JP2010286406A - X-ray transmission inspection apparatus and X-ray transmission inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED To prevent over-detection and false detection by clearly discriminating only contrast caused by a foreign object.
A first X-ray tube 11 that irradiates a sample S with a first characteristic X-ray having energy lower than the X-ray absorption edge of the element to be measured, and a second X-ray tube having energy higher than the X-ray absorption edge of the element. A second X-ray tube 12 that irradiates the sample with characteristic X-rays of the first, and the first and second transmission X-rays when the first characteristic X-ray and the second characteristic X-ray pass through the sample. A first X-ray detector 13 and a second X-ray detector 14 for detecting X-rays; a first transmission image of the first transmission X-ray; and a second transmission image of the second transmission X-ray; A calculation unit 15 that obtains a contrast image from the difference between the first X-ray absorption edge of the element having an X-ray absorption edge higher in energy than the first characteristic X-ray between the sample and the first X-ray tube. A second element F2 having an X-ray absorption edge higher in energy than the second characteristic X-ray is disposed between the sample and the second X-ray tube while the filter F1 is disposed. The filter F2 is arranged.
[Selection] Figure 1

Description

  The present invention relates to an X-ray transmission inspection apparatus and an X-ray transmission inspection method capable of detecting a foreign substance made of a specific element in a sample.

  In recent years, lithium ion secondary batteries having higher energy density than nickel metal hydride batteries are being adopted as batteries for automobiles, hybrid cars, electric cars and the like. This lithium ion secondary battery is a kind of non-aqueous electrolyte secondary battery, which is a secondary battery in which the lithium ion in the electrolyte is responsible for electrical conduction and does not contain metallic lithium in the battery. Many telephones have already been adopted.

  Although this lithium ion secondary battery has excellent battery characteristics, reliability such as deterioration of battery characteristics such as heat generation and life when foreign matter such as Fe (iron) enters the electrode during the manufacturing process Until now, it has been delayed for in-vehicle use. For example, as shown in FIG. 7A, the lithium ion secondary battery electrode (positive electrode) is usually formed with a lithium Mn oxide film or a lithium cobalt oxide film 2 of about 100 μm on both surfaces of an Al film 1 having a thickness of 20 μm. However, as shown in FIG. 7 (b), foreign matter X such as Fe (iron) or SUS (stainless steel) may be mixed therein, and the foreign matter X is several tens of μm or more. If so, a short circuit can occur, which can cause the battery to burn out or degrade performance. For this reason, about a lithium ion secondary battery, it is calculated | required that a battery in which the foreign material X was mixed at the time of manufacture is detected rapidly by inspection, and removed beforehand.

  Generally, a method using a transmission X-ray image is known as a method for detecting a foreign substance or the like in a sample. Using this technique, as described in Patent Document 1, for example, carbon that detects the presence or absence of foreign matter in a carbon-based material or the like used as a negative electrode of a lithium ion secondary battery by a transmission X-ray image. A foreign material detection method for a quality material has been proposed.

Japanese Patent Laying-Open No. 2004-239776 (Claims)

The following problems remain in the conventional technology.
That is, in the conventional foreign matter detection method, since the presence or absence of foreign matter is simply detected based on the intensity of the transmitted X-ray image, a clear contrast can be obtained if the atomic number of the foreign matter is greatly different. There is a problem that contrast is weak and difficult to discriminate. For example, the same contrast is produced between Co contained in the constituent material of the electrode (positive electrode plate) and Fe as foreign matter. Therefore, in the conventional foreign matter detection method, as shown in FIG. 7A, for example, in the transmission X-ray image T of the electrode (positive electrode plate) that is the sample S, the contrast of the locally thick component 2a is increased. Alternatively, as shown in FIG. 7 (b), the contrast due to the foreign matter X cannot be determined, resulting in inconvenience of overdetection or erroneous detection.

  The present invention has been made in view of the above-described problems, and provides an X-ray transmission inspection apparatus and an X-ray transmission inspection method that can clearly discriminate only the contrast caused by a foreign substance and prevent overdetection and erroneous detection. For the purpose.

