JP2016122363A - Method of measuring haptic sensation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a haptic sensation evaluation method that allows for quantitatively evaluating various haptic sensations.SOLUTION: An evaluation method for evaluating haptic sensation on a smooth surface of a base material involves bringing a piezoelectric element 28 into contact with a smooth surface of a material (base material) 12, moving the piezoelectric element on the base material surface relative to the base material surface, and acquiring an output signal from the piezoelectric element. The acquired signal is processed by a signal processing unit to obtain at least one of; a mean absolute value of the output signal, a variance of the output signal, a power spectral distribution ratio of a mid-frequency component to mid and high frequency components of the output signal, and a sum of frequency components in a specific frequency band.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for measuring the feel of a smooth surface.

  With the rapid spread of smartphones, tablet terminals, and the like in recent years, there is an increasing interest in technologies for improving the touch feeling of the operation surface (for example, touch panel), for example, surface treatment technology.

  Conventionally, the tactile sensation of the surface of the base material treated in this way, especially glass, resin (plastic), smooth surface such as a metal plate, especially tactile sensation (sliding property) when a finger is slid on the surface is determined. For example, a method of measuring a dynamic friction coefficient of the surface of a base material is used as a method for evaluating it as described in Patent Document 1, for example.

JP2013-253228A

  The slipperiness is one of the sensations when a person touches an object (that is, the tactile sensation), but the present inventors consider that the human tactile sensation is not only slippery but also various other sensations such as adhesion, It has been found that a feeling of dryness, roughness, softness, warmth, coolness, elasticity, lightness, thinness, fit, etc. can be included.

  According to the conventional evaluation method using a dynamic friction coefficient, the slipperiness can be quantitatively evaluated, but a method for quantitatively evaluating other senses has not yet been established.

  Therefore, an object of the present invention is to provide an evaluation method capable of quantitatively evaluating not only slipperiness but also other tactile sensations.

  As a result of intensive studies, the inventors contacted and moved the piezoelectric element to the surface of the substrate, and the piezoelectric element output a specific signal according to the magnitude of pressure sensitivity. From the above characteristics (characteristics of output voltage), it was found that the tactile sensation can be evaluated, and the present invention has been completed.

  According to an aspect of the present invention, there is provided a method for evaluating the tactile sensation of a smooth surface of a substrate, wherein the piezoelectric element is brought into contact with the smooth surface of the substrate and the surface of the substrate is relatively relative to the surface of the substrate. A method is provided that includes moving and acquiring an output signal from a piezoelectric element.

  According to the evaluation method of the present invention, it is possible to evaluate not only the slipperiness but also other characteristics of the smooth surface of the substrate.

FIG. 1 is a plan view schematically showing an apparatus 10 used in the evaluation method of the present invention. FIG. 2 is a cross-sectional view of the apparatus of FIG. 1 taken along line xx. FIG. 3 shows the measurement result of the dynamic friction coefficient at a scanning speed of 3.3 mm / s in the comparative example. FIG. 4 shows the measurement result of the dynamic friction coefficient at a scanning speed of 8.3 mm / s in the comparative example. FIG. 5 shows the measurement results in Example 1 under conditions of a scanning speed of 50 mm / s and a contact force of 0.2 N. FIG. 6 shows the measurement results in Example 1 under conditions of a scanning speed of 50 mm / s and a contact force of 0.4 N. FIG. 7 shows the measurement results under the conditions of a scanning speed of 50 mm / s and a contact force of 1 N in Example 1. FIG. 8 shows the measurement results in Example 1 under conditions of a scanning speed of 75 mm / s and a contact force of 0.2 N. FIG. 9 shows the measurement results in Example 1 under conditions of a scanning speed of 75 mm / s and a contact force of 0.4 N. FIG. 10 shows the measurement results under the conditions of a scanning speed of 75 mm / s and a contact force of 1 N in Example 1. FIG. 11 shows the evaluation result of the dispersion value under the condition of the scanning speed of 50 mm / s in Example 2. FIG. 12 shows the evaluation result of the dispersion value under the condition of the scanning speed of 75 mm / s in Example 2. FIG. 13 shows the evaluation result of the R _s value under the condition of the scanning speed of 50 mm / s in Example 3. FIG. 14 shows the evaluation result of the R _s value under the condition of the scanning speed of 75 mm / s in Example 3. FIG. 15 shows the evaluation results of FFTsum _10-150 and FFTsum _150-500 in Example 4 under the condition of a scanning speed of 50 mm / s. FIG. 16 shows the evaluation results of FFTsum _10-150 and FFTsum _150-500 in Example 4 under a scanning speed of 75 mm / s.

