JP5413275B2 - Periodic defect detection method, apparatus, and sheet-like object manufacturing method - Google Patents

Description

  The present invention relates to a periodic defect detection method and apparatus for detecting a periodic defect formed in a process of manufacturing a sheet-like object, and a method for manufacturing a sheet-like object.

  In the manufacturing process of a sheet-like object such as a film, a plurality of rolls are used for conveyance, stretching and the like. Due to scratches or deposits on the surface of the roll, defects (periodic defects) may occur continuously on the surface of the sheet-like object with a period of the roll diameter. These periodic defects are mainly scratches, but they are discovered by inspection by humans and defect detectors in the manufacturing process and before product shipment, leading to quality assurance and process improvement.

  However, in recent years, the quality requirements for sheet-like objects have become stricter. In particular, the requirements for periodic defects are required to guarantee a very small level in both size and strength. Along with this, the setting of the defect detection device is made strict, many defects of the sheet-like object are detected, and period determination is performed on them.

Here, a known method of period determination will be described with reference to Patent Document 1. Patent Document 1
(1) Classifying the defects in which the generated sheet width direction positions are close within a preset sheet width direction allowable range into the same group,
・ In the defect group classified in the same group, the distance in the sheet conveyance direction at the position where any two defects occur is the basic cycle (there are multiple),
(3) In the defect group classified into the same group, the first defect having a (one) basic period is determined,
(4) In the defect group classified in the same group, the defects are sequentially extracted and the sheet conveyance direction distance from the leading defect is calculated.
(5) When it becomes an integral multiple of the basic period, the period determination is performed in which the (sequentially extracted) defects are determined as the periodic defects having the basic period. General cycle determination is based on the same concept, and has an allowable range in the sheet conveyance direction that allows some amount of deviation at an integral multiple of (5). This is shown in FIG. FIG. 5 is an explanatory diagram of an example of period determination.

  Reference numerals 101 to 105 indicate defects, and attention is now focused on the defect 101 (corresponding to “first defect” in Patent Document 1). At this time, 106 corresponds to the permissible range in the sheet width direction, and the defects 101 to 104 existing in the permissible range 106 in the sheet width are the target defects for period determination (corresponding to “same group” in Patent Document 1). Defects 105 (two of them) that do not exist in 106 are not subject defects. That is, the permissible range in the sheet width direction is a value set to permit (determine that they are the same) the amount of shift assuming that the position of each of the periodic defects having the same period is slightly shifted in the sheet width direction. It is.

Then, the sheet conveyance direction distance 107 between the defect 101 and the defect 102 is the first basic cycle, and the sheet conveyance direction distance between the defect 101 and the defect 103 and the sheet conveyance direction distance between the defect 101 and the defect 104 are considered. If these sheet conveyance direction distances are integral multiples of the first basic period sheet conveyance direction distance 107, or are within a range in which the sheet conveyance direction allowable range 108 is taken into consideration (addition subtraction), the same period is obtained. It is determined as a periodic defect. In FIG. 5, the distance in the sheet conveyance direction between the defect 101 and the defect 103 is within the deviation within the allowable sheet conveyance direction 108 from the distance twice the distance 107 in the sheet conveyance direction. Are determined to be periodic defects having the same period. Further, the distance in the sheet conveyance direction between the defect 101 and the defect 104 is within a deviation within the allowable sheet conveyance direction 108 from a distance three times the sheet conveyance direction distance 107. The defect 104 is defined as the defect 101, the defect 102, It is determined as a periodic defect having the same period as the defect 103. In other words, the sheet conveyance direction allowable range is the amount of deviation assuming that the theoretically calculated sheet conveyance direction position and the actual sheet conveyance direction position are slightly deviated in each of the periodic defects generated from the same roll. Is set to allow (same).
If it is not determined as a periodic defect having the first basic period, the distance in the sheet conveyance direction between the defect 101 and the defect 103 is the second (th) basic period, and the period is determined based on the defects after the defect 104. When such period determination is completed for the defect 101, the defect 102 is refocused and executed again. However, if the defect 102 is determined as a periodic defect, the next defect 103 may be focused. In general, if three or more defects (in FIG. 5, defect 101, defect 102, and defect 103) satisfy the condition for period determination, the defect becomes a period defect.

  In recent years, it is also possible to set a plurality of ranges in which the basic cycle should be, and it is possible to perform more accurate cycle determination. The range that should have the basic period at this time is calculated from the roll diameter, the stretching ratio in the sheet conveyance direction, and the like, and there is a period that is not within this range (or within the range that additionally considers the allowable range in the sheet conveyance direction). When the basic period is reached, it is not determined as a period defect.

  However, according to the knowledge of the present inventor, it is difficult to carry out highly accurate period determination only when such a technique is detected when many defects are detected. This is shown in FIG. FIG. 6 is an explanatory diagram of an example of period determination.

  Reference numerals 111 to 114 indicate defects, and attention is now paid to the defect 111. At that time, 115 corresponds to the permissible range in the sheet width direction, and all the defects 112 to 114 are the object defects for the period determination. The sheet conveyance direction distance 116 between the defect 111 and the defect 112 is the first basic period, but the sheet conveyance direction distance between the defect 111 and the defect 113 and the defect 114 (two of them) is the first basic period. It is within the deviation of the sheet conveyance direction allowable range 117 from twice, and it cannot be actually determined which defect is a periodic defect.

  According to the knowledge of the present inventor, as a solution to this problem, it is possible to consider the feature amount of the defect that has occurred (defect feature amount). Here, the defect feature amount refers to a value such as the length, width, and intensity of a defect obtained from a defect image obtained by a defect detection device or the like, and is newly obtained by weighted addition of these values. The given value may be used. The defect image at this time may be a captured image itself captured by a defect detection device or the like, or may be a processed image obtained by performing image processing such as differentiation on the captured image.

