JP7424750B2 - Temperature sensor film, conductive film and manufacturing method thereof - Google Patents

Description

The present invention relates to a temperature sensor film comprising a patterned metal thin film on a film base material, and a conductive film used for producing the temperature sensor film.

Many temperature sensors are used in electronic devices. Thermocouples and chip thermistors are commonly used as temperature sensors. When measuring the temperature at multiple locations within a surface using thermocouples, chip thermistors, etc., it is necessary to place a temperature sensor at each measurement point and connect each temperature sensor to a printed wiring board, etc., which reduces the manufacturing process. becomes complicated. Furthermore, in order to measure the in-plane temperature distribution, it is necessary to arrange a large number of sensors on the substrate, which increases the cost.

Patent Document 1 proposes a temperature sensor film in which a metal film is provided on a film base material, and the metal film is patterned to form a temperature measuring resistor part and a lead part. In the case of patterning a metal film, it is possible to form a temperature-measuring resistor part and a lead part connected to the temperature-measuring resistor part from one layer of metal film, and it is necessary to connect each temperature-measuring sensor with wiring. I don't. Furthermore, since a film base material is used, it has the advantage of being excellent in flexibility and easily adaptable to large-area applications.

In a temperature sensor in which a metal film is patterned, a voltage is applied to a temperature-measuring resistance section through a lead section, and temperature is measured by utilizing the characteristic that the resistance value of metal changes depending on temperature. In order to improve the accuracy of temperature measurement, it is preferable to use a material that has a large resistance change with respect to temperature changes. Patent Document 2 describes that nickel has about twice the temperature sensitivity (resistance change) as copper.

Japanese Patent Application Publication No. 2005-91045 Japanese Patent Application Publication No. 7-333073

Metals such as nickel exhibit the characteristic that the higher the temperature, the higher the resistance (positive characteristic), and bulk nickel has a rate of change in resistance (temperature coefficient of resistance; TCR) of approximately 6000 ppm/°C with respect to temperature rise. Are known. On the other hand, thin metal films often have different properties from those of bulk metal due to the effects of their surfaces and interfaces.

The present inventors formed a nickel thin film on a resin film base material by sputtering and evaluated its properties, and found that the temperature coefficient of resistance (TCR) was less than half that of bulk nickel, making it suitable for use as a temperature sensor film. It was found that sufficient temperature measurement accuracy could not be obtained. Further, the temperature coefficient of resistance of a temperature sensor film including a nickel thin film formed on a resin film base material may change significantly with use.

In view of the above problems, an object of the present invention is to provide a conductive film and a temperature sensor film including a metal thin film having a large temperature coefficient of resistance on a resin film base material. Another object of the present invention is to provide a conductive film and a temperature sensor film in which the temperature coefficient of resistance of a metal thin film is highly stable.

The present inventors have discovered that the amount of carbon atoms in a nickel thin film and the crystallinity of the nickel thin film are closely related to the temperature coefficient of resistance, leading to the present invention.

A conductive film for a temperature sensor includes a nickel thin film on one main surface of a resin film base material. The carbon atom concentration in the nickel thin film provided on the resin film base material is preferably 1.0×10 ²¹ atm/cm ³ or less. The nickel thin film can be formed by sputtering. The half width of the diffraction peak of the (111) plane in the X-ray diffraction pattern of the nickel thin film is preferably 0.8° or less.

By patterning the nickel thin film of this conductive film, a temperature sensor film can be formed. The temperature sensor film includes a nickel thin film patterned on one main surface of a resin film base material, and the nickel thin film is patterned into a temperature sensing resistor portion and a lead portion. A nickel thin film may be provided on both sides of the resin film base material.

The temperature-measuring resistor section is provided in a portion where temperature is measured, and is patterned into a thin line. The lead portion is patterned to have a larger line width than the resistance temperature measurement portion, and one end of the lead portion is connected to the resistance temperature measurement portion. The other end of the lead portion is connected to an external circuit or the like. A connector may be connected to the lead portion, and connection to an external circuit may be made via the connector.

The nickel thin film of the conductive film and temperature sensor film preferably has a specific resistance of 1.6×10 ⁻⁵ Ω·cm or less. The temperature coefficient of resistance of the nickel thin film is preferably 3000 ppm/°C or more. The thickness of the nickel thin film is preferably 20 to 500 nm. A base layer may be provided between the film base material and the nickel thin film. Inorganic materials are preferred as the material for the underlayer.

Since the carbon atom concentration in the nickel thin film provided on the film base material is low, a temperature sensor film with a large resistance temperature coefficient and high temperature measurement accuracy can be formed. Since the half width of the diffraction peak of the (111) plane of the nickel thin film is small, a temperature sensor film with excellent stability during heating can be formed.

FIG. 2 is a cross-sectional view showing an example of a laminated structure of conductive films. FIG. 2 is a cross-sectional view showing an example of a laminated structure of conductive films. It is a top view of a temperature sensor film. It is an enlarged view of the vicinity of the temperature measuring resistor part in the temperature sensor, where A shows a two-wire type and B shows a four-wire type. It is an X-ray diffraction pattern of a conductive film of an example.

FIG. 1 is a cross-sectional view showing an example of a laminated structure of conductive films used for forming a temperature sensor film, in which a nickel thin film 10 is provided on one main surface of a resin film base material 50. By patterning the nickel thin film of this conductive film 101, a temperature sensor film 110 shown in the plan view of FIG. 3 is obtained.

