JPH08143613A - Photo-setting composition for coating and information recording medium having protective coat by curing the same - Google Patents

Abstract

PURPOSE: To obtain a composition capable of forming a well-serviceable cured coat excellent in a sliding property, therefore capable of forming an information recording medium without developing any reading error for a long period, comprising a photo-setting material, a fatty acid ester and two kinds of specific silicone oils. CONSTITUTION: This composition comprises (A) a photo-setting material (containing a polyester acrylate, etc., and a polymerization initiator such as benzoin), (B) a fatty acid ester (pref. n-butyl stearate), (C) silicone oil having a viscosity of 1000-10000cps at 25 deg.C and (D) silicone oil having a viscosity of 1.0 to <1000cps (where polyether-modified polysiloxane, etc., are used as the silicone oils). The other objectives of this invention are a photomagnetic recording medium, an information recording medium and a magnetic recording medium, each having a protective coat by curing this composition on the outermost layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photocurable composition for coating and an information recording medium having a protective film formed by curing the composition, and more specifically, it can form a coating excellent in slidability. The present invention relates to such a photocurable composition for coating, and an information recording medium such as a magneto-optical recording medium or a magnetic recording medium having a protective film formed by curing the composition and having excellent slidability as an outermost layer.

[0002]

2. Description of the Related Art Conventionally, recording disks such as magnetic disks and magneto-optical disks have been used as information recording media. Such a recording disc is generally recorded with a rotating disc and a head in contact with each other,
Reading is performed in a slightly raised state.

As described above, in the recording disk, the disk and the head come into contact and slide with each other at the time of recording or at the beginning of reading or at the end of reading. Therefore, the disk surface is required to have excellent slidability. For this reason, a lubricant layer is formed on the surface of the recording disk for improving slidability and running durability and stability.

Conventionally, such a lubricant layer is a fatty acid,
It was formed by applying a fatty acid ester, paraffin, a fluorine-based compound, a silicon-based compound or the like on the disk surface.

However, it cannot be said that the frictional force between the head and the disk having the lubricant layer formed by applying such a lubricant is sufficiently small, and the lubricant may be consumed. It is desired to reduce the frictional force between and for a long period of time to improve the slidability.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such circumstances, and a photocurable composition for coating capable of forming a coating film having excellent slidability and an excellent sliding property. It is an object to provide an information recording medium having a protective film as the outermost layer.

[0007]

SUMMARY OF THE INVENTION The coating photocurable composition of the present invention comprises (a) a photocurable material, (b) a fatty acid ester, (c) a silicone oil having a viscosity at 25 ° C. of 1000 cps or more and 10000 cps or less, and (D) Viscosity at 25 ° C is 1.0 cps or more and 1
It is characterized by being composed of silicone oil having a viscosity of less than 000 cps.

Such a photocurable composition for coating can form a coating having a small friction coefficient and excellent durability. The information recording medium of the present invention is characterized by having a protective film formed by curing the photocurable composition in the outermost layer.

Examples of such information recording media include magneto-optical recording media and magnetic recording media. The information recording medium of the present invention is excellent in durability and running stability because the frictional force with the head during recording or reading is small.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The photo-curable composition for coating of the present invention and the information recording medium having a protective film formed by curing the composition are specifically described below.

First, the coating photocurable composition of the present invention will be described. The photocurable composition for coating of the present invention comprises (a) a photocurable material, (b) a fatty acid ester, (c) a silicone oil having a viscosity at 25 ° C. of 1000 cps or more and 10000 cps or less, and (d) 25 ° C. Viscosity of 1.0 cps or more and 1
It contains silicone oil that is less than 000 cps.

As the photocurable material (a) for forming the coating photocurable composition, a resin which is cured by irradiation with light is widely used, and examples thereof include an ultraviolet curable resin. This photocurable material generally contains (a-1) a compound having a polymerizable unsaturated bond, and (a-2) a polymerization initiator. Examples of (a-1) a compound having a polymerizable unsaturated bond and (a-2) a polymerization initiator are shown below.

