JP2010208035A - Optical film and manufacturing method thereof - Google Patents

Abstract

The present invention provides an optical film having both improved curl and improved surface strength, an electromagnetic wave shielding function and an antireflection function, and a method for producing the same.
An optical film according to the present invention is disposed so as to cover a base material, a conductive layer having a plurality of openings arranged on one main surface of the base material, and the conductive layer. An optical film including a hard coat layer 13 as a resin layer and an antireflection layer 14 disposed on the hard coat layer 13, wherein the hard coat layer 13 as the resin layer has a thiol group having three or more functional groups. It is obtained by curing a resin composition containing 5 to 20% by weight of a photocurable monomer having a total of resin components.
[Selection] Figure 1

Description

  The present invention relates to an optical film having a plurality of optical functions combined and a method for producing the same.

  In a plasma display panel (PDP), a mixed gas containing xenon and neon is sealed between two glass plates. When a high voltage is applied to the mixed gas, ultraviolet rays are generated, and the phosphor applied to the glass plate The ultraviolet light hits and emits light. In general, a display surface of a display such as a PDP is provided with a filter having an antireflection function, an ultraviolet and near infrared cut function, an antistatic function, a neon cut function, an electromagnetic wave shielding function, and the like. Examples of the filter include a glass filter and a film filter. A glass filter is generally produced by laminating one or more films having various functions on glass, or providing a layer having an electromagnetic wave shielding function on the glass by a sputtering method. In recent years, glassless type film filters tend to be used for the purpose of further reduction in thickness and weight.

  In these film filters, a plurality of functions are imparted to the film, and the methods are diverse. For example, a metal mesh or a sputtered film is disposed on one main surface of the film to provide an electromagnetic wave shielding function by providing a conductive layer, a near-infrared absorbing layer and a neon cut layer are provided on the same main surface, and the other main surface is further provided. Some have a hard coat layer or an antireflection layer on the surface. On the other hand, a hard coat layer and an antireflection layer are provided on the same main surface as the main surface on which the conductive layer is disposed, and a near infrared absorption layer and a neon cut layer are provided on the other main surface (for example, Patent Document 1).

  In order to impart a near infrared absorption function or a neon cut function, various dyes are generally contained in a resin layer or an adhesive layer for bonding to glass to form a near infrared absorption layer or a neon cut layer. However, if a near-infrared absorbing layer or a neon cut layer is provided on the same main surface as the conductive layer, the reduction in both functions is promoted by direct contact between the dye and the metal mesh. There is a problem that the material used for them is limited.

  On the other hand, when a hard coat layer or an antireflection layer is provided on the same main surface as the conductive layer, a film thickness sufficient to cover the conductive layer is required, and an acrylic monomer generally used for the hard coat layer is required. In the cured product, there is a problem that curling (film warpage) occurs, and there is a problem that surface hardness becomes weak when a urethane monomer is mixed as a means for preventing the curling (for example, Patent Document 2).

JP 2007-328284 A JP 2006-196737 A

  When a hard coat layer or an antireflection layer is provided on the same main surface as the main surface on which the conductive layer is arranged in this way, the conventional film filter cannot achieve both curl improvement and surface strength improvement. .

  In order to solve the above-mentioned problems, the present invention provides an optical film having both improved curl and improved surface strength, and provided with an electromagnetic wave shielding function and an antireflection function, and a method for producing the same.

  The optical film of the present invention includes a base material, a conductive layer having a plurality of openings disposed on one main surface of the base material, a resin layer disposed to cover the conductive layer, and the resin layer. An optical film including an antireflection layer disposed on the resin layer, wherein the resin layer contains 5 to 20% by weight of a photocurable monomer having three or more functional groups of thiol groups based on the entire resin component It is characterized by being cured.

  Moreover, the manufacturing method of the optical film of the present invention includes a base material, a conductive layer having a plurality of openings disposed on one main surface of the base material, and a resin layer disposed to cover the conductive layer. A method for producing an optical film comprising an antireflection layer disposed on the resin layer, wherein the photocurable monomer having three or more functional groups of thiol groups is contained in an amount of 5 to 20% by weight based on the entire resin component The resin composition is cured to form the resin layer.

  According to the present invention, it is possible to provide an optical film having both improved curl and improved surface strength, and also provided with an electromagnetic wave shielding function and an antireflection function.

It is a schematic sectional drawing which shows an example of the optical film of this invention. It is a schematic sectional drawing which shows the other example of the optical film of this invention.

  The optical film of the present invention includes a base material, a conductive layer having a plurality of openings disposed on one main surface of the base material, a resin layer disposed to cover the conductive layer, and the resin layer. And an antireflection layer disposed thereon. Moreover, the said resin layer hardens | cures the resin composition which contains 5-20 weight% of photocurable monomers which have a thiol group 3 functional groups or more with respect to the whole resin component.

