Protective film composition and metal surface layer preparation method based on same

Abstract

The invention discloses a protective film composition and a metal surface layer preparation method based on the same, and relates to the field of metal processing shielding. The protective film composition is formed by mixing the monomer, the photoinitiator, the color paste and the resin according to a specific proportion, and the protective film formed by combining the protective film composition with the metal piece is high in adhesive force, good in durability and easy to remove. The metal part can bear soaking of cutting fluid for about 6 hours, long-acting protection of CNC machining is guaranteed, and precision and follow-up treatment are not affected. The shape stability and the crosslinking degree are ensured through two-stage curing, and the cutting fluid resistance is improved. The material has good comprehensive performance, and is safe and non-corrosive. The film feeding device can save cost, the protective film is easy to peel off through pretreatment liquid, and the hardness, toughness and wear resistance of the protective film are enhanced through resin.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing shielding, and specifically to a protective film composition and a method for preparing a metal surface layer based on the composition. Background Art

[0002] In the processing of hardware and electronic products (such as titanium alloy mobile phone accessories), the surface protection of non-processing areas is crucial. Since the non-processing areas of these products often have high surface quality requirements, any scratches, abrasions or other accidental damages may affect the overall quality and performance of the products.

[0003] Currently, during CNC processing, the surface of metal parts needs to be properly protected as described above to prevent the influence of cutting fluid, metal chips, or processing stress on the overall quality and performance. For the current protection methods on the market, most are carried out by traditional spraying, film laminating or manual coating, etc., but there are still the following problems and deficiencies to be improved:

[0004] First, insufficient adhesion: Directly spraying ink is likely to fall off during the processing, affecting the protection effect.

[0005] Second, insufficient durability: The durability of some coatings in cutting fluid is limited and cannot withstand long-term processing requirements.

[0006] Third, difficult to remove: The protective film on the metal surface after processing is difficult to remove and requires strong solvents or physical scraping, affecting production efficiency.

[0007] Therefore, how to solve the above-mentioned conventional problems and deficiencies is the direction that the applicant of the present invention and related manufacturers in this industry urgently want to research and improve. Summary of the Invention

[0008] The purpose of the present invention is to provide a protective film composition and a method for preparing a metal surface layer based on the composition to solve the problems existing in the prior art.

[0009] To solve the above technical problems, the present invention provides the following technical solutions:

[0010] The protective film composition includes:

[0011] Monomer from 20% to 75% by weight;

[0012] Photoinitiator from 5% to 20% by weight;

[0013] Color paste from 10% to 40% by weight;

[0014] And resin from 10% to 20% by weight.

[0015] As an optimization, the photoinitiator is at least one of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2,4-diethylthiazolidin-4-one, and 2-isopropylthioxanthone.

[0016] As an optimization, the color paste includes a dispersant and pigment powder.

[0017] The color paste includes, by mass parts: 55 - 70 parts of monomer, 10 - 15 parts of dispersant, and 20 - 30 parts of pigment powder.

[0018] As an optimization, the monomer includes a mono-functional monomer and a multi-functional monomer, and the mass ratio of the mono-functional monomer to the multi-functional monomer is 1:5.

[0019] As an optimization, the mono-functional monomer is at least one of β-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, trimethylolpropane formal acetal acrylate, trimethylolcyclohexyl acrylate, ethoxyphenol acrylate, benzyl acrylate, o-phenylphenoxyethyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, N,N-dimethylacrylamide, N-acryloylmorpholine, and N-vinylpyrrolidone.

[0020] As an optimization, the multi-functional monomer is at least one of 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, n(ethoxylated) bisphenol A diacrylate, n(ethoxylated) trimethylolpropane triacrylate, n(propoxylated) trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, bis(trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate.

[0021] As an optimization, the resin is at least one of polyester resin, polyurethane resin, epoxy resin, vinyl chloride-vinyl acetate copolymer resin, rosin resin, maleic resin, and polyvinyl butyral resin.

[0022] A method for preparing a metal surface layer based on any one of the above-mentioned protective film compositions, characterized in that the protective film composition is placed in a film coating device; a pretreatment liquid is applied to a metal part; the film coating device places the protective film composition on the metal part; a first-stage curing operation is performed on the surface of the metal part; and a second-stage curing operation is performed on the surface of the metal part, and the curing time of the second-stage curing operation is shorter than the curing time of the first-stage curing operation to complete a metal surface protective film.