Examples of the compound (a-1) having a polymerizable unsaturated bond include polyester acrylate, polyether acrylate, acrylic oligomer acrylate,
Oligomers such as urethane acrylate, polybutazine acrylate, polystyryl methacrylate, polyether methacrylate, and epoxy acrylate; long-chain aliphatic acrylate (CH ₂ = CHCOOC _n H _{2n + 1} , n = 12,13), allyl (meth) acrylate , Benzyl (meth) acrylate, butoxyethyl (meth) acrylate, butanediol monoacrylate, butoxytriethylene glycol acrylate, ECH-modified butyl acrylate, t-
Butylaminoethyl methacrylate, caprolactone acrylate, 3-chloro-2-hydroxypropyl methacrylate, 2-cyanoethyl acrylate, cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, alicyclic modified neopentyl glycol acrylate, 2,3 -Dibromopropyl (meth) acrylate,
Dicyclopentenyl acrylate, dicyclopentenyl oxyethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, 2-ethoxyethyl (meth)
Acrylate, 2- (2-ethoxyethoxy) ethyl acrylate, 2-ethylhexyl (meth) acrylate, glycerol methacrylate, glycidyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate,
2-hydroxyethyl (meth) acrylate, caprolactone-modified 2-hydroxyethyl (meth) acrylate, 2-
Hydroxy-3-methacryloxypropyl trimethylammonium chloride, 2-hydroxypropyl (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate, isooctyl acrylate, lauryl (meth) acrylate, γ-methacryloxypropyltrimethoxysilane , 2-methoxyethyl acrylate, methoxydiethylene glycol methacrylate, methoxytriethylene glycol (meth) acrylate, methoxytetraethylene glycol methacrylate, methoxypolyethylene glycol methacrylate,
Methoxydipropylene glycol acrylate, methoxylated cyclodecatriene acrylate, morpholine acrylate, nonylphenoxy polyethylene glycol acrylate, nonylphenoxy polypropylene glycol acrylate, octafluoropentyl (meth) acrylate, octyl acrylate, phenoxyhydroxypropyl acrylate, phenoxyethyl (meth) acrylate , Phenoxydiethylene glycol acrylate, phenoxytetraethylene glycol acrylate, phenoxyhexaethylene glycol acrylate, EO-modified phenoxyphosphoric acid (meth) acrylate, phenoxymethacrylate, EO-modified phosphoric acid (meth) acrylate, EO-modified butoxylated phosphoric acid (meth)
Acrylate, EO-modified octoxylated phosphoric acid (meth) acrylate, EO-modified phthalic acid (meth) acrylate,
EO, PO modified methacrylic acid phthalate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol / polypropylene glycol methacrylate, polyethylene glycol / polybutylene glycol methacrylate, stearyl (meth) acrylate, EO modified succinic acid (meth) acrylate, sodium sulfonate sulfonate (Meth) acrylate, tetrafluoropropyl (meth) acrylate,
Tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, trifluoroethyl (meth) acrylate, vinyl acetate, N-vinylcaprolactam, N-vinylpyrrolidone, vinyl acetate and other monofunctional compounds; allylated cyclohexyl diacrylate , Acrylated isocyanurate, bis (acryloxy neopentyl glycol) adipate,
EO modified bisphenol A diacrylate, EO modified bisphenol S diacrylate, bisphenol A dimethacrylate, EO modified bisphenol A dimethacrylate, EO modified bisphenol F diacrylate, 1,4-
Butanediol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, dicyclopentanyl diacrylate, diethylene glycol di (meth) acrylate, ECH-modified diethylene glycol dimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol mono Hydroxy pentaacrylate, alkyl modified dipentaerythritol pentaacrylate, alkyl modified dipentaerythritol tetraacrylate, alkyl modified dipentaerythritol triacrylate, caprolactone modified dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, ECH modified ethylene glycol diacrylate, ethylene Glycol di (meth) acrylate, ECH modified Ethylene glycol dimethacrylate, glycerol acrylate / methacrylate, glycerol dimethacrylate, ECH modified glycerol triacrylate, 1,6-hexanediol diacrylate, ECH modified 1,6-hexanediol diacrylate,
1,6-hexanediol dimethacrylate, long-chain aliphatic di (meth) acrylate, methoxylated cyclohexyl diacrylate, neopentyl glycol (meth) acrylate, hydroxypivalic acid neopentyl glycol diacrylate, caprolactone modified hydroxypivalic acid neopentyl glycol Diacrylate, pentaerythritol triacrylate, pentaerythritol tetra (meth) acrylate, stearic acid-modified pentaerythritol diacrylate, EO-modified phosphoric acid di (meth) acrylate, EO-modified phosphoric acid triacrylate,
Caprolactone, EO-modified phosphoric acid dimethacrylate, E
CH-modified phthalic acid diacrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ECH-modified propylene glycol diacrylate, tetraethylene glycol di (meth) acrylate, tetrabromobisphenol A
Diacrylate, triethylene glycol di (meth) acrylate, triethylene glycol divinyl ether, triglycerol diacrylate, neopentyl glycol modified trimethylolpropane diacrylate,
Trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, PO-modified trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ECH-modified trimethylolpropane triacrylate, tripropylene glycol diacrylate, tris (acryloxyethyl) isocyanurate And polyfunctional compounds such as caprolactone-modified tris (acryloxyethyl) isocyanurate, tris (methacryloxyethyl) isocyanurate, and zinc di (meth) acrylate.

