JP7760928B2 - Adhesive structure - Google Patents

Description

The present invention relates to an adhesive structure.

A known adhesive structure has a base and multiple protrusions provided on the surface of the base. Patent Document 1 discloses an adhesive structure with protrusions whose tips are spherical with a radius of 300 nm or less and whose cross section perpendicular to the longitudinal direction has a radius of 500 nm or less. It is said that this adhesive structure with nano-level protrusions is able to penetrate into the irregularities on the surface of the adherend at the nano-level, thereby exerting strong adhesive strength.

International Publication No. 2007/032164

It is preferable that the adhesive structure be able to stably adhere and hold the adherend in a variety of environments and be resistant to contaminating the adherend. However, the adhesive structure described in Patent Document 1 is formed from a resin material. Resin materials may be decomposed or altered by heat, resulting in a decrease in adhesive strength. Furthermore, resin materials may contaminate the adherend with decomposition products.

This invention was made in consideration of the above-mentioned circumstances, and aims to provide an adhesive structure that is resistant to thermal decomposition and deterioration and has high adhesive strength.

In order to solve the above problems, the adhesive structure of the present invention is an adhesive structure that adheres and holds an object to be adhered, and comprises a base and triangular wave-shaped protrusions provided on at least a portion of the surface of the base, and is made of an inorganic material, wherein the pitch of the triangular wave-shaped protrusions is in the range of 100 nm or more and 1000 nm or less, and the height of the triangular wave-shaped protrusions is in the range of 100 nm or more and 1000 nm or less.

The adhesive structure of the present invention comprises a substrate and triangular wave-shaped protrusions provided on at least a portion of the surface of the substrate. Because the structure is made of an inorganic material, it is resistant to thermal decomposition and deterioration, and is less likely to contaminate the adherend. Furthermore, because the average pitch of the triangular wave-shaped protrusions is in the range of 100 nm to 1000 nm and the average height of the triangular wave-shaped protrusions is in the range of 100 nm to 1000 nm, the surface elasticity is high, and the triangular wave-shaped protrusions deform greatly when pressed by the adherend. Therefore, the adhesive structure of this embodiment has high adhesive strength and can stably adhere and hold the adherend in a variety of environments.

Here, in the bonded structure of the present invention, the ratio of the height to the pitch of the triangular wave-shaped protrusions may be in the range of 0.8 to 2.0.
In this case, the adhesive strength of the triangular wave-shaped protrusions to the adherend increases, and when the adherend separates from the triangular wave-shaped protrusions, the adhesive strength of the triangular wave-shaped protrusions is more likely to recover.

In the bonded structure of the present invention, the pitch of the triangular wave-shaped protrusions may be 500 nm or less.
In this case, the narrower pitch of the triangular wave-shaped protrusions makes it easier for the triangular wave-shaped protrusions to deform in accordance with the surface shape of the adherend, thereby further improving the adhesive strength.

In the bonded structure of the present invention, the inorganic material may be a metal.
In this case, the surface elastic modulus of the triangular wave-shaped protrusions is increased, improving the restoring force after deformation and improving repeatability.

In the bonded structure of the present invention, the metal may include any one of copper, a copper alloy, aluminum, an aluminum alloy, and a NiP alloy.
In this case, the surface elastic modulus of the triangular wave-shaped protrusions becomes even higher, and the adhesive strength becomes even higher.

Furthermore, the adhesive structure of the present invention may be configured such that the adhesive strength is 35 N/cm2 or ^more when a spherical indenter having a diameter of 40 μm is pressed into the triangular wave-shaped protrusions using a nanoindenter to an indentation depth of at least one of 10 nm and 20 nm.
In this case, since the adhesive strength is high, it is unlikely to decompose or change in quality due to heat, and can be suitably used as an adhesive structure with high adhesive strength.

The present invention makes it possible to provide an adhesive structure that is resistant to thermal decomposition and deterioration and has high adhesive strength.

