Inspection method and manufacturing method for laminated sheets

Abstract

To provide a technique that can inspect with high accuracy physical properties, which can be an indicator of the quality of a fiber layer, in a production line for a laminated sheet containing the fiber layer.SOLUTION: An inspection method for a laminated sheet of the present invention is to inspect, regarding the laminated sheet in which a fiber layer is placed on one surface of a base material sheet, the fiber layer on a production line of the laminated sheet, and includes the following steps: 1) a step of taking an image of the laminated sheet to obtain a gray-scale image and a binary image; 2) a step of measuring the center of gravity or the center of a circumscribed rectangle of the fiber layer in the binary image and determining that the center of gravity or the center is the center of the fiber layer; 3) an inspection position checking and correcting step of checking whether the center of a predetermined inspection area coincides with the center of the fiber layer, and if not, correcting the position of the inspection area so that it coincides; and 4) a determination step of inspecting a predetermined inspection item using the grayscale image or the binary image for the fiber layer in the inspection area, and determining whether the fiber layer is good or bad based on results of the inspection.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for inspecting and manufacturing a laminated sheet.

Background Art

[0002] As a cosmetic sheet that is attached to the skin to conceal stains and wrinkles, a laminated sheet in which a nanofiber layer mainly composed of nanofibers, which are ultrafine fibers obtained by an electrospinning method, is disposed on one surface of a base sheet has been conventionally known. In order to stably manufacture such a laminated sheet by an industrial method, it is preferable to measure and manage physical properties such as the basis weight and area of the nanofiber layer during the manufacture of the laminated sheet. However, since nanofibers are extremely lightweight and have poor visibility, it is very difficult to measure the basis weight, area, etc. of a fiber layer mainly composed of nanofibers. In view of such problems, Patent Document 1 describes a method of measuring the basis weight of a sheet based on the measured charge amount by measuring the charge amount of a sheet being conveyed while relatively moving a measuring element with respect to the sheet in a sheet manufacturing apparatus for manufacturing a long strip-shaped sheet by depositing nanofibers.

[0003] Furthermore, various techniques have been proposed to accurately measure the physical properties, such as basis weight, of manufactured products or intermediate products in the manufacturing lines of various types of sheets. For example, Patent Document 2 describes a method for measuring the thickness of a translucent material, such as nonwoven fabric, paper, or film-like plastic, and for use in detecting whether or not there are quality defects due to the thickness of the translucent material. The thickness measurement method described in Patent Document 2 involves illuminating the translucent material with transmitted light, measuring the amount of transmitted light, and measuring the thickness of the translucent material from the measured value. Patent Document 3 also describes a sheet-like material inspection method for continuously measuring the basis weight of a sheet-like material in motion, comprising: 1) an illumination step of irradiating the sheet-like material with light from an illumination device at the imaging position; 2) an imaging step of continuously imaging the sheet-like material with an imaging device positioned at a different position on the same side as the illumination device with respect to the perpendicular line of the sheet-like material at the imaging position while the sheet-like material is irradiated with the light; and 3) an inspection step of inspecting the sheet-like material by analyzing the brightness of the image captured by the imaging device. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-224327 [Patent Document 2] Japanese Patent Publication No. 2002-236004 [Patent Document 3] Japanese Patent Publication No. 2015-212646 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a technology that can accurately inspect the physical properties of a fiber layer in a manufacturing line for a laminated sheet containing a fiber layer, which can serve as an indicator of the quality of the fiber layer. [Means for solving the problem]

[0006] The present invention relates to a laminated sheet inspection method for a laminated sheet manufactured by a process in which fibers are deposited on one side of a base sheet while the base sheet is conveyed in a predetermined conveying direction to form a fiber layer, and the fiber layer is inspected in-line. A preferred embodiment of the inspection method includes an imaging step of imaging the surface on which the fiber layer is formed in the laminated sheet in the manufacturing line of the laminated sheet to obtain a grayscale image. A preferred embodiment of the inspection method includes a binarization step to generate a binary image by binarizing the grayscale image. A preferred embodiment of the inspection method includes the step of measuring the centroid or the center of the circumscribed quadrilateral of the fiber layer in the binary image and determining the centroid or the center to be the center of the fiber layer. A preferred embodiment of the inspection method includes an inspection position confirmation and correction step, which involves confirming whether the center of a predetermined inspection area coincides with the center of the fiber layer, and correcting the position of the inspection area so that it coincides if it does not. A preferred embodiment of the inspection method includes a determination step in which the fiber layer within the inspection area is inspected for predetermined inspection items using the grayscale image or the binary image, and the quality of the fiber layer is determined based on the inspection results.

[0007] The present invention also relates to a method for manufacturing a laminated sheet, comprising a base sheet and a fiber layer disposed on one side of the base sheet. A preferred embodiment of the above manufacturing method is a laminated sheet manufacturing step in which, while conveying the base sheet, fibers obtained by electrospinning are deposited on one side of the base sheet to form the fiber layer, thereby manufacturing the laminated sheet, An inspection step for inspecting the fiber layer of the laminated sheet in-line, The process includes a cutting step of cutting the laminated sheet, which has undergone the inspection step, into a predetermined shape. A preferred embodiment of the manufacturing method includes an imaging step in which the inspection step images the surface on which the fiber layer is formed in the laminated sheet on the manufacturing line of the laminated sheet and obtains a grayscale image. A preferred embodiment of the above manufacturing method includes a binarization step in which the inspection step binarizes the grayscale image to generate a binary image. A preferred embodiment of the manufacturing method is that the inspection step includes measuring the centroid or the center of the circumscribed quadrilateral of the fiber layer in the binary image and determining the centroid or the center to be the center of the fiber layer. A preferred embodiment of the manufacturing method includes an inspection position confirmation and correction step in which the inspection step confirms whether the center of a predetermined inspection area coincides with the center of the fiber layer, and if not, corrects the position of the inspection area so that it coincides. A preferred embodiment of the manufacturing method is that the inspection step includes a determination step in which the fiber layer within the inspection area is inspected for predetermined inspection items using the grayscale image or the binary image, and the quality of the fiber layer is determined based on the inspection results. A preferred embodiment of the manufacturing method is that in the cutting step, the laminated sheet is cut along a predetermined cutting guide line set in the binary image such that the laminated sheet after cutting contains only the fiber layer that was determined to be a good product in the determination step, and Prior to cutting the laminated sheet, it is checked whether the center of the region enclosed by the cutting guide line coincides with the center of the fiber layer, and if they do not coincide, the position of the cutting guide line is corrected so that they coincide. Other features, effects, and embodiments of the present invention are described below. [Effects of the Invention]

[0008] According to the present invention, a method for inspecting and manufacturing laminated sheets is provided that allows for high-precision inspection of physical properties (basis weight, area, etc.) that can serve as indicators of the quality of a fiber layer in a manufacturing line for laminated sheets containing a fiber layer. According to the present invention, even when the fiber layer is formed using ultrafine fibers such as nanofibers obtained by electrospinning, which have conventionally been difficult to measure the physical properties of, the physical properties of the fiber layer can be accurately inspected. [Brief explanation of the drawing]

