JP7487690B2 - Material measuring device, material measuring method, electrode manufacturing device, and electrode manufacturing method - Google Patents

Description

The technical field of this specification relates to a material measuring device, a material measuring method, an electrode manufacturing device, and an electrode manufacturing method.

Electrodes for lithium ion secondary batteries are formed by laminating a positive electrode active material or a negative electrode active material on a metal foil current collector. In the manufacturing process for electrodes for lithium ion secondary batteries, a coating liquid containing a positive electrode active material or a negative electrode active material is applied to the metal foil current collector, and the coating liquid layer is dried. If necessary, the dried coating layer is pressed. Here, the coating liquid contains a positive electrode active material or a negative electrode active material and a binder. If necessary, the coating liquid also contains a conductive assistant and a thickener.

For this reason, technologies for determining the quality of raw materials, etc., have been developed. For example, Patent Document 1 discloses a technology in which hollow active material, which is a material for electrodes, is immersed in NMP and the nitrogen content is measured before and after immersion (claim 1 of Patent Document 1). In this case, absorptiometry is used (paragraph [0031] of Patent Document 1). It is disclosed that the quality of hollow active material is determined using the increment in the nitrogen content (paragraph [0010] of Patent Document 1).

JP 2018-6188 A

Generally, a small amount of solvent remains in the coating layer of the electrode after drying. Because the electrode is immersed in the electrolyte, it is preferable that no solvent remains in the coating layer. With the technology described in Patent Document 1, it is difficult to measure the amount of solvent contained in the coating layer of the electrode after coating and drying and to judge whether it is good or bad. The technology in Patent Document 1 is not a technology for measuring the solvent in the first place. Furthermore, even if it is necessary to judge whether the hollow active material is good or bad, it is necessary to extract a part of the electrode and take out the hollow active material from the coating layer of the electrode. In other words, it is difficult to perform non-destructive testing with the technology in Patent Document 1.

In addition, it is generally difficult to non-contact measure the amount of solvent present in a mixed material, not limited to electrodes of lithium-ion secondary batteries, in which a solvent and a solid material are mixed.

The problem that the technology of this specification aims to solve is to provide a material measuring device and a material measuring method, as well as an electrode manufacturing device and an electrode manufacturing method, that can non-contactly measure the amount of solvent present during drying in a mixed material in which a solvent and a solid material are mixed.

A material measuring device according to a first aspect includes a light emitting unit that irradiates light onto a mixed material, a light receiving unit that receives light from the mixed material, a thickness measuring unit that measures a thickness of the mixed material, and a control unit. The mixed material contains a solvent and a solid material. The solvent is a light-transmitting material having an absorbance peak. The light emitting unit irradiates light including a wavelength that is absorbed by the solvent. The control unit has a light intensity acquisition unit that acquires the light intensity of a first wavelength and the light intensity of a second wavelength of the light received by the light receiving unit, an absorbance difference calculation unit that calculates an absorbance difference that is the difference between the absorbance of the first wavelength and the absorbance of the second wavelength from the light intensity of the first wavelength and the light intensity of the second wavelength acquired by the light intensity acquisition unit, a first calibration curve storage unit that stores a first calibration curve that shows the relationship between the content or content rate of the solvent in the mixed material and the film thickness of the mixed material, a second calibration curve storage unit that stores a second calibration curve that shows the relationship between the content or content rate of the solvent in the mixed material and the absorbance difference, and a content calculation unit that calculates the content or content rate of the solvent from the first calibration curve and the second calibration curve. The light intensity at the first wavelength and the light intensity at the second wavelength of the light irradiated to the mixed material are equal. The difference between the first wavelength and the second wavelength is small enough that the reduction in light intensity due to light in a direction other than the light receiving direction at the first wavelength can be approximately equal to the reduction in light intensity due to light in a direction other than the light receiving direction at the second wavelength.

This material measuring device can non-contact measure the amount of solvent present in a mixed material in the process of drying, in which the solvent and solid material are mixed. Therefore, for example, there is no need to destroy the mixed material. In addition, the material measuring device can measure the content or content rate of the solvent in the mixed material in-line.

This specification provides a material measuring device and a material measuring method, as well as an electrode manufacturing device and an electrode manufacturing method, that can non-contactly measure the amount of solvent present during drying in a mixed material in which a solvent and a solid material are mixed.

1 is a diagram illustrating a schematic structure of a measurement object M10 according to a first embodiment. 1 is a schematic configuration diagram of a material measuring device 100 according to a first embodiment. 2 is a block diagram showing a control system of the material measuring apparatus 100 of the first embodiment. FIG. 4 is a graph illustrating the relationship between the amount of solvent and the absorbance difference in the first embodiment. 1 is a graph showing the absorbance of NMP. 1 is a graph showing the absorbance of water. 4 is a flowchart illustrating processing executed by a control unit 140 of the material measuring device 100 of the first embodiment. FIG. 2 is a schematic configuration diagram of a material measuring device 200 in a modified example of the first embodiment. FIG. 2 is a schematic configuration diagram of a material measuring device 300 in a modified example of the first embodiment. A diagram showing a stacked structure of positive electrode plates PE and negative electrode plates NE of the second embodiment. FIG. 11 is a schematic configuration diagram of an electrode manufacturing apparatus 1000 according to a second embodiment. 1 is a graph showing the change over time in film thickness and solvent amount in a test piece. 1 is a graph showing the relationship between the amount of solvent in a test strip and the absorbance difference. 1 is a graph showing the relationship between film thickness and absorbance difference and the amount of solvent. This is a graph showing suitable amounts for calculating the amount of solvent extracted from FIG. 14. 13 is a graph showing prediction accuracy when a calibration curve is used in which the film thickness and the absorbance difference are two explanatory variables and the amount of solvent is the response variable. 13 is a graph showing prediction accuracy when a first calibration curve is used in a first period, in which the film thickness is an explanatory variable and the amount of solvent is a response variable, and a second calibration curve is used in a second period, in which the absorbance difference is an explanatory variable and the amount of solvent is a response variable.

Specific embodiments are described below using examples of a material measuring device, a material measuring method, and an electrode manufacturing device and an electrode manufacturing method. However, the technology of this specification is not limited to these embodiments.

First Embodiment
1. Measurement Object 1-1. Mixed Material Fig. 1 is a diagram showing a schematic structure of a measurement object M10 in the first embodiment. The measurement object M10 has a base material M11 and a mixed material M12. The base material M11 is for supporting the mixed material M12. The mixed material M12 has a solvent M12a and a solid material M12b.

Solvent M12a is the material that is the target of measurement by material measuring device 100. Solvent M12a is a light-transmitting material that has an absorbance peak. The absorbance of solvent M12a is wavelength-dependent. Solid material M12b is a non-light-transmitting particle. Solvent M12a exists around solid material M12b. Solvent M12a and solid material M12b are stacked in layers in this mixed state. Here, light-transmitting property refers to the property of transmitting light of at least some wavelengths.

Figure 1 shows the state when light is irradiated onto the object to be measured M10. As shown in Figure 1, light L1 is reflected by solid material M12b on the surface of mixed material M12. Light L2 is repeatedly reflected inside mixed material M12 and reaches the depths of mixed material M12 before proceeding to the outside of mixed material M12. Light L2 passes through the solvent M12a while being reflected by solid material M12b inside mixed material M12.

1-2. Drying In the first embodiment, the measurement target M10 gradually dries. That is, the solvent M12a evaporates and decreases over time. The material measuring apparatus 100 measures the content or content rate of the solvent M12a that is decreasing.

