JP3890430B2 - Surface inspection method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface inspection method and apparatus for detecting defects existing on the surface and inside of a web, and in particular, by applying a two-dimensional tension to a web to be inspected to improve its planarity. The present invention relates to a surface inspection method and apparatus capable of performing inspection.
[0002]
[Prior art]
Plastic films such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), and polyethylene naphthalate (PEN) are used for the support for photographic films and the polarizing plate members for liquid crystal panels. In a photographic film, if there is a defect on the surface or inside of the support, a defect image is produced when the photographic paper is exposed and developed. In the liquid crystal panel, the alignment of the liquid crystal is disturbed by a defect of the polarizing plate member, and a visual defect occurs. Therefore, it is desired to supply a plastic film with few defects. In particular, a plastic film used for a liquid crystal panel is desired to have no defect of 30 μm or more.
[0003]
In order to reduce defects in the plastic film, it is necessary to carry out a high-precision defect inspection on the manufactured plastic film. In this inspection, an inspection sheet is prepared from a wide plastic film web immediately after manufacture, and the inspection sheet is inspected by visual inspection by an inspector, observation by a polarizing microscope, or the like.
[0004]
[Problems to be solved by the invention]
However, visual inspection by an inspector makes it difficult to identify defects with a size of about 50 μm or less, and furthermore, the inspection accuracy varies depending on the level of skill in the work and the state at the time of work, which is a problem in terms of quality control. was there. In addition, the inspection using the polarizing microscope can find even minute defects that cannot be found by visual inspection, but there is a problem that the inspection takes an enormous amount of time.
[0005]
Furthermore, when cutting the inspection sheet from the web or setting the inspection sheet on a polarizing microscope, foreign matter such as dust or dirt may adhere to the inspection sheet, and the foreign matter is not as manufactured. It was not possible to distinguish whether it was attached after manufacturing, and there was a fatal problem in the accuracy of the inspection.
[0006]
In order to solve the above problem, the web roll is unwound from a web roll manufactured in a clean environment, and the web is continuously transported. The continuous transported web is irradiated with laser light, and the laser light irregularly reflected by scratches and dust is received. There is a surface inspection device (for example, Japanese Patent No. 2684460) that is designed to detect with a detector. However, in this surface inspection apparatus, since the detection accuracy of the light receiver is not so good, it is impossible to detect a defect of about 200 μm or less, and the inspection light is incident from a certain direction. There are defects that do not reflect irregularly, and undetected defects may occur.
[0007]
In particular, when the object to be inspected is a thin flexible material such as a film or a magnetic sheet, it is not easy to keep these surface properties very uniform. For this reason, particularly when detecting defects with reflected light, if the object to be inspected has undulations or tilts, the reflected light from non-defective parts and defective parts will not be correctly incident on the light receiving part, and the detection accuracy will deteriorate. It was.
[0008]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a surface inspection method and apparatus capable of reducing time for high-precision defect inspection and improving inspection accuracy.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the surface inspection method according to the present invention unwinds and intermittently conveys a web wound in a roll shape, and when the web conveyance is stopped, the web conveyance direction and The surface of the web is scanned by moving the photoelectric element while acting at least twice as much as the 5 kg / m value normally applied when the web is conveyed in the manufacturing process in both directions perpendicular to this. In addition, the defect and the position of the defect are detected. In the surface inspection method according to the present invention, the photoelectric element is scanned at least twice on the same part of the web, the position of the defect is detected by the first scan, and the defect state is identified by the second scan. It is characterized by doing so.
[0010]
On the other hand, the surface inspection apparatus according to the present invention is a web conveyance unit that pulls out a web wound in a roll shape and intermittently conveys the web, and the web normally produces tension in a direction perpendicular to the conveyance direction when the web is stopped. The tension acting member that acts at least twice the value of 5 kg / m when transported in the process, the light projecting unit that irradiates the web with inspection light, and the photoelectric element that receives irregularly reflected light from the web are transported. And a scanning mechanism that scans the surface of the web by moving it in a direction perpendicular to the direction to detect the defect and the position of the defect.
[0011]
The surface inspection apparatus according to the present invention is characterized in that a line CCD is used as the photoelectric element, and the longitudinal direction of the line CCD is arranged along the web conveyance direction. Further, the same part of the web is scanned at least twice by the photoelectric element, the position of the defect is detected by the first scanning, and the form of the defect is imaged by the second scanning. To do.
