Resin film and its manufacturing method, as well as metallized resin film and printed wiring board

Abstract

The purpose of the present invention is to provide a novel resin film, etc., having excellent solder resistance and adhesion. The above purpose is achieved by configuring a resin film in which a layer A including a polyimide resin and a fumed metal oxide is formed on at least one surface of a layer B which is a heat-resistant resin film having a coefficient of linear expansion of 20 ppm / °C or less, and the coefficient of linear expansion of the polyimide resin is 30 ppm / °C to 100 ppm / °C.

Description

[Technical Field]

[0001] The present invention relates to a resin film and a method for producing the same, as well as a metallized resin film and a printed wiring board. [Background technology]

[0002] Printed wiring boards, which have circuits made of metal conductors on an insulating substrate, are widely used as components that enable the functions of electronic devices, with various electronic components mounted on the board. As electronic devices become more functional, more powerful, and more compact, printed wiring boards are required to have finer-pitch circuit wiring. Specifically, there is a demand for printed wiring boards with fine-pitch circuits formed on flexible film portions, such as (a) flexible printed wiring boards, (b) rigid-flex boards, (c) multilayer flexible boards, and (d) COF (chip-on-film) that can be folded and stored compactly inside electronic devices.

[0003] As a method for forming narrow-pitch circuits, Patent Document 1 discloses a method in which a thin copper foil with a carrier is bonded to a polyimide sheet.

[0004] Furthermore, Patent Document 2 discloses a method for forming a metal layer on a polyimide film using a physical vapor deposition method such as vacuum deposition, sputtering, or ion plating.

[0005] Furthermore, Patent Document 3 discloses an example in which copper plating is performed directly by electroless plating on a material containing a polyimide resin containing a silicone structure and fumed silica. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-76091 [Patent Document 2] Patent No. 6706013 [Patent Document 3] Patent No. 5037168 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional techniques are not sufficient in terms of solder resistance and adhesion, and there is room for further improvement.

[0008] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a novel resin film having excellent solder resistance and adhesion, a method for producing the same, and a metallized resin film and a printed wiring board obtained from the resin film. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be overcome.

[0010] That is, in a resin film according to one embodiment of the present invention, Layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of Layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0011] In addition, in a method for producing a resin film according to one embodiment of the present invention, Layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of Layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, and Layer A containing a polyimide resin and a fumed metal oxide is obtained by mixing a polyamic acid solution of a polyimide resin precursor with a fumed metal oxide and imidizing the obtained fumed metal oxide-dispersed polyamic acid solution. [Effects of the Invention]

[0012] According to one embodiment of the present invention, it is possible to provide a material and method thereof that exhibits excellent solder heat resistance and is capable of forming narrow-pitch circuits; specifically, a resin film and method for producing the same that can form an electroless plating layer that exhibits excellent solder heat resistance and strong adhesion to a surface with low roughness; and a metallized resin film and printed wiring board obtained from the resin film. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Technical idea of ​​one embodiment of the present invention] As a result of extensive research, the present inventors have found that the techniques described in the above-mentioned prior art documents 1 to 3 have room for improvement or have problems as described below.

[0014] For example, in Patent Document 1, irregularities are intentionally formed on the copper foil surface to ensure adhesion between the insulating substrate and the copper foil. Therefore, although the copper layer thickness in Patent Document 1 is thinner than the limit for normal copper foil, there is an adverse effect on the circuit shape in the etching process, there is a limit to how narrow the pitch can be, and there is an adverse effect on the transmission characteristics.

[0015] Furthermore, in the technology of Patent Document 2, metals such as nickel, chromium, vanadium, titanium, molybdenum, etc. are formed on the surface of a substrate by physical vapor deposition. However, with the technology of Patent Document 2, metals such as nickel, chromium, and titanium cannot be completely removed by simply etching with a copper etching solution during circuit formation, and a separate etching solution must be used to completely remove them, which creates a problem of complicated processes.

[0016] Furthermore, Patent Document 3 discloses a resin film that can form an electroless plating layer on a surface with low roughness, but there is room for improvement in solder resistance and the like.

[0017] The present invention was made in consideration of the above-mentioned problems, and its object is to provide a novel resin film having excellent solder resistance and adhesion, a method for producing the same, and a metallized resin film and printed wiring board obtained from the resin film. One embodiment of the present invention aims to provide, for example, a material (resin film) that exhibits excellent solder heat resistance and is suitable for forming narrow-pitch circuits, and a method for producing the same. Specifically, one embodiment of the present invention aims to provide a resin film that has excellent solder heat resistance and can form an electroless plated layer that exhibits strong adhesion to low-roughness surfaces, and a method for producing the same. Another embodiment of the present invention aims to provide a metallized resin film and printed wiring board obtained from the resin film.

[0018] [Resin film] A resin film according to one embodiment of the present invention is characterized in that Layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of Layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0019] The resin film according to one embodiment of the present invention has the above-described structure, and thus has the advantages of excellent solder resistance and adhesion. As an example, in this specification, adhesion is evaluated by peel strength (N / cm), and solder resistance is evaluated by moisture absorption solder heat resistance.

[0020] Layer A (sometimes referred to as layer A) containing a polyimide resin and a fumed metal oxide will be described.

[0021] <Layer A containing polyimide resin and fumed metal oxide (Layer A)> In one embodiment of the present invention, Layer A essentially contains a polyimide resin and a fumed metal oxide. This composition significantly improves the adhesion between the resin film and the electroless metal plating layer, particularly immediately after the formation of the electroless metal plating layer, without the need for heating or other treatments. The mechanism by which this adhesion is achieved is described below.

[0022] The electroless metal plating process consists of multiple independent chemical baths. These chemical baths are controlled under predetermined conditions (e.g., concentration, temperature), and the surface of the workpiece is exposed to these chemicals for a predetermined period of time by methods such as immersion or showering, resulting in chemical changes and, in some cases, physical changes to the surface. These chemicals contain various components, and their pH varies depending on the type of chemical, with some being strongly alkaline and others being strongly acidic. Meanwhile, the polyimide resin and fumed metal oxide, both essential to one embodiment of the present invention, interact with these chemicals, causing changes in their chemical structure and physical shape, which we believe affect the improved adhesion of the electroless metal plating. Both fumed metal oxide and polyimide resin undergo chemical changes in alkaline environments. For example, fumed metal oxide dissolves in alkaline environments, generating ionic metal oxides. For example, polyimide resin generates ionic amic acid groups through imide ring cleavage in alkaline environments. These ionic compounds (such as ionic metal oxides and ionic amic acid groups) react with metal ions in the electroless metal plating bath, forming compounds at the interface between the polyimide resin and the metal plating, which are derived from the three components of "fumed metal oxide," "metal (e.g., copper)," and "polyimide resin." We believe that these compounds contribute to adhesion, resulting in high adhesion between polyimide resin and metal plating.

[0023] On the other hand, the dissolution rates of polyimide resin and fumed metal oxide in an alkaline environment are thought to be affected by the chemical structure and aggregation structure of the polyimide resin and the chemical structure and specific surface area of ​​the fumed metal oxide, respectively. When Layer A, which contains a polyimide resin and a fumed metal oxide according to one embodiment of the present invention, is exposed to an alkaline environment, dissolution occurs according to the respective dissolution rates of the polyimide resin and the fumed metal oxide. Layer A according to one embodiment of the present invention has a structure in which the fumed metal oxide is embedded in the polyimide resin phase. Therefore, when Layer A according to one embodiment of the present invention is exposed to an alkaline environment, fine irregularities of the same order as the particle size of the fumed metal oxide are generated on the surface of Layer A depending on the respective dissolution rates of the polyimide resin and the fumed metal oxide in alkaline chemicals, which can result in an increase in the surface area of ​​Layer A. It is believed that this increase in the surface area of ​​Layer A also contributes to improved adhesion strength.

[0024] The fumed metal oxide essential to one embodiment of the present invention has a structure in which primary particles are aggregated and exists embedded in the polyimide resin phase. Furthermore, some of the structural units of the fumed metal oxide essential to one embodiment of the present invention are exposed to the surface and / or present near the surface, while the remaining portions are present in the bulk direction, resulting in a strong bond between the two, which is believed to contribute to improved adhesion strength. Specifically, we believe that (i) the increase in the interface area where compounds derived from the three components of "fumed metal oxide," "metal (e.g., copper)," and "polyimide resin" exist, and (ii) the fumed metal oxide is embedded in the polyimide resin phase and firmly bonded to it, contribute to the increased adhesion strength with electroless metal plating. Note that the present invention is in no way limited to the above-mentioned idea (speculation) regarding the mechanism of adhesion development.

[0025] <Polyimide resin of layer A> Next, the polyimide resin used in Layer A will be described. Polyimide resins are characterized by the inclusion of imide groups in their chemical skeletons. It is believed that the imide groups (functional groups) in the polyimide resin interact with the fumed metal oxide and metal elements (e.g., copper) to improve adhesion with the electroless metal plating layer. Therefore, in order to achieve the adhesion effect of one embodiment of the present invention, it is essential that the polyimide resin contain imide groups. Meanwhile, the inventors, through extensive research, independently discovered that the linear expansion coefficient of the polyimide resin used in Layer A affects adhesion, specifically, that a coefficient of 30 ppm / °C or higher exhibits good adhesion, leading to one embodiment of the present invention. In this specification, the linear expansion coefficient of the polyimide resin refers to the linear expansion coefficient in the in-plane direction when the polyimide resin used in Layer A is formed into a film, and reflects the degree of in-plane orientation of the polyimide molecular chains within Layer A. A smaller linear expansion coefficient of the polyimide resin indicates a higher degree of in-plane orientation of the polyimide molecular chains, while a larger linear expansion coefficient indicates a higher degree of orientation of the polyimide molecular chains in the thickness direction.

[0026] It is known that the linear expansion coefficient of polyimide resin can be controlled by the type of monomer used. To reduce the linear expansion coefficient of polyimide resin, it is effective to use a monomer with a rigid chemical structure and increase its composition ratio. By using a monomer with a rigid chemical structure and increasing its composition ratio, polyimide molecular chains are oriented in the plane direction when processed (molded) into a film, and further, the molecular chains can be accumulated in the thickness direction.

[0027] As mentioned above, the present inventors independently discovered that if the linear expansion coefficient of the polyimide resin of Layer A is too small, the adhesion between the resin film and the electroless metal plating layer decreases. While the reason for this is unclear, it is speculated as follows: When a polyimide obtained from a monomer mixture containing a high proportion of a monomer with a rigid chemical structure is exposed to an alkaline chemical solution, the polyimide molecules near the surface are modified to polyamic acid through imide ring cleavage, resulting in a state in which polyamic acid molecules oriented in the plane direction are deposited in the thickness direction. The cohesive strength between polyamic acid molecular chains is weaker than that between polyimide molecular chains. Therefore, when an electroless metal plating layer (film) is formed on the surface of a film obtained by exposing the polyimide to an alkaline chemical solution and the adhesion is evaluated, it is speculated that peeling occurs at the interface where the polyamic acid molecular chains, which have weak cohesive strength, are broken down into layers, resulting in a tendency for the adhesion strength between the film and the plating layer (film) to be low. However, the present invention is in no way limited by this speculation.

[0028] Conversely, in order to increase the linear expansion coefficient of a polyimide resin, it is effective to use a monomer with a flexible chemical structure and increase its composition ratio. By using a monomer with a flexible chemical structure and increasing its composition ratio, when the polyimide resin is molded into a film, the polyimide molecular chains tend to be oriented not only in the plane direction but also in the thickness direction, i.e., to exhibit random orientation.

[0029] As mentioned above, the present inventors independently discovered that a high linear expansion coefficient (e.g., 30 ppm / °C or higher) of the polyimide resin of Layer A enhances adhesion between the resin film and the electroless metal plating layer. While the reason for this is unclear, it is speculated as follows: When a polyimide obtained from a monomer mixture containing a high proportion of a monomer having a flexible chemical structure is exposed to an alkaline chemical solution, the polyimide molecules near the surface are modified to polyamic acid through imide ring cleavage. However, numerous covalent bonds between the polymer chains are present in the thickness direction, maintaining a high cohesive force between the molecular chains. Therefore, when an electroless metal plating film is formed on the surface of a film obtained by exposing the polyimide to an alkaline chemical solution and the adhesion is evaluated, it is speculated that the polyimide has a low linear expansion coefficient as described above, and thus does not experience layer-like delamination between the polyamic acid molecular chains, as occurs in polyimides with advanced in-plane molecular orientation. As a result, it is speculated that the adhesion strength with the electroless metal plating tends to be high. However, the present invention is in no way limited by this speculation.

