Curable resin compositions, cured products, and printed circuit boards

Abstract

To provide a curable resin composition that has high reflectivity and adhesion, and can suppress discoloration and deterioration of the cured product due to heating, particularly when mounting electronic components (such as light-emitting elements); a cured product of the resin composition; and a printed circuit board having the cured product. [Solution] A curable resin composition comprising a curable resin (A) having a carboxyl group and a plurality of unsaturated groups in one molecule, an epoxy compound (B), a white inorganic filler (C), and at least one of a curing accelerator and a curing catalyst (D), wherein the epoxy compound (B) has an aromatic structure, the average primary particle diameter of the white inorganic filler (C) is 0.15 μm or more and 0.3 μm or less, and the total chlorine concentration of the cured product of the curable resin composition is 250 ppm or less.

Description

[Technical Field]

[0001] The present invention relates to a curable resin composition, a cured product of the curable resin composition, and a printed circuit board. [Background technology]

[0002] Backlights and light-emitting elements such as LEDs are mounted on printed circuit boards used in the display devices of electronic devices such as personal computers. Reflective materials are provided on these boards to reflect visible light emitted from a light source in order to improve the efficiency of extracting visible light in the direction of illumination. For example, cured products of curable resin compositions containing titanium dioxide are widely used as these reflective materials. However, such cured products are prone to discoloration (yellowing) due to light and heat from the light source, and their reflectivity decreases over time.

[0003] Therefore, as a curable resin composition to solve the above problem, for example, a white solder resist composition containing (A) rutile-type titanium oxide produced by the chlorine method and (B-1) a thermosetting resin (however, not containing an active energy ray curable resin) has been proposed, which is used as an electroluminescent or light-emitting diode reflector in a printed circuit board on which a light-emitting element is mounted (see Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6134671 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0005] On the other hand, for example, a cured product of a curable resin composition formed on a printed circuit board as a reflective material may discolor due to heating when light-emitting elements such as LEDs are mounted on the printed circuit board, and in particular, the reflectivity of visible light may decrease. However, the white solder resist composition disclosed in Patent Document 1 does not address this problem.

[0006] From the above, the main object of the present invention is to provide a curable resin composition that has high reflectivity and adhesion, and can suppress discoloration and deterioration of the cured product due to heating, particularly when mounting electronic components (such as light-emitting elements), a cured product of the resin composition, and a printed circuit board having the cured product. [Means for solving the problem]

[0007] (1) A curable resin composition according to one aspect of the present invention comprises a curable resin (A) having a carboxyl group and a plurality of unsaturated groups in one molecule, an epoxy compound (B), a white inorganic filler (C), and at least one of a curing accelerator and a curing catalyst (D), wherein the epoxy compound (B) has an aromatic structure, the average primary particle diameter of the white inorganic filler (C) is 0.15 μm or more and 0.3 μm or less, and the total chlorine concentration of the cured product of the curable resin composition is 250 ppm or less.

[0008] (2) In the configuration described in (1) above, the curable resin composition may further include a photopolymerization initiator (E).

[0009] (3) In the configuration described in (1) or (2) above, it is preferable that the lower limit of the total chlorine concentration of the cured product of the curable resin composition is 100 ppm.

[0010] (4) In the configuration described in any one of (1) to (3) above, it is preferable that the epoxy compound (B) includes an epoxy compound having a plurality of glycidyl groups.

[0011] (5) In the configuration described in (4) above, it is preferable that the epoxy compound having a plurality of glycidyl groups includes a bisphenol A type epoxy resin.

[0012] (6) In the configuration described in any one of (1) to (5) above, it is preferable that the white inorganic filler (C) includes at least one selected from the group consisting of titanium oxide, zirconium oxide, yttria-stabilized zirconium, barium titanate, barium sulfate, alumina, and silica.

[0013] (7) In the configuration described in any one of (1) to (6) above, the white inorganic filler (C) comprises titanium oxide (C-1) having a coating layer made of at least one selected from the group consisting of zirconium oxide, alumina, and silica, and it is preferable that the titanium oxide content in the titanium oxide (C-1) having the coating layer is 90% by mass or more.

[0014] (8) In the configuration described in any one of (1) to (7) above, it is preferable that the curable resin composition includes the white inorganic filler (C) which has been surface-treated with an organic substance.

[0015] (9) In the configuration described in any one of (1) to (8) above, it is preferable that at least one of the curing accelerator and curing catalyst (D) includes at least one of a compound (D-1) having at least one of an amino group and an imino group in one molecule, and a compound (D-2) having at least one of a sulfonium cation and an iodonium cation.

