JP6767211B2 - A metal member for a piezoelectric / electrostrictive film and a method for manufacturing the metal member for a piezoelectric / electrostrictive film. - Google Patents

Description

The present invention relates to a metal member for a piezoelectric / electrostrictive film and a method for manufacturing the metal member for a piezoelectric / electrostrictive film, and more specifically, includes an insulating film capable of directly forming a piezoelectric / electrostrictive film on the surface. The present invention relates to a metal member for a piezoelectric / electrolytic film and a method for manufacturing the metal member for a piezoelectric / electrolytic film.

The piezoelectric / electrolytic strain film utilizes the fact that distortion is generated by applying an electric field to a conductor or semiconductor, and that the electric resistance value changes due to expansion and contraction of the conductor or semiconductor. When a piezoelectric / electrostrictive film is provided on the metal substrate of the above, an electrical insulating layer is required, and as the insulating layer, an organic film such as a resin or an inorganic film such as silicon oxide is used.

Since the organic film has low heat resistance, it is difficult to form a piezoelectric / electrolytic strain film thin film by sputtering or the like, and the piezoelectric / electrolytic strain film that can be formed is limited.

Further, although the insulating film of silicon oxide has heat resistance, there is a problem that it takes time and cost when it is formed by CVD or thermal oxidation. Further, when an insulating film of silicon oxide is formed by a wet process such as a sol-gel method, cracks are likely to occur during firing of the coating film, it is difficult to form a dense insulating film, and there is a problem that the manufacturing yield is lowered. ..

Therefore, a dense and highly insulating inorganic film that can be formed by a wet process is expected.
Japanese Unexamined Patent Publication No. 2006-188408 of Patent Document 1 discloses a clay film having high heat resistance and excellent electrical insulation.

Japanese Unexamined Patent Publication No. 2006-188408

The one described in Patent Document 1 is obtained by applying that the dispersion liquid of the layered clay mineral is dried to form a film by overlapping the layered clay minerals to obtain a self-supporting film of the layered clay mineral.
Then, according to the technique disclosed in Patent Document 1, a self-supporting film having excellent electrical insulation can be produced from a layered clay mineral.

However, since the self-supporting film contains a polymer resin in order to maintain the strength and flexibility of the film, it cannot be said that the self-supporting film has sufficient heat resistance. Further, the self-supporting film is a self-supporting film of a layered clay mineral containing a resin, and is not an insulating film in close contact with a metal substrate.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is that it can be easily formed on the surface of a metal substrate, is dense and has high insulating properties, and is a piezoelectric / electrolytic strain film. It is an object of the present invention to provide a metal member for a piezoelectric / electrostrictive film having a heat-resistant insulating film capable of forming the above.

As a result of diligent studies to achieve the above object, the present inventor has formed a coating film having a laminated structure in which plate-shaped or disk-shaped particles are in close contact with each other, and cracks occur even when fired. We have found that a dense and highly insulating film can be formed without using the above, and have completed the present invention.

That is, the metal member for a piezoelectric / electrostrictive film of the present invention has an insulating film on the surface of the metal base material.
Then, a SUS material the metal substrate, the insulating film is a shall comprise a clay layer from smectite clay minerals, the thickness of the insulating film is at 0.7μm or 20μm or less, the wherein the resistance value is 1.00 × 10 ⁹ Ω or more.

Further, the method for manufacturing a metal member for a piezoelectric / electrolytic film with an insulating film of the present invention includes a step of firing a metal base material on which a coating film of an insulating film composition is formed to form an insulating film.
The metal base material is a SUS material, and the insulating coating composition contains a smectite clay mineral, a thickener, and a dispersion medium, and has a pH of 10.0 or more. It is characterized in that the firing temperature is 500 ° C. or higher.

According to the present invention, since it was decided to form an insulating coating comprising a clay layer from smectite clay minerals SUS material surface, the piezoelectric / electrostrictive whose resistance comprises 1.00 × least 10 ⁹ Omega heat-resistant insulating coating A metal member for a strain film can be provided.

