Photocurable resin compositions, cured films, and molded articles with cured films

Abstract

The objective of this invention is to provide a photocurable resin composition capable of forming a cured film with excellent smoothness, adhesion, transparency, abrasion resistance, scratch resistance, crack resistance, and weather resistance. The photocurable resin composition of the present invention is a photocurable resin composition containing urethane (meth)acrylate (A), (meth)acrylate monomer (B), photopolymerization initiator (C) and leveling agent (D). The aforementioned (meth)acrylate monomer (B) contains at least difunctional (meth)acrylate monomer (b1) and hexafunctional (meth)acrylate monomer (b2). The content of the aforementioned urethane (meth)acrylate (A) is 45% by mass or more and 75% by mass or less relative to the solid content of the aforementioned photocurable resin composition. The content of the aforementioned (meth)acrylate monomer (B) is 20% by mass or more and 45% by mass or less relative to the solid content of the aforementioned photocurable resin composition. The content of the aforementioned difunctional (meth)acrylate monomer (b1) is 35% by mass or more relative to the content of the aforementioned (meth)acrylate monomer (B).

Description

Technical Field

[0001] This invention relates to photocurable resin compositions. Furthermore, this invention also relates to a cured film formed from a photocurable resin composition and a molded article having the cured film. Background Technology

[0002] Polycarbonate resin is generally widely used as an engineering plastic due to its excellent transparency, moldability, and impact resistance. For example, it is extensively used in vehicle headlight lenses and side lamp lenses. However, polycarbonate resin has poor scratch resistance and weather resistance, so a cured film is applied to its surface as a protective coating. The cured film is formed by applying a coating agent to the surface and allowing it to cure. This cured film requires properties such as smoothness without compromising appearance, weather resistance (without discoloration even after prolonged exposure to outdoor environments), crack resistance, scratch resistance, and abrasion resistance.

[0003] In addition, in recent years, with the shift of headlight light sources from halogen bulbs to HID bulbs, a phenomenon has occurred where the cured coating on the surface of the headlight lens becomes bluish-white and blurry. To solve this technical problem, an active energy ray curable coating material composition has been proposed, which contains a specific monomer and / or oligomer (A) having one or more free radical polymerizable unsaturated double bonds within one molecule (see, for example, Patent Document 1).

[0004] In addition, in order to improve outdoor durability, UV stability, thermal stability and flexibility, a UV-curable coating composition containing specific first and second urethane acrylate resins and specific difunctional and trifunctional acrylate monomers has been proposed (Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-238845

[0008] Patent Document 2: Japanese Patent No. 6413130 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] There is a growing trend towards a shift in headlight light sources from HID bulbs to LEDs. The inventors of this application have discovered that in headlight lenses with conventionally cured films on their surfaces, when using LEDs as the light source, the cured film becomes cloudy under LED illumination. Therefore, for LED illumination, a cured film with excellent transparency, smoothness, adhesion, abrasion resistance, scratch resistance, crack resistance, and weather resistance—all properties required for headlight lenses—is needed.

[0011] Therefore, the object of the present invention is to provide a photocurable resin composition capable of forming a cured film with excellent smoothness, adhesion, transparency, abrasion resistance, scratch resistance, crack resistance and weather resistance.

[0012] Methods for solving problems

[0013] To address the aforementioned problems, the inventors of this application conducted in-depth research and discovered that by adjusting the content of urethane (meth)acrylate (A), (meth)acrylate monomer (B) (which comprises difunctional (meth)acrylate monomer (b1) and hexafunctional (meth)acrylate monomer (b2)), photopolymerization initiator (C), and leveling agent (D) in a photocurable resin composition, the aforementioned problems can be solved. This invention is based on the above insights.

[0014] That is, according to the present invention, the following technical solution is provided.

[0015] [1] A photocurable resin composition comprising urethane (meth)acrylate (A), (meth)acrylate monomer (B), photopolymerization initiator (C) and leveling agent (D),

[0016] The aforementioned (meth)acrylate monomer (B) comprises at least a difunctional (meth)acrylate monomer (b1) and a hexafunctional (meth)acrylate monomer (b2).

[0017] The content of the aforementioned urethane (meth)acrylate (A) is 45% by mass or more and 75% by mass or less, relative to the solid content of the aforementioned photocurable resin composition.

[0018] The content of the aforementioned (meth)acrylate monomer (B) is 20% by mass or more and 45% by mass or less, relative to the solid content of the aforementioned photocurable resin composition.

[0019] The content of the aforementioned difunctional (meth)acrylate monomer (b1) is 35% by mass or more, relative to the content of the aforementioned (meth)acrylate monomer (b).

[0020] [2] The photocurable resin composition as described in [1], wherein the content of the aforementioned hexafunctional (meth)acrylate monomer (b2) is 5% by mass or more relative to the content of the aforementioned (meth)acrylate monomer (B).

[0021] [3] The photocurable resin composition as described in [1] or [2], wherein the aforementioned urethane (meth)acrylate (A) comprises urethane (meth)acrylate having an isocyanurate backbone.

[0022] [4] The photocurable resin composition as described in any one of [1] to [3], wherein the weight-average molecular weight (Mw) of the aforementioned leveling agent (D) is 30,000 or less.

[0023] [5] The photocurable resin composition as described in any one of [1] to [4] further comprises an ultraviolet absorber (E).

[0024] [6] The photocurable resin composition as described in any one of [1] to [5] further comprises a light stabilizer (F).

[0025] [7] The photocurable resin composition as described in any one of [1] to [6] is used as a coating for lamp lenses.

[0026] [8] A cured film, which is formed from any one of the photocurable resin compositions described in [1] to [7].

[0027] [9] A molded article having at least a portion of its surface covered with the cured film described in [8].

[0028]

[10] The molded article as described in [9] is a lamp lens for a vehicle.

[0029]

[11] A method for manufacturing a molded article, comprising:

[0030] The coating process involves coating at least one side of the molded article with the photocurable resin composition described in any one of [1] to [8]; and

[0031] The curing process involves curing the aforementioned photocurable resin composition by irradiation with ultraviolet light after the coating process to form a cured film.

[0032] Invention Effects

[0033] According to the present invention, a photocurable resin composition capable of forming a cured film with excellent smoothness, adhesion, transparency, abrasion resistance, scratch resistance, crack resistance, and weather resistance can be provided. Furthermore, according to the present invention, a cured film formed from such a photocurable resin composition and a molded article having the cured film can also be provided. Molded articles having a cured film formed from the photocurable resin composition of the present invention on a portion of their surface exhibit excellent transparency and are less prone to clouding under LED irradiation. Detailed Implementation

[0034] The present invention will now be described in more detail.

[0035] It should be noted that in this specification, "(meth)acrylate" refers to acrylate and methacrylate, "(meth)acrylic" refers to acrylic and methacrylic, and "(meth)acryloyl" refers to acryloyl and methacryloyl.

[0036] "Solid components" refers to the components remaining after removing volatile components such as organic solvents from a photocurable resin composition, indicating the components that form the cured film during curing.