  It has been found that periodic defects originating from the same roll have a similar shape. Therefore, if a clustering technique for classifying defects having similar defect feature amounts is introduced, the accuracy of period determination is improved.

  Various methods have been proposed as a clustering technique. In general, statistical methods (cluster analysis, etc.) are used, but many learning methods such as neural networks and brute force searches (so-called decision tree methods) have been proposed. Among these, there is Patent Document 2 as a method aiming at classification of scratches.

  In Patent Document 2, optimization processing using a genetic algorithm is performed using weighted teacher data as fitness. Thereby, the defect feature quantity important for classification is automatically selected, and the optimization process for handling a huge amount of data is simplified.

  According to the knowledge of the present inventor, the accuracy of period determination can be improved by setting the range where the basic period should be, after utilizing the clustering technique as described above. FIG. 7 shows a cycle determination flow when these are combined. FIG. 7 is an explanatory diagram of a cycle determination flow after paying attention to one defect.

  121 is a step of paying attention to one defect and extracting all the defects in the allowable range in the sheet width direction. 122 is a step of using the clustering technique to obtain the defect feature amount of the defect noticed in step 121 and selecting only the defects having the same defect feature amount from the defects extracted in step 121. Reference numeral 123 denotes a step of performing cycle determination for the defects selected in 122. At this time, the basic cycle takes into account the range that should be, and highly accurate cycle determination is performed.

  FIG. 8 and FIG. 9 show the results of the cycle determination according to the cycle determination method described in FIG. 5 and the flow of FIG. FIG. 8 is an explanatory diagram of all defect occurrence positions before cycle determination, and FIG. 9 is an explanatory diagram of defect occurrence positions after cycle determination according to the cycle determination flow of FIG. A circle in FIG. 8 indicates that a defect exists at that position. FIG. 9 shows a result of extracting periodic defects from the periodic determination method described in FIG. 5 and the flow in FIG. That is, all the circles in FIG. 9 are determined to be periodic defects. Although a periodic defect exists at the position of the arrow 131 in FIG. 9, defects that are not periodic defects are also determined to be periodic. Thus, the cycle determination accuracy is insufficient with this alone.

The inventor believes that this cause is
(1) Classification by clustering is not optimal (2) It has been found that the allowable range in the sheet width direction and / or the allowable range in the sheet conveyance direction in the period determination is not optimal.

  First, regarding “non-optimal classification by clustering”, we try to classify all the different flaws at the same time, targeting all periodic defects (here, flaws) that occur in the whole process of manufacturing a sheet-like object. The cause is.

  In other words, there are many types of scratches, such as “longitudinal scratches” that are elongated in the sheet conveying direction, “lateral scratches” that are elongated in the sheet width direction, and “uneven scratches” that occur even on the surface of the sheet. This is because it tries to classify at the same time with high accuracy, so it remains in overall optimization. In FIG. 9, classification (discrimination) based on Mahalanobis distances, in which three of ten types of defect feature quantities such as the length, width, and strength of defects are selected, is performed, so that the discriminant midpoint is the highest.

  In addition, regarding “the sheet width direction allowable range and / or the sheet conveyance direction allowable range in the period determination is not optimal”, the same sheet width direction allowable range (and / or sheet conveyance direction allowable range) is set for every scratch. It is mentioned that.

  Originally, even in a scratch that occurs in a process that can set the allowable range in the sheet width direction, an unnecessarily large value is set according to the process that should set the allowable range in the sheet width direction. is there. As a result, the number of defects for period determination increases, and the period determination accuracy decreases as shown in FIG. The same applies to the allowable range in the sheet conveyance direction.

Japanese Patent No. 3845958 Japanese Patent Laid-Open No. 2005-227054

  In view of the above, an object of the present invention is to provide a periodic defect detection method and apparatus having a highly accurate periodic determination, and a method for manufacturing a sheet-like object.

  In order to achieve the above object, the present invention has the following configuration.

That is, the periodic defect detection method of the present invention irradiates a sheet-like object to be conveyed with light, receives reflected light or transmitted light through the sheet-like object, and based on the received light, In a periodic defect detection method for detecting a defect and determining whether or not the defect is a periodic defect that occurs periodically,
(1) A defect feature amount range is set for each step of manufacturing the sheet-like object,
(2) The period is determined by setting an allowable range in the sheet width direction or an allowable range in the sheet width direction and an allowable range in the sheet conveyance direction for each step.

  Furthermore, according to a preferred embodiment of the present invention, the sheet width direction allowable range and the sheet conveyance direction allowable range are set based on a draw ratio in a drawing step of the step of manufacturing the sheet-like object. It is.

  Furthermore, according to a preferred embodiment of the present invention, the defect feature amount range is set based on a draw ratio in a drawing step of the step of manufacturing the sheet-like object.

  Furthermore, according to a preferred aspect of the present invention, the sheet width direction allowable range and the sheet conveyance direction allowable range are set based on a final thickness of the sheet-like object.

  Furthermore, according to a preferred embodiment of the present invention, the defect feature amount range is set based on a final thickness of the sheet-like object.

Further, the periodic defect detection device of the present invention is based on an irradiation means for irradiating a sheet-like object to be conveyed with light, a light-receiving means for receiving reflected light or transmitted light through the sheet-like object, and received light. In the periodic defect detection apparatus, the periodic determination unit includes: a defect detection unit that detects a defect of the sheet-like object; and a cycle determination unit that determines whether the defect is a periodic defect that occurs periodically.
(1) Defect feature amount range setting means for setting a defect feature amount range for each step of manufacturing the sheet-like object;
(2) It is characterized by having an allowable range setting means for setting an allowable range in the sheet width direction or an allowable range in the sheet width direction and an allowable range in the sheet conveyance direction for each process.

  Furthermore, according to a preferred embodiment of the present invention, the allowable range setting means sets the allowable range in the sheet width direction and the allowable range in the sheet conveyance direction based on a stretching ratio in the stretching step of the step of manufacturing the sheet-like object. It is what is characterized by.

