Local anodic oxidation resistant process for mobile phone metal middle frame

Abstract

The application provides a local anodic oxidation resistance process for a mobile phone metal middle frame, corrosion-resistant glue is coated at the edge point of a titanium arc surface of the middle frame, acid-resistant protective ink is sprayed on a large surface of the titanium arc surface, and the point coating and spraying composite process are used in a targeted manner, so that the protection capability of the middle frame, especially the edge of the arc surface, can be effectively improved. Meanwhile, the corrosion-resistant glue and the acid-resistant protective ink are respectively optimized, polyurethane acrylate and epoxy acrylate are combined, the corrosion-resistant glue and the acid-resistant protective ink have good acid resistance and toughness, have excellent adhesion, are not easy to fall off, and have excellent protection on the titanium arc surface of the middle frame in the anodic oxidation process.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic equipment processing, and in particular to a local anti-anodization process for a mobile phone metal middle frame. Background Art

[0002] The mobile phone midframe is the backbone of the phone. Currently, the most popular metal materials for midframes include aluminum alloy, stainless steel, and titanium alloy. Titanium alloy offers the best appearance, strength, and fatigue resistance, while aluminum alloy boasts advantages in weight, cost, and process maturity. Stainless steel falls in between. It's speculated that titanium-aluminum composites will be a future trend in mobile phone midframes. Ideally, aluminum alloy forms the bulk of the midframe, while titanium alloy forms the outer shell.

[0003] After the metal midframe is formed, especially when it contains aluminum alloy, it is usually anodized to improve its protection and functionality. If titanium alloy is also used on the outside of the midframe, since the anodizing conditions for aluminum and titanium are different, the titanium alloy in this area needs to be protected from anodization while the aluminum alloy is anodized. Otherwise, discoloration may occur and affect the appearance. It is easy to think of covering the titanium alloy area of ​​the midframe with a protective layer, but at least the following conditions must be met simultaneously:

[0004] 1. The anodizing liquid is a strong acid liquid, and the protective layer needs to have strong acid resistance;

[0005] 2. Due to the influence of titanium alloy itself, its ink adhesion requirements are more difficult to achieve than other materials such as stainless steel and aluminum alloy.

[0006] 3. The metal middle frame has steep and large curved edges, and the protection of the large outer surface of the middle frame and the curved edges must be considered at the same time.

[0007] CN102363894A discloses a method for localized anodization of a workpiece surface. By forming an extremely thin, colorless film on the workpiece surface, the adhesion of the tape to the workpiece surface is increased, making the tape less likely to fall off during the oxidation process. This reduces the need for machining after oxidation, reduces product processing costs, and avoids the poor repeatability caused by secondary machining. However, this invention cannot meet the protection needs of large areas, and debonding still requires manual tearing, which is labor-intensive. CN107177232A discloses a UV-curable, acid-resistant, and etch-resistant ink comprising the following components by weight: 10-15% monomer, 50-60% photosensitive resin, 3-8% photoinitiator, and 15-30% powder. The monomer is a mixture of trimethylolpropane trimethacrylate and isocyanurate, and the photosensitive resin is a mixture of polyether aromatic polyurethane acrylate and phenolic epoxy acrylate. The new ink composition and materials used in this invention offer excellent corrosion resistance against strong acids like hydrochloric acid when used to create high-precision etching patterns on metal substrates such as copper, aluminum, iron, and stainless steel, while effectively protecting the gloss and essential properties of the substrate. While this invention exhibits acid resistance, its adhesion to titanium alloys is uncertain, and it also suffers from the drawback of being unable to effectively oil the curved edges when used for spray coating the sides of the midframe.

[0008] When applying anodized titanium alloy areas for protection, spraying acid-resistant protective ink is typically the preferred method. This approach offers the advantage of being suitable for large-scale oiling operations. However, due to the curved nature of the side frames, the edge of the paint can be thin. Film thickness significantly impacts the acid resistance of the protective ink, and areas with thinner oiling are more likely to experience defects. Spot-coating corrosion-resistant glue can effectively protect the areas covered by the glue, but is clearly not suitable for large-scale applications. Therefore, a localized anti-anodization process for mobile phone metal midframes was proposed to address this issue. Summary of the Invention

[0009] The purpose of the present invention is to provide a local anti-anodization process for the metal middle frame of a mobile phone, which adopts UV acid-resistant protective ink and corrosion-resistant glue, and uses UV curing to be faster and more environmentally friendly. At the same time, a spraying and dispensing composite process is used to effectively protect the middle frame, especially the edge position of the curved surface.