[0037] <Photocurable Resin Composition>

[0038] The photocurable resin composition of the present invention contains at least urethane (meth)acrylate (A), a specific (meth)acrylate monomer (B), a photopolymerization initiator (C), and a leveling agent (D). In the present invention, by including components (A) to (D) in the photocurable resin composition and adjusting the content of urethane (meth)acrylate (A) and (meth)acrylate monomer (B), a cured film with excellent smoothness, adhesion, transparency, abrasion resistance, scratch resistance, crack resistance, and weather resistance can be formed. Furthermore, the photocurable resin composition of the present invention may also contain an ultraviolet absorber (E), a light stabilizer (F), inorganic particles (G), and a solvent (H). Molded articles having such a cured film are less prone to clouding under LED irradiation, and therefore can be suitable for use as coatings for vehicle headlight lenses. The components constituting the photocurable resin composition will be described in detail below.

[0039] (Carbamate (Meth)acrylate (A))

[0040] Carbamate (meth)acrylate (A) is a substance having an acryloyl group (CH2=CHCO-) ​​and / or a methacryloyl group (CH2=C(CH3)-CO-) and a carbamate bond (-NH·COO-) as functional groups in its molecule. Carbamate (meth)acrylate is not particularly limited; for example, it can be obtained by reacting a polyisocyanate, a hydroxyl-containing (meth)acrylate, or a polyol other than a hydroxyl-containing (meth)acrylate, as needed. Carbamate (meth)acrylate (A) is preferably an oligomer or a polymer, more preferably an oligomer.

[0041] The aforementioned polyisocyanates are obtained by reacting polyols with diisocyanates. There are no particular limitations on the polyols used as raw materials for the synthesis of polyisocyanates; examples include polyester polyols, polyether polyols, and polycarbonate polyols. Only one of these can be used, or two or more can be used in combination.

[0042] As a polyester polyol, there are no particular limitations on the manufacturing method. For example, polyester polyols obtained by known methods such as polycondensation reaction of diol with dicarboxylic acid or dicarboxylic acid acyl chloride, or transesterification reaction of diol or dicarboxylic acid.

[0043] The diols used in the synthesis of polyester polyols are not particularly limited, and examples include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, and tetrapropylene glycol.

[0044] The dicarboxylic acids used in the synthesis of polyester polyols are not particularly limited, and examples include adipic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, dimaleic acid, terephthalic acid, isophthalic acid, and phthalic acid.

[0045] As a polyether polyol, there is no particular limitation; for example, polyethylene oxide, polypropylene oxide, and random copolymers of ethylene oxide and propylene oxide can be cited.

[0046] The polyol used for polycarbonate is not particularly limited; for example, it can be the reaction product obtained by polycondensation of component A and component B. That is, component A is not particularly limited; for example, it can be diols such as 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, 1,4-cyclohexanediol, 2-methylpropanediol, dipropylene glycol, and diethylene glycol, or reaction products of these diols with dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, and hexahydrophthalic acid. In addition, as component B, there are no particular limitations. For example, aromatic carbonates or aliphatic carbonates such as diphenyl carbonate, bis(chlorophenyl) carbonate, dinaphthalene carbonate, phenyltoluene carbonate, phenylchlorophenyl carbonate, 2-tolyl-4-tolyl carbonate, dimethyl carbonate, diethyl carbonate, diethylene carbonate, and ethylene carbonate can be cited.

[0047] There are no particular restrictions on diisocyanates used as raw materials for the synthesis of polyisocyanates; linear, alicyclic, or aromatic diisocyanates can be used. Specifically, examples include linear hydrocarbons containing isocyanate groups such as tetramethylene diisocyanate and hexamethylene diisocyanate; branched hydrocarbons containing isocyanate groups such as 2,2,4-trimethylhexamethylene diisocyanate; cyclic hydrocarbons containing isocyanate groups such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated toluene diisocyanate; p-phenylene diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, 1,3-xylene diisocyanate, bianisidine diisocyanate, tetramethylxylene diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate, and 4,4-diphenylmethane diisocyanate; and aromatic hydrocarbons containing isocyanate groups.

[0048] As the aforementioned hydroxyl-containing (meth)acrylate, a (meth)acrylate having at least one, preferably one to five, hydroxyl groups can be used. Furthermore, it is ideal for such a hydroxyl-containing (meth)acrylate to have a hydrocarbon moiety with a preferred number of carbon atoms of 2 to 20. Here, the hydrocarbon moiety refers to an organic group having a straight-chain or branched aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group; the aliphatic hydrocarbon group or the alicyclic hydrocarbon group can be saturated or unsaturated. It should be noted that a portion of this hydrocarbon moiety may contain an ether bond (COC bond).

[0049] Examples of hydroxyl-containing (meth)acrylate monomers include, for example, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and their caprolactone adducts (such as PLACEL FA1, FA2, etc. manufactured by Daicel Co., Ltd.), OH-terminated polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate, their ethylene oxide modified derivatives (such as AM-90G, AM-130G manufactured by Shin-Nakamura Chemical Industry Co., Ltd., and Light Acrylate EC-A, MTG-A, EHDG-AT manufactured by Kyoeisha Chemical Co., Ltd.), glycerol mono(meth)acrylates (such as BLEMMER GLM manufactured by Nippon Oil Co., Ltd.), glycerol di(meth)acrylates (such as Aronix MT3560 manufactured by Toa Synthetic Co., Ltd.), and EO-modified di(meth)acrylates of isocyanuric acid (such as Aronix manufactured by Toa Synthetic Co., Ltd.). The following are examples of polyacrylates: M-313, 315, etc.; pentaerythritol tri(meth)acrylate (Viscoat 300 manufactured by Osaka Organic Chemicals Co., Ltd., Aronix M-305, M-306, MT-3548 manufactured by Toa Synthetic Co., Ltd., Light Acrylate PE-3A manufactured by Kyoei Chemical Co., Ltd., NK Ester A-TMM-3L manufactured by Shin-Nakamura Chemical Co., Ltd., etc.); dipentaerythritol penta(meth)acrylate (Aronix M-400, M-402, M-403, MT-3549 manufactured by Toa Synthetic Co., Ltd., Light Acrylate DPE-6A manufactured by Kyoei Chemical Co., Ltd., NK Ester A-DPH manufactured by Shin-Nakamura Chemical Co., Ltd., etc.). Among these, considering the weather resistance, abrasion resistance, and scratch resistance of the cured film, isocyanuric acid EO-modified diacrylate and pentaerythritol triacrylate are preferred. Such hydroxyl-containing (meth)acrylates can be used alone or in combination of two or more.

[0050] As polyols other than the aforementioned hydroxyl-containing (meth)acrylates, which may be used as needed, known polyols such as polyether polyols, polyester polyols, and polyolefin polyols can be used. Specifically, examples include polyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, polycaprolactone polyols, and alkylene glycols. Such polyols can be used alone or in combination of two or more.

[0051] Of the aforementioned urethane (meth)acrylate oligomers (A), from the viewpoint of the abrasion resistance and scratch resistance of the cured film, multifunctional urethane (meth)acrylates are preferred, more preferably urethane (meth)acrylates with 2 to 12 functionalities, and even more preferably urethane (meth)acrylates with 3 to 10 functionalities. Furthermore, from the viewpoint of weather resistance, aliphatic urethane (meth)acrylates and urethane (meth)acrylates containing an alicyclic backbone are preferred, and urethane (meth)acrylates having an isocyanurate backbone are even more preferred.

