Black photosensitive solder resist ink and preparation method thereof

Abstract

The invention relates to black photosensitive solder resist ink and a preparation method thereof.The black photosensitive solder resist ink is composed of a main agent and a curing agent, the weight ratio of the main agent to the curing agent is 2.5-4: 1, and the main agent comprises, by weight, 43-45 parts of acrylic resin, 2.6 parts of composite pigment and 4.8-5.1 parts of photoinitiator; the acrylic resin comprises 20-25 parts of carboxyl-containing high-molecular-weight epoxy acrylate half-ester resin, 8-10 parts of carboxyl-containing low-molecular-weight epoxy acrylate half-ester resin and 10-15 parts of carboxyl and allyl-containing copolymerized acrylate half-ester resin, and the black composite pigment comprises 1-1.1 parts of pigment red, 0.9-1 part of pigment yellow and 0.6 part of phthalocyanine blue. The curing agent comprises 6-7 parts of bisphenol A phenolic epoxy resin, 5-6 parts of triglycidyl isocyanurate and 4-8 parts of an active monomer.

Description

Technical Field

[0001] The invention relates to the technical field of photosensitive solder resist ink, and in particular to a black photosensitive solder resist ink and a preparation method thereof. Background Art

[0002] Solder resist ink plays an important role in the preparation of circuit boards. Solder resist ink is a special coat covering the outer layer of PCB, which is used to prevent short circuits between wires when various components are welded. At the same time, it adjusts the amount of solder adhesion and reduces the dissolution and pollution of copper in the weld, ultimately achieving the purpose of saving solder materials, increasing insulation, adapting to high density of wiring, avoiding cold solder joints, protecting circuits from oxidation and scratches, and increasing inspection speed. Among them, according to the curing method, solder resist ink can be divided into light-curing ink and heat-curing ink. Light-curing ink includes photosensitive developing ink and UV light-curing UV ink. Among them, UV is a light with a wavelength of 10-400nm.

[0003] In the field of consumer electronics such as smartphones, tablet computers, and high-end game consoles, in order to create a more high-end, technological visual effect and improve the overall texture and aesthetics of the product, PCB substrates made of black photosensitive solder mask ink are often used.

[0004] At present, some black photosensitive solder mask inks that can be applied to PCB substrates have been developed on the market. However, when traditional black photosensitive solder mask inks are used on PCB substrates, there is generally a serious problem of side etching during exposure and development, resulting in a low product yield rate, making the black ink unable to meet the high-resolution usage requirements of terminal products. Traditional black photosensitive inks are difficult to simultaneously meet the requirements of having a black color within a specific LAB value range and making the ink coating have a high-resolution texture. Summary of the invention

[0005] Based on this, it is necessary to provide a black photosensitive solder resist ink and a preparation method thereof that can solve the problems of poor bottom curing of the existing black solder resist ink and insufficient resolution after exposure.

[0006] On the one hand, an embodiment of the present invention provides a black photosensitive solder resist ink, which is composed of a main agent and a curing agent, wherein the weight ratio of the main agent to the curing agent is 2.5-4:1, and the main agent includes 43-45 parts of acrylic resin, 2.6 parts of composite pigment and 4.8-5.1 parts of photoinitiator, in parts by weight, the acrylic resin includes 20-25 parts of high molecular weight epoxy acrylate half ester resin containing carboxyl group, 8-10 parts of low molecular weight epoxy acrylate half ester resin containing carboxyl group and 10-15 parts of copolymerized polyacrylate half ester resin containing carboxyl group and allyl group, the black composite pigment is composed of 1-1.1 parts of pigment red, 0.9-1 parts of pigment yellow and 0.6 parts of phthalocyanine blue, and the curing agent includes 6-7 parts of bisphenol A novolac epoxy resin, 5-6 parts of triglycidyl isocyanurate and 4-8 parts of active monomer.

