Alkali-soluble flexible photosensitive resin and photosensitive solder resist ink composition

Abstract

The invention discloses an alkali-soluble flexible photosensitive resin and a photosensitive solder resist ink composition. The preparation method of the alkali-soluble flexible photosensitive resin comprises the following steps: in an organic solvent, carrying out ring-opening reaction on flexible epoxy resin and a hydroxyl linking agent to obtain an epoxy acrylate solution with hydroxyl; carrying out ring-opening reaction on the epoxy acrylate solution and rigid epoxy resin to obtain a flexible epoxy acrylate solution; carrying out ring-opening reaction on the flexible epoxy acrylate solution and unsaturated monocarboxylic acid in the presence of a polymerization inhibitor to obtain a photosensitive flexible epoxy acrylate solution; and reacting the photosensitive flexible epoxy acrylate solution with polybasic acid anhydride to obtain the alkali-soluble flexible photosensitive resin solution. The flexibility of the solder resist ink is improved by introducing the connecting agent with hydroxyl and the epoxy resin containing a rigid structure.

Description

Technical Field

[0001] The present invention relates to the technical field of photosensitive solder resist inks, and in particular to an alkali-soluble flexible photosensitive resin and a photosensitive solder resist ink composition. Background Art

[0002] Printed circuit boards (PCBs) are important materials used in the integrated circuit field to carry electronic components and achieve electrical connections between them. Electronic components are usually soldered to the connection areas on the circuit pattern using methods such as soldering, while non-connection areas need to be coated with a layer of photosensitive solder resist ink to prevent them from being soldered. In addition, photosensitive solder resist ink can also serve as a protective layer to prevent the circuit from being corroded, contaminated, and damaged by external forces, effectively avoiding the occurrence of faults such as short circuits between circuits. In recent years, flexible circuit boards (FPCs) manufactured based on PCBs have gradually been used in the integrated circuit industry. They are made of polyimide or polyester film as a substrate. This requires that the photosensitive solder resist ink needs to have the same excellent flexibility as the FPC to prevent cracking, peeling, and even falling off during actual use.

[0003] PCB boards and FPC boards usually go through a soldering process at temperatures above 260°C, which requires the photosensitive solder resist coating to have high heat resistance (high glass transition temperature, T g However, the photosensitive solder mask inks that are widely used in the market currently mostly use epoxy resin as the raw material to prepare the main resin. The epoxy resin is modified with acrylic acid to graft double bonds and acid anhydride to graft carboxyl groups to make it photosensitivity and alkali-soluble respectively. The main resin and auxiliary agents such as photoinitiators, photosensitizers, and curing agents together form the solder mask ink composition. Although the photosensitive solder mask ink prepared with epoxy resin as the raw material has good light curing properties, high adhesion and low curing shrinkage, due to its low glass transition temperature (generally below 160°C) and poor flexibility, it is prone to cracking and other failure phenomena in actual use, limiting its application in FPC boards.

[0004] In the prior art, the following technical means are used to improve the flexibility of photosensitive solder resist inks: Invention patent CN103619960A uses a method of adding block copolymers to improve flexibility. In order to improve the heat resistance of photosensitive solder resist inks, a common practice is to add inorganic fillers such as silica or increase the crosslinking density. For example, invention patent CN110895381A discloses a method of adding silica and vinyl silica to improve the heat resistance and adhesion of solder resist inks. The inorganic filler added in this patent contains reactive functional groups on the surface that can react with the resin, which can increase the crosslinking density between the inorganic filler and the resin, thereby improving the thermal properties. However, the amount of inorganic filler added is limited, and the improvement in thermal properties is limited. In addition, the heat resistance of photosensitive solder resist inks increases with the increase of crosslinking density, inorganic filler content, etc., but the flexibility tends to decrease, and the balance between heat resistance and flexibility is usually difficult to strike. In summary, it is a difficult problem to prepare photosensitive solder resist ink with both high glass transition temperature and excellent flexibility in the existing technology, and it is difficult to meet the application requirements of high-performance FPC. Summary of the Invention

[0005] To address the above technical issues, the present invention provides an alkali-soluble flexible photosensitive resin and a photosensitive solder resist ink composition. The alkali-soluble flexible photosensitive resin provided by the present invention, on the one hand, enhances the flexibility of the photosensitive resin by alternately copolymerizing a hydroxyl-containing linker and an epoxy resin, while simultaneously introducing an epoxy resin with a rigid structure to improve heat resistance. Furthermore, the flexible photosensitive resin is cross-linked with the composition within the photosensitive solder resist ink through blending, resulting in a final photosensitive solder resist ink composition that combines excellent photolithographic development performance, high heat resistance, and excellent flexibility, thus enabling its application in FPCs.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In one aspect, the present invention provides a method for preparing an alkali-soluble flexible photosensitive resin, comprising the following steps:

[0008] (1) In an organic solvent, a flexible epoxy resin and a hydroxy linker undergo a ring-opening reaction to obtain an epoxy acrylate solution having a hydroxyl group; the hydroxy linker is an alkyl diacid containing at least one hydroxyl group, and the ring-opening reaction is a ring-opening reaction between the epoxy group of the flexible epoxy resin and the carboxyl group of the hydroxy linker;

