Laminated Film and Strain Sensor

Abstract

To provide a laminated film having a resistance layer which is less susceptible to cracking, and a strain sensor having a strain sensor unit which is less susceptible to cracking.SOLUTION: A laminated film is provided, comprising a flexible base material film 2 and a resistance layer 3 arranged in the described order in the thickness direction. The resistance layer 3 contains chromium nitride. A lattice spacing on a (200) plane of the resistance layer 3 as determined by the X-ray diffraction method is 1.454 Å or greater.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminated film and a strain sensor. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a strain sensor is known that includes an insulating substrate and a patterned Cr-N thin film disposed on the surface of the insulating substrate (see, for example, Patent Document 1 below).

[0003] As the insulating substrate, a hard silicon substrate is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-31633 A Summary of the Invention [Problem to be solved by the invention]

[0005] Depending on the application and purpose, a flexible insulating substrate may be used. However, if the insulating substrate is flexible, the Cr-N thin film is susceptible to stress, which can cause cracks.

[0006] The present invention provides a laminated film including a resistive layer in which cracks are suppressed, and a strain sensor including a strain sensor portion in which cracks are suppressed. [Means for solving the problem]

[0007] The present invention (1) includes a laminated film comprising a flexible base film and a resistive layer in that order in a thickness direction, the resistive layer containing chromium nitride, and the lattice spacing in the (200) plane of the resistive layer as determined by X-ray diffraction method is 1.454 Å or more.

[0008] The present invention (2) includes the laminate film according to (1), in which the resistance layer has a thickness of 50 nm or more and 150 nm or less.

[0009] The present invention (3) includes the laminate film according to (1) or (2), in which the material of the base film is a polyimide resin.

[0010] The present invention (4) includes the laminate film according to any one of (1) to (3), in which the thickness of the base film is 10 μm or more and 200 μm or less.

[0011] The present invention (5) includes a strain sensor comprising a flexible base film and a strain sensor portion in that order in a thickness direction, the strain sensor portion including patterned chromium nitride, and the lattice spacing of the (200) plane of the strain sensor portion as determined by X-ray diffraction method is 1.454 Å or more.

[0012] The present invention (6) includes the strain sensor according to (5), wherein the thickness of the strain sensor portion is 50 nm or more and 150 nm or less.

[0013] The present invention (7) includes the strain sensor according to (5) or (6), in which the material of the base film is a polyimide resin.

[0014] The present invention (8) includes the strain sensor according to any one of (5) to (7), wherein the thickness of the base film is 10 μm or more and 200 μm or less. Effect of the Invention

[0015] In the laminated film of the present invention, cracks in the resistance layer are suppressed.

[0016] In the strain sensor of the present invention, cracks in the strain sensor portion are suppressed. [Brief description of the drawings]

[0017] [Figure 1]FIG. 1 is a cross-sectional view of one embodiment of the laminated film of the present invention. [Diagram 2] FIG. 2 shows a strain sensor in which the resistive layer shown in FIG. 1 is patterned, with FIG. 2A being a cross-sectional view and FIG. 2B being a plan view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] One embodiment of the laminated film and strain sensor of the present invention will be described with reference to Figs. 1 to 2B.

[0019] [Laminated film] The laminated film 1 is a film for a strain sensor used in manufacturing a strain sensor 15 (see Figs. 2A and 2B) described later. The laminated film 1 has a flat plate shape extending in a plane direction perpendicular to the thickness direction. Specifically, the laminated film 1 includes a base film 2 and a resistance layer 3 in this order toward one side in the thickness direction.

[0020] [Base film] The base film 2 forms the other thickness-wise surface of the laminate film 1. The base film 2 has a flat plate shape extending in the planar direction.

[0021] The base film 2 is flexible. This allows the laminate film 1, and further the strain sensor 15, to be suitably used in fields requiring flexibility. Specifically, the base film 2 has a folding endurance test (JIS C 5016 (1994)) of, for example, 250 times or more, preferably 500 times or more. If the folding endurance test result of the base film 2 is equal to or higher than the above-mentioned lower limit, the laminate film 1, and further the strain sensor 15, can be suitably used in the above-mentioned fields.

[0022] The base film 2 has, for example, insulating properties.