These (a-1) compounds having a polymerizable unsaturated bond can be used alone or in combination of two or more kinds. (A-2) Specific examples of the polymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin i-propyl ether,
Benzoin ethers such as benzoin i-butyl ether, benzophenone, Michler's ketone, o-benzoyl-
Benzophenones such as methylbenzoate, xanthone, thioxanthone, 2-chlorothioxanthone, 2-alkylthioxanthone, thioxanthones such as 2,4-dialkylthioxanthone, acetophenone, trichloroacetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyltrichloroacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane
-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-
Methylpropan-1-one, 4- (2-hydroxyethoxy)
-Phenyl (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-
{4- (Methylthio) phenyl} -2-morpholinopropane-
Acetophenone derivatives such as 1, and α-acyloxime ester, acylphosphine oxide, methylphenylglyoxylate, benzyl, 9,10-phenanthrenequinone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 4 ′ , 4 ''-Diethylisophthalophenone, 3,3 ', 4,4'-Tetra (t-butylperoxycarbonyl) benzophenone, triethanolamine, methyldiethanolamine, triisopropanolamine, 4,4'
-Dimethylaminobenzophenone, 4,4'-diethylaminobenzophenone, 2-dimethylaminobenzoic acid ethyl ester, 4-
Examples include ethyl dimethylaminobenzoate, (n-butoxy) ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, and the like.

These (a-2) polymerization initiators are
Alternatively, two or more kinds can be used in combination. (A-
2) The polymerization initiator is 0.1 to 30% by weight, and preferably 1 to 30% by weight based on (a-1) the compound having a polymerizable unsaturated bond.
It is preferably blended in a proportion of 20% by weight.

