JP2022068708A - Multi-layered adhesive film - Google Patents

Abstract

To provide an adhesive film which can exhibit an excellent dielectric property in a wide temperature range.SOLUTION: An adhesive layer containing thermoplastic polyimide is disposed at least on one surface of a non-thermoplastic polyimide film so as to form a multi-layered adhesive film. When a dielectric loss tangent of the multi-layered adhesive film at 10 GHz and at -50°C is represented by Df-50, that at 0°C is represented by Df0, that at 50°C is represented by Df5, that at 100°C is represented by Df100, and that at 150°C is represented by Df150, a difference between the maximum and minimum values of them is 0.0005 or less, and all of Df-50, Df0, Df5, Df100 and Df150 are 0.0020 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multilayer adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one surface of a non-thermoplastic polyimide film. More specifically, a multilayer adhesive film that can be suitably used for a flexible printed circuit board that is expected to be used under harsh conditions from low temperature to high temperature, a flexible metal-clad laminate having a metal layer on at least one side thereof, and flexible. Regarding printed circuit boards.

Polyimide film is widely used as an electronic substrate material because it has excellent mechanical strength, heat resistance, electrical insulation, and chemical resistance. For example, a flexible copper-clad laminate (hereinafter, also referred to as FCCL) in which a polyimide film is used as a substrate material and a copper foil is laminated on at least one side, and a flexible printed circuit board (hereinafter, also referred to as FPC) in which a circuit is created are manufactured. , Used in various electronic devices.

In recent years, in the high frequency of electric signals propagating in circuits accompanying high-speed signal transmission of electronic devices, there is an increasing demand for low dielectric constant and low dielectric loss tangent of electronic substrate materials. This is because it is effective to lower the permittivity and the dielectric loss tangent in order to suppress the transmission loss of the electric signal. In recent years, which is the dawn of the IoT society, the tendency toward higher frequencies is advancing, and there is a demand for substrate materials, FCCL, and FPC that can suppress transmission loss even in the region of, for example, 10 GHz or higher.

As a technology represented by IoT, automatic driving technology for automobiles and drones is under development. In electronic devices such as camera modules and millimeter-wave antenna modules used for these, large-capacity and high-speed transmission of acquired data is required. In addition, especially when used in in-vehicle applications, it is expected to be exposed to high temperatures due to waste heat from the engine and drive unit, or to be used in cold regions, so it is stable in a wide temperature range in addition to high-speed transmission characteristics. The feasibility of high-speed transmission is required. Further, if high-speed transmission can be realized in a wide temperature range, it is possible to increase the degree of freedom in the installation location of the signal circuit in the automobile. Therefore, the development of a substrate material that can be suitably used for FPCs that are expected to be used under such harsh conditions is awaited.

By the way, liquid crystal polyester (LCP) may be used as a substrate material other than polyimide. Although LCP is generally poor in processability, it is a material having excellent low moisture absorption and low dielectric loss tangent due to its crystallinity. Then, in order to realize a lower dielectric loss tangent, a method of improving the dielectric property by heat-treating an all-aromatic liquid crystal polyester satisfying a specific condition is known, whereby in the range of 30 ° C to 100 ° C. It is known that a low dielectric loss tangent can be realized (Patent Document 1).

WO2020 / 003690

Attempts have been made to develop a polyimide film with a low dielectric constant and dielectric loss tangent, but little attention has been paid to the temperature dependence of the dielectric properties of the polyimide film. However, in recent years, the parts and applications used by FPC have diversified, and it is expected that they will be exposed to high temperatures or specified at extremely low temperatures. A material that expresses the above is desired. Therefore, an object of the present invention is to provide a multilayer adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one surface of a non-thermoplastic polyimide film capable of exhibiting excellent dielectric properties, particularly low dielectric loss tangent, in a wide temperature range. To provide.

The present invention can solve the above problems by the following novel multilayer adhesive film, flexible metal-clad laminate and flexible printed substrate.