[0010] To achieve the above-mentioned object, the present invention provides a local anti-anodization process for a mobile phone metal middle frame, characterized in that the process steps are as follows:

[0011] Step 1: preparing spray-coated acid-resistant protective ink;

[0012] Step 2: preparing corrosion-resistant glue;

[0013] Step 3: Apply corrosion-resistant glue on the edge of the titanium arc surface of the middle frame and cure it;

[0014] Step 4: Spray acid-resistant protective ink on the large surface of the titanium arc and cure it;

[0015] Step five, anodic oxidation treatment of the whole workpiece;

[0016] Step six, cleaning and removing ink, the conventional alkaline deinking agent is used in the deinking process to remove the ink at 80℃ within about one hour.

[0017] The acid-resistant protective ink comprises, by mass fraction, 30-50 parts of polyurethane acrylate, 10-15 parts of epoxy acrylate, 5-15 parts of UV monomer, 1-2 parts of defoaming agent, 0.5-1 part of color paste, 2-6 parts of photoinitiator, 20-40 parts of filler, 1-3 parts of fumed silica, and 5-10 parts of solvent.

[0018] The corrosion-resistant adhesive comprises, by mass fraction, 60-75 parts of polyurethane acrylate, 10-20 parts of epoxy acrylate, 5-10 parts of UV monomer, 1-2 parts of defoaming agent, 0.5-1 part of color paste, 2-6 parts of photoinitiator, and 3-5 parts of fumed silica.

[0019] Preferably, the polyurethane acrylate has a molecular weight of 1000-3000 and a functionality of 2-4.

[0020] Preferably, the epoxy acrylate is phenolic epoxy acrylate, has a molecular weight of 500-1000, and a functionality of 2.

[0021] Preferably, the UV monomer is one or a combination of TMPTA, IBOA, DPGDA, and PHEA.

[0022] Preferably, the photoinitiator is 1-hydroxycyclohexyl phenyl ketone.

[0023] Preferably, the filler is 5000-mesh talc powder.

[0024] Preferably, the preparation method of the acid-resistant protective ink comprises the following steps: while stirring, adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoaming agent, and color paste in sequence, uniformly mixing, then adding photoinitiator and filler, uniformly mixing, using a sand mill to grind the mixture to a fineness of less than 8 microns, adding solvent, and uniformly mixing to obtain the acid-resistant protective ink.

[0025] Preferably, the preparation method of the corrosion-resistant adhesive comprises the following steps: while stirring, adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoaming agent, and color paste in sequence, uniformly mixing, then adding photoinitiator and fumed silica, and uniformly mixing at a slow stirring speed of 300-500 rpm to avoid generating a large number of bubbles.

[0026] Beneficial effects of the present invention: The present invention provides a local anti-anodization process for the metal middle frame of a mobile phone, wherein corrosion-resistant glue is spot-coated on the edge of the titanium arc surface of the middle frame, and acid-resistant protective ink is sprayed on the large surface of the titanium arc surface. The targeted use of a composite process of spot coating and spraying can effectively improve the protection of the middle frame, especially the edge of the arc surface. At the same time, the corrosion-resistant glue and the acid-resistant protective ink are optimized respectively, and have good acid resistance and toughness, as well as excellent adhesion, and are not easy to fall off, and can provide excellent protection for the titanium arc surface in the middle frame during the anodizing process. At the same time, UV monomers and photoinitiators are added to both the acid-resistant protective ink and the corrosion-resistant glue to achieve a UV curing effect, which is faster and more environmentally friendly than thermal baking curing, and effectively saves the time required for ink curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the side structure of the metal middle frame of the present invention after being partially coated with corrosion-resistant glue and sprayed with acid-resistant protective ink.

[0028] In the figure: 1-corrosion-resistant glue, 2-acid-resistant protective ink. DETAILED DESCRIPTION

[0029] The embodiments described below are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The present invention provides a local anti-anodization process for a mobile phone metal middle frame, characterized in that the process steps are as follows:

[0031] Step 1: preparing spray-coated acid-resistant protective ink;

[0032] Step 2: preparing corrosion-resistant glue;

[0033] Step 3: Apply corrosion-resistant glue on the edge of the titanium arc surface of the middle frame and cure it;

[0034] Step 4: Spray acid-resistant protective ink on the large surface of the titanium arc and cure it;

[0035] Step 5: Anodizing the entire workpiece;

[0036] Step 6: Cleaning and deinking: During the deinking process, a conventional alkaline aqueous deinking agent is used at 80°C and the deinking is completed within about one hour.

