JP3140150B2 - Coating forming method and optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a method for forming a coating such as a hard coat layer provided on the surface of an optical disk or the like to prevent scratches, and an optical disk using the same.

[0002]

2. Description of the Related Art Optical discs have attracted attention as large-capacity information carrying media. Optical disks are generally broadly classified into optical recording disks and read-only optical disks. The optical recording disk includes an erasable type such as a magneto-optical recording disk and a write-once type such as a pit-formed optical recording disk, and the read-only optical disk includes a laser disk and a compact disk.

[0003] These optical discs have a structure in which a recording layer or an information carrying layer is provided on a substrate. As a substrate material, molding is easy, light weight, hard to break, easy to handle, and low cost. For this reason, various resins having transparency are used. However, the resin substrate is easily damaged due to low hardness. Generally, an optical disk irradiates recording light or reproduction light through a substrate, so that if the substrate is damaged, it may be difficult to record or reproduce information.

For this reason, a hard coat layer for preventing damage is formed on at least the light incident side surface of the substrate. As the hard coat layer provided on the light incident surface side of the substrate, for example, there is an ultraviolet cured film of an oligoester acrylate-containing composition disclosed in Japanese Patent Application No. 62-72888.

Incidentally, Japanese Patent Application Laid-Open Nos. 60-168708, 61-120816, and 61-1
No. 15912, Japanese Patent Application Laid-Open No. 61-115916,
Japanese Patent Application No. 61-95905, Japanese Patent Application No. 61-9090
No. 6, JP-A-61-271308, JP-A-61-271308
Japanese Patent Application Laid-Open No. 1-272216 discloses that an amorphous polyolefin obtained by blending two or more copolymers of a cyclic olefin and ethylene is used as a substrate material of an optical disk. This is a material that has been widely used as a substrate material for optical discs,
Compared with polymethyl methacrylate, it shows remarkably excellent optical characteristics, has extremely low water absorption, and is extremely advantageous as a substrate material for optical disks.

[0006] However, it has been found that the adhesiveness and adhesion to various transparent resin coatings such as an ultraviolet-curable hard coat layer are extremely low.

[0007] To cope with this, a method of treating the surface of the substrate with various coupling agents or a method of applying a primer when forming the coating, and a method of treating the surface of the substrate with chromic acid, flame, or corona discharge And so on.

However, among these, the coupling treatment is generally performed when an inorganic substance and an organic substance are combined, and has little effect.

In addition, the effect of the primer treatment can only be obtained with a combination of a specific primer and a resin, but the effect cannot always be obtained uniformly by applying the primer treatment. Furthermore, other methods cannot provide a sufficient effect.

[0010]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a method for forming a transparent resin coating on a polymer of a cyclic olefin, in which the adhesion is significantly improved, and a method for forming the coating using the coating method. To provide an optical disk having a hard coat layer.

[0011]

This and other objects are attained by the present invention which is defined below as (1) to (18). (1) An ethylene-
A method for forming a coating, comprising: forming an undercoat layer using at least one thermoplastic resin of a vinyl acetate copolymer and a low-density polyethylene; and forming a coating of a transparent resin on the surface of the undercoat layer. (2) The coating forming method according to the above (1), wherein a component that can be a coating component of the transparent resin is further used in addition to the thermoplastic resin. (3) The coating forming method according to (1) or (2), wherein the coating solvent used for forming the undercoat layer contains at least one of an aromatic hydrocarbon solvent and an alicyclic hydrocarbon solvent. . (4) The method for forming a coating according to (3), wherein the aromatic hydrocarbon solvent is toluene. (5) The thickness of the undercoat layer is 0.1 to 1 as a dry film thickness.
The coating forming method according to any one of the above (1) to (4), wherein the coating thickness is 00 μm. (6) The method according to any one of the above (1) to (5), wherein the polymer is a transparent molded article. (7) The coating forming method according to any one of the above (1) to (6), wherein the polymer of the cyclic olefin has a repeating structural unit represented by the following chemical formula 3.

[0012]

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(8) The cyclic olefin polymer is
The method for forming a coating according to any one of the above (1) to (7), which is a copolymer of a cyclic olefin of the following formula 4 and ethylene.

[0014]

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(9) The coating forming method according to any one of the above (1) to (8), wherein the coating of the transparent resin is obtained by radiation-curing a coating film of a radiation-curable compound. (10) The coating forming method according to (9), wherein the radiation-curable compound has an acrylic group. (11) having a substrate of the cyclic olefin polymer,
At least one surface of the substrate has a transparent resin coating formed by the coating forming method according to any one of the above (1) to (10), and a recording layer or an information carrying layer is carried on the other surface. Optical disk. (12) The optical disk according to (11), wherein the substrate is obtained by injection-molding a polymer of a cyclic olefin. (13) The surface softening point of the substrate is 140 ° C.
The optical disc according to the above (12), having the following skin layer. (14) The optical disc according to the above (12) or (13), wherein the substrate carries a recording layer, and the substrate has a skin layer having a thermal softening point of 140 ° C. or less on the recording layer side surface portion. (15) The substrate carries a recording layer on one surface, and after forming an undercoat layer on the surface on which the recording layer is formed,
The above (11) to (1) provided with a resin protective coat.
The optical disc according to any of 4). (16) The optical disc according to (15), wherein the undercoat layer is formed using a thermoplastic resin. (17) The optical disc according to (16), wherein the thermoplastic resin is an ethylene-based polymer. (18) The optical disc according to any one of (11) to (17), wherein the protective coat is obtained by curing a radiation-curable compound with ultraviolet light.

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

In order to achieve the above object, the applicant of the present invention is characterized in that the surface of a cyclic olefin polymer is first irradiated with ultraviolet rays, and then a transparent resin coating is formed on this surface. (Japanese Patent Application No. 3-177162). Further, the present inventors have studied a method for improving the adhesiveness with the transparent resin coating, and have accomplished the present invention.

[0034]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

In the present invention, the transparent resin coating is formed on the surface of the polymer of the cyclic olefin. As the cyclic olefin polymer to which the present invention can be applied, various known polymers may be used. Particularly, as the cyclic olefin polymer useful as an optical disk substrate, an amorphous polymer having the above-mentioned chemical formula 3 as a repeating structural unit may be used. Is preferred.

In the above formula 3, R ₁ and R ₂ are preferably a hydrocarbon residue, particularly preferably an unsubstituted alkyl group having 1 to 5 carbon atoms.
The cyclic polyolefin used is preferably a homopolymer consisting of only the same unit among the repeating units of the above formula 3, but a copolymer comprising a plurality of repeating units of the formula 3 having different R ₁ , R ₂ or q. It may be. In some cases, a copolymer containing other structural units in addition to the above may be used. And, the number average molecular weight is preferably 5,000 to 100,000, particularly preferably 10,000 to 40,000.

