JP2022116520A - Method for evaluating anti-glare property of metal plate - Google Patents

Abstract

To provide a method for evaluating anti-glare property of a metal plate capable of objectively and quantitatively evaluating anti-glare property of the metal plate.SOLUTION: With a method for evaluating anti-glare property of a metal plate, image sharpness of the metal plate is measured according to JIS K7374 using an optical comb having two or more different slit widths, and anti-glare property of the metal plate is evaluated based on an obtained image sharpness value.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a method for evaluating antiglare property of a metal plate.

Metal sheets (steel sheets) used for applications such as roofing materials and exterior wall materials are often used for large buildings such as airports and dome roofs. In such applications, metal sheets are often used because they are excellent in environmental resistance such as corrosion resistance, are relatively inexpensive, and are easy to maintain. For example, a metal plate such as a ferritic stainless steel plate has a peculiar black metal feeling and texture, and is excellent in external appearance, and is being applied to large outdoor buildings.

Reflection of light by a large building obstructs the visibility of pedestrians walking around and drivers of vehicles and the like. For this reason, when metal plates are used for roofing materials, exterior wall materials, etc. of large buildings, anti-glare properties are required from the viewpoint of safety. “Anti-glare” refers to the degree of reduction in glare subjectively perceived by people due to the reflection of light. Although the concept of antiglare property is a subjective concept, it is an important factor in designing outdoor buildings, kitchen products, and the like. When a steel plate, which is a metal material, is used for a building or the like, unlike materials such as concrete, stone, and resin, excellent antiglare properties are required on the premise of beauty provided by the texture peculiar to metal. Reflected light from large structures can enter the field of view of pedestrians and vehicle drivers, both near and far. For this reason, in the case of metal plates used outdoors such as large buildings, both anti-glare properties when viewed from a short distance of several meters and anti-glare properties when viewed from a long distance of 10 m or more. need to improve.

On the other hand, in Patent Document 1, the specular reflection index of the steel plate before cold rolling, the reduction ratio in cold rolling, and the specular reflection index of the rolling rolls are set to predetermined conditions, thereby improving the antiglare property. A method for manufacturing a steel sheet is described. The specular reflection index is an index that takes into consideration the three-dimensional spread (diffusion) of specularly reflected light when the steel plate surface is irradiated with light. This is an index that quantifies the degree of spread of reflected light, and indicates that the smaller the specular reflection index, the duller the specular reflection and the less sharp the reflected light, and the better the anti-glare property.

In Patent Document 2, on the premise that the anti-glare property is determined by the reflected light distribution representing the spread of reflected light, the uneven form of the surface of the steel sheet is defined so that the spread of reflected light is increased. Specifically, a ferritic stainless steel excellent in antiglare property having a center line average roughness Ra obtained from two-dimensional roughness measurement of 0.5 to 5 μm and an average inclination angle of unevenness of 4 to 11° A steel plate is disclosed. According to Patent Document 2, the smaller the ridge angle at the tip of the surface convex portion, the easier it is to diffusely reflect incident light. Further, Patent Document 2 discloses, as a method for manufacturing such a steel sheet, a manufacturing method by cold rolling using a dull roll having a Cr-plated layer on its surface.

Patent Document 3 describes a ferritic stainless steel having a maximum roughness Rmax of 10 μm or less obtained by two-dimensional roughness measurement and a number of irregularities having a difference of 1 μm or more is 10/mm or more. A steel plate is disclosed. Also disclosed is a method for producing a ferritic stainless steel sheet that provides a total elongation of 0.2 to 0.8% by light reduction rolling using a dull roll having a predetermined unevenness. Here, the elongation rate is an index calculated from the difference in material length before and after rolling, but when the elongation rate is 1% or less, the reduction rate value calculated from the plate thickness difference before and after rolling is almost the same as

Japanese Patent No. 3688763 Japanese Patent No. 3287302 Japanese Patent No. 3338538

In Patent Document 1, a three-dimensional spread of reflected light is obtained by scanning a light-receiving side detector in the vicinity of a specular reflection position using a variable-angle spectral colorimeter. At this time, since the distance between the reflecting surface, which is the object to be measured, and the detector on the light receiving side is substantially fixed, this corresponds to detecting the angular distribution of the intensity of the reflected light. However, the glare felt by a person looking at the light reflected on the object to be measured varies depending on how far away from the steel plate the object is to be observed. In Patent Document 1, only the angular distribution of reflected light intensity is measured. Therefore, the difference in glare perceived by a person depending on the distance from the steel plate is not evaluated.

The ferritic stainless steel sheet with excellent anti-glare properties described in Patent Document 2 has an uneven surface shape on the premise that the anti-glare properties are determined by the spread of reflected light (angular distribution of reflected light intensity). is. Also in this case, the difference in glare perceived by a person depending on the distance from the steel plate is not considered.

The steel sheet described in Patent Document 3 is intended to improve the antiglare property by increasing the maximum surface roughness and the number density of the unevenness. However, similar to the above, it does not take into consideration the difference in anti-glare properties that people perceive depending on the distance at which the reflected light is observed.

Conventional anti-glare evaluation is mainly based on measurement of spread of reflected light. FIG. 1 schematically shows a method for measuring the scattering characteristics (diffusivity) of reflected light with a goniophotometer (diffuse reflection method), which is an example of a conventional antiglare evaluation method. The light receiver rotates 360° around the circumference or spherical surface of the object to be measured (steel plate), with the light receiving surface always directed toward the center (the direction of the sample). That is, the spread of reflected light is measured. In this case, it can be said that the larger the spread of the reflected light, the more blurred the reflected image, and the better the anti-glare property. However, in this method, the distance between the light receiver (light receiving portion) and the measurement object (steel plate) is constant. Therefore, no consideration is given to the fact that when the distance between the light receiving part and the steel plate changes, the range of reflected light that can be received by the light receiving part changes. For example, when the distance between the light-receiving part and the steel plate increases, the light-receiving part can receive only the range of reflected light diffused at an angle close to total reflection. For this reason, it is difficult to capture and analyze the total reflected light including the diffused light unless the light receiving part is moved at the same distance from the steel plate. In this regard, there is a possibility that a discrepancy may occur between the glare perceived by humans and the anti-glare property evaluation method of the prior art.

The present invention has been made to solve the above problems, and provides a method for evaluating the antiglare property of a metal plate that can objectively and quantitatively evaluate the antiglare property of the metal plate. The purpose is to

The gist of the present invention is as follows.
[1] Using an optical comb with two or more different slit widths, the image definition of the metal plate is measured in accordance with JIS K7374, and the protection of the metal plate is determined based on the obtained image definition value. Antiglare evaluation method for metal plate for evaluating glare.
[2] The two or more different slit widths are
a first slit width that is at least one of 0.25 mm, 0.5 mm and 1.0 mm;
a second slit width of 2.0 mm;
The method for evaluating antiglare properties of the metal plate according to [1].
[3] An optical comb having a measured value C _w1 of 0% or more and 0.50% or less of image definition obtained using an optical comb having the first slit width and having the second slit width. If the measured value C _w2 of the image definition obtained using the
[2] The method for evaluating the antiglare property of the metal plate.

ADVANTAGE OF THE INVENTION According to this invention, the glare-proof property of a metal plate can be evaluated. For this reason, it is possible to select a steel plate that does not cause glare to pedestrians and others around the building, thereby expanding options in designing the building.

FIG. 1 is an example of an anti-glare evaluation method according to a conventional technique, and is a diagram schematically showing a method for measuring scattering characteristics (diffusivity) of reflected light with a goniophotometer (diffuse reflection method). 1 is a schematic diagram of an evaluation device for image definition, which is an index of image clarity; FIG. FIG. 3 is a diagram showing the optical comb and the measurement principle, (a) a diagram showing an example of the slit of the optical comb and a diagram showing the fluctuation waveform of the amount of received light detected through the slit of the optical comb, FIG. b) is a schematic diagram showing the maximum and minimum values of the amount of light received for each slit width. FIG. 4 is a diagram for explaining the relationship between the evaluation of image clarity and the evaluation of anti-glare properties, and FIG. FIG. 4(b) is a schematic diagram showing the light receiving range of the reflected light when an optical comb with a narrow slit width is applied, and FIG. 4(c) is a schematic diagram showing the reflected light when an optical comb with a wide slit width is applied. is a schematic diagram showing a light receiving range of .

The present inventors investigated the antiglare properties of steel sheets. As a result, it was found that the antiglare properties of the steel sheet differed when observed at a short distance and when observed at a long distance, even for the same steel sheet. That is, a steel sheet that does not feel glare even when the reflected light is observed at a short distance feels dazzling when observed at a long distance, or conversely, a steel sheet that feels dazzling when the reflected light is observed from a short distance but does not feel dazzling when observed at a long distance. I discovered that there is a steel plate that does not feel dazzling.

An example of the former is an austenitic stainless steel sheet exhibiting a milky white surface. This has a milky white appearance when observed at hand, and has a glass-like smoothness that does not make the surface uneven. An austenitic stainless steel sheet does not give glare when viewed from a close distance, but gives a glare when viewed from a distance. An example of the latter is ferritic stainless steel whose surface is roughened by temper rolling with a dull roll. When viewed from a distance, it becomes cloudy and does not give glare. On the other hand, when observed from a closer distance, the point-like reflected light existing in high density on the entire surface of the steel plate changes depending on the angle of observation, giving an appearance that gives a somewhat unpleasant impression of glare, such as "glare". .

Furthermore, the present inventors investigated the reason why people's sense of glare differs depending on the distance from the steel plate. As a result, we learned that the glare that people perceive is affected by both the glare perceived by the intensity of the light reflected on the steel plate surface and the glare perceived by the clarity of the image projected on the steel plate surface. Obtained.

The glare sensed according to the reflection intensity of the light on the steel plate surface is divided into specular reflection and diffuse reflection. A person at a distance from the steel plate feels glare mainly due to the intensity of the specularly reflected light. On the other hand, there is a difference in that a person who is close to the steel plate is dazzled not only by the specularly reflected light but also by the diffusely reflected light. On the other hand, regarding the definition of the image projected on the surface of the steel plate, it is easy to feel the glare if the object looks sharp, and it is difficult to feel the glare if it looks blurry. It is considered that whether a projected object is seen clearly or blurred depends on the human visual acuity, the size of the projected object, and the observation distance. As a result of further investigation, it was found that objects tend to appear brighter when viewed from a short distance from the steel plate. It is considered that the "glare feeling" exhibited by the above-mentioned roughened ferritic stainless steel is caused by such irregularly reflected light and the sharpness of the projected object.

Based on these findings, the present inventors have extensively studied methods for evaluating antiglare properties of metal plates. As a result, unlike the evaluation based on the angular distribution of the reflected light intensity as in Patent Documents 1 and 2, we devised a method for evaluating the antiglare property of a metal plate as image definition, which is an index of image clarity. .

The present invention uses an optical comb having two or more different slit widths to measure the image definition of a metal plate in accordance with JIS K7374, and based on the obtained image definition value, the metal plate. It is characterized by evaluating antiglare properties.

The image definition, which is an index of image clarity, is the definition of the image according to how the light reflected by the object spreads. In the present invention, reflection measurement is performed on a metal plate, and the measurement result is called image definition, which is an index of image clarity.

FIG. 2 shows an overview of an evaluation apparatus for image definition, which is an index of image clarity.

As shown in FIG. 2, the light emitted from the light source is passed through a light source slit with a width of 0.03 mm, and after being converted into parallel light by a lens, the incident angle is 60° on the metal plate to be measured. Place the light source. The reflected light from the metal plate is imaged on an optical comb by a lens, the reflected light passing through the optical comb is received by a light receiver, and the amount of received light is measured.

FIG. 3 shows a schematic diagram of the optical comb and the principle of measurement.

As shown in FIG. 3(a), the optical comb has a width ratio of 1:1 between the light shielding portion (black in FIG. 3) and the passing portion (white in FIG. 3, corresponding to the slit width). It is a component that transmits reflected light and reflected images, with comb-like filters arranged in a line. A reflected image refers to the shape of the reflected light that is imaged on an optical comb through an optical lens. As an optical comb, one optical comb has a plurality of filters with different slit widths such as 0.125 mm, 0.25 mm, 0.5 mm, and 2.0 mm (Fig. 3). In some cases, the optical comb has a filter with one slit width, and the filter is appropriately exchanged for each different slit width.

In the present invention, the case of using one optical comb having a plurality of filters with different slit widths as shown in FIG. 3(a) will be described. By moving the optical comb so that the reflected light to be measured passes through the filters of each slit width, the maximum and minimum amounts of light received at each slit width are continuously measured by the light receiver. As shown in FIG. 3(b), the value of image definition, which is an evaluation index of image clarity, can be calculated from the fluctuation waveform of the amount of received light detected through the moving optical comb.

Specifically, using the maximum and minimum values of the amount of received light for each slit width (see FIG. 3C), the image definition, which is an evaluation index of image clarity, is calculated according to the following equation.
_Cw [%] = ( _{Qw - Rw) / (Qw + Rw ) x 100}
However, Cw represents the image definition at the slit width _w of the optical comb, Qw represents the maximum received light amount at the slit width _w , and Rw represents the minimum received light amount at the slit width _w .
At this time, the image definition _Cw becomes a value close to 100% when the reflected image is not distorted and is clear as if it were reflected on a mirror, and the value becomes lower when the reflected image is broken.

