JP2006130667A - Antistatic hard coat film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coat film excellent in antistatic properties used in a display device such as CRT, PDP, LCD and the like and used for the purpose of the prevention of dust adhesion, surface protection and the enhancement of visibility due to antistatic properties. <P>SOLUTION: The antistatic hard coat film is obtained by forming an antistatic hard coat layer, wherein metal oxide particles (A), with an average primary particle size of 1-10 nm and metal oxide particles (B) with an average primary particle size of 20-50 nm are dispersed in a ratio of A/B=10/90-30/70, at least on one side of a plastic film base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is suitably used for display devices such as a cathode ray tube (hereinafter abbreviated as CRT), a plasma display panel (hereinafter abbreviated as PDP), a liquid crystal display (hereinafter abbreviated as LCD), etc. The present invention relates to a hard coat film excellent in antistatic property, which is suitably used for surface protection and visibility improvement.

  Conventionally, a plastic film is bonded to a display device such as a glass-made CRT, PDP, or LCD for the purpose of preventing scattering when broken or improving the optical properties of the glass surface. . The plastic film is generally provided with a hard coat layer in order to protect the surface (see Patent Document 1).

  This anti-static function of the hard coat layer can form a highly transparent conductive thin film by vapor deposition of metal oxides, for example, and can prevent dust adhesion due to static electricity at a high level, but the vapor deposition process has high productivity. There is a problem that the cost is high due to inferior reasons and the scratch resistance is not sufficient.

  Further, as the hard coat layer, for example, an ultraviolet curable resin composition coating is generally known, but as a method for imparting antistatic properties thereto, inorganic conductive particles are dispersed, a surfactant or the like is used. A technique of mixing an antistatic agent is known.

  However, in the case of the inorganic particle dispersion type, when the amount of particles added is increased in order to give excellent antistatic performance, that is, to reduce the surface resistance value, the refractive index of the antistatic layer increases and the reflection strength of the surface increases, resulting in poor visibility. Even if the amount of particles added is reduced, it is necessary to increase the thickness of the coating film in order to reduce the surface resistance value, which is disadvantageous in terms of cost. On the other hand, in the case of using a surfactant, the conductive form becomes ionic conductivity, so that there is a problem that the humidity dependency of the surface resistance value is increased.

Furthermore, when considering a multilayer coating design, if the outermost layer is provided with a layer to which inorganic particles are added in an amount that can exhibit excellent antistatic performance, the refractive index increases and the surface reflection strength increases. On the contrary, a method of obtaining a target surface resistance value in two layers by providing a layer lower than the target surface resistance value in the lower layer and providing a layer higher than the target surface resistance value in the upper layer. There is. In this case, however, both layers are antistatic layers, which is disadvantageous in terms of cost.
JP 2000-94590 A

  As described above, the conventional plastic film with a hard coat layer has a problem that a sufficient antistatic function cannot be obtained, or even if obtained, the visibility is inferior, the cost is high, and there is no scratch resistance. there were.

  An object of the present invention is to provide economically advantageous antistatic performance, hard coat performance, and highly transparent antistatic hard coat film having luminous reflectance equivalent to that of glass.

  The antistatic hard coat film of the present invention has a ratio of metal oxide particles (A) having an average primary particle diameter of 1 to 10 nm and metal oxide particles (B) having an average primary particle diameter of 20 to 50 nm on at least one surface of a plastic film substrate. Is an antistatic hard coat film in which an antistatic hard coat layer having A / B = 10/90 to 30/70 is laminated.

  The antistatic hard coat film according to the present invention has a luminous reflectance equivalent to that of glass, and achieves excellent antistatic performance, hard coat properties and low haze.

  The material of the plastic film in the present invention is not particularly limited, but polyethylene terephthalate film, polyethylene naphthalate film, polymethyl methacrylate film, polycarbonate film, triacetyl cellulose film, polyarylate film, polyethersulfone film, etc. Preferably, a polyethylene terephthalate (hereinafter abbreviated as PET) film is preferably used.

  The plastic film in the present invention is preferably transparent.

  The thickness of the plastic film in the present invention is usually 25 μm or more and 250 μm or less, preferably 50 μm or more and 200 μm or less.

