Photocurable coating composition having excellent hardness and impact resistance

Abstract

The present invention relates to a photocurable coating composition having excellent hardness and impact resistance, and more particularly to a photocurable coating composition having excellent impact resistance by utilizing an ethylene oxide copolymerized urethane acrylate oligomer to obtain flexibility while maintaining high hardness properties.

Description

PHOTOCURABLE COATING COMPOSITION HAVING EXCELLENT HARDNESS AND IMPACT RESISTANCE

[0001] The present invention relates to a photocurable coating composition having excellent hardness and impact resistance, and more particularly to a photocurable coating composition having excellent impact resistance by utilizing an ethylene oxide copolymerized urethane acrylate oligomer to obtain flexibility while maintaining high hardness properties.

[0002] The green trend is driving research to replace glass with lighter and more durable plastics in an effort to lighten automobiles. The increasing use of displays is also driving interest in hard-coating materials that can protect displays in a variety of environments.

[0003] Hard coating materials for glass replacement must have excellent hardness and transmittance. However, there are limits to realizing the hardness of glass, so it is necessary to develop coatings to compensate for the lack of hardness.

[0004] Especially to develop the substrate having excellent hardness and transparency and a impact resistance to endure the external impact apart from mechanical / physical reliability such as scratch resistance and weather resistance, a coating resin with high hardness and excellent impact resistance came to be needed.

[0005] To achieve high hardness properties of photocurable coating compositions, as disclosed in Korean Published Patent No. 2017-0070836 (published on June 22, 2017), photocurable multifunctional acrylate oligomers are used, wherein the oligomers are produced by urethan-reaction of dipentaerythritolpentahydroxyacrylate monomer with polyisocyanate, wherein dipentaerythritolpentahydroxyacrylate is produced by the reaction of pentaerythritol, a solid tetrahydric alcohol, with acrylic acid. Or dipentaerythritol pentaacrylate or dipentaerythritol hexaacrylate monomers in resins and coatings are used, but the high hardness of the tetrahydric chains of the tetrahydric alcohols makes it possible to achieve high hardness properties, but the problem of poor impact resistance must be overcome.

[0006] Photocure coating compositions using oligomers synthesized by urethane reaction of pentaerythritol polyols with pentaerythritol trihydroxyacrylate or dipentaerythritolpentahydroxyacrylate can improve hardness, but they have the following problems:

[0007] i) During photocuring, multiple functional group chains are cured and the cohesion of the molecular chains becomes stronger, causing shrinkage, resulting in curls on the coating surface.

[0008] ii) Cracks develop on the coating surface over time due to the mechanism described above.

[0009] iii) Due to the hard surface caused by the mechanism described above, surface cracking occurs even with a weak impact.

[0010] Therefore, there is a need to develop new photocuring urethane acrylate oligomers and photocuring coating compositions that can solve the above problems.

[0011] The present invention is designed to solve the above problems, and and aims to provide a photocurable coating composition having improved impact resistance while maintaining high hardness properties by giving flexibility to a conventional stiff chain,and by using ethylene oxide-pentaerythritol polyol (Chemical Formula 1) in synthesizing oligomer, wherein the polyol is modified with ethylene oxide to give flexibility to pentaerythritol, a solid tetrahydric alcohol.

[0012] [Chemical Formula 1]

[0013]

[0014] (In the formula, n is an integer from 1 to 10, 1 to 5, or 1 to 2).

[0015] The present invention may also aim to achieve other purposes, other than the above-mentioned clear purpose, which can be easily derived by a person skilled in the art from this purpose and the overall description of the present specification.

[0016] To accomplish the purposes described above, the photocured coating compositions of the present invention, with excellent hardness and impact resistance, is characterized by including

[0017] urethane acrylate oligomer 100 parts by weight,

[0018] the second photocured monomer 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,

[0019] nanosilica sol 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,

[0020] photoinitiator 2.7 to 5.1 parts by weight, 3.1 to 4.7 parts by weight , or 3.5 to 4.3 parts by weight, and

[0021] organic solvents 192 to 357 parts by weight, 220 to 329 parts by weight, or 247 to 302 parts by weight.

