JP2005114615A - Method and apparatus for measuring wetting properties on solid surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating the wetting properties of a solid surface for evaluating wetting properties at an arbitrary location in a sample surface efficiently, even in a large-area sample, especially a sample which includes a curved surface and an inclined surface, and easily obtaining the distribution. <P>SOLUTION: The method for evaluating the wetting properties of the solid surface comprises a process of measuring the three-dimensional shape of a sample surface, in which a plurality of drops adhere, by a light interference type shape measuring means arranged at the upper portion of the sample; a process of obtaining the contact angle of each drop with respect to the sample from the obtained three-dimensional shape; and a process of obtaining the distribution of the wetting properties in the sample surface, from the contact angle with the three-dimensional shape in the sample. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for measuring wettability of a liquid with respect to a solid.

  Control of wettability of a solid surface is an important issue in many industrial fields such as adhesion, molding, painting, and sliding. In order to obtain a surface with the desired wettability, a technology to chemically control surface properties was developed by various methods such as coating treatment with various surface treatment agents such as silane coupling agents, ion implantation, UV ozone treatment, It's being used.

  The wettability on a solid surface is generally expressed by the contact angle of the liquid. Conventionally, the contact angle is measured by observing a sample in which a droplet is dropped on a flat solid with a magnifying optical system such as a microscope from the horizontal direction. The droplet is a solid surface (hereinafter referred to as a solid surface). The method of measuring the angle which touches is taken. In recent years, there is a method of taking a photograph of a droplet on a solid, which is a conventional measurement method, and a method of acquiring an image of a droplet on a solid with a CCD camera and processing data with a computer.

  According to the general method, when measuring the contact angle, as shown in FIG. 7, a sample in which a droplet 73 is dropped on a solid surface 72 of a plate-like solid 71 is subjected to a surface 72 using a magnifier optical system such as a microscope. The angle at which the liquid droplet 73 contacts the surface 72, that is, the contact angle θ is measured.

  However, in such a method, since it is necessary to observe the sample from the lateral direction, the size of the sample has to be limited to be small. For this reason, it was very difficult to measure a large sample and evaluate the distribution of the surface state over a wide range.

  Therefore, in recent years, a method has been proposed in which a droplet is observed from above and the contact angle is obtained. For example, Patent Document 1 and Patent Document 2 propose a method of calculating a contact angle by reading a projected diameter using a volume of a droplet and a camera installed above the droplet.

  Patent Document 3 proposes a method of measuring a contact angle α by arranging a mirror in the vicinity of a droplet and observing a side image of the droplet from above, and Patent Document 4 further discloses a method for measuring a flat solid. A method for obtaining a contact angle θ by acquiring a three-dimensional image of a liquid using a laser confocal microscope with respect to a sample on which a droplet is dropped is proposed.

JP-A-1-126523 JP-A-5-232009 Japanese Patent Laid-Open No. 11-230886 JP-A-8-50088

  However, the conventional contact angle measurement has the following problems.

  That is, in the method of chemically controlling the surface physical properties by various surface treatments, the surface treatment within the surface is not necessarily formed uniformly, and there may be a variation in wettability within the surface. Further, the wettability of the surface changes with time, and there may be variations in the surface. For example, in the surface treatment of a mold, there are cases where variations in the film formation state of the release film formed on the mold surface, variations due to film peeling due to molding, adhesion due to molding material, and the like occur. Therefore, it has been desired to efficiently evaluate the variation and distribution of wettability in these planes.

  Furthermore, these solid surfaces are not necessarily flat, and often have a spherical shape or an inclined shape. In such a case, variations in the formation state of the surface treatment film and changes over time are likely to be uneven depending on the location, and it is desired to efficiently evaluate the variation in wettability especially in such a surface. .

  In the conventionally proposed method for measuring a contact angle, since the observation field of view is approximately several mmφ or less, it takes a lot of labor to evaluate a wide area. Although it is possible to apply a plurality of droplets to a wide range of a sample by spraying or the like, there is a problem that measurement takes time, and droplets evaporate or change in shape and the measurement accuracy deteriorates. Further, in order to measure a wide range of shapes, it is necessary to move the sample, and in this case, the shape of the droplet may change due to vibration. This is especially a problem for spherical surfaces and inclined surfaces.

  Furthermore, in the conventional proposal for determining the contact angle by observing the droplet from the top, a method for calculating the contact angle from the diameter and height of the droplet has been used. When a curved surface or an inclined surface is included, it is difficult to calculate the contact angle by this method.

