Photosensitive resin composition, dry film, cured product, and electronic component

Abstract

A photosensitive resin composition capable of obtaining excellent whiteness, reflectivity, resolution, and high sensitivity, a dry film, a cured product, and an electronic component. The photosensitive resin composition is a photosensitive resin composition containing a carboxyl-containing resin (A), a phosphorus-based photopolymerization initiator (B), a photobleaching oxime ester-based photopolymerization initiator (C), and titanium oxide (D), wherein the photobleaching oxime ester-based photopolymerization initiator (C) has an absorbance of 0.01-0.20 in THF, at a concentration of 200 ppm, and at an optical wavelength of 405 nm, and has an absorbance of 0.10-1.00 at an optical wavelength of 385 nm, and with respect to 100 parts by mass of a solid component, namely, the carboxyl-containing resin (A), the blending amount of the photobleaching oxime ester-based photopolymerization initiator (C) is 0.2-1.5 parts by mass.

Description

Photosensitive resin composition, dry film, cured product, and electronic component Technical Field

[0001] The present invention relates to a photosensitive resin composition, a dry film having a resin layer comprising the photosensitive resin composition, a cured product of the resin layer comprising the dry film, and an electronic component comprising the cured product. Background Art

[0002] Conventionally, contact exposure, where a photomask is brought into contact with the solder resist to prevent air from entering the surface, has been the mainstream method for exposing a photosensitive resin composition for solder resist to a predetermined pattern. However, with the recent increase in the density of printed wiring boards, direct imaging (DI) exposure, which does not require a photomask, has become increasingly popular due to its superior alignment accuracy. White photosensitive resin compositions, in particular, can form solder resists that reflect LED light and also enable smaller diameters and narrower pitches for LED component mounting areas.

[0003] Direct imaging exposure (sometimes abbreviated as DI exposure) is an exposure method that exposes a photosensitive resin composition while directly scanning using an LED light source, laser light source, or the like. Due to the scanning or repeated exposure, insufficient sensitivity of the photosensitive resin composition associated with exposure in air has become a technical problem. Furthermore, in the case of white photosensitive resin compositions used as white inks, exposure at relatively long wavelengths, such as 385nm to 405nm, has recently become commonplace to prevent side etching. In particular, for white photosensitive resin compositions, which are prone to insufficient sensitivity and side etching, there is a growing demand for photosensitive resin compositions that can achieve sufficient sensitivity.

[0004] As such a material, a photosensitive resin composition containing a resin having a carboxyl group, an epoxy resin, and an oxime ester-based photopolymerization initiator is used as described in Patent Documents 1 to 4.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: CN115903378A

[0008] Patent Document 2: CN104977806A

[0009] Patent Document 3: CN102822284A

[0010] Patent Document 4: CN102770495A Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, the photosensitive resin composition of Patent Document 1 is limited to acylphosphine oxide-based photopolymerization initiators and oxime ester-based photopolymerization initiators with a specific structure. Although the surface curing and degassing properties are excellent, sufficient whiteness and reflectivity may not be obtained. The photosensitive resin composition of Patent Document 2 contains an acylphosphine oxide-based photopolymerization initiator (TPO), an oxime ester-based photopolymerization initiator that does not have absorbance at a light wavelength of 385nm to 405nm, and phthalocyanine blue. Therefore, sufficient sensitivity, whiteness, and reflectivity may not be obtained. Photopolymerization initiators such as TPO (diphenylphosphine oxide-based) and BPO (benzoyl peroxide-based) are not sufficiently sensitive at a light wavelength of 385nm to 405nm, and adding a large amount may also cause problems such as particles. In addition, the photosensitive resin compositions of Patent Documents 3 and 4 contain an acylphosphine oxide-based photopolymerization initiator and an oxime ester-based photopolymerization initiator (NCI-831) that has absorption at a light wavelength of 385nm to 405nm. This indicates that when a photopolymerization initiator such as NCI-831 or titanocene-based photopolymerization initiator (Omnirad 784) is added for exposure at a wavelength of 385 nm to 405 nm, the b* value of the solder resist increases and the reflectivity decreases because these photopolymerization initiators are strongly yellow compounds.

[0013] An object of the present invention is to provide a photosensitive resin composition that can provide a cured product having excellent whiteness, reflectivity, and resolution and that has high sensitivity.

[0014] Another object of the present invention is to provide a dry film having a resin layer composed of the photosensitive resin composition, a cured product thereof, and an electronic component having the cured product.

[0015] The present inventors conducted intensive research and discovered that all of the aforementioned technical problems can be solved by simultaneously blending a phosphorus-based photopolymerization initiator and an oxime ester-based photopolymerization initiator having a specific absorbance and photobleaching properties into a photosensitive resin composition. This led to the completion of the present invention. Photobleaching occurs when a photopolymerization initiator absorbs light and decomposes, resulting in the loss of its original absorbance in the decomposed residue, which in turn allows light to penetrate deeper into the photosensitive resin composition.

[0016] That is, the present invention has the following technical solutions.

[0017] [1] A photosensitive resin composition comprising (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) an oxime ester-based photopolymerization initiator having photobleaching properties, and (D) titanium oxide.

[0018] The (C) photobleachable oxime ester-based photopolymerization initiator has an absorbance of 0.01 to 0.20 at a wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a concentration of 200 ppm in THF,

[0019] The amount of the (C) photobleachable oxime ester photopolymerization initiator is 0.2 parts by mass or more and 1.5 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin solid content.

[0020] In this specification, (C) the oxime ester-based photopolymerization initiator having photobleaching properties may be simply referred to as (C) oxime ester-based photopolymerization initiator. THF is an abbreviation of tetrahydrofuran.

[0021] [2] The photosensitive resin composition according to item 1, wherein the amount of the titanium oxide (D) added is 100 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin (A) solid content.

[0022] [3] A photosensitive resin composition comprising at least a two-component resin composition, characterized in that it comprises (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) an oxime ester-based photopolymerization initiator having photobleaching properties, (D) titanium oxide, (E) an epoxy resin, and (F) a photosensitive monomer.

[0023] The (A) carboxyl group-containing resin, the (B) phosphorus-based photopolymerization initiator, the (C) photobleachable oxime ester-based photopolymerization initiator, and the (D) titanium oxide are contained in different resin compositions from the (E) epoxy resin and the (F) photosensitive monomer.

[0024] The (C) photobleachable oxime ester-based photopolymerization initiator has an absorbance of 0.01 to 0.20 at a wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a concentration of 200 ppm in THF,

[0025] The amount of the (C) photobleachable oxime ester photopolymerization initiator is 0.2 parts by mass or more and 1.5 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin solid content.

[0026] [4] The photosensitive resin composition according to 3, characterized in that the amount of the titanium oxide (D) added is 100 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the solid content of the carboxyl group-containing resin (A).

[0027] [5] A dry film characterized in that it has a resin layer, and the resin layer contains the photosensitive resin composition described in any one of 1 to 4.

[0028] [6] A cured product, characterized in that it is obtained by curing the photosensitive resin composition according to any one of 1 to 4 or the resin layer of the dry film according to 5.

[0029] [7] An electronic component comprising the cured product described in 6.

[0030] Effects of the Invention

[0031] The present invention can provide a photosensitive resin composition that can produce a cured product having excellent whiteness, reflectivity, and resolution, and that is highly sensitive. Furthermore, the present invention can provide a dry film having a resin layer comprising the photosensitive resin composition, a cured product thereof, and an electronic component having the cured product. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 1 is a graph showing the photobleaching properties of a mixed solution of TPO (B) a phosphorus-based photopolymerization initiator and NCI-730 (C) a photobleachable oxime ester-based photopolymerization initiator, that is, the photobleaching phenomenon at 100 ppm TPO and 10 ppm NCI-730.