[0052] From the viewpoint of the crack resistance and weather resistance of the cured film, the content of urethane (meth)acrylate oligomer (A) is 45% to 75% by mass and less than 75% by mass, preferably 50% to 72% by mass and more preferably 55% to 70% by mass and less than 70% by mass, relative to the solid content of the photocurable resin composition.

[0053] ((Meth)acrylate monomer (B))

[0054] The (meth)acrylate monomer (B) is a monomer having at least one (meth)acryloyl group and functions as a reactive diluent to adjust the viscosity of the photocurable resin composition. When the photocurable resin composition is irradiated with ultraviolet light, it forms a cured film together with the above-mentioned urethane (meth)acrylate oligomer (A).

[0055] (2-functional (meth)acrylate monomer (b1))

[0056] (B) meth)acrylate monomers contain at least two functional (meth)acrylate monomers (b1). A difunctional (meth)acrylate monomer is a compound having two (meth)acryloyloxy groups as functional groups within its molecule. Examples of difunctional (meth)acrylate monomers include, for example, alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate. Acrylic esters, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate, etc., are polyoxyalkylene glycol di(meth)acrylates; halogen-substituted alkylene glycol di(meth)acrylates, such as tetrafluoroethylene glycol di(meth)acrylate; trimethylolpropane di(meth)acrylate, di(trimethylolpropane)di(meth)acrylate, pentaerythritol di(meth)acrylate, etc., are aliphatic polyol di(meth)acrylates; hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, etc. Di(meth)acrylates of hydrogenated dicyclopentadiene or tricyclodecanediol, such as acrylates; di(meth)acrylates of dioxanediol or dioxanediol, such as 1,3-dioxane-2,5-dimethyl acrylate (also known as dioxanediol di(meth)acrylate); di(meth)acrylates of bisphenol A or bisphenol F ethylene oxide adducts, such as ethylene oxide adducts of bisphenol A or bisphenol F; acrylic adducts of bisphenol A diglycidyl ether and propylene adducts of bisphenol F diglycidyl ether. Epoxy di(meth)acrylates of bisphenol A or bisphenol F, such as acrylate adducts; organosilicon di(meth)acrylates; di(meth)acrylates of neopentyl glycol hydroxypentanoate; 2,2-bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane; 2,2-bis[4-(meth)acryloyloxyethoxyethoxycyclohexyl]propane; di(meth)acrylates of 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane; tri(hydroxyethyl)isocyanurate di(meth)acrylates; etc.Among these difunctional (meth)acrylate monomers, preferred are alkylene glycol di(meth)acrylate, polyoxyalkylene glycol di(meth)acrylate, halogen-substituted alkylene glycol di(meth)acrylate, aliphatic polyol di(meth)acrylate, hydrogenated dicyclopentadiene or tricyclodecanediol di(meth)acrylate, dioxanediol or dioxanediol di(meth)acrylate, organosilicon di(meth)acrylate, neopentyl glycol hydroxypentanoate di(meth)acrylate, and 2,2-bis[ [4-(meth)acryloyloxyethoxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxyethoxycyclohexyl]propane, 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane]di(meth)acrylate, tri(hydroxyethyl)isocyanurate di(meth)acrylate, more preferably alkylene glycol di(meth)acrylate, particularly preferably 1,6-hexanediol di(meth)acrylate and 1,9-nonanediol di(meth)acrylate. These monomers may be used individually or in combination of two or more.

[0057] (6-functional (meth)acrylate monomer (b2))

[0058] The (meth)acrylate monomer (B) further comprises a hexafunctional (meth)acrylate monomer (b2). A hexafunctional (meth)acrylate monomer refers to a compound having six (meth)acryloyloxy groups as functional groups within its molecule. Examples of hexafunctional (meth)acrylate monomers include, for example, dipentaerythritol hexa(meth)acrylate, alkoxylated dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, and polycaprolactone-modified dipentaerythritol hexa(meth)acrylate. Only one of these monomers may be used, or two or more may be used in combination. The hexafunctional (meth)acrylate monomer (b2) is preferably a caprolactone-modified variety, more preferably caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0059] (Other multifunctional (meth)acrylate monomers (b3))

[0060] The (meth)acrylate monomer (B) may further comprise other polyfunctional (meth)acrylate monomers (b3) besides the difunctional (meth)acrylate monomer (b1) and hexafunctional (meth)acrylate monomer (b2) described above. As other polyfunctional (meth)acrylate monomers (b3), for example, (meth)acrylate monomers with 3 or more functions but less than 5 functions are preferably used. Examples of (meth)acrylate monomers with 3 or more functions but less than 5 functions include, for example, glycerol trimethacrylate, trimethylolpropane trimethacrylate, di(trimethylolpropane)trimethacrylate, di(trimethylolpropane)tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetramethacrylate, and dipentaerythritol pentamethacrylate. Only one of these may be used, or two or more may be used in combination.

[0061] From the viewpoint of the scratch resistance, adhesion, and weather resistance of the cured film, the content of (meth)acrylate monomer (B) relative to the solid component amount of the photocurable resin composition is 20% by mass or more and 45% by mass or less, preferably 21% by mass or more and 42% by mass or less, and more preferably 22% by mass or more and 40% by mass or less. Furthermore, from the viewpoint of the adhesion and weather resistance of the cured film, the content of difunctional (meth)acrylate monomer (b1) in (meth)acrylate monomer (B) is 35% by mass or more, more preferably 40% by mass or more and 95% by mass or less. From the viewpoint of the scratch resistance of the cured film, the content of hexafunctional (meth)acrylate monomer (b2) in (meth)acrylate monomer (B) is preferably 5% by mass or more and 65% by mass or less, more preferably 10% by mass or more and 60% by mass or less.

[0062] (Photopolymerization initiator (C))

[0063] The photopolymerization initiator (C) is not particularly limited, and conventionally known photopolymerization initiators for UV curing can be used. Examples of photopolymerization initiators include acylphosphine oxide-based polymerization initiators, acetophenone-based polymerization initiators, benzoyl carbamate-based polymerization initiators, thioxanone-based polymerization initiators, oxime ester-based polymerization initiators, hydroxybenzoyl-based polymerization initiators, benzophenone-based polymerization initiators, and α-aminoalkylphenyl ketone-based polymerization initiators.

[0064] Examples of acylphosphine oxide polymerization initiators include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl phenyl ethoxyphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0065] Examples of acetophenone-based polymerization initiators include acetophenone, 3-methylacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-one, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]phenyl}-2-methyl-propane-1-one.

[0066] Examples of benzoyl ester polymerization initiators include methyl benzoate.

[0067] Examples of thioxanthone-based polymerization initiators include isopropylthioxanthone.

[0068] Examples of oxime ester polymerization initiators include 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime) and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-ethylone 1-(O-acetyl oxime).

[0069] Examples of hydroxybenzoyl polymerization initiators include 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenylone, and benzoin alkyl ethers.

[0070] Examples of benzophenone-based polymerization initiators include benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone.

[0071] Examples of α-aminoalkylphenyl ketone polymerization initiators include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.

[0072] The polymerization initiator mentioned above can be used alone or in combination of two or more.

[0073] From the viewpoint of curability and transparency of the cured film, the content of photopolymerization initiator (C) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 7.0% by mass or less, and even more preferably 1.0% by mass or more and 5.0% by mass or less, relative to the amount of solid components in the photocurable resin composition.