[0009] [Figure 1]FIG. 1 is a schematic plan view of the fiber layer side of an embodiment of the laminated sheet to which the present invention is applied. [Figure 2] FIG. 2 is a schematic cross-sectional view of the cross-section taken along the line I-I of FIG. 1 (cross-section along the thickness direction). [Figure 3] FIG. 3 is a schematic perspective view of the laminated sheet shown in FIG. 1 as observed from the fiber layer side. [Figure 4] FIG. 4 is an explanatory diagram of an embodiment of the manufacturing method of the laminated sheet of the present invention, and is a perspective view schematically showing the schematic configuration of the manufacturing apparatus for the laminated sheet shown in FIG. 1. [Figure 5] FIG. 5 is a schematic side view of the inspection unit of the manufacturing apparatus shown in FIG. 4. [Figure 6] FIGS. 6(a) and (b) are explanatory diagrams of the imaging process performed in the inspection unit shown in FIG. 4, respectively, and are schematic plan views of the imaging region of the laminated sheet to be inspected and its vicinity. [Figure 7] FIG. 7 is a flowchart showing the processing flow of an embodiment of the manufacturing method of the laminated sheet of the present invention. [Figure 8] FIGS. 8(a) to (f) are explanatory diagrams of step S3 of the flowchart shown in FIG. 7, respectively, and are schematic plan views of the fiber layer in the binary image obtained through step S3. [Figure 9] FIG. 9 is an explanatory diagram of steps S1 to S3 of the flowchart shown in FIG. 7. FIG. 9(a) is a schematic plan view of an example of the grayscale image obtained in step S1, FIG. 9(b) is a schematic plan view of an example of the binary image obtained in step S2, and FIG. 9(c) is a schematic plan view of an example of the binary image after the end of step S3. [Figure 10] FIGS. 10(a) to (e) are schematic plan views of an example of the inspection region according to the present invention, respectively. [Figure 11] FIGS. 11(a) to (f) are schematic plan views of another example of the inspection region according to the present invention, respectively. [Figure 12] FIGS. 12(a) and (b) are explanatory diagrams of step S5 of the flowchart shown in FIG. 7, respectively, and are schematic plan views of the fiber layer in the image used for inspection. [Figure 13] Figure 13 is an explanatory diagram of step S6 of the flowchart shown in Figure 7, where Figure 13(a) is a schematic plan view of the image used when inspecting the basis weight of the fiber layer, and Figure 13(b) is a schematic plan view of the image used when inspecting the area of ​​the fiber layer. [Modes for carrying out the invention]

[0010] The present invention will be described below with reference to the drawings, based on its preferred embodiments. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. The drawings are basically schematic, and the proportions of the dimensions may differ from those of reality.

[0011] First, the laminated sheet to which the present invention applies will be described. Figures 1 to 3 show a laminated sheet 1, which is an example of a laminated sheet to which the present invention applies. The laminated sheet 1 has a base sheet 2 and a fiber layer 3 arranged on one side of the base sheet 2.

[0012] The laminated sheet 1 has a first surface 1a on the fiber layer 3 side and a second surface 1b on the base sheet 2 side. In this embodiment, as shown in Figure 2, the first surface 1a has an uneven surface and is not flat, while the second surface 1b is flat. In this embodiment, as shown in Figure 1, the base sheet 2 and the fiber layer 3 are similar in relationship. The base sheet 2 has a larger area than the fiber layer 3, and the periphery 2R of the base sheet 2 is located further out than the periphery 3R of the fiber layer 3. In the illustrated configuration, the base sheet 2 and the fiber layer 3 have a crescent shape in plan view, but the shape of the laminated sheet 1 is not particularly limited and can be set as appropriate depending on the application of the laminated sheet 1. For example, the fiber layer 3 can have a circular or triangular shape in plan view (see Figure 8, etc.).

[0013] The material of the base sheet 2 is not particularly limited, and various materials can be used depending on the application of the laminated sheet 1, for example, fiber sheets and sponges. Examples of the fiber sheet include various nonwoven fabrics, woven fabrics, knitted fabrics, paper, and mesh sheets; and laminates of one or more of these. Examples of the nonwoven fabric include meltblown nonwoven fabrics, spunbond nonwoven fabrics, air-through nonwoven fabrics, and spunlace nonwoven fabrics. Examples of the aforementioned sponge include porous materials obtained by foaming synthetic resin or natural resin, or materials made from foamed resin. Examples of the aforementioned synthetic resin or natural resin include urethane, polyethylene, melamine, natural rubber, chloroprene rubber, ethylene propylene rubber, nitrile rubber, silicone rubber, and fluororubber. The base sheet 2 may or may not be breathable.

[0014] The fiber layer 3 is formed by depositing fibers on one side of the base sheet 2 and is a fiber aggregate mainly composed of fibers. The fiber content in the fiber layer 3 is not particularly limited, but typically it is preferably 50% by mass or more of the total mass of the fiber layer 3, and it may even be 100% by mass, i.e., the fiber layer 3 may contain only fibers. The fiber layer 3 may contain other components besides fibers. For example, when the fiber layer 3 is applied to the skin, the other components may include medicinal ingredients, moisturizing ingredients, and other ingredients used in cosmetics.

[0015] In this embodiment, nanofibers obtained by electrospinning are used as the constituent fibers of the fiber layer 3. That is, the fiber layer 3 in this embodiment is a nanofiber layer formed by depositing nanofibers obtained by electrospinning onto one side of the base sheet 2, and the laminated sheet 1 can also be called a "nanofiber sheet".

[0016] Electrospinning is a spinning method in which a raw material liquid containing resin is discharged into an electric field generated by applying a high voltage to a conductive nozzle and a charged electrode spaced apart from the nozzle, which are equipped in a spinning apparatus. The discharged raw material liquid is stretched into an elongated shape in the electric field, forming nanofibers, which are fine-diameter fibers. Electrospinning is broadly classified into solvent-type, which uses a resin-containing solution as the raw material liquid, and melt-type, which uses a resin molten liquid as the raw material liquid. In this invention, either type of electrospinning can be used. Conventionally known materials can be used without particular limitation as nanofiber materials, and can be appropriately selected depending on the application of the laminated sheet 1.

[0017] In this specification, "nanofiber" generally refers to a nanofiber whose thickness, expressed as a circular diameter, is between 10 nm and 3000 nm, and more particularly between 10 nm and 1000 nm. The thickness of a nanofiber can be measured, for example, by observing it with a scanning electron microscope (SEM) at a magnification of 10,000 times, selecting 10 fibers arbitrarily from the two-dimensional image after removing defects (clumps of nanofibers, intersections of nanofibers, polymer droplets), drawing a line perpendicular to the longitudinal direction of the fiber, and directly reading the fiber diameter.

