JP2007114699A - Optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film provided with an antireflection layer having high light translucency, a high antistatic characteristic and high abrasion resistance. <P>SOLUTION: The optical film comprises a light translucent base material 10 and a antireflection layer arranged on one main surface side of the light translucent base material 10. The antireflection layer comprises a hard coat layer 12 and a low refractive index layer 15 arranged on the hard coat layer 12. The hard coat layer 12 is formed of resins containing an ionization radiation curing type resin, a refractive index of the low refractive index layer 15 is lower than that of the hard coat layer 12 and the hard coat layer 12 contains ≥5 mass% and ≤15 mass% of electro-conductive metal oxide toward total mass of the hard coat layer 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical film having an antistatic function and an antireflection function.

  Development of a high-definition and large-screen display represented by a plasma display panel (PDP) or the like is rapidly progressing. In the display, it is necessary to dispose an antireflection layer having an antireflection function on the surface in order to prevent external light from being reflected on the screen. The display also needs an antistatic function in order to prevent adhesion of dust, dirt, etc. due to static electricity on the screen surface. For this reason, in the conventional display, an optical film having an antireflection function and an antistatic function is disposed on the front surface of the screen.

  This conventional optical film is formed by disposing an antireflection layer on a translucent substrate, and this antireflection layer is formed from the translucent substrate side, a hard coat layer, and a high refraction with a thickness of 1 μm or less. A three-layer structure in which a refractive index layer and a low refractive index layer were laminated in this order was employed. Further, in the usual case, an antistatic agent is added to the high refractive index layer to impart an antistatic function.

  On the other hand, examples of the antistatic agent that imparts an antistatic function to the optical film include cationic, anionic, and nonionic surfactants or conductive polymers. However, the surfactant has a large environmental dependency, and the antistatic function becomes unstable depending on the situation. In addition, since the conductive polymer is structurally conjugated, there is a problem that it is colored when mixed with a photosensitive resin. Therefore, recently, conductive metal oxide has been used as an antistatic agent.

  Since this conductive metal oxide absorbs light of a specific wavelength, when the thickness of the antistatic layer to which these are added becomes 1 μm or more, or when the addition amount is excessive, the entire optical film There arises a problem that the light transmittance is lowered. Conventionally, as described above, since the antistatic agent is added to the high refractive index layer having a thickness of 1 μm or less, there is no problem that the total light transmittance is lowered.

However, recently, in order to streamline the manufacturing process, it has been proposed to omit the high refractive index layer and make the antireflection layer have a two-layer structure of a hard coat layer and a low refractive index layer (for example, patents). Reference 1).
JP 2000-233467 A

  However, in Patent Document 1, a considerable amount of conductive metal oxide fine particles are added as an antistatic agent to the conductive transparent layer having a thickness of several μm disposed under the low refractive index layer. The maximum transmittance is less than 91%, and the total light transmittance is not sufficient.

  The present invention solves the above-described problems, and provides an optical film provided with an antireflection layer having high translucency and antistatic properties and further having high scratch resistance.

  The optical film of the present invention is an optical film including a translucent substrate and an antireflection layer disposed on one main surface side of the translucent substrate, and the antireflection layer includes the translucent layer. From the optical substrate side, it includes a hard coat layer and a low refractive index layer disposed on the hard coat layer, and the hard coat layer is formed from a resin containing an ionizing radiation curable resin, The refractive index of the refractive index layer is lower than the refractive index of the hard coat layer, and the hard coat layer contains 5% by mass or more and 15% by mass or less of a conductive metal oxide based on the total mass of the hard coat layer. It is characterized by including.

  According to the present invention, an optical film provided with an antireflection layer having high translucency and antistatic properties and having high scratch resistance can be provided.

  The optical film of this invention is equipped with the translucent base material and the antireflection layer arrange | positioned at the one main surface side of the translucent base material. The antireflection layer is formed in a two-layer structure in which a hard coat layer and a low refractive index layer disposed on the hard coat layer are laminated from the translucent substrate side. By making it a two-layer structure, the manufacturing process of an optical film can be rationalized.

