JP2003270117A - Method and apparatus for measuring dynamic contact angle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a versatile measuring method and a versatile measuring instrument capable of measuring a dynamic contact angle, as to all the solid samples and all the liquid samples. <P>SOLUTION: The liquid sample is pushed out on a surface of the solid sample 1 arranged horizontally, from a needle like tube body 11 arranged vertically in an upper side of the solid sample 1, a liquid drop 2 is formed thereby, and a contact angle θ1 is measured between the solid sample 1 and the liquid drop 2 in an advancing directional front side of the solid sample 1, while moving the solid sample 1, under the condition where a tip of the needle like tube body 11 is inserted into the liquid drop 2, so as to obtain a retreat contact angle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring a dynamic contact angle between a liquid and a solid.

[0002]

2. Description of the Related Art The dynamic contact angle between a liquid and a solid includes an advancing contact angle and a receding contact angle. Conventionally, as a method for measuring these dynamic contact angles, for example, (1) Wilhelmy method, (2) expansion-contraction method,
(3) The fall method etc. are known.

(1) The Wilhelmy method measures the load in the process of submerging a solid sample in a liquid sample in a sample tank and in the process of pulling up the submerged sample. The measured value and the surface area value of the solid sample are compared with each other. This is a method of obtaining the dynamic contact angle from
The contact angle obtained in the process of sinking a solid sample is the advancing contact angle,
The contact angle obtained in the process of pulling up is the receding contact angle.
However, this measuring method has a problem that a large amount of liquid sample is required and that if the surface of the solid sample is not uniform, proper measurement cannot be performed. Therefore, the dynamic contact angle can be measured by this measuring method only for a solid sample having a uniform surface.

(2) In the expansion / contraction method, a liquid sample is extruded from a tip of an injection needle, a glass capillary tube or the like onto a solid surface at a constant flow rate to form liquid droplets, and contact between the solid surface and the liquid droplets is made. To obtain the advancing contact angle by measuring the angle, and conversely to measure the contact angle between the solid surface and the liquid droplet while drawing the liquid sample forming the liquid droplet from the tip of the injection needle or glass capillary tube. Is a method of obtaining the receding contact angle. However, this measuring method has a disadvantage in that proper measurement cannot be performed when the wettability such that the contact angle between the solid surface and the droplet is 90 ° or more is small.

(3) In the falling method, a droplet is formed on a solid sample, and the solid sample is tilted, or the liquid on the solid sample is made to fall vertically to make contact with the solid sample and the droplet. It measures the angle. The contact angle in the front of the moving direction of the liquid is the advancing contact angle, and the contact angle in the rear is the receding contact angle. However, in this measuring method, depending on the surface state of the solid sample and the physical properties of the liquid droplet, the liquid droplet often does not move even if the solid sample is made vertical, and thus the measurable solid sample and liquid sample are limited.

As described above, there is a disadvantage in any of the dynamic contact angle measuring methods, and there has been a problem that there are limitations on the measurable solid sample and liquid sample. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly versatile measuring method and measuring apparatus capable of measuring a dynamic contact angle for all solid samples and liquid samples.

[0007]

In order to solve the above-mentioned problems, the method for measuring a contact angle according to the present invention has a method in which a contact point is arranged vertically on a surface of a horizontally arranged solid sample. The liquid sample is extruded from the tip of the needle-shaped tube to form a droplet, and while the tip of the needle-shaped tube is inserted into the droplet, the solid sample is moved horizontally while It is characterized in that the contact angle between the solid sample and the droplet is measured in front of or in the rear of the traveling direction of the solid sample.

In the present invention, when measuring the contact angle, the tip of the needle-shaped tubular body 11 is placed in the droplet 2 formed on the surface of the solid sample 1 as illustrated in FIG. 3 (a), for example. The solid sample 1 is moved horizontally in the inserted state. Since the needle-shaped tubular body 11 is inserted in the droplet 2, the interfacial tension between the droplet 2 and the needle-shaped tubular body 11 causes the liquid to move as the solid sample 1 moves, as shown in FIG. The droplet 2 is deformed so as to be dragged by the needle tube 11.

