Method for evaluating hair and method for evaluating hair cosmetics or hair treatment agents

Abstract

To evaluate an influence of extension operation on an internal structure of hair.SOLUTION: A method for evaluating hair includes: an acquisition step of executing a spectrum acquisition cycle including extension operation to extend hair and acquisition operation to acquire an infrared absorption spectrum of hair after the extension operation at least two or more times, and on the basis of, the infrared absorption spectra acquired in the respective acquisition operations and the total number of times of the extension operations executed until the execution of the respective acquisition operations, acquiring data of a change in the infrared absorption spectrum of hair according the total number of times of the extension operations; an analysis step of analyzing the data of a change in the infrared absorption spectrum of hair acquired in the acquisition step by using multivariate spectral analysis to check a change in a structure of hair according to the total number of times of the extension operations; and an evaluation step of evaluating a state of hair on the basis of, a result of the analysis step.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating hair and a method for evaluating a hair cosmetic or hair treatment agent. [Background technology]

[0002] For example, a hair evaluation method is known in which a stretching operation is first performed to apply a pulling force to the hair, and then the condition of the hair is observed to evaluate the effect of the stretching operation on the hair, as disclosed in Non-Patent Document 1. Non-Patent Document 1 describes that damage to the hair cuticle can be detected by first performing a hair stretching operation and then observing the surface of the hair under a microscope. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Journal of the Society of Cosmetic Chemists, Vol 49, No. 4 p213-222 Summary of the Invention [Problem to be solved by the invention]

[0004] Most existing studies that perform a hair stretching operation and then observe the condition of the hair have performed a hair stretching operation only once to evaluate the damage caused to the hair by the stretching operation. In contrast, in normal hair styling behavior, hair is thought to be gradually damaged by being repeatedly pulled. Therefore, methods that perform a hair stretching operation only once may not adequately reproduce the damage caused to hair during normal hair styling behavior.

[0005] Furthermore, in the method described in Non-Patent Document 1, although the hair is stretched multiple times, the method for observing the state of the hair after the stretching is only to observe the surface using a microscope, which makes it impossible to evaluate the effect of the stretching on the internal structure of the hair.

[0006] The present invention has been made in consideration of the above circumstances, and aims to evaluate the effect of a stretching operation on the internal structure of hair. [Means for solving the problem]

[0007] The hair evaluation method according to the present invention comprises: an acquisition step of performing a spectrum acquisition cycle at least a plurality of times, the spectrum acquisition cycle including a stretching operation of stretching the hair and an acquisition operation of acquiring an infrared absorption spectrum of the hair after the stretching operation, and acquiring data on changes in the infrared absorption spectrum of the hair according to the total number of stretching operations based on the infrared absorption spectrum acquired in each of the acquisition operations and the total number of stretching operations performed up to the execution of each of the acquisition operations; an analysis step of analyzing the data of the change in the infrared absorption spectrum of the hair acquired in the acquisition step by multivariate spectral analysis to confirm a change in the structure of the hair depending on the total number of times of the stretching operation; and an evaluation step of evaluating the condition of the hair based on the results of the analysis step.

[0008] The hair evaluation method according to the present invention comprises: The method may further include a removing step of removing cuticles from the hair before the obtaining step.

[0009] In the hair evaluation method according to the present invention, One stretching operation may involve pulling the hair at a constant speed of 120 mm / min to 240 mm / min to stretch it by a constant ratio of 30% or less, or pulling the hair at a constant speed of 120 mm / min to 240 mm / min until the tensile force applied to the hair reaches a constant value of 0.4 N or less.

[0010] In the hair evaluation method according to the present invention, In the evaluation step, the total number of stretching operations when the acquisition operation is performed in which, based on the changes in the hair structure confirmed in the analysis step, a 2.0-fold or greater increase in the methylene group component concentration in the hair and a 1.5-fold or greater increase in the carbonyl group component concentration are confirmed compared to an acquisition operation performed one less in total, the value of the methylene group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair is 0.0001 or greater, and the value of the carbonyl group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair is 0.0001 or greater, may be determined to be the total number of times a first structural change event occurs in the hair.

[0011] In the hair evaluation method according to the present invention, In the evaluation step, the total number of stretching operations when an acquisition operation is performed in which the change in the structure of the hair confirmed in the analysis step indicates an increase in the sulfonic acid group component concentration in the hair of 1.4 times or more compared to an acquisition operation with one less total number of times, and the value of the sulfonic acid group component concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair is 0.0001 or more, may be determined to be the total number of times a second structural change event occurs in the hair.

[0012] The method for evaluating a hair cosmetic or hair treatment agent according to the present invention comprises: a treatment step of treating the hair with a hair cosmetic or a hair treatment agent; an acquisition step of performing a spectrum acquisition cycle at least a plurality of times, the spectrum acquisition cycle including a stretching operation of stretching the hair and an acquisition operation of acquiring an infrared absorption spectrum of the hair after the stretching operation, and acquiring data on changes in the infrared absorption spectrum of the hair according to the total number of stretching operations based on the infrared absorption spectrum acquired in each of the acquisition operations and the total number of stretching operations performed up to the execution of each of the acquisition operations; an analysis step of analyzing the data of the change in the infrared absorption spectrum of the hair acquired in the acquisition step by multivariate spectral analysis to confirm a change in the structure of the hair depending on the total number of times of the stretching operation; and an efficacy evaluation step of evaluating the efficacy of the hair cosmetic or the hair treatment agent on the hair based on the results of the analysis step. [Effects of the Invention]

[0013] According to the present invention, it is possible to evaluate the effect of a stretching operation on the internal structure of hair. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of the structure of hair that is the subject of a hair evaluation method. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a hair evaluation system used in the hair evaluation method. [Figure 3] FIG. 3 is a side view showing an example of the stretching operation executing unit 2 included in the hair evaluation system. [Figure 4] FIG. 4 is a diagram showing an example of the procedure of the acquisition step. [Figure 5] FIG. 5 is a diagram showing an example of changes in the concentration of methylene groups in hair calculated in the analysis step. [Figure 6] FIG. 6 is a diagram showing an example of changes in the concentration of carbonyl groups in hair calculated in the analysis step. [Figure 7] FIG. 7 is a diagram showing an example of changes in the concentration of sulfonic acid group components in hair calculated in the analysis step. [Figure 8] FIG. 8 is a diagram showing an infrared absorption spectrum acquired in the acquisition step of Example 1. [Figure 9] FIG. 9 is a diagram showing the results of multivariate spectral decomposition of a part of the infrared absorption spectrum shown in FIG. [Figure 10] FIG. 10 is a diagram showing the results of multivariate spectral decomposition of a part of the infrared absorption spectrum shown in FIG. [Figure 11] FIG. 11 is a diagram showing the results of multivariate spectral decomposition of a part of the infrared absorption spectrum shown in FIG. [Figure 12] FIG. 12 is a graph showing the change in the concentration of methylene group components in the hair in Example 1. [Figure 13] FIG. 13 is a graph showing the change in the concentration of carbonyl group components in the hair in Example 1. [Figure 14] FIG. 14 is a graph showing the change in the concentration of sulfonic acid group components in the hair in Example 1. [Figure 15] FIG. 15 is a graph showing the change in concentration of methylene group components in hair in Example 2. [Figure 16] FIG. 16 is a graph showing the change in the concentration of carbonyl group components in hair in Example 2. [Figure 17] FIG. 17 is a graph showing the change in the concentration of sulfonic acid group components in the hair in Example 2. [Figure 18] FIG. 18 is a diagram showing changes in the hysteresis ratio of hair in Comparative Examples 1 and 2. [Figure 19] FIG. 19 is a graph showing the change in concentration of methylene group components in hair in Example 3. [Figure 20] FIG. 20 is a graph showing the change in the concentration of carbonyl group components in hair in Example 3. [Figure 21] FIG. 21 is a graph showing the change in the concentration of sulfonic acid group components in the hair in Example 3. [Figure 22] FIG. 22 is a graph showing the change in concentration of methylene group components in hair in Example 4. [Figure 23] FIG. 23 is a graph showing the change in the concentration of carbonyl group components in hair in Example 4. [Figure 24] FIG. 24 is a graph showing the change in the concentration of sulfonic acid group components in the hair in Example 4. [Figure 25] FIG. 25 is a diagram showing the change in curvature before and after the hair 50 in Examples 3 and 4 was repeatedly pulled. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below with reference to the drawings. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of clarity and ease of understanding.

[0016] First, the hair 50 that is the target of the hair 50 evaluation method according to the present embodiment will be described. In the present embodiment, the hair 50 is hair that grows on a human head and may have multiple layers made of different materials. FIG. 1 shows the structure of a typical hair 50. In the example shown in FIG. 1, the hair 50 has a cuticle 51 that forms the surface of the hair 50, a cortex 53 that is the main component inside the hair 50, and a medulla 55 that extends through the center of the hair 50. Note that the hair 50 that is the target of the hair 50 evaluation method may have an unclear boundary between the medulla 55 and the cortex 53, or may not have a medulla 55.