[0074] (Leveling agent (D))

[0075] Leveling agents (D) refer to substances that adjust the flowability of photocurable resin compositions and make the coated film flat. Examples of leveling agents include fluorinated leveling agents, silicone leveling agents, and acrylic polymer leveling agents.

[0076] Examples of fluorinated leveling agents include perfluoroalkenyl carboxylates, perfluoroalkenyl sulfonates, perfluoroalkenyl phosphates, and perfluoroalkenyl betaine, which have perfluoroalkenyl groups in the main chain or side chain; and perfluoroalkyl polyoxyethylene ethers, perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, perfluoroalkyl phosphates, and perfluoroalkyl betaine, which have perfluoroalkyl groups in the main chain or side chain.

[0077] Examples of silicone-based leveling agents include polydimethylsiloxane, polymethylphenylsiloxane, polymethylhydrosiloxane, polyether-modified polydimethylsiloxane, polyether-modified polymethylphenylsiloxane, and polyether-modified polymethylhydrosiloxane.

[0078] As an acrylic polymer leveling agent, a polyether-modified (meth)acrylic compound represented by the following general formula (1) can be used.

[0079] [Chemical Formula 1]

[0080]

[0081] In general formula (1), R1 to R8 may be the same or different, at least one of R1 to R8 represents a polyether group represented by the aforementioned general formula (2), and at least one represents a (meth)acryloyl group or a straight-chain or branched alkyl group of C1 to C20 having a (meth)acryloyl group.

[0082] [Chemical Formula 2]

[0083]

[0084] In general formula (2), R9 represents a straight-chain or branched alkylene group of C1 to C20, R 10 R9 represents a hydrogen atom, a C1-C20 straight-chain or branched alkyl group, a C2-C20 straight-chain or branched alkenyl group, or a C2-C20 straight-chain or branched alkynyl group. Multiple R9s may be the same or different. k represents an integer greater than 1. Other R1-R8s represent C1-C20 straight-chain or branched alkyl groups. Multiple R2-R5s may be the same or different.

[0085] m and n can be the same or different, representing integers greater than 0, preferably integers from 1 to 20, and even more preferably integers from 1 to 10.

[0086] Commercially available leveling agents can also be used. For example, fluorinated leveling agents include Neos Co., Ltd.'s trade name Ftergent 602A. Silicone leveling agents include BYK Co., Ltd.'s trade names BYK-315N and BYK-325N, Kyoeisha Chemical Co., Ltd.'s trade name Polyflow KL-401, and EVONIK Co., Ltd.'s trade name Tegoflow 425. Acrylic polymer leveling agents include Kyoeisha Chemical Co., Ltd.'s trade name Polyflow No.75, BYK Co., Ltd.'s trade names BYK-350 and BYK-381. Other leveling agents include BYK Co., Ltd.'s trade name BYK-399.

[0087] From the viewpoint of the smoothness of the cured film and its transparency under LED irradiation, the weight-average molecular weight (Mw) of the leveling agent (D) is preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and even more preferably 3,000 to 30,000. It should be noted that the weight-average molecular weight (Mw) can be determined using gel permeation chromatography (GPC).

[0088] From the viewpoint of the smoothness and weather resistance of the cured film, the content of leveling agent (D) is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, and even more preferably 0.1% by mass or more and 1% by mass or less, relative to the amount of solid components in the photocurable resin composition.

[0089] (UV absorber (E))

[0090] The ultraviolet absorber (E) is not particularly limited, and conventionally known ultraviolet absorbers can be used. Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, hydroxyphenyltriazine-based ultraviolet absorbers, and benzophenone-based ultraviolet absorbers. Only one of these ultraviolet absorbers may be used, or two or more may be used in combination.

[0091] Examples of benzotriazole-based ultraviolet absorbers include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, and 2-[2'-hydroxy-5'-(methacryloyloxyhexyl)phenyl]-2H-benzotriazole. H-benzotriazole, 2-[2'-hydroxy-3'-tert-butyl-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-tert-butyl-3'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl] [Phenyl]-5-methoxy-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-5-cyano-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-5-tert-butyl-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl) Examples of benzotriazoles include 2-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-C7-9-branched straight-chain alkyl esters, 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, and 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol.

[0092] Examples of hydroxyphenyl triazine-based ultraviolet absorbers include, for instance, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-(2-hydroxy-3-tetrazyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-[4-[( [2-Hydroxy-3-(2-ethylhexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-bisbutoxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-[1-octoxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, etc.

[0093] Examples of benzophenone-based ultraviolet absorbers include 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxyethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, and sodium 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-5,5'-disulfonic acid.

[0094] Regarding the content of ultraviolet absorber (E), from the viewpoint of the weather resistance of the cured film, based on 100% by mass of the solid component of the photocurable resin composition, it is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less.

[0095] (Light stabilizer (F))

[0096] As for the light stabilizer (F), there are no particular limitations, and conventionally known light stabilizers can be used, but hindered amine-based light stabilizers are preferred. Examples of light stabilizers include, for instance, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-[2-[3-(3,5-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4,5]decane-2,4-dione, bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-( 3,5-Di-tert-butyl-4-hydroxybenzyl)-2-n-butylmalonate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidinyl) ester of 1,2,3,4-butanetetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidinyl) ester of 1,2,3,4-butanetetracarboxylate (mixed 1,2,2,6,6-pentamethyl-4-piperidinyl / tridecyl) ester, mixed {1,2,2,6,6-pentamethyl-4-piperidinyl / β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxazolo(5,5)undecane]diethyl} ester of 1,2,3,4-butanetetracarboxylate ( Mixed 2,2,6,6-tetramethyl-4-piperidinyl / tridecyl) ester, 1,2,3,4-butanetetracarboxylic acid mixed {2,2,6,6-tetramethyl-4-piperidinyl / β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxazolo(5,5)undecane]diethyl} ester, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)][(2,2,6,6-tetramethyl-4-piperidinyl)imino]hexamethylene[(2,2,6,6-tetramethyl Polymers of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, N,N',N”,N”'-tetra-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine-1,3,5-triazin-N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethylpiperidinyl)butylamine, and bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl) sebacate, etc.

[0097] From the viewpoint of the weather resistance of the cured film, the content of light stabilizer (F) is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 3% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less, relative to the amount of solid components in the photocurable resin composition.

[0098] (Inorganic particles (G))

[0099] There are no particular limitations on the inorganic particles (G), and any previously known inorganic particles can be used. Inorganic particles can be substances obtained by dispersing them in a colloidal state in a dispersion medium such as water or organic solvents.

[0100] Examples of inorganic particles include metal oxides such as silica, aluminum, titanium, zirconium, and zinc. From the viewpoint of scratch resistance of the resulting cured film, silica is preferred. Silica can be in powder or colloidal form. The average particle size of the silica particles is 0.001–20 μm, preferably 0.001–2 μm, more preferably 0.001–0.3 μm, and particularly preferably 0.005–0.08 μm. Furthermore, the shape is not particularly limited and can be any shape including spherical, hollow, porous, rod-shaped, plate-shaped, and fibrous, with spherical shapes being preferred. The average particle size of the silica particles can be determined using laser diffraction.

