Adhesive film, and connection structure and method for producing same

Abstract

An adhesive film according to the present invention exhibits rapid low-temperature curability, good adhesive strength, and good connection reliability, and can be stably slit into narrow widths and also has good temporary adhesiveness. This adhesive film has a base material film on which a release treatment has been executed, and has an insulating resin layer that is provided on the base material film and that exhibits radical polymerizability and anionic polymerizability. The adhesive film has a film width of not more than 1.0 mm or not more than 0.8 mm, and has a length of at least 5 m. The insulating resin layer contains: a film-forming component containing two types of film components having different molecular weights; a radical-polymerizable component containing a first acrylic compound; an anionic polymerizable component containing an epoxy compound; a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of not more than 125°C; and an anionic polymerization curing agent containing an organic acid hydrazide compound that is a solid at ordinary temperatures.

Description

Adhesive film, connection structure and method for manufacturing the same

[0001] The present invention relates to an adhesive film, a connection structure, and a method for producing the same.

[0002] Adhesive films having an insulating resin layer provided on a release-treated substrate film are widely used, and examples thereof include adhesive films having a substrate film provided with a conductive particle-containing insulating resin layer in which conductive particles are dispersed or regularly arranged, and adhesive films having a substrate film provided with an insulating resin layer containing no conductive particles and a conductive particle-containing layer in which conductive particles are incorporated into a binder resin, which are widely used as anisotropic conductive films. As such anisotropic conductive films, from the viewpoint of low-temperature, short-time curing (low-temperature fast curing), a film has been proposed in which conductive particles are mixed with a radical-polymerizable resin composition containing a radical-polymerizable compound such as a (meth)acrylate and a radical polymerization initiator (organic peroxide) and the mixture is molded into a film (Patent Document 1), and from the viewpoint of good adhesive strength, heat resistance, water resistance, and flexibility, a film has been proposed in which conductive particles are mixed with an anionic-polymerizable resin composition containing an anionic-polymerizable epoxy compound, a glycidyl ether group-containing acrylic rubber, and an anionic polymerization curing agent and the mixture is molded into a film (Patent Document 2).

[0003] In recent years, from the viewpoint of simultaneously achieving the advantages of producing an anisotropic conductive film from such a radical polymerizable resin composition (low-temperature rapid curing property) and the advantages of producing an anisotropic conductive film from an anionic polymerizable resin composition (good adhesive strength, heat resistance, water resistance, and flexibility), a hybrid curable resin composition containing a radical polymerizable compound, an anionic polymerizable compound, a radical polymerization initiator, and an anionic polymerization curing agent has been proposed, in which conductive particles are mixed with the composition and the composition is molded into a film (Patent Document 3).

[0004] WO1998044067A1WO1998003047A1 JP 2007-224228 A

[0005] However, the initial adhesive strength of a semiconductor device obtained by anisotropically conductively connecting an IC chip to a circuit board using the anisotropic conductive film disclosed in Patent Document 3 may not be sufficient, and if a semiconductor device obtained in this manner is accidentally placed in a high-temperature, high-humidity environment, there is a problem that the connection reliability may decrease, or even if the connection reliability does not decrease, the visibility of the indentations of the conductive particles at the connection portion of the connection structure may decrease, and a ``floating'' may occur at the connection portion that may impair the connection reliability of the connection structure. Furthermore, to achieve finer connection structures, higher-density packaging, and improved handleability, it is necessary to slit an anisotropic conductive film to a narrow width of 1.0 mm or less, even 0.8 mm or less, and a length of 5 m or more. However, with the anisotropic conductive film disclosed in Patent Document 3, when attempting to slit to a narrow width, various slitting defects occur during film production, such as the insulating resin layer adhering to the slitting blade during slitting or a portion of the insulating resin layer peeling off from the substrate film, causing contamination of the equipment. In particular, if a portion of the insulating resin layer peels off from the substrate film, it becomes impossible to produce a long wound body. Even if a long wound body can be produced without causing equipment contamination, blocking occurs in the wound body due to peeling of the anisotropic conductive film from the substrate film or resin overflow caused by such peeling. Another problem is the reduced temporary adhesion of the anisotropic conductive film during the anisotropic conductive connection process. Thus, the narrower the slit width, the more difficult it becomes to slit reliably.

[0006] The object of the present invention is to solve the problems of the related art, and to provide a base film that has been subjected to a release treatment, on which an insulating resin layer formed from a hybrid curable resin composition containing a radical polymerizable compound, an anionic polymerizable compound, a radical polymerization initiator, and an anionic polymerization curing agent is provided, and when a connection structure is created by connecting a first electronic component and a second electronic component using an adhesive film slit into a narrow width of 1.0 mm or less, or even 0.8 mm or less, and a length of 5 m or more, the connection structure exhibits low-temperature rapid curing properties, achieves good initial adhesive strength, and even if the connection structure is accidentally placed in a high-temperature, high-humidity environment, the connection reliability is not reduced, good visibility of the conductive particle impressions at the connection portion of the connection structure is ensured, and lifting is not caused at the connection portion. The adhesive film itself can be stably slit into a narrow width that allows the creation of a wound body that does not cause blocking, and further, temporary adhesion properties are not reduced even when slit into a very narrow width.

[0007] The inventors have discovered that by forming the insulating resin layer of an adhesive film from a composition for forming an insulating resin layer that is prepared from specific components and exhibits radical polymerization and anionic polymerization, not only low-temperature rapid curing properties but also good initial adhesive strength can be achieved for the connection structure, and even if the connection structure is accidentally placed in a high-temperature, high-humidity environment, good visibility of the conductive particle impressions at the connection portion of the connection structure is ensured without reducing connection reliability, and floating at the connection portion can be prevented.Furthermore, they have discovered that adhesive films such as anisotropic conductive films can be stably slit to narrow widths that allow the creation of wound bodies that do not cause blocking, and that temporary adhesion properties are not reduced even when slit to narrow widths, thereby completing the present invention.

[0008] That is, the present invention provides an adhesive film having a base film that has been subjected to a release treatment and an insulating resin layer that is provided thereon and exhibits both radical and anionic polymerizability, wherein the insulating resin layer contains the following components A, B, C, D, and E: (Component A) a film-forming component containing a first film component having a weight-average molecular weight of 50,000 or more and 80,000 or less, and a second film component having a weight-average molecular weight of 30,000 or more and less than 50,000; (Component B) a radically polymerizable component containing a first acrylic compound; (Component C) an anionic polymerizable component containing an epoxy compound; (Component D) a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125°C or less; and (Component E) an anionic polymerization curing agent containing an organic acid hydrazide compound that is solid at room temperature; and the adhesive film has a film width of 1.0 mm or less and a length of 5 m or more.

[0009] The present invention also provides a method for producing an adhesive film, which comprises forming a composition for forming an insulating resin layer on a base film that has been subjected to a release treatment, and slitting the film to a width of 1.0 mm or less and a length of 5 m or more, wherein the insulating resin layer contains the aforementioned components A, B, C, D, and E. The present invention also provides a connection structure in which a first electronic component and a second electronic component are connected via the adhesive film of the present invention, and a method for producing a connection structure in which the first electronic component and the second electronic component are connected by sandwiching the adhesive film of the present invention between them and pressing them together.

[0010] In order to obtain good low-temperature, rapid curing properties in the adhesive film of the present invention, the preferred one-minute half-life temperature of the organic peroxide of component D is 100°C or higher and 120°C or lower, and the preferred melting point of the organic acid hydrazide compound of component E is 80°C or higher and 160°C or lower.

[0011] In addition, in the adhesive film of the present invention, the first film component and the second film component of component A are preferably both bisphenol A phenoxy resin from the viewpoint of impact resistance, etc., the first acrylic compound of component B is preferably urethane (meth)acrylate from the viewpoint of improving the adhesive strength of the cured product and improving the conduction reliability, the epoxy compound of component C is preferably bisphenol A liquid epoxy resin, the organic peroxide of component D is preferably dilauroyl peroxide, and the organic acid hydrazide compound of component E is preferably salicylic acid hydrazide.