[0022] And, the photocured coating compositions of the present invention, with excellent hardness and impact resistance may further comprise 1.6 to 3.1 parts by weight, 1.9 to 2.8 parts by weight, or 2.1 to 2.6 parts by weight of an ultraviolet absorber. Further, the UV absorber may be a single compound or a mixture of two or more different compounds.

[0023] And, the photocured coating compositions of the present invention, with excellent hardness and impact resistance may further comprise 1.1 to 2.0 parts by weight, 1.3 to 1.9 parts by weight, or 1.4 to 1.7 parts by weight of a leveling stabilizer. Further, the leveling stabilizer may be a single compound or a mixture of two or more different compounds.

[0024] Further, the second photocuring monomer may be selected from the group consisting of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylpropanetriacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and mixtures thereof.

[0025] And, the nanosilica sol may have an average particle size of 10 to 40 nm, 20 to 30 nm, or 10 to 20 nm.

[0026] Further, the photoinitiator may be selected from the group consisting of benzophenone, hydroxycyclohexylphenylketone, and mixtures thereof.

[0027] And, the photoinitiator may be a mixture of

[0028] benzophenone 100 parts by weight, and

[0029] hydroxycyclohexylphenylketone 23 to 43 parts by weight, 27 to 40 parts by weight, or 30 to 37 parts by weight.

[0030] Further, the organic solvent may be selected from the group consisting of n-butyl acetate, ethyl acetate, isopropyl alcohol, methylisobutyl ketone, and mixtures thereof.

[0031] Further, the urethane acrylate oligomers may be the product of reacting isophorone diisocyanate 100 parts by weight, and the first photocured monomer 317 to 589 parts by weight, 362 to 544 parts by weight, or 408 to 498 parts by weight with a urethane reaction catalyst 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight.

[0032] And, the urethane acrylate oligomer may be the product of the reaction further including 29 to 54 parts by weight of ethylene oxide pentaerythritol polyol of Chemical Formula 1 below, 33 to 49 parts by weight, or 37 to 45 parts by weight.

[0033] [Chemical Formula 1]

[0034]

[0035] (In the formula, n is an integer from 1 to 10, 1 to 5, or 1 to 2).

[0036] And, the ethylene oxide pentaerythritol polyol may have a weight average molecular weight of 100 to 1,500, 200 to 1,000, or 300 to 500.

[0037] The urethane acrylate oligomer may be produced via

[0038] (A) a first reaction step of reacting 100 parts by weight of said isophorone diisocyanate and 29 to 54 parts by weight, 33 to 49 parts by weight, or 37 to 45 parts by weight of said ethylene oxide pentaerythritol polyol with 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight of a urethane reaction catalyst; and

[0039] (B) a second reaction step of reacting 317 to 589 parts by weight, 362 to 544 parts by weight, or 408 to 498 parts by weight of the first photocuring monomer and the product of said first reaction step.

[0040] And, the urethane acrylate oligomer may be the product of the reaction further including 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight of polymerization stabilizer.

[0041] Further, the first photocuring monomer may be selected from the group consisting of pentaerythritol triacrylate, dipentaerythritolpentaacrylate, and mixtures thereof.

[0042] Further, the urethane reaction catalyst may be selected from the group consisting of copper naphthenate, cobalt naphthenate, zinc naphthenate, n-butyl tin laurate, dibutyl tin dilaurate, tristilamine, 2-methyltriethylenediamide, and mixtures thereof.

[0043] Further, the polymerization stabilizer may be selected from the group consisting of butylated hydroxytoluene, hydroquinone, hydroquinonemonomethyl ether, para-benzoquinone, phenothiazine, and mixtures thereof.

[0044] And, the reaction temperature of the first reaction step may be 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃.

[0045] And, the first reaction step may comprise partitively adding the urethane reaction catalyst to the mixture of isophorondiisocyanate and ethylene oxide pentaerythritol polyol at 50 to 80 ℃, 55 to 75 ℃, or 60 to 70 ℃, followed by raising the temperature to 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃.

