CN110591581A - A kind of coating covering film and its preparation method and application - Google Patents

Abstract

The present invention provides a coating covering film and a preparation method and application thereof, comprising a polyimide film and a release paper arranged on one side of the polyimide film, wherein an adhesive is arranged between the polyimide film and the release paper; wherein the coating covering film further comprises a protective coating arranged on the other side of the polyimide film. The coating covering film provided by the present invention has excellent softness and heat aging resistance, and after being treated by desmear and plasma processes, its mechanical properties, folding resistance and reliability do not decrease, and can meet the processing requirements and performance requirements of the rigid-flexible board for the covering film.

Description

A kind of coating covering film and its preparation method and application

technical field

The invention belongs to the technical field of covering films, and relates to a coating covering film, a preparation method and application thereof.

Background technique

Reducing the assembly size and weight of electronic products, avoiding connection errors, increasing assembly flexibility, improving reliability and realizing three-dimensional installation under different assembly conditions are inevitable requirements for the increasing development of electronic products. The birth and development of rigid circuit board (PCB) and flexible circuit board (FPC) gave birth to the new product of soft and hard board; soft and hard board is the process of lamination of flexible circuit board and rigid circuit board. Combined according to relevant process requirements, a circuit board with FPC characteristics and PCB characteristics is formed. Rigid-flex board combines the advantages of flexible circuit board and rigid circuit board, which can realize three-dimensional installation and effectively use the installation space. The emergence of rigid-flex boards provides a new connection method for the interconnection between electronic components. With the development of electronic information technology and people's demand for electronic equipment tends to be light, small and multi-functional, rigid-flex boards are just right in line with this trend.

However, the technical threshold of rigid-flex boards is high and the manufacturing process is complicated. Its processing flow must go through high-strength desmear (drill removal) and plasma (plasma treatment) processes. Most of the desmear processes in circuit board factories use high-strength alkali. Potassium permanganate solution treatment, and plasma will cause inevitable damage to organic materials. Ordinary cover films use polyimide film (PI film) as the base film. Polyimide is usually not resistant to alkali. After desmear and plasma processes, it is easy to cause the PI film to be bitten, thus making the cover film The mechanical properties, folding resistance and reliability are reduced. At present, many manufacturers in the industry increase the thickness of the PI film to slow down the impact of PI film biting on the performance of the cover film in the desmear and plasma processes. However, this method does not meet the development requirements of thin and short electronic products, and will make The overall rigidity of the cover film increases the cost of the cover film considerably.

CN102083271A discloses a cover film for a printed circuit board, comprising a core layer, a black composite material layer with a low refractive index and an adhesive layer for adhering the cover film to a printed circuit board, the core layer fixing clip Placed between the composite material layer and the adhesive layer, the composite material layer is composed of a mixture of resin, black substance and inorganic filler, the composite material layer has a low refractive index and black color, the cover film provided by the patent It has good folding resistance and is suitable for flexible printed circuit boards, but this patent does not conduct research on slowing down the biting of PI films in desmear and plasma processes. CN102143645A discloses a cover film and a printed circuit board with the cover film. The cover film includes a base material with protective and electrical insulation functions and an adhesive layer for adhering the cover film to a copper foil substrate. The substrate has opposite first and second surfaces, and the adhesive layer contains silicon-containing additives, and the adhesive layer is fixedly covered on the first surface of the substrate. The covering film of this patent has relatively high hardness, but Damage to the cover film by the desmear and plasma processes is still unavoidable.

Therefore, it is necessary to develop a new cover film to meet the processing requirements and performance requirements of the cover film for the rigid-flex board.

Contents of the invention

The object of the present invention is to provide a kind of coating covering film and its preparation method and application; The coating covering film provided by the present invention is excellent in softness and heat aging resistance, and after desmear and plasma process processing, its mechanical properties, folding resistance The performance and reliability are not reduced, and it can meet the processing requirements and performance requirements of the rigid-flex board for the cover film.

For reaching this purpose, the present invention adopts following technical scheme:

In a first aspect, the present invention provides a coating cover film, comprising a polyimide film and a release paper arranged on one side of the polyimide film, the polyimide film and the release paper Adhesive is set in the middle of the paper;

Wherein, the coating cover film further includes a protective coating disposed on the other side of the polyimide film.

