Filler-containing film, connection structure, and method for manufacturing same

Abstract

To provide a filler-containing film capable of performing accurate alignment and forming a matte black tone black matrix when manufacturing a connection structure such as a μ LED display by mounting a light emitting element such as a μ LED on a substrate via the filler-containing film containing a black pigment capable of forming a black matrix.SOLUTION: In the filler-containing film in which the conductive particles are held in the insulating adhesive layer, the average transmittance of near infrared rays having a wavelength of 800 nm or more and 1,200 nm or less is 20% or more, and further, the 60 ° gloss value by ASTMD523 (60 °) of the film surface is less than 60.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a filler-containing film that can be used for a wide variety of applications, such as a matte film, a film for capacitors, an optical film, a film for labels, a spacer film, an antistatic film, and a conductive film. In particular, the present invention relates to a filler-containing film, such as a conductive film or an anisotropic conductive film, that is useful when manufacturing connection structures for display devices and light-emitting devices that include fine or minute components such as light-emitting elements such as μLEDs. [Background technology]

[0002] μLED displays, which are micro light-emitting elements with sides of 100 μm or less arranged on a display substrate, can eliminate the color filters, polarizers, and backlights required for LCD displays, allowing for thinner displays. They are also expected to be used as display devices or light sources that can achieve a wider color gamut, higher resolution, and lower power consumption. They are also expected to be applied to large displays with a high number of pixels. Such μLED displays have a black matrix formed around each μLED as a light-blocking pattern layer to prevent color mixing and achieve high contrast.

[0003] As a method for manufacturing a μLED display, Patent Document 1 (paragraphs 0083 to 0089, etc.) describes a method that performs a process of forming a black matrix as a light-shielding pattern layer having an opening for mounting a μLED on a transparent substrate using photolithography technology (light-shielding patterned substrate forming process), and then a process of mounting a μLED in the opening via an anisotropic conductive film (μLED mounting process), as well as a method that performs a light-shielding patterned substrate forming process after the μLED mounting process.

[0004] However, in the manufacturing method of the μLED display in Patent Document 1, the black matrix must be formed in a process separate from the μLED mounting process, which raised concerns that the manufacturing costs and cycle time of the μLED display would increase.

[0005] Therefore, in order to resolve the concerns regarding the manufacturing method of the μLED display of Patent Document 1, Patent Document 2 proposes to mount the μLED after placing a filler array film containing conductive particles for anisotropic conductive connection and black pigment on the entire surface of the display substrate as an anisotropic conductive film capable of forming a black matrix. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-124312 [Patent Document 2] Japanese Patent Publication No. 2023-152865 Summary of the Invention [Problem to be solved by the invention]

[0007] However, as described in Patent Document 2, when attempting to manufacture μLED displays using filler array films containing black pigments, inorganic black pigments such as carbon black and titanium black are used, which substantially absorb not only visible light but also near-infrared light, which poses a problem that the alignment marks cannot be accurately read with an infrared camera, which is required for the high-precision alignment required for μLED implementation. Furthermore, because the black matrix does not have a matte black gloss, it is not possible to sufficiently suppress light reflections on the display, which poses a problem of reduced visibility in car navigation systems, smartwatches, and other devices exposed to large amounts of sunlight.

[0008] In contrast to such conventional technology, the present invention aims to provide a filler-containing film that can perform high-precision alignment when manufacturing connection structures such as display devices by mounting fine or minute components such as light-emitting elements such as μLEDs on a substrate via a filler-containing film such as an anisotropic conductive film containing a black pigment that can form a black matrix, and that can also form a matte black black matrix. [Means for solving the problem]

[0009] The inventors discovered that by setting the average transmittance in the near-infrared region of a filler-containing film such as an anisotropic conductive film to a predetermined numerical range or higher, high-precision alignment is possible with an infrared camera, and further that by constructing an insulating adhesive layer from at least epoxy resin and acrylic rubber and setting the gloss value of the film surface to less than a predetermined numerical value, a matte black-toned black matrix can be formed, leading to the completion of the present invention.

[0010] That is, the present invention provides a filler-containing film in which a filler is held in an insulating adhesive layer containing an epoxy resin and an acrylic rubber, Provided is a filler-containing film having an average transmittance of 20% or more for near-infrared rays with wavelengths of 800 nm or more and 1200 nm or less, and a 60° gloss value of the film surface according to ASTM D523 (60°) of less than 60. By appropriately selecting the type and amount of filler and the type and amount of binder, this filler-containing film can function as an insulating film, conductive film, or an anisotropic conductive film, which may have adhesive properties. It may be used as a spacer film, optical film, or matte film, and can also be used as a black adhesive film or black matrix film (BM film).

[0011] The present invention also provides a connection structure in which one or more microcomponents such as light-emitting elements are connected to a substrate via the filler-containing film of the present invention. A preferred connection structure is a light-emitting device such as a display device or light source in which the substrate is a display substrate (including a substrate for a light-emitting device), the microcomponents are light-emitting elements, particularly μLEDs, and a black matrix is ​​formed around the microcomponents such as light-emitting elements. The microcomponents such as light-emitting elements are connected to the substrate by conductive connection or anisotropic conductive connection.

[0012] The present invention also provides a method for manufacturing a connection structure that functions as a display device or a light-emitting device, in which a substrate and a minute component such as a light-emitting element are connected via the filler-containing film of the present invention.

[0013] A preferred embodiment of this manufacturing method includes a manufacturing method of a connection structure that functions as a display device or a light-emitting device, in which the filler-containing film of the present invention is placed on an electrode of a display substrate (including a substrate for a light-emitting device), one or more microcomponents such as light-emitting elements are aligned and attached to the filler-containing film, and then heated and pressurized to connect the electrodes of the microcomponents such as light-emitting elements to the electrodes of the display substrate; and a manufacturing method of a connection structure for a display device or a light-emitting device, in which a microcomponent such as a light-emitting element placed on the surface of a light-transmitting substrate is irradiated with laser light from the light-transmitting substrate side, causing one or more microcomponents such as light-emitting elements to land on the filler-containing film of the present invention placed on the electrodes of the display substrate, thereby connecting the electrodes of the microcomponents such as light-emitting elements to the electrodes of the display substrate. In these manufacturing methods, the light-emitting element is preferably a μLED, and when connecting the electrodes of the light-emitting element to the electrodes of the display substrate, a black matrix is ​​preferably formed around the light-emitting element. In these manufacturing methods, the light-emitting element is preferably connected to the display substrate via a conductive connection or an anisotropic conductive connection. [Effects of the Invention]

[0014] The filler-containing film of the present invention, in which a filler is held in the insulating adhesive layer, has an average transmittance of 20% or more for near-infrared rays with wavelengths of 800 nm or more and 1200 nm or less. Therefore, due to sufficient transmittance to near-infrared rays, even when a substrate is covered with the filler-containing film of the present invention, alignment marks on the substrate can be identified with an infrared camera. Furthermore, by forming the insulating adhesive layer from at least an epoxy resin and an acrylic rubber, the 60° gloss value of the film surface according to ASTM D523 (60°) is less than 60, making it possible to form a matte black black matrix. [Brief explanation of the drawings]

[0015] [Figure 1A] FIG. 1A is a cross-sectional view of an anisotropic conductive film, which is a representative embodiment of the filler-containing film of the present invention. [Figure 1B] FIG. 1B is a cross-sectional view of an anisotropic conductive film, which is a representative embodiment of the filler-containing film of the present invention. [Figure 1C] FIG. 1C is a cross-sectional view of an anisotropic conductive film, which is another embodiment of the filler-containing film of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of a μLED display. [Figure 3] FIG. 3 is a flowchart showing an outline of the manufacturing process for a μLED display device using a conductive film (or conductive sheet) as the filler-containing film of the present invention. [Figure 4] Figure 4 is a cross-sectional view showing a portion of a connection structure in which μLEDs are connected via a conductive sheet made of an anisotropic conductive material. [Figure 5] Figure 5 is a cross-sectional view showing a portion of a connection structure in which μLEDs are connected via individual pieces. [Figure 6] FIG. 6 is a cross-sectional view illustrating one embodiment of a μLED display device. [Figure 7] FIG. 7 is a cross-sectional view illustrating another embodiment of a μLED display device. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will now be described in detail with reference to the drawings, in which the same reference numerals represent the same or equivalent components.

[0017] <Filler-containing film> The filler-containing film of the present invention has a filler held in an insulating adhesive layer. The filler can be appropriately selected from known fillers depending on the application of the filler-containing film. Therefore, by appropriately selecting the type and amount of filler, the type and amount of binder, etc., the filler-containing film of the present invention can function as an insulating film, a conductive film, or an anisotropic conductive film, which may have adhesive properties. The filler-containing film of the present invention will be described below using an anisotropic conductive film as an example, but the filler-containing film of the present invention is not limited to an anisotropic conductive film. Furthermore, the description of an anisotropic conductive film can be applied to conductive films, and also to filler-containing films. As described below, the filler-containing film of the present invention has the functions of visible light blocking and near-infrared light transmission, and therefore can also be applied to black adhesive films and black matrix films (BM films). A combination of these can also be considered a conductive black film. Therefore, when applied to connecting a substrate and a μLED, the portion where the substrate and μLED are connected becomes an adhesive film, but the portion where the substrate and μLED are not connected is exposed (visible to the naked eye), so it can be considered a black matrix film (BM film). Thus, the ability of a single filler-containing film to fulfill multiple functions is an important advantage of the present invention. The difference between the filler-containing film of the present invention and conventional BM films is that it is provided on a base film whose surface has been treated with a release agent, and the film itself is separated and attached to an object for use, or in some cases cured before use.

[0018] (anisotropic conductive film) An anisotropic conductive film 10, a representative embodiment of a filler-containing film such as the conductive film or anisotropic conductive film of the present invention, has a structure in which conductive particles 2 are held in an insulating adhesive layer 1, as shown in FIG. 1A, from the viewpoint of ease of handling. In this case, a known release film may be laminated on one or both sides, if necessary. Furthermore, the insulating adhesive layer 1 may be a single layer, as shown in FIG. 1A, or a laminate of multiple insulating resin layers, as shown in FIG. 1B. For example, the insulating adhesive layer 1 may be composed of a binder resin layer 1a that holds the conductive particles 2 and another binder resin layer 1b. The binder resin layer 1b may be laminated on the back surface of the binder resin layer 1a, as shown in FIG. 1C. The binder resin layer 1a and the binder resin layer 1b may have the same composition and viscosity, or the binder resin layer 1a may have a higher viscosity than the binder resin layer 1b.

[0019] (Near-infrared transmittance and visible light blocking) The filler-containing film, such as the conductive film or anisotropic conductive film, of the present invention has near-infrared transmittance. Furthermore, it preferably has visible light blocking properties. Therefore, this filler-containing film can also be used as a black matrix material, and when light-emitting elements such as μLEDs are mounted on a filler-containing film, such as an anisotropic conductive film, applied to a display substrate, alignment marks and other markers built into the surface of the display substrate can be identified through the black matrix using an infrared camera. Thus, the filler-containing film of the present invention functions as a black matrix material due to its visible light blocking properties, and as a connecting material that does not impair the workability of the connecting process due to its near-infrared transmittance.