  Furthermore, according to a preferred aspect of the present invention, the defect feature amount range setting means sets the defect feature amount based on a stretching ratio in a stretching step of the step of manufacturing the sheet-like object. It is what.

  Furthermore, according to a preferred aspect of the present invention, the allowable range setting means sets the allowable range in the sheet width direction and the allowable range in the sheet conveyance direction based on the final thickness of the sheet-like object. It is what.

  Furthermore, according to a preferred aspect of the present invention, the allowable range setting means sets the defect feature amount range based on a final thickness of the sheet-like object.

  The “process for producing a sheet-like object” in the present invention refers to a process in which the production of a sheet-like object is divided into a plurality of roles (functions). For example, in the case of a film, the molten polymer is discharged from the gap of the die, and a “casting” process for receiving it into a sheet, a “longitudinal stretching” process for stretching the film in the conveying direction, and a “lateral” stretching film in the width direction. Examples include a “stretching” process, a “conveying” process for transporting the film before winding, a “winding” process for winding the film, and a “slit” process for cutting the wound film according to the customer's desired width. The “longitudinal stretching” process and the “lateral stretching” process may be collectively referred to as “stretching” process.

  In addition, the “defect feature amount” in the present invention refers to a value characterizing a defect obtained from a defect image. For example, the length, width, strength, etc. of the defect may be mentioned, and a new value obtained by weighted addition of these values may be used.

  Further, the “stretching ratio in the stretching process” in the present invention refers to a ratio when the sheet-like object is stretched in the sheet conveying direction and the sheet width direction in the “stretching” process. There are stretching ratios in the sheet conveying direction in the “longitudinal stretching” process and stretching ratios in the sheet width direction in the “lateral stretching” process. Further, when there are a plurality of “longitudinal stretching” steps and / or “lateral stretching” steps, the stretching ratios in the respective steps are indicated.

  Further, the “final thickness of the sheet-like object” in the present invention refers to the thickness of the sheet-like object in the last step (for example, “slit” step in the film) in the process of manufacturing the sheet-like object. That is, it is the thickness of the sheet-like object in which no further thickness change occurs. Since this final thickness is also the thickness of the final product, it can be determined in advance as the target thickness. Since the thickness can be controlled with accuracy up to several μm level depending on the setting conditions of each step of manufacturing the sheet-like object, this target thickness may be set as the final thickness. Further, the final thickness may be determined based on the actually measured value. Measurement may be performed in-line in a process of manufacturing a sheet-like object, particularly a “conveying” process or a “slit” process, or may be performed offline after a “slit” process. The measuring means may be a β-ray thickness gauge, an X-ray thickness gauge, an infrared thickness gauge, an optical interference thickness gauge, or a contact thickness gauge. However, the contact thickness gauge is preferably used off-line. An average value of measured values over several minutes may be used, or a measured value at a preset location may be used.

  According to the present invention, as described below, it is possible to obtain a periodic defect detection method, apparatus, and sheet-like object manufacturing method that are excellent in periodic determination accuracy.

It is flow explanatory drawing in the period determination of this invention. It is explanatory drawing of the manufacturing process of a sheet-like object in one Embodiment of this invention. It is a schematic block diagram which shows the apparatus structure in one Embodiment of this invention. It is explanatory drawing of the period determination result in one Embodiment of this invention. It is explanatory drawing of the period determination method of a prior art. It is explanatory drawing of the subject of the period determination method of a prior art. It is flow explanatory drawing in period determination of a prior art. It is explanatory drawing of the fault distribution before the period determination in one Embodiment of this invention. It is explanatory drawing of the period determination result of a prior art. It is explanatory drawing of the classification | category by Mahalanobis distance of this invention. It is explanatory drawing of the classification | category by Mahalanobis distance of this invention.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings, taking as an example a case where the present invention is applied to a defect detection apparatus for off-line inspection after a manufacturing process of a single-layer transparent polymer film by sequential biaxial stretching.

  First, the manufacturing process of the single layer transparent polymer film by sequential biaxial stretching in this embodiment is shown in FIG. FIG. 2 is an explanatory view of a single-layer transparent polymer film production process by sequential biaxial stretching.

  Reference numeral 10 denotes a base, which discharges a molten polymer. 11 is a process for forming a molten polymer into a sheet, which is called a “casting” process. Reference numeral 12 denotes a step of stretching the sheet-like polymer in the sheet conveying direction, which is called a “longitudinal stretching” step. More specifically, there are a “longitudinal / preheating” step for warming the film before stretching, a “longitudinal / stretching” step for stretching the film, and a “longitudinal / cooling” step for fixing the film shape after stretching. Reference numeral 13 denotes a step of stretching the film in the sheet width direction, which is called a “lateral stretching” step. Here, no roll is used. Reference numeral 14 denotes a process of transporting the film before winding the film, which is called a “transport” process. Reference numeral 15 denotes a step of winding the film once into a roll, which is called a “winding” step. Reference numeral 16 denotes a process in which the film wound in the roll shape in the “winding” process 15 is unwound again and cut into a width desired by the customer, which is called a “slit” process. More specifically, the “slit / winding” process for transporting the film, the “slit / winding” process just before winding the roll in the “slit” process, and the “slit / winding” winding roll in the “slit” process. There is a process. Although the fine distinction was described only about the "longitudinal stretching" process and the "slit" process, other processes may be subdivided.

  When the film is wound in the “winding” step 15 or when the film is unwound in the “slit” step 16, the roll may be reciprocated in the width direction. This is called oscillation, and there are cases where the round-trip distance is several mm to several hundred mm.

