TWI707771B - Highly reflective ultrathin cover film for led and manufacturing method thereof - Google Patents

Abstract

The present invention provides a highly reflective ultrathin cover film and manufacturing method thereof, wherein the highly reflective ultrathin cover film comprises a highly transparent polyimide layer, a metal plating layer, and an adhesive layer. The highly reflective ultrathin cover film provided by the present invention has advantages of good bonding, light weight, great bending resistance, long life time and excellent optical performance, and the reflectivity can reach more than 90%, up to 98% at 450 nm.

Description

Highly reflective ultra-thin covering film for LED and manufacturing method thereof

The present invention relates to a highly reflective ultra-thin cover film for LED (light emitting diode).

With the development of the information and communication industries driving the microelectronics industry, flexible printed circuit boards (FPC) emerged and developed vigorously, and are widely used in many fields such as mobile phones, liquid crystal displays, and tablets. . The biggest difference between a flexible printed circuit board and a PCB (Printed Circuit Board, rigid printed circuit board) is that the former uses a cover film, whose function exceeds the solder mask used for PCB. It not only has a solder mask effect, but also protects the FPC from dust, Moisture, chemical erosion, and can reduce the impact of stress in the bending process. In addition, with the development of the FPC market, cover films have been given more functions. The special cover film with reflective effect is vigorously applied in the field of LED and light bar. In the context of the current rise in global energy shortage concerns, energy conservation is an important issue facing us in the future. In the field of lighting, the application of LED light-emitting products is attracting the attention of the world. As a new type of green light source product, LED is bound to be the future development trend. The 21st century will enter the era of new lighting source represented by LED.

There are two main types of reflective cover films for LEDs currently on the market:

1. White ink type cover film, this cover film is usually composed of white ink layer and adhesive layer with extremely low dielectric constant and dielectric loss, extremely high ion purity, high reflectivity, low transmittance, low The ultra-thin white cover film with surface gloss, high flexibility, low rebound force and high surface hardness is especially suitable for use in high-performance LED lighting of the soft-hard combination version. This kind of cover film can achieve a very low thickness (about 10μm), but the disadvantage is that the reflectivity cannot reach more than 90%, and it tends to produce yellowing during the high-temperature process, resulting in a further drop in reflectivity and long-term It is easier to crack or even fall off when used, which will affect the service life;

2. White polyimide type cover film, this kind of cover film also has the problem of yellowing, and because of the various types of polyimide, the group containing bisphenol A and other groups that cause the film to yellow will cause the product to undergo high temperature processing The back reflectivity decreases, and the use of high-temperature yellowing resistant polyimide requires consideration of cost; at the same time, after adding white pigments and fillers to the polyimide, the elastic modulus and elongation of the polyimide itself Physical properties such as, tensile strength, etc. will be reduced; in addition, in order to cover the underlying circuit, white polyimide is difficult to achieve ultra-thin thickness, which has cost problems. If it is ultra-thin thickness, there will also be processing and operability problems.

There are many problems with the above two kinds of conventional cover films for LEDs. At present, the industry is designing new reflective covering films. For example, Chinese Patent No. 201710365861.3 discloses a high-haze colored ultra-thin high-frequency covering film and its preparation method, and Chinese Patent No. 201720667887.9 discloses a white covering film for LED substrates and its use. The white cover film LED substrate, Chinese Patent No. 201410031886.6 discloses a cover protection film for printed circuit boards with high temperature resistance and high reflectivity. However, the technical solutions provided by the above patents are difficult to meet the requirements of high reflectivity (above 90%) and ultra-thin thickness of the cover film.

In order to solve the above-mentioned cover film problem, the present invention provides a highly reflective ultra-thin cover film, which includes: a transparent polyimide layer with a thickness of 3 to 50 μm; a metal layer formed on the transparent polyimide layer On the surface; and an adhesive layer with a thickness of 3 to 100 μm is formed on the surface of the metal layer so that the metal layer is located between the transparent polyimide layer and the adhesive layer.

