Resin composition, copper foil with resin, and composite material

Abstract

To provide a resin composition which enables the bonding of a copper foil and a glass substrate by a lamination method, while having excellent dimensional stability.SOLUTION: This resin composition contains a polyimide resin that has a glass transition temperature Tg of 150°C or less, an epoxy resin and a curing agent; and the storage elastic modulus at 200°C of the resin composition in a C-stage state after curing is 10 MPa or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition, a resin-coated copper foil, and a composite material. [Background technology]

[0002] Glass substrates are used for glass antennas that impart antenna functions to glass for automobiles and buildings, various flat panel displays, glass interposers, etc. For example, Patent Document 1 (International Publication No. 2020 / 195661) discloses a resin composition intended for application to glass substrates, which comprises (a) an acrylic polymer having a tensile modulus of 200 MPa or less, (b) a resin that is solid at 25 ° C, (c) a resin that is liquid at 25 ° C and can be crosslinked with at least one of the components (a) and (b), and (d) a polymerization initiator, and in which the content of the component (a) is 35 parts by weight or more and 93 parts by weight or less, the content of the component (b) is 3 parts by weight or more and 60 parts by weight or less, and the content of the component (c) is 1 part by weight or more and 25 parts by weight or less, relative to a total amount of 100 parts by weight of the components (a), (b), and (c).

[0003] In addition, the resin composition is used for various applications other than the above-mentioned glass substrate, for example, in electronic devices such as flexible printed wiring boards. For example, Patent Document 2 (JP 2007-168123 A) discloses a method for producing a metal foil-attached flexible substrate in which a metal foil is provided on at least one side of a resin film, the method comprising a step of thermocompression bonding the metal foil to the resin film at 300°C or more and 500°C or less, the resin film containing a non-thermoplastic polyimide resin. Patent Document 3 (WO 2018 / 139559 A) discloses a curable resin composition containing a curable resin, an imide oligomer having an imide skeleton in the main chain and a crosslinkable functional group at the end and a number average molecular weight of 4000 or less, and a curing accelerator, the cured product having an initial adhesive strength to polyimide of 3.4 N / cm or more, and the adhesive strength of the cured product to polyimide after storage at 200°C for 100 hours is 0.8 times or more the initial adhesive strength. Patent Document 4 (JP Patent Publication 5-179220 A) discloses a heat-resistant adhesive that contains, as resin components, (A) 100 parts by weight of a soluble aromatic polyamideimide, (B) 25 to 300 parts by weight of an epoxy resin, and (C) an epoxy curing agent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 195661 [Patent Document 2] JP 2007-168123 A [Patent Document 3] International Publication No. 2018 / 139559 [Patent Document 4] Japanese Patent Application Publication No. 5-179220 Summary of the Invention

[0005] As mentioned above, resin compositions are used in various applications, but unlike applications such as laminating a resin material such as prepreg with a metal foil, as disclosed in Patent Documents 2 to 4, among printed wiring boards, laminating a metal foil (e.g., copper foil) with a glass substrate via a resin composition causes unique problems. For example, when a composite material is produced by laminating a copper foil with a glass substrate via a resin composition as a resin layer, if a press method is used, not only is it time-consuming and the size of the composite material itself is limited, but the glass substrate may also break. On the other hand, the lamination method is a method of laminating two or more sheets by roll-to-roll at a lower pressure than the press method, so continuous production is possible and the glass substrate is less likely to break. Therefore, when laminating a copper foil with a glass substrate via a resin composition as a resin layer, it is desirable to use a lamination method instead of a press method. However, although the lamination method has the above-mentioned advantages, it is difficult to increase the pressure to the same level as the press method, so a resin composition that enables adhesion by the lamination method of copper foil and glass substrate is required. However, when a copper foil is attached to a resin layer made of such a resin composition to form a circuit pattern, there is a problem that wrinkles occur in the circuit due to dimensional fluctuations of the resin layer. Therefore, there is a demand for a resin composition that makes it difficult for wrinkles to occur in the circuit when a circuit pattern is formed on the resin layer, i.e., has high dimensional stability.

