JP2004331687A - Transparent hard coat film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coat film excellent in antistatic properties, transparency, and antiglare properties. <P>SOLUTION: The transparent hard coat film has a hard coat layer composed of an ionizing radiation curable resin containing spherical particles and electroconductive particles on at least one surface of a transparent base film. The thickness of the ionizing radiation curable resin portion in the hard coat layer is 50-90% of the average particle diameter of the spherical particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５２】
【発明の効果】
本発明によれば、帯電防止性と透明性および防眩性に優れたハードコートフィルムを提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transparent hard coat film having both antistatic performance and antiglare properties.
[0002]
[Prior art]
In general, polymer materials and glass have excellent insulation properties, but are easily charged. Therefore, on the surface of a product made of these materials, dirt due to adhesion of dust or the like may be conspicuous. Further, in precision machines using these materials, there is a problem that a failure occurs due to charging caused by the materials.
[0003]
[Patent Document 1]
JP-A-10-25388
[Patent Document 2]
JP 10-147739 A
[Problems to be solved by the invention]
An object of the present invention is to provide a hard coat film having excellent antistatic properties, transparency and antiglare properties.
[0006]
[Means for Solving the Problems]
The inventor of the present invention has conducted intensive studies to solve the above-described problems. As a result, the hard code layer is combined with spherical particles and conductive particles, and the conductive particles are substantially easily brought into contact with each other. It has been found that the properties can be increased and the above problem can be solved.
[0007]
That is, the present invention is a transparent hard coat film having an antiglare hard coat layer comprising a polymer binder containing spherical particles and conductive particles on at least one surface of the transparent base film, wherein the antiglare hard coat layer Wherein the thickness of the polymer binder portion is 50 to 90% of the average particle size of the spherical particles.
[0008]
Hereinafter, the present invention will be described in detail.
[Transparent substrate film]
As the transparent substrate film, a plastic film such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, acryl, triacetyl cellulose and the like can be used. Stretching, particularly biaxially stretched, is preferred because of its excellent mechanical strength and dimensional stability. The transparent substrate film is a film having a transmittance of, for example, 60% or more, preferably 80% or more. The thickness of the transparent substrate film can be appropriately selected according to the material, but is usually 25 to 500 μm.
[0009]
The transparent substrate film may have a hard coat layer. The hard coat layer in this case is a hard coat layer different from the antiglare hard coat layer described below, and is usually formed of a polymer binder mainly composed of a thermosetting resin or an ionizing radiation-curable resin. be able to. In this case, the “transparent substrate film” refers to a structure in which a hard coat layer is provided on a plastic film.
[0010]
[Anti-glare hard cord layer]
An antiglare hard code layer is formed on the transparent substrate film. This antiglare hard coat layer plays a role in providing properties such as antiglare property and antistatic property all at once.
[0011]
In the present invention, the antiglare hard coat layer can be formed of a polymer binder, spherical particles, and conductive particles. As the polymer binder, a thermosetting resin or an ionizing radiation-curable resin can be used, and an ionizing radiation-curable resin is preferable in view of work environment and productivity.
[0012]
In the present invention, the thickness of the polymer binder portion in the antiglare hard coat layer is adjusted so as to fall within a range of 50 to 90%, preferably 60 to 80% of the average particle size of the synthetic resin particles. . If the thickness is less than 50%, the synthetic resin particles tend to drop off, and the coating strength is reduced. If the thickness is more than 90%, the synthetic resin particles are buried in the coating film and sufficient antiglare property cannot be obtained.
[0013]
[Polymer binder]
The polymer binder is preferably an ionizing radiation-curable resin, which is formed from a paint containing at least a resin which is cured by irradiation with an electron beam or ultraviolet rays. Specifically, it contains a photopolymerizable prepolymer, a photopolymerizable monomer, a photopolymerization initiator, and further contains a sensitizer, a non-reactive resin, an additive such as a leveling agent, and a solvent, if necessary. Is also good.