It is the schematic which shows the state which smectite clay minerals were laminated in the coating film of an insulating film composition. It is a photograph which shows the surface state of the metal member for a piezoelectric / electric strain film of Example 1 and the metal member for a piezoelectric / electric strain film of Comparative Example 7. It is the schematic of the load application mechanism. It is a graph which shows the relationship between the strain amount and the resistance value of the strain sensor of Example 8.

Piezoelectric / piezoelectric films have an electrolytic strain effect that expands and contracts when a voltage is applied, and a piezoelectric effect that generates a voltage when a force is applied, and performs conversion between mechanical energy and electrical energy. is there.

The piezoelectric / electrolytic strain film is widely applied in the field of energy conversion such as actuators and sensors. For example, in addition to strain sensors such as load cells and contact sensors and slip sensors used in robots, power generation circuits, drive devices, and gyros. Used in sensors, pressure sensors, inkjet printers, etc.

The metal member for a piezoelectric / electrostrictive film of the present invention has an insulating film on the surface of a metal base material.
The metal member for a piezoelectric / electrostrictive film will be described in detail by taking a strain sensor as an example.

Generally, strain sensors are known to have a grid-shaped or rosette-shaped metal wire of about 10 to 30 μm or a metal foil of about 3 to 5 μm bonded to a base such as paper or resin. It is used by adhering to the object to be measured.

When the strain sensor is adhered to the object to be measured with an adhesive, the characteristics of the strain sensor vary due to the influence of the adhesive, so a metal film is formed on the object to be measured without using an adhesive, and the strain sensor It is desirable to build.

As a method for forming a metal film (hereinafter, may be referred to as a strain sensor) as a strain sensor on an object to be measured, a physical method such as a vapor deposition method, a sputtering method or a molecular beam epitaxy (MBE) method, or a chemical vapor deposition method is used. In addition to a method capable of forming a thin metal film such as a chemical method such as a deposition (CVD) method and a hot wall method, a method capable of forming a thick metal film such as a method of firing after coating or printing can be mentioned.

Then, the strain sensor indirectly measures the strain generated in the object to be measured by utilizing the fact that the amount of change Δρ / ρ in the specific electrical resistance (ρ) of the metal film changes with the deformation of the object to be measured. Therefore, when the object to be measured is a metal base material, an insulating coating that electrically insulates the strain sensor and the metal base material is required.

The insulating coating is required not only to have excellent adhesion to a metal base material but also to have chemical resistance capable of forming a strain sensor.

Further, the strain sensor must not have a physical quantity other than strain, particularly a large amount of change in electrical resistance with respect to temperature (resistance temperature coefficient (TCR)). Examples of the metal film used for the strain sensor having a small change in characteristics with respect to a temperature change include a Cr—N alloy thin film, a Cu—Ni alloy, and a Ni—Cr alloy.

Among the above metal films, the Cr—N alloy thin film has a large change amount Δρ / ρ of the specific electrical resistivity (ρ) and a large strain sensitivity (gauge ratio), and therefore is a metal for a highly sensitive strain sensor. It can be suitably used as a film.
That is, the Cr—N alloy thin film can obtain a sufficient output even when it is formed on a metal base material having high rigidity, and can detect strain in a portion requiring rigidity such as a structural material of a machine.

The resistance temperature coefficient (TCR) of the Cr—N alloy thin film changes depending on the heat treatment temperature, and heat treatment is usually required after the strain sensor is formed. Therefore, a strain sensor is formed using the Cr—N alloy thin film. It is preferable that the insulating coating has heat resistance to enable the above.

<Insulating film>
The insulating film in the metal member for a piezoelectric / electrostrictive film of the present invention includes a clay layer derived from a smectite clay mineral, and the clay layer has a structure in which plate-like particles of the smectite clay mineral are oriented and closely laminated. It is a thing.

The structure of the insulating coating can be confirmed by observing the cross section of the metal member with TEM, TEM-EDS, or the like.

Since the insulating film contains smectite clay mineral as a main component and contains almost no organic substances, it has chemical resistance and heat resistance, and can only directly form a piezoelectric / electrolytic strain film to be the strain sensor. not having a 1.00 × 10 ⁹ Ω or more high resistance value.