[0012]
In the surface inspection apparatus according to the present invention, at least one ring lamp disposed in the light projecting portion so as to surround the outer periphery of the scanning position of the light receiving element, preferably a cylinder having a certain length in the vertical direction. A ring-shaped lamp is used and is moved by a scanning mechanism together with a light receiving element.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing a configuration of a surface inspection apparatus according to an embodiment of the present invention. This surface inspection apparatus winds up a web supply unit 4 in which a web roll 3 on which a web 2 of a plastic film is wound is set, an inspection unit 5 that inspects the web 2, and the web 2 after the inspection. The web collection part 6 is comprised.
[0014]
The web 2 is, for example, a plastic film used as a support for a magnetic tape, and is in a wide state before being cut into the width of the magnetic tape. Further, the web 2 may be wound in a roll shape with the laminated films 7 and 8 overlapped on both sides so that dust, dust, scratches and the like are not attached. In that case, it is necessary for the web supply unit 4 to peel off and roll up the laminate films 7 and 8 of the web 2 that has been rewound from the web roll 3. It is arranged above and below.
[0015]
The web 2 unwound from the web roll 3 is wound around the collection roller 12 of the web collection unit 6 through the inspection unit 5. The collection roller 12 is intermittently rotated in a direction of winding the web 2 by a motor (not shown). Thereby, the web 2 of the web supply unit 4 is intermittently conveyed to the inspection unit 5. Between the web supply unit 4 and the inspection unit 5, there is disposed a static elimination blower 13 that removes static electricity from the web 2 and blows off adhering dust and dirt.
[0016]
In the inspection unit 5, a pair of rollers 15 and 16 are disposed as tension acting members that impart flatness to the web 2. The light projecting unit 17 that irradiates the web 2 with inspection light, the imaging unit 18 including a photoelectric element, and the light projecting unit 17 and the imaging unit 18 face the web 2 with the flatness. And a scanning drive unit 19 that is moved in a direction perpendicular to the conveying direction.
[0017]
As the above-mentioned rollers 15 and 16, in order to prevent the movement of the web 2 to be conveyed in the width direction, a roller having a high surface static friction coefficient, for example, a mirror surface having a surface roughness of 0.4 S or less. Those having a synthetic rubber layer (for example, NBR85) are preferable. Further, the web 2 is conveyed with a predetermined tension in the conveying direction, for example, a tension of about 10 kg / m to 60 kg / m. The static friction coefficients of the rollers 15 and 16 are necessary to prevent the web 2 from contracting in a direction perpendicular to the conveying direction when the web 2 is subjected to the tension in the above range.
[0018]
More specifically, the tension applied in the conveyance direction of the web 2 described above is at least twice as large as about 5 kg / m applied during normal production. For this reason, as shown in the theory by so-called Poisson's ratio, The amount of the web 2 to shrink in the width direction is larger than the amount in the normal manufacturing process. However, the rollers 15 and 16 having a high coefficient of static friction on the surface prevent the web 2 from contracting in the width direction by preventing the web 2 from contracting in the width direction, and are positioned between the rollers 15 and 16. A predetermined tension can be applied to the web 2 in both the transport direction and the direction orthogonal to the transport direction. By using such rollers 15 and 16, the flatness of the part to be inspected becomes extremely uniform, and defect inspection can be performed easily and with high accuracy.
[0019]
As shown in FIGS. 2 and 3, the imaging unit 18 includes a high-resolution line CCD 21 that is a photoelectric element, an imaging lens 22 that forms an image of the light reflected on the surface of the web 2 on the line CCD 21, and these And a housing 23 in which is incorporated. The line CCD 21 is arranged such that the longitudinal direction is along the conveyance direction of the web 2.
[0020]
The light projecting unit 17 is disposed between a cylindrical case 25, a plurality of ring-shaped lamps 26a, 26b, 26c, and 26d housed in the case 25, and the ring-shaped lamps 26a to 26d. It comprises a plurality of reflectors 27a, 27b, 27c that irradiate the light emitted from 26a-26d toward the surface of the web 2. As the ring-shaped lamps 26a to 26d, for example, a ring-shaped fluorescent lamp, an EL light emitting element, or the like is used.
