Cover film and circuit board

Abstract

The invention discloses a cover film and a circuit board, the cover film comprises a bonding layer and a color developing layer, one side, close to the bonding layer, of the color developing layer is provided with an isolation layer, and the thickness of the isolation layer accounts for 1 / 8-2 / 5 of the total thickness of the cover film. By adopting the technical means provided by the invention, the isolating layer with a certain thickness is arranged in the covering film, so that interpenetration of molecules between the bonding layer and the color developing layer can be effectively prevented, the uniformity of the color developing layer is ensured, and the quality of the covering film can be effectively improved while the bending resistance is not influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic information materials, and particularly relates to a cover film and a circuit board. Background Art

[0002] In existing circuit boards, a glue layer is usually provided on the surface of the circuit as a protective film, which covers the entire surface of the circuit board to play roles such as protection, moisture-proof, dust-proof, and interlayer insulation, and also has certain identification and aesthetic functions.

[0003] Currently, the protective film of a circuit board generally includes a colored ink layer and an adhesive layer. However, since the cover film is laminated on the circuit board, when the circuit board is manufacturing electronic components, it needs to go through a high-temperature process, and the maximum temperature range reaches 230 - 300 °C. After this high-temperature process, color bleeding is likely to occur between the adhesive layer and the colored ink layer on the cover film, resulting in phenomena such as miscellaneous colors and color changes on the cover film, which affects the quality. Summary of the Invention

[0004] An object of the embodiments of the present invention is to provide a cover film and a circuit board. By providing an isolation layer with a certain thickness in the cover film, it can effectively prevent the molecular mutual penetration between the adhesive layer and the color display layer, ensure the uniformity of the color display layer, and effectively improve the quality of the cover film without affecting the bending resistance performance.

[0005] To achieve the above object, an embodiment of the present invention provides a cover film, which includes an adhesive layer and a color display layer. An isolation layer is provided on one side of the color display layer close to the adhesive layer, and the thickness of the isolation layer accounts for 1 / 8 - 2 / 5 of the total thickness of the cover film.

[0006] As an improvement of the above solution, the color display layer, the isolation layer, and the adhesive layer are sequentially laminated along the thickness direction.

[0007] As an improvement of the above solution, the isolation layer is provided in the color display layer and is located on the side close to the adhesive layer.

[0008] As an improvement of the above solution, the color display layer is formed by mutually pressing a first glue layer and a second glue layer, and a part of the mutually pressing sides of the first glue layer and the second glue layer mutually penetrates to form the isolation layer.

[0009] As an improvement of the above solution, the pressing surfaces of the first glue layer and the second glue layer are in mutually adapted shapes.

[0010] As an improvement of the above solution, the roughness of the pressing surfaces of the first glue layer and the second glue layer is 1 - 10 μm.

[0011] As an improvement of the above solution, the thickness of the isolation layer is 1 - 10 μm.

[0012] As an improvement of the above solution, the density of the isolation layer is more than 1.5 times that of the adhesive layer.

[0013] As an improvement of the above solution, the density of the isolation layer is 2 g / cm 3 or more.

[0014] As an improvement of the above solution, the glass transition temperature Tg of the isolation layer is greater than or equal to 230 °C.

[0015] As an improvement of the above solution, the light transmittance of the cover film is less than or equal to 60%.

[0016] As an improvement of the above solution, the cover film further includes a carrier layer, and the carrier layer is detachably disposed on the surface of the color display layer away from the isolation layer.

[0017] An embodiment of the present invention further provides a circuit board, which includes a circuit board substrate and a cover film as described in any one of the above, and the cover film is pressed against the circuit board substrate.

[0018] Compared with the prior art, for the cover film and the circuit board disclosed in the present invention, an isolation layer is added between the adhesive layer and the color display layer in the cover film, and the thickness range of the isolation layer in the cover film is controlled, which can effectively prevent the molecular mutual penetration between the adhesive layer and the color display layer, avoid the chemical components in the adhesive layer from infiltrating into the color display layer after high-temperature manufacturing process, thereby causing uneven color display or generating miscellaneous colors, and can effectively improve the quality of the cover film without affecting the bending resistance performance; and the isolation layer can also prevent the adhesive layer from reacting excessively with other materials, thereby enhancing the stability and adhesion of the adhesive layer to extend the service life of the cover film. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the first cover film provided by an embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of the second cover film provided by an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of the third cover film provided by an embodiment of the present invention;

