Laminated foam sheet

Abstract

The present invention provides a laminated foam sheet that offers good support stability with suppressed buckling and bottoming-out sensations. [Solution] The laminated foam sheet 1 has at least one laminate 4 arranged between two foam sheet materials 2 and 3, the first layer 5 having a first space S1 partitioned by the foam material, and the second layer 6 having a second space S2 partitioned by the foam material. The first layer 5 has a first space volume ratio R1 occupied by the first space S1 of 13% to 60%. The second layer 6 has a second space volume ratio R2 occupied by the second space S2 of 13% to 40%.

Description

Technical Field

[0001] The present invention relates to a laminated foam sheet.

Background Art

[0002] As a conventional laminated foam sheet, a mat base material is known in which a plurality of rod-shaped members are arranged at intervals so as to obtain a good sleeping comfort in consideration of hardness, elasticity, and air permeability, and the rod-shaped members are laminated so as to cross each other in the vertical direction (for example, see Patent Document 1). Further, as another conventional laminated foam sheet, there is also known a three-dimensional lattice cushion having the same structure as the above mat base material (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The improvement in sleeping comfort by the above-mentioned conventional laminated foam sheet is limited, and further improvement in sleeping comfort has been desired. Therefore, the inventors conducted various studies on sleeping comfort, and found that there is room for improvement in that the technologies proposed in Patent Documents 1 and 2 do not consider two factors that affect sleeping comfort. That is, the two factors are the buckling feeling (a sense of discomfort felt when the sheet suddenly sinks) and the bottom feeling (a sense of discomfort felt when the sheet suddenly becomes hard), which a person feels when lying on their side. The conventional laminated foam sheet still has room for improvement in terms of suppressing the buckling feeling and the bottom feeling.

[0005] The object of the present invention is to provide a laminated foam sheet that suppresses buckling and bottoming-out sensations. [Means for solving the problem]

[0006] (1) The laminated foam sheet according to the present invention is a laminated foam sheet in which at least one laminate is arranged between two foam sheet materials, the first layer having a first space partitioned by a foaming material and the second layer having a second space partitioned by a foaming material, wherein the first layer has a first space volume ratio of 13% to 60% and the second layer has a second space volume ratio of 13% to 40%.

[0007] (2) In the laminated foam sheet described in (1) above, it is preferable that the first spatial volume ratio is equal to or greater than the second spatial volume ratio, and the difference between the first spatial volume ratio and the second spatial volume ratio is 20% or less.

[0008] (3) In the laminated foam sheet according to (1) or (2) above, the first layer comprises a plurality of first rod-shaped foam materials arranged in parallel to partition the first space, and the second layer comprises a plurality of second rod-shaped foam materials arranged in parallel to partition the second space, and the laminate is preferably a lattice-like body formed by laminating the first layer and the second layer such that the plurality of first rod-shaped foam materials and the plurality of second rod-shaped foam materials intersect each other.

[0009] (4) In any one of the laminated foam sheets described in (1) to (3) above, the first spatial volume ratio is preferably 40% or more and less than 60%, and the second spatial volume ratio is preferably 40%.

[0010] (5) In any one of the laminated foam sheets described in (1) to (3) above, it is preferable that the first spatial volume ratio is greater than 13% and 20% or less, and the second spatial volume ratio is greater than 13% and 20% or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a laminated foam sheet in which buckling and bottoming-out sensations are suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic perspective view of a laminated foam sheet, which is one embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view showing a schematic representation of the laminated foam sheet. [Figure 3] Figure 1 is a schematic front view showing the laminated foam sheet. [Figure 4] Figure 2 is a schematic right-side view of the laminated foam sheet. [Figure 5] This image shows an example of a measurement sample in a grayscale, oblique view. [Figure 6] This image shows other examples of measurement samples in a grayscale, oblique view. [Figure 7] This graph shows the relationship between compressive strain and compressive stress, measured by performing a compression test on Sample 1, which is a first comparative example of the present invention. [Figure 8] This graph shows the relationship between strain and stress, measured by performing a compression test on Sample 2, which is a second embodiment of the present invention. [Figure 9] This graph shows the relationship between strain and stress, measured by performing a compression test on Sample 3, which is the first embodiment of the present invention. [Figure 10] This graph shows the relationship between strain and stress, measured by performing a compression test on Sample 4, which is a third embodiment of the present invention. [Figure 11] This graph shows the relationship between strain and stress, measured by performing a compression test on Sample 5, which is a fourth embodiment of the present invention. [Figure 12] This graph shows the relationship between strain and stress, measured by performing a compression test on Sample 6, which is a fourth comparative example of the present invention. [Figure 13]A graph showing the relationship between strain and stress, measured by performing a compression test on Sample 7, which is the third comparative example for the present invention. [Figure 14] A graph showing the relationship between strain and stress, measured by performing a compression test on Sample 8, which is the second comparative example for the present invention.

Mode for Carrying Out the Invention

[0013] Hereinafter, a laminated foam sheet, which is an embodiment of the present invention, will be described with reference to the drawings.

[0014] In FIG. 1, reference numeral 1 denotes a laminated foam sheet, which is an embodiment of the present invention. The laminated foam sheet 1 can be used, for example, as a base material for a mattress.

