TWI856927B - Method for producing polyimide film, method for producing metal-clad laminate, and method for producing circuit substrate - Google Patents

Abstract

The manufacturing method of the metal-clad laminate 100 includes: forming a first polyamide resin layer 20A on a metal foil 10A; imidizing the polyamide acid in the first polyamide resin layer 20A to form a first polyimide layer 20; performing surface treatment on the first polyimide layer 20; forming a second polyamide resin layer 30A on the first polyimide layer 20; and imidizing the polyamide acid in the second polyamide resin layer 30A to form a second polyimide layer 30 and forming an insulating resin layer 40. The thickness (L1) of the first polyimide layer 20 is within the range of 0.5 μm to 100 μm, the thickness (L) of the entire insulating resin layer 40 is within the range of 5 μm to less than 200 μm, and the ratio (L/L1) is within the range of more than 1 to less than 400.

Description

Method for producing polyimide film, method for producing metal-clad laminate, and method for producing circuit substrate

The present invention relates to a method for manufacturing a metal-clad laminate that can be used as a material for a circuit board and the like, and a method for manufacturing the circuit board.

In recent years, with the progress of miniaturization, lightness and space saving of electronic equipment, the demand for flexible circuit substrates (Flexible Printed Circuits (FPC)) that are thin, lightweight, flexible and have excellent durability even when bent repeatedly has increased. FPC can achieve three-dimensional and high-density installation even in limited space, so its use is gradually expanding in wiring, cables, connectors and other parts of electronic equipment such as hard disk drives (HDD), digital video disks (DVD), mobile phones, and smartphones. As an insulating resin used in FPC, polyimide with excellent heat resistance and adhesion has attracted attention.

Regarding the manufacturing method of metal-clad laminates as FPC materials, there is a known method of forming a polyimide precursor layer by coating a resin liquid of polyamide on a metal foil, and then imidizing the polyimide layer. When a metal-clad laminate having multiple polyimide layers as insulating resin layers is manufactured by the casting method, the following operation is usually performed: multiple layers of polyimide precursor layers are sequentially formed on a substrate such as a copper foil, and then these layers are imidized together. However, if a plurality of polyimide precursor layers are imidized at the same time, the solvent or imidization water in the polyimide precursor layer cannot be completely removed, and the residual solvent or imidization water causes foaming or peeling between the polyimide layers, thereby causing a problem of reduced yield.

The foaming or peeling problem can be solved by repeatedly performing the following operations: imidizing the polyimide precursor layer by layer and coating the polyamide resin liquid thereon. However, if the polyamide resin liquid is further coated on the imidized polyimide layer and imidized, it is difficult to obtain sufficient interlayer adhesion. In the prior art, it is proposed that before coating the polyamide resin liquid, the surface of the polyimide film or polyimide layer of the base is subjected to surface treatment such as corona treatment and plasma treatment to improve interlayer adhesion (for example, Patent Document 1, Patent Document 2). [Prior art literature] [Patent literature]

[Patent document 1] Japanese Patent No. 5615253 [Patent document 2] Japanese Patent No. 5480490

[Problem to be solved by the invention] The purpose of the present invention is to improve the adhesion between polyimide layers while suppressing foaming when manufacturing a metal-clad laminate having a plurality of polyimide layers as insulating resin layers by a casting method. [Means for solving the problem]

The inventors of the present invention have found that by controlling the thickness of a plurality of polyimide layers formed by a casting method, it is possible to improve the adhesion between the polyimide layers while suppressing foaming, thereby completing the present invention.

That is, the method for manufacturing a metal-clad laminate of the present invention is a method for manufacturing the following metal-clad laminate, wherein the metal-clad laminate includes: an insulating resin layer including a plurality of polyimide layers, and a metal layer laminated on at least one side of the insulating resin layer. The manufacturing method of the metal-clad laminate of the present invention comprises the following steps 1 to 5: Step 1) a step of laminating a first polyamide resin layer of a single layer or multiple layers by coating a polyamide solution on the metal layer; Step 2) a step of imidizing the polyamide acid in the first polyamide resin layer to form a first polyimide layer of a single layer or multiple layers; Step 3) a step of surface treating the surface of the first polyimide layer; Step 4) Further coating a polyamide solution on the first polyimide layer to form a monolayer or multilayer second polyamide resin layer; and Step 5) Imidizing the polyamide acid in the second polyamide resin layer to form a monolayer or multilayer second polyimide layer, and forming the insulating resin layer formed by laminating the first polyimide layer and the second polyimide layer. Furthermore, in the method for manufacturing a metal-clad laminate of the present invention, the thickness (L1) of the first polyimide layer is within the range of 0.5 μm or more and 100 μm or less, and the thickness (L) of the entire insulating resin layer is within the range of 5 μm or more and less than 200 μm, and the ratio (L/L1) of L to L1 is within the range of more than 1 and less than 400.

In the method for manufacturing a metal-clad laminate of the present invention, the polyimide constituting the layer in contact with the metal layer in the first polyimide layer may be a thermoplastic polyimide.

In the method for manufacturing the metal-clad laminate of the present invention, the moisture permeability of the metal layer can be 100 g/m ² /24 hr or less at a thickness of 25 μm and a temperature of 25°C.

The manufacturing method of the circuit substrate of the present invention includes: a step of performing wiring circuit processing on the metal layer of the metal-clad laminate manufactured by the method. [Effect of the invention]

According to the method of the present invention, a metal-clad laminate having an insulating resin layer in which foaming is suppressed and excellent adhesion between polyimide layers can be manufactured by a casting method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate.

[First embodiment] The method for manufacturing a metal-clad laminate of the first embodiment of the present invention is a method for manufacturing a metal-clad laminate comprising: an insulating resin layer including a plurality of polyimide layers, and a metal layer laminated on at least one side of the insulating resin layer.

(1) to (5) in FIG1 are step diagrams showing the main sequence of the method for manufacturing a metal-clad laminate according to the first embodiment. The method of this embodiment includes the following steps 1 to 5. In (1) to (5) in FIG1, the numbers next to the arrows refer to steps 1 to 5.

Step 1) In step 1, a polyamide solution is applied on the metal foil 10A to form the metal layer 10, thereby forming a single or multiple first polyamide resin layer 20A. There is no particular limitation on the method of applying the polyamide resin solution on the metal foil 10A by the casting method. For example, the coating can be performed by a coating machine such as a comma, a die, a knife, or a lip. Furthermore, when the first polyamide resin layer 20A is set as a multi-layer, for example, the following methods can be adopted: a method of repeatedly applying a polyamide solution to the metal foil 10A and drying it; or a method of simultaneously applying polyamide on the metal foil 10A in a multi-layer state by multi-layer extrusion and drying it.

In step 1, it is preferred to form the first polyimide resin layer 20A in such a manner that the thickness (L1) of the first polyimide layer 20 after curing in step 2 is within a range of 0.5 μm or more and 100 μm or less as described later. In the casting method, the polyamide resin layer is imidized while being fixed to the metal foil 10A, so that the expansion and contraction change of the polyimide layer during the imidization process can be suppressed, and the thickness or dimensional accuracy can be maintained.

The material of the metal foil 10A is not particularly limited, and examples thereof include copper, stainless steel, iron, nickel, cobalt, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among them, copper or copper alloys are particularly preferred. The copper foil may be a rolled copper foil or an electrolytic copper foil, and commercially available copper foil may be preferably used.

In the present embodiment, for example, when used in the manufacture of an FPC, the thickness of the metal layer 10 is preferably in the range of 3 μm to 80 μm, more preferably in the range of 5 μm to 30 μm.

The metal foil 10A used as the metal layer 10 may be subjected to surface treatment such as rust prevention, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc. The metal foil 10A may be in the form of a slice, a roll, or an endless belt. In order to achieve productivity, it is efficient to set it in the form of a roll or an endless belt and set it in a form that can be continuously produced. Furthermore, from the viewpoint of showing a more significant improvement effect on the accuracy of the wiring pattern in the circuit board, the metal foil 10A is preferably in the form of a roll formed in a long strip.

The moisture permeability of the metal layer 10 is preferably 100 g/m ² /24 hr or less at 25° C. when the moisture permeability of the metal layer 10 is low and the solvent or imidized water is difficult to escape from the metal layer 10, the effect of the method of this embodiment can be greatly exerted.

Step 2) In step 2, the polyamide acid in the first polyamide resin layer 20A formed in step 1 is imidized to form a first polyamide layer 20 including a single layer or multiple layers. By imidizing the polyamide acid contained in the first polyamide resin layer 20A, most of the solvent or imidized water contained in the first polyamide resin layer 20A can be removed.

The method for imidizing the polyamine is not particularly limited, and for example, heat treatment is preferably performed at a temperature in the range of 80° C. to 400° C. for a time in the range of 1 minute to 60 minutes. In order to suppress oxidation of the metal layer 10, the heat treatment is preferably performed in a low oxygen environment, specifically, in an inert gas environment such as nitrogen or a rare gas, in a reducing gas environment such as hydrogen, or in a vacuum.

Step 3) In step 3, the surface of the first polyimide layer 20 is subjected to surface treatment. The surface treatment is not particularly limited as long as it is a treatment that can improve the interlayer adhesion between the first polyimide layer 20 and the second polyimide layer 30, and examples thereof include: plasma treatment, corona treatment, flame treatment, ultraviolet treatment, ozone treatment, electron beam treatment, radiation treatment, sandblasting, hairline treatment, embossing, chemical treatment, steam treatment, surface grafting treatment, electrochemical treatment, primer treatment, etc. In particular, when the first polyimide layer 20 is a thermoplastic polyimide layer, surface treatment such as plasma treatment, corona treatment, and ultraviolet treatment is preferred, and the conditions thereof are preferably set to 300 W/min/m ² or less, for example.

Step 4) In step 4, a single-layer or multi-layer second polyamide resin layer 30A is formed by further coating a polyamide solution on the first polyamide layer 20 surface-treated in step 3. There is no particular limitation on the method of coating the polyamide resin solution on the first polyamide layer 20 by casting. For example, coating can be performed by a coating machine such as a notch wheel, a mold, a scraper, or a die lip. Furthermore, when the second polyamide resin layer 30A is set as a multi-layer, for example, the following methods can be used: a method of repeatedly applying a polyamide solution on the first polyimide layer 20 and drying it; or a method of simultaneously applying polyamide on the first polyimide layer 20 in a multi-layer state by multi-layer extrusion and drying it.

In step 4, the second polyamide resin layer 30A is preferably formed so that the thickness (L) of the entire insulating resin layer 40 after the next step 5 is within a range of 5 μm or more and less than 200 μm as described later.

Step 5) In step 5, the polyamide acid contained in the second polyamide resin layer 30A is imidized to change into the second polyimide layer 30, and the insulating resin layer 40 including the first polyimide layer 20 and the second polyimide layer 30 is formed. In step 5, the polyamide acid contained in the second polyamide resin layer 30A is imidized to synthesize polyimide. The imidization method is not particularly limited and can be implemented under the same conditions as step 2.

<Optional Step> The method of this embodiment may include any steps other than those described above.

Through the above steps 1 to 5, a metal-clad laminate 100 having an insulating resin layer 40 with excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30 can be manufactured. In the method of this embodiment, even if the first polyimide layer 20 is formed on the metal layer 10 by a casting method, by performing imidization before forming the second polyimide layer 30, the solvent or imidization water can be removed, thereby preventing problems such as foaming or interlayer peeling. In addition, by performing surface treatment on the first polyimide layer 20 before forming the second polyimide resin layer 30A, the adhesion between the first polyimide layer 20 and the second polyimide layer 30 can be ensured.

In the insulating resin layer 40 of the metal-clad laminate 100 manufactured by the method of this embodiment, the thickness (L1) of the first polyimide layer is within the range of 0.5 μm or more and 100 μm or less. Here, when the first polyimide layer 20 is a single layer, its thickness (L1) is preferably within the range of 0.5 μm or more and 5 μm or less, and more preferably within the range of 1 μm or more and 3 μm or less. In this case, in step 2, by hardening in a thin state where the thickness (L1) after imidization is less than 5 μm, the solvent or imidization water can be substantially removed. In addition, when the first polyimide layer 20 is a single layer, by controlling its thickness (L1) to 5 μm or less, the polyamide residue in the interface with the metal layer 10, which is one of the reasons for the reduction of the peel strength with the metal layer 10, disappears, and complete imidization can be performed, thereby improving the peel strength. If the thickness (L1) is less than 0.5 μm, the adhesion with the metal layer 10 is reduced, and the insulating resin layer 40 is easily peeled. On the other hand, when the first polyimide layer 20 includes multiple layers, its thickness (L1) is preferably in the range of 5 μm or more and 100 μm or less, and more preferably in the range of 25 μm or more and 100 μm or less. When the first polyimide layer 20 includes multiple layers, if its thickness (L1) exceeds 100 μm, foaming is likely to occur.

In addition, the thickness (L) of the insulating resin layer 40 as a whole is within the range of 5 μm or more and less than 200 μm. Here, when the first polyimide layer 20 is a single layer, the thickness (L) of the insulating resin layer 40 as a whole is preferably within the range of 5 μm or more and less than 30 μm, and more preferably within the range of 10 μm or more and less than 25 μm. When the first polyimide layer 20 is a single layer, if the thickness (L) of the insulating resin layer 40 as a whole is less than 5 μm, it is difficult to show the foaming suppression effect as the effect of the invention, and it is also difficult to obtain the effect of improving dimensional stability. On the other hand, when the first polyimide layer 20 includes multiple layers, the thickness (L) of the insulating resin layer 40 as a whole is preferably in the range of 10 μm or more and less than 200 μm, and more preferably in the range of 50 μm or more and less than 200 μm. When the first polyimide layer 20 includes multiple layers, if the thickness (L) of the insulating resin layer 40 as a whole is greater than 200 μm, foaming is likely to occur.

As described above, the thickness (L1) of the first polyimide layer 20 and the thickness (L) of the insulating resin layer 40 as a whole affect the improvement of foaming suppression or dimensional stability and the adhesion with the metal layer 10, so the ratio (L/L1) of the thickness (L) to the thickness (L1) is set to be greater than 1 and less than 400. The ratio (L/L1) is preferably within the range of greater than 1 and less than 60, more preferably greater than 4 and less than 45, and most preferably greater than 5 and less than 30.

Furthermore, the insulating resin layer 40 may include a polyimide layer other than the first polyimide layer 20 and the second polyimide layer 30. In addition, the polyimide layer constituting the insulating resin layer 40 may contain an inorganic filler as needed. Specifically, for example, there can be listed: silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. These can be used alone or in combination of two or more.

<Polyimide> Next, a preferred polyimide for forming the first polyimide layer 20 and the second polyimide layer 30 will be described. When forming the first polyimide layer 20 and the second polyimide layer 30, anhydride components and diamine components generally used as synthetic raw materials for polyimide can be used without particular limitation.

In the metal-clad laminate 100, the polyimide constituting the first polyimide layer 20 may be either thermoplastic polyimide or non-thermoplastic polyimide, but thermoplastic polyimide is preferred because it is easy to ensure adhesion with the metal layer 10 serving as the base.

In addition, the polyimide constituting the second polyimide layer 30 may be either thermoplastic polyimide or non-thermoplastic polyimide. When it is non-thermoplastic polyimide, the effect of the invention can be significantly exerted. That is, even if a resin layer of polyamide acid, which is a precursor of non-thermoplastic polyimide, is laminated on an imidized polyimide layer by a method such as a casting method and imidization is performed, it is usually almost impossible to obtain close contact between the polyimide layers. However, in this embodiment, as described above, the second polyimide resin layer 30A is laminated on the first polyimide layer 20 after surface treatment, thereby achieving excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30, regardless of whether the polyimide constituting the second polyimide layer 30 is thermoplastic or non-thermoplastic. In addition, by making the second polyimide layer 30 a non-thermoplastic polyimide, it can function as a main layer (base layer) that guarantees the mechanical strength of the polyimide layer in the metal-clad laminate 100.

Based on the above, in the metal clad laminate 100, the best aspect is to form a structure in which a thermoplastic polyimide layer is laminated as the first polyimide layer 20 and a non-thermoplastic polyimide layer is laminated as the second polyimide layer 30.

