JPH05287215A - Abrasion-resistant ultraviolet-curable coating composition - Google Patents

Abstract

PURPOSE:To prepare a coating compsn. which can form a coating film excellent in adhesion to a plastic substrate, transparency, and abrasion resistance by compounding a reactional product of a specific silane coupling agent having an isocyanate group with a hydroxylated polyacrylate, a polyacrylate, a silica sol. and a photopolymn. initiator. CONSTITUTION:This compsn. comprises a reactional product of an isocyanate- group-contg. silane coupling agent of the formula (wherein R<1> and R<2> are each a monovalent hydrocarbon group and they may be the same or different; R<3> is a 2-8C divalent hydrocarbon group; (a) is 2 or 3; (b) is 0 or 1; and (c) is 4-a-b) with a hydroxylated polyacrylate having at least three acryloyl groups in the molecule, a polyacrylate having at least three acryloyl groups in the molecule, a silica sol dispersed in an org. solvent, and a photopolymn. initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UV-curable coating composition which is applied to a plastic substrate and UV-cured to form a coating film having excellent abrasion resistance. More specifically, it relates to an ultraviolet-curable coating composition which forms a coating film having excellent adhesion to a transparent plastic substrate, transparency and abrasion resistance.

[0002]

2. Description of the Related Art Generally, plastic products,
For example, polycarbonate, polymethylmethacrylate, polyethylene terephthalate, ABS resin, etc.
Since it is excellent in its lightness, easy workability and impact resistance, it is used for various purposes. However, these plastic products have the drawback that they are easily scratched due to their low surface hardness, and the original transparency or appearance of the resin is significantly impaired, so the use of plastic products in fields requiring abrasion resistance is It's difficult. Various hard coating agents such as an acrylic hard coating agent and a silicon hard coating agent have been proposed as a coating material that imparts abrasion resistance to such a plastic substrate and enhances the surface hardness. Among these hard coat agents, acrylic hard coat agents can be cured by ultraviolet light, so they have the characteristics of short curing time and excellent productivity.
It has a drawback that it is inferior in abrasion resistance as compared with a silicon-based hard coat agent.

In order to improve the abrasion resistance of this acrylic hard coat agent, JP-A-57-500984 discloses a silica sol containing acrylate as a water dispersion medium and an acryloxy-functional or glycidoxy-functional silane compound. A UV curable coating composition having a hydrolyzate added is disclosed. However, since the silica sol used in the above invention is a water-dispersed system, it is necessary to use a hydroxy group-containing acrylate having good miscibility with water as the acrylate, not a polyfunctional acrylate having excellent abrasion resistance. There are no restrictions, and sufficient abrasion resistance is not yet obtained. In order to avoid this drawback, JP-A-59-204669 discloses that a polyfunctional acrylate is added with a hydrophobic silica sol having an organic solvent as a dispersion medium, and a hydrolyzate of a silane compound having an unsaturated group. Abrasive coating compositions are disclosed. In this coating composition, since a hydrophobic silica sol having an organic solvent as a dispersion medium is used as the silica sol, the selection range of usable polyfunctional acrylates is expanded and the hardness is further improved. However, the silane compound having an unsaturated group used in this composition is, for example, a monofunctional (meth) acryloyl compound such as 3- (meth) acryloxypropyltrimethoxysilane. When viewed from the whole of the product, the acryloyl group density was reduced, and as a result, the reduction of the crosslinking density during UV curing was unavoidable, and the abrasion resistance comparable to that of the silicon-based hard coating agent could not be obtained yet.