1 is a perspective view of an adhesive structure according to one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 2 is a plan view of the adhesive structure shown in FIG. 1 . 10 is a focus curve of triangular wave-shaped protrusions of an adhesive structure according to one embodiment of the present invention. FIG. 4A is a conceptual diagram showing the state before the probe of the nanoindenter is pressed into the triangular wave-shaped protrusions of the bonded structure according to one embodiment of the present invention (FIG. 4A). FIG. 4B is a conceptual diagram showing a state in which the probe of a nanoindenter is pressed into the triangular wave-shaped protrusions of an adhesive structure according to one embodiment of the present invention. FIG. 4C is a conceptual diagram showing the state in which the probe of the nanoindenter pressed into the triangular wave-shaped protrusion of the bonded structure according to one embodiment of the present invention is pulled up. 4D is a conceptual diagram showing the state in which the probe of the nanoindenter pressed into the triangular wave-shaped protrusion of the bonded structure according to one embodiment of the present invention has been released from the bonded structure. FIG.

Below, an adhesive structure embodying the present invention will be described with reference to the attached drawings.

Fig. 1 is a perspective view of an adhesive structure according to one embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1, and Fig. 3 is a plan view of the adhesive structure shown in Fig. 1.
1 to 3, the bonded structure 1 according to this embodiment has a base 2 and triangular wave-shaped protrusions 3 provided on one surface of the base 2. The base 2 and the triangular wave-shaped protrusions 3 are integral with each other. The triangular wave-shaped protrusions 3 have the property of deforming when pressurized and restoring to their original shape when the pressurized state is released.

The bonded structure 1 is made of an inorganic material. Examples of inorganic materials include, but are not limited to, metal, ceramic, and glass. The inorganic material preferably has a melting point of 100°C or higher and a decomposition temperature of 100°C or higher, a melting point of 300°C or higher and a decomposition temperature of 300°C or higher, and a melting point of 500°C or higher and a decomposition temperature of 500°C or higher. The metal may be a simple metal or an alloy. Alloys include those composed of multiple metal elements and those composed of a metal element and a non-metal element. Examples of simple metals include aluminum, nickel, iron, and copper. Examples of alloys include aluminum alloys, NiP, stainless steel, and copper alloys. Examples of ceramics include oxides, nitrides, and carbides. Examples of ceramics include alumina. The inorganic material constituting the bonded structure 1 is preferably a metal, and more preferably contains copper, copper alloys, aluminum, aluminum alloys, or NiP alloys.

The substrate 2 is plate-shaped. There are no particular restrictions on the size of the substrate 2. The thickness of the substrate 2 is, for example, in the range of 10 μm to 10 cm.

The triangular wave-shaped protrusion portion 3 is configured with multiple elongated protrusions 4 arranged along the longitudinal direction. The cross-sectional shape of the protrusions 4 is triangular. The cross-sectional shape of the protrusions 4 is preferably an isosceles triangle. The base angle of the protrusions 4 (θ in Figure 2) is preferably 60 degrees or more, and is preferably in the range of 60 degrees to 80 degrees.

The average pitch of the triangular wavy protrusions 3 is in the range of 100 nm to 1000 nm, preferably 500 nm or less. The average pitch of the triangular wavy protrusions 3 is the average value of the distance between the apexes 4a of adjacent protrusions 4 of the triangular wavy protrusions 3 (P in Figures 2 and 3). The average pitch of the triangular wavy protrusions 3 can be measured from a cross-sectional SEM photograph of the adhesive structure 1 taken with an SEM (scanning electron microscope).

The average height of the triangular wavy protrusions 3 is in the range of 100 nm to 1000 nm, preferably 500 nm or less. The average height of the triangular wavy protrusions 3 is the average of the heights of the protrusions 4 (H in Figure 2) with the base between the valleys 4b of the protrusions 4 of the triangular wavy protrusions 3. The average height of the triangular wavy protrusions 3 can be measured from a cross-sectional SEM photograph of the adhesive structure 1 taken with an SEM.