  The present invention relates to a method for evaluating the tactile sensation of a smooth surface of a base material, and moves relative to the base material surface while bringing a piezoelectric element into contact with the smooth surface of the base material. And obtaining an output signal from the piezoelectric element in accordance with the magnitude of the pressure sensitivity. Hereinafter, the evaluation method of the present invention will be described in detail.

  The apparatus used in the evaluation method of the present invention includes a tactile sensor having a piezoelectric element, a moving unit that moves the tactile sensor, a control unit that controls movement of the tactile sensor, and a signal that processes a signal obtained from the tactile sensor. And a processing unit. Moreover, the said apparatus may have a fixing | fixed part which fixes a to-be-evaluated base material, a display part etc. which display a signal processing result.

  In FIG. 1, an example of a structure of the apparatus 10 used for the evaluation method of this invention is shown with a schematic plan view. FIG. 2 is a schematic sectional view taken along line xx of the apparatus.

  As shown in the figure, in the apparatus 10 used in the evaluation method of the present invention, a sample (base material) 12 is fixed on a sample fixing base 14. The sample fixing base 14 is installed on the Z-axis stage 16. A cantilever beam 20 that moves along the X-axis slider 18 is attached. The cantilever 20 has a strain gauge 22, and a tactile sensor 24 is attached to the tip of the cantilever. The tactile sensor 24 includes a base material 26 and a piezoelectric element 28 installed on the surface thereof.

  Although not shown, the apparatus used in the evaluation method of the present invention further controls a measurement unit for measuring the moving speed and / or contact pressure of the tactile sensor 24, and controls the moving speed and / or contact pressure of the tactile sensor. A control unit that performs signal processing, a signal processing unit that calculates signals, a display unit that displays the obtained signals and calculation results, and the like may be provided. Moreover, the apparatus used for the evaluation method of the present invention is not limited to the illustrated apparatus, and any apparatus that can move the piezoelectric element in contact with the substrate may be used.

  The piezoelectric element 28 has a piezoelectric material and an electrode. Preferably, the piezoelectric material is in the form of a film, and the entire surface is covered with electrodes. The piezoelectric material is not particularly limited, but polyvinylidene fluoride (PVDF) or a vinylidene fluoride copolymer such as vinylidene fluoride and trifluoroethylene, vinyl fluoride, vinyl chloride, chlorofluoroethylene, chloro And copolymers with one or more monomers selected from trifluoroethylene, chlorodifluoroethylene, hexafluoroacetone and hexafluoropropylene. Piezoelectric material is one of the tactile receptors that exist in the finger pad undercutaneous tissue, has high sensitivity to detect the acceleration of skin displacement, and the response characteristic of the patina body that is involved in perceptual recognition of fine textures A piezoelectric material similar to the above is preferable. For example, it is preferable to use polyvinylidene fluoride. Polyvinylidene fluoride is also preferred because it has high sensitivity and flexibility and is easy to process.

  The base material used for the tactile sensor preferably has the same elasticity as a human finger. Such a material having elasticity equivalent to that of a human finger is not particularly limited. For example, various resins (for example, silicon resin), rubber (for example, vulcanized rubber), and the like can be used.

