Curable coating resin composition and information recording medium using the same

Abstract: A curable coating resin composition comprising (A) a compound having at least one polymerizable acrylic radical, methacrylic radical or vinyl radical, or a mixture thereof; (B) an organic solvent comprising not less than 40% by weight of an alcohol; (C) a compound having at least one pentavalent p with bonding represented by formula (1) and (D) a polymerization initiator. Information recording media can have cured surface coatings of the resin composition.

Description: The present invention relates to curable resin compositions for coating of surfaces of inorganic materials like glass and polymer materials like polymethylmethacrylate, polycarbonate and polyolefin. The present invention further relates to information recording media including disk media like optical disks and opto-magnetic disks, and card media like optical cards, and specifically relates to those having on at least one surface a coating of the resin composition of the invention. Usually, molded materials made of polyolefins like polyethylene and polypropylene, and polymers like polymethylmethacrylate and polycarbonate, are not only lighter in weight and superior in impact resistance in comparison with materials made of metal, glass, etc. but also have various advantages as inexpensiveness and easily fabricated. Accordingly, they are used widely in many fields of motorcars, motorcycles, domestic electrical goods, general marchandise, etc. in place of those materials. However, these molded polymers are, when compared with metals or glass, not so high in the surface hardness and not so resistant to scratch and abrasion that they are defective in being suscective to scratches on the surface. For example, since molded polymers are apt to be damaged on the surface by contacting, colliding scratching, etc. during their transportation, usages, fixation of parts thereon, etc., molded polymers are limited in their application due to the defect in surface characteristics. For the purpose of obviating the above mentioned defects of molded polymers, various methods have been proposed, and most of the methods are coating surfaces of molded polymers with layers of film composed of crosslinked curable resins. Among the film forming elements, proposed resins or resin forming components include silicone monomers or their compositions with various polymers, resin compositions of methylolmelamine with hardening components, and compositions of polyfunctional acrylic carbonic acid ester derivatives or their compositions with other polymer components. Among various polymer materials indicated above, mentions are made on polyolefins as that when a coated layer composed of a film forming element is formed on the surface of molded polyolefin like polyethylene, polypropylene, etc., the coated molded material has a defect of having a coated layer readily peelable due to the poor adherence between the coated layer and polyolefin substrate. Methods for obviating the defect on the surface of molded polyolefin include surface treatments with corona discharging, coating with primers, etc. However, the surface treatment hardly improves the adhesion between the polyolefin substrate and coated film composed of curable resins to an extent of being bearable to practical usages. Among the above mentioned film forming elements, silicone film forming elements are expensive and are not preferred economically. Among the aforesaid film forming elements, various types of compounds belonging to polyfunctional acrylic carbonic acid ester derivatives are proposed. For example, such types of compounds as poly(meth)acrylates of alkanepolyols, poly (meth)acrylates of polyoxyalkyleneglycols, poly (meth)acrylates of aromatic (phenolic) polyhydroxyl compounds, etc. are proposed for usage in film forming elements. In this specification, acrylates and methacrylates represent (meth)acrylates in the abbreviation form and hereinafter the same abbreviations are used. When coated films are formed on molded polyolefin substrates by the sole use of these polyfunctional acrylic carbonic acid ester derivatives as film forming elements, the coated resin shows shortcomings in the curing characteristics including in the curing speed of coated resin under atmosphere, and in the cured film properties including surface hardness, resistance to scratching, resistance to abrasion, flexibility, surface luster, resistance to heat, resistance to water, resistance to solvent, resistance to weathering, adhesion to substrate, etc., which made the coated film unsatisfactory for practical industrial usages. Combinations of more than two kinds of compound belonging to the film forming element were put to the test to obviate these defects, however, the trial created new difficulties in coating surfaces of polyolefin substrates, though the drawbacks of sole usage were remedied to same extent. In these years, in accordance with the progress of informative society, needs for large volume information recording media have increased. One of optical recording media (opto-magnetic recording media) possesses advantages of being able to rewrite data, a large capacity, portable, capable of non-contact reading out and resistant to scratch or dust. Accordingly, applications of optical recording media have being expanded not only in auxiliary memories of computers but also in memories for