Low-chromatic-aberration high-tack adhesive, preparation method thereof and light-shielding adhesive film

Abstract

This invention discloses a low-color-difference, high-viscosity adhesive, its preparation method, and a light-shielding film, relating to the field of adhesive technology. The low-color-difference, high-viscosity adhesive comprises an acrylate-based polymer and a modified carbon material covalently bonded to the acrylate-based polymer, wherein the modified carbon material acts on the end groups of the acrylate-based polymer. The preparation method of the modified carbon material includes the steps of: (1) acidifying the carbon material; and (2) modifying the surface of the carbon material using epoxy propylene acrylate and epoxy resin. The modified carbon material acts as an end-capping material on the end groups of the adhesive, connecting with the polymer in the adhesive through -C-C bonds. The carbon material is in a stable state during coating, thus exhibiting good dispersibility in the adhesive and not precipitating during coating, resulting in good coating uniformity. The prepared light-shielding film has low color difference, low surface roughness, and a lower carbon material precipitation rate.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a low-color-difference, high-viscosity adhesive, its preparation method, and a light-shielding adhesive film. Background Technology

[0002] The applications of light-shielding tape in electronic products cover a wide range of areas, including protection against electromagnetic interference and electrostatic damage, fixing LCD and backlight modules, light-shielding treatment, reflective and light-shielding functions, and protection under complex environments such as high temperature and high pressure. These applications not only improve the performance and stability of electronic devices but also bring more convenience and possibilities to the manufacturing and use of electronic products.

[0003] Currently, adhesives used in light-shielding tapes often employ dispersants or silane coupling agents to disperse colorants within the adhesive, followed by a coating process to prepare the light-shielding film. Colorants dispersed with dispersants rely on physical dispersion within the adhesive, making them prone to sedimentation. This can lead to colorant precipitation during coating, resulting in uneven coating, significant color differences in the light-shielding tape, and unstable optical properties. Conversely, the dispersion method using silane coupling agents leaves the colorant in a thermodynamically unstable state, making it susceptible to leaching from the pressure-sensitive adhesive film, thus reducing the film's lifespan.

[0004] When ordinary carbon material is added as a commonly used black colorant, it interacts with the adhesive, reducing the number of effective functional groups such as carboxyl and hydroxyl groups in the adhesive that interact with the substrate, thus affecting the bonding effect. Furthermore, the addition of ordinary carbon material results in a higher surface roughness of the adhesive, and the main substance in contact with the substrate is the carbon material itself. Since carbon material does not have functional groups that play a bonding role, it will lead to a decrease in the bonding effect. Summary of the Invention

[0005] The purpose of this invention is to provide a low-color-difference, high-adhesion adhesive, its preparation method, and a light-shielding film to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A low-color-difference, high-tack adhesive comprises an acrylate-based polymer and a modified carbon material covalently bonded to the acrylate-based polymer, the modified carbon material acting on the end sites of the acrylate-based polymer.

[0008] The preparation method of the modified carbon material includes the following steps:

[0009] (1) Acidification treatment of carbon materials: Disperse carbon materials in deionized water, add potassium permanganate and concentrated sulfuric acid, stir at room temperature, dialyze, freeze dry to obtain acidified carbon materials;

[0010] (2) Surface modification of carbon materials: Disperse the acidified carbon materials in a mixed solution of propylene epoxy acrylate, epoxy resin and ethyl acetate and react at 60-80℃ for 8-24 hours to obtain modified carbon materials.

[0011] Furthermore, the molar ratio of the epoxy acrylate to the epoxy resin is 1:5 to 5:1.

[0012] Furthermore, the epoxy acrylate has an epoxy group and a carbon-carbon double bond at both ends.

[0013] Furthermore, the epoxy resin is a polyhydroxy epoxy resin, which may be one or more of epoxy resin 128, epoxy resin 828, epoxy resin DY-040LR-7518, LR-7601, LR-7602, and LR-7609.

[0014] Furthermore, the epoxy resin is epoxy 828.

[0015] Furthermore, the carbon material is one or more of carbon black, carbon nanotubes, graphite, and graphene.

[0016] Further, the acrylate-based polymer comprises, by mass parts: 60-80 parts of soft monomer, 15-35 parts of hard monomer, 5-10 parts of modified carbon material, 100-150 parts of solvent, and initiator; the mass of the initiator is 0.1-1% of the total mass of the soft monomer and hard monomer.

[0017] Further, the soft monomer is one or more of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, lauryl acrylate, n-octyl methacrylate, and octadecyl methacrylate.