[0033] 2 is a graph showing the absorbance of NCI-730 as (C) an oxime ester-based photopolymerization initiator having photobleaching properties, namely, the absorbance of NCI-730 (200 ppm, vertical axis abs, horizontal axis 350 to 450 nm).

[0034] 3 is a graph showing the photobleaching phenomenon of NCI-730 as (C) an oxime ester-based photopolymerization initiator having photobleaching properties, namely, the photobleaching phenomenon of NCI-730 (200 ppm, vertical axis abs, horizontal axis 350-450 nm).

[0035] 4 is a graph showing the absorbance of the non-photobleachable oxime ester-based photopolymerization initiator OXE-02 used in Comparative Example 3. That is, the absorbance of OXE-02 (200 ppm, vertical axis abs, horizontal axis 350 to 450 nm).

[0036] Figure 5 is a graph comparing the absorbance of Omnirad 784 used in Comparative Example 2, OXE02 used in Comparative Example 3, and NCI-730 used in Examples 1 to 4. Specifically, it shows the absorbance of NCI-730 (200 ppm, vertical axis abs, horizontal axis 350 to 550 nm). DETAILED DESCRIPTION

[0037] The present invention relates to a photosensitive resin composition, characterized in that it is a photosensitive resin composition comprising (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) an oxime ester-based photopolymerization initiator having photobleaching properties, and (D) titanium oxide.

[0038] The (C) photobleachable oxime ester-based photopolymerization initiator has an absorbance of 0.01 to 0.20 at a wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a concentration of 200 ppm in THF,

[0039] The amount of the photobleachable oxime ester-based photopolymerization initiator (C) is 0.2 parts by mass or more and 1.5 parts by mass or less per 100 parts of the solid content of the carboxyl group-containing resin (A). The photosensitive resin composition of the present invention may be a one-component photosensitive resin composition comprising the above components (A) to (D) or a two-component photosensitive resin composition comprising a base composition comprising the above components (A) to (D) and a curing agent composition comprising other components.

[0040] Hereinafter, each component of the photosensitive resin composition of the present invention will be described in detail.

[0041] (A) Carboxyl-containing resin

[0042] The carboxyl group-containing resin can be alkali-developable by containing a carboxyl group. As the carboxyl group-containing resin (A), various carboxyl group-containing resins known in the art having a carboxyl group in the molecule can be used. In addition, from the perspective of curability and development resistance, it is preferred that the resin have an ethylenically unsaturated bond in the molecule in addition to the carboxyl group, but it is also possible to use a carboxyl group-containing resin that does not have an ethylenically unsaturated double bond.

[0043] Specific examples of carboxyl group-containing resins include the following compounds (both oligomers and polymers). It should be noted that, in this specification, (meth)acrylate refers to a term collectively referring to acrylate, methacrylate and mixtures thereof, and the same applies to other similar expressions.

[0044] (1) Carboxyl group-containing resins obtained by copolymerizing an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, a lower alkyl (meth)acrylate, or isobutylene.

[0045] (2) Carboxyl group-containing polyurethane resins obtained by the polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, and diol compounds containing carboxyl groups such as dimethylol propionic acid and dimethylol butyric acid, as well as diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A-based alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0046] (3) A polyurethane resin obtained by reacting a diisocyanate compound such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, an alicyclic diisocyanate, an aromatic diisocyanate with a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, an acrylic polyol, a bisphenol A-based alkylene oxide adduct diol, a compound having a phenolic hydroxyl group and an alcoholic hydroxyl group, and obtaining a terminal carboxyl-containing polyurethane resin by reacting the terminal of the polyurethane resin with an acid anhydride.

[0047] (4) A photosensitive carboxyl-containing polyurethane resin obtained by a polyaddition reaction of a diisocyanate with a (meth)acrylate of a bifunctional epoxy resin such as a bisphenol A epoxy resin, a hydrogenated bisphenol A epoxy resin, a bisphenol F epoxy resin, a bisphenol S epoxy resin, a dimethylphenol epoxy resin, or a biphenol epoxy resin, or a partially anhydride-modified product thereof, a carboxyl-containing diol compound, and a diol compound.

[0048] (5) A carboxyl group-containing polyurethane resin obtained by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, to the synthesis of the resin of (2) or (4) above, and performing terminal (meth)acrylation.

[0049] (6) A carboxyl group-containing polyurethane resin obtained by adding an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate to the synthesis of the resin of (2) or (4) above, followed by terminal (meth)acrylation of a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule.

[0050] (7) A photosensitive carboxyl group-containing resin obtained by reacting a polyfunctional epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the hydroxyl groups present in the side chains.

[0051] (8) A carboxyl group-containing resin obtained by reacting a polyfunctional epoxy resin obtained by further epoxidizing the hydroxyl groups of a bifunctional epoxy resin with epichlorohydrin with (meth)acrylic acid, and adding a dibasic acid anhydride to the generated hydroxyl groups.

[0052] (9) A carboxyl group-containing polyester resin obtained by reacting a polyfunctional oxetane resin with a dicarboxylic acid and adding a dibasic acid anhydride to the generated primary hydroxyl group.

[0053] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, a reaction product obtained by reacting the reaction product with an unsaturated group-containing monocarboxylic acid, and a polybasic acid anhydride.

[0054] (11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, and then reacting the resulting reaction product with a monocarboxylic acid containing an unsaturated group, and then reacting the resulting reaction product with a polyacid anhydride.

[0055] (12) A carboxyl group-containing photosensitive resin obtained by reacting an epoxy compound having multiple epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenylethanol, and a monocarboxylic acid containing an unsaturated group, such as (meth)acrylic acid, and reacting the alcoholic hydroxyl group of the resulting reaction product with a polybasic acid anhydride, such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic anhydride.

[0056] (13) A carboxyl group-containing resin having at least one of an amide structure and an imide structure.

[0057] (14) A photosensitive carboxyl resin obtained by further adding a compound having one epoxy group and one or more (meth)acryloyl groups in the molecule, such as glycidyl (meth)acrylate, α-methylglycidyl (meth)acrylate, or 3,4-epoxycyclohexylmethyl methacrylate, to any of the carboxyl resins (1) to (13).

[0058] The carboxyl group-containing resin preferably comprises at least one of the carboxyl group-containing resins described in (1), (7), (8), (10), (11), and (13). In view of whiteness, reflectivity, resolution, high sensitivity, and low sulfur content, the carboxyl group-containing resin (14) is particularly preferably a carboxyl group-containing resin (1) comprising a compound having one epoxy group and one or more (meth)acryloyl groups in its molecule added to the carboxyl group-containing resin described in (1).

[0059] (A) The carboxyl group-containing resin may be used alone or in combination of two or more.

[0060] (A) The acid value of the carboxyl group-containing resin is preferably in the range of 20 mgKOH / g to 140 mgKOH / g, more preferably in the range of 30 mgKOH / g to 120 mgKOH / g. (A) By setting the acid value of the carboxyl group-containing resin in the above range, alkali development can be performed well, and a normal cured product pattern can be formed.