various communication equipments like telephones, facsimiles, etc. as well as media for audio equipments. Previously, the opto-magnetic recording had a disadvantage of being unable to overwrite, and for the purpose of overcoming the defect, so called magnetic modulation recording has become widely employed these years in which the magnetic field for recording is reversed in conformity with recording signals during the recording. In case of conducting a high frequency recording with the recording method, the floating head system is employed so as a magnet head will be able to follow the vibrating surface of medium rotating in high speed. As for the motion of a floating type head, the head is in a floating state while the medium keeps rotating, but is in a state of contact with the medium while the medium is under stop or at the start of rotation, and the phenomenon is referred to as CSS (Contact Start and Stop). Under the CSS motion, friction between the medium and head is produced, and repeated friction has a possibility of causing breakdown of medium or breaking of head (head-crush), which deteriorates the credibility of equipment so remarkably. Accordingly, magnetic heads and recording media being resistant to friction at Contact Start and Stop (CSS resistant) are required, and surface coatings for recording media are especially desired to be superior in resistant to friction. For satisfying the requests, various methods of coating with crosslinking curable type resins information recording media like opto-magnetic media on the surface of recording layer (over-coat) or the surface opposite to recording layer (top-coat) have been proposed. For top-coats on the surface opposite to the recording layer of information recording media, superior antistatic characteristics are desired in addition to the above-mentioned properties for coated films. It is known that addition of surface active agents to a resin composition mainly composed of polyfunctional acrylic monomers increases the antistatic effects. However, since the surfactants added heretofore show a tendency to come out as a resinous liquid on the surface of the cured resin ("breed out"), they are not suitable for use in top-coats of optical disks. Further, a satisfactory antistatic property causes problems such as an opaqueness in coated films and a decrease in adhesion to substrates. Surface coatings highly resistant to abrasion used for overcoats or top-coats of information recording media are generally hard and exhibit inferior adhesion to other layers. In particular, since opto-magnetic disks contain reflecting layers composed of metals like aluminum and nickel alloys, or thermoconductive layers composed of aluminum alloys, adhesion between these metallic layers and the abrasion resistant surface coating is an important problem. It is an object of the present invention to solve problems of the aforementioned prior art, and to provide curable resin compositions for coating which exhibit superior curing under atmosphere and adhesion to molded resins, have satisfactory adhesion without heat treatment, and supply surface hardness, resistance to scratch, resistance to scratch, resistance to abrasion, surface luster, transparency and antistatic properties. Another object of the present invention is to provide information recording media in which the coating compositions exhibit superior adhesion to resins or metals, have satisfactory adhesion without heat treatment, and supply surface hardness, resistance to scratch, antistatic properties and resistance to CSS. A further object of the present invention is to provide information recording media having a top-coat superior in antistatic properties. A still further object of the present invention is to provide information recording media having a surface layer superior in the above mentioned properties as well as having an inner layer superior in adhesion to the surface layer and to another layer. The present invention provides a curable coating resin composition consisting essentially of (A) 100 parts by weight of at least one urethane (meth)acrylate; (B) 5 to 1,500 parts by weight of an organic solvent comprising not less than 40% by weight of an alcohol; (C) 0.005 to 25 parts by weight of a compound having at least one pentavalent P with bonding represented by formula (1) and (D) 0.01 to 20 parts by weight of a polymerization initiator. The present invention provides an information recording medium having a recording portion and/or a reproducing portion on a substrate, and a cured surface layer of a composition as defined above. The information recording medium may be a magnetic disk, or an optical disk capable of recording with laser light, or an opto-magnetic disk capable of rewriting with magnetic signals from a floated magnetic head while said recording portion and/or a reproducing portion is irradiated with continuous light. Preferably, said substrate is a disk made of a metal, glass or plastics material. The optical recording medium may be capable of reversing the direction of an applied magnetic field in accordance with recording signals during recording. Brief Description of the Drawings Fig. 1, Fig. 2, Fig. 3 and Fig. 4 are schematic diagrams showing constructions of the optical disk. The meanings of the reference numerals are explained below. As to the alcoholic organic solvent (B) used for compositions of the present invention, the solvent is