TWI691978B - Anisotropic conductive film and sheet for liquid crystal display - Google Patents

Abstract

The anisotropic conductive film (10) includes a resin film (20). The resin film (20) has a plurality of through holes (25). The plurality of through holes (25) are respectively defined by the inner wall surface (24) covered with the conductive material (33). The conductive material (33) is a cylindrical body (30) having a hollow (15) extending from the front surface (11) to the back surface (12). Because of having holes (15), the anisotropic conductive film (10) is suitable for ensuring the light transmittance in the thickness direction.

Description

Anisotropic conductive film and sheet for liquid crystal display

The present invention relates to an anisotropic conductive film.

It is known that there is a film with high conductivity in the thickness direction and high insulation in the in-plane direction perpendicular to the thickness direction. Such a film is sometimes called an anisotropic conductive film. An example of the anisotropic conductive film is described in Patent Documents 1 and 2. The anisotropic conductive film of Patent Document 1 is filled with a metal substance derived from a plating method in a plurality of through holes formed in an insulating film. The anisotropic conductive film of Patent Document 2 is filled with conductive particles and a filler in a plurality of through holes formed in an insulating film.

In one example, the anisotropic conductive film is inserted between the circuit boards, and is fixed between the circuit boards by heating and pressure bonding. The conductivity of the anisotropic conductive film in the thickness direction is relatively high, thus ensuring electrical connection between the electrodes of one circuit board and the electrodes of another circuit board. On the other hand, the in-plane insulation of the anisotropic conductive film is high, so it is not easy to generate unnecessary short circuits between the electrodes in one circuit substrate, and it is not easy to generate electrodes between the other circuit substrates. Unnecessary short circuit. In another example, the anisotropic conductive film is interposed between the electronic component and the circuit substrate. Specifically, the anisotropic conductive film is used as a connecting member for mounting electronic components such as semiconductor elements or electronic parts, or as a connector for functional inspection.

Prior technical literature Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 5-325669

Patent Literature 2: Japanese Patent Laid-Open No. 2002-75064

The anisotropic conductive films described in Patent Documents 1 and 2 are formed in which a plurality of through holes in the insulating film are completely blocked. According to studies by the present inventors, if the through-holes are completely blocked, it is difficult to ensure the light transmittance in the thickness direction of the anisotropic conductive film.

In order to solve the shortcomings of the above-mentioned conventional technology, the present invention provides an anisotropic conductive film having a front surface and a back surface, and the anisotropic conductive film includes a resin film having a plurality of through holes and a plurality of the above The through holes are each defined by an inner wall surface covered with a conductive material, and the conductive material constitutes a cylindrical body having a hollow hole extending from the surface to the back surface inside.

The anisotropic conductive film of the present invention is a conductive material covering the inner wall surface of a through hole of a predetermined resin film, but a void is formed inside the conductive material. Therefore, the different guides of the present invention The electrical film is suitable for ensuring light transmittance in the thickness direction.

10: Anisotropic conductive film

11: Surface

12: back

15: empty hole

20: resin film

21: Surface

22: back

24: inner wall surface

25: through hole

27: The solid part

30: cylindrical body

33: conductive material

39: outer contour

FIG. 1 is a cross-sectional view schematically showing an example of an anisotropic conductive film.

2 is a plan view schematically showing an example of an anisotropic conductive film.

FIG. 3 schematically shows a cross-sectional view of an example of a resin film.

Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, but the following are only examples of the embodiments of the present invention and are not intended to limit the present invention.

