Resin film, metal-clad laminate, circuit board, electronic device and electronic equipment

Abstract

To provide a resin film comprising a single-layer polyimide layer excellent in transparency, heat resistance and dimension stability, and to provide a metal-clad laminate capable of being used for an insulation resin layer directly laminated on a metal layer even as a single layer, and excellent in adhesiveness between the insulation resin layer and the metal layer.SOLUTION: A single-layer polyimide resin film satisfies the following conditions a-c: a) a thickness is 5 μm or more and 100 μm or less; b) a total light transmittance is 80% or more; and c) a yellowness YI with a thickness of 25 μm is 30 or less. The single-layer polyimide resin film is such that: polyimide constituting a polyimide layer contains an aromatic tetracarboxylic dianhydride residue, and a diamine residue, and contains based on the total diamine residue, 60 mol% or more and 99 mol% or less of a residue comprising a first aromatic diamine represented by the following formula (1), and 1 mol% or more and 40 mol% or less of a diamine residue comprising a second aromatic diamine such as 1,3-bis(3-aminophenoxy) benzene.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin film (insulating resin layer) that is excellent in heat resistance, adhesiveness, flexibility, and transparency, a metal-clad laminate obtained by laminating the same, and a circuit board, an electronic device, and an electronic appliance that utilize them. [Background technology]

[0002] Polyimide is a heat-resistant resin obtained by ring-closing polyamic acid, which is synthesized by the condensation reaction of tetracarboxylic anhydride and diamine as raw materials. It has excellent resistance to thermal decomposition due to its rigid molecular chain, resonance stabilization, and strong chemical bonds. It has high durability against chemical changes such as oxidation and hydrolysis, and has excellent flexibility, mechanical properties, and electrical properties. Polyimide is widely used in the insulating resin layer of flexible printed circuit boards (FPCs), which are commonly used in electronic devices.

[0003] Generally, the polyimide insulating resin layer in commercially available copper clad laminates (CCL) used in FPCs is yellowish-brown, making it difficult to apply to FPCs that require transparency. The excellent transparency of CCL allows for excellent visibility from the insulating resin layer side when mounting semiconductor elements on a wiring board. Therefore, when bonding semiconductor elements to FPCs via photocurable resins, CCL is advantageous for light irradiation from the insulating resin layer side, making it promising for use in transparent FPCs.

[0004] Therefore, in order to make polyimides colorless and transparent, studies have been conducted to suppress the formation of intramolecular and intermolecular charge-transfer complexes by using alicyclic diamines or alicyclic acid anhydrides as diamine components. For example, Patent Document 1 proposes a colorless and transparent semi-alicyclic polyimide formed from an alicyclic diamine and an aromatic acid dianhydride, and Patent Document 2 proposes a colorless and transparent fully alicyclic polyimide formed from an alicyclic diamine and an alicyclic acid anhydride. However, the glass transition temperatures of the resulting polyimides are all approximately 280°C or lower, and their heat resistance is insufficient, making them difficult to use as a main component such as an insulating layer in an FPC.

[0005] Patent Documents 3 and 4 propose a laminate of metal and polyimide in which a fluorinated polyimide is used as an insulating resin layer. However, while the transparency is excellent, the control of the thermal expansion coefficient and other properties of the insulating layer is insufficient, and the adhesive strength with the smooth metal layer is low, so the properties as a laminate for a wiring board suitable for FPC applications are not fully satisfactory.

[0006] Therefore, in Patent Document 5, the present applicant proposed a resin film with excellent heat resistance, adhesiveness, flexibility, and high transparency, which is formed by using multiple polyimide layers including a non-thermoplastic polyimide layer and a thermoplastic polyimide layer. However, since multiple polyimide layers are formed by sequential coating using a casting method, the manufacturing time (coating time) is long, and there are concerns about a decrease in yield. Furthermore, in Patent Document 6, a metal-clad laminate plate is proposed in which a single polyimide layer made of transparent polyimide is laminated. However, since the metal layer is formed on the polyimide film by sputtering, there are concerns about adhesion to the metal layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-10993 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-163210 [Patent Document 3] Japanese Patent Application Publication No. 4-47933 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-198842 [Patent Document 5] Patent No. 7222089 [Patent Document 6] Japanese Patent Publication No. 2023-20715 Summary of the Invention [Problem to be solved by the invention]