[0015] Here, the "vertical direction" is based on the state where the laminated foam sheet 1 is placed on an installation surface such as a floor. The "front-rear direction" refers to a direction orthogonal to the vertical direction, and "front" and "rear" are based on the laminated foam sheet 1. Further, the "left-right direction" refers to a direction orthogonal to the vertical direction and the front-rear direction, and "right" and "left" are based on the laminated foam sheet 1. However, in the present embodiment, the front-rear direction and the left-right direction are defined for convenience of explanation, and it is needless to say that the front-rear direction and the left-right direction may be interchanged during use.

[0016] The laminated foam sheet 1 is one in which at least one laminate 4 is disposed between two foam sheet materials, namely, a first foam sheet material 2 and a second foam sheet material 3. The laminate 4 includes a first layer 5 having a first space S1 partitioned by a foam material and a second layer 6 having a second space S2 partitioned by a foam material. In the present embodiment, the first foam sheet material 2, the second foam sheet material 3, and the laminate 4 (the first layer 5 and the second layer 6) are each a foam material made of a foamed resin. Examples of the foamed resin include foamed polyurethane.

[0017] In Figure 1, the first foamed sheet material 2 is positioned on the upper side, while the second foamed sheet material 3 is positioned on the lower side. In other words, in Figure 1, the first layer 5 is positioned on the upper side, while the second layer 6 is positioned on the lower side. However, the laminated foamed sheet 1 can also be used upside down. In this embodiment, the first foamed sheet material 2 is a foamed sheet material with a profiled upper surface, and the second foamed sheet material 3 is a flat foamed sheet material.

[0018] The first layer 5 comprises a plurality of first rod-shaped foam materials 5a arranged in parallel to partition the first space S1. The second layer 6 also comprises a plurality of second rod-shaped foam materials 6a arranged in parallel to partition the second space S2. The laminate 4 is a lattice-like body formed by laminating the first layer 5 and the second layer 6 such that the plurality of first rod-shaped foam materials 5a and the plurality of second rod-shaped foam materials 6a intersect each other. Here, "rod-shaped foam material" refers to a foam material having a long, elongated shape. In this embodiment, the first rod-shaped foam material 5a and the second rod-shaped foam material 6a are each plate-shaped rod-shaped foam materials. In this embodiment, the first rod-shaped foam material 5a and the second rod-shaped foam material 6a are also made of a foamed resin such as foamed polyurethane.

[0019] Figure 2 schematically shows the laminated foam sheet 1 in a state where it has been separated in the vertical direction.

[0020] In this embodiment, the first rod-shaped foam material 5a is a rod-shaped foam member having a rectangular cross-section. In Figure 2, the first rod-shaped foam material 5a is arranged to extend in the front-to-back direction and is spaced apart in the left-to-right direction. Also in this embodiment, the second rod-shaped foam material 6a is a rod-shaped foam member having a rectangular cross-section. The second rod-shaped foam material 6a is arranged to extend in the left-to-right direction and is spaced apart in the front-to-back direction. However, the cross-sectional shapes of the first rod-shaped foam material 5a and the second rod-shaped foam material 6a are not limited to rectangles, but can be, for example, squares, circles, or polygons.

[0021] In this embodiment, the laminate 4 is formed by laminating a plurality of first rod-shaped foam materials 5a arranged in parallel and a plurality of second rod-shaped foam materials 6a arranged in parallel so as to intersect with the plurality of first rod-shaped foam materials 5a. As a result, as shown in Figure 1, the first layer 5 has a plurality of first spaces S1 that are closed in the vertical direction by the first foam sheet material 2 and the second layer 6. In this embodiment, the first spaces S1 are formed to extend in the front-to-back direction and are spaced apart in the left-to-right direction. Furthermore, in this embodiment, the first spaces S1 are open to the outside in the front-to-back direction. Also, as shown in Figure 1, the second layer 6 has a plurality of second spaces S2 that are closed in the vertical direction by the first layer 5 and the second foam sheet 3. In this embodiment, the second spaces S2 are formed to extend in the left-to-right direction and are spaced apart in the front-to-back direction. Furthermore, in this embodiment, the second spaces S2 are open to the outside in the left-to-right direction. The first space S1 and the second space S2 are connected vertically in the portion that intersects them vertically.

[0022] The first layer 5 comprises four first rod-shaped foam materials 5a. This forms three first spaces S1 in the first layer 5. In this embodiment, the second layer 6 comprises four second rod-shaped foam materials 6a. This forms three second spaces S2 in the second layer 6. However, the number of first spaces S1 and second spaces S2 can be selected as appropriate. For example, the number of first spaces S1 and second spaces S2 can be the same, or they can be different. In this case, the relative size of the number of first spaces S1 and the number of second spaces S2 can also be selected as appropriate.

[0023] In the first layer 5, the first space volume ratio R1 occupied by the first space S1 is 13% to 60%. Here, the first space volume ratio R1 is the ratio of the total volume of the first space S1 formed in the first layer 5 to the total volume of the first layer 5 (including the first space S1), that is, the ratio of the total volume of all the first spaces S1 to the total volume of the first layer 5. Note that the volume of the first space S1 in the calculation of the first space volume ratio R1 does not include the air bubbles of the first rod-shaped foam material 5a.

