Filler-containing film

Abstract

To make it possible to realize excellent filler retention and excellent temporary adhesion, without using a throughhole as a site for placing a filler in a filler-containing film such as an anisotropic conductive film, and also to realize excellent conduction resistance and insulation resistance when the filler-containing film is applied as the filler to the anisotropic conductive film in which the conductive particles are used.SOLUTION: A filler-containing film has a first adhesive layer having recesses formed on a surface thereof, and a filler filled in the recesses formed on the surface of the first adhesive layer, wherein the recesses having a bottom surface, and a gap exists between at least a peripheral edge of the bottom surface and the filler. A second adhesive layer may be laminated on the first adhesive layer.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] This invention relates to a filler-containing film. [Background technology]

[0002] Filler-containing films, in which fillers are dispersed in a resin layer, are used in a wide variety of applications, including matte films, capacitor films, optical films, label films, antistatic films, conductive films, and anisotropic conductive films. When filler-containing films are used by heat-pressing them onto articles, it is desirable from the standpoint of optical, mechanical, or electrical properties to suppress the unnecessary flow of the resin forming the filler-containing film during heat-pressing and to suppress the uneven distribution of the filler. In particular, when conductive particles are included as fillers and the filler-containing film is used as a conductive film or anisotropic conductive film for mounting electronic components, if the conductive particles are dispersed at high density in the insulating resin layer to accommodate high-density mounting of electronic components, excessive resin flow during mounting of electronic components can cause the conductive particles to move unnecessarily and become unevenly distributed between terminals, leading to short circuits. Therefore, it is necessary to suppress such excessive resin flow.

[0003] In response to such demands, a conductive connecting film with a microparticle arrangement has been proposed, which has a laminate comprising an adhesive film and release films laminated on both sides thereof, with through-holes provided and conductive microparticles arranged in these through-holes (Patent Document 1). However, in this conductive connecting film with a microparticle arrangement, the through-holes are open on both sides of the film, in other words, the conductive microparticles are exposed at the openings above and below the through-holes. This leads to unstable retention of the conductive microparticles, problems such as the conductive microparticles falling out of the through-holes when the release film is peeled off, and the conductive microparticles moving unnecessarily during compression. Furthermore, because there is no adhesive resin between the conductive microparticles and the substrate or other adherend, there is also the problem that the temporary adhesion to the substrate or other adherend is insufficient. In addition, since the lower limit of the particle size of the conductive microparticles intended for use is 10 μm, there is also the problem that there are limitations on the layout of the electrodes to be mounted. Even if it could be applied to smaller particle sizes, there are concerns that the film structure would impose constraints on its use.

[0004] To address these problems, an anisotropic conductive film has been proposed that has a conductive particle-containing layer formed by pressing conductive particles into an insulating resin layer adjusted to a predetermined viscosity range (Patent Document 2). In the anisotropic conductive film of Patent Document 2, the bottom and sides of the pressed conductive particles are encased in insulating resin, improving the retention of conductive particles and also improving the ability to temporarily adhere to the substrate. Furthermore, in order to make it easier for conductive particles to be pressed by terminals during anisotropic conductive connection and to improve the capture of conductive particles at the terminals, conductive particles with a particle diameter CV value of 20% or less are used, and in addition, the surface of the conductive particle-containing layer near where the conductive particles are pressed is given a slope or undulation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-31030 [Patent Document 2] Patent No. 6187665 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in the conductive particle-containing layer of the anisotropic conductive film described in Patent Document 2, the conductive particles are sufficiently retained because they are completely enclosed in the insulating resin on all surfaces except the surface on which the conductive particles are pressed into the conductive particle-containing layer. However, in the event of an irregular situation (for example, if an anisotropic conductive connection is made at an unexpectedly high temperature while continuously pressing a large number of units together), the insulating resin may flow excessively when the conductive particles are pressed between terminals. In such cases, the flow of the insulating resin may cause unnecessary movement of the conductive particles, potentially leading to an undesirable situation where the insulation resistance between adjacent terminals decreases significantly. Furthermore, even if unnecessary movement of conductive particles does not occur in such an unforeseen situation, there is concern that the conductivity resistance between opposing terminals may increase significantly.

[0007] The object of the present invention is to solve the problems of the conventional technology described above, and to enable good filler retention and good temporary adhesion in filler-containing films such as anisotropic conductive films without using through holes as sites for positioning the filler, and to enable good conductivity resistance even when irregular situations occur when the filler-containing film is applied to conductive films or anisotropic conductive films that use conductive particles as fillers, and in the case of anisotropic conductive films, to also enable good insulation resistance. [Means for solving the problem]

[0008] The inventors of the present invention have discovered that the objective of the present invention can be achieved not by pressing the filler into the insulating resin layer, nor by filling through holes provided in the insulating resin layer, but by filling the recesses provided in the insulating resin layer with filler such that a gap exists between the peripheral edge of the bottom surface of the recess and the filler, and have thus completed the present invention.

[0009] That is, the present invention relates to a filler-containing film having a first adhesive layer having recesses formed on its surface, and a filler filling the recesses formed on the surface of the first adhesive layer, The present invention provides a filler-containing film in which the recess has a bottom surface, and a void exists between at least the peripheral edge of the bottom surface and the filler. The filler-containing film of the present invention may have a second adhesive layer laminated on a first adhesive layer.

[0010] Furthermore, the present invention relates to a method for producing the aforementioned filler-containing film, A step of preparing a recess-forming mold having a protrusion corresponding to a recess formed on the surface of the first adhesive layer, A step of obtaining a first adhesive layer with recesses formed on its surface by applying a resin composition for forming a first adhesive layer to the protruding surface of a recess-forming mold, drying it, and then removing the recess-forming mold, and Steps to fill the recesses of the first adhesive layer with filler. The present invention provides a manufacturing method having the following steps: The manufacturing method further includes the step of forming a second adhesive layer by applying a resin composition for forming a second adhesive layer to the surface or back surface of the first adhesive layer and drying it, and If a second adhesive layer is formed on the back surface of the first adhesive layer, the third adhesive layer is formed by applying a resin composition for forming the third adhesive layer to the surface of the first adhesive layer and drying it. The present invention provides a manufacturing method for which the present invention is located.

[0011] Furthermore, the present invention provides a connection structure in which a first member and a second member are joined via the aforementioned filler-containing film. Preferably, the present invention provides a connection structure in which a first electronic component and a second electronic component are anisotropically conductively connected via a filler-containing film used as an anisotropic conductive film.

[0012] Furthermore, the present invention provides a method for manufacturing a connecting structure in which a first member and a second member are joined via the aforementioned filler-containing film. Preferably, the present invention provides a method for manufacturing a connecting structure in which a first electronic component and a second electronic component are anisotropically conductively connected via a filler-containing film used as a conductive film or an anisotropic conductive film.

Advantages of the Invention

[0013] The filler-containing film of the present invention has a structure composed of a filler and a first adhesive layer that holds the filler. However, the through-holes of the first adhesive layer are not filled with the filler, nor is the filler forcibly pushed into the first adhesive layer. In the filler-containing film of the present invention, recesses are provided in the first adhesive layer in advance, and the recesses are filled with the filler. Therefore, good retention of the filler can be achieved. Further, since the bottom of the recess is made of an insulating resin, good temporary adhesion can be achieved for the filler-containing film. Furthermore, a gap is provided between at least the peripheral portion of the bottom surface of the recess and the filler. Since this gap functions as a resin reservoir, unnecessary movement of the filler can be suppressed even if the insulating resin flows. Therefore, when the filler-containing film is applied to a conductive film or an anisotropic conductive film that uses conductive particles as the filler, good conduction resistance can be achieved, and in the case of an anisotropic conductive film, good insulation resistance can also be achieved.

