JP2018124147A - Evaluation method of hygiene thin paper and hygiene thin paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method of a hygiene thin paper capable of easily managing a quality of the hygiene thin paper.SOLUTION: An evaluation method of a hygiene thin paper formed with a sheet 100 having a crepe includes: an imaging step of acquiring an original image of the sheet by imaging the sheet by an optical system 22 shallow in the depth of focus; a processing step of performing an image processing for partitioning the original image into a first image whose luminance of the original image is equal to or less than the predetermined threshold value and a second image exceeding the predetermined threshold value; and a calculation step of calculating an area ratio of the first image or the area ratio of the second image to the original image.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sanitary thin paper evaluation method and a sanitary thin paper.

  For sanitary thin paper such as tissue paper, crepe paper in which fine wrinkles (crepes) are formed on the surface of the base paper in the paper making process is used. Since the crepe formed on the crepe paper affects the quality of the sanitary thin paper, such as the softness and the touch, the crepe is managed by the touch or visual observation of the production manager when the sanitary thin paper is manufactured. However, the quality control of the crepe paper by the subjective method such as human visual sense and tactile sensation varies depending on the production manager. Therefore, objectively evaluating crepe paper has been studied. For example, Japanese translations of PCT publication No. 2009-506322 (Patent Document 1) discloses a method of measuring a crepe pattern of a moving sheet. Japanese Patent Application Publication No. 2014-534358 discloses a method for measuring a crepe structure on a paper sheet.

Special table 2009-506322 Special table 2014-534358 gazette

  However, although the conventional method for evaluating sanitary thin paper enables objective evaluation of crepe paper, it is technically sophisticated, complicated and expensive, and has not been put to practical use. Therefore, it has been a challenge to easily manage the quality of sanitary thin paper.

  The objective of this invention is providing the evaluation method of the sanitary thin paper which can manage the quality of a sanitary thin paper easily.

  A first aspect of the present invention is a method for evaluating sanitary thin paper formed of a sheet having a crepe, the imaging step of capturing the sheet with an optical system having a shallow depth of focus and acquiring an original image of the sheet; A processing step of performing image processing for classifying the original image into a first image having a luminance of the original image equal to or lower than a predetermined threshold and a second image exceeding the predetermined threshold; A sanitary thin paper evaluation method including a calculation step of calculating an area ratio of one image or an area ratio of the second image.

  In the evaluation method according to the first aspect, sanitary thin paper formed of a sheet having a crepe is an object of evaluation. The sanitary thin paper is not particularly limited, and includes sanitary thin paper such as tissue paper, toilet paper, and kitchen paper. The use of sanitary thin paper can be used for both home use and business use. The sanitary thin paper may be formed of one sheet, or two or more sheets may be stacked and integrated.

  As the sheet used for the sanitary thin paper, a known crepe paper on which a crepe is formed can be used. Crepe is formed on the surface of the base paper by applying a blade called a doctor blade at the exit of the paper machine dryer when scraping the base paper from the paper machine dryer (drum) in the paper making process of the sheet (base paper). It is a fine wrinkle.

  In the imaging step, the sheet forming the sanitary thin paper is imaged using an optical system with a shallow depth of focus, and an original image of the sheet is acquired. Depth of focus means that when a sheet is imaged, the in-focus state can be maintained even if the distance between the lens of the optical system and the imaged sheet is changed from the in-focus position. Is the distance. In addition, an optical system with a shallow depth of focus means that the distance between the lens and the sheet of the optical system that can maintain a focused state when the sheet is imaged is short.

  Imaging of a sheet refers to creating a digital image of a sheet by reading the surface of the sheet by optical processing. The original image is a digital image of the read sheet.

  In the processing step, image processing is performed in which the luminance of the original image is divided into a first image having a predetermined threshold value or less and a second image exceeding the predetermined threshold value. The first image and the second image are converted into two images that can be distinguished from each other based on the luminance of the original image. For example, it is possible to use two images obtained by converting an original image into two gradations under conditions such as image density. Note that the luminance of the original image is the degree or intensity of brightness of the original image obtained by imaging the sheet.

  The predetermined threshold value is a boundary value of luminance that separates the first image and the second image, and can be arbitrarily determined according to the form of sanitary thin paper, usage, and the like. For example, the predetermined threshold value based on the luminance of the original image can be used as an index that can distinguish the unevenness of the crepe formed on the sheet. Specifically, the first image whose luminance of the original image is not more than a predetermined threshold value can be indicated by a black image, and the second image exceeding the predetermined threshold value can be indicated by a white image. In this case, a black image can be regarded as a concave portion of the crepe, and a white image can be regarded as a convex portion of the crepe. Such image processing can be performed using a known image scanner.

  In the calculating step, an area ratio of the first image or an area ratio of the second image with respect to the original image is calculated. Specifically, the area of the original image, the area of the first image, and the area of the second image are calculated, and the ratio of the area of the first image to the area of the original image or the area of the original image is calculated. The ratio of the area of the second image occupied is calculated. The calculation of each area of the original image, the first image, and the second image, and the calculation of the area ratio of the first image and the area ratio of the second image can be performed using known image analysis software. .