[0021]
The light projecting unit 17 is disposed below the imaging unit 18 so as to surround the imaging position of the web 2 by the imaging unit 18. Thereby, the inspection light can be incident on the imaging position of the imaging unit 18 from the outer periphery at various angles, and the inspection light can be irregularly reflected by scratches, dust, dust, and the like having various reflectances and directivities, The inspection accuracy of the surface inspection apparatus can be improved. A black support plate 29 is disposed below the web 2 in order to increase detection efficiency.
[0022]
The light projecting unit 17 and the imaging unit 18 are held by a substantially T-shaped support stay 31. The support stay 31 is incorporated in a scanning drive unit arranged along the width direction of the web 2, and is reciprocated in the width direction of the web 2 by the scan drive unit. The light projecting unit 17 illuminates the surface of the web 2 while moving in the width direction of the web 2, and the imaging unit 18 moves the surface of the web 2 illuminated by the light projecting unit 17 while moving together with the light projecting unit 17. Take an image.
[0023]
There are various types of defects in the web 2, and the ring-shaped lamps 26a to 26d have the widest application range. However, as shown in FIG. 4, defect inspection is possible even with inspection light from the backlight 50 disposed so as to sandwich the web 2 so as to face the imaging unit 18, and opaque foreign matters and strong scratches are effective. Can be detected.
[0024]
The scanning drive unit incorporates a scanning mechanism that moves the imaging unit 18 and the light projecting unit 17. Although not shown in detail as the scanning mechanism, the scanning mechanism includes a pulley disposed along the width direction of the web 2 and a belt to which the support stay 31 is attached. The pulley is rotated by a motor. The support stay 31 is moved by the movement of the belt at the time. The scanning mechanism is not limited to pulleys and belts, and sprockets and chains, solenoids and springs, cam mechanisms, air cylinders, hydraulic cylinders, ball screws and ball nuts, and the like can be used.
[0025]
As shown in FIG. 1, the surface inspection apparatus is controlled by a computer 33. The computer 33 stores a control program for controlling the surface inspection apparatus and inspection conditions such as a threshold level at the time of inspection, and the surface inspection apparatus is controlled according to these.
[0026]
The imaging unit 18 scans the same part of the web 2 twice, detects the position of the defect on the web 2 by the first scan, and images the state of each defect by the second scan. The defect position data and defect image data imaged by the imaging unit 18 are input to the computer 33 and stored in a storage device such as a memory. The stored data can be observed by a monitor 35 connected to the computer 33, and can be printed out by a printer 36 connected to the computer 33 and used for various studies. In this way, inspection speed can be dramatically increased by performing defect position recognition and defect shape imaging during separate scans, and when performing defect position recognition and defect shape imaging in a single scan In comparison with this, the inspection time can be shortened by about 10 times.
[0027]
Between the inspection unit 5 and the web collection unit 6, a marking device 38 that performs marking at the position of the defect detected by the inspection unit 5 is disposed. Although not shown in detail, the marking device 38 includes a printer head that performs marking on the web 2 and a moving mechanism that moves the printer head in the width direction of the web 2. The marking device 38 stores defect position data stored in the computer 33. Based on this, the moving mechanism moves the printer head and performs marking on the surface of the web 2 at a predetermined position.
[0028]
As a mark to be marked by the marking device 38, for example, as shown in FIG. 5, it is effective to change the mark shape according to the size of the defect. Here, the pentagonal mark 40 shown in FIG. 5A is used for a large defect, the square mark 41 shown in FIG. 5B is used for a medium-sized defect, and the small mark shown in FIG. A circular mark 42 is used. Thereby, the size and distribution of defects can be easily checked after inspection. As the printer head, for example, an ink jet type printer head, a thermal transfer type printer head using an ink ribbon, a back ink supply type stamp, or the like can be used.
[0029]
Next, the operation of the surface inspection apparatus of the above embodiment will be described with reference to the flowchart shown in FIG.
As shown in FIG. 1, the web 2 of a plastic film is set in the web supply part 5 of a surface inspection apparatus with the form of the web roll 3 wound by roll shape. After the web 2 is unwound from the web roll 3 set in the web supply unit 5 and the laminate films 7 and 8 sandwiching both sides are peeled off, the collection roller of the web collection unit 6 passes through the inspection unit 5. 12 is locked. Laminate films 7 and 8 are locked to peeling rollers 9 and 10, respectively. Thus, since the web roll 3 can be set directly on the inspection device and inspected, the accuracy of the inspection is improved as compared with the conventional case where the inspection sheet is created.
