JP2000241146A - Method and apparatus for manufacturing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate quality by irradiating a surface of a sheet with a light in an oblique direction, forming a photoreceiving image based on a reflected light from the sheet, and measuring protrusions and recesses of the sheet represented on the image in a short time. SOLUTION: A light emitted from an emitting means 1 irradiates a surface of the sheet 4. The light reflected on the surface of the sheet is received by a photoreceiving means 2, converted into an analog electric signal, which is, in turn, transmitted to an image processing means 3. The means 3 A-D converts the transmitted signal to form a photoreceiving image from the converted signal. A standard deviation of a density distribution of the image is calculated, and the sheet is evaluated according to protrusions and recesses of the surface of the sheet represented on the image.

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 manufacturing a sheet for suitably evaluating unevenness and quality of the sheet.

[0002]

2. Description of the Related Art A resin foam produced by heating and foaming a sheet, for example, a polymer sheet added with a foaming agent, is prepared by applying an adhesive to the resin foam with a roll coater or the like and laminating a leather sheet or the like. Used for car door interior.

[0003] However, such sheets suffer from various disadvantages in the manufacturing process. In particular, when the heating medium is a liquid and the polymer sheet is immersed in the liquid and foamed, bubbles generated by the foaming remain at the boundary between the lower surface of the polymer sheet and the liquid without being released into the air,
The air bubbles form irregularities on the entire lower surface of the resin foam. As a result, even if an attempt is made to apply an adhesive to the resin foam using a roll coater or the like, there is a portion where the adhesive is not applied due to the unevenness formed on the surface, and air remains after the leather sheet or the like is attached. Further, the expansion of the air results in unevenness on the leather seat surface, resulting in impaired appearance. Therefore, it is necessary to evaluate the unevenness of the sheet before applying the adhesive.

As a method of evaluating the quality of a sheet as described above, a method of measuring unevenness of the sheet surface with a stylus-type roughness meter is generally used. However, this method has a problem that it takes an enormous amount of time to measure the entire surface of the target sheet.

In Japanese Patent Publication No. 7-18695,
An apparatus for observing unevenness formed on a flat surface using image processing is described. This device covers a flat surface of the object to be observed and is arranged so that a small gap is formed between the flat surface and the shield. A light projecting device provided outside the shield so that irradiation can be performed, and an imaging device in which the objective lens is arranged above the flat surface to be observed and inside the shield so as to face the flat surface Thus, the presence or absence of wrinkles generated on the surface of a sheet-like material such as paper or cloth is observed, and the undulation or unevenness generated on the flat surface of the object is observed. However, in this apparatus, since the plate-like light is irradiated in parallel to the flat surface, the light hits the unevenness closest to the light emitting portion, but the unevenness existing farther from the light emitting portion is
No light hits because it is the shadow of the nearest unevenness. Therefore, this apparatus can be used to determine the presence or absence of unevenness on a flat surface, but cannot evaluate the period or height of the unevenness on an object having unevenness formed on the entire surface.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet manufacturing method and apparatus for measuring the quality of a sheet by measuring irregularities on the entire surface of the sheet in a short time.

[0007]

In order to achieve the above object, the present invention irradiates the surface of a sheet with light in an oblique direction, creates a light-receiving image based on light reflected from the sheet, and creates a light-receiving image based on the light-receiving image. The present invention is characterized by a sheet manufacturing method for evaluating the quality of a sheet based on the unevenness of the sheet that appears.

[0008] At this time, 5 to 20 with respect to the surface of the sheet.
It is preferable to irradiate light at an angle in the range of degrees, receive reflected light above the sheet, and evaluate the sheet based on the standard deviation of the density distribution of the received image. Further, the average image data value profile f (x) in the vertical direction and the average image data value profile g in the horizontal direction of the received light image are obtained.
(Y) and obtains the pixel position (x _i, y _j) as well as create an average image from the average value of the image data value f of (x _i) and g (y _j), the image data values of the average image Dividing or subtracting by the image data value of the pixel at the same position of the received light image, evaluating the sheet based on the image after the calculation, and further performing band-pass filter processing of the unevenness period on the received light image, It is preferable to evaluate the sheet based on the processed image. And, to evaluate the sheet obtained by the polymer and the foaming agent, and to evaluate the sheet of the resin foam produced by the foam on bath method,
It is also preferable to manage the sheet manufacturing process based on the evaluation result.

Further, the present invention for achieving the above object is characterized by a sheet manufacturing apparatus provided with means for performing any one of the above methods.