  The present invention employs the following configuration in order to solve the above problems. That is, the X-ray transmission inspection apparatus of the present invention includes a first X-ray tube that irradiates a sample with first characteristic X-rays having energy lower than the X-ray absorption edge of the element to be measured, and the X-rays of the element. The second X-ray tube that irradiates the sample with a second characteristic X-ray having energy higher than the absorption edge, and the first transmitted X-ray when the first characteristic X-ray passes through the sample. A first X-ray detector that detects the intensity of the first X-ray detector, and a second X-ray detection that receives the second transmitted X-ray when the second characteristic X-ray passes through the sample and detects the intensity And a first transmission image indicating the detected intensity distribution of the first transmitted X-ray and a second transmission image indicating the detected intensity distribution of the second transmitted X-ray. A calculation unit that obtains a contrast image from a difference between the first transmission image and the second transmission image, and the sample and the first X-ray A first filter formed of an element having an X-ray absorption edge with energy higher than that of the first characteristic X-ray is disposed between the sample and the second X-ray tube. And a second filter formed of an element having an X-ray absorption edge with energy higher than that of the second characteristic X-ray.

  The X-ray transmission inspection method of the present invention includes a step of irradiating a sample with a first characteristic X-ray having energy lower than that of an X-ray absorption edge of an element to be measured; Irradiating the sample with a second characteristic X-ray; receiving the first transmitted X-ray when the first characteristic X-ray is transmitted through the sample; and detecting the intensity thereof; Receiving the second transmitted X-ray when the characteristic X-ray passes through the sample and detecting the intensity thereof, and a first transmission image showing the distribution of the detected intensity of the first transmitted X-ray And a second transmission image showing the distribution of the detected intensity of the second transmission X-ray, and obtaining a contrast image from the difference between the first transmission image and the second transmission image; And the first characteristic X-ray between the sample and the first X-ray tube A first filter formed of an element having an X-ray absorption edge with a higher energy is disposed, and is higher than the second characteristic X-ray between the sample and the second X-ray tube. A second filter formed of an element having an X-ray absorption edge of energy is provided.

  In these X-ray transmission inspection apparatuses and X-ray transmission inspection methods, the first transmission image obtained by irradiating the sample with the first characteristic X-ray having energy lower than the X-ray absorption edge of the element to be measured and the element Since the contrast image is obtained from the difference from the second transmission image obtained by irradiating the sample with the second characteristic X-ray having higher energy than the X-ray absorption edge, a clear contrast image can be obtained for a specific element. . That is, it is not an X-ray in which various energies such as white X-rays are mixed, but a characteristic X-ray with different energy that causes a difference in the detected amount of transmitted X-rays before and after the X-ray absorption edge of the element and depending on the X-ray absorption edge By separately irradiating (the first characteristic X-ray and the second characteristic X-ray), it becomes possible to obtain a clear contrast image of the element to be measured even if there is another element having an atomic number close to it. .

  In addition, a first filter formed of an element having an X-ray absorption edge with higher energy than the first characteristic X-ray is disposed between the sample and the first X-ray tube, and the sample and the second X-ray tube. Since the second filter formed of an element having an X-ray absorption edge with higher energy than the second characteristic X-ray is disposed between the first X-ray tube and the second X-ray tube, In the case where not only the first characteristic X-ray or the second characteristic X-ray but also characteristic X-rays with higher energy or background X-rays are emitted from the X-ray tube, It can cut with a filter and a 2nd filter. Accordingly, since only the desired first characteristic X-ray or second characteristic X-ray is extracted and the sample can be irradiated, the contrast of the element to be measured becomes clearer.

In the X-ray transmission inspection apparatus of the present invention, the element is Fe, the first X-ray tube is a Co target tube, and the second X-ray tube is an Ni target tube. It is a sphere, and the first filter is an Fe foil, and the second filter is a Co foil.
That is, in this X-ray transmission inspection apparatus, when Fe is an element to be measured, a Co target tube capable of emitting Co characteristic X-rays having energy located before and after the X-ray absorption edge of Fe and a characteristic of Ni By using the Ni target tube capable of emitting X-rays, Fe foreign matter can be detected with a clear contrast image by an inexpensive X-ray tube.
Since the first filter is an Fe foil and the second filter is a Co foil, only the Co-Kα characteristic X-ray (6.93 keV) is extracted from the X-ray absorption edge (7.111 keV) of Fe. At the same time, only the Ni-Kα characteristic X-ray (7.477 keV) can be extracted by the X-ray absorption edge (7.709 keV) of Co.

