Protective film that can be processed by laser and cured by UV reaction.

Abstract

We provide a protective film that can be subjected to both laser processing and UV curing reactions. [Solution] The present invention relates to a film manufactured by melt-mixing a polyolefin and a pigment, wherein the pigment is contained in an amount of 6,000 to 20,000 ppm relative to the total weight of the film, resulting in a light transmittance of 35 to 75% of the film and a reduction in adhesive strength of 94 to 96% after UV curing.

Description

[Technical Field]

[0001] The present invention relates to a protective film that can be laser processed and UV cured. [Background technology]

[0002] In modern society, to meet the diverse desires and needs of consumers, companies are shifting their electronic product production methods from traditional mass production to high-mix, low-volume production. This method allows for a rapid response to individual consumer preferences and changing trends, and enables the creation of customized products by producing a wider variety of items in smaller quantities. This shift is a result of the increasing demand for more personalized products and innovative designs as consumer expectations rise with technological advancements.

[0003] However, when manufacturing electronic products using a high-mix, low-volume production method, there is a problem in that the fixed costs incurred in the process of manufacturing the electronic product cases are high due to the application of conventional mold processes such as punching, pressing, and bending, resulting in poor cost efficiency. This is because when producing various electronic products in small quantities, a lot of time is required to manufacture molds tailored to each electronic product, which significantly increases costs.

[0004] To solve these problems, laser processing technology was introduced as an alternative to molds. The laser processing method involves cutting sheet metal used as a case for electronic products into the desired shape with a laser, and then joining the cut sheets together in a pressing process. This allows for rapid and efficient processing without the need for complex mold making.

[0005] However, a frequent problem arose where the surface of the steel plate would oxidize or discolor due to the high heat generated during laser processing. To address this, high-pressure treatment in a nitrogen atmosphere was implemented to keep the processed surface of the steel plate clean after laser processing. While this high-pressure nitrogen treatment is effective in improving the processing quality of the steel plate, it requires that a protective film be applied to the surface of the steel plate before the laser process. However, when nitrogen treatment is applied, the protective film easily detaches from the steel plate due to the high pressure, and is damaged or melts off due to the high temperature, contaminating the surface of the steel plate. This not only reduces the quality of the steel plate but also necessitates additional post-processing.

[0006] In the related prior art document, "Laser-printable film and packaging using the same (Korean Published Patent No. 10-2022-0119075)," a polyolefin film is disclosed having at least one layer that can be printed by laser irradiation, and containing 100 to 3,000 ppm of a pigment that enables laser irradiation printing throughout the entire film layer, resulting in a haze of 1 to 30% and a thickness variation of 0.1 to 25% in either the length or width direction.

[0007] However, the pigments used in prior art are reactive to laser irradiation, creating laser-reactive films in which specific patterns or structures are formed by the laser. However, because the pigment concentration is set to 100-3,000 ppm, the haze is limited to a level of 1-30%, which inevitably limits transparency and processability.

[0008] This has created a need for a film that improves the efficiency and productivity of laser processing and UV curing. Therefore, the inventors focused on the above technical requirements and conducted research to develop a film that is easy to remove by UV curing while maintaining precision during laser processing. As a result, they found that by optimizing light transmittance and haze, they could realize a film suitable for laser processing and UV curing, and thus completed the present invention. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent No. 10-2022-0119075 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention was made to solve the above-mentioned problems, and its objective is to provide a protective film that can undergo both laser processing and UV curing reactions, minimizing laser reflection and reducing adhesive strength after UV curing, making it easy to remove. [Means for solving the problem]

[0011] To solve the above technical problems, the present invention provides a protective film that can be laser processed and UV cured, characterized in that the film is manufactured by melt-mixing a polyolefin and a pigment, wherein the pigment is contained in an amount of 6,000 to 20,000 ppm relative to the total weight of the film, the light transmittance of the film is 35 to 75%, and the adhesive strength after UV curing is reduced by 94 to 96%.

[0012] In the present invention, the haze of the film is characterized by being 35-55%.

[0013] In the present invention, the pigment is characterized by being composed of a black pigment and a white pigment.