[0007] Preferably, the molecular weight of the high molecular weight epoxy acrylate half ester resin containing carboxyl groups is 14000-17000 and the acid value is 44-48 mgKOH / g, the molecular weight of the low molecular weight epoxy acrylate half ester resin containing carboxyl groups is 7000-9000 and the acid value is 52-60 mgKOH / g, and the molecular weight of the copolymerized acrylate half ester resin containing carboxyl groups and allyl groups is 19000-21000 and the acid value is 40-50 mgKOH / g.

[0008] Preferably, the black composite pigment is composed of 1 part of pigment red, 1 part of pigment yellow and 0.6 part of phthalocyanine blue.

[0009] Preferably, the photoinitiator is composed of 3.5-4 parts of 1-(9,9-dibutyl-9H-fluorene-2-yl)-2-methyl-2-morpholin-4-yl-propane-1-one, 0-1 parts of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 0.5-0.8 parts of 2-isopropylthioxanthone and 0.01-0.02 parts of bis-2,6-difluoro-3-pyrrolophenyl titanocene.

[0010] Preferably, the main agent further comprises, by weight, 1-2 parts of a defoamer, 1-2 parts of fumed silica, 0.1-0.2 parts of an antioxidant, 0.5-0.5 parts of an epoxy curing agent, 1-3 parts of a DPM diluent and 18-20 parts of a filler.

[0011] Preferably, the curing agent further comprises, by weight, 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine and 3-5 parts of filler; or,

[0012] The curing agent further comprises 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine tetraphthalic acid and 3-5 parts of filler.

[0013] Preferably, the active monomer is selected from one or more of dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated pentaerythritol tetraacrylate.

[0014] Preferably, the filler is selected from one or more of barium sulfate, talc, calcium carbonate and quartz powder.

[0015] Preferably, in parts by weight, the main agent consists of 43-45 parts of acrylic resin, 2.6 parts of composite pigment, 4.8-5.1 parts of photoinitiator, 1-2 parts of defoamer, 1-2 parts of fumed silica, 0.1-0.2 parts of antioxidant, 0.5-0.5 parts of epoxy curing agent, 1-3 parts of DPM diluent and 18-20 parts of filler; the acrylic resin consists of 20-25 parts of carboxyl-containing high molecular weight epoxy acrylate half ester resin, 8-10 parts of carboxyl-containing low molecular weight epoxy acrylate half ester resin and 10-15 parts of carboxyl- and allyl-containing copolymerized acrylate half ester resin; the curing agent consists of 6-7 parts of bisphenol A novolac epoxy resin, 5-6 parts of triglycidyl isocyanurate, 4-8 parts of active monomer, 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine and 3-5 parts of filler.

[0016] The present invention provides a method for preparing a black solder resist ink, comprising the following steps:

[0017] S1. Preparation of main agent:

[0018] Add acrylic resin, pigment and additives into the dispersion barrel according to proportion;

[0019] Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes;

[0020] Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns;

[0021] After adding a diluent to adjust the viscosity to 200-300 dPa.s, filter using a filter cloth with a mesh size of 150-300 to obtain the main agent;

[0022] S2. Preparation of curing agent:

[0023] Add epoxy resin and additives into the dispersion tank according to the proportion;

[0024] Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes;

[0025] Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns;

[0026] After adding a diluent to adjust the viscosity to 50-150 dPa.s, filter using a filter cloth with a mesh size of 150-300 to obtain a curing agent;

[0027] S3. Preparation of finished black ink:

[0028] The main agent and the curing agent are evenly mixed in a ratio of 2.5-4:1 to obtain a finished black ink product.