[0046] And, the reaction time of said first reaction step may be 0.5 to 4 hours, 1 to 3 hours, or 1.5 to 2.5 hours.

[0047] And, the stirring rate of said first reaction step may be 30 to 50 Hz.

[0048] And, the first reaction step may be terminated at a percentage of isocyanate (NCO%) of 13 to 15%.

[0049] And, the reaction temperature of the second reaction step may be 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃.

[0050] And, the reaction time of the second reaction step may be 0.5 to 6 hours, 1 to 5 hours, or 2 to 4 hours.

[0051] And, the second reaction step may be terminated when the isocyanate peak (2250 cm-1) in Fourier transform infrared spectroscopy disappears.

[0052] And, the urethane acrylate oligomer may have a weight average molecular weight of 4,000 to 20,000, 6,000 to 18,000, or 8,000 to 16,000.

[0053] And, the viscosity at 25 ℃ of said urethane acrylate oligomer may be 10,000 to 40,000 cP, 15,000 to 35,000 cP, or 20,000 to 30,000 cP.

[0054] As described above, the problem-solving means of the present invention can be expected to have a variety of effects, including the following. However, it is not necessary for the invention to have all of the following effects.

[0055] The photocurable coating composition according to the present invention uses an ethylene oxide pentaerythritol polyol for oligomer synthesis to give flexibility to pentaerythritol, a tetrahydric alcohol, wherein the polyol is produced from pentaerythritol modified with ethylene oxide. The said composition can solve problems such as curl formation after photocuring, surface cracking, and poor impact resistance, which are weaknesses of conventional high-hardness multifunctional oligomers. In addition, by improving hardness and impact resistance, it can exhibit excellent scratch resistance, abrasion resistance, and light transmission properties.

[0056] FIG. 1 is a photograph of the impact tester used to test the present invention.

[0057] FIG. 2 is a diagram illustrating the adhesion grades used as a reference in the testing of the present invention.

[0058] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0059] However, below is only to describe specific embodiments in detail. The present invention may be changed in various ways and may have a number of forms, and thus, the present invention is not limited to specific embodiments illustrated. It is to be understood that the present invention includes all changes, equivalents, and alternatives falling within the spirit and scope of the present invention.

[0060] In addition, in the following description, many specific details such as specific components are described. However, they are only provided to aid in further understanding of the present invention, and thus, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Also, in describing the present invention, detailed descriptions of related known functions or configurations will be omitted when it is determined that the detailed descriptions may unnecessarily obscure the gist of the present invention.

[0061] Also, the terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Unless defined otherwise, all the terms used herein, including technical or scientific terms, may have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains. Terms that are defined in a commonly used dictionary should be construed as having meanings consistent with the meanings in the context of the related art, and should meaning not be construed as having an ideal or overly formal meaning unless explicitly defined in the present application.

[0062] In the present application, the terms of a singular form may include a plural form unless the context clearly indicates otherwise.

[0063] In the present application, % refers to weight % unless otherwise specified, and molecular weight refers to weight average molecular weight unless otherwise specified.

[0064] In the present application, terms such as first, second, and the like may be used to describe various components, but the components are not to be limited by such terms. These terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, a second component may be named a first component, without departing from the scope of the present invention.

[0065] In the present application, terms such as ‘include,’ ‘contain,’ or ‘have’ are intended to refer to the presence of features, components (or elements), and the like described in the specification, and do not imply that one or more other features or components are not present or cannot be added.

[0066] The present invention relates to a photocurable coating composition comprising a urethane acrylate oligomer with ethylene oxide pentaerythritol comprising a tetrahydroxyl group in the main backbone exhibiting properties, and more particularly to a photocurable ethylene oxide copolymerized urethane acrylate oligomer having high hardness and improved impact resistance by including ethylene oxide pentaerythritol with excellent hardness and flexibility in the resin backbone, and to a photocurable coating composition for paints using the same.

