A uv inkjet printing ink with excellent viscosity thermal stability and a preparation method thereof

Abstract

This invention discloses a UV inkjet printing ink with excellent viscosity and thermal stability, and its preparation method, relating to the field of inkjet printing ink technology. The UV inkjet printing ink, by weight, comprises the following raw materials: 3-8 parts of blocked thermosetting acrylate, 8-20 parts of epoxy acrylate resin, 2-6 parts of silicone acrylate oligomer, 20-70 parts of acrylate monomer, 3-7 parts of photoinitiator, 1-10 parts of pigment, and 0.1-1 parts of additives. This ink possesses excellent substrate adhesion and thermal shock resistance, while also exhibiting excellent thermal stability. It overcomes the technical defect that the ink system viscosity rises sharply with increasing heating time during long-term operation of the printhead at 50°C, easily clogging the printhead.

Description

Technical Field

[0001] This invention relates to the field of ink technology, and in particular to a UV inkjet printing ink and its preparation method that possesses excellent substrate adhesion, thermal shock resistance, and viscosity thermal stability. Background Technology

[0002] In the manufacturing process of printed circuit boards (PCBs), UV inkjet printing inks are widely used in key processes such as character marking, circuit forming, and solder mask coating. Compared with traditional screen printing, UV inkjet printing technology has significant advantages such as non-contact, high precision, digitalization, and no need for plate making, making it particularly suitable for the production of multi-variety, small-batch, and high-density interconnect (HDI) boards. However, as PCB designs evolve towards finer linewidths, denser spacing, and higher reliability requirements, technologies such as Taiyo Ink Technology from Taiyo Holdings Co., Ltd. (see patents JP6259394B2 or JP6069300B2) have emerged. Taiyo Ink utilizes the physical mixing of closed mono(poly)isocyanate groups with acrylic monomers / resins, leveraging the thermosetting properties of isocyanates to achieve final curing after UV curing and thermosetting. This significantly enhances the adhesion and solder thermal shock resistance of the cured product in the post-inkjet curing process of PCBs.

[0003] However, the above-mentioned inks still have the following defects in actual spraying applications: 1. Because the formation of closed mono(poly)isocyanate groups usually requires the addition of 10-40% by mass of diluent to dilute them to a certain viscosity liquid state in order to complete the formation process, the physically mixed closed mono(poly)isocyanate groups themselves contain a large amount of diluent, which is not conducive to environmental protection.

[0004] 2. The mono(poly)isocyanate groups of the above ink and the acrylic monomer / resin are two independent materials physically mixed. However, under the condition of printing at 50°C for a long time, the closed isocyanate of the simple physical mixture is heated for a long time, the solvent is easy to evaporate, and the closed isocyanate is easy to self-polymerize, separate, precipitate and migrate with the system, which ultimately leads to the increase of ink system viscosity and clogging of the printhead. That is, the existing ink system has poor thermal stability, which causes the ink system viscosity to rise sharply with the continuous increase of heating time, which easily clogs the printhead.

[0005] Therefore, it is necessary to develop a UV inkjet printing ink that has excellent substrate adhesion and thermal shock resistance, as well as excellent thermal stability, to solve the technical defect that causes the ink system viscosity to rise sharply and clog the printhead when the printhead is operated at 50°C for a long time. Summary of the Invention

[0006] The main objective of this invention is to develop a UV inkjet printing ink and its preparation method that possesses excellent substrate adhesion, thermal shock resistance, and viscosity thermal stability.

[0007] This invention achieves the above objective through the following technical solution: providing a UV inkjet printing ink with excellent viscosity and thermal stability, wherein the UV inkjet printing ink comprises, by weight, the following raw materials: 3-8 parts of closed-cell thermosetting acrylate 8-20 parts of epoxy acrylate resin 2-6 parts of organosilicon acrylate oligomer 20-70 parts of acrylate monomer 3-7 parts of photoinitiator 0.1-1 part of auxiliary agent 1-10 parts pigment; The blocked thermosetting acrylate is formed by chemical bonding of blocked isocyanate groups and acrylate double bonds.

[0008] Further, the closed-type thermosetting acrylate is prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of 2-isocyanoethyl methacrylate (IEM) and 0.001-0.003 mol of hydroquinone monomethyl ether (MEHQ) are added to a dry four-necked flask, and the temperature is raised to 50-65°C; 0.8-1.2 mol of butanone oxime is slowly added dropwise, wherein each 1 mol of butanone oxime contains 0.001 mol of dibutyltin dilaurate (DBTDL), and the addition time is 0.4-0.6 h; after the addition is completed, the reaction is maintained at 55-65°C for 1-2 h, and the reaction is monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO absorption peak completely disappeared, and the product was cooled to room temperature to obtain a colorless and transparent liquid product, which was denoted as blocked thermosetting acrylate A.