[0029] The present application adopts red, yellow and blue pigments to mix into a black composite pigment to replace the existing carbon black pigment, so that the solder mask ink presents a black visual effect. The composite pigment mixed into black has a high transmittance to UV light, so UV light can easily pass through the composite pigment black ink coating to reach the bottom of the ink coating, so that the bottom of the ink coating can absorb sufficient UV light, and under the action of the initiator, the bottom of the ink coating can achieve a good curing effect, thereby solving the problems of poor bottom curing and low ink resolution in the existing black photosensitive ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other purposes, features and advantages of the present invention will become more clear by more specific description of the preferred embodiments of the present invention shown in the accompanying drawings. The same reference numerals indicate the same parts in all the accompanying drawings, and the accompanying drawings are not deliberately scaled to the actual size, and the focus is on illustrating the main purpose of the present invention.

[0031] Figure 1 This is a color comparison diagram of the black ink of Example 1 of the present invention and Comparative Example 1;

[0032] Figure 2 It is a comparative curve diagram of the transmittance of light of different wavelengths of the black ink of Example 1 of the present invention and Comparative Example 1;

[0033] Figure 3 This is a cross-sectional photograph of the black ink of Example 1 at the undercut notch after exposure and development;

[0034] Figure 4 This is a cross-sectional photograph of the black ink of Comparative Example 1 at the undercut notch after exposure and development;

[0035] Figure 5 This is a photograph of the film layer of the black ink of Example 1 when the window size is 49*56 μm;

[0036] Figure 6This is a photograph of the film layer of the black ink of Comparative Example 1 when the window size is 49*56 μm;

[0037] Figure 7 Schematic diagram of the molecular structure of carboxyl-containing epoxy acrylate half-ester resin;

[0038] Figure 8 It is a schematic diagram of the molecular structure of a copolymer polyacrylate half ester resin containing carboxyl and allyl groups. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0040] like Figure 1-Figure 8 As shown, a black photosensitive solder resist ink is composed of a main agent and a curing agent, the weight ratio of the main agent to the curing agent is 2.5-4:1, and the main agent includes 43-45 parts of acrylic resin, 2.6 parts of composite pigment and 4.8-5.1 parts of photoinitiator, the acrylic resin includes 20-25 parts of high molecular weight epoxy acrylate half ester resin containing carboxyl group, 8-10 parts of low molecular weight epoxy acrylate half ester resin containing carboxyl group and 10-15 parts of copolymerized acrylate half ester resin containing carboxyl group and allyl group, the black composite pigment is composed of 1-1.1 parts of pigment red, 0.9-1 parts of pigment yellow and 0.6 parts of phthalocyanine blue, and the curing agent includes 6-7 parts of bisphenol A novolac epoxy resin, 5-6 parts of triglycidyl isocyanurate and 4-8 parts of active monomer.

[0041] In a preferred embodiment, the black composite pigment is composed of 1 part of pigment red, 1 part of pigment yellow and 0.6 part of phthalocyanine blue by weight. Preferably, the phthalocyanine blue is copper phthalocyanine blue.

[0042] The applicant has found through a large number of experiments that the absorbance of conventional black solder resist ink is relatively high, resulting in a low transmittance of light through the conventional black solder resist ink.

[0043] After repeated experiments, the applicant further discovered that the black pigment used in the existing traditional black solder mask ink is carbon black. Due to the high absorbance of carbon black, the transmittance of the ink containing carbon black is low, which leads to the problem of base curing when using traditional carbon black formulas, and the high resolution requirement cannot be achieved. However, the black effect cannot be achieved without using carbon black.

[0044] During exposure, when UV light is used to irradiate the ink coating, the UV light enters from the top surface of the ink coating and irradiates toward the bottom surface of the ink coating. As the UV light penetrates the ink coating, it is continuously absorbed and lost by the black ink coating, and most of the UV light is absorbed and lost by the carbon black pigment, so that the UV light reaching the bottom surface of the ink coating is not sufficient to achieve a good curing of the ink at the bottom, so that the bottom is not completely cured, resulting in serious side erosion problems, and the ink resolution will not be able to meet the use needs of the terminal product.