[0012] In the present invention, the insulating resin layer preferably further contains a polyfunctional (meth)acrylate as a crosslinking agent in order to improve the mechanical strength of the adhesive film, and particularly preferably contains an isocyanuric acid EO-modified di- or tri(meth)acrylate.

[0013] The insulating resin layer preferably contains an adhesion improver to improve the aging resistance of the adhesive film. As the adhesion improver, a silane coupling agent is preferred, and among them, an alkoxysilane having an epoxy group, particularly 3-glycidoxypropyltriethoxysilane, is preferred.

[0014] In the adhesive film of the present invention, conductive particles can be contained in the insulating resin layer. This allows the adhesive film to function as a conductive film or an anisotropic conductive film. When the description of an anisotropic conductive film is replaced with conductive film, it can be replaced if there is no problem.

[0015] The adhesive film of the present invention preferably further comprises a conductive particle-containing layer containing the following components a to d on the surface of the insulating resin layer opposite the base film: By laminating the conductive particle-containing layer on the insulating resin layer in this manner, it becomes easy to adjust the total thickness of the adhesive film, and the degree of freedom in designing the adhesive film according to the object to be connected increases.

[0016] (Component a) a third film component, preferably a film-forming component containing a bisphenol A-type phenoxy resin; (Component b) a second acrylic compound, preferably a radical-polymerizable component containing a urethane (meth)acrylate; (Component c) conductive particles; and (Component d) a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125°C or less, preferably 100°C or higher and 120°C or lower, in particular dilauroyl peroxide.

[0017] From the viewpoint of ease of handling, the adhesive film of the present invention is preferably wound around a reel to form a wound body.

[0018] The adhesive film of the present invention has a structure in which a radically polymerizable and anionically polymerizable insulating resin layer containing specific components is provided on a release-treated substrate film. Hybrid curing of this insulating resin layer by anionic polymerization and radical polymerization improves the crosslink density and the adhesiveness of the insulating resin layer. Therefore, the adhesive film of the present invention exhibits low-temperature, rapid curing properties, achieving good initial adhesive strength in connection structures manufactured using the adhesive film of the present invention. Furthermore, even if the connection structure is accidentally placed in a high-temperature, high-humidity environment, the connection reliability is not reduced, and good visibility of the conductive particle impressions at the connection portion of the connection structure is ensured, preventing the connection portion from floating. Furthermore, the adhesive film of the present invention itself can be stably slit to a narrow width that allows the creation of a wound structure that suppresses blocking to an extent that does not interfere with use, and even when slit to a narrow width, good temporary adhesion is achieved.

[0019] Fig. 1A is a schematic cross-sectional view of an adhesive film of the present invention. Fig. 1B is a schematic cross-sectional view of an anisotropic conductive film as an example of an adhesive film of the present invention. Fig. 2 is a schematic cross-sectional view of an anisotropic conductive film as an example of an adhesive film of another embodiment of the present invention.

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0021] <<Adhesive Film>> As shown in FIG. 1A , the adhesive film 10 of the present invention comprises a substrate film 4 that has been subjected to a release treatment necessary for applying a composition for forming an insulating resin layer during production of the adhesive film, and an insulating resin layer 1 that contains specific components and exhibits both radical and anionic polymerization properties and is provided thereon. To achieve finer connection structures, higher density mounting, and improved handleability, the film width is 1.0 mm or less, or even 0.8 mm or less, and a length of 5 m or more. A release-treated cover film may also be disposed on the surface of the insulating resin layer 1 opposite the substrate film 4. Thus, the insulating resin layer 1 of the adhesive film 10 of the present invention exhibits both radical and anionic polymerization properties. Furthermore, the film-forming components include a first film component having a weight-average molecular weight of 50,000 to 80,000 and a second film component having a weight-average molecular weight of 30,000 to less than 50,000. When the adhesive film of the present invention configured in this manner is used to connect a first electronic component and a second electronic component, a sufficient amount of adhesive resin can be present between them to achieve good initial adhesive strength.

[0022] 1B, the insulating resin layer 1 of the adhesive film 10 of the present invention can contain conductive particles 3. In this case, the conductive particles 3 may be randomly dispersed and held in the insulating resin layer 1, or may be regularly arranged. This allows the adhesive film 10 to function as a conductive film or an anisotropic conductive film.

[0023] <Anisotropic Conductive Film> As shown in Figure 2, the adhesive film of the present invention is an anisotropic conductive film 100 having a structure including an insulating resin layer 1 exhibiting radical polymerization and anionic polymerization properties, and a conductive particle-containing layer 2 exhibiting radical polymerization properties laminated thereon, on a base film 4 that has been subjected to a release treatment. In this anisotropic conductive film 100, a cover film that has also been subjected to a release treatment may be disposed on the conductive particle-containing layer 2 side. In the conductive particle-containing layer 2, the conductive particles 3 may be randomly dispersed and held in the conductive particle-containing layer 2, or may be regularly arranged.

[0024] <Constituent Components of the Insulating Resin Layer 1 in the Adhesive Film 10 and the Anisotropic Conductive Film 100> The insulating resin layer 1 contains the following components A, B, C, D, and E. Each component will be described below.

[0025] (Component A) Component A is a film-forming component containing two types of film components with different weight-average molecular weights. In the present invention, two types of film components with different weight-average molecular weights are used in combination as the film-forming component. In other words, a first film component with a relatively high molecular weight and a second film component with a relatively low molecular weight are used in combination. The reason for this combination is that when slitting an adhesive film 10 having an insulating resin layer 1 and a base film 4, which uses only the first film component with a relatively high molecular weight as component A, the presence of the base film 4, which has a higher elastic modulus and is more impact-resistant than the insulating resin layer 1, can prevent the adhesive film 10 from peeling off at a portion of the slit long film due to the impact applied to the adhesive film 10 during slitting. However, the tackiness of the insulating resin layer 1 tends to be somewhat lower, which reduces adhesion to the base film 4 and raises concerns about slitting defects, such as peeling occurring at a portion of the interface between the base film 4 and the insulating resin layer 1. Here, partial peeling at the interface between the base film 4 and the insulating resin layer 1 means peeling of the insulating resin layer 1 from the base film 4, which is estimated by observation to be due to poor adhesion of the insulating resin layer 1 to the base film 4. On the other hand, when slitting an adhesive film 10 having an insulating resin layer 1 and a base film 4 using only a second film component with a relatively low molecular weight as component A, there is a risk of slitting defects occurring, such as the resin adhering to the slitting blade during slitting. Therefore, by using two types of film components with different weight-average molecular weights in combination, flexibility is imparted to the insulating resin layer 1 and the adhesion between the insulating resin layer 1 and the base film 4 is improved, and the insulating resin layer 1 can be prevented from floating (or peeling) from the release-treated base film 4. Furthermore, even when slitting the adhesive film 10 to a narrow width (e.g., 0.8 mm or less), adhesion of the resin to the slitting blade can be prevented, thereby suppressing the occurrence of slitting defects.

[0026] The weight-average molecular weight of the first membrane component having a relatively high molecular weight as described above is specifically 50,000 or more, preferably 55,000 or more, and 80,000 or less, preferably 70,000 or less. The weight-average molecular weight of the second membrane component having a relatively low molecular weight is specifically 30,000 or more, preferably 35,000 or more, and less than 50,000, preferably 45,000 or less. The weight-average molecular weights of these membrane components can be measured by gel permeation chromatography using polystyrene as a standard substance, using a general gel permeation chromatograph available, for example, from Shimadzu Corporation.

[0027] If the content of component A (film-forming component) in the insulating resin layer 1 is too small, the adhesive film will be prone to bending, and if it is too large, the fluidity of the resin will decrease during connection, making it difficult to obtain good conductivity, and flexibility will also decrease, tending to result in low adhesive strength. Therefore, the content is preferably 20.0 mass % or more, more preferably 25.0 mass % or more, and preferably 50.0 mass % or less, more preferably 35.0 mass % or less.

[0028] If the relative content of the second film component to the first film component in component A is too small, flexibility and adhesive strength tend to decrease, while if it is too large, the elastic modulus during adhesive film formation and slitting properties tend to decrease. Therefore, the content of the second film component per 100 parts by mass of the first film component is preferably 40 parts by mass or more, and preferably 150 parts by mass or less.