[0004]

As a result of earnest studies, the present inventors were able to solve the above-mentioned conventional problems. That is, the present invention provides (a) the general formula

[0005]

[Chemical 2]

(Wherein R ¹ and R ² are the same or different monovalent hydrocarbon groups, R ³ is a divalent hydrocarbon group having 2 to 8 carbon atoms,
a is an integer of 2 to 3, b is an integer of 0 to 1, c is 4-ab
A compound obtained by reacting an isocyanate group-containing silane coupling agent represented by the formula (1) with a hydroxyl group-containing polyfunctional acrylate having a hydroxyl group and three or more acryloyl groups in the molecule, (b) in the molecule A wear-resistant ultraviolet-curable coating composition comprising a polyfunctional acrylate having three or more acryloyl groups, (c) a silica sol containing an organic solvent as a dispersion medium, and (d) a photopolymerization initiator. The object of the present invention is to provide a coating film having excellent adhesion to a plastic substrate, transparency and abrasion resistance.

The present invention will be described in more detail below.
(Component (a)) The present invention comprises reacting an isocyanate group-containing silane coupling agent having the general formula shown below with a hydroxyl group-containing polyfunctional acrylate having a hydroxyl group and three or more acryloyl groups in the molecule. The main features of using the resulting compound are:

[0008]

[Chemical 3]

(Wherein R ¹ and R ² are the same or different monovalent hydrocarbon groups, and preferably R ¹ and R ² are lower alkyl groups such as methyl, ethyl, propyl, etc. R ³
Is a divalent hydrocarbon group having 2 to 8 carbon atoms. a is an integer of 2 to 3, b is an integer of 0 to 1, and c is an integer equal to 4-ab. ) Since this compound has three or more acryloyl groups and a trialkoxysilyl group or a dialkoxysilyl group in the same molecule, even if this compound is mixed with the polyfunctional acrylate as the component (b), the acryloyl group density There is almost no decrease, and the trialkoxysilyl group or dialkoxysilyl group reacts with the silanol groups present on the surface of the silica sol particles by mixing with the silica sol which is the component (c). High wear resistance can be realized by the effects of both.

Specific examples of the isocyanate group-containing silane coupling agent include 3-isocyanatopropyltrimethoxysilane, 2-isocyanatoethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane,
2-isocyanatoethyltriethoxysilane, 3-isocyanatopropylmethyldimethoxysilane, 2-isocyanatoethylmethyldimethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, 2-isocyanatoethylmethyldiethoxysilane and the like can be mentioned. .. next,
Examples of the hydroxyl group-containing polyfunctional acrylate having a hydroxyl group and three or more acryloyl groups in the molecule include pentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and a mixture thereof.

The reaction between the isocyanate group-containing silane coupling agent and the hydroxyl group-containing polyfunctional acrylate is carried out by mixing each compound at a ratio of --NCO /-OH group≤1, and then 60 to 11
Obtained by stirring at 0 ° C. for 1 to 20 hours. In this reaction, in order to prevent polymerization due to the acryloyl group during the reaction, it is preferable to use a polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, catechol, pt-butylcatechol, phenothiazine, and the like. The amount is 0.0 with respect to the reaction mixture.
1 to 1% by weight, particularly preferably 0.05 to 0.5% by weight. In order to accelerate the reaction, for example, di-n-butyltin dilaurate or 1,4-diazabicyclo [2.
A known reaction catalyst such as 2.2] octane may be added. Further, this reaction is carried out, for example, in the presence of an organic solvent such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, ethyl acetate, propyl acetate, butyl acetate, toluene, xylene, or ( It can be carried out in the presence of a polyfunctional acrylate having 3 or more acryloyl groups in the molecule which is the component b).

(Component (b)) Examples of the polyfunctional acrylate having three or more acryloyl groups in the molecule, which is one component of the composition of the present invention, include trimethylolpropane triacrylate and EO-modified trimethylolpropane triacrylate. , PO-modified trimethylolpropane triacrylate, trimethylolpropane tetraacrylate, tris (acryloxyethyl) isocyanurate,
Caprolactone modified tris (acryloxyethyl) isocyanurate, pentaerythritol triacrylate, pentaerythritol pentaacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, alkyl modified dipentaerythritol triacrylate, alkyl modified dipentaerythritol tetraacrylate, alkyl Examples include modified dipentaerythritol pentaacrylate, caprolactone modified dipentaerythritol hexaacrylate, and mixtures of two or more thereof. Among these, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, and mixtures thereof are particularly desirable from the viewpoint of abrasion resistance. (a) component and
The amount of component (b) used is (a) / (b) = 0.1-10 (weight ratio)
Is preferable from the viewpoint of abrasion resistance of the ultraviolet curable coating film.