[0061] (A) carboxyl-containing resin is not particularly limited to the resin backbone as long as it has a carboxyl group in the molecule. From the viewpoint of further improvement in insulation reliability and reflectivity, it is preferably free of a phenol backbone. When the carboxyl-containing resin does not contain a phenol backbone, it is less likely to be colored by thermal degradation, and therefore has a tendency to improve reflectivity. A phenol backbone refers to a backbone of an aromatic compound having one or more hydroxyl groups directly bonded to an aromatic ring.

[0062] The weight-average molecular weight of the carboxyl-containing resin (A) varies depending on the resin backbone, but is generally preferably 2,000 to 150,000. A weight-average molecular weight of 2,000 or greater provides excellent non-tackiness of the dried coating, and excellent moisture resistance and resolution of the exposed coating. On the other hand, a weight-average molecular weight of 150,000 or less provides excellent developability and storage stability. More preferably, the weight-average molecular weight is 5,000 to 100,000.

[0063] The amount of the carboxyl group-containing resin (A) blended is preferably in the range of 5% to 80% by mass relative to the solid content of the photosensitive resin composition, more preferably in the range of 10% to 70% by mass, and particularly preferably in the range of 12% to 60% by mass. A blend of 5% to 5% by mass can suppress a decrease in the strength of the cured film. On the other hand, a blend of 80% to 80% by mass prevents excessive viscosity of the photosensitive resin composition, resulting in excellent coating properties.

[0064] (B) Phosphorus-based photopolymerization initiator

[0065] The photosensitive resin composition of the present invention contains (B) a phosphorus-based photopolymerization initiator other than the (C) oxime ester-based photopolymerization initiator having a specific absorbance and photobleaching properties, which will be described later. The (B) phosphorus-based photopolymerization initiator can be used alone or in combination of two or more. The (B) phosphorus-based photopolymerization initiator preferably has photobleaching properties. By having photobleaching properties together with the (C) oxime ester-based photopolymerization initiator, the resolution can be further improved. It can be understood from the absorbance spectrum of Figure 1 that the (B) phosphorus-based photopolymerization initiator and the (C) oxime ester-based photopolymerization initiator have photobleaching properties. That is, a mixed solution of TPO as the (B) phosphorus-based photopolymerization initiator and NCI-730 as the (C) oxime ester-based photopolymerization initiator is prepared, and when the exposure amount of the mixed solution is increased, the absorbance of the mixed solution at three wavelengths (365nm, 385nm, 405nm) basically disappears. Therefore, it was found that both the (B) phosphorus-based photopolymerization initiator and the (C) oxime ester-based photopolymerization initiator have photobleaching properties.

[0066] As the phosphorus-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator is preferred. Specifically, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, etc. can be listed. As commercial products, Omnirad TPO H and Omnirad TPO H819 manufactured by IGM Resins BV can be listed. All of these acylphosphine oxide-based photopolymerization initiators are initiators with photobleaching properties.

[0067] The compounding amount of these (B) phosphorus-based photopolymerization initiators is preferably 0.01 mass parts or more and 15 mass parts or less relative to 100 mass parts of (A) carboxyl-containing resin solid content. When it is 0.01 mass parts or more, the light curing property on the copper is improved, the peeling of the cured film is prevented, and the characteristics of the cured film such as chemical resistance are improved. On the other hand, when it is 15 mass parts or less, the light absorption of the surface of the cured film becomes appropriate, and the deep curing property is improved. More preferably, it is 0.5 mass parts or more and 12 mass parts or less.

[0068] In addition, examples of photopolymerization initiators (sometimes referred to simply as "other photopolymerization initiators") that can be suitably used in the photosensitive resin composition of the present invention, other than the above-mentioned (B) phosphorus-based photopolymerization initiator and (C) photobleachable oxime ester-based photopolymerization initiator, include benzoin compounds, acetophenone compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds.

[0069] Specific examples of the benzoin compound include benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.

[0070] Specific examples of the acetophenone compound include acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone.

[0071] Specific examples of the anthraquinone compound include 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 1-chloroanthraquinone.

[0072] Specific examples of the thioxanthone compound include 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone.

[0073] Specific examples of the ketal compound include acetophenone dimethyl ketal and benzyl dimethyl ketal.

[0074] Specific examples of the benzophenone compound include benzophenone, 4-benzoyl diphenyl sulfide, 4-benzoyl-4′-methyl diphenyl sulfide, 4-benzoyl-4′-ethyl diphenyl sulfide, and 4-benzoyl-4′-propyl diphenyl sulfide.

[0075] Specific examples of the tertiary amine compound include ethanolamine compounds and compounds having a dialkylaminobenzene structure. Examples of commercially available products include dialkylaminobenzophenones such as 4,4'-dimethylaminobenzophenone (NISSOCURE (registered trademark) MABP manufactured by Nippon Soda Co., Ltd.) and 4,4'-diethylaminobenzophenone (EAB manufactured by Hodogaya Chemical Co., Ltd.), coumarin compounds containing a dialkylamino group such as 7-(diethylamino)-4-methyl-2H-1-benzopyran-2-one (7-(diethylamino)-4-methylcoumarin), ethyl 4-dimethylaminobenzoate (KAYACURE (registered trademark) EPA manufactured by Nippon Kayaku Co., Ltd.), ethyl 2-dimethylaminobenzoate (Quantacure DMB manufactured by International Bio-Synthetics Co., Ltd.), and (n-butyloxy)ethyl 4-dimethylaminobenzoate (Quantacure BEA), isopentyl ethyl p-dimethylaminobenzoate (KAYACURE DMBI manufactured by Nippon Kayaku Co., Ltd.), 2-ethylhexyl 4-dimethylaminobenzoate (Esolol 507 manufactured by Van Dyk Co., Ltd.), etc.

[0076] Among these, thioxanthone compounds and tertiary amine compounds are preferred. In particular, from the perspective of deep curing properties, it is preferred to include a thioxanthone compound. Among these, thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone are preferred. For example, commercially available products include 2,4-diisopropylthioxanthone (manufactured by ITX Tianjin Jiuri New Materials Co., Ltd.).

[0077] The amount of the thioxanthone compound added is preferably 10 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin (A). When the amount of the thioxanthone compound added is 10 parts by mass or less, thick film curing properties are good. More preferably, it is 5 parts by mass or less.

[0078] The total amount of such other photopolymerization initiators is preferably 0 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin (A). When the amount is 35 parts by mass or less, deep curing properties are good.

[0079] It should be noted that these other photopolymerization initiators absorb specific wavelengths, sometimes resulting in reduced sensitivity and acting as UV absorbers. However, they are not solely used to enhance the sensitivity of photosensitive resin compositions. They can absorb specific wavelengths of light as needed to enhance surface photoreactivity, modify the line shape and opening of the cured product to vertical, tapered, or inverted tapered shapes, and improve the processing accuracy of line width and opening diameter.

[0080] (C) Oxime ester-based photopolymerization initiator with photobleaching properties

[0081] The photosensitive resin composition of the present invention can obtain a photosensitive resin composition having high sensitivity and low sulfur content, by adding (C) an oxime ester photopolymerization initiator having specific absorbance and photobleaching properties, thereby obtaining a cured product having excellent whiteness, reflectivity, and resolution.

[0082] That is, the present inventors conducted intensive research and found that by using (C) an oxime ester-based photopolymerization initiator as a photopolymerization initiator, which is blended in THF in a specific amount and has an absorbance of 0.010 to 0.20 at a concentration of 200 ppm at a light wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a light wavelength of 385 nm, it is possible to suppress discoloration of the cured product and achieve high sensitivity under DI exposure at a light wavelength of 385 nm to 405 nm.

