A high-thermal-conductivity high-adhesion copper foil coating ink, a preparation method and application thereof

Abstract

The application belongs to the field of composite ink coating, and particularly discloses a high-thermal-conductivity and high-adhesion copper foil coating ink, a preparation method and application thereof.The ink coating comprises, by weight, 15-25 parts of epoxy resin, 10-20 parts of polyurethane resin, 5-12 parts of modified cellulose, 30-45 parts of thermal-conductivity filler, 8-15 parts of aliphatic polyisocyanate curing agent, 20-35 parts of solvent, 2-5 parts of silane coupling agent and 0.5-3 parts of pigment.The modified cellulose is prepared by modification of halogen-free betaine hydroxide, can synergize with the double-resin matrix to enhance the interface bonding force and build a three-dimensional thermal-conductivity network.After the ink coating is coated on the surface of electrolytic or calendered copper foil, the thermal conductivity coefficient of the coating is greater than 0.4 W / (m·K), the darcy value is greater than 38, the crosshatch test is greater than or equal to 4B, there is no peeling after alcohol wiping, the color difference ΔE is less than 1, and the ink coating is suitable for high-frequency circuit substrates and lithium battery current collectors.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of composite ink coatings, and specifically discloses a high-thermal-conductivity high-adhesion copper foil coating ink coating, a preparation method and application thereof. BACKGROUND

[0002] With the development of electronic devices towards high-density integration, high frequency and high speed, the heat dissipation and interface stability requirements of copper foil as a circuit substrate are increasingly stringent. In order to improve the thermal conductivity, the traditional copper foil coating ink usually uses a high proportion of thermal conductive fillers such as aluminum oxide and boron nitride, but the introduction of excessive fillers leads to the destruction of the continuity of the resin matrix, the increase of the internal stress of the coating, and the easy occurrence of edge peeling or grid shedding in the mesh test, which is difficult to stably reach the 4B level standard. At the same time, the high filler content aggravates the surface roughness of the coating, which is easy to cause local failure due to mechanical wear in the alcohol wiping test. In addition, the existing resin system, such as a single epoxy resin or acrylic resin, has a weak physical anchoring effect on the surface of the copper foil, and the interface adhesion value is generally lower than 36, which is difficult to meet the fine requirements of the micron-level circuit etching process on the surface energy of the coating. Some studies attempt to improve the interface bonding by adding a silane coupling agent, but the compatibility of the coupling agent with the resin is insufficient, which easily leads to filler aggregation or uneven solvent evaporation, resulting in significant color difference fluctuation of the coating and affecting the appearance consistency of the product.

[0003] Therefore, it is urgent to develop a coating ink with high thermal conductivity, excellent adhesion and processing stability. In recent years, cellulose materials have attracted attention due to their renewability, high film-forming strength and low cost characteristics, but unmodified cellulose has obvious defects: a large number of hydroxyl groups in the molecular chain lead to poor compatibility with hydrophobic resins, and easily form phase separation in the ink system, which in turn reduces the coating density; at the same time, cellulose itself has very low thermal conductivity, and direct addition will offset the gain effect of the thermal conductive filler. SUMMARY

[0004] To solve the above-mentioned problems in the prior art, the application discloses a high-thermal-conductivity high-adhesion copper foil coating ink coating, a preparation method and application thereof. The application optimizes the interface bonding of the resin matrix and the thermal conductive filler by using a specific halogen-free modified cellulose, thereby significantly improving the adhesion value, alcohol resistance and color difference stability.

[0005] To achieve the above-mentioned purposes, the technical problems of the application are solved by the following technical solutions:

[0006] The application discloses a high-thermal-conductivity and high-adhesion copper foil coating ink paint, which comprises the following components in parts by weight: 15-25 parts of epoxy resin, 10-20 parts of polyurethane resin, 5-12 parts of modified cellulose, 30-45 parts of mixed thermal conductive filler of alumina and boron nitride, 8-15 parts of aliphatic polyisocyanate curing agent, 20-35 parts of propylene glycol methyl ether acetate solvent, 2-5 parts of silane coupling agent and 1-3 parts of carbon black pigment.

[0007] The preparation of the modified cellulose comprises the following steps: mixing microcrystalline cellulose and betaine hydroxide at a mass ratio of 1:0.4-0.6, reacting at 60-80 DEG C under alkaline conditions for 4-6 hours, and washing and drying to obtain the modified cellulose.