[0020] The near-infrared transmittance of a filler-containing film, such as a conductive film or anisotropic conductive film, of the present invention specifically means that the average transmittance of near-infrared light at wavelengths of 800 nm to 1200 nm or 900 nm to 1200 nm is 20% or more, preferably 40% or more, and more preferably 60% or more. In particular, it is preferable for the filler-containing film to exhibit maximum transmittance in the wavelength range of 850 nm to 950 nm, since this allows for a good black color to be visually observed. Note that if the average near-infrared transmittance is less than 20%, it may be difficult to identify alignment marks through a black matrix when mounting μLEDs, or the alignment may become more difficult, resulting in reduced productivity.

[0021] Furthermore, the visible light blocking property of the filler-containing film of the present invention specifically means that the average transmittance of visible light having a wavelength of 400 nm or more and 700 nm or less is preferably less than 30%, more preferably less than 20%, and particularly preferably less than 5%. If the average transmittance of visible light is 30% or more, when the film is used as a black matrix material for a display device equipped with light-emitting elements such as a μLED display, significant color mixing may occur between adjacent light-emitting elements (e.g., between adjacent μLEDs), resulting in a deterioration in image quality.

[0022] The near-infrared transmittance and visible light blocking ability of the filler-containing film of the present invention can be measured using a commercially available spectrophotometer (for example, a spectrophotometer (UV-Vis UV2600, Shimadzu Corporation)), and the measurement can be performed using the filler-containing film itself, such as an anisotropic conductive film, as a measurement sample.

[0023] (L*a*b* color system) The visible light blocking property of the filler-containing film of the present invention can be estimated by the L* value (lightness) of the L*a*b* color system, which can be determined in accordance with JIS Z 8781-4. That is, when the filler-containing film has good visible light blocking properties (low visible light transmittance), the proportion of incident light absorbed by the black pigment is thought to be large, resulting in a relatively small L* value. Conversely, when the visible light blocking properties are poor (high visible light transmittance), the proportion of incident light absorbed by the black pigment is thought to be small, resulting in a relatively large L* value. Therefore, when the L* values ​​of the L*a*b* color system are measured for multiple filler-containing films, it can be estimated that films with relatively small L* values ​​have better visible light blocking properties than films with relatively large L* values.

[0024] The a* value can be used to evaluate the greenish and reddish tints of black, and the b* value can be used to evaluate the blueish and yellowish tints of black. The L* value, a* value, and b* value of the filler-containing film can be determined in accordance with JIS Z 8781-4.

[0025] Specifically, the L* value of the filler-containing film of the present invention is preferably 50 or less, more preferably 30 or less, and particularly preferably 10 or less. If the L* value exceeds 50, the black color (blackness) of the filler-containing film may become pale, making it difficult to use as a black matrix.

[0026] The a* value of the filler-containing film of the present invention is preferably -30 or more and 30 or less, more preferably -10 or more and 10 or less, and particularly preferably -5 or more and 5 or less. If it is less than -30, the film tends to have too strong a green tinge, and if it exceeds 30, the film tends to have too strong a red tinge. The b* value of the filler-containing film of the present invention is preferably -30 or more and 30 or less, more preferably -10 or more and 10 or less, and particularly preferably -5 or more and 5 or less. If it is less than -30, the film tends to have too strong a blue tinge, and if it exceeds 30, the film tends to have too strong a yellow tinge.

[0027] Furthermore, when the filler-containing film of the present invention is used as a black matrix material for a display device equipped with light-emitting elements, such as a μLED display, the filler-containing film itself becomes easily visible during use, so a certain level of quality is also required for the appearance when the μLED is not lit. For these reasons, it is preferable that the a* and b* values ​​of the L*a*b* color system both fall within the above-mentioned ranges, more preferably both a* and b* values ​​are between -20 and 20, even more preferably either a* or b* value is between -15 and 15, and particularly preferably both a* and b* values ​​are between -15 and 15.

[0028] (gross value) The filler-containing film of the present invention has a 60° gloss value of the film surface according to ASTM D523 (60°) of less than 60, preferably less than 50, and more preferably less than 40. A 60° gloss value of 60 or greater tends to make it difficult to achieve a matte black black black matrix, which in turn makes it difficult to achieve high-definition displays. Gloss values ​​can be measured using various gloss measurement devices (e.g., Micro Trigloss, BYK Instruments) that comply with ASTM D523 (60°). Furthermore, because a certain level of quality is required for the appearance of the μLED when it is not lit, the gloss value is adjusted to match the specifications for the unlit appearance. Specifically, a matte black finish reduces external reflection, making it easier to create a visually subdued appearance for the finished product. When installed as a display, when the finished product is installed as a large display, it is easy to achieve a color that harmonizes well with the installation location (e.g., it is easy to match the environment of the installation location). It is also advantageous for relatively small mobile devices, as it allows for a subdued color.

[0029] (insulating adhesive layer) The insulating adhesive layer constituting the filler-containing film, such as the anisotropic conductive film of the present invention, contains a black colorant (preferably a black pigment) to function as a black matrix material. This black colorant exhibits near-infrared transmittance in wavelengths of 800 nm to 1200 nm, and preferably exhibits visible light blocking properties in wavelengths of 400 nm to 700 nm. The near-infrared transmittance and visible light blocking properties (which can also be referred to as visible light absorbance) of the black colorant itself can be measured using a commercially available spectrophotometer (e.g., UV-Vis UV2600, Shimadzu Corporation). The insulating adhesive layer constituting the filler-containing film, such as the anisotropic conductive film of the present invention, can contain, in addition to the black colorant, a film-forming component, a thermosetting component, a thermosetting agent, and an inorganic filler. In addition, the insulating adhesive layer can contain known additives such as a rubber component, a photocurable component and a photocurable agent, as well as ultraviolet absorbing components, softeners, colorants, flame retardants, thixotropic agents, silane coupling agents, and diluent monomers, provided that the effects of the present invention are not impaired.

[0030] The thickness of such an insulating adhesive layer is preferably 1 μm or more, more preferably 2 μm or more, particularly preferably 3 μm or more, and preferably 50 μm or less, more preferably 20 μm or less, even more preferably 10 μm or less, particularly preferably 6 μm or less. If the thickness is less than 1 μm, the tackiness of the filler-containing film will be insufficient, the visible light blocking ability will be insufficient, and the visible light blocking ability of the black matrix will also be significantly reduced. If the thickness is more than 50 μm, the tackiness will be sufficient, but the near-infrared transmittance will be significantly reduced. The insulating adhesive layer may be laminated with a layer that does not impair its performance. In other words, a second insulating adhesive layer may be present. In such a laminated structure, the thickness of the insulating adhesive layer may be the total thickness. Note that the thinner the thickness, the higher the relative content of the black colorant in the film volume, which affects the film-forming properties of the insulating adhesive layer (making application more difficult). Therefore, the thickness of one layer containing the black colorant is preferably greater than 2 μm, and more preferably 2.4 μm or more. If the thickness of a single layer containing a black colorant becomes too large, the thickness unevenness becomes relatively large, which can have a negative impact on the appearance when the appearance specification is at a high level, so it may be less than 10 μm. It is preferable that the total thickness falls within the above range, but since a large number of layers is more likely to induce other problems such as air bubble entrapment, the number of layers is preferably four or less, more preferably three or less, and even more preferably two or less (i.e., no layers, in other words, a single layer). In the case of a three-layer or more structure, the outermost layer may be a filler-free layer to reduce the influence of adhesion and color due to the filler, and part of the filler may protrude from the outermost layer.

[0031] (black coloring material) As described above, the black colorant (preferably a black pigment) to be contained in a filler-containing film such as the anisotropic conductive film of the present invention is a pigment that transmits near-infrared light with a wavelength of 800 nm or more and 1200 nm or less, and preferably blocks (absorbs) visible light with a wavelength of 400 nm or more and 700 nm or less. In order to ensure the amount of resin needed to improve the tackiness of the filler-containing film, it is preferable to use an organic pigment (organic black pigment; the term "organic pigment" in this specification may also be rephrased as "black organic pigment").

[0032] Preferred organic pigments include at least one organic pigment selected from the group consisting of lactam-based black pigments (e.g., lactam black), perylene-based black pigments (e.g., perylene black), azo-based black pigments (e.g., monoazochromium complex compounds), aniline-based black pigments (e.g., aniline black), bisbenzofuranone-based black pigments (e.g., black colorants composed of bisbenzofuranone compounds or black pigments having bisbenzofuranone as the main skeleton), and cyanine-based black pigments (e.g., cyanine black). Among these, lactam-based black pigments, perylene-based black pigments, and bisbenzofuranone-based black pigments are preferred. Lactam-based, perylene-based, azo-based, aniline-based, benzodifuranone-based, and cyanine-based black pigments can also be used. These can be considered organic fillers (black organic fillers). From the standpoint of spectroscopic properties and availability, perylene black (e.g., Black S 0084, DIC Corporation) is preferred. Furthermore, in view of high black color development, black pigments having bisbenzofuranone as the main skeleton (e.g., Irgaphor Black S0100CF, DIC Corporation) can be more preferably used. This Irgaphor Black S0100CF (DIC Corporation) may also be used as lactam black. This Irgaphor Black S0100CF (DIC Corporation) may also be considered as lactam black.

[0033] Furthermore, to achieve the effects of the present invention, black inorganic pigments (preferably titanium black) such as carbon black, titanium black, and composite oxide black pigments that exhibit high light absorption over a wide range from the visible light region to the near-infrared region, and black dyes such as leuco dyes may be used in combination. This is because the color needs to be adjusted depending on the appearance specifications of the display. Dyes disclosed in JP-A-2014-149918 and JP-A-2014-210856 may also be used. Known colorants may also be combined, as disclosed in JP-A-2019-081831, JP-A-2019-081857, and JP-A-2020-132776. In this way, two or more black colorants may be used in combination, or may be used in combination with colorants of other colors to adjust the color.

[0034] The average particle size (primary particle size) of the black pigment applicable to the present invention is not particularly limited as long as the effects of the invention can be exhibited, but in order to achieve both visible light blocking and near-infrared transmittance, the lower limit should be 1 nm or more, preferably 10 nm or more, and more preferably 30 nm or more, and the upper limit should be 700 nm or less, preferably 500 nm or less, and more preferably 400 nm or less. The average particle size of the pigment or colorant can be determined by observation using a particle size distribution analyzer using a known laser diffraction scattering method, an imaging particle size distribution analyzer (e.g., FPIA-3000, Malvern Panalytical, N=1000 or more is preferred), or a transmission electron microscope (TEM, N=200 or more is preferred).

[0035] The content of the black colorant, preferably the black pigment, in the insulating adhesive layer may be 2% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. If the content is less than 2% by mass, the visible light blocking properties of the filler-containing film, such as an anisotropic conductive film, will be insufficient, and the visible light blocking properties of the black matrix will be reduced. If the content exceeds 30% by mass, not only will the near-infrared transmittance be reduced, but there is also concern that the conductivity and fixation of light-emitting elements such as μLEDs will be reduced when the filler-containing film is used as a conductive film or anisotropic conductive film.

[0036] Furthermore, when an inorganic pigment is used in combination, in order to achieve both near-infrared transmittance and visible light blocking properties, the organic pigment is used in an amount of preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less per 1 part by mass of the inorganic pigment. If the organic pigment is used in an amount of less than 1 part by mass per 1 part by mass of the inorganic pigment, the visible light blocking properties of the filler-containing film, such as a conductive film or an anisotropic conductive film, will be insufficient, and the visible light blocking properties of the black matrix will be reduced. If the organic pigment is used in an amount of more than 20 parts by mass per 1 part by mass of the inorganic pigment, not only will the near-infrared transmittance be reduced, but there is also a concern that the conductivity and fixation of light-emitting elements such as μLEDs will be reduced when the filler-containing film is used as a conductive film or an anisotropic conductive film.

