SOLUTION: An adhesive layer 5 is disposed between a pair of the substrates 3 and 3 and the substrates are pressed by a flat plate press 7 via the elastic sheets 6, 6 having the modulus of elasticity in compression of 0.5 to 40kgf/cm<2> from both sides. The substrates are pressed via the elastic sheets 6 by specifying the range of the modulus of elasticity in compression, by which the nonuniform generation of the relieving of the internal stresses of the adhesive layer 5 is prevented. The optical recording medium which is not deteriorated in the mechanical characteristics in spite of resting in the high-temp. atmosphere is produced. Moldings or foamed sheets of foamed materials having closed cells, for example, butyl rubber, isoprene rubber, chloroprene rubber, silicone rubber and ethylene propylene rubber and foamed sheets of polyethylene and polypropylene are usable as the elastic sheets 6.

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 optical recording medium, and more particularly to a method for manufacturing an optical recording medium in which a pair of substrates are bonded together using a hot melt adhesive.

[0002]

2. Description of the Related Art An optical recording medium is provided with an information recording section capable of optically recording and reproducing information on a substrate, and is used as a disk for files of documents and data. These irradiate a laser beam narrowed down to about 1 μm while rotating the disk at a high speed, and read or record a recording pit of about 1 μm while performing focus adjustment and position detection. For this reason, in the optical recording medium, slight warpage or deformation of the substrate, flaws, adhesion of foreign matter, and the like lead to a signal error. For this reason, in an optical recording medium, an information recording unit is provided on a substrate with as little thickness unevenness and deformation as possible. Further, in order to prevent the information recording section from being scratched or foreign matter from adhering, a protective layer is provided on the information recording section, and the information recording sections of a pair of substrates are attached inside.

By the way, in the above-mentioned manufacturing process, a hot-melt adhesive is applied to the protective layer side of the substrate with a roll coater, and these adhesive layers are made to face each other and are inserted between two flat plate presses to press them. It is usual to bond a pair of substrates to obtain an optical recording medium.

In this application step, the adhesive is applied in a streak-like shape and an uneven shape according to the shape of the recording surface of the substrate, and its application thickness is not uniform. In addition, the thickness of the substrate formed by injection molding is not always constant, and there is unevenness depending on the location. When such substrates with uneven thickness are stuck together, unevenness in the deformation and flow of the adhesive occurs corresponding to the uneven thickness, causing internal stress. This internal stress is generated in response to the deformation and uneven flow of the adhesive, and is distributed in the surface of the adhesive layer. Then, there is a possibility that the adhesive force may be reduced at the place where the internal stress occurs.

It is considered that the in-plane unevenness of the adhesive force does not significantly deform the optical recording medium while it is left at room temperature. However, at high temperatures, the relaxation of internal stress occurs nonuniformly, causing warping or deformation of the optical recording medium. Such an optical recording medium has problems that the surface wobbling and the surface wobbling acceleration become large, a signal error occurs when the tracking response range of the optical pickup is exceeded, and recording / reproducing becomes impossible. As a means for improving such a problem, as disclosed in JP-B-1-133238, it has been proposed to press a pair of substrates via various elastic sheets when they are bonded together.

However, the above method is still inadequate, uneven relaxation of the above-mentioned internal stress of the adhesive layer occurs, and especially when left in a high temperature atmosphere, surface runout and surface runout acceleration increase, There is a problem that the bit error rate increases. Furthermore, JP-A 1-24
As disclosed in Japanese Patent No. 1046, a method of pressure-bonding under reduced pressure has been proposed, but it is not practical because the device becomes complicated.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to make a pair of substrates uniform so as not to increase the surface wobbling or the surface wobbling acceleration and to increase the bit error rate not only at room temperature but also in a high temperature atmosphere. An object of the present invention is to provide a method for manufacturing an optical recording medium that can be attached.

[0008]

In order to solve the above-mentioned problems, a method of manufacturing an optical recording medium according to the present invention is an optical system in which a pair of substrates are bonded to each other, and an information recording portion is provided on at least one of both substrates. In manufacturing a recording medium, an adhesive layer is provided between a pair of substrates, and a pair of substrates are attached while being pressed from both sides of the pair of substrates via elastic sheets. The compression elastic modulus of the sheet is not less than 0.5 kgf / cm ^{2 and} less than 40 kgf / cm ² .