[0018] In this embodiment, as shown in Figure 2, the thickness T2 of the base sheet 2 is uniform, while the thickness T3 of the fiber layer 3 is non-uniform. Specifically, the fiber layer 3 has a gradient region 4 in which the thickness T3 gradually increases from its periphery 3R toward the interior of the fiber layer 3, and the thickness T3 is non-uniform in the gradient region 4. Furthermore, the fiber layer 3 has an inner region 5 adjacent to the gradient region 4, more specifically, an inner region 5 surrounded by the gradient region 4, and the thickness T3 is uniform in the inner region 5. Typically, the thickness T3 of the inner region 5 is the maximum thickness of the fiber layer 3. The term "uniform thickness" as used here includes cases where the thickness is the same throughout the entire inner region 5, and cases where, although the thickness differs microscopically in parts of the inner region 5, the thickness can be considered substantially the same macroscopically. A specific example of the latter case is when neither the low-thickness region nor the high-thickness region described below exists in the inner region 5. • Low-thickness region: A region where the thickness is less than or equal to half the average thickness of the inner region. • High-thickness region: A region whose thickness is more than twice the average thickness of the inner region.

[0019] The basis weight of the fiber layer 3, that is, the mass per unit area of ​​the fiber layer 3, is the same as the thickness T3, the basis weight of the gradient region 4 is non-uniform, and the basis weight of the inner region 5 is uniform. The term "uniform basis weight" as used here includes cases where the basis weight is the same throughout the entire inner region 5, and cases where, although the basis weight differs microscopically in parts of the inner region 5, it can be considered substantially the same macroscopically. A specific example of the latter case is when neither the low basis weight region nor the high basis weight region described below exists in the inner region 5. • Low basis weight area: An area where the basis weight is 1 / 2 or less of the average basis weight of the inner area. • High basis weight area: An area where the basis weight is more than twice the average basis weight of the inner area.

[0020] The thickness T3 and basis weight of the fiber layer 3 are not particularly limited and can be set appropriately depending on the application of the fiber layer 3. For example, if the fiber layer 3 is mainly made of nanofibers and is used by being attached to the skin, it is preferable to set it as follows. The thickness T3 of the inner region 5 (maximum thickness of the fiber layer 3) is preferably 5 μm or more, more preferably 10 μm or more, and preferably 500 μm or less, and more preferably 400 μm or less. The thickness T3 of the gradient region 4 is less than or equal to the thickness of the inner region 5. The basis weight of the inner region 5 is preferably 0.01 g / m². 2 Above all, a comfortable 0.1 g / m 2 The above, and preferably 50 g / m² 2 More preferably 40 g / m2 The following applies: The basis weight of gradient region 4 is less than or equal to the basis weight of inner region 5. The area of ​​the fiber layer 3 in a plan view (the area of ​​the projection when the fiber layer 3 is projected in the thickness direction) is preferably 1 mm 2 More preferably 10 mm 2 The above, and preferably 250,000 mm 2 More preferably 20,000 mm 2 The following applies: The thickness T3, basis weight, area, etc. of the fiber layer 3 may be included in the inspection items of the inspection process according to the present invention, which will be described later.

[0021] In this embodiment, the laminated sheet 1 consists of a base sheet 2 and a fiber layer 3, and does not have any other layers. The base sheet 2 and the fiber layer 3 are in contact with each other and are integrated. The laminated sheet to which the present invention applies may also include layers other than the base sheet 2 and the fiber layer 3. In that case, other layers may be interposed between the base sheet 2 and the fiber layer 3. For example, when the fiber layer 3 is used by being attached to an object such as skin, an adhesive layer that allows the fiber layer 3 to be attached to the surface of the object may be interposed between the base sheet 2 and the fiber layer 3.

[0022] Laminated sheet 1 is used to improve the appearance or surface condition of an object. When using laminated sheet 1, the base sheet 2 and the fiber layer 3 are delaminated, the base sheet 2 is removed, and the fiber layer 3 is attached to the object, such as skin. For example, if the object is skin, the appearance of the skin can be improved by attaching the fiber layer 3 to the skin to conceal blemishes and wrinkles. Alternatively, the surface condition of the skin can be improved by attaching the fiber layer 3 to the skin to improve the adhesion of foundation, i.e., the way foundation is applied. The fiber layer 3 can also be used with a liquid substance such as a beauty serum impregnated into it.

[0023] Next, the method for manufacturing the laminated sheet of the present invention will be explained using the example of manufacturing the aforementioned laminated sheet 1, which is a type of laminated sheet, with reference to the drawings. Figure 4 shows the manufacturing apparatus 10 for the laminated sheet 1. The manufacturing apparatus 10 has, in this order on the MD, a manufacturing section 20 for manufacturing the laminated sheet 1, an inspection section 30 for inspecting the laminated sheet 1 manufactured in the manufacturing section 20, and a cutting section 40 for cutting the laminated sheet 1 inspected in the inspection section 30 into a predetermined shape.

[0024] In this specification, "MD" is an abbreviation for Machine Direction and refers to the flow direction during the manufacturing of the laminated sheet 1 or its raw material (e.g., base sheet 2) or manufacturing intermediate. In this specification, the direction perpendicular to MD (Cross machine Direction) is also referred to as "CD".

[0025] The manufacturing unit 20 has a spinning apparatus 21 as a manufacturing apparatus for the constituent fibers of the fiber layer 3. As described above in this embodiment, the constituent fibers of the fiber layer 3 are nanofibers obtained by electrospinning, so the spinning apparatus 21 is an electrospinning apparatus. The spinning apparatus 21 is basically configured in the same way as conventionally known electrospinning apparatuses, and has a conductive nozzle 22 for discharging raw material liquid, a counter electrode (not shown) spaced apart from the nozzle 22, a nozzle 22 movement mechanism 23, etc. The spinning apparatus 21 has a nozzle arrangement region 24 in which a plurality of nozzles 22 are intermittently arranged, and the counter electrode faces the nozzle arrangement region 24 with the conveyed base material sheet 2 in between. The movement mechanism 23 is configured to allow the nozzle 22 to move in the planar direction.

[0026] As shown in Figures 4 and 5, the inspection unit 30 includes an imaging means 31 for imaging the first surface 1a (the surface on the fiber layer 3 side) of the laminated sheet 1 while it is being transported, an illumination means 32 used for imaging, and a control unit 33. Typically, the inspection unit 30 is configured as a device built on a computer or image controller with image processing software installed.

[0027] The imaging means 31 can be any device suitable for imaging sheets moving along a manufacturing line, without any particular limitations. Examples include CCD area cameras and line scan cameras. In particular, it is preferable to use an imaging device having an image sensor to facilitate image processing, and it is even more preferable to use a line scan camera. The image sensor may be a charge-coupled element (CCD) or a CMOS sensor. The image sensor may also be a color image sensor. The illumination means 32 can be any means that can provide sufficient brightness for imaging by the imaging means 31, and there are no particular restrictions on which such means can be used. For example, LED lighting can be used. The control unit 33 controls each part of the inspection unit 30, including the imaging means 31, and the inspection process described later is carried out under the control of the control unit 33. The control unit 33 performs, for example, imaging by the imaging means 31, saving the captured images and image processing such as binarization, saving the calibration curve described later, and pass / fail judgment based on the inspection results. The control unit 33 is composed of a CPU, ROM, RAM, etc. Typically, a display unit (not shown), such as an image monitor, is connected to the control unit 33, and the display unit is capable of displaying various images such as grayscale images and binary images.