[0037] The insulating adhesive layer contains, in addition to the black colorant, epoxy resin and acrylic rubber, which is not compatible with epoxy resin, to impart a matte black color to the filler-containing film. It also contains a film-forming component, a thermosetting component, a thermosetting agent, and a rubber component.

[0038] The epoxy resin is not particularly limited, and liquid epoxy resin (e.g., EPICLON 850, DIC Corporation) is preferred, but bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin, etc., or urethane-modified epoxy resin may also be used. Among these, high-purity bisphenol A epoxy resin (e.g., YL980, Mitsubishi Chemical Corporation) is preferably used. These compounds may be monomers, oligomers, or polymers. The content of the epoxy resin in the insulating adhesive layer is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less.

[0039] The acrylic rubber is not particularly limited and can be appropriately selected from known acrylic rubbers. The content of the acrylic rubber in the insulating adhesive layer may be 2% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, preferably 15% by mass or less, more preferably less than 15% by mass, and even more preferably 10% by mass or less. If the content is less than 2% by mass, the 60° gloss value will be 60 or more, making it difficult to achieve a matte black tone. If the content exceeds 15% by mass, the relative resin amount will be reduced, which may result in a decrease in tackiness. By blending the epoxy resin with the acrylic rubber, which is not well compatible with it, in this manner, it is expected that the effect of easily adjusting the dispersibility of the organic black pigment and inorganic filler, which is presumed to contribute to the effects of the present invention, can be expected.

[0040] To achieve satisfactory color adjustment, tackiness, and conductivity, the acrylic rubber is preferably 2 times or less by mass relative to the black colorant (black pigment), more preferably 1 time or less, and even more preferably 0.7 times or less. For the same reasons, it is preferably 0.12 times or more, even more preferably 0.2 times or more, and even more preferably 0.33 times (1 / 3 times) or more. These may be adjusted appropriately depending on the thickness of the film. The upper and lower limits of the numerical ranges described may be selected appropriately within the described ranges depending on the indicators related to the effects of the invention.

[0041] *Film-forming ingredients The insulating adhesive layer constituting the filler-containing film of the present invention can contain various resins, such as phenoxy resin, polyester resin, polyurethane resin, polyesterurethane resin, acrylic resin, polyimide resin, and butyral resin, as film-forming components, preferably having a weight-average molecular weight of about 10,000 to 80,000, from the viewpoint of film-forming properties. These may be used alone or in combination of two or more. Among these, phenoxy resin (e.g., PKHH, Tomoe Engineering Co., Ltd.) is preferred from the viewpoint of film formation state, connection reliability, and the like. The content of the film-forming components in the insulating adhesive layer is preferably 20% by mass or more, more preferably 25% by mass or more, and preferably 50% by mass or less, and more preferably 45% by mass or less. In the present invention, when the filler-containing film is pressure-bonded, pressure may be applied from room temperature (25°C ± 15°C) or nearby before heating. Therefore, the melt viscosity may be lowered to facilitate pressing of the film at around room temperature. This tends to result in a formulation design that results in lower film properties than conventional ones, making handling difficult, such as peeling off the cover film or base film, attaching it to a substrate, etc. Therefore, a higher level of adjustment and selection of the film-forming components and other compounds is required than in conventional techniques.

[0042] *Thermosetting component The insulating adhesive layer constituting the filler-containing film of the present invention may contain, as a thermosetting component, an epoxy compound other than the epoxy resin described above, a (meth)acrylate compound, etc. These compounds may be monomers, oligomers, or polymers. The content of the thermosetting component in the insulating adhesive layer is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less.

[0043] *Heat curing agent The thermosetting agent is selected depending on the thermosetting component. For example, when the thermosetting component is an epoxy compound, a thermal anionic polymerization initiator or a thermal cationic polymerization initiator can be preferably selected, and a thermal cationic polymerization initiator that can suppress the curing reaction caused by laser light and rapidly cure by heat can be more preferably selected. The content of the thermosetting agent in the insulating adhesive layer can be determined depending on the type of thermosetting agent and the type of thermosetting component, and is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 8% by mass or less.

[0044] Thermal cationic polymerization initiators suitable for use with epoxy compounds are those that generate an acid capable of cationic polymerization of a cationic polymerizable compound by heat, and include known iodonium salts, sulfonium salts, phosphonium salts, quaternary ammonium salts, ferrocenes, and the like. Among these, aromatic sulfonium salts (e.g., SI-60L, Sanshin Chemical Industry Co., Ltd.) and quaternary ammonium salts, which exhibit good temperature latency, are preferred. Examples of such quaternary ammonium salts include salts of quaternary ammonium cations with hexafluoroantimonate anion, hexafluorophosphate anion, trifluoromethanesulfonate anion, perfluorobutanesulfonate anion, dinonylnaphthalenesulfonate anion, dinonylnaphthalenesulfonate anion, p-toluenesulfonate anion, dodecylbenzenesulfonate anion, or tetrakis(pentafluorophenyl)borate anion. Examples of quaternary ammonium cations include salts of NR1R2R3R4 +Examples of quaternary ammonium salts include cations represented by the formula: where R1, R2, R3, and R4 are linear, branched, or cyclic alkyl or aryl groups having 1 to 12 carbon atoms, each of which may have a hydroxyl group, halogen, alkoxyl, amino, or ester group. Specific examples of quaternary ammonium salts include CXC-1612, CXC-1733, CXC-1738, TAG-2678, CXC-1614, TAG-2689, TAG-2690, TAG-2700, CXC-1802-60, and CXC-1821 manufactured by King Industries, Inc. These are available from Kusumoto Chemicals Co., Ltd.

[0045] *Rubber component The insulating adhesive layer constituting the filler-containing film of the present invention may contain a rubber component other than the acrylic rubber described above to impart cushioning properties (shock absorption) to the filler-containing film and further adjust the storage modulus at a frequency of 200 Hz and the storage modulus after curing. Since the effects of the invention are adjusted by the compatibility between the acrylic rubber and the epoxy resin, the acrylic rubber can be considered to contribute to the effects of the invention. The rubber component other than the acrylic rubber is not particularly limited as long as it is an elastomer with good cushioning properties. Specific examples include silicone rubber, butadiene rubber, and polyurethane resin (polyurethane-based elastomer). Among these, silicone rubber is preferably used. The content of the rubber component in the insulating adhesive layer is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 10% by mass or less.

[0046] (filler) The filler-containing film of the present invention, such as the conductive film or anisotropic conductive film, can contain various fillers such as inorganic particles or conductive particles other than the black pigment described above in order to impart the desired optical, electrical, or mechanical properties to the filler-containing film depending on the application of the filler-containing film (e.g., optical film, spacer film, conductive film, anisotropic conductive film, etc.). The filler-containing film of the present invention is characterized by low visible light transmittance and high near-infrared transmittance due to the inclusion of a black colorant in the insulating adhesive layer, and the filler complements the visible light blocking ability to function as a black matrix when the entire film is viewed in a planar field of view. This can be considered to be a difference from conventional black matrix materials. This effect is further enhanced by the filler being arranged in an orderly fashion rather than randomly.

[0047] *Inorganic filler As the inorganic filler, at least one of silica, talc, titanium oxide, calcium carbonate, magnesium oxide, and the like other than inorganic black pigments (not included in inorganic black pigments) can be used. Among these, silica is preferably used. Since an organic filler is contained as an essential component of the black colorant, the content of the inorganic filler in the insulating adhesive layer is preferably 1% by mass or more, more preferably 5% by mass or more, so that the inorganic filler can at least easily exert its viscosity adjusting effect. For the same reason, if the inorganic filler is too much, the surface condition of the film is likely to deteriorate, so the content is preferably 20% by mass or less, more preferably 15% by mass or less.

[0048] The average particle size (primary particle size) of these inorganic fillers is not particularly limited, but is usually 1 nm or more, preferably 3 nm or more, more preferably 6 nm or more, and preferably 60 nm or less, more preferably 40 nm or less. The average particle size of the inorganic filler can be measured using an imaging particle size distribution analyzer (FPIA3000, Malvern Panalytical, N=3000 or more), a general scanning electron microscope (SEM, N=200 or more), or a transmission electron microscope (TEM, N=200 or more).

[0049] *Conductive particles When the filler-containing film of the present invention is used as a conductive film or anisotropic conductive film, applicable conductive particles can be appropriately selected from conductive particles used in known anisotropic conductive films. Examples include metal particles such as nickel, copper, silver, gold, palladium, and solder, and metal-coated resin particles in which the surface of resin particles such as polyamide and polybenzoguanamine is coated with a metal such as nickel or gold. The surfaces of the conductive particles may be subjected to an insulating treatment using known techniques that does not impair the conductive properties, and protrusions may be formed on the surfaces. In addition to the conductive particles, spacer particles or known fillers for adjusting color or achieving optical properties may also be used, as long as they do not impair the objectives and effects of the present invention. The shape and average particle size may be similar to those of known conductive particles.

[0050] The average particle diameter of the conductive particles is typically 1 μm or more and 50 μm or less. From the viewpoint of the conductive particle capture efficiency in display devices equipped with light-emitting elements such as μLEDs, the average particle diameter is preferably 1 μm or more, more preferably 1.5 μm or more, preferably 20 μm or less, and more preferably 15 μm or less. For application to micro-sized electrodes such as μLEDs, the average particle diameter may be 1.5 μm or more and less than 2.5 μm. The average particle diameter of the conductive particles can be measured using an imaging particle size distribution analyzer (e.g., FPIA-3000, Malvern Panalytical, N=3000 or more). Measurements can also be performed using a general electron microscope (e.g., SEM or TEM) (N=200 or more).

[0051] Furthermore, when the conductive particles are metal-coated resin particles, the hardness thereof is preferably 2000 N / mm 2 in terms of the compressive hardness at 20% deformation (20% K value) according to JIS K-6767-1999 from the viewpoint of electrical conductivity reliability. 2 More than 25000N / mm 2 Less than or equal to 5000N / mm 2 More than 10000N / mm 2 The following is the result.

[0052] Furthermore, when the filler-containing film is an anisotropic conductive film, the particle surface density of the conductive particles can be determined depending on the electrode area of ​​the light-emitting element such as μLED, and is preferably 30 particles / mm , in order to stabilize the conductive performance. 2 More than 500 pieces / mm 2 More than 500,000 pieces / mm 2 Less than or equal to 200,000 pieces / mm 2 Less than 150,000 pieces / mm 2 The particle surface density can be determined by observation using a metallurgical microscope, or by measuring an observed image using image analysis software (for example, WinROOF (Mitani Corporation) or A-Zo-kun (registered trademark) (Asahi Kasei Engineering Corporation)). Measurements can also be made using a general metallurgical microscope or an electron microscope (SEM, TEM, etc.) (N=200 or more).

[0053] (Arrangement of filler in filler-containing film) The filler, e.g., conductive particles, in the filler-containing film of the present invention may be arranged randomly or regularly. However, in order to improve the capture of conductive particles in electrodes of light-emitting elements such as μLEDs, it is preferable that the filler particles are arranged independently in the field of view of the film surface. In this case, it is preferable that 95% or more of the conductive particles are independent by number. Furthermore, it is preferable that the conductive particles are not only arranged independently, but also arranged regularly.