(Component (c)) Next, as the other component of the composition of the present invention, as a silica sol having an organic solvent as a dispersion medium, a silica sol having a particle size of about 5 to 30 nm is used as a solid component 1
What is dispersed at a concentration of 0 to 40% by weight using methyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethylene glycol, ethyl cellosolve, dimethylacetamide, a mixed solvent of xylene and n-butyl alcohol as a dispersion medium. Can be mentioned. Among them, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethyl cellosolve, and silica sol using a mixed solvent of xylene and n-butyl alcohol are compatible with the components (a) and (b) used. Is preferable, and it is particularly desirable from the viewpoint of transparency of the obtained coating film.

The amount of silica sol using an organic solvent as a dispersion medium is preferably 0.1 to 5 in terms of solid content of silica sol / {(a) component + (b) component} (weight ratio). Weight ratio is 0.1
If it is less than the above, almost no improvement in abrasion resistance due to silica sol is observed. On the other hand, if the weight ratio exceeds 5, the crosslink density due to the acryloyl group will decrease, and the abrasion resistance will decrease.

(Component (d)) Next, as the photopolymerization initiator, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, diethoxy acetophenone, benzyl dimethyl ketal, 2-hydroxy-2-methyl propylene Piophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, 2,4,6-trimethylbenzoindiphenylphosphine oxide, 2-methyl- [4
-(Methylthio) phenyl] -2-morpholino-1-
Propanone, 2-benzyl-2-dimethylamino-1-
(4-morpholinophenyl) -butan-1-one, Michler's ketone, isoamyl N, N-dimethylaminobenzoate, 2-chlorothioxanthone, 2,4-diethylthioxanthone and the like can be mentioned. These photopolymerization initiators can also be used in appropriate combination of two or more kinds. The photopolymerization initiator is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the total amount of the components (a) and (b).

The abrasion-resistant ultraviolet-curable coating composition of the present invention contains an ultraviolet absorber (for example, benzotriazole-based, benzophenone-based, salicylic acid-based, cyanoacrylate-based ultraviolet absorber) for the purpose of improving the physical properties of the coating film. UV stabilizers (eg hindered amine UV stabilizers),
Various additives such as antioxidants (for example, phenol-based, sulfur-based, phosphorus-based antioxidants), anti-blocking agents, slip agents, leveling agents and the like which are compounded in this type of composition can be added. Also, for the purpose of adjusting the viscosity, add an organic solvent (for example, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, ethyl acetate, propyl acetate, butyl acetate, toluene, xylene). You can also

The present coating composition is applied to a plastic substrate such as polycarbonate, polymethylmethacrylate, polyethylene terephthalate or ABS resin by a dipping method, a flow coating method, a spraying method, a bar coating method,
And, by a coating method using a coating machine such as gravure coat, roll coat, blade coat, air knife coat, etc., a hard coat layer of 1 to 50 μm, preferably 3 to 20 μm is formed on the surface of the plastic substrate after solvent drying and ultraviolet irradiation. It is applied under the conditions obtained. Curing of the present coating composition,
It is performed by irradiating with ultraviolet rays for 1 to 60 seconds using a lamp such as a xenon lamp, a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a carbon arc lamp, and a tungsten lamp.