In the X-ray transmission inspection apparatus of the present invention, the element is Cr, the first X-ray tube is a Cr target tube, and the second X-ray tube is an Fe target tube. It is a sphere, and the first filter is a V (vanadium) foil, and the second filter is a Mn foil.
That is, in this X-ray transmission inspection apparatus, when Cr is an element to be measured, the characteristics of the Cr target tube capable of emitting characteristic X-rays of Cr with energy located before and after the X-ray absorption edge of Cr and the characteristics of Fe By using an Fe target tube capable of emitting X-rays, foreign materials such as SUS containing Cr can be detected with a clear contrast image by an inexpensive X-ray tube.
Since the first filter is a V foil and the second filter is an Mn foil, only the Cr-Kα characteristic X-ray (5.414 keV) is extracted by the X-ray absorption edge (5.463 keV) of V. In addition, only the Fe-Kα characteristic X-ray (6.403 keV) can be extracted by the X-ray absorption edge (6.537 keV) of Mn.

In the X-ray transmission inspection apparatus of the present invention, the element is Cr, the first X-ray tube is a Mn target tube, and the second X-ray tube is an Fe target tube. The first filter is a Cr foil, and the second filter is a Mn foil.
That is, in this X-ray transmission inspection apparatus, when Cr is an element to be measured, the characteristics of Mn target tube and Fe that can emit characteristic X-rays of Mn whose energy is located before and after the X-ray absorption edge of Cr. By using an Fe target tube capable of emitting X-rays, foreign materials such as SUS containing Cr can be detected with a clear contrast image by an inexpensive X-ray tube.
Since the first filter is a Cr foil and the second filter is a Mn foil, only the Mn-Kα characteristic X-ray (5.898 keV) is extracted from the X-ray absorption edge (5.988 keV) of Cr. In addition, only the Fe-Kα characteristic X-ray (6.403 keV) can be extracted by the X-ray absorption edge (6.537 keV) of Mn.

In the X-ray transmission inspection apparatus according to the present invention, the calculation unit calculates the thickness of the element from the contrast image and the mass absorption coefficient and density of the element.
That is, in this X-ray transmission inspection apparatus, the calculation unit calculates the thickness of the element from the contrast image and the mass absorption coefficient and density of the element, so that not only the detection of the element to be measured but also its thickness is calculated. Therefore, it is possible to grasp the three-dimensional size of the foreign matter containing this element. Therefore, it is possible to sort out whether or not the foreign matter is a problem as a secondary battery or the like from the size of the foreign matter obtained by this inspection.

The present invention has the following effects.
That is, according to the X-ray transmission inspection apparatus and the X-ray transmission inspection method according to the present invention, the first characteristic X-ray obtained by irradiating the sample with the first characteristic X-ray having energy lower than the X-ray absorption edge of the element to be measured. Since a contrast image is obtained from the difference between the transmission image of the element and the second transmission image acquired by irradiating the sample with the second characteristic X-ray having an energy higher than the X-ray absorption edge of the element, a clear contrast is obtained for a specific element. An image can be obtained. In addition, a first filter formed of an element having an X-ray absorption edge with higher energy than the first characteristic X-ray is disposed between the sample and the first X-ray tube, and the sample and the second X-ray tube. Since the second filter formed of an element having an X-ray absorption edge having higher energy than the second characteristic X-ray is disposed between the X-ray tube and the X-ray tube, the desired first characteristic X-ray or second Only the characteristic X-rays of 2 can be extracted and irradiated, and the contrast of the element to be measured becomes clearer.
Therefore, by using this X-ray transmission inspection apparatus and X-ray transmission inspection method, it is possible to detect a foreign substance of a specific element in a lithium ion secondary battery or the like with high accuracy and speed.

1 is a schematic overall configuration diagram showing an embodiment of an X-ray transmission inspection apparatus and an X-ray transmission inspection method according to the present invention. In this embodiment, it is a graph which shows the X-ray transmittance with respect to the case where only lithium Coate and the case where Fe foreign material is contained in this. In this embodiment, when the second characteristic X-ray is irradiated from the Ni target tube, the second transmission when there is a locally thick portion (a) and when the Fe foreign matter is contained (b) It is explanatory drawing which shows an image. In this embodiment, when the first characteristic X-ray is irradiated from the Co target tube, the first transmission when there is a locally thick portion (a) and when the Fe foreign matter is contained (b) It is explanatory drawing which shows an image. In this embodiment, it is a graph which shows the X-ray transmittance with respect to the case where only lithium Niate and the case where Fe foreign material is contained in this. In this embodiment, it is a graph which shows the X-ray transmittance with respect to the case where only Al (aluminum) and C (graphite), and the case where Fe foreign material is contained in this. In the conventional example of the X-ray transmission inspection apparatus and the X-ray transmission inspection method according to the present invention, when X-rays are irradiated, there is a locally thick portion (a) and a case where Fe foreign matter is contained (b) FIG.