  The hard coat layer is formed from a resin including an ionizing radiation curable resin. Thereby, a hard coat layer can be rationally formed.

  The refractive index of the low refractive index layer is set lower than the refractive index of the hard coat layer. Thereby, even if the antireflection layer has a two-layer structure, an antireflection function can be provided.

  The hard coat layer contains 5% by mass or more and 15% by mass or less, more preferably 9% by mass or more and 12% by mass or less of conductive metal oxide with respect to the total mass of the hard coat layer. If it is less than 5% by mass, the antistatic function is lowered, and if it exceeds 15% by mass, the total light transmittance of the optical film is lowered.

The surface resistance value on the antireflection layer side is preferably 5 × 10 ¹² Ω / □ or less, more preferably 1 × 10 ¹¹ Ω / □ or less. This is because if the surface resistance value exceeds 5 × 10 ¹² Ω / □, dust tends to adhere, which is not preferable. The lower the surface resistance value, the better. However, in actuality, if the amount of the conductive metal oxide is increased in an attempt to lower the surface resistance value, the coloration increases and the total light transmittance decreases. Since the hardness of the coating film decreases and scratch resistance decreases, the lower limit of the surface resistance value is limited to about 10 ⁸ Ω / □.

  The material for the translucent substrate is not particularly limited. For example, a saturated polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, triacetyl cellulose resin, or the like is processed into a film or sheet Things can be used. Examples of the processing method into a film or sheet include extrusion molding, calender molding, compression molding, injection molding, and a method in which the above resin is dissolved in a solvent and cast. The thickness of the substrate is usually about 10 to 500 μm. In addition, additives, such as antioxidant, a flame retardant, a heat-resistant agent, a ultraviolet absorber, and a lubricant, may be added to the resin. Further, the total light transmittance of the translucent substrate is preferably 80% or more, and more preferably 90% or more.

  As the ionizing radiation curable resin for forming the hard coat layer, monomers, prepolymers and polymers having a vinyl group, a (meth) acryloyl group, an epoxy group or an oxetanyl group can be used.

Examples of the conductive metal oxide contained in the hard coat layer include antimony-titanium composite oxide (ATO), indium-titanium composite oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), and antimony. Zinc acid (ZnSb ₂ O ₆ ) or the like can be used. The conductive metal oxide is preferably used in the form of fine particles, and the primary particle diameter is preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less. This is because dispersibility in the ionizing radiation curable resin is improved within this range.

  The fine particles of the conductive metal oxide can be easily obtained as an organosol dispersed in an organic solvent. As the dispersion medium for the organosol, it is preferable to use an organic solvent having a solubility parameter of 9.5 or higher because the conductivity of the hard coat layer is improved. Further, in order to improve the conductivity of the hard coat layer, an organic solvent having a solubility parameter of 9.5 or more is added to the material of the hard coat layer in an amount of 0.05 to 80 with respect to the total mass of the coating liquid for the hard coat layer. It is preferable to include it by mass%.

  When the conductive metal oxide fine particles are uniformly dispersed in the hard coat layer, the conductivity is improved. Therefore, it is preferable to include a dispersant in the hard coat layer. As the dispersant, a cationic, weakly cationic, nonionic or amphoteric surfactant can be used. In particular, alkylamine surfactants modified with lower (C2 to C3) alkylene oxides such as propylene oxide or ethylene oxide are preferred. The addition amount is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the conductive metal oxide. If it is in this range, the effect of the dispersant can be obtained reliably, the transparency of the hard coat layer can be maintained, and the strength does not decrease.

  There is no restriction | limiting in particular about the method of forming a hard-coat layer on a translucent base material, It can form by apply | coating the coating liquid containing the said material on a translucent base material. 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 surface hardness of the hard coat layer is preferably H or higher, more preferably 2H or higher, as evaluated by a pencil hardness test specified in JIS K5400. Moreover, 2-7 micrometers is preferable and, as for the thickness of a hard-coat layer, 3-5 micrometers is more preferable. If the thickness is less than 2 μm, it is difficult to maintain the hardness, and if it exceeds 7 μm, cracks occur, curl (curvature of the film) occurs, or the total light transmittance of the optical film decreases.

