High-performance UV base plate and preparation process thereof

Abstract

The high-performance UV base plate comprises a wood fiber plate core layer, a putty layer, a primer layer and a finish paint layer, the shrinkage rate of the putty layer after UV curing is 2-3%, the transmittance of the primer layer after UV curing is 30-50%, the curing shrinkage rate of the primer layer after UV curing is 5-8%, the putty layer is subjected to delayed curing by adopting a photo-alkali production system, and the finish paint layer is subjected to ultraviolet curing. After the putty layer is coated on the wood fiber board core layer through roller coating for primary UV semi-curing, the primer layer is coated and then is completely cured again, and the problem that the embedding adhesion effect of the putty layer and the wood fiber board core layer is poor is solved by utilizing the equivalent expansion effect formed by the UV curing shrinkage rate difference of the putty layer and the primer layer; and finally, the primer layer is coated with the finish paint layer with the low shrinkage rate. The preparation of the UV base plate with high adhesive force and high flatness is realized.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit board manufacturing, and particularly to a high-performance UV board and its preparation process. Background Art

[0002] A backing plate is placed under the plate to be processed during the mechanical drilling of a printed circuit board (referred to as PCB) to meet the requirements of the processing technology. The main functions of the backing plate are: (1) reducing the burrs at the drilling opening of the base material; (2) protecting the drilling machine table during the drilling process that penetrates the PCB board; (3) reducing the drill bit temperature and drill bit wear; (4) cleaning part of the drilling dirt on the drill bit; (5) playing its positioning function to a certain extent and improving the drilling accuracy.

[0003] Common PCB backing plates include: high-density wood backing plates, phenolic wood backing plates, melamine wood backing plates, phenolic paper backing plates, high-density fiber boards, and aluminum foil composite wood backing plates, etc. Backing plates made of different materials provide different functions, such as high hardness, heat dissipation, low cost, environmental protection, etc. For backing plates with wood fibers as the base material, different surface-centered backing plate products are mainly provided through the design of the coating layer, such as UV-curable topcoats, paper coatings, etc. The prepared products have the characteristics of low cost and environmental protection. Related prior arts are as follows: CN201510987837.4 discloses a backing plate for PCB drilling and its preparation method. The backing plate includes a wood fiber board and ultraviolet radiation-curable resin layers coated on the upper and lower surfaces of the wood fiber board. Among them, the ultraviolet radiation-curable resin layer has the performance of being curable by an LED ultraviolet radiation curing lamp. The backing plate of the present invention obtained after being ultraviolet radiation-cured by the LED ultraviolet radiation curing lamp has the advantages of smaller warpage deformation, higher flatness, more acceptable appearance, extremely low odor, higher hardness, long service life, and environmental protection.

[0004] CN201510191340.1 discloses a backing plate for PCB drilling and its manufacturing method. The method includes the steps of: adding 50-70% of phenolic epoxy acrylate resin, 20-50% of filler, and 0-10% of diluent into a stirring tank in sequence by weight ratio, heating to 40-60 °C, stirring and mixing for 30-60 minutes, then adding 0.5-5% of a photoinitiator, and then continuing to stir for 10-15 minutes and then cooling and discharging to obtain a composite resin; using a wood fiber board as the substrate, coating the obtained composite resin on the upper and lower surfaces of the substrate respectively, and curing under predetermined conditions to form a backing plate. The surface hardness of the backing plate for PCB drilling of the present invention is significantly improved, and the burrs generated during drilling are effectively reduced, improving the production efficiency of PCB drilling processing.

[0005] In the prior art, the free radical acrylate UV curing market is relatively large, but there are problems such as poor solvent resistance, large shrinkage rate, oxygen inhibition of polymerization, and large interfacial stress in adhesion. Among them, cationic UV delayed curing adhesives can achieve delayed curing to reduce the shrinkage rate, but there is still a problem of large interfacial stress in adhesion. Therefore, how to solve the conflict between UV curing adhesion and stress on the wood fiberboard substrate and improve the stress state is the design direction of the present invention. Summary of the Invention

[0006] In view of the problems in the related art, the present invention provides a high-adhesion UV backing plate and its preparation process to overcome the above technical problems existing in the prior related art.