In addition, polyimide includes low thermal expansion polyimide and high thermal expansion polyimide. Generally, thermoplastic polyimide has high thermal expansion, and non-thermoplastic polyimide has low thermal expansion. For example, when the first polyimide layer 20 is a thermoplastic polyimide layer, the thermal expansion coefficient is preferably set to a range of more than 30×10 ^-6 /K and less than 80×10 ^-6 /K. By setting the thermal expansion coefficient of the thermoplastic polyimide layer to the above range, the adhesion between the first polyimide layer 20 and the metal layer 10 can be ensured. In addition, by using the second polyimide layer 30 as a polyimide layer with low thermal expansion, it can function as a main layer (base layer) for ensuring the dimensional stability of the polyimide layer in the metal-clad laminate 100. Specifically, the thermal expansion coefficient of the polyimide layer with low thermal expansion can be in the range of 1×10 ^-6 (1/K) to 30×10 ^-6 (1/K), preferably in the range of 1×10 ^-6 (1/K) to 25×10 ^-6 (1/K), and more preferably in the range of 10×10 ^-6 (1/K) to 25×10 ^-6 (1/K). In addition, since non-thermoplastic polyimide has low thermal expansion, the thermal expansion coefficient can be suppressed to a low level by increasing the thickness ratio of the non-thermoplastic polyimide layer. Furthermore, the first polyimide layer 20 and the second polyimide layer 30 can be made into polyimide layers having a desired thermal expansion coefficient by appropriately changing the combination of raw materials used, thickness, and drying/hardening conditions.

In addition, "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed, but in the present invention, it refers to a polyimide whose storage elastic modulus at 30°C is 1.0×10 ⁹ Pa or more and whose storage elastic modulus at 350°C is less than 1.0×10 ⁸ Pa as measured using a dynamic viscoelasticity measuring device (dynamic mechanical analyzer (DMA)). In addition, "non-thermoplastic polyimide" generally refers to a polyimide that does not show softening and adhesiveness even when heated, but in the present invention, it refers to a polyimide having a storage elastic modulus of 1.0×10 ⁹ Pa or more at 30°C and a storage elastic modulus of 1.0×10 ⁸ Pa or more at 350°C as measured using a dynamic viscoelasticity measuring apparatus (DMA).

As the diamine compound used as the raw material of the polyimide, an aromatic diamine compound, an aliphatic diamine compound, etc. can be used, for example, an aromatic diamine compound represented by _NH2 -Ar1- _NH2 is preferred. Here, Ar1 can be selected from the groups represented by the following formulas. Ar1 may have a substituent, but preferably has no substituent, or when having a substituent, the substituent may be a lower alkyl group or a lower alkoxy group having 1 to 6 carbon atoms. These aromatic diamine compounds may be used alone or in combination of two or more.

[Chemistry 1]

As the acid anhydride reacting with the diamine compound, an aromatic tetracarboxylic anhydride is preferred in terms of ease of synthesis of the polyamide. The aromatic tetracarboxylic anhydride is not particularly limited, and for example, a compound represented by O(CO) ₂ Ar2(CO) ₂ O is preferred. Here, Ar2 can be exemplified by a tetravalent aromatic group represented by the following formula. The substitution position of the acid anhydride group [(CO) ₂ O] is an arbitrary position, preferably a symmetrical position. Ar2 may also have a substituent, but preferably has no substituent, or if it has a substituent, the substituent may be a lower alkyl group having 1 to 6 carbon atoms.

[Chemistry 2]

(Synthesis of polyimide) The polyimide constituting the polyimide layer can be produced by reacting anhydride and diamine in a solvent, and heating and ring-closing after generating a precursor resin. For example, the anhydride component and the diamine component are dissolved in an organic solvent in approximately equimolar amounts, and the polymerization reaction is carried out by stirring at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours, thereby obtaining a polyamide acid as a precursor of the polyimide. During the reaction, the reaction components are dissolved in a manner such that the generated precursor is in the range of 5% by weight to 30% by weight, preferably in the range of 10% by weight to 20% by weight in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, etc. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. In addition, the amount of such organic solvent used is not particularly limited, and it is preferably used in an amount adjusted to a concentration of about 5% to 30% by weight of the polyamide solution (polyimide precursor solution) obtained by the polymerization reaction. The synthesized precursor is usually advantageously used as a reaction solvent solution, and can be concentrated, diluted or replaced with other organic solvents as needed. In addition, the precursor is usually advantageously used due to its excellent solvent solubility.

In the synthesis of polyimide, the acid anhydride and diamine may be used alone or in combination of two or more. By selecting the types of acid anhydride and diamine, or the molar ratio of two or more acid anhydrides or diamines, thermal expansion, adhesion, storage elastic coefficient, glass transition temperature, etc. can be controlled. Furthermore, in the case of having a plurality of structural units of polyimide in the polyimide, they may exist in the form of blocks or randomly, preferably randomly.

As described above, the metal-clad laminate obtained in this embodiment has excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30 and can be used as a circuit board material represented by FPC, thereby improving the reliability of electronic equipment.

In the first embodiment, the imidized polyimide is surface treated to obtain interlayer adhesion. When surface treatment is performed, equipment for surface treatment may be required and the number of steps may increase. Therefore, in the second embodiment of the present invention described below, a polyimide precursor layer is deposited while the polyimide precursor layer formed by the casting method is in a semi-hardened state, thereby suppressing foaming and improving interlayer adhesion without requiring a special step such as surface treatment.

[Second embodiment] The method for manufacturing a metal-clad laminate of the second embodiment of the present invention is a method for manufacturing a metal-clad laminate comprising: an insulating resin layer including a plurality of polyimide layers, and a metal layer laminated on at least one side of the insulating resin layer.

(a) to (d) in FIG. 2 are step diagrams showing the main sequence of the method for manufacturing a metal-clad laminate of the second embodiment. The method of this embodiment includes the following steps (a) to (d). In (a) to (d) in FIG. 2, the English letters next to the arrows refer to steps (a) to (d). In addition, in this embodiment, the same structure as the first embodiment is sometimes omitted by referring to the first embodiment.

Step (a) In step (a), a single or multiple first polyamide resin layer 20A is formed by coating a polyamide solution on a metal foil 10A to be a metal layer 10. There is no particular limitation on the method of coating the polyamide resin solution on the metal foil 10A by a casting method. For example, coating can be performed by a coating machine such as a notch wheel, a die, a scraper, or a die lip. Furthermore, when the first polyamide resin layer 20A is set as a multi-layer, for example, the following methods can be adopted: a method of repeatedly applying a polyamide solution to the metal foil 10A and drying it; or a method of simultaneously applying polyamide on the metal foil 10A in a multi-layer state by multi-layer extrusion and drying it.

In step (a), it is preferred that the first polyimide resin layer 20A is formed so that the thickness (L1) of the first polyimide layer 20 after curing in step (d) is within the range of 0.5 μm or more and 10 μm or less as described later. In the casting method, the polyamide resin layer is imidized while being fixed to the metal foil 10A, so that the expansion and contraction change of the polyimide layer during the imidization process can be suppressed, and the thickness or dimensional accuracy can be maintained.

The material, thickness, surface treatment, shape/form, and moisture permeability of the metal foil 10A are the same as those of the first embodiment.

Step (b) The polyamide acid contained in the first polyamide resin layer 20A is partially imidized in such a manner that the weight loss rate in the temperature range from 100°C to 360°C measured by a thermogravimetric differential thermal analyzer (TG-DTA) is within the range of 0.1% to 20%, thereby forming a single-layer or multi-layer semi-hardened resin layer 20B. In step (b), the polyamide acid contained in the first polyamide resin layer 20A is semi-hardened, so that most of the solvent or imidized water contained in the first polyamide resin layer 20A can be removed. In addition, if it is in a semi-cured state, unlike the cured state after the imidization is completed, sufficient inter-layer adhesion can be obtained between the second polyimide layer 30 of the upper layer formed by the subsequent steps (c) and (d).

Here, the semi-cured state after partial imidization is different from the simple dry state or the cured state after complete imidization, and is a state in which the imidization reaction occurs in the polyamide but is not completed. The degree of imidization can be evaluated, for example, by the weight loss rate in the temperature range from 100°C to 360°C measured by a thermogravimetric differential thermal analyzer (TG-DTA). If the weight loss rate in the temperature range is within the range of 0.1% to 20%, it can be considered to be a semi-cured state after partial imidization. If the weight loss rate is less than 0.1%, there is a possibility that imidization is excessively advanced, and sufficient interlayer adhesion cannot be obtained. On the other hand, when the weight reduction rate exceeds 20%, the imidization reaction hardly proceeds and cannot be distinguished from simple drying, so there is a high possibility that the solvent contained in the first polyamide resin layer 20A remains. In addition, the amount of imidization water generated before the imidization is completed is also large, so there is a concern that it may cause foaming. In step (b), it is preferred to adjust the degree of imidization so that the weight reduction rate is within the range of 1% to 15%.

In addition, the degree of imidization can also be evaluated by the imidization rate. In step (b), it is preferably adjusted so that the imidization rate of the semi-hardened resin layer 20B is in the range of 20% to 95%, and more preferably adjusted so that it is in the range of 22% to 90%. If the imidization rate is less than 20%, the imidization reaction hardly proceeds and cannot be distinguished from simple drying, so there is a high possibility that the solvent contained in the first polyamide resin layer 20A remains. In addition, the amount of imidization water generated before the imidization is completed is also large, so there is a concern that it may cause foaming. On the other hand, if the imidization rate exceeds 95%, there is a possibility that imidization may be excessively advanced, and sufficient interlayer adhesion may not be obtained. In addition, the imidization rate can be calculated as follows: the infrared absorption spectrum of the resin layer is measured using a Fourier transform infrared spectrophotometer and the attenuated total reflectance (ATR) method is used to measure the infrared absorption spectrum of the resin layer, and the absorbance derived from the imide group at 1778 cm ^-1 is calculated based on the benzene ring hydrocarbon bond at 1009 cm ^-1 . Here, the first polyamide resin layer 20A is subjected to a stepwise heat treatment from 120°C to 360°C, and the imidization rate after the heat treatment at 360°C is set to 100%.

The method for semi-curing the polyamide in step (b) is not particularly limited, and for example, preferably, heat treatment is performed by adjusting the time to achieve the weight reduction rate or imidization rate at a temperature in the range of 120°C to 300°C, preferably in the range of 140°C to 280°C. Furthermore, in order to suppress oxidation of the metal layer 10, the heat treatment is preferably performed in a low oxygen environment, specifically, in an inert gas environment such as nitrogen or a rare gas, in a reducing gas environment such as hydrogen, or in a vacuum.

Step (c) In step (c), a single-layer or multi-layer second polyamide resin layer 30A is formed by further coating a polyamide solution on the semi-hardened resin layer 20B formed in step (b). There is no particular limitation on the method of coating the polyamide resin solution on the semi-hardened resin layer 20B by casting. For example, coating can be performed by a coating machine such as a notch wheel, a die, a scraper, or a die lip. Furthermore, when the second polyamide resin layer 30A is set as a multi-layer, for example, the following methods can be adopted: a method of repeatedly applying a polyamide solution on the semi-hardened resin layer 20B and drying it; or a method of applying polyamide on the semi-hardened resin layer 20B in a multi-layer state by multi-layer extrusion and drying it at the same time.

In step (c), the second polyamide resin layer 30A is preferably formed so that the thickness (L) of the entire insulating resin layer 40 after step (d) is within a range of 10 μm to 200 μm, as described later.

Step (d) In step (d), the polyamide contained in the semi-hardened resin layer 20B and the polyamide contained in the second polyamide resin layer 30A are imidized to form the first polyimide layer 20 and the second polyimide layer 30, thereby forming the insulating resin layer 40. In step (d), the polyamide contained in the semi-hardened resin layer 20B and the second polyamide resin layer 30A are imidized together to synthesize polyimide. The imidization method is not particularly limited, and for example, heat treatment such as heating at a temperature in the range of 80°C to 400°C for a time in the range of 1 minute to 60 minutes can be appropriately adopted. In order to suppress oxidation of the metal layer 10, the heat treatment is preferably performed in a low oxygen environment, specifically, in an inert gas environment such as nitrogen or a rare gas, in a reducing gas environment such as hydrogen, or in a vacuum. Furthermore, regarding the end point of imidization in step (d), for example, the following conditions can be set as indicators: the weight loss rate in the temperature range from 100°C to 360°C measured by a thermogravimetric differential thermal analyzer (TG-DTA) is less than 0.1%, or the imidization rate exceeds 95%.

<Optional Step> The method of this embodiment may include any steps other than those described above. For example, it may further include a step of surface treating the surface of the semi-hardened resin layer 20B after step (b) and before step (c) within the scope of not impairing the effect of the invention. The surface treatment is not particularly limited as long as it is a treatment that can improve the interlayer adhesion between the first polyimide layer 20 and the second polyimide layer 30, and the same treatment as the first embodiment may be listed.

Through the above steps (a) to (d), the metal-clad laminate 100 having the insulating resin layer 40 with excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30 can be manufactured without causing a decrease in throughput due to an increase in the number of steps. In the method of this embodiment, even if the first polyimide layer 20 is formed on the metal layer 10 by a casting method, the solvent or imidization water can be removed by semi-hardening before forming the second polyimide layer 30, thereby preventing problems such as foaming and interlayer peeling.

In the insulating resin layer 40 of the metal-clad laminate 100 manufactured by the method of this embodiment, the thickness (L1) of the first polyimide layer 20 is preferably in the range of 0.5 μm or more and 10 μm or less, and more preferably in the range of 1 μm or more and 7 μm or less. In step (b), by semi-hardening in a thin state where the thickness (L1) after imidization is 10 μm or less, most of the solvent or imidization water can be removed. If the thickness (L1) after imidization exceeds 10 μm, it is difficult to remove the solvent or imidization water, and the dimensional stability is also deteriorated. In addition, if the thickness (L1) of the first polyimide layer 20 is less than 0.5 μm, the adhesion with the metal layer 10 is reduced, and the insulating resin layer 40 is easily peeled off.

In addition, the thickness (L) of the insulating resin layer 40 as a whole is preferably in the range of 10 μm or more and 200 μm or less, and more preferably in the range of 12 μm or more and 150 μm or less. If the thickness (L) is less than 10 μm, it is difficult to show the foaming suppression effect, and it is also difficult to obtain the effect of improving dimensional stability. On the other hand, if the thickness (L) exceeds 200 μm, foaming is likely to occur.

As described above, the thickness (L1) of the first polyimide layer 20 and the thickness (L) of the insulating resin layer 40 as a whole affect the improvement of foaming suppression or dimensional stability, so the ratio (L/L1) of the thickness (L) to the thickness (L1) is preferably greater than 1 and less than 400, more preferably greater than 4 and less than 200, and further preferably greater than 5 and less than 100.

Furthermore, the insulating resin layer 40 may include a polyimide layer other than the first polyimide layer 20 and the second polyimide layer 30. In addition, the polyimide layer constituting the insulating resin layer 40 may contain an inorganic filler as needed. Specifically, for example, there can be listed: silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. These can be used alone or in combination of two or more.

<Polyimide> Preferable polyimide for forming the first polyimide layer 20 and the second polyimide layer 30 in the second embodiment is described. When forming the first polyimide layer 20 and the second polyimide layer 30, anhydride components and diamine components generally used as synthetic raw materials for polyimide can be used without particular limitation.

In the metal-clad laminate 100, the polyimide constituting the first polyimide layer 20 may be either thermoplastic polyimide or non-thermoplastic polyimide, but thermoplastic polyimide is preferred because it is easy to ensure adhesion with the metal layer 10 serving as the base.

In addition, the polyimide constituting the second polyimide layer 30 may be either thermoplastic polyimide or non-thermoplastic polyimide. When it is non-thermoplastic polyimide, the effect of the invention can be significantly exerted. That is, even if a resin layer of polyamide acid, which is a precursor of non-thermoplastic polyimide, is laminated on an imidized polyimide layer by a method such as a casting method and imidization is performed, it is usually almost impossible to obtain close contact between the polyimide layers. However, in this embodiment, as described above, the second polyimide resin layer 30A is laminated while the first polyimide resin layer 20A is semi-cured, thereby achieving excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30, regardless of whether the polyimide constituting the second polyimide layer 30 is thermoplastic or non-thermoplastic. In addition, by making the second polyimide layer 30 a non-thermoplastic polyimide, it can function as a main layer (base layer) that guarantees the mechanical strength of the polyimide layer in the metal-clad laminate 100.

Based on the above, in the metal clad laminate 100, the best aspect is to form a structure in which a thermoplastic polyimide layer is laminated as the first polyimide layer 20 and a non-thermoplastic polyimide layer is laminated as the second polyimide layer 30.