[Conductive film]
The conductive film includes a nickel thin film 10 on one main surface of a resin film base material 50. As shown in FIG. 2, the conductive film includes a base layer 20 between the resin film base material 50 and the nickel thin film 10. You can leave it there.

<Film base material>
The resin film base material 50 may be transparent or opaque. Examples of the resin material include polyester such as polyethylene terephthalate, polyimide, polyolefin, cyclic polyolefin such as norbornene, polycarbonate, polyether sulfone, polyarylate, and the like. From the viewpoint of heat resistance, dimensional stability, electrical properties, mechanical properties, chemical resistance properties, etc., polyimide or polyester is preferable.

The thickness of the resin film base material is not particularly limited, but is generally about 2 to 500 μm, preferably about 20 to 300 μm. An easily adhesive layer, an antistatic layer, a hard coat layer, etc. may be provided on the surface of the resin film base material. Further, the surface of the resin film base material 50 is subjected to treatments such as corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, and sputter etching treatment for the purpose of improving adhesion with the nickel thin film 10 (or base layer 20). It's okay.

The arithmetic mean roughness Ra of the surface of the resin film base material 50 on which the nickel thin film 10 is formed is preferably 5 nm or less, more preferably 3 nm or less, and even more preferably 2 nm or less. By reducing the surface roughness of the base material, the coverage of the thin film becomes better, a dense film is formed, and the specific resistance of the nickel thin film 10 tends to become smaller. The arithmetic mean roughness Ra is determined from an observation image of 1 μm square using a scanning probe microscope.

<Nickel thin film>
The nickel thin film 10 provided on the resin film base material 50 plays a central role in temperature measurement in the temperature sensor. By patterning the nickel thin film 10, a lead portion 11 and a temperature measuring resistor portion 12 are formed as shown in FIG.

When the carbon atom concentration of the nickel thin film 10 is 1×10 ²¹ atm/cm ³ or less, the temperature coefficient of resistance (TCR) tends to increase, and the temperature measurement accuracy in the temperature sensor film improves. The carbon atom concentration of the nickel thin film 10 is preferably 8.0×10 ²⁰ atm/cm ³ or less, more preferably 3.0×10 ²⁰ atm/cm ³ or less, and 1.0×10 ²⁰ atm/cm ³ or less More preferred.

Since TCR tends to increase as the carbon atom concentration of the nickel thin film 10 decreases, it is preferable that the carbon atom concentration is as low as possible. When forming a nickel thin film on a glass substrate, the carbon atom concentration can be reduced to about 1×10 ¹⁸ atm/cm ³ or lower. On the other hand, when a nickel thin film is formed on a resin film base material, the carbon atom concentration is generally 1.0×10 ¹⁸ atm/cm ³ or more because the incorporation of carbon atoms from the resin film is unavoidable. The carbon atom concentration of the nickel thin film 10 may be 5.0×10 ¹⁸ atm/cm ³ or more or 1.0×10 ¹⁹ atm/cm ³ or more.

The carbon atom concentration of the nickel thin film is determined by depth profile measurement using secondary ion mass spectrometry (SIMS), and the carbon atom concentration at the center in the thickness direction is defined as the carbon atom concentration of the nickel thin film.

The thickness of the nickel thin film 10 is not particularly limited, but from the viewpoint of reducing resistance (particularly from the viewpoint of reducing the resistance of the lead portion), it is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. On the other hand, from the viewpoint of shortening film formation time and improving patterning accuracy, the thickness of the nickel thin film 10 is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less.

The specific resistance of the nickel thin film 10 at a temperature of 25° C. is preferably 1.6×10 ⁻⁵ Ω·cm or less, more preferably 1.5×10 ⁻⁵ Ω·cm or less. From the viewpoint of reducing the resistance of the lead portion, the specific resistance of the nickel thin film is preferably as small as possible, and may be 1.2×10 ⁻⁵ Ω·cm or less, or 1.0×10 ⁻⁵ Ω·cm or less. . The lower the carbon atom concentration in the nickel thin film, the lower the specific resistance tends to be. Furthermore, when the arithmetic mean roughness Ra of the surface of the resin film base material 50, which is the base for forming the nickel thin film, is small, the specific resistance of the nickel thin film 10 tends to be small. The smaller the specific resistance of the nickel thin film, the better, but it is difficult to make the specific resistance lower than that of bulk nickel, and the specific resistance is generally 7.0×10 ⁻⁶ Ω·cm or more.

The temperature coefficient of resistance (TCR) of the nickel thin film 10 is preferably 3000 ppm/°C or more, more preferably 3500 ppm/°C or more, and even more preferably 4000 ppm/°C or more. TCR is the rate of change of resistance with increasing temperature. Nickel has a characteristic (positive characteristic) in which resistance increases linearly as temperature rises. The TCR of a material having positive characteristics is calculated from the resistance value R ₀ at temperature T ₀ and the resistance value R ₁ at temperature T ₁ using the following formula.
TCR={(R ₁ -R ₀ )/R ₀ }/(T ₁ -T ₀ )

In this specification, the average value of TCR calculated from the resistance values at T ₀ = 25°C and T ₁ = 5°C and the TCR calculated from the resistance values at T ₀ = 25°C and T ₁ = 45°C is used for nickel. This is a thin film TCR.

