JP2010043988A - Composition for coating of rear face of dial plate on photovoltaic time piece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent defective appearance which may occur when a dial plate and a solar cell are brought into contact with each other. <P>SOLUTION: A composition for coating of a rear face of a dial plate 106 on a photovoltaic time piece includes a photopolymerizable compound, a photopolymerization starting agent and fumed silica. The composition includes the fumed silica of 0.2 to 10 pts.mass relative to the photopolymerizable compound of 100 pts.mass. The composition for coating further includes PTFE particles preferably having 0.2 to 5.0 pts.mass relative to the photopolymerizable compound of 100 pts.mass. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a back coating composition for a dial of a photovoltaic watch. More specifically, the present invention relates to a composition for coating the back surface of a dial of a photovoltaic timepiece comprising a photopolymerizable compound, a photopolymerization initiator, and fumed silica.

In a timepiece having a photovoltaic power generation function (photovoltaic timepiece), as shown in FIG. 1, in a case 104 covered with a cover glass 102, a dial 106 made of a plastic that transmits light, a solar cell 108, and a secondary A movement 112 including a battery 110 is mounted (for example, Non-Patent Document 1). When the light 114 hits the photovoltaic timepiece, the light 114 passes through the dial 106 and reaches the solar cell 108, where the light 114 is converted into electric energy and the timepiece moves. Further, since surplus electrical energy is stored in the secondary battery 110, the photovoltaic timepiece has the advantage that there is no need to replace the battery.
Citizen, Technology, Eco Drive [online], [Search June 26, 2008], Internet <URL: http://citizen.jp/technology/eco.html>

  By the way, since the dial and the solar cell are arranged close to each other, if the watch is left in an automobile or the like and the temperature rises, the solar cell may be curved and contact toward the center of the dial. is there. If such a contact state is long, even if the temperature drops and the two are separated, a part of the solar cell may remain attached to the contact portion of the dial plate as a black deposit. Since this deposit can be seen through from the cover glass side, the beauty of the watch is impaired.

In addition, even when the watch is impacted, the dial and the solar cell may come into contact with each other, and the beauty of the watch may be impaired.
Therefore, an object of the present invention is to prevent the above-described appearance defects from occurring even after the dial plate and the solar cell come into contact with each other.

The present inventors have found that the above problem can be solved by using a composition containing a photopolymerizable compound, a photopolymerization initiator, and fumed silica.
That is, the back coating composition for the dial of a photovoltaic watch according to the present invention contains a photopolymerizable compound, a photopolymerization initiator, and fumed silica, and the fumed silica is added to 100 parts by mass of the photopolymerizable compound. In contrast, 0.2 to 10 parts by mass is included.

  The back coating composition for the dial of the photovoltaic watch further includes polytetrafluoroethylene particles, and the polytetrafluoroethylene particles are added in an amount of 0.2 to 5.0 masses per 100 parts by mass of the photopolymerizable compound. It is preferable to include a part.

The photopolymerizable compound is preferably a (meth) acryloyl group-containing compound having one or more (meth) acryloyl groups in the molecule, or an epoxy compound.
The dial according to the present invention has a coating layer obtained from the back coating composition for the dial of the photovoltaic timepiece on the back surface.

  The photovoltaic timepiece according to the present invention has the dial described above.

  If the composition for the back surface coating of the dial of the photovoltaic watch according to the present invention is used, even if the dial of the watch comes into contact with the solar cell, the beauty of the watch is not impaired.

Hereinafter, the present invention will be specifically described.
<Composition for the backside coating of the dial of a photovoltaic watch>
The composition for coating the back surface of the dial of the photovoltaic timepiece according to the present invention (also referred to herein as “coating composition”) includes a photopolymerizable compound, a photopolymerization initiator, and fumed silica. The coating composition preferably further contains polytetrafluoroethylene particles (also referred to as “PTFE particles” in the present specification).

  The photopolymerizable compound and the photopolymerization initiator are not particularly limited as long as the photopolymerizable compound is polymerized by ultraviolet irradiation and can be cured to form a coat layer. Specifically, when the photopolymerizable compound is a (meth) acryloyl group-containing compound having at least one (meth) acryloyl group in the molecule, and the photopolymerization initiator is a radical polymerization initiator (in this specification, The composition containing this combination is also referred to as “coating composition (1)”), or the photopolymerizable compound is an epoxy compound, and the photopolymerization initiator is a cationic polymerization initiator (in this specification, The composition containing this combination is also referred to as “coating composition (2)”). Hereinafter, the coating compositions (1) and (2) will be described.