[0045] The formula of the present application adopts red, yellow and blue pigments to be mixed into a black composite pigment to replace the existing carbon black pigment, so that the solder mask ink can present a black visual effect. The composite pigment mixed into black has a high transmittance to UV light, so UV light can easily pass through the composite pigment black ink coating to reach the bottom of the ink coating, so that the bottom of the ink coating can absorb sufficient UV light, and under the action of the initiator, the bottom of the ink coating can be cured well, which solves the problems of poor bottom curing and low ink resolution in the existing black photosensitive ink.

[0046] The present application ensures that the resolution of the black ink during exposure and development is high through a reasonable formula, which can ensure the accuracy and clarity of the pattern printed using the ink, and the edge lines of the pattern printed with the ink are sharp and the lines are uniform. In this way, while meeting the requirements of precision manufacturing, it can also present a high-quality black visual effect. On the premise of meeting the color requirements, the present application improves the curing effect by introducing the idea of ​​composite pigments, and can meet the customer's requirements for higher resolution of black ink, solving the problem that the existing black photosensitive ink is difficult to have a black color in a specific LAB value range and the ink coating has a high-resolution texture.

[0047] In a preferred embodiment, the molecular weight of the high molecular weight epoxy acrylate half ester resin containing carboxyl groups is 14000-17000 and the acid value is 44-48 mgKOH / g, the molecular weight of the low molecular weight epoxy acrylate half ester resin containing carboxyl groups is 7000-9000 and the acid value is 52-60 mgKOH / g, and the molecular weight of the copolymerized acrylate half ester resin containing carboxyl groups and allyl groups is 19000-21000 and the acid value is 40-50 mgKOH / g. Figure 7 is the molecular structure formula of a carboxyl-containing high molecular weight epoxy acrylate half ester resin and a carboxyl-containing low molecular weight epoxy acrylate half ester resin, that is, Figure 7 It is the molecular structure formula of epoxy acrylate half ester resin containing carboxyl group. Figure 8 It is the molecular structure formula of copolymerized polyacrylate half ester resin containing carboxyl and allyl groups.

[0048] Among them, the high molecular weight epoxy acrylate half ester resin containing carboxyl groups and the low molecular weight epoxy acrylate half ester resin containing carboxyl groups both have carboxyl functional groups, and the carboxyl functional groups provide the resin with more reaction activity and cross-linking points, which can improve the curing performance and coating performance of the resin. Among them, the molecular chain of the low molecular weight epoxy acrylate half ester resin is relatively short and has a lower viscosity. The cross-linking reaction between molecules is easier to proceed during curing, so the curing speed is relatively fast; while the molecular chain of the high molecular weight epoxy acrylate half ester resin containing carboxyl groups is longer, and the cross-linking reaction between molecules during curing requires more time and energy, so the curing speed is slower; the applicant has found through a large number of experiments that by adding a copolymerized polyacrylate half ester resin containing carboxyl groups and allyl groups to the epoxy acrylate half ester resin containing carboxyl groups, and by using epoxy acrylate half ester resins containing carboxyl groups with different molecular weights and a specific ratio between the resins, the bonding strength between the resin and the plate is improved under the action of the photoinitiator, and a better photocuring effect of the ink bottom layer is achieved. Reasonable molecular weight and acid value of carboxyl-containing epoxy acrylate half-ester resin can, on the one hand, achieve better cross-linking and curing during curing; on the other hand, it can also make the ink develop better and avoid unclean development, thereby improving the resolution of the ink.

[0049] In a preferred embodiment, the photoinitiator includes 3.5-4 parts of 1-(9,9-dibutyl-9H-fluorene-2-yl)-2-methyl-2-morpholine-4-yl-propane-1-one, 0-1 parts of 2-benzyl-2-dimethylamino-1-(4-morpholinephenyl)butanone, 0.5-0.8 parts of 2-isopropylthioxanthone and 0.01-0.02 parts of bis-2,6-difluoro-3-pyrrolephenyl titanocene. The photoinitiator type and reasonable ratio of the present application are used in combination with the macromolecular photosensitive resin in the formula to promote the photocuring effect during exposure, which is beneficial to reduce the side erosion problem of the ink. By using the photoinitiator reasonably, the deep curing of the ink is enhanced while ensuring good surface curing.