[0028] In this invention, the imaging method by the imaging means 31 is not particularly limited and can be appropriately selected according to the inspection items of the inspection process described later (basis weight, area, etc. of the fiber layer). For example, reflected light illumination and transmitted light illumination can be used as imaging methods. In this embodiment, a reflected light illumination method is employed. Specifically, as shown in Figure 5, both the imaging means 31 and the illumination means 32 are positioned directly facing the first surface 1a of the laminated sheet 1 on which the fiber layer 3, which is the object to be imaged, is located. The illumination means 32 is irradiated toward the first surface 1a, and the reflected light reflected from the fiber layer 3 is captured by the imaging means 31. The reflected light includes light irradiated from the illumination means 32 that is reflected at the outermost surface of the fiber layer 3, and light irradiated from the illumination means 32 that passes through the outermost surface of the fiber layer 3 and is reflected inside the fiber layer 3. Therefore, by using the imaging means 31 and the illumination means 32, the amount of reflected light changes according to the basis weight of the fiber layer 3, making it possible to inspect the basis weight. According to the inventors' findings, images (grayscale images) acquired by the reflected light illumination method are suitable for inspecting basis weight, and their use can be expected to improve the accuracy of the inspection. Therefore, if the basis weight of the fiber layer is included in the inspection items of the inspection process described later, it is preferable to use the reflected light illumination method as the imaging method.

[0029] In this embodiment, as shown in Figure 5, the imaging means 31 images a predetermined imaging area 34 and acquires an image (grayscale image) that includes one or more fiber layers 3 contained within the imaging area 34. The imaging area 34 is a light-emitting area illuminated by the illumination means 32. Note that in Figure 5, the fiber layers 3 present in areas other than the imaging area 34 are not shown.

[0030] In the inspection process according to the present invention, which will be described later, the transport of the laminated sheet to be inspected is typically stopped when the imaging area 34 is imaged by the imaging means 31. Referring to Figure 6, in the present invention, the laminated sheet to be inspected may be a continuous body continuous with the MD, or it may be a single sheet. Figure 6(a) is an example of the former, and Figure 6(b) is an example of the latter. In the imaging configuration shown in Figure 6(a), when the continuous laminated sheets 1A and 1B are transported in the same direction as their continuity (MD), the transport of the continuous sheets 1A and 1B is stopped each time they have been transported a distance corresponding to the length of the MD of the imaging region 34 (the rectangular area enclosed by the dotted line in Figure 6). While the transport is stopped, the imaging means 31 takes an image of the portion of the laminated sheets 1A and 1B located in the imaging region 34, and then the transport is resumed. This series of operations is repeated during the inspection process of the continuous sheets 1A and 1B, so the transport of the continuous sheets 1A and 1B in the manufacturing apparatus 10 is intermittent. In the imaging configuration shown in Figure 6(b), when multiple laminated sheets 1C and 1D are intermittently arranged on the MD and transported together, the transport is stopped each time one sheet 1C or 1D is transported to the imaging area 34. While the transport is stopped, the imaging means 31 takes an image of one sheet 1C or 1D in the imaging area 34, after which the transport is resumed. This series of operations is repeated during the inspection process of the sheets 1C and 1D, so the transport of the sheets 1C and 1D in the manufacturing apparatus 10 is intermittent. In Figure 6, the corner of the imaging region 34, indicated by the symbol P, is the origin of the coordinates for the positional information of the center 3C of the fiber layer 3, which is determined in the fiber layer center position determination process according to the present invention, which will be described later.

[0031] In each imaging configuration shown in Figure 6, the number of fiber layers 3 present in the imaging region 34, that is, the number of fiber layers 3 captured in one imaging (the number of fiber layers 3 included in a single image), may be one, as shown in the upper part of Figure 6, or multiple, as shown in the lower part of Figure 6. In the latter case, information on multiple fiber layers 3 can be obtained in a single imaging, making the inspection more efficient. Therefore, in the imaging process by the imaging means 31, it is preferable to set the imaging range so that multiple fiber layers 3 are included in a single image (grayscale image). Specifically, for example, it is preferable to adjust the imaging region 34 (imaging range) as shown in Figure 5 or the lower part of Figure 6.

[0032] In addition, in all imaging configurations shown in Figure 6, the number of fiber layers 3 present in the imaging region 34 is constant, so the number of fiber layers 3 captured in one imaging is constant. However, the number of such fiber layers 3 does not have to be constant. That is, in the present invention, when the laminated sheet to be inspected is a continuum such as a continuum 1A, 1B, the number of fiber layers 3 included in each image (grayscale image) obtained by imaging multiple locations on the continuum may differ. Also in the present invention, when the laminated sheet to be inspected is a single-sheet body such as a single-sheet body 1C, 1D, and multiple such single-sheet bodies are transported together, the number of fiber layers 3 included in each image (grayscale image) obtained by imaging multiple single-sheet bodies individually may differ.

[0033] The cutting section 40 has a cutting means 41 for cutting the laminated sheet 1. The cutting means 41 can be any means capable of cutting the laminated sheet 1, and any known cutting means can be used without particular limitation, such as a blade, laser cutter, water cutter, etc. In the illustrated embodiment, the cutting means 41 is a laser cutter, and a laser is irradiated toward the part of the laminated sheet 1 to be cut to cut that part.

[0034] The method for manufacturing the laminated sheet 1 using the manufacturing apparatus 10 comprises the following steps. (1) Laminated sheet manufacturing process: A process to manufacture a laminated sheet 1 by transporting a base sheet 2 and depositing fibers F (nanofibers) obtained by electrospinning onto one side of the base sheet 2 to form a fiber layer 3. (2) Inspection process: A process for inspecting the fiber layer 3 of the laminated sheet 1 in-line. "In-line inspection" here means inspecting on the same production line as the production line for the laminated sheet 1 (the production line on which the laminated sheet production process described above was carried out). (3) Cutting process: A process of cutting the laminated sheet 1 that has undergone the inspection process into a predetermined shape.

[0035] The aforementioned laminated sheet manufacturing process is carried out in the manufacturing unit 20. In the manufacturing unit 20, as shown in Figure 4, a continuous strip-shaped base sheet 2 wound in a roll shape is unwound and conveyed to the spinning device 21, and the fibers F (nanofibers) produced by the spinning device 21 are deposited on one side of the base sheet 2 while it is being conveyed to form a fiber layer 3, thereby manufacturing the laminated sheet 1. The laminated sheet 1 thus manufactured has a configuration in which multiple fiber layers 3 are scattered on one side of a strip-shaped base sheet 2 that is continuous in the MD, and similar to the continuous laminated sheet 1B described above (see Figure 6(b)), multiple fiber layers 3 are intermittently arranged in both the MD and CD.

