JP5971977B2 - White curable resin composition - Google Patents

Description

  The present invention relates to a white curable resin composition suitable for an insulating film such as a solder resist and various resists that can be used as a permanent mask, a printed wiring board coated with the same, and a white curable resin that can be used as a reflective film. The present invention relates to a composition and a reflective sheet coated with the composition.

  A circuit board, for example, a printed wiring board, is used to form a pattern of a conductor circuit on a circuit board, and to mount an electronic component on a soldering land of the pattern by soldering. It is covered with a solder resist film as a permanent protective film. This prevents solder from adhering to unnecessary parts when soldering electronic components to a printed wiring board, and prevents circuit conductors from being directly exposed to air and being corroded by oxidation or humidity. To do.

  In order to apply the solder resist film to the printed wiring board, after applying the curable resin composition to the printed wiring board, pre-drying to make the coating film of the curable resin composition tack-free, This preliminary drying may be performed in a state where the printed wiring board is leaned. In order to prevent sagging of the applied curable resin composition during the preliminary drying, the curable resin composition is required to have high thixotropic properties.

  Further, when the printed wiring board is used as a mounting substrate such as a light emitting diode element (LED), the curable resin composition is colored white in order to improve the reflectance of light from the light source. In this case, titanium oxide which is a white pigment is mix | blended with curable resin composition (patent document 1). However, when titanium oxide is added to the curable resin composition, there is a problem that the thixotropic property of the curable resin composition is lowered due to its specific gravity and the applied curable resin composition is likely to sag. It was.

  In recent years, regulations on carbon dioxide emissions have been implemented as a measure to prevent global warming. Along with that, renewable energy technology has been attracting attention. In particular, since solar cells generate power based on inexhaustible sunlight, they can generate power semipermanently and have no fuel costs. In addition, since it is possible to generate electricity where it is exposed to sunlight, it can be installed near facilities that require electricity, and transmission costs can be reduced. Furthermore, the solar cell can generate power even with diffused light.

  However, many technical problems still remain in solar cells. One example is power generation efficiency. As a means for increasing the power generation efficiency, use of reflected light using a solar battery back sheet (reflective sheet) can be considered. Sunlight has a wavelength from about 300 nm to about 3000 nm, that is, ultraviolet light, visible light, and infrared light. Therefore, it is possible to improve power generation efficiency by sufficiently absorbing light in this range in the solar cell. Is possible. Conventionally, however, the reflective material has a reflectivity for visible light in the vicinity of 400 nm to 800 nm, but has a problem that it can reflect only about 30% of infrared light. The reason why the light cannot be reflected is that the transmittance increases as the wavelength of light increases. Therefore, in order to improve the power generation efficiency of the solar cell, a reflector capable of efficiently reflecting infrared light (for example, light having a wavelength of about 2000 nm) has been demanded.

JP 2011-138037 A

  In view of the above circumstances, the present invention provides a white curable resin composition that can prevent sagging of the applied curable resin composition and that has high reflectivity for infrared light. Objective.

Aspects of the present invention include (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) a diluent, (D) an epoxy compound, and (E) acicular titanium oxide. a white color curable resin composition you, the needle-like long axis of the titanium oxide 1.0Myuemu～10myuemu, aspect ratio of 10 to 30, wherein the needle-like titanium oxide, said carboxyl group-containing photosensitive 40 mass parts-90 mass parts is contained with respect to 100 mass parts of resin, It is a white curable resin composition characterized by the above-mentioned. “Acicular titanium oxide” means titanium oxide having a shape in which the ratio of the length to the diameter of titanium oxide (aspect ratio) exceeds 1.0, in particular, a high aspect ratio, for example, the aspect ratio is 5 And titanium oxide that is 0.0 or more.