In the chemical formula 3, the halogen atom, ester group, nitrile group and pyridyl group may be hereinafter referred to as polar groups.

Such cyclic polyolefins include, as monomers, for example, norbornene and its alkyl and / or alkylidene-substituted products, for example, 5-methyl-2-norbornene, 5,6-dimethyl-2-norbornene, -Ethyl-2-norbornene, 5-butyl-2
-Norbornene, 5-ethylidene-2-norbornene and the like: dicyclopentadiene, 2,3-dihydrodicyclopentadiene, alkyl-substituted products such as methyl, ethyl, propyl and butyl, and polar-substituted products such as halogen: di Methanooctahydronaphthalene, its alkyl and / or alkylidene-substituted products, and polar group-substituted products such as halogens, for example, 6-methyl-1,4: 5,8
-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-
Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8
-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-
Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8, 8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:
5,8-Dimethano-1,4,4a, 5,6,7,8,8
a-octahydronaphthalene or the like; cyclopentadiene trimer or tetramer, for example, 4,9: 5,8-dimethano-3
a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9
-Trimethano-3a, 4,4a, 5,5a, 6,9,9
a, 10,10a, 11,11a-Dodecahydro-1H
A saturated polymer produced by subjecting a ring-opened polymer obtained by polymerization using cyclopentaanthracene or the like by a known ring-opening polymerization method to hydrogenation by an ordinary hydrogenation method.

Such cyclic polyolefins are described in JP-A-3-223341 and Japanese Patent Application No. 60-26.
024 and the like.

As such a cyclic polyolefin, a commercially available product may be used. For example, a product commercially available as Zeonex 280 manufactured by Zeon Corporation can be used.

The cyclic olefin polymer includes:
Preferably, a blend of a copolymer of ethylene and the cyclic olefin represented by Chemical Formula 4 described in JP-A-2-257446 is also suitable. The cyclic olefin represented by Chemical Formula 4 may be synthesized by condensing cyclopentadiene and the corresponding olefin by a Diels-Alder reaction.

Specific examples of the cyclic olefin represented by Chemical Formula ⁴ include tetracyclo [4.4.0.1 ^2,5 .
1 ^7,10 ] -3-dodecene (1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene), 2-methyl-1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-ethyl-1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-propyl-1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-hexyl-1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2,3-dimethyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8, 8a-octahydronaphthalene, 2-methyl-3-ethyl-1,4,5
8-Dimethano-1,2,3,4,4a, 5,8,8a-
Octahydronaphthalene, 2-chloro-1,4,5,8
-Dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-bromo-1,4,5,8-
Memethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-fluoro-1,4,5,8-
Dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2,3-dichloro-1,4,5
8-Dimethano-1,2,3,4,4a, 5,8,8a-
Octahydronaphthalene, 2-cyclohexyl-1,
4,5,8-Dimethano-1,2,3,4,4a, 5
8,8a-octahydronaphthalene, 2-n-butyl-
-1,4,5,8-Dimethano-1,2,3,4,4a,
5,8,8a-octahydronaphthalene, 2-isobutyl-1,4,5,8-dimethano-1,2,3,4,4
Compounds such as octahydronaphthalenes such as a, 5,8,8a-octahydronaphthalene can be mentioned.