[0008] In order to solve the above-mentioned problems, the object of the present invention is to provide a resin film consisting of a single polyimide layer which has excellent transparency, heat resistance and dimensional stability, and to provide a metal clad laminate which, even though it is a single layer, can be used as an insulating resin layer to be directly laminated on a metal layer and which has excellent adhesion between the insulating resin layer and the metal layer. [Means for solving the problem]

[0009] As a result of extensive investigations into solving the above-mentioned problems, the present inventors discovered that the above-mentioned problems can be solved by using a specific polyimide for the insulating resin layer of a laminate for wiring boards or an FPC, and by controlling the thickness and specific physical properties of the polyimide layer, and thus completed the present invention.

[0010] That is, the present invention provides a resin film comprising a single polyimide layer, Conditions a-c below: a) The thickness is within the range of 5 μm to 100 μm; b) Total light transmittance is 80% or more; c) Yellowness index YI at a thickness of 25 μm is 30 or less; Fulfilling the polyimide constituting the polyimide layer contains an aromatic tetracarboxylic dianhydride residue derived from an aromatic tetracarboxylic dianhydride component and a diamine residue derived from a diamine component; For all diamine residues, the following general formula (1): [ka] [In formula (1), the substituents X independently represent an alkyl group having 1 to 3 carbon atoms substituted with a fluorine atom, and m and n independently represent an integer of 1 to 4.] and a diamine residue derived from a first aromatic diamine represented by the following general formula (2): [ka] [In formula (2), the linking group Y independently represents a divalent group selected from -O- and -S-, and the linking group X represents a group represented by formula (x1), formula (x2), or formula (x3); [ka] In formula (x3), Z represents a divalent group selected from -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -SO2-, -NH-, or -NHCO-. The resin film is characterized by containing a diamine residue derived from a second aromatic diamine represented by the following formula in an amount of 1 mol % or more and 40 mol % or less.

[0011] In the resin film of the present invention, the polyimide is a compound represented by the following formula (3): [ka] The content of the acid dianhydride residue derived from pyromellitic anhydride represented by the formula (I) is in the range of 50 mol % to 90 mol %; The following general formula (4): [ka] [In formula (4), X represents a divalent group selected from a single bond, —O—, or —C(CF3)2—.] The present invention is characterized in that the acid dianhydride residue derived from an aromatic tetracarboxylic dianhydride represented by the following formula is contained in an amount of 10 mol % to 50 mol %.

[0012] The resin film of the present invention further satisfies the following condition d in addition to the above conditions a to c: d) The coefficient of thermal expansion is in the range of 10 ppm / K to 40 ppm / K; The present invention is characterized in that: The resin film of the present invention further satisfies the following condition e in addition to the above conditions a to c: e) Haze is 5% or less; The present invention is characterized in that:

[0013] The present invention relates to a metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, wherein the insulating resin layer is made of the above-mentioned resin film, and also to a circuit board, an electronic device, or an electronic device. [Effects of the Invention]

[0014] The resin film of the present invention has excellent dimensional stability, adhesiveness, and high transparency, and is therefore particularly suitable for use as an insulating material for electronic components such as FPCs, particularly for transparent FPCs, which require colorless transparency. Furthermore, since it is a single layer, it can significantly reduce production time and improve yield compared to multi-layer polyimide resin films, and is also desirable from the perspectives of energy conservation and carbon dioxide emission reduction (carbon neutrality). The resin film and metal clad laminate of the present invention can also be applied to display devices such as liquid crystal display devices, organic EL display devices, touch panels, color filters, and electronic paper, as well as their component parts. DETAILED DESCRIPTION OF THE INVENTION

[0015] The resin film of the present invention will be described below. From the viewpoint of transparency, the resin film of the present invention must have a thickness in the range of 5 μm or more and 100 μm or less, a total light transmittance in the visible region of 80% or more, and a yellowness index YI at a thickness of 25 μm of 30 or less. The resin film of the present invention is a single polyimide layer, which makes it possible to provide a resin film that is excellent not only in transparency but also in physical properties such as heat resistance and dimensional stability.

