A photosensitive resin composition, a dry film, a cured film, a printed circuit board, and a dry film production method

Abstract

The present application relates to the technical field of photosensitive material, and particularly discloses a photosensitive resin composition, a dry film, a cured film, a printed circuit board and a dry film preparation method. To ensure that the flexibility, cracking resistance and touch-dryness of the cured film formed on the printed circuit board meet the use requirements, and to ensure that the cured film can retain a proper amount of carboxyl groups after the photocuring reaction in the processing process to facilitate the development work, the photosensitive resin composition provided by the present application comprises: A. a carboxyl and vinyl-containing resin; B. a carboxyl-containing and vinyl-free acrylic resin; C. an epoxy resin; and D. a photoinitiator. In the present application, the epoxy groups in component C react with the carboxyl groups in components A and B, and therefore the ratio of the total content of the carboxyl groups in components A and B to the total content of the epoxy groups in component C is limited to 0.8-1.6.

Description

Technical Field

[0001] This invention relates to the field of photosensitive materials technology, specifically to a photosensitive resin composition, a dry film, a cured film, a printed circuit board, and a method for preparing the dry film. Background Technology

[0002] With the increasing application of electronic products in consumer electronics, communications, automotive electronics, industrial control, and medical fields, printed circuit boards (PCBs) have become indispensable components. They serve both as a support for electronic components and as a provider of electrical connections for these components.

[0003] In the PCB manufacturing process, several key steps involve the curing film processing technology. The resulting curing film mainly covers the copper foil surface of the PCB board. On the one hand, it protects the copper lines of the PCB from the effects of moisture, chemicals and other environmental factors. On the other hand, the areas covered by the curing film are mostly areas on the PCB that do not require soldering, such as unused pads. Therefore, the curing film can also prevent the formation of unnecessary connections during the soldering process.

[0004] Generally, the processing of cured films relies on two methods. One method involves directly coating the resin composition into a liquid onto a PCB board, followed by drying, photocuring, and thermal curing to form the cured film. If modifications to the shape of the cured film are needed, a developing step can be added between photocuring and thermal curing. The second method first involves coating the resin composition onto a carrier film, drying it to prepare a dry film for storage. When needed, the dry film is laminated onto the PCB board, and then subjected to photocuring and thermal curing to obtain the cured film. Similarly, a developing step can be added as required. In both of these processing methods, the thermal curing stage utilizes the carboxyl and epoxy groups in the resin composition to undergo cross-linking reactions, increasing the cross-linking density of the resin composition to meet the requirements for the cured film's heat resistance, weather resistance, and even strength.

[0005] However, when the resin composition contains a large number of carboxyl groups, the resin composition as a whole will exhibit good hydrophilicity. This may cause the solvent to be difficult to evaporate, whether in the drying step of the dry film production process or in the drying step of the adhesive on the PCB board. Ultimately, this will result in defects such as poor touch dryness during the preparation process.

[0006] Simply reducing the amount of carboxyl groups in the resin composition can easily lead to an excessively low crosslinking density in the cured film, making it difficult for the physical properties of the cured film, such as heat resistance, weather resistance, and even strength, to meet the requirements for use. On the other hand, if there is a developing step in the overall processing of the cured film, an insufficient amount of carboxyl groups will affect the progress of the developing step, such as causing excessively long developing time, excessively large developing debris, incomplete developing, and low resolution, thereby affecting the PCB board processing qualification rate. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a photosensitive resin composition that has good touch-drying properties during the preparation of dry film or cured film, and the prepared dry film or cured film has good flexibility and crack resistance; at the same time, the photosensitive resin composition can retain an appropriate amount of carboxyl groups during the curing film processing, which facilitates processing steps such as development.

[0008] The present invention is achieved through the following technical solution.

[0009] A photosensitive resin composition comprises: component A: a resin containing carboxyl and vinyl groups; component B: an acrylic resin containing carboxyl groups but not vinyl groups; component C: an epoxy resin; and component D: a photoinitiator; wherein the content of component C is related to the content of components A and B as follows:

[0010]

[0011] a A m represents the average carboxyl group value of component A mentioned above. A a represents the mass of component A mentioned above. B m represents the average carboxyl group value of component B mentioned above. B This represents the mass of component B mentioned above, b. C This represents the average epoxy equivalent of component C mentioned above, m. C M represents the mass of component C mentioned above. COOH It represents the relative molecular mass of the carboxyl group.

[0012] This invention introduces a relational expression to demonstrate and determine the relationship between the content of component C and the contents of components A and B. This relational expression is not a traditional physical law expression; it primarily involves inputting multiple physical quantities of different units, calculating, and then outputting a manually defined composite value. This composite value does not possess the units of traditional physical quantities, but is solely used to determine whether the relationship between components A, B, and C meets the requirements of this invention and to demonstrate the dosage relationship between the three.

[0013] Within the above relation, a AThe average carboxyl group value represents component A above. This average carboxyl group value refers to the mass of carboxyl groups (-COOH) contained in each unit mass of the polymer or compound, usually expressed in mg / g. The method for determining the average carboxyl group value generally involves neutralizing the carboxyl groups in the sample with a standard alkali solution (usually sodium hydroxide solution), then determining the required volume of alkali solution by titration, and finally calculating the average carboxyl group value using the following formula:

[0014]

[0015] V is the volume (ml) of NaOH standard titration solution consumed by the sample.

[0016] V0 is the volume (ml) of NaOH standard titration solution consumed in the blank test, which is usually close to 0.01 ml.

[0017] C NaOH This is the concentration (mol / L) of the NaOH standard titration solution.

[0018] M COOH It represents the relative molecular mass (g / mol) of the carboxyl group.

[0019] m is the mass of the sample (g).

[0020] As a further improvement of the present invention, the photosensitive resin composition further includes: component E, wherein component E is selected from at least one of photopolymerizable monomers and photopolymerizable oligomers.

[0021] As a further improvement of the present invention, the molecular chain end of the above-mentioned component E contains at least two carbon-carbon double bonds.