  When using an aromatic polyester film as the plastic film in the present invention, an anchor-coated film is preferably used for the purpose of improving the adhesion with the hard coat layer. Examples of the anchor coating agent include aliphatic polyester, alicyclic polyester, acrylic ester, polyurethane, polyethyleneimine, silane coupling agent, and mixtures and copolymers thereof. The thickness of the anchor coat layer is preferably in the range of 0.05 to 1.0 μm. If it is thinner than 0.05 μm, it is difficult to obtain sufficient adhesiveness, and if it is thicker than 1.0 μm, the adhesive effect is saturated. The easy adhesion layer may be formed after the transparent plastic film substrate is manufactured, or may be formed in-line when the transparent plastic film substrate is manufactured.

  The antistatic hard coat layer in the present invention has both hard coat properties and antistatic properties. The antistatic coating layer is preferably composed of an ultraviolet curable resin or a thermosetting resin to which a metal oxide is added, and more preferably a polyester acrylate, a urethane acrylate, an epoxy acrylate, or a cationic polymerization ultraviolet curable epoxy resin. Resins such as silicone acrylate and thermosetting silicone resin are preferably used. In the present invention, an ultraviolet curable resin is particularly preferably used for the hard coat layer.

  In the present invention, the hard coat property means that the hard coat surface is highly rigid with respect to indentation by a pencil hardness test or the like, or the indentation trace cannot be visually judged by restoration. Recoatability means that when another layer such as an antistatic hard coat layer is applied on the hard coat layer, it cannot be applied or even if it can be applied, the interfacial adhesion to the hard coat layer Is insufficient and the scratch resistance is poor. Having hard coat property preferably means having a pencil hardness of 3H or more.

  As the metal oxide particles in the antistatic hard coat layer in the present invention, any metal oxide particles having conductivity can be used, but zinc-containing antimony oxide, indium oxide, tin oxide, tin-containing Indium oxide, antimony-containing tin oxide, and aluminum-containing zinc oxide are preferably used in terms of transparency and conductivity.

  The metal oxide in the present invention is added in the form of particles, and the ratio of metal oxide particles (A) having an average primary particle diameter of 1 to 10 nm and metal oxide particles (B) having an average primary particle diameter of 20 to 50 nm is A / B = It is essential that the ratio is 10/90 to 30/70. When the metal oxide particles (A) having an average primary particle size of 1 to 10 nm and the metal oxide particles (B) having an average primary particle size of 20 to 50 nm are not included, it is difficult to achieve both high surface resistance and high haze. On the other hand, when the average primary particle size of the metal oxide (A) is 1 nm or less, the haze value is good but the surface resistance value is low, and the average primary particle size of the metal oxide (B) is 50 nm or more. Conversely, the haze value increases. In addition, when the average primary particle size of the metal oxide (A) is 10 nm or more and the average primary particle size of the metal oxide (B) is 20 nm or less, the effect when mixed becomes insufficient.

  The ratio of the metal oxide particles (A) having an average primary particle size of 1 to 10 nm and the metal oxide particles (B) having an average particle size of 20 to 50 nm is preferably A / B = 20% to 80%. Preferably, A / B = 30% to 60%. When A / B is less than 20%, the antistatic property is insufficient. On the other hand, when A / B is more than 80%, the haze is increased or the cost is disadvantageous.

  The thickness of the antistatic hard coat layer in the present invention is preferably 2 μm or more and 8 μm or less, more preferably 2 μm or more and 5 μm or less. When the thickness is less than 2 μm, the antistatic property is insufficient. On the other hand, when the thickness exceeds 8 μm, the film tends to curl, which is not preferable.

The surface resistivity of the hard coat layer in the present invention is preferably 10 ¹⁰ Ω / □ or less in order to exhibit antistatic properties.

  In the present invention, the antistatic hard coat layer preferably has a pencil hardness of 3H or more, more preferably 4H or more. When the pencil hardness is less than 3H, the protective film for the display device may be inferior in practicality because it is easily scratched.

  The hard coat layer in the antistatic hard coat film of the present invention may be a single layer, but preferably the antistatic hard coat layer is the outermost layer and a plurality of hard coat layers are provided in the lower layer. Hereinafter, the hard coat layer provided in the lower layer is referred to as a hard coat layer 2, and the outermost hard coat layer is referred to as a hard coat layer 1.

  In the antistatic hard coat film of the present invention, the hard coat layer 2 provided in the lower layer preferably has both hard coat properties and recoat properties.

