Photochromic OCA (optically clear adhesive), preparation method thereof, photochromic explosion-proof membrane and application of photochromic explosion-proof membrane

Abstract

The invention discloses a photochromic OCA (Optical Clear Adhesive), a preparation method thereof, a photochromic explosion-proof membrane and application thereof. The photochromic OCA is prepared from the following raw material components in parts by weight: 95 parts of acrylic resin, 0.005 to 2.5 parts of cross-linking agent, 0.005 to 2.5 parts of silane coupling agent, 0.01 to 2 parts of antioxidant, 0.1 to 1 part of ultraviolet absorbent and 0.1 to 2 parts of photochromic powder. According to the invention, the photochromic material is introduced into the OCA adhesive, and when the OCA adhesive is irradiated by light with a certain wavelength, molecular bonds are broken / recombined, a closed-loop structure is changed into an open-loop structure and the like in the photochromic material, so that the color of an explosion-proof membrane is changed; and when the light source disappears, the original color can be recovered. The photochromic explosion-proof membrane provided by the invention not only provides screen protection, but also can enhance the visual attraction of a mobile phone through dynamic color change, so that the mobile phone stands out of numerous devices, and the mobile phone is endowed with a sense of breathing, and the appearance has a sense of science and technology and a future style; and the preparation method provided by the invention is simple in technological process and high in repeatability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of explosion-proof film materials, in particular to a photochromic OCA adhesive, a preparation method thereof, a photochromic explosion-proof film and application thereof. BACKGROUND

[0002] The innovative design of product appearance can bring strong visual impact to consumers. For example, in the past, smart phones focused on the improvement of functions and performance, and the appearance design was conservative. However, in today's serious homogenization of smart phones, users and suppliers are pursuing more personalized appearance design. Research has found that a unique and fashion-forward phone can stimulate consumers' purchasing desire to some extent. Therefore, product appearance design has become an important aspect of mobile phone innovation.

[0003] The back cover explosion-proof film of the mobile phone is a high-performance thin film used to prevent the mobile phone glass back cover or ceramic back cover from breaking. In addition to improving the safety and convenience of mobile phone users, it can also maintain the naked machine hand feeling and design aesthetics. Compared with the traditional direct pattern printing on the mobile phone back cover, the pattern and color effect are now usually processed on the explosion-proof film by silk screen printing, transfer printing, PVD, etc.

[0004] Photochromic compounds are a class of substances that can undergo reversible changes in structure or conformation under the irradiation of specific wavelength light, which will cause changes in color, fluorescence and other physical properties on the macroscopic level.

[0005] There are two common methods for decorating the back cover of a mobile phone on the market:

[0006] One is to directly print or spray on the surface of PMMA or PC, and then heat press to form the shape of the mobile phone back cover. However, this method lacks the texture and brightness of glass, and the printed colors are not rich and bright enough, so it can only be used in some low-end mobile phone market. High-end panels or mobile phone back covers on the market are still mainly made of glass.

[0007] The other is to print, transfer, sputter and coat on the explosion-proof film inside the back cover, and then adhere to the back cover glass plate to meet the appearance requirements. By processing the explosion-proof film, it is easier to increase the three-dimensional level and color fluidity of the back cover, and the visual effect is more rich.

[0008] Publication No. CN110527448A discloses a decorative film: the reverse side of the base material layer is processed, first a nano-imprint layer is made by nano-imprint technology, and then a sputter coating is made on the nano-imprint layer by magnetron sputtering technology. The final finished decorative film has more texture, increased reflectivity, and more rich visual effect.

[0009] The decorative film in the disclosure No. CN110527448A has high surface energy, so it can be more easily processed by UV glue transfer, ink printing, PVD coating, etc. Different color patterns can be selected according to requirements.

[0010] But the two kinds of explosion-proof films represented by the above have certain shortcomings: multiple metal elements are needed for sputtering coating, although the reflectivity can be improved, but the transmittance will be lost, the color after processing cannot be reflected as expected, and the three-dimensional level and color conversion feeling are also missing. Secondly, the explosion-proof film prepared by this method is biased towards conventional design, and cannot achieve a surprising effect. SUMMARY

[0011] The technical problem to be solved by the present application is to provide a photochromic OCA glue, its preparation method, a photochromic explosion-proof film and its application, in view of the above-mentioned shortcomings in the prior art.