[0024] Furthermore, in the second layer 6, the second space volume ratio R2 occupied by the second space S2 is 13% to 40%. Here, the second space volume ratio R2 is the ratio of the total volume of the second space S2 formed in the second layer 6 to the total volume of the second layer 6 (including the second space S2), that is, the ratio of the total volume of all the second spaces S2 to the total volume of the second layer 6. Note that the volume of the second space S6 in the calculation of the second space volume ratio R2 does not include the air bubbles of the second rod-shaped foam material 6a.

[0025] In addition, in the laminated foam sheet 1 shown in Figure 1, the first spatial volume ratio R1 is greater than or equal to the second spatial volume ratio R2, and the difference between the first spatial volume ratio R1 and the second spatial volume ratio R2 is 20% or less, including 0%. A specific example is when the first spatial volume ratio R1 is greater than the second spatial volume ratio R2, and the difference between the first spatial volume ratio R1 and the second spatial volume ratio R2 is 20% or less. In this case, for example, the first spatial volume ratio R1 can be 60% or less, and the second spatial volume ratio R2 can be 40% or less. Another specific example is when the first spatial volume ratio R1 is equal to the second spatial volume ratio R2. In this case, for example, both the first spatial volume ratio R1 and the second spatial volume ratio R2 can be 40%, 20%, or 13%. In this disclosure, it is preferable that the first spatial volume ratio R1 and the second spatial volume ratio R2 are equal in value. In other words, it is most preferable that the difference between the first spatial volume ratio R1 and the second spatial volume ratio R2 be 0%.

[0026] For example, a solid laminated foam sheet that does not have spaces between each layer (excluding the air bubbles in the foam material) is not designed with buckling in mind. Therefore, when a solid laminated foam sheet is compressed vertically, it is initially hard, but may suddenly sink (dent) when compressed further. This sudden sinking gives the user an uncomfortable feeling (buckling sensation) that the laminated foam sheet is sinking suddenly. For this reason, there is room for improvement in suppressing the buckling sensation in solid laminated foam sheets that do not have spaces between each layer.

[0027] On the other hand, while the aforementioned conventional laminated foam sheets have suppressed buckling, when these sheets are compressed vertically, they are initially soft but can suddenly harden after being compressed to a certain extent. This rapid hardening gives the user an uncomfortable feeling (a sense of bottoming out) as if the laminated foam sheet has suddenly become hard. Therefore, even conventional laminated foam sheets with spaces between each layer have room for improvement in terms of suppressing the feeling of bottoming out.

[0028] In other words, the inventors of this application have diligently conducted tests and research, and have come to realize that while solid laminated foam sheets without spaces between each layer have room for improvement in suppressing buckling, which affects sleeping comfort, conventional laminated foam sheets with spaces between each layer do not focus on buckling and bottoming out, which affect sleeping comfort, and therefore have room for further improvement in suppressing buckling and bottoming out.

[0029] In contrast, the laminated foam sheet 1 according to the present invention has a first spatial volume ratio R1 in the range of 13% to 60% and a second spatial volume ratio R2 in the range of 13% to 40%. In this case, according to the test results in Examples 1 to 4 described later, that is, the "compressive stress-strain characteristics" obtained when a compression test is performed in accordance with JIS K 6400-2 E method ((method for determining the compressive deflection coefficient and hysteresis loss rate)), it became clear that buckling sensation increases when both the first spatial volume ratio R1 and the second spatial volume ratio R2 are less than 13%, while buckling sensation is suppressed when both the first spatial volume ratio R1 and the second spatial volume ratio R2 are 13% or more. Furthermore, the test results from Examples 1 to 4, described later, revealed that when the first spatial volume ratio R1 exceeds 60% and the second spatial volume ratio R2 exceeds 40%, the feeling of bottoming out becomes more pronounced, while when the first spatial volume ratio R1 is 60% or less and the second spatial volume ratio R2 is 40% or less, the feeling of bottoming out is suppressed.

[0030] Therefore, laminated foam sheet 1 is a laminated foam sheet that suppresses buckling and bottoming out compared to both a solid laminated foam sheet without spaces between layers and conventional laminated foam sheets with spaces between layers. As a result, laminated foam sheet 1 makes it possible to obtain a laminated foam sheet with spaces between layers that provides a good sleeping experience, compared to both a solid laminated foam sheet without spaces between layers and conventional laminated foam sheets with spaces between layers.

[0031] In addition, with the laminated foam sheet 1, for example, as shown in Figure 1, the first space S1 formed in the first layer 5 and the second space S2 formed in the second layer 6 can be opened to the outside to function as heat dissipation passages. Therefore, with the laminated foam sheet 1, the breathability (heat dissipation) of the laminated foam sheet 1 can be ensured by opening the first space S1 formed in the first layer 5 and the second space S2 formed in the second layer 6 to the outside. It is clear that the laminated foam sheet 1 heats up and cools down more easily when the spatial volume (at least one of the volume of the first space S1 and the volume of the second space S2) is larger.

