Heating implement

Abstract

To provide a heating implement capable of generating a large amount of steam without excessively heating a target portion.SOLUTION: A heating implement 1 includes: a front surface sheet 5; a rear surface sheet 6; and a heating element 3 held between the front surface sheet 5 and the rear surface sheet 6. The heating element 3 contains oxidizable metal, a carbon material, an electrolyte and water. The heating element 3 is configured so as to generate steam from the heating element 3 itself along with power generation. The rear surface sheet 6 is made of a breathable fiber sheet including a fiber containing at least a polyethylene terephthalate resin. The rear surface sheet 6 contains rear surface-side first fibers each having a fiber diameter exceeding 15 μm, measured by electron microscope observation in its plane view.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a heating device. [Background technology]

[0002] The present applicant has previously proposed a heating device capable of supplying hot water vapor to the user's body (see Patent Documents 1 and 2). Patent Document 1 discloses a water vapor generating thermal sheet for eyes that contains a water vapor generating composition and is covered in sequence with at least a first moisture permeable sheet and a second moisture permeable sheet. In this thermal sheet, the first moisture permeable sheet and the second moisture permeable sheet are arranged so that a space for retaining water vapor can be generated between them. Patent Document 2 discloses a heating device that includes a water vapor generating section that releases water vapor and a sheet made of nonwoven or woven fabric that holds a water-soluble moisturizing agent and is positioned on the wearer's skin side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-73688 A [Patent Document 2] JP 2015-123336 A Summary of the Invention [Problem to be solved by the invention]

[0004] The heating devices capable of generating water vapor described in Patent Documents 1 and 2 are required to generate a large amount of water vapor. Increasing the heating temperature of the heating element is considered as a means for generating a large amount of water vapor. However, in that case, there is a risk that the part of the body to which the heating device is attached may be excessively heated. Therefore, there has been a demand for a heating device that can generate a large amount of water vapor without excessively heating the target part. Therefore, an object of the present invention is to provide a heating device capable of generating water vapor that is capable of generating a large amount of water vapor without excessively heating the target area. [Means for solving the problem]

[0005] The present disclosure relates to a heating device comprising a top sheet positioned closer to the user's skin, a back sheet positioned further from the user's skin, and a heating element held between the top sheet and the back sheet. In one embodiment of the present disclosure, the heating element includes an oxidizable metal, a carbon material, an electrolyte, and water. In one embodiment of the present disclosure, the heating element is configured to generate steam from the heating element itself as heat is generated. In one embodiment of the present disclosure, the back sheet is made of a breathable fiber sheet including fibers containing at least polyethylene terephthalate resin. In one embodiment of the present disclosure, the back sheet includes back side first fibers having a fiber diameter of more than 15 μm when measured in a plan view by scanning electron microscope observation. Effect of the Invention

[0006] According to the heating device of the present disclosure, a large amount of water vapor can be generated without excessively heating the target area. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view showing one embodiment of the heating device of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of the heating device shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along the horizontal direction, which is the longitudinal direction, of the heating device shown in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a main part of the heating device shown in FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of a main part of another embodiment of the heating device taken along the lateral direction. [Figure 6]FIG. 6 is an enlarged cross-sectional view of a main part of another embodiment of the heating device taken along the lateral direction. [Figure 7] FIG. 7 is a schematic diagram of a device for measuring the amount of steam generated from a heating device. [Figure 8] FIG. 8 is a plan view showing another embodiment of the heating device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will be described below based on preferred embodiments with reference to the drawings. The heating device of the present invention is used to apply heat to an object to be heated (e.g., a human body) by contacting the object to be heated during use.

[0009] One embodiment of the heating device of the present invention is shown in Figure 1. The heating device 1 shown in the figure is a so-called eye mask type, which is placed in contact with both eyes of a person, which is the object to be heated, to apply heat to the eyes and the surrounding area. The heating device 1 is designed to generate steam heated to a predetermined temperature, which can provide heat to an object to be heated. In the following explanation, unless otherwise specified, the object to be heated will be the skin or eyes of the user.

[0010] As shown in FIG. 1, the heating device 1 comprises a main body 2 that is elongated in the horizontal direction X and has a shape that covers both eyes of the user when in use, a heating element 3 held within the main body 2, and a pair of ear hooks 4, 4. The ear hooks 4 are provided at both outer end regions in the lateral direction X of the main body 2 and can be turned around outward in the lateral direction X. This allows the ear hooks 4, 4 to be hung on the user's ears, respectively, so that the main body 2 can maintain the state in which both of the user's eyes are covered. From the viewpoint of improving the wearing comfort, it is preferable that the sheet material constituting the ear hook part 4 is a stretchable sheet. In the following explanation, the direction corresponding to the longitudinal direction of the heating device 1 is also called the horizontal direction X, and the direction perpendicular to the horizontal direction X is also called the vertical direction Y.

[0011] Fig. 2 shows an exploded perspective view of the heating device 1. Fig. 3 shows a cross-sectional view along the lateral direction X (longitudinal direction) of the heating device 1. The main body 2 in the heating device 1 shown in these figures has a long dimension in one direction. The main body 2 is flat and includes a top sheet 5 located on the side closest to the user's skin, and a back sheet 6 located on the side farther from the user's skin. The top sheet 5 preferably constitutes a surface that comes into contact with an object to be heated, such as a person's eyes, when the heating device 1 is in use. The back sheet 6 is the surface away from the user's skin and forms the outer surface of the heating device 1. That is, in Figures 2 and 3, the upper side is the side closer to the user's skin, and the lower side is the side farther from the user's skin.

[0012] The top sheet 5 and the back sheet 6 shown in Figures 2 and 3 are overlapped and directly bonded to each other with an adhesive 7 such as a hot melt adhesive, so that two heating elements 3, 3 are housed between the two sheets 5, 6 at a distance from each other in the lateral direction X. Of the top sheet 5 and the back sheet 6, at least the surface of the top sheet 5 that faces the object to be heated, such as the skin (hereinafter also referred to as the "skin-facing surface") is preferably made of a breathable fiber sheet, and it is more preferable that the entire top sheet 5 is made of a fiber sheet. Similarly, the outermost surface of the back sheet 6 is also preferably made of a breathable fiber sheet, and it is more preferable that the entire back sheet 6 is made of a fiber sheet. The top sheet 5 and the back sheet 6 may each independently have a single-layer structure or a multi-layer structure. A detailed description will be given later of each of the sheets 5 and 6. The fiber sheet is an assembly of constituent fibers in which a plurality of fibers are entangled, fused, or bonded to maintain a sheet-like shape.

[0013] The heating element 3 held between the top sheet 5 and the back sheet 6 in the main body 2 is configured to react with oxygen in the air to generate heat, and generate water vapor heated to a predetermined temperature as the heat is generated. In other words, the heating element 3 generates steam from itself as the heat is generated. Specifically, the heating element 3 includes a heating portion 3a containing an oxidizable metal that generates heat through an oxidation reaction with oxygen in the air, a carbon material such as activated carbon that serves as a catalyst for the oxidation reaction, an electrolyte, and water. The oxidizable metal and the carbon material are both preferably in the form of powder.

[0014] The heat generating portion 3a may be, for example, a heat generating sheet composed of a fiber sheet containing a fiber material in addition to an oxidizable metal, a carbon material, an electrolyte, and water, or a layer of a paste-like or powder-like heat generating composition containing an oxidizable metal, a carbon material, an electrolyte, and water. From the viewpoint of retaining a sufficient amount of water that can increase the amount of water vapor generated by the heat generated by the heat generating element 3, it is preferable that the heat generating element 3 further comprises a water retention agent layer containing a water retention agent such as a water-absorbent polymer adjacent to the heat generating portion 3a. Alternatively, it is also preferable that a water retention agent is mixed in the heat generating sheet or the heat generating composition.

[0015] The heat generating sheet and the heat generating composition may be used alone, or at least one of the heat generating sheet and the heat generating composition may be used in a bag made of a plurality of sheets bonded together. As various materials constituting the heat generating sheet and the heat generating composition, for example, the materials described in JP-A-2003-102761 and JP-A-2006-340928 can be used.

[0016] The cross-sectional view shown in Fig. 3 shows the fixed state of the flat heating element 3 formed by containing the heating part 3a in the bag body 3b. The heating element 3 shown in the figure is fixed to the outer surface of the bag body 3b and the inner surface of the back sheet 6 of the heating device 1 by adhesive fixing parts 7a, 7a formed by adhesive 7, and the other surfaces are not fixed to the back sheet 6. Each adhesive fixing part 7a, 7a is provided in the central area of ​​the heating device 1 in the horizontal direction X and extends along the vertical direction Y of the heating device 1. With this configuration, the heating element 3 is arranged so as to be highly flexible and in close contact with the heating object such as the user's eyes and their vicinity when the heating device 1 is used, and heat can be efficiently applied to the heating object.

[0017] Returning to Fig. 2, the ear hook part 4 shown in the figure is made of a sheet material, and the sheet material has an insertion part 4A formed thereon, which extends in the lateral direction X. The insertion part 4A is a hole through which the ear passes when the ear hook part 4 is hung on the ear. Alternatively, the insertion part 4A may be formed as a through slit through which the ear can pass. 2 and 4, the ear hook portion 4 is joined at both outer end regions in the lateral direction X to the outer surface of the topsheet 5 of the main body portion 2, thereby forming a joining region 9 where the main body portion 2 and the ear hook portion 4 are joined. The joining region 9 also functions as a folding portion when the ear hook portion 4 is turned over, with the joining end portion 9s as an axis.

[0018] Fig. 4 is a cross-sectional view showing one embodiment of the arrangement relationship of the heating element 3, the top sheet 5, the back sheet 6, and the joint area 9. The joint area 9 between the main body 2 and the ear hooking part 4 shown in Figs. 2 and 4 is continuously joined from a joint end 9s, which is the inner end of the joint area 9 in the horizontal direction X, to the outer end of the main body 2 in the horizontal direction X, and has a semi-elliptical shape. As shown in Fig. 4, the joint area 9 is formed by joining the top sheet 5 and the ear hooking portion 4. The joint area 9 also functions as a folding portion when the ear hooking portion 4 is turned over around the joint end portion 9s. The joint area 9 shown in Figs. 2 and 4 is formed by continuous joining, but instead, it may be formed by intermittent joining.

[0019] In the heating device 1 having the above-mentioned configuration, the back sheet 6, which is the part that faces outward when in use, preferably contains fibers having a specific configuration. In the following explanation, a breathable fiber sheet, which is a suitable embodiment of the back sheet 6, will be used as an example.

[0020] Specifically, the fibers constituting the back sheet 6 preferably contain at least polyethylene terephthalate (hereinafter also referred to as "PET") resin. In other words, the back sheet 6 is an aggregate of fibers that contain at least PET resin as one of the constituent fibers. When a fiber sheet containing at least PET resin is used as the back sheet 6 forming the outer surface of the heating device 1, the heat generated during use of the heating device 1 increases the volume of the back sheet 6, and a large amount of air layer is generated in the back sheet 6. This air layer acts as an insulating layer to keep the heating element 3 warm. As a result, the amount of water vapor generated from the heating element 3 increases. In addition, when the heat retention is improved by the back sheet 6, the amount of water vapor generated from the heating element 3 increases. This means that the thermal energy generated by the heat retention effect is consumed by the heat of vaporization of water. As a result, the heating temperature generated by the heating device 1 can be suppressed from rising excessively. Therefore, according to the heating device 1 of the present disclosure, the amount of water vapor generated increases, but the temperature of the heated area can be suppressed from rising excessively.

[0021] The inventors believe that the reason why the bulk of the back sheet 6 increases due to the heat generated when the heating device 1 is in use is because the back sheet 6 contains fibers that contain at least PET resin. The glass transition temperature of PET resin is approximately 69°C, which is sufficiently higher than the maximum heat generation temperature of the heating device 1. As a result, it is believed that fibers that contain at least PET resin are more likely to undergo elastic recovery due to the heat generated by the heating device 1. The bulk of the back sheet 6 increases due to elastic recovery.

[0022] The back sheet 6 includes back side first fibers having a predetermined fiber diameter. In detail, the back side first fibers have a fiber diameter of preferably more than 15 μm, more preferably 20 μm or more, even more preferably 25 μm or more, and preferably 60 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, and even more preferably 40 μm or less. In another embodiment, the fiber diameter may be even more preferably 30 μm or less. By having such a fiber diameter, the back side first fibers are more likely to undergo elastic recovery due to the heat generated by the heating device 1. As a result, the back sheet 6 including the back side first fibers increases in volume due to the heat generated by the heating device 1, and the amount of water vapor generated from the heating device 1 increases.

