Cushioning Material, Packaging Material, and Packaged Item

The present application is based on, and claims priority from JP Application Serial Number 2024-051313, filed Mar. 27, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.

The present disclosure relates to a cushioning material, a packaging material, and a packaged item.

For example, JP-A-2023-120487 discloses a cushioning material in which a plurality of cushioning sheets configured to cushion an external force applied to an electronic device are laminated, and a packaging material and a packaged item using this cushioning material. The plurality of cushioning sheets include a first cushioning sheet arranged so as to intersect a direction of the external force applied to the electronic device, and a second cushioning sheet having a higher strength in the direction of the external force applied to the electronic device than that of the first cushioning sheet and arranged so as to intersect the direction of the external force applied to the electronic device. The cushioning material includes corrugated cardboard. The first cushioning sheet and the second cushioning sheet constitute different layers among a plurality of layers constituting the corrugated cardboard. Use of corrugated cardboard including two types of cushioning sheets having different strengths enhances a cushioning effect of the cushioning material.

However, required cushioning characteristics vary depending on the type of electronic devices. A known cushioning material has a configuration in which the first cushioning sheet and the second cushioning sheet are laminated in series in a direction facing the electronic device. Therefore, depending on the difference in required cushioning characteristics, it is necessary to produce the cushioning material by selecting various conditions such as the thickness, the number of layers, and the material of the cushioning sheet, which is poor in versatility. Therefore, a cushioning material having a high cushioning effect and high versatility is required.

A cushioning material for solving the above problem is a cushioning material configured to cushion an external force applied to an electronic device, the cushioning material including a support plate configured to support the electronic device, and a cushioning portion provided at the support plate and configured to cushion an external force applied to the electronic device, the cushioning portion including a first cushioning portion including a first surface fixed to the support plate and a second surface facing the electronic device, and a second cushioning portion including a third surface fixed to the support plate and a fourth surface facing the electronic device, wherein in a graph in which a vertical axis represents an external force applied to the electronic device and a horizontal axis represents time from when the external force starts to be applied to the electronic device, types of waveforms of the graph are different between the first cushioning portion and the second cushioning portion.

A cushioning material for solving the above problem is a cushioning material configured to cushion an external force applied to an electronic device, the cushioning material including a support plate configured to support the electronic device, and a cushioning portion provided at the support plate and configured to cushion an external force applied to the electronic device, the cushioning portion including a first cushioning portion including a first surface fixed to the support plate and a second surface facing the electronic device, and a second cushioning portion including a third surface fixed to the support plate and a fourth surface facing the electronic device, wherein in a stress-strain diagram where a vertical axis represents compressive stress applied to the cushioning portion and a horizontal axis represents strain applied to the cushioning portion, (a) maximum stress in an elastic region of the first cushioning portion is larger than maximum stress in an elastic region of the second cushioning portion, (b) a slope indicating a ratio of stress with respect to strain in a plastic region of the first cushioning portion takes a value of zero or close to zero, and a slope indicating a ratio of stress with respect to strain in a plastic region of the second cushioning portion takes a positive value larger than the value of the slope of the first cushioning portion, and (c) maximum stress in an elastic region of a composite cushioning portion configured by arranging the first cushioning portion and the second cushioning portion in parallel in a direction facing the electronic device is larger than the maximum stress of the second cushioning portion, and the slope in the plastic region of the composite cushioning portion takes a positive value larger than the value of the slope of the first cushioning portion.

A packaging material for solving the above problem includes a packaging box configured to accommodate the electronic device, and the cushioning material described above.

A packaged item for solving the above problem includes the packaging material described above and the electronic device.

Hereinafter, an embodiment of a packaged item and a cushioning material will be described with reference to. First, an overall outline of the packaged item and a packaging material will be described with reference to.

is an exploded perspective view illustrating an example of the configurations of a packaged itemand a packaging material. The packaged itemincludes the packaging materialand an electronic device. The packaged itemis configured by packaging the electronic devicewith the packaging material.