  By calculating the area ratio of the first image or the area ratio of the second image, for example, the first image can be regarded as a crepe concave portion, and the second image can be regarded as a crepe convex portion. it can. Further, by calculating the first image or the second image that occupies the area of the original image, it is possible to confirm the state of unevenness of the crepe, and from the state of unevenness of the crepe, the smoothness or roughness of the sheet It is possible to quantify the degree.

  The determination step can determine whether the area ratio of the first image to the original image or the second area ratio exceeds a predetermined threshold value. The predetermined threshold value used in the determination step can be arbitrarily determined according to the form, application, etc. of the sanitary thin paper. For example, a crepe formed on a sheet tends to have a fine crepe when the range of the crepe concave portion is relatively smaller than the range of the crepe convex portion, and the touch of the sanitary thin paper is good. From such a viewpoint, in the present embodiment, the predetermined threshold value can be set so that the area of the first image (crepe concave portion) is smaller than the area of the second image (crepe convex portion).

  According to the first aspect, by calculating the area ratio of the first image or the area ratio of the second image as described above, the unevenness state of the crepe formed on the sheet can be quantified. it can. Further, by determining whether or not such an area ratio exceeds a predetermined threshold value, it is possible to objectively recognize the uneven state of the crepe formed on the sheet. Therefore, according to the 1st form, the quality of the sanitary thin paper formed with the sheet | seat which has a crepe can be managed easily.

  In the first aspect, since the original image of the sheet is captured using an optical system with a shallow depth of focus, only information on the sheet surface can be captured. That is, only the crepe formed on the surface of the sheet can be imaged, and information on the back of the sheet (for example, a wire pattern) is not imaged. Therefore, the crepe of the sheet is calculated by calculating the area ratio of the first image or the second image that has been image-processed using the original image of the sheet picked up by such an optical system with a shallow depth of focus to the original image. When measuring the unevenness, the noise is small, and the quality of sanitary thin paper can be evaluated easily and objectively.

  In the second aspect of the present invention, the optical system includes a light source arranged one-dimensionally along a direction orthogonal to a direction in which the crepe on the sheet extends, and the direction of imaging the sheet is the light source Is a direction orthogonal to the direction in which the light source is disposed, and the light source moves relative to the sheet.

  Here, the direction in which the crepe extends on the sheet is the direction in which the crepe is formed on the moving sheet when the blade or the like is applied to the sheet conveyed in the paper making process (the moving direction of the conveyed sheet). Means. The direction in which the sheet is imaged means the direction in which the sheet or scanner sensor is moved when the sheet or scanner sensor is moved relatively. The direction orthogonal to the direction in which the light source is arranged means a direction orthogonal to the direction in which the light source is arranged one-dimensionally. The direction in which the light source moves is the direction in which the light source moves in synchronization with the sensor while irradiating the sheet with light in the optical system for imaging the sheet.

  As in the second aspect, an optical system including a light source arranged one-dimensionally along a direction orthogonal to the direction in which the crepe on the sheet extends is orthogonal to the direction in which the light source is arranged, and the light source When the sheet is imaged while moving the light source in the moving direction, only the unevenness of the crepe formed on the surface of the sheet can be reliably imaged. That is, the light source moves along the direction in which the crepe extends, and the direction in which the crepe is imaged is the direction along the direction in which the crepe extends, so noise can be reduced when measuring the crepe irregularities on the sheet surface. The quality of sanitary thin paper can be evaluated with high accuracy.

  In the third aspect of the present invention, the angle between the direction in which the light source is disposed and the direction orthogonal to the direction in which the crepe on the sheet extends is 0 ° to 38 °. When the angle between the direction in which the light source is arranged and the direction orthogonal to the direction in which the crepe on the sheet extends is within such an angle range, the original image of the sheet is displayed to the extent that the unevenness of the crepe on the sheet can be distinguished. An image can be distinguished from a second image. If the angle between the direction in which the light source is arranged and the direction perpendicular to the direction in which the crepe on the sheet extends exceeds 38 °, the first image and the second image do not correspond to the unevenness of the crepe, and It may be difficult to distinguish the unevenness of the crepe.

  In the fourth aspect of the present invention, the light source is further disposed at a position where the light is irradiated from only one direction on the sheet. Irradiating light from only one direction on the sheet indicates that light is not irradiated from a plurality of directions. By irradiating the sheet with light from only one direction as described above, a shadow due to the unevenness of the crepe is clearly generated on the sheet, and the original image obtained by capturing the shadow is converted into the first image and the second image. By converting, the unevenness of the crepe can be reliably distinguished. Therefore, the quality of sanitary thin paper can be managed with high accuracy.