The larger the TCR, the greater the change in resistance with respect to temperature changes, and the greater the temperature measurement accuracy in the temperature sensor film. Therefore, the TCR of the nickel thin film is preferably as large as possible, but it is difficult to make the TCR larger than that of bulk nickel, and the TCR of the nickel thin film is generally 6000 ppm/°C or less.

As mentioned above, TCR tends to increase by reducing the amount of carbon atoms in the nickel thin film. Although it is not clear why the TCR increases by reducing the carbon atom concentration, it is presumed that carrier scattering by carbon atoms mixed in the nickel thin film affects the TCR.

The resistance value of a substance is influenced by the carrier density and carrier mobility in the substance, and the lower the carrier density and carrier mobility, the higher the resistance. Since metals such as nickel have an abundance of free electrons, the influence of carrier density is small, and carrier mobility is a factor that dominates resistance. Factors that affect carrier mobility include carrier scattering due to lattice vibration and carrier scattering due to impurities and lattice defects.

As the temperature rises, lattice vibrations (thermal vibrations) increase and the movement of free electrons is hindered, resulting in a decrease in carrier mobility. Therefore, in materials exhibiting positive characteristics, the resistance increases linearly as the temperature rises near room temperature. On the other hand, carrier scattering due to impurities or lattice defects is less affected by temperature than carrier scattering due to lattice vibration. It is thought that as carrier scattering due to impurities and lattice defects increases, the ratio of carrier scattering due to lattice vibrations and the resulting change in resistance decrease, leading to a decrease in TCR.

In addition to carbon, the nickel thin film contains impurities such as hydrogen, oxygen, and nitrogen. Carbon (C ⁴ - ionic radius: 2.60 Å) is hydrogen (H ^- ionic radius: The ionic radius is larger than that of oxygen (O ^2- ionic radius: 1.35 Å) and nitrogen (N ^3- ionic radius: 1.46 Å). Therefore, carbon contained in the nickel thin film tends to become a carrier scattering factor, and as the amount of carbon increases, carrier scattering due to impurities and lattice defects increases, and the temperature dependence of resistance becomes smaller. This is thought to be the cause of a decrease in

The nickel thin film exhibits a diffraction peak of the (111) plane of the face-centered cubic lattice around 2θ=43° in an X-ray diffraction pattern using CuKα rays (wavelength: 1.541 Å) as an X-ray source. The half width of the diffraction peak of the (111) plane of nickel is preferably 0.8° or less, more preferably 0.6° or less, and even more preferably 0.4° or less. The half width of the diffraction peak of the (111) plane of nickel may be 0.35° or less or 0.30° or less. The half width of the diffraction peak of the (111) plane of nickel may be 0.10° or more, 0.15° or more, or 0.20° or more.

The smaller the half width of the (111) plane diffraction peak of the nickel thin film 10, the larger the TCR tends to be. The lower the carbon atom concentration in the nickel thin film, the smaller the half width of the X-ray diffraction peak tends to be. Since carbon atoms as an impurity element inhibit crystal growth of the nickel thin film, it is thought that the lower the carbon atom concentration, the higher the crystallinity and the higher the TCR. It is also believed that the higher the crystallinity, the less carrier scattering due to defects, which contributes to the improvement in TCR.

When the half-value width of the (111) plane diffraction peak of the nickel thin film 10 is 0.4° or less, heating reliability tends to improve, and changes in resistance value and TCR when exposed to a high temperature environment for a long time are A small conductive film is obtained. The half-width of the X-ray diffraction peak is correlated with the size of the crystallite, and the smaller the half-width, the larger the crystallite, indicating that the crystal is growing more. One of the presumed reasons why the heating reliability is improved when the half width of the X-ray diffraction peak is small is that the change in crystallinity under the heating environment is small.

When the half-width of the (111) plane diffraction peak of nickel is about 1°, the crystallinity is low and hardly any crystals grow even if the nickel thin film is heated, so the change in resistance due to heating is small. If the half-value width of the (111) plane diffraction peak is about 0.8°, it means that there are many ungrown crystallites, and the crystallites grow by heating and the resistance of the nickel thin film decreases. It is presumed that this is the cause of the change. On the other hand, if the half-width of the (111) plane diffraction peak is 0.4° or less, the crystallites have already grown sufficiently, so crystal growth due to heating and resistance change due to crystal growth are unlikely to occur, and reliability is improved. It is considered to be excellent in

The arithmetic mean roughness Ra of the surface of the nickel thin film 10 is, for example, about 1 to 20 nm. As the crystal growth of the nickel thin film increases, the arithmetic mean roughness Ra of the surface tends to increase. Ra of the surface of the nickel thin film may be 2 nm or more or 3 nm or more. The arithmetic mean roughness of the surface of the nickel thin film 10 is preferably larger than the arithmetic mean roughness of the base material surface.

<Method for forming nickel thin film>
As a method for forming the nickel thin film, a sputtering method is preferable because a thin film with excellent film thickness uniformity can be formed. especially. By using a roll-to-roll sputtering device to form a film while continuously moving a long resin film base material in the longitudinal direction, the productivity of the conductive film can be increased.