Therefore, the metal thin film formed on the insulating film can be corroded and shaped into a grid shape or a rosette shape with an etching solution to form a strain sensor.

Further, the strain sensor formed on the insulating coating can be heat-treated in a non-oxidizing atmosphere in the air or vacuum in a temperature range of 200 ° C. or higher and 700 ° C. or lower at which thermal decomposition of smectite clay minerals begins. The resistance temperature coefficient (TCR) can be adjusted.

Further, the insulating coating has excellent adhesion to the metal base material and can suppress peeling due to deformation of the metal base material. Although the reason why the above-mentioned insulating coating has excellent adhesion has not been clarified, a solid solution containing a constituent element of the metal base material and a constituent element of the smectite clay mineral between the metal base material and the insulating coating has not been clarified. It is presumed that this is because the layer is formed and the anchor effect is obtained.

The film thickness of the insulating coating is preferably 0.7 μm or more and 20 μm or less. Thickness that is 0.7μm or more, the resistance value can not insulating coating of 1.00 × 10 ⁹ Ω or more defects, also by at 20μm or less, deformation of the metal substrate It is possible to form a highly sensitive distortion sensor by following the above.

<Metal base material>
A SUS material can be used as the metal base material. As the SUS material, austenitic stainless steel such as SUS304, ferritic stainless steel such as SUS430, martensitic stainless steel such as SUS403 and SUS410, and precipitation hardening stainless steel such as SUS630 can be used.
Since the precipitation hardening stainless steel has high substrate strength and excellent high-speed response to external force, it is suitably used as a metal member for a strain sensor for robots.

The surface of the SUS material is preferably hydrophilized by plasma treatment, polishing or the like. By hydrophilizing the surface of the SUS material, a coating film of the insulating coating composition described later can be uniformly formed, and a strain sensor without variation can be formed.

<Manufacturing method>
Next, a method for manufacturing the metal member for a piezoelectric / electrostrictive film of the present invention will be described.
The above-mentioned metal member for piezoelectric / electrolytic strain film can be formed by forming a coating film of an insulating coating composition on the surface of a metal base material and firing at 500 ° C. or higher.

The insulating coating composition has a pH of 10.0 or higher, contains a smectite clay mineral, a thickener, a dispersant, and if necessary, contains other additives.

The smectite clay mineral is a layered clay mineral, and forms a layered structure in which plate-like or disk-like primary particles having a thickness of about 1 nm (hereinafter, may be simply referred to as “plate-like particles”) are stacked. It is a thing.

When the smectite clay mineral is dispersed in the aqueous phase, the plate surface of the plate-shaped particles becomes negatively charged, the ions between the plate-shaped primary particles are hydrated, and the distance between the primary particles is widened. Electrostatic repulsion occurs between them, and the layered smectite clay mineral is subdivided into plate-like primary particles.
Then, the plate-like particles that are close to each other are electrostatically repelled to form a low-viscosity sol.

However, since the plate-like particles of the smectite clay mineral have a weak positive charge at the edge thereof, the positive charge interacts with the negative charge on the plate surface of the adjacent plate-like particles with the passage of time. It is difficult to apply because it forms a card house structure by ionic bonding and becomes a highly viscous gel.

The gel has thixotropic properties and its fluidity can be restored by re-stirring, but when the stirring is stopped, it gels and its viscosity increases.

Since the insulating coating composition contains a thickener, the smectite clay mineral dispersed in the aqueous phase is maintained in a sol state without gelation, and an increase in viscosity is prevented, so that the coating can be easily applied. Can be constructed.

When the insulating coating composition is applied to the surface of a metal substrate and dried, as shown in FIG. 1, the plate-like particles are oriented and bonded to each other by Coulomb force and Van der Waals force, and the plate-like particles are bonded to each other. It becomes a coating film with a tightly laminated structure.

In the coating film, the plate-like particles are slightly dissolved in an alkaline environment, and the plate-like particles are in close contact with each other. Probably, there are no places having a high ion concentration due to adsorbed water or the like between the layers of the plate-like particles. , Has high insulation.