[0016] (10) In the configuration described in (9) above, it is preferable that the compound (D-1) contains at least one of melamine and a melamine derivative.

[0017] (11) In the configuration described in (9) above, it is preferable that the compound (D-2) includes a compound having a fluoride anion.

[0018] (12) The cured product according to one aspect of the invention of the present application is obtained by curing the curable resin composition according to any one of (1) to (11) above.

Effects of the Invention

[0019] The curable resin composition according to the present invention has high reflectivity and adhesiveness, and can suppress discoloration and deterioration of the cured product due to heating, particularly heating during mounting of electronic components (such as light-emitting elements).

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments.

[0021] (1) Curable resin composition The curable resin composition of the present embodiment contains a curable resin (A) having a carboxyl group and a plurality of unsaturated groups in one molecule, an epoxy compound (B), a white inorganic filler (C), and at least one of a curing accelerator and a curing catalyst (D).

[0022] Curable resin (A) having a carboxyl group and a plurality of unsaturated groups in one molecule Examples of the curable resin (A) include a curable resin (A-1) obtained by reacting a hydroxyl group of a product (radical-polymerizable unsaturated monocarboxylated epoxy resin) obtained by reacting a radical-polymerizable unsaturated monocarboxylic acid with an epoxy compound having a plurality of epoxy groups in one molecule with a polybasic acid or a polybasic acid anhydride.

[0023] The epoxy equivalent of the epoxy compound having a plurality of epoxy groups in one molecule is not particularly limited, but is preferably 3,000 g / eq or less, more preferably 1,000 g / eq or less, and particularly preferably 100 g / eq or more and 500 g / eq or less. Examples of epoxy compounds having multiple epoxy groups in a single molecule include biphenyl-type epoxy resins; naphthalene-type epoxy resins; dicyclopentadiene-type epoxy resins; rubber-modified epoxy resins such as silicone-modified epoxy resins; ε-caprolactone-modified epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol AD-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin; novolac-type epoxy resins such as phenol novolac-type epoxy resin, o-cresol novolac-type epoxy resin, and p-tert-butylphenol novolac-type epoxy resin; alicyclic epoxy resins having cyclohexene oxide groups, tricyclodecane oxide groups, and cyclopentene oxide groups; triglycidyl isocyanurates having a triazine ring, such as (2-hydroxyethyl) isocyanurate; dicyclopentadiene-type epoxy resins; and adamantane-type epoxy resins. These can be used individually or in combination of multiple types.

[0024] Examples of the radical polymerizable unsaturated monocarboxylic acid include acrylic acid, Methacrylic acid, crotonic acid, and cinnamic acid can be used. Among these, acrylic acid and methacrylic acid are preferred.

[0025] Furthermore, the epoxy compound having multiple epoxy groups in one molecule and the radically polymerizable unsaturated monocarboxylic acid can be reacted by known methods. For example, the epoxy compound having multiple epoxy groups in one molecule and the radically polymerizable unsaturated monocarboxylic acid can be reacted by heating in a suitable diluent.

[0026] The aforementioned polybasic acid or polybasic anhydride can be either saturated or unsaturated. Examples of the polybasic acids include 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, methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid, and diglycolic acid. Examples of the polybasic acid anhydrides include these anhydrides. These can be used individually or in combination. The polybasic acid or polybasic anhydride is introduced into the radical polymerizable unsaturated monocarboxylated epoxy resin by reacting it with the hydroxyl groups generated in the radical polymerizable unsaturated monocarboxylated epoxy resin.

[0027] Furthermore, as the curable resin (A), in addition to the curable resin (A-1), a curable resin (A-2) obtained by reacting the carboxyl group of the curable resin (A-1) with a glycidyl compound having one or more radically polymerizable unsaturated groups and epoxy groups may also be used. These can be used individually or in combination of multiple types.

[0028] Examples of glycidyl compounds having one or more radically polymerizable unsaturated groups and epoxy groups include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and pentaerythritol triacrylate monoglycidyl ether. Note that multiple glycidyl groups may be present in a single molecule of these glycidyl compounds.