Brief Description of the Drawings

[0014] [Figure 1A] FIG. 1A is a schematic cross-sectional view of the filler-containing film of the present invention. [Figure 1B] FIG. 1B is a partially enlarged cross-sectional view of the filler-containing film of FIG. 1A. [Figure 2] FIG. 2 is a schematic cross-sectional view of the filler-containing film of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view of the filler-containing film of the present invention. [Figure 4A] FIG. 4A is an explanatory view of the manufacturing process of the filler-containing film of the present invention. [Figure 4B] FIG. 4B is an explanatory view of the manufacturing process of the filler-containing film of the present invention. [Figure 4C] FIG. 4C is an explanatory view of the manufacturing process of the filler-containing film of the present invention. [Figure 4D] FIG. 4D is an explanatory view of the manufacturing process of the filler-containing film of the present invention. [Figure 4E] Figure 4E is an explanatory diagram of the manufacturing process of the filler-containing film of the present invention. [Figure 4F] Figure 4F is an explanatory diagram of the manufacturing process of the filler-containing film of the present invention. [Figure 4G] Figure 4G is an explanatory diagram of the manufacturing process of the filler-containing film of the present invention. [Figure 5] Figure 5 is a schematic cross-sectional view of the filler-containing film of Comparative Example 1. [Figure 6] Figure 6 is a schematic cross-sectional view of the filler-containing film of Reference Example 1. [Modes for carrying out the invention]

[0015] An example of the filler-containing film of the present invention will be described in detail below with reference to the drawings.

[0016] <Overall composition of filler-containing film> Figure 1A is a schematic cross-sectional view of the filler-containing film 10 of the present invention, and Figure 1B is a partially enlarged cross-sectional view of the vicinity of the filler. This filler-containing film 10 has a structure in which a second adhesive layer 2 is laminated on a first adhesive layer 1, and a filler 4 is held in a recess 3 formed on the surface of the first adhesive layer 1 on the second adhesive layer side. A gap 3c is formed between at least the peripheral edge 3b of the bottom surface 3a of the recess 3 and the filler 4. In Figure 1A, the second adhesive layer 2 is laminated on the first adhesive layer 1, but the filler-containing film 10 of the present invention may be a single layer of the first adhesive layer 1.

[0017] In Figure 1A, the recess 3 of the first adhesive layer 1 opens towards the second adhesive layer 2, but as shown in Figure 2, it may open on the opposite side from the second adhesive layer 2. In either case, a gap is formed between the filler and the bottom surface of the recess, and this gap becomes surplus space that can receive resin. Therefore, it becomes possible to fill the recess of the filler with resin (for example, adhesive) while controlling the load on the filler more precisely. As a means of performing the above control more precisely, a third adhesive layer 5 is laminated on the surface of the first adhesive layer 1 opposite to the second adhesive layer 2.

[0018] (1st adhesive layer 1) The first adhesive layer 1 constituting the filler-containing film 10 of the present invention is a base layer for holding the filler 4 and for forming the second adhesive layer 2 on it when manufacturing the filler-containing film 10. Such a first adhesive layer 1 may be composed of a single insulating resin layer or a laminate of multiple insulating resin layers. Furthermore, it is preferable that the first adhesive layer 1 exhibits adhesive properties.

[0019] (Resin composition constituting the first adhesive layer 1) The resin composition constituting the first adhesive layer 1 is appropriately selected according to the application of the filler-containing film, and examples include thermoplastic resin compositions, high-viscosity adhesive resin compositions, or curable resin compositions. When the recess 3 is formed using a press mold, a thermoplastic resin composition is preferred. Furthermore, when the filler-containing film is an anisotropic conductive film, a curable resin composition formed from a polymerizable compound and a polymerization initiator can be used, similar to the resin composition used to form the insulating resin layer of a conventional anisotropic conductive film. In this case, a thermal polymerization initiator may be used as the polymerization initiator, a photopolymerization initiator may be used, or both may be used in combination. For example, a cationic polymerization initiator may be used as the thermal polymerization initiator and an epoxy resin as the thermal polymerizable compound, and a photoradical polymerization initiator may be used as the photopolymerization initiator and an acrylate compound as the photopolymerizable compound. A thermal anionic polymerization initiator may also be used as the thermal polymerization initiator. As a thermal anionic polymerization initiator, it is preferable to use a microencapsulated latent curing agent having an imidazole modified material as a nucleus and its surface coated with polyurethane.

[0020] (Minimum melt viscosity of the first adhesive layer 1) The minimum melt viscosity of the first adhesive layer 1 is preferably 1500 Pa·s or more, more preferably 2000 Pa·s or more, even more preferably 3000 Pa·s or more, preferably 15000 Pa·s or less, more preferably 10000 Pa·s or less, and particularly preferably 8000 Pa·s or less, in order to suppress the unwanted movement of the filler 4 due to resin flow when the filler-containing film 10 is heat-pressed onto the article and to guide appropriate resin flow. Here, the temperature at which the minimum melt viscosity is exhibited is preferably 60°C or more, more preferably 70°C or more, preferably 110°C or less, and more preferably 100°C or less. The minimum melt viscosity can be determined, for example, using a rotary rheometer (manufactured by TA Instruments), maintaining a constant measurement pressure of 5g, and using a measurement plate with a diameter of 8mm. More specifically, it can be determined in the temperature range of 30 to 200°C, with a heating rate of 10°C / min, a measurement frequency of 10Hz, and a load variation of 5g on the measurement plate. The minimum melt viscosity can be adjusted by changing the type and amount of fine solids used as a melt viscosity modifier, or by changing the preparation conditions of the resin composition.

[0021] (Thickness of the first adhesive layer 1) The thickness of the first adhesive layer 1 should be at least 0.6 times the average particle diameter of the filler 4, preferably 1.2 times or more, and more preferably 1.5 times or more, in order to stably hold the filler 4. Furthermore, the upper limit of the thickness of the first adhesive layer 1 varies depending on the method of use, but when both sides of the film are sandwiched, it should preferably be 10 times or less, and more preferably 5 times or less, the average particle diameter of the filler 4, in order to prevent unwanted movement of the filler 4 due to resin flow. The layer thickness can be measured using a known thickness gauge or film thickness measuring instrument.

[0022] (Adhesive strength of the first adhesive layer 1) The first adhesive layer 1 preferably has an adhesive strength that allows for preliminary bonding to the article to which the filler-containing film 10 is to be heat-pressed before heat-pressing. The adhesive strength can be measured in accordance with JIS Z 0237, or it can be measured as tack force by the probe method in accordance with JIS Z 3284-3 or ASTM D 2979-01. The tack force of the first adhesive layer 1 constituting the filler-containing film 10, measured by the probe method, is preferably 1.0 kPa (0.1 N / cm²) when measured, for example, with a probe pressing speed of 30 mm / min, a pressing force of 196.25 gf, a pressing time of 1.0 sec, a peeling speed of 120 mm / min, and a measurement temperature of 23°C ± 5°C. 2 ) or more, more preferably 1.5 kPa (0.15 N / cm²). 2 ) or more, particularly preferably 3.0 kPa (0.3 N / cm²). 2 That's all.

[0023] Such adhesive strength can be adjusted by appropriately adjusting the resin composition constituting the first adhesive layer 1, and by improving the smoothness of the first adhesive layer 1 forming the outer surface of the filler-containing film using a method for manufacturing the filler-containing film described later.

[0024] (Recess 3 formed in the first adhesive layer 1) In the present invention, the first adhesive layer 1 is provided with a recess 3 on the surface or back surface facing the second adhesive layer 2. This recess 3 has the function of accommodating and holding the filler 4. It is preferable that the surface or back surface of the first adhesive layer 1 where the recess 3 is not formed is flat in order to ensure good adhesion of the filler-containing film 10 to other components.

[0025] The recess 3 can be any shape that can accommodate and securely hold the filler 4, and is preferably a cylindrical, tumbler-shaped, or cup-shaped hole, with a cylindrical shape being preferred from the standpoint of allowing for more precise positional control in a plan view. If the filler diameter is larger than the film thickness, more than half of the filler may be accommodated and held. Therefore, a portion of the filler may be exposed. In order to facilitate the stable accommodation of the filler 4, it is preferable that the hole diameter of such a recess 3 is the same from the opening to the bottom, but it may also have a taper such that the hole diameter decreases towards the bottom. Having such a taper improves the retention of the filler. The shape of such a recess 3 can be confirmed by observing the cross-section of the filler-containing film with a metallurgical microscope or by observing reflected light with a metallurgical microscope.

