Photocurable coating composition and laminate having a cured layer thereof

Abstract

To provide a photocurable coating agent composition that has sufficiently low moisture permeability even with a small thickness, and also has excellent wear resistance and a laminate having a cured layer thereof.SOLUTION: A photocurable coating agent composition contains a 2-8 functional methacrylate having an isocyanuric acid skeleton, surface-treated nano silica, and a photopolymerization initiator. The methacrylate includes a urethane methacrylate produced from a reaction between a hexamethylene diisocyanate trimer and an OH group-bearing methacrylate and / or an isocyanuric acid EO-modified methacrylate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable coating composition with low moisture permeability that is cured by irradiation with light such as ultraviolet light and has excellent water vapor barrier properties, and to a laminate having a cured layer of the composition. [Background technology]

[0002] Taking advantage of their ability to harden in a short time, UV-curable resins are widely used in a variety of applications, from industrial materials such as coatings for films and molded objects, and sealants for electronic components and electrical contacts, to everyday products such as adhesives and gel nails. Among these, the hard coating agent for liquid crystal panel components is particularly well known, and in recent years, their applications have become more diverse, with increasingly stringent requirements for durability, including stability against environmental changes.

[0003] Cellulose ester films, which are prone to absorbing moisture, are often used to protect the surface of polarizing plates, which are one of the components of liquid crystal panels, but Patent Document 1 describes that by making the surface film of a polarizing plate low in moisture permeability, it is possible to suppress deterioration of the display screen caused by environmental changes in the liquid crystal display device. Therefore, as a method for reducing moisture permeability, for example, a film having a low-moisture permeable hard coat layer composed of a compound having three or more ethylenically unsaturated double bonds, two types of alicyclic epoxy compounds, a radical polymerization initiator, and a cationic polymerization initiator has been proposed (Patent Document 2).

[0004] By using such resins, it has become possible to achieve low moisture permeability even when using cellulose ester-based films, but in order to reduce moisture permeability, it is necessary to make the hard coat layer thick, which can cause problems such as flexibility and warping. Therefore, there has been a demand for hard coat resins that have good steel wool resistance and can achieve low moisture permeability even when the hard coat layer is thin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-256747 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-194566 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a photocurable coating composition that has sufficiently low moisture permeability and good abrasion resistance even when the coating is thin, and a laminate having a cured layer of the composition. [Means for solving the problem]

[0007] In order to address the above-mentioned problems, the invention of claim 1 provides a composition comprising a di- to octafunctional (meth)acrylate (A) having an isocyanuric acid skeleton, surface-treated nanosilica (B), and a photopolymerization initiator (C), wherein (A) comprises a urethane (meth)acrylate (a1) and / or an isocyanuric acid EO-modified (meth)acrylate (a2) obtained by reacting a hexamethylene diisocyanate trimer with a (meth)acrylate having an OH group, and the blending amount of (B) is 100 to 800 parts by weight per 100 parts by weight of (A). and (B) contains surface-treated nanosilica (b1) having an average primary particle diameter of 1 to 30 nm and surface-treated nanosilica (b2) having an average primary particle diameter of 35 to 100 nm. The present invention provides a photocurable coating composition characterized by the above-mentioned.

[0008] The invention described in claim 2 is also characterized in that (B) The mixing ratio of (b1) and (b2) is 1:1 to 1:2. The present invention provides a photocurable coating composition according to claim 1.

[0009] The invention described in claim 3 is as follows: A laminate having a cured layer of the photocurable coating agent according to claim 1 or 2 on at least one side of a plastic substrate film. to provide. [Effects of the Invention]

[0012] The composition of the present invention has good curability when exposed to light such as ultraviolet light, has sufficiently low moisture permeability even when the film thickness is thin, and has good abrasion resistance, and is therefore useful as a photocurable coating composition for use on triacetyl cellulose films, etc. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below.

[0014] The composition of the present invention comprises (A) a di- to octafunctional (meth)acrylate having an isocyanuric acid skeleton, (B) nanosilica, and (C) a photopolymerization initiator. In this specification, the term "(meth)acrylate" encompasses both acrylate and methacrylate.

[0015] The di- to octafunctional (meth)acrylate (A) having an isocyanuric acid skeleton used in the present invention is the main resin constituting the cured coating, and contains at least a urethane (meth)acrylate (hereinafter referred to as urea) (a1) obtained by reacting a hexamethylene diisocyanate (hereinafter referred to as HDI) trimer with a (meth)acrylate having an OH group, and / or an isocyanuric acid EO-modified (meth)acrylate (a2).