exemplified by methanol, propanol, butanol, isobutylalcohol, isopentylalcohol, hexanol, diacetonealcohol, 2-methoxy ethanol and 2-ethoxy ethanol. These alcohols may be used in mixtures of more than two kinds. The alcoholic solvent may be mixed with other organic solvents. These organic solvents other than alcoholic and capable of mixing therewith are exemplified by hydrocarbons like benzene, toluene, xylene, cumene, hexane, ethylbenzene, heptane, octane, petroleum ether, ligroin, cyclohexane and methyl cyclohexane; halogenated hydrocarbons like methylene chloride, chloroform, carbon tetrachloride, bromoform, trichlene, ethylene dichloride, perchlene, ethane trichloride, tetrachloro ethane, propylene dichloride, chlorobenzene and bromobenzene; ketones like acetone, methyl ethyl ketone and methyl isobutyl ketone; and esters like methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, benzyl acetate, methyl benzoate and ethyl benzoate. These organic solvents may be used in mixtures of more than two kinds. The amount of the organic solvent (B) is 5 ∼ 1500, preferably 10 ∼ 1000 parts by weight per 100 parts by weight of component (A). In the organic solvent, the alcohol is contained in an amount of 40% by weight or more, more preferably 60% by weight or more. The reason is that an organic solvent containing 40% by weight or more of an alcohol prevents corrosion of the materials like polycarbonate, poly(meth)acrylates, polyolefins to be coated with the resin compositions of the present invention, and prevents the surface from turning opaque and generating cracks. This gives satisfactory films. The compound (C) used for the present invention having at least one pentavalent P with bonding (phosphoryl bonding) represented by formula (1) may, for example, be of formula (2) in which R, R 1 and R 2 each are H, C 1 -C 24 alkyl (optionally branched), aryl or aralkyl, provided that at least one of R, R 1 and R 2 is not H. When R, R 1 or R 2 is H, the compound having formula (2) may form a salt with an amino compound containing at least one primary, secondary or tertiary amino group. The compound represented by formula (2) may further contain at least one polymerizable unsaturated group. The amino compounds preferably contain C 1 -C 20 alkyl (optionally branched), aryl, oxyalkylene, (meth) acrylol alkylene, and secondary and tertiary amines are specifically preferred. Examples of compounds of formula (2) follow, in which R 3 denotes H or CH 3 . Acidphosphoxyethyl (meth)acrylate, (meth)acryloyloxyethyl acidphosphate monoethanolamine half salt and dialkyl(hydroxyalkyl)amidophosphate are used preferably. The compound represented by formula (2) is contained per 100 parts by weight of compound (A) in an amount of 0.005 ∼ 25 parts by weight, preferably 0.01 ∼ 20 parts by weight, more preferably 0.02 ∼ 18 parts by weight. This range provides the coated film with satisfactory antistatic properties and transparency. In order to form a film on the surface of a molded material composed of polyolefin by coating a composition of the invention and causing the composition to crosslink and cure, it is necessary that a polymerization initiator is added to the composition. As to the curing methods, curing by ultra violet rays and curing by heat are usually employed. For ultra violet curing, suitable polymerization initiators are photosensitizers, which are exemplified by benzoins or their ethers like benzoin, benzoin methylether, benzoin ethylether, benzoin isopropylether and benzoin isobutylether; benzophenone-type compounds like benzophenone, p-chlorobenzophenone and p-methoxybenzophenone; benzil type compounds like benzil, benzil dimethylketal and benzil ethyl ketal; and hydroxyalkyl phenyl ketone type compounds like 1-(4-isopropylphenyl)-2-hydroxy-2-methyl-1-propanone, 1-phenyl-2-hydroxy-2-methyl-1-propanone and 1-(4-tert-butylphenyl)-2-hydroxy-2-methyl-1 propanone. For curing by heat, radical initiators are added, which are exemplified by azo compounds like azobisisobutyionitrile; and peroxides like benzoyl peroxide, lauryl peroxide, di tert-butyl peroxide, dicumyl peroxide and cumene hydropeoxide. Further, to curable coating resin compositions of the present invention there may be added both photosensitizers and radical initiators, which enables simultaneous ultra violet curing and thermal curing, ultra violet curing first and then thermal curing, or thermal curing first and then ultra violet curing. The amount of polymerization initiator to be added per 100 parts by weight of compound (A) is 0.01 ∼ 20 parts by weight, preferably 0.1 ∼ 10 parts by weight. This range provides favorable curing characteristics, and cured films have superior surface hardness, resistance to scratch, resistance to abrasion, resistance to solvents and adhesion to substrates. Curable coating resin compositions of the present invention may be composed only of the afore-mentioned essential components, however, other additives are incorporated optionally and they include polymerization inhibitors, transparent fillers, solvents, ultra violet ray absorbers, stabilizers like antioxidants, optical whiteners, (reactive) oligomers like methyl (meth)acrylate, polyurethane acrylates, polyester acrylates, and polymers like polymethylmethacrylate. These additives are added in an appropriate amount. Curable coating resin compositions of the present invention may be incorporated upon necessary with fine powdery inorganic