  When needle-like titanium oxide is used as the white pigment titanium oxide, the thixotropic property of the white curable resin composition is improved or the decrease in thixotropic property is suppressed while coloring the curable resin composition white. The occurrence of sagging can be prevented. Furthermore, a white curable resin composition having high reflectivity with respect to infrared light can be obtained. In addition, in the curable resin composition of this invention, since photosensitive resin is used, it is mainly used as an ultraviolet curable resin composition.

  An aspect of the present invention is the white curable resin composition, wherein the acicular titanium oxide is contained in an amount of 40 to 90 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin.

  An aspect of the present invention is the white curable resin composition, wherein the acicular titanium oxide has an aspect ratio of 10 to 30.

An aspect of the present invention is the white curable resin composition , wherein a major axis of the acicular titanium oxide is 1.0 μm to 10 μm. An aspect of the present invention is a white curable resin composition that is used for an insulating film of a printed wiring board.

  The aspect of this invention is a printed wiring board which has the cured film of the said white curable resin composition. Moreover, the aspect of this invention is a reflective sheet which has the cured film of the said white curable resin composition.

  According to the aspect of the present invention, the use of titanium oxide having a needle-like shape as the white pigment improves the thixotropy of the curable resin composition even when titanium oxide is blended for coloring in white or thixotropy. Therefore, the sagging of the coated white curable resin composition can be prevented. Further, by using titanium oxide having a needle shape, it is possible to prevent the occurrence of sagging without impairing the solder heat resistance, so that it can be used, for example, as an insulating film of a printed wiring board.

  According to the aspect of the present invention, by using acicular titanium oxide, a white curable resin composition having high reflectivity with respect to infrared light can be obtained. When used for the coating, the power conversion efficiency of the solar cell module can be further improved.

  Next, each component of the white curable resin composition of this invention is demonstrated. The white curable resin composition of the present invention includes (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) a diluent, (D) an epoxy compound, and (E) an acicular shape. It contains titanium oxide, and each of the above components is as follows.

(A) Carboxyl group-containing photosensitive resin
It will not specifically limit if it is a photosensitive resin containing a carboxyl group, For example, the carboxyl group-containing photosensitive resin which has 1 or more of photosensitive unsaturated double bonds can be mentioned. As the component (A), for example, at least a part of the epoxy group of a polyfunctional epoxy resin having two or more epoxy groups in the molecule is reacted with a radical polymerizable unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid. A resin obtained by obtaining an unsaturated monocarboxylic oxide epoxy resin and reacting the produced hydroxyl group with a polybasic acid or an anhydride thereof can be mentioned.

  Any polyfunctional epoxy resin can be used as long as it is a bifunctional or higher functional epoxy resin. Moreover, especially an epoxy equivalent is although it does not restrict | limit, For example, 100-1000 are preferable and 100-500 are especially preferable. Examples of the polyfunctional epoxy resin include biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, rubber modified epoxy resin such as silicone modified epoxy resin, ε-caprolactone modified epoxy resin, bisphenol A type, bisphenol. Phenol type novolak type epoxy resin such as F type, bisphenol AD type, cresol novolak type epoxy resin such as о-cresol novolak type, bisphenol A novolak type epoxy resin, cyclic aliphatic polyfunctional epoxy resin, glycidyl ester type polyfunctional epoxy resin, Glycidylamine type polyfunctional epoxy resin, heterocyclic polyfunctional epoxy resin, bisphenol modified novolac type epoxy resin, polyfunctional modified novolak type epoxy resin, phenols and phenolic hydroxyl group Examples thereof include condensate type epoxy resins with aromatic aldehydes. Moreover, you may use what introduce | transduced halogen atoms, such as Br and Cl, into these resin. These epoxy resins may be used alone or in combination of two or more.

  The radically polymerizable unsaturated monocarboxylic acid to be used is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, and the like. At least one of acrylic acid and methacrylic acid (hereinafter referred to as (meta) ) May be referred to as acrylic acid.) Is preferred, and acrylic acid is particularly preferred. The unsaturated monocarboxylic oxide epoxy resin obtained by reacting (meth) acrylic acid is epoxy (meth) acrylate. It is not specifically limited to the reaction method of an epoxy resin and radically polymerizable unsaturated monocarboxylic acid, For example, it can be made to react by heating an epoxy resin and radically polymerizable unsaturated monocarboxylic acid in a suitable diluent. .

