JP6435229B2 - Resin film roll for food packaging, inspection method and apparatus, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a transparent food packaging resin film roll made of polyvinyl chloride, an inspection method and apparatus, and a manufacturing method thereof.

  Conventionally, a flexible and transparent resin film made of polyvinyl chloride or the like has been provided for packaging food. Such a resin film is provided as a wound product wound around a winding core having a predetermined diameter, such as paper, with a predetermined winding length (hereinafter referred to as a resin film wound product for food packaging). . This wound product is further distributed and stored in a paper box or the like.

  In the production of a resin film wound product for food packaging, the resin film cannot be wound sufficiently evenly around the core, and wrinkles may occur inside the wound resin film. When wrinkles are generated inside the wound resin film, light is reflected by the air in the gaps of the wrinkles, which may impair the aesthetic appearance of the originally wrapped resin film for food packaging. Furthermore, depending on the degree of wrinkles, adhesiveness, which is an important characteristic as a resin film for food packaging, may not be sufficiently developed.

  Various techniques are provided for inspecting wrinkles generated on a rolled resin film for food packaging. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for capturing diffused light caused by wrinkles with a line sensor and detecting wrinkles by image processing. Patent Documents 2 and 3 below disclose a technique for capturing wrinkles reflected by a line sensor and detecting wrinkles by image processing. Patent Document 4 below discloses a technique for applying a threshold to pixels of an image captured by a line sensor.

Japanese Patent Laid-Open No. 9-133638 JP 2001-41726 A JP 2001-41727 A JP 2012-251983 A

  However, the technique for inspecting wrinkles of a resin film roll for food packaging requires a complicated algorithm for image processing detected by a line sensor. For this reason, a complicated process is required to determine whether or not the wrinkles of the food packaging resin film roll are within an allowable range, and the apparatus for performing the process is also complicated and expensive.

  The present invention is proposed in view of the above-described circumstances, and is a food packaging resin film that can easily determine whether or not the wrinkles of the food packaging resin film roll are within an allowable range. It is an object to provide a wound product, an inspection method and apparatus thereof, and a manufacturing method.

In order to solve the above-mentioned problems, an inspection method according to the present invention is an inspection method for a food packaging resin film roll, and provides a food packaging resin film roll serving as a subject; and According to the L ^* a ^* b ^* color system, the step of measuring the lightness L ^* , chromaticity a ^* and b ^* of the subject, and providing the chroma C ^* based on the chromaticity a ^* and b ^* And a step of discriminating the subject as passing if the saturation C ^* exceeds a predetermined threshold, and discriminating that the subject fails otherwise.

The saturation C ^* is the chromaticity a ^* and b ^* .

により与えられる。前記彩度Ｃ^＊の所定の閾値は、６．１から８．１までの範囲にあってもよい。

Given by. The predetermined threshold value of the saturation C ^* may be in a range from 6.1 to 8.1.

If the lightness L ^* does not reach a predetermined threshold value, the object further includes a step of determining that the subject is acceptable, and otherwise, determining that the object is unacceptable, and this step is determined to be acceptable based on the saturation C ^*. It may be determined whether the subject is passed or not based on the lightness L ^* . The predetermined threshold value of the saturation L ^* may be in a range from 76 to 77.5.

  The measuring step may be performed by a diffuse illumination vertical light receiving method including specularly reflected light. The rolled resin film for food packaging may include at least one of polyvinyl chloride, polyvinylidene chloride, and polyethylene.

  The resin film roll for food packaging may be a roll of a film having a thickness of 1 to 20 μm. The winding length of the food packaging resin film roll may be in the range of 50 to 110 m. The resin film roll for food packaging may have an average degree of polymerization of 750 or more and less than 1750.

  The food packaging resin film roll according to the present invention is an object that has been determined to be acceptable by the inspection method.

  The manufacturing method which concerns on this invention is a manufacturing method of the resin film roll for food packaging, Comprising: The step which test | inspects the manufactured resin film roll for food using the said inspection method is included.

The inspection apparatus according to the present invention is an inspection apparatus for a food packaging resin film roll, and is irradiated with light from a light source that irradiates a subject of the food packaging resin film roll and light from the light source. A measuring unit for measuring the lightness L ^* , chromaticity a ^* and b ^* of the subject in accordance with the L ^* a ^* b ^* color system from the return light from the subject, and the color measured by the measuring unit A control unit that provides a saturation C ^* based on the degrees a ^* and b ^* , and determines that the subject is acceptable if the saturation C ^* exceeds a predetermined threshold; Is included.