  Hereinafter, an embodiment of an X-ray transmission inspection apparatus and an X-ray transmission inspection method according to the present invention will be described with reference to FIGS. 1 to 6.

  As shown in FIG. 1, the X-ray transmission inspection apparatus of the present embodiment is a first X-ray tube that irradiates a sample S with first characteristic X-rays having energy lower than the X-ray absorption edge of the element to be measured. 11, the second X-ray tube 12 that irradiates the sample S with the second characteristic X-ray having energy higher than the X-ray absorption edge of the element, and the first characteristic X-ray transmitted through the sample S The first X-ray detector 13 that receives the first transmitted X-ray and detects its intensity, and receives the second transmitted X-ray when the second characteristic X-ray passes through the sample S, and the intensity thereof The second X-ray detector 14 to detect, the first transmission image showing the distribution of the detected intensity of the first transmitted X-ray, and the second showing the intensity distribution of the detected second transmitted X-ray. And a calculation unit 15 that obtains a contrast image from the difference between the first transmission image and the second transmission image.

The X-ray transmission inspection apparatus includes a belt conveyor 16 that is a sample stage on which a sample S is placed and can move in the horizontal direction, a control unit 17 that is connected to each of the above-described components and controls each of the components. 15 and a display unit 18 that is a display device that displays the contrast image and the like.
Furthermore, in the X-ray transmission inspection apparatus, the first filter formed of an element having an X-ray absorption edge with higher energy than the first characteristic X-ray between the sample S and the first X-ray tube 11. F2 is disposed, and the second filter F2 formed of an element having an X-ray absorption edge with higher energy than the second characteristic X-ray between the sample S and the second X-ray tube 12 Is arranged.

The computing unit 15 has a function of calculating the thickness of the element from the contrast image and the mass absorption coefficient and density of the element.
The sample S is, for example, an electrode used for a lithium ion secondary battery, and the element to be measured is, for example, Fe or Cr in SUS, which may be mixed as a foreign substance in the electrode.

When the element to be measured is Fe, the first X-ray tube 11 is a Co target tube having a Co target, and the second X-ray tube 12 is a Ni target having a Ni target. A target tube is adopted. From the first X-ray tube 11 of the Co target tube, for example, as a first characteristic X-ray having energy lower than that of the K absorption edge (7.111 keV) of Fe, a Co-Kα characteristic X-ray (6. 93 keV) is emitted. Further, from the second X-ray tube 12 of the Ni target tube, for example, a Ni-Kα characteristic X-ray (as a second characteristic X-ray having higher energy than the K absorption edge (7.111 keV) of Fe). 7.477 keV) is emitted.
At this time, the first filter F1 employs an Fe foil, and the second filter F2 employs a Co foil.

When the element to be measured is Cr, the first X-ray tube 11 is a Cr target tube having a Cr target or a Mn target tube having a Mn target. As the X-ray tube 12, an Fe target tube having an Fe target is employed.
From the first X-ray tube 11 of the Cr target tube, for example, a Cr-Kα characteristic X-ray (5. 5) is used as a first characteristic X-ray having a lower energy than the K absorption edge (5.988 keV) of Cr. 414 keV) is emitted. Further, from the first X-ray tube 11 of the Mn target tube, for example, as a first characteristic X-ray having a lower energy than the K absorption edge (5.988 keV) of Cr, an Mn-Kα characteristic X-ray ( 5.898 keV) is emitted. Further, from the second X-ray tube 12 of the Fe target tube, for example, as a second characteristic X-ray having higher energy than the K absorption edge (5.988 keV) of Cr, an Fe-Kα characteristic X-ray ( 6.403 keV) is emitted.

When the first X-ray tube 11 is a Cr target tube and the second X-ray tube 12 is an Fe target tube, a V foil is used for the first filter F1, and For the second filter F2, a Mn foil is employed.
When the first X-ray tube 11 is a Mn target tube and the second X-ray tube 12 is an Fe target tube, the first filter F1 is made of Cr foil, For the second filter F2, a Mn foil is employed.