[0022] As a further improvement of the present invention, neither component A nor component B contains an aromatic ring.

[0023] As a further improvement of the present invention, the weight-average molecular weight of both component A and component B is 10,000 to 50,000 g / mol.

[0024] As a further improvement of the present invention, the double bond equivalent in component A is 200~800g / mol.

[0025] As a further improvement of the present invention, the above-mentioned photosensitive resin composition further includes: component F; the above-mentioned component F is a white filler, and the median particle size, i.e., D50, of the above-mentioned white filler is 200~800nm.

[0026] As a further improvement of the present invention, the product comprises, by weight, 15 to 40 parts of component A, 0.5 to 10 parts of component B, and 0.5 to 5 parts of component D.

[0027] Secondly, the present invention provides a dry film, which is prepared by coating any of the above-mentioned photosensitive resin compositions onto a carrier film and then drying it.

[0028] Thirdly, the present invention provides a method for preparing a dry film, comprising the following steps: S1. providing any of the components of the above-mentioned photosensitive resin composition; S2. mixing and dispersing the components evenly, and grinding and dispersing until the particle size reaches below 10 μm to obtain a mixture; S3. coating the mixture onto a carrier film, drying it to form a dry film.

[0029] Fourthly, the present invention provides a cured film, which is prepared by coating, drying, photocuring and heat curing using any of the above-mentioned photosensitive resin compositions, or by photocuring and heat curing using one of the above-mentioned dry films.

[0030] Fifthly, the present invention provides a printed circuit board comprising the above-mentioned cured film.

[0031] The main beneficial effects of this invention include:

[0032] (1) The carboxyl and epoxy groups in the photosensitive resin composition of the present invention are appropriate, which ensures that in the heat curing step of the curing film preparation process, an appropriate amount of carboxyl groups can undergo cross-linking reaction with epoxy groups to enhance the strength and hardness of the final cured film, and also improve its heat resistance, chemical resistance and solvent resistance.

[0033] (2) The proper control of the carboxyl content in the photosensitive resin composition in this invention also ensures that the unexposed area has a sufficient and appropriate dissolution rate in the alkaline developer during the development step of the cured film processing. This ensures that the unexposed area can be completely, uniformly and quickly dissolved and removed by the developer, thereby ensuring the rapid and smooth progress of the development work. Specifically, the carboxyl content in the photosensitive resin composition in this invention will not be too low, which would lead to difficulties in development and defects such as residual glue, nor will it be too high, which would lead to excessively fast development and thus cause phenomena such as excessive side etching on the sidewall of the pattern.

[0034] (3) The proper control of the carboxyl content in the photosensitive resin composition in this invention also avoids the presence of too many hydrophilic groups in the cured film, thereby significantly reducing the hygroscopicity of the cured film and improving the intrinsic quality and reliability of the cured film.

[0035] (4) Component A in the photosensitive resin composition of the present invention contains a variety of flexible segments in its structure. The introduction and use of this component can improve flexibility, but correspondingly, it is easy to cause defects such as decreased touch dryness and decreased heat resistance and yellowing resistance. Component B has a higher glass transition temperature, which helps to improve the overall touch dryness and hardness of the resin composition in which it is located. Therefore, in the present invention, the combination of component A and component B makes the resulting photosensitive resin composition have both good flexibility and better touch dryness. Detailed Implementation

[0036] The invention will now be described in further detail with reference to specific implementation examples.

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0038] In this invention, the photosensitive resin composition comprises: component A: a resin containing carboxyl and vinyl groups; component B: an acrylic resin containing carboxyl groups but not vinyl groups; component C: an epoxy resin; and component D: a photoinitiator. The relationship between the content of component C and the contents of components A and B is as follows:

[0039]

[0040] In this formula, a A m represents the average carboxyl group value of component A. A a represents the mass of component A. B m represents the average carboxyl group value of component B. B Indicates the mass of component B, b C This indicates the average epoxy equivalent of component C, which in this example is 100~800 g / mol, m C M represents the mass of component C. COOH It represents the relative molecular mass of the carboxyl group.

[0041] The photosensitive resin composition of the present invention can be processed into a dry film. The processed dry film can be stored for later use and then bonded to a PCB board for subsequent use. After photocuring and thermal curing, a cured film is formed. If the shape of the cured film needs to be modified, a developing step is added between photocuring and thermal curing.

[0042] The preparation process of the dry film is as follows: First, the above raw materials are weighed according to the specified ratio, then mixed and stirred, dispersed, etc., to ensure uniform mixing and form a uniform photosensitive resin composition. Then, the particle size of the components in the photosensitive resin composition is controlled to below 10 μm by grinding, sand milling, etc. Organic solvents can be added during this process to adjust viscosity, etc.

[0043] The organic solvents used include, but are not limited to, any one or more of the following: ketone solvents such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbon solvents such as toluene, xylene, and tetramethylbenzene; glycol ether solvents 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 tripropylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbon solvents such as octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha.

[0044] After the photosensitive resin composition is prepared, it is uniformly coated onto a carrier film (such as a polyolefin film, polyester film, or polyimide film). The coating method can include spin coating, blade coating, or spray coating. The carrier film coated with the photosensitive resin composition is then fed into a drying device, where heat is used to remove the solvent and moisture, allowing the photosensitive resin composition to dry and form a dry film. More preferably, a protective film can be applied to the dry film to form a laminate, making the prepared dry film easier to store.

[0045] Meanwhile, the photosensitive resin composition in this invention can also be directly coated onto a PCB board and then processed into a cured film after passing through drying, photocuring and thermal curing steps. Similarly, if it is necessary to modify the shape of the cured film, a developing step can be interspersed between the photocuring and thermal curing steps.

[0046] Printed circuit boards (PCBs) covered with a curing film are protected from moisture, chemicals, and other environmental factors by the curing film's properties, including copper traces. Furthermore, the addition of a developing step ensures that the resulting curing film typically covers areas of the PCB that do not require soldering, preventing unnecessary connections from forming during subsequent PCB soldering processes.