Further, the cyclic olefin represented by the chemical formula (4)
Examples of the compound include the compounds described below.
Wear. Bicyclo [2.2.1] hept-2-ene, 6-
Methylbicyclo [2.2.1] hept-2-ene, 5,
6-dimethylbicyclo [2.2.1] hept-2-e
1-methylbicyclo [2.2.1] hept-2-e
6-ethylbicyclo [2.2.1] hept-2-e
, 6-n-butylbicyclo [2.2.1] hept-2
-Ene, 6-isobutylbicyclo [2.2.1] hept
-2-ene, 7-methylbicyclo [2.2.1] hept
Bicyclo [2.2.1] hept such as 2-ene, etc.
To-2-ene derivative; tetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 5,10-dimethylte
Toracyclo [4.4.0.1^2,5 . 1^7,10] -3-Dode
Sen, 2,10-dimethyltetracyclo [4.4.0.
1^2,5 . 1^7,10] -3-dodecene, 11,12-dimethyl
Letetracyclo [4.4.0.1^2,5 . 1^7,10] -3-
Dodecene, 2,7,9-trimethyltetracyclo [4.
4.0.1.^2,5 . 1^7,10] -3-dodecene, 9-ethyl
-2,7-dimethyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 9-isobutyl-2,
7-dimethyltetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-dodecene, 9,11,12-trimethylte
Toracyclo [4.4.0.1^2,5 . 1^7,10] -3-Dode
Sen, 9-ethyl-11,12-dimethyltetracyclo
[4.4.0.1^2,5 . 1^7,10] -3-dodecene, 9-
Isobutyl-11,12-dimethyltetracyclo [4.
4.0.1.^2,5 . 1^7,10] -3-dodecene, 5,8,
9,10-tetramethyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8-methyltetracycline
B [4.4.0.1^2,5 . 1^7,10] -3-dodecene, 8
-Ethyltetracyclo [4.4.0.1^2,5 . 1^7,10]
-3-dodecene, 8-propyltetracyclo [4.4.
0.1^2,5 . 1^7,10] -3-dodecene, 8-hexylte
Toracyclo [4.4.0.1^2,5 . 1^7,10] -3-Dode
Sen, 8-stearyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8,9-dimethyltet
Lacyclo [4.4.0.1^2,5 . 1^7,10] -3-Dodece
, -Methyl-9-ethyltetracyclo [4.4.0.
1^2,5 . 1^7,10] -3-dodecene, 8-chlorotetracy
Black [4.4.0.1^2,5 . 1^7,10-3-dodecene,
8-bromotetracyclo [4.4.0.1^2,5 .
1^7,10] -3-dodecene, 8-fluorotetracyclo
[4.4.0.1^2,5 . 1^7,10-3-dodecene, 8,
9-dichlorotetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-Dodecene, 8-cyclohexyltetracycline
B [4.4.0.1^2,5 . 1^7,10] -3-dodecene, 8
-Isobutyltetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-dodecene, 8-butyltetracyclo [4.
4.0.1.^2,5 . 1^7,10] -3-Dodecene, 8-ethylidene
Dentetracyclo [4.4.0.1^2,5 . 1^7,10] -3
-Dodecene, 8-ethylidene-9-methyltetracyclo
[4.4.0.1^2,5 . 1^7,10] -3-dodecene, 8-
Ethylidene-9-ethyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8-ethylidene-9-
Isopropyltetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-dodecene, 8-ethylidene-9-butylte
Toracyclo [4.4.0.1^2,5 . 1^7,10] -3-Dode
Sen, 8-n-propylidenetetracyclo [4.4.
0.1^2,5 . 1^7,10] -3-dodecene, 8-n-propyl
Lidene-9-methyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8-n-propylidene
-9-ethyltetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-dodecene, 8-n-propylidene-9-i
Sopropyltetracyclo [4.4.0.1^2,5 .
1^7,10] -3-dodecene, 8-n-propylidene-9-
Butyltetracyclo [4.4.0.1^2,5 . 1^7,10]-
3-dodecene, 8-isopropylidenetetracyclo
[4.4.0.1^2,5 . 1^7,10] -3-dodecene, 8-
Isopropylidene-9-methyltetracyclo [4.4.
0.1^2,5 . 1^7,10] -3-dodecene, 8-isopropylene
Ridene-9-ethyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8-isopropylidene
-9-isopropyltetracyclo [4.4.0.1
^2,5 . 1^7,10] -3-dodecene, 8-isopropylidene
-9-butyltetracyclo [4.4.0.1^2,5 . 1
^7,10] -3-dodecene, tetracyclo [4.4.
0.1^2,5 . 1^7,10] -3-dodecene derivative;
Black [6.6.1.1^3,6 . 1^10,13 . 0^2,7 .
0^9,14] -4-heptadecene, 12-methylhexacyclo
B [6.6.1.1^3,6 . 1^10,13 . 0^2,7 . 0^9,14]
-4-heptadecene, 12-ethylhexacyclo [6.
6.1.1^3,6 . 1^10,13 . 0^2,7 . 0^9,14] -4-F
Ptadecene, 12-isobutylhexacyclo [6.6.
1.1^3,6 . 1^10,13 . 0^2,7 . 0^{9, 14}] -4-hepta
Decene, 1,6,10-trimethyl-12-isobutyl
Hexacyclo [6.6.1.1^{3, 6} . 1^10,13 . 0
^2,7 . 0^9,14] -4-Heptadecene, etc.
B [6.6.1.1^3,6 . 1^10,13 . 0^2,7 . 0^9,14]
-4-heptadecene derivative; octacyclo [8.8.
0.1^2,9 . 1^4,7 . 1^11,18 . 1^13,16 . 0^3,8 . 0
^12,17 ] -5-Docosene, 15-methyloctacyclo
[8.8.0.1^2,9 . 1^4,7 . 1^11,18 . 1^13,16.
0^3,8 . 0^12,17 ] -5-Docosene, 15-ethyloctane
Tacyclo [8.8.0.1^2,9 . 1^4,7 . 1^11,18 . 1
^13,16. 0^3,8 . 0^12,17 -5-docosene, etc.
Kutacyclo [8.8.0.1^2,9 . 1^4,7 . 1^11,18 .
1^13,16 . 0^{3, 8} . 0^12,17 ] -5-docosene derivatives;
Pentacyclo [6.6.1.1^3,6 . 0^2,7 . 0^9,14]
-4-hexadecene, 1,3-dimethylpentacyclo
[6.6.1.1^3,6 . 0^2,7 . 0^9,14] -4-Hexa
Decene, 1,6-dimethylpentacyclo [6.6.1.
1^3,6 . 0^2,7 . 0^9,14-4-hexadecene, 15,
16-dimethylpentacyclo [6.6.1.1^3,6 . 0
^2,7 . 0^9,14] -4-hexadecene, etc.
B [6.6.1.1^3,6 . 0^2,7 . 0^9,14] -4-hex
Sadecene derivative; heptacyclo [8.7.0.1^2,9 .
1^4,7 . 1^11,17 . 0^3,8 . 0^12,16 ] -5-Ikose
Heptacyclo [8.7.0.1^2,9 . 1^4,7 . 1
^11,17 . 0^3,8 . 0^12,16 ] -5-Hen Eikosen
Any heptacyclo-5-icosene derivative or hepta
Cyclo-5-heneicosene derivative; tricyclo [4.
3.0.1.^2,5 ] -3-decene, 2-methyltricyclo
[4.3.0.1^2,5 ] -3-decene, 5-methyl-
Licyclo [4.3.0.1^2,5 -3-decene, etc.
Tricyclo [4.3.0.1^2,5 ] -3-Decene induction
Body; tricyclo [4.4.0.1^2,5 ] -3-Undesse
10-methyl-tricyclo [4.4.0.1^2,5 ]
-3-undecene, and other tricyclo [4.4.0.1
^2,5 ] -3-undecene derivative; pentacyclo [6.
5.1.1^3,6 . 0^2,7 . 0^9,13] -4-Pentadece
1,3-dimethyl-pentacyclo [6.5.1.1
^3,6 . 0^2,7 . 0^9,13-4-pentadecene, 1,6-
Dimethylpentacyclo [6.5.1.1^3,6 . 0^2,7 .
0^9,13] -4-pentadecene, 14,15-dimethylpe
Nantacyclo [6.5.1.1^3,6 . 0^2,7 . 0^9,13]-
4-pentadecene, pentacyclo [6.5.1.
1^3,6 . 0^2,7 . 0^9,13] -4-pentadecene derivatives;
Pentacyclo [6.5.1.1^3,6 . 0^2,7 . 0^9,13]
-4,10-pentadecadiene derivative; pentacyclo
[4.7.0.1^2,5 . 0^8,13. 0^9,12] -3-penta
Decene, methyl-substituted pentacyclo [4.7.0.1
^2,5 . 0^8,13. 0^9,12-3-pentadecene, etc.
Nantacyclo [4.7.0.1^2,5 . 0^8,13. 0^9,12]-
3-pentadecene derivative; heptacyclo [7.8.
1^3,6 . 0^2,7 . 1^10,17 . 0^11,16 . 1^12,15 ] -4
-Eicosene, dimethyl-substituted heptacyclo [7.8.
0.1^3,6 . 0^2,7 . 1^10,17 . 0^11,16. 1^12,15 ]
Heptacyclo [7.8.0.
1^3,6 . 0^2,7 . 1^10,17 . 0^11,16 . 1^{12 , 15} ] -4
-Eicosene derivative; nonacyclo [9.10.1.1]
^4,7 . 0^3,8 . 0^2,10. 0^12,21 . 1^13,20 . 0
^14,19 . 1^15,18 ] -5-pentacocene, trimethyl
The substituted nonacyclo [9.10.1.1]^4,7 . 0^3,8 .
0^2,10. 0^12,21. 1^13,20 . 0^14,19 . 1^15,18 ]-
Nonacyclo [9.10.1.
1^4,7 . 0^3,8 . 0^2,10. 0^12,21 . 1^{13,2 0} . 0
^14,19 . 1^15,18 ] -5-pentacocene derivative.

