Photocurable resin composition, hard coat film for molding, and molded article using the same

Abstract

To provide a resin composition usable in film molding, and a hard coat film having the composition applied thereto, the composition having moldability as well as excellent scratch and nail mark resistance.SOLUTION: There are provided a photocurable resin composition comprising an acrylic copolymer, a polyfunctional (meth)acrylate, nanoalumina fine particles, and a photopolymerization initiator, wherein the acrylic copolymer includes an acrylic copolymer having a siloxane skeleton in its side chain, and the content of the nanoalumina fine particles is 0.5 to 7.0 wt.% relative to the total solid content, and a hard coat film having a cured layer thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable resin composition having excellent moldability, a moldable hard coat film having a cured resin layer thereof, and a molded article using the same. [Background technology]

[0002] Conventionally, spray painting has been the standard method for coloring automotive exterior parts, such as fenders, bumpers, and hoods. However, this method requires repeated painting and drying, which requires large equipment, space, and labor. It also consumes a huge amount of energy, and when the paint is solvent-based, evaporation increases the environmental impact, posing many problems.

[0003] To address these issues, there is a film molding method that uses pre-colored decorative film. This method is widely adopted because it allows for greater design freedom compared to methods using paint such as spray painting, makes it easy to decorate surfaces with three-dimensional irregularities, and is also highly productive. For example, a well-known method is insert molding, in which a pattern is printed on the film surface, which is then heated to soften it and then three-dimensionally molded, and then set in a mold for injection molding.

[0004] Molded films used in insert molding typically have a hard coat (hereinafter referred to as HC) layer to improve surface hardness and scratch resistance. However, if the HC resin layer is too hard, microcracks will occur on the curved surface when processed into a three-dimensional shape, making molding difficult. For this reason, the applicant previously invented a composition containing a urethane acrylate reacted with specific components, a light stabilizer, and a fluorine-based silicone compound with reactive functional groups as an HC resin for insert molding (Patent Document 1). This composition was an excellent HC agent that exhibited good moldability and weather resistance in addition to abrasion resistance and chemical resistance.

[0005] By selecting an HC agent that is suitable for these molding applications, processing restrictions have been alleviated to a certain extent. However, as the applications of insert molding products have expanded in recent years, there has been a demand for greater moldability. In particular, in the case of automotive parts that are decorated with paint, deep drawing is often required, and there is a growing demand for molding HC films that offer better moldability than ever before and can be used as a replacement for painting. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7293518 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a resin composition that can be used in film molding, which has excellent formability as well as scratch resistance and scratch resistance with fingernails, and an HC film coated with the same. [Means for solving the problem]

[0008] In order to solve the above problems, the invention of claim 1 provides a photocurable resin composition comprising an acrylic copolymer (A), a polyfunctional (meth)acrylate (B), nanoalumina fine particles (C), and a photopolymerization initiator (D), wherein (A) comprises an acrylic copolymer (a1) having a siloxane skeleton in a side chain, and the amount of (C) is 0.5 to 7.0 wt % of the total solid content.

[0009] A second aspect of the present invention provides the photocurable resin composition according to the first aspect, further comprising an acrylic copolymer (a2) having no siloxane skeleton in the side chain.

[0010] The invention of claim 3 provides a hard coat film characterized by having a cured layer of the photocurable resin composition according to claim 1 or 2 on a plastic substrate.

[0011] The invention of claim 4 provides the hard-coated film for molding according to claim 3, wherein the hard-coated film is used for molding.

[0012] The invention of claim 5 provides a method for producing an insert-molded product, in which the molding hard coat film according to claim 3 is shaped using a mold, and then molten resin is injected from the side opposite to the photocurable resin cured layer to form a resin molded product.

[0013] The sixth aspect of the present invention provides an insert-molded product or an out-molded product using the hard coat film for molding according to the third aspect of the present invention.

[0014] The resin composition and film of the present invention have good moldability and excellent scratch resistance and scratch resistance by fingernails, and are therefore useful as an HC resin composition and a moldable HC film that can be used in insert molding and out-mold molding as an alternative to painting. BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The photocurable resin composition of the present invention comprises an acrylic copolymer (A), a polyfunctional (meth)acrylate (B), nanoalumina fine particles (C), and a photopolymerization initiator (D). In this specification, the term "(meth)acrylate" encompasses both acrylate and methacrylate.

