JP7199185B2 - Antireflection hard coat film for molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to an antireflection hard-coated film used for film molding.

Acrylic photocurable resins are used in many fields to impart special properties to the surfaces of plastic films and plastic moldings. For example, a hard coat film obtained by applying a high hardness to a PET (polyethylene terephthalate) film is used in large quantities as a touch panel film or a molding film.

Among these, for molding, an insert film is well known, in which a pattern is printed on the surface of the film and then three-dimensionally molded in a softened state by heating, and is widely used for display covers. Recently, in order to improve visibility, particularly when used in displays for in-vehicle applications, there has been a demand for prevention of reflection of external light.

In response to such demands, for example, a urethane acrylate oligomer having 6 or more (meth)acryloyl groups and/or a polyfunctional (meth)acrylate or oligomer having 3 or more (meth)acryloyl groups, hollow silica, and photopolymerization A molding antireflection film coated with an ultraviolet curable resin containing an initiator has been proposed. However, when this resin is used to provide an antireflection function, the thickness of the resin layer is 1 μm or less due to the reflectance, so the hard coat performance is insufficient. There was a demand for a film for

JP 2017-171715 A

The present invention provides an optical film for molding that has low reflectance and excellent elongation. To provide a coated film.

In the invention according to claim 1, a thermoplastic transparent substrate film has a hard coat resin layer on one surface, a low refractive index layer is provided on the hard coat resin layer surface, and the hard coat resin layer contains ethylene glycol. and a hexafunctional or higher urethane (meth)acrylate oligomer (A) having a skeleton reacted with isophorone diisocyanate , a (meth)acrylate (B) having a fluorene skeleton, and a photopolymerization initiator (C). and (A) having a weight average molecular weight of 2,500 to 10,000 .

The invention according to claim 2 provides the antireflection hard coat film for molding according to claim 1, wherein the number of functional groups of the polyfunctional urethane (meth)acrylate oligomer (A) is hexafunctional.

The invention according to claim 3 is characterized in that the amount of the (meth)acrylate (B) having a fluorene skeleton is 35 to 80% by weight based on the total solid content. provides a moldable antireflective hard-coated film.

The invention according to claim 4 provides the antireflection hard coat film for molding according to any one of claims 1 to 3 , which is for insert molding.

The hard coat film of the present invention has a low reflectance and excellent elongation properties, and is suitable as an antireflection hard coat film for molding suitable for three-dimensional molding processing such as insert molding for decoration of electronic equipment and vehicle interiors such as automobiles. Useful.

The present invention will be described in detail below.

The composition of the present invention comprises a polyfunctional urethane (meth)acrylate oligomer (A), a (meth)acrylate having a fluorene skeleton (B), and a photopolymerization initiator (C). In this specification, (meth)acrylate includes both acrylate and methacrylate.

The polyfunctional urethane (meth)acrylate oligomer (A) used in the present invention is produced, for example, by reacting both ends of a compound obtained by reacting a low-molecular-weight polyol and polyisocyanate with hydroxy (meth)acrylate, It is a structure having two or more (meth)acryloyl groups and urethane bonds in one molecule. The number of functional groups is preferably 4 or more, particularly preferably 6 or more, in terms of the balance between reactivity and optical properties. If there is only one functional group, the reactivity at the time of polymerization is low and the molecular weight does not increase, which is not suitable. It is preferable from the viewpoint that the refractive index can be increased because the properties can be secured.

Examples of low-molecular-weight polyols used in (A) include ethylene glycol, propylene glycol, diethylene glycol, butanediol, cyclohexanediol, and the like, and these can be used alone or in combination of two or more. Among these, ethylene glycol, which has the smallest number of carbon atoms in the alkyl group, is preferable because it can increase the concentration of urethane bonds in the oligomer. By increasing the concentration of urethane bonds, a tough cured film can be formed. Even in the same ethylene glycol type, polyethylene glycol with a polyether skeleton has a low urethane bond concentration and is inferior in chemical resistance, etc., and cannot be used.

Examples of the polyisocyanate used in (A) include hexamethylene diisocyanate (hereinafter HDI), isophorone diisocyanate (hereinafter IPDI), diphenylmethane diisocyanate, tolylene diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, and hydrogenated xylylene diisocyanate. , methylcyclohexylene diisocyanate, HDI isocyanurate, IPDI isocyanurate, etc. These may be used alone or in combination of two or more. Among these, aliphatic and alicyclic diisocyanates having low weather resistance and less yellowing are preferred, and IPDI having high bulkiness and high rigidity is particularly preferred.