[0032] Furthermore, the laminated foam sheet 1 can have a first spatial volume ratio R1 in the range of 40% or more and less than 60%, and a second spatial volume ratio R2 of 40%. According to the test results in the examples described later, it became clear that, basically, as the first spatial volume ratio R1 increases, the feeling of buckling tends to be suppressed, while as the first spatial volume ratio R1 decreases, the feeling of bottoming out tends to be suppressed. In particular, according to the test results in Examples 3 and 4 described later, when the first spatial volume ratio R1 is set to 40% or more and less than 60%, and the second spatial volume ratio R2 is set to 40%, specifically in Example 3 where both the first spatial volume ratio R1 and the second spatial volume ratio R2 are 40%, it became clear that the feeling of bottoming out was suppressed more than in Example 4. Therefore, by setting the first spatial volume ratio R1 to 40% or more and less than 60%, and the second spatial volume ratio R2 to 40%, a laminated foam sheet with a more suppressed feeling of bottoming out can be obtained.

[0033] Furthermore, the laminated foam sheet 1 can have a first spatial volume ratio R1 greater than 13% and 20% or less, and a second spatial volume ratio R2 greater than 13% and 20% or less. As described above, the test results in Examples 1 to 4 and Comparative Examples 1 to 4 described later revealed that, basically, as the first spatial volume ratio R1 increases, the feeling of buckling tends to be suppressed. In particular, the test results in Examples 1 to 2 described later revealed that when the first spatial volume ratio R1 is greater than 13% and 20% or less, and the second spatial volume ratio R2 is greater than 13% and 20% or less, specifically in the first example where the first spatial volume ratio R1 is 20% and the second spatial volume ratio R2 is 20%, the feeling of buckling is suppressed more than in the second example. Therefore, by setting the first spatial volume ratio R1 to be greater than 13% and 20% or less, and the second spatial volume ratio R2 to be greater than 13% and 20% or less, a laminated foam sheet with more suppressed buckling can be obtained.

[0034] Here, Figure 3 schematically shows the laminated foam sheet 1 from the front-to-back direction. In Figure 3, the symbol H is the vertical height (thickness in the lamination direction) of the laminated foam sheet 1. Height H is the height (thickness in the lamination direction) between the upper end and lower end of the laminated foam sheet 1. The symbol W is the left-to-right width of the laminated foam sheet 1. Width W is the width between the right end and left end of the laminated foam sheet 1. Furthermore, the symbol h1 is the height (thickness) of the first layer 5. Height h1 is the height (thickness in the lamination direction) between the upper end and lower end of the first layer 5. In this embodiment, the height (thickness in the lamination direction) of the first rod-shaped foam material 5a and the height (thickness in the lamination direction) of the first space S1 are equal to height h1. The symbol h3 is the height (thickness) of the first foam sheet material 2. Height h3 is the height (thickness in the lamination direction) between the upper end and lower end of the first foam sheet material 2. Also, the symbol w5 is the left-to-right width of the first rod-shaped foam material 5a. In this embodiment, the width w5 is the width between the right end and the left end of the first rod-shaped foam material 5a. Furthermore, the reference numeral w1 denotes the width of the first space S1 in the left-right direction. In this embodiment, the width w1 is the width between the right end and the left end of the first space S1.

[0035] Figure 4 schematically shows the laminated foam sheet 1 of Figure 2 from a side view. In Figure 4, the symbol L is the length of the laminated foam sheet 1 in the depth direction (hereinafter also simply referred to as "length L"). Length L is the length between the front end and the rear end of the laminated foam sheet 1. The symbol h2 is the height (thickness in the lamination direction) of the second layer 6 in the vertical direction. Height h2 is the height (thickness in the lamination direction) between the upper end and the lower end of the second layer 6. In this embodiment, the height (thickness in the lamination direction) of the second rod-shaped foam material 6a and the height (thickness in the lamination direction) of the second space S2 are equal to height h2. The symbol h4 is the height (thickness) of the second foam sheet material 3. Height h4 is the height (thickness in the lamination direction) between the upper end and the lower end of the second foam sheet material 3. The symbol w6 is the width of the second rod-shaped foam material 6a in the depth direction. In this embodiment, width w6 is the length between the front end and the rear end of the second rod-shaped foam material 6a. Furthermore, the symbol w2 represents the width of the second space S2 in the depth direction. In this embodiment, the width w2 is the length between the front end and the rear end of the second space S2.

[0036] [Examples] The following describes the results of compression tests conducted using the measurement samples.

[0037] (1) Measurement sample Figure 5 shows an example of a measurement sample as a grayscale image. Figure 6 shows another example of a measurement sample as a grayscale image. In this test, the measurement sample in Figure 6 was used as the reference and served as Comparative Example 1 to the embodiment of the present invention. The measurement sample in Figure 6 is a solid laminated foam sheet with no spaces between each layer. The measurement sample in Figure 5 is a laminated foam sheet with spaces between each layer. By keeping the external dimensions (width × length (depth) × height) of the measurement sample in Figure 5 the same as the measurement sample in Figure 6, and changing its internal structure (for example, the presence or absence of the first space S1 and the second space S2, and the size and number of the first space S1 and the second space S2), embodiments 1 to 4 and comparative examples 2 to 4 to the embodiment of the present invention were created. In embodiments 1, 3 to 4 and comparative examples 2 to 4, the number of the first space S1 and the second space S2 was set to 3 each, while in embodiment 2, the number of the first space S1 and the second space S2 was set to 2 each. Furthermore, in Examples 1-4 and Comparative Examples 2-4, the thicknesses in the lamination direction (vertical thickness) of the first foamed sheet material 2, the first layer 5, the second layer 6, and the second foamed sheet material 3 were set to 3 cm, 1.5 cm, 1.5 cm, and 2 cm, respectively.