  In the fifth aspect of the present invention, the optical system is a CIS (Contact Image Sensor) (contact image sensor) type scanner. A known image scanner can be used as the CIS scanner. As a sensor used for a CIS scanner, both a line sensor and an area sensor can be used.

  For example, when a CCD (Charge Coupled Devices) (charge coupled device) type scanner is used, the optical path length becomes long, and the depth of focus becomes deep. Therefore, when imaging a sheet using a CCD scanner, not only the information on the crepe formed on the surface of the sheet, but also the information inside the back sheet from the surface of the sheet (for example, information such as the wire pattern formed in the paper making process) ) Is also read.

  On the other hand, since the CIS scanner has a short optical path length and a shallow depth of focus, it can image only the crepe on the sheet surface. Therefore, in the imaging of the sheet using the CIS scanner according to the second aspect, there is little noise when measuring the unevenness of the crepe of the sheet, and the quality of the sanitary thin paper can be evaluated easily and objectively. Also, in sheet imaging using a CIS scanner, the apparatus can be downsized compared to a CCD scanner, can be used with less power, and does not require warm-up time. There are also benefits.

A sixth aspect of the present invention includes a sheet having a basis weight of 15 to 35 g / m ² , a paper thickness of 100 to 250 μm, and an average friction coefficient of 1.3 to 2.0, and a CIS method When the original image of the sheet captured by the scanner is divided into a first image that is equal to or less than a predetermined threshold and a second image that exceeds the predetermined threshold, the area of the first image is the second image The sanitary thin paper is smaller than the image area. By configuring the sanitary thin paper using a sheet in which the area of the first image is smaller than the area of the second image, the sanitary thin paper having a fine crepe on the sheet can be provided.

  In the seventh aspect of the present invention, the area ratio of the first image to the original image is 33% to 43%. As described above, the first image distinguished as described above is obtained by imaging the sheet having the basis weight and the paper thickness and having the average friction coefficient of 1.3 to 2.0 with the CIS scanner. By using a sanitary thin paper having an area ratio of 33% to 43% with respect to the original image, it is possible to provide a sanitary thin paper having a good touch while maintaining strength. When the area ratio of the first image to the original image is less than 33% or exceeds 43%, there is a possibility that smoothness as a sanitary thin paper cannot be obtained.

  In the seventh aspect, the condition of the sheet used for the sanitary thin paper is defined by the area ratio of the first image to the original image, but may be defined by the area ratio of the second image to the original image. When the sheet condition is defined by the area ratio of the second image to the original image, the area ratio of the first image to the original image may be converted into the area ratio of the second image to the original image.

  According to one embodiment of the present invention, a sanitary thin paper evaluation method capable of easily managing the quality of sanitary thin paper can be provided.

(A) is the photograph which shows the external appearance of the sheet | seat used as the object of the evaluation method of the sanitary thin paper based on this embodiment, (B) is the original image of the sheet | seat which imaged the sheet | seat of (A). It is a figure which shows the imaging device (CIS system scanner) for enforcing the sanitary thin paper evaluation method which concerns on embodiment of this invention. It is a flowchart which implements the sanitary thin paper evaluation method which concerns on this embodiment. (A) is a photograph showing the appearance of a conventional sheet, and (B) is an original image of the sheet obtained by imaging the sheet of (A) using a CCD scanner. (A) shows a state in which a sheet is imaged using a CIS scanner when the angle between the direction in which the light source is arranged and the direction perpendicular to the direction in which the crepe on the sheet extends is 0 ° in this embodiment. It is a figure and (B) is the original image of the sheet | seat imaged by (A). (A) shows a state in which a sheet is imaged using a CIS scanner when the angle between the direction in which the light source is arranged and the direction perpendicular to the direction in which the crepe on the sheet extends is 30 ° in the present embodiment. It is a figure and (B) is the original image of the sheet | seat imaged by (A). (A) is a figure which shows the state which images a sheet | seat using a CIS system scanner, when the angle of the direction where a light source is arrange | positioned, and the direction orthogonal to the direction where the crepe on a sheet extends is 45 degrees, B) is an original image of the sheet imaged in (A).

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the drawings, unless otherwise specified, the same or corresponding components may be denoted by the same reference numerals and description thereof may be omitted.

  First, the structure of the apparatus used for the sanitary thin paper evaluation method according to the present embodiment will be described. FIG. 1 shows a sheet (web) that is an object of the sanitary thin paper evaluation method according to the present embodiment, (A) is a photograph showing the appearance of the sheet, and (B) is an image pickup apparatus for the sheet of (A). It is the original image imaged using. FIG. 2 shows an imaging apparatus (CIS scanner) 200 and an image processing control apparatus (personal computer) 300 used in the sanitary thin paper evaluation method according to the embodiment of the present invention. The imaging device is an example of an optical system used in the sanitary thin paper evaluation method according to the present embodiment.