[0008] Further, the ink paint is characterized in that the epoxy resin is bisphenol A type epoxy resin with an epoxy equivalent of 350-450 g / eq, and the polyurethane resin is aliphatic polyester type polyurethane with a solid content of 50-60%.

[0009] Further, the ink paint is characterized in that the average particle size of the thermal conductive filler is 2-8 mu m, the alumina is alpha phase spherical particles, and the boron nitride is in a sheet structure with a sheet diameter to thickness ratio of 10:1-20:1.

[0010] Further, the ink paint is characterized in that the mass ratio of the alumina to the boron nitride is 3:1-5:1.

[0011] The application further discloses a preparation method of the ink paint.

[0012] (1) mixing the epoxy resin, the polyurethane resin and the propylene glycol methyl ether acetate solvent, and stirring at 50-60 DEG C until completely dissolved;

[0013] (2) adding the silane coupling agent KH550 and the modified cellulose, and ultrasonic dispersing for 20-30 minutes;

[0014] (3) adding the alumina and the boron nitride thermal conductive filler, and grinding to a fineness of less than or equal to 5 mu m;

[0015] (4) adding the aliphatic polyisocyanate curing agent and the carbon black pigment, and high-speed dispersing and then filtering to obtain the ink paint.

[0016] Further, the preparation method is characterized in that the grinding in step (3) is performed by using a three-roll mill with a roll spacing of 10-20 mu m, and the grinding is performed for 3-5 times.

[0017] The application further discloses application of the ink paint to electrolytic copper foil or rolled copper foil, which is coated on the surface of the electrolytic copper foil or the rolled copper foil with a coating thickness of 8-15 mu m and curing conditions of baking at 80-100 DEG C for 10-15 minutes.

[0018] Further, the application is used for high-frequency circuit substrate or lithium battery negative electrode current collector, and the surface roughness Ra of the coating is less than 0.3 microns.

[0019] Further, the application is used for high-frequency circuit substrate or lithium battery negative electrode current collector, and the surface roughness Ra of the coating is less than 0.3 microns.

[0020] Compared with the prior art, the application has the following outstanding beneficial effects:

[0021] 1. The application forms a continuous heat conduction path by compounding aluminum oxide with flaky boron nitride and directional arrangement of modified cellulose, and the heat conductivity coefficient reaches 0.43-0.59 W / (m·K), and the carboxyl group of betaine modified cellulose forms a coordination bond with the copper foil, and the quaternary ammonium group enhances the electrostatic adsorption, so that the prepared ink coating has good heat conductivity and adhesion.

[0022] 2. The application optimizes the proportion of silane coupling agent and modified cellulose, inhibits alcohol penetration and pigment aggregation, and the coating does not fall off after alcohol wiping, and has good chemical resistance and color difference stability.

[0023] 3. The application uses epoxy resin and polyurethane double resins to consider flexibility and curing strength, is suitable for processes such as slot coating and micro-gravure coating, and can be used for copper foils with different thicknesses.

[0024] 4. The application uses modified cellulose to replace part of the resin, reduces the amount of filler, and the whole preparation process is halogen-free and releases no toxic solvent, which is green and environmentally friendly. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be described below in conjunction with specific embodiments, obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0026] In the application, if no special description is made, the numerical range is regarded as continuous and includes the minimum value and the maximum value of the range and each value between the minimum value and the maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all the ranges disclosed in the present application should be understood as including any and all sub-ranges.

[0027] In the application, the specific dispersion and stirring treatment methods are not particularly limited.

[0028] In the present application, the test methods used are conventional methods unless otherwise specified; the materials, reagents, etc. used are commercially available reagents and materials unless otherwise specified.

[0029] The raw materials and equipment used in the following examples are shown in Tables 1 and 2 below.

[0030] Table 1 Raw material source table

[0031]

[0032] Table 2 Instrument equipment parameter table

[0033]

[0034]

[0035] Example 1

[0036] One kind of high-thermal-conductivity high-adhesion copper foil coating ink paint, by weight parts, including 15 parts of bisphenol A type epoxy resin (E-51), 10 parts of polyurethane resin (aliphatic polyester type, Desmocoll 540), 5 parts of modified cellulose, 30 parts of thermal conductive filler, 8 parts of aliphatic polyisocyanate curing agent (HDI trimer, Covestro Desmodur N3300), 20 parts of solvent (propylene glycol methyl ether acetate, PMA), 2 parts of coupling agent (KH550), 1 part of pigment (carbon black).