[0067] The synthesis of ethylene oxide copolymerized urethane acrylate oligomers having excellent high hardness, impact resistance, scratch resistance, abrasion resistance, and light transmission properties, and the photocurable coating compositions thereof, according to a preferred embodiment of the present invention, will be described in detail as follows.

[0068] To accomplish the purposes described above, the photocured coating compositions of the present invention, with excellent hardness and impact resistance, is characterized by including

[0069] urethane acrylate oligomer 100 parts by weight,

[0070] the second photocured monomer 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,

[0071] nanosilica sol 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,

[0072] photoinitiator 2.7 to 5.1 parts by weight, 3.1 to 4.7 parts by weight , or 3.5 to 4.3 parts by weight, and

[0073] organic solvents 192 to 357 parts by weight, 220 to 329 parts by weight, or 247 to 302 parts by weight.

[0074] The hardness and impact resistant photocurable coating composition of the present invention may further comprise 1.6 to 3.1 parts by weight, 1.9 to 2.8 parts by weight, or 2.1 to 2.6 parts by weight of an ultraviolet absorber. Further, said UV absorber may be a single compound or a mixture of two or more different compounds. If the content of the UV absorber is below the above range, yellowing may occur during the weathering reliability test, and conversely, if the content exceeds the above range, it may interfere with the photocuring, resulting in uncuring, and the film performance may not be realized.

[0075] And, the photocured coating compositions of the present invention, with excellent hardness and impact resistance may further comprise 1.1 to 2.0 parts by weight, 1.3 to 1.9 parts by weight, or 1.4 to 1.7 parts by weight of a leveling stabilizer. Further, the leveling stabilizer may be a single compound or a mixture of two or more different compounds. If the content of the leveling stabilizer is below the above range, the leveling property of the coating surface is poor, and conversely, if the content exceeds the above range, it may interfere with photocuring, resulting in uncuring, and the film performance may not be realized.

[0076] Further, the second photocuring monomer may be selected from the group consisting of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylpropanetriacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and mixtures thereof. If the content of the second photocuring monomer is below the above range, there may be a problem with workability due to an increase in viscosity of the coating composition, and if the content of the second photocuring monomer is exceeds the above range, there is a problem with a decrease in impact resistance due to an increase in hardness after curing, caused by an increase in the content of single-molecule monomers.

[0077] And, the nanosilica sol may have an average particle size of 10 to 40 nm, 20 to 30 nm, or 10 to 20 nm. If the average particle size exceeds 40 nm, an uneven appearance of the coating film after curing may occur, as well as a sharp decrease in transparency. If the content of nanosilica sol is less than the above range, there is a problem of decreased pencil hardness and abrasion resistance, and if it exceeds the above range, there is a problem of decreased scratch resistance.

[0078] Further, the photoinitiator may be selected from the group consisting of benzophenone, hydroxycyclohexylphenylketone, and mixtures thereof. If the content of the photoinitiator is less than the above range, uncuring may occur and the coating film performance cannot be realized, and conversely, if the content of the photoinitiator exceeds the above range, rapid curing may result in high heat generation and damage to the coating film, and economic efficiency may be reduced.

[0079] And, the photoinitiator may be a mixture of

[0080] benzophenone 100 parts by weight, and

[0081] hydroxycyclohexylphenylketone 23 to 43 parts by weight, 27 to 40 parts by weight, or 30 to 37 parts by weight.

[0082] Further, the organic solvent may be selected from the group consisting of n-butyl acetate, ethyl acetate, isopropyl alcohol, methylisobutyl ketone, and mixtures thereof. If the content of the organic solvent is less than the above range, the surface may not be sprayed evenly during coating, and conversely, if the content exceeds the above range, the thickness of the coating film may be reduced and the performance of the coating film may be difficult to realize.

[0083] Further, the urethane acrylate oligomers may be the product of reacting isophorone diisocyanate 100 parts by weight, and the first photocured monomer 317 to 589 parts by weight, 362 to 544 parts by weight, or 408 to 498 parts by weight with a urethane reaction catalyst 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight.

[0084] If the content of the first photocuring monomer is less than the above range, there is a problem that the NCO- peak remains in the urethane reaction and the reaction is not terminated, and if it exceeds the above range, there is a problem that the impact resistance is reduced due to the increase in Hradness.