The anisotropic conductive film of this embodiment will be described using FIGS. 1 and 2. The anisotropic conductive film 10 has a resin film 20 and a conductive material 33. The resin film 20 is a film with high insulation (that is, low conductivity). The conductive material 33 is a material with high conductivity. The conductive material 33 is constituted by a cylindrical body (cylindrical conductive layer) 30 having voids 15 extending from the front surface 11 to the rear surface 12 inside. Specifically, there are a plurality of cylindrical bodies 30 made of conductive material 33. The plurality of cylindrical bodies 30 are spaced apart from each other, and extend from the front surface 11 to the back surface 12 of the anisotropic conductive film 10. With this configuration, although the plurality of cylindrical bodies 30 provide the conductivity in the thickness direction of the anisotropic conductive film 10, the conductivity in the in-plane direction perpendicular to the thickness direction cannot be greatly improved. The resin film 20 ensures insulation in the in-plane direction. That is, the combination of the resin film 20 and the conductive material 33 provides the anisotropic conductivity of the anisotropic conductive film 10. In addition, the hole 15 of the cylindrical body 30 has a function of transmitting light in the thickness direction of the anisotropic conductive film 10 (ensuring transparency in the thickness direction). Furthermore, in this specification, the anisotropic conductivity means that the conductivity of the anisotropic conductive film 10 in the thickness direction is High and high insulation in the in-plane direction.

As shown in FIG. 3, a plurality of through holes 25 are formed in the resin film 20. The plurality of through holes 25 are each defined by the inner wall surface 24 of the resin film 20. In other words, the plurality of through holes 25 are each surrounded by the inner wall surface 24. The inner wall surface 24 should be covered by the conductive material 33. The resin film 20 of this embodiment is composed of a solid portion 27 filled with resin inside, and a plurality of through holes 25. The front surface 21 and the back surface 22 of the resin film 20 constitute a part of the front surface 11 and the back surface 12 of the anisotropic conductive film 10.

From the viewpoint of securing the anisotropic conductivity by ensuring the in-plane direction insulation of the anisotropic conductive film 10, it is preferable that the insulation of the front surface 21 and the back surface 22 is high. From this point of view, the material of the resin film 20 may be selected from materials whose insulation is somewhat high. Specifically, the material of the resin film 20 may be selected from the group consisting of polyethylene terephthalate (PET), polycarbonate, polyethylene naphthalate, polyimide, and polyvinylidene fluoride At least one kind of material in the group.

From the viewpoint of ensuring light transmittance in the thickness direction of the anisotropic conductive film 10, it is preferable that the thickness of the resin film 20 is not excessively large. From the viewpoint of ensuring the conductivity in the thickness direction of the anisotropic conductive film 10, it is preferable that the thickness of the resin film 20 is not excessively large. Considering these points of view, the thickness of the resin film 20 is, for example, 4 to 130 μm, and, for example, 10 to 130 μm, preferably 10 to 100 μm, and more preferably 10 to 60 μm.

From the viewpoint of ensuring the light transmittance in the thickness direction of the anisotropic conductive film 10, it is preferable that the diameter of the through hole 25 is not too small. From this viewpoint, the diameter (diameter) of the through-hole 25 is, for example, 0.5 to 35 μm, and for example, 1 to 35 μm, or for example, 1 to 15 μm, and 2 to 15 μm. In the present embodiment, the through-hole 25 is formed on the front surface 21 or the back surface 22 to form a diameter An opening of 35 μm or less (specifically, 15 μm or less).

From the viewpoint of ensuring the number of conductive paths in the thickness direction of the anisotropic conductive film 10 and thereby ensuring the electrical conductivity in the thickness direction, thereby ensuring the anisotropic conductivity, the density of the through holes 25 is preferably larger to a certain extent . However, if the density of the through-hole 25 is too large, the light transmittance in the thickness direction of the anisotropic conductive film 10 may be greatly impaired by the scattering of light in the through-hole 25. Taking these aspects into consideration, the density of the plurality of through holes 25 is preferably 1×10 ³ to 1×10 ¹⁰ pieces/cm ² , and more preferably 1×10 ⁴ to 1×10 ⁹ pieces/cm ² . Furthermore, if the anisotropic conductivity of the anisotropic conductive film 10 is ensured and the thickness of the anisotropic conductive film 10 is reduced, the resin film 20 preferably has a plurality of through holes 25 having a small diameter. It is also suitable for this purpose to set both the diameter and the density of the through-hole 25 to the above-mentioned range.

