JPH06180859A - Coating material for optical disk and optical disk excellent in scratching resistance and antistatic property - Google Patents

Abstract

PURPOSE:To provide an antistatic UV-curing coating material for optical disks excellent in hardening property, transparency, scratching resistance, antistatic property, durability, and stability. CONSTITUTION:This coating material for optical disks consists of the following components (A)-(F). (A) Copolymers consisting of unsatd. compd. having quaternary ammonium salt groups and compd. expressed by general formula CH2=C (R<5>)COO(AO)mR<6>(R<5> is H or CH3, R<3> is H or a 1-18C hydrocarbon group, m is an integer 0 to 500, A is a 2-4C alkylene group). (B) (Meth)acrylate having three or more functional groups. (C) (Meth)acrylate having two functional groups. (D) Unifunctional (meth)acrylate. (E) (Meth)acrylate having hydroxyl groups. (F) Photopolymn. initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic UV-curable coating material for an optical disk which is excellent in curability, transparency, scratch resistance, antistatic property, durability and stability, and an optical disk coated with this coating material. Regarding

[0002]

2. Description of the Related Art At present, glass, polycarbonate resin, polymethylmethacrylate resin, epoxy resin and the like are used as base materials for industrial and consumer optical discs.

Among them, a plastic-based optical disk has a characteristic that it is easily charged, and suction of dust and an increase in error rate due to adhesion are obstacles to product use. That is, the information recorded on the optical disk is read by a laser, but at that time, particles such as dust on the surface of the disk become a shield on the optical path and obstruct the reading.

As a method for eliminating this obstacle, 100 μm to 180 μm is used for defocusing particles such as dust on the reading surface, so-called pickup side.
Applying a μm overcoat, applying a hard coat material to prevent scratches when physically wiping off particles such as dust, and applying an antistatic coat to prevent adhesion of particles such as dust And the like.

However, in the method of applying the overcoat, a soft material such as the silicone elastomer described in US Pat. No. 4,101,907 is used as the material of the light-transmitting protective overcoat layer. , This coating material is sticky and easy to absorb and retain dust,
There are problems that the curing temperature is high and the curing time is long.

Further, inorganic hard materials such as SiO ₂ and SiO have problems such as deterioration of optical characteristics due to a large film thickness in a portion where moisture permeability, adhesiveness, and refractive index change.

Among the methods of applying the hard coat material, the solvent type hard coat material has a problem of shrinkage due to the dissipation of the solvent. In addition to the wide selection of base materials and the short processing time, UV-curable coating materials are excellent in terms of chemical resistance, scratch resistance, abrasion resistance and other coating film performance. It had a drawback that static electricity was generated and dust was easily attached.

Further, the conventional antistatic coating material used in the method of applying the antistatic coat is not sufficiently effective, for example, when the humidity is low, and after the application, heating in a process such as drying or heat setting, There is a drawback that the effect disappears due to rubbing, washing, etc., and there are many cases where durability is insufficient, and therefore, those having good durability have been desired.

As a solution to such a problem, Japanese Unexamined Patent Publication No.
As disclosed in JP-A 3-6064, by adding a phosphoric acid ester to a conventional UV-curable coating material, the balance of compatibility is utilized to promote the surface orientation of the antistatic agent and combine the antistatic performance and the hard coat. There are suggestions. However, it is difficult to form a coating film that has a good balance of mechanical strength, durability, antistatic performance persistence, etc. in a long-term test such as a moisture resistance test. It was desired to combine the two.