[0006] The present inventors have now discovered that a resin composition which contains a specified polyimide resin, an epoxy resin, and a curing agent, and which has specified properties in a C-stage state after curing, enables bonding of a copper foil and a glass substrate by a lamination method, and also has excellent dimensional stability.

[0007] Therefore, an object of the present invention is to provide a resin composition which enables bonding of a copper foil and a glass substrate by a lamination method and has excellent dimensional stability.

[0008] According to one aspect of the present invention, A polyimide resin having a glass transition temperature Tg of 150° C. or lower; Epoxy resin, A hardener; The resin composition has a storage modulus of 10 MPa or more at 200° C. in a C-stage state after curing.

[0009] According to another aspect of the present invention, A copper layer having a smooth surface with an aspect ratio Str of 0.3 to 1 as measured in accordance with ISO 25178; a resin layer formed on the smooth surface and composed of the resin composition; The present invention provides a resin-coated copper foil comprising:

[0010] According to another aspect of the present invention, A glass substrate; the resin-coated copper foil being provided on at least one surface of the glass substrate such that the resin layer is in contact with the glass substrate; A composite material is provided, comprising: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] resin composition The resin composition of the present invention contains a polyimide resin having a glass transition temperature Tg of 150° C. or less, an epoxy resin, and a curing agent. This resin composition has a storage modulus of 10 MPa or more at 200° C. in a C-stage state after curing. In this way, a resin composition containing a specific polyimide resin, an epoxy resin, and a curing agent and having specific properties in a C-stage state after curing enables adhesion of a copper foil and a glass substrate by a lamination method and exhibits excellent dimensional stability. And, the excellent dimensional stability can suppress the occurrence of wrinkles in the circuit and the resin composition when a circuit pattern is formed on the resin composition.

[0012] As mentioned above, when a composite material is produced by bonding a copper foil and a glass substrate via a resin composition as a resin layer, a lamination method is desirable because it allows continuous production and has a low possibility of cracking the glass substrate. However, although the lamination method has the above-mentioned advantages, it is difficult to increase the pressure as much as the pressing method, so a resin composition that enables adhesion of a copper foil and a glass substrate by the lamination method is required. However, when a circuit pattern is formed by bonding a copper foil on a resin layer composed of such a resin composition, there is a problem that wrinkles occur in the circuit. That is, a resin composition that makes it difficult for wrinkles to occur in the circuit when a circuit pattern is formed on a resin layer (i.e., has high dimensional stability) is also required. In addition, the resin does not usually complete the C-stage by lamination alone, and additional heat treatment for main curing is required. The problem of wrinkle generation can also occur during this additional heat treatment. Furthermore, in the post-process, a heating process may be performed for annealing (baking) or component mounting, and a resin composition with high dimensional stability that can withstand such an environment is also required. In this respect, the resin composition of the present invention can advantageously solve the above problem. In addition, since a glass substrate has low roughness and excellent flatness, it is difficult to ensure adhesion between the glass substrate and the resin composition. In addition, in order to form a fine pattern circuit (to avoid the generation of residues and thinning of the circuit), it is preferable that the copper foil itself has low roughness and is extremely thin, but it is also difficult to ensure adhesion between such copper foil and the resin composition. In contrast, the resin composition of the present invention can ensure adhesion between the glass substrate and the resin composition, and adhesion between the copper foil and the resin composition.

[0013] The resin composition of the present invention has a storage modulus of 10 MPa or more, preferably 30 MPa or more, more preferably 100 MPa or more, at 200°C in a C-stage state after curing. When the storage modulus is high, the dimensional stability can be effectively increased when a circuit pattern is formed on the resin composition. The higher the storage modulus, the more preferable it is, and the upper limit is not particularly limited, but is typically 10,000 MPa or less, more typically 5,000 MPa or less, and even more typically 1,000 MPa or less. The storage modulus at 200°C is measured using a DMA (dynamic viscoelasticity measurement) device. Specifically, this DMA measurement is performed in accordance with JIS K 7244-4:1999 by placing a resin with a test piece width of 5.0 mm and a test piece thickness of 100 μm in a clamp with a clamp length of 20.0 mm, and heating from 30°C to 280°C at a temperature increase rate of 5°C / min under air atmosphere at a measurement frequency of 1 Hz.