[0047] Hereinafter, each component of the photosensitive resin composition of the present invention will be described in detail.

[0048] Component A: Resin containing carboxyl and vinyl groups.

[0049] Component A contains both double bonds and carboxyl groups. Therefore, when processing the photosensitive resin composition into dry film or other forms, component A can undergo photocuring with component D, and can also synergistically undergo thermocuring with component C in conjunction with component B.

[0050] Therefore, in the process of processing the photosensitive resin composition or the dry film prepared therefrom into a cured film, the first step is to use photocuring to form a preliminary curing. If the curing process involves a developing step, the parts that need to be removed can be covered in the photocuring step to prevent them from participating in the photocuring reaction. The parts that have not been photocured can dissolve in the developing solution, so that the cured film, after shape modification, only covers the parts on the PCB board that need protection. The subsequent thermal curing step can enhance the cross-linking effect between the components in the photosensitive resin composition, enhance the mechanical properties, heat resistance, weather resistance, and other properties of the processed cured film, and give the cured film functions such as water resistance, solvent resistance, and solder resistance.

[0051] Specific examples of component A include, for instance, one or more of the following: alkali-soluble acrylates, epoxy acrylates, polyurethane acrylates, polyester acrylates, and polyether acrylates.

[0052] The double bond equivalent in component A is preferably 200-800 g / mol, more preferably 300-500 g / mol. Taking 300 g / mol as an example, it specifically means that there are 300 mol of double bonds per gram of resin. If the double bond equivalent in component A is too low, it will easily lead to a low crosslinking density in the photosensitive resin composition, affecting the strength and hardness of the material and making the material more susceptible to interference from external factors such as temperature. On the other hand, if the double bond equivalent is too high, it will easily lead to an excessively high crosslinking density in the photosensitive resin composition, which will negatively affect the flexibility and processing performance of the photosensitive resin composition.

[0053] Component B: Acrylic resin containing carboxyl groups but without vinyl groups.

[0054] Component B is obtained by copolymerization of methacrylic acid or acrylic acid and its alkyl esters, and component B has the following structure:

[0055]

[0056] A1 and A2 represent H or CH3 groups, respectively. R represents an alkyl group, preferably an alkyl group with 8 or fewer carbon atoms. Alkyl groups within this range can achieve a balance between core properties such as hardness, flexibility, strength, and solubility. However, if the carbon chain in the supported group is too long, it will lead to a decrease in strength, an increase in hydrophobicity, and defects such as stickiness.

[0057] Preferably, the weight-average molecular weight of component A is 10,000 to 50,000 g / mol, more preferably 10,000 to 30,000 g / mol; and the weight-average molecular weight of component B is 10,000 to 50,000 g / mol, more preferably 10,000 to 20,000 g / mol.

[0058] In photosensitive resin compositions, a weight-average molecular weight (MAM) of components A and B exceeding 10,000 g / mol ensures good strength and toughness, as well as appropriate viscosity. This allows the composition to adhere to the substrate during processing, forming stable coatings and films. Furthermore, it facilitates vitrification and lowers the overall transition temperature of the photosensitive resin composition, making thermosetting easier. However, excessively high MAM results in poor flowability during processing, hindering uniform coating and molding, increasing processing difficulty and cost. It also leads to excessive rigidity and poor flexibility, limiting its application in printed circuit boards.

[0059] Preferably, neither component A nor component B contains aromatic rings. That is, component A is preferably a carboxyl and vinyl resin that does not contain aromatic rings, and component B is preferably a carboxyl acrylic resin that does not contain aromatic rings and vinyl groups. Further restrictions on components A and B are beneficial to improving the yellowing resistance of the photosensitive resin composition.

[0060] Aromatic ring structures are highly conjugated systems. When π electrons in their molecular orbitals absorb ultraviolet (UV) energy, they are easily excited to unstable high-energy states, which can cause yellowing in several ways. First, the energy of the excited state can trigger molecular rearrangement or bond breaking. In resin compositions, these changes easily generate chromophores such as quinone structures. These chromophores exhibit specific absorption in the visible light region, macroscopically manifesting as yellowing. Second, after absorbing UV energy, aromatic ring structures not only readily decompose but also transfer energy to surrounding oxygen or other polymer molecules. This acts as a catalyst, inducing and accelerating oxidative degradation reactions within the system, ultimately generating carbonyl-containing yellow products, also macroscopically manifesting as yellowing.

[0061] Furthermore, during the high-temperature curing process or long-term high-temperature working environment, the adjacent CH bonds of the aromatic ring structure are relatively active and easily undergo auto-oxidation with oxygen to generate peroxide free radicals, which can then trigger free radical chain reactions and ultimately produce yellow degradation products, causing the overall yellowing change of the system on a macroscopic scale.

[0062] Therefore, further restricting components A and B to exclude aromatic ring structures from the resin composition not only avoids the yellowing effect easily caused by aromatic ring structures themselves, but also benefits from the fact that aliphatic resins without aromatic rings are more stable, have higher CH bond energies, and are less prone to initiating oxidation reaction chains, thus avoiding the impact of aromatic ring structures on the surrounding environment. Ultimately, this results in the resin composition possessing excellent resistance to heat and oxygen yellowing.

[0063] This preferred method enables the cured film and the like, ultimately prepared from the resin, to be applied to printed circuit boards in the field of LCD display technology. In this field, it is required to reflect LED light as much as possible with low energy consumption to improve luminous efficiency. Therefore, the solder resist and encapsulation materials for related printed circuit boards need to be prepared using photosensitive resin compositions or their dry films with strong resistance to yellowing to obtain the corresponding cured films.

[0064] Component C: Epoxy resin

[0065] The epoxy groups in component C are highly reactive and can undergo cross-linking reactions with carboxyl groups and other groups in the other components to form a three-dimensional network structure. This cross-linking reaction can enhance the strength and hardness of the photosensitive resin composition, and also improve its heat resistance, chemical resistance, and solvent resistance.