[0016] The resin film of the present invention is a non-thermoplastic polyimide that does not soften even when heated, has excellent dimensional stability, and has a coefficient of thermal expansion (CTE) of preferably 1 ppm / K or more and 50 ppm / K or less, more preferably 10 ppm / K or more and 40 ppm / K or less. From the viewpoint of transparency, the resin film of the present invention has a total light transmittance in the visible region of 80% or more. For example, it is preferable that this is satisfied when the resin film has a thickness of 25 μm. More preferably, the total light transmittance is 85% or more. By controlling the transmittance within this range, cloudiness due to light reflection and scattering in the resin film is suppressed, resulting in excellent transparency. Furthermore, the position of the metal layer can be recognized and seen through the insulating resin layer. The resin film of the present invention preferably has a haze (turbidity) of 5% or less, more preferably 2% or less. If the haze exceeds 5%, for example, visibility and light transmittance tend to decrease. The resin film of the present invention has a YI (yellowness index) of 30 or less when the thickness is 25 μm, and more preferably 20 or less. By controlling the YI within this range, the resin film can be made nearly colorless.

[0017] The resin film of the present invention comprises a single polyimide layer, and the polyimide constituting the polyimide layer contains an aromatic tetracarboxylic dianhydride residue derived from an aromatic tetracarboxylic dianhydride component and a diamine residue derived from a diamine component.

[0018] The polyimide contains, as diamine components, an aromatic diamine residue derived from a first aromatic diamine represented by general formula (1) (hereinafter also referred to as a first aromatic diamine residue), and an aromatic diamine residue derived from a second aromatic diamine represented by general formula (2) (hereinafter also referred to as a second aromatic diamine residue).

[0019] The primary aromatic diamine residue is represented by the following general formula (1): [ka] [In formula (1), the substituents X independently represent an alkyl group having 1 to 3 carbon atoms substituted with a fluorine atom, and m and n independently represent an integer of 1 to 4.] It is a diamine residue derived from an aromatic diamine represented by the formula: The substituent X is preferably a trifluoromethyl group, and m and n are preferably 1 or 2. The content of primary aromatic diamine residues is in the range of 60 mol % to 99 mol % of all diamine residues, preferably 95 mol % or less, and more preferably 90 mol % or less.

[0020] By containing a predetermined amount of primary aromatic diamine residue, the resin film can be made colorless and transparent, an increase in the coefficient of thermal expansion (CTE) can be suppressed, and dimensional stability can be improved. Preferred examples of the primary aromatic diamine include diamines represented by the following structural formula: [ka]

[0021] The secondary aromatic diamine residue is represented by the following general formula (2): [ka] [In formula (2), the linking group Y independently represents a divalent group selected from -O- and -S-, and the linking group X represents a group represented by formula (x1), formula (x2), or formula (x3); [ka] In formula (x3), Z represents a divalent group selected from -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -SO2-, -NH-, or -NHCO-. is a diamine residue derived from a second aromatic diamine represented by the formula: The secondary aromatic diamine residue is contained in an amount of 1 mol % to 40 mol % of the total diamine residues, preferably 5 mol % or more, and more preferably 10 mol % or more.

[0022] Secondary aromatic diamines are represented by general formula (2). The main backbone contains a heteroatom (-O-, -S-) as the linking group Y, allowing the molecular chain to rotate freely and providing high flexibility. The highly flexible molecular chains facilitate non-planar structures, preventing electron cloud overlap and reducing charge transfer (CT) between the aromatic tetracarboxylic acid residue and the aromatic diamine residue, resulting in polyimides that are close to colorless and transparent. Polyimides with highly flexible molecular chains exhibit high adhesion to substrates such as metal layers due to the entanglement of the molecular chains. In general formula (2), molecular chains containing the linking group Y or the linking group X (x1-3) in the main backbone, and molecular chains containing the linking group Z in the case of the formula (x3) structure, exhibit high chemical bonding and other interactions with metals and metal surface treatment agents, providing excellent adhesion. For the reasons described above, by blending a predetermined amount of a primary aromatic diamine represented by general formula (1), which is excellent in improving the transparency and dimensional stability of polyimide, with a secondary aromatic diamine represented by general formula (2), which is excellent in improving the transparency of polyimide and the adhesion to a support such as a metal layer, it is possible to obtain a polyimide film that is excellent in transparency, high dimensional stability, and adhesion. Preferred examples of the secondary aromatic diamine include diamines represented by the following structural formula: [ka] [ka] [ka] As the second aromatic diamine, those having a structure in which it is linked to the amino group at the m-position are particularly preferred.