  The hard coat layer 2 is preferably an ultraviolet curable resin, a thermosetting resin, or the like as a resin component. Specifically, polyester acrylate, urethane acrylate, epoxy acrylate, cationic polymerization ultraviolet curable epoxy resin, silicone acrylate, A resin such as a thermosetting silicone resin can be used. The polyester acrylate is composed of an oligomer acrylate or methacrylate of a polyester polyol or a mixture thereof. Urethane acrylate is comprised from what acrylate-ized the oligomer which consists of a polyol compound and a diisocyanate compound. Epoxy acrylate consists of acrylated epoxy oligomer. The cationic polymerization ultraviolet curable epoxy resin is composed of a resin having a reactive functional group such as an epoxy group. Silicone acrylate is composed of an acrylate or methacrylate oligomer of a silicone-based oligomer. In the thermosetting silicone resin, the silicone is cured by heat.

  In particular, in the present invention, the hard coat layer 2 is preferably an ultraviolet curable resin.

  In the present invention, inorganic particles or organic particles can be added to the hard coat layer 2 for the purpose of enhancing the hard coat properties. As the inorganic particles to be added, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate and the like can be used as representative ones. As the organic particles, acrylic, styrene, olefin, imide, or the like can be used. These particles preferably have an average particle size of 0.01 μm to 5 μm, more preferably 0.05 μm to 2 μm. If it is less than 0.01 μm, the effect is not sufficient, and if it exceeds 5 μm, the haze increases and the transparency is significantly impaired, which is not preferable.

  Further, since the antistatic hard coat layer 1 is laminated on the hard coat layer 2, it is not preferable to add a so-called leveling agent. This is because the addition of the leveling agent inhibits appearance defects such as repellency and adhesion of the antistatic hard coat layer, and by using no leveling agent, further excellent scratch resistance can be exhibited. Examples of the leveling agent include compounds that reduce the surface tension, such as silicone oil, fluorinated polyolefin, and polyacrylate.

  The thickness of the hard coat layer 2 in the present invention is 2 μm or more and 20 μm or less, preferably 5 μm or more and 10 μm or less.

  The antistatic hard coat film of the present invention preferably has a light transmittance of 70% or more and a haze of 2% or less. Therefore, it is desirable that the plastic film substrate, hard coat layer and antistatic hard coat layer used in the present invention are transparent. Moreover, since it is used for display apparatuses, such as a display, it is preferable that the light transmittance including an adhesion layer is 40% or more.

  The antistatic hard coat film of the present invention is preferably a film for application to a display surface such as a CRT. Preferably, an adhesive is provided on the opposite side of the hard coat layer 2 and the antistatic hard coat layer 1. A layer is formed. The pressure-sensitive adhesive layer 4 has only a good transparency and an initial pressure-sensitive adhesive strength of 100 to 2000 g / 25 mm width and can be re-peeled. If necessary, an ultraviolet absorber, a selective light absorber, and a near-infrared absorber are appropriately used. May be added.

  Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples. Prior to each example, a method for measuring each characteristic used in the following examples will be described.

(1) Pencil hardness Using a pencil scratch tester for coating film (made by Haydon) defined in JISK5400, and using an evaluation method defined in JISK5400, using a 3H pencil for Mitsubishi pencil hardness measurement with a length of 10 mm, a length of 10 mm Now draw 5 lines and count the number of lines that are not damaged by visual judgment.

(2) Surface resistance (unit: Ω / □)
According to the evaluation method stipulated in JISK6911, measurement is performed using “High Lester” manufactured by Mitsubishi Yuka.

(3) Cross-cut tape test 1.5 mm grid cross-cut according to JISK5400. A 405 tape was affixed, surface peeling was examined by a 90-degree peeling method, and the number of coating films after peeling was counted.

(4) Light transmittance (unit:%)
It measures using the total light transmittance meter (Nippon Denshoku Industries Co., Ltd. NDH-2000) prescribed | regulated to JISK7136.

(5) Haze (Unit:%)
It measures using the total light transmittance meter (Nippon Denshoku Industries Co., Ltd. NDH-2000) prescribed | regulated to JISK7136.

(6) Luminous reflectance (unit:%)
Measurement is performed using a spectrophotometer (UV-3100PC, manufactured by Shimadzu Corporation) defined in JISK7105.

(7) Appearance Judging by visual observation, applying the antistatic hard coat layer 1 and recognizing the level at which the surface of the hard coat layer 2 can be confirmed. .