[0026] Since the recess 3 is not a through hole, it has a bottom surface 3a. As a result of the presence of this bottom surface 3a, a void 3c can be created between at least its peripheral edge 3b and the filler 4. The void 3c of the peripheral edge 3b may extend directly below the filler 4. This void 3c functions as a receiving space for the flowing resin when resin flow occurs, and can suppress excessive resin flow. The presence or absence of such a void 3c can be confirmed by observing the cross-section of the filler-containing film 10 with a metallurgical microscope, a laser microscope, or by observing reflected light with a metallurgical microscope. In the case of observed reflected light, the void 3c can be seen as bubbles or as a white interference haze around the filler. The fact that the recess is not completely filled with resin, in other words, that the filler and the filler-containing film are not completely integrated and a void exists, is what distinguishes this invention from the conventional invention. The volume of the void can be determined by subtracting the volume of the filler from the volume of the recess. Here, the volume of the recess can be determined or approximated by multiplying the opening area of ​​the recess by the depth of the recess, and the filler volume can be determined from the particle size, assuming the filler is a sphere. On the film bottom surface side of the filler, the space between the filler and the film bottom surface maintains a space in which the filler and the resin forming the film can move, and this can be separately defined as a movable region.

[0027] The bottom surface 3a of the recess 3 only needs to have a shape that can hold the filler 4 and allow for the existence of a void 3c, and is preferably provided substantially parallel to the planar direction of the filler-containing film 10. For example, if the recess 3 is cylindrical, the bottom surface 3a will be circular. In addition, the bottom surface 3a may be a cone, pyramidal shape, frustoconical shape, or frustoconical shape that is convex towards the filler 4 side. It may also be a round shape that is convex downwards (for example, a flat round dish shape that can secure a void). The shape of the bottom surface 3a can be confirmed by observing the cross-section of the filler-containing film 10 with a metallurgical microscope or by observing reflected light with a metallurgical microscope.

[0028] The volume of the recess 3 should be at least 1.1 times the average volume of the filler, preferably 1.3 times or more, more preferably 1.5 times or more, in order to ensure contact between the filler and the filler-containing film and to accurately control its position. For ease of filling for productivity, it should be at least 8 times, more preferably 5 times or less.

[0029] The depth of the recess 3 (i.e., the distance from the surface of the first adhesive layer to the bottom surface of the recess 3) varies depending on the size of the filler 4, which will be described later, but is usually preferably 0.5 times or more, more preferably 0.6 times or more, and even more preferably 0.8 times or more, the average particle diameter of the filler 4 for particle-containing purposes, and preferably 1.5 times or less, and more preferably 1.2 times or less, the average particle diameter of the filler 4 to prevent unwanted movement of the filler 4 due to resin flow.

[0030] The diameter of the recess 3 may vary in the depth direction of the recess 3, so it is defined as the maximum diameter. For example, if the shape of the recess 3 is cylindrical, the recess diameter will be approximately the same as the opening diameter and the bottom diameter. If the shape of the recess 3 is a frustoconical shape that narrows towards the bottom, the opening diameter will be the recess diameter. The recess diameter, bottom diameter, and maximum diameter of the recess 3 will also vary depending on the size of the filler 4, which will be described later, but usually, for particle-containing capacity, they are preferably 1.0 times or more, more preferably 1.2 times or more, the average particle diameter of the filler 4, and preferably 2.0 times or less, more preferably 1.5 times or less, the average particle diameter of the filler 4, so as not to cause unnecessary movement of the filler 4 due to resin flow.

[0031] The recesses 3 may be arranged in a random pattern on the first adhesive layer 1, but it is sometimes preferable to arrange them in a regular pattern in order to bring out the properties of the filler. These arrangement patterns are, in other words, synonymous with the arrangement patterns of the filler. Examples of regular patterns include grid arrangements such as square grids, rectangular grids, and orthorhombic grids. Multiple grids of different shapes may be combined. Rows of recesses 3 arranged linearly at predetermined intervals may be placed in parallel at predetermined intervals. Regions in which the recesses 3 are densely arranged and regions in which they are sparsely arranged may be regularly repeated. When the filler-containing film 10 is an anisotropic conductive film, it is more preferable to arrange the recesses 3 in a regular pattern with them spaced apart from each other in order to achieve both trapping stability at the terminals and short-circuit suppression. Whether or not the recesses 3 are regularly arranged can be determined, for example, by observing whether a predetermined arrangement of the recesses 3 or filler 4 is repeated in the longitudinal direction of the film (the winding direction when the filler-containing film is wound into a roll).

[0032] Also, the filler filling rate in the recesses can be determined as {(the number of fillers / the number of recesses) × 100 (%)}. This can be determined by observing the film surface field similar to the following number density. The filler filling rate should be 95% or more, preferably 98% or more, and more preferably 99.5% or more. It is desirable that the residual fillers (residual rate) not filled with the filler are few (close to zero).

[0033] The distance between the recesses 3 can be determined according to the articles or applications to be connected, and there is no particular limitation. However, the number density of the recesses 3 is usually 10 per mm 2 or more and 500000 per mm 2 or less, preferably 30 per mm 2 or more and 100000 per mm 2 or less, and can be appropriately determined within this range. For example, when the filler-containing film 10 is used as an anisotropic conductive film, the number density of the recesses 3 (that is, the number density of the conductive particles) should be 30 per mm 2 or more, and the upper limit can be 360000 per mm 2 or less, preferably 250000 per mm 2 or less, and more preferably 100000 per mm 2 or less. The number density can be measured by observing the film surface field with a microscope. The observation area should be 2 mm 2 or more, preferably 10 mm 2 or more.

[0034] (Filler 4) In the present invention, the filler 4 is appropriately selected from known inorganic fillers (metal particles, metal oxide particles, metal nitride particles, etc.), organic fillers (resin particles, rubber particles, etc.), and fillers containing a mixture of organic and inorganic materials (for example, particles with a core made of resin material and a metal-plated surface (metal-coated resin particles), conductive particles with insulating fine particles attached to the surface, conductive particles with an insulating treatment on the surface, etc.) according to the performance required for the application, such as hardness and optical performance. For example, in optical films and matte films, silica fillers, titanium oxide fillers, styrene fillers, acrylic fillers, melamine fillers, and various titanates can be used. In capacitor films, titanium oxide, magnesium titanate, zinc titanate, bismuth titanate, lanthanum oxide, calcium titanate, strontium titanate, barium titanate, barium zirconate titanate, lead zirconate titanate, and mixtures thereof can be used. In adhesive films, polymer-based rubber particles, silicone rubber particles, etc. can be included. Conductive films and anisotropic conductive films contain conductive particles. Examples of conductive particles include metal particles such as nickel, cobalt, silver, copper, gold, and palladium; alloy particles such as solder; metal-coated resin particles; and metal-coated resin particles with insulating fine particles attached to the surface. Two or more types can be used in combination. Among these, metal-coated resin particles are preferred because the resin particles repel each other after connection, making it easier to maintain contact with the terminals and resulting in stable conductivity. Furthermore, the surface of the conductive particles may be treated with an insulating treatment using known techniques that does not impair the conductivity characteristics.

[0035] (Average particle size of filler 4) The average particle size of the filler 4 can be determined according to the application of the filler-containing film 10. For example, when the filler-containing film is used as an anisotropic conductive film, the average particle size is preferably 1 μm or more, more preferably 2.5 μm or more, in order to improve the accuracy of the indentation of the filler 4 during the manufacture of the filler-containing film 10. Also, in order to suppress the effect of misalignment of the filler 4 during the manufacture of the filler-containing film 10, the average particle size is preferably 200 μm or less, more preferably 50 μm or less. The average particle size of the filler 4 can be determined from a planar image or a cross-sectional image. Furthermore, the average particle size of the filler 4 as raw material particles before being incorporated into the filler-containing film 10 can be determined using a wet flow particle size and shape analyzer FPIA-3000 (Malvern Panalytical). If fine particles such as insulating fine particles are attached to the filler 4, the particle size will be the diameter excluding the fine particles.

