JP7356873B2 - Embossed pattern and absorbent article inspection method, and absorbent article manufacturing method - Google Patents

Description

The present invention relates to an embossed pattern and a method for inspecting an absorbent article, and a method for manufacturing an absorbent article.

Absorbent articles such as sanitary napkins typically include an absorbent body containing an absorbent material such as hydrophilic fibers or water-absorbing polymers, and an absorbent body placed on a side closer to the wearer's skin than the absorbent body. It includes a top sheet and a leak-proof sheet placed on a side farther from the wearer's skin than the absorbent body. In order to improve the appearance and absorbency of body fluids, embossed parts may be formed on the top sheet placed on the wearer's skin side, or on both the top sheet and the absorbent body, by pressing these in the thickness direction. be.

As a method for inspecting the quality of formation of such an embossed part, for example, Patent Document 1 discloses that an area in which a compressed part is formed is imaged, data of a planar image of the area is generated as planar image data, and data of a planar image of the area is generated as planar image data. It is disclosed that the image data is binarized based on a first threshold value and a second threshold value different from the first threshold value to determine the presence or absence of a perforation abnormality or a joint abnormality in the compressed portion.

Further, Patent Document 2 discloses an inspection method for inspecting a plurality of openings formed through the skin-side sheet of an absorbent article in the thickness direction. In this inspection method, before the skin-side sheet is superimposed on the absorbent body, the area where the opening is formed is imaged to generate planar image data, and a binarization process is performed based on the planar image data. This document discloses that a binarized image is generated by performing a binarized image, and the presence or absence of an abnormality in the aperture is determined based on the binarized image.

Japanese Patent Application Publication No. 2013-68537 Japanese Patent Application Publication No. 2013-85759

However, in the inspection methods described in Patent Documents 1 and 2, the formed embossed portions are inspected without distinguishing between the formed embossed portions and the basis weight unevenness that occurs in the constituent members of the absorbent article. cannot be excluded, and a position where an embossed portion is normally formed may be erroneously detected as being poorly formed, or a position where an embossed portion is not normally formed may be erroneously detected as being well formed. As a result, the inspection accuracy of absorbent articles has been poor, and the production efficiency of absorbent articles has been reduced.

Therefore, it is an object of the present invention to provide a method for inspecting absorbent articles that can overcome the drawbacks of the prior art.

The present invention is a method for inspecting the quality of an embossed pattern consisting of a plurality of embossed parts formed by compressing a liquid-retaining absorbent body and a liquid-permeable sheet in a stacked state, comprising:
irradiating a region including the embossed pattern with light to obtain a transmitted light image;
correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
The present invention provides an emboss pattern inspection method that determines the quality of the emboss pattern based on the binarized image.

Further, the present invention comprises a liquid-retaining absorbent body, a liquid-permeable top sheet, and a liquid-impermeable or barely liquid-permeable back sheet, and the absorbent body and the top sheet are pressed in a laminated state. A method for inspecting the quality of an embossed pattern in an absorbent article having an embossed pattern consisting of a plurality of embossed parts formed by
irradiating a region including the embossed pattern with light to obtain a transmitted light image;
correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
The present invention provides an absorbent article inspection method that determines the quality of the embossed pattern based on the binarized image.

Furthermore, the present invention provides an embossed pattern consisting of a plurality of embossed portions by compressing a liquid-retaining absorbent body and a liquid-permeable surface sheet in a laminated state,
irradiating a region including the embossed pattern with light to obtain a transmitted light image;
correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
The present invention provides a method for manufacturing an absorbent article, which includes a step of determining the quality of the embossed pattern based on the binarized image.

According to the present invention, the formation state of the embossed pattern can be accurately inspected without depending on the uneven basis weight of the constituent members.

FIG. 1 is a plan view showing an embodiment of an absorbent article to which the present invention is applied. FIG. 2 is a schematic diagram showing an embodiment of an absorbent article manufacturing apparatus including an embossed pattern inspection apparatus suitably used in the present invention. FIG. 3 is a diagram showing a transmitted light image, a multi-tone image, a binary image, and a reference image in an example of forming an emboss pattern. FIGS. 4A to 4C are schematic diagrams showing the arrangement of the absorber, the embossed pattern, and its center of gravity.

Hereinafter, the present invention will be described based on preferred embodiments thereof with reference to the drawings. In the method for manufacturing an absorbent article of the present invention, a liquid-retaining absorbent body, which is a material constituting the absorbent article, and a liquid-permeable sheet are bonded in one of the steps of manufacturing the absorbent article. The method includes a step of determining the quality of an embossed pattern formed by compressing both layers in a stacked state and formed by a plurality of embossed portions.

Absorbent articles to which the present invention is applied broadly include those that are worn on the body and have the function of absorbing and retaining excrement excreted from the body. Examples of such absorbent articles include disposable diapers, sanitary napkins, incontinence pads, auxiliary pads (urinary pads) used in conjunction with diapers, panty liners, and the like.

FIG. 1 shows a sanitary napkin as an example of an absorbent article 1 to which the present invention is applicable. The absorbent article 1 shown in the figure has a vertically elongated shape having a longitudinal direction X corresponding to a direction extending from the ventral side of the wearer to the back side via the crotch region and a width direction Y perpendicular to this direction. . The absorbent article 1 has a crotch region 1M disposed in the wearer's crotch region, and a ventral region 1F and a dorsal region 1R extending in front and behind the crotch region 1M. The crotch area has an excretory part facing part (not shown) that is arranged opposite to the wearer's excretory part when the absorbent article is worn, and the excretory part facing part usually extends in the longitudinal direction of the absorbent article 1. It is located at or near the center of X.