The packaging materialincludes a cushioning materialconfigured to cushion an external force applied to the electronic device. The packaging materialmay include a packaging boxconfigured to accommodate the electronic device, and the cushioning material. The packaging boxincludes a bodyhaving a bottomed box shape including an openingopened upward, and four flapsextending from four sides surrounding the openingof the body.

As illustrated in, the cushioning materialis interposed between the packaging boxand the electronic device. That is, the electronic deviceis accommodated in the packaging boxvia the cushioning material. The packaging materialmay include a plurality of the cushioning materials. The electronic deviceis accommodated in the packaging boxin a state of being protected by the plurality of cushioning materials. The plurality of cushioning materialsare arranged so as to surround the electronic device. In the example illustrated in, the electronic devicehas a cuboid shape, for example. The electronic devicehaving a cuboid shape has four corner portions (corners) at parts of four sides parallel to one another. In the example illustrated in, four cushioning materialsare arranged at the four corner portions of the electronic device.

The cushioning materialincludes a cushioning portionconfigured to cushion an external force (impact force) applied to the electronic deviceaccommodated in the packaging box. The packaged itemreceives an external force (impact force) due to an impact when a worker erroneously drops the packaged itemduring sorting work, loading work, conveyance, or the like, or an impact caused by shaking, vibration, or the like during conveyance. The cushioning materialprotects the electronic devicefrom this type of external force.

Here, the electronic deviceis, for example, a recording device. The recording deviceis an inkjet printer or the like. However, the recording deviceis not limited to, for example, an inkjet printer, and may be a laser printer, a dot impact printer, or the like. The recording devicemay be a printer dedicated to recording, or may be a multifunction peripheral having both a recording function and other functions. The other functions of the multifunction peripheral include a scanner function, a copy function, and a facsimile function. In the present embodiment, as the electronic device, a device other than the recording device, such as a scanner, a television, a refrigerator, a washing machine, a microwave oven, or a personal computer may be adopted.

The example illustrated inassumes that the packaging materialincludes four cushioning materialsA toD. The electronic deviceand the four cushioning materialsA toD are accommodated in the packaging boxfrom the opening. That is, the electronic devicein which four sites (four corner portions) of upper, lower, left, and right are protected by the four cushioning materialsillustrated inis accommodated in the packaging box. Thereafter, the openingof the packaging boxis closed by the four flaps. The four flapsare held in a closed state by an adhesive tape or an adhesive. This provides the packaged item. In the packaged item, the electronic deviceis protected by the four cushioning materialsA toD interposed between the electronic deviceand the packaging box. The electronic devicefaces the cushioning portionincluded in the four cushioning materialsA toD.

Hereinafter, for convenience of description, a packaging box coordinate system fixed to the packaging boxis introduced. The packaging box coordinate system is a three-axis coordinate system having an XW axis, a YW axis, and a ZW axis orthogonal to one another. The ZW axis extends in a ZW direction, which is a direction from the openingof the packaging boxtoward a bottom surface. The XW axis extends in an XW direction orthogonal to the ZW direction. The YW axis extends in a YW direction orthogonal to the ZW direction and the XW direction. Note that the XW axis, the YW axis, and the ZW axis are not limited to being orthogonal to one another, and may be any axes as long as they intersect one another. Hereinafter, a direction opposite to the XW direction is referred to as a −XW direction, a direction opposite to the YW direction is referred to as a −YW direction, and a direction opposite to the ZW direction is referred to as a −ZW direction.

In the example illustrated in, the electronic deviceis protected at four sites by the four cushioning materialsA toD. The cushioning materialA protects the lower left end portion of the electronic devicein the ZW direction and the −XW direction. The cushioning materialB protects the lower right end portion of the electronic devicein the ZW direction and the +XW direction. The cushioning materialC protects the upper left end portion of the electronic devicein the −ZW direction and the −XW direction. The cushioning materialD protects the upper right end portion of the electronic devicein the −ZW direction and the +XW direction.