[0009]

In the process of the invention DETAILED DESCRIPTION OF THE INVENTION, the compression modulus bonding the pair of substrates is 0.5 kgf / cm ² or more 40 kgf / cm ² less than the elastic sheet.
Furthermore, 1.0 kgf / cm ² or more and 20 kgf / cm ²
Less than is preferred. As the elastic sheet, a molded sheet having a compression elastic modulus in the specific range or a foam material having closed cells can be used. For example, molded sheets of butyl rubber, isoprene rubber, chloroprene rubber, silicone rubber, ethylene propylene rubber or foamed sheets thereof, foamed sheets of polyethylene, polypropylene, etc., and nylon fibers, polyester fibers, fluorine fibers (polytetrafluoroethylene, etc.) Nonwoven fabrics and the like can be used. However, it is not limited to these as long as the compression elastic modulus is in the above range.

When the compressive elastic modulus is 40 kgf / cm ² or more, it is not possible to absorb the unevenness of the thickness of the substrate and the unevenness of the application of the adhesive at the time of pressing, and a pressure distribution is generated on the substrate. Due to such pressure distribution, the adhesive causes non-uniform flow and partially causes internal stress. When the optical recording medium is left in a high temperature atmosphere, this internal stress suddenly causes a relaxation phenomenon and causes deformation of the optical recording medium. On the other hand, if the compressive elastic modulus is less than 0.5 kgf / cm ² , when a predetermined pressing pressure is applied at the time of pressing, the sheet will be deformed beyond the elastic limit, resulting in loss of elasticity and thickness of the substrate. Unevenness and uneven coating of the adhesive layer cannot be absorbed, pressure distribution is generated on the substrate, and the compression elastic modulus is 40 kgf / cm ^2.
The result is similar to the above case.

The thickness of the elastic sheet is preferably 0.5 mm or more. When it is less than 0.5 mm, when the compression elastic modulus of the sheet is small and the pressing pressure is high, the deformation of the sheet exceeds the elastic limit range, and the uneven thickness of the substrate and the uneven application of the adhesive layer are absorbed. I can't. The upper limit of the sheet thickness is not particularly limited, but if the configuration of the device is taken into consideration, it is 100 mm or less, especially 10 mm.
The following is preferred.

With respect to the tolerance of the thickness of the sheet, the sheet having the compression elastic modulus of the present invention does not require strictness because the sheet itself absorbs the uneven thickness, but the thickness tolerance of the sheet is required to prevent uneven pressure. Is preferably within ± 5%.

Although the structure of the optical recording medium of the present invention is not particularly limited, for example, as shown in FIG. 5, a dielectric layer 12a, a recording layer 13, a dielectric layer 12b, and a reflection cooling layer 14 are formed on a substrate 11. It is possible to show a configuration in which the organic resin protective layer 15 and the adhesive layer 16 are laminated on the above. The structure will be described with reference to an example of a record-erasable phase-change optical recording medium in which a pair of the thus-configured ones are prepared and the adhesive layers 16 are faced to each other and bonded to each other.

As the substrate used in the present invention, it is preferable to use a material through which laser light can be transmitted in order to record / reproduce from the substrate side. For example, polymethylmethacrylate resin, polycarbonate resin, polyolefin resin, epoxy resin. An organic polymer resin such as or glass can be used.

The dielectric layer plays a role of preventing the substrate and the recording layer from being deformed by heat due to recording and from deteriorating the recording / erasing / reproducing characteristics, and also having a resistance to moist heat and an oxidation resistance of the recording layer. As such a dielectric layer, ZnS,
SiO ₂ , Ta ₂ O ₅ , ITO, ZrC, TiC, Mg
An inorganic film such as F 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.

The recording layer is a Ge-Sb-Te-based thin film, an M-Ge-Sb-Te-based thin film, and M is Pd, Cu, A.
Examples thereof include metal elements such as g, Tl, and Co, In—Sb—Te-based thin films, and the like. Especially Ge-Sb-Te based thin film, Pd
-Ge-Sb-Te thin film, Pd-Ge-Sb-Te-
The Nb-based thin film is preferable because it is less likely to deteriorate even after repeated recording / erasing and is excellent in thermal stability.