[0029] Furthermore, the curable resin (A) may include curable resins other than the curable resins (A-1) and (A-2), as long as it is a curable resin having a carboxyl group and a plurality of unsaturated groups in one molecule. For example, as curable resin (A-3), a curable resin having a carboxyl group and a plurality of ethylenically unsaturated groups in one molecule can be obtained by reacting a copolymer obtained by reacting (meth)acrylic acid with a (meth)acrylic acid ester with an alicyclic epoxy skeleton having an ethylenically unsaturated bond to some of the carboxyl groups. (Meth)acrylic acid esters are not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl (meth)acrylate, butyl (meth)acrylate, hydroxybutyl (meth)acrylate, propyl (meth)acrylate, and hydroxypropyl (meth)acrylate. Alicyclic epoxy is a compound or resin having an alicyclic skeleton and epoxy groups, where the skeleton is formed by an aliphatic cyclic compound or a chain thereof. The epoxy equivalent is not particularly limited, but is preferably 100 to 1000, and particularly preferably 100 to 500. Examples of aliphatic cyclic compounds include cyclohexane and cyclopentane. Examples of alicyclic epoxy include 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, vinylcyclohexene monooxide 1,2-epoxy-4-vinylcyclohexane, and the 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol. Examples of ethylenically unsaturated bonds include acrylic groups and methacrylic groups. When a copolymer obtained by reacting (meth)acrylic acid with a (meth)acrylic acid ester is reacted with the epoxy groups of an alicyclic epoxy skeleton having ethylenically unsaturated bonds, the epoxy groups cleave due to the reaction between the epoxy groups and the carboxyl groups, generating hydroxyl groups and ester bonds. This results in a curable resin having carboxyl groups and multiple ethylenically unsaturated groups in a single molecule.

[0030] The amount of the curable resin (A) can be 20% to 90% by volume relative to the total solid content of the curable resin composition. Alternatively, the amount of the curable resin (A) can be 30% to 80% by volume or 40% to 70% by volume relative to the total solid content of the curable resin composition.

[0031] Examples of epoxy compounds (B) include epoxy compounds having an aromatic structure. Examples of such epoxy resins include glycidylphenyl ether, glycidylaniline type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, p-tert-butylphenol novolac type epoxy resin, and triphenylmethane type epoxy resin. These can be used individually or in combination of multiple types. Among these, epoxy compounds having multiple glycidyl groups, particularly bisphenol A type epoxy resin, are preferred.

[0032] The content of epoxy compound (B) can be adjusted such that, when the reactive functional group of the curable resin (A) is a carboxyl group, the number of moles of epoxy groups in epoxy compound (B) is 0.7 to 1.2 per mole of carboxyl group.

[0033] White inorganic filler (C) Examples of white inorganic fillers (C) include titanium dioxide, zirconium oxide, yttria-stabilized zirconium, niobium oxide, antimony oxide, tartan oxide, tin oxide, zinc oxide, magnesium oxide, iron oxide, calcium carbonate, barium titanate, barium sulfate, aluminum borate, alumina, talc, silica, mica, graphite, and glass fillers. These can be used individually or in combination. Among these, titanium dioxide, zirconium oxide, yttria-stabilized zirconium, barium titanate, barium sulfate, alumina, and silica are preferred.

[0034] The white inorganic filler (C) exhibits at least one of the following forms: spherical, massive, or chain-like. Among these, the spherical form is preferred. The average primary particle diameter of the white inorganic filler (C) is between 0.15 μm and 0.3 μm, and can be between 0.2 μm and 0.3 μm, or between 0.25 μm and 0.3 μm. The average primary particle diameter of the white inorganic filler (C) is measured using a transmission electron microscope (TEM), by measuring the diameters of 200 randomly selected particles and calculating the average value of these particle diameters.

[0035] Furthermore, it is preferable that the surface of the white inorganic filler (C) is treated with an organic substance such as a silane coupling agent.

[0036] Furthermore, as the white inorganic filler (C), titanium dioxide having a coating layer made of at least one of zirconium oxide, alumina, and silica is preferably used. The titanium dioxide content in the titanium dioxide (C-1) having the coating layer is preferably 90% by mass or more. This titanium dioxide content is calculated from the mass of the titanium dioxide (C-1) based on the ratio (molar ratio) of the molar mass of titanium dioxide to the molar mass of the compounds constituting the coating layer. The method for forming the coating layer (coating method) can be any known method such as the sol-gel method, the precipitation method, and the spray drying method, and the titanium dioxide content in the titanium dioxide (C-1) is adjusted as appropriate during the formation of the coating layer.

[0037] The content of the white inorganic filler (C) is preferably 10% to 50% by volume relative to the total amount of solids in the curable resin composition, and may also be 10% to 50% by volume or 20% to 40% by volume.