In the second embodiment, the contents of the diamine compound and acid anhydride used as raw materials of polyimide, the synthesis of polyimide, etc. are the same as those of the first embodiment.

As described above, the manufacturing method of the metal-clad laminate of the second embodiment of the present invention includes the following steps (a) to (d): Step (a) is a step of laminating a first polyamide resin layer of a single layer or multiple layers by coating a polyamide solution on the metal layer; Step (b) is a step of partially imidizing the polyamide contained in the first polyamide resin layer to form a single layer or multiple layers of semi-hardened resin layer in such a manner that the weight reduction rate in the temperature range from 100°C to 360°C measured by a thermogravimetric differential thermal analyzer (TG-DTA) is within the range of 0.1% to 20%; Step (c) is a step of further coating a polyamide solution on the semi-hardened resin layer to form a single or multiple second polyamide resin layers; and Step (d) is a step of imidizing the polyamide contained in the semi-hardened resin layer and the polyamide contained in the second polyamide resin layer to form the insulating resin layer.

In the method for producing a metal-clad laminate according to the second embodiment of the present invention, the imidization rate in the step (b) may be in the range of 20% to 95%.

In the method for manufacturing a metal-clad laminate of the second embodiment of the present invention, the thickness (L1) of the resin layer formed by the first polyamide resin layer can be in the range of 0.5 μm to 10 μm, and the thickness (L) of the entire insulating resin layer can be in the range of 10 μm to 200 μm, and the ratio (L/L1) of L to L1 can be in the range of more than 1 and less than 400.

In the method for manufacturing a metal-clad laminate according to the second embodiment of the present invention, the polyimide constituting the layer in contact with the metal layer in the resin layer formed of the first polyamide resin layer may be a thermoplastic polyimide.

In the method for producing a metal-clad laminate according to the second embodiment of the present invention, the moisture permeability of the metal layer can be 100 g/m ² /24 hr or less at a thickness of 25 μm and a temperature of 25° C.

The method for manufacturing a metal-clad laminate according to the second embodiment of the present invention may further include a step of surface treating the surface of the semi-hardened resin layer after the step (b) and before the step (c).

The manufacturing method of the circuit board according to the second embodiment of the present invention includes the step of performing wiring circuit processing on the metal layer of the metal-clad laminate manufactured by any of the above methods.

As described above, the metal-clad laminate obtained in this embodiment has excellent adhesion between the first polyimide layer 20 and the second polyimide layer 30 and can be used as a circuit board material represented by FPC, thereby improving the reliability of electronic equipment.

In the first embodiment, the imidized polyimide is surface treated to obtain interlayer adhesion, but when surface treatment is performed, equipment for surface treatment is required and the number of steps increases. Therefore, in the third and fourth embodiments of the present invention described below, the interaction between the resin component of the polyimide precursor layer formed by the casting method and the resin component of the polyimide layer serving as the base is utilized, so that the adhesion between the polyimide layers can be improved without requiring a special step such as surface treatment.

[Third embodiment: Method for producing a polyimide film] The method for producing a polyimide film of the third embodiment is a method for producing a polyimide film comprising: a first polyimide layer (A), and a second polyimide layer (B) laminated on at least one side of the first polyimide layer (A). The polyimide film obtained by this embodiment may also have a polyimide layer other than the first polyimide layer (A) and the second polyimide layer (B), and may also be laminated on any substrate.

The method for producing the polyimide film of this embodiment includes the following steps I to III.

(Step I): In step I, a first polyimide layer (A) containing a polyimide having a ketone group is prepared. The polyimide having a ketone group has a ketone group (-CO-) in its molecule. The ketone group is derived from an acid dianhydride and/or a diamine compound as a raw material of the polyimide. That is, the polyimide constituting the first polyimide layer (A) contains a tetracarboxylic acid residue (1a) and a diamine residue (2a), and a residue having a ketone group is contained in either or both of the tetracarboxylic acid residue (1a) or the diamine residue (2a). In addition, in the present invention, "tetracarboxylic acid residue" means a tetravalent group derived from tetracarboxylic dianhydride, and "diamine residue" means a divalent group derived from a diamine compound. In addition, in "diamine compounds", the hydrogen atoms in the two terminal amino groups can be substituted.

Examples of the residue having a keto group contained in the tetracarboxylic acid residue (1a) include residues derived from "tetracarboxylic acid dianhydrides having a keto group in the molecule" such as 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-(p-phenylenedicarbonyl)phthalic anhydride, and 4,4'-(m-phenylenedicarbonyl)phthalic anhydride.

In the tetracarboxylic acid residue (1a), as the residue other than the residue having a keto group, for example, in addition to the residues shown in the Examples described below, there can be mentioned residues derived from tetracarboxylic dianhydride generally used in the synthesis of polyimide.

Examples of the ketone group-containing residue contained in the diamine residue (2a) include 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis(4-aminophenoxy)benzophenone, 4,4'-bis(3-aminophenoxy)benzophenone (4,4'-bis(3-aminophenoxy)benzophenone), Residues derived from "diamine compounds having a keto group in the molecule" such as 1,3-bis[4-(3-aminophenoxy)benzophenone (BABP), 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB), 1,4-bis(4-aminobenzyl)benzene, and 1,3-bis(4-aminobenzyl)benzene.

In the diamine residue (2a), as the residue other than the residue having a keto group, for example, in addition to the residues shown in the Examples described below, there can be exemplified residues derived from diamine compounds generally used in the synthesis of polyimide.

The first polyimide layer (A) may also contain other polyimides other than polyimide having a ketone group. In order to ensure sufficient adhesion with the second polyimide layer (B), it is preferred that 10 mol% or more of the total amount of polyimide constituting the first polyimide layer (A) is polyimide having a ketone group, and it is more preferred that 30 mol% or more of the polyimide is polyimide having a ketone group. In addition, the amount of ketone groups (in terms of -CO-) present in the polyimide constituting the first polyimide layer (A) is preferably in the range of 5 mol to 200 mol, and more preferably in the range of 15 mol to 100 mol, relative to 100 mol of the total of tetracarboxylic acid residues (1a) and diamine residues (2a). If the ketone groups present in the polyimide constituting the first polyimide layer (A) are less than 5 mol, the probability of interaction with the functional groups (e.g., terminal amine groups) present in the resin layer containing polyamide (b) deposited in step II becomes low, and sometimes sufficient interlayer adhesion cannot be obtained.

The first polyimide layer (A) can be formed by a method such as coating a resin solution containing polyamide (a) having a keto group on an arbitrary substrate (casting method); or laminating a gel film containing polyamide (a) having a keto group on an arbitrary substrate.

In the casting method, the method of applying the resin solution containing polyamide (a) is not particularly limited, and for example, the coating can be performed using a coating machine such as a notch wheel, a die, a doctor blade, or a die lip.

Furthermore, the first polyimide layer (A) may be in a state of being laminated with other resin layers, or may be in a state of being laminated on any substrate.

In addition, the first polyimide layer (A) is preferably formed by laminating a resin layer containing polyimide (a) having a keto group on a substrate and imidizing the polyimide (a) together with the substrate. In this way, even when the first polyimide layer (A) is formed on the substrate by a casting method, imidization is completed before the second polyimide layer (B) is formed, so that the solvent or imidization water can be removed, thereby preventing problems such as foaming and interlayer peeling.

The first polyimide layer (A) may be in the form of a slice, a roll, or an endless belt. In order to improve productivity, it is more efficient to use a roll or an endless belt so that continuous production can be performed. Furthermore, from the viewpoint of achieving a greater improvement in the accuracy of the wiring pattern in the circuit board, the first polyimide layer (A) is preferably in the form of a roll formed in a long strip.

(Step II) In step II, a resin layer containing polyamide (b) containing a functional group capable of interacting with the keto group is formed on the first polyimide layer (A) obtained in step I. In step II, the "functional group capable of interacting with the keto group" is not particularly limited as long as it is a functional group capable of interacting with the keto group, for example, by physical interaction based on intermolecular force or chemical interaction based on covalent bond, and an amino group (-NH ₂ ) can be cited as a representative example. When the functional group is an amino group, as the polyamine (b), a polyamine having an amino group at the terminal can be used, preferably a polyamine having most of the terminals as amino groups, and more preferably a polyamine having all of the terminals as amino groups. Thus, the polyamine (b) rich in amino group terminals can be formed by adjusting the molar ratio of the two components so that the diamine compound is excessive relative to the tetracarboxylic dianhydride in the raw material. For example, by adjusting the input ratio of the raw material so that the tetracarboxylic dianhydride is less than 1 mol relative to 1 mol of the diamine compound, most of the synthesized polyamine can be probabilistically set to polyamine (b) having an amino group terminal (-NH ₂ ). If the ratio of tetracarboxylic dianhydride to be added exceeds 1 mol per 1 mol of the diamine compound, the amino terminal (-NH ₂ ) is hardly left, which is not preferable. On the other hand, if the ratio of tetracarboxylic dianhydride to be added is too small, the molecular weight of the polyamide is not sufficiently increased. Therefore, the ratio of tetracarboxylic dianhydride to be added per 1 mol of the diamine compound is preferably set to, for example, 0.970 mol to 0.998 mol, more preferably 0.980 mol to 0.995 mol.

The polyamide (b) can be synthesized using tetracarboxylic dianhydride and diamine compounds generally used in the synthesis of polyimide as raw materials. Alternatively, tetracarboxylic dianhydride having a keto group in the molecule or a diamine compound having a keto group in the molecule may be used as a raw material.

In addition, by replacing part or all of the diamine compound of the raw material with a compound rich in amine groups in the molecule (for example, a triamine compound, etc.), a polyamine (b) rich in amine group terminals can also be synthesized. Furthermore, by setting the input ratio of tetracarboxylic dianhydride and diamine compound in the raw material to equimolar and adding a small amount of a compound containing an amine group (for example, a triamine compound, etc.), a resin layer containing a polyamine (b) rich in amine group terminals can also be formed.

When forming the resin layer containing polyamide (b), other polyamides other than polyamide (b) can be mixed with polyamide (b) for use. As the other polyamide, a polyamide synthesized in an equimolar ratio using tetracarboxylic dianhydride and diamine compounds generally used in the synthesis of polyimide as raw materials can be used. Among them, from the viewpoint of ensuring sufficient adhesion with the first polyimide layer (A), the resin layer containing polyamide (b) preferably contains polyamide (b) in an amount of 10 mol% or more, and more preferably 30 mol% or more, of the total amount of polyamide to be formed.

The resin layer containing polyamide (b) can be formed by the following methods: a method of coating a resin solution containing polyamide (b) on the first polyimide layer (A) (casting method); a method of laminating a gel film containing polyamide (b) on the first polyimide layer (A). In order to improve the adhesion between the first polyimide layer (A) and the second polyimide layer (B), the casting method is preferably used. In addition, when forming the resin layer containing polyamide (b), it is not necessary to perform surface treatment such as plasma treatment and corona treatment on the surface of the first polyimide layer (A) in advance, but these surface treatments may be performed.

In the casting method, the method of applying the resin solution containing polyamide (b) is not particularly limited, and for example, the coating can be performed using a coating machine such as a notch wheel, a film, a doctor blade, or a die lip.

The resin layer containing polyamine (b) thus obtained is a resin layer comprising tetracarboxylic acid residues (1b) and diamine residues (2b), wherein the tetracarboxylic acid residues (1b) are contained in an amount of less than 1 mol, preferably in a range of 0.970 mol to 0.998 mol, more preferably in a range of 0.980 mol to 0.995 mol, based on 1 mol of diamine residues (2b), and are rich in terminal amino groups ( _-NH2 ).

(Step III) In step III, the resin layer containing polyamide (b) is heat-treated together with the first polyimide layer (A) to imidize the polyamide (b) to form a second polyimide layer (B). The imidization method is not particularly limited, and for example, heat treatment such as heating at a temperature in the range of 80°C to 400°C for a time in the range of 1 minute to 60 minutes can be appropriately adopted. In the case of a metal layer, in order to suppress oxidation, heat treatment in a low oxygen environment is preferred, and specifically, it is preferably performed in an inert gas environment such as nitrogen or a rare gas, a reducing gas environment such as hydrogen, or in a vacuum.

In addition, it is believed that, in parallel with the imidization, an interaction occurs between the keto group present in the polyimide chain of the first polyimide layer (A) and the functional group (e.g., abundant terminal amine group) present in the resin layer containing the polyamide (b), and the adhesion between the first polyimide layer (A) and the second polyimide layer (B) is greatly improved beyond the properties of the polyimides constituting the two layers (e.g., thermoplasticity or non-thermoplasticity, etc.). It is not possible to clarify all the mechanisms of the interaction, but it is speculated that, in the case where the functional group is an amine group, as one possibility, an imide bond is generated between the keto group and the terminal amine group by heat treatment during imidization of the polyamide (b). That is, it is inferred that a dehydration condensation reaction occurs between the ketone group in the polyimide chain of the first polyimide layer (A) and the amino group at the end of the polyamine (b) by heating to form an imide bond, and the polyimide chain in the first polyimide layer (A) and the imidized second polyimide layer (B) are chemically bonded, thereby enhancing the bonding strength between the first polyimide layer (A) and the second polyimide layer (B).

Furthermore, when the first polyimide layer (A) and the second polyimide layer (B) have a relationship opposite to that described above, the effect of improving the inter-layer adhesion cannot be obtained. That is, in the case where, first, a resin layer containing polyamide (b) is imidized to form a first polyimide layer, and a resin layer containing polyamide (a) having a keto group is formed thereon, and then imidized by heat treatment to form a second polyimide layer, the adhesion between the first layer and the second layer is not improved beyond the properties (for example, thermoplasticity or non-thermoplasticity, etc.) of the polyimide constituting the two layers. The reason for this is considered to be that in the cured polyimide, the movement of the amine group, which is the terminal of the functional group, is restricted and the reactivity is reduced, so that the interaction is difficult to occur.

The first polyimide layer (A) and the second polyimide layer (B) may contain an inorganic filler as needed. Specifically, for example, there can be mentioned: silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. These can be used alone or in combination of two or more.

Through the above steps I to III, a polyimide film having excellent adhesion between the first polyimide layer (A) and the second polyimide layer (B) can be manufactured without causing a decrease in yield due to an increase in the number of steps.

[Fourth embodiment: Method for manufacturing a metal-clad laminate] The fourth embodiment of the present invention is a method for manufacturing a metal-clad laminate, and includes the following steps i to iv, wherein the metal-clad laminate includes: a metal layer, a first polyimide layer (A), and a second polyimide layer (B) laminated on one side of the first polyimide layer (A).

(Step i) In step i, at least one layer of a polyamine resin layer is formed on the metal layer, wherein the polyamine resin layer includes a polyamine (a) resin layer having a keto group in the surface layer.

As the metal layer, a metal foil can be preferably used. The material of the metal foil is not particularly limited, and examples thereof include: copper, stainless steel, iron, nickel, cobalt, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among them, copper or a copper alloy is particularly preferred. As the copper foil, it can be a rolled copper foil or an electrolytic copper foil, and commercially available copper foil can be preferably used.

In the present embodiment, for example, when used in the manufacture of an FPC, the thickness of the metal layer is preferably in the range of 3 μm to 50 μm, more preferably in the range of 5 μm to 30 μm.

The metal foil used as the metal layer may be subjected to surface treatment such as rust prevention, trimming, aluminum alcoholate, aluminum chelate, silane coupling agent, etc. The metal foil may be in the form of a slice, a roll, or an endless belt. In order to achieve productivity, it is efficient to use a roll or an endless belt in a form that allows continuous production. Furthermore, from the perspective of more significantly showing the effect of improving the accuracy of the wiring pattern in the circuit board, the metal foil is preferably in the form of a roll formed in a long strip.

When forming the first polyimide layer (A), at least one layer of a resin layer of polyamide (a) having a keto group is formed on the metal layer in such a way that the resin layer includes the polyamide (a) having a keto group as the surface layer. In this case, the resin layer can be formed by the following methods: a method of coating a resin solution of polyamide on the metal layer (casting method); a method of laminating a gel film containing polyamide (a) on the metal layer. Furthermore, there may be an arbitrary resin layer (a resin layer containing other polyamides) between the metal layer and the resin layer containing polyamide (a) having a keto group. In this case, the resin layer containing polyamide (a) having a keto group may be formed on the arbitrary resin layer using the above method. In addition, when the resin layer containing polyamide (a) having a keto group is directly formed on the metal layer, it is preferred to use a casting method in order to improve the adhesion between the metal layer and the first polyimide layer (A).