The absorbent article 1 shown in the figure includes a liquid-permeable sheet 2 which is a top sheet located on the side facing the wearer's skin, and a liquid-impermeable or barely liquid-permeable back side located on the non-skin facing side. It includes a sheet 3 and a liquid-retaining absorbent body 4 interposed between the sheets 2 and 3. As the liquid permeable sheet 2, for example, a nonwoven fabric, a perforated film, or the like can be used alone or in a stack of two or more sheets. As the back sheet 3, for example, a liquid-impermeable film, spunbond, meltblown, spunbond laminated nonwoven fabric, etc. can be used. A film having low liquid permeability may be provided with a plurality of micropores to impart water vapor permeability to the film. In order to make the absorbent article even more comfortable to the touch, a sheet with a good texture, such as a nonwoven fabric, may be laminated on the outer surface of the backsheet.

The absorbent body 4 includes an absorbent core 41. The absorbent core 41 is, for example, a stack of hydrophilic fibers such as cellulose including pulp, a mixed stack of the hydrophilic fibers and an absorbent polymer, a pile of absorbent polymers, or two absorbent sheets. It is composed of a laminated structure with an absorbent polymer supported between them. The absorbent core 41 may have at least its skin-facing surface covered with a liquid-permeable core-wrap sheet 42, and the entire surface including the skin-facing surface and non-skin-facing surface may be covered with the core-wrap sheet. Good too. As the core wrap sheet, for example, thin paper made of hydrophilic fibers, nonwoven fabric having liquid permeability, etc. can be used. From the viewpoint of improving the usability such as improving the retention of body fluids and the fit to the wearer, the absorbent body 4 has a low basis weight part and a high basis weight part whose basis weight is higher than the low basis weight part. It is preferable to have. As an absorber having such a structure, for example, the one described in JP-A No. 2013-255567 can be used.

The absorbent article 1 has a plurality of embossments formed by pressing the liquid-permeable sheet 2 and the absorbent core 4 together so that the absorbent core 4 is depressed toward the side on which the liquid-permeable sheet 2 is not disposed. 7. A plurality of embossed portions 7 shown in the figure are formed in a circular shape, and are arranged so as to form a combination of approximately elliptical and arcuate embossed patterns when viewed from above.

In addition to the liquid-permeable sheet 2, back sheet 3, and absorbent body 4 described above, leak-proof cuffs 8 and wing portions 9 may be arranged as shown in FIG. 1 depending on the specific use of the absorbent article 1. Good too. The leak-proof cuff 8 shown in FIG. 1 is formed on both sides of the skin-facing surface along the longitudinal direction X so as to extend along the longitudinal direction. The leak-proof cuff 8 has a proximal end and a free end. The leak-proof cuff 8 has a base end on the skin-facing surface side of the absorbent article, and stands up from the skin-facing surface side. The leak-proof cuff is made of a liquid-resistant or water-repellent material that is breathable. An elastic member made of rubber thread or the like may be disposed in a stretched state at or near the free end of the leak-proof cuff. By contracting this elastic member when the absorbent article is worn, the leak-proof cuff stands up toward the wearer's body, and the liquid excreted onto the top sheet flows through the top sheet and absorbs the absorbent material. Leakage outward in the width direction of the article is effectively prevented.

The wing portion 9 is a portion that extends outward from both side edges in the width direction Y of the absorbent article, and is fixed to the outer surface of the crotch portion of the shorts by folding it back when the absorbent article 1 is worn on shorts, for example. This is the part where The absorbent article may further have an adhesive layer on the non-skin facing surface. The adhesive layer is used to fix the absorbent article to underwear or another absorbent article when the absorbent article is worn.

FIG. 2 shows an embodiment of an absorbent article manufacturing apparatus 10 including an emboss pattern inspection device, which is suitably used in the process of determining the quality of an emboss pattern. The manufacturing apparatus 10 shown in the figure includes an embossing roll unit for forming an emboss pattern consisting of a plurality of embossed parts on a laminate 1A of a liquid-permeable sheet 2 and an absorbent body 4 that are being conveyed in one direction MD. 20, an imaging device 30 for capturing an image of the formed state of the embossed pattern, and a light source 40 for illuminating a predetermined imaging area.

The embossing roll part 20 is for forming a plurality of embossing parts on the laminate 1A. The embossing roll unit 20 includes a convex roll 21 having a convex portion formed on its circumferential surface in a shape corresponding to a desired embossing pattern, and an anvil roll 22 having a smooth circumferential surface, and is capable of forming a laminate. 1A between the rolls 21 and 22, the liquid-permeable sheet 2 and the absorbent body 4 constituting the laminate 1A are pressed together and embossed. This results in a processed laminate 1B in which an embossed pattern consisting of a plurality of embossed portions is formed on the liquid-permeable sheet 2 side of the laminate 1A.