The ratio (aperture ratio) of the sum of the cross-sectional areas of all the plurality of through holes 25 to the area defined by the outline of the anisotropic conductive film 10 when viewing the anisotropic conductive film 10 from the thickness direction is, for example, 0.05 to 0.5, or It can be 0.2~0.4. In addition, the details of the cause are still under investigation, but the total volume (total volume) of all the cylindrical bodies (cylindrical conductive layers) 30 of the anisotropic conductive film 10 is somewhat larger, which is easy The tendency to ensure the conductivity of the anisotropic conductive film 10 in the thickness direction. That is, when the cylindrical body 30 with a specific thickness is formed in each through-hole 25 by sputtering (and etching) described below, etc., the opening ratio is as high as the above-mentioned degree and the diameter of the through-hole 25 In the case where it is relatively small (for example, 15 μm or less), in other words, the total area (total area) of all the inner wall surfaces 24 such as the through-holes 25 with small diameters to a certain extent is greater. Under such circumstances, there is a tendency to easily ensure conductivity in the thickness direction.

From the viewpoint of ensuring the light transmittance in the thickness direction of the anisotropic conductive film 10, the angle between the thickness direction of the resin film 20 and the axial direction of the through hole 25 is preferably not too large. Also, from the viewpoint of ensuring the anisotropic conductivity by ensuring the electrical conductivity in the thickness direction of the anisotropic conductive film 10, the angle is preferably not too large. From these viewpoints, the angle is preferably 0 to 30°, more preferably 0 to 15°, and further preferably 0 to 2°.

The shape of the through hole 25 is not particularly limited. For example, the through hole 25 is a straight hole extending linearly. As a specific shape of the through-hole 25, a cylindrical shape, a truncated cone shape, and an hourglass shape (a shape in which two truncated cones are combined, and a shape formed by connecting the bottom surfaces of the sides with smaller areas) can be exemplified.

The conductive material 33 covers the inner wall surface 24 of each of the plurality of through holes 25 defining the resin film 20. The conductive material 33 is formed inside a cylindrical body 30 having a cavity 15 extending from the front surface 11 to the rear surface 12. The hole 15 preferably transmits light. Specifically, there are a plurality of cylindrical bodies 30 made of conductive material 33. The plurality of cylindrical bodies 30 cover the plurality of inner wall surfaces 24 of the resin film 20 and are spaced apart from each other. The plurality of cylindrical bodies 30 extend from the front surface 11 to the rear surface 12 of the anisotropic conductive film 10, respectively, and assume a cylindrical shape. That is, the plurality of cylindrical bodies 30 constitute part of the front surface 11 and the back surface 12 of the anisotropic conductive film 10 and are spaced apart from each other. Due to the arrangement in this manner, although the plurality of cylindrical bodies 30 provide higher conductivity in the thickness direction of the anisotropic conductive film 10, they cannot significantly improve the conductivity in the in-plane direction. The present embodiment is based on the front surface 11 and/or the back surface 12, and each of the plurality of cylindrical bodies 30 is formed with an outer contour 39 along the inner wall surface 24. Specifically, the cylindrical body 30 covers only the inner wall surface 24 of the resin film 20 and does not cover the front surface 21 and the back surface 22 of the resin film 20. However, as long as the separation and insulation between the plurality of cylindrical bodies 30 are ensured, a part of the conductive material 33 may also be attached to the front surface 21 and the back surface 22.

The material of the conductive material 33 is not particularly limited as long as it has conductivity. Typically, the material of the conductive material 33 is metal or metal oxide. Specifically, the conductive material 33 The material may be at least one material selected from the group consisting of gold (Au), silver (Ag), copper (Cu), indium tin oxide (ITO), and indium zinc oxide (IZO).