[0023] As an optimization, after the second-stage curing operation, the metal part is subjected to cutting processing, and the metal part after cutting processing is subjected to fluid immersion, and ultrasonic vibration is applied at the same time to separate the metal surface protective film from the metal part.

[0024] As an optimization, the ultrasonic vibration is any one of warm water ultrasonic vibration or sodium cyanide solvent ultrasonic vibration for plastics.

[0025] As an optimization, the method of placing the protective film composition on the metal part is any one of spraying or screen printing.

[0026] As an optimization, the first-stage curing operation and the second-stage curing operation are performed using a light-curing device, and the light-curing device emits ultraviolet light of 365-395 nm.

[0027] As an optimization, the pretreatment liquid includes, by mass: 4-6 parts of phosphate acrylate resin, 4-6 parts of monofunctional monomer, and 88-92 parts of ethyl acetate.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0029] The UV spraying and printing adopted in this application can effectively save costs, accurately spray and print, reduce unnecessary cost waste; and UV spraying and printing can improve efficiency, dry with a UV lamp at one time, reduce processes, and do not require secondary processing, and dry while spraying and printing;

[0030] And the formulated ink adopted in this application has stronger adhesion. For example, in the titanium alloy shielding experiment, the hardness grade is 100 in 2 hours, which means that in the Brinell hardness test, a steel ball with a diameter of 10 mm is used, and the applied pressure is 100 kgf, and the material can remain unscratched. It can pass the 2H hardness test and the cross-cut test;

[0031] Moreover, the formulated ink is safe and does not damage the processing material itself. The ink material itself is neutral and will not corrode or damage the material itself. Additionally, a phosphate acrylate resin is added to the pretreatment solution, which has highly excellent chemical stability, transparency, and UV resistance. The function of the resin is to increase the hardness, toughness, and wear resistance of the material. The high content of ethyl acetate enables it to dry quickly and has low toxicity.

[0032] The formulated ink is more environmentally friendly, has a small odor, is cured by a UV lamp, and the removal method is simple and convenient. It is water-soluble and can fall off on its own after soaking in warm water for 1 hour without residue. In industry, it is used for shielding before metal processing, etc., to achieve an insulating effect. The application fields are very extensive, including machinery manufacturing, automotive manufacturing, aerospace, electronics industry, etc. Additionally, three materials, acrylate substances, photoinitiators, and resins, are added, which have good plasticity, chemical resistance, transparency, impact resistance, and weather resistance when dissolved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the process flow chart of the present application;

[0034] Figure 2 is the exploded view of the UV spraying printer of the present application;

[0035] Figure 3 is the schematic diagram of the protective film composition of the present application;

[0036] Figure 4 is the process flow chart of the metal surface layer implementation steps of the present application;

[0037] Figure 5 is the process flow chart of the metal surface layer implementation and detachment steps of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] Please refer to the first and second figures, which are the schematic diagram of the protective film composition and the process flow chart of the first preferred embodiment of the present invention. It can be clearly seen from the figures that the present invention includes:

[0041] Monomer 1 in a weight percentage of 20% to 75% by weight, the monomer 1 includes β - carboxyethyl acrylate, which is easy to copolymerize with vinyl and acrylic monomers in emulsion polymerization and radiation curing systems, has a low glass transition temperature, can effectively promote adhesion, improve the stability of the emulsion, has a long side carboxylic acid chain to give good flexibility, promotes more effective interaction between the polymer and the substrate, thereby enhancing adhesion and peel strength, and this strength has a tendency to increase over time;

[0042] Photoinitiator 2 in a weight percentage of 5% to 20% by weight, and the photoinitiator 2 is at least one of bis(2,4,6 - trimethylbenzoyl)phenylphosphine oxide, 2,4,6 - trimethylbenzoyldiphenylphosphine oxide, 2 - hydroxy - 2 - methyl - 1 - phenyl - 1 - propanone, 2 - benzyl - 2 - dimethylamino - 1 - (4 - morpholinophenyl)butanone, 2 - (4 - methylbenzyl)-2-(dimethylamino)-1-(4 - morpholinophenyl)-1 - butanone, and 2,4 - diethylthiazolium ketone and 2 - isopropylthioxanthone;

[0043] Color paste 3 in a weight percentage of 10% to 40% by weight, and the color paste 3 includes a dispersant and pigment powder;

[0044] And resin 4 in a weight percentage of 10% to 20% by weight, and the resin is at least one of polyester resin, polyurethane resin, epoxy resin, vinyl chloride - acetate resin, rosin resin, maleic resin, and polyvinyl butyral resin.