Examples of the composition of the photocurable material (a) used in the present invention include the following compositions. Alicyclic monofunctional acrylate compound: 10 to 50% by weight Aliphatic diacrylate compound: 10 to 50% by weight Polyfunctional (trifunctional or higher) acrylate compound: 1 to 50% by weight Polymerization initiator: 1 to 20% by weight The fatty acid ester having a total number of carbon atoms of 11 or more is used as the (b) fatty acid ester forming the photocurable composition for coating of, specifically, methyl undecylate, ethyl undecylate, methyl laurate, lauryl. Ethyl acid, vinyl laurate, n-butyl laurate, i-butyl laurate, n-amyl laurate, n-benzyl laurate, 2-naphthyl laurate, cholesterol laurate, methyl tridecylate, ethyl tridecylate, myristin Methyl acid, ethyl myristate, vinyl myristate, i-propyl myristate, n-butyl myristate
I-Butyl myristate, heptyl myristate, 2-naphthyl myristate, cholesterol myristate, methyl pentadecylate, ethyl pentadecylate, methyl palmitate, ethyl palmitate, vinyl palmitate,
I-Propyl palmitate, n-butyl palmitate, i-butyl palmitate, heptyl palmitate, dodecyl palmitate, n-hexadecyl palmitate, methyl heptadecylate, ethyl heptadecylate, cholesterol heptadecylate, methyl stearate, stearic acid Saturated fatty acid esters such as ethyl, vinyl stearate, i-propyl stearate, n-butyl stearate, phenyl stearate, octyl stearate, dodecyl stearate, cholesterol stearate; methyl oleate, ethyl oleate, n oleate n -Unsaturated fatty acid esters such as butyl, i-butyl oleate, i-amyl oleate, heptyl oleate, oleyl oleate, methyl elaidate, methyl erucate, ethyl erucate, and ethylene brassidate And the like.

Among these, saturated fatty acid esters are preferable, saturated fatty acid esters having a total carbon atom number of 13 or more, preferably 15 to 30 are more preferable, and n-butyl stearate is particularly preferable. The melting point of fatty acid ester is
It is desirable to be in the range of 20 ° C or higher, preferably 22 to 60 ° C.

The coating photocurable composition of the present invention has, in addition to the photocurable material (a) and the fatty acid ester (b), a viscosity at 25 ° C. of 1000 cps or more and 1
Silicone oil (c) of 0000 cps or less (hereinafter sometimes referred to as “medium viscosity silicone oil”), and viscosity at 25 ° C. of 1.0 cps or more and 10
It contains at least two kinds of silicone oils having different viscosities, that is, silicone oil (d) having a viscosity of less than 00 cps (hereinafter sometimes referred to as "low viscosity silicone oil").

The intermediate viscosity silicone oil (c) forming the photocurable composition for coating of the present invention has a viscosity at 25 ° C. of 1000 cps or more and 10000 cps or less, preferably 1200 cps or more and 6000 cps.
Examples thereof include dimethyl polysiloxane, methylphenyl polysiloxane, methyl hydrogen polysiloxane, and modified polysiloxane having s or less.

Examples of the modified polysiloxane include epoxy modified polysiloxane, alkyl modified polysiloxane, amino modified polysiloxane, carboxyl modified polysiloxane, alcohol modified polysiloxane, fluorine modified polysiloxane, alkyl aralkyl polyether modified polysiloxane, and epoxy polysiloxane. Examples thereof include ether-modified polysiloxane and polyether-modified polysiloxane.

Among these, polyether-modified polysiloxane is particularly preferable. The low-viscosity silicone oil (d) forming the photocurable composition for coating of the present invention has a viscosity at 25 ° C. of 1.0 cps or more and 10 or less.
Less than 00 cps, preferably more than 50 cps and 60
Examples thereof include dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and modified polysiloxane having 0 cps or less.

Examples of the modified polysiloxane include the same ones as described above. Among these, polyether modified polysiloxane is particularly preferable. A preferable combination of the medium-viscosity silicone oil and the low-viscosity silicone oil has a viscosity at 25 ° C. of 1600 to 4100c.
A combination of a medium viscosity silicone oil having a ps range and a low viscosity silicone oil having a viscosity at 25 ° C. of 200 to 400 cps may be mentioned.

In order to obtain a coating film having excellent slidability in the present invention, the photocurable composition for coating of the present invention contains 80 to 99.8% by weight, preferably 80 to 99.8% by weight of the photocurable material (a). 80 to 98% by weight, more preferably 90 to 96% by weight, 0.1 to 10% by weight of the (b) fatty acid ester,
Preferably 0.1 to 8% by weight, more preferably 0.2 to
5% by weight, 0.1% of the medium viscosity silicone oil (c)
It is desirable to contain 1 to 10% by weight, preferably 0.15 to 8% by weight, more preferably 0.2 to 5% by weight.