From the viewpoint of ensuring the conductivity in the thickness direction of the anisotropic conductive film 10, the wall thickness of the cylindrical body 30 is preferably large. On the other hand, if the wall thickness is too large, the coloring of the anisotropic conductive film 10 derived from the material of the cylindrical body 30 may become conspicuous, so that there is a large loss of light transmission in the thickness direction due to this condition, etc. Sexual situation. Considering these aspects, the wall thickness is preferably 100 to 1000 nm.

The diameter of the cavity 15 is, for example, 0.1 to 30 μm, and for example, 1 to 30 μm, and for example, 1 to 14 μm.

Other layers may also be interposed between the conductive material 33 and the inner wall surface 24 of the resin film 20. For example, by interposing inorganic material layers such as silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), niobium oxide, etc., the adhesion of the conductive material 33 to the inner wall surface 24 may be improved, or the transparency of the anisotropic conductive film 10 may be improved Sex.

As an index of the insulation (conductivity) of the anisotropic conductive film 10 in the thickness direction, the volume resistance of the anisotropic conductive film 10 in the thickness direction can be cited. As an index of the insulation in the in-plane direction of the anisotropic conductive film 10, the surface resistance of the anisotropic conductive film 10 in the film plane direction can be cited. From the viewpoint of seeing through the opposite side of the anisotropic conductive film 10 (the viewpoint of ensuring visibility in the thickness direction), as long as the relevant wear in the thickness direction of the light of the wavelength of 300 to 800 nm of the anisotropic conductive film 10 is ensured Transparency is enough. The volume resistance is, for example, 1.0×10 ^-2 to 1.0×10 ¹⁵ Ω‧cm, preferably 1.0×10 ^-2 to 1.0×10 ¹³ Ω‧cm. The surface resistance is, for example, 1.0×10 ² Ω/□ or more, preferably 1.0×10 ¹⁴ Ω/□ or more. The above-mentioned penetration rate is preferably 25 to 90%. As long as these three parameters are within the above range, the anisotropic conductive film 10 can be said to have high conductivity in the thickness direction and high insulation in the film surface direction (ie, high anisotropic conductivity), and has a thickness direction Visibility. The above-mentioned penetration rate is more preferably 30% to 90%, and further preferably 60 to 90%.

The anisotropic conductive film 10 can be used as a sheet for liquid crystal displays attached to a liquid crystal display panel. For example, the front surface 11 constitutes the surface to be in contact with the conductive portion of the liquid crystal display panel, and the rear surface 11 constitutes the back to be in contact with the target material. In a specific example, the conductive part of the liquid crystal display panel is an electrode or a control circuit, and the target material is a semiconductor element (electronic circuit) such as a TAB (Tape Automated Bonding) module or a COG (Chip On Glass) module. In other specific examples, the liquid crystal display panel is a touch panel (a display element that can manually input text or graphics), and the object material is a stylus. The higher conductivity in the thickness direction of the anisotropic conductive film 10 realizes a lower driving voltage and a higher response speed of the sheet for liquid crystal displays. The higher transmittance in the thickness direction of the anisotropic conductive film 10 achieves higher visibility (higher transparency) of the sheet for liquid crystal displays. Needless to say, these effects of the anisotropic conductive film 10 can also be exerted in other applications.

Next, an example of a manufacturing method suitable for manufacturing the anisotropic conductive film 10 as described above will be described.

First, a resin film 20 having a plurality of through holes 25 and each of the plurality of through holes 25 defined by the inner wall surface 24 is prepared. In this example, ion beam irradiation of the original film (resin film) and chemical etching of the film after irradiation were performed. With this, the resin film 20 is produced. According to ion beam irradiation and etching, a resin film 20 having a plurality of through holes 25 having the same opening diameter on the front surface 21 and the rear surface 22 can be produced. In addition, when ion beam irradiation and etching are performed without further processing or treatment of the main surface (front and back) of the film, in addition to forming the opening of the through-hole 25, a main surface with the original film can be obtained The resin film 20 on the main surface in the same state. Therefore, for example, if a film with a higher smoothness on the main surface is selected as the original film, a film with a higher smoothness corresponding to it can be obtained The resin film 20 on the main surface (for example, the main surface is flat except for the opening). Typically, the original film is a non-porous resin film. The material of the original film may be the same material as the resin film 20.