Example 1
Production Example of Antistatic Hard Coat Film Using Conductive Particles with Different Particle Distributions Thickness of 188 μm Polyester film A4300 (manufactured by Toyobo Co., Ltd.) UV curable acrylic resin hard coat agent to which no leveling agent is added After coating and drying, a 5 μm hard coat layer 1 was formed by irradiating with ultraviolet rays. Next, on this hard coat layer, a zinc-containing antimony oxide dispersed with a ratio of particles (A) having an average primary particle size of 5 nm and particles (B) having a particle size of 30 nm of A / B = 20/80 is obtained. After coating and drying the UV curable acrylic resin hard coating agent added 30% in terms of conversion, the transparent conductive hard coat layer 2 of 3 μm is formed by irradiating with UV rays, and at the same time, the lower hard coat coating layer is completely formed The antistatic hard coat film of Example 1 was obtained.

Example 2
Production Example of Antistatic Hard Coat Film Containing Filler in Hard Coat Layer 2 No leveling agent was added, and a filler-containing hard coat agent containing 30% silica particles having an average particle size of 0.08 μm was used. In the same manner as in Example 1, an antistatic hard coat film of Example 2 was obtained.

Example 3
The antistatic hard coat layer 1 as the metal oxide particles having a production example conductive antistatic hard coat film obtained by dispersing tin-containing indium oxide as the metal oxide particles, the average primary particle diameter of 6nm particles (A) Example 3 in the same manner as in Example 1 except that 30% of tin-containing indium oxide dispersed in a ratio of 35/35 nm particles (B) at A / B = 25/75 was added in terms of solid content. An antistatic hard coat film was obtained.

Comparative Example 1
Example of production of antistatic hard coat film using conductive particles of single distribution (small particle size) An ultraviolet curable acrylic resin hard coat agent containing 30% zinc-containing antimony oxide having an average primary particle size of 10 nm is applied. After being processed and dried, an antistatic hard coat film of Comparative Example 1 was obtained in the same manner as in Example 1 except that a 3 μm transparent conductive hard coat layer 2 was formed by irradiating ultraviolet rays.

Comparative Example 2
Example of production of antistatic hard coat film using conductive particles of single distribution (large particle diameter) An ultraviolet curable acrylic resin hard coat agent containing 30% zinc-containing antimony oxide having an average primary particle diameter of 40 nm is applied. After being processed and dried, an antistatic hard coat film of Comparative Example 2 was obtained in the same manner as in Example 1 except that a 3 μm transparent conductive hard coat layer 2 was formed by irradiating ultraviolet rays.

Comparative Example 3
Production Example of Single Layer Antistatic Hard Coat Film Ratio of particles (A) having an average primary particle diameter of 5 nm and particles (B) having an average primary particle diameter of 5 nm on one surface of a polyester film A4300 having a thickness of 188 μm (manufactured by Toyobo Co., Ltd.) Is coated with an ultraviolet curable acrylic resin hard coating agent containing 30% zinc-containing antimony oxide dispersed at A / B = 20/80, dried, and then irradiated with ultraviolet rays to form a transparent conductive hard of 8 μm. A coating film layer was formed, and the antistatic hard coat film of Comparative Example 4 was obtained.

  Table 1 below shows the pencil hardness, surface resistance value, cross-cut tape test, light transmittance, haze, and appearance of each of the antistatic hard coat films of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3. Shown in

As shown in Table 1, with respect to the results of Examples 1, 2, and 3, Comparative Example 1 has a surface resistance value of the order of 10 ¹⁰ Ω / □, and Comparative Example 2 has a haze of 2.0% or more. It was. In Comparative Example 3, the line transmittance was low and the transparency was impaired.

Claims (5)

The ratio of metal oxide particles (A) having an average primary particle size of 1 to 10 nm and metal oxide particles (B) having an average primary particle size of 1 to 10 nm is A / B = 10/90 to 30 / on at least one surface of the plastic film substrate. An antistatic hard coat film in which an antistatic hard coat layer of 70 is laminated. The antistatic hard coat film according to claim 1, wherein the antistatic hard coat layer is an outermost layer, and a plurality of hard coat layers are provided in a lower layer. The antistatic hard coat film according to claim 1 or 2, wherein the metal oxide particles are zinc-containing antimony oxide, indium oxide, tin oxide, tin-containing indium oxide, antimony-containing tin oxide, or aluminum-containing zinc oxide. The antistatic hard coat film according to any one of claims 1 to 3, wherein the hard coat layer has a surface specific resistance value of 10 ¹⁰ Ω / □ or less. The antistatic hard coat film according to any one of claims 1 to 4, which has a light transmittance of 70% or more and a haze of 2% or less.