[0018] Furthermore, the hard monomer is one or more selected from methyl acrylate, methyl methacrylate, vinyl acetate, isobornyl methacrylate, styrene, acrylonitrile, and n-butyl methacrylate.

[0019] Furthermore, the solvent is ethyl acetate or acetone.

[0020] Furthermore, the initiator is one or more of azobisisobutyronitrile, BPO, and AIBN.

[0021] A method for preparing a low-color-difference, high-viscosity adhesive involves adding soft and hard monomers to a solvent, heating the mixture to 70°C, adding an initiator, reacting for 24 hours, adding modified carbon material, reacting at 80°C for 5 hours, and then obtaining the desired low-color-difference, high-viscosity adhesive.

[0022] A light-shielding adhesive film prepared from a low-color-difference, high-viscosity adhesive is obtained by adding a diluent to the adhesive to adjust the solid content to 20%, coating the diluted adhesive onto a release film, and baking it.

[0023] A light-shielding film prepared from a low-color-difference, high-viscosity adhesive has light-shielding properties defined by the L / a / b colorimetric system under a standard light source D65, where L is 25 ± 2.5. The film exhibits good light-shielding properties. Its uniformity is assessed by transmittance, transmittance variance, reflectance, reflectance variance, and average ΔE. 94 To characterize this, a transmittance range of 0-1% at 550 nm, a transmittance variance less than 1.0E-04, and a reflectance range of 0-5% at 550 nm, with a reflectance variance less than 1.0E-04, indicate that the light-shielding film has good uniformity, with an average ΔE 94 A smaller value indicates less color difference and more uniform coating. A light-shielding film that meets these specifications, when applied to display materials, can block light reflection from the light-emitting element onto the metal plate, thereby minimizing the impact on display performance.

[0024] Specifically, the light-shielding adhesive film is used to bond high-reflectivity metal plates in electronic devices to reduce the reflectivity of the metal plates. The adhesive film is applied to high-reflectivity metal materials, and after testing, the reflectivity is below 5%. Even when the metal plate has a high reflectivity of 46-50%@550nm, after applying the light-shielding adhesive film of this application to the surface of the metal plate, the reflectivity can be reduced to 4.3-5%.

[0025] Specifically, the light-blocking film is used to bond high-transmittance glass plates, with a measured transmittance of less than 1%, ensuring excellent light-blocking effect.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] 1. This invention discloses an adhesive with low color difference and high light absorption, wherein modified carbon material acts as a capping material on the end group of the adhesive and is connected to the polymer in the adhesive through a C-C bond. The carbon material is in a stable state during the coating process, so the carbon material has good dispersibility in the adhesive and will not precipitate during the coating process. The coating uniformity is good, and the prepared light-shielding film has small color difference, low surface roughness, and lower carbon material precipitation rate. The service life and product performance can reach the optimal state.

[0028] 2. After acidification treatment, the carbon material has a large number of carboxyl groups on its surface. Some of the carboxyl groups react with the epoxy groups in the surface modifier, while some of the carboxyl groups continue to exist on the surface of the carbon material.

[0029] 3. Using epoxy propylene acrylate to modify carbon materials allows the carboxyl groups on the carbon material surface to react with the epoxy groups of epoxy propylene acrylate, grafting carbon-carbon double bonds onto the carbon material surface. The carbon material then connects with the double bonds of the polymer in the adhesive through these carbon-carbon double bonds, avoiding the interaction between the carbon material and the functional groups in the adhesive. This relatively increases the number of effective functional groups such as carboxyl and hydroxyl groups in the adhesive, ultimately enhancing the bonding effect.

[0030] 4. Epoxy resin is used to modify the carbon material, giving it hydroxyl groups on the surface. Combined with the acidification process before use, the carbon material possesses both carboxyl and hydroxyl groups. By adjusting the proportion of epoxy resin, the ratio of carboxyl and hydroxyl groups on the carbon material surface can be adjusted to achieve strong adhesion to various substrates. Furthermore, the carboxyl and hydroxyl groups on the carbon material surface are well-dispersed, providing effective adhesion even to low-polarity substrates. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 without creative effort are within the scope of protection of the present invention.

