JP2002188986A - Method and instrument for measuring contact angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a contact angle of a sample by simple constitution without feeding the sample. SOLUTION: A diagonal view image of a liquid drop P dropped on a field surface F by a liquid drop dropping device 11 is photographed by a CCD camera 12, the photographed image of the liquid drop P is read into an image processor 13, a photographing angle α of the CCD camera 12 is measured by a camera angle measuring instrument 15, a diameter and a height of a circular cone circumscribed with the liquid drop P are found using image data of the drop P and the photographing angle α, and the contact angle θ of the drop P is calculated based thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a contact angle used for evaluating the water repellency of a surface such as a floor.

[0002]

2. Description of the Related Art Conventionally, floors of bathrooms and flooring, etc.
As a method for evaluating the water repellency of a material surface, a method is known in which a test piece is cut out from a material to be evaluated, a droplet is dropped on the surface of the test piece, and the contact angle is measured. As shown in FIG. 7, the contact angle is the contact point X of the droplet P dropped on the test piece surface Q with the test piece surface Q (strictly, the contact point of the three phases of solid, liquid and gas). In), the angle θ on the droplet P side among the angles formed by the tangent line drawn on the droplet P and the test piece surface Q. In general, the contact angle θ is obtained by observing the droplet P from a side using a microscope or the like, photographing an enlarged photograph of the droplet P, and obtaining a photograph of the side surface image of the photographed droplet P on the surface of the test piece. It is determined by measuring the inclination of the tangent at the contact point X with Q.

[0003]

However, in the above method, it is difficult to accurately observe the test piece on which the droplet has been dropped from the side, and the contact point X cannot be determined. Was not enough. In addition, there is a problem that the size of the test piece is limited due to the device. Therefore, a droplet of a known volume or mass is dropped on the sample surface, the diameter of the droplet is measured by observing the droplet from above, and the droplet is measured using the measured diameter and the volume or mass. There has been proposed a method of estimating the shape of the object and calculating the contact angle (for example, JP-A-1-126523 and JP-A-5-232009). However, in the above method, it is difficult to accurately drop a droplet of a predetermined volume or mass on a sample, and further, the volume or mass of the droplet changes due to evaporation of the liquid during measurement. In some cases, there was a problem with the measurement accuracy.

In addition, the diameter of the droplet is measured by observing the droplet from above, and the height of the droplet is measured using a non-contact distance measuring device such as an ultrasonic distance measuring device. ,
A method of calculating a contact angle from the above height and diameter has also been proposed (Japanese Patent Application Laid-Open No. H08-059988). However, in order to increase measurement accuracy, preparation and operation are required, such as the need to condense droplets. Not only is it complicated but also an expensive device is used, so it cannot be said to be a simple measurement method. Furthermore, in the above-mentioned conventional measurement method, in any case, a test piece of an appropriate size is cut out from the material to be evaluated to prepare a sample, which must be measured in a test room.
It was not possible to directly measure the contact angle of the product at the actual site where the product was used.

The present invention has been made in view of the conventional problems, and can directly measure a contact angle with a simple configuration without cutting out a test piece at a site where a product is actually used. It is an object of the present invention to provide a method and a device for measuring a contact angle.

[0006]