[0017] A hair evaluation system 1 used in the method for evaluating hair 50 according to this embodiment will be described. FIG. 2 is a diagram schematically illustrating an example of the configuration of the hair evaluation system 1. In the example illustrated in FIG. 2, the evaluation system 1 includes a stretching operation execution unit 2, an acquisition unit 3, an analysis unit 4, and an evaluation unit 5. Note that the evaluation system 1 does not necessarily have to include the evaluation unit 5. When the evaluation system 1 does not include the evaluation unit 5, the evaluation step in the method for evaluating hair 50 may be performed by an operator performing the method for evaluating hair 50, without using the evaluation unit 5, as will be described later.

[0018] Fig. 3 is a side view schematically showing an example of the stretching operation executing unit 2. In the example shown in Fig. 3, the stretching operation executing unit 2 has a first gripping tool 21 and a second gripping tool 22 that can hold the hair 50 by pinching it.

[0019] The acquisition unit 3 is a part capable of acquiring the infrared absorption spectrum of the hair 50. The acquisition unit 3 is a Fourier transform infrared spectrophotometer, and in particular a microscopic infrared spectrophotometer (microscopic FT-IR). In this case, the acquisition unit 3 can acquire the infrared absorption spectrum of the hair 50 by Fourier transform infrared spectroscopy (FT-IR). As the microscopic infrared spectrophotometer, for example, one capable of using the microscopic ATR (Attenuated Total Reflection) method can be used.

[0020] The analysis unit 4 is a part capable of multivariate analysis of data on changes in the infrared absorption spectrum of the hair 50. The analysis unit 4 is a part capable of, for example, performing multivariate spectral decomposition on the infrared absorption spectrum of the hair 50. The analysis unit 4 may be integrated with the acquisition unit 3 described above.

[0021] The evaluation unit 5 is a part that can evaluate the condition of the hair based on the results of multivariate analysis of data on changes in the infrared absorption spectrum of the hair 50 using the analysis unit 4. The evaluation unit 5 may be integrated with the acquisition unit 3 described above, or may be integrated with the analysis unit 4 described above.

[0022] Next, a method for evaluating hair 50 according to this embodiment will be described. The evaluation method according to this embodiment includes an acquisition step, an analysis step, and an evaluation step. The evaluation method according to this embodiment further includes a removal step prior to the acquisition step. The evaluation method according to this embodiment may also include a collection step of collecting hair 50 to be used in the evaluation method for hair 50.

[0023] In the method for evaluating the hair 50 according to the present embodiment, first, in the collection step, the hair 50 is collected from the head of a subject.

[0024] Next, in the removal step, the cuticle 51 is removed from the hair 50. As an example, the cuticle 51 can be removed from the hair 50 by using a file, particularly a diamond file, to trace the hair 50 and scrape the surface of the hair 50.

[0025] The removing step may include a checking step of checking whether the cuticle 51 has been sufficiently removed from the hair 50.

[0026] The confirmation step can be performed, for example, by the following method. Before shaving the surface of the hair 50, the diameter of the hair 50 is measured. Then, after shaving the surface of the hair 50, the diameter of the hair 50 is measured again. If, in the remeasurement, the diameter of the hair 50 has been reduced to a thickness equal to or greater than that of a typical cuticle 51, it is determined that the cuticle 51 has been sufficiently removed from the hair 50. Specifically, if, in the remeasurement, the diameter of the hair 50 has been reduced by 5.0 μm or more, it is determined that the cuticle 51 has been sufficiently removed from the hair 50.

[0027] In the checking step, it may be possible to check whether the cuticle 51 has been sufficiently removed from the hair 50 by observing the surface of the hair 50 using a microscope, particularly a laser microscope.

[0028] The effect of the removal step will now be described. When the hair 50 is pulled, the cortex 53 is more likely to undergo large structural changes than the cuticle 51. By removing the cuticle 51 from the hair 50 in the removal step, the cortex 53 can be exposed. This leaves the cortex 53 unprotected by the cuticle 51, making it easier for structural changes to occur in the cortex 53 during the stretching operation described below. Furthermore, in the acquisition operation described below, it is possible to obtain an infrared absorption spectrum of the cortex 53, which is more likely to undergo large structural changes.

[0029] After the removing step, an acquiring step is performed. In the acquiring step, a spectrum acquiring cycle including a stretching operation for stretching the hair 50 and an acquiring operation for acquiring the infrared absorption spectrum of the hair 50 after the stretching operation is performed at least a plurality of times. Then, based on the infrared absorption spectrum acquired in each acquiring operation and the total number of stretching operations performed up to the execution of each acquiring operation, data on the change in the infrared absorption spectrum of the hair 50 according to the total number of stretching operations is acquired.

[0030] A single stretching operation will be described. As an example, the stretching operation can be performed as follows using the stretching operation execution unit 2 described above. First, as shown in FIG. 3, one end of the hair 50 is held by the first gripping tool 21, and the other end of the hair 50 is held by the second gripping tool 22. Then, at least one of the first gripping tool 21 and the second gripping tool 22 is moved away from the other. This allows the hair 50 to be pulled and stretched.

[0031] In one stretching operation, the hair 50 may be stretched by a certain percentage of 30% or less by pulling at a constant speed of 120 mm / min to 240 mm / min. Alternatively, in one stretching operation, the hair 50 may be stretched by pulling at a constant speed of 120 mm / min to 240 mm / min until the force applied to the hair 50, specifically the tensile force applied to the hair 50, reaches a certain value of 0.4 N or less. The stretching percentage of the hair 50 in the stretching operation is greater than 0% and less than 30%. When the hair 50 is stretched so that the stretching percentage is 30% or less, the force applied to the hair 50 can reach 0.4 N. More preferably, the stretching percentage of the hair 50 in the stretching operation is 2% to 30%. More preferably, the force applied to the hair 50 in the stretching operation is less than 0.4 N. By performing the stretching operation under the above conditions, the conditions under which the hair 50 is pulled during the stretching operation can be made sufficiently close to the conditions under which the hair 50 is pulled during normal hair styling. Here, the hair styling action refers to, for example, brushing.

[0032] By moving at least one of the first gripping tool 21 and the second gripping tool 22 and moving the first gripping tool 21 and the second gripping tool 22 away from each other at a constant speed of 120 mm / min to 240 mm / min, the hair 50 can be pulled at the constant speed.

[0033] Furthermore, by adjusting the distance by which the first gripping tool 21 and the second gripping tool 22 are separated during the stretching operation, it is possible to adjust the stretching rate of the hair 50. Here, the stretching rate of the hair 50 refers to the rate at which the length w1 of the portion of the hair 50 located between the portion gripped by the first gripping tool 21 and the portion gripped by the second gripping tool 22 increases during the stretching operation compared to before the stretching operation.

[0034] In addition, in one acquisition operation, as an example, an infrared absorption spectrum of the hair 50 can be acquired by Fourier transform infrared spectroscopy using a Fourier transform infrared spectrophotometer, which is the acquisition unit 3 described above.

[0035] Here, in the acquisition step, a spectrum acquisition cycle including a stretching operation and an acquisition operation after the stretching operation is executed multiple times. The spectrum acquisition cycle will be described below. FIG. 4 is a diagram showing an example of the procedure of the acquisition step. As shown in FIG. 4, one spectrum acquisition cycle includes one or more stretching operations and one acquisition operation after the stretching operation.

[0036] The number of extension operations included in one spectrum acquisition cycle may be one or more, and the number of extension operations included in the multiple spectrum acquisition cycles executed in the acquisition step may be different for each spectrum acquisition cycle or may be the same for each spectrum acquisition cycle.

[0037] In the example shown in Fig. 4, the number of extension operations included in the multiple spectrum acquisition cycles executed in the acquisition process is equal for each spectrum acquisition cycle. In the example shown in Fig. 4, each of the multiple spectrum acquisition cycles executed in the acquisition process includes five extension operations and one acquisition operation after the five extension operations. In this case, the first spectrum acquisition cycle includes the first to fifth extension operations in total and the first acquisition operation in total. The second spectrum acquisition cycle includes the sixth to tenth extension operations in total and the second acquisition operation in total. The nth spectrum acquisition cycle (n is any positive integer) includes the 5n-4th to 5nth extension operations in total and the nth acquisition operation in total.

[0038] By way of example, the spectrum acquisition cycle is repeated until the hair 50 breaks during the drawing operation. The spectrum acquisition cycle may also be repeated a predetermined number of times.

[0039] By performing the spectrum acquisition cycle as described above multiple times, data on changes in the infrared absorption spectrum of the hair 50 corresponding to the total number of stretching operations can be obtained based on the infrared absorption spectrum acquired in each acquisition operation and the total number of stretching operations performed up to the execution of each acquisition operation. For example, according to the acquisition process procedure shown in FIG. 4, the first acquisition operation can acquire the infrared absorption spectrum of the hair 50 that has been stretched a total of five times. The second acquisition operation can acquire the infrared absorption spectrum of the hair 50 that has been stretched a total of 10 times. The nth acquisition operation can acquire the infrared absorption spectrum of the hair 50 that has been stretched a total of 5n times. As described above, when a total of N spectrum acquisition cycles (N is a positive integer) are performed, N infrared absorption spectra at different times when the total number of stretching operations has been performed on the hair 50 are acquired as data on changes in the infrared absorption spectrum of the hair 50. By combining N infrared absorption spectra, it is possible to capture the change in the infrared absorption spectrum of the hair 50 according to the total number of stretching operations.