1). A multilayer adhesive film in which an adhesive layer containing thermoplastic polyimide is provided on at least one side of a non-thermoplastic polyimide film, and every time the temperature rises by 50 ° C including -50 ° C in the temperature range of -50 ° C to 150 ° C. The dielectric loss tangent at 10 GHz of the multilayer adhesive film measured in is -50 ° C, dielectric loss tangent Df-50, 0 ° C. dielectric loss tangent Df0, 50 ° C. dielectric loss tangent Df5, 100 ° C. dielectric loss tangent Df100, and 150 ° C. In the case of the dielectric loss tangent Df150 in, the difference between the maximum and the minimum of these values is 0.0005 or less, and all of Df-50, Df0, Df5, Df100 and Df150 are 0.0020 or less. Multilayer adhesive film.

2). The multilayer adhesive film according to 1), wherein the maximum and minimum difference between Df-50, Df0, Df5, Df100 and Df150 is 0.0004 or less.

3). The polyimide film according to 1) or 2), wherein all of Df-50, Df0, Df5, Df100 and Df150 are in the range of 0.0013 to 0.0020.

4). The non-thermoplastic polyimide film is characterized in that it is a film using at least 1,4-diaminobenzene, a diamine component of 1,3-bis (4-aminophenoxy) benzene, and an acid dianhydride component as raw materials. The multilayer adhesive film according to any one of 1) to 3).

5). The multilayer adhesive film according to 4), wherein the non-thermoplastic polyimide film further uses 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride as an acid dianhydride component.

6). The non-thermoplastic polyimide film is characterized by using 4,4'-oxydiphthalic acid dianhydride as an acid dianhydride component in addition to 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride. The multilayer adhesive film according to 5).

7). A flexible metal-clad laminate having a metal layer on at least one side of the multilayer adhesive film according to any one of 1) to 6).

8). A flexible printed substrate obtained by forming a circuit on a metal layer of the flexible metal-clad laminate according to claim 7.

Since the multilayer adhesive film of the present invention is a multilayer adhesive film in which an adhesive layer containing thermoplastic polyimide is provided on at least one side of a non-thermoplastic polyimide film, a flexible copper-clad laminate is formed by forming a metal layer on the surface of the adhesive layer. It can be manufactured as a plate (FCCL), and a flexible printed substrate (FPC) can be manufactured by forming a circuit on the metal layer, and the obtained FCCL and FPC can be changed from low temperature to high temperature. Since it exhibits low polyimide positive contact in a wide range of temperature ranges and the dielectric positive contact is within a certain range in any temperature range, it can be suitably used for special applications such as those used under harsh conditions, for example, as in-vehicle parts. .. Specific examples thereof include camera modules, image processing ECUs, millimeter-wave radar components, inverters, motors, etc. in advanced driver assistance systems, and even when used in the above applications, stable high-speed transmission in a wide temperature range can be realized. ..

It is a plot of the dielectric loss tangent of the multilayer adhesive film of the example and the film of the comparative example at −50 ° C. to 150 ° C.

Embodiments of the present invention will be described below, but the present invention is not limited thereto. All academic and patent documents described in this specification are incorporated herein by reference. Unless otherwise specified in the present specification, "A to B" representing a numerical range means "A or more (including A and larger than A) and B or less (including B and smaller than B)".

The multilayer film of the present invention is a multilayer adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one surface of a non-thermoplastic polyimide film, and includes -50 ° C in a temperature range of -50 ° C to 150 ° C. The dielectric loss tangent at 10 GHz of the multilayer adhesive film measured every time the temperature rises by 50 ° C. is the dielectric loss tangent Df-50 at -50 ° C, the dielectric loss tangent Df0 at 0 ° C, the dielectric loss tangent Df5 at 50 ° C, and 100 ° C. When the dielectric loss tangent Df100 and the dielectric loss tangent Df150 at 150 ° C are used, the difference between the maximum and minimum of these values is 0.0005 or less, and all of Df-50, Df0, Df5, Df100 and Df150 are 0.0020 or less. It has become.

The liquid crystal polyester (LCP) as disclosed in Patent Document 1 exhibits a low dielectric constant and dielectric loss tangent to some extent in the vicinity of cold to room temperature, but the dielectric loss tangent tends to increase in a high temperature environment. It is assumed that this is caused by the low heat resistance of the LCP and the large permanent dipole moment of the molecules constituting the LCP. Therefore, LCP is disadvantageous for use in in-vehicle applications where severe temperature changes can occur. Further, Patent Document 1 does not suggest whether the dielectric constant and the dielectric loss tangent are low and within a certain range in a wider temperature range of -50 ° C to 150 ° C as in the present invention.