[0023] The resin film of the present invention may contain diamine residues derived from other diamines as long as the object of the present invention is not impaired. However, when other diamine residues are contained, the content of such other diamine residues is preferably less than 30 mol %, more preferably less than 10 mol %, based on the total diamine residues.

[0024] As the other diamine, any of those known as diamine components for polyimides, particularly transparent polyimides, can be used. Specific examples include, but are not limited to, the following: [ka] [ka]

[0025] The polyimide preferably contains, as the acid dianhydride component, a predetermined amount of an acid dianhydride residue derived from pyromellitic anhydride represented by formula (3) and an acid dianhydride residue derived from an aromatic tetracarboxylic acid anhydride represented by general formula (4).

[0026] The pyromellitic acid residue is represented by formula (3); [ka] It is an acid dianhydride residue derived from pyromellitic acid represented by the following formula: The content of pyromellitic acid residues is preferably within the range of 50 mol % to 95 mol % of the total acid dianhydride residues, with the lower limit being more preferably 70 mol % or more, and even more preferably 80 mol % or more, and the upper limit being more preferably 90 mol % or less.

[0027] By containing a predetermined amount of pyromellitic acid residue, the heat resistance (Tg) of the single-layer polyimide can be increased, the coefficient of thermal expansion (CTE) can be appropriately controlled, and the dimensional stability can be improved.

[0028] The aromatic tetracarboxylic dianhydride residue that is preferably present together with the pyromellitic acid residue is represented by the general formula (4): [ka] [In formula (4), X represents a divalent group selected from a single bond, —O—, or —C(CF3)2—.] It is an acid dianhydride residue derived from an aromatic tetracarboxylic acid dianhydride represented by the following formula: The aromatic tetracarboxylic dianhydride residue of formula (4) is preferably contained in the range of 5 mol % to 50 mol %. The lower limit is more preferably 10 mol % or more, and the upper limit is more preferably 30 mol % or less, and even more preferably 20 mol % or less.

[0029] By containing a predetermined amount of the aromatic tetracarboxylic dianhydride residue of formula (4), it is possible to impart strength and flexibility to the single-layer polyimide, and it is possible to provide excellent heat resistance and transparency, and to control the CTE within an appropriate range. Preferred examples of the aromatic tetracarboxylic dianhydride of formula (4) include acid dianhydrides of the following structural formula: [ka]

[0030] The resin film of the present invention may contain other acid dianhydride residues as long as the object of the present invention is not impaired. However, when other acid dianhydride residues are contained, the amount of such other acid dianhydride residues is preferably less than 30 mol %, more preferably less than 10 mol %, based on the total acid dianhydride residues.

[0031] As the other acid dianhydride, any of those known as an acid dianhydride component of polyimide, particularly transparent polyimide, can be used. Specific examples include, but are not limited to, the following: [ka] [ka]

[0032] In the polyimide constituting the resin film of the present invention, various physical properties such as transparency, heat resistance, dimensional stability, and adhesiveness can be controlled by selecting the types and molar ratios of the diamine and acid dianhydride.

[0033] Next, a method for synthesizing the polyimide constituting the resin film of the present invention (hereinafter also referred to as single-layer polyimide) will be described. The single-layer polyimide of the present invention can be produced by reacting the diamine and dianhydride in a solvent to form a polyamic acid, followed by heating and ring-closure. For example, approximately equimolar amounts of the diamine and dianhydride are dissolved in an organic solvent and the resulting mixture is stirred at a temperature between 0°C and 100°C for 30 minutes to 24 hours to polymerize the polyamic acid, which serves as the polyimide precursor. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and γ-butyrolactone. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of organic solvent used is not particularly limited, but it is preferable to adjust the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction to about 5% to 30% by weight. The single-layer polyimide of the present invention may contain a terminal blocking agent. The terminal blocking agent is preferably a monoamine or a dicarboxylic acid. The amount of the terminal blocking agent to be introduced is preferably within a range of 0.0001 mol to 0.1 mol per mol of the acid anhydride component.

[0034] The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. The method for imidizing the polyamic acid is not particularly limited, and for example, it is heat-treated in a solvent at a temperature of 80°C to 400°C for 1 to 24 hours.