Then, by firing the coating film at a temperature of 500 ° C. or higher, substances that reduce the insulating resistance such as moisture between the plate-shaped particles are removed, and the plate-shaped particle components slightly dissolved in an alkaline environment are formed. It is considered that the film has high insulating properties because it acts as a material and the plate-like particles adhere to each other and melt and integrate with each other.

When the precipitation hardening stainless steel having high substrate strength is used as the SUS material, the firing temperature is preferably equal to or lower than the precipitation hardening heat treatment temperature for making the precipitation hardening stainless steel by heat treatment. By firing at less precipitation hardening heat treatment temperature of the precipitation hardening type stainless steel, it is possible to maintain the effect of the curing process for SUS material.

The above insulating coating composition can be applied to a metal substrate by a conventionally known method, and examples thereof include a spin coating method, a gap coater coating method, a dip coating method, a bead coating method, and a ring coating method. ..

Further, examples of the method for drying the coating film of the insulating coating composition include standing at room temperature and drying with warm air, and examples of the firing method include a firing furnace and an oven.

(Smectite clay mineral)
Examples of smectite clay minerals that can be used in the insulating coating composition include saponite, hectorite, saponite, stevensite, sine holderite, montmorillonite, biderite, nontronite, and volconstite.

Among them, hectorite, stephensite, and montmorillonite have excellent film forming properties and can be preferably used. These may be either synthetic or natural products, but synthetic products having a controlled primary particle size can be preferably used.

Generally, the particle size of the smectite clay mineral has a primary particle size (median diameter) of 10 nm to 500 nm, but the primary particle size (median size) of the smectite clay mineral of the insulating coating composition of the present invention is 10 nm or more and 150 nm. The following is preferable. When the primary particle diameter (median diameter) is within the above range, the film forming property and peeling resistance to the metal substrate are improved.

The reason why the film forming property and the peeling resistance are improved when the particle size is within the above range is not clear, but the particles having the above particle size, in combination with the gelation suppressing effect, are on the surface of the metal substrate. It is thought that this is because it gets caught in the fine irregularities.

The particle size of smectite clay minerals can be measured by dynamic light scattering or laser diffraction scattering. An aqueous dispersion of smectite clay minerals is prepared by vigorous stirring using a homodisper or an ultrasonic generator, and the particle size is measured by a dynamic light scattering method or a laser diffraction scattering type measuring device. The measurement result of the particle size is displayed on a volume basis.

The content of smectite clay mineral in the insulating coating composition is preferably 10% by mass or more and 30% by mass or less, and more preferably 15% by mass or more and 20% by mass or less.

If the content of the smectite clay mineral is less than 10% by mass, the adhesion of the plate-like particles forming the coating film may decrease, and the insulating property may decrease. Further, if it exceeds 30% by mass, it is difficult to completely wet the clay mineral, and it may precipitate without sufficient hydration to form a low-viscosity sol, which makes coating difficult.

(Thickening agent)
Examples of the slimming agent include phosphate compounds, phosphonic acids and derivatives thereof, and low molecular weight amine salts.
Examples of the above-mentioned phosphate compound include sodium and potassium salts of tripolyphosphoric acid, hexamethaphosphoric acid, and pyrophosphoric acid.
Examples of the phosphonic acid and its derivative include sodium salts, potassium salts, ammonium salts and amine salts of phosphonic acid and its derivatives, and among them, sodium etidronate can be preferably used.

The content of the thickener in the insulating coating composition depends on the thickener used and the smectite clay mineral, but is preferably 0.1 to 2% by mass.

By containing the thickener in the above range, the aqueous dispersion of smectite clay mineral does not gel, the sol state with low viscosity is maintained, the coatability is improved, and a uniform insulating film can be formed.

It is also possible to use smectite clay minerals containing a thickener and having water dispersion stability in which gelation is suppressed. Smectite clay minerals having water dispersion stability are generally on the market, and examples thereof include Laponite S482 and Laponite SL25 (both manufactured by BYK Adaptives & instruments).

(PH regulator)
The pH adjuster adjusts the pH of the insulating coating composition.
By the pH of the insulating coating composition above 10.0, can be the resistance of the insulating coating 1.00 × least 10 ⁹ Omega.