300℃、硬度為3H以上(例如3H、4H、5H、6H...等)、穿透率

90%、反射率

5%、L*值為90至100、a*值及b*值各為-2至2、霧度(Haze)<1%。 In a specific embodiment, the thickness of the transparent polyimide layer is 5 to 12 μm, and the glass transition temperature (Tg)

300℃, hardness above 3H (such as 3H, 4H, 5H, 6H... etc.), penetration rate

90%, reflectivity

5%, L* value is 90 to 100, a* value and b* value are -2 to 2 respectively, haze (Haze)<1%.

In a specific embodiment, the thickness of the metal layer is 0.01 to 3 μm.

In a specific embodiment, the metal used in the metal layer is selected from at least one of gold, silver, copper, aluminum, and nickel. In one embodiment, the metals used in the metal layer are silver, aluminum, and nickel.

In a specific embodiment, the thickness of the adhesive layer is 6 to 50 μm.

In one embodiment, the highly reflective ultra-thin cover film includes an optical film, which is formed on the other surface of the transparent polyimide layer so that the transparent polyimide layer is located on the optical film and the metal Between layers. In a specific embodiment, the optical film is a PET optical film.

In a specific embodiment, the highly reflective ultra-thin cover film includes a release layer such as a carrier film, a release film or a release paper, which is formed on the other surface of the adhesive layer.

In a specific embodiment, the carrier film is a low-adhesion carrier film, and the release film is at least one of a PET fluoroplastic release film, a PET silicone oil-containing release film, a PET sub-light release film, and a PE release film One kind, the release paper is PE coated paper.

95MPa、該高反射性超薄覆蓋膜之伸長率係

5%、該高反射性超薄覆蓋膜之彈性模量係

3000MPa、該高反射性超薄覆蓋膜之反射率

90%、該高反射性超薄覆蓋膜之穿透率

1%。該高反射性超薄覆蓋膜之L*值為90至100，例如90、91、92、93、94、95、96、97、98、99、100，a*值及b*值各為-1至7，例如-1、0、1、2、3、4、5、6、7。 In a specific implementation aspect, the tensile strength of the highly reflective ultra-thin cover film is

95MPa, the elongation of the highly reflective ultra-thin cover film is

5%, the elastic modulus of the highly reflective ultra-thin cover film

3000MPa, the reflectivity of the highly reflective ultra-thin cover film

90%, the penetration rate of the highly reflective ultra-thin cover film

1%. The L* value of the highly reflective ultra-thin cover film is 90 to 100, such as 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, a* value and b* value are each- 1 to 7, such as -1, 0, 1, 2, 3, 4, 5, 6, 7.

In one embodiment, the adhesive layer includes an adhesive, and the adhesive is selected from epoxy adhesive, acrylic adhesive or pressure sensitive adhesive.

The present invention also provides a method for manufacturing a highly reflective ultra-thin cover film, which includes: coating polyimide on the surface of the optical film to form the transparent polyimide layer; and applying the polyimide to the transparent polyimide The metal layer is formed on the surface of the layer; the adhesive is coated on the surface of the release layer to form the adhesive layer; the adhesive layer is attached to the metal layer to obtain the highly reflective ultra-thin cover membrane.

The present invention further provides a method for manufacturing a highly reflective ultra-thin cover film, which includes: coating polyimide on the surface of an optical film to form the transparent polyimide layer; and applying polyimide to the transparent polyimide The metal layer is formed on the surface of the layer; the adhesive is coated on the metal layer to form an adhesive layer; the release layer is attached to the adhesive layer to obtain the highly reflective ultra-thin covering film.

In a specific embodiment, a metal layer is formed on the surface of the transparent polyimide layer by an evaporation method or a sputtering method. In a specific embodiment, the metal layer is formed by an evaporation method.

It can be seen from the above that the highly reflective ultra-thin cover film with a three-layer structure provided by the present invention includes a transparent polyimide (PI) protective layer, a metal layer (ie, a highly reflective layer) and an adhesive layer, and can An optical film is set on the surface of the transparent polyimide (PI) layer, on the adhesive layer A release layer is provided on the lower surface. By designing a transparent polyimide (PI) protective layer, the anti-scratch and anti-oxidation ability of the reflective film is improved, and the life span is increased; the high reflection effect of the reflective film is achieved by setting the metal layer; and the covering film is improved by setting the adhesive layer The scope of application is convenient for the use of covering film. The highly reflective ultra-thin covering film provided by the present invention has the advantages of high reflectivity, good combination, light and thin materials, bending resistance, long service life, excellent optical performance, etc., and the reflectivity can reach more than 90%.