[0014] In the present invention, the film is characterized in that 0.1 to 0.4 parts by weight of the black pigment and 0.1 to 0.8 parts by weight of the white pigment are melt-mixed with 80 to 100 parts by weight of the polyolefin to form a gray film.

[0015] In the present invention, the polyolefin is at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, polyolefin elastomer, and polyolefin ionomer.

[0016] In the present invention, the film is characterized by being composed of multiple layers.

Advantages of the Invention

[0017] According to the present invention by the above means for solving the problems, by melt-mixing a polyolefin and a pigment to produce a film, a protective film capable of both laser processing and UV curing reaction can be realized. In particular, by containing the pigment at a concentration of 6,000 to 20,000 ppm with respect to the total weight of the film, the light transmittance of the film is adjusted to 35 to 75%, and the haze is set to 35 to 55%, so that laser energy is concentrated on the film and stable laser cutting is possible. As a result, there is an effect that the possible energy loss generated during laser cutting can be minimized, and the phenomenon of the film floating due to high-pressure gas can also be suppressed.

[0018] In addition, the protective film of the present invention has the property that the adhesive force decreases by 94 to 96% after being adhered to the adherend, laser processed, and subjected to UV curing reaction. Therefore, the film can be easily removed from the adherend even after UV irradiation. This means that the film can protect the surface of the adherend during laser processing and can greatly reduce the adhesive force of the cured adhesive layer thereafter, so that the film residue can be removed neatly without leaving any residue on the surface of the adherend. For this reason, there is an advantage that the surface quality of the adherend after laser processing can be maintained and the film peeling process can be performed smoothly.

[0019] Therefore, the protective film of the present invention can simultaneously meet the surface protection and peeling performance during the laser processing of various electronic products or industrial parts by optimizing the optical properties of the film, the adhesion adjustment, and the interaction between laser processing and UV curing reaction. In particular, the film embodied in gray can adjust the absorption and dispersion of laser energy to improve the processing efficiency, and is easy to remove after the UV curing reaction, thus improving the productivity.

Brief Description of the Drawings

[0020] [Figure 1] It is an exemplary diagram showing the state in which the film according to the present invention is designed in a multilayer structure. [Figure 2] It is a graph showing the elongation rate and tensile strength according to the film thickness before UV irradiation. [Figure 3] It is a graph showing the elongation rate and tensile strength according to the film thickness after UV irradiation. [Figure 4a] It is a photo of the laser cutting result of the film according to Example 1. [Figure 4b] It is a photo of the laser cutting result of the film according to Comparative Example 1. [Figure 4c] It is a photo of the laser cutting result of the film according to Comparative Example 3. [Figure 4d] It is a photo of the laser cutting result of the film according to Comparative Example 4. [Figure 4e] It is a photo of the laser cutting result of the film according to Comparative Example 5.

Modes for Carrying Out the Invention

[0021] The present invention can be subjected to various modifications and can have various embodiments. Therefore, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. Similar reference numerals are used for similar components while explaining each drawing.

[0022] The terms used in this invention are used solely to describe specific embodiments and are not intended to limit the invention. A singular expression includes plural expressions unless the context clearly indicates otherwise. In this invention, terms such as “includes” or “having” are intended to specify the presence of features, figures, stages, actions, components, or combinations thereof as described in the specification, and should be understood not to preemptively exclude the possibility of the presence or addition of one or more other features, figures, stages, actions, components, or combinations thereof.

[0023] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted in the sense that they have in the context of the relevant art, and not in an ideal or overly formal sense unless explicitly defined herein.

[0024] The present invention relates to a film that can be subjected to both laser processing and UV curing reactions, and can be manufactured in film form using polyolefin and pigment via a blown film method or a T-die method.

[0025] The blow method involves feeding polyolefin and masterbatch-like pigments into an extruder, heating them to a melt state, and then extruding them into a tubular shape using an annular die to produce a film. The T-die method involves feeding polyolefin and masterbatch-like pigments into an extruder, heating them to a melt state, and then extruding them into a flat plate shape using a T-shaped die to produce a film.