The imaging device 30 captures an image of the formed state of the embossed pattern on the processed laminate 1B being conveyed in one direction MD. The imaging device 30 is equipped with a lens and a photoelectric conversion section, and is a device that can image the processed laminate 1B being transported as a still image. Examples of such an imaging device include an area camera and a line scan camera that include a photoelectric conversion element. The photoelectric conversion element may be a charge coupled device (CCD) or a CMOS sensor. The photoelectric conversion element may be a photoelectric conversion element capable of expressing gradations in RGB colors, or may be a photoelectric conversion element capable of expressing gradations in a gray scale of 256 gradations, preferably with even higher gradations. It may also be a photoelectric conversion element that can express various gradations.

As long as the light source 40 illuminates the imaging area of the imaging device 30, there are no particular limitations on its arrangement position, color, and shape of the light source. As for the arrangement position, for example, as shown in FIG. 2, the imaging device 30 and the light source 40 are arranged facing each other, and the processed laminate 1B is arranged so as to be able to move between them to obtain an image of transmitted light. Alternatively, the imaging device 30 may be placed on the front or back side in the direction in which light is emitted from the light source 40, and an image of reflected light may be obtained. In either case, it is preferable that the imaging device 30 and the light source 40 be placed at a position separated from the processed laminate 1B being transported.

From the viewpoint of making the imaging of the embossed pattern clearer in the imaging device 30, the light source 40 is arranged to face the imaging device 30, so that the processed laminate 1B can move between the imaging device 30 and the light source. It is preferable that the It is also preferable to arrange the imaging device 30 on the side of the absorber 4 on which the liquid-permeable sheet 2 is arranged, and to arrange the light source 40 on the side on which the liquid-permeable sheet 2 is not arranged. By arranging the imaging device 30 and the light source 40 in this way, it is possible to clearly depict the embossed pattern in the captured image, and also to clearly depict the embossed pattern in the absorbent article, such as the liquid-permeable sheet and the absorbent body. There is an advantage in that it is possible to reduce the adverse effects on the depiction of the embossed pattern caused by uneven basis weights caused by unevenness in basis weight or differences in designed basis weight intentionally formed in the member. The imaging device 30 and the light source 40 may be electrically connected to a control unit 50, which will be described later.

The manufacturing apparatus 10 has been developed from the viewpoint of being able to determine in real time the formation state of the embossed pattern of the processed laminate 1B from the images obtained by imaging while taking images of the processed laminate 1B over time during the manufacturing process of an absorbent article. It is preferable that the control unit 50 is provided. The control unit 50 shown in FIG. 2 is connected to the imaging device 30. Inside the control unit 50, there are a plurality of components, such as an electrical signal processing unit, a storage unit, an image processing unit, a grayscale processing unit, a binarization processing unit, an arithmetic unit, an analysis unit, a determination processing unit, and an electrical signal transmission unit. It has a section (not shown) that can convert electrical signals transmitted from the imaging device 30 into images and perform image processing.

The control unit 50 is electrically connected to the imaging device 30 and the light source 40, and controls the laminate 1A and the processed laminate 1B based on the electrical signals transmitted from the imaging device 30 to the control unit 50 and the analysis results thereof. The conveyance speed and the roll interval of the embossing roll section 20 may be adjusted automatically. Further, as shown in FIG. 2, an encoder 51 is provided between the control unit 50 and the anvil roll 22, the rotation state of the anvil roll 22 is detected by the encoder 51, and based on the detection signal, the rotation state of the anvil roll 22 is detected. The timing of imaging can be controlled by the control unit 50.

The control unit 50 may be, for example, a computer installed with image processing software or the like, or a device constructed based on an image controller. In addition, an interface (not shown) is connected to the control unit 50, and the control unit 50 can be controlled based on electrical signals input manually via the interface, and electric signals transmitted from the control unit 50 can be controlled. Based on the signal, warnings, problems, etc. regarding the embossed pattern formed on the processed laminate 1B can be displayed on the interface.

In the manufacturing process of the absorbent article 1, after the laminate 1A is compressed to form an embossed pattern to form the processed laminate 1B, a step of disposing the back sheet 3 may be further performed. The manufacturing apparatus 10 shown in FIG. 2 connects a supply roll 60 that supplies the backsheet 3 and a cutter section 70 that cuts the liquid-permeable sheet 2 and the backsheet 3 at predetermined positions in the processed laminate 1B to an imaging device. 30 and the light source 40 on the downstream side. The back sheet 3 fed out from the supply roll 60 was arranged so as to come into contact with the surface of the absorber 4 of the processed laminate 1B on the side where the liquid-permeable sheet 2 was not arranged, and was laminated together with the processed laminate 1B. transported in the same condition. The cutter section 70 includes a cutter roll 71 and a smooth roll 72 disposed opposite to the roll 71, and supplies the processed laminate 1B and the back sheet 3 between these rolls 71 and 72 to absorb the The liquid-permeable sheet 2 and the back sheet 3 are cut at a position where the body 4 is not present to obtain an absorbent article 1.

Next, a method for determining the quality of an embossed pattern when using the above-described manufacturing apparatus 10 will be described. This method includes the steps of: irradiating a region including an embossed pattern with light to obtain a transmitted light image; correcting the image through multi-tone processing based on its brightness to generate a multi-tone image; The method includes the steps of generating a binarized image by performing binarization processing on the multi-gradation image based on a preset threshold value, and determining the quality of the embossed pattern based on the binarized image.