When the element to be measured is Fe or Cr, examples of energy of characteristic X-rays that can be adopted as the first characteristic X-ray and the second characteristic X-ray, and the first filter F1 and the second filter F2 Table 1 below shows examples of energy at the X-ray absorption edge of elements that can be used as

  In the X-ray tube, which is the first X-ray tube 11 and the second X-ray tube 12, the thermoelectrons generated from the filament (anode) in the tube are a filament (anode) and a target (cathode). X-rays generated by colliding with the target accelerated by the voltage applied between and are emitted as primary X-rays (first characteristic X-rays and second characteristic X-rays) from windows such as beryllium foil It is.

The first X-ray detector 13 and the second X-ray detector 14 are arranged below the belt conveyor 16 so as to face the corresponding first X-ray tube 11 and second X-ray tube 12, respectively. X-ray line sensor. As this X-ray line sensor, a scintillator method in which X-rays are converted into fluorescence by a fluorescent plate and converted into a current signal by a light receiving element arranged in a row, a semiconductor method in which a plurality of semiconductor detection elements are arranged in a row, etc. are adopted. . These X-ray sensors may be X-ray area sensors in which light receiving elements are arranged two-dimensionally in addition to a single line.
The first X-ray detector 13 and the second X-ray detector 14 are also used as one X-ray detector, and this X-ray detector is used as the first X-ray tube 11 and the second X-ray detector. It may be possible to move to positions facing the tube 12 and detect the first transmitted X-ray and the second transmitted X-ray, respectively.

The control unit 17 is a computer configured with a CPU or the like.
In addition, the calculation unit 15 performs image processing based on signals from the first X-ray detector 13 and the second X-ray detector 14 input via the control unit 17 to obtain the first transmission image and the first transmission image. An arithmetic processing circuit or the like that creates a second transmission image, creates a contrast image by performing differential processing on these images, and further displays the image on the display unit 18. Note that a processing circuit of the calculation unit 15 may be provided in the control unit 17 so that both are integrated. The display unit 18 can display various information according to control from the control unit 17.

  Next, an X-ray transmission inspection method using the X-ray transmission inspection apparatus of this embodiment will be described with reference to FIGS. In this X-ray transmission inspection method, for example, the element to be measured is Fe as the foreign matter X in the lithium Co oxide electrode, the Co target tube is adopted as the first X-ray tube 11, and the second X-ray tube A Ni target tube is adopted as 12.

First, the sample S is set on the belt conveyor 16, and the controller 17 moves the sample S to a position facing the first X-ray tube 11 by the belt conveyor 16.
Next, the sample S is irradiated with Co-Kα characteristic X-rays as the first characteristic X-rays from the first X-ray tube 11 of the Co target tube, and the sample X is irradiated with the first X-ray detector 13. The transmitted first transmitted X-ray is detected. At this time, the entire sample is scanned by moving the sample S on the belt conveyor 16, and the entire intensity distribution of the first transmitted X-ray is acquired.

  At this time, among the X-rays emitted from the first X-ray tube 11 of the Co target tube, a characteristic X-ray (Co-Kβ characteristic) having energy higher than the X-ray absorption edge (7.111 keV) of Fe. X-rays (7.649 keV, etc.) and background X-rays are absorbed by the first filter F1 of Fe foil and cut to form the first characteristic X-rays. The sample S is irradiated with only 93 keV).

Next, the sample S is moved to a position facing the second X-ray tube 12 by the belt conveyor 16.
Then, the second S-ray tube 12 of the Ni target tube irradiates the sample S with a Ni-Kα characteristic X-ray as a second characteristic X-ray, and the second X-ray detector 14 transmits the sample S. The second transmitted X-ray is detected. At this time, the entire sample is scanned by moving the sample S on the belt conveyor 16, and the entire intensity distribution of the second transmitted X-ray is acquired.

  At this time, among the X-rays emitted from the second X-ray tube 12 of the Ni target tube, a characteristic X-ray having a higher energy than the Co X-ray absorption edge (7.709 keV) (Ni-Kβ characteristic) Ni-Kα characteristic X-rays (7.477 keV) in which X-rays (8.264 keV, etc.) and background X-rays are absorbed and cut by the second filter F2 made of Co foil and become the second characteristic X-rays. Only the sample S is irradiated.