[0007] The technical solution of the present invention is realized as follows: Design a delayed curing putty layer and coat a high-shrinkage primer layer on the semi-cured putty layer to form a double-layer structure with a UV curing shrinkage rate difference. Then, completely cure the putty layer and the primer layer with UV light again. The equivalent expansion of the putty layer caused by the shrinkage rate difference is used to increase the degree of embedding in the voids of the wood fiberboard. Finally, coat the topcoat. In the invention design, by changing the resin substrate, selecting different functional group active monomers and additives, the material shrinkage rate and crosslinking degree of the putty layer, primer layer and topcoat layer are regulated to improve the comprehensive performance of the coating.

[0008] The specific content of the invention is as follows: A high-performance UV backing plate and its preparation process, including a wood fiberboard core layer, a putty layer, a primer layer and a topcoat layer arranged in sequence from inside to outside. The putty layer material composition contains a photo-curing retarder, and the curing shrinkage rate of the primer layer is greater than that of the putty layer.

[0009] Preferably, the thickness of the wood fiberboard core layer of the high-performance UV backing plate is 2.4 - 2.5 mm.

[0010] Preferably, the total thickness of the coating of the high-performance UV backing plate is 50 - 80 um.

[0011] More preferably, the thickness of the primer layer is less than that of the putty layer.

[0012] Preferably, the photo-curing retarder is a photo-base generator system.

[0013] Preferably, the material shrinkage rate of the putty layer is 2 - 3%, the material shrinkage rate of the primer layer is 5 - 8%, and the material shrinkage rate of the topcoat layer is 3 - 5%.

[0014] Preferably, the ultraviolet transmittance of the primer layer after complete curing is 30 - 50%.

[0015] Preferably, the Shore D hardness of the high-performance UV backing plate is greater than 80 ± 3 N / mm 2 .

[0016] Preferably, the density of the high-performance UV backing plate is 880-920 kgs / mm 3 .

[0017] Preferably, the surface of the high-performance UV backing plate is white.

[0018] Preferably, the preparation process of the high-performance UV backing plate is as follows: S1: Coat the surface of the wood fiber board core layer with the paint of the putty layer of 20-30 um, and carry out semi-curing for 10-30 s with 320-365 nm UV light to prepare matrix A, and the curing energy is 250-300 mW / cm 2 ; S2: Coat the paint of the primer layer of 10-20 um on the matrix A, and carry out complete curing for 400-60 s with 320-365 nm UV light to prepare matrix B, and the curing energy is 150-200 mW / cm 2 ; S3: Coat the paint of the topcoat layer of 20-30 um on the matrix B, and carry out complete curing for 400-60 s with 320-365 nm UV light to prepare the high-performance UV backing plate, and the curing energy is 200-300 mW / cm 2 .

[0019] Preferably, the coating method is roll coating.

[0020] More preferably, the roll coating method first uses a rubber roller to roll and coat, and then a gravure roller to level.

[0021] The invention contents of the components, preparation process and coating method of the putty layer, primer layer and topcoat layer are as follows: (1) Components, preparation and coating of the putty layer Preferably, the material components of the putty layer are: 20-30 parts of epoxy resin, 25-40 parts of acrylate, 10-20 parts of reactive monomer, 2-4 parts of photoinitiator, 1-3 parts of photo-curing retarder, 1-3 parts of polyfunctional mercaptan, 20-50 parts of filler, and 0-5 parts of other additives.

[0022] Preferably, the epoxy resin is composed of one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin.

[0023] Preferably, the material of the acrylate is epoxy resin-modified acrylate.

[0024] More preferably, the epoxy-modified acrylate is composed of one or more of bisphenol A-modified acrylate and epoxy-modified acrylate.

[0025] Preferably, the active monomer is composed of monofunctional acrylates.

[0026] More preferably, the monofunctional acrylate is composed of one or more of β-hydroxyethyl methacrylate, isobornyl acrylate, ethoxyethoxyethyl acrylate, and tetrahydrofurfuryl acrylate.

[0027] Preferably, the photoinitiator is composed of one or more of methyl benzoylformate, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoyl phenylphosphinate.

[0028] Preferably, the photocuring retarder is a photo-base generator.

[0029] More preferably, the photocuring retarder is one or more of carbamates, carboxylates, borates, quaternary ammonium salts, and benzyl amidines.