[Coating composition (1)]
As described above, the coating composition (1) contains a (meth) acryloyl group-containing compound as a photopolymerizable compound, a radical polymerization initiator as a photopolymerization initiator, and fumed silica. Further, it preferably contains PTFE particles. When a (meth) acryloyl group-containing compound and a radical polymerization initiator are used, there is an advantage that a coating layer that is quickly cured by ultraviolet irradiation can be obtained.

  The (meth) acryloyl group-containing compound is polymerized by ultraviolet irradiation to form a coat layer. Here, the (meth) acryloyl group-containing compound is one or more (meth) acryloyl groups (also referred to as “(meth) acryloyl group” in this specification in combination with an acryloyl group and a methacryloyl group) in the molecule. It is a compound that has.

  Specific examples of the monofunctional (meth) acryloyl group-containing compound having one (meth) acryloyl group in the molecule include 2-ethylhexyl (meth) acrylate, ethoxydiethylene glycol di (meth) acrylate, phenoxyethyl (meth) ) Acrylate, 2-hydroxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, dicyclopentenyl (meth) acrylate, phenol ethylene oxide (EO) modified (meth) acrylate, nonylphenol EO modified (meth) acrylate, nonylphenol propylene Examples include oxide (PO) -modified (meth) acrylate, 2-ethylhexyl EO-modified (meth) acrylate, and N- (meth) acryloyloxyethyl hexahydrophthalimide. Of these, phenol EO-modified acrylate, nonylphenol EO-modified acrylate, nonylphenol PO-modified acrylate, 2-ethylhexyl EO-modified acrylate, and N-acryloyloxyethyl hexahydrophthalimide are preferably used.

Specific examples of the polyfunctional (meth) acryloyl group-containing compound having two or more (meth) acryloyl groups in the molecule include neopentyl glycol di (meth) acrylate, 1,
6-hexanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, bis ((meth) acryloxyethyl) bisphenol A, tricyclodecane dimethylol di (meth) ) Acrylates, bifunctional compounds such as isocyanuric acid EO-modified di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane PO-modified tri (meth) acrylate, isocyanuric acid EO-modified tri (meth) acrylate, penta Erythritol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate DOO, compounds having three or more functional such as dipentaerythritol hexa (meth) acrylate. In addition, examples of the polyfunctional (meth) acryloyl group-containing compound include polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and polyol (meth) acrylate prepolymers in the molecule. And a polyfunctional (meth) acrylic prepolymer having two or more (meth) acryloyl groups. A polyester (meth) acrylate-based prepolymer is obtained, for example, by esterifying hydroxyl groups of a polyester oligomer having hydroxyl groups at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid. It is done. It can also be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding alkylene oxide to a polyvalent carboxylic acid with (meth) acrylic acid. The epoxy (meth) acrylate-based prepolymer is obtained by, for example, reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. The urethane (meth) acrylate-based prepolymer is obtained, for example, by esterifying a polyurethane oligomer obtained by a reaction between a polyether polyol or a polyester polyol and a polyisocyanate with (meth) acrylic acid. The polyol (meth) acrylate-based prepolymer is obtained by esterifying a hydroxyl group of a polyether polyol with (meth) acrylic acid. Among these, tricyclodecane dimethylol diacrylate, isocyanuric acid EO-modified diacrylate, trimethylolpropane triacrylate, trimethylolpropane PO-modified triacrylate, isocyanuric acid EO-modified triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate Ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and polyester acrylate prepolymers are preferably used.

  The said (meth) acryloyl group containing compound may be used individually by 1 type, or may be used in combination of 2 or more type, as long as the hardened | cured coating layer is obtained. From the viewpoint of curability, it is preferable to use, for example, one or more polyfunctional (meth) acryloyl group-containing compounds. It is also preferable to use a combination of one or more monofunctional (meth) acryloyl group-containing compounds and one or more polyfunctional (meth) acryloyl group-containing compounds.