  By providing the conductive layer and the antireflection layer, the optical film of the present invention can be provided with an electromagnetic wave shielding function and an antireflection function. Moreover, by providing the resin layer, a hard coat function can be imparted to the optical film of the present invention. Furthermore, the resin layer is obtained by curing a resin composition containing 5 to 20% by weight of a photocurable monomer having three or more functional groups of thiol groups with respect to the entire resin component, thereby improving curling and surface It is possible to achieve both strength improvement.

  The conductive layer is preferably formed in a predetermined pattern such as a lattice pattern. Thereby, formation of a conductive layer becomes easy and the light transmittance of an optical film can be made uniform.

  Moreover, it is preferable that the thickness of the said conductive layer is 2 micrometers or more and 5 micrometers or less. If the thickness is less than 2 μm, the electromagnetic wave shielding effect tends to be insufficient. If the thickness exceeds 5 μm, the electromagnetic wave shielding effect is saturated, and the thickness of the resin layer is increased, which tends to be disadvantageous in cost.

  Further, the resin layer covers the conductive layer, but the surface of the antireflection layer is smoothed by making the thickness of the resin layer from the base material larger than the thickness of the conductive layer. Can do. However, if the thickness of the resin layer becomes too thick, problems such as curling of the resin layer tend to occur. Therefore, the thickness of the resin layer from the base material is more preferably 6 μm or less. . Further, from the viewpoint of cost reduction, the thickness of the resin layer from the base material is preferably 1.1 times or more and 1.3 times or less than the thickness of the conductive layer.

  The antireflection layer preferably contains hollow silica particles. This facilitates adjustment of the refractive index of the antireflection layer and improves surface strength such as scratch resistance.

  Moreover, it is preferable that the shielding property of the electric field of 1 MHz or more and 1000 MHz or less is 40 dB or more in the optical film of the present invention. Thereby, the electromagnetic wave shielding function can be sufficiently exhibited against high frequency electromagnetic waves.

  Moreover, a near-infrared absorption layer can be further arranged on the other main surface of the substrate. Thereby, the near-infrared absorption function can be provided to the optical film of the present invention.

  The optical film of the present invention preferably has a visibility reflectance of 1.5% from the viewpoint of preventing reflection of external light on the screen.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic sectional view showing an example of the optical film of the present invention. In FIG. 1, an optical film 10 of the present invention covers a translucent base material 11, a conductive layer 12 having a plurality of openings 12 a arranged on one main surface of the base material 11, and the conductive layer 12. And a hard coat layer 13 as a resin layer disposed on the hard coat layer 13 and an antireflection layer 14 disposed on the hard coat layer 13.

  The substrate 11 is not particularly limited as long as it is formed of a light-transmitting material. For example, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethersulfone resin, triacetyl cellulose What processed the material, such as resin, into the film form or the sheet form can be used. Examples of the method for processing into a film or sheet include extrusion molding, calendar molding, compression molding, injection molding, and a method in which the above resin is dissolved in a solvent and cast. Additives such as antioxidants, flame retardants, heat resistance inhibitors, ultraviolet absorbers, lubricants and antistatic agents may be added to the above materials. Moreover, you may provide a primer layer in the base material 11 in order to improve adhesiveness with the layer provided in the upper layer. The thickness of the base material 11 is usually about 10 to 500 μm.

  The conductive layer 12 is formed in a predetermined pattern, and the predetermined pattern is preferably a pattern in which the same shape is continuously arranged. The patterns include, for example, a lattice pattern in which a plurality of squares and rectangles are drawn, triangles, quadrangles (parallelograms, rhombuses, trapezoids, etc.), hexagons, octagons, dodecagons, circles, ellipses, trefoil A pattern in which a plurality of shapes such as a shape, a petal shape, and a star shape are drawn can be used. As a material for forming the conductive layer 12, metal particles such as copper, silver, and gold, conductive metal oxides such as indium-tin oxide (ITO), and zinc oxide (ZnO) can be used. The surface electrical resistance of the conductive layer 12 is preferably 10 Ω / square or less, more preferably 1 Ω / square or less, and most preferably 0.5 Ω / square or less in order to maintain electric field shielding properties. As a method for forming the conductive layer 12 in a predetermined pattern in which the same shape is continuously arranged, in addition to an etching method, a printing plating method, etc., a heat treatment is performed after a predetermined pattern is directly formed using a conductive ink. A method etc. can be used suitably. The line width of the conductive layer 12 formed in a predetermined pattern is preferably 3 μm to 10 μm, and the thickness of the conductive layer 12 is preferably 2 μm to 5 μm. This is because, within these ranges, a sufficient electromagnetic wave shielding effect can be surely obtained. Moreover, when making a pattern into a grid | lattice pattern, it is preferable that a line interval (lattice interval) shall be 50 micrometers or more and 2000 micrometers or less. This is because if the line spacing exceeds 2000 μm, a sufficient electromagnetic wave shielding effect tends to be difficult to obtain, and if the line spacing is less than 50 μm, the translucency tends to decrease.

