JP2007040730A - Liquid repellent characteristic evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid repellent characteristic evaluation device capable of measurement of a slip drop angle under dynamic friction which is impossible by a conventional device, in addition to measurement of the slip drop angle under static friction performed by the conventional device. <P>SOLUTION: This liquid repellent characteristic evaluation device, which is a device for evaluating the liquid repellent characteristic of the sample surface, is characterized by being equipped with a syringe for dropping liquid held on an upper part of a pedestal with adjustable height; a sample stage held rotatably around a horizontal rotation axis orthogonal to the liquid dropping direction from the syringe under the syringe on a middle part of the pedestal, for holding the sample in the state where the rotation axis agrees with the sample surface; and a measuring means of a rotation angle of the sample stage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for evaluating liquid repellency characteristics such as water repellency and oil repellency on a sample surface.

  Conventionally, as an apparatus for evaluating liquid repellency characteristics such as water repellency and oil repellency on a sample surface, Non-Patent Document 1, for example, discloses an apparatus for measuring a sliding angle of a droplet attached to a sample surface. This device is originally configured as a contact angle measuring device, but also has a sliding angle measuring function. That is, after the droplet is attached to the horizontally held sample surface, the angle at which the droplet starts to slide when the sample is tilted can be measured as the sliding angle. The syringe for dropping liquid and the sample stage are fixed to an integral frame, and the sample stage is tilted by rotating the frame, so that the syringe is also tilted together. With respect to a test method in which a sample surface is tilted after a droplet is attached to a horizontal sample surface, this apparatus can sufficiently cope with the test method.

  However, the liquid repellency of the sample surface can be evaluated by the above-mentioned apparatus based on the sliding angle of the droplets adhering to the horizontal sample surface under static friction, and under the dynamic friction of the droplets dropped on the inclined sample surface. The sliding angle cannot be evaluated.

  In this apparatus, it is also conceivable to measure the sliding angle under dynamic friction by dropping a liquid from a syringe with the sample surface tilted. However, this measurement causes problems in the following points.

  1) Since the sample surface and the syringe are inclined together as described above, the distance between the lower end of the syringe and the sample surface, that is, the dropping height changes depending on the inclination angle.

  2) Further, since the orifice contour at the lower end of the syringe is inclined with respect to the horizontal, the shape and volume of the droplet appearing downward therefrom are not constant, and the measurement accuracy (reproducibility) is lowered.

  3) Further, when the tilt angle is increased, the liquid droplet dropped from the syringe is detached from the sample surface, so that measurement requiring a large tilt angle cannot be performed.

  Similarly, Patent Document 1 discloses a device that places a droplet on a horizontal sample and continuously inclines at a low speed, stops the inclination when sliding starts, and measures the tilt angle after the stop as the sliding angle. ing. This apparatus also considers only measurement under static friction, and cannot be measured under dynamic friction.

  In addition, Patent Document 2 discloses an apparatus that captures a contact angle of a droplet on a sample surface with a camera and measures the image by computer image processing. The sliding angle cannot be measured with this device.

  As described above, the conventional apparatus can measure the sliding angle under static friction, but cannot measure under dynamic friction.

  Furthermore, in addition to the sliding angle, the liquid repellency is not only the sliding angle but also the sliding speed, the presence / absence of liquid remaining on the sample surface, the influence of airflow, the influence of the sample surface temperature and liquid temperature, but the above-mentioned conventional devices There is no function to evaluate these.

Japanese Utility Model Publication No. 7-26751 JP-A-5-232009 Catalog of Kyowa Interface Science Co., Ltd. ("Drop Master Series" published September 2004)

  The present invention provides a liquid-repellent property evaluation apparatus that enables measurement of sliding angle under dynamic friction, which is impossible with a conventional apparatus, in addition to the sliding angle measurement under static friction performed with a conventional apparatus. The main purpose.

  The present invention further provides a liquid repellency evaluation apparatus capable of evaluating not only the sliding angle measurement but also the sliding speed, the presence or absence of liquid remaining on the sample surface, the influence of airflow, the influence of the sample surface temperature and the liquid temperature. This is an additional purpose.

In order to achieve the above object, according to the present invention, an apparatus for evaluating liquid repellency characteristics of a sample surface,
Syringe for liquid dripping held at the top of the pedestal so that the height can be adjusted,
A sample stage that is held below the syringe in the middle of the gantry so as to be rotatable around a horizontal rotation axis that is orthogonal to the direction of liquid dripping from the syringe, and that holds the sample by aligning the rotation axis with the sample surface; Means for measuring the rotation angle of the sample stage,
An apparatus for evaluating liquid repellency characteristics is provided.