[0035] The weight-average molecular weight (Mw) of the polyamic acid is preferably in the range of 10,000 to 400,000, more preferably 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the film tends to be weak and brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during coating.

[0036] The single-layer polyimide resin film of the present invention may be a single insulating resin film (sheet), or may be an insulating resin film laminated on a substrate such as a resin sheet, such as a copper foil, a glass plate, a polyimide film, a polyamide film, or a polyester film. Examples of methods for preparing the resin film of the present invention include a method in which a polyamic acid solution is applied to a support substrate, dried, and then imidized to produce a resin film, or a method in which a polyamic acid solution is applied to a support substrate, dried, and then the polyamic acid gel film is peeled off from the support substrate and imidized to produce a resin film. The method for applying the polyimide solution (or polyamic acid solution) to the substrate is not particularly limited, and it can be applied using, for example, a coater such as a comma, die, knife, or lip coater.

[0037] The metal-clad laminate of the present invention will be described below. The metal-clad laminate of the present invention uses the resin film of the present invention as an insulating resin layer, and has a metal layer on at least one side of the insulating resin layer, i.e., on one or both sides.

[0038] The thickness of the insulating resin layer is in the range of 5 μm to 100 μm. If it is less than the lower limit, electrical insulation cannot be ensured, and there is a concern that handling may be impaired. If it exceeds the upper limit, dimensional changes before and after etching become large, and visibility tends to be impaired. The preferred range is 10 μm to 50 μm.

[0039] The insulating resin layer preferably has a glass transition temperature (Tg) of 270°C or higher, more preferably 300°C or higher, and even more preferably 350°C or higher. The thermal decomposition temperature (1% weight loss temperature, Td1) is preferably 500°C or higher, and the thermal decomposition temperature (5% weight loss temperature, Td5) is preferably 550°C or higher. The insulating resin layer preferably has a coefficient of thermal expansion (CTE) in the range of 10 ppm / K to 50 ppm / K. From the viewpoint of transparency and visibility, the insulating resin layer preferably has a total light transmittance (TT) in the visible region of 80% or more. For example, it is preferable that this is satisfied when the insulating resin layer has a thickness of 20 μm. More preferably, the total light transmittance is 85% or more. The insulating resin layer preferably has a yellowness index (YI) of not more than 30. For example, it is preferable that this is satisfied when the insulating resin layer has a thickness of 25 μm. The insulating resin layer preferably has a haze of 5% or less, more preferably 3% or less. The insulating resin layer preferably has an elastic modulus of 10 GPa or less, a maximum strength of 130 MPa or more, and a maximum elongation of 5% or more.

[0040] In the metal-clad laminate of the present invention, the insulating resin layer can be formed, for example, by applying a polyamic acid solution to a metal layer (metal foil) and drying it, followed by imidization to produce a resin film (casting method), by thermocompression bonding a preformed resin film and a metal foil (lamination method), or by sputtering a metal onto a preformed resin film (sputtering method). In particular, when the insulating resin layer is formed by the casting method, the resin film of the present invention can produce a metal-clad laminate having excellent adhesion to the metal layer.

[0041] The insulating resin layer may contain an inorganic filler as needed, such as silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride.

[0042] In the metal-clad laminate, the material of the metal layer is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof, etc. Copper, iron, or nickel is particularly preferred.

[0043] The thickness of the metal layer is not particularly limited, but is preferably 100 μm or less, and more preferably in the range of 1 μm or more and 20 μm or less.

[0044] When manufacturing a metal-clad laminate having metal layers on both sides, for example, it can be obtained by directly laminating a metal layer onto the insulating resin layer side of a single-sided metal-clad laminate obtained by the above-mentioned casting method or the like by means of thermocompression bonding or the like. The heat-pressing temperature for thermocompression bonding is preferably equal to or higher than the glass transition temperature of the single-layer polyimide. The heat-pressing pressure is, for example, in the range of 1 kg / m2 to 500 kg / m2.

[0045] Since the resin film of the present invention has excellent adhesion to a metal layer, the metal layer does not necessarily require surface roughening treatment. However, if the surface is roughened, it is preferable that the ten-point average roughness Rzjis of the surface is 0.5 μm or less. In the metal-clad laminate of the present invention, the peel strength between the insulating resin layer and the metal layer is desirably 0.5 kN / m or more.

