JP2008036927A - Scratch-resistant resin plate and display window protection plate for information terminals using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scratch-resistant resin plate which is hard to break by pressure, covered with a scratch-resistant film and suitably used for display window protection plates for information terminals. <P>SOLUTION: A cured film is formed on one side of a resin substrate using a curable coating not containing electroconductive fine particles. A cured film is formed on the other side of the resin substrate using a curable coating containing electroconductive fine particles. Preferably, the curable coating contains a compound having at least two (meth)acryloyloxy groups in the molecule and the resin substrate is a methacryl resin plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a scratch-resistant resin plate suitable as a display window protective plate for a portable information terminal, and a display window protective plate for a portable information terminal using the same.

  In recent years, portable telephones such as cellular phones and PHS (Personal Handy-phone System) have become popular with the Internet, and in addition to simple voice transmission functions, portable information terminals have a function to display text information and image information. Has been widely spread as. In addition to such portable telephones, PDAs (Personal Digital Assistants) that have functions such as an address book as well as Internet functions and e-mail functions are also widely used. In this specification, such mobile phones, PHS, PDAs, and the like are collectively referred to as “portable information terminals”. That is, the “portable information terminal” in the present specification is a generic name for a device that has a window (display) for displaying character information, image information, and the like that is large enough to be carried by a person.

  These portable information terminals display character information and image information by a method such as liquid crystal or EL (electroluminescence). The display window is made of a transparent resin as a protective plate. Generally used (see, for example, Patent Documents 1 to 3). In order to prevent scratches on the surface of the protective plate, it has been proposed to provide a scratch-resistant (hard coat) cured film with a curable coating, and the conductive fine particles are applied to the curable coating. It has also been proposed to impart antistatic properties to the cured coating by containing the above (see the patent document).

Japanese Patent Laid-Open No. 2002-6676 JP 2004-143365 A JP 2004-299199 A

  The cured film is provided on at least one surface of the protective plate, and when it is provided only on one surface, the surface may be directed to the front side (side on which the user directly sees or touches), but the cured film is formed only on one surface. The provided protective plate has a problem that it is likely to warp when exposed to high temperature and high humidity for a long time. For this reason, it is better to provide the cured coating on both sides of the protective plate. At that time, if the cured coating is formed with a curable coating that does not contain conductive fine particles, the protective plate is likely to break when pressed. On the other hand, there is a problem that it is difficult to obtain sufficient scratch resistance when performed with a curable coating containing conductive fine particles.

  Therefore, the inventors of the present invention have conducted extensive studies to develop a display window protection plate for a portable information terminal that is hard to break even when pressed and is provided with a highly scratch-resistant cured film. The cured film is formed using a curable paint that does not contain conductive fine particles, and the cured film on the other surface is formed using a curable paint that contains conductive fine particles, thereby achieving the desired performance. The present inventors have found that a scratch-resistant resin plate suitable as a display window protection plate for a portable information terminal having the above can be obtained, thereby completing the present invention.

  That is, according to the present invention, a cured film is formed on one surface of a resin substrate with a curable paint containing no conductive fine particles, and a cured film is formed on the other surface with a curable paint containing conductive fine particles. The present invention provides a scratch-resistant resin plate. The present invention also provides a display window protection plate for a portable information terminal made of this scratch-resistant resin plate.

  The scratch-resistant resin plate of the present invention has a cured film that is hard to break even when pressed and has high scratch resistance, and this scratch-resistant resin plate is used as a display window protection plate for a portable information terminal. Thus, the display window can be effectively protected.

  Examples of the resin constituting the substrate of the scratch-resistant resin plate of the present invention include methacrylic resin, polycarbonate resin, polystyrene resin, styrene-acrylonitrile copolymer, and triacetyl cellulose resin. Among these, methacrylic resin is suitable as a resin constituting the substrate because it has high transparency and high rigidity.