[0066] Component C can be any one of glycidyl ether type epoxy resin, alicyclic epoxy resin, or oxetane type epoxy resin. Specific examples include, but are not limited to, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic type epoxy resin, o-cresol type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, aliphatic type epoxy resin, and heterocyclic type epoxy resin.

[0067] In the photosensitive resin composition of the present invention, components A and B can react with component C through carboxyl groups. On the one hand, this promotes the cross-linking reaction in the photosensitive resin composition, ensuring that the photosensitive resin composition achieves a certain cross-linking density; on the other hand, it improves the mechanical properties, heat resistance, weather resistance, and other properties of the photosensitive resin composition. The limitation on the amount of components A, B, and C in the present invention actually limits the carboxyl group content in components A and B, and the ratio between these carboxyl groups and the epoxy group content in component C.

[0068] Firstly, the proper control of carboxyl group content gives the resulting cured film an advantage in the developing process. Specifically, in the developing step, the unexposed areas in the cured film processed in this invention have a suitable dissolution rate in the alkaline developing solution, thus ensuring that the unexposed areas are completely, uniformly, and quickly dissolved and removed by the developing solution, thereby enabling the developing process to proceed quickly and accurately. Furthermore, the proper control of carboxyl group content also avoids leaving excessive hydrophilic groups in the cured film, thereby significantly reducing the hygroscopicity of the cured film.

[0069] Secondly, controlling the ratio between carboxyl and epoxy groups can promote a good crosslinking density in the resin composition, resulting in good mechanical strength, heat resistance, and chemical resistance. Specifically, if the ratio is too high, a dense crosslinking network cannot be formed in the resin composition, leading to defects such as low hardness, poor adhesion, poor heat resistance (e.g., substandard solderability), poor chemical resistance, and weak mechanical strength in the cured film. Furthermore, the cured film may be too soft and easily scratched, hindering its processing and use. Conversely, if the ratio is too low, excessive epoxy groups may lead to an overly high degree of crosslinking in the resin composition. This change results in excessively high overall hardness, brittleness, and reduced flexibility in the cured film, making it prone to microcracks when subjected to thermal stress (e.g., thermal cycling, or dip soldering). Excessive crosslinking also introduces significant internal stress, affecting its adhesion to copper foil or substrates.

[0070] Therefore, the limitation on the amount of components A, B and C used in this invention is more reasonable and can overcome the above-mentioned defects.

[0071] Component D: Photoinitiator

[0072] In the process of processing the photosensitive resin composition or the dry film prepared therefrom into a cured film, a photocuring reaction is required. When exposed to ultraviolet or visible light, component D absorbs the light energy and undergoes a photochemical reaction, thereby triggering the other components in the photosensitive resin composition to participate in the polymerization reaction.

[0073] Specific examples of component D include, but are not limited to: benzoin and its derivatives (benzoin, benzoin dimethyl ether, benzoin isopropyl ether, benzoin butyl ether), alkyl phenyl ketones (α,α-diethoxyacetophenone, α-hydroxyalkyl phenyl ketone, α-amine alkyl phenyl ketone), acylphosphine oxides (aromatic acylphosphine oxide, bisbenzoylphenylphosphine oxide), and other cleavage-type photoinitiators, such as IGM 651, 184, TPO, 819, 907, etc.; it can also be benzophenones (benzophenone, 2,4-dihydroxybenzophenone, michalcone), thioxanthones (thiopropoxythioxanthone, isopropylthioxanthone), and other hydrogen-abstracting photoinitiators, such as ITX, DETX, BP, etc.; it can also be at least one of oxime esters (OXE-1, OXE-2, etc.) and dicene compounds (784, etc.).

[0074] Preferably, the photosensitive resin composition further includes component E, which is selected from any one or more of photopolymerizable monomers and photopolymerizable oligomers.

[0075] The addition of component E can reduce the viscosity of the photosensitive resin composition. Adding component E to the photosensitive resin composition reduces resistance during processing, improving processing efficiency. For example, when processing the photosensitive resin composition into a dry film form, it facilitates coating. Furthermore, the improved flowability of the photosensitive resin composition reduces defects such as bubbles during processing, improving the surface quality of the product. Simultaneously, due to the flexible groups (such as ether bonds and ester bonds) contained in component E, the photosensitive resin composition maintains strength while possessing good flexibility and impact resistance.

[0076] Preferably, component E has at least two carbon-carbon double bonds at the end of its molecular chain. This structure ensures that component E can work synergistically with component A in the photocuring process, further enhancing the stability of the part involved in photocuring and preventing it from being washed away by the developer during the developing step.

[0077] Specific examples of component E may include, but are not limited to: monofunctional acrylates, difunctional acrylates, trifunctional acrylates or polyfunctional acrylates, monofunctional methacrylates, difunctional methacrylates, trifunctional methacrylates or polyfunctional methacrylates. Specifically, such as any one or more of the following: (ethoxy)phenol methacrylate, (ethoxy)phenol acrylate, stearic acid acrylate, ethoxy(propoxy)nonylphenol methacrylate, ethoxy(propoxy)nonylphenol acrylate, ethoxy(propoxy)tetrahydrofurfuryl acrylate, ethoxy(propoxy)tetrahydrofurfuryl methacrylate, 1,6-hexanediol diacrylate, tricyclodecanediethanol diacrylate, dioxanediol diacrylate, ethoxy(propoxy)bisphenol A di(meth)acrylate, polyethylene glycol (400) diacrylate, polypropylene glycol (600) diacrylate, ethoxy(propoxy)trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

[0078] Based on the manufacturing requirements of printed circuit boards in the field of LCD display technology, the above-mentioned photosensitive resin composition preferably further includes component F, which is a white filler with a median particle size of 200-800 nm. The addition of component F improves the overall reflectivity of the photosensitive resin composition. Combined with components A and B, which do not contain aromatic rings, it ensures that the dry film prepared from the photosensitive resin composition can maintain its white color for a long time, thus ensuring its high reflectivity over a long period.