Further, these compositions are preferably in the range represented by the following formula from the viewpoint of excellent thermal stability and repeated stability. M _z (Sb _x Te _(1-x) ) _1-yz (Ge _0.5 Te _0.5 ) _y 0.35 ≦ x ≦ 0.5 0.20 ≦ y ≦ 0.5 0 ≦ z ≦ 0.05 where M Represents at least one metal selected from palladium, niobium, platinum, silver, gold and cobalt. Also,
x, y, z and numerals represent the number of atoms of each element (the number of moles of each element). In particular, palladium and niobium preferably contain at least one kind. In this case, z is 0.
0005 or more.

For the reflective cooling layer, a mixture of a metal or a metal oxide, a metal nitride, a metal carbide and the like and a metal, for example, a metal such as Zr, Cr, Ta, Mo, Si, Al, Au or an alloy thereof, or these. Zr oxide, Si oxide,
A mixture of Si nitride and Al oxide can be used. In particular, Al, Au, Ta, alloys thereof, etc. are preferable because the film formation is easy.

The thickness of the dielectric layer, the recording layer and the reflection cooling layer is 50 to 300 nm for the dielectric layer 12a and 1 for the dielectric layer 12b.
It is preferable that the recording layer has a thickness of 0 to 300 nm, the recording layer has a thickness of 10 to 100 nm, and the reflective cooling layer has a thickness of 20 to 150 nm from the viewpoint of recording / erasing / reproducing characteristics.

As a method for forming the dielectric layer, the recording layer, and the reflection cooling layer on the substrate, a thin film forming method in vacuum, such as a vacuum vapor deposition method, an ion plating method and a sputtering method, 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 layer, an actinic radiation curable resin composition containing a polymerizable monomer and an oligomer as a main component or a thermosetting resin composition can be used.

The polymerizable monomer used in the present invention is, for example, a compound having an acryloyloxy group or a methacryloyloxy group (hereinafter, both groups are collectively referred to as a (meth) acryloyloxy group). It is preferably used, and specific examples thereof include (meth) acrylic acid esters shown below.
Methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-
Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylate of tetrahydrofurfuryl derivative, 1H · 1
Examples include, but are not limited to, H.5H-octafluoropentyl (meth) acrylate, 1.6 hexanediol (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

Further, for the purpose of improving the curability of the organic resin protective layer and adjusting the elastic modulus, other monomers copolymerizable with the above-mentioned monomers can be mixed and used. For example, a diisocyanate compound and a compound having two or more alcoholic hydroxyl groups are preliminarily reacted with a terminal isocyanate group-containing compound to react with a (meth) acrylate containing an alcoholic hydroxyl group. The above urethane (meth) acrylates having a (meth) acryloyloxy group, (meth) acrylic acid diesters of alkylene glycols having 2 to 12 carbon atoms, (meth) acrylic acid cyesters of polyoxyalkylene glycols, polyhydric alcohols (Meth) acrylic acid polyesters having two or more (meth) acryloyloxy groups, ethylene oxide and bispropylene A hydride ethylene oxide and propylene oxide adducts (meth) acrylic acid diesters, 2
Epoxy (meth) acrylates having two or more (meth) acryloyloxy groups in the molecule obtained by reacting acrylic acid or methacrylic acid with a compound having two or more epoxy groups, but are not limited thereto. Not to be.

Further, one or more photopolymerization initiators can be added to the organic resin protective layer composition. As the photopolymerization initiator, various types can be used, for example, benzoin-based compounds such as acetophenone and benzophenone, sulfide-based compounds such as tetramethylmonosulfide, thioxane-based compounds such as thioxane, and benzoin peroxide di-t.
And oxides such as -butyl oxide. The addition amount of the photopolymerization initiator is appropriately 0.01 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.

The organic resin protective layer composition is cured by coating the composition on a recording layer formed on a substrate and then irradiating it with actinic rays, that is, active energy rays such as ultraviolet rays, electron rays or gamma rays. , By heating.

As the coating method, various methods such as a spin coating method, a roll coating method and a spray coating method can be used. The thickness of the organic resin protective layer is 0.5 to 30 μm.
The range of m is preferred.