[0037] The metal middle frame structure obtained by applying corrosion-resistant glue on the edge of the titanium arc surface and spraying acid-resistant protective ink on the large surface of the titanium arc surface is as follows: Figure 1 As shown, the corrosion-resistant glue is distributed on the upper and lower ends of the titanium arc surface, and the acid-resistant protective ink is distributed on the titanium arc surface.

[0038] The acid-resistant protective ink is composed of 30-50 parts by mass of polyurethane acrylate, 10-15 parts by mass of epoxy acrylate, 5-15 parts by mass of UV monomer, 1-2 parts by mass of defoamer, 0.5-1 part by mass of color paste, 2-6 parts by mass of photoinitiator, 20-40 parts by mass of filler, 1-3 parts by mass of silica gel, and 5-10 parts by mass of solvent.

[0039] The corrosion-resistant glue is composed of 60-75 parts of polyurethane acrylate, 10-20 parts of epoxy acrylate, 5-10 parts of UV monomer, 1-2 parts of defoamer, 0.5-1 part of color paste, 2-6 parts of photoinitiator and 3-5 parts of gaseous silicone in terms of mass fraction.

[0040] The molecular weight of the polyurethane acrylate is 1000 to 3000, and the functionality is 2 to 4. The molecules of polyurethane acrylate (PUA) contain acrylic functional groups and urethane bonds. The cured adhesive has the high wear resistance, adhesion, flexibility, high peel strength and excellent low-temperature resistance of polyurethane and the excellent optical properties and weather resistance of polyacrylate. It is a radiation-cured material with excellent comprehensive performance. The polyurethane acrylate molecule has good acid resistance and can effectively resist the corrosion during the anodizing process. Selecting the right functionality can meet the cross-linking density, and it also has a greater impact on the acid resistance effect. In addition, the expansion coefficient of the metal itself is different from that of the ink, and appropriate toughness needs to be ensured. Therefore, selecting the right functionality and molecular weight distribution range is of great significance for acid-resistant protective inks or corrosion-resistant glues.

[0041] The epoxy acrylate is a novolac epoxy acrylate with a molecular weight of 500-1000 and a functionality of 2. Epoxy acrylate resin shares the excellent properties of epoxy resin, with exceptional curability and formability. It exhibits excellent water resistance, hot water resistance, drug resistance, adhesion, toughness, and corrosion resistance. It can be cured using an organic peroxide curing method (low-temperature to high-temperature) or a light-curing method. When used in combination with polyurethane acrylate, it further enhances the protective effect of acid-resistant protective inks or corrosion-resistant adhesives on the center frame.

[0042] The UV monomer is one or a combination of TMPTA, IBOA, DPGDA and PHEA, which plays a role in adjusting the curing rate, viscosity and toughness.

[0043] The photoinitiator is 1-hydroxycyclohexylphenyl ketone, also known as photoinitiator 184. The photoinitiator is used to initiate resin curing. Insufficient amount of photoinitiator will lead to insufficient curing and sticky film formation, while excessive amount will make the film brittle and reduce adhesion.

[0044] The filler is 5000 mesh talc powder, which can play a skeleton supporting role by adding an appropriate amount of talc powder.

[0045] The defoamer is a silicone defoamer, preferably Digo 900, which suppresses and eliminates foam generated during ink production and application. A small amount of defoamer will produce a poor defoaming effect, while a large amount will cause poor recoatability and other problems, so the amount should be controlled.

[0046] The pigment is phthalocyanine blue, which can provide color to facilitate subsequent processing operations and also facilitate identification of whether ink remains on the metal middle frame.

[0047] The solvent is alcohol, which plays a diluting role and has the function of adjusting the viscosity of the ink.

[0048] Cabot M5 is the preferred gas silicone, as it has a strong thixotropic effect.

[0049] The preparation method of the acid-resistant protective ink comprises: adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoamer and color paste in sequence while stirring, stirring evenly, adding a photoinitiator and filler, stirring evenly to obtain a mixture, grinding the mixture to a fineness of less than 8 microns using a sand mill, adding a solvent and mixing evenly to obtain the acid-resistant protective ink.

[0050] The preparation method of the corrosion-resistant glue is as follows: adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoamer and color paste in sequence while stirring, adding photoinitiator and gas silicon after stirring evenly, and stirring evenly at a slow speed of 300-500 rpm.