fillers of an amount of maintaining the transparency of cured films obtained therefrom. The fine powderly inorganic filler may have any average particle size proper for powder, and usually has a size of 1 nm to 10 µm, preferably of 1.5 nm to 1 µm. For the purpose of maintaining the transparency of outer coated film, the fine powdery inorganic filler has usually a refractive index of 1.40 to 1.60, preferably of 1.42 to 1.58. The fine powdery inorganic filler is exemplified by glass powder, mica, glass beads, glass flake, diatomaceous earth, anhydrous silica, hydrated silica, silica, silica sand, quartz, kaolinite, montmorillonite, sericite, talc, chlorite, pottery stone, feldspar. Fine powdery inorganic fillers may be surface treated with an alkyl carbonic acid salt, a silane coupling agent, a titanium coupling agent, Cl 2 Si(CH 3 ) 2 and an alcohol, and the treated materials are used similarly. Aqueous or alcoholic suspensions of the fine powdery inorganic fillers like colloidal silica, methanol silicasol, ethanol silicasol, isopropanol silicasol may be used. Among these fine powdery inorganic fillers, fine powdery silica is most preferred since the incorporation thereof provides outer coating films with enhanced surface hardness, resistant to scratch and resistant to abrasion without deteriorating the transparency and surface luster. Amounts of the fine powdery inorganic fillers to be added per 100 parts by weight of the aforementioned compound (A) or the mixtures thereof are 0.5 ∼ 200 parts by weight, preferably 0.5 ∼ 100 parts by weight, more preferably 1.0 ∼ 50 parts by weight. The reason is that the coated film is improved in surface hardness, resistance to scratch and resistance to abrasion without deterioration of the transparency and surface luster. Curable coating resin compositions of the present invention may be incorporated upon necessary with solvents for improving the coating workability in addition to the afore-mentioned essential organic solvent so as to maintain the composition in a liquid state or a suspension state. The added solvent may be used for liquefying or suspension-liquefying of the composition, for adjusting viscosity of the composition or for providing improved wetting to molded materials. Solvents used for the purpose are exemplified by hydrocarbons like benzene, toluene, xylene, cumene, ethylbenzene, hexane, heptane, octane, petroleum ether, ligroin, cyclohexane, methylcyclohexane; halogenated hydrocarbons like methylene chloride, chloroform, carbon tetrachloride, bromoform, trichlene, ethylenedichloride, perchlene, trichloro ethane, tetrachloro ethane, propylene dichloride, monochlonobenzene, monobromo benzene alcohols like methanol, ethanol, isopropanol, butanol, pentanol, hexanol, cyclohexanol, ethylene glycol, propylene glycol, glycerin, ethylene glycol monomethylether, diethylene glycol; ketones, like acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; ethers like diethyl ether, dipropyl ether, butyl ethyl ether, dibutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; nitriles like acetonitrite, propionitrile, capronitrile; esters like methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, pentyl acetate, methyl benzoate, ethyl benzoate. Amounts of these organic solvents to be added per 100 parts by weight of compound (A) or the mixture thereof are 5 ∼ 1000 parts by weight, preferably 5 ∼ 300 parts by weight, more preferably 5 ∼ 100 parts by weight. The range provides to the coating composition of the present invention with favorable coating workability and to coated films with improved transparency and flatness. From compositions of the present invention containing the aforementioned essential components and various other optional additives including inorganic and organic fillers, solvents and stabilizers are prepared compositions in a solution state or a suspension state by the method described below. The above-mentioned raw material mixture is compounded, kneaded and mixed by the use of such equipments as rolls, Bumbury's mixers, ball mills, attritor, whipper, aux-mixer, dissolver, homogenizer, colloid mill, sand mill, vibrating mill, mixer, mixing-agitating tank, etc. to obtain compositions being homogeneously dissolved or dispersed. Methods for coating the liquid state composition or suspended state composition on the surface of molded polyolefin are those conventional ones including brush, spray, dip, barcoat, rollcoater, spincoater and gelcoater methods, and coated compositions are dried by natural drying, forced drying with carrier gas, thermal drying in infra red ray furnaces, far infrared rays furnaces, hot wind furnaces. A laminated molded material is available by the curing treatment of the outer coated layer of molded material formed by coating the curable coating resin composition of the present invention. As to curing of the dried composition to form films, polymerizaticn-crosslinking-curing methods by irradiation of light or ultra violet rays or by heating are exemplified. Among the methods, the optical curing is conducted usually at a temperature of - 10 ∼ 150°C, preferably 5 ∼ 130°C under irradiation of light for 1 second to 1 hour, preferably for 1 second to 10 minutes. The thermal curing method is conducted usually at a temperature of - 10 ∼ 150°C, preferably 5 ∼ 130°C with a necessary length of time usually of 0.05 ∼ 10 hours, preferably 0.1 ∼ 8 hours. For substrate materials constituting