[0026] The films produced by these methods consist of a single film substrate layer, and can also be formed by laminating multiple film substrate layers in multiple layers. In this regard, Figure 1 is an illustrative diagram showing a film according to the present invention designed with a multilayer structure. As shown in Figure 1, the protective film 100 can consist of at least two layers, and preferably a three-layer structure consisting of an outer layer 130, a middle layer 120, and an inner layer 110. The raw material blending ratios of the outer layer 130, middle layer 120, and inner layer 110 may be the same or slightly different. When the film is constructed with a multilayer structure, the physical strength and durability of the film can be improved. In the case of the outer layer 130, reflection is minimized during laser processing and processability is improved, while the inner layer 110 can help maintain adhesion to the iron plate, which is the adherend.

[0027] Incidentally, by applying corona discharge treatment to at least one of the outer layer 130, middle layer 120, and inner layer 110, preferably the inner layer 110 that is in direct contact with the adhesive layer, the coating properties of the adhesive layer can be effectively improved. Such a corona discharge treatment process can further strengthen the adhesion of the adhesive layer to the film, simultaneously improving coating properties and durability.

[0028] The polyolefin of the present invention is a polymer made by polymerizing olefin compounds such as ethylene and propylene, and is nearly colorless in itself. By adding a pigment to such a polyolefin, a film of a desired color can be obtained.

[0029] The polyolefin may be at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, polyolefin elastomer, and polyolefin ionomer.

[0030] Specifically, the type of polyolefin is not particularly limited and can be freely used without departing from the spirit of the present invention. For example, homopolymers such as polyethylene (PE) and polypropylene (PP) can be used. In the case of polypropylene, isotactic, syndiotactic, and atactic structures are all applicable. Furthermore, polyethylene can be used in various densities, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (MLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). In addition to homopolymers, copolymers obtained by copolymerizing two or more monomers can also be used, with ethylene-α-olefin copolymers and propylene-α-olefin copolymers being examples. Here, α-olefins are unsaturated hydrocarbons in which the double bond is located between the first and second carbon atoms of the hydrocarbon chain, and include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The copolymer can be formed by either random copolymerization or block copolymerization. Furthermore, polyolefin elastomers, which have elastomeric properties while using polyolefins as the basic structure, or polyolefin ionomers, in which ionic bonds are introduced into the polyolefin system, can also be used.

[0031] If the polyolefin content is less than 80 parts by weight, the structural stability and durability of the film will decrease. This means that the film is more likely to be easily damaged or torn by impact or external stimuli, and the processing accuracy during laser processing may decrease. On the other hand, if the polyolefin content exceeds 100 parts by weight, the pigment content will be relatively low, which may reduce the functional properties of the film, such as color realism and light transmittance. Thus, excessive use of polyolefin exceeding 100 parts by weight will affect laser reflection prevention and UV curing performance, reducing the processing and UV curing efficiency of the film.

[0032] The pigment of the present invention is not a functional pigment that reacts to laser irradiation, but rather a colored masterbatch used for applications that produce color.

[0033] The reason for using pigments is to cut stainless steel (SUS) and PCM (Pre-coated metal) and VCM (Vinyl-coated metal), which are commonly used as exterior materials for home appliances, with a laser without damaging the surface. The areas not being cut must be protected from high heat and high-pressure gas, and the film must not lift or become contaminated. Therefore, pigments play an important role in adhering the film to protect the area being laser-irradiated.

[0034] The film can be available in various colors, including transparent, white, black, and blue. The color of the film can affect the output during laser irradiation, potentially resulting in differences in laser cutting performance. According to this invention, colored films exhibit superior laser cutting performance compared to transparent films. However, with colored films, light transmittance decreases, making it difficult for UV light to pass through the film and reach the adhesive layer during UV irradiation. Therefore, we concluded that a gray film is the most suitable, as it ensures sufficient light transmittance for UV light to penetrate while minimizing laser reflection during laser processing. For this purpose, it is preferable to create a gray film by melt-mixing a black pigment masterbatch and a white pigment masterbatch into polyolefin.