[0030]
After setting the web 2 on the surface inspection apparatus, the computer 33 is operated to make various settings. The setting here includes the material to be inspected, the thickness of the web 2, the inspection area, the threshold level relating to the size and state of the defect, and the implementation / non-execution of the marking.
[0031]
When the inspection is started after the setting is completed, a motor (not shown) intermittently rotates the collecting roller 12 in the web winding direction, and the web 2 is pulled out from the web supply unit 4 and intermittently conveyed to the inspection unit 5. At this time, the web 2 is tensioned in both the conveying direction and the direction orthogonal thereto by the action of the rollers 15 and 16 as described above, and extremely good flatness is obtained. Further, as shown in FIGS. 2 and 3, the ring-shaped lamps 26 a to 26 d are turned on in the light projecting unit 17. When the conveyance of the web 2 is stopped, the scanning drive unit 19 is operated, and the light projecting unit 17 and the imaging unit 18 held by the support stay 31 are moved at a constant speed along the width direction of the web 2. At that time, the line CCD 21 is driven in the imaging unit 18 and images the surface of the web 2 illuminated by the light projecting unit 17.
[0032]
When the light projecting unit 17 is formed of ring-shaped lamps 26a to 26d, the ring-shaped lamps 26a to 26d of the light projecting unit 17 are stacked in the vertical direction and reflected by the reflecting plates 27a to 27c. The inspection light thus made is incident on the surface of the web 2 at various angles. Therefore, the inspection light can be irregularly reflected by the defects of the web 2 with high accuracy regardless of the reflectivity and directivity of the defects existing on the surface and inside of the web 2.
[0033]
Further, since the irregularly reflected light is detected by the high-resolution line CCD 21, it is possible to detect a defect with higher accuracy than an inspection apparatus using a conventional light receiver. At the time of inspection scanning, which is the first scan, the position of a defect on the web 2 is detected, and defect position data obtained by inspection scanning is input to the computer 33 and stored in a recording device.
[0034]
In the case of inspection scanning, if a defect of a level higher than a preset level is not found, the web 2 is intermittently conveyed again, and inspection scanning is performed on a new portion of the web 2. In addition, when a defect having a size larger than a preset size is found by inspection scanning, confirmation scanning is performed when returning the light projecting unit 17 and the imaging unit 18 to the initial positions. In this confirmation scanning, each detected defect is imaged. This defect image data is also input and recorded in the computer 33.
[0035]
The defect image can be observed on the monitor 35 in real time in addition to later observation on the monitor 35 or printing out by the printer 36. At this time, if the defect can be removed immediately such as dust or dust and has little adverse effect, the computer 33 can be operated to exclude the defect from the defect position data and the defect image data.
[0036]
If a line CCD having the same length as the width direction of the web 2 is used, the inspection time can be further shortened, but the cost of the surface inspection apparatus is significantly increased. Therefore, in the present invention, the web 2 is scanned in the width direction with a short line CCD in order to balance cost and function.
[0037]
When there is a defect in the web 2, after the intermittent conveyance of the web 2, the marking device 38 marks the position of the defect in the web 2 based on the defect position data recorded in the computer 33. This marking is changed as indicated by reference numerals 40 to 41 in FIGS. 5A to 5C in accordance with the size of the defect. Thereby, the defect distribution situation can be easily examined by directly observing the web 2.
[0038]
The above-described inspection scanning, confirmation scanning, and marking are repeated until the inspection of the preset specified area is completed. When the inspection of the specified area is completed, the inspection result can be displayed on the monitor 35 and observed, or printed out by the printer 36 and used for various studies.
[0039]
【Example】
The surface inspection apparatus according to the above-described embodiment was manufactured using rollers 15 and 16 having a surface roughness of 0.4 S or less and an interval of 300 mm. As an inspection object, a magnetic tape 2 having a width L shown in FIG. 2 of 1000 mm, a PET support having a thickness of 10 μm, and a magnetic layer thickness of 3 μm was used. The surface inspection was performed with the scanning width L1 of the line CCD 21 being 50 mm and the resolution of the line CCD 21 being 5000. The magnetic tape 2 was given tensions of 13 kg / m and 30 kg / m in the transport direction.