On the other hand, a multilayer adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one side of a non-thermoplastic polyimide film has been widely used for FPC in recent years, but its dielectric loss tangent has no temperature dependence. It has not been noticed.

In response to such conventional findings, the present inventors have focused on the temperature dependence of the dielectric positive contact of a multilayer adhesive film in which an adhesive layer containing a thermoplastic polyimide is provided on at least one side of the non-thermoplastic polyimide film. If a polyimide resin having a certain structure is used for the multilayer adhesive film, the dielectric positive contact of the electronic circuit base material, which is generally considered to fluctuate in a harsh temperature environment, especially in a high temperature region, is made constant. Moreover, it was found that it is possible to keep it low. FPCs manufactured using this multilayer adhesive film can be used even under harsh conditions.

Here, the dielectric loss tangent at 10 GHz measured every time the temperature rises by 50 ° C. including -50 ° C in the temperature range of 50 ° C to 150 ° C means the dielectric loss tangent measured as follows.

<Device used>
1. Network analyzer N5290A (manufactured by Keysight Technology)
2. Split cylinder resonator 10GHz CR710 (manufactured by EM Lab)
3. Dielectric constant measurement software for split cylinder resonator CRMA (manufactured by EM Lab)
4. Environmental tester SH662 (manufactured by Espec)

<Measurement method>
The sample was set in a split cylinder resonator connected to a network analyzer and allowed to stand in an environmental tester kept at a constant temperature for 2 hours. After standing still, the permittivity and the dielectric loss tangent are measured. The measurement order of each temperature is 150 ° C., 100 ° C., 50 ° C., 0 ° C., −50 ° C. in order from the highest temperature.
The dielectric loss tangents thus obtained are the dielectric loss tangent Df-50 at -50 ° C, the dielectric loss tangent Df0 at 0 ° C, the dielectric loss tangent Df5 at 50 ° C, the dielectric loss tangent Df100 at 100 ° C, and the dielectric loss tangent Df150 at 150 ° C. , Find the maximum and minimum. The difference between the maximum and the minimum is preferably 0.0005 or less, and more preferably 0.0004 or less. It is more preferable that all of Df-50, Df0, Df5, Df100 and Df150 are 0.0020 or less, and all of these are 0.0018 or less.

The multilayer adhesive film of the present invention is a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer.

The total thickness of the multilayer adhesive film is preferably 7 μm or more, more preferably 10 μm to 100 μm, from the viewpoint of handleability when the film is processed into FCCL or the like.

The thickness of the non-thermoplastic polyimide film and the adhesive layer is preferably in the range of 75:25 to 60:40.

Hereinafter, the non-thermoplastic polyimide film, the adhesive layer containing the thermoplastic polyimide, the production of the multilayer adhesive film, the flexible metal-clad laminate, and the flexible printed substrate will be described in this order.

(Non-thermoplastic polyimide film)
An example of the method for producing the non-thermoplastic polyimide film of the present invention will be described in detail. The polyamic acid (hereinafter, also referred to as polyamic acid) which is a precursor of the polyimide used for producing the non-thermoplastic polyimide film of the present invention is substantially composed of at least one diamine and at least one acid dianhydride in an organic solvent. It is obtained by mixing and reacting so as to be equimolar.

The diamine used for the polyamic acid of the non-thermoplastic polyimide film of the present invention is not particularly limited, but is 2,2-bis {4- (4-aminophenoxy) phenyl} propane and 1,3-bis. (4-Aminophenoxy) Benzene, 1,4-bis (4-Aminophenoxy) Benzene, 4,4'-diaminodiphenylpropane, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-diamino Diphenylmethane, 4,4'-diaminodiphenylsulfide, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diamino-1,1'-biphenyl, 4,4 '-Diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-hydroxybiphenyl, 1,4-diaminobenzene, 1,3-diaminobenzene, 4,4'-diaminodiphenyl ether, 1 , 3-Bis (3-aminophenoxy) benzene and the like.

