UV / EB dual-cured black tri-proof paint and preparation method thereof

Abstract

The application discloses a UV / EB dual-cured black three-protection paint and a preparation method thereof. The paint comprises the following raw material components in parts by weight: 100 parts of aliphatic polyurethane acrylate; 70-80 parts of acrylate monomer; 10-25 parts of propylene modifier; 30-50 parts of UV photocuring acrylate monomer; and 5-15 parts of black filler. The black filler is a mixture of carbon black and white carbon black, and the mass ratio of the carbon black to the white carbon black is 1:0.5-2. The three-protection paint can be subjected to polymerization reaction under the UV and EB dual action in the case that the apparent color is black, and the glue has good curing degree, shear strength and high temperature and high humidity resistance after curing.

Description

Technical Field

[0001] This invention belongs to the field of paint coating technology, and relates to a black conformal coating, specifically a UV / EB dual-curing black conformal coating and its preparation method. Background Technology

[0002] Printed circuit boards (PCBs) are manufactured by mounting integrated circuits, transistors, diodes, passive components (such as resistors, capacitors, connectors, etc.) and various other electronic parts, which are then connected by wires to form electronic signal connections and functionalities. PCBs can consist of one, two, or multiple layers of circuitry, made with dielectric core materials of poor conductivity to ensure pure circuit transmission, and may include additional metal and dielectric layers as needed. The standard dielectric material used for PCBs is a flame-retardant composite material made of woven fiberglass cloth and epoxy resin, known as FR-4, while the metal traces and planes of the circuitry are typically made of copper.

[0003] Conformal coating (also known as circuit board coating or insulating varnish) is used to protect circuit boards and related equipment from environmental corrosion. The coating is applied to the surface of the circuit board, forming a light, flexible protective film with a thickness of approximately 25–250 μm. This film isolates sensitive electrical components from harsh environments, thereby improving the reliability of the circuit board, increasing its safety factor, and ensuring its service life. Chinese invention patent CN109749698A discloses the preparation of a two-component transparent LED silicone coating adhesive, comprising component A and component B. Component A is composed of α-ω-dihydroxy polydimethylsiloxane and diluent in a weight ratio of (50.0-75.0):(25.0-50.0). Component B is composed of crosslinking agent, diluent, tackifier, catalyst and anti-yellowing agent in a weight ratio of (35.0-50.0):(20.0-40.0):(15.0-30.0):(0.0-0.3):(0.5-1.5). Component A and component B are mixed in a weight ratio of 10:1. The preparation of this two-component transparent LED silicone coating adhesive possesses advantages such as low viscosity, good transparency, good elasticity, good adhesion, good resistance to yellowing, good weather resistance, non-corrosiveness, and environmental friendliness. It can also withstand the alternating temperature changes during LED display use without cracking or causing a decrease in LED light transmittance due to yellowing of the adhesive layer, thus providing long-term and effective protection for the display module. The aforementioned silicone coating adhesive is transparent.

[0004] With the continuous development of science and technology, more and more companies are opting for black coating adhesives to protect the confidentiality of circuit designs and electronic components used on PCBs and to prevent competitors from copying and replicating them at low cost. Conventional curing methods for coating adhesives include thermosetting and photopolymerization. Thermosetting may cause thermal damage to electronic components (it is not suitable for some heat-sensitive electronic components), and both heating and cooling require time. During thermosetting, a damming process is also needed on the PCB substrate to prevent adhesive leakage. As a result, the overall unit hour productivity (UPH) of heating processes is relatively low. Radiation polymerization can significantly increase UPH, offering unique advantages for this specific application.

[0005] Electron beam (EB) and ultraviolet (UV) initiation methods are the two most commonly used initiation methods for commercial radiation polymerization. Although both UV and EB initiation fall under radiation polymerization, the initiating particles and their interactions with the material result in drastically different energy deposition profiles, and these different energy distributions affect the appropriate application of each initiation method. In UV polymerization, energy deposition is governed by the Beer-Lambert law, where energy deposition is always maximum at the surface and then decreases exponentially into the depths of the film or coating, resulting in a polymer surface strength greater than its internal strength (and even cases where the polymer's internal strength is insufficient). Unlike photopolymerization, the force of electron energy-accelerated deposition makes EB polymerization more susceptible to oxygen inhibition, but it is superior in curing thick or opaque films. Because oxygen inhibition is a problem in EB polymerization, most industrial processes use nitrogen inertization to ensure acceptable surface curing; however, continuous nitrogen flow is costly, so a cheaper method to overcome oxygen inhibition is needed. Summary of the Invention

[0006] To address the aforementioned shortcomings, this invention provides a UV / EB dual-curing black conformal coating.