[0083] (C) Oxime ester-based photopolymerization initiators having photobleaching properties, as shown in FIG2 , preferably have an absorbance of 0.01 to 0.10 at a wavelength of 405 nm and a value of 0.10 to 0.80 at a concentration of 200 ppm in THF, in order to more effectively achieve the effects of the present invention. If the absorbance at 405 nm is less than 0.01 and / or the absorbance at 385 nm is less than 0.10, sufficient sensitivity cannot be achieved. If the absorbance at 405 nm is greater than 0.10 and / or the absorbance at 385 nm is greater than 0.80, the cured product tends to turn yellow, making it difficult to achieve excellent whiteness and reflectivity, which is not preferred.

[0084] The absorbance measurement method used in this specification is as follows: Each photopolymerization initiator was dissolved in THF to a concentration of 200 ppm, and the absorbance was measured at a wavelength of 300-600 nm using an ultraviolet-visible near-infrared spectrophotometer (V-670 manufactured by JASCO Corporation) based on UV-vis (Ultraviolet-visible spectroscopy).

[0085] Figure 3 shows the photobleaching phenomenon of the photobleachable oxime ester-based photopolymerization initiator (C). As the exposure dose to the photobleachable oxime ester-based photopolymerization initiator (C) increases, the absorbance decreases. This indicates that when the photobleachable oxime ester-based photopolymerization initiator (C) absorbs light and decomposes, the decomposed residue loses its original absorbance, allowing light to penetrate deeper into the structure.

[0086] The amount of the photobleachable oxime ester photopolymerization initiator (C) is 0.2 to 1.5 parts by mass relative to 100 parts by mass of the carboxyl group-containing resin solids. It is more preferably 0.3 to 1.5 parts by mass. If the amount is less than 0.2 parts by mass, high sensitivity may be difficult to achieve. On the other hand, if the amount is greater than 1.5 parts by mass, resolution may decrease (easily causing side erosion).

[0087] It should be noted that when the amount of the photobleachable oxime ester-based photopolymerization initiator (C) having a specific absorbance is increased, there is a tendency for the b* value to become higher (turn yellow). By adding a blue colorant, it is possible to suppress the increase in the b* value while maintaining high sensitivity. In addition, regarding blue colorants, ultramarine blue and cobalt blue are generally used for white solder resist, but phthalocyanine blue is not used. Cobalt blue does not contain sulfur and is therefore more preferred. The amount of cobalt blue mixed is preferably 0.1 parts by mass or more and 3.8 parts by mass or less relative to 100 parts by mass of the carboxyl-containing resin solid content (A), and more preferably 0.1 parts by mass or more and 3.5 parts by mass or less. When it is less than 0.1 parts by mass, there is a tendency for the b* value to be difficult to reduce. When it is greater than 3.8 parts by mass, it is possible to affect the reflectivity.

[0088] Examples of commercially available products of the (C) photobleachable oxime ester-based photopolymerization initiator having a specific absorbance include Adeka Argus NCI-730 and NCI-930 (manufactured by ADEKA Corporation).

[0089] (D) Titanium oxide

[0090] The photosensitive resin composition of the present invention contains (D) titanium oxide as a white colorant from the viewpoint of improving high colorability and reflectivity.

[0091] As the titanium oxide contained in the photosensitive resin composition of the present invention, titanium oxide produced by the sulfuric acid method or the chlorine method, rutile titanium oxide, anatase titanium oxide, or titanium oxide that has been surface-treated with a hydrated metal oxide or a surface-treated with an organic compound can be used. Titanium oxide is classified into rutile and anatase types based on its crystal structure. Titanium oxide can be rutile or anatase, but rutile is preferred from the perspectives of colorability, shielding properties, and stability. Anatase, which is also a titanium oxide, has a higher whiteness than rutile and is generally used as a white pigment. However, anatase titanium oxide has photocatalytic activity, so sometimes, especially light irradiated from an LED, can cause discoloration of the resin in the photosensitive resin composition. In contrast, although the whiteness of rutile titanium oxide is slightly inferior to that of anatase, since it has almost no photoactivity, it significantly suppresses the degradation (yellowing) of the resin caused by the photoactivity of titanium oxide, and is also stable against heat. Therefore, when used as a white colorant in the insulating layer of a printed circuit board encapsulating an LED, high reflectivity can be maintained for a long period of time.

[0092] From the perspective of exerting the reflectivity-enhancing effect brought about by (D) titanium oxide, the amount of titanium oxide added is preferably 100 parts by mass or more and 400 parts by mass or less, more preferably 150 parts by mass or more and 300 parts by mass or less, and particularly preferably 180 parts by mass or more and 250 parts by mass or less, relative to 100 parts by mass of the solid content of the (A) carboxyl group-containing resin.

[0093] (D) The average particle size of titanium oxide is preferably less than 50 μm, more preferably an average particle size of 0.1 μm or more and 25 μm or less, and particularly preferably an average particle size of 0.2 μm or more and 10 μm or less. Here, the average particle size refers to the average particle size of titanium oxide monomer or titanium oxide dispersion. In addition, a nanofiller having a partial average particle size of less than 100 nm can also be used. Here, in this specification, the average particle size of titanium oxide is an average particle size (D50) that includes not only the particle size of primary particles but also the particle size of secondary particles (agglomerates). The average particle size can be measured using a measuring device based on a laser diffraction method such as Microtrac MT 3300EXII manufactured by Microtrac BEL, or a measuring device based on a dynamic light scattering method such as Nanotrac Wave II UT 151 manufactured by Microtrac BEL.

[0094] The titanium oxide (D) may also be a surface-treated filler (i.e., a surface-treated filler). The surface treatment of the inorganic filler (B) is not particularly limited, and known and commonly used methods such as surface treatment with coupling agents such as silane-based, titanate-based, aluminate-based, and zircoaluminate-based agents, and surface treatment without the introduction of organic groups such as alumina treatment may be used.

[0095] Examples of commercially available products of titanium oxide (D) include commercially available rutile titanium oxide such as Taipaque R-820, Taipaque R-830, Taipaque R-930, Taipaque R-550, Taipaque R-630, Taipaque R-680, Taipaque R-670, Taipaque R-780, Taipaque R-850, Taipaque CR-50, Taipaque CR-57, Taipaque CR-Super70, Taipaque CR-80, Taipaque CR-90, Taipaque CR-93, Taipaque CR-95, Taipaque CR-97, Taipaque CR-60, Taipaque CR-63, Taipaque CR-67, Taipaque CR-58, and Taipaque CR-70. CR-85, TaipaqueUT771 (manufactured by Ishihara Sangyo Co., Ltd.); Ti-Pure R-100, Ti-Pure R-101, Ti-Pure R-102, Ti-Pure R-103, Ti-Pure R-104, Ti-Pure R-105, Ti-Pure R-108, Ti-Pure R-900, Ti-Pure R-902, Ti-Pure R-960, Ti-Pure R-706, Ti-Pure R-931 (DuPont Co., Ltd.); R-25, R-21, R-32, R-7E, R-5N, R-61N, R-62N, R-42, R-45M, R-44, R-49S, GTR-100, GTR-300, D-918, TCR-29, TCR-52, FTR-700 (manufactured by Sakai Chemical Industry Co., Ltd.), etc.