[0054] Furthermore, it is preferable to arrange the conductive particles uniformly and regularly over the entire surface of the insulating adhesive layer. This allows the filler-containing film of the present invention to be applied over a relatively large area when applied to large displays, etc. In other words, in the case of large displays, the areas where μLEDs are arranged and the areas where they are not are regularly spaced, but in the present invention, the filler-containing film is applied over a relatively large area. Therefore, to avoid the need for highly accurate alignment of the filler arranged in the filler-containing film and the film itself, it is preferable to arrange the conductive particles uniformly and regularly over the entire surface of the film. For these reasons, it is preferable for one side of the film to be 20 mm or more x 20 mm or more, since this makes it easier to achieve the effects of the present invention, and more preferably 60 mm or more x 60 mm or more, and even more preferably 100 mm or more x 100 mm or more. In particular, an arrangement in which the particle arrangement in each of the mutually orthogonal directions in a planar view is periodically repeated is preferable. Examples of lattice arrangements include hexagonal lattice, rectangular lattice, oblique lattice, square lattice, and other rectangular lattices. Among these, a hexagonal lattice arrangement or a square lattice arrangement is preferred. Alternatively, the conductive particles may be arranged in a linear array with a predetermined spacing between them, and the array may be arranged in parallel with a predetermined spacing between them. Alternatively, a plurality of conductive particles (e.g., 2 to 5 particles) may be arranged in close proximity to one another to form a unit, and the units may be arranged in a lattice pattern. By regularly arranging the conductive particles in this way in a planar view, the number density of the conductive particles can be made uniform, further improving the transfer rate when transferring μLEDs to a display substrate by irradiating them with laser light. There are no particular limitations on the specific method for regularly arranging the conductive particles, and the methods for arranging conductive particles in known anisotropic conductive films, as disclosed in the following publications, may be appropriately adopted. Furthermore, a unit shape that combines these methods may also be used.

[0055] *WO2014021424A1 *Patent Publication No. 2016-085983 *Patent Publication No. 2016-066573 *Patent Publication No. 2017-204461 *Patent Publication No. 2017-204463 *Patent Publication No. 2016-015205 *Patent Publication No. 2016-103476 (Conductive particles in clusters) *Patent Publication No. 2015-201435 *Patent Publication No. 2020-027798 *Patent Publication No. 2021-128936 *WO2016068168A1 (An example where conductive particle omission and aggregation are acceptable) *Patent Publication No. 2022-151821 (arrangement of μLEDs uniformly arranged on one surface to reduce the effort required for arrangement)

[0056] (base film, cover film) In order to improve the handling properties during production and storage stability of the filler-containing film of the present invention, a base film that has been subjected to a release treatment using silicone or the like may be provided on the back surface of the insulating adhesive sheet, rather than on the surface where the conductive particles are pressed in. A cover film that has been subjected to a release treatment using silicone or the like may also be provided on the surface of the filler-containing film where the filler, such as conductive particles, is pressed in. When using the filler-containing film, the cover film is usually peeled off first, followed by the base film. These base films and cover films can be made from polyethylene terephthalate, which is used in known, general anisotropic conductive films. The thickness of these cover films and base films may be appropriately selected within the range of 10 μm to 100 μm. Although the thicknesses may be the same, it is preferable that the base film be thicker than the cover film.

[0057] (Laminated structure of filler-containing film) Examples of the laminate structure of the filler-containing film of the present invention include a structure in which the cover film / filler-containing film / base film are laminated in this order when the filler-containing film is a single layer. When the filler-containing film has a two-layer structure (e.g., a conductive particle-containing layer (A layer) and a conductive particle-free layer (N layer)), the structure includes a structure in which the cover film / conductive particle-containing layer (A layer) / conductive particle-free layer (N layer) / base film are laminated in this order. When the filler-containing film has a three-layer structure, the structure includes a structure in which the cover film / conductive particle-free layer (N layer) / conductive particle-containing layer (A layer) / base film are laminated in this order, or a structure in which the cover film / conductive particle-free layer (N layer) / conductive particle-containing layer (A layer) / conductive particle-free layer (N layer) / base film are laminated in this order. The resin layer material can be selected from known materials. It is preferable that 95% or more of the conductive particles are uniform in number in the thickness direction of the film. The conductive particle-containing layer and the conductive particle-free layer can be referred to as a filler-containing layer and a filler-free layer, respectively.

[0058] (Curling of filler-containing film) The filler-containing film of the present invention may curl mainly due to the influence of the roll-to-roll manufacturing process, such as lamination or coating. When the cover film side is placed on a flat glass plate or the like, the maximum distance from the glass plate to the curled cover film surface is preferably within 10 mm, more preferably within 7 mm, and even more preferably within 5 mm. This is because if the curl is large, the area of ​​the filler-containing film is large, which is likely to cause problems during the process of temporarily attaching the film.

[0059] (DSC behavior of filler-containing films) Furthermore, the filler-containing film of the present invention preferably has a reaction property suitable for use in a vacuum laminator, particularly when the film has a large area. This reaction property can be determined by evaluating the reaction time measured with a differential scanning calorimeter (DSC measurement device).

[0060] (Measurement of reaction time) Approximately 5 mg of sample cut from the filler-containing film is placed in an aluminum pan (TA Instruments) and placed in a DSC measuring device (Q2000, TA Instruments). Differential scanning calorimetry (DSC) measurements are performed from 30°C to 250°C at a heating rate of 10°C / min. From the resulting DSC chart, the temperature at which the exothermic peak rises is read as the reaction start temperature, and the temperature at which the exothermic peak changes to the baseline is read as the reaction end temperature. The reaction time can be calculated using the following formula:

[0061]

number

[0062] The reaction initiation temperature is preferably 85°C or higher, more preferably 90°C or higher, and particularly preferably 100°C or higher. The reaction completion temperature (the temperature at which the exothermic peak changes to the baseline) is preferably 230°C or lower, more preferably 200°C or lower, and particularly preferably 180°C or lower. In particular, when performing compression bonding using a vacuum laminator, the temperature is raised relatively slowly to the final compression bonding temperature, and then a holding time is required without immediately pressing out. For this reason, the reaction initiation and completion temperatures must be higher than those of conventional COG bonding. This is because the entire filler-containing film holding the μLEDs is pressed in, allowing the resin of the filler-containing film to flow between the multiple μLEDs and between the bumps on the μLEDs. Furthermore, since the multiple conductive particles must be sandwiched to ensure uniform conductivity, such DSC behavior is required. Furthermore, the temperature rise in the present invention is more gradual than in conventional COG connections, which require low temperatures and short times, and since the resin and conductive particles are sandwiched uniformly over a wide area, a steep change from the reaction start temperature to the reaction peak temperature is required. Therefore, the difference between the reaction start temperature and the peak temperature is preferably within 30°C, more preferably within 20°C, and even more preferably within 15°C.

[0063] (Melt viscosity characteristics of filler-containing films) In order to bond electronic components accurately and firmly to the filler-containing film of the present invention, it is necessary to understand and adjust the melt viscosity and minimum melt viscosity characteristics.

[0064] (Melt viscosity measurement) The melt viscosity of a filler-containing film can be determined under the same measurement conditions as the minimum melt viscosity of conventional anisotropic conductive films. For example, it can be determined using a rotational rheometer (manufactured by TA Instruments) with a measurement pressure held constant at 5 g and a measurement plate with a diameter of 8 mm. More specifically, it can be determined in the temperature range of 30 to 200°C, at a heating rate of 10°C / min, a measurement frequency of 10 Hz, and a load fluctuation of 5 g on the measurement plate.

[0065] (Measurement of minimum melt viscosity and viscosity at 35°C) The minimum melt viscosity of the filler-containing film of the present invention is required to allow the resin to flow uniformly over a wide area between μLEDs and between μLED electrodes. Therefore, the lower limit is preferably 80 Pa·s or more, more preferably 90 Pa·s or more, and even more preferably 100 Pa·s or more. Furthermore, if the minimum melt viscosity is too high, there is a concern that the resin flow will not progress even if the temperature is raised slowly during the final pressure bonding. Therefore, the upper limit is preferably 2000 Pa·s or less, more preferably 1500 Pa·s or less, even more preferably 1000 Pa·s or less, and particularly preferably less than 1000 Pa·s. Furthermore, in the present invention, in order to prevent slight misalignment of microcomponents during pressure bonding and to stabilize the filler sandwiched between the microcomponents and the substrate, it is preferable to apply pressure from room temperature (25°C ± 15°C) during the final pressure bonding and then raise the temperature. Therefore, it is necessary to control the melting property of the filler-containing film within a predetermined range at or near the start of the temperature rise. Therefore, the lower limit of the viscosity at 35°C is preferably 5,000 Pa·s or higher, more preferably 10,000 Pa·s or higher, and even more preferably 35,000 Pa·s or higher. This is because if the resin does not flow at temperatures near room temperature, uniform pressure bonding over a wide area becomes difficult. Furthermore, if the upper limit is too high, the resin flow becomes too large, which may lead to defects such as difficulty in controlling the position of the μLED itself or poor capture of conductive particles. Therefore, the viscosity is preferably 100,000 Pa·s or lower, more preferably 70,000 Pa·s or lower, and even more preferably 50,000 Pa·s or lower. In the present invention, multiple microcomponents placed on a substrate are connected, and the flow of resin between the microcomponents and the flow of resin directly below the microcomponents (e.g., between two or more bumps) must be simultaneously controlled. This is because in visually inspected applications such as displays, even minor resin flow defects are easily visible and affect the appearance. Even when considered as a black matrix material, such resin flow affects the appearance. Therefore, satisfying these characteristics is desirable to achieve the effects of the invention during and after connection. Such resin melt viscosity behavior is particularly preferable when the insulating adhesive layer of the filler-containing film is a multilayer structure of two or more layers, but is similar for a single layer.These viscosities are measured for the entire film, whether it is a single layer or two or more layers. Furthermore, the total layer thickness of the filler-containing film is thin, at 20 μm or less, making it preferable for it to be in sheet form rather than a long length such as a reel. When a conductive sheet is slit into a film width of 5 mm or less and wound multiple times around a reel, even partial blocking or overflow can cause defects in the connection process and affect productivity. However, in the sheet form of the present invention, such problems associated with conventional reel forms are unlikely to occur. Furthermore, in the case of the present invention, the conductive sheet may be transported in a stacked sheet form. However, even if the resin overflows from the edge, the large sheet area makes it less likely to cause blocking associated with conventional reel forms. Furthermore, after temporary application during the connection process, the edge can be cut off and not used for connection, making it easy to avoid overflow and blocking associated with conventional reel forms. Therefore, to obtain the effects of the present invention, the total thickness of the conductive sheet is preferably 15 μm or less, more preferably 10 μm or less.

[0066] The filler-containing film of the present invention requires extremely delicate handling and remarkably high appearance characteristics. To simultaneously satisfy these requirements, a multilayer structure consisting of two or more layers may be used to design the required characteristics. For example, a laminated structure consisting of a filler-containing layer and a filler-free layer can be adopted. The thickness of these layers and the blending ratio of the black pigment and inorganic filler can also be changed. This also facilitates the management of development factors required for design changes. However, unless the total thickness is within a specified range, it is difficult to demonstrate the function as a black matrix material. Therefore, the lower limit of the total thickness is preferably greater than 2 μm, more preferably 3 μm or more, and even more preferably 4 μm or more. Furthermore, if the microcomponent is a μLED, which has a relatively small size, it is preferable that the μLED itself be thin, so it may be desirable to avoid an excessively thick total film. Therefore, the upper limit of the total thickness is preferably less than 10 μm, more preferably 9 μm or less, and even more preferably 8 μm or less.