the laminated molded material, those usable include inorganic materials like glass, aluminum; acrylic resins like polymethylmethacrylate, polymethacrylate; polycarbonate; polystyrene; copolymers of ethylene with cyclic olefin as disclosed in U,S. Patent NO.4614778 exemplified by a copolymer of ethylene with 1,4,5,8 -dimethano-1,2,3,4,4a,5,8,8a - octahydronaphthalene (tetracyclo dodecene), a copolymer of ethylene with 2-methyl- 1,4,5,8 - dimethano- 1,2,3,4,4a,5,8,8a -octahydronaphthalene(methyl tetracyclo dodecene) and a copolymer of ethylene with 2-ethyl- 1,4,5,8 -dimethano- 1,2,3,4,4a,5,8,8a - octahydronaphihalene; poly 4-methyl-a-pentene; epoxy resins; polyether sulfones; polysulfons; polyether imido; those disclosed in Japanese Application Kokai (laid open) 60-26024 like hydrogenated ring-opening polymers of tetra cyclododecenes, or norbornenes; polymer alloys obtained by mixing of same polymers or different polymers like those from polycarbonate and polystyrene. Forms of substrate constituting the laminated molded material are any of film sheet, plate or others. When the surface of molded substrate is coated with the curable coating resin composition of the present invention, a resin surface of the molded substrate may be subjected to washing with various solvents, washing with aqueous alkali solutions, washing with surfactants, ultrasonic washing, electrolytic washing, blast treatment, sand blast treatment, etching with acid or alkali, frame treatment, corona discharge treatment, arc discharge treatment, glow discharge treatment, plasma discharge treatment and chemical treatment. when the surface of molded substrate is to be laminated with a coated film of the molded substrate is to be laminated with a coated film of the curable coating resin composition of the present invention, an intermediate adhesive layer composed of a primer may be placed between the substrate and the coated film for the purpose of improving the adhesion between the both. Primers used usually for the purpose are modified polyolefins having grafted α,β - unsaturated carboxylic acids, anhydrides thereof, esters thereof or derivatives thereof. Thus, the composition of the present invention is coated on the surface of substrate subjected optionally to surface treatments or primer treatments, and cured in accordance with the method mentioned above. The information recording medium of the invention has at least one surface coated with the curable coating resin composition of the invention, which thus constitutes an over-coat and/or a top-coat of the recording medium. The medium may have a layer of resin inside the surface layer formed with the curable coating resin composition for the purpose of improving adhesion of the surface layer and/or another layer. A preferable embodiment will be explained hereunder by reference to drawings. Fig. 1 is a schematic diagram showing the constitution of optical disk 1. The optical disk 1 is composed of substrate 2, recording pit 3 for recording or reproduction, reflecting layer 4, surface layer 6 as an over-coat and top-coat 8 on the other side of substrate 2 for protection. The reflecting layer 4 serves as a protective layer and an enhancing layer, and multi-layered constructions may intensify the reflecting ratio. Fig. 2 is a schematic diagram showing the constitution of opto-magnetic disk 10. The opto-magnetic disk 10 is composed of substrate 2, recording layer 9 for recording or reproduction, surface layer 6 as an over-coat aria top-coat 8 on the other side of substrate 2 for protection. Fig. 3 is a schematic diagram showing constitution of optical disk 11. The optical disk 11 has transparent substrate 2, recording pit 3 for recording or reproduction, reflecting layer 4 and protective layer 7 as a over-coat. The protective layer 7 is composed of at least two layers including inner layer 5 of an adhesive resin layer and surface layer 6. Top-coat protects the other side of substrate 2. Fig. 4 is a schematic diagram showing constitution of another opto-magnetic disk 12. The opto-magnetic disk 12 has substrate 2, recording layer 9 for recording or reproduction and protective layer 7 as a over-coat. Protective layer 7 is composed of at least two layers including inner layer 5 of an adhesive resin layer and surface layer 6 being coated with a curable coating resin composition of the present invention. Top-coat 8 protects the other side of substrate 2. In the present invention, at least one side of the outer surface of information recording medium is characteristically coated with the curable coating resin composition of the present invention. The coated surface is allowable to be either surface (overcoat) layer 6 or top-coat 8. For enhancing resistance to CSS, the information recording medium is preferably intended to reduce contact area between the head and medium surface and to ease floating of the head by means of texture treatments of surface with a file or inclusion of fine particles in the surface layer. In the information recording medium of the present invention, substrate 2 may be molded in any form including film sheet, card, plate or round plate. Typically, it is formed in 3.5 inch disk, 5.25 inch disk, 8 inch disk, 64mm diameter disk, etc., however, optical cards, floptical disks, etc. may be included. When at least one side of the surface is coated with the aforementioned composition, at least one side of the surface or the surface of