[0023] Examples of materials for the base film 2 include resins. Examples of resins include polyester resins such as polyethylene terephthalate, (meth)acrylic resins (acrylic resins and / or methacrylic resins) such as polymethacrylate, olefin resins such as polyethylene and polypropylene, and polycarbonate resins, polyethersulfone resins, polyarylate resins, melamine resins, polyamide resins, polyimide resins, cellulose resins, polystyrene resins, and norbornene resins. These may be used alone or in combination of two or more. From the viewpoint of obtaining insulating properties and better flexibility, polyimide resins are preferable.

[0024] The thickness of the base film 2 is not particularly limited, and is, for example, 2 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and is, for example, 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less. If the thickness of the base film 2 is the above-mentioned lower limit or more, the occurrence of wrinkles can be suppressed. If the thickness of the base film 2 is the above-mentioned upper limit or less, the base film 2 can be transported by roll-to-roll.

[0025] One surface in the thickness direction of the base film 2 may be subjected to treatment such as corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, sputter etching treatment, etc., in order to improve adhesion with the resistance layer 3.

[0026] The number of base films 2 in the laminate film 1 is not particularly limited, but is preferably one.

[0027] [Resistance layer] The resistive layer 3 is a layer that is patterned when the strain sensor 15 (see FIGS. 2A and 2B) is manufactured from the laminated film 1. The resistive layer 3 is disposed on one surface in the thickness direction of the base film 2. The resistive layer 3 forms one surface in the thickness direction of the laminated film 1. Specifically, the resistive layer 3 is in contact with the entire one surface in the thickness direction of the base film 2.

[0028] The resistive layer 3 includes chromium nitride. Specifically, the material of the resistive layer 3 contains chromium nitride as a main component. Meanwhile, the material of the resistive layer 3 is allowed to contain, for example, inevitable impurities. The proportion of the inevitable impurities in the resistive layer 3 is, for example, 1 atomic % or less, preferably 0.1 atomic % or less, and more preferably 0.05 atomic % or less. Preferably, the resistive layer 3 is made of chromium nitride.

[0029] In the case of chromium nitride, the molar ratio of nitrogen to 100 molar parts of chromium is not particularly limited, and is, for example, 0.1 part or more and 10 parts or less by mole.

[0030] The lattice spacing in the (200) plane of the resistance layer 3 determined by X-ray diffraction is 1.454 Å or more. If the lattice spacing in the (200) plane of the resistance layer 3 is less than 1.454 Å, cracks cannot be suppressed. The lattice spacing in the (200) plane of the resistance layer 3 is preferably 1.455 Å or more, more preferably 1.460 Å or more, and even more preferably 1.465 Å or more. The lattice spacing in the (200) plane of the resistance layer 3 is, for example, 1.500 Å or less. The lattice spacing in the (200) plane of the resistance layer 3 means the lattice distance in the plane direction of chromium nitride. The lattice spacing in the (200) plane of the resistance layer 3 is determined from the diffraction peak near 2θ=64° from the X-ray diffraction spectrum by substituting it into the Bragg equation (λ=2d·sinθ). In the formula, d is the lattice spacing (Å). λ is the wavelength (Å) of the characteristic X-ray.

[0031] The lattice spacing in the (110) plane of the resistance layer 3 determined by X-ray diffraction is, for example, 2.045 Å or more, preferably 2.048 Å or more, more preferably 2.050 Å or more, and is, for example, 2.100 Å or less. If the lattice spacing in the (110) plane of the resistance layer 3 is equal to or greater than the above-mentioned lower limit, cracks can be further suppressed. The lattice spacing in the (110) plane of the resistance layer 3 means the lattice distance in the thickness direction of chromium nitride. The lattice spacing in the (110) plane of the resistance layer 3 is determined by substituting the diffraction peak near 2θ=44° from the X-ray diffraction spectrum into the Bragg equation (λ=2d·sinθ). In the formula, d and λ are the same as above.

[0032] The thickness of the resistive layer 3 is, for example, 10 nm or more, preferably 25 nm or more, more preferably 50 nm or more. If the thickness of the resistive layer 3 is equal to or more than the above-mentioned lower limit, a high gauge factor described next can be ensured.

[0033] The thickness of the resistance layer 3 is, for example, not more than 300 nm, or preferably not more than 150 nm. When the thickness of the resistance layer 3 is not more than the above upper limit, cracks can be further suppressed.

[0034] The gauge factor of the resistive layer 3 is, for example, 10 or more, or preferably 11 or more.