The size of the contact angle between the solid sample 1 and the droplet 2 in the state where the droplet 2 is thus deformed depends on the surface tension of the liquid forming the droplet 2 and the surface of the solid forming the solid sample 1. The dynamic contact angle can be obtained by measuring the contact angle in this state because it depends on the tension, the interfacial tension between the liquid and the solid, the frictional force, the adsorption force, the surface roughness of the solid, and the like. In the present invention, the receding contact angle is obtained from the front contact angle θ1 in the moving direction of the solid sample 1, and the advancing contact angle is obtained from the rear contact angle θ2.

Therefore, according to the measuring method of the present invention, by moving the solid sample in the horizontal direction with the tip of the needle-shaped tube inserted in the droplet on the solid sample, the above-mentioned factors such as surface energy and friction can be obtained. It is possible to measure only the resulting dynamic contact angle without investigating, and it is possible to appropriately measure the dynamic contact angle for all solid and liquid samples.

In the present invention, in particular, the solid sample is moved in the horizontal direction at a constant speed, and the contact angle between the solid sample and the liquid droplet is kept substantially constant. The contact angle is preferable.

In the present invention, when the solid sample is moved at a constant speed, the adhesive force between the droplet and the needle tube and the adhesive force between the droplet and the solid sample are balanced at a certain point of time. Then, even if the solid sample continues to move, the shape of the droplet will be kept constant. FIG. 4 shows an example of the change over time in the contact angle between the solid sample 1 and the droplet 2 when the solid sample 1 is moved at a constant speed. In FIG. 4, the solid line indicates the change over time in the contact angle θ1 in the forward direction of the solid sample 1, and the broken line indicates the change over time in the contact angle θ2 in the forward direction of the solid sample 1. Thus, the front contact angle θ1
Decreases when the solid sample 1 starts to move, and when the solid sample 1 reaches a certain angle, the value is kept constant even if the solid sample 1 moves. The receding contact angle can be obtained by measuring the contact angle θ1 when this is constant. On the other hand, the rear contact angle θ2 increases when the solid sample 1 starts moving,
After reaching a certain angle, the solid sample 1 is kept constant even if it moves. The advancing contact angle can be obtained by measuring the contact angle θ2 when this is constant.

Therefore, according to the measuring method of the present invention,
As described above, it is possible to create a state in which factors such as surface energy, friction, and surface state are in equilibrium, and by measuring the contact angle in this state, the dynamic contact angle can be obtained more appropriately.

In the present invention, when the contact angle between the solid sample and the droplet is measured, the droplet is imaged from the horizontal direction perpendicular to the moving direction of the solid sample, and the obtained image is obtained. It is preferable to process the data based on the tangent method. According to this configuration, the contact angle between the moving solid sample and the droplet that is deformed on the solid sample so as to be dragged by the needle-shaped tube can be accurately measured.

The dynamic contact angle measuring apparatus of the present invention comprises a stage for holding a solid sample horizontally, a driving means for moving the stage in the horizontal direction, and a needle tube vertically arranged above the stage. A body, a liquid supply mechanism for pushing out the liquid sample from the tip of the needle-shaped tube body, and means for measuring the contact angle between the liquid droplets formed on the solid sample and the solid sample. Is characterized by.

According to the measuring apparatus of the present invention, the solid sample is held horizontally on the stage, and the liquid sample is extruded from the tip of the needle tube by the liquid supply mechanism to form droplets on the surface of the solid sample. Furthermore, the solid sample can be moved in the horizontal direction by moving the stage in the horizontal direction while the tip of the needle-shaped tube is inserted in the droplet. Therefore, the dynamic contact angle can be measured by creating an equilibrium state of each of the above factors.

In the apparatus of the present invention, it is preferable that the moving speed of the stage is variable. This is because the stage velocity at which each of the aforementioned factors reaches an equilibrium state differs depending on the type of liquid-solid. With such a configuration, the moving speed of the solid sample can be adjusted to a specific speed at which the shape of the droplet is kept constant even if the solid sample continues to move. By moving the stage at such a specific moving speed, it is possible to create an equilibrium state of each of the above factors,
The dynamic contact angle can be obtained more appropriately by measuring the contact angle in this state.