  The methacrylic resin is a polymer mainly composed of a methacrylic acid ester. For example, the methacrylic acid ester may be a homopolymer of a methacrylic acid ester, or a methacrylic acid ester of 50% by weight or more and other monomers of 50% by weight or less. And a copolymer thereof. In the case of a copolymer, the proportion of the methacrylic acid ester in all the monomers is preferably 70% by weight or more, and more preferably 90% by weight or more. As the methacrylate ester, alkyl methacrylate is preferably used, and methyl methacrylate is particularly preferably used. Examples of monomers other than methacrylic acid esters include acrylic acid esters such as methyl acrylate and ethyl acrylate, aromatic alkenyl compounds such as styrene and methyl styrene, and unsaturated carboxylic acids such as acrylic acid and methacrylic acid. And alkenyl cyanide compounds such as acrylonitrile and methacrylonitrile.

  The resin substrate may have a flat surface such as a normal plate (sheet) or film, or may have a curved surface such as a convex lens or a concave lens. Further, a fine structure such as fine irregularities may be provided on the surface.

  The resin substrate may be colored with a dye or a pigment as necessary, or may contain an antioxidant, an ultraviolet absorber, rubber particles, or the like. The thickness of the resin substrate is preferably 0.1 mm or more and 3.0 mm or less.

  In the present invention, a cured film is formed on both surfaces of a resin substrate to obtain a scratch-resistant resin plate. At this time, the cured film on one surface is formed by a curable paint containing no conductive fine particles (hereinafter referred to as this The curable paint is sometimes referred to as paint (A)], and the cured film on the other surface is formed using a curable paint containing conductive fine particles (hereinafter, this curable paint is referred to as paint (B). May be used]. In this way, by forming a cured film using different paints (A) and (B) on both the front and back surfaces, the scratch-resistant resin plate is hard to break even when pressed and has a highly scratch-resistant cured film. Can be obtained.

  In this scratch-resistant resin plate, the cured film formed with the paint (A) usually does not contain conductive fine particles, so that the cured film formed with the paint (B) is more resistant to scratches. On the other hand, the cured film formed from the paint (B) has more antistatic properties and antistatic properties than the cured film formed from the paint (B) because it contains conductive fine particles. It will be excellent. Moreover, the case where it presses from the surface side in which the cured film was formed with the coating material (A) becomes difficult to crack compared with the case where it pressed from the surface side in which the cured film was formed with the coating material (B) normally. Therefore, when this scratch-resistant resin plate is used as a display window protection plate for a portable information terminal, the surface on which the cured film is formed by the paint (A) is the front side (the side on which the user directly sees or touches). The surface on which the cured film is formed by the paint (B) is directed to the back side (display side), so that even if the user touches it, it is difficult to be scratched and hard to break. In addition, the back side, which is difficult to wipe off when dust or dirt adheres, can be made difficult to adhere dust or dirt due to its antistatic property.

  As the curable compound contained in the paints (A) to (B), a compound having a property of being cured when irradiated with an activation energy beam such as an electron beam or ultraviolet rays is preferably used, and in particular, polyfunctional (meth). An acrylate compound is preferably used. Here, the polyfunctional (meth) acrylate compound means a compound having at least two (meth) acryloyloxy groups in the molecule, and more than trifunctional, that is, at least three (meth) in the molecule. A compound having an acroyloxy group is preferably used. In the present specification, the (meth) acryloyloxy group means an acryloyloxy group or a methacryloyloxy group, and the same applies to “(meth)” when referred to as (meth) acrylate, (meth) acrylic acid, etc. Is the meaning.

  Examples of polyfunctional (meth) acrylate compounds include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and trimethylol. Propane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, pentaglycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerin tri (meth) acrylate, dipentaerythritol Tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol Sa (meth) acrylate, tris [(meth) acryloyloxyethyl] isocyanurate, etc. tripentaerythritol octa (meth) acrylate.

  A phosphazene-based (meth) acrylate compound having a (meth) acryloyloxy group introduced into the phosphazene ring of the phosphazene compound; a polyisocyanate having at least two isocyanate groups in the molecule, and at least one (meth ) Urethane (meth) acrylate compound obtained by reaction with a polyol compound having an acryloyloxy group and a hydroxyl group; a compound having at least two carboxylic acid halide groups in the molecule, and at least one (meth) acryloyl in the molecule Polyester (meth) acrylate compounds obtained by reaction with a polyol compound having an oxy group and a hydroxyl group; oligomers such as dimers and trimers of the above-mentioned compounds can also be used. These polyfunctional (meth) acrylate compounds are used alone or in admixture of two or more.