The control unit further determines the lightness L ^* for the subject determined to be acceptable based on the saturation C ^* , and determines that the subject is acceptable if the lightness L ^* does not reach a predetermined threshold value. Otherwise, it may be determined as not acceptable.

  According to the present invention, it is possible to easily determine whether or not the wrinkles of the food packaging resin film roll are within an allowable range. As a result, the manufacturing process can be simplified, the manufacturing cost can be reduced, and the quality can be improved.

It is a block diagram which shows the schematic structure of an inspection apparatus. It is a top view which shows an example of a structure of a measurement part roughly. It is a flowchart which shows a series of processes of a 1st test | inspection method. It is a flowchart which shows a series of processes of the 2nd inspection method. 3 is a color tone diagram of Example 1. FIG. 6 is a color tone diagram of Example 2. FIG.

  Hereinafter, embodiments of a resin film wound product for food packaging, an inspection method and apparatus, and a manufacturing method according to this embodiment will be described in detail with reference to the drawings.

  In this embodiment, the resin film roll for food packaging is assumed to have a thickness of 6 to 7 μm and a winding length of 100 m produced using polyvinyl chloride as a material. The average degree of polymerization of polyvinyl chloride is assumed to be 750 or more and less than 1750.

  The degree of polymerization is in the above range because if the molecular weight is too large, the fluidity is poor and the additive mixing and film formation method is limited, and if it is too small, it is brittle and the gas permeation amount becomes large. This is because they are not satisfied.

  Additives such as stabilizers and antifogging agents are added to the polyvinyl chloride used in the resin film rolls for food packaging. Resin film rolls for food packaging may be colored, but this is highly effective when additives such as zinc / calcium soap and tetrahydric or higher alcohol are used in combination as a stabilizer for the resin.

  In addition, the material of the resin film roll for food packaging is not limited to polyvinyl chloride, and may be polyvinylidene chloride, polyethylene, or the like. Moreover, the thickness of the film winding for food packaging is not restricted to 6-7 micrometers, What is necessary is just 1-20 micrometers, Preferably it is 5-10 micrometers. The winding length is not limited to 100 m, and may be in the range of 20 to 200 m, and preferably in the range of 50 to 110 m.

  FIG. 1 is a block diagram showing a schematic configuration of an inspection apparatus 10 for inspecting such a food packaging film roll. This inspection apparatus 10 determines whether or not the wrinkles of the food packaging resin film roll are within an allowable range using color analysis.

The inspection apparatus 10 includes a measurement unit 11 that measures lightness L ^* , chromaticity a ^* , and b ^* using a food resin film roll as an object according to the L ^* a ^* b ^* color system. The measurement unit 11 performs measurement by the SCI method including regular reflection light from the subject. The measurement unit 11 includes a light source that irradiates a subject with predetermined light, a lens that collects return light from the subject, a filter having a predetermined wavelength characteristic, and a photodetector that detects light transmitted through the filter. May contain. Note that the chromaticities a ^* and b ^* are sometimes referred to as chromaticity index chromaticities a ^* and b ^* .

  The inspection apparatus 10 includes a holding unit 12 that takes out one sample as a subject in order from a plurality of resin film rolls for food to be inspected, and fixes and holds the measurement unit 11 so that it can be measured. . For example, the holding unit 12 replaces and holds the food resin film roll in order at a predetermined time period required for the measurement of the subject.

  The inspection apparatus 10 includes a control unit 13 that controls the entire inspection apparatus 10 and determines whether or not the wrinkles of the food packaging resin film roll of the subject are within an allowable range. The control unit 13 executes a series of procedures of a predetermined inspection method in accordance with a program stored in the storage 14 provided in the inspection apparatus 10, and stores the result of the determination of the wound food packaging resin film roll of the subject. To store.

  In the inspection apparatus 10 of this embodiment, for example, a commercially available color measurement apparatus is applied to the measurement unit 11, and an appropriate mechanism such as a mounting table including a desk is used as the holding unit 12, and the control unit 13 and the storage 14 are personalized. It can be configured using a computer. In addition, the holding | maintenance part 12 may be abbreviate | omitted and you may provide the measurement part 11 with the resin film winding material for food packaging of a test object manually.