[0079] Specific examples of component F may include, but are not limited to, one or more combinations of titanium dioxide, zinc oxide, zinc barium white, lead white, etc.; more preferably titanium dioxide, and more preferably rutile titanium dioxide.

[0080] Preferably, the photosensitive resin composition further comprises component G, which is an additive filler. Component G includes, but is not limited to, at least one of reinforcing fillers, color developers, plasticizers, defoamers, polymerization inhibitors, leveling agents, dispersants, and antioxidants. The addition of additive fillers can improve some properties of the photosensitive resin composition, such as making the photosensitive resin composition uniformly dispersed, and providing certain antioxidant and yellowing resistance.

[0081] The reinforcing fillers include, but are not limited to, at least one of barium sulfate, silica, talc, and calcium carbonate.

[0082] The colorimetric reagents include, but are not limited to, at least one of pentyl bromide, ethylene dibromide, benzyl bromide, dibromomethane, tribromomethylphenyl sulfone, trichloroacetamide, pentyl iodide, and chloroethane.

[0083] The plasticizer includes, but is not limited to, at least one of phthalic acid compounds or sulfonamide compounds; more preferably, at least one of diethyl phthalate, diphenyl phthalate, and p-toluenesulfonamide is selected.

[0084] Defoamers include, but are not limited to, at least one of the following: non-silicone defoamers, polyether defoamers, silicone defoamers, and polyether-modified silicone defoamers.

[0085] The polymerization inhibitors include, but are not limited to, at least one of p-methoxyphenol, hydroquinone, pyrogallol, tert-butylcatechol, and aluminum salt of N-nitrosophenylhydroxylamine.

[0086] Leveling agents include, but are not limited to, high molecular weight dispersants such as polycarboxylic acid-based, naphthalene sulfonic acid formalin condensation-based, polyethylene glycol, polycarboxylic acid partially alkyl ester-based, polyether-based, and polyalkylene polyamine-based, and low molecular weight dispersants such as alkyl sulfonic acid-based, quaternary ammonium-based, higher alcohol epoxide-based, polyol ester-based, and alkyl polyamine-based.

[0087] Dispersants include, but are not limited to, compounds with polar groups such as carboxyl, hydroxyl, and acid esters, polymers such as acidic compounds such as phosphate esters, copolymers containing acid groups, hydroxyl-containing polycarboxylic acid esters, polysiloxanes, and salts of long-chain polyaminoamides and acid esters.

[0088] Antioxidants include, but are not limited to, at least one of amine antioxidants, phenolic antioxidants, thioester-assisted antioxidants, phosphite-assisted antioxidants, and thioether-assisted antioxidants.

[0089] In this invention, the raw materials are mixed in the corresponding proportions to form a photosensitive resin composition, wherein the content of component A is 15-40 parts by weight, the content of component B is 0.5-10 parts by weight, and the content of component D is 0.5-5 parts by weight. Preferably, the content of component A is 20-30 parts by weight, the content of component B is 0.5-5 parts by weight, and the content of component D is 3-5 parts by weight.

[0090] More preferably, to improve the viscosity and reflectivity of the photosensitive resin composition, the aforementioned components E, F, and G can be added additionally, with the following amounts: component E is 1-15 parts by weight, component F is 30-70 parts by weight, and component G is 0.1-5 parts by weight. Preferably, component E is 5-15 parts by weight, component F is 40-60 parts by weight, and component G is 0.1-3 parts by weight.

[0091] Example 1:

[0092] In the photosensitive resin composition, component A is selected from Daicel ACA Z250, which does not contain aromatic rings. The double bond equivalent in component A is 380 g / mol, and the weight-average molecular weight is 22000 g / mol.

[0093] Component B is a carboxyl-containing acrylic resin that does not contain aromatic rings or vinyl groups, and its general chemical formula is shown below:

[0094]

[0095] In this embodiment, A1 is a CH3 group, A2 is a CH3 group, and R is a CH3 group. The solid portion of resin in component B has a carboxyl value of 100 mg / g, meaning that each gram of solid resin in component B contains 100 mg of carboxyl groups. The weight-average molecular weight of component B is 16000 g / mol. In actual processing of photosensitive resin compositions, component B is usually added to the photosensitive resin composition in solution form. Therefore, exemplarily, the solution containing component B used in this embodiment is synthesized by the following method:

[0096] S1. In a pressure-resistant reactor equipped with a thermometer, condenser and mechanical stirrer, add 200 parts by weight of deionized water and 0.3 parts by weight of sodium sulfate, and start stirring until they are completely dissolved.

[0097] S2. First, thoroughly mix 80.8 parts by weight of methyl methacrylate (MMA) and 19.2 parts by weight of methacrylic acid (MAA). Then, add 4.0 parts by weight of polymerization initiator (BPO) and 3.8 parts by weight of chain transfer agent (MSD) to the monomer mixture, and stir until all components are completely dissolved to obtain a uniform and transparent oil phase.

[0098] S3. Add the oil phase to the aqueous system in the reactor, along with 500 ppm of polyvinyl alcohol as a dispersant. Maintain efficient stirring and completely replace the air in the reactor with nitrogen. Then, slowly raise the temperature to 80°C to initiate suspension polymerization. During polymerization, control the stirring speed to ensure that the monomer droplets remain in a stable suspension.

[0099] S4. After the reaction is complete, the resulting suspension is filtered through a 30μm sieve to separate the particles. The collected granular resin is placed in a 40℃ warm air drying oven for constant temperature drying until all moisture is removed.

[0100] S5. Using dipropylene glycol methyl ether (DPM) as a solvent, the dried copolymer resin is redissolved and its solid content concentration is adjusted to 50 wt%, thus obtaining the resin solution required for component B in this embodiment.