[0030] More preferably, the photocuring retarder is one or more of tetraphenylboroguanidine, 1,1,3,3-tetramethylguanidine, and quaternary ammonium tetraphenylborate.

[0031] Preferably, the polyfunctional thiol is composed of one or more of pentaerythritol tetra-3-mercaptopropionate, trihydroxypropane (3-mercaptopropionate), ethylene glycol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), diethanol bis(mercaptoacetate), and ethoxylated trimethylolpropane tris(3-mercaptopropionate).

[0032] Preferably, the ratio of the photoinitiator to the photocuring retarder is 1:0.5 to 0.8.

[0033] Preferably, the other additives are composed of one or more of 0.5 to 1.5 parts of a dispersant, 0.1 to 0.5 parts of an antifoaming agent, and 0.01 to 1.0 parts of a leveling agent.

[0034] Preferably, the dispersant is a polymer dispersant, the leveling agent is a silicone leveling agent, and the antifoaming agent is a silicone antifoaming agent or a polyether antifoaming agent.

[0035] More preferably, the antifoaming agent is one of silicone oil and polyoxyethylene alcohol.

[0036] More preferably, the dispersant is one or more than two of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxypropylene ether, isomeric alcohol polyoxypropylene ether, and isomeric alcohol polyoxyethylene polyoxypropylene ether.

[0037] More preferably, the leveling agent is one or more than two of diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, and triethylene glycol monobutyl ether.

[0038] Preferably, the filler is one or more of silica, glass microspheres, titanium oxide, talcum powder, and aluminum hydroxide.

[0039] Preferably, the preparation method of the putty layer coating is as follows: S1: Mix epoxy resin, polyfunctional thiol, and photo-curing retarder, heat at 80 - 100 °C, stir for 30 - 40 min, and cool to 50 - 60 °C; S2: Add acrylate and reactive monomer, heat at 50 - 60 °C, and stir evenly for 30 - 40 min; S2: Add filler and stir evenly for 50 - 60 min; S3: Add photo-initiator and other additives, stir for 20 - 30 min, and perform vacuum degassing.

[0040] Preferably, the stirring speed is 1300 - 1500 r / min.

[0041] (2) Components, preparation, and coating of the primer layer Preferably, the material components of the primer layer are: 50 - 70 parts of acrylate, 10 - 20 parts of reactive monomer, 2 - 4 parts of photo-initiator, 5 - 10 parts of filler, and 0 - 5 parts of other additives.

[0042] Preferably, the acrylate material is composed of one or several of bisphenol A acrylate, polyester acrylate, polyurethane acrylate, and epoxy-modified acrylate.

[0043] Preferably, the reactive monomer is a polyfunctional acrylate.

[0044] More preferably, the reactive monomer is composed of one or more of pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, di-trimethylolpropane tetraacrylate, and dipentaerythritol pentaacrylate.

[0045] Preferably, the photo-initiator is composed of one or more of methyl benzoylformate, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoyl phenylphosphinate.

[0046] Preferably, the other additives are composed of one or more of 0.5 - 1.5 parts of dispersant, 0.1 - 0.5 parts of defoamer, and 0.01 - 1.0 part of leveling agent.

[0047] Preferably, the dispersant is a polymer dispersant, the leveling agent is a silicone-based leveling agent, and the defoamer is a silicone defoamer or a polyether defoamer.

[0048] More preferably, the defoaming agent is one of silicone oil and polyoxyethylene alcohol.

[0049] More preferably, the dispersant is one or more of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxypropylene ether, isomeric alcohol polyoxypropylene ether, and isomeric alcohol polyoxyethylene polyoxypropylene ether.

[0050] More preferably, the leveling agent is one or more of diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, and triethylene glycol monobutyl ether.

[0051] More preferably, the filler includes one or more of silicon oxide, glass microspheres, titanium oxide, talcum powder, and aluminum hydroxide.

[0052] Preferably, the preparation method of the primer layer coating is as follows: S1: Mix acrylate and reactive monomer, heat at 50 - 60 °C, and stir evenly for 30 - 40 min; S2: Add filler and stir evenly for 50 - 60 min; S3: Add photoinitiator and other additives, stir for 20 - 30 min, and perform vacuum degassing.