[0040] Although not shown in Fig. 4, the acquisition process may include a pre-acquisition operation for acquiring an infrared absorption spectrum before executing the first spectrum acquisition cycle. The pre-acquisition operation can be executed in the same manner as a single acquisition operation. The pre-acquisition operation can acquire an infrared absorption spectrum of the hair 50 when the total number of stretching operations performed on the hair 50 is 0. When the acquisition process includes the pre-acquisition operation and a total of N spectrum acquisition cycles are executed in the acquisition process, a total of N+1 infrared absorption spectra are acquired in the acquisition process, including N infrared absorption spectra acquired in the spectrum acquisition cycles and one infrared absorption spectrum acquired in the pre-acquisition operation.

[0041] In addition, an analysis step is performed to analyze the data of the change in the infrared absorption spectrum of the hair 50 acquired in the acquisition step. In the analysis step, the data of the change in the infrared absorption spectrum of the hair 50 is analyzed by multivariate spectral analysis to confirm the change in the structure of the hair 50 according to the total number of stretching operations. As an example, the analysis step is performed using the analysis unit 4 described above.

[0042] As an example, in the analyzing step, multivariate spectral decomposition of the infrared absorption spectrum acquired in the acquiring step is performed as multivariate spectral analysis.

[0043] An example of an analysis step of performing multivariate spectral decomposition as multivariate spectral analysis will be described in detail. First, the infrared absorption spectrum acquired in the acquisition step is second-order differentiated. Next, the second-order differentiated infrared absorption spectrum is decomposed by multivariate spectral decomposition. Then, it is confirmed to which component in the hair 50 each of the decomposed spectra belongs. For example, it is confirmed to which group in the hair 50 each of the decomposed spectra belongs. Because the object of acquiring the infrared absorption spectrum in the acquisition step is the hair 50, each of the infrared absorption spectra decomposed by multivariate spectral decomposition belongs to a methylene group (CH), a carbonyl group (C=O), a sulfonic acid group (SO3H), etc.

[0044] Next, based on the correspondence between each of the decomposed spectra and the components assigned to each of the decomposed spectra, the component concentrations of the components in the hair 50 at different times when the total number of stretching operations has been performed on the hair 50 are calculated from the multiple infrared absorption spectra obtained at different times when the total number of stretching operations has been performed on the hair 50. The component concentrations of the components in the hair 50, for example, the concentrations of methylene groups (CH), carbonyl groups (C=O), sulfonic acid groups (SOH), etc., can be calculated. Based on the calculation results, changes in the component concentrations of the components in the hair 50 according to the total number of stretching operations can be confirmed. Figures 5, 6, and 7 are graphs showing an example of changes in the component concentrations of the components in the hair 50 calculated in the analysis step when a pre-acquisition operation is performed and a spectrum acquisition cycle including five stretching operations and one acquisition operation is executed N times to acquire infrared absorption spectra in the acquisition step. FIG. 5 shows the change in the component concentration of methylene groups (CH2) in hair 50 depending on the total number of acquisition operations and the total number of stretching operations. FIG. 6 shows the change in the component concentration of carbonyl groups (C=O) in hair 50 depending on the total number of acquisition operations and the total number of stretching operations. FIG. 7 shows the change in the component concentration of sulfonic acid groups (SO3H) in hair 50 depending on the total number of acquisition operations and the total number of stretching operations. In the analysis process, the change in the component concentration of the components in hair 50 can be confirmed as a change in the structure of hair 50 depending on the total number of stretching operations, as shown in FIGS. 5, 6, and 7.

[0045] Further, an evaluation step is performed to evaluate the condition of the hair 50 based on the results of the analysis step. As an example, the evaluation step is performed using the above-mentioned evaluation unit 5. The evaluation step may also be performed by an operator of the method for evaluating the hair 50 checking graphs showing changes in component concentrations of components in the hair 50, such as those shown in Figures 5, 6, and 7, without using the evaluation unit 5 or the like.

[0046] As an example, in the evaluation step, the total number of stretching operations at which a structure change event occurs in the hair 50 is identified from the structural change of the hair 50 confirmed in the analysis step. Here, a structure change event refers to a phenomenon in which the structure of the hair 50 changes significantly when the stretching operation is repeatedly performed on the hair 50 and the total number of stretching operations reaches a specific number. A structure change event is considered to occur along with a change in the state of the hair 50. Furthermore, when the stretching operation is repeatedly performed on the hair 50, visually observable phenomena such as breakage or the development of stronger curls occur in the hair 50, as will be described later. However, a structure change event may occur prior to such visually observable phenomena. As an example, a structure change event is a phenomenon that occurs in a total number of stretching operations that is less than the total number of stretching operations at which the hair 50 breaks. In this case, the structure change event can be considered a phenomenon that is a precursor to breakage of the hair 50.

[0047] The occurrence of stronger curls in the hair 50 means, for example, a phenomenon in which the curvature of the hair 50 becomes larger.

[0048] An example of a method for identifying the total number of stretching operations at which a structural change event occurs in the hair 50 in the evaluation step will be described below. Among the structural changes in the hair 50 confirmed in the analysis step, attention is focused on the changes in the component concentrations of methylene groups and carbonyl groups, as shown in Figure 5. Then, in a certain acquisition operation, compared to an acquisition operation with one fewer total number of operations, if an increase of 2.0 times or more in the component concentration of methylene groups in the hair 50 is confirmed, an increase of 1.5 times or more in the component concentration of carbonyl groups in the hair 50 is confirmed, the value of the component concentration of methylene groups calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more, and the value of the component concentration of carbonyl groups calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more, it is determined that a first structural change event occurred in the hair 50 in the stretching operation immediately before the acquisition operation. Then, based on this determination, the total number of stretching operations at which the first structural change event occurs in the hair 50 is identified.

[0049] More specifically, first, an acquisition operation is identified in which, compared to an acquisition operation with one fewer total number of times, an increase in the methylene group component concentration in the hair 50 of 2.0 times or more is confirmed, an increase in the carbonyl group component concentration of 1.5 times or more is confirmed, the value of the methylene group component concentration calculated by analysis of the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more, and the value of the carbonyl group component concentration calculated by analysis of the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more. As an example, among the acquisition operations for which an increase in the methylene group component concentration of 2.0 times or more is confirmed, an increase in the carbonyl group component concentration of 1.5 times or more is confirmed, the value of the methylene group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more, and the value of the carbonyl group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more, the acquisition operation with the fewest total number of acquisition operations is identified. Then, the total number of stretching operations when an acquisition operation is performed in which an increase of 2.0 times or more in the methylene group component concentration is confirmed, an increase of 1.5 times or more in the carbonyl group component concentration is confirmed, the value of the methylene group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more, and the value of the carbonyl group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or more is determined to be the total number of times the first structural change event occurs in the hair 50.

[0050] In the change in the methylene group component concentration shown in Figure 5, the methylene group component concentration H1 when the total number of acquisition operations is a (a is a positive integer) is assumed to be 2.0 times or more the methylene group component concentration H2 when the total number of acquisition operations is a-1. The methylene group component concentration shown in Figure 5 is calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50, and the methylene group component concentration H1 when the total number of acquisition operations is a (a is a positive integer) is assumed to be 0.0001 or more. In the change in the carbonyl group component concentration shown in Figure 6, the carbonyl group component concentration H1 when the total number of acquisition operations is a is assumed to be 1.5 times or more the carbonyl group component concentration H2 when the total number of acquisition operations is a-1. 6 is calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50, and the carbonyl group component concentration H1 is 0.0001 or more when the total number of acquisition operations is a (a is a positive integer). The a-th acquisition operation is considered to be the acquisition operation with the fewest total number of acquisition operations, among which a 2.0-fold or greater increase in the methylene group component concentration and a 1.5-fold or greater increase in the carbonyl group component concentration are confirmed, the methylene group component concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 is 0.0001 or greater, and the carbonyl group component concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 is 0.0001 or greater. In this case, the total number of stretching operations is 5a when an acquisition operation is performed in which a 2.0-fold or greater increase in the methylene group component concentration is confirmed, a 1.5-fold or greater increase in the carbonyl group component concentration is confirmed, the methylene group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of hair 50 is 0.0001 or greater, and the carbonyl group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of hair 50 is 0.0001 or greater. In this case, it may be determined that the total number of stretching operations in which a first structural change event occurs in hair 50 is 5a.

[0051] The inventors of the present invention have now explained how they came up with the idea of ​​specifying the total number of stretching operations at which a first structural change event occurs in the hair 50 in the evaluation step in order to evaluate the condition of the hair 50. The inventors of the present invention have repeatedly studied the influence of stretching operations on the internal structure of the hair 50 when multiple stretching operations are performed on the hair 50, and have found that the first structural change event in the hair 50 is a 2.0-fold or greater increase in the concentration of methylene groups and a 1.5-fold or greater increase in the concentration of carbonyl groups, and that the value of the methylene group concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or greater, and that the value of the carbonyl group concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair 50 is 0.0001 or greater. Then, we came up with the idea of ​​identifying the total number of stretching operations at which the first structural change event occurs in the hair 50 in the evaluation process, based on the idea that the total number of stretching operations at which the first structural change event occurs in the hair 50 is an indicator representing the state of the internal structure of the hair 50.