[0016] The (a1) has an HDI trimer (isocyanurate) skeleton, which provides excellent scratch resistance, and its aliphatic nature provides excellent weather resistance and water vapor barrier properties. Examples of (meth)acrylates having OH groups that can be reacted with HDI include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and dipentaerythritol penta(meth)acrylate. Among these, 2-hydroxyethyl acrylate (hereinafter referred to as 2HEA) is preferred, but it may also be combined with, for example, pentaerythritol triacrylate (hereinafter referred to as PETA) as long as the number of functional groups is within the range of 8 or less.

[0017] The (a1) can be obtained by adjusting the molar ratio of the functional groups, isocyanate groups and OH groups, of HDI and reacting them. Specifically, the ratio of isocyanate groups to OH groups is preferably 1:1.5 to 1:8, and more preferably 1:2 to 1:6. The reaction can be carried out according to a conventional method, for example, by placing HDI and a (meth)acrylate having OH groups at 50 to 90°C and using a tin-based compound such as dibutyltin dilaurate as a catalyst. The reaction can be carried out either solvent-free or in an organic solvent, and examples of solvents that can be used include methyl ethyl ketone and ethyl acetate.

[0018] The (a2) is represented by, for example, the following formula (1), and like (a1), it has an isocyanuric acid skeleton, which gives it excellent scratch resistance, and it also has alkyl group substituents, which give it good weather resistance and water vapor barrier properties. Commercially available products include Aronix M-313 (trade name: manufactured by Toagosei Co., Ltd., a mixture of isocyanuric acid EO-modified di- and triacrylates, with a diacrylate ratio of 30 to 40% by weight), and Aronix M-315 (trade name: manufactured by Toagosei Co., Ltd., a mixture of isocyanuric acid EO-modified di- and triacrylates, with a diacrylate ratio of 3 to 13% by weight). [ka] ·····(1) R = "(CH2)2OCOCH=CH2" or "(CH2)2OH"

[0019] The blending amount of (A) is preferably 8 to 40 wt % of the total solid content, and more preferably 10 to 35 wt %. By making it 8 wt % or more, sufficient curability and water vapor barrier properties can be ensured, and by making it 40 wt % or less, sufficient steel wool resistance can be ensured. Furthermore, the blending ratio of (a1) and / or (a2) in (A) is preferably 50 wt % or more, more preferably 80 wt % or more, and particularly preferably 90 wt % or more. By making it 50 wt % or more, a coating with sufficiently low moisture permeability and excellent scratch resistance can be formed.

[0020] The nanosilica (B) used in the present invention is blended for the purpose of improving abrasion resistance and water vapor barrier properties. The average particle size is preferably 0.5 to 300 nm, more preferably 1 to 150 nm, and particularly preferably 3 to 100 nm. (B) may be one having a single average particle size, but blending multiple types of nanosilica with different average particle sizes makes it possible to highly load silica into the coating. For example, combining two types of nanosilica (b1) with a small average particle size of 1 to 30 nm and nanosilica (b2) with a large average particle size of 35 to 100 nm can further improve water vapor barrier properties.

[0021] The (B) is surface-treated to provide good dispersibility in (A), for example, acryloyl group coating, alkoxy coating, epoxy group coating, etc. Among these, acryloyl group coating is preferred because it has good reactivity with the acryloyl group of the binder (A), bonds firmly, and is prevented from falling off from the coating surface after curing.

[0022] The average particle size of (b1) is preferably 1 to 30 nm, more preferably 3 to 25 nm, and particularly preferably 5 to 20 nm. The average particle size of (b2) is preferably 35 to 100 nm, more preferably 35 to 70 nm, and particularly preferably 40 to 60 nm. The average particle size is the median diameter (d=50) measured by a laser diffraction / scattering method in accordance with JIS Z 8825-1.

[0023] The blending amount of (B) is preferably 100 to 800 parts by weight, more preferably 150 to 700 parts by weight, and particularly preferably 220 to 650 parts by weight, per 100 parts by weight of (A). By using 100 parts by weight or more, sufficient abrasion resistance can be ensured, and by using 800 parts by weight or less, sufficient water vapor barrier properties of the coating can be ensured.