[0038] Curing accelerator (D) Examples of at least one of the curing accelerator and curing catalyst (D) include amine compounds, imidazole compounds, acid anhydride compounds, and thermal acid generators. These can be used individually or in combination. Among these, compounds having at least one of an amino group and an imino group in one molecule (D-1), and compounds having at least one of a sulfonium cation and an iodonium cation (D-2) are preferably used.

[0039] Examples of compounds (D-1) having at least one of an amino group or an imino group in one molecule include melamine and melamine derivatives. Examples of melamine derivatives include alkylated melamine having functional groups such as an imino group, a methylol group, and a methoxymethyl group.

[0040] Compounds (D-2) having at least one of a sulfonium cation and an iodonium cation include compounds represented by the following general formula (1) and compounds represented by the following general formula (2).

[0041] [ka] (In the above general formula (1), R1 represents a phenyl group in which a hydroxyl group is substituted at any position from position 1 to position 6, R2 represents any alkyl group having 1 to 4 carbon atoms, R3 represents a benzyl group, and X represents any anion.)

[0042] As the compound represented by the above general formula (1), a compound having a 4-hydroxyphenylbenzylmethylsulfonium cation is preferably used. Among these, a compound in which X is a fluoride anion is preferably used.

[0043] [ka] (In the general formula (2) above, R4 represents a phenyl group in which a branched alkyl group having 2 to 4 carbon atoms is substituted at any position from 1 to 6, R5 represents any alkyl group having 1 to 4 carbon atoms, and X represents any anion.)

[0044] As the compound represented by the above general formula (2), a compound having a 3-tert-butyl-4-methoxyphenyliodonium cation is preferably used. Among these, a compound in which X is a fluoride anion is preferably used.

[0045] Examples of commercially available compounds represented by the above general formula (1) or (2) include SunAid SI-60L, SunAid SI-80L, SunAid SI-100L, SunAid SI-110, SunAid SI-150 (all manufactured by Sanshin Chemical Industry Co., Ltd.), TA-100, TA-100FG, IK-1, IK-1FG (manufactured by SunApro Co., Ltd.), Omnicat 250, Omnicat 270 (all manufactured by IGM Resins BV).

[0046] The content of compound (D) is adjusted as appropriate to suppress curability and discoloration, but can be 0.001 parts by mass or more and 10 parts by mass or 0.1 parts by mass or more and 5 parts by mass or 0.5 parts by mass or more and 1 part by mass or less per 100 parts by mass of solid content of epoxy compound (B).

[0047] Photopolymerization initiator (E) The curable resin composition of this embodiment may contain a photopolymerization initiator (E). The photopolymerization initiator (E) is not particularly limited as long as it initiates the polymerization reaction of the curable resin composition by irradiation with active energy rays, for example, 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanoone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-1-(O-acetyloxime), 2-(acetyloxyiminomethyl)thioxanthene-9-one, 1,8-Octanedione, 1,8-bis[9-ethyl-6-nitro-9H-carbazole-3-yl]-1,8-bis(O-acetyloxime), 1,8-bis[9-(2-ethylhexyl)-6-nitro-9H-carbazole-3-yl]-1,8-bis(O-acetyloxime), (Z)-[9-ethyl-6-nitro-9H-carbazole-3-yl](4-((1-methoxypropane-2-yl)oxy)-2-methylphenyl)methanone Oxime ester-based photopolymerization initiators such as O-acetyloxime; α-aminoalkylphenone-based photopolymerization initiators such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; benzoin-based photopolymerization initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, and benzoin isobutyl ether; acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy-2-phenylacetophenone Acetophenone-based photopolymerization initiators such as 2,2-diethoxy-2-phenylacetophenone; benzophenone-based photopolymerization initiators such as benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, and dichlorobenzophenone; anthraquinone-based photopolymerization initiators such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 2-aminoanthraquinone; thioxanthone-based photopolymerization initiators such as 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorthioxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone;Examples include dimethyl ketal-based photopolymerization initiators such as benzyl dimethyl ketal and acetophenone dimethyl ketal; phosphine oxide-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide; and other ketone-based photopolymerization initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl) ketone. These can be used individually or in combination.

[0048] When using a photopolymerization initiator (E), the amount it is added is adjusted as appropriate to suppress curability and discoloration, but it can be 0.001 parts by mass or more and 10 parts by mass or less, 0.1 parts by mass or more and 5 parts by mass or less, or 0.5 parts by mass or more and 1 part by mass or less, per 100 parts by mass of solid content of the curable resin (A).