[0052] As an example, the total number of stretching operations at which the first structural change event occurs in the hair 50 is considered to be an indicator of whether the internal structure of the hair 50 is prone to breakage due to repeated pulling. That is, the first structural change event can be considered as a precursor to the first breakage, and the total number of stretching operations at which the first structural change event occurs in the hair 50 can be considered as the total number of stretching operations at which the first structural change event occurs in the hair 50. If the total number of stretching operations at which the precursor to the first breakage occurs in the hair 50 is small, the hair 50 can be evaluated as having an internal structure that is prone to breakage due to repeated pulling. If the total number of stretching operations at which the precursor to the first breakage occurs in the hair 50 is small, or if the precursor to the first breakage does not occur in the hair 50 even after repeating the spectrum acquisition cycle a predetermined number of times, the hair 50 can be evaluated as having an internal structure that is resistant to breakage due to repeated pulling.

[0053] Whether the total number of stretching operations that causes a precursor phenomenon of breakage in the hair 50 is large or small can be determined, for example, by comparing with a predetermined reference value of the total number of times.

[0054] Another example of a method for identifying the total number of stretching operations at which a structural change event occurs in the hair 50 in the evaluation step will be described below. Among the structural changes in the hair 50 confirmed in the analysis step, attention is focused on the change in the sulfonic acid group component concentration as shown in FIG. 7 and the magnitude of the sulfonic acid group component concentration value. If, in a certain acquisition operation, a 1.4-fold or greater increase in the sulfonic acid group component concentration in the hair 50 is confirmed compared to an acquisition operation with one fewer total number of operations, and the component concentration value calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or greater, it is determined that a second structural change event occurred in the hair 50 in the stretching operation immediately preceding the acquisition operation. Based on this determination, the total number of stretching operations at which a second structural change event occurs in the hair 50 is identified. The component concentrations calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 are, for example, the component concentrations calculated by subjecting the infrared absorption spectrum acquired in the acquisition process to second-order differentiation in the analysis process, followed by multivariate spectral decomposition, and then using the results of this multivariate spectral decomposition.

[0055] More specifically, first, an acquisition operation is identified in which the sulfonic acid group concentration in the hair 50 is confirmed to have increased by 1.4 times or more compared to an acquisition operation with one less total number of times, and the sulfonic acid group concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more. As an example, the acquisition operation with the fewest total number of times is identified from among the acquisition operations in which the sulfonic acid group concentration is confirmed to have increased by 1.4 times or more and the sulfonic acid group concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more. Then, the total number of stretching operations when an acquisition operation is performed in which the sulfonic acid group concentration is confirmed to have increased by 1.4 times or more and the sulfonic acid group concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more is determined to be the total number of times a second structural change event occurs in the hair 50.

[0056] In the change in sulfonic acid group component concentration shown in Figure 7, the sulfonic acid group component concentration H3 when the total number of acquisition operations is b (b is a positive integer) is assumed to be 1.4 times or more the sulfonic acid group component concentration H4 when the total number of acquisition operations is b-1. The sulfonic acid group component concentration shown in Figure 7 is calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50, and the sulfonic acid group component concentration H3 when the total number of acquisition operations is b (b is a positive integer) is assumed to be 0.0001 or more. The bth acquisition operation in total is assumed to be the acquisition operation with the fewest total number of acquisition operations in which an increase in the sulfonic acid group component concentration of 1.4 times or more was confirmed and the sulfonic acid group component concentration H3 was 0.0001 or more. In this case, the total number of stretching operations when the sulfonic acid group component concentration was confirmed to have increased by 1.4 times or more and the sulfonic acid group component concentration H3 was 0.0001 or more was 5b. Therefore, it may be determined that the total number of stretching operations when the second structural change event occurs in the hair 50 is 5b.

[0057] The inventors of the present invention have come up with the idea of ​​specifying the total number of stretching operations at which a second structural change event occurs in the hair 50 in order to evaluate the condition of the hair 50 in the evaluation step. The inventors of the present invention have repeatedly studied the influence of multiple stretching operations on the internal structure of the hair 50, and have found that the second structural change event in the hair 50 occurs when the sulfonic acid group component concentration increases by 1.4 times or more, and the value of the sulfonic acid group component concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 is 0.0001 or more. They then considered that the total number of stretching operations at which a second structural change event occurs in the hair 50 is an index representing the condition of the internal structure of the hair 50, and have come up with the idea of ​​specifying the total number of stretching operations at which a second structural change event occurs in the hair 50 in the evaluation step.

[0058] The total number of drawing operations at which the second structural change event occurs in the hair 50 can also be used as an indicator of whether the internal structure of the hair 50 is prone to breakage due to repeated pulling, similar to the total number of drawing operations at which the first structural change event occurs in the hair 50. That is, the second structural change event can be regarded as a precursor phenomenon of the second breakage, and the total number of drawing operations at which the second structural change event occurs in the hair 50 can be regarded as the total number of drawing operations at which the precursor phenomenon of the second breakage occurs in the hair 50.

[0059] As a result of research, the inventors have found that the total number of stretching operations that cause the second structural change event tends to be greater than the total number of stretching operations that cause the first structural change event. That is, the total number of stretching operations 5b shown in Figure 7 tends to be greater than the total number of stretching operations 5a shown in Figure 5. Possible reasons for this tendency will be discussed later.

[0060] In the evaluation step, the occurrence of a structural change event in the hair 50 may be determined based on a change in the concentration of components in the hair 50 other than the methylene group and the sulfonic acid group.

[0061] The reasons why the first structural change event is an increase in the concentration of methylene and carbonyl groups in hair 50, as described above, the second structural change event is an increase in the concentration of sulfonic acid groups in hair 50 at a total number of stretching operations greater than the total number of stretching operations at which the first structural change event occurred, the first structural change event can be considered a precursor to the first breakage, and the second structural change event can be considered a precursor to the second breakage may be, for example, the following phenomena.

[0062] Let us consider the process that occurs when hair 50 is repeatedly stretched until it breaks. In this case, as the number of stretching operations performed on hair 50 increases, first, oily components in hair 50, particularly in cortex 53, ooze out to the surface of hair 50. This causes a first structural change event. That is, the concentration of methylene groups increases by 2.0 times or more, and the concentration of carbonyl groups increases by 1.5 times or more, and the value of the concentration of methylene groups calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 becomes 0.0001 or more, and the value of the concentration of carbonyl groups calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 becomes 0.0001 or more. As the number of stretching operations performed on hair 50 increases after the first structural change event occurs, disulfide bonds (SS bonds) in hair 50, particularly in cortex 53, are broken. This causes a second structural change event. That is, the sulfonic acid group component concentration increases by 1.4 times or more, and the sulfonic acid group component concentration calculated by analyzing the second-order derivative infrared absorption spectrum of the hair 50 becomes 0.0001 or more. If the number of stretching operations performed on the hair 50 increases after the second structural change event occurs, the hair 50 will break. It is believed that this process causes a first structural change event and a second structural change event to occur prior to the breakage of the hair 50. For this reason, it is believed that the first structural change event can be regarded as a precursor to the first breakage, and the second structural change event can be regarded as a precursor to the second breakage. Furthermore, if it is believed that the component concentrations of the hair 50 are destroyed in accordance with this process, it is believed that the component concentrations of the hair 50 change rapidly in a single specific stretching operation.

[0063] As an example, the analysis step and evaluation step can be performed after all of the multiple spectrum acquisition cycles in the acquisition step have been completed. Furthermore, some of the steps included in the analysis step and evaluation step may be performed between the execution of one spectrum acquisition cycle and the execution of the next spectrum acquisition cycle in the acquisition step, or in parallel with the execution of the spectrum acquisition cycle. For example, after the first spectrum acquisition cycle is performed, some of the analysis step and evaluation step may be performed using the infrared absorption spectrum acquired in the first spectrum acquisition cycle, and then the second spectrum acquisition cycle may be performed.

[0064] The effects of the method for evaluating hair 50 according to this embodiment will be described. In the method for evaluating hair 50 according to this embodiment, in the acquisition step, the hair 50 is stretched multiple times to acquire data on changes in infrared absorption spectrum depending on the total number of stretching operations. Then, in the analysis step, the acquired data is analyzed to confirm changes in the structure of the hair 50 depending on the total number of stretching operations. Then, in the evaluation step, the state of the hair 50 is evaluated based on the results of the analysis step. This makes it possible to evaluate the effect of repeated stretching operations on the hair 50. In particular, by repeating the stretching operation, the hair 50 is pulled under conditions similar to those under which it is pulled in normal hair styling behavior, and the effect of pulling on the hair 50 can be evaluated. In particular, it is possible to evaluate how the hair 50 is damaged under pulling conditions similar to those under normal hair styling behavior.

[0065] Furthermore, since data on changes in the infrared absorption spectrum are obtained from the hair 50, it is possible to evaluate the effect of the stretching operation on the internal structure of the hair.

[0066] In particular, in the evaluation step, by specifying the total number of stretching operations at which structural change events such as the first structural change event and the second structural change event occur, and regarding this as the total number of stretching operations at which precursor phenomena to breakage such as the first precursor phenomenon to breakage and the second precursor phenomenon to breakage occur, the following effects can be obtained: The state of the hair 50 can be evaluated without necessarily repeating the stretching operation until the hair 50 breaks, and the time required to evaluate the hair 50 can be shortened.