Examples of the pH adjuster include alkaline components such as sodium hydroxide (NaOH) and ammonium hydroxide (NH ₄ OH).

The amount of the pH adjuster added depends on the alkaline component and the like, but is preferably 0.1 to 5.0 mmol per 1 g of the smectite clay mineral.
The pH of the insulating coating composition can be adjusted not only by adding the above pH adjuster but also by using an alkaline slimming agent.
(Additive)
The metal surface coating composition of the present invention can contain additives such as a water-soluble organic solvent and a surfactant, if necessary.
The above-mentioned water-soluble organic solvent improves the affinity between the insulating coating composition and the surface of the metal base material, prevents the occurrence of repellent and uneven coating, and improves the drying property of the insulating coating composition. is there.

The surface of the metal base material itself is hydrophilic, but by storing the metal base material in the atmosphere, organic substances (hydrocarbons) and the like existing in the atmosphere are adsorbed on the surface of the metal base material, and the metal base material has a surface. The surface becomes hydrophobic.
Therefore, by containing a water-soluble organic solvent having an organic group, the affinity with the surface of the metal substrate is improved, and the coating property is improved.

Further, if the water-soluble organic solvent is volatile, the drying property is improved, and gas is generated inside the coating film formed on the surface of the metal substrate to prevent the film from peeling off. Therefore, the adhesion between the insulating film and the metal substrate is improved.

Examples of the water-soluble organic solvent include alcohol solvents such as methyl alcohol, ethyl alcohol, isopropanol and butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether and propylene glycol monomethyl. Examples thereof include glycol ether solvents such as ether and ketone solvents such as acetone and methyl ethyl ketone, and these may be used alone or in admixture of two or more.
Among them, the glycol ether-based solvent can be preferably used because it has a high flash point, is excellent in safety, and has a thickening effect, and especially ethylene glycol monobutyl ether can be preferably used.

The content of the water-soluble organic solvent in the insulating coating composition is preferably 1% by mass or more and 30% by mass or less, depending on the water-soluble organic solvent used, and is 3% by mass or more and 10% by mass or less. It is preferable to have. If it is less than 1% by mass, repelling may occur or the drying property may be lowered, and if it exceeds 30% by mass, the dispersibility of smectite clay mineral may be lowered and sedimentation may occur.

The above-mentioned surfactant lowers the surface energy of the insulating coating composition, improves the wettability to the surface of the metal substrate, improves the film-forming property of the coating film, and improves the adhesion to the metal substrate. It is something to make. A uniform coating film can be formed by containing a surfactant.

The surfactant is not particularly limited as long as it does not inhibit the inhibition of gelation of smectite clay minerals, but among them, a nonionic surfactant is most preferable. Nonionic surfactants are particularly preferable because they do not become ions and do not affect the dispersed state of smectite clay minerals.

The nonionic surfactant may be an ester type, an ether type, or an ester / ether type having both an ester bond and an ether bond in the molecule, but those having an HLB value of 4 to 16 are used. preferable.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitol ester, sucrose ester, and polyoxyethylene ether of glycerin ester. Examples thereof include polyoxyethylene ether of sorbitol ester and polyoxyethylene ether of sorbitol ester, and these may be used alone or in combination of two or more.

The content of the surfactant in the insulating coating composition is preferably 0.1% by mass or more and 5% by mass or less, and preferably 0.2% by mass or more and 3% by mass or less.
Within the above range, the wettability to the surface of the metal substrate can be improved without lowering the dispersibility of the smectite clay mineral.

The insulating composition can be prepared by adding smectite clay mineral without stirring the aqueous phase containing the thickener and uniformly dispersing the smectite clay mineral in the aqueous phase, if necessary. , Smectite It is prepared by adding an additive to a dispersion of clay minerals.