First, a region including the embossed pattern in the processed laminate 1B on which the embossed pattern has been formed is irradiated with light from the light source 40 to obtain a transmitted light image. Acquisition of the transmitted light image may be performed, for example, by continuously or intermittently imaging a part of a plurality of embossed portions forming an embossed pattern or the entire embossed pattern. I can do it. The transmitted light image may be acquired for the processed laminate 1B that is being transported in one direction MD, or for the processed laminate 1B that is stationary. Further, the region including the embossed pattern to be imaged may be a region including all the embossed portions forming the embossed pattern, or may be a region including some embossed portions of the embossed pattern. As a result, a transmitted light image regarding the state of formation of the embossed pattern is obtained.

In acquiring a transmitted light image, light is irradiated from the side of the processed laminate 1B where the liquid-permeable sheet 2 is not arranged, and the transmitted light in the irradiated area is transmitted from the side where the liquid-permeable sheet 2 is arranged. It is preferable to take an image from By acquiring a transmitted light image in this way, it is possible to acquire an image that clearly depicts the embossed pattern, and it is also possible to avoid unintended tsubo due to blurring during processing of components that constitute absorbent articles such as liquid-permeable sheets and absorbers. It is possible to reduce the adverse effects on the depiction of the embossed pattern due to unevenness in quantity and differences in design basis weight intentionally formed in the member. In order to obtain a transmitted light image using such a method, the arrangement positions of the imaging device 30 and the light source 40 may be changed as appropriate.

Further, it is preferable that the region including the embossed pattern to be imaged is the region having the largest number of embossed portions per unit area. From the viewpoint of improving productivity, it is preferable that the embossed portions be formed continuously by the embossing roll unit 20 described above, but in areas where a large number of embossed portions are formed, the laminate is The pressure applied to the laminate 1A may become non-uniform in the surface direction of the laminate 1A, resulting in formation defects of the embossed portion, such as insufficient opening area and depth of the embossed portion. In this regard, by subjecting the image containing the area with the largest number of embossed areas per unit area to pass/fail determination, it is possible to focus on inspecting areas where embossed areas and embossed pattern formation defects may occur. Therefore, the quality of the embossed pattern can be determined more accurately.

Next, the obtained transmitted light image is corrected by multi-gradation processing based on its brightness to generate a multi-gradation image. Multi-gradation processing refers to the process of smoothing pixel brightness in an area containing multiple pixels. For example, the brightness based on the average value of pixel brightness of a transmitted light image in a predetermined range is sequentially output as the brightness of the processed image. Examples of known processing methods include moving average filter processing and median filter processing. In other words, the multi-gradation process in this step does not include the process of converting the pixel brightness into two gradations, that is, the binarization process. This process may be performed by the control unit 50 in parallel with the image capture by the image capture device 30, or may be performed by the control unit 50 or another image processing device after the image capture device 30 captures the image.

In the transmitted light image, the part where the embossed part of the embossed pattern is formed has a high light transmittance, so the pixel brightness of the part is high, and the part is displayed as a color containing a large amount of white component on the image. On the other hand, areas where embossed areas are not formed or areas where embossed areas are poorly formed have low light transmittance, so the pixel brightness of these areas is compared to areas where embossed areas are formed. The color becomes low, and the color is displayed as a color containing a large amount of black component on the image. In addition to these, the light transmittance changes depending on the uneven basis weight and design basis weight difference of the liquid-permeable sheet 2 and absorber 4 that constitute the processed laminate 1B to be imaged, so in a transmitted light image, Pixel brightness is depicted according to the area where the difference in basis weight occurs.

When such a transmitted light image is subjected to multi-tone processing based on brightness, changes in tone values based on brightness are corrected and rendered as a multi-tone gray scale, depending on the position where the embossed part is formed. A multi-tone image can be obtained. For example, when a transmitted light image as shown in FIG. In the "non-embossed area B1"), the pixel brightness is low and the change in gradation value of adjacent pixels is small, so the pixel brightness is smoothed to eliminate the change in gradation value. As a result, pixel brightness is corrected so that the area on the image has a large amount of black components such as black. Similarly, in the region W1 where the embossed portion is formed (hereinafter, this region is also referred to as the "embossed portion forming region W1"), the pixel brightness is high and the change in gradation value of adjacent pixels is small, so the image The pixel brightness is corrected so that the upper part has more white components. On the other hand, at the boundary between the non-embossed part B1 and the embossed part W1, the change in the gradation value of adjacent pixels is large, so pixel brightness is not smoothed at this boundary, and the difference in pixel brightness is It is corrected so that it remains as . As a result, the boundary between the embossed part non-formed part B1 and the embossed part formed part W1 is clearly depicted, and other parts are smoothed according to the gradation values of adjacent pixels to obtain a multi-tone image. I can do it.

Subsequently, the obtained multi-gradation image is subjected to a binarization process based on a preset threshold value to generate a binarized image, and the quality of the emboss pattern is determined based on this binarized image. The binarization process may be performed by the control unit 50 in parallel with imaging by the imaging device 30, or may be performed by the control unit 50 or another image processing device after imaging by the imaging device 30.

The threshold value in the binarization process may be set in advance at the pixel luminance boundary between the embossed portion forming portion W1 and the embossed portion non-forming portion B1 in the multi-tone image. When white and black are binarized based on such a threshold value, as shown in FIG. 3, in the binarized image, the embossed part forming part W1 is depicted as white, and the embossed part non-forming part B1 is depicted as black. It is depicted as.