The hydroxy (meth) acrylate used in (A) includes, for example, bifunctional trimethylolpropane di(meth)acrylate, glycerol di(meth)acrylate, pentaerythritol di(meth)acrylate, diglycerol di(meth)acrylate, ditri Methylolpropane di(meth)acrylate, dipentaerythritol di(meth)acrylate, etc., trifunctional or more, diglycerin tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipenta There are erythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate and dipentaerythritol penta(meth)acrylate. Among these, trifunctional or higher (the number of functional groups of synthesized (A) is equivalent to hexafunctional or higher) is preferred, and pentaerythritol triacrylate (hereinafter referred to as PETA) having high curability is particularly preferred.

The weight average molecular weight (hereinafter referred to as Mw) of (A) is preferably from 2,000 to 30,000, more preferably from 2,500 to 20,000, and most preferably from 3,000 to 10,000. When it is 2,000 or more, sufficient strength and elongation can be secured as a cured film, and when it is 30,000 or less, it becomes easy to adjust the viscosity to an appropriate level as a coating agent. The Mw was calculated by measuring the molecular weight in terms of standard polystyrene by gel permeation chromatography using a column using a styrene-divinylbenzene-based packing material and using a tetrahydrofuran eluent.

The amount of (A) is preferably 15 to 64% by weight, more preferably 18 to 60% by weight, based on the total solid content. When the amount is 15% by weight or more, sufficient cohesive force and film strength can be ensured, and when the amount is 64% by weight or less, the viscosity of the composition can be appropriately controlled and good workability can be ensured.

The (meth)acrylate (B) having a fluorene skeleton used in the present invention is blended to increase the refractive index of the hard coat resin layer. In order to lower the reflectance of the antireflection film, it is effective to increase the difference in refractive index from the low refractive index layer laminated on the hard coat resin layer. It should be higher or the refractive index of the low refractive index layer should be lower. The refractive index (nD25, after curing) of (B) is around 1.5 for general (meth)acrylates, while it is around 1.6, which is about 0.1 higher, so the refractive index of the hard coat resin layer can be made higher.

The refractive index (nD25, after curing) of (B) is preferably 1.555 to 1.675, more preferably 1.600 to 1.655. This range has the effect of increasing the refractive index of the hard coat resin layer, making it possible to keep the reflectance low. Also, the number of functional groups is preferably bifunctional so as not to increase the crosslink density that hinders the elongation of the cured film.

The blending amount of (B) is preferably 35 to 80% by weight, more preferably 38 to 77% by weight, based on the total solid content. By making it 35% by weight or more, it becomes possible to increase the refractive index, and by making it 80% by weight or less, it is possible to secure a sufficient elongation rate. Further, in order to increase the refractive index, it is preferable to use (B) alone as the monomer to be reacted with (A). In that case, the number of functional groups of (A) is preferably 6 or more in order to increase curing reactivity.

The photopolymerization initiator (C) used in the present invention generates radicals when irradiated with ultraviolet rays, electron beams, or the like, and the radicals trigger a polymerization reaction. general-purpose photopolymerization initiators such as Curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region by arbitrarily selecting the light absorption wavelength of the polymerization initiator. Specifically, 2,2-dimethoxy-1,2-diphenylethan-1-one is a benzyl ketal system, and 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2- hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1 as α-aminoacetophenone -on includes acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, either singly or in combination of two or more can be used in combination. Among these, it is preferable to contain α-hydroxyacetophenone, which is resistant to yellowing.

The ratio of (C) to 100 parts by weight of the ultraviolet curable resin component is preferably 1 to 10 parts by weight, more preferably 3 to 8 parts by weight. When the amount is 1 part by weight or more, sufficient curability is exhibited, and when the amount is 10 parts by weight or less, excessive addition can be avoided, and yellowing of the coating film and deterioration of storage stability can be prevented.

The hard coat resin forming the hard coat layer of the present invention is diluted with a solvent to a solid content of 10 to 70% in order to improve coatability onto the thermoplastic transparent substrate film. Examples of solvents include alcohol solvents such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol and diacetone alcohol, ketone solvents such as acetone, methyl ethyl ketone (hereinafter referred to as MEK), methyl isobutyl ketone and cyclohexanone. , ester solvents such as methyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate (hereinafter PGMEA), ether solvents such as propylene glycol monomethyl ether (hereinafter PGM), diethyl ether, and diisopropyl ether, and the like. The above can be used in combination. Among these, MEK, PGM, PGMEA, etc., which have good compatibility with (A) and (B), are preferred.

In addition, the photocurable resin composition of the present invention contains, if necessary, a reactive diluent, an antioxidant, an ultraviolet absorber, a (near) infrared absorber, a fluorescent brightener, Sensitizers, flame retardants, fillers, organic fine particles, inorganic fine particles, dispersants, silane coupling agents, leveling agents, antifoaming agents, surfactants, anti-fingerprint agents, antistatic agents, antibacterial agents, antiviral agents, Polymerization inhibitors, coloring agents such as pigments, dyes, and dyes, and additives such as plasticizers can be used in combination.