Usually, since a watch is required not to be deteriorated by use at −10 to 80 ° C., the glass transition temperature (Tg) of the (meth) acryloyl group-containing compound is preferably 100 ° C. or more, more preferably 150 ° C. or more. It is desirable to be. When a mixture of two or more (meth) acryloyl group-containing compounds is used, the (meth) acryloyl group-containing compounds are used in combination so that the Tg of the mixture is preferably 100 ° C or higher, more preferably 150 ° C or higher. It is desirable. For example, in the case of using a monofunctional and polyfunctional (meth) acryloyl group-containing compound, from the viewpoint of Tg, the monofunctional compound is used in an amount of 5 to 70% by weight based on the total of the compound. It is desirable to use functional compounds in a total amount of 30 to 95% by weight. Here, the Tg of the (meth) acryloyl group-containing compound is measured as follows. First, a (meth) acryloyl group-containing compound (99 wt%) and Irgacure 651 (1 wt%) as a photopolymerization initiator are mixed, and a 1 mm thick photocured product is prepared from the mixture. At this time, the photocured product is completely cured by a large excess of light irradiation. Next, the dynamic viscoelastic spectrum of this photocured product is measured, and the temperature at which the tan δ value is maximized is defined as Tg.

  The radical polymerization initiator generates radicals by irradiation with ultraviolet rays and initiates polymerization of the (meth) acryloyl group-containing compound. As radical polymerization initiators, benzophenone initiators such as benzophenone and Michler's ketone, diketone initiators such as benzyl and phenylmethoxy diketone, acetophenone initiators such as acetophenone, benzoin initiators such as benzoin ethyl ether and benzyldimethyl ketal Thioxanthone initiators such as 2,4-diethylthioxanthone, and quinone initiators such as 2-methylanthraquinone and camphorquinone. Among these, acetophenone-based initiators are preferably used from the viewpoint of absorption wavelength. The radical polymerization initiators may be used alone or in combination of two or more.

  Fumed silica is usually produced by vaporizing a volatile silicon compound such as silicon tetrachloride and subjecting it to combustion hydrolysis in an oxygen hydrogen flame, for example. In this invention, it does not restrict | limit in particular, A well-known thing can be used. The fumed silica used in the present invention includes those containing spherical silica having a particle size of about 1 μm, which is obtained by further heat-treating the above-mentioned fumed silica having an irregular shape. Fumed silica may be used alone or in combination of two or more.

About fumed silica, it is preferable that the surface area by BET is 100-300 m < ² > / g. Moreover, it is preferable that the particle | grains whose particle size is 1 micrometer or less occupy 95 weight% or more of the whole.

  The coating composition (1) is applied to the back surface of the dial plate to form a coating layer. Since this coating layer contains fumed silica, the beauty of the photovoltaic watch can be maintained. it can. Specifically, when the solar cell and the dial plate come into contact with each other for some reason and then leave, a part of the solar cell does not remain as a black deposit on the back surface of the dial plate. Therefore, even if the dial is viewed from the cover glass side, the beauty of the photovoltaic timepiece is not impaired. This is considered to be due to the following mechanism. That is, fumed silica is present near the surface of the cured coat layer, and forms irregularities on the surface of the coat layer. And since the contact area with a solar cell becomes small by this unevenness | corrugation, it is thought that a part of solar cell sticks and remains on the dial plate back surface.

  The coating composition (1) preferably further contains PTFE particles. The PTFE particles may be produced by any of bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization. PTFE particles may be used alone or in combination of two or more.

The PTFE particles are preferably in the form of powder, and the average particle size is preferably 1 μm or less.
When PTFE particles are contained together with fumed silica in the coating film formed from the coating composition (1), the occurrence of the appearance defect is further suppressed. As in the case of fumed silica, this is considered to be due to the smaller contact area with the solar cell due to the PTFE particles present on the surface of the hardened coating layer and the sliding properties of the PTFE particles.

  The radical polymerization initiator is usually contained in an amount of 0.2 to 10 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. If the amount of the radical polymerization initiator is less than the above range, polymerization may not occur, and if it exceeds the above range, light cannot reach the deep part of the coat layer, and only the vicinity of the surface may polymerize.

  Fumed silica is contained in an amount of 0.2 to 10 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. If the amount of fumed silica is less than the above amount, a part of the solar cell may remain as deposits on the back surface of the dial. If the amount of fumed silica is larger than the above amount, the composition may be whipped (thixotropic properties increase) and may be difficult to apply. Moreover, if it is forcibly applied at this time, the coat layer is formed thick, which may reduce the power generation efficiency of the watch. Furthermore, in consideration of the balance between the occurrence of deposits on the back of the dial and the power generation efficiency of the watch, the preferred amount of fumed silica is 0.2 to 1.0 mass relative to 100 parts by mass of the photopolymerizable compound. Part. In addition, when a photopolymerizable compound consists of 2 or more types of compounds, the said quantity is a total amount of 2 or more types of photopolymerizable compounds. When the fumed silica is a mixture of two or more, the above amount is the amount of the mixture.