[0085] If the content of urethane reaction catalyst is less than the above range, there is a problem of decreasing the reaction speed due to decreased reactivity, and if it exceeds the above range, there is a possibility of gel generation due to rapid reaction.

[0086] And, the urethane acrylate oligomer may be the product of the reaction further including 29 to 54 parts by weight of ethylene oxide pentaerythritol polyol of Chemical Formula 1 below, 33 to 49 parts by weight, or 37 to 45 parts by weight.

[0087] [Chemical Formula 1]

[0088]

[0089] (In the formula, n is an integer from 1 to 10, 1 to 5, or 1 to 2).

[0090] If the content of ethylene oxide pentaerythritol polyol is less than the above range, there is a problem of decreased impact resistance due to increased hardness, and if it exceeds the above range, there is a problem of decreased pencil hardness and abrasion resistance due to increased softness.

[0091] The urethane acrylate oligomers of the present invention are oligomers copolymerized using the above weight ratios of ethylene oxide pentaerythritol polyol, isophorone diisocyanate, and dipentaerythritol pentaacrylate as monomers.

[0092] And, the ethylene oxide pentaerythritol polyol may have a weight average molecular weight of 100 to 1,500, 200 to 1,000, or 300 to 500. If the weight average molecular weight is less than the above range, there is a problem of decreased impact resistance due to increased hardness, and if it exceeds the above range, there is a problem of decreased physical properties such as pencil hardness and of increased viscosity due to high molecular weight.

[0093] And the said urethane acrylate oligomers may be produced from said monomers using methods known in the art, in particular may be produced via

[0094] (A) a first reaction step of reacting 100 parts by weight of said isophorone diisocyanate and 29 to 54 parts by weight, 33 to 49 parts by weight, or 37 to 45 parts by weight of said ethylene oxide pentaerythritol polyol with 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight of a urethane reaction catalyst; and

[0095] (B) a second reaction step of reacting 317 to 589 parts by weight, 362 to 544 parts by weight, or 408 to 498 parts by weight of the first photocuring monomer and the product of said first reaction step.

[0096] And, the urethane acrylate oligomer may be the product of the reaction further including 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight of polymerization stabilizer. If the polymerization stabilizer content is less than the above range, there is a problem of gel formation or yellowing of the liquid appearance during the reaction, and if it exceeds the above range, there is a problem of slowing down the urethane reaction rate.

[0097] Further, the first photocuring monomer may be selected from the group consisting of pentaerythritol triacrylate, dipentaerythritolpentaacrylate, and mixtures thereof. When the first photocuring monomer is dipentaerythritol pentaacrylate, the produced urethane acrylate oligomer is as shown in Chemical Formula 2 below.

[0098] [Chemical Formula 2]

[0099] [Rectified under Rule 91, 24.12.2024]

[0100] (In the formula, n is an integer from 1 to 10, 1 to 5, or 1 to 2).

[0101] Further, the urethane reaction catalyst may be selected from the group consisting of copper naphthenate, cobalt naphthenate, zinc naphthenate, n-butyl tin laurate, dibutyl tin dilaurate, tristilamine, 2-methyltriethylenediamide, and mixtures thereof.

[0102] Further, the polymerization stabilizer may be selected from the group consisting of butylated hydroxytoluene, hydroquinone, hydroquinonemonomethyl ether, para-benzoquinone, phenothiazine, and mixtures thereof.

[0103] And, the reaction temperature of the first reaction step may be 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃

[0104] And, the first reaction step may comprise partitively adding the urethane reaction catalyst to the mixture of isophorondiisocyanate and ethylene oxide pentaerythritol polyol at 50 to 80 ℃, 55 to 75 ℃, or 60 to 70 ℃, followed by raising the temperature to 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃.

[0105] And, the reaction time of said first reaction step may be 0.5 to 4 hours, 1 to 3 hours, or 1.5 to 2.5 hours.

[0106] And, the stirring rate of said first reaction step may be 30 to 50 Hz.