[0029] The first and second film components described above can be one or more selected from common film-forming components such as phenoxy resin, epoxy resin, polyester resin, urethane resin, butadiene resin, polyamide resin, polyimide resin, polyolefin resin, polyvinyl butyral resin, and ethylene-vinyl acetate copolymer resin. Among these, phenoxy resin can be preferably selected from the viewpoints of mechanical properties such as flexibility, impact resistance, and abrasion resistance, and chemical properties such as heat resistance and chemical resistance. Phenoxy resin is generally an epoxy-free polyhydroxypolyether (thermoplastic resin) synthesized from bisphenols and epichlorohydrin, and bisphenol A is a preferred bisphenol component from the viewpoint of ease of availability. Therefore, bisphenol A-type phenoxy resin can be preferably used as the first and second film components of component A. When component A is the same type as component B or component C, the weight-average molecular weight of component A is preferably 0.1 to 1,000 times the weight-average molecular weight of component B or component C, which will be described later.

[0030] (Component B) Component B is a radical polymerizable component containing a first acrylic compound. Examples of the first acrylic compound include known monofunctional (meth)acrylates such as alkyl (meth)acrylates, polyfunctional (meth)acrylates such as polypropylene glycol di(meth)acrylate, and urethane (meth)acrylates. Among these, in order to improve the adhesive strength of the cured product and thereby improve the electrical conductivity reliability, it is necessary to improve the adhesiveness of flexible printed circuit boards (FPCs) to polyimides. Therefore, urethane (meth)acrylates, which are reaction products of hydroxyalkyl (meth)acrylates and diisocyanates, are preferred. These first acrylic compounds may be monomers, oligomers, or polymers. The polyfunctional (meth)acrylates can also function as crosslinking agents, and preferred crosslinking agents include EO-modified isocyanuric acid di- or tri(meth)acrylates. The term "(meth)acrylate" refers to both acrylate and methacrylate.

[0031] The content of component B (radical polymerizable component) in the insulating resin layer 1 is preferably 20.0 mass % or more, more preferably 30.0 mass % or more, and preferably 50.0 mass % or less, more preferably 40.0 mass % or less, because if the content is too low, the cohesive force of the insulating resin will be weakened and the adhesive film may not achieve the desired adhesive strength, and if the content is too high, the liquid component will increase relatively, the insulating resin layer will become soft, and slitting defects such as the resin adhering to the slitting blade or the like will occur during slitting. Note that component B can contain a radical polymerizable component other than the first acrylic compound, such as an alkene compound, as long as it does not impair the effects of the present invention.

[0032] (Component C) Component C is an anionically polymerizable component containing an epoxy compound. Examples of epoxy compounds include compounds that have two or more epoxy groups per molecule and can be three-dimensionally cured in the presence of a curing agent or catalyst. Examples of such epoxy compounds include epoxy group-containing reaction products of bisphenols and epichlorohydrin, preferably bisphenol A-type liquid epoxy resins. These epoxy compounds may be monomers, oligomers, or polymers. Therefore, the reaction products can be in the form of oligomers or prepolymers.

[0033] The content of component C (anionically polymerizable component) in the insulating resin layer 1 is preferably 1.0 mass % or more, more preferably 5.0 mass % or more, preferably 20.0 mass % or less, and more preferably 10.0 mass % or less, because if it is too small, the adhesiveness of the adhesive film will decrease and lifting will easily occur at the connection between the adherend such as an FPC and the adhesive film, raising concerns about reduced connection reliability, and if it is too much, there will be concerns about reduced toughness and reduced adhesive strength. Here, lifting at the connection between the adherend and the adhesive film (in other words, the connection of the connection structure) means poor adhesion between the adherend and the adhesive film.

[0034] (Component D) Component D is a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125° C. or lower, preferably 85° C. or higher, and more preferably 100° C. or higher and 120° C. or lower. Use of such an organic peroxide enables the radically polymerizable component of Component B to be rapidly cured at a low temperature of 150° C. or lower. Note that an organic peroxide having a one-minute half-life temperature of higher than 125° C. may be used in combination, provided that the effects of the present invention are not impaired.

[0035] Specific examples of organic peroxides (one-minute half-life temperatures) for component D are shown below. When component D is selected from these exemplified organic peroxides in the present invention, the selection can be made taking into consideration the connection temperature when producing a connection structure using the adhesive film and the types of other essential components. Diisobutyl peroxide (85.1°C) Cumyl peroxyneodecanoate (94.0°C) Di-n-propyl peroxydicarbonate (94.0°C) Diisopropyl peroxydicarbonate (88.3°C) Di-sec-butyl peroxydicarbonate (92.4°C) 1,1,3,3-tetramethylbutyl peroxyneodecanoate (92.4°C) Di(4-t-butylcyclohexyl) peroxydicarbonate (92.1°C) Di(2-ethylhexyl) peroxydicarbonate (90.6°C) t-hexyl peroxyneodecanoate (100.9°C) t-butyl peroxyneodecanoate (103.5°C) t-hexyl peroxypivalate (109.1°C) t-butyl peroxypivalate (110.3°C) Di(3,5,5-trimethylhexanoyl)peroxide (112.6°C) Dilauroyl peroxide (116.4°C) 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3°C) 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (118.8°C)

[0036] Among the above-mentioned organic peroxides, dilauroyl peroxide (116.4°C) can be preferably used because it can obtain properties such as conductivity, indentation, and adhesiveness even when pressure-bonded at a low temperature of 150°C. The content of component D in the insulating resin layer 1 can be appropriately determined taking into account the content of component B (radical polymerizable component) and the pressure-bonding properties and tackiness of the insulating resin layer 1, but it can also be determined taking into account the content of component E (anionic polymerization curing agent) from the viewpoint of crosslink density. This point will be described later.

[0037] (Component E) Component E is an anionic polymerization curing agent containing an organic acid hydrazide compound that is solid at room temperature (usually 15 to 30°C) in order to anionically polymerize the anionically polymerizable component of Component C. The anionic polymerization curing agent preferably contains an organic acid hydrazide compound with a melting point of 160°C or less, more preferably 80°C or higher and 160°C or lower. The reason for using an anionic polymerization curing agent in Component E is that if only the radical polymerization initiator of Component D is used as the polymerization initiator, the adhesive strength of the adhesive film will be insufficient, making the connection between the adhesive film and the adherend more likely to become loose, resulting in concerns about reduced connection reliability. To alleviate these concerns, a hybrid curing method combining radical polymerization and anionic polymerization is achieved. The reason for using an organic acid hydrazide compound as an anionic polymerization curing agent is that it can be handled in solid form (e.g., as microcrystals or fine powder), and therefore can be easily incorporated into a resin to produce a one-component curing resin formulation. The reason for using an organic acid hydrazide compound that is solid at room temperature (or an organic acid hydrazide compound having a melting point of 160° C. or lower) is that there is a concern that the pot life may be impaired if an organic acid hydrazide compound that is liquid at room temperature (or an organic acid hydrazide compound having a melting point of 160° C. or lower) is used. Such an organic acid hydrazide compound can be selected from known aliphatic dicarboxylic acid hydrazides and aromatic carboxylic acid hydrazides.

[0038] Specific examples of organic acid hydrazide compounds (melting points) for component E are shown below. When selecting component E from these exemplified organic acid hydrazide compounds in the present invention, the selection may be made taking into consideration the connection temperature when producing a connection structure using the adhesive film and the types of other essential components. Salicylic acid hydrazide (145 to 155°C) 2-thiophenecarboxylic acid hydrazide (136 to 139°C) 3-(phenylamino)propionic acid hydrazide (93 to 95°C) N,N-di(carboxyethyl)aniline hydrazide (141 to 145°C) Eicosanedicarboxylic acid dihydrazide (155 to 156°C) 7-ethyloctadecanedicarboxylic acid dihydrazide (50 to 90°C)

[0039] Among the above-mentioned organic acid hydrazide compounds, when 5 mg of the composition for forming an insulating resin layer is subjected to DSC measurement using a differential scanning calorimeter (DSC6200, Hitachi High-Tech Science Corporation) at a temperature rise rate of 10°C / minute, the acrylic compound may start to generate heat at a relatively low temperature, for example, 70°C or lower. Therefore, from the viewpoint of pot life, salicylic acid hydrazide (melting point: 145 to 155°C) can be preferably used.