According to a first aspect of the present invention, there is provided a method for measuring a contact angle, wherein a droplet dropped on a substrate is photographed from a predetermined angle, and the photographed image and the photographing angle are photographed. Is used to calculate the contact angle of the droplet. The method for measuring a contact angle according to claim 2, wherein the image of the photographed droplet is printed, and the diameter and the apparent height of the bottom surface of a cone circumscribing the droplet are determined using the printed image. After calculating the apparent height, the apparent height is converted to the actual cone height using the shooting angle, and the contact angle of the droplet is calculated using the cone height and the diameter of the bottom surface. It is characterized by doing. 4. The contact angle measuring device according to claim 3, wherein: a unit for dropping a droplet on a substrate; a camera for photographing a perspective image of the droplet; a unit for measuring a photographing direction of the camera; Means for capturing and processing the image of the droplet, and using the image data of the image-processed droplet and the shooting direction of the camera, the height of the cone circumscribing the droplet and the diameter of the bottom surface. Means for calculating the contact angle of the droplet in order to calculate the contact angle of the droplet using the image data of the photographed droplet and the photographing direction of the camera. is there.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a contact angle measuring device 10 according to the present embodiment.
FIG. 2 is a schematic diagram showing a method for measuring the contact angle. In each figure, reference numeral 11 denotes a droplet dropping device, and a discharge port 11s
Stand 11b so that is perpendicular to the field surface F.
The droplet discharging means 11a held by the moving handle 1 is connected to a well-known rack and pinion mechanism 11z.
The height of the discharge port 11s is adjusted by raising and lowering by 1h, and the droplet P is dropped on the field surface F which is the measurement surface.
Reference numeral 12 denotes a CCD camera as a photographing means, which includes a camera position adjusting means 12a, and which drops a droplet P dropped on the field surface F by a camera fixing jig 12b set at a predetermined position on the field surface F. , The field surface F
Is photographed from a direction at a predetermined angle α. Also, 13
Has storage means 13M for storing image data of the liquid droplets P photographed by the CCD camera 12, and performs image processing of the image data stored in the memory means 13M to form an apparent cone circumscribing the liquid droplets P. From the apparent height h 'and the photographing angle α detected by the camera angle measuring means 15 described later. Drop height calculator 13b for calculating the height h of a cone circumscribing the droplet P, and contact angle calculator for calculating the contact angle θ of the droplet P using the calculated radius r and height h 13c, and an image processing apparatus including a contact angle calculation unit 13K that calculates a contact angle θ of the droplet P based on the input image data. The image processing apparatus includes: an image data stored in the storage unit 13M; , Calculated by the contact angle calculator 13K And a contact angle θ which is an image display device for displaying on the screen. 15 is the camera fixing jig 1
2b equipped with an angle sensor (not shown) attached to
A camera angle measuring means for measuring and displaying the photographing angle α of the CCD camera 12;
Displays the measured camera angle data on the angle display 16 formed of a liquid crystal display panel or the like, and outputs the angle data to the image processing device 13.

Next, a description will be given of a method of measuring a contact angle by the above-configured apparatus. First, the droplet dropping device 11 is set on a field surface F such as a floor in a bathroom or a flooring floor where a contact angle is to be measured, and the droplet discharging means 11a is set.
A predetermined amount of the droplet P is dropped on the field surface F from the discharge port 11s. Next, the image of the dropped droplet P is represented by C
An image is taken with the CD camera 12. At this time, an appropriate photographing position of the CCD camera 12 is adjusted by the camera position adjusting means 12a, and a photographing angle α, which is an angle between the field plane F and the photographing direction, is measured by the camera angle measuring means 15. . The image data of the photographed droplet P and the data of the photographing angle α are respectively stored in the image processing device 13.
Is sent to the storage means 13M. FIG. 3A shows an example in which the image data stored in the storage unit 13M is displayed on the image display device 14.
FIG. 7 is a diagram showing an example displayed on the screen of FIG. 5. From this image, the apparent height h ′ of the cone circumscribing the image of the droplet P and the radius r of the bottom surface are calculated by the droplet shape calculating means 13a Can be. That is, since the radius r of the bottom surface does not depend on the photographing angle α, it can be immediately obtained from the major axis of the ellipse forming the bottom surface of the image of the droplet P. The apparent height h ′ is the height of a cone circumscribing the droplet P, that is, the major axis of the ellipse is the base, and the other two sides AH ′ and BH ′ are the isosceles sides that contact the droplet P. It can be obtained as the height of the triangle. By the way, as shown in FIG. 3B, when the center of the cone circumscribing the actual droplet is O, the vertex is H, and the radius of the bottom surface is r, as shown in FIG.
It can be expressed by the following equation (1). θ = tan ⁻¹ (h / r) ‥‥ (1) However, the height h cannot be directly read from the photographed image of the droplet P. However, the above h ′
Is the length of the orthographic projection of the OH onto the plane inclined by the photographing angle α, and therefore, as shown in FIG.
There is a relation of h ′ = hcosα. Therefore, the contact angle θ can be calculated by the following equation (2) using the above r, h ′, and α. θ = tan ⁻¹ {(h / (r · cos α)} (2) The droplet height calculating means 13b calculates the apparent height h ′ and the photographing angle α using the above expression h ′ = hcos α. The true height h is calculated, and the contact angle calculation means 13c calculates the contact angle θ of the droplet P using the calculated radius r and the height h.
It is calculated using the above equation (2). The image display device 14
As shown in FIG. 1, the image data stored in the storage unit 13M and the contact angle θ calculated by the contact angle calculation unit 13K are displayed on a screen. Thus, the contact angle θ of the droplet P photographed by the CCD camera 12 can be automatically calculated and displayed.