Abrasion resistance of the base material is obtained by forming a resin film obtained by copolymerizing a monomer having a quaternary ammonium salt group and a polyfunctional monomer such as ethylene glycol dimethacrylate on the surface of the base material resin. And a method for improving the antistatic property is already known from Japanese Patent Publication No. 54-15074. According to the method described in this publication, since the hygroscopicity of the monomer having a quaternary ammonium salt group is too high,
A large amount of water is contained in the resin raw material that forms the coating film, so that during the polymerization of the coating film, quality unevenness such as polymerization and curing unevenness and surface roughening that results in a mandarin orange surface is likely to occur. Furthermore, since the monomer having a quaternary ammonium salt group has high polymerizability, a polymerization reaction occurs during heating or depressurization, and it is practically impossible to obtain a monomer having an anhydrous quaternary ammonium salt group. It was extremely difficult to form an antistatic coating by this method.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have previously proposed Japanese Patent Application No. 2-192428 and Japanese Patent Application No. 2-307499.
No. 1 proposed a coating material with antistatic function using thiocyanate. Although the original purpose could be achieved by using such a salt, it was found that it is difficult to store the coating material for a long period of time. Therefore,
As a result of further intensive studies, the present invention has been achieved.

[0012]

Means for Solving the Problems That is, the present invention comprises (A) 20 to 99% by weight of a compound having a quaternary ammonium salt group represented by the following general formula (1) and the following general formula (2):
0.5 to 40% by weight of a copolymer containing 80 to 1% by weight of a compound represented by the formula: CH ₂ = C (R ¹ ) COO (CH ₂ ) _k N ⁺ (R ² ) (R ³ ) R ⁴ · X ⁻ (1) (In the formula, R ¹ is H or CH ₃ , R ^{2 to} R ⁴ are H or an alkyl group having 1 to 9 carbon atoms which may have a substituent, and k is 1 An integer of -10, X represents an anion of the quaternizing agent.) CH ₂ = C (R ⁵ ) COO (AO) _m R ⁶ (2) (In the formula, R ⁵ is H or CH ₃ , and R ⁶ is H or a hydrocarbon group having 1 to 18 carbon atoms which may contain a substituent, m
Represents an integer of 0 to 500, and A represents an alkylene group having 2 to 4 carbon atoms. ) (B) Trifunctional or higher functional (meth) acrylic acid ester 30 to
65 parts by weight, (C) bifunctional (meth) acrylic acid ester 10 to 40 parts by weight, (D) monofunctional (meth) acrylic acid ester 10 to 30 parts by weight, (E) hydroxyl group-containing (meth) acrylic acid ester 0 ˜20 parts by weight, 0.1 to 5 parts by weight of (F) photopolymerization initiator (however, the total of (A) to (F) is 1
It is an antistatic UV-curable coating material for optical disks, which is characterized by containing 100 parts by weight).

[0013]

The copolymer (A) used in the present invention comprises 20 to 99% by weight of the compound having the quaternary ammonium salt group represented by the general formula (1) and 80 to 80% of the compound represented by the general formula (2). It is a copolymer containing 1% by weight as an essential component.

The compound represented by the general formula (1) is obtained by quaternizing an amino group-containing (meth) acrylate with a quaternizing agent. Examples of the (meth) acrylate having an amino group include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl methacrylate, dimethylaminobutyl methacrylate, dihydroxyethylaminoethyl methacrylate, dipropylaminoethyl methacrylate, dibutyl. Aminoethyl methacrylate and the like can be mentioned.

Examples of the quaternizing agent include dimethyl sulfate,
Alkylsulfates such as diethylsulfate and dipropylsulfate; p
-Sulfonic acid esters such as methyl toluene sulfonate and methyl benzene sulfonate; alkyl phosphoric acid such as trimethyl phosphite, various halides such as alkylbenzyl chloride, benzyl chloride, alkyl chloride, alkyl bromide, etc. 20
The following alkyl sulfates and sulfonates are more preferable in consideration of thermal decomposition resistance. K in the general formula (1) is an integer of 1 to 10, but 2 to 6 is particularly preferable.

In the general formula (2), the compound represented by m = 0 is, for example, methyl (meth) acrylate,
Ethyl (meth) acrylate, butyl methacrylate,
Examples thereof include lauryl methacrylate, 2-ethylhexyl methacrylate, stearimethacrylate, benzyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate and the like.

