Curable resin composition and printed circuit board

Abstract

To provide a curable resin composition that can suppress the decrease in visible light reflection efficiency during electronic component mounting and has excellent solder heat resistance. [Solution] A curable resin composition comprising (A) a curable compound having two or more unsaturated groups and one or more carboxyl groups in one molecule, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) titanium dioxide, wherein the average primary particle size of component (E) is 0.15 μm or more and 0.3 μm or less, component (D) has an aromatic structure, and the total chlorine concentration in 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 and a printed wiring board.

Background Art

[0002] In recent years, optical semiconductor devices such as LEDs (light emitting diodes) emit light with high efficiency and have excellent driving characteristics or lighting repetition characteristics. Therefore, optical semiconductor devices are widely used as indicators or light sources. In particular, white LEDs are widely applied as backlights for display devices or flashes for cameras, and are further expected as next-generation lighting devices. Printed wiring boards on which such optical semiconductor devices are mounted are provided with a solder resist or a reflective material that reflects the emitted visible light in order to increase the extraction efficiency of visible light in the irradiation direction. With the miniaturization or weight reduction of white LEDs or printed wiring boards, high reflectivity with thin films is required. Currently, as materials used for solder resists or reflective materials, compositions in which a white inorganic filler is used in combination with a photocurable resin or a thermosetting resin such as an acrylic resin or an epoxy resin are widely used (see Patent Document 1). [[ID=​​​​​​​​​​​​​​​​​​​​However, in the reflective material described in Patent Document 1, it was necessary to use a large amount of white inorganic filler or to make the cured film thick in order to increase the visible light reflection efficiency. As a result, problems arose such as peeling of the coating, a decrease in mechanical strength, problems with dimensional accuracy of microfabrication due to the thickness of the cured film, and problems with weight reduction or miniaturization, making it difficult to apply the reflective material described in Patent Document 1 to recent high-power light-emitting devices. In addition, there was a problem of discoloration due to heating when mounting electronic components (such as LEDs), which reduced the visible light reflection efficiency. Furthermore, the above heating also caused a problem of reduced adhesion to the substrate.

[0005] The present invention aims to provide a curable resin composition and a printed circuit board that can suppress the decrease in visible light reflection efficiency during electronic component mounting and have excellent solder heat resistance. [Means for solving the problem]

[0006] The present invention provides the following curable resin composition and printed circuit board: [1] A curable resin composition comprising (A) a curable compound having two or more unsaturated groups and one or more carboxyl groups in one molecule, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) titanium dioxide, The average primary particle diameter of component (E) is 0.15 μm or more and 0.3 μm or less. The aforementioned component (D) has an aromatic structure, The total chlorine concentration in the cured product of the curable resin composition is 250 ppm or less. Curable resin composition. [2] In the curable resin composition described in [1], The total chlorine concentration in the cured product of the curable resin composition is 100 ppm or less. Curable resin composition. [3] In the curable resin composition described in [1] or [2], The aforementioned component (D) contains a bisphenol A type epoxy resin. Curable resin composition. [4] In the curable resin composition described in any of [1] to [3], The aforementioned component (E) is a core-shell type titanium oxide comprising a core layer and a shell layer, The aforementioned core layer is made of TiO2, The shell layer is made of at least one metal oxide selected from the group consisting of ZrO2, Al2O3, and SiO2. The TiO2 content is 90% by mass or more relative to 100% by mass of component (E). Curable resin composition. [5] A solder resist film comprising a cured product of any of the curable resin compositions described in [1] to [4], Printed circuit board. [Effects of the Invention]

[0007] According to the present invention, a curable resin composition that can suppress the decrease in visible light reflection efficiency during electronic component mounting and has excellent solder heat resistance, as well as a printed wiring board using the same, can be provided. [Modes for carrying out the invention]

[0008] [Curable resin composition] First, the curable resin composition according to this embodiment will be described. The curable resin composition according to this embodiment contains (A) a curable compound having two or more unsaturated groups and one or more carboxyl groups in one molecule, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) titanium dioxide, as described below. Furthermore, the average primary particle size of component (E) must be 0.15 μm or more and 0.3 μm or less, component (D) must have an aromatic structure, and the total chlorine concentration in the cured product of the curable resin composition must be 250 ppm or less. If the total chlorine concentration in the cured product of the curable resin composition exceeds 250 ppm, the decrease in the visible light reflectivity during electronic component mounting cannot be suppressed. Similarly, from the same viewpoint, the total chlorine concentration in the cured product of the curable resin composition is preferably 150 ppm or less, more preferably 100 ppm or less, and particularly preferably 50 ppm or less. The total chlorine concentration can be measured by the method described in the examples below.