After loading the roll-shaped film base material into the sputtering equipment and before starting sputtering film formation, it is preferable to exhaust the inside of the sputtering equipment to create an atmosphere in which impurities such as organic gas generated from the film base material are removed. . By removing the gas in the device and film substrate in advance, the carbon atom concentration in the nickel thin film tends to be reduced. The vacuum degree (ultimate vacuum degree) in the sputtering apparatus before starting sputter film formation is, for example, 1×10 ⁻² Pa or less, preferably 5×10 ⁻³ Pa or less, and more preferably 1×10 ⁻³ Pa or less. It is preferably 5×10 ⁻⁴ Pa or less, more preferably 5×10 −5 Pa or less, and particularly preferably 5×10 ⁻⁵ Pa or less.

Sputter deposition of a nickel thin film is performed using a metal Ni target while introducing an inert gas such as argon. Although the film-forming conditions for the nickel thin film are not particularly limited, it is preferable to select the film-forming conditions so as to reduce the contamination of carbon caused by organic gas etc. from the film base material. As a method for reducing the amount of carbon in the nickel thin film, (1) as mentioned above, treat the film base material under vacuum before sputtering to remove organic gases, etc. in the film base material; 2) Reducing damage to the film base material during sputter film formation; (3) Providing a base layer on the film base material to block organic gas etc. from the film base material.

Examples of methods for reducing damage to the film base material during sputter film formation include lowering the substrate temperature during film formation and lowering the discharge power density. For example, when forming a nickel thin film directly on a film base material, the substrate temperature is preferably 80°C or less, more preferably 60°C or less, and 50°C or less, from the viewpoint of suppressing the generation of organic gas from the film base material. is even more preferable.

As described later, when a base layer is provided on a film base material and a nickel thin film is formed thereon, the base layer has the effect of blocking organic gas etc. from the film base material even if the substrate temperature is high. Therefore, the substrate temperature during the formation of the nickel thin film can be appropriately set within a range where the film base material has heat resistance. Furthermore, the higher the substrate temperature, the higher the crystallinity of the nickel thin film, and the half width of the diffraction peak of the (111) plane tends to become smaller. Therefore, when a base layer is provided on a film base material and a nickel thin film is formed thereon, the substrate temperature is preferably 30°C or higher, more preferably 50°C or higher, and even more preferably 70°C or higher. The substrate temperature may be 100°C or higher, 120°C or higher, or 130°C or higher.

From the viewpoint of preventing embrittlement of the film base material, the substrate temperature is preferably −30° C. or higher. From the viewpoint of suppressing damage to the film base material while stabilizing plasma discharge, the discharge power density is preferably 0.1 to 5.0 W/cm ² , more preferably 1.0 to 3.5 W/cm ^2. .

<Base layer>
As shown in FIG. 2, by providing the base layer 20 on the resin film base material 50 and forming the nickel thin film 10 thereon, plasma damage to the resin film base material 50 is suppressed when the nickel thin film 10 is formed. can. Further, by providing the base layer 20, it is possible to block moisture, organic gas, etc. generated from the resin film base material 50, and to suppress the incorporation of carbon atoms into the nickel thin film 10. Further, by forming the nickel thin film 10 on the base layer 20, crystal growth of the nickel thin film tends to be promoted.

From the viewpoint of suppressing the incorporation of carbon into the nickel thin film, the base layer 20 is preferably made of an inorganic material. Underlayer 20 may be conductive or insulating. When the base layer 20 is made of a conductive inorganic material (inorganic conductor), the base layer 20 may be patterned together with the nickel thin film 10 when producing the temperature sensor film. When the base layer 20 is made of an insulating inorganic material (inorganic dielectric), the base layer 20 may or may not be patterned.

Inorganic materials include Si, Ge, Sn, Pb, Al, Ga, In, Tl, As, Sb, Bi, Se, Te, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V , Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, etc. metallic elements or metalloid elements , and their alloys, nitrides, oxides, nitride oxides, and the like. When the underlayer is an oxide, the material of the underlayer may be nickel oxide. Silicon or silicon oxide is preferable as the material for the underlayer because it has excellent adhesion to both the resin film base material and the nickel thin film, has a high effect of suppressing carbon incorporation into the nickel thin film, and can promote crystal growth of the nickel thin film. . A silicon oxide layer may be formed on the silicon layer as the base layer.

The base layer may include multiple layers. For example, an inorganic dielectric material may be formed on an inorganic conductor as a base layer, and a nickel thin film may be formed thereon. In this embodiment, since the dielectric layer is in contact with the nickel thin film, there is no need to pattern the base layer 20 when producing the temperature sensor film.

The thickness of the base layer is not particularly limited. From the viewpoint of reducing plasma damage to the film base material and enhancing the effect of blocking outgas from the film base material, the thickness of the base layer is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. From the viewpoint of improving productivity and reducing material costs, the thickness of the base layer is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. When the base layer 20 consists of multiple layers, it is preferable that the total thickness is within the above range.

The method for forming the base layer 20 is not particularly limited, and either dry coating or wet coating may be employed. When forming the nickel thin film by sputtering, from the viewpoint of productivity, it is preferable that the base layer 20 is also formed by sputtering.

Conditions for forming the base layer by sputtering are not particularly limited, and may be appropriately set depending on the type of material and the like. A metal target or an oxide target may be used to form the oxide thin film. The oxide thin film is preferably formed by reactive sputtering using a metal target because the film formation rate is high.