[0022] Figure 4 is a schematic structural diagram of the fourth cover film provided by an embodiment of the present invention;

[0023] Figure 5 is a schematic structural diagram of the fifth cover film provided by an embodiment of the present invention;

[0024] Figure 6It is a schematic structural diagram of the sixth type of cover film provided by an embodiment of the present invention;

[0025] Figure 7 It is a schematic structural diagram of a circuit board provided by an embodiment of the present invention;

[0026] In the figure, 10 is the cover film; 11 is the adhesive layer; 12 is the color display layer; 121 is the first glue layer; 122 is the second glue layer; 13 is the isolation layer; 14 is the filler; 15 is the carrier layer; 20 is the circuit board; 21 is the circuit board substrate. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0029] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0030] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0031] See Figure 1, which is a schematic structural diagram of the first covering film provided by the embodiments of the present invention. The embodiments of the present invention provide a covering film 10, which includes an adhesive layer 11 and a color display layer 12. An isolation layer 13 is provided on the side of the color display layer 12 close to the adhesive layer 11, and the thickness of the isolation layer 13 accounts for 1 / 8 - 2 / 5 of the total thickness of the covering film 10.

[0032] It should be noted that the covering film provided by the embodiments of the present invention is a protective film used to cover the surfaces of products such as printed circuit boards and semiconductor materials. It can be thermally pressed onto products such as printed circuit boards, capable of covering the surface of the printed circuit board, thereby playing roles such as protection, moisture and dust prevention, and interlayer insulation. At the same time, it can also have functions of identification and aesthetics.

[0033] In the embodiments of the present invention, the covering film 10 includes an adhesive layer 11. Through the adhesive layer 11, the covering film can be thermally pressed and adhered to the surface of the printed circuit board. At the same time, the covering film 10 further includes a color display layer 12, which is arranged at the top. Users can customize the color display layer with corresponding display colors according to needs. The color display layer 12 can improve the aesthetic requirements of the covering film while performing shielding, and play functions such as shielding, protecting, and beautifying the printed circuit board. Optionally, the color display layer 12 can be any color such as red, orange, yellow, green, cyan, blue, purple, black, white, etc. The color of the adhesive layer 11 is different from the background color of the printed circuit board, and the color display layer 12 is generally selected to have a large color difference from the adhesive layer 11.

[0034] Since the covering film is laminated on the printed circuit board, when the printed circuit board is installing electronic components, it needs to go through a high-temperature Reflow process (1 - 5 times), and the highest temperature range reaches 230 - 300 °C. After this high-temperature process, the color of the adhesive layer on the covering film is likely to diffuse into the color display layer, resulting in phenomena such as miscellaneous colors and color changes in the color display layer, affecting the aesthetics. Therefore, an isolation layer 13 is added between the adhesive layer 11 and the color display layer 12, and the isolation layer is limited to have a certain thickness, which can effectively prevent the molecular penetration between adjacent layers, play an isolation role, and prevent the color of the adhesive layer 11 from easily penetrating upward into the color display layer 12 during the high-temperature lamination of the printed circuit board, resulting in miscellaneous colors in the color display layer 12 and affecting the aesthetics and shielding effect of the printed circuit board.

[0035] The embodiments of the present invention further optimize the thickness of the isolation layer 13. The thickness of the isolation layer 13 accounts for 1 / 8 - 2 / 5 of the total thickness of the covering film 10, so that the thickness of the isolation layer 13 is within a suitable range, avoiding poor isolation effect of the covering film 10 caused by too low thickness of the isolation layer, and at the same time avoiding the overall excessive thickness of the covering film 10 and the decline of its bending resistance due to too large thickness of the isolation layer.

[0036] Preferably, the color display layer 12, the isolation layer 13, and the adhesive layer 11 are sequentially stacked along the thickness direction.

[0037] By adopting the technical means of the embodiments of the present invention, the covering film has at least the following beneficial effects:

[0038] (1) Prevent molecular interpenetration and ensure pure color development: An isolation layer is provided between the color development layer and the adhesive layer, effectively preventing the free diffusion of oxygen and other small molecules between the two layers, and avoiding the possible infiltration of chemical components in the adhesive layer into the color development layer, resulting in uneven color development or the generation of miscellaneous colors. Thus, the color of the color development layer is ensured to be pure and bright, greatly enhancing the visual aesthetic feeling of the product.