  The PTFE particles are preferably contained in an amount of 0.2 to 5.0 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. When the above amount is included, it is possible to effectively prevent a part of the solar cell from remaining as a deposit on the back surface of the dial. In other words, if the amount of PTFE particles is less than the above amount, the remaining deposits may not be effectively prevented. When the amount of PTFE particles is larger than the above amount, the coat layer is formed white, and the power generation efficiency of the watch may be reduced. Or the fluidity | liquidity of a coating composition may worsen and it may become difficult to apply | coat. In addition, if the coating is forcibly performed at this time, the coat layer is formed thick, so that the power generation efficiency of the watch may also decrease. Furthermore, in consideration of the balance between the occurrence of deposits on the back of the dial and the power generation efficiency of the watch, the more preferable amount of PTFE particles is 0.5 to 1.0 mass relative to 100 mass parts of the photopolymerizable compound. Part. In addition, when a photopolymerizable compound consists of 2 or more types of compounds, the said quantity is a total amount of 2 or more types of photopolymerizable compounds. When PTFE is a mixture of two or more, the above amount is the amount of the mixture.

  The coating composition (1) of the present invention contains other components such as a solvent; leveling agents, antifoaming agents, thickeners, flame retardants, antioxidants, stabilizers and the like as necessary. Further, it may be included. Solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol. 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and other ethers, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxy Examples include ether esters such as ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and esters such as ethyl acetate, propyl acetate, and butyl acetate. . The said solvent and additive may be used individually by 1 type, or may be used in combination of 2 or more type.

The solvent is usually contained in an amount of 5.0 to 30 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. Additives are generally contained in an amount of 0.1 to 20 parts by mass in total with respect to 100 parts by mass of the photopolymerizable compound.
The coating composition (1) of the present invention is usually produced by appropriately mixing a (meth) acryloyl group-containing compound, a radical polymerization initiator, fumed silica, and if necessary, PTFE particles and other components.

  The viscosity of the coating composition (1) at normal temperature (25 ° C.) is preferably 100 to 40000 cp, more preferably 100 to 10000 cp, from the viewpoint of ease of application.

[Coating composition (2)]
As described above, the coating composition (2) contains an epoxy compound as a photopolymerizable compound, a cationic polymerization initiator as a photopolymerization initiator, and fumed silica. Further, it preferably contains PTFE particles. When an epoxy compound and a cationic polymerization initiator are used, there is an advantage that a coating layer with a less stickiness can be obtained by ultraviolet irradiation.

The epoxy compound is polymerized or crosslinked with a cationic polymerization initiator activated by ultraviolet irradiation to form a coat layer.
Examples of the epoxy compound include aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. Specific examples of the aromatic epoxy resin include polyglycidyl ethers (for example, bisphenol A, bisphenol F, and bisphenol S) of polyhydric phenol having at least one aromatic ring or an alkylene oxide adduct thereof, and further alkylene oxide. The glycidyl ether of the compound to which is added, epoxy novolac resin, and the like. As the alicyclic epoxy resin, specifically, a cyclohexene oxide structure-containing compound obtained by epoxidizing a polyglycidyl ether, cyclohexene or cyclopentene ring-containing compound of a polyhydric alcohol having at least one alicyclic ring with an oxidizing agent Alternatively, a cyclopentene oxide structure-containing compound and a vinylcyclohexane oxide structure-containing compound obtained by epoxidizing a compound having a vinylcyclohexane structure with an oxidizing agent can be mentioned. Specific examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, and aliphatic long-chain unsaturated hydrocarbons as oxidizing agents. Examples thereof include an epoxy-containing compound obtained by oxidation, a homopolymer of glycidyl acrylate or glycidyl methacrylate, a copolymer of glycidyl acrylate or glycidyl methacrylate, and the like. Among these, more specifically, bisphenol A type glycidyl ether, bisphenol F type glycidyl ether, bisphenol S type glycidyl ether, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxy Rate, allyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, sec-butylphenol glycidyl ether, 2-methyloctyl glycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, glycerol diglycidyl ether Ether, glycerol triglycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol Le diglycidyl ether are preferably used. The said epoxy compound may be used individually by 1 type, or may be used in combination of 2 or more type.