[0014] The resin composition of the present invention preferably has a temperature at which it exhibits a minimum melt viscosity in a semi-cured B-stage state of 60° C. to 150° C., more preferably 90° C. to 150° C., and even more preferably 110° C. to 150° C. Within such a range, the copper foil and the glass substrate can be effectively bonded together by a lamination method. That is, the adhesion between the glass substrate and the resin composition, and the adhesion between the copper foil and the resin composition can be effectively ensured.

[0015] The resin composition of the present invention contains a polyimide resin having a glass transition temperature Tg of 150°C or less. The polyimide resin contributes to improving the heat resistance and toughness of the resin composition, and by using a polyimide resin having a Tg of 150°C or less, the viscosity of the resin composition at the lamination temperature can be reduced, and lamination properties can be exhibited. The glass transition temperature Tg is 150°C or less. The lower limit of the glass transition temperature Tg of the polyimide resin is not particularly limited, but is typically -45°C or more.

[0016] In this specification, the glass transition temperature Tg means the peak temperature of the loss factor (tan δ) measured by dynamic viscoelasticity measurement (DMA) in accordance with JIS K 7244-4: 1999. Specifically, a resin having a test piece width of 5.0 mm and a test piece thickness of 100 μm is placed in a clamp with a clamp distance of 20.0 mm, and heated from 30° C. to 280° C. at a temperature increase rate of 5° C. / min in an air atmosphere, and the measurement is performed at a frequency of 1 Hz.

[0017] The content of the polyimide resin having a glass transition temperature Tg of 150° C. or lower is preferably 15 parts by weight or more and 65 parts by weight or less, more preferably 20 parts by weight or more and 60 parts by weight or less, even more preferably 25 parts by weight or more and 50 parts by weight or less, and particularly preferably 35 parts by weight or more and 50 parts by weight or less, relative to 100 parts by weight of the total amount of the resin composition.

[0018] The resin composition of the present invention includes an epoxy resin. The epoxy resin contributes to improving the adhesiveness, rigidity, and heat resistance of the resin composition. In particular, from the viewpoint of adjusting the functional group density, it is preferable that the epoxy resin includes an epoxy resin having a functional group number of 3 or more and an epoxy resin having a functional group number of less than 3. It is more preferable that the epoxy resin includes an epoxy resin having a functional group number of 3 or more per molecule and an epoxy resin having a functional group number of less than 3 per molecule. In addition, in this specification, the number of functional groups means the average number of functional groups per molecule present in the resin. For example, in a resin having a structure in which a repeating unit has a functional group in the repeating unit, it is difficult to make the number of repeating units (generally represented by n) of all molecules uniform in production, and molecules having different numbers of repeating units may be mixed. In that case, since molecules having different numbers of functional groups may be mixed, the sum of the number of functional groups x the existence ratio in the molecules present in the resin (i.e., the value obtained by averaging the number of functional groups by the existence ratio, and the total existence ratio is 1.) is used as the number of functional groups of the resin. For example, when the ratio of molecules having a functional group number of 2 in a resin is 0.5 and the ratio of molecules having a functional group number of 3 is 0.5, the number of functional groups of the resin is 2×0.5+3×0.5=2.5. By including an epoxy resin having a functional group number of 3 or more, the heat resistance of the cured resin composition can be improved, but the cured resin composition may become brittle. By including an epoxy resin having a functional group number of less than 3, the brittleness of the cured resin composition can be improved, but the heat resistance of the cured resin composition may decrease. That is, by including an epoxy resin having a functional group number of 3 or more and an epoxy resin having a functional group number of less than 3, the physical properties of the resin composition can be adjusted, and in particular, the heat resistance of the cured resin composition can be secured while the brittleness can be improved. When the epoxy resin having a functional group number of 3 or more is a monomer, it preferably has a functional group number of 3 or more and 4 or less.Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, alkyl type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, phenol aralkyl type epoxy resin, trisphenol type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, bisphenol fluorene type epoxy resin, triazine type epoxy resin, isocyanurate type epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, naphthol aralkyl type epoxy resin, naphthol novolac type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolac type epoxy resin, naphthalene type epoxy resin, naphthylene ether type epoxy resin, binaphthyl type epoxy resin, anthracene type epoxy resin, and the like. These epoxy resins having a functionality of 3 or more and less than 3 can be used in combination.