  Examples of the conductive fine particles contained in the paint (B) include metal oxides such as antimony oxide, indium / tin composite oxide (ITO), tin oxide doped with antimony (ATO), and phosphorus. And fine particles such as tin oxide (PTO) and antimony / zinc composite oxide.

  The conductive fine particles preferably have a particle diameter of 0.001 to 1 μm. When the particle size is too small, industrial production is difficult, and when the particle size is too large, the transparency of the cured film is lowered, which is not preferable. Moreover, it is preferable that the usage-amount of the electroconductive fine particles in a coating material (B) is 1-100 weight part with respect to 100 weight part of curable compounds. If the amount used is too small, the resulting scratch-resistant resin plate is easily cracked when pressed, and sufficient antistatic effect cannot be obtained, and if it is too large, the scratch resistance of the cured coating is reduced, It is not preferable because the film formability is lowered.

  The paints (A) to (B) may contain a solvent in order to adjust the viscosity, the thickness of the cured film, and the like. Examples of the solvent include methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol (sec-butyl alcohol), 2-methyl-1-propanol (isobutyl alcohol), 2 Alcohols such as methyl-2-propanol (tert-butyl alcohol), 2-ethoxyethanol, 2-butoxyethanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 1-ethoxy-2- Alkoxy alcohols such as propanol, ketols such as diacetone alcohol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, aromatic hydrocarbons such as toluene, xylene, ethyl acetate, butyl acetate, etc. D Such as ethers, and the like. The amount of the solvent used is appropriately adjusted according to the substrate material, shape, coating method, target thickness of the cured film, etc., but usually in the paint (A), 100 parts by weight of the curable compound, It is about 20-10000 weight part, and is about 20-10000 weight part with respect to 100 weight part of total amounts of a sclerosing | hardenable compound and electroconductive fine particles in a coating material (B).

  In addition, the coating materials (A) to (B) may contain additives such as a stabilizer, an antioxidant, a colorant, and a leveling agent as necessary. By containing the leveling agent, the smoothness and scratch resistance of the cured film can be improved.

  As the leveling agent, silicone oil is preferably used. Examples thereof include dimethyl silicone oil, phenylmethyl silicone oil, alkyl / aralkyl modified silicone oil, fluorosilicone oil, polyether modified silicone oil, fatty acid ester modified silicone oil, methyl Hydrogen silicone oil, silanol group-containing silicone oil, alkoxy group-containing silicone oil, phenol group-containing silicone oil, methacryl-modified silicone oil, amino-modified silicone oil, carboxylic acid-modified silicone oil, carbinol-modified silicone oil, epoxy-modified silicone oil, mercapto Examples include modified silicone oil, fluorine-modified silicone oil, and polyether-modified silicone oil. These silicone oils may be used alone or in combination of two or more.

  The amount of silicone oil used is usually 0.01 to 20 parts by weight with respect to 100 parts by weight of the curable compound in the paint (A), and 100 parts by weight in total of the curable compound and the conductive fine particles in the paint (B). The amount is usually 0.01 to 20 parts by weight. If the amount used is too small, it is difficult to obtain the intended effect, and if it is too large, the strength of the cured film is lowered, which is not preferable.

  Each of the paints (A) and (B) described above is applied to one side of a resin substrate, then dried as necessary, and then the formed coating film is cured, whereby the scratch-resistant resin of the present invention. A board can be obtained. In addition, the order of application | coating hardening of both coating materials is arbitrary, and it is also possible to carry out simultaneously.

  Application of the paints (A) to (B) is performed by applying a mask on one side as necessary, for example, micro gravure coating method, roll coating method, dipping coating method, spin coating method, die coating method, cast transfer method, flow coating method. It can be performed by a method such as spray coating.

  The coating film is suitably cured by irradiating with an activation energy ray. Examples of the activation energy rays include electron beams, ultraviolet rays, and visible rays, and are appropriately selected according to the type of curable compound. In the case where ultraviolet rays or visible light is used as the activation energy ray, a photopolymerization initiator is usually used.