[0096] Among the above, Taipaque CR-50, Taipaque CR-57, Taipaque CR-80, Taipaque CR-90, Taipaque CR-93, Taipaque CR-95, Taipaque CR-97, Taipaque CR-60, Taipaque CR-63, Taipaque CR-67, Taipaque CR-58, Taipaque CR-85, and Taipaque UT771 (manufactured by Ishihara Sangyo Co., Ltd.) produced by the chlorine process; Ti-Pure R-100, Ti-Pure R-101, Ti-Pure R-102, Ti-Pure R-103, Ti-Pure R-104, Ti-Pure R-105, Ti-Pure R-108, Ti-Pure R-900, Ti-Pure R-902, and Ti-Pure R-960, Ti-Pure R-706, Ti-Pure R-931 (manufactured by DuPont Co., Ltd.).

[0097] In addition, as anatase-type titanium oxide, a known substance can be used. As commercially available anatase-type titanium oxide, TITON A-110, TITON TCA-123E, TITON A-190, TITON A-197, TITON SA-1, TITON SA-1L (manufactured by Sakai Chemical Industry Co., Ltd.); TA-100, TA-200, TA-300, TA-400, TA-500, TP-2 (manufactured by Fuji Titanium Industry Co., Ltd.); TITANIX JA-1, TITANIX JA-3, TITANIX JA-4, TITANIX JA-5, TITANIX JA-C (manufactured by Teika Co., Ltd.); KA-10, KA-15, KA-20, KA-30 (manufactured by Titanium Industry Co., Ltd.); Taipaque A-100, Taipaque A-220, Taipaque W-10 (manufactured by Ishihara Industry Co., Ltd.), etc.

[0098] In addition, based on the general purpose of this field, (D) inorganic fillers other than titanium oxide may be included. Examples of inorganic fillers other than titanium oxide (D) include silicon dioxide, barium sulfate, barium titanate, Neuburg silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, etc. Such inorganic fillers other than titanium oxide (D) may be used alone or in combination of two or more. Of course, they may not be used.

[0099] (E) Epoxy resin

[0100] The photosensitive resin composition of the present invention preferably contains an epoxy resin from the perspective of obtaining a cured product having excellent surface curability, insulation reliability, and solder heat resistance. Examples of the epoxy resin include conventionally known epoxy resins such as bisphenol A-type, bisphenol F-type, aminophenol-type, and phenol novolac-type epoxy resins.

[0101] It should be noted that, in the photosensitive resin composition of the present invention, these epoxy resins may be used alone or in combination of two or more, and either liquid epoxy resin or solid epoxy resin may be used.

[0102] Examples of commercially available products of the epoxy resin (E) include jER828, jER834, jER1001, and jER1004 manufactured by Mitsubishi Chemical Corporation; EPICLON840, EPICLON850, EPICLON1050, and EPICLON2055 manufactured by DIC Corporation; and YD-011, YD-013, YD-127, and YD-128 manufactured by Nippon Steel Chemicals & Materials Co., Ltd. Bisphenol A epoxy resins such as NPEL-128E (all trade names) manufactured by Plastics Co., Ltd.; brominated epoxy resins such as jERYL903 manufactured by Mitsubishi Chemical Corporation, EPICLON152 and EPICLON165 manufactured by DIC Corporation, and Epotote YDB-400 and YDB-500 (all trade names) manufactured by Nippon Steel Chemicals & Materials Co., Ltd.; jER152 and jER154 manufactured by Mitsubishi Chemical Corporation, EPICLONN-730, EPICLONN-770 and EPICLONN-865 manufactured by DIC Corporation, Epotote YDCN-701 and YDCN-704 manufactured by Nippon Steel Chemicals & Materials Co., Ltd., EPPN-201 and EOC Novolac-type epoxy resins such as N-1025, EOCN-100, EOCN-104S, and RE-306 (all trade names); bisphenol F-type epoxy resins such as EPICLON 830 manufactured by DIC Corporation, jER807 manufactured by Mitsubishi Chemical Corporation, and Epotote YDF-170, YDF-175, and YDF-2004 manufactured by Nippon Steel Chemicals & Materials Co., Ltd.; hydrogenated bisphenol A-type epoxy resins such as Epotote ST-2004, ST-2007, and ST-3000 manufactured by Nippon Steel Chemicals & Materials Co., Ltd.; jER604 manufactured by Mitsubishi Chemical Corporation, Epotote YH-434 manufactured by Nippon Steel Chemicals & Materials Co., Ltd., and Sumiepoxy manufactured by Sumitomo Chemical Co., Ltd. ELM-120 (both trade names) and other glycidylamine epoxy resins; Daicel Chemical Industry Co., Ltd.Alicyclic epoxy resins such as Celoxide 2021 (trade name) manufactured by Mitsubishi Chemical Corporation; trihydroxyphenylmethane type epoxy resins such as YL-933 manufactured by Mitsubishi Chemical Corporation, EPPN-501 and EPPN-502 (all trade names) manufactured by Nippon Kayaku Co., Ltd.; bixylenol type or biphenol type epoxy resins such as YL-6056, YX-4000 and YL-6121 (all trade names) manufactured by Mitsubishi Chemical Corporation, or mixtures thereof; EBPS-200 manufactured by Nippon Kayaku Co., Ltd., ADEKA EPX-30 manufactured by EPX-30, EXA-1514 manufactured by DIC Corporation (both trade names) and other bisphenol S type epoxy resins; jER157S manufactured by Mitsubishi Chemical Corporation, BNE200D75 manufactured by Shanghai Hongze Chemical Co., Ltd. (both trade names) and other bisphenol A novolac type epoxy resins; jERYL-931 (trade name) manufactured by Mitsubishi Chemical Corporation and other tetrahydroxyphenylethane type epoxy resins; TEPIC (trade name) manufactured by Nissan Chemical Co., Ltd. and other heterocyclic epoxy resins; Blemmer DGT (trade name) manufactured by NOF Corporation and other diglycidyl phthalate resins; ZX-1063 (trade name) manufactured by Nippon Steel Chemical & Materials Co., Ltd. and other tetraglycidyl xylenoyl ethane ethane) resins; naphthalene-containing epoxy resins such as ESN-190 and ESN-360 manufactured by Nippon Steel Chemicals & Materials Co., Ltd., and HP-4032, EXA-4750, and EXA-4700 manufactured by DIC Corporation (all trade names); epoxy resins having a dicyclopentadiene skeleton such as HP-7200 and HP-7200H manufactured by DIC Corporation (both trade names); glycidyl methacrylate copolymer-based epoxy resins such as CP-50S and CP-50M manufactured by NOF Corporation (both trade names); and copolymerized epoxy resins of cyclohexylmaleimide and glycidyl methacrylate. These epoxy compounds may be used alone or in combination of two or more.

[0103] The amount of the epoxy resin (E) blended is preferably 8 parts by mass or more and 60 parts by mass or less, and more preferably 12 parts by mass or more and 40 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin (A) solid content.

[0104] (F) Photosensitive monomer

[0105] The photosensitive resin composition of the present invention may further contain (F) a photosensitive monomer having one or more ethylenically unsaturated groups in the molecule.

[0106] As such photosensitive monomers, for example, conventionally known polyester (meth)acrylates, polyether (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, and urethane (meth)acrylates can be used. Specifically, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-hydroxymethylacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, trishydroxyethyl isocyanurate. Polyacrylates of polyols such as propylene oxide adducts, phenoxyacrylates, bisphenol A diacrylates, and ethylene oxide adducts or propylene oxide adducts of these phenols; polyacrylates of glycidyl ethers such as glycerol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; not limited to the above, examples include acrylates obtained by directly acrylateing a polyol such as polyether polyol, polycarbonate diol, hydroxyl-terminated polybutadiene, and polyester polyol, or by urethane acrylated with a diisocyanate, melamine acrylates, and at least one of various methacrylates corresponding to the above acrylates.