[0012] To solve the above technical problems, the technical scheme adopted by the present application is: the first aspect of the present application provides a photochromic OCA glue, which comprises the following raw material components by weight: 95 parts of acrylic resin, 0.005-2.5 parts of crosslinking agent, 0.005-2.5 parts of silane coupling agent, 0.01-2 parts of antioxidant, 0.1-1 part of ultraviolet light absorber, and 0.1-2 parts of photochromic powder.

[0013] Preferably, the preparation raw materials of the acrylic resin include, by weight: 50-70 parts of alkyl methacrylate, 5-25 parts of hydroxyl-containing (methyl) acrylate, 1-10 parts of nitrogen-containing functional methacrylate, 0.05-1 part of chain transfer agent, 0.05-1 part of grafting monomer, 0.5-0.7 part of initiator, and 100-200 parts of organic solvent.

[0014] Preferably, the alkyl methacrylate is one or more of n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, isononyl acrylate, and isodecyl acrylate;

[0015] The hydroxyl-containing (methyl) acrylate is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate;

[0016] The nitrogen-containing functional methacrylate is one or more of acrylamide, methacrylamide, N-hydroxyethyl acrylamide, N-vinyl pyrrolidone, 4-acryloyl morpholine, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and N,N-dimethyl acrylamide.

[0017] Preferably, the chain transfer agent is one or more selected from dodecyl mercaptothiol, isooctyl mercaptoacetate, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, and pentaerythritol tetra(3-mercaptobutyrate).

[0018] The grafting monomer is one or more of 2-isocyanoethyl acrylate and 2-isocyanoethyl methacrylate;

[0019] The initiator is one or more of BPO, DCP, and AIBN.

[0020] Preferably, the acrylic resin is prepared by the following method:

[0021] S1. Add alkyl methacrylate, hydroxyl (meth)acrylate, nitrogen-containing functional methacrylate, chain transfer agent and organic solvent to the reactor, stir and purge with nitrogen, heat to 60-70℃ and keep at that temperature for 20-80 min, add the first batch of initiator, and react for 1-4 h.

[0022] S2. Heat to 65-75℃, add the second batch of initiator, and react for 1-4 hours;

[0023] S3. Heat to 75-80℃, add the remaining third batch of initiator, and reflux for 1.5-6 hours;

[0024] S4. Introduce oxygen to cool to 40-60℃, add grafted monomer, react for 2.5-10 hours, cool and discharge to obtain acrylic resin.

[0025] Preferably, the crosslinking agent is one or more of the isocyanate GA-79, GA-20, and TKA-100.

[0026] The silane coupling agent is one or more of KH550, KH560, and KH570;

[0027] One or more of the antioxidants BHT, BHA, and 1010 are mentioned.

[0028] Preferably, the ultraviolet light absorber is one or more of TINUVIN1130 and Tinuvin 400;

[0029] The photochromic powder is one or more of the following: 1,3,3-trimethylindolinespiropyran, 5-chloro-1,3-dihydro-1,3,3-trimethylspiropyran[2H-indo-2,3-(3H)naphtho[2,1-b](1,4)oxazine], 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene, and 3,3-diphenyl-3H-naphtho[2,1-b]pyran.

[0030] A second aspect of the present invention provides a method for preparing the photochromic OCA adhesive as described above, comprising the following steps:

[0031] 1) Mix and stir the acrylic resin, crosslinking agent, silane coupling agent, antioxidant, and ultraviolet light absorber until homogeneous to obtain the adhesive;

[0032] 2) Add the photochromic powder to the adhesive, stir evenly, and filter using a 200-500 mesh filter bag to obtain the photochromic OCA adhesive.

[0033] In a third aspect, the present invention provides a photochromic explosion-proof film, which is prepared by the following method: uniformly coating the photochromic OCA adhesive as described above onto a substrate with a coating thickness of 23-25 ​​μm, drying it, covering the adhesive surface with a release film, and curing it to obtain a photochromic explosion-proof film whose color can change under light conditions.