The (d) low-viscosity silicone oil was added to
It is desirable that the content is 11 to 10% by weight, preferably 0.15 to 8% by weight, and more preferably 0.2 to 5% by weight.

In particular, when the blending ratio of (b) fatty acid ester, (c) medium viscosity silicone oil and (d) low viscosity silicone oil is within the above range, the sliding property is excellent,
There is an advantage that a film having a smooth surface can be obtained.

In the present invention, it is preferable to combine (a) the photocurable material, a saturated fatty acid ester having a total carbon atom number of 13 or more, preferably 15 to 30, and a polyether-modified polysiloxane.

The coating photocurable composition of the present invention can be produced by mixing the above-mentioned components by a conventional method. The viscosity of the photocurable composition for coating thus obtained is 25
1 to 150 cps, preferably 20 to
It is preferably 100 cps.

The coating photocurable composition of the present invention is cured by light irradiation, usually ultraviolet irradiation. The film formed by curing the photocurable composition for coating has excellent slidability. It is presumed that this is not only due to the characteristics of the lubricant itself, but also because a large number of fine holes are formed on the surface of the coating film formed by curing the coating photocurable composition, and the contact area with the contact product is reduced. It Further, according to the present invention, it is possible to form a coating film having a large number of fine pores formed on such a surface without using a volatile solvent.

The coating formed from the photocurable coating composition of the present invention also has excellent abrasion resistance. The coating photocurable composition of the present invention is used as a coating material for various molded bodies. Specifically, an information recording medium, for example, an information recording disk such as a magnetic disk or a magneto-optical disk; a shower dome of a coffee maker, a coffee container / water tank, a cover of an illuminator, a cover of a stereo device such as a player, a clothes dryer. Home appliances such as electric washing machines and dryers; curtains, screens, tablecloths, tableware,
Household items such as chairs, mirrors, various containers such as soy sauce bottles and cosmetic bottles; covers for automobile headlights or taillights, window glass (windshield, rear window, opera window, triangular window, sunroof), fenders,
Automotive parts such as automobile wheels, automobile interior materials, glove box panel boards, bumpers, brakes, motorcycle windshields, side covers, mudguards; floor tiles, floor sheets, doors, table boards, wall tiles, counters Top decorative boards, shelf boards, wall sheets, wallpaper, furniture, wall boards, bathtubs, toilets, refrigerators, wall panels, water supply and drainage pipes, wiring pipes, ducts, curtain rolls, rain gutters, heat insulating materials, curtains, window frames, makeup Stand, flower box, particle board,
Roof tiles, shutters, shutters, waterproof pans, pipes, wiring materials,
Lighting plate, sky dome, panel panel of solar water heater, window glass for greenhouses / houses, building materials such as glass for aquarium, glass shatterproof film, release film, insulating film, agricultural film, waterproof / moisture proof Films, tarpaulins, insulation films and other film sheets; relay cases, fuse boxes, gear cams, knobs, solenoid valve frames,
General industrial materials such as viewing windows for various devices such as fans and oil tanks, dials and covers for various meters, level sensors, various containers; various lenses such as glasses, cameras and contact lenses, optical prisms, optics such as watch glass Supplies; medical materials such as blood bags and the like.

The coating photocurable composition of the present invention is particularly preferably used as a material for a surface protective film of a recording disk such as a magneto-optical recording medium or a magnetic recording medium. When the photocurable coating composition of the present invention is used as a material for a surface protective film of a recording disk, a protective film having excellent slidability can be formed. Further, since this protective film also has excellent wear resistance, it is not necessary to form a wear resistant protective layer and a lubricant layer as in the conventional case, and a recording disk can be manufactured with high productivity.

Next, the information recording medium of the present invention will be described. Examples of the information recording medium of the present invention include a magneto-optical recording medium and a magnetic recording medium. 1 and 2 are partial sectional views showing an example of the magneto-optical recording medium of the present invention, and FIG. 3 is a partial sectional view showing an example of the magnetic recording medium of the present invention.