The ratio of the average height to the average pitch of the triangular wavy protrusions 3 (average height/average pitch) is preferably in the range of 0.8 to 2.0, more preferably 1.0 to 1.5. An average height/average pitch of 0.8 or more allows the protrusions 4 to easily deform along the adherend, enhancing their ability to conform to the shape of the adherend. The triangular wavy protrusions 3 are periodically arranged with protrusions 4 that have high conformability to the shape of the adherend. Therefore, when the triangular wavy protrusions 3 are pressed against the adherend, the amount of deformation of the triangular wavy protrusions 3 is large, increasing the contact area between the adherend and the triangular wavy protrusions 3. This increases the adhesive strength of the triangular wavy protrusions 3 to the adherend. Furthermore, an average height/average pitch of 2.0 or less allows the protrusions 4 to easily return to their original shape when the adherend is detached from the triangular wavy protrusions 3, enhancing the recovery of the adhesive strength of the triangular wavy protrusions 3. This allows the triangular wave-shaped protrusions 3 to be reused over a long period of time.

The adhesive strength of the triangular wave-shaped protrusions 3 of the bonded structure 1 can be determined by creating a focus curve using a nanoindenter.
Fig. 4 shows a focus curve of the triangular wave-shaped protrusion 3 of the bonded structure 1 measured using a nanoindenter. Fig. 5 is a conceptual diagram showing the state (A in Fig. 4) before the probe 10 of the nanoindenter is pressed into the triangular wave-shaped protrusion 3 of the bonded structure 1. Fig. 6 is a conceptual diagram showing the state (B in Fig. 4) after the probe 10 of the nanoindenter has been pressed into the triangular wave-shaped protrusion 3 of the bonded structure 1. Fig. 7 is a conceptual diagram showing the state (C in Fig. 4) after the probe 10 of the nanoindenter pressed into the triangular wave-shaped protrusion 3 of the bonded structure 1 has been pulled up. Fig. 8 is a conceptual diagram showing the state (D in Fig. 5) after the probe 10 of the nanoindenter pressed into the triangular wave-shaped protrusion 3 of the bonded structure 1 has been released from the bonded structure 1.

As shown in Figure 5, when the adhesive structure 1 and the probe 10 are separated, no load is applied between the triangular wave-shaped protrusion 3 of the adhesive structure 1 and the probe 10 (A in Figure 4). In this embodiment, a spherical indenter with a diameter of 40 μm was used as the probe 10.

To create a focus curve, first, the probe 10 is pressed into the triangular wave-shaped protrusion 3 of the adhesive structure 1 with a predetermined load. The conditions for pressing the probe 10 vary depending on the shape of the probe 10. When the probe 10 is a spherical indenter with a diameter of 40 μm, the load is set to a range of 20 μN to 100 μN, and the pressing speed is set to a range of 10 nm/sec to 20 nm/sec. Pressing the probe 10 causes the triangular wave-shaped protrusion 3 of the adhesive structure 1 to deform in accordance with the shape of the probe 10. As the pressing depth of the probe 10 increases, the amount of deformation of the triangular wave-shaped protrusion 3 increases. Then, as shown in Figure 6, pressing the probe 10 is stopped when the probe 10 has been pressed to a predetermined depth (B in Figure 4). In this embodiment, the pressing depth of the probe 10 is set to 10 nm or 20 nm.

Next, the probe 10 is pressed into the triangular-wave-shaped protrusion 3 with a predetermined load and held there for a predetermined time, and then the probe 10 is lifted from the triangular-wave-shaped protrusion 3. The conditions for lifting the probe 10 vary depending on the shape of the probe 10. When the probe 10 is a spherical indenter with a diameter of 40 μm, the lifting speed is set to a range of 10 nm/sec to 20 nm/sec. By lifting the probe 10, the load applied to the triangular-wave-shaped protrusion 3 decreases, and the triangular-wave-shaped protrusion 3 returns to its original shape. Furthermore, when the probe 10 is lifted, the probe 10 and the triangular-wave-shaped protrusion 3 do not separate even when the load is removed, and the adhesive force is observed as a negative load. Furthermore, when the probe 10 is lifted, the probe 10 separates from the triangular-wave-shaped protrusion 3, and the load applied to the triangular-wave-shaped protrusion 3 becomes zero. Then, as shown in FIG. 7, the probe 10 and the triangular-wave-shaped protrusion 3 completely separate (D in FIG. 4). The adhesive strength of the triangular wave-shaped protrusion 3 is the negative maximum value (C in FIG. 4, unit: N) from when this negative load is observed until the probe 10 separates from the triangular wave-shaped protrusion 3 divided by the contact area (cm ² ) between the probe 10 and the triangular wave-shaped protrusion 3 when the probe 10 is pressed in. The adhesive strength of the triangular wave-shaped protrusion 3 varies depending on the shape of the probe 10 and the pressing depth of the probe 10. The adhesive structure 1 of this embodiment preferably has an adhesive strength of 35 N/cm ² or more at a pressing depth of at least 10 nm or 20 nm.