The present invention is by setting protective coating on one side of polyimide film, after desmear and plasma process are processed, protective coating is removed and can not damage polyimide film, therefore, coating covering film provided by the present invention It can ensure that the mechanical properties and folding resistance of the cover film will not decrease after being treated by desmear and plasma processes.

In the present invention, the protective coating is any one of polyester coating, polyurethane coating or epoxy coating.

The polyester composition used in the polyester coating can be any polyester composition in the prior art, which needs to include 100 parts by weight polyester resin and 5-10 parts by weight curing agent, and the polyester resin can be Selected from VYLON 600, GK140, GK150 produced by Japan Toyobo Co., Ltd.; L411, L411-03 produced by Evonik, etc.; the curing agent is any one of anhydride curing agent or isocyanate curing agent or a combination of at least two, Preferably, the anhydride curing agent is one or a combination of at least two of tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. The isocyanate curing agent should not be an aromatic isocyanate curing agent. Any one of isocyanate curing agent, alicyclic isocyanate curing agent or a mixture of two; the aliphatic isocyanate curing agent is selected from any of hexamethylene diisocyanate dimer, trimer or adduct One or a mixture of at least two; the alicyclic isocyanate curing agent is selected from any one of isophorone diisocyanate dimers, trimers or adducts or a mixture of at least two. The selection of aliphatic isocyanate curing agent or alicyclic isocyanate curing agent can effectively avoid yellowing and aging of the coating during high temperature and multiple pressing processes.

The polyurethane composition used in the polyurethane coating can be any polyurethane composition in the prior art, which needs to include 100 parts by weight polyurethane resin and 8-15 parts by weight curing agent, and the 8-15 parts by weight can be 10 parts by weight. parts by weight, 11 parts by weight, 13 parts by weight, etc.; the polyurethane resin can be selected from UR-3500, SD-5000 produced by Japan Toyobo Co., Ltd.; the curing agent is a multifunctional epoxy resin, which can be selected from One of ERISYS GA-240 from CVC Corporation of the United States and NPPN-431A70 from Nanya Corporation. Using multifunctional epoxy resin as the curing agent can improve the heat resistance of the coating on the one hand to make up for the lack of heat resistance of polyurethane resin. On the other hand, using multifunctional epoxy resin as the curing agent can improve the crosslinking performance. Density, improving the performance of the coating against desmear and plasma bites.

The epoxy resin composition used in the epoxy resin coating can be any epoxy resin composition in the prior art, which needs to include 100 parts by weight epoxy resin and 20-30 parts by weight curing agent, the 20 parts by weight -30 parts by weight can be 22 parts by weight, 25 parts by weight, 28 parts by weight, etc.; generally, flexible epoxy resin and flexible curing agent are used to make the cured coating have better flexibility and improve the compatibility with PI film Adhesiveness, specifically, the epoxy resin can be selected from one of HyPox UA10 produced by CVC in the United States, NPER-133L of Nanya Company; the curing agent is an amine curing agent, which can be selected from Gabriel One of the company's Versamid 125 and BASF's Baxxodur EC301.

The preparation method of the resin composition of the present invention is to dissolve in a solvent, and the solvent can be any one or a combination of at least two of butanone, acetone, cyclohexanone, toluene or N,N'-dimethylformamide.

Since the processing process of the soft-rigid board requires multiple high-temperature pressing processes, the protective coating selected in the present invention should have good heat aging resistance, and the corrosion resistance of the protective coating selected in the present invention should be moderate. If the corrosion resistance is too good, the protective coating cannot be effectively removed after the desmear process, which will cause the overall thickness of the cover film to become thicker, and the folding resistance and flex resistance will deteriorate; if the corrosion resistance is too poor, the During the desmear and plasma processes, the PI film will be bitten, resulting in thinning of the covering film and performance degradation. Therefore, the polyester coating, polyurethane coating or epoxy resin coating selected in the present invention all have moderate corrosion resistance.

In the present invention, the protective coating has a thickness of 3-5 μm, such as 3.5 μm, 4 μm, 4.5 μm and the like.

