Stretchable film and stretchable wiring board using the same

Abstract

To provide a film material which is flexible and also has excellent laser processability.SOLUTION: A stretchable film is formed using a resin composition containing an acrylic resin (A) and a curing agent (B) and has an ultraviolet absorbance at 355 nm of 1.5 or more at a thickness of 100 μm and a glass transition temperature of 0°C or higher and lower than 50°C. In the resin composition, the acrylic resin (A) contains a polymerization unit (a1) of a (meth)acrylate having an epoxy group and a polymerization unit (a2) of a (meth)acrylate having one or more kinds of non-epoxy groups and has a weight average molecular weight of 50,000 or more and 3,000,000 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a stretchable film and a stretchable wiring board using the same.

Background Art

[0002] In recent years, circuit boards used in various electrical devices have been required to be further miniaturized and highly integrated. In response to such needs, a multilayer wiring board in which the circuit board is multilayered has been provided.

[0003] As a manufacturing method for multilayer wiring boards, a build-up type manufacturing method is known. In this method, an insulating film is laminated on a circuit board, and after the film is cured, via holes are formed using laser processing or the like. As a technique for improving the laser processability at that time, using a resin composition containing a specific styrene-based polymer, a specific inorganic filler, and a curing agent in a specific ratio (Patent Document 1), a film containing a fluororesin or a thermosetting resin and an inorganic filler having a predetermined specific surface area as an ultraviolet absorber in a specific ratio (Patent Documents 2 and 3) have been reported.

[0004] On the other hand, for devices and substrate materials used in various interfaces in the electronics field, particularly sensors, displays, artificial skin for robots, etc., the requirements for wearability and shape followability are increasing. Depending on the application, flexible devices and materials that can be arranged on curved surfaces, uneven surfaces, etc. or freely deformed are being demanded.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The techniques described in Patent Documents 1 to 3 focus on the laser processability of multilayer wiring boards. However, the resins disclosed in these documents have a high elastic modulus and poor stretchability. In addition, when the inorganic fillers used as ultraviolet absorber substances in the techniques described in these documents are highly filled in the resin composition, the elastic modulus further increases, and sufficient stretchability cannot be obtained.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a film material that can be used for a stretchable substrate having excellent followability and also has excellent laser processability.

Means for Solving the Problems

[0008] As a result of intensive studies, the present inventors have found that the above problems can be solved by the following configuration, and based on such findings, the present invention has been completed by further studies.

[0009] That is, the stretchable film according to one aspect of the present invention is formed using a resin composition containing an acrylic resin (A) and a curing agent (B), has an ultraviolet absorbance at 355 nm of 1.5 or more at a thickness of 100 μm, and a glass transition temperature of 0°C or more and less than 50°C. In the resin composition, the acrylic resin (A) contains a polymerization unit (a1) of (meth)acrylate having an epoxy group and a polymerization unit (a2) of (meth)acrylate having one or more non-epoxy groups, and the weight average molecular weight of the acrylic resin (A) is 50,000 or more and 3,000,000 or less.

Effects of the Invention

[0010] According to the present invention, a film material having flexibility and excellent laser processability can be provided.

Modes for Carrying Out the Invention

[0011] The stretchable film of this embodiment is formed using a resin composition containing an acrylic resin (A) and a curing agent (B). In the resin composition, the acrylic resin (A) contains a polymerization unit (a1) of (meth)acrylate having an epoxy group and a polymerization unit (a2) of one or more (meth)acrylates having no epoxy group, and the weight average molecular weight of the acrylic resin (A) is 50,000 or more and 3,000,000 or less. Further, the stretchable film of this embodiment has an ultraviolet absorbance at 355 nm of 1.5 or more and a glass transition temperature of 0°C or more and less than 50°C at a thickness of 100 μm.

[0012] The film of this embodiment has stretchability at room temperature, flexibility, and excellent heat resistance. Further, since it has excellent processability such as a UV (ultraviolet) laser, it can be suitably used for a stretchable multilayer wiring board.

[0013] Hereinafter, specific embodiments of the present invention will be described. However, the following embodiments are only one of various embodiments of the present invention, and various modifications can be made according to the design as long as the object of the present invention can be achieved.

[0014] (Resin composition) First, the resin composition for forming the stretchable film of this embodiment will be described. The resin composition of this embodiment contains at least an acrylic resin (A) and a curing agent (B).