[0053] Preferably, the stirring speed is 1100 - 1300 r / min.

[0054] (3) Components, preparation, and coating of the topcoat layer Preferably, the material components of the topcoat layer are: 50 - 70 parts of acrylate, 15 - 25 parts of reactive monomer, 2 - 4 parts of photoinitiator, 20 - 30 parts of filler, and 0 - 5 parts of other additives.

[0055] Preferably, the acrylate material is composed of one or several of bisphenol A acrylate, polyester acrylate, polyurethane acrylate, and epoxy - modified acrylate.

[0056] Preferably, the reactive monomer is a bifunctional acrylate.

[0057] More preferably, the reactive monomer is composed of one or more of 1,6 - hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate.

[0058] Preferably, the photoinitiator is composed of one or more of methyl benzoylformate, 1 - hydroxycyclohexyl phenyl ketone, 2,4,6 - trimethylbenzoyl diphenyl phosphine oxide, and ethyl 2,4,6 - trimethylbenzoyl phenylphosphinate.

[0059] Preferably, the other additives are composed of one or more of 0.5 - 1.5 parts of dispersant, 0.1 - 0.5 parts of defoamer, and 0.01 - 1.0 parts of leveling agent.

[0060] Preferably, the dispersant is a polymer dispersant, the leveling agent is a silicone leveling agent, and the defoamer is a silicone defoamer or a polyether defoamer.

[0061] More preferably, the dispersant is one or more of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxypropylene ether, isomeric alcohol polyoxypropylene ether, and isomeric alcohol polyoxyethylene polyoxypropylene ether.

[0062] More preferably, the leveling agent is one or more of diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, and triethylene glycol monobutyl ether.

[0063] More preferably, the filler includes one or more of silicon oxide, glass microspheres, titanium oxide, talcum powder, and aluminum hydroxide.

[0064] Preferably, the components of the other additives further include 1 - 5 parts of matting powder. More preferably, the matting powder is composed of one or several of organic matting powder, organically modified fumed silica, and fumed silica.

[0065] Preferably, the preparation method of the topcoat layer coating is as follows: S1: Mix acrylate and reactive monomers, heat at 50 - 60 °C, and stir evenly for 30 - 40 min; S2: Add fillers and stir evenly for 50 - 60 min; S3: Add photoinitiator and other additives, stir for 20 - 30 min, and degas under vacuum.

[0066] Preferably, the stirring speed is 1100 - 1300 r / min.

[0067] Preferably, the particle size of the fillers used in the putty layer, primer layer, and topcoat layer is 200 - 300 mesh.

[0068] Compared with the prior art, the beneficial effects of the present invention are: By preparing the putty layer and primer layer with different shrinkage rates, the equivalent expansion effect of the putty layer is achieved. By delaying curing, the embedding degree between the putty layer and the wood fiber board core layer is increased, thereby improving the adhesion of the UV backing plate and improving the warpage and flatness of the UV backing plate.

[0069] The shrinkage rate and crosslinking degree are regulated by the differences in resin matrix, active monomer functionality, and photoinitiator used in different layers, achieving a structure with the minimum internal stress in the putty layer, the second minimum internal stress in the topcoat layer, and the maximum internal stress in the primer layer. This internal stress change structure improves the drilling cutting quality. Description of the Drawings

[0070] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0071] Figure 1 It is a schematic structural diagram of the UV backing plate of the present invention.

[0072] Figure 2 It is a schematic stress-strain curve diagram of the primer layer coating prepared from active monomers with different functional groups of the present invention.

[0073] Among them, 1 is the wood fiber board core layer, 2 is the putty layer with low shrinkage rate, 3 is the primer layer with high shrinkage rate, and 4 is the topcoat layer with medium shrinkage rate. Specific Embodiments

[0074] The endpoints and any values within the ranges disclosed in the present invention are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in the present invention.

[0075] In the specific embodiments of the present invention, the molecular weight of the epoxy resin used is 3000 - 4000, the molecular weight of the polyurethane acrylate is 4000 - 5000, the molecular weight of the polyester acrylate is 2000 - 3000, and the D50 particle size of the filler is 200 mesh.