[0019] The content of the epoxy resin is preferably 20 parts by weight or more and 80 parts by weight or less, more preferably 25 parts by weight or more and 70 parts by weight or less, even more preferably 30 parts by weight or more and 60 parts by weight or less, and particularly preferably 35 parts by weight or more and 55 parts by weight or less, relative to 100 parts by weight of the total amount of the resin composition. The content of the epoxy resin having 3 or more functional groups is preferably 10 parts by weight or more and 60 parts by weight or less, more preferably 20 parts by weight or more and 60 parts by weight or less, even more preferably 25 parts by weight or more and 60 parts by weight or less, and particularly preferably 30 parts by weight or more and 55 parts by weight or less, relative to 100 parts by weight of the total amount of the resin composition. The content of the epoxy resin having less than 3 functional groups is preferably 10 parts by weight or more and 60 parts by weight or less, more preferably 20 parts by weight or more and 60 parts by weight or less, even more preferably 25 parts by weight or more and 60 parts by weight or less, and particularly preferably 30 parts by weight or more and 55 parts by weight or less, relative to 100 parts by weight of the total amount of the resin composition.

[0020] The epoxy resin preferably has a naphthalene skeleton, which allows the resin composition after curing to have a higher storage modulus.

[0021] Examples of epoxy resins having a naphthalene skeleton include, but are not limited to, those having a naphthalene skeleton, such as those having the following formula: [ka] [ka] [ka] [ka] [ka] [ka] Examples of commercially available epoxy resins having a naphthalene skeleton include HP4710, HP4770, HP4032D, HP5000, and HP6000 manufactured by DIC Corporation, and NC7000H and NC7300L manufactured by Nippon Kayaku Co., Ltd., and are preferably binaphthyl-type epoxy resins.

[0022] The resin composition of the present invention contains a curing agent. The curing agent contributes to promoting the crosslinking reaction between the polyimide resin and the epoxy resin, and the reaction between epoxy resins. The curing agent is not particularly limited as long as it can promote the formation of a three-dimensional network such as crosslinking, and preferred examples include phenol-based curing agents, imidazole-based curing agents, amine-based curing agents, and acid anhydride-based curing agents.

[0023] The content of the curing agent is preferably 0.5 parts by weight or more and 15 parts by weight or less, more preferably 1 part by weight or more and 10 parts by weight or less, and even more preferably 1 part by weight or more and 3 parts by weight or less, based on 100 parts by weight of the total amount of the resin composition.

[0024] Resin Coated Copper Foil The resin composition of the present invention is preferably used as a resin layer of a resin-coated copper foil. By forming the resin-coated copper foil in advance, it is possible to efficiently manufacture a member having a glass substrate without separately forming a resin layer. That is, according to a preferred embodiment of the present invention, a resin-coated copper foil is provided, which comprises a copper layer having a smooth surface with an aspect ratio Str of the surface property measured in accordance with ISO25178 of 0.3 to 1, and a resin layer composed of a resin composition provided on the smooth surface. Typically, the resin composition is in the form of a resin layer, and the resin composition is applied to the copper foil (copper layer) using a bar coater so that the thickness of the resin layer after drying is a predetermined value, and then dried to obtain a resin-coated copper foil. The coating method is arbitrary, but can be applied using a doctor blade or a bar coater, and can also be a gravure coating method, a die coating method, a knife coating method, or the like.

[0025] The copper foil may be a metal foil (so-called raw foil) that has been electrolytically or rolled, or may be in the form of a surface-treated foil that has been surface-treated on at least one side. The surface treatment may be any of various surface treatments that are performed to improve or impart certain properties (e.g., rust resistance, moisture resistance, chemical resistance, acid resistance, heat resistance, and adhesion to a substrate) to the surface of the metal foil. The surface treatment may be performed on at least one side of the metal foil, or on both sides of the metal foil. Examples of surface treatments performed on copper foil include rust prevention treatment, silane treatment, roughening treatment, and barrier formation treatment.