[0035] For this reason, the pigment may be included in the form of 0.1 to 0.4 parts by weight of black pigment and 0.1 to 0.8 parts by weight of white pigment. If the amount of black pigment is less than 0.1 parts by weight, the color realization of the film may be insufficient, making it difficult to achieve the target gray color. In this case, the cutting performance and processing efficiency during laser processing may also decrease, and there is a problem that the opacity of the film decreases and the light transmittance becomes too high. If the amount of black pigment exceeds 0.4 parts by weight, the transparency of the film decreases excessively, and the light transmittance becomes lower than necessary. As a result, UV curing does not proceed smoothly, and UV may not reach the adhesive layer sufficiently after UV irradiation, potentially leading to incomplete curing. If the amount of white pigment is less than 0.1 parts by weight, the color balance of the film will be off, and the gray film may become too dark or the proportion of black pigment may be too emphasized, affecting the accuracy of laser cutting. If the amount of white pigment exceeds 0.8 parts by weight, the opacity of the film may increase, potentially reducing the efficiency of laser processing. This can lead to a situation where the light transmittance becomes too low, preventing the light necessary for UV curing from reaching the adhesive layer. This can result in a reduction in adhesive strength. Furthermore, if too much white pigment is added, exceeding 0.8 parts by weight, the film's color will become brighter, which may cause the energy concentration during laser processing to be dispersed, potentially reducing laser cutting performance.

[0036] The gray film of the present invention is preferably semi-transparent, allowing some light to pass through, but appearing cloudy or blurred in the process. This can be explained by light transmittance and haze.

[0037] In other words, light transmittance is a measure of how much light passes through a film. It indicates the percentage of incident light that passes through the film and exits, and it represents the percentage of light that passes through the film. A higher light transmittance means that more light passes through the film.

[0038] The light transmittance of the film according to the present invention is in the range of 35 to 75%. This means that 35 to 75% of the light incident on the film passes through, indicating that the film is not transparent and instead of absorbing or reflecting most of the light, it allows only a portion to pass through.

[0039] If the light transmittance of the film is less than 35%, light will not pass through the film sufficiently, and UV curing may not occur properly. This can lead to insufficient curing of the adhesive, making it difficult to remove the film from the substrate, and potentially causing adhesive residue and contamination on the substrate surface after laser processing. If the light transmittance of the film exceeds 75%, the amount of light reflected during laser processing will not decrease, resulting in poor processing quality, and the surface of the laser-cut substrate may not be clean or the processing accuracy may be reduced. Preferably, the light transmittance of the film is 37.62%.

[0040] Haze, separate from light transmittance, indicates how much light is scattered after passing through a film, and how cloudy the light appears. It represents the proportion of incident light that is scattered rather than traveling in a straight line. Since haze refers to the cloudy or indistinct appearance of an object when a lot of scattering occurs as light passes through a film, it is used to measure the degree of cloudiness, not the transparency of the film.

[0041] The haze of the film according to the present invention is 35-55%, meaning that 35-55% of the light transmitted through the film is scattered. If the film's haze is lower than 35%, the film becomes too transparent, causing light to reflect during laser processing and preventing efficient transmission of laser energy to the substrate, which may lead to unstable laser processing. If the haze exceeds 55%, excessive light scattering may result in uneven cut surfaces or contamination after laser processing, and the adhesive may not cure properly because sufficient light necessary for UV curing does not pass through. Preferably, the film's haze value can be 48.45%.

[0042] As mentioned above, a film light transmittance of 35-75% and a haze of 35-55% can be achieved by including pigment at a concentration of 6,000-20,000 ppm relative to the total weight of the film.

[0043] If the pigment concentration is less than 6,000 ppm, the light transmittance of the film becomes excessively high, preventing light from being reflected during laser processing. This allows too much light to pass through the film, resulting in insufficient absorption of laser energy by the substrate and a decrease in processing quality. Conversely, if the pigment concentration is low, below 6,000 ppm, the haze decreases and the film becomes too transparent, potentially leading to poor surface condition of the substrate after processing and weakening the protective function of the film.