To obtain a multilayer film in which the maximum and minimum difference between Df-50, Df0, Df5, Df100 and Df150 is 0.0005 and all of them are 0.0020 or less, these characteristics of non-thermoplastic polyimide film are obtained. Is the easiest way to control. This is because the non-thermoplastic polyimide film is the main component of the multilayer adhesive film. From this point of view, among the above, it is preferable to use 1,4-diaminobenzene and 1,3-bis (4-aminophenoxy) benzene in combination. Further, the amount of 1,4-diaminobenzene used is preferably 70 mol% or more, more preferably 70 mol% to 95 mol%, and 80 mol% to 90 mol, based on 100 mol% of the diamine component. It is more preferable to use in the range of%, and it is preferable to use 1,3-bis (4-aminophenoxy) benzene in an amount of 5 mol% or more based on 100 mol% of the diamine component, in the range of 5 mol% to 30 mol%. It is more preferable to use it in the range of 10 mol% to 20 mol%. If a non-thermoplastic polyimide film produced by using 1,4-diaminobenzene and 1,3-bis (4-aminophenoxy) benzene as raw materials in this range is used as the multilayer adhesive film, the Df of the multilayer adhesive film is used. The difference between the maximum and minimum of -50, Df0, Df5, Df100 and Df150 tends to be small, and all these values tend to be small.

The acid dianhydride is also not particularly limited, but specifically, pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 2,2', 3, 3'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2 -Bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, p-phenylenebis (trimellitic acid monoesteric acid anhydride), 4,4'-oxydiphthalic acid dianhydride, 3,4'-oxydiphthalic acid Anhydrides and the like can be mentioned.

Among the above, 3,3', 4,4 from the viewpoint that the difference between the maximum and minimum of the multilayer adhesive films Df-50, Df0, Df5, Df100 and Df150 can be reduced, and all these values can be reduced. '-It is preferable to use biphenyltetracarboxylic acid dianhydride. The amount of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride used is preferably 40 mol% or more, preferably in the range of 50 mol% to 70 mol%, based on 100 mol% of the acid dianhydride component. It is more preferable to use it. Further, it is preferable to use 4,4'-oxydiphthalic acid dianhydride in addition to the use of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride. The 4,4'-oxydiphthalic acid dianhydride is preferably used in an amount of 20 mol% or more, more preferably in the range of 30 mol% to 50 mol%, based on 100 mol% of the acid dianhydride component.

In addition to the acid dianhydride monomer, other acid dianhydrides exemplified above such as pyromellitic acid dianhydride may be added as long as the dielectric properties are not deteriorated. The amount of the other acid dianhydride added is preferably 10 mol% or less, more preferably 6 mol% or less, and 3 mol% or less with respect to 100 mol% of the acid dianhydride component. It is more preferable to add in the range.

Based on the above, 1,4-diaminobenzene and 1,3-bis (4-aminophenoxy) benzene were used as the diamine component, and 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride was used as the acid dianhydride component. When a substance is used, or 1,4-diaminobenzene and 1,3-bis (4-aminophenoxy) benzene are used as the amine component, and 4,4'-oxydiphthalic acid dianhydride is used as the acid dianhydride component. In some cases, it is easy to reduce the difference between the maximum and minimum of the finally obtained multilayer adhesive film Df-50, Df0, Df5, Df100 and Df150, and to reduce all these values. In addition, 1,4-diaminobenzene and 1,3-bis (4-aminophenoxy) benzene are used as the diamine component, and 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride is used as the acid dianhydride component. And 4,4'-oxydiphthalic acid dianhydride is used to reduce the maximum and minimum differences between the final multi-layer adhesive films Df-50, Df0, Df5, Df100 and Df150, and all of these. It is even easier to reduce the value.

The polyamic acid, which is a precursor of the non-thermoplastic polyimide, is obtained by mixing and reacting the diamine and the acid dianhydride in an organic solvent so as to be substantially equimolar. Any organic solvent can be used as long as it dissolves polyamic acid, but amide-based solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like can be used. Is preferable, and N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used. The solid content concentration of the polyamic acid is not particularly limited, and if it is in the range of 5% by weight to 35% by weight, the polyamic acid having sufficient mechanical strength when made into polyimide can be obtained.