[0034] A fourth aspect of the present invention provides the application of the photochromic explosion-proof film as described above in the back cover of a mobile phone.

[0035] The beneficial effects of this invention are:

[0036] This invention provides a photochromic OCA adhesive, its preparation method, a photochromic explosion-proof film, and its application. This invention introduces a photochromic material into the OCA adhesive. When irradiated with light of a certain wavelength, changes occur inside the photochromic material, such as the breaking / reorganization of molecular bonds and the transformation of closed-loop structures into open-loop structures, causing the color of the explosion-proof film to change. When the light source disappears, it can return to its original color.

[0037] The photochromic explosion-proof film provided by this invention is an innovative functional film that not only provides screen protection but also enhances the visual appeal of mobile phones through dynamic color changes, making them stand out among numerous devices and giving them a "breathing" feel, with a more technological and futuristic appearance. Furthermore, the preparation method provided by this invention is simple and highly repeatable.

[0038] The photochromic explosion-proof film provided by this invention can retain the drop-resistant and scratch-resistant properties of explosion-proof film, and break through the single appearance of traditional protective film. Attached Figure Description Figure 1 The left and right figures are comparisons of Examples 1-3 under natural light without specific wavelength (light outside the ultraviolet band) and under specific wavelength (LED light irradiation at 365nm for 10s). Detailed Implementation

[0039] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0040] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0042] The present invention provides a photochromic OCA adhesive, comprising the following raw material components by weight: 95 parts acrylic resin, 0.005-2.5 parts crosslinking agent, 0.005-2.5 parts silane coupling agent, 0.01-2 parts antioxidant, 0.1-1 parts ultraviolet light absorber, and 0.1-2 parts photochromic powder.

[0043] In a preferred embodiment, the raw materials for preparing the acrylic resin include, by weight: 50-70 parts of alkyl methacrylate, 5-25 parts of hydroxyl (meth)acrylate, 1-10 parts of nitrogen-containing functional methacrylate, 0.05-1 part of chain transfer agent, 0.05-1 part of graft monomer, 0.5-0.7 parts of initiator, and 100-200 parts of organic solvent.

[0044] In a preferred embodiment, the alkyl methacrylate is one or more of the following: n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, isononyl acrylate, and isodecanyl acrylate.

[0045] In a preferred embodiment, the hydroxyl-containing (meth)acrylic resin is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0046] In a preferred embodiment, the nitrogen-containing functional methacrylate is one or more of acrylamide, methacrylamide, N-hydroxyethylacrylamide, N-vinylpyrrolidone, 4-acryloylmorpholine, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and N,N-dimethylacrylamide.

[0047] In a preferred embodiment, the chain transfer agent is one or more of dodecyl mercaptothiol, isooctyl mercaptoacetate, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, and pentaerythritol tetra(3-mercaptobutyrate).

[0048] In a preferred embodiment, the grafting monomer is one or more of 2-isocyanoethyl acrylate and 2-isocyanoethyl methacrylate.

[0049] In a preferred embodiment, the initiator is one or more of BPO, DCP, and AIBN.

[0050] In a preferred embodiment, the organic solvent is ethyl acetate.

[0051] In a preferred embodiment, the acrylic resin is prepared by the following method:

[0052] S1. Add alkyl methacrylate, hydroxyl (meth)acrylate, nitrogen-containing functional methacrylate, chain transfer agent and organic solvent to the reactor, stir and purge with nitrogen, heat to 60-70℃ and keep at that temperature for 20-80 min, add the first batch of initiator, and react for 1-4 h.

[0053] S2. Heat to 65-75℃, add the second batch of initiator, and react for 1-4 hours;

[0054] S3. Heat to 75-80℃, add the remaining third batch of initiator, and reflux for 1.5-6 hours;

[0055] S4. Introduce oxygen to cool to 40-60℃, add grafted monomer, react for 2.5-10 hours, cool and discharge to obtain acrylic resin.

[0056] In a preferred embodiment, the crosslinking agent is one or more of the isocyanates GA-79, GA-20, and TKA-100.