The low refractive index layer provided on the hard coat layer surface of the present invention may be a vapor deposition film such as a silicon oxide film or a wet coating film. Films are preferred. The binder resin in this case is preferably an acrylic resin that has good adhesion to the hard coat layer, and raw materials to be blended to lower the refractive index include, for example, hollow silica and fluorine compounds. . A commercially available coating agent is Z-825-12L (IPA) (trade name: acrylic resin, refractive index: 1.35, manufactured by Aica Kogyo Co., Ltd.).

Examples of the thermoplastic transparent substrate film to which the hard coat resin of the present invention is applied include polyethylene terephthalate (hereinafter referred to as PET) film, polyethylene naphthalate film, polyvinyl chloride film, polystyrene film, acrylic film, polycarbonate film, and cycloolefin (co). Polymer films, polyimide films, polyolefin films (PP, PE, etc.) and composite films thereof can be exemplified. Among these, biaxially stretched PET film is preferably used from the viewpoint of price, workability, dimensional stability, etc., and acrylic film, polycarbonate film, or laminated film thereof is preferably used from the viewpoint of weather resistance.

For the purpose of improving adhesion to the hard coat resin, the thermoplastic transparent substrate film is subjected to surface roughening treatment such as primer treatment, corona treatment, sandblasting, solvent treatment, chromic acid treatment, and ozone treatment. - Surface treatment such as surface oxidation treatment such as ultraviolet irradiation treatment can be applied.

Methods for applying the hard coat resin of the present invention to a thermoplastic transparent substrate film include a bar coater method, an applicator method, a curtain coater method, a roll coater method, a gravure coater method, a reverse coater method, a comma coater method, and a lip coater method. , a die coater method, and the like can be applied. As for the coating film thickness, a dry film thickness of 1 to 20 μm is generally exemplified, but it is not specified and can be selected at any time.

After applying the hard coat resin, it is dried at 60 to 120° C. to volatilize the solvent, and cured using an ultraviolet irradiation machine. Examples of ultraviolet irradiation conditions include an irradiation intensity of 500 mW/cm ² to 3,000 mW/cm ² and an integrated light quantity of 100 mJ/cm ² to 2,000 mJ/cm ² . As the light source, known light sources such as high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, xenon lamps, LED lamps, and electrodeless ultraviolet lamps can be applied.

The thickness of the molded sheet is appropriately determined depending on the application, but if it is too thin, the strength will be insufficient, and if it is too thick, the formability will decrease. There is no problem even if there is. A coating film imparting other functions may be formed on the surface of the molded sheet using the present photocurable resin composition, or a composite sheet may be formed by laminating other materials. When using a PET film substrate having a sheet thickness of 125 μm, if the elongation rate at an ambient temperature of 130° C. is 50% or more, moldability as a molding sheet for decorative purposes can be ensured.

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but these are specific examples and are not particularly limited to these. Unless otherwise specified, the measurement was performed at a room temperature of 25° C. and a relative humidity of 65%. In addition, a compounding quantity shows a weight part.

Synthesis of urethane acrylate (Ureac, hereinafter) A 200 parts by weight of ethylene glycol (hereinafter, EG) and 778 parts by weight of IPDI (manufactured by Sumika Bayer Urethane Co., Ltd. under the trade name of Desmodur I NCO group 37.5%) were mixed with MEK. The mixture was added to a solvent (60% solids content) and stirred at 30° C. for 30 minutes for reaction. Next, 150 parts by weight of PETA (manufactured by Nippon Kayaku Co., Ltd., trade name PET30, solid content 100%) was added, stirred and reacted at 10 ° C. for 30 minutes, then stirred and reacted at 60 ° C. for 30 minutes, and infrared absorption. It was confirmed by analysis that the isocyanate groups had disappeared, and the solid content was adjusted to 60% with MEK, and the Mw. 4,200 of hexafunctional ureac A were obtained.

Synthesis of Ureac B 200 parts by weight of ethylene glycol (hereinafter referred to as EG) and 892 parts by weight of IPDI (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmodur I NCO group 37.5%) were mixed in an MEK solvent (solid content: 40%), and stirred and reacted at 30° C. for 30 minutes, and the reaction was terminated when the peak of the isocyanate group reached a predetermined amount in infrared absorption analysis. Next, 150 parts by weight of PETA (trade name PET30 solid content 100% manufactured by Nippon Kayaku Co., Ltd.) was added, stirred and reacted at 10 ° C. for 30 minutes, then stirred and reacted at 60 ° C. for 30 minutes, and infrared absorption. It was confirmed by analysis that the isocyanate group had disappeared, and the solid content was adjusted to 40% by PGM, and the Mw. 8,000 of hexafunctional ureac B were obtained.