[0037] In this embodiment, the thermal conductive filler is a mixture of aluminum oxide (alpha phase, particle size 3 μm) and boron nitride (flaky, flake thickness ratio 15:1) in a mass ratio of 3:1.

[0038] In this embodiment, the modified cellulose is prepared as follows:

[0039] (1) Mix microcrystalline cellulose and betaine hydroxide in a mass ratio of 1:0.5;

[0040] (2) Add the mixture to an aqueous solution containing 5% NaOH and react at 80°C for 5 hours;

[0041] (3) After reaction, filter, wash with deionized water until neutral, vacuum dry at 60°C for 12 hours, and crush to pass through a 200 mesh sieve.

[0042] Two, a preparation method of a high-thermal-conductivity high-adhesion copper foil coating ink paint, comprising the following steps:

[0043] (1) Resin dissolution: mix epoxy resin, polyurethane resin and PMA, stir at 60°C and 800 rpm for 30 minutes;

[0044] (2) Coupling dispersion: add KH550 and modified cellulose, 40 kHz ultrasonic dispersion (power 300 W) for 25 minutes;

[0045] (3) Filler grinding: three-roll mill grinding (roller spacing 20 pm, roller temperature 25 °C) for 4 times, fineness ≤5 pm;

[0046] (4) Curing dispersion: add HDI trimer curing agent and carbon black, high-speed dispersion at 2000 rpm for 15 minutes, and then pressure filtration on a 200 mesh nylon filter screen (0.2 MPa) to obtain an ink coating.

[0047] Example 2

[0048] One kind of high-thermal-conductivity high-adhesion copper foil coating ink coating, by weight parts, including 20 parts of bisphenol F type epoxy resin (E-44), 15 parts of polyurethane resin (aromatic, Uralane5770), 10 parts of modified cellulose, 45 parts of thermal conductive filler, 12 parts of aliphatic polyisocyanate curing agent (HDI trimer, Covestro Desmodur N3300), 30 parts of solvent (propylene glycol methyl ether acetate, PMA), 4 parts of coupling agent (KH550), 2 parts of pigment (carbon black).

[0049] In this embodiment, the thermal conductive filler is mixed by alumina (alpha phase, particle size 3 pm) and boron nitride (flaky, flake diameter thickness ratio 15:1) in a mass ratio of 5:1.

[0050] In this embodiment, the modified cellulose is prepared as in Example 1.

[0051] Two, a method for preparing a high-thermal-conductivity high-adhesion copper foil coating ink coating, comprising the following steps:

[0052] (1) Resin dissolution: mix the epoxy resin, polyurethane resin and PMA, stir at 65 °C and 1000 rpm for 40 minutes;

[0053] (2) Coupling dispersion: add KH550 and modified cellulose, 50 kHz ultrasonic dispersion (power 350 W) for 30 minutes;

[0054] (3) Filler grinding: three-roll mill grinding (roller spacing 10 pm, roller temperature 30 °C) for 5 times, fineness ≤5 pm;

[0055] (4) Curing dispersion: add HDI trimer curing agent and carbon black, high-speed dispersion at 2500 rpm for 20 minutes, and then pressure filtration on a 300 mesh nylon filter screen (0.3 MPa) to obtain an ink coating.

[0056] Example 3

[0057] One, a high-thermal-conductivity high-adhesion copper foil coating ink paint, by weight parts, including 18 parts of bisphenol A type epoxy resin (E-51), 12 parts of polyurethane resin (aliphatic polyester type, Desmocoll 540), 8 parts of modified cellulose, 40 parts of thermal conductive filler, 10 parts of aliphatic polyisocyanate curing agent (HDI trimer, Covestro Desmodur N3300), 25 parts of solvent (propylene glycol methyl ether acetate, PMA), 3 parts of coupling agent (KH550), 1.5 parts of pigment (carbon black).

[0058] In this embodiment, the thermal conductive filler is mixed by mass ratio of 4:1 of aluminum oxide (alpha phase, particle size 3 μm) and boron nitride (flaky, flake diameter thickness ratio 15:1).