  Further, the tactile sensor may have a simulated fingerprint portion for imitating a human fingerprint on the outermost layer in order to approximate a tactile sensation with a human finger. The simulated fingerprint portion may be formed by processing (for example, etching) the surface of the piezoelectric element, or a simulated fingerprint material on which the simulated fingerprint portion is formed may be placed on the outermost layer. The material constituting the simulated fingerprint material is not particularly limited, but various resins can be used, for example, an acetate resin film.

  In the evaluation, the sample (base material) 12 is fixed on the sample fixing base 14, and the tactile sensor 24 (specifically, the piezoelectric element 28) is brought into contact with the smooth surface of the sample (base material) 12 on the sample fixing base 14. In this state, the cantilever 20 is moved along the X-axis slider 18 in the rightward direction in FIGS. 1 and 2.

The contact area between the piezoelectric element and the base material is not particularly limited, but is preferably equal to the area that the finger contacts when a person touches the base material. For example, the contact area between the piezoelectric element and the substrate, for example, it is preferable 1.0～3.0Cm ^2, for example, 2.0 cm ^2.

  The contact force between the piezoelectric element and the substrate is not particularly limited, but is, for example, 0.01 to 20N, preferably 0.01 to 10N, more preferably 0.05 to 5.0N, and still more preferably 0.1. It may be -3.0N, even more preferably 0.3-2.0N. The contact force between the piezoelectric element 28 and the substrate 12 can be measured with the strain gauge 22. This contact force can be adjusted by adjusting the height of the Z-axis stage 16. The contact force is a force with which the piezoelectric element pushes the substrate, and means a force perpendicular to the surface of the substrate.

Contact pressure of the piezoelectric element and the base material is not particularly limited, for example, a 0.01~20N / cm ^2, preferably 0.01~5.0N / ^cm 2 near the pressure a person touching the substrate, More preferably, it may be 0.1-3.0 N / cm < ² >, More preferably, it may be 0.2-2.0 N / cm < ² >, More preferably, it may be 0.3-1.0 N / cm < ² >. The contact pressure between the piezoelectric element 28 and the substrate 12 can be measured with the strain gauge 22. Further, this contact pressure can be adjusted by adjusting the height of the Z-axis stage 16.

  The scanning speed (movement speed) of the piezoelectric element with respect to the base material is not particularly limited, but is preferably close to the speed at which a person touches the base material. The scanning speed may be, for example, 5 to 1,000 mm / s, preferably 10 to 800 mm / s, more preferably 30 to 500 mm / s, and further preferably 30 to 200 mm / s.

  The contact pressure between the tactile sensor (specifically, the piezoelectric element) and the substrate and / or the scanning speed of the piezoelectric element with respect to the substrate may be constant or may be changed. Further, the tactile sensor may be moved at a constant speed from a state where it is stopped by being in contact with the base material, and may finally be stopped. Alternatively, the tactile sensor may be contacted with the base material while being moved in a non-contact state. The distance may be moved and finally separated from the substrate again. When changing the contact pressure and / or the scanning speed, it is not always necessary to change the contact pressure and / or scanning speed at a constant rate.

  When changing the contact pressure, for example, the evaluation may be started when the contact pressure between the piezoelectric element and the substrate is 0 and gradually increased while the tactile sensor is moved, or at a predetermined contact pressure. The evaluation may be started and gradually decreased while the tactile sensor is moved, and may finally be set to zero. Further, the contact pressure may be increased and then decreased, or vice versa.

  When changing the scanning speed, for example, the tactile sensor may be gradually accelerated from a stopped state (that is, a state where the scanning speed is 0), or may be gradually reduced from a predetermined scanning speed, You may stop at the end. In addition, after increasing the scanning speed, it may be decreased or vice versa.

  The contact pressure and / or scanning speed can be appropriately selected according to the substrate to be evaluated, the use of the substrate, and the like.