The thickness of the mixed material M12 of the measurement object M10 changes depending on the stage of drying. The mixed material M12 of the measurement object M10 dries through a first period and a second period. The second period is the period following the first period, and the first period and the second period are continuous.

The first period is a period during which the film thickness of the mixed material M12 changes. During the first period, the solvent M12a is mainly responsible for the film thickness of the mixed material M12. During the first period, the solvent M12a evaporates, and the film thickness of the mixed material M12 decreases accordingly. In this way, during the first period, the film thickness of the mixed material M12 changes due to the reduction in the solvent M12a.

The second period is a period in which the film thickness of the mixed material M12 changes very little. In the second period, most of the solvent M12a of the mixed material M12 has evaporated. In the second period, the solid material M12b is mainly responsible for the film thickness of the mixed material M12. Therefore, although the solvent M12a evaporates in the second period, the film thickness of the mixed material M12 changes very little. In the second period, the amount of change in film thickness due to the reduction in the solvent is less than in the first period.

2 is a schematic diagram of a material measuring device 100 according to a first embodiment. The material measuring device 100 can measure the amount of translucent material present in a mixed material M12 in which a plurality of materials are mixed. The material measuring device 100 has a light emitting unit 110, a light receiving unit 120, a film thickness measuring unit 130, a control unit 140, and rolls R1 and R2.

The light emitting unit 110 is a light irradiating unit that irradiates light onto the mixed material M12 of the measurement target M10. The light emitting unit 110 irradiates light having a broad wavelength distribution. It is preferable that the light emitting unit 110 is capable of irradiating light locally. The light emitting unit 110 irradiates light including a wavelength that is absorbed by the solvent M12a.

The light receiving unit 120 receives light from the mixed material M12 of the measurement object M10. The light receiving unit 120 can transmit information about the received light to the control unit 140. It is preferable that the light receiving unit 120 be capable of separating the received light into wavelengths. It is preferable that the light receiving unit 120 is, for example, a spectrophotometer.

The film thickness measuring unit 130 can non-contactly measure the film thickness of the mixed material M12 of the measurement object M10 transported by the rolls R1 and R2. The film thickness measuring unit 130 is, for example, a laser displacement meter. The rolls R1 and R2 may be free rolls or may be rotationally driven by a motor or the like.

The control unit 140 measures the amount of solvent M12a present in the measurement object M10 based on the light received by the light receiving unit 120. The control unit 140 can acquire information on the light received by the light receiving unit 120 from the light receiving unit 120. The control unit 140 may also control the light emitting state of the light emitting unit 110.

3. Control system Fig. 3 is a block diagram showing a control system of the material measuring device 100 of the first embodiment. As shown in Fig. 3, the control unit 140 has a material information acquisition unit 141, a film thickness acquisition unit 142, a received light information acquisition unit 143, a light intensity acquisition unit 144, an absorbance difference calculation unit 145, a content calculation unit 146, a calibration curve storage unit 147, a period determination unit 148, and a material information storage unit 149. The calibration curve storage unit 147 has a first calibration curve storage unit 147a and a second calibration curve storage unit 147b.

The material information acquisition unit 141 acquires information about what materials are contained in the mixed material M12 of the measurement target M10.

The film thickness acquisition unit 142 acquires the film thickness of the mixed material M12 measured by the film thickness measurement unit 130.

The received light information acquisition unit 143 acquires information on the spectrum of the light received by the light receiving unit 120.

The light intensity acquisition unit 144 acquires the light intensity I (λ1) of the first wavelength λ1 and the light intensity I (λ2) of the second wavelength λ2 from the light received by the light receiving unit 120. Specifically, the light intensity acquisition unit 144 selects the first wavelength λ1 and the second wavelength λ2 from the spectrum of the light acquired by the received light information acquisition unit 143, and acquires the light intensity I (λ1) of the first wavelength λ1 and the light intensity I (λ2) of the second wavelength λ2.

The absorbance difference calculation unit 145 calculates the absorbance difference ΔA. The absorbance difference calculation unit 145 calculates the absorbance difference ΔA (=A1-A2), which is the difference between the absorbance A1 of the first wavelength λ1 and the absorbance A2 of the second wavelength λ2, from the light intensity I (λ1) of the first wavelength λ1 and the light intensity I (λ2) of the second wavelength λ2 acquired by the light intensity acquisition unit 144.

In the first period in which the film thickness of the mixed material M12 changes, the content calculation unit 146 calculates the content or content rate of the solvent M12a from the film thickness of the mixed material M12 and the first calibration curve stored in the first calibration curve storage unit 147a. In the second period in which the film thickness of the mixed material M12 hardly changes, the content calculation unit 146 calculates the content or content rate of the solvent M12a from the absorbance difference ΔA calculated by the absorbance difference calculation unit 145 and the second calibration curve stored in the second calibration curve storage unit 147b. The second calibration curve is prepared according to the film thickness range, as described below. The content calculation unit 146 calculates the content or content rate of the solvent using the second calibration curve according to the film thickness of the mixed material M12.

The first calibration curve memory unit 147a stores the first calibration curve. The first calibration curve shows the relationship between the content of solvent M12a in the mixed material M12 and the film thickness of the mixed material M12. The first calibration curve is, for example, a calibration curve determined by regression analysis in which the objective variable is the content of solvent M12a and the explanatory variable is the film thickness of the mixed material M12.

The second calibration curve memory unit 147b stores the second calibration curve. The second calibration curve shows the relationship between the content of the solvent M12a in the mixed material M12 and the absorbance difference ΔA. The second calibration curve is, for example, a calibration curve determined by regression analysis in which the target variable is the content of the solvent M12a and the explanatory variable is the absorbance difference ΔA. The second calibration curve is prepared for each range of the film thickness of the mixed material M12. For example, the second calibration curve for a film thickness of 90 μm or more and less than 100 μm, and the second calibration curve for a film thickness of 80 μm or more and less than 90 μm are stored in the second calibration curve memory unit 147b. Of course, the interval width of the numerical range of the film thickness may be changed.

The period determination unit 148 determines whether the mixed material M12 is in the first period or the second period from the film thickness of the mixed material M12 acquired by the film thickness acquisition unit 142. The period determination unit 148 determines that the mixed material M12 is in the first period when the film thickness of the mixed material M12 is equal to or greater than a predetermined threshold, and determines that the mixed material M12 is in the second period when the film thickness of the mixed material M12 is less than the predetermined threshold.

The material information storage unit 149 stores the types of materials for the calibration curves stored by the first calibration curve storage unit 147a and the second calibration curve storage unit 147b. The material information storage unit 149 may also store the values of the first wavelength λ1 and the second wavelength λ2 that the light intensity acquisition unit 144 should select depending on the type of mixed material M12.

4. Measurement principle 4-1. Beer-Lambert law The Beer-Lambert law is used. The Beer-Lambert law is expressed by the following formula (1).
I = I ₀ exp(-εlc) ……… (1)
I: Intensity of transmitted light
I ₀ : Intensity of incident light
ε: Molar absorption coefficient ( ^m2 /mol)
l: optical path length (m)
c: Concentration of the substance through which light passes (mol/m ³ )
By taking the common logarithm of equation (1), the following equation (2) is obtained.
A = -log(I/I ₀ ) = εlc ... (2)
A: absorbance

The Beer-Lambert law states that the proportion of light intensity absorbed by a substance when light passes through it is constant. Furthermore, from equation (2), absorbance A is the product of the molar absorption coefficient ε, the optical path length l, and the concentration c of the substance through which the light passes. The molar absorption coefficient ε is a value specific to a substance and depends on the wavelength of light. Absorbance A can be measured in advance and depends on the wavelength of light. Therefore, if the optical path length l is determined from equation (2), the concentration of the substance through which the light passes can be found.