The ion irradiation amount when the ion beam is irradiated to the original film can be appropriately adjusted according to the density of the through-hole 25 that the resin film 20 should have.

The etching for forming the through-hole 25 is an etching treatment liquid corresponding to the material of the original film (that is, the material of the resin film 20). Examples of the etching treatment liquid include alkaline solutions and oxidant solutions. The alkaline solution is, for example, a solution containing potassium hydroxide and/or sodium hydroxide as a main component, and may further contain an oxidizing agent. The resin constituting the original film can be hydrolyzed by using an alkaline solution. The oxidant solution is, for example, a solution containing at least one selected from chlorous acid, chlorite, hypochlorous acid, hypochlorite, hydrogen peroxide, and potassium permanganate as a main component. The resin constituting the original film can be oxidized and decomposed by using an oxidant solution. An example of the combination of the resin constituting the resin film and the original film and the etching solution is an alkaline solution for polyethylene naphthalate, polycarbonate, and polyethylene naphthalate (for example, sodium hydroxide is the main solution Component solution), and polyimide and polyvinylidene fluoride as oxidant solutions (for example, a solution containing sodium hypochlorite as the main component).

The etching time and the concentration of the etching solution can be adjusted as appropriate according to the diameter of the through-hole 25 that the resin film 20 should have.

As the resin film 20, a commercially available film can be used. Commercially available membranes are sold by Oxyphen and Millipore as membrane filters, for example.

Next, the conductive material 33 is supplied to the resin film 20 by sputtering so that the inner wall surface 24 is covered with the conductive material 33. The material of the conductive material 33 is as described above.

Sputtering can make the conductive material splash to both the surface 21 and the back surface 22 of the resin film 20, or it can make the conductive material splash only to one of the surface 21 and the back surface 22. In any mood In the shape, the conductive material 33 covers not only the front surface 21 and/or the back surface 22, but also the inner wall surface 24, so that a film is formed on the inner wall surface 24.

Next, the conductive material 33 covering the surface 21 and/or the back surface 22 of the resin film 20 is removed. By this, the in-plane conductive paths on the surface 21 and/or the back surface 22 are removed, and the anisotropic conductive film 10 shown in FIGS. 1 and 2 is obtained.

The method of removing the conductive material 33 from the front surface 21 and/or the back surface 22 is not particularly limited. In one example, ion milling using argon (Ar) plasma can be used. In other examples, the etching of the conductive material 33 may be used. For the etching of the conductive material 33, an acidic solution (for example, a solution containing at least one selected from hydrochloric acid, sulfuric acid, and nitric acid as a main component) can be used as an etching treatment liquid. In addition, when a part of the surface 21 and/or the back surface 22 of the resin film 20 is exposed, the resin film 20 may be etched from the exposed portion to the portion covered by the conductive material 33 to adhere to the surface 21 And/or the conductive material 33 on the back surface 22 comes off. As the etching treatment liquid in this case, an etching treatment liquid used for etching for forming the through-hole 25 can be used.

According to the studies of the present inventors, it is difficult to use the techniques described in Patent Documents 1 and 2 to form a cylindrical conductive layer having voids inside. On the other hand, according to the sputtering of the conductive material 33, a cylindrical body (cylindrical conductive layer) 30 having voids 15 extending from the front surface 11 to the back surface 12 can be formed inside. That is, sputtering is suitable for providing the anisotropic conductive film 10 excellent in light transmittance in the thickness direction. In addition, when the plating method described in Patent Document 1 is used, it is easy to form a metal substance in a biased manner, so that a part of the through-holes tends to have uneven electrical characteristics due to insufficient metal substance. With the technique of Patent Document 2, it is difficult to uniformly disperse conductive particles. On the other hand, according to sputtering, the conductive material 33 can be uniformly supplied into the plurality of through holes 25. According to the etching, the conductive path in the in-plane direction can be easily removed. That is, the combination of sputtering and etching is suitable The anisotropic conductive film 10 is provided in which the conductivity in the thickness direction and the insulation in the in-plane direction are high and the conductivity and insulation are uniform. This combination meets the requirements of recent years to improve the fineness of electrical connections (here, to ensure anisotropic conductivity and achieve thinner, shorter, and shorter).