[0040]
According to the above setting, in any case, since the shrinkage in the width direction is suppressed by the rollers 15 and 16, the flatness of the part to be inspected becomes extremely good, and a defect having a size of 20 μm can be detected at the minimum. Even if the light projecting unit 17 and the imaging unit 18 were moved at a speed, it took only 5 minutes to inspect the web 2 having an area of 1 m ² . Moreover, the marking was 5 seconds / piece on average. Therefore, it is possible to greatly shorten the web inspection time while improving the inspection accuracy.
[0041]
In the above embodiment, the inspection of the magnetic tape web has been described as an example. However, the surface inspection method and inspection apparatus of the present invention can be used for inspection of various transparent or opaque webs. In addition, here, one image pickup unit and one light projecting unit are used, but two or more of these may be provided to improve inspection accuracy. When two or more imaging units and light projecting units are used, one may be used separately for inspection scanning and the other for confirmation scanning.
[0042]
In the above-described embodiment, an example in which the rollers 15 and 16 have a surface roughness of 0.4 S or less is shown. However, the hardness, surface roughness, and the like are the types of the web 2 to be inspected Needless to say, it may be determined as appropriate according to the thickness and the like.
[0043]
【The invention's effect】
As described above, according to the present invention, good flatness of the part to be inspected of the web is ensured, and the inspection time can be greatly shortened while improving the inspection accuracy of the web defect, It is possible to realize a surface inspection method and apparatus that greatly contributes to improving the quality of products such as magnetic tape and photographic film using this web and improving the production efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of a surface inspection apparatus according to the present invention.
FIG. 2 is a perspective view showing a configuration of an inspection unit.
FIG. 3 is a cross-sectional view of main parts of an imaging unit and a light projecting unit.
FIG. 4 is a cross-sectional view showing the main parts of another imaging unit and a light projecting unit.
FIG. 5 is an explanatory diagram showing an example of marks to be marked.
FIG. 6 is a flowchart showing an operation sequence of the surface inspection apparatus.
[Explanation of symbols]
2 Web 3 Web roll 4 Web supply unit 5 Inspection unit 6 Web collection unit 15, 16 Roller 17 Light projection unit 18 Imaging unit 19 Scanning drive unit 21 Line CCD
26a-26d Ring-shaped lamp

Claims (7)

In a surface inspection method of irradiating a web with inspection light and detecting light irregularly reflected by defects existing on the surface and inside of the web by a photoelectric element, the web wound in a roll shape is unwound and intermittently conveyed, when the conveyance is stopped or while working at least twice such 5 kg / m in the normal the web the tension in both the conveying direction and the direction perpendicular thereto is conveyed in the manufacturing process, the A surface inspection method characterized by detecting a defect and a position of the defect by moving the photoelectric element to scan the surface of the web. 2. The same part of the web is scanned at least twice by the photoelectric element, the position of the defect is detected by the first scanning, and the state of the defect is identified by the second scanning. The surface inspection method as described. In a surface inspection apparatus that includes a light projecting unit that irradiates a web with inspection light, and a photoelectric element that detects light irregularly reflected by defects on the surface and inside of the web, the web wound in a roll shape is wound. A web conveyance section that returns and intermittently conveys, and a tension that causes the tension to act at least twice as much as 5 kg / m that is normally applied when the web is conveyed in the manufacturing process in a direction perpendicular to the conveyance direction when the web is stopped. A surface inspection apparatus comprising: an action member; and a scanning mechanism that scans the surface of the web by moving the photoelectric element in a direction orthogonal to the conveyance direction, and detects a defect and a position of the defect. .  The surface inspection apparatus according to claim 3, wherein a line CCD is used as the photoelectric element, and the longitudinal direction of the line CCD is arranged along the conveyance direction of the web.  5. The same part of the web is scanned at least twice by the line CCD, the position of the defect is detected by the first scanning, and the form of the defect is imaged by the second scanning. The surface inspection apparatus described in 1. Claim wherein the light projecting unit, which comprises at least one ring-shaped lamp is disposed so as to surround the outer periphery of the scanning position of the photoelectric element, characterized by being configured to move by with the scanning mechanism the photoelectric elements The surface inspection apparatus according to any one of 3 to 5.  The surface inspection apparatus according to claim 6, wherein the ring lamp is a cylindrical ring lamp having a certain length in a vertical direction.

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