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. The parts and% in the examples mean parts by weight and% by weight, respectively. Example 1 A mixture of 3-isocyanatopropyltrimethoxysilane, dipentaerythritol hexaacrylate containing 67 mol% of dipentaerythritol pentaacrylate and dipentaerythritol pentaacrylate (manufactured by Nippon Kayaku Co., Ltd .: Kayarad DPHA, hydroxyl value 69 mgK
OH / g), and 205 g and 813 g of each are placed in a flask so that the ratio of -NCO group / -OH group = 1, and 1 g of hydroquinone monomethyl ether and 0.2 g of di-n-butyltin dilaurate are added at 110 ° C. Reacted for 3 hours. When this reaction product was analyzed by infrared absorption spectrum-
No absorption of NCO groups at 2250 cm ^-1 was observed, confirming the completion of the reaction. The resulting composition (I)
Contains 71.6% and 28.4% of dipentaerythritol hexaacrylate and a reaction product of 3-isocyanatopropyltrimethoxysilane and dipentaerythritol pentaacrylate, respectively. 30 parts of composition (I),
Silica sol with xylene and n-butyl alcohol as a dispersion medium (Nissan Chemical Co., Ltd .: XBA-ST, solid content 30%, xylene 45%, n-butyl alcohol 25%) 100
Parts and 1.5 parts of benzyl dimethyl ketal were mixed to obtain an ultraviolet curable coating composition. This UV-curable coating composition was applied to a transparent polycarbonate plate having a thickness of 2 mm by using a bar coater so that the coating film thickness after drying would be 10 μm, and was dried by heating at 100 ° C. for 10 minutes. Using a high-pressure mercury lamp with an output of 7.5 kw and an output density of 120 w / cm installed vertically to the sample passage direction, this was irradiated with ultraviolet rays at a conveyor speed of 2 m / min at a position 10 cm below the light source to be ultraviolet-cured. .. The adhesion of the hard coat layer formed on the polycarbonate plate to the polycarbonate plate is
When 100 cross-cuts were formed on the hard coat layer with a cutter knife at intervals of 1 mm, a Nichiban adhesive tape was pressure-bonded and strongly peeled off, and evaluated. As a result, a good adhesion of 100/100 was obtained. (Conforms to the cross-cut tape method JIS K5400) Further, the transparency of the obtained hard-coated polycarbonate plate was evaluated by the haze value (%), which was 0.5%, and the transparency was good. In addition, 2 before the hard coat treatment
The haze value of the mm-thick polycarbonate plate was 0.5%. (Haze value = Td / Tt × 100, where Td: scattered light transmittance, Tt: total light transmittance according to JIS K7105). Next, wear resistance was measured by using a wear wheel of Caliberase CS-10F A 100-rotation Taber abrasion test was performed at 500 g, and a difference ΔH in haze value between before and after the Taber abrasion test was measured. As a result, it was only 0.6% and the abrasion resistance was good. A similar Taber abrasion test was conducted on a 2 mm-thick polycarbonate plate which was not hard-coated, and the obtained ΔH was 46.7%. (Based on Taber abrasion test method ASTM D1044)

Example 2 30 parts of the composition (I) obtained in Example 1, xylene and n
50 parts of silica sol (XBA-ST manufactured by Nissan Chemical Industries, Ltd.) containing butyl alcohol as a dispersion medium and 1.1 parts of benzyl dimethyl ketal were mixed to obtain an ultraviolet-curable coating composition. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used. When the adhesiveness, transparency and abrasion resistance were evaluated in the same manner as in Example 1, the adhesiveness was 100/100 and the haze value was:
Good results were obtained with 0.6% and ΔH: 0.8%.

Example 3 30 parts of the composition (I) obtained in Example 1, xylene and n
-200 parts of silica sol (XBA-ST manufactured by Nissan Chemical Industries, Ltd.) containing butyl alcohol as a dispersion medium and 2.2 parts of benzyl dimethyl ketal were mixed to obtain an ultraviolet-curable coating composition. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used. Adhesion, transparency and abrasion resistance were evaluated in the same manner as in Example 1. Adhesion: 100/100, haze value: 0.5%, ΔH: 0.5%, and good results were obtained. It was