[Example]

The present invention will be described in detail by examples. However, the following examples represent an example of the present invention, and the present invention is not limited to the following examples. First, the evaluation methods of samples in Examples and Comparative Examples will be described.

<film thickness>

Using a dial gauge (manufactured by Mitutoyo Co., Ltd.), the film thickness of each sample was measured at 5 points selected arbitrarily, and the average value was used as the film thickness.

<diameter and angle of through hole>

Using a scanning electron microscope (SEM: manufactured by JEOL Corporation (Japan Electronics Co., Ltd.), JSM-6510LV), the surface and back surface of each sample were observed, and the diameters of 10 through holes arbitrarily selected from the obtained SEM image were obtained. The average value is regarded as the diameter of the through hole (through hole diameter). Furthermore, using the same SEM, the cross-sectional SEM images of each sample were observed, and the angles of 10 through-holes arbitrarily selected from the obtained cross-sectional SEM images were obtained, and the average value was used as the angle of the through-holes.

<opening rate>

With the above SEM, the surface and back surface of the sample were observed, and the number of through holes per unit area in the obtained SEM image was counted visually. Then, the area of the through-holes determined from the through-hole diameters measured by the above method was calculated. The product of the number of through holes and the area of the through holes divided by the area of the SEM image was multiplied by 100 to determine the aperture ratio of each sample.

<pore density>

The number of through holes per unit area in the SEM images of the surface and back of the sample was counted visually and converted into the density of through holes (pore density, unit: pcs/cm ² ).

<Wall thickness of cylindrical body (Cu layer)>

The cross section of each sample was observed by the SEM described above, and at 10 points arbitrarily selected from the obtained cross-sectional SEM image, the wall thickness of the cylindrical body of the through-hole wall surface was measured, and the average value thereof was taken as the wall thickness of the cylindrical body.

<diameter of hole>

The diameter of the hollow hole (empty hole diameter) is calculated by subtracting twice the wall thickness of the cylindrical body from the through hole diameter.

<surface resistance>

The surface resistance of each sample was measured using a resistivity meter (manufactured by Mitsubishi Chemical Corporation ANALYTECH Co., Ltd., MCP-HT450 type), and the value when 10 V was applied to the front and back of the sample, respectively. In addition, this resistivity meter performs measurement according to JIS-K6911. Specifically, the surface resistance of each sample is measured by pressing the positive electrode and the negative electrode against the surface of the sample, and placing the shield electrode on the back of the sample. This configuration is suitable for flowing the current flowing in the thickness direction of the sample to the ground, and measuring only the current flowing on the surface. The pressure between the electrode on the front side (positive electrode and negative electrode) and the shield electrode was set to 100 Pa. In addition, when the sample is thin, it is also considered to reduce the pressure (for example, to approximately 0 Pa) to improve the measurement accuracy of the surface resistance.

<Volume resistance>

The volume resistance of each sample was measured as follows. First, a small piece of 3 cm×3 cm was obtained by cutting the sample. Then, a small piece is sandwiched between the positive and negative electrodes that have been gold-plated, and in this state, A current of 1 mA was flowed between the positive and negative electrodes, the voltage between the positive and negative electrodes at this time was measured, and the volume resistance was measured by dividing the voltage by the current.

<optical characteristics>

The transmittance in the film thickness direction of each sample was measured using a spectrophotometer (manufactured by Japan Spectroscopy Co., Ltd., V560). The measurement wavelength range is set to 300 to 800 nm.