[0036] Regarding the variation in the average particle size of the filler 4 in the filler-containing film 10, it is preferable to set the CV value (standard deviation / mean) to 20% or less. This makes it easier for the filler-containing film 10 to be pressed evenly when it is pressed onto an article, preventing localized concentration of pressure. Therefore, when the filler-containing film 10 is configured as an anisotropic conductive film, the stability of the connection is improved, and after connection, the connection state can be accurately evaluated by observing the indentation and the state in which the filler 4 is held. Specifically, in inspection after anisotropic conductive connection between electronic components using an anisotropic conductive film, the connection state can be accurately confirmed by observing the indentation and the state in which the conductive particles are held, whether the terminal size is relatively large (such as FOB) or relatively small (such as COG). Therefore, inspection after anisotropic connection becomes easier, and it is expected that the productivity of the connection process will improve.

[0037] On the other hand, in cross-sectional views of the filler-containing film 10 cut in the film thickness direction (Figures 1A and 1B), it is preferable that the vertices of each filler 4 in the film thickness direction are aligned flush with a plane parallel to the interface between the first adhesive layer 1 and the second adhesive layer 2. This makes it easier to uniformly press the filler-containing film 10 onto an article.

[0038] (Second adhesive layer 2) The filler-containing film 10 of the present invention has a second adhesive layer 2 on the recessed surface (Figure 1A) or back surface (Figure 2) of the first adhesive layer 1. This second adhesive layer 2 is a layer for temporarily bonding the filler-containing film 10 to an article. Such a second adhesive layer 2 may be composed of a single insulating resin layer or a laminate of multiple insulating resin layers.

[0039] (Resin composition constituting the second adhesive layer 2) The resin composition constituting the second adhesive layer 2 is appropriately selected according to the application of the filler-containing film 10, similar to the first adhesive layer 1, and examples include thermoplastic resin compositions, high-viscosity adhesive resin compositions, or curable resin compositions. For example, when the filler-containing film 10 is an anisotropic conductive film, a curable resin composition formed from a polymerizable compound and a polymerization initiator can be used, similar to the resin composition that forms the adhesive layer of a conventional anisotropic conductive film. In this case, a thermal polymerization initiator may be used as the polymerization initiator, a photopolymerization initiator may be used, or both may be used in combination. For example, a cationic polymerization initiator may be used as the thermal polymerization initiator, and an epoxy resin as the thermal polymerizable compound, while a photoradical polymerization initiator may be used as the photopolymerization initiator, and an acrylate compound as the photopolymerizable compound. A thermal anionic polymerization initiator may also be used as the thermal polymerization initiator. As the thermal anionic polymerization initiator, it is preferable to use a microencapsulated latent curing agent having an imidazole modified material as a nucleus and its surface coated with polyurethane.

[0040] (Minimum melt viscosity of the second adhesive layer 2) The minimum melt viscosity of the second adhesive layer 2 is preferably 100 Pa·s or more, more preferably 200 Pa·s or more, even more preferably 400 Pa·s or more, preferably 5000 Pa·s or less, more preferably 3000 Pa·s or less, and particularly preferably 1500 Pa·s or less, in order to suppress the unwanted movement of the filler 4 due to resin flow when the filler-containing film 10 is heat-pressed onto the article and to promote appropriate resin flow. Here, the temperature at which the minimum melt viscosity is exhibited is preferably 60°C or more, more preferably 70°C or more, preferably 110°C or less, and more preferably 100°C or less. The measurement and adjustment of the minimum melt viscosity of the second adhesive layer 2 can be carried out in the same manner as in the case of the first adhesive layer 1. Note that the minimum melt viscosity of the second adhesive layer 2 is preferably lower than the minimum melt viscosity of the first adhesive layer 1 from the viewpoint of filling properties.

[0041] (Thickness of the second adhesive layer 2) The thickness of the second adhesive layer 2 is preferably 0.5 times or more, more preferably 1.0 times or more, the average particle diameter of the filler 4, in order to impart appropriate adhesiveness to the filler-containing film 10. Furthermore, the upper limit of the thickness of the second adhesive layer 2 is preferably 30 times or less, 10 times or less, and more preferably 5 times or less, the average particle diameter of the filler 4, in order to prevent unwanted movement of the filler 4 due to resin flow. Specifically, it is preferably 0.1 μm or more, more preferably 0.5 μm or more. It may be 20 μm or more in order to properly fill the filler. If it is too thick, there is a concern that the resin will overflow when it is made into a wound assembly, so it is preferably 50 μm or less. In this way, the layer thickness can be set appropriately according to the purpose.

[0042] (Adhesive strength of the second adhesive layer 2) The second adhesive layer 2 preferably has an adhesive strength that allows for preliminary bonding to the article to which the filler-containing film 10 is to be heat-pressed before heat-pressing. The adhesive strength can be measured in the same way as in the case of the first adhesive layer 1. The adhesive strength can be adjusted by appropriately adjusting the resin composition constituting the second adhesive layer 2, and by improving the smoothness of the second adhesive layer 2 which forms the outer surface of the filler-containing film 10 by the manufacturing method of the filler-containing film 10 described later. It is preferable that the adhesive strength of the second adhesive layer 2 be higher than that of the first adhesive layer 1 from the viewpoint of handling. Furthermore, since the second adhesive layer 2 (and the third adhesive layer 5 described later) is the surface that comes into contact with the adherend, it is practically preferable that its adhesive strength be higher than that of the first adhesive layer.

[0043] (Third adhesive layer 5) In the present invention, when the filler-containing film 10 has a second adhesive layer 2 on the back surface (Figure 3) of the surface facing the recess 3 of the first adhesive layer 1, it is preferable to laminate a third adhesive layer 5 on the surface facing the recess 3. This third adhesive layer 5 is a layer for preventing the filler 4 from falling out of the recess 3, and is also a layer for temporarily pressing the filler-containing film 10 onto an article. Such a third adhesive layer 5 may be composed of a single insulating resin layer, or it may be composed of a laminate of multiple insulating resin layers.

[0044] (Resin composition constituting the third adhesive layer 5) The resin composition constituting the third adhesive layer 5 is appropriately selected according to the application of the filler-containing film 10, similar to the first adhesive layer 1. Examples include thermoplastic resin compositions, high-viscosity adhesive resin compositions, or curable resin compositions. For example, when the filler-containing film 10 is an anisotropic conductive film, a curable resin composition formed from a polymerizable compound and a polymerization initiator can be used, similar to the resin composition used to form the adhesive layer of a conventional anisotropic conductive film. In this case, a thermal polymerization initiator may be used as the polymerization initiator, a photopolymerization initiator may be used, or both may be used in combination. For example, a cationic polymerization initiator may be used as the thermal polymerization initiator and an epoxy resin as the thermal polymerizable compound, and a photoradical polymerization initiator may be used as the photopolymerization initiator and an acrylate compound as the photopolymerizable compound. A thermal anionic polymerization initiator may also be used as the thermal polymerization initiator. As a thermal anionic polymerization initiator, it is preferable to use a microencapsulated latent curing agent having an imidazole modified material as a nucleus and its surface coated with polyurethane.

[0045] (Minimum melt viscosity of the third adhesive layer 5) The minimum melt viscosity of the third adhesive layer 5 can be the same as that of the second adhesive layer 2 in order to suppress the unwanted movement of the filler 4 due to resin flow when the filler-containing film 10 is heat-pressed onto the article, and to promote appropriate resin flow. The minimum melt viscosity of the third adhesive layer 5 can be measured and adjusted in the same way as in the case of the first adhesive layer 1. However, from the viewpoint of filling properties, it is preferable that the minimum melt viscosity of the third adhesive layer 5 be lower than that of the first adhesive layer 1.