  As a main effect of the apparatus of the present invention, since the dropping direction is orthogonal to the rotation axis that coincides with the sample surface, the distance between the sample surface and the lower end of the dropping syringe, that is, the dropping height is always used regardless of the tilt angle of the sample due to rotation Since the drop position on the sample surface is always kept constant, the sliding angle under dynamic friction can be stably measured with high accuracy.

  Of course, the apparatus of the present invention can also measure the sliding angle under static friction. What is necessary is just to measure a rotation angle at the time of starting a sliding as a sliding angle, after rotating a sample stage continuously after dropping and mounting a droplet on the horizontal sample surface.

  Additional effects of the present invention will be described in the following embodiments.

  FIG. 1 shows an example of a liquid repellent property evaluation apparatus according to a preferred embodiment of the present invention. 1 (1) is a front view, and FIG. 1 (2) is a side view.

  In the illustrated liquid repellent property evaluation apparatus 100, a syringe 12 for dropping liquid is held on an upper portion of a gantry 10 so that the height can be adjusted. The syringe 12 includes an upper cylinder 12A and a lower narrow tube 12B. In the middle of the gantry 10, below the syringe 12, is held rotatably around a horizontal rotation axis R perpendicular to the liquid dropping direction from the syringe 12, and the sample S is placed with the rotation axis R coincident with the sample surface Z. The sample stage 14 to hold | maintain is provided. Although not shown in the figure, a means for measuring the rotation angle of the sample stage 14 is provided.

  The sample stage 14 is rotated by the drive motor 16 and tilted to an arbitrary angle θ, and can be stopped at that position. The stage tilt angle θ with respect to the horizontal is a rotation angle by the motor 16 and is measured, for example, as an output of a potentiometer linked to the motor 16.

  In order to measure the sliding angle of the droplet on the surface Z of the sample S, the stage 14 is stopped at various inclination angles, and a droplet is dropped from the syringe 12 at each inclination angle to determine the presence or absence of sliding. By repeating this, the sliding angle under dynamic friction is obtained.

  The apparatus 100 further includes a mechanism for measuring the sliding speed V. The basic configuration is shown in FIG. 2A is a perspective view of the inclined sample surface Z as viewed from above the side, and FIG. 2B is a perspective view of the inclined sample surface Z as viewed from below.

  In the measurement symmetry section of the sliding speed V, two positions P1 and P2 are set in advance on the sample stage 14, and the laser beam X from the laser beam emitting / receiving device L is arranged between the mirrors M (illustrated) at the respective positions P1 and P2. In this example, the liquid is reciprocated between a total of three mirrors), and a droplet F is dropped onto the sample surface Z from the syringe 12 above the sample surface Z with the inclination angle θ, and the sample surface Z slides down. The sliding speed V of the droplet F is obtained from each time when the droplet F crosses the laser beam X at each position P1, P2 and the distance d between the positions P1, P2. It should be noted that the trigger can be set so that the timing device automatically starts and stops when the droplet F crosses the laser beam X at the positions P1 and P2.

  The apparatus 100 of FIG. 1 further includes a CCD camera 18 and can determine whether or not liquid remains on the locus of the droplet F sliding down the sample surface Z.

  The rotation axis R by the drive motor 16 for inclining the sample S is horizontal and within the sample surface Z, and is orthogonal to the droplet dropping direction (vertical direction) from the syringe 12. Therefore, since the dropping position of the droplet from the syringe 12 is always on this orthogonal point on the sample surface Z, the lower end of the syringe 12 (lower end of the narrow tube 12B) and the orthogonal point on the sample surface Z even if the sample surface Z is inclined. That is, the drop distance is always constant, and the drop velocity is always kept constant. As a result, the sliding angle θ, sliding speed V, and liquid residual Y / N under dynamic friction can be measured with high accuracy and good reproducibility.

  Of course, the apparatus 100 of the present invention can measure under static friction with the tip of the syringe 12 close to the sample surface Z and the drop distance 0, that is, the drop speed 0.

  The observation results of the sliding angle θ, the sliding speed V, and the liquid remaining Y / N described above are processed by the arithmetic processing unit CP and then output to the display / recording devices D1, D2, and D3, respectively.

  Examples in which various measurements are performed using the liquid repellent property evaluation apparatus 100 of the present invention will be described below. In each embodiment, additional improvements are made.

[Example 1]
In FIG. 3, the lower end part of the thin tube 12B which comprises the lower part of the syringe 12 is shown. Liquid is dropped from the upper cylinder 12A (FIG. 1) through a conduit 12P that penetrates the center of the narrow tube 12B. The illustrated thin tube 12B has a tapered shape T having a tapered lower end.