[0107] The amount of the photosensitive monomer is preferably 5 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin solid content (A). More preferably, it is in the range of 10 parts by mass or more and 50 parts by mass or less. When the amount of the photosensitive monomer is 5 parts by mass or more, the photocurability imparting effect is better. On the other hand, when it is 60 parts by mass or less, the dryness to touch of the coating film becomes good.

[0108] additive

[0109] The photosensitive resin composition of the present invention may further contain, as necessary, known additives such as a colorant, a thermosetting catalyst, an anti-aging agent, an antibacterial / antifungal agent, an anti-sagging agent, a thixotropy-imparting agent, a photobase generator, a thermoplastic resin, an elastomer, an organic filler, a release agent, a surface treatment agent, a dispersant, a dispersing aid, a surface modifier, a stabilizer, a phosphor, a cellulose resin, a defoaming agent, a surface tension modifier, a coupling agent, a leveling agent, a sensitizer, a release agent, a lubricant, a plasticizer, an antioxidant, an ultraviolet absorber, a flame retardant, a polymerization inhibitor, a thickener (thixotropic agent), an adhesion-imparting agent, an adhesion aid, and a crosslinking agent as additives other than the above-mentioned (B) phosphorus-based photopolymerization initiator, (C) photobleachable oxime ester-based photopolymerization initiator, and (D) titanium oxide.

[0110] Among them, melamine and its derivatives are preferred. Melamine and its derivatives act as antioxidants, inhibiting oxidation of the conductor (copper) on the substrate, thereby improving the adhesion between the substrate and the cured film. Furthermore, as a thermal curing catalyst, by promoting the reaction between the epoxy resin (E) and the carboxyl group-containing resin (A), the cured product can be improved in terms of chemical resistance, plating resistance, adhesion, hardness, and other properties.

[0111] The photosensitive resin composition of the present invention preferably contains a blue colorant. By including a blue colorant, a cured product exhibiting excellent whiteness, reflectivity, and resolution can be obtained, while also exhibiting high sensitivity. Cobalt blue is particularly preferred as the blue colorant. Cobalt blue exhibits a strong, bright blue color, can reduce the total sulfur content in the composition, and provides an excellent coloring effect for aesthetics.

[0112] The reason for suppressing the total sulfur content in the composition is as follows. Specifically, to improve visible light reflectance and electrode connection reliability, the surface of the conductive circuit in the mounting portion of a printed circuit board is silver-plated. This silver plating corrodes and discolors black simply when exposed to air. To prevent this, it is desirable to reduce the sulfur content of the photosensitive resin composition.

[0113] organic solvents

[0114] Furthermore, the photosensitive resin composition of the present invention may contain an organic solvent for the purpose of synthesizing the carboxyl group-containing resin (A), adjusting the photosensitive resin composition, or adjusting the viscosity when coating on a substrate or a carrier film.

[0115] Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. More specifically, examples include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, diethylene glycol ethyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and propylene glycol butyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol; aliphatic hydrocarbons such as octane and decane; and petroleum-based solvents such as petroleum ether, naphtha, hydrogenated naphtha, and solvent naphtha. These organic solvents can be used alone or in combination of two or more.

[0116] dry film

[0117] The photosensitive resin composition of the present invention can also be formed into a dry film, comprising: a support (carrier) film; and a resin layer formed from the photosensitive resin composition on the support film. To form a dry film, the photosensitive resin composition of the present invention is diluted with the aforementioned organic solvent to an appropriate viscosity, and then applied to the support film in a uniform thickness using a notch wheel coater, knife coater, lip coater, bar coater, extrusion coater, reverse coater, transfer roll coater, gravure coater, spray coater, or the like. The film is then dried, typically at a temperature of 50-130°C for 1-30 minutes. The film thickness is not particularly limited, but is generally selected within the range of 1-150 μm, preferably 10-60 μm, after drying.

[0118] After forming the resin layer of the photosensitive resin composition of the present invention on a support film, a removable protective (cover) film is preferably laminated on the surface of the resin layer for the purpose of preventing dust from adhering to the surface of the resin layer. Examples of removable protective films include polyethylene films, polytetrafluoroethylene films, polypropylene films, and surface-treated paper. Any protective film may be used as long as the adhesion between the resin layer and the protective film is smaller than the adhesion between the resin layer and the support film when the protective film is peeled off.

[0119] It should be noted that in the present invention, the photosensitive resin composition of the present invention can be applied onto the protective film and dried to form a resin layer, and a support film can be laminated on the surface of the resin layer. That is, in the present invention, when producing a dry film, either a support film or a protective film can be used as the film to which the photosensitive resin composition of the present invention is applied.

[0120] Cured material

[0121] The cured product of the present invention is obtained by curing the photosensitive resin composition of the present invention or the resin layer of the dry film of the present invention, and has whiteness, reflectivity, resolution, and low sulfur content.

[0122] printed circuit boards

[0123] The printed wiring board of the present invention comprises a cured product obtained from a resin layer of the photosensitive resin composition or dry film of the present invention. A method for producing the printed wiring board of the present invention includes, for example, adjusting the photosensitive resin composition of the present invention to a viscosity suitable for the coating method using the aforementioned organic solvent, applying the composition to a substrate using a method such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating, and then volatilizing and drying the organic solvent contained in the photosensitive resin composition at a temperature of 60 to 100°C (temporary drying) to form a non-stick resin layer on the surface of the substrate. Alternatively, in the case of a dry film, the resin layer is applied to the surface of the substrate using a laminator or the like so that the resin layer contacts the substrate, and then the carrier film is removed to form the resin layer on the surface of the substrate.

[0124] As the above-mentioned substrate, in addition to printed circuit boards and flexible printed circuit boards with circuits pre-formed with copper or the like, there can also be mentioned: copper-clad laminates of all grades (FR-4, etc.) for high-frequency circuits using materials such as paper phenolic resin, paper epoxy resin, glass cloth epoxy resin, glass polyimide resin, glass cloth / non-woven epoxy resin, glass cloth / paper epoxy resin, synthetic fiber epoxy resin, fluororesin / polyethylene / polyphenylene ether resin, polyphenylene oxide / cyanate resin, etc.; as well as metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafer plates, etc.

[0125] The volatilization drying after coating the photosensitive resin composition of the present invention can be carried out using a hot air circulation drying furnace, an IR furnace, a hot plate, a convection oven, or the like (using a device equipped with a heat source using steam-based air heating, a method of causing convection contact of the hot air in the dryer, or a method of blowing the hot air onto the support using a nozzle).

[0126] After forming a resin layer on the surface of a substrate, it is selectively exposed to active energy rays, and the unexposed areas are developed with a dilute aqueous alkali solution (e.g., a 0.3-3 wt% aqueous sodium carbonate solution) to form a pattern of a cured product. Furthermore, after irradiating the cured product with active energy rays, it is heat-cured (e.g., at 100-220°C), or irradiated with active energy rays after heat-curing, or finally fully cured (mainly cured) by heat-curing alone, thereby forming a cured film with excellent properties such as adhesion and hardness.