[0067] To put it simply, conventional anisotropic conductive films (ACFs) that are slit can cause resin overflow and blocking, which can lead to problems when pulling out the reel. However, this problem is less likely to occur when the ACF is made into a sheet. For example, if the μLED size is 100 μm or less (maximum length is 100 μm or less), the thickness of the μLED itself is thin, so the sheet thickness can be 12 μm or less, and preferably 10 μm or less, making overflow less likely to occur. In this case, the base film and cover film used for the conductive sheet should be at least 15 μm thick, preferably 20 μm or more, and more preferably 25 μm or more.

[0068] (Tackiness of filler-containing film) The filler-containing film of the present invention preferably exhibits tackiness when temporarily attached, and the tackiness can be evaluated by the adhesive strength of the insulating adhesive layer of the filler-containing film.

[0069] (Measurement of adhesive strength of insulating adhesive layer of filler-containing film) The tackiness of a filler-containing film is closely related to the decrease in productivity of the connection structure in terms of its adhesion to the substrate during the production of the connection structure and the mounting of small components. Therefore, when peeling a base film or cover film from a filler-containing film, it is usually desirable to reduce the film area, narrow the film width, and increase the film thickness to prevent poor appearance of the filler-containing film. Even in such cases, the tackiness of the filler-containing film must be measured over a small area. It can be determined using a measuring instrument conforming to JIS Z3284 (JIS Z3284-3), JIS Z0237, or ASTM D2979-01, or the peel force obtained from a nanoindentation test conforming to ISO 14577-1 / JIS Z2255 can be measured as the tackiness. Specifically, in a method of measurement in which the tip of a hemispherical probe with a diameter of 5 mm is pressed against the film, a tack tester (Rhesca Corporation) is used to measure the tack under the following conditions: pressing speed 60 mm / sec, pressure 50 gf, pressing time 15 sec, peeling speed 198 mm / min, and measurement temperature 33±5°C. From the viewpoint of ease of application and workability, the tack is required to be 1 gf or more, preferably 50 gf or more, and more preferably 100 gf or more. This measurement in which the tip of the hemispherical probe is pressed against the film can be obtained by averaging multiple measurements, with N=3 or more being preferred, N=5 or more being more preferred, and N=10 or more being even more preferred. Furthermore, in a measurement method using a 20 μm × 20 μm square protrusion-shaped probe, when measuring tack using an ENT-NEXUS ultra-microindentation hardness tester (Elionix Co., Ltd.) under conditions of a pressing speed of 0.3 μm / sec, a pressure of 0.2 mN, a set indentation depth of 1 μm, a peel speed (not adjustable), and a measurement temperature of 23 ± 5°C, the required hardness, from the perspective of mounting microcomponents, is preferably 50 μN or more, more preferably 200 μN or more, and even more preferably 400 μN or more. Because the area of ​​the measurement using the 20 μm × 20 μm square protrusion-shaped probe is extremely small, it is appropriate to obtain the average of multiple measurements, preferably N=10 or more, more preferably N=15 or more, and even more preferably N=20 or more.Since the film is thin, the tack measurement is performed multiple times by shifting the position of the film. In the filler-containing film of the present invention, the filler arranged over a large area is sandwiched between a minute component and a substrate to which the filler-containing film is attached, so that the effect of the present invention is achieved by exhibiting good tack even over a minute area within the above-mentioned tack test temperature range.

[0070] (Method for producing filler-containing film) The filler-containing film of the present invention can be produced in the same manner as known filler-containing films. For example, as described in Japanese Patent No. 6187665 (paragraphs 0111-0112, etc.), the film can be produced by using a transfer mold having recesses for accommodating conductive particles (the recesses are filled with conductive particles, and an insulating adhesive film (preferably an insulating adhesive film with a side of a sheet planar shape of 20 mm or more) that serves as an insulating adhesive layer is attached to the filled surface (or an insulating adhesive film formed by applying and drying a paste-like insulating adhesive is laminated), and the conductive particles are transferred to the insulating adhesive film, and the transferred conductive particles are pressed into the insulating adhesive film as needed. If necessary, another insulating adhesive film can be laminated on the front or back surface of the insulating adhesive film on the side where the conductive particles are pressed.

[0071] The insulating adhesive film may be produced in a continuous process by producing a long raw roll, or it may be produced as individual sheets by printing. When producing a raw roll, it is preferable to use a base sheet with a release-treated surface, but when producing by printing, the insulating adhesive film may be applied by coating or coating on a flat substrate such as glass (with a release-treated surface), and each process may be carried out using individual films. From the viewpoint of productivity, it is preferable to work on raw rolls, and from the viewpoint of quality control, it is preferable to print individually because it is easy to inspect and sort good and bad products.

[0072] <Shipping form of filler-containing film> The filler-containing film of the present invention is preferably shipped in sheet form, and is preferably stored in a tray having a storage area of ​​the same size as the sheets, with 10 to 500 sheets stacked, and then packed in a bag with the tray and degassed before shipping. It is preferable that the tray has a recess on the side for degassing. This is because curling of large sheets can be suppressed by sealing the stacked sheets together with the tray in a bag and degassing them.

[0073] (Connection structure) The present invention also provides a connection structure in which one or more microcomponents, such as light-emitting elements, are connected to a substrate via a filler-containing film that may contain conductive particles as a filler. The substrate can be appropriately selected from known substrates, and glass, plastic, and polyimide substrates, which are used in light-emitting devices such as display devices and light sources, are preferred. A rigid substrate may also be used. This is because the substrate can vary depending on the object into which the light-emitting elements or other microcomponents are incorporated. Known light-emitting elements, such as LEDs, mini-LEDs, μLEDs, and laser diodes, can also be used as light-emitting elements. Semiconductor elements may also be used. Examples of applications of the connection structure include light-emitting devices such as display devices, lighting devices, and backlight devices. In particular, when the connection structure functions as a display device or light-emitting device, it is preferable that a black matrix be formed around the light-emitting elements or other microcomponents, i.e., that the light-emitting elements or other microcomponents are exposed from the black matrix. Furthermore, it is preferable that the light-emitting elements or other microcomponents are connected to the substrate used in the display device or light-emitting device via a conductive connection or an anisotropic conductive connection.

[0074] A μLED display device or light-emitting device, which is a specific example of the connection structure of the present invention, is a μLED display device in which μLEDs are mounted on a display substrate via at least one conductive sheet of the present invention, and in which 1,000 or more, preferably 1,500 or more, more preferably 100,000 or more, specifically 100,000 to 5,000,000 μLEDs are mounted. In particular, the conductive sheet surrounding the μLEDs functions as a black matrix in μLED display devices. As described below, it may also be considered as a combination of multiple mounted components. The pitch of the electronic components (e.g., μLEDs) when mounting microelectronic components on a substrate varies depending on the application of the connection structure, and the upper limit of the pitch (i.e., the distance between the centers of adjacent μLEDs) in the case of μLEDs is usually 15 μm.

[0075] (Method of manufacturing connection structure) The present invention provides a method for producing a connection structure, in which a substrate and a microcomponent such as a light-emitting element are connected via the filler-containing film of the present invention.

[0076] A preferred embodiment of this manufacturing method includes a method for manufacturing a connection structure for a display device or a light-emitting device, in which the filler-containing film of the present invention is placed on an electrode of a display substrate (including a substrate for a light-emitting device), one or more microcomponents such as light-emitting elements are aligned with and attached to the filler-containing film, and then heated and pressurized to connect the electrodes of the microcomponents such as light-emitting elements to the electrodes of the display substrate; and a method for manufacturing a connection structure that functions as a display device or a light-emitting device, in which laser light is irradiated from the light-transmitting substrate side to a microcomponent such as a light-emitting element arranged on the surface of the light-transmitting substrate, causing one or more microcomponents such as light-emitting elements to land on the filler-containing film of the present invention arranged on the electrodes of the display substrate, thereby connecting the electrodes of the microcomponents such as light-emitting elements to the electrodes of the display substrate. The light-emitting elements may be landed on a separate transfer material and then transferred onto the substrate to which the filler-containing film has been attached. The transfer may be performed in one step or multiple steps.

[0077] In these manufacturing methods, the alignment method, lamination method, heat and pressure method, connection method, laser light irradiation method, etc. can be appropriately selected from known methods and applied. Furthermore, in these manufacturing methods, it is preferable to use μLEDs as the light-emitting elements, and when connecting the electrodes of the light-emitting elements to the electrodes of the display substrate, it is preferable to form a black matrix around the light-emitting elements. In these manufacturing methods, it is preferable to connect the light-emitting elements to the display substrate by conductive connection or anisotropic conductive connection. When arranging the filler-containing film on various substrates, it may be slit into narrow widths, but it is preferable to arrange it solid in order to maximize its applications and performance.

[0078] In the manufacture of connection structures, a filler-containing film is temporarily attached and pressed onto a display substrate, and a microcomponent is connected to the display substrate through a final pressure bond. The temporary attachment and pressure bond procedures can be performed in the same manner as when manufacturing connection structures using conventional anisotropic conductive films (conductive films). A standard bonding tool can be used for temporary attachment and pressure bond. However, if a vacuum laminator is used, temporary attachment can be performed at 40-60°C for 10-120 seconds under reduced pressure (0.1-0.2 MPa). A standard bonding tool can also be used for final pressure bond. However, if a vacuum laminator is used, the temperature is increased at a rate of 5-20°C / min, and after reaching 100-200°C, the temperature is held for 10-60 seconds before pressure bond. The pressure is reduced to 0.01-0.2 MPa, resulting in a total tool pressure of 0.05-0.3 MPa. A vacuum laminator may be used in place of a vacuum environment.

[0079] The manufacturing method of the connection structure of the present invention will be described in detail with reference to the drawings. Specifically, the anisotropic conductive film, which is one embodiment of the filler-containing film of the present invention, contains a black colorant (preferably a black pigment) that is visible light-blocking and near-infrared-transparent, and is therefore useful for mounting μLEDs 22 on a display substrate 21. Specifically, as shown in FIG. 2, a μLED display 20 has a structure in which a display substrate 21, which is a wiring substrate having terminals 21a, and μLEDs 22, which have terminals 22a, are anisotropically conductively connected via an anisotropic conductive film 10 of the present invention disposed between them. Display substrates and μLEDs used in known μLED displays can be used as the display substrate 21 and μLEDs 22. Here, the anisotropic conductive film 10a around the μLEDs 22 (or between adjacent μLEDs) contains a black pigment that is highly visible light-blocking and near-infrared-transparent. Therefore, it not only functions as a black matrix, but also allows alignment marks formed on the display substrate to be identified through the black matrix using an infrared camera. 2, the entire surface of the display substrate 21 is covered with a single anisotropic conductive film 10, and multiple μLEDs are simultaneously anisotropically conductively connected to it. This eliminates the need for an alignment process, anisotropically conductive connection process, and black matrix formation process for each μLED, thereby reducing manufacturing costs. This is because a single film can function as both a connection material and a black matrix material. The anisotropic conductive film of the present invention may also be arranged in individual pieces on each terminal of the display substrate corresponding to the μLED (see JP 2024-17711 A).