If the thickness of the protective coating is relatively thick, after the desmear and plasma processes, the protective coating on the surface of the cover film will remain in a large area, which will lead to an increase in the overall thickness of the cover film, which in turn will lead to the resistance of the obtained rigid-flex board. If the thickness of the protective coating is thin, it will be difficult to protect the polyimide film after the desmear and plasma processes.

In the present invention, we hope that the protective coating is completely removed without damaging the polyimide film, but in the actual operation process, the protective coating may have a very small amount remaining on the polyimide film in a very small area. On the film, but does not affect the performance of the polyimide, at this point we believe that the protective coating has been removed as much as possible.

Preferably, the visible light transmittance of the protective coating is ≥85%, such as 87%, 89%, 90%, 91%, 92%, 95%, etc.

Preferably, the haze of the protective coating is ≤4%, such as 1%, 2%, 3%, 4% and so on.

In order not to affect the appearance of the cover film, the visible light transmittance and haze of the protective coating should be moderate.

Preferably, the glass transition temperature of the protective coating is 20-50°C, such as 22°C, 25°C, 30°C, 35°C, 40°C, 45°C and the like.

If the glass transition temperature is too high, the cover film will be hard; if the glass transition temperature is too low, the surface of the protective coating will be sticky, which will affect the workability.

In the present invention, the polyimide film has a thickness of 10-50 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm and the like.

In the present invention, the adhesive has a thickness of 15-50 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm and the like.

In the present invention, the adhesive is a modified epoxy resin adhesive.

In a second aspect, the present invention provides a method for preparing the coating cover film according to the first aspect, the preparation method comprising the following steps:

(1) coating the resin composition solution of the protective coating on one side of the polyimide film, drying and curing to obtain the protective coating-polyimide film;

(2) Coating an adhesive on the other side of the obtained polyimide film and drying it, and then compounding it with a release paper to obtain the coating cover film.

In the present invention, corona treatment is performed on the polyimide film before the coating in step (1).

In the present invention, the solid content of the resin composition solution is 40-50wt%, such as 42wt%, 45wt%, 47wt%, 48wt%, 49wt%, etc.

In a third aspect, the present invention provides an application of the coating cover film according to the first aspect in a rigid-flex board.

Compared with the prior art, the present invention has the following beneficial effects:

(1) the present invention is by setting protective coating on one side of polyimide film, after desmear and plasma process are processed, protective coating is removed and can not damage polyimide film, therefore, coating provided by the present invention A layer of covering film can ensure that the mechanical properties and folding resistance of the covering film will not decrease after being treated by desmear and plasma processes;

(2) If the thickness of the protective coating is relatively thick, after the desmear and plasma processes, the protective coating on the surface of the cover film will remain in a large area, which will lead to an increase in the overall thickness of the cover film, which will lead to the obtained soft-hard combination. The folding resistance of the board decreases; if the thickness of the protective coating is thin, it is difficult to protect the polyimide film after desmear and plasma processing;

(3) After the coating cover film provided by the present invention is processed through the desmear and plasma processes, its mechanical properties, folding resistance and reliability do not decline, and its aging resistance is excellent, wherein the heat resistance is above 280 ° C, and its tensile strength is Above 93MPa, the folding resistance is above 142 times.

Description of drawings

Fig. 1 is a schematic structural view of the coating covering film provided by Example 1 of the present invention.

Among them, 1-release paper; 2-adhesive; 3-polyimide film; 4-protective coating.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

The modified epoxy adhesive is the adhesive for SF305C cover film produced by Shengyi Technology; the polyimide film can be one of DuPont HN type PI film in the United States and Taiwan Damai TH type PI film; the release paper can be Taiwan Bo PEK type release paper.

Example 1

A coating covering film is composed of a release paper 1, an adhesive 2, a polyimide film 3 and a protective coating 4 arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 15 μm; the polyimide film is Taiwan Damai TH type PI film with a thickness of 12.5 μm; the protective coating is a polyester coating with a thickness of 3 μm.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of VYLON 600 and 5 parts by weight of tetrahydrophthalic anhydride with methyl ethyl ketone, mix well, and control the solid content to 40wt%, to obtain a polyester composition solution;

(2) Take a 12.5 μm PI film for corona treatment, then coat the polyester composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 120°C for 2 hours to obtain a protective coating - polyimide film;

(3) Coat 15 μm of modified epoxy adhesive on the other side of the obtained PI film, dry at 160°C for 3 minutes, and then compound with release paper at 70°C to obtain a coating cover film.