[0050] In a preferred embodiment, the main agent further comprises, by weight, 1-2 parts of a defoamer, 1-2 parts of fumed silica, 0.1-0.2 parts of an antioxidant, 0.5-0.5 parts of an epoxy curing agent, 1-3 parts of a DPM diluent and 18-20 parts of a filler.

[0051] In a preferred embodiment, the curing agent further comprises, by weight, 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine and 3-5 parts of filler, wherein melamine can be replaced by melamine tetraphthalic acid.

[0052] In a preferred embodiment, the active monomer is selected from one or more of dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated pentaerythritol tetraacrylate.

[0053] In a preferred embodiment, the filler is selected from one or more of barium sulfate, talc, calcium carbonate, and quartz powder.

[0054] The present invention also provides a method for preparing a black photosensitive solder resist ink, comprising the following steps:

[0055] S1. Preparation of main agent:

[0056] Add acrylic resin, pigment and additives into the dispersion barrel according to proportion;

[0057] Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes.

[0058] Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns;

[0059] After adding a diluent to adjust the viscosity to 200-300 dPa.s, filter with a filter cloth to obtain the main agent;

[0060] S2. Preparation of curing agent:

[0061] Add epoxy resin and additives into the dispersion tank according to the proportion;

[0062] Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes.

[0063] Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns;

[0064] After adding a diluent to adjust the viscosity to 50-150 dPa.s, filter using a filter cloth to obtain a curing agent;

[0065] S3. Preparation of finished black ink:

[0066] Wherein, in steps S1 and S2, filter cloth with a mesh size of 150-300 is used for filtration.

[0067] The main agent and the curing agent are uniformly mixed in a weight ratio of 2.5-4:1 to obtain a finished black ink product.

[0068] In order to better illustrate the technical solution of the present invention, several preferred embodiments are now cited for further explanation.

[0069] The components and weight proportions of Examples 1-2 and Comparative Example 1 are shown in Table 1 below:

[0070] Table 1

[0071]

[0072]

[0073] In Table 1, photoinitiator 1 is 1-(9,9-dibutyl-9H-fluorene-2-yl)-2-methyl-2-morpholin-4-yl-propane-1-one, photoinitiator 2 is 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, photoinitiator 3 is 2-isopropylthioxanthone, and photoinitiator 4 is bis-2,6-difluoro-3-pyrrolophenyl titanocene; among them, photoinitiator 1 is produced by Qiangli Company, NPI-20400; photoinitiator 2, photoinitiator 3 and photoinitiator 4 are all produced by BASF AG;

[0074] The carboxyl-containing high molecular weight epoxy acrylate half ester resin was produced by Guangzhou Starley Company, GF-105;

[0075] The carboxyl-containing low molecular weight epoxy acrylate half ester resin was produced by Shenzhen Rongda Photosensitive Co., Ltd., LPI-360;

[0076] The copolymerized polyacrylate half-ester resin containing carboxyl and allyl groups was produced by Guangzhou Starley Company, GF-210;

[0077] Pigment Red 176 was produced by Shanghai Yuanye Biological Company, T81642;

[0078] Pigment Yellow 83 was produced by Shanghai Yuanye Biological Company, T24917;

[0079] Phthalocyanine blue is produced by BASF AG, 7110.

[0080] The above Examples 1-2 and Comparative Example 1 were prepared according to the following preparation method:

[0081] Step 1: Preparation of the main agent:

[0082] Add the components of the main agent into the dispersion barrel according to the proportions in Table 1. Disperse at high speed in a high-speed disperser, wherein the speed of the high-speed disperser is 1000 rpm and the time is 60 minutes. Grind 4 times with a three-roller mill or grind with a sand mill to a particle size of less than 20 microns. Add a diluent to adjust the viscosity to 300 dPa.s, and filter with a filter cloth with a mesh size of 300 to obtain the main agent for standby use.