[0016] The acrylic copolymer (A) used in this composition contains an acrylic copolymer (a1) having a siloxane skeleton in the side chain. (a1) is a non-reactive copolymer without reactive functional groups, which has a siloxane skeleton in the side chain of an acrylic main chain formed by polymerizing a reactive monomer having an acryloyl group. Unlike urethane acrylates, it does not contain a urethane bond in the molecular skeleton, making it a binder with very good weather resistance as a resin.

[0017] The weight-average molecular weight (hereinafter referred to as Mw) of (a1) is preferably 10,000 to 100,000, more preferably 20,000 to 80,000, and particularly preferably 30,000 to 60,000. A weight-average molecular weight of 10,000 or more ensures sufficient moldability, while a weight-average molecular weight of 100,000 or less ensures sufficient reactivity and facilitates viscosity adjustment for workability. Mw was measured and calculated by gel permeation chromatography using a column packed with a styrene-divinylbenzene base material and a tetrahydrofuran eluent, relative to standard polystyrene.

[0018] Preferably, (A) further contains an acrylic copolymer (a2) that does not have a siloxane skeleton in its side chain. The incorporation of (a2) can significantly improve the scratch resistance of the cured coating. The monomers constituting (a2) are not particularly limited. Examples include linear alkyl monomers such as methyl (meth)acrylate, branched alkyl monomers such as ethylhexyl (meth)acrylate, alicyclic monomers such as isobornyl (meth)acrylate, hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate, and amide group-containing monomers such as acryloylmorpholine. These monomers can be used alone or in combination of two or more. Among these, copolymers containing methyl methacrylate (hereinafter referred to as MMA) are preferred because of their relatively high Tg and ease of handling and availability.

[0019] The Mw of (a2) is preferably 10,000 to 150,000, more preferably 20,000 to 100,000, and particularly preferably 30,000 to 80,000. By making it 10,000 or more, sufficient improvement in abrasion resistance can be expected, and by making it 150,000 or less, sufficient reactivity and viscosity adjustment to good workability can be easily achieved.

[0020] The blending amount of (a1) is preferably 30 to 90 wt %, more preferably 33 to 85 wt %, and particularly preferably 35 to 80 wt %, based on the total solid content. By making it 30 wt % or more, sufficient scratch resistance and scratch resistance can be ensured, and by making it 90 wt % or less, sufficient curability can be ensured. The blending amount of (a1) in (A) is preferably 30 to 90 wt %, more preferably 40 to 80 wt %, and particularly preferably 45 to 70 wt %.

[0021] The blending amount of (A) including (a1) and (a2) is preferably 60 to 93 wt % of the total solid content, more preferably 65 to 90 wt %, and particularly preferably 70 to 85 wt %. By making it 60 wt % or more, sufficient moldability and scratch resistance can be ensured, and by making it 93 wt % or less, sufficient reactivity and scratch resistance can be ensured.

[0022] The polyfunctional (meth)acrylate (B) used in the present invention is blended for the purpose of imparting reactivity to the composition. Examples of such polyfunctional (meth)acrylates include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, and dicyclopentanyl diacrylate; trifunctional (trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; tetrafunctional (ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and diglycerin tetra(meth)acrylate; pentafunctional (dipentaerythritol penta(meth)acrylate); and hexafunctional (dipentaerythritol hexa(meth)acrylate. These polyfunctional (meth)acrylates can be used alone or in combination of two or more. Among these, trifunctional or higher functional compounds are preferred, and tetrafunctional or higher functional compounds are even more preferred, since they can improve reactivity with the addition of a small amount.

[0023] The blending amount of (B) is preferably 5 to 25% by weight, more preferably 8 to 22% by weight, and particularly preferably 10 to 20% by weight, based on the total solid content. By making it 5% by weight or more, sufficient reactivity can be ensured, and by making it 25% by weight or less, sufficient moldability and scratch resistance can be ensured.

[0024] The nanoalumina fine particles (C) used in the present invention are blended to increase the hardness of the cured layer and improve abrasion resistance. The average primary particle size of (C) is preferably 30 to 250 nm, more preferably 50 to 200 nm, and particularly preferably 70 to 150 nm. A particle size of 30 nm or more can improve scratch resistance, while a particle size of 250 nm or less can ensure good optical properties in the film. The average particle size is the median diameter (d=50) measured by dynamic light scattering (DLS).