  The coating liquid for the hard coat layer preferably contains 0.05 to 5.0% by mass of water with respect to the total mass of the coating liquid. It is because the electrical conductivity of a hard-coat layer improves more by including the water in this range in the material of a hard-coat layer. In addition to directly adding water to the coating solution, the coating solution may be incorporated in the coating solution by stirring for a predetermined time in an environment with a relative humidity of 40 to 80%.

  Moreover, it is preferable to perform at least 1 process, especially the application | coating process, such as the application | coating process of the said hard-coat layer, a drying process, an aging process, and a hardening process, in an environment with a relative humidity of 40 to 80%. This is because the conductivity of the hard coat layer can be further improved.

  When curing the ionizing radiation curable resin contained in the hard coat layer, when performing ultraviolet irradiation, a photopolymerization initiator is added to the coating liquid for the hard coat layer. Examples of the photopolymerization initiator include 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2,2-dimethoxy-2-phenyl. Acetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, Benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one Thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. These can be used alone or in combination of two or more.

  The low refractive index layer disposed on the hard coat layer has an optical film thickness, which is a product of the refractive index and the film thickness, set to λ / 4 (λ: a wavelength of light having a high human eye visibility, 550 nm). It is preferable that the reflectance is lower. Further, the greater the difference between the refractive index of the low refractive index layer and the refractive index of the hard coat layer, the better the antireflection property. Furthermore, since the low refractive index layer is located on the outermost surface of the optical film of the present embodiment, it is preferable to have strength and antifouling properties.

  The material for forming the low refractive index layer is not particularly limited as long as it has a refractive index lower than that of the hard coat layer, and an ionizing radiation curable resin can be used as in the case of the hard coat layer. In addition, thermosetting resins can also be used. As the thermosetting resin, for example, a polyester resin, a polyurethane resin, a polyvinyl chloride resin, a melamine resin, an epoxy resin, or the like can be used together with a curing agent.

  The refractive index of the low refractive index layer is preferably set to, for example, 1.5 or less, more preferably 1.48 or less, in order to improve the reflectance. As the ionizing radiation curable resin having a low refractive index, for example, a low refractive index acrylate such as trifluoroacrylate (refractive index: 1.32) can be used. Further, an ionizing radiation curable silicone resin, for example, an ultraviolet curable silicone resin “X-12-2400” (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. can be suitably used. Moreover, what polymerized the monomer which has a fluorine, and those which made these block polymers can also be used.

  As a material for forming the low refractive index layer, a general ionizing radiation curable resin having a refractive index higher than 1.5 can be used together with an ionizing radiation curable resin having a low refractive index. Thereby, the scratch resistance and solvent resistance of the low refractive index layer can be improved, and the strength of the low refractive index layer can be improved. As the ionizing radiation curable resin having a high refractive index, the same resin as the ionizing radiation curable resin used for the hard coat layer described above can be used. For example, a polyfunctional acrylate having two or more unsaturated groups is preferable. Can be used for The addition amount of this polyfunctional acrylate is better from the viewpoint of the refractive index, but in order to improve the scratch resistance, it is usually 5 mass for 100 mass parts of ionizing radiation curable resin having a low refractive index. The upper limit is generally 60 parts by mass or less, preferably about 40 parts by mass or less, although it depends on the resin to be blended.

It is preferable to further add ultrafine particles having a low refractive index to the low refractive index layer. Thereby, the reflectance of an antireflection layer can be made lower. The addition amount of the ultrafine particles having a low refractive index is about 100 to 400 parts by mass, preferably about 100 to 300 parts by mass with respect to 100 parts by mass of the resin component in the low refractive index layer. In addition, when a general ionizing radiation curable resin having a high refractive index is used in combination for the purpose of improving the strength of the low refractive index layer, it is preferable to use these low refractive index ultrafine particles in combination. The particle diameter of the ultrafine particles having a low refractive index is usually 5 to 50 nm, and the refractive index is 1.5 or less, preferably 1.45 or less. Examples of the low refractive index fine particles include LiF (refractive index: 1.39), MgF ₂ (refractive index: 1.38), AlF ₃ (refractive index: 1.38), Na ₃ AlF ₆ (ice crystal). Ultrafine particles such as stone, refractive index: 1.33), SiO _x (silica sol of 1.50 <x <2.0, refractive index: 1.30 to 1.48) can be used.