Here, it is preferable that the means for irradiating light is a line light guide in which optical fibers are linearly arranged, and that a light condensing means is provided at an emission portion of the line light guide.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sheet manufacturing method according to the present invention comprises an irradiating means 1 for irradiating a sheet 4 to be inspected with light and a light receiving means for receiving reflected light from the sheet 4 as shown in FIG. 2 and an image processing device 3 for creating a light receiving image based on a signal from the light receiving means 2 is used. The light receiving means 2 is connected to the image processing device 3 so as to receive the reflected light from the sheet 4, convert the reflected light into an analog electric signal, and transmit the signal to the image processing device 3. A / D of captured analog electric signal
It has a converter and means for creating a light receiving image from the converted signal and calculating the standard deviation of the density distribution of the light receiving image.

The irradiating means 1 controls the surface of the sheet 4 to be evaluated so that irregularities present on the surface of the sheet 4 apart from the irradiating means do not become shadows of irregularities present at positions closer to the irradiating means. It is necessary to irradiate the oblique direction. The irradiation angle is preferably in the range of 5 to 20 degrees so that the difference in lightness and darkness due to unevenness appears on the received light image. The light receiving means 2 is provided so as to receive the reflected light from above the sheet 4.
The light receiving angle is preferably in the range of 70 to 120 degrees with respect to the surface of the sheet 4 so as to prevent the focus from being shifted.

In the above-described manufacturing apparatus, the light emitted from the irradiating means 1 irradiates the surface of the sheet 4. Then, the light reflected on the sheet surface is received by the light receiving means 2 and converted into an analog electric signal, and the analog electric signal is sent to the image processing means 3. The image processing means 3 performs A / D conversion of the transmitted analog electric signal, and creates a light receiving image from the converted signal. Then, the standard deviation of the density distribution of the received light image is calculated, and the sheet is evaluated based on the unevenness of the sheet surface appearing in the received light image.

Here, the state of light reflection on the surface of the sheet 4 will be described. As shown in FIG. 2, when the height of the irregularities on the sheet surface is large, 5 to 20
By irradiating at an angle of degree, the slope on the illuminating means side of the unevenness of the sheet surface becomes bright and the slope on the opposite side becomes dark with shadow, so that the received image becomes an image having a large difference in brightness. on the other hand,
When the height of the unevenness on the sheet surface is small, the light is applied almost uniformly to the entire sheet surface, and thus the received light image is an image having a small difference in brightness. As described above, the difference between the lightness and darkness of the received light image increases as the height of the unevenness increases. FIG. 3 shows the density distribution of the received light image when the height of the irregularities is large and small. When the standard deviation of these distributions is obtained, the value is large in a sheet having a large unevenness, and the value is smaller as the height of the unevenness is smaller. Therefore, the degree of unevenness existing on the sheet surface and the quality of the sheet can be evaluated from the standard deviation of the density distribution. Further, when the evaluation is made based on the standard deviation of the density distribution, the influence of the color of the formation on the sheet surface is not affected, so that the sheet can be evaluated more accurately.

Further, the present invention, as shown in FIG.
It can also be implemented by an apparatus in which another operation means 11 is added to the image processing means 3 in.

In the present invention, depending on the irradiation means used,
Since the sheet is illuminated from one direction, the received light image may be brighter as it is closer to the illuminating means, and may become darker as the distance from the illuminating means. Further, also in the direction perpendicular to the irradiation direction, the central part may be bright and the edges may be darker. However, the present invention evaluates the unevenness of the sheet surface based on the standard deviation of the density distribution of the received light image. Will have an effect.
Therefore, it is impossible to accurately evaluate the unevenness of the sheet surface. Therefore, the arithmetic means 11 removes illumination unevenness by the following method.

The average image data value profile f (x) in the vertical direction and the average image data value profile g (y) in the horizontal direction of the received light image are obtained, and the image data value f (x) at the pixel position (x _i , y _j ) is obtained. _An average image is created from the average values of _i ) and g (y _j ). Then, the average image is divided or subtracted by the image data value of the pixel at the same position in the received light image, and the calculated data is amplified at a fixed magnification and an offset is added. In the light-receiving image, the light and darkness due to the unevenness on the sheet surface is periodically distributed throughout the image. Only information is included. Then, by dividing or subtracting the light receiving image and the average image, the calculated image contains only the information of the brightness due to the unevenness of the sheet surface.

After obtaining an image containing only the information of the lightness and darkness due to the unevenness, the sheet is evaluated by calculating the standard deviation of the density distribution as in the apparatus shown in FIG.

Further, the present invention, as shown in FIG.
It is also possible to implement the present invention in an apparatus in which another operation means 12 is added to the image processing means 3 in the above.