As explained in FIG. 1, light is reflected and scattered in the measurement object M10 containing the mixed material M12. In this case, there is reflected light and scattered light that does not enter the light receiving unit 120, and the intensity of the light acquired by the light receiving unit 120 decreases accordingly. Because the apparent absorbance increases in this way, the Beer-Lambert law cannot be applied as is. In addition, it is difficult to determine the optical path length l.

Two-wavelength spectrophotometry By adding the scattering term As to equation (2) and substituting the two wavelengths λ1 and λ2, we obtain the following equations (3) and (4).
A(λ1)=-log(I(λ1)/I ₀ )=ε(λ1)lc+As(λ1)
………(3)
A(λ2)=-log(I(λ2)/ _I0 )=ε(λ2)lc+As(λ2)
………(4)

Considering that the two wavelengths λ1 and λ2 are relatively close to each other, and approximating that As(λ1) is equal to As(λ2), the difference between equations (3) and (4) is obtained as follows:
ΔA = A (λ1) - A (λ2)
= -log(I(λ1)/I(λ2))
= (ε(λ1) - ε(λ2))lc ……… (5)
ΔA: absorbance difference

Even if equation (5) is used, it is difficult to determine the optical path length l, just as with the Beer-Lambert law.

4-3. Second calibration curve Since the optical path length l is unknown, the second calibration curve is used instead. That is, the concentration of the solvent M12a in the mixed material M12 is calculated using formula (5) and the second calibration curve. For this purpose, first, two wavelengths λ1 and λ2 are selected. Then, the absorbance difference ΔA=-log(I(λ1)/I(λ2)) of a sample prepared in advance is measured. Here, the absorbance difference ΔA=-log(I(λ1)/I(λ2)) does not include the intensity I ₀ of the incident light. Therefore, the intensity I ₀ of the incident light may remain unknown. In addition, since the explanatory variable of the second calibration curve is the absorbance difference ΔA, the absorbance A1 (λ1) of the first wavelength λ1 and the absorbance A2 (λ2) of the second wavelength λ2 may remain unknown.

Fig. 4 is a graph illustrating the relationship between the amount of solvent and the absorbance difference ΔA in the first embodiment. The horizontal axis of Fig. 4 is the amount of solvent (wt%). The vertical axis of Fig. 4 is the absorbance difference ΔA = -log (I (λ1) / I (λ2)). In formula (5), the unit of concentration c of the substance through which light transmits is (mol/m ³ ), but if the type and approximate amount of mixed material M12 are known, the unit of concentration can be easily converted to (wt%).

As shown in Figure 4, the absorbance difference ΔA decreases as the amount of solvent increases. Furthermore, the relationship between the amount of solvent and the absorbance difference ΔA can be approximated by a straight line.

The second calibration curve can be derived in advance and stored.

4-4. Examples of wavelengths 4-4-1. NMP
Figure 5 is a graph showing the absorbance of NMP. The horizontal axis of Figure 5 is the wavelength of light. The vertical axis of Figure 5 is absorbance. Here, NMP is N-methyl-2-pyrrolidone. This absorbance graph is substance specific. That is, if the absorbance of the same type of material is measured, a similar graph will be obtained.

As shown in Figure 5, there are peaks near 1720 nm and near 2280 nm. In wavelength regions where the absorbance is close to zero, NMP transmits almost all of the light at that wavelength. In the vicinity of the above peaks, NMP absorbs light in that wavelength region.

For this reason, the two wavelengths selected are one close to the peak and one with an absorbance close to zero. For example, 1713 nm is selected as wavelength λ1, and 1823 nm is selected as wavelength λ2. As shown in Figure 5, light with a wavelength of 1713 nm is absorbed to some extent by NMP, and light with a wavelength of 1823 nm is hardly absorbed by NMP. By selecting two wavelengths λ1 and λ2 with different absorbance in this way, the measurement accuracy is improved.

In principle, a wavelength near 2280 nm may be selected as the wavelength to be measured. However, elements capable of measuring light with a long wavelength of 2280 nm with high accuracy are generally expensive. For this reason, it is not practical to apply such elements to an in-line measurement device.

4-4-2. Water Figure 6 is a graph showing the absorbance of water. The horizontal axis of Figure 6 is the wavelength of light. The vertical axis of Figure 6 is the absorbance. For water, peaks exist near 1450 nm and near 1900 nm. Therefore, for example, 1450 nm can be selected as the wavelength λ1 and 1350 nm can be selected as the wavelength λ2.

4-4-3. Wavelength Selection As described above, the wavelength can be freely selected according to the absorption spectrum of the solvent M12a to be measured. However, the first wavelength of the two wavelengths must be selected as a wavelength with a non-zero absorbance. The second wavelength of the two wavelengths preferably has an absorbance close to zero. For example, the first wavelength may be a wavelength near the peak, and the second wavelength may be a wavelength other than the peak.

Here, the light-emitting unit 110 needs to irradiate light that includes a wavelength that is absorbed by the solvent M12a. In addition, the absorbance A1 of the first wavelength and the absorbance A2 of the second wavelength need to be different. When ΔA = 0 in formula (5), it is theoretically impossible to measure the concentration of the solvent M12a.

5. Material measurement method 5-1. S101
7 is a flowchart for explaining the process executed by the control unit 140 of the material measuring device 100 of the first embodiment. First, the material information acquisition unit 141 acquires information on the mixed material M12 (S101). In this way, the material information acquiring unit 141 acquires information on the materials contained in the mixed material M12. That is, the material information acquiring unit 141 acquires information that the mixed material M12 contains the solvent M12a and the solid material M12b. For example, if the solvent M12a is water, the material information acquisition unit 141 acquires information that the solvent M12a is water.

5-2. S102
Next, the film thickness acquisition unit 142 acquires the film thickness of the mixed material M12 measured by the film thickness measurement unit 130 (S102).

5-3. S103
Next, the period determination unit 148 determines whether the period is the first period or the second period (S103). When the film thickness of the mixed material M12 is equal to or greater than a predetermined threshold value, the period determination unit 148 If the thickness of the mixed material M12 is less than a predetermined threshold value (S103: No), the period determination unit 148 determines that the mixed material M12 is in the first period and proceeds to S104. ), it is determined that the mixed material M12 is in the second period, and the process proceeds to S105.

5-4. S104
The content calculation unit 146 calculates the content of the solvent M12a using the first calibration curve (S104). The first calibration curve is a relationship between the content of the solvent M12a in the mixed material M12 and the film thickness of the mixed material M12. The content calculation unit 146 calculates the content of the solvent from the film thickness of the mixed material M12 and the first calibration curve.

5-5. S105
Next, the light emitter 110 irradiates the mixed material M12 containing the solvent M12a and the solid material M12b with light having a wavelength that is absorbed by the solvent M12a, and the light receiver 120 receives the light from the mixed material M12. The received light information acquiring unit 143 acquires information about the light received by the light receiving unit 120 (S105). This light information includes information about the light intensity for each wavelength.