  Therefore, the main object of the present invention is to efficiently evaluate the wettability of an arbitrary location in the sample surface and easily obtain these distributions even in a large area sample, particularly a sample including a curved surface or an inclined surface. An object of the present invention is to provide a method and an apparatus for evaluating the wettability of a solid surface.

  The method for evaluating the wettability of a fixed surface according to the present invention includes a step of measuring a three-dimensional shape of a sample surface to which a plurality of droplets are attached by means of an optical interference type shape measuring means arranged above the sample, and the obtained tertiary The method includes a step of obtaining a contact angle of each droplet with respect to the sample from the original shape, and a step of obtaining a wettability distribution in the sample surface from the three-dimensional shape and contact angle of the sample.

  As one aspect thereof, a white interferometer is used as the optical interference type shape measuring means.

  As another aspect, a laser interferometer is used as the optical interference type shape measuring means.

  The shape measurement area of the laser interferometer is 10 mmφ or more and 200 mmφ or less.

  In still another aspect, the sample shape includes a slope or a spherical surface.

  Further, as a method for calculating the shape of the droplet, the shape is calculated from the difference in the three-dimensional shape of the sample surface between the state where the droplet is not attached and the state where the droplet is attached.

  As another aspect, the change in the tilt angle of the sample and the contact angle of the droplet with respect to the sample is obtained in advance.

  The solid surface wettability evaluation apparatus according to the present invention includes an optical interference type three-dimensional shape measuring means, a means for applying a plurality of droplets to a sample, a sample position information and image information capturing, a liquid It comprises a computer that calculates the contact angle from the shape of the droplet and corrects the contact angle by tilting the sample.

  As one aspect thereof, the means for applying the plurality of droplets is characterized by using droplet spraying means or droplet applying means by an ink jet method.

  As another aspect, the sample stage is provided with a tilting mechanism.

  By using the measurement method and the measurement apparatus according to the present invention as described above, even in a large area sample, particularly a sample including a curved surface or an inclined surface, the wettability of an arbitrary portion in the sample surface is efficiently evaluated. Can be easily obtained.

  According to the present invention, even in a large-area sample, particularly a sample including a curved surface or an inclined surface, it is possible to efficiently evaluate the wettability of an arbitrary portion in the sample surface and easily obtain these distributions.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a wettability evaluation apparatus according to the present invention. Here, an apparatus using a white interferometer as the shape measuring means is shown.

  In FIG. 1, 1 is a sample stage, 2 is a sample, 3 is a droplet, 4 is a three-dimensional shape measuring device using an interferometer, 5 to 9 are components of a laser interferometer, 5 is an objective lens, and 6 is vertical. A scanning drive unit, 7 is an optical system, 8 is a light source, and 9 is a CCD camera. Further, 10 is a droplet applying means, 11 and 12 are position control means, and 13 is a computer.

  The sample stage 1 is a seismic isolation mechanism that absorbs vibration transmitted from the outside by an air spring provided inside. Even if vibration occurs around the apparatus, the sample stage 1 absorbs the vibration, so that the droplet 3 and the interferometer 4 on the sample 2 are prevented from shaking. This ensures that the contact angle is measured.

  The position control means 11 and 12 are controlled by the computer 13 and can be driven in the X, Y, and Z axis directions. In addition, the stage can be tilted to an arbitrary angle as necessary.

  The interferometer 4 is a means for measuring the three-dimensional surface shape of the measurement object based on the interference fringes obtained when the reflected light from the surface of the measurement object interferes with the reflected light from the reference surface. It is known as a device capable of contact, high-precision and high-speed shape measurement. In the interferometer 4, the objective lens 5 itself is an equal optical path interferometer such as a Mirau interferometer, a Michelson interferometer, etc., and the light is branched by a half mirror (not shown), and the surface to be measured and the internal reference mirror Interference occurs when the optical path differences reflected by (not shown) and coupled again on the half mirror are equal.

  Since the white light source 7 has a short coherence distance and a narrow range in which interference fringes are generated, the interference fringes are collected by the CCD camera 8 while the objective lens 5 is vertically driven by the vertical scanning drive unit (piezo element) 6 in the optical axis direction. Then, the obtained interference fringe information is used for height information detection.

  As the interferometer 4, a laser interferometer using a laser light source such as He—Ne can be used as the light source 7. An example of interference fringes obtained when a droplet on a flat substrate is observed with a laser interferometer using a Michelson interferometer is shown in FIG. As shown in FIG. 2, it is observed that stripes appear as contour lines in the droplet portion.