Further, in the measuring apparatus of the present invention, the measuring means uses the image pickup means for picking up the droplet from the horizontal direction perpendicular to the moving direction of the stage, and the contact angle using the image data from the image pickup means. It is preferable to include a calculating means for obtaining According to this configuration, the contact angle between the moving solid sample and the droplet that is deformed on the solid sample so as to be dragged by the needle-shaped tube can be accurately measured.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
FIG. 1 is a schematic configuration diagram showing an embodiment of a dynamic contact angle measuring device of the present invention. The measuring device 10 of the present embodiment is formed on the stage 12, a needle-shaped tube body 11 arranged above the stage 12, a liquid supply mechanism 13 for pushing out a liquid sample from the tip of the needle-shaped tube body 11, and a stage 12. The measuring means 20 for measuring the contact angle of the formed droplet 2 is roughly configured.

The stage 12 is constructed so that the solid sample 1 can be held horizontally thereon. See stage 1
2 is configured to be movable in at least one direction (X direction) in the horizontal direction and also movable in the vertical direction (Z direction). Therefore, X-axis direction drive means (not shown) and Z-axis are provided. Direction driving means (not shown) is provided. The Z-axis direction driving means is composed of the stage 12 and the needle-shaped tubular body 1.
The distance from the tip of 1 is finely adjustable and controlled by driving a motor. The X-axis direction driving means is configured to be able to adjust the moving speed of the stage 12 in the horizontal direction, and is similarly controlled by driving the motor.

The needle-like tube 11 is used so that a liquid sample of several μm can be pushed out from the tip thereof so as not to drop, and is arranged so that its length direction is vertical. The inner diameter of the needle-shaped tubular body 11 is preferably about 0.1 to 1.2 mm because it is difficult to control the amount of liquid to be pushed out if it is too large. If the outer diameter of the needle-shaped tube body 11 is too large, the liquid sample is attracted to the needle-shaped tube body 11 when the contact angle is measured with the needle-shaped tube body 11 inserted in the droplet 2. Therefore, the thickness is preferably about 0.5 to 1.5 mm. In this embodiment, the needle-shaped tubular body 11 having an inner diameter of 0.8 mm and an outer diameter of 1.0 mm is used.

The material of the surface of the needle-shaped tube body 11 is preferably selected as appropriate according to the physical properties of the droplet 2. That is, depending on the material of the surface of the needle tube 11, the stage 1
The needle-like tubular body 11 on the droplet 2 on the solid sample 1 held on
When the stage 12 is moved in a state where the needle-shaped tube 11 is inserted, the droplet 2 may not be deformed by being dragged by the needle-shaped tube 11, so that the needle-shaped tube 11 is prevented from occurring. Select an appropriate material as. As a guide, when the surface tension of the liquid sample is about 30 mN / m or less, preferably when the surface tension of the liquid sample is 40 N / m or less, the outer surface is made of Teflon (registered trademark). It is preferable to use the needle-shaped tubular body 11 that has been coated. For example, ethanol (surface tension 2
4.05 mN / m) and the liquid sample C (surface tension 30.2 mN / m) used in the examples described later correspond to this case. On the other hand, when the surface tension of the liquid sample is large enough to exceed 30 mN / m, preferably when the surface tension of the liquid sample is larger than 40 N / m, it is preferable to use the needle-shaped tubular body 11 made of stainless steel. For example, water (surface tension 75.7 mN / m) corresponds to this case.

The liquid supply mechanism 13 supplies the liquid sample to the needle-shaped tube body 11 by a predetermined amount set in advance, thereby pushing out the liquid sample by a predetermined amount from the tip of the needle-shaped tube body 11 to form droplets. 2 can be formed.

The measuring means 20 includes a CCD camera (imaging means) 21 for enlarging and imaging the droplet 2 on the solid sample 1 held on the stage 12 and outputting the image data as a signal, and the droplet 2 during imaging. A light source 22 for illuminating, a computer (arithmetic means) 23 for computing image data signals from the CCD camera 21 to obtain a contact angle, and a computer 2.
3 has a monitor 24 connected to it. The CCD camera 21 is arranged so as to image the droplet 2 from a horizontal direction (Y direction) perpendicular to the moving direction (X direction) of the stage 12. Further, reference numeral 15 is a liquid supply mechanism 1.
3 is a control device that controls each operation of liquid supply from 3 to the needle-shaped tubular body 11, movement of the stage 12, and imaging by the CCD camera 21.