In the present invention, as the hot-melt adhesive used for laminating a pair of substrates, one having a base polymer, a softening agent and a tackifier as main components can be used. Examples of the base polymer include a block-like thermoplastic elastomer represented by the following formula. ABBABAB (where A represents a polystyrene block having a molecular weight of 2,000 to 25,000, and B represents a polybutadiene block, a polyisoprene block, or an ethylene-butylene copolymer block having a molecular weight of 1,000 to 25,000. .)

You may use these 1 type or in mixture of 2 or more types. Further, a synthetic rubber such as polyisoprene, styrene rubber, butadiene rubber and butyl rubber, or a polyolefin-based copolymer such as polyolefin and ethylene-vinyl acetate copolymer may be appropriately mixed and used.

As the softening agent, polysess oil, paraffin oil, polybutene, polyisobutylene, etc. can be used.

Further, as a tackifier, a rosin resin,
A hydrogenated petroleum resin, a hydrogenated terpene resin, a phenol resin, a cumarone resin, or the like can be used. The hydrogenated tackifier has good compatibility with the above-mentioned block-like thermoplastic elastomer, good thermal stability and low water absorption, so that it shows good corrosion resistance.

As a method of applying the hot melt adhesive,
A roll coater 1 can be used as shown in FIG. A substrate 3 provided with a recording layer as described above between the pair of rolls 2a and 2b (hereinafter, referred to as a substrate including the recording layer, the dielectric layer, the reflection cooling layer, etc.) is sent, and hot melt is applied to the recording surface. Apply the adhesive 4. Application temperature is usually 12
It is performed between 0 ° C and 160 ° C. In this case, the viscosity of the hot-melt adhesive becomes about 1000 cp to 200,000 cp, and the surface shape of the coating film becomes streaky.

Then, as shown in FIG. 2, a pair of substrates 3 provided with a layer 5 of an adhesive 4 are attached so that the adhesive layers 5 face each other, and both sides have the above-mentioned specific compression elastic modulus. The elastic sheets 6 and 6 are provided and pressed from both sides.

As a bonding method, a flat plate press 7 as shown in FIG. 3 or a roll press can be used. At this time, the elastic sheet 6 can be attached to the pressing plate or the pressing roll. Further, as shown in the figure, a pair of substrates 3 sandwiched by the elastic sheets 6 can be flat-pressed or roll-pressed. The laminating pressure is 0.05 kg / cm ^{2 as the} disc surface pressure.
To 5 kg / cm ² can be performed. From the viewpoint of the flatness of the laminated recording medium and the mechanical characteristics of the recording medium when left in a high temperature state, more preferably 0.2 kg / cm.
^{It is} advisable to carry out in the range of ² to 2 kg / cm ² .

By the above-mentioned bonding, an optical recording medium 8 for double-sided recording in which a pair of substrates 3 and 3 are bonded as shown in FIG. 4 is obtained.

[Measurement Method] (1) Compressive Elastic Modulus It was determined as the compressive elastic modulus at the initial stage of compression measured by the method according to JIS7220.

(2) Surface runout acceleration Using an optical pickup equipped with a capacitance type displacement sensor, the recording medium was rotated at 1800 rpm to measure the displacement of the optical pickup in the focusing and tracking states, and the displacement was obtained by data processing.

(3) Bit error rate In the 2-7 modulation recording system, a single signal of 1.5T (3.7 MHz) is repeatedly overwritten, and then a 2-7 random pattern is overwritten once, and the bit error rate is overwritten. I asked.

(4) Acceleration test The optical recording medium bonded in an atmosphere of 80 ° C. and 80% RH was left for 1500 hours, and the surface runout acceleration and the bit error rate before and after the standing were compared.