[0051] Example 1

[0052] This embodiment provides a process for local anti-anodization of a metal middle frame of a mobile phone, characterized in that the process steps are as follows:

[0053] Step 1: preparing spray-coated acid-resistant protective ink;

[0054] Step 2: preparing corrosion-resistant glue;

[0055] Step 3: Apply corrosion-resistant glue on the edge of the titanium arc surface of the middle frame and cure it;

[0056] Step 4: Spray acid-resistant protective ink on the large surface of the titanium arc and cure it;

[0057] Step 5: Anodizing the entire workpiece;

[0058] Step 6: Cleaning and de-inking.

[0059] The acid-resistant protective ink comprises, by mass, 40 parts of polyurethane acrylate, 10 parts of novolac epoxy acrylate, 10 parts of DPGDA, 1 part of defoamer, 0.5 parts of color paste, 3 parts of photoinitiator 184, 25 parts of talc, 2 parts of silica gel, and 8.5 parts of alcohol. The preparation method comprises: sequentially adding the corresponding amounts of polyurethane acrylate, novolac epoxy acrylate, DPGDA, defoamer, and color paste while stirring, stirring evenly, then adding photoinitiator 184 and talc, stirring evenly to obtain a mixture, grinding the mixture to a fineness of less than 8 microns using a sand mill, and adding alcohol and mixing evenly to obtain the acid-resistant protective ink.

[0060] The corrosion-resistant glue is composed, by mass, of 70 parts polyurethane acrylate, 15 parts phenolic epoxy acrylate, 5.5 parts DPGDA, 1 part defoamer, 0.5 part color paste, 4 parts photoinitiator 184, and 4 parts silica gel. The preparation method comprises sequentially adding the corresponding amounts of polyurethane acrylate, phenolic epoxy acrylate, DPGDA, defoamer, and color paste while stirring, stirring evenly, then adding photoinitiator 184 and silica gel, and slowly stirring at a speed of 350 rpm to achieve uniform mixing.

[0061] Comparative Example 1

[0062] This embodiment provides a process for local anti-anodization of a metal middle frame of a mobile phone, characterized in that the process steps are as follows:

[0063] Step 1: preparing spray-coated acid-resistant protective ink;

[0064] Step 2: preparing corrosion-resistant glue;

[0065] Step 3: Apply corrosion-resistant glue on the edge of the titanium arc surface of the middle frame and cure it;

[0066] Step 4: Spray acid-resistant protective ink on the large surface of the titanium arc and cure it;

[0067] Step 5: Anodizing the entire workpiece;

[0068] Step 6: Cleaning and de-inking.

[0069] The acid-resistant protective ink comprises, by mass, 40 parts of polyurethane acrylate, 10 parts of novolac epoxy acrylate, 10 parts of DPGDA, 1 part of defoamer, 0.5 parts of color paste, 3 parts of photoinitiator 184, 25 parts of talc, 2 parts of silica gel, and 8.5 parts of alcohol. The preparation method comprises: sequentially adding the corresponding amounts of polyurethane acrylate, novolac epoxy acrylate, DPGDA, defoamer, and color paste while stirring, stirring evenly, then adding photoinitiator 184 and talc, stirring evenly to obtain a mixture, grinding the mixture to a fineness of less than 8 microns using a sand mill, and adding alcohol and mixing evenly to obtain the acid-resistant protective ink.

[0070] The corrosion-resistant glue is composed, by mass, of 85 parts polyurethane acrylate, 0 parts phenolic epoxy acrylate, 5.5 parts DPGDA, 1 part defoamer, 0.5 parts color paste, 4 parts photoinitiator 184, and 4 parts silica gel. The preparation method comprises sequentially adding the corresponding amounts of polyurethane acrylate DPGDA, defoamer, and color paste while stirring, then adding photoinitiator 184 and silica gel after stirring evenly, and slowly stirring at a stirring speed of 350 rpm.

[0071] Comparative Example 2

[0072] This embodiment provides a process for local anti-anodization of a metal middle frame of a mobile phone, characterized in that the process steps are as follows:

[0073] Step 1: preparing spray-coated acid-resistant protective ink;

[0074] Step 2: Spray acid-resistant protective ink on the large surface of the titanium arc of the middle frame and cure it;

[0075] Step 3: Anodizing the entire workpiece;

[0076] Step 4: Cleaning and de-inking.