  Examples of the photopolymerization initiator include acetophenone, acetophenone benzyl ketal, anthraquinone, 1- (4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one, carbazole, xanthone, 4-chlorobenzophenone, 4,4 '-Diaminobenzophenone, 1,1-dimethoxydeoxybenzoin, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2,2-dimethoxy-2-phenylacetophenone, 1- (4-dodecylphenyl) -2-hydroxy 2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, triphenylamine, 2,4,6-trimethylbenzoyldiphenylphosphine oxide 1-hydroxy Chlohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, fluorenone, fluorene, benzaldehyde, benzoin ethyl ether, benzoisopropyl ether, benzophenone, Michler ketone, 3-methylacetophenone, 3,3 ′, 4,4′-tetra-tert-butylperoxycarbonylbenzophenone (BTTB), 2- (dimethylamino) -1- [4- (morpholinyl) phenyl] -2- (phenylmethyl) -1-butanone, 4-benzoyl -4'-methyldiphenyl sulfide, benzyl and the like.

  The photopolymerization initiator may be used in combination with a dye sensitizer. Examples of the dye sensitizer include xanthene, thioxanthene, coumarin, and ketocoumarin. Examples of the combination of the photopolymerization initiator and the dye sensitizer include a combination of BTTB and xanthene, a combination of BTTB and thioxanthene, a combination of BTTB and coumarin, and a combination of BTTB and ketocoumarin.

  Since said photoinitiator is marketed, such a commercial item can be used. Examples of commercially available photopolymerization initiators include “IRGACURE 651”, “IRGACURE 184”, “IRGACURE 500”, “IRGACURE 1000”, “IRGACURE 2959”, sold by Ciba Specialty Chemicals, Inc., respectively. “DAROCUR 1173”, “IRGACURE 907”, “IRGACURE 369”, “IRGACURE 1700”, “IRGACURE 1800”, “IRGACURE 819”, and “IRGACURE 784”, respectively, “KAYACURE” sold by Nippon Kayaku Co., Ltd. "ITX", "KAYACURE DETX-S", "KAYACURE BP-100", "KAYACURE BMS", and "KAYACURE 2-EAQ" ".

  When using a photoinitiator, the usage-amount is 0.1 weight part or more normally with respect to 100 weight part of curable compounds. If the amount used is too small, the curing rate tends not to increase as compared with the case where no photopolymerization initiator is used. In addition, the upper limit of the usage-amount of a photoinitiator is about 10 weight part normally with respect to 100 weight part of curable compounds.

  Moreover, the intensity | strength and irradiation time of an activation energy ray are suitably adjusted according to the kind of curable compound, the thickness of the coating film, etc. The activation energy ray may be irradiated in an inert gas atmosphere, and as this inert gas, nitrogen gas, argon gas, or the like can be used.

  The thickness of the cured film thus formed is preferably 1 to 10 μm, and more preferably 2 to 6 μm. If the thickness is too small, the scratch resistance may be insufficient, and if it is too large, cracks are likely to occur when exposed to high temperature and high humidity. The thickness of the cured coating film can be adjusted by adjusting the amount per area of the curable coating applied to the surface of the resin substrate and the solid content concentration contained in the curable coating.

  The scratch-resistant resin plate of the present invention thus obtained has a cured film that is hard to break even when pressed and has high scratch resistance, and is a display window protection plate for portable information terminals typified by mobile phones and the like. Can be suitably used. Further, it can be used as various members in fields where scratch resistance is required, such as a finder portion of a digital camera or a handheld video camera, or a display window protection plate of a portable game machine.

  In order to produce a display window protection plate for a portable information terminal from the scratch-resistant resin plate of the present invention, first, if necessary, processing such as printing and drilling may be performed and cut to a required size. After that, preferably, as described above, if the surface on which the cured coating is provided by the paint (A) is faced up and set on the display window of the portable information terminal, the display window is effectively protected. be able to.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. Moreover, the measuring method or evaluation method of physical properties is as follows.

[Thickness of cured film]
It measured using the film thickness measuring apparatus [F-20 of Filmmetrics.

[Surface resistance]
Measured according to ASTM D-257.

[Abrasion resistance test]
Using steel wool # 0000, it was rubbed with a load of 2000 g / 4 cm ² for 10 reciprocations, 150 reciprocations, hereinafter 100 reciprocation increments until scratches could be visually confirmed, and the number of reciprocations was evaluated.

[Pressing test]
A 55 × 85 mm test piece is placed on a metal frame with an outer diameter of 60 × 100 mm and an inner diameter of 30 × 50 mm, and the center of the test piece is pressed at a speed of 10 mm / min with a 10 mm diameter spherical tip. Then, the strength at which the test piece breaks was measured. The test was carried out three times, and the average value was taken as the measurement result.