[0044] On the other hand, if the pigment content exceeds 20,000 ppm, it inhibits the light transmittance of the film, preventing UV curing of the adhesive layer during UV irradiation. In other words, if the pigment is added in excess to exceed 20,000 ppm, the light transmittance of the film becomes too low, and the light necessary for UV curing does not pass sufficiently through to the adhesive layer. This can lead to unstable UV curing, preventing the adhesive layer located beneath the film from curing properly, and potentially making it difficult to remove the film from the substrate. Preferably, the pigment content can be 7,000 ppm relative to the total weight of the film.

[0045] As described above, polyolefin and pigment are melt-mixed, and with the pigment contained at a concentration of 6,000 to 20,000 ppm, the film thickness that results in a light transmittance of 35 to 75% and a haze of 35 to 55% is in the range of 50 to 100 μm. If the film thickness is less than 50 μm, there is a problem that the film will adhere to the substrate and tear when UV cured after laser processing, and if the film thickness exceeds 100 μm, the unit price of the film product will increase, which is undesirable.

[0046] In particular, when the pigment is contained at a concentration of 6,000 to 20,000 ppm relative to the total weight of the film, the film's light transmittance becomes 35 to 75% and its haze becomes 35 to 55%, resulting in a 94 to 96% reduction in the adhesive strength of the film after UV curing.

[0047] If the tack reduction rate is less than 94%, the tackiness after UV curing is reduced to a small extent, resulting in insufficient film release. This can lead to the film not separating well from the substrate, and some adhesive residue remaining on the substrate. Consequently, unnecessary force may be required during the film removal process, or the film may not be easily removed, potentially damaging the surface of the substrate. In particular, the substrate surface may not be properly finished after laser processing, requiring additional steps and resulting in production inefficiencies and additional costs.

[0048] A tackiness reduction rate exceeding 96% means that the tackiness after UV curing is excessively reduced. In this case, the film may detach too easily or even lift up, resulting in a failure to protect the substrate during laser processing. This inevitably leads to reduced film stability and decreased work efficiency during processing or transport.

[0049] The rate of change in adhesive strength after UV curing of a film can be calculated using the formula: ((Adhesive strength before UV curing - Adhesive strength after UV curing) / (Adhesive strength before UV curing)) × 100. In other words, by expressing the difference in adhesive strength before and after UV curing as a percentage, the amount of decrease in adhesive strength can be calculated. For example, if the adhesive strength of the film before UV curing is 950 gf / 25 mm and the adhesive strength of the film after UV curing is 45 gf / 25 mm, this represents a 95.26% decrease in adhesive strength. This satisfies the excellent peelability of the film after UV curing, allowing it to fully fulfill its role as a protective film, while the significant decrease in adhesive strength after UV curing makes the film easy to remove, thus leaving no residue on the surface of the adherend.

[0050] The UV-curable adhesive layer of the present invention can be further positioned beneath the film. When the adhesive layer is located beneath the film, the film is fixed to the surface of the substrate during laser processing, improving the accuracy and stability of the laser processing. Specifically, the adhesive layer adheres the film tightly to the substrate, providing surface protection during laser processing and helping to maintain a clean cut surface after laser processing. In particular, the reduced adhesive strength of the adhesive layer after UV curing allows for easy removal of the film after laser processing, thus simplifying post-processing.

[0051] The following describes embodiments of the present invention in more detail. However, the following embodiments are merely illustrative to aid in understanding the present invention and do not limit the scope of the present invention.

[0052] First, the physical properties of the polyolefin types used in Example 1 and Comparative Examples 1-5 are shown in Table 1 below.

[0053] [Table 1] JPEG2026079692000002.jpg27170

[0054] <Example 1> A film was extruded using the Blown method from 84.14 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), 7.58 parts by weight of linear low-density polyethylene (LLDPE), 0.5 parts by weight of a white pigment masterbatch, and 0.2 parts by weight of black pigment.

[0055] <Comparative Example 1> A film was manufactured by extruding 68.18 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), 7.58 parts by weight of linear low-density polyethylene (LLDPE), 16.25 parts by weight of a white pigment masterbatch, and 0.41 parts by weight of black pigment using the Blown method.

[0056] <Comparative Example 2> A film was manufactured by extruding 79.43 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), 7.58 parts by weight of linear low-density polyethylene (LLDPE), 5 parts by weight of a white pigment masterbatch, and 0.41 parts by weight of black pigment using the Blown method.