The bonded structure 1 of this embodiment can also be manufactured by a method including, for example, a polishing step, a cutting step, and an etching step.
In the polishing step, the surface of the raw inorganic material substrate is polished. The polishing of the inorganic material substrate can be performed by, for example, grinder polishing, polishing with waterproof paper, or buff polishing. The surface of the inorganic material substrate after polishing preferably has a surface roughness Ra of 0.02 μm or less.

In the cutting process, the surface of the inorganic material substrate polished in the polishing process is cut to form triangular wave-shaped protrusions. There are no particular restrictions on the cutting method, and various methods can be selected. Cutting methods that can be used include, for example, a method in which the cutting tool is periodically moved up and down while moving the cutting tool in a direction perpendicular to the cutting surface to form grooves (NP method: nanopecking method), and a method in which the cutting tool is moved linearly without moving up and down to form grooves (conventional method).

In the NP method, a processing device having a cutting tool and an ultrasonic vibration device that ultrasonically vibrates the cutting tool can be used. There are no particular restrictions on the shape of the cutting edge of the cutting tool, and it can be, for example, triangular or rectangular. In the NP method, for example, the cutting tool is pressed obliquely into the surface of the inorganic material substrate while being ultrasonically vibrated, and then the cutting tool is moved in a direction perpendicular to the cutting edge while periodically moving up and down. This forms triangular wave-shaped protrusions on the surface of the inorganic material substrate, each having multiple inverted triangular grooves extending in a direction perpendicular to the direction of cutting tool movement.

In the conventional method, a processing device having a cutting tool and an ultrasonic vibration device that ultrasonically vibrates the cutting tool can be used as the processing device. The cutting edge of the cutting tool is triangular. In the conventional method, for example, the cutting tool is pressed vertically into the surface of the inorganic material substrate while being ultrasonically vibrated, and then the cutting tool is moved in a direction perpendicular to the cutting edge while being fixed so that it does not move up and down. This forms inverted triangular grooves on the surface of the inorganic material substrate that extend parallel to the direction of movement of the cutting tool. By repeating this operation, triangular wave-shaped protrusions having multiple inverted triangular grooves that extend parallel to the direction of movement of the cutting tool are formed on the surface of the inorganic material substrate.
In this way, the bonded structure 1 of this embodiment is manufactured.

The adhesive structure 1 of this embodiment, configured as described above, comprises a base 2 and triangular wave-shaped protrusions 3 provided on at least a portion of the surface of the base 2. Because the triangular wave-shaped protrusions 3 are made of an inorganic material, they are resistant to thermal decomposition or deterioration and are less likely to contaminate the adherend. Furthermore, because the average pitch of the triangular wave-shaped protrusions 3 is in the range of 100 nm to 1000 nm and the average height of the triangular wave-shaped protrusions 3 is in the range of 100 nm to 1000 nm, the surface elasticity of the triangular wave-shaped protrusions 3 is high, resulting in a large amount of deformation of the protrusions when pressure is applied by the adherend. Therefore, the adhesive structure 1 of this embodiment has high adhesive strength and can stably adhere and hold the adherend in a variety of environments.