  The paints (A) and (B) were prepared as follows.

[Preparation of paint (A)]
15 parts of dipentaerythritol hexaacrylate and 15 parts of pentaerythritol tetraacrylate as a curable compound, 1.5 parts of a photopolymerization initiator [IRGACURE 184 of Ciba Specialty Chemicals Co., Ltd.], and 34 parts of isobutyl alcohol and 1- A paint (A) was prepared by mixing 34 parts of methoxy-2-propanol.

[Preparation of paint (B)]
15 parts by weight of tin oxide doped with antimony (particle size: 0.05 to 0.5 μm), 7.5 parts of dipentaerythritol hexaacrylate and 7.5 parts of pentaerythritol tetraacrylate as a curable compound, a photopolymerization initiator [ 0.8 parts of IRGACURE 184 from Ciba Specialty Chemicals Co., Ltd. and 69 parts of 1-methoxy-2-propanol as a solvent were mixed to prepare paint (B).

Example 1
The coating material (A) was applied to one side of a methacrylic resin plate (Sumitex E, Sumitomo Chemical Co., Ltd.) having a thickness of 2 mm and a size of 100 mm × 60 mm by a flow coating method, followed by drying at room temperature for 5 minutes, and further at 50 ° C. And dried for 7 minutes to form a coating film on the surface of the methacrylic resin plate. Next, the coating film was cured by irradiating ultraviolet rays of 0.5 J / cm ² using a 120 W high-pressure mercury lamp to form a cured film having a thickness of 3.5 μm. Next, the paint (B) was applied to only the surface opposite to the surface on which the cured film was formed by the flow coating method, then dried at room temperature for 1 minute, and further dried at 50 ° C. for 2 minutes. Was formed on the surface of a methacrylic resin plate. Subsequently, the coating film was hardened by irradiating ultraviolet rays of 0.5 J / cm ² using a 120 W high-pressure mercury lamp to form a cured film having a thickness of 2.3 μm. Table 1 shows the surface resistance of the scratch-resistant resin plate thus obtained and the results of the scratch resistance test and pressing test. In addition, the press test evaluated the surface in which the cured film was formed with the coating material (A) as the upper surface.

Comparative Example 1
The coating material (A) was applied to both sides of a methacrylic resin plate (Sumitex E, Sumitomo Chemical Co., Ltd.) having a thickness of 2 mm and a size of 100 mm × 60 mm by a dipping coating method, followed by drying at room temperature for 5 minutes, and further at 50 ° C. And dried for 7 minutes to form a coating film on the surface of the methacrylic resin plate. Next, the coating film was cured by irradiating ultraviolet rays of 0.5 J / cm ² using a 120 W high-pressure mercury lamp to obtain a scratch-resistant resin plate having a cured coating thickness of 3.2 μm. Table 1 shows the surface resistance of the scratch-resistant resin plate and the results of the scratch resistance test and the pressing test. In addition, when this scratch-resistant resin plate was cut, adhesion of many cutting powders was recognized.

Comparative Example 2
Except that the paint (B) was used in place of the paint (A), the same operation as in Comparative Example 1 was performed to obtain a scratch-resistant resin plate having a cured coating thickness of 2.8 μm. Table 1 shows the surface resistance of the scratch-resistant resin plate and the results of the scratch resistance test and the pressing test.

Claims (6)

  A cured film is formed on one surface of the resin substrate with a curable paint containing no conductive fine particles, and a cured film is formed on the other surface with a curable paint containing conductive fine particles. Scratch-resistant resin plate.   The scratch-resistant resin plate according to claim 1, wherein each of the curable paints contains a compound having at least two (meth) acryloyloxy groups in the molecule.   The scratch-resistant resin plate according to claim 1 or 2, wherein the resin substrate is a methacrylic resin plate.   The scratch-resistant resin plate according to any one of claims 1 to 3, wherein the resin substrate has a thickness of 0.1 to 3 mm.   A display window protection plate for a portable information terminal comprising the scratch-resistant resin plate according to claim 1. The display window protection plate according to claim 5, wherein a surface on which a cured film is formed with a curable coating material that does not contain conductive fine particles is directed to the front side.