  The method for forming the low refractive index layer on the hard coat layer is not particularly limited, and can be formed by applying a coating solution containing the above material on the hard coat layer in the same manner as the hard coat layer described above.

  In order to impart antifouling properties to the surface of the low refractive index layer, an antifouling surfactant (dispersant) may be added to the coating solution. Examples of the antifouling surfactant include silicon-based surfactants and fluorine-based surfactants. The addition amount is about 0.01 to 10 parts by mass with respect to 100 parts by mass of the resin component in the low refractive index layer.

  By disposing the antireflection layer on the above-described translucent substrate, the total light transmittance of the optical film of the present embodiment can be 91% or more, and the total light transmittance of the optical film is further increased. Can be made higher than the single total light transmittance of the translucent substrate. This is because the amount of light incident on the entire optical film is increased by providing the antireflection layer.

The total light transmittance of the optical film of this embodiment is 91% or more, and the total light transmittance of this optical film is made higher than the single total light transmittance of the translucent substrate, and the antireflection layer is used. In order to make the surface resistance value of the optical film on the side 5 × 10 ¹² Ω / □ or less, the amount of the conductive metal oxide added to the hard coat layer is reduced as much as possible, and the total light of the optical film It is necessary to maximize the conductivity of the hard coat layer while making the transmittance as high as possible. For this purpose, it is preferable to use the following means (1) to (7) as appropriate.
(1) The thickness of the translucent substrate is 10 to 500 μm, and the total light transmittance is 85% or more, more preferably 90% or more.
(2) The thickness of the hard coat layer is 3 to 5 μm.
(3) The primary particle diameter of the conductive metal oxide fine particles contained in the hard coat layer is 100 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less.
(4) A small amount of surfactant is included in the hard coat layer.
(5) At least one process such as a hard coat layer coating process, a drying process, an aging process, and a curing process is performed in an environment with a relative humidity of 40 to 80%.
(6) The hard coat layer coating solution contains 0.05 to 5.0% by mass of water with respect to the total mass of the coating solution.
(7) An organic solvent (hygroscopic solvent) having a solubility parameter of 9.5 or more is contained in the coating liquid for the hard coat layer in an amount of 0.05 to 80% by mass with respect to the total mass of the coating liquid.

  It is preferable that an easy adhesion layer is further disposed between the translucent substrate and the antireflection layer. Thereby, the joint strength of the said translucent base material and the hard-coat layer of the said antireflection layer can be improved. As the resin used for the easy-adhesion layer, for example, a polyester resin, a polyurethane resin, an acrylic resin, or the like can be used. These resins can be used alone, but these resins can be used in combination as a polymer blend. it can. It is more preferable to copolymerize these resins with a component having a hydrophilic group such as a carboxyl group or a hydroxyl group, since the adhesion between the easy adhesion layer and the translucent substrate is further improved.

  The easy-adhesion layer improves the handling properties such as slipperiness, rollability and blocking resistance of the translucent substrate, and wear characteristics such as wear resistance and scratch resistance, and adjusts the refractive index. In addition, at least one selected from inorganic particles and heat-resistant polymer particles may be contained. These particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide and other inorganic particles, crosslinked polymer particles, calcium oxalate Organic particles such as can be used. Among these particles, silica particles are preferable because the refractive index is relatively close to that of the polyester resin and high transparency is easily obtained. The average particle diameter of the particles is usually 0.005 to 1.0 μm, preferably 0.005 to 0.5 μm, and more preferably 0.005 to 0.1 μm. When the average particle diameter exceeds 1.0 μm, the surface of the easy-adhesion layer tends to be rough, and the transparency of the film tends to be lowered. The content of particles contained in the easy-adhesion layer is usually 60% by mass or less, preferably 50% by mass or less, and more preferably 40% by mass or less. If the particle content exceeds 60% by mass, the easy adhesion of the film may be impaired.