[0015] · Acrylic resin (A) The acrylic resin in this embodiment refers to a polymer compound obtained by subjecting a compound having one or more acryloyl groups or methacryloyl groups to a polymerization reaction. In this embodiment, the acrylic resin serves as a binder and imparts flexibility to the cured product (film) of the composition.

[0016] The acrylic resin (A) of this embodiment has a weight average molecular weight of 50,000 or more and 3,000,000 or less, and contains a polymerization unit (a1) of (meth)acrylate having an epoxy group and a polymerization unit (a2) of one or more (meth)acrylates having no epoxy group.

[0017] When the weight-average molecular weight of the acrylic resin (A) used in this embodiment is within the above range, a resin film excellent in flexibility (stretchability), tensile strength (fracture resistance), and resin fluidity can be obtained. A more preferable lower limit value of the weight-average molecular weight is 100,000 or more, and more preferably 200,000 or more. On the other hand, a more preferable upper limit value is 2,000,000 or less, and more preferably 1,000,000 or less.

[0018] The acrylic resin (A) of this embodiment preferably does not have an unsaturated bond such as a double bond or a triple bond between carbon atoms. That is, it is preferable that the carbon atoms of the acrylic resin (A) are bonded by a saturated bond (single bond). By not having an unsaturated bond between carbon atoms, it is considered that it is not oxidized over time and can maintain more elasticity.

[0019] The acrylic resin (A) of this embodiment is a resin in which the polymerization unit (a1) and the polymerization unit (a2) are randomly polymerized. The form of polymerization is not particularly limited, and it may be a block copolymer, an alternating copolymer, a random copolymer, a graft copolymer, or the like.

[0020] In this embodiment, the polymerization unit (a1) of (meth)acrylate having an epoxy group imparts a crosslinking point to the acrylic resin (A) of this embodiment and enables curing. Further, since the acrylic resin (A) has an epoxy group, it is considered that the heat resistance of the cured product after heat curing is improved.

[0021] The content of the polymerization unit (a1) in the acrylic resin (A) is not particularly limited, but it is preferably such that the epoxy equivalent is about 500 g / eq or more and 5000 g / eq or less with respect to the total amount of the acrylic resin (A). When the epoxy equivalent is within such a range, it is considered that a resin composition having heat resistance and an appropriate elastic modulus can be obtained more reliably. When the epoxy equivalent is less than 500 g / eq, the elastic modulus after curing becomes too high, and there is a risk of breakage during stretching. Further, when the epoxy equivalent exceeds 5000 g / eq, the elastic modulus after curing at high temperature becomes low, and for example, the film may be deformed in the reflow process, resulting in a mounting defect. A more preferable range of the epoxy equivalent is 1000 g / eq or more and 3000 g / eq or less.

[0022] Specific examples of the (meth)acrylate monomer constituting the polymerization unit (a1) having an epoxy group include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, β-ethylglycidyl (meth)acrylate, glycidyl vinyl ether, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, o-isopropenylbenzyl glycidyl ether, m-isopropenylbenzyl glycidyl ether, p-isopropenylbenzyl glycidyl ether, and the like. These may be used alone or in combination of two or more.

[0023] In the present embodiment, in addition to the polymerization unit (a1) described above, the acrylic resin contains a polymerization unit (a2) of one or more (meth)acrylates having no epoxy group.

[0024] Examples of the non-epoxy group include a cyano group, an isobornyl group, an ethyl group, a hydroxyethyl group, a butyl group, a methyl group, an ethylhexyl group, a cyclohexyl group, a benzyl group, etc. The (meth)acrylate of the polymerization unit (a2) has one or two or more of these non-epoxy groups. Preferably, the polymerization unit (a2) of the (meth)acrylate has a cyano group and / or an isobornyl group.

[0025] Specific examples of the (meth)acrylate monomer constituting the polymerized unit (a2) having a cyano group are not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, and the like. Specific examples of the acrylate or (meth)acrylate monomer constituting the polymerized unit (a2) having an isobornyl group are not particularly limited, and examples thereof include isobornyl (meth)acrylate and the like.

[0026] The resin composition of the present embodiment preferably contains the polymerized unit (a2) component in an amount of 70 parts by mass or more and 99 parts by mass or less with respect to 100 parts by mass of the acrylic resin (A). With the content within this range, it is considered that the above-described effects can be obtained more reliably. A more preferable content of the polymerized unit (a2) component is 80 parts by mass or more and 97 parts by mass or less with respect to 100 parts by mass of the acrylic resin (A).

[0027] The blending ratio of the acrylic resin (A) in the resin composition of the present embodiment is not particularly limited as long as the effects of the present invention such as flexibility and laser processability can be obtained. For example, it is preferably about 30 to 95% by mass with respect to the entire resin composition.

[0028] Furthermore, the resin composition of the present embodiment may contain a resin other than the acrylic resin (A), and an epoxy resin, a urethane resin, an acrylic resin, a fluororesin, a silicone resin, etc. can be further added according to the purpose.

[0029] · Curing agent (B) The resin composition of this embodiment further contains a curing agent (B). The curing agent (B) that can be used in this embodiment is not particularly limited as long as it functions as a curing agent for epoxy. Specifically, for example, phenol resins, amine compounds, acid anhydrides, imidazole compounds, sulfide resins, dicyandiamide, mercapto compounds, onium salts, peroxides, etc. can be cited as examples. Also, photo / ultraviolet curing agents, thermal cationic curing agents, etc. can also be used. These may be used singly, one type at a time, or in combination of two or more types, depending on the situation. Preferably, the curing agent of this embodiment contains at least one selected from acid anhydrides, amine-based curing agents, phenol-based curing agents, and carboxylic acid-based curing agents.

[0030] Among these, it is preferable to use an acid anhydride as the curing agent (B). Examples of acid anhydride curing agents include maleic anhydride, succinic anhydride, itaconic anhydride, citraconic anhydride, phthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride, methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride, and the like.

[0031] Preferably, the curing agent (B) of this embodiment desirably contains a polyfunctional acid anhydride having two or more functional groups. Thereby, there is an advantage that three-dimensional crosslinking can be achieved and deformation at high temperatures can be particularly suppressed. Also, the curing shrinkage can be reduced.

[0032] As the polyfunctional acid anhydride having two or more functional groups, commercially available ones can be used. For example, Rikacid BT-100, TDA-100, TBN-100 (all manufactured by Shin Nippon Rika Co., Ltd.), ENEHYDE CpODA (manufactured by JXTG Energy Corporation), etc. can be cited.

[0033] In the resin composition of the present embodiment, the content of the curing agent (B) can be appropriately set according to the epoxy equivalent. For example, the content of the curing agent (B) in the total amount of the resin composition is preferably 5% by mass or more and 70% by mass or less, and more preferably 7% by mass or more and 60% by mass or less.

[0034] · Ultraviolet absorber (C) The resin composition of the present embodiment preferably further contains an ultraviolet absorber (C). Thereby, excellent laser processability can be more reliably obtained.

[0035] The ultraviolet absorber (C) preferably contains a triazine derivative. Thereby, the compatibility of the ultraviolet absorber (C) in the resin composition becomes good, and the efficiency of UV absorption becomes more excellent. Therefore, the workability when preparing a resin varnish using the resin composition of the present embodiment is improved, and laser processability can also be more reliably obtained.

[0036] Examples of the triazine derivative include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine, 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2,4-dihydroxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)phenol, tri-(m-tolyl)-1,3,5-triazine-2,4,6-triamine, 2,4,6-tris(2,4-dihydroxyphenyl)-1,3,5-triazine, 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine, ethylhexyl triazone, 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-n-octyloxyphenyl)-1,3,5-triazine, bemotrizinol, 2-(2-hydroxy-4-(1-octyloxycarbonylmethyl)oxyphenyl)-4,6-bis(4-phenyl)phenyl-1,3,5-triazine, 2-(4-(2-hydroxy-3-tridecyloxypropyl)oxy)-2-hydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and the like.

[0037] Commercially available triazine derivatives may be used. Specific examples include "Tinuvin 400", "Tinuvin 477", "Tinuvin 479", "Tinuvin 405", etc. manufactured by BASF Japan Ltd.

[0038] From the viewpoints of the heat resistance of the film and the compatibility of the ultraviolet absorber (C) in the resin composition, the ultraviolet absorber (C) of this embodiment preferably has a weight average molecular weight of 200 or more and 2000 or less. More preferably, it is 500 or more and 1500 or less.

[0039] In this embodiment, the content of the ultraviolet absorber (C) in the total amount of the resin composition is preferably 0.2% by mass or more and 10% by mass or less. Thereby, it is considered that the heat resistance of the film and the compatibility of the ultraviolet absorber (C) in the resin composition can be more reliably obtained. A more preferable content is 1% by mass or more and 5% by mass or less, and an even more preferable content is 1% by mass or more and 3% by mass or less.

[0040] Furthermore, the resin composition according to this embodiment may contain other additives, such as a curing accelerator (curing catalyst), a surfactant, a flame retardant, a flame retardant aid, a leveling agent, a coloring agent, an infrared absorber, an antistatic agent, a conductive aid, inorganic fine particles, etc., as long as the effects of the present invention are not impaired.

[0041] The curing accelerator (curing catalyst) that can be used in this embodiment is not particularly limited. For example, imidazoles and their derivatives, organophosphorus compounds, metal soaps such as zinc octanoate, secondary amines, tertiary amines, quaternary ammonium salts, etc. can be used. These may be used alone or in combination of two or more depending on the situation.

[0042] When using a curing accelerator, its content is preferably used so as to be 0.01% by mass or more and 3% by mass or less with respect to 100 parts by mass of the resin composition.

[0043] (Preparation of Resin Composition and Film) The stretchable film of this embodiment is formed using the resin composition as described above. There is no particular limitation on the method for preparing the resin composition of this embodiment. For example, the acrylic resin (A), the curing agent (B), and, if necessary, the ultraviolet absorber (C) and other additives are mixed with a solvent so as to be uniform. There is no particular limitation on the solvent to be used. For example, toluene, xylene, methyl ethyl ketone, acetone, etc. can be used. These solvents may be used alone or in combination of two or more. Furthermore, here, an organic solvent for adjusting the viscosity and various additives may be blended as necessary.

[0044] By heating and drying the resin composition obtained as described above to evaporate the solvent, the stretchable film of the present embodiment can be obtained.

[0045] Regarding the method, apparatus, and their conditions for heating and drying the resin composition, various means similar to the conventional ones or their improved means may be used. The specific heating temperature and time can be appropriately set depending on the curing agent, solvent, etc. used. For example, by drying at 80 to 110°C for about 5 to 15 minutes, the resin composition can be made into a resin film. Further, by heating and curing at 120 to 180°C for about 20 to 60 minutes, it may be a cured film in which the resin composition is completely cured.

[0046] Note that the stretchable film of the present embodiment may be composed only of the resin composition described above or its semi-cured product or cured product, but it may also be in the form of a film with resin having a resin layer containing the resin composition or its semi-cured product and a support (support film). Examples of the support include electrically insulating films such as polyimide films, PET (polyethylene terephthalate) films, polyester films, polyparabanic acid films, polyether ether ketone films, polyphenylene sulfide films, aramid films, polycarbonate films, and polyarylate films.

[0047] The resin-coated film (resin sheet material) of the present embodiment may be a resin-coated film including the resin composition before curing (the resin composition in the A stage) and a support, or a resin-coated film including a semi-cured product of the resin composition (the resin composition in the B stage) and a support.

[0048] As a method for manufacturing such a film with resin, for example, after applying a resin composition in the form of a resin varnish as described above to the surface of a film support substrate, the solvent is volatilized from the varnish to reduce or remove the solvent, thereby obtaining a resin-coated film in a pre-cured (A stage) or semi-cured state (B stage).

[0049] In the present embodiment, the "semi-cured product" refers to a state in which the resin composition is cured halfway to such an extent that it can be further cured. That is, the semi-cured product is in a state where the resin composition is semi-cured (B-staged). For example, when the resin composition is heated, first, the viscosity gradually decreases, and then, curing starts and the viscosity gradually increases. In such a case, examples of semi-curing include the state after the viscosity starts to increase and before complete curing.

[0050] (Stretchable film) The stretchable film of the present embodiment has an ultraviolet absorbance at 355 nm of 1.5 or more and a glass transition temperature of 0°C or more and less than 50°C at a thickness of 100 μm. With such a configuration, the stretchable film of the present embodiment has stretchability at room temperature, is flexible, and is excellent in heat resistance and processability such as UV (ultraviolet) laser.

[0051] The ultraviolet absorbance is a value measured in the cured stretchable film and is a value obtained by ultraviolet-visible absorption spectroscopy (UV-VIS). A more preferable range of the ultraviolet absorbance is 1.5 or more.

[0052] The glass transition (Tg) temperature is also a value measured in the cured stretchable film and is a value obtained by the method described in the examples below.

[0053] In addition, in this embodiment, "being stretchable" and "being flexible" mean that in the film (or the cured product of the resin composition), the elongation rate until breakage is 5.0% or more, preferably 10% or more, more preferably 25% or more, still more preferably 50%, and most preferably 100% or more. There is no particular need to provide an upper limit value. However, from the perspective of damaging the original shape when stretched more than necessary, it is preferable that the elongation rate does not exceed 500%. Further, the tensile elastic modulus at 25°C room temperature in the film (or the cured product of the resin composition) of this embodiment is 0.1 MPa or more and 0.5 GPa or less, preferably 1 MPa or more and 300 MPa or less, more preferably 5 MPa or more and 100 MPa or less. The values of the "elongation rate until breakage" and the "tensile elastic modulus at 25°C room temperature" in this embodiment are the values obtained by the following methods.

[0054] First, cut the film into dumbbell No. 6 shape (JIS K 6251, 2017), and attach it to a universal testing machine (AGS-X manufactured by Shimadzu Corporation). Then, conduct the test at a tensile speed of 25 mm / min, and calculate the initial tensile elastic modulus by obtaining the slope of r-σ using the least squares method from all stress (σ) data corresponding to the strain (r) from 0 to 0.05. Strain (r) = x / x0 (x is the moving distance of the grip, x0 is the initial distance between grips) Stress (σ) = F / (d·l) (F is the test force, d is the film thickness, l is the width of the test piece)

[0055] In addition, the "elongation rate until breakage" in this embodiment is indicated by the elongation at break rate (%), and can be obtained by measuring the elongation rate when the resin film breaks with the said tester.

[0056] The stretchable film of this embodiment may be a cured product obtained by completely curing the resin composition as described above, or a semi-cured product obtained by semi-curing. When it is a film in a cured state, it preferably has an adhesive performance with a peel strength of 0.5 N / mm or more. By having such a peel strength, the stretchable film of this embodiment is excellent in adhesiveness in addition to flexibility and heat resistance, and can be suitably used for purposes such as lamination and circuit protection.

[0057] The thickness of the stretchable film of this embodiment is not particularly limited, but from the viewpoints of an electronic substrate, lamination of electronic substrates, handling in manufacturing, etc., it is preferably 10 μm or more and 200 μm or less. A more preferable film thickness is 25 μm or more and 100 μm or less.

[0058] (Applications of the stretchable film) The stretchable film of this embodiment can be used as a material or substrate for various electronic components and the like in various applications. In particular, since it is excellent in flexibility, adhesiveness, and laser processability, for example, it is very suitable as a circuit material used in devices such as smartphones, sensors, flat cables, and wearable devices that require two or more layers of high-density wiring.

[0059] The stretchable film of this embodiment may be provided with a metal foil on at least one surface. That is, this embodiment includes a metal foil with resin using the stretchable film, a metal-clad laminate, a wiring board, and the like.

[0060] The metal foil with resin of this embodiment has a resin layer including the above-described film and a metal foil overlapping the resin layer. That is, it has a configuration in which the metal foil is laminated on at least one side of the stretchable film. The metal foil may be on both sides of the resin layer. The metal foil with resin of this embodiment may be a metal foil with resin including a resin layer containing the resin composition before curing (the resin composition in the A stage) and a metal foil, or a metal foil with resin including a resin layer containing a semi-cured product of the resin composition (the resin composition in the B stage) and a metal foil.

[0061] Examples of a method for producing such a resin-coated metal foil include a method in which the resin composition in the form of a resin varnish as described above is applied to the surface of a metal foil such as a copper foil, and then dried. Examples of the application method include a bar coater, a comma coater, a die coater, a roll coater, a gravure coater, etc.

[0062] The metal foil may be any metal foil used in general metal-clad laminates, wiring boards, etc., without any limitations, and examples thereof include copper foil, aluminum foil, etc. The thickness of such metal foil may be appropriately set according to the desired purpose.

[0063] The drying or heat drying conditions in the method for producing a resin-coated metal foil are not particularly limited, but may be the same as the drying or heat drying conditions in the method for producing the film described above.

[0064] The resin-coated metal foil may be provided with a cover film, etc., if necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited as long as it can be peeled off without damaging the shape of the resin composition, but for example, a polyolefin film, a polyester film, a TPX film, a film formed by providing a release agent layer on these films, and further a paper in which these films are laminated on a paper base material can be used.

[0065] The metal-clad laminate included in this embodiment has an insulating layer containing the above-mentioned stretchable film or the above-mentioned cured product of the resin composition, and a metal foil overlapping the insulating layer. The metal foil used in the metal-clad laminate can be the same as the above-mentioned metal foil.

[0066] In addition, the metal-clad laminate of the present embodiment can be produced, for example, by stacking one or more of the above-mentioned stretchable films, further stacking metal foils such as copper foils on both sides or one side of the upper and lower surfaces thereof, and integrally laminating them by heating and pressing. The heating and pressing conditions can be appropriately set according to the thickness of the laminate to be produced, the type of the resin composition, etc. For example, the temperature can be 150 to 220 °C, the pressure can be 0.1 to 3.0 MPa, and the time can be 60 to 180 minutes.

[0067] And the wiring board included in the present embodiment has an insulating layer containing the above-mentioned stretchable film or a cured product of the above-mentioned resin composition, and wiring. The wiring is provided on at least one selected from the surface and the inside of the insulating layer.

[0068] The stretchable film of the present embodiment is suitably used as a material for the insulating layer of a multilayer wiring board manufactured by the build-up method. As a method for manufacturing a wiring board, for example, by forming a circuit (wiring) by etching the metal foil on the surface of the metal-clad laminate obtained above, a wiring board provided with a conductor pattern (wiring) as a circuit on the surface of the laminate can be obtained. As a method for forming a circuit, in addition to the method described above, for example, circuit formation by the semi-additive method (SAP: Semi Additive Process) or the modified semi-additive method (MSAP: Modified Semi Additive Process) can be mentioned.

[0069] The resin-coated metal foil, metal-clad laminate, and wiring board obtained by using the stretchable film of the present embodiment are excellent in flexibility, heat resistance, and adhesion, and are also excellent in laser processability, so they are very useful in industrial applications.

[0070] This specification discloses various aspects of technology as described above, and the main technologies are summarized below.

[0071] The stretchable film according to the first aspect of the present invention is formed using a resin composition containing an acrylic resin (A) and a curing agent (B), has an ultraviolet absorbance at 355 nm of 1.5 or more at a thickness of 100 μm, and a glass transition temperature of 0°C or more and less than 50°C. In the resin composition, the acrylic resin (A) contains a polymerization unit (a1) of (meth)acrylate having an epoxy group and a polymerization unit (a2) of (meth)acrylate having one or more non-epoxy groups, and the weight average molecular weight of the acrylic resin (A) is 50,000 or more and 3,000,000 or less.

[0072] The stretchable film according to the second aspect is the stretchable film of the first aspect, wherein the resin composition further contains an ultraviolet absorber (C).

[0073] The stretchable film according to the third aspect is the stretchable film of the second aspect, wherein the ultraviolet absorber (C) contains a triazine derivative.

[0074] The stretchable film according to the fourth aspect is the stretchable film of the second or third aspect, characterized in that the content of the ultraviolet absorber (C) in the total amount of the resin composition is 0.2% by mass or more and less than 10% by mass.

[0075] The stretchable film according to the fifth aspect is the stretchable film of any one of the second to fourth aspects, characterized in that the weight average molecular weight of the ultraviolet absorber (C) is 500 or more and 1000 or less.

[0076] The stretchable film according to the sixth aspect is the stretchable film of any one of the first to fifth aspects, characterized in that the epoxy equivalent of the acrylic resin (A) is 1000 g / eq or more and 5000 g / eq or less.

[0077] The stretchable film according to the seventh aspect is the stretchable film of any one of the first to sixth aspects, characterized in that the content of the curing agent (B) in the total amount of the resin composition is 5% by mass or more and 30% by mass or less.

[0078] The stretchable film according to the eighth aspect is characterized in that, among the stretchable films of any one of the first to seventh aspects, it has an adhesive strength of 0.5 N / mm or more.

[0079] The stretchable film according to the ninth aspect is characterized in that, among the stretchable films of any one of the first to eighth aspects, it is provided with a metal foil on at least one surface.

[0080] The stretchable multilayer wiring board according to the tenth aspect is formed using the stretchable film of any one of the first to ninth aspects.

[0081] Hereinafter, the present invention will be described more specifically with reference to examples, but the scope of the present invention is not limited thereto.

Examples

[0082] First, the various materials used in this example are as follows.

[0083] <Acrylic resin (A)> · Preparation of acrylic resin In addition to acrylonitrile and isobornyl acrylate as polymerization units (a2), the polymerization unit represented by the following formula (1) was used at a blending ratio (polymerization%) of 10:20:70, respectively. Further, glycidyl methacrylate was added as the polymerization unit (a1) so that the epoxy equivalent with respect to the total amount of the acrylic resin was 1818 g / eq. Then, the mixture was subjected to a polymerization reaction to obtain Acrylic Resin 1 (manufactured by Nagase ChemteX Corporation, "PMS-14-67", weight average molecular weight 290,000) containing methyl ethyl ketone as a solvent. The solid content ratio was 40% by weight.

[0084]

Chemical formula

[0085] (In the formula, R1 is hydrogen or a methyl group, and R2 is hydrogen or an alkyl group. Also, X represents an integer.)

[0086] <Hardening agent (B)> · Acid anhydride (Rika Acid TBN-100, Shin Nippon Rika Co., Ltd.) <Ultraviolet absorber (C)> (Ultraviolet absorber (C) containing a triazine derivative) · Ultraviolet absorber 1: 2,4,6-Tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine (Product name: "LA-F70", manufactured by Adeka Corporation, weight average molecular weight 700) · Ultraviolet absorber 2: 2-[4,6-Bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol (Product name: "Tinuvin400", manufactured by BASF Japan Ltd., weight average molecular weight 1293) · Ultraviolet absorber 3: Black dye (Product name: "RN-1", manufactured by Chuo Gosei Chemical Co., Ltd., weight average molecular weight of the mixture 500 - 1000) · Ultraviolet absorber 4: 7-Diethylamino-4-methylcoumarin (weight average molecular weight 231) · Ultraviolet absorber 5: Pyrazoline-based coloring agent (Product name: "HR-101", manufactured by Chuo Gosei Chemical Co., Ltd., weight average molecular weight 231) · Ultraviolet absorber 6: 2,3-Dimethyl-4-(dimethylamino)-1-phenyl-3-pyrazolin-5-one (weight average molecular weight 203) <Hardening catalyst> · Imidazole-based hardening catalyst "2PZ-CN" (manufactured by Shikoku Chemicals Corporation)

[0087] [Method for preparing the resin composition] Based on the blending ratios (parts by mass) shown in Table 1, various components were blended to prepare mixtures of Formulations 1 to 13. Methyl ethyl ketone was used as the carrier solvent, and the solid content concentration in the mixture was adjusted to 35%. The mixture was stirred at 1000 RPM for 10 minutes using a homodisper to obtain a solution of the resin composition (resin varnish).

[0088]

Table 1

[0089] · Preparation of Samples for Laser Processability Evaluation Among the obtained resin varnishes, the resin varnishes of Formulations 1 to 4 and Formulations 10 to 13 were used, coated on a copper foil (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., thickness 18 μm), dried at 100 °C for 10 minutes to remove the solvent. Then, it was heat-cured at 170 °C for 90 minutes to obtain a copper foil with a resin layer having a cured resin layer thickness of 100 μm (a film provided with a copper foil).

[0090] (Evaluation of Laser Processability) For the samples (films provided with a copper foil) of Examples 1 to 4 and Comparative Examples 1 to 4, drilling was performed under the same conditions using a laser (a UV-YAG laser manufactured by ESIA Japan Co., Ltd.), and the cross-section of the hole diameter was observed and measured with an optical microscope. The hole diameters of the upper surface hole diameter (upper surface diameter) and the lower surface hole diameter (bottom surface diameter) were measured respectively, and the ratio of the upper surface diameter / bottom surface diameter was determined. In this test, if the ratio of the bottom surface diameter / upper surface diameter was 0.5 or more, it was judged as qualified.