[0083] Step 2: Preparation of curing agent:

[0084] Add the components of the curing agent into the dispersion barrel according to the proportions in Table 1; disperse at high speed in a high-speed disperser, wherein the speed of the high-speed disperser is 1000 rpm and the time is 60 minutes. Grind with a three-roller mill for 4 times or grind with a sand mill to a particle size of less than 20 microns. Add a diluent to adjust the viscosity to 150 dPa.s, filter with a filter cloth with a mesh size of 300 to obtain the curing agent for standby use.

[0085] Step 3: Evenly mix the above-prepared main agent and curing agent in a weight ratio of 3:1 to obtain a finished black ink product.

[0086] Effect example

[0087] The finished inks prepared in Examples 1-2 and Comparative Example 1 are analyzed below.

[0088] 1. Finished black ink color

[0089] (1) Appearance color

[0090] 10 g of the finished inks prepared in Examples 1-2 and Comparative Example 1 were scooped out with a scraper and coated on a white substrate. The coating area on the white substrate was 5*10 cm in size. After standing for 5 minutes, the color of the finished ink coating was observed. Figure 1 Shown are photos comparing the appearance colors of the inks of Example 1 and Comparative Example 1.

[0091] It can be seen that the inks prepared in Example 1 and Comparative Example 1 both look like black inks, and there is no difference in color when observed with the naked eye.

[0092] This shows that the formula of the present invention is reasonable, has a black appearance color, and can achieve the same black effect as the existing black ink using carbon black.

[0093] (2) LAB value test

[0094] The LAB value of the ink prepared in Example 1-2 and Comparative Example 1 was tested using a CM-26d spectrophotometer. The results are shown in Table 2 below:

[0095] Table 2

[0096] L value A Value B value Example 1 28.43 0.04 -0.70 Example 2 29.01 0.09 -0.90 Comparative Example 1 28.53 -0.02 -0.85

[0097] According to the LAB values ​​measured in Table 2 above, the color difference ΔE between the LAB values ​​of Example 1 and Comparative Example 1 is 0.19, and the color difference ΔE between the LAB values ​​of Example 2 and Comparative Example 1 is 0.49. It can be seen that from the comparison of the color values ​​obtained from the test, the difference between the two colors is very small, and there is almost no difference.

[0098] This shows that the formula of the present invention is reasonable, can meet the LAB color value requirements of the black pigment, and can achieve the same black effect as the existing black ink using carbon black.

[0099] 2. Transmittance test

[0100] After the black ink prepared in Example 1 and Comparative Example 1 was coated under the same conditions, a composite light with a wavelength of 300-800nm ​​was used for illumination experiment to test the transmittance data of light passing through the ink film layer. The transmittance data of Example 1 and Comparative Example 1 were plotted to obtain Figure 2 Transmittance diagram.

[0101] From the attached Figure 2 It can be seen that when illuminated in the wavelength range of 300-400nm, the light transmittance of the black ink prepared by the composite pigment in Example 1 of the present application is much higher than the light transmittance of the black ink prepared by carbon black in Comparative Example 1.

[0102] In the UV light band with a wavelength of 300-400nm, the light transmittance of the formulated ink in Example 1 of the present application is relatively high. In this band, its transmittance is much higher than the transmittance of the existing black ink using carbon black. The formulated ink in Example 1 of the present application has a low absorption rate for UV light, so that more light reaches the bottom, so that the light initiator at the bottom of the ink film layer can also absorb sufficient light, thereby achieving a good curing effect at the bottom of the ink film layer.