[0032] First, the raw materials used in this application are shown in the table below:

[0033] name illustrate Manufacturer carbon black CAS1333-86-4 Cabot glycidyl acrylate CAS: 106-g0-1 Aladdin Ethyl acetate CAS No.: 141-78-6 Aladdin Epoxy 828 CAS No.: 38891-59-7 Kaiyin Chemical KH560 CAS No.: 2530-83-8 Sigma-Aldrich concentrated sulfuric acid CAS No.: 7664-93-9 Sigma-Aldrich potassium permanganate CAS No.: 7722-64-7 Aladdin Butyl acrylate CAS No.: 141-32-2 Aladdin Methyl methacrylate CAS No.: 80-62-6 Aladdin AIBN CAS No.: 78-67-1 Aladdin ethanol CAS No.: 64-17-5 Aladdin dispersant DISPERBYK-2118 BYK

[0034] Example 1:

[0035] Preparation steps of modified carbon materials:

[0036] (1) Acidification process: Take 100g of carbon black and disperse it in 200g of deionized water, add 3ml of 1mol / L potassium permanganate solution, and then add 3ml of 0.01mol / L concentrated sulfuric acid; stir at room temperature for 24 hours, then dialyze for 24 hours, and freeze dry at -20℃ for 24 hours to obtain acidified carbon black.

[0037] (2) Carbon black modification: 100g of acidified carbon black and 1g of surface modifier (epoxy propylene acrylate and epoxy 828 in a molar ratio of 1:5) were dispersed in 200g of ethyl acetate and reacted at 65℃ for 12 hours to obtain modified carbon black with double bond modification and hydroxyl modification.

[0038] Adhesive synthesis:

[0039] Add 80g of butyl acrylate and 10g of methyl methacrylate to 150g of ethyl acetate, heat to 70℃, add 0.1g of AIBN and react for 24 hours, then add 10g of modified carbon black and react at 80℃ for 5 hours to obtain the adhesive.

[0040] Film preparation:

[0041] Ethyl acetate was added to the above adhesive to dilute the solid content to 20%. A 50µm adhesive film was coated on a 75µm release film, and another 75µm release film was placed on the other side of the adhesive film. The film was then baked in an oven at 110℃ for 10 minutes to obtain a low-color-difference, high-adhesion light-blocking adhesive film with 75µm release films on both sides.

[0042] Example 2:

[0043] The process is similar to that in Example 1, except that carbon black is replaced with the same amount of graphene.

[0044] Example 3:

[0045] The process is similar to that in Example 1. Epoxy propylene acrylate and epoxy 828 are mixed in a molar ratio of 3:1.

[0046] Example 4:

[0047] The process is similar to that in Example 1. Epoxy propylene acrylate and epoxy 828 are mixed in a molar ratio of 5:1.

[0048] Comparative Example 1:

[0049] The process is similar to that in Example 1. The carbon black modification step in the preparation of the modified carbon material is as follows: acidified carbon black and silane coupling agent KH560 are dispersed in ethyl acetate at a mass ratio of 100:1, and the mixture is reacted at 65°C for 12 hours to obtain modified carbon black.

[0050] Comparative Example 2:

[0051] The process is similar to that in Example 1. In the carbon black modification step of the preparation steps of the modified carbon material, only the surface modifier glycidyl acrylate is used, and the amount is 1g.

[0052] Comparative Example 3:

[0053] The process is similar to that in Example 1. In the carbon black modification step of the preparation steps of the modified carbon material, only the surface modifier epoxy 828 is used, and the amount is 1g.

[0054] Comparative Example 4:

[0055] The process is similar to that in Example 1. In the carbon black modification step of the modified carbon material preparation process, the molar ratio of surface modifiers glycidyl acrylate and epoxy 828 is 8:1.

[0056] Comparative Example 5:

[0057] Adhesive synthesis:

[0058] 80g of butyl acrylate and 10g of methyl methacrylate were added to 150g of ethyl acetate, heated to 70℃, and 0.1g of AIBN was added. After reacting for 24 hours, the temperature was raised to 80℃ and reacted for 5 hours to obtain an acrylate-based polymer.

[0059] 100g of carbon black and 1g of dispersant DISPERBYK-2118 were dispersed in 200g of ethyl acetate and stirred until homogeneous to obtain a carbon black dispersion.

[0060] 10g of carbon black dispersion was added to the above acrylate-based polymer and stirred until homogeneous to obtain an adhesive. Ethyl acetate was added to the adhesive to dilute the solid content to 20%. A 50µm adhesive film was coated on a 75µm release film, and another 75µm release film was placed on the other side of the adhesive film. The film was baked in an oven at 110℃ for 10 minutes to obtain a low-color-difference, high-viscosity, light-blocking adhesive film with 75µm release films on both sides.