  In FIG. 2, the “longitudinal stretching” step 12 and the “lateral stretching” step 13 are each performed only once, but may be performed multiple times, and the “longitudinal stretching” step 12 and the “lateral stretching” step 13 are not performed. It may be uniaxial stretching without the “longitudinal stretching” step 12 or the “lateral stretching” step 13. The order of the “longitudinal stretching” step 12 and the “lateral stretching” step 13 may be reversed. Simultaneous biaxial stretching may be used instead of sequential. Further, there may be a “coating” step of coating the film with a coating material, or a “surface modification” step of modifying the film surface by corona discharge or the like.

  In the present embodiment, the present invention is introduced into a defect detection device (not shown) for inspecting a roll cut to a customer's desired width after the “slit” step 16. However, the present invention is not limited to the defect detection apparatus after the “slit” process 16, and may be introduced into the defect detection apparatus installed in the “conveyance” process 14, the “winding” process 15, the “slit” process 16, etc. Is possible.

  Next, the apparatus configuration of the present embodiment is shown in FIG. FIG. 3 is a schematic configuration diagram of the present embodiment.

  17 is a sheet-like object, and here is a single-layer transparent polymer film produced by sequential biaxial stretching. It does not specifically limit as the sheet-like object 17, A film, paper, glass, a metal, etc. may be sufficient. In the case of a film, it may be a film having a multilayer structure, or a film having a coating material coated on the front surface and / or the back surface. Moreover, if it is set as the structure which receives reflected light, a colored film may be sufficient. Moreover, although it is set as the film by sequential biaxial stretching here, it may be unstretched, may be uniaxial stretching, and may be simultaneous biaxial stretching. That is, it is not concerned with the form of stretching in production.

  Reference numeral 18 denotes irradiation means for irradiating the sheet-like object 17 with light. The irradiation unit 18 may be a fluorescent lamp, a halogen light source, a metal halide light source, a xenon light source, or an LED light source. Moreover, it may have a specific wavelength characteristic or may have a specific directivity. Preferably, it has a light projection part long in one direction, and the light quantity irradiated from the light projection part is substantially uniform. Here, a metal halide light source is used, light from the light source is transmitted to the rod illumination by an optical fiber bundle, and substantially uniform light having high directivity in one direction is irradiated from the rod illumination. The longitudinal direction of the rod illumination is substantially uniform with the width direction of the sheet-like object 17. The longitudinal direction of the rod illumination may be a plane (parallel plane) parallel to the plane of the sheet-like object 17 (generally having a vertical direction in the normal direction), and may be rotated within that plane.

  A light receiving unit 19 is disposed so as to receive the transmitted light from the irradiation unit 18 via the sheet-like object 17. Preferably, the sheet-like object 17 is less wrinkled or fluttered at and near the portion through the transmitted light. The light receiving means 19 may be a line sensor camera, an area sensor camera, or may be a component composed of a plurality of photoelectric conversion elements. Preferably, the photoelectric conversion element of the light receiving means 19 has good sensitivity, is resistant to noise, and has a small difference between the elements. Here, a line sensor camera is used, and the alignment direction of the photoelectric conversion elements is substantially uniform with the longitudinal direction of the irradiation means 18.

  Preferably, the light receiving means 19 is maintained in a relative positional relationship with the sheet-like object 17 and / or the irradiating means 18 so that the distribution of received light quantity varies depending on the type of defect of the sheet-like object 17. It is that you are. Here, the positional relationship is such that scattered light generated on the surface of the scratch existing on the sheet-like object 17 is received. Specifically, when the sheet-like object 17 is not scratched, the light from the irradiation means 18 is not strongly received, and when there is a scratch, the scattered light on the scratch surface is additionally received. ing. As an installation method, for example, the angle is adjusted so that the irradiation center optical axis from the irradiation unit 18 and the light reception center optical axis of the light receiving unit 19 coincide with each other, and then the irradiation unit 18 and / or the light reception so that the optical axis is shifted. For example, the means 19 is translated. Such a method may be used, and the angle between the irradiation center optical axis of the irradiation unit 18 and the light reception center optical axis of the light receiving unit 19 may be shifted.

  Further, regarding the positional relationship between the sheet-like object 17, the irradiation unit 18, and the light receiving unit 19, a difference in light transmittance, reflectance, refraction, and the like may be detected depending on the presence or absence of defects.

  In addition, in order to obtain a light amount distribution and / or some optical difference depending on the type of defect, optical auxiliary means such as a light shielding plate, a polarizing plate, and a wavelength selection filter may be used. Information may be used.

  In FIG. 3, it is arranged so as to receive the transmitted light from the irradiation means 18 through the sheet-like object 17, but as described above, it is arranged so as to receive the reflected light from the sheet-like object 17. You may do it. In the case of receiving reflected light, the robustness against bending, wrinkles, and fluttering of the sheet-like object 17 is generally reduced, but it may be easier to detect scratches with smaller scattered light. Moreover, if it is a colored film, the front and back of the film can be easily distinguished.

  Reference numeral 20 a denotes a defect detecting means, which is connected to the light receiving means 19. Information on the light received by the light receiving means 19 is photoelectrically converted and received by the defect detecting means 20a. A defect location is extracted by the defect detection means 20a, and the information (defect image) is transmitted to the period determination means 20b together with the defect occurrence position. The defect occurrence position in the sheet conveyance direction may be determined based on a signal from a length measuring encoder (not shown). The defect occurrence position in the sheet width direction may be determined based on which of the photoelectric conversion elements arranged in one direction of the light receiving means 19 is detected. The period determining unit 20b includes a defect feature amount range setting unit 20c and an allowable range setting unit 20d, and the period is determined based on information from the defect detecting unit 20a (defect image, defect occurrence position) and each process information. And the period determination result is transmitted to the external output means 21.

  The defect detection means 20a extracts defect points based on the received optical information. Various parameters used at this time may be a threshold value set for the signal value received from the light receiving means 19, or may be a signal / image processing filter for processing the received signal value, or may be processed. It may be a threshold value set for the signal value. These parameters may be optimized in advance during non-inspection, or may be sequentially optimized during inspection. Preferably, it is optimized beforehand. More preferably, the amount of data used for this optimization is large.