It is considered that the image definition has the following relationship with the antiglare properties.

FIG. 4 schematically shows the relationship between the slit width of the optical comb and the anti-glare property in the evaluation of image clarity. As shown in FIG. 4A, when a person visually recognizes the reflected light of the object to be measured, the angle of diffused light that can be recognized differs depending on the distance from the object to be measured.

As shown in FIG. 4(b), when the slit width is narrow (when w is small), among the reflected light of the object to be measured, the reflected light with a narrow range of diffusion angles, that is, the specular reflected light is mainly the slit part. easy to pass through. The sharpness of the image formation at this time, that is, the sharpness of the image obtained from the maximum value _Qw and the minimum value _Rw of the received light amount can be used to evaluate the glare felt by a person at a position away from the measurement object. corresponds to This is because a person at a position distant from the measurement object cannot perceive the light diffused over a wide angle.

On the other hand, as shown in FIG. 4(c), when the slit width is wide (when w is large), the reflected light from the measurement object includes not only regular reflected light but also diffusely reflected light scattered at a wide angle. passes through the slit of the optical comb. The sharpness of the image formed by this, that is, the sharpness of the image obtained by the maximum value _Qw and the minimum value _Rw of the received light amount at this time is the glare felt by a person near the measurement object. Equivalent to evaluation. This is because a person near the object to be measured can perceive not only specularly reflected light but also light scattered over a wide range of angles.

As described above, the evaluation of the image definition obtained under the condition that the slit width w is small corresponds to the evaluation of the glare felt by a person at a distance from the measurement object. On the other hand, the evaluation of the image definition obtained under the condition that the slit width w is large corresponds to the evaluation of the glare felt by a person near the object to be measured.

Therefore, in the present invention, an optical comb having two or more different slit widths is used to measure the image definition of the metal plate in accordance with JIS K7374, thereby evaluating the antiglare property of the metal plate. can be done.

In the present invention, the two or more different slit widths are a first slit width that is at least one of 0.25 mm, 0.5 mm, and 1.0 mm, and a second slit width that is 2.0 mm. Preferably. The image definition measured using an optical comb having the first slit width (small slit width) corresponds to the antiglare evaluation index when observing the metal plate, which is the object to be measured, at a long distance. In addition, the image clarity measured using an optical comb with the second slit width (larger slit width) corresponds to the anti-glare evaluation index when observing the metal plate, which is the object of measurement, at a short distance. do.

The first slit width may be evaluated using any one slit width, but in the present invention, all the first slit widths of 0.25 mm, 0.5 mm and 1.0 mm are used. It is more preferable to evaluate

In the present invention, a short distance means a distance of 1 m or less from the target metal plate, and a long distance means a distance of 10 m or more from the metal plate.

In the present invention, a metal plate with excellent antiglare properties has a small value of image clarity C _w under the condition that the slit width w is small, and the value of image clarity C _w under the condition that the slit width w is large is also small. is preferred. Specifically, in the present invention, the measured value C _w1 of the image definition obtained using an optical comb having the first slit width (w1) is 0% or more and 0.50% or less, and the second It is preferable that the measured value Cw2 of the image definition obtained by using an optical comb having a slit width ( _w2 ) is 0% or more and 10% or less. When this range is satisfied, it can be determined that the metal plate has excellent antiglare properties.

Anti-glare properties at a long distance are satisfied if the measured value Cw1 of the image definition obtained using the optical comb having the first slit width ( _w1 ) is 0.50% or less. Anti-glare properties at a long distance are satisfied if the measured value Cw2 of image definition obtained using an optical comb having the second slit width ( _w2 ) is 10% or less. The image definition measurement _Cw2 is preferably less than or equal to 5%. Note that both C _w1 and C _w2 always show a numerical value of 0 or more from the relationship between the maximum and minimum amounts of received light, and never become a negative value. Therefore, both C _w1 and C _w2 are preferably 0% or more.

More preferably, the image definition C _1.0 when the slit width is 1.0 mm is 0.50% or less, and the image definition C _2.0 when the slit width is 2.0 mm is 5% or less. be. More preferably, the image clarity C _0.25 , C _0.5 and C _1.0 in the case of slit widths of 0.25 mm, 0.5 mm and 1.0 mm are all 0.50% or less, And _C2.0 is 5% or less.

By using the present invention, it is possible to quantitatively evaluate the anti-glare property of a steel sheet and to make pass/fail judgments.

Among thin steel sheets of SUS430, SUS443J1, and SUS445J1 components, SUS430, SUS443J1, and SUS445J1 steel sheets having different thicknesses were prepared, and antiglare properties were evaluated.