  Preferably, contact pressure and scanning speed close to actual use are selected. For example, when the base material is for a touch panel of a smartphone, the contact pressure and the scanning speed corresponding to the contact pressure and speed of the finger and the touch panel at the time of operations such as flick, swipe, pinch, and scrub can be selected.

  As described above, the piezoelectric element generates an output signal corresponding to the change in its pressure sensitivity by moving the surface of the substrate relative to the substrate surface while making the piezoelectric element contact the substrate surface. To do. From the characteristics of the output signal obtained (for example, waveform, intensity, peak position, etc.), or from the result of arithmetic processing of the obtained output signal by a signal processing unit (for example, a computer, etc.) Can be evaluated.

  From the result of the arithmetic processing, the average of the absolute value of the output signal, the dispersion of the output signal, the power spectrum of the medium frequency component with respect to the medium frequency component (eg, 100 to 500 Hz) and the high frequency component (eg, 500 to 2000 Hz) of the output signal. The distribution ratio and the sum of frequency components in a specific frequency band, for example, a frequency band (10 to 150 Hz) corresponding to the reaction area of the Meissner body or a frequency band (150 to 500 Hz) corresponding to the reaction area of the Patini body Can be obtained.

［式中、
Ｉは絶対値の平均を表し、
Ｎはサンプリング数を表し、
Ｖは測定値（電圧）を表す。］
により求められる。 The average of the absolute values is the following formula:

[Where:
I represents the average of absolute values,
N represents the number of samples,
V represents a measured value (voltage). ]
Is required.

［式中、
Ｖ_ａはサンプリングされた出力信号の分散を表し、
Ｎサンプリング数を表し、
Ｖは測定値（電圧）を表し、

により求められる。 The variance of the sampled output signal is:

[Where:
V _a represents the variance of the sampled output signal,
N represents the number of samplings,
V represents the measured value (voltage),

Is required.

［式中、Ｒ_Ｓは、出力信号の中周波数成分および高周波数成分に対する中周波数成分のパワースペクトル分布比を表し、
Ｐ（ｆ）は出力信号のパワースペクトル密度を表し、
ｆ_１は、中周波数成分の下限の周波数を表し、
ｆ_２は、中周波数成分の上限および高周波数成分の下限の周波数を表し、
ｆ_３は、高周波数成分の上限の周波数成分を表す。］
により求められる。例えば、この式において、ｆ_１を１００Ｈｚ、ｆ_２を５００Ｈｚ、ｆ_３を２０００Ｈｚとすることにより、測定周波数領域の中および高周波数成分（１００〜２０００Ｈｚ）の積分値に対する中周波数成分（１００〜５００Ｈｚ）の積分値の比Ｒ_Ｓが求められる。 The power spectrum distribution ratio of the medium frequency component to the medium frequency component and high frequency component of the output signal is given by the following formula:

[Wherein R _S represents the power spectrum distribution ratio of the medium frequency component to the medium frequency component and the high frequency component of the output signal,
P (f) represents the power spectral density of the output signal,
f ₁ represents the lower limit frequency of the medium frequency component,
f ₂ represents the upper limit frequency of the medium frequency component and the lower limit frequency of the high frequency component,
f ₃ represents the upper limit of the frequency components in the high frequency components. ]
Is required. For example, in this equation, f _{1 is set} to 100 Hz, f _{2 is set} to 500 Hz, and f _{3 is set} to 2000 Hz, so that the medium frequency component (100 to 500 Hz) with respect to the integration value of the middle and high frequency components (100 to 2000 Hz) in the measurement frequency region. the ratio R _S of the integrated value of) can be obtained.

The characteristics of these I, R _S and V _a , and the output signal can be used as an index indicating the tactile sensation of the substrate using only one, or using any two or three or more.

  The substrate evaluated according to the present invention has a smooth surface (smooth surface), and preferably at least a part of the smooth surface is hard.

  In this specification, the “smooth surface” means a surface having a surface roughness Ra of 100 μm or less. Here, the surface roughness Ra means the arithmetic average roughness Ra, and is measured in accordance with JIS B0601.