[0039] (2) Reduce oxidation reaction and ensure color stability: Since the isolation layer has a certain thickness, it can effectively reduce the chance of oxygen passing through the isolation layer and contacting the color development layer. Oxygen promotes oxidation reactions in the color development layer in many chemical reactions, thereby changing the color or causing color changes. The isolation layer with a certain thickness can slow down the oxidation rate of the color development layer, making the color more stable and reducing color changes caused by oxidation.

[0040] (3) Enhance adhesion: The oxygen transmission rate of the adhesive layer is relatively high, which enables it to better form chemical bonds with the material surface when contacting other materials. However, too high an oxygen transmission rate may cause the adhesive layer to react with other materials, affecting the adhesion effect. The isolation layer can prevent the adhesive layer from reacting excessively with other materials, thereby enhancing the adhesion of the adhesive layer.

[0041] (4) Extend service life: By preventing molecular interpenetration between the adhesive layer and the color development layer, the isolation layer helps to extend the service life of the product. Whether in long-term use or in harsh environments, the stability of the color development layer is ensured, and the performance of the adhesive layer can also remain in good condition, reducing quality problems caused by color changes, adhesive failure, etc., and reducing production costs.

[0042] (5) Environmentally friendly, energy-saving, and promote sustainable development: Materials with low oxygen transmission rate and high density can be used as the isolation layer, which helps to reduce waste generated due to material aging and frequent replacement, meeting the current environmental protection concept of green and low-carbon. At the same time, the high-efficiency isolation performance means that the covering film can better play its protective role during the service life cycle, indirectly reducing resource consumption and environmental pollution.

[0043] As a preferred implementation manner, the embodiments of the present invention are further implemented on the basis of any of the above embodiments. Refer to Figure 2 , which is a schematic structural diagram of the second covering film provided by the embodiments of the present invention. The isolation layer 13 is provided in the color development layer 12 and is located on the side close to the adhesive layer 11.

[0044] In the embodiment of the present invention, the isolation layer 13 is disposed in the color display layer 12, that is, the isolation layer 13 and the color display layer 12 are integrally formed. During the manufacturing process of the cover film 10, the color display layer 12 and the adhesive layer 11 are laminated, and the isolation layer 13 is formed on one side of the color display layer 12 close to the adhesive layer 11 through a special process.

[0045] By adopting the technical means of the embodiment of the present invention, disposing the isolation layer in the color display layer can further enhance the structural stability of the entire cover film, ensure good adhesion between the color display layer and the adhesive layer, and simplify the processing steps and improve the production efficiency during the manufacturing process.

[0046] As a preferred embodiment, the embodiment of the present invention is further implemented on the basis of any of the above embodiments. Refer to Figure 3 , which is a schematic structural diagram of the third cover film provided by the embodiment of the present invention. The color display layer 12 is formed by pressing the first adhesive layer 121 and the second adhesive layer 122 against each other, and the pressed side portions of the first adhesive layer 121 and the second adhesive layer 122 penetrate each other to form the isolation layer 13.

[0047] In the embodiment of the present invention, by providing the color display layer 12 including the first adhesive layer 121 and the second adhesive layer 122, and pressing the first adhesive layer 121 and the second adhesive layer 122 against each other, the isolation layer 13 is formed by mutual penetration on the pressed side. The density of the isolation layer 13 is relatively dense in the color display layer 12, and can form a function similar to an isolation belt, so that the molecules of the lower half of the color display layer 12 and the adhesive layer 11 cannot penetrate upward through the isolation layer 13 to reach the top surface of the color display layer 12, that is, the lower part is blocked on the surface of the color display layer 12, preventing the color of the adhesive layer 11 from easily penetrating upward to the top surface of the color display layer 12 during the high-temperature lamination of the circuit board, resulting in miscellaneous colors on the top surface of the color display layer 12, thereby improving the quality of the cover film.

[0048] Optionally, the first adhesive layer 121 and the second adhesive layer 122 forming the color display layer 12 are adhesive layers of the same material and color, which can be any color such as red, orange, yellow, green, cyan, blue, purple, black, white, etc. The color of the adhesive layer 11 is different from the background color of the circuit board, and the color display layer 12 is generally selected with a large color difference from the adhesive layer 11.