  The web 100 is an example of a sheet constituting a sanitary thin paper that is an object of evaluation by the sanitary thin paper evaluation method of the present embodiment. The web 100 is crepe paper used for household tissue paper. The web 100 is formed with crepes (fine wrinkles formed on the surface of the base paper by applying a blade called a doctor blade at the outlet of a paper machine dryer in the paper making process).

  A CIS scanner (hereinafter referred to as a CIS scanner) 200 includes a mounting table 20, an LED 21, a lens 22, and a sensor 23 with a web 100, which is an example of a sheet of the present invention, as a reading target. In this embodiment, GT-S650 (image type: monochrome, resolution 2400 dpi, scan area 20 mm × 20 mm, threshold value 250, scan angle 0 °) manufactured by EPSON was used as the CIS scanner.

  The mounting table 20 is formed of a transparent glass plate. The mounting table 20 can transmit light. The mounting table 20 constitutes a mounting table for a flatbed image scanner.

  The LED 21 is an example of a light source of a CIS scanner used in the sanitary thin paper evaluation method of the present embodiment. The LEDs 21 are arranged one-dimensionally along a direction orthogonal to the direction in which the crepe of the web 100 placed on the mounting table 20 extends. Specifically, it is composed of a plurality of LEDs arranged linearly along a direction orthogonal to the direction in which the crepe of the web 100 extends (the moving direction of the sheet conveyed in the paper making process, the vertical direction of the paper surface in FIG. 4). Thus, linear light can be irradiated onto the web 100. In this example, an LED is used as the light source of the CIS scanner 200, but the type of the light source is not limited.

  As shown in FIG. 2, the LED 21 can move while irradiating the web 100 with light LL. Specifically, the LED 21 is arranged so as to move along the direction in which the crepe of the web 100 placed extends (the direction in which the crepe is formed on the sheet by the doctor blade). The LED 21 may be disposed so as to move relative to the web 100. For example, the LED 21 that moves the web 100 and does not move relative to the moving web 100 may be disposed. Specifically, the web 100 is transported between a pair of rollers by using a transport device including a pair of rollers so that the web 100 wound around one roller is wound around the other roller. The CIS scanner (imaging device) can be fixed between the rollers.

  The lens 22 is installed in a sensor 23 described later, and can collect the light RL irradiated and reflected from the LED 21 to the web 100 as shown in FIG. An optical lens such as a rod eye lens is used for the lens 22.

  The sensor 23 is a CIS sensor (contact image sensor), and can convert the light collected by the lens 22 into a digital signal. Thereby, the light reflected on the web 100 is converted into a digital signal, and the original image 101 of the web 100 can be formed using this digital signal. In this example, a line sensor camera is used as the sensor 23 as shown in FIG. 2, but an area sensor camera may be used.

  The sensors 23 are arranged at an interval of 16 to 48 mm from the mounting table 20. By setting the distance between the sensor 23 and the mounting table 20 in such a range, the distance between the lens 22 provided on the sensor 23 and the web 100 placed on the mounting table 20 is changed by the sensor 23 of the imaging device 200. This is a distance that can maintain a state of focus when 100 is imaged. Therefore, the focal depth of the optical system (imaging device 200) that images the web 100 can be reduced.

  The sensor 23 is installed so as to move in synchronization with the LED 21 (light source). Therefore, the sensor 23 can move following the movement of the LED 21. Further, when the web 100 moves and the LED 21 (light source) does not move, the sensor 23 may be provided so as not to move.

  An imaging device 200 is connected to the personal computer 300, and the original image 101 of the web 100 captured by the imaging device 200 is transferred to the personal computer 300 as a digital signal. The personal computer 300 captures the captured original image 101 of the web 100 as a digital signal and performs image processing on the captured original image 101. The original image 101 (digital signal) captured in the personal computer 300 can be recorded in a memory (not shown) built in the personal computer 300 so as to be input / output.

  Next, the sanitary thin paper evaluation method according to the present embodiment will be described. FIG. 3 is a flowchart for carrying out the sanitary thin paper evaluation method according to the present embodiment. The sanitary thin paper evaluation method according to the present embodiment includes an imaging step, a processing step, a calculation step, and a determination step.

  In the imaging step, the web 100 is imaged to acquire the original image 101 of the web 100 (step ST1). Imaging of the web 100 is performed by the CIS scanner 200 described above. The acquisition (image processing or the like) of the original image 101 of the web 100 is performed by the personal computer 300 described above.

  In the processing step, image processing is performed to classify the original image 101 of the web 100 into a first image in which the luminance is equal to or lower than a predetermined threshold and a second image that exceeds the predetermined threshold. The luminance indicating the predetermined threshold can be any luminance that can distinguish the original image 101 from the first image and the second image.

  In the present embodiment, binarization by monochrome conversion can be performed as image processing. For example, the original image 101 of the web 100 is converted into two gradations of white and black, a predetermined threshold value is defined based on the luminance of the original image 101, and if the luminance of each pixel exceeds the threshold value, white, If it is below the threshold, it can be replaced with black.