recording layer or reflecting layer to be coated is optionally treated as mentioned previously or treated with a primer prior to the coating. Thereafter, the surface is coated with the composition and then cured. The recording and/or reproducing portion constituting the present invention is a magnetic layer in magnetic recording media, and is a plastic portion or SiO 2 layer forming a recording pit in optical recording media. In magnetic recording media, the recording layer is exemplified as following by a opto-magnetic recording layer having an anisotropy recording layer directed vertically to the layer surface. The recording layer is preferably composed of either (i) at least one element selected from 3d transition metals, and (iii) at least one element selected from rare earth elements; or (i) at least one element selected from 3d transition metals, and (ii) a corrosion resistant: metal, and (iii) at least one element selected from rare earth elements. (i) As to 3d transition metals, Fe, Co, Ti, V, Cr, Mn, Ni, Cu, Zn are mentioned, in which Fe and/or Co are preferred. (ii) Corrosion resistant metals can enhance antioxidation properties of the opto-magnetic recording layer by the incorporation. These corrosion resistant metals include Pt, Pd, Ti, Zr, Ta, Mo, Nb, Hf, Cr, in which Pt, Pd and Ti are preferred, and Pt and/or Pd are more preferred. (iii) As to rare earth metals, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, La, Ce, Pr, Nd, Pm, Sm, Eu are mentioned, in which Gd, Tb, Dy, Ho, Nd, Sm, Pr are preferred. In opto-magnetic recording layer, (i) 3d transition metal of an amount of 30-85, preferably 40-70% by atom, (ii) corrosion resistant metal of up to 30, preferably 5-25% by atom, and (iii) rare earth metal of 5-50, preferably 25-45% by atom, exist preferably. For a phase-transition type recording layer, it is composed of, for example, with a thin film of Te-prime alloy, Se-prime alloy, Te-Ge-Sb alloy, In-Sb-Te alloy, Se-Ge-Cr alloy, Te-Ge-Zn alloy. Recording layers capable of recording only once (additional writing type recording layer) have a film of Te-C-H, Te-Cr-C-H or Te-Ag alloy. For these recording layers, organic coloring materials like polymethine compounds, cyanin compounds may be used also for the recording layer. In the recording media of the present invention, in addition to the substrate, recording and/or reproduction portions, such other layers may be installed optionally between the surface coating and recording and/or reproduction portion a reflecting layer of Al, Ni alloys; a protective layer composed of inorganic compounds likes Si 3 N 4 , SiNx(o<x<4/3), Al, Au, Zn Se, ZnS, Si, SiO 2 ·ZrO 2 , Cr, CdS; an enhancing layer; and a protective layer composed of organic compounds like ultra violet rays radiation curable acrylic resins. Further, an enhancing layer composed of inorganic compounds like Si 3 N 4 , SiNx(o<x<4/3), Al, Au, Zn Se, ZnS, Si, SiO 2 ·ZrO 2 , Cr, CdS may be installed between the substrate and recording and/or reproducing portion. When an adhesive resin layer is placed inside of the surface layer composed of the curable coating resin composition, the resin layer must adhere to another resin or metal layers (Al, Al alloy, Ni alloy,etc). In the present invention, the resin has preferably a high adhesion to Al of not to be peeled by the cross-cut test. Resins of highly adhesive to metals includes acrylate resins, methacrylate resins, polyimido resins, epoxy resins. Commercially available ultra violet rays radiation curable resins like DAICURE CLEAR SD-101, DAICURE CLEAR SD-301 (Product names of Dainippon Ink and Chemicals Inc.) are usable, though other resins adhesive to metals may be used. When protective layers 7 are composed of a surface layer 6 and an inner layer 5, the thickness of surface layer 6 is 0.01 ∼ 20 µm, preferably 0.02 ∼ 20 µm, and that of inner layer 5 is 0.01 ∼ 30 µm, preferably 0.02 ∼ 20 µm. The protective layer 7 is not necessarily composed of two layers but may have other layers like antistatic layers, primer layers, etc. For the primer layers, modified polyolefins having grafted α,β-unsaturated carboxylic acids, anhydrids thereof, esters thereof or derivatives thereof may usually employed. For forming on a substrate a protective layer 7 compose of at least two layes, the surface of recording layer or reflecting layer to be coated is subjected to surface treatments like washing with various solvents, washing with aqueous alkali solutions, washing with surfactants, ultrasonic washing, electrolytic washing, blast treatment, sand blast treatment, etching with acid or alkali, frame treatment, corona discharge treatment, arc discharge treatment, glow discharge treatment, plasma discharge treatment and chemical treatment. On the treated surface, an adhesive resin is coated to form the inner layer, and then the surface layer is formed by coating and curing. The composition of the present invention comprises the specified monomer component, the specified solvent, the specified phosphine compound and a polymerization initiator. The composition shows satisfactory curing under atmosphere, superior adhesion to molded materials like resin, etc. without heat treatments when coated on the surface of molded inorganic or organic materials and cured. The cured coating is superior in surface hardness, resistance to scratch, resistance to abrasion, surface luster, transparency and antistatic properties. The