[0101] Component C is hydrogenated bisphenol A type epoxy resin, specifically Guodu Chemical ST-3000, with an average epoxy equivalent of 220 g / mol. In the compositional relationship between components A, B, and C, Where a A It is 25 mg / g, a B Therefore, considering only the solid content in the solution, it is 100 mg / g, M COOH It is 45 g / mol.

[0102] Component D is TPO.

[0103] Component E is a polyester-type polyurethane acrylate monomer with two carbon-carbon double bonds at its end. For example, in this embodiment, Sartoma CN 9001 NS is used.

[0104] Component F is rutile titanium dioxide with a median particle size of 360 nm. For example, Chemours R706 is used in this embodiment.

[0105] Component G contains a leveling agent and an antioxidant, wherein the leveling agent is an acrylate leveling agent, and for example, in this embodiment, DIGIC FLOW300 is used; the antioxidant is a hindered phenolic antioxidant, and for example, in this embodiment, BASFIrganox 1010 is used.

[0106] In this embodiment, by weight, the photosensitive resin composition contains 25 parts by weight of component A, 3 parts by weight of component B (solid portion only), 4.5 parts by weight of component C, 3 parts by weight of component D, 10 parts by weight of component E, 50 parts by weight of component F, and 3 parts by weight of component G.

[0107] Example 2:

[0108] The difference between this embodiment and Example 1 is that in this embodiment, component A is selected from Daicel ACA Z320, which does not contain an aromatic ring. The double bond equivalent in component A is 450 g / mol, the weight-average molecular weight is 23000 g / mol, and the average carboxyl value is 43 mg / g.

[0109] In this embodiment, regarding the compositional relationship between components A, B, and C, By weight, the photosensitive resin composition contains 17 parts by weight of component A, 10 parts by weight of component B (solid portion only), 8.5 parts by weight of component C, 3 parts by weight of component D, 10 parts by weight of component E, 50 parts by weight of component F, and 3 parts by weight of component G.

[0110] Example 3:

[0111] The difference between this embodiment and Example 1 is that in this embodiment, component A is Daicel ACA Z300, which does not contain an aromatic ring. The double bond equivalent in component A is 450 g / mol, the weight-average molecular weight is 21000 g / mol, and the average carboxyl value is 42 mg / g.

[0112] In this embodiment, regarding the compositional relationship between components A, B, and C, By weight, the photosensitive resin composition contains 15 parts by weight of component A, 3 parts by weight of component B (solid portion only), 4.5 parts by weight of component C, 3 parts by weight of component D, 10 parts by weight of component E, 50 parts by weight of component F, and 3 parts by weight of component G.

[0113] Example 4:

[0114] The difference between this embodiment and Example 1 is that in this embodiment, component B is a carboxyl-containing acrylic resin that does not contain aromatic rings or vinyl groups. In its general chemical formula, A1 and A2 are both CH3 groups, and R is an ethyl group. The carboxyl value of component B is 150 mg / g, meaning that each gram of solid component B resin contains 150 mg of carboxyl groups. The weight-average molecular weight of component B is 20000 g / mol.

[0115] For example, the solution containing component B used in this embodiment is synthesized by the following method:

[0116] S1. In a pressure-resistant reactor equipped with a thermometer, condenser and mechanical stirrer, add 200 parts by weight of deionized water and 0.3 parts by weight of sodium sulfate, and start stirring until they are completely dissolved.

[0117] S2. First, thoroughly mix 71.3 parts by weight of ethyl methacrylate and 28.7 parts by weight of methacrylic acid (MAA). Then, add 5.0 parts by weight of polymerization initiator (BPO) and 4.5 parts by weight of chain transfer agent (MSD) to the monomer mixture, and stir until all components are completely dissolved to obtain a uniform and transparent oil phase.

[0118] S3. Add the oil phase to the aqueous system in the reactor, along with 500 ppm of polyvinyl alcohol as a dispersant. Maintain efficient stirring and completely replace the air in the reactor with nitrogen. Then, slowly raise the temperature to 80°C to initiate suspension polymerization. During polymerization, control the stirring speed to ensure that the monomer droplets remain in a stable suspension.

[0119] S4. After the reaction is complete, the resulting suspension is filtered through a 30μm sieve to separate the particles. The collected granular resin is placed in a 40℃ warm air drying oven for constant temperature drying until all moisture is removed.

[0120] S5. Using dipropylene glycol methyl ether (DPM) as a solvent, the dried copolymer resin is redissolved and its solid content concentration is adjusted to 50 wt%, thus obtaining the resin solution required for component B in this embodiment.

[0121] In this embodiment, regarding the compositional relationship between components A, B, and C, By weight, the photosensitive resin composition contains 25 parts by weight of component A, 0.5 parts by weight of component B (solid portion only), 3.4 parts by weight of component C, 3 parts by weight of component D, 10 parts by weight of component E, 50 parts by weight of component F, and 3 parts by weight of component G.

[0122] Example 5:

[0123] The difference between this embodiment and Embodiment 1 is that, in this embodiment, component B is a carboxyl-containing acrylic resin that does not contain aromatic rings or vinyl groups. In its general chemical formula, A1 represents a CH3 group, A2 represents an H group, and R represents a propyl group. The carboxyl value of component B is 60 mg / g, meaning that each gram of solid component B resin contains 60 mg of carboxyl groups. The weight-average molecular weight of component B is 12000 g / mol.

[0124] For example, the solution containing component B used in this embodiment is synthesized by the following method:

[0125] S1. In a pressure-resistant reactor equipped with a thermometer, condenser and mechanical stirrer, add 200 parts by weight of deionized water and 0.3 parts by weight of sodium sulfate, and start stirring until they are completely dissolved.

[0126] S2. First, thoroughly mix 90.4 parts by weight of propyl methacrylate and 9.6 parts by weight of acrylic acid. Then, add 5.0 parts by weight of polymerization initiator (BPO) and 4.8 parts by weight of chain transfer agent (MSD) to the monomer mixture, and stir until all components are completely dissolved to obtain a uniform and transparent oil phase.