According to the present invention, as described above, the unevenness of the sheet surface is evaluated based on the standard deviation of the density distribution of the received light image. At this time, the period of the unevenness is not considered. But,
When the adhesive is actually applied to the surface of the sheet, if the period of the unevenness is small, the portion where the adhesive is not applied is reduced, so that there may be no problem. Therefore, even if the density distribution of the received light image is the same, it is necessary to reduce the evaluation value when the period of the unevenness is small. Therefore, it is preferable to perform band-pass filter processing on the received light image before calculating the standard deviation. By performing the band-pass filter processing having the same width as the period of the irregularities, the difference in brightness between the irregularities having a small period can be reduced. By calculating the standard deviation of the density distribution for this processed image, the unevenness of the sheet surface can be evaluated in consideration of the cycle of the unevenness.

Further, by using a line light guide having strong directivity and having optical fibers arranged linearly as the irradiating means 1, the shadow caused by the unevenness of the sheet surface becomes almost the same irrespective of the place, so that it can be accurately obtained. The quality of the sheet can be evaluated. Further, by using a light condensing means, for example, a cylindrical lens at the emission part of the line light guide, the directivity of the irradiation means 1 is enhanced, so that the quality of the sheet can be evaluated more accurately.

As described above, the present invention evaluates the degree of sheet unevenness and the sheet quality from the standard deviation of the density distribution of the sheet appearing in the received light image, so that even a non-skilled inspector can easily and accurately evaluate the sheet. Can be evaluated. In addition, since the present invention applies the above-described evaluation in a sheet manufacturing process, a defective portion in the manufacturing process can be immediately corrected and the manufacturing process can be managed, and the manufacturing cost of the sheet can be reduced. In addition, since defective defects can be removed before shipping, damage due to defective sheets can be suppressed.

The present invention mainly uses a sheet obtained by a polymer and a foaming agent, and further comprises a polymer such as polyethylene or polypropylene and an azodicarbonamide formed by a foaming method in a bath as shown in FIG. It can be suitably carried out in the production process of a sheet having irregularities, such as a resin foam as a component.

[0024]

EXAMPLE 1 Using the apparatus shown in FIG. 1, evaluation was made of two types of sheets having large and small irregularities, which were produced by a bath foaming method mainly comprising polyethylene and a foaming agent. Was done.

The irradiating means was arranged so as to irradiate the sheet surface at an angle of 5 degrees, and the light receiving means was arranged above the sheet so as to face the sheet. As the irradiation means 1, optical fibers were linearly arranged with a width of 100 mm.
A light source using halogen as a light source was used. As the light receiving section 2, an area sensor camera having 512 × 480 CCD elements arranged two-dimensionally was used.

FIG. 6 shows a light receiving image of a resin foam having a large uneven height, and FIG. 7 shows a light receiving image of a resin foam having a small uneven height. The standard deviation of the density distribution of each light-receiving image was 27 and 22, and from this value, the unevenness of the sheet surface could be evaluated. Example 2 Using the apparatus shown in FIG. 4, the unevenness of the sheet surface was evaluated. The sample used was the same sheet as in Example 1.

The average image data value profile f (x) in the vertical direction and the average image data value profile g (y) in the horizontal direction of the received image are obtained, and the image data value f (x) at the pixel position (x _i , y _j ) is obtained. _A two-dimensional average image was created from the average values of _i ) and g (y _j ), and the image data value of the pixel at the same position between the two-dimensional average image and the two-dimensional average image was calculated. The processed image data was processed in the same manner as in the first embodiment.

FIG. 8 shows a light-receiving image before processing, and FIG. 9 shows a light-receiving image after calculation. It can be seen from these images that the illumination unevenness has been removed. When the standard deviation of the density distribution of the image after the calculation of the two samples was calculated, the ratio of each value was 1.65 from 1.23 in Example 1, and
Further, the unevenness of the sheet could be evaluated more accurately. Example 3 Using the apparatus shown in FIG. 5, the unevenness of the sheet surface was evaluated. The same sheets as in Examples 1 and 2 were used as samples.

Since the period of the unevenness on the sheet surface having a large unevenness is about 5 mm, band-pass processing was performed using the number of pixels of the received light image corresponding to the period. The standard deviation of the density distribution of the processed images of the two samples was determined, and the ratio of each was found to be 2.16, and the sheet could be more accurately evaluated.

[0030]

According to the present invention, the surface of a sheet is irradiated with light in an oblique direction, a light-receiving image based on the reflected light from the sheet is created, and the quality of the sheet is determined based on the unevenness of the sheet appearing in the light-receiving image. Since the sheet is manufactured while being evaluated, even a non-skilled inspector can easily and accurately evaluate the unevenness of the sheet surface, and as a result, a defective portion in the manufacturing process can be immediately corrected, and the sheet can be immediately corrected. Can be reduced in manufacturing cost.