  When the surface tension of the liquid is smaller than the material of the main body 12BO of the thin tube 12B, the liquid emerging from the lower end opening of the conduit 12P may crawl up along the outer periphery of the thin tube 12B, and the dripping amount is not stable.

  The taper shape T in FIG. 3 is a preventive measure. Since the adhesion force due to the surface tension increases as the adhesion area increases, the taper shape T reduces the surface area of the lower end, thereby reducing the adhesion force causing the scooping up.

  In the example of FIG. 3A, the tapered shape T is used, and the region 12BS near the lower end of the narrow tube 12B including the tapered portion T is further roughened by shot blasting to reduce the surface tension.

  In the example of FIG. 3B, the low surface tension layer 12BX is further coated on the shot blast layer 12BS. A typical material of the thin tube main body 12BO is stainless steel or the like, while the low surface tension layer 12BX is formed of alumina or the like. The formation of the alumina layer 12BX can be performed by plasma spraying or the like.

  By using the narrow tube 12B that reduces the adhesion of the liquid droplets in this way and suppresses the liquid droplets from rising, it is possible to precisely control a small amount of liquid droplets without variation, so that the sliding angle and sliding speed can be accurately determined. Can be measured.

  Thus, the amount of dripping was measured when the tip of the thin tube was tapered T, when the tapered shape T was further modified by surface coating with alumina coating, and when the normal shape was normal. The taper angle was 6 degrees and the shot particle size was 1.2 mm. Light oil was used as the liquid. The capacity of the cylinder 12A of the microsyringe 12 was 50 μl. The ambient temperature including the measurement system was 25 ° C.

  FIG. 4 summarizes the above measurement results.

  As is apparent from the figure, the drop amount was 8 μl in the case of the non-treated normal shape, whereas the drop amount was reduced by half to 4 μl in the case of the taper shape (surface shot blasting). In the case where surface modification was applied, the amount dropped was reduced to 3.5 μl. From this result, it is considered that the scooping up of the light oil to the outer periphery of the thin tube can be substantially suppressed by the taper shape (surface shot blasting process), and further the scooping up suppression is achieved almost completely by applying the alumina coating.

[Example 2]
FIG. 5 shows only the sample stage 14 of the liquid repellent property evaluation apparatus 100. The sample stage 14 holds the sample S with the measurement target surface Z facing upward, and the sample S can be heated and held at a predetermined temperature by a built-in heater 14H.

  In general, the surface tension of a liquid decreases as the temperature increases. Therefore, as the temperature rises, the sliding angle decreases and the sliding speed increases. The temperature of the liquid is affected by the temperature of the sample S to which it is attached. Particularly, since a small droplet has almost the same temperature as the sample immediately after the attachment, the liquid repellency of the sample S is strongly influenced by the temperature.

  By using the heater built-in stage 14 according to the present embodiment, the temperature dependence of the liquid repellency of the sample surface Z is obtained when the temperature of the sample S is changed variously and the liquid adhering to the sample surface Z becomes a corresponding temperature. Sex can be evaluated.

  The sample stage 14 with a built-in heater shown in FIG. 5 was attached to the liquid repellent property evaluation apparatus 100 shown in FIG. 1, and the sliding speed was measured by changing the sample temperature in various ways. The measurement conditions were as follows.

<Sliding speed measurement conditions>
Liquid: Light oil Drop volume: 5 μl
Dropping distance (distance between thin tube lower end and sample surface Z): 10 mm
Sliding speed measurement distance (d): 10 mm
Ambient temperature during measurement: 25 ° C
Sample tilt angle: 60 ° (constant)
Measurement position: 5 points along the rotation axis R passing through the center of the sample surface Z (see FIG. 6).

  The measurement results are shown in FIG. The sliding speed of the five measurement positions (A, B, C, D, E) significantly increases as the temperature of the sample surface Z increases.

Example 3
FIG. 8 shows only the liquid dropping syringe 12 of the liquid repellent property evaluation apparatus 100. The main part of the syringe 12 includes an upper cylinder 12A and a lower capillary 12B, and the liquid stored in the cylinder 12A is ejected from the lower end of the capillary 12B by sliding of the piston 12P.

  In the illustrated syringe 12, the entire outer periphery including the cylinder 12 </ b> A to the thin tube 12 </ b> B is covered with a membrane heater 20, and the outside is further covered with a heat insulating layer 22. The film heater 20 is formed, for example, by laminating a nichrome thin film with a heat-resistant film (for example, a polyimide film) to form a film, and can heat the syringe 12 over its entire length. The heat insulation layer 22 is a molded body mainly made of alumina / silica, for example.