Example 2

A coated cover film consisting of release paper, adhesive, polyimide film and protective coating arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 15 μm; the polyimide film is Taiwan Damai TH type PI film with a thickness of 12.5 μm; the protective coating is a polyester coating with a thickness of 4 μm.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of GK140 and 7 parts by weight of hexahydrophthalic anhydride with acetone, mix uniformly, and control the solid content to 40 wt%, to obtain a polyester composition solution;

(2) Take a 12.5 μm PI film for corona treatment, then coat the polyester composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 120°C for 2 hours to obtain a protective coating - polyimide film;

(3) Coat 15 μm of modified epoxy adhesive on the other side of the obtained PI film, dry at 160°C for 3 minutes, and then compound with release paper at 70°C to obtain a coating cover film.

Example 3

A coated cover film consisting of release paper, adhesive, polyimide film and protective coating arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 15 μm; the polyimide film is Taiwan Damai TH type PI film with a thickness of 12.5 μm; the protective coating is a polyester coating with a thickness of 5 μm.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of L411-03 and 7 parts by weight of methylhexahydrophthalic anhydride with acetone, mix uniformly, and control the solid content to 45wt%, to obtain a polyester composition solution;

(2) Take a 12.5 μm PI film for corona treatment, then coat the polyester composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 120°C for 2 hours to obtain a protective coating - polyimide film;

(3) Coat 15 μm of modified epoxy adhesive on the other side of the obtained PI film, dry at 160°C for 3 minutes, and then compound with release paper at 70°C to obtain a coating cover film.

Example 4-5

The difference from Example 1 is that by controlling the coating amount of the polyester composition, the thickness of the final protective coating is 2 μm (Example 4) and 6 μm (Example 5).

Example 6

A coated cover film consisting of release paper, adhesive, polyimide film and protective coating arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 15 μm; the polyimide film is Taiwan Damai TH type PI film with a thickness of 12.5 μm; the protective coating is a polyester coating with a thickness of 4 μm.

The preparation method is as follows:

(1) Stir and dissolve the adduct of 100 parts by weight of L411 and 10 parts by weight of hexamethyl diisocyanate with acetone, mix uniformly, and control the solid content to 45 wt%, to obtain a polyester composition solution;

(2) Take a 12.5 μm PI film for corona treatment, then coat the polyester composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 120°C for 2 hours to obtain a protective coating - polyimide film;

(3) Coat 15 μm of modified epoxy adhesive on the other side of the obtained PI film, dry at 160°C for 3 minutes, and then compound with release paper at 70°C to obtain a coating cover film.

Example 7-8

The difference with Example 1 is that in this example, the polyester composition is replaced by a polyurethane composition, specifically as follows:

100 parts by weight of SD-5000 and 9 parts by weight of ERISYS GA-240 were stirred and dissolved with toluene, mixed uniformly, and the solid content was controlled to be 45 wt%, to obtain a polyurethane composition (Example 7).

100 parts by weight of UR-3500 and 15 parts by weight of NPPN-431A70 were stirred and dissolved with N,N'-dimethylformamide, mixed uniformly, and the solid content was controlled to 50 wt%, to obtain a polyurethane composition (Example 8).

Example 9-10

The difference with Example 1 is that in this example, the polyester composition is replaced by an epoxy resin composition, specifically as follows:

100 parts by weight of HyPox UA10 and 20 parts by weight of Versamid 125 were stirred and dissolved with acetone, mixed uniformly, and the solid content was controlled to be 45 wt%, to obtain an epoxy resin composition (Example 9).

100 parts by weight of NPER-133L and 30 parts by weight of Baxxodur EC301 were stirred and dissolved with cyclohexanone, mixed uniformly, and the solid content was controlled to be 48 wt%, to obtain an epoxy resin composition (Example 10).