[0009] Further, the closed-type thermosetting acrylate is prepared by the following method: Under nitrogen protection, 1.8-2.2 mol of isophorone diisocyanate (IPDI) and 0.001-0.003 mol of DBTDL are added to a four-necked flask, and the temperature is raised to 50-60°C; 1.8-2.2 mol of hydroxypropyl acrylate (HPA) is added dropwise, wherein each 2 mol of hydroxypropyl acrylate (HPA) contains 0.004 mol of MEHQ, and the addition time is 1-2 h; after the addition is completed, the temperature is maintained at 60-70°C for 2-3 h; 0.8-1.2 mol of polyethylene glycol 200 is added, and the temperature is raised to 70-80°C for 2.5-3.5 h; the temperature is lowered to 60-70°C, and 1.8-2.2 mol of 3,5-dimethylpyrazole is added dropwise, with a dropwise addition time of 0.8-1.2 h; after the addition is completed, the temperature is maintained for 1.5-2.5 h, and the reaction is monitored at 2270 cm⁻¹ by FTIR.-1 The -NCO peak disappeared, and a pale yellow viscous liquid product was obtained, which was denoted as blocked thermosetting acrylate B.

[0010] Further, the closed-type thermosetting acrylate is prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of HDI trimer and 0.001-0.002 mol of DBTDL are added to a four-necked flask, and the temperature is raised to 55-65℃; 2.5-3.5 mol of ethoxylated hydroxyethyl acrylate EO-HEA is added dropwise, wherein each 3 mol of ethoxylated hydroxyethyl acrylate EO-HEA contains 0.006 mol of MEHQ, the dropwise addition time is 1.5-2.5 h, and after the dropwise addition is completed, the temperature is maintained at 65-75℃ for 2.5-3.5 h; 0.4-0.6 mol of bisphenol A is added, the temperature is raised to 75-85℃, and the reaction is carried out for 3.5-4.5 h; the temperature is lowered to 65-75℃, and 2.5-3.5 mol of ε-caprolactam is added dropwise, the dropwise addition time is 1.5 h, and after the dropwise addition is completed, the temperature is maintained for 2-3 h, and the reaction is monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO peak disappeared, and a pale yellow, high-viscosity liquid product was obtained, which was denoted as blocked thermosetting acrylate C.

[0011] Further, the closed-type thermosetting acrylate is prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of 2-acryloyloxyethyl isocyanate (AOI) and 0.001-0.003 mol of hydroquinone monomethyl ether (MEHQ) are added to a dry four-necked flask, and the temperature is raised to 45-55°C; 0.8-1.2 mol of 3,5-dimethyl-1H-pyrazole is slowly added dropwise, wherein each 1 mol of 3,5-dimethyl-1H-pyrazole contains 0.001 mol of dibutyltin dilaurate (DBTDL), and the addition time is 0.4-0.6 h. After the addition is complete, the reaction is maintained at 55-65°C for 1-2 h, and the reaction is monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO absorption peak completely disappeared; after the reaction was completed, the reaction solution was cooled to room temperature, and the product precipitated as a white solid. After vacuum filtration, washing with ether, and vacuum drying, a white powder was obtained, which was designated as closed-type thermosetting acrylate D.

[0012] Furthermore, the epoxy acrylate is selected from at least one of bisphenol A type epoxy acrylate resin, bisphenol F type epoxy acrylate resin, bisphenol S type epoxy acrylate resin, biphenyl type epoxy acrylate resin, naphthalene type epoxy acrylate resin, Novolacs type epoxy acrylate resin, epoxy acrylate resin with fluorene backbone, glycidyl ether type epoxy acrylate resin, and epoxy acrylate resin made from copolymers of phenolic compounds and dicyclopentadiene.

[0013] Furthermore, the organosilicon acrylate oligomer is selected from organosilicon polyurethane acrylate oligomers; the organosilicon polyurethane acrylate oligomer includes at least one of Changxing DR-U187B and Sartoma CN990.

[0014] Further, the acrylate monomer is one or more of monofunctional acrylate monomers, difunctional acrylate monomers, and polyfunctional acrylate monomers; wherein, the monofunctional acrylate monomer is selected from at least one of PHEA, IBOA, THFA, THF(EO)A, LMA, IDA, IBOMA, 2-EHA, EOEOEA, 4HBA, and CTFA; the difunctional acrylate monomer is selected from at least one of PEGDMA, TPGDA, TEGDMA, PO2-NPGDA, PEGDA, PDDA, NPGDA, HDDA, EO4-BPADA, EO10-BPADA, and DPGDA; and the polyfunctional acrylate monomer is selected from at least one of TMPTA, TMPTMA, GPTA, EO3-TMPTA, TMPT3A, PET3A, and THEICTA.

[0015] Furthermore, the initiator is selected from any one or a combination of at least two of benzoin-based photoinitiators, alkyl phenyl ketone-based photoinitiators, acyl phosphorus oxide-based photoinitiators, or anthrone-based photoinitiators; The pigment includes one or a mixture of two or more of titanium dioxide, azo red, phthalocyanine blue, and carbon black; The additives include at least one of wetting and dispersing agents, leveling agents, defoamers, or film-forming aids.

[0016] The present invention also provides a method for preparing a UV inkjet printing ink with excellent viscosity and thermal stability as described above, specifically including the following steps: mixing the formulated amounts of closed-type thermosetting acrylate, epoxy acrylate resin, silicone acrylate oligomer, acrylate monomer, photoinitiator, additives, and pigment, stirring at 1000-1400 rpm for 1-3 hours, and then filtering with a 1μm filter to obtain the UV inkjet printing ink. Beneficial effects

[0017] This invention designs a UV inkjet printing ink. By compounding a specific ratio of closed-type thermosetting acrylate, silicone acrylate oligomer and acrylate monomer, the resulting UV inkjet printing ink has excellent substrate adhesion and thermal shock resistance, as well as excellent thermal stability. This invention solves the technical defect that the viscosity of the ink system increases sharply with the heating time when the printhead is operated at 50°C for a long time, which easily clogs the printhead.