[0009] 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 this coating film is adjusted so that the DRY film thickness (dry coating 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 this substrate is used as a sample, and the total chlorine concentration is measured 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) at 1,000°C for 30 minutes.

[0010] According to this embodiment, a curable resin composition can be obtained that suppresses the decrease in visible light reflection efficiency during electronic component mounting and has excellent solder heat resistance. The reason for this is not entirely clear, but the inventors speculate as follows. Specifically, when (E) the average primary particle size of titanium dioxide is 0.15 μm or more and 0.3 μm or less, (D) the epoxy compound has an aromatic structure, and the total chlorine concentration in the cured product of the curable resin composition is 250 ppm or less, the structure is less susceptible to the effects of heating during curing, thus achieving a high light reflectivity for visible light. Furthermore, such cured products are less prone to discoloration due to heating when mounting electronic components (such as light-emitting elements), thus maintaining high light reflectivity. Moreover, such cured products exhibit excellent solder heat resistance.

[0011] [(A) component] Examples of curable compounds used in this embodiment include curable resins (hereinafter also referred to as component (A1)) obtained by reacting the hydroxyl groups of a product (radical polymerizable unsaturated monocarboxylic acid epoxy resin) obtained by reacting a polybasic acid or polybasic acid anhydride with an epoxy product (radical polymerizable unsaturated monocarboxylic acid epoxy resin) obtained by reacting a polybasic acid or polybasic acid anhydride with an epoxy product (radical polymerizable unsaturated monocarboxylic acid epoxy resin) obtained by reacting a polybasic acid or polybasic acid anhydride with an epoxy product (hereinafter also referred to as component (A1)).

[0012] The epoxy equivalent of an epoxy compound having multiple epoxy groups in one molecule is not particularly limited, but is preferably 3,000 g / eq or less, preferably 1,000 g / eq or less, and particularly preferably 100 g / eq to 500 g / eq. Examples of the epoxy compound having a plurality of epoxy groups in one molecule include biphenyl type epoxy resin; naphthalene type epoxy resin; dicyclopentadiene type epoxy resin; rubber-modified epoxy resins such as silicone-modified epoxy resin; ε-caprolactone-modified epoxy resin; 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, о-cresol novolac type epoxy resin and p-tert-butylphenol novolac type epoxy resin; alicyclic epoxy resins having a cyclohexene oxide group, a tricyclodecane oxide group and a cyclopentene oxide group; triglycidyl isocyanurate having a triazine ring such as (2-hydroxyethyl) isocyanurate; dicyclopentadiene type epoxy resin; and adamantane type epoxy resin and the like. These can be used alone or in combination of two or more.

[0013] Examples of the radically polymerizable unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid and the like. Among these, acrylic acid and methacrylic acid are preferably used.

[0014] The epoxy compound having a plurality of epoxy groups in one molecule and the radically polymerizable unsaturated monocarboxylic acid can be reacted by a known method. For example, they can be reacted by heating the epoxy compound having a plurality of epoxy groups in one molecule and the radically polymerizable unsaturated monocarboxylic acid in a suitable diluent.

[0015] As the polybasic acid or polybasic acid anhydride, those having a saturated structure or an unsaturated structure can both be used. Examples of the polybasic acid 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, methylethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid, and diglycolic acid. Further, examples of the polybasic acid anhydride include these anhydrides. These may be used alone or in combination of two or more. The polybasic acid or polybasic acid anhydride is reacted with the hydroxyl group formed in the radically polymerizable unsaturated monocarboxylic acid-modified epoxy resin to introduce a free carboxyl group into the radically polymerizable unsaturated monocarboxylic acid-modified epoxy resin.

[0016] In addition to the component (A1), as the component (A), a curable resin obtained by reacting a glycidyl compound having one or more radically polymerizable unsaturated groups and an epoxy group with the carboxyl group of the component (A1) (hereinafter also referred to as the component (A2)) may be used. These may be used alone or in combination of two or more.