Example 11

A coated cover film consisting of release paper, adhesive, polyimide film and protective coating arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 25 μm; the polyimide film is a DuPont HN type PI film with a thickness of 25 μm; the protective coating is a polyurethane coating with a thickness of 4 μm.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of UR-3500 and 15 parts by weight of ERISYS GA-240 with toluene, mix uniformly, and control the solid content to 45wt%, to obtain a polyurethane composition;

(2) Take a 25 μm PI film for corona treatment, then coat the polyester composition solution on the corona-treated PI film, dry at 120°C for 3 minutes, and cure at 150°C for 1 hour to obtain a protective coating-polymer imide film;

(3) Coat 25 μm modified epoxy adhesive on the other side of the obtained PI film, dry at 160° C. for 3 minutes, and then compound with release paper at 70° C. to obtain a coating cover film.

Example 12

A coated cover film consisting of release paper, adhesive, polyimide film and protective coating arranged in sequence.

Among them, the adhesive is a modified epoxy adhesive with a thickness of 50 μm; the polyimide film is Taiwan Damai TH type PI film with a thickness of 50 μm; the protective coating is a polyurethane coating with a thickness of 5 μm.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of SD-5000 and 13 parts by weight of NPPN-431A70 with N,N'-dimethylformamide, mix well, and control the solid content to 50wt%, to obtain a polyurethane composition;

(2) Take a 50 μm PI film for corona treatment, then coat the polyurethane composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 160°C for 1 hour to obtain a protective coating-polymer imide film;

(3) Coat 50 μm modified epoxy adhesive on the other side of the obtained PI film, dry at 160° C. for 3 minutes, and then compound with release paper at 70° C. to obtain a coating cover film.

Example 13

The difference from Embodiment 11 is that the cover film protective coating in this embodiment is a silicone coating.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of hydroxyl-terminated silicone oil and 5 parts by weight of ethyl orthosilicate with toluene, mix uniformly, and control the solid content to 45 wt%, to obtain a silicone composition;

(2) Take a 25 μm PI film for corona treatment, then coat the silicone composition solution on the corona-treated PI film, dry at 120°C for 3 minutes, and cure at 150°C for 1 hour to obtain a protective coating-polymer imide film;

(3) Coat 25 μm modified epoxy adhesive on the other side of the obtained PI film, dry at 160° C. for 3 minutes, and then compound with release paper at 70° C. to obtain a coating cover film.

Example 14

The difference from Example 12 is that the cover film protective coating in this example is a polyacrylate coating.

The preparation method is as follows:

(1) Stir and dissolve 100 parts by weight of polyacrylate resin and 8 parts by weight of hexamethylene diisocyanate adduct with methyl ethyl ketone, mix uniformly, and control the solid content to 50 wt%, to obtain a polyacrylate composition;

(2) Take a 50 μm PI film for corona treatment, then coat the polyacrylate composition solution on the corona-treated PI film, dry at 160°C for 3 minutes, and cure at 160°C for 1 hour to obtain a protective coating - polyimide film;

(3) Coat 50 μm modified epoxy adhesive on the other side of the obtained PI film, dry at 160° C. for 3 minutes, and then compound with release paper at 70° C. to obtain a coating cover film.

Comparative example 1

The difference from Example 10 is that the cover film in this comparative example does not include a protective coating.

Performance Testing

The sample that embodiment 1-14 and comparative example 1 provides is carried out performance test, and method is as follows:

(1) Thickness: Remove the release paper from the cover film samples prepared in Examples and Comparative Examples and press against itself, the modified epoxy adhesive layers are bonded to each other, the protective coating is on the outside, and cured at 160°C for 1 hour Finally, after the desmear and plasma processes are carried out successively, the total thickness is measured by a micrometer, and the thickness of the single-layer covering film is calculated;

(2) Heat resistance: Remove the release paper from the cover film samples prepared in the examples and comparative examples and press them on both sides of the copper foil, the protective coating is on the outside, and after curing at 160°C for 1 hour, desmear in turn After processing with the plasma process, test the limit soldering resistance temperature, that is, immerse in tin furnaces at different temperatures for 20s and then take it out for observation to check whether there is layered foaming; the test temperature starts at 280°C and gradually increases with 10°C as a step In the temperature rise test, the temperature before stratification and blistering is the limit soldering resistance temperature;

(3) Tensile strength: The cover film samples prepared in the examples and comparative examples were torn off the release paper and pressed against themselves, the modified epoxy adhesive layers were bonded to each other, the protective coating was on the outside, and cured at 160°C After 1 hour, after the desmear and plasma processes are carried out in sequence, the universal material testing machine is used to test according to ASTM D-882;

(4) Folding resistance: The cover film samples of the examples and comparative examples were torn off the release paper and pressed on both sides of the line, the protective coating was on the outside, and after curing at 160°C for 1 hour, the desmear and plasma processes were carried out in sequence Test after treatment, according to JISC-6471 test, test condition 0.5kg/0.8R.