[0025] The surface of (C) is preferably surface-modified to improve dispersibility. Examples include treatment with a silane coupling agent, titanate coupling agent, aluminate coupling agent, or reactive functional group such as (meth)acryloyl group, vinyl group, or epoxy group. Among these, coating treatment with a (meth)acryloyl group is preferred because it can firmly bond with component (B) and is prevented from falling off the coating surface, thereby improving surface hardness.

[0026] The blending amount of (C) is 0.5 to 7.0 wt % of the total solid content of the resin composition, preferably 0.8 to 6.0 wt %, and more preferably 1.0 to 5.0 wt %. If it is less than 0.5 wt %, sufficient scratch resistance may not be ensured, and if it exceeds 7.0 wt %, sufficient moldability may not be ensured.

[0027] The photopolymerization initiator (D) used in the present invention generates radicals upon irradiation with ultraviolet light or an electron beam, and these radicals trigger the polymerization reaction, and general-purpose photopolymerization initiators such as benzyl ketals, acetophenones, and phosphine oxides can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, it is possible to impart curability over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, benzyl ketals include 2,2-dimethoxy-1,2-diphenylethan-1-one, α-hydroxyacetophenones include 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, α-aminoacetophenones include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, and acylphosphine oxides include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and these can be used alone or in combination of two or more.

[0028] Among these, it is preferable to use an α-hydroxyacetophenone-based compound, which is less prone to yellowing. Commercially available products include Omnirad2959 (trade name: α-hydroxyacetophenone-based compound, manufactured by IGM Resins). The amount of (D) added per 100 parts by weight of the radically polymerizable component is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight.

[0029] The present composition may contain, as necessary, an antioxidant, a leveling agent, a bluing agent, an antifoaming agent, a thickener, an antistatic agent, an antifogging agent, an antibacterial agent, a matting agent, inorganic fine particles, organic fine particles, and the like, within the range that does not impair the performance.

[0030] When applying the composition to a plastic substrate, it may be diluted with a solvent to improve coating properties. Examples of suitable solvents include alcohol-based solvents such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and diacetone alcohol; ketone-based solvents such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as ethyl acetate and butyl acetate; ether-based solvents such as propylene glycol monomethyl ether (PGM), diethyl ether, and diisopropyl ether; and hydrocarbon-based solvents such as cyclohexane and methylcyclohexane. These solvents may be used alone or in combination. The solids content of the diluted composition is typically 10 to 70%, but there are no specific limitations and the viscosity can be adjusted appropriately to achieve a coating viscosity that is easy to apply.

[0031] Examples of plastic substrates onto which the composition can be applied include polyester films, triacetyl cellulose films, polycarbonate films, polysulfone films, nylon films, cycloolefin films, acrylic (hereinafter referred to as PMMA) films, polyimide films, ABS films, polyolefin films, PVC films, and PVA films.

[0032] Among these, it is preferable to use a composite substrate made of a polycarbonate (hereinafter referred to as PC) substrate, which has excellent impact resistance and high heat resistance, and an acrylic substrate, which has high transparency and hardness. Here, the composite substrate made of a PC substrate and an acrylic substrate (hereinafter referred to as the present composite substrate) means a resin laminate having an acrylic resin layer on at least one side of a PC resin layer. The method for laminating the PC resin and the acrylic resin is preferably co-extrusion molding.

[0033] In order to improve adhesion to the composition, the plastic substrate may be subjected to a surface treatment such as a primer treatment, a sandblasting method, a solvent treatment to create a rough surface, or a surface oxidation treatment such as a corona discharge treatment, a chromic acid treatment, or an ozone / ultraviolet irradiation treatment.

[0034] The method for applying the composition is not particularly limited, and the composition can be formed by known coating methods such as spray coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, wire bar coating, etc., or printing methods such as gravure printing, screen printing, offset printing, inkjet printing, etc. The thickness of the coated film when dried can be, for example, 1 μm to 10 μm, but is not limited to this.

