JP2023159921A - Antireflection hard coat film - Google Patents

Abstract

To provide an antireflection hard coat film which reflects less light from an outside light source and can secure an excellent visibility and can maintain a sufficient resistance to rubbing even if the film is rubbed with steal wool.SOLUTION: The antireflection hard coat film includes the lamination of an optically transmissive base material film, a hard coat layer, and a low refractive index layer in that order. The low refractive index layer includes a binder resin, hollow silica fine particles, amine-modified (meth) acrylate, and alumina fine particles. The amine-modified (meth) acrylate is mixed in a ratio of 8-25 parts by weight to 100 parts by weight of binder resin.SELECTED DRAWING: None

Description

The present invention relates to an antireflection hard-coated film that has low reflection from an external light source, good visibility, and excellent scratch resistance.

Antireflection hard coat films are widely used in image display devices, such as liquid crystal displays and organic EL displays, because of their low reflection from external light sources such as fluorescent lamps and good visibility. In particular, when touching the image display surface with a finger or inputting with a touch pen, such as on a touch panel, it is necessary to lower the reflectance of the external light source and to have higher abrasion and scratch resistance. It's coming.

Anti-reflection hard-coated films generally have a structure in which a hard-coat layer is provided on the surface of the film base material, and an anti-reflection layer with a low refractive index is placed on top of the hard-coat layer. It is well known to include hollow silica containing air with a ratio of 1.0. As such a low refractive index resin, for example, a composition containing a silicone-grafted acrylic polymer, a compound having a methacryloyl group, and hollow colloidal silica has been proposed (Patent Document 1).

However, the abrasion resistance of the low refractive index layer that forms voids tends to decrease, and although the above formulation has excellent abrasion resistance, the scratch resistance was evaluated using steel wool at a load of 500 g/cm2. The evaluation was based on 10 reciprocations, and it could not be said that the scratch resistance was sufficient. Therefore, there has been a need for an antireflection film that has low reflectance, good visibility, and sufficient scratch resistance even when rubbed with steel wool.

JP2006-306950

An object of the present invention is to provide an antireflection hard coat film that has good visibility with little reflection from an external light source and has sufficient scratch resistance even when rubbed with steel wool.

In order to solve the above problem, the invention according to claim 1 is such that a hard coat layer and a low refractive index layer are laminated in this order on a base film having light transmittance, and the low refractive index layer is made of a binder resin ( A), hollow silica fine particles (B), amine-modified (meth)acrylate (C), and alumina fine particles (D), and the amount of the above (C) is based on 100 parts by weight of the above (A). Provided is an antireflection hard coat film characterized in that the amount is 8 to 25 parts by weight.

The invention according to claim 2 provides the antireflection hard coat film according to claim 1, wherein the (C) is an amine-modified polyether (meth)acrylate and/or an aminoacrylate.

The invention according to claim 3 provides the antireflection hard coat film according to claim 1 or 2, wherein the amount of (D) is 30 to 100 parts by weight per 100 parts by weight of (A). provide.

The invention according to claim 4 provides the antireflection hard coat film according to claim 1 or 2, further comprising a leveling agent (E) in the low refractive index layer.

The hard coat film of the present invention has good visibility with little reflection from external light sources, and also has good scratch resistance even when rubbed with a highly hard material such as steel wool. , is useful as an antireflection film for image display devices.

The antireflection hard coat film of the present invention uses two types of resin compositions: an HC resin composition for forming a hard coat (hereinafter referred to as HC) layer and a low refractive index resin composition for forming a low refractive index layer. Manufactured. The low refractive index resin composition is a composition containing a binder resin (A), hollow silica particles (B), amine-modified (meth)acrylate (C), and alumina particles (D). Note that (meth)acrylate in this specification includes both acrylate and methacrylate.

The binder resin (A) used in the present invention is a main resin that disperses the above (B) and (D) to form a low refractive index layer, and includes, for example, urethane (meth)acrylate, epoxy (meth)acrylate, polyester ( Examples include oligomers such as meth)acrylate, polycarbonate (meth)acrylate, acrylic (meth)acrylate, and diene (meth)acrylate. Examples of low molecular weight binders include aliphatic, alicyclic, polyether skeletons, hydroxyl groups and Examples include (meth)acrylates having a functional group such as an amino group, which can be used alone or in combination of two or more types.