[0046] The metal-clad laminate of the present invention can be suitably used as a circuit board material such as an FPC, etc. For example, it is useful as a circuit board such as an FPC, an electronic circuit including active elements such as a transistor and a diode, and passive devices such as a resistor, a capacitor and an inductor, as well as a sensor element for sensing pressure, temperature, light, humidity, etc., a light-emitting element, an image display element such as a liquid crystal display, an electrophoretic display and a self-luminous display, a wireless or wired communication element, an arithmetic element, a memory element, an MEMS element, a solar cell, a thin-film transistor, etc.

[0047] [Electronic Devices and Electronic Equipment] The electronic devices and electronic equipment according to the embodiments of the present invention include the above-described circuit board. Examples of the electronic devices according to the present embodiments include display devices such as liquid crystal displays, organic EL displays, and electronic paper, as well as organic EL lighting, solar cells, touch panels, camera modules, inverters, converters, and components thereof. Examples of the electronic equipment include hard disk drives, DVDs, mobile phones, smartphones, tablet devices, automotive electronic control units (ECUs), and power control units (PCUs). Circuit boards are preferably used in these electronic devices and electronic equipment as components such as wiring for moving parts, cables, and connectors. [Example]

[0048] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurements and evaluations of various physical properties were carried out as follows.

[0049] [Viscosity of polyamic acid] The polyamic acid solutions obtained in the synthesis examples were measured at 25°C using a cone-plate viscometer equipped with a thermostatic water bath (manufactured by Tokimec Co., Ltd.). [Number average molecular weight (Mn) Weight average molecular weight (Mw)] Measurement was performed by gel permeation chromatography (manufactured by Tosoh Corporation, product name: HLC-8220GPC). Polystyrene was used as a standard substance, and N,N-dimethylacetamide was used as a developing solvent.

[0050] [Calculation of Yellowness Index (YI)] The yellowness index (YI) of the polyimide film (50 mm × 50 mm) was measured using a UV-3600 spectrophotometer manufactured by Shimadzu Corporation. Here, YI was calculated based on the following formula (1) in accordance with JIS Z 8722. YI=100×(1.2879X-1.0592Z) / Y (1) X, Y, and Z: Tristimulus values ​​of the test piece The YI(25) of the polyimide film having a thickness of 20 μm was calculated by substituting the value of YI calculated by the above formula (1) into the following formula (2). YI(25)=YI / L×25 (2) L: Polyimide film thickness (μm) [Measurement of haze (turbidity) and total light transmittance (TT)] The haze (turbidity) and total light transmittance (TT) of the polyimide film (50 mm x 50 mm) were measured using a Haze Meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7136.

[0051] [Measurement of coefficient of thermal expansion (CTE)] A polyimide film (3 mm × 15 mm) was heated from 30°C to 280°C at a heating rate of 10°C / min while applying a load of 5.0 g in a thermomechanical analyzer (TMA), and then cooled from 250°C to 100°C. The thermal expansion coefficient was measured from the elongation (linear expansion) of the polyimide film during cooling. [Measurement of glass transition temperature (Tg)] The polyimide layer (5 mm x 22.6 mm) was heated from 30°C to 400°C at a rate of 10°C / min using a dynamic thermomechanical analyzer, and the dynamic viscoelasticity was measured to determine the glass transition temperature (Tan δ maximum value: °C). [Calculation of thermal decomposition temperatures (Td1, Td5)] A polyimide film weighing 10 to 20 mg was heated at a constant rate from 30°C to 550°C in a nitrogen atmosphere using a thermogravimetric analyzer (TG) TG / DTASTA200 manufactured by Seiko Corporation, and the weight change was measured. The weight at 200°C was set to zero, and the temperature at which the weight loss rate was 1% was defined as the thermal decomposition temperature (Td1), and the temperature at which the weight loss rate was 5% was defined as the thermal decomposition temperature (Td5).

[0052] [Measurement of tensile strength] Using a tensile tester Strograph VG1F (manufactured by TOYOSEIKI), a tensile test was performed on a protective film test sample (size 10 mm x 110 mm) at a speed of 10 mm / min under a load of 100 N to determine the elastic modulus, maximum point strength, and maximum point elongation.