[0017] Examples of the glycidyl compound having one or more radically polymerizable unsaturated groups and an epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and pentaerythritol triacrylate monoglycidyl ether. Note that a plurality of glycidyl groups may be present in one molecule of these glycidyl compounds.

[0018] Furthermore, component (A) may also include curable resins other than component (A1) and component (A2) (hereinafter also referred to as component (A3)), as long as the curable resin has two or more unsaturated groups and one or more carboxyl groups in one molecule. (A3) Examples of components include curable resins having carboxyl groups and multiple ethylenically unsaturated groups in one molecule, obtained by reacting a copolymer obtained by reacting (meth)acrylic acid with a (meth)acrylic acid ester with an alicyclic epoxy skeleton having ethylenically unsaturated bonds 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 two or more ethylenically unsaturated groups and one or more carboxyl groups in one molecule.

[0019] From the viewpoint of reducing the total chlorine concentration in the cured product of the curable resin composition, the total chlorine concentration of component (A) is preferably 300 ppm or less, more preferably 200 ppm or less, and particularly preferably 150 ppm. Component (A) is the main component of the curable resin composition, and its amount is not particularly limited. The amount of component (A) is preferably 10% by mass or more and 50% by mass or less, more preferably 12% by mass or more and 40% by mass or less, and particularly preferably 15% by mass or more and 30% by mass or less, based on 100% by mass of the total solid content of the curable resin composition.

[0020] [(B) Component] The (B) photopolymerization initiator used in this embodiment is not particularly limited, and any known one can be used as appropriate. Examples of photopolymerization initiators include 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone, (9-ethyl-6-nitro-9H-carbazole-3-yl)(4-((1-methoxypropane-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethanolone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-1-(O-acetyloxime), benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy-2-phenylacetophenone. Examples include 2,2-diethoxy-2-phenylacetophenone, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorbenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, and p-dimethylaminobenzoate ethyl ester. These may be used individually or in combination of two or more. Among these, from the viewpoint of photosensitivity, it is preferable to use bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide in combination.

[0021] The amount of component (B) is not particularly limited, but from the viewpoint of photosensitivity and resolution, it is preferably 0.2 parts by mass or more and 40 parts by mass or less, more preferably 0.4 parts by mass or more and 30 parts by mass or less, and particularly preferably 0.6 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of component (A).

[0022] [(C) component] The (C) reactive diluent used in this embodiment is, for example, a photopolymerizable monomer, which is a compound having at least one polymerizable double bond per molecule. The reactive diluent can improve the photocurability of the curable resin composition.

[0023] Reactive diluents include 2-hydroxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 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, Neopentyl glycol di(meth)acrylate hydroxypivalate, Dicyclopentanyl di(meth)acrylate, Caprolactone-modified dicyclopentenyl di(meth)acrylate, Ethylene oxide-modified phosphate di(meth)acrylate, Allylated cyclohexyl di(meth)acrylate, Isocyanurate di(meth)acrylate, Trimethylolpropane tri Examples include (meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, propionic acid-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified (meth)acrylate (such as caprolactone-modified dipentaerythritol hexa(meth)acrylate), and dipentaerythritol hexa(meth)acrylate. These may be used individually or in combination of two or more. Among these, caprolactone-modified (meth)acrylate is preferred from the viewpoint of the various physical properties of the cured film.

[0024] The amount of component (C) is not particularly limited, but is preferably 10 parts by mass or more and 150 parts by mass or less, more preferably 20 parts by mass or more and 120 parts by mass or less, and particularly preferably 30 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of component (A).

[0025] [(D) component] The epoxy compound (D) used in this embodiment is a compound having an aromatic structure and an epoxy group. This epoxy compound can increase the crosslinking density of the cured product of the curable resin composition. Furthermore, this epoxy compound can suppress the decrease in visible light reflectivity when electronic components are mounted. From the viewpoint of reducing the total chlorine concentration in the cured product of the curable resin composition, the total chlorine concentration of component (D) is preferably 3000 ppm or less, more preferably 2000 ppm or less, and particularly preferably 1500 ppm. Examples of epoxy compounds 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, and p-tert-butylphenol novolac type epoxy resin and triphenylmethane type epoxy resin. Among these, epoxy compounds having multiple glycidyl groups are preferred, and bisphenol A type epoxy resin is more preferred. These may be used individually or in combination of two or more.