The blending amount of (A) is preferably 10 to 30% by weight, more preferably 15 to 25% by weight, particularly preferably 18 to 23% by weight based on the total solid content of the resin composition. When the content is 10% by weight or more, sufficient film hardening properties can be ensured, and when the content is 30% by weight or less, the reflectance can be lowered and sufficient scratch resistance can be ensured.

The hollow silica fine particles (B) used in the present invention are blended for the purpose of lowering the refractive index of the low refractive index layer. (B) is a silica particle that has a function of lowering the refractive index of the low refractive index layer while maintaining its coating strength, and has a cavity containing air with a refractive index of 1 inside. While the refractive index of solid silica particles is about 1.45, the refractive index of (B) decreases as the occupancy of internal cavities increases, and is about 1.15 to 1.40.

The average primary particle diameter of (B) is preferably 5 to 100 nm, more preferably 20 to 80 nm, and particularly preferably 40 to 70 nm. By setting it as this range, good dispersibility can be obtained without impairing the transparency of a low refractive index layer. In particular, if the thickness is 40 to 70 nm, it is possible to increase the cavity occupancy and lower the refractive index while ensuring a thickness of the outer shell that does not cause insufficient strength. Note that the average particle diameter is the median diameter (d=50) measured by a laser diffraction/scattering method in accordance with JIS Z8825-1.

The blending amount of (B) is preferably 30 to 50% by weight, more preferably 35 to 45% by weight based on the total solid content of the resin composition. By setting the content to 30% by weight or more, the refractive index can be made sufficiently low, and by setting the content to 50% by weight or less, sufficient scratch resistance can be ensured. As a commercially available product, Sururia 2320 (trade name: manufactured by JGC Catalysts & Chemicals Co., Ltd., solid content 20.5%, primary average particle diameter 50 nm) may be mentioned.

The amine-modified (meth)acrylate (C) used in the present invention is a compound having at least one amino group and at least one acryloyl group or methacryloyl group, which alleviates polymerization inhibition caused by oxygen during ultraviolet curing and cures. It is blended for the purpose of improving the strength. In order to avoid curing inhibition caused by oxygen, it is well known to expose in an environment using an inert gas such as nitrogen, but in production processes where the exposed object is transported at high speed, It is said that it is difficult to completely eliminate this effect, and by combining it with (C), the curability is significantly improved. The amino group may be any of a primary amino group, a secondary amino group, and a tertiary amino group, but a tertiary amino group is preferred from the viewpoint of curing acceleration.

Examples of (C) include amino (meth)acrylate, amine-modified aliphatic (meth)acrylate, amine-modified polyether (meth)acrylate, amine-modified polyester (meth)acrylate, amine-modified epoxy (meth)acrylate, and amine. Examples include modified urethane (meth)acrylate, which can be used alone or in combination of two or more types. Among these, amine-modified polyether (meth)acrylate is preferred because of its high reactivity, and amino (meth)acrylate is preferred because it has a high polymerization promoting effect.

The number of functional groups in (C) is preferably 2 to 8 functional groups, more preferably 2 to 6 functional groups, and particularly preferably 2 to 4 functional groups. By setting it as this range, surface hardness and abrasion resistance can be improved without increasing curing shrinkage.

The blending amount of (C) is 8 to 25 parts by weight, preferably 10 to 20 parts by weight, and more preferably 12 to 18 parts by weight, based on 100 parts by weight of (A). If it is less than 8 parts by weight, scratch resistance tends to decrease, and if it exceeds 25 parts by weight, scratch resistance tends to decrease or yellowing occurs over time. Further, the blending amount based on the total solid content of the resin composition is preferably 1.5 to 5.5% by weight, more preferably 2.0 to 4.5% by weight, and particularly preferably 2.5 to 4.0% by weight. .

The alumina fine particles (D) used in the present invention are blended for the purpose of increasing the hardness of the low refractive index layer and improving the scratch resistance. The average primary particle diameter of (D) is preferably 1 to 100 nm, more preferably 5 to 50 nm, and particularly preferably 10 to 30 nm. When the thickness is 1 nm or more, an improvement in scratch resistance can be expected, and when the thickness is 100 nm or less, sufficient total light transmittance can be ensured without increasing the haze.

The blending amount of (D) is preferably 40 to 85 parts by weight, more preferably 45 to 80 parts by weight, and particularly preferably 55 to 70 parts by weight, based on 100 parts by weight of (A). When the amount is 40 parts by weight or more, sufficient wear resistance can be ensured, and when it is 85 parts by weight or less, the reflectance can be kept sufficiently low. Further, the blending amount based on the total solid content of the resin composition is preferably 5 to 25% by weight, more preferably 8 to 20% by weight, and particularly preferably 10 to 18% by weight. A commercially available product includes ALMIBK-M47 (trade name: manufactured by CIK Nanotech, solid content 15%, average particle size 20 nm).

In the present invention, it is preferable to further include a leveling agent (E). By blending (E), it is possible to improve the slip property of the low refractive index layer and improve the abrasion resistance, and also to improve the water repellency and stain resistance. For example, silicone-based, fluorine-based, acrylic-based, etc. can be mentioned, but they can be used to polymerize with binder resin and form a cured coating because they do not come off over time due to bleeding etc. after curing and can maintain their effects over a long period of time. It is preferable to have a reactive functional group capable of forming . In particular, fluorine-based silicone compounds are preferred because their low surface free energy makes them easy to segregate on the coating surface after coating and drying, and can stabilize wear resistance and antifouling properties over a long period of time.

The blending amount of (E) is preferably 30% by weight or less, more preferably 10 to 28% by weight, and particularly preferably 15 to 25% by weight based on the total solid content of the resin composition. In particular, when the content is 10% by weight or more, it can be expected to improve wear resistance and antifouling properties, and when the content is 30% by weight or less, sufficient curability can be ensured. A commercially available product includes X-71-1203M (trade name: manufactured by Shin-Etsu Chemical Co., Ltd., solid content 20%, fluorine-based silicone compound having a reactive functional group).

The HC resin composition for forming the HC layer located below the low refractive index layer of the present invention preferably contains polyfunctional urethane (meth)acrylate (hereinafter referred to as polyfunctional ureac) as a binder.

The polyfunctional ureac preferably included in the HC resin composition has excellent scratch resistance due to the cohesive force of hydrogen bonds derived from urethane bonds. For example, it can be obtained by reacting polyisocyanate with (meth)acrylate having a hydroxyl group. Examples of the polyisocyanate to be used include hexamethylene diisocyanate (hereinafter HDI), isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, hydrogenated xylylene diisocyanate, methylcyclohexylene diisocyanate, HDI isocyanurate. and IPDI isocyanurate, and these may be used alone or in combination of two or more. Among these, aliphatic and alicyclic diisocyanates that have high weather resistance and are resistant to yellowing are preferred, and among these, HDI is particularly preferred because of its high stretchability.

Examples of (meth)acrylates having a hydroxyl group used in the polyfunctional ureac include trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, and diglycerin di(meth)acrylate for difunctional ureacs. , ditrimethylolpropane di(meth)acrylate, dipentaerythritol di(meth)acrylate, etc., and those with trifunctional or higher functionality include diglycerin tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, There are dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and dipentaerythritol penta(meth)acrylate. Among these, pentaerythritol triacrylate (hereinafter referred to as PETA), which is trifunctional and has high curability, is preferred.

It is preferable to mix a photopolymerization initiator into the HC resin composition and low refractive index resin composition of the present invention in order to improve curability by ultraviolet irradiation. Photopolymerization initiators generate radicals when irradiated with ultraviolet rays or electron beams, and these radicals trigger polymerization reactions.General-purpose photopolymerization initiators such as benzyl ketal, acetophenone, and phosphine oxide are used. can. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2,2-dimethoxy-1,2-diphenylethan-1-one is used as a benzyl ketal type, and 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2- hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is converted into 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1 as an α-aminoacetophenone system. -one is acylphosphine oxide, such as 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2.4.6-trimethylbenzoyl)-phenylphosphine oxide, either singly or in combination. Can be used in combination.

In the case of the HC resin composition, the photopolymerization initiator preferably contains α-hydroxyacetophenone, which does not easily yellow, and commercially available products include Omnirad 127, Omnirad 184, and Omnirad 2959 (trade name: manufactured by IGM Resins). Among these, Omnirad 2959 is particularly preferred because it has little yellowing and excellent scratch resistance. The amount of the photopolymerization initiator to be added to 100 parts by weight of the radically polymerizable component in the HC resin composition is preferably 1 to 15 parts by weight, more preferably 2 to 10 parts by weight.

In the case of a low refractive index resin composition, the photopolymerization initiator preferably contains α-hydroxyacetophenone as in the case of the HC resin composition, and Omnirad 127 (2-hydroxy- 1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one) is preferred. The amount of the photopolymerization initiator to be added to 100 parts by weight of the radically polymerizable component in the low refractive index resin composition is preferably 1 to 10 parts by weight, more preferably 2 to 8 parts by weight.

The composition of the present invention may contain ultraviolet absorbers, antioxidants, adhesion promoters, bluing agents, silane coupling agents, antifoaming agents, thickeners, and anti-settling agents as necessary to the extent that performance is not impaired. , antistatic agents, antifogging agents, antibacterial agents, organic fine particles, etc. may be added.

When coating the HC resin composition and the low refractive index resin composition, they may be diluted with a solvent in order to improve coating properties. Examples of diluting solvents include alcoholic solvents such as ethanol, n-propyl alcohol, isopropyl alcohol (hereinafter referred to as IPA), n-butyl alcohol, isobutyl alcohol, and diacetone alcohol, acetone, methyl ethyl ketone (hereinafter referred to as MEK), methyl isobutyl ketone, and cyclohexanone. Examples include ketone solvents such as ethyl acetate and butyl acetate, ester solvents such as ethyl acetate and butyl acetate, and ether solvents such as PGM, diethyl ether and diisopropyl ether, which can be used alone or in combination of two or more. The solid content when diluting is exemplified as 1 to 70%, but there is no particular specification and it can be set as appropriate so as to provide a viscosity that is easy to coat.

The base film to which the HC resin composition is applied includes polyester film, triacetylcellulose film, polycarbonate film, polysulfone film, nylon film, cycloolefin film, acrylic film, polyimide film, ABS film, polyolefin film, and PVC film. , PVA film, etc. Among these, a biaxially stretched polyester film is preferably used from the viewpoint of weather resistance, processability, dimensional stability, and the like. The thickness of the film may be approximately 25 μm to 500 μm.

The base film may be subjected to surface roughening treatment such as primer treatment, sandblasting, solvent treatment, corona discharge treatment, chromic acid treatment, or ozone/ultraviolet irradiation in order to improve adhesion with the HC resin composition. Surface treatment such as surface oxidation treatment can be performed.

The method of applying the HC resin composition and the low refractive index resin composition is not particularly limited, and may include known spray coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, wire bar, etc. It can be formed by a coating method or a printing method such as gravure printing, screen printing, offset printing, or inkjet printing.

The film thickness of the HC resin composition is, for example, 1 μm to 10 μm when dry, but is not limited thereto. The film thickness of the low refractive index resin composition coated on the hard coat resin layer is preferably 50 to 200 nm, more preferably 80 to 150 nm when dry. If the thickness of the low refractive index layer is within this range, it is possible to make the reflectance sufficiently low.

The light source for ultraviolet irradiation used when curing the HC resin composition and the low refractive index resin composition includes a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, an LED lamp, Electrodeless ultraviolet lamps are available, and the irradiation atmosphere may be air or an inert gas such as nitrogen or argon. Moreover, by heating the back roll or heating the coating film with an IR heater or the like during ultraviolet irradiation, the curability can be further improved. Irradiation conditions include, but are not limited to, an irradiation intensity of 500 mW/cm ² to 3000 mW/cm ² and an exposure amount of 50 to 400 mJ/cm ² . Ultraviolet irradiation is performed after film molding, but semi-curing with a low exposure dose (for example, 15 to 30 mJ/cm ² ) may be performed before molding.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but these are intended to be specific examples and are not particularly limited to these. Unless otherwise specified, measurements were performed at a room temperature of 25° C. and a relative humidity of 65%. Moreover, the blending amount indicates parts by weight.

HC resin composition : 100 parts of hexafunctional ureac made by reacting HDI and PETA as a binder, 5 parts of Omnirad 2959 (trade name: manufactured by IGM Resins) as a photopolymerization initiator, and the solid content is 40%. The HC resin composition was diluted with ethyl acetate and PGM so as to have the following properties, and stirred until uniformly dissolved and dispersed to obtain an HC resin composition.

Low refractive index resin composition (A) is DPHA (product name: Nippon Kayaku Co., Ltd., a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate), and (B) is Surulia 2320 (product name: JGC Catalyst). (manufactured by Kasei Co., Ltd., solid content 20.5%, primary average particle diameter 50 nm) as (C) EBECRYL80 (trade name: manufactured by Daicel Ornex, amine-modified polyether acrylate, solid content 100%, tetrafunctional tertiary amino group compound) and EBECRYL 7100 (trade name: manufactured by Daicel Allnex, solid content 100%, amino acrylate, bifunctional tertiary amino group compound) as (D) M47 (trade name: manufactured by CIK Nanotech, manufactured by CIK Nanotech, Solid content 30%, average particle size 20 nm, MIBK dilution) as (E), X-71-1203M (trade name: manufactured by Shin-Etsu Chemical Co., Ltd., solid content 20%, reactive functional group-containing fluorosilicone compound) , Omnirad 127 (trade name: manufactured by IGM Resins) was used as a photopolymerization initiator in the formulation shown in Tables 1 and 2, and diluted with IPA and PGM so that the solid content was 3% (IPA:PGM=1: 1) and stirred until uniformly dissolved and dispersed to obtain a low refractive index resin composition.

Table 1

Table 2

The evaluation method was as follows.

Creation of HC layer The HC resin composition was applied to PET film U403 (product name: Toray Industries, Ltd., thickness 100 μm, with easy adhesive layer) to a dry film thickness of 3 μm, and dried at 80° C. for 1 minute. . Thereafter, the film was cured using an ultraviolet exposure device ECS-151U manufactured by Eye Graphics under conditions of 100 mW/cm ² and 800 mJ/cm ² to prepare an HC film.

Preparation of antireflection film A low refractive index resin composition was coated on the hard coat layer prepared above to a dry film thickness of 100 nm, and dried at 80° C. for 1 minute. Thereafter, using an ultraviolet exposure device ECS-151U manufactured by Eye Graphics Co., Ltd., the film was cured under conditions of 100 mW/cm ² , 800 mJ/cm ² and a nitrogen atmosphere to form an antireflection film.

Haze: The above antireflection film was measured in accordance with JIS K7361-1 using Haze-GARD2 manufactured by Toyo Seiki Seisakusho Co., Ltd., and 1.0% or less was evaluated as ○, and over 1.0% was evaluated as ×.

Minimum reflectance: Using the above anti-reflection film, scratch the surface opposite to the coated surface with sandpaper, fill it in with a black pigment marker, and then paste black PET to make the reflectance of the opposite surface 0%. After that, the reflectance of the HC side was plotted every 1 nm in the range of 300 nm to 780 nm using a spectrophotometer, and the lowest reflectance was measured, and 1.8% or less was marked as ○, and over 1.8% was marked as ×. .

Scratch resistance: Place a load of 1000 g/cm2 on steel wool #0000 and make it reciprocate 300 times. If there is no scratch by visual observation, ○, if there is a slight scratch, △, if there are many scratches was marked as ×.

Evaluation results Table 3

Evaluation results Table 4

Examples had no problems and were good in all aspects of haze, minimum reflectance, and scratch resistance.

On the other hand, Comparative Example 1 without (C) has poor scratch resistance, Comparative Example 2 without (B) has a high minimum reflectance, and Comparative Example 5 without (D) has poor scratch resistance. was inferior. Furthermore, Comparative Example 3, in which the amount of (C) blended was less than the lower limit, and Comparative Example 4, in which the amount exceeded the upper limit, had poor scratch resistance, and both were unsuitable for the present invention.

Claims (4)

A hard coat layer and a low refractive index layer are laminated in this order on a base film having optical transparency, and the low refractive index layer is made of a binder resin (A), hollow silica particles (B), and an amine-modified ( Antireflection hard, comprising meth)acrylate (C) and alumina fine particles (D), wherein the blending amount of (C) is 8 to 25 parts by weight per 100 parts by weight of (A). coat film. The antireflection hard coat film according to claim 1, wherein the (C) is an amine-modified polyether (meth)acrylate and/or an aminoacrylate. 3. The antireflection hard coat film according to claim 1, wherein the amount of (D) is 30 to 100 parts by weight per 100 parts by weight of (A). 3. The antireflection hard coat film according to claim 1, further comprising a leveling agent (E) in the low refractive index layer.