Next, an embodiment for measuring the dynamic contact angle by using the apparatus having such a configuration will be described. In this embodiment, the receding contact angle is measured. First, the solid sample 1 whose dynamic contact angle is to be measured is fixed and held on the stage 12, and the liquid sample is set in the liquid supply mechanism 13. Then, as shown in FIG. 2, a predetermined amount of the liquid sample is extruded from the tip of the needle tube 11 arranged above the solid sample 1, and then the stage 12 is moved upward in the Z direction to be extruded. By bringing the solid sample 1 into contact with the liquid sample, droplets 2 are formed on the solid sample 1 as shown in FIG. It is preferable that the amount of the liquid sample extruded from the tip of the needle-shaped tubular body 11 be such that the influence of gravity on the droplet 2 due to its own weight can be ignored. Specifically, it is preferable to set the outer diameter of the droplet 2 formed on the solid sample 1 at the contact surface to be about 3 to 5 mm.

Next, as shown in FIG. 3 (b), while moving the stage 12 in the X direction at a constant speed, the CCD camera 21 images the droplet 2, and from the obtained image data,
Contact angle θ of the droplet 2 in front of the traveling direction of the stage 12
Measure 1. When the stage 12 starts moving, the droplet 2
Is deformed so as to be dragged by the needle-shaped tubular body 11, and the front contact angle θ1 decreases with time as shown by the solid line in FIG. 4, and when the solid sample 1 moves, the contact angle θ1 decreases. θ1
Is constant. Contact angle θ1 when this is constant
The value of is adopted as the receding contact angle. The moving speed of the stage 12 in the X direction is not particularly limited, and the liquid droplet 2 may be moved by the needle-shaped tubular body 1.
After being deformed so as to be dragged to 1, it may be set so as to maintain a constant shape even if the stage 12 moves.
Therefore, the moving speed of the stage 12 is adjusted if necessary. The moving speed of the stage 12 in the X direction is preferably set to, for example, about 1 to 4 mm / sec.

As a method of measuring the contact angle θ1 by the computer 23 using the image data captured by the CCD camera 21, the following tangent method is preferably used.
FIG. 5 is a diagram for explaining in principle the method of measuring the contact angle θ1 in the front of the moving direction by the tangent method. When measuring the receding contact angle, first, as shown in FIG. 5A, in front of the moving direction (X direction) of the stage 12, the first end point of the tip of the droplet 2 (the left end point in the figure). )
L1, a second end point L2 and a third end point L3 selected at preset intervals from the first end point L1 are acquired. Next, as shown in FIG. 5B, assuming that the first to third end points L1, L2, L3 are on the arc of one circle O1, the center M1 of this circle O1 is obtained, End point L1
The tangent line m of the circle O1 at is obtained. Droplet 2 and solid sample 1
The angle formed by the straight line S corresponding to the contact surface with and the calculated tangent line m is the contact angle θ1 in the front in the moving direction. Then, while moving the stage 12, the contact angle θ1 in the front of the moving direction is measured at predetermined intervals with time, and the difference from the immediately preceding measured value is obtained. When the difference from the previous measured value is small and the value of the contact angle θ1 becomes substantially constant, the value of θ1 at this time is adopted as the value of the receding contact angle. For example,
It can be considered that the value of the contact angle θ1 is substantially constant when the difference between the measured values when the contact angle θ1 is continuously measured twice is 5 ° or less.

According to the present embodiment, the receding contact angle is obtained by measuring the contact angle at the tip of the droplet 2 which is deformed so as to be dragged backward on the solid sample 1 which is moving in the horizontal direction. To be Further, in the present embodiment, the solid sample 1 is moved in the horizontal direction at an appropriate constant speed while the tip of the needle tube 11 is inserted into the droplet 2 formed on the solid sample 1. Since the equilibrium state of all factors can be achieved regardless of the surface state and physical properties of the liquid sample 1 and the liquid sample, the receding contact angle can be appropriately measured for all solid samples and liquid samples. For example, even for a solid sample with low surface uniformity, which was difficult to perform appropriate measurement by the conventional Wilhelmy method, a solid sample and a liquid sample with high water repellency, which were difficult to perform appropriate measurement by the conventional expansion and contraction method, were used. The dynamic contact angle can be appropriately measured for the combination, and also for the combination of the solid sample and the liquid sample having high adhesive force, which was difficult to be appropriately measured by the conventional falling method.