[0049] By adopting the technical means of the embodiment of the present invention, the cover film has at least the following beneficial effects:

[0050] (1) Prevent molecular interpenetration and enhance the isolation effect: The color display layer is formed by pressing the first adhesive layer and the second adhesive layer against each other. The isolation layer formed by their partial interpenetration during the pressing process has a high degree of compactness, effectively preventing molecular-level penetration between the adhesive layer and the color display layer. This physical isolation mechanism ensures that even under high-temperature lamination processes, the color of the adhesive layer will not easily penetrate to the top surface of the color display layer, thus avoiding the appearance of miscellaneous colors on the surface of the color display layer and maintaining the purity and beauty of the product appearance.

[0051] (2) Enhance structural stability and extend service life: The existence of the isolation layer not only plays an isolation role but also enhances the overall structural strength of the color display layer through its compact characteristics. In complex and changing processing and use environments, such as temperature changes and humidity fluctuations, this enhanced structure can effectively resist deformation or damage caused by external factors, extend the service life of the product, reduce product replacement or repair due to problems such as color change and adhesive failure, and lower production costs.

[0052] (3) Enhance the adhesion of the adhesive layer: The highly compact isolation layer can prevent the adhesive layer from reacting excessively with other materials, thereby enhancing the adhesion of the adhesive layer.

[0053] As a preferred embodiment, the embodiment of the present invention is further implemented on the basis of any of the above embodiments, and the thickness of the isolation layer 13 is greater than or equal to 1 / 10 of the thickness of the color display layer 12.

[0054] In the embodiment of the present invention, the thickness of the isolation layer 13 is further optimized. Since the isolation layer 13 is formed after the first adhesive layer 121 and the second adhesive layer 122 are pressed against each other, and the three together constitute the color display layer 12, it is necessary to control the proportion of the thickness of the isolation layer 13 in the entire color display layer 12. By setting the thickness of the isolation layer 13 formed by the lamination of the first adhesive layer 121 and the second adhesive layer 122 to be more than 1 / 10 of the thickness of the entire color display layer 12, for example, it can be 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 5, 1 / 3, 1 / 2, etc. Of course, it can also be set to other qualified values according to the actual situation, which is not specifically limited here. The greater the lamination thickness of the two adhesive layers, the better the compactness of the isolation layer.

[0055] By adopting the technical means of the embodiments of the present invention, the isolation layer is a structure similar to an isolation belt, and an increase in its thickness can more effectively prevent molecular penetration between the adhesive layer and the color display layer. When the thickness of the isolation layer reaches 1 / 10 or more of the thickness of the color display layer, it forms a thicker barrier between the two, such that during the high-temperature lamination process, the molecules of the adhesive layer need to pass through a thicker isolation layer to reach the top surface of the color display layer, greatly reducing the possibility of penetration. Moreover, with the increase in the thickness of the isolation layer, its stability is also improved, enabling the isolation layer to still maintain a good isolation effect under different environmental changes, thereby enabling the circuit board to maintain the stability of the color display layer under different environments and reducing color changes caused by molecular penetration.

[0056] In addition, an increase in the thickness of the isolation layer helps to improve the uniformity and anti-aging performance of the color display layer, thereby improving the color display quality of the color display layer. Also, with the increase in the thickness of the isolation layer, it can better resist the influence brought about by temperature changes, prevent heat transfer between the adhesive layer and the color display layer due to excessive temperature, and the isolation layer has a certain strength and toughness, which can, to a certain extent, improve the compressive capacity of the circuit board, thereby improving the thermal stability and mechanical properties of the circuit board.

[0057] As a preferred implementation manner, referring to Figure 4 , it is a schematic structural diagram of the fourth cover film provided by the embodiments of the present invention, and the lamination surfaces of the first adhesive layer 121 and the second adhesive layer 122 are in mutually adapted shapes.

[0058] In the embodiments of the present invention, the contact surfaces of the first adhesive layer and the second adhesive layer being laminated are in mutually adapted shapes, which can be mutually occluding shapes scraped by scrapers of different shapes, such as concave-convex shapes, wave shapes, etc., such that the lamination surfaces of the first adhesive layer and the second adhesive layer can be closely attached.

[0059] By adopting the technical means of the embodiments of the present invention, the mutually adapted shapes effectively increase the contact area between the two adhesive layers, making the lamination penetration effect of the laminated part better. The adapted shapes ensure that during the lamination process, the pressure can be evenly distributed over the entire lamination surface, avoiding uneven problems caused by excessive or too small local pressure and preventing local stress concentration, making the penetration and combination between the two adhesive layers more stable.