[0045] Among them, the monomer 1 includes a monofunctional monomer and a polyfunctional monomer, and the weight ratio of the monofunctional monomer to the polyfunctional monomer is 1:5.

[0046] Among them, the monofunctional monomer is at least one of tetrahydrofurfuryl acrylate, trimethylolpropane formal acetal acrylate, trimethylolcyclohexyl acrylate, ethoxyphenol acrylate, benzyl acrylate, o - phenylphenoxyethyl acrylate, 4 - tert - butylcyclohexyl acrylate, dicyclopentenyl acrylate, N,N - dimethylacrylamide, N - acrylylmorpholine, and N - vinylpyrrolidone.

[0047] Among them, the polyfunctional monomer is at least one of 1,6 - hexanediol diacrylate, 1,4 - butanediol diacrylate, dipropylene glycol triacrylate, diethylene glycol triacrylate, n(ethoxylated)bisphenol A diacrylate, n(ethoxylated)trimethylolpropane triacrylate, n(propoxylated)trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate.

[0048] When the above-mentioned protective film composition 5 is to be applied to a metal piece to form a protective film on the metal surface layer, the following steps can be followed:

[0049] (A), Place the above-mentioned protective film composition in a film coating device;

[0050] (B), Apply a pretreatment liquid to a metal piece;

[0051] (C), The film coating device places the protective film composition on the metal piece;

[0052] (D), Perform the first-stage curing operation on the surface of the metal piece; and

[0053] (E), Perform the second-stage curing operation on the surface of the metal piece, and the curing time of the second-stage curing operation is shorter than that of the first-stage curing operation to complete a protective film on the metal surface layer.

[0054] Among them, the method of placing the protective film composition 5 on the metal piece can be one of inkjet printing and screen printing. That is to say, the film coating device can be an inkjet printer, a screen printer, or a spray gun. When the film coating device takes an inkjet printer as an example in this embodiment, the film coating device can have a platform for placing the metal piece, and an inkjet head that can move in the XYZ axes and two light curing devices (which can be UV ultraviolet lamps) are provided above the platform, and the inkjet head and several light curing devices can be controlled by a control panel.

[0055] Specifically, taking a titanium alloy as an example for the metal piece, and a pretreatment liquid (containing phosphate acrylate resin, having chemical stability and transparency, capable of increasing the hardness, toughness and wear resistance of the material, high content of ethyl acetate makes it dry quickly and is low-toxic, can improve the adhesion of the protective film on the metal surface layer, avoid peeling off during the processing, ensure the best adhesion and subsequent easy peelability, and the so-called easy peelability refers to the characteristics of the pretreatment liquid itself. When the pretreatment liquid encounters a fluid, it can easily peel the protective film on the metal surface layer from the metal piece) is used for the metal piece before film coating. After the treatment is completed, the subsequent steps are carried out.

[0056] After completing the above actions, place the protective film composition 5 in a film applying device (this step can be exchanged with the timing of using the pretreatment liquid, that is, the protective film composition 5 can be placed in the film applying device first and then the pretreatment liquid can be used). At this time, the user can place the metal part on the platform and operate the control panel to turn on the film applying device, and make the inkjet head start to move to spray the protective film composition 5 on the surface of the metal part. After the spraying is completed, use a light curing device to emit ultraviolet light with a wavelength of 365 nm to 395 nm to perform the first-stage curing action on the metal part. This can prevent the protective film composition 5 from spreading or flowing, ensure the stable shape of the protective film on the metal surface layer, and after the irradiation is completed, perform the second-stage curing action. Similarly, use the light curing device to emit ultraviolet light with a wavelength of 365 nm to 395 nm to irradiate the metal part to ensure that the protective film on the metal surface layer is completely crosslinked, improving the cutting fluid resistance performance, but the irradiation time is shorter than that of the first-stage curing action, about 2 minutes to 3 minutes.

[0057] In this way, through the above technology, the present case can achieve an efficient metal surface layer protective film technology applicable to CNC machining. This technology significantly improves the durability of the metal surface layer protective film on the metal part and the easy peelability of the subsequent used fluid, avoiding the defects of traditional coating technologies, and is applicable to fields such as aviation, electronics, medical, or precision manufacturing, with extremely high market value.

[0058] Please refer to the flowchart of the steps of the second preferred embodiment of the present invention shown in the third figure. It can be clearly seen from the figure that the difference between this embodiment and the above embodiment is that after step (E), step (F) can be carried out to perform cutting processing on the metal part, and after the cutting processing, the metal part is immersed in a fluid, and ultrasonic vibration is applied for about 20 minutes to 30 minutes at the same time to make the protective film on the metal surface layer separate from the metal part. And the ultrasonic vibration can be one of warm water ultrasonic vibration or sodium cyanide solvent ultrasonic vibration for plastics. In this way, because the protective film on the metal surface layer of the present case is mainly composed of the protective film composition 5, the metal part can withstand immersion in cutting fluid for about 6 hours (that is, the fluid, and the fluid can be oil-based or water-based coolant), ensuring long-term protection during the CNC machining process, and the protective film on the metal surface layer does not affect the CNC cutting accuracy, and there is no residue on the surface after processing, and it does not affect subsequent surface treatments (such as anodizing, plating). That is to say, the material of the metal part can be high-precision CNC machining materials such as aluminum alloy, titanium alloy, stainless steel, copper, magnesium alloy, etc.

[0059] Therefore, the key to improving the conventional technology for the protective film composition of the present invention and the method of forming a metal surface layer using the protective film composition lies in:

[0060] First, a protective film composition 5 is formed by mixing monomer 1 including β-carboxyethyl acrylate and accounting for 20% to 75% by weight, photoinitiator 2 accounting for 5% to 20% by weight, color paste 3 accounting for 10% to 40% by weight, and resin 4 accounting for 10% to 20% by weight, and it is bonded to a metal part to form a metal surface protective film, so that the metal surface protective film has high adhesion, high durability, and is also easy to remove.

[0061] Second, since the metal surface protective film in this case is mainly composed of the protective film composition 5, the metal part can withstand immersion in cutting fluid (i.e., fluid, and the fluid can be oil-based or water-based coolant) for about 6 hours, ensuring long-term protection during the CNC machining process, and the metal surface protective film does not affect the CNC cutting accuracy, and there is no residue on the surface after machining, which does not affect subsequent surface treatment.

[0062] Third, through the first-stage curing action, the diffusion or flow of the protective film composition 5 can be prevented, ensuring the stable shape of the metal surface protective film, and through the second-stage curing action, the complete cross-linking of the metal surface protective film can be ensured, improving the cutting fluid resistance performance.

[0063] Fourth, through the design of monomer 1, photoinitiator 2, and resin 4, it has good plasticity, chemical resistance, transparency, impact resistance, and weather resistance under fusion. And it is safe and does not damage the processing material itself. The material itself is weakly acidic and will not corrode and damage the material itself.

[0064] Fifth, through a film coating device with an inkjet head moving in the XYZ axes and two light-curing devices, the cost can be effectively saved, the spraying and printing can be precise, and unnecessary cost waste can be reduced.

[0065] Sixth, the pretreatment liquid has highly excellent characteristics such as chemical stability, transparency, and ultraviolet resistance. Especially when the metal part is immersed in the fluid, it provides the characteristic of good peeling of the metal surface protective film, which can fall off by itself without residue.

[0066] Seventh, the resin can increase the hardness, toughness, and wear resistance of the metal surface protective film.

[0067] Example 2

[0068] I. Test preparation

[0069] 1. Determine the test materials: The test materials are titanium alloy with dimensions of 40*20*5.0 mm. The titanium alloy plates are all treated with the pretreatment liquid before the subsequent step experiments.

[0070] 2. Prepare relevant materials and equipment: Prepare materials such as ordinary ink, materials for UV spray printing, formulated ink, materials for screen printing, pretreatment liquid, formulated ink, cutting solution, and clean water. Prepare relevant equipment such as spray guns, ovens, UV lamps, ultraviolet irradiation equipment, copper plate printing equipment, air drying equipment, and UV spray printing

[0071] 3. Test procedures for different inks and printing methods:

[0072] (I) Ordinary ink (spraying in large areas with a spray gun)

[0073] 1. Use a spray gun to spray ordinary ink on the surface of titanium alloy in large areas and then put it into an oven and bake at 190 - 210 °C for 30 min;

[0074] 2. Soak it in cutting fluid for 6 - 8 hours for removal treatment;

[0075] (II) Formulated ink (UV spray printing of this application)

[0076] 1. Conduct UV spray printing on the carbon alloy plate and dry it synchronously with the printing by irradiating with a UV lamp;

[0077] 2. After the above spraying process, a second-stage UV lamp re-curing is required. The curing time in the second stage varies according to the metal properties, and the curing time is about 2 - 5 minutes;

[0078] 3. The above protective film can still not fall off after being soaked in cutting fluid for more than 4 hours and passes the cross-cut test;

[0079] 4. The protective film can be soaked in warm water for 1 hour, and then the protective layer will automatically fall off, achieving the effect of environmental protection and energy saving.

[0080] (III) Formulated ink (copper plate printing)

[0081] 1. Bake the titanium alloy with formulated ink for copper plate printing at 200 °C for 30 - 40 s;

[0082] 2. Soak it in cutting fluid for 4 hours for removal treatment or soak it in clean water for 8 hours for removal treatment;

[0083] (IV) Formulated ink (screen printing)

[0084] 1. Air dry the titanium alloy after screen printing for 30 min.

[0085] 2. Soak it in cutting fluid for 4 hours for removal treatment or soak it in clean water for 8 hours for removal treatment;

[0086]

[0087] From the data comparison, it can be seen that among them, the UV spray printing group has the shortest drying time, is easy to remove, has a short removal time, good removal effect, good water solubility, high utilization rate, extremely low waste, strong adhesion, and strong protection for the material. In all aspects, the performance of ordinary ink is inferior to the other three methods using formulated ink. Its removal effect is average, it is not environmentally friendly, has a low cost performance, and has an adverse impact on the material surface.

[0088] UV spray printing, copper plate printing, and screen printing using formulated ink all perform well in terms of removal effect, environmental friendliness, cost performance, and adhesion. In practical applications, these three methods can all be good choices for shielding treatment before metal processing. The specific choice can be further determined according to other factors such as operational convenience and equipment conditions in actual production.

[0089] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claimed invention.

Claims

1. A protective film composition, characterized in that: include: 20% to 75% by weight of monomers; 5 to 20% by weight of a photoinitiator; 10% to 40% by weight of color paste; and 10 to 20 weight percent of resin.

2. The protective film composition according to claim 1, characterized in that: The photoinitiator is at least one of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, 2,4-diethylthiazolone and 2-isopropylthioxanthone.

3. The protective film composition according to claim 1, characterized in that: The color paste comprises, by weight, 55 to 70 parts of monomer, 10 to 15 parts of dispersant and 20 to 30 parts of pigment toner.

4. The protective film composition according to claim 1, characterized in that: The monomers include monofunctional monomers and polyfunctional monomers, wherein the mass ratio of the monofunctional monomers to the polyfunctional monomers is 1:

5.

5. The protective film composition according to claim 4, characterized in that: The monofunctional monomer is at least one of β-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, cyclotrimethylolpropane formal acrylate, trimethylolcyclohexyl acrylate, ethoxyphenol acrylate, benzyl acrylate, o-phenylphenoxyethyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, N,N-dimethylacrylamide, N-acryloylmorpholine and N-vinylpyrrolidone.

6. The protective film composition according to claim 4, characterized in that: The multifunctional monomer is at least one of 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, n(ethoxylated) bisphenol A diacrylate, n(ethoxylated) trimethylolpropane triacrylate, n(propoxylated) trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, di(trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate and dipentaerythritol pentaacrylate.

7. The protective film composition according to claim 1, characterized in that: The resin is at least one of polyester resin, polyurethane resin, epoxy resin, chloroacetic acid resin, rosin resin, maleic acid resin and polyvinyl butyral resin.

8. A method for preparing a metal surface layer based on the protective film composition according to any one of claims 1 to 7, characterized in that: A protective film composition is placed in a film-laying device; a pretreatment liquid is applied to a metal part; the film-laying device places the protective film composition on the metal part; a first-stage curing action is performed on the surface of the metal part; and a second-stage curing action is performed on the surface of the metal part, and the curing time of the second-stage curing action is shorter than the first-stage curing action time, so as to complete a metal surface protective film.

9. The method for preparing a metal surface layer according to claim 8, characterized in that: After the second stage of curing, the metal part is cut and then immersed in a fluid while being subjected to ultrasonic vibration to separate the metal surface protective film from the metal part.

10. The method for preparing a metal surface layer according to claim 8, characterized in that: The ultrasonic vibration is any one of warm water ultrasonic vibration or plastic sodium cyanide solvent ultrasonic vibration.

11. The method for preparing a metal surface layer according to claim 8, characterized in that: The protective film composition is disposed on the metal part by spraying or screen printing.

12. The method for preparing a metal surface layer according to claim 8, characterized in that: The first stage curing action and the second stage curing action are performed using a light curing device, and the light curing device emits ultraviolet light of 365-395nm.

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