  In the present embodiment, the first image whose luminance of the original image 101 is equal to or lower than a predetermined threshold is indicated by a black image (hereinafter referred to as black image), and the second image exceeding the predetermined threshold is a white image (hereinafter referred to as white image). (Step ST2). In this case, the black image can be regarded as a concave portion of the crepe, and the white image can be regarded as a convex portion of the crepe. In the present embodiment, such image processing is performed by the CIS scanner 200, and a predetermined threshold value based on luminance can be set by the CIS scanner 200.

  In the calculation step, the ratio of the area of the black image to the area of the original image (hereinafter referred to as the area ratio of the black image) is calculated (step ST3). In this example, as shown in FIG. 1B, the area of the original image 101 of the web 100 and the area of the black image are calculated, and the area ratio of the black image is calculated as the ratio of the area of the black image to the area of the original image. Calculate (step ST3). In the present embodiment, the calculation of the area of the original image, the area of the black image, and the area ratio of the black image can be performed using known image analysis software (for example, free software ImageJ). Further, the image analysis software can be installed in the personal computer 300, and each area of the original image and the black image and the area ratio of the black image can be calculated by the personal computer 300 in which the image analysis software is installed.

  Based on the area ratio of the black image calculated as described above, as shown in FIG. 1B, the concave portion of the crepe existing on the web 100 as the black image occupied in the original image can be confirmed. Further, the unevenness state (for example, smoothness or roughness) of the web 100 can be quantified from the area ratio of the black image. Therefore, the uneven state of the crepe formed on the web 100 can be objectively grasped.

  In the determination step, it can be determined whether or not the area ratio of the first image exceeds a predetermined threshold. In this embodiment, it is determined whether the area ratio of the black image exceeds a predetermined threshold (steps ST4 and ST5). The threshold value of the area ratio of the black image used in the determination step can be arbitrarily determined according to the form of sanitary thin paper, usage, and the like. The crepe formed on the web 100 has a tendency that the crepe is fine when the range of the crepe concave portion 11 is relatively small with respect to the range of the crepe convex portion 10, and the touch of the sanitary thin paper tends to be good. In the embodiment, the predetermined threshold is set so that the area of the black image (crepe concave portion 11) is smaller than the area of the white image (crepe convex portion 10).

  If it is determined in step ST5 that the area ratio of the black image exceeds a predetermined threshold, it can be evaluated that the crepe is rough (step ST6). If it is determined that the area ratio of the black image is equal to or less than the predetermined threshold, it can be evaluated that the crepe is fine (step ST7).

  By adopting the sanitary thin paper evaluation method of this embodiment, the ratio of the area of the first image (black image) to the area of the original image (area ratio of the first image (black image)) is calculated. It is possible to quantify the unevenness of the crepe formed on the web 100 (steps ST1 to ST3). Further, by determining whether or not such an area ratio exceeds a predetermined threshold value, it is possible to objectively grasp the uneven state of the crepe formed on the web 100 (steps ST4 to ST7). Through this series of steps (steps ST1 to ST7), the quality of the sanitary thin paper formed with the web 100 (sheet) having the crepe can be easily and objectively managed.

  In the sanitary thin paper evaluation method of the present embodiment, the web 100 is imaged by a CIS (contact image sensor) type scanner in the imaging step (step ST1), and the original image 101 of the web 100 is formed. Since the CIS sensor used for the sensor 23 has a short optical path length and a shallow depth of focus, only the surface of the web 100 can be imaged.

  By using such a CIS sensor, only the information on the crepe formed on the surface of the web 100 is read (see FIG. 1), and the information on the wire patterns 12, 13, etc. at the back of the web 100 is not read (see FIG. 1). (See FIG. 4). Therefore, noise when measuring the unevenness of the crepe of the web 100 can be reduced, and the quality control of the sanitary thin paper can be performed with high accuracy. In addition, the CIS sensor can reduce the size of the device as compared with, for example, a CCD sensor, can be used with a small amount of power, and does not require warm-up time.

  In the present embodiment, the LEDs 21 of the CIS scanner 200 are arranged one-dimensionally (in a straight line) along the direction orthogonal to the direction in which the crepe on the web 100 extends as described above, and image the web 100. The direction (the direction in which the sensor 23 moves relative to the web 100) is orthogonal to the direction in which the LEDs 21 are arranged in a straight line, and the LED moves relative to the web 100. . That is, the direction in which the web 100 is imaged is the direction along which the crepe extends (see FIG. 2).

  Thereby, only the unevenness | corrugation of the crepe formed in the surface of the web 100 can be imaged reliably. Therefore, noise can be reliably reduced when measuring the unevenness of the crepe on the surface of the web 100, and the quality of the sanitary thin paper can be evaluated with high accuracy.