In this embodiment, the case where the receding contact angle is obtained by measuring the contact angle θ1 in the front of the moving direction of the stage 12 has been described as an example. Contact angle at
The advancing contact angle can be determined by measuring 2. As shown by the broken line in FIG. 4, the contact angle θ2 at the rear of the moving direction increases with time when the stage 12 starts moving, and when the solid sample 1 moves, the contact angle θ2 is constant. Therefore, the value of the contact angle θ2 when this is constant is adopted as the advancing contact angle.

In this embodiment, the measuring device 20 for measuring the contact angle between the droplet 2 and the solid sample 1 is as follows.
Although a method in which an image is captured using a CCD camera and image data is arithmetically processed by the tangent method is used, other methods can be used as long as the contact angle θ1 (or θ2) between the droplet 2 and the solid sample 1 can be measured. The method of can also be used.

[0031]

EXAMPLES The effects of the present invention will be clarified below with reference to specific examples. As an example of the solid sample 1, a solid sample A having a surface subjected to eutectoid plating and a solid sample B having a Teflon film formed on the surface thereof were prepared. The solid sample A was obtained by immersing a stainless steel plate in an electrolytic solution in which metal ions (nickel ions) and particles of a water-repellent resin (polytetrafluoroethylene) were dispersed, followed by plating, and then a temperature above the melting point of the water-repellent resin. A product having a strong water-repellent eutectoid plating layer formed by heat treatment at a temperature was used.

As the solid sample B, a stainless steel plate subjected to water repellent treatment by a plasma polymerization method was used. Specifically, first, the vapor of the raw material liquid composed of linear PFC such as C ₄ F ₁₀ or C ₈ F ₁₆ is converted into plasma in the plasma processing apparatus. When the vapor of the linear PFC is plasmatized in this way, the bond of the linear PFC is partially broken and activated. The activated PFC was brought into contact with the surface of the stainless steel plate, whereby the PFCs were polymerized with each other on the stainless steel plate, and a fluororesin polymer film having liquid repellency was formed.

On the other hand, as a liquid sample, 0.4% by weight of polydioctylfluorene as a light emitting material was added to 99.6% by weight of an polar solvent prepared by mixing dodecylbenzene and tetralin in a volume ratio of 1: 1. A material (hereinafter referred to as a liquid sample C) for forming a light emitting layer of the organic EL device is formed. The surface tension of this liquid sample C is 30.
It was 2 mN / m.

(Embodiment 1) Measuring apparatus 1 having the structure shown in FIG.
0 was used to measure the receding contact angle between the solid sample A and the liquid sample C by the measuring method according to the present invention. First, the solid sample A was fixed and held on the stage 12, and the liquid sample C was set in the liquid supply mechanism 13. As the needle-shaped tubular body 11, a Teflon-coated needle having an outer diameter of 1.0 mm and an inner diameter of 0.8 mm, the outer surface of which was coated with Teflon (registered trademark), was used. Then, as shown in FIG. 2, the needle-shaped tubular body 1 arranged above the solid sample A.
By extruding 4 μl of the liquid sample C from the tip of 1, and moving the stage 12 upward in the Z direction,
As shown in FIG. 3A, droplets 2 made of a liquid sample C were formed on the solid sample A. Next, as shown in FIG. 3B, while moving the stage 12 in the X direction at a constant speed of 2 mm / sec, the droplet 2 is moved from the Y direction to the CCD.
An image was taken by the camera 21, and the contact angle θ1 of the droplet 2 in the forward direction of the stage 12 was measured by the tangent method from the obtained image data. While the stage 12 is moving, the contact angle θ
The value of the contact angle θ1 when 1 became almost constant was determined as the receding contact angle. The receding contact angle was measured 5 times, and the average of the 5 measurements and the difference between the maximum and minimum values (Max
-Min) was calculated for each. The results are shown in Table 1 below.

Example 2 The receding contact angle between the solid sample B and the liquid sample C was measured in the same manner as in Example 1 except that the solid sample B was used instead of the solid sample A. The average value of the receding contact angles obtained by five times of measurement, and the difference between the maximum value and the minimum value (Max-Mi
n) is shown in Table 1 below.