  “Hard” means a substrate having a flexural modulus of 100 MPa or more. Here, the flexural modulus is measured according to JIS K-7171.

  Although the base material which can be used in this invention is not specifically limited, For example, it is comprised from building materials, such as glass, sapphire glass, resin, a metal, ceramics, a semiconductor, wood, ceramics, a stone material, etc. Preferably, the substrate is made of glass, resin, metal or ceramic.

  Examples of the glass include, but are not limited to, soda lime glass, alkali aluminosilicate glass, borosilicate glass, alkali-free glass, crystal glass, and quartz glass, and these may be chemically strengthened.

  Although it does not specifically limit as said resin, For example, natural or synthetic resin and a general plastic material may be sufficient, for example, an acrylic resin and a polycarbonate are mentioned.

  Although it does not specifically limit as said metal, For example, metal, such as aluminum, copper, and iron, or composites, such as an alloy, are mentioned.

  Although it does not specifically limit as said semiconductor, A silicon semiconductor, a germanium semiconductor, etc. are mentioned.

  The shape of the substrate is not particularly limited as long as it has a smooth surface and can be touched by hand (or finger). For example, a plate shape, a film shape, a sheet shape, a spherical shape, The shape may be a rod shape, a cylindrical shape, a conical shape, a polygonal column shape, a polygonal pyramid shape, a dome shape, or any combination thereof. The smooth surface of the substrate is preferably a flat surface, but may be a curved surface. In the case of a curved surface, the radius of curvature is preferably 3 mm or more, more preferably 10 mm or more, and further preferably 5 cm or more. In this case, the evaluation can be performed by moving the tactile sensor along the curved surface or by deforming the tactile sensor into the same shape as the curved surface.

  The said base material may be used for the various articles | goods which a human may touch. For example, the article is not particularly limited, but includes various electronic or electrical equipment, building materials, furniture, tableware, stationery, automobile parts, optical members, packaging (for example, food packaging bags), medical instruments, and the like. . In particular, the smooth surface of the substrate constitutes the surface of these articles, preferably the smooth surface of the substrate is the surface of an electronic or electrical device, such as the surface of an electronic or electrical device housing, or the display surface and It may be an operation surface. More preferably, the smooth surface of the substrate may be an operation surface of a touch panel of a portable information terminal such as a mobile phone, a smartphone, or a tablet personal computer, or other electronic or electric equipment.

In one aspect, the smooth surface of the substrate may be surface treated. For example, the smooth surface of the base material may have various layers on the smooth surface. Examples of such a layer include an antifouling layer, an antireflection layer, an antiglare layer, a hard coat layer, a DLC (Diamond-Like Carbon) layer, and other SiO ₂ layers.

  In one embodiment, the smooth surface of the substrate may be treated with a surface treatment agent. According to the method of the present invention, the tactile sensation of the substrate whose surface has been treated in this way can also be evaluated, so that it can be used for evaluating the performance of the surface treatment agent.

  In one embodiment, the surface treatment agent includes a fluorine-based compound, for example, a perfluoroalkyl group-containing compound or a perfluoropolyether group-containing compound, preferably a perfluoropolyether group-containing compound.

  Examples of the perfluoropolyether group-containing compound include a compound having a perfluoropolyether group and a curable site (for example, an acrylate group), a Si having a perfluoropolyether group and a hydrolyzable group (for example, an alkoxy group). Examples thereof include compounds having an atom. Surface treatment agents containing such a perfluoropolyether group-containing compound are known, and are described, for example, in WO 97/07155, WO 2003/002628, and the like.