  Although the laser light source has high coherence, when measuring a surface shape having irregularities of submicron or more, interference fringes become too dense and measurement becomes difficult. In the present invention, the oblique incidence type interference that can measure a larger concavo-convex shape by lowering the sensitivity of the contour line by making light incident on the sample from an oblique direction as compared with a general interference method. A total is also preferably used. In this method, shape measurement of an area of about several tens mm to 200 mmφ is possible, and shape measurement using an interferometer is effective for measurement of a large area sample.

  The droplet applying means 10 may be any means as long as it can apply a plurality of droplets to the sample surface in a short time, and spraying or ink jet type droplet applying means can be used.

  The computer 13 controls driving of the interferometer 4, the droplet applying unit 10, and the position control units 11 and 12, and takes in coordinate data and image information sent from the interferometer 4. The computer 13 also performs an operation for calculating the contact angle θ from the droplet shape.

  Regarding the method for calculating the contact angle θ, the surface shape is measured in advance for a sample in a state where no droplet is attached, and is calculated from the difference in the three-dimensional shape of the sample surface in the state where the droplet is attached.

  When the sample is smooth, the shape of the droplet is regarded as a part of a sphere, and the contact angle θ between the droplet 31 and the sample surface 32 can be obtained from the radius r and height h of the droplet as shown in FIG. it can. However, in a sample including a slope or a spherical surface, as shown in FIG. 4, the droplet 42 on the sample 41 cannot be regarded as a part of a sphere. Therefore, the wettability of the sample including these surfaces is evaluated. For this purpose, a method of obtaining the shape of the droplet itself from the difference in shape before and after the application of the droplet as described above is preferable.

  The wettability of the droplet on the inclined surface or spherical surface is evaluated by the advancing contact angle indicated by θ1 or the receding contact angle indicated by θ2 in FIG. The advancing contact angle θ1 and the receding contact angle θ2 that the droplet on the flat surface having a certain wettability shows due to the inclination of the sample differs depending on the solid and the droplet. Therefore, it is desirable to obtain the correlation between the inclination angle α of the sample shown in FIG. 4 and the contact angles θ1 and θ2 in advance.

  As an example, FIG. 5 shows the correlation between the water contact angles θ1 and θ2 with respect to the glass substrate subjected to the silane coupling treatment and the sample inclination. Even when the inclination angle in the sample surface with respect to the horizontal direction is not uniform as in the case of a spherical surface, the correlation between the inclination angle α and the contact angles θ1 and θ2 is obtained and converted to the value of the contact angle on the plane, In-plane wettability can be compared regardless of the sample shape.

  Note that when the inclination of the sample is large and there is an inconvenience in the appearance of interference fringes, or when the drop angle is greater than or equal to the drop falling angle, the sample itself can be appropriately inclined by the stage tilt mechanism.

  One mode of a measurement method using the measurement apparatus of the present invention will be described below with reference to FIG.

  First, the shape of an arbitrary region of the sample 2 on the stage 1 is measured using the interferometer 4. The position coordinates (X1, Y1) of the interferometer 4 with respect to the sample 2 and the three-dimensional shape data of the sample surface are taken into the computer 13. Next, after the droplet applying unit 10 is moved above the sample 2 using the position control unit 12, the droplet applying unit 10 is operated to form a plurality of micro droplets 3 in the shape measurement region of the sample 2. Next, the interferometer 4 is moved again to the coordinates (X1, Y1) using the position control means 12 and then the interferometer 4 is driven to measure the three-dimensional shape of the sample surface including the droplet 3. The shape of the sample surface is calculated from the interference fringe data before and after application of the droplet taken in the computer 13, and the 3D shape and contact angle θ of the droplet 3 are calculated based on the shape.

  In the above operation, when the sample is regarded as a flat surface in the entire measurement region, measurement of the shape of the sample surface before applying the droplet is omitted, and only the droplet 3 is obtained from the three-dimensional shape of the sample surface including the droplet 3. A 3D shape may be obtained. In any case, the contact angle of all droplets applied to the measurement region of the sample 2, the position of the droplets, and the sample surface shape at that location can be obtained by one operation. As a result, it is possible to obtain variation in wettability and distribution data for the liquid in the sample surface. When the interferometer used in the present invention is used, it is possible to measure an area of several tens of mmφ at a time. However, if the area that needs to be measured exceeds that, the above operation is repeated a plurality of times. good.