[0059] In this embodiment, the modified cellulose is prepared as in Example 1.

[0060] Two, a preparation method of a high-thermal-conductivity high-adhesion copper foil coating ink paint, comprising the following steps:

[0061] (1) Resin dissolution: mix epoxy resin, polyurethane resin and PMA, 60℃, 900rpm stirring for 35 minutes;

[0062] (2) Coupling dispersion: add KH550 and modified cellulose, 45kHz ultrasonic dispersion (power 320W) for 28 minutes;

[0063] (3) Filler grinding: three-roll mill grinding (roll spacing 15 μm, roll temperature 28℃) for 4 times, fineness ≤5 μm;

[0064] (4) Curing dispersion: add HDI trimer curing agent and carbon black, high-speed dispersion at 2200rpm for 18 minutes, and then pressure filtration (0.25MPa) through a 250 mesh nylon filter screen to obtain the ink paint.

[0065] Example 4

[0066] One, a high-thermal-conductivity high-adhesion copper foil coating ink paint, by weight parts, including 15 parts of bisphenol F type epoxy resin (E-44), 18 parts of polyurethane resin (aromatic, Uralane 5770), 7 parts of modified cellulose, 35 parts of thermal conductive filler, 9 parts of aliphatic polyisocyanate curing agent (HDI trimer, Covestro Desmodur N3300), 28 parts of solvent (propylene glycol methyl ether acetate, PMA), 2.5 parts of coupling agent (KH550), 1.2 parts of pigment (carbon black).

[0067] In this embodiment, the modified cellulose is prepared as in Example 1.

[0068] In this embodiment, the heat conductive filler is mixed by aluminum oxide (α phase, particle size 3 μm) and boron nitride (flaky, flake diameter thickness ratio 15:1) in a mass ratio of 2.4:1.

[0069] II. A high-thermal-conductivity high-adhesion copper foil coating ink coating, comprising the following steps:

[0070] (1) Resin dissolution: mix epoxy resin, polyurethane resin and PMA, stir at 62°C and 850 rpm for 38 minutes;

[0071] (2) Coupling dispersion: add KH550 and modified cellulose, ultrasonic dispersion (power 310W) for 26 minutes at 42 kHz;

[0072] (3) Filler grinding: three-roll mill grinding (roll spacing 18 μm, roll temperature 26°C) for 4 times, fineness ≤5 μm;

[0073] (4) Curing dispersion: add HDI trimer curing agent and carbon black, high-speed dispersion at 2100 rpm for 17 minutes, and then pressure filtration (0.22 MPa) through a 220 mesh nylon filter screen to obtain the ink coating.

[0074] Example 5

[0075] I. A high-thermal-conductivity high-adhesion copper foil coating ink coating, comprising, by weight parts, 22 parts of bisphenol A type epoxy resin (E-51), 16 parts of polyurethane resin (aliphatic polyester type, Desmocoll 540), 12 parts of modified cellulose, 42 parts of heat conductive filler, 14 parts of aliphatic polyisocyanate curing agent (HDI trimer, Covestro Desmodur N3300), 35 parts of solvent (propylene glycol methyl ether acetate, PMA), 5 parts of coupling agent (KH550), and 3 parts of pigment (carbon black).

[0076] In this embodiment, the modified cellulose is prepared as in Example 1.

[0077] In this embodiment, the heat conductive filler is mixed by aluminum oxide (α phase, particle size 3 μm) and boron nitride (flaky, flake diameter thickness ratio 15:1) in a mass ratio of 5:1.

[0078] II. A high-thermal-conductivity high-adhesion copper foil coating ink coating, comprising the following steps:

[0079] (1) Resin dissolution: mix epoxy resin, polyurethane resin and PMA, stir at 70°C and 950 rpm for 45 minutes;

[0080] (2) Coupling dispersion: add KH550 and modified cellulose, ultrasonic dispersion (power 380W) for 32 minutes at 55 kHz;

[0081] (3) Filler grinding: three-roll mill grinding (inter-roller distance 12 μm, roller temperature 32℃) for 5 times, fineness ≤5 μm;

[0082] (4) Curing dispersion: adding HDI trimer curing agent and carbon black, high-speed dispersion at 2600 rpm for 22 minutes, followed by pressure filtration (0.35 MPa) on a 350 mesh nylon filter screen to obtain an ink coating.