[0026] (D) The amount of component (D) is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 8 parts by mass or more and 70 parts by mass or less, and more preferably 12 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of component (A).

[0027] [(E) component] The titanium dioxide (E) used in this embodiment is capable of producing a white cured product of a curable resin composition. Furthermore, the average primary particle diameter of component (E) must be between 0.15 μm and 0.3 μm. If this average primary particle diameter is outside the above range, the reflectivity will be insufficient when the cured product of the curable resin composition is used as a reflective material. From a similar viewpoint, the average primary particle diameter of component (E) is preferably between 0.2 μm and 0.3 μm, and particularly preferably between 0.25 μm and 0.3 μm. The average primary particle diameter of component (E) is measured using a transmission electron microscope (TEM), by measuring the diameters of 200 randomly selected particles and calculating the average value of those particle diameters.

[0028] From the viewpoint of the dispersibility of component (E) in the resin component, component (E) is preferably a core-shell type titanium oxide comprising a core layer and a shell layer. Furthermore, it is preferable that the core layer is made of TiO2 and the shell layer is made of at least one metal oxide selected from the group consisting of ZrO2, Al2O3, and SiO2. In addition, it is preferable that the TiO2 content is 90% by mass or more relative to 100% by mass of component (E). Furthermore, from the viewpoint of further improving the dispersibility of component (E), it is preferable that the white inorganic filler is subjected to an organic surface treatment (such as a silane coupling agent).

[0029] From the viewpoint of the reflectance of the cured product of the curable resin composition, the amount of component (E) is preferably 30 parts by mass or more and 400 parts by mass or less, more preferably 70 parts by mass or more and 350 parts by mass or less, and more preferably 150 parts by mass or more and 300 parts by mass or less, per 100 parts by mass of component (A).

[0030] [Thermosetting catalyst] The curable resin composition according to this embodiment may contain a thermosetting catalyst. This cresol novolac type epoxy acrylate can improve the thermosetting properties of the curable resin composition. Examples of thermosetting catalysts include boron trifluoride-amine complex, dicyandiamide (DICY) and its derivatives, organic acid hydrazides, diaminomaleonitrile (DAMN) and its derivatives, guanamine and its derivatives, melamine and its derivatives, amineimide (AI), aromatic dimethylurea, and polyamines. These may be used individually or in combination of two or more.

[0031] The amount of thermosetting catalyst added is not particularly limited, but is preferably 0.1 parts by mass or more and 20 parts by mass or less, and particularly preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of component (A).

[0032] In the curable resin composition according to this embodiment, in addition to components (A) to (E) and the thermosetting catalyst, inorganic fillers other than component (E), various additives, flame retardants, colorants, and non-reactive diluents may be added as needed.

[0033] Inorganic fillers other than component (E) include talc, barium sulfate, alumina, silica, and mica. When using extender pigments, the amount of extender pigment is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 5 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of component (A).

[0034] Examples of additives include silicone-based, hydrocarbon-based, and acrylic-based defoamers, (meth)acrylic polymers, urethane beads, and organic bentonite fillers, as well as thixotropic agents such as polycarboxylic acid amides. However, from the viewpoint of insulation reliability, it is preferable to reduce the amount of organic fillers used, and it is particularly preferable not to use them. When various additives are used, the amount used is preferably 20 parts by mass or less, and more preferably 1 to 10 parts by mass, per 100 parts by mass of component (A).

[0035] Examples of flame retardants include aluminum hydroxide and phosphorus-based flame retardants. The amount of flame retardant is not particularly limited, but it is preferably 2 parts by mass or more and 60 parts by mass or less, and more preferably 5 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of component (A).

[0036] Non-reactive diluents are components used to adjust the viscosity, coatability, or drying properties of a curable resin composition. Examples of non-reactive diluents include organic solvents. Examples of organic solvents include ketones such as methyl ethyl ketone, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, n-propanol, isopropanol, cyclohexanol, and propylene glycol monomethyl ether, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, cellosolves such as cellosolve and butyl cellosolve, carbitols such as carbitol and butyl carbitol, and esters such as ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, diethylene glycol monomethyl ether acetate, ethyl diglycol acetate, and propylene glycol monomethyl ether acetate. The amount of non-reactive diluent is not particularly limited, but is preferably 2 to 50 parts by mass, and particularly preferably 5 to 25 parts by mass, per 100 parts by mass of component (A).