[0040] If the content of component E (anionic polymerization curing agent) in the insulating resin layer 1 is too small relative to the epoxy content, peeling is likely to occur at some interfaces between the substrate film and the insulating resin layer after the adhesive film is subjected to an unsaturated (85% RH) pressure cooker test (HAST: High Accelerated Stress Test), whereas if the content is too large, reactivity tends to increase and the storage life of the product tends to be shortened. Therefore, the content is preferably 0.1 mass % or more, more preferably 0.2 mass % or more, and preferably less than 10.0 mass %, more preferably 1.0 mass % or less.

[0041] The thickness of the insulating resin layer 1 containing the above components A to E is preferably 3 μm or more, more preferably 5 μm or more, and preferably 40 μm or less, more preferably 35 μm or less, because if it is too thin, it becomes difficult to obtain sufficient adhesive strength, and if it is too thick, stable slits tend to be difficult to form. Note that the insulating resin layer 1 may be configured as a laminate in which multiple resin layers are stacked, and in that case, the thickness of the insulating resin layer 1 means the thickness of the entire laminate.

[0042] Furthermore, the insulating resin layer 1 may contain an adhesion improver such as a silane coupling agent or a phosphate ester compound to improve aging resistance (85°C, 85 RH, 250 hours or 500 hours). From the viewpoint of adhesion improvement effect, preferred silane coupling agents include alkoxysilane compounds having an epoxy group, preferably alkoxysilane compounds having a glycidyloxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. Of these, 3-glycidoxypropyltrimethoxysilane is preferred. A preferred phosphate ester compound is the reaction product of a 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate with phosphoric anhydride.

[0043] Furthermore, the content of component E (anionic polymerization curing agent) in the insulating resin layer 1 can be evaluated in terms of the content ratio (by mass) relative to component C (anionic polymerizable component) from the viewpoint of obtaining the amount necessary for the reaction of the epoxy compound that contributes to improving the heat resistance and weather resistance of the insulating resin layer 1 and stable properties, as will be described below. Alternatively, the content can also be evaluated in terms of the content ratio (by mass) relative to component D (radical polymerization initiator) from the viewpoint of maintaining good compression bonding properties even if the density of the crosslinked structure changes depending on the reaction ratio between the epoxy compound and the acrylic compound.

[0044] Specifically, the content ratio (by mass) of component E (anionic polymerization curing agent) to component C (anionic polymerizable component) in the insulating resin layer 1 is (= [component E] / [component C]) × 10 ２ If the ρ is too low, the reactivity of the epoxy will be low and the density of the crosslinked structure will be low, which may cause peeling to occur at part of the interface between the substrate film and the insulating resin layer in an unsaturated (85% RH) pressure cooker test (HAST), whereas if the ρ is too high, there is a risk that peeling will occur at part of the interface between the substrate film and the insulating resin layer in HAST due to an excess of anionic polymerization curing agent. Therefore, the ρ is preferably 1 or more, more preferably 2 or more, and is preferably 30 or less, more preferably 20 or less.

[0045] The insulating resin layer 1 can contain conductive particles 3 in order to allow the adhesive film 10 to function as a conductive film or anisotropic conductive film. The type and amount of the conductive particles 3 can be the same as those of the conductive particles 3 used in the conductive particle-containing layer 2 described below.

[0046] Furthermore, if the content ratio (by mass) of component E (anionic polymerization curing agent) to component D (radical polymerization initiator) in the insulating resin layer 1 is too low, interfacial peeling from the substrate after pressure-bonding tends to occur more easily, and there is a risk that it may be difficult to obtain adhesive strength. If the content ratio is too high, the reactivity of acrylic at 150°C tends to be low, and it may be difficult to obtain pressure-bonding properties. Therefore, the content ratio is preferably 0.1 or more, more preferably 0.2 or more, and preferably 60.0 or less, and more preferably 5.0 or less.

[0047] The insulating resin layer 1 may contain various additives that have been used in adhesive films 10 such as conventional anisotropic conductive films, for example, softeners such as butadiene rubber, fillers (viscosity adjusters) such as silica filler, coloring pigments such as carbon black, and internal release agents such as calcium stearate, within the range that does not impair the effects of the present invention.

[0048] <Constituents of the Conductive Particle-Containing Layer 2 of the Anisotropic Conductive Film 100> By providing the conductive particle-containing layer 2 on the insulating resin layer 1, the adhesive film 10 of the present invention can function as an anisotropic conductive film 100 as shown in Fig. 2. Such a conductive particle-containing layer 2 preferably contains the following components a to d. Each component will be explained below.

[0049] (Component a) Component a is a film-forming component containing a third film component. The reason for using the third film component is to improve the adhesion between the insulating resin layer 1 and the conductive particle-containing layer 2. There are no particular restrictions on the type, weight-average molecular weight, or polydispersity of the third film component, but it is preferable to use the same type as the first film component in order to increase the affinity with the first film component, which is contained in a relatively large amount in the insulating resin layer 1. Therefore, bisphenol A-type phenoxy resin can be preferably used as the third film component of component a.

[0050] The content of the film-forming component of component a in the conductive particle-containing layer 2 is preferably 15.0 mass % or more, more preferably 20.0 mass % or more, preferably 50.0 mass % or less, and more preferably 35.0 mass % or less, because if the content is too low, the anisotropic conductive film before use is prone to bending and is easily affected when slit, and if the content is too high, the fluidity of the resin during anisotropic conductive connection is reduced, making it difficult to obtain good conductivity, and flexibility also tends to decrease, resulting in low adhesive strength. Furthermore, component a preferably contains at least 15.0 mass % or more of the third film component, but may also contain other known film-forming components, such as thermoplastic resins such as polyamides and polyolefins, and thermoplastic elastomers, as long as the effects of the present invention are not impaired.

[0051] (Component b) Component b is a radically polymerizable component containing a second acrylic compound. The content of the second acrylic compound in component b is preferably at least 20.0% by mass. The same acrylic compound as the first acrylic compound can be used as the second acrylic compound. Among these, urethane (meth)acrylates, which are reaction products of hydroxyalkyl (meth)acrylates and diisocyanates, are preferred in terms of improving the adhesive strength of the cured product, improving electrical conductivity reliability, and further improving adhesion of the FPC substrate to polyimide. These second acrylic compounds may be monomers, oligomers, or polymers. Polyfunctional (meth)acrylates can also function as crosslinkers, and isocyanuric acid EO-modified di- or tri(meth)acrylates are preferred crosslinkers.

[0052] If the content of the radical polymerizable component of component b in the conductive particle-containing layer 2 is too low, the tackiness of the anisotropic conductive film will decrease, and there will be concerns that part of the conductive particle-containing layer 2 will peel off after slitting, contaminating the manufacturing equipment; that the anisotropic conductive film will have a lower ability to be temporarily attached to a glass substrate when applied to an anisotropic conductive connection, making the connection work more difficult; and that the elastic modulus of the anisotropic conductive film will decrease even after connection, thereby tending to reduce connection reliability. If the content is too high, there will be a risk that the resin component will easily protrude when the anisotropic conductive film is slit and wound around a reel to form a wound body, and that the slit anisotropic conductive film will be unable to be pulled out properly from the wound body (a blocking state). Therefore, the content is preferably 20.0 mass % or more, more preferably 30.0 mass % or more, and preferably 50.0 mass % or less, more preferably 40.0 mass % or less.

[0053] (Component c) Component c is conductive particles 3 for imparting anisotropic conductivity to the anisotropic conductive film 100. The same known conductive particles used in general anisotropic conductive films can be used as the conductive particles 3. For example, metal particles such as nickel, alloy particles such as solder, metal-coated resin particles, etc. can be appropriately selected and used.