[0076] Example 1, Preparation of UV backing plate 1 Steps for preparing the coating for the putty layer 2: S1: 30 parts of bisphenol A epoxy resin, 2 parts of diethanol ester of dimercaptoacetic acid, and 2 parts of tetraphenylboroguanidine are mixed, heated in a stirring tank at 80°C, stirred at 1400 r / min for 30 min, and then cooled to 50°C; S2: 30 parts of bisphenol A modified acrylate and 15 parts of isobornyl acrylate are added, stirred at 50°C for 35 min, and the stirring speed is 1500 r / min; S3: Add 40 parts of talcum powder and stir at 1500 r / min for 60 min; S4: Add 3 parts of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1 part of fatty alcohol polyoxyethylene ether, 1 part of diethylene glycol butyl ether, and 0.3 part of silicone oil, stir at 1300 r / min for 30 min, and perform vacuum degassing to prepare the putty layer coating; Preparation steps of the primer layer 3 coating: S1: Mix 40 parts of epoxy-modified acrylate, 20 parts of polyurethane acrylate, and 15 parts of pentaerythritol tetraacrylate, heat in a stirring tank at 55 °C, and stir at 1100 r / min for 35 min; S2: Add 8 parts of silicon oxide and stir at 1200 r / min for 50 min; S3: Add 3 parts of ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, 1 part of isomeric alcohol polyoxyethylene polyoxypropylene ether, 0.5 part of diethylene glycol dibutyl ether, and 0.3 part of polyoxyethylene alcohol, stir at 1300 r / min for 30 min, and perform vacuum degassing to prepare the primer layer coating; Preparation of the topcoat layer 4: S1: Mix 20 parts of bisphenol A acrylate, 20 parts of polyester acrylate, 20 parts of polyurethane acrylate, and 20 parts of diethylene glycol diacrylate, heat in a stirring tank at 55 °C, and stir at 1100 r / min for 35 min; S2: Add 30 parts of titanium oxide and stir at 1300 r / min for 60 min; S3: Add 4 parts of ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, 1.5 parts of fatty alcohol polyoxypropylene ether, 1 part of triethylene glycol butyl ether, and 0.5 part of silicone oil, stir at 1300 r / min for 30 min, and perform vacuum degassing to prepare the topcoat layer coating; Preparation of the UV backing plate: S1: Clean the wood fiber board core layer 1, apply the putty layer 2 coating with a rubber roller at 20 μm, level it with a gravure roller, and then semi-cure it with 365 nm-UV light, with a curing energy of 250 mW / cm 2 , and a curing time of 20 s to prepare the substrate A; S2: Apply the primer layer 3 coating with a rubber roller at 15 μm on the substrate A, level it with a gravure roller, and then fully cure it with 320 nm-UV light, with a curing energy of 180 mW / cm 2 , and a curing time of 40 s to prepare the substrate B; S3: Apply the topcoat layer 4 coating with a rubber roller at 30 μm on the substrate A, level it with a gravure roller, and then fully cure it with 365 nm-UV light, with a curing energy of 300 mW / cm 2 , and a curing time of 60 s to prepare the UV backing plate 1.