[0107] And, the first reaction step may be terminated at a percentage of isocyanate (NCO%) of 13 to 15%.

[0108] The urethane reaction may proceed through the first reaction step to form a quaternized NCO-terminated prepolymer, which may be represented by Chemical Formula 3 below.

[0109] [Chemical Formula 3]

[0110]

[0111] (In the formula, n is an integer from 1 to 10, 1 to 5, or 1 to 2).

[0112] And, the reaction temperature of the second reaction step may be 60 to 100 ℃, 70 to 90 ℃, or 75 to 85 ℃.

[0113] And, the reaction time of the second reaction step may be 0.5 to 6 hours, 1 to 5 hours, or 2 to 4 hours.

[0114] And, the second reaction step may be terminated when the isocyanate peak (2250 cm-1) in Fourier transform infrared spectroscopy disappears.

[0115] And, the urethane acrylate oligomer may have a weight average molecular weight of 4,000 to 20,000, 6,000 to 18,000, or 8,000 to 16,000. If the weight average molecular weight of the urethane acrylate oligomer is less than the above range, the cured coating film may be brittle, resulting in poor impact resistance or adhesion performance. Conversely, if the weight average molecular weight of the urethane acrylate oligomer is higher than the above range, the viscosity becomes very high, which is very uncomfortable to handle, and uneven leveling of the cured coating may occur. It can also lead to an excessive increase in flexibility, which can prevent the desired hardness from being achieved.

[0116] And, the viscosity at 25 ℃ of said urethane acrylate oligomer may be 10,000 to 40,000 cP, 15,000 to 35,000 cP, or 20,000 to 30,000 cP. If the viscosity is less than the above range, there is a problem of increasing the hardness of the photocured coating composition due to a decrease in the weight average molecular weight, and if the weight average molecular weight exceeds the above range, there is a problem of increasing the softness due to an increase in the weight average molecular weight and decreasing properties such as pencil hardness.

[0117]

[0118] Embodiments of the present invention will be described below.

[0119] Example

[0120] Preparation Example 1: Synthesis of Multifunctional Urethane Acrylate Oligomers with High Hardness

[0121] After adding 7 parts by weight isophorone diisocyanate (IPDI. VECOREX, France) and 93 parts by weight dipentaerythritol pentahydroxyacrylate (Green Chemicals, Korea), 0.02 parts by weight hydroquinone monomethyl ether (HQ-MME), a polymerization stabilizer, was added to the reactor and stirred at 40 Hz.

[0122] Then, at a temperature of 65 ℃, 0.02 parts by weight of dibutyltindilaurate (DBTDL), the urethane reaction catalyst, was added partitively, and the mixture was maintained at 80 ℃ for 3 h, being careful not to exothermize. The reaction was carried out until the NCO-peak (2250 cm-1) disappeared in FT-IR to synthesize a photocurable urethane acrylate oligomer.

[0123] Preparation Example 2: Synthesis of ethylene oxide copolymerized urethane acrylate oligomer (1)

[0124] 9 parts by weight of ethylene oxide pentaerythritol polyol, 21 parts by weight of isophorone diisocyanate (IPDI. VECOREX, France), and 0.02 parts by weight of hydroquinone monomethyl ether (HQ-MME), a polymerization stabilizer, were added to the reactor and stirred at 40 Hz.

[0125] Then, 0.02 parts by weight of dibutyltindilaurate (DBTDL), a urethane reaction catalyst, was added partitively at a temperature of 65 ℃, and the mixture was maintained at 80 ℃ for 2 h, being careful not to exothermize. If the NCO% was within the range of 13-15% when measured, 70 parts by weight of pentaerythritol trihydroxyacrylate (Green Chemicals, Korea) was added after cooling to below 70 ℃. The mixture was maintained at 80 ℃ for 3.5 h, taking care not to exothermize, and then reacted until the NCO-peak (2250 cm-1) disappeared in FT-IR to synthesize a photocurable ethylene oxide copolymerized urethane acrylate oligomer.