The cushioning materialA includes a plurality of the cushioning portionsfacing the electronic devicein the −ZW direction, the XW direction, the YW direction, and the −YW direction. The cushioning materialB includes the plurality of cushioning portionsfacing the electronic devicein the −ZW direction, the −XW direction, the YW direction, and the −YW direction. The cushioning materialC includes the plurality of cushioning portionsfacing the electronic devicein the ZW direction, the XW direction, the YW direction, and the −YW direction. The cushioning materialD includes the plurality of cushioning portionsfacing the electronic devicein the ZW direction, the −XW direction, the YW direction, and the −YW direction. In this manner, all of the plurality of surfaces (six surfaces) forming the outer peripheral surface of the electronic deviceface at least one cushioning portion. In the present embodiment, all of the plurality of surfaces (six surfaces) forming the outer peripheral surface of the electronic deviceface the plurality of cushioning portions.

Hereinafter, an example of the configurations of the cushioning materialand the cushioning portionwill be described with reference to. Note that the four cushioning materialsA toD illustrated inhave the same configurations basically. In the following description, unless otherwise distinguished, the four cushioning materialsA toD are simply referred to as the cushioning material.

As illustrated in, the cushioning materialincludes a support portionconfigured to support the electronic deviceand the cushioning portionconfigured to cushion an external force applied to the electronic device. The cushioning portionis included in the support portion. The cushioning materialillustrated inis an example in which the support portionincludes the plurality of cushioning portions.

The support portionincludes four support platesA toD. The four support platesA toD are different from one another in the directions in which the surfaces to which the cushioning portionsare fixed face. The support portionhas a predetermined shape illustrated inin which the four support platesA toD can face four surfaces of a part including two corner portions on both sides of one side of the electronic device. The support portionmay be formed in the predetermined shape illustrated inby a plurality of plate members, or may be formed in the predetermined shape illustrated inby bending one plate material. The support portionmay be formed of corrugated cardboard, for example. The corrugated cardboard may be made of paper or may be made of synthetic resin.

Specifically, the support portionincludes two support platesA andD orthogonal to each other, and two support platesB andC whose surfaces are orthogonal to the two support platesA andD, the two support platesB andC facing each other. The support portionhas a predetermined shape in which the four support platesA toD can face four surfaces of a part including two corner portions on both sides of one side of the electronic devicehaving the cuboid shape.

Hereinafter, the four support platesA toD included in the support unitillustrated inare defined as a first support plateA, a second support plateB, a third support plateC, and a fourth support plateD. The first support plateA constitutes a bottom surface of the cushioning material. The second support plateB constitutes a side surface of one of the two side surfaces of the cushioning material. The third support plateC constitutes a side surface of the other of the two side surfaces of the cushioning material. The fourth support plateD constitutes a back surface of the cushioning material. Note that the present embodiment assumes, as an example, a case where each of the plurality of support platesA toD constituting the support portionis made of corrugated cardboard.

In the example illustrated in, two cushioning portionsare fixed to the first support plateA. One cushioning portionis fixed to the second support plateB. One cushioning portionis fixed to the third support plateC. Two cushioning portionsare fixed to the fourth support plateD. Note that the present embodiment is characterized by the configuration of the cushioning portionincluded in the cushioning material.

Hereinafter, for convenience of description, a cushioning material coordinate system corresponding to a direction facing the electronic deviceis introduced with respect to each of the cushioning portions. Unless otherwise distinguished, the four support platesA toD included in the cushioning materialare simply referred to as the support plate.

illustrates an Xaxis, a Yaxis, and a Zaxis of the cushioning material coordinate system, focusing on the first support plateA, which is one plate-shaped portion among the four support platesA toD. The cushioning material coordinate system is a three-axis coordinate system having the Xaxis, the Yaxis, and the Zaxis orthogonal to one another. The X axis extends in an Xdirection. The Y axis extends in a Ydirection. The Z axis extends in a Zdirection. The Xdirection, the Ydirection, and the Zdirection of the cushioning material coordinate system are a three-axis coordinate system defined for each support platebased on the following definition.