information recording medium of the present invention has a surface coating which is superior in curing under atmosphere, adheres strongly to resins, metals, glass, etc., shows the adhesion without heat treatments, and superior in surface hardness, resistance to scratch, resistance to abrasion and antistatic properties. The medium is useful for magnetic recording media, optical recording media and opto-magnetic recording media. Further, the information recording media having protective layer on the surface which is composed of at least two layers has an inner surface layer of satisfactory adhesion to other layers of resin, metal, etc., and an outer surface layer of superior in surface hardness, resistance to scratch, resistance to abrasion and antistatic properties. Example The present invention will be explained in detail hereunder by reference to Examples, however, they never restrict the present invention. The evaluation was conducted with the under-mentioned methods. (1) Haze Measured in accordance with the method of ASTM D-1003. (2) Pencil Hardness Measured in accordance with the method of JIS K-5651. (3) Adherence Tested with a cross-cut test in accordance with the method JIS K-5400-1979. The test result was indicated with numbers of cross-cut left adhered in 100 cuts. (4) Surface Resistivity Measured in accordance with the method of ASTM D-257-78. (5) Resistance to Humidity A specimen was stored for 100 hours in a chamber kept at 60°C and 85% relative humidity. After the storage, the specimen was allowed to cool to room temperature, and the measurements for haze, adherence and surface resistivity were conducted. (Example 1) Into a 1 liter reaction vessel were charged 223g (1 mol eq.) of isophorone diisocyanate, 0.05g of dibutyltin laureate and 300g of trimethylolpropane triacrylate. To the charge was added dropwisely from a dropping funnel during 30 minutes 232g (2 mol eq.) of 2-hydroxyethyl acrylate and allowed to react at 85°C under nitrogen gas atmosphere. After continuing the reaction for 1 hour, a viscous urethane-acrylate compound (A) was obtained. Into a vessel equipped with an agitator were charged 350g of urethane-acrylate (A), 10g of benzoin ethyl ether, 150g of toluene, 150g of ethylacetate, 350g of isobutylalcohol and 3g of didecyl-di (2-hydroxyethyl) amidophosphate, and the charge was mixed to become a homogeneous mixture named as Sample 1. On the cleaned surface of a molded transparent amorphous polyolefin (ethylene-tetracyclododecene random copolymer) plate was dropped about 5cc of the above-stated coating composition (Sample 1), and was coated with a spincoater. Being kept at room temperature for 5 minutes, the coated composition was cured with radiation energy of about 28000 mJ/cm 2 using a UV radiation equipment. Physical properties of the obtained cured film are shown in Table 1. (Example 2) Into a 1 liter reaction vessel were charged 223g (1 mol eq.) of isophorone diisocyanate, 0.05g of dibutyltin laureate and 300g of trimethylolpropane triacrylate. To the charge was added dropwisely from a dropping funnel during 30 minutes 600g (2 mol eq.) of pentaerythritoltriacrylate and allowed to react at 85°C under nitrogen gas atmosphere. After continuing the reaction for 1 hour, a viscous urethane-acrylate compound (B) was obtained. Into a vessel equipped with an agitator were charged 350g of urethane-acrylate (B), 10g of diethoxyacetophenone, 150g of xylene, 150g of butylacetate, 350g of isopropylalcohol and 1.4g of methacryloyloxyethyl acidphosphate, and the charge was mixed to become a homogeneous mixture named as Sample 2. A cured film of Sample 2 prepared in the same manner as Example 1 was evaluated for its physical properties. The result is shown in Table 1. (Comparative Example 1) Into a vessel equipped with an agitator were charged 180g of dipentaerythritol hexa-acrylate, 20g of hydroxyethyl acrylate, 10g of 1-phenyl-2-hydroxy-2-methylpropane-1-one, 100g of toluene, 150g of xylene, 100g of diacetonealcohol, 450g of isopropylalcohol and 18g of acidphosphoxyethyl acrylate, and the charge was mixed to become a homogenous mixture named as Comparative Sample 1. A cured film of Comparative Sample 1 prepared in the same manner as Example 1 was evaluated for its physical properties. the result is shown in Table 1. (Comparative Example 2) Into a vessel equipped with an agitator were charged 330g of ethyleneoxide-modified bisphenol-A diacrylate (BP-4EA; Kyoeisha Yushikagaku Co.), 20g of N-vinylpyrrolidone, 100g of toluene, 100g of ethylacetate, 350g of isobutylalcohol, 100g of 2-methoxymethanol, 2g of t-butylhydroperoxide, 3g of 1-hydroxycyclohexyl phenyl ketone and 15g of acidphosphoxypropyl methacrylate, and the charge was mixed to become a homogenous mixture named as Comparative Sample 2. A cured film of Comparative Sample 2 prepared in the same manner as Example 1 was evaluated for its physical properties. The result is shown in Table 1. (Comparative Example 3) Into a vessel equipped with an agitator were charged 350g of urethane-acrylate compound (A) prepared by the method of Example 1, 10 g of benzoinethylether, 150 g of toluene, 150g of ethylacetate and 350g of isobutylalcohol, and the charge was mixed to become a homogenous mixture named as Comparative Sample 3. A cured film of Comparative Sample 3 prepared in the same manner as Example 1 was evaluated for its physical properties. The result is shown in Table 1. (Examples 3 ∼ 6) Samples