[0101] Colloidal silica particles are preferred as silica. Commercially available colloidal silica particles can also be used. Examples of commercially available products include those manufactured by Nissan Chemical Co., Ltd. under the following brand names: IPA-ST, IPA-ST-L, IPA-ST-ZL, PGM-ST, etc.

[0102] As inorganic particles, organic-inorganic hybrid resins, i.e., reactive inorganic particles, can be used to chemically bond inorganic particles to resins to form composites.

[0103] As a resin, any resin capable of chemically bonding with inorganic particles to form an organic-inorganic hybrid resin is acceptable, and there are no particular limitations. Preferred resins are those polymerized by photocuring, such as urethane (meth)acrylates, (meth)acrylates, etc. Only one type may be used, or two or more may be used in combination.

[0104] There are no particular limitations on the manufacturing method of organic-inorganic hybrid resins, as long as the method can chemically bond inorganic particles to the resin to form a composite. For example, when using a resin containing hydrolyzable silyl groups as the resin and using silica as the inorganic particles, the hydrolyzable silyl groups of the resin and the silica can react to form a composite. Hereinafter, a preferred embodiment using silica as the inorganic particles will be described.

[0105] In a preferred embodiment of the present invention, silica particles having a reactive (meth)acryloyl group can be used as reactive inorganic particles. For example, the reactive silica particles described in Japanese Patent Application Publication No. 9-100111 can be used as reactive silica particles. The reactive silica particles (B) comprise silica particles and a silane compound chemically bonded to the silica particles. The silane compound has a hydrolyzable silyl group and a (meth)acryloyl group at its terminal, and also has groups represented by the following formulas (a) and (b):

[0106] [Chemical Formula 3]

[0107]

[0108] [Chemical Formula 4]

[0109]

[0110] (In the formula, X is selected from -NH-, -O- and -S-, and Y is selected from oxygen atoms and sulfur atoms. When X is -O-, Y is a sulfur atom).

[0111] Hydrolyzable silyl groups are bonded to silanol groups present on the surface of silica particles through hydrolysis and condensation reactions. Additionally, (meth)acryloyl groups are used in the intermolecular chemical crosslinking via addition polymerization through active free radicals. Furthermore, it is inferred that the groups represented by formulas (a) and (b) above are structural units that directly bond molecules with hydrolyzable silyl groups to molecules with (meth)acryloyl groups or are bonded through other molecules, while simultaneously generating moderate cohesive forces between molecules due to hydrogen bonds. This contributes to the excellent mechanical strength, adhesion to the substrate, and heat resistance of the cured composition.

[0112] Such silane compounds can be synthesized, as described in Japanese Patent Application Publication No. 9-100111, by, for example, the following method: to prepare a mono-hydroxyl-terminated alkoxysilane by adding a polyalkylene glycol to an adduct of a mercaptoalkoxysilane and a polyisocyanate compound having an active isocyanate group at the end; then, reacting it with a separately synthesized adduct (which is an adduct of a compound having a hydroxyl group at one end and a (meth)acryloyl group at the other end and a polyisocyanate compound) to link the two using a carbamate bond; or, reacting the adduct of a mercaptoalkoxysilane and a polyisocyanate compound having an active isocyanate group at the end with a separately synthesized adduct (which is an adduct of a polyalkylene glycol polyisocyanate compound having an active hydroxyl group at one end and a compound having a hydroxyl group at one end and a (meth)acryloyl group at the other end) to link the two using a carbamate bond; and so on.

[0113] Reactive silica particles can be prepared using silane compounds and silica particles. Specifically, they can be manufactured using the following methods:

[0114] (1) A method of hydrolyzing a silane compound with a reactive (meth)acryloyl group, then mixing it with silica particles and performing heating and stirring operations;

[0115] (2) A method for hydrolyzing silane compounds with reactive (meth)acryloyl groups in the presence of silica particles; etc.

[0116] Reactive silica particles can also be commercially available. Examples of commercially available products include those manufactured by Nissan Chemical Co., Ltd., under the trade names PGM-AC-2140Y and PGM-AC-4130Y.

[0117] From the viewpoint of scratch resistance and abrasion resistance of the cured film, the content of inorganic particles (G) is preferably 0.1% to 10% by mass and less than the amount of solid components in the photocurable resin composition, more preferably 0.2% to 7% by mass and less than 7% by mass, and even more preferably 0.5% to 5% by mass and less than 5% by mass.

[0118] (solvent (H))

[0119] The photocurable resin composition can be diluted with a solvent as needed to adjust its viscosity to a suitable consistency for use as a coating. The solvent (H) is any substance that dissolves the resin components in the photocurable resin composition and is not particularly limited. Specifically, examples include aromatic hydrocarbons (e.g., toluene, xylene, and ethylbenzene), esters or ether esters (e.g., ethyl acetate, butyl acetate, and methoxybutyl acetate), ethers (e.g., diethyl ether, tetrahydrofuran, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and diethylene glycol monoethyl ether), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone, and cyclohexanone), alcohols (e.g., methanol, ethanol, n-propanol or isopropanol, n-butanol, isobutanol, sec-butanol or tert-butanol, 2-ethylhexyl alcohol, and benzyl alcohol), amides (e.g., dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.), sulfoxides (e.g., dimethyl sulfoxide), water, and mixtures of two or more of these solvents.

[0120] (Other ingredients)

[0121] The photocurable resin composition of the present invention may contain other components besides those described in (A) to (H) to a extent that does not impair the purpose of the present invention. Other components may be added as needed, such as antistatic agents, polymerization inhibitors, non-reactive diluents, matting agents, defoamers, dispersants, antisettling agents, antioxidants, heat stabilizers, adhesion enhancers, photosensitizers, antibacterial agents, antifungal agents, antiviral agents, silane coupling agents, plasticizers, etc.

[0122] <Preparation Method of Photocurable Resin Composition>

[0123] The photocurable resin composition of the present invention is obtained by mixing and stirring the above-mentioned components using conventionally known apparatus such as mixers, dispersers, and agitators. Examples of such apparatus include mixing and dispersing mills, homogenizers, mortar mixers, rollers, paint shakers, and homogenizers.

[0124] The viscosity of the photocurable resin composition (resin solution) at 25°C is preferably 0.5–500 mPa·s, more preferably 1–250 mPa·s, and even more preferably 5–100 mPa·s. Viscosity can be measured using a type B viscometer. Viscosities within the above range are readily usable as coatings and exhibit excellent processing adaptability.

[0125] <Curing film>

[0126] The cured film of the present invention is formed from the above-described photocurable resin composition. The thickness of the cured film is not particularly limited, but from the viewpoint of maintaining weather resistance, scratch resistance, and abrasion resistance, it is preferably 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 30 μm. In the present invention, film thickness refers to the thickness of the cured film when its cross-section is observed using an optical microscope, scanning electron microscope (SEM), or the like. When forming a film of such thickness, the desired thickness can be formed by a single coating or by multiple coatings.

[0127] Regarding the cured film of the present invention, when the thickness is 13 μm, the haze measured according to JIS K-7136 is preferably less than 1.0%, more preferably less than 0.5%, and even more preferably less than 0.3%. As long as the haze is within the above range, the transparency is excellent.