  The polybasic acid or polybasic acid anhydride reacts with a hydroxyl group generated by the reaction between the epoxy resin and the radically polymerizable unsaturated monocarboxylic acid to give the resin a free carboxyl group. The polybasic acid to be used or its anhydride is not particularly limited, and either saturated or unsaturated can be used. Polybasic acids include, for example, succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4- Ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydro Examples include phthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid, and diglycolic acid. Examples of polybasic acid anhydrides include these anhydrides. These compounds may be used alone or in combination of two or more.

  The polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin can also be used as a photosensitive resin, but the carboxyl group of the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin has one or more radical polymerizable unsaturated groups and A polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin having further improved photosensitivity by further introducing a radical polymerizable unsaturated group by reacting with a glycidyl compound having an epoxy group may be used.

  The above-mentioned polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin with improved photosensitivity has a radically polymerizable unsaturated group bonded to the side chain of the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin by the reaction of the glycidyl compound. Therefore, the photopolymerization reactivity is higher and the photosensitive property is more excellent. Examples of the compound having one or more radically polymerizable unsaturated groups and an epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether, and the like. In addition, you may have multiple glycidyl groups in 1 molecule. The above-mentioned compound having one or more radically polymerizable unsaturated groups and an epoxy group may be used alone or in combination of two or more.

  In addition to the above, as the component (A), for example, an ethylenically unsaturated bond is formed on a part of the carboxyl group of the copolymer obtained by reacting (meth) acrylic acid and (meth) acrylic ester. A carboxyl group-containing photosensitive resin obtained by reacting an alicyclic skeleton epoxy having the same can also be exemplified.

  The (meth) acrylic acid ester is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, hydroxyethyl (meth) acrylate, butyl (meth) acrylate, hydroxybutyl (meth) acrylate, propyl (meth) Examples thereof include acrylate and hydroxypropyl (meth) acrylate.

  The alicyclic skeleton epoxy is a compound or resin having an alicyclic skeleton and an epoxy group, and the skeleton is formed by an aliphatic cyclic compound or a chain thereof. Although an epoxy equivalent is not specifically limited, 100-1000 are preferable and 100-500 are especially preferable. Examples of the aliphatic cyclic compound include cyclohexane and cyclopentane. Examples of the alicyclic skeleton epoxy include 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, vinylcyclohexene monooxide 1,2-epoxy-4-vinylcyclohexane, and 2,2-bis. Examples include 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of (hydroxymethyl) -1-butanol. Examples of the ethylenically unsaturated bond include unsaturated bonds such as an acryl group and a methacryl group.

  When an epoxy group of an alicyclic skeleton epoxy having an ethylenically unsaturated bond is reacted with a part of the carboxyl group of a copolymer obtained by reacting (meth) acrylic acid and (meth) acrylic acid ester, an epoxy is obtained. By the reaction between the group and the carboxyl group, the epoxy group is cleaved to form a hydroxyl group and an ester bond. Therefore, the obtained carboxyl group-containing photosensitive resin has an ethylenically unsaturated bond derived from an epoxy group.

  The acid value of the carboxyl group-containing photosensitive resin as component (A) is not particularly limited. For example, the lower limit is preferably 30 mg KOH / g, particularly preferably 40 mg KOH / g, from the viewpoint of reliable alkali developability. On the other hand, for example, the upper limit of the acid value is preferably 200 mgKOH / g from the viewpoint of preventing dissolution of the exposed portion with an alkali developer, and particularly preferably 150 mgKOH / g from the viewpoint of preventing moisture from being cured and preventing deterioration of electrical characteristics.