[0127] As the exposure machine used in the above-mentioned active energy ray irradiation, any device that irradiates ultraviolet rays equipped with an LED light source lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a mercury short arc lamp, etc. can be used. In addition, a direct drawing device (for example, a laser direct imaging device that uses CAD data from a computer to directly draw an image in a laser manner) can also be used. The exposure wavelength of the direct drawing machine is preferably in the range of 380 to 450 nm. The exposure amount used for image formation varies depending on the film thickness, etc., and can usually be set to 10 to 1500 mJ / cm 2 , preferably can be set to 20 to 1000 mJ / cm 2 within the range.

[0128] As the above-mentioned development method, immersion, showering, spraying, brushing, etc. can be used, and as the developer, an alkaline aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, etc. can be used.

[0129] The photosensitive resin composition of the present invention may be composed of a two-component resin composition. For example, a two-component resin composition may be used, wherein one resin composition serves as a base composition and another resin composition serves as a curing agent composition. In this case, for example, the base composition preferably comprises (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) a photobleachable oxime ester-based photopolymerization initiator, (D) titanium oxide, and an organic solvent as needed. The curing agent composition preferably comprises (E) an epoxy resin, (F) a photosensitive monomer, and an organic solvent as needed.

[0130] Here, from the viewpoint of preventing chemical reactions during storage, the (E) epoxy resin and the (A) carboxyl group-containing resin, as well as the (B) phosphorus-based photopolymerization initiator, the (C) photobleachable oxime ester-based photopolymerization initiator, and the (F) photosensitive monomer are preferably contained in separate compositions.

[0131] The photosensitive resin composition of the present invention is suitable for forming cured films on electronic components of electronic devices that require miniaturization and high performance. It is particularly suitable for forming white solder resist layers on printed circuit boards equipped with LEDs, which require miniaturization and high density. The photosensitive resin composition of the present invention can also be used to form interlayer insulating layers or coverlays.

[0132] The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. It should be noted that "parts" and "%" below are based on mass unless otherwise specified.

[0133] Example

[0134] <Preparation of Photosensitive Resin Composition>

[0135] The components were blended according to the formulation shown in Table 1 below, stirred, and kneaded and dispersed using a three-roll mixer to prepare photosensitive resin compositions of Examples 1 to 4 and Comparative Examples 1 to 7.

[0136] Table 1 *1(A) Carboxyl group-containing resin described in the following synthesis example

[0137] Synthesis example

[0138] A 2-liter separable flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen inlet tube was charged with 900 g of diethylene glycol dimethyl ether as a solvent and 21.4 g of t-butyl peroxy-2-ethylhexanoate (PERBUTYL O, manufactured by NOF Corporation) as a polymerization initiator, and heated to 90°C. Following the addition, 309.9 g of methacrylic acid, 116.4 g of methyl methacrylate, and 109.8 g of lactone-modified 2-hydroxyethyl methacrylate (PLACCEL FM1, manufactured by DAICEL CHEMICAL INDUSTRIES, LTD.) were added dropwise over 3 hours along with 21.4 g of bis(4-t-butylcyclohexyl) peroxydicarbonate (PEROYL TCP, manufactured by NOF Corporation) as a polymerization initiator, and the mixture was aged for 6 hours to obtain a carboxyl group-containing copolymer resin. The reaction was carried out under a nitrogen atmosphere.

[0139] Next, 363.9 g of 3,4-epoxycyclohexyl methacrylate (Cyclomer A200, manufactured by DAICEL CHEMICAL INDUSTRIES, LTD.), 3.6 g of dimethylbenzylamine as a ring-opening catalyst, and 1.80 g of hydroquinone monomethyl ether as a polymerization inhibitor were added to the resulting carboxyl copolymer resin, and the mixture was heated to 100° C. and stirred to carry out an epoxy ring-opening addition reaction. After 16 hours, a solution containing 54% by mass (solids content) of the aromatic-free carboxyl resin was obtained. The solid content of the resin had an acid value of 109 mgKOH / g and a weight-average molecular weight of 25,000.

[0140] *2 Anti-sagging agent: BYK-R606, manufactured by BYK Additives (Shanghai) Co., Ltd.

[0141] *3 Silicone defoamer: KS-66, manufactured by Shin-Etsu Chemical Co., Ltd.

[0142] *4 Leveling agent: BYK-1791, manufactured by BYK Additives (Shanghai) Co., Ltd.

[0143] *5 Melamine: MELAMINE-JC, manufactured by Jiangsu Jinxiang Sairui Chemical Technology Co., Ltd.

[0144] *6 Antioxidant: IRGANOX 1010, manufactured by BASF JAPAN LTD.

[0145] *7 Blue colorant: F-B201: Dongguan Fulu New Materials Co., Ltd.

[0146] *8 Blue colorant: F-5008: Dongguan Fulu New Materials Co., Ltd.

[0147] *9 Thioxanthone compounds as other photopolymerization initiators: manufactured by ITX Tianjin Jiuri New Materials Co., Ltd.

[0148] *10(B) Phosphorus-based photopolymerization initiator: Omnirad TPO H, IGM Resins BV, manufactured by BASF

[0149] *11 Oxime ester-based photopolymerization initiator having the absorbance shown in Figure 4: IRGACURE OXE02, manufactured by BASF Japan

[0150] *12 (C) Oxime ester photopolymerization initiator with photobleaching properties having absorbance shown in FIG2: Adeka Argus NCI-730 manufactured by Adeka Corporation, in THF, at a concentration of 200 ppm, the absorbance at a wavelength of 405 nm is 0.04, and the absorbance at a wavelength of 385 nm is 0.63

[0151] *13 Titanocene-based photopolymerization initiator, Omnirad 784, manufactured by IGM RESINS BV

[0152] *14(D) Titanium oxide, CR-97, manufactured by Ishihara Sangyo Co., Ltd.

[0153] *15(F) Photosensitive monomer: DPHA, dipentaerythritol hexaacrylate, manufactured by Nippon Kayaku Co., Ltd.

[0154] *16(E) Epoxy resin: N770-75EA, manufactured by DIC Corporation, novolac-type multifunctional epoxy resin, solid content 75%

[0155] 1. Preparation of evaluation substrate

[0156] The photosensitive resin compositions of the above-described examples and comparative examples were applied by screen printing to the entire surface of a copper-clad laminate substrate that had been pre-treated by polishing. The resulting layers were dried at 80°C for 30 minutes and cooled to room temperature to form resin layers with a thickness of 20 μm or 40 μm. The resin layers were exposed using a DI exposure machine equipped with an LED light source (Ledia6 manufactured by SCREEN Corporation). To confirm the sensitivity, a Kodak photographic Step Tablet No. 2 was placed on the substrate surface and the exposure was performed using a 405 nm light source with an output power of 100% and a light source of 150 mJ / cm. 2 Perform full-surface exposure. After removing Step Tablet No. 2 from the substrate surface, develop the substrate using a 1% by mass sodium carbonate aqueous solution at 30°C at a spray pressure of 0.15 MPa for 60 seconds. Then, dry (post-cure) the resin layer in a hot air circulation drying oven set at 150°C for 60 minutes to obtain an evaluation substrate.

[0157] 2. Characteristic test

[0158] 1) Sensitivity

[0159] After the exposure and development, the remaining state of the resin layer on the substrate surface is observed to check the number of remaining segments of the resin layer. A larger number of remaining segments indicates higher sensitivity and better photocurability, which is preferred.

[0160] ○: Number of remaining segments ≥ 9

[0161] ×: Number of remaining segments ≤ 8

[0162] 2) Sulfur content

[0163] The sulfur content in the photosensitive resin composition was investigated according to the ion chromatography test method referred to EN14582:2016.