  Usually, since the timepiece is required not to be deteriorated by use at −10 to 80 ° C., the Tg of the epoxy compound is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. When using a mixture of two or more epoxy compounds, it is desirable to combine the epoxy compounds so that the Tg of the mixture is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. Here, Tg of the epoxy compound is a value measured by the TMA method.

  The cationic polymerization initiator releases a substance that initiates cationic polymerization by ultraviolet irradiation. Specific examples of the cationic polymerization initiator include a double salt that is an onium salt that releases a Lewis acid by ultraviolet irradiation, or a derivative thereof. The cationic polymerization initiators may be used alone or in combination of two or more.

The fumed silica is specifically the same as in the case of the coating composition (1). The coating composition (2) is applied to the back surface of the dial plate to form a coating layer. Since the obtained coating layer contains fumed silica, the beauty of the photovoltaic watch is maintained. be able to. Specifically, when the solar cell and the dial plate come into contact with each other for some reason and then leave, a part of the solar cell does not remain as a black deposit on the back surface of the dial plate. Therefore, even if the dial is viewed from the cover glass side, the beauty of the photovoltaic timepiece is not impaired. In addition,
The mechanism is considered as in the coating composition (1).

  The coating composition (2) preferably further contains PTFE particles. The PTFE particles are specifically the same as in the case of the coating composition (1). When PTFE particles are contained together with fumed silica in the coating film formed from the coating composition (2), the occurrence of the appearance defect is further suppressed. In addition, about a mechanism, it is thought similarly to the composition (1) for a coat.

  The cationic polymerization initiator is usually contained in an amount of 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. When the amount of the cationic polymerization initiator is less than the above range, polymerization may not be performed. When the amount is more than the above range, light may not reach the deep part of the coat layer, and only the vicinity of the surface may be polymerized.

The content of fumed silica and its preferred reason and the content of PTFE particles and its preferred reason are the same as in the case of the coating composition (1).
In addition, the coating composition (2) of the present invention comprises, as necessary, a sensitizer; a solvent; an additive such as a leveling agent, an antifoaming agent, a thickener, a flame retardant, an antioxidant, and a stabilizer. It may further contain other components.

Examples of the sensitizer include sensitizers such as anthracene derivatives and pyrene derivatives. When a sensitizer is used, the curing rate can be increased.
Examples of the solvent include acetone, isopropyl alcohol, ethanol, toluene, xylene, ethyl acetate, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether and the like. The above sensitizers, solvents and additives may be used singly or in combination of two or more.

  The sensitizer is usually contained in an amount of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the cationic polymerization initiator. The solvent is usually contained in an amount of 5.0 to 30 parts by mass with respect to 100 parts by mass of the photopolymerizable compound. The additive is generally contained in an amount of 0.1 to 20 parts by mass in total with respect to 100 parts by mass of the photopolymerizable compound.

The coating composition (2) of the present invention is usually produced by appropriately mixing an epoxy compound, a cationic polymerization initiator, fumed silica, and if necessary, PTFE particles and other components.
The viscosity of the coating composition (2) at normal temperature (25 ° C.) is preferably 100 to 40000 cp, more preferably 100 to 10000 cp, from the viewpoint of ease of application.

<Dial plate having a coat layer on the back surface and photovoltaic watch having the dial plate>
The dial according to the present invention has a coating layer on the back surface obtained from the coating composition (specifically, the coating composition (1) or (2)).

The dial used in the present invention is made of a plastic that transmits light, and is usually made of polycarbonate. This dial is usually provided with a coat layer as follows.
First, the coating composition according to the present invention is specifically applied to the back surface of the dial by a known method such as brushing, spraying, spin coating, gravure, or comma coating. Here, it coat | covers so that the hardened | cured coating layer may be 0.5-30 micrometers normally, Preferably it is 5-30 micrometers, More preferably, it is 5-10 micrometers.

  When the coating composition contains a solvent, the coating composition is applied to the dial and then the solvent is dried and removed. The drying conditions are not particularly limited, and are appropriately determined depending on the boiling point of the solvent, the coating amount, and the like.

  Next, the applied coating composition is irradiated with ultraviolet rays, and the photopolymerizable compound is polymerized and cured to obtain a coat layer. For ultraviolet irradiation, a high-pressure mercury lamp and a metal halide lamp are usually used. Irradiation conditions are not particularly limited as long as a cured coat layer is obtained. Thus, the dial according to the present invention, that is, the dial having the coating layer obtained from the coating composition on the back surface is obtained.