  The easy-adhesion layer can be formed by preparing a coating solution containing the resin, inorganic particles, heat-resistant polymer particles, and the like and applying the coating solution to a light-transmitting substrate. The coating method is not particularly limited. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating Method, curtain coating method and the like, and these methods can be used alone or in combination.

The coating solution may be applied to a translucent substrate that has been biaxially stretched and heat-set, or may be applied to a translucent substrate before stretching, and then stretched and heat-set. Although it is good, in order to apply | coat a coating liquid uniformly, it is preferable to apply | coat before extending | stretching. The solid content concentration in the coating solution is usually 30% by mass or less, preferably 10% by mass or less. The coating amount of the coating solution is 0.01 to 5 g, preferably 0.2 to 4 g, per 1 m ² of the running film. In order to obtain sufficient adhesion with the hard coat layer, at least the coating amount needs to be 0.01 g or more per 1 m ² of film. The degree of cleanness when applying the coating solution is preferably a class of 1000 or less from the viewpoint of reducing the adhesion of dust.

The thickness of the easy adhesion layer is preferably 20 nm or more and less than 1 μm, and more preferably 50 nm or more and less than 0.7 μm. When the thickness of the easy adhesion layer is less than 20 nm, the effect of improving the adhesion between the hard coat layer and the translucent substrate is reduced, and when the thickness is 1 μm or more, the effect of improving the adhesion not only reaches saturation, This is disadvantageous economically, and the thickness of the optical film is unnecessarily thick. When it is necessary to reduce the reflected light at the interface between the hard coat layer and the translucent substrate and reduce the occurrence of interference fringes by the hard coat layer, it is easy to satisfy the following relational expression. When the thickness (d _P ) of the adhesive layer is set, the reflected light at the interface is effectively reduced, and the generation of interference fringes can be prevented. Here, N is a natural number, λ is the wavelength of light with high visibility to human eyes (often set to 550 nm), and n _P is the refractive index of the easy adhesion layer.

(Equation 1)
d _P = (2N−1) × λ / (4n _P )
A near-infrared absorbing layer can be further arranged on the other main surface side of the translucent substrate. Thereby, if the optical film of the present embodiment is arranged on the surface of the PDP, unnecessary near infrared rays emitted when plasma discharge is generated are blocked, and there is no adverse effect on devices using peripheral electronic components. In particular, problems such as malfunctions of remote controls such as televisions and air conditioners can be solved. In this case, the above-mentioned easy adhesion layer can be further arranged between the translucent substrate and the near-infrared absorbing layer. Since the optical film of the present embodiment is provided with the above-described antireflection layer, even when the infrared absorption layer is further provided, the optical film has a high total light transmittance, so the near infrared absorption. The degree of freedom in designing the layer is increased. For this reason, a suitable optical film for display can be designed.

  The material of the near-infrared absorbing layer is not particularly limited as long as it is a light-transmitting material that absorbs near-infrared rays. Usually, a resin in which a compound that absorbs near-infrared rays is dispersed is used.

  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 contains the above compound, it is possible to reduce the near-infrared transmittance in the wavelength region of 850 to 1100 nm without greatly reducing the visible-light transmittance in the wavelength range 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 pigments such as naphthoquinone, diimonium, phthalocyanine, cyanine, and polymethine can be used.

  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.

  There is no restriction | limiting in particular about the method of forming a near-infrared absorption layer on a translucent base material, It can form by apply | coating the coating liquid containing the said material to a base material similarly to the case of the above-mentioned hard-coat layer. 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 thickness of the near infrared absorbing layer 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 occur or curl (film warpage) occurs.

  A compound that cuts the neon emission line spectrum (orange) of PDP can be appropriately added to the near-infrared absorbing layer. 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 said near-infrared absorption layer, the kind of material, content rate, etc. so that the spectral transmittance of an optical film may be 20% or less in the whole area | region of wavelength 850-1100 nm.