[0077] Example 2, Preparation of UV backing plate 2 Steps for preparing the putty layer 1 coating: S1: Mix 25 parts of bisphenol F epoxy resin, 2.5 parts of pentaerythritol tetra-3-mercaptopropionate, and 2.5 parts of 1,1,3,3-tetramethylguanidine, heat at 100°C in a stirring tank, stir at 1300 r / min for 40 min, and then cool to 60°C; S2: Add 25 parts of epoxy-modified acrylate and 10 parts of ethoxyethoxyethyl acrylate, stir at 60°C for 40 min, and the stirring speed is 1500 r / min; S3: Add 30 parts of titanium oxide and stir at 1500 r / min for 60 min; S4: Add 4 parts of 1-hydroxycyclohexyl phenyl ketone, 1 part of fatty alcohol polyoxypropylene ether, 1 part of diethylene glycol butyl ether, and 0.2 part of silicone oil, stir at 1300 r / min for 40 min, and perform vacuum degassing to prepare the putty layer coating; Steps for preparing the primer layer 3 coating: S1: Mix 40 parts of polyester acrylate, 20 parts of polyurethane acrylate, and 10 parts of ethoxylated pentaerythritol tetraacrylate, heat at 50°C in a stirring tank, and stir at 1100 r / min for 30 min; S2: Add 10 parts of silicon oxide and stir at 1200 r / min for 50 min; S3: Add 2.5 parts of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, 1 part of fatty alcohol polyoxyethylene ether, 0.5 part of diethylene glycol dibutyl ether, and 0.2 part of poly(ethylene oxide) alcohol, stir at 1300 r / min for 30 min, and perform vacuum degassing to prepare the primer layer coating; Preparation of the topcoat layer 4: S1: Mix 20 parts of bisphenol A acrylate, 20 parts of epoxy-modified acrylate, 30 parts of polyurethane acrylate, and 25 parts of 1,6-hexanediol diacrylate, heat at 60°C in a stirring tank, and stir at 1100 r / min for 40 min; S2: Add 30 parts of titanium oxide and stir at 1300 r / min for 60 min; S3: Add 4 parts of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, 1.5 parts of fatty alcohol polyoxypropylene ether, 1 part of triethylene glycol butyl ether, and 0.5 part of silicone oil, stir at 1300 r / min for 30 min, and perform vacuum degassing to prepare the topcoat layer coating; Preparation of the UV backing plate: S1: Clean the wood fiber board core layer 1, apply the putty layer 2 coating with a thickness of 30 μm by a rubber roll, level it with a gravure roll, and then semi-cure it with 365 nm-UV light. The curing energy is 300 mW / cm 2 , and the curing time is 25 s to prepare substrate A; S2: Coat the primer layer 3 coating of 20 μm on the substrate A with a rubber roll, level the anilox roll, and then fully cure it with 320 nm - UV light. The curing energy is 200 mW / cm 2 , and the curing time is 50 s to prepare the substrate B; S3: Coat the topcoat layer 4 coating of 20 μm on the substrate A with a rubber roll, level the anilox roll, and then fully cure it with 365 nm - UV light. The curing energy is 250 mW / cm 2 , and the curing time is 50 s to prepare the UV backing plate 2.

[0078] Example 3: Prepare the UV backing plate 3 Steps for preparing the putty layer 2 coating: S1: Mix 25 parts of alicyclic epoxy resin, 1.5 parts of diethanol ester of dimercaptoacetic acid, and 2 parts of tetrabutylammonium tetraphenylborate, heat it in a stirring tank at 90 °C, stir at 1300 r / min for 40 min, and then cool it to 55 °C; S2: Add 30 parts of epoxy - modified acrylate and 20 parts of ethoxylated pentaerythritol tetraacrylate, stir at 55 °C for 40 min, and the stirring speed is 1400 r / min; S3: Add 40 parts of titanium oxide and stir at 1500 r / min for 60 min; S4: Add 4 parts of 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide, 1 part of fatty alcohol polyoxyethylene ether, 1 part of diethylene glycol butyl ether, and 0.5 part of silicone oil, stir at 1500 r / min for 30 min, and carry out vacuum degassing to complete the preparation of the putty layer coating; Steps for preparing the primer layer 3 coating: S1: Mix 30 parts of epoxy - modified acrylate, 30 parts of polyurethane acrylate, and 15 parts of ethoxylated pentaerythritol tetraacrylate, heat it in a stirring tank at 50 °C, stir at 1200 r / min for 35 min; S2: Add 10 parts of glass microspheres and stir at 1200 r / min for 60 min; S3: Add 3 parts of 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide, 1.5 parts of fatty alcohol polyoxyethylene ether, 1 part of diethylene glycol dibutyl ether, and 0.5 part of silicone oil, stir at 1300 r / min for 30 min, and carry out vacuum degassing to complete the preparation of the primer layer coating; Preparation of the topcoat layer 4: S1: Mix 35 parts of polyurethane acrylate, 35 parts of polyester acrylate, and 20 parts of dipropylene glycol diacrylate, heat it in a stirring tank at 60 °C, stir at 1200 r / min for 35 min; S2: Add 25 parts of titanium oxide and stir at 1300 r / min for 50 min; S3: Add 4 parts of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 0.5 part of dispersant fatty alcohol polyoxypropylene ether, 0.3 part of diethylene glycol monobutyl ether, and 0.3 part of silicone oil, stir at 1300 r / min for 30 min, and perform vacuum degassing to complete the preparation of the topcoat layer coating; UV backing plate preparation: S1: Clean the wood fiber board core layer 1, apply the putty layer 2 coating with a thickness of 25 μm by rubber roll coating, level it with a gravure roll, and then semi-cure it with 365 nm - UV light, with a curing energy of 280 mW / cm 2 , and the curing time is 25 s to prepare substrate A; S2: Apply the primer layer 3 coating with a thickness of 15 μm on substrate A by rubber roll coating, level it with a gravure roll, and then fully cure it with 320 nm - UV light, with a curing energy of 180 mW / cm 2 , and the curing time is 45 s to prepare substrate B; S3: Apply the topcoat layer 4 coating with a thickness of 25 μm on substrate B by rubber roll coating, level it with a gravure roll, and then fully cure it with 365 nm - UV light, with a curing energy of 230 mW / cm 2 , and the curing time is 50 s to prepare the UV backing plate 3.