The quality of the embossed pattern based on the binarized image is determined based on at least one of the number of embossed parts in the image, the area where each embossed part is formed, and the position where each embossed part is formed. The quality of the embossed pattern is preferably determined based on the number of embossed parts, the area of each embossed part, the area and position of each embossed part, or a combination of the number of embossed parts and the position of each embossed part. , the number of embossed parts, the area where each embossed part is formed, and the position where each embossed part is formed.

When making a quality judgment based on the number of embossed parts, for example, in a binarized image, it is set in advance so that a part where white pixels exist over a predetermined area is determined to be a part where an embossed part is formed. , the number of parts determined to be embossed parts is counted. If the measured number matches the designed number of embossed parts existing in the same area as the image, it is determined that the embossed pattern is well formed, and the measured number and the designed number of embossed parts are determined to be good. If they do not match, it is determined that the formation of the embossed pattern is defective.

In addition, when making a pass/fail judgment based on the formation area of each embossed part, for example, a predetermined numerical range based on the total design area value of the embossed parts in the target embossed pattern is set in advance as a threshold, and the The threshold value is compared with the total area of white pixels in the binarized image. If the total area of white pixels in the binarized image is within the range of the threshold area, it is determined that the emboss pattern is well formed, and even if the total area of the white pixels in the binarized image is outside the range of the threshold area. For example, it is determined that the formation of the embossed pattern is defective.

Similarly, when making a pass/fail judgment based on the formation position of each embossed part, for example, the design centroid position of each embossed part in the target embossed pattern and a predetermined distance from the design centroid position are used as thresholds. The design centroid position is set in advance and the centroid position of the figure drawn by white pixels in the binarized image is compared. If the design centroid position and the centroid position in the binarized image match, or if the deviation of each centroid position is within a predetermined distance, it is determined that the embossed pattern is well formed; If the deviation of each centroid position is outside the predetermined distance, it is determined that the formation of the embossed pattern is defective.

The determination process and result of the pass/fail determination performed as described above are calculated and analyzed by the control unit 50. At this time, if the formation state of the emboss pattern based on the binarized image is determined to be poor or undeterminable, the control unit 50 outputs an electric signal based on the determination, and controls the imaging field of view of the imaging device 30 and the light intensity of the light source 40. or adjust it. Alternatively, the processed laminate 1B determined to be defective is discharged out of the production line. These adjustments may be performed manually using an interface connected to the control unit 50, or may be controlled to be performed automatically within the control unit 50.

Information regarding the determination process and results of these pass/fail determinations can also be displayed on the interface via electrical signals output from the control unit 50. The information displayed on the interface is not particularly limited, and for example, it may display that the embossed pattern formation state of the processed laminate 1B is good, or it may display that the embossed pattern formation state is poor and its location. Or, it is possible to display that it is impossible to determine the quality of the embossed pattern. This information may be displayed and updated in real time, or may be set to be displayed and updated at regular intervals.

In this technical field, in addition to forming embossed patterns, in order to improve the usability of absorbent articles such as absorbency of body fluids, texture, fit, etc. Each component of an article may be intentionally designed to have a difference in basis weight. Further, in each component of the absorbent article, wobbling may occur during processing of the member, and this wobbling may cause unintended unevenness in basis weight. To determine the quality of an embossed pattern formed on a component with a difference in basis weight or uneven basis weight as described above, the transmitted light image or reflected light image was directly binarized without undergoing any other processing. When performing inspection based on a binarized image, the emboss pattern and the basis weight difference or basis weight unevenness are depicted without being distinguished, so it is difficult to accurately inspect the emboss pattern. As a result, the processed laminate 1B or absorbent article 1, which is originally a defective product, may be erroneously determined as a good product, or the processed laminate 1B or absorbent article 1, which is originally a good product, may be erroneously determined as a defective product. There is a risk that the inspection accuracy of the absorbent article will decrease.

In this regard, according to the present method, by using a binarized image obtained by performing multi-gradation processing and binarization processing of a transmitted light image, images of basis weight differences or basis weight unevenness of constituent members can be drawn. Since it is possible to reduce the adverse effects of embossed pattern detection caused by This enables accurate and efficient inspection. As a result, production efficiency of absorbent articles can be improved. Particularly, as a preferred embodiment of the present invention, even if the absorber 4 is designed to have a low basis weight section and a high basis weight section, the adverse effects of embossed pattern detection can be reduced, so the embossed pattern The quality of the formed state of the absorbent article can be accurately and efficiently inspected, and the manufactured absorbent article has improved usability such as absorbency of body fluids, texture, and fit.

From the perspective of determining the quality of the emboss pattern formation with higher accuracy, the information contained in the binarized image is compared with the information contained in a preset reference image, and a correlation value is calculated from the difference in the information between the two. It is preferable to calculate. The information included in the binarized image for calculating the correlation value is based on the distribution of white pixels and black pixels in the image, and these distributions are based on the number of embossed parts in the binarized image, each This is related to the area where the embossed portions are formed and the position where each embossed portion is formed. Calculation of the correlation value can be performed, for example, by performing arithmetic processing in the control unit 50 using a device constructed based on a computer or an image controller in which image processing software or the like is installed.