The polymer of the cyclic olefin represented by the chemical formula (4) contains ethylene and the cyclic olefin represented by the chemical formula (4) as essential components. In addition, if necessary, another copolymerizable unsaturated monomer may be used. A body component may be contained. For example, propylene, 1-butene, 4-methyl-1-pentene, 1-
Examples thereof include α-olefins having 3 to 20 carbon atoms such as hexene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

One of these cyclic olefin polymers may be used alone, or two or more thereof may be blended and used as a substrate material. Such one or more cyclic olefin copolymers are disclosed in JP-A-60-168708 and JP-A-61-1.
No. 20816, JP-A-61-115912,
JP-A-61-115916, Japanese Patent Application No. 61-959
No. 05, Japanese Patent Application No. 61-90906,
1-2271308, JP-A-61-272216 and the like by appropriately selecting conditions according to the method,
Can be manufactured.

Further, a polymer containing a repeating unit formed by ring-opening polymerization of a cyclic olefin represented by the formula (4) together with a random copolymer of a cyclic olefin;
Alternatively, it may contain a copolymer, and may further contain a polymer or copolymer containing a repeating unit formed by hydrogenating this repeating unit.

Further, these polymers of various cyclic olefins may contain an antioxidant and a stabilizer. Such a cyclic olefin polymer may be formed into a transparent molded article such as a substrate of an optical disk by injection molding or the like according to a conventional method.

Such a cyclic olefin polymer includes:
When forming the resin coating, an undercoat layer is formed.

The undercoat layer may be formed using a thermoplastic resin. Specifically, ethylene-vinyl acetate copolymer, which is an ethylene-based polymer, and low-density polyethylene are used. That is, it is preferable to use a material having a low glass transition point (Tg) and having tackiness, and the Tg is preferably about 100 ° C. or less, particularly preferably −150 ° C. to 80 ° C.

By providing the undercoat layer of such a resin material, tackiness is imparted, and adhesion to the resin coating is significantly improved.

The undercoat layer is formed using a coating solution containing such a thermoplastic resin. The coating solvent used at this time is one of solvents such as aromatic hydrocarbons such as toluene and xylene and alicyclic hydrocarbons such as cyclohexane.
It is desirable to include more than one species.

The above-mentioned solvent such as toluene has solubility in the polymer of the cyclic olefin, and has an action of partially dissolving or roughening the surface layer of the polymer during coating. Therefore, the use of such a solvent improves the adhesion between the polymer and the undercoat layer. However, even if such a solvent is used, the skin layer of the polymer of the cyclic olefin described below is not sufficiently dissolved and removed, and the skin layer still exists.

In the present invention, an acrylate compound or the like which is preferably used as a resin coating material may be used in addition to the above-mentioned thermoplastic resin, as will be described later in detail. The acrylate compound may be used in any form such as a monomer, an oligomer, and a polymer.

The acrylate compound is used in an amount of not more than 20% by weight, preferably 0.5 to 0.5% by weight, based on the whole mixture with the thermoplastic resin.
Preferably, the content is 10 wt%.

The combined use of this compound is particularly effective when it is used as a resin coating material, and by using a material partially identical to the resin coating material, the adhesiveness to the resin coating is further improved.

The content of the whole resin in the coating solution is 1
It may be about 50 wt%.

The coating solvent may be a solvent obtained by mixing a ketone such as methyl isobutyl ketone, a cellosolve such as ethyl cellosolve, an alcohol such as isopropyl alcohol, etc., in addition to the above solvents. In such a mixed solvent, the content of toluene or the like may be 5 vol% or more, preferably 10 vol% or more.

The coating may be performed by any known method, such as spin coating, gravure coating, spray coating,
Any of dipping and the like may be used. The application conditions and the like can be in accordance with ordinary methods.

The thickness of the undercoat layer is from 0.1 to 0.1% by dry film thickness.
The thickness may be 100 μm, preferably 1 to 50 μm. With such a thickness, the effect of the present invention can be obtained without any change in the optical characteristics of the polymer. When the thickness is small, the effect of the present invention cannot be obtained. When the thickness is large, the effect of the present invention is saturated, which is disadvantageous in terms of productivity and the like.

By forming the undercoat layer in this way, the optical properties of the polymer, for example, transparency, birefringence, etc., are not changed at all, so that the adhesion is high and the polymer has no influence on the optical properties. Coating such as a resin hard coat is realized.

In the formation of the undercoat layer, in the present invention,
A preliminary treatment for applying a solvent containing a solvent such as toluene to the surface of the polymer of the cyclic olefin may be performed. This further improves the adhesion between the polymer and the undercoat layer.

The preliminary treatment may be carried out by a method of applying a solvent to the surface of the polymer of the cyclic olefin, or by a method of dipping the polymer of the cyclic olefin in the solvent.

The application may be performed by any method such as spin coating, gravure coating, spray coating, dipping and the like, and the conditions and the like can be in accordance with ordinary methods. The immersion time for immersion is 1
Seconds to 30 seconds.

In the present invention, as will be described later, since it is used as a substrate for an optical disk, it may be preferable to treat only one surface of the substrate, and in such a case, it is preferable to apply by coating.

Further, as described above, such a preliminary treatment does not completely dissolve and remove the skin layer.

In the present invention, a method of irradiating the polymer with ultraviolet light while exposing the surface of the polymer of the cyclic olefin to ozone may be applied in combination with the method of forming the undercoat layer as described above.

In this case, the undercoat layer may be formed after irradiating ultraviolet rays.

Further, by using the method of irradiating ultraviolet rays together, the adhesiveness with the resin coating can be improved.

The ultraviolet rays may be irradiated in the presence of oxygen.
In order to continuously generate and decompose ozone, it is preferable that the ultraviolet rays to be irradiated have a wavelength of at least 270 nm or less.

The details of the method of irradiating the ultraviolet rays are described in Japanese Patent Application No. 3-177162 filed by the present applicant.

Although there is no particular limitation on the resin material constituting the coating, the coating of radiation, especially an ultraviolet-curable compound, is simpler and more favorable in that it has good physical properties of the film and that the adhesive strength is remarkably improved. It is preferable that the film is cured by irradiation with radiation, particularly ultraviolet light. And radiation, particularly as an ultraviolet-curable compound, those having an acrylic group or those containing an epoxy resin and a cationic photopolymerization catalyst are preferable from the viewpoint of improving adhesion, and other radiations, particularly It is preferable to use a coating composition containing an ultraviolet-curable compound, another resin component, a photopolymerization initiator, a sensitizer, and the like. These will be described later in detail.