  Further, the weight average molecular weight of the carboxyl group-containing photosensitive resin is not particularly limited, but for example, the lower limit is preferably 3000, particularly preferably 5000, from the viewpoint of toughness of the cured product and dryness to touch. On the other hand, for example, the upper limit of the weight average molecular weight is preferably 200000, particularly preferably 50000, from the viewpoint of compatibility with the diluent (C) and the like and smooth alkali developability.

  Examples of commercially available carboxyl group-containing photosensitive resins include ZFR-1124, FLX-2089 (manufactured by Nippon Kayaku Co., Ltd.), Cyclomer P (ACA) Z-250, Cyclomer P ( ACA) Z-300 (manufactured by Daicel Cytec Co., Ltd.), lipoxy SP-4621 (manufactured by Showa Polymer Co., Ltd.), and the like. These resins may be used alone or in combination of two or more.

(B) Photopolymerization initiator The photopolymerization initiator is not particularly limited as long as it is generally used. For example, oxime initiators, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin -N-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane- 1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy -2-propyl Ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2- Ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, P-dimethylaminobenzoic acid ethyl ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide And phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide. These may be used alone or in combination of two or more.

  When the white curable resin composition of the present invention is irradiated with ultraviolet light having a wavelength of 300 to 400 nm, the photopolymerization initiator promotes photocuring of the carboxyl group-containing photosensitive resin. Although the compounding quantity of a photoinitiator is not specifically limited, For example, 5-20 mass parts is preferable with respect to 100 mass parts of carboxyl group-containing photosensitive resin, and 8-15 mass parts is especially preferable.

(C) Diluent Examples of the diluent include a reactive diluent and a non-reactive diluent. As the diluent, either a reactive diluent or a non-reactive diluent may be used, and both a reactive diluent and a non-reactive diluent may be used as necessary.

  The reactive diluent is, for example, a photopolymerizable monomer and a compound having at least two polymerizable double bonds per molecule. The reactive diluent is used to sufficiently cure the carboxyl group-containing photosensitive resin and obtain a cured product having acid resistance, heat resistance, alkali resistance, and the like. The reactive diluent is not particularly limited as long as it is the above compound. For example, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate , Diethylene glycol di (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate , Ethylene oxide modified phosphoric acid di (meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylo Rupropanetetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxy) And ethyl) isocyanurate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  Although the compounding quantity of a reactive diluent is not specifically limited, For example, 2.0-60 mass parts is preferable with respect to 100 mass parts of carboxyl group-containing photosensitive resin, and 10-50 mass parts is especially preferable.

  A non-reactive diluent is mix | blended in order to adjust the viscosity and drying property of a white curable resin composition. Non-reactive diluents include, for example, organic solvents. Examples of the organic solvent include ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, isopropanol and cyclohexanol, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. Petroleum solvents such as petroleum ether and petroleum naphtha, cellosolves such as cellosolve and butylcellosolve, carbitols such as carbitol and butylcarbitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl Examples thereof include esters such as carbitol acetate and diethylene glycol monoethyl ether acetate. These may be used alone or in combination of two or more.

  Although the compounding quantity of a non-reactive diluent is not specifically limited, 10-500 mass parts is preferable with respect to 100 mass parts of carboxyl group-containing photosensitive resin.

(D) Epoxy compound The epoxy compound is for increasing the crosslinking density of the cured product to obtain a cured coating film having sufficient mechanical strength. Examples of the epoxy compound include an epoxy resin. The epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolak type epoxy resin (phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-tert-butylphenol novolak) Type), bisphenol F type or bisphenol S type epoxy resin obtained by reacting bisphenol F or bisphenol S with epichlorohydrin, and cycloaliphatic epoxy resin having cyclohexene oxide group, tricyclodecane oxide group, cyclopentene oxide group, etc. , Triglycidyl isocyanurate having a triazine ring such as tris (2,3-epoxypropyl) isocyanurate, triglycidyltris (2-hydroxyethyl) isocyanurate Over DOO, dicyclopentadiene type epoxy resins, adamantane type epoxy resin. These compounds may be used alone or in combination of two or more.