Specifically, it can be produced by adding smectite clay mineral to ion-exchanged water containing a thickener and sufficiently stirring and defoaming with a planetary stirrer / defoaming device capable of stirring and defoaming at the same time.
By this method, it is possible to prepare an insulating composition (low-viscosity sol) in which gelation of smectite clay mineral is suppressed at a high concentration.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

[Insulating coating composition A]
5. Using a disper, while stirring 85.7 parts by mass of ion-exchanged water at 1000 rpm, a slimming agent-containing smectite clay mineral (manufactured by BYK Adaptives & instruments: Laponite S482: primary particle diameter (median diameter) 60 nm). 5 parts by mass and 2.5 parts by mass of a natural layered clay mineral (bentonite: Kunipia M: manufactured by Kunimine Kogyo) were added little by little to uniformly disperse the clay mineral.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4.4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol was added, and the mixture was rotated. [Insulating film composition A] having a clay solid content of 8% by mass was obtained by stirring and defoaming with a revolving mixer.

[Insulating coating composition B]
Using a disper, while stirring 80 parts by mass of ion-exchanged water at 1000 rpm, a thickener-containing smectite clay mineral (manufactured by BYK Adaptives & instruments: Laponite S482: primary particle diameter (median diameter) 60 nm) 17.5 mass Part and 2.5 parts by mass of natural layered clay mineral (bentonite: Kunipia M: manufactured by Kunimine Kogyo) are added little by little, the clay mineral is uniformly dispersed, and the clay solid content is stirred and defoamed with a rotation / revolution mixer. Obtained [insulating coating composition B] in an amount of 20% by mass.

[Insulating coating composition C]
Using a disper, add 2 parts by mass of a thickener (tetrasodium etidroate; PH-214 manufactured by Killest) to 77.1 parts by mass of ion-exchanged water, and while stirring at 1000 rpm, a thickener-containing smectite. 15 parts by mass of clay mineral (manufactured by BYK Adaptives & instruments: Laponite S482: primary particle diameter (median diameter) 60 nm) was added little by little, and the clay mineral was uniformly dispersed.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol is added to a rotation / revolution mixer. [Insulating film composition C] having a clay solid content of 15% by mass was obtained by stirring and defoaming with.

[Insulating coating composition D]
Using a disper, add 3.5 parts by mass of a thickener (tetrasodium etidroate; PH-214 manufactured by Killest) to 75.6 parts by mass of ion-exchanged water, and stir at 1000 rpm to reduce the thickener. 15 parts by mass of smectite clay mineral (manufactured by BYK Adaptives & instruments: Laponite S482: primary particle diameter (median diameter) 60 nm) was added little by little, and the clay mineral was uniformly dispersed.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol is added to a rotation / revolution mixer. [Insulating film composition D] having a clay solid content of 15% by mass was obtained by stirring and defoaming with.

[Insulating film composition E]
Using a disper, while stirring 77.1 parts by mass of ion-exchanged water at 1000 rpm, a thickener-containing smectite clay mineral (BYK Adaptives & instruments): Laponite S482: primary particle size (median size) 60 nm) 15 mass Parts were added little by little to evenly disperse the clay minerals.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol was added.
Further, 1.77 parts by mass of 10% sodium hydroxide was added, and the mixture was stirred and defoamed with a rotation / revolution mixer to obtain [insulating coating composition E] having a clay solid content of 15.03% by mass.

[Insulating film composition F]
Using a disper, while stirring 74.6 parts by mass of ion-exchanged water at 1000 rpm, a thickener-containing smectite clay mineral (BYK Adaptives & instruments: Laponite S482: primary particle diameter (median diameter) 60 nm) 17 mass Parts were added little by little to evenly disperse the clay minerals.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol was added.
Further, 2.5 parts by mass of 10% sodium hydroxide was added, and the mixture was stirred and defoamed with a rotation / revolution mixer to obtain [insulating coating composition F] having a clay solid content of 17% by mass.

[Insulating film composition G]
Using a disper, while stirring 73.6 parts by mass of ion-exchanged water at 1000 rpm, a thickener-containing smectite clay mineral (BYK Adaptives & instruments: Laponite S482: primary particle size (median diameter) 60 nm) 18 mass Parts were added little by little to evenly disperse the clay minerals.
Next, a mixed solution of 0.4 parts by mass of a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: DKS NL-40), 4 parts by mass of ethylene glycol monobutyl ether, and 1.5 parts by mass of ethanol was added.
Further, 2.5 parts by mass of 10% sodium hydroxide was added, and the mixture was stirred and defoamed with a rotation / revolution mixer to obtain [insulating coating composition G] having a clay solid content of 17% by mass.