[0037] The method for producing the curable resin composition according to the above embodiment is not limited to a specific method. For example, after blending each of the above components in a predetermined proportion, the composition can be produced by kneading or mixing at room temperature using a kneading means such as a three-roll mill, ball mill, or sand mill, or by a stirring means such as a super mixer or planetary mixer. Furthermore, pre-kneading or pre-mixing may be performed before the kneading or mixing as needed.

[0038] [Printed circuit board] Next, a printed circuit board according to this embodiment will be described. The printed circuit board according to this embodiment comprises a solder resist film made from a cured product of the curable resin composition according to this embodiment described above. The printed circuit board according to this embodiment can be manufactured by forming a solder resist film using the curable resin composition according to this embodiment described above. The printed circuit board may be a flexible printed circuit board or a rigid printed circuit board.

[0039] Specifically, first, the curable resin composition according to this embodiment is applied to the entire surface of the printed circuit board, and then pre-dried to form a coating film. Here, examples of coating methods include screen printing, bar coating, applicator coating, blade coating, knife coating, roll coating, gravure coating, and spray coating. The pre-drying conditions vary depending on the type of curable resin composition and are not particularly limited, but for example, heating at a temperature in the range of 60°C to 80°C for a period of 15 minutes to 60 minutes is sufficient. Such pre-drying volatilizes solvents and other substances in the curable resin composition, allowing for the formation of a tack-free coating film. The thickness of the coating film (DRY film thickness) is not particularly limited, but is usually between 5 μm and 200 μm, and preferably between 10 μm and 70 μm.

[0040] Furthermore, a dry film may be used when forming the coating. The dry film has a laminated structure comprising a support film (a thermoplastic resin film such as polyethylene terephthalate film or polyester film), a curable resin composition layer coated on the support film, and a cover film (a thermoplastic resin film such as polyethylene terephthalate film or polyester film) that protects the curable resin composition layer. By peeling off the cover film of the dry film and bonding the curable resin composition layer to the printed circuit board, a coating can be formed on the printed circuit board.

[0041] Next, a negative film having a pattern in which areas other than the lands of the circuit pattern are translucent is placed in close contact with the coating of the curable resin composition, and ultraviolet light is irradiated from above. The exposure dose at this time can be appropriately set depending on the type of curable resin composition and the type of exposure equipment. For example, the exposure dose may be 10 mJ / cm². 2More than 1000mJ / cm 2 The following is preferable:

[0042] Next, the exposed coating is developed by removing the unexposed areas with a dilute alkaline aqueous solution. This allows openings corresponding to the circuit pattern to be created in the coating. Examples of development methods include the spray method and the shower method. Examples of dilute alkaline aqueous solutions include aqueous solutions of sodium carbonate containing 0.5% to 5% by mass.

[0043] Next, the developed printed circuit board is subjected to heat treatment (hereinafter sometimes referred to as post-curing). This allows for the formation of an insulating film (solder resist film) with the desired pattern on the printed circuit board. The heat treatment conditions vary depending on the type of curable resin composition and are not particularly limited. For example, a hot air circulation type dryer and a far-infrared furnace can be used as the heat treatment furnace. When using a hot air circulation type dryer, the heat treatment temperature is preferably 130°C to 170°C, and the heat treatment time is preferably 30 minutes to 120 minutes. Furthermore, when using a far-infrared furnace, the heat treatment temperature is preferably 200°C to 250°C, and the heat treatment time is preferably 3 minutes to 10 minutes. [Examples]

[0044] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited in any way by these examples. The materials used in the examples and comparative examples are listed below.