  Although the compounding quantity of an epoxy compound is not specifically limited, 1.0-50 mass parts is preferable with respect to 100 mass parts of carboxyl group-containing photosensitive resin from the point which obtains the coating film of sufficient mechanical strength after hardening. 0.0 to 30 parts by mass is particularly preferable.

(E) Acicular titanium oxide Acicular titanium oxide is a long needle-shaped or fiber-shaped titanium oxide having an aspect ratio of more than 1.0, particularly 5.0 or more. Using acicular titanium oxide improves the thixotropy of the white curable resin composition or suppresses the reduction of thixotropy to prevent the occurrence of sag, while preventing infrared light (for example, infrared light having a wavelength of about 2000 nm). ) Can also be obtained.

  Examples of the acicular titanium oxide include anatase acicular titanium oxide and acicular titanium oxide having a rutile crystal structure (rutile acicular titanium oxide). Among these, examples of the rutile needle-like titanium oxide include “FTL-100”, “FTL-110”, “FTL-200”, “FTL-300” and the like manufactured by Ishihara Sangyo Co., Ltd. it can. These may be used alone or in combination of two or more.

  The aspect ratio of the acicular titanium oxide is not particularly limited as long as it exceeds 1.0. For example, the lower limit is preferably 10 from the viewpoint of surely preventing the sagging from occurring in the coating film. 15 is particularly preferable from the viewpoint of further improving the reflectivity of the light. On the other hand, the upper limit of the aspect ratio is preferably 30 from the viewpoint of productivity of the white curable resin composition, and particularly preferably 25 from the viewpoint of preventing the coating property from being lowered.

  The major axis dimension of the acicular titanium oxide is not particularly limited. For example, the lower limit is preferably 1.0 μm from the viewpoint of preventing sagging and reliably improving the reflectivity to infrared light. From the viewpoint of improving the reflectivity with respect to outside light in a well-balanced manner, 2.0 μm is particularly preferable. On the other hand, the upper limit is preferably 10 [mu] m from the viewpoint of obtaining a smooth coating film surface, and particularly preferably 7.0 [mu] m from the viewpoint of obtaining the resolution of the coating film while preventing a decrease in coating properties.

  Although the compounding quantity of acicular titanium oxide is not specifically limited, For example, the lower limit is 40 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin from the viewpoint of surely improving the reflectivity for infrared light. Preferably, 50 parts by mass is more preferable from the viewpoint of further improving the reflectance of infrared light, and 55 parts by mass is particularly preferable from the viewpoint of improving the thixotropy and reliably preventing the occurrence of sagging. On the other hand, the upper limit is preferably 90 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin from the viewpoint of surely preventing a decrease in reflectivity with respect to infrared light, and the sensitivity of the white curable resin composition. 80 parts by mass is more preferable from the viewpoint of preventing a decrease in light intensity, and 70 parts by mass is particularly preferable from the viewpoint of more reliably preventing a decrease in reflectivity with respect to infrared light.

  In addition to the components (A) to (E) described above, the curable resin composition of the present invention may appropriately contain various additive components such as extender pigments and various additives as necessary. it can.

  The extender pigment is for increasing the strength and rigidity of the coating film. For example, potassium titanate whisker, magnesium sulfate whisker, silicon carbide whisker, calcium carbonate whisker, barium sulfate, crystalline silica, alumina, aluminum hydroxide, Examples include talc and mica.

  Various additives include silicone, hydrocarbon, acrylic and other antifoaming agents, dicyandiamide (DICY) and its derivatives, latent curing agents such as melamine and its derivatives, and rheology control agents such as amorphous silicon dioxide And phenol-based and phosphorus-based antioxidants, silane-based, titanate-based, and alumina-based coupling agents, and triphenylphosphine, imidazole, imidazolium salts, and curing accelerators such as triethanolamine borate.