[0009] (2) subjecting the epoxy acrylate solution obtained in step (1) to a ring-opening reaction with a rigid epoxy resin to obtain a flexible epoxy acrylate solution; the ring-opening reaction is a ring-opening reaction between the epoxy group of the rigid epoxy resin and the hydroxyl group of the epoxy acrylate;

[0010] (3) subjecting the flexible epoxy acrylate solution obtained in step (2) to a ring-opening reaction with an unsaturated monocarboxylic acid in the presence of a polymerization inhibitor to obtain a photosensitive flexible epoxy acrylate solution; the ring-opening reaction is a ring-opening reaction between the epoxy group of the flexible epoxy acrylate and the carboxyl group of the unsaturated monocarboxylic acid;

[0011] (4) reacting the photosensitive flexible epoxy acrylate solution obtained in step (3) with a polyacid anhydride to obtain an alkali-soluble flexible photosensitive resin solution.

[0012] In the technical solution of the present invention, in step (1), the type of the flexible epoxy resin is not particularly limited. Specifically, bifunctional aromatic epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol F epoxy resin, brominated bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, and brominated bisphenol A epoxy resin, and aliphatic epoxy resins such as aliphatic ring epoxy resin and aliphatic chain epoxy resin can be listed. The above epoxy resins can be used alone or in any combination.

[0013] Preferably, the carbon number of the hydroxy linker is 3 to 10; the hydroxy linker can specifically include 2-hydroxymalonic acid, 2-hydroxysuccinic acid, 3-hydroxyglutaric acid, 3-hydroxyoctanedioic acid, 4-hydroxypimelic acid, 3-hydroxysebacic acid, etc., which can be used alone or in any combination; the hydroxy linker can increase the molecular weight of the alkali-soluble flexible photosensitive resin through a ring-opening reaction;

[0014] Preferably, the molar ratio of the epoxy group of the flexible epoxy resin to the carboxyl group of the hydroxyl linker is 1:0.35-0.60;

[0015] Preferably, the temperature of the ring-opening reaction is 90-100°C;

[0016] Preferably, the ring-opening reaction time is 5 to 10 hours;

[0017] Preferably, the ring-opening reaction is carried out in an inert atmosphere.

[0018] In certain specific embodiments, the ring-opening reaction in step (1) is carried out under the action of catalyst I; the catalyst I is selected from one or more of tetrabutylammonium chloride, tetraethylammonium bromide, benzyltriethylammonium chloride and triphenylethylphosphonium bromide, triphenylphosphine, N,N-dimethylaniline, N,N-dimethylbenzylamine and hexadecyltrimethylammonium bromide.

[0019] In the technical solution of the present invention, in step (2), the type of the rigid epoxy resin is not particularly limited, and specifically includes: bisphenol S type epoxy resin, phenol novolac epoxy resin, bisphenol A novolac epoxy resin, naphthalene type epoxy resin, phenol biphenyl type epoxy resin, dimethylol type epoxy resin, biphenol type epoxy resin, o-cresol novolac epoxy resin, alkylphenol novolac epoxy resin, dicyclopentadiene type epoxy resin, glycidylamine type epoxy resin, trihydroxyphenylmethane type epoxy resin, tetraphenolethane type epoxy resin, diglycidyl phthalate resin and epoxy compounds of condensates of phenols and aromatic aldehydes having phenolic hydroxyl groups. The above-mentioned epoxy resins can be used alone or in any combination.

[0020] Preferably, the molar ratio of the hydroxyl group of the hydroxyl linker to the epoxy group of the rigid epoxy resin is 1:0.35-0.55;

[0021] Preferably, the temperature of the ring-opening reaction is 110°C to 135°C;

[0022] Preferably, the ring-opening reaction time is 6 to 10 hours;

[0023] In certain specific embodiments, the ring-opening reaction in step (2) is carried out under the action of catalyst II; the catalyst II is selected from one or more of 1-methylpyridinium chloride, 1-butylpyridinium chloride, 1-ethylpyridinium chloride and dodecylpyridinium bromide.

[0024] In certain specific embodiments, the ring-opening reaction in step (2) can be carried out after adding an organic solvent for dilution, in order to reduce the viscosity of the reaction system to prevent explosion or reaction failure due to stirring difficulties. The amount of the organic solvent added is such that the viscosity of the reaction system is reduced to 7500-15000 mPa.s.

[0025] As a preferred embodiment, in step (3), the polymerization inhibitor is selected from one or more of cuprous chloride, hydroquinone, toluene diol, p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol;

[0026] Preferably, the mass ratio of the flexible epoxy resin to the polymerization inhibitor is 1:0.006-0.015; in the technical solution of the present invention, the polymerization inhibitor can prevent the self-polymerization reaction of the unsaturated monocarboxylic acid;

[0027] Preferably, the type of the unsaturated monocarboxylic acid is not particularly limited, and specific examples include acrylic acid, acrylic acid dimer, methacrylic acid, β-styryl acrylic acid, β-furfuryl acrylic acid, crotonic acid, α-cyanocinnamic acid, cinnamic acid, reaction products of saturated / unsaturated dibasic acid anhydrides and hydroxyl-containing (meth)acrylates, reaction products of saturated / unsaturated dibasic acids and unsaturated monoglycidyl compounds, etc. The above-mentioned can be used alone or in any combination.