[0049] The curable resin composition of this embodiment is adjusted so that the total chlorine concentration of the cured product is 250 ppm or less. Furthermore, the total chlorine concentration is preferably 100 ppm or more and 250 ppm or less, and more preferably 100 ppm or more and 200 ppm or less.

[0050] The total chlorine concentration is measured by the following method. A curable resin composition is printed onto a copper foil substrate (with copper foil formed on the surface; substrate thickness: 1.9 mm, copper foil thickness: 50 μm) whose surface has been buffed using a screen printing method to form a coating film. The thickness of the coating film is adjusted so that the DRY film thickness (dry film thickness) is between 20 μm and 70 μm. Next, each substrate is dried in a dryer at 80°C for 30 minutes, and then heated in the dryer at 150°C for 1 hour to produce a substrate with a cured material. Then, the cured material collected and weighed from the copper foil substrate is used as a sample, and the total chlorine concentration is measured at 1,000°C for 30 minutes using an organic elemental analysis system (product name: XS-2100H, manufactured by Nitto Seiko Analytech Co., Ltd., which is a system combining the company's automatic sample combustion device AQF-2100H and Thermo Fisher Scientific's ion chromatograph).

[0051] The cured product formed using the curable resin composition of this embodiment, having such a structure, has a structure that is less susceptible to the effects of heating during curing, and therefore can achieve a high light reflectivity for visible light. Furthermore, such a cured product is less prone to discoloration due to heating when mounting electronic components (such as light-emitting elements), and can maintain high light reflectivity. Therefore, the curable resin composition of this embodiment can provide a cured product that can be suitably used, for example, as a reflective material for printed circuit boards on which light-emitting elements such as LEDs are mounted.

[0052] Furthermore, as described above, the cured product is less susceptible to the effects of heating during curing and when mounting electronic components. Therefore, even when its thickness (film thickness) is reduced, a decrease in light reflection efficiency due to discoloration, etc., can be prevented. For this reason, the curable resin composition of this embodiment provides a cured product that can be suitably used as a reflective material for printed circuit boards where microfabrication and weight reduction are required.

[0053] Furthermore, the curable resin composition of this embodiment can form a cured product that has good adhesion to the material to be coated, such as a printed circuit board. Moreover, as described above, the cured product is less affected by heating, and therefore has excellent insulating properties and solder heat resistance. For this reason, the curable resin composition of this embodiment can provide a highly reliable printed circuit board.

[0054] The curable resin composition of this embodiment may contain the following components, provided that the total chlorine concentration of the cured product does not exceed 250 ppm.

[0055] (Other resins) Examples include photocurable resins and thermosetting resins other than the curable resin (A) and epoxy compound (B) mentioned above.

[0056] (Diluting solvent) Examples include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, cellosolve acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and esters of the above glycol ethers; and alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol. These can be used individually or in combination.

[0057] (Other ingredients) Examples include colorants, defoamers, flame retardants, antioxidants, and additives.

[0058] The curable resin composition of this embodiment is prepared using known methods. For example, it is prepared by kneading or mixing predetermined amounts of each of the above components at room temperature (e.g., 25°C) using a kneading device such as a three-roll mill, ball mill, and sand mill, or a stirring means such as a super mixer or planetary mixer. Pre-kneading or pre-mixing may also be performed as needed.

[0059] (2) Cured product The cured product of this embodiment is produced by curing the curable resin composition obtained as described above. For example, when the cured product is used as a reflector provided on a printed circuit board, the cured product is produced by the following method.

[0060] First, the curable resin composition is printed onto a printed circuit board on which a predetermined circuit is formed to a desired thickness, thereby forming a printed layer. Known printing methods such as screen printing, spray coating, bar coating, applicator coating, blade coating, knife coating, roll coating, and gravure coating can be used. Next, the coating on the substrate is dried in a dryer at 80°C for 30 minutes to form a dried coating. Then, the dried coating on the substrate is heated (post-cured) for 1 hour at 150°C using a hot air circulation type dryer or the like to form a cured product. This provides the cured product on the printed circuit board. Furthermore, if the resin composition contains a photocurable component (such as a photocurable resin), the process may include a step of irradiating the dried coating with active energy rays to photocur it.

[0061] Since the cured product of this embodiment is a cured product of the curable resin composition obtained as described above, it is less affected by heating during curing and can achieve a high light reflectivity for visible light. Furthermore, the cured product is less prone to discoloration due to heating when mounting electronic components, and can maintain high light reflectivity. For this reason, the cured product of this embodiment can be suitably used, for example, as a reflective material for printed circuit boards on which light-emitting elements such as LEDs are mounted.