(Comparative Example 1) The receding contact angle between the solid sample A and the liquid sample C was measured by using a conventional expansion / contraction method. First, an inner diameter of 0.8 on the solid sample A
After ejecting 4 μl of the liquid sample C from the mm injection needle to form a droplet, the liquid sample C is drawn out from the droplet at a constant flow rate while the tip of the injection needle is inserted into the droplet. The process of the droplet shrinking was imaged with a CCD camera. The diameter L of the contact surface between the droplet and the solid sample A and the height H of the droplet were measured from the obtained image data, and the receding contact angle θr represented by the following mathematical formula (1) was obtained. θr = 2 tan ⁻¹ 2H / L (1) In this way, the receding contact angle θr is measured 5 times, and the average value of the 5 measured values and the difference between the maximum value and the minimum value (Ma
x-Min) was calculated. The results are shown in Table 1 below.

Comparative Example 2 The receding contact angle θr between the solid sample B and the liquid sample C was measured in the same manner as in Comparative Example 1 except that the solid sample B was used in place of the solid sample A. . The average value of the receding contact angle θr obtained by five measurements and the difference between the maximum value and the minimum value (Ma
x-Min) is shown in Table 1 below.

[0038]

[Table 1]

From the results shown in Table 1, the variation in measured values was 3.5 ° in Comparative Examples 1 and 2, whereas it was as small as 2.4 ° to 3.2 ° in Examples 1 and 2. It was confirmed that the reproducibility was good. Further, the difference between the average values by both measuring methods is 1.9 ° when the solid sample A is used and 1.3 ° when the solid sample B is used. The difference is smaller than the variation of, and it is recognized that it is within the range of measurement error. Therefore, it was confirmed that the measurement results of Examples 1 and 2 were in good agreement with the measurement results of Comparative Examples 1 and 2.

[0040]

As described above, according to the present invention,
The dynamic contact angle can be measured for almost all materials regardless of the surface condition and physical properties of the solid sample and the liquid sample, and a highly versatile measuring method and measuring device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a dynamic contact angle measuring device according to the present invention.

FIG. 2 is a diagram for explaining a method for measuring a dynamic contact angle according to the present invention, and is a side view showing a state in which a liquid material is extruded from the tip of a needle-shaped tubular body.

3A and 3B are diagrams for explaining a method for measuring a dynamic contact angle according to the present invention, in which FIG. 3A is a side view showing a state where droplets are formed on a solid sample, and FIG. It is a side view showing a moved state.

FIG. 4 is a graph showing an example of a change with time of a measured value of a contact angle in the measuring method according to the present invention.

FIG. 5 is an explanatory diagram showing a method of obtaining a contact angle by a calculation process using a tangent method in the measuring method according to the present invention.

[Explanation of symbols]

1 ... Solid sample 2 ... Droplet 11 ... Needle tube 12 ... Stage 13 ... Liquid supply mechanism 15 ... Control device 20 ... Measuring means 21 ... CCD camera (imaging means) 23 ... Computer (calculation means)

Claims (6)

[Claims] 1. On the surface of a horizontally arranged solid sample,
The liquid sample is extruded from the tip of the needle-shaped tube vertically disposed above the solid sample to form a droplet, and the tip of the needle-shaped tube is inserted into the droplet, A method for measuring a dynamic contact angle, which comprises moving a solid sample in a horizontal direction and measuring a contact angle between the solid sample and a droplet in front of or behind the moving direction of the solid sample. 2. The contact angle when the solid sample is moved in the horizontal direction at a constant speed and the contact angle between the solid sample and the droplet is kept substantially constant is defined as a dynamic contact angle. The method for measuring a dynamic contact angle according to claim 1, wherein 3. When measuring the contact angle between the solid sample and the droplet, the droplet is imaged from a horizontal direction perpendicular to the moving direction of the solid sample, and the obtained image data is obtained. The arithmetic processing is performed based on the tangent method.
Or the method for measuring a dynamic contact angle according to any one of 2). 4. A stage for holding a solid sample horizontally,
A drive means for moving the stage in the horizontal direction, a needle-shaped tubular body vertically arranged above the stage, a liquid supply mechanism for pushing out a liquid sample from the tip of the needle-shaped tubular body, and a solid sample on the solid sample. A device for measuring a dynamic contact angle, comprising means for measuring a contact angle between a droplet formed on the surface and the solid sample. 5. The dynamic contact angle measuring device according to claim 4, wherein the moving speed of the stage is variable. 6. The measuring means includes an image pickup means for picking up an image of the liquid droplet from a horizontal direction perpendicular to the moving direction of the stage, and a calculating means for obtaining a contact angle by using image data from the image pickup means. The dynamic contact angle measuring device according to claim 4, further comprising: