JP2009115626A - Method for evaluating strength of thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating a strength of a thin film, which effectively eliminates the influence of a substrate. <P>SOLUTION: A horizontal force acting on a cutting blade 100 is measured, while obliquely pressing the cutting blade 100 into a sample 200 having the thin film formed therein, in a direction of the film thickness of the thin film, and a graph is obtained which is plotted with measured data respect to movement amounts of the cutting blade 100. Since the gradient of the graph changes at a border at which an elastic deformation area shifts to a cutting area, an inflection point P appears. Since the external force at the start of a cutting operation depends on the strength of the thin film, a horizontal force value Fp at the inflection point P at which the variation amount of the horizontal force for the unit movement amount of the cutting blade 100 changes, is extracted as an index of the strength of the thin film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention particularly relates to a thin film strength evaluation method for quantitatively evaluating the strength of a thin film formed on an elastic substrate.

  Thin films are used in various places such as antireflection films, magnetic tapes, semiconductor films, and coatings covering automobile bodies. Ink printed on paper is also a kind of thin film. It is important to measure the properties of the thin film as a means of knowing whether these thin films can perform their intended functions such as antireflection and substrate protection. Among the thin film properties, the mechanical properties of the thin film include the adhesion between the thin film and the substrate (substrate), and the strength and hardness of the thin film itself.

  To measure the adhesion of the thin film, the diamond indenter is pushed into the thin film, the indentation depth-load curve characteristics are measured, the displacement point of the curve is taken as the peeling point, and the integrated value up to the peeling point is an indicator of the adhesion strength of the thin film Has been proposed (see Patent Document 1).

  However, this method assumes a case where a substrate such as plastic is hard, and it is not assumed that a thin film formed on a soft substrate such as paper includes the influence of elastic deformation of the substrate. Since the indentation depth includes the deformation amount of the substrate in addition to the deformation of the thin film, the integrated value calculated as the thin film adhesion force is an inaccurate value.

  In addition, in the phenomenon of thin film peeling, peeling that starts from a partial peeling of a minute region and does not have a clear starting point can be considered. In the push-in operation, it is difficult to evaluate this type of delamination without a clear starting point.

  In addition, as a method for measuring the peel strength and shear strength of a thin film, a method called a SAICAS (Surface And Interfacial Cutting Analysis System) method is effective. The cycas method is disclosed in Patent Document 2.

JP 2006-284453 A JP-A 61-169745

  In the cycas method, a cutting blade having a clearance angle α, a rake angle β, and a blade width W is used, and the force applied to the cutting blade when the thin film is cut with the cutting blade is measured. This is a technique for obtaining the shear strength of a thin film from the cutting depth-horizontal force curve characteristics.

  However, the cycas method is good at a homogeneous film on a hard substrate such as a coating film covering a car body of an automobile, and an inaccurate value is obtained when a thin film on a soft substrate such as paper is evaluated by the above-described method. The main factor is that although the value of the cutting depth must be used for the analysis, the value of the cutting depth appears larger than the actual value due to the elastic deformation of the substrate.

  As described above, there is no method for accurately evaluating the characteristics of thin films formed on soft substrates where the effects of elastic deformation cannot be ignored, and a method for measuring the film strength of thin films that effectively eliminates the effects of the substrates is desired. It is rare.

  An object of the present invention is to provide a thin film strength evaluation method capable of accurately eliminating the influence of a substrate (substrate) and accurately evaluating the thin film strength.

  The thin film strength evaluation method of the present invention is a thin film strength evaluation method for evaluating the strength of a thin film formed on a substrate, and a cutting blade capable of cutting the thin film is placed on the substrate held horizontally. A measuring step of measuring a change in horizontal force received by the cutting blade and a moving amount of the cutting blade while pushing obliquely with respect to the film thickness direction of the thin film so as to cut after elastically deforming the thin film; and A step of extracting a horizontal force value at an inflection point where a rate of change of the horizontal force with respect to the moving amount of the cutting blade changes from measurement data of the measuring step; a step of evaluating the strength of the thin film using the horizontal force value as an index; It is characterized by having.

  While pushing the cutting blade diagonally against the thin film, measure the change in horizontal force accompanying the movement of the cutting blade, and identify the inflection point at which the rate of change of the horizontal force changes as the start of thin film cutting. The horizontal force value, which is an external force, is used as an index of thin film strength. This makes it possible to evaluate the strength of the thin film that effectively eliminates the influence of the substrate, even on a thin film provided on a substrate on which elastic deformation such as paper cannot be ignored.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIGS. 1A and 1B show a cutting edge 100 used in a thin film strength evaluation method and a thin film strength evaluation apparatus according to an embodiment in a cross-sectional view and a perspective view. ) Having a clearance angle α, a rake angle β, and a blade width W. The clearance angle α is an angle formed between the sample surface and the bottom surface 101 of the cutting edge 100, and the rake angle β is an angle formed between a plane perpendicular to the sample surface and the upper surface 102 of the cutting edge 100. The apparatus has a mechanism (not shown) that holds the cutting blade 100 and a sample stage that can horizontally hold a sample 200 in which a thin film is formed on a base as shown in FIGS. 1 (c) and 1 (d). Thus, the relative angle between the cutting edge 100 and the sample 200 is always kept constant.

  As shown in FIG. 1C, the cutting edge 100 is advanced toward the sample 200 at a horizontal direction moving speed V1 and a vertical direction moving speed V2. However, the horizontal direction is a direction parallel to the sample stage holding the sample 200, and the vertical direction is the film thickness direction of the thin film perpendicular to the direction. The approach angle of the cutting blade 100 to the sample 200 is determined depending on how the speeds V1 and V2 are determined. In the measurement process shown in FIGS. 1C and 1D, the horizontal / vertical force (horizontal force / vertical force) applied to the cutting blade 100 is measured by the measuring means, and the cutting blade in the horizontal direction / vertical direction is measured. Measurement data of horizontal force / vertical force with respect to 100 movement amount (movement distance) is acquired. Then, a graph is obtained in which the amount of movement in the vertical direction is plotted on the horizontal axis and the horizontal force is plotted on the vertical axis. However, the horizontal axis may be a value proportional to the amount of movement of the cutting blade, and is not limited to the amount of movement in the vertical direction.

  When cutting a homogeneous thin film, a graph is drawn in which the horizontal force is proportional to the amount of vertical movement of the cutting edge. This is because as the cutting proceeds, the number of sample pieces on the upper surface of the cutting blade increases, and the frictional resistance between the cutting blade and the sample piece and the shearing force necessary for cutting increase.

  On the other hand, in the cutting of a sample in which a thin film is formed on a substrate (base) such as paper or film whose influence of elastic deformation cannot be ignored, as shown in FIG. Elastically deforms. Thereafter, as shown in FIG. 2B, the cutting edge 100 enters the thin film of the sample 200, and then the cutting edge enters the substrate. Therefore, as shown in FIG. 2C, the measured data of the amount of movement of the cutting blade in the vertical direction-horizontal force includes an elastic deformation region (a region), a thin film cutting region (b region), and a substrate cutting region (not shown). The graphs have different slopes in each of the (c regions).

  Since the slopes are different in this way, an inflection point is generated at the boundary of each region. Of these, the inflection point P, which is the boundary between the elastic deformation region (region a) and the thin film cutting region (region b), is the starting point at which the cutting edge 100 starts to enter the thin film. Therefore, it can be said that the external force applied to the thin film at the inflection point P is an external force necessary for breaking the thin film. That is, the horizontal force value Fp, which is the component force in the horizontal direction of the external force at this point, is a value reflecting the strength of the thin film. Therefore, the horizontal force value Fp at the inflection point corresponding to the boundary between the elastic deformation region (a region) and the thin film cutting region (b region) on the graph is extracted from the measurement data as an index of the thin film strength. The thin film strength as used herein refers to the strength of the thin film that indicates the limit at which the thin film is not destroyed even when a force is applied.