[0007] To achieve the above objectives, the present invention provides a UV / EB dual-curing black conformal coating, which comprises the following raw material components in parts by weight:

[0008]

[0009] The black filler is a mixture of carbon black and silica, with a mass ratio of carbon black to silica of 1:0.5 to 2, and the photoinitiator has an absorption wavelength of 320-350 nm.

[0010] Ideally, the aliphatic polyurethane acrylate has a functionality of 2–6 and a molecular weight of 1 × 10⁻⁶. 4 ~5×10 4 .

[0011] Furthermore, the aliphatic polyurethane acrylate has a refractive index of 1.40 to 1.50 and a glass transition temperature of 83.0 to 85.0 °C.

[0012] Furthermore, the aliphatic polyurethane acrylate is a mixture of one or more of the following: Changxing DR-U282, Changxing DR-U384, Changxing DR-U386, Changxing DR-U388, Changxing DR-U331, and Sartoma CN8881 NS.

[0013] Furthermore, the acrylic monomer is a mixture of one or more selected from isobornyl methacrylate, isodecyl acrylate, tetrahydrofurfuryl acrylate and isobornyl acrylate.

[0014] Specifically, the propylene modifier is a mixture of one or more selected from hydroxyethyl methacrylate, acryloylmorpholine, and N,N-dimethylacrylamide.

[0015] Specifically, the UV-curable acrylate monomer is a mixture of one or more selected from tricyclodecanediethanol diacrylate, dodecyl acrylate, and triethylene glycol dimethacrylate.

[0016] Optimally, the photoinitiator is selected from photoinitiator 369, photoinitiator 907, photoinitiator TPO, photoinitiator BMS, photoinitiator ITX, photoinitiator 184, photoinitiator DETX, photoinitiator 1173 and photoinitiator BDK.

[0017] Specifically, it comprises the following raw material components in parts by weight:

[0018]

[0019] Another objective of this invention is to provide a method for preparing the above-mentioned UV / EB dual-curing black conformal coating, comprising the following steps: dispersing the black filler in the prescribed amount in the prescribed amount of the acrylic monomer to form a black slurry; and mixing the black slurry with the prescribed amounts of the aliphatic polyurethane acrylate, the acrylic modifier, the photoinitiator, and the UV-curable acrylate monomer until homogeneous.

[0020] The present invention provides a UV / EB dual-curing black conformal coating. By using specific types and amounts of components, the adhesive, while appearing black, can undergo a polymerization reaction under the dual action of UV and EB, resulting in a cured adhesive with good curing degree, shear strength, and resistance to high temperature and humidity. Detailed Implementation

[0021] This invention relates to a UV / EB dual-curing black conformal coating, comprising the following raw material components in parts by weight: 100 parts aliphatic polyurethane acrylate; 70-80 parts acrylate monomer; 10-25 parts acrylic modifier; 30-50 parts UV-curable acrylate monomer; 3-10 parts photoinitiator; and 5-15 parts black filler. The black filler is a mixture of carbon black and silica, with a mass ratio of carbon black to silica of 1:0.5-2. The photoinitiator has an absorption wavelength of 320-350 nm. By employing specific types and amounts of components, the adhesive, while appearing black, can undergo polymerization under both UV and EB conditions, resulting in a cured adhesive with good curing degree, shear strength, and resistance to high temperature and humidity.

[0022] The aliphatic polyurethane acrylate preferably has a functionality of 2 to 6 and a molecular weight preferably of 1 × 10⁻⁶. 4 ~5×10 4 The refractive index of the aliphatic polyurethane acrylate is preferably 1.40 to 1.50, and the glass transition temperature is preferably 83.0 to 85.0℃. Specifically, the aliphatic polyurethane acrylate is preferably a mixture of one or more of the following: Changxing DR-U282, Changxing DR-U384, Changxing DR-U386, Changxing DR-U388, Changxing DR-U331, and Sartoma CN8881 NS.