[0126] Preparation Example 3: Synthesis of ethylene oxide copolymerized urethane acrylate oligomer (2)

[0127] 5 parts by weight of ethylene oxide pentaerythritol polyol, 12 parts by weight of isophorone diisocyanate (IPDI. VECOREX, France), and 0.02 parts by weight of hydroquinone monomethyl ether (HQ-MME), a polymerization stabilizer, were added to the reactor and stirred at 40 Hz.

[0128] Then, at a temperature of 65 ℃, 0.02 parts by weight of dibutyltindiraurate (DBTDL) was added partitively, the urethane reaction catalyst, and the mixture was maintained at 80 ℃ for 2 h, being careful not to exothermize. If the NCO% was within the range of 13-15% when measured, 83 parts by weight of dipentaerythritol pentahydroxyacrylate (Green Chemicals, Korea) was added after cooling to below 70 ℃. The mixture was maintained at 80 ℃ for 3.5 h, taking care not to exothermize, and then reacted until the NCO-peak (2250 cm-1) disappeared in FT-IR to synthesize a photocurable ethylene oxide copolymerized urethane acrylate oligomer.

[0129] Example 1, Example 2 and Comparative Example: Formulation of Coating Compositions

[0130] Coating compositions were formulated using the oligomers synthesized in Preparation Examples 1 to 3 above according to the formulation ratios shown in Table 1 below.

[0131] (Unit: Weight Parts)Example 1Example 2ComparativeExamplePreparation Example 125.5Preparation Example 225.5Preparation Example 325.5nanosilica sol5dipentaerythritol hexaacrylate5benzophenone0.75hydroxycyclohexylphenylketone0.25n-butylacetate40isopropyl alcohol20ethylacetate5methylisobutylketone5*TINUVIN-292HP0.4*TINUVIN-4790.2**BYK-3330.4

[0132] * TINUVIN-292HP,TINUVIN-479: UV absorbers (CIBA Specialty Chemicals, Switzerland)

[0133] **BYK-333: Leveling stabilizer (BYK CHEMIE, Germany)

[0134] Test Example 1: Appearance observation

[0135] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0136] The condition of the fabricated specimens was visually observed and the results are shown in Table 2.

[0137] Test Example 2: Measure Gloss, DOI, and Haze

[0138] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0139] For the fabricated specimens, the Rhopoint IQ gloss meter (Rhopoint, UK) was used to measure the Gloss, Haze, and DOI values of the coated specimens, and the results are shown in Table 2.

[0140] Gloss: A measurement proportional to the total amount of light reflected from a surface measured at 60° (medium gloss).

[0141] Haze: An optical effect caused by fine texture or residue on a surface.

[0142] Distinctness of Image (DOI): A measure of how clearly a reflected image appears on a reflective surface.

[0143] Test Example 3. Measure Light Transmittance

[0144] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0145] UV Spectrometer (SHIMADZU, Japan) was used to measure, and the results are shown in Table 2.

[0146] Test Example 4. Measure pencil hardness

[0147] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0148] As a test to evaluate the hardness of the coating surface and the hardness of the surface due to adhesion with the substrate, the point where the surface is not damaged when scratched at an angle of 45° with a pencil under a load of 750 g was recorded, and the results are shown in Table 2.

[0149] Test Example 5: Measuring impact resistance

[0150] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80 °C oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0151] A metal ball weighing 500 g was dropped from a height of 10 to 50 cm from the impact tester shown in Fig. 1 on the fabricated specimen to visually check whether the coating layer of the specimen breaks, and the results are shown in Table 2.

[0152] Test Example 6: Measure Adhesion

[0153] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80 °C oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0154] On the fabricated specimen, 36 grids (6Х6) with a width of 1 mm were made and repeatedly peeled off with 3M scotch tape five times, and the adhesion grade was judged according to the criteria of Fig. 2, and the results are shown in Table 2.

[0155] Test Example 7: Measure scratch resistance

[0156] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0157] The fabricated specimen was rubbed against a tip of #0000 steel wool at a speed of 20 rpm under a load of 500 g for 10 times, applying friction to the surface of the specimen, and the gloss value of the tested surface was measured with a Rhopoint IQ gloss meter (Rhopoint, UK), the results of which are shown in Table 2.