At this time, 5 to 20 with respect to the surface of the sheet
When light is emitted at an angle in the range of degrees and reflected light is received above the sheet, height information of unevenness on the sheet surface can be accurately obtained as a received light image. In addition, when the sheet is evaluated based on the standard deviation of the density distribution of the received light image, the unevenness of the sheet surface can be accurately evaluated without being affected by the formation color of the sheet surface.

Then, the average image data value profile f (x) in the vertical direction and the average image data value profile g (y) in the horizontal direction of the received light image are obtained, and the pixel position (x _i , y _j ) is obtained.
An average image is created from the average value of the image data values f (x _i ) and g (y _j ), and the image data value of the average image is divided or subtracted by the image data value of the pixel at the same position in the received light image. However, when the sheet is evaluated based on the image after the calculation, the unevenness of the sheet surface can be accurately evaluated without being affected by the illumination unevenness. In the case where the sheet is subjected to the filtering process and the sheet is evaluated based on the processed image, the evaluation can be performed in consideration of the period of the unevenness.

Further, by using a line light guide having strong directivity and optical fibers arranged linearly as the irradiating means, the shadow caused by the unevenness of the sheet surface becomes almost the same regardless of the place, so that the sheet can be accurately formed. Irregularities on the surface can be evaluated. If the light converging means is provided at the emission part of the line light guide, the directivity of the irradiating means 1 is further enhanced, so that the sheet surface can be more accurately evaluated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a sheet manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of light reflection on a sheet surface.

FIG. 3 is a diagram showing a density distribution of a received light image.

FIG. 4 is a block diagram of a sheet manufacturing apparatus according to another embodiment of the present invention.

FIG. 5 is a block diagram of a sheet manufacturing apparatus according to still another embodiment of the present invention.

FIG. 6 is a light reception image of a resin foam having a large unevenness obtained in Example 1.

FIG. 7 is a received light image of a resin foam having a small height of irregularities obtained in Example 1.

FIG. 8 is a received light image (before processing) obtained in Example 2.

FIG. 9 is a light reception image (after processing) obtained in Example 2.

FIG. 10 is a schematic diagram of a sheet manufacturing process by a foaming on bath method.

[Explanation of symbols]

 1: irradiating means 2: light receiving means 3: image processing means 4: sheet 11: calculating means 12: calculating means 20: bathtub 21: heating medium

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA49 AA61 BB26 CC00 CC02 FF04 FF42 HH03 HH12 JJ03 JJ26 LL03 LL08 QQ03 QQ26 QQ33 QQ41 QQ42 QQ43 QQ45 UU01

Claims (11)

[Claims] 1. A method for irradiating light obliquely to the surface of a sheet, creating a light receiving image based on light reflected from the sheet, and evaluating the quality of the sheet based on unevenness of the sheet surface appearing in the light receiving image. A method for producing a sheet, comprising: 2. The method for manufacturing a sheet according to claim 1, further comprising irradiating light at an angle in the range of 5 to 20 degrees with respect to the surface of the sheet and receiving reflected light above the sheet. 3. The sheet manufacturing method according to claim 1, wherein the sheet is evaluated based on a standard deviation of a density distribution of the received light image. 4. An image data value profile f (x) in the vertical direction and an average image data value profile g (y) in the horizontal direction of the light-receiving image are obtained, and the image data value at the pixel position (x _i , y _j ) is obtained. An average image is created from the average values of f (x _i ) and g (y _j ), and the image data value of the average image is
The sheet manufacturing method according to any one of claims 1 to 3, wherein the sheet is evaluated based on the image after the division by dividing or subtracting the image data value of the pixel at the same position in the received light image. 5. The production of a sheet according to claim 1, wherein the light-receiving image is subjected to band-pass filter processing with a period of irregularities on the sheet surface, and the sheet is evaluated based on the processed image. Method. 6. The method for producing a sheet according to claim 1, wherein the sheet obtained by using the polymer and the foaming agent is evaluated. 7. The method for producing a sheet according to claim 1, wherein the resin foam sheet produced by the on-bath foaming method is evaluated. 8. The sheet manufacturing method according to claim 1, wherein a sheet manufacturing process is managed based on the evaluation result. 9. An apparatus for manufacturing a sheet, comprising: means for performing the method according to claim 1. 10. The sheet manufacturing apparatus according to claim 9, wherein the means for irradiating light is a line light guide in which optical fibers are linearly arranged. 11. The sheet manufacturing apparatus according to claim 10, wherein a light condensing means is provided at an emission portion of the line light guide.