[0023] The above-mentioned "constituent fiber containing at least PET resin" may be the back side first fiber itself having the above-mentioned fiber diameter, or may be a fiber other than the back side first fiber. From the viewpoint of making the elastic recovery caused by the heat generated from the heating device 1 remarkable, it is preferable that at least the back side first fiber contains PET resin. In this case, the ratio of PET resin contained in the back side first fiber is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 70% by mass or more, and most preferably 100% by mass.

[0024] The fiber diameter of the back surface side first fibers can be measured, for example, by observing the back surface sheet 6 in a plan view with a scanning electron microscope (SEM) as follows. This method of measuring fiber diameter is commonly applied as a method of measuring fiber diameter of all fibers in the present disclosure. First, a histogram of the frequency of the number of fibers and the distribution of fiber diameters (hereinafter, simply referred to as a "histogram") is created to determine whether the back sheet 6 contains fibers of only one type of fiber diameter or further contains fibers of multiple fiber diameters. In detail, a measurement sample of the back sheet 6 to be measured is obtained by spraying the heating device 1 with cold spray to solidify the adhesive and carefully peeling it off, or by cutting it directly from the heating device 1. The measurement sample has a size of 2 cm x 2 cm. At this time, the measurement sample is prepared so that the surface facing the heating element 3 (hereinafter also referred to as the "inner surface") and the surface facing outward (hereinafter also referred to as the "outer surface") can be distinguished by any method. The above-mentioned method of taking out the measurement sample from the back sheet 6 is common to other methods in this disclosure.

[0025] Next, the fiber diameter and the number of fibers are measured from this measurement sample to create a histogram. The fiber diameter and the number of fibers are derived from a two-dimensional image obtained by observing the fibers, for example, at 2000 times magnification, by SEM observation of one side of the measurement sample in plan view. The number of fibers is measured by counting a continuous fiber within the range of the obtained two-dimensional image as one fiber. Then, the position of the SEM observation is changed and the observation is repeated until the number of fibers reaches 100 or more. Note that this observation can also be performed using image analysis software. For example, Photoshop (manufactured by Adobe Co., Ltd.) can be used as the image analysis software. The fiber diameter is the maximum diameter measured when a line perpendicular to the longitudinal direction of the fiber is drawn on the fiber, excluding defects such as fiber clumps, fiber intersections, and polymer droplets.

[0026] The above-mentioned measurements are carried out on the inner surface of the measurement sample, the width of the fiber diameter classes for creating the histogram is selected from the range of 0.1 to 0.5 μm, and a histogram of the frequency of the fiber count and the fiber diameter distribution is created based on the measurement results. When only one peak in the fiber diameter distribution is present in the created histogram, it is determined that the measurement side of the back sheet 6 is composed of only a single type of fiber. Alternatively, when two or more peaks in the fiber diameter distribution are present, it is determined that multiple types of fibers are present in the measurement side of the back sheet 6. The peak is the position of the fiber diameter at the apex where the frequency of the fiber count turns from positive to negative.

[0027] Whether the back sheet 6 comprises a single fiber layer or multiple fiber layers can be determined, for example, by observing the cross section of the measurement sample using a microscope or SEM to confirm the presence or absence of fiber layers and their boundaries based on differences in fiber diameter and fiber structure, or by dyeing the fibers, etc. If it is difficult to visually confirm whether or not there are multiple fiber layers, a histogram is also created on the other surface (outer surface) of the measurement sample using the above method, and the shape of the histogram on one surface (inner surface) of the measurement sample is compared with the shape of the histogram on the other surface of the measurement sample. If the number of peaks or the positions at which they appear are different, it is determined that there are multiple fiber layers. On the other hand, if the number of peaks and the positions at which they appear are the same, it is determined that there is a single fiber layer.

[0028] Using the above-mentioned method, it is determined whether the back sheet 6 contains only the back side first fibers or further contains fibers other than the back side first fibers. When only one peak exists in the fiber diameter distribution, the position of the fiber diameter at which the peak exists in the histogram is determined as the fiber diameter of the back side first fibers. When two or more peaks exist in the fiber diameter distribution, the position of the fiber diameter indicated by the peak located on the side with the largest fiber diameter among the peaks in the fiber diameter distribution is determined as the fiber diameter of the back side first fibers.

[0029] In order to make the elastic recovery caused by the heat generated by the heating device 1 even more pronounced, it is preferable that the back sheet 6 further contains, in addition to the above-mentioned back side first fibers, one or more types of other fibers different in type from the back side first fibers.

[0030] Examples of the fiber configuration in the back sheet 6 include the following: (i) a configuration in which the back side first fibers and fibers other than the back side first fibers are uniformly mixed in the region in contact with the heating element 3, (ii) a configuration in which, when the region in contact with the heating element 3 is viewed in plan, the region is composed of a region in which only the back side first fibers are present and a region in which only fibers other than the back side first fibers are present, or (iii) a configuration in which the back sheet 6 is composed of a multilayer structure having two or more fiber layers, and the back side first fibers are contained in only one of the fiber layers.

[0031] Of these, from the viewpoint of suppressing fiber fuzzing, improving the feel of the sheet, and more effectively exhibiting flexibility and fit, it is preferable that the back sheet 6 be in the form shown in (iii) above. From a similar viewpoint, it is preferable that the fiber sheet constituting the back sheet 6 maintains its sheet form by at least one of fusion and entanglement of the fibers so that the constituent fibers have contact portions where they are in contact with each other. In particular, the above-mentioned sheet form is preferably made of a nonwoven fabric. Examples of nonwoven fabrics in which fibers are entangled include spunlace nonwoven fabrics, air-through nonwoven fabrics, needle-punched nonwoven fabrics, chemically bonded nonwoven fabrics, and thermally bonded nonwoven fabrics. In order to obtain the above-mentioned embodiment (iii), a method of entangling or fusing two or more fiber webs or nonwoven fabrics can be mentioned. For example, in the case of an air-through nonwoven fabric, the above-mentioned contact portion is formed including a portion where some of the fibers are fused together in addition to a portion where the constituent fibers are simply in contact with each other and entangled, so that the constituent fibers are easily fixed to each other, which is advantageous in that fluffing and falling off of the constituent fibers are reduced. In addition, the nonwoven fabric or its constituent fibers may be surface-treated with silicone, a surfactant, or the like.

[0032] Furthermore, in addition to the nonwoven fabrics described above, foam sheets made of thermoplastic resins such as polyethylene, polyurethane, etc. can also be used. These sheet materials can also be used by mixing multiple fibers with different fiber materials, fiber diameters, degrees of crimp, etc., or by combining multiple sheet materials to achieve desired properties.

[0033] In a preferred embodiment of the back sheet 6, when the back sheet 6 has a multi-layer structure having two or more fiber layers, it preferably has at least a back sheet first fiber layer 61 including back sheet first fibers and a back sheet second fiber layer 62 including fibers other than the back sheet first fibers that have a fiber diameter different from that of the back sheet first fibers, as shown in Fig. 5. Specifically, it is preferred to have the back sheet second fiber layer 62 including back sheet second fibers that are fibers having a smaller fiber diameter than the back sheet first fibers. In addition, it is preferable that the back-side first fiber layer 61 does not contain the back-side second fibers, and the back-side second fiber layer 62 does not contain the back-side first fibers. That is, it is preferable that the backsheet 6 has at least a fiber layer containing the back-side first fibers and a fiber layer containing fibers other than the back-side first fibers. By providing multiple fiber layers containing fibers with different fiber diameters in this way, the heating device 1 can be provided with the desired functions in each fiber layer, such as the fiber layer containing the back side first fibers exhibiting the function of increasing bulk when heated, and the fiber layer containing the back side second fibers exhibiting good touch, texture, printability, etc. of the back sheet 6. As a result, the back sheet 6 is configured to efficiently and simultaneously exhibit the multiple functions described above, and the manufacturing efficiency of such a back sheet 6 is further improved.

[0034] For convenience of explanation, the following description will be given taking as an example the form of the back sheet 6 having a two-layer structure in which the back side first fiber layer 61 and the back side second fiber layer 62 are adjacently arranged as shown in Fig. 5, but the number of fiber layers is not particularly limited as long as the effect of the present invention is achieved. For example, as an example of the embodiment (Example 1), the back side first fiber layer 61 and the back side second fiber layer 62 are adjacently arranged, and one or more other fiber layers can be provided on the outer surface of at least one of the back side first fiber layer 61 and the back side second fiber layer 62. Alternatively, as an example of another embodiment (Example 2), one or more other fiber layers can be further provided between the back side first fiber layer 61 and the back side second fiber layer 62. The fibers contained in the adjacent fiber layers preferably have different fiber diameters. Therefore, in the case of Example 1, when the third fiber layer (not shown) is provided on the outer surface of the back side first fiber layer 61, the fiber diameter of the third fiber layer may be the same as the fiber diameter of the back side second fiber layer 62, or may be different from both the fiber diameter of the back side first fiber layer 61 and the fiber diameter of the back side second fiber layer 62.

[0035] For ease of explanation, the backsheet 6 shown in Fig. 5 is illustrated with clear boundaries between the fiber layers constituting the backsheet 6, but this is not limited to the above. In other words, when the backsheet 6 has a multi-layer structure, the boundaries between the fiber layers may be clear or may be unclear. In either case, when the back sheet 6 is viewed along the thickness direction, it is preferable from the viewpoint of handleability during manufacture and use that the proportion of the constituent fibers in each fiber layer changes stepwise, continuously, or a combination thereof.

[0036] In the present disclosure, "not containing fibers" means that the fibers are not intentionally contained in the fiber layer, and includes both the case where the fibers are not contained in the fiber layer at all and the case where the fibers are inevitably mixed in the fiber layer. In the latter case, for example, the back side first fibers constituting the back side first fiber layer 61 cross the boundary between the fiber layers and unintentionally enter the back side second fiber layer 62, and other unintentional fibers are inevitably mixed in.

[0037] When the back sheet 6 has at least a back side first fiber layer 61 and a back side second fiber layer 62, the fiber diameter of the back side second fibers constituting the back side second fiber layer 62 is preferably 6 μm or more, more preferably 10 μm or more, even more preferably 13 μm or more, and is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less, and particularly preferably 17 μm or less. It is also preferable that the fiber diameter of the back surface side second fibers is smaller than the fiber diameter of the back surface side first fibers. By making the back surface side second fibers have such a fiber diameter, the stiffness of the fibers is reduced, and when the back surface sheet 6 contacts the skin, a good feel and a smooth texture are obtained. In addition, the printability of the back surface sheet 6 is improved. The fiber diameter of the back surface side second fibers can be measured in the same manner as for the fiber diameter of the back surface side first fibers by observing the back sheet 6 in a plan view with a scanning electron microscope.

[0038] In addition, when the back sheet 6 has at least the back side first fiber layer 61 and the back side second fiber layer 62, the back side first fiber layer 61 is preferably arranged on the heating element contact surface when the heating device is in use, as shown in Fig. 5. In other words, the back side first fiber layer 61 is preferably arranged so as to face the heating element 3. Also, as shown in the same figure, the back side second fiber layer 62 is preferably arranged so as to form the outer surface of the heating device 1 when the heating device 1 is in use. This arrangement of the fiber layers is preferable because the bulk of the back side first fiber layer 61 can be easily increased by the heat generated by the heating element 3, thereby improving the heat retention of the heating element 3, and the back side second fiber layer 62 improves the printability and feel of the back sheet 6.

[0039] When the back sheet 6 has a back side first fiber layer 61, the back side first fiber layer 61 preferably further includes, in addition to the back side first fibers, back side third fibers having a fiber diameter smaller than that of the back side first fibers and larger than that of the back side second fibers. That is, the back side first fiber layer 61 preferably contains a plurality of fibers including at least the back side first fibers and the back side third fibers. It is more preferable that the back side first fiber layer 61 is made of only the back side first fibers and the back side third fibers, except for fibers inevitably mixed in, and does not contain the back side second fibers. By including the back side third fibers having such a predetermined fiber diameter relationship in the back side first fiber layer 61, the bulk of the back side first fiber layer 61 is significantly increased compared to when the back side first fiber layer 61 is composed only of the highly rigid back side first fibers, and the heat retention of the heating element 3 by the back sheet 6 is further improved.