  Moreover, in order to fully exhibit the electromagnetic wave shielding function with respect to the high frequency electromagnetic wave, it is preferable to set the shielding property of the electric field of 1 MHz to 1000 MHz in the conductive layer 12 to 40 dB or more.

  The hard coat layer 13 is formed by curing a resin composition containing 5 to 20% by weight of a photocurable monomer having three or more functional groups of thiol groups with respect to the entire resin component.

  Examples of the photocurable monomer having three or more thiol groups include tris- (ethyl-3-mercaptopropionate) isocyanurate (TEMPIC) and / or dipentaerythritol hexa-3-mercaptopropionate (DPMP). Is preferably used.

  The resin composition contains, in addition to a photocurable monomer having three or more thiol groups, a further resin component, preferably a photocurable resin having a high surface hardness. As said photocurable resin, the monomer, prepolymer, oligomer, polymer etc. which have a vinyl group, a (meth) acryloyl group, an epoxy group, an oxetanyl group etc. are used, for example. The photocurable resins can be used alone or in combination of two or more. Moreover, as the photocurable resin, it is preferable to use a polyfunctional resin from the viewpoint of improving the productivity of the hard coat layer 13 and the hardness after curing, and further a bond that forms a hydrogen bond in the molecule. It is preferable to have a large number of groups and functional groups because adhesion to the substrate 11 is improved. Further, a high refractive index type resin such as bisphenol A-modified (meth) acrylate may be used.

  As the polyfunctional resin, a polyfunctional acrylic resin monomer having two or more unsaturated groups can be used. Examples of the polyfunctional acrylic resin monomer having two or more unsaturated groups include, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and 1,4-cyclohexane diacrylate. , Pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) ) Acrylate, dipentaerythritol hexa (meth) acrylate, 1,2,3-cyclohexane trimethacrylate; pentaerythritol triacrylate hex Polyurethane polyacrylates such as methylene diisocyanate urethane prepolymers; esters formed from polyhydric alcohols such as polyester polyacrylates and (meth) acrylic acid; 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl Examples thereof include vinylbenzene such as ester and 1,4-divinylcyclohexanone and derivatives thereof. These may be used alone or in combination of two or more. Among these, it is preferable to contain at least one selected from pentaerythritol triacrylate and dipentaerythritol hexaacrylate from the viewpoint of further improving the scratch resistance. In the above, “(meth) acrylate” means “acrylate and / or methacrylate”.

  When hardening the resin composition which forms the hard-coat layer 13, a photoinitiator is added to the coating liquid for hard-coat layer formation containing the said resin composition. As photopolymerization initiators, acetophenones, benzophenones, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkyldione compounds, disulfide compounds, thiuram compounds, fluoroamine compounds Etc. are used. These can be used alone or in combination of two or more. Although the usage-amount of the said photoinitiator is not specifically limited, Usually, it is about 1-15 weight% with respect to the whole resin component to be used.

  The film refractive index of the hard coat layer 13 is preferably 1.49 to 1.85. When the film refractive index of the hard coat layer is 1.49 to 1.85, it may be formed of a resin composition containing only the above resin component, or a resin composition containing a filler such as a metal oxide. It may be formed. In the optical film 10 of the present invention, since the hard coat layer 13 is disposed so as to cover the conductive layer 12, charging is possible without adding a conductive filler such as a conductive metal oxide to the hard coat layer 13. Although a prevention function can be provided, in order to further improve the electromagnetic wave shielding function, a conductive metal oxide or a conductive polymer may be added to the resin composition. Examples of the conductive polymer include polypyrrole, ponianiline, polythiophene, and the like.

  The thickness T of the hard coat layer 13 from the substrate 11 is thicker than the thickness of the conductive layer 12. If the thickness T of the hard coat layer 13 from the base material 11 is thicker than the thickness of the conductive layer 12, there is no problem with respect to the development of the hard coat function, but if the thickness T becomes too thick, problems such as curling of the coating film occur. May occur. For this reason, the thickness T from the base material 11 of the hard coat layer 13 is preferably 6 μm or less.