1.‧‧Transparent polyimide layer

2‧‧‧Metal layer

3‧‧‧Adhesive layer

4‧‧‧Optical film

5‧‧‧Release layer

Figure 1 is a schematic diagram of the structure of the highly reflective ultra-thin cover film of the present invention.

The following is a description of the implementation of the present invention through specific specific implementation modes, and those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this manual are only used to match the contents disclosed in the manual for the understanding and reading of those familiar with the art, and are not intended to limit the implementation of the present invention Therefore, it does not have any technical significance. Any structural modification, proportional relationship change, or size adjustment should still fall within the scope of the present invention without affecting the effects and objectives that can be achieved. The technical content disclosed by the invention can be covered. At the same time, the words such as "一" and "上" cited in this specification are only for ease of description and are not used to limit the scope of implementation of the present invention. There is no change or adjustment of the relative relationship. Substantial changes to the technical content should also be regarded as the scope of the present invention. In addition, All ranges and values herein are inclusive and combinable. Any value or point falling within the range described herein, for example, any integer can be used as the minimum or maximum value to derive the lower range and so on.

As shown in Figure 1, it is a schematic diagram of the structure of the highly reflective ultra-thin cover film of the present invention, including a transparent polyimide (PI) layer 1, a metal layer 2 and an adhesive layer 3, and may further include an optical film 4 and release layer 5.

The transparent polyimide layer 1 is formed of a modified polyimide solution, and the modified polyimide solution is colorless and transparent. Solvents such as N-methylpyrrolidone (NMP), γ-butyrolactone (GBL) or dimethylformamide (DMF) are usually used. The raw materials are mainly composed of polyimide monomer and solvent.

The transparent polyimide layer 1, as a protective layer, has a thickness of 3 to 50 μm, such as 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45 or 50 μm, and the preferred thickness is 5 to 12 μm. Polyimide material has very low water absorption rate, moisture is not easy to invade, and has excellent reliability in high temperature and high humidity environments, long service life, bending resistance, light and thin materials, and good processing performance; polyimide There are many types of imines, and they have high glass transition temperature (Tg), high hardness, high temperature resistance of the system, high L* value, low a*, b* value, transparency, low haze, low expansion coefficient, and low rebound Polyimide materials with high strength, low thermal conductivity and low refractive index are preferred.

300℃，並且在高溫狀態下，其物性能夠保持穩定。 The glass transition temperature directly affects the use performance and process performance of the material. When the polymer undergoes glass transition, many physical properties such as modulus, enthalpy, thermal expansion coefficient, refractive index, thermal conductivity, dielectric constant, dielectric loss And mechanical losses will change drastically. Therefore, the selected polyimide needs to reach a higher glass transition temperature, such as Tg

300℃, and its physical properties can remain stable at high temperature.

5%)、高L*值(90至100)、低a*及b*值(-2至2)、極低霧度(Haze<1%)的透明聚醯亞胺，並且透明聚醯亞胺在QUV照射240小時後上述光學特性變化率極小。 At the same time, in order to reduce the absorption and scattering of light, choose high hardness (above 3H), low refractive index, high transmittance (90%), low reflectivity (

5%), high L* value (90 to 100), low a* and b* value (-2 to 2), very low haze (Haze<1%) transparent polyimide, and transparent polyimide The rate of change of the above-mentioned optical properties of amine after 240 hours of QUV irradiation is extremely small.

At the same time, in order to achieve a very low surface roughness on the surface of the cover film (ie the polyimide surface), it is necessary to coat the transparent polyimide on the release layer with a smooth surface during product preparation. The material of is preferably an optical grade PET release film that has undergone pre-shrinking treatment to ensure the reflectivity of the reflective layer; alternatively, other release layers (fluorine or halogen release treatment) can also be used.