The film formation conditions and characteristics of the underlayer may affect the crystallinity of the nickel thin film formed on the underlayer. For example, when forming a silicon layer and a silicon oxide layer as underlayers, the stronger the magnetic field (larger the magnetic flux density) when sputtering these underlayers, the more the (111) There is a tendency for the half-value width of the peak of the surface to become smaller. The magnetic flux density on the target surface when forming the underlayer by sputtering is preferably 20 mT or more, more preferably 35 mT or more, even more preferably 45 mT or more, and particularly preferably 55 mT or more.

<Heat treatment>
A heat treatment may be performed after forming the nickel thin film. By heating a conductive film comprising a thin nickel film on a film base material, the crystallinity of nickel is increased, and the half-value width of the peak of the (111) plane tends to become smaller and the thermal stability tends to improve. . When performing heat treatment, the heating temperature is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher. The upper limit of the heating temperature may be determined in consideration of the heat resistance of the film base material, and is generally 200°C or lower or 180°C or lower. When using a highly heat-resistant film substrate such as a polyimide film, the heating temperature may exceed the above range. The heating time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. The timing of the heat treatment is not particularly limited as long as it is after the nickel thin film is formed. For example, heat treatment may be performed after patterning the nickel thin film.

[Temperature sensor film]
A temperature sensor film is formed by patterning the nickel thin film 10 of the conductive film. As shown in FIG. 3, in the temperature sensor film, the nickel thin film has a lead portion 11 formed in the shape of a wire, and a temperature measuring resistor portion 12 connected to one end of the lead portion 11. The other end of the lead portion 11 is connected to a connector 19.

The temperature-measuring resistor section 12 is a region that acts as a temperature sensor, and temperature measurement is performed by applying a voltage to the temperature-measuring resistor section 12 via the lead section 11 and calculating the temperature from the resistance value. By providing a plurality of temperature-measuring resistance sections within the plane of the temperature sensor film 110, temperatures at a plurality of locations can be measured simultaneously. For example, in the form shown in FIG. 3, the temperature measuring resistance sections 12 are provided at five locations within the plane.

FIG. 4A is an enlarged view of the vicinity of a temperature-measuring resistor in a two-wire temperature sensor. The temperature measuring resistor section 12 is formed by sensor wirings 122 and 123 in which a nickel thin film is patterned into thin lines. The sensor wiring has a serpentine pattern in which a plurality of vertical electrodes 122 are connected at their ends via horizontal wiring 123 to form a hairpin-shaped bent part.

The smaller the line width (smaller cross-sectional area) of the thin wire forming the pattern shape of the resistance temperature sensor section 12 and the larger the line length from one end 121a of the sensor wiring of the resistance temperature sensor section 12 to the other end 121b, the greater the distance between two points. Since the resistance is large and the amount of resistance change due to temperature change is also large, temperature measurement accuracy is improved. By using a zigzag wiring pattern as shown in FIG. 4, the area of the temperature sensing resistor section 12 can be reduced and the length of the sensor wiring (line length from one end 121a to the other end 121b) can be increased. Note that the pattern shape of the sensor wiring of the temperature measuring section is not limited to the shape shown in FIG. 4, but may be a spiral pattern or the like.

The line width of the sensor wiring 122 (vertical wiring) and the distance between adjacent wirings (space width) may be set according to the patterning accuracy of photolithography. The line width and space width are generally about 1 to 150 μm. From the viewpoint of preventing disconnection of the sensor wiring, the line width is preferably 3 μm or more, and preferably 5 μm or more. From the viewpoint of increasing resistance change and improving temperature measurement accuracy, the line width is preferably 100 μm or less, more preferably 70 μm or less. From the same viewpoint, the space width is preferably 3 to 100 μm, more preferably 5 to 70 μm.

Both ends 121a and 121b of the sensor wiring of the temperature measuring resistance section 12 are connected to one end of the lead sections 11a and 11b, respectively. The two lead portions 11a and 11b are formed in an elongated pattern while facing each other with a slight gap therebetween, and the other ends of the lead portions are connected to the connector 19. The lead portion is formed wider than the sensor wiring of the temperature measuring resistor portion 12 in order to ensure sufficient current capacity. The width of the lead portions 11a and 11b is, for example, about 0.5 to 10 mm. The line width of the lead portion is preferably 3 times or more, more preferably 5 times or more, and even more preferably 10 times or more the line width of the sensor wiring 122 of the temperature-measuring resistance section 12.

The connector 19 is provided with a plurality of terminals, and the plurality of lead portions are connected to different terminals, respectively. The connector 19 is connected to an external circuit, and by applying a voltage between the lead portion 11a and the lead portion 11b, a current flows through the lead portion 11a, the temperature measuring resistor portion 12, and the lead portion 11b. The resistance value is calculated from the current value when a predetermined voltage is applied or the applied voltage when a voltage is applied so that the current becomes a predetermined value. The temperature is calculated from the resistance value based on a relational expression between the obtained resistance value and the temperature determined in advance, or a table recording the relationship between the resistance value and the temperature.

The resistance value determined here includes the resistance of the lead portions 11a and 11b in addition to the resistance of the resistance temperature sensing portion 12. Since the measured value is sufficiently larger than , the measured value may be regarded as the resistance of the temperature measuring resistor section 12. In addition, from the viewpoint of reducing the influence of the resistance of the lead part, the lead part may be of a four-wire type.