[0018] The closed-type thermosetting acrylate of this invention uses a closed-type isocyanate acrylate monomer, thus achieving 100% solids content and no volatile diluents, making the ink formulation more environmentally friendly. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] To address the aforementioned technical problems, this invention proposes a UV inkjet printing ink, comprising the following raw materials by weight: 3-8 parts of blocked thermosetting acrylate, 8-20 parts of epoxy acrylate resin, 2-6 parts of silicone acrylate oligomer, 20-70 parts of acrylate monomer, 3-7 parts of photoinitiator, 1-10 parts of pigment, and 0.1-1 parts of additives.

[0023] As a further preferred embodiment, the UV inkjet printing ink, by weight, comprises the following raw materials: 3-6 parts of blocked thermosetting acrylate, 12-16 parts of epoxy acrylate resin, 3-5 parts of silicone acrylate oligomer, 40-65 parts of acrylate monomer, 4-6 parts of photoinitiator, 2-6 parts of pigment, and 0.2-0.8 parts of additives.

[0024] In one embodiment, the blocked thermosetting acrylate includes, but is not limited to, blocked thermosetting acrylates prepared by the following four methods.

[0025] Specifically, the synthesis steps of the first type of closed-type thermosetting acrylate are as follows: Under nitrogen protection, 1 mol of 2-isocyanoethyl methacrylate (IEM) and 0.002 mol of hydroquinone monomethyl ether (MEHQ) are added to a dry four-necked flask, and the temperature is raised to 50°C; 1 mol of butanone oxime (containing 0.001 mol of dibutyltin dilaurate (DBTDL)) is slowly added dropwise over a period of 0.5 h; after the addition is complete, the reaction is maintained at 60°C for 1.5 h, and the reaction is monitored at 2270 cm⁻¹ using FTIR. -1 The -NCO absorption peak completely disappeared, and the temperature was lowered to room temperature to obtain a colorless and transparent liquid product (denoted as blocked thermosetting acrylate A).

[0026] Identification data for the blocked thermosetting acrylate A product: ¹H-NMR ( , δ ppm): 5.5-6.1 (m, 2H, Double bond); 4.3 (t, 2H, ); 3.2 (t, 2H, ); 2.0 (s, 3H, ); 1.9 (s, 3H, ); 1.0-1.6 (m, 5H, butanone oxime alkyl chain); 8.0 (s, 1H, ).

[0027] FTIR (cm) -1 ): 1730 (ester carbonyl C=O), 1640 (acrylate C=C), 3300 (NH), no 2270 (-NCO) absorption peak.

[0028] Physical parameters: molecular weight Mn=280, PDI=1.08; viscosity (25℃)=35mPa·s; blocked NCO content (theoretical value 22.1%, measured value 21.5%).

[0029] The synthesis steps for the second type of closed-type thermosetting acrylate are as follows: Under nitrogen protection, 2 mol of isophorone diisocyanate (IPDI) and 0.002 mol of DBTDL are added to a four-necked flask, and the temperature is raised to 55°C. 2 mol of hydroxypropyl acrylate (HPA, containing 0.004 mol of MEHQ) are added dropwise over 1.5 h, and the reaction is maintained at 65°C for 2.5 h. 1 mol of polyethylene glycol 200 (PEG200) is added, and the temperature is raised to 75°C for 3 h. The temperature is lowered to 65°C, and 2 mol of 3,5-dimethylpyrazole is added dropwise over 1 h, and the reaction is maintained at this temperature for 2 h. FTIR is monitored at 2270 cm⁻¹. -1The -NCO peak disappeared, and a pale yellow viscous liquid product was obtained (denoted as blocked thermosetting acrylate B).

[0030] Product identification data: ¹H-NMR ( , δ ppm): 5.7-6.3 (m, 4H, Double bond); 3.5-3.8 (m, 8H, polyether) ); 3.1 (m, 8H, ); 2.2 (s, 12H, pyrazole ring) ); 6.0 (s, 2H, pyrazole ring CH); 7.8 (s, 2H, ).

[0031] FTIR (cm) -1 ): 1725 (ester carbonyl C=O), 1635 (acrylate C=C), 3320 (NH), no 2270 (-NCO) absorption peak.

[0032] Physical parameters: molecular weight (GPC) Mn=850, PDI=1.13; viscosity (25℃)=110mPa·s; blocked-NCO content (theoretical value 15.3%, measured value 14.8%).

[0033] The synthesis steps of the third type of closed-type thermosetting acrylate are as follows: Under nitrogen protection, 1 mol of HDI trimer and 0.0015 mol of DBTDL are added to a four-necked flask, and the temperature is raised to 60°C; 3 mol of ethoxylated hydroxyethyl acrylate (EO-HEA, containing 0.006 mol of MEHQ) are added dropwise over 2 hours, and the reaction is maintained at 70°C for 3 hours; 0.5 mol of bisphenol A is added, and the temperature is raised to 80°C for 4 hours; the temperature is lowered to 70°C, and 3 mol of ε-caprolactam is added dropwise over 1.5 hours, and the reaction is maintained at 2.5 hours. FTIR is monitored at 2270 cm⁻¹. -1 The -NCO peak disappeared, and a pale yellow, high-viscosity liquid product was obtained (denoted as blocked thermosetting acrylate C).

[0034] Product identification data: ¹H-NMR ( , δppm): 5.8-6.4 (m, 6H, Double bond); 3.6-4.2 (m, 12H, ); 6.8-7.2 (m, 8H, aromatic CH); 1.6 (s, 6H, bisphenol) ); 2.0-2.5 (m, 18H, caprolactam alkyl chain); 7.9 (s, 3H, ).

[0035] FTIR (cm) -1: 1735 (ester carbonyl C=O), 1645 (acrylate C=C), 3310 (NH), no 2270 (-NCO) absorption peak.

[0036] Physical parameters: molecular weight (GPC) Mn=1420, PDI=1.18; viscosity (25℃)=340mPa·s; blocked NCO content (theoretical value 12.3%, measured value 11.8%).

[0037] The synthesis steps of the fourth type of blocked thermosetting acrylate are as follows: Under nitrogen protection, 1 mol of 2-acryloyloxyethyl isocyanate (AOI) and 0.002 mol of hydroquinone monomethyl ether (MEHQ) are added to a dry four-necked flask, and the temperature is raised to 50°C; 1 mol of 3,5-dimethyl-1H-pyrazole (containing 0.001 mol of dibutyltin dilaurate DBTDL) is slowly added dropwise over a period of 0.5 h; after the addition is complete, the reaction is maintained at 60°C for 1.5 h, and the -NCO absorption peak at 2270 cm⁻¹ is completely eliminated by FTIR monitoring; after the reaction is completed, the reaction solution is cooled to room temperature, and the product precipitates as a white solid. After vacuum filtration, washing with ether (20 mL × 2), and vacuum drying, a white powder product (denoted as blocked thermosetting acrylate D, AOI-BP) is obtained with a yield of 96%.

[0038] Product identification data: ¹H-NMR ( , δ ppm): 6.3-6.5 (m, 1H, ); 6.1-6.2 (m, 1H, ); 5.8-5.9 (m, 1H, ); 4.3 (t, 2H, ); 3.5 (t, 2H, ); 2.3 (s, 3H, pyrazole) ); 2.2 (s, 3H, pyrazole) ); 6.0 (s, 1H, pyrazole-H); 8.5 (s, 1H, ).

[0039] FTIR (cm⁻¹): 1730 (ester carbonyl C=O), 1640 (acrylate C=C), 3300 (NH), no absorption peak at 2270 (-NCO).

[0040] Appearance: White powder. NCO content: Theoretical value 17.71%, measured value ≥17.3% (purity ≥98%).

[0041] It should be noted that the blocked thermosetting acrylate of the present invention achieves the intercalation and coexistence of the blocked isocyanate groups and acrylate double bonds in the molecular structure through chemical bonding. That is, the molecular structure is designed to contain acrylate double bonds and block isocyanate groups. The blocked isocyanate groups on the same molecule are fixed at the crosslinking points. The two networks are chemically bonded to form a true IPN (interpenetrating polymer network), which is the same molecule containing acrylate double bonds and blocked isocyanate groups, rather than a simple physical mixture of the two as in Japanese Taiyo Ink.

[0042] Furthermore, the closed-type thermosetting acrylate of the present invention uses a closed-type isocyanate acrylate monomer, thus achieving 100% solids content and no volatile diluents, making the ink formulation more environmentally friendly.

[0043] In this invention, compound A is 2-[(butanone oxime)formamido]ethyl methacrylate, an aliphatic isocyanate with no benzene ring. It is a low-viscosity liquid, solvent-free, low-VOC, and resistant to yellowing. It exhibits good compatibility with polyether / ester segments, polyols, and acrylates, and good compatibility with ink systems. A dense network is formed by controlling the crosslinking density of double bonds and unblocked -NCO double crosslinking points.

[0044] Compound B is an IPDI-HPA-PEG200-DMP-terminated bifunctional acrylate with one 3,5-dimethylpyrazole-terminated -NCO at each end (thermal descaling temperature approximately 160-180°C). It exhibits high reactivity, flexible PEG segments, and good flexibility and hydrophilicity.

[0045] Compound C is an HDI polymer-EO-HEA-bisphenol A-caprolactam-terminated polyacrylate with high functionality, fast reaction rate, high hardness, and a desealing temperature of 170-190°C. It contains a bisphenol A backbone and has good rigidity, heat resistance, and adhesion.

[0046] Compound D is an AOI-BP monofunctional powder with excellent solubility and dispersion in acrylate monomers. It has a low molecular weight and high purity, making it suitable for electronic products. Its unsealing temperature is 120-140℃, which is similar to that of inkjet printing.

[0047] In one embodiment, the epoxy acrylate comprises at least one of the following components: bisphenol A type epoxy acrylate resin, bisphenol F type epoxy acrylate resin, bisphenol S type epoxy acrylate resin, biphenyl type epoxy acrylate resin, naphthalene type epoxy acrylate resin, Novolacs type epoxy acrylate resin, epoxy acrylate resin having a fluorene backbone, glycidyl ether type epoxy acrylate resin, and epoxy acrylate resin made from a copolymer of phenolic compounds and dicyclopentadiene. Preferably, the glycidyl ether type epoxy acrylate resin is at least one of diglycidylresorcinol, tetra(glycidyloxyphenyl)ethane, and tri(glycidyloxyphenyl)methane. In one embodiment, the epoxy acrylate is selected from at least one of Sartoma CN120 or Changxing 6250.

[0048] Specifically, the epoxy groups in epoxy acrylates enhance the adhesion and heat resistance of the cured product. They contain both photocurable double bonds that participate in the initial photocuring and inkjet printing reaction, and thermocurable epoxy groups that further react with NCO groups during the post-baking process.

[0049] In one embodiment, the organosilicon acrylate oligomer is selected from organosilicon polyurethane acrylate oligomers; the organosilicon polyurethane acrylate oligomer includes at least one of Changxing DR-U187B and Sartoma CN990.

[0050] It should be noted that silicone polyurethane acrylate oligomers in UV inks have a dual role of enhancing functionality and optimizing surface properties. These oligomers combine the flexibility of polyurethane with the low surface energy of silicone, giving the ink higher flexibility, folding resistance, and abrasion resistance after curing. They are suitable for flexible substrates or products that require post-processing such as stamping or bending. The silicone component significantly reduces the surface tension of the ink system, which helps improve the leveling of the ink, reduce defects such as pinholes and orange peel, and improve the gloss and smoothness of the printed film.

[0051] In one embodiment, the acrylate monomer can be one or more of the following: monofunctional, difunctional, and polyfunctional.

[0052] In one specific embodiment, the monofunctional acrylate monomer may be at least one of 2-phenoxyethyl acrylate (PHEA), isobornyl acrylate (IBOA), isobornyl methacrylate (IBOMA), tetrahydrofuran acrylate (THFA), tetrahydrofuran acrylate (THF(EO)A), lauryl methacrylate (LMA), isodecanyl acrylate (IDA), isooctyl acrylate (2-EHA), ethoxyethoxyethyl acrylate (EOEOEA), 4-hydroxybutyl acrylate UV monomer (4HBA), and cyclotrimethylolpropane formal acrylate (CTFA).

[0053] In one specific embodiment, the bifunctional acrylate monomer may be at least one of polyethylene glycol dimethacrylate (PEGDMA), tripropylene glycol diacrylate (TPGDA), triethylene glycol dimethacrylate (TEGDMA), propoxy neopentyl glycol diacrylate (PO2-NPGDA), polyethylene glycol diacrylate (PEGDA), diethylene glycol diacrylate (PDDA), neopentyl glycol diacrylate (NPGDA), hexamethylene diacrylate (HDDA), ethoxylated 4-bisphenol A diacrylate (EO4-BPADA), ethoxylated (10) bisphenol A diacrylate (EO10-BPADA), and dipropylene glycol diacrylate (DPGDA).

[0054] In one specific embodiment, the multifunctional acrylate monomer may be at least one of trimethylolpropane trimethacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), propoxylated triglyceride (GPTA), ethoxylated trimethylolpropane triacrylate (EO3-TMPTA), TMPT3A, pentaerythritol triacrylate (PET3A), and tris(2-hydroxyethyl)isocyanurate triacrylate (THEICTA). However, it is not limited to the combinations listed above, and other combinations not listed within the above range are also applicable.

[0055] In one embodiment, the photoinitiator may be any one or a combination of at least two of benzoin-based photoinitiators, alkylphenyl ketone-based photoinitiators, acylphosphide-based photoinitiators, or anthrone-based photoinitiators. In a preferred embodiment, the photoinitiator may be a combination of benzoin-based photoinitiators and alkylphenyl ketone-based photoinitiators; in a preferred embodiment, the photoinitiator may be a combination of alkylphenyl ketone-based photoinitiators and acylphosphide-based photoinitiators; in a preferred embodiment, the photoinitiator may be a combination of acylphosphide-based photoinitiators and anthrone-based photoinitiators; the combination is not limited to those listed above, and other combinations not listed within the above range are also applicable.

[0056] In one embodiment, the pigment includes one or a mixture of two or more of titanium dioxide, azo red, phthalocyanine blue, and carbon black.

[0057] In one embodiment, the additive includes at least one of a wetting and dispersing agent, a leveling agent, a defoamer, or a film-forming aid. It is understood that the additive may be a combination of a wetting and dispersing agent and a defoamer, a combination of a defoamer and a film-forming aid, or a combination of a leveling agent and a film-forming aid, but is not limited to the combinations listed above; other unlisted combinations are also applicable.

[0058] In one embodiment, the UV inkjet printing ink has a viscosity of 9-12 mPa·s at 50°C.

[0059] In one embodiment, the surface tension of the UV inkjet printing ink at 50°C is 21-24 mN / m.

[0060] In a preferred embodiment, the UV inkjet printing ink has a viscosity of 9-12 mPa·s at 50°C and a surface tension of 21-24 mN / m at 50°C.