  In addition, the hard coat layer forming coating solution containing the resin composition includes a polymerization inhibitor, an antioxidant, a dispersant, a surfactant, a surface modifier, a light stabilizer, and the like so as not to greatly change the refractive index. You may add additives, such as a leveling agent, suitably. Further, if it is possible to dissolve a resin component such as a photocurable resin without breaking the dispersion system, it is possible to include a solvent in the hard coat layer forming coating solution.

  There is no restriction | limiting in particular about the method of forming the hard-coat layer 13 on the base material 11, It can form by apply | coating the coating liquid for hard-coat layer formation containing the said resin composition on the base material 11, and making it harden | cure. The coating method is not particularly limited, for example, a coating method such as roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, or printing methods such as gravure printing, screen printing, offset printing, and ink jet printing. Etc. can be used.

  The antireflection layer 14 having an antireflection function disposed on the hard coat layer 13 has a single layer structure in which only the low refractive index layer having a lower film refractive index than the hard coat layer is provided on the hard coat layer. A medium refractive index layer having a higher film refractive index than the hard coat layer, a high refractive index layer having a higher film refractive index than the medium refractive index layer, and a low refractive index having a lower film refractive index than the hard coat layer. A three-layer structure or the like in which the rate layers are provided in this order can be used as appropriate according to the optical design.

  For example, in the case of the antireflection layer having the single layer structure, the film refractive index of the low refractive index layer may be smaller than the film refractive index of the hard coat layer, and the thickness thereof may be 80 to 150 nm. The film refractive index of the low refractive index layer is preferably 1.30 to 1.45. It is preferable to design the optical thickness nd, which is the product of the film refractive index n of the low refractive index layer and the thickness d thereof, to be λ / 4, since the reflectance becomes lower. Usually, λ is often set to a wavelength around 550 nm of light with particularly high visibility to the human eye among wavelengths of visible light. Therefore, the thickness d is preferably 80 to 150 nm.

  If the film refractive index is in the above range, the low refractive index layer is a monomer, prepolymer, oligomer, polymer or the like having a vinyl group, (meth) acryloyl group, epoxy group, oxetanyl group, thiol group, etc. It can be formed using a curable resin. The photocurable resins can be used alone or in combination of two or more. Moreover, as said photocurable resin, it is preferable to use polyfunctional resin from a viewpoint of the productivity of a low refractive index layer, and the improvement of the hardness after hardening. As said polyfunctional resin, the thing similar to the polyfunctional acrylic resin monomer which has two or more unsaturated groups used for the above-mentioned hard-coat layer can be used.

  Examples of the material for adjusting the film refractive index of the low refractive index layer to a preferable range of 1.30 to 1.45 include silica, fluororesin, and hollow silica particles. From the viewpoint of scratch resistance of the layer, it is preferable to use at least hollow silica particles. Moreover, since the average particle diameter of the hollow silica particles is designed so that the thickness of the low refractive index layer is 80 nm to 150 nm, it is preferably 80 nm or less, and more preferably 60 nm or less. Here, the average particle diameter refers to that measured by a dense particle size analyzer “FPAR-1000” manufactured by Otsuka Electronics. Moreover, the porosity of the hollow silica fine particles may be more than 30% and 50% or less. If it is 30% or less, the antireflection effect tends to be insufficient, and if it exceeds 50%, it tends to be difficult to maintain the hardness as an inorganic oxide during the synthesis of the hollow silica fine particles. Here, the “void ratio” refers to the ratio of the volume of the void portion to the total volume.

  If at least one of the photocurable resin components forming the low refractive index layer is the same as the photocurable resin component forming the hard coat layer, the low refractive index layer and the hard coat layer are bonded. This is preferable because of improved properties.

  When the photocurable resin for forming the low refractive index layer is cured, the photopolymerization initiator used in the hard coat layer is similarly used in the coating solution for forming the low refractive index layer containing the photocurable resin. Can be added.

  The coating liquid for forming the low refractive index layer includes a polymerization inhibitor, an antioxidant, a dispersant, a surfactant, a surface modifier, a light stabilizer, a leveling agent, etc. to such an extent that the refractive index is not greatly changed. Additives may be added. Since the optical film of the present embodiment is disposed on the outermost surface of the display, in order to improve the strength and antifouling property, silicone-based and fluorine-based additives are added to such an extent that the refractive index does not change greatly. Also good. If the photocurable resin can be dissolved without breaking the dispersion system, a solvent can be contained in the coating solution for forming a low refractive index layer.

  The method for forming the low refractive index layer on the hard coat layer 13 is not particularly limited, and can be formed by applying a low refractive index layer forming coating solution containing the above-mentioned material onto the hard coat layer 13 and curing it. . The coating method is not particularly limited, for example, a coating method such as roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, or printing methods such as gravure printing, screen printing, offset printing, and ink jet printing. Etc. can be used.