The following three types of glass plates (samples A to C) were used as samples (base materials).
・ Sample A
Untreated chemically tempered glass (Corning, “Gorilla” glass, thickness 0.7 mm)

・ Sample B
Chemically strengthened glass (manufactured by Corning, "Gorilla" glass, thickness 0.7 mm) the surface _{of, F- (CF 2 CF 2 CF} 2 O) n - silane-modified compound having a perfluoropolyether group represented by Treated with a surface treatment containing

・ Sample C
The surface of chemically strengthened glass (Corning, “Gorilla” glass, thickness 0.7 mm) is CF ₂ O— (CF ₂ CF ₂ CF ₂ CF ₂ O) _a — (CF ₂ CF ₂ CF ₂ O) _{b - (CF 2 CF 2 O)} c - (CF 2 O) d - with those treated with a surface treating agent containing a silane-modified compound having a perfluoropolyether group represented.
In the formula, the order of presence of (CF ₂ CF ₂ CF ₂ CF ₂ O), (CF ₂ CF ₂ CF ₂ O), (CF ₂ CF ₂ O) and (CF ₂ O) is arbitrary.

The treatment with the surface treatment agent was performed as follows.
A surface treatment composition containing the above compound was deposited on the surface of the chemically strengthened glass using a commercially available vacuum deposition apparatus.

Comparative Example 1
Measurement of Dynamic Friction Coefficient About the above samples A to C, using a surface property measuring machine ("Tribogear TYPE: 14FW", manufactured by Shinto Kagaku Co., Ltd.), the contact area between the friction element and the substrate surface is 1 cm ² (1 cm × 1 cm). ) The coefficient of dynamic friction (−) under the conditions of 4 cm ² (2 cm × 2 cm), 9 cm ² (3 cm × 3 cm) and 25 cm ² (5 cm × 5 cm), a contact force of 2 N, and a scanning speed of 3.3 and 8.3 mm / s. ) Was measured. The obtained dynamic friction coefficients are shown in the following Table 1 and FIGS.

  As shown in Table 1, FIG. 3, and FIG. 4, the coefficient of dynamic friction was larger in the order of sample A, sample B, and sample C. This tendency was not changed even when the contact pressure and the scanning speed were changed. That is, in the evaluation by the conventional dynamic friction coefficient, it was shown that the slipperiness was higher in the order of Sample C, Sample B, and Sample A, but other information could not be obtained.

Example 1
Using the apparatus shown in FIGS. 1 and 2, the output (voltage) was measured under the following conditions, and the surfaces of the samples A to C were evaluated. As the piezoelectric element, polyvinylidene fluoride showing a response characteristic similar to that of the patinny body was used.

Condition Contact force: 0.2N, 0.4N, 1N
Scanning speed: 50 mm / s, 75 mm / s
Scanning distance: 50mm
Sampling frequency: 5 kHz

The evaluation results of Samples A to C under each condition are shown in FIGS.
Figure 5: Scanning speed 50mm / s, contact force 0.2N
Figure 6: Scanning speed 50mm / s, contact force 0.4N
Figure 7: Scanning speed 50mm / s, contact force 1N
Figure 8: Scanning speed 75mm / s, contact force 0.2N
Figure 9: Scanning speed 75mm / s, contact force 0.4N
Figure 10: Scanning speed 75mm / s, contact force 1N

As shown in FIGS. 5 to 10, the following characteristics were observed with respect to the output signal.
When the scanning speed was constant (50 mm / s or 75 mm / s), the sensor output behavior with the increase in contact force (0.2 N, 0.4 N, 1.0 N) showed the following characteristics.
In sample A, the output increased as the contact force increased.
In Sample B, the output was the smallest when the contact force was 0.4 N.
In sample C, the output decreased as the contact force increased.
The above features were the same regardless of the scanning speed.

-When the contact force was constant (0.2N, 0.4N, or 1.0N), the magnitude relationship of the sensor output behavior between samples showed the following characteristics.
When the contact force was 1.0 N, the output of the sample A was the largest and decreased in the order of B and C.
When the contact force was 0.4 N or less, the output of sample A was larger than that of B and C, but the output of B and C was similar.
Further, in sample A, a large increase / decrease in output was observed immediately after the start of scanning with a contact force of 0.4 N or more, and the fluctuation increased as the contact force increased.
In Samples A and B, a large increase / decrease in output was observed just before stopping at a contact force of 1.0 N.
The above features were seen almost the same regardless of the scanning speed, but were remarkably confirmed at 50 mm / s.