Calculation of the correlation value can be performed, for example, in the control unit 50 using an image controller (manufactured by Keyence Corporation, XG-X2900). Taking the case of using this image controller as an example, a method of calculating a correlation value will be described below.

Calculation of the correlation value using the image controller described above can be performed, for example, by pattern search measurement. In pattern search measurement, information included in a reference image that is a model image of an embossed pattern to be detected and information included in a binarized image to be compared are stored in a storage unit in an image controller in the control unit 50. Then, information similar to information regarding the emboss pattern of the reference image is detected from among the information of the stored binarized image, and a correlation value is calculated based on the difference between each piece of information. Information regarding the emboss pattern is based on the distribution of pixels within the image.

First, information included in a reference image, which is a model image of an embossed pattern to be detected, is stored in advance in a storage unit (not shown) in an image controller in the control unit 50. Specifically, with the reference image displayed on the interface, an area including the embossed pattern of the reference image is set as a search area. Thereafter, a pattern area surrounding the emboss pattern of the reference image existing within the search area is set, and information regarding the emboss pattern existing within the pattern area is stored in the storage unit. Separately from this, information regarding the emboss pattern included in the binarized image to be compared is stored in the storage unit.

The reference image may be, for example, an image based on the design dimensions of the embossed pattern, or an image based on the shape of the convex portion formed on the circumferential surface of the convex roll 21 in the embossing roll section 20. An image based on the embossed pattern of the processed laminate 1B or absorbent article 1 that has been determined to be well formed may be used. In order to prevent unintended false detections when comparing the binarized image of the embossed pattern to be inspected with the reference image, and to reduce the computational load, use a binarized image as the reference image. is preferred. In this case, the information included in the reference image for calculating the correlation value is based on the distribution of white pixels and black pixels within the image.

Next, information similar to information regarding the emboss pattern of the reference image is detected from among the information included in the stored binarized image, and a correlation value is calculated. In pattern search measurement, information about the embossed pattern included in the binarized image is searched within the above-mentioned search area, information similar to the information about the embossed pattern in the reference image is detected, and the information is calculated based on the difference between the two pieces of information. , calculate the correlation value. The difference between the two pieces of information can be specified, compared, or calculated from the position coordinates, inclination angle, etc. of the pattern area, based on the distribution of white pixels and black pixels existing in the pattern area, for example.

The correlation value is a value indicating the degree of similarity of the emboss pattern shape in the binarized image to the emboss pattern shape in the reference image. Generally, the higher the correlation value is calculated, the more the shapes being compared match each other. The correlation value can be calculated by, for example, normalized correlation based on pixel brightness or a known pattern matching method using geometric shapes. When calculating a correlation value using the image controller described above, the calculation of the correlation value can be performed using, for example, a pattern search measurement tool using the image controller described above. In this case, the correlation value can be obtained by reading the numerical value of the correlation value in the measurement results displayed on the interface.

In the emboss pattern formation example 1 and formation example 2 shown in FIG. 3, the correlation value is calculated using a binarized image as the reference image. In Formation Example 1, the correlation value with respect to the reference image is calculated as 53.439. Further, in Formation Example 2 shown in the figure, the correlation value with respect to the reference image is calculated to be 99.999. Therefore, it can be seen that Formation Example 2 of the embossed pattern has higher similarity to the reference image than Formation Example 1.

Subsequently, it is preferable to compare the correlation value obtained by the above-described method with a preset threshold value to determine whether the embossed pattern is good or bad. The threshold value in this step can be changed as appropriate depending on the desired embossing pattern. The threshold value can be set, for example, by calculating in advance a correlation value between an emboss pattern whose formation state is determined to be good through visual inspection and a reference image, and setting the correlation value as the threshold value. By determining the quality of the embossed pattern based on the correlation value, the quality of the embossed part can be improved compared to the case where the quality of the embossed pattern is determined based on either the number of embossed parts, the formation area, or the formation position. Since the determination based on the number of embossed parts, the area where each embossed part is formed, and the position where each embossed part is formed can be made in one process, the quality of the embossed pattern can be determined with fewer steps and with higher accuracy. As a result, the production efficiency of absorbent articles can be further improved.

As a specific example, when the threshold value of the correlation value is set as 70.0, the correlation value with respect to the reference image is calculated as 53.439 in the emboss pattern formation example 1 shown in FIG. is determined to be less than the threshold value, and as a result, the formation state of the embossed pattern in Formation Example 1 is determined to be poor. In addition, in Formation Example 2 of the embossed pattern shown in the figure, the correlation value with respect to the reference image is calculated to be 99.999, so it is determined that the correlation value exceeds the threshold value, and as a result, in Formation Example 2 The formation condition of the embossed pattern is determined to be good. The setting of the threshold value and the quality determination can be performed, for example, in the control unit 50.

In the explanations so far, for convenience of explanation, we have taken as an example a case in which the quality of the formation state of the embossed pattern is determined by focusing on a specific area where the embossed part is formed in the embossed pattern. Alternatively, or in addition to this, it is also preferable to judge the quality of the formed state of the embossed pattern based on the position of the center of gravity of the embossed pattern with respect to the absorbent body 4 for the entire embossed pattern. By making a quality determination based on the position of the center of gravity of the embossed pattern, in addition to determining the quality of the formation of the embossed part, it is also possible to determine whether or not there is a shift in the rotational phase of the embossing roll part 20 in the manufacturing apparatus 10, and the laminate 1A and processed laminate 1B. Since it is possible to check the presence or absence of misalignment during conveyance, it is possible to further improve the production efficiency of absorbent articles on which embossed patterns are formed.