[0036] Figure 7 shows the processing flow in the inspection process and the cutting process. The inspection process is performed in the inspection unit 30, and the cutting process is performed in the cutting unit 40. Steps S1 to S7 in Figure 7 are the inspection process, and steps S8 to S10 are the cutting process. Figures 8 and 9 relate to the first three steps S1 to S3 of the inspection process, and Figures 10 to 13 relate to steps S4 to S7 of the inspection process. The inspection and cutting steps in the method for manufacturing the laminated sheet of the present invention will be described below with reference to these drawings.

[0037] In the inspection process, first, an imaging process (step S1) is performed in which the first surface 1a, which is the surface where the fiber layer 3 of the laminated sheet 1 is formed, is imaged on the manufacturing line of the laminated sheet 1 to obtain a grayscale image. Typically, the imaging process is initiated when the control unit 33 of the inspection unit 30 acquires a signal emitted from a predetermined part of the manufacturing apparatus 10, and this signal is used as an inspection trigger signal. As the inspection trigger signal, for example, a sensor can be placed at a predetermined position upstream of the MD from the inspection unit 30 (imaging means 31), and a signal generated when the fiber layer 3 approaches the sensor can be used. In this embodiment, as shown in Figure 5, the imaging process is carried out by imaging the imaging area 34 using the imaging means 31 in a reflected light illumination manner, thereby obtaining a grayscale image of the imaging area 34. The acquired grayscale image is stored in the control unit 33.

[0038] In this invention, "grayscale image" refers to an image other than a binary image (black and white binary image, color binary image). Specific examples of grayscale images include black and white grayscale images (e.g., 256 gradations) or color grayscale images, which can be appropriately selected depending on the configuration of the fiber layer being imaged.

[0039] In the inspection process, a binarization process (step S2) is then performed to generate a binary image by binarizing the grayscale image. The binarization process is performed by the control unit 33, and the generated binary image is stored in the control unit 33. The binary image may be a black and white binary image or a color binary image, provided that it consists of two tones, but it is typically a black and white binary image. The binarization process can be performed according to a conventional method based on a predetermined threshold value set in advance.

[0040] When the fiber layer to be inspected has the aforementioned gradient region and an adjacent inner region, it is preferable to set the threshold value for the binarization process to a value that allows detection only of the inner region adjacent to the gradient region where the thickness and basis weight are uniform, or to a value that allows detection of a region that includes part or all of the gradient region, from the viewpoint of improving inspection accuracy. From the viewpoint of further improving inspection accuracy, it is even more preferable to set the threshold value for the binarization process to a value that allows detection only of the inner region that is not adjacent to the gradient region.

[0041] In the inspection process, the next step is to measure the centroid or the center of the circumscribed quadrilateral of the fiber layer 3 in the binary image, and to determine the centroid or the center as the center of the fiber layer 3 in a fiber layer center position determination process (step S3). The fiber layer center position determination process is performed by the control unit 33.

[0042] Figure 8 shows a specific example of a fiber layer 3 whose center has been determined through the fiber layer center position determination process. The cross mark "+" indicated by the symbol 3C in Figure 9 is the center of the fiber layer 3. Figures 8(a) to (c) show an example where the centroid of the fiber layer 3 is set as center 3C, and Figures 8(d) to (f) show an example where the center of the fiber layer 3, more specifically the center of the circumscribing quadrilateral 14 of the inner region 5, is set as center 3C. The fiber layers 3 shown in Figure 8 have different shapes in plan view: the fiber layers 3 in Figures 8(a) and (d) are crescent-shaped, the fiber layers 3 in Figures 8(b) and (e) are circular, and the fiber layers 3 in Figures 8(c) and (f) are triangular. Furthermore, all of the fiber layers 3 shown in Figure 8 have a gradient region 4 located at the periphery and an inner region 5 surrounded by the gradient region 4, with the former having non-uniform thickness and basis weight, and the latter having uniform thickness and basis weight. Thus, when the fiber layer 3 has a gradient region 4 and an adjacent inner region 5 with uniform thickness and basis weight, it is preferable to make the center of the inner region 5 the center of the fiber layer 3 from the viewpoint of improving inspection accuracy. The circumscribed quadrilateral 14 in Figures 8(d) to (f) is the quadrilateral with the smallest area that contains the entire fiber layer 3 or inner region 5. Typically, of the two pairs of opposing sides of the circumscribed quadrilateral 14, one pair of sides is parallel to MD and the other pair of sides is parallel to CD. However, the present invention is not limited to this, and the sides of the circumscribed quadrilateral 14 do not have to be parallel to MD and CD. Whether to use the "centroid of the fiber layer" or the "center of the circumscribing quadrilateral of the fiber layer" as the center 3C of the fiber layer 3 can be appropriately selected considering the inspection items, the composition of the fiber layer being inspected, etc.

[0043] Figure 9 shows examples of images obtained in steps S1 to S3 described above. The image indicated by reference numeral 11 in Figure 9(a) is an example of a grayscale image acquired in step S1 (imaging step). The binary image 12 in Figure 9(b) is obtained by binarizing this grayscale image 11 in step S2 (binarization step). The binary image 12 shown is a black and white binary image. Then, when this binary image 12 goes through step 3 (fiber layer center position determination step), the center 3C of each of the multiple fiber layers 3 in the binary image 12 is determined, as shown in Figure 9(c).

[0044] The positional information of the center 3C of the fiber layer 3 is represented as coordinates in the image containing the fiber layer 3. In this embodiment, as shown in Figure 6, the origin P(0,0) is set at one corner on the upstream side of the MD (e.g., the machine side during manufacturing) in the imaging area 34, which is rectangular in plan view. The coordinates of the MD (Y coordinate) increase as one moves downstream from the origin, and the coordinates of the CD (X coordinate) increase as one moves opposite to the origin (e.g., the operation side during manufacturing). Therefore, in the binary image 12 derived from the image acquired by imaging the imaging area 34, the position of the center 3C of the fiber layer 3 is represented with respect to the origin P.

[0045] In the grayscale image 11 shown in Figure 9(a), multiple (specifically nine) circular fiber layers 3 are scattered on the base sheet 2 in a plan view. Although these multiple fiber layers 3 are designed to be intermittently arranged at equal intervals on both the MD and CD layers, in the grayscale image 11 obtained by imaging the actually manufactured laminated sheet, one fiber layer 3 located in the upper left corner (closest to the reference point P) is shifted from its design position. If the physical properties (basis weight, area, etc.) of the fiber layer are inspected based on the design position without considering this "positional shift of the fiber layer," the accuracy of the inspection will decrease, making it difficult to accurately grasp the quality of the fiber layer. In particular, the electrospinning method used as the manufacturing method for the fiber layer in this embodiment is prone to such positional shifts of the fiber layer due to the characteristics of the manufacturing method. Therefore, when forming the fiber layer by the electrospinning method, measures that take this positional shift of the fiber layer into consideration are necessary. Therefore, in the present invention, as a countermeasure, the center of the fiber layer is measured using an image of the laminated sheet, and as described later, a method (steps S3 to S7) is adopted in which the fiber layer is inspected in a predetermined inspection area centered on this "center of the fiber layer" to determine its quality. Since the inspection process according to the present invention includes such steps S3 to S7, even if a misalignment of the fiber layer occurs in the laminated sheet manufacturing process, various physical properties of the fiber layer, such as basis weight and area, can be inspected with high precision.