[0060] As a preferred implementation manner, the embodiments of the present invention are further implemented on the basis of any of the above embodiments, and the roughness of the lamination surfaces of the first adhesive layer 121 and the second adhesive layer 122 is 1 to 10 μm.

[0061] In the embodiment of the present invention, the roughness of the bonding surfaces of the two adhesive layers is further optimized to be within a reasonable roughness range. Among them, the roughness of the bonding surface of the first adhesive layer 121 is controlled to be between 1 and 10 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc. The roughness of the bonding surface of the second adhesive layer 122 is controlled to be between 1 and 10 μm, for example, it can be 1 μm, 1.3 μm, 1.8 μm, 2 μm, 2.6 μm, 3.2 μm, 4 μm, 5 μm, 6.3 μm, 6.9 μm, 7.5 μm, 8.1 μm, 8.5 μm, 9 μm, 9.6 μm, 10 μm, etc. Of course, it can also be set to other qualified values according to the actual situation, and no specific limitation is made here.

[0062] The way to increase the roughness of the bonding surfaces of the two adhesive layers can be to form micro-nano structures such as micro-pits, micro-protrusions, and roughening particles on the surface of the adhesive layer through a special spraying process. Of course, it can also be other ways to increase the surface roughness of the adhesive layer, and no specific limitation is made here.

[0063] By adopting the technical means of the embodiment of the present invention, the two contact surfaces of the pressed adhesive layers have a certain roughness, and the roughness range is approximately 1.0 - 10.0 μm. The greater the roughness, the better the compactness of the lamination. The bonding surface with a certain roughness helps the first adhesive layer and the second adhesive layer to penetrate each other better during the pressing process, and this penetration can make the isolation layer more compact. For example, when the roughness of the bonding surface is large, the contact area between the adhesive layers increases, and the penetration is more sufficient, thereby making the isolation layer more compact. Moreover, appropriate roughness can increase the friction between the adhesive layers, enabling the adhesive layers to interact better during the pressing process, which helps to improve the isolation effect of the isolation layer.

[0064] As a preferred implementation manner, the embodiment of the present invention is further implemented on the basis of any of the above embodiments, and the thickness of the isolation layer is 1 - 10 μm.

[0065] In the embodiment of the present invention, the thickness of the isolation layer is further optimized so that the thickness of the isolation layer 13 is between 1 and 10 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Of course, it can also be set to other qualified values according to the actual situation, and no specific limitation is made here.

[0066] By adopting the technical means of the embodiments of the present invention, by controlling the thickness of the isolation layer within a reasonable range, neither too large nor too small, it can effectively avoid the excessive thickness of the cover film occupying space and affecting the quality of products such as circuit boards, and at the same time avoid the too small thickness of the cover film failing to play a good isolation role. The improvement of the embodiments of the present invention can effectively improve the isolation effect of the isolation layer and improve the quality of products such as the covered circuit boards.

[0067] As a preferred embodiment, the density of the isolation layer 13 is more than 1.5 times the density of the adhesive layer 11.

[0068] In the embodiments of the present invention, the density of the isolation layer 13 is further optimized. By increasing the density of the isolation layer 13, specifically, by controlling the density of the isolation layer 13 to be at least 1.5 times the density of the adhesive layer 11, for example, it can be 1.5 times, 1.6 times, 1.7 times, 1.8 times, 2 times, 2.2 times, 2.3 times, 2.5 times, 2.8 times, 3 times, 3.1 times, etc. Of course, it can also be set to other qualified values according to the actual situation and is not specifically limited here. It can further reduce the probability of small molecules after the high-temperature reaction of the color display layer 12 or the adhesive layer 11 penetrating to the other side and improve the isolation performance.

[0069] More preferably, the density of the isolation layer 13 is 2 g / cm 3 or more. For example, it can be 2 g / cm 3 、3 g / cm 3 、5 g / cm 3 、10 g / cm 3 、15 g / cm 3 、17 g / cm 3 、20 g / cm 3 、25 g / cm 3 、30 g / cm 3 、35 g / cm 3 etc. Of course, it can also be set to other qualified values according to the actual situation and is not specifically limited here.

[0070] By adopting the technical means of the embodiments of the present invention, the increase in the density of the isolation layer means that its internal structure is more compact, which can further reduce the probability of small molecules after the high-temperature reaction of the color display layer or the adhesive layer penetrating to the other side, improve the isolation performance, and reduce the color change on the top surface of the color display layer due to molecular penetration. Moreover, the isolation layer with a higher density can better absorb and reflect light, making the color display layer present a more vivid, bright, pure and uniform color and maintaining the color stability of the color display layer. In addition, the isolation layer with a high density also has better mechanical properties and heat resistance, which helps to improve the mechanical properties and heat dissipation performance of the circuit board.