  Among the inflection points where the amount of change (rate of change) of the horizontal force with respect to the unit movement amount of the cutting edge generally changes, the points that change only after the cutting edge begins to receive force are the elastic deformation region (a region) and the thin film cutting region ( b region).

  By the way, in the initial elastic deformation region (region a), contributions of the respective elastic deformations of the thin film and the substrate are included. If the substrate is hard, it proceeds rapidly from the elastic deformation region (a region) to the thin film cutting region (b region). On the other hand, if the substrate is soft, the amount of elastic deformation of the substrate increases, so that the transition from the elastic deformation region (a region) to the thin film cutting region (b region) is delayed. As a result, the inflection point between the elastic deformation region (a region) and the thin film cutting region (b region) appears remarkably. That is, the thin film strength index derivation method proposed in the present invention can be said to be a more suitable method for a substrate having a large elastic deformation.

  In this embodiment, the horizontal force applied to the cutting blade is measured while the cutting blade is moved obliquely in the depth direction (film thickness direction) of the thin film, and the horizontal force relative to the unit movement amount is measured after the cutting blade starts to receive the force. In this evaluation method, the horizontal force value at the inflection point at which the amount of change changes is regarded as an index of the strength of the thin film. This makes it possible to effectively eliminate the influence of the substrate and quantitatively evaluate the strength of the thin film formed on the soft substrate where the influence of elastic deformation cannot be ignored.

  A cutting blade made of diamond and having a relief angle of 10 degrees, a rake angle of 20 degrees, and a blade width of 0.3 mm was used. The cutting speed conditions were (V1, V2) = (10, 8) and (20, 10). The approach angle of the cutting blade is determined by the cutting speed.

  FIG. 3 shows data when the sample S1 is cut. Sample S1 is a special paper in which a thin receiving layer is formed on paper. The receptive layer is a coat layer made mainly of silica or alumina on paper. In the raw data (measurement data) in FIG. 3, it is observed that an inflection point exists in the vicinity of 25N. Therefore, the measured data is divided before and after the inflection point, and in the data analyzed by drawing the approximate lines A and B, the intersection of the two approximate lines A and B is determined as the inflection point, and the horizontal force value is determined. Extracted as an index for evaluating the strength of the thin film.

  Subsequently, samples S2, S3, and S4 in which different types of thin films were formed on the substrate were measured. The measurement conditions are the same as for sample 1. Samples S2 to S4 are obtained by forming different types of pigment ink films (recording layers) on a substrate. The measured raw data and the analyzed data are shown in FIGS. 4A, 4B, and 4C, respectively. It can be confirmed that the inflection point is reached at different horizontal force values.

  The horizontal force values at the inflection points of samples S2 to S4 are shown in FIG. Cutting speeds (V1, V2) = values obtained for (10, 8) and (20, 10), respectively. Regardless of the cutting speed condition, the horizontal force value is the same for the same sample. From this, it was confirmed that the horizontal force value at the inflection point is unique to the sample.

  Consider the case where the cutting edge 100 has a bottom surface 101 with a clearance angle α and a top surface 102 with a rake angle β on the front surface in the traveling direction, as shown in FIG. The approach angle when the cutting edge 100 is pushed into the sample 200 is not less than the clearance angle α with respect to the surface of the sample 200 placed on the sample stage, and the rake angle β from the film thickness direction of the thin film of the sample 200. The angle is preferably equal to or less than the angle obtained by subtracting. In particular, if the approach angle is in the range of 20 to 60 degrees with respect to the surface of the sample 200, it is desirable that cutting is not started with contact and the influence of elastic deformation of the substrate is small.

  It goes without saying that the present invention is not limited to the measurement of thin film strength using a substrate as paper, but is also effective for measuring thin film strength provided on a substrate having elasticity other than paper.