When coating, it is necessary to consider the volatilization point of the solvent in the polyimide solution to set the temperature of the preparation process, and the maturation stage of the finished product also needs to be cured according to the boiling point of the solvent in the finished material.

The metal layer 2 is used as a reflective film and has a thickness of 0.01 to 3.0 μm, such as 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5 Or 3.0 μm, preferably the thickness is about 0.10-0.2 μm. Generally, metals have a large extinction coefficient. When the light beam is incident on the metal surface from the air, the amplitude of the light entering the metal is rapidly attenuated, so that the light energy entering the metal is correspondingly reduced, while the reflected light energy increases. Among them, the higher the extinction coefficient Larger, the faster the light amplitude decays, the less light energy enters the metal, and the higher the reflectivity. For the metal layer 2 of the present invention, it is preferable to use a metal with a large extinction coefficient and relatively stable optical properties as the material of the metal layer 2. Generally, the metal material commonly used in the ultraviolet light region is aluminum Al, and aluminum Al, nickel Ne, and silver Ag are commonly used in the visible light region, while gold Au, silver Ag and copper Cu are commonly used in the infrared light region. The above metals can be selected as the metal layer according to requirements 2 of materials. In view of the application range of the reflective film, the present invention preferentially uses metals such as silver Ag, aluminum Al, and nickel Ne. In addition, since the metal layer 2 is provided as the reflective film, the composite structure including the transparent polyimide layer and the reflective film can have high transmittance and low reflectivity.

Moreover, in the present invention, the thickness of the metal layer 2 is directly proportional to the reflectivity. For example, when the metal layer 2 is a silver layer, the reflectivity can reach 94% when the thickness is 0.1 μm; the reflectivity can reach 98% when the thickness is 0.15 μm ; And if you continue to increase the thickness of the silver layer, the reflectivity basically remains at about 98%.

The metal coating methods mainly include evaporation, sputtering, electroplating, and so on. The evaporation method is a process in which the material to be formed into a film is placed in a vacuum for evaporation or sublimation, so that it is deposited on the surface of the device. The heating methods used in vacuum evaporation mainly include resistance heating, electron beam heating, radio frequency induction heating, arc heating and laser heating. Regardless of the heating method, the material used as the evaporation source is required to have the following properties: high melting point, low vapor pressure, no chemical reaction or mutual solubility with most evaporation materials at the evaporation temperature, and a certain mechanical strength at the same time. The sputtering method is to pass in a suitable inert gas as a medium in a vacuum environment, and rely on the inert gas to accelerate the impact on the target material, so that the atoms on the surface of the target material are knocked out and a coating film is formed on the surface. The electroplating method is to make the metal ions in the electrolyte swim to the cathode under the action of the electric field, and reduce and deposit the metal neutral atoms at the plated part of the drill bit to form a plating layer on the surface of the device.

Both the evaporation method and the sputtering method are used to deposit various metal and non-metal films on the surface of the device through distillation or sputtering under vacuum conditions. In this way, a very thin surface coating can be obtained, and at the same time, it has fast speed and adhesion. Outstanding advantages of good power. Compared with the electroplating method, the two coating methods, the evaporation method and the sputtering method, are more environmentally friendly in process, and the metal adhesion in the coating formed by the evaporation method and the sputtering method is higher. In view of the required characteristics of the highly reflective ultra-thin coating film of the present invention, the metal coating is preferably carried out by the vapor deposition method.

The adhesive layer 3 serves as a primer layer that does not affect the reflectivity of the overall optical film, which can increase the application range of the reflective film and is convenient to use. The thickness of the adhesive layer 3 can be 3 to 100 μm, such as 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 , 70, 75, 80, 85, 90, 95 or 100μm, preferably 6 to 50μm. conventional The reflective film is a metal layer directly processed on the substrate or device, which is easy to detach, resulting in a low service life. Adding an adhesive layer to it can reduce this loss and increase the scope of use of the reflective film.

In the present invention, the adhesive layer 3 includes an adhesive, and the adhesive usually adopts a conventional cover film adhesive (epoxy adhesive system), in which rubber, epoxy resin, flame retardant and other ingredients are added; in addition, acrylic Adhesives, PSA (pressure sensitive adhesive), etc. are used as adhesives.