The formulations of the insulating coating compositions A to G are shown in Table 1.

[Comparative Example 1]
The insulating coating composition A is spin-coated (1000 rpm, 10 seconds) on the surface of SUS304, left at room temperature for 1 hour to dry, further dried at 105 ° C. for 1 hour, and then fired at 600 ° C. for 2 hours. Then, a metal member for a piezoelectric / electrostrictive film was obtained.

[Comparative Example 2]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 1 except that the metal base material was changed to SUS444 hydrolyzed by plasma treatment and the insulating coating composition A was changed to the insulating coating composition B. ..

[Comparative Example 3]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 2 except that the metal base material was changed to SUS304 which was hydrophilized by plasma treatment and the firing temperature was set to 500 ° C.

[Comparative Example 4]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 3 except that the insulating coating composition B was changed to the insulating coating composition C and the firing temperature was set to 600 ° C.

[Comparative Example 5]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 4 except that the insulating coating composition C was changed to the insulating coating composition D.

[Example 1]
A metal member for a piezoelectric / electric strain film was obtained in the same manner as in Comparative Example 4 except that the insulating coating composition C was changed to the insulating coating composition E.

[Comparative Example 6]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Example 1 except that the insulating coating composition E was changed to the insulating coating composition F and the firing temperature was set to 400 ° C.

[Example 2]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 6 except that the firing temperature was set to 500 ° C.

[Example 3]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 6 except that the firing temperature was set to 550 ° C.

[Example 4]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Comparative Example 6 except that the firing temperature was set to 600 ° C.

[Example 5]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Example 4 except that the firing time was set to 10 minutes.

[Example 6]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Example 4 except that the firing time was set to 30 minutes.

[Example 7]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Example 4 except that the firing time was set to 60 minutes.

[Example 8]
A metal member for a piezoelectric / electrostrictive film was obtained in the same manner as in Example 4 except that the insulating coating composition F was changed to the insulating coating composition G.

[Comparative Example 7]
A solution of perhydropolysilazane (manufactured by AZ Electronic Materials Co., Ltd .: AZ-NAX120-20) is applied to the surface of SUS304 degreased with isopropyl alcohol with a gap applicator, dried at 50 ° C. for 30 minutes, and then calcined at 500 ° C. for 30 minutes. A metal member for a piezoelectric / electrolytic strain film was obtained.

<Piezoelectric / electrostrictive film formation>
A strain sensor was formed on the metal member for the piezoelectric / electrostrictive film of the above Examples and Comparative Examples as follows.

A Cr—N alloy thin film having a thickness of about 500 nm was formed by a reactive sputtering method in which a small amount of nitrogen gas was introduced together with argon gas onto the insulating film of the metal member for a piezoelectric / electrostrictive film to form a film. ..
As the sputtering conditions, a Cr disk with a nominal purity of 99.9% was used as the target, and the degree of vacuum before film formation (background vacuum degree), the distance between the target and the substrate (TS distance), the film formation gas pressure, and the input. The electric power is 2 × ^10-5 Pa, 70 mm, 2.1 Pa and 100 W, respectively, and the amount of nitrogen added to chromium is 0.03% depending on the nitrogen gas flow rate ratio (N ₂ / (Ar + N ₂ )) to be introduced. It was controlled.

Next, by photolithography technology and corrosion shaping with Cr etching solution, a grid-like structure with 8 diffractions, a line width and spacing of 0.05 mm, and a length of 2 mm was formed, and the temperature was 200 ° C. in the atmosphere. Heat-treated at the same temperature for 30 minutes.

Then, a Cr—N alloy thin film strain sensor was obtained by superimposing a Ni thin film electrode for resistance measurement on a predetermined position of the Cr—N alloy thin film by the lift-off method.