[0030] From the viewpoint of preventing a decrease in the cohesive strength of the polyimide resin itself even when exposed to an alkaline chemical solution, it is preferable that the polyimide resin used in Layer A be a polyimide resin that tends to be randomly oriented, i.e., a polyimide resin that tends to be isotropically oriented, rather than a polyimide resin with advanced in-plane molecular orientation.

[0031] For polyimide resins, there is a correlation between the degree of in-plane molecular orientation and the linear expansion coefficient. When the in-plane molecular orientation of a polyimide resin is highly advanced, resulting in a weakened peel strength between the planarly oriented polymer chains, the linear expansion coefficient is less than 30 ppm / °C. The polyimide resin used in Layer A preferably has a random orientation tendency, being oriented not only in the plane direction but also in the thickness direction, thereby improving adhesion to electroless metal plating. The linear expansion coefficient of the polyimide resin is preferably 30 ppm / °C or higher, more preferably greater than 30 ppm / °C, more preferably 35 ppm / °C or higher, even more preferably 40 ppm / °C or higher, even more preferably 45 ppm / °C or higher, and particularly preferably 50 ppm / °C or higher.

[0032] On the other hand, as the linear expansion coefficient of the polyimide resin of Layer A increases, the linear expansion coefficient of the entire resin film of one embodiment of the present invention, which is composed of Layers A and B, also tends to increase. When the resin film of one embodiment of the present invention is used for a printed wiring board, an increase in the linear expansion coefficient of the entire resin film tends to deteriorate the dimensional accuracy required in the mounting process, which is undesirable. Furthermore, through extensive research, the present inventors independently and surprisingly discovered that by setting the linear expansion coefficient of the polyimide resin to 100 ppm or less, the film tends to have excellent heat resistance, such as solder heat resistance, or in other words, tends to have excellent solder resistance. Therefore, the linear expansion coefficient of the polyimide resin of Layer A is preferably 100 ppm / °C or less, more preferably 90 ppm / °C or less, more preferably 80 ppm / °C or less, more preferably 75 ppm / °C or less, even more preferably 70 ppm / °C or less, still more preferably 65 ppm / °C or less, and particularly preferably 60 ppm / °C or less.

[0033] <Heat resistance, glass transition temperature, and high temperature elastic modulus of polyimide resin of Layer A> The linear expansion coefficient of the polyimide resin used in Layer A is preferably 30 ppm / °C or higher, and more preferably greater than 30 ppm / °C. As the linear expansion coefficient of a polyimide resin increases, the polyimide resin tends to exhibit thermoplasticity. Thermoplastic resins soften at a certain temperature, which can be utilized to allow processing, for example, thermocompression bonding to copper foil. From the perspective of improving adhesion with electroless metal plating, which is the objective of one embodiment of the present invention, thermoplasticity is not an essential requirement.

[0034] On the other hand, when considering the use of the resin film of one embodiment of the present invention for a printed wiring board, it is preferable that the polyimide resin withstands the high process temperatures during the processing and the high temperatures when components are mounted. Therefore, it is preferable that the polyimide resin used in Layer A has a high glass transition temperature and high elastic modulus at high temperatures, and there is no particular disadvantage in that the temperature is too high. From the above perspective, it is preferable that the glass transition temperature of the polyimide resin, which is an indicator of heat resistance, is as high as possible, for example, preferably 180°C or higher, and more preferably 230°C or higher. Furthermore, in order to exhibit good solder heat resistance, it is preferable that the polyimide resin used in Layer A has a certain elastic modulus or higher even near the melting point of the solder. Specifically, the polyimide resin contained in Layer A has a storage elastic modulus of 0.2 × 10 at 300°C. 8 Pa or more, and 0.5 × 10 8 Pa or more is more preferable, and 0.8 × 10 8 More preferably, the temperature is 1.0×10 Pa or higher. 8 It is particularly preferable that the viscosity is 100 Pa or more.

[0035] <Solubility of Polyimide Resin in Layer A> It is possible to produce a resin film according to one embodiment of the present invention by using a soluble polyimide soluble in an organic solvent as the polyimide resin for Layer A. Specifically, a soluble polyimide is dissolved in an organic solvent, and a fumed metal oxide is further dispersed in the resulting solution. The resulting dispersion is applied to Layer B, which is a heat-resistant resin film, and Layer B is then dried to obtain a resin film according to one embodiment of the present invention. However, when the resin film according to one embodiment of the present invention is used for a printed wiring board, the polyimide resin used in Layer A is preferably insoluble so as to prevent problems such as resin dissolution during processes using organic solvents in the manufacturing and mounting of printed circuit boards. Furthermore, even if the polyimide resin is insoluble in organic solvents, it is more preferable that it does not swell with organic solvents. On the other hand, from the viewpoint of reliability, it is preferable that the polyimide resin of Layer A and Layer B, which is a heat-resistant resin film, are firmly adhered to each other. To improve the adhesion between the polyimide resin of Layer A and Layer B, it is preferable to imidize a precursor of the polyimide resin of Layer A (or a solution containing the precursor) after contacting the precursor with Layer B.

[0036] As described above, although one embodiment of the present invention can be achieved whether the polyimide resin used in Layer A is soluble or insoluble, it is preferably insoluble. In other words, it is preferable that the polyimide resin contained in Layer A is an insoluble polyimide resin. A precursor of an insoluble polyimide resin (or a solution containing the precursor) is brought into contact with Layer B, and then the precursor is imidized to obtain a resin film of one embodiment of the present invention, which includes Layer A containing an insoluble polyimide resin. This makes it possible to obtain a resin film that has excellent durability against solvents and excellent adhesion between Layer A and Layer B, and is therefore preferably implemented.

[0037] Here, the insolubility of polyimide resins will be explained. In this specification, the term "insolubility of a polyimide resin" refers to the insolubility of the polyimide resin in organic solvents commonly used in industrial applications. Specifically, the polyimide resin preferably does not dissolve in organic solvents at 20°C to 30°C to a concentration of 10% by weight or more, and more preferably 5% by weight or more. Examples of organic solvents include, but are not limited to, alcoholic solvents such as methanol, ethanol, and propanol; ketone solvents such as acetone and methyl ethyl ketone; aromatic solvents such as toluene, xylene, cresol, and benzene; ether solvents such as dioxolane, dioxane, tetrahydrofuran, and diethyl ether; and aprotic polar solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and acetonitrile.

[0038] <Polyimide resin formulation for Layer A> Next, the type of monomer used in the polyimide resin for Layer A, the polymerization method, etc. will be described. The polyimide resin used in Layer A must have a linear expansion coefficient of 30 ppm / °C or more and 100 ppm / °C or less. It is also preferable that the polyimide resin also have other physical properties such as glass transition temperature, storage modulus at high temperatures, and solubility in organic solvents that are appropriately controlled. One way to control these physical properties within appropriate ranges is to select the raw materials used. Raw material monomers for polyimide resins include monomers with flexible skeletons and monomers with rigid skeletons. By appropriately selecting these and adjusting the compounding ratio, it is possible to achieve desired physical properties.

[0039] Diamines having a flexible skeleton include 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, bis{4-(4-aminophenoxy)phenyl}sulfone, 2,2'-bis{4-(4-aminophenoxy)phenyl}propane, bis{4-(3-aminophenoxy)phenyl}sulfone, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl. Phenyl thioether, 3,4'-diaminodiphenyl thioether, 3,3'-diaminodiphenyl thioether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl Nilsulfone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4- (3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, and the like.

[0040] On the other hand, examples of diamines having a rigid skeleton include 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)benzidine, 1,5-diaminonaphthalene, 4,4'-diaminobenzanilide, 3,4'-diaminobenzanilide, and 3,3'-diaminobenzanilide.

[0041] Among these, from the viewpoints of controllability of thermal properties and ease of industrial availability, one or more diamines having a flexible skeleton selected from the group consisting of 4,4'-oxydianiline, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-oxydianiline, 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, bis{4-(4-aminophenoxy)phenyl}sulfone, 2,2'-bis{4-(4-aminophenoxy)phenyl}propane, bis{4-(3-aminophenoxy)phenyl}sulfone, 1,3-bis(3-aminophenoxy)benzene, 3,3'-diaminobenzophenone, and 4,4'-diaminobenzophenone can be preferably used. In particular, one or more selected from the group consisting of 4,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis{4-(4-aminophenoxy)phenyl}propane are preferably used. As diamines having a rigid skeleton, one or more selected from the group consisting of 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, and 2,2'-dimethylbenzidine are preferably used because they exhibit the effect of stiffening the polymer chain with a relatively small amount and are easily available industrially. In particular, at least one of 1,4-diaminobenzene (p-phenylenediamine) and 2,2'-dimethylbenzidine is preferably used. These diamines may be used alone or in combination of two or more.

[0042] Tetracarboxylic dianhydrides having a flexible backbone include 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,4'-oxydiphthalic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)phthalic anhydride, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propan ... Examples of suitable anhydrides include 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylene bis(trimellitic acid monoester acid anhydride), ethylene bis(trimellitic acid monoester acid anhydride), and bisphenol A bis(trimellitic acid monoester acid anhydride).

[0043] On the other hand, examples of tetracarboxylic dianhydrides having a rigid skeleton include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, and 3,4,9,10-perylenetetracarboxylic dianhydride.

[0044] Among these, from the viewpoints of controllability of thermal properties and industrial availability, one or more tetracarboxylic dianhydrides having a flexible backbone selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-oxydiphthalic anhydride can be preferably used. Of these, 3,3',4,4'-biphenyltetracarboxylic dianhydride is more preferred, and can be effectively used to achieve a good balance of various physical properties desired in a preferred embodiment of the present invention, such as adhesion to electroless plated films, elastic modulus at high temperatures, glass transition temperature, and linear expansion coefficient of the polyimide resin. As the tetracarboxylic acid dianhydride having a rigid skeleton, pyromellitic dianhydride is preferably used because it exhibits the effect of stiffening the polymer chain with a relatively small amount and is easily available industrially. Two or more of these tetracarboxylic acid dianhydrides may be used in combination.

[0045] The relationship between adhesion and the chemical structure of the polyimide resin of Layer A in one embodiment of the present invention remains unclear, making a clear explanation difficult. Empirically, obtained through extensive research by the inventors, it has been found that the use of a combination of an acid dianhydride and a diamine that reduces the polarization of the imide ring of the polyimide resin tends to provide good adhesion. Specifically, a combination of at least one of 4,4'-oxydiphthalic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride as the acid dianhydride and 2,2'-bis(trifluoromethyl)benzidine as the diamine is effective. The preferred combination of diamine and acid dianhydride is not particularly limited. A preferred combination is one or more diamines selected from the group consisting of 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis{4-(4-aminophenoxy)phenyl}propane, and at least one acid dianhydride selected from 4,4'-oxydiphthalic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, with an appropriate type and amount of fumed metal oxide. This configuration (combination) is advantageous in that it can improve adhesion to the electroless metal plating layer of one embodiment of the present invention, particularly significantly improving the initial condition after formation of the electroless metal plating layer. Furthermore, in order to achieve a good balance of high-temperature elastic modulus, glass transition temperature, linear expansion coefficient, and other properties, it is also preferable to use other diamines and acid dianhydrides in addition to the preferred diamines and acid dianhydrides described above.

[0046] The polyamic acid, which is the precursor of the polyimide of Layer A, is obtained by mixing the diamine and the acid dianhydride in an organic solvent in substantially equimolar or nearly equimolar amounts and then reacting them. Any organic solvent can be used as long as it can dissolve the polyamic acid. Preferred organic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, with at least one of N,N-dimethylformamide and N,N-dimethylacetamide being particularly preferred. The solids concentration of the polyamic acid is not particularly limited; a concentration in the range of 5% by weight to 35% by weight will result in a polyamic acid with sufficient mechanical strength when converted into a polyimide.

[0047] The order of addition of the diamine and acid dianhydride raw materials is not particularly limited. The properties of the resulting polyimide can be controlled not only by controlling the chemical structures of the diamine and acid dianhydride raw materials but also by controlling the order of addition of these raw materials.