Example 4 A hard-coated polyethylene terephthalate film was obtained in the same manner as in Example 1, except that a transparent 100 μm-thick polyethylene terephthalate film was used in place of the transparent 2 mm-thick polycarbonate plate. It was When the adhesion of the hard coat layer formed on the polyethylene terephthalate film to the polyethylene terephthalate film was evaluated, a good adhesion of 100/100 was obtained. The transparency of the obtained hard coat-treated polyethylene terephthalate film was evaluated by the haze value (%), and it was 3.7%, and the transparency was good. The haze value of the 100 μm thick polyethylene terephthalate film before the hard coat treatment is 3.
It was 7%. Next, when the abrasion resistance was evaluated, ΔH was 0.5% and the abrasion resistance was good. The .DELTA.H of 100 .mu.m thick polyethylene terephthalate not subjected to the hard coat treatment was 23.1%.

Example 5 A mixture of 3-isocyanatopropyltriethoxysilane, dipentaerythritol hexaacrylate containing 67 mol% of dipentaerythritol pentaacrylate and dipentaerythritol pentaacrylate (Kayarad DPHA manufactured by Nippon Kayaku Co., Ltd.). Is an -NCO group /
198 g and 813 g of each were placed in a flask so that the —OH group was 0.8, and hydroquinone monomethyl ether 1 was added.
g, 0.2 g of di-n-butyltin dilaurate was added,
The reaction was carried out at 0 ° C for 3 hours. When this reaction product was analyzed by infrared absorption spectrum, no absorption of -NCO group at 2250 cm ^-1 was observed, and it was confirmed that the reaction was completed. The composition (II) thus obtained contained 61.0% and 28% dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate, respectively, which was a reaction product of 3-isocyanatopropyltriethoxysilane and dipentaerythritol pentaacrylate. It contains 0.6% and 10.4%. 30 parts of the composition (II), silica sol having xylene and n-butyl alcohol as a dispersion medium (manufactured by Nissan Chemical Co., Ltd .: X
100 parts of BA-ST) and 1.5 parts of benzyl dimethyl ketal were mixed to obtain an ultraviolet curable coating composition. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used.
When the adhesiveness, transparency and abrasion resistance were evaluated in the same manner as in Example 1, the adhesiveness was 100/100 and the haze value was 0.5.
%, ΔH: 0.9%, and good results were obtained.

Example 6 3-isocyanatopropylmethyldimethoxysilane,
67 mol of dipentaerythritol pentaacrylate
% Dipentaerythritol hexaacrylate and a mixture of dipentaerythritol pentaacrylate (Kayarad DPHA manufactured by Nippon Kayaku Co., Ltd.)
Group / -OH group = 0.7, so that each is 133 g and 81
3 g was placed in a flask, and hydroquinone monomethyl ether (0.9 g) and di-n-butyltin dilaurate (0.2 g) were added, and the reaction was carried out at 110 for 3 hours. When this reaction product was analyzed by infrared absorption spectrum, no absorption of -NCO group at 2250 cm ^-1 was observed, and it was confirmed that the reaction was completed. The composition (III) thus obtained contained 52.9% each of a reaction product of 3-isocyanatopropylmethyldimethoxysilane and dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol pentaacrylate.
Contains 30.5% and 16.6%. Composition (III) 20
Parts, 100 parts of silica sol having n-butyl alcohol as a dispersion medium (Nissan Chemical Co., Ltd .: NBA-ST, solid content 20%, n-butyl alcohol 80%), and 1 part of benzyl dimethyl ketal are mixed by UV curing. A composition was obtained. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used. When the adhesiveness, transparency and abrasion resistance were evaluated in the same manner as in Example 1, the adhesiveness was 100/100 and the haze value was:
Good results were obtained with 0.8% and ΔH: 1.0%.

Comparative Example 1 A silica sol containing 30 parts of the composition (I) obtained in Example 1 as a dispersion medium (manufactured by Nissan Kagaku: ST-30, solid content: 3)
(0%) was stirred and mixed, but the liquid became cloudy and separated when left to stand, and an ultraviolet-curable coating composition forming a transparent film was not obtained.