The highly reflective ultra-thin cover film of the present invention can be additionally provided with an optical film 4 on the surface of the transparent polyimide layer 1, preferably a PET optical film. When polyimide is applied to the optical film 4, the surface roughness of the optical film 4 will directly affect the reflectance of the product surface, so the surface of the optical film material needs to have a very small surface roughness, preferably smooth, transparent, and roughness Very low (for example, Rz is between 0.01 μm and 5.0 μm, Ra is between 0.01 μm and 1.0 μm) negligible optical film to meet the physical property requirements of transparent polyimide as much as possible.

The highly reflective ultra-thin cover film of the present invention can also be provided with a release layer 5 under the adhesive layer 3. The release layer 5 closely adheres to the adhesive surface of the adhesive layer 3, which not only protects the adhesive surface from impurities, but also Convenient for no sticking during winding.

The manufacturing method of the highly reflective ultra-thin cover film of the present invention can be carried out as follows, but is not limited to this:

the first method:

Step 1: Coating a polyimide material on the optical film 4 to form a transparent polyimide layer 1;

Step 2: Then, metal is deposited on the surface of the transparent polyimide layer 1 by evaporation or sputtering to form the metal layer 2;

Step 3: Coating adhesive on the release layer 5 to form the adhesive layer 3;

Step 4. Laminate the adhesive layer 3 produced in Step 3 with the metal layer 2 produced in Step 2 to obtain a highly reflective ultra-thin covering film.

The second method:

Step 1: Coating a polyimide material on the optical film 4 to form a transparent polyimide layer 1;

Step two: plating metal on the surface of the transparent polyimide layer 1 by evaporation or sputtering to form the metal layer 2;

Step 3: Coating adhesive on the metal layer 2 to form the adhesive layer 3;

Step four: stick the release layer 5 on the adhesive layer 3 to obtain a highly reflective ultra-thin covering film.

Hereinafter, the present invention will illustrate the details through examples of embodiments. However, the interpretation of the present invention should not be limited to the description of the following embodiments.

In order to facilitate the understanding of the advantages of the present invention, the highly reflective ultra-thin covering films prepared in Examples 1 to 5 were compared with other products on the market in Comparative Examples 1 and 2. The test results are shown in Table 1 below. Show.

The transparent polyimide layer selected in the examples is formed by a polyimide solution using γ-butyrolactone as a solvent. The glass transition temperature of the polyimide film is Tg>300°C and the hardness is 4H, reflectance of 0.12%, transmittance of 91.1%, L* value of 95.5, a* value of 0.56, b* value of -0.15, haze of 0.9%. The adhesive layer selected includes epoxy adhesive.

Table 1

In Table 1, the surface hardness is measured by the GB/T 6739-2006 test method, the L* value, a* value and b* value are measured by the ASTM E313 test method, the transmittance, reflectance and Haze is measured by ISO 14782 test method, tensile strength, elongation and elastic modulus are measured by ASTM D882 test method, and dielectric strength is measured by ASTM D149 test method.

The results in Table 1 show that the silver-plated high-reflective covering film of the present invention has the highest reflectivity, reaching about 95%, compared with the aluminum-plated and nickel-plated high-reflective covering film, and is significantly better than the other two white inks. Type and white PI type cover film.

In order to highlight that the present invention has better reliability and reliability than other products on the market, the highly reflective covering films of Examples 1 and 4 and other products on the market of Comparative Examples 1 and 2 are compared. The test results As shown in Table 2 below.

Table 2

It can be seen from Table 2 above that, compared with the white PI type and white ink type cover films on the market, the high reflectivity cover film of the present invention has better reflectivity than the latter under normal conditions. Among them, Example 1 (silver Layer 0.10um) the reflectivity under normal conditions is 94.6%, Example 4 (silver layer 0.15um) under normal conditions reflectivity is 98.10%; and, after SMT*3, the reflectivity of Example 1 (silver layer 0.10um) is 94.1% (silver 0.10um) um), Example 4 (silver layer 0.15um) reflectivity 98.01%, and after vulcanization test, Example 1 (silver layer 0.10um) reflectivity 93.8% (silver 0.10um), Example 4 (silver (Layer 0.15um) reflectivity of 97.99%, which shows that the silver-plated high-reflective covering film of the present invention has excellent high temperature resistance and sulfuration resistance, and good reliability.