  The optimization of the parameter in the defect detection means 20a means that the defect location extracted by the parameter is the same as the location where the person has confirmed the defect image and determined as the defect location. Actually, it is difficult for the extracted defect part and the defect part determined by humans to coincide with each other. However, by performing such optimization, the accuracy of period determination described later is improved.

  In the period determining means 20b, information (defect image, defect occurrence position) from the defect detecting means 20a and each process information (roll diameter of the process, while utilizing the defect feature range setting means 20c and the allowable range setting means 20d. The period is determined based on the stretching ratio in the “stretching” step and the final thickness of the sheet-like object 17. The period determination in the period determination unit 20b will be described with reference to FIG. FIG. 1 is an explanatory diagram of a cycle determination flow according to the present invention.

  1 is a step of acquiring the draw ratio and the final thickness of the sheet-like object in the “stretching” step of the production process of the single-layer transparent polymer film by sequential biaxial stretching in this embodiment, and may not be acquired. good. Specifically, the stretching ratio in the sheet conveying direction in the “longitudinal stretching” process, the stretching ratio in the sheet width direction in the “lateral stretching” process, and the thickness of the sheet-like object in the “slit” process. In other processes, when finer stretching is performed, they may be additionally acquired.

  2 is a step of paying attention to one defect among the defects detected by the defect detection means 20a. In a step performed for all the defects that are not determined to be periodic defects, a defect feature amount of the focused defect is calculated. This defect feature amount is used for classification, and may be each value such as the length, width, and intensity of the defect obtained from the defect image received from the defect detection means 20a, or may be a weighted addition value thereof.

  A plurality of these defect feature quantities may be calculated. For example, a defect feature for determining whether or not it has occurred in the “cast” process, and a defect feature for determining whether or not it has occurred in the “vertical / preheating” process, for each process The defect feature amount may be calculated. Others, such as a defect feature for determining whether or not it is “vertical scratch” and a defect feature for determining whether or not it is “horizontal scratch”, calculate the defect feature for each scratch. Also good.

  Moreover, you may consider the draw ratio acquired at step 1, and the final thickness of a sheet-like object (when acquired). For example, when the stretching ratio in the sheet width direction in the “lateral stretching” process is 2 times or less, 4 times or more, and other times, each process of the “cast” process to the “longitudinal stretching” process The defect feature used to determine whether or not it has occurred may be changed, and if there is a weighted addition value related to the width of the defect without changing the defect feature itself, the weight is used as the stretch ratio. You may change with the curve according to. The draw ratio may be further finely divided. This is because the degree of deformation of the defects generated in the process before the “lateral stretching” process varies depending on the stretching ratio in the “lateral stretching” process. As long as the degree of deformation can be interpolated, stepwise interpolation as described above or continuous interpolation may be performed, or the defect feature amount itself corresponding to the axis of the space in clustering may be changed. The same applies to the case of based on the draw ratio in the sheet conveying direction in the “longitudinal drawing” step.

  In addition, depending on the final thickness of the sheet-like object, there may be a difference in the contact state between the roll used in each process and the sheet-like object, and it is necessary to change the defect feature amount of the defect generated in each process. It may occur. In this case, for example, when it is 100 μm or less, when it is 300 μm or more, or otherwise, the same interpolation may be performed as in the case of the draw ratio. Also at this time, stepwise interpolation or continuous interpolation may be performed, or the defect feature amount itself corresponding to the axis of space in clustering may be changed. These vary depending on the clustering technique performed in the next step.

  3 is a step of using the defect feature amount calculated in step 2 to estimate the occurrence point of the noted defect. For this, a general clustering technique may be used. Here, the Mahalanobis distance is used to estimate in which process the noted defect has occurred. The Mahalanobis distance is a widely used technique that classifies (discriminates) phenomena (here, defects) assumed to occur according to a normal distribution, and is a geometric space centered on defect feature quantities (generally multiple). It is characterized by dividing the distance at the standard deviation. Thereby, the classification considering the spread of the (normal) distribution becomes possible.

  For example, when determining whether or not it has occurred in the “longitudinal stretching” process, the Mahalanobis distance is calculated by using defect feature quantities (generally plural) suitable for determining whether the process is “longitudinal stretching” or other processes. Calculate (selection and calculation of defect feature quantity is performed in step 2). This will be described with reference to FIG. FIG. 10 is an explanatory diagram of classification according to the Mahalanobis distance of the present invention.

  At step 2, the defect feature A and defect feature B are calculated, and the center coordinates of the defect group determined by the “longitudinal stretching” process (by the human) (ie, defect feature A, defect) 141) (average value of each feature amount B). At this time, connecting points having the same Mahalanobis distance from the center coordinate 141 generally forms an ellipse, and can be drawn as 141a, 141b, 141c, and 141d. Here, 141a to 141d correspond to Mahalanobis distances of 0.5, 1.0, 1.5, and 2.0, respectively. The center coordinate of the defect group determined to have occurred (by a human) in a process other than the “longitudinal stretching” process is 142. Similarly, 142a, 142b, 142c, and 142d are obtained by connecting points corresponding to Mahalanobis distances from the center coordinate 142 corresponding to 0.5, 1.0, 1.5, and 2.0, respectively. At this time, if the target defect is located at a coordinate corresponding to 143, this target defect has a Mahalanobis distance of 1.5 from the center coordinate 141 of the “longitudinal stretching” process. It is determined that the smaller the Mahalanobis distance from the central coordinate 141, the higher the possibility that the defect of interest has occurred in the “longitudinal stretching” step.

  In FIG. 10, the process is divided into two processes other than the “longitudinal stretching” process and the “longitudinal stretching” process. This is for improving the accuracy of classification. For example, dividing the process into “longitudinal stretching” process, “conveyance” process, and other processes means that the central coordinates are increased by one in FIG. In general, as the number of types to be classified increases, classification becomes more difficult and accuracy decreases.