Comparative Example 2 3-isocyanatopropyltrimethoxysilane 20.5
g, 340 g of silica sol (XBA-ST, manufactured by Nissan Chemical Industries, Ltd.) containing xylene and n-butyl alcohol as a dispersion medium are placed in a flask, and 0.4 g of hydroquinone monomethyl ether and 0.07 g of di-n-butyltin dilaurate are added. And reacted at 80 ° C. for 3 hours. When this reaction product was analyzed by infrared absorption spectrum, it was found that the NCO group was 2250.
No absorption of cm ^-1 was observed, and it was confirmed that 3-isocyanatopropyltrimethoxysilane reacted with n-butyl alcohol, which is a dispersion medium of silica sol. This reaction 1
Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate containing 67 mol% of dipentaerythritol pentaacrylate in 06 parts (Nippon Kayaku Co., Ltd .: Kayarad DPHA) 24
Parts and 1.5 parts of benzyl dimethyl ketal were mixed to obtain an ultraviolet curable coating composition. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used. When the adhesiveness, transparency and abrasion resistance were evaluated in the same manner as in Example 1, the adhesiveness: 1
It was 00/100, haze value: 1.2%, ΔH: 5.7%, and the wear resistance was not sufficient.

Comparative Example 3 3-isocyanatopropyltrimethoxysilane and 2-hydroxyethyl acrylate were combined with -NCO group / -OH.
205 g and 116 g of each were placed in a flask so that the number of groups was 1, and 0.3 g of hydroquinone monomethyl ether and 0.06 g of di-n-butyltin dilaurate were added, and the mixture was heated to 100 ° C.
And reacted for 3 hours. When this reaction product was analyzed by infrared absorption spectrum, no absorption of -NCO group at 2250 cm ^-1 was observed, and it was confirmed that the reaction was completed. A mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate containing 20 parts of the obtained compound and 67 mol% of dipentaerythritol pentaacrylate (manufactured by Nippon Kayaku Co., Ltd .: Kayarad DP
HA) 10 parts, silica sol having xylene and n-butyl alcohol as a dispersion medium (manufactured by Nissan Chemical Co., Ltd .: XBA-ST) 1
A UV-curable coating composition was obtained by mixing 00 parts and 0.75 part of benzyl dimethyl ketal. A hard-coated polycarbonate plate was obtained in the same manner as in Example 1 except that this ultraviolet-curable coating composition was used. Adhesion, transparency and abrasion resistance were evaluated in the same manner as in Example 1. Adhesion: 100/100, haze value: 0.5%, ΔH: 7.
It was 8% and the abrasion resistance was not sufficient.

[0027]

Since the composition of the present invention is constituted as described above, the compound of component (a) has three or more acryloyl groups and a tri- or dialkoxysilyl group in the same molecule. Even when mixed with a polyfunctional acrylate, the density of acryloyl groups is hardly reduced, and the tri- or dialkoxysilyl groups react with silanol groups existing on the surface of silica sol particles. From these facts, it is possible to form a coating film having excellent adhesion to a transparent plastic substrate, transparency and abrasion resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C09D 5/00 175/16 PHM 8620-4J // C08G 18/77 NFJ 8620-4J

Claims (2)

[Claims] 1. (a) General formula: (In the formula, R ¹ and R ² are the same or different monovalent hydrocarbon groups, R ³ is a divalent hydrocarbon group having 2 to 8 carbon atoms, and a is 2 to 3
, B is an integer of 0 to 1, and c is an integer equal to 4-a-b), and an isocyanate group-containing silane coupling agent, and a hydroxyl group having a hydroxyl group and three or more acryloyl groups in the molecule are contained. A compound obtained by reacting with a polyfunctional acrylate, (b) a polyfunctional acrylate having three or more acryloyl groups in the molecule, (c) a silica sol containing an organic solvent as a dispersion medium, and (d) a photopolymerization initiator An abrasion-resistant UV-curable coating composition comprising: 2. The polyfunctional acrylate having 3 or more acryloyl groups in the molecule of component (b) is selected from the group consisting of dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate and mixtures thereof. The composition according to 1.