[0040] Furthermore, the inventors have found through their research that the back sheet 6 has a first back fiber layer 61 and a second back fiber layer 62, the first back fiber layer 61 includes the first back fiber and the third back fiber, and the second back fiber layer 62 includes the second back fiber, so that the back sheet 6 has good extensibility. By using such a back sheet 6, the heating device 1 easily stretches when worn, and the contact area between the heating object and the heating device 1 increases. As a result, there is an advantage that the heating object area can be increased without lowering the surface temperature of the heating object. In order to make the above-mentioned advantages more pronounced, it is preferable that the top sheet 5, like the back sheet 6, has a top side first fiber layer and a top side second fiber layer, the top side first fiber layer containing top side first fibers and top side third fibers similar to the back side first fibers and back side third fibers, and the top side second fiber layer containing top side second fibers similar to the back side second fibers. Furthermore, in order to make the above-mentioned advantages even more pronounced, it is preferable that the back sheet 6 and, if necessary, the top sheet 5 are incorporated into the heating device 1 so that their maximum elongation direction is the same as the direction connecting the pair of ear hooks 4 in the heating device 1. Furthermore, in order to make the above-mentioned advantages more pronounced, the back sheet 6 and, if necessary, the top sheet 5, preferably have an elongation rate of 5% or more under a load of 1 N / 5 cm in their maximum elongation direction, more preferably 10% or more, and even more preferably 15% or more. Furthermore, in order to prevent the heating device 1 from stretching completely until the very end of use and to maintain a good fit to the skin, the back sheet 6 and, if necessary, the top sheet 5, preferably have an elongation rate under a load of 1 N / 5 cm in the maximum elongation direction of 40% or less, more preferably 35% or less, and even more preferably 30% or less. In particular, from the viewpoint of alleviating the feeling of pressure on the wearer caused by insufficient stretching of the back sheet 6 when wearing the heating device 1, the stretch rate is preferably 16% or more under a load of 1 N / 5 cm in the maximum stretch direction, and more preferably 18% or more. Also, from the viewpoint of preventing the heating device 1 from stretching completely until the end of use and maintaining a good fit to the skin, the stretch rate is preferably 30% or less, and more preferably 25% or less.

[0041] The stress (N) applied to the back sheet 6 and the top sheet 5 when tensile can be measured by a method based on JIS L1913. The elongation rate is measured by cutting out 5 cm wide rectangular test pieces from the back sheet 6 and, if necessary, the top sheet 5. A tensile tester (Tensilon universal tester) is used for the measurement. The measurement conditions are a chuck distance of 100 mm and a tensile speed of 300 mm / min.

[0042] When the back side first fiber layer 61 further includes back side third fibers, the fiber diameter of the back side third fibers is preferably 15 μm or more, more preferably 18 μm or more, even more preferably 20 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 24 μm or less, provided that the fiber diameter of the back side third fibers is smaller than the fiber diameter of the back side first fibers and larger than the fiber diameter of the back side second fibers. Because the back-side third fibers have such a fiber diameter, they have lower rigidity than the back-side first fibers, which have a relatively larger fiber diameter, and the back-side third fibers are more likely to follow the elastic recovery of the back-side first fibers caused by heat generation from the heating device 1, making the increase in bulk of the back-side first fiber layer 61 even more noticeable, and further improving the heat retention of the heating element 3 by the back sheet 6. The fiber diameter of the back surface side third fibers can be measured in the same manner as for the fiber diameter of the back surface side first fibers, by observing the back sheet 6 in a plan view with a scanning electron microscope. When the back side first fiber layer 61 contains the back side first fiber and the back side third fiber, the two fibers may be present in a mixed state, or the back side first fiber layer 61 may have a multi-layer structure consisting of a layer essentially of the back side first fiber and a layer essentially of the back side third fiber.

[0043] In a preferred embodiment of the back sheet 6, when it has a two-layer structure consisting of a back side first fiber layer 61 facing the heating element 3 and a back side second fiber layer 62 forming the outer surface of the heating device 1, the fiber diameter of the constituent fibers can be measured, for example, by the following method. First, confirm that there are two fiber layers using the measurement method described above, and create a histogram. For example, when the back side first fiber layer 61 is composed of only the back side first fiber, the histogram on the surface of the back side first fiber layer 61 side of the measurement sample has only one peak, and the position of the fiber diameter indicated by the apex of the peak is the fiber diameter of the back side first fiber. On the other hand, when the back side first fiber layer 61 is composed of the back side first fiber and the back side third fiber, the histogram on the surface of the back side first fiber layer 61 side of the measurement sample has two peaks, and the position of the fiber diameter indicating the peak located on the side with the larger fiber diameter is the fiber diameter of the back side first fiber, and the position of the fiber diameter indicating the peak located on the side with the smaller fiber diameter is the fiber diameter of the back side third fiber. Furthermore, when the back side second fiber layer 62 is composed only of the back side second fibers, the histogram on the surface constituting the back side second fiber layer 62 side has only one peak, and the position of the fiber diameter indicated by the apex of the peak is taken as the fiber diameter of the back side second fiber.

[0044] From the viewpoint of improving the heat retention caused by the increased bulk of the heating device 1 during use, the mass ratio of the back side third fiber to the back side first fiber layer 61 in the back sheet 6 is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. From a similar viewpoint, the mass ratio of the back side first fiber to the back side first fiber layer 61 in the back sheet 6 is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less.

[0045] On the other hand, the mass ratio of the back side second fibers to the back side second fiber layer 62 in the back sheet 6 is preferably 80 mass % or more, more preferably 90 mass % or more, even more preferably 95 mass % or more, and even more preferably 100 mass %. In other words, it is preferable that the back side second fiber layer 62 is composed only of the back side second fibers, excluding fibers that are inevitably mixed in. This configuration is preferable because the bulk of the back side first fiber layer 61 can be easily increased by the heat generated by the heating element 3, thereby improving the heat retention of the heating element 3, and also improving the printability and feel of the back side second fiber layer 62.

[0046] The proportions of the first back side fibers, the second back side fibers, and the third back side fibers constituting the back sheet 6 can be measured, for example, as follows. The ratio of the first backside fiber and the third backside fiber is measured by randomly selecting 100 fibers from the first backside fiber layer 61 with a digital microscope, and measuring the width in plan view as the fiber diameter. After calculating the arithmetic mean value of the diameters of the 100 fibers, if the fiber diameter of each fiber is different from the arithmetic mean value by 2 μm or more, it is determined that the fibers are different fibers, and the fibers with a fiber diameter larger than the arithmetic mean value are determined as the first backside fiber, and the fibers with a fiber diameter smaller than the arithmetic mean value are determined as the third backside fiber. Note that the fibers with a fiber diameter less than 2 μm from the average value are determined as the first backside fiber. After measuring the fiber diameter, the fibers are sorted into the first backside fiber and the third backside fiber, and the mass of each is measured to calculate the ratio of the first backside fiber and the third backside fiber per 100 randomly selected fibers. Next, the first backside fiber layer 61 and the second backside fiber layer 62 are each cut into 1 cm×1 cm, the mass of each is measured, and the ratio of the first backside fiber layer 61 and the second backside fiber layer 62 is calculated. From the above measurements, the proportions of the back side first fibers, the back side second fibers, and the back side third fibers are calculated.

[0047] The following describes suitable raw materials for the back side first fiber, the back side second fiber, and the back side third fiber. It is preferable that the back side first fiber, the back side second fiber, and the back side third fiber are all composed of a thermoplastic resin from the viewpoint of convenience and cost in manufacturing the heating device 1.

[0048] Examples of the thermoplastic resin used in each fiber include, independently, polyester resins such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT); ethylene-α-olefin copolymers such as ethylene-propylene copolymers; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polystyrene; acrylic resins such as polyacrylic acid, polyacrylic acid esters, polymethacrylic acid, and polymethacrylic acid esters; polyamide resins; and combinations thereof. Other examples include those described in JP-A-9-296325.

[0049] When the above-mentioned thermoplastic resins are used in combination, two or more thermoplastic resins having different constituent components may be present in the fiber in a mixed state, or the thermoplastic resins may be present in the fiber with a clear boundary between them, such as in the case of concentric core-sheath type or eccentric core-sheath type composite fibers or side-by-side type composite fibers containing two types of thermoplastic resins having different constituent components. Examples of the core / sheath combination in core-sheath fibers, or the combination of the first resin / second resin in side-by-side composite fibers, include fibers made of combinations of polypropylene / polyethylene, polypropylene / ethylene propylene copolymer, polyethylene terephthalate / polyethylene, polyethylene terephthalate / polypropylene, etc. These can be used alone or in combination of two or more types. In the present invention, the type of thermoplastic resin constituting the fibers can be determined by measuring the melting point by differential scanning calorimetry (DSC).

[0050] As described above, the back side first fiber preferably contains at least PET resin, more preferably is a fiber made of only PET resin or is a fiber made of only PET resin and a thermoplastic resin other than PET resin, and even more preferably is a fiber made of only PET resin. With this configuration, the first fiber on the back side elastically recovers as the heating device 1 generates heat, which makes the back sheet 6 bulky and helps to keep the heating element 3 warm. In addition, the change in thickness of the back sheet 6 increases, improving the fit during use.

[0051] The back surface side second fibers preferably contain PE resin, more preferably contain PET resin or PP resin in addition to PE resin, and further preferably are fibers made only of PE resin and PET resin or PP resin. This configuration suppresses the fuzzing of the fibers in the back sheet 6, allowing the user to perceive a good smoothness, further improving the feeling of use. This is also advantageous in that when heat is applied by air-through processing or the like in the manufacturing process of the back sheet 6, the second fibers on the back side having the above-mentioned configuration are thermally fused together, reducing the fuzzing of the fibers in the resulting sheet. Furthermore, even when the back sheet 6 is transported in the manufacturing process of the heating implement, the generation of fiber peeling pieces and fiber falling pieces of the back sheet 6, as well as fine particles derived from the constituent fibers (hereinafter, these are also collectively referred to as "paper powder"), and the adhesion of paper powder to the sheet surface can be reduced, so that the sheet surface is prevented from becoming rough, and a heating implement 1 with a good feel can be obtained. In addition to this, it is possible to reduce the amount of sheets discarded and increase production efficiency.

[0052] When the back side first fiber further contains a thermoplastic resin other than PET resin, it is even more preferable that the back side first fiber be a core-sheath fiber made of PET resin and another thermoplastic resin, from the viewpoint of further improving the feel of the sheet and the usability of the heating device due to improved flexibility and reduced fiber fuzzing while reducing the generation and adhesion of paper dust. Furthermore, from the viewpoint of further improving the feel of the sheet and the comfort of the heating device due to improved flexibility and reduced fiber fuzz while reducing the generation and adhesion of paper dust, it is even more preferable that the second fiber on the back side is a core-sheath fiber made of PE resin and other thermoplastic resin.

[0053] The back side third fibers preferably contain a thermoplastic resin other than PET resin, more preferably contain PE resin, even more preferably contain PP resin in addition to PE resin, and even more preferably consist of only PP resin and PE resin. It is also preferable that the back side second fibers and the back side third fibers contain resins whose components are different from each other. This configuration suppresses the fuzzing of the fibers in the back sheet 6, allowing the user to perceive a good smoothness, further improving the feeling of use. This is also advantageous in that when heat is applied by air-through processing or the like in the manufacturing process of the back sheet 6, the second fibers on the back side having the above-mentioned configuration are thermally fused together, reducing the fuzzing of the fibers in the resulting sheet. Furthermore, even when the back sheet 6 is transported in the manufacturing process of the heating implement 1, the generation of paper powder and the adhesion of paper powder to the sheet surface can be reduced, preventing the sheet surface from becoming rough and providing a heating implement with a good feel. In addition to this, it is possible to reduce the amount of sheets discarded and increase production efficiency.

[0054] When the backside third fibers further contain a thermoplastic resin other than PET resin, from the viewpoint of further improving the feel of the sheet and the comfort of the heating device due to improved flexibility and reduced fiber fuzzing while reducing the generation and adhesion of paper powder, it is more preferable that the backside third fibers are core-sheath fibers made of PP resin and another thermoplastic resin. In this case, it is preferable that the core of the third fibers is PP resin and the sheath is PE resin.