[0028] Preferably, the molar ratio of the epoxy group of the rigid epoxy resin to the carboxyl group of the unsaturated monocarboxylic acid is 1:1.2-1.8; in the technical solution of the present invention, after the unsaturated monocarboxylic acid is grafted onto the flexible epoxy acrylate, it has an unsaturated bond to impart photosensitivity;

[0029] Preferably, the temperature of the ring-opening reaction is 110°C to 135°C;

[0030] Preferably, the ring-opening reaction time is 8 to 12 hours.

[0031] In certain specific embodiments, the ring-opening reaction in step (3) is carried out under the action of catalyst I; the catalyst I is selected from one or more of tetrabutylammonium chloride, tetraethylammonium bromide, benzyltriethylammonium chloride and triphenylethylphosphonium bromide, triphenylphosphine, N,N-dimethylaniline, N,N-dimethylbenzylamine and hexadecyltrimethylammonium bromide.

[0032] In the technical solution of the present invention, catalyst I and catalyst II are different catalysts, the purpose of which is to ensure the rapid progress of each step of the reaction.

[0033] In the technical solution of the present invention, in step (4), the polyacid anhydride is a saturated or unsaturated polyacid anhydride, specifically dibasic acid anhydrides such as maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride; polybasic aromatic carboxylic anhydrides such as trimellitic anhydride, pyromellitic anhydride and benzophenonetetracarboxylic dianhydride; and other acid anhydride derivatives such as 5-(2,5-dioxytetrahydrofuranyl)-3-methyl-3-cyclohexenyl-1,2-dicarboxylic anhydride. The above-mentioned anhydrides can be used alone or in any combination.

[0034] Preferably, the molar ratio of epoxy group to polyacid anhydride of the flexible epoxy resin is 1:0.8-1.1;

[0035] Preferably, the reaction temperature is 80°C to 105°C;

[0036] Preferably, the reaction time is 4 to 6 hours.

[0037] In the technical solution of the present invention, the type of the organic solvent is not particularly limited. Specifically, ethers such as ethylene glycol monomethyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, etc.; esters such as ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether Acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate, dipropylene glycol butyl ether acetate, etc.; ketones, such as butanone, cyclohexanone, isophorone; petroleum solvents, such as naphtha, oxidized naphtha, solvent naphtha, etc.; the above-mentioned can be used alone or in any combination.

[0038] In some specific embodiments, a post-treatment is further included; the post-treatment is to purify the alkali-soluble flexible photosensitive resin solution obtained in step (4) to obtain an alkali-soluble flexible photosensitive resin; the purification treatment can be carried out by the following steps: stirring to precipitate in a 5-10 times volume of a deionized water-methanol mixed solution, and vacuum drying to constant weight.

[0039] In another aspect, the present invention provides an alkali-soluble flexible photosensitive resin obtained by the above preparation method.

[0040] In another aspect, the present invention provides a photosensitive solder resist ink composition comprising the above-mentioned alkali-soluble flexible photosensitive resin and alkali-soluble photosensitive modified epoxy resin.

[0041] Preferably, the mass ratio of the alkali-soluble flexible photosensitive resin to the alkali-soluble photosensitive modified epoxy resin is 1:1-4.

[0042] As a preferred embodiment, the alkali-soluble photosensitive modified epoxy resin is an epoxy resin containing a photosensitive group and an alkali-soluble group on the molecular chain; the photosensitive group is selected from one or more of a carbonyl group, a carboxyl group, a peroxide group and a carbon-carbon double bond; the alkali-soluble group is selected from one or more of a carboxyl group, an acid anhydride group and an ester group;

[0043] Preferably, the number average molecular weight of the alkali-soluble photosensitive modified epoxy resin is 1,000 to 50,000, more preferably 5,000 to 15,000;

[0044] In the technical solution of the present invention, the alkali-soluble photosensitive modified epoxy resin is prepared from a conventional difunctional or multifunctional epoxy resin, specifically bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol A epoxy resin, brominated bisphenol A epoxy resin, phenol novolac epoxy resin, bisphenol A novolac epoxy resin, naphthalene epoxy resin, phenol biphenyl epoxy resin, bixylenol epoxy resin, biphenol epoxy resin, o-cresol novolac epoxy resin, alkylphenol novolac epoxy resin, dicyclopentadiene epoxy resin, glycidylamine epoxy resin, trihydroxyphenylmethane epoxy resin, tetraphenolethane epoxy resin, diglycidyl phthalate resin and epoxy compounds of condensates of phenols and aromatic aldehydes having phenolic hydroxyl groups. The above-mentioned epoxy compounds can be used alone or in any combination.

[0045] In certain specific embodiments, the alkali-soluble photosensitive modified epoxy resin is obtained by the following preparation method: (a) a multifunctional epoxy compound and (b) an unsaturated monocarboxylic acid are subjected to a ring-opening esterification reaction, and then the obtained ester is reacted with (c) a saturated / unsaturated polyacid anhydride;

[0046] Examples of the unsaturated monocarboxylic acid (b) include acrylic acid, acrylic acid dimer, methacrylic acid, β-styryl acrylic acid, β-furfuryl acrylic acid, crotonic acid, α-cyanocinnamic acid, cinnamic acid, reaction products of saturated / unsaturated dibasic acid anhydrides and hydroxyl-containing (meth)acrylates, and reaction products of saturated / unsaturated dibasic acids and unsaturated monoglycidyl compounds. These can be used alone or in any combination.