Here, the Zdirection is a direction from one surface in contact with the support platetoward the other surface positioned on the opposite side of this one surface among the plurality of surfaces included in the cushioning portion. The Zdirection is a direction orthogonal to the extending direction of the support plate. The Xdirection is a direction orthogonal to the Zdirection and is a direction parallel to the extending direction of the support plate. The Ydirection is a direction orthogonal to the Zdirection and the Xdirection, and is a direction parallel to the extending direction of the support plate. Note that the X axis, the Y axis, and the Z axis may be any axes as long as they intersect one another. Hereinafter, a direction opposite to the Xdirection is referred to as an Xdirection, a direction opposite to the Ydirection is referred to as a Ydirection, and a direction opposite to the Zdirection is referred to as a Zdirection. The cushioning material coordinate system is set such that the direction of the cushioning portionas viewed from the electronic device(see) is the Zdirection. Note that the cushioning material coordinate system is set for each cushioning portion.

Next, the configuration of the cushioning materialwill be described with reference to. Hereinafter, one cushioning portionof the plurality of cushioning portionsincluded in the cushioning materialwill be described.illustrates a perspective view of the cushioning portion.illustrates a cross section of the cushioning portiontaken along a plane orthogonal to a fixed surfaceP of the support plate.

As illustrated in, the one cushioning portionis fixed to the fixed surfaceP orthogonal to the Zdirection in the support plate. The cushioning portionincludes a first cushioning portionand a second cushioning portion. The first cushioning portionand the second cushioning portionare fixed in a state of being arranged in parallel with respect to the fixed surfaceP of the support plate.

The first cushioning portionincludes a first surfacefixed to the support plateand a second surfacefacing the electronic device. The second cushioning portionincludes a third surfacefixed to the support plateand a fourth surfacefacing the electronic device. That is, the surface on which the first cushioning portionis fixed to the support plateis the first surface. The surface on which the second cushioning portionis fixed to the support plateis the third surface. The surface on which the first cushioning portionfaces the electronic deviceis the second surface. The surface on which the second cushioning portionfaces the electronic deviceis the fourth surface.

The second surfaceand the fourth surfacemay be flush with each other. Since the first cushioning portionand the second cushioning portionare flush with each other, the second surfaceand the fourth surfacecan be substantially simultaneously in contact with a surface facing the electronic devicewhen the packaged itemdrops. For example, the second surfaceand the fourth surfacemay be arranged to be flush with each other by making the thickness of the first cushioning portionand the thickness of the second cushioning portionthe same.

As illustrated in, the first cushioning portionand the second cushioning portionmay be arranged in contact with each other. Furthermore, as illustrated in, any one of the first cushioning portionand the second cushioning portionmay be arranged with the periphery surrounded by the other. In the cushioning portion, any one of the first cushioning portionand the second cushioning portionmay have a plate shape of a predetermined shape and the other may have an annular plate shape surrounding the periphery of the one. In the examples illustrated in, the first cushioning portionthat is an example of the one is arranged with the periphery surrounded by the second cushioning portionthat is an example of the other. In the examples illustrated in, the predetermined shape is a rectangle. The first cushioning portion, which is an example of the one, has a quadrangular plate shape. The second cushioning portion, which is an example of the other, has a square annular plate shape surrounding the periphery of the first cushioning portion. The predetermined shape may be a circle, a triangle, a pentagon, a hexagon, or the like. Note that the cushioning portionof the present embodiment constitutes a composite cushioning portionin the form of one assembly by arranging the first cushioning portionand the second cushioning portionin parallel in a state of being in contact with each other.