1.‧‧Transparent polyimide layer

2‧‧‧Metal layer

3‧‧‧Adhesive layer

4‧‧‧Optical film

5‧‧‧Release layer

Claims (22)

A highly reflective ultra-thin covering film, which includes: a transparent polyimide layer with a thickness of 3 to 50 μm, with

90% transmittance; a metal layer is formed on the surface of the transparent polyimide layer; and an adhesive layer with a thickness of 3 to 100 μm is formed on the surface of the metal layer to make the metal layer Located between the transparent polyimide layer and the adhesive layer, the reflectivity of the highly reflective ultra-thin covering film

90%. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the thickness of the transparent polyimide layer is 5 to 12 μm. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the glass transition temperature of the transparent polyimide layer

300°C. The high-reflective ultra-thin cover film described in the first item of the scope of patent application, wherein the hardness of the transparent polyimide layer is 3H or more. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the reflectivity of the transparent polyimide layer

5%. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the L* value of the transparent polyimide layer is 90 to 100, and the a* value and b* value are -2 to 2 respectively. The high-reflective ultra-thin cover film described in the first item of the scope of patent application, wherein the haze of the transparent polyimide layer is less than 1%. As described in the first item of the scope of patent application, the highly reflective ultra-thin cover film, wherein the thickness of the metal layer is 0.01 to 3.0 μm. The high-reflective ultra-thin coating film described in the first item of the scope of patent application, wherein the metal forming the metal layer is at least one selected from the group consisting of gold, silver, copper, aluminum and nickel. The highly reflective ultra-thin cover film described in the first item of the scope of patent application, wherein the thickness of the adhesive layer is 6 to 50 μm. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, including an optical film, is formed on the surface of the transparent polyimide layer so that the transparent polyimide layer is located between the optical film and the Between metal layers. The highly reflective ultra-thin cover film described in item 11 of the scope of patent application, wherein the optical film is a PET optical film. The high-reflective ultra-thin covering film described in item 1 of the scope of patent application includes a release layer, which is formed on the surface of the adhesive layer, so that the adhesive layer is located between the metal layer and the release layer . The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the tensile strength of the high-reflective ultra-thin cover film is

95MPa. The high-reflective ultra-thin covering film as described in item 1 of the scope of patent application, wherein the elongation of the high-reflective ultra-thin covering film is

5%. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the elastic modulus of the high-reflective ultra-thin cover film is

3000MPa. The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the transmittance of the high-reflective ultra-thin cover film

1%. The highly reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the L* value of the highly reflective ultra-thin cover film is 90 to 100, and the a* value and b* value are each -1 to 7 . The high-reflective ultra-thin cover film described in item 1 of the scope of patent application, wherein the adhesive layer includes an adhesive, and the adhesive is selected from the group consisting of epoxy adhesive, acrylic adhesive or pressure Sensitive glue. A method for manufacturing a highly reflective ultra-thin cover film as described in item 1 of the scope of patent application, comprising: coating polyimide on the surface of the optical film to form the transparent polyimide layer; The metal layer is formed on the surface of the transparent polyimide layer; an adhesive is applied on the surface of the release layer to form the adhesive layer; and the adhesive layer is attached to the metal layer to obtain the high Reflective ultra-thin cover film. A method for manufacturing a highly reflective ultra-thin cover film as described in item 1 of the scope of patent application, comprising: coating polyimide on the surface of the optical film to form the transparent polyimide layer; The metal layer is formed on the surface of the transparent polyimide layer; an adhesive is applied on the metal layer to form an adhesive layer; and the release layer and the adhesive layer are attached to obtain the highly reflective ultra-thin Cover film. According to the method for manufacturing a highly reflective ultra-thin cover film described in item 20 or 21 of the scope of the patent application, the metal layer is formed on the surface of the transparent polyimide layer by an evaporation method or a sputtering method.

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