[0158] Test Example 8. Measuring Wear Resistance

[0159] The coating compositions of Example 1, Example 2, and the Comparative Example were applied to a PC specimen measuring 100 Х 100 mm, respectively, and the coating was spread using a barcoater No. 7 and placed in an 80 ℃ oven for 10 minutes to volatilize the organic solvent contained in the coating composition. The coated specimens were taken out and passed through a UV curing machine with a 2.5 kW metal-halide lamp at a speed of 5.5 m / min to produce 14~18 μm thick coated PC specimens. The UV dose value was 800 mJ / cm2in the UV range 200-400 nm.

[0160] The fabricated specimens were subjected to a Taber abrasion tester (Taber, USA) at a load of 500 g and a speed of 40 rpm for 1,000 reciprocations to apply friction to the surface of the specimen, and then the haze value of the tested surface was measured with a Rhopoint IQ gloss meter (Rhopoint, UK), and the results are shown in Table 2.

[0161] [Rectified under Rule 91, 28.03.2025]

[0162] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above. Various modifications may be implemented by those skilled in the art without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments described above, but should be defined by the following claims as well as the equivalents thereof.

[0163] The photocurable coating composition according to the present invention uses an ethylene oxide pentaerythritol polyol for oligomer synthesis to give flexibility to pentaerythritol, a tetrahydric alcohol, wherein the polyol is produced from pentaerythritol modified with ethylene oxide. The said composition can solve problems such as curl formation after photocuring, surface cracking, and poor impact resistance, which are weaknesses of conventional high-hardness multifunctional oligomers. In addition, by improving hardness and impact resistance, it can exhibit excellent scratch resistance, abrasion resistance, and light transmission properties.

Claims

1.The photocured coating compositions with excellent hardness and impact resistance, includingurethane acrylate oligomer 100 parts by weight,the second photocured monomer 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,nanosilica sol 14 to 25 parts by weight, 16 to 24 parts by weight, or 18 to 22 parts by weight,photoinitiator 2.7 to 5.1 parts by weight, 3.1 to 4.7 parts by weight , or 3.5 to 4.3 parts by weight, andorganic solvents 192 to 357 parts by weight, 220 to 329 parts by weight, or 247 to 302 parts by weight.2.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 1,wherein the second photocuring monomer may be selected from the group consisting of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylpropanetriacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and mixtures thereof.3.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 1,wherein the photoinitiator may be selected from the group consisting of benzophenone, hydroxycyclohexylphenylketone, and mixtures thereof.4.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 1,wherein the organic solvent may be selected from the group consisting of n-butyl acetate, ethyl acetate, isopropyl alcohol, methylisobutyl ketone, and mixtures thereof.5.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 1,wherein the urethane acrylate oligomers may be the product of reacting isophorone diisocyanate 100 parts by weight, and the first photocured monomer 317 to 589 parts by weight, 362 to 544 parts by weight, or 408 to 498 parts by weight with a urethane reaction catalyst 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight.6.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 5,wherein the urethane acrylate oligomer may be the product of the reaction further including 0.08 to 0.15 parts by weight, 0.09 to 0.14 parts by weight, or 0.11 to 0.13 parts by weight of polymerization stabilizer.7.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 5,wherein the first photocuring monomer may be selected from the group consisting of pentaerythritol triacrylate, dipentaerythritolpentaacrylate, and mixtures thereof.8.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 5,wherein the urethane reaction catalyst may be selected from the group consisting of copper naphthenate, cobalt naphthenate, zinc naphthenate, n-butyl tin laurate, dibutyl tin dilaurate, tristilamine, 2-methyltriethylenediamide, and mixtures thereof.9.The photocured coating compositions of the present invention, with excellent hardness and impact resistance according to claim 5,wherein the polymerization stabilizer may be selected from the group consisting of butylated hydroxytoluene, hydroquinone, hydroquinonemonomethyl ether, para-benzoquinone, phenothiazine, and mixtures thereof.

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