were prepared in the same manner as Example 1 with the exception that the compound mentioned in Table 2 was used in place of didecyl-di(2-hydroxyethyl) amidophosphate, and were evaluated. The result is shown in Table 2. (Example 7) On a transparent amorphous polyolefin (ethylene-tetracyclododecene random copolymer) substrate disc of 3.5 inch diameter having grooves of 6 µm pitch, a thin film was formed by the spattering method. The film formed was; Silicon nitride 0.13 µm/ TbfeCo 0.025 µm/Silicon nitride 0.03 µm/Al alloy 0.15 µm. On the film, the coating composition of Examples 1-6 was coated with a spincoater to obtain a coated composition having 1 µm thickness. The coated composition was allowed to stand at room temperature for 5 minutes, and was cured by irradiating 28000 mJ/cm 2 UV radiation. The obtained disk was evaluated for CSS resistance under one following conditions. CSS Experiment conditions; Floating length = 0.2 µm Rotation of disk = 3600 rpm Measuring position = at the point of disk radius 25 mm Repeat (Rotation start, stop) cycle = 10 sec. Experiment circumstances = clean room of class 1000, 23°C, 50% RH. CSS Experiment result; No change was found on the disk and head after 30000 times CSS. (Example 8) On a transparent amorphous polyolefin (ethylene-tetracyclododecene random copolymer) substrate disc of 3.5 inch diameter having grooves of 6 µm pitch, a thin film was formed by the spattering method. The film formed was; Silicon nitride 0.13 µm/ TbFeCo 0.025 µm/Silicon nitride 0.03 µm/Al alloy 0.15 µm. On the film, a UV radiation curable resin DAICURE CLEAR SD-101 (Product name of Dainippon Ink Kagaku Co.) was coated with a spincoat method to have a coating of 1.5 µm thickness. The coated resin was cured by irradiating about 28000 mJ/cm 2 UV radiation. On the cured resin film the coating composition of Examples 1-6 was coated with a spincoater to obtain a coated composition having 1 µm thickness. The coated composition was allowed to stand at room temperature for 5 minutes, and was cured by irradiating about 28000 mJ/cm 2 UV radiation. The coated surface of the disk was subjected to a texture treatment in the circumference direction by use of a wrapping tape (A 8000; Fuji Film Co.). The treated disk was evaluated for CSS resistance under the following conditions. CSS Experiment conditions; Floating length = 0.2 µm Rotation of disk = 3600 rpm Measuring position = at the point of disk radius 25 mm Repeat (Rotation start, stop) cycle = 10 sec. Experiment circumstances = clean room of class 1000, 23°C, 50% RH CSS Experiment result No change was found on the disk and head after 1 x 10 6 times CSS.

Claims: A curable coating resin composition consisting essentially of (A) 100 parts by weight of at least one urethane (meth)acrylate; (B) 5 to 1,500 parts by weight of an organic solvent comprising not less than 40% by weight of an alcohol; (C) 0.005 to 25 parts by weight of a compound having at least one pentavalent P with bonding represented by formula (1) and (D) 0.01 to 20 parts by weight of a polymerization initiator. A composition according to claim 1, wherein said pentavalent P compound (C) is of formula (2) wherein R, R 1 and R 2 are each H, C 1 -C 24 alkyl, aryl or aralkyl; provided that at least one of R, R 1 and R 2 is not H. A composition according to claim 2 wherein R, R 1 or R 2 is H and the pentavalent P compound of formula (2) is in the form of a salt with an amino compound containing at least one primary, secondary or tertiary amino group. A composition according to claim 1, wherein (C) is at least one of an acidphosphoxyethyl (meth)acrylate, a (meth)acryloyloxyethyl acidphosphate monoethanolamine salt and a dialkyl(hydroxyalkyl) amidophosphate. An information recording medium comprising a recording portion and/or a reproducing portion on a substrate, and a cured surface layer of a composition according to any one of the preceding claims. A medium according to claim 5, in which said cured surface layer is located on the same or opposite side as the recording portion and/or reproducing portion. A medium according to claim 5 or 6 which comprises a protective layer of at least two layers, which layers are a said cured surface layer and an inner layer of a resin adhesive which adheres to the said cured surface layer and/or another layer of the medium. A medium according to claim 7, in which said another layer is a layer comprising at least one of a metal, a semi-metal and an alloy thereof. A medium according to any one of claims 5 to 8 which is a magnetic disk. A medium according to any one of claims 5 to 8 which is an optical disk capable of laser light recording.

Inventors: HATTORI YUKARI, INAGAKI HAJIME, KURISU MASAYOSHI, MIYAMOTO KAZUYUKI, MURAKOSHI NORIYUKI, SAITO TSUTOMU, TOKITA SUGURU, UTAKA KOJI, HATTORI, YUKARI, INAGAKI,HAJIME, KURISU, MASAYOSHI, MIYAMOTO, KAZUYUKI, MURAKOSHI, NORIYUKI, SAITO, TSUTOMU, TOKITA, SUGURU, UTAKA, KOJI, HATTORI, YUKARI, MITSUI PETROCHEM.IND.LTD.,, INAGAKI,HAJIME, MITSUI PETROCHEMICAL IND.LTD., KURISU, MASAYOSHI, MITSUI PETROCHEMICAL IND.LTD., MIYAMOTO, KAZUYUKI, MITSUI PETROCHEM.IND.LTD.,, Murakoshi, Noriyuki, c/o CHEMITECH INC., Saito, Tsutomu, c/o CHEMITECH INC., TOKITA, SUGURU C/O MITSUI PETROCHEM.IND.LTD.,, Utaka, Koji, c/o Chemitech Inc.
Applicants: MITSUI PETROCHEMICAL IND, MITSUI PETROCHEMICAL INDUSTRIES, LTD.
Application year: 1992
Main classification: C09D4
IPC codes: G11B7, C09D4, G11B11