The first transmission X-ray intensity distribution and the second transmission X-ray intensity distribution thus obtained are image-processed by the calculation unit 15 to create a first transmission image and a second transmission image. .
The X-ray transmittance with respect to the lithium Co oxide electrode is, as shown in FIG. 2, the energy corresponding to the X-ray absorption edge of Fe when, for example, 20 μm of Fe foreign matter is contained, compared to the case where no foreign matter is present. As a result, the X-ray transmittance decreases. Further, the Co-Kα characteristic X-ray that is the first characteristic X-ray and the Ni-Kα characteristic X-ray that is the second characteristic X-ray each have energy corresponding to before and after the X-ray absorption edge of Fe. is doing.

  Therefore, as shown in FIG. 3A, when the constituent material of the sample S (the electrode material in which the lithium cobalt oxide film 2 is laminated on both surfaces of the Al film 1) has a locally thick portion 2a, Ni In the second transmission image T2 of the target tube by the second X-ray tube 12, a clear contrast is shown in a portion corresponding to the locally thick portion 2a. Further, as shown in FIG. 3B, when the foreign matter X of Fe is present in the sample S, the second transmission image T2 by the second X-ray tube 12 of the Ni target tube shows the foreign matter X. Clear contrast is shown in the corresponding part. That is, since the Ni-Kα characteristic X-ray having higher energy than the X-ray absorption edge of Fe has a lower X-ray transmittance with respect to the foreign matter X of Fe, the amount transmitted through the foreign matter X portion is transmitted through the other portions. The amount is lower than the amount to be dark, and a dark portion is produced, resulting in a contrast.

  On the other hand, as shown in FIG. 4A, when the sample S has a locally thick portion 2a, the first transmission image T1 by the first X-ray tube 11 of the Co target tube has a local region. A clear contrast is shown in the portion corresponding to the thick portion 2a. However, as shown in FIG. 4B, when the sample S has the foreign substance X of Fe, the first transmission image T1 of the Co target tube by the first X-ray tube 11 shows the foreign object X. No clear contrast is shown in the corresponding part. That is, Co-Kα characteristic X-rays with energy lower than the X-ray absorption edge of Fe have the same amount of X-ray transmittance as that of lithium Coate with respect to the foreign matter X of Fe, and the amount of the foreign matter X transmitted through other parts Since the amount of light transmitted through the portion is almost the same, a clear contrast is unlikely to occur.

  Next, the calculation unit 15 creates a contrast image by taking the difference between the first transmission image T1 and the second transmission image T2 obtained as described above, and displays the contrast image on the display unit 18. That is, the difference between the first transmission image T1 and the second transmission image T2 that are transmission images by monochromatic X-rays, respectively, is distinguished from the locally thick portion 2a and corresponds to the foreign matter X of Fe. A contrast image with enhanced is obtained.

Further, the calculation unit 15 calculates the thickness of the element, that is, the thickness of the foreign matter X from the contrast image obtained from the difference between the two transmission images and the mass absorption coefficient and density of the element to be measured. That is, the mass absorption coefficient μ and the density ρ relating to the element (Fe) to be measured are set in advance in the calculation unit 15, and the transmitted X-ray intensity (foreign matter) of a strong contrast portion corresponding to the foreign matter X portion of the contrast image. (Partial transmitted X-ray intensity) I _Fe and the transmitted X-ray intensity (non-foreign part transmitted X-intensity) I _Co of the low-contrast part corresponding to the part where no foreign substance X exists, the average thickness of the foreign substance X based on the following formula D is calculated.

I _Fe : X-ray intensity of foreign matter part transmitted by _Co I _Co : Non-foreign part transmitted X-ray intensity by Co μ: Mass absorption coefficient of foreign substance (Fe) ρ: Density of foreign substance (Fe) D: Average thickness of foreign substance (Fe)

In the above description, the X-ray transmission inspection method for detecting the foreign matter X in the lithium Coate electrode is exemplified. However, as an electrode material used in the lithium ion secondary battery, the foreign matter in the lithium Niate used in the positive plate is used. The present invention can be similarly applied to inspection and inspection of foreign matters in a laminated material of Al (aluminum) and C (graphite) used for the negative electrode plate.
FIG. 5 shows the X-ray transmittance graph for the lithium Niate and the X-ray transmittance graph for the laminated material of Al (aluminum) and C (graphite) with and without foreign matter (Fe). And shown in FIG.