[0047] Examples of the (c) saturated / unsaturated polybasic acid anhydride include: dibasic acid anhydrides such as maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride; polybasic aromatic carboxylic anhydrides such as trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride; and other acid anhydride derivatives such as 5-(2,5-dioxotetrahydrofuranyl)-3-methyl-3-cyclohexenyl-1,2-dicarboxylic anhydride. The above-mentioned anhydrides may be used alone or in any combination. In view of the properties of the cured resin film, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and maleic anhydride are preferred.

[0048] Preferably, the molar ratio of the carboxyl group of the (b) unsaturated monocarboxylic acid to the epoxy group of the (a) multifunctional epoxy compound is 0.8-0.95:1; the molar ratio of the (c) saturated / unsaturated polyacid anhydride to the epoxy group of the (a) multifunctional epoxy compound is 0.85-0.95:1.

[0049] As a preferred embodiment, the invention further comprises a photoinitiator, a photopolymerizable monomer, a thermosetting component and an inorganic filler.

[0050] In the technical solution of the present invention, the type of the photoinitiator is not particularly limited, and specific examples include oxime ester photopolymerization initiators, such as OXE-1, OXE-2, etc.; acylphosphine oxide photopolymerization initiators, such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc.; acetophenone photopolymerization initiators, such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, etc.; benzoin and its alkyl ether photopolymerization initiators, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ethers, etc.; anthraquinone photopolymerization initiators, such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, etc.; thioxanthone photopolymerization initiators, such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, etc.; ketal photopolymerization initiators, such as acetophenone dimethyl ketal, benzyl dimethyl ketal, etc.; benzophenone photopolymerization initiators, such as benzophenone, 4,4'-bisdiethylaminobenzophenone, etc.; the above-mentioned can be used alone or in any combination, and oxime ester-based photopolymerization initiators are preferred;

[0051] Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the photoinitiator is 3 to 8 parts by mass.

[0052] In the technical solution of the present invention, the photopolymerizable monomer is selected from one or more of monofunctional (meth)acrylates and multifunctional (meth)acrylates; specifically, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate and the like; monofunctional (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate and the like; 1,6-hexanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, neopentyl glycol diethoxy / propoxy di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and polydipentaerythritol hexa(meth)acrylate, etc.

[0053] Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the photopolymerizable monomer is 5 to 10 parts by mass.

[0054] In the technical solution of the present invention, the thermosetting component is an epoxy resin, specifically bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol F epoxy resin, brominated bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, brominated bisphenol A epoxy resin, bixylenol epoxy resin, biphenol epoxy resin, alicyclic epoxy resin, novolac epoxy resin, cresol-soluble epoxy resin, trisphenol methane epoxy resin, N-glycidyl epoxy resin, triglycidyl isocyanurate, 2,6-xylenol dimer diglycidyl ether, alicyclic epoxy resin and xylene epoxy resin; the above-mentioned can be used alone or in any combination;

[0055] Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the heat-curable component is 25 to 40 parts by mass.

[0056] In the technical solution of the present invention, the inorganic filler is selected from one or more of barium sulfate, barium titanate, calcium oxide, talc, fumed silica, silica, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, titanium oxide, mica powder and kaolin, preferably one or more of barium sulfate, silica, aluminum oxide, aluminum hydroxide and calcium carbonate;

[0057] Preferably, the particle size of the inorganic filler is 0.001 to 20 μm, more preferably 0.05 to 15 μm, and particularly preferably 0.05 to 3 μm. In particular, when the photosensitive solder resist ink composition needs to be further ground, the particle size of the inorganic filler may also be in other ranges, without particular limitation.

[0058] Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the inorganic filler is 30 to 70 parts by mass.

[0059] In certain specific embodiments, the photosensitive solder resist ink composition further comprises a pigment, wherein the pigment is selected from one or more of phthalocyanine green, phthalocyanine blue, titanium dioxide, carbon black, and lithopone, and is preferably a pigment free of free halogen; the content of the pigment can be arbitrarily set within a range that does not affect the performance of the photosensitive solder resist ink composition;

[0060] In certain specific embodiments, the photosensitive solder resist ink composition further includes additives, which include one or more of an epoxy resin thermal curing accelerator, a photoinitiator auxiliary, a thixotropic tackifier, a diluent, an inhibitor, a tackifier, a defoaming agent, a leveling agent, a coupling agent, an antioxidant, and a rust inhibitor; the content of the additives can be arbitrarily set within a range that does not affect the performance of the photosensitive solder resist ink composition.

[0061] In certain specific embodiments, the photosensitive solder resist ink composition is mechanically stirred at a speed of 500 to 1000 rpm for 2 to 8 hours, and then ground with a three-roll mill after being mixed evenly to obtain the photosensitive solder resist ink composition.