[0038] The measurement samples used were flat, laminated foam sheets with dimensions of width × length (depth) × height = 300 × 300 × 80 (mm). The individual internal structures of the measurement samples in Figure 6 were varied. The material of the measurement samples was consistent across all samples, consisting of a four-layer structure: first foam sheet material 2, second foam sheet material 3, first layer 5, and second layer 6. The apparent density of the aforementioned material, measured in accordance with Japanese Industrial Standards (JIS K 6400:1997), was 35 kg / m³. 3 ~39kg / m 3 Furthermore, foamed polyurethane was used, whose hardness, as measured in accordance with the Japanese Industrial Standard (JIS K6400-2 Method D), was between 150N and 190N.

[0039] (2) Compression test Compression tests were conducted in accordance with JIS K 6400-2 Method E (Method for determining the compression deflection coefficient and hysteresis loss rate). (a) Pre-compression Pre-compression is performed as follows: a) Place the measurement sample (test piece) on the support plate of the compression testing machine so that the center of the measurement sample (test piece) is in the center of the pressure plate of the compression testing machine. At this time, the measurement sample should be placed with the second foam sheet 3 facing the support plate. b) The initial position of the pressure plate when a force of 5 + 0 - 2 N is applied is taken as the initial position, and the thickness of the sample to be measured is read to the nearest 0.1 mm. Then, the sample is pressurized at a speed of 100 ± 20 mm / min to (70 ± 2.5)% of its thickness, and immediately returned to the initial position at the same speed. (i) Measurement method After pre-compression, the sample is left to stand for 3-5 minutes, then pressurized at a speed of 100±20 mm / min to (70±2.5)% of the sample's initial thickness, and the pressurizing plate is returned at the same speed. From this series of operations, stress-deflection curves as shown in Figures 6-12 are plotted. The holding time from pressurization to recovery should be within 2 seconds. (c) Compression method Full-surface compression: Pressure is applied to the entire surface of the sample being measured to compress it.

[0040] Figures 7 to 14 show the relationship between compressive strain and compressive stress as stress-strain curves (hereinafter referred to as "SS curves"), which were measured by performing compression tests on eight samples 1 to 8.

[0041] Figure 7 shows the SS curve measured by performing a compression test on Sample 1, which is the first comparative example (Comparative Example 1) of the present invention. Comparative Example 1 in Figure 7 is a comparative example that uses a solid laminated foam sheet with no spaces between each layer.

[0042] In contrast, Figure 8 shows the SS curve measured by performing a compression test on sample 2, which is a second embodiment (Example 2) of the present invention. In Example 2, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were both set to 2 (cm). Also, Figure 9 shows the SS curve measured by performing a compression test on sample 3, which is a first embodiment (Example 1) of the present invention. In Example 1, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were both set to 2 (cm). Furthermore, Figure 10 shows the SS curve measured by performing a compression test on sample 4, which is a third embodiment (Example 3) of the present invention. In Example 3, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were both set to 4 (cm). Figure 11 shows the SS curve measured by performing a compression test on sample 5, which is a fourth embodiment (Example 4) of the present invention. In Example 4, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were set to 6 cm and 4 cm, respectively. Samples 2 to 5 in Figures 8 to 11 are examples using laminated foam sheets with spaces in each layer.

[0043] On the other hand, Figure 12 shows the SS curve measured by performing a compression test on sample 6, which is the fourth comparative example (Comparative Example 4) of the present invention. In Comparative Example 4, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were set to 8 cm and 2 cm, respectively. Also, Figure 13 shows the SS curve measured by performing a compression test on sample 7, which is the third comparative example (Comparative Example 3) of the present invention. In Comparative Example 3, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were set to 6 cm, respectively. Furthermore, Figure 14 shows the SS curve measured by performing a compression test on sample 8, which is the second comparative example (Comparative Example 2) of the present invention. In Comparative Example 2, the width w1 in the left-right direction of the first space S1 and the width w1 in the depth direction of the second space S2 were set to 8 cm, respectively. Samples 6 to 8 in Figures 12 to 14 are comparative examples using laminated foam sheets having spaces in each layer.

[0044] Sample 1 in Figure 7 is Comparative Example 1, which is a solid laminated foam sheet with no spaces between each layer. The SS curve of Comparative Example 1 is a hysteresis curve. As shown in Figure 7, the SS curve of Comparative Example 1 shows that the compressive stress increases in accordance with the increase in compressive strain from immediately after the start of compression (indentation) of Sample 1. However, the SS curve of Comparative Example 1 has a point, indicated by the symbol P1 in Figure 7, where the compressive stress with respect to compressive strain increases sharply, and then the rate of increase of said compressive stress decreases sharply. At this point P1, Comparative Example 1 gives the user a feeling of buckling.