[0055] As long as the effects of the present invention are achieved, in addition to or instead of the above-mentioned fibers, the back sheet 6 may contain fibers other than the fibers containing a thermoplastic resin. Examples of such other fibers include natural fibers such as wood pulp, cotton, and hemp, and regenerated fibers such as rayon and cupra, etc. These may be used alone or in combination.

[0056] Next, a preferred embodiment of the top sheet 5 in the heating device 1 of the present disclosure will be described. A preferred embodiment of the top sheet 5 is the same as the preferred embodiment of the back sheet 6. Therefore, in the following description of the top sheet 5, the description of the back sheet 6 applies appropriately to any points not specifically mentioned.

[0057] The top sheet 5 is preferably made of a breathable fiber sheet containing fibers that contain at least PET resin. The top sheet 5 preferably contains a surface-side first fiber having a fiber diameter of more than 15 μm as measured by SEM observation in a plan view. In other words, the top sheet 5 is an assembly of fibers that contain at least PET resin as one of its constituent fibers. Fibers that contain at least PET resin tend to be more rigid than fibers that contain other thermoplastic resins, so by using a surface sheet 5 containing fibers that contain at least PET resin, even if the heating device 1 is compressed in the sheet thickness direction during pre-use processes such as packaging and distribution, the bulk of the surface sheet 5 will easily and quickly recover when the packaging bag is opened and the compressed state is released, and the heating device will have high flexibility, fit and feel immediately after use.

[0058] The fiber diameter of the surface side first fibers is more preferably 20 μm or more, even more preferably 25 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, even more preferably 40 μm, and even more preferably 30 μm or less. By having the first fiber on the surface side have such a fiber diameter, even if the heating device 1 is compressed in the thickness direction, for example by being contained in a packaging bag, the bulk of the surface sheet 5 is restored immediately after the compression is released, for example by removing it from the packaging bag, improving the fit when in use. The fiber diameter of the front surface side first fibers can be measured in the same manner as the fiber diameter of the back surface side first fibers.

[0059] From the viewpoint of achieving a more remarkable bulk recovery of the topsheet 5, the surface side first fibers are more preferably fibers made of only PET resin, or fibers made of only PET resin and a thermoplastic resin other than PET resin. More preferably, the surface side first fibers are fibers made of only PET resin. It is also preferable that the surface side first fibers contain PET resin and PE resin, and it is particularly preferable that the surface side first fibers are core-sheath fibers in which the core is PET resin and the sheath is PE resin.

[0060] Generally, heating devices that utilize heat generated by the oxidation reaction of iron are sealed in a packaging bag that blocks the intrusion of outside air in an oxygen-free and compressed state before use in order to prevent contact with oxygen and the unintended oxidation reaction of iron from progressing. In this case, even if the top sheet is configured to exhibit flexibility and fit during production, the sheet is easily compressed in the thickness direction when or after the heating device with the top sheet is sealed in the packaging bag, or during distribution of the heating device sealed in the packaging bag, and the flexibility and fit due to the top sheet may not be exhibited as designed, leaving room for improvement.

[0061] According to this embodiment, by using fibers having a predetermined fiber diameter and containing PET resin as the constituent fibers of the top sheet 5, the high rigidity of PET exhibits compression resistance, and even if the sheet is compressed in the thickness direction during pre-use processes such as packaging and distribution, the bulk of the top sheet easily recovers when the packaging bag is opened and the compressed state is released, resulting in a high fit and feel immediately after use, and a pleasant texture. In addition, the heat and steam generated during use, as well as the air warmed by the heat, can further increase the distance between the fibers that make up the top sheet 5, efficiently increasing the bulk of the sheet. As a result, the heating device 1 exhibits high levels of flexibility and fit over a long period of time, from the start to the end of use.

[0062] From the viewpoint of combining the quick recovery of bulkiness of the top sheet 5 with flexibility, fit and feel during use while suppressing fiber fuzzing and improving the feel on the surface that comes into contact with the skin, it is preferable that the top sheet 5 further contains, in addition to the above-mentioned first fibers, one or more types of other fibers different in type from the first fibers.

[0063] In a preferred embodiment of the top sheet 5, when the top sheet 5 has a multi-layer structure having two or more fiber layers, it is preferable to have at least a top side first fiber layer 51 including top side first fibers and a top side second fiber layer 52 including fibers other than the top side first fibers that have a fiber diameter different from that of the top side first fibers, as shown in Fig. 6. Specifically, as in this embodiment, it is preferable to have a top side second fiber layer 52 including top side second fibers that are fibers having a fiber diameter smaller than that of the top side first fibers. In other words, the top sheet 5 has a multi-layer structure including the top side first fiber layer 51 and the top side second fiber layer 52, and only one of the fiber layers includes the top side first fibers, and fibers having a fiber diameter different from that of the top side first fibers are included in the fiber layer that does not include the top side first fibers. In addition, it is preferable that the surface-side first fiber layer 51 does not contain the surface-side second fibers, and the surface-side second fiber layer 52 does not contain the surface-side first fibers. That is, it is preferable that the topsheet 5 has at least a fiber layer containing the surface-side first fibers, and a fiber layer containing fibers other than the surface-side first fibers. By providing multiple fiber layers containing fibers with different fiber diameters in this way, the heating device 1 can have the desired function in each fiber layer, that is, the fiber layer containing the first fiber on the surface side exhibits the function of restoring the sheet bulkiness, and the fiber layer containing the second fiber on the surface side exhibits good touch and texture of the top sheet. As a result, the top sheet 5 is configured to efficiently and simultaneously exhibit the multiple functions described above, and the manufacturing efficiency of such a top sheet 5 is further improved. In order to make the above-mentioned advantages more pronounced, the topsheet 5 preferably has a two-layer structure including only the top-side first fiber layer 51 and the top-side second fiber layer 52.

[0064] In particular, from the viewpoint of making the above-mentioned advantages even more pronounced, it is preferable that the surface side first fiber layer 51 contains surface side first fibers, and the surface side second fiber layer 52 contains surface side second fibers whose fiber diameter is smaller than that of the surface side first fibers and whose fiber diameter is 6 μm or more and 30 μm or less. In this case, the fiber diameter of the surface side second fibers is smaller than the fiber diameter of the surface side first fibers, and is more preferably 10 μm or more, even more preferably 13 μm or more, more preferably 25 μm or less, even more preferably 20 μm or less, and particularly preferably 17 μm or less.

[0065] The surface side second fibers preferably contain PE resin, more preferably contain PE resin and PET resin or PP resin, and further preferably consist of only PE resin and PET resin or PP resin. In particular, the surface side second fibers are preferably core-sheath fibers having a core made of PET resin or PP resin and a sheath made of PE resin.

[0066] When the top sheet 5 has at least the top first fiber layer 51 and the top second fiber layer 52, it is preferable that the top first fiber layer 51 is disposed on the surface farthest from the user's skin when the heating device 1 is in use, as shown in Fig. 6. Also, as shown in the same figure, it is preferable that the top second fiber layer 52 is disposed on the skin contact surface, which is the surface that comes into direct contact with the user's skin when in use. That is, the surface-side second fiber layer 52 constitutes the skin-facing surface and is preferably disposed so as to abut against the user's skin. In addition, the front side first fiber layer 51 is preferably disposed at a position that does not contact the user's skin. In the embodiment shown in Fig. 6, the front side first fiber layer 51 constitutes the non-skin facing surface of the topsheet 5, and is disposed at a position closest to the heating element 3 and adjacent to the heating element 3. By arranging each fiber layer in this manner, direct contact of the first fiber on the surface side, which has relatively high rigidity due to the inclusion of PET resin, with the user's skin is reduced, allowing the user to perceive the flexibility and smooth texture of the surface sheet 5.

[0067] When the topsheet 5 has a topside first fiber layer 51, the topside first fiber layer 51 preferably further contains, in addition to the topside first fibers, topside third fibers having a fiber diameter smaller than that of the topside first fibers and larger than that of the topside second fibers. That is, the topside first fiber layer 51 preferably contains a plurality of fibers including at least the topside first fibers and the topside third fibers, and more preferably is made up of only the topside first fibers and the topside third fibers, excluding fibers that are inevitably mixed in, and does not contain the topside second fibers. By including the surface side third fibers having such a predetermined fiber diameter relationship in the surface side first fiber layer 51, the flexibility of the surface sheet 5 can be increased compared to a configuration containing only the highly rigid surface side first fibers, and the fit during use can be further improved.

[0068] When the surface side first fiber layer 51 further contains surface side third fibers, the fiber diameter of the surface side third fibers is preferably 15 μm or more, more preferably 18 μm or more, even more preferably 20 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 24 μm or less, provided that the fiber diameter of the surface side third fibers is smaller than the fiber diameter of the surface side first fibers and larger than the fiber diameter of the surface side second fibers. By having the surface side third fibers have such a fiber diameter, the rigidity is lower than that of the surface side first fibers, which have a relatively larger fiber diameter, and the flexibility of the surface sheet 5 is increased, further improving the feel and usability of the heating device 1.

[0069] From the viewpoint of making the above-mentioned advantages more prominent, when the surface side first fibers are fibers made of only PET resin and a thermoplastic resin other than PET resin, the surface side third fibers are preferably fibers containing a thermoplastic resin other than PET resin. In particular, the surface side third fibers preferably contain a thermoplastic resin other than PET resin, more preferably contain PE resin, further preferably contain PE resin and PET resin or PP resin, and even more preferably contain only PP resin and PE resin. From a similar viewpoint, it is also preferable that the surface side third fibers are core-sheath fibers having a core made of PET resin or PP resin and a sheath made of PE resin. From the same viewpoint, when the surface side second fiber layer 52 contains the surface side second fibers, the surface side second fibers and the surface side third fibers preferably contain resins whose components are different from each other.

[0070] From the viewpoint of improving the flexibility and fit resulting from the recovery of bulkiness when the heating device 1 is in use, the mass ratio of the surface side third fiber to the surface side first fiber layer 51 in the surface sheet 5 is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. From a similar viewpoint, the mass ratio of the surface side first fibers to the surface side first fiber layer 51 in the top sheet 5 is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less.

[0071] On the other hand, the mass ratio of the surface-side second fibers to the surface-side second fiber layer 52 in the topsheet 5 is preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and even more preferably 100 mass%. In other words, the surface-side second fiber layer 52 is preferably composed only of the surface-side second fibers, excluding fibers that are unavoidably mixed in. With this configuration, when the topsheet 5 comes into contact with the skin, the surface-side second fibers, which have a relatively low rigidity, tend to come into contact with the skin, effectively achieving a pleasant feel and smooth texture.

[0072] The following describes a particularly preferred embodiment of the top sheet 5. According to this embodiment, the top sheet 5 has extremely good bulk recovery after the heating device 1 is opened from the packaging bag, and provides a heating device 1 that fits well and feels great even immediately after use. The surface side first fiber layer 51 is made of only surface side first fibers and surface side third fibers having a smaller fiber diameter than the surface side first fibers, excluding other fibers that are inevitably mixed in. The surface side second fiber layer 52 is made of only surface side second fibers having a smaller fiber diameter than the surface side first fibers and a fiber diameter of 6 μm to 30 μm, excluding other fibers that are inevitably mixed in. The fiber diameter of the surface side third fibers is larger than the fiber diameter of the surface side second fibers.

[0073] The basis weight of the surface side first fiber layer 51 is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 The basis weight of the front side first fiber layer 51 is preferably 100 g / m 2 It is preferable that the thickness is less than 80 g / m 2 More preferably, it is 60 g / m or less. 2 It is even more preferable that:

[0074] The basis weight of the surface side second fiber layer 52 is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2 More preferably, it is 15 g / m or more. 2 The basis weight of the surface-side second fiber layer 52 is preferably 50 g / m 2 It is preferable that the thickness is less than 40 g / m 2 More preferably, it is 30 g / m or less. 2 It is even more preferable that:

[0075] The following describes matters commonly applicable to the heating devices of the present disclosure. The sheet materials that can be used for the heating element 3, ear loops 4, top sheet 5, and back sheet 6 can be appropriately selected in consideration of their breathability, moisture permeability, texture, stretchability, strength, and properties such as prevention of leakage of the constituent materials of the heating sheet and the heating composition. For example, fiber sheets such as nonwoven fabric, woven fabric, and paper, resin foam sheets, metal sheets, or combinations of these can be used.