[0079] Comparative Example 1: Change all the reactive monomers in Example 1 to monofunctional acrylate - isobornyl acrylate.

[0080] Comparative Example 2: Change all the reactive monomers in Example 1 to difunctional acrylate - diethylene glycol diacrylate.

[0081] Comparative Example 3: Change all the reactive monomers in Example 1 to polyfunctional acrylate - pentaerythritol tetraacrylate.

[0082] Comparative Example 4: Change the epoxy resin share in Example 1 to 30 parts of polyurethane acrylate, change the share of the photo-curing retarder to 15 parts of isobornyl acrylate, and cancel the share of the polyfunctional mercaptan and step S1.

[0083] For the primer layer coatings without fillers prepared in Examples 1 - 3 and Comparative Examples 1 - 3, corresponding shrinkage stresses were measured. Monofunctional, difunctional, and polyfunctional reactive monomers were selected for shrinkage stress testing. The sample preparation requirements were circular with a diameter of 20 mm and a thickness of 100 μm. Infrared-rheology coupling technology was used to monitor the change of shrinkage stress. The specific test results are shown in Figure 1 . It can be seen that with the increase of the functional groups, the shrinkage stress increases significantly. It can be seen that the coatings prepared by the present invention can adjust the shrinkage stress and shrinkage rate by changing the functional group reactive monomers.

[0084] Furthermore, the shrinkage rates of each layer in Examples 1 to 3 and Comparative Examples 1 to 3 (measured by the laser confocal volume method) and the performance tests of the UV backing plates were carried out. The specific data are shown in Table 1.

[0085] Table 1 It can be seen from the data in Table 1 that in Examples 1 to 3, by designing that the shrinkage rate difference between the putty layer coating with a low shrinkage rate and the primer layer coating with a high shrinkage rate is greater than 3%, the tensile shear strength of the prepared coating is significantly higher than that of Comparative Examples 1 to 4. It can be seen that the implementation effect of the present invention is obvious.

[0086] At the same time, due to the designed stress difference structure of low / high / low putty layer / primer layer / topcoat layer, the guarantee of the surface warpage degree is realized. Although the multi-functional group active monomers used in Comparative Example 3 can also achieve high hardness, the accumulation of internal stress leads to an increase in warpage degree.

[0087] In Comparative Example 4, due to the lack of photo-curing delay design in the putty layer, the effect of equivalent expansion of the putty layer cannot be achieved, and the bonding force between its material and the wood fiber board core layer is about 40% weaker than that of the example.

[0088] The UV backing plate prepared by the present invention and the preparation process significantly improve the disadvantages of the prior art, can provide a backing plate with higher performance for PCB drilling, and ensure low cost and environmental protection requirements.

[0089] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-performance UV pad, characterized in that: The invention comprises a wood fiber board core layer and a surface coating, wherein the coating is provided with a putty layer, a primer layer and a topcoat layer in sequence from the inside to the outside, the material components of the putty layer contain a light curing retarder, the resin material of the putty layer is composed of epoxy resin and epoxy-modified acrylate, the active monomers of the putty layer, the primer layer and the topcoat layer are monofunctional, multifunctional and bifunctional acrylates respectively, and the UV curing shrinkage rates of the materials of the putty layer, the primer layer and the topcoat layer are 2-3%, 5-8% and 3-5% respectively.