[0046] In the inspection process, after the completion of step S3, an inspection position confirmation and correction process (steps S4, S5) is performed to check whether the center of a predetermined inspection area coincides with the center 3C of the fiber layer 3 determined in step S3, and if they do not coincide, to correct the position of the inspection area so that they coincide. The inspection position confirmation and correction process is performed by the control unit 33.

[0047] The aforementioned inspection area defines the inspection range on the image (grayscale image or binary image) used for inspection. Prior to the inspection, specifications such as the position and range (size, shape) are set and stored in the control unit 33. The position of the inspection area when it is set (hereinafter also referred to as the "standard position") is typically set based on the design position of the fiber layer to be inspected. Specifically, for example, the center of the inspection area is set to coincide with the center of the design position of the fiber layer. The scope (size, shape) of the inspection area can be appropriately selected depending on the inspection items, etc. The inspection area may include only a part of the fiber layer to be inspected, or it may include the entire layer.

[0048] Figures 10 and 11 show inspection areas 15 as examples of the inspection areas. The inspection area 15 shown in Figure 10 is a type that includes only a part of the fiber layer 3 to be inspected (hereinafter also referred to as the "partial type"), while the inspection area 15 shown in Figure 11 is a type that includes the entirety of the material to be inspected (hereinafter also referred to as the "entire type").

[0049] Some types of inspection areas may be similar in shape to the plan view shape of the fiber layer 3 to be inspected, as shown in Figures 10(a) to (c), or they may be dissimilar in shape to the plan view shape of the fiber layer 3 to be inspected, as shown in Figures 10(d) and (e). The inspection areas 15 in Figures 10(d) and (e) are circular in shape, but they may also be rectangular, for example. The fiber layer 3 shown in Figure 10 has a gradient region 4 in which the thickness and basis weight are non-uniform. When applying a certain type of inspection area to a fiber layer that includes such a region in which the thickness and / or basis weight are non-uniform, it is preferable to apply the inspection area to the region other than that region, i.e., the region in the fiber layer in which the thickness and basis weight are uniform, from the viewpoint of improving inspection accuracy. In the configuration shown in Figure 10, the inspection area 15 of the certain type is applied only to the inner region 5 in which the thickness and basis weight are uniform. While there are no particular limitations on the area of ​​some types of inspection regions, from the viewpoint of improving inspection accuracy, it is preferably 10-95%, more preferably 50-95%, of the total area of ​​the fiber layer to be inspected in a plan view.

[0050] The inspection area of ​​all types may include the fiber layer 3 (inner region 5) to be inspected and its surrounding area, as shown in Figures 11(a) to (c), or it may include only the fiber layer 3 (inner region 5) to be inspected, as shown in Figures 11(d) to (f), that is, it may be a similar shape to the plan view shape of the fiber layer 3 (inner region 5) to be inspected. The inspection area 15 in Figures 11(a) to (c) is a quadrilateral circumscribing the fiber layer 3 (inner region 5) to be inspected, but it does not have to be circumscribing the fiber layer 3 (inner region 5) to be inspected, and its shape is not limited to a quadrilateral but can be set arbitrarily. Furthermore, the fiber layer 3 shown in Figure 11 has a gradient region 4 in which the thickness and basis weight are non-uniform. When applying a full-type inspection area to a fiber layer that includes such a region in which the thickness and / or basis weight are non-uniform, it is preferable to apply the full-type inspection area to the region other than that region, i.e., the region in the fiber layer in which the thickness and basis weight are uniform, from the viewpoint of improving inspection accuracy. In the configuration shown in Figure 11, the full-type inspection area 15 is applied only to the inner region 5 in which the thickness and basis weight are uniform.

[0051] Whether to use a partial inspection area like the inspection area 15 shown in Figure 10, or a full inspection area like the inspection area 15 shown in Figure 11, can be appropriately selected considering the inspection items, the composition of the fiber layer to be inspected, etc. For example, when inspecting the basis weight of a fiber layer, either type can be used, but when inspecting the area of ​​a fiber layer, it is preferable to use a full inspection area because the entire fiber layer to be inspected must be included in the inspection area.

[0052] As mentioned above, a standard position is set in advance for the inspection area 15. If a misalignment of the fiber layer 3 occurs during the laminated sheet manufacturing process, and the formation position of the fiber layer 3 on the base sheet 2 differs from the design position, then when inspecting the misaligned fiber layer 3 in the inspection process, the center 15C of the inspection area 15 at the standard position will be offset from the center 3C of the fiber layer 3, as shown in Figure 12(a). Inspecting the fiber layer 3 with such a "misalignment of the inspection area" may lead to a decrease in inspection accuracy. Therefore, in this invention, before performing the judgment steps (steps S6, S7) for inspecting and determining the quality of the fiber layer 3, it is checked whether the center 15C of the inspection area 15 at the standard position coincides with the center 3C of the fiber layer 3 (step S4). If they do not coincide, the position of the inspection area 15 is corrected by moving the inspection area 15 so that both centers 3C and 15C coincide, as shown in Figure 12(b) (step S5). On the other hand, if the result of the check in step S4 shows that the center 15C of the inspection area 15 at the standard position coincides with the center 3C of the fiber layer 3, step S5 is not performed, and the process proceeds to step S6, where the fiber layer 3 within the inspection area 15 is inspected with both centers 3C and 15C coincided. By performing the inspection position confirmation and correction steps including steps S4 and S5 described above, the inspection accuracy can be improved. The center 15C of the inspection area 15, like the center 3C of the fiber layer 3, can be the "centroid of the inspection area 15" or the "center of the circumscribed quadrilateral of the inspection area 15". Although Figure 12 illustrates the position correction using a partial type of inspection area 15 (see Figure 10) as an example, the same position correction is performed when using all types of inspection areas 15 (see Figure 11). The aforementioned inspection position confirmation and correction process is typically performed using a binary image, but it can also be performed using a grayscale image.

[0053] In the inspection process, after the completion of steps S4 and S5, a determination process (steps S6 and S7) is performed in which predetermined inspection items are inspected using a grayscale image or a binary image of the fiber layer 3 within the inspection area, and the quality of the fiber layer 3 is determined based on the inspection results. The determination process is performed by the control unit 33.