[0103] 3. Side etching results after exposure and development

[0104] After the black ink prepared in Example 1, Example 2 and Comparative Example 1 was coated on a substrate under the same conditions to form a film, it was exposed and developed according to the circuit board manufacturing process, and observed using an FTM3000 electron microscope to obtain the sizes of the gaps at the edges of the bottom of the film layer of the Example and the Comparative Example that were etched away by the side. The measured size values ​​of the side etched gaps are shown in Table 3 below, where: Figure 3 The cross-sectional photograph of the black ink of Example 1 at the undercut notch after exposure and development is attached. Figure 4 This is a cross-sectional photograph of the black ink layer of Comparative Example 1 at the undercut notch after exposure and development:

[0105] Table 3

[0106] Ink thickness (μm) Side erosion 1(μm) Side erosion 2(μm) Example 1 42.504 13.402 11.870 Example 2 43.128 16.851 16.223 Comparative Example 1 43.651 34.081 34.846

[0107] It can be seen from Table 3 above that the ink thickness of the ink layer of Example 1 and Comparative Example 1 is roughly the same, the depths of the side erosion notches at the two side edges of the ink layer of Example 1 are 11.870 μm and 13.402 μm, the depths of the side erosion notches of Example 2 are 16.223 μm and 16.851 μm, and the depths of the side erosion notches of Comparative Example 1 are 34.081 μm and 34.846 μm. It can be seen that the side erosion notches of Comparative Example 1 are larger, indicating that the bottom layer of the film layer of Comparative Example 1 is poorly cured during exposure, resulting in larger side erosion during development, indicating that the light energy reaching the bottom layer of the film layer of Comparative Example 1 is insufficient, and better deep photocuring cannot be achieved.

[0108] 4. Coating window resolution

[0109] After the black ink prepared in Example 1 and Comparative Example 1 was coated under the same conditions to form a film, the black ink film layer prepared in Example 1 and Comparative Example 1 was exposed and developed according to the circuit board manufacturing process, thereby preparing a film layer window with a length and width of 49*56μm. Figure 5 This is a photo schematic diagram of the film window opening of Example 1. Figure 6 This is a schematic diagram of the photo of the film window opening of Comparative Example 1.

[0110] from Figure 5 It can be seen from the photos that the edges of the openings of the film layer of Example 1, which are 49*56μm in size, are relatively smooth and neat, indicating that the black ink of Example 1 can achieve a high resolution effect of the small-size openings of 49*56μm.

[0111] from Figure 6 From the photos, we can see that the edges of the windows of the film layer of Comparative Example 1, which have a size of 49*56μm, have many gaps and are uneven, indicating that the resolution of the black ink of Comparative Example 1 at the small-sized windows of 49*56μm is not high, and the effect of higher resolution of the small-sized windows cannot be achieved.

[0112] In summary, the black solder resist ink of the present invention uses reasonable raw materials and proportions to achieve better curing effect and high-resolution performance of the ink coating.

[0113] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A black photosensitive solder resist ink, characterized in that: The invention is composed of a main agent and a curing agent, wherein the weight ratio of the main agent to the curing agent is 2.5-4:

1. In parts by weight, the main agent comprises 43-45 parts of acrylic resin, 2.6 parts of composite pigment and 4.8-5.1 parts of photoinitiator, the acrylic resin comprises 20-25 parts of high molecular weight epoxy acrylate half ester resin containing carboxyl group, 8-10 parts of low molecular weight epoxy acrylate half ester resin containing carboxyl group and 10-15 parts of copolymerized polyacrylate half ester resin containing carboxyl group and allyl group, the black composite pigment comprises 1-1.1 parts of pigment red, 0.9-1 parts of pigment yellow and 0.6 parts of phthalocyanine blue, and the curing agent comprises 6-7 parts of bisphenol A novolac epoxy resin, 5-6 parts of triglycidyl isocyanurate and 4-8 parts of active monomer.