(Embodiment 2)
FIG. 2 is a schematic cross-sectional view showing another example of the optical film of the present invention. In FIG. 2, the optical film 20 of the present invention is the same as the optical film 10 of Embodiment 1 shown in FIG. 1 except that the near-infrared absorbing layer 15 is further disposed on the other main surface of the substrate 11. In FIG. 2, the same parts as those in FIG. 2 and 1 have the same function.

  The near-infrared absorbing layer 15 may be directly formed on the other main surface of the substrate 11 or may be disposed via an adhesive. By providing the near-infrared absorbing layer 15 having a near-infrared absorbing function, if the optical film of this embodiment is disposed on the surface of the PDP, unnecessary near-infrared rays that are emitted when plasma discharge occurs are blocked, Thus, it is possible to solve problems such as malfunction of remote controllers such as TVs and air conditioners. By integrating and combining the electromagnetic wave shielding function, the antireflection function, and the near-infrared absorbing function on a single base material as in the present embodiment, the number of members to be bonded to the front plate of the PDP can be reduced.

  The near-infrared absorbing layer 15 is not particularly limited as long as it is formed of a light-transmitting material that absorbs near-infrared rays, and is usually formed of a resin composition in which a compound that absorbs near-infrared rays is dispersed. .

  The compound that absorbs near infrared rays is preferably a compound having a maximum absorption wavelength in a wavelength region of 850 to 1100 nm. When the near-infrared absorbing layer 15 contains the above-mentioned compound, it is possible to reduce the near-infrared transmittance in the wavelength region of 850 to 1100 nm without greatly reducing the transmittance of visible light having a wavelength of 400 to 850 nm. . Thereby, the optical film of this embodiment can be used suitably also as near-infrared absorption filters, such as PDP.

  Examples of the compound having the maximum absorption wavelength in the wavelength region of 850 to 1100 nm include, for example, aminium-based, azo-based, azine-based, anthraquinone-based, indigoid-based, oxazine-based, quinophthalonine-based, squalium-based, stilbene-based, and triphenylmethane-based compounds. Organic dyes such as naphthoquinone, diimonium, phthalocyanine, cyanine, and polymethine can be used in appropriate combination.

  In particular, the near-infrared absorbing layer 15 includes a sulfonic acid imide derivative as a compound having a maximum absorption wavelength in the wavelength range of 850 to 1100 nm and includes at least one substituent bonded to the nitrogen atom at the terminal of the cation moiety. Counterion of diimonium compound, one of which is an alkyl group having a branched chain structure, a substituted benzenedithiol metal complex anion having a structure represented by the following formula (1), and a cation having a structure represented by the following formula (2) It is preferable to include a compound which is a conjugate because it is excellent in long-term storage stability.

However, in the expression _{(1), R 1, R} 2 is an alkyl group having 1 to 6 carbon atoms, an alkylamino group having 1 to 8 carbon atoms, a substituted or unsubstituted morpholino group, a substituted or unsubstituted thio It represents at least one substituent selected from the group consisting of a morpholino group, a substituted or unsubstituted piperazino group and a substituted or unsubstituted phenyl group, and M represents a transition metal.

In the formula (2), Q ₁ and Q ₂ are a 5-membered nitrogen-containing heterocyclic ring, a condensed ring containing a 5-membered nitrogen-containing heterocyclic ring, a 6-membered nitrogen-containing heterocyclic ring and a 6-membered ring. 1 represents at least one heterocyclic compound selected from the group consisting of condensed rings including a nitrogen-containing heterocyclic ring, R ₃ and R ₄ represent an alkyl group having 1 to 8 carbon atoms, and n represents 2, 3 or 4 Indicates the number.

  As the resin for dispersing the near-infrared absorbing compound, polyester resin, acrylic resin, polyurethane resin, polyvinyl chloride resin, epoxy resin, polyvinyl acetate resin, polystyrene resin, cellulose resin, polybutyral resin, or the like may be used. It can also be used as a polymer blend by combining two or more of these resins.

  The method for forming the near-infrared absorbing layer 15 on the back surface side of the base material 11 in which the hard coat layer 13 and the antireflection layer 14 are sequentially laminated is not particularly limited, and has been described above as in the case of the hard coat layer 13 described above. It can form by apply | coating to the base material 11 the coating liquid for near-infrared absorption layer formation containing the material for near-infrared absorption layer formation. The thickness of the near infrared absorption layer 15 is preferably 1 to 10 μm, and more preferably 2 to 7 μm. If the thickness is less than 1 μm, it is difficult to absorb near-infrared rays, and if it exceeds 10 μm, cracks or curls occur.