[0054] The average particle size of the conductive particles 3 of component c is preferably 1.5 μm or more, more preferably 2.0 μm or more, and is preferably equal to or less than the thickness of the conductive particle-containing layer, more preferably 6.0 μm or less, because if it is too small, the indentation strength tends to be low, and if it is too large, the insulation reliability between wirings tends to deteriorate. This average particle size can be measured using a commercially available laser diffraction / scattering particle size distribution analyzer using a laser diffraction / scattering method, a commercially available digital image analysis particle size distribution analyzer (N=1000 or more), or the like.

[0055] If the content of the conductive particles 3 of component c in the conductive particle-containing layer 2 is too low, the connection reliability of the anisotropic conductive film will be insufficient, and if it is too high, there will be concerns about the occurrence of short circuits. Therefore, the content may be adjusted so as to fall within the range of the number density of the conductive particles described below.

[0056] The conductive particles 3 of component c may be randomly dispersed and held in the conductive particle-containing layer 2, or may be arranged regularly, for example, in a lattice pattern, by a known method. The conductive particles 3 may be held so as to be exposed on the surface of the conductive particle-containing layer 2, or may be embedded. They may be held so as not to overlap in the film thickness direction in a planar view of the film. If the number density of the conductive particles in a planar view of the film is too low, it may be difficult for the particles to be captured on the terminals, which may make it impossible to accommodate narrower picture frames of image display devices or finer pitches of electrodes on circuit boards. If the number density is too high, the reliability of insulation between wirings tends to decrease. Therefore, the number density is preferably 10 particles / mm. ２ More preferably, 500 pieces / mm ２ More preferably, 1000 pieces / mm ２ or more, and ２ It may be less than 500,000 particles / mm ２ Less than or equal to 50,000 pieces / mm ２ More preferably, 20,000 pieces / mm ２ The following is the result.

[0057] (Component d) Component d, like component D of the insulating resin layer 1, is a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125°C or less, preferably 100°C or more and 120°C or less. By using such an organic peroxide, the radical polymerizable component of component b can be rapidly cured at low temperature. Among them, dilauroyl peroxide (116.4°C) can be preferably used because it can obtain pressure-bonding properties at 150°C.

[0058] If the content of component d (radical polymerization initiator) in the conductive particle-containing layer 2 is too small relative to the radical polymerizable component of component b, it becomes difficult to obtain compression bonding properties from 150°C, and if it is too large, tackiness tends to be reduced. Therefore, the content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the radical polymerizable component of component b.

[0059] The thickness of the conductive particle-containing layer 2 containing the above components a to d is preferably equal to or greater than the particle diameter of the conductive particles, more preferably 3 μm or more, and is preferably 40 μm or less, more preferably 35 μm or less, since if it is too thin, it becomes difficult to obtain sufficient adhesive strength, and if it is too thick, the electrical conductivity reliability tends to decrease.

[0060] The conductive particle-containing layer 2 may contain various additives used in conventional anisotropic conductive films, such as softeners such as butadiene rubber, fillers (viscosity modifiers) such as silica filler, coloring pigments such as carbon black, adhesion improvers such as silane coupling agents and phosphate ester compounds, and internal mold release agents such as calcium stearate, within the scope of not impairing the effects of the present invention. A preferred phosphate ester compound is a reaction product of a 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate with phosphoric anhydride.

[0061] <Substrate Film 4 Subjected to Release Treatment> In the adhesive film 10 of the present invention, the insulating resin layer 1 is provided on a substrate film 4 that has been subjected to a release treatment. This substrate film 4 can function as a film onto which the insulating resin layer-forming composition is applied when forming the insulating resin layer 1. Furthermore, a substrate film 4 that has been subjected to a release treatment can also be provided on the conductive particle-containing layer 2 side as a cover film. As such a substrate film 4, substrate films used in known adhesive films, anisotropic conductive films, etc. can be used. For example, a polyethylene terephthalate film that has been subjected to a silicone release treatment can be used as the substrate film. Generally, slitting an adhesive film having an insulating resin layer provided on a release-treated substrate film into a narrow width is likely to cause slitting defects. However, in the adhesive film 10 of the present invention, a composition that exhibits both radical and anionic polymerizability is prepared from specific components, and the insulating resin layer 1 of the adhesive film 10 is formed from this composition, thereby suppressing such slitting defects.

[0062] The narrow adhesive film of the present invention can be slit stably to a width of 1.0 mm or less, or even 0.8 mm or less, to a length of 5 m or more, and the temporary adhesion property is not reduced even when slit to such a narrow width. It is presumed that the characteristics of the present invention are more effectively exhibited with a slit width of less than 0.8 mm, or more preferably 0.6 mm or less, which is considered technically difficult.

[0063] <<Manufacturing of Adhesive Films>> The adhesive film of the present invention having a substrate film / insulating resin layer structure can be manufactured by applying the insulating resin layer-forming composition obtained by uniformly mixing Components A to E, optionally together with a general-purpose solvent, to one side of a substrate film such as a release-treated polyethylene terephthalate film using a conventional method, for example, a bar coater, and drying to form an insulating resin layer. The resulting adhesive film can be slit to a width of 1.0 mm or less, or even 0.8 mm or less, and a length of 5 m or more, using, for example, the shear-cut method described in JP 2020-168716 A, to produce a narrow adhesive film. Note that the adhesive film of the present invention can be slit to a narrow width using other slitting methods, without being limited to shear-cut slitting methods. The slit adhesive film will be present on the entire surface of the substrate film (the adhesive film will be present on the substrate film without any gaps, resulting in a so-called "solid film").

[0064] Furthermore, an anisotropic conductive film, which is one embodiment of the adhesive film of the present invention having a base film / insulating resin layer / conductive particle-containing layer structure, can be produced by uniformly mixing Components A to E, optionally together with a general-purpose solvent, to form an insulating resin layer by applying an insulating resin layer-forming composition to one side of a release-treated base film such as a polyethylene terephthalate film in a conventional manner, for example, with a bar coater, and then drying the composition. Similarly, a conductive particle-containing layer can be formed by applying an insulating particle-containing layer-forming composition to one side of another release-treated base film (used as a cover film) in a conventional manner and then drying the composition. Next, the insulating resin layer and the conductive particle-containing layer are placed opposite each other and laminated to produce an anisotropic conductive film having a laminate structure of base film / insulating resin layer / conductive particle-containing layer / cover film. The resulting anisotropic conductive film can be slit into a width of 1.0 mm or less, or even 0.8 mm or less, and a length of 5 m or more by a conventional method, for example, by the shear cutting method described in JP-A-2020-168716, etc., to produce an anisotropic conductive film, which is one embodiment of a narrow adhesive film. The same applies to an adhesive film provided on a release film.

[0065] The narrow, long adhesive film of the present invention produced in this manner can be wound around a reel member and distributed as a wound body, and in such a wound body, not only the resin extrusion phenomenon but also blocking is greatly suppressed. From the viewpoint of practicality, the film length in such a wound body is preferably 5 m or more, more preferably 50 m or more, and preferably 5,000 m or less, more preferably 1,000 m or less. Furthermore, in the adhesive film, conductive film, and anisotropic conductive film of the present invention, the release force between the insulating resin layer 1 and the base film 4 is preferably 100 to 400 mN / 5 cm, more preferably 125 to 250 mN / 5 cm, as measured by a T-type release test according to JIS K 6854. The measurement can be performed by cutting out a film from the raw sheet before slitting. If the thickness is below this range, when the adhesive film is slit, part of the interface between the insulating resin layer and the base film tends to peel off, causing blocking. If the thickness exceeds this range, temporary adhesion tends to decrease when the adhesive film is used (for example, it tends to be difficult to attach the adhesive film to a second electronic component (such as a glass substrate) described below). As the reel member for the wound body, a known reel member for narrow adhesive films can be used. In particular, a reel member having a flange formed with ribs whose rib tops are narrower than their bases (JP 2021-080098 A) can be preferably used. With such a reel member, the contact area of ​​the wound adhesive film with the flange side surface is minimized. Therefore, even if the adhesive film has a resin layer that is easily peeled off from the base film and requires delicate handling, using the reel member disclosed in JP 2021-080098 A as the reel member for the wound body makes it possible to easily pull out the adhesive film from the wound body, significantly improving workability in the connection process. This is preferable.