The metal member for the piezoelectric / electrolytic strain film of Comparative Example 7 had a lot of uneven coating, and the insulating film was cracked by firing, so that the Cr—N alloy thin film strain sensor could not be formed.
FIG. 2 shows photographed images of the surfaces of the metal members for the piezoelectric / electrostrictive film of Example 1 and Comparative Example 7.
From FIG. 2, the insulating film of the metal member for the piezoelectric / electrostrictive film of Example 1 has a glossy and smooth surface, whereas the polysilazane film of Comparative Example 7 is not glossy and has a rough surface. I understand.

<Evaluation>
The state of the insulating coating on which the Cr—N alloy thin film strain sensor was formed was observed with an optical microscope to confirm the presence or absence of peeling of the insulating coating. Moreover, the resistance value and the film thickness of the insulating coating were measured as follows.
The evaluation results are shown in Table 2.

(Film thickness of insulating film)
The film thickness of the insulating film was measured using a film thickness measuring device (manufactured by Ferimetrics Co., Ltd .; F20).

(Resistance value of insulating film)
The resistance value of the insulating film is determined by depositing 2 mm square gold in two places on the insulating film using a sputtering device (JEOL; JFC1600 Auto Fine coater), pasting conductive tape on it, and attaching the tester terminals. It was the part to hit.
For the insulation resistance value, an insulation resistance tester (manufactured by Advantest Co., Ltd .; high resistance tester R8340A ULTRA HIGH REGISTANCE METER) was used, and PROG. The setting was 110V.

(Bending test measurement)
A commercially available strain gauge is attached to the same position on the surface of the metal member on which the Cr—N alloy thin film strain sensor film is formed, which is opposite to the surface of the strain sensor film, and a bending test is performed using the load application mechanism shown in FIG. The measurement was performed.
Specifically, one end of the metal member is fixed, and the other end is pushed by the tip of the universal testing machine to apply force to bend and bend the metal member, and the voltage (resistance) change when the load is applied is sensed. The gauge ratio was determined using the amount of strain measured as an output and measured with a commercially available strain gauge on the back side.
FIG. 4 shows the relationship between the strain amount and the voltage (resistance) of the Cr—N alloy thin film strain sensor of Example 8. The linearity was good, the hysteresis was small, and the gauge ratio obtained from the slope of the straight line showed a large value of 6.9.

From the above results, it can be seen that the metal member for a piezoelectric / electrostrictive film of the present invention can form a thin film element without peeling or cracking.
In addition, the insulating coating almost smoothly smoothes out fine irregularities at the rolling mark level on the surface of the stainless steel base material, alleviates steps due to micro defects on the surface of the stainless steel base material, and forms a good sensor thin film. Was made.

1 Metal base material 2 Smectite clay mineral

Claims (5)

A metal member for a piezoelectric / electrostrictive film having an insulating film on the surface of a metal substrate.
The metal base material is a SUS material,
The insulating film is a shall comprise a clay layer from smectite clay minerals,
The thickness of the insulating coating is at 0.7μm or 20μm or less, the piezoelectric / electrostrictive film metal member whose resistance value is equal to or is 1.00 × 10 ⁹ Ω or more. The metal member for a piezoelectric / electrostrictive film according to claim 1, wherein the piezoelectric / electrostrictive film is a strain sensor. The metal member for a piezoelectric / electrostrictive film according to claim 1 or 2, wherein the heat resistant temperature is 200 ° C. to 700 ° C. A method for manufacturing a metal member for a piezoelectric / electrostrictive film that forms an insulating film by firing a metal base material on which a coating film of the insulating film composition is formed.
The metal base material is a SUS material,
The insulating coating composition contains a smectite clay mineral, a thickener, and a dispersant, and has a pH of 10.0 or higher.
A method for manufacturing a metal member for a piezoelectric / electrostrictive film, wherein the firing temperature for firing is 500 ° C. or higher. The above SUS material is precipitation hardening stainless steel.
The method for manufacturing a metal member for a piezoelectric / electrolytic strain film according to claim 4, wherein the firing temperature is equal to or lower than the precipitation hardening heat treatment temperature of the precipitation hardening stainless steel.

Images