[0045] (Component A) Carboxyl group-containing curable resin: Acrylic oligomer (Mw: 14000, Solids content: 45%, Dipropylene glycol monomethyl ether: 55%, Solids content acid value: 66 mg KOH / g, Total chlorine concentration: 115 ppm), Product name "Cychromer ACA-Z251", Manufactured by Daicel Ornex Co., Ltd. ((B) component) Photopolymerization initiator A: 2,4,6-trimethylbenzoyldiphenylphosphine oxide, trade name "Chemcure TPO", manufactured by Chembridge. Photopolymerization initiator B: Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, trade name "Chemcure 81", manufactured by Chembridge. ((C) component) Reactive diluent A: Dipentaerythritol penta and hexaacrylate, trade name "M-400", manufactured by Toagosei Co., Ltd. Reactive diluent B: Caprolactone-modified acrylate, trade name "DPCA-120", manufactured by Nippon Kayaku Co., Ltd. Reactive diluent C: Glycerin triacrylate, trade name "M-930", manufactured by Toagosei Co., Ltd. ((D) component) Epoxy compound A: Bisphenol A type epoxy resin (total chlorine concentration: 1720 ppm), trade name "jER828EL", manufactured by Mitsubishi Chemical Corporation. Epoxy compound B: Bisphenol A type epoxy resin (total chlorine concentration: 1260 ppm), trade name "jER828US", manufactured by Mitsubishi Chemical Corporation. Epoxy compound C: Bisphenol A type epoxy resin (total chlorine concentration: 460 ppm), product name "EPICLON EXA-850CRP", manufactured by DIC Corporation. Epoxy compound D: Bisphenol A type epoxy resin (total chlorine concentration: 8600 ppm), trade name "jER828", manufactured by Mitsubishi Chemical Corporation. Epoxy compound E: Alicyclic epoxy resin (total chlorine concentration: 5 ppm), trade name "Showfree CDMDG", manufactured by Resonaq Corporation. ((E) component) Titanium dioxide: Titanium dioxide (silica, alumina, siloxane treated), product name "PF-728", manufactured by Ishihara Sangyo Co., Ltd. (Other ingredients) Inorganic filler A: Barium sulfate, product name "B-30", manufactured by Sakai Chemical Industry Co., Ltd. Inorganic filler B: Fumed silica, product name "Leoseal DM-20S", manufactured by Tokuyama Corporation. Thermosetting catalyst: Melamine, manufactured by Nissan Chemical Corporation. Antifoaming agent: Silicone-based antifoaming agent, product name "X-50-1095C", manufactured by Shin-Etsu Chemical Co., Ltd. Non-reactive diluent: Diethylene glycol monomethyl ether acetate, trade name "EDGAC", manufactured by Sanyo Chemical Industries, Ltd.

[0046] [Example 1] 33.3 parts by mass of carboxyl group-containing curable resin, 1.5 parts by mass of photopolymerization initiator A, 0.9 parts by mass of photopolymerization initiator B, 5.1 parts by mass of reactive diluent A, 4.5 parts by mass of reactive diluent B, 2 parts by mass of reactive diluent C, 4.7 parts by mass of epoxy compound A, 0.4 parts by mass of thermosetting catalyst, 0.6 parts by mass of defoamer, 37 parts by mass of titanium dioxide, 8.2 parts by mass of inorganic filler A, 0.5 parts by mass of inorganic filler B, and 1.3 parts by mass of non-reactive diluent were placed in a container, pre-mixed with a stirrer, and then mixed and dispersed at room temperature using a three-roll roller to obtain a curable resin composition. Then, a copper-clad laminate (conductor (Cu foil) thickness: 50 μm, substrate thickness: 1.6 mm) was surface-treated by buff polishing, and the resulting curable resin composition was applied by screen printing to obtain a coated substrate with a dry film thickness of 20-70 μm. After application, pre-drying was performed in a box oven at 80°C for 20 minutes. After pre-drying, the coating film was exposed to light using an exposure device (HMW-680GW manufactured by Oak Manufacturing Co., Ltd.) at an exposure dose of 300 mJ / cm². 2 Exposure was performed under the following conditions. After exposure, development was carried out using a 1% by mass sodium carbonate aqueous solution under the conditions of developer temperature 30°C, spray pressure 0.2 MPa, and development time 60 seconds. Subsequently, post-curing was performed in a box furnace at 150°C for 60 minutes to form a solder resist film on the substrate, and evaluation substrates were prepared. Three evaluation substrates with different coating thicknesses (20 μm, 50 μm, and 70 μm) were prepared.

[0047] [Examples 2-3] A curable resin composition and an evaluation substrate were obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1. [Comparative Examples 1-2] A curable resin composition and an evaluation substrate were obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1.