[0026] The copper layer has a smooth surface from the viewpoint of downsizing (miniaturization) of the circuit. The aspect ratio Str of the surface texture is an index for judging the smoothness of the copper layer surface. The aspect ratio Str of the surface texture is an index showing the anisotropy of the surface height (presence or absence of abruptly changing areas). The closer Str is to 0, the more anisotropic it is, and the closer Str is to 1, the less anisotropic it is. In the case of bonding an ultra-smooth glass to a copper layer, it is preferable that the Str of the copper layer surface is close to 1 (no anisotropy) from the viewpoint of reducing bonding defects. From this viewpoint, the aspect ratio Str of the surface texture of the copper layer is preferably 0.3 to 1, more preferably 0.4 to 1, even more preferably 0.5 to 1, and particularly preferably 0.6 to 1.

[0027] The maximum height Sz of the surface of the copper layer on the side in contact with the resin layer is preferably 6.8 μm or less, more preferably 0.15 μm to 6.8 μm, even more preferably 0.25 μm to 5.0 μm, and particularly preferably 0.3 μm to 3.0 μm. Within such a range, the resin layer can adequately follow and ensure sufficient adhesion between the copper layer and the glass substrate. In this specification, the "maximum height Sz" is a parameter that represents the distance from the highest point to the lowest point on the surface measured in accordance with ISO25178.

[0028] The maximum peak height Sp on the surface of the copper layer in contact with the resin layer is preferably 3.3 μm or less, more preferably 0.06 μm or more and 3.1 μm or less, even more preferably 0.06 μm or more and 3.0 μm or less, and particularly preferably 0.07 μm or more and 2.9 μm or less. Within such a range, the resin layer can follow suitably and ensure sufficient adhesion between the copper layer and the glass substrate. In this specification, the "maximum peak height Sp" is a three-dimensional parameter that represents the maximum value of the height from the average plane of the surface, measured in accordance with ISO25178.

[0029] The root mean square gradient Sdq on the surface of the copper layer in contact with the resin layer is preferably 0.01 to 2.3, more preferably 0.02 to 2.0, and even more preferably 0.04 to 1.8. Within such a range, the resin layer can follow suit to ensure sufficient adhesion between the copper layer and the glass substrate. In this specification, the "root mean square gradient Sdq" is a parameter calculated by the root mean square of the inclination at all points of the defined area measured in accordance with ISO25178. In other words, since it is a three-dimensional parameter that evaluates the magnitude of the local inclination angle, the steepness of the surface unevenness can be quantified. For example, the Sdq of a completely flat surface is 0, and if the surface is inclined, the Sdq becomes large. The Sdq of a plane consisting of a 45-degree inclination component is 1.

[0030] The above-mentioned Str, Sz, Sp and Sdq can be measured using a commercially available laser microscope (for example, OLS5000 manufactured by Olympus Corporation) in accordance with ISO25178, according to the procedure shown in the examples described below.

[0031] The thickness of the copper layer is preferably 5 μm or less, more preferably 0.5 μm to 4 μm, even more preferably 1 μm to 4 μm, and particularly preferably 1 μm to 3 μm. With such a thickness, when cutting a fine pattern circuit, it is possible to reduce circuit thinning such as undercut. However, when using such a thin copper layer, it is preferable to provide a carrier layer on the surface opposite to the smooth surface of the copper layer in order to improve the handleability of the resin-coated copper foil. That is, it is preferable that a copper layer (ultra-thin copper foil) having a thickness of 5 μm or less is provided in the form of a carrier-coated copper foil. Therefore, according to a preferred embodiment of the present invention, a resin-coated copper foil is provided in which the copper layer has a thickness of 5 μm or less and further includes a carrier layer on the surface opposite to the smooth surface of the copper layer. In addition, for circuit formation, a copper layer of a desired thickness can be further formed on the copper layer, typically using a known method such as copper plating.

[0032] The thickness of the resin layer is not particularly limited, but is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, even more preferably 2 μm or more and 7 μm or less, and particularly preferably 3 μm or more and 7 μm or less. With such a thickness, the above-mentioned characteristics of the present invention can be more effectively realized, and the resin layer can be easily formed by applying the resin composition. Furthermore, the handling property is improved.