[0076] As a sheet material having high breathability, a meltblown nonwoven fabric is preferably used, and as a sheet material for improving the texture, an air-through nonwoven fabric or a thermal bond nonwoven fabric is preferably used. Examples of sheet materials used for the purpose of exhibiting elasticity include air-through nonwoven fabrics, spunbond nonwoven fabrics, and thermal bond nonwoven fabrics, which contain synthetic fibers such as polyesters such as polyethylene terephthalate, polyethylene, and polypropylene. As the sheet material used for the purpose of imparting strength, a spunbond nonwoven fabric, a spunlace nonwoven fabric, a needle punch nonwoven fabric, a chemically bonded nonwoven fabric, or the like is suitably used.

[0077] In particular, in the heating device 1 of the present disclosure, the top sheet 5 and / or the back sheet 6 are fiber sheets in which the sheet form is maintained by at least one of fusion and entanglement of the constituent fibers, and it is preferable that the constituent fibers have contact portions where they are in contact with each other. The fiber sheets are preferably air-through nonwoven fabrics or needle-punched nonwoven fabrics.

[0078] In addition to or instead of the nonwoven fabrics described above, nonwoven fabrics that have been surface-treated with silicone, a surfactant, or the like can be used, or foamed sheets made from thermoplastic resins such as polyethylene, polyurethane, etc. These sheet materials can also be used by mixing multiple fibers with different fiber materials, fiber diameters, degrees of crimp, etc., or by combining multiple sheet materials to achieve desired properties. The heating element 3, ear hook portion 4, top sheet 5 and back sheet 6 may be a unitary structure consisting of only one sheet material, whether single-layer or multi-layer, or may be a laminated structure consisting of two or more types of sheet materials layered on top of each other.

[0079] It is preferable to use a fiber sheet as the top sheet 5 and the back sheet 6, and from the viewpoint of easily obtaining a fiber sheet containing a thermoplastic resin, at least one of a needle-punched nonwoven fabric, an air-through nonwoven fabric, a spun-bonded nonwoven fabric, and a chemical-bonded nonwoven fabric can be preferably used. When the top sheet 5 and the back sheet 6 are a laminate of sheet materials and each sheet material contains crimped fibers, the above-mentioned crimp percentage and number of crimps are satisfied independently by each sheet material.

[0080] When breathable fiber sheets are used as the top sheet 5 and the back sheet 6, the air permeability of the top sheet 5 and the back sheet 6 is preferably 0.01 seconds / 100 mL or more, more preferably 50 seconds / 100 mL or more, and even more preferably 2000 seconds / 100 mL or more. The air permeability of the top sheet 5 and the back sheet 6 is preferably 15000 seconds / 100 mL or less, more preferably 50000 seconds / 100 mL or less, and even more preferably 10000 seconds / 100 mL or less. The air permeability is measured by the method described in JIS P8117. A low air permeability means that it does not take long for air to pass through, and therefore means that the air permeability is high.

[0081] When a nonwoven fabric is used as the back sheet 6, it is preferable to use a fiber sheet as the back sheet 6 having the same or higher air permeability than the top sheet 5. That is, it is preferable that the back sheet 6 has the same or higher air permeability as the top sheet 5, as measured by the method described in JIS P8117. The air permeability of the back sheet 6 is preferably as high as possible, and is preferably 50 sec / 100 mL or more, more preferably 4000 sec / 100 mL or more, even more preferably 20000 sec / 100 mL or more, and it is even more preferable that the back sheet 6 is a non-air permeable sheet.

[0082] When nonwoven fabrics are used as the top sheet 5 and the back sheet 6, the basis weight of the top sheet 5 and the back sheet 6 is independently 10 g / m 2 It is preferable that the thickness is 20 g / m or more. 2 More preferably, it is 30 g / m or more. 2 The basis weight of the top sheet 5 and the back sheet 6 is preferably 200 g / m or more. 2 It is preferable that the thickness is less than 130 g / m 2 More preferably, it is 90 g / m or less. 2 It is more preferable that the thickness be less than or equal to the thickness of the heat generating element 3. This configuration can further improve the heat retention of the heat generating element 3. In addition, the thickness and flexibility of the top sheet 5 can be compatible, and a good feel and fit can be achieved.

[0083] When the top sheet 5 has the top side first fiber layer 51, the basis weight of the top side first fiber layer 51 is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 The basis weight of the front side first fiber layer 51 is preferably 100 g / m 2 It is preferable that the thickness is less than 80 g / m 2 More preferably, it is 60 g / m or less. 2 It is even more preferable that: With this configuration, when the packaging bag is opened and the compressed state is released, the bulk of the top sheet easily recovers, the amount of change in thickness is large immediately after use, and the sheet has a good fit and feel when used, and is pleasant to the touch.

[0084] When the top sheet 5 has the top side second fiber layer 52, the basis weight of the top side second fiber layer 52 is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2 More preferably, it is 15 g / m or more. 2 The basis weight of the surface-side second fiber layer 52 is preferably 50 g / m or more. 2 It is preferable that the thickness is less than 40 g / m 2 More preferably, it is 30 g / m or less. 2 It is more preferable that the thickness of the sheet is less than or equal to the thickness of the sheet. With this configuration, it is possible to prevent highly rigid fibers such as the first fibers constituting the front-side first fiber layer 51 from unintentionally protruding toward the front-side second fiber layer 52 side or the surface facing the skin, and to obtain a satisfactory smoothness of the sheet surface at the surface that comes into contact with the heated object such as the skin.

[0085] When the back sheet 6 has a back side first fiber layer 61, the basis weight of the back side first fiber layer 61 is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 The basis weight of the back surface side first fiber layer 61 is preferably 100 g / m 2 It is preferable that the thickness is less than 80 g / m 2 More preferably, it is 60 g / m or less. 2 It is more preferable that the thickness be less than or equal to the thickness of the back surface side first fiber layer 61. With this configuration, the bulk of the back surface side first fibers contained in the back surface side first fiber layer 61 is easily increased, and the heat retention of the heat generating element 3 is further improved.

[0086] When the back sheet 6 has a back side second fiber layer 62, the basis weight of the back side second fiber layer 62 is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2More preferably, it is 15 g / m or more. 2 The basis weight of the back surface side second fiber layer 62 is preferably 50 g / m or more. 2 It is preferable that the thickness is less than 40 g / m 2 More preferably, it is 30 g / m or less. 2 It is more preferable that the surface of the back surface side second fiber layer 62 has the following characteristics: The surface of the back surface side second fiber layer 62 has a better printability and a better smoothness.

[0087] When the top sheet 5 has the top side first fiber layer 51 and / or the back sheet 6 has the back side first fiber layer 61, the fiber density of the top side first fiber layer 51 and the fiber density of the back side first fiber layer 61 are each independently preferably 1500 fibers / cm 2 Less than 1000 fibers / cm, more preferably 1000 fibers / cm 2 Less than 700 / cm, more preferably 700 / cm 2 Less than 150 fibers / cm 2 The above is realistic. With such a configuration, the thickness of the top sheet 5 and the back sheet 6 is increased, and a good fit can be obtained.

[0088] When the top sheet 5 has the top side second fiber layer 52 and / or the back sheet 6 has the back side second fiber layer 62, the fiber density of the top side second fiber layer 52 and the fiber density of the back side second fiber layer 62 are each independently preferably 200 fibers / cm 2 More preferably, 300 fibers / cm 2 More preferably, 400 fibers / cm 2 More preferably, 1500 fibers / cm 2 Less than or equal to 1200 fibers / cm, more preferably 1200 fibers / cm 2 More preferably, 1000 fibers / cm or less. 2 The following is the result. This configuration prevents the relatively stiff fibers such as the front-side first fiber and the front-side third fiber constituting the front-side first fiber layer 51 from unintentionally protruding toward the front-side second fiber layer 52 side or the surface facing the skin, thereby making it possible to obtain a good smoothness of the sheet surface at the surface that comes into contact with the object to be heated, such as the skin. The back sheet 6 also has the same advantage. In order to make such advantages more pronounced, it is preferable that the density of fibers in the front side second fiber layer 52 and / or the back side second fiber layer 62 is higher than the density of fibers in the front side first fiber layer 51 and / or the back side first fiber layer 61.

[0089] The density of fibers present in the top sheet 5 and the back sheet 6 can be measured by the following method. First, the cross section of the measurement sample obtained by the above method is observed with a microscope or SEM to confirm the difference in fiber diameter and fiber structure, and to confirm that there are two fiber layers. Then, the first fiber layer and the second fiber layer are separated from the measurement sample, and the number of fibers present in the sheet cut into a 1 cm x 1 cm square is counted by SEM observation. The number of fibers counted is then divided into 1 cm 2 It is calculated as the density of fibers per unit area.

[0090] It is also preferable that the thickness of the top sheet 5 and the back sheet 6 is within a predetermined range at the start of heat generation. In detail, the thickness of the top sheet 5 at the start of heat generation of the heating device is preferably 1.3 mm or more, more preferably 1.5 mm or more, even more preferably 3.5 mm or more, and is preferably 6.0 mm or less, more preferably 5.5 mm or less, even more preferably 5.0 mm or less. This thickness allows the bulk of the surface sheet 5 to be restored immediately after use, making the heating device 1 flexible and pleasant to the touch immediately after use, and improving the fit to the object to be heated. On the other hand, the thickness of the back sheet 6 at the start of heat generation of the heating implement is preferably 1.8 mm or more, more preferably 2.5 mm or more, even more preferably 3.5 mm or more, and is preferably 6.0 mm or less, more preferably 5.5 mm or less, even more preferably 5.0 mm or less. With this thickness, the bulk of the back sheet 6 increases after the heating device 1 generates heat, so that the heat retention of the heating element 3 can be improved immediately after the heating device 1 is used, and the amount of water vapor generated by the heating device 1 can be increased.

[0091] Furthermore, the thickness of the top sheet 5 10 minutes after the heating device begins to generate heat is preferably 1.6 mm or more, more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and is preferably 8.0 mm or less, more preferably 7.5 mm or less, even more preferably 7.0 mm or less. This thickness allows the bulk of the surface sheet 5 to be restored and maintained during use, thereby maintaining good flexibility and feel on the skin over the long term while the heating device is in use, and improving the fit to the object to be heated. On the other hand, the thickness of the back sheet 6 10 minutes after the heating device starts to generate heat is preferably 2.0 mm or more, more preferably 3.5 mm or more, even more preferably 5.8 mm or more, and preferably 10.0 mm or less, more preferably 9.0 mm or less, even more preferably 8.0 mm or less. With such a thickness, the bulk of the back sheet 6 increases and is maintained during use, so that a high amount of water vapor can be generated over a long period of time while the heating device 1 is in use, and the surface temperature of the object to be heated is less likely to rise excessively.

[0092] The thickness and the increase in thickness of the top sheet 5 and back sheet 6 can be measured by the following method using the heating device 1 that is sealed in a packaging bag or the like and has not yet been heated. 3.7gf / cm for unheated heating devices sealed in a package etc. 2A load of this magnitude is applied to the sheet, and measurements are taken at three or more points using a constant pressure thickness gauge or the like, with the arithmetic mean value being the sheet thickness T1 (mm) at the start of heat generation. Similarly, the sheet thickness is measured under the same load after 10 minutes has elapsed, and the arithmetic mean value is the sheet thickness T2 (mm) after 10 minutes has elapsed. At this time, the time required from starting to open the packaging bag, exposing the heating device 1 to an oxygen-containing atmosphere such as air, and spreading and placing the top sheet 5 on a flat table, that is, 30 seconds after starting to open, is defined as the "start time of heat generation." At this time, it is preferable that the thickness of the top sheet 5 of this embodiment is increased or maintained.

[0093] The basis weight of the back sheet 6 is 10 g / m2 from the viewpoint of improving heat retention in the applicable area during use. 2 It is preferable that the thickness is 30 g / m or more. 2 The back sheet 6 preferably has a basis weight of 200 g / m or more. 2 It is preferable that the thickness is less than 150 g / m 2 It is even more preferable that:

[0094] In the present disclosure, "steam is generated" means that the total amount of water vapor generated in 10 minutes, as measured by the following method, is 10 mg / 10 minutes or more. This amount of water vapor generation can be easily achieved by using, for example, a paste-like material containing an oxidizable metal, a carbon material, and water as the heat generating part 3a. The amount of generated water vapor can be measured, for example, by using an apparatus 100 having a configuration shown in FIG. 7. The apparatus 100 includes an aluminum measurement chamber 101 (volume 4.2 L), an inflow passage 102 arranged in communication with the lower part of the measurement chamber 101, and an outflow passage 103 arranged in communication with the upper part of the measurement chamber 101. The inflow passage 102 allows dehumidified air (humidity less than 2% RH, flow rate 2.1 L / min) supplied from an air supply unit (not shown) to flow into the measurement chamber 101. In addition, the apparatus 100 includes an inlet thermometer / hygrometer 104 and an inlet flowmeter 105 provided in the inflow passage 102, an outlet thermometer / hygrometer 106 and an outlet flowmeter 107 provided in the outflow passage 103, and a thermometer (thermistor) 108 provided in the measurement chamber 101. The thermometer 108 is preferably one having a temperature resolution of about 0.01°C.