The magneto-optical recording medium of the present invention is a recording disk for storing information in a magnetic thin film by utilizing the thermal effect of light and reading it out by utilizing the magneto-optical effect. For example, as shown in FIG. It has a substrate 1, a magneto-optical recording film 2, a metal film 3 and a protective film 4.

The material of the substrate 1 is not particularly limited, but in addition to inorganic materials such as glass and aluminum, acrylic resin, polycarbonate, a polymer alloy of polycarbonate and polystyrene, and an amorphous material as shown in US Pat. No. 4,614,778. Ethylene-cyclic olefin copolymers, such as ethylene and 1,4,5,8-dimethano-1,2,3,4,4
Copolymer with a, 5,8,8a-octahydronaphthalene (tetracyclododecene), ethylene and 2-methyl-1,4,5,8-dimethano-1,2,3,4,4a, 5 Copolymer with 2,8,8a-octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8 Copolymer with 8,8a-octahydronaphthalene, or poly 4-
Organic materials such as methyl-1-pentene, epoxy resin, polyether sulfone, polysulfone, and polyetherimide can be used. When light is incident from the substrate direction, a transparent substrate is preferable. The thickness of the substrate 1 is not particularly limited, but is usually 0.5 to 5 m.
m, preferably 1-2 mm.

As the magneto-optical recording film 2, a magnetic thin film having a large perpendicular magnetic anisotropy is used. Such a magnetic thin film is, for example, an alloy of a transition metal element such as iron and cobalt and a rare earth element such as terbium, neodymium, dysprosium, and gadolinium, or a corrosion-resistant metal such as a transition metal element and a rare earth element and platinum or palladium. It is formed from an alloy with. The thickness of such a magneto-optical recording film 2 is not particularly limited, but is usually 100 to 600 Å.

The metal film 3 is, for example, aluminum, Al-Hf, Al-Ti, Al-Hf-Ti, Al.
An aluminum alloy such as —Cr—Ti or a nickel alloy is used. The metal film 3 has a function as a heat conduction film or a reflection film. The thickness of such a metal film 3 is not particularly limited, but is usually 100 to 500.
It is 0Å, preferably 500 to 3000Å.

The protective film 4 is a film formed by curing the coating photocurable composition. Such a protective film 4 can be formed by applying the photocurable composition for coating on the metal film 3 by, for example, a roll coating method, a spin coating method or the like, and irradiating it with light or ordinary ultraviolet rays. The thickness of the protective film 3 is not particularly limited, but is usually 1 to 20 μm.
m, preferably 5 to 15 μm.

The magneto-optical recording medium 10 of the present invention is provided between the substrate 1 and the magneto-optical recording film 2 as well as the magneto-optical recording film 2 and the outermost protective film 4 as shown in FIG. And / or Si between the magneto-optical recording film 2 and the metal film 3.
_It may have a dielectric film made of ₃ N ₄ , SiN _x (0 <x <4/3), Si, ZnS or the like. The film thickness of the dielectric film 5 provided between the substrate 1 and the magneto-optical recording film 2 is not particularly limited, but is usually 300 to 2000Å.
It is preferably 500 to 1500 Å, and the magneto-optical recording film 2
The thickness of the dielectric film 6 provided between the metal film 3 and the metal film 3 is not particularly limited, but is usually 50 to 2000 Å, preferably 5
It is 0 to 1000Å.

Since the magneto-optical recording medium of the present invention has the protective film formed by coating the photocurable composition for coating on the outermost layer, it has excellent slidability with the magnetic head and can be used for a long period of time. However, reading errors are unlikely to occur.

The magnetic recording medium of the present invention is a recording disk for performing recording / reading by using electro-magnetic conversion on a magnetic film coated and vapor-deposited with a magnetic material. For example, a substrate 11 as shown in FIG. Recording film 12 (magnetic film) and protective film 4
And have.