[0062] In another aspect, the present invention provides a photosensitive dry film, comprising a photosensitive film obtained by curing the above-mentioned photosensitive solder resist ink composition;

[0063] Preferably, the thickness of the photosensitive film is 5 to 40 μm, more preferably 10 to 35 μm, and particularly preferably 15 to 30 μm;

[0064] Preferably, the curing is carried out under heating conditions;

[0065] Preferably, the heating temperature is 50-110°C, more preferably 60-100°C, and particularly preferably 70-90°C;

[0066] Preferably, the heating time is 10 to 60 minutes, more preferably 15 to 50 minutes, and particularly preferably 20 to 40 minutes;

[0067] In certain specific embodiments, the photosensitive dry film further comprises a protective film covering the surface of the photosensitive film and a carrier film supporting the photosensitive film; the carrier film and the protective film may be made of heat-resistant and solvent-resistant polymers such as polyethylene terephthalate, polypropylene, polyethylene, and polyester;

[0068] In the technical solution of the present invention, the preparation method of the photosensitive dry film includes the following steps: using a known coating equipment such as a reverse roll coater, a gravure roll coater, a notch wheel coater, a curtain coater, a four-sided coater, etc. to coat the photosensitive polyamic acid ester resin on a carrier film, and then laminating a protective film after drying.

[0069] Preferably, the drying is hot air drying or far infrared / near infrared drying machine;

[0070] Preferably, the drying temperature is 50-110°C, more preferably 60-100°C, and particularly preferably 70-90°C;

[0071] Preferably, the drying time is 10 to 60 minutes, more preferably 15 to 50 minutes, and particularly preferably 20 to 40 minutes.

[0072] The above technical solution has the following advantages or beneficial effects:

[0073] The present invention prepares a photosensitive resin by introducing a linker with a hydroxyl group and an epoxy resin containing a rigid structure. The photosensitive resin not only has a high molecular weight, high heat resistance, and excellent photolithography development performance, but also has excellent flexibility, further improving the flexibility of the photosensitive solder mask ink. In addition, its glass transition temperature is maintained above 175°C, which can fully meet the requirements of the solder mask dry film for excellent flexibility and high heat resistance, and has good application prospects and value in FPC circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 1 is a graph showing the variation of the loss tangent value of the cured photosensitive film in the embodiments of the present invention and the comparative example with temperature. DETAILED DESCRIPTION

[0075] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0076] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0077] Preparation Examples 1a-1g

[0078] Preparation Example 1a

[0079] (1) First, 50.26 g of bisphenol F epoxy resin (epoxy equivalent weight: 169 g / eq) and 75 g of diethylene glycol ethyl ether acetate (solvent) were added to a four-necked flask at room temperature and stirred. The temperature was raised to 95° C. using an oil bath and nitrogen was introduced. After the epoxy resin was completely dissolved, 0.68 g of triphenylphosphine and 11.45 g of 2-hydroxybutanedioic acid were added, and 25 g of diethylene glycol ethyl ether acetate was added for dilution. The mixture was continuously stirred for 7 h to perform a polymerization reaction to obtain an epoxy acrylate solution.

[0080] (2) The solution was heated to 110° C., and 0.53 g of 1-methylpyridinium chloride, 12.41 g of phenol biphenyl type epoxy resin 324 (epoxy equivalent weight 291 g / eq), and 35 g of diethylene glycol ethyl ether acetate were added and stirred for 8 h to convert the epoxy acrylate solution into a flexible epoxy acrylate solution;

[0081] (3) maintaining the flexible epoxy acrylate solution at 110° C., adding 0.42 g of toluene diphenol, 1.98 g of triphenylphosphine, and 4.63 g of acrylic acid, and reacting for 10 h to obtain a photosensitive flexible epoxy acrylate solution;

[0082] (4) cooling the photosensitive flexible epoxy acrylate solution and maintaining it at 90° C., adding 31.86 g of maleic anhydride and reacting for 6 h to obtain an alkali-soluble flexible photosensitive resin solution;

[0083] (5) The above alkali-soluble flexible photosensitive resin solution was slowly poured into a 5L deionized water-methanol mixed solution, mechanically stirred for 1 hour, and the precipitate was collected. After repeating three times, the light yellow alkali-soluble flexible photosensitive resin precipitate was collected and placed in a vacuum oven to dry to constant weight to obtain alkali-soluble flexible photosensitive resin-1.

[0084] Preparation Example 1b: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in step (1) and step (3) is replaced by tetrabutylammonium chloride.

[0085] Preparation Example 1c: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in steps (1) and (3) is replaced by tetraethylammonium bromide.

[0086] Preparation Example 1d: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in steps (1) and (3) is replaced by benzyltriethylammonium chloride.

[0087] Preparation Example 1e: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in steps (1) and (3) is replaced by triphenylethylphosphonium bromide.

[0088] Preparation Example 1f: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in steps (1) and (3) is replaced by N,N-dimethylaniline.

[0089] Preparation Example 1g: The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the catalyst in steps (1) and (3) is replaced by N,N-dimethylbenzylamine.

[0090] Preparation Example 2. The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the bisphenol F epoxy resin in step (1) is replaced by bisphenol A epoxy resin (epoxy equivalent is 182 g / eq), the hydroxyl linker is replaced by 2-hydroxysuccinic acid with 3-hydroxyoctanedioic acid, and the amount is adjusted to 13.25 g; the amount of phenol biphenyl epoxy resin 324 in step (2) is adjusted to 10.12 g; the amount of acrylic acid in step (3) is adjusted to 3.77 g; and the amount of maleic anhydride in step (4) is adjusted to 27.05 g to prepare an alkali-soluble flexible photosensitive resin-2.