[0061] The present invention also proposes a method for preparing the above-mentioned UV inkjet printing ink, which specifically includes the following steps: mixing the formulated amounts of closed-type thermosetting acrylate, epoxy acrylate resin, silicone acrylate oligomer, acrylate monomer, photoinitiator, additives, and pigment, stirring at 1000-1400 rpm for 1-3 hours, and then filtering with a 1μm filter to obtain the UV inkjet printing ink.

[0062] The present invention will be further illustrated below through specific embodiments:

[0063] Examples 1-6

[0064] Weigh the raw materials according to the proportions in Table 1, and prepare the UV inkjet printing inks according to the preparation methods in Table 1 to obtain UV inkjet printing inks corresponding to different embodiments. See Table 1 for details:

[0065] Table 1. Formulation table of UV inkjet printing inks for Examples 1-6

[0066] The preparation methods of the UV inkjet printing inks in Examples 1-6 include the following steps: Blocked thermosetting acrylate, epoxy acrylate resin, silicone acrylate oligomer, acrylate monomer, photoinitiator and additives, and pigment were mixed and stirred at 1200 rpm for 2 hours. The mixture was then filtered through a 1 μm filter to obtain the UV inkjet printing inks for each example.

[0067] Comparative Example 1 Compared with Example 3, the difference in Comparative Example 1 is that the amount of compound A in the formulation is 0 parts, while the other formulation amounts and preparation conditions are the same as in Example 3.

[0068] Comparative Example 2 Compared with Example 3, the difference in Comparative Example 2 is that the amount of compound A in the formulation is too large, which is 10 parts. The other formulation amounts and preparation conditions are the same as those in Example 3.

[0069] Comparative Example 3 Compared with Example 3, the difference in Comparative Example 3 is that the amount of organosilicon acrylate oligomer in the formulation is 0 parts, while the other formulation amounts and preparation conditions are the same as in Example 3.

[0070] Comparative Example 4 Compared with Example 3, the difference in Comparative Example 4 is that the amount of compound D in the formulation is too small, at 0.5 parts, while the other formulation amounts and preparation conditions are the same as in Example 3.

[0071] Comparative Example 5 Compared with Example 3, the difference in Comparative Example 5 is that in the formulation, Comparative Example 5 uses an existing solvent-based blocking curing agent (non-bonded structure) instead of the blocking thermosetting acrylate compound A, that is, it purchases the blocking curing agent BI7982 from Taiyo Holdings Co., Ltd. of Japan (for the specific preparation method, please refer to patent JP6259394B2). The remaining formulation amounts and preparation conditions are the same as those in Example 3.

[0072] Effect evaluation and performance testing

[0073] The performance of the UV inkjet printing inks of Examples 1-6 and Comparative Examples 1-5 was tested. The test items and results are shown in Tables 2-3.

[0074] (1) Printing performance test: The UV inkjet printing inks of Examples 1-6 and Comparative Examples 1-5 were injected into the ink cartridges of the inkjet printer. A 395nm LED lamp was used, and the exposure lamp energy was set to 300-500mJ / cm. 2 The printhead temperature was set to 45-55℃, the substrate was an FR-4 substrate, and inkjet printing was performed using the inkjet printing mode program to obtain a sample. The performance of the ink coating was then evaluated. Pass: Printer prints normally, without oblique spraying or clogging; Fail: Printing is oblique, or the printer is clogged.

[0075] (2) Viscosity measurement: Samples of UV inkjet printing inks from Examples 1-6 and Comparative Examples 1-5 were placed in the sleeve of a Burleffs DV2T viscometer. The samples were heated and maintained at 50°C. After 15 minutes, the viscosity data were recorded.

[0076] Evaluation criteria: Acceptable: Viscosity within the range of 9-12 mPa·s; Unacceptable: Viscosity outside the range of 9-12 mPa·s.

[0077] (3) Surface tension test: UV inkjet printing ink samples from Examples 1-6 and Comparative Examples 1-5 were placed in a BZY-2 surface tension meter. The temperature was set to room temperature. The sample was added to half of the glass dish. The platinum plate was brought close. When the sample came into contact with the platinum plate and stabilized, the surface tension data was recorded.

[0078] The testing standards are as follows: Acceptable: Surface tension is within the range of 21-24 mN / m; Unacceptable: Surface tension is not within the range of 21-24 mN / m.

[0079] (4) Adhesion test: The UV inkjet printing inks of Examples 1-6 and Comparative Examples 1-5 were injected into the ink cartridges of the inkjet printer. A 395nm LED lamp was used, and the exposure lamp energy was set to 300-500mJ / cm. 2 The printhead temperature was set to 45-55℃, and an FR-4 substrate was used. Inkjet printing was performed in inkjet mode to form an ink layer. Adhesion was tested using the cross-cut adhesion test. The ink coating was cut to the substrate surface, creating a grid pattern. 3M tape was then used to adhere and peel off the cut, and the extent of coating peeling was observed and the number of missing grid lines was recorded. The fewer the number of missing grid lines, the higher the adhesion.

[0080] (5) Solder thermal shock resistance test: Place the inkjet-coated sample in a solder bath at 288°C, apply appropriate flux to the sample surface coating, immerse it in the solder bath for 10 seconds, then remove it and cool it to room temperature. Repeat the above process a total of three times. Then, according to the adhesion test method, record the number of missing 100-cell bars. The fewer the number of missing 100-cell bars, the higher the solder thermal shock resistance.