[0077] The acid-resistant protective ink comprises, by mass, 40 parts of polyurethane acrylate, 10 parts of novolac epoxy acrylate, 10 parts of DPGDA, 1 part of defoamer, 0.5 parts of color paste, 3 parts of photoinitiator 184, 25 parts of talc, 2 parts of silica gel, and 8.5 parts of alcohol. The preparation method comprises: sequentially adding the corresponding amounts of polyurethane acrylate, novolac epoxy acrylate, DPGDA, defoamer, and color paste while stirring, stirring evenly, then adding photoinitiator 184 and talc, stirring evenly to obtain a mixture, grinding the mixture to a fineness of less than 8 microns using a sand mill, and adding alcohol and mixing evenly to obtain the acid-resistant protective ink.

[0078] The acid-resistant protective ink, corrosion-resistant glue and antioxidant properties of Example 1 and Comparative Examples 1 and 2 were tested. The test results are shown in Table 1:

[0079] Table 1 is the performance test data of acid-resistant protective ink and corrosion-resistant glue in Example 1 and Comparative Examples 1 and 2

[0080]

[0081] From the above data, we can see that the acid-resistant protective ink sprayed on the large surface of the titanium arc surface of the middle frame has good anti-anodic oxidation protection effect, and the acid-resistant protective ink has good adhesion and flatness effect, is not easy to fall off, and no shrinkage hole and no bubble are generated. It can be seen from Example 1 and Comparative Example 2 that adding point-coated corrosion-resistant glue on the edge of the titanium arc surface of the middle frame can effectively prevent the occurrence of discoloration on the edge of the titanium arc surface. As can be seen from Example 1 and Comparative Example 1, the compounding of polyurethane acrylate and phenolic epoxy acrylate can improve the acid resistance of the corrosion-resistant glue and improve the protection effect on the titanium area.

[0082] The above describes the present application in detail in combination with the examples, and in addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined and changed in any appropriate manner without contradiction, and the present application will not further describe various possible combination manners. In addition, other modifications and combinations of each technical feature according to the present application should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A local anti-anodization process for a mobile phone metal middle frame, characterized in that: The process steps are as follows: Step 1: preparing spray-coated acid-resistant protective ink; Step 2: preparing corrosion-resistant glue; Step 3: Apply corrosion-resistant glue on the edge of the titanium arc surface of the middle frame and cure it; Step 4: Spray acid-resistant protective ink on the large surface of the titanium arc and cure it; Step 5: Anodizing the entire workpiece; Step 6: Cleaning and de-inking; The acid-resistant protective ink is composed of 30-50 parts by mass of polyurethane acrylate, 10-15 parts by mass of epoxy acrylate, 5-15 parts by mass of UV monomer, 1-2 parts by mass of defoamer, 0.5-1 part by mass of color paste, 2-6 parts by mass of photoinitiator, 20-40 parts by mass of filler, 1-3 parts by mass of silica gel, and 5-10 parts by mass of solvent. The corrosion-resistant glue is composed of 60-75 parts of polyurethane acrylate, 10-20 parts of epoxy acrylate, 5-10 parts of UV monomer, 1-2 parts of defoamer, 0.5-1 part of color paste, 2-6 parts of photoinitiator, and 3-5 parts of gaseous silicon. The polyurethane acrylate has a molecular weight of 1000 to 3000 and a functionality of 2 to 4; the epoxy acrylate is novolac epoxy acrylate with a molecular weight of 500 to 1000 and a functionality of 2.

2. The process for local anti-anodization of a mobile phone metal middle frame according to claim 1, characterized in that: The UV monomer is one or a combination of TMPTA, IBOA, DPGDA and PHEA.

3. The local anti-anodization process for a mobile phone metal middle frame according to claim 1, characterized in that: The photoinitiator is 1-hydroxycyclohexyl phenyl ketone.

4. The process for local anti-anodization of a mobile phone metal middle frame according to claim 1, characterized in that: The filler is 5000 mesh talc powder.

5. The local anti-anodization process for a mobile phone metal middle frame according to claim 1, characterized in that: The preparation method of the acid-resistant protective ink comprises: adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoamer and color paste in sequence while stirring, stirring evenly, adding a photoinitiator and filler, stirring evenly to obtain a mixture, grinding the mixture to a fineness of less than 8 microns using a sand mill, adding a solvent and mixing evenly to obtain the acid-resistant protective ink.

6. The process for local anti-anodization of a mobile phone metal middle frame according to claim 1, characterized in that: The preparation method of the corrosion-resistant glue is as follows: adding corresponding amounts of polyurethane acrylate, epoxy acrylate, UV monomer, defoamer and color paste in sequence while stirring, adding photoinitiator and gas silicon after stirring evenly, and stirring evenly at a slow speed of 300-500 rpm.

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