[0048] Furthermore, when 1,4-diaminobenzene and pyromellitic dianhydride are used as raw materials, a polyimide structure obtained by bonding the two has low durability against a desmear solution. Therefore, it is preferable to adjust the order of addition of 1,4-diaminobenzene and pyromellitic dianhydride so as not to form a structure in which the two are directly bonded to each other.

[0049] Layer A may contain a resin other than the polyimide resin described above as a resin component. The resin component contained in Layer A preferably contains a high proportion of polyimide resin. For example, of 100% by weight of the resin components contained in Layer A, the polyimide resin preferably accounts for 50% by weight or more, more preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. Of 100% by weight of the resin components contained in Layer A, the polyimide resin most preferably accounts for 100% by weight. In other words, Layer A most preferably contains only polyimide resin as a resin component.

[0050] <Fumed Metal Oxides> The fumed metal oxide used in one embodiment of the present invention is a metal oxide primarily composed of silica, alumina, titania, or the like. The fumed metal oxide used in one embodiment of the present invention is preferably a metal oxide obtained by gas-phase synthesis. When obtained by gas-phase synthesis, the resulting fumed metal oxide is characterized by the fact that its structural units are structures formed by agglomeration of primary particles due to the characteristics of the manufacturing method. In other words, the fumed metal oxide preferably has structural units formed by agglomeration of primary particles (e.g., an agglomerated structure resembling a cluster of grapes). The fumed metal oxide is mixed with a polyimide resin to form Layer A in one embodiment of the present invention. As a result of various studies by the present inventors, it has been found that Layer A is preferably in a state in which (i) the structural units of the fumed metal oxide are embedded in the polyimide resin with low voids, (ii) the structural units are present at the surface and / or near the surface of Layer A in the bulk direction, and (iii) the structural units are uniformly present and dispersed throughout Layer A. It is believed that such a state is effective for achieving the adhesion desired in one embodiment of the present invention. Unlike the fumed metal oxide having an aggregated structure that is preferably used in one embodiment of the present invention, spherical or irregular metal oxide particles (e.g., colloidal silica) in which primary particles exist independently tend to have a weaker binding strength with polyimide resin than fumed metal oxide, and are therefore not preferred.

[0051] As long as Layer A contains a polyimide resin and a fumed metal oxide, it may further contain spherical or irregularly shaped metal oxide particles in which the primary particles exist independently. The smaller the amount of the metal oxide particles in Layer A, the better. For example, in Layer A, the number of parts of the metal oxide particles blended per 100 parts by weight of the polyimide resin precursor is preferably less than 10 parts by weight, more preferably 5 parts by weight or less, even more preferably 1 part by weight or less, even more preferably 0.5 parts by weight or less, and particularly preferably 0.1 parts by weight or less.

[0052] In the blending of polyimide resin and fumed metal oxide, increasing the blending ratio of fumed metal oxide tends to increase the porosity in Layer A. If the porosity in Layer A is not too high, the bonding strength between the polyimide resin and the fumed metal oxide is not reduced, and the strength of Layer A itself tends to be good, resulting in good adhesion to electroless metal plating and also good adhesion between Layer A and Layer B. Therefore, it is preferable that the blending ratio of fumed metal oxide is not too high. Conversely, in the blending of polyimide resin and fumed metal oxide, a low blending ratio of fumed metal oxide tends to decrease the porosity. If the porosity in Layer A is not too low, sufficient adhesion to electroless metal plating is easily achieved, which is preferable. This is believed to be because the ratio of fumed metal oxide is not too low, resulting in a sufficient amount of compounds derived from the three components: "fumed metal oxide", "metal (e.g., copper)", and "polyimide resin". However, the present invention is not limited to such a speculation.

[0053] From the above, it is preferable to control the blending ratio of polyimide resin to fumed metal oxide within an appropriate range in order to achieve good adhesion. On the other hand, there are various grades of fumed metal oxide that differ in primary particle size, structure of aggregated primary particles, and surface treatment type, and it is believed that an appropriate blending ratio exists that is influenced by these factors.

[0054] <Primary particle size and specific surface area of ​​fumed metal oxides> Although the fumed metal oxide near the surface is partially dissolved by the chemical solution used in the electroless metal plating process, it is preferable that the dissolution does not result in excessive surface roughness of Layer A. Therefore, it is preferable that the primary particle size of the fumed metal oxide is small, specifically, preferably from 5 to 1,000 nanometers, more preferably from 5 to 100 nanometers, even more preferably from 5 to 50 nanometers, and even more preferably from 10 to 20 nanometers. The specific surface area of ​​the fumed metal oxide is also a physical property that expresses the primary particle size, and the larger the primary particle size, the smaller the specific surface area. The specific surface area of ​​the fumed metal oxide is preferably from 30 to 400 square meters / gram, more preferably from 100 to 250 square meters / gram.

[0055] <Apparent specific gravity of fumed metal oxides> Fumed metal oxides are structures formed by agglomeration of primary particle diameters, and apparent specific gravity can be used as an index of the structural state of the fumed metal oxide. If the apparent specific gravity of the fumed metal oxide is low, the fumed metal oxide structure has a bulky structure and large voids. Conversely, if the apparent specific gravity of the fumed metal oxide is high, the fumed metal oxide structure has a less bulky structure and small voids.

[0056] By filling the voids in the structure formed by agglomeration of the primary particle size of fumed metal oxide with a polyimide resin component, a layer A with low porosity can be produced. The smaller the apparent specific gravity of the fumed metal oxide, the more voids there are in the fumed metal oxide structure, and the more polyimide resin component can be used to fill these voids. The higher the apparent specific gravity of the fumed metal oxide, the smaller the amount of polyimide resin component that can fill the voids in the fumed metal oxide structure. Conversely, when blending fumed metal oxide with a certain amount of polyimide resin to produce a layer A with low porosity, (i) if the fumed metal oxide has a low apparent specific gravity, the upper limit of the blending amount of fumed metal oxide is low, and conversely, (ii) if the fumed metal oxide has a high apparent specific gravity, a larger amount of fumed metal oxide can be blended, i.e., the upper limit of the blending amount of fumed metal oxide is high. As mentioned above, if the blending amount of fumed metal oxide is not too high, there is no risk of excessive voids occurring in Layer A. As a result, the bonding strength between the polyimide resin and the fumed metal oxide is not reduced, and the strength of Layer A itself tends to be good, which in turn tends to improve adhesion to electroless metal plating and adhesion between Layer A and Layer B. Therefore, when blending the polyimide resin and the fumed metal oxide, it is preferable that the blending ratio of the fumed metal oxide is not too high. Conversely, when the blending ratio of the fumed metal oxide is not too low, sufficient adhesion to electroless metal plating is likely to be achieved. In other words, when blending the polyimide resin and the fumed metal oxide, blending the fumed metal oxide near the upper limit of the blending amount is effective in achieving good adhesion.

[0057] The upper limit of the amount of fumed metal oxide to be blended relative to a given amount of polyimide resin to produce a layer A with a low porosity varies depending on the apparent specific gravity of the fumed metal oxide and the type of surface treatment. In other words, adjusting the amount of fumed metal oxide to be blended relative to a given amount of polyimide resin depending on the apparent specific gravity and type of surface treatment of the fumed metal oxide can further improve adhesion. In one embodiment of the present invention, the apparent specific gravity of the fumed metal oxide is preferably 20 g / L or more and 250 g / L or less, and more preferably 20 g / L or more and 220 g / L or less. Furthermore, the higher the apparent specific gravity of the fumed metal oxide, the higher the upper limit of the amount of fumed metal oxide to be blended, and adhesion tends to be further improved. Therefore, the apparent specific gravity of the fumed metal oxide is preferably greater than 50 g / L and less than or equal to 250 g / L, more preferably between 60 g / L and 250 g / L, even more preferably between 70 g / L and 250 g / L, and even more preferably between 70 g / L and 220 g / L. The apparent specific gravity of the fumed metal oxide can also be changed by structurally modifying the fumed metal oxide by applying mechanical stress such as shear to the fumed metal oxide.

[0058] Various surface treatments are possible for fumed metal oxides. Surface conditions of fumed metal oxides include silanol (untreated), dimethylsilyl, octylsilyl, trimethylsilyl, dimethylsiloxane, dimethylpolysiloxane, aminoalkylsilyl, and methacrylsilyl, all of which are commercially available. When the polarity of the surface treatment of the fumed metal oxide is similar to that of the polyimide resin component, the upper limit of the amount of fumed metal oxide to be incorporated tends to be higher. Furthermore, when the surface of the fumed metal oxide is untreated, its wettability with the alkaline chemical solution during the electroless metal plating process tends to be too high, resulting in a large amount of fumed metal oxide dissolved, which tends to increase the surface roughness of Layer A. Therefore, it is preferable that the surface of the fumed metal oxide be subjected to an appropriate hydrophobic treatment. The apparent specific gravity of the fumed metal oxide can be measured according to ISO 787 / XI.

[0059] <Specific examples of fumed metal oxides> Specific examples of fumed metal oxides that can be preferably used in one embodiment of the present invention are shown below, but are not limited to these. Fumed metal oxides that satisfy various property requirements, including apparent specific gravity, can be more preferably used in one embodiment of the present invention. Various grades of fumed metal oxides with different primary particle sizes, specific surface areas, surface treatment types, apparent specific gravities, and metal oxide types are available from Nippon Aerosil Co., Ltd., Wacker Asahi Kasei Silicone Co., Ltd., and Cabot Corporation, and can be preferably used. Specific examples of fumed metal oxides manufactured by Nippon Aerosil Co., Ltd. are described below. Aerosil R972, R972CF, R972V, and the like, which are substantially equivalent in properties other than apparent gravity, can be preferably used, and of these, R972 (50 grams / liter), which has a high apparent specific gravity, can be more preferably used. Similarly, Aerosil R974, R9200, VP RS920, and the like, which are equivalent except for the apparent density, can be preferably used, and among these, Aerosil R9200 (200 g / L) and Aerosil VP RS920 (80 g / L to 120 g / L), which have a high apparent density, are more preferably used. In addition to these, Aerosil NX130, RY200S, R976, NAX50, NX90G, NX90S, RX200, RX300, R812, R812S, and the like can be preferably used as fumed metal oxides manufactured by Nippon Aerosil Co., Ltd., which have a relatively low apparent density of 70 g / L or less, which is one of the preferred physical properties of one embodiment of the present invention. In addition, fumed metal oxides with a relatively high apparent specific gravity of 70 grams / liter or more manufactured by Nippon Aerosil Co., Ltd., such as Aerosil 200V, AEROIDE TiO2 P90, AEROIDE TiO2 NKT90, OX50, RY50, RY51, AEROIDE TiO2 P25, R8200, RM50, RX50, AEROIDE TiO2 T805, and R7200, can also be preferably used. Note that Aerosil VP RS920 has been sold under the name "Aerosil E9200" since November 2021. "Aerosil" and "AEROSIL" are registered trademarks of Evonik Operations GmbH. As the fumed metal oxide, a fumed metal oxide synthesized by gas phase synthesis and having a structure in which the primary particle size is aggregated can be preferably used.

[0060] Among these fumed metal oxides, fumed silica such as Aerosil R972, 972V, NX130, R9200, VP RS920, R974, R976, and R8200 is preferred because the surface shape of Layer A formed by dissolution in an alkaline environment is good and the surface roughness is within an appropriate range.

[0061] <Parts of fumed metal oxide> Layer A containing a polyimide resin and a fumed metal oxide is preferably an imidized product of a mixture of a precursor of the polyimide resin and a fumed metal oxide (for example, a fumed metal oxide-dispersed polyamic acid solution, as described below). Specifically, the resin film of one embodiment of the present invention can be obtained by mixing the fumed metal oxide with a polyamic acid solution, which is a precursor of the polyimide resin constituting Layer A, (a) applying the resulting mixture to a heat-resistant film of Layer B, drying Layer B, and imidizing the mixture, (b) applying the resulting mixture to a precursor film of Layer B, drying the film, and imidizing the mixture, or (c) co-extruding the resulting mixture with a resin precursor solution of Layer B or a resin solution of Layer B, drying the resulting extrudate, and imidizing the mixture, or the like.

[0062] The amount of fumed metal oxide blended is preferably 10 to 130 parts by weight per 100 parts by weight of the polyimide resin precursor of Layer A. As described above, the preferred amount of fumed metal oxide blended relative to the polyimide precursor (polyimide resin) of Layer A can be adjusted to some extent by the apparent specific gravity of the fumed metal oxide, but due to factors such as the influence of surface treatment of the fumed metal oxide, it is difficult to say for sure. Here, the preferred amount of fumed metal oxide blended is described as a guideline.