[0057] In a preferred embodiment, the silane coupling agent is one or more of KH550, KH560, and KH570.

[0058] In a preferred embodiment, one or more of the antioxidants BHT, BHA, and 1010 are used.

[0059] In a preferred embodiment, the ultraviolet absorber is one or more of TINUVIN1130 and Tinuvin 400.

[0060] In a preferred embodiment, the photochromic powder is one or more of 1,3,3-trimethylindolinespiropyran, 5-chloro-1,3-dihydro-1,3,3-trimethylspiropyran[2H-indo-2,3-(3H)naphtho[2,1-b](1,4)oxazine], 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene, and 3,3-diphenyl-3H-naphtho[2,1-b]pyran.

[0061] This invention also provides a method for preparing the above-mentioned photochromic OCA adhesive, comprising the following steps:

[0062] 1) Mix and stir the acrylic resin, crosslinking agent, silane coupling agent, antioxidant, and ultraviolet light absorber until homogeneous to obtain the adhesive;

[0063] 2) Add the photochromic powder to the glue, stir evenly, filter with a 200-500 mesh filter bag, discard the filter residue, and obtain the photochromic OCA glue.

[0064] The present invention also provides a photochromic explosion-proof film, which is prepared by the following method: the above photochromic OCA adhesive is uniformly coated on the substrate with a coating thickness of 23-25μm, dried, and then a release film is covered on the adhesive surface and cured to obtain a photochromic explosion-proof film whose color can change under light conditions.

[0065] The present invention also provides the application of the above-mentioned photochromic explosion-proof film in the back cover of mobile phones.

[0066] The selected substrate is one or more of PET, PP, and PE.

[0067] This invention incorporates photochromic materials into OCA adhesive. By utilizing the reversible color change characteristics of photochromic materials under light irradiation of different specific wavelengths and intensities, a decorative explosion-proof film with sensitive light response speed and rich color changes is prepared. When the light conditions change, the color also changes accordingly. When applied to mobile phone appearance design, it can give people a refreshing visual effect.

[0068] The main mechanism of this invention:

[0069] This invention introduces a photochromic material into OCA adhesive to prepare an explosion-proof film whose color changes reversibly under light conditions. Specifically, Examples 1 and 2 of this invention patent exhibit color change at wavelengths of 365-400 nm; Example 3 exhibits color change at wavelengths of 365-600 nm.

[0070] When irradiated, the internal molecular structure of the material changes, resulting in a macroscopic color change. When the light source disappears, it can return to its original color.

[0071] Taking Example 1 as an example, under illumination, the indoline unit and benzopyran unit in the spirocyclic structure break through the CO bond, changing from the original closed ring to an open ring. In the open ring state, the aromatic ring and some other groups in the structure form an overall large conjugated structure that is not present in the original structure. The appearance of the large conjugated structure affects the absorption of light by the material, resulting in a color change. When the illumination stops, the open ring body changes back to the closed ring structure under the action of the kinetic process, realizing color reversal.

[0072] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0073] Example 1

[0074] A photochromic explosion-proof film is prepared by the following method:

[0075] S1. Preparation of acrylic resin:

[0076] S1-1. By weight, 60 parts of 2-ethylhexyl acrylate, 25 parts of hydroxyethyl acrylate, 8 parts of acrylamide, 0.2 parts of dodecyl mercaptan, and 130 parts of ethyl acetate are added to a reaction vessel equipped with a thermometer and a stirrer. The mixture is stirred and mixed evenly, and nitrogen gas is introduced. The temperature is raised to 65°C and kept at that temperature for 40 minutes. Then, 0.2 parts of azobisisobutyronitrile (AIBN) initiator are added, and the reaction is carried out for 3 hours.

[0077] S1-2, then heat to 75℃, add 0.15 parts of AIBN, and react for 2 hours;

[0078] S1-3, Finally, heat to 77-80℃, add 0.2 parts of azobisisobutyronitrile, and reflux for 3 hours;

[0079] S1-4. After reaching the reaction endpoint, allow the mixture to cool naturally to 50°C, add 0.5 parts of the grafted monomer 2-isocyanoethyl methacrylate, react for 5 hours, cool down and discharge to obtain acrylic resin.