FIG. 4B is an enlarged view of the vicinity of a temperature-measuring resistor in a four-wire temperature sensor. The pattern shape of the temperature measuring resistor section 12 is the same as that in FIG. 4A. In the four-wire type, four lead parts 11a1, 11a2, 11b1, and 11b2 are connected to one temperature-measuring resistance part 12. The lead parts 11a1 and 11b1 are voltage measurement leads, and the lead parts 11a2 and 11b2 are current measurement leads. The voltage measurement lead 11a1 and the current measurement lead 11a2 are connected to one end 121a of the sensor wiring of the resistance temperature measurement section 12, and the voltage measurement lead 11b1 and the current measurement lead 11b2 are connected to the sensor wiring of the resistance temperature measurement section 12. It is connected to the other end 121b of the wiring. In the four-wire system, the resistance value of only the temperature-measuring resistor section 12 can be measured by excluding the resistance of the lead section, so that measurement with fewer errors is possible. In addition to the 2-wire system and the 4-wire system, a 3-wire system may be adopted.

The method of patterning the nickel thin film is not particularly limited. It is preferable to perform patterning by photolithography because patterning is easy and has high precision. In photolithography, an etching resist is formed on the surface of the nickel thin film in a manner corresponding to the shape of the lead part and the temperature sensing resistor part, and after removing the nickel thin film in areas where the etching resist is not formed by wet etching, etching is performed. Peel off the resist. Patterning of the nickel thin film can also be performed by dry etching such as laser processing.

In the above embodiment, by forming the nickel thin film 10 on the resin film base material 50 by sputtering or the like and patterning the nickel thin film, a plurality of lead parts and temperature measuring resistance parts can be formed within the substrate surface. . By connecting the connector 19 to the end of the lead portion 11 of this temperature sensor film, a temperature sensor element is obtained. In this embodiment, lead parts are connected to a plurality of temperature measuring resistance parts, and it is sufficient to connect the plurality of lead parts to one connector 19. Therefore, a temperature sensor element capable of measuring temperatures at multiple locations within a plane can be easily formed.

In the above embodiment, the nickel thin film was provided on one main surface of the film base material, but the nickel thin film may be provided on both sides of the film base material. Alternatively, a nickel thin film may be provided on one main surface of the film base material, and a thin film made of another material may be provided on the other main surface.

The method of connecting the lead portion of the temperature sensor film and the external circuit is not limited to the method using a connector. For example, a controller may be provided on the temperature sensor film to apply a voltage to the lead portion and measure the resistance. Further, the lead portion and the lead wiring from the external circuit may be connected by soldering or the like without using a connector.

The temperature sensor film has a simple structure in which a thin film is provided on a film base material, and has excellent productivity, is easy to process, and can be applied to curved surfaces. Furthermore, since the nickel thin film has a small amount of carbon and a high TCR, it is possible to achieve more accurate temperature measurement.

EXAMPLES The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples.

[Evaluation method]
<Carbon content>
Using a quadrupole secondary ion mass spectrometer (“PHI ADEPT-1010” manufactured by ULVAC-PHI), primary ion species: Cs ⁺ , acceleration energy: 2.0 keV, raster area: 300 μm x 300 μm, detection area: 100 μm. The concentration distribution in the depth direction (depth profile) from the surface of the conductive film (the surface of the nickel layer) was measured by secondary ion mass spectrometry (SIMS) under the condition of ×100 μm. The region where the Ni concentration was 1×10 ¹⁹ atm/cm ³ or more was defined as the Ni layer, and the concentration of carbon atoms at the center in the thickness direction was defined as the carbon content of the nickel layer.

<Specific resistance>
The surface resistance was measured using a resistivity meter (Loresta GP MCP-T610 manufactured by Mitsubishi Chemical Analytic Tech) under an environment of a temperature of 25°C and a relative humidity of 50% by the four-probe method, and the relationship between surface resistance and thickness was determined. The specific resistance of the nickel layer was calculated from the product. The thickness of the nickel layer was measured by observing the cross section using a transmission electron microscope (manufactured by Hitachi High-Tech, "HF-2000").

<Surface shape>
Using an atomic force microscope (Dimension 3100 manufactured by Bruker), the three-dimensional surface shape of the nickel layer was measured under the following conditions, a roughness curve with a length of 1 μm was extracted, and the arithmetic mean roughness was calculated according to JIS B0601. Ra was calculated.
Controller: Nanoscope V
Measurement mode: Tapping mode Cantilever: Si single crystal Measurement field of view: 1μm x 1μm

<X-ray diffraction>
Using a powder X-ray diffraction device (Rigaku "RINT-2000"), X-ray diffraction measurements were carried out by the out-of-plane method under the following conditions, and from the obtained X-ray diffraction pattern, 2θ = 43 The half-width of the diffraction peak near the angle ((111) plane diffraction peak of Ni (fcc)) was determined.
X-ray source: CuKα ray (wavelength: 1.541 Å), 40 KV, 40 mA
Optical system: Parallel beam optical system Divergence slit: 0.05mm
Light receiving slit: solar slit

<Temperature coefficient of resistance (TCR)>
(Preparation of temperature sensor film)
The conductive film was cut into a size of 10 mm x 200 mm, and the nickel layer was patterned into a stripe shape with a line width of 30 μm by laser patterning to form a temperature measuring resistor section having the shape shown in FIG. 4A. During patterning, the length of the pattern was adjusted so that the overall wiring resistance was about 10 kΩ and the resistance of the temperature-measuring resistor part was 30 times the resistance of the lead part, and a temperature sensor film was produced.