In the general formula (2), the compound represented by the integer m = 1 to 500 is, for example, polyethylene glycol (4) monomethacrylate, polyethylene glycol (23) mono (meth) acrylate, polyethylene glycol (300). Monomethacrylate, polypropylene glycol (23) monomethacrylate, polybutylene glycol (23) monomethacrylate, polyethylene glycol (23) monomethacrylate monomethyl ether, polypropylene glycol (23) monomethacrylate monobutyl ether, polyethylene glycol (23) monomethacrylate monostearyl ether , Polyethylene glycol (23) monomethacrylate monophenyl ether, polyethylene glycol (2
3) Monomethacrylate monobenzyl ether, polyethylene glycol (23) monomethacrylate monooleyl ether and the like (the values in parentheses represent the number of polyalkylene glycol units).

The amount of the copolymer (A) used is 0.5 with respect to 100 parts by weight of the coating material for an optical disk.
-40 parts by weight is suitable. When it is used in excess of 40 parts by weight, the antistatic effect is not further improved, and the surface hardness of the cured coating film tends to be low.

In the coating material for an optical disk of the present invention, a trifunctional or higher functional (meth) acrylic acid ester (B) is used as an acrylic acid ester-based cross-linking agent which is effective in scratch resistance of a coating film and surface protection of a substrate. And a bifunctional (meth) acrylic acid ester (C) are used together.

Specific examples of the trifunctional or higher functional (meth) acrylic acid ester (B) include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, glycerin tri (meth) acrylate, and pentaerythritol triacrylate. (Meth) acrylate,
Examples thereof include pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.

Specific examples of the bifunctional (meth) acrylic acid ester (C) include 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate and 1,6-. Hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate and the like can be mentioned.

Further, examples of the reactive oligomeric (meth) acrylate compound (B or C) include polybasic acids such as phthalic acid and adipic acid, ethylene glycol,
Polyester poly (meth) acrylate obtained by reaction of polyhydric alcohol such as hexanediol and butanediol with (meth) acrylic acid, epoxy (meth) acrylate obtained by esterifying epoxy group of epoxy compound with (meth) acrylic acid, Urethane poly (meth) obtained by reacting hexamethylene diisocyanate with (meth) acrylate having a hydroxyl group, for example, 2-hydroxyethyl acrylate, or by reacting a polyol, polyisocyanate and a hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate. Polysiloxane obtained by reaction of acrylate or polysiloxane with (meth) acrylic acid compound Poly (meth) acrylate, polyamide obtained by reaction of polyamide with (meth) acrylic acid compound Poly (meth) Acrylate, and the like.

The amount of the polyfunctional (meth) acryl ester used is preferably 30 to 65 parts by weight of the trifunctional or higher functional (meth) acryl ester and 10 to 40 parts of the bifunctional (meth) acryl ester. Parts by weight.

When the amount of the trifunctional or higher functional monomer used is less than 30 parts by weight, the crosslink density of the coating film does not increase and the surface protection performance such as scratch resistance tends to deteriorate, and 65 parts by weight is used. If it exceeds, it tends to interfere with the surface orientation of the antistatic agent and fail to exhibit sufficient antistatic performance. If the amount of the bifunctional or higher monomer used is less than 10 parts by weight, the antistatic performance tends to be insufficient, and if it exceeds 40 parts by weight, the crosslink density does not increase and the bleeding of the antistatic agent occurs. It tends to occur.

Monofunctional (meth) acrylic acid ester (D)
As, 2-ethylhexyl (meth) acrylate,
Ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N-hydroxymethyl (meth) acrylamide, N-methoxymethyl (meth)
Examples include acrylamide.

Monofunctional (meth) acrylic acid ester (D)
10 to 30 parts by weight is suitable for 100 parts by weight of the coating material for an optical disk. Usage is 10
If it is less than parts by weight, the viscosity of the coating material increases,
It is not preferable because the workability in spin coater coating is poor and the adhesion of the cured coating film to the substrate is also reduced. Three
If the amount exceeds 0 part by weight, the curing performance of the coating film tends to decrease.