5-6. S106
Next, the light intensity acquisition unit 144 acquires the light intensity. Specifically, the light intensity acquisition unit 144 acquires the light intensity based on the material information acquired by the material information acquisition unit 141. Then, the light intensity acquisition unit 144 selects the first wavelength λ1 and the second wavelength λ2. At that time, the light intensity acquisition unit 144 refers to the information stored in the material information storage unit 149. The light intensity acquisition unit 144 acquires the light intensity I(λ1) of the first wavelength λ1 and the light intensity I(λ2) of the second wavelength λ2 of the light received by the light receiving unit 120. (S106).

5-7. S107
Next, the absorbance difference calculation unit 145 calculates the absorbance difference ΔA (S107). The absorbance difference calculation unit 145 calculates the absorbance difference ΔA, which is the difference between the absorbance A1 of the first wavelength λ1 and the absorbance A2 of the second wavelength λ2, from the light intensity I(λ1) of the first wavelength λ1 and the light intensity I(λ2) of the second wavelength λ2 acquired by the light intensity acquisition unit 144.

5-8. S108
The content calculation unit 146 calculates the content of the solvent M12a by using the second calibration curve (S108). The content of the solvent is calculated from the second calibration curve showing the relationship between the content of the solvent M12a in the mixed material M12 and the absorbance difference ΔA. The second calibration curve shows the relationship between the content of the solvent M12a in the mixed material M12 and the absorbance difference ΔA. The second calibration curve is prepared for each numerical range of the thickness of the mixed material M12. Therefore, the content calculation unit 146 calculates the content of the mixed material M12 based on the thickness of the mixed material M12 acquired by the thickness acquisition unit 142. A corresponding second calibration curve is extracted, and the content of the solvent M12a is calculated using the second calibration curve. The amount calculation unit 146 picks up the second calibration curve that includes 73 μm. For example, if there is a second calibration curve with a film thickness range of 70 μm or more and less than 75 μm, the content calculation unit 146 uses that second calibration curve.

6. Effects of the First Embodiment The material measuring device 100 can calculate the content of the solvent M12a in the mixed material M12, which is a mixture of the solvent M12a and the solid material M12b, without contact. In addition, when the mixed material M12 dries, the content of the solvent M12a in the mixed material M12 can be calculated regardless of the degree of drying. In particular, the content of the solvent M12a can be calculated with high accuracy for the mixed material M12, which is dried so that the film thickness of the mixed material M12 hardly changes. In the first period, the solvent M12a is the main material that determines the film thickness, and in the second period, the solid material M12b is the main material that determines the film thickness. In the first period, the amount of the solvent M12a is calculated based on the film thickness value. Therefore, the measurement accuracy of the material measuring device 100 is high.

7. Modification 7-1. Hyperspectral camera FIG. 8 is a schematic diagram of a material measuring device 200 in a modification of the first embodiment. The material measuring device 200 has a light emitting unit 210, a light receiving unit 220, and a control unit 140. The light emitting unit 210 is, for example, a halogen lamp. The light receiving unit 220 is, for example, a hyperspectral camera. The hyperspectral camera can separate light into wavelengths and capture the light. The material measuring device 200 can measure the content of the solvent M12a in the same manner as the material measuring device 100. In order to measure various materials as the measurement object M10, it is preferable that the light emitting unit 110 can irradiate light of a wide range of wavelengths and the light receiving unit 120 can receive light of a wide range of wavelengths. It is also preferable that the light receiving unit 120 can resolve light of a wide range of wavelengths.

7-2. Two-Wavelength Band Prism Spectroscopic Camera FIG. 9 is a schematic diagram of a material measuring device 300 in a modified example of the first embodiment. The material measuring device 300 has a light emitting unit 210, a light receiving unit 320, and a control unit 140. The light receiving unit 320 has, for example, a two-wavelength band prism spectroscopic camera and a bandpass filter. When the type of the solvent M12a is determined to be, for example, water, the two wavelengths used for measurement can be determined in advance. In this case, the absorbance A1 of the first wavelength λ1 and the absorbance A2 of the second wavelength λ2 can be measured by using the two-wavelength band prism spectroscopic camera and the bandpass filter. Two cameras may be used instead of the two-wavelength band prism spectroscopic camera.

The period determination unit 148 may determine that the mixed material M12 is in the first period when the amount of change in film thickness of the mixed material M12 is equal to or greater than a predetermined threshold, and may determine that the mixed material M12 is in the second period when the amount of change in film thickness of the mixed material M12 is less than the predetermined threshold.

7-4. State Determination Unit The material measuring device 100 may have a state determination unit instead of the period determination unit 148. The state determination unit determines whether the mixed material M12 is in the first state or the second state. The first state corresponds to a first period of the mixed material M12. The second state corresponds to a second period of the mixed material M12. The state determination unit does not need to confirm the transition from the first state to the second state. Whether the mixed material M12 is in the first state or the second state is determined from the amount of change in the film thickness of the mixed material M12. In this case, a separate threshold value may be set.

It is preferable that the calibration curve storage unit 147 stores calibration curves for a large number of materials. This is because more materials can be measured. It is preferable that the second calibration curve storage unit 147b stores second calibration curves for a plurality of combinations of the solvent M12a and the solid material M12b in the mixed material M12.

The second calibration curve used by the material measuring device 100 is not a second calibration curve for only the solvent M12a, but a second calibration curve for the mixed material M12 having the solvent M12a and the solid material M12b.

7-6. Content The material measuring device 100 can measure the content of the solvent M12a. To do so, the content calculation unit 146 may acquire information on the material from the material information acquisition unit 141 or the material information storage unit 149. The content calculation unit 146 may calculate the content of the solvent M12a from the mass ratio of the materials in the mixed material M12. The second calibration curve storage unit 147b may store a second calibration curve determined by a regression analysis in which the content of the solvent M12a is the objective variable and the absorbance difference ΔA is the explanatory variable. The second calibration curve storage unit 147b stores a second calibration curve determined by a regression analysis in which the content or content of the solvent M12a is the objective variable and the absorbance difference ΔA is the explanatory variable. The content calculation section 146 can calculate the content or content rate of the solvent from the absorbance difference ΔA calculated by the absorbance difference calculation section 145 and the second calibration curve stored in the second calibration curve storage section 147b.

7-7. Calibration curve The calibration curve may be derived by a method other than regression analysis. A machine learning model may be used to derive the calibration curve.

7-8. Substrate The material measuring device 100 can measure the mixed material M12 that does not contain a substrate. Therefore, the substrate M11 is not necessarily required.

7-9. Combinations The above modifications may be freely combined.

Second Embodiment
A second embodiment will be described. In the second embodiment, an electrode manufacturing apparatus measures the residual solvent in an electrode. That is, in the second embodiment, the measurement target is an electrode of a lithium ion secondary battery.

1. Electrodes 1-1. Electrode structure The electrodes are positive and negative plates arranged alternately with separators between them.

Figure 10 is a diagram showing the laminated structure of the positive electrode plate PE and the negative electrode plate NE of the second embodiment. The positive electrode plate PE is a positive electrode plate of a lithium ion secondary battery. The positive electrode plate PE has a current collector P1 and a coating layer P2. The current collector P1 has a first surface P1a and a second surface P1b. The second surface P1b is the surface opposite to the first surface P1a. The coating layer P2 is formed on the first surface P1a and the second surface P1b of the current collector P1.

The current collector P1 is a metal foil. The current collector P1 is, for example, an aluminum foil. The coating layer P2 contains a positive electrode active material, a conductive assistant, and a binder. The positive electrode active material is, for example, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, or a ternary material. The conductive assistant is, for example, carbon black or acetylene black. The binder is, for example, polyvinylidene fluoride (PVdF) or styrene-butadiene rubber (SBR).