[0083] Comparative Example 1

[0084] Comparative Example 1 differs from Example 1 in that Comparative Example 1 uses an equal amount of microcrystalline cellulose instead of modified cellulose, and the other conditions are the same.

[0085] Comparative Example 2

[0086] Comparative Example 2 differs from Example 1 in that Comparative Example 2 does not add polyurethane resin, and the weight fraction of epoxy resin is 25 parts, and the other conditions are the same.

[0087] Comparative Example 3

[0088] Comparative Example 3 differs from Example 1 in that the weight fraction of the thermally conductive filler in Comparative Example 3 is 55 parts, and the other conditions are the same.

[0089] The thermally conductive filler is a mixture of aluminum oxide (α phase, particle size 3 μm) and boron nitride (flaky, flake thickness ratio 15:1) in a mass ratio of 3:1.

[0090] Comparative Example 4

[0091] Comparative Example 4 differs from Example 2 in that Comparative Example 4 does not add coupling agent KH550, and the other conditions are the same.

[0092] Application Example 1

[0093] In order to eliminate the interference of the coating process on the test results, all examples and comparative examples are coated and performance tested under the following uniform conditions:

[0094] 1. Substrate pretreatment:

[0095] Electrolytic copper foil (thickness 18 μm, surface roughness Rz ≤1.5 μm) and calendered copper foil (thickness 12 μm, Rz ≤0.8 μm) are used as the coating substrate;

[0096] The surface of the copper foil is plasma cleaned (power 300 W, argon flow rate 10 L / min, treatment time 30 seconds).

[0097] 2. Coating process:

[0098] Equipment: slot coater (coating head gap 10 μm, coating speed 15 m / min);

[0099] Wet film thickness: 10 ± 1 μm (controlled by the gap and speed of the coating head);

[0100] Drying conditions: 80°C preheating for 3 minutes, removing solvent.

[0101] 3. Curing process:

[0102] Curing oven temperature: 90°C constant temperature zone baking for 12 minutes;

[0103] Cooling method: natural cooling to below 25°C at room temperature.

[0104] 4. Test sample preparation:

[0105] The coated copper foil was cut into 10 cm x 10 cm test samples;

[0106] Five parallel samples were prepared for each group of examples and comparative examples, and the average value was taken.

[0107] Test Example 1

[0108] Thermal conductivity test

[0109] 1. Test purpose: to verify whether the thermal conductivity of the ink coating meets the requirement of thermal conductivity > 0.4 W / (m-K) in claim 1, and to analyze the influence of filler ratio, structure and modified cellulose on the thermal conduction path.

[0110] 2. Test method:

[0111] Sample preparation: the ink was coated on electrolytic copper foil or calendered copper foil according to the uniform application example conditions, and the coating was peeled off after curing to prepare 10 mm x 10 mm x 1 mm standard test samples.

[0112] Test equipment: Hot Disk TPS2500 thermal flow method thermal conductivity instrument.

[0113] Test parameters: heat source power 0.5 W, test time 10 s, ambient temperature 25°C, and copper foil type was recorded respectively.

[0114] 3. Test grouping:

[0115] Examples 1-5: covering different filler ratios, resin ratios and modified cellulose contents;

[0116] Comparative examples 1 and 3: to verify the influence of unmodified cellulose and excessive filler.

[0117] Table 3 Thermal conductivity test results

[0118]

[0119]

[0120] From table 3, the thermal conductivity of example 2 is significantly higher than other groups, because of the high proportion of high thermal conductivity filler and the directional arrangement of sheet-like boron nitride, forming a continuous thermal conduction network, the thermal conductivity reaches 0.59 W / (m·K); while the comparative example 1 using unmodified cellulose hinders the dispersion of fillers, the thermal conduction path is discontinuous, and the thermal conductivity is only 0.29 W / (m·K), which shows that the ink coating of the application has good thermal conductivity.

[0121] Then, the thermal conductivity of comparative example 3 using excess filler is relatively high, close to the requirement, but it is not feasible in practical application, because the excess filler is easy to cause the destruction of the continuity of the resin matrix, the stress in the coating causes cracking, and also increases the production cost.

[0122] Test example 2

[0123] Dyne value test

[0124] 1. Test purpose: to evaluate whether the surface energy (dyne value) of the coating meets the requirement of dyne value > 38 in claim 1, and to verify the synergistic effect of modified cellulose and coupling agent on interfacial bonding force.