  FIG. 2 is a top view schematically showing an example of the configuration of the measurement unit 11. In the drawing, the resin film 101 wound around the winding core 102 is placed by a holding part 12 (not shown) so that the longitudinal direction of the food packaging resin film roll 100 is substantially horizontal.

In this example, the measurement unit 11 has in its longitudinal direction on the upper side of the food packaging resin film wound material 100 a plurality of detectors 21 ₁ to 21 _7, which are arranged at predetermined intervals. Also it has a line 11 for sending the control unit 13 (not shown) the signals from the plurality of detectors ₂₁ 1 to 21 _7.

A plurality of detectors ₂₁ 1 to 21 _7, the lightness L of the portion, each of which faces the ^L * ^a * ^{b *} of the food packaging resin film wound material 100 in accordance with the color system the detector detectors ₂₁ 1 to 21 ₇ ^* , A color detector for measuring chromaticity a ^* , b ^* . A plurality of detectors ₂₁ 1 to 21 ₇ brightness detected by the ^{L *,} chromaticity ^a *, ^{b *} is sent to the control unit 13 via a line 22.

Or control unit 13, the lightness ^{L *} is detected by the detectors ₂₁ 1 to 21 _7, the chromaticity ^a *, based on ^{b *,} wrinkle food packaging resin film wound material 100 is within the permissible range Determine if. In this example, the control unit 11 includes a plurality of detectors 21 _{1 to} 21 ₇ , but the number of detectors is not limited to seven, and may be one or two or more. May be.

  FIG. 3 is a flowchart showing a series of procedures of the first inspection method. This series of procedures is executed by the control unit 13 in accordance with a program stored in the storage 14 of the inspection apparatus 10.

  In the first step S1, the control unit 13 controls the holding unit 12, takes out and fixes one of the specimens from a plurality of food packaging resin rolls to be inspected, and the measurement unit 11 performs measurement. To be able to Moreover, the control part 13 specifies the resin film winding material for food packaging of a subject by a serial number etc.

In step S <b ^> 2, the control unit 13 controls the measurement unit 11 to irradiate light onto the subject food packaging resin film roll fixed by the holding unit 12, and L ^* a ^* b ^* from the return light ^. The lightness L ^* , chromaticity a ^* , and b ^* are measured according to the color system.

In step S3, the control unit 13 uses the chromaticity a ^* and b ^* obtained by the measurement unit 11 measuring the wound food packaging resin film of the subject, and the relational expression given by the following equation (2): Is used to derive the chroma C ^{* of the} subject.

In step S4, the control unit 13 branches the processing flow according to the condition “C> C ^* ₀ ” that the chroma C ^* of the subject exceeds a predetermined threshold C ^* ₀ . If the condition “C> C ^* ₀ ” is satisfied, the control unit 13 proceeds to step S5, and if not, proceeds to step S6.

  In step S5, the controller 13 determines that the subject food packaging resin film roll is acceptable. The control unit 13 specifies the food packaging resin film wound object of the subject by a serial number or the like, and records that it has passed in the storage 14.

  On the other hand, in step S6, the control unit 13 determines that the subject food packaging resin film roll is unacceptable. The control unit 13 identifies the food packaging resin film roll of the subject by a serial number or the like, and records that it is unacceptable in the storage 14.

  The inspection apparatus 10 repeats such a series of procedures of the first inspection method until the plurality of food packaging resin rolls to be inspected are exhausted. With such an operation, it is determined whether all of the plurality of food packaging resin film rolls for food packaging to be inspected are acceptable or unacceptable.

According to the first inspection method, whether or not the wrinkles of the resin film roll for food packaging are within an allowable range is determined based on the saturation C ^* of the L ^* a ^* b ^* color system. Accordingly, there is no need for complicated image processing, the configuration of the inspection apparatus can be simplified, and the processing speed can be increased.

  Further, the first inspection method is carried out by an SCI (regular reflection light included) method in which there is no light trap and the color is measured without removing the regular reflection light. In this SCI method, since measurement is performed including specularly reflected light, the color of the material itself is evaluated regardless of the surface state. Therefore, the measurement independent of the surface state such as wrinkles formed on the surface of the resin film roll for food packaging can be performed.