The negative electrode plate NE is a negative electrode plate of a lithium ion secondary battery. The negative electrode plate NE has a current collector N1 and a coating layer N2. The current collector N1 has a first surface N1a and a second surface N1b. The second surface N1b is the surface opposite the first surface N1a. The coating layer N2 is formed on the first surface N1a and the second surface N1b of the current collector N1.

The current collector N1 is a metal foil. The current collector N1 is, for example, a copper foil. The coating layer N2 contains a negative electrode active material and a binder. The negative electrode active material is, for example, a carbon material such as graphite. The binder is, for example, polyvinylidene fluoride (PVdF) or styrene-butadiene rubber (SBR).

The thickness of the coating layer P2 is, for example, 30 μm or more and 200 μm or less. The thickness of the coating layer P2 in an in-vehicle lithium-ion secondary battery is, for example, 35 μm or more and 75 μm or less. The thickness of the coating layer N2 on the negative electrode plate NE is approximately the same as the thickness of the coating layer P2 on the positive electrode plate PE. Of course, the thickness of the coating layer N2 on the negative electrode plate NE may be different from the thickness of the coating layer P2 on the positive electrode plate PE.

1-2. Residual Solvent The positive electrode plate PE is manufactured by applying a slurry in which a positive electrode active material and the like are dispersed in a solvent to a current collector P1 and then drying the slurry. The negative electrode plate NE is manufactured by applying a slurry in which a negative electrode active material and the like are dispersed in a solvent to a current collector N1 and then drying the slurry. However, depending on the drying conditions and the drying environment, there is a risk that a small amount of solvent will remain in the coating layer P2 of the positive electrode plate PE and the coating layer N2 of the negative electrode plate NE.

In a lithium-ion secondary battery, the positive electrode plate PE and the negative electrode plate NE are immersed in an electrolyte solution or the like. For this reason, it is preferable that such residual solvent is not present. In reality, as mentioned above, trace amounts of solvent remain in the coating layer P2 of the positive electrode plate PE and the coating layer N2 of the negative electrode plate NE.

For quality control of lithium-ion secondary batteries, it is preferable to measure the residual solvent in the coating layer P2 of the positive electrode plate PE and the coating layer N2 of the negative electrode plate NE. The solvent of the coating liquid containing the active material, etc. is, for example, water or NMP. These solvents correspond to the solvent M12a. The positive electrode active material and the negative electrode active material correspond to the solid material M12b. The coating layer P2 and the coating layer N2 are a type of mixed material M12 containing the solvent M12a and the solid material M12b.

2. Electrode Manufacturing Apparatus Fig. 11 is a schematic diagram of an electrode manufacturing apparatus 1000 according to a second embodiment. The electrode manufacturing apparatus 1000 is a coating and drying apparatus that applies a coating layer P2 to a current collector P1 and dries the applied layer. The electrode manufacturing apparatus 1000 includes a coating section 1100, a drying furnace 1200, and a material measuring apparatus 100. The material measuring apparatus 100 has the same configuration as that of the first embodiment.

The coating unit 1100 applies a coating layer to the first surface P1a or the second surface P1b of the current collector P1. The coating unit 1100 has a coating die 1110 and a backup roll 1120. The coating die 1110 applies a coating liquid to the current collector P1, which is supported and transported by the backup roll 1120. The coating liquid contains an active material and a binder.

The drying furnace 1200 is a drying section that dries the coating layer P2 on the current collector P1. The drying furnace 1200 has an air blowing section 1210. The air blowing section 1210 is capable of blowing hot air alternately onto the current collector P1 from above and below, which are perpendicular to the transport direction of the current collector P1.

The light emitting unit 110 irradiates light onto the coating layer P2. The light receiving unit 120 receives light from the coating layer P2. The content calculation unit 146 of the control unit 140 then calculates the content or content rate of the solvent M12a from the film thickness of the coating layer P2 measured by the film thickness measurement unit 130, the absorbance difference ΔA calculated by the absorbance difference calculation unit 145, and the calibration curve stored in the calibration curve memory unit 147.

The electrode manufacturing device 1000 can manufacture the negative electrode plate NE in a similar manner.

3. Manufacturing method of an electrode The coating die 1110 of the coating unit 1100 applies a coating liquid to a first surface P1a of the current collector P1 that is supported and transported by a backup roll 1120. The air blower 1210 of the drying furnace 1200 dries the coating layer P2 on the current collector P1.

Next, the film thickness measuring unit 130 measures the film thickness of the coating layer P2. Then, the light emitting unit 110 of the material measuring device 100 irradiates light onto the coating layer P2 on the first surface P1a side of the current collector P1. The light receiving unit 120 receives the light from the coating layer P2. The control unit 140 measures the amount of residual solvent present.

A coating layer P2 is also formed on the second surface P1b, and measurements are performed using the material measuring device 100. This produces a positive electrode plate PE. Similarly, a negative electrode plate NE is also produced.

If the solvent content or percentage content is equal to or greater than a predetermined threshold, the electrode having that coating layer is determined to be defective, and if the solvent content or percentage content is less than a predetermined threshold, the electrode having that coating layer is determined to be non-defective.

Then, the positive electrode plates PE and negative electrode plates NE that are determined to be good products are sent to the next process, and the positive electrode plates PE and negative electrode plates NE that are determined to be defective are not sent to the next process.

4. Effects of the Second Embodiment The electrode manufacturing apparatus 1000 of the second embodiment can manufacture the positive electrode plate PE and the negative electrode plate NE, and can measure the content or content rate of the residual solvent inside the coating layer P2 and the coating layer N2. The electrode manufacturing apparatus 1000 can measure the residual solvent in the positive electrode plate PE and the negative electrode plate NE in a non-destructive and non-contact manner.

5. Modification 5-1. Maximum value of residual solvent content or content rate The electrode manufacturing apparatus 1000 has information on the positions of the positive electrode plate PE and the negative electrode plate NE and the content or content rate of the residual solvent at those positions. Therefore, the maximum amount of residual solvent can be used to determine whether the positive electrode plate PE and the negative electrode plate NE are good or bad. In this case, if the maximum value of the content or content rate of the residual solvent is equal to or greater than a predetermined threshold value, the positive electrode plate PE or the negative electrode plate NE is determined to be defective, and if the maximum value of the content or content rate of the residual solvent is less than the predetermined threshold value, the positive electrode plate PE or the negative electrode plate NE is determined to be good.

5-2. Re-Drying When the content or maximum value of the content rate of the residual solvent is equal to or greater than a predetermined threshold value, the positive electrode plate PE or the negative electrode plate NE may be dried again.

5-3. Partial Removal of Positive and Negative Electrode Plates The electrode manufacturing apparatus 1000 can obtain information on the relationship between the position of the foil-like positive electrode plate PE and the amount of residual solvent present. Therefore, the positive electrode plate PE and the negative electrode plate NE may be partially removed in portions where there is a large amount of residual solvent.

5-4. Resetting of Drying Furnace Various settings of the drying furnace 1200, such as the dew point or furnace temperature inside the drying furnace 1200, and the temperature of the hot air blown out by the blower 1210, may be changed. In other words, the measurement results by the material measuring device 100 are fed back to the various settings of the drying furnace 1200. This makes it possible to make the quality of the positive electrode plates PE and negative electrode plates NE manufactured by the electrode manufacturing device 1000 less susceptible to the effects of weather, etc.