[0023] The acrylic monomer is preferably a mixture selected from one or more of isobornyl methacrylate, isodecaacrylate, tetrahydrofurfuryl acrylate, and isobornyl acrylate. The propylene modifier is preferably a mixture selected from one or more of hydroxyethyl methacrylate, acrylmorpholine, and N,N-dimethylacrylamide. The UV-curable acrylate monomer is preferably a mixture selected from one or more of tricyclodecanediethanol diacrylate, dodecyl acrylate, and triethylene glycol dimethacrylate. The photoinitiator is selected from one of photoinitiator 369, photoinitiator 907, photoinitiator TPO, photoinitiator BMS, photoinitiator ITX, photoinitiator 184, photoinitiator DETX, photoinitiator 1173, and photoinitiator BDK, with photoinitiator 369 being the most preferred.

[0024] The above-mentioned UV / EB dual-curing black conformal coating is preferably composed of the following raw material components in parts by weight: 100 parts aliphatic polyurethane acrylate; 76 parts acrylate monomer; 24 parts acrylic modifier; 40 parts UV-curable acrylate monomer; 5 parts photoinitiator; and 6-12 parts black filler. This can improve the physical and chemical properties of the black coating.

[0025] The preparation method of the above-mentioned UV / EB dual-curing black conformal coating includes the following steps: dispersing the black filler in the formula amount in the acrylic monomer in the formula amount to form a black slurry; and mixing the black slurry with the aliphatic polyurethane acrylate, the acrylic modifier, the photoinitiator and the UV-curable acrylate monomer in the formula amount until uniform.

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art under the premise of equivalent changes and modifications should fall within the protection scope of the present invention.

[0027] Examples 1-10, Comparative Examples 1-10

[0028] Examples 1-10 and Comparative Examples 1-10 each provide a UV / EB dual-curing black conformal coating, the raw material components and contents of which are shown in Table 1.

[0029] Table 1. Raw material formulations (in g) for black conformal coatings in Examples 1-10 and Comparative Examples 1-10.

[0030]

[0031]

[0032] Note: Isoborneol methacrylate was purchased from Changxing EM90, isodecyl acrylate (ISODA) from Changxing EM219, tetrahydrofurfuryl acrylate (THFA) from Changxing EM214, and isoborneol acrylate (IBOA) from Changxing EM70; hydroxyethyl methacrylate (HEMA) was purchased from Guangzhou Yuanda, acrylmorpholine (ACMO) from Kejuxi, and N,N-dimethylacrylamide (DMAA) from Kejuxi; dodecyl acrylate was purchased from SR335, tricyclodecanedimethyl diacrylate from SR833NS, and triethylene glycol dimethacrylate from SR205NS (all purchased from Sartoma); carbon black and silica were purchased from Cabot.

[0033] Note: The raw material formulations in Example 1 and Comparative Example 8 are the same; the only difference is the polymerization conditions used in subsequent applications: in Example 1, UV polymerization + EB polymerization is used, while in Comparative Example 8, only EB polymerization is used.

[0034] The above-mentioned UV / EB dual-curing black conformal coating is prepared by the following method: dispersing the black filler in the formula amount in the acrylic monomer to form a black slurry; mixing the black slurry with the aliphatic polyurethane acrylate, the acrylic modifier and the UV-curable acrylate monomer in the formula amount until uniform.

[0035] The performance of the aforementioned UV / EB dual-cured black coating adhesive was then tested using the following methods:

[0036] (1) Viscosity: In this experiment, the viscosity of the light-shielding composition was measured using a Brookfield rotational viscometer at an ambient temperature of 25°C using a CP51 rotor head (the viscosity is generally required to be less than 3000 cPs).

[0037] (2) Optical density OD value: For the light-shielding film material, this experiment uses a UV-Vis spectrophotometer to test the average transmittance T% of the sample in the wavelength range of 400nm to 700nm. The optical density OD value is calculated according to the formula OD = log10(1 / T%). The larger the OD value, the better the light-shielding performance of the sample (generally, the OD value of the light-shielding film material should be greater than 2). (The optical density OD value test is carried out after the storage test, which is: aging at 40℃ for 14 days).

[0038] (3) Degree of curing: In this experiment, an infrared spectrometer was used to test the depth distribution of double bond conversion rate of a 200-micrometer-thick light-shielding composition sample after curing. The test results required that the double bond conversion rate of each layer of the sample was greater than 90% (i.e., the degree of curing was above 90%).

[0039] (4) Hardness: This experiment uses a Shore A or D hardness tester to test the hardness of the light-shielding film material at a sample thickness of 4 mm. Since a single layer of film is thin, multiple layers are generally stacked to achieve a thickness of 4 mm for testing. Based on the test results, the readings corresponding to the A and D type numbers are compared. The larger the value, the higher the hardness of the sample. If two readings are at the same level, the larger value indicates higher hardness.