The order of addition of the raw materials diamine and acid dianhydride is not particularly limited, but it is possible to control the dielectric adpositivity of the non-thermoplastic polyimide film by controlling not only the chemical structure of the raw materials but also the order of addition. It is possible to reduce the maximum and minimum differences between the resulting multilayer adhesive films Df-50, Df0, Df5, Df100 and Df150, and all these values.

A filler can be added to the polyamic acid for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

Further, a thermosetting resin such as an epoxy resin or a phenoxy resin, or a thermoplastic resin such as polyetherketone or polyetheretherketone may be mixed as long as the characteristics of the obtained non-thermoplastic polyimide film as a whole are not impaired. .. Examples of the method for adding these resins include a method of adding these resins to the above-mentioned polyamic acid as long as they are soluble in a solvent. If the polyimide is also soluble, it may be added to the polyimide solution. If it is insoluble in a solvent, a method of first imidizing the above polyamic acid and then compositing by melt-kneading can be mentioned. However, it is desirable to use a soluble resin to be mixed with polyimide.

In order to obtain the non-thermoplastic polyimide film of the present invention, it is preferable to include the following steps.
i) A step of reacting an aromatic diamine with an aromatic tetracarboxylic acid dianhydride in an organic solvent to obtain a polyamic acid solution.
ii) A step of casting a film-forming dope containing the above polyamic acid solution onto a support,
iii) The step of peeling the gel film from the support after heating on the support,
iv) A step of further heating to imidize the remaining amic acid and dry it.

The steps after ii) are roughly classified into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is used as a film-forming dope and is spilled onto a support without using a dehydration ring closure agent or the like, and imidization is promoted only by heating. On the other hand, the chemical imidization method is a method of promoting imidization by using a polyamic acid solution to which at least one of a dehydration ring-closing agent and a catalyst is added as an imidization accelerator as a film-forming dope. Either the thermal imidization method or the chemical imidization method may be used, but the chemical imidization method is superior in productivity.

As the dehydration ring closure agent, an acid anhydride typified by acetic anhydride can be preferably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be preferably used.

In the steps after ii), a glass plate, aluminum foil, an endless stainless belt, a stainless drum, or the like can be preferably used as the support for spreading the film-forming dope. Heating conditions are set according to the thickness of the finally obtained film and the production rate, and after at least one of partial imidization and drying is performed, the film is peeled off from the support to form a polyamic acid film (hereinafter referred to as gel film). , Or gel film).

iv) In the subsequent steps, the edges of the gel film are fixed to avoid shrinkage during curing and dried to remove water, residual solvent, imidization accelerator remaining in the film, and the remaining amic. The acid is completely imidized to give a film containing polyimide. It is preferable that the end portion of the gel film is not only fixed but also stretched in the transport direction or in a direction perpendicular to the transport direction.

The polyimide film thus obtained has a small dielectric loss tangent at −50 ° C., 0 ° C., 50 ° C., 100 ° C., and 150 ° C. and is constant, so that it can be suitably used as a high-frequency compatible circuit board for in-vehicle use.

(Adhesive layer containing thermoplastic polyimide)
Examples of the diamine and acid dianhydride used in the thermoplastic polyimide used in the adhesive layer of the present invention include those used in the non-thermoplastic polyimide resin layer. Since the thickness of the adhesive layer is thinner than that of the non-thermoplastic polyimide film, the effect is not so large as that of the non-thermoplastic polyimide film, but it is also possible to use a preferable component as the thermoplastic polyimide contained in the adhesive layer. It is possible to control the maximum and minimum differences between Df-50, Df0, Df5, Df100 and Df150 of the finally obtained multilayer adhesive film, and these values. From this point of view, diamines that can be preferably used include 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, and 1,3-bis (3). -Aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis It is preferable to use at least one selected from (4-aminophenoxyphenyl) propane and 2,2'-dimethyl-4,4'-diaminobiphenyl.

Examples of the acid dianhydride preferably combined with these diamines include pyromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'. It is preferable to use at least one selected from -biphenyltetracarboxylic acid dianhydride and 4,4'-oxydiphthalic acid dianhydride.