The thickness of the coating is generally about 1 to 30 μm. The present invention can be applied to optical parts such as various optical disks, various lenses, mirrors, and filters, and transparent covers and transparent casings.

Next, a case where the coating forming method of the present invention is applied to an optical disk will be described.

The optical disk of the present invention refers to both a read-only optical disk that previously carries information and an optical recording disk that has a recording layer capable of carrying information by optical recording. However, here, the magneto-optical recording disk shown in FIG. 1 will be described as a preferred example. The magneto-optical recording disk 1 shown in FIG.
An intermediate layer 5, a recording layer 6, a protective layer 7, and a protective coat 8 are sequentially provided. At this time, a hard coat 3 is provided on the front surface of the disk, that is, on the back surface side of the substrate 2. The hard coat 3 is preferably formed in advance before each constituent layer is provided.

As described above, such a hard coat 3 is formed, in particular, by using a radiation-curable compound or a composition for polymerization thereof.
It is preferred to be composed of a radiation cured material.
Acrylic acid, methacrylic acid having an unsaturated double bond exhibiting radical polymerizability in response to ionization energy, acrylic double bond such as an ester compound thereof, and diallyl phthalate such as such. Allyl double bond, maleic acid, monomer containing or introduced in the molecule a group that crosslinks or polymerizes by irradiation such as unsaturated double bond such as maleic acid derivative,
Oligomer and polymer can be mentioned. These are preferably polyfunctional, especially trifunctional or more,
One type may be used alone, or two or more types may be used in combination.

The radiation-curable monomer has a molecular weight of 2
Compounds having a molecular weight of less than 20
Those having a size of from 00 to 10,000 are suitable.

Of these, it is preferable to use acrylic modified products of various urethane elastomers, which are radiation-curable oligomers, or may be those in which a functional group such as COOH is introduced.

Further, styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate and the like may be used. Preferable examples include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), and an acrylic modified product of urethane elastomer (Nipporan 4040). Alternatively, those in which a functional group such as COOH is introduced, phenol ethyleneoxy Acrylates (methacrylates) as adducts, compounds having an acrylic group (methacrylic group) or ε-caprolactone-acrylic group attached to a pentaerythritol condensed ring shown in Japanese Patent Application No. 62-072888, and Japanese Patent Application No. 62-072888. And acrylic group-containing monomers such as special acrylates and / or
Or an oligomer is mentioned. In addition, examples of the radiation-curable oligomer include an oligoester acrylate and an oligomer into which a functional group such as COOH is introduced.

A radiation-curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification in addition to or instead of the above compounds may be used. Specific examples of such a radiation-curable resin include acrylic double bonds having an unsaturated double bond exhibiting radical polymerizability, methacrylic acid, or an acrylic double bond such as an ester compound thereof, such as diallyl phthalate. A resin in which a group that crosslinks or polymerizes upon irradiation with radiation, such as an allylic double bond or an unsaturated bond such as maleic acid or a maleic acid derivative, is contained or introduced into a thermoplastic resin molecule. Examples of the thermoplastic resin that can be modified into a radiation-curable resin include a vinyl chloride copolymer, a saturated polyester resin, a polyvinyl alcohol resin, an epoxy resin, a phenoxy resin, and a cellulose derivative. Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (P
(VP olefin copolymer), a polyamide resin, a polyimide resin, a phenol resin, a spiroacetal resin, an acrylic resin containing at least one hydroxyl-containing acrylic ester or methacrylic ester as a polymerization component, and the like are also effective.

Since the coating composition for polymerization is cured by irradiation with radiation, particularly ultraviolet irradiation, it is preferable that the polymerization composition contains a photopolymerization initiator or a sensitizer. The photopolymerization initiator or sensitizer used is not particularly limited, and may be appropriately selected from, for example, acetophenone, benzoin, benzophenone, and thioxanthone. In addition, a plurality of compounds may be used in combination as a photopolymerization initiator or a sensitizer. The content of the photopolymerization initiator in the composition for polymerization may be usually about 0.5 to 5% by weight. The composition for polymerization for forming such a transparent resin hard coat may be synthesized according to a conventional method,
It may be prepared using a commercially available compound.

As the composition containing the radiation-curable compound for forming the hard coat 3, a composition containing an epoxy resin and a cationic photopolymerization catalyst can also be used.

The epoxy resin is preferably an alicyclic epoxy resin, particularly preferably an epoxy resin having two or more epoxy groups in the molecule.

Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis- (3,4-epoxycyclohexylmethyl) adipate, and bis- (3,4-
Epoxycyclohexyl) adipate, 2- (3,4-
One or more of epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (2,3-epoxycyclopentyl) ether and vinylcyclohexene dioxide are preferred. The epoxy equivalent of the alicyclic epoxy resin is not particularly limited,
From the viewpoint of obtaining good curability, it is preferably from 60 to 300, particularly preferably from 100 to 200.

As the cationic photopolymerization catalyst, any known one may be used without any particular limitation. For example, a complex of one or more metal fluoroborates and boron trifluoride,
Bis (perfluoroalkylsulfonyl) methane metal salt, aryldiazonium compound, aromatic onium salt of group 6A element, aromatic onium salt of group 5A element, group 3A ~
Group 5A element dicarbonyl chelate, thiopyrylium salt, MF ₆ anion (where M is P, As or S
Group 6A element having b), triarylsulfonium complex salt, aromatic iodonium complex salt, aromatic sulfonium complex salt and the like can be used. In particular, polyarylsulfonium complex salt, aromatic sulfonium salt or iodonium salt of halogen-containing complex ion, 3A It is preferable to use at least one of aromatic onium salts of Group 5A, Group 5A and Group 6A elements.

Further, a cationic photopolymerization catalyst containing an organometallic compound and an organosilicon compound having photodegradability can be used. Since such a cationic photopolymerization catalyst is a non-strong acid-based catalyst, adverse effects on a highly corrosive recording layer such as a magneto-optical recording disk can be avoided. Organometallic compounds include Ti, V, Cr, Mn, Fe, C
Complex compounds in which an alkoxy group, a phenoxy group, a β-diketonato group, or the like is bonded to metal atoms such as o, Ni, Cu, Zn, Al, and Zr are preferable. Of these, an organoaluminum compound is particularly preferred, and specifically, trismethoxyaluminum, trispropionatoaluminum, tristrifluoroacetylaluminum, and trisethylacetoacetonatoaluminum are preferred.