In this step, first, edges between the periphery of the absorber 4 and the background in the transmitted light image are detected by edge detection processing. Edge detection processing refers to the process of detecting areas with large changes in gradation values in the pixel brightness of an image. For example, the edge detection processing refers to the process of detecting areas with large gradation values based on the gradient obtained by differentiating the gradation values in one direction. Examples of known detection processing methods include a process of extracting . This process may be performed by the control unit 50 in parallel with the imaging by the imaging device 30, or may be performed by the control unit 50 or another image processing device after the imaging device 30 takes an image. The transmitted light image to be subjected to this processing is preferably one that has been imaged with an area including the periphery of the absorber 4 and the background as well, on the premise that the area including the embossed pattern is included in the imaging area. . In addition, from the perspective of increasing the accuracy of edge detection and accurately determining the quality of the embossed pattern, the binarized image obtained by performing multi-gradation processing and binarization processing on the transmitted light image is subjected to edge detection processing. It is preferable.

As shown in FIGS. 4(a) to 4(c), the edge detection process targets the peripheral edge of the absorbent body 4 and a region R1 including the embossed pattern, and detects the edges along the longitudinal direction It is preferable to set the setting so that at least the edges E1 and E2 detected along the width direction Y of the absorbent body 4 and the edges E3 and E4 detected at both ends along the width direction Y of the absorbent body 4 can be detected, and the entire peripheral edge of the absorbent body 4 is set as an edge. It is more preferable to set it so that it can be detected.

Next, the center of gravity position G of the area where the embossed pattern is formed is detected. In detecting the center of gravity position, for example, a pattern area is set in advance to detect the entire area in which the embossed pattern is formed, and a transmitted light image or a binarized image of the area is obtained. Then, the emboss pattern in the obtained transmitted light image or binarized image is compared with the emboss pattern in the reference image, a location with high similarity of the emboss patterns is detected, and the center of gravity of the emboss pattern in the reference image is detected. This can be done by detecting the center of gravity position of the pattern area based on . If the center of gravity position G of the area where the embossed pattern is formed cannot be detected, it may be determined that the embossed pattern is poorly formed. Detection of the center of gravity position G and determination of the quality of the embossed pattern based on the detection can be performed by the control unit 50, for example.

Subsequently, based on the position of each detected edge and the position of the center of gravity G of the embossed pattern, it is determined whether the embossed pattern is in good condition or not. For example, the method for determining quality is as follows. First, a distance D1 between the detected edge E1 at one end in the longitudinal direction and the center of gravity G, and a distance D2 between the edge E2 at the other end in the longitudinal direction and the center of gravity G are calculated based on the total value of pixels. Similarly, the distance D3 between the detected edge E3 at one end in the width direction and the center of gravity position G, and the distance D4 between the detected edge E4 at the other end in the longitudinal direction and the center of gravity position G are calculated based on the total value of the pixels. . By comparing each of the calculated distances D1, D2, D3, and D4 with a preset threshold range, it is possible to determine the quality of the emboss pattern formation.

For example, as shown in FIG. 4(a), when the distance D1 and the distance D2 substantially match, and the distance D3 and the distance D4 substantially match, the formation of the embossed pattern is considered to be good. It will be judged. In addition, the absolute value of the difference between distance D1 and distance D2 and the absolute value of the difference between distance D3 and distance D4 are respectively calculated, and if each absolute value is within the respective threshold value, it is determined that the embossed pattern is well formed. It can be determined that there is.

On the other hand, as shown in FIGS. 4(b) and 4(c), if the distance D1 and the distance D2 or the distance D3 and the distance D4 do not match, it is determined that the formation of the embossed pattern is defective. be done. Further, if at least one of the absolute value of the difference between the distance D1 and the distance D2 and the absolute value of the difference between the distance D3 and the distance D4 is outside the range of the threshold value, it is determined that the formation of the embossed pattern is defective. I can do it. The above-described quality determination of the embossed pattern can be performed by the control unit 50, for example. The threshold value based on the distance D1 and the distance D2 can be set based on the total length of the absorber 4 in the longitudinal direction, for example. Moreover, the threshold value based on the distance D3 and the distance D4 can be set based on the total length of the absorber 4 in the width direction, for example.

As described above, according to the present invention, as is clear from the above description, there is provided not only a method for manufacturing an absorbent article that includes an embossed pattern inspection step as one step, but also a method for inspecting an embossed pattern and a method for inspecting an absorbent article. is also provided.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. For example, although a sanitary napkin has been described as an example of an absorbent article to which the present invention is applied, the present invention is not limited to this, and any article on which an embossed pattern is formed can be applied to the present invention.

Further, although the above-described evaluation of the quality of the embossed pattern was performed on the processed laminate 1B manufactured in the manufacturing process of the absorbent article 1, the present invention is not limited to this. The quality of the embossed pattern may be determined for a laminate including a back sheet 3 and an absorbent body 4 interposed between both sheets 2 and 3, on which an embossed pattern is formed. Specifically, the quality of the embossed pattern may be determined for the absorbent article 1 on which the embossed pattern is formed.