[0080] S2. Preparation of photochromic OCA adhesive:

[0081] By weight, 95 parts of the above acrylic resin, 0.2 parts of crosslinking agent, 0.15 parts of ultraviolet light absorber, 0.1 parts of leveling agent, 0.3 parts of silane coupling agent, and 0.2 parts of antioxidant are mixed and stirred evenly. 0.3 parts of photochromic powder are added and stirred evenly again. The mixture is then filtered through a 400-mesh filter cloth, and the filter residue is discarded to obtain the photochromic OCA adhesive that can change color.

[0082] The crosslinking agent is GA-20, the ultraviolet absorber is 400, the leveling agent is BYK330, the silane coupling agent is KH560, the antioxidant is 1010, and the photochromic powder is 1,3,3-trimethylindoline spiropyran.

[0083] S3. Preparation of photochromic explosion-proof film:

[0084] After degassing and allowing the photochromic OCA adhesive to stand, it is evenly coated onto a 23μm PET substrate with a thickness of 25μm. The substrate is then dried at 120℃ for three minutes, and a release film is attached to the adhesive surface. The substrate is then cured at room temperature for 2 days to obtain a photochromic explosion-proof film whose color can change reversibly under different light conditions.

[0085] Example 2

[0086] The difference between this example and Example 1 is that the added photochromic powder is 5-chloro-1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3-(3H)naphtho[2,1-b](1,4)oxazine].

[0087] Example 3

[0088] The difference between this example and Example 1 is that the added photochromic powder is diarylexyl (1,2-di(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene).

[0089] Comparative Example 1

[0090] The difference between the comparative example and Example 1 is that no photochromic powder is added in step S2 in this example.

[0091] Performance testing

[0092] one, Figure 1 The left and right figures show a comparison of Examples 1-3 under natural light without a specific wavelength (light outside the ultraviolet band) and under light with a specific wavelength (365nm LED light for 10 seconds). It can be clearly seen that the color changed after being exposed to light. The photochromic material used in Examples 1-3 of this invention can change color in the ultraviolet band, so it can be applied under sunlight or by using an ultraviolet lamp to achieve color change. When the sunlight or ultraviolet lamp disappears, it can return to colorless.

[0093] II. The explosion-proof films prepared in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests:

[0094] (1) Transmittance: The transmittance of visible light at 550nm was tested using a transmittance tester. The sample was cut into 5CM*5CM size, and after the release film was removed, the adhesive side was placed facing the light source for testing at room temperature.

[0095] (2) Haze: The haze meter was used for testing. As above, the sample was cut into 3CM*3CM size, the release film was removed and the sample was placed on the equipment for testing at room temperature.

[0096] (3) Refractive index: The Abbe refractometer was used for measurement. As above, the sample was cut into 3CM*3CM size, the release film was removed and the sample was placed on the equipment for testing at room temperature.

[0097] (4) Peeling force: According to the JIS K5600 tape adhesion test standard, a 5KG tensile testing machine was used to conduct a 180° tensile test on the sample. One sample was randomly cut: 25mm wide and 120mm long. First, double-sided tape was applied to the steel plate for backing treatment. The sample was then attached to the middle of the steel plate, and 3M 9495 tape was attached to the other side of the same sample. The sample was repeatedly rolled twice with a 2KG roller. After 20 minutes, the sample was tested on the tensile testing machine.

[0098] The test results are shown in Table 1 below:

[0099] Table 1

[0100] Test item Example 1 Example 2 Example 3 Comparative Example 1 % transmittance 93.1％ 92.8％ 93.5％ 92.3％ % haze 0.85％ 0.92％ 0.88％ 0.87％ refractive index 1.63 1.59 1.61 1.60 peel force gf 16.2 15.5 14.9 15.7

[0101] The test results above show that, compared with Comparative Example 1, the addition of photochromic powder in the examples had no impact on the basic performance of the explosion-proof film. Therefore, it can be concluded that the photochromic explosion-proof film offers a more attractive appearance while maintaining performance.