The organic silicon compound having photodegradability is one that generates silanol upon irradiation with light such as ultraviolet rays.
Silicon compounds having a peroxysilano group, an o-nitrobenzyl group, an α-ketosilyl group and the like are preferred.

The content of the cationic photopolymerization catalyst in the composition is from 0.05 to 0.1 based on 100 parts by weight of the epoxy resin.
It is preferably 7 parts by weight, particularly preferably 0.1 to 0.5 part by weight.

The hard coat 3 may be formed, for example, as follows. First, a coating film of the composition for a hard coat as described above is formed on at least the back surface of the substrate 2. There is no particular limitation on the method of forming the coating film, and the coating film may be generally formed by combining various known methods such as spin coating, gravure coating, spray coating, and dipping.
The application conditions at this time may be appropriately determined in consideration of the viscosity of the composition for polymerization, the desired thickness of the coating film, and the like.

Next, the coating film is heated. The heating temperature may be generally about 60 to 90 ° C. Then, after heating, the coating film is cured by irradiating ultraviolet rays. In some cases, ultraviolet rays may be applied without heating, or an electron beam or the like may be applied instead of ultraviolet rays.

The intensity of the ultraviolet light applied to the coating film is usually 50
mW / cm ² or more, irradiation amount is usually 500 to 2000 mJ
/ cm ² may be used. Further, as the ultraviolet ray source, a usual one such as a mercury lamp may be used. The above compounds undergo radical polymerization by irradiation with ultraviolet rays.

The thickness of the cured coating film, that is, the thickness of the hard coat 3, is preferably 1 to 30 μm, particularly preferably 3 to 10 μm. If the film thickness is too small, it becomes difficult to form a uniform film, and the durability becomes insufficient. On the other hand, if the thickness is too large, cracks occur due to shrinkage during curing, and the disk is likely to warp.

The transmittance of the substrate 2 coated with the hard coat 3 to recording light and reproduction light is preferably 80% or more, particularly preferably 85% or more. In the case of a double-sided recording type magneto-optical disk, both substrates are provided with a hard coat. Further, the hard coat may be formed not only on the main surface of the disk but also on the outer peripheral side surface or the inner peripheral side surface.

As described above, a cyclic olefin polymer is used as the material of the substrate 2. A skin layer is present on the surface layer of the substrate 2 on the side of the recording layer, and the skin layer has a thermal softening point of 140 ° C. or less, particularly 100 to 140 ° C.
More preferably 100 to 135 ° C, still more preferably 1 to 135 ° C.
The temperature is preferably from 10 to 135 ° C. Thermal softening point 140
The skin layer at a temperature of not more than ° C. is also present on the back surface of the substrate 2 on the side of the recording layer, and by providing such a skin layer, the adhesiveness of the hard coat is further improved. However, if the thermal softening point is too low, there may be a problem with heat resistance during film formation,
Dimensional accuracy may decrease.

In this case, the thermal softening point of the skin layer in the surface layer is a temperature measured as described below. First, a needle is placed on the substrate to be tested, a load of about 5 g is applied, the temperature is raised from about 30 ° C. at a rate of temperature rise of about 2 ° C./min, and the amount of needle penetration is measured. The cross section of the needle is cylindrical with a diameter of about 1 mm. FIG. 2 shows the relationship between the temperature thus measured and the amount of needle entry. As shown in FIG. 2, in the substrate of the present invention, a first inflection point and a second inflection point occur in the temperature characteristic profile of the needle penetration amount.

For example, in the case of a casting substrate or a certain type of injection molded substrate, only one bending point appears in the temperature characteristics of the amount of needle entry, or the first bending point appears only slightly. The first-stage needle penetration amount caused by the first inflection point is about 200 μm or less. Therefore, it is considered from these that the first bending point is derived from the softening point of the skin layer on the surface of the substrate. Therefore, in the vicinity of the first bending point of the temperature characteristic profile, the linear portion before the needle enters and the 1
The intersection of the straight line portion of upon entry stage as T _1, which is defined as the thermal softening point T ₁ of the skin layer. Then, it restricts the T ₁ as described above.

[0096] On the other hand, in the second bending point near the intersection of the linear portion of the time of the first stage enters at the second stage enters a T _2, which defines a second heat softening point T ₂ I do. This second thermal softening point T ₂ is considered to be the thermal softening point at the center of the substrate. The second heat softening point T ₂ is 10 ° C. or more, more preferably 10 to 50 ° C., than the first heat softening point T _1.
Temperature higher than 140 ° C, especially 145 to 180 ° C.
Preferably, the temperature is in ° C. Thereby, dimensional accuracy, mechanical characteristics, heat resistance, and the like are improved.

The skin layer was formed by the SE of the cross section of the surface layer of the substrate.
From the M image, it can be confirmed as a layer different in color from the surroundings, and its thickness is generally 1 to 200 μm, particularly 10 to 100 μm.
It is considered to be about. Further, the temperature characteristic profile of the needle penetration amount may be measured by various devices commercially available as TMA (thermomechanical analyzer, thermomechanical analyzer), for example, a 943 thermomechanical analyzer manufactured by DuPont.

In order to form such a skin layer, it is particularly preferable to form a substrate by injection molding a polymer of a cyclic olefin. And the injection pressure is 250 ~ 400kg / c
is preferably set to approximately m ^2. The melting temperature is 3
The mold temperature is about 80 to 120 ° C, and the holding pressure, mold clamping force, and the like may be set to normal conditions.

Note that a tracking groove may be formed on the surface of the substrate 2 on which the recording layer 6 is formed.

In the magneto-optical recording disk shown in FIG. 1, a protective layer 4 as an underlayer, an intermediate layer 5
The recording layer 6 is formed via the. The mid layer 5 has a C /
It is provided to improve the N ratio, and is preferably formed from various dielectric materials, and has a layer thickness of 30 to 150 nm.
It is preferred that it is about.

A protective layer 7 can be provided on the recording layer 6 together with the protective layer 4. When used in combination, the compositions of the protective layer 4 and the protective layer 7 may be the same or different. Protective layer 4 and protective layer 7 provided as needed
Are provided for improving the corrosion resistance of the recording layer 6, and it is preferable that at least one of them, and preferably both of them are provided. These protective layers are preferably composed of an inorganic thin film made of various oxides, carbides, nitrides, sulfides or mixtures thereof. Further, the protective layers 4 and 7 may be formed of the above-mentioned intermediate layer material. The thickness of the protective layer is preferably about 30 to 300 nm from the viewpoint of improving corrosion resistance. Such protective layers 4 and 7 and the intermediate layer 5
Is preferably formed by various vapor phase film forming methods such as sputtering, vapor deposition, and ion plating, in particular, by sputtering.