In the casting method, the method of applying the resin solution containing polyamide (a) is not particularly limited, and for example, the coating can be performed using a coating machine such as a notch wheel, a die, a doctor blade, or a die lip.

(Step ii) In step ii, the resin layer of polyamide acid is heat-treated together with the metal layer to imidize the polyamide acid, wherein the resin layer of polyamide acid includes a resin layer containing polyamide acid (a) having a ketone group in the surface layer. Thus, an intermediate having a polyimide layer laminated thereon is formed, wherein the polyimide layer includes a first polyimide layer (A) containing polyimide having a ketone group as the surface layer.

The imidization of polyamide can be carried out by the method described in step (III) of the third embodiment. In this embodiment, even when a polyamide resin layer is formed on a metal foil by a casting method, imidization is completed before forming the second polyamide layer (B), so the solvent or imidization is removed, thereby preventing problems such as foaming and interlayer peeling. The polyamide resin layer includes a resin layer containing polyamide (a) having a keto group in the surface layer.

(Step iii) In step iii, a resin layer containing polyamine (b) is layered on the first polyimide layer (A), wherein the polyamine (b) contains a functional group having a property of interacting with the ketone group. This step iii can be implemented in the same manner as step II of the third embodiment.

(Step iv) The resin layer containing polyamide (b) laminated on the intermediate in step iii is heat-treated together with the intermediate to imidize the polyamide (b) to form a second polyimide layer (B). This step iv can be implemented in the same manner as step III of the third embodiment.

Through the above steps i to iv, a metal-clad laminate having excellent adhesion between the first polyimide layer (A) and the second polyimide layer (B) can be manufactured without causing a decrease in yield due to an increase in the number of steps.

The other structures and effects of this embodiment are the same as those of the third embodiment.

<Polyimide> Next, preferred polyimide for forming the first polyimide layer (A) and the second polyimide layer (B) will be described. When forming the first polyimide layer (A), it is preferred to use the "tetracarboxylic dianhydride having a ketone group in the molecule" and/or "diamine compound having a ketone group in the molecule" in combination with an acid anhydride component and a diamine component generally used as a synthetic raw material for polyimide. When forming the second polyimide layer (B), an acid anhydride component and a diamine component generally used as a synthetic raw material for polyimide can be used without particular limitation.

In the polyimide film or the metal-clad laminate, the polyimide constituting the first polyimide layer (A) may be either thermoplastic polyimide or non-thermoplastic polyimide, but thermoplastic polyimide is preferred because it is easy to ensure adhesion with a base material, metal foil, or resin layer serving as a base.

In addition, the polyimide constituting the second polyimide layer (B) may be either a thermoplastic polyimide or a non-thermoplastic polyimide, and the effect of the invention can be significantly exerted when it is a non-thermoplastic polyimide. That is, even if a resin layer of polyamide acid, which is a precursor of a non-thermoplastic polyimide, is laminated on the imidized first polyimide layer (A) by a method such as a casting method and imidization is performed, it is usually almost impossible to obtain close contact between the polyimide layers. However, in this embodiment, due to the interaction between the ketone group and the functional group (e.g., terminal amine group), excellent adhesion between the first polyimide layer (A) and the second polyimide layer (B) can be obtained regardless of whether the polyimide constituting the second polyimide layer (B) is thermoplastic or non-thermoplastic. In addition, by making the second polyimide layer (B) a non-thermoplastic polyimide, it can function as a main layer (base layer) that guarantees the mechanical strength of the polyimide layer in the polyimide film or metal-clad laminate.

Based on the above, in the polyimide film or metal-clad laminate, the best aspect is to form a structure in which a thermoplastic polyimide layer is laminated as the first polyimide layer (A) and a non-thermoplastic polyimide layer is laminated as the second polyimide layer (B).

(Thermoplastic polyimide) Thermoplastic polyimide can be obtained by reacting an acid anhydride component with a diamine component. As the acid anhydride component that is the raw material of the thermoplastic polyimide, any acid anhydride commonly used in the synthesis of polyimide can be used without particular limitation. From the viewpoint of particularly taking both adhesion to metal layers and low dielectric properties into consideration, it is preferred to use biphenyltetracarboxylic dianhydride and pyromellitic dianhydride (PMDA) in combination. Biphenyltetracarboxylic dianhydride has the effect of lowering the glass transition temperature to a level that does not affect the reduction of the solder heat resistance of the polyimide, and can ensure sufficient adhesion to metal layers and the like. In addition, biphenyltetracarboxylic dianhydride reduces the imide group concentration of polyimide, and easily forms an ordered structure of the polymer, and improves the dielectric properties by inhibiting the movement of molecules. Furthermore, biphenyltetracarboxylic dianhydride contributes to the reduction of polar groups in polyimide, thereby improving the moisture absorption properties. In this way, biphenyltetracarboxylic dianhydride can reduce the transmission loss of FPC. In addition, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire structure of the polyimide.

Examples of biphenyl tetracarboxylic dianhydride include 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 2,3',3,4'-biphenyl tetracarboxylic dianhydride, and 2,2',3,3'-biphenyl tetracarboxylic dianhydride. By using biphenyl tetracarboxylic dianhydride within the above range, an ordered structure based on a rigid structure is formed, thereby achieving a low dielectric loss tangent, and obtaining a thermoplastic polyimide that is thermoplastic, has low gas permeability, and has excellent long-term heat-resistant adhesion. Pyromellitic dianhydride is a monomer that is responsible for controlling the glass transition temperature, and contributes to improving the solder heat resistance of the polyimide.

Furthermore, the thermoplastic polyimide may use an acid anhydride other than the above as the acid anhydride component. Examples of such anhydrides include 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-p-triphenyl tetracarboxylic dianhydride, 2,3,3'',4''-p-triphenyl tetracarboxylic dianhydride or 2,2'',3,3''-p-triphenyl tetracarboxylic dianhydride. Carboxylic acid dianhydrides, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfonate dianhydride or bis(3,4-dicarboxyphenyl)sulfonate dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3 ,6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, and the like.

As the diamine component serving as the raw material of the thermoplastic polyimide, any diamine commonly used in the synthesis of polyimide can be used without particular limitation, but it is preferably a diamine compound containing at least one selected from the diamine compounds represented by the following general formulae (1) to (8).

[Chemistry 3]

In the above formulae (1) to (7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and _n1 independently represents an integer from 0 to 4. In the above formulae (3), the part repeated with formula (2) is removed, and the part repeated with formula (4) is removed from formula (5). Here, "independently" means that in one or more of the above formulae (1) to (7), multiple linking groups A, multiple _R1 or multiple _n1 may be the same or different.

[Chemistry 4]

In the formula (8), the linking group X represents a single bond or -CONH-, Y independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms which may be substituted with a halogen atom, n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4.

Furthermore, in the above formulae (1) to (8), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR ₂ R ₃ (wherein R ₂ and R ₃ independently represent any substituent such as an alkyl group).

The diamine represented by formula (1) (hereinafter, sometimes described as "diamine (1)") is an aromatic diamine having two benzene rings. The diamine (1) is believed to increase the degree of freedom of the polyimide molecular chain and have high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being located at the meta position, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (1), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-, _-CH2- , -C( _CH3 ) _2- , -CO-, _-SO2- , or -S-.

Examples of the diamine (1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-diamino)diphenylamine.

The diamine represented by formula (2) (hereinafter, sometimes described as "diamine (2)") is an aromatic diamine having three benzene rings. The diamine (2) is believed to increase the degree of freedom of the polyimide molecular chain and have high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being located at the meta position, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (2), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

Examples of the diamine (2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]aniline, and 3-[3-(4-aminophenoxy)phenoxy]aniline.

The diamine represented by formula (3) (hereinafter, sometimes described as "diamine (3)") is an aromatic diamine having three benzene rings. The diamine (3) is believed to increase the degree of freedom of the polyimide molecular chain and have high flexibility due to the two divalent linking groups A directly bonded to one benzene ring being located at the meta position, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (3), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

Examples of the diamine (3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, and 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline. Among these, 1,3-bis(4-aminophenoxy)benzene (TPE-R) is particularly preferred as a monomer that contributes to increasing the CTE (Coefficient of Thermal Expansion) of thermoplastic polyimide, reducing the imide group concentration, and improving the dielectric properties.

The diamine represented by formula (4) (hereinafter, sometimes described as "diamine (4)") is an aromatic diamine having four benzene rings. The diamine (4) is considered to have high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being located at the meta position, and thus contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (4), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O-, _-CH2- , -C( _CH3 ) _2- , _-SO2- , -CO-, and -CONH- are preferred.

Examples of the diamine (4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, and bis[4,4'-(3-aminophenoxy)]benzanilide.

The diamine represented by formula (5) (hereinafter, sometimes described as "diamine (5)") is an aromatic diamine having four benzene rings. The two divalent linking groups A directly bonded to at least one benzene ring of the diamine (5) are located at the meta position to each other, and the degree of freedom of the polyimide molecular chain is increased and the flexibility is high, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (5), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

Examples of the diamine (5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline and 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline.

The diamine represented by formula (6) (hereinafter, sometimes described as "diamine (6)") is an aromatic diamine having four benzene rings. It is believed that the diamine (6) has high flexibility due to having at least two ether bonds, and contributes to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (6), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -C( _CH3 ) _2- , -O-, _-SO2- , and -CO- are preferred.

Examples of the diamine (6) include 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), and bis[4-(4-aminophenoxy)phenyl]ketone (BAPK). Among these, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is particularly preferred as it is a monomer that greatly contributes to improving the adhesion to the metal layer.

The diamine represented by formula (7) (hereinafter, sometimes described as "diamine (7)") is an aromatic diamine having four benzene rings. Since the diamine (7) has a highly flexible divalent linking group A on both sides of the diphenyl skeleton, it is considered that it contributes to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (7), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

Examples of the diamine (7) include bis[4-(3-aminophenoxy)]biphenyl and bis[4-(4-aminophenoxy)]biphenyl.

The diamine represented by the general formula (8) (hereinafter, sometimes described as "diamine (8)") is an aromatic diamine having one to three benzene rings. Since diamine (8) has a rigid structure, it has the function of imparting an ordered structure to the polymer as a whole. Therefore, by using one or more of diamines (1) to diamines (7) and one or more of diamines (8) in combination at a predetermined ratio, a low dielectric loss tangent can be achieved, and a thermoplastic polyimide with low gas permeability and excellent long-term heat-resistant adhesion can be obtained. Here, the linking group X is preferably a single bond, -CONH-.

Examples of the diamine (8) include paraphenylenediamine (PDA), 4,4'-diamino-2,2'-dimethyl biphenyl (m-TB), 4,4'-diamino-3,3'-dimethyl biphenyl, 4,4'-diamino-2,2'-n-propyl biphenyl (m-NPB), 2'-methoxy-4,4'-diamino benzanilide (MABA), 4,4'-diamino benzanilide (DABA), and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. Among these, 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) is particularly preferred as a monomer that greatly contributes to the improvement of the dielectric properties of thermoplastic polyimide and further to the reduction of moisture absorption or the improvement of heat resistance.

By using diamine (1) to diamine (7), the flexibility of the polyimide molecular chain can be improved and thermoplasticity can be imparted.

In addition, by using diamine (8), the rigid structure derived from the monomer is utilized to form an ordered structure in the entire polymer, thereby achieving a low dielectric loss tangent, and obtaining a thermoplastic polyimide with low gas permeability and excellent long-term heat-resistant adhesion.

In addition, the thermoplastic polyimide may use diamines other than those mentioned above as the diamine component.

(Non-thermoplastic polyimide) Non-thermoplastic polyimide can be obtained by reacting an anhydride component with a diamine component. As the anhydride component that becomes the raw material of the non-thermoplastic polyimide, the common anhydride used in the synthesis of polyimide can be used without particular limitation. In order to impart low dielectric properties, it is preferred to use at least one selected from pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride, and naphthalenetetracarboxylic dianhydride as the raw material acid anhydride component. Here, as the biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is particularly preferred, and as the naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-naphthalenetetracarboxylic dianhydride, NTCDA) is particularly preferred.

PMDA can reduce the coefficient of thermal expansion (CTE) of polyimide. BPDA has the effect of reducing the glass transition temperature to a level that does not affect the reduction of the solder heat resistance of polyimide. In addition, BPDA reduces the imide group concentration of polyimide, and easily forms an ordered structure of the polymer, and improves the dielectric properties by inhibiting the movement of molecules. Furthermore, BPDA helps reduce the polar groups of polyimide, thereby improving the moisture absorption characteristics. Therefore, by using BPDA, the transmission loss of FPC can be reduced.

In addition, the non-thermoplastic polyimide may use an acid anhydride other than the above-mentioned ones as the acid anhydride component.

As the diamine component serving as the raw material of the non-thermoplastic polyimide, any diamine commonly used in the synthesis of polyimide can be used without particular limitation. Preferably, it is a diamine selected from the diamines (1) to (8) exemplified in the description of the thermoplastic polyimide, and more preferably, diamine (8).

Diamine (8) is an aromatic diamine, which contributes to lower CTE or improvement of dielectric properties, and further contributes to lower moisture absorption or higher heat resistance. Among diamine (8), in the general formula (8), Y is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) and 4,4'-diamino-3,3'-dimethylbiphenyl. Among these, 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) is the most preferred.

Furthermore, the non-thermoplastic polyimide may use diamines other than those described above as the diamine component within a range not hindering the effects of the present invention.

(Synthesis of polyimide) The polyimide constituting the polyimide layer can be produced by reacting an acid anhydride and a diamine in a solvent, and heating and ring-closing the reaction mixture after the precursor resin is generated. For example, the acid anhydride component and the diamine component are dissolved in an organic solvent in approximately equal molar amounts [wherein the ratio of the diamine component is increased when forming the second polyimide layer (B)], and the polymerization reaction is carried out by stirring at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours, thereby obtaining a polyamide acid as a precursor of the polyimide. During the reaction, the reaction components are dissolved in an organic solvent in a range of 5 wt% to 30 wt%, preferably 10 wt% to 20 wt%. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, etc. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. In addition, the amount of such organic solvent used is not particularly limited, and it is preferably used in an amount adjusted to a concentration of about 5 wt% to 30 wt% of the polyamide solution (polyimide precursor solution) obtained by the polymerization reaction.

In the synthesis of polyimide, the acid anhydride and diamine may be used alone or in combination. By selecting the types of the acid anhydride and diamine, or the molar ratio of the two or more acid anhydrides or diamines, thermal expansion, adhesion, glass transition temperature, etc. can be controlled.

The synthesized precursor is usually advantageously used as a reaction solvent solution, and can be concentrated, diluted or replaced with other organic solvents as needed. In addition, the precursor is usually advantageously used due to its excellent solvent solubility. The method for imidizing the precursor is not particularly limited, for example, a heat treatment such as heating in the solvent at a temperature condition in the range of 80°C to 400°C for 1 hour to 24 hours can be appropriately adopted.

As described above, the method for manufacturing a polyimide film of the third embodiment of the present invention is a method for manufacturing a polyimide film, wherein the polyimide film comprises: a first polyimide layer (A), and a second polyimide layer (B) laminated on at least one side of the first polyimide layer (A). The method for producing a polyimide film of the third embodiment of the present invention comprises the following steps I to III: I) a step of preparing a first polyimide layer (A) comprising a polyimide having a ketone group; II) a step of laminating a resin layer comprising polyamide (b) on the first polyimide layer (A), wherein the polyamide (b) comprises a functional group having a property of interacting with the ketone group; and III) a step of heat-treating the resin layer comprising polyamide (b) together with the first polyimide layer (A) to imidize the polyamide (b) and form a second polyimide layer (B).

In the method for producing a polyimide film of the third embodiment of the present invention, the polyimide constituting the first polyimide layer (A) comprises tetracarboxylic acid residues (1a) and diamine residues (2a), and the ketone group may be 5 mol parts or more relative to 100 mol parts in total of the tetracarboxylic acid residues (1a) and the diamine residues (2a).

In the method for producing a polyimide film of the third embodiment of the present invention, the resin layer containing polyamide (b) contains tetracarboxylic acid residues (1b) and diamine residues (2b), and the tetracarboxylic acid residues (1b) may be less than 1 mol relative to 1 mol of the diamine residues (2b).