(Measurement of temperature coefficient of resistance)
The temperature measuring resistance portion of the temperature sensor film was set to 5°C, 25°C, and 45°C in a small heating and cooling oven. The two-terminal resistance at each temperature was measured by connecting one tip and the other tip of the lead portion to a tester, flowing a constant current, and reading the voltage. The average value of the TCR calculated from the resistance values at 5°C and 25°C and the TCR calculated from the resistance values at 25°C and 45°C was taken as the TCR of the nickel layer.

<Heating durability test>
After measuring TCR, the temperature sensor film was placed in a hot air oven at 80°C, and after 240 hours and 500 hours, it was taken out of the oven and the two-terminal resistance was measured at 5°C, 25°C, and 45°C, and TCR was calculated. did. Regarding TCR and resistance value at 25°C, the rate of change was determined from the initial value (before putting it in the oven).

[Comparative example 1]
A roll of polyethylene terephthalate (PET) film (surface arithmetic mean roughness Ra: 1.6 nm) with a thickness of 150 μm was set in a roll-to-roll sputtering device, and the degree of vacuum reached within the sputtering device was 5.0×10 ⁻ After evacuating to a pressure of ³ Pa, argon was introduced, and DC sputtering was performed under the conditions of a substrate temperature of 150°C, a pressure of 0.3 Pa, and a power density of 5.6 W/cm ² to form a 70 nm thick Ni film on the PET film. A conductive film comprising layers was prepared. A metallic nickel target was used to form the Ni layer. The magnetic flux density on the surface of the nickel target was 100 mT.

[Example 1]
A conductive film was produced in the same manner as Comparative Example 1 except that the substrate temperature was changed to 0°C.

[Example 2]
On the PET film, a silicon layer with a thickness of 5 nm and a silicon oxide layer with a thickness of 10 nm were sequentially formed by sputtering as a base layer, and a Ni layer was formed thereon under the same conditions as in Comparative Example 1, and on the PET film, A conductive film including a Si layer (5 nm), _two SiO layers (10 nm), and a Ni layer (70 nm) was produced. A B-doped Si target was used to form the Si layer and the SiO ₂ layer. The Si layer was formed by DC sputtering under conditions of a substrate temperature of 150° C., a pressure of 0.3 Pa, and a power density of 1.0 W/cm ² by introducing argon as a sputtering gas. For the SiO ₂ layer, in addition to argon as a sputtering gas, oxygen was introduced as a reactive gas (O ₂ /Ar=1.0), the substrate temperature was 150°C, the pressure was 0.3 Pa, and the power density was 1.8 W/cm ² The film was formed by DC sputtering under the following conditions. The magnetic flux density on the surface of the Si target was 100 mT.

[Example 3]
A conductive film was produced in the same manner as in Example 2, except that the thickness of the nickel layer was changed to 140 nm.

[Example 4]
The magnet used when forming the Si layer and the SiO ₂ layer was changed, and film formation was performed at a magnetic flux density of 30 mT on the surface of the Si target. Further, the substrate temperature during film formation of each layer was changed to 75° C., and the thickness of the nickel layer was changed to 160 nm. A conductive film was produced in the same manner as in Example 2 except for these changes.

[Example 5]
The conductive film of Example 4 was heated in a hot air oven at 155° C. for 60 minutes to produce a conductive film.

[Example 6]
In Example 2, the magnet used when forming the Si layer was changed, and the film was formed at a magnetic flux density of 30 mT on the surface of the Si target. In Example 6, a nickel layer was formed on the silicon layer without forming a silicon oxide layer, and a conductive film including a Si layer (5 nm) and a Ni layer (70 nm) on a PET film was produced.

[Evaluation results of Examples 1 to 6 and Comparative Example 1]
Laminated structure and manufacturing conditions of the conductive films of Examples 1 to 6 and Comparative Example 1 (substrate temperature, base layer structure and magnetic flux density during film formation, nickel layer thickness, heat treatment conditions after film formation), and Table 1 shows the evaluation results of the properties of the nickel layer (carbon content, TCR, and specific resistance).

In Comparative Example 1, in which a nickel layer was formed on a PET film base material at a substrate temperature of 150° C., the carbon content exceeded 1×10 ²¹ atm/cm ³ and the TCR was below 3000 ppm/° C. On the other hand, in Example 1 where the substrate temperature was 0° C., the amount of carbon in the nickel layer decreased and the TCR increased. In Example 1, it is thought that by performing sputtering film formation at a low temperature, the amount of organic gas generated from the PET film base material was reduced, the amount of carbon incorporated into the nickel layer was reduced, and the TCR was increased. .

In Examples 2 to 6, in which a base layer was formed on the PET film base material and a nickel layer was formed on it, the carbon content was further reduced compared to Example 1, and the TCR increased accordingly. Was. These results show that by adjusting the film forming conditions when forming the nickel layer and forming the base layer, the amount of carbon mixed in from the film base material to the nickel layer can be reduced, and as a result, nickel with a large TCR can be reduced. It can be seen that layers can be formed.