In the recording layer 6, information is magnetically recorded by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magneto-optical conversion. The material of the recording layer 6 is not particularly limited as long as it can perform magneto-optical recording. An alloy containing a rare earth metal element, particularly an alloy of a rare earth metal and a transition metal, is formed by sputtering, vapor deposition, ion plating. For example, it is preferable that the film is formed as an amorphous film by sputtering. As rare earth metals, Tb, Dy, Nd, Gd, S
It is preferable to use one or more of m and Ce. As the transition metal, Fe and Co are preferable. In this case, the total content of Fe and Co is preferably 65 to 85 at%. The balance is substantially a rare earth metal.

The composition of the recording layer preferably used is
TbFeCo, DyTbFeCo, NdDyFeCo,
NdGdFeCo and the like. In the recording layer, 10
Cr, Al, Ti, Pt, Si, M within the range of at% or less
o, Mn, V, Ni, Cu, Zn, Ge, Au and the like may be contained. In addition, Sc, within the range of 10 at% or less,
Y, La, Ce, Pr, Pm, Sm, Eu, Ho, E
Other rare earth metal elements such as r, Tm, Yb, and Lu may be contained. The layer thickness of the recording layer 6 is usually 10 to
It is about 1000 nm. Then, a metal reflective layer may be provided on the protective layer 7.

Even if such a recording layer 6 and the protective layer 4 and the intermediate layer 5 as the underlayer are formed by a vapor deposition method such as sputtering, the recording layer and the underlayer are formed by the skin layer. Substrate 2
From the film can be effectively prevented.

It is preferable that a protective coat 8 is provided on the protective layer 7. The protective coat 8 is typically made of various resin materials such as an ultraviolet curable resin, for example, from 0.1 to 100 μm.
The layer may be formed to a thickness of about m. The protective coat 8 may be in the form of a layer or a sheet. The protective coat 8
In particular, it is preferable that the coating film containing the radiation-curable compound and the photopolymerization sensitizer or initiator is cured with radiation, particularly ultraviolet rays. As such a radiation-curable compound, those containing the aforementioned acrylic group are preferred.
Then, in the same manner as in the hard coat, a photopolymerization sensitizer or an initiator is added, and preferably ultraviolet curing.

In such a case, after each constituent layer is formed on the substrate by the vapor phase method, the surface of the uppermost layer of the constituent layer (protective layer 7) and the region where the constituent layer of the substrate on the recording layer forming side is not formed are formed. In the same manner as described above, it is preferable to form an undercoat layer formed using a thermoplastic resin, preferably an ethylene-based polymer (eg, ethylene-vinyl acetate copolymer, low-density polyethylene, etc.). Thereby, the adhesion of the protective coat 8 is improved.

The present invention can also be applied to an optical recording disk having a recording layer of a so-called phase change type or the like, and performing recording / reproduction by changing the reflectance. Further, the recording layer may be an optical recording disk in which a dye coating film or the like is used as a recording layer and a gap is provided on the recording layer, or a reflective layer is closely adhered and laminated on the dye layer. In particular, the close contact type is suitable as an optical recording disk for a compact disk (CD) standard, a video disk, and the like, but in this case, the sensitivity and C / N are improved by the generation of a skin layer.
It is preferable to provide the protective coat described above for those having a close contact type dye layer or phase change type. At this time, it is preferable to form an undercoat layer before forming the protective coat as described above.

[0108]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Example 1 A commercially available pellet of Zeonex 280 manufactured by Zeon Corporation was obtained as a cyclic polyolefin having a repeating unit represented by Chemical Formula 3. This was melted at 350 ° C. and the mold temperature was 100
Injection molding was performed at 350 ° C. and an injection pressure of 350 kg / cm ² to obtain a substrate sample No. 1 having a diameter of 120 mm and a thickness of 1.2 mm.

The thermal softening point of the substrate was measured by TMA as follows. Needle cross section: 1mm diameter cylinder Load: 5g Heating rate: 2 ℃ / min

Under the above conditions, the temperature profile of the needle penetration amount was measured, and the first and second thermal softening points T ₁ and T ₂ were calculated. T ₁ = 130 ° C. and T ₂ = 165 ° C. Was. From the SEM image of the substrate, it was considered that the thickness of the skin layer was about 100 μm or less.

Next, an undercoat layer was formed on the back surface of the substrate No. 1 on the recording layer forming side of the substrate. At this time, a mixed solvent of toluene and methyl isobutyl ketone (toluene is 40
vol%) as a coating solvent, a coating solution containing 20% by weight of an ethylene-vinyl acetate copolymer was prepared.

Using this coating solution, a coating film was formed by spin coating. As a result, an undercoat layer having a dry film thickness of 10 μm was formed to obtain a substrate No. 2.

EVA is a commercially available product [trade name: EVA-
AD-5: manufactured by Showa Polymer Co., Ltd.].

On the substrate No. 2, instead of forming the undercoat layer, 3-methacryloxypropyltrimethoxysilane [CH ₂ ＣC (CH ₃ ) COOC ₃ H ₆ Si (OC
Substrate No. 3 was obtained in the same manner except that the coupling treatment was performed using H ₃ ) ₃ ]. However, after the above silane coupling agent was applied, drying was performed at 70 ° C. for 2 hours.

In the substrate No. 2, the primer treatment was performed in the same manner as described above except that a primer for a cyanoacrylate-based instant adhesive (trade name: Polyprimer: manufactured by Toagosei Co., Ltd.) was used instead of forming the undercoat layer. No. 4
I got

Using each of the substrates No. 1 to No. 4, a coating film of the composition for a hard coat layer was formed on the back surface and the peripheral surface of the substrate on the side where the recording layer was formed. Was formed. The hard coat was formed by applying an acrylate-based polymerization composition [trade name: SD-17: commercially available from Dainippon Ink Co., Ltd.] by spin coating, heating, and then irradiating with ultraviolet rays to cure. The average thickness after curing was 5 μm.

An adhesion test was performed on the hard coat of each substrate thus manufactured. Adhesion test is JI
The test was performed according to the cross-cut test of SK5400. That is, on the hard coat of the sample, 11 parallel vertical and horizontal parallel lines were drawn at 2 mm intervals using a cutter knife, and a grid-like cut was made so that 100 squares could be formed in 4 cm ^2. Then, a cellophane tape (manufactured by Nichiban) was stuck thereon, and the peeling evaluation was performed.