<Examples 1 to 14>

A commercially available PET film (manufactured by it4ip, Track etched membrane) with a plurality of through holes formed in the thickness direction is prepared. This film is a resin film produced by irradiating an ion beam to a non-porous PET film and chemically etching the irradiated film. The thickness of the film is 5 to 115 μm, the through pore diameter is 0.8 to 10 μm, and the aperture ratio is 7.5 to 45%. By sputtering, a Cu layer of 300 to 900 nm is formed on the front surface, back surface of the PET film, and the inner wall surface of the through hole. As a target, a Cu target manufactured by Sumitomo Metal Mining Co., Ltd. was used. For the sputtering system, a sputtering vapor deposition device (manufactured by ULVC (ULVAC Co., Ltd., SMH-2306RE)) was used. The applied voltage is set to DC 0.5~3.0kV. Ar gas flow rate is set to 50~300 SCCM. After sputtering, the resin film is immersed in 10-30 wt% potassium hydroxide aqueous solution at 60°C to 80°C. By etching the front and back surfaces of the resin film in this way, the Cu layer is removed (the extent to which the thickness of the resin film caused by etching is small cannot be measured with a dial gauge). Each sample was made in this way.

<Example 15>

By irradiating the non-porous PET film with laser, a resin film with a film thickness of 45 μm, a through hole diameter of 30 μm, and an opening ratio of 25% was produced. By sputtering, a 300 nm Cu layer was formed on the surface, back surface of the PET film, and the inner wall surface of the through hole. As a target, a Cu target manufactured by Sumitomo Metal Mining Co., Ltd. was used. Sputtering system uses sputtering evaporation equipment (ULVC (ULVAC Co., Ltd.) Made by the company, SMH-2306RE). The applied voltage is set to DC 0.5~3.0kV. The Ar gas flow rate is set to 50 SCCM. After sputtering, the resin film was immersed in a 12 wt% potassium hydroxide aqueous solution at 65°C. In this way, the Cu layer on the surface and the back of the resin film is removed. Make samples in this way.

<Comparative Example 1>

Samples were prepared by simulating the method of the embodiment of Patent Document 1 (method combining laser processing and plating method). In the obtained sample, the through holes formed in the polyimide film were completely blocked by nickel.

The results obtained by measuring the film thickness, through-hole diameter, aperture ratio, pore density, pore angle, Cu layer wall thickness, pore diameter, volume resistance, surface resistance, and penetration in each example and comparative example are shown in Table 1. in.

Furthermore, the reason why the surface resistance of the sample of Example 10 is relatively small is that the thin and non-rigid sample of Example 10 has the terminal of the resistivity meter penetrated into the sample surface (terminal Drilling into the sample), resulting in the possibility that the Cu layer in the through hole will affect the measurement result. In Table 1, it is the reason why the symbol "≧" is added to the measured value "7.9E+02". The reason why the surface resistance of the sample of Example 14 is relatively small is that in the sample of Example 14 having a large aperture ratio, the electrode is likely to come into contact with the Cu layer on the inner wall surface of the through hole near the surface, so that the contact affects the measurement result. Possibility. In Table 1, it is the reason why the symbol "≧" is added to the measured value "2.9E+03". In addition, the volume resistance of the sample of Example 12 with a small through-hole diameter and the sample of Example 15 with a large through-hole diameter were relatively large. In the sample of Example 12, the through-hole diameter is small, and it is difficult for Cu particles to enter the through-hole during sputtering. As a result, it can be predicted that a defect occurs in the Cu layer near the center of the through-hole in the film thickness direction unit. In the sample of Example 15, there are relatively few through-holes with relatively large diameters, so the total area (total area) of the inner wall surfaces of all the through-holes is relatively small, and the volume of all the Cu layers in the sample as a whole The total (total volume) is small. It is predicted that this situation is the main reason for increasing the volume resistance of Example 15.

[Industry availability]

The anisotropic conductive film of the present invention can be used for applications requiring transparency in the thickness direction (applications requiring visibility, etc.), for example. Specifically, it can be used as a sheet for liquid crystal displays.