[0035] The number of resistance layers 3 in the laminate film 1 is not particularly limited, and is preferably 1. Specifically, the number of resistance layers 3 per base film 2 is preferably 1.

[0036] [Method of manufacturing laminated film and strain sensor] In the manufacturing method of the laminated film 1, for example, the laminated film 1 is formed by a roll-to-roll method.

[0037] For example, while conveying a long substrate film 2, the resistive layer 3 is formed on one surface in the thickness direction of the substrate film 2. Examples of the film formation method include sputtering, vacuum deposition, and ion plating. Preferably, sputtering is used, more preferably reactive sputtering, and even more preferably reactive magnetron sputtering.

[0038] In reactive sputtering, the target is made of chromium, and the sputtering gas is a mixture of an inert gas such as argon and nitrogen. The volumetric ratio of nitrogen to 100 volumetric parts of the inert gas is, for example, 0.5 to 15 volumetric parts.

[0039] In reactive magnetron sputtering, a magnet is placed on the opposite side of the target to the substrate film 2. The magnetic flux density on the surface of the target (the surface facing the substrate film 2) is 80 mT or less, preferably 60 mT or less, more preferably 50 mT or less, and even more preferably 40 mT or less. If the magnetic flux density is equal to or less than the above-mentioned upper limit, it is possible to form a resistive layer 3 in which the lattice spacing in the (200) plane is equal to or greater than the above-mentioned lower limit, and thus it is possible to obtain a resistive layer 3 in which cracks are suppressed.

[0040] The magnetic flux density on the surface of the target is, for example, 1 mT or more, preferably 5 mT or more, more preferably 15 mT or more. If the magnetic flux density is equal to or more than the lower limit described above, the plasma can be continued, and the resistive layer 3 can be reliably formed by magnetron sputtering (specifically, reactive magnetron sputtering).

[0041] The shape of the target is not particularly limited, and examples thereof include a flat plate shape and a cylindrical shape.

[0042] In reactive magnetron sputtering, when a voltage is applied to the target, a plasma consisting of argon particles and nitrogen particles is generated, and the above-mentioned particles collide with the target, causing chromium particles to fly out of the target and adhere to the base film 2. At this time, nitrogen particles contained in the plasma also adhere to the base film 2 together with the chromium particles. As a result, a resistive layer 3 consisting of chromium nitride is formed on one surface of the base film 2 in the thickness direction.

[0043] In this way, a laminate film 1 including the base film 2 and the resistance layer 3 is obtained.

[0044] If necessary, the laminated film 1 can be heated thereafter. The heating temperature is not particularly limited as long as it does not damage the base film 2, and is, for example, 250° C. or less, preferably 200° C. or less, and for example, 100° C. or more, preferably 120° C. or more.

[0045] 2A, the resistive layer 3 in the laminated film 1 is then patterned to form a resistive pattern 4. Examples of the patterning of the resistive layer 3 include etching, and specific examples include dry etching and wet etching.

[0046] The resistance pattern 4 integrally includes a strain sensor portion 5, a terminal 6, and a wiring 7.

[0047] 2B, the strain sensor section 5 has a generally zigzag shape in a plan view. Specifically, the strain sensor section 5 has a plurality of first wires 8, a plurality of first connection wires 9, and a plurality of second connection wires 10.

[0048] Each of the first lines 8 extends along a first direction (a direction included in the surface direction). The first lines 8 are aligned and spaced apart in a second direction (a direction included in the surface direction and perpendicular to the first direction).

[0049] The multiple first connection lines 9 connect one end in the first direction of the first lines 8 adjacent to each other in the second direction.

[0050] The second connection lines 10 connect the other ends in the first direction of the first lines 8 adjacent to each other in the second direction. When projected in the first direction, the first connection lines 9 and the second connection lines 10 are arranged alternately.

[0051] The terminal 6 is spaced apart in the surface direction from the strain sensor section 5. The terminal 6 has, for example, a land shape that is generally rectangular in plan view. Two terminals 6 are provided with a space therebetween.

[0052] The wiring 7 connects the two terminals 6 to both ends of the strain sensor unit 5 .

[0053] In the strain sensor section 5, one conductive path is formed from one terminal 6, passing through one wiring 7, the strain sensor section 5 and the other wiring 7, to the other terminal 6.