In the method for producing a polyamic acid solution which is a precursor of the thermoplastic polyimide used for the adhesive layer of the present invention, the thermoplastic polyimide obtained by imidizing the obtained polyamic acid has the characteristics required for a conventional flexible printed substrate material. Any known method can be used as long as it is.

Using the obtained polyamic acid solution, a multilayer film can be produced by the method for producing a multilayer film described later. In addition to the thermoplastic polyimide, the adhesive layer may contain silica, calcium phosphate, or the like as long as the smoothness of the adhesive layer is not impaired.

(Manufacturing of multilayer adhesive film)
The multilayer adhesive film of the present invention is a multilayer adhesive film having two or more layers in which at least one non-thermoplastic polyimide resin layer described above is used as a core film and an adhesive layer containing thermoplastic polyimide is provided.

In the present invention, as a method for producing a multilayer adhesive film, at least one surface of the non-thermoplastic polyimide film obtained as described above is coated with a polyamic acid solution which is a precursor of the thermoplastic polyimide, and dried / imide. A method of converting (coating method) can be mentioned.

Alternatively, the step for obtaining the non-thermoplastic polyimide film exemplified in the above item (non-thermoplastic polyimide film),
i) A step of reacting an aromatic diamine with an aromatic tetracarboxylic acid dianhydride in an organic solvent to obtain a polyamic acid solution.
ii) A step of casting a film-forming dope containing the above polyamic acid solution onto a support,
iii) The step of peeling the gel film from the support after heating on the support,
iv) Further heating to imidize the remaining amic acid and dry it,
In step ii), a coextruding die having a plurality of flow paths may be used to simultaneously form a multi-layered resin layer. That is, in the case of obtaining a multilayer polyimide film having an adhesive layer containing a thermoplastic polyimide on at least one side of the above-mentioned non-thermoplastic polyimide film, a precursor solution of the non-thermoplastic polyimide and a precursor solution of the thermoplastic polyimide are used together. It can be obtained by casting on a support using an extrusion die and carrying out the steps after iii).

Since a very high temperature is required for imidization, when a resin layer other than polyimide is provided, it is preferable to adopt a coating method in order to suppress thermal decomposition. When the adhesive layer containing the thermoplastic polyimide is provided by coating, a precursor of the thermoplastic polyimide may be applied and then imidization may be performed, or a thermoplastic polyimide solution may be applied and dried. ..

(Flexible metal-clad laminate and flexible printed substrate)
The multilayer polyimide film thus obtained can be a flexible metal-clad laminate by providing a metal layer on at least one side of the multilayer polyimide film. As a means for forming a metal layer on a multilayer polyimide film,
a) Means for obtaining a flexible metal-clad laminate by laminating metal foils by heating and pressurizing after obtaining a multilayer polyimide film as described above b) Casting an organic solvent solution containing polyamic acid on the metal foils. Then, a means for obtaining a flexible metal-clad laminate by removing the solvent and imidizing by heating can be mentioned. Details of a) and b) will be described below.

In the means of a), the flexible metal foil laminated plate of the present invention can be obtained by laminating a metal foil on the obtained multilayer polyimide film by heating and pressurizing (laminating). As the means and conditions for laminating the metal foils, conventionally known ones may be appropriately selected.

In the means of b), the means for casting an organic solvent solution containing polyamic acid (a solution containing a precursor of thermoplastic polyimide or an amic acid solution which is a precursor of non-thermoplastic polyimide) on a metal foil is particularly limited. Instead, conventionally known means such as a die coater, a comma coater (registered trademark), a reverse coater, and a knife coater can be used. Conventionally known means can be used as the heating means for removing the solvent and imidizing, and examples thereof include a hot air furnace and a far-infrared furnace.

When the chemical imidization method is adopted when forming a non-thermoplastic polyimide film or an adhesive layer by the means (b), an acid is generated from an acid anhydride which is a dehydration ring-closing agent in the process of imidization. Therefore, depending on the type of metal foil, oxidation may proceed. It is preferable to appropriately select the addition of the dehydration ring closure agent according to the type of the metal leaf and the heating conditions.

When providing an adhesive layer containing a non-thermoplastic polyimide film and a thermoplastic polyimide, a means of repeating the above casting and heating steps multiple times, or forming a multi-layered cast layer by coextrusion or continuous casting and heating at one time is preferable. Can be used.