[0127] S3. Add the oil phase to the aqueous system in the reactor, along with 500 ppm of polyvinyl alcohol as a dispersant. Maintain efficient stirring and completely replace the air in the reactor with nitrogen. Then, slowly raise the temperature to 80°C to initiate suspension polymerization. During polymerization, control the stirring speed to ensure that the monomer droplets remain in a stable suspension.

[0128] S4. After the reaction is complete, the resulting suspension is filtered through a 30μm sieve to separate the particles. The collected granular resin is placed in a 40℃ warm air drying oven for constant temperature drying until all moisture is removed.

[0129] S5. Using dipropylene glycol methyl ether (DPM) as a solvent, the dried copolymer resin is redissolved and its solid content concentration is adjusted to 50 wt%, thus obtaining the resin solution required for component B in this embodiment.

[0130] In this embodiment, regarding the compositional relationship between components A, B, and C, By weight, the photosensitive resin composition contains 40 parts by weight of component A, 2 parts by weight of component B (solid portion only), 5.5 parts by weight of component C, 3 parts by weight of component D, 10 parts by weight of component E, 50 parts by weight of component F, and 3 parts by weight of component G.

[0131] Example 6:

[0132] The difference between this embodiment and Embodiment 1 is that in this embodiment, component E is a polyester acrylate oligomer. For example, Sartoma CN2254 is used in this embodiment, and its molecular chain ends with two carbon-carbon double bonds.

[0133] Example 7:

[0134] The difference between this embodiment and Embodiment 1 is that in this embodiment, component E is a polyurethane acrylate oligomer. For example, CN968 is used in this embodiment, and its molecular chain ends with six carbon-carbon double bonds.

[0135] Example 8:

[0136] The difference between this embodiment and Embodiment 1 is that in this embodiment, component C is an alicyclic epoxy resin. For example, Yantai Donghua DE-1701 is used in this embodiment, with an average epoxy equivalent of 220 g / mol. In the compositional relationship between components A, B, and C... .

[0137] Example 9:

[0138] The difference between this embodiment and Embodiment 1 is that in this embodiment, component C is a bisphenol A type epoxy resin. For example, Nanya NPEL-128E is used in this embodiment, with an average epoxy equivalent of 190 g / mol. In the compositional relationship between components A, B, and C... .

[0139] Example 10:

[0140] The difference between this embodiment and Embodiment 1 is that this embodiment does not include component F and component G.

[0141] Example 11:

[0142] The difference between this embodiment and Embodiment 1 is that, in this embodiment, component B is a carboxyl-containing acrylic resin without vinyl groups, in which A1 and A2 are both CH3 groups and R is a benzyl group. The carboxyl value of component B is 100 mg / g, that is, each gram of solid component B resin contains 100 mg of carboxyl groups. The weight-average molecular weight of component B is 51000 g / mol.

[0143] For example, the solution containing component B used in this embodiment is synthesized by the following method:

[0144] S1. In a pressure-resistant reactor equipped with a thermometer, condenser and mechanical stirrer, add 200 parts by weight of deionized water and 0.3 parts by weight of sodium sulfate, and start stirring until they are completely dissolved.

[0145] S2. First, thoroughly mix 80.8 parts by weight of benzyl methacrylate with 19.2 parts by weight of methacrylic acid (MAA). Then, add 1.2 parts by weight of polymerization initiator (BPO) and 0.8 parts by weight of chain transfer agent (MSD) to the monomer mixture, and stir until all components are completely dissolved to obtain a uniform and transparent oil phase.

[0146] S3. Add the oil phase to the aqueous system in the reactor, along with 500 ppm of polyvinyl alcohol as a dispersant. Maintain efficient stirring and completely replace the air in the reactor with nitrogen. Then, slowly raise the temperature to 80°C to initiate suspension polymerization. During polymerization, control the stirring speed to ensure that the monomer droplets remain in a stable suspension.

[0147] S4. After the reaction is complete, the resulting suspension is filtered through a 30μm sieve to separate the particles. The collected granular resin is placed in a 40℃ warm air drying oven for constant temperature drying until all moisture is removed.

[0148] S5. Using dipropylene glycol methyl ether (DPM) as a solvent, the dried copolymer resin is redissolved and its solid content concentration is adjusted to 50 wt%, thus obtaining the resin solution required for component B in this embodiment.

[0149] Comparative Example 1:

[0150] The difference between this comparative example and Example 1 is that in this comparative example, component C is a heterocyclic epoxy resin, triglycidyl isocyanate, with an average epoxy equivalent of 102 g / mol. Regarding the compositional relationship between components A, B, and C... .

[0151] Comparative Example 2:

[0152] The difference between this comparative example and Example 1 is that in this comparative example, component C is an alicyclic epoxy resin, bis((3,4-epoxycyclohexyl)methyl)adipate, with an average epoxy equivalent of 190 g / mol. Regarding the compositional relationship between components A, B, and C... .

[0153] Test results:

[0154] The photosensitive resin compositions described in Examples 1-11 and Comparative Examples 1-2 were prepared into dry films, and the dry films were subjected to a finger-touch dryness test. Then, a cured film was prepared by laminating the dry film onto a polyimide substrate and completing exposure, development, and thermal curing. The cured film was tested for reflectivity, yellowing resistance, and bending resistance.

[0155] The preparation steps of the dry film include:

[0156] After weighing the raw materials according to the proportions described in the corresponding examples or comparative examples, the raw materials were dispersed evenly using a high-speed disperser, and the particle size was controlled to be around 10 μm by grinding. The viscosity and other parameters of the photosensitive resin composition were adjusted by adding the organic solvent DPM. Then, the photosensitive resin composition was coated onto a carrier film using a roller coater and dried at 80°C to form a dry film. The thickness of the prepared dry film was 40 μm.

[0157] (1) Touch dryness

[0158] After the dry film was prepared, its tack-to-tack state was tested. The results are shown in Table 1.