[0063] When the apparent specific gravity of the fumed metal oxide is 20 g / L or more and 70 g / L or less, the blending amount of the fumed metal oxide (relative to the solid content of the polyimide (precursor) resin) is preferably 15 parts by weight or more and 80 parts by weight or less, and more preferably 20 parts by weight or more and 60 parts by weight or less, per 100 parts by weight of the polyimide resin precursor. When the apparent specific gravity of the fumed metal oxide is 70 g / L or more and 250 g / L or less, the blending amount of the fumed metal oxide (based on 100 parts by weight of the solid content of the polyimide (precursor) resin) is preferably 10 parts by weight or more and 130 parts by weight or less, more preferably 15 parts by weight or more and 120 parts by weight or less, and even more preferably 20 parts by weight or more and 100 parts by weight or less.

[0064] As mentioned above, the preferred number of parts varies depending on the apparent specific gravity of the fumed metal oxide. The higher the apparent specific gravity of the fumed metal oxide, the greater the amount that can be incorporated, and the preferred amount tends to be higher. By incorporating the fumed metal oxide in the above-mentioned range per 100 parts by weight of the polyimide resin precursor, it is possible to achieve better adhesion strength, particularly stronger adhesion in the initial state after formation of the electroless plating film. It is also possible to mix (combine) multiple types of fumed metal oxides that differ in primary particle size, specific surface area, surface treatment type, apparent specific gravity, metal oxide type, etc.

[0065] <Fumed metal oxide dispersed polyamic acid solution> To obtain Layer A according to one embodiment of the present invention, it is preferable to mix and disperse a precursor solution of the polyimide resin for Layer A with a fumed metal oxide to obtain a fumed metal oxide-dispersed polyamic acid solution (hereinafter, sometimes referred to as Layer A dispersion). Layer A can be obtained by imidizing the Layer A dispersion. In other words, Layer A is preferably an imidized product of a mixture of a polyimide resin precursor and the fumed metal oxide. This configuration has the advantage of increasing the adhesion between Layer A and Layer B. The procedure for obtaining the Layer A dispersion will be specifically described below, but one embodiment of the present invention is not limited thereto.

[0066] (1) An organic solvent is added to the fumed metal oxide, and the fumed metal oxide is dispersed in the organic solvent to the structural unit of a structure formed by aggregation of primary particles. Dispersion methods include a disperser, homogenizer, planetary mixer, bead mill, planetary mixer, roll, kneader, high-pressure disperser, ultrasonic wave, resolver, and the like. It is not necessary to disperse the fumed metal oxide in the organic solvent to the structural unit as long as the effects of one embodiment of the present invention are obtained. If the fumed metal oxide is dispersed to the structural unit, the fumed metal oxide will not be present in Layer A as agglomerates. In this case, the surface roughness of Layer A is small, which is advantageous for the fine wiring formation aimed at one embodiment of the present invention. It is also possible to disperse and pulverize the fumed metal oxide under conditions that further reduce the structural unit of the fumed metal oxide. The organic solvent may be a solvent used in the polymerization of polyamic acid, and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred, but are not limited thereto.

[0067] (2) The liquid obtained in (1) and a precursor solution of the polyimide resin of Layer A are mixed and stirred at a desired blending ratio to obtain a Layer A dispersion. If the fumed metal oxide is already dispersed in an organic solvent in the step (1), the liquid obtained in (1) and the precursor solution can be mixed and then stirred to obtain a Layer A dispersion. Alternatively, the Layer A dispersion can be obtained by using not only simple stirring but also the various dispersion methods described in (1).

[0068] The concentration of the final Layer A dispersion is not particularly limited, but it is preferable to set the concentration and viscosity to be suitable for the subsequent process. An organic solvent can be used as needed to adjust the concentration and viscosity of the Layer A dispersion. Furthermore, amines for imparting adhesion to Layer B, dehydrating agents for imidizing the polyamic acid, catalysts, etc. may be further added to the Layer A dispersion.

[0069] A filler may also be added to the Layer A dispersion for the purpose of improving various film properties such as tribological properties, thermal conductivity, electrical conductivity, corona resistance, loop stiffness, etc. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc.

[0070] Furthermore, thermosetting resins such as epoxy resins and phenoxy resins, and thermoplastic resins such as polyether ketone and polyether ether ketone may be used as long as they do not impair the overall properties of the resulting resin layer. As a method for adding these resins, if they are soluble in a solvent, they may be added to the polyamic acid. If the polyimide is also soluble, they may be added to a polyimide solution. The Layer A dispersion can be obtained by the above procedure.

[0071] <Layer B> Layer B, which is a heat-resistant resin film according to one embodiment of the present invention, has Layer A formed on one or both sides. From the viewpoint of dimensional stability when the resin film according to one embodiment of the present invention is used for printed wiring board applications, the linear expansion coefficient of Layer B is preferably 20 ppm / °C or less. The resin composition of Layer B is not particularly limited, but is preferably a liquid crystal polymer film, a resin film containing reinforcing fibers, a resin film containing inorganic filler, or polyimide. From the viewpoints of heat resistance, flexibility, heat resistance, etc., Layer B is more preferably a film containing (or consisting of) polyimide, and even more preferably a film containing (or consisting of) a non-thermoplastic polyimide.

[0072] It is known that the linear expansion coefficient of a polyimide resin film can be controlled by the type of monomer used. To reduce the linear expansion coefficient of a polyimide resin film, it is effective to use a monomer with a rigid chemical structure and increase its composition ratio. By using a monomer with a rigid chemical structure and increasing its composition ratio, the polyimide molecular chains are oriented in the plane direction when molded (processed) into a film, and the molecular chains can be accumulated in the thickness direction. Conversely, to increase the linear expansion coefficient of a polyimide resin film, it is effective to use a monomer with a flexible chemical structure and increase its composition ratio. By using a monomer with a flexible chemical structure and increasing its composition ratio, the polyimide molecular chains tend to be oriented not only in the plane direction but also in the thickness direction when molded into a film, i.e., they tend to exhibit random orientation. When a non-thermoplastic polyimide film is used for Layer B, the diamine used in producing the non-thermoplastic polyimide film is not particularly limited, but the linear expansion coefficient of the final polyimide film must be 20 ppm / °C or less. Therefore, in the production of a non-thermoplastic polyimide film, it is preferable to use an appropriate combination of a diamine having a rigid structure and a diamine having a flexible structure in accordance with the structure of the acid dianhydride.

[0073] Examples of diamines having a rigid structure that are suitable for use in producing non-thermoplastic polyimide films include 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-dihydroxybiphenyl, 1,4-diaminobenzene, 1,3-diaminobenzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diaminobenzanilide.

[0074] Examples of diamines having a flexible structure that are suitable for use in producing a non-thermoplastic polyimide film include 4,4'-diaminodiphenyl ether, 2,2-bis{4-(4-aminophenoxy)phenyl}propane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, etc. In producing a non-thermoplastic polyimide film, the diamines listed in the description of the polyimide resin of Layer A can also be used as appropriate.

[0075] When a non-thermoplastic polyimide film is used for Layer B, the acid dianhydride used in producing the non-thermoplastic polyimide film is not particularly limited, but the linear expansion coefficient of the final polyimide must be 20 ppm / °C or less. Therefore, in producing a non-thermoplastic polyimide film, it is preferable to use an appropriate combination of an acid dianhydride with a rigid structure and an acid dianhydride with a flexible structure in accordance with the structure of the diamine. Specific examples of acid dianhydrides with a rigid structure that are suitable for use in producing a non-thermoplastic polyimide film include 3,3',4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride. Examples of acid dianhydrides with a flexible structure that are suitable for use in producing a non-thermoplastic polyimide film include 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-oxydiphthalic dianhydride. In producing a non-thermoplastic polyimide film, the acid dianhydrides listed in the description of the polyimide resin for Layer A can also be used as appropriate.

[0076] Polyamic acid, a precursor of polyimide, can be obtained by mixing the diamine and the acid dianhydride in an organic solvent in substantially equimolar or nearly equimolar amounts and then reacting them. Any organic solvent can be used as long as it can dissolve polyamic acid. Preferred organic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, with at least one of N,N-dimethylformamide and N,N-dimethylacetamide being particularly preferred. The solids concentration of the polyamic acid is not particularly limited; a concentration in the range of 5% to 35% by weight will yield a polyamic acid with sufficient mechanical strength when converted into polyimide.

[0077] The order of addition of the diamine and acid dianhydride raw materials is not particularly limited. The properties of the resulting polyimide can be controlled not only by controlling the chemical structures of the diamine and acid dianhydride raw materials but also by controlling the order of addition of these raw materials.

[0078] A filler can be added to the polyamic acid for the purpose of improving various film properties such as sliding properties, thermal conductivity, electrical conductivity, corona resistance, loop stiffness, etc. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc.

[0079] Additionally, thermosetting resins such as epoxy resins and phenoxy resins, and thermoplastic resins such as polyether ketone and polyether ether ketone may be used as long as they do not impair the overall properties of the resulting resin layer. As a method for adding these resins, if they are soluble in a solvent, they can be added to the polyamic acid. If the polyimide is also soluble, they can be added to a polyimide solution. If the polyimide is insoluble in a solvent, they can be first imidized, and then the polyimide obtained by imidization and a further polyimide insoluble in the solvent can be melt-kneaded to form a composite. However, in one embodiment of the present invention, it is desirable to avoid using meltable polyimides because they may deteriorate the solder heat resistance and / or heat shrinkage rate of the resulting flexible metal-clad laminate. Therefore, it is desirable to use a soluble resin to be mixed with the polyimide.

[0080] A method for obtaining a non-thermoplastic polyimide film preferably used for Layer B in one embodiment of the present invention preferably includes the following steps (i) to (iv).

[0081] (i) a step of reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution; (ii) casting a membrane-forming dope containing the polyamic acid solution onto a support; (iii) heating the film-forming dope on a support, and then peeling off the resulting gel film from the support; (iv) A step of further heating the gel film to imidize the polyamic acid remaining in the gel film and drying it.

[0082] (ii) The methods for the subsequent steps are broadly divided into thermal imidization and chemical imidization. Thermal imidization is a method in which a polyamic acid solution is used as a film-forming dope and cast onto a support, without using a dehydrating ring-closing agent or the like, and imidization is promoted simply by heating. On the other hand, chemical imidization is a method in which a polyamic acid solution to which at least one of a dehydrating ring-closing agent and a catalyst has been added as an imidization accelerator is used as a film-forming dope to accelerate imidization. Either method may be used, but chemical imidization is superior in productivity.

[0083] As the dehydration ring-closing agent, an acid anhydride typified by acetic anhydride can be suitably used. As the catalyst, a tertiary amine such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine can be suitably used.

[0084] Suitable supports for casting the film-forming dope include glass plates, aluminum foils, endless stainless steel belts, stainless steel drums, etc. Heating conditions are set depending on the thickness and / or production rate of the final film to be obtained, and the film-forming dope is either partially imidized or dried, and then the imidized product is peeled off from the support to obtain a polyamic acid film (hereinafter referred to as a gel film).

[0085] The gel film is dried while fixing the edges to prevent shrinkage during curing, and water, residual solvent, and imidization accelerator are removed from the gel film. The remaining amic acid in the gel film is then completely imidized to obtain a polyimide-containing film. Heating conditions can be appropriately set depending on the thickness and / or production speed of the final film.

[0086] In one embodiment of the present invention, an industrially available polyimide film can be preferably used as Layer B. Examples of commercially available polyimide films that can be used as Layer B include "Apical" (manufactured by Kaneka), "Kapton" (manufactured by DuPont and Toray DuPont), and "Upilex" (manufactured by Ube Industries).

[0087] The resin film according to one embodiment of the present invention may have the following aspects: It includes Layer A and Layer B, the layer A includes a polyimide resin and a fumed metal oxide; the layer B includes or is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, The layer A is formed on at least one surface of the layer B, The polyimide resin has a linear expansion coefficient of 30 ppm / °C or more and 100 ppm / °C or less.