[0066] <<Uses of Adhesive Film>> The adhesive film of the present invention can be preferably used when connecting a first electronic component such as an FPC, IC chip, or IC module to a second electronic component such as an FPC, rigid substrate, ceramic substrate, glass substrate, or plastic substrate. The connection structure thus obtained, i.e., a connection structure in which a first electronic component and a second electronic component are connected via the adhesive film of the present invention, also constitutes part of the present invention. Also constitutes part of the present invention is a method for producing a connection structure in which the adhesive film of the present invention is sandwiched between the first electronic component and the second electronic component and pressure-bonded to form a connection.

[0067] The present invention will be described in more detail below with reference to examples and comparative examples. The anisotropic conductive films as adhesive films in Examples 1 to 17 and Comparative Examples 1 to 7 shown below have a structure in which an insulating resin layer and a conductive particle-containing layer are sequentially laminated on a release-treated substrate film, while the adhesive films in Examples 18 to 19 and Comparative Examples 8 to 11 have a structure in which an insulating resin layer containing conductive particles is laminated on a release-treated substrate film.

[0068] <Preparation of composition for forming conductive particle-containing layer> PMA (propylene glycol monomethyl ether acetate) was added to the composition in Table 1 so that the solid content was 45 mass %, and the mixture was mixed uniformly to prepare formulation A1 as a composition for forming a conductive particle-containing layer.

[0069] <Preparation of compositions for forming insulating resin layer> PMA was added to the formulations shown in Tables 2A and 2B so that the solid content was 42 mass %, and the mixture was mixed uniformly to prepare formulations N1 to N24 as compositions for forming insulating resin layers that did not contain conductive particles, and formulations N25 to N30 as compositions for forming insulating resin layers that contained conductive particles.

[0070]

[0071]

[0072]

[0073] Examples 1 to 17, Comparative Examples 1 to 7 (Formation of Conductive Particle-Containing Layer) A composition for forming a conductive particle-containing layer was prepared by adding propylene glycol monomethyl ether acetate (PMA) to Formulation A1 in Table 1 so that the solids content was 45 mass %, and mixing the mixture uniformly. The composition was applied to a 25 μm-thick polyethylene terephthalate substrate film having a silicone release-treated surface using a bar coater to a dry thickness of 5 μm, and then dried in an oven at 55° C. for 3 minutes to form a conductive particle-containing layer on the substrate film.

[0074] (Formation of an insulating resin layer not containing conductive particles) Separately from the conductive particle-containing layer, a composition for forming an insulating resin layer not containing conductive particles was prepared by adding PMA to formulations N1 to N24 in Tables 2A and 2B so that the solid content was 42 mass % and mixing them uniformly. The composition was applied using a bar coater to a 50 μm thick polyethylene terephthalate substrate film having a silicone release-treated surface to a dry thickness of 15 μm, and dried in an oven at 70°C for 4 minutes to form an insulating resin layer on the substrate film.

[0075] (Formation of anisotropic conductive films as adhesive films) The obtained insulating resin layer and conductive particle-containing layer were placed opposite each other and laminated at 45°C and 0.5 MPa to obtain anisotropic conductive films having a laminate structure of substrate film / insulating resin layer / conductive particle-containing layer / substrate film (Examples 1 to 17 and Comparative Examples 1 to 7). Thereafter, the substrate film on the conductive particle-containing layer side was removed, and a general cover film was laminated at 45°C onto the exposed conductive particle-containing layer.

[0076] Examples 18-19, Comparative Examples 8-11 (Formation of an Insulating Resin Layer Containing Conductive Particles) PMA was added to the formulations N25-N30 in Table 2B to a solids content of 42% by mass, and the mixture was uniformly mixed to prepare a composition for forming an insulating resin layer containing conductive particles. The composition was applied to a 50 μm-thick polyethylene terephthalate substrate film having a silicone release-treated surface using a bar coater to a dry thickness of 20 μm. The composition was then dried in an oven at 70°C for 4 minutes to form an insulating resin layer containing conductive particles on the substrate film. This resulted in anisotropic conductive films (Examples 18-19 and Comparative Examples 8-11) with a substrate film / insulating resin layer containing conductive particles structure. A conventional cover film was then laminated onto the exposed insulating resin layer at 45°C.

[0077] <<Evaluation>> The anisotropic conductive films used as adhesive films in the Examples and Comparative Examples were tested and evaluated for "slit processability" as described below. Furthermore, the anisotropic conductive films in the Examples and Comparative Examples were tested and evaluated for "temporary adhesion," "adhesion strength," "connection reliability," "indentation visibility," and "state of lifting of connection portions" at the following timings: initial, after HAST (held at 110°C, 85% RH, 24 hours), and after aging (storage at 85°C, 85% RH, 250 hours), as described below. The results are shown in Tables 3A and 3B.

[0078] <Slitting Processability (Part 1)> 100 m of each of the anisotropic conductive films produced in Examples 1 to 17 and Comparative Examples 1 to 7 was slit into 0.5 mm widths using a general slitting device to produce anisotropic conductive films, which were then evaluated according to the following evaluation criteria. From a practical standpoint, a rating of B is acceptable, and a rating of A is more preferable.

[0079] (Slitting processability (part 1) evaluation criteria) Rank Evaluation criteria A: When slitting the anisotropic conductive film, no resin adhered to the slitting blade that would interfere with slitting, and the insulating resin layer was able to be slit without peeling off from the base film B: When slitting the anisotropic conductive film, no resin adhered to the slitting blade that would interfere with slitting, but some of the insulating resin layer peeled off from the base film, but this did not cause any practical problems C: When slitting the anisotropic conductive film, resin adhered to the slitting blade to an extent that it interfered with slitting, or the insulating resin layer peeled off, causing practical problems (including cases where slitting became impossible midway)

[0080] <Slitting processability (part 2)> For each of the anisotropic conductive films produced in Examples 18 to 19 and Comparative Examples 8 to 11, the cover film was peeled off and the anisotropic conductive film having a length of 100 m was slit into widths of 1.0 mm, 0.8 mm, 0.6 mm, and 0.5 mm using a general slitting device to produce tape-like anisotropic conductive films, which were then wound around a φ90 mm flanged core with a tension of 0.05 to 0.20 N to produce a wound body. The tape-like anisotropic conductive film was manually pulled out from the outer end of the obtained wound body and evaluated according to the following evaluation criteria.

[0081] (Slitting processability (part 2) evaluation criteria) Rank Evaluation criteria A: When the anisotropic conductive film was pulled out from the wound body, there was no blocking and it could be pulled out to the end. B: When the anisotropic conductive film was pulled out from the wound body, there was some blocking that did not cause any practical problems, but it could be pulled out to the end (if it was rated B or higher, there was no problem in use). C: When the anisotropic conductive film was pulled out from the wound body, there was blocking that caused problems in use (there was a problem in use).

[0082] <Temporary Adhesion> For each of the anisotropic conductive films prepared in Examples 1 to 17 and Comparative Examples 1 to 7, the cover film was peeled off and the resulting 100 m long anisotropic conductive film was slit into 0.5 mm widths using a standard slitting device to produce a tape-shaped anisotropic conductive film. Similarly, for each of the anisotropic conductive films prepared in Examples 18 to 19 and Comparative Examples 8 to 11, slitting was performed in the same manner to produce tape-shaped anisotropic conductive films with widths of 1.0 mm, 0.8 mm, 0.6 mm, and 0.5 mm. Next, small pieces 4 cm long were cut from the resulting tape-shaped anisotropic conductive film, and the conductive particle-containing layer or conductive particle-containing insulating resin layer was attached to plain glass. The piece was placed on a hot plate set to 45°C so that it was in contact with the base film. Hand pressure was applied from the base film side, and the piece was then cooled to room temperature. After cooling, the edge of the release-treated base film was pinched with tweezers to peel off the base film, and the evaluation was performed according to the following criteria.

[0083] (Evaluation criteria for temporary adhesion) Rank Evaluation criteria A: The base film was easy to peel off and could be attached neatly to the plain glass without creating bubbles or wrinkles. B: It took longer to peel off the base film than in the case of rank A, but it could be attached neatly to the plain glass without creating bubbles or wrinkles. C: It was not possible to attach it to the plain glass, or it was possible to attach it but the base film could not be peeled off.