[0102] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A photochromic OCA adhesive, characterized in that, It includes the following raw material components by weight: 95 parts acrylic resin, 0.005-2.5 parts crosslinking agent, 0.005-2.5 parts silane coupling agent, 0.01-2 parts antioxidant, 0.1-1 parts ultraviolet light absorber, and 0.1-2 parts photochromic powder.

2. The photochromic OCA adhesive according to claim 1, characterized in that, The raw materials for preparing the acrylic resin include, by weight: 50-70 parts of alkyl methacrylate, 5-25 parts of hydroxyl (meth)acrylate, 1-10 parts of nitrogen-containing functional methacrylate, 0.05-1 part of chain transfer agent, 0.05-1 part of graft monomer, 0.5-0.7 parts of initiator, and 100-200 parts of organic solvent.

3. The photochromic OCA adhesive according to claim 2, characterized in that, The alkyl methacrylate is one or more selected from the following: n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, isononyl acrylate, and isodecanyl acrylate. The hydroxyl-containing (meth)acrylic resin is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; The nitrogen-containing functional methacrylate is one or more of acrylamide, methacrylamide, N-hydroxyethylacrylamide, N-vinylpyrrolidone, 4-acryloylmorpholine, dimethylaminoethyl acrylate, and N,N-dimethylacrylamide.

4. The photochromic OCA adhesive according to claim 2, characterized in that, The chain transfer agent is one or more of the following: dodecyl mercaptan, isooctyl mercaptoacetate, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, and pentaerythritol tetra(3-mercaptobutyrate); The grafting monomer is one or more of 2-isocyanoethyl acrylate and 2-isocyanoethyl methacrylate; The initiator is one or more of BPO, DCP, and AIBN.

5. The photochromic OCA adhesive according to claim 2, characterized in that, The acrylic resin is prepared by the following method: S1. Add alkyl methacrylate, hydroxyl (meth)acrylate, nitrogen-containing functional methacrylate, chain transfer agent and organic solvent to the reactor, stir and purge with nitrogen, heat to 60-70℃ and keep at that temperature for 20-80 min, add the first batch of initiator, and react for 1-4 h. S2. Heat to 65-75℃, add the second batch of initiator, and react for 1-4 hours; S3. Heat to 75-80℃, add the remaining third batch of initiator, and reflux for 1.5-6 hours; S4. Introduce oxygen to cool to 40-60℃, add grafted monomer, react for 2.5-10 hours, cool and discharge to obtain acrylic resin.

6. The photochromic OCA adhesive according to claim 1, characterized in that, The crosslinking agent is one or more of the isocyanates GA-79, GA-20, and TKA-100. The silane coupling agent is one or more of KH550, KH560, and KH570; One or more of the antioxidants BHT, BHA, and 1010 are mentioned.

7. The photochromic OCA adhesive according to claim 1, characterized in that, The ultraviolet light absorber is one or more of TINUVIN1130 and Tinuvin 400; The photochromic powder is one or more of the following: 1,3,3-trimethylindolinespiropyran, 5-chloro-1,3-dihydro-1,3,3-trimethylspiropyran[2H-indo-2,3-(3H)naphtho[2,1-b](1,4)oxazine], 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene, and 3,3-diphenyl-3H-naphtho[2,1-b]pyran.

8. A method for preparing a photochromic OCA adhesive as described in any one of claims 1-7, characterized in that, Includes the following steps: 1) Mix and stir the acrylic resin, crosslinking agent, silane coupling agent, antioxidant, and ultraviolet light absorber until homogeneous to obtain the adhesive; 2) Add the photochromic powder to the glue, stir evenly, filter with a 200-500 mesh filter bag, discard the filter residue, and obtain the photochromic OCA glue.

9. A photochromic explosion-proof film, characterized in that, It is prepared by the following method: the photochromic OCA adhesive as described in any one of claims 1-7 is uniformly coated on the substrate with a coating thickness of 23-25 ​​μm, dried, and then a release film is covered on the adhesive surface and cured to obtain a photochromic explosion-proof film whose color can change under light conditions.

10. The application of the photochromic explosion-proof film as described in claim 9 in the back cover of a mobile phone.

Images