  Although the manufacturing method of the above-mentioned white curable resin composition of the present invention is not limited to a specific method, for example, after blending the above components (A) to (E) and other components at a predetermined ratio as necessary, It can be produced by kneading or mixing at room temperature by a kneading means such as a three-roll, ball mill or sand mill, or a stirring means such as a super mixer or a planetary mixer. Further, prior to the kneading or mixing, if necessary, preliminary kneading or premixing may be performed.

  Next, a method for using the above-described white curable resin composition of the present invention will be described. First, the case where the curable resin composition of the present invention is applied to a printed wiring board as a solder resist will be described as an example.

  The white curable resin composition of the present invention produced as described above, for example, on a printed wiring board having a circuit pattern formed by etching a copper foil, screen printing method, roll coater method, bar coater method, spray coater The film is applied to a desired thickness using a method, a curtain flow coater method, a gravure coater method, or the like. Next, in order to volatilize the diluent (organic solvent) in the white curable resin composition, the printed wiring board coated with the white curable resin composition is vertically leaned at a temperature of about 60 to 80 ° C. Preliminary drying is performed for about 15 to 60 minutes to form a tack-free coating film. Then, the negative film which has the pattern which made translucent except the land of the said circuit pattern was closely_contact | adhered on the white curable resin composition dried previously, and an ultraviolet-ray is irradiated from it. Then, the coating film is developed by removing a non-exposed area corresponding to the land with a dilute alkaline aqueous solution. The development method is not particularly limited, and for example, a spray method, a shower method, or the like is used, and examples of the diluted alkaline aqueous solution used include 0.5 to 5% sodium carbonate aqueous solution. Next, the coating film is thermally cured by performing post-cure for 20 to 80 minutes with a hot-air circulating dryer or the like at 130 to 170 ° C., and a cured coating film of the desired white curable resin composition on the printed wiring board. Can be formed.

  Next, the case where the white curable resin composition of the present invention is applied to a sheet-like base film to produce a reflective sheet will be described as an example. The method for coating the white curable resin composition of the present invention on the sheet-like base film is not particularly limited. For example, after the surface of the base film having a thickness of 40 μm is treated with 3% sulfuric acid and the surface is washed. The white curable resin composition is applied to the cleaned surface using a known printing method such as the above-described screen printing method so as to have a predetermined thickness, for example, a film thickness after curing of 20 to 23 μm. . Although the application site | part of a white curable resin composition is not specifically limited, For example, it carries out about the whole surface of the base film surface facing the solar cell module back surface, or the substantially whole surface. After coating, preliminary drying is performed by heating at a temperature of about 60 to 80 ° C. for about 15 to 60 minutes to make the coating film tack-free. Next, the coating film is thermally cured by performing post-cure at a temperature of about 130 to 170 ° C. for 10 to 80 minutes to form a target white reflective film on the sheet-like base film, thereby producing a reflective sheet. can do.

  The material of the base film to which the white curable resin composition of the present invention is applied is not particularly limited. For example, polyimide, polyethylene terephthalate (PET), polyvinyl fluoride (PVF), fluorinated ethylene / propylene copolymer (FEP) ), Polytetrafluoroethylene (PTFE), aramid, polyamide-imide, epoxy, polyetherimide, polysulfone, polyethylene naphthalate (PEN), liquid crystal polymer (LCP), and the like.

  Next, examples of the present invention will be described. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Examples 1-4, Comparative Examples 1-3
The components shown in Table 1 below are blended in the proportions shown in Table 1 below, mixed and dispersed at room temperature using three rolls, and used in Examples 1-4 and Comparative Examples 1-3. A curable resin composition was prepared. The compounding amount of each component shown in Table 1 below indicates parts by mass.