[0128] <Molded articles with cured coating>

[0129] The molded article of the present invention has a cured film formed from the above-described photocurable resin composition on at least a portion of its surface. There are no particular limitations on the raw materials used for the molded article; various resins can be used. Examples of molded articles made from polyester resin, polycarbonate resin, polystyrene resin, polyolefin resin, polyethersulfone resin, acrylonitrile-styrene copolymer resin, polyamide resin, cellulose resin, polyaryl ester resin, polymethyl methacrylate resin, polymethacrylamide resin, etc., are used. It should be noted that the cured film formed from the photocurable resin composition of the present invention has low haze and high transparency; therefore, molded articles made from transparent resins are preferred.

[0130] As a molded article, there are no particular limitations, and various resin-based molded articles can be used. In particular, the molded article with a cured film of the present invention is less prone to clouding when illuminated by LEDs, and therefore can be applied to components for, for example, LED illumination. Examples include headlight lenses, taillight lenses, and side lamp lenses for vehicles, as well as lighting covers for residential and train interior decoration.

[0131] <Method for manufacturing molded articles with cured coating>

[0132] The method for manufacturing a molded article with a cured film according to the present invention includes:

[0133] The coating process involves applying the above-described photocurable resin composition to at least one side of the molded article; and

[0134] The curing process involves curing the aforementioned photocurable grease composition by irradiation with ultraviolet light after the coating process to form a cured film.

[0135] The following is a detailed explanation of each process.

[0136] (Coating process)

[0137] The coating process is a process of applying the above-mentioned photocurable resin composition to one side of a molded article using conventionally known methods. For example, coating machines such as sprayers, bar coaters, gravure coaters, roller coaters (natural roll coaters and reverse roll coaters, etc.), air knife coaters, spin coaters, and doctor blade coaters can be used.

[0138] When the resin composition is diluted with a solvent before use, it is preferable to dry it after coating. Examples of drying methods include hot air drying (using a dryer, etc.). The drying temperature is preferably 10–200°C, with a further preferred upper limit of 150°C from the viewpoint of coating smoothness and appearance, and a further preferred lower limit of 30°C from the viewpoint of drying speed.

[0139] (Curing process)

[0140] The curing process involves irradiating the coated surface of a molded article with ultraviolet light to cure the coated photocurable resin composition, thereby forming a cured film. Examples of methods for curing with ultraviolet light include using high-pressure mercury lamps, metal halide lamps, xenon lamps, chemical lamps, and UV-LEDs that emit light in the 200-500 nm wavelength range. From the viewpoint of curability of the photocurable resin composition and flexibility of the cured product, the ultraviolet irradiation dose is preferably 100-10,000 mJ / cm². 2 More preferably, it is 500–5,000 mJ / cm². 2 .

[0141] Example

[0142] The present invention will be described in more detail below with reference to embodiments, but the present invention is not limited to the following embodiments.

[0143] [Synthesis of carbamate (meth)acrylate (A)]

[0144] • Carbamate acrylates (A1)

[0145] First, hydrogenated diphenylmethane diisocyanate (hydrogenated MDI, isocyanate group content 31.8%) was prepared as an isocyanate compound (a1). Additionally, pentaerythritol triacrylate (hydroxyl value 110 mg / KOH) was prepared as a (meth)acrylate monomer (a2) having hydroxyl and photopolymerizable unsaturated groups.

[0146] Next, in a 200 mL reaction vessel equipped with a stirrer, thermometer, and air inlet, 32.8 g of component (a1), 102 g of component (a2), 3.3 g of diethylene glycol, 0.05 g of p-methoxyphenol, 0.17 g of butylated hydroxytoluene, 0.17 g of dibutyltin dilaurate, and 17.3 g of butyl acetate were added, and the mixture was reacted at 80 °C for 5 hours. Then, 17.3 g of propylene glycol monomethyl ether was added for dilution to obtain the urethane acrylate oligomer (A1). This component (A1) has 6 functional groups, a weight-average molecular weight (MW) of 2,400, and a solid content of 80%.

[0147] • Carbamate acrylates (A2)

[0148] First, hexamethylene diisocyanate (isocyanurate body, isocyanate group content of 23.1%) was prepared as the isocyanate compound (a1). Additionally, pentaerythritol triacrylate (hydroxyl value of 116 mg KOH / g) was prepared as the (meth)acrylate monomer (a2) having hydroxyl and photopolymerizable unsaturated groups.

[0149] Next, in a 200 mL reaction vessel equipped with a stirrer, thermometer, and air inlet, 100 g of component (a2), 0.01 g of p-methoxyphenol, 0.04 g of butylated hydroxytoluene, and 0.26 g of dibutyltin dilaurate were added, and the mixture was heated to 80 °C. While maintaining the internal temperature of the flask at 80 °C, 34.2 g of component (a1) was added after 1 hour, and the reaction was allowed to proceed for 4 hours, thereby obtaining the urethane acrylate oligomer (A2). Component (A2) has 9 functional groups and a weight-average molecular weight (MW) of 3,500.

[0150] • Carbamate acrylates (A3)

[0151] First, as an isocyanate compound (a1), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), an alicyclic isocyanate, is prepared. Additionally, as a polycarbonate diol compound (a2), ETERNACOLL UM-90 (3 / 1) (manufactured by Ube Industries, Ltd.) is prepared. Furthermore, as a photoreactive compound (a3), EO-modified di and triacrylates of isocyanuric acid (manufactured by Toa Synthetic Co., Ltd., Aronix M-313) is prepared.

[0152] Next, in a four-necked flask equipped with a stirrer, reflux condenser, and thermometer, 192.8 g of component (a2), 480.8 g of component (a3), 0.15 g of 4-methoxyphenol, 0.45 g of butylated hydroxytoluene, and 1.5 g of dibutyltin dilaurate were added. The mixture was heated to 80°C in an oil bath, and after 1 hour, 112.3 g of component (a1) was added. The reaction was then carried out at 90°C for 3 hours. After the reaction was complete, 450 g of PGM was added, thus obtaining the urethane acrylate oligomer (A3). It should be noted that the endpoint of the reaction was confirmed by the disappearance of the peak from the isocyanate group using infrared absorption analysis. In the resulting mixture, PGM, as the organic solvent, accounted for 36.3%, and the solid content was 63.7%. Furthermore, component (A3) has 4 functional groups and a weight-average molecular weight (MW) of 2,900.

[0153] The following materials are used to obtain a light-curable resin composition.

[0154] (ingredient (A))

[0155] • 1:6 functional urethane (meth)acrylate oligomers, the oligomer (A1) synthesized above.

[0156] • Carbamate (meth)acrylate oligomer 2: A 9-functional carbamate acrylate with an isocyanurate backbone, the oligomer synthesized above (A2).

[0157] • Carbamate (meth)acrylate oligomer 3: A tetrafunctional carbamate acrylate with an isocyanurate backbone, the oligomer synthesized above (A3).