The material of the substrate 11 is not particularly limited, but the same substrate as that used for the magneto-optical recording medium is used. The recording film 12 is made of, for example, γ-Fe ₂ O ₃ , C.
A magnetic film made of o-Fe ₂ O ₃ or the like is used.

The protective film 4 is a film formed by curing the photocurable composition for coating. Such a protective film 4 can be formed by applying the coating photocurable composition onto the recording film 12 by, for example, a roll coating method or a spin coating method, and irradiating it with light or ordinary ultraviolet rays.

The thickness of the protective film 4 is preferably 1 to 20 μm.
m, particularly preferably 5 to 15 μm. The magnetic recording medium 20 of the present invention may have a protective film between the substrate 11 and the recording film 12 in addition to the recording film 12 and the outermost protective film 4.

Since the magnetic recording medium of the present invention has the protective film formed by curing the above-mentioned photocurable composition for coating in the outermost layer, it has excellent slidability with the magnetic head and can be used for a long period of time. However, reading errors are unlikely to occur.

[0044]

The photocurable composition for forming a film of the present invention comprises
Since it is formed from a photocurable material, a fatty acid ester, and two kinds of silicone oils having different viscosities, it is possible to form a coating film having excellent slidability and durability. Further, the film formed from the photocurable composition for film formation of the present invention is excellent in slidability and durability in a wide temperature range.

The information recording medium such as the magneto-optical recording medium and the magnetic recording medium according to the present invention has excellent slidability with respect to the magnetic head and is less likely to cause a read error even when used for a long period of time.

[0046]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. In the following examples, the viscosity is JIS
It is a value measured at 25 ° C. by a test method based on Z8803.

[0047]

[Example 1] UV curable resin [KAY manufactured by Nippon Kayaku Co., Ltd.
ARAD MD-341] 100 parts by weight, n-butyl stearate 3
Part by weight is mixed and stirred, and the viscosity is 2600 cp.
3 parts by weight of polyether-modified silicone oil [SF8410 manufactured by Toray Dow Corning Silicone Co., Ltd.] and viscosity of 270 cps polyether-modified silicone oil [SH8 manufactured by Toray Dow Corning Silicone Co., Ltd.]
400] 1 part by weight was mixed and stirred to prepare a photocurable composition for coating.

A substrate made of polycarbonate resin (thickness: 1.2 mm), a first dielectric film made of Si ₃ N ₄ (thickness: 1000 Å), and a magneto-optical recording film made of Tb-Fe-Co (thickness). S: 270Å), a second dielectric film made of Si ₃ N ₄ (thickness: 160Å), and Al ₉₆ Ti ₂ Hf.
_The photocurable composition for coating is applied by spin coating to the surface of a magneto-optical disk having a diameter of 6.4 cm, which is formed by laminating a metal film (thickness: 1500Å) composed of ₂ (atomic ratio) in this order. Then, ultraviolet rays were irradiated to form a protective film having a thickness of 10 μm.

The frictional force of the protective film of the obtained magneto-optical disk was measured at room temperature, 70 ° C and -20 ° C. The results are shown in Table 1. The frictional force was measured by rotating the magneto-optical disk at a linear velocity of 1.4 m / sec and placing a polyarylate resin (made by Unitika) on the magneto-optical disk with a load of 2 g.
AX1500) head chip.

[0050]

[Example 2] The composition of the photocurable composition for coating was 100% UV curable resin [KAYARAD MD-341 manufactured by Nippon Kayaku Co., Ltd.].
Parts by weight, 3 parts by weight of n-butyl stearate, 3 parts by weight of polyether-modified silicone oil [SF8410 manufactured by Toray Dow Corning Silicone Co., Ltd.] and a viscosity of 270c.
A protective film was formed and frictional force was measured in the same manner as in Example 1 except that 2 parts by weight of ps polyether-modified silicone oil [SH8400 manufactured by Toray Dow Corning Silicone Co., Ltd.] was used. The results are shown in Table 1.