[0088] <Method for producing a resin film containing Layer A and Layer B> In one embodiment of the present invention, a method for producing a resin film includes forming a layer A containing a polyimide resin and a fumed metal oxide on at least one surface of a layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, and the layer A containing the polyimide resin and the fumed metal oxide, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, by mixing a polyamic acid solution of the polyimide resin precursor with the fumed metal oxide and imidizing the resulting fumed metal oxide-dispersed polyamic acid solution.

[0089] The method for producing a resin film according to one embodiment of the present invention may be implemented as follows: A method for producing a resin film, comprising: Step 1: Mixing a polyamic acid solution of a polyimide resin precursor with a fumed metal oxide; and step 2 of imidizing the fumed metal oxide-dispersed polyamic acid solution obtained in step 1, The resin film is The layer A and the layer B are included, the layer A includes the polyimide resin and the fumed metal oxide, the layer B includes or is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, The layer A is formed on at least one surface of the layer B, The polyimide resin has a linear expansion coefficient of 30 ppm / °C or more and 100 ppm / °C or less.

[0090] Step 1 and the fumed metal oxide-dispersed polyamic acid solution obtained in Step 1 are the same as those described above in the section <Fummed metal oxide-dispersed polyamic acid solution>, and therefore that description is incorporated herein by reference and will not be repeated here. The preferred embodiments described above in the section <Fumed metal oxide-dispersed polyamic acid solution> are also preferred embodiments for Step 1 and the fumed metal oxide-dispersed polyamic acid solution obtained in Step 1.

[0091] A resin film according to one embodiment of the present invention includes Layer A and Layer B. Furthermore, a resin film according to one embodiment of the present invention is composed of Layer A and Layer B. Layer B according to one embodiment of the present invention is required to be a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less. Examples of Layer B, i.e., the heat-resistant resin film, include liquid crystal polymer films, resin films containing reinforcing fibers, resin films containing inorganic fillers, industrially available polyimide films, and non-thermoplastic polyimide films produced through the steps (i) to (iv) above. The resin film according to one embodiment of the present invention can be preferably obtained by coating (applying) the Layer A dispersion obtained in Step 1 onto the surface of such a heat-resistant resin film (Layer B), drying the Layer A dispersion, and allowing it to imidize.

[0092] Alternatively, in step (ii), a multi-layered resin film according to one embodiment of the present invention may be obtained using a co-extrusion die with multiple flow channels. Alternatively, in step (iii), the layer A dispersion may be applied to the surface of the gel film, and both the gel film and layer A may be simultaneously dried and imidized to obtain a resin film according to one embodiment of the present invention. In either case, the heating conditions may affect various film properties and / or adhesion to the electroless metal plating layer. Therefore, it is preferable to set appropriate heating temperatures and heating times. It is also preferable to set appropriate heating conditions depending on the chemical structure, concentration, solvent type, and / or final thickness of the polyamic acid contained in the layer A dispersion, and it is not possible to generalize optimal heating conditions. For example, assume that the thickness of layer A is 10 microns or less. In this case, it is preferable to imidize the layer A dispersion liquid, etc. by carrying out the following steps (1) to (3) (however, (2) is carried out as necessary): (1) drying the layer A dispersion liquid, etc. at a relatively low heating temperature, i.e., a heating temperature of 100°C to 200°C for 1 minute to 5 minutes; (2) subsequently, if necessary, heating the layer A dispersion liquid, etc. at a temperature of 200°C to 300°C; (3) as a final heating condition, heating the layer A dispersion liquid, etc. at a temperature of 300°C to 500°C for 1 minute to 5 minutes.

[0093] There are two main methods for imidization in Step 2: thermal imidization and chemical imidization. For imidization of the fumed metal oxide-dispersed polyamic acid solution (Layer A dispersion), it is preferable to use the thermal imidization method, which proceeds with imidization only by heating without using a dehydrating ring-closing agent or the like.

[0094] Layer A functions to adhere an electroless metal plating layer. It is assumed that a copper clad laminate is produced by laminating copper foil to Layer A. In this case, it is preferable for the adhesive layer to be thick enough to fit into the surface irregularities of the roughened surface of the copper foil. However, since Layer A of one embodiment of the present invention obtains a metal layer by depositing an electroless metal plating layer on its surface, even if Layer A is relatively thin, it can still exhibit its original function of adhesion to the electroless metal plating layer. From the perspective of industrially stable formation of Layer A, Layer A preferably has a thickness of 0.1 microns to 30 microns, and more preferably a thickness of 1 micron to 10 microns. On the other hand, when the resin film of one embodiment of the present invention is used in a printed wiring board, it is preferable to appropriately design the linear expansion coefficient, which makes it possible to control warpage of the composite with a conductor layer containing an electroless metal plating layer due to changes in the temperature environment. The linear expansion coefficient of the resin film of one embodiment of the present invention can be controlled by considering parameters such as the thickness of Layer A, the linear expansion coefficient of Layer A alone, the thickness of Layer B, and the linear expansion coefficient of Layer B alone. By taking the above parameters into consideration, it is preferably possible to make the linear expansion coefficient of copper, which is the conductor layer, match the linear expansion coefficient of the resin film of one embodiment of the present invention.

[0095] <Electroless metal plating> An electroless metal plating layer can be formed on the surface of Layer A of the resin film of one embodiment of the present invention. By forming an electroless metal plating layer on the surface of Layer A, a metallized resin film can be obtained. A metallized resin film having an electroless metal plating layer formed on the surface of Layer A is also one embodiment of the present invention. The electroless metal plating layer (film) obtained by electroless metal plating can be thinner than general copper foil. The thickness of the electroless metal plating layer is preferably 0.01 microns to 10.00 microns, more preferably 0.10 microns to 2.00 microns, and even more preferably 0.20 microns to 1.00 microns.

[0096] In one embodiment of the present invention, electroless metal plating is preferably a reduction-type electroless plating that utilizes a chemical reaction. Metal species for electroless metal plating include copper, nickel, gold, and silver, and all of these are applicable to one embodiment of the present invention. Of these, electroless copper plating and electroless nickel plating are preferred. Electroless copper plating, in particular, is most preferred because it has been widely used as a process for making the insulating resin surface of the walls of through holes and vias in printed wiring boards conductive. In other words, electroless metal plating in one embodiment of the present invention is preferably electroless copper plating. The electroless copper plating process widely used for printed wiring boards can utilize chemical processes from various plating solution manufacturers. Desmearing is also commonly performed before electroless copper plating. Desmearing is primarily performed to remove smears on the copper surface generated during the through-hole formation process and laser via formation process. Desmearing also chemically alters the surface of the resin film of one embodiment of the present invention, making it suitable for use. The desmearing process and electroless copper plating process each involve sequentially treating the substrate with multiple chemicals. For example, the desmear process is composed of chemicals responsible for swelling, etching, and reduction. The electroless copper plating process is composed of a series of chemicals that perform various functions, such as cleaning and conditioning chemicals, soft etching chemicals, pre-dip chemicals, catalysis chemicals, activation chemicals, and electroless copper plating chemicals. Chemical processes from various plating chemical manufacturers can be used for this series of processes. For example, chemicals manufactured by Atotech, Adcopper IW manufactured by Okuno Chemical Industries, Ltd., ThruCup PEA manufactured by Uemura Industries, Ltd., chemicals manufactured by Rohm and Haas Electronic Materials Co., Ltd., and chemicals manufactured by Meltex Inc. are applicable, and appropriate combinations are also possible. While these electroless copper plating processes may contain trace amounts of nickel, these electroless metal plating processes (electroless copper plating) can be used as long as they do not impair the effects of one embodiment of the present invention.When electroless plating is performed on layer A, electroless plating may be performed directly on layer A, or pretreatment such as alkali treatment or desmear treatment may be performed on layer A, and then electroless plating may be performed on the pretreated layer A. Examples of aqueous alkaline solutions for alkali treatment include aqueous sodium hydroxide solutions and aqueous potassium hydroxide solutions.

[0097] One embodiment of the present invention aims to achieve sufficient adhesion between the resin film and the electroless metal plating in a metallized resin film obtained by only performing a process for forming an electroless metal plating layer on a resin film (electroless metal plating process). Poor adhesion can lead to problems such as circuit peeling from the resin film substrate during the subsequent circuit formation process. To improve the adhesion between the resin film and the electroless metal plating in a metallized resin film, the metallized resin film may be heated, for example, at a temperature of 150°C or higher after the electroless plating process. However, heating the metallized resin film (a) is cumbersome; (b) the surface oxidation of the electroless metal plating layer caused by heating can cause adverse effects and problems in subsequent processes; and (c) heating may not sufficiently improve adhesion. One embodiment of the present invention achieves good adhesion even without high-temperature heating of the metallized resin film, and also provides heat resistance for use as a printed wiring board. In other words, the resin film according to one embodiment of the present invention has excellent adhesion. This means that, at least for a metallized resin film obtained by forming an electroless metal plating layer on the surface of Layer A of a resin film, the electroless metal plating layer of the metallized resin film has excellent peel strength (for example, exhibits a peel strength of 3 N / cm or more) without subjecting the metallized resin film to a heat treatment of 150°C or higher. In this specification, the peel strength of the electroless metal plating layer of a metallized resin film obtained by forming an electroless metal plating layer on the surface of Layer A of a resin film, which has not been subjected to a heat treatment of 150°C or higher, may also be referred to as "initial peel strength." In one embodiment of the present invention, for a metallized resin film obtained by forming an electroless metal plating layer on the surface of Layer A of a resin film, the electroless metal plating layer of the metallized resin film preferably exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without subjecting the metallized resin film to a heat treatment of 150°C or higher.In one embodiment of the present invention, the metallized resin film preferably exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without performing a heat treatment at 150°C or higher after forming the electroless metal plating layer.

[0098] Furthermore, when a substrate (resin film) is made conductive by electroless metal plating, good adhesion strength may be achieved when there is no circuit pattern on the back surface of the substrate (resin film), but sufficient adhesion strength may not be achieved when there is a circuit pattern on the back surface of the substrate (resin film). In a preferred embodiment of the present invention, good adhesion can be achieved even without high-temperature heating of the metallized resin film, regardless of the presence or absence of a circuit pattern on the back surface, and the film also has heat resistance when used as a printed wiring board. In other words, although not essential, the resin film according to one embodiment of the present invention is preferably such that, for a metallized resin film obtained by forming an electroless metal-plated layer on both sides of Layer A of the resin film, the electroless metal-plated layer in the metallized resin film has excellent peel strength (for example, exhibits a peel strength of 3 N / cm or more) without subjecting the metallized resin film to a heat treatment of 150°C or higher. In one embodiment of the present invention, a metallized resin film obtained by forming electroless metal plating layers on both sides of Layer A of a resin film preferably exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without subjecting the metallized resin film to a heat treatment of 150° C. or higher. In one embodiment of the present invention, the metallized resin film preferably exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without subjecting the metallized resin film to a heat treatment of 150° C. or higher after forming the electroless metal plating layers on both sides.

[0099] Furthermore, in one embodiment of the present invention, a metallized resin film obtained by forming an electroless metal plating layer on the surface of Layer A of a resin film can achieve sufficient adhesion even when dried at room temperature without active heating. If the metallized resin film obtained after the electroless metal plating layer formation process is wet with a cleaning solution such as water, problems may occur in subsequent processes, such as the lamination process of a dry film resist. Therefore, a heat drying process for drying the metallized resin film obtained by the electroless metal plating layer formation process is preferably performed. The heating temperature in the heat drying process is preferably 150°C or less, more preferably less than 150°C, and even more preferably 100°C or less. The heating time in the heat drying process is preferably 30 minutes or less, and even more preferably 10 minutes or less. Heat drying the metallized resin film under mild conditions within the above range can suppress oxidation of the electroless metal plating to a practically acceptable level, while also achieving good adhesion. Therefore, a heat drying process for the metallized resin film under mild conditions within the above range is preferably performed.

[0100] To prevent circuit pattern peeling during the circuit formation process in printed wiring board manufacturing, it is preferable that the metallized resin film obtained by only subjecting a resin film to a treatment for forming an electroless metal plating layer (a metallized resin film that has not been subjected to a heat treatment at 150°C or higher) has sufficient adhesion. The peel strength (initial peel strength) of the metallized resin film is preferably 3 N / cm or more, more preferably 5 N / cm or more, even more preferably 6 N / cm or more, and even more preferably 7 N / cm or more.