The details of each component in Table 1 are as follows.
(A) Carboxy group-containing photosensitive resin / Cyclomer P (ACA) Z-300: manufactured by Daicel Cytec Co., Ltd., acrylic resin having carboxyl group and acryloyl group (obtained by reacting acrylic acid and acrylic ester) A resin obtained by reacting an acryloyl group-containing alicyclic skeleton epoxy with a part of the carboxyl group of the copolymer.
(B) Photopolymerization initiator-SPEEDCURE TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide manufactured by Nippon Siberhegner Co., Ltd.
IRGACURE 819: Phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide manufactured by Ciba Specialty Chemicals.
SPEEDCURE DETX: 2,4-diethylthioxanthone manufactured by Nippon Shibel Hegner Co., Ltd.
(C) Diluent Aronix M-408: Ditrimethylolpropane tetraacrylate manufactured by Toagosei Co., Ltd.
(D) Epoxy compound / EPICLON 850: A type liquid epoxy resin manufactured by DIC Corporation.
(E) Acicular titanium oxide FTL-300: manufactured by Ishihara Sangyo Co., Ltd., rutile titanium oxide (fiber length 5.15 μm, fiber diameter 0.27 μm, aspect ratio 19.1).

About other ingredients
Spherical titanium oxide CR-80: Spherical rutile titanium oxide (average primary particle size 0.25 μm) manufactured by Ishihara Sangyo Co., Ltd.
Extending pigment / Tismo D: manufactured by Otsuka Chemical Co., Ltd., potassium titanate fiber, white needle crystal (fiber length 10-20 μm, fiber diameter 0.3-0.6 μm).
-Variace B-30: Sakai Chemical Industry Co., Ltd. barium sulfate.
Min-u-sil 5: manufactured by Air Brown Co., Ltd., main component: crystalline silica.

Additive : KS-66: Silicone defoamer manufactured by Shin-Etsu Chemical Co., Ltd.
-Leolosil DM-20S: manufactured by Tokuyama Corporation, rheology control agent, amorphous silicon dioxide.
-DICY-7: Japan Epoxy Resin Co., Ltd., latent curing agent, dicyandiamide.
Melamine: A product made by Nissan Chemical Industries, Ltd., a latent curing agent.
・ SUMILIZER GA-80: manufactured by Sumitomo Chemical Co., Ltd., phenolic antioxidant, bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] (2,4,8,10) -Tetraoxaspiro [5.5] undecane-3,9-diyl) bis (2,2-dimethyl-2,1-ethanediyl).

Test piece preparation process After surface-treating a printed wiring board with a circuit pattern formed on a copper clad laminate (FR-4, thickness 1.6 mm, conductor thickness 35 μm) with dilute sulfuric acid (3% by mass), screen printing is applied. The white curable resin compositions used in Examples 1 to 4 and Comparative Examples 1 to 3 (those after standing in a constant temperature bath at 30 ° C. for 24 hours) were respectively applied. Next, preliminary drying was performed at 80 ° C. for 20 minutes in a BOX furnace in a state where the applied printed wiring board was stood vertically. After preliminary drying, the coating film was exposed to ultraviolet light (wavelength 300 to 450 nm) with an exposure device (OMW, HMW-680 GW) at 500 mJ / cm ² and then developed at 30 ° C. with a 1% sodium carbonate aqueous solution. A post-cure was performed at 150 ° C. for 60 minutes in a BOX furnace to form a cured coating film of a white curable resin composition on the printed wiring board, thereby preparing a test piece. The thickness of the cured coating film was 20 to 23 μm.