[0071] Preferably, refer toFigure 5 , which is a schematic structural diagram of the fifth cover film provided by the embodiments of the present invention. The color display layer 12 contains a filler 14; alternatively, the isolation layer 13 contains the filler 14.

[0072] In the embodiments of the present invention, the function of the filler 14 is to increase the density of the isolation layer 13, thereby improving the strength of the isolation layer and better controlling the expansion and contraction of the entire cover film. By filling the filler in the color display layer 12 in the embodiments of the present invention, the formed isolation layer 13 after lamination is also filled with the filler, or by filling the filler 14 in the isolation layer 13 and other methods to control the density of the isolation layer 13, so that the density of the isolation layer 13 is within a reasonable range, further enhancing the isolation effect. The high-density characteristic of the isolation layer provides an excellent physical barrier effect, which not only prevents molecular penetration, but also enhances the strength and stability of the overall structure, reducing problems such as material aging, deformation or delamination that may be caused by long-term exposure to the external environment, thereby significantly extending the service life of the cover film. And it can reduce the quality control steps in the production process to a certain extent and simplify the process flow.

[0073] By adopting the technical means of the embodiments of the present invention, the means of optimizing the density of the isolation layer can further enhance the following advantages of the cover film:

[0074] (1) Enhance structural stability and extend service life: The high-density characteristic of the isolation layer provides an excellent physical barrier effect, which not only prevents molecular penetration, but also enhances the strength and stability of the overall structure, reducing problems such as material aging, deformation or delamination that may be caused by long-term exposure to the external environment, thereby significantly extending the service life of the cover film.

[0075] (2) Improve weather resistance and adapt to diverse applications: The high-density isolation layer can more effectively resist the erosion of external factors such as ultraviolet rays, moisture, and oil stains, protecting the adhesive layer from damage. This enables the cover film to maintain good adhesive performance in outdoor or harsh environments such as high humidity and high pollution.

[0076] As a preferred implementation manner, the embodiments of the present invention are further implemented on the basis of any of the above embodiments, and the glass transition temperature Tg of the isolation layer is greater than or equal to 230 °C.

[0077] In the embodiment of the present invention, when the isolation layer is separately formed between the color display layer and the adhesive layer, the isolation layer 13 may need to be made of a high-temperature resistant material so that the cover film can better withstand the high-temperature environment without changing its properties. Preferably, the glass transition temperature Tg of the isolation layer 13 is greater than or equal to 230 °C. For example, it can be 230 °C, 235 °C, 240 °C, 250 °C, 255 °C, 260 °C, 265 °C, 270 °C, 280 °C, 300 °C, 350 °C, 500 °C, etc. Of course, it can also be set to other qualified values according to the actual situation, and no specific limitation is made here.

[0078] Preferably, the material of the isolation layer 13 is made of high-performance organic polymer materials such as PI (polyimide) and TPI (thermoplastic polyimide).

[0079] The PI material has the advantages of high temperature resistance, high insulation, good mechanical properties, chemical corrosion resistance, etc. On the basis of the PI material, the TPI material has more excellent thermoplasticity and is easy to process and form. By setting the isolation layer 13 to be made of PI or TPI material, it can effectively ensure that the isolation layer has a high glass transition temperature and ensure the high temperature resistance of the isolation layer.

[0080] By adopting the technical means of the embodiment of the present invention, by setting the glass transition temperature Tg of the isolation layer in the cover film to be greater than or equal to 230 °C, it can ensure that the isolation layer can still maintain its physical form and mechanical properties in a high-temperature environment, effectively prevent structural deformation or failure caused by temperature rise, and thus enhance the structural stability of the entire system or product. Moreover, the high glass transition temperature also means that the isolation layer can remain solid at a higher temperature, effectively isolate the direct heat conduction of the high-temperature heat source to the internal components or materials, reduce heat transfer, protect sensitive components from high-temperature damage, ensure that the components or reactions of the circuit board operate at a temperature close to their optimal working temperature, extend the service life, and improve the performance and working efficiency of the overall system. The isolation layer is made of a high-temperature resistant material and has good chemical stability, and can resist the erosion of various chemical substances, which makes the isolation layer not easily corroded in a high-temperature environment and further improves the durability of the product.