In the present embodiment, the first cushioning portionis a corrugated cardboard material. The second cushioning portionis a foamed resin material. The corrugated cardboard material may be made of paper or may be made of synthetic resin. The first cushioning portionmay be a corrugated cardboard material of the same type as the support portion(support plate) or a corrugated cardboard material of a different type from the support portion. Here, the type of the corrugated cardboard material refers to a type that defines strength. The strength of the corrugated cardboard material is defined by the structure, the number of layers, and the thickness of the corrugated cardboard sheet constituting the corrugated cardboard material, for example. In this regard, the type of the corrugated cardboard material may be the type of the structure of the corrugated cardboard sheet, the number of layers of the corrugated cardboard sheet, or the type of the thickness (thickness per layer) of the corrugated cardboard sheet.

As illustrated in, the corrugated cardboard material constituting the first cushioning portionhas a multilayer structure in which a plurality of corrugated cardboard sheetsA are laminated. The corrugated cardboard sheetA has a structure in which two liners made of flat paper and a center core made of wavy paper are joined together with an adhesive. The plurality of corrugated cardboard sheetsA constituting the first cushioning portionhave the identical layer structures. The plurality of corrugated cardboard sheetsA have the identical thicknesses. The corrugated cardboard material constituting the first cushioning portionhas a layer structure of two or more layers. The example illustrated inincludes four layers, but may include three layers, five layers, six layers, or seven or more layers. The number of layers of the corrugated cardboard sheetA is set according to necessary cushioning characteristics.

The foamed resin material constituting the second cushioning portionis a foamed material made of a synthetic resin material. The synthetic resin material is, for example, polyethylene (PE). The synthetic resin material may be polybutene (PB), polystyrene (PS), polyurethane (PU), or the like. The foamed resin material may have a foam expansion ratio within a range of, for example, 10 to 80 times. The thickness of the foamed resin material that is the material of the second cushioning portionmay be set to the same thickness as the thickness of the corrugated cardboard material determined from the number of layers of the corrugated cardboard sheetA.

The reason for using the first cushioning portionand the second cushioning portionhaving different types of materials is to obtain cushioning characteristics suitable for protection of the electronic deviceby configuring the composite cushioning portionin which members made of two types of materials having different cushioning characteristics are combined. In this case, the cushioning characteristics of the composite cushioning portioncan be adjusted by adjusting the area ratio between the first cushioning portionand the second cushioning portion. That is, the cushioning characteristics of the composite cushioning portioncan be adjusted by adjusting the area ratio that is the ratio between the area of the second surfaceof the first cushioning portionand the area of the fourth surfaceof the second cushioning portion.

In the examples illustrated in, where the second surfaceand the fourth surfaceare flush with each other, the thickness of the first cushioning portionand the thickness of the second cushioning portionare the same. The cushioning characteristics of the cushioning portioncan be adjusted by adjusting the area ratio between the second surfaceand the fourth surfacewhile maintaining the condition that the second surfaceand the fourth surfaceare flush with each other. In the present embodiment, the area ratio between the second surfaceof the first cushioning portionand the fourth surfaceof the second cushioning portionis set to a value at which a cushioning characteristics necessary for protection of the electronic devicecan be obtained. For example, the area ratio may be determined based on the test results of the drop impact test.

Next, a stress-strain diagram of the cushioning portionwill be described with reference to.are stress-strain diagrams when each of the cushioning portions,, andis applied with an external force (compressive force) in the compression direction. Stress o on the vertical axis is compressive stress. The horizontal axis represents strain ε.is a stress-strain diagram of the first cushioning portion. That is,is a stress-strain diagram of a corrugated cardboard material that is a material of the first cushioning portion.is a stress-strain diagram of the second cushioning portion. That is,is a stress-strain diagram of a foamed resin material that is a material of the second cushioning portion.is a stress-strain diagram of the cushioning portion. That is,is a stress-strain diagram of the composite cushioning portionconfigured by arranging the corrugated cardboard material and the foamed resin material in parallel with respect to the compression direction. Each stress-strain diagram includes a usable region UA and a nonusable region NA. The usable region UA is a region that can be used as a cushioning material. The nonusable region NA is a region that cannot be used as a cushioning material. The nonusable region NA is not considered for the characterization of the cushioning material.