[0054] The dimensions of the strain sensor section 5 are appropriately set depending on the application and purpose. The widths of the first line 8, the first connection line 9 and the second connection line 10 are, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and for example, 150 μm or less, preferably 100 μm or less, more preferably 70 μm or less.

[0055] The shape of the base film 2 is also appropriately set depending on the application and purpose of the strain sensor 15, and is formed into desired dimensions by, for example, outer shaping.

[0056] Next, a method of placing the strain sensor 15 on the object 20 and measuring the amount of strain (amount of deformation) of the object 20 will be described.

[0057] 2A, the laminated film 1 of the strain sensor 15 is attached to the surface of the specimen 20 via an adhesive layer 21. Furthermore, lead wires 23 are connected to the two terminals 6 via a conductive adhesive layer 22. The lead wires 23 are electrically connected to an external resistance measurement circuit (not shown).

[0058] When the object under test 20 is distorted, the resistance value of the strain sensor section 5 changes. Based on this, the amount of strain is calculated in the resistance measuring circuit.

[0059] Specifically, when the specimen 20 expands in the first direction, a tensile strain is applied to the first wire 8, the cross-sectional area of ​​the first wire 8 decreases, and the resistance of the strain sensor unit 5 increases. On the other hand, when the specimen 20 contracts, a compressive strain is applied to the first wire 8, the cross-sectional area of ​​the first wire 8 increases, and the resistance of the strain sensor unit 5 decreases. The amount of strain in the specimen 20 is calculated from such a change in resistance.

[0060] [Effects of one embodiment] In this laminated film 1, the lattice spacing in the (200) plane of the resistance layer 3 determined by X-ray diffraction is 1.454 Å or more, which can suppress cracks in the resistance layer 3. Therefore, the laminated film 1 has excellent reliability.

[0061] Furthermore, if the thickness of the resistive layer 3 is 50 nm or more, a high gauge factor can be ensured. If the thickness of the resistive layer 3 is 150 nm or less, cracks can be further suppressed.

[0062] In this strain sensor 15, the lattice spacing in the (200) plane of the strain sensor section 5 determined by X-ray diffraction is 1.454 Å or more, which can suppress cracks in the strain sensor section 5. Therefore, the strain sensor 15 has excellent reliability.

[0063] Moreover, since the base film 2 is flexible, it can be suitably used in fields where flexibility is required. That is, the laminated film 1 and the strain sensor 15 are suitable for use in fields where flexibility is required, while suppressing the above-mentioned cracks and providing excellent reliability.

[0064] [Variations] In the following modifications, the same components and steps as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition, each modification can achieve the same effects as those in the above-described embodiment, unless otherwise specified. Furthermore, the embodiment and its modifications can be appropriately combined.

[0065] In one embodiment, the timing of the heating is before the patterning of the resistive layer 3, but it may also be after the patterning of the resistive layer 3, for example.

[0066] The substrate film 2 may include, on one surface in the thickness direction, a functional layer (not shown), such as a hard coat layer, an easy-adhesion layer, or an antistatic layer.

[0067] Moreover, the strain sensor 15 can further include a cover layer 12 (dotted chain line) that covers the strain sensor portion 5 and is made of a resin.

[0068] In one embodiment, one is illustrated as a suitable number of resistive layers 3 in the laminate film 1, but it may be, for example, two, although not shown. In this case, each of the two resistive layers 3 is disposed on both sides in the thickness direction of the base film 2. That is, in a suitable example of this modification, the number of resistive layers 3 for one base film 2 is preferably two. EXAMPLES

[0069] The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the examples and comparative examples. The specific numerical values ​​of the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Form for carrying out the invention".

[0070] Example 1 A base film 2 made of flexible polyimide (150EN, 38 μm thick, manufactured by Toray DuPont Co., Ltd.) was prepared. The folding endurance test (JIS C 5016 (1994)) of the base film 2 was 1000 times.

[0071] The substrate film 2 was set on a delivery roll and a take-up roll of a roll-to-roll system, and was also set in a sputtering device disposed between them.

[0072] Next, the vacuum level in the sputtering device was set to 1×10 -3 After evacuation to a pressure of 1 Pa or less, a resistive layer 3 made of chromium nitride was formed by reactive magnetron sputtering under the following conditions. The resistive layer 3 had a thickness of 100 nm.