FIG. 4 is a flowchart showing a series of procedures of the second inspection method. The inspection apparatus 10 can execute the second inspection method instead of the first inspection method. Since the second inspection method is the same as the first inspection method except for the step of discriminating using the lightness L ^* , the corresponding step uses the same code to clarify the correspondence.

In the second inspection method, Step S1 for providing a sample of a food packaging resin film for packaging food, measuring lightness L ^* , chromaticity a ^* , b ^* according to the L ^* a ^* b ^* color system, Step S3 for deriving the degree C ^*, and step S4 for branching the processing flow depending on whether the condition “C> C ^* ₀ ” that the saturation C ^* exceeds the threshold C ^* ₀ is satisfied. It is the same.

The second inspection method is different from the first embodiment in that the process proceeds to step S11 if the condition “C> C ^* ₀ ” is satisfied in step S4. In step S11, if the condition “L> L ^* ₀ ” that the lightness L ^* does not reach the predetermined threshold L ^* ₀ is satisfied, the process proceeds to step S5, and if not, the process proceeds to step S6.

  In the second inspection method, step S5 for determining that the subject food packaging resin film roll is acceptable, and step S5 for determining that the subject food packaging resin film roll is unacceptable. This is the same as the first inspection method.

According to a second inspection method, whether wrinkles food packaging resin film wound material is in the allowable range L ^* a ^* b ^* was determined based on the color system of chroma C ^* and lightness L ^* Yes. Therefore, similarly to the first inspection method, there is no need for complicated image processing, and the configuration of the inspection apparatus can be simplified, and the processing speed can be increased. Moreover, since the measurement is performed by the SCI method as in the first inspection method, measurement independent of the surface state can be performed.

Further, the second inspection method is determined in consideration of the lightness L ^{* as} compared with the first inspection method that is determined based on the saturation C ^* . Therefore, the second inspection method can more precisely determine whether or not the wrinkles of the food packaging resin film roll of the subject are within an allowable range, as compared with the first inspection method. Therefore, the determination by the second inspection method can be more reliable.

According to this embodiment, using the inspection apparatus configured as described above, the first or second inspection method is applied, and the resin film winding for food packaging that is determined to be acceptable because the wrinkles are in an acceptable range Things can be provided. Since such a food packaging roll for food packaging is determined according to the L ^* a ^* b ^* color system, complicated image processing is not required, and the manufacturing cost can be reduced and provided at low cost.

Moreover, according to this embodiment, it is a manufacturing method of the resin film winding thing for food packaging, Comprising: The manufacturing method including the process of discriminating whether it is a pass or a failure by the 1st or 2nd inspection method. Can be provided. Since such a manufacturing method is discriminated according to the L ^* a ^* b ^* color system, it does not require complicated image processing and the like, and thus can provide quick processing with a simple configuration, which in turn reduces the manufacturing cost. Reduction can also be achieved.

  In Example 1, it was examined whether or not the determination of whether or not wrinkles are within an allowable range is correctly performed according to the first inspection method for a plurality of food packaging resin rolls to be inspected.

Table 1 shows the results of measurement of lightness L ^* and chromaticity a ^* , b ^* according to the L ^* a ^* b ^* color system for a plurality of food packaging resin rolls to be inspected, and the wrinkle is within an allowable range. Whether it is in or not. Here, wrinkles are described as “possible” as those that are not allowed to be seen by visual inspection as being within the allowable range, and “others” are described as “impossible”. Table 1 also shows the saturation C ^* derived from the chromaticity a ^* and b ^* by the relational expression of Equation 2.

  Here, a color difference meter CR-300 manufactured by KONICA MINOLTA was used as the measuring instrument, the measurement diameter was φ8 mm, and the light source was a pulsed xenon lamp. The optical conditions were a diffuse illumination vertical light receiving method (conforming to JIS Z 8723), and a light including regular reflected light (SCI method). Moreover, the winding length of the resin film roll for food packaging of a test object was 100 m.

In Table 1, the first group G ₁ including 5 from the sample 1 is a resin film for food packaging commercial companies, any wrinkles was in the acceptable range. Samples 1 to 5 are all from different manufacturers.