  Hereinafter, the present invention will be described with reference to the drawings, but the description of matters common to the above-described embodiments may be omitted.

  FIG. 1 is a cross-sectional view showing an example of the optical film of the present invention. In FIG. 1, an optical film 1 includes a translucent base material 10, a hard coat layer 12 disposed on one main surface 10 a of the translucent base material 10 via a first easy-adhesion layer 11, The near-infrared absorption layer 14 arrange | positioned through the 2nd easily bonding layer 13 on the other main surface 10b of the base material 10 is provided. A low refractive index layer 15 is provided on the hard coat layer 12. The hard coat layer 12 and the low refractive index layer 15 form an antireflection layer.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to a following example. In the examples and comparative examples, “part” means mass part, and “average particle diameter” means number average particle diameter.

Example 1
An optical film for evaluation having the same structure as that of the optical film shown in FIG. 1 was produced as follows.

<Preparation of translucent substrate>
As the translucent base material, a first easy-adhesion layer made of a silica fine particle-containing polyester resin (refractive index: 1.58) is formed on one main surface, and the other main surface is made of a silica-containing acrylic resin. 2 An ultraviolet-cutting polyethylene terephthalate (PET) film (total light transmittance: 92.4%) having a thickness of 100 μm on which an easy adhesion layer was formed was prepared.

<Preparation of paint for hard coat layer>
The following materials were sufficiently mixed and stirred to prepare a hard coat layer coating.
(1) Zinc antimonate fine particles “CELNAX CX-Z210IP-F2” (manufactured by Nissan Chemical Co., Ltd., isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 5 parts (2) pentaerythritol triacrylate: 9 Part (3) Dipentaerythritol hexaacrylate: 9 parts (4) Photopolymerization initiator “IRGACURE (registered trademark) 907” (manufactured by Ciba Specialty Chemicals): 1 part (5) Isopropyl alcohol (solubility parameter: 11. 5): 76 parts Next, on the first easy-adhesion layer of the light-transmitting substrate with the easy-adhesion layer, the hard coat layer coating material was compared with a microgravure coater (manufactured by Yasui Seiki Co., Ltd.). It was applied in an environment of 60% humidity and then dried. Subsequently, the coating film was cured by irradiating the coating film with ultraviolet rays at a dose of 100 mJ / cm ² to form a hard coat layer having a thickness of 3 μm.

<Preparation of coating material for low refractive index layer>
The following materials were mixed and stirred to prepare a coating material for a low refractive index layer.
(1) Hollow silica fine particles (Catalyst Kasei Co., Ltd.): 60 parts (2) Pentaerythritol triacrylate: 20 parts (3) Dipentaerythritol hexaacrylate: 20 parts (4) Photopolymerization initiator “IRGACURE® 907” "(Manufactured by Ciba Specialty Chemicals): 4 parts (5) Polymer surface modifier" MODIPER F600 "(manufactured by NOF Corporation): 1 part (6) Isopropyl alcohol: 2000 parts The coating material for low refractive index layer was applied onto the hard coat layer of the light-transmitting substrate using the microgravure coater and dried. Thereafter, the coating film was cured by irradiating the coating film with ultraviolet rays at a dose of 300 mJ / cm ² to form a low refractive index layer having a thickness of 107 nm.

<Preparation of near-infrared absorbing layer coating material>
The following materials were mixed and stirred to prepare a near-infrared absorbing layer coating material.
(1) Acrylic resin “Dianar” (manufactured by Mitsubishi Rayon Co., Ltd.): 100 parts (2) Aromatic dimonium dye “CIR-1085” (manufactured by Nippon Carlit): 6 parts (3) Cyanine moiety / dithiol metal complex moiety contained Near-infrared absorbing compound “SD50-E04N” (manufactured by Sumitomo Seika Co., Ltd., maximum absorption wavelength: 877 nm): 1 part (4) Near-infrared absorbing compound “SD50-E05N” (Sumitomo Seika Co., Ltd.) containing cyanine and dithiol metal complex sites Manufactured, maximum absorption wavelength: 833 nm): 1 part (5) methyl ethyl ketone: 125 parts (6) toluene: 460 parts Next, on the second easy-adhesion layer of the translucent substrate with the easy-adhesion layer, The infrared ray absorbing layer coating was applied using the above micro gravure coater, a near infrared ray absorbing layer was formed so as to have a thickness of 4 μm, and an optical film for evaluation was produced.