[0080] Such a μLED display can be manufactured by placing the anisotropic conductive film of the present invention on the electrodes of a display substrate, aligning and bonding the μLED to the anisotropic conductive film, and then applying heat and pressure to form an anisotropic conductive connection between the electrodes of the μLED and the electrodes of the display substrate.

[0081] In addition, μLEDs arranged on the surface of a light-transmitting substrate can be manufactured by irradiating laser light from the light-transmitting substrate side using a laser lift-off method, causing the μLEDs to land on the anisotropic conductive film of the present invention arranged on one side of the display substrate.

[0082] In addition, in the manufacturing method of a connection structure, a process is typically performed in which an adhesive film is attached to one side of a substrate, and a micro-component such as a μLED is placed on the side of the substrate opposite the adhesive film via a filler-containing film. In this case, peeling the base film or cover film from the filler-containing film is more difficult than in the past. On the other hand, if the filler-containing film is a conventional so-called "adhesive film" that does not require peeling of the base film or cover film, the filler-containing film itself will not peel off from the base film, making it less likely to cause appearance defects such as wrinkles, creases, or warping. Furthermore, if the filler-containing film is slit to a film width of 5 mm or less and further wound around a flanged core, the narrow width makes it relatively easy to peel off the base film or cover film attached to the substrate surface. However, when the filler-containing film is slit into wider widths, such as 5 mm or more, further 30 mm or more, and particularly 50 mm or more, or when it is cut into rectangular sheets with sides of 50 mm or more, deformation due to peeling of the base film or cover film is likely to occur, resulting in significant defects in the appearance of the filler-containing film. This problem becomes more pronounced as the filler-containing film itself becomes thinner, i.e., as the thickness of the filler-containing film becomes 30 μm or less, further 20 μm or less, and even further 10 μm or less.

[0083] <Another embodiment of the connection structure for μLED display devices and the manufacturing method thereof> The present invention provides a connection structure in which one or more electronic components, such as light-emitting elements, are connected to a substrate via the anisotropic conductive film or conductive sheet, which is one embodiment of the filler-containing film of the present invention. The present invention also provides a method for producing a connection structure in which a substrate and light-emitting elements are connected via the conductive sheet.

[0084] The substrate can be appropriately selected from known substrates, and glass substrates, plastic substrates, and polyimide substrates used in so-called display applications are preferred. The substrate may be a flexible or rigid substrate. The wiring material of the substrate can be appropriately selected from known wiring materials (e.g., Au, Ti, Al, Cu, Ag, ITO, etc.), and the wiring may be composed of two or more wiring materials. The substrate may be a flexible or rigid substrate. The wiring material can be appropriately selected from known wiring materials (e.g., Au, Ti, Al, Cu, Ag, ITO, etc.), and the wiring may be composed of two or more wiring materials. The electronic component can be a known light-emitting element such as an LED, mini LED, μLED, or laser diode. Examples of applications of the connection structure include display devices, lighting devices, backlight devices, and light source devices. The connection structure can also be used in digital signage and flexible displays. It is preferable that microcomponents such as light-emitting elements are connected to the substrate for display applications, etc., via conductive or anisotropic conductive connections.

[0085] Regarding the relationship between the number of pixels per inch of a μLED display and the μLED size, as the μLED size decreases, the device size of the μLED display also decreases, and the PPI (Pixels per inch) increases. For example, if the μLED size is 10 μm x 20 μm and its electrode size is 7 μm x 5 μm (35 μm 2In this case, red, green, and blue μLEDs can be mounted in a predetermined array with a 25 μm pitch within a 75 μm × 75 μm rectangle, resulting in a small μLED display with a resolution of 300 to 400 PPI. Furthermore, for example, if the μLED size is 15 μm × 30 μm and the electrode size is 10 μm × 8 μm, red, green, and blue μLEDs can be mounted at a 37 μm pitch, resulting in a medium-sized μLED display with a resolution of 200 to 300 PPI. The present invention is preferably applied when the maximum length of the μLED is 100 μm or less. When the maximum length of the μLED exceeds 100 μm, the total thickness of the film is preferably 10 μm or more. This is because as the μLED size increases, the thickness of the μLED also increases, making it necessary to increase the total thickness of the film. In this case, a total film thickness of 15 μm or more, preferably 20 μm or more, is practically appropriate.

[0086] The filler-containing film will be described as a relatively large-area conductive sheet. Figure 3 is a flowchart showing an outline of the manufacturing process for a μLED display (structure) using a conductive sheet. As shown in Figure 3, the process includes a blending step S1 of an insulating resin composition, a sheet forming step S2, a sheet cutting step S3, a packaging step S4 of the conductive sheet, a connecting step S5 of connecting the substrate and μLEDs via the conductive sheet, and a manufacturing step S6 of manufacturing the μLED display (structure).

[0087] (Blending process S1) In the blending step S1, an insulating resin composition is obtained by blending a film-forming component, a thermosetting component, a thermosetting agent, etc., which constitute the insulating adhesive layer of the conductive sheet described above. In addition, the black pigment described above is blended to allow the conductive sheet to function as a black matrix.

[0088] (Sheet forming process S2) In the sheet formation step S2, an insulating adhesive sheet of a predetermined thickness can be obtained by applying the insulating resin composition to a release substrate and drying it. When producing an aligned conductive sheet in which conductive particles are regularly arranged on an insulating adhesive sheet, the conductive particles are filled into the recesses of a transfer mold having recesses for accommodating the conductive particles, an insulating adhesive film is attached to the filled surface to transfer the conductive particles to the insulating adhesive sheet, and the transferred conductive particles are pressed into the insulating adhesive sheet as needed.

[0089] To obtain a two-layer conductive sheet, another insulating adhesive film is laminated on the front or back side of the insulating adhesive sheet where the conductive particles are pressed. A three-layer structure may also be obtained by laminating on both sides. Furthermore, when the conductive sheet is to function as a black matrix, it is preferable to use a two-layer or more insulating adhesive layer containing a black pigment. This can reduce pinholes in the conductive sheet.

[0090] (Sheet cutting process S3) In the sheet cutting step S3, the conductive sheet is cut to a predetermined size. The size of the conductive sheet is preferably 20 mm or more × 20 mm or more, more preferably 60 mm or more × 60 mm or more, and even more preferably 100 mm or more × 100 mm or more, and can be selected according to, for example, the screen size of a display device.

[0091] (Conductive sheet packaging process S4) In the conductive sheet packaging step S4, conductive sheets of a predetermined size are stacked with release sheets interposed therebetween and packaged in a tray. Alternatively, a long conductive sheet of a predetermined width may be wound up and packaged in a tray.

[0092] (Connection step S5) In the connection step S5, the substrate and the μLED are connected via a conductive sheet.

[0093] In the connection process, a conductive sheet laminated on a base film, for example, is temporarily attached to a display substrate. If air bubbles are trapped during the temporary attachment, this can cause the sheet to float after connection, resulting in poor electrical conductivity and poor appearance. Therefore, after the temporary attachment, vacuum lamination is performed by evacuation (suction, reduced pressure). The temperature during lamination is preferably 40 to 70°C, and the pressure is preferably 1 MPa or more. Here, if the size of the conductive sheet is larger than the size of the display substrate, it is preferable to cut the conductive sheet to the size of the display substrate. If the thickness of the display substrate is sufficiently greater than the protruding portion of the sheet, the edge can be folded into the thickness of the substrate, eliminating the need to cut.

[0094] In the connection process, the red μLEDs from the red μLED wafer, the green μLEDs from the green μLED wafer, and the blue μLEDs from the blue μLED wafer are arranged on the carrier substrate in a predetermined subpixel arrangement, for example, by laser lift-off. The subpixel arrangement can be a known stripe arrangement or a pentile arrangement.

[0095] Next, in the connection process, a stamp head is used to pick up a predetermined number of μLEDs 32 from the carrier substrate, and the predetermined number of μLEDs 32 are aligned and mounted on the conductive sheet 40 attached to the display substrate 31.

[0096] In the connection process, pressure may be applied prior to heating at room temperature (25°C ± 15°C). This is to prevent even slight movement of the microcomponents. Filler can be sandwiched between the substrate and the microcomponents (conductive particles can be sandwiched between the substrate and the μLED bumps). Conventional anisotropic conductive film (ACF) bonding involves pressing the object to be connected with a heated tool (heat tool) to apply heat and pressure. However, in this case, the tool is pressed without heating (for example, at 25°C ± 15°C or below 50°C), and heating begins while maintaining pressure on the object to be connected. The tool head is not particularly limited as long as it is suitable for the connection of the present invention. While the temporary fixation process described in JP 2019-216097 A can be performed, applying pressure for the actual compression bonding from the beginning, as in conventional ACF bonding (however, heating begins after pressure application), is preferable because it minimizes pressure fluctuations and facilitates filler sandwiching.

[0097] Next, in the connection process, a heat tool is used to permanently bond the display substrate and multiple μLEDs via the conductive sheet, electrically connecting them all together. The temperature during thermocompression bonding is preferably 140°C or higher, and the pressure varies depending on the number of microcomponents to be connected and the connection device, but should be 0.1 MPa or higher, preferably 10 MPa or higher. Final bonding can be performed under vacuum using a vacuum laminator or other similar device. Conventional tool bonding devices or semiconductor mounting devices can also be used. A known buffer material can be inserted between the microcomponents, or a glass plate or plastic sheet can be used to align the height of the microcomponents. Bonding can be performed using a heat tool, as with conventional anisotropic conductive films, or a laminator. It is sufficient to select a method and device that does not impair the effects of the invention. While a conventional bonding tool can be used, when using a vacuum laminator, temporary bonding can be performed at 40-60°C for 10-120 seconds under reduced pressure (0.1-0.2 MPa). A normal bonding tool can also be used for this bonding, but if a vacuum laminator is used, the temperature is increased at a rate of 5-20°C / min, and once it reaches 100-200°C, it is held for 10-60 seconds for bonding. The pressure is reduced to 0.01-0.2 MPa, with a total tool pressure of 0.05-0.3 MPa. A vacuum laminator can also be used in place of a vacuum environment.

[0098] 4 is a cross-sectional view showing a portion of a connection structure 45 in which μLEDs 32 are connected via a conductive sheet 40 made of an anisotropic conductive material. As shown in FIG. 4, the connection structure has a structure in which terminals (not shown) of the display substrate 31 and terminals (not shown) of the μLEDs 32 are conductively connected (or anisotropically conductively connected) via the conductive sheet 40 on which conductive particles 42 are arranged. When the conductive sheet 40 is made to function as a black matrix, pinholes can be reduced by including black pigment in both the binder resin layer 40a and the binder resin layer 40b.

[0099] In one embodiment of the connection process described above, the conductive sheet 40 is solidly laminated on the display substrate 31. However, in another embodiment, the conductive sheet 40 may be placed on the surface of a light-transmitting substrate, and laser light may be irradiated from the light-transmitting substrate side to cause individual pieces 40c of the conductive sheet to land on the electrodes of the display substrate 31 (see JP 2024-17711 A). The size of the individual pieces 40c is, for example, an inner diameter of 10 μm to 150 μm and can be selected depending on the size of the μLEDs 32. In this case, the conductive sheet of the present invention serves as the raw material for the individual pieces 40c. What has been described as a conductive sheet so far may also be subjected to a connection method similar to a conventional connection method, such as a known anisotropic conductive film, in which an anisotropic conductive film is applied and formed, then slit into a narrow width (e.g., less than 20 mm), attached to an electronic component with wiring, and another electronic component is aligned and mounted on the opposing component, followed by final pressure bonding using a heat tool appropriate for the film width and component outer shape. As mentioned above, conventional techniques may be applied.