2. The ink according to claim 1, characterized in that The molecular weight of the high molecular weight epoxy acrylate half ester resin containing carboxyl groups is 14000-17000 and the acid value is 44-48 mgKOH / g, the molecular weight of the low molecular weight epoxy acrylate half ester resin containing carboxyl groups is 7000-9000 and the acid value is 52-60 mgKOH / g, and the molecular weight of the copolymerized acrylate half ester resin containing carboxyl groups and allyl groups is 19000-21000 and the acid value is 40-50 mgKOH / g.

3. The ink according to claim 1, characterized in that The black composite pigment is composed of 1 part of pigment red, 1 part of pigment yellow and 0.6 part of phthalocyanine blue.

4. The ink according to claim 1 or 2, characterized in that The photoinitiator is composed of 3.5-4 parts of 1-(9,9-dibutyl-9H-fluorene-2-yl)-2-methyl-2-morpholin-4-yl-propane-1-one, 0-1 part of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 0.5-0.8 part of 2-isopropylthioxanthone and 0.01-0.02 part of bis-2,6-difluoro-3-pyrrolephenyl titanocene.

5. The ink according to claim 1, characterized in that In parts by weight, the main agent further comprises 1-2 parts of a defoamer, 1-2 parts of fumed silica, 0.1-0.2 parts of an antioxidant, 0.5-0.5 parts of an epoxy curing agent, 1-3 parts of a DPM diluent and 18-20 parts of a filler.

6. The ink according to claim 1, characterized in that In parts by weight, the curing agent further comprises 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine and 3-5 parts of filler; or, In parts by weight, the curing agent further comprises 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine tetraphthalic acid and 3-5 parts of filler.

7. The ink according to claim 6, characterized in that The active monomer is selected from one or more of dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated pentaerythritol tetraacrylate.

8. The ink according to claim 4 or 6, characterized in that The filler is selected from one or more of barium sulfate, talcum powder, calcium carbonate and quartz powder.

9. The ink according to claim 1, characterized in that In parts by weight, the main agent consists of 43-45 parts of acrylic resin, 2.6 parts of composite pigment, 4.8-5.1 parts of photoinitiator, 1-2 parts of defoamer, 1-2 parts of fumed silica, 0.1-0.2 parts of antioxidant, 0.5-0.5 parts of epoxy curing agent, 1-3 parts of DPM diluent and 18-20 parts of filler; the acrylic resin consists of 20-25 parts of high molecular weight epoxy acrylate half ester resin containing carboxyl group, 8-10 parts of low molecular weight epoxy acrylate half ester resin containing carboxyl group and 10-15 parts of copolymerized acrylate half ester resin containing carboxyl group and allyl group; the curing agent consists of 6-7 parts of bisphenol A novolac epoxy resin, 5-6 parts of triglycidyl isocyanurate, 4-8 parts of active monomer, 0.5-2 parts of DPM diluent, 0.5-2 parts of melamine and 3-5 parts of filler.

10. A method for preparing a black photosensitive solder resist ink, characterized in that: The steps include: S1. Preparation of main agent: Add acrylic resin, pigment and additives into the dispersion barrel according to proportion; Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes; Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns; After adding a diluent to adjust the viscosity to 200-300 dPa.s, filter using a filter cloth with a mesh size of 150-300 to obtain the main agent; S2. Preparation of curing agent: Add epoxy resin and additives into the dispersion tank according to the proportion; Disperse at high speed in a high-speed disperser; the speed of the high-speed disperser is 600-1000 rpm and the time is 30-60 minutes; Grind with a three-roll mill 2-5 times or with a sand mill until the particle size is less than 20 microns; After adding a diluent to adjust the viscosity to 50-150 dPa.s, filter using a filter cloth with a mesh size of 150-300 to obtain a curing agent; S3. Preparation of finished black ink: The main agent and the curing agent are evenly mixed in a ratio of 2.5-4:1 to obtain a finished black ink product.

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