[0159] The icons in the "Touch Dryness" section are as follows: ◎: Not sticky at all; ○: Not sticky; △: Slightly sticky; ×: Sticky.

[0160] (2) Reflectivity

[0161] Using a spectrophotometer (Konika-Minolta CM-26d), at a color temperature of 6500K and a 10° viewing window, five random locations were selected on the surface of the cured film on the test sample to measure the SCI reflectance at a wavelength of 460nm. The average value R1 of the results was taken.

[0162] The final reflectance data of each cured film sample are shown in Table 1.

[0163] (3) Resistance to yellowing

[0164] After placing the sample in a 250℃ hot air circulating oven for 3 minutes, a spectrophotometer (Konika-MinoltaCM-26d) was used to measure the SCI reflectance at a wavelength of 460nm at 5 randomly selected locations on the surface of the cured film on the test sample under the conditions of 6500K color temperature and 10° observation window. The average value R2 of the results was taken.

[0165] Finally, ΔR = R2 - R1 was calculated, and ΔR was used to reflect the resistance to yellowing. The relevant data are shown in Table 1.

[0166] (4) Bending resistance

[0167] With the cured film surface of the cured film sample as the outer side, the cured film sample was bent so that its inner side was in contact with a 5.0 mm φ cylinder. The results of visually observing whether cracks or fractures occurred were used as the test results for bending resistance, and the test results are shown in Table 1.

[0168] In Table 1, the icons for the section on flexural strength are: ○: No cracks in the cured coating; ×: Cracks in the cured coating.

[0169] Table 1 Summary of test results for Examples 1-11 and Comparative Examples 1-2 .

[0170] The test results show that the dry films prepared in Examples 1 to 11 of the present invention can all achieve good touch dryness, and the corresponding cured films have good bending resistance and meet the basic requirements for the use of cured films.

[0171] Based on this, the test results of Comparative Examples 1 and 2 show that when the amounts of components A, B, C, and D in the photosensitive resin composition are controlled beyond the requirements of this invention, in Comparative Example 1, although the dry film obtained has good touch-drying properties, the corresponding cured film's flexural strength decreases, making it difficult to meet conventional usage requirements. In Comparative Example 2, although a cured film meeting usage requirements was ultimately obtained, the touch-drying problem was not effectively solved in the previously obtained dry film. However, the test results of Example 9 and Comparative Example 2 show that when the overall carboxyl content in the photosensitive resin composition is high but does not exceed the limits of this invention, although the performance of the cured film in other aspects such as reflectivity and yellowing resistance decreases, the corresponding dry film can still maintain good touch-drying properties, thus enabling it to meet some usage scenarios where touch-drying requirements are strict. The test results of Example 10 show that, without the addition of component F, the dry film still has good touch dryness and the corresponding cured film also has good bending resistance. However, the yellowing resistance and reflectivity of the cured film have decreased significantly. Therefore, the dry film and its cured film can still be used in application scenarios with low requirements for reflectivity and yellowing resistance.

[0172] Based on the above test results, it can be seen that, under the selection and dosage control of the four components A, B, C, and D in this invention, the prepared dry film can have excellent touch-drying properties, thus solving the pain point of touch-drying properties in dry films in the industry; and the corresponding cured film can also have bending resistance, thus meeting the basic requirements for the use of cured films. That is, the photosensitive resin composition in this invention can produce dry films and cured films that meet the requirements.

[0173] Furthermore, this photosensitive resin composition can be further optimized in terms of reflectivity and yellowing resistance of the cured film without affecting the aforementioned properties by combining it with various additional components such as E, F, and G. This allows it to meet more complex usage requirements and become a product that is easier to promote and use.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photosensitive resin composition, characterized in that, Includes: Component A: Resin containing carboxyl and vinyl groups; Component B: Acrylic resin containing carboxyl groups but without vinyl groups; Component C: Epoxy resin; Component D: Photoinitiator; The relationship between the content of component C and the contents of components A and B is as follows: ， a A m represents the average carboxyl group value of component A. A a represents the mass of component A. B m represents the average carboxyl group value of component B. B This indicates the mass of component B, b C The average epoxy equivalent of component C is represented by m. C M represents the mass of component C. COOH It represents the relative molecular mass of the carboxyl group.

2. The photosensitive resin composition according to claim 1, characterized in that, The photosensitive resin composition also contains component E; The E component is selected from at least one of photopolymerizable monomers and photopolymerizable oligomers; the molecular chain end of the E component contains at least two carbon-carbon double bonds.

3. The photosensitive resin composition according to claim 1, characterized in that, Neither component A nor component B contains an aromatic ring.

4. The photosensitive resin composition according to claim 1, characterized in that, The weight-average molecular weight of both component A and component B is 10,000 to 50,000 g / mol. The double bond equivalent in component A is 200~800 g / mol.

5. The photosensitive resin composition according to claim 1, characterized in that, The photosensitive resin composition further includes component F; The F component is a white filler, wherein the median particle size of the white filler is 200~800nm.

6. The photosensitive resin composition according to claim 1, characterized in that, The product comprises, by weight, 15 to 40 parts of component A, 0.5 to 10 parts of component B, and 0.5 to 5 parts of component D.

7. A dry film, characterized in that, It is prepared by coating the photosensitive resin composition according to any one of claims 1 to 6 onto a carrier film and then drying it.

8. A method for preparing a dry film, characterized in that, It includes the following steps: S1. Provide each component of the photosensitive resin composition according to any one of claims 1 to 6; S2. Mix and disperse the components evenly, and grind and disperse them until the particle size reaches below 10μm to obtain a mixture; S3. The mixture is coated onto a carrier film and dried to form a dry film.

9. A cured film, characterized in that, The photosensitive resin composition according to any one of claims 1 to 6 is prepared by coating, drying, photocuring and heat curing, or a dry film according to claim 7 is prepared by photocuring and heat curing.

10. A printed circuit board, characterized in that, It includes a cured film as described in claim 9.

Images