  Moreover, in this embodiment, LED21 is arrange | positioned in the position which irradiates light only from one direction with respect to the web 100. FIG. That is, since the light is not irradiated from two or more directions, the shadow generated on the web 100 when the light is irradiated from the LED 21 is not canceled. Therefore, a shadow due to the unevenness of the crepe is clearly generated on the web 100, and the unevenness of the crepe can be reliably distinguished by performing image processing on the original image 101 obtained by capturing the shadow. Therefore, the quality of sanitary thin paper can be managed with high accuracy.

  In the present embodiment, the angle between the direction in which the LEDs 21 are arranged in a straight line and the direction perpendicular to the direction in which the crepe on the web 100 extends can be 0 ° to 38 °. That is, the web 100 is placed on the mounting table 20 so that the direction perpendicular to the direction in which the crepe on the web 100 extends is in the range of 0 ° to 38 ° with respect to the direction in which the linearly arranged LEDs 21 are arranged. Can be placed.

  For example, in FIG. 5A, the angle between the direction in which the LEDs 21 are arranged in a straight line (X direction) and the direction orthogonal to the direction in which the crepe on the web 100 extends (the direction of the arrow CD) is 0 °. Yes. In FIG. 6A, the angle between the X direction and the direction of the arrow CD is about 30 °. 5A and 6A, the moving direction of the LED 21 is the direction of the arrow LD. This direction is a direction (Y direction) orthogonal to the direction (X direction) in which the LEDs 21 are linearly arranged. If the web 100 is mounted on the mounting table 20 in such an angle range, the original image 101 of the web 100 is divided into a black image and a white image so that the unevenness of the crepe on the web 100 can be clearly distinguished. They can be distinguished (see FIGS. 5B and 6B).

  If the angle between the direction in which the LEDs 21 are arranged in a straight line (X direction) and the direction orthogonal to the direction in which the crepe on the web 100 extends (the direction of the arrow CD) exceeds 38 °, a black image and a white image May not correspond to the unevenness of the crepe, and it may be difficult to distinguish the unevenness of the crepe on the sheet (see FIGS. 7A and 7B).

Next, the sanitary thin paper according to the present embodiment will be described. First, a web 100 having a basis weight of 15 to 35 g / m ² , a paper thickness of 100 to 250 μm, and an average friction coefficient of 1.3 to 2.0 is prepared. As for the average friction coefficient, a friction test was performed in a direction of about 90 ° with respect to the direction in which the crepe of the web 100 extends. The prepared web 100 is evaluated using the sanitary thin paper evaluation method described above. Specifically, the prepared web 100 is imaged by the CIS scanner 200, and an original image 101 of the web 100 is obtained.

  The area of the black image when the luminance of the obtained original image 101 is divided into a black image (first image) having a luminance equal to or lower than a predetermined threshold and a white image (second image) exceeding the predetermined threshold is a white image The web 100 managed to be smaller than the area is selected. By configuring the sanitary thin paper using the web 100 selected under such conditions, it is possible to provide the sanitary thin paper with a fine crepe on the sheet.

  Further, in the sanitary thin paper of the present embodiment, it is preferable to use a web in which the area ratio of the first image to the original image is 33% to 43% as the web 100 in which the area of the black image is smaller than the area of the white image. A sheet having the above basis weight and paper thickness and having an average friction coefficient of 1.3 to 2.0 is imaged by a CIS scanner, and the area ratio of the black image divided as described above is the original image. On the other hand, by using a web of 33% to 43%, it is possible to provide a sanitary thin paper having a good touch while maintaining the strength. When the area ratio of the black image to the original image is less than 33% or sanitary thin paper using a web that exceeds 43%, smoothness as sanitary thin paper may not be obtained.

  In this embodiment, the condition of the sheet (web 100) is defined by the area ratio of the black image to the original image, but may be defined by the area ratio of the white image to the original image. When the sheet condition is defined by the area ratio of the white image to the original image, the area ratio of the black image to the original image may be converted into the area ratio of the white image to the original image.

  Hereinafter, the present embodiment will be specifically described using examples. Note that the present embodiment is not limited to these examples. Measurement and evaluation of each example and comparative example were performed as follows.

[Basis weight]
The basis weight of the crepe paper (base paper) was measured by a method based on JIS P 8124 (1998).

[Paper thickness]
After the crepe paper (base paper) was sufficiently conditioned under the conditions of JIS P 8111 (1998), the paper thickness of the base paper was measured using a dial gauge (Pecock G type, manufactured by Ozaki Seisakusho). Specifically, confirm that there is no dust, dust, etc. between the plunger and the measuring table, lower the plunger on the measuring table, move the scale of the dial thickness gauge to adjust the zero point, and then Raise the plunger, place the sample on the test bench, slowly lower the plunger and read the gauge at that time. At this time, only the plunger is placed. The terminal of the plunger was made of metal so that a circular plane having a diameter of 10 mm was perpendicular to the paper plane. The load at the time of measuring the paper thickness is about 70 gf. The paper thickness was an average value obtained by performing measurement 10 times. The paper thickness was measured on the base paper per ply.