  Such calculation is performed in each process, and the process having the shortest Mahalanobis distance is estimated as the generation process. The average values of the defect feature amounts (center coordinates 141 and 142 in FIG. 10) necessary for calculating the Mahalanobis distance are obtained by collecting data in advance. At this time, there may be a plurality of generation processes as candidates, and in that case, the process proceeds to the following steps in the descending order of possibility. In the case of a plurality of steps, all the steps whose Mahalanobis distance is equal to or less than the set value may be candidates, or a plurality of Mahalanobis distances may be selected side by side from the smallest. In this case, the most likely process order is the order from the smallest Mahalanobis distance.

  4 is a step of setting the defect feature amount range and the sheet width direction allowable range, or the defect feature amount range, the sheet width direction allowable range, and the sheet conveyance direction allowable range in the generation process estimated in step 3.

  The defect feature amount range is set by the defect feature amount range setting means 20c, and may be a range setting method using a general clustering technique. Here, the Mahalanobis distance is used. For example, if the estimated generation process is the “longitudinal stretching” process, when determining whether the “longitudinal stretching” process is any other process, the range in which the Mahalanobis distance between the “longitudinal stretching” process is small becomes the defect feature amount range. . This will be described with reference to FIG. FIG. 11 is an explanatory diagram of classification according to the Mahalanobis distance of the present invention.

  Now, the center coordinates of the defect group generated in the “longitudinal stretching” step is 151, and the positions corresponding to the Mahalanobis distances 0.5, 1.0, 1.5, and 2.0 are 151a, 151b, 151c, 151d. Further, the center coordinates of the defect group generated in the processes other than the “longitudinal stretching” process are 152, and the positions corresponding to the Mahalanobis distances 0.5, 1.0, 1.5, and 2.0 are 152a and 152b. 152c and 152d. At this time, the boundary line for determining (classifying) whether or not it belongs to the “longitudinal stretching” step is 153, and the region closer to the central coordinate 151 than the boundary line 153 belongs to the “longitudinal stretching” step. It becomes the feature amount range. Specifically, a conditional expression that is closer to the center coordinate 151 than the boundary line 153 may be prepared, or the coordinate positions of the center coordinates 151 and 152 may be prepared. In the latter case, in step 5, the Mahalanobis distance is specifically calculated.

  Further, the allowable range in the sheet width direction and the allowable range in the sheet conveyance direction are set by the allowable range setting unit 20d, and are set in consideration of the estimated generation process. For example, if oscillation is performed, the allowable range in the sheet width direction differs greatly between the “cast” process and the “winding” process and the “slit” process. Specifically, the permissible range in the sheet width direction in the “slit” process may be set to several millimeters, but in other processes, it is necessary to set the value several times that in the “slit” process in consideration of oscillation. Come. More precisely, there may be differences from the “casting” process to the “longitudinal stretching” process and from the “conveying” process to the “winding” process (in some cases, it may be better to change due to stretching in the “lateral stretching” process). is there). The same applies to the allowable range in the sheet conveyance direction, and there may be differences between the “casting” process and the “longitudinal / stretching” process, and the subsequent processes (if it is better to change due to stretching in the “longitudinal stretching” process) There is also.)

  At this time, the draw ratio and the final thickness of the sheet-like object acquired in step 1 may be considered (when acquired). For example, when the draw ratio in the sheet width direction is 2 times and 5 times, the allowable range in the sheet width direction may be changed in each process. In addition, regarding the final thickness of the sheet-like object, the contact state between the roll and the sheet-like object varies depending on the thickness, and thus the allowable range in the sheet width direction may be changed. Generally, the sheet width direction allowable range is set to be larger when the final thickness of the sheet-like object is larger.

5 is a step of performing an actual cycle determination based on the information obtained up to step 4.
Defects in the sheet width direction allowable range set in step 4 are extracted, and defects within the defect feature amount range set in step 4 are selected, and the sheet conveyance direction allowable range set in step 4 is used. Determine the period. The period determination method may be a known method as described in FIG.

  At this time, it is preferable to calculate a high-accuracy “period” using the roll diameter in each process and the stretching ratio in the sheet conveyance direction acquired in step 1 and perform a period determination based on this. It is.

  6 is a step of determining whether or not the noticed defect is a periodic defect. If the defect is a periodic defect, the process proceeds to Step 8;

  7 is a step for determining whether Steps 4 and 5 have been performed in all the processes that can be estimated that the noted defect has occurred. Although it depends on how many candidate processes are set in step 3, it is preferably limited to three processes. More preferably, it is narrowed down within two steps.

8 is a step of determining whether Steps 2 to 5 have been performed for all the defects that are not regarded as periodic defects. If it is carried out, the period determination is completed, and if it is not carried out, the routine proceeds to step 9.
9 is a step for focusing on defects that have not been regarded as periodic defects so far, and starts from step 2 based on the newly focused defects.

  Reference numeral 21 denotes external output means, which is connected to the cycle determination means 20b. The information received from the period determining means 20b is output to the outside. The external output means 21 is represented by a display, a printer, an alarm device and the like.

  Now, the fact that the period can be accurately determined by the flow shown in FIG. 1 will be described below.

  First, as described above, there are many types of scratches. In other words, “longitudinal scratches” that are elongated in the sheet conveyance direction, “horizontal scratches” that are elongated in the sheet width direction, “diagonal scratches” that are elongated in the direction between the vertical and lateral scratches, film surface irregularities These are “uneven scratches” that occur up to the point, and “dot-like scratches” that are punctiform. However, for example, when a process in which vertical flaws occur is examined in detail, most of them occur in a certain process. As described above, when the process of generating each scratch is examined in detail, it has been found that the process of generating each scratch can be narrowed down.