5-5. Backup Roll The coating unit does not have to be of a type that coats the current collector P1 on the backup roll 1120. In addition, the drying furnace does not have to be of a type that blows hot air onto the coating liquid on the current collector P1. The coating unit and the drying furnace may be of a type other than those in the second embodiment.

5-6. Single-sided coating The positive and negative electrode plates may be single-sided coated instead of double-sided coated. The material measuring device 100 can measure the residual solvent in the single-sided coated electrodes in the same manner. The coating unit applies a coating layer to at least one of the current collector P1 having a first surface P1a and a second surface P1b.

5-7. Combinations The above modifications may be freely combined.

(Combination of embodiments)
The first and second embodiments may be freely combined, including modified examples.

(experiment)
1. Preparation of test pieces A positive electrode plate was prepared. An aluminum plate with a thickness of 5 mm was used as a current collector. Since the aluminum plate was thick enough, the effects of bending and tilting were eliminated as much as possible in the experiment. The slurry is a material that becomes the coating layer of the positive electrode. The slurry contains a positive electrode active material, a conductive assistant, a binder, and a solvent. Lithium nickel-manganese-cobalt oxide (LiNiMnCoO ₂ ) was used as the positive electrode active material. Acetylene black was used as the conductive assistant. Polyvinylidene fluoride (PVdF) was used as the binder. NMP was used as the solvent. The solid content concentration of the positive electrode slurry was 53.5 wt%.

First, a solution was prepared by adding PVdF to NMP. Next, acetylene black was added to the solution and mixed. The mixture was then stirred using a planetary centrifugal mixer. Lithium nickel-manganese-cobalt oxide was added to the mixture and stirred to produce a slurry. The slurry was applied to an aluminum plate.

2. Measurement method A halogen lamp was used as the light-emitting unit, and a hyperspectral camera was used as the light-receiving unit. A displacement sensor was used as the film thickness measuring unit. The stage on which the test piece was placed was designed to be movable between a position where the light-receiving unit could receive light from the test piece, and a position where the film thickness measuring unit could measure the film thickness of the test piece. The test piece was irradiated with light from the halogen lamp and was dried by applying heat. Therefore, the test piece was placed near the halogen lamp at regular intervals.

3. Drying Profile FIG. 12 is a graph showing the change over time in film thickness and solvent amount in the test piece. The horizontal axis of FIG. 12 is time. The vertical axis of FIG. 12 is film thickness or solvent amount. The dashed line in FIG. 12 indicates the film thickness of the test piece. The dotted line in FIG. 12 indicates the solvent amount. As shown in FIG. 12, the film thickness of the test piece becomes thinner as the solvent evaporates, and becomes constant at a predetermined film thickness. In this experiment, the film thickness of the test piece became constant at about 70 μm. Meanwhile, the solvent amount continued to decrease even after the decrease in film thickness stopped. In this experiment, the film thickness of the test piece became almost constant when the solvent amount was about 18 wt % or less.

4. Relationship between absorbance difference and solvent amount FIG. 13 is a graph showing the relationship between the solvent amount and absorbance difference in the test piece. The horizontal axis of FIG. 13 is the solvent amount. The vertical axis of FIG. 13 is the absorbance difference. In FIG. 13, a wavelength of 1713 nm and a wavelength of 1823 nm are adopted as two wavelengths, and the absorbance difference is measured. In addition, a simple regression analysis was performed on the relationship between the absorbance difference and the solvent amount in the latter stage of drying. The explanatory variable is the absorbance difference, and the objective variable is the solvent amount. As shown in FIG. 13, it is believed that a highly accurate calibration curve was obtained. Note that in FIG. 13, the film thickness of the test piece is not taken into account.

5. First calibration curve and second calibration curve FIG. 14 is a graph showing the relationship between the film thickness and absorbance difference and the amount of solvent. The horizontal axis of FIG. 14 is the amount of solvent (wt%). The vertical axis of FIG. 14 is the absorbance difference or film thickness. The amount of solvent gradually decreases due to drying. That is, in FIG. 14, the state shifts from the right side of the horizontal axis to the left side with the passage of time. When actually focusing on the film thickness, the film thickness decreases linearly in the first half of drying, and the film thickness hardly changes in the second half of drying.

In the first half of the drying process, the absorbance difference rises and then falls as the drying progresses. In the second half of the drying process, the absorbance difference rises linearly as the drying progresses.

As shown in Figure 14, in the first half of the drying, the film thickness changes linearly, and the absorbance difference rises once and then falls. Therefore, in the first half of the drying, there is no one-to-one correspondence between the absorbance difference and the amount of solvent. In contrast, there is a one-to-one correspondence between the film thickness and the amount of solvent. In other words, in the first half of the drying, there is a one-to-one correspondence between the film thickness and the amount of solvent, which indicates that the film thickness is a suitable indicator for calculating the amount of solvent.

As shown in Figure 14, in the latter half of the drying, the film thickness is almost constant regardless of the amount of solvent. As the absorbance difference increases, the amount of solvent decreases. Thus, in the latter half of the drying, there is no one-to-one correspondence between the film thickness and the amount of solvent. However, there is a one-to-one correspondence between the absorbance difference and the amount of solvent. This shows that in the latter half of the drying, the absorbance difference and the amount of solvent are suitable indicators for calculating the amount of solvent.

Figure 15 is a graph showing suitable amounts for calculating the amount of solvent extracted from Figure 14. The horizontal and vertical axes in Figure 15 are the same as those in Figure 14. As shown in Figure 15, in the first period, it is recommended to use the first calibration curve showing the relationship between film thickness and amount of solvent. In the second period, it is recommended to use the second calibration curve showing the relationship between absorbance difference and amount of solvent.

6. Calculation of Solvent Amount The amount of solvent was calculated using two methods. In the first method, a calibration curve is used in which the film thickness and absorbance difference are the explanatory variables and the amount of solvent is the objective variable. In the second method, the method of the first embodiment is used. That is, in the first period, a first calibration curve is used in which the film thickness is the explanatory variable and the amount of solvent is the objective variable. In the second period, a second calibration curve is used in which the absorbance difference is the explanatory variable and the amount of solvent is the objective variable.

Figure 16 is a graph showing the prediction accuracy when using a calibration curve with film thickness and absorbance difference as explanatory variables and solvent amount as the objective variable. The horizontal axis of Figure 16 is the actual measured value of the solvent amount (wt%). The vertical axis of Figure 16 is the predicted value of the solvent amount. The leave-one-out method was used to calculate the predicted value. The mean square error in this case was 5.99 wt%.

Figure 17 is a graph showing the prediction accuracy when using a first calibration curve with film thickness as the explanatory variable and solvent amount as the objective variable in the first period, and using a second calibration curve with absorbance difference as the explanatory variable and solvent amount as the objective variable in the second period. The horizontal axis of Figure 17 is the actual measured value (wt%) of the solvent amount. The vertical axis of Figure 17 is the predicted value of the solvent amount. The leave-one-out method was used to calculate the predicted value. The mean square error in this case was 1.39 wt%.

7. Summary of the experiment When the first calibration curve, which uses the film thickness as the explanatory variable and the amount of solvent as the response variable, is used in the first period, and the second calibration curve, which uses the absorbance difference as the explanatory variable and the amount of solvent as the response variable, is used in the second period, the amount of solvent can be measured with high accuracy.