[0073] Target material: Chromium metal Target shape: Flat Target size: 500mm x 150mm Magnetic flux density on the target surface: 30mT Power: 5kW (power density: 6.7W / cm 2 ) Substrate temperature: 150℃ Sputtering gas: Ar and N mixed gas Film forming pressure: 0.085Pa

[0074] The ratio of nitrogen was adjusted so that the ratio of the number of moles of nitrogen to the number of moles of chromium was as shown in Table 1.

[0075] In this way, a laminate film 1 including the base film 2 and the resistance layer 3 was produced.

[0076] Example 2 to Example 3 A laminate film 1 was produced in the same manner as in Example 1, except that the ratio of the number of moles of nitrogen in the mixed gas was adjusted so that the ratio of the number of moles of nitrogen to the number of moles of chromium was as shown in Table 1.

[0077] Example 4 to Example 5 Laminated film 1 was produced in the same manner as in Example 1, except that the target was changed to a rotating cylindrical target, the size was changed to an axial length of 500 mm and a diameter (outer dimension) of 150 mm, and the ratio of nitrogen in the mixed gas was adjusted so that the ratio of the number of moles of nitrogen to the number of moles of chromium was as shown in Table 1.

[0078] Comparative Example 1 to Comparative Example 2 Laminated film 1 was produced in the same manner as in Example 1, except that the magnetic flux density on the target surface was changed to 100 mT and the ratio of nitrogen in the mixed gas was adjusted so that the ratio of the number of moles of nitrogen to the number of moles of chromium was as shown in Table 1.

[0079] (evaluation) The laminated film 1 of each of the Examples and Comparative Examples was evaluated for the following items. The results are shown in Table 1.

[0080] (percentage of nitrogen) The molar parts of nitrogen relative to 100 molar parts of chromium in the resistive layer 3 was measured by Rutherford backscattering spectrometry (RBS) under the following conditions.

[0081] (Measurement conditions) Equipment: National Electrostatics Corporation Pelletron 3SDH Measurement conditions: Incident ions: 4 He ++ Incident energy: 2300keV Incident angle: 0deg Scattering angle: 160deg Specimen current: 4nA Beam diameter: 2mmΦ In-plane rotation: None Irradiation dose: 40μC

[0082] (Grid spacing) The resistive layer 3 was subjected to X-ray diffraction measurement. Specifically, an X-ray diffraction device (Rigaku's "SmartLab") was used to obtain the diffraction spectrum of the resistive layer 3. Then, the lattice spacing in the (200) plane of the resistive layer 3 was calculated from the diffraction peak near 2θ=64°. The lattice spacing in the (110) plane of the resistive layer 3 was calculated from the diffraction peak near 2θ=44°.

[0083] (crack) The presence or absence of cracks in the resistance layer 3 was visually observed and evaluated according to the following criteria.

[0084] ◯: No cracks were observed. ×: Cracks were observed.

[0085] [Table 1] [Explanation of symbols]

[0086] 1. Laminated film 2. Base film 3 resistance layer 5 Strain sensor section 15 Strain Sensor

Claims

1. A flexible base film and a resistive layer are provided in this order in a thickness direction, the resistive layer comprises chromium nitride; A laminated film, wherein the lattice spacing in the (200) plane of the resistive layer, as determined by X-ray diffraction, is 1.454 Å or more and 1.470 Å or less.

2. 2. The laminated film according to claim 1, wherein the resistive layer has a thickness of 50 nm or more and 150 nm or less.

3. 3. The laminated film according to claim 1, wherein the material of the base film is a polyimide resin.

4. The laminate film according to any one of claims 1 to 3, wherein the thickness of the base film is 10 µm or more and 200 µm or less.

5. A flexible base film and a strain sensor unit are provided in this order in the thickness direction. the strain sensor portion includes patterned chromium nitride; A strain sensor, characterized in that the lattice spacing of the (200) plane of the strain sensor portion, as determined by X-ray diffraction, is 1.454 Å or more and 1.470 Å or less.

6. 6. The strain sensor according to claim 5, wherein the thickness of the strain sensor portion is 50 nm or more and 150 nm or less.

7. 7. The strain sensor according to claim 5, wherein the material of the base film is a polyimide resin.

8. The strain sensor according to any one of claims 5 to 7, wherein the thickness of the substrate film is 10 µm or more and 200 µm or less.

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