[0062] Furthermore, since the cured material is less susceptible to the effects of heating during curing and when mounting electronic components, even when its thickness (film thickness) is reduced, a decrease in light reflection efficiency due to discoloration, etc., can be prevented. For this reason, the cured material of this embodiment can be suitably used as a reflective material for printed circuit boards where microfabrication and weight reduction are required.

[0063] Furthermore, the cured product of this embodiment exhibits good adhesion to the material to be coated, such as a printed circuit board, and, as described above, is less susceptible to the effects of heating, thus providing excellent insulation and solder heat resistance. Therefore, the cured product of this embodiment can provide a highly reliable printed circuit board.

[0064] (3) Printed circuit board The printed circuit board of this embodiment has a cured product obtained as described above. Therefore, the printed circuit board of this embodiment is suitable as a printed circuit board for mounting light-emitting elements such as LEDs. [Examples]

[0065] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples.

[0066] <Preparation of curable resin compositions> The components were mixed and dispersed using a three-roll mixer according to the compositions and formulations shown in Table 1 to obtain the curable resin compositions for the examples and comparative examples. Unless otherwise specified, the units of the numerical values ​​representing the compositional content in Table 1 are parts by mass.

[0067] [Table 1] *1 Daicel Ornex Co., Ltd. Carboxyl group-containing acrylic copolymer with an alicyclic skeleton, chlorine content: 115 ppm, solids content: 45% by mass, solids density: 1.06 g / cm³ 3 *2 Bisphenol A type epoxy resin manufactured by DIC Corporation, chlorine content: 1,620 ppm, solids content: 100% by mass, solids density: 1.17 g / cm³ 3 *3 Bisphenol A type epoxy resin manufactured by Mitsubishi Chemical Corporation, chlorine content: 1,260 ppm, solids content: 100% by mass, solids density: 1.17 g / cm³ 3 ※4 Bisphenol F type epoxy resin manufactured by DIC Corporation, chlorine content: 520 ppm, solids content: 100% by mass, solids density: 1.17 g / cm 3 ※5 Bisphenol A type epoxy resin manufactured by DIC Corporation, chlorine content: 1,240 ppm, solids content: 100% by mass, solids density: 1.17 g / cm 3 ※6 Bisphenol A type epoxy resin manufactured by DIC Corporation, chlorine content: 1,360 ppm, solids content: 100% by mass, solids density: 1.17 g / cm 3 ※7 Bisphenol A type epoxy resin manufactured by DIC Corporation, chlorine content: 460 ppm, solids content: 100% by mass, solids density: 1.15 g / cm 3 ※8 Alicyclic epoxy resin manufactured by Resonac Co., Ltd., chlorine content: 5 ppm, solids content: 100% by mass, solids density: 1.07 g / cm 3 ※9 Hydrogenated bisphenol A type epoxy resin manufactured by Anhui Xinyuan Technology Co., Ltd., chlorine content: 1,010 ppm, solids content: 100% by mass, solids density: 1.10 g / cm 3 ※10 Titanium oxide manufactured by Ishihara Sangyo Co., Ltd. (titanium oxide with a silica coating layer, surface-treated with siloxane), solids content: 100% by mass, solids density: 3.90 g / cm 3 ※11 Solids content: 100% by mass, solids density: 1.49 g / cm 3 ※12 Product manufactured by San-Apro Ltd., solids content: 10% by mass, solids density: 0.93 g / cm 3 ※13 Hydrophobic fumed silica manufactured by Tokuyama Corporation, shape:块状, average particle size: 12 nm, refractive index: 1.43 - 1.48, chlorine content: 10 ppm, solids content: 100% by mass, solids density: 1.80 g / cm 3 ※14 Silicone-based defoaming agent manufactured by Shin-Etsu Chemical Co., Ltd., solids content: 100% by mass, solids density: 1.03 g / cm 3

[0068] Measurement of total chlorine content in cured products of curable resin compositions A copper foil substrate (with copper foil formed on the surface, substrate thickness: 1.9 mm, copper foil thickness: 50 μm) whose surface had been buffed was printed with each curable resin composition using a screen printing method to form a coating film. The thickness of the coating film was adjusted so that the DRY film thickness (dry film thickness) was in the range of 20 μm to 70 μm. Next, the substrate was dried in a dryer at 80°C for 30 minutes, and then heated in the dryer at 150°C for 1 hour to produce a substrate with a cured product. Then, the cured material collected and weighed from the copper foil substrate was used as a sample, and its total chlorine concentration was measured using an organic elemental analysis system (product name: XS-2100H, manufactured by Nitto Seikou Analytech Co., Ltd., a system combining the company's automatic sample combustion device AQF-2100H and Thermo Fisher Scientific's ion chromatograph) at 1,000°C for 30 minutes. The results are shown in Table 1.