[0091] Preparation Example 3. The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the bisphenol F epoxy resin in step (1) is replaced by hydrogenated bisphenol A epoxy resin (epoxy equivalent is 211 g / eq), and the hydroxyl linker is replaced by 2-hydroxysuccinic acid with 3-hydroxy; the amount of phenol biphenyl epoxy resin 324 in step (2) is adjusted to 9.93 g; the amount of acrylic acid in step (3) is adjusted to 3.76 g; and the amount of maleic anhydride in step (4) is adjusted to 23.39 g to prepare alkali-soluble flexible photosensitive resin-3.

[0092] Preparation Example 4. The preparation method of this preparation example is the same as that of Preparation Example 1a, except that the bisphenol F epoxy resin in step (1) is replaced by brominated bisphenol A epoxy resin (epoxy equivalent is 400 g / eq), the hydroxyl linker is replaced by 2-hydroxysuccinic acid by 4-hydroxypimelic acid, and the amount is adjusted to 6.14 g; the amount of phenol biphenyl epoxy resin 324 in step (2) is adjusted to 5.06 g; the amount of acrylic acid in step (3) is adjusted to 2.05 g; and the amount of maleic anhydride in step (4) is adjusted to 12.31 g to prepare alkali-soluble flexible photosensitive resin-4.

[0093] Preparation Example 5 Alkali-soluble photosensitive modified epoxy resin

[0094] (1) Add 50.14 g of o-cresol-type epoxy resin 704M (epoxy equivalent of 175 g / eq) and 100 g of diethylene glycol ethyl ether acetate (solvent) to a four-necked flask at room temperature and stir, heat to 110° C. using an oil bath and introduce nitrogen; after the epoxy resin is completely dissolved, add 0.68 g of triphenylphosphine, 0.42 g of toluene diphenol and 19.42 g of acrylic acid, add 15 g of diethylene glycol ethyl ether acetate solvent to dilute, and continue stirring for 5 h to obtain an epoxy acrylate solution by reaction;

[0095] (2) cooling the solution to 90° C., adding 38.97 g of tetrahydrophthalic anhydride and 15 g of solvent, and continuing to stir and react for 5 h to obtain an alkali-soluble photosensitive modified epoxy resin solution;

[0096] (3) The above-mentioned alkali-soluble photosensitive modified epoxy resin solution was slowly poured into a mixed solution of 5 L of deionized water and methanol, mechanically stirred for 20 min, and the precipitate was collected. After repeating three times, the white alkali-soluble photosensitive modified resin precipitate was collected and placed in a vacuum oven to dry to constant weight to obtain an alkali-soluble photosensitive modified epoxy resin (number average molecular weight of 5235).

[0097] Photosensitive solder resist ink composition Examples 1-7:

[0098] Example 1

[0099] A mixture of the alkali-soluble flexible photosensitive resin-1 obtained in Preparation Example 1a and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5 was prepared at a solid content of 65%, wherein the mass of the alkali-soluble flexible photosensitive resin-1 was 20% of the total mass of the alkali-soluble flexible photosensitive resin-1 and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5; the solvent was diethylene glycol ethyl ether acetate; and the preparation process was mechanically stirred for 2 hours.

[0100] 58.42 g of the above-mentioned mixture glue, 2.1 g of photoinitiator 907, 3 g of polydipentaerythritol hexaacrylate, 12 g of thermosetting component (the thermosetting component in this embodiment is a biphenyl epoxy resin purchased from Mitsubishi, Japan, with the brand name YX4000H), 15 g of silicon dioxide (particle size of 10 μm), 5 g of barium sulfate (particle size of 12 μm), 0.8 g of phthalocyanine green, 0.4 g of melamine, 0.9 g of dicyandiamide, and 20 g of diethylene glycol ethyl ether acetate were stirred at 800 rpm for 4 h under mechanical stirring, mixed evenly, and then ground with a three-roll mill to obtain a photosensitive solder resist ink composition.

[0101] Example 2

[0102] The difference between this embodiment and Example 1 is that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1b, and the mass of the alkali-soluble flexible photosensitive resin is 25% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0103] Example 3

[0104] The preparation method of this embodiment differs from that of Example 1 in that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1c, and the mass of the alkali-soluble flexible photosensitive resin is 30% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0105] Example 4

[0106] The preparation method of this embodiment differs from that of Example 1 in that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1d, and the mass of the alkali-soluble flexible photosensitive resin is 35% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0107] Example 5

[0108] The preparation method of this embodiment differs from that of Example 1 in that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1e, and the mass of the alkali-soluble flexible photosensitive resin is 40% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0109] Example 6

[0110] The preparation method of this embodiment differs from that of Example 1 in that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1f, and the mass of the alkali-soluble flexible photosensitive resin is 45% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0111] Example 7

[0112] The preparation method of this embodiment differs from that of Example 1 in that the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1a is replaced by the alkali-soluble flexible photosensitive resin prepared in Preparation Example 1g, and the mass of the alkali-soluble flexible photosensitive resin is 50% of the total mass of the alkali-soluble flexible photosensitive resin and the alkali-soluble photosensitive modified epoxy resin obtained in Preparation Example 5.