[0081] As a preferred implementation manner, the embodiment of the present invention is further implemented on the basis of any of the above embodiments, and the light transmittance of the cover film 10 is less than or equal to 60%.

[0082] It should be noted that the light transmittance is the ability of light of a specific wavelength to pass through the cover film, usually expressed as a percentage (the ratio of the transmitted light intensity to the incident light intensity). It is measured according to the ISO 13468 standard, and the compensation method is used for measurement with the light source D65. The light transmittance of the cover film can be tested by a double-beam scanning spectrophotometer.

[0083] In the embodiment of the present invention, after adding the isolation layer 13, the light transmittance of the covering film 10 is less than or equal to 60%, for example, it can be 60%, 55%, 50%, 48%, 45%, 43%, 40%, 35%, 30%, 25%, 21%, 17%, 14%, 12%, 10%, 8%, 6%, 3%, 0%, etc. While enhancing the isolation effect, the isolation layer 13 also enhances the shielding property, reduces the light transmittance, makes the color of the adhesive layer 11 invisible, enhances the light-shielding performance, and effectively shields the surface of products such as circuit boards.

[0084] By adopting the technical means of the embodiment of the present invention, the light transmittance of the covering film is less than or equal to 60%. It can not only effectively shield the complex circuits and components on the surface of the circuit board, reduce visual interference, make the appearance of the final product cleaner and more beautiful, but also enhance the concealment of the product, contribute to protecting the design details and intellectual property rights of the product, and prevent technology leakage. Moreover, the low light transmittance of the color display layer ensures that light is difficult to penetrate the covering film, effectively avoids the light leakage problem caused by light transmission, can enhance the light-shielding performance, reduce light pollution, and improve the display quality.

[0085] As a preferred embodiment, the color display layer is a white ink layer or a film layer, and the adhesive layer is a black film layer.

[0086] By adopting the technical means of the embodiment of the present invention, through optimizing the color difference between the surfaces of the color display layer and the adhesive layer, the color difference between the two is made more obvious, so that it can effectively play the role of shielding products such as circuit boards, and can also add a unique visual effect and aesthetic feeling to the product, improving the aesthetic degree of the product.

[0087] As a preferred embodiment, the embodiment of the present invention is further implemented on the basis of any of the above embodiments. Refer to Figure 6 , which is a schematic structural diagram of the sixth covering film provided by the embodiment of the present invention. The covering film 10 further includes a carrier layer 15, and the carrier layer 15 is detachably disposed on the surface of the color display layer 12 away from the isolation layer 13.

[0088] In the embodiment of the present invention, generally when laminating the covering film, a carrier layer 15 is set as an intermediate medium. The carrier layer 15 is used to carry and protect the covering film, so that the covering film is not damaged by external contact or collision, etc. After laminating the covering film with an application carrier such as a circuit board substrate at a high temperature through the carrier layer 15, the carrier layer 15 is peeled off.

[0089] Specific examples are used to test the various performances of the ordinary covering film and the covering film with the structure of the embodiment of the present invention respectively.

[0090] The test data of the cover film S of the structure of the embodiment of the present invention and the control cover film R are shown in Table 1:

[0091] Table 1

[0092]

[0093] It should be noted that the density ratio refers to the ratio of the density of the isolation layer to the density of the adhesive layer. When the ratio is greater than 1, it means that the density of the isolation layer is greater than the density of the adhesive layer, and when the ratio is less than 1, it means that the density of the isolation layer is less than the density of the adhesive layer.

[0094] After the high-temperature process of the circuit board, the comparison results of the isolation effect and the bending resistance performance of the cover film S of the structure of the embodiment of the present invention and the control cover film R are shown in Table 2:

[0095] Table 2

[0096] Covering film Isolation effect Flexural resistance performance Sample S1 The uniformity is good and there are no miscellaneous colors in the color display layer Excellent Sample S2 The uniformity is good and there are no miscellaneous colors in the color display layer Excellent Sample S3 The uniformity is good and there are no miscellaneous colors in the color display layer Excellent Sample S4 The uniformity is good and there are no miscellaneous colors in the color display layer Excellent Sample S5 The uniformity is good and there are no miscellaneous colors in the color display layer Good Control R1 The uniformity is poor and there are miscellaneous colors in the color display layer Excellent Control R2 The uniformity is good and there are no miscellaneous colors in the color display layer Unqualified