  When a part of the sample has an inclined surface or a spherical surface, the advancing or receding contact angle is obtained, and the contact angle value when the sample is a flat plate is calculated from the contact angle value and the sample inclination angle. . Thereby, the wettability of the sample and its in-plane distribution can be evaluated regardless of the sample shape.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.
[Example 1]
In this example, using a device equipped with a white interferometer as a shape measuring means and a means for spraying a liquid in a spray form as a droplet applying means, a silane coupling agent was spray-coated on a glass plate sample of 5 mm × 5 mm. The wettability of the sample was evaluated. This will be described with reference to FIG.

  First, the white interferometer 4 was moved above the sample 2, and the position coordinates (X1, Y1) of the interferometer 4 were taken into the computer 13. Next, as a result of measuring the three-dimensional shape of the surface on the entire surface of the sample with the interferometer 4, the surface had a roughness RMS (Root Mean Square) of 0.01 μm or less, and no swell in the sample surface was detected. This value was taken into the table computer 13.

Next, after the droplet applying means 10 is moved to above the sample 2 using the position control means 12, this is operated, and pure water is sprayed in the shape measuring region of the sample 2 in the form of a mist. Drop 3 was formed. Next, the interferometer 4 was moved again to the coordinates (X1, Y1) and then driven to measure the three-dimensional shape of the sample surface including the droplet 3. The position coordinates and 3D shape of each droplet 3 on the measurement region were calculated from the interference fringe data captured by the computer 13. There are 30 droplets formed on the measurement region, the average contact angle θ = 20.5 °, and the standard deviation is 1.0 °. No in-plane variation is observed, and the silane coupling agent is on the surface. It was found that the film was uniformly formed.
[Example 2]
In this embodiment, an apparatus equipped with a grazing incidence laser interferometer is used as the shape measuring means, and a means for spraying droplets in the form of a spray is used as the droplet applying means, and silane coupling is performed on a 30 mm × 30 mm Si wafer. The wettability of the sample coated with the agent and hydrophilized was evaluated.

  First, the shape measurement of the front surface of the sample 2 before droplet application was performed in the same manner as in Example 1. Next, as a result of measuring the three-dimensional shape of the entire surface of the sample with the interferometer 4, it was observed that the sample had a slightly raised central portion and a height difference of about 1 μm from the end portion. This shape data was taken into the computer 13. After moving the droplet applying means 10 above the sample 2, pure water was sprayed on the entire surface of the sample 2 to form a plurality of micro droplets 3.

Next, the interferometer 4 was moved to the position where the shape measurement was performed and then driven to measure the three-dimensional shape of the entire sample surface including the droplet 3. The position coordinates and 3D shape of each droplet 3 on the measurement region were calculated from the interference fringe data captured by the computer 13. About 100 droplets formed on the measurement region, the average contact angle θ = 20.0 °, and the standard deviation is 10.0 °, and the average of the average contact angle value at the center of the sample end It was relatively low and the variation was large. It was shown that the treated film was not uniformly formed at the end of the sample.
[Example 3]
In the present embodiment, a device equipped with a white interferometer was used as the shape measuring means, and a means for spraying the liquid in the form of a spray was used as the droplet applying means. In addition, normal hexane was used as a liquid to be applied to the sample. The sample in this example is an optical lens molding die having a diameter of 15 mm and a curvature radius of 75 mm as shown in FIG. 6, and a silicone-based release agent is applied to the surface.

  Sample shape measurement, droplet application, and shape measurement with a droplet attached were performed in the same manner as in Example 1, and the contact angle of the droplet was determined from the shape measurement of only the droplet. Here, angles formed by the droplet and the sample (advancing contact angle θ1 and receding contact angle θ2 in FIG. 4) in a case of cutting along a cross section including the center of the droplet and the bottom center of the mold were obtained. In this sample, as shown in FIG. 5, the correlation between the inclination angle α of the sample and the contact angles θ1, θ2 is obtained in advance immediately after forming the release film, and the wetting at each measurement position is based on the correlation. The property was evaluated by converting it into the value of the contact angle on a plane.

As a result, when the contact angle value at each position of the sample was converted into the value of the contact angle on the plane, the average conversion value was 30.0 ° and the standard deviation was 2.0 °. It was found that the release variation was small and the release film was uniformly formed.
[Example 4]
In this example, the same mold as used in Example 3 was used as a sample after applying a fluorine-based mold release agent on the surface and repeatedly molding the lens.