(Additional Note)
A material measuring device according to a first aspect includes a light emitting unit that irradiates light onto a mixed material, a light receiving unit that receives light from the mixed material, a thickness measuring unit that measures a thickness of the mixed material, and a control unit. The mixed material contains a solvent and a solid material. The solvent is a light-transmitting material having an absorbance peak. The light emitting unit irradiates light including a wavelength that is absorbed by the solvent. The control unit has a light intensity acquisition unit that acquires the light intensity of a first wavelength and the light intensity of a second wavelength from the light received by the light receiving unit; an absorbance difference calculation unit that calculates an absorbance difference, which is the difference between the absorbance of the first wavelength and the absorbance of the second wavelength, from the light intensity of the first wavelength and the light intensity of the second wavelength acquired by the light intensity acquisition unit; a first calibration curve memory unit that stores a first calibration curve indicating the relationship between the solvent content or content rate in the mixed material and a film thickness of the mixed material; a second calibration curve memory unit that stores a second calibration curve indicating the relationship between the solvent content or content rate in the mixed material and the absorbance difference; and a content calculation unit that calculates the solvent content or content rate from the first calibration curve and the second calibration curve.

In the material measuring device of the second aspect, the mixed material has a first period in which the film thickness changes due to a decrease in the solvent, and a second period that follows the first period and in which the film thickness changes less than in the first period due to a decrease in the solvent. In the first period, the content calculation unit calculates the content or percentage of the solvent from the film thickness of the mixed material and the first calibration curve stored in the first calibration curve storage unit, and in the second period, calculates the content or percentage of the solvent from the absorbance difference calculated by the absorbance difference calculation unit and the second calibration curve stored in the second calibration curve storage unit.

In the material measuring device of the third aspect, the control unit has a film thickness acquisition unit and a period determination unit. The film thickness acquisition unit acquires the film thickness of the mixed material from the film thickness measurement unit. The period determination unit determines that the mixed material is in the first period when the film thickness of the mixed material is equal to or greater than a predetermined threshold, and determines that the mixed material is in the second period when the film thickness of the mixed material is less than the predetermined threshold.

In the material measuring device of the fourth aspect, the control unit has a film thickness acquisition unit and a period determination unit. The film thickness acquisition unit acquires the film thickness of the mixed material from the film thickness measurement unit. The period determination unit determines that the mixed material is in the first period when the amount of change in the film thickness of the mixed material is equal to or greater than a predetermined threshold, and determines that the mixed material is in the second period when the amount of change in the film thickness of the mixed material is less than the predetermined threshold.

In the material measuring device of the fifth aspect, the second calibration curve storage unit stores the second calibration curve for each film thickness range of the mixed material. The content calculation unit calculates the content or content rate of the solvent using the second calibration curve corresponding to the film thickness of the mixed material.

The electrode manufacturing apparatus in the sixth aspect has a coating unit that applies a coating layer to at least one of a current collector having a first surface and a second surface, a drying unit that dries the coating layer, a light emitting unit that irradiates light onto the coating layer, a light receiving unit that receives light from the coating layer, a film thickness measuring unit that measures the film thickness of the coating layer, and a control unit. The coating layer contains a solvent and a solid material. The solvent is a light-transmitting material that has an absorbance peak. The light emitting unit irradiates light that includes a wavelength that is absorbed by the solvent. The control unit includes a light intensity acquisition unit that acquires the light intensity of the first wavelength and the light intensity of the second wavelength from the light received by the light receiving unit, an absorbance difference calculation unit that calculates the absorbance difference, which is the difference between the absorbance of the first wavelength and the absorbance of the second wavelength, from the light intensity of the first wavelength and the light intensity of the second wavelength acquired by the light intensity acquisition unit, a first calibration curve storage unit that stores a first calibration curve that shows the relationship between the solvent content or content rate in the coating layer and the film thickness of the coating layer, a second calibration curve storage unit that stores a second calibration curve that shows the relationship between the solvent content or content rate in the coating layer and the absorbance difference, and a content calculation unit that calculates the solvent content or content rate from the first calibration curve and the second calibration curve.

In the seventh aspect, the material measurement method measures the film thickness of a mixed material containing a solvent and a solid material. The mixed material is irradiated with light including a wavelength absorbed by the solvent, and light from the mixed material is received. The solvent is a light-transmitting material having an absorbance peak. The light intensity of a first wavelength and the light intensity of a second wavelength are acquired from the received light. The absorbance difference, which is the difference between the absorbance of the first wavelength and the absorbance of the second wavelength, is calculated from the light intensity of the first wavelength and the light intensity of the second wavelength. From the film thickness of the mixed material, it is determined whether the mixed material is in a first period in which the film thickness changes due to a decrease in the solvent, or a second period which is the period following the first period and in which the change in film thickness is smaller than that in the first period due to a decrease in the solvent. If it is determined to be in the first period, the content or content of the solvent is calculated from the film thickness of the mixed material and a first calibration curve showing the relationship between the content or content of the solvent in the mixed material and the film thickness of the mixed material. If it is determined that the second period is occurring, the solvent content or percentage is calculated from the absorbance difference and a second calibration curve that shows the relationship between the absorbance difference and the solvent content or percentage in the mixed material.

In the eighth aspect, the method for manufacturing an electrode includes applying a coating layer containing a solvent and an active material to at least one of a current collector having a first surface and a second surface. While drying the coating layer, the thickness of the coating layer is measured, the coating layer is irradiated with light including a wavelength absorbed by the solvent, and the light from the coating layer is received. The solvent is a light-transmitting material having an absorbance peak. The light intensity of a first wavelength and the light intensity of a second wavelength are obtained from the received light. The absorbance difference, which is the difference between the absorbance of the first wavelength and the absorbance of the second wavelength, is calculated from the light intensity of the first wavelength and the light intensity of the second wavelength. From the thickness of the coating layer, it is determined whether the coating layer is in a first period in which the thickness changes due to a decrease in the solvent, or a second period which is the period following the first period and in which the change in thickness is smaller than that in the first period due to a decrease in the solvent. If it is determined to be in the first period, the content or content of the solvent is calculated from the thickness of the coating layer and a first calibration curve showing the relationship between the content or content of the solvent in the coating layer and the thickness of the coating layer. If it is determined that the second period is occurring, the solvent content or percentage is calculated from the absorbance difference and a second calibration curve that shows the relationship between the absorbance difference and the solvent content or percentage in the coating layer.