[0061] The light-shielding films prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to the following tests:

[0062] First, nine points are evenly selected on the A4 sample to test the L / a / b values, transmittance, and reflectance. The L, a, b, transmittance, and reflectance listed in Table 1 are the average values ​​of these measurement points, and the transmittance variance and reflectance variance listed are calculated from the transmittance and reflectance of these measurement points.

[0063] 1. L / a / b value test and color difference ΔE 94 calculate

[0064] L / a / b value test:

[0065] ① After adjusting the CM3700D colorimeter to D65 light source, perform zero-point calibration and white board calibration;

[0066] ② Clean the SUS304 test plate with ethanol;

[0067] ③ Cut the light-blocking film with release film on both sides into 2.5cm*2.5cm squares using scissors;

[0068] ④ Remove the release film, place the cut film flat on the cleaned SUS-304 plate, and then conduct the test.

[0069] Color difference ΔE 94 calculate

[0070] ⑤ Take the average value of L from the 9 test points as the standard value L. sThe average of the 'a' values ​​from the 9 test points is taken as the standard value 'a'. s The average of the b values ​​measured at 9 points is used as the standard value of b. s ;

[0071] ⑥ Calculate the color difference ΔE according to the ΔE*94 color difference formula in the CIELab color space. 94 Numerical value.

[0072] Calculate ΔE for each point 94 Then calculate ΔE at the 9 points. 94 The average color difference "ΔE" is obtained by taking the average value. 94 ".

[0073] 2. Transmittance test

[0074] ① Wipe both sides of the high-transmittance glass plate clean;

[0075] ② Adjust the UV spectrophotometer to transmittance test mode, and place the high-transmittance glass plate in the test port for baseline calibration;

[0076] ③ Cut the light-blocking film with release film on both sides into 2.5cm*2.5cm squares using scissors;

[0077] ④ Remove the release film, then apply the light-blocking adhesive film flat onto the glass plate before testing.

[0078] 3. Reflectivity Test

[0079] ① After adjusting the CM3700D colorimeter to D65 light source, perform zero-point calibration and white board calibration, and set 550nm as the measurement wavelength;

[0080] ②After cleaning the SUS-304 test plate with ethanol, its reflectivity was measured first. The results showed that the reflectivity of the SUS-304 test plate after cleaning was 46%.

[0081] ③ Cut the light-blocking film with release film on both sides into 2.5cm*2.5cm squares using scissors;

[0082] ④ Remove the release film, and then apply the light-blocking adhesive film flat onto the cleaned SUS-304 board before testing.

[0083] 4. Peel strength test (ASTM D3330)

[0084] ① Transfer the adhesive film onto 50µm PET;

[0085] ② Make the above-mentioned transferred material into a strip 300mm long and 25.4mm wide;

[0086] ③ After the strip is flatly attached to the SUS-304 board, it is rolled back and forth twice with a 2Kg roller at a speed of 600mm / min;

[0087] ④ After the above-mentioned SUS-304 adhesive film has been left to stand for 20 minutes, test the 180° peel strength.

[0088] The average ΔE was calculated by taking the L / a / b values, transmittance, and reflectance of each film obtained from the tests of Examples 1-4 and Comparative Examples 1-5. 94 The variances of transmittance and reflectance are recorded in Table 1.

[0089] Table 1

[0090]

[0091]

[0092] The peel strength of each adhesive film in Examples 1-4 and Comparative Examples 1-5 to substrates SUS, PE, and PP is recorded in Table 2.

[0093] Table 2

[0094] Substrate SUS(gf / 25m) PE / (gf / 25m) PP / (gf / 25mm) Example 1 2540 700 1023 Example 2 2321 830 1107 Example 3 2153 945 1254 Example 4 2055 948 1258 Comparative Example 1 1238 430 658 Comparative Example 2 2056 569 823 Comparative Example 3 1623 430 623 Comparative Example 4 2043 604 932 Comparative Example 5 1523 650 758

[0095] Conclusion: Based on the data in Tables 1 and 2, it can be seen that Comparative Example 1, which used KH560 as a surface modifier for the carbon material, did not interact with the carbon material directly. Instead, KH560 was linked through -Si-O- bonds, which are less stable than ester bonds. Therefore, it was prone to aggregation during the modification process and precipitation during film storage. Consequently, its reflectivity and transmittance were higher than those of the Example, resulting in poorer coverage and absorption. Furthermore, due to aggregation and precipitation, the adhesive surface roughness was greater, leading to lower peel strength to the substrate. The relatively small number of hydroxyl functional groups also resulted in lower peel strength to low-polarity substrates.