[0158] (Component (b1))

[0159] • 1:1,10-decanediol diacrylate, a difunctional (meth)acrylate monomer, manufactured by MIWON Corporation, trade name: MIRAMER M-2010

[0160] • 2-functional (meth)acrylate monomer 2:1,9-nonanediol diacrylate, manufactured by Kyoei Chemical Co., Ltd., trade name: Light Acrylate 1.9ND-A

[0161] • 3,1,6-hexanediol diacrylate, a difunctional (meth)acrylate monomer, manufactured by Sartomer Chemicals Ltd., trade name: SR238NS

[0162] (Component (b2))

[0163] • 6-functional (meth)acrylate monomer 1: Dipentaerythritol hexa(meth)acrylate (DPHA), manufactured by MIWON Corporation, trade name: MIRAMER M-600

[0164] • 6-functional (meth)acrylic acid monomer 2: caprolactone-modified DPHA, manufactured by Changxing Chemical Co., Ltd., trade name: EM2692

[0165] (ingredient (b3))

[0166] • Other (meth)acrylic acid monomers 1: TMPTA (3-functional), manufactured by MIWON Corporation, trade name: MIRAMER M-300

[0167] (Ingredient (C))

[0168] • Photopolymerization initiator 1 (acetophenone-based polymerization initiator, manufactured by IGM Resin, trade name: Omnirad 184)

[0169] • Photopolymerization initiator 2 (acylphosphine oxide polymerization initiator, manufactured by IGM Resin, trade name: Omnirad TPO-H)

[0170] (Ingredient (D))

[0171] Leveling agent 1: Non-silicone and non-fluorine leveling agent (surface-active polymer), Mw: 7,000, manufactured by BYK Corporation, trade name: BYK-399

[0172] Leveling agent 2: Fluorine-based leveling agent (nonionic fluorinated prepolymer containing UV reactive groups), Mw: 25,000, manufactured by Neos Co., Ltd., trade name: Ftergent 602A

[0173] Leveling agent 3: Organosilicon-based leveling agent (polyether-modified polymethylalkylsiloxane), Mw: 18,000, manufactured by BYK Corporation, trade name: BYK-325N

[0174] Leveling agent 4: Acrylic polymer leveling agent, Mw: 22,000, manufactured by BYK Corporation, trade name: BYK-350

[0175] Leveling agent 5: Organosilicon-based leveling agent (polyether siloxane polymer), Mw: 2,100, manufactured by EVONIK Co., Ltd., trade name: Tego flow 425

[0176] Leveling Agent 6: Organosilicon-based leveling agent (polyester-modified polymethylalkylsiloxane), Mw: 26,700, manufactured by BYK Corporation, trade name: BYK-315N

[0177] (Component (E))

[0178] • UV absorber 1: Manufactured by BASF, trade name: TINUVIN 479

[0179] (ingredient (F))

[0180] • Light stabilizer 1: Hindered amine light stabilizer, manufactured by BASF, trade name: TINUVIN 123)

[0181] (Ingredient (G))

[0182] Inorganic Particle 1: Nano-silica, manufactured by Nikko Chemical Co., Ltd., trade name: PGM-AC2140Y

[0183] (Component (H))

[0184] Solvent 1: Propylene glycol monomethyl ether (PGM)

[0185] [Preparation of Photocurable Resin Compositions]

[0186] [Example 1]

[0187] Add 24.0 parts by mass of urethane (meth)acrylate oligomer (A)1, 3.2 parts by mass of urethane (meth)acrylate oligomer (A)3, 1.0 parts by mass of hexafunctional (meth)acrylate monomer (b2)2, 8.5 parts by mass of difunctional (meth)acrylate monomer (b1)2, 1.0 parts by mass of photopolymerization initiator (C)1 and 0.2 parts by mass of photopolymerization initiator (C)2 as components (C), 0.1 parts by mass of leveling agent (D)2, 1.4 parts by mass of ultraviolet absorber (E)1, and 0.3 parts by mass of light stabilizer (F)1 to 60.3 parts by mass of solvent (H)1, dissolve and stir to obtain a photocurable resin composition.

[0188] [Examples 2-15, Comparative Examples 1-6]

[0189] Except for changing the composition and the amount of composition according to the formulations described in Tables 1 and 2, the same procedure as in Example 1 was followed to obtain the photocurable resin composition.

[0190] [Manufacturing of molded articles with cured coating]

[0191] The photocurable resin composition prepared above was sprayed onto a polycarbonate plate with a thickness of approximately 2 mm to achieve a dry film thickness of approximately 13 μm, and placed in a dryer set at 80°C for 3 minutes. Then, it was irradiated with ultraviolet light using a high-pressure mercury lamp (irradiation dose: 3,000 mJ / cm²). 2 This process cures the coating, forming a cured film, resulting in a molded product with the cured film.

[0192] [Evaluation of substrates with cured coatings]

[0193] (Coating appearance)

[0194] The appearance of the cured film of the molded product obtained above is observed visually. Specifically, observe whether there are abnormalities such as whitening, shrinkage, insufficient smoothness, and cracks in the cured film, and evaluate it according to the following criteria. The evaluation results are shown in Tables 3 and 4.

[0195] (Evaluation Criteria)

[0196] ○: No abnormalities such as whitening, shrinkage, insufficient smoothness, or cracks.

[0197] ×: There is at least one abnormality such as whitening, shrinkage, insufficient smoothness, and cracks.

[0198] (Initial adhesion)

[0199] Following the checkerboard test method described in JIS K-5400:1990, 100 mass-sized, 1mm-wide scratches were made on the cured film of the molded product obtained above using a cutting tool to create a test piece with a checkerboard pattern. Next, a Sellotape (registered trademark) (trade name, manufactured by Nichiban Co., Ltd.) was pasted onto the test piece, and then the Sellotape was quickly pulled at a 45-degree angle diagonally upward relative to the checkerboard to peel it off. The number of remaining cured film pieces in the checkerboard pattern was counted, and this number was used as an indicator of adhesion. Initial adhesion was evaluated using the following criteria. The evaluation results are shown in Tables 3 and 4.

[0200] (Evaluation Criteria)

[0201] ◎: The number of remaining squares on the chessboard is 100 / 100.

[0202] ○: The number of remaining squares on the chessboard is between 90 / 100 and 99 / 100.

[0203] △: The number of remaining squares on the chessboard is between 80 / 100 and 89 / 100.

[0204] ×: The number of remaining squares on the chessboard is less than 79 / 100.

[0205] (Transparency)

[0206] The transparency of the cured film of the molded product obtained above was evaluated by haze (Hz). Specifically, in accordance with JIS K-7136, the haze of the cured film was measured using a haze meter (Murakami Color Technology Research Institute Co., Ltd., model: HazeMeter HM-65W), and evaluated according to the following criteria. The evaluation results are shown in Tables 3 and 4. It should be noted that a haze of less than 1.0% is considered as low turbidity and high transparency of the cured film.

[0207] (Evaluation Criteria)

[0208] ◎: Haze level less than 0.5%.

[0209] ○: Haze level is 0.5% or higher but less than 1.0%.

[0210] △: Haze level is above 1.0% and below 2.0%.

[0211] ×: Haze is above 2.0%.

[0212] In addition, simulating the situation when the headlight is on, the uncured surface of the molded article obtained above was illuminated with an LED (GENTOS BLUSTER BR-434EG, 480 lumens), and the transparency of the illuminated area was observed visually and evaluated according to the following criteria. The evaluation results are shown in Tables 3 and 4.

[0213] (Evaluation Criteria)

[0214] ◎: Albinism is very rare.

[0215] ○: Several cases of whitening were observed.

[0216] △: Slight whitening was observed, but there are no practical problems.