  A compound that cuts the neon emission line spectrum (orange) of the PDP can be appropriately added to the near infrared absorption layer 15. Thereby, red color can be more vividly developed in the PDP. As the compound that cuts off the neon emission line spectrum, an organic dye having a maximum absorption wavelength in the wavelength region of 580 to 620 nm can be used. For example, cyanine-based, azulenium-based, squalium-based, diphenylmethane-based, triphenylmethane-based, oxazine-based, Organic dyes such as azine, thiopylium, viologen, azo, azo metal complex, azaporphyrin, bisazo, anthraquinone, and phthalocyanine can be used.

  What is necessary is just to determine suitably the thickness of the near-infrared absorption layer 15, the kind of material, content rate, etc. so that the spectral transmittance of the optical film 20 may be 20% or less in the whole range of wavelength 850-1100 nm.

  In the present embodiment, an example in which only the near-infrared absorbing layer 15 is disposed has been described. However, in addition to or in place of the near-infrared absorbing layer 15, another function such as a layer that absorbs visible light having a specific wavelength, an ultraviolet cut layer, or the like. One or more layers may be arranged.

  Hereinafter, based on an Example, this invention is demonstrated more concretely. However, the present invention is not limited to the following examples. In the following, “parts” means “parts by weight” unless otherwise specified.

  First, the measurement method and the evaluation method used in the examples will be described.

<Surface electrical resistance of conductive layer>
It measured using the conductive surface low resistivity meter "Loresta-AP, MCP-T400" (made by Mitsubishi Yuka Co., Ltd.).

<Electric field shielding>
The electric field shielding property of the conductive layer was measured by the KEC method. The KEC method is a method for measuring the electromagnetic shielding effect developed at Kansai Electronics Industry Promotion Center. That is, two metal cases having an antenna and having an opening are prepared, the two metal cases are opposed to communicate with each other, a sample is sandwiched therebetween, and then the antenna provided in one metal case The electric field (magnetic field) is transmitted from the antenna, the electric field (magnetic field) that has passed through the sample is received by the antenna in the other metal case, and the attenuation rate of the electromagnetic wave due to the passage of the sample is calculated. Specifically, a square sample having a length of 20 cm and a width of 20 cm cut out from the optical film was sandwiched between two metal cases, and an electromagnetic wave of 500 MHz was transmitted from one antenna to calculate the attenuation rate of the electromagnetic wave.

<Visibility reflectance>
Before providing the near-infrared absorbing layer, scrape the surface of the substrate (PET film) opposite the side on which the antireflection layer is formed with sandpaper, and then paint the surface black with an oil-based felt pen of black ink Using a spectrophotometer “Ubest V-570 type” (manufactured by JASCO Corporation), the visibility reflectance was measured in the wavelength region of 300 to 800 nm.

<Surface electrical resistance on the side where the antireflection layer is formed>
The surface electrical resistance on the side where the antireflection layer was formed was measured using a conductive surface high resistivity meter “HIRESTA HT-20” (manufactured by Mitsubishi Oil Chemical Co., Ltd.).

<Pencil hardness>
The pencil hardness of the antireflection layer in the optical film was measured based on JIS (K5400).

<Abrasion resistance>
After placing steel wool (# 0000) on the antireflection layer (low refractive index layer) of the optical film and applying a load of 1.96 N / cm ² , the steel wool was reciprocated 10 times, and then the low refractive index. The state of the surface of the layer was observed and evaluated in the following four stages.
A: There was no scratch at all.
B: Scratches almost invisible.
C: Scratches were clearly confirmed.
D: Peeling occurred.

<Total light transmittance>
Using a spectrophotometer “Ubest V-570 type” (manufactured by JASCO Corporation), the total light transmittance of the optical film before providing the near infrared absorption layer was measured. Light was incident from the opposite side of the substrate on which the hard coat layer was formed.

<Measurement method of curl (film warpage)>
A rectangular sample piece having a width of 15 cm and a length of 20 cm cut out from the optical film is allowed to stand with a coated surface on which a conductive layer is formed on a flat table, and the four corners of this sample are at a height from the table. Was measured. The case where the height of all four points was less than 1 cm was designated as A, and the case where the height of any one point was 1 cm or more was designated as B.

Example 1
An optical film was produced as follows.

<Formation of conductive layer>
As a transparent base material, a polyethylene terephthalate (PET) film having a thickness of 100 μm was prepared with both front and back surfaces treated with an acrylic resin for easy adhesion. Next, a conductive layer having a plurality of openings was formed on the PET film as follows.