[0057] <Comparative Example 3> A film was manufactured by extruding 83.43 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), 7.58 parts by weight of linear low-density polyethylene (LLDPE), 1 part by weight of white pigment masterbatch, and 0.41 parts by weight of black pigment using the Blown method.

[0058] <Comparative Example 4> A film was manufactured by extruding 84.34 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), 7.58 parts by weight of linear low-density polyethylene (LLDPE), and 0.5 parts by weight of a white pigment masterbatch using the Blown method. In Comparative Example 4, no black pigment masterbatch was added.

[0059] <Comparative Example 5> A film was manufactured by extruding 84.84 parts by weight of low-density polyethylene (LDPE), 7.58 parts by weight of high-density polyethylene (HDPE), and 7.58 parts by weight of linear low-density polyethylene (LLDPE) using the Blown method. In Comparative Example 5, neither the white pigment masterbatch nor the black pigment masterbatch was added.

[0060] <Test Example 1> In this test example 1, the physical properties and laser-cutting properties of the films in Example 1 and Comparative Examples 1 to 5 were analyzed. For this purpose, each of the films in Example 1 and Comparative Examples 1 to 5 was constructed with a three-layer structure consisting of an outer layer, a middle layer, and an inner layer. The content of each layer is summarized in Tables 2 and 3 below. The unit is parts by weight.

[0061] [Table 2] JPEG2026079692000003.jpg37170

[0062] [Table 3] JPEG2026079692000004.jpg34170

[0063] 1-1. Analysis of adhesive strength, elongation, and tensile strength based on film thickness In Test Example 1-1, the films of Example 1 were manufactured with thicknesses of 58 μm (Sample A), 68 μm (Sample B), 75 μm (Sample C), and 98 μm (Sample D), and a UV-curing adhesive was used as the adhesive layer. The adhesive strength, elongation, and tensile strength were then analyzed based on the film thickness.

[0064] In relation to this, Figure 2 shows a graph illustrating the changes in elongation and tensile strength with respect to film thickness (58 μm, 68 μm, 75 μm, 98 μm) before UV irradiation. Figures 2(a) and 2(b) show the changes in elongation and tensile strength for MD and TD, respectively. Furthermore, Figure 3 shows a graph illustrating the changes in elongation and tensile strength with respect to film thickness after UV irradiation. Figures 3(a) and 3(b) show the changes in elongation and tensile strength for MD and TD, respectively.

[0065] Along with such changes in elongation rate and tensile strength, Table 4 summarizes the changes in adhesive strength before and after UV irradiation according to the film thickness. At this time, the adhesive strength of the film was measured by attaching the film to 304BA which was surface-treated with BA (Bright annealed) on a stainless steel of grade 304.

[0066] [Table 4] JPEG2026079692000005.jpg29170

[0067] In sample A with a film thickness of 58 μm, the tensile strength before UV irradiation was 283 gf / cm in the MD 2 and 204 gf / cm in the TD 2 . The elongation rate before UV irradiation was 422% in the MD and 701% in the TD. The tensile strength after UV irradiation was 277 kgf / cm in the MD 2 and 214 kgf / cm in the TD 2 . The elongation rate after UV irradiation was 422% in the MD and 705% in the TD, showing almost no change.

[0068] In sample B with a film thickness of 68 μm, the tensile strength before UV irradiation was 298 kgf / cm in the MD 2 and 210 kgf / cm in the TD 2 . The elongation rate before UV irradiation was 555% in the MD and 700% in the TD. The tensile strength after UV irradiation was 300 kgf / cm in the MD 2 and 234 kgf / cm in the TD 2 . The elongation rate after UV irradiation was 508% in the MD and 705% in the TD.

[0069] In sample C with a film thickness of 75 μm, the tensile strength before UV irradiation was 319 kgf / cm in the MD 2 and 236 kgf / cm in the TD[[ID=3{]] 2 [[ID=]]The elongation rate before UV irradiation was 601% in the MD and 700% in the TD. The tensile strength after UV irradiation was 327 kgf / cm in the MD 2 and 245 kgf / cm in the TD 2The growth rate after UV irradiation was 555% for MD and 705% for TD, showing no change.

[0070] In sample D, which has a film thickness of 98 μm, the tensile strength before UV irradiation was 348 kgf / cm² in MD. 2 TD is 265 kgf / cm² 2 The elongation before UV irradiation was 766% for MD and 708% for TD. The tensile strength after UV irradiation was 356 kgf / cm for MD. 2 TD is 250 kgf / cm² 2 The elongation rates after UV irradiation were 616% for MD and 708% for TD, indicating only a slight change.

[0071] As a result, UV irradiation either slightly decreased or maintained the same tensile strength, and there was no significant difference in elongation before and after UV irradiation. However, the tensile strength in the MD direction was relatively higher than the tensile strength in the TD direction before and after UV irradiation. For reference, MD (Machine direction) refers to the direction in which the film is pulled in the length direction, and TD (Transverse direction) refers to the direction in which the film is pulled in the width direction.

[0072] Furthermore, as shown in Table 4, the adhesive strength of all samples was maintained at 910-930 gf / 25 mm before UV irradiation, and decreased to 40 gf / 25 mm after UV irradiation. This means that the adhesive strength after UV curing decreased by approximately 95.7%, and the tendency for the adhesive strength to decrease after UV irradiation was similar regardless of the thickness of each sample. Therefore, it was confirmed that the change in adhesive strength before / after UV irradiation occurred independently of the film thickness, and that the adhesive strength of the adhesive layer decreased due to the UV curing reaction, making the film easier to peel off.

[0073] 1-2. Analysis of laser-cuttable properties of films based on pigment content In Test Example 1-2, the laser cutting performance of films containing various pigment concentrations was analyzed to evaluate the effect of the pigment content of the film on laser cutting performance. To confirm this, the films related to Example 1, Comparative Example 1, and Comparative Examples 3-5 were processed with a laser, and the results are shown in Figures 4a-4e.

[0074] Figure 4a is a photograph of the laser-cut film according to Example 1, showing a clean and precise cut with good results. Figure 4b is a photograph of the laser-cut film according to Comparative Example 1, which appears to have been cut relatively well, but the laser-cut boundary is irregular in some areas, or traces of contamination are visible, indicating an unclean cut. Figure 4c is a photograph of the laser-cut film according to Comparative Example 3, which appears to have been cut relatively well, but traces of lifting are visible in some areas. Figure 4d is a photograph of the laser-cut film according to Comparative Example 4, where the film partially melted or lifted during the laser-cutting process, and a fine tearing phenomenon occurred. Figure 4e is a photograph of the laser-cut film according to Comparative Example 5, where the cut boundary was not uniform, and the film showed traces of contamination during laser cutting and lifting, making processing impossible. Therefore, it can be confirmed that the film according to Example 1 showed the most precise and clean cut results, and that the films according to Comparative Examples 1 and 3 to 5 showed inconsistent levels of deterioration in cut quality.

[0075] The elongation and tensile strength shown in the aforementioned test examples were not directly related to the lifting phenomenon that occurs during laser processing. It was hypothesized that when film lifting occurs during laser cutting, it is mainly related to the composition and wettability of the adhesive that makes up the adhesive layer. In particular, it was found that the higher the transparency of the film, the less the laser energy is concentrated in the film, and the more it is refracted and dispersed, resulting in a decrease in cutting performance. Therefore, it was found that the high-pressure gas emitted from the laser cutting equipment induces the film lifting phenomenon.

[0076] 1-3. Analysis of light transmittance, haze, and adhesive strength of the film. In Test Examples 1-3, after coating the films produced in Example 1 and Comparative Examples 1-5 with an adhesive layer, the light transmittance, haze, and adhesive strength before and after UV curing were analyzed. The results are summarized in Table 5 below. A UV-curing adhesive was used as the adhesive layer.

[0077] [Table 5] JPEG2026079692000006.jpg39170

[0078] In terms of light transmittance, the film of Example 1 showed a light transmittance of 37.62%, which is the highest light transmittance compared to the comparative examples, indicating that the film has the ability to sufficiently transmit the light necessary for UV curing. Comparative Example 1 showed a very low light transmittance of 2.30%, which indicates that the film is very opaque and transmits very little light. Comparative Example 3 showed a light transmittance of 29.95%, which is a relatively high value among the comparative examples, but is still lower than that of Example 1.

[0079] In terms of haze, the haze value of Example 1 was 48.42%, which is lower than the comparative example. However, it was found that the film had appropriate transparency while exhibiting a moderate level of light scattering, making laser processing and UV curing possible. Comparative Example 1 showed a very high haze value of 89.06%, indicating that the film had strong opacity, resulting in excessive light scattering. Comparative Example 3 showed a haze value of 63.71%, which is relatively low among the comparative examples, but still exhibited even higher light scattering than Example 1.

[0080] In terms of adhesive strength, the adhesive strength of Example 1 decreased from an initial 950 gf / 25 mm before UV curing to 45 gf / 25 mm after UV irradiation, a decrease of 95.26%. This confirmed that the adhesive strength after UV curing decreased significantly, making the film easily removable. Comparative Example 1 maintained the same adhesive strength of 950 gf / 25 mm as the initial value, with no decrease in adhesive strength even after UV irradiation. This indicates that UV curing was not performed properly, and the film lacked the peelability required for protective films. Comparative Example 2 showed a small decrease in adhesive strength, with an adhesive strength of 800 gf / 25 mm after UV irradiation, a decrease of 15.79%. Comparative Example 3 showed a decrease in adhesive strength of 300 gf / 25 mm after UV irradiation, a decrease of 68.42%. This decrease was greater than that of Comparative Examples 1 and 2, but the rate of decrease was lower than that of Example 1. Comparative Examples 4 and 5 showed similar results to Example 1, with adhesive strengths decreasing by 93.68% and 94.73% at 60 gf / 25 mm and 50 gf / 25 mm, respectively. However, processing was impossible due to the film lifting phenomenon during laser cutting.

[0081] Therefore, as with Example 1, laser processing and UV curing reactions are possible while maintaining appropriate light transmittance and haze values, resulting in an adhesion reduction rate of 95.26% and smooth removal of the film. In particular, in Comparative Examples 1 and 2, the imbalance between light transmittance and haze makes them unsuitable for laser processing and UV curing reactions, and the adhesion reduction rate is also poor, resulting in reduced film peelability.

[0082] In summary, the present invention features a protective film with optimized light transmittance and haze, which facilitates the reduction of adhesive strength after laser processing and UV curing. This feature is significant because it allows for the protection of the substrate surface during laser processing while enabling easy removal of the film after UV curing, thereby maximizing production efficiency. In particular, the 94-96% reduction in adhesive strength after UV curing allows for smooth film removal, ensuring not only undamaged substrate surface protection but also improved work quality and productivity.

[0083] The above description is merely illustrative of the technical concept of the present invention, and any person with ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted by the claims, and all technical concepts within an equivalent scope should be interpreted as being included in the scope of rights of the present invention. [Explanation of Symbols]

[0084] 100 protective film 110 Inner layer 120 middle class 130 Outer layer

Claims

1. Polyolefins and A film manufactured by melting and mixing a pigment, A protective film that can be laser processed and UV cured, characterized in that the pigment is contained in an amount of 6,000 to 20,000 ppm relative to the total weight of the film, the light transmittance of the film is 35 to 75%, and the adhesive strength after UV curing is reduced by 94 to 96%.

2. A protective film that can be laser processed and UV cured, as described in claim 1, characterized in that the haze of the film is 35 to 55%.

3. A protective film that can be laser processed and UV cured, as described in claim 1, characterized in that the pigment is composed of a black pigment and a white pigment.

4. The protective film according to claim 3, characterized in that the film is formed in gray by melt-mixing 80 to 100 parts by weight of the polyolefin with 0.1 to 0.4 parts by weight of the black pigment and 0.1 to 0.8 parts by weight of the white pigment.

5. The protective film for laser processing and UV curing according to claim 1, characterized in that the polyolefin is at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, polyolefin elastomer, and polyolefin ionomer.

6. The protective film according to claim 1, characterized in that the film is composed of multiple layers, and is capable of laser processing and UV curing.

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