10: Anisotropic conductive film

11: Surface

12: back

15: empty hole

20: resin film

21: Surface

22: back

30: cylindrical body

33: conductive material

39: outer contour

Claims (13)

An anisotropic conductive film having a front surface and a back surface, and the anisotropic conductive film includes a resin film having a plurality of through-holes, and the plurality of through-holes are each defined by an inner wall surface covered with a conductive material , The conductive material constitutes a cylindrical body, the cylindrical body internally has hollow holes extending from the front surface to the back surface, the diameter of the through holes is 1 to 15 μm, and all of the observation of the anisotropic conductive film from the thickness direction The ratio of the total cross-sectional area of the through hole to the area defined by the outline of the anisotropic conductive film is 0.2 to 0.4. An anisotropic conductive film as claimed in item 1 of the patent scope, wherein the conductive material covers only the inner wall surface. For example, the anisotropic conductive film according to item 1 of the patent application, wherein the thickness of the resin film is 4 to 130 μm. For example, the anisotropic conductive film according to item 1 of the patent scope, wherein the volume resistance of the anisotropic conductive film in the thickness direction is 1.0×10 ⁻² to 1.0×10 ¹⁵ Ω‧cm, where the volume resistance is borrowed It is measured by cutting the anisotropic conductive film to make a small piece of 3 cm×3 cm, and with a gold plated positive and negative electrode sandwiching the small piece, a current of 1 mA flows into the positive and negative electrode. Measure the voltage between the positive and negative electrodes at this time, and divide the voltage by the current. An anisotropic conductive film as claimed in item 1 of the patent application, wherein the surface resistance in the film plane direction perpendicular to the thickness direction is 1.0×10 ² Ω/□ or more, and the surface resistance is based on JIS-K6911. For example, the anisotropic conductive film according to item 1 of the patent application, wherein the transmittance of light with a wavelength of 300 to 800 nm in the thickness direction is 25 to 90%. For example, the anisotropic conductive film according to item 1 of the patent application, wherein the volume resistance of the anisotropic conductive film in the thickness direction is 1.0×10 ^-2 to 1.0×10 ¹³ Ω‧cm and is perpendicular to the thickness direction The surface resistance in the film surface direction is 1.0×10 ¹⁴ Ω/□ or more, and the transmittance of light with a wavelength of 300 to 800 nm with respect to the above thickness direction is 25 to 90%, where the above volume resistance is measured by the following method, namely , By cutting the anisotropic conductive film to make a small piece of 3 cm × 3 cm, and with the gold plated positive and negative electrodes sandwiching the small pieces, a current of 1 mA flows into the positive and negative electrodes, and the above measurement at this time is measured. The voltage between the positive electrode and the negative electrode, and the voltage is divided by the current, the surface resistance is based on JIS-K6911. For example, the anisotropic conductive film according to item 1 of the patent application, wherein the wall thickness of the cylindrical body is 100 to 1000 nm. An anisotropic conductive film as claimed in item 1 of the patent application, wherein the conductive material contains at least one selected from the group consisting of gold, silver, copper, indium tin oxide, and indium zinc oxide. As for the anisotropic conductive film according to item 1 of the patent application range, the angle between the thickness direction of the resin film and the axial direction of the plurality of through holes is 0 to 30°. An anisotropic conductive film as claimed in item 1 of the patent application, wherein the through hole has a cylindrical shape, a truncated cone shape, or a combination of two truncated cone shapes, and a shape that connects the bottom surfaces of the sides with smaller areas. For example, the anisotropic conductive film according to item 1 of the patent application, wherein the material of the resin film contains a material selected from the group consisting of polyethylene terephthalate, polycarbonate, polyethylene naphthalate, polyimide and At least one of the groups consisting of polyvinylidene fluoride. A sheet for liquid crystal display attached to a liquid crystal display panel, the sheet for liquid crystal display has a surface that should be in contact with the conductive portion of the liquid crystal display panel, and a back surface that should be in contact with the target material, and is patented The anisotropic conductive film of the first item in the range.

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