  As for the X-ray transmittance of these materials, it can be seen that the X-ray transmittance is decreased at the X-ray absorption edge of Fe when the foreign substance X of Fe is present. Therefore, even when detecting the foreign matter X in these materials, the first characteristic X-rays of energy located before and after the X-ray absorption edge of Fe (for example, Co-Kα characteristic X-rays from a Co target tube) and By using the second characteristic X-ray (for example, the Ni-Kα characteristic X-ray from the Ni target tube), the contrast image in which the part of the foreign matter X is emphasized from the difference between the two X-ray transmission images and the foreign matter X Thickness can be obtained.

  As described above, in the X-ray transmission inspection apparatus and the X-ray transmission inspection method of the present embodiment, the first characteristic X-ray having energy lower than the X-ray absorption edge of the element to be measured is obtained by irradiating the sample S with the first characteristic X-ray. The contrast image is obtained from the difference between the transmission image T1 of the sample and the second transmission image T2 acquired by irradiating the sample S with the second characteristic X-ray having energy higher than the X-ray absorption edge of the element. A clear contrast image can be obtained. That is, it is not an X-ray in which various energies such as white X-rays are mixed, but a characteristic X-ray with different energy that causes a difference in the detected amount of transmitted X-rays before and after the X-ray absorption edge of the element and depending on the X-ray absorption edge By separately irradiating (the first characteristic X-ray and the second characteristic X-ray), it becomes possible to obtain a clear contrast image of the element to be measured even if there is another element having an atomic number close to it. .

  In addition, a first filter F1 formed of an element having an X-ray absorption edge with higher energy than the first characteristic X-ray is arranged between the sample S and the first X-ray tube 11, and the sample Since the second filter F2 formed of an element having an X-ray absorption edge with higher energy than the second characteristic X-ray is disposed between S and the second X-ray tube 12, the first X The X-ray tube 11 and the second X-ray tube 12 emit not only the first characteristic X-ray or the second characteristic X-ray, but also characteristic X-rays with higher energy and background X-rays. If they are, they can be cut by the first filter F1 and the second filter F2. Accordingly, since only the desired first characteristic X-ray or second characteristic X-ray is extracted and can be irradiated to the sample S, the contrast of the element to be measured becomes clearer.

In addition, when Fe is an element to be measured, the first X-ray tube 11 of the Co target tube that can emit Co characteristic X-rays with energy located before and after the X-ray absorption edge of Fe and the Ni By using the second X-ray tube 12 of the Ni target tube capable of emitting characteristic X-rays, the foreign matter X of Fe can be detected with a clear contrast image by an inexpensive X-ray tube.
Since the first filter is an Fe foil and the second filter is a Co foil, only the Co-Kα characteristic X-ray (6.93 keV) is extracted from the X-ray absorption edge (7.111 keV) of Fe. At the same time, only the Ni-Kα characteristic X-ray (7.477 keV) can be extracted by the X-ray absorption edge (7.709 keV) of Co. That is, the Co-Kβ characteristic X-ray (7.649 keV) or the like is cut by the X-ray absorption edge (7.111 keV) of Fe, and the Ni-Kβ characteristic X-ray is cut by the X-ray absorption edge (7.709 keV) of Co. (8.264 keV) is cut.

  Further, when Cr is an element to be measured, the first X of the Cr target tube or the Mn target tube capable of emitting characteristic X-rays of Cr or Mn whose energy is located before and after the X-ray absorption edge of Cr. By using the X-ray tube 11 and the second X-ray tube 12 of the Fe target tube capable of emitting characteristic X-rays of Fe, foreign matter X such as SUS containing Cr by an inexpensive X-ray tube Can be detected with a clear contrast image.

  When the first X-ray tube 11 is a Cr target tube and the second X-ray tube 12 is an Fe target tube, the first filter F1 is a V foil and the second Filter F2 is Mn foil, so that only the Cr-Kα characteristic X-ray (5.414 keV) is extracted by the X-ray absorption edge of V (5.463 keV) and the X-ray absorption edge of Mn (6.537 keV). Thus, only the Fe-Kα characteristic X-ray (6.403 keV) can be extracted. That is, the Cr-Kβ characteristic X-ray (5.946 keV) or the like is cut by the X-ray absorption edge (5.463 keV) of V, and the Fe-Kβ characteristic X-ray is cut by the X-ray absorption edge (6.537 keV) of Mn. (7.057 keV) is cut.