[0040] (5) Shear strength: The shear strength of the light-shielding film material was tested using a universal tensile testing machine. During the test, the upper limit of the force sensor was set to 10000N, and the mechanical pulling speed was adjusted to 100mm / min. The separation of the substrate and the sample under tension was recorded. The shear strength of the light-shielding film was obtained by dividing the maximum tensile force of substrate separation by the bonding area.

[0041] (6) High temperature and high humidity resistance: This test was conducted at 85℃ and 85% relative humidity, and the accelerated aging time of the light-shielding film material exceeded 500 hours. After the test, the samples were evaluated as follows: 1. Color change: No obvious color difference; 2. Shear strength: The decrease was controlled within 50% compared with before the test.

[0042] (7) Water Absorption Rate: A light-shielding film sample with a thickness of 200 μm and a size of 5 cm × 5 cm was selected for this experiment. The sample was immersed in pure water at room temperature for 24 hours. The masses of the sample before and after the test were measured as m1 and m2, respectively. The water absorption rate corresponding to the difference in sample mass before and after immersion was calculated using the formula: Water Absorption Rate = (m2 - m1) / m1 × 100%. Where m1 is the sample mass before immersion, and m2 is the sample mass after immersion. The water absorption rate of the sample is required to be no greater than 1.5%.

[0043] (8) Curing method: This experiment tested the samples for UV polymerization and EB polymerization. UV polymerization conditions: The light source was a 365nm LED cold light source with a light intensity of 60mW / cm². 2 The irradiation time was 40 seconds; EB polymerization conditions: carried out on an EB Lab200 electron beam processing system, with nitrogen gas supply not turned on, acceleration voltage 200 keV, and moving speed set to 3 m / min.

[0044] The performance of each UV / EB dual-cured black coating adhesive in Table 1 was tested according to the above method, and the results are shown in Table 2.

[0045] Table 2 Performance test table of black coating adhesive in Examples 1-10 and Comparative Examples 1-10

[0046]

[0047]

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. At the same time, those skilled in the art should understand and implement the above description. Therefore, any equivalent changes or modifications made without departing from the concept disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A UV / EB dual-curing black conformal coating, characterized in that, It comprises the following raw material components in parts by weight: 100 parts of aliphatic polyurethane acrylate; 70-80 parts of acrylate monomer; 10-25 parts of propylene modifier; 30-50 parts of UV-curable acrylate monomers; 3-10 parts of photoinitiator; 5-15 parts of black filler; The black filler is a mixture of carbon black and silica, with a mass ratio of carbon black to silica of 1:0.5~2, and the photoinitiator has an absorption wavelength of 320-350nm. The aliphatic polyurethane acrylate has a functionality of 2-6 and a molecular weight of 1×10⁻⁶. 4 ~5×10 4 The aliphatic polyurethane acrylate has a refractive index of 1.40~1.50 and a glass transition temperature of 83.0~85.0℃; the aliphatic polyurethane acrylate is a mixture of one or more of Changxing DR-U282, Changxing DR-U384, Changxing DR-U386, Changxing DR-U388, Changxing DR-U331 and Sartoma CN8881 NS; the acrylate monomer is a mixture of one or more of isobornyl methacrylate, isodecayl acrylate, tetrahydrofurfuryl acrylate and isobornyl acrylate; the propylene modifier is a mixture of one or more of hydroxyethyl methacrylate, acrylmorpholine and N,N-dimethylacrylamide; the UV-curable acrylate monomer is a mixture of one or more of tricyclodecanediethanol diacrylate, dodecyl acrylate and triethylene glycol dimethacrylate; the photoinitiator is photoinitiator 369.

2. The UV / EB dual-curing black conformal coating according to claim 1, characterized in that, It comprises the following raw material components in parts by weight: 100 parts of aliphatic polyurethane acrylate; 76 parts of acrylate monomer; 24 parts of propylene modifier; 40 parts of UV-curable acrylate monomers; 5 parts of photoinitiator; 6-12 parts of black filler.

3. The method for preparing the UV / EB dual-curing black conformal coating according to any one of claims 1 to 2, characterized in that, Includes the following steps: The black filler in the specified amount is dispersed in the specified amount of the acrylate monomer to form a black slurry; The black slurry is mixed evenly with the formulated amounts of the aliphatic polyurethane acrylate, the propylene modifier, the photoinitiator, and the UV-curable acrylate monomer.

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