In the adhesive structure 1 of this embodiment, when the pitch of the triangular wavy protrusions 3 is 500 nm or less, the narrower pitch of the triangular wavy protrusions 3 makes it easier for the triangular wavy protrusions 3 to deform along the surface shape of the adherend, thereby further improving adhesive strength. Furthermore, when the inorganic material constituting the triangular wavy protrusions 3 is a metal, the surface elastic modulus of the triangular wavy protrusions 3 becomes higher, improving the recovery force after deformation and repeatability. In particular, when the inorganic material constituting the triangular wavy protrusions 3 is copper, a copper alloy, aluminum, an aluminum alloy, or a NiP alloy, the surface elastic modulus of the triangular wavy protrusions 3 becomes higher, improving adhesive strength. Furthermore, in the adhesive structure 1 of this embodiment, when a nanoindenter using a spherical indenter with a diameter of 40 μm is used as the probe 10 to press the probe 10 into the triangular wave-shaped protrusion 3 to a pressing depth of at least 10 nm or 20 nm, if the adhesive strength is 35 N/ ^cm2 or more, the adhesive strength is high and therefore the structure is unlikely to decompose or change in quality due to heat, and can be suitably used as an adhesive structure with high adhesive strength.

In the adhesive structure 1 of this embodiment, when the ratio of the average height to the average pitch of the triangular wave-shaped protrusions 3 (average height/average pitch) is within the range of 0.8 to 2.0, the adhesive strength of the triangular wave-shaped protrusions 3 to the adherend increases, and when the adherend detaches from the triangular wave-shaped protrusions 3, the adhesive strength of the triangular wave-shaped protrusions 3 is more likely to recover. Furthermore, because the protrusions of the adhesive structure 1 of this embodiment are triangular wave-shaped, it has the effect of being less likely to have planar anisotropy in the adhesive strength.

Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of the invention.
For example, in the adhesive structure 1 of this embodiment, the triangular wave-shaped protrusions 3 are provided over the entire surface of one surface (upper surface) of the base 2, but the position of the triangular wave-shaped protrusions 3 is not limited to this. The triangular wave-shaped protrusions 3 may be provided on both surfaces of the base 2. Furthermore, the triangular wave-shaped protrusions 3 may be provided on only a portion of the surface of the base 2.

[Example 1]
A metal aluminum substrate (length: 30 mm, width: 30 mm, thickness: 30 mm) was prepared as the substrate. The surface of the prepared metal aluminum substrate was polished to a surface roughness Ra of 0.02 μm or less to form a smooth surface.

Next, triangular wave-shaped protrusions were formed on the polished surface of the metal aluminum base using the NP method. The processing equipment used was a processing device equipped with a cutting tool and an ultrasonic vibration device that ultrasonically vibrates the cutting tool in an elliptical motion. The cutting tool was inserted obliquely while ultrasonically vibrating, and then, while ultrasonically vibrating the cutting tool, it was moved in a cycle in which the cutting edge moved 1000 nm up and down while moving 1000 nm in a direction perpendicular to the cutting surface. This formed inverted equilateral triangular grooves extending in a direction perpendicular to the direction of cutting tool movement on the surface of the metal aluminum base, producing a substrate with triangular wave-shaped protrusions having equilateral triangular wave-shaped protrusions. The average pitch of the triangular wave-shaped protrusions on the substrate with triangular wave-shaped protrusions was 1000 nm, the average height was 1000 nm, and the average height/average pitch was 1.0.

[Inventive Examples 2 and 3, Comparative Examples 1 and 2]
A substrate with triangular wavy protrusions was produced in the same manner as in Example 1 of the present invention, except that a metal substrate made of the material listed in Table 1 below was used as the substrate, and the substrate was cut so that the average pitch, average height, and average height/average pitch of the triangular wavy protrusions were the values listed in Table 1 below.

[evaluation]
The surface elastic modulus and adhesive strength were measured by the following methods for the substrates with triangular wavy protrusions produced in Examples 1 to 3 of the present invention and Comparative Examples 1 and 2. The results are shown in Table 1.