In the method for producing a polyimide film according to the third embodiment of the present invention, the first polyimide layer (A) may be formed by laminating a resin layer containing polyamide (a) having a keto group on a substrate and imidizing the polyamide (a) together with the substrate.

In addition, the manufacturing method of the metal-clad laminate of the fourth embodiment of the present invention is the following manufacturing method of the metal-clad laminate, wherein the metal-clad laminate includes: a metal layer, a first polyimide layer (A), and a second polyimide layer (B) laminated on one side of the first polyimide layer (A). The manufacturing method of the metal-clad laminate of the fourth embodiment of the present invention includes the following steps i to iv: i) forming at least one layer of a polyamide resin layer on the metal layer, wherein the polyamide resin layer includes a resin layer containing a polyamide (a) having a keto group in the surface layer; ii) heat-treating the resin layer of the polyamine together with the metal layer to imidize the polyamine, thereby forming an intermediate having a polyimide layer laminated on the metal layer, wherein the polyimide layer includes a first polyimide layer (A) containing a polyimide having a ketone group as a surface layer; iii) laminating a resin layer containing polyamine (b) on the first polyimide layer (A), wherein the polyamine (b) contains a functional group having a property of interacting with the ketone group; and iv) heat-treating the resin layer of the polyamide (b) together with the intermediate to imidize the polyamide (b) to form a second polyimide layer (B).

A method for manufacturing a circuit board according to an embodiment of the present invention includes the step of performing wiring circuit processing on the metal layer of the metal-clad laminate manufactured by the method of the fourth embodiment.

As described above, the polyimide film obtained in the third embodiment of the present invention and the metal-clad laminate obtained in the fourth embodiment have excellent adhesion between the first polyimide layer (A) and the second polyimide layer (B) and are used as circuit board materials represented by FPC, thereby improving the reliability of electronic equipment.

<Circuit board> A circuit board of one embodiment of the present invention includes: an insulating resin layer including a plurality of polyimide layers, and a wiring layer laminated on at least one side of the insulating resin layer. The circuit board can be manufactured by processing the metal layer of the metal-clad laminate obtained by the method of the first embodiment, the second embodiment or the fourth embodiment into a pattern to form the wiring layer by a conventional method. The patterning of the metal layer can be performed by any method such as photolithography and etching.

Furthermore, when manufacturing a circuit substrate, the steps that are usually performed, such as the through-hole processing in the previous step, or the terminal plating and shape processing in the subsequent step, can be performed according to conventional methods. [Implementation Example]

The following examples are shown to more specifically describe the features of the present invention. However, the scope of the present invention is not limited to the examples. Furthermore, in the following examples, comparative examples and reference examples, unless otherwise specified, various measurements and evaluations are based on the following contents.

[Viscosity measurement] The viscosity of the resin was measured at 25°C using an E-type viscometer (Brookfield, trade name: DV-II+Pro). The speed was set so that the torque was 10% to 90%, and the value when the viscosity stabilized was read 2 minutes after the start of the measurement.

[Evaluation of Foaming] If peeling was observed between the first polyimide layer and the second polyimide layer, or cracking occurred in the polyimide layer, it was determined as "foaming was present", and if there was no peeling or cracking, it was determined as "no foaming".

[Measurement of dimensional change rate after etching] Prepare a metal-clad laminate of 80 mm × 80 mm size. After applying a dry film resist on the metal layer of the laminate, perform exposure and development, and form 16 resist patterns with a diameter of 1 mm in a regular quadrilateral as a whole, as shown in Figure 3, and prepare a position measurement target that can measure 5 locations at intervals of 50 mm in the longitudinal direction (machine direction, MD) and the transverse direction (transverse direction, TD).

For the prepared sample, the distance between the targets in the longitudinal direction (MD) and the transverse direction (TD) of the resist pattern in the position measurement target was measured in an environment of temperature: 23±2°C and relative humidity: 50±5%. After that, the exposed portion of the metal layer in the opening of the resist pattern was removed by etching (etching liquid temperature: below 40°C, etching time: within 10 minutes). As shown in Figure 4, an evaluation sample with 16 metal layer residual points was prepared. After the evaluation sample is placed in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24±4 hours, the distance between the metal layer residual points in the longitudinal direction (MD) and the transverse direction (TD) is measured. The dimensional change rate relative to the normal state at 5 points in the longitudinal direction and the transverse direction is calculated, and the average value of each is taken as the dimensional change rate after etching. Each dimensional change rate is obtained by the following formula. Dimensional change rate after etching (%) = (B-A)/A×100 A: The distance between targets after resist development B: The distance between metal layer residual points after metal layer etching The absolute value of the dimensional change rate after etching is set to "good" if it is less than 0.2%, "acceptable" if it exceeds 0.2% and is less than 0.4%, and "no" if it exceeds 0.4%.

[Evaluation of curl] Film curl is measured by etching the entire copper foil of the metal-clad laminate and measuring the floating height of the four corners of the polyimide film with a size of 100 mm × 100 mm after removing the copper foil, with the first polyimide layer placed at the bottom. If the average value of the floating height of the four corners exceeds 10 mm, it is evaluated as "curling".

[Evaluation of moisture permeability] According to Japanese Industrial Standards (JIS) Z0208, a moisture absorbent/calcium chloride (anhydrous) is sealed in a moisture permeability cup, and the increase in the cup mass after 24 hours is evaluated as the amount of water vapor permeability.

[Determination of moisture absorption rate] Prepare 2 test pieces of polyimide film (width 4 cm × length 25 cm) and dry them at 80°C for 1 hour. After drying, immediately place them in a constant temperature and humidity chamber at 23°C/50%RH and leave them for more than 24 hours. Calculate the moisture absorption rate (weight %) using the following formula based on the weight change before and after.

[Measurement of glass transition temperature (Tg)] The dynamic viscoelasticity of a polyimide film (10 mm × 40 mm) was measured by heating it from 20°C to 500°C at 5°C/min using a dynamic thermomechanical analyzer (DMA: manufactured by TA Instruments Japan, trade name: RSA-G2), and the glass transition temperature (Tanδ maximum value: °C) was determined.

[Measurement of storage elastic coefficient] The storage elastic coefficient was measured using a dynamic viscoelasticity measuring apparatus (DMA). Polyimide having a storage elastic coefficient of 1.0×10 ⁹ Pa or more at 30°C and a storage elastic coefficient of 1.0×10 ⁸ Pa or more at 350°C was defined as "non-thermoplastic polyimide", and polyimide having a storage elastic coefficient of 1.0×10 ⁹ Pa or more at 30°C and a storage elastic coefficient of less than 1.0×10 ⁸ Pa at 350°C was defined as "thermoplastic polyimide".

[Measurement of thermal expansion coefficient (CTE)] For a polyimide film with a thickness of 25 μm and a size of 3 mm × 20 mm, a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA) was used to increase the temperature from 30°C to 300°C at a constant rate while applying a load of 5.0 g. After maintaining the temperature for 10 minutes, the film was cooled at a rate of 5°C/min to obtain the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

[Determination of volatile content] For the volatile content in each example, the thermogravimetry-differential thermal analysis (TG-DTA) of the semi-cured first polyamide resin layer film was performed at a temperature increase rate of 10°C/min in the range of 30°C to 500°C, and the weight of the film at 100°C was set as 100%. The weight reduction rate from 100°C to 360°C was set as the volatile content.

[Evaluation of Imidization Ratio] The imidization ratio of the polyimide layer can be calculated as follows: The infrared absorption spectrum of the polyimide film is measured by the single reflection ATR method using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, trade name FT/IR), and the absorbance derived from the imide group at 1778 cm ^-1 is calculated based on the benzene ring hydrocarbon bond at 1009 cm ^-1 . Furthermore, the first polyimide resin layer is subjected to stepwise heat treatment from 120°C to 360°C, and the imidization ratio of the polyimide film after the heat treatment at 360°C is set to 100%.

[Peel strength measurement] For the peel strength, a Tensilon Tester (manufactured by Toyo Seiki Seisaku-sho, trade name: Strograph VE-1D) was used to fix the second polyimide layer side of a 10 mm wide sample to an aluminum plate using double-sided tape, and the metal-clad laminate on the first polyimide layer side was stretched in a 180° direction at a speed of 50 mm/min to determine the force generated between the first polyimide layer and the second polyimide layer when peeling.

The abbreviations used in the synthesis examples represent the following compounds. m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl BAFL: 9,9-bis(4-aminophenyl)fluorene APB: 1,3-bis(3-aminophenoxy)benzene TPE-Q: 1,4-bis(4-aminophenoxy)benzene 4,4'-DAPE: 4,4'-diaminodiphenyl ether 3,4'-DAPE: 3,4'-diaminodiphenyl ether PDA: p-phenylenediamine PMDA: pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride DMAc: N,N-dimethylacetamide

(Synthesis Example A1) 75.149 g of m-TB (353.42 mmol) and 850 g of DMAc were placed in a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 74.851 g of PMDA (342.82 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamide solution A-A. The viscosity of the obtained polyamide solution A-A was 22,700 cP. The polyimide obtained after imidization of the obtained polyamide was non-thermoplastic. In addition, the CTE of the obtained polyimide film (thickness: 25 μm) was 6.4 ppm/K.

(Synthesis Example A2) 65.054 g of m-TB (310.65 mmol), 10.090 g of TPE-R (34.52 mmol), and 850 g of DMAc were placed in a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 73.856 g of PMDA (338.26 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamide solution AB. The viscosity of the obtained polyamide solution AB was 26,500 cP. The polyimide obtained after imidization of the obtained polyamide was non-thermoplastic and had a glass transition temperature (Tg) of 303°C. The obtained polyimide film (thickness: 25 μm) had a CTE of 16.2 ppm/K, a moisture absorption rate of 0.61% by weight, and a moisture permeability of 64 g/m ² /24 hr.

(Synthesis Example A3) 89.621 g of TFMB (279.33 mmol) and 850 g of DMAc were placed in a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 60.379 g of PMDA (276.54 mmol) was added and stirred at room temperature for 4 hours to obtain polyamide solution A-C. The viscosity of the obtained polyamide solution A-C was 21,200 cP. The polyimide obtained after imidization of the obtained polyamide was non-thermoplastic. In addition, the CTE of the obtained polyimide film (thickness: 25 μm) was 0.5 ppm/K.

(Synthesis Example A4) 49.928 g of TFMB (155.70 mmol), 33.102 g of m-TB (155.70 mmol), and 850 g of DMAc were placed in a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 66.970 g of PMDA (307.03 mmol) was added and stirred at room temperature for 4 hours to obtain polyamide solution A-D. The viscosity of the obtained polyamide solution A-D was 21,500 cP. The obtained polyimide after imidization of the polyamide was non-thermoplastic. In addition, the CTE of the obtained polyimide film (thickness: 25 μm) is 6.0 ppm/K.

(Synthesis Example A5) 29.492 g of BAPP (71.81 mmol) and 255 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 15.508 g of PMDA (71.10 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamide solution AE. The viscosity of the obtained polyamide solution AE was 10,700 cP. The polyimide obtained after imidization of the obtained polyamide was thermoplastic and had a glass transition temperature (Tg) of 312°C. The obtained polyimide film (thickness: 25 μm) had a CTE of 63.1 ppm/K, a moisture absorption rate of 0.54% by weight, and a moisture permeability of 64 g/m ² /24 hr.

(Synthesis Example A6) 25.889 g of TPE-R (88.50 mmol) and 255 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 19.111 g of PMDA (87.62 mmol) was added and stirred at room temperature for 4 hours to obtain polyamide solutions A-F. The viscosity of the obtained polyamide solutions A-F was 13,200 cP. The polyimide obtained after imidization of the obtained polyamide was non-thermoplastic. In addition, the CTE of the obtained polyimide film (thickness: 25 μm) was 57.7 ppm/K.

(Synthesis Example A7) 27.782 g of BAFL (79.73 mmol) and 255 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 17.218 g of PMDA (78.94 mmol) was added and stirred at room temperature for 4 hours to obtain polyamide solution A-G. The viscosity of the obtained polyamide solution A-G was 10,400 cP. The polyimide obtained after imidization of the obtained polyamide was non-thermoplastic. In addition, the CTE of the obtained polyimide film (thickness: 25 μm) was 52.0 ppm/K.

[Example A1] On an electrolytic copper foil having a thickness of 12 μm, a polyamide solution AE is uniformly applied to form a first polyimide layer in a manner that the thickness after curing is 2 μm, and then the temperature is gradually raised from 120°C to 360°C to remove the solvent and perform imidization. The obtained first polyimide layer is subjected to a corona treatment at 120 W·min/ ^m2 . Next, a polyamide solution AA is uniformly applied thereon in a manner that the thickness after curing is 25 μm to form a second polyimide layer, and then the solvent is removed by heating and drying at 120°C for 3 minutes. Thereafter, the temperature was gradually raised from 130°C to 360°C for imidization to prepare a metal-clad laminate A1. The thickness (L1) of the first polyimide layer was 2 μm, the thickness (L) of the entire insulating resin layer was 27 μm, and the ratio (L/L1) was 13.5. An adhesive tape was attached to the resin surface of the prepared metal-clad laminate A1, and a peeling test was performed by instantaneous tearing in the vertical direction, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A2] Metal-clad laminate A2 was prepared in the same manner as in Example A1 except that polyamide solution A-F was used instead of polyamide solution A-E. The prepared metal-clad laminate A2 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A3] Metal-clad laminate A3 was prepared in the same manner as in Example A1 except that polyamide solution A-G was used instead of polyamide solution A-E. The prepared metal-clad laminate A3 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A4] Metal-clad laminate A4 was prepared in the same manner as in Example A1 except that polyamide solution A-C was used instead of polyamide solution A-E. The prepared metal-clad laminate A4 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A5] Metal-clad laminate A5 was prepared in the same manner as in Example A1 except that polyamide solution A-B was used instead of polyamide solution A-A. The prepared metal-clad laminate A5 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A6] Metal-clad laminate A6 was prepared in the same manner as in Example A1 except that polyamide solution A-B was used instead of polyamide solution A-A, and polyamide solution A-F was used instead of polyamide solution A-E. The prepared metal-clad laminate A6 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A7] Metal-clad laminate A7 was prepared in the same manner as in Example A1 except that polyamide solution A-B was used instead of polyamide solution A-A, and polyamide solution A-G was used instead of polyamide solution A-E. The prepared metal-clad laminate A7 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A8] Metal-clad laminate A8 was prepared in the same manner as in Example A1 except that polyamide solution A-B was used instead of polyamide solution A-A, and polyamide solution A-A was used instead of polyamide solution A-E. The prepared metal-clad laminate A8 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A9] Metal-clad laminate A9 was prepared in the same manner as in Example A1 except that polyamide solution A-B was used instead of polyamide solution A-A, and polyamide solution A-C was used instead of polyamide solution A-E. The prepared metal-clad laminate A9 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A10] Metal-clad laminate A10 was prepared in the same manner as in Example A1 except that polyamide solution A-C was used instead of polyamide solution A-A. The prepared metal-clad laminate A10 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A11] A metal-clad laminate A11 was prepared in the same manner as in Example A1 except that polyamide solution A-C was used instead of polyamide solution A-A, and polyamide solution A-F was used instead of polyamide solution A-E. The prepared metal-clad laminate A11 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A12] Metal-clad laminate A12 was prepared in the same manner as Example A1 except that polyamide solution A-C was used instead of polyamide solution A-A, and polyamide solution A-G was used instead of polyamide solution A-E. The prepared metal-clad laminate A12 was subjected to a peeling test in the same manner as Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A13] Metal-clad laminate A13 was prepared in the same manner as in Example A1 except that polyamide solution A-C was used instead of polyamide solution A-A, and polyamide solution A-A was used instead of polyamide solution A-E. The prepared metal-clad laminate A13 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A14] Metal-clad laminate A14 was prepared in the same manner as Example A1 except that polyamide solution A-D was used instead of polyamide solution A-A. The prepared metal-clad laminate A14 was subjected to a peeling test in the same manner as Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A15] Metal-clad laminate A15 was prepared in the same manner as in Example A1 except that polyamide solution A-D was used instead of polyamide solution A-A, and polyamide solution A-F was used instead of polyamide solution A-E. The prepared metal-clad laminate A15 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A16] Metal-clad laminate A16 was prepared in the same manner as in Example A1 except that polyamide solution A-D was used instead of polyamide solution A-A, and polyamide solution A-G was used instead of polyamide solution A-E. The prepared metal-clad laminate A16 was subjected to a peeling test in the same manner as in Example A1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example A17] Metal-clad laminate A17 was prepared in the same manner as in Example A1 except that polyamide solution A-D was used instead of polyamide solution A-A, and polyamide solution A-A was used instead of polyamide solution A-E. The prepared metal-clad laminate A17 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example A18] Metal-clad laminate A18 was prepared in the same manner as in Example A1 except that polyamide solution A-D was used instead of polyamide solution A-A, and polyamide solution A-C was used instead of polyamide solution A-E. The prepared metal-clad laminate A18 was subjected to a peeling test in the same manner as in Example A1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

Comparative Example A1 Except that the corona treatment is not performed, the metal-clad laminate A19 is prepared in the same manner as in Example A1. The prepared metal-clad laminate A19 is subjected to a peeling test in the same manner as in Example A1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurs.