(Example 2)
An optical film for evaluation was produced by forming a low refractive index layer and a near-infrared absorbing layer in the same manner as in Example 1 except that the hard coat layer paint having the following composition was used.
(1) Zinc antimonate fine particles “Selnax CX-Z210IP-F2” (manufactured by Nissan Chemical Co., Ltd., isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 15 parts (2) pentaerythritol triacrylate: 8 Part (3) Dipentaerythritol hexaacrylate: 8 parts (4) Photopolymerization initiator “IRGACURE (registered trademark) 907” (manufactured by Ciba Specialty Chemicals): 1 part (5) Isopropyl alcohol (solubility parameter: 11. 5): 68 copies

(Example 3)
<Preparation of paint for hard coat layer>
After thoroughly mixing and stirring the following materials, 0.05 parts of distilled water was added, and further mixed and stirred to prepare a hard coat layer coating material.
(1) Zinc antimonate fine particles “CELNAX CX-Z210IP-F2” (manufactured by Nissan Chemical Co., Ltd., isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 10 parts (2) pentaerythritol triacrylate: 8 .3 parts (3) Dipentaerythritol hexaacrylate: 8.3 parts (4) Photopolymerization initiator “IRGACURE (registered trademark) 907” (manufactured by Ciba Specialty Chemicals): 1.4 parts (5) Methyl isobutyl Ketone (solubility parameter: 8.57): 72 parts Next, on the first easy-adhesion layer of the light-transmitting substrate with the easy-adhesion layer, the hard coat layer coating material was applied to a microgravure coater (Yasui Seiki Co., Ltd.). Was used in an environment with a relative humidity of 30%, and then dried. Subsequently, the coating film was cured by irradiating the coating film with ultraviolet rays at a dose of 100 mJ / cm ² to form a hard coat layer having a thickness of 3 μm.

  Except for the above, a low refractive index layer and a near-infrared absorbing layer were formed in the same manner as in Example 1 to produce an optical film for evaluation.

Example 4
To the hard coat layer coating material of Example 2, 0.2 part of a cationic surfactant “Solsperse 20000” (manufactured by Zeneca) was added, and the dilution solvent was changed from isopropyl alcohol to methyl isobutyl ketone (solubility parameter: 8.57). Except for changing to), a low refractive index layer and a near-infrared absorbing layer were formed in the same manner as in Example 2 to prepare an optical film for evaluation.

(Comparative Example 1)
An optical film for evaluation was prepared by forming a low refractive index layer and a near-infrared absorbing layer in the same manner as in Example 1 except that a hard coat layer paint was prepared using the following materials.
(1) Zinc antimonate fine particles “Selnax CX-Z210IP-F2” (manufactured by Nissan Chemical Co., Ltd., isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 3 parts (2) pentaerythritol triacrylate: 9 2 parts (3) Dipentaerythritol hexaacrylate: 9.2 parts (4) Photopolymerization initiator “IRGACURE® 907” (manufactured by Ciba Specialty Chemicals): 0.9 parts (5) Isopropyl alcohol (Solubility parameter: 11.5): 77.6 parts

(Comparative Example 2)
An optical film for evaluation was prepared by forming a low refractive index layer and a near-infrared absorbing layer in the same manner as in Example 1 except that a hard coat layer paint was prepared using the following materials.
(1) Zinc antimonate fine particles “CELNAX CX-Z210IP-F2” (manufactured by Nissan Chemical Co., Ltd., isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 20 parts (2) pentaerythritol triacrylate: 8 Part (3) Dipentaerythritol hexaacrylate: 7.2 parts (4) Photopolymerization initiator “IRGACURE (registered trademark) 907” (manufactured by Ciba Specialty Chemicals): 0.8 part (5) Isopropyl alcohol (solubility) Parameter: 11.5): 64 parts The characteristics of the optical films of Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated as follows.