[0046] (Thickness of the third adhesive layer 5) The thickness of the third adhesive layer 5 may be the same as that of the second adhesive layer 2. When the third adhesive layer 5 is the surface that is first attached to the adherend, it is preferably 0.1 times or more, more preferably 0.3 times or more, the average particle diameter of the filler 4 in order to impart appropriate tackiness to the filler-containing film 10. Furthermore, the upper limit of the thickness of the third adhesive layer 5 may be preferably 2.0 times or less, more preferably 1.0 times or less, the average particle diameter of the filler 4 in order to prevent unwanted movement of the filler 4 due to resin flow.

[0047] (Adhesive strength of the third adhesive layer 5) The third adhesive layer 5 preferably has an adhesive strength that allows for temporary bonding to the article to which the filler-containing film 10 is to be heat-pressed, and can be the same as the adhesive strength of the second adhesive layer 2. It may also be higher than the adhesive strength of the second adhesive layer 2. This makes it easier to fix the film to the adherend and to mount components (especially minute components with sides of 100 μm or less) onto the second adhesive layer.

[0048] <Manufacturing of filler-containing film 10> The filler-containing film 10 of the present invention can be manufactured by the following manufacturing method. That is, a step of preparing a recess-forming mold having a protrusion corresponding to a recess formed on the surface of the first adhesive layer, A step of obtaining a first adhesive layer with recesses formed on its surface by applying a resin composition for forming a first adhesive layer to the protruding surface of a recess-forming mold, drying it, and then removing the recess-forming mold, and Steps to fill the recesses of the first adhesive layer with filler. It can be manufactured by a manufacturing method having the following steps: This manufacturing method further includes the step of forming a second adhesive layer by applying a resin composition for forming a second adhesive layer to the surface or back surface of the first adhesive layer and drying it, and If a second adhesive layer is formed on the back surface of the first adhesive layer, the third adhesive layer is formed by applying a resin composition for forming the third adhesive layer to the surface of the first adhesive layer and drying it. It is preferable that it has

[0049] The filler-containing film 10 can be manufactured as shown in Figures 4A to 4G, but is not limited to this manufacturing method. The following explanation will be given with reference to the drawings.

[0050] First, as shown in Figure 4A, a recess-forming mold 40 is prepared, which has a protrusion 40a corresponding to a recess (42a in Figure 4C) formed on the surface of the first adhesive layer (see Figure 4C) (Figure 4A). The recess-forming mold 40 can be obtained by mechanical processing (such as cutting) or by photolithography.

[0051] Next, as shown in Figure 4B, the resin composition 41 for forming the first adhesive layer is applied to the protruding surface of the recess-forming mold 40 and dried. Subsequently, as shown in Figure 4C, the recess-forming mold 40 is removed to form the first adhesive layer 42 with recesses 42a on its surface. Although not shown, a light-tack release film can be attached to the surface of the first adhesive layer 42 that does not have recesses before removing the recess-forming mold 40.

[0052] Next, as shown in Figure 4D, filler 43 is filled into the recess 42a of the first adhesive layer 42 in accordance with a conventional method.

[0053] Next, as shown in Figure 4E, the second adhesive layer 44 is formed by applying the resin composition for forming the second adhesive layer to the surface of the first adhesive layer 42 (the surface where the recess is formed) and drying it. This yields a filler-containing film 10 with the structure shown in Figure 1A.

[0054] As shown in Figure 4F, if the second adhesive layer 44 is formed on the back surface (the side without recesses) of the first adhesive layer 42, the third adhesive layer 45 is formed by applying the resin composition for forming the third adhesive layer to the surface (the side with recesses) of the first adhesive layer 42 and drying it, as shown in Figure 4G. This yields a filler-containing film 10 with the structure shown in Figure 3. The reaction rate of the filler-containing film is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. This allows for stable manufacturing of the connecting structure. The meaning of the reaction rate, measurement method, etc. will be described later.

[0055] <Deformation patterns of filler-containing films> When the filler-containing film is used in minute components such as micro-LEDs, it may be in predetermined units, such as one pixel (one pixel unit) for one set of RGB. The shape of the individual pieces is not particularly limited and can be appropriately set according to the dimensions of the electronic component to be connected. When the individual pieces of the filler-containing film are formed on a base film by a laser lift-off processing method using a laser lift-off (LLO) device (for example, product name: Invisi LUM-XTR, Shin-Etsu Chemical Co., Ltd.) (see Japanese Patent Publication No. 2017-157724), the shape of the individual pieces is preferably at least one selected from a polygon with obtuse angles, a polygon with rounded corners, an ellipse, an oblong, and a circle, in order to suppress the occurrence of peeling and chipping.

[0056] The dimensions (length × width) of each piece of filler-containing film are appropriately set according to the dimensions of the electronic component to be connected, and the ratio of the area of ​​each piece to the area of ​​the electronic component is preferably 2 or more, more preferably 4 or more, and even more preferably 5 or more. The thickness of each piece is similar to the thickness of the filler-containing film, preferably the average particle size of the conductive particles plus 1 to 4 μm, particularly preferably 1 to 2 μm, and preferably 1 μm to 10 μm, more preferably 1 μm to 6 μm, and even more preferably 2 μm to 4 μm.

[0057] Furthermore, the distance between individual pieces on the base film is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The upper limit of the distance between individual pieces is preferably 3000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. If the distance between individual pieces is too small, it becomes difficult to transfer the pieces by LLO, and if the distance between individual pieces is too large, a method of attaching the pieces becomes preferable. The distance between individual pieces can be measured using microscopic observation (optical microscope, metallurgical microscope, electron microscope, etc.).

[0058] <Method for manufacturing a deformed form of a filler-containing film> The individual pieces of the filler-containing film may be formed by slitting or half-cutting, or by using a laser lift-off device. When forming individual pieces using an LLO device, the base film only needs to be transparent to laser light, and is preferably quartz glass having high light transmittance across all wavelengths.

[0059] When forming individual pieces of filler-containing film using an LLO (Laser Laser Oscillator) device, laser light is irradiated onto the filler-containing film provided on the base film from the base film side, and the filler-containing film in the irradiated area is removed, thereby forming individual pieces of filler-containing film of a predetermined shape on the base film.

[0060] For example, by using a mask with a square-shaped opening window and removing the unnecessary portion of the filler-containing film from the base film, individual pieces of a predetermined shape can be formed from the remaining portion of the filler-containing film. Alternatively, for example, by using a mask with a predetermined-shaped light-shielding portion formed within the opening window and removing the unnecessary portion of the filler-containing film around the individual pieces from the base film, individual pieces of a predetermined shape can be formed from the remaining portion of the filler-containing film.

[0061] Furthermore, when individual pieces of filler-containing film are prepared using a laser lift-off device, the reaction rate of the individual pieces is 25% or less, preferably 20% or less, and more preferably 15% or less. This allows for excellent transferability. The reaction rate of the curable resin film before laser irradiation and the individual pieces obtained after laser irradiation can be determined, for example, by measuring the rate of decrease of reactive groups using FT-IR. For example, in the case of a curable resin film utilizing the reaction of an epoxy compound, the IR spectrum is measured by irradiating the sample with infrared light, and the methyl group (2930cm²) in the IR spectrum is determined. -1 (Nearby) and epoxy group (914cm) -1 The peak heights in the vicinity can be measured and calculated as the ratio of the peak height of the epoxy group to the peak height of the methyl group before and after the reaction (for example, before and after laser irradiation), as shown in the formula below.

[0062]

number

[0063] In the above formula, A is the peak height of the epoxy group before the reaction, B is the peak height of the methyl group before the reaction, a is the peak height of the epoxy group after the reaction, and b is the peak height of the methyl group after the reaction. If other peaks overlap with the epoxy group peak, the peak height of the fully cured (100% reaction rate) sample should be set to 0%.