[0067] Furthermore, from the total number of stretching operations that cause the precursor phenomenon of breakage, it can be estimated how many times normal hair styling actions need to be performed on the hair 50 before the hair 50 breaks. For example, if the total number of stretching operations that cause the first precursor phenomenon of breakage is small, it can be estimated that the hair 50 is likely to break even with normal hair styling actions. Furthermore, based on this estimation, it is also possible to determine a hair care method for the subject who provided the hair 50.

[0068] Furthermore, when the total number of stretching operations that cause precursor phenomena of breakage is small, by providing the subject with hair care that makes the precursor phenomena of breakage less likely to occur, it is possible to suppress breakage of the hair 50. For example, when the total number of stretching operations that cause precursor phenomena of the first breakage is small, by providing the subject with hair care that makes the first precursor phenomena of breakage less likely to occur, it is possible to suppress breakage of the hair 50.

[0069] Furthermore, by determining both the total number of stretching operations that result in the first structural change event and the total number of stretching operations that result in the second structural change event in the evaluation step, the following effects can be obtained: The internal structure of the hair 50 can be evaluated more accurately. Furthermore, based on the evaluation results, a hair care method for the subject to whom the hair 50 is provided can be determined. For example, if the total number of stretching operations that result in the first structural change event is considered to be the total number of stretching operations that result in the first precursory phenomenon of breakage, and the total number of stretching operations that result in the second structural change event is considered to be the total number of stretching operations that result in the second precursory phenomenon of breakage, and the total number of stretching operations that result in the first precursory phenomenon of breakage is considered to be the total number of stretching operations that result in the second precursory phenomenon of breakage, and the total number of stretching operations that result in the first precursory phenomenon of breakage is low but the total number of stretching operations that result in the second precursory phenomenon of breakage is high, breakage of the hair 50 can be effectively suppressed by preferentially providing the subject to a hair care method that makes the first precursory phenomenon of breakage less likely to occur.

[0070] As described above, one embodiment has been described with reference to specific examples, but the above-described specific examples are not intended to limit the embodiment. The above-described embodiment can be implemented with various other specific examples, and various omissions, substitutions, and modifications can be made without departing from the spirit of the embodiment. Modifications of this embodiment will be described below.

[0071] (Variation 1) As the method for evaluating the hair 50 according to the above-described embodiment, an example has been described in which, in the evaluation step, a structural change event is regarded as a precursor to breakage, and the total number of stretching operations at which a structural change event occurs in the hair 50 is regarded as the total number of stretching operations at which a precursor to breakage occurs in the hair 50. However, the specific method of the evaluation step is not limited to this. In the evaluation step, any method for evaluating the state of the hair 50 based on the results of the analysis step can be used without any particular limitation. For example, repeated pulling of the hair 50 may cause the hair 50 to become more strongly curled. For this reason, in the evaluation step, a structural change event may be regarded as a precursor to the hair 50 becoming more curly (referred to as a "precursor to stronger curl"), and the total number of stretching operations at which a structural change event occurs in the hair 50 may be regarded as the total number of stretching operations at which a precursor to stronger curl occurs in the hair 50.

[0072] As an example, the evaluation process can be carried out as follows.

[0073] Except for the points specifically described below, the total number of stretching operations at which the first structural change event described above occurs is determined using the same method as in the above-described embodiment. That is, in the change in component concentration of components in hair 50 confirmed in the analysis step, compared to an acquisition operation with one fewer total number of operations, if the component concentration of methylene groups in hair 50 increases by 2.0 times or more, the component concentration of carbonyl groups in hair 50 increases by 1.5 times or more, the component concentration of methylene groups calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 is 0.0001 or more, and the component concentration of carbonyl groups calculated by analyzing the second-order differentiated infrared absorption spectrum of hair 50 is 0.0001 or more, it is determined that the first structural change event occurred in hair 50 in the stretching operation immediately before the acquisition operation. Based on this determination, the total number of stretching operations at which the first structural change event occurred in hair 50 is determined. The total number of stretching operations at which the first structural change event occurs is regarded as the total number of stretching operations at which the precursor phenomenon of the first stronger curl occurs in the hair 50.

[0074] Furthermore, except for the points specifically described below, the total number of stretching operations at which the second structural change event described above occurs is determined using a method similar to that of the above-described embodiment. That is, in the change in component concentration of components in the hair 50 confirmed in the analysis step, an acquisition operation is identified in which, compared to an acquisition operation with one fewer total number, an increase in the component concentration of sulfonic acid groups in the hair 50 is confirmed to be 1.4 times or more, and the value of the component concentration of sulfonic acid groups calculated by analyzing the second-order derivative infrared absorption spectrum of the hair 50 is 0.0001 or more. The total number of stretching operations when an acquisition operation is performed in which an increase in sulfonic acid groups is confirmed to be 1.4 times or more, and the value of the component concentration of sulfonic acid groups calculated by analyzing the second-order derivative infrared absorption spectrum of the hair 50 is 0.0001 or more is determined to be the total number of times at which the second structural change event occurs in the hair 50. Based on this determination, the total number of stretching operations at which the second structural change event occurs in the hair 50 is determined. The total number of stretching operations at which the second structural change event occurs is regarded as the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs in the hair 50. The condition of the hair 50 is then evaluated from the total number of stretching operations at which the identified precursor phenomenon of the first stronger curl occurs in the hair 50 and the total number of stretching operations at which the identified precursor phenomenon of the second stronger curl occurs in the hair 50.

[0075] The following explains the reasons why the increase in the concentration of methylene and carbonyl groups in hair 50, which is the first structural change event, can be considered a precursor to the first breakage and a precursor to the first stronger curl. Additionally, the following explains the reasons why the increase in the concentration of sulfonic acid groups in hair 50, which is the second structural change event, can be considered a precursor to the second breakage and a precursor to the second stronger curl.

[0076] The breakage of the hair 50 can be considered as a phenomenon that occurs when the internal structure of the hair 50 is destroyed over the entire cross section of the hair 50. On the other hand, the development of stronger curls in the hair 50 can be considered as a phenomenon that occurs when the internal structure of a portion of the cross section of the hair 50 is destroyed. For this reason, it is considered that precursor phenomena similar to those that occur in the process leading up to the breakage of the hair 50 also occur in the process leading up to the development of stronger curls in the hair 50.

[0077] When evaluating the condition of the hair 50, the total number of times the first structural change event occurs may be the total number of stretching operations performed when the acquisition operation with the smallest total number of acquisition operations was performed among the acquisition operations in which an increase in the concentrations of methylene groups and carbonyl groups in the hair 50 was confirmed. In this case, one value is used as the total number of times the first structural change event occurs. On the other hand, multiple values ​​may be used as the total number of times the first structural change event occurs. For example, when an increase in the concentrations of methylene groups and carbonyl groups in the hair 50 is confirmed multiple times, the total number of times the first structural change event occurs in the hair 50 may be calculated as follows. The total number of times the first structural change event occurs in the hair 50 may be the total number of stretching operations performed when each of the multiple acquisition operations in which an increase in the concentrations of methylene groups and carbonyl groups in the hair 50 was confirmed.

[0078] Furthermore, when evaluating the condition of the hair 50, the total number of times a second structural change event occurs may be the total number of stretching operations performed when the acquisition operation with the smallest total number of acquisition operations was performed among the acquisition operations in which an increase in the sulfonic acid group component concentration in the hair 50 was confirmed. In this case, one value is used as the total number of times a second structural change event occurs. On the other hand, multiple values ​​may be used as the total number of times a second structural change event occurs. For example, when an increase in the sulfonic acid group component concentration in the hair 50 is confirmed multiple times, the total number of times a second structural change event occurs in the hair 50 may be calculated as follows. The total number of times a second structural change event occurs in the hair 50 may be the total number of stretching operations performed when each of the multiple acquisition operations in which an increase in the sulfonic acid group component concentration in the hair 50 was confirmed.

[0079] For example, similarly to the above-described embodiment, if the total number of stretching operations when the least number of stretching operations was performed among the above-described stretching operations in which an increase in the concentrations of methylene and carbonyl groups in the hair 50 was confirmed is regarded as the total number of stretching operations at which the first structural change event occurs, the condition of the hair 50 can be evaluated as follows: If the total number of stretching operations at which the first precursor phenomenon of stronger curl occurs in the hair 50 is smaller than the reference value, the hair 50 is evaluated as having an internal structure that is prone to stronger curls when pulled repeatedly. Also, if the total number of stretching operations at which the first precursor phenomenon of stronger curl occurs in the hair 50 is larger than the reference value, the hair 50 is evaluated as having an internal structure that is resistant to stronger curls when pulled repeatedly.

[0080] Furthermore, similarly to the above-described embodiment, if the total number of stretching operations when the least number of stretching operations was performed among the above-described stretching operations in which an increase in the sulfonic acid group component concentration in the hair 50 was confirmed is regarded as the total number of stretching operations at which the second structural change event occurs, the condition of the hair 50 can be evaluated as follows: If the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs in the hair 50 is smaller than the reference value, the hair 50 is evaluated as having an internal structure that is prone to stronger curls when pulled repeatedly. Furthermore, if the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs in the hair 50 is larger than the reference value, the hair 50 is evaluated as having an internal structure that is resistant to stronger curls when pulled repeatedly.