[0125] 2. Test method:

[0126] Sample preparation: after coating and curing according to the conditions of application example, select the surface defect-free area.

[0127] Test equipment: Arcotest dyne pen (38-44 mN / m gradient).

[0128] Operation steps: drop different dyne value test liquids on the surface of the coating, and observe the lowest value of the liquid film maintaining integrity for 2 seconds.

[0129] 3. Test groups:

[0130] Example 2, 5: verify the influence of the proportion of modified cellulose and coupling agent;

[0131] Comparative example 4, 2: analyze the defects of the absence of coupling agent and single resin.

[0132] Table 4 dyne value test result table

[0133] Group Dyne value (mN / m) Example 2 42 Example 5 44 Comparative Example 4 35 Comparative Example 2 38

[0134] From table 4, the quaternary ammonium group of example 5 forms chemical bonding with the surface of copper foil, and at the same time, the coupling agent KH550 enhances the interfacial bonding between resin and filler, and the dyne value reaches 44 mN / m; while comparative example 4 without adding coupling agent relies on physical adsorption, and the dyne value is only 35 mN / m, which is seriously insufficient in interfacial bonding force; comparative example 2 uses single epoxy resin system with poor flexibility and low surface energy, which cannot meet the requirement of microcircuit etching.

[0135] Test example 3

[0136] Crosshatch test

[0137] 1. Test purpose: Verify the adhesion of the coating to meet the requirement of crosshatch test ≥ 4B in claim 1, analyze the influence of resin type, filler distribution and modified cellulose on adhesion.

[0138] 2. Test method:

[0139] Test standard: ASTM D3359, use 11-blade crosshatch tool (1mm interval).

[0140] Operation steps: After crosshatching, paste 3M 600 tape, quickly peel off and count the number of detached grids under a microscope.

[0141] 3. Test grouping:

[0142] Examples 3, 4: Verify the effect of filler structure (flaky boron nitride) and high polyurethane resin ratio;

[0143] Comparative examples 1, 2, 3: Analyze the defects of unmodified cellulose, single resin and excessive filler.

[0144] Table 5 Crosshatch test result table

[0145] Group Number of shed grid Rating Example 3 1 4B Example 4 0 5B Comparative Example 1 5 3B Comparative Example 2 8 2B Comparative Example 3 3 4B (but coating cracked)

[0146] As shown in Table 5, Example 4 uses more polyurethane resin to improve the flexibility of the coating, and the curing stress buffering effect is significant, with a crosshatch test of 5B and no detachment; Comparative Example 2 uses single epoxy resin with high brittleness, and the internal stress is concentrated after curing, with 8 detached grids and a rating of only 2B; Comparative Example 3 uses more heat-conducting filler, resulting in a weak resin matrix, although the crosshatch test rating is 4B, but the coating is actually not usable due to cracking.

[0147] Test Example 4

[0148] Alcohol wiping resistance test

[0149] 1. Test purpose: Verify whether the chemical corrosion resistance and mechanical strength of the coating meet the requirement of "no detachment after alcohol wiping" in claim 1.

[0150] 2. Test method:

[0151] Test conditions: 500g weight load, non-woven fabric dipped in 99% alcohol, back and forth rubbing at a speed of 10cm / s for 30 times.

[0152] Evaluation criteria: Microscopic observation of the detached area ratio of the coating (<5% is passed).

[0153] 3. Test grouping:

[0154] Examples 1, 2: Verify the wash resistance of the base formula and the preferred formula.

[0155] Comparative Examples 3, 4: Analyze the impact of filler excess and the absence of coupling agent.

[0156] Table 6: Results of the alcohol wash test

[0157] Group Shed area Rating Example 1 <1％ Pass Example 2 0％ Pass Comparative Example 4 15％ Fail Comparative Example 3 20% (cracked) Fail

[0158] As can be seen from Table 6, the high filler dispersibility and dense coating structure of Example 2 have no peeling after alcohol wash; while the absence of coupling agent in Comparative Example 4 leads to weak filler-resin interface bonding, and the coating peels off in large areas after alcohol penetration; the use of more thermally conductive fillers in Comparative Example 3 easily causes coating cracking, and the alcohol penetration into the cracks aggravates the peeling.