(Method for measuring surface elastic modulus)
Measurements were made using a nanoindenter (ENT-NEXUS, manufactured by Elionix Co., Ltd.). A spherical indenter (made of titanium) with a diameter of 40 μm was used as the probe. The load was increased from 20 μN to 100 μN in 10 μN increments, and the surface elastic modulus was measured at each load. The surface elastic modulus when the probe's indentation depth reached 1/10 of the height of the triangular wave-shaped protrusions is shown in Table 1 below.
The measurements were carried out at room temperature (25°C).

(Method for evaluating adhesive strength)
The adhesive strength was measured by the above method using a nanoindenter (ENT-NEXUS, manufactured by Elionix Co., Ltd.). A spherical indenter (made of titanium) with a diameter of 40 μm was used as the probe. The indentation depth of the spherical indenter was the depth listed in Table 1, similar to the above method for measuring the surface elastic modulus. The indentation speed of the probe was set to 10 nm/sec when the indentation depth was 10 nm, and 20 nm/sec when the indentation depth was 20 nm. The lift-up speed of the probe was set to 10 nm/sec when the indentation depth was 10 nm, and 20 nm/sec when the indentation depth was 20 nm. The measurements were carried out at room temperature (25°C).

The results in Table 1 confirm that the substrates with triangular wavy protrusions obtained in Invention Examples 1 to 3, in which the average pitch and average height of the triangular wavy protrusions are within the ranges of the present invention, have higher adhesive strength than the substrates with triangular wavy protrusions obtained in Comparative Examples 1 and 2, and are useful as bonded structures. The high adhesive strength of the substrates with triangular wavy protrusions obtained in Invention Examples 1 to 3 is due to the low surface elasticity and the large amount of deformation of the protrusions when pressure is applied by the adherend.

The substrate with triangular wavy protrusions obtained in Comparative Example 1, in which the average pitch and average height of the triangular wavy protrusions were larger than the ranges of the present invention, had a lower adhesive strength, even though the average height/average pitch was the same as in Invention Examples 1 to 3. This is because the surface elastic modulus increased due to the larger average pitch and excessively large protrusion size.
The substrate with protrusions obtained in Comparative Example 2, in which the average pitch and average height of the triangular wavy protrusions were smaller than the ranges of the present invention, did not allow the probe to adhere, even though the average height/average pitch was the same as in Invention Examples 1 to 3. This is because the surface elastic modulus increased due to the average height becoming too small.

The bonded structure of this embodiment has high heat resistance and high adhesive strength, making it suitable for use as a structure for bonding and temporary fixation. The bonded structure of this embodiment is particularly suitable for use in fields where the environment is subject to large changes and where minimal contamination by impurities is required, such as aerospace, semiconductors, and medicine.

1 Adhesive structure 2 Base 3 Triangular wave-like protrusion 4 Protrusion 4a Top 4b Valley 10 Probe

Claims (6)

An adhesive structure that adhesively holds an object to be adhered,
a substrate and triangular wave-shaped protrusions provided on at least a part of the surface of the substrate;
the triangular wave-shaped protrusions are made of an inorganic material,
The average pitch of the triangular wave-shaped protrusions is in the range of 100 nm or more and 1000 nm or less,
An adhesive structure in which the average height of the triangular wave-shaped protrusions is in the range of 100 nm or more and 1000 nm or less. The adhesive structure described in claim 1, wherein the ratio of the average height to the average pitch of the triangular wave-shaped protrusions is in the range of 0.8 to 2.0. The adhesive structure described in claim 1 or 2, wherein the average pitch of the triangular wave-shaped protrusions is 500 nm or less. The bonded structure described in any one of claims 1 to 3, wherein the inorganic material is a metal. The bonded structure according to claim 4, wherein the metal includes copper, a copper alloy, aluminum, an aluminum alloy, or a NiP alloy. 6. The adhesive structure according to claim 1, wherein the adhesive strength is 35 N/cm2 or ^more when a spherical indenter having a diameter of 40 μm is pressed into the triangular wave-shaped protrusions using a nanoindenter to an indentation depth of at least one of 10 nm and 20 nm.