[0033] composite material The resin composition of the present invention is preferably used as a resin layer of a composite material comprising a glass substrate and a resin-coated copper foil. That is, according to a preferred embodiment of the present invention, a composite material is provided comprising a glass substrate and a resin-coated copper foil provided on at least one surface of the glass substrate so that the resin layer is in contact with the glass substrate. As described above, when a composite material is produced by bonding a copper foil and a glass substrate via a resin composition as a resin layer, a lamination method is desirable because it allows continuous production and has a low possibility of cracking the glass substrate. However, although the lamination method has the above-mentioned advantages, it is difficult to increase the pressure as much as the pressing method, and it is difficult to ensure the adhesion between the copper foil and the glass substrate. Therefore, by using the resin composition of the present invention as a resin layer, the copper foil and the glass substrate can be bonded by the lamination method to efficiently produce a composite material. EXAMPLES

[0034] The present invention will now be further illustrated by the following examples.

[0035] Examples 1-9 (1) Preparation of varnish First, the resin components shown below were prepared as raw materials for the varnish. (a) Polyimide resin with a Tg of 150°C or less: - Polyimide manufactured by JFE Chemical Corporation (weight average molecular weight less than 50,000, Tg: 140℃) - PIAD150L (Arakawa Chemical Industries, Ltd., low molecular weight thermoplastic polyimide, Tg: 40°C) (b1) Epoxy resins having three or more functional groups: - HP4710 (has naphthalene structure) (manufactured by DIC Corporation, functional group number: 3 or more, epoxy equivalent: 170g / eq) - KR470 (Shin-Etsu Chemical Co., Ltd., functional group number: 4, epoxy equivalent: 200g / mol) - EPPN502H (manufactured by Nippon Kayaku Co., Ltd., number of functional groups: 3 or more, epoxy equivalent: 158 g / eq or more and 178 g / eq or less) (b2) Epoxy resins having a functionality of less than 3: - HP4770 (has naphthalene structure) (manufactured by DIC Corporation, functional group number: less than 3, epoxy equivalent: 160g / eq to 170g / eq) - NC3000H (manufactured by Nippon Kayaku Co., Ltd., functional group number: less than 3, epoxy equivalent: 280g / eq to 300g / eq) (c1) Phenol-based hardener: - MEH7500 (manufactured by Meiwa Kasei Co., Ltd.) - GPH65 (manufactured by Nippon Kayaku Co., Ltd.) (c2) Imidazole-based hardener: - TBZ (manufactured by Shikoku Chemical Industry Co., Ltd.) - 2P4MHZ (manufactured by Shikoku Chemical Industry Co., Ltd.)

[0036] The raw material components and organic solvent were weighed and placed in a flask so as to obtain the compounding ratio (parts by weight) and solid content (% by weight) shown in Table 1. The flask was heated to 60°C with a mantle heater while stirring with a stirring blade to dissolve the raw material components in the solvent, and then cooled to room temperature to obtain a varnish.

[0037] (2) Preparation of diluted varnish A portion of the obtained varnish was set aside, and toluene (Example 1) or cyclopentanone (Examples 2 to 9) was added as a dilution solvent so as to obtain a diluted solid concentration (wt %) shown in Table 1, followed by stirring to obtain a diluted varnish.

[0038] (3) Preparation of resin film The varnish obtained in (1) above was applied to a fluororesin film (Aflex (registered trademark), manufactured by AGC Inc.) and air-dried for 15 seconds, and then placed in an oven preheated to 150°C and dried by heating for 5 minutes. In this way, a resin layer with Aflex was obtained. At this time, the coating conditions were adjusted so that the thickness of the resin layer after drying (not including the thickness of the Aflex) would be 20 μm. The Aflex was peeled off from the obtained resin layer with Aflex, and five sheets of only the resin layer were laminated. The obtained resin laminate was pressed in a vacuum press at 220°C and 40 kgf / cm. 2 The mixture was cured under these conditions for 90 minutes to obtain a resin film.