[0081] (Variation 2) The methods for evaluating hair 50 according to the above-described embodiments and modifications can be used as methods for evaluating hair cosmetics or hair treatment agents by performing the evaluation on hair 50 treated with the hair cosmetics or hair treatment agents. In this case, the methods for evaluating hair cosmetics or hair treatment agents include a treating step, an obtaining step, an analyzing step, and an efficacy evaluating step.

[0082] In the method for evaluating hair cosmetics or hair treatment agents, first, in the treatment step, hair 50 is treated with a hair cosmetic or hair treatment agent. Here, hair cosmetics refer to hair care products that are applied to hair 50, such as hair rinses, hair conditioners, hair treatments, hair packs, hair creams, leave-on treatments, etc. Furthermore, hair treatment agents refer to treatment agents such as hair color treatment agents, bleach treatment agents, perm treatment agents, and hair growth agents that are applied to hair 50 in treatment steps such as hair coloring, bleaching, perming, and hair growth / stimulation.

[0083] Next, in the acquisition step, data on changes in the infrared absorption spectrum of the hair 50 processed in the treatment step is acquired by a method similar to the acquisition step of the hair 50 evaluation method according to the above-described embodiment. That is, first, a spectrum acquisition cycle including a stretching operation for stretching the hair 50 and an acquisition operation for acquiring the infrared absorption spectrum of the hair 50 after the stretching operation is performed at least multiple times. Then, based on the infrared absorption spectrum acquired in each acquisition operation and the total number of stretching operations performed up to the execution of each acquisition operation, data on changes in the infrared absorption spectrum of the hair 50 according to the total number of stretching operations is acquired.

[0084] In addition, in the analysis step, the change in the structure of the hair 50 depending on the total number of stretching operations is confirmed by a method similar to the analysis step of the evaluation method for the hair 50 according to the above-mentioned embodiment. That is, the data on the change in the infrared absorption spectrum of the hair 50 acquired in the acquisition step is analyzed by multivariate spectral analysis to confirm the change in the structure of the hair 50 depending on the total number of stretching operations. Note that, in the analysis, various preprocessing steps such as smoothing, baseline correction, and differentiation may be performed on the obtained infrared absorption spectrum.

[0085] Furthermore, in the efficacy evaluation step, the efficacy of the hair cosmetic or hair treatment agent on the hair 50 is evaluated using a method similar to the method for evaluating the condition of the hair 50 in the evaluation step of the method for evaluating the hair 50 according to the above-described embodiment. That is, the efficacy of the hair cosmetic or hair treatment agent on the hair 50 is evaluated based on the results of the analysis step.

[0086] As an example, in the efficacy evaluation step, the efficacy of a hair cosmetic or hair treatment agent on hair 50 can be evaluated by the following method. First, the total number of stretching operations that result in a structural change event, such as a first structural change event or a second structural change event, is identified. Then, the total number of stretching operations that result in a structural change event is considered to be the total number of stretching operations that result in a precursory phenomenon to breakage. For example, the total number of stretching operations that result in a first structural change event is considered to be the total number of stretching operations that result in a precursory phenomenon to first breakage, and the total number of stretching operations that result in a second structural change event is considered to be the total number of stretching operations that result in a precursory phenomenon to second breakage. If the total number of stretching operations that result in a precursory phenomenon to breakage is low, the efficacy of the hair cosmetic or hair treatment agent that is the subject of the evaluation method is determined to be unfavorable. On the other hand, if the total number of stretching operations that result in a precursory phenomenon to breakage is high, the efficacy of the hair cosmetic or hair treatment agent that is the subject of the evaluation method is determined to be favorable.

[0087] For example, when evaluating a hair cosmetic or hair treatment agent that is expected to have the effect of suppressing breakage of the hair 50, if the total number of stretching operations that cause precursory phenomena of breakage is small, it is judged that the effect of suppressing breakage of the hair 50 is insufficient. On the other hand, if the total number of stretching operations that cause precursory phenomena of breakage is large, it is judged that the effect of suppressing breakage of the hair 50 is sufficient.

[0088] As another example, when evaluating a hair cosmetic or hair treatment agent that may promote breakage of the hair 50, if the total number of stretching operations that cause precursory phenomena of breakage is small, it is determined that the effect of promoting breakage of the hair 50 is unacceptably large. On the other hand, if the total number of stretching operations that cause precursory phenomena of breakage is large, it is determined that the effect of promoting breakage of the hair 50 is acceptably small.

[0089] Whether the total number of stretching operations that cause precursor phenomena of breakage in the hair 50 is large or small can be determined by comparing it with a predetermined reference value of the total number of times, as in the evaluation method for hair 50 according to the above-described embodiment.

[0090] Alternatively, whether the total number of stretching operations is high or low may be determined by the following method. First, a comparative hair that has not been treated with a hair cosmetic or hair treatment agent is separately prepared. Next, the comparative hair is subjected to the acquisition step, analysis step, and evaluation step to identify the total number of stretching operations at which a precursor phenomenon to breakage occurs for the comparative hair. Then, a reference value for the total number of stretching operations is determined based on the identified total number of stretching operations, and whether the total number of stretching operations is high or low is determined by comparing it with the reference value.

[0091] Furthermore, the method for evaluating a hair cosmetic or hair treatment agent may further include a removal step of removing the cuticle 51 from the hair 50 before the acquisition step, similar to the method for evaluating the hair 50 according to the above-described embodiment.

[0092] The method for evaluating hair cosmetics or hair treatment agents may also be used to evaluate hair cosmetics or hair treatment agents that are expected to have the effect of suppressing curl in the hair 50 or that may accelerate curl in the hair 50. In this case, the efficacy evaluation step may be performed as follows: The total number of stretching operations that result in a first structural change event is considered to be the total number of stretching operations that result in a first, more severe curl precursor. The total number of stretching operations that result in a second structural change event is considered to be the total number of stretching operations that result in a second, more severe curl precursor. The efficacy of the hair cosmetics or hair treatment agents on the hair 50 is then evaluated using the total number of stretching operations that result in the first, more severe curl precursor and the total number of stretching operations that result in the second, more severe curl precursor. [Example]

[0093] Next, the present invention will be explained in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0094] Example 1 As Example 1, hair 50 was evaluated by the method for evaluating hair 50 described in the present embodiment. In the collection step, hair 50 that had been bleached three times was collected.

[0095] In the removal step, the hair 50 was traced with a diamond file (manufactured by Sankyo Corporation, #600) to remove the cuticle 51 from the hair 50. The diameter of the hair 50 before and after tracing the hair 50 with the diamond file was measured with a micrometer, and it was confirmed that the diameter of the hair 50 had decreased by 5.0 μm or more after tracing the hair 50 with the diamond file. Thereafter, the surface of the hair 50 was observed from all directions 360° using a laser microscope.

[0096] Observation using a laser microscope confirmed that cuticle 51 had been removed from hair 50. This shows that cuticle 51 can be removed from hair 50 by scraping the surface of hair 50 so that the diameter of hair 50 is reduced by 5.0 μm or more.

[0097] In the acquisition process, first, a pre-acquisition operation was performed to acquire the infrared absorption spectrum of the hair 50 when the total number of stretching operations performed on the hair 50 was 0. Next, a spectrum acquisition cycle including five stretching operations and one acquisition operation was performed using a texture analyzer. Because the hair 50 broke after the 85th stretching operation, the spectrum acquisition cycle was only able to be performed 16 times.

[0098] For one stretching run, 50 strands of hair were stretched by 5.0% at a rate of 180 mm / min.

[0099] As a pre-acquisition operation and one acquisition operation, an infrared absorption spectrum of the hair 50 was acquired by the microscopic ATR method using a microscopic FT-IR (Nicolet iN10 manufactured by Thermo Scientific). The conditions for acquiring the infrared absorption spectrum are as follows. Aperture: 50μm x 50μm ATR Pressure: 15 Accumulation count: 64 times Resolution:8cm-1 Cell: Germanium (Ge)

[0100] In the acquisition step, a total of 17 infrared absorption spectra were acquired, including one infrared absorption spectrum acquired in the pre-acquisition operation and 16 infrared absorption spectra acquired in the acquisition operations during the 16 spectrum acquisition cycles, as shown in Fig. 8. Note that "ABs." on the vertical axis in Fig. 8 and Figs. 9 to 12, which will be described later, stands for absorbance.

[0101] In the analysis step, the data on the changes in the infrared absorption spectrum of the hair 50 was analyzed by multivariate spectral analysis using multivariate analysis software, Unscrambler (registered trademark) X (Camo Analytics). Other analysis software that can be used includes Panorama (LabCognition) and PLS_TOOLBOX (Eigenvector Research).

[0102] Specifically, first, a part of the infrared absorption spectrum shown in Figure 8 acquired in the acquisition step was subjected to second-order differentiation and then multivariate spectral decomposition, and it was confirmed to which component in the hair 50 each of the decomposed spectra belonged. Figure 9 shows the part of the infrared absorption spectrum shown in Figure 8 at wavenumbers of 2800-3000 cm -1 The results of multivariate spectral decomposition are shown in Figure 10. -1 Figure 11 shows the results of multivariate spectral decomposition of the range of wavenumbers 1000-1060 cm of a part of the infrared absorption spectrum shown in Figure 8. -1 This is the result of multivariate spectral decomposition after second-order differentiation of the range.