First, 500 parts of alumina sol (“Alumina sol 520” manufactured by Nissan Chemical Industries, Ltd.) as a pigment, 15 parts of polyvinyl alcohol (“PVA217” manufactured by Kuraray Co., Ltd.) as a binder, and a melamine compound (“Sumirez, manufactured by Sumitomo Chemical Industries, Ltd.) as a crosslinking agent. Resin 617 ") 1.25 parts and 135 parts of water as a dispersion medium were prepared, and these were mixed in a ball mill to prepare a coating solution. This coating solution was applied onto the PET film so as to have a thickness of 5 μm, and then dried to form a coating layer. Next, a paste (Dotite “XA-9024” manufactured by Fujikura Kasei Co., Ltd.) containing nano-order size silver oxide particles, an organic silver compound (carboxylate silver: C ₈ H ₁₅ O ₂ Ag) and a solvent (terpineol). A grid pattern having a line width of 4 μm, a thickness of 2.5 μm, and a line interval (lattice interval) of 150 μm was screen printed on the coating layer. Subsequently, after removing the solvent from the printed paste by heating at 80 ° C. for 30 minutes, the conductive particles formed in the lattice pattern as described above are heated in the atmosphere at 150 ° C. for 30 minutes. A conductive layer was formed. The surface electrical resistance and electric field shielding property of the conductive layer made of the conductive particles formed in the lattice pattern as described above were measured as described above. The results are shown in Table 1 below.

<Formation of hard coat layer>
First, the following materials were mixed and stirred to prepare a coating solution for forming a hard coat layer.
(1) Dipentaerythritol hexaacrylate (DPHA, Nippon Kayaku Co., Ltd.): 9 parts (2) Tris- (ethyl-3-mercaptopropionate) isocyanurate (TEMPIC, thiol group: trifunctional group, Sakai Chemical Industry 1 part (content to the whole resin component: 10% by weight)
(3) Dispersant “Disperbyk-180” (by Big Chemie): 0.5 part (4) Photopolymerization initiator “IRGACURE907” (manufactured by Ciba Specialty Chemicals): 0.3 part (5) Polypyrrole dispersion (10 % By mass, average particle size: 0.3 to 0.4 μm): 0.3 part (6) Toluene: 10 parts (7) Methyl ethyl ketone: 10 parts

Next, the hard coat layer forming coating solution was applied onto the conductive layer using a micro gravure coater (manufactured by Yasui Seiki Co., Ltd.), and then dried. Subsequently, the coating film was cured by irradiating the coating film with ultraviolet rays at a dose of 500 mJ / cm ² to form a hard coat layer having a refractive index of 1.55 and a thickness of 4.0 μm.

<Formation of antireflection layer (low refractive index layer)>
The following materials were mixed and stirred to prepare a coating solution for forming an antireflection layer (low refractive index layer).
(1) Hollow silica fine particles (manufactured by Catalyst Kasei Co., Ltd., porosity: 35%, average particle size: 50-60 nm): 60 parts (2) Pentaerythritol triacrylate (PETA): 20 parts (3) Dipentaerythritol hexaacrylate (DPHA): 20 parts (4) Photopolymerization initiator “IRGACURE (registered trademark) 907” (manufactured by Ciba Specialty Chemicals): 1.6 parts (5) Polymer surface modifier “Modiper F600” (Nippon Yushi Co., Ltd.) Manufactured): 1 part (6) Isopropyl alcohol: 2000 parts

  Next, on the hard coat layer, the low refractive index layer forming coating solution is applied using the micro gravure coater and dried to form a low refractive index layer having a refractive index of 1.37 and a thickness of 107 nm. Thus, an antireflection layer having a single layer structure was obtained.

<Formation of near-infrared absorbing layer>
The following materials were mixed and stirred to prepare a coating solution for forming a near infrared absorption layer.
(1) Acrylic resin “Foret GS-1000” (manufactured by Soken Chemical Co., Ltd.): 100 parts (2) Aromatic dimonium dye “CIR-1085” (manufactured by Nippon Carlit): 6 parts (3) Cyanine site / dithiol metal complex Site-containing near-infrared absorbing compound “SD50-E04N” (manufactured by Sumitomo Seika Co., Ltd., maximum absorption wavelength: 877 nm): 1 part (4) Cyanine site / dithiol metal complex site-containing near-infrared absorbing compound “SD50-E05N” (Sumitomo Manufactured by Kasei Co., Ltd., maximum absorption wavelength: 833 nm): 1 part (5) tetraazaporphyrin compound “TAP-2” (manufactured by Yamada Chemical Co., Ltd.): 2 parts (6) methyl ethyl ketone: 70 parts (7) toluene: 140 parts

  Next, on the PET film opposite to the side on which the antireflection layer is formed, the near-infrared absorbing layer forming coating solution is applied and dried using the microgravure coater, and the thickness is 4 μm. An infrared absorption layer was formed.