[0053] [Peel strength measurement] (copper clad laminate) Using a tension tester, the polyimide layer side of a test sample having a 1 mm-wide circuit obtained from a laminate (copper-clad laminate) of copper foil and polyimide layer as a support was fixed to an aluminum plate with double-sided tape, and the copper was peeled off in a 180° direction at a rate of 50 mm / min to determine the peel strength between the copper foil and polyimide layer.

[0054] The abbreviations used in the examples represent the following compounds. PMDA: Pyromellitic dianhydride [ka] 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropanoic dianhydride [ka] TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl [ka] APB: 1,3-bis(3-aminophenoxy)benzene [ka] M-BAPS: bis[4-(3-aminophenoxy)phenyl]sulfone [ka] DMAc: N,N-dimethylacetamide

[0055] Synthesis Example 1 To synthesize polyamic acid solution A, the solvent DMAc was added to a 500 ml separable flask under a nitrogen stream to a solids concentration of 15 wt %, and the diamine and acid anhydride components shown in Table 1 were added and dissolved with stirring at 40°C. The solution was then stirred at room temperature for one day to carry out a polymerization reaction, producing a viscous polyamic acid solution A. The viscosity was 27,940 cP.

[0056] Synthesis Example 2 To synthesize polyamic acid solution B, the solvent DMAc was added to a 300 ml separable flask under a nitrogen stream to a solids concentration of 15 wt %, and the diamine and acid anhydride components shown in Table 1 were added and dissolved with stirring at 40°C. The solution was then stirred at room temperature for two days to carry out a polymerization reaction, producing a viscous polyamic acid solution B. The viscosity was 4310 cP.

[0057] Synthesis Example 3 To synthesize polyamic acid solution C, the solvent DMAc was added to a 300 ml separable flask under a nitrogen stream to a solids concentration of 15 wt %, and the diamine and acid anhydride components shown in Table 1 were added and dissolved with stirring at 40°C. The solution was then stirred at room temperature for one day to carry out a polymerization reaction, producing a viscous polyamic acid solution C. The viscosity was 6279 cP.

[0058] Synthesis Example 4 Polyamic acid solution D was prepared by changing the monomer type as shown in Table 1 and carrying out polymerization in the same manner as in Synthesis Example 3. A viscous polyamic acid solution D was prepared. The viscosity was 2913 cP.

[0059] Synthesis Example 5 Polyamic acid solution E was prepared by changing the type of monomer as shown in Table 1 and carrying out polymerization in the same manner as in Synthesis Example 3. A viscous polyamic acid solution E was prepared. The viscosity was 1945 cP.

[0060] Synthesis Example 6 Polyamic acid solution F was prepared by changing the type of monomer as shown in Table 1 and carrying out polymerization in the same manner as in Synthesis Example 1. A viscous polyamic acid solution F was prepared. The viscosity was 32,385 cP.

[0061] Synthesis Example 7 Polyamic acid solution G was prepared by changing the type of monomer as shown in Table 1 and carrying out polymerization in the same manner as in Synthesis Example 2. A viscous polyamic acid solution G was prepared. The viscosity was 3802 cP.

[0062] Synthesis Example 8 To synthesize polyamic acid solution H, the solvent DMAc was added to a 500 ml separable flask under a nitrogen stream to a solids concentration of 15 wt %, and the diamine and acid anhydride components shown in Table 1 were added and dissolved with stirring at 40°C. The solution was then stirred at room temperature for two days to carry out a polymerization reaction, producing a viscous polyamic acid solution H. The viscosity was 26,950 cP.

[0063] [Table 1]

[0064] Example 1 Polyamic acid solution A was uniformly applied to copper foil (electrolytic copper foil, manufactured by Fukuda Metal Foil & Powder Co., Ltd., product name: CF-T9DA-SV18, thickness: 18 μm) so that the thickness after curing would be 19 μm, and then the solution was dried by stepwise heating in a temperature range up to 120 ° C. to remove the solvent. After forming a single-layer polyamic acid layer in this way, stepwise heat treatment was performed from 130 ° C. to 360 ° C. to complete imidization, forming a 19 μm-thick insulating resin layer made of single-layer polyimide A, and metal-clad laminate 1A was prepared. The copper foil was removed from the resulting single-sided metal-clad laminate 1A by etching using an aqueous ferric chloride solution to prepare a single-layer polyimide resin film 1a. The single-layer polyimide resin film 1a was measured for YI, TT, haze, CTE, Td1, Td5, modulus of elasticity, maximum strength, and maximum elongation. The results are shown in Table 2. Table 3 shows the results of measuring the peel strength of the polyamic acid-coated surface of the obtained single-sided metal-clad laminate 1A when wiring was processed to 1 mm.