[0100] Fig. 5 is a cross-sectional view showing a portion of a connection structure 45 in which μLEDs 32 are connected via individual pieces 40c. As shown in Fig. 5, the connection structure has a structure in which terminals (not shown) of the display substrate 31 and terminals (not shown) of the μLEDs 32 are anisotropically conductively connected via individual pieces 40c of a conductive sheet in which conductive particles are arranged. This connection structure can achieve an average transmittance of 90% or more for visible light with a wavelength of 400 nm or more and 700 nm or less.

[0101] (Manufacturing process S6) In manufacturing process S6, a μLED display (structure) is manufactured.

[0102] Fig. 6 is a cross-sectional view showing one embodiment of a μLED display. As shown in Fig. 6, the μLED display includes a connection structure to which μLEDs are connected, an optical resin 33 such as OCA (Optically-clear Adhesive) or OCR (Optical Clear Resin), a cover film 34, and the like. The optical resin 33 may be transparent or colored.

[0103] FIG. 7 is a cross-sectional view of another embodiment of a μLED display device 50. As shown in FIG. 7, a large μLED display device 50 is constructed by connecting (connecting) display substrates 31, each of which is, for example, approximately 10 to 12 inches, with connecting portions 36. For example, the display substrates can be connected as described in JP 2021-140093 A. This allows for even larger displays, such as displays of 90 inches or larger. Large μLED display devices 50 can also be constructed by mounting multiple display substrates 31 on a large base substrate 35. The connected substrates can be electrically connected directly or via the large substrate 35. This electrical connection can be achieved using the conductive sheet of the present invention, a known conductive sheet, or an anisotropic conductive film, or by another known method. The present invention can also be used for relatively small display substrates 31, approximately 2 to 3 inches in size. Therefore, the lower limit of one side of the film can be 20 mm or more. The size of the substrate is not particularly limited, but since it is intended for visual viewing, one side can be 20 mm or more. Although the film and substrate of the present invention are described as having one side of a rectangle or square, they are not limited to this shape, and any shape other than a rectangle or square can be interpreted accordingly and applied. The height (total thickness) of the μLED, including the terminals, is considered to be equal to or greater than the thickness of the filler-containing film, since it is not suitable for the μLED to be embedded in the filler-containing film after the connection process for the purpose of the invention. Therefore, the μLED does not have a shape or total thickness that cannot be adhered and fixed by the thickness of the filler-containing film. The upper and lower limits of the numerical ranges described in this specification may be selected appropriately within the described range depending on the indicators related to the effects of the invention. [Example]

[0104] The present invention will be specifically described below with reference to examples.

[0105] Examples 1 to 9, Reference Examples 1 to 5 <Creating a filler-containing film> The insulating adhesive layer compositions of Examples 1 to 9 and Reference Examples 1 to 5, in which the types and amounts of epoxy resin, acrylic rubber, black pigment, etc. were adjusted as shown in Table 1, were mixed, and the resulting mixtures were applied to release substrates and dried at 60°C for 3 minutes to obtain insulating adhesive layers having thicknesses of 1 μm to 21 μm. Note that a perylene-based black pigment (perylene black) was used as the black pigment.

[0106] Thereafter, conductive particles (Micropearl AU, Sekisui Chemical Co., Ltd.) with an average particle diameter of 2.2 μm were deposited at a particle surface density of 58,000 particles / mm by the conductive particle regular array treatment described in paragraphs 0111 to 0112 and FIG. 1A of Japanese Patent No. 6187665. 2 The conductive particles were arranged in a regular hexagonal lattice pattern in a resin mold so that the conductive particles were arranged in a regular hexagonal lattice pattern, and then transferred to an insulating adhesive layer. This resulted in the production of black pigment-containing anisotropic conductive films of Examples 1 to 9 and Reference Examples 1 to 5. All of the following evaluations were performed with the surface onto which the conductive particles were transferred serving as the attachment surface (attachment surface).

[0107] [Table 1]

[0108] <<Evaluation test and evaluation results>> For each anisotropic conductive film of the Examples and Reference Examples, "optical properties (L*a*b*)," "tackiness," "60° gloss value," "visible light blocking property," "near-infrared transmittance," and "conductive resistance" were measured and evaluated as described below, and the results are shown in Table 2. Ranks A, B, and C were evaluated as good, meaning that the film could be used practically without any problems, and Rank D was evaluated as poor.

[0109] <Optical properties (L*a*b*)> The L* value, a* value, and b* value of the L*a*b* color system on the surface of each anisotropic conductive film of the Examples and Reference Examples were measured in accordance with JIS Z 8781 using a spectrophotometer (CM-700d, Konica Minolta Japan, Inc.), and the optical properties were evaluated according to the following evaluation criteria.

[0110] (L* value evaluation criteria) Rank Criteria A 10 or less B Over 10 and under 30 C over 30 but below 50 D over 50

[0111] (a* value evaluation criteria) Rank Criteria A -5 or more and 5 or less B -10 or more and 10 or less C -30 or more and 30 or less D -less than 30, more than 30

[0112] (b* value evaluation criteria) Rank Criteria A -5 or more and 5 or less B -10 or more and 10 or less C -30 or more and 30 or less D -less than 30, more than 30

[0113] <Tackiness> The tackiness of the surface of the anisotropic conductive film of each Example and Reference Example was measured using a Nanointender device (Nanomechanics), and the tackiness was evaluated according to the following evaluation criteria.

[0114] (Tackiness evaluation criteria) Rank Criteria A 60gf or more B: 40gf or more but less than 60gf C 20gf or more and less than 40gf D Less than 20gf

[0115] <60° gloss value> The surface gloss value of each anisotropic conductive film of each example and reference example was measured using a commercially available surface gloss measuring device (Micro Trigloss, BYK Instruments) conforming to ASTM D523, and the 60° gloss value was evaluated according to the following evaluation criteria.

[0116] (60° gloss value evaluation criteria) Rank Criteria A. Under 40 B. 40 or more and less than 50 C. 50 or more and less than 60 D 60 or more

[0117] <Near infrared transparency> Each anisotropic conductive film of the Examples and Reference Examples was temporarily attached to a 5 mm thick glass substrate (5 cm square), and its near-infrared transmittance was determined as the average transmittance of near-infrared rays with wavelengths of 800 nm or more and 1200 nm or less using a spectrophotometer (UV-Vis UV2600, Shimadzu Corporation), and the near-infrared transmittance was evaluated according to the following evaluation criteria.

[0118] (Near-infrared transmittance evaluation criteria) Rank Criteria A: Near-infrared transmittance of 60% or more B: Near-infrared transmittance is 40% or more and less than 60% C: Near-infrared transmittance is 20% or more and less than 40% D: Near-infrared transmittance less than 20%

[0119] <Visible light blocking property> Each anisotropic conductive film of the Examples and Reference Examples was temporarily attached to a 5 mm thick glass substrate (5 cm square), and its visible light transmittance was determined as the average transmittance of visible light with wavelengths of 400 nm to 700 nm using a spectrophotometer (UV-Vis UV2600, Shimadzu Corporation), and the visible light blocking ability was evaluated according to the following evaluation criteria.

[0120] (Visible light blocking evaluation criteria) Rank Criteria A: Visible light transmittance less than 5% B: Visible light transmittance is 5% or more and less than 20% C: Visible light transmittance is 20% or more but less than 30% D: Visible light transmittance is 30% or more

[0121] <Conduction resistance> Each anisotropic conductive film of the Examples and Reference Examples was temporarily attached to a glass substrate with an ITO / NbMo wiring pattern formed on its surface. An evaluation IC chip simulating a μLED was attached to the temporarily attached anisotropic conductive film under heating and pressure conditions of 150°C, 30 MPa, and 10 seconds to obtain a package. The surface of the evaluation IC chip facing the anisotropic conductive film had an electrode layout consisting of a pair of 10 μm square bumps (7 μm spacing between bumps) arranged at a 30 μm pitch in a 1.5 cm square area. The conductive resistance of the evaluation IC chip was measured at 30 locations through the wiring pattern of this package using a commercially available tester, and the conductive resistance was evaluated according to the following evaluation criteria.

[0122] (Conductivity resistance evaluation criteria) Rank Criteria A: Conduction resistance is less than 50 Ω B: Conduction resistance is 50Ω or more and less than 100Ω C: Conduction resistance is 100Ω or more and less than 200Ω D: Conduction resistance value is 200Ω or more

[0123] [Table 2]

[0124] <Discussion of evaluation results> The anisotropic conductive films of Examples 1 to 9 had an average transmittance of 20% or more for near-infrared rays with wavelengths of 800 nm or more and 1200 nm or less, and therefore were rated A or B for near-infrared transmittance, enabling highly accurate alignment with an infrared camera. Furthermore, the 60° gloss value of the film surface according to ASTM D523 (60°) was less than 60, and therefore the 60° gloss value was rated A or B. This enabled the formation of a matte black-like black matrix, which adequately suppressed light reflection on the display and prevented a decrease in visibility in devices such as car navigation systems and smartwatches that are exposed to large amounts of sunlight.

[0125] On the other hand, in the case of the anisotropic conductive film of Reference Example 1, the content of acrylic rubber was too low, so the 60° gloss value was rated D, and a matte black-toned black matrix could not be realized.

[0126] In the case of the anisotropic conductive film of Reference Example 2, since it did not contain acrylic rubber, the 60° gloss value was rated D, and a matte black-toned black matrix could not be realized.

[0127] In the case of the anisotropic conductive film of Reference Example 3, the 60° gloss value was rated A because the acrylic rubber content was relatively high, but the resin content was relatively low and the tackiness was rated D.

[0128] In the case of the anisotropic conductive film of Reference Example 4, since the insulating adhesive layer was relatively thin, the 60° gloss value was rated A, but the visible light blocking property was rated D.

[0129] In the case of the anisotropic conductive film of Reference Example 5, the insulating adhesive layer was relatively thick, so the 60° gloss value was rated A, but the near-infrared transmittance and the conductive resistance were both rated D.

[0130] (Visible Light Blocking and Near-Infrared Transmittance of the Anisotropic Conductive Film of Example 1) The anisotropic conductive film of Example 1, which uses a black pigment that is visible light-blocking and near-infrared-transparent, was attached to an inspection TEG equipped with an alignment mark, and the alignment mark was observed with a visible light camera or an infrared camera. The alignment mark could not be identified with the visible light camera, but could be identified with the infrared camera.

[0131] Examples 10 to 18 The anisotropic conductive films of Examples 10 to 18 were prepared in the same manner as in Examples 1 to 9, except that a black pigment having a bisbenzofuranone main skeleton and also serving as a lactam black (Irgaphor Black S0100CF, DIC Corporation) was used instead of perylene black as a black pigment, and were similarly evaluated for evaluation items other than optical properties (L*a*b*). The evaluation results were equal to or better than those of Examples 1 to 9. Furthermore, the anisotropic conductive films of Examples 10 to 18 exhibited maximum transmittance in the wavelength range of 850 nm or more and 950 nm or less, and in visual evaluation, exhibited better black color development than the anisotropic conductive films of Examples 1 to 9. Other evaluation results were also equal to or better than those of Examples 1 to 9.