[0024] The blending ratio of (b1) to (b2) in (B) is preferably (b1):(b2)=1:1 to 1:2, more preferably 1:1.3 to 1:1.8, and particularly preferably 1:1.5 to 1:1.7. By maintaining this blending ratio, it becomes possible to highly fill the cured coating with silica, effectively improving the water vapor barrier property.

[0025] The photopolymerization initiator (C) 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.

[0026] Among these, it is preferable to use an α-hydroxyacetophenone-based compound that is resistant to yellowing, and commercially available products include Omnirad 127, 184, and 2959 (trade names: manufactured by IGM Resins), etc. The amount of the compound (C) added per 100 parts by weight of the radical polymerization resin component is preferably 2 to 12 parts by weight, more preferably 3 to 10 parts by weight.

[0027] In addition to the above, a (meth)acrylate monomer may be contained as a reactive diluent to adjust the viscosity of the composition and improve adhesion to the substrate. Examples include butyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyethyl (meth)acrylate, (poly)ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, diglycerin tetra(meth)acrylate, and dipentaerythritol penta(meth)acrylate, and these may be used alone or in combination of two or more.

[0028] Furthermore, the encapsulating resin composition of the present invention may contain additives such as antioxidants, polymerization inhibitors, ultraviolet absorbers, flame retardants, antifoaming agents, silane coupling agents, colorants, and organic particles, as needed, within the range that does not impair performance.

[0029] The coating composition of the present invention is diluted with a solvent to a solids content of 10 to 70% to improve its applicability to substrates. Examples of 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 (hereinafter referred to as 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 (hereinafter referred to as PGM), diethyl ether, and diisopropyl ether; and hydrocarbon-based solvents such as cyclohexane and methylcyclohexane (hereinafter referred to as MCH). These solvents can be used alone or in combination. Among these, PGM and MEK are preferred from the viewpoint of solubility.

[0030] Substrates to which the coating composition of the present invention can be applied include organic plastic films, such as polyester films, polyethylene films, polypropylene films, diacetyl cellulose films, triacetyl cellulose films (hereinafter referred to as TAC films), acetyl cellulose butyrate films, polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, ethylene vinyl alcohol films, polystyrene films, polycarbonate films, polymethylpentene films, polysulfone films, polyether ether ketone films, polyether sulfone films, polyether imide films, polyimide films, fluororesin films, nylon films, acrylic films, and cycloolefin (co)polymer films. The properties of TAC films can be fully utilized in particular.

[0031] The method for applying the coating composition of the present invention is not particularly limited, and known coating methods such as spray coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, and wire bar coating, as well as gravure printing, screen printing, offset printing, and inkjet printing can be used. There are no limitations on the coating film thickness, but the film thickness after curing can be, for example, 0.5 μm to 30 μm.

[0032] After application, the coating composition of the present invention is dried at 60 to 120°C and cured using an ultraviolet irradiator. Examples of light sources for ultraviolet irradiation include 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 curing conditions are 50 mW / cm. 2 ~3000mW / cm 2 The irradiation intensity is 50 to 2,000 mJ / cm as the cumulative light amount. 2 The irradiation atmosphere may be air or an inert gas such as nitrogen or argon.

[0033] The present invention will be described in detail below based on examples and comparative examples, but these are intended to be specific examples and are not intended to limit the scope of the invention. Unless otherwise specified, measurements were taken at a room temperature of 25°C and a relative humidity of 65%. The blend amounts are in parts by weight. [Example]

[0034] Example 1 Urea 1 (a trifunctional reaction product of an HDI trimer and 2HEA) was used as (A), PGM-AC-2140Y (trade name: Nissan Chemical Industries, Ltd., acrylic-modified nanosilica having an average particle size of 10 to 15 nm, PGM dispersion, solids content 47 wt%) was used as (b1), PGM-AC-4130Y (trade name: Nissan Chemical Industries, Ltd., acrylic-modified nanosilica having an average particle size of 40 to 50 nm, PGM dispersion, solids content 32 wt%) was used as (b2), and Omnirad 2959 (trade name: iGM Resins) was used as (C) in a stirring vessel in the proportions shown in Table 1. The mixture was diluted with PGM to a solids content of 40 wt%, and the mixture was stirred and degassed until uniformly dissolved, to prepare the photocurable coating composition of Example 1.