[0065] Examples 2 to 10 In the same manner as in Example 1, single-sided metal-clad laminates 2A to 10G were prepared by applying resins A to G listed in Table 1 to copper foil (same as above), and polyimide films 2a to 10g were prepared. The YI, TT, haze, CTE, Td1, Td5, modulus of elasticity, maximum strength, and maximum elongation were measured for polyimide films 2a to 10g. The results are shown in Table 2. Furthermore, the peel strength of the single-sided metal-clad laminates 2A to 10G was measured in the same manner as in Example 1, and the results are shown in Table 3.

[0066] Comparative Examples 1 and 2 Single-sided metal-clad laminates 1H and 2H and single-layer polyimide resin films 1h and 2h were prepared in the same manner as in Example 1, except that single-layer polyimide H shown in Table 1 was used. These single-layer polyimide resin films 1h and 2h and single-sided metal-clad laminates 1H and 2H were evaluated in the same manner as in Examples. The measurement results are also shown in Tables 2 and 3.

[0067] [Table 2]

[0068] [Table 3]

Claims

1. A resin film consisting of a single polyimide layer, The following conditions a to c: a) the thickness is in the range of 5 μm or more and 100 μm or less; b) total light transmittance is 80% or more; c) Yellowness index YI at a thickness of 25 μm is 30 or less; Fulfilling the polyimide constituting the polyimide layer contains an aromatic tetracarboxylic dianhydride residue derived from an aromatic tetracarboxylic dianhydride component and a diamine residue derived from a diamine component; With respect to all diamine residues, the following general formula (1): 【Chemical 1】 [In formula (1), each substituent X independently represents an alkyl group having 1 to 3 carbon atoms substituted with a fluorine atom, and each of m and n independently represents an integer of 1 to 4.] and a diamine residue derived from a first aromatic diamine represented by the following general formula (2): 【Chemistry 2】 [In formula (2), the linking group Y independently represents a divalent group selected from -O- and -S-, and the linking group X represents a group represented by formula (x1), formula (x2), or formula (x3); 【Chemistry 3】 In formula (x3), Z represents a divalent group selected from -O-, -S-, -CH 2 -, -CH(CH 3 ) -, -C(CH 3 ) 2 -, -CO-, -SO 2 represents a divalent group selected from -, -NH-, or -NHCO-.] A resin film characterized by containing 1 mol % or more and 40 mol % or less of a diamine residue derived from a second aromatic diamine represented by the following formula:

2. The polyimide is a compound represented by the following formula (3): 【Chemistry 4】 The content of the acid dianhydride residue derived from pyromellitic anhydride represented by the formula (I) is in the range of 50 mol % to 90 mol %; and The following general formula (4): 【Chemistry 5】 [In formula (4), X represents a single bond, —O—, or —C(CF ３ ) ２ - represents a divalent group selected from the group consisting of 2. The resin film according to claim 1, wherein the resin film contains 10 mol % or more and 50 mol % or less of an acid dianhydride residue derived from an aromatic tetracarboxylic dianhydride represented by the following formula:

3. In addition to the above conditions a to c, the following condition d is further met: d) a thermal expansion coefficient in the range of 10 ppm / K or more and 40 ppm / K or less; 2. The resin film according to claim 1, wherein the above formula (1) is satisfied.

4. In addition to the above conditions a to c, the following condition e is further satisfied: e) HAZE is 5% or less; 2. The resin film according to claim 1, wherein the above formula (1) is satisfied.

5. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, wherein the insulating resin layer is made of the resin film described in claim 1.

6. 6. The metal-clad laminate according to claim 5, wherein the 180° peel strength between the insulating resin layer and the metal layer is 0.5 kN / m or more.

7. A circuit board comprising an insulating resin layer and a conductor circuit layer laminated on one or both sides of the insulating resin layer, wherein the insulating resin layer is made of the resin film according to claim 1.

8. An electronic device comprising the circuit board according to claim 7.

9. An electronic device comprising the electronic device according to claim 8.

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