[0132] (Tackiness of Anisotropic Conductive Films of Examples 10 to 18) Furthermore, the tackiness of the insulating adhesive layer of each of the anisotropic conductive films of Examples 10 to 18 was measured as the peel force obtained from a nanoindentation test in accordance with ISO 14577-1 / JIS Z2255. Specifically, using a tacking tester (Rhesca Corporation) to measure by pressing the tip of a 5 mm diameter hemispherical probe against the film, the tackiness was measured under the following conditions: pressing speed 60 mm / sec, pressure 50 gf, pressure time 15 sec, peel speed 198 mm / min, and measurement temperature 33±5°C. The results were in the range of 50 gf to 250 gf. In addition, in the method of measurement by pressing a 20 μm x 20 μm square rod-shaped probe against the sample, the tack was measured using the ultra-micro hardness tester ENT-NEXUS (Elionix Co., Ltd.) under the conditions of a pressing speed of 0.3 μm / sec, a pressure of 0.2 mN, a set pressing amount of 1 μm, a peeling speed (not adjustable), and a measurement temperature of 23 ± 5°C, and was found to be in the range of 200 μN to 600 μN.

[0133] (Lamination of conductive particle-free layer onto anisotropic conductive films of Examples 10 to 18) Furthermore, in the anisotropic conductive films of Examples 10 to 18, a 2 μm thick conductive particle-free layer and a 4 μm thick conductive particle-free layer were laminated on a conductive particle-containing layer (5 μm thick) in the same manner as in Examples 10 to 18, except that they did not contain conductive particles. The laminated anisotropic conductive films had total thicknesses of 7 μm and 9 μm, and the optical properties (L*a*b*), tackiness, 60° gloss value, visible light blocking property, near-infrared transmittance, and conduction resistance were evaluated. The properties were found to be equal to or better than those of the anisotropic conductive films of Examples 10 to 18 that did not have a conductive particle-free layer laminated thereon.

[0134] (Film lighting evaluation) The anisotropic conductive films of Examples 10 to 18, as well as anisotropic conductive films laminated with conductive particle-free layers as described above to a total thickness of 7 μm and 9 μm, were evaluated in the form of 4 cm × 4 cm sheets. A 2 cm × 2 cm area in the center of a 5 cm × 5 cm evaluation substrate was used, with a wiring pattern of 40 μm × 20 μm μLEDs (each of which had a bump height of 2 μm) for each color of RGB as one pixel, resulting in a total of 40 × 40 μLEDs (1600 μLEDs, 500 μm pitch). After the film was temporarily attached, air bubbles were removed using a vacuum laminator (40°C, 2 minutes, reduced pressure of 0.1 MPa, total tool pressure of 0.2 MPa). While applying pressure with a vacuum laminator, the temperature was raised from room temperature at a rate of 10°C / min, and a compression evaluation was performed by pressing out immediately after reaching 150°C, and by holding the temperature for 30 seconds after reaching 150°C (a vacuum of 0.1 MPa was used, with a total tool pressure of 0.2 MPa). A lighting test of the μLEDs on the resulting connection structure was conducted, and over 99.9% of all the μLEDs installed successfully lit up.

[0135] Example 19 A laminated anisotropic conductive film (310mm x 190mm) with a total thickness of 7μm was temporarily attached to a glass substrate (280mm x 160mm) with a wiring pattern formed on its surface, and air bubbles were removed using a vacuum laminator (40°C, 2 minutes, reduced pressure of 0.1MPa, total tool pressure of 0.2MPa). Next, the black pigment-containing anisotropic conductive film that protruded from the glass substrate was cut off. Next, more than 100,000 pre-prepared 40μm x 20μm RGB μLEDs were mounted at a pixel pitch of 500μm. The temperature was raised from room temperature at 10°C / min while pressurized with a vacuum laminator, and after reaching 150°C, it was held for 30 seconds for compression bonding (reduced pressure of 0.1MPa, total tool pressure of 0.2MPa). A lighting test of the μLEDs in the resulting connection structure showed that more than 99.9% of the mounted μLEDs successfully lit.

[0136] Furthermore, all of the black pigment-containing anisotropic conductive films (black pigment conductive films) of the above-mentioned examples, with thicknesses ranging from 5 μm to 9 μm, were fabricated in a 310 mm × 190 mm size. They were similarly temporarily bonded to a 280 mm × 160 mm glass plate, and air bubbles were removed using a vacuum laminator (40°C, 2 minutes, reduced pressure of 0.1 MPa, total tool pressure of 0.2 MPa). Next, the film was heated using the same device under the same pressure bonding conditions as above, and the appearance of only the large-area anisotropic conductive film (black pigment conductive film) was evaluated. In this invention, microcomponents are interspersed and connected, but since there are also many areas without microcomponents, evaluating the appearance of the film without applying pressure is also considered effective in confirming the effects of the invention. Therefore, this appearance evaluation can be considered to be approximately equivalent to the appearance evaluation of the μLED when it is not lit. The evaluation results showed good color appearance when visually inspected, and no pinholes were observed even when a light was shone on the back. Therefore, all of the black pigment-containing anisotropic conductive films (black pigment conductive films) subjected to the appearance evaluation were found to be sufficient for use in display devices. Furthermore, when a 280 mm × 160 mm area was divided into 7 × 4 equal parts and evaluated for visible light blocking, near-infrared transmittance, and L*, a*, and b* values, all results were approximately equivalent. Similar results were obtained in eight randomly selected 6 cm × 6 cm areas (4 × 2), including corners, demonstrating that the black pigment-containing anisotropic conductive films (black pigment conductive films) of the present invention are suitable for practical use even when one side is 4 cm or more or 6 cm or more. The uncured appearance of the black pigment-containing anisotropic conductive films (black pigment conductive films) evaluated here was visually evaluated by shining a light from the backside when attached to a base film (before application) and when attached to a glass plate (after application). No pinholes were observed. [Industrial Applicability]

[0137] The anisotropic conductive film of the present invention, which is a filler-containing film having conductive particles held in an insulating adhesive layer, has an average transmittance of 20% or more for near-infrared light with wavelengths of 800 nm to 1200 nm. Therefore, if the film has sufficient light-shielding properties against visible light, it can be used as a material for forming a black matrix. Furthermore, because it is sufficiently transparent to near-infrared light, even when a substrate is covered with the filler-containing film of the present invention, alignment marks on the substrate can be identified with an infrared camera. Therefore, when mounting light-emitting elements such as μLEDs on a display substrate via the filler-containing film of the present invention, multiple light-emitting elements can be aligned with high precision at once, rather than individually. Furthermore, the connection process (preferably a conductive connection or anisotropic conductive connection process) and the black matrix formation process can be performed simultaneously, thereby shortening the process and reducing costs. Furthermore, since the 60° gloss value is less than 60, a matte black-like black matrix can be formed, which sufficiently suppresses light reflections on the display and prevents a decrease in visibility in devices such as car navigation systems and smartwatches exposed to large amounts of sunlight, making the film industrially useful. [Explanation of symbols]

[0138] 1. Insulating adhesive layer 1a Binder resin layer 1b Binder resin layer 2. Conductive particles 10 Anisotropic conductive film 20μ LED display 21 Display board 21a Display board terminal 22μLED 22a μLED terminal 31 Display board 32μLED 33 Optical resin 34 Cover film 35 large boards 36 Connecting part 40 Conductive sheet 40a Binder resin layer 40b Binder resin layer 40c piece 41 Conductive particles 45 Connection Structure 50 μ LED display device

Claims

1. A filler-containing film in which a filler is held in an insulating adhesive layer containing an epoxy resin and an acrylic rubber, The average transmittance of near-infrared light having a wavelength of 800 nm or more and 1200 nm or less is 20% or more, A filler-containing film having a 60° gloss value of less than 60 according to ASTM D523 (60°) on the film surface.

2. 10. The filler-containing film according to claim 1, which functions as a conductive film or an anisotropic conductive film.

3. 3. The filler-containing film according to claim 1, which has an average transmittance of near-infrared rays of 40% or more.

4. 3. The filler-containing film according to claim 1, which has an average transmittance of near-infrared rays of 60% or more.

5. 3. The filler-containing film according to claim 1, wherein the 60° gloss value of the film surface according to ASTM D523 (60°) is less than 50.

6. 3. The filler-containing film according to claim 1, wherein the 60° gloss value of the film surface according to ASTM D523 (60°) is less than 40.

7. 3. The filler-containing film according to claim 1, which has an average transmittance of less than 30% for visible light having a wavelength of 400 nm or more and 700 nm or less.

8. 3. The filler-containing film according to claim 1, which has an average transmittance of less than 20% for visible light having a wavelength of 400 nm or more and 700 nm or less.

9. 3. The filler-containing film according to claim 1, which has an average transmittance of less than 5% for visible light having a wavelength of 400 nm or more and 700 nm or less.

10. 3. A filler-containing film according to claim 1 or 2, wherein the content of the acrylic rubber in the insulating adhesive layer is 2% by mass or more and 15% by mass or less, and the content of the epoxy resin is 20% by mass or more and 50% by mass or less.

11. 3. The filler-containing film according to claim 1, wherein the insulating adhesive layer contains a black colorant in an amount of 2% by mass to 30% by mass, and has a thickness of 1 μm to 50 μm.

12. 11. The filler-containing film according to claim 10, wherein the black colorant is an organic pigment.

13. 12. The filler-containing film according to claim 11, wherein the organic pigment is at least one of lactam-based black pigments, perylene-based black pigments, azo-based black pigments, aniline-based black pigments, bisbenzofuranone-based black pigments, and cyanine-based black pigments.

14. 12. The filler-containing film according to claim 11, wherein the organic pigment is a lactam-based black pigment, a perylene-based black pigment, or a bisbenzofuranone-based black pigment.

15. A connection structure in which one or more microcomponents are connected to a substrate via the filler-containing film according to claim 1.

16. The connection structure according to claim 14, wherein the filler of the filler-containing film is conductive particles, the substrate is a display substrate, the microcomponent is a light-emitting element, and a black matrix is ​​formed around the light-emitting element, and the connection structure functions as a display device or a light-emitting device.

17. 16. The connection structure according to claim 15, wherein the light emitting element is electrically conductively connected or anisotropically conductively connected to the substrate.

18. A method for producing a connection structure in which a substrate and a microcomponent are connected via the filler-containing film according to claim 1.

19. A method for manufacturing a connection structure that functions as a display device or a light-emitting device, comprising: placing the filler-containing film according to claim 1, wherein the filler is conductive particles, on an electrode of a display substrate; aligning and bonding one or more light-emitting elements to the filler-containing film; and applying heat and pressure to connect the electrodes of the light-emitting elements to the electrodes of the display substrate.

20. A method for manufacturing a connection structure that functions as a display device or a light-emitting device, in which a light-emitting element arranged on the surface of a light-transmitting substrate is irradiated with laser light from the light-transmitting substrate side, and one or more light-emitting elements are caused to land on a filler-containing film according to claim 1, in which the filler arranged on the electrode of the display substrate is conductive particles, thereby connecting the electrode of the light-emitting element to the electrode of the display substrate.

21. 20. The manufacturing method according to claim 18, wherein a black matrix is ​​formed around the light emitting element when connecting the electrodes of the light emitting element and the electrodes of the display substrate.

22. 21. The method of claim 20, wherein the connection of the light-emitting element to the display substrate is a conductive connection or an anisotropic conductive connection.

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