[0096] In Comparative Example 2, only epoxy acrylate was used as a surface modifier, which improved the dispersibility, but no polyhydroxy epoxy resin was introduced as a modifier. Therefore, the surface of the carbon material was all carboxyl groups, which had high polarity, resulting in low peel force to low polarity substrates and poor adhesion performance.

[0097] In Comparative Example 3, only polyhydroxy epoxy resin was used as a surface modifier. Since it does not contain carbon-carbon double bonds, the surface modifier cannot participate in the polymerization reaction. As a result, the carbon material is physically dispersed in the adhesive, which has poor dispersibility and is prone to precipitation. Therefore, the transmittance and reflectance are relatively high, and the viscosity is relatively low.

[0098] In Comparative Example 4, the surface modifiers were propylene epoxy acrylate and polyhydroxy epoxy resin, which had good dispersibility. However, the proportion of polyhydroxy epoxy resin was relatively small and the number of carboxyl functional groups was relatively large, which resulted in poorer adhesion to low-polarity substrates compared to the examples.

[0099] In Comparative Example 5, commercially available carbon black was used. The carbon black was dispersed in the adhesive in the form of a dispersant, relying on the physical effect of steric hindrance for dispersion. The dispersion effect was worse than that of the form connected by chemical bonds. Therefore, carbon material precipitation and uneven distribution of carbon material occurred during the coating process, resulting in high transmittance and reflectance, and large variances in transmittance and reflectance, which reduced the performance.

[0100] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-color-difference, high-adhesion adhesive, characterized in that, It includes an acrylate-based polymer and a modified carbon material covalently bonded to the acrylate-based polymer, the modified carbon material acting on the end sites of the acrylate-based polymer; The composition, by weight, includes: 60-80 parts of soft monomer, 15-35 parts of hard monomer, 5-10 parts of modified carbon material, 100-150 parts of solvent, and initiator; the initiator accounts for 0.1-1% of the total weight of the soft and hard monomers. The preparation method of the modified carbon material includes the following steps: (1) Acidification treatment of carbon materials: Disperse carbon materials in deionized water, add potassium permanganate and concentrated sulfuric acid, stir at room temperature, dialyze, freeze dry to obtain acidified carbon materials; (2) Surface modification of carbon materials: Disperse the acidified carbon materials in a mixed solution of propylene epoxy acrylate, epoxy resin and ethyl acetate and react at 60-80℃ for 8-24 hours to obtain modified carbon materials; The molar ratio of the epoxy acrylate to the epoxy resin is 1:5-5:

1.

2. The low color difference, high viscosity adhesive according to claim 1, characterized in that, The epoxy resin is epoxy resin 128 or / and epoxy resin 828.

3. The low color difference, high viscosity adhesive according to claim 1, characterized in that, The epoxy resin is epoxy 828.

4. The low color difference, high viscosity adhesive according to claim 1, characterized in that, The carbon material is one or more of carbon black, carbon nanotubes, graphite, and graphene.

5. The low color difference, high viscosity adhesive according to claim 1, characterized in that, The soft monomer is one or more of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, lauryl acrylate, n-octyl methacrylate, and octadecyl methacrylate; the hard monomer is one or more of methyl methacrylate, vinyl acetate, isobornyl methacrylate, styrene, acrylonitrile, and n-butyl methacrylate; the solvent is ethyl acetate or acetone; and the initiator is one or more of azobisisobutyronitrile and BPO.

6. A method for preparing the low color difference, high viscosity adhesive as described in claim 5, characterized in that, The soft monomer and hard monomer are added to the solvent, the temperature is raised to 70°C, an initiator is added, and the reaction is carried out for 24 hours. After adding the modified carbon material and reacting at 80°C for 5 hours, the desired low color difference and high viscosity adhesive is obtained.

7. A light-shielding adhesive film prepared with the low-color-difference, high-adhesion adhesive as described in any one of claims 1-5, characterized in that, Add a diluent to the adhesive to adjust the solid content to 20%, apply the diluted adhesive onto a release film, and bake to obtain an adhesive film.

8. The use of a light-shielding adhesive film for bonding high-reflectivity metal plates in electronic devices to reduce the reflectivity of the metal plates, characterized in that, The adhesive film comprises the adhesive as described in any one of claims 1-5, wherein the reflectance of the adhesive film when applied to a high-reflectivity metallic material is less than 5%.

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