Comparative Example A2 Except that the corona treatment is not performed, the metal-clad laminate A20 is prepared in the same manner as in Example A2. The prepared metal-clad laminate A20 is subjected to a peeling test in the same manner as in Example A1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurs.

Comparative Example A3 Except that the corona treatment is not performed, the metal-clad laminate A21 is prepared in the same manner as in Example A14. The prepared metal-clad laminate A21 is subjected to a peeling test in the same manner as in Example A1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurs.

Comparative Example A4 Except that the corona treatment is not performed, the metal-clad laminate A22 is prepared in the same manner as in Example A15. The prepared metal-clad laminate A22 is subjected to a peeling test in the same manner as in Example A1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurs.

[Example A19] On an electrolytic copper foil having a thickness of 12 μm, a polyamide solution AE was uniformly coated to form a first polyimide layer with a thickness of 2.5 μm after curing, and then the temperature was gradually raised from 120°C to 360°C to remove the solvent and perform imidization. The obtained first polyimide layer was subjected to a corona treatment at 120 W·min/ ^m2 . Next, polyamide solution AA was uniformly applied thereon to a thickness of 20 μm after curing to form a second polyimide layer, and then polyamide solution AE was uniformly applied thereon to a thickness of 2.5 μm after curing to form a third polyimide layer, and the solvent was removed by heating and drying at 120°C for 3 minutes. Thereafter, the temperature was gradually raised from 130°C to 360°C to perform imidization, and a metal-clad laminate A23 was prepared. The thickness (L1) of the first polyimide layer was 2.5 μm, the thickness (L) of the entire insulating resin layer was 25 μm, and the ratio (L/L1) was 10.0. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "good".

[Example A20] Instead of polyamide solutions A-E to form the first polyimide layer and the third polyimide layer, polyamide solutions A-F were uniformly applied in a manner to have a thickness of 2.7 μm after curing, and polyamide solution A-A to form the second polyimide layer was uniformly applied in a manner to have a thickness of 19.6 μm after curing. A metal-clad laminate A24 was prepared in the same manner as in Example A19. The thickness (L1) of the first polyimide layer was 2.7 μm, the thickness (L) of the entire insulating resin layer was 25 μm, and the ratio (L/L1) was 9.3. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "good".

[Example A21] Instead of the polyamide solutions A-E that form the first and third polyamide layers, polyamide solutions A-G are uniformly applied in a manner that the thickness after curing is 3.2 μm, and the polyamide solution A-A that forms the second polyamide layer is uniformly applied in a manner that the thickness after curing is 18.6 μm. The same method as in Example A19 is used to prepare a metal-clad laminate A25. The thickness (L1) of the first polyimide layer is 3.2 μm, the thickness (L) of the entire insulating resin layer is 25 μm, and the ratio (L/L1) is 7.8. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "acceptable".

[Example A22] Metal-clad laminate A26 was prepared in the same manner as Example A19 except that polyamide solution A-E to be the first polyimide layer and the third polyimide layer were uniformly applied in a manner that the thickness after curing was 1.7 μm, polyamide solution A-A to be the second polyimide layer was uniformly applied in a manner that the thickness after curing was 22 μm, and the heating time from 130°C to 360°C after applying polyamide solution A-A and polyamide solution A-E to be the third polyimide layer was shortened to 1/3. The thickness of the first polyimide layer (L1) was 1.7 μm, the thickness of the entire insulating resin layer (L) was 25.4 μm, and the ratio (L/L1) was 14.9. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example A23] Metal-clad laminate A27 was prepared in the same manner as Example A19 except that polyamide solution A-E to be the first polyimide layer and the third polyimide layer were uniformly applied in a manner that the thickness after curing was 1.8 μm, polyamide solution A-A to be the second polyimide layer was uniformly applied in a manner that the thickness after curing was 22 μm, and the heating time from 130°C to 360°C after applying polyamide solution A-A and polyamide solution A-E to be the third polyimide layer was shortened to 1/3. The thickness of the first polyimide layer (L1) was 1.8 μm, the thickness of the entire insulating resin layer (L) was 25.6 μm, and the ratio (L/L1) was 14.2. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example A24] Metal-clad laminate A28 was prepared in the same manner as Example A19 except that polyamide solution A-E to be the first polyimide layer and the third polyimide layer were uniformly applied in a manner that the thickness after curing was 2.2 μm, polyamide solution A-A to be the second polyimide layer was uniformly applied in a manner that the thickness after curing was 20 μm, and the heating time from 130°C to 360°C after applying polyamide solution A-A and polyamide solution A-E to be the third polyimide layer was shortened to 1/3. The thickness of the first polyimide layer (L1) was 2.2 μm, the thickness of the entire insulating resin layer (L) was 24.4 μm, and the ratio (L/L1) was 11.1. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example A25] Metal-clad laminate A29 was prepared in the same manner as in Example A19, except that polyamide solutions A-E, which became the first polyimide layer and the third polyimide layer, were uniformly applied in a manner that the thickness after curing was 2.4 μm, respectively, and polyamide solution A-D, which became the second polyimide layer, was uniformly applied in a manner that the thickness after curing was 20.2 μm. The thickness (L1) of the first polyimide layer was 2.4 μm, the thickness (L) of the entire insulating resin layer was 25 μm, and the ratio (L/L1) was 10.4. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "good".

[Example A26] A metal-clad laminate A30 was prepared in the same manner as in Example A19, except that the polyamide solutions A-F to be the first polyimide layer and the third polyimide layer were uniformly applied in a manner to have a thickness of 2.7 μm after curing, and the polyamide solution A-D to be the second polyimide layer was uniformly applied in a manner to have a thickness of 20 μm after curing. The thickness (L1) of the first polyimide layer was 2.7 μm, the thickness (L) of the entire insulating resin layer was 25.4 μm, and the ratio (L/L1) was 9.4. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "good".

[Example A27] A metal-clad laminate A31 was prepared in the same manner as in Example A19, except that the polyamide solutions A-G, which would become the first polyimide layer and the third polyimide layer, were uniformly applied in a manner to have a thickness of 3.2 μm after curing, and the polyamide solution A-D, which would become the second polyimide layer, was uniformly applied in a manner to have a thickness of 19 μm after curing. The thickness (L1) of the first polyimide layer was 3.2 μm, the thickness (L) of the entire insulating resin layer was 25.4 μm, and the ratio (L/L1) was 7.9. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "acceptable".

[Example A28] On a 12 μm thick electrolytic copper foil, polyamide solution AE was uniformly coated to a thickness of 2.0 μm after curing, and then the solvent was removed at 120°C. On the foil, polyamide solution AA was uniformly coated to a thickness of 50 μm after curing, and then the solvent was removed at 120°C for 3 minutes. Furthermore, a polyamide solution AE was uniformly coated thereon in a manner to have a thickness of 2.0 μm after curing, and then the solvent was removed at 120°C, and the temperature was gradually raised from 120°C to 360°C to remove the solvent and perform imidization, thereby obtaining a single-sided metal-clad laminate A28B having a first polyimide layer formed thereon. The polyimide layer of the obtained single-sided metal-clad laminate A28B was subjected to a corona treatment at 120 W·min/ ^m2 . Next, polyamide solution AA was uniformly applied thereon to a thickness of 50 μm after curing to form a second polyimide layer. After removing the solvent, polyamide solution AE was uniformly applied thereon to a thickness of 2.0 μm after curing to form a third polyimide layer. The solvent was removed by heating and drying at 120°C for 3 minutes. Thereafter, the temperature was gradually raised from 130°C to 360°C for imidization to prepare a single-sided metal-clad laminate A28. The thickness (L1) of the first polyimide layer was 54 μm, the thickness (L) of the entire insulating resin layer was 106 μm, and the ratio (L/L1) was 1.96. No bubbling was observed, and no curling of the polyimide film was observed after etching of the copper foil. In addition, the dimensional change rate was "good".

[Example A29] A single-sided metal-clad laminate A29 was prepared in the same manner as Example A28 except that the polyamide solution A-E used to constitute the two layers of the first polyimide layer and the polyamide solution A-E to become the third polyimide layer were uniformly applied in a manner to have a thickness of 10 μm after curing. The thickness (L1) of the first polyimide layer was 70 μm, the thickness (L) of the entire insulating resin layer was 130 μm, and the ratio (L/L1) was 1.86. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example A30] The single-sided metal-clad laminate A30 was prepared in the same manner as in Example A28 except that the polyamide solution A-E used to form the two layers of the first polyimide layer and the polyamide solution A-E used to form the third polyimide layer were respectively set as polyamide solution A-F and were uniformly applied in a manner to have a thickness of 2.0 μm after curing, and the polyamide solution A-B used to form the second polyimide layer was uniformly applied in a manner to have a thickness of 50 μm after curing. The thickness of the first polyimide layer (L1) was 54 μm, the thickness of the entire insulating resin layer (L) was 106 μm, and the ratio (L/L1) was 1.96. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example A31] A single-sided metal-clad laminate A31 was prepared in the same manner as Example A30 except that the polyamide solution A-F used to constitute the two layers of the first polyimide layer and the polyamide solution A-F used to constitute the third polyimide layer were uniformly applied in a manner to have a thickness of 10 μm after curing. The thickness (L1) of the first polyimide layer was 70 μm, the thickness (L) of the entire insulating resin layer was 130 μm, and the ratio (L/L1) was 1.86. No bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

Comparative Example A5 Except that the corona treatment was not performed, the metal-clad laminate A32 was prepared in the same manner as in Example A19. As a result, curling of the polyimide film was confirmed after etching of the copper foil.

Comparative Example A6 Except that the corona treatment was not performed, the metal-clad laminate A33 was prepared in the same manner as in Example A20. As a result, curling of the polyimide film was confirmed after etching of the copper foil.

Comparative Example A7 Except that the corona treatment was not performed, the metal-clad laminate A34 was prepared in the same manner as in Example A21. As a result, curling of the polyimide film was confirmed after etching of the copper foil.

Comparative Example A8 Metal-clad laminate A35 was prepared in the same manner as Example A22 except that the corona treatment was not performed. As a result, foaming was confirmed.

Comparative Example A9 Metal-clad laminate A36 was prepared in the same manner as Example A23 except that the corona treatment was not performed. As a result, foaming was confirmed.

Comparative Example A10 Metal-clad laminate A37 was prepared in the same manner as Example A24 except that the corona treatment was not performed. As a result, foaming was confirmed.

(Synthesis Example B1) 75.149 g of m-TB (353.42 mmol) and 850 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 74.851 g of PMDA (342.82 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution B-A. The viscosity of the obtained polyamine solution B-A was 22,700 cP.

(Synthesis Example B2) In a 1000 ml separable flask, 65.054 g of m-TB (310.65 mmol), 10.090 g of TPE-R (34.52 mmol), and 850 g of DMAc were added and stirred at room temperature under a nitrogen flow. After complete dissolution, 73.856 g of PMDA (338.26 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution B-B. The viscosity of the obtained polyamine solution B-B was 26,500 cP.

(Synthesis Example B3) 89.621 g of TFMB (279.33 mmol) and 850 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 60.379 g of PMDA (276.54 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution B-C. The viscosity of the obtained polyamine solution B-C was 21,200 cP.

(Synthesis Example B4) 49.928 g of TFMB (155.70 mmol), 33.102 g of m-TB (155.70 mmol), and 850 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 66.970 g of PMDA (307.03 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution B-D. The viscosity of the obtained polyamine solution B-D was 21,500 cP.

(Synthesis Example B5) 29.492 g of BAPP (71.81 mmol) and 255 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 15.508 g of PMDA (71.10 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution B-E. The viscosity of the obtained polyamine solution B-E was 10,700 cP.

(Synthesis Example B6) 25.889 g of TPE-R (88.50 mmol) and 255 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 19.111 g of PMDA (87.62 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution B-F. The viscosity of the obtained polyamine solution B-F was 13,200 cP.

(Synthesis Example B7) 27.782 g of BAFL (79.73 mmol) and 255 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 17.218 g of PMDA (78.94 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution B-G. The viscosity of the obtained polyamine solution B-G was 10,400 cP.

[Example B1] On an electrolytic copper foil with a thickness of 12 μm, a polyamide solution B-E is uniformly applied to form a first polyimide layer in a manner that the thickness after curing is 2 μm, and then the temperature is gradually raised from 120°C to 240°C to perform appropriate solvent removal and imidization. At this time, the volatile component rate and imidization rate of the semi-cured first polyimide layer are 3.0% and 80%. Next, a polyamide solution B-A is uniformly applied thereon in a manner that the thickness after curing is 25 μm, and then the solvent is removed by heating and drying at 120°C for 3 minutes. Afterwards, the temperature was gradually raised from 130°C to 360°C for imidization to form the first polyimide layer and the second polyimide layer, thereby preparing the metal-clad laminate B1. An adhesive tape was pasted on the resin surface of the prepared metal-clad laminate B1, and a peeling test was performed by instantaneous tearing in the vertical direction, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B2] Metal-clad laminate B2 was prepared in the same manner as Example B1 except that polyamide solution B-F was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 5.6% and 55% respectively. The prepared metal-clad laminate B2 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B3] Metal-clad laminate B3 was prepared in the same manner as Example B1 except that polyamide solution B-G was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 6.7% and 28% respectively. The prepared metal-clad laminate B3 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B4] Metal-clad laminate B4 was prepared in the same manner as Example B1 except that polyamide solution B-C was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 2.6% and 73% respectively. The prepared metal-clad laminate B4 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B5] Metal-clad laminate B5 was prepared in the same manner as Example B1 except that polyamide solution B-B was used instead of polyamide solution B-A. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 3.2% and 70% respectively. The prepared metal-clad laminate B5 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B6] Metal-clad laminate B6 was prepared in the same manner as Example B1 except that polyamide solution B-B was used instead of polyamide solution B-A, and polyamide solution B-F was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 4.0% and 65% respectively. The prepared metal-clad laminate B6 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B7] Metal-clad laminate B7 was prepared in the same manner as Example B1 except that polyamide solution B-B was used instead of polyamide solution B-A, and polyamide solution B-G was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 5.5% and 53% respectively. The prepared metal-clad laminate B7 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B8] Metal-clad laminate B8 was prepared in the same manner as Example B1 except that polyamide solution B-B was used instead of polyamide solution B-A, and polyamide solution B-A was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 4.0% and 66% respectively. The prepared metal-clad laminate B8 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B9] Metal-clad laminate B9 was prepared in the same manner as Example B1 except that polyamide solution B-B was used instead of polyamide solution B-A, and polyamide solution B-C was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 1.2% and 80% respectively. The prepared metal-clad laminate B9 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B10] Metal-clad laminate B10 was prepared in the same manner as Example B1 except that polyamide solution B-C was used instead of polyamide solution B-A. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 2.6% and 83% respectively. The prepared metal-clad laminate B10 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B11] Metal-clad laminate B11 was prepared in the same manner as Example B1 except that polyamide solution B-C was used instead of polyamide solution B-A, and polyamide solution B-F was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 4.4% and 59% respectively. The prepared metal-clad laminate B11 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B12] Metal-clad laminate B12 was prepared in the same manner as Example B1 except that polyamide solution B-C was used instead of polyamide solution B-A, and polyamide solution B-G was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 10.1% and 23% respectively. The prepared metal-clad laminate B12 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B13] Metal-clad laminate B13 was prepared in the same manner as Example B1 except that polyamide solution B-C was used instead of polyamide solution B-A, and polyamide solution B-A was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 10.0% and 22% respectively. The prepared metal-clad laminate B13 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B14] Metal-clad laminate B14 was prepared in the same manner as Example B1 except that polyamide solution B-D was used instead of polyamide solution B-A. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 15.1% and 20% respectively. The prepared metal-clad laminate B14 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B15] Metal-clad laminate B15 was prepared in the same manner as Example B1 except that polyamide solution B-D was used instead of polyamide solution B-A, and polyamide solution B-F was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 8.3% and 31% respectively. The prepared metal-clad laminate B15 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B16] Metal-clad laminate B16 was prepared in the same manner as Example B1 except that polyamide solution B-D was used instead of polyamide solution B-A, and polyamide solution B-G was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 12.0% and 22% respectively. The prepared metal-clad laminate B16 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B17] Metal-clad laminate B17 was prepared in the same manner as Example B1 except that polyamide solution B-D was used instead of polyamide solution B-A, and polyamide solution B-A was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 7.0% and 25% respectively. The prepared metal-clad laminate B17 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example B18] Metal-clad laminate B18 was prepared in the same manner as Example B1 except that polyamide solution B-D was used instead of polyamide solution B-A, and polyamide solution B-C was used instead of polyamide solution B-E. The volatile component rate and imidization rate of the semi-cured first polyimide layer were 8.2% and 21% respectively. The prepared metal-clad laminate B18 was subjected to a peeling test in the same manner as Example B1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

Comparative Example B1 Metal-clad laminate B19 was prepared in the same manner as Example B1 except that the temperature of the polyamide solution to be the first polyimide layer was gradually raised from 120°C to 360°C. The volatile component rate and the imidization rate of the first polyimide layer were 0.0% and 100% at this time. The prepared metal-clad laminate B19 was subjected to a peeling test in the same manner as Example B1, and as a result, interlayer peeling occurred between the first polyimide layer and the second polyimide layer.