[0045] On the other hand, Sample 8 in Figure 14 is Comparative Example 2, which is a laminated foam sheet having a first space S1 and a second space S2 in each layer. In Comparative Example 2, both the volume fraction R1 of the first space and the volume fraction R2 of the second space are set to 80%. However, in the case of Comparative Example 2, as shown in Figure 14, for a while after starting to compress Sample 8, only the compressive strain increases, but once the compressive strain reaches a certain value, compressive stress is generated, and the increase in this compressive stress is also rapid. For this reason, Comparative Example 2, which has spaces in each layer, does not give the user the same buckling sensation as Comparative Example 1 after starting to compress Sample 8, but it can be seen that at point P2 after starting to compress Sample 7, the user feels a strong bottoming out sensation.

[0046] Next, Sample 7 in Figure 13 is Comparative Example 3, which is also a laminated foam sheet having a first space S1 and a second space S2 in each layer. In Comparative Example 3, both the volume fraction R1 of the first space and the volume fraction R2 of the second space are set to 60%. Although the time period is shorter in Comparative Example 3 compared to Comparative Example 2, similar to Comparative Example 2, for a while after the compression of Sample 7 begins, only the compressive strain increases. However, once the compressive strain reaches a certain value, compressive stress is generated, and the increase in this compressive stress is also rapid. Therefore, even in Comparative Example 3, which has spaces in each layer, similar to Comparative Example 2, the user does not experience the buckling sensation seen in Comparative Example 1 after the compression of Sample 7 begins. However, compared to Comparative Example 2, although the time during which only the compressive strain increases is shorter, the user experiences a strong bottoming-out sensation at point P2 after the compression of Sample 7 begins.

[0047] Sample 6 in Figure 12 is Comparative Example 4, which is also a laminated foam sheet having a first space S1 and a second space S2 in each layer. In Comparative Example 4, the volume fraction R1 of the first space is 80%, and the volume fraction R2 of the second space is 20%. Although the time is shorter than that of Comparative Example 3, in Comparative Example 4, similar to Comparative Examples 2 or 3, only the compressive strain increases for a while after the start of compression of Sample 7. However, once the compressive strain reaches a certain value, compressive stress is generated, and the increase in this compressive stress is also rapid. Therefore, even in Comparative Example 4, which has spaces in each layer, although the time during which only the compressive strain increases is shorter than in Comparative Example 3, it can be seen that at point P2 after the start of compression of Sample 7, the user experiences a strong feeling of bottoming out.

[0048] Therefore, referring to Comparative Example 1 in Figure 7 and Comparative Examples 2 to 4 in Figures 14 to 12, it can be seen that while solid laminated foam sheets without spaces between layers have room for improvement in suppressing buckling, which affects sleeping comfort, conventional laminated foam sheets with spaces between layers do have room for improvement in suppressing buckling and bottoming, which affect sleeping comfort, although this does not focus on buckling and bottoming out.

[0049] In contrast, Sample 5 in Figure 11 is Example 4 of the present invention, and is a laminated foam sheet having a first space S1 and a second space S2 in each layer. In Example 4, the volume fraction R1 of the first space is 60%, and the volume fraction R2 of the second space is 40%. According to Example 4, the compressive stress increases in accordance with the compressive strain immediately after the start of compression of Sample 5. In Example 4, after the compressive stress increases after the start of compression of Sample 5, the rate of increase of the compressive stress decreases sharply at point P1. Therefore, according to Example 4, the user does not feel bottoming out from the start of compression of Sample 5 until point P1 is reached.

[0050] On the other hand, according to Example 4, as shown in Figure 11, there is a possibility of buckling at point P1 after the start of compression of Sample 5, but the value of the compressive stress at point P1 is kept lower compared to Comparative Example 1 in Figure 7. Therefore, according to Example 4, the buckling sensation felt by a person lying down is smaller compared to Comparative Example 1.

[0051] Furthermore, Sample 4 in Figure 10 is Example 3 of the present invention, and is a laminated foam sheet having a first space S1 and a second space S2 in each layer. In Example 3, both the volume fraction R1 of the first space and the volume fraction R2 of the second space are set to 40%. According to Example 3, the compressive stress increases in accordance with the compressive strain immediately after the start of compression of Sample 4. In Example 3, after the compressive stress increases after the start of compression of Sample 4, the rate of increase of the compressive stress decreases sharply at point P1. Therefore, according to Example 3, the user does not feel bottoming out from the start of compression of Sample 5 until point P1 is reached.

[0052] On the other hand, in Example 3, similar to Example 4, as shown in Figure 10, there is a possibility of buckling at point P1 after compression of Sample 4 begins. However, in Example 3 as well, the compressive stress value at point P1 is kept lower compared to Comparative Example 1 in Figure 7. Therefore, it can be seen that in Example 3 as well, the buckling sensation felt by a person lying down is smaller compared to Comparative Example 1.

[0053] In addition, according to Example 3, as shown in Figure 10, the rate of change of compressive stress immediately after passing point P1 (the rate of change of the tangent to the SS curve) increases sharply compared to Example 4 in Figure 11. That is, from Figure 10, it can be seen that even though Example 3 is a laminated foam sheet with spaces between each layer, it does not give the user a feeling of bottoming out, and even after passing point P1, the user can feel a rebound force that is closer to their own movement compared to Example 4. For this reason, according to Example 3, the feeling of buckling that occurs after the start of compression of Sample 3 is also suppressed to a smaller degree compared to Example 4.