[0039]

【Example】

Example 1 A spirally grooved polycarbonate substrate having a thickness of 1.2 mm, a diameter of 130 mm and a pitch of 1.6 μm was prepared.
The following recording layers were formed and laminated by a sputtering method in an atmosphere with an argon pressure of 0.5 Pa while rotating at 30 rpm. 200 nm thick ZnS / Si on the substrate
A dielectric layer of O ₂ (molar ratio 80:20) is formed, then a recording layer of Te, Ge, Sb, and Pd with a thickness of 20 nm is formed, and a dielectric layer of ZnS.SiO _{2 with} a thickness of 20 nm is formed. A body layer was formed, and an Al alloy layer having a thickness of 100 nm was formed thereon as a reflection cooling layer. Next, an organic resin coating liquid was applied by a spin coating method and irradiated with ultraviolet rays to form an organic resin protective layer having a thickness of 10 μm. Further, a hot-melt adhesive was applied by a roll coating method to an average thickness of 30 μm. Two such discs were prepared and the adhesive layer surfaces were opposed to each other, and the compression elastic modulus was 6.8 kg / cm ² , and the thickness was 3 m.
The chloroprene foam sheet of m was inserted into between the pressing plates, pressed with a pressure of 0.5 kg / cm ² for 30 seconds and then taken out to obtain a bonded optical recording medium.

Example 2 A sheet attached to a pressing plate was compressed to a modulus of elasticity of 2.5 kg / c.
A bonded optical recording medium of Example 2 was obtained in the same manner as in Example 1 except that the polyethylene-propylene foam sheet having m ² and a thickness of 3 mm was used.

Comparative Example 1 A sheet attached to a pressing plate was compressed to a modulus of elasticity of 42.0 kg /
A bonded optical recording medium of Comparative Example 1 was obtained in the same manner as in Example 1 except that the silicon rubber sheet having a cm ² and a thickness of 3 mm was used.

Comparative Example 2 A sheet attached to a pressing plate has a compression elastic modulus of 68.0 kg /
A bonded optical recording medium of Comparative Example 2 was obtained in the same manner as in Example 1 except that a nitrile rubber sheet having a cm ² and a thickness of 3 mm was used.

Table 1 shows the results of an acceleration test conducted on the bonded optical recording media obtained in each of the examples and comparative examples.

[0044]

[Table 1]

[0045]

According to the method of manufacturing an optical recording medium of the present invention, as described above, the compression elastic modulus between the pressing plate and the pair of substrates to be bonded is 0.5 kgf / cm ² or more and 40 kg or more.
By providing an elastic sheet of less than f / cm ² ,
It is possible to obtain a bonded optical recording medium having excellent mechanical properties and having high reliability that does not deteriorate even when left in a high temperature atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing how a hot melt adhesive is applied by a roll coater.

FIG. 2 is a schematic perspective view in which elastic sheets are provided on both sides of a pair of substrates at the time of bonding.

FIG. 3 is a schematic configuration diagram showing a state of pressing and bonding by a flat plate press.

FIG. 4 is a perspective view of an optical recording medium that has been bonded.

FIG. 5 is a schematic cross-sectional view showing a configuration example of layers formed on a substrate.

[Explanation of symbols]

 1 Roll Coater 2a, 2b Roll 3 Substrate 4 Hot Melt Adhesive 5 Adhesive Layer 6 Elastic Sheet 7 Flat Plate Press 8 Laminated Optical Recording Medium 11 Substrate 12a, 12b Dielectric Layer 13 Recording Layer 14 Reflective Cooling Layer 15 Organic Resin Protective Layer 16 Adhesive layer

Claims (5)

[Claims] 1. An adhesive layer is provided between a pair of substrates when manufacturing an optical recording medium in which a pair of substrates are bonded together and an information recording portion is provided on at least one of the two substrates. In a method for manufacturing an optical recording medium, in which a pair of substrates are bonded together while being pressed from both sides of the elastic sheet through the elastic sheet, the elastic modulus of the elastic sheet is 0.5 kgf / cm.
² or more and less than 40 kgf / cm ^{2. A} method for producing an optical recording medium, which is characterized in that: 2. The method of manufacturing an optical recording medium according to claim 1, wherein the elastic sheet is a foamed sheet having closed cells. 3. The elastic sheet according to claim 1, wherein the elastic sheet is selected from butyl rubber, isoprene rubber, chloroprene rubber, silicone rubber, ethylene propylene rubber molded body or foamed sheet, and polyethylene, polypropylene foamed sheet. Optical recording medium manufacturing method. 4. The method for manufacturing an optical recording medium according to claim 1, wherein the elastic sheet has a thickness of 0.5 mm or more. 5. The pressing pressure at the time of bonding is 0.05 to 5
The method for producing an optical recording medium according to claim 1, which is in the range of kg / cm ² .