Second group G ₂ including a sample 6 8 is a resin film for food packaging the applicant has produced, any wrinkles was in the acceptable range. Third group G ₃ from the sample 9 containing 11 also a food packaging resin film applicant has produced, any wrinkles did not enter into the acceptable range.

Second group G ₂ and the third group G ₃ Applicant has manufactured, taking into account the time course of food packaging resin film wound material was prepared that the time elapsed since production is different. Samples 8 and 10 were manufactured after 0 months, samples 7 and 9 were manufactured after February, and samples 6 and 11 were manufactured after 3 months. A food packaging film may change its winding state over time due to bleed-out of additives, air release due to tightening, and the like.

As is apparent from Table 1, the third group G ₃ where the wrinkles are not in the allowable range is higher in the lightness L and lower than the first group G ₁ and the second group G ₂ in which the wrinkles are within the allowable range. Although the chroma C ^* value is shown, the chromaticity a ^* indicating the intensity of green is small, and the chromaticity b ^* indicating yellowness is not significantly changed.

The second group G ₂ and the third group G ₃ manufactured by the applicant have a low saturation C * as compared to the first group G ₁ which is a commercially available resin film roll for food packaging of other companies. Show. Therefore, the resin film roll for food packaging manufactured by the applicant is lighter in color than the resin film rolls for food packaging of other companies on the market, and it does not hinder the confirmation and visibility of the contents as packaging materials. Is preferred.

FIG. 5 is a color tone diagram of saturation C ^* and lightness L ^* for samples 1 to 11 shown in Table 1. In FIG. 5, the saturation C that can separate the first group G ₁ and the second group G ₂ where the wrinkles are within the allowable range and the third group G ₃ where the wrinkles are not within the allowable range. ^* are also described threshold ^C _{* 0} for.

Referring to Table 1 and Figure 5, the threshold value C ^* ₀ for chroma C ^* is greater than the third upper limit of the groups G ₃ which wrinkles do not fall within the allowable range, the first group of wrinkles is within the permissible range G ₁ and to be less than the second lower limit of the group _{G 2,} it is apparent that may be set to 8.28 smaller range greater than 5.97.

Specifically, the threshold value C ^* ₀ for the saturation C ^* may be larger than 5.97 and smaller than 8.28, and is preferably in the range of 6.1 to 8.1. It is more preferable that it is in the range of 7.7, for example, it may be 7.

When the threshold value C ^* ₀ is set in such a range and the samples 1 to 11 in Table 1 are inspected by the first inspection method, the first group G1 and the _first group G1 are compared with the threshold value C ^* ₀ in step S4. proceeds from the sample 1 contained in the second group _{G 2} 8 in step S5 pass satisfies the condition ^"C> C _{* 0",} the sample 9 to 11 included in the third group _{G 3} are conditions "C> C ^* ₀ ”is not satisfied, and the process proceeds to step S6 which is rejected.

Therefore, by the first inspection method, the first group G ₁ and the second group G ₂ of wrinkles is within the allowable range passes, the third group G ₃ which wrinkles do not fall within the allowable range is rejected, It became clear that the wrinkles were correctly judged as to whether they were within an acceptable range.

  In Example 2, it was examined whether or not the determination of whether or not wrinkles are within an allowable range is correctly performed according to the second inspection method for a plurality of food packaging resin rolls to be inspected. In Example 2 as well, a plurality of food packaging resin film rolls shown in Table 1 of Example 1 are to be inspected.

FIG. 6 is a color diagram of chroma C ^* and lightness L ^* for samples 1 to 11 shown in Table 1. FIG During 6, in addition to the threshold C ^* ₀ for chroma C ^*, the first group G ₁ and the second group G ₂ of wrinkles is within the allowable range, a third that wrinkles do not fall within the allowable range threshold L ^* ₀ for lightness L ^* of the group G ₃ may be separated also been described.

Referring to Table 1 and FIG. 6, the threshold L ^* ₀ for lightness L ^*, the wrinkle is greater than the first group G ₁ and second upper groups G ₂ within the allowable range, the wrinkles tolerance the third group _G to be smaller than the lower limit of ₃ does not enter, it is clear that may be set to 77.94 smaller range greater than 75.65.

Specifically, the threshold value L ^* ₀ for the lightness L ^* may be larger than 75.65 and smaller than 77.94, preferably in the range of 76 to 77.5, and in the range of 76.5 to 77. For example, it may be 76.6.