[Example 7]
The conductive film of Example 3 was heated in a hot air oven at 155° C. for 60 minutes to produce a conductive film.

[Example 8]
The conductive film of Example 4 was heated in a hot air oven at 155° C. for 60 minutes to produce a conductive film.

[Evaluation results of Examples 1 to 8 and Comparative Example 1]
Laminated structure and manufacturing conditions of the conductive films of Examples 1 to 8 and Comparative Example 1, characteristics of the nickel layer (arithmetic mean roughness Ra, half width of Ni (111) surface diffraction peak, and TCR), and after heating durability test Table 2 shows the rate of change in TCR. Moreover, the X-ray diffraction patterns of the conductive films of Example 4 and Example 7 are shown in FIG.

In Comparative Example 1, in which a nickel layer was formed on a PET film base material at a substrate temperature of 150°C, the half width of the (111) plane peak of nickel exceeded 1°; In Example 1, the half width was smaller than in Comparative Example 1, and the TCR was increased. In Example 1, it is considered that the crystallization of nickel was promoted due to the reduction in the amount of carbon mixed in.

In Examples 2 to 8, in which a base layer was formed on the PET film base material and a nickel layer was formed on it, the half width of the (111) plane peak of nickel was smaller than in Example 1. Accordingly, TCR increased.

In the temperature sensor film of Example 4, the resistance value decreased by 10% or more after the heating durability test, the TCR also changed significantly, and the heating stability could not be said to be sufficient. In Example 8, in which a conductive film produced under the same conditions as Example 4 was heat-treated at 155°C for 15 minutes, Ra was larger and the half-width of the (111) plane peak of nickel was smaller than in Example 4. was. The temperature sensor film of Example 8 had a smaller change in resistance after the heating durability test than Comparative Example 4, and had improved stability. In Example 5, in which the heating time at 155°C was changed to 60 minutes, the half width of the (111) plane peak of nickel was even smaller than in Example 8, and the change in resistance after the heating durability test was smaller. .

These results show that heat treatment after forming a nickel layer increases the size of nickel crystallites, lowers resistance and increases TCR, and improves heating stability. .

In Examples 2 and 3 in which the substrate temperature was raised, the half width of the (111) plane peak of nickel was smaller than in Example 4, and the heating stability was improved. In Examples 2 and 3, it is thought that the high magnetic flux density during the formation of the underlayer also contributed to the reduction in the half-width of the (111) plane peak (improved crystallinity). In Example 7, in which a conductive film produced under the same conditions as Example 3 was heat-treated at 155°C for 60 minutes, the half width of the (111) plane peak of nickel was smaller than in Example 3, and the heating stability was improved. It was improving. In Example 3, the half-value width of the peak of the (111) plane of nickel is already sufficiently small immediately after film formation (heat treatment not performed), so the stability improvement effect due to heat treatment (stability improvement effect in Example 7) ) was not as pronounced as in the comparison between Example 4 and Example 8.

Even in Example 6 in which only a Si layer was formed as the base layer and a nickel layer was formed on the Si layer, the peak half width of the (111) plane of nickel was small, and the temperature sensor film had excellent heating stability. was.

From the above results, a conductive film whose nickel layer has a small X-ray diffraction peak width has a high TCR and a small rate of change in resistance and TCR even when exposed to a high temperature environment for a long time, and is useful as a temperature sensor film. It can be said.

50 Film base material 20 Base layer 10 Nickel thin film 11 Lead portion 12 Temperature-measuring resistance portion 122, 123 Sensor wiring 19 Connector 101, 102 Conductive film 110 Temperature sensor film

Claims (8)

A thin nickel film is provided on one main surface of a resin film base material,
The conductive film for a temperature sensor, wherein the nickel thin film is a sputtered film, and in an X-ray diffraction pattern, the half width of the diffraction peak of the (111) plane of nickel is 0.8° or less. The conductive film for a temperature sensor according to claim 1 , wherein the carbon atom concentration in the nickel thin film is 1.0×10 ²¹ atm/cm ³ or less. 3. The conductive film for a temperature sensor according to claim 1 , wherein the nickel thin film has a specific resistance of 1.6×10 ⁻⁵ Ω·cm or less. The conductive film for a temperature sensor according to any one of claims 1 to 3 , wherein the nickel thin film has a temperature coefficient of resistance of 3000 ppm/°C or more. The conductive film for a temperature sensor according to any one of claims 1 to 4 , wherein the nickel thin film has a thickness of 20 to 500 nm. The conductive film according to any one of claims 1 to 5 , comprising an inorganic underlayer between the resin film base material and the nickel thin film. A method for manufacturing the conductive film according to any one of claims 1 to 6 , comprising:
A method for producing a conductive film, comprising forming the nickel thin film by a sputtering method. Equipped with a patterned nickel thin film on one main surface of the resin film base material,
The nickel thin film is patterned into a thin line and is used for temperature measurement, and a lead part is connected to the temperature-measuring resistor part and is patterned to have a larger line width than the temperature-measuring resistor part. It is patterned,
The nickel thin film is a sputtered film, and in the X-ray diffraction pattern, the half width of the diffraction peak of the (111) plane of nickel is 0.8° or less, and the carbon atom concentration is 1.0×10 ²¹ atm/cm ³ Below is a temperature sensor film.

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