<Refractive index>
The refractive indexes of the hard coat layer and the low refractive index layer of the optical film for each evaluation were measured with a refractive index measuring apparatus “FilmTek 3000” (manufactured by SCI).

<Pencil hardness>
The pencil hardness of the hard coat layer of each optical film for evaluation was measured based on JIS K5400.

<Total light transmittance>
Using a spectrophotometer "Ubest V-570 type" (manufactured by JASCO Corporation), the total light transmittance of each optical film for evaluation before providing the near-infrared absorbing layer, the hard coat layer of the translucent substrate The surface opposite to the provided surface was measured as the incident light side.

<Surface resistance value>
Using a high surface resistivity meter “HIRESTA HT-20” (manufactured by Mitsubishi Yuka Kabushiki Kaisha), the surface resistance value on the low refractive index layer side is measured using an optical film for evaluation after providing a near infrared absorption layer. did.

<Near-infrared transmittance>
Using the above spectrophotometer, the maximum value of the transmittance in the near infrared wavelength region of 850 to 1100 nm was measured using the optical film after providing the near infrared absorbing layer, with the near infrared absorbing layer side being the incident light side. . As a result, the near-infrared transmittances of the optical films for evaluation in Examples 1 to 4 and Comparative Examples 1 and 2 were all 12% or less.

  Table 1 shows the measurement results excluding the near-infrared transmittance. In addition, in the column of the characteristics of the hard coat layer in Table 1, A is a humidity controlled at a relative humidity of 60% at the time of coating, and B is an organic solvent (hygroscopic solvent) having a solubility parameter of 9.5 or more in the coating solution. , C represents a solution obtained by adding water to the coating solution, and D represents a solution obtained by adding a surfactant to the coating solution.

  As is clear from Table 1, the optical films of Examples 1 to 4 have a lower surface resistance value than the optical film of Comparative Example 1, and the total light transmittance is higher than that of the optical film of Comparative Example 2, It turns out that translucency and antistatic property are favorable. Moreover, in all the optical films of Examples 1 to 4, it can be seen that the pencil hardness of the hard coat layer can be set to 2H and has high scratch resistance.

  As described above, the present invention can provide an optical film provided with an antireflection layer having high translucency and antistatic properties and having high scratch resistance. By using the optical film of the present invention, a front filter suitable for various displays, particularly PDPs, can be provided.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical film 10 Translucent base material 11 1st easily bonding layer 12 Hard-coat layer 13 2nd easily bonding layer 14 Near-infrared absorption layer 15 Low refractive index layer

Claims (6)

An optical film comprising a translucent substrate and an antireflection layer disposed on one main surface side of the translucent substrate,
The antireflection layer includes a hard coat layer and a low refractive index layer disposed on the hard coat layer from the translucent substrate side,
The hard coat layer is formed from a resin containing an ionizing radiation curable resin,
The refractive index of the low refractive index layer is lower than the refractive index of the hard coat layer,
The said hard-coat layer contains 5 to 15 mass% of conductive metal oxides with respect to the total mass of the said hard-coat layer, The optical film characterized by the above-mentioned. The optical film according to claim 1, wherein a surface resistance value of the optical film on the antireflection layer side is 5 × 10 ¹² Ω / □ or less.   The optical beam according to claim 1 or 2, wherein the total light transmittance of the optical film is 91% or more, and the total light transmittance of the optical film is higher than a single total light transmittance of the light-transmitting substrate. the film.   The optical film according to any one of claims 1 to 3, wherein an easy adhesion layer is further disposed between the translucent substrate and the antireflection layer.   The optical film of any one of Claims 1-4 by which the near-infrared absorption layer is further arrange | positioned at the other main surface side of the said translucent base material.   The optical film according to claim 5, wherein an easy-adhesion layer is further disposed between the translucent substrate and the near-infrared absorbing layer.

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