  Although not shown, since the thin tube 12B is typically made of stainless steel and has low thermal conductivity, aluminum with high thermal conductivity is deposited on the outer peripheral surface to increase the heating efficiency of the film heater 20.

  In the second embodiment, the sample stage 14 including the heater 14H is used to evaluate the liquid repellency when the temperature of the sample S changes variously. However, if the syringe 12 of this embodiment is used, the liquid itself to be dripped is used. It is possible to evaluate the liquid repellency when the temperature changes variously.

  The heater built-in syringe 12 of FIG. 8 was attached to the liquid repellent property evaluation apparatus 100 of FIG. 1, and the sliding angle was measured by changing the liquid temperature in various ways.

  The sliding angle was measured under the following conditions and procedures.

<Sliding angle measurement conditions>
Liquid: Light oil Drop volume: 4 μl
Dropping distance (distance from the lower end of the thin tube to the sample surface): 10 mm
<Measurement procedure of sliding angle>
The sample stage 14 was tilted to the maximum possible tilt angle of 60 ° of the liquid repellent property evaluation apparatus 100 used, and it was confirmed that a droplet was dropped from the syringe 12 and slid down.

  Next, the stage tilt angle θ is slightly reduced, the liquid is dropped, the tilt angle is gradually decreased or gradually increased depending on the presence or absence of sliding, and the same operation is repeated, and the angle at which the sliding starts is determined as the sliding angle.

  FIG. 9 (1) shows the measurement result of the sliding angle. It can be seen that the sliding angle monotonously decreases as the liquid temperature increases.

  FIG. 9 (2) shows the measurement results of kinematic viscosity at various temperatures of the same light oil. The kinematic viscosity was measured by the falling body method, and the container to be dropped was placed in a thermostatic bath. It can be seen that the kinematic viscosity decreases monotonically as the liquid temperature increases.

  It can be seen that the temperature dependence of the sliding angle shown in FIG. 9 (1) has a clear correlation with the temperature dependence of the kinematic viscosity shown in FIG. 9 (2).

Example 4
FIG. 10 shows an example of a liquid repellency evaluation apparatus according to another preferred embodiment of the present invention.

  The illustrated liquid repellent property evaluation apparatus 200 includes a blower system 24 that supplies an airflow W to the surface of the sample S on the sample stage 14. The blower system 24 guides a stable gas G such as air, nitrogen, and argon supplied from the right end through the flow rate adjusting valve 26 to the wind tunnel 30 through the pipe 28 to the sample surface Z as an air flow W from the wind tunnel 30. Spray in parallel. The flow rate of the air flow W is finely adjusted by the flow rate adjustment valve 26, and the flow rate is controlled in advance within a certain range by a gas supply system (not shown) arranged upstream of the flow rate adjustment valve 26.

  By using this air blowing system 24, the airflow W is blown to the droplet F that is on the sample surface Z and does not slide down to forcibly start sliding, thereby evaluating various factors that cancel the liquid repellency. The peel flow rate can be measured as an important parameter.

  Further, depending on the use environment, an airflow such as wind may act on the droplets F on the sample S, and it is important to evaluate the influence of the airflow on the liquid repellency characteristics.

  Using the wind tunnel 30 shown in FIG. 11, the airflow velocity when the droplets started moving when the airflow velocity was changed in various ways was measured. For measurement of the flow velocity of the air flow W, a measurement unit in which heat rays are arranged on the downstream side of the air flow with respect to the sample surface Z can be used.

  FIG. 11 (1) shows the specifications of the wind tunnel 30 used. The cone angle is 15 ° in order to prevent drift, and a rectifying plate 32 is arranged at the tip of the wind tunnel.

  As shown in FIG. 11 (2), the airflow W blown from the wind tunnel 30 has a uniform flow velocity distribution.

  Using this air blowing system 24, the sliding speed was measured when stationary liquid droplets started moving when the air flow velocity was varied. The measurement conditions were as follows.

<Measurement conditions>
Liquid: Light oil Measurement ambient temperature: 25 ° C
Airflow velocity: Air flow velocity obtained with a hot wire anemometer Sliding angle: 180 °
As shown in FIG. 12 (1), a droplet F0 is placed on the surface of a sample S coated with an oil repellent coating C on the surface, and the airflow W from the wind tunnel 30 (FIG. 11) is applied to the stationary droplet F0. When the droplet F0 was sprayed and moved as indicated by F1, the air flow velocity at the start of movement was obtained.