[0081] (6) Thermal stability test: The UV inkjet printing inks of Examples 1-6 and Comparative Examples 1-5 were sampled and the initial viscosity was measured as W1. They were put into sealed bottles and placed in an oven at 60°C. After two weeks, the viscosity was measured as W2. The viscosity change rate S = (W2-W1) / W1×100%.

[0082] The evaluation criteria are as follows:

[0083] Pass: Viscosity change rate S < 10%; Fail: Viscosity change rate S ≥ 10%.

[0084] Table 2 Test Results of UV Inkjet Printing Inks in Examples 1-6

[0085] Table 3 Test results of UV inkjet printing inks for Comparative Examples 1-5

[0086] As can be seen from the data in Table 2, the present invention, by compounding a specific ratio of closed-type thermosetting acrylate, silicone acrylate oligomer and acrylate monomer, produces a UV inkjet printing ink that, while possessing excellent substrate adhesion and thermal shock resistance, also exhibits excellent thermal stability. This solves the technical defect that the ink system viscosity increases sharply with heating time due to long-term operation of the printhead at 50°C, easily clogging the printhead.

[0087] Compared with Example 3, the difference in Comparative Example 1 is that the amount of closed thermosetting acrylate A is less than 3 parts, the ink shows weaker adhesion, the resistance to solder thermal shock is somewhat reduced, and the viscosity of the ink in a 60°C oven for 2 weeks is greater than 10%.

[0088] Compared with Example 3, the difference in Comparative Example 2 is that the amount of closed-type thermosetting acrylate A is too large. As the amount increases, the viscosity of the thermosetting acrylate in a 60°C oven will be greater than 10% after 2 weeks.

[0089] Compared with Example 3, the difference in Comparative Example 3 is that the amount of organosilicon acrylate oligomer in the formulation is 0 parts, the ink shows weaker adhesion, the resistance to solder thermal shock is somewhat reduced, and the viscosity of the ink in a 60°C oven for 2 weeks is greater than 10%.

[0090] Compared with Example 3, the difference in Comparative Example 4 is that the amount of closed thermosetting acrylate A in the formulation is too small, only 0.5 parts. This results in decreased printing performance, blockage, and a significant impact on thermal stability. The viscosity of the acrylate in a 60°C oven will exceed 10% after 2 weeks.

[0091] Compared with Example 3, the difference in Comparative Example 5 is that the existing BI7982 blocking curing agent (BI7982 is mainly composed of HDI trimer, DMP is the blocking agent, PM is the solvent, with a solid content of 70% and PM solvent content of 30%) is used instead of the blocked thermosetting acrylate compound A. The viscosity of the thermosetting acrylate compound A will be greater than 10% after 2 weeks of thermal stability in a 60°C oven.

[0092] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A UV inkjet printing ink with excellent viscosity and thermal stability, characterized in that, The UV inkjet printing ink comprises, by weight, the following raw materials: 3-8 parts of closed-cell thermosetting acrylate 8-20 parts of epoxy acrylate resin 2-6 parts of organosilicon acrylate oligomer 20-70 parts of acrylate monomer 3-7 parts of photoinitiator 0.1-1 part of auxiliary agent 1-10 parts pigment; The blocked thermosetting acrylate is formed by chemical bonding of blocked isocyanate groups and acrylate double bonds.

2. The UV inkjet printing ink with excellent viscosity and thermal stability as described in claim 1, characterized in that, The closed-type thermosetting acrylate was prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of 2-isocyanoethyl methacrylate (IEM) and 0.001-0.003 mol of hydroquinone monomethyl ether (MEHQ) were added to a dry four-necked flask, and the temperature was raised to 50-65°C; 0.8-1.2 mol of butanone oxime (DBTDL) was slowly added dropwise, wherein each 1 mol of DBTDL contained 0.001 mol of dibutyltin dilaurate, and the addition time was 0.4-0.6 h; after the addition was completed, the reaction was maintained at 55-65°C for 1-2 h, and the reaction was monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO absorption peak completely disappeared, and the product was cooled to room temperature to obtain a colorless and transparent liquid product, which was denoted as blocked thermosetting acrylate A.

3. The UV inkjet printing ink with excellent viscosity and thermal stability as described in claim 1, characterized in that, The closed-type thermosetting acrylate is prepared by the following method: Under nitrogen protection, 1.8-2.2 mol of isophorone diisocyanate (IPDI) and 0.001-0.003 mol of DBTDL are added to a four-necked flask, and the temperature is raised to 50-60°C; 1.8-2.2 mol of hydroxypropyl acrylate (HPA) is added dropwise, wherein each 2 mol of hydroxypropyl acrylate (HPA) contains 0.004 mol of MEHQ, and the addition time is 1-2 h; after the addition is complete, the temperature is maintained at 60-70°C for 2-3 h; 0.8-1.2 mol of polyethylene glycol 200 is added, and the temperature is raised to 70-80°C for 2.5-3.5 h; the temperature is lowered to 60-70°C, and 1.8-2.2 mol of 3,5-dimethylpyrazole is added dropwise, with a dropwise addition time of 0.8-1.2 h; after the addition is complete, the temperature is maintained for 1.5-2.5 h, and the reaction is monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO peak disappeared, and a pale yellow viscous liquid product was obtained, which was denoted as blocked thermosetting acrylate B.