[0048] [Evaluation of curable resin compositions] The curable resin composition was evaluated (total chlorine concentration, reflectance, reflectance after reflow treatment, decrease in reflectance after reflow treatment, solder heat resistance) using the following method. The results are shown in Table 1. (1) Total chlorine concentration A coating film was taken from an evaluation substrate and used as a sample. The total chlorine concentration (in ppm) of this sample was measured using an automated sample combustion device "AQF-2100H" and an ion chromatograph manufactured by Chromeleon, at a temperature of 1000°C for 30 minutes. (2)Reflectance For three evaluation substrates with different coating thicknesses, the SCI at 450 nm was measured using a spectrophotometer (product name "CM-700d," manufactured by Konica Minolta). The obtained reflectances were plotted, and the reflectance converted to a thickness of 25 μm was calculated from the approximation curve. (3) Reflectance after reflow treatment Three evaluation substrates with different coating thicknesses were subjected to three reflow processes under nitrogen atmosphere (oxygen concentration: 2000 ppm), with a peak temperature of 260°C or higher for 6 seconds and a melting temperature of 240°C or higher for 64 seconds. For each of these reflow-treated evaluation substrates, the SCI at 450 nm was measured using a spectrophotometer (product name "CM-700d," Konica Minolta). The obtained reflectances were plotted, and the reflectance converted to a thickness of 30 μm was calculated from the approximation curve. (4) Amount of reflectivity reduction after reflow treatment Based on the reflectivity of the evaluation substrate (post-curing reflectivity) and the reflectivity after reflow processing, the amount of reflectivity reduction after reflow processing was calculated using the following formula. (Reduction in reflectivity after reflow treatment) = (Reflectivity after post-curing) - (Reflectivity after reflow treatment) Then, the amount of reflectivity reduction after reflow treatment was evaluated according to the following criteria. ○: The decrease in reflectivity after reflow treatment is less than 6%. ×: The decrease in reflectivity after reflow treatment is 6% or more. (5) Solder heat resistance Using an evaluation substrate with a coating thickness of 50 μm, Tamura Corporation's flux "ULF-210R" was applied to the coating surface, and after drying, it was immersed in a 260°C solder bath for 10 seconds. After removal, the coating surface was cleaned with IPA, and the presence or absence of coating peeling was checked using a tape peel test. The above procedure was repeated until coating peeling was observed, and the number of times coating peeling did not occur was measured as the durability cycle. Then, the solder heat resistance was evaluated according to the following criteria. ○: The number of times the paint film does not peel off is 3 or more. ×: The number of times paint peeling does not occur is less than 3.

[0049] [Table 1]

[0050] As is clear from the results shown in Table 1, when the curable resin composition according to the present invention was used (Examples 1-3), all results for sensitivity evaluation, gloss value, adhesion, and electrical insulation were confirmed to be good. Therefore, it was confirmed that the present invention can suppress the decrease in visible light reflection efficiency during electronic component mounting and provide a curable resin composition with excellent solder heat resistance. [Industrial applicability]

[0051] The curable resin composition according to the present invention can be suitably used as a technique for forming an insulating coating film having a pattern on a printed circuit board or the like. The curable resin composition according to the present invention is particularly useful as a solder resist for white LEDs.

Claims

1. A curable resin composition comprising (A) a curable compound having two or more unsaturated groups and one or more carboxyl groups in one molecule, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) titanium dioxide, The average primary particle diameter of component (E) is 0.15 μm or more and 0.3 μm or less. The above component (D) has an aromatic structure, The total chlorine concentration in the cured product of the curable resin composition is 250 ppm or less. Curable resin composition.

2. In the curable resin composition according to claim 1, The total chlorine concentration in the cured product of the curable resin composition is 100 ppm or less. Curable resin composition.

3. In the curable resin composition according to claim 1 or claim 2, The aforementioned component (D) contains a bisphenol A type epoxy resin. Curable resin composition.

4. In the curable resin composition according to claim 1 or claim 2, The aforementioned component (E) is a core-shell type titanium oxide comprising a core layer and a shell layer, The aforementioned core layer is TiO ２ It consists of, The aforementioned shell layer is ZrO ２ Al ２ O ３ , and SiO ２ It consists of at least one metal oxide selected from the group comprising, TiO ２ The content of is 90% by mass or more relative to 100% by mass of component (E). Curable resin composition.

5. The invention comprises a solder resist film made from a cured product of the curable resin composition according to claim 1 or claim 2. Printed circuit board.

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