By the means of b), the flexible metal leaf laminate of the present invention is obtained at the same time as the imidization is completed. When the metal foil layers are provided on both sides of the resin layer, the metal foil may be attached to the resin layer surface on the opposite side by heating and pressurizing.

The metal foil that can be used in the present invention is not particularly limited, but when the flexible metal-clad laminate of the present invention is used for electronic equipment / electrical equipment applications, for example, copper, a copper alloy, or stainless steel. Alternatively, a foil made of the alloy, nickel or a nickel alloy (including 42 alloys), aluminum or an aluminum alloy can be mentioned. In general flexible laminated plates, copper foils such as rolled copper foils and electrolytic copper foils are often used, but they can also be preferably used in the present invention. A rust preventive layer, a heat-resistant layer, or an adhesive layer may be applied to the surface of these metal foils. Further, the thickness of the metal foil is not particularly limited, and may be any thickness as long as it can exhibit sufficient functions according to its use.

A flexible printed substrate can be obtained by etching the metal layer of the flexible metal-clad laminate thus obtained by a known method.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The methods for evaluating the relative permittivity and the dielectric loss tangent of the laminated body in the synthesis example, the example, and the comparative example are as follows.

(Measurement of dielectric loss tangent)
An environmental tester that sets a multilayer polyimide film cut into 50 mm x 70 mm in a split cylinder resonator CR710 (10 GHz, manufactured by EM Lab) connected to a network analyzer N5290A (manufactured by Keysight Technology) and keeps it at a constant temperature. It was allowed to stand inside for 2 hours. After standing still, the permittivity and the dielectric loss tangent were measured. The measurement was carried out sequentially from high temperature such as 150 ° C., 100 ° C., 50 ° C., 0 ° C. and −50 ° C. In addition, every time the inside of the environmental tester was set to a predetermined temperature, it was allowed to stand for 2 hours.

As a comparative example, the dielectric loss tangent of an LCP film (FELIOS R-F705T, manufactured by Panasonic Corporation) was measured by the same method as in the above-mentioned "measurement of dielectric loss tangent".

(Synthesis Example 1)
656.66 g of N, N-dimethylformamide (hereinafter, also referred to as DMF) and 12.12 g of 1,3-bis (4-aminophenoxy) benzene (hereinafter, also referred to as TPE-R) in a glass flask having a capacity of 2000 ml. And 1,4-diaminobenzene (hereinafter, also referred to as PDA) were added in an amount of 25.44 g, and 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter, also referred to as BPDA) was added in an amount of 48.86 g. After the addition, the mixture was stirred under a nitrogen atmosphere. After confirming the dissolution of BPDA, 31.77 g of 4,4'-oxydiphthalic acid dianhydride (also referred to as ODPA) was added, and the mixture was stirred for 30 minutes. Finally, prepare a solution in which 1.8 g of pyromellitic acid dianhydride (hereinafter, also referred to as PMDA) is dissolved in DMF so that the solid content concentration is 7.2%, and be careful of the increase in viscosity of this solution. However, it was gradually added to the above reaction solution, and when the viscosity at 23 ° C. reached 2000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Manufacturing of non-thermoplastic polyimide film)
An imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.1 / 1.1 / 0.8) was added to the polyamic acid solution of Synthesis Example 1 at a weight ratio of 40% with respect to the polyamic acid solution. , Continuously stirred with a mixer, extruded from the T-die and poured onto a stainless steel endless belt. After heating this resin film at 100 ° C. x 330 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and the hot air oven 250 ° C. x 41 seconds, hot air oven 350 ° C. x 37 seconds, hot air oven. It was dried and imidized at 380 ° C. × 32 seconds and a far infrared heater oven 380 ° C. × 97 seconds to obtain a non-thermoplastic polyimide film having a thickness of 33 μm.