[0035] Examples 2 to 7 In addition to the materials used in Example 1, UreaC 2 (a reaction product of HDI trimer with PETA and 2HEA, pentafunctional) and M-315 (trade name: Toagosei Co., Ltd., isocyanuric acid EO-modified di- and triacrylate mixture) were placed in a stirring vessel as (A) in the formulations shown in Table 1, diluted with PGM to a solid content of 40% by weight, and stirred and degassed until uniformly dissolved, to prepare the photocurable coating compositions of Examples 2 to 7.

[0036] Comparative Examples 1 to 4 In addition to the materials used in the examples, oligomers Ureac 3 (a reaction product of a trimer of HDI and PETA, 9 functional groups), Ureac 4 (a reaction product of HDI and PETA, 6 functional groups), and Ureac 5 (a reaction product of a trimer of isophorone diisocyanate and PETA, 9 functional groups) were added to a stirring vessel in the proportions shown in Table 1, along with surface-untreated silica PGM-ST (trade name: manufactured by Nissan Chemical Industries, Ltd., average particle size 10-15 nm, PGM dispersion, 30% solids) and IPA-ST-L (trade name: manufactured by Nissan Chemical Industries, Ltd., average particle size 40-50 nm, IPA dispersion, 30% solids). The mixture was diluted with PGM to a solids content of 40% by weight, and the mixture was stirred and degassed until uniformly dissolved, to prepare photocurable coating compositions for Comparative Examples 1 to 4.

[0037] [Table 1]

[0038] Evaluation items and evaluation methods

[0039] Preparation of evaluation sheet The coating composition obtained above was applied to TG40UL (trade name: Fujifilm Corporation, thickness: 40 μm) using a bar coater so that the film thickness after curing would be 2 μm. After drying at 80°C for 60 seconds, the coating composition was irradiated with a 4 kW I-Grandage (ECS-4011GX) inverter-type high-pressure mercury UV irradiation device manufactured by I-Graphics Co., Ltd. at an output of 60 mW / cm. 2 , cumulative light intensity 150mJ / cm 2 The mixture was cured under the following conditions.

[0040] Moisture permeability: The evaluation sheet prepared above was placed on a moisture permeability cup (manufactured by Yasuda Seiki Co., Ltd.) containing 30 g of calcium chloride, with the coated side facing up, and a rubber packing and lid were attached. The mass was measured before and after a 24-hour test at 40°C and a relative humidity of 90%, and the moisture permeability was calculated by dividing the mass difference by the surface area of ​​the coating film (a circle with a radius of 30 mm). 2 24hr or less ◎, 360 to 500g / m 2 24hr or less: ○, 500g / m 2 -More than 24 hours was marked as ×.

[0041] Coatability: When the above evaluation sheet was prepared, if there were fine defects or uneven coating but no obvious cissing, it was marked as ◯, and if there were obvious cissing and defects, it was marked as x.

[0042] Abrasion resistance: A load of 500 g (contact area 25 mmφ) was placed on steel wool #0000 and moved back and forth 10 times. Visual observation showed that no scratches were observed and the result was rated as ◯, and that scratches were observed and x.

[0043] Evaluation results The evaluation results are shown in Table 2.

[0044] [Table 2]

[0045] Each of the coating compositions of the Examples obtained good results in the evaluations of moisture permeability, coatability, and abrasion resistance.

[0046] On the other hand, Comparative Example 1, which used surface-untreated silica, had poor moisture permeability and abrasion resistance, and Comparative Examples 2 and 4, which used 9-functional ureac, and Comparative Example 3, which used ureac that contained non-trimeric HDI, had poor moisture permeability, and none of these were suitable for the present invention.

Claims

1. 1. A photocurable coating composition comprising: (A) a di- to octafunctional (meth)acrylate having an isocyanuric acid skeleton; (B) a surface-treated nanosilica; and (C) a photopolymerization initiator, wherein (A) comprises a urethane (meth)acrylate (a1) and / or an isocyanuric acid EO-modified (meth)acrylate (a2) obtained by reacting a hexamethylene diisocyanate trimer with a (meth)acrylate having an OH group; the amount of (B) is 100 to 800 parts by weight per 100 parts by weight of (A); and (B) comprises surface-treated nanosilica (b1) having an average primary particle size of 1 to 30 nm and surface-treated nanosilica (b2) having an average primary particle size of 35 to 100 nm.

2. 2. The photocurable coating composition according to claim 1, wherein the mixing ratio of (b1) to (b2) in (B) is 1:1 to 1:

2.

3. A laminate comprising a plastic substrate film and a cured layer of the photocurable coating agent according to claim 1 or 2 on at least one side of the film.

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