[0091] (Ultraviolet Absorbance) All the copper foils were removed from the samples (films) of Examples 1 to 4 and Comparative Examples 1 to 4 by etching, and after drying sufficiently, the absorbance at 355 nm (ultraviolet light) was measured with a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies).

[0092] (Glass Transition Temperature) The glass transition temperature of the cured film was measured by DMS6100 (manufactured by SII NanoTechnology Inc.). The measurement thickness was 50 μm.

[0093] The above results are summarized in Table 2.

[0094]

Table 2

[0095] (Evaluation of Solubility) In the resin varnishes of Formulations 1 to 13 prepared above, the dissolution time of the ultraviolet absorber was measured, and the time until it dissolved was measured and evaluated as the dissolution time. Also, formulations that did not dissolve even after 10 minutes were evaluated as non-conforming. The results are shown in Table 3.

[0096]

Table 3

[0097] (Discussion) In the samples of Examples 1 to 4, it was confirmed that the ultraviolet absorbance at 355 nm was 1.5 or more, and all the lasers had penetrated. From this result, it was confirmed that the stretchable film of the present embodiment can provide a material that has stretchability and excellent processability.

[0098] On the other hand, in one of the comparative examples, the absorbance at 355 nm was low, and it was also impossible to penetrate in laser processing.

[0099] In the resin composition of Comparative Example 1, a pyrazoline-based derivative was used as the ultraviolet absorber, and it was found that when a pyrazoline-based derivative was used, sufficient absorption efficiency of ultraviolet light at 355 nm could not be obtained.

[0100] Comparative Example 2 did not contain an ultraviolet absorber, and in that case, it was confirmed that the ultraviolet absorbance was extremely low.

[0101] In Comparative Examples 3 and 4, a pyrazoline-based compound was used, and the absorption efficiency when made into a varnish was lower than that of a triazine-based compound. Also, in the formulation of the triazine-based compound, the addition amount was insufficient, so sufficient absorption efficiency of ultraviolet light at 355 nm could not be obtained, and for laser processability, the laser light passed through and processing could not be performed.

[0102] Regarding the solubility of the ultraviolet absorber, as shown in Table 3, all of them became uniform solutions except that in Formulation 1, although a black dye was used, it did not completely dissolve. Formulation 9 took the longest time until the ultraviolet absorber dissolved. Formulation 1 was dark in color and almost black. Also, Formulation 2 was clearly yellow, and the others were light yellow to transparent. From the results in this Table 3, it was found that by containing the ultraviolet absorber in an appropriate content, the compatibility between the acrylic resin and the ultraviolet absorber was excellent, and the workability during the preparation of the resin varnish was improved.

Claims

1. Formed using a resin composition containing an acrylic resin (A) and a curing agent (B), At a thickness of 100 μm, the ultraviolet absorbance at 355 nm is 1.5 or more, The glass transition temperature is 0°C or more and less than 50°C, In the resin composition, the acrylic resin (A) contains a polymerization unit (a1) of (meth)acrylate having an epoxy group and a polymerization unit (a2) of (meth)acrylate having one or more non-epoxy groups, and the weight average molecular weight of the acrylic resin (A) is 50,000 or more and 3,000,000 or less, A stretchable film.

2. The stretchable film according to Claim 1, wherein the resin composition further contains an ultraviolet absorber (C).

3. The stretchable film according to Claim 2, wherein the ultraviolet absorber (C) contains a triazine derivative.

4. The stretchable film according to Claim 2, wherein the content of the ultraviolet absorber (C) in the total amount of the resin composition is 0.2% by mass or more and less than 10% by mass.

5. The stretchable film according to Claim 2, wherein the weight average molecular weight of the ultraviolet absorber (C) is 500 or more and 1000 or less.

6. The stretchable film according to Claim 1, wherein the epoxy equivalent of the acrylic resin (A) is 1000 g / eq or more and 5000 g / eq or less.

7. The stretchable film according to Claim 1, wherein the content of the curing agent (B) in the total amount of the resin composition is 5% by mass or more and 30% by mass or less.

8. The stretchable film according to Claim 1, having an adhesive strength of 0.5 N / mm or more.

9. The stretchable film according to Claim 1, having a metal foil provided on at least one surface.

10. A stretchable wiring board formed using the stretchable film according to any one of Claims 1 to 9.

11. The stretchable wiring board according to Claim 10, which is multilayer.