  The above paper refers to inkjet coated paper, glossy paper, OHP film, and the like. However, it is not limited to these. The recording layer is not limited to the ink layer, and represents the entire recording layer including the toner layer.

  In the above embodiment, among the points where the rate of change of the horizontal force with respect to the amount of movement of the cutting edge changes, the first inflection point after the cutting edge starts receiving the force is the elastic deformation region (a region) and the thin film cutting region (b region). However, the method of specifying the inflection point is not limited to this. The present invention is also effective when the target inflection point is extracted by another method, such as by observing the tip of the cutting edge with an image sensor and determining the starting point of the thin film cutting region (b region).

The cutting blade used for the thin film strength evaluation method by one Embodiment is shown, (a) is the side view, (b) is a perspective view, (c) is a figure which defines the cutting speed by cycas, (d) is cutting It is a figure which shows the state of time. It is a figure which shows the method and graph which extract the horizontal force value used as the parameter | index of thin film strength. It is a graph which shows the raw data of the horizontal force when cutting sample S1 of Example 1, and the analyzed data. It is a graph which shows the raw data of the horizontal force when cutting sample S2-S4 of Example 1, and the analyzed data. It is a graph which shows the horizontal force value in the inflection point of samples S1-S4.

Explanation of symbols

100 Cutting edge 101 Bottom surface 102 Upper surface 200 Sample

Claims (9)

A thin film strength evaluation method for evaluating the strength of a thin film formed on a substrate,
While pushing the cutting blade capable of cutting the thin film obliquely with respect to the film thickness direction of the thin film so as to cut after elastically deforming the thin film on the substrate held horizontally, A measuring step for measuring a change in horizontal force received by the cutting blade and a moving amount of the cutting blade;
From the measurement data of the measurement step, a step of extracting a horizontal force value at an inflection point at which the rate of change of the horizontal force with respect to the moving amount of the cutting blade changes;
And a step of evaluating the strength of the thin film using the horizontal force value as an index.   The cutting edge has a clearance angle α and a rake angle β with respect to the thin film, and an approach angle when pushing the cutting blade is equal to or more than the clearance angle α, and the rake angle β is subtracted from the film thickness direction of the thin film. The thin film strength evaluation method according to claim 1, wherein the thin film strength is less than an angle.   3. The thin film strength evaluation method according to claim 1, wherein an approach angle when the cutting blade is pushed in is in a range of 20 degrees to 60 degrees with respect to the surface of the thin film.   4. The thin film strength evaluation method according to claim 1, wherein the substrate is paper or a film.   The thin film strength evaluation method according to claim 1, wherein the thin film is a coat layer formed on the substrate.   6. The thin film strength evaluation method according to claim 5, wherein the coating layer is a recording layer.   The thin film strength evaluation method according to claim 5, wherein the coat layer is a receiving layer. A thin film strength evaluation apparatus for evaluating the strength of a thin film formed on a substrate,
A sample stage for horizontally holding the substrate having the thin film;
A cutting blade capable of cutting the thin film on the substrate held on the sample stage;
Measuring the change in horizontal force applied to the cutting blade and the amount of movement of the cutting blade while pushing the cutting blade obliquely with respect to the film thickness direction of the thin film so that the thin film is cut after being elastically deformed. Measuring means,
From the measurement data of the measuring means, a horizontal force value at an inflection point at which the rate of change of the horizontal force with respect to the moving amount of the cutting edge changes is extracted and used as an index for evaluating the strength of the thin film. Thin film strength evaluation device.   The cutting edge has a clearance angle α and a rake angle β with respect to the thin film, and an approach angle when pushing the cutting blade is equal to or more than the clearance angle α, and the rake angle β is subtracted from the film thickness direction of the thin film. The thin film strength evaluation apparatus according to claim 8, wherein the thin film strength evaluation apparatus is an angle or less.

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