[0069] (1) Reflectance of the dried coating film (SCI method) For each curable resin composition in the examples and comparative examples, a dried coating film was formed under the following conditions. Three copper foil substrates (with copper foil formed on the surface, substrate thickness: 1.9 mm, copper foil thickness: 50 μm) were prepared, and a curable resin composition was printed onto each of them by screen printing to form a coating film. The thickness of the coating film was adjusted so that the dry film thickness (dry coating film thickness) differed for each substrate (however, all were in the range of 20 μm to 70 μm). Next, each substrate was dried in a dryer at 80°C for 30 minutes to produce each substrate (a) with a dried coating film. For each substrate (a), the reflectance of the dried coating film was measured using the SCI method at a wavelength of 450 nm with a spectrophotometer (product name: CM-700d, manufactured by Konica Minolta Japan, Inc.). The obtained reflectances were then plotted, and the reflectance at a film thickness of 30 μm was calculated from the approximation curve. These values ​​are shown in Table 2.

[0070] (2) Reflectance of the cured material (SCI method) Each substrate (a) was heated in a dryer at 150°C for 1 hour to produce each substrate (b) with a cured material. For the cured material on each substrate (b), the reflectance of a 30 μm film thickness was calculated under the same conditions as (1) Reflectance of the dried coating film (SCI method) described above, and evaluated based on the following criteria. The results, along with the numerical values, are shown in Table 2. 〇:92% or more (pass) △: 91% or higher, less than 92% (Pass) ×: Less than 91% (failed)

[0071] (3) Reflectance of the cured material after reflow treatment (1 pass) (SCI method) Each substrate (b) was reflowed (heated) using a reflow apparatus under nitrogen atmosphere (oxygen concentration: 2,000 ppm), with a peak temperature of 260°C or higher for 6 seconds and 240°C or higher for 60 seconds, to produce each substrate (c) having the cured material after each reflow treatment (first pass). For the cured material on each substrate (c) after the first reflow process, the reflectance of a 30 μm film thickness was calculated under the same conditions as for (1) the reflectance of the dried coating film (SCI method) described above, and evaluated based on the following criteria. The results, along with the numerical values, are shown in Table 2. 〇:92% or more (pass) △: 91% or higher, less than 92% (Pass) ×: Less than 91% (failed)

[0072] (4) Reflectance of the cured material after reflow treatment (3 times) (SCI method) Each substrate (c) was subjected to two more reflow processes under the same conditions to produce substrates (d) with cured material after each reflow process (third time). For the cured material on each substrate (d) after the third reflow process, the reflectance of a 30 μm film thickness was calculated under the same conditions as for (1) the reflectance of the dried coating film (SCI method) described above, and evaluated based on the following criteria. The results, along with the numerical values, are shown in Table 2. 〇:91% or more (pass) △: 90% or higher, less than 91% (Pass) ×: Less than 90% (failed)

[0073] (5) Difference in reflectivity The difference was calculated by subtracting the reflectance value of the cured material after reflow treatment (1 pass) (SCI method) from the reflectance value of the cured material after a film thickness of 30 μm calculated using the method described in (2) above (SCI method), and the difference obtained was evaluated based on the following criteria. The results are shown in Table 2 along with the numerical values. ○: Less than 1.0% (Pass) △: 1.0% or higher, less than 1.3% (Pass) ×: 1.3% or more (fail)

[0074] (6) Solder heat resistance test For each curable resin composition in the examples and comparative examples, substrates having cured products were prepared under the following conditions. A copper foil substrate (with copper foil formed on the surface, substrate thickness: 1.9 mm, copper foil thickness: 50 μm) whose surface had been buffed was printed with a curable resin composition using a screen printing method to form a coating film. The thickness of the coating film was adjusted so that the dry film thickness (dry coating film thickness) was 50 μm. Next, the substrate was dried in a dryer at 80°C for 30 minutes, and then heated in the dryer at 150°C for 1 hour to produce a substrate with a cured product. Next, flux (product name: ULF-210R, manufactured by Tamura Corporation) was applied to the surface of the cured material, and after the flux was dried, soldering was performed by immersing it in a 260°C solder bath for 10 seconds. Then, the surface of the soldered substrate (the soldered side) was cleaned with isopropyl alcohol, and a tape test was performed. The tape test was conducted in accordance with the provisions of JIS standard H8504:1999, and the test tape used was one with a nominal width of 12 mm to 19 mm as specified in JIS standard Z1522:2009. The tape test was repeated until peeling of the cured material from the substrate was observed, and the number of times until peeling of the cured material occurred (excluding the number of times peeling occurred) was measured and evaluated based on the following criteria. The results, along with the number of times, are shown in Table 2. 〇: 3 times or more (passed) ×: Less than 3 times (failed)