(Synthesis Example 2)
After adding 642.12 g of DMF, 53.02 g of TPE-R and 38.16 g of BPDA to a glass flask having a capacity of 2000 ml, the mixture was stirred under a nitrogen atmosphere for 30 minutes. Next, 8.49 g of PMDA was added and stirred for 30 minutes. Subsequently, 16.52 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (hereinafter, also referred to as m-TB) and 18.11 g of PMDA were added, and the mixture was stirred for 30 minutes. Finally, a solution in which 1.7 g of PMDA was dissolved in DMF so as to have a solid content concentration of 7.2% was prepared, and this solution was gradually added to the above reaction solution while paying attention to the increase in viscosity. When the viscosity at ° C reached 1000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Example 1)
After diluting the polyamic acid solution, which is the precursor of the thermoplastic polyimide produced in Synthesis Example 2, with DMF until the solid content concentration reaches 10% by weight, the final single-sided thickness is applied to one side of the non-thermoplastic polyimide film obtained from Synthesis Example 1. Polyimide acid was applied with a comma coater so that the concentration was 8.5 μm, and the mixture was heated in a drying furnace set at 120 ° C. for 4 minutes. Similarly, the other side was coated with polyamic acid so as to have a final thickness of 8.5 μm, and then heated in a drying oven set at 120 ° C. for 4 minutes. Subsequently, heat treatment was performed for 15 seconds in a hot air oven having an atmospheric temperature of 380 ° C. to obtain a multilayer adhesive film having a total thickness of 50 μm.

(Comparative Example 1)
An LCP film with a thickness of 50 μm (FELIOS R-F705T, manufactured by Panasonic Corporation) was prepared. Table 1 and FIG. 1 show the results of measuring the dielectric loss tangent for Examples and Comparative Examples.

The multilayer adhesive film according to the present invention has a maximum and minimum difference between the maximum and minimum dielectric loss tangent values at −50 ° C., 0 ° C., 50 ° C., 100 ° C., and 150 ° C. of 0.0005 or less, and the dielectric loss tangent measured at the above-mentioned temperature. All of the values of are 0.0020 or less, and it can be seen that they show a low and constant dielectric loss tangent in a wide temperature range.

Therefore, it can be said that it is a suitable base material for an FPC substrate for in-vehicle use, which requires operational reliability in a temperature range below zero or in a temperature range exceeding 100 ° C. Specific applications include camera modules in advanced driver assistance systems, image processing ECUs, millimeter-wave radar components, inverters, motors, and the like. Therefore, it is possible to increase the degree of freedom in the installation location of the FPC having excellent high-speed transmission characteristics.

Claims (8)

A multilayer adhesive film in which an adhesive layer containing thermoplastic polyimide is provided on at least one side of a non-thermoplastic polyimide film, and every time the temperature rises by 50 ° C including -50 ° C in the temperature range of -50 ° C to 150 ° C. The dielectric loss tangent at 10 GHz of the multilayer adhesive film measured in is -50 ° C, dielectric loss tangent Df-50, 0 ° C. dielectric loss tangent Df0, 50 ° C. dielectric loss tangent Df5, 100 ° C. dielectric loss tangent Df100, and 150 ° C. In the case of the dielectric loss tangent Df150 in, the difference between the maximum and the minimum of these values is 0.0005 or less, and all of Df-50, Df0, Df5, Df100 and Df150 are 0.0020 or less. Multilayer adhesive film. The multilayer adhesive film according to claim 1, wherein the maximum and minimum difference between Df-50, Df0, Df5, Df100 and Df150 is 0.0004 or less. The polyimide film according to claim 1 or 2, wherein all of Df-50, Df0, Df5, Df100 and Df150 are in the range of 0.0013 to 0.0020. The non-thermoplastic polyimide film is characterized in that it is a film using at least 1,4-diaminobenzene, a diamine component of 1,3-bis (4-aminophenoxy) benzene, and an acid dianhydride component as raw materials. The multilayer adhesive film according to any one of claims 1 to 3. The multilayer adhesive film according to claim 4, wherein the non-thermoplastic polyimide film further uses 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride as an acid dianhydride component. The non-thermoplastic polyimide film is characterized by using 4,4'-oxydiphthalic acid dianhydride as an acid dianhydride component in addition to 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride. The multilayer adhesive film according to claim 5. A flexible metal-clad laminate having a metal layer on at least one side of the multilayer adhesive film according to any one of claims 1 to 6. A flexible printed substrate obtained by forming a circuit on a metal layer of the flexible metal-clad laminate according to claim 7.

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