[0054] Therefore, the test results from Examples 3-4 and Comparative Examples 2-4 show that when the first spatial volume ratio R1 exceeds 60% and the second spatial volume ratio R2 exceeds 40%, the feeling of bottoming out increases, while when the first spatial volume ratio R1 is 60% or less and the second spatial volume ratio R2 is 40% or less, the feeling of bottoming out is suppressed.

[0055] In contrast, Sample 2 in Figure 8 is Example 2 of the present invention, and is a laminated foamed sheet having a first space S1 and a second space S2 in each layer. In Example 2, both the volume fraction R1 of the first space and the volume fraction R2 of the second space are set to 13%. According to Example 2, from the start of compression (indentation) of Sample 2 until the compression is released, it has a shape similar to the SS curve of Comparative Example 1 in Figure 7. In addition, the SS curve from the release of compression of Sample 2 until Sample 2 returns to its original state also has a shape similar to the SS curve of Comparative Example 1, as shown in Figure 8.

[0056] According to Example 2, the compressive stress increases in accordance with the compressive strain immediately after the start of compression of Sample 2. In Example 2, after the compressive stress increases from the start of compression of Sample 2, the rate of increase of the compressive stress decreases sharply at point P1. Therefore, according to Example 2, it can be seen that the user does not feel bottoming out from the start of compression of Sample 2 until reaching point P1, similar to Example 4. However, according to Example 2, as shown in Figure 8, there is a possibility of buckling at point P1 from the start of compression of Sample 2. However, according to Example 2, as shown in Figure 8, the value of the compressive stress at point P1 is kept lower compared to Comparative Example 1 in Figure 7. Therefore, according to Example 2, the feeling of buckling felt when a person lies down is smaller compared to Comparative Example 1.

[0057] Furthermore, Sample 3 in Figure 9 is Example 1 of the present invention, and is a laminated foamed sheet having a first space S1 and a second space S2 in each layer. In Example 1, both the volume fraction R1 of the first space and the volume fraction R2 of the second space are set to 20%. Like Example 2 in Figure 8, Example 1 also has a shape similar to the SS curve of Comparative Example 1 in Figure 7 from the start of compression of Sample 3 until the compression is released. In addition, the SS curve from the release of compression of Sample 3 until Sample 3 is restored also has a shape similar to the SS curve of Comparative Example 1, as shown in Figure 9.

[0058] According to Example 1, similar to Example 2, the compressive stress increases in accordance with the compressive strain immediately after the start of compression of Sample 3. Also, similar to Example 2, in Example 1, after the compressive stress increases from the start of compression of Sample 3, the rate of increase of the compressive stress decreases sharply at point P1. Therefore, according to Example 1, similar to Example 2, the user does not feel bottoming out from the start of compression of Sample 2 until reaching point P1. However, according to Example 1, as shown in Figure 9, similar to Example 2, there is a possibility of buckling at point P1 after the start of compression of Sample 3. However, as shown in Figure 9, in Example 1, similar to Example 2 in Figure 8, the value of the compressive stress at point P1 is kept lower compared to Comparative Example 1 in Figure 7. Therefore, according to Example 1, the buckling feeling felt by a person lying down is smaller compared to Comparative Example 1.

[0059] In addition, according to Example 1, as shown in Figure 9, the rate of change of compressive stress immediately after passing point P1 (the rate of change of the tangent to the SS curve) increases sharply compared to Example 2 in Figure 8. That is, Figure 9 shows that even though Example 1 is a laminated foam sheet with spaces between each layer, it does not give the user a feeling of bottoming out, and even after passing point P1, the user can feel a rebound force that is closer to their own movement compared to Example 2. For this reason, according to Example 1, the feeling of buckling that occurs after the start of compression of Sample 3 is also suppressed to a smaller degree compared to Example 2.

[0060] Therefore, based on the test results in Comparative Example 1 and Examples 2 and 1, it can be seen that when both the first and second spatial volume ratios R1 and R2 are less than 13%, the buckling sensation increases, while when both the first and second spatial volume ratios R1 and R2 are 13% or more, the buckling sensation is suppressed.

[0061] Therefore, Examples 1 to 4 are laminated foam sheets that suppress buckling and bottoming out, not only compared to Comparative Example 1, which is solid and has no spaces between layers, but also compared to Comparative Examples 2 to 4, which have spaces between layers. This shows that with Laminated Foam Sheet 1, it is possible to obtain a laminated foam sheet with spaces between layers that provides a good sleeping experience, not only compared to a solid laminated foam sheet with no spaces between layers, but also compared to a conventional laminated foam sheet with spaces between layers.