[0064] <Utilization of filler-containing films (connecting structures, methods for manufacturing the same)> The filler-containing film of the present invention can be used by laminating it to an article, similar to conventional filler-containing films, and there are no particular restrictions on the article to which it is laminated. Therefore, a connecting structure in which a first member and a second member are connected via a filler-containing film, and a method for manufacturing a connecting structure by arranging and connecting a filler-containing film between a first member and a second member are also part of the present invention. For example, when the filler-containing film is configured as an anisotropic conductive film by employing conductive particles as the filler, the anisotropic conductive film can be used with a thermocompression bonding tool to make anisotropic conductive connections between first electronic components such as semiconductor elements (power generation elements such as solar cells, image sensors such as CCDs, light-emitting elements such as mini-LEDs with a chip side length of about 50 μm to 200 μm and micro-LEDs with a chip side length of less than 50 μm, Peltier elements), various other semiconductor elements, IC chips, IC modules, FPCs, etc., and second electronic components such as FPCs, glass substrates, plastic substrates, rigid substrates, ceramic substrates, etc. This filler-containing film can also be used as a conductive film in electronic components for applications other than anisotropic conductive connections. The surface of the article to which the filler-containing film is laminated may be smooth, or it may have stepped or convex shapes.

[0065] <Connection Structure> In the connecting structure of the present invention, in which a first member and a second member are connected via a filler-containing film, there are no particular restrictions on the shape, size, application, etc., of the first member and the second member connected by the filler-containing film. These members may be small and have narrow terminal sizes, and high-precision alignment may be required for mounting the members. For example, the bump area may be several tens of micrometers. 2 ~several thousand μm 2 Miniaturized electronic components can also be connected. On the other hand, components such as large electronic components can also be mounted using filler-containing film. Furthermore, mounted components can be divided into smaller pieces for use. In addition, when used in large TVs, the filler-containing film may be attached to one side for 1m or more, for example, 4.5m or more. In this case, in addition to using the filler-containing film as an anisotropic conductive film, it may also be used as a spacer film with the filler acting as a spacer.

[0066] IC chips and wafers may be stacked and multilayered using the filler-containing film of the present invention. The electronic components connected by the filler-containing film functioning as a conductive film or anisotropic conductive film of the present invention are not limited to the examples of electronic components described above. It can be used in a variety of electronic components, which have become increasingly diverse in recent years. The present invention also encompasses film-laminated materials obtained by bonding the filler-containing film of the present invention to various articles.

[0067] The method for laminating a filler-containing film onto an article (in other words, the method for mounting a filler-containing film onto an article) can be reflow, pressure bonding, preferably heat bonding, depending on the application of the filler-containing film and the type of filler, or the laser lift-off processing method described above may be used. Furthermore, with the laser lift-off processing method, not only the filler-containing film but also first electronic components such as micro-LEDs or second electronic components can be arranged on a transfer material (silicone rubber sheet) using a stamping material (for example, Japanese Patent Application Publication No. 2021-141160) or the laser lift-off method and transferred to the first electronic component.

[0068] <Method for manufacturing a connecting structure> A more specific method of using a filler-containing film as an anisotropic conductive film is, for example, when the first electronic component is an IC chip or FPC containing semiconductor elements and the second electronic component is a substrate, the first electronic component is generally placed on the pressure tool side and the second electronic component is placed on a stage facing the first electronic component. The anisotropic conductive film is then attached to the second electronic component in advance, and the first and second electronic components are thermally bonded using the pressure tool. In this case, the anisotropic conductive film may be attached to the first electronic component instead of the second electronic component in advance, and the first electronic component is not limited to an IC chip or FPC containing semiconductor elements. When the first or second electronic component is a substrate, it may have, for example, a silicone rubber layer. The silicone rubber layer may be polydimethylsiloxane (PDMS). Also, when the conductive particles are solder, the first and second electronic components can be joined by reflow soldering.

[0069] When connecting the first and second electronic components by thermocompression bonding, if necessary, preliminary bonding may be performed before thermocompression bonding by removing the resin around the conductive particles. This reduces the influence of resin flow that occurs when the anisotropic conductive film is thermocompressed onto the electronic article and suppresses the unwanted flow of conductive particles. Specifically, one electronic component to be connected is attached to one side of the anisotropic conductive film, and the other electronic component is pressed with a pressure tool when performing preliminary bonding to the other side of the anisotropic conductive film, partially removing the resin between the electronic components, and then the electronic components are connected by thermocompression bonding as the final bonding (hereinafter, the connection method that involves pressing not only during thermocompression bonding but also during preliminary bonding is called two-stage pressing bonding). International Publication WO2016 / 143789 describes a two-stage pressing method for connecting electronic components using an anisotropic conductive film in which conductive particles are randomly dispersed. However, when connecting electronic components using an anisotropic conductive film in which conductive particles are regularly arranged, as in the present invention, performing such a two-stage pressing method can significantly reduce the unwanted flow of conductive particles during thermocompression bonding.

[0070] <Modified Method of Manufacturing a Connecting Structure> Furthermore, when mounting extremely small first electronic components onto second electronic components such as wiring boards, mounting can also be performed by using the laser lift-off processing method described above to cause the first electronic components to land on the second electronic components. For example, if the first electronic components are a vast number of micro-LEDs formed on the surface of a light-transmitting substrate, mounting can be performed by irradiating each individual first electronic component with laser light onto a filler-containing film placed at a predetermined location on the second electronic component (e.g., each electrode on the wiring board), causing the first electronic components to land on the film. The laser lift-off processing conditions can be appropriately determined depending on the type and constituent materials of the first electronic component.

[0071] The filler-containing film may be placed over the entire surface of the connection area of ​​a second electronic component, such as a wiring board, or it may be placed in predetermined units of individual pieces on a part of the display area, such as one pixel (one pixel unit) for one set of RGB.

[0072] There are no particular limitations on the method of placing the filler-containing film on the display area of ​​the second electronic component. For example, when placing the filler-containing film over the entire display area, lamination is one possible method. Also, when placing individual pieces of the filler-containing film on a part of the display area, methods include directly transferring and placing the individual pieces from the base film to the second electronic component using an LLO (Lamination-Low Equipment) device, or transferring and placing the individual pieces from the transfer material (stamp material) to the second electronic component using a transfer material with the individual pieces already adhered to it.

[0073] Furthermore, when a first electronic component such as a micro-LED is placed on a filler-containing film positioned at a predetermined location on a second electronic component by thermocompression bonding, or when a piece of filler-containing film transferred by a laser lift-off process is projected onto the film using a laser lift-off process, it is preferable that the first adhesive layer and / or second adhesive layer of the filler-containing film contain rubber components (e.g., acrylic rubber, silicone rubber, butadiene rubber, polyurethane elastomer, etc.) that provide cushioning to mitigate the impact of the projectile, or inorganic fillers (e.g., silica, talc, titanium dioxide, calcium carbonate, etc.) that provide mechanical strength.

[0074] The first or second connecting layer, which contains such rubber components and inorganic fillers, has a durometer A hardness (in accordance with JIS K6253) of preferably 20 to 40, more preferably 20 to 35, and particularly preferably 20 to 30 before laser irradiation, and a storage modulus obtained by a dynamic viscoelasticity tester (temperature 30°C, frequency 200Hz; Vibron, A&D Co., Ltd.) in accordance with JIS K7244, preferably 60 MPa or less, more preferably 30 MPa or less, and particularly preferably 10 MPa or less.

[0075] On the other hand, the first or second connecting layer after laser irradiation preferably has a storage modulus of 100 MPa or higher, more preferably 2000 MPa or higher, obtained by dynamic viscoelastic testing (temperature 30°C, frequency 200 Hz). If the storage modulus falls below this range, it tends to become difficult to obtain good conductivity and connection reliability. The storage modulus can be measured in tensile mode using a viscoelastic testing machine (Vibron, A&D Co., Ltd.) in accordance with JIS K7244, for example, under conditions of frequency 11 Hz and heating rate 3°C / min.

[0076] Alternatively, a first electronic component placement sheet, on which a first electronic component such as a micro-LED is transferred (deployed) to a predetermined position on a silicone rubber sheet such as polydimethylsiloxane (i.e., a position corresponding to the predetermined position of the second electronic component to which the first electronic component should be retransferred) using a laser lift-off process, can be positioned with the first electronic component side facing the second electronic component, and then transferred. [Examples]

[0077] The present invention will be described in detail below with reference to examples.