[0164] ○: The sulfur content in the photosensitive resin composition is 500 ppm or less

[0165] ×: The sulfur content in the photosensitive resin composition is greater than 500 ppm

[0166] 3) Opening shape

[0167] The opening cross-section of the evaluation substrate (film thickness 40 μm) obtained above was observed using an optical microscope. The opening shape was evaluated based on the difference between the top and bottom values ​​of the opening according to the following evaluation criteria. The smaller the difference between the (bottom value) and (top value), the better the resolution.

[0168] ○: (opening bottom value) - (opening top value) less than 25μm

[0169] △: (Opening bottom value) - (opening top value) is 25 μm or more and less than 35 μm

[0170] ×: (Opening bottom value) - (opening top value) is 35 μm or more

[0171] 4) <b value (whiteness)>[

[0172] The substrate after the above exposure and development is heated in a hot air circulation drying oven adjusted to 200 °C for 60 minutes to obtain an evaluation substrate with a cured film. For the cured film of the obtained evaluation substrate, using a spectrophotometer (CM-26d manufactured by KONICA MINOLTA), the values of the L*a*b* color system on copper based on the SCI method are measured according to JIS Z 8729, and the b* value, which is the index indicating whiteness, is shown in the table. The evaluation criteria are as follows. The smaller the b* value, the more excellent the whiteness of the cured film.

[0173] ○: b* value is less than 1.5

[0174] ×: b* value is 1.5 or more

[0175] 5) Reflectance

[0176] For the evaluation substrate, using a spectrophotometer CM-26d manufactured by KONICA MINOLTA, the reflectance of the obtained cured film at a wavelength of 460 nm is measured, and evaluation is carried out according to the following judgment criteria.

[0177] ○ Reflectance > 85%

[0178] × Reflectance ≤ 85%

[0179] 6) Method for confirming the photo-bleaching phenomenon of Figure 1

[0180] Dissolve TPO as (B) a phosphorus-based photoinitiator and NCI-730 as (C) an oxime ester-based photoinitiator with photo-bleaching properties in THF, and prepare a THF solution in such a way that TPO is 100 ppm and NCI-730 is 10 ppm. Then, using UV-vis (V-670), the absorbance is measured in the wavelength range of 300 - 600 nm. At this time, the absorbance at a light wavelength of 365 nm is 0.27, the absorbance at a light wavelength of 385 nm is 0.18, and the absorbance at a light wavelength of 405 nm is 0.08.

[0181] Next, after sealing the solution in a sample bottle, light irradiation is carried out using an LED light source (3 wavelengths: 365 nm, 385 nm, 405 nm), and irradiated for 15 seconds at an exposure amount of 100 mJ / cm 2 in such a way, and the absorbance spectrum in the wavelength range of 300 - 600 nm is confirmed. With a cumulative exposure amount of 200 mJ / cm2 、300mJ / cm 2 Repeat the light irradiation until almost no change in the spectrum is seen.

[0182] The cumulative exposure is 300mJ / cm 2 When , the absorbance at three wavelengths (365 nm, 385 nm, and 405 nm) almost disappears, indicating that both the phosphorus-based photopolymerization initiator (B) and the oxime ester-based photopolymerization initiator (C) have photobleaching properties.

[0183] As shown in Table 1, at an exposure wavelength of 405 nm, Example 1, which contains a photobleachable oxime ester photopolymerization initiator (C), exhibits significantly improved sensitivity compared to Comparative Example 1, which does not contain the photobleachable oxime ester photopolymerization initiator (C). Compared to Comparative Example 2, which contains a cationic photopolymerization initiator with high absorbance on the long-wavelength side (see Figure 5), Examples 1 and 2 exhibit significantly improved b* values ​​and reflectance. Compared to Comparative Example 3, which contains a non-photobleachable oxime ester photopolymerization initiator with no absorbance at an exposure wavelength of 405 nm (see Figure 1), Examples 1 and 2 exhibit significantly improved sensitivity and reflectance, and also improved aperture shape (resolution). Compared to Comparative Example 4, in which the photobleachable oxime ester photopolymerization initiator (C) was added in an amount of 0.1 parts by mass, Examples 1 and 2 exhibit significantly improved sensitivity. Compared to Comparative Example 5, in which the amount of the photobleachable oxime ester-based photopolymerization initiator (C) was 2.0 parts by mass, the aperture shape (resolution) of Example 4 was significantly improved. Compared to Comparative Example 5, Comparative Example 6, in which 4.0 parts by mass of cobalt blue was further added, showed a lower b* value, but also a lower reflectivity. Compared to Comparative Example 7, which contained ultramarine blue, the sulfur content of Examples 3, 4, and 6, which contained cobalt blue, was improved.

[0184] Furthermore, increasing the amount of the photobleachable oxime ester-based photopolymerization initiator (C) further improves sensitivity, while also tending to increase the b* value (Examples 1 and 2). Adding a blue colorant allows for the production of cured films that maintain high sensitivity while also exhibiting excellent whiteness, reflectivity, and resolution (Examples 3 and 4).

[0185] These results demonstrate that the photosensitive resin composition of the present invention has good photocurability, and the cured product exhibits excellent resolution, whiteness, and reflectivity, while also having a suppressed sulfur content. The photosensitive resin composition of the present invention is most suitable for electronic components requiring miniaturization and high performance.

Claims

1. A photosensitive resin composition, characterized in that The photosensitive resin composition comprises (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) an oxime ester-based photopolymerization initiator having photobleaching properties, and (D) titanium oxide. The (C) photobleachable oxime ester-based photopolymerization initiator has an absorbance of 0.01 to 0.20 at a wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a concentration of 200 ppm in THF, The amount of the (C) photobleachable oxime ester photopolymerization initiator is 0.2 parts by mass or more and 1.5 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin solid content.

2. The photosensitive resin composition according to claim 1, wherein The amount of the titanium oxide (D) blended is 100 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the solid content of the carboxyl group-containing resin (A).

3. A photosensitive resin composition comprising at least a two-component resin composition, characterized in that: The photosensitive resin composition comprises (A) a carboxyl group-containing resin, (B) a phosphorus-based photopolymerization initiator, (C) an oxime ester-based photopolymerization initiator having photobleaching properties, (D) titanium oxide, (E) an epoxy resin, and (F) a photosensitive monomer. wherein the (A) carboxyl group-containing resin, the (B) phosphorus-based photopolymerization initiator, the (C) photobleachable oxime ester-based photopolymerization initiator, and the (D) titanium oxide are contained in different resin compositions from the (E) epoxy resin and the (F) photosensitive monomer. The (C) photobleachable oxime ester-based photopolymerization initiator has an absorbance of 0.01 to 0.20 at a wavelength of 405 nm and an absorbance of 0.10 to 1.00 at a concentration of 200 ppm in THF, The amount of the (C) photobleachable oxime ester photopolymerization initiator is 0.2 parts by mass or more and 1.5 parts by mass or less relative to 100 parts by mass of the carboxyl group-containing resin solid content.

4. The photosensitive resin composition according to claim 3, wherein The amount of the titanium oxide (D) blended is 100 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the solid content of the carboxyl group-containing resin (A).

5. A dry film, characterized in that The photosensitive resin composition comprises a resin layer, and the resin layer comprises the photosensitive resin composition according to any one of claims 1 to 4.

6. A cured product, characterized in that: The photosensitive resin composition according to any one of claims 1 to 4 or the resin layer of the dry film according to claim 5 is cured. 7 . An electronic component comprising the cured product according to claim 6 .

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