［式中、
Ｖ_ａはサンプリングされた出力信号の分散を表し、
Ｎサンプリング数を表し、
Ｖは測定値（電圧）を表し、

Example 2
Measurement of Dispersion Value Each sample was measured five times in the same manner as in Example 1, and the dispersion value was obtained from the following formula. The results at a scanning speed of 50 mm / s are shown in FIG. 11, and the results at a scanning speed of 75 mm / s are shown in FIG.

[Where:
V _a represents the variance of the sampled output signal,
N represents the number of samplings,
V represents the measured value (voltage),

As shown in FIG. 11 and FIG. 12, the following characteristics were observed regarding the dispersion value.
When the scanning speed was constant (50 mm / s or 75 mm / s), the dispersion value showed the following characteristics as the contact force (0.2N, 0.4N, 1.0N) increased.
In sample A, the dispersion value increased as the contact force increased.
In sample B, the dispersion value was the smallest when the contact force was 0.4 N.
In sample C, the dispersion value decreased as the contact force increased.
In Samples A and B, the dispersion value significantly increased with a change from 0.4 N to 1.0 N, while in Sample C, there was no significant difference in the dispersion value depending on the contact force.
The above-mentioned characteristics were almost the same regardless of the scanning speed, but were remarkably confirmed at 75 mm / s.

-When the contact force was constant (0.2N, 0.4N, or 1.0N), the magnitude relationship of the sensor output behavior between samples showed the following characteristics.
In the case of a contact force of 1.0 N, the output of sample A was the largest and decreased in the order of B and C.
When the contact force was 0.4 N or less, the output of the sample A was larger than those of the samples B and C, but B and C were comparable.
The above features were seen almost the same regardless of the scanning speed, but were remarkably confirmed at 75 mm / s.

［式中、Ｐ（ｆ）は出力信号のパワースペクトル密度を表し、
ｆ_１は１００Ｈｚであり、
ｆ_２は５００Ｈｚであり、
ｆ_３は２０００Ｈｚである。］ Example 3
Measurement of R _s Value In the same manner as in Example 1, each sample was measured five times, and the R _s value was determined from the following formula. The results at a scanning speed of 50 mm / s are shown in FIG. 13, and the results at a scanning speed of 75 mm / s are shown in FIG.

[Where P (f) represents the power spectral density of the output signal,
f ₁ is 100 Hz,
f ₂ is a 500Hz,
f ₃ is a 2000Hz. ]

As shown in FIG. 13 and FIG. 14, the following characteristics were observed regarding the R _s value.
When the scanning speed was constant (50 mm / s or 75 mm / s), the Rs value exhibited the following characteristics as the contact force (0.2N, 0.4N, 1.0N) increased.
In sample A, the Rs value increased as the contact force increased.
Sample B had the smallest Rs value when the contact force was 0.4 N.
Sample C had a smaller Rs value as the contact force increased.

-When the contact force was the same (0.2N, 0.4N, or 1.0N), the magnitude relationship of Rs values between samples showed the following characteristics.
When the contact force is 1.0 N, the sample C has a smaller Rs value than the samples A and B.
When the contact force is 0.4 N, the sample B has a smaller Rs value than the samples A and C.
When the contact force is 0.2 N, the sample C has a slightly larger Rs value than the samples A and B.
The above features were seen almost the same regardless of the scanning speed, but were remarkably confirmed at 50 mm / s.

Example 4
The sensor output behavior obtained in Example 1 was analyzed for examining the frequency component distribution in detail. The frequency distribution was divided into a low frequency band of 10 to 150 Hz and a high frequency band of 150 to 500 Hz, and the sum of each band was obtained. The results at a scanning speed of 50 mm / s are shown in FIG. 15, and the results at a scanning speed of 75 mm / s are shown in FIG.