[0113] Comparative Example

[0114] The preparation method of this comparative example is different from that of Example 1 in that 58.75 g of the alkali-soluble photosensitive modified epoxy resin glue (solid content of 65%) obtained in Preparation Example 5 is used to replace the mixture glue of alkali-soluble flexible photosensitive resin-1 and alkali-soluble photosensitive modified epoxy resin.

[0115] Effect embodiment

[0116] The photosensitive solder resist ink compositions of the Examples and Comparative Examples were applied to a polyethylene terephthalate carrier film and dried at 80°C for 25 minutes to form a photosensitive film (20 μm thick) formed on the carrier film. The film was exposed for 30 seconds using an exposure apparatus equipped with a metal halide lamp, developed for 60 seconds with a 1 wt % aqueous sodium carbonate solution, and then thermally cured at 170°C for 1 hour to obtain a cured photosensitive film. The properties of the cured photosensitive film were tested, and the results are shown in Table 1.

[0117] Table 1

[0118]

[0119] In Table 1:

[0120] The glass transition temperature was measured by a dynamic thermomechanical analyzer with a heating rate of 5°C / min in the range of room temperature to 270°C. The glass transition temperature was represented by the abscissa temperature corresponding to the maximum value of the loss tangent value ( Figure 1 ).

[0121] The thermal expansion coefficient in different temperature ranges was measured by a thermomechanical analyzer with a heating rate of 10°C / min and a test range from room temperature to 270°C.

[0122] Flexibility test method: The cured photosensitive film of the obtained single-sided coated substrate is bent 180° repeatedly several times with the cured film facing outward. The occurrence of cracks in the cured film is observed visually and under an optical microscope with a magnification of 200. The number of bends when cracks occur is counted. A number of bends when cracks occur of 0-1 indicates poor flexibility of the cured film, 2-3 indicates acceptable flexibility, 4-5 indicates good flexibility, and 6 or more indicates excellent flexibility.

[0123] The line or hole resolution of the photolithographic pattern is judged as excellent if it reaches 40μm < resolution < 60μm, good if it reaches 60μm < resolution < 80μm, and passing if it reaches 80μm < resolution < 100μm.

[0124] from Figure 1 As can be seen from Table 1, the addition of an alkali-soluble flexible photosensitive resin significantly increases the glass transition temperature of the photosensitive solder mask ink composition, reaching a maximum temperature of over 175°C. The coefficient of thermal expansion can be reduced to 25.35 ppm / K, while the glass transition temperature remains above 190°C. Compared to the comparative example, the thermal performance of the photosensitive solder mask ink composition is significantly improved.

[0125] From the perspective of photolithography performance and development performance, the photolithography performance of the embodiment is better than that of the comparative example, and the development time is significantly shortened.

[0126] The present invention also prepares a photosensitive solder resist ink composition by using the alkali-soluble flexible photosensitive resin obtained in other preparation examples, and proves that the composition has the same effect through corresponding experimental tests.

[0127] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an alkali-soluble flexible photosensitive resin, characterized in that: The following steps are involved: (1) In an organic solvent, a flexible epoxy resin and a hydroxy linker undergo a ring-opening reaction to obtain an epoxy acrylate solution having a hydroxyl group; the hydroxy linker is an alkyl diacid containing at least one hydroxyl group, and the ring-opening reaction is a ring-opening reaction between the epoxy group of the flexible epoxy resin and the carboxyl group of the hydroxy linker; (2) subjecting the epoxy acrylate solution obtained in step (1) to a ring-opening reaction with a rigid epoxy resin to obtain a flexible epoxy acrylate solution; the ring-opening reaction is a ring-opening reaction between the epoxy group of the rigid epoxy resin and the hydroxyl group of the epoxy acrylate; (3) subjecting the flexible epoxy acrylate solution obtained in step (2) to a ring-opening reaction with an unsaturated monocarboxylic acid in the presence of a polymerization inhibitor to obtain a photosensitive flexible epoxy acrylate solution; the ring-opening reaction is a ring-opening reaction between the epoxy group of the flexible epoxy acrylate and the carboxyl group of the unsaturated monocarboxylic acid; (4) reacting the photosensitive flexible epoxy acrylate solution obtained in step (3) with a polyacid anhydride to obtain an alkali-soluble flexible photosensitive resin solution.

2. The preparation method according to claim 1, characterized in that In step (1), the flexible epoxy resin is selected from one or more of a difunctional aromatic epoxy resin and an aliphatic epoxy resin; the difunctional aromatic epoxy resin is selected from one or more of a bisphenol A epoxy resin, a bisphenol F epoxy resin, a hydrogenated bisphenol F epoxy resin, a brominated bisphenol F epoxy resin, a hydrogenated bisphenol A epoxy resin, and a brominated bisphenol A epoxy resin; the aliphatic epoxy resin is selected from one or more of an aliphatic cyclic epoxy resin and an aliphatic chain epoxy resin; Preferably, the number of carbon atoms of the hydroxyl linker is 3 to 10; Preferably, the molar ratio of the epoxy group of the flexible epoxy resin to the carboxyl group of the hydroxyl linker is 1:0.35-0.60; Preferably, the temperature of the ring-opening reaction is 90-100°C; Preferably, the ring-opening reaction time is 5 to 10 hours; Preferably, the ring-opening reaction is carried out in an inert atmosphere.