  When the first X-ray tube 11 is a Mn target tube and the second X-ray tube 12 is an Fe target tube, the first filter F1 is a Cr foil and the second Since the filter F2 of the Mn foil is a Mn foil, only the Mn-Kα characteristic X-ray (5.898 keV) is extracted from the X-ray absorption edge (5.988 keV) of Cr, and the X-ray absorption edge (6.537 keV) of Mn is extracted. Thus, only the Fe-Kα characteristic X-ray (6.403 keV) can be extracted. That is, the Mn-Kβ characteristic X-ray (6.49 keV) or the like is cut by the Cr X-ray absorption edge (5.988 keV), and the Fe-Kβ characteristic X-ray is cut by the Mn X-ray absorption edge (6.537 keV). (7.057 keV) is cut.

  Further, since the calculation unit 15 calculates the thickness of the element from the contrast image, the mass absorption coefficient and the density of the element, not only the detection of the element to be measured but also the thickness of the element can be calculated. It is also possible to grasp the three-dimensional size of X. Therefore, it is possible to sort out whether or not the foreign material X is a problem as a secondary battery or the like from the size of the foreign material X obtained by this inspection.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 11 ... 1st X-ray tube, 12 ... 2nd X-ray tube, 13 ... 1st X-ray detector, 14 ... 2nd X-ray detector, 15 ... Operation part, 16 ... Belt conveyor, DESCRIPTION OF SYMBOLS 17 ... Control part, 18 ... Display part, F1 ... 1st filter, F2 ... 2nd filter, S ... Sample, T1 ... 1st transmission image, T2 ... 2nd transmission image, X ... Foreign material

Claims (6)

A first X-ray tube that irradiates the sample with first characteristic X-rays having energy lower than the X-ray absorption edge of the element to be measured;
A second X-ray tube that irradiates the sample with a second characteristic X-ray having an energy higher than the X-ray absorption edge of the element;
A first X-ray detector that receives the first transmitted X-ray when the first characteristic X-ray passes through the sample and detects its intensity;
A second X-ray detector that receives the second transmitted X-ray when the second characteristic X-ray passes through the sample and detects its intensity;
Creating a first transmission image showing the detected intensity distribution of the first transmitted X-ray and a second transmission image showing the detected intensity distribution of the second transmitted X-ray; A calculation unit that obtains a contrast image from the difference between the first transmission image and the second transmission image,
A first filter formed of an element having an X-ray absorption edge with energy higher than that of the first characteristic X-ray is disposed between the sample and the first X-ray tube, and A second filter formed of an element having an X-ray absorption edge having an energy higher than that of the second characteristic X-ray is disposed between the sample and the second X-ray tube source. X-ray transmission inspection equipment. The X-ray transmission inspection apparatus according to claim 1,
The element is Fe;
The first X-ray tube is a Co target tube and the second X-ray tube is a Ni target tube;
The X-ray transmission inspection apparatus, wherein the first filter is an Fe foil and the second filter is a Co foil. The X-ray transmission inspection apparatus according to claim 1,
The element is Cr;
The first X-ray tube is a Cr target tube, and the second X-ray tube is an Fe target tube,
The first filter is a V foil, and the second filter is a Mn foil. The X-ray transmission inspection apparatus according to claim 1,
The element is Cr;
The first X-ray tube is a Mn target tube, and the second X-ray tube is an Fe target tube,
The first filter is a Cr foil, and the second filter is a Mn foil. The X-ray transmission inspection apparatus according to any one of claims 1 to 4,
The X-ray transmission inspection apparatus, wherein the arithmetic unit calculates the thickness of the element from the contrast image and the mass absorption coefficient and density of the element. Irradiating the sample with first characteristic X-rays having energy lower than the X-ray absorption edge of the element to be measured;
Irradiating the sample with a second characteristic X-ray having an energy higher than the X-ray absorption edge of the element;
Receiving the first transmitted X-ray when the first characteristic X-ray is transmitted through the sample, and detecting the intensity;
Receiving the second transmitted X-ray when the second characteristic X-ray is transmitted through the sample and detecting the intensity thereof;
Creating a first transmission image showing the detected intensity distribution of the first transmitted X-ray and a second transmission image showing the detected intensity distribution of the second transmitted X-ray; Obtaining a contrast image from the difference between the first transmission image and the second transmission image,
A first filter formed of an element having an X-ray absorption edge having an energy higher than that of the first characteristic X-ray is disposed between the sample and the first X-ray tube; An X-ray transmission characterized by disposing a second filter formed of an element having an X-ray absorption edge with higher energy than the second characteristic X-ray between the second X-ray tube. Inspection method.