[0159] Test Example 5

[0160] Color difference test

[0161] 1. Test purpose: Verify whether the color difference of the coating meets the requirement of ΔE < 1 in Claim 1, and analyze the synergistic effect of modified cellulose and coupling agent on pigment dispersion.

[0162] 2. Test method:

[0163] Test equipment: X-Rite Ci64 color difference meter (CIE Lab standard).

[0164] Operation steps: Compare the color difference of 5 points on the coating surface with the reference sample (ΔE = 0), and take the average value.

[0165] 3. Test groups:

[0166] Examples 1, 5: Verify the effect of the base formula and the high modified cellulose ratio.

[0167] Comparative Examples 1, 2, 4: Analyze the impact of unmodified cellulose, single resin, and the absence of coupling agent.

[0168] Table 7: Results of the color difference test

[0169] Group Delta E value Example 5 0.7 Example 1 0.9 Comparative Example 1 1.8 Comparative Example 2 2.1 Comparative Example 4 1.5

[0170] As can be seen from Table 7, the pigment in the ink coating prepared in Example 5 is uniformly dispersed, and the color difference is the smallest. While the use of unmodified cellulose in Comparative Example 1 has poor compatibility with the resin, and the pigment agglomeration leads to a color difference ΔE = 1.8. The use of single epoxy resin in Comparative Example 2 has poor release, and the pigment settlement causes a color difference ΔE = 2.1.

[0171] In summary, the ink coating prepared in Example 2 has a thermal conductivity of 0.59 W / (m·K), a darcy value of 42, a 5B rating in the crosshatch test, and the best comprehensive performance, proving that the ink coating prepared by the method of the application has good thermal conductivity, adhesion, and color difference control, and is suitable for high-frequency circuit substrates and lithium battery current collectors.

[0172] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A high thermal conductivity and high adhesion copper foil coating ink, characterized in that, By weight, it includes: 15-25 parts epoxy resin, 10-20 parts polyurethane resin, 5-12 parts modified cellulose, 30-45 parts mixed thermally conductive filler of alumina and boron nitride, 8-15 parts aliphatic polyisocyanate curing agent, 20-35 parts propylene glycol methyl ether acetate solvent, 2-5 parts silane coupling agent, and 1-3 parts carbon black pigment; The preparation of modified cellulose includes: mixing microcrystalline cellulose and betaine hydroxide at a mass ratio of 1:0.4-0.6, reacting at 60-80℃ for 4-6 hours under alkaline conditions, and then washing and drying to obtain modified cellulose.

2. The ink coating according to claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 350-450 g / eq, and the polyurethane resin is an aliphatic polyester type polyurethane with a solid content of 50-60%.

3. The ink coating according to claim 1, characterized in that, The thermally conductive filler has an average particle size of 2-8 μm, with alumina in the form of α-phase spherical particles and boron nitride in the form of plate-like structures, with a plate diameter-to-thickness ratio of 10:1-20:

1.

4. The ink coating according to claim 1, characterized in that, The mass ratio of alumina to boron nitride is 3:1 to 5:

1.

5. The method for preparing ink coatings according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Mix epoxy resin, polyurethane resin and propylene glycol methyl ether acetate solvent, and stir at 50-60℃ until completely dissolved; (2) Add silane coupling agent KH550 and modified cellulose, and ultrasonically disperse for 20-30 minutes; (3) Add alumina and boron nitride thermally conductive fillers, and grind to a fineness ≤5μm; (4) Add aliphatic polyisocyanate curing agent and carbon black pigment, disperse at high speed and filter to obtain ink coating.

6. The preparation method according to claim 5, characterized in that, In step (3), a three-roll mill is used for grinding, with a roller spacing of 10-20 μm and a grinding frequency of 3-5 times.

7. The application of the ink coating as described in any one of claims 1-4 in electrolytic copper foil or rolled copper foil, characterized in that, Apply the coating to the surface of electrolytic copper foil or rolled copper foil with a coating thickness of 8-15μm, and cure it by baking at 80-100℃ for 10-15 minutes.

8. The application according to claim 7, characterized in that, The coated copper foil is used as a high-frequency circuit board or a negative electrode current collector for lithium batteries, and the surface roughness of the coating Ra < 0.3 μm.

9. The application according to claim 7, characterized in that, The coating process is slot coating or micro-gravure coating, with a coating speed of 10-30 m / min.

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