[0101] <Printed wiring board> A printed wiring board using a resin film according to one embodiment of the present invention or a metallized resin film according to one embodiment of the present invention is also one embodiment of the present invention. A method for producing a printed wiring board using a resin film according to one embodiment of the present invention will be described below. The resin film according to one embodiment of the present invention can be a metallized resin film in which a tightly adhered electroless copper plating film (electroless copper plating layer) is formed on the surface of a low-roughness layer A using electroless metal plating, particularly a general-purpose electroless copper plating solution. By using a resin film or metallized film according to one embodiment of the present invention, narrow-pitch circuits can be formed using either a subtractive or additive method, without the need for complicated processes such as button plating. Furthermore, by using a resin film or metallized film according to one embodiment of the present invention, thin conductor layers and circuits with narrow pitches and good circuit shapes, excellent transmission characteristics, and thin thicknesses can be obtained. That is, by using a resin film or metallized film according to one embodiment of the present invention, highly flexible printed wiring boards can be produced, and flexible printed wiring boards, multilayer flexible printed wiring boards, rigid-flex boards, chip-on-film boards, and the like can be produced.

[0102] It is also possible to combine the process of forming an electroless metal plating layer on at least one surface of a resin film according to one embodiment of the present invention with known subtractive and additive circuit formation processes, multilayering, build-up multilayering, and other technologies. In the case of multilayering, it is possible to combine it with an appropriate adhesive and adhesive sheet. It is also possible to combine it with through-hole and blind via formation. For example, the various printed wiring boards described above can be obtained by subjecting the resin film according to one embodiment of the present invention to the following methods (1) to (3): (1) first forming through-holes and then subjecting them to an electroless metal plating layer formation treatment to simultaneously form an electroless metal plating layer (film) on the through-hole walls and the resin film surface; then (2) forming circuits using a known method; and finally (3) performing a multilayering treatment, a protective film formation treatment, and a surface treatment using known methods. It is preferable that the surface roughness of the resin film according to one embodiment of the present invention be low in order to form narrow-pitch circuits. In one embodiment of the present invention, the surface roughness Ra of the resin film (layer A) exposed by removing the electroless metal plating layer (film) by etching is preferably 200 nanometers or less, more preferably 150 nanometers or less, and even more preferably 100 nanometers or less. The surface roughness can be adjusted by changing the number of parts of fumed metal oxide added to the polyimide precursor, the type of fumed metal oxide (apparent specific gravity, surface treatment, etc.), the chemical structure of the polyimide resin of layer A, the desmear conditions, the conditions for forming the electroless metal plating layer, etc.

[0103] By using the resin film or metallized resin film according to one embodiment of the present invention, a printed wiring board obtained by one embodiment of the present invention can transmit electrical signals in the GHz band. Here, "transmitting electrical signals in the GHz band" means that, when the insertion loss S21 parameter of a microstrip line transmission line having, in order, a 12-micron-thick signal line, a 25-micron-thick resin film according to one embodiment of the present invention, and a 12-micron-thick ground layer processed to have a characteristic impedance of 50 Ω is measured using a network analyzer E5071C (Keysight Technologies) and a GSG250 probe, the transmission loss at 10 GHz is less than 7 dB / 100 mm, the transmission loss at 20 GHz is less than 11 dB / 100 mm, and the transmission loss at 30 GHz is less than 14 dB / 100 mm. Here, the 12-micron-thick signal line refers to wiring consisting of a conductor layer with a total thickness of 12 microns, which is made up of an electroless metal plating layer and an electrolytic copper plating layer. Furthermore, a 12-micron-thick ground layer refers to a ground layer made of a conductor layer consisting of an electroless metal plating layer and an electrolytic copper plating layer with a total thickness of 12 microns. Furthermore, (i) a film (laminate) having, in order, a 12-micron-thick signal line and a 25-micron-thick resin film according to one embodiment of the present invention, and (ii) a film (laminate) having, in order, a 12-micron-thick signal line, a 25-micron-thick resin film according to one embodiment of the present invention, and a 12-micron-thick ground layer can also be considered a metallized resin film according to one embodiment of the present invention.

[0104] [1] Layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of Layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less; A resin film characterized in that the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0105] [2] The resin film according to [1], characterized in that the apparent specific gravity of the fumed metal oxide is 20 g / L or more and 220 g / L or less.

[0106] [3] The resin film according to [1] or [2], characterized in that the blending ratio of the fumed metal oxide to 100 parts by weight of the precursor of the polyimide resin is 10 to 130 parts by weight.

[0107] [4] The resin film according to any one of [1] to [3], wherein the fumed metal oxide is fumed silica.

[0108] [5] The resin film according to any one of [1] to [4], wherein Layer A containing the polyimide resin and the fumed metal oxide is an imidized product of a mixture of a precursor of the polyimide resin and the fumed metal oxide.

[0109] [6] The storage modulus of the polyimide resin at 300 ° C. is 1 × 10 8 The resin film according to any one of [1] to [5], characterized in that the elastic modulus is 100 Pa or more.

[0110] [7] The resin film according to any one of [1] to [6], wherein the polyimide resin is a non-soluble polyimide resin.

[0111] [8] The resin film according to any one of [1] to [7], wherein Layer B contains a polyimide resin.

[0112] [9] A metallized resin film in which an electroless metal plating layer is formed on the surface of the layer A of the resin film according to any one of [1] to [8].

[0113]

[10] The metallized resin film according to [9], wherein the electroless metal plating is electroless copper plating.

[0114]

[11] The metallized resin film according to [9] or

[10] , characterized in that the electroless metal plating layer of the metallized resin film is removed by etching, and the surface roughness Ra of the exposed resin film is 200 nanometers or less.

[0115]

[12] The metallized resin film according to any one of [9] to

[11] , characterized in that the metallized resin film exhibits a peel strength of 5 N / cm or more without performing a heat treatment at 150°C or higher after forming the electroless metal plating layer.

[0116]

[13] A printed wiring board using the resin film according to any one of [1] to [8] or the metallized resin film according to any one of [9] to

[12] .

[0117]

[14] The printed wiring board according to

[13] , which is capable of transmitting electrical signals in the GHz band.

[0118]

[15] A method for producing a resin film, wherein Layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of Layer B, which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, and Layer A containing the polyimide resin and the fumed metal oxide is obtained by mixing a polyamic acid solution of a precursor of the polyimide resin with the fumed metal oxide and imidizing the obtained fumed metal oxide-dispersed polyamic acid solution.

[0119]

[16] A method for producing a resin film according to

[15] , characterized in that the fumed metal oxide-dispersed polyamic acid solution is applied to the layer B consisting of the heat-resistant resin film, and the fumed metal oxide-dispersed polyamic acid solution is dried and imidized.

[0120]

[17] A method for producing a resin film according to

[15] , characterized in that the fumed metal oxide-dispersed polyamic acid solution is co-extruded with a precursor solution of Layer B consisting of the heat-resistant resin film, and the fumed metal oxide-dispersed polyamic acid solution and the precursor solution are dried and imidized. [Example]

[0121] Hereinafter, one embodiment of the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to the following examples.

[0122] <Preparation of Layer A Polyimide Resin Single-Layer Film> The polyamic acid solution obtained in Synthesis Example was coated on aluminum foil, and the polyamic acid solution was sequentially heated at 120°C for 360 seconds, 200°C for 60 seconds, 350°C for 200 seconds, and 450°C for 30 seconds to perform imidization. The aluminum foil was then dissolved and removed using an etching solution to obtain a monolayer film of polyimide resin for Layer A. The monolayer film was used to evaluate the linear expansion coefficient, storage modulus, glass transition temperature, and solubility.

[0123] <Measurement of linear expansion coefficient> The linear expansion coefficient was measured using a TMA120C manufactured by Seiko Electronics Co., Ltd. The sample size was 3 mm in width and 10 mm in length. The sample was first heated from 10°C to 400°C at a rate of 10°C / min under a load of 3 g, then cooled to 10°C and further heated at a rate of 10°C / min. The average value of the thermal expansion coefficient during the second heating cycle from 100°C to 200°C was calculated.

[0124] <Measurement of storage modulus and glass transition temperature of Layer A> The monolayer film obtained in the above section <Preparation of a monolayer film of polyimide resin for Layer A> was used as a sample to measure the storage modulus and glass transition temperature using a DMS6100 manufactured by Seiko Electronics Co., Ltd. The sample size was 9 mm wide and 50 mm long. Measurements were performed at frequencies of 1, 5, and 10 Hz, with a heating rate of 3°C / min, over a temperature range from 20°C to 400°C, and the storage modulus value at 300°C was read. The glass transition temperature (hereinafter referred to as "Tg") was determined from the inflection point of the storage modulus.

[0125] <Solubility> The monolayer film obtained in the above section <Preparation of a monolayer film of polyimide resin of Layer A> was evaluated for solubility in the following organic solvents. If any of the organic solvents was soluble at a concentration of 10% by weight or more, the film was rated as soluble (×) (bad), and if the film was not soluble in 10% by weight or more, the film was rated as insoluble (◯) (good). The temperature of the organic solvent was 25°C. Organic solvents: methanol, methyl ethyl ketone, toluene, tetrahydrofuran, N,N-dimethylformamide <Preparation of double-sided copper-clad laminate for evaluation> The resin films obtained in the examples and comparative examples were subjected to a desmear treatment, electroless copper plating, and electrolytic copper plating in that order under the conditions (Atotech) in Tables 1 to 3 to obtain double-sided laminates for evaluation. The thickness of the electrolytic copper plating was 12 microns. [Table 1] [Table 2]

[0126] [Table 3] <Peel strength> In one embodiment of the present invention, the adhesion between a resin film and an electroless metal plating layer in a metallized resin film is as follows: (a) A metallized resin film obtained by only performing a treatment to form an electroless metal plating layer exhibits sufficient adhesion; (b) Good adhesion is achieved without heat treatment of the metallized resin film at high temperatures; (c) to obtain good adhesion regardless of the presence or absence of a circuit pattern on the backside of the metallized resin film; and (d) The metallized resin film has heat resistance as a printed wiring board, in other words, has good adhesion even after being left at high temperatures. This makes it possible to avoid problems such as a decrease in reliability of the printed wiring board due to the circuit peeling off from the resin film substrate during the circuit formation process. In light of the above, peel strength was measured in the following manner to evaluate adhesion.

[0127] (Preparing a sample for measuring peel strength) From the metallized resin films (double-sided copper-clad laminates) prepared from the resin films obtained in the Examples and Comparative Examples, peel strength measurement samples were prepared, one with no copper on the backside and one with copper on the backside. The initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured for each peel strength measurement sample.

[0128] (Type 1 - No copper on the back side) The copper layer on one side of the double-sided copper-clad laminate was completely removed by etching, and a 5 mm wide copper pattern was created on the remaining copper layer by etching using masking tape. The initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured using the following procedures.

[0129] "Initial peel strength - no copper on the back side": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the peel strength was immediately measured. The adhesion of the double-sided copper-clad laminate was evaluated immediately after the formation of the electroless plating layer without drying or heating.

[0130] "Peel strength after high-temperature heat treatment - no copper on the back side": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the laminate was dried at 50°C for 10 minutes. The double-sided copper-clad laminate was then placed in a heat resistance test environment at 180°C for 15 minutes, after which the peel strength was measured. This was done to confirm the effect of high-temperature treatment on adhesion.

[0131] "Heat resistance peel strength - no copper on the back side": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the laminate was dried at 50°C for 10 minutes. The double-sided copper-clad laminate was then placed in a heat resistance test environment at 150°C for 168 hours, after which the peel strength was measured. This test was carried out to evaluate heat resistance.

[0132] (Type 2 - with copper backing) A 5 mm wide copper pattern was created on the copper layer on one side of the double-sided copper-clad laminate by etching with masking tape, and an evaluation pattern with a copper layer covering the entire back side was created. The initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured using the following procedures.

[0133] "Initial peel strength - with copper on the back": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the peel strength was immediately measured. This was done to evaluate the adhesion of the double-sided copper-clad laminate immediately after the formation of the electroless plating layer, without drying or heating to a high temperature.

[0134] "Peel strength after high-temperature heat treatment - with copper on the back": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the laminate was dried at 50°C for 10 minutes. The double-sided copper-clad laminate was then placed in a heat resistance test environment at 180°C for 15 minutes, after which the peel strength was measured. This test was conducted to confirm the effect of high-temperature treatment on adhesion.