  Therefore, the present inventor has paid attention to this fact, and as a result of diligent investigation, the clustering technique used for period determination does not classify all the flaws at the same time, but can classify only whether or not flaws may occur in each process. I found it sufficient. That is, it is only necessary to be able to classify a scratch that occurs in a specific process or a scratch that occurs outside the process. For example, it is to classify the scratches that occur in the “longitudinal stretching” process or the scratches that occur in other processes. In the classification based on Mahalanobis distance, which selected three from a plurality of defect feature quantities such as width, strength, and the like, the discriminant probability (= (number of correctly classified defects) / (total number of defects)) is 62% to 91%. Improved. For other processes, the discriminant probability is over 80%. This value of 62% is the discriminatory probability when all the scratches are classified at the same time.

  In addition, it is clear that setting for each process is also effective in the permissible range in the sheet width direction and the permissible range in the sheet conveyance direction in consideration of the “stretching” process and oscillation. In particular, the permissible range in the sheet width direction is not considered at all in the conventional method, and thus the present invention has been achieved.

  By using the periodic defect detection device described above, the sheet-like object to be conveyed is irradiated with light, reflected light or transmitted light through the sheet-like object is received, and the defect of the sheet-like object is determined based on the received light. In the periodic defect detection method for detecting and determining whether or not the defect is a periodic defect that occurs periodically, a defect feature amount range is set for each process of manufacturing a sheet-like object, and a sheet width direction allowable range for each process Alternatively, it is possible to set the sheet width direction allowable range and the sheet conveyance direction allowable range and perform the cycle determination.

  Further, it is possible to realize setting of the sheet width direction allowable range and the sheet conveying direction allowable range based on the stretching ratio in the “stretching” step of the process of manufacturing the sheet-like object. It is possible to realize a periodic defect detection method for setting a defect feature amount range based on the stretching ratio in the “stretching” step.

  In addition, it is possible to set the allowable range in the sheet width direction and the allowable range in the sheet conveyance direction based on the final thickness of the sheet-like object, and further, the periodic defect that sets the defect feature amount range based on the final thickness of the sheet-like object. A detection method can be realized.

  Further, by using the above-described periodic defect detection device, it is possible to realize a method for manufacturing a sheet-like object that performs periodic defect detection.

[Example 1]
After the molten polymer is discharged from the gap between the caps and formed into a sheet by a large drum (“cast” process), the “longitudinal stretching” process, the “lateral stretching” process, and the “conveying” process are followed by the “winding” process. To wind the film into a roll. A “slit” process was performed in which the wound roll was unwound while reciprocating in the sheet width direction, and wound while being cut to the customer's desired width. Thereafter, an off-line inspection using a periodic defect detection apparatus was performed using a roll cut to a desired width. The produced film is a single-layer transparent polymer film.

  Next, 7 types A to G were mainly designated as scratches and 8 steps were designated as processes, and it was set in which process each scratch could occur. There were 1 to 2 types of scratches that could occur in each process, and 1 to 3 types of processes that could generate each scratch.

  A 350 W metal halide light source / optical fiber bundle / rod illumination was used as the irradiation means 18, and the longitudinal direction of the rod illumination was tilted 20 degrees from the film width direction in a plane parallel to the film surface. When viewed from the sheet conveying direction, the left end is inclined downstream in the sheet conveying direction. The highly directional light emitted from the rod illumination is directed vertically upward and is adjusted to be substantially uniform in the longitudinal direction.

  As the light receiving means 19, a line sensor camera of 7500 pixels, 8-bit gradation, 40 Hz was used. The alignment direction of the photoelectric conversion elements substantially coincides with the longitudinal direction of the irradiating means 18, and the light receiving center optical axis is inclined 6.5 degrees from the vertically downward direction.

  The defect detection means 20a multiplies the signal obtained from the light receiving means 19 with a weighted average of 3 × 3 pixels, and then detects a spot that is equal to or greater than the threshold value for a bright spot. This threshold value is almost optimized in advance while looking at the defect image.

The period determination unit 20b performs period determination along the flow of FIG. 1, and a specific setting method is as follows.
(1) The draw ratio in the drawing process and the final thickness of the sheet-like object were obtained. And, the draw ratio in the sheet conveyance direction (stretch ratio in the “longitudinal stretching” step) is H times or less, or the draw ratio in the sheet width direction (stretch ratio in the “lateral stretching” step) is more than I times or less. Or, the final thickness of the sheet-like object is classified into eight cases of Jμm or less, selection of defect feature amount, defect feature amount range, sheet width direction tolerance range, sheet conveyance direction tolerance range in each process In each case, the settings were as follows. In this embodiment, the draw ratio in the sheet conveyance direction is less than H times, the draw ratio in the sheet width direction is less than I times, and the final thickness of the sheet-like object is J μm or more.
(2) The defect feature amount and the defect feature amount range are determined by calculating the Mahalanobis distance for each process. There are 10 types of defect feature quantities (defect length, width, strength, etc.) in total, and three defect feature quantities are selected from them so as to have the best discriminant probability. The defect feature amount range was also set based on these.
(3) The permissible range in the sheet width direction was set from the “cast” process to the “longitudinal stretching” process, from the “conveyance” process to the “winding” process, and the “slit” process. Since the oscillation was performed in the “slit” process, it was also taken into account. Specifically, Kmm in the “slit” process, K + from the “conveying” process to the “winding” process, and K + from the “casting” process to the “longitudinal stretching” process. (Amount in the sheet width direction to be moved by oscillation) + Lmm.
(4) The allowable range in the sheet conveying direction was set in each of the “casting” process to the “longitudinal / stretching” process and the subsequent processes. Specifically, a coefficient of (roll diameter) × (stretching ratio in the sheet conveying direction (stretching ratio in the “longitudinal stretching” step)) × (coefficient) was set for each.
(5) The cycle determination itself was performed according to FIGS.