[0095] The method for measuring the total amount of water vapor generated using the device 100 is as follows. First, for the heating device to be measured that is sealed in an oxygen-shielding bag, the oxygen-shielding bag is opened and one heating element is taken out. If the heating element is contained in a bag, the heating element is taken out together with the bag. The removed bag of the heating element is placed in the measurement chamber 101 with one side facing outward, and the thermometer 108 is placed on top of it. If one side and the other side of the bag are made of sheet materials with different air permeabilities, the bag is placed in the measurement chamber 101 with the side of the sheet material with higher air permeability facing outward, and the thermometer 108 is placed on that side. In this state, dehumidified air is flowed from the bottom of the measurement chamber 101 through the inlet passage 102, and the difference in absolute humidity before and after the air flow in the measurement chamber 101 is calculated from the temperatures and humidities measured by the inlet thermometer / hygrometer 104 and the outlet thermometer / hygrometer 106. Furthermore, the amount of water vapor released from the heating device is calculated from the air flow rates measured by the inlet flowmeter 105 and the outlet flowmeter 107. The total amount of water vapor is calculated as the total amount (mg / 10 min) measured over 10 minutes from the start of measurement, which is the time when the heating device is removed from the oxygen barrier bag and the heating element is brought into contact with air.

[0096] The shape of the ear hooks 4 in the heating implement 1 is not limited to the sheet-like material shown in Figures 1 and 2, so long as the main body 2 can be fixed to both eyes of the user. For example, as shown in Figure 8, ear hooks 4 made of a string-like material or a thread- or band-like material may be used. From the viewpoint of improving the fit of the heating implement, it is preferable to use an elastic material such as rubber to make the ear hooks 4 stretchable.

[0097] The heating element 3 in the heating device 1 described above has two heating elements 3 held at a distance from each other, but the heating device may have any shape as long as it can provide a warm sensation to the user's eyes and the area around them. For example, one heating element having a shape and size that can cover the user's eyes and the area around them may be held between the top sheet 5 and the back sheet 6, or three or more heating elements may be held between the top sheet 5 and the back sheet 6.

[0098] 2 and 3, only a part of the heating element 3 is fixed in the central region in the lateral direction X of the heating device 1, but this is not limited to the embodiment. For example, the heating element 3 and the back sheet 6 may be bonded continuously or intermittently with an adhesive in the central region and in regions other than the central region, or may be bonded by applying an adhesive to the entire surface of the back sheet 6 where the heating element 3 is located.

[0099] The present disclosure also provides a packaging body for a heating device, comprising a packaging bag and a heating device packaged in the packaging bag. The packaging bag is made of, for example, an oxygen-impermeable sheet material, and examples of the sheet material include a resin film used alone, or a resin film laminated with a thin metal film such as aluminum, etc. This can improve the light-shielding and airtightness when the heating device is packaged.

[0100] When the heating device is in the form of a package, the heating device 1 is preferably contained in a packaging bag with a predetermined pressure being applied thereto. In detail, the pressure applied to the heating device 1 in the package is preferably 500 Pa or more, more preferably 1000 Pa or more, and even more preferably 2000 Pa or more, from the viewpoint of saving space in the package during storage and distribution. From the viewpoint of easily restoring the bulkiness of the sheet laminate after the packaging bag is opened, the pressure is preferably 5000 Pa or less, more preferably 4000 Pa or less, and further preferably 3000 Pa or less.

[0101] The above-mentioned heating device 1 can be manufactured, for example, by the following method. The manufacturing method of the heating device 1 includes a step of manufacturing the top sheet 5 and / or the back sheet 6. One embodiment of the manufacturing process for the topsheet 5 and / or the backsheet 6 is a method in which a process of blowing hot air onto a fiber web containing any fiber is carried out to convert the fiber web into a nonwoven fabric. This process is a so-called air-through process.

[0102] In a preferred embodiment of the back sheet 6, when manufacturing a back sheet 6 having a two-layer structure of a back side first fiber layer 61 containing a back side first fiber and a back side second fiber layer 62 containing a back side second fiber, the following method can be adopted, for example. First, a fiber web consisting of only the first backside fiber or a mixture of the first backside fiber and the third backside fiber (hereinafter, also referred to as the "first backside fiber web") is laminated with a fiber web consisting of only the second backside fiber (hereinafter, also referred to as the "second backside fiber web") to obtain a laminate. Then, hot air is blown onto the laminate to perform an air-through process, and the desired backsheet 6 is obtained. The backsheet 6 is classified as a so-called air-through nonwoven fabric, and is a fiber sheet having breathability. The backsheet 6 thus manufactured is generally in the form of a long strip, but may be cut to a predetermined size as necessary.

[0103] As in the preferred embodiment described above, when heat is applied by air-through processing or the like in the manufacturing process of the back sheet 6, if the back sheet contains the second back fiber or the third back fiber, the fibers including the first back fiber containing PET resin are thermally fused together, which is advantageous in that the fuzzing of the fibers in the resulting sheet can be reduced. In addition, since many fusion points are formed between the fibers that make up the back sheet 6, even when the back sheet 6 is transported to the subsequent manufacturing process of the heating implement 1, the generation of paper dust can be reduced, preventing roughness of the sheet surface and allowing the heating implement 1 with a good feel to be obtained with high productivity. In addition, the amount of sheets that no longer meet the required quality due to paper dust can be reduced, thereby reducing the environmental impact.

[0104] Each of the above-mentioned fiber webs can be produced by a known web forming method such as a carding method. When the fiber layer is a single layer (single layer structure), the above-mentioned method may be carried out using only the back side first fiber web. When the fiber layer is three or more layers, the back side first and second fiber webs may be laminated with other fiber webs made of other fibers to form a laminate, and hot air may be blown onto the laminate. Alternatively, the above-mentioned back sheet 6 can be obtained by needle punching a fiber web or a laminate thereof. In this case, the back sheet 6 obtained is classified as a so-called needle punched nonwoven fabric, and is a breathable fiber sheet.

[0105] When the topsheet 5 has a two-layer structure of a top-side first fiber layer 51 containing a top-side first fiber and a top-side second fiber layer 52 containing a top-side second fiber, the topsheet 5 can be manufactured by the same method as described above for the method for manufacturing the backsheet 6. In particular, the manufacturing method includes a step of manufacturing the topsheet 5, and in the step, it is preferable to subject a laminate obtained by laminating a web of fibers containing PET resin and a web containing fibers other than the above fibers to an air-through treatment.

[0106] The top sheet 5 and back sheet 6 thus manufactured are transported to be subjected to the subsequent steps, and the heating device 1 is manufactured through a predetermined processing step. As a method for manufacturing the heating implement 1, for example, first, while conveying the top sheet 5 and the back sheet 6 in the same direction, adhesive is applied to one side of at least one of the top sheet 5 and the back sheet 6. The adhesive may be applied continuously or intermittently in the conveying direction of the sheet, or continuously or intermittently in a direction perpendicular to the conveying direction. In addition, the adhesive may be applied so as to form non-applied areas of the adhesive. Next, the heating element 3 manufactured in a separate process is laminated on the adhesive-coated surface of the sheet to which the adhesive has been applied. After that, the other sheet is further laminated on the heating element 3, and the two sheets 5, 6 are bonded together via the adhesive. Through this process, the main body 2 is formed in which the heating element 3 is held between the top sheet 5 and the back sheet 6. When bonding the two sheets 5, 6, for example, the bondability may be improved by introducing the laminate including the top sheet 5, the heating element 3, and the back sheet 6 between a pair of press rolls and pressing them.

[0107] Although the present invention has been described based on the preferred embodiment, the present invention is not limited to the above embodiment.

[0108] In relation to the above-mentioned embodiment of the present invention, the following heating device is further disclosed.

[0109] <1> The device comprises a top sheet located close to the user's skin, a back sheet located away from the user's skin, and a heating element held between the top sheet and the back sheet, The heating element includes an oxidizable metal, a carbon material, an electrolyte, and water, The heating element is configured to generate steam from the heating element itself as heat is generated, The back sheet is made of a breathable fiber sheet including fibers containing at least polyethylene terephthalate resin, The heating device, wherein the back sheet comprises back side first fibers having a fiber diameter of more than 15 μm when measured in plan view by scanning electron microscope observation.

[0110] <2> The fiber diameter of the back surface side first fibers is more preferably 20 μm or more, even more preferably 25 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, even more preferably 40 μm, even more preferably 30 μm or less. <1> A heating device as described above. <3> More preferably, the back surface side first fibers are fibers made of only polyethylene terephthalate resin, or fibers made of only polyethylene terephthalate resin and a thermoplastic resin other than polyethylene terephthalate resin, More preferably, the fiber is made of only polyethylene terephthalate resin. <1> or <2> A heating device as described above.

[0111] <4> The back surface side first fiber is a core-sheath fiber having a core made of polyethylene terephthalate resin and a sheath made of polyethylene resin. <1> ~ <3> 13. The heating device according to claim 12 . <5> the back sheet has a multi-layer structure including a back side first fiber layer and a back side second fiber layer, Only one of the fiber layers includes a back side first fiber, The fiber layer not including the back side first fibers contains fibers having a fiber diameter different from that of the back side first fibers. <1> ~ <4> 13. The heating device according to claim 12 . <6> The back sheet has a two-layer structure having only a back side first fiber layer and a back side second fiber layer. <5> A heating device as described above.

[0112] <7> the back surface side first fiber layer includes a back surface side first fiber, The back surface side second fiber layer includes back surface side second fibers having a fiber diameter smaller than that of the back surface side first fibers and having a fiber diameter of 6 μm or more and 30 μm or less. <5> or <6> A heating device as described above. <8> The fiber diameter of the back side second fibers is smaller than the fiber diameter of the back side first fibers, and More preferably, the thickness is 10 μm or more, even more preferably, 13 μm or more, and more preferably, the thickness is 25 μm or less, even more preferably, the thickness is 20 μm or less, and particularly preferably, the thickness is 17 μm or less. <7> A heating device as described above. <9> The back surface side second fibers preferably contain a polyethylene resin, more preferably contain a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and further preferably are made of only a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and The fiber diameter of the back surface side second fibers is 6 μm or more and 30 μm or less. <7> or <8> A heating device as described above. <10> The back surface side second fiber is a core-sheath fiber having a core made of polyethylene terephthalate resin or polypropylene resin and a sheath made of polyethylene resin. <7> ~ <9> 13. The heating device according to claim 12 .

[0113] <11> the back surface side first fiber layer is disposed so as to face the heating element during use, The second fiber layer on the back side is arranged so as to form the outer surface of the heating device when in use. <5> ~ <10> 13. The heating device according to claim 12 . <12> The back side first fiber layer further includes back side third fibers having a fiber diameter smaller than that of the back side first fibers and larger than that of the back side second fibers. <5> ~ <11> 13. The heating device according to claim 12 . <13> The fiber diameter of the back side third fibers is preferably 15 μm or more, more preferably 18 μm or more, and even more preferably 20 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 24 μm or less, provided that the fiber diameter of the back side third fibers is smaller than the fiber diameter of the back side first fibers and larger than the fiber diameter of the back side second fibers. <12> A heating device as described above.

[0114] <14> The back side third fibers preferably contain a thermoplastic resin other than polyethylene terephthalate resin, more preferably contain a polyethylene resin, further preferably contain a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and further preferably are made of only a polypropylene resin and a polyethylene resin, and The fiber diameter is smaller than the fiber diameter of the back side first fibers and larger than the fiber diameter of the back side second fibers. <12> or <13> A heating device as described above. <15> The back side third fiber is a core-sheath fiber having a core made of polyethylene terephthalate resin or polypropylene resin and a sheath made of polyethylene resin. <12> ~ <14> 13. The heating device according to claim 12 . <16> the back-side second fiber layer includes a back-side second fiber, The second back side fibers and the third back side fibers contain resins whose components are different from each other. <12> ~ <15> 13. The heating device according to claim 12 . <17> the back surface side first fibers are fibers made only of a polyethylene terephthalate resin and a thermoplastic resin other than a polyethylene terephthalate resin, The third fiber on the back side is a fiber containing a thermoplastic resin other than a polyethylene terephthalate resin. <12> ~ <16> 13. The heating device according to claim 12 .