As shown in FIGS. 15 and 16, the following features were observed with respect to FFTsum _10-150 and FFTsum _150-500 .
-The sum total of low frequencies (FFT (10-150)) became large as the contact force became large also in any sample AC. This feature was seen similarly regardless of the scanning speed.
-On the other hand, the following features were observed for the sum of high frequencies (FFT (150-500)).
Regarding sample A, the contact force increased as the contact force increased at the scanning speed of 50 mm / s. However, at the scanning speed of 75 mm / s, the contact force decreased as the contact force increased from 0.2 N to 0.4 N, and the contact force decreased to 1 N. Then it was the largest value.
For sample B, regardless of the scanning speed, the contact force decreased from 0.2N to 0.4N, and the maximum value was obtained when the contact force was 1N.
For sample C, it became smaller as the contact force increased, regardless of the scanning speed.

  As shown in the comparative example, in the conventional evaluation based on the dynamic friction coefficient, although information on slipperiness was obtained, information on other characteristics could not be obtained. On the other hand, in the method of the present invention, data having characteristics different from the dynamic friction coefficient data can be acquired. In particular, the characteristics can be changed variously by changing the scanning speed and / or the contact pressure. It was found. Therefore, it is considered that evaluation of tactile sensations other than slipperiness becomes possible by making these features correspond to tactile sensations when a person touches the substrate surface.

  The present invention can be used to evaluate the feel of the surface of various substrates.

10 ... Apparatus 12 ... Sample (base material)
DESCRIPTION OF SYMBOLS 14 ... Sample fixing stand 16 ... Z-axis stage 18 ... X-axis slider 20 ... Cantilever 22 ... Strain gauge 24 ... Tactile sensor 26 ... Base material 28 ... Piezoelectric element

Claims (15)

  A method for evaluating the tactile sensation of a smooth surface of a substrate, wherein the piezoelectric element is moved relative to the surface of the substrate while contacting the smooth surface of the substrate, and output from the piezoelectric element A method comprising obtaining a signal.   Furthermore, the obtained output signal is processed by the signal processing unit, the average of the absolute value of the output signal, the dispersion of the output signal, the power spectrum distribution ratio of the medium frequency component to the medium and high frequency components of the output signal, and a specific frequency The method of claim 1, comprising obtaining at least one of a sum of frequency components of bands. The method according to claim 1, wherein the contact pressure between the piezoelectric element and the substrate is in the range of 0.01 to 50 N / cm ² .   The method according to claim 1, wherein the moving speed of the piezoelectric element relative to the substrate is in the range of 5 to 1,000 mm / s.   The method according to claim 1, wherein the contact pressure between the piezoelectric element and the substrate and / or the moving speed of the piezoelectric element relative to the substrate is constant.   The method according to claim 1, wherein the contact pressure between the piezoelectric element and the substrate and / or the moving speed of the piezoelectric element relative to the substrate is changed.   The method according to claim 1, wherein the piezoelectric element is moved relative to the substrate surface on the substrate surface and then stopped.   The method according to claim 1, wherein the substrate is used as an element constituting an electronic or electric device.   The method according to claim 8, wherein the element constituting the electronic or electric device is a housing.   The method according to claim 1, wherein the substrate is used as an element constituting a display surface and / or an operation surface of an electronic or electric device.   The method according to claim 10, wherein the element constituting the display surface and / or the operation surface of the electronic or electric device is a touch panel.   The method according to claim 1, wherein the smooth surface of the substrate is treated with a surface treatment agent.   The method according to claim 12, wherein the surface treatment agent comprises a perfluoropolyether group-containing compound.   The method according to claim 1, wherein the substrate is composed of glass, sapphire glass, resin, metal or ceramic.   The method according to claim 1, wherein the piezoelectric element is composed of polyvinylidene fluoride and an electrode.

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