[0039] (4) Preparation of resin-coated copper foil An electrolytic copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd.) having a thickness of 2 μm and a smooth surface with a surface texture aspect ratio Str of 0.39, a maximum height Sz of 0.81, a maximum peak height Sp of 0.40, and a root-mean-square gradient Sdq of 0.22 was prepared. The aspect ratio Str, maximum height Sz, maximum peak height Sp, and root-mean-square gradient Sdq of the surface texture were measured by surface roughness analysis using a laser microscope (manufactured by Olympus Corporation, OLS5000) in accordance with ISO25178 as follows. First, an area of ​​16384 μm on the smooth surface of the copper foil was measured. 2 The surface profile of the region was measured with the above laser microscope using a 100x objective lens under the conditions of scanning mode "3D standard + color" and shooting mode "Auto". After removing spike noise from the obtained smooth surface surface profile by noise removal and automatically removing the inclination, the aspect ratio Str of the surface texture was measured by surface texture analysis. At this time, shape removal was performed by F calculation (selecting "multiple surface 3rd order"), and the cutoff wavelength by the S filter was set to 0.55 μm and the cutoff wavelength by the L filter was set to 10 μm. The above Str, Sz, Sp, and Sdq were measured in eight different fields of view, and the average values ​​of Str, Sz, Sp, and Sdq in all fields of view were adopted as the values ​​of the smooth surface of the sample.

[0040] The diluted varnish obtained in (2) above was applied to the smooth surface of the copper foil using a bar coater, and then placed in an oven preheated to 150° C. for 2 minutes for heating and drying to obtain a resin-coated copper foil. At this time, the coating conditions were adjusted so that the thickness of the resin layer after drying would be 5 μm.

[0041] (5) Lamination with glass substrate The resin-coated copper foil obtained in (4) above was cut into a square of 10.5 cm x 10.5 cm. The cut resin-coated copper foil was placed on a 0.5 mm thick glass substrate (Corning, alkali-free glass, Eagle XG) measuring 10 cm x 10 cm so that the resin surface was in contact with the glass substrate, and laminated using a vacuum laminator. This lamination was performed by evacuation for 20 seconds, and then holding the laminate under conditions of 170°C and 0.95 MPa for 70 seconds. In this way, a laminated composite material comprising a glass substrate and a resin-coated copper foil was obtained.

[0042] (6) Main curing The laminated composite material obtained in (5) above was subjected to additional heat treatment to complete the curing, and a fully cured (C-stage) composite material comprising a glass substrate and a resin-coated copper foil was obtained. The additional heat treatment was performed by placing the composite material in an oven preheated to 230°C and holding it there for 30 minutes.

[0043] (7) Various evaluations The prepared resin films, resin-coated copper foils, and composite materials were evaluated as follows.

[0044] <Storage modulus> A rectangular sample of 5 mm x 50 mm was cut out from the resin film obtained in (3) above, and DMA measurement was performed using a DMA (dynamic viscoelasticity measurement) device (Hitachi High-Tech Science, DMA7100). This measurement was performed in accordance with JIS K 7244-4:1999, by placing a resin with a test piece width of 5.0 mm and a test piece thickness of 100 μm in a clamp with a clamp-to-clamp length of 20.0 mm, and heating it from 30 ° C. to 280 ° C. at a temperature increase rate of 5 ° C. / min in an air atmosphere, at a measurement frequency of 1 Hz. The obtained measurement data was analyzed, and the storage modulus E' (MPa) at 200 ° C. was calculated and evaluated according to the following criteria. The results were as shown in Table 2. - Rating AA: 100MPa or more - Rating A: 30MPa or more and less than 100MPa - Rating B: 10MPa or more and less than 30MPa - Rating C: Less than 10MPa

[0045] <Lamination properties (presence or absence of voids)> The composite material obtained in (5) above was visually observed from its glass surface to check for the presence or absence of voids and was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: No voids visible to the naked eye - Rating B: Voids can be visually confirmed - Evaluation C: The resin-coated copper foil is not attached to the glass substrate.

[0046] <Lamination properties (void occupancy rate)> The composite material obtained in (5) above was photographed from its glass surface using an optical microscope (Keyence, VHX7100). The photographed image was imported into image analysis software ImageJ (free software) and analyzed, and the ratio (%) of the void area to the photographed image area was calculated and evaluated according to the following criteria. The results are shown in Table 2. - Grade A: The void area is less than 1% - Grade B: The void area is 1% or more - Evaluation C: The resin-coated copper foil is not attached to the glass substrate.