Examples of the hydroxyl group-containing (meth) acrylic acid ester (E) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4
-Hydroxybutyl (meth) acrylate, 2-hydroxypentyl (meth) acrylate, 4-hydroxypentyl (meth) acrylate and other hydroxyl group-containing (meth)
Acrylic ester; Addition of ethylene oxide or propylene oxide to 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, of 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate Examples include dimers or trimers.

The amount (E) of the hydroxyl group-containing (meth) acrylic acid ester used is in the range of 0 to 20 parts by weight, based on 100 parts by weight of the coating material for an optical disk.
A range of 0 parts by weight is preferred. By adding this component to the coating material, the compatibility of the copolymer (A) with the coating material can be improved. However, if the amount used exceeds 20 parts by weight, the adhesion between the coating film and the substrate tends to decrease.

Among the above-mentioned (meth) acrylic acid esters (components B to E) used in the coating material for an optical disk of the present invention, those having an acryloyl group in the molecule are better cured than those having a methacryloyl group. It is particularly preferably used for imparting the property.

As the photopolymerization initiator (F), 260 to 4
Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, acetoin, butyroin, toluoin, benzyl, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, α, α-dimethoxy-α-having absorption in the ultraviolet region of 50 nm. Carbonyl compounds such as phenylacetophenone, methylphenylglyoxylate, ethylphenylglyoxylate, 4,4′-bis (dimethylamino) benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, tetramethyl Sulfur compounds such as thiuram monosulfide and tetramethyl thiuram disulfide, azo compounds such as azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile, and benzoylperoxide And peroxides such as ditertiary butyl peroxide. The photopolymerization initiator may be one kind or a mixture of two or more kinds, and the amount of the photopolymerization initiator is appropriately 0.1 to 5 parts by weight based on 100 parts by weight of the coating material for an optical disk. .

The (meth) acrylic ester (G) having a perfluoroalkyl group represented by the following general formula (3) is preferably added to the coating material for an optical disk of the present invention. This compound is obtained by the addition reaction of perfluoroalkylethoxyepoxypropane and (meth) acrylic acid, and exhibits the effect of suppressing the bleeding of the surface of the antistatic component in the moisture resistance test of the coating film.

CF ₃ (CF ₂ ) _n CH ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OCO (R ⁷ ) C = CH ₂ (3) (In the formula, n is an integer of 3 to 8 and R ⁷ is H. Or CH ₃ )) Specific examples of perfluoroalkyl (meth) acrylate include 3- (2-perfluorobutyl) ethoxy-2-hydroxy-1- (meth) acryloyloxypropane and 3- (2-per). Fluoropentyl) ethoxy-2-hydroxy-1- (meth) acryloyloxypropane, 3- (2-perfluorohexyl) ethoxy-
2-hydroxy-1- (meth) acryloyloxypropane, 3- (2-perfluoroheptyl) ethoxy-2
-Hydroxy-1- (meth) acryloyloxypropane, 3- (2-perfluorooctyl) ethoxy-2-
Hydroxy-1- (meth) acryloyloxypropane and the like can be mentioned.

These perfluoroalkyl groups have n =
When it is 2 or less, the effect of suppressing bleeding for a long period of time tends to be insufficient, and when n = 9 or more, compatibility is poor and the coating material itself tends to become cloudy.

The amount of perfluoroalkyl (meth) acrylate (G) used is not particularly limited because it is evenly distributed in the coating material system, but from the viewpoint of curability and surface hardness of the cured film, coating for optical disks is performed. The amount is preferably 0.05 to 10 parts by weight with respect to 100 parts by weight of the material.

The coating material for an optical disk of the present invention is
In order to satisfy the quality performance, a conventionally known surface modifier,
Additives such as an ultraviolet absorber and an antioxidant can be appropriately contained.

A coating method for a coating material for an optical disk, which is obtained by mixing the above-mentioned components by a general mixing method,
The curing method is not particularly limited, but since the main application is an optical disc as a base material, the coating material blended is filtered with a 0.2 μm membrane filter, and the suspended particles per 1 [ft ³ ] is 1 It may be applied to at least one surface of the optical disc by a spin coater in an environment of 1,000 or less so that the dry film thickness is 4 to 5 μm, and then irradiated with ultraviolet rays to be cured. A high pressure mercury lamp, a metal halide lamp, or the like can be used as a source of ultraviolet rays.