[0054] The aforementioned "inspection items" are not particularly limited, provided that they can be inspected using the grayscale images obtained by imaging the laminated sheet. Examples of inspection items for a fiber layer applicable to the present invention include basis weight, area, shape, foreign matter, pinholes, and fiber clumps. The present invention is particularly effective when the inspection items for a fiber layer include one or more selected from the basis weight and area of ​​the fiber layer. In the inspection items for fiber layers, the term "shape" refers to the shape of the fiber layer in a plan view. When inspecting the shape of a fiber layer, typically, the inspection checks whether the shape of the fiber layer being inspected can be identified with a predetermined shape. In the context of fiber layer inspection items, "foreign matter" refers to objects other than the constituent fibers of the fiber layer (e.g., insects, hair). When inspecting for foreign matter in a fiber layer, the inspection typically involves checking whether or not foreign matter is present in the fiber layer being inspected. In the context of fiber layer inspection, "pinholes" refers to minute holes in the fiber layer (for example, holes or depressions with a diameter of approximately 0.5 to 5 mm). When inspecting for pinholes in a fiber layer, the inspection typically involves checking whether or not pinholes are present in the fiber layer being inspected. In the context of fiber layer inspection items, "fiber clumps" refers to areas where fibers have aggregated into a mass. When inspecting fiber clumps in a fiber layer, the typical procedure involves checking whether or not fiber clumps are present in the fiber layer being inspected.

[0055] In the determination process described above, the inspection in step S6 is performed using a grayscale image or a binary image. The choice of which image to use can be appropriately selected depending on the inspection item, etc. According to the inventor's knowledge, when inspecting the "basis weight of the fiber layer," it is preferable to use a grayscale image obtained by imaging the surface on which the fiber layer is formed in the laminated sheet, and when inspecting the "area of ​​the fiber layer," it is preferable to use a binary image obtained by binarizing the grayscale image. In the latter case, typically, the area of ​​the portion corresponding to the fiber layer in the binary image can be measured, and the measured value can be taken as the area of ​​the fiber layer. If the fiber layer to be inspected has the aforementioned gradient region and an adjacent inner region, the area of ​​the portion corresponding to the inner region can be measured, and the measured value can be taken as the area of ​​the fiber layer.

[0056] One example of an inspection method for checking the basis weight of the fiber layer in step S6 is a method using a calibration curve. That is, a calibration curve (image density basis weight conversion curve) showing the relationship between the image density of a grayscale image and the basis weight of the fiber layer is prepared in advance, and when checking the basis weight of the fiber layer to be inspected, the basis weight of the fiber layer to be inspected is calculated using the calibration curve and a grayscale image obtained by imaging the surface on which the fiber layer is formed in the laminated sheet to be inspected. According to the inventor's findings, there is a positive correlation between the "image density of the fiber layer" in the grayscale image (median, mean, or mode in 256 grayscale levels with black being zero and white being 255) and the "basis weight of the fiber layer," and the larger the value of the former, the larger the value of the latter. In the manufacturing apparatus 10, the calibration curve is stored in the control unit 33.

[0057] Figure 13(a) shows a specific example of inspecting the "basis weight of the fiber layer" in step S6. In the basis weight inspection shown in Figure 13(a), a binary image 12 containing images of multiple (9) fiber layers 3 is used to confirm the position of the inspection area 15 for each of the multiple fiber layers 3 in the binary image 12, and correct the position as necessary (steps S4, S5) to obtain a binary image 12 in which the position of the inspection area 15 is appropriate (hereinafter also called the "appropriate binary image"), and the basis weight within the inspection area 15 of the fiber layer 3 is inspected using the grayscale image 11 corresponding to the appropriate binary image 12. In this basis weight inspection, the basis weight of the fiber layer 3 to be inspected is calculated from the calibration curve and the image density of the fiber layer 3 to be inspected in the grayscale image 11. In the basis weight inspection shown in Figure 13(a), some types are used as the inspection area 15.

[0058] Figure 13(b) shows a specific example of inspecting the "area of ​​the fiber layer" in step S6. In the area inspection shown in Figure 13(b), the appropriate binary image 12 is used directly for inspecting the area of ​​the fiber layer 3, and the entire type is used as the inspection area 15. In the area inspection, the area of ​​the part of the appropriate binary image 12 corresponding to the fiber layer 3 to be inspected (the white part if the binary image 12 is a black and white binary image) is measured, and this measured value is taken as the area of ​​the fiber layer 3 to be inspected. Except for the above points, it is the same as the basis weight inspection shown in Figure 13(a).

[0059] In the aforementioned determination process, the determination in step S7 is typically performed by determining whether the inspection results from step S6 (e.g., measured basis weight, measured area) for predetermined inspection items (e.g., basis weight, area) of the fiber layer fall within a predetermined threshold range. The threshold range is stored in the control unit 33. If the inspection results from step S6 fall within the predetermined threshold range for all inspection items, the fiber layer being inspected is determined to be a "good product" (OK). Otherwise, the fiber layer being inspected is determined to be a "defective product" (NG).

[0060] This completes the inspection process (imaging process, binarization process, fiber layer center position determination process, inspection position confirmation / correction process, and judgment process). Furthermore, the inspection method for the laminated sheet of the present invention is basically the same as the inspection step in the manufacturing method of the laminated sheet of the present invention, and the description of the inspection step described above applies as appropriate to this inspection method.

[0061] In the cutting process (steps S8 to S10), as shown in Figure 4, the continuous strip-shaped laminated sheet 1 that has passed through the inspection section 30 is cut in the cutting section 40 using the cutting means 41 to obtain single-sheet laminated sheets 1. The laminated sheet 1 in this embodiment has a structure in which multiple fiber layers 3 are scattered on one side of a base sheet 2 which is a continuous body continuous in the MD. In the cutting process, the base sheet 2 is cut into a predetermined shape so as to include a single fiber layer 3, and multiple single-sheet laminated sheets 1 consisting of a laminated structure of base sheet 2 and fiber layer 3 are manufactured in succession. The single-sheet laminated sheets 1 thus manufactured are placed on the conveyor 50 and transported to the next process.

[0062] In the cutting step, the laminated sheet 1 is cut along predetermined cutting guide lines set in the binary image. That is, in the cutting step, the cutting position of the laminated sheet 1 (the position of the cutting guide lines) is adjusted using the binary image obtained in the binarization step, and the laminated sheet 1 is cut at the adjusted cutting position. The cutting guide lines form the contour line of the laminated sheet 1 after cutting. The cutting guide line has its specifications, such as position and range (size, shape), set in advance before the cutting process is performed and stored in the control unit of the cutting unit 40. The control unit controls the operation of each part of the cutting unit 40, including the cutting means 41, and is composed of a CPU, ROM, RAM, etc.

[0063] The position of the cutting guide line (standard position) is typically set based on the design position of the fiber layer to be inspected, similar to the inspection area. Specifically, for example, the center of the area enclosed by the cutting guide line is set to coincide with the center of the design position of the fiber layer. Therefore, if a misalignment of the fiber layer 3 occurs during the laminated sheet manufacturing process, a problem similar to the "misalignment of the inspection area" (see Figure 12(a)) will occur in the cutting guide line, and the desired cutting shape may not be obtained. Therefore, in the cutting process, before cutting the laminated sheet 1 (step S10), the position of the cutting guide line (cutting position) is checked (step S8), and if it is determined that the cutting position is not appropriate, the cutting position is corrected (step S9). On the other hand, if it is determined that the cutting position is appropriate as a result of the check in step S8, step S9 is not performed, and the process proceeds to step S10. By performing such a cutting position check and correction process including steps S8 and S9, the cutting accuracy can be improved.