Evaluation
(1) Thixo ratio White curable resin composition immediately after preparation as described above ("Initial" in Table 2) and white curable resin composition after standing at 30 ° C for 24 hours in a thermostat after preparation ( With respect to “after 24 hours” in Table 2, using a Brookfield viscometer “HVT type”, a BF viscosity (η5) at a spindle rotation speed of 5 rpm at a sample temperature of 25 ° C. and a spindle at a sample temperature of 25 ° C. The BF viscosity (η50) at a rotation speed of 50 rpm was measured, and the thixo ratio was calculated from the viscosity ratio (η5 / η50).
(2) Sag property A printed wiring board after preliminary drying performed in a vertically leaning state was visually observed and evaluated according to the following criteria.
○: The coating film on the printed wiring board is not sagging.
Δ: Slight sagging in the coating film of the circuit pattern portion on the printed wiring board.
X: The sagging by the offset is recognized in the coating film of the circuit pattern part on a printed wiring board.
(3) Solder heat resistance The cured coating film of the test piece prepared in the above-mentioned test piece preparation process is immersed in a solder bath at 260 ° C. for 30 seconds in accordance with the test method of JIS C-6481, and then a peeling test using a cellophane tape is performed. The state of the coating film was visually observed after 1 to 3 cycles, and evaluated according to the following criteria. In addition, all the said peeling tests were done in the site | part in which the circuit pattern was formed.
A: No change is observed in the coating film even after 3 cycles.
○: Only a slight change is observed in the coating film after repeating 3 cycles.
(Triangle | delta): A change is recognized by the coating film after 2 cycles repetition.
X: Peeling is recognized in the coating film after 1 cycle.
(4) Reflectance (%)
Using a spectrophotometer U-4100 (manufactured by Hitachi, Ltd .: φ60 mm integrating sphere), the reflectance at 2000 nm of the test piece prepared in the test piece preparation step was measured.

Table 2 shows the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 3.

  As shown in Examples 1 to 4 of Table 2 above, when acicular titanium oxide is used, the thixo ratio of the white curable resin composition is improved without impairing solder heat resistance, and the occurrence of sagging is prevented. Furthermore, a coating film having excellent reflectance with respect to infrared light having a wavelength of 2000 nm could be obtained. From Examples 1 to 3, when the acicular titanium oxide contains 40 parts by mass to 90 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin, a higher reflectance is obtained, and the carboxyl group-containing photosensitive resin 100 is obtained. When 60 mass parts was contained with respect to mass parts, particularly high reflectance was obtained. Moreover, in the white curable resin composition of an Example, the fall of the thixo ratio could be suppressed even if it was left for 24 hours.

  On the other hand, in Comparative Examples 1 to 3 in which no acicular titanium oxide was blended, good reflectance was not obtained for infrared light having a wavelength of 2000 nm. Further, sagging occurs even if spherical titanium oxide is not blended from Comparative Example 1, and further, when spherical titanium oxide is used from Example 1 and Comparative Example 2, the thixo ratio of the white curable resin composition Was reduced and sagging occurred, and good reflectivity was not obtained for infrared light having a wavelength of 2000 nm. Further, from Comparative Example 3, by using a high aspect ratio potassium titanate fiber, the thixo ratio increased and the occurrence of sagging could be prevented, but a good reflectance for infrared light having a wavelength of 2000 nm could not be obtained. It was.

  Since the white curable resin composition of the present invention can obtain a cured coating film having excellent reflectance with respect to infrared light while preventing the coating film from sagging, for example, printed wiring The utility value is high in the fields of insulating films for plates, reflective sheets for solar cells, and back sheets for liquid crystal televisions.

Claims (4)

(A) a carboxyl group-containing photosensitive resin, (B) a and a light polymerization initiator, (C) a diluent, (D) an epoxy compound and, (E) white color curable you containing a needle-like titanium oxide a resin composition,
The acicular titanium oxide has a major axis of 1.0 μm to 10 μm and an aspect ratio of 10 to 30, and the acicular titanium oxide is 40 to 90 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin. A white curable resin composition characterized by containing a part . The white curable resin composition according to claim 1, wherein the white curable resin composition is used for an insulating film of a printed wiring board . A printed wiring board having a cured film of the white curable resin composition according to claim 1 . A reflective sheet having a cured film of the white curable resin composition according to claim 1 .