[0035] The light source of ultraviolet radiation used to cure this composition includes low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, LED lamps, and electrodeless ultraviolet lamps. The irradiation atmosphere may be air or an inert gas such as nitrogen or argon. Furthermore, the curing property can be further improved by heating the coating film during ultraviolet irradiation using a back roll or an IR heater. The irradiation conditions are an irradiation intensity of 500 mW / cm. 2 ~3000mW / cm 2 , exposure dose 50-400mJ / cm 2 are exemplified, but are not limited to these.

[0036] The HC film can be provided with a decorative layer if necessary. Examples of decorative methods include printing and metal deposition, and both methods may be used. Furthermore, an adhesive layer or a primer layer may be provided to improve adhesion with the injection molding resin.

[0037] A protective film may be attached to the HC film to protect the surface to which the composition is applied. Using a protective film can prevent scratches during insert molding and out-molding processes, which is expected to improve yield.

[0038] The present HC film can be used in insert molding, for example, by placing the surface coated with the present composition facing the inner wall of the mold (so that the surface opposite the cured layer of the present composition is in contact with the molding resin), and preforming the present HC film to conform to the shape of the mold as needed. Next, the mold is closed and the molten molding resin is injected into the cavity, allowing the resin to solidify, thereby forming a resin molded product.

[0039] The preforming method may be a method in which the HC film is preheated to above its softening point and placed in a mold, followed by vacuum suction through suction holes in the mold, or a known molding method such as vacuum forming, compressed air forming, or press molding using a molding mold separate from the injection molding mold. It is also possible to simultaneously perform molding and integral molding of the injected resin by the injection pressure of the molding resin without performing these preforming methods.

[0040] The resin to be injection-molded can be any known resin that can be injection-molded. Examples include polyethylene resin, polypropylene resin, polystyrene resin, ABS resin, AS resin, acrylic resin, urethane resin, polyester resin, polycarbonate resin, polyphenylene ether resin, polyacetal resin, and polysulfone resin. These resins can be used alone or in combination of two or more. In the case of large sizes such as automobile bodies, or small sizes but thin thicknesses, problems such as warping can be avoided by making the shrinkage rate after molding similar to that of HC film.

[0041] Furthermore, by coloring the injection molding resin itself, it is possible to eliminate the decorative layer of the HC film or to blend the color of the decorative layer with the color of the injection molding resin, resulting in a more sophisticated appearance. Furthermore, when replacing products that typically have their exteriors colored with paint, such as automobile bodies, with insert molding, coloring the injection-molded resin makes it possible to omit the exterior painting with paint. In this case, it is possible to eliminate appearance defects such as orange peel and pitting that often occur with exterior painting.

[0042] Furthermore, this HC film can also be used for out-molding. For example, it can be used for TOM (Three-Dimensional Overlay Method) molding. TOM molding is a film molding method in which a pre-formed substrate is subjected to three-dimensional surface decoration using vacuum and pressure molding inside an airtight box. By using this molded film, it is possible to handle large three-dimensional products regardless of the substrate material. When using this molded film for TOM molding, it is preferable that the surface that comes into contact with the molded product is an adhesive layer.

[0043] The present invention will be described in detail below with reference to examples and comparative examples, but these are intended to be specific examples and are not intended to limit the scope of the present invention. Unless otherwise specified, measurements were carried out at a room temperature of 25°C and a relative humidity of 65%. The blend amounts are expressed in parts by weight as solid content. [Example]

[0044] Example 1 Acrylic copolymer 1 (structure: acrylic copolymer having a siloxane skeleton in a side chain of an MMA-based acrylic main chain, Mw 40,000) as (a1), DPHA (dipentaerythritol hexaacrylate) as (B), surface-treated alumina 1 (alumina having an acryloyl group coating on the surface, average particle size 100 nm) as (C), and Omnirad2959 (trade name: α-hydroxyacetophenone-based, manufactured by IGM Resins) as (D) were stirred in the formulation shown in Table 1 until uniformly dissolved and dispersed, and then butyl acetate was added thereto so that the solid content was 20%, followed by dilution and stirring, to obtain a photocurable resin composition of Example 1.