As described above, according to the present embodiment, a perspective image of the droplet P dropped on the field surface F is photographed by the CCD camera 12 by the droplet dripping device 11, and the photographed droplet P Of the CCD camera 1 detected by the camera angle measuring means 15
2, the contact angle θ of the droplet P is calculated from the image data of the droplet P and the image data of the droplet P. Therefore, with a simple configuration, just by bringing the measuring instrument to the site, the product The contact angle θ can be measured. In addition, since the measurement can be performed after the product is completed, a change with time at the delivery destination can also be measured.

In the above embodiment, the case where the height of the droplet P is smaller than the radius of the base has been described. However, when the height of the droplet P is larger than the radius of the base, FIG.
As shown in (a) to (c), the contact angle θ may be calculated assuming a cone drawn from the bottom surface of the image of the droplet P in a direction opposite to the actual droplet. Since the apparent contact angle obtained from the virtual cone is (π−θ), this is later converted into the contact angle θ.

In the above example, the contact angle θ is calculated by using the image processing device 13, but as shown in FIG. 5, an image of the droplet P taken by the CCD camera 12 is printed out. Then, the worker may calculate the contact angle θ from the printed image of the droplet P by drawing and manual calculation. Specifically, first, the image of the droplet P captured by the CCD camera 12 is sent to the image device 21 having the storage unit 13M to be displayed, the image of the droplet P is confirmed, and the image is stored. The stored image data is sent to the printer 22 and printed out. Next, the operator measures and records the radius r of the bottom surface and the apparent height h ′ shown in FIG. 3A from the printed image of the droplet P, The reading angle α displayed on the angle display 16 of FIG.
As shown in (c), the printed droplet P
The true height h is calculated by drawing an auxiliary line corresponding to the angle α on the image of the above, and the contact angle θ is calculated from the above r and h using the above equation (2). Thus, the contact angle θ can be calculated without bringing the image processing device 13 to the site. As a photographing unit, a prism camera 30 having a prism 30P as shown in FIG. 6 may be used instead of the CCD camera 12. This facilitates adjustment of the position angle α, so that measurement can be performed more efficiently.

[0012]

As described above, according to the present invention,
Since the contact angle of the droplet is calculated from the image of the droplet dropped on the base material photographed by the camera and the photographing angle of the camera, the field measurement of the contact angle θ is performed with a simple configuration. be able to. In addition, since it is a field measurement, a change with time at a delivery destination can be measured.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing a method for measuring a contact angle according to the present embodiment.

FIG. 3 is a diagram showing a method for calculating a contact angle according to the present embodiment.

FIG. 4 is a diagram showing a method of calculating a contact angle according to the present embodiment.

FIG. 5 is a diagram showing another configuration of the contact angle measuring device according to the present invention.

FIG. 6 is a diagram showing a schematic configuration of a prism camera.

FIG. 7 is a diagram showing a conventional method for calculating a contact angle.

[Explanation of symbols]

10 contact angle measuring device, 11 droplet dropping device, 12
CCD camera, 13 image processing device, 13M storage unit, 13K contact angle calculation unit, 13a droplet shape calculation unit, 13b droplet height calculation unit, 13c contact angle calculation unit, 15 camera angle measurement unit, 16 angle display, F
Field plane, P droplet.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA31 BB00 FF04 GG10 JJ03 JJ26 QQ23 QQ31 5B057 AA01 BA02 BA19 DA01 DB02 DC02

Claims (3)

[Claims] 1. A method according to claim 1, wherein a droplet dropped on the substrate is photographed from a predetermined angle, and a contact angle of the droplet is calculated using the photographed image and the photographing angle. Measurement method of contact angle. 2. An image of the photographed droplet is printed,
Using the printed image, after determining the diameter and apparent height of the bottom surface of the cone circumscribing the droplet, the apparent height, the actual cone height using the shooting angle The method for measuring a contact angle according to claim 1, wherein the contact angle of the droplet is calculated using the converted cone height and the diameter of the bottom surface. 3. A means for dropping a droplet on a base material, a camera for photographing a perspective image of the droplet, a means for measuring a photographing direction of the camera, and capturing an image of the photographed droplet. Using the image processing means, image data of the image-processed droplets, and the shooting direction of the camera to determine the height of the cone and the diameter of the bottom surface circumscribing the droplets and contact the droplets And a means for calculating an angle.