[0084] <Adhesive Strength> (Initial Adhesive Strength Test) Each anisotropic conductive film prepared in the Examples and Comparative Examples was slit to a width of 0.5 mm, and the cover film was peeled off to obtain a tape-shaped anisotropic conductive film. Next, the tape-shaped anisotropic conductive film was temporarily attached to the edge of an ITO glass substrate (0.7 mm thick) on which an indium tin oxide transparent electrode was formed, starting from the conductive particle-containing layer, and placed on a hot plate at 45 ° C., and uniformly pressed from the substrate film side on the insulating resin layer side. Thereafter, the substrate film was peeled off, and the metal wiring portion of an FPC (thickness 50 μm) for evaluation was attached so that the exposed insulating resin layer side was completely covered. Further, the FPC and the glass substrate were thermocompression bonded (150 ° C., 4 MPa, 5 seconds) to bond the opposing electrodes of the FPC and the glass substrate with the cured anisotropic conductive film, thereby obtaining an anisotropically conductive connection connection structure. The FPC specifications were a polyimide film thickness of 66 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch 120 μm, L / S=1 / 1).

[0085] The resulting connection structure including the FPC for evaluation was cut into a 1 cm width, and the FPC for evaluation was pulled up at an angle of 90° at a speed of 50 mm / sec using a tensile tester (RTC1201, manufactured by A&D Co., Ltd.). The adhesive strength was measured and evaluated according to the following criteria: In practical terms, a rating of B is acceptable, and a rating of A is more preferable.

[0086] (Post-HAST Adhesion Strength Test) As in the case of the initial adhesive strength test, a tape-shaped anisotropic conductive film was prepared and subjected to an unsaturated (85% RH) pressure cooker test (HAST) in which the film was held in a constant temperature and humidity chamber (110°C, 85% RH) for 24 hours. Then, as in the case of the initial adhesive strength test, a 1 cm wide connection structure including an FPC for evaluation was prepared, and the adhesive strength was measured in the same way and evaluated according to the following criteria. In practical terms, a rating of B is acceptable, and a rating of A is more preferable.

[0087] (Post-Aging Adhesion Strength Test) As in the case of the initial adhesive strength test, a tape-shaped anisotropic conductive film was prepared and aged (storage at 85°C, 85% RH for 250 hours). Then, as in the case of the initial adhesive strength test, a 1 cm wide connection structure including an FPC for evaluation was prepared, and the adhesive strength was measured in the same way and evaluated according to the following criteria. In practical terms, a rating of B is acceptable, and a rating of A is more preferable.

[0088] (Adhesion strength evaluation criteria) Rank Evaluation criteria A: Adhesion strength is 7 N / cm or more B: Adhesion strength is 5 N / cm or more and less than 7 N / cm C: Adhesion strength is less than 5 N / cm

[0089] <Connection Reliability> (Initial Connection Reliability Test) As in the case of the initial adhesive strength test, a connection structure was obtained by anisotropically conductively connecting a glass substrate and an FPC using each of the anisotropic conductive films produced in Examples and Comparative Examples. However, instead of an FPC with a polyimide film thickness of 66 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch of 120 μm, L / S=1 / 1), an FPC with a polyimide film thickness of 44 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch of 120 μm, L / S=1 / 1) was used.

[0090] The electrical resistance between the anisotropically conductively connected electrodes of the connection structure immediately after it was obtained was measured by a four-terminal method and evaluated according to the following criteria: In practice, a rating of B is acceptable, and a rating of A is more preferable.

[0091] (Initial connection reliability evaluation criteria) Rank Evaluation criteria A: When the conduction resistance value is less than 5 Ω B: When the conduction resistance value is 5 Ω or more and less than 10 Ω C: When the conduction resistance value is 10 Ω or more

[0092] (Post-HAST Connection Reliability Test) A connection structure was prepared in the same manner as in the initial adhesive strength test, and subjected to an unsaturated (85% RH) pressure cooker test (HAST) in which the connection structure was held in a constant temperature and humidity chamber (110°C, 85% RH) for 24 hours. Then, as in the initial connection reliability test, the conduction resistance between the anisotropically conductively connected electrodes of the connection structure was measured by the four-terminal method and evaluated according to the following criteria. In practice, a rating of B is sufficient, and a rating of A is more preferable.

[0093] (Connection reliability test after aging) A connection structure was prepared in the same manner as in the initial adhesive strength test, and after aging (storage at 85°C, 85% RH for 250 hours), the conduction resistance between the anisotropically conductively connected electrodes of the connection structure was measured by the four-terminal method in the same manner as in the initial connection reliability test, and evaluated according to the following criteria. In practice, a rating of B is sufficient, and a rating of A is more preferable.

[0094] (Connection reliability evaluation criteria) Rank Evaluation criteria A: When the conduction resistance value is less than 10 Ω B: When the conduction resistance value is 10 Ω or more and less than 15 Ω C: When the conduction resistance value is 15 Ω or more

[0095] <Indentation Visibility> (Indentation Visibility Test after HAST) As in the case of the initial connection reliability test, a connection structure was obtained by anisotropically conductively connecting a glass substrate and an FPC using each of the anisotropic conductive films produced in Examples and Comparative Examples, except that an IZO-wired glass substrate was used as the glass substrate instead of the ITO glass substrate.

[0096] The resulting connection structure was subjected to a pressure cooker test (HAST) in which it was held in a constant temperature and humidity chamber (110°C, 85% RH) for 24 hours. After that, the state of the indentations made by the conductive particles on the IZO electrode was visually observed from the glass substrate side using a differential interference microscope, and the result was evaluated according to the following criteria: In practice, a rating of B is acceptable, and a rating of A is more preferable.

[0097] (Indentation visibility test after aging) A connection structure was prepared in the same manner as in the initial connection reliability test, and then subjected to an aging test (storage at 85°C, 85% RH, 250 hours). Then, in the same manner as in the indentation visibility test after HAST, the state of the indentations caused by the conductive particles on the IZO electrode was visually observed from the glass substrate side using a differential interference microscope, and evaluated according to the following criteria. In practice, a rating of B is sufficient, and a rating of A is more preferable.

[0098] (Indentation visibility evaluation criteria) Rank Evaluation criteria A: Visual observation with a differential interference microscope reveals that the indentation is strong and clear, and the number of particles captured on the bump can be counted accurately without missing any. B: Visual observation with a differential interference microscope reveals that the indentation is somewhat weak, but the particles captured on the bump can be counted. C: Visual observation with a differential interference microscope reveals that there is no indentation, and the particles captured on the bump cannot be counted.

[0099] <State of Floating Connection> (Inspection of Floating State After HAST) As in the case of the initial connection reliability test, a connection structure was obtained by connecting a glass substrate and an FPC using each anisotropic conductive film produced in Examples and Comparative Examples, except that a SiN glass substrate on which a silicon nitride thin film was formed was used as the glass substrate instead of an ITO glass substrate.

[0100] The resulting connection structure was subjected to an unsaturated (85% RH) pressure cooker test (HAST) in which it was held in a constant temperature and humidity chamber (110°C, 85% RH) for 24 hours. Then, using a differential interference microscope, the electrode portion of the FPC was visually observed from the glass substrate side for the presence or absence of lifting, and evaluated according to the following criteria. In practice, a rating of A or B is sufficient, with a rating of A being more preferable. The observations were performed on a total of three areas (area dimensions: 2.5 mm x 0.5 mm), one each on the left, center, and right sides of the connection structure. In the evaluation criteria, the "area area" refers to the total area of ​​the three areas, and the "lifted area" refers to the total area of ​​the lifted area at the interface between the glass substrate and the conductive particle-containing layer and the lifted area at the interface between the insulating resin layer and the FPC. Here, "floating" can be confirmed by visual observation with an optical microscope as a region where a part of the interface between the glass substrate and the conductive particle-containing layer is discolored (usually discolored to white) compared to other regions, and as a region where a part of the interface between the insulating resin layer and the FPC is discolored (usually discolored to black) compared to other regions.