[Blade elapsed time]
The blade elapsed time is the time during which one blade is applied to a dryer (drum) of a rotating paper machine when a crepe is formed on the base paper. A stainless (SK51) doctor blade was used as the blade.

[Creep rate]
As the crepe rate, a value calculated by a conditional expression of ((peripheral speed of the dryer) − (peripheral speed of the take-up reel)) / (peripheral speed of the dryer) × 100 (%) was used.

[Tensile strength]
The dry tensile strength according to JIS P 8113 (1998) was measured. The measurement was performed for each of the vertical direction and the horizontal direction per ply. The test width of the measurement sample was 25 mm. The unit is indicated by cN.

[Average friction coefficient]
The average friction coefficient was measured using a pin-on-plate friction test apparatus (manufactured by Trinity Lab Co., Ltd., Tribomaster TYPE μv1000). In the measurement of the average friction coefficient, crepe paper is placed on the plate of a pin-on-plate type friction test apparatus, one edge of the crepe paper is fixed with a jig or the like, and the crepe paper is removed from one fixed end. To the other non-fixed end, horizontally move in the Y direction in FIG. 5 while contacting the contact with the sliding speed of 1.0 mm / s, the vertical load F of 50 gf, and the sliding distance of 5.0 mm. The average value of the dynamic friction coefficient at this time was measured. The measurement conditions are an experimental room temperature of 20 ° C., a laboratory humidity of 20 RH%, and the lubrication state is no lubrication in the atmosphere. The measurement sample used is a sample left in a chamber at 25 ° C. and 20% RH for 24 hours. The size of the measurement sample was 100 mm × 100 mm.

[B / W area ratio]
Analyze Particles (particle analysis) is performed using Image J's Analyze tool. The number of objects (black portions) was counted in an image binarized in black and white or an image set as a threshold, and the area ratio of the black image was measured. The area ratio of the black image was calculated under the condition of the sum of the areas of the respective objects / total area (20 × 20) = area ratio.

[Sensory evaluation (smoothness)]
The sample surface was boiled with a finger from 90 ° direction with respect to the crepe direction to confirm smoothness. The sensory evaluation was performed by 20 people, and the evaluation was performed according to the following criteria using the average value of the total values scored according to the following criteria.
4 points = “feel smooth”
3 points = “Slightly smooth”
2 points = "I feel a little rough"
1 point = “I feel rough”.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
In Example 1, US basis weight (basis weight) 16.78 g / m ² , paper thickness 126 μm, blade elapsed time 90 minutes, crepe rate 23%, tensile strength (longitudinal) 303 cN, tensile strength (lateral) 116 cN, average friction coefficient 1.585 crepe paper (see web 100) was prepared. In Example 1, the web 100 was placed on the mounting table 20 of the CIS scanner 200 and imaged so that the angle between the direction in which the LEDs 21 were arranged and the direction perpendicular to the direction in which the crepe on the web 100 extends was 0 °. . In Example 1, the area ratio of the black image was 37.86%, and the sensory evaluation (smoothness) was 3.6. The results of measurement and evaluation are shown in Table 1.

[Example 2]
In Example 2, the same crepe paper as in Example 1 was prepared except that the blade time was 180 minutes, the paper thickness was 124 μm, the tensile strength (longitudinal) was 298 cN, and the average friction coefficient was 1.655. In Example 2, the area ratio of the black image was 39.76%, and the sensory evaluation (smoothness) was 3.4. The results of measurement and evaluation are shown in Table 1.

[Example 3]
In Example 3, the blade time is 270 minutes, the rice basis weight (basis weight) is 16.71 g / m ² , the paper thickness is 125 μm, the tensile strength (length) is 328 cN, the tensile strength (width) is 128 cN, and the average friction coefficient is 1.612. Except for this, the same crepe paper as in Example 1 was prepared. In Example 3, the area ratio of the black image was 39.42%, and the sensory evaluation (smoothness) was 3.2. The results of measurement and evaluation are shown in Table 1.

[Example 4]
In Example 4, the blade time is 360 minutes, the rice basis weight (basis weight) is 16.90 g / m ² , the paper thickness is 136 μm, the tensile strength (length) is 331 cN, the tensile strength (width) is 129 cN, and the average coefficient of friction is 1.652. Except for this, the same crepe paper as in Example 1 was prepared. In Example 4, the area ratio of the black image was 39.26%, and the sensory evaluation (smoothness) was 3.1. The results of measurement and evaluation are shown in Table 1.

[Example 5]
In Example 5, the blade time is 450 minutes, the rice basis weight (basis weight) is 16.64 g / m ² , the paper thickness is 140 μm, the tensile strength (length) is 295 cN, the tensile strength (width) is 110 cN, and the average friction coefficient is 1.839. Except for this, the same crepe paper as in Example 1 was prepared. In Example 5, the area ratio of the black image was 40.66%, and the sensory evaluation (smoothness) was 3.0. The results of measurement and evaluation are shown in Table 1.