When the above was performed on the defect group shown in FIG. 8, the period determination result of FIG. 4 was obtained. FIG. 4 is a period determination result in one embodiment of the present invention. The circle in FIG. 4 shows the defect occurrence position determined as a periodic defect, but only the actual periodic defect was successfully extracted, and a highly accurate periodic determination could be realized.
[Comparative Example 1]
Except for the following conditions, the cycle determination was performed on the defect group shown in FIG.
(1) The defect feature quantity and the defect feature quantity range are determined by calculating the Mahalanobis distance so as to discriminate all the defect types A to G. There are 10 types of defect features (defect length, width, strength, etc.), and 3 feature values are selected from them to have the best discriminative mid-rate. The defect feature amount range was also set based on these.
(2) The allowable range in the sheet width direction is the same as that from the “cast” process to the “longitudinal stretching” process in Example 1 throughout the entire process.
(3) The allowable range in the sheet conveying direction is the same as that from the “cast” process to the “longitudinal stretching” process in Example 1 over the entire process.
As a result, the period determination result of FIG. 9 was obtained. Compared to FIG. 4, it can be seen that defects other than the periodic defects are also determined for the period.

  The present invention can be applied not only to period determination but also to secondary processing of data, but the application range is not limited to these.

1 1 step in period determination of the present invention 2 1 step in period determination of the present invention 3 1 step in period determination of the present invention 4 1 step in period determination of the present invention 5 1 step in period determination of the present invention 6 period of the present invention 1 step in determination 7 1 step in period determination of the present invention 8 1 step in period determination of the present invention 9 1 step in period determination of the present invention 10 Base 11 “Casting” process 12 “Longitudinal stretching” process 13 “Transverse stretching” process 14 “Conveyance” process 15 “Winding” process 16 “Slit” process 17 Sheet-like object 18 Irradiating means 19 Light receiving means 20 a Defect detecting means 20 b Period determining means 20 c Defect feature amount range setting means 20 d Allowable range setting means 21 External output means 101 Defect 102 Defect 103 Defect 104 Defect 1 5 Defects 106 Allowable range of sheet width 107 Distance in sheet conveyance direction 108 Allowable range of sheet conveyance direction 111 Defects 112 Defects 113 Defects 114 Defects 115 Allowable range of sheet width direction 116 Distance in sheet conveyance direction 117 Acceptable range of sheet conveyance direction 121 Period determination of conventional technology 1 step 122 in the prior art period determination 123 1 step in the prior art period determination 131 Arrow indicating the position where the periodic defect exists 141 Center coordinates of the defect group 141a Position of the same Mahalanobis distance 141b Position of the same Mahalanobis distance 141c Position of the same Mahalanobis distance 141d Position of the same Mahalanobis distance 142 Center coordinates of the defect group 142a Position of the same Mahalanobis distance 142b Position of the same Mahalanobis distance 142c Position of the same Mahalanobis Position of the distance 142d position of the same Mahalanobis distance 143 coordinate position of the defect of interest 151 central coordinates of the defect group 151a position of the same Mahalanobis distance 151b position of the same Mahalanobis distance 151c position of the same Mahalanobis distance 151d position of the same Mahalanobis distance 152 of the defect group Central coordinates 152a Position of the same Mahalanobis distance 152b Position of the same Mahalanobis distance 152c Position of the same Mahalanobis distance 152d Position of the same Mahalanobis distance 153 Boundary line

Claims (11)

The sheet-like object to be conveyed is irradiated with light, the reflected light or the transmitted light through the sheet-like object is received, the defect of the sheet-like object is detected based on the received light, and the defect is periodically In the periodic defect detection method for determining whether or not the periodic defect occurs,
(1) A defect feature amount range is set for each step of manufacturing the sheet-like object,
(2) A periodic defect detection method, wherein a period is determined by setting a sheet width direction allowable range or a sheet width direction allowable range and a sheet conveyance direction allowable range for each of the steps.   The periodic defect detection method according to claim 1, wherein the sheet width direction allowable range and the sheet conveyance direction allowable range are set based on a stretching ratio in a stretching step of the step of manufacturing the sheet-like object.   The periodic defect detection method according to claim 1, wherein the defect feature amount range is set based on a stretching ratio in a stretching process of the process of manufacturing the sheet-like object.   The periodic defect detection method according to claim 1, wherein the sheet width direction allowable range and the sheet conveyance direction allowable range are set based on a final thickness of the sheet-like object.   The periodic defect detection method according to claim 1, wherein the defect feature amount range is set based on a final thickness of the sheet-like object. Irradiation means for irradiating a sheet-like object to be conveyed, light-receiving means for receiving reflected or transmitted light through the sheet-like object, and a defect for detecting a defect of the sheet-like object based on the received light In the periodic defect detection device having detection means and period determination means for determining whether the defect is a periodic defect that occurs periodically, the period determination means includes:
(1) Defect feature amount range setting means for setting a defect feature amount range for each step of manufacturing the sheet-like object;
(2) An apparatus for detecting a periodic defect having a sheet width direction allowable range or a sheet width direction allowable range and a sheet conveyance direction allowable range for each step.   The permissible range setting means sets the permissible range in the sheet width direction and the permissible range in the sheet conveyance direction based on a stretching ratio in a stretching step of the step of manufacturing the sheet-like object. 6. The periodic defect detection device according to 6.   The period according to claim 6 or 7, wherein the defect feature amount range setting means sets the defect feature amount based on a stretching ratio in a stretching step of the step of manufacturing the sheet-like object. Defect detection device.   7. The periodic defect detection according to claim 6, wherein the allowable range setting means sets the allowable range in the sheet width direction and the allowable range in the sheet conveyance direction based on a final thickness of the sheet-like object. apparatus.   The periodic defect detection device according to claim 6, wherein the allowable range setting unit sets the defect feature amount range based on a final thickness of the sheet-like object.   A method for manufacturing a sheet-like object, wherein a defect is detected using the periodic defect detection method according to claim 1.