[0047] <Lamination properties (adhesion)> When the composite material obtained in (5) above was handled (transported for the main curing in (6) above), it was checked whether the resin-coated copper foil peeled off from the glass (whether it was possible to handle it) and was evaluated according to the following criteria. The results are shown in Table 2. - Evaluation A: No peeling occurred and handling was possible without any problems. - Rating B: Handling caused peeling of less than 1 mm between the glass and resin at the edge of the sample. - Rating C: Handling caused peeling of 1 mm or more between the glass and resin at the edge of the sample.

[0048] <Adhesive strength> The composite material obtained in (6) above was copper plated to form copper wiring with a wiring width of 10 mm and a wiring thickness of 20 μm by a subtractive method, and the adhesive strength (peel strength) was measured in accordance with JIS C 6481. The measurement was performed five times, and the average value was taken as the adhesive strength value and evaluated according to the following criteria. The adhesive strength measured here is a value that reflects three failure modes: interfacial peeling between glass and resin, cohesive failure in the resin, and interfacial peeling between resin and copper foil, and the higher the value, the better the adhesion to glass, the strength of the resin layer, and the adhesion to the low roughness foil. The results are shown in Table 2. - Rating AA: Adhesive strength is 1.0kgf / cm or more - Rating A: Adhesive strength is 0.5kgf / cm or more and less than 1.0kgf / cm - Rating B: Adhesive strength is 0.1kgf / cm or more and less than 0.5kgf / cm - Rating C: Adhesive strength is less than 0.1kgf / cm

[0049] <Warping> The composite material obtained in (6) above was used to measure the amount of warping of the substrate using a 3D heating surface profiler (Thermoray PS200S, manufactured by Akrometrix). The amount of warping was calculated from the difference between the maximum and minimum Z coordinates of the glass laminate. The measurement was carried out five times in an atmosphere of 27°C, and the average of the measured values ​​was taken as the warping, which was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: Warpage is less than 500 μm - Rating C: Warpage is 500μm or more

[0050] <Dimensional stability (circuit formation)> The composite material obtained in (6) above was copper plated to a total thickness of the copper layer and the plating layer of 18 μm, and a parallel line circuit of L / S=100 μm / 100 μm was formed by a subtractive method. The composite material sample with the parallel line circuit formed was placed in an oven preheated to 250° C. and heat-treated for 30 minutes. After removing the sample and allowing it to cool, the sample was observed with an optical microscope to check for the presence or absence of wrinkles in the circuit and the base (resin composition), and evaluated according to the following criteria. The results are shown in Table 2. - Rating A: No wrinkles - Rating C: Wrinkled

[0051] [Table 1]

[0052] [Table 2]

Claims

1. A polyimide resin having a glass transition temperature Tg of 150° C. or lower; Epoxy resin, A hardener; A resin composition comprising: a resin composition having a storage modulus of 10 MPa or more at 200°C in a C-stage state after curing.

2. The resin composition according to claim 1 , wherein the epoxy resin comprises an epoxy resin having a functionality of 3 or more and an epoxy resin having a functionality of less than 3.

3. The resin composition according to claim 1 or 2, wherein the epoxy resin has a naphthalene skeleton.

4. The resin composition according to any one of claims 1 to 3, comprising 15 parts by weight or more and 65 parts by weight or less of the polyimide resin relative to 100 parts by weight of the total amount of the resin composition.

5. A copper layer having a smooth surface with an aspect ratio Str of a surface property of 0.3 or more and 1 or less as measured in accordance with ISO 25178; A resin layer formed on the smooth surface and composed of the resin composition according to any one of claims 1 to 4; The resin-coated copper foil is provided with:

6. 6. The resin-coated copper foil according to claim 5, wherein the copper layer has a thickness of 5 μm or less, and further comprises a carrier layer on the surface of the copper layer opposite to the smooth surface.

7. A glass substrate; The resin-coated copper foil according to claim 5 or 6, wherein the resin layer is provided on at least one surface of the glass substrate so as to be in contact with the glass substrate; A composite material comprising:

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