[0075] (7) Adhesion confirmation test A substrate with a cured material was prepared under the same conditions as those described in (6) above for the solder heat resistance confirmation test. Then, the adhesion properties of the aforementioned substrates were confirmed in accordance with the provisions of JIS standard K5600-5-6:1999 (General Test Methods for Paints, Part 5: Mechanical Properties of Paint Films, Section 6: Adhesion (Cross-Cut Method)), and evaluated based on the following criteria. The results, along with the classification, are shown in Table 2. ○: Classification 0 or Classification 1 (Pass) ×: Classification 2 to Classification 5 (Fail)

[0076] [Table 2]

[0077] As described above, each curable resin composition in the examples has a structure that is less susceptible to the effects of heating during curing, and can form cured products with high light reflectivity for visible light. Furthermore, such cured products are less prone to discoloration even when heated (reflow heating) during the mounting of electronic components, thus maintaining high light reflectivity. Therefore, such a curable resin composition can provide a cured product that can be suitably used, for example, as a reflective material for printed circuit boards on which light-emitting elements such as LEDs are mounted.

[0078] Furthermore, each curable resin composition in the examples can form a cured product that prevents a decrease in light reflection efficiency due to discoloration, even at a film thickness of 30 μm. Therefore, such curable resin compositions can provide cured products that can be suitably used as reflective materials for printed circuit boards where microfabrication and weight reduction are required.

[0079] Furthermore, each curable resin composition in the examples can form a cured product that has good adhesion to the material to be coated, such as a printed circuit board. Moreover, the cured product has excellent insulating properties and solder heat resistance. Therefore, such a curable resin composition can provide a highly reliable printed circuit board.

Claims

1. The material comprises a curable resin (A) having a carboxyl group and multiple unsaturated groups in one molecule, an epoxy compound (B), a white inorganic filler (C), and at least one of a curing accelerator and a curing catalyst (D), The epoxy compound (B) has an aromatic structure, The average primary particle size of the white inorganic filler (C) is 0.15 μm or more and 0.3 μm or less. A curable resin composition in which the total chlorine concentration of the cured product is 250 ppm or less.

2. Furthermore, the curable resin composition according to claim 1, further comprising a photopolymerization initiator (E).

3. The curable resin composition according to claim 1, wherein the lower limit of the total chlorine concentration of the cured product of the curable resin composition is 100 ppm.

4. The curable resin composition according to claim 1, wherein the epoxy compound (B) comprises an epoxy compound having a plurality of glycidyl groups.

5. The curable resin composition according to claim 4, wherein the epoxy compound having a plurality of glycidyl groups comprises a bisphenol A type epoxy resin.

6. The curable resin composition according to claim 1, wherein the white inorganic filler (C) comprises at least one selected from the group consisting of titanium dioxide, zirconium oxide, yttria-stabilized zirconium, barium titanate, barium sulfate, alumina, and silica.

7. The white inorganic filler (C) comprises titanium oxide (C-1) having a coating layer made of at least one selected from the group consisting of zirconium oxide, alumina, and silica. The curable resin composition according to claim 6, wherein the titanium dioxide content in the titanium dioxide (C-1) having the coating layer is 90% by mass or more.

8. The curable resin composition according to claim 6, comprising the white inorganic filler (C) surface-treated with an organic substance.

9. The curable resin composition according to claim 1, wherein at least one of the curing accelerator and curing catalyst (D) comprises at least one of a compound having at least one of an amino group and an imino group in one molecule (D-1), and a compound having at least one of a sulfonium cation and an iodonium cation (D-2).

10. The curable resin composition according to claim 9, wherein the compound (D-1) comprises at least one of melamine and a melamine derivative.

11. The curable resin composition according to claim 9, wherein the compound (D-2) comprises a compound having a fluoride anion.

12. A cured product obtained by curing a curable resin composition according to any one of claims 1 to 11.

13. A printed circuit board having the cured product according to claim 12.

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