[Comparative Example 1]
In Comparative Example 1, the blade time is 540 minutes, the rice basis weight (basis weight) is 16.53 g / m ² , the paper thickness is 143 μm, the tensile strength (length) is 299 cN, the tensile strength (width) is 115 cN, and the average friction coefficient is 2.131. Except for this, the same crepe paper as in Example 1 was prepared. In Comparative Example 1, the area ratio of the black image was 46.50%, and the sensory evaluation (smoothness) was 2.1. The results of measurement and evaluation are shown in Table 1.

[Comparative Example 2]
In Comparative Example 2, blade time 90 minutes, crepe rate 19%, rice basis weight (basis weight) 16.65 g / m ² , paper thickness 98 μm, tensile strength (longitudinal) 296 cN, tensile strength (lateral) 123 cN, average friction coefficient 1 The same crepe paper as Example 1 was prepared except that it was .342. In Comparative Example 2, the area ratio of the black image was 32.60%, and the sensory evaluation (smoothness) was 3.8. The results of measurement and evaluation are shown in Table 1.

表１より、坪量が１５〜３５ｇ/ｍ^２、紙厚が１００〜２５０μｍ、平均摩擦係数が１．３〜２．０のクレープ紙であり、これを焦点深度の浅い光学系（ＣＩＳ方式のスキャナ）で撮像して得られた原画像の輝度が所定の閾値以下の黒画像と所定の閾値を超える白画像とに区分し、黒画像の面積比（原画像の面積に対する黒画像の面積の比率）が３３％〜４３％のクレープ紙は、強度を維持しながら官能評価（滑らかさ）が良好であった（実施例１〜５）。

From Table 1, it is a crepe paper having a basis weight of 15 to 35 g / m ² , a paper thickness of 100 to 250 μm, and an average friction coefficient of 1.3 to 2.0. The brightness of the original image obtained by scanning with a scanner is divided into a black image with a predetermined threshold value or less and a white image with a predetermined threshold value, and the black image area ratio (the area of the black image with respect to the area of the original image) The crepe paper having a ratio of 33% to 43% had good sensory evaluation (smoothness) while maintaining strength (Examples 1 to 5).

  On the other hand, except for the area ratio of the black image, the conditions are the same as those in the example. However, a crepe paper having an area ratio of the black image of less than 33% or more than 43% provides a good sensory evaluation (smoothness). (Comparative Examples 1 and 2). Note that the crepe paper of Comparative Example 2 is too thin to be used as a sanitary thin paper sheet.

  In this way, crepe paper satisfying a predetermined condition is imaged by a CIS scanner, and the captured original image is processed into a white image and a black image, so that the area of the black image is smaller than the area of the white image By manufacturing sanitary thin paper using crepe paper, the quality of the sanitary thin paper can be controlled. In addition, by controlling the quality of the sanitary thin paper in this way, it is possible to provide a sanitary thin paper having a good touch.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to specific embodiment, A various deformation | transformation and change are possible within the range of the invention described in the claim. .

DESCRIPTION OF SYMBOLS 100 Sheet 101 Original image 10 Crepe convex part 11 Crepe concave part 12, 13 Wire pattern 200 Scanner 20 Mounting stand 21 LED
22 lens 23 sensor LD LED moving direction CD crepe extending direction

Claims (7)

A method for evaluating sanitary thin paper formed of a sheet having a crepe,
An imaging step of capturing the sheet with an optical system having a shallow depth of focus to obtain an original image of the sheet;
A processing step of performing image processing for classifying the original image into a first image in which the luminance of the original image is equal to or lower than a predetermined threshold and a second image exceeding the predetermined threshold;
A method for evaluating sanitary thin paper, comprising: calculating an area ratio of the first image to the original image or an area ratio of the second image. The optical system includes a light source arranged one-dimensionally along a direction orthogonal to a direction in which a crepe on the sheet extends,
The method for evaluating sanitary thin paper according to claim 1, wherein a direction in which the sheet is imaged is a direction orthogonal to a direction in which the light source is disposed, and the light source is moved relative to the sheet. .   The sanitary thin paper evaluation method according to claim 2, wherein an angle between a direction in which the light source is disposed and a direction orthogonal to a direction in which the crepe on the sheet extends is 0 ° to 38 °.   The sanitary thin paper evaluation method according to claim 2, wherein the light source is disposed at a position where light is emitted from only one direction to the sheet.   The sanitary thin paper evaluation method according to any one of claims 1 to 4, wherein the optical system is a CIS scanner. The basis weight is 15 to 35 g / m ² ,
The paper thickness is 100-250 μm,
Having a sheet with an average coefficient of friction of 1.3-2.0,
When the original image is divided into a first image in which the luminance of the original image of the sheet captured by a CIS scanner is a predetermined threshold or less and a second image that exceeds the predetermined threshold, the first image Sanitary thin paper in which the area of the image is smaller than the area of the second image.   The sanitary thin paper according to claim 6, wherein an area ratio of the first image to the original image is 33% to 43%.

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