[0103] Wave number 2800-3000cm -1After second-order differentiation of the infrared absorption spectrum in the range of 1700-1780 cm, a single spectrum was isolated by multivariate spectral decomposition, as shown in Figure 9. The isolated spectrum was confirmed to be attributable to a methylene group (CH2). -1 After second-order differentiation of the infrared absorption spectrum in the range of 1000-1060 cm, multivariate spectral decomposition was performed to separate one spectrum shown in Figure 10. The separated spectrum was confirmed to be attributed to a carbonyl group (C=O). -1 After second-order differentiation of the infrared absorption spectrum in the range, multivariate spectral decomposition was performed to isolate one spectrum, as shown in Figure 11. The isolated spectrum was confirmed to be attributable to sulfonic acid groups (SO3H).

[0104] Next, based on the correspondence between each of the resolved spectra and the components assigned to each of the resolved spectra, the component concentrations of the components in the hair 50 at different times after the total number of stretching operations of the hair 50 were calculated. FIG. 12 is a graph showing the change in the component concentration of methylene groups (CH) in the hair 50 in Example 1 depending on the total number of stretching operations. The component concentrations shown on the vertical axis in FIG. 12 are component concentration values ​​calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50. The component concentrations shown on the vertical axis in FIGS. 13 to 22, which will be described later, are also component concentration values ​​calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50. FIG. 13 is a graph showing the change in the component concentration of carbonyl groups (C═O) in the hair 50 in Example 1 depending on the total number of stretching operations. FIG. 14 is a graph showing the change in the concentration of sulfonic acid groups (SO3H) in the hair 50 depending on the total number of stretching operations.

[0105] In the evaluation step, the total number of stretching operations at which a first structural change event occurred in the hair 50 was identified based on the structural changes in the hair 50 confirmed in the analysis step. In particular, among the acquisition operations in which a 2.0-fold or greater increase in the methylene group concentration in the hair 50 was confirmed, a 1.5-fold or greater increase in the carbonyl group concentration in the hair 50 was confirmed, the methylene group concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 was 0.0001 or greater, and the carbonyl group concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair 50 was 0.0001 or greater, the total number of stretching operations at which the first structural change event occurred was determined to be the total number of stretching operations at which the first structural change event occurred. The total number of stretching operations at which the identified first structural change event occurred was then considered to be the total number of stretching operations at which the first breakage precursor phenomenon occurred. Furthermore, the total number of stretching operations at which a second structural change event occurs in the hair 50 was identified based on the structural changes in the hair 50 confirmed in the analysis process. In particular, among the acquisition operations at which a 1.4-fold or greater increase in the sulfonic acid group component concentration in the hair 50 was confirmed and the sulfonic acid group component concentration value calculated by analyzing the second-order derivative infrared absorption spectrum of the hair 50 was 0.0001 or greater, the total number of stretching operations at which the second structural change event occurs was determined to be the total number of stretching operations at which the second structural change event occurs. The total number of stretching operations at which the identified second structural change event occurs was then considered to be the total number of stretching operations at which the second breakage precursor phenomenon occurs in the hair 50. The dashed line L1 in Figures 12 and 13 indicates the total number of stretching operations at which the first breakage precursor phenomenon occurs in the hair 50. 14 is a line showing the total number of stretching operations until the precursor phenomenon of the second breakage occurs in the hair 50.

[0106] Example 2 In Example 2, in the collection step, hair 50 that had not been treated, such as bleaching, was collected as the hair 50. The condition of the untreated hair 50 was then evaluated. In the acquisition step, 20 spectrum acquisition cycles were performed on the hair 50. As a result, the hair 50 was stretched 100 times, but the hair 50 did not break. Except for the above points, the condition of the hair 50 was evaluated using the same method as that described in Example 1. FIG. 15 is a graph showing the change in the concentration of methylene groups (CH) in the hair 50 in Example 2 depending on the total number of stretching operations. FIG. 16 is a graph showing the change in the concentration of carbonyl groups (C═O) in the hair 50 in Example 2 depending on the total number of stretching operations. FIG. 17 is a graph showing the change in the concentration of sulfonic acid groups (SO═H) in the hair 50 in Example 2 depending on the total number of stretching operations.

[0107] (Comparative Example 1) In Comparative Example 1, the hair 50, which had been bleached three times, similar to the hair 50 evaluated in Example 1, was stretched and an evaluation method was performed to calculate the hysteresis ratio. Specifically, when a spectrum acquisition cycle including five stretching operations and one acquisition operation was performed on the hair 50 in Example 1, the hysteresis ratio was calculated at the same timing as the acquisition operation. That is, Comparative Example 1 was performed in parallel with Example 1. This confirmed the change in the hysteresis ratio depending on the total number of stretching operations. The hysteresis ratio is the value obtained by dividing the work load required to stretch the hair 50 by the work load required to return the hair 50 to its original state. Because Comparative Example 1 was performed in parallel with Example 1, the hair 50 broke after the 85th stretching operation in Comparative Example 1, similar to Example 1.

[0108] (Comparative Example 2) In Comparative Example 2, evaluation was performed on hair 50 that had not been subjected to any treatment, such as bleaching, similar to the hair 50 evaluated in Example 2. Specifically, when a spectrum acquisition cycle including five stretching operations and one acquisition operation was performed on the hair 50 in Example 2, the hysteresis ratio was calculated at the same timing as the acquisition operation. That is, Comparative Example 2 was performed in parallel with Example 2. Except for the above points, the hair 50 was evaluated by the same method as the method described in Comparative Example 1. Because Comparative Example 2 was performed in parallel with Example 2, in Comparative Example 2, the 100th stretching operation was performed, as in Example 2, but the hair 50 did not break.

[0109] FIG. 18 is a graph showing the change in the hysteresis ratio of the hair 50 in Comparative Examples 1 and 2 depending on the total number of stretching operations.

[0110] (Results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2) In Example 1, as shown in FIG. 12, the total number of drawing operations at which the first precursor to breakage occurred in the hair 50 was determined to be 55. In addition, in Example 1, as shown in FIG. 14, the total number of drawing operations at which the second precursor to breakage occurred in the hair 50 was determined to be 60. As such, it was found that in Example 1, the total number of drawing operations at which the first precursor to breakage occurred and the total number of drawing operations at which the second precursor to breakage occurred could be determined. Note that in Example 2, the first and second precursors to breakage were not observed in the hair 50. This is thought to be because the hair 50 of Example 2, which had not been treated with bleaching or the like and was thought to be less damaged than the hair 50 of Example 1, did not experience the first and second precursors to breakage even after 100 drawing operations.

[0111] Furthermore, in the hair 50 of Example 1, which was considered to be damaged by bleaching and broke after 85 stretching operations, the first precursor to breakage occurred after a total of 55 stretching operations, and the second precursor to breakage occurred after a total of 60 stretching operations. On the other hand, in the hair 50 of Example 2, which was considered to be less damaged than the hair 50 of Example 1 and did not break even after 100 stretching operations, the first and second precursors to breakage did not occur even after 100 stretching operations. From this, it was found that the total number of stretching operations at which the first precursor to breakage occurs and the total number of stretching operations at which the second precursor to breakage occurs are indicators of the condition of the hair 50, such as the susceptibility of the hair 50 to breakage and the degree of damage to the hair 50.

[0112] Furthermore, from the results of Comparative Examples 1 and 2, it was confirmed that the hysteresis ratio decreased in the 85th stretching operation, at which the hair 50 broke in Comparative Example 1, but no precursory phenomena that preceded breakage could be confirmed from the change in the hysteresis ratio depending on the total number of stretching operations. In contrast, the first and second precursory phenomena of breakage were confirmed in Example 1. From these results, it was found that the evaluation method for the hair 50 according to Example 1 is superior to the evaluation methods for the hair 50 according to Comparative Examples 1 and 2 in that it can evaluate the state of the hair 50 taking precursory phenomena of breakage into consideration.

[0113] Example 3 In Example 3, the condition of the hair 50 was evaluated using the same method as in Example 1, except for the following points. In the collection step, curly hair that was visually confirmed to be curly was collected as the hair 50. Curly hair refers to hair 50 whose curvature is 0.51 to 1.74 and whose cross-sectional flatness is 0.083 to 0.381. The curvature of the hair 50 was measured using an image scanner (product name GTX-830) manufactured by Seiko Epson Corporation by the following method. First, the hair was immersed in ion-exchange water for 10 minutes to remove any temporary set shape. Then, a two-dimensional image was obtained using the image scanner, and the curvature of the curled portion of the hair was calculated using image analysis software. The flatness of the hair 50 was calculated based on the measured major and minor diameters of the curled portion using a thickness gauge (product name WDT-10SPC) manufactured by Niigata Seiki Co., Ltd. In addition, in the acquisition process, a spectrum acquisition cycle including 25 stretching operations and one acquisition operation was performed 20 times on the hair 50. As a result, 500 stretching operations were performed on the hair 50, but the hair 50 did not break. Note that one stretching operation involved stretching the hair 50 at a speed of 180 mm / min until the force applied to the hair 50 reached 0.3 N.