Comparative Example B2 Except that the polyamide solution to be the first polyimide layer was gradually heated from 120°C to 360°C, the metal-clad laminate B20 was prepared in the same manner as in Example B2. The volatile component rate and the imidization rate of the first polyimide layer were 0.0% and 100% respectively. The prepared metal-clad laminate B20 was subjected to a peeling test in the same manner as in Example B1, and as a result, interlayer peeling occurred between the first polyimide layer and the second polyimide layer.

Comparative Example B3 Metal-clad laminate B21 was prepared in the same manner as Example B14 except that the polyamide solution to be the first polyimide layer was gradually heated from 120°C to 360°C. The volatile component rate and imidization rate of the first polyimide layer were 0.0% and 100% at this time. The prepared metal-clad laminate B21 was subjected to a peeling test in the same manner as Example B1, and as a result, interlayer peeling occurred between the first polyimide layer and the second polyimide layer.

Comparative Example B4 Metal-clad laminate B22 was prepared in the same manner as Example B15 except that the polyamide solution to be the first polyimide layer was gradually heated from 120°C to 360°C. The volatile component rate and imidization rate of the first polyimide layer were 0.0% and 100% at this time. The prepared metal-clad laminate B22 was subjected to a peeling test in the same manner as Example B1, and as a result, interlayer peeling occurred between the first polyimide layer and the second polyimide layer.

[Example B19] On an electrolytic copper foil with a thickness of 12 μm, a polyamide solution B-E is uniformly applied to form a first polyimide layer in a manner such that the thickness after curing is 2.5 μm. Thereafter, the temperature is gradually raised from 120°C to 240°C to perform appropriate solvent removal and imidization. At this time, the volatile component rate and imidization rate of the semi-cured first polyimide layer are 5.5% and 53% respectively. Next, polyamide solution B-A was uniformly coated thereon to a thickness of 20 μm after curing to form a second polyimide layer, and then polyamide solution B-E was uniformly coated thereon to a thickness of 2.5 μm after curing to form a third polyimide layer, and the solvent was removed by heating and drying at 120°C for 3 minutes. Afterwards, the temperature was gradually raised from 130°C to 360°C for imidization to prepare a metal-clad laminate B23, but no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good".

[Example B20] Instead of the polyamide solution B-E that becomes the first polyimide layer and the third polyimide layer, the polyamide solution B-F is uniformly applied in a manner that the thickness after curing is 2.7 μm, and the polyamide solution B-A that becomes the second polyimide layer is uniformly applied in a manner that the thickness after curing is 19.6 μm. Metal-clad laminate B24 was prepared in the same manner as Example B19, but no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". At this time, the volatile component rate and imidization rate of the semi-cured first polyimide layer are 2.6% and 83% respectively.

[Example B21] Instead of the polyamide solution B-E that becomes the first polyimide layer and the third polyimide layer, the polyamide solution B-G is uniformly applied in a manner that the thickness after curing is 3.2 μm, and the polyamide solution B-A that becomes the second polyimide layer is uniformly applied in a manner that the thickness after curing is 18.6 μm. In addition, the same method as Example B19 was used to prepare a metal-clad laminate B25, but no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "acceptable". At this time, the volatile component rate and imidization rate of the semi-cured first polyimide layer are 3.2% and 70% respectively.

[Example B22] The polyamide solution B-E to be the first polyimide layer and the third polyimide layer is uniformly applied in a manner such that the thickness after curing is 1.7 μm, and the polyamide solution B-A to be the second polyimide layer is uniformly applied in a manner such that the thickness after curing is 22 μm. μm, and the heating time from 130°C to 360°C after applying the polyamide solution B-A and the polyamide solution B-E that becomes the third polyimide layer was shortened to 1/3. In addition, the metal-clad laminate B26 was prepared in the same manner as in Example B19. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 10.1% and 23%.

[Example B23] The polyamide solution B-E to be the first polyimide layer and the third polyimide layer is uniformly applied in a manner such that the thickness after curing is 1.8 μm, and the polyamide solution B-A to be the second polyimide layer is uniformly applied in a manner such that the thickness after curing is 22 μm. μm, and the heating time from 130°C to 360°C after applying the polyamide solution B-A and the polyamide solution B-E that becomes the third polyimide layer was shortened to 1/3. In addition, the metal-clad laminate B27 was prepared in the same manner as in Example B19. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 6.7% and 28%.

[Example B24] The polyamide solution B-E to be the first polyimide layer and the third polyimide layer is uniformly applied in a manner such that the thickness after curing is 2.2 μm, and the polyamide solution B-A to be the second polyimide layer is uniformly applied in a manner such that the thickness after curing is 20 μm. μm, and the heating time from 130°C to 360°C after applying the polyamide solution B-A and the polyamide solution B-E to become the third polyimide layer was shortened to 1/3. In addition, the metal-clad laminate B28 was prepared in the same manner as Example B19. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 15.1% and 20%.

[Example B25] The same method as Example B19 was used to prepare a metal-clad laminate B29 except that the polyamide solution B-E, which became the first polyimide layer and the third polyimide layer, was uniformly applied in a manner to a thickness of 2.4 μm after curing, and the polyamide solution B-D, which became the second polyimide layer, was uniformly applied in a manner to a thickness of 20 μm after curing. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 15.1% and 20%.

[Example B26] The same method as Example B19 was used to prepare a metal-clad laminate B30 except that the polyamide solution B-F, which became the first polyimide layer and the third polyimide layer, was uniformly applied in a manner to a thickness of 2.7 μm after curing, and the polyamide solution B-D, which became the second polyimide layer, was uniformly applied in a manner to a thickness of 20 μm after curing. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "good". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 8.3% and 31%.

[Example B27] The same method as Example B19 was used to prepare a metal-clad laminate B31 except that the polyamide solution B-G, which became the first polyimide layer and the third polyimide layer, was uniformly applied in a manner to a thickness of 3.2 μm after curing, and the polyamide solution B-D, which became the second polyimide layer, was uniformly applied in a manner to a thickness of 19 μm after curing. As a result, no bubbling was confirmed, and no curling of the polyimide film was confirmed after etching the copper foil. In addition, the dimensional change rate was "acceptable". The volatile component rate and imidization rate of the semi-cured first polyimide layer at this time were 12.0% and 22%.

Comparative Example B5 Except that the polyamide solution to become the first polyimide layer was heat-dried at 120°C for 3 minutes, the metal-clad laminate B32 was prepared in the same manner as in Example B19. As a result, curling of the polyimide film was confirmed after etching the copper foil. At this time, the volatile component rate and imidization rate of the layer to become the first polyimide layer in the state of heat drying were 35.0% and 0%.

Comparative Example B6 Except that the polyamide solution to become the first polyimide layer was heat-dried at 120°C for 3 minutes, the metal-clad laminate B33 was prepared in the same manner as in Example B20. As a result, curling of the polyimide film was confirmed after etching the copper foil. At this time, the volatile component rate and imidization rate of the layer to become the first polyimide layer in the state of heat drying were 32.0% and 0%.

Comparative Example B7 Metal-clad laminate B34 was prepared in the same manner as Example B21 except that the polyamide solution to become the first polyimide layer was heat-dried at 120°C for 3 minutes. As a result, curling of the polyimide film was confirmed after etching the copper foil. At this time, the volatile component rate and imidization rate of the layer to become the first polyimide layer in the state of heat drying were 30.0% and 0%.

Comparative Example B8 Metal-clad laminate B35 was prepared in the same manner as Example B22 except that the polyamide solution to be the first polyimide layer was heat-dried at 120°C for 3 minutes. As a result, foaming was confirmed. At this time, the volatile component rate and imidization rate of the layer to be the first polyimide layer in the state of being heat-dried were 34.0% and 0%.

Comparative Example B9 Metal-clad laminate B36 was prepared in the same manner as Example B23 except that the polyamide solution to be the first polyimide layer was heat-dried at 120°C for 3 minutes. As a result, foaming was confirmed. At this time, the volatile component rate and imidization rate of the layer to be the first polyimide layer in the state of being heat-dried were 30.0% and 0%.

Comparative Example B10 Metal-clad laminate B37 was prepared in the same manner as Example B24 except that the polyamide solution to be the first polyimide layer was heat-dried at 120°C for 3 minutes. As a result, foaming was confirmed. At this time, the volatile component rate and imidization rate of the layer to be the first polyimide layer in the state of being heat-dried were 31.0% and 0%.

(Synthesis Example C1) 45.989 g of m-TB (216.63 mmol), 15.832 g of TPE-R (54.16 mmol), and 680 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 58.179 g of PMDA (266.73 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-A. The viscosity of the obtained polyamine solution C-A was 22,000 cP.

(Synthesis Example C2) 9.244 g of 4,4'-DAPE (46.16 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 14.756 g of BTDA (45.79 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-B. The viscosity of the obtained polyamine solution C-B was 1,200 cP.

(Synthesis Example C3) 11.464 g of TPE-Q (39.22 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 12.536 g of BTDA (38.90 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-C. The viscosity of the obtained polyamine solution C-C was 2,200 cP.

(Synthesis Example C4) 11.464 g of TPE-R (39.22 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 12.536 g of BTDA (38.90 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-D. The viscosity of the obtained polyamine solution C-D was 1,100 cP.

(Synthesis Example C5) 11.386 g of APB (38.95 mmol) and 176 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 12.614 g of BTDA (39.14 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution C-E. The viscosity of the obtained polyamine solution C-E was 200 cP.

(Synthesis Example C6) 13.493 g of BAPP (32.87 mmol) and 176 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 10.507 g of BTDA (32.61 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-F. The viscosity of the obtained polyamine solution C-F was 1,400 cP.

(Synthesis Example C7) 9.227 g of 3,4'-DAPE (46.08 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 14.773 g of BTDA (45.85 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-G. The viscosity of the obtained polyamine solution C-G was 500 cP.

(Synthesis Example C8) 4.660 g of PDA (43.09 mmol), 2.157 g of 4,4'-DAPE (10.77 mmol), and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 17.183 g of BTDA (53.33 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-H. The viscosity of the obtained polyamine solution C-H was 1,500 cP.

(Synthesis Example C9) 12.053 g of TFMB (37.64 mmol) and 176 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 11.947 g of BTDA (37.07 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution C-I. The viscosity of the obtained polyamine solution C-I was 1,200 cP.

(Synthesis Example C10) 9.498 g of 4,4'-DAPE (47.43 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 7.581 g of BTDA (23.53 mmol) and 6.922 g of BPDA (23.53 mmol) were added and stirred at room temperature for 4 hours to obtain polyamine solution C-J. The viscosity of the obtained polyamine solution C-J was 2,500 cP.

(Synthesis Example C11) 9.727 g of 4,4'-DAPE (48.58 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 11.646 g of BTDA (36.14 mmol) and 2.628 g of PMDA (12.05 mmol) were added and stirred at room temperature for 4 hours to obtain polyamine solution C-K. The viscosity of the obtained polyamine solution C-K was 1,100 cP.

(Synthesis Example C12) 4.575 g of 4,4'-DAPE (22.85 mmol), 4.850 g of m-TB (22.85 mmol), and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 14.576 g of BTDA (45.23 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-L. The viscosity of the obtained polyamine solution C-L was 1,100 cP.

(Synthesis Example C13) 9.807 g of 4,4'-DAPE (48.97 mmol) and 176 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 14.193 g of BPDA (48.24 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-M. The viscosity of the obtained polyamine solution C-M was 1,000 cP.

(Synthesis Example C14) 62.734 g of BAPP (152.82 mmol) and 704 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 33.266 g of PMDA (152.51 mmol) was added and stirred at room temperature for 4 hours to obtain polyamine solution C-N. The viscosity of the obtained polyamine solution C-N was 4,800 cP.

(Synthesis Example C15) 38.27 g of m-TB (180.27 mmol) and 704 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 57.102 g of BTDA (177.21 mmol) and 0.629 g of PMDA (2.88 mmol) were added and stirred at room temperature for 4 hours to obtain polyamine solution C-O. The viscosity of the obtained polyamine solution C-O was 43,000 cP.

(Synthesis Example C16) 19.536 g of PDA (180.66 mmol), 13.087 g of BAPP (31.88 mmol), and 704 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 56.73 g of BPDA (192.82 mmol) and 6.646 g of ODPA (21.42 mmol) were added and stirred at room temperature for 4 hours to obtain a polyamine solution C-P. The viscosity of the obtained polyamine solution C-P was 51,000 cP.

(Synthesis Example C17) 76.91 g of BAPP (187.35 mmol) and 680 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 34.805 g of PMDA (159.57 mmol) and 8.285 g of BPDA (28.16 mmol) were added and stirred at room temperature for 4 hours to obtain a polyamine solution C-Q. The viscosity of the obtained polyamine solution C-Q was 9,500 cP.

(Synthesis Example C18) 77.298 g of BAPP (188.30 mmol) and 680 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 34.492 g of PMDA (158.13 mmol) and 8.210 g of BPDA (27.91 mmol) were added and stirred at room temperature for 4 hours to obtain a polyamine solution C-R. The viscosity of the obtained polyamine solution C-R was 2,200 cP.

(Synthesis Example C19) 50.803 g of m-TB (239.31 mmol), 7.773 g of TPE-R (26.59 mmol), and 680 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 45.934 g of PMDA (210.59 mmol) and 15.490 g of BPDA (52.65 mmol) were added and stirred at room temperature for 4 hours to obtain a polyamide solution C-S. The viscosity of the obtained polyamide solution C-S was 23,000 cP.

(Synthesis Example C20) 44.203 g of m-TB (208.22 mmol), 6.763 g of TPE-R (23.14 mmol), and 680 g of DMAc were placed in a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 59.043 g of BTDA (183.23 mmol) and 9.992 g of PMDA (45.81 mmol) were added and stirred at room temperature for 4 hours to obtain a polyamine solution C-T. The viscosity of the obtained polyamine solution C-T was 12,000 cP.

(Synthesis Example C21) 33.475 g of TPE-R (114.51 mmol), 14.346 g of TPE-Q (49.08 mmol), and 704 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 48.179 g of BPDA (163.75 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-U. The viscosity of the obtained polyamine solution C-U was 15,000 cP.

(Synthesis Example C22) 33.542 g of TPE-R (114.74 mmol), 14.375 g of TPE-Q (49.17 mmol), and 704 g of DMAc were added to a 1000 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 48.083 g of BPDA (163.42 mmol) was added and stirred at room temperature for 4 hours to obtain a polyamine solution C-V. The viscosity of the obtained polyamine solution C-V was 10,000 cP.