The threshold value L ^* ₀ was set in such a range, the threshold value C ^* ₀ of Example 1 was applied, and samples 1 to 11 in Table 1 were inspected by the second inspection method. By comparison with the threshold value ^C _{* 0} at step S4, the first group _{G 1} and the sample 1-8 in the second group _{G 2} is satisfies the condition ^"C> C _{* 0"} that saturation exceeds the threshold proceeds to step S11 Te, a third group _{G 3} samples 9 to 11 included in the proceeds to fail step S6 without satisfying the condition ^"C> C _{* 0".}

Samples 1 to 8, which is contained in the group _{G 2} and _the first group _{G 1} advanced second in step S11, is compared with a threshold ^L _{* 0,} a condition that lightness does not reach the threshold value ^{_"L <L} _* 0" Was passed and it progressed to step S5 of the pass.

Accordingly, the second inspection process, the first group G ₁ and the second group G ₂ of wrinkles is within the allowable range passes, the third group G ₃ which wrinkles do not fall within the allowable range is rejected, It became clear that the wrinkles were correctly judged as to whether they were within an acceptable range.

This invention can apply the chroma C ^* according to the L ^* a ^* b ^* color system to the resin wrap for food packaging, its inspection and production.

DESCRIPTION OF SYMBOLS 10 Inspection apparatus 11 Measuring part 12 Holding part 13 Control part 14 Storage

Claims (13)

A method for inspecting a rolled resin film for food packaging,
Providing a resin film roll for food packaging as a subject;
Measuring the lightness L ^* , chromaticity a ^* and b ^* of the subject according to the L ^* a ^* b ^* color system;
Providing a chroma C ^* based on the chromaticity a ^* and b ^* ;
And a step of determining that the subject is acceptable when the saturation C ^* exceeds a predetermined threshold, and otherwise determining that the subject is unacceptable. The saturation C ^* is the chromaticity a ^* and b ^* .

The inspection method according to claim 1, which is given by: The inspection method according to claim 1 or 2, wherein the predetermined threshold value of the saturation C ^* is in a range from 6.1 to 8.1. If the lightness L ^* does not reach a predetermined threshold value, the object further includes a step of determining that the subject is acceptable, and otherwise, determining that the object is unacceptable, and this step is determined to be acceptable based on the saturation C ^*. The inspection method according to claim 1, wherein the test object is determined as pass or fail based on the lightness L ^* . Predetermined threshold value of the Lightness L ^*, the inspection method according to claim 4 in the range of from 76 to 77.5.   The inspection method according to any one of claims 1 to 5, which is based on a diffuse illumination vertical light receiving system including specularly reflected light.   The inspection method according to any one of claims 1 to 6, wherein the food packaging roll for food packaging includes at least one of polyvinyl chloride, polyvinylidene chloride, and polyethylene.   The inspection method according to any one of claims 1 to 7, wherein the food-wrapped resin film wound product is obtained by winding a film having a thickness of 1 to 20 µm.   The inspection method according to any one of claims 1 to 8, wherein the wound length of the food packaging resin film roll is in the range of 50 m to 110 m.   The inspection method according to any one of claims 1 to 9, wherein the food film wound product for food packaging has an average degree of polymerization of 750 or more and less than 1750.   It is a manufacturing method of the resin film winding product for food packaging, Comprising: The manufacturing method including the step which test | inspects the manufactured resin film winding product for food using the inspection method in any one of Claim 1 to 10. An inspection device for a resin film roll for food packaging,
A light source for irradiating light to a specimen of a resin film roll for food packaging;
A measurement unit that measures the lightness L ^* , chromaticity a ^*, and b ^* of the subject in accordance with the L ^* a ^* b ^* color system from the return light from the subject irradiated with light from the light source;
Wherein providing chroma C ^* said measured by the measuring unit based on the chromaticity a ^* and b ^*, the chroma C ^* is determined as acceptable the subject exceeds a predetermined threshold value, not the case And a control unit that discriminates the failure. The control unit further determines the lightness L ^* for the subject determined to be acceptable based on the saturation C ^* , and determines that the subject is acceptable if the lightness L ^* does not reach a predetermined threshold value. The inspection apparatus according to claim 12 , wherein the inspection device is determined, and otherwise, it is determined as a failure.

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