Reference Signs List 100... Material measuring device 110... Light emitting unit 120... Light receiving unit 130... Film thickness measuring unit 140... Control unit M10... Measurement object M11... Substrate M12... Mixed material M12a... Solvent M12b... Solid material

Claims (8)

a light emitting unit that irradiates the mixed material with light;
A light receiving unit that receives light from the mixed material;
A thickness measuring unit for measuring a thickness of the mixed material;
A control unit;
having
The mixed material is
A method for preparing a liquid dispersion comprising the steps of:
The solvent is
a light-transmitting material having an absorbance peak;
The light emitting unit includes:
Irradiating the solvent with light having a wavelength that is absorbed by the solvent;
The control unit is
a light intensity acquiring unit that acquires a light intensity of a first wavelength and a light intensity of a second wavelength of the light received by the light receiving unit;
an absorbance difference calculation unit that calculates an absorbance difference that is a difference between an absorbance of the first wavelength and an absorbance of the second wavelength from the light intensity of the first wavelength and the light intensity of the second wavelength acquired by the light intensity acquisition unit;
a first calibration curve storage unit that stores a first calibration curve indicating a relationship between a content or a content rate of the solvent in the mixed material and a film thickness of the mixed material;
a second calibration curve storage unit that stores a second calibration curve indicating a relationship between the absorbance difference and the content or content ratio of the solvent in the mixed material;
a content calculation unit that calculates a content or a content rate of the solvent from the first calibration curve and the second calibration curve;
Including,
the light intensity of the light irradiated to the mixed material at the first wavelength is equal to the light intensity of the light irradiated to the mixed material at the second wavelength,
A material measuring device, wherein the difference between the first wavelength and the second wavelength is small enough that a reduction in light intensity due to light in a direction other than the light receiving direction at the first wavelength can be approximately equal to a reduction in light intensity due to light in a direction other than the light receiving direction at the second wavelength. 2. The material measuring device according to claim 1,
The mixed material is
a first period in which the film thickness changes due to a decrease in the solvent;
a second period which is a period following the first period and in which the amount of change in film thickness is smaller than that in the first period due to a decrease in the amount of the solvent;
having
The content calculation unit is
In the case of the first period,
calculating a content or a content rate of the solvent from a film thickness of the mixed material and the first calibration curve stored in the first calibration curve storage unit;
In the case of the second period,
A material measuring apparatus comprising: a step of calculating a content or a content rate of the solvent from the absorbance difference calculated by the absorbance difference calculation unit and the second calibration curve stored in the second calibration curve memory unit. 3. The material measuring device according to claim 2,
The control unit is
A film thickness acquisition unit;
A period determination unit,
The film thickness acquisition unit is
acquiring a thickness of the mixed material from the thickness measuring unit;
The period determination unit is
When the film thickness of the mixed material is equal to or greater than a predetermined threshold value,
determining that the mixed material is in the first period;
When the thickness of the mixed material is less than a predetermined threshold value,
determining that the mixed material is in the second period. 3. The material measuring device according to claim 2,
The control unit is
A film thickness acquisition unit;
A period determination unit,
The film thickness acquisition unit is
acquiring a thickness of the mixed material from the thickness measuring unit;
The period determination unit is
When the change in the thickness of the mixed material is equal to or greater than a predetermined threshold value,
determining that the mixed material is in the first period;
When the change in the thickness of the mixed material is less than a predetermined threshold value,
determining that the mixed material is in the second period. The material measuring device according to any one of claims 1 to 4,
The second calibration curve storage unit is
storing the second calibration curve for each thickness range of the mixed material;
The content calculation unit is
calculating a content or a concentration rate of the solvent using the second calibration curve according to a film thickness of the mixed material. a coating section that applies a coating layer to at least one of a current collector having a first surface and a second surface;
A drying section for drying the coating layer;
a light emitting unit that irradiates the coating layer with light;
A light receiving section that receives light from the coating layer;
A film thickness measuring unit for measuring a film thickness of the coating layer;
A control unit;
having
The coating layer is
A method for preparing a liquid dispersion comprising the steps of:
The solvent is
a light-transmitting material having an absorbance peak;
The light emitting unit includes:
Irradiating the solvent with light having a wavelength that is absorbed by the solvent;
The control unit is
a light intensity acquiring unit that acquires a light intensity of a first wavelength and a light intensity of a second wavelength of the light received by the light receiving unit;
an absorbance difference calculation unit that calculates an absorbance difference that is a difference between an absorbance of the first wavelength and an absorbance of the second wavelength from the light intensity of the first wavelength and the light intensity of the second wavelength acquired by the light intensity acquisition unit;
a first calibration curve storage unit that stores a first calibration curve indicating a relationship between a content or a content rate of the solvent in the coating layer and a film thickness of the coating layer;
a second calibration curve storage unit configured to store a second calibration curve indicating a relationship between the absorbance difference and the content or content ratio of the solvent in the coating layer;
a content calculation unit that calculates a content or a content rate of the solvent from the first calibration curve and the second calibration curve;
Including,
the light intensity of the light irradiated to the coating layer at the first wavelength is equal to the light intensity of the light irradiated to the coating layer at the second wavelength,
an electrode manufacturing apparatus, wherein a difference between the first wavelength and the second wavelength is small enough that a reduction in light intensity due to light in a direction other than the light receiving direction at the first wavelength and a reduction in light intensity due to light in a direction other than the light receiving direction at the second wavelength can be approximately equal. Measure the thickness of a mixed material containing a solvent and a solid material;
Irradiating the mixed material with light having a wavelength that is absorbed by the solvent;
receiving light from the mixed material;
the solvent is a light-transmitting material having an absorbance peak,
Obtaining a light intensity of a first wavelength and a light intensity of a second wavelength of the received light;
calculating an absorbance difference between the absorbance of the first wavelength and the absorbance of the second wavelength from the light intensity of the first wavelength and the light intensity of the second wavelength;
The thickness of the mixed material is
a first period in which the film thickness changes due to a decrease in the solvent;
a second period which is a period following the first period and in which the amount of change in film thickness is smaller than that in the first period due to a decrease in the amount of the solvent;
and determining whether the
When it is determined that the first period exists,
Calculating the content or percentage content of the solvent from the film thickness of the mixed material and a first calibration curve showing the relationship between the content or percentage content of the solvent in the mixed material and the film thickness of the mixed material;
When it is determined that the second period is present,
calculating the content or percentage of the solvent from the absorbance difference and a second calibration curve showing a relationship between the absorbance difference and the content or percentage of the solvent in the mixed material;
the light intensity of the light irradiated to the mixed material at the first wavelength is equal to the light intensity of the light irradiated to the mixed material at the second wavelength,
A material measurement method, wherein the difference between the first wavelength and the second wavelength is small enough that a decrease in light intensity due to light in a direction other than the light receiving direction at the first wavelength can be approximately equal to a decrease in light intensity due to light in a direction other than the light receiving direction at the second wavelength. A coating layer containing a solvent and an active material is applied to at least one of a current collector having a first surface and a second surface;
While drying the coating layer,
Measure the thickness of the coating layer;
Irradiating the coating layer with light having a wavelength that is absorbed by the solvent;
receiving light from the coating layer;
the solvent is a light-transmitting material having an absorbance peak,
Obtaining a light intensity of a first wavelength and a light intensity of a second wavelength of the received light;
calculating an absorbance difference between the absorbance of the first wavelength and the absorbance of the second wavelength from the light intensity of the first wavelength and the light intensity of the second wavelength;
The coating layer is formed from the thickness of the coating layer.
a first period in which the film thickness changes due to a decrease in the solvent;
a second period which is a period following the first period and in which the amount of change in film thickness is smaller than that in the first period due to a decrease in the amount of the solvent;
Determine whether the
When it is determined that the first period exists,
calculating the content or percentage content of the solvent from the film thickness of the coating layer and a first calibration curve showing a relationship between the content or percentage content of the solvent in the coating layer and the film thickness of the coating layer;
When it is determined that the second period is present,
calculating the content or percentage content of the solvent from the absorbance difference and a second calibration curve showing a relationship between the absorbance difference and the content or percentage content of the solvent in the coating layer;
the light intensity of the light irradiated to the coating layer at the first wavelength is equal to the light intensity of the light irradiated to the coating layer at the second wavelength,
a difference between the first wavelength and the second wavelength is small enough that a decrease in light intensity due to light in a direction other than the light receiving direction at the first wavelength can be approximately equal to a decrease in light intensity due to light in a direction other than the light receiving direction at the second wavelength.

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