[0101] (Inspection of "floating" state after aging) A connection structure was prepared in the same manner as in the initial connection reliability test, and then aged (storage at 85°C, 85% RH, 250 hours). Then, in the same manner as in the post-HAST indentation visibility test, the state of the indentations caused by the conductive particles on the IZO electrode was visually observed from the glass substrate side using a differential interference microscope, and evaluated according to the following criteria. In practice, a rating of B is sufficient, and a rating of A is more preferable.

[0102] (Evaluation criteria for the condition of "floating" joints) Rank Evaluation criteria A: When the ratio of the floating area to the total area is less than 1% B: When the ratio of the floating area to the total area is 1% or more but less than 5% C: When the ratio of the floating area to the total area is 5% or more

[0103]

[0104]

[0105] (Discussion of Evaluation Results) The anisotropic conductive films of Examples 1 to 19 were rated A or B for "slit processability," "temporary adhesion," "adhesion strength (initial, after aging)," and "connection reliability (initial, after HAST, or after aging)." The anisotropic conductive films of Examples 1 to 17 were also rated A or B for "indentation visibility (after HAST or after aging)" and "floating state of the connection (after HAST or after aging)." When the anisotropic conductive films of Examples 1 to 19 and Comparative Examples 1 to 3 were wound onto reels to create wound bodies, no blocking occurred. When adhesive films consisting of only a single insulating resin layer were prepared in the same manner as the anisotropic conductive films of Examples 18 to 19, except that the conductive particles were removed, these films were evaluated in the same manner as in Example 1. Similar evaluation results were obtained for evaluation items other than those related to conductivity. These films were found to be useful as adhesive films.

[0106] Furthermore, the anisotropic conductive films of Examples 9 to 16 contained a silane coupling agent in the insulating resin layer, which prevented deterioration of adhesive strength due to aging. In particular, Example 16 received an A rating for all evaluation items even when stored at 85°C, 85% RH, and for 500 hours.

[0107] In the case of the anisotropic conductive film of Comparative Example 1, only radical polymerization initiators with a one-minute half-life temperature exceeding 125°C were used in the insulating resin layer, and therefore the "state of floating of the connection part" after the HAST test was rated C.

[0108] In the case of the anisotropic conductive films of Comparative Examples 2 and 3, since no anionic polymerization curing agent was used in the insulating resin layer, the items of "indentation visibility" after the HAST test and "state of floating of connection part" after the HAST test were both rated C.

[0109] In the case of the anisotropic conductive films of Comparative Examples 4 to 7, only one of the phenoxy resins with a weight-average molecular weight of 70,000 and the phenoxy resin with a weight-average molecular weight of 45,000 was used as the film-forming component of the insulating resin layer, and therefore the "temporary adhesion" item was rated C.

[0110] Furthermore, in the case of the anisotropic conductive film of Example 18, since the insulating resin layer contained a silane coupling agent, even when the slit width was 1.0 mm, 0.8 mm, 0.6 mm, or 0.5 mm, the "slit processability," "temporary adhesion," "adhesion strength (initial, after aging)," and "connection reliability (initial, after aging)" were rated A or B. In particular, even when the aging conditions were changed from "storage at 85°C, 85% RH, 250 hours" to "storage at 85°C, 85% RH, 500 hours," all evaluation items were rated A or B. The evaluations of connection reliability, indentation visibility, and lifting state after the HAST test, as well as the evaluations of indentation visibility and lifting state after aging, were also rated A or B.

[0111] In the case of the anisotropic conductive films of Comparative Examples 8 to 11, because only one of the phenoxy resins with a weight-average molecular weight of 70,000 and the phenoxy resin with a weight-average molecular weight of 45,000 was used as the film-forming component of the insulating resin layer, the temporary adhesion was rated C for all slit widths of 1.0 mm, 0.8 mm, 0.6 mm, and 0.5 mm. Furthermore, when the slit width was 0.6 mm or 0.5 mm, the slit processability was rated C.

[0112] The adhesive film of the present invention has a structure in which a radically polymerizable and anionically polymerizable insulating resin layer containing specific components is provided on a release-treated substrate film. Hybrid curing of this insulating resin layer by anionic polymerization and radical polymerization improves the crosslink density and the adhesiveness of the insulating resin layer. Therefore, the adhesive film of the present invention exhibits low-temperature, rapid curing properties, achieving good initial adhesive strength in connection structures manufactured using the adhesive film of the present invention. Furthermore, even if the connection structure is accidentally placed in a high-temperature, high-humidity environment, the connection reliability is not reduced, ensuring good visibility of the conductive particle impressions at the connection portion of the connection structure and preventing the connection portion from floating. Furthermore, such an adhesive film itself can be stably slit to narrow widths, and the temporary adhesion of the narrowly slit adhesive film can also be improved. In addition, since the adhesive film can perform satisfactorily in practical use with a slit width of 0.5 mm to 1.0 mm, it is easy to adapt to design changes and is highly convenient. Therefore, the adhesive film of the present invention is useful for manufacturing structures for mobile electronic devices such as smartphones and tablet PCs, which are evolving toward finer pitches and narrower frames, and for products requiring high-density packaging.

[0113] REFERENCE SIGNS LIST 1 insulating resin layer 2 conductive particle-containing layer 3 conductive particles 4 substrate film 10 adhesive film 100 anisotropic conductive film

Claims

1. An adhesive film having a base film that has been subjected to a release treatment and an insulating resin layer that is provided thereon and exhibits both radical and anionic polymerizability, wherein the insulating resin layer contains the following components A, B, C, D, and E: (Component A) a film-forming component containing a first film component having a weight-average molecular weight of 50,000 or more and 80,000 or less, and a second film component having a weight-average molecular weight of 30,000 or more and less than 50,000; (Component B) a radically polymerizable component containing a first acrylic compound; (Component C) an anionic polymerizable component containing an epoxy compound; (Component D) a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125°C or less; and (Component E) an anionic polymerization curing agent containing an organic acid hydrazide compound that is solid at room temperature; and the adhesive film has a film width of 1.0 mm or less and a length of 5 m or more.

2. The adhesive film according to claim 1, wherein the insulating resin layer contains conductive particles.

3. The adhesive film according to claim 1, wherein a conductive particle-containing layer is laminated on the insulating resin layer.

4. An adhesive film according to any one of claims 1 to 3, wherein the one-minute half-life temperature of the organic peroxide of component D is 100°C or higher and 120°C or lower, and the melting point of the organic acid hydrazide compound of component E is 80°C or higher and 160°C or lower.

5. The adhesive film according to any one of claims 1 to 3, wherein the insulating resin layer further contains a polyfunctional (meth)acrylate as a crosslinking agent.

6. The adhesive film according to claim 5, wherein the polyfunctional (meth)acrylate is an EO-modified isocyanuric acid di- or tri(meth)acrylate.

7. The adhesive film according to any one of claims 1 to 3, wherein the insulating resin layer further contains a silane coupling agent.

8. The adhesive film according to claim 7, wherein the silane coupling agent is an alkoxysilane having an epoxy group.

9. The adhesive film according to any one of claims 1 to 3, which is wound around a reel to form a wound body.

10. A method for producing an adhesive film, comprising forming a film of an insulating resin layer-forming composition on a release-treated substrate film and slitting the film into a width of 1.0 mm or less and a length of 5 m or more, wherein the insulating resin layer contains the following components A, B, C, D, and E: (component A) a film-forming component containing a first film component having a weight-average molecular weight of 50,000 or more and 80,000 or less, and a second film component having a weight-average molecular weight of 30,000 or more but less than 50,000; (component B) a radically polymerizable component containing a first acrylic compound; (component C) an anionically polymerizable component containing an epoxy compound; (component D) a radical polymerization initiator containing an organic peroxide having a one-minute half-life temperature of 125°C or less; and (component E) an anionically polymerizable curing agent containing an organic acid hydrazide compound that is solid at room temperature.

11. A connection structure comprising a first electronic component and a second electronic component connected via the adhesive film according to any one of claims 1 to 3.

12. A method for producing a connection structure, comprising sandwiching the adhesive film according to any one of claims 1 to 3 between a first electronic component and a second electronic component, and connecting them by pressure bonding.

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