4. The UV inkjet printing ink with excellent viscosity and thermal stability as described in claim 1, characterized in that, The closed-type thermosetting acrylate was prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of HDI trimer and 0.001-0.002 mol of DBTDL were added to a four-necked flask, and the temperature was raised to 55-65℃; 2.5-3.5 mol of ethoxylated hydroxyethyl acrylate (EO-HEA) was added dropwise, wherein each 3 mol of EO-HEA contained 0.006 mol of MEHQ, and the addition time was 1.5-2.5 h; after the addition was completed, the temperature was maintained at 65-75℃ for 2.5-3.5 h; 0.4-0.6 mol of bisphenol A was added, and the temperature was raised to 75-85℃ for 3.5-4.5 h; the temperature was lowered to 65-75℃, and 2.5-3.5 mol of ε-caprolactam was added dropwise over 1.5 h; after the addition was completed, the temperature was maintained for 2-3 h, and the reaction was monitored by FTIR at 2270 cm⁻¹. -1 The -NCO peak disappeared, and a pale yellow, high-viscosity liquid product was obtained, which was denoted as blocked thermosetting acrylate C.

5. The UV inkjet printing ink with excellent viscosity and thermal stability as described in claim 1, characterized in that, The closed-type thermosetting acrylate was prepared by the following method: Under nitrogen protection, 0.8-1.2 mol of 2-acryloyloxyethyl isocyanate (AOI) and 0.001-0.003 mol of hydroquinone monomethyl ether (MEHQ) were added to a dry four-necked flask, and the temperature was raised to 45-55°C. 0.8-1.2 mol of 3,5-dimethyl-1H-pyrazole was slowly added dropwise, wherein each 1 mol of 3,5-dimethyl-1H-pyrazole contained 0.001 mol of dibutyltin dilaurate (DBTDL), with a dropping time of 0.4-0.6 h. After the addition was complete, the reaction was maintained at 55-65°C for 1-2 h, and the reaction was monitored at 2270 cm⁻¹ by FTIR. -1 The -NCO absorption peak completely disappeared; after the reaction was completed, the reaction solution was cooled to room temperature, and the product precipitated as a white solid. After vacuum filtration, washing with ether, and vacuum drying, a white powder was obtained, which was designated as closed-type thermosetting acrylate D.

6. The UV inkjet printing ink with excellent viscosity and thermal stability as described in any one of claims 1-5, characterized in that, The epoxy acrylate is selected from at least one of the following: bisphenol A type epoxy acrylate resin, bisphenol F type epoxy acrylate resin, bisphenol S type epoxy acrylate resin, biphenyl type epoxy acrylate resin, naphthalene type epoxy acrylate resin, Novolacs type epoxy acrylate resin, epoxy acrylate resin with fluorene backbone, glycidyl ether type epoxy acrylate resin, and epoxy acrylate resin made from copolymers of phenolic compounds and dicyclopentadiene.

7. The UV inkjet printing ink with excellent viscosity and thermal stability as described in any one of claims 1-5, characterized in that, The organosilicon acrylate oligomer is selected from organosilicon polyurethane acrylate oligomers.

8. The UV inkjet printing ink with excellent viscosity and thermal stability as described in any one of claims 1-5, characterized in that, The acrylate monomer is one or more of monofunctional acrylate monomers, difunctional acrylate monomers, and polyfunctional acrylate monomers; wherein, the monofunctional acrylate monomer is selected from at least one of PHEA, IBOA, THFA, THF(EO)A, LMA, IDA, IBOMA, 2-EHA, EOEOEA, 4HBA, and CTFA; the difunctional acrylate monomer is selected from at least one of PEGDMA, TPGDA, TEGDMA, PO2-NPGDA, PEGDA, PDDA, NPGDA, HDDA, EO4-BPADA, EO10-BPADA, and DPGDA; and the polyfunctional acrylate monomer is selected from at least one of TMPTA, TMPTMA, GPTA, EO3-TMPTA, TMPT3A, PET3A, and THEICTA.

9. The UV inkjet printing ink with excellent viscosity and thermal stability as described in any one of claims 1-5, characterized in that, The initiator is selected from any one or a combination of at least two of benzoin photoinitiators, alkyl phenyl ketone photoinitiators, acyl phosphorus oxide photoinitiators, or anthrone photoinitiators; The pigment includes one or a mixture of two or more of titanium dioxide, azo red, phthalocyanine blue, and carbon black; The additives include at least one of wetting and dispersing agents, leveling agents, defoamers, or film-forming aids.

10. A method for preparing a UV inkjet printing ink with excellent viscosity and thermal stability as described in any one of claims 1-9, characterized in that, Specifically, the steps include: mixing the formulated amounts of closed-type thermosetting acrylate, epoxy acrylate resin, silicone acrylate oligomer, acrylate monomer, photoinitiator, additives, and pigments, stirring at 1000-1400 rpm for 1-3 hours, and then filtering with a 1μm filter to obtain UV inkjet printing ink.

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