[0115] <18> The mass ratio of the back side third fiber to the total mass of the back side first fiber layer is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. <12> ~ <17> 13. The heating device according to claim 12 . <19> The mass ratio of the back side first fibers to the total mass of the back side first fiber layer is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. <12> ~ <18> 13. The heating device according to claim 12 . <20> The back side first fiber layer includes a back side first fiber including a polyethylene terephthalate resin and a polyethylene resin. <5> ~ <19> 13. The heating device according to claim 12 . <21> the back-side second fiber layer includes a back-side second fiber, The content of the back side second fibers in the back side second fiber layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. <5> ~ <20> 13. The heating device according to claim 12 .

[0116] <22> The density of the fibers in the first fiber layer on the back side is preferably 1500 fibers / cm 2 Less than 1000 fibers / cm, more preferably 1000 fibers / cm 2 Less than 700 / cm, more preferably 700 / cm 2 Less than 150 fibers / cm 2 The above <5> ~ <21> 13. The heating device according to claim 12 . <23> The density of the fibers in the second fiber layer on the back side is 200 fibers / cm 2 More than 1500 pieces / cm 2 The above-mentioned <5> ~ <22> 13. The heating device according to claim 12 . <24> The density of the fibers in the second fiber layer on the back side is preferably 300 fibers / cm2 More preferably, 400 fibers / cm 2 More preferably, 1200 fibers / cm 2 Less than 1000 fibers / cm, more preferably 1000 fibers / cm 2 The above-mentioned <5> ~ <23> 13. The heating device according to claim 12 .

[0117] <25> the back-side first fiber layer is composed only of back-side first fibers and back-side third fibers having a fiber diameter smaller than that of the back-side first fibers, excluding other fibers inevitably mixed therein; the back-side second fiber layer is composed only of back-side second fibers having a fiber diameter smaller than that of the back-side first fibers and having a fiber diameter of 6 μm or more and 30 μm or less, excluding other fibers inevitably mixed therein; The fiber diameter of the back side third fibers is larger than the fiber diameter of the back side second fibers. <5> ~ <24> 13. The heating device according to claim 12 . <26> The basis weight of the first fiber layer on the back side is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 More preferably, 100g / m 2 It is preferable that the thickness is less than 80 g / m 2 More preferably, it is 60 g / m or less. 2 It is more preferable that <5> ~ <25> 13. The heating device according to claim 12 . <27> The basis weight of the second fiber layer on the back side is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2 More preferably, it is 15 g / m or more. 2 More preferably, 50g / m 2 It is preferable that the thickness is less than 40 g / m 2 More preferably, it is 30 g / m or less. 2 It is more preferable that <5> ~ <26> 13. The heating device according to claim 12 .

[0118] <28> The back sheet is a fiber sheet in which the sheet shape is maintained by at least one of fusion and entanglement of constituent fibers, The constituent fibers have contact portions where they are in contact with each other. <1> ~ <27> 13. The heating device according to claim 12 . <29> The back sheet is an air-through nonwoven fabric or a needle-punched nonwoven fabric. <28> A heating device as described above. <30> The thickness of the back sheet at the start of heat generation of the heating device is 1.8 mm or more and 6.0 mm or less. <1> ~ <29> 13. The heating device according to claim 12 . <31> the top sheet is made of a breathable fiber sheet including fibers containing at least a polyethylene terephthalate resin, The top sheet includes a surface-side first fiber having a fiber diameter of more than 15 μm as measured by scanning electron microscope observation in a plan view. <1> ~ <30> 13. The heating device according to claim 12 . <32> The fiber diameter of the surface side first fibers is more preferably 20 μm or more, even more preferably 25 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, even more preferably 40 μm, even more preferably 30 μm or less. <31> A heating device as described above. <33> More preferably, the surface side first fibers are fibers made of only polyethylene terephthalate resin, or fibers made of only polyethylene terephthalate resin and a thermoplastic resin other than polyethylene terephthalate resin, More preferably, the fiber is made of only polyethylene terephthalate resin. <31> or <32> A heating device as described above.

[0119] <34> The surface side first fiber is a core-sheath fiber having a core made of polyethylene terephthalate resin and a sheath made of polyethylene resin. <31> ~ <33> 13. The heating device according to claim 12 . <35> the top sheet has a multilayer structure including a top-side first fiber layer and a top-side second fiber layer, Only one of the fiber layers contains surface-side first fibers, The fiber layer not including the surface-side first fibers contains fibers having a fiber diameter different from that of the surface-side first fibers. <31> ~ <34> 13. The heating device according to claim 12 . <36> The top sheet has a two-layer structure including only a top-side first fiber layer and a top-side second fiber layer. <35> A heating device as described above.

[0120] <37> the surface side first fiber layer includes a surface side first fiber, the surface side second fiber layer includes surface side second fibers having a fiber diameter smaller than that of the surface side first fibers and having a fiber diameter of 6 μm or more and 30 μm or less; <35> or <36> A heating device as described above. <38> The fiber diameter of the surface-side second fibers is smaller than the fiber diameter of the surface-side first fibers, and More preferably, the thickness is 10 μm or more, even more preferably, 13 μm or more, and more preferably, the thickness is 25 μm or less, even more preferably, the thickness is 20 μm or less, and particularly preferably, the thickness is 17 μm or less. <37> A heating device as described above. <39> The surface side second fibers preferably contain a polyethylene resin, more preferably contain a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and further preferably are made of only a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and The fiber diameter of the surface side second fibers is 6 μm or more and 30 μm or less. <37> or <38> A heating device as described above. <40> The surface side second fiber is a core-sheath fiber having a core made of polyethylene terephthalate resin or polypropylene resin and a sheath made of polyethylene resin. <37> ~ <39> 13. The heating device according to claim 12 .

[0121] <41> the surface-side first fiber layer is disposed on a surface farther from the user's skin during use; The second fiber layer on the surface side is disposed on the skin contact surface during use. <35> ~ <40> 13. The heating device according to claim 12 . <42> the surface side first fiber layer further includes surface side third fibers having a fiber diameter smaller than that of the surface side first fibers and larger than that of the surface side second fibers; <35> ~ <41> 13. The heating device according to claim 12 . <43> The fiber diameter of the surface side third fibers is preferably 15 μm or more, more preferably 18 μm or more, and even more preferably 20 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 24 μm or less, provided that the fiber diameter of the surface side third fibers is smaller than the fiber diameter of the surface side first fibers and larger than the fiber diameter of the surface side second fibers. <42> A heating device as described above.

[0122] <44> The surface side third fibers preferably contain a thermoplastic resin other than polyethylene terephthalate resin, more preferably contain a polyethylene resin, further preferably contain a polyethylene resin and a polyethylene terephthalate resin or a polypropylene resin, and further preferably are made of only a polypropylene resin and a polyethylene resin, and The fiber diameter is smaller than the fiber diameter of the surface side first fibers and larger than the fiber diameter of the surface side second fibers. <42> or <43> A heating device as described above. <45> The third fiber on the surface side is a core-sheath fiber having a core made of polyethylene terephthalate resin or polypropylene resin and a sheath made of polyethylene resin. <42> ~ <44> 13. The heating device according to claim 12 . <46> the surface side second fiber layer includes a surface side second fiber, the surface side second fibers and the surface side third fibers contain resins whose components are different from each other; <42> ~ <45> 13. The heating device according to claim 12 . <47> the surface side first fibers are fibers made only of a polyethylene terephthalate resin and a thermoplastic resin other than a polyethylene terephthalate resin, The third fiber on the surface side is a fiber containing a thermoplastic resin other than a polyethylene terephthalate resin. <42> ~ <46> 13. The heating device according to claim 12 .

[0123] <48> The mass ratio of the surface-side third fiber to the total mass of the surface-side first fiber layer is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. <42> ~ <47> 13. The heating device according to claim 12 . <49> The mass ratio of the surface side first fibers to the total mass of the surface side first fiber layer is preferably 10 mass% or more, more preferably 25 mass% or more, even more preferably 30 mass% or more, and is preferably 90 mass% or less, more preferably 75 mass% or less, even more preferably 70 mass% or less. <42> ~ <48> 13. The heating device according to claim 12 . <50> The surface side first fiber layer includes first fibers containing polyethylene terephthalate resin and polyethylene resin. <35> ~ <49> 13. The heating device according to claim 12 . <51> the surface side second fiber layer includes a surface side second fiber, The content of the surface-side second fibers in the surface-side second fiber layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. <35> ~ <50> 13. The heating device according to claim 12 .

[0124] <52> The density of the fibers in the first fiber layer on the surface side is preferably 1500 fibers / cm 2 Less than 1000 fibers / cm, more preferably 1000 fibers / cm 2 Less than 700 / cm, more preferably 700 / cm 2 Less than 150 fibers / cm 2The above <35> ~ <51> 13. The heating device according to claim 12 . <53> The density of the fibers in the second fiber layer on the surface side is 200 fibers / cm 2 More than 1500 pieces / cm 2 The above-mentioned <35> ~ <52> 13. The heating device according to claim 12 . <54> The density of the fibers in the second fiber layer on the surface side is preferably 300 fibers / cm 2 More preferably, 400 fibers / cm 2 More preferably, 1200 fibers / cm 2 Less than 1000 fibers / cm, more preferably 1000 fibers / cm 2 The above-mentioned <35> ~ <53> 13. The heating device according to claim 12 .

[0125] <55> the surface-side first fiber layer is composed only of surface-side first fibers and surface-side third fibers having a fiber diameter smaller than that of the surface-side first fibers, excluding other fibers inevitably mixed therein; the surface-side second fiber layer is composed only of surface-side second fibers having a fiber diameter smaller than that of the surface-side first fibers and having a fiber diameter of 6 μm or more and 30 μm or less, excluding other fibers inevitably mixed therein; The fiber diameter of the third fibers on the surface side is larger than the fiber diameter of the second fibers on the surface side. <35> ~ <54> 13. The heating device according to claim 12 . <56> The basis weight of the first fiber layer on the surface side is 10 g / m 2 It is preferable that the weight is 15 g / m or more. 2 More preferably, it is 20 g / m or more. 2 More preferably, 100g / m 2 It is preferable that the thickness is less than 80 g / m 2 More preferably, it is 60 g / m or less. 2 It is more preferable that <35> ~ <55> 13. The heating device according to claim 12 . <57> The basis weight of the second fiber layer on the surface side is 5 g / m 2 It is preferable that the content is 10 g / m or more. 2More preferably, it is 15 g / m or more. 2 More preferably, 50g / m 2 It is preferable that the thickness is less than 40 g / m 2 More preferably, it is 30 g / m or less. 2 It is more preferable that <35> ~ <56> 13. The heating device according to claim 12 .

[0126] <58> The top sheet is a fiber sheet in which the sheet shape is maintained by at least one of fusion and entanglement of constituent fibers, The constituent fibers have contact portions where they are in contact with each other. <1> ~ <57> 13. The heating device according to claim 12 . <59> The top sheet is an air-through nonwoven fabric or a needle-punched nonwoven fabric. <58> A heating device as described above. <60> The thickness of the surface sheet at the start of heat generation of the heating device is 1.8 mm or more and 6.0 mm or less. <1> ~ <59> 13. The heating device according to claim 12 . <61> The heating element includes a layer including an oxidizable metal, a carbon material, an electrolyte, and water, and a water retention agent layer including a water-absorbent polymer and disposed adjacent to the layer. <1> ~ <60> 13. The heating device according to claim 12 . EXAMPLES

[0127] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. The fiber diameter and number of fibers were observed by SEM observation of the top sheet and back sheet in plan view, magnifying the fibers 2000 times. Then, the position of the SEM observation was changed and repeated observation was performed until the number of fibers reached 100 or more to confirm the number of layers of the top sheet and back sheet. In this observation, the fibers were color-coded and their lengths were measured using image analysis software (Photoshop, Adobe Co., Ltd.). Then, the width of the fiber diameter class was selected from the range of 0.1 to 0.5 μm, and a histogram of the frequency of the number of fibers and the distribution of fiber diameters was created based on the measurement results, and it was determined from the number of peaks whether the top sheet and back sheet contained a single type of fiber or multiple types of fibers. In addition, the type of fiber and the mass ratio of the fiber in the fiber layer were calculated from the number of layers of the top sheet and back sheet of each example and comparative example, and the fiber diameter contained in each layer. In the following description, "%" means "% by mass" unless otherwise specified.