  Furthermore, a photovoltaic timepiece is manufactured by using the dial according to the present invention together with a movement including a cover glass, a solar cell, and a secondary battery (see FIG. 1). In the photovoltaic watch according to the present invention, since the coating layer is provided on the back surface of the dial, when the solar cell and the dial come into contact with each other for some reason, the solar cell is formed on the back of the dial. Does not remain as black deposits. Therefore, even if the dial is viewed from the cover glass side, the beauty of the photovoltaic timepiece is not impaired.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.
[Example]
<Evaluation method>
The following evaluation was performed on the dial plate and the watch having the coating layers prepared in the examples and comparative examples. The evaluation results are shown in Tables 1-1 to 1-10 and 2-1 to 2-11.

(1) Coating property The coating property of the coating composition was evaluated when the coating composition was brushed on the back of the dial plate to form the coating layer. The evaluations in Tables 1-1 to 1-10 and 2-1 to 2-11 specifically represent the following.

AA: The thickness of the coating layer obtained by curing the coating layer was 5 to 10 μm.
A: The thickness of the coating layer obtained by curing the coating layer was 10 to 30 μm.
B: When the thickness of the coating layer obtained by curing the coating layer was large, it exceeded 50 μm.

The thickness of the coat layer was measured with a micrometer after the coat layer was peeled off.
(2) Contamination of dial plate The following test was conducted on a dial plate having a coating layer obtained by coating a coating composition on the back of the dial plate to form a coating layer and curing the coating layer. An evaluation was made to see if the plate was contaminated.

  As shown in FIG. 2, the dial plate 106 was placed so that the back surface (the surface having the coat layer 116) was on top, and the solar cell 108 was placed thereon. Next, a weight 118 (weight 60 g) substantially the same shape as the dial 106 was placed on the solar cell 108. In this state, the dial plate 106 was placed in a furnace at 80 ° C., and the dial plate 106 was taken out after 120 hours. It was observed whether a black deposit due to a part of the solar cell 108 remaining on the back surface of the dial 106 remained. In addition, when the furnace temperature was set to 100 ° C., tests and observations were performed in the same manner as described above. Furthermore, when the weight of the weight was set to 80 g and the furnace temperature was set to 80 ° C. and 100 ° C., tests and observations were performed in the same manner as described above. The evaluation of Tables 1-1 to 1-10 and 2-1 to 2-11 specifically represents the following.

  AAA: In any of the tests, no deposit was observed on the back of the dial. That is, in the 80 ° C. test with the 80 g weight and the 100 ° C. test with the 80 g weight, no deposit was observed on the back surface of the dial.

  AA: In the test at 80 ° C. with a weight of 60 g and the test at 100 ° C. with a weight of 60 g, no deposit was observed on the back of the dial. However, in the 80 ° C. test using an 80 g weight and the 100 ° C. test using an 80 g weight, deposits were found on the back of the dial.

  A: In the test at 80 ° C. with a weight of 60 g, no deposit was found on the back of the dial. However, in a test at 100 ° C. with a 60 g weight, deposits were seen on the back of the dial.

B: Deposits were also observed on the back of the dial in a test at 80 ° C. with a 60 g weight.
(3) Power generation efficiency The operation of a photovoltaic watch (Eco-Drive, manufactured by Citizen Watch) assembled using a dial having a coat layer was checked to evaluate the power generation efficiency. The evaluations in Tables 1-1 to 1-10 and 2-1 to 2-11 specifically represent the following.

AA: After placing the assembled photovoltaic watch in the dark until it stopped, it was returned to the room and the time until the battery voltage reached 1 V was measured, and it was 5 hours or less.
A: After placing the assembled photovoltaic watch in the dark until the watch stopped, it was returned to the room and the time until the battery voltage reached 1 V was measured, and it was over 5 hours.