In this way, an optical disk having a coating film having the excellent scratch resistance and solvent resistance of the conventional UV-curable coating material and the antistatic property is formed.

As a base material to be coated with the coating material for an optical disk of the present invention, a plastic material such as a polycarbonate resin, a polymethylmethacrylate resin, an epoxy resin or the like can be mentioned, and the application to a polycarbonate resin base is particularly effective. .

Hereinafter, the present invention will be described more specifically with reference to Examples. All "parts" and "%" in the examples are based on weight.

Synthesis Example 1 187 parts of diethylaminoethyl methacrylate and 220 parts of methanol were placed in a glass flask equipped with stirring blades, and a mixture of 126.2 parts of dimethylsulfate and 80 parts of methanol was stirred at an internal temperature of 30 ° C. or lower. After completion of the dropping, stirring was continued for 30 minutes, and as a result, a methanol solution of the monomer (M-1) having a quaternary ammonium salt group was obtained.

3 parts of azobisisobutyronitrile, 2.5 parts of n-octyl mercaptan, 243 parts of methanol, polyethylene glycol (23) monomethacrylate monomethyl ether (number of polyethylene glycol units in parentheses) 311. Add 4 parts, 60 ℃
Polymerize by reacting in a nitrogen atmosphere for 6 hours and then at 70 ° C.
By vacuum drying for 1 day, a copolymer (A-1) having antistatic property was obtained.

Synthesis Examples 2 to 10 Quaternary ammonium was prepared in the same manner as in Synthesis Example 1, except that a solution of 178.6 parts of methyl p-toluenesulfonate in 220 parts of methanol was used instead of the methanol solution of dimethylsulfate. A methanol solution of a monomer (M-2) having a base was obtained. A monomer having a quaternary ammonium salt group (M-3) was prepared in the same manner as in Synthesis Example 1 except that a mixed solution of 180 parts of diethylaminoethyl acrylate and 220 parts of methanol was used in place of the methanol solution of diethylaminoethyl methacrylate. To obtain a methanol solution.

Copolymers (A-2) to (A-10) having chargeability were obtained in the same manner as in Synthesis Example 1 except that these monomers were used in the proportions shown in Table 1. .

[0044]

[Table 1] MMA: Methyl Methacrylate BMA: Butyl Methacrylate EO (4): Polyethylene Glycol (4) Monomethacrylate Nenomethyl Ether, Numerical values in parentheses are the number of polyethylene glycol units Examples 1 to 18 Component (A) to Component (E) The ingredients were uniformly mixed in the proportions shown in Table 2 to obtain a coating material for an optical disc. Each coating material was applied on a polycarbonate disk substrate with a spin coater to a dry film thickness of 5 μm, and irradiated with ultraviolet rays of 1000 mj / cm ² by an 80 W / cm high pressure mercury lamp set to a lamp height of 10 cm. Is formed, and the coating film has antistatic performance, disk performance,
Storage stability was tested.

The evaluation results of the obtained coating films are shown in Tables 4 and 5. In addition, each evaluation was based on the following. Surface resistance: TR-8601 type (Advantest Corporation)
(Manufactured by Mitsui Chemicals, Inc.) and applied voltage of 100 V for 1 minute. Charging half-life: Static paper analyzer SP-
Type 428. (Kawaguchi Electronics Co., Ltd.), applied voltage 8k
Measured at V.