2. The preparation process of the high-performance UV pad according to claim 1 is characterized in that: The components of the putty layer, primer layer and topcoat layer are: Putty layer: 20-30 parts of epoxy resin, 25-40 parts of epoxy-modified acrylate, 10-20 parts of monofunctional active monomer, 2-4 parts of photoinitiator, 1-3 parts of photocuring delay agent, 1-3 parts of multifunctional thiol, 20-50 parts of filler and / or 0-5 parts of other additives; Primer layer: 50-70 parts of acrylate, 10-20 parts of multifunctional active monomer, 2-4 parts of photoinitiator, 5-10 parts of filler and / or 0-5 parts of other additives; Topcoat layer: 50-70 parts of acrylate, 15-25 parts of bifunctional active monomer, 2-4 parts of photoinitiator, 20-30 parts of filler and / or 0-5 parts of other additives.

3. The preparation process of the high-performance UV pad according to claim 2 is characterized in that: The ratio of the photoinitiator to the photocuring retarder is 1:0.5-0.

8.

4. The high performance UV pad according to claim 2, characterized in that: The epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin; the epoxy-modified acrylate is one or more of bisphenol A modified acrylate and epoxy modified acrylate; the acrylate is one or more of bisphenol A acrylate, polyester acrylate, polyurethane acrylate, and epoxy modified acrylate.

5. The preparation process of the high-performance UV pad according to claim 2, characterized in that: The photoinitiator is composed of one or more of methyl benzoylformate, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoylbenzene-diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphonate; the photocuring retarder is composed of one or more of carbamates, carboxylates, borates, quaternary ammonium salts, and benzyl amidines; the multifunctional thiol is composed of one or more of pentaerythritol tetrakis-3-mercaptopropionate, trihydroxypropane (3-mercaptopropionate), di(3-mercaptopropionic acid) ethylene glycol ester, trimethylolpropane tris(2-mercaptoacetate), diethanol dimercaptoacetate, and ethoxytrimethylolpropane tris(3-mercaptopropionic acid) ester.

6. The preparation process of the high-performance UV pad according to claim 2, characterized in that: The other additives are one or more of a dispersant, a leveling agent, a defoaming agent and a matting agent. The dispersant is a polymer dispersant, the leveling agent is an organosilicon leveling agent, the defoaming agent is an organosilicon defoaming agent or a polyether defoaming agent, the matting agent is a matting powder which is one or more of an organic matting powder, organic-modified fumed silica, and fumed silica, and the filler is one or more of silicon oxide, glass beads, titanium oxide, talc and aluminum hydroxide.

7. The high performance UV pad according to claim 2, characterized in that: The monofunctional active monomer is composed of one or more of β-hydroxyethyl methacrylate, isobornyl acrylate, ethoxyethoxyethyl acrylate, and tetrahydrofurfuryl acrylate; the bifunctional active monomer is composed of one or more of 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate; the multifunctional active monomer is composed of one or more of pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, di-trimethylolpropane tetraacrylate, and dipentaerythritol pentaacrylate.

8. A process for preparing a high-performance UV pad according to any one of claims 1 to 7, characterized in that: Prepared by the following steps: S1: The surface of the wood fiber board core layer is coated with the coating of the putty layer with a thickness of 20 to 30 μm, and semi-cured with 320 to 365 nm UV light for 10 to 30 seconds to prepare the matrix A, and the curing energy is 250 to 300 mW / cm 2 ; S2: The substrate A is coated with a 10-20 μm primer layer, and then completely cured with 320-365 nm UV light for 400-60 seconds to prepare the substrate B, with a curing energy of 150-200 mW / cm 2 ; S3: The substrate B is coated with a topcoat layer of 20 to 30 μm, and completely cured by 320 to 365 nm UV light for 400 to 60 seconds to prepare the high-performance UV backing plate, with a curing energy of 200 to 300 mW / cm 2 .

9. The preparation process of the high-performance UV pad according to claim 8, characterized in that: The curing degree of the putty layer on the substrate A is 40-60%.

10. The preparation process of the high-performance UV pad according to claim 8, characterized in that: The UV transmittance of the primer layer on the substrate B at 320-365 nm is 30-50%.

Images