B: Since the coat layer had a thick part of 50 μm or more, the photovoltaic watch could not be assembled.
<Ingredients used for preparing the coating composition>
(1) (meth) acryloyl group-containing compound As polyfunctional compounds, tricyclodecane dimethylol diacrylate, isocyanuric acid EO-modified diacrylate, trimethylolpropane triacrylate, trimethylolpropane PO-modified triacrylate, isocyanuric acid EO-modified di and Triacrylate (diacrylate accounts for 30-40% by weight), pentaerythritol tri and tetra (meth) acrylate (triacrylate accounts for 65-70% by weight), ditrimethylolpropane tetraacrylate, dipentaerythritol penta and hexaacrylate Polyester acrylate-based prepolymer (all manufactured by Toagosei Co., Ltd.) and phenol EO-modified acrylate (produced by Toagosei Co., Ltd.) as a monofunctional compound Using.

(2) Radical polymerization initiator Commercially available 2-methyl-1- (4-methylthiophenyl) -2-morpholino-propan-1-one, which is an acetophenone initiator, was used.

(3) Epoxy compound Commercially available bisphenol A type glycidyl ether, bisphenol F type glycidyl ether, and bisphenol S type glycidyl ether are used as aromatic epoxy resins, and commercially available 3,4-epoxy as alicyclic epoxy resins. Using cyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, commercially available allyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, sec-butylphenol glycidyl ether, 2 -Methyl octyl glycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, glycerol diglycidyl ether, glycerol tri Glycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether was used.

(4) Cationic polymerization initiator Adeka optomer SP152 (trade name, manufactured by ADEKA Corporation), which is a sulfonium salt-based cationic polymerization initiator, was used.

(5) Fumed silica AEROSIL 200 (registered trademark, manufactured by Nippon Aerosil Co., Ltd.) was used.
(6) PTFE particles Commercially available PTFE particles were used.

[Example 1-1]
The components described in Table 1-1 were mixed to prepare a coating composition (1). The above composition was brushed onto the back of a dial made of polycarbonate to form a coating layer, and the dial having a coating layer obtained by curing the coating layer was obtained. Curing was performed using a high pressure mercury lamp. Furthermore, a photovoltaic watch (Eco-Drive, manufactured by Citizen Watch) was assembled using the cover glass, solar cell, and movement together with the dial (see FIG. 1).

[Examples 1-2 to 1-47 and Comparative Examples 1-1 to 1-2]
A coating composition (1), a dial plate having a coating layer, and a photovoltaic watch were produced in the same manner as in Example 1-1 except that the components listed in Tables 1-1 to 1-10 were mixed.

[Example 2-1]
The components described in Table 2-1 were mixed to prepare a coating composition (2). The above composition was brushed onto the back of a dial made of polycarbonate to form a coating layer, and the dial having a coating layer obtained by curing the coating layer was obtained. Curing was performed using a high pressure mercury lamp. Furthermore, a photovoltaic watch (Eco-Drive, manufactured by Citizen Watch) was assembled using the cover glass, solar cell, and movement together with the dial (see FIG. 1).

[Examples 2-2 to 2-52 and Comparative Examples 2-1 to 2-2]
A coating composition (2), a dial plate having a coating layer, and a photovoltaic watch were prepared in the same manner as in Example 2-1, except that the components listed in Tables 2-1 to 2-11 were mixed.

FIG. 1 is a diagram for explaining a photovoltaic timepiece. FIG. 2 is a diagram for explaining evaluation of contamination of the dial.

Explanation of symbols

102: Cover glass 104: Case 106: Dial 108: Solar cell 110: Secondary battery 112: Movement 114: Light 116: Coat layer 118: Weight

Claims (6)

  A character of a photovoltaic watch comprising a photopolymerizable compound, a photopolymerization initiator, and fumed silica, and containing 0.2 to 10 parts by mass of the fumed silica with respect to 100 parts by mass of the photopolymerizable compound. A composition for coating the back surface of a plate.   2. The photovoltaic power generation according to claim 1, further comprising polytetrafluoroethylene particles, and 0.2 to 5.0 parts by mass of the polytetrafluoroethylene particles with respect to 100 parts by mass of the photopolymerizable compound. A composition for the back surface coating of a clock face.   The back surface of the dial of the photovoltaic timepiece according to claim 1 or 2, wherein the photopolymerizable compound is a (meth) acryloyl group-containing compound having at least one (meth) acryloyl group in the molecule. Coat composition.   The said photopolymerizable compound is an epoxy compound, The composition for back surface coating of the dial of the photovoltaic timepiece of Claim 1 or 2 characterized by the above-mentioned.   A dial having a coat layer obtained from the composition for coating a back surface of the dial of the photovoltaic timepiece according to claim 1 on the back.   A photovoltaic timepiece comprising the dial according to claim 5.

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