[0135] "Heat resistance peel strength - with copper on the back": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the laminate was dried at 50°C for 10 minutes. The double-sided copper-clad laminate was then placed in a heat resistance test environment at 150°C for 168 hours, after which the peel strength was measured. This test was carried out to evaluate heat resistance.

[0136] (peel strength measurement) The six types of peel strength measurements were carried out on one double-sided copper-clad laminate. Peel strength was measured by peeling at a crosshead speed of 50 mm / min and a peel angle of 180°, and the resulting load was measured.

[0137] <Moisture absorption and solder heat resistance> The double-sided copper-clad laminates for evaluation obtained in the Examples and Comparative Examples were cut into 3.5 cm squares. Next, 15 samples were prepared by etching the 3.5 cm square double-sided copper-clad laminates for evaluation so that a 2.5 cm square copper foil layer remained in the center of one side (conveniently referred to as Side A) and the copper foil layer remained on the entire surface of the other side (conveniently referred to as Side B). The obtained samples were left under humid conditions of 40°C and 90% RH for 96 hours to undergo moisture absorption treatment. After the moisture absorption treatment, five samples each were immersed in a solder bath at 260°C, 280°C, or 300°C for 10 seconds. In other words, five samples were used per temperature condition. After solder immersion, the copper foil layer on Side B of the samples was completely removed by etching, and the appearance of the area where the copper foil had overlapped was observed. If any of whitening, blistering, or peeling of the copper foil layer was observed, it was determined that there was a change in appearance. If there was no change in appearance for all five samples at 300°C, the sample was rated as ○ (good); if there was a change in appearance for one or more of the five samples at 300°C but no change in appearance at 260°C, the sample was rated as △ (pass); and if there was a change in appearance for one or more of the five samples at 260°C, the sample was rated × (poor).

[0138] <Surface roughness Ra> The copper layer of each of the double-sided copper-clad laminates for evaluation obtained in the Examples and Comparative Examples was dissolved and removed by etching. The surface roughness (Ra) of the exposed resin film was measured using a scanning probe microscope (SPM, Dimension Icon, manufactured by Bruker AXS) in accordance with JIS C 0601-2001.

[0139] (Synthesis Example 1: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 322.3 g of N,N-dimethylformamide (DMF) and 33.9 g of 1,3-bis(4-aminophenoxy)benzene (TPE-R). Next, while stirring the solution in the flask under a nitrogen atmosphere, 33.6 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added and the solution was stirred at 25°C for 1 hour. A solution (BPDA solution (1)) was prepared by dissolving 0.51 g of BPDA in 9.7 g of DMF. BPDA solution (1) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (1) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0140] (Synthesis Example 2: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.4 g of N,N-dimethylformamide (DMF), 12.5 g of 4,4'-oxydianiline (ODA), and 18.3 g of TPE-R. Next, 36.4 g of BPDA was added to the flask while stirring the solution in the flask under a nitrogen atmosphere, and the solution in the flask was stirred at 25°C for 1 hour. A separate solution was prepared by dissolving 0.55 g of BPDA in 10.5 g of DMF (hereinafter referred to as BPDA solution (2)). BPDA solution (2) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (2) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0141] (Synthesis Example 3: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.8 g of N,N-dimethylformamide (DMF), 24.7 g of TPE-R, and 7.6 g of 2,2'-dimethylbenzidine (m-TB). Next, 35.0 g of BPDA was added to the flask while stirring the solution in the flask under a nitrogen atmosphere, and the solution in the flask was stirred at 25°C for 1 hour. A separate solution was prepared by dissolving 0.53 g of BPDA in 10.1 g of DMF (hereinafter referred to as BPDA solution (3)). BPDA solution (3) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (3) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0142] (Synthesis Example 4: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.9 g of N,N-dimethylformamide (DMF) and 35.0 g of TPE-R. Next, while stirring the solution in the flask under a nitrogen atmosphere, 6.5 g of pyromellitic dianhydride (PMDA) and 25.9 g of BPDA were added to the flask, and the solution was stirred at 25°C for 1 hour. A solution was prepared by dissolving 0.52 g of BPDA in 10.0 g of DMF (hereinafter referred to as BPDA solution (4)). BPDA solution (4) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (4) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0143] (Synthesis Example 5: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.6 g of N,N-dimethylformamide (DMF) and 36.2 g of TPE-R. Next, while stirring the solution in the flask under a nitrogen atmosphere, 13.5 g of PMDA and 17.6 g of BPDA were added to the flask, and the solution was stirred at 25°C for 1 hour. A solution was prepared by dissolving 0.54 g of BPDA in 10.3 g of DMF (hereinafter referred to as BPDA solution (5)). The BPDA solution (5) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of the BPDA solution (5) and the stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0144] (Synthesis Example 6: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 320.4 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 27.5 g of ODA. Next, while stirring the solution in the flask under a nitrogen atmosphere, 39.8 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.60 g of BPDA in 11.5 g of DMF (hereinafter also referred to as BPDA solution (6)). BPDA solution (6) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (6) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0145] (Synthesis Example 7: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.6 g of N,N-dimethylformamide (DMF), 25.2 g of 2,2'-bis{4-(4-aminophenoxy)phenyl}propane (BAPP), and 6.6 g of 1,4-diaminobenzene (p-PDA). Next, 35.6 g of BPDA was added to the flask while stirring under a nitrogen atmosphere, and the solution was stirred at 25°C for 1 hour. A solution was prepared by dissolving 0.54 g of BPDA in 10.3 g of DMF (hereinafter referred to as BPDA solution (7)). BPDA solution (7) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (7) and stirring of the reaction solution were stopped. By this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0146] (Synthesis Example 8: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 319.0 g of N,N-dimethylformamide (DMF), 14.6 g of ODA, and 7.9 g of p-PDA. Next, while stirring the solution in the flask under a nitrogen atmosphere, 44.7 g of 4,4'-oxydiphthalic dianhydride (ODPA) was added to the flask, and the solution was stirred at 25°C for 1 hour. A separate solution was prepared by dissolving 0.68 g of ODPA in 12.9 g of DMF (hereinafter referred to as ODPA solution (1)). ODPA solution (1) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (1) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0147] (Synthesis Example 9: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.1 g of N,N-dimethylformamide (DMF) and 35.7 g of TPE-R. Next, while stirring the solution in the flask under a nitrogen atmosphere, 13.3 g of PMDA and 18.3 g of ODPA were added to the flask, and the solution was stirred at 25°C for 1 hour. A solution was prepared by dissolving 0.56 g of ODPA in 10.8 g of DMF (hereinafter referred to as ODPA solution (2)). ODPA solution (2) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (2) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0148] Synthesis Example 10: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 321.7 g of N,N-dimethylformamide (DMF), 12.2 g of ODA, and 22.5 g of 4,4'-bis(4-aminophenoxy)biphenyl (4-APBP). Next, 8.0 g of PMDA and 24.6 g of BPDA were added to the flask while stirring under a nitrogen atmosphere, and the solution was stirred at 25°C for 1 hour. A separate solution was prepared by dissolving 0.54 g of BPDA in 10.2 g of DMF (hereinafter referred to as BPDA solution (8)). The BPDA solution (8) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (8) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0149] Synthesis Example 11: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 323.9 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 39.6 g of BAPP. Next, while stirring the solution in the flask under a nitrogen atmosphere, 39.6 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.42 g of BPDA in 8.0 g of DMF (hereinafter also referred to as BPDA solution (9)). BPDA solution (9) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (9) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0150] Synthesis Example 12: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 320.0 g of N,N-dimethylformamide (DMF) and 26.0 g of ODA. Next, while stirring the solution in the flask under a nitrogen atmosphere, 41.3 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) was added to the flask, and the solution was stirred at 25°C for 1 hour. A separate solution was prepared by dissolving 0.62 g of BTDA in 11.9 g of DMF (BTDA solution (1)). BTDA solution (1) was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BTDA solution (1) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0151] Synthesis Example 13: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 318.8 g of N,N-dimethylformamide (DMF), 14.2 g of ODA, and 7.7 g of p-PDA. Next, while stirring the solution in the flask under a nitrogen atmosphere, 45.3 g of BTDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.68 g of BTDA in 13.1 g of DMF (hereinafter referred to as BTDA solution (2)). BTDA solution (2) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BTDA solution (2) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0152] Synthesis Example 14: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 11.7 g of N,N-dimethylformamide (hereinafter referred to as DMF) and 26.6 g of ODA. Next, while stirring the solution in the flask under a nitrogen atmosphere, 40.7 g of ODPA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.61 g of ODPA in 11.7 g of DMF (hereinafter referred to as ODPA solution (3)). ODPA solution (3) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (3) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0153] Synthesis Example 15: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 322.0 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 32.9 g of TPE-R. Next, while stirring the solution in the flask under a nitrogen atmosphere, 34.4 g of ODPA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.52 g of ODPA in 9.9 g of DMF (hereinafter also referred to as ODPA solution (4)). ODPA solution (4) was gradually added to the reaction solution while paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (4) and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0154] (Synthesis Example 16: Synthesis of polyimide precursor for layer A) A 2000 ml glass flask was charged with 321.3 g of N,N-dimethylformamide (DMF), 25.8 g of ODA, and 4.6 g of p-PDA. Next, 36.9 g of PMDA was added to the flask while stirring the solution in the flask under a nitrogen atmosphere, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.56 g of PMDA in 10.6 g of DMF (hereinafter referred to as the PMDA solution). The PMDA solution was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of the PMDA solution and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor.

[0155] Synthesis Example 17: Synthesis of polyimide precursor for layer A A 2000 ml glass flask was charged with 320.9 g of N,N-dimethylformamide (DMF), 10.4 g of ODA, and 18.7 g of Shin-Etsu Chemical Co., Ltd.'s KF-8010. Next, while stirring the solution in the flask under a nitrogen atmosphere, 38.1 g of 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) was added to the flask, and the solution was stirred at 25°C for 1 hour. A separate solution (BPADA solution) was prepared by dissolving 0.58 g of BPADA in 11.0 g of DMF. The BPADA solution was gradually added to the reaction solution while carefully monitoring the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of the BPADA solution and stirring of the reaction solution were stopped. This procedure yielded a polyamic acid solution, a polyimide precursor. The chemical structure of KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd. is shown in general formula (1).

[0156] [ka] Formulation Example 1: Fumed Metal Oxide Dispersion for Layer A 20 g of Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. was mixed with 80 g of DMF. The resulting mixture was stirred for 5 minutes at 10,000 rpm using a rotary blade homogenizer (rotary blade diameter: 20 mm) to obtain a dispersion of fumed metal oxide.

[0157] Formulation Example 2: Fumed Metal Oxide Dispersion for Layer A A dispersion of fumed metal oxide was obtained by the same procedure as in Formulation Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. in Formulation Example 1 was replaced with Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.

[0158] Formulation Example 3: Fumed Metal Oxide Dispersion for Layer A A dispersion of fumed metal oxide was obtained by the same procedure as in Formulation Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. in Formulation Example 1 was replaced with Aerosil NX130 manufactured by Nippon Aerosil Co., Ltd.

[0159] Formulation Example 4: Fumed Metal Oxide Dispersion for Layer A A dispersion of fumed metal oxide was obtained by the same procedure as in Formulation Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. in Formulation Example 1 was replaced with Aerosil VP RS920 manufactured by Nippon Aerosil Co., Ltd.

[0160] The fumed metal oxide concentration in the fumed metal oxide dispersions obtained in Formulation Examples 1 to 4 was 20 wt / wt %.

[0161] Formulation Example 5: Fumed Metal Oxide Dispersion for Layer A A dispersion was obtained by mixing 60 g of a dispersion liquid (solvent: DMF, concentration: 30 wt / wt %) of Admanano particles having a particle diameter of 10 nm manufactured by Admatechs Co., Ltd. with 30 g of DMF.

[0162] Formulation Example 6: Fumed Metal Oxide Dispersion for Layer A A dispersion of Admanano particles with a particle diameter of 50 nm (solvent: DMF, concentration: 20 wt / wt %) manufactured by Admatechs Co., Ltd. was used as the dispersion liquid as it was.