Measurement was performed in the same manner as in Example 3 to evaluate the change in wettability of the mold surface and in-plane variation. As a result, no change was seen in the wettability at any location in the sample surface, and it was confirmed that the function of the release film was maintained after the lens molding.
[Example 5]
In the present embodiment, an apparatus equipped with a laser interferometer as the shape measuring means and an ink jet type droplet applying means as the droplet applying means were used. In addition, normal hexane was used as a liquid to be applied to the sample. As a sample in this example, a 30 mm × 30 mm flat plate sample having a surface treatment agent made of a fluororesin applied on its surface was used.

  In this measurement, when the sample was placed without tilting the stage, there was a problem that the contact angle between the fluororesin and the droplet was large and interference fringes did not appear well. Therefore, the wettability of the sample surface was evaluated by applying a stage inclination of 30 ° and observing the receding contact angle between the sample and the droplet. The measurement procedure was the same as in Example 1, and the position coordinates, droplet shape, and receding contact angle of each droplet 3 on the measurement region were calculated from the interference fringe data captured by the computer 13. About 100 droplets are formed on the measurement region, the average receding contact angle θ = 20.0 °, and the standard deviation is 1.0 °, and the fluororesin film is uniformly formed in the sample surface. It was shown that.

  By using the measuring method and measuring apparatus of the present invention, even in a large area sample, particularly a sample including a curved surface or an inclined surface, the wettability of an arbitrary portion in the sample surface can be efficiently evaluated, and these distributions can be easily performed. It is possible to obtain.

It is a figure which shows the structure of the wettability evaluation apparatus which concerns on this invention. It is a figure which shows an example of the interference fringe seen when a droplet part is observed with an interferometer. It is a figure which shows the relationship between the diameter and height of a droplet, and a contact angle. It is a figure explaining the advancing contact angle and receding contact angle of the droplet adhering to an inclined surface. It is a figure which shows the correlation with a sample inclination angle, a forward contact angle, and a backward contact angle. It is a figure which shows the shape of the sample used for Example 3 of this invention. It is a prior art figure which shows the measuring method of a contact angle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample stand 2 Sample 3 Droplet 4 White interferometer 5 Objective lens 6 Vertical scanning drive part (piezo element)
7 Optical System 8 White Light Source 9 CCD Camera 10 Droplet Application Unit 11 Position Control Unit 12 Position Control Unit 13 Computer 31 Droplet 32 Sample 41 Sample 42 Droplet 71 Flat Solid 72 Solid Surface 73 Droplet θ Contact Angle

Claims (10)

  A step of measuring the three-dimensional shape of the surface of the sample to which a plurality of droplets are attached by the optical interference type shape measuring means disposed above the sample, and obtaining the contact angle of each droplet with respect to the sample from the obtained three-dimensional shape A method for evaluating the wettability of a solid surface, comprising the steps of: obtaining a wettability distribution in a sample surface from a three-dimensional shape and a contact angle of the sample.   2. The solid surface wettability evaluation method according to claim 1, wherein a white interferometer is used as the optical interference type shape measuring means.   2. The solid surface wettability evaluation method according to claim 1, wherein a laser interferometer is used as the optical interference type shape measuring means.   4. The method for evaluating the wettability of a solid surface according to claim 3, wherein the shape measurement region is 10 mmφ or more and 200 mmφ or less.   2. The method for evaluating the wettability of a solid surface according to claim 1, wherein the sample shape includes a slope or a spherical surface.   2. The wettability of a solid surface according to claim 1, wherein the shape of the liquid droplet is calculated from a difference in three-dimensional shape of the sample surface between the state where the liquid droplet is not attached and the state where the liquid droplet is attached. Evaluation methods.   2. The method for evaluating the wettability of a solid surface according to claim 1, wherein a change in the inclination angle of the sample and the contact angle of the droplet with respect to the sample is obtained in advance.   Optical interference type three-dimensional shape measuring means, means for applying a plurality of droplets to the sample, capturing of position information and image information of the sample, calculation of the contact angle from the shape of the droplet, and contact angle by the sample tilt An apparatus for evaluating wettability of a solid surface, comprising a computer for correcting the above.   9. The solid surface wettability evaluation apparatus according to claim 8, wherein as the means for applying the plurality of droplets, droplet spraying means or droplet applying means by an ink jet method is used.   9. The solid surface wettability evaluation apparatus according to claim 8, wherein an inclination mechanism is provided on the sample stage.

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