[0014]
The structure and molecular weight of the photopolymerizable prepolymer relate to the curing of the ionizing radiation-curable coating material, and determine the properties of the ionizing radiation-curable resin, such as adhesiveness, hardness, and crack resistance. The photopolymerizable prepolymer undergoes radical polymerization when the acryloyl group introduced into the skeleton is irradiated with ionizing radiation. Those cured by radical polymerization are particularly preferred because they have a high curing rate and a high degree of freedom in resin design.
[0015]
As the photopolymerizable prepolymer, an acrylic prepolymer having an acryloyl group is particularly preferable, which has two or more acryloyl groups in one molecule and has a three-dimensional network structure. As the acrylic prepolymer, for example, urethane acrylate, epoxy acrylate, melamine acrylate, and polyester acrylate can be used.
[0016]
The photopolymerizable monomer is used for diluting a high-viscosity photopolymerizable prepolymer, lowering the viscosity and improving workability, and for imparting coating strength as a crosslinking agent.
[0017]
Examples of the photopolymerizable monomer include monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and butoxyethyl acrylate, 1,6-hexadiol acrylate, neopentyl glycol diacrylate, and hydroxypropyl acrylate. For example, bifunctional acrylic monomers such as biphosphate neopentyl glycol acrylate, and polyfunctional acrylic monomers such as dipentaerythritol hexaacrylate, trimethylpropane triacrylate, and pentaerythritol triacrylate can be used. These may be used alone or in combination of two or more.
[0018]
In addition, when the mixing amount of the photopolymerizable monomer increases, the coating film becomes harder than necessary. Therefore, the mixing ratio may be appropriately selected so as to obtain a desired hardness or a desired flexibility. For example, when used for bending the transparent hard coat film of the present invention, the hardness is adjusted by mixing a non-reactive resin such as a thermosetting resin having excellent flexibility, a thermoplastic acrylic resin, or an epoxy resin. can do.
[0019]
The photopolymerization initiator is added to start the reaction of the acryloyl group in a short time by irradiation with ionizing radiation and promote the reaction, and has a catalytic action. The photopolymerization initiator is required particularly when curing is performed by ultraviolet irradiation, and may not be required when irradiating a high energy electron beam. Types of photopolymerization initiators include those that undergo radical polymerization by cleavage, those that undergo radical polymerization by extracting hydrogen, and those that undergo cationic polymerization by generating ions.
[0020]
Examples of the photopolymerization initiator include benzoin ether-based, ketal-based, acetophenone-based, thioxanthone-based radical-type photopolymerization initiators, diazonium salts, diaryliodonium salts, triarylsulfonium salts, and the like, and composite-type cationic photopolymerization initiators. Can be used, for example. These may be used alone or in combination of two or more. The photopolymerization initiator is used, for example, by mixing 2 to 10% by weight, preferably 3 to 6% by weight, based on the solid resin component.
[0021]
In order to cure the ionizing radiation-curable paint, it is irradiated with an electron beam or ultraviolet rays. Irradiation with an electron beam can be performed by using a scanning or curtain type electron beam accelerator and irradiating an electron beam having an acceleration voltage of 1000 keV or less, preferably energy of 100 to 300 keV, and a wavelength region of 100 nm or less. it can. When irradiating ultraviolet rays, an ultrahigh-pressure mercury lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a carbon arc, a metal halide lamp, or the like is used. Irradiate.
[0022]
[Spherical particles]
In the present invention, as the spherical particles used in the antiglare hard cord layer, synthetic resin particles are preferably used. Examples of the synthetic resin particles include acrylic resin particles, silicone resin particles, nylon resin particles, styrene resin particles, polyethylene resin particles, benzoguanamine resin particles, and urethane resin particles. Among these, acrylic resin particles are preferable, and for example, polyacrylate particles and polymethacrylate particles can be used.
[0023]
The shape of the spherical particles is preferably spherical or nearly spherical. Classified particles are more preferable, and by using the classified spherical synthetic resin particles, more uniform unevenness can be obtained on the surface of the hard coat layer.
[0024]
The average particle size of the spherical particles is usually 0.5 to 10 μm, preferably 2 to 8 μm, and more preferably 4 to 6 μm. If it is smaller than 0.5 μm, the surface of the formed hard coat layer is not sufficiently provided with irregularities, so that the antiglare performance cannot be sufficiently exhibited. If it is larger than 10 μm, the ratio of the synthetic resin particles in the hard coat layer And the binding ability of the polymer binder to the synthetic resin particles is reduced, and the strength of the coating film is undesirably reduced.
[0025]
The addition amount of the spherical particles is preferably 0.3 to 5% by weight, more preferably 0.5 to 4% by weight, based on the solid resin content of the antiglare hard cord layer. If it is less than 0.3% by weight, sufficient anti-glare properties cannot be obtained, and if it exceeds 5% by weight, the haze increases, and the transmittance deteriorates, which is not preferable.
[0026]
[Conductive particles]
The conductive particles used in the present invention in combination with the antiglare hard cord layer are usually 1 to 500 nm, preferably 1 to 100 nm, more preferably 1 to 50 nm so as not to cause light scattering. Use particles of a diameter. As the conductive particles, for example, metal oxides such as ITO, ATO, SnO ₂ , and ZnO, for example, metals such as Au, Ag, and Cu can be used. Among these, ITO and ATO are preferable from the viewpoint of transparency. The conductive particles are preferably blended in a ratio of 10 to 80%, more preferably 30 to 60%, of the total mass of the hard coat layer.
[0027]
[Formation of antiglare hard coat layer]
When an ionizing radiation-curable resin is used as a polymer binder to form an antiglare hard coat layer, an ionizing radiation-curable resin coating containing spherical particles is applied to a plastic film and irradiated with an electron beam or ultraviolet rays. Formed.
[0028]
The application of the ionizing radiation-curable paint to the plastic film can be performed by a usual coating method, for example, coating with a bar, blade, gravure, spin, spray or the like.
[0029]
When an ionizing radiation-curable paint is cured by irradiation with an electron beam or ultraviolet rays, the presence of oxygen and the thickness of the coating film are closely related to the curing. Radicals generated by the irradiation with ionizing radiation supplement oxygen, thereby suppressing curing. For this reason, when the thickness of the coating film is small, the surface area occupying the coating film volume increases, and the coating is easily affected by curing in the air. In addition, when the thickness of the coating film is large, ionizing radiation hardly penetrates to the inside, and even when the surface is cured, the inside is not sufficiently cured, and the presence of an uncured portion at the coating interface causes the hard coating layer to be hardened. Poor adhesion to the transparent substrate occurs. In order to prevent such curing inhibition and uncuring, especially in the case of electron beam irradiation, irradiation can be performed under an inert gas such as N ₂ gas. In addition, curing inhibition can be prevented by adjusting the thickness of the coating film, selecting a photopolymerizable prepolymer and a photopolymerizable monomer having a high curing rate, and increasing the mixing amount of the photopolymerization initiator.
[0030]
[Low refractive index layer]
In the present invention, it is preferable that a low refractive index layer is provided on the hard code layer. The refractive index of the low refractive index layer is preferably from 1.38 to 1.49, and more preferably from 1.38 to 1.44. The low refractive index layer preferably satisfies the following formula (I) from the viewpoint of reducing the reflectance.
[0031]
(Equation 1)
(Mλ / 4) × 0.7 <n ₁ d ₁ <(mλ / 4) × 1.3 (I)
In the formula, m is a positive odd number, n ₁ is the refractive index of the low refractive index layer, and d ₁ is the thickness (nm) of the low refractive index layer. Λ is a wavelength, which is a value in the range of 500 to 550 nm. Satisfying the above formula (I) means that m (positive odd number, usually 1) that satisfies the formula (I) exists in the above wavelength range.
[0032]
The low refractive index layer is made of a low refractive index binder. This low refractive index binder is preferably made of a crosslinked product of a fluorine-containing compound. The crosslinked product of the fluorine-containing compound is preferably a crosslinked product formed by heating or ionizing radiation irradiation of a crosslinkable fluorine-containing polymer compound. Further, the low refractive index layer preferably contains inorganic fine particles for improving the film strength.
[0033]
As a crosslinkable fluorine-containing polymer compound for forming a crosslinked product of a fluorine-containing compound, which is preferably used as a binder for the low refractive index layer, a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,1) , 2,2-tetradecyl) triethoxysilane), and a fluorine-containing copolymer having a fluorine-containing monomer and a monomer for providing a crosslinking group as constituent units.
[0034]
Examples of the fluorinated monomer include fluoroolefins (eg, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole), (meth) Partial or fully fluorinated alkyl ester derivatives of acrylic acid (for example, Biscoat 6FM (manufactured by Osaka Organic Chemicals), M-2020 (manufactured by Daikin)), and fully or partially fluorinated vinyl ethers can be mentioned.
[0035]
Examples of the monomer for providing a crosslinkable group include a (meth) acrylate monomer having a crosslinkable functional group in the molecule in advance, such as glycidyl methacrylate, a carboxyl group, a hydroxyl group, an amino group, and a sulfonic acid group ( (Meth) acrylate monomers (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, and allyl acrylate can be exemplified.
[0036]
It is known from JP-A-10-25388 and JP-A-10-147739 that the latter can introduce a crosslinked structure after copolymerization.
[0037]
Further, not only a polymer having the above-mentioned fluorine-containing monomer as a constitutional unit but also a copolymer with a monomer containing no fluorine atom may be used. There is no particular limitation on the monomer units that can be used in combination, and for example, olefins (ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylates (methyl acrylate, methyl acrylate, ethyl acrylate, acrylic acid 2) -Ethylhexyl), methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinylbenzene, vinyltoluene, α-methylstyrene, etc.), vinyl ethers (methyl Vinyl ethers), vinyl esters (vinyl acetate, vinyl propionate, vinyl cinnamate, etc.), acrylamides (N-tertbutylacrylamide, N-cyclohexylacrylamide, etc.), methacrylamides, Krilo nitrile derivatives and the like can be mentioned.
[0038]
As the inorganic fine particles used for the low refractive index layer, those having a low refractive index are preferably used. Examples of the inorganic fine particles include silica and magnesium fluoride, and silica is preferable.
[0039]
The average particle size of the inorganic fine particles is preferably in the range of 1 to 200 nm, more preferably 1 to 50 nm. It is preferable that the particle size of the fine particles is as uniform (monodispersed) as possible. The addition amount of the inorganic fine particles is preferably in the range of 5 to 90% by weight, more preferably in the range of 10 to 70% by weight, and more preferably in the range of 10 to 50% by weight of the total amount of the low refractive index layer. Is most preferred.
[0040]
The inorganic fine particles are also preferably subjected to a surface treatment before use. As the surface treatment method, there are a physical surface treatment such as a plasma discharge treatment or a corona discharge treatment and a chemical surface treatment using a coupling agent, but the use of a coupling agent is preferable. As the coupling agent, an organoalkoxy metal compound (eg, a titanium coupling agent, a silane coupling agent) is preferably used. When the inorganic fine particles are silica, silane coupling treatment is particularly effective.
[0041]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. Preparation of the coating solution was performed according to the following methods, and evaluation of physical properties was performed according to the following methods.
[0042]
Preparation of coating solution for hard coat layer:
75 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.) and 75 g and 439 g of bis (4-methacryloylthiophenyl) sulfide (MPSMA, manufactured by Sumitomo Seika Co., Ltd.) It was dissolved in a mixed solvent of methyl ethyl ketone / cyclohexanone (50% / 50%). In the resulting solution, 5.0 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Co., Ltd.) and 3.0 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were dissolved in 49 g of methyl ethyl ketone. The solution was added to prepare a coating solution for the hard cord layer.
[0043]
Preparation of coating solution for antiglare hard coat layer:
75 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.), 75 g of bis (4-methacryloylthiophenyl) sulfide (MPSMA, manufactured by Sumitomo Seika Co., Ltd.), average particle size 100 g of ITO particles having a diameter of 50 nm (manufactured by CI Kasei Co., Ltd.) was dissolved in 439 g of a mixed solvent of methyl ethyl ketone / cyclohexanone (50% / 50%). In the resulting solution, 5.0 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Co., Ltd.) and 3.0 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were dissolved in 49 g of methyl ethyl ketone. The solution was added. Further, 10 g of crosslinked polystyrene particles having an average particle size of 2 μm (trade name: SX-200H, manufactured by Soken Chemical Co., Ltd.) was added to the solution, and the mixture was stirred and dispersed at 5000 rpm for 1 hour with a high-speed disperser. The mixture was filtered through a polypropylene filter to prepare a coating solution for an antiglare hard coat layer.
[0044]
Preparation of coating liquid for low refractive index layer:
To 210 g of a thermally crosslinkable fluoropolymer having a refractive index of 1.42 (OPSTAR JN7228, manufactured by JSR Corporation, solid content concentration 6%), silica sol (MIBK-ST, average particle size 10 to 20 nm, solid content concentration 30%, Nissan) After adding 15.2 g and 174 g of methyl isobutyl ketone, and stirring, the mixture was filtered through a polypropylene filter having a pore size of 1 μm to prepare a coating solution for a low refractive index layer.
[0045]
Surface resistivity:
It was measured by a surface resistance measuring device loresta-GP (MCD-T600) manufactured by Mitsubishi Chemical Corporation.
[0046]
Haze:
The haze of the obtained film was measured with a haze meter POIC Co., Ltd., SEP-HS-D1 type.
[0047]
Anti-glare evaluation:
An exposed fluorescent lamp (8000 cd / m ² ) without a louver was projected on the produced antiglare film, and the degree of blurring of the reflected image was evaluated according to the following criteria.
：: The outline of the fluorescent lamp is completely unknown. ：: The outline of the fluorescent lamp is slightly recognized. △: The fluorescent lamp is blurred, but the outline is discernable. X: The fluorescent lamp is hardly blurred.
[0048]
[Example 1]
The above coating liquid for a hard coat layer is applied to a biaxially oriented polyethylene terephthalate film (OPFW, manufactured by Teijin Limited) having a thickness of 100 μm using a bar coater, dried at 120 ° C., and dried at 160 W / cm. Using an air-cooled metal halide lamp (manufactured by I-Graphics Co., Ltd.), the coating layer is cured by irradiating ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 300 mJ / cm ² to form a hard coat layer having a thickness of 2.5 μm. Formed. The coating liquid for the antiglare hard coat layer was applied thereon using a bar coater, dried and cured under the same conditions as the hard coat layer, and the thickness of the polymer binder portion was 1.5 μm. To form an antiglare hard coat layer. The low-refractive-index layer coating solution is applied thereon using a bar coater, dried at 80 ° C., and then thermally crosslinked at 120 ° C. for 10 minutes to form a low-refractive-index layer having a thickness of 0.096 μm. did.
Table 1 shows the evaluation results.
[0049]
[Comparative Example 1]
The procedure was performed in the same manner as in Example 1 except that no ITO particles were added to the antiglare hard coat layer. Table 1 shows the evaluation results.
[0050]
[Comparative Example 2]
The same procedure was performed as in Example 1 except that no spherical particles were added to the antiglare hard coat layer. Table 1 shows the evaluation results.
[0051]
[Table 1]

[0052]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the hard-coat film excellent in antistatic property, transparency, and anti-glare property can be provided.

Claims (5)

A transparent hard coat film having an antiglare hard coat layer made of a polymer binder containing spherical particles and conductive particles on at least one surface of the transparent substrate film, wherein the polymer binder portion in the antiglare hard coat layer Wherein the thickness of the transparent hard coat film is 50 to 90% of the average particle size of the spherical particles. The transparent hard coat film according to claim 1, wherein the polymer binder is an ionizing radiation-curable resin. The transparent hard coat film according to claim 1, wherein the conductive particles are transparent conductive particles having a particle size of 1 to 100 nm. The transparent hard coat film according to claim 1, wherein the spherical particles are synthetic resin particles. The hard coat film according to claim 1, wherein a low refractive index layer is provided on the antiglare hard coat layer.