[0045] Examples 2 to 7 and Comparative Examples Acrylic copolymer 2 (acrylic copolymer containing MMA as a monomer, Mw 40,000) and acrylic copolymer 3 (acrylic copolymer containing MMA as a monomer, Mw 85,000) as (a2), PETA (pentaerythritol tetraacrylate) as (B), and surface-treated alumina 2 (alumina having an acryloyl group coating on the surface, average particle size 120 nm) as (C) were stirred in the formulations shown in Tables 1 and 2 until uniformly dissolved and dispersed, and then butyl acetate was added to adjust the solid content to 20%, followed by dilution and stirring to obtain photocurable resin compositions of Examples 2 to 7 and the comparative example.

[0046] Table 1 JPEG2025178686000001.jpg90135

[0047] Table 2 JPEG2025178686000002.jpg103135

[0048] The evaluation method was as follows.

[0049] Preparation of molding film The photocurable resin compositions prepared in the examples and comparative examples were applied to Iupilon film (product name: DF02PU, manufactured by Mitsubishi Gas Chemical Company, Inc., thickness 125 μm, PMMA / PC laminate film) on the PMMA side so that the dry film thickness was 3 μm. The film was then dried in a thermostatic chamber at 80°C for 1 minute, and then irradiated with ultraviolet light using an electrodeless ultraviolet lamp in a nitrogen atmosphere at an output of 1300 mW / cm2 and an accumulated light amount of 150 mJ to prepare a film for evaluation.

[0050] Total light transmittance: Measured using a haze meter Haze-GARD2 manufactured by Toyo Seiki Seisakusho in accordance with JIS K7361-1.

[0051] Scratch resistance: Using a Toyo Seiki abrasion tester, the contact area is 4cm 2A 500g load was placed on the #0000 steel wool and the test piece was reciprocated 10 times at a speed of 100 revolutions per minute. The haze before and after the test was then measured in accordance with JIS K7136 using a Toyo Seiki Seisakusho Haze-GARD2. A haze increase rate (Δhaze) of less than 2% was evaluated as ◎, 2-3% as ○, and more than 3% as ×.

[0052] Vacuum formability: Using a vacuum forming machine, Model Forming 300X, manufactured by Seiko Sangyo Co., Ltd., the formed film was heated to a substrate temperature of 190°C, and then vacuum formed using a square mold 30 mm in diameter x 30 mm in height. The depth (H) at which the film could be completely formed without whitening or cracking was measured. Evaluation was given for 30 mm or more as ◯, and for less than 30 mm as ×.

[0053] Fingernail scratch resistance (slipperiness): The coated surface was scratched with a fingernail and the presence or absence of scratches was visually confirmed. When no scratches were observed, it was rated as ◯, and when scratches were observed, it was rated as ×.

[0054] Example evaluation results Table 3 JPEG2025178686000003.jpg86135

[0055] Table 4 JPEG2025178686000004.jpg101135

[0056] The examples were satisfactory in all respects, including total light transmittance, scratch resistance, vacuum formability, and scratch resistance with fingernails.

[0057] On the other hand, Comparative Example 1, in which the blending amount of (C) exceeded the upper limit, exhibited poor vacuum formability, Comparative Example 2, which did not contain (C), and Comparative Example 3, which did not contain (B), exhibited poor scratch resistance, and Comparative Example 4, which did not contain (a1), exhibited poor scratch resistance and scratch resistance with a fingernail, and none of these were suitable for the present invention.

Claims

1. A photocurable resin composition comprising an acrylic copolymer (A), a polyfunctional (meth)acrylate (B), nanoalumina fine particles (C), and a photopolymerization initiator (D), wherein (A) comprises an acrylic copolymer (a1) having a siloxane skeleton in a side chain, and the blending amount of (C) is 0.5 to 7.0 wt % based on the total solid content.

2. 2. The photocurable resin composition according to claim 1, further comprising an acrylic copolymer (a2) having no siloxane skeleton in the side chain.

3. A hard coat film comprising a cured layer of the photocurable resin composition according to claim 1 or 2 on a plastic substrate.

4. 4. The hard-coated film for molding according to claim 3, wherein the hard-coated film is used for molding.

5. A method for producing an insert-molded article, comprising shaping the hard coat film for molding according to claim 3 using a mold, and then injecting a molten resin from the side opposite to the photocurable resin cured layer to form a resin molded article.

6. An insert-molded or out-molded product using the hard coat film for molding according to claim 3.

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