Numerical values in the table: Upper stage after curing Initial middle stage After wiping with ethanol Lower stage After moisture resistance test (60 ° C., 90% RH, 24 hours) Surface condition: Haze value and visual evaluation Table: Upper stage: 500g weighted taper abrasion test Haze value in the middle: Visual evaluation after wiping with ethanol Lower: Visual evaluation after humidity resistance test (60 ° C, 90% RH, 24 hours) Evaluation of coating film

[0047]

[Table 2] PEDA: Polyethylene glycol hexaacrylate THFA: Tetrahydrofurfuryl acrylate HEA: 2-Hydroxyethyl acrylate MPG: Methylphenylglyoxylate B-1: Dipentaerythritol hexaacrylate B-2: Trimethylolpropane triacrylate B-3: Pentaerythritol Triacrylate G-1: C ₆ F ₁₃ CH ₂ CH ₂ OCH ₂ C (OH) CH ₂ OCOCH = CH ₂ G-2: C ₄ F ₉ CH ₂ CH ₂ OCH ₂ C (OH) CH ₂ OCOCH = CH ₂ G-3: C ₈ F ₁₇ CH ₂ CH ₂ OCH ₂ C (OH) CH ₂ OCOCH = CH ₂

[0048]

[Table 3] G-4: C ₁₃ F ₂₇ CH ₂ CH ₂ OCH ₂ C (OH) CH ₂ OCOCH = CH ₂ G-5: C ₅ F ₁₁ OCOCHCH ₂

[0049]

[Table 4]

[0050]

[Table 5] Comparative Examples 1 to 10 Coating materials obtained by uniformly blending components (A) to (G) in the proportions shown in Table 3 were tested in the same manner as in Example 1, and the evaluation results are shown in Table 6. It was

Comparative Example 11 22 g of DPHA as polyfunctional acrylate, 6 g of polyethylene glycol diacrylate, 6 g of HEA as monofunctional acrylate, 7 g of THFA, 3- (2-
Perfluoro) ethoxy-2-hydroxy-1-acryloyloxypropane in 1.4 g of barium thiocyanate (hereinafter Ba (SCH) ₂ ) and C ₁₁ H ₂₃ PhO (EO) ₆ SO as an anionic surfactant. 1 of ₃ Na
20 g of the 0: 1 mixture was uniformly mixed, and 1 g of MPG was added as a photopolymerization initiator.

The coating material thus obtained was tested in the same manner as in Example 1, and the evaluation results are shown in Table 5.

[0053]

[Table 6]

[0054]

As is clear from the above embodiment,
The coating material for an optical disc of the present invention has an antistatic property,
It has excellent scratch resistance, long-term storage stability, and good adhesion to substrates.

Front page continued (72) Inventor Osamu Kawai 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Otake Works (72) Inventor Suehiro Tayama 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon shares Company Otake Office

Claims (2)

[Claims] 1. (A) 20 to 99% by weight of a compound having a quaternary ammonium salt group represented by the following general formula (1) and 80 to 1% by weight of a compound represented by the following general formula (2) are essential. copolymer 0.5 to 40% by weight of a ^{_{component, CH 2 = C (R 1}} ) COO (CH 2) k N + (R 2) (R 3) R 4 · X - (1) ( in the formula, R ¹ is H or CH ₃ , R ^{2 to} R ⁴ are H or an alkyl group having 1 to 9 carbon atoms which may contain a substituent, k is an integer of 1 to 10, and X is an anion of a quaternizing agent. CH ₂ ═C (R ⁵ ) COO (AO) _m R ⁶ (2) (wherein R ⁵ is H or CH ₃ , R ⁶ is H or a carbon number which may contain a substituent) 1-18 hydrocarbon groups, m
Represents an integer of 0 to 500, and A represents an alkylene group having 2 to 4 carbon atoms. ) (B) Trifunctional or higher functional (meth) acrylic acid ester 30 to
65 parts by weight, (C) bifunctional (meth) acrylic acid ester 10 to 40 parts by weight, (D) monofunctional (meth) acrylic acid ester 10 to 30 parts by weight, (E) hydroxyl group-containing (meth) acrylic acid ester 0 ~ 20
And (F) 0.1 to 5 parts by weight of a photopolymerization initiator (provided that the total of (A) to (F) is 100 parts by weight). UV curable coating material. 2. An optical disk excellent in antistatic property and scratch resistance, which is obtained by forming a cured coating film of the coating material according to claim 1 on at least one surface of a plastic optical disk.