(Example 2)
In the coating liquid for hard coat layer of Example 1, 1 part of dipentaerythritol hexa-3-mercaptopropionate (DPMP, thiol group: 6 functional group, manufactured by Sakai Chemical Industry Co., Ltd.) was used instead of TEMPIC. Produced an optical film in the same manner as in Example 1.

(Comparative Example 1)
An optical film was produced in the same manner as in Example 1 except that a hard coat layer coating solution prepared by mixing and stirring the following materials was used.
(1) Dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.): 10 parts (2) Dispersant “Disperbyk-180” (manufactured by Big Chemie): 0.5 part (3) Photopolymerization initiator “IRGACURE907” (Ciba Specialty Chemicals): 0.3 parts (4) Toluene: 10 parts (5) Methyl ethyl ketone: 10 parts

(Comparative Example 2)
An optical film was produced in the same manner as in Example 1 except that the hard coat layer coating solution prepared as described below was used.
(1) Antimony-doped tin oxide fine particles (ATO, manufactured by Mitsubishi Materials Corporation, average particle diameter 20 nm): 5.5 parts (2) Zirconium oxide fine particles (ZrO ₂ , manufactured by Daiichi Rare Element Chemical Industries, average particle diameter 10 nm) : 4.5 parts (3) Dispersant “Disperbyk-180” (by Big Chemie): 1 part (4) Acetylacetone: 5 parts (5) Propylene glycol monomethyl ether: 30 parts Zirconia beads having a diameter of 0.3 mm were added as beads for stirring and dispersing and dispersed for 3 hours with a paint shaker, and then the zirconia beads were removed to prepare a dispersion having an ATO: ZrO ₂ weight ratio of 55:45. To this dispersion, 2 parts of pentaerythritol triacrylate, 2.7 parts of dipentaerythritol hexaacrylate, and 0.3 parts of photopolymerization initiator “IRGACURE907” (manufactured by Ciba Specialty Chemicals) were added to form a hard coat layer. A coating solution to be used was prepared.

(Comparative Example 3)
An optical film was produced in the same manner as in Example 1 except that the amount of TEMPIC 1 added was 3% by weight based on the entire resin component.

(Comparative Example 4)
An optical film was produced in the same manner as in Example 1 except that the amount of TEMPIC 1 added was 25% by weight based on the entire resin component.

  The characteristics of the optical films of Examples 1 and 2 and Comparative Examples 1 to 4 were measured as described above. The results are shown in Table 1 below together with the thickness of the conductive layer and the thickness of the hard coat layer.

  As is clear from Table 1, in the optical films of Examples 1 and 2, compared with the films of Comparative Examples 1 to 4, the pencil strength was excellent and no curling was generated. In the optical film having the antireflection function, it can be seen that the improvement of curl and the improvement of the surface strength are compatible.

  As described above, the present invention can provide an optical film having both improved curl and improved surface strength, and also provided with an electromagnetic wave shielding function and an antireflection function.

DESCRIPTION OF SYMBOLS 10, 20 Optical film 11 Base material 12 Conductive layer 12a Opening part 13 Hard-coat layer 14 Antireflection layer 15 Near-infrared absorption layer

Claims (8)

A base material, a conductive layer having a plurality of openings disposed on one main surface of the base material, a resin layer disposed to cover the conductive layer, and an antireflection disposed on the resin layer An optical film comprising a layer,
The said resin layer hardens | cures the resin composition which contains 5-20 weight% of photocurable monomers which have a thiol group 3 functional groups or more with respect to the whole resin component, The optical film characterized by the above-mentioned.   The optical film according to claim 1, wherein the conductive layer is formed in a predetermined pattern.   The optical film according to claim 1, wherein the conductive layer has a thickness of 2 μm or more and 5 μm or less.   The optical film according to any one of claims 1 to 3, wherein a thickness of the resin layer from the base material is larger than a thickness of the conductive layer and is 6 µm or less.   The optical film according to claim 1, wherein the antireflection layer includes hollow silica particles.   The optical film according to any one of claims 1 to 5, wherein a shielding property of an electric field of 1 MHz to 1000 MHz is 40 dB or more.   The optical film according to claim 1, wherein a near-infrared absorbing layer is further disposed on the other main surface of the substrate. A base material, a conductive layer having a plurality of openings disposed on one main surface of the base material, a resin layer disposed to cover the conductive layer, and an antireflection disposed on the resin layer A method for producing an optical film comprising a layer,
A method for producing an optical film, comprising: curing a resin composition containing 5 to 20% by weight of a photocurable monomer having three or more functional groups of thiol groups with respect to the entire resin component to form the resin layer.

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