[0062] Furthermore, in Examples 3 and 4, the first spatial volume ratio R1 is set to 40% or more and less than 60%, and the second spatial volume ratio R2 is set to 40%. According to the test results in Examples 1 to 4 and Comparative Examples 1 to 4, when the SS curves from Sample 1 to Sample 8 are examined sequentially, it can be seen that as the first spatial volume ratio R1 increases, the feeling of buckling tends to be suppressed. Conversely, when the SS curves from Sample 8 to Sample 1 are examined sequentially, it can be seen that, basically, as the first spatial volume ratio R1 decreases, the feeling of bottoming out tends to be suppressed. In particular, according to the test results in Example 3 shown in Figure 10 and the test results in Example 4 shown in Figure 11, when the first spatial volume ratio R1 is set to 40% or more and less than 60%, and the second spatial volume ratio R2 is set to 40%, specifically in Example 3 where both the first spatial volume ratio R1 and the second spatial volume ratio R2 are 40%, the feeling of bottoming out is suppressed more than in Example 4. Therefore, according to Examples 3 and 4, it can be seen that by setting the first spatial volume ratio R1 to 40% or more and less than 60%, and the second spatial volume ratio R2 to 40%, a laminated foam sheet with a more suppressed bottoming-out sensation can be obtained.

[0063] Furthermore, in Examples 1 and 2, the first spatial volume ratio R1 is set to be greater than 13% and 20% or less, and the second spatial volume ratio R2 is set to be greater than 13% and 20% or less. As described above, the test results in Examples 1 to 4 and Comparative Examples 1 to 4, i.e., the test results of Samples 1 to 8, show that as the first spatial volume ratio R1 increases, there is a tendency for the buckling sensation to be suppressed. In particular, the test results in Example 1 shown in Figure 9 and the test results in Example 2 shown in Figure 8 show that when the first spatial volume ratio R1 is greater than 13% and 20% or less, and the second spatial volume ratio R2 is greater than 13% and 20% or less, specifically in the first example where the first spatial volume ratio R1 is 20% and the second spatial volume ratio R2 is 20%, the buckling sensation is suppressed more than in the second example. Therefore, according to Examples 1 and 2, it can be seen that if the first spatial volume ratio R1 is greater than 13% and 20% or less, and the second spatial volume ratio R2 is greater than 13% and 20% or less, a laminated foam sheet with more suppressed buckling can be obtained.

[0064] Table 1 below shows the results of the sensory evaluations conducted for each of Examples 1-4 and Comparative Examples 1-4. The sensory evaluations were performed by six subjects.

[0065] [Table 1] JPEG2026080566000002.jpg25170

[0066] In this sensory evaluation, a rating of A was assigned to each of samples 1-8 if no discomfort was felt when pressed with a finger, with a rating of 10 points. Next, a rating of B was assigned to a sample if some discomfort was felt when pressed, with a rating of 5 points. Furthermore, a rating of C was assigned to a sample if no discomfort was felt when pressed, with a rating of 0 points. In other words, in this sensory evaluation, the comfort level is assessed as increasing from rating C to rating B and then to rating A.

[0067] As shown in the sensory evaluation results in Table 1, all of Examples 1 to 4 received higher average values ​​for sleeping comfort compared to Comparative Example 4, which used a solid laminated foam sheet with no spaces between layers. Furthermore, based on the sensory evaluation results of Comparative Examples 1 to 3, it became clear that even laminated foam sheets with spaces between layers received higher evaluations than Comparative Examples 1 to 3. In addition, according to the sensory evaluation results in Table 1, Example 1 received the highest evaluation among Examples 1 to 4, followed by Examples 2, 3, and 4, in that order, all of which received high average values ​​for sleeping comfort.

[0068] The above-described embodiments are exemplary embodiments of the present invention. Therefore, the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the claims. For example, in the laminated foam sheet 1, at least one laminate 4 can be interposed between the first foam sheet material 2 and the second foam sheet material 3. Furthermore, the laminated foam sheet 1 is not limited to having a flat rectangular shape. The external shape of the laminated foam sheet 1 can be a flat circle. In addition, the laminated foam sheet 1 can be used for bedding such as mattresses, cushions, seat pads, and other seat cushions. [Explanation of symbols]

[0069] 1: Laminated foam sheet, 2: First foam sheet material (foam sheet material), 3: Second foam sheet material (foam sheet material), 4: Laminate, 5: First layer, 5a: First rod-shaped foam material, 6: Second layer, 6a: Second rod-shaped foam material, S1: First space, S2: Second space

Claims

1. A laminated foam sheet having at least one laminate arranged between two foam sheet materials, the laminate comprising a first layer having a first space partitioned by a foam material, and a second layer having a second space partitioned by a foam material, The first layer has a first space volume ratio of 13% to 60%. The second layer is a laminated foam sheet in which the second space occupies a volume ratio of 13% to 40%.

2. The laminated foam sheet according to claim 1, wherein the first spatial volume ratio is equal to or greater than the second spatial volume ratio, and the difference between the first spatial volume ratio and the second spatial volume ratio is 20% or less.

3. The first layer comprises a plurality of first rod-shaped foam materials arranged in parallel to partition the first space, and the second layer comprises a plurality of second rod-shaped foam materials arranged in parallel to partition the second space. The laminated foam sheet according to claim 1, wherein the laminate is a lattice-like body formed by laminating the first layer and the second layer such that the plurality of first rod-shaped foam materials and the plurality of second rod-shaped foam materials intersect each other.

4. The laminated foam sheet according to claim 1 or 2, wherein the first spatial volume ratio is 40% or more and less than 60%, and the second spatial volume ratio is 40%.

5. The laminated foam sheet according to claim 1 or 2, wherein the first spatial volume ratio is greater than 13% and 20% or less, and the second spatial volume ratio is greater than 13% and 20% or less.

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