[0078] Examples 1-3, Comparative Example 1, Reference Example 1 (1) Preparation of resin composition for forming adhesive layer Using the formulations shown in Table 1, a first adhesive layer forming resin composition, a second adhesive layer forming resin composition, and a third adhesive layer forming resin composition were prepared according to conventional methods.

[0079] [Table 1]

[0080] (2) Preparation of anisotropic conductive film as a filler-containing film (a) Preparation of an anisotropic conductive film of Example 1 (structure of Figure 1A) The protrusion diameter is 3.5 μm, the protrusion height is 3.0 μm, the protrusion pitch is 6.4 μm, and the number density of protrusions is 28,000 per mm. 2 A mold having a square lattice arrangement convex pattern was fabricated (Figure 4A). Specifically, the convex pattern of the mold was a square lattice arrangement, and the pitch of the convex parts along the lattice axis was approximately 2.1 times the average conductive particle diameter.

[0081] As shown in Figure 4B, a resin composition for forming the first adhesive layer was melted and applied to the convex pattern surface of the mold, cooled and solidified, and then peeled off the mold to form a first adhesive layer with a thickness of 4 μm and recesses with an inner diameter of 3.5 μm and a depth of 3.0 μm (Figure 4C). Furthermore, metal-coated resin particles (Sekisui Chemical Co., Ltd., AUL703, average particle diameter 3 μm) were filled into the recesses as conductive particles to create a first adhesive layer in which conductive particles were filled into the recesses.

[0082] A second adhesive layer with a thickness of 8 μm was created by melting and applying a resin composition for forming the second adhesive layer to a release PET film, and then cooling and solidifying it.

[0083] The second adhesive layer was placed over the recessed surface filled with conductive particles of the first adhesive layer, and bonded by pressing at 60°C and 0.5 MPa. By removing the release PET film, an anisotropic conductive film with the structure shown in Figure 1A was obtained. The CV value of the metal-coated resin particles used was 20% or less when measured with FPIA-3000 (Malvern) at a particle count of 1000 or more.

[0084] Furthermore, the presence or absence of voids beneath the conductive particles used as fillers was observed using a laser microscope. As a result, the presence of voids was confirmed. The volume of the voids can be determined by subtracting the volume of the fillers from the volume of the recesses. Here, the volume of the recesses can be determined by multiplying the opening area of ​​the recesses by the depth of the recesses, and the volume of the fillers can be determined from the particle diameter, assuming the fillers are spherical.

[0085] (b) Preparation of an anisotropic conductive film of Example 2 (structure in Figure 2) An anisotropic conductive film with the structure shown in Figure 2 was created by repeating the same procedure as in Example 1, except that the second adhesive layer was laminated onto the surface of the first adhesive layer where no recesses were formed.

[0086] Furthermore, the presence or absence of voids beneath the conductive particles used as fillers was observed in the same manner as in Example 1. As a result, the presence of voids was confirmed.

[0087] (c) Preparation of an anisotropic conductive film of Example 3 (structure in Figure 3) A third adhesive layer with a thickness of 1 μm was created by melting and applying a resin composition for forming a third adhesive layer to a release PET film, and then cooling and solidifying it.

[0088] Next, an anisotropic conductive film with the structure shown in Figure 3 was created by repeating the same procedure as in Example 2, except that the third adhesive layer was laminated onto the surface on the side where the recess of the first adhesive layer was formed. However, the thickness of the second adhesive layer was set to 7 μm.

[0089] Furthermore, the presence or absence of voids beneath the conductive particles used as fillers was observed in the same manner as in Example 1. As a result, the presence of voids was confirmed.

[0090] (d) Preparation of an anisotropic conductive film of Comparative Example 1 (structure in Figure 5) The first adhesive layer forming resin composition, the second adhesive layer forming resin composition, and the third adhesive layer forming resin composition were melted and applied to separate release PET films, and then cooled and solidified to create a first adhesive layer 51 with a thickness of 4 μm, a second adhesive layer 52 with a thickness of 7 μm, and a third adhesive layer 55 with a thickness of 1 μm.

[0091] Next, the second adhesive layer 52 was laminated to one side of the first adhesive layer 51 and the third adhesive layer 55 to the other side. The layers were then bonded by pressing them at 60°C and 0.5 MPa, and the release PET film was removed to obtain a laminate.

[0092] A mold with a convex pattern was pressed into the resulting three-layer laminate to form through-holes 53. By scattering conductive particles 54 so that the number of particles equals 110% of the number of through-holes in the laminate, an anisotropic conductive film with the structure shown in Figure 5 was created, and the portion with a particle filling rate of 95% or more was used for evaluation.

[0093] Furthermore, the presence or absence of voids below the conductive particles was observed in the same manner as in Example 1. As a result, the presence of through-holes, rather than voids as defined in the present invention, was confirmed.

[0094] (e) Fabrication of an anisotropic conductive film of Reference Example 1 (structure in Figure 6) First, a mold similar to that in Example 1 was created. Molten pellets of a known transparent resin were poured into this mold and cooled to solidify, thereby creating a transfer mold with recesses. The recesses of the created transfer mold were filled with the conductive particles used in Example 1.

[0095] Next, a resin composition for forming the first adhesive layer was melted and applied to a release PET film, and then cooled and solidified to create a first adhesive layer 61 with a thickness of 4 μm. This first adhesive layer 61 was placed over a surface in which recesses filled with transfer-type conductive particles were formed, and adhered by pressing at 60°C and 0.5 MPa. Then, the first adhesive layer 61 was peeled off the mold, and the conductive particles 63 on the first adhesive layer 61 were pressed into the first adhesive layer 61 by applying pressure (pressure conditions: 60~70°C, 0.5 MPa).

[0096] Next, a second adhesive layer 62 with a thickness of 8 μm was created by melting and applying a resin composition for forming the second adhesive layer to the release PET film and then cooling and solidifying it. This second adhesive layer 62 was placed over the surface of the first adhesive layer 61 on which the conductive particles 63 were pressed, and adhered by pressing at 60°C and 0.5 MPa. By removing the release PET film, an anisotropic conductive film with the structure shown in Figure 6 was created.

[0097] Furthermore, the presence or absence of voids below the conductive particles was observed in the same manner as in Example 1. As a result, the presence of voids could not be confirmed.

[0098] (3) Evaluation of the manufactured anisotropic conductive film The anisotropic conductive films of the prepared examples, comparative examples, and reference examples were tested and evaluated for (a) conductivity, (b) insulation, (c) particle trapping ability, and (d) temporary adhesion, as follows. The results are shown in Table 2.

[0099] (a) Conductivity The anisotropic conductive films of each example, comparative example, and reference example were sandwiched between an IC for conductivity evaluation and a glass substrate, and heated and pressurized (170°C, 20MPa, 10 seconds) to create an evaluation connection structure. The initial conductivity resistance was measured and evaluated according to the conductivity evaluation criteria below. The results are shown in Table 2. For practical purposes, an initial conductivity resistance of A or B is required.

[0100] Here, the evaluation IC and the glass substrate have corresponding terminal (bump) patterns, and their sizes are as follows. Furthermore, when connecting the evaluation IC and the glass substrate, the longitudinal direction of the anisotropic conductive film was aligned with the short direction of the bumps.

[0101] IC for evaluating conductivity characteristics External size 1.8×20.0mm Thickness: 0.5mm Bump specification: Width 30μm x Length 85μm, distance between bumps 50μm, bump height 15μm

[0102] Glass substrate (Ti / Al wiring) Glass material: Corning 1737F External size 30×50mm Thickness: 0.5mm

[0103] Conductivity evaluation criteria A: Initial conduction resistance is less than 1.0Ω B: Initial conduction resistance is 1.0Ω or more and less than 2.0Ω C: Initial conduction resistance is 2.0Ω or more and less than 4.0Ω D: Initial conduction resistance is 4.0Ω or higher

[0104] (b) Insulation The same evaluation connection structure used in the conductivity evaluation was created, and the conductivity resistance was measured for 100 spaces of adjacent bumps with a width of 7 μm. 7 A short circuit was determined to have occurred if the resistance reading was below Ω, and the insulation performance was evaluated according to the following insulation performance evaluation criteria. The results are shown in Table 2. For practical purposes, insulation performance should be rated A, B, or C.