[0163] Example 1 40 g of the polyamic acid solution obtained in Synthesis Example 1 was mixed with 17 g of the dispersion obtained in Formulation Example 1. 40 g of DMF and 2 g of lutidine were then added to the resulting mixture to obtain a Layer A dispersion. The Layer A dispersion was applied to one side of a non-thermoplastic polyimide film (Apical FP, 17 microns thick, manufactured by Kaneka Corporation) so that the final thickness of Layer A on that side was 4 microns. The Layer A dispersion was then dried at 120°C for 2 minutes. The remaining side was then coated with the Layer A dispersion and dried in the same manner. The non-thermoplastic polyimide film coated with the Layer A dispersion was then heated at 450°C for 12 seconds to imidize the polyamic acid in Layer A, resulting in a resin film having a configuration in which Layer A (containing a polyimide resin and a fumed metal oxide) / non-thermoplastic polyimide film / Layer A were laminated in this order. The non-thermoplastic polyimide film (Apical FP) corresponds to Layer B. That is, in Example 1, Layer B is made of a polyimide resin, specifically, made of only a non-thermoplastic polyimide film. The linear expansion coefficient of the Apical FP was 12 ppm / °C.

[0164] The resin film was subjected to desmear treatment, electroless copper plating, and electrolytic copper plating under the conditions shown in Table 1 to obtain a double-sided copper-clad laminate, which was then evaluated for peel strength, moisture absorption solder heat resistance, and surface roughness Ra. The compositions and results are shown in Tables 4 to 7.

[0165] Example 2 The same operations as in Example 1 were carried out except that the dispersion liquid of Preparation Example 1 used in Example 1 was changed to the dispersion liquid of Preparation Example 2, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0166] Example 3 The same operations as in Example 1 were carried out, except that the dispersion liquid of Preparation Example 1 used in Example 1 was changed to the dispersion liquid of Preparation Example 3, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0167] Example 4 The same operations as in Example 1 were carried out except that the dispersion liquid of Preparation Example 1 used in Example 1 was changed to the dispersion liquid of Preparation Example 4, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0168] (Comparative Example 1) 40 g of the polyamic acid solution obtained in Synthesis Example 1 was mixed with 40 g of DMF and 2 g of lutidine to obtain a mixed solution. The same procedures as in Example 1 were carried out, except that the Layer A dispersion used in Example 1 was replaced with the mixed solution. A resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The initial peel strength did not show sufficient values ​​both in the case without a copper backing and in the case with a copper backing. Furthermore, the peel strength after high-temperature heat treatment showed good adhesion without a copper backing but not in the case with a copper backing, indicating that the adhesion results differed depending on whether or not there was a copper backing. The compositions and results are shown in Tables 4 to 7.

[0169] Example 5 The same procedures as in Example 2 were carried out except that the amount of the dispersion liquid of Preparation Example 2 used in Example 2 was changed to 3.4 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0170] Example 6 The same procedures as in Example 2 were carried out except that the amount of the dispersion liquid of Preparation Example 2 used in Example 2 was changed to 6.8 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0171] Example 7 A resin film and a double-sided copper-clad laminate were obtained in the same manner as in Example 2, except that the amount of the dispersion liquid of Formulation Example 2 used in Example 2 was changed to 10.2 g, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0172] Example 8 The same procedures as in Example 2 were carried out except that the amount of the dispersion liquid of Formulation Example 2 used in Example 2 was changed to 34 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0173] Example 9 The same procedures as in Example 3 were carried out except that the amount of the dispersion liquid of Preparation Example 3 used in Example 3 was changed to 3.4 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0174] Example 10 A resin film and a double-sided copper-clad laminate were obtained in the same manner as in Example 3, except that the amount of the dispersion liquid of Formulation Example 3 used in Example 3 was changed to 6.8 g, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0175] Example 11 A resin film and a double-sided copper-clad laminate were obtained in the same manner as in Example 3, except that the amount of the dispersion liquid of Formulation Example 3 used in Example 3 was changed to 10.2 g, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0176] Example 12 The same procedures as in Example 3 were carried out except that the amount of the dispersion liquid of Formulation Example 3 used in Example 3 was changed to 34 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0177] Example 13 A resin film and a double-sided copper-clad laminate were obtained in the same manner as in Example 1, except that the amount of the dispersion liquid of Preparation Example 1 used in Example 1 was changed to 6.8 g, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0178] Example 14 The same procedures as in Example 1 were carried out except that the amount of the dispersion liquid of Preparation Example 1 used in Example 1 was changed to 10.2 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0179] Example 15 The same procedures as in Example 1 were carried out except that the amount of the dispersion liquid of Formulation Example 1 used in Example 1 was changed to 34 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0180] Example 16 The same procedures as in Example 1 were carried out except that the amount of the dispersion liquid of Preparation Example 1 used in Example 1 was changed to 51 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0181] Example 17 The same procedures as in Example 4 were carried out except that the amount of the dispersion liquid of Formulation Example 4 used in Example 4 was changed to 6.8 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0182] Example 18 The same procedures as in Example 4 were carried out except that the amount of the dispersion liquid of Formulation Example 4 used in Example 4 was changed to 10.2 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0183] Example 19 The same procedures as in Example 4 were carried out except that the amount of the dispersion liquid of Formulation Example 4 used in Example 4 was changed to 34 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0184] Example 20 The same procedures as in Example 4 were carried out except that the amount of the dispersion liquid of Formulation Example 4 used in Example 4 was changed to 51 g, and a resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0185] Example 21 The double-sided copper-clad laminate of Example 1 was produced using the same procedures as in Example 1, except that, among the processing conditions listed in Table 1, the conditions for the drying step after electroless copper plating were changed to only wiping off water droplets, and the drying step after copper sulfate plating was changed to only wiping off water droplets. The compositions and results are shown in Tables 4 to 7. The metallized resin film (double-sided copper-clad laminate) of Example 21 exhibited good peel strength values ​​for the six types of samples, similar to those of Example 1. That is, the metal plating layer adhered well to the resin film without heating after the electroless metal plating layer formation process.

[0186] Example 22 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 2, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0187] Example 23 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 3, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0188] Example 24 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 4, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0189] Example 25 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 5, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0190] Example 26 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 6, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0191] Example 27 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 7, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0192] Example 28 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 8, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0193] Example 29 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 9, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0194] Example 30 The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 10, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluations were carried out. The compositions and results are shown in Tables 4 to 7.

[0195] Example 31 The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 11, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The moisture absorption solder heat resistance was evaluated as Fair. The composition and results are shown in Tables 4 to 7.

[0196] Example 32 The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 12, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The moisture absorption solder heat resistance was evaluated as Fair. The composition and results are shown in Tables 4 to 7.

[0197] (Comparative Example 2) The same operations as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 13, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The moisture absorption solder heat resistance evaluation was x. The composition and results are shown in Tables 4 to 7.

[0198] Example 33 The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 14, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The moisture absorption solder heat resistance was evaluated as Fair. The composition and results are shown in Tables 4 to 7.

[0199] Example 34 The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 15, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The moisture absorption solder heat resistance was evaluated as Fair. The composition and results are shown in Tables 4 to 7.

[0200] (Comparative Example 3) The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was changed to the polyamic acid solution of Synthesis Example 16, to obtain a resin film and a double-sided copper-clad laminate, which were then evaluated in the same manner. The evaluation of moisture absorption solder heat resistance was also poor. The compositions and results are shown in Tables 4 to 7.

[0201] Comparative Example 4 The same procedures as in Example 1 were carried out, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution of Synthesis Example 17. A resin film and a double-sided copper-clad laminate were obtained and evaluated in the same manner. The polyimide resin of Layer A contains a silicone skeleton, and there is a risk of contact failure in electronic devices and process contamination due to volatilization of siloxane components from the main chain skeleton. Layer A also has a large linear expansion coefficient, and its moisture absorption solder heat resistance was evaluated as ×. It has poor dimensional stability, is soluble in organic solvents, and also has poor resistance to organic solvents used in the printed wiring board manufacturing process. The composition and results are shown in Tables 4 to 7.

[0202] (Comparative Example 5) The polyamic acid solution of Synthesis Example 17 was placed in a tray coated with a fluorine-based resin and heated in a vacuum oven at 200°C for 120 minutes under reduced pressure of 665 Pa to obtain a polyimide resin. The obtained polyimide resin was dissolved in a mixed solvent of dioxolane and toluene (mixing ratio = 50 wt% / 50 wt%) to obtain a 17 wt% polyimide solution. Separately, 20 g of Aerosil R9200 (manufactured by Nippon Aerosil Co., Ltd.) was mixed with 80 g of the mixed solvent, and the resulting mixture was stirred at 10,000 rpm for 5 minutes using a rotary blade homogenizer (rotary blade diameter: 20 mm) to obtain a fumed metal oxide dispersion. 40 g of the polyimide solution was mixed with 17 g of the fumed metal oxide dispersion to obtain a fumed metal oxide-dispersed polyimide solution (hereinafter also referred to as Layer A solution). The Layer A solution was applied to one side of a non-thermoplastic polyimide film (Apical FP, 17 microns thick, manufactured by Kaneka Corporation) so that the final thickness of Layer A on one side was 4 microns. The Layer A solution was dried at 60°C for 5 minutes and then at 150°C for 5 minutes. The remaining side was then coated and dried in the same manner. This procedure yielded a resin film with a configuration of Layer A / non-thermoplastic polyimide film / Layer A. The same procedures as in Example 1 were then performed to obtain a double-sided copper-clad laminate, which was then evaluated in the same manner. The polyimide resin of Layer A contains a silicone skeleton, which may lead to contact failure and process contamination in electronic devices due to volatilization of siloxane components from the main chain skeleton. Furthermore, the moisture absorption solder heat resistance evaluation was evaluated as ×. Layer A also has a high linear expansion coefficient, poor dimensional stability, and is soluble in organic solvents, resulting in poor resistance to organic solvents used in the printed wiring board manufacturing process. The composition and results are shown in Tables 4 to 7. [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] Table 9 Table 10 Table 11

Claims

1. a layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of a layer B which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less; A resin film characterized in that the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

2. 2. The resin film according to claim 1, wherein the apparent specific gravity of the fumed metal oxide is 20 g / liter or more and 220 g / liter or less.

3. 2. The resin film according to claim 1, wherein the fumed metal oxide is blended in an amount of 10 to 130 parts by weight per 100 parts by weight of the polyimide resin precursor.

4. 2. The resin film according to claim 1, wherein the fumed metal oxide is fumed silica.

5. 2. The resin film according to claim 1, wherein the layer A containing the polyimide resin and the fumed metal oxide is an imidized product of a mixture of a precursor of the polyimide resin and the fumed metal oxide.

6. The storage modulus of the polyimide resin at 300°C is 1 × 10 ８ 2. The resin film according to claim 1, wherein the modulus is 100 Pa or more.

7. 2. The resin film according to claim 1, wherein the polyimide resin is a non-soluble polyimide resin.

8. 2. The resin film according to claim 1, wherein the layer B contains a polyimide resin.

9. 2. A metallized resin film according to claim 1, wherein an electroless metal plating layer is formed on the surface of said layer A.

10. 10. The metallized resin film according to claim 9, wherein the electroless metal plating is electroless copper plating.

11. 10. The metallized resin film according to claim 9, wherein the electroless metal plating layer of the metallized resin film is removed by etching, and the exposed resin film has a surface roughness Ra of 200 nanometers or less.

12. 10. The metallized resin film according to claim 9, wherein the metallized resin film exhibits a peel strength of 5 N / cm or more without being subjected to a heat treatment of 150°C or more after the electroless metal plating layer is formed.

13. A printed wiring board using the resin film according to any one of claims 1 to 8 or the metallized resin film according to any one of claims 9 to 12.

14. 14. The printed wiring board according to claim 13, capable of transmitting electrical signals in the GHz band.

15. a layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of a layer B which is a heat-resistant resin film having a linear expansion coefficient of 20 ppm / °C or less; the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less; A method for producing a resin film, wherein the layer A containing the polyimide resin and the fumed metal oxide is obtained by mixing a polyamic acid solution of a precursor of the polyimide resin with the fumed metal oxide, and imidizing the resulting fumed metal oxide-dispersed polyamic acid solution.

16. 16. The method for producing a resin film according to claim 15, wherein the fumed metal oxide-dispersed polyamic acid solution is applied to the layer B consisting of the heat-resistant resin film, and the fumed metal oxide-dispersed polyamic acid solution is dried and imidized.

17. 16. The method for producing a resin film according to claim 15, wherein the fumed metal oxide-dispersed polyamic acid solution is co-extruded with a precursor solution of the Layer B consisting of the heat-resistant resin film, and the fumed metal oxide-dispersed polyamic acid solution and the precursor solution are dried and imidized.

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