Each steel plate was cut into a size of 300×300 mm, and the image definition was measured according to the image definition measurement method specified in JIS K7374. The image definition was measured using a surface analyzer (Canon; surface analyzer RA-532H). Measurements were taken twice each when the incident light was parallel to the rolling direction and when the incident light was perpendicular to the rolling direction, and the average value of the measurements was used as the image definition value. The image definition value C _w1 when the slit width w is 0.25 mm, 0.5 mm, or 1.0 mm, and the image definition value C _w2 when the slit width w is 2.0 mm are obtained. rice field.

Regarding image definition, _Cw1 , which is an index of long-distance antiglare, is in the range of 0% or more and 0.50% or less, and _Cw2 , which is an index of short-distance antiglare, is all When it was 0% or more and 10% or less, the image definition was judged as pass (◯). When C _w1 and C _w2 did not satisfy the predetermined range, it was determined to be unacceptable (x).

Furthermore, the appearance of each steel plate was visually evaluated by humans. As evaluation 1 by human visual observation, evaluation was made based on whether or not the steel sheet felt dazzling when viewed from a standing position with the sun behind it on a fine day. The evaluation at a distance of 10 m from the steel plate was defined as the long-distance evaluation. A short-distance evaluation was made by holding the steel plate in a hand and viewing it from a distance of 30 to 50 cm from the steel plate. Five evaluators continuously observed the steel plate for 5 seconds or more at each of the short distance and the long distance. If even one of the evaluators felt glare, it was judged to have no antiglare property (x), and if all the evaluators judged that there was no sense of discomfort even after continuous viewing for 5 seconds or more, it was judged to have antiglare property (o).

Table 1 shows the evaluation results.

No. Nos. 1, 3 to 5, 10 to 12, and 15 to 16 are examples judged to be excellent in antiglare properties. In other words, _Cw1 is in the range of 0% or more and 0.50% or less, and the long-distance antiglare property is excellent. In addition, _Cw2 is 0% or more and 10% or less in all cases, and the antiglare property at a short distance is also excellent. Therefore, the evaluation method of the present invention has a relative relationship with the index of glare perceived by humans, and it was possible to evaluate that the anti-glare property is good. In particular, No. Samples 3 to 5 had a _Cw2 value of 5% or less, exhibiting particularly excellent anti-glare properties with little change in glare even when the angle was changed.

No. In No. 2, the value of _Cw1 exceeds 0.5%, and the value of _Cw2 exceeds 10%. In particular, there were a number of people who felt glare when viewed from a long distance, and there were also people who felt glare in the short-distance anti-glare property.

No. 6 and 13 exceeded 10% only in _Cw2 values. When viewed at a short distance, this steel plate has a sand-like, so-called "glare" feeling that reflects light in a so-called dot-like manner, and some people feel glare, and the anti-glare property is unsatisfactory.

No. In No. 7, the value of C _1.0 out of C _w1 exceeded 0.5%, and the value of C _w2 also exceeded 10%. Some people felt that it was too bright even at a long distance, and some people complained that it was too bright even at a short distance.

No. In 8, 9, and 14, _Cw1 was all 0.5% or more, and _Cw2 was greater than 10%. Especially No. The steel sheet No. 8 had a strong luster at a long distance, and all the evaluators felt that it was dazzling both at a long distance and at a short distance, and it was rejected. No. 9 is No. It feels more dazzling than No.8. As in 8, all the members felt that the light was too bright both at a long distance and at a short distance, and failed the test.

From these evaluation results, the measured value of image definition agrees with the results of human subjective evaluation of anti-glare property. It was confirmed that the evaluation method of the present invention is useful for evaluating antiglare properties.

Claims (3)

Using an optical comb having two or more different slit widths, the image definition of the metal plate is measured according to JIS K7374, and the antiglare property of the metal plate is evaluated based on the obtained image definition. A method for evaluating the antiglare property of a metal plate. The two or more different slit widths are
a first slit width that is at least one of 0.25 mm, 0.5 mm and 1.0 mm;
a second slit width of 2.0 mm;
The antiglare evaluation method for the metal plate according to claim 1 . The measured value C _w1 of the image definition obtained using the optical comb having the first slit width is 0% or more and 0.50% or less, and obtained using the optical comb having the second slit width. If the measured value C _w2 of the image definition satisfies 0% or more and 10% or less, it is determined that the metal plate has excellent antiglare properties.
The antiglare evaluation method for the metal plate according to claim 2 .

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