[0097] It can be seen from the experimental data in Table 2 that compared with the cover film samples in the comparative example, the cover film of the present invention has a better isolation effect, the color uniformity of the color display layer is better, there are no defects or minor defects, after the high-temperature process, the mutual molecular penetration rate between the color display layer and the adhesive layer is lower, there is obviously no variegated color in the white color display layer, and an isolation layer with a certain thickness does not affect the overall bending resistance performance of the cover film. For the sample of Comparative Example R1, although it has an isolation layer, its thickness is too small and the isolation effect is poor, and there is still a penetration phenomenon after the high-temperature process. For the sample of Comparative Example R2, although the isolation effect is good, due to its too large thickness, it seriously affects the bending resistance performance of the cover film itself. In summary, the cover film provided with an isolation layer within a certain thickness range in this application has more excellent performance.

[0098] It should be noted that in this embodiment, the isolation effect is judged by the direct observation method, and the bending resistance performance is judged by the IPC 6013A 3.6.1 test method. The evaluation between the three grades of excellent, good and unqualified is distinguished by the number of different static bending tests, and the specific measurement criteria are set according to the actual needs of the manufacturer.

[0099] See Figure 7 , which is a schematic structural diagram of a circuit board provided by an embodiment of the present invention. The embodiment of the present invention also provides a circuit board 20, the circuit board 20 includes a circuit board substrate 21, and a cover film 10 as described in any of the above embodiments, and the cover film 10 is pressed together with the circuit board substrate 21.

[0100] It should be noted that the cover film includes an adhesive layer 11, a color display layer 12 and an isolation layer 13, and its specific structure can refer to the structure of the cover film described in any of the above embodiments, and will not be repeated here.

[0101] By adopting the technical means of the embodiments of the present invention, the structure of the cover film covering the circuit board substrate is improved. An isolation layer is added between the adhesive layer and the color developing layer of the cover film, and the thickness ratio of the isolation layer is controlled and the density is high, preventing the molecular interpenetration between the adhesive layer and the color developing layer, avoiding uneven color development or the generation of miscellaneous colors in the color developing layer, and improving the stability and bonding force of the adhesive layer while not affecting the bending resistance performance of the circuit board after lamination, and prolonging the service life of the cover film. Through the structural improvement of the cover film, this application is applicable to the production of high-frequency and high-density circuit boards, can effectively improve the quality of the cover film product, and then improve the quality and storage effect of the circuit board product, and reduce the defective rate of the circuit board product.

[0102] The above is the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A covering film, characterized in that: It comprises an adhesive layer and a color development layer. An isolation layer is arranged on the side of the color development layer close to the adhesive layer, and the thickness of the isolation layer accounts for 1 / 8 to 2 / 5 of the total thickness of the covering film.

2. The covering film according to claim 1, characterized in that The color development layer, the isolation layer and the adhesive layer are stacked in sequence along the thickness direction.

3. The covering film according to claim 1, characterized in that The isolation layer is arranged in the color development layer and is located at a side close to the bonding layer.

4. The covering film according to claim 3, characterized in that The color development layer is formed by pressing a first adhesive layer and a second adhesive layer against each other, and the pressed side portions of the first adhesive layer and the second adhesive layer penetrate each other to form the isolation layer.

5. The covering film according to claim 4, characterized in that The pressing surface of the first adhesive layer and the pressing surface of the second adhesive layer are shapes that match each other.

6. The covering film according to claim 4, characterized in that The roughness of the pressing surface of the first adhesive layer and the pressing surface of the second adhesive layer are both 1-10 μm.

7. The covering film according to claim 1, characterized in that The thickness of the isolation layer is 1-10 μm.

8. The covering film according to claim 1, characterized in that The density of the isolation layer is more than 1.5 times the density of the adhesive layer.

9. The covering film according to claim 8, characterized in that The density of the isolation layer is 2 g / cm 3 above.

10. The covering film according to claim 2, characterized in that The glass transition temperature Tg of the isolation layer is greater than or equal to 230°C.

11. The covering film according to claim 1, characterized in that: The light transmittance of the covering film is less than or equal to 60%.

12. The covering film according to claim 1, characterized in that The covering film further comprises a carrier layer, and the carrier layer is disposed on a surface of the color developing layer on a side away from the isolation layer in a releasable manner.

13. A circuit board, characterized in that: The circuit board comprises a circuit board substrate and a covering film as claimed in any one of claims 1 to 12, wherein the covering film is pressed against the circuit board substrate.

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