In addition, when determining the quality of the formation state of the embossed pattern based on the position of the center of gravity of the embossed pattern with respect to the absorbent body 4, the edge of the periphery of the absorbent body is set to be detected, and the edge defined by the edge is set to be detected. The position of the center of gravity of the area may be detected as the position of the center of gravity of the absorbent body 4, and then the determination may be made based on the distance between the position of the center of gravity of the absorbent body 4 and the position of the center of gravity G of the embossed pattern.

In addition, when the above-described image controller is used in the control unit 50, the multi-gradation processing and the binarization processing of the captured transmitted light image are performed in parallel with the imaging of the transmitted light image by the imaging device 30, or the transmitted light image is The image controller in the control unit 50 may be used after the optical image is captured. Furthermore, when the above-mentioned image controller is used in the control unit 50, the pattern search method in the pattern search measurement is, for example, detecting edges in each of the reference image and the binarized image, and detecting the edges based on the information of each image regarding the edge strength. The correlation value may also be calculated.

1 Absorbent article 1A Laminate 1B Processed laminate 2 Liquid permeable sheet (top sheet)
3 Back sheet 4 Absorber 7 Embossed part 10 Manufacturing device 20 Embossed roll part 30 Imaging device 40 Light source W1 Embossed part forming part B1 Embossed part non-formed part

Claims (9)

A liquid-retaining absorbent body having a low basis weight portion and a high basis weight portion having a higher basis weight than the low basis weight portion and a liquid permeable sheet are laminated and then pressed together. A method for inspecting the quality of an embossed pattern consisting of a plurality of embossed parts,
irradiating a region including the embossed pattern with light to obtain a transmitted light image, correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
Determining the quality of the embossed pattern based on at least one of the number of embossed portions in the binarized image, the formation area of each embossed portion, and the formation position of each embossed portion, and
The edge between the periphery of the absorber and the background in the image is detected by edge detection processing, and the position of the detected edge and the center of gravity of the embossed pattern detected based on the image or the binarized image. An emboss pattern inspection method that determines the quality of an emboss pattern based on its position . Comparing the information included in the binarized image and the information included in a preset reference image, calculating a correlation value from the difference in the information between the two,
2. The emboss pattern inspection method according to claim 1, wherein the correlation value is compared with a preset threshold value to determine whether the emboss pattern is good or bad. Light is irradiated from the side of the absorber on which the liquid-permeable sheet is not arranged, and the transmitted light in the irradiated area is imaged from the side on which the liquid-permeable sheet is arranged to obtain the image. , The method for inspecting an embossed pattern according to claim 1 or 2. The method for inspecting an embossed pattern according to claim 3 , wherein the image is acquired by imaging a region having the largest number of embossed portions per unit area among the irradiation regions. In the multi-tone processing,
For pixels where the change in gradation value of adjacent pixels is small, the pixel brightness is corrected so as to eliminate the change in gradation value,
5. The embossed pattern according to claim 1, wherein for a pixel in which a change in gradation value between adjacent pixels is large, the emboss pattern is corrected so that the change in gradation value remains as a difference in luminance of the pixel. inspection method. Any one of claims 1 to 5 , comprising the absorbent body, the liquid-permeable sheet, and a liquid-impermeable or barely liquid-permeable sheet, and the quality of the embossed pattern consisting of a plurality of embossed parts is inspected. The method for inspecting an embossed pattern according to item (1). A liquid-retentive absorbent body having a low basis weight part and a high basis weight part whose basis weight is higher than the low basis weight part, a liquid-permeable top sheet, and a liquid-impermeable or barely liquid-permeable back sheet. A method for inspecting the quality of an embossed pattern in an absorbent article having an embossed pattern consisting of a plurality of embossed parts formed by compressing the absorbent body and the top sheet in a laminated state, comprising: ,
irradiating a region including the embossed pattern with light to obtain a transmitted light image;
correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
Determining the quality of the embossed pattern based on at least one of the number of embossed portions in the binarized image, the formation area of each embossed portion, and the formation position of each embossed portion, and
The edge between the periphery of the absorber and the background in the image is detected by edge detection processing, and the position of the detected edge and the center of gravity of the embossed pattern detected based on the image or the binarized image. An absorbent article inspection method that determines the quality of an embossed pattern based on its position . A liquid-retentive absorbent body having a low basis weight part and a high basis weight part whose basis weight is higher than the low basis weight part and a liquid-permeable surface sheet are laminated and then compressed to produce a plurality of products. An embossed pattern consisting of embossed parts is formed,
irradiating a region including the embossed pattern with light to obtain a transmitted light image;
correcting the image by multi-gradation processing based on its brightness to generate a multi-gradation image;
Binarizing the multi-gradation image based on a preset threshold to generate a binary image;
Determining the quality of the embossed pattern based on at least one of the number of embossed portions in the binarized image, the formation area of each embossed portion, and the formation position of each embossed portion, and
The edge between the periphery of the absorber and the background in the image is detected by edge detection processing, and the position of the detected edge and the center of gravity of the embossed pattern detected based on the image or the binarized image. A method for manufacturing an absorbent article, comprising the step of determining the quality of an embossed pattern based on its position . According to claim 8 , an absorbent article is manufactured, comprising the absorbent body, the top sheet, and a liquid-impermeable or barely liquid-permeable back sheet, and in which an embossed pattern consisting of a plurality of the embossed portions is formed. A method of manufacturing the absorbent article described.

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