The test results are shown in Table 1:

Table 1

The protective coating thickness of embodiment 1-3 and embodiment 6-12 is 3-5 μ m, within the optimal scope of the present invention, after desmear and plasma process process, its coating is completely removed, can effectively protect PI film , Therefore, its mechanical properties, folding resistance and heat resistance do not decrease, the heat resistance is above 350°C, the tensile strength is above 174MPa, and the folding resistance is above 385 times. And the protective coating thickness of embodiment 4-5 is respectively 2 μ m and 6 μ m, is not in the optimal range of the present invention, after desmear and plasma process process, the protective coating of embodiment 4 can not effectively protect PI film, causes PI film to be damaged However, the protective coating in Example 5 is too thick. After desmear and plasma treatment, the protective coating cannot be completely removed, resulting in an increase in the total thickness. Therefore, the mechanical properties, folding resistance and durability of the two Although the thermal property is worse than Comparative Example 1 (after treatment), it is not as good as Examples 1-3 and Examples 6-12. Example 13 uses a silicone coating, which has excellent corrosion resistance. After desmear and plasma treatment, the coating cannot be completely removed, thereby affecting mechanical properties and folding resistance; Example 14 uses a polyacrylate coating , the corrosion resistance is poor, and after desmear and plasma treatment, the PI film cannot be effectively protected, resulting in a decrease in mechanical properties, heat resistance and folding resistance.

From the performance test of the comparative example, it can be seen that the comparative example 1 has no protective coating, and after desmear and plasma treatment, its mechanical properties, heat resistance and folding resistance are greatly reduced.

It can be seen that only by selecting the optimal coating resin composition and thickness range of the present invention can a coating covering film with excellent performance be obtained, which can meet the application requirements of rigid-flex boards.

The applicant declares that the present invention illustrates the coating cover film of the present invention and its preparation method and application through the above-mentioned examples, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to implement . Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the selected raw materials in the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. a coating cover film, is characterized in that, comprises polyimide film and is arranged on the release paper of described polyimide film one side, in the middle of described polyimide film and described release paper set glue; Wherein, the coating cover film further includes a protective coating disposed on the other side of the polyimide film. 2. The coating cover film according to claim 1, characterized in that, the protective coating is any one or a combination of at least two of polyester coating, polyurethane coating or epoxy coating. 3. The coating cover film according to claim 1 or 2, characterized in that, the thickness of the protective coating is 3-5 μm; Preferably, the visible light transmittance of the protective coating is ≥85%; Preferably, the haze of the protective coating is ≤4%; Preferably, the glass transition temperature of the protective coating is 20-50°C. 4. The coating cover film according to any one of claims 1-3, characterized in that, the polyimide film has a thickness of 10-50 μm. 5. The coating cover film according to any one of claims 1-4, characterized in that, the thickness of the adhesive is 15-50 μm. 6. The coating cover film according to any one of claims 1-5, characterized in that, the adhesive is a modified epoxy resin adhesive. 7. according to the preparation method of coating cover film according to any one of claim 1-6, it is characterized in that, described preparation method comprises the steps: (1) coating the resin composition solution of the protective coating on one side of the polyimide film, drying and curing to obtain the protective coating-polyimide film; (2) Coating an adhesive on the other side of the obtained polyimide film and drying it, and then compounding it with a release paper to obtain the coating cover film. 8. The preparation method according to claim 7, characterized in that, the polyimide film is subjected to corona treatment before the coating in step (1). 9. The preparation method according to claim 7 or 8, characterized in that, the solid content of the resin composition solution is 40-50wt%. 10. Application of the coating cover film according to any one of claims 1-6 in a rigid-flex board.