[0051]

[Example 3] The composition of the photocurable composition for coating was 100% UV curable resin [KAYARAD MD-341, manufactured by Nippon Kayaku Co., Ltd.].
3 parts by weight, n-butyl stearate 3 parts by weight, polyether modified silicone oil [Toray Dow Corning Silicone Co., Ltd. SF8410] 3 parts by weight and polyether modified silicone oil [Toray Dow Corning Silicone Co., Ltd.] SH8400] A protective film was formed in the same manner as in Example 1 except that the amount was 3 parts by weight, and the frictional force was measured. The results are shown in Table 1.

[0052]

[Comparative Example 1] A composition of a photocurable composition for coating was prepared by using an ultraviolet curable resin [KAYARAD MD-341] manufactured by Nippon Kayaku Co., Ltd. 100.
A protective film was formed in the same manner as in Example 1 except that 3 parts by weight, 3 parts by weight of n-butyl stearate and 2 parts by weight of polyether-modified silicone oil [SH8400 manufactured by Toray Dow Corning Silicone Co., Ltd.] were used to form a protective film. The force was measured. The results are shown in Table 1.

[0053]

[Comparative Example 2] The composition of the photocurable composition for coating was 100% UV curable resin [KAYARAD MD-341 manufactured by Nippon Kayaku Co., Ltd.].
3 parts by weight of n-butyl stearate and 3 parts by weight of polyether-modified silicone oil [SF8410 manufactured by Toray Dow Corning Silicone Co., Ltd.] were used to form a protective film and rub in the same manner as in Example 1. The force was measured. The results are shown in Table 1.

[0054]

[Comparative Example 3] The composition of the photocurable composition for coating was 100% UV curable resin [KAYARAD MD-341 manufactured by Nippon Kayaku Co., Ltd.].
A protective film was formed and the frictional force was measured in the same manner as in Example 1 except that 3 parts by weight of n-butyl stearate was used. The results are shown in Table 1.

[0055]

[Comparative Example 4] The composition of the photocurable composition for coating was 100% UV curable resin [KAYARAD MD-341 manufactured by Nippon Kayaku Co., Ltd.].
A protective film was formed and frictional force was measured in the same manner as in Example 1 except that 2 parts by weight and 2 parts by weight of polyether-modified silicone oil [SF8410 manufactured by Toray Dow Corning Silicone Co., Ltd.] were used. The results are shown in Table 1.

[0056]

[Comparative Example 5] The composition of the coating photocurable composition was 100% by using an ultraviolet curable resin [KAYARAD MD-341] manufactured by Nippon Kayaku Co., Ltd.
A protective film was formed and the frictional force was measured in the same manner as in Example 1 except that 2 parts by weight and 2 parts by weight of polyether-modified silicone oil [SH8400 manufactured by Toray Dow Corning Silicone Co., Ltd.] were used. The results are shown in Table 1.

[0057]

[Table 1]

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of a magneto-optical recording medium of the present invention.

FIG. 2 is a partial cross-sectional view showing another example of the magneto-optical recording medium of the present invention.

FIG. 3 is a partial cross-sectional view showing an example of a magnetic recording medium of the present invention.

[Explanation of Codes] 1, 11 ... Substrate 2 ... Magneto-optical recording film 3 ... Metal film 4 ... Protective film 5, 6 ... Dielectric film 10 ... Magneto-optical recording medium 12 ... Recording film 20 ... Magnetic recording medium

Claims (4)

[Claims] 1. A photocurable material, (b) a fatty acid ester, (c) a silicone oil having a viscosity at 25 ° C. of 1000 cps or more and 10000 cps or less, and (d) a viscosity at 25 ° C. of 1.0 cps. A photocurable composition for coating, comprising a silicone oil having the above content and less than 1000 cps. 2. An information recording medium having a protective film formed by curing the photocurable composition according to claim 1 as an outermost layer. 3. A magneto-optical recording medium having a protective film formed by curing the photocurable composition according to claim 1 as an outermost layer. 4. A magnetic recording medium having a protective film formed by curing the photocurable composition according to claim 1 as an outermost layer.