Hard coat resin compositions 1 to 8
(A) Ureac A and B; Name: BASF Japan), Ureac C (IPDI reacted with PETA, Mw 1,400, hexafunctional) and D (HDI reacted with PETA, Mw 800, hexafunctional) and DPHA (dipentaerythritol hexaacrylate) was diluted with PGM to a solid content of 30% according to the formulation shown in Table 1 and stirred until uniformly dissolved to prepare hard coat resin compositions (hereinafter referred to as resin compositions) of formulations 1 to 8.

Test film A
The above hard coat resin compositions 1 to 8 were coated on PET film 125U403 (trade name: manufactured by Toray Industries, Inc., thickness 125 μm) so that the dry film thickness was 3 μm, and dried in a constant temperature bath at 80° C. for 1 minute. After that, ultraviolet rays were irradiated with an electrodeless lamp so that the output was 1,000 mW/cm 2 and the integrated amount of light was 150 mJ to prepare a test film A.

Test film B
On the resin composition layer of test film A, Z-825-12L (IPA) (trade name: manufactured by Aica Kogyo Co., Ltd.) was applied as a low refractive index layer so that the film thickness after drying was 100 nm, and the temperature was constant. After drying in a bath at 80°C for 1 minute, a test film B was prepared by irradiating ultraviolet rays with an electrodeless lamp at an output of 1,000 mW/cm 2 and an integrated light quantity of 150 mJ in a nitrogen atmosphere.

Table 1

The evaluation method was as follows.

Total light transmittance: Test films A and B are measured using a haze meter-Haze-gard2 manufactured by Toyo Seiki Seisakusho in accordance with JISK7361-1. For film B, 93% or more was rated as ◯, and less than 93% was rated as x.

Elongation rate: Cut the test film A into 25 mm × 50 mm and use a tensile tester TGI-1 kN manufactured by Minebea to perform a tensile test at an ambient temperature of 130 ° C. and a crosshead speed of 300 mm / min. A rate of 50% or more was indicated by ○, and a rate of less than 50% was indicated by ×.
Calculation formula: Calculated by how many mm it has grown based on 50 mm.
Elongation rate (%) = Elongated length (mm) / 50 mm x 100

Refractive index: A test film was obtained by coating a PET film 125U403 (trade name: manufactured by Toray Industries, Inc., thickness 125 μm) with a curable resin composition to a thickness of 5 μm using a bar coater. The refractive index at the D line of 589 nm was measured using an Atago Refractometer DR-M2. The test film was set on the prism surface, and 1-bromonaphthalene was used as the intermediate liquid.

Minimum reflectance: Using test films A and B, the surface opposite to the coated surface was evenly scratched with sandpaper, painted over with a black pigment marker, and then laminated with a black PET film on the opposite side. Let the reflectance of the surface be 0%. Using a spectrophotometer V650 manufactured by JASCO Corporation, plot the reflectance every 1 nm in the range of 380 to 780 nm and measure the smallest reflectance, ○ 0.5% or less in film B, more than 0.5% was x.

Evaluation results Table 2

Each resin composition of Examples gave good results in all the evaluation items of total light transmittance, elongation, and minimum reflectance.

On the other hand, Comparative Example 1, which does not contain (B), has a large minimum reflectance. are low, and none of them are suitable for the present invention.

The present invention is an optical film for molding that has a low reflectance and excellent elongation. It is suitable for three-dimensional molding such as insert molding as a decoration for electronic devices and vehicle interiors such as automobiles. It is useful as a coat film.

Claims (4)

A skeleton having a hard coat resin layer on one surface of a thermoplastic transparent substrate film, a low refractive index layer on the hard coat resin layer surface, and the hard coat resin layer reacting ethylene glycol and isophorone diisocyanate . A urethane (meth)acrylate oligomer (A) having a functionality of 6 or more, a (meth)acrylate having a fluorene skeleton (B), and a photopolymerization initiator (C), the weight average of (A) An antireflection hard coat film for molding characterized by having a molecular weight of 2,500 to 10,000 . 2. The antireflection hard coat film for molding according to claim 1 , wherein the number of functional groups of said polyfunctional urethane (meth)acrylate oligomer (A) is hexafunctional. 3. The antireflection hard-coated film for molding according to claim 1, wherein the amount of the (meth)acrylate (B) having a fluorene skeleton is 35 to 80% by weight based on the total solid content. . The antireflection hard coat film for molding according to any one of claims 1 to 3 , which is for insert molding.