[Example C1] On an electrolytic copper foil having a thickness of 12 μm, a polyamide solution C-B is uniformly applied to form a first polyimide layer in a manner to a thickness of 2 μm after curing, and then the temperature is gradually raised from 120°C to 360°C to remove the solvent and perform imidization. Next, a polyamide solution C-A is uniformly applied thereon in a manner to a thickness of 25 μm after curing, and then the solvent is removed by heat drying at 120°C for 3 minutes. Thereafter, the temperature is gradually raised from 130°C to 360°C to perform imidization, thereby preparing a metal-clad laminate C1. An adhesive tape was pasted on the resin surface of the prepared metal-clad laminate C1, and a peeling test was performed by tearing it off instantly in the vertical direction, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C2] Metal-clad laminate C2 was prepared in the same manner as Example C1 except that polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C2 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C3] Metal-clad laminate C3 was prepared in the same manner as Example C1 except that polyamide solution C-C was used instead of polyamide solution C-B. The prepared metal-clad laminate C3 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C4] Metal-clad laminate C4 was prepared in the same manner as Example C1 except that polyamide solution C-C was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C4 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C5] Metal-clad laminate C5 was prepared in the same manner as Example C1 except that polyamide solution C-D was used instead of polyamide solution C-B. The prepared metal-clad laminate C5 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C6] Metal-clad laminate C6 was prepared in the same manner as Example C1 except that polyamide solution C-D was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C6 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C7] Metal-clad laminate C7 was prepared in the same manner as Example C1 except that polyamide solution C-E was used instead of polyamide solution C-B. The prepared metal-clad laminate C7 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C8] Metal-clad laminate C8 was prepared in the same manner as Example C1 except that polyamide solution C-E was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C8 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C9] Metal-clad laminate C9 was prepared in the same manner as Example C1 except that polyamide solution C-F was used instead of polyamide solution C-B. The prepared metal-clad laminate C9 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C10] A metal-clad laminate C10 was prepared in the same manner as Example C1 except that polyamide solution C-F was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C10 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C11] A metal-clad laminate C11 was prepared in the same manner as Example C1 except that the polyamide solution C-G was used instead of the polyamide solution C-B. The prepared metal-clad laminate C11 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C12] Metal-clad laminate C12 was prepared in the same manner as Example C1 except that polyamide solution C-G was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C12 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C13] Metal-clad laminate C13 was prepared in the same manner as Example C1 except that polyamide solution C-H was used instead of polyamide solution C-B. The prepared metal-clad laminate C13 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C14] Metal-clad laminate C14 was prepared in the same manner as Example C1 except that polyamide solution C-H was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C14 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C15] Metal-clad laminate C15 was prepared in the same manner as Example C1 except that polyamide solution C-I was used instead of polyamide solution C-B. The prepared metal-clad laminate C15 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C16] Metal-clad laminate C16 was prepared in the same manner as Example C1 except that polyamide solution C-I was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C16 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C17] Metal-clad laminate C17 was prepared in the same manner as Example C1 except that polyamide solution C-J was used instead of polyamide solution C-B. The prepared metal-clad laminate C17 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C18] Metal-clad laminate C18 was prepared in the same manner as Example C1 except that polyamide solution C-J was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C18 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C19] Metal-clad laminate C19 was prepared in the same manner as Example C1 except that polyamide solution C-K was used instead of polyamide solution C-B. The prepared metal-clad laminate C19 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C20] Metal-clad laminate C20 was prepared in the same manner as Example C1 except that polyamide solution C-K was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C20 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C21] Metal-clad laminate C21 was prepared in the same manner as Example C1 except that polyamide solution C-L was used instead of polyamide solution C-B. The prepared metal-clad laminate C21 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C22] Metal-clad laminate C22 was prepared in the same manner as Example C1 except that polyamide solution C-L was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C22 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C23] Metal-clad laminate C23 was prepared in the same manner as Example C1 except that polyamide solution C-O was used instead of polyamide solution C-B. The prepared metal-clad laminate C23 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C24] Metal-clad laminate C24 was prepared in the same manner as Example C1 except that polyamide solution C-O was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C24 was subjected to a peeling test in the same manner as Example C1, but peeling between the first polyimide layer and the second polyimide layer was not observed.

[Example C25] Metal-clad laminate C25 was prepared in the same manner as Example C1 except that polyamide solution C-T was used instead of polyamide solution C-B. The prepared metal-clad laminate C25 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

[Example C26] Metal-clad laminate C26 was prepared in the same manner as Example C1 except that polyamide solution C-T was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. The prepared metal-clad laminate C26 was subjected to a peeling test in the same manner as Example C1, but no peeling between the first polyimide layer and the second polyimide layer was observed.

Comparative Example C1 A metal-clad laminate C27 was prepared in the same manner as Example C1 except that the polyamide solution C-M was used instead of the polyamide solution C-B. A peeling test of the prepared metal-clad laminate C27 was conducted in the same manner as Example C1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred.

Comparative Example C2 A metal-clad laminate C28 was prepared in the same manner as Example C1 except that polyamide solution C-M was used instead of polyamide solution C-B, and polyamide solution C-N was used instead of polyamide solution C-A. A peeling test of the prepared metal-clad laminate C28 was conducted in the same manner as Example C1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred.

Comparative Example C3 A metal-clad laminate C29 was prepared in the same manner as Example C1 except that the polyamide solution C-N was used instead of the polyamide solution C-B. A peeling test of the prepared metal-clad laminate C29 was conducted in the same manner as Example C1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred.

Comparative Example C4 A metal-clad laminate C30 was prepared in the same manner as Example C1 except that the polyamide solution C-P was used instead of the polyamide solution C-A. A peeling test of the prepared metal-clad laminate C30 was conducted in the same manner as Example C1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred.

Comparative Example C5 A metal-clad laminate C31 was prepared in the same manner as Example C1 except that polyamide solution C-A was used instead of polyamide solution C-B, and polyamide solution C-B was used instead of polyamide solution C-A. A peeling test of the prepared metal-clad laminate C31 was conducted in the same manner as Example C1, and as a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred.

[Example C27] Metal-clad laminate C32 was prepared in the same manner as Example C1 except that the heating time from 130°C to 360°C after application of polyamide solution C-A was shortened to 1/3, but no foaming was observed.

[Example C28] Metal-clad laminate C33 was prepared in the same manner as Example C1 except that polyamine solution C-A was used instead of polyamine solution C-B and the heating time from 130°C to 360°C after application of polyamine solution C-A was shortened to 1/3, but no foaming was observed.

Comparative Example C6 Instead of polyamine solution C-B, polyamine solution C-M was used, and the heating time from 130°C to 360°C after the application of polyamine solution C-A was shortened to 1/3. Metal-clad laminate C34 was prepared in the same manner as Example C1. As a result, foaming occurred.

Comparative Example C7 Instead of polyamine solution C-B, polyamine solution C-N was used, and the heating time from 130°C to 360°C after the application of polyamine solution C-A was shortened to 1/3. Metal-clad laminate C35 was prepared in the same manner as Example C1. As a result, foaming occurred.

[Example C29] A polyamide solution C-O is applied to a stainless steel substrate to form a first polyimide layer, and then dried at 120°C to prepare a polyamide gel film. The prepared gel film is peeled off from the stainless steel substrate, fixed on a tenter clip, and the temperature is gradually raised from 130°C to 360°C to perform imidization, thereby preparing a polyimide film C36 with a thickness of 12.5 μm. On the prepared polyimide film C36, a polyamide solution C-R is applied to form a second polyimide layer in a manner of 3 μm in thickness after curing, and then dried at 120°C. Afterwards, the temperature was gradually raised from 130°C to 360°C for imidization to prepare a laminated polyimide film C36. The prepared laminated polyimide film C36 was cut with a cutter, and no interlayer peeling between the first polyimide layer and the second polyimide layer was observed using a scanning electron microscope (SEM).

[Example C30] A laminated polyimide film C37 was prepared in the same manner as Example C29 except that the polyimide solution C-T was used instead of the polyimide solution C-O. No interlayer delamination was observed in the prepared laminated polyimide film C37 by SEM observation.

[Example C31] A laminated polyimide film C38 was prepared in the same manner as Example C29 except that the thickness of the first polyimide layer was set to 17 μm and the thickness after curing was set to 4 μm by using polyimide solution C-V instead of polyimide solution C-R. Interlayer delamination of the prepared laminated polyimide film C38 was not confirmed by SEM observation.

[Example C32] A laminated polyimide film C39 was prepared in the same manner as Example C29, except that the polyimide solution C-T was used instead of the polyimide solution C-O and the thickness of the first polyimide layer was set to 17 μm, and the polyimide solution C-V was used instead of the polyimide solution C-R and the thickness after curing was set to 4 μm. Interlayer delamination of the prepared laminated polyimide film C39 was not confirmed by SEM observation.

Comparative Example C8 A laminated polyimide film C40 was prepared in the same manner as Example C29 except that the polyimide solution C-Q was used instead of the polyimide solution C-R. Interlayer peeling was confirmed by SEM observation of the prepared laminated polyimide film C40.

Comparative Example C9 A laminated polyimide film C41 was prepared in the same manner as Example C29 except that the polyimide solution C-P was used instead of the polyimide solution C-O. Interlayer peeling was confirmed by SEM observation of the prepared laminated polyimide film C41.

Comparative Example C10 A laminated polyimide film C42 was prepared in the same manner as Example C29 except that the thickness of the first polyimide layer was set to 17 μm and the thickness after curing was set to 4 μm by using polyimide solution C-U instead of polyimide solution C-R. Interlayer peeling was confirmed by SEM observation of the prepared laminated polyimide film C42.

[Example C33] On an electrolytic copper foil having a thickness of 12 μm, a polyamide solution C-T is uniformly applied to form a first polyimide layer in a manner that the thickness after curing is 25 μm, and then the temperature is gradually raised from 120°C to 360°C to remove the solvent and perform imidization. Next, a polyamide solution C-S is uniformly applied thereon in a manner that the thickness after curing is 25 μm, and then heat-dried at 120°C to remove the solvent. Thereafter, the temperature is gradually raised from 130°C to 360°C to perform imidization, and a metal-clad laminate C43 is prepared. The peeling strength of the first polyimide layer and the second polyimide layer in the prepared metal-clad laminate C43 is above 1.5 kN/m.

[Example C34] On an electrolytic copper foil having a thickness of 12 μm, polyamide solution C-S is uniformly applied to a thickness of 23 μm after curing, and heat-dried at 120°C to remove the solvent. On top of it, polyamide solution C-B is uniformly applied to a thickness of 2 μm after curing, and heat-dried at 120°C to remove the solvent. Thereafter, the temperature is gradually raised from 130°C to 360°C to perform imidization, thereby forming a first polyimide layer. Next, a polyamide solution C-S is uniformly applied thereon to a thickness of 25 μm after curing to form a second polyimide layer, and then the solvent is removed by heat drying at 120°C. Thereafter, the temperature is gradually raised from 130°C to 360°C to perform imidization to prepare a metal-clad laminate C44. The peel strength of the first polyimide layer and the second polyimide layer in the prepared metal-clad laminate C44 is 1.5 kN/m or more.

Comparative Example C11 A metal-clad laminate C45 was prepared in the same manner as Example C33 except that the polyamide solution C-S was used instead of the polyamide solution C-T. The peeling strength of the first polyimide layer and the second polyimide layer in the prepared metal-clad laminate C45 was 0.1 kN/m or less.

Comparative Example C12 A metal-clad laminate C46 was prepared in the same manner as Example C34 except that the polyamide solution C-M was used instead of the polyamide solution C-B. The peel strength of the first polyimide layer and the second polyimide layer in the prepared metal-clad laminate C46 was 0.1 kN/m or less.

Reference Example C 0.45 g of phthalic anhydride (3.02 mmol) was added to 100 g of polyamide solution C-A and stirred for 4 hours to prepare polyamide solution C-A2. Metal-clad laminate C47 was prepared in the same manner as in Example C1 except that polyamide solution C-A2 was used instead of polyamide solution C-A. As a result, foaming occurred. In addition, a peeling test of the prepared metal-clad laminate C47 was conducted in the same manner as in Example C1. As a result, interlayer peeling of the first polyimide layer and the second polyimide layer occurred. The reason is believed to be that the amino groups of the second polyimide layer react with phthalic anhydride, thereby eliminating the functional groups that can react with the first polyimide layer, and chemical bonding between the resin layers will not occur.

Although the embodiments of the present invention have been described in detail for the purpose of illustration, the present invention is not limited to the embodiments described above.

This international application claims priority based on Japanese Patent Application No. 2018-185874 (filing date: September 28, 2018), Japanese Patent Application No. 2018-185875 (filing date: September 28, 2018), and Japanese Patent Application No. 2018-185876 (filing date: September 28, 2018), and all the contents of those applications are incorporated herein by reference.

10: Metal layer 10A: Metal foil 20: First polyimide layer 20A: First polyamide resin layer 20B: Semi-hardened resin layer 30: Second polyimide layer 30A: Second polyamide resin layer 40: Insulating resin layer 100: Metal-clad laminate L: Overall thickness of insulating resin layer L1: Thickness of first polyimide layer

(1) to (5) in FIG. 1 are step diagrams showing the sequence of the method for manufacturing a metal-clad laminated board according to the first embodiment of the present invention. (a) to (d) in FIG. 2 are step diagrams showing the sequence of the method for manufacturing a metal-clad laminated board according to the second embodiment of the present invention. FIG. 3 is an explanatory diagram of a position measurement target used in the measurement of the dimensional change rate after etching. FIG. 4 is an explanatory diagram of an evaluation sample used in the measurement of the dimensional change rate after etching.

10: Metal layer

10A: Metal foil

20: First polyimide layer

20A: First polyamide resin layer

30: Second polyimide layer

30A: Second polyamide resin layer

40: Insulating resin layer

100: Metal-clad laminate

L: The overall thickness of the insulating resin layer

L1: Thickness of the first polyimide layer

Claims (5)

A method for manufacturing a polyimide membrane, which is a method for manufacturing a polyimide membrane, the polyimide membrane comprising: a first polyimide layer (A), and a second polyimide layer (B) laminated on at least one side of the first polyimide layer (A), the method for manufacturing a polyimide membrane is characterized in that: It comprises the following steps I to III: I) preparing a first polyimide layer (A) containing a polyimide having a ketone group; II) laminating a resin layer containing polyamide (b) on the first polyimide layer (A), wherein the polyamide (b) contains a functional group having a property of interacting with the ketone group; III) heat-treating the resin layer containing polyamide (b) together with the first polyimide layer (A) to imidize the polyamide (b) to form a second polyimide layer (B), and the resin layer containing polyamide (b) contains tetracarboxylic acid residues (1b) and diamine residues (2b), and the tetracarboxylic acid residues (1b) are less than 0.998 mol relative to 1 mol of the diamine residues (2b). A method for producing a polyimide film as described in claim 1, wherein the polyimide constituting the first polyimide layer (A) comprises tetracarboxylic acid residues (1a) and diamine residues (2a), and the ketone groups are present in an amount of 5 mol parts or more relative to a total of 100 mol parts of the tetracarboxylic acid residues (1a) and the diamine residues (2a). The method for producing a polyimide film according to claim 1 or 2, wherein the first polyimide layer (A) is formed by laminating a resin layer containing polyamide (a) having a keto group on a substrate and imidizing the polyamide (a) together with the substrate. A method for manufacturing a metal-clad laminate, which is a method for manufacturing a metal-clad laminate, the metal-clad laminate comprising: a metal layer, a first polyimide layer (A), and a second polyimide layer (B) laminated on one side of the first polyimide layer (A), the method for manufacturing a metal-clad laminate being characterized in that: It comprises the following steps i to iv: i) forming at least one layer of a polyamide resin layer on the metal layer, the polyamide resin layer having a resin layer containing a polyamide (a) having a keto group on the surface; ii) a step of heat-treating the resin layer of the polyamine together with the metal layer to imidize the polyamine, thereby forming an intermediate having a polyimide layer laminated on the metal layer, wherein the polyimide layer has a first polyimide layer (A) containing a polyimide having a ketone group as a surface layer; iii) a step of laminating a resin layer containing polyamine (b) on the first polyimide layer (A), wherein the polyamine (b) contains a functional group having a property of interacting with the ketone group; iv) heat-treating the resin layer of the polyamide (b) together with the intermediate to imidize the polyamide (b) to form a second polyimide layer (B), and the resin layer containing the polyamide (b) contains tetracarboxylic acid residues (1b) and diamine residues (2b), and the tetracarboxylic acid residues (1b) are less than 0.998 mol relative to 1 mol of the diamine residues (2b). A method for manufacturing a circuit substrate, comprising: performing wiring circuit processing on the metal layer of the metal-clad laminate manufactured by the method for manufacturing a metal-clad laminate as described in claim 4.

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