[0105] Insulation performance evaluation criteria A: There were 0 spaces where a short circuit occurred. B: There is one space where a short circuit occurred. C: There are two spaces where a short circuit occurred. D: There are three or more spaces where a short circuit occurred.

[0106] (c) Particle trapping ability For each example, comparative example, and reference example, an anisotropic conductive film was sandwiched between an IC for evaluating particle capture performance and a glass substrate (ITO wiring) with terminal (bump) patterns corresponding to those films, with an alignment offset of 6 μm. The films were then heated and pressurized (180°C, 60 MPa, 5 seconds) to create an evaluation connection structure. In this connection structure, the number of captured conductive particles was measured for 100 areas of 6 μm × 66.6 μm where the bumps of the evaluation IC and the terminals of the glass substrate overlapped. The minimum number of captured particles was determined and evaluated according to the following particle capture performance evaluation criteria. The results are shown in Table 2. For practical purposes, an A or B rating is desirable.

[0107] IC for evaluating particle capture capabilities External size 1.6×29.8mm Thickness: 0.3mm Bump specifications: Size 12μm x 66.6μm, bump pitch 22μm (L / S = 12μm / 10μm), bump height 12μm

[0108] Particle capture performance evaluation criteria A: Minimum number of captured items is 5 or more. B: Minimum number of captured items is 3 or more but less than 5. C: Minimum number of captures is 1 or more but less than 3 D: Minimum number of captures is 0

[0109] (d) Temporary adhesive properties The anisotropic conductive films of each example, comparative example, and reference example were placed on the SiN coating of a glass substrate on which a SiN coating had been formed, and temporarily bonded by heating and pressurizing (60°C, 1 MPa, 1 second) to obtain a connection structure for temporary bonding evaluation, which was then evaluated according to the following temporary bonding evaluation criteria. The results obtained are shown in Table 2. In practical terms, an A, B, or C rating is desirable.

[0110] Criteria for evaluating the suitability of temporary adhesive A: Temporary application is possible without any air bubbles being observed in the temporary application area. B: Some air bubbles are observed in the temporary application area, but temporary application is possible. C: Relatively large air bubbles and slight peeling are observed in the temporary application area, but temporary application is possible. D: Temporary application impossible

[0111] [Table 2]

[0112] In Example 1, the anisotropic conductive film has a cylindrical recess formed in the first adhesive layer, with the second adhesive layer laminated on the recess side. Furthermore, conductive particles are held in the recess such that a gap is formed between the bottom edge of the recess and the conductive particles. As a result, all evaluation items for "conductivity," "insulation," "particle capture ability," and "temporary adhesion ability" were rated A.

[0113] In Example 2, the anisotropic conductive film has a cylindrical recess formed in the first adhesive layer, with the second adhesive layer laminated on the opposite side of the recess. Furthermore, conductive particles are held in the recess such that a gap is formed between the bottom edge of the recess and the conductive particles. As a result, all evaluation items for "conductivity," "insulation," "particle capture," and "temporary adhesion" received an A rating.

[0114] In Example 3, the anisotropic conductive film has a third adhesive layer formed to seal the recesses in the first adhesive layer of the anisotropic conductive film of Example 2. Therefore, it is expected to have better temporary adhesion to the substrate and better prevention of particle fallout than the anisotropic conductive film of Example 2. In addition, the conductive particles are held in the recesses such that a gap is formed between the bottom edge of the recess and the conductive particles. For this reason, all evaluation items for "conductivity," "insulation," "particle capture," and "temporary adhesion" were rated A.

[0115] In contrast, the anisotropic conductive film of Comparative Example 1 has a laminated structure in which a third adhesive layer / first adhesive layer / second adhesive layer are stacked, but the conductive particles are not held in the recesses of the first adhesive layer, but rather near the first adhesive layer in the through holes provided in this laminated structure. For this reason, conductivity was rated A and insulation was rated B, but particle capture and temporary bonding properties were rated D. This is thought to be because the void portion (excess void) in the recess is large, so the distance from the adherend surface to the conductive particles becomes too wide, making the conductive particles more likely to flow during bonding. Furthermore, it is thought that the increased void portion reduces the contact surface between the resin and the adherend, resulting in poor temporary bonding properties.

[0116] Furthermore, in the anisotropic conductive film of Reference Example 1, conductive particles were simply pressed into the first adhesive layer without creating recesses, resulting in no voids being formed, and consequently, the conductivity was rated as B. [Explanation of Symbols]

[0117] 1,42,51,61 1st adhesive layer 2,44,52,62 Second adhesive layer 3,42a recess 3a Bottom 3b Periphery of the base 3c void 53 Through hole 4, 43, 54, 63 Fillers, conductive particles 5,45,55 Third adhesive layer 10, 50, 60 Filler-containing film 40 Recessed mold 40a Convex part 41 Resin composition for forming first adhesive layer

Claims

1. A filler-containing film having a first adhesive layer with a recess formed on its surface and a filler filled in the recess formed on the surface of the first adhesive layer, wherein the recess has a bottom surface, and there is a gap between at least the peripheral portion of the bottom surface and the filler.

2. The filler-containing film according to claim 1, wherein the volume of the recess is 1.1 times or more and 8 times or less the average volume of the conductive particles.

3. The filler-containing film according to claim 1, wherein a second adhesive layer is further laminated on the first adhesive layer.

4. The filler-containing film according to claim 3, wherein the second adhesive layer is laminated on the surface of the first adhesive layer where the recess is formed.

5. The filler-containing film according to claim 3, wherein the second adhesive layer is laminated on the back surface of the first adhesive layer where the recess is not formed, and further, a third adhesive layer is laminated on the surface of the first adhesive layer where the recess is formed.

6. The filler-containing film according to claim 1, wherein the recess is cylindrical.

7. The filler-containing film according to claim 1, wherein the bottom surface of the recess is provided substantially parallel to the plane direction of the filler-containing film.

8. The filler-containing film according to claim 1, wherein the recess diameter of the recess is 1.0 times or more and 2.0 times or less the average particle diameter of the filler.

9. The filler-containing film according to claim 1, wherein the layer thickness of the first adhesive layer is 1.2 times or more and 10 times or less the average particle diameter of the filler.

10. The filler-containing film according to claim 1, wherein the reaction rate of the film is 25% or less.

11. The filler-containing film according to claim 1, wherein the filler is a conductive particle and is used as a conductive film.

12. The filler-containing film according to claim 11, wherein the conductive film is an anisotropic conductive film.

13. A method for manufacturing a filler-containing film according to claim 1, comprising: preparing a recess forming die having a convex portion corresponding to the recess formed on the surface of the first adhesive layer; applying a resin composition for forming the first adhesive layer onto the convex portion forming surface of the recess forming die, drying it, and then removing the recess forming die to obtain a first adhesive layer having recesses formed on the surface; and filling the recesses of the first adhesive layer with fillers The manufacturing method comprising these steps.

14. Further, a step of forming a second adhesive layer by applying and drying a resin composition for forming the second adhesive layer on the front or back surface of the first adhesive layer, and When forming the second adhesive layer on the back surface of the first adhesive layer, a step of forming a third adhesive layer by applying and drying a resin composition for forming the third adhesive layer on the front surface of the first adhesive layer The manufacturing method according to claim 13, comprising these steps.

15. A connection structure in which a first member and a second member are joined via the filler-containing film according to any one of claims 1 to 11.

16. A connection structure in which a first electronic component and a second electronic component are anisotropically conductively connected via the filler-containing film according to claim 12, which is used as an anisotropic conductive film.

17. A method for manufacturing a connection structure, in which a first member and a second member are joined via the filler-containing film according to any one of claims 1 to 11.

18. A method for manufacturing a connection structure, in which a first electronic component and a second electronic component are anisotropically conductively connected via the filler-containing film according to claim 12, which is used as an anisotropic conductive film.

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