[0114] Fig. 19 is a graph showing the change in the concentration of methylene groups (CH2) in the hair 50 in Example 3 depending on the total number of stretching operations. Fig. 20 is a graph showing the change in the concentration of carbonyl groups (C=O) in the hair 50 in Example 3 depending on the total number of stretching operations. Fig. 21 is a graph showing the change in the concentration of sulfonic acid groups (SO3H) in the hair 50 in Example 3 depending on the total number of stretching operations.

[0115] In the evaluation process, the total number of stretching operations at which the first structural change event occurred in the hair 50 was determined using the same method as in Example 1, and was considered to be the total number of stretching operations at which the first precursor to stronger curling occurred. The dashed line L3 shown in Figures 19 and 20 indicates the total number of stretching operations at which the second precursor to stronger curling occurred in the hair 50. The total number of stretching operations at which the second structural change event occurred was determined as the total number of stretching operations at which the second structural change event occurred, when a 1.4-fold or greater increase in the sulfonic acid group component concentration in the hair 50 was confirmed and the sulfonic acid group component concentration calculated by analyzing the second-order derivative infrared absorption spectrum of the hair 50 was 0.0001 or greater. The total number of stretching operations at which the second structural change event occurred was determined using the same method as in Example 1, except for the above points. Moreover, the dashed line L4 shown in FIG. 21 is a line indicating the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs in the hair 50.

[0116] In addition, the curvature of the hair 50 was measured by the above-described measurement method before the spectrum acquisition cycle was performed on the hair 50 and after 20 spectrum acquisition cycles were performed on the hair 50.

[0117] Example 4 In Example 4, straight hair with no visible curls was collected as the hair 50 in the collection step. Straight hair refers to hair 50 with a curvature of less than 0.51 and a cross-sectional flatness of less than 0.083, for example. Furthermore, in the acquisition step, a spectrum acquisition cycle, including 25 stretching operations and one acquisition operation, was performed 20 times on the hair 50. As a result, the hair 50 was stretched 500 times, but the hair 50 did not break. Except for the above points, the condition of the hair 50 was evaluated using the same method as in Example 1. Figure 22 is a graph showing the change in the concentration of methylene groups (CH2) in the hair 50 in Example 4 depending on the total number of stretching operations. 23 is a graph showing the change in the component concentration of carbonyl groups (C=O) in hair 50 in Example 4, and FIG. 24 is a graph showing the change in the component concentration of sulfonic acid groups (SO3H) in hair 50 in Example 4 according to the total number of stretching operations. Furthermore, the curvature of hair 50 was measured by the measurement method described above in Example 3 before and after 100 spectrum acquisition cycles were performed on hair 50.

[0118] (Results of Examples 3 and 4) Fig. 25 is a diagram showing the results of measuring the curvature of the hair 50 before and after performing a spectrum acquisition cycle in Examples 3 and 4. As shown in Fig. 25, the curvature of the hair 50 in Example 3 was 0.936 before performing a spectrum acquisition cycle on the hair 50, and was 1.307 after performing 20 spectrum acquisition cycles on the hair 50. In contrast, the curvature of the hair 50 in Example 4 was 0.210 before performing a spectrum acquisition cycle on the hair 50, and was 0.302 after performing 20 spectrum acquisition cycles on the hair 50. Thus, the hair 50 in Example 3 showed a larger change in curvature before and after performing a spectrum acquisition cycle than the hair 50 in Example 4.

[0119] In Example 3, as shown in Figures 19 and 20, the total number of stretching operations at which the precursor phenomenon of the first stronger curl occurs in the hair 50 was identified as 75 times. Also, in Example 3, as shown in Figure 21, the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs in the hair 50 was identified as 125 times and 300 times. Thus, it was found that in Example 3, the total number of stretching operations at which the precursor phenomenon of the first stronger curl occurs and the total number of stretching operations at which the precursor phenomenon of the second stronger curl occurs can be identified. Note that, in Example 4, the precursor phenomena of the first and second stronger curls were not observed in the hair 50.

[0120] Considering that the change in curvature before and after the spectrum acquisition cycle was larger for the hair 50 of Example 3 than for the hair 50 of Example 4, the reason for this is thought to be as follows: The straight hair 50 of Example 4 was less damaged than the curly hair 50 of Example 3, and therefore less likely to curl and less likely to develop precursor phenomena to stronger curls. For this reason, it is thought that the hair 50 of Example 4 did not develop the first and second precursor phenomena to stronger curls even after 500 stretching operations. From this, it was found that the total number of stretching operations at which the first and second precursor phenomena to stronger curls occur can be used as an indicator of the condition of the hair 50, such as the tendency of the hair 50 to become frizzy and the degree of damage to the hair 50.

[0121] In Example 3, the precursory phenomenon of the second stronger curl was observed multiple times. Specifically, as shown in FIG. 21 , the precursory phenomenon of the second stronger curl was observed twice: when the total number of stretching operations reached 125 and when the total number of stretching operations reached 300. The reason why the precursory phenomenon of the second stronger curl was observed twice, when the total number of stretching operations reached 125 and 300, is thought to be because the curl of the hair 50 gradually increased with repeated stretching operations, and accordingly, the precursory phenomenon of the second stronger curl also repeatedly occurred. Thus, the change in the sulfonic acid group component concentration shown in FIG. 21 is thought to indicate that the precursory phenomenon of the second stronger curl may repeatedly occur as the curl of the hair 50 progresses. From this, it is thought that, for example, when evaluating the progress of curl of the hair 50 as the condition of the hair 50, it is also effective to use information on the precursory phenomenon that repeatedly occurs multiple times.

[0122] The aspects of the present invention are not limited to the above-described embodiments, but include various modifications that may be conceived by those skilled in the art, and the effects of the present invention are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present invention that can be derived from the contents defined in the claims and their equivalents. [Explanation of symbols]

[0123] 1. Rating System 2. Extension operation execution unit 3 Acquisition part 4 Analysis section 5 Evaluation section 50 Hair 51 Cuticle 53 Cortex 55 Medulla

Claims

1. an acquisition step of performing a spectrum acquisition cycle at least a plurality of times, the spectrum acquisition cycle including a stretching operation of stretching the hair and an acquisition operation of acquiring an infrared absorption spectrum of the hair after the stretching operation, and acquiring data on changes in the infrared absorption spectrum of the hair according to the total number of stretching operations based on the infrared absorption spectrum acquired in each of the acquisition operations and the total number of stretching operations performed up to the execution of each of the acquisition operations; an analysis step of analyzing the data of the change in the infrared absorption spectrum of the hair acquired in the acquisition step by multivariate spectral analysis to confirm a change in the structure of the hair depending on the total number of times of the stretching operation; and an evaluation step of evaluating the condition of the hair based on the results of the analysis step.

2. The hair evaluation method according to claim 1 , further comprising a removal step of removing cuticles from the hair before the obtaining step.

3. 3. The hair evaluation method according to claim 1 or 2, wherein a single stretching operation comprises pulling the hair at a constant speed of 120 mm / min to 240 mm / min to stretch it by a constant ratio of 30% or less, or pulling the hair at a constant speed of 120 mm / min to 240 mm / min until the tensile force applied to the hair reaches a constant value of 0.4 N or less.

4. 4. The hair evaluation method according to claim 1, wherein, in the evaluation step, the total number of stretching operations when the acquisition operation is performed in which, based on the change in the hair structure confirmed in the analysis step, a 2.0-fold or greater increase in the methylene group component concentration in the hair and a 1.5-fold or greater increase in the carbonyl group component concentration are confirmed compared to an acquisition operation performed one less in total, the value of the methylene group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair is 0.0001 or greater, and the value of the carbonyl group component concentration calculated by analyzing the second-derivative infrared absorption spectrum of the hair is 0.0001 or greater is determined to be the total number of times a first structural change event occurs in the hair.

5. 5. The hair evaluation method according to claim 1, wherein, in the evaluation step, a total number of stretching operations when an acquisition operation is performed in which a change in the hair structure confirmed in the analysis step indicates an increase in the sulfonic acid group component concentration in the hair of 1.4 times or more compared to an acquisition operation with a total number of operations that is one less, and the value of the sulfonic acid group component concentration calculated by analyzing the second-order differentiated infrared absorption spectrum of the hair is 0.0001 or more, is determined to be the total number of times a second structural change event occurs in the hair.

6. a treatment step of treating the hair with a hair cosmetic or a hair treatment agent; an acquisition step of performing a spectrum acquisition cycle at least a plurality of times, the spectrum acquisition cycle including a stretching operation of stretching the hair and an acquisition operation of acquiring an infrared absorption spectrum of the hair after the stretching operation, and acquiring data on changes in the infrared absorption spectrum of the hair according to the total number of stretching operations based on the infrared absorption spectrum acquired in each of the acquisition operations and the total number of stretching operations performed up to the execution of each of the acquisition operations; an analysis step of analyzing the data of the change in the infrared absorption spectrum of the hair acquired in the acquisition step by multivariate spectral analysis to confirm a change in the structure of the hair depending on the total number of times of the stretching operation; an efficacy evaluation step of evaluating the efficacy of the hair cosmetic or hair treatment agent on the hair based on the results of the analysis step.

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