[0128] Example 1 A heating device was manufactured with the structure shown in Figures 1 and 6. Details of the top sheet, back sheet and heating element in this heating device are as follows.

[0129] (1) Surface sheet The top sheet was composed of an air-through nonwoven fabric consisting of a first fiber layer and a second fiber layer. The elongation of the air-through nonwoven fabric in the CD direction measured by the above-mentioned method was 20%. The first fiber layer was composed of a first fiber and a third fiber. The first fiber was a PET fiber with a fiber diameter of 27 μm. The third fiber was a core-sheath type composite fiber with a fiber diameter of 22 μm, in which the core was made of PP and the sheath was made of PE. The proportion of the first fiber was 60%, and the proportion of the third fiber was 40%. The basis weight of the first fiber layer was 40 g / m 2 The fiber density of the first fiber layer measured by the above-mentioned method is shown in Table 1. The second fiber layer was composed of the second fiber. The second fiber was a core-sheath type composite fiber with a fiber diameter of 15 μm, in which the core was made of PET and the sheath was made of PE. The basis weight of the second fiber layer was 20 g / m 2The fiber density of the second fiber layer measured by the above-mentioned method is shown in Table 1.

[0130] (2) Back sheet The back sheet was composed of an air-through nonwoven fabric consisting of a first fibrous layer and a second fibrous layer. The elongation of the air-through nonwoven fabric in the CD direction measured by the above-mentioned method was 20%. The first fiber layer was composed of a first fiber and a third fiber. The first fiber was a PET fiber with a fiber diameter of 27 μm. The third fiber was a core-sheath type composite fiber with a fiber diameter of 22 μm, in which the core was made of PP and the sheath was made of PE. The proportion of the first fiber was 60%, and the proportion of the third fiber was 40%. The basis weight of the first fiber layer was 40 g / m 2 The fiber density of the first fiber layer measured by the above-mentioned method is shown in Table 1. The second fiber layer was composed of the second fiber. The second fiber was a core-sheath type composite fiber with a fiber diameter of 15 μm, in which the core was made of PET and the sheath was made of PE. The basis weight of the second fiber layer was 20 g / m 2 The fiber density of the second fiber layer measured by the above-mentioned method is shown in Table 1.

[0131] (3) Heating element Iron powder was added to an aqueous solution of salt and a thickener in water and stirred, and activated carbon was further added and stirred sufficiently until it was uniformly dispersed, to obtain a paste-like heat generating composition. The heat generating composition paste described above is applied to a polyethylene-laminated tissue paper with a basis weight of 600 g / m 2 Next, particles of a water-absorbing polymer (AQUALIC (registered trademark) CA, manufactured by Nippon Shokubai Co., Ltd.) were applied on the heat-generating composition at a basis weight of 70 g / m. 2 Then, a crepe paper (basis weight 65 g / m2) was placed on the water-absorbent polymer layer. 2 ) was laminated to obtain a heat generating part equipped with a water retention agent layer. After that, this heat generating part was cut to a size of 50 mm x 50 mm. The heat generating portion was sandwiched between a moisture permeable sheet cut to 63 mm x 63 mm and a moisture impermeable sheet, and the four sides of these sheets were heat sealed to obtain a heat generating element with the heat generating portion housed within a bag.

[0132] (4) Heating equipment The first fiber layer of the top sheet was disposed to form the surface facing the heating element, and the second fiber layer was disposed to form the surface farther from the heating element, and the heating element was disposed so that the moisture permeable sheet of the heating element faced the top sheet. On the other hand, the first fiber layer of the back sheet constituted the surface facing the heating element, and the second fiber layer constituted the surface on the side farther from the heating element. The heating element was placed so that the moisture impermeable sheet of the heating element faced the back sheet. With each component positioned in this way, the above-mentioned top sheet and back sheet were joined so that the heating element was housed between the two sheets, to obtain a heating device having the structure shown in Figures 1 and 6. The top sheet and back sheet were positioned so that their CD directions were parallel to the direction connecting the pair of ear hooks in the heating device.

[0133] Example 2 In this example, a heating device having the structure shown in Figs. 1 and 5 was manufactured. A single-layered air-through nonwoven fabric was used as the top sheet. This air-through nonwoven fabric was made of core-sheath type composite fibers with a fiber diameter of 19 μm, with the core made of PET and the sheath made of PE. The basis weight of this air-through nonwoven fabric was 30 g / m 2 The elongation rate of the air-through nonwoven fabric in the CD direction measured by the above-mentioned method was 5%. Other than these, the heating device was obtained in the same manner as in Example 1.

[0134] Example 3 In this example, a heating device having the structure shown in Figs. 1 and 5 was manufactured. A needle-punched nonwoven fabric having a single layer structure was used as the top sheet. This needle-punched nonwoven fabric was composed of a first fiber and a third fiber. The first fiber was a core-sheath type composite fiber with a fiber diameter of 20 μm, with a core made of PP and a sheath made of PE. The third fiber was a PP fiber with a fiber diameter of 10 μm. The proportion of the first fiber was 30%, and the proportion of the third fiber was 70%. The basis weight of this needle-punched nonwoven fabric was 80 g / m 2 The elongation of the needle-punched nonwoven fabric in the CD direction measured by the above method was 15%. Other than these, the heating device was obtained in the same manner as in Example 1.

[0135] Comparative Example 1 In this comparative example, a heating device having the structure shown in Figs. 1 and 4 was manufactured. A single-layered air-through nonwoven fabric was used as the top sheet. This air-through nonwoven fabric was made of core-sheath type composite fibers with a fiber diameter of 19 μm, with the core made of PET and the sheath made of PE. The basis weight of this air-through nonwoven fabric was 30 g / m 2 The elongation rate of the air-through nonwoven fabric in the CD direction measured by the above-mentioned method was 5%. A needle-punched nonwoven fabric having a single layer structure was used as the back sheet. This needle-punched nonwoven fabric was composed of a first fiber and a third fiber. The first fiber was a core-sheath type composite fiber with a fiber diameter of 20 μm, with a core made of PP and a sheath made of PE. The third fiber was a PP fiber with a fiber diameter of 10 μm. The proportion of the first fiber was 30%, and the proportion of the third fiber was 70%. The basis weight of this needle-punched nonwoven fabric was 80 g / m 2 The elongation of the needle-punched nonwoven fabric in the CD direction measured by the above method was 15%. Other than these, the heating device was obtained in the same manner as in Example 1.

[0136] 〔evaluation〕 The amount of water vapor generated was measured for the heating devices obtained in the Examples and Comparative Examples by the method described above. In addition, the highest skin temperature and the skin temperature after 10 minutes were measured by the following method. Furthermore, the smoothness and flexibility of the top sheet and the fit of the heating device were evaluated by the following method. The results are shown in Table 1.

[0137] [Skin maximum temperature] The maximum skin temperature of each heating device in each Example and Comparative Example was measured by the following method. First, a temperature sensor of a data collection type thermometer (LT-8, manufactured by Gram Co., Ltd.) was attached to the upper eyelid of the subject and fixed with surgical tape. Next, in an environment of room temperature 20°C and humidity 50% RH, the heating device sealed and stored in the oxygen-blocking bag was opened and taken out of the oxygen-blocking bag. After that, the subject was made to wear the heating device so that the top sheet was in contact with the temperature sensor. With the thermometer's measuring device connected to the temperature sensor, the temperature was measured at 10-second intervals starting from the start of heat generation, and measurements were performed for 30 minutes. The maximum temperature in the measured temperature profile was taken as the maximum temperature. If the maximum temperature is 40°C or higher, it can be said that the heating device has excellent heat generation properties.

[0138] [Skin temperature after 10 minutes] The heating devices of each Example and Comparative Example were measured in the same manner as in [Maximum Skin Temperature]. The temperature 10 minutes after the start of heat generation in the measured temperature profile was taken as the skin temperature after 10 minutes. If the skin temperature after 10 minutes is 40°C or higher and 41°C or lower, it can be said that the heating device has excellent heat generation properties.

[0139] [Smoothness and flexibility of the surface sheet and fit of the heating device] For each of the examples and comparative examples, two expert panelists evaluated the smooth feel of the surface sheet when touched by hand, while wearing and after use, the flexibility of the surface sheet, and the fit when the heating device was worn over both eyes for 20 minutes, according to the following criteria. The arithmetic mean of the evaluation scores of the two expert panelists in each evaluation was taken as the evaluation result. The higher the score of each evaluation result, the smoother, more flexible, and more fit the heating device has on its surface sheet when in contact with the skin.

[0140] <Evaluation criteria for surface sheet smoothness> 4 points: The texture is very smooth before use and continues to be smooth even after use, with no noticeable fuzzing of the fibers even after use. 3 points: The texture is very smooth before use, and remains smooth during use, but some fuzziness of the fibers is noticeable after use. 2 points: The texture is smooth before use, but the fibers become frayed during and after use, making the texture less smooth. 1 point: Fuzziness of the fibers was perceived before, during and after use, and smoothness was very poor.

[0141] <Evaluation criteria for surface sheet flexibility> 5 points: The surface sheet is very soft and adheres firmly from immediately after use until the end of use, with excellent flexibility and feel. 4 points: The surface sheet is sufficiently soft and adheres closely from immediately after use until the end of use, and has good flexibility and feel. 3 points: The surface sheet has appropriate rigidity, fits tightly enough that you can feel heat during use, and feels fine. 2 points: The surface sheet is a little hard and has poor rigidity, but adheres well when in use. 1 point: The surface sheet is very hard and has poor rigidity, resulting in a lack of adhesion when in use.

[0142] <Fit evaluation criteria> 5 points: The heating device adheres firmly to the eye area and the surrounding area while it is being worn, providing an excellent fit until use is terminated. 4 points: The heating device fits snugly around the eyes while in use and maintains a good fit until use is terminated. 3 points: The heating device is held in place near or around the eyes while it is being worn, and fits comfortably until use is terminated. 2 points: While wearing the heating device, it does not adhere well to the eye area, and the fit is poor until the end of use. 1 point: While wearing the heating device, there is no adhesion between the heating device and the eye area, and the fit is very poor until the end of use.

[0143] [Table 1]

[0144] As is clear from the results shown in Table 1, the heating devices of each Example have an appropriate maximum skin temperature and an appropriate skin temperature after 10 minutes, and generate a high amount of water vapor. In particular, the heating device of Example 1 has a smooth top sheet, and is highly flexible and fits well.

Claims

1. The device comprises a top sheet positioned closer to the user's skin, a back sheet positioned farther from the user's skin, and a heating element held between the top sheet and the back sheet, the heating element contains an oxidizable metal, a carbon material, an electrolyte, and water; The heating element is configured to generate steam from the heating element itself as it generates heat, the back sheet is made of a breathable fiber sheet including fibers containing at least polyethylene terephthalate resin, The back sheet comprises back-side first fibers having a fiber diameter of more than 15 μm when measured by scanning electron microscope observation in a plan view.

2. the backsheet has a multilayer structure including a backside first fiber layer and a backside second fiber layer, Only one of the fiber layers contains back-side first fibers, 2. The heating implement according to claim 1, wherein fibers having a different fiber diameter from the back-side first fibers are contained in a fiber layer that does not contain the back-side first fibers.

3. the back-side first fiber layer includes back-side first fibers, 3. The heating implement according to claim 2, wherein the backside second fiber layer includes backside second fibers having a fiber diameter smaller than that of the backside first fibers and having a fiber diameter of 6 μm or more and 30 μm or less.

4. The heating device according to claim 3, wherein the second fibers on the back side contain polyethylene resin.

5. the back surface-side first fiber layer is disposed on the heating element contact surface, The heating implement according to claim 2 or 3, wherein the second backside fiber layer is disposed on the surface farther from the heating element.

6. 4. The heating implement according to claim 2 or 3, wherein the backside first fiber layer comprises backside first fibers containing polyethylene terephthalate resin and polyethylene resin.

7. 3. The heating implement according to claim 1 or 2, wherein the first fibers on the back side contain polyethylene terephthalate resin and have a fiber diameter of more than 15 μm and not more than 60 μm.

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