  As shown in FIG. 12 (2), it can be seen that as the air flow velocity increases, the sliding speed of the droplets that start moving increases accordingly. In this way, the peeling flow rate is obtained as a parameter for canceling the oil repellent coating and the surface tension of the sample surface, the intermolecular attractive force generated between them, and the viscosity of the dropped liquid as parameters relating to sliding.

  According to the present invention, in addition to the sliding angle measurement under static friction performed by the conventional apparatus, the liquid repellency characteristic evaluation apparatus that enables measurement of the sliding angle under dynamic friction, which is impossible with the conventional apparatus. Provided. In addition to measuring the sliding angle, the present invention also provides a liquid repellency evaluation apparatus capable of evaluating the sliding speed, the presence or absence of liquid on the sample surface, the influence of airflow, the influence of the sample surface temperature and the liquid temperature. Is done.

It is (1) front view and (2) side view which show the structure of the liquid-repellent property evaluation apparatus by desirable one Embodiment of this invention. It is a perspective view which shows the mechanism which measures sliding speed by this invention. It is sectional drawing which shows the example which made the tip of the thin tube of the syringe lower part for liquid dripping into a taper by this invention, and gave the example of (1) shot blasting, and (2) the alumina coating after shot blasting. It is a graph which shows the liquid dripping amount at the time of using the thin tube shown in FIG. 3 compared with the normal case. It is sectional drawing which shows the sample stage provided with the built-in heater by this invention. It is a top view which shows the position where a liquid is repeatedly dripped at the sample surface by this invention. It is a graph which shows the measurement result of the sliding speed when changing sample temperature variously using the heater built-in sample stage of FIG. It is sectional drawing which shows the syringe provided with the built-in heater by this invention. It is a graph which respectively shows the measurement result of (1) sliding angle and (2) corresponding kinematic viscosity when liquid temperature is changed variously using the heater built-in syringe of FIG. It is a front view which shows the liquid-repellent property evaluation apparatus provided with the ventilation system by this invention. It is a graph which shows the airflow velocity distribution of (1) a wind tunnel used for the ventilation system of FIG. 10, and (2) the exit of a wind tunnel. (1) Cross-sectional view schematically showing the movement of a droplet and (2) measured airflow velocity and sliding velocity in an experiment for forcibly sliding a stationary droplet on a sample using the air blowing system shown in FIGS. It is a graph which shows the relationship.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Liquid repellency characteristic evaluation apparatus 10 Base 12 Syringe for liquid dropping 12A Cylinder 12B Narrow tube 12BS Shot blast processing layer of 12 tubule 12 Alumina layer on shot blast processing layer of 12BX narrow tube 12P Piston of syringe 12 14 Stage 14H Stage 14 Built-in Heater 16 Drive motor 18 CCD camera 20 Membrane heater 22 Heat insulation layer 24 Blower system 26 Flow control valve 28 Pipe 30 Wind tunnel 32 Rectification plate R Rotating shaft S Sample Z Sample surface θ Stage inclination angle V Sliding speed P1, P2 For sliding speed measurement 2 Position d Distance between P1 and P2 L Laser beam light emitting / receiving device X Laser beam M Mirror F Droplet D1, D2, D3 Display / Recording device

Claims (6)

An apparatus for evaluating the liquid repellency of the sample surface,
Syringe for liquid dripping held at the top of the pedestal so that the height can be adjusted,
A sample stage that is held below the syringe in the middle of the gantry so as to be rotatable around a horizontal rotation axis that is orthogonal to the direction of liquid dripping from the syringe, and that holds the sample by aligning the rotation axis with the sample surface; Means for measuring the rotation angle of the sample stage,
An apparatus for evaluating liquid repellency, comprising: In claim 1,
A sliding speed measuring means for detecting the position of a droplet sliding down the sample surface inclined by the rotation of the sample stage at two positions and measuring the sliding speed;
An apparatus for evaluating liquid repellency, further comprising: In claim 1 or 2,
Means for detecting the liquid remaining on the sliding track of the sample surface after the liquid droplet has slipped,
An apparatus for evaluating liquid repellency, further comprising: In any one of Claim 1 to 3,
An apparatus for evaluating liquid repellency, wherein the sample stage includes a heater for holding the sample at various temperatures. In any one of Claims 1-4,
An apparatus for evaluating liquid repellency, wherein the liquid dropping syringe includes a heater for holding the liquid contained therein at various temperatures. In any one of Claim 1-5,
Means for spraying a gas stream at various flow rates onto the droplets stationary on the sample surface;
And a liquid repellent property evaluation apparatus.

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