[0217] ×: Abundant whitening was observed.

[0218] (Abrasion resistance)

[0219] The abrasion resistance of the cured film of the molded product obtained above was evaluated by measuring the change in haze before and after the abrasion resistance test. Specifically, the abrasion resistance test of the cured film was conducted using a Taber abrasion tester (manufactured by Yasuda Seiki Co., Ltd.). Using an abrasion wheel CS-10F, a load of 500g was applied and the wheel was rotated 500 times. The difference in haze (ΔHZ) before and after the abrasion resistance test was measured, and the evaluation was performed according to the following criteria. The evaluation results are shown in Tables 3 and 4.

[0220] (Evaluation Criteria)

[0221] ◎: ΔHZ is less than 5%.

[0222] ○: ΔHZ is 5% or more but less than 15%.

[0223] △: ΔHZ is 15% or more but less than 20%.

[0224] ×: ΔHZ is above 20%.

[0225] (Abrasion resistance)

[0226] The abrasion resistance of the cured film of the molded product obtained above was evaluated by measuring the change in haze before and after the abrasion resistance test. Specifically, the abrasion resistance test of the cured film was conducted using a surface abrasion testing machine (PAS-400, manufactured by Daiei Scientific Instruments Co., Ltd.). Steel wool (#000) was used, and an application rate of 125 g / cm³ was applied. 2 The load was applied 50 times, and the haze difference (ΔHZ) before and after the scratch resistance test was measured. The results were evaluated according to the following criteria. The evaluation results are shown in Tables 3 and 4.

[0227] (Evaluation Criteria)

[0228] ◎: ΔHZ is less than 0.5%.

[0229] ○: ΔHZ is greater than 0.5% and less than 3%.

[0230] △: ΔHZ is 3% or more but less than 5%.

[0231] ×: ΔHZ is above 5%.

[0232] (Crack resistance)

[0233] The crack resistance of the cured coating of the molded product obtained above was evaluated by whether or not cracks appeared after a crack resistance test. Specifically, the crack resistance test of the cured coating was conducted using a thermal shock apparatus (ESPEC Co., Ltd., model: TSA-41L-A). One cycle consisted of placing the coating at 130°C for 2 hours, followed by placing it at -40°C for 2 hours, and four cycles were performed. The cured coating was then visually observed and evaluated according to the following criteria. No cracks were considered to indicate good crack resistance. Furthermore, the haze difference (ΔHZ) before and after the crack resistance test was measured to evaluate the whitening (exudation) of the coating. The evaluation results are shown in Tables 3 and 4.

[0234] (Evaluation criteria for crack resistance)

[0235] ○: No cracks have been formed.

[0236] ×: Cracks appear.

[0237] (Evaluation criteria for coating whitening)

[0238] ◎: ΔHZ is less than 0.5%.

[0239] ○: ΔHZ is greater than 0.5% and less than 3%.

[0240] △: ΔHZ is 3% or more but less than 5%.

[0241] ×: ΔHZ is above 5%.

[0242] (Weather resistance)

[0243] The weather resistance of the cured film of the molded product obtained above was evaluated by measuring the changes in appearance, haze difference (ΔHZ), and yellowing difference (ΔYI) of the cured film before and after the weather resistance test. Specifically, the weather resistance test of the cured film was conducted using an accelerated weather resistance testing machine (manufactured by Suga Test Instruments Co., Ltd., model: SX2D-75). The irradiance was 180W / m². 2 The weather resistance test was conducted under cyclic conditions of 63°C on a black panel and 120 minutes of pure water spray for 18 minutes. Weather resistance was evaluated after 1000 hours and 2000 hours according to the following criteria. The evaluation results are shown in Tables 3 and 4. It should be noted that comparative examples 3, 5, and 6 did not undergo a weather resistance test after 2000 hours, therefore the result is "-".

[0244] (Evaluation criteria for changes in the appearance of the cured film)

[0245] ○: No cracks or peeling or other abnormalities.

[0246] ×: There is at least one abnormality such as crack or peeling.

[0247] (Evaluation criteria for poor haze)

[0248] ◎: ΔHZ is less than 1%.

[0249] ○: ΔHZ is greater than 1% and less than 4%.

[0250] △: ΔHZ is 4% or more but less than 6%.

[0251] ×: ΔHZ is above 6%.

[0252] (Evaluation criteria for poor yellowing)

[0253] ◎: ΔYI is less than 0.5.

[0254] ○: ΔYI is greater than 0.5 and less than 1.0.

[0255] △: ΔYI is greater than 1.0 and less than 1.5.

[0256] ×: ΔYI is 1.5 or higher.

[0257] [Table 1]

[0258]

[0259] [Table 2]

[0260]

[0261] [Table 3]

[0262]

[0263] [Table 4]

[0264]

Claims

1. A photocurable resin composition comprising urethane (meth)acrylate (A), (meth)acrylate monomer (B), a photopolymerization initiator (C), and a leveling agent (D). The urethane (meth)acrylate (A) is a urethane (meth)acrylate oligomer with more than 10 functions. The (meth)acrylate monomer (B) comprises at least a difunctional (meth)acrylate monomer (b1) and a hexafunctional (meth)acrylate monomer (b2). The content of urethane (meth)acrylate (A) is 45% by mass or more and 75% by mass or less, relative to the solid content of the photocurable resin composition. The content of (meth)acrylate monomer (B) is 20% by mass or more and 45% by mass or less, relative to the solid content of the photocurable resin composition. The content of the difunctional (meth)acrylate monomer (b1) is 35% by mass or more relative to the content of the (meth)acrylate monomer (b). The leveling agent (D) is at least one selected from the group consisting of fluorinated leveling agents, silicone leveling agents, acrylic polymer leveling agents, and non-silicone and non-fluorinated leveling agents. The leveling agent (D) has a weight-average molecular weight (Mw) of 2,000 to 30,000. The leveling agent (D) content is 0.1% by mass or more and 1% by mass or less relative to the solid component content of the photocurable resin composition.

2. The photocurable resin composition as described in claim 1, wherein, The content of the hexafunctional (meth)acrylate monomer (b2) is 5% by mass or more relative to the content of the (meth)acrylate monomer (B).

3. The photocurable resin composition according to claim 1 or 2, wherein, The urethane (meth) acrylate (A) comprises an urethane (meth) acrylate having an isocyanurate backbone.

4. The photocurable resin composition according to claim 1 or 2, wherein, The leveling agent (D) has a weight-average molecular weight (Mw) of 3,000 to 30,000.

5. The photocurable resin composition of claim 1 or 2, further comprising an ultraviolet absorber (E).

6. The photocurable resin composition of claim 1 or 2, further comprising a light stabilizer (F).

7. The photocurable resin composition as described in claim 1 or 2, used as a coating for vehicle headlight lenses.

8. A cured film formed from any one of the photocurable resin compositions according to claims 1 to 7.

9. A molded article having at least a portion of its surface covered with the cured film of claim 8.

10. The molded article as claimed in claim 9, which is a lamp lens for a vehicle.

11. A method for manufacturing a molded article, comprising: The coating process involves coating the photocurable resin composition according to any one of claims 1 to 7 onto at least one side of the molded article; and The curing process involves curing the photocurable resin composition by ultraviolet irradiation after the coating process to form a cured film.

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