[0064] The cutting position confirmation and correction steps (steps S8, S9) are performed in the same manner as the inspection position confirmation and correction steps. That is, prior to cutting the laminated sheet 1, it is checked whether the center of the area enclosed by the cutting guide line at the standard position coincides with the center 3C of the fiber layer 3 of the planned cutting area in the laminated sheet 1 (see Figure 8) (step S8). If they do not coincide, the position of the cutting guide line is corrected so that they coincide (step S9). The correction of the cutting position in step S9 is performed by moving the cutting guide line so that the center of the area enclosed by the cutting guide line coincides with the center 3C of the fiber layer 3. The aforementioned "center of the region enclosed by the cutting guide lines" may be the "centroid of the region enclosed by the cutting guide lines" or the "center of the circumscribed quadrilateral of the cutting guide lines," similar to the center 3C of the fiber layer 3. The aforementioned cutting position confirmation and correction process is typically performed using the binary image, but it can also be performed using the grayscale image.

[0065] In the cutting step, the laminated sheet 1 is cut along the cutting guide line so that only the fiber layer 3 determined to be good in the judgment step is included. That is, only the portion of the laminated sheet 1 containing the fiber layer 3 determined to be good in step S7 of the judgment step is cut in the cutting step. The portion of the laminated sheet 1 containing the fiber layer 3 determined to be defective in step S7 is not cut and is discharged from the manufacturing line as waste along with the cut base sheet 2 (step S11). As shown in Figure 4, the cut base sheet 2 discharged as waste has many through holes 2A formed by the removal of portions corresponding to the fiber layer 3. In Figure 4, the uncut portion of the base sheet 2 indicated by reference numeral 2B is the portion containing the fiber layer 3 determined to be defective in step S7.

[0066] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited in any way to the above embodiments and can be modified as appropriate without departing from the spirit of the invention. In the above embodiment, nanofibers obtained by electrospinning were used as the constituent fibers of the fiber layer in the laminated sheet. However, in the present invention, the constituent fibers of the fiber layer are not particularly limited, and for example, fibers obtained by manufacturing methods other than electrospinning, or fibers thicker than nanofibers, can also be used. [Explanation of Symbols]

[0067] 1 Laminated sheet 2. Base sheet 3 Fiber layer 3C fiber layer center 4. Gradient area 5 Inner area 10. Laminated sheet manufacturing equipment 11. Grayscale images 12. Binary Images 15 Examination Areas 15C Center of the Inspection Area 20 Manufacturing Department 21 Electrospinning apparatus 30 Inspection Department 31 Imaging means 32 Lighting means 33 Control Unit 34 Imaging area 40 Cut section 41 Cutting means F fiber (nanofiber)

Claims

1. A method for inspecting a laminated sheet, which is manufactured by a process of depositing fibers on one side of a base sheet while conveying the base sheet in a predetermined conveying direction to form a fiber layer, wherein the fiber layer is inspected in-line, The manufacturing line for the laminated sheet includes an imaging step in which the surface where the fiber layer is formed in the laminated sheet is imaged to obtain a grayscale image, A binarization step to generate a binary image by binarizing the aforementioned grayscale image, A step of measuring the centroid or the center of the circumscribed quadrilateral of the fiber layer in the binary image and determining the centroid or the center as the center of the fiber layer, An inspection position confirmation and correction step, which involves checking whether the center of a predetermined inspection area coincides with the center of the fiber layer, and correcting the position of the inspection area so that it coincides if it does not. A method for inspecting a laminated sheet, comprising: a determination step of inspecting the fiber layer within the inspection area using the grayscale image or the binary image to determine predetermined inspection items, and determining whether the fiber layer is of good or bad quality based on the inspection results.

2. The method for inspecting a laminated sheet according to claim 1, wherein the imaging step involves irradiating the fiber layer with light and acquiring the grayscale image by imaging the reflected light.

3. The method for inspecting a laminated sheet according to claim 1 or 2, wherein the inspection items include one or more selected from the basis weight, area, shape, foreign matter, pinholes, and fiber clumps of the fiber layer.

4. A calibration curve showing the relationship between the image density of the fiber layer in the aforementioned grayscale image and the basis weight of the fiber layer is prepared in advance. The method for inspecting a laminated sheet according to claim 3, wherein, when inspecting the basis weight of the fiber layer, the basis weight of the fiber layer is calculated using the calibration curve and the grayscale image.

5. The method for inspecting a laminated sheet according to claim 1 or 2, wherein in the imaging step, the imaging range is set so that a single grayscale image includes multiple fiber layers.

6. The fiber layer has a gradient region in which the thickness gradually increases from the outside to the inside, and an inner region adjacent to the gradient region in which the thickness and basis weight are uniform. The method for inspecting a laminated sheet according to claim 1 or 2, wherein the binarization step involves binarizing the grayscale image based on a predetermined threshold value, the threshold value being such that only the inner region can be detected.

7. The method for inspecting a laminated sheet according to claim 1 or 2, wherein the fiber layer is obtained by depositing fibers obtained by electrospinning onto one surface of the base sheet.

8. A method for manufacturing a laminated sheet, comprising a base sheet and a fiber layer disposed on one side of the base sheet, A laminated sheet manufacturing process involves transporting the base sheet and depositing fibers obtained by electrospinning onto one side of the base sheet to form the fiber layer, thereby manufacturing the laminated sheet. An inspection step for inspecting the fiber layer of the laminated sheet in-line, The process includes a cutting step of cutting the laminated sheet that has undergone the inspection step into a predetermined shape, The aforementioned inspection process is, The manufacturing line for the laminated sheet includes an imaging step in which the surface where the fiber layer is formed in the laminated sheet is imaged to obtain a grayscale image, A binarization step to generate a binary image by binarizing the aforementioned grayscale image, A step of measuring the centroid or the center of the circumscribed quadrilateral of the fiber layer in the binary image and determining the centroid or the center as the center of the fiber layer, An inspection position confirmation and correction step, which involves checking whether the center of a predetermined inspection area coincides with the center of the fiber layer, and correcting the position of the inspection area so that it coincides if it does not. The process includes a determination step of inspecting the fiber layer within the inspection area using the grayscale image or the binary image to determine predetermined inspection items and determining the quality of the fiber layer based on the inspection results, In the cutting step, the laminated sheet is cut along a predetermined cutting guide line set in the binary image so that the laminated sheet after cutting contains only the fiber layer that was determined to be a good product in the determination step, and A method for manufacturing a laminated sheet, comprising: checking whether the center of the region enclosed by the cutting guide line coincides with the center of the fiber layer prior to cutting the laminated sheet; and correcting the position of the cutting guide line if it does not coincide so that it does.

Images