The adhesion test was performed immediately after the hard coat was formed.
The test was performed after storage for 1000 hours under the conditions of a temperature of 80 ° C. and a humidity of 80% RH.

Table 1 shows the results. In addition, 100 /
100 is one of the 100 cells that did not exfoliate.
It indicates that there are 00 pieces.

[0121]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear.

Next, a protective layer made of glass was formed in a predetermined area on the other surface of the substrate on which the hard coat was formed as described above to a thickness of 40 nm by high-frequency magnetron sputtering. On this protective layer, a SiN _x intermediate layer was formed to a thickness of 80 nm by high-frequency magnetron sputtering. Next, a recording layer having a composition of Tb ₂₃ Fe ₇₂ Co ₅ was formed on the intermediate layer to a thickness of 80 nm by sputtering.

Further, on the recording layer, a protective layer having the same composition as that of the protective layer and having the same composition as that of the protective layer was formed by high-frequency magnetron sputtering, and a protective coat was formed on the protective layer.
The protective coat was obtained by applying the same polymerization composition as that used for the hard coat by spin coating, heating, and then irradiating with ultraviolet rays, and the average thickness after curing was 5 μm. And

The disk of the present invention using the coating method of the present invention exhibited good recording and reproducing characteristics.

Example 2 In the substrate No. 2 of Example 1, when forming the undercoat layer,
An undercoat layer was formed in the same manner except that VA and butyl acrylate were used in combination to obtain Substrate No. 21.

Incidentally, the addition amount of butyl acrylate was EV
The content was 5 wt% of the whole A-butyl acrylate.

An adhesion test was performed on this substrate No. 21 in the same manner as in Example 1. As a result, a good result equal to or better than that of substrate No. 2 was shown.

Also, good results were shown for an optical disc.

Example 3 In the substrate No. 2 of Example 1, before forming the undercoat layer, light irradiation was performed from the back side of the recording layer forming side of the substrate using a low-pressure mercury lamp under the following conditions. Board No.
31 was obtained. A commercially available ultraviolet-ozone cleaning device was used for light irradiation.

UV irradiation output 100 W UV irradiation time 3 min Distance between light source and sample 50 mm Atmosphere 1 atm / air Sample temperature Room temperature This substrate No. 31 was subjected to an adhesion test in the same manner as in Example 1 to obtain a substrate. No. 2 showed good results equivalent to or better.

Also, good results were obtained for an optical disc.

Example 4 In the substrate No. 2 of Example 1, before forming the undercoat layer, a preliminary treatment of applying by spin coating to the recording layer forming side surface of the substrate is performed using a coating solvent for forming the undercoat layer. Otherwise, the substrate No. 41 was obtained in the same manner.

An adhesion test was performed on this substrate No. 41 in the same manner as in Example 1. The result was as good as or better than that of substrate No. 2.

Example 5 In each optical disk using substrate No. 2 of Example 1, substrate No. 21 of Example 2, substrate No. 31 of Example 3, and substrate No. 41 of Example 4, protection was performed. Immediately before coating film formation, an optical disc was produced in the same manner as above except that an undercoat layer was formed on the recording layer forming surface so as to correspond to each substrate in the same manner as the back surface of the substrate on the recording layer forming side.

The formation of the undercoat layer improved the adhesion of the protective coat.

[0137]

According to the present invention, the adhesiveness of a substrate of a cyclic olefin polymer to a hard coat of a transparent resin or the like is remarkably improved, and extremely high durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing one example of an optical disk of the present invention.

FIG. 2 is a graph for explaining a thermal softening point of a substrate.

[Explanation of symbols]

Reference Signs List 1 optical disk 2 substrate 3 hard coat 4 protective layer 5 intermediate layer 6 recording layer 7 protective film 8 protective coat T ₁ first softening point T ₂ second softening point

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Komaki 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-2-70431 (JP, A) JP-A Heisei 3-223341 (JP, A) JP-A-5-306378 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J ^7/ 04-7/06 G11B 7/26

Claims (18)

(57) [Claims] An undercoat layer is formed on the surface of a polymer of a cyclic olefin using at least one or more thermoplastic resins of an ethylene-vinyl acetate copolymer and a low-density polyethylene. A method for forming a coating, comprising forming a coating of a transparent resin. 2. The coating forming method according to claim 1, wherein a component that can be a coating component of the transparent resin is used in addition to the thermoplastic resin. 3. The coating forming method according to claim 1, wherein the coating solvent used for forming the undercoat layer contains at least one of an aromatic hydrocarbon solvent and an alicyclic hydrocarbon solvent. 4. The method according to claim 3, wherein the aromatic hydrocarbon solvent is toluene. 5. The undercoat layer having a thickness of 0.
5. The method according to claim 1, wherein the thickness is 1 to 100 [mu] m. 6. The polymer according to claim 1, wherein said polymer is a transparent molded product.
6. The method for forming a film according to any one of items 1 to 5, 7. The method according to claim 1, wherein the cyclic olefin polymer has a repeating structural unit represented by the following chemical formula 1. Embedded image 8. The coating forming method according to claim 1, wherein the polymer of the cyclic olefin is a copolymer of a cyclic olefin of the following formula 2 and ethylene. Embedded image 9. The method according to claim 1, wherein the coating of the transparent resin is obtained by radiation-curing a coating film of a radiation-curable compound. 10. The method according to claim 9, wherein the radiation-curable compound has an acrylic group. 11. A substrate of the cyclic olefin polymer, wherein at least one surface of the substrate has a transparent resin coating formed by the coating forming method according to any one of claims 1 to 10. An optical disc having a recording layer or an information carrying layer on the other surface. 12. The optical disk according to claim 11, wherein the substrate is formed by injection molding a polymer of a cyclic olefin. 13. The substrate has a heat softening point of 1 on its surface.
The optical disc according to claim 12, having a skin layer at a temperature of 40 ° C or lower. 14. The optical disk according to claim 12, wherein the substrate carries a recording layer, and the substrate has a skin layer having a thermal softening point of 140 ° C. or less on a surface layer on the recording layer side. 15. The substrate according to claim 11, wherein a recording layer is carried on one surface of the substrate, and an undercoat layer is formed on the surface on which the recording layer is formed, and then a protective coating made of resin is provided.
4. The optical disc according to any one of 4. 16. The optical disk according to claim 15, wherein the undercoat layer is formed using a thermoplastic resin. 17. The optical disk according to claim 16, wherein the thermoplastic resin is an ethylene polymer. 18. The optical disk according to claim 11, wherein the protective coat is obtained by curing a radiation-curable compound with ultraviolet rays.