3. The preparation method according to claim 1, characterized in that In step (2), the rigid epoxy resin is selected from one or more epoxy compounds of bisphenol S type epoxy resin, phenol novolac epoxy resin, bisphenol A novolac epoxy resin, naphthalene type epoxy resin, phenol biphenyl type epoxy resin, dimethylol type epoxy resin, biphenol type epoxy resin, o-cresol novolac epoxy resin, alkylphenol novolac epoxy resin, dicyclopentadiene type epoxy resin, glycidylamine type epoxy resin, trihydroxyphenylmethane type epoxy resin, tetraphenolethane type epoxy resin, diglycidyl phthalate resin and condensation products of phenols and aromatic aldehydes having phenolic hydroxyl groups; Preferably, the molar ratio of the hydroxyl group of the hydroxyl linker to the epoxy group of the rigid epoxy resin is 1:0.35-0.55; Preferably, the temperature of the ring-opening reaction is 110°C to 135°C; Preferably, the ring-opening reaction time is 6 to 10 hours.

4. The preparation method according to claim 1, characterized in that In step (3), the polymerization inhibitor is selected from one or more of cuprous chloride, hydroquinone, toluene diol, p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol; Preferably, the mass ratio of the flexible epoxy resin to the polymerization inhibitor is 1:0.006-0.015; Preferably, the unsaturated monocarboxylic acid is selected from one or more of acrylic acid, acrylic acid dimer, methacrylic acid, β-styryl acrylic acid, β-furfuryl acrylic acid, crotonic acid, α-cyanocinnamic acid, cinnamic acid, the reaction product of a saturated / unsaturated dibasic acid anhydride and a hydroxyl-containing (meth)acrylate, and the reaction product of a saturated / unsaturated dibasic acid and an unsaturated monoglycidyl compound; Preferably, the molar ratio of the epoxy group of the rigid epoxy resin to the carboxyl group of the unsaturated monocarboxylic acid is 1:1.2-1.8; Preferably, the temperature of the ring-opening reaction is 110°C to 135°C; Preferably, the ring-opening reaction time is 8 to 12 hours.

5. The preparation method according to claim 1, characterized in that In step (4), the polyanhydride is a saturated or unsaturated polyanhydride selected from one or more dibasic acid anhydrides or dibasic acid anhydride derivatives; Preferably, the molar ratio of epoxy group to polyacid anhydride of the flexible epoxy resin is 1:0.8-1.1; Preferably, the reaction temperature is 80°C to 105°C; Preferably, the reaction time is 4 to 6 hours; Preferably, the method further comprises post-processing; the post-processing is to purify the alkali-soluble flexible photosensitive resin solution obtained in step (4) to obtain an alkali-soluble flexible photosensitive resin.

6. An alkali-soluble flexible photosensitive resin obtained by the preparation method according to any one of claims 1 to 5.

7. A photosensitive solder resist ink composition, characterized in that: The photosensitive solder resist ink composition comprises an alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin according to claim 6; Preferably, the mass ratio of the alkali-soluble flexible photosensitive resin to the alkali-soluble photosensitive modified epoxy resin is 1:1-4.

8. The photosensitive solder resist ink composition according to claim 7, characterized in that: The alkali-soluble photosensitive modified epoxy resin is an epoxy resin containing a photosensitive group and an alkali-soluble group on the molecular chain; the photosensitive group is selected from one or more of a carbonyl group, a carboxyl group, a peroxide group and a carbon-carbon double bond; the alkali-soluble group is selected from one or more of a carboxyl group, an acid anhydride group and an ester group; Preferably, the number average molecular weight of the alkali-soluble photosensitive modified epoxy resin is 1,000 to 50,000, more preferably 5,000 to 15,000.

9. The photosensitive solder resist ink composition according to claim 7, characterized in that: It also includes a photoinitiator, a photopolymerizable monomer, a thermosetting component and an inorganic filler; Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the photoinitiator is 3 to 8 parts by mass; Preferably, the photopolymerizable monomer is selected from one or more of monofunctional (meth)acrylates and multifunctional (meth)acrylates; Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the photopolymerizable monomer is 5 to 10 parts by mass; Preferably, the thermosetting component is an epoxy resin, selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol F epoxy resin, brominated bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, brominated bisphenol A epoxy resin, bixylenol epoxy resin, biphenol epoxy resin, alicyclic epoxy resin, soluble novolac epoxy resin, cresol soluble epoxy resin, trisphenol methane epoxy resin, N-glycidyl epoxy resin, triglycidyl isocyanurate, 2,6-xylenol dimer diglycidyl ether, alicyclic epoxy resin and xylene epoxy resin; Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the heat-curing component is 25 to 40 parts by mass; Preferably, the inorganic filler is selected from one or more of barium sulfate, barium titanate, calcium oxide, talc, fumed silica, silica, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, titanium oxide, mica powder and kaolin, preferably one or more of barium sulfate, silica, aluminum oxide, aluminum hydroxide and calcium carbonate; Preferably, based on 100 parts by mass of the composition of the alkali-soluble photosensitive modified epoxy resin and the alkali-soluble flexible photosensitive resin, the mass fraction of the inorganic filler is 30 to 70 parts by mass.

10. A photosensitive dry film, characterized in that: The invention comprises a photosensitive film obtained by curing the photosensitive solder resist ink composition according to claim 7.

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