As shown in, the corrugated cardboard material elastically deforms to maximum stress σ. That is, elastic deformation occurs in an elastic region EA from the compression start point (σ=0) to the maximum stress σ. In the elastic region EA, the change rate of the stress σ with respect to the strain ε is a constant value. In the elastic region EA, a substantially straight line having a constant slope is drawn. In a plastic region PA after reaching the maximum stress σ, the change rate of the stress σ with respect to the strain ε is smaller than the change rate of the elastic region EA. As shown in, in the case of the corrugated cardboard material, the stress σ takes on a constant value σin the plastic region PA. This means that in the elastic region EA, all the plurality of layers of corrugated cardboard sheetsA constituting the corrugated cardboard material have the same strengths, and therefore they are crushed almost simultaneously at the time point of reaching the maximum stress. The corrugated cardboard sheetA absorbs impact force in the process of being crushed. Therefore, in the plastic region PA, there is almost no cushioning capacity (impact absorbing capacity). As seen from the graph shown in, the corrugated cardboard material that is the material of the first cushioning portionis large in the maximum stress σand thus it is high in creep characteristics, but is extremely low in cushioning capacity in the plastic region PA.

As shown in, the foamed resin material elastically deforms to maximum stress σ. That is, in the elastic region EA until reaching the maximum stress σ, the change rate of the stress σ with respect to the strain ε is a constant value. In the plastic region PA after reaching the maximum stress σ, the change rate of the stress σ with respect to the strain ε takes on a positive value. That is, unlike the corrugated cardboard material, the foamed resin material has a cushioning capacity (impact absorbing capacity) by plastically deforming (viscoelastically deforming) in the plastic region PA. The foamed resin material that is the material of the second cushioning portionis small in the maximum stress σ, but has a cushioning capacity even in the plastic region PA. Since the maximum stress σis small, the foamed resin material is low in creep characteristics. Therefore, when the foamed resin material is used alone, it is necessary to increase the area of the surface on the cushioning portionside facing the electronic device. In this case, since a large area is required for the surface facing the electronic device, there is a case where of not being able to handle depending on the shape and size of the electronic device.

As shown in, the composite cushioning portionelastically deforms to maximum stress σ. That is, in the elastic region EA, the change rate of the stress σ with respect to the strain ε takes on a relatively large constant value. This maximum stress σis larger than the maximum stress σof the foamed resin material shown in. By arranging the first cushioning portionand the second cushioning portionin parallel, the maximum stress σthat is large can be obtained. This large maximum stress σis caused by the corrugated cardboard material. On the other hand, in the plastic region PA after reaching the maximum stress σ, the change rate of the stress σ with respect to the strain ε takes on a positive value. By arranging the first cushioning portionand the second cushioning portionin parallel, the composite cushioning portionplastically deforms in the plastic region PA. This plastic deformation is viscoelastic deformation. This plastic deformation is caused by the foamed resin material. Thus, the composite cushioning portionhas high creep characteristics due to the large maximum stress σand plastically deforms in the plastic region PA, and therefore has high cushioning capacity (impact absorbing capacity).

As seen from, the composite cushioning portionin which the first cushioning portionand the second cushioning portionare arranged in parallel has a larger maximum stress σthan that in the case of the foamed resin material alone. Moreover, the change rate (slope) of the stress σ with respect to the strain ε takes on a positive value in the plastic region PA. As seen from the stress-strain diagrams shown in, the first cushioning portion, the second cushioning portion, and the composite cushioning portionhave relationships presented in the following (a) to (c). In the present embodiment, the composite cushioning portionsatisfying this relationship is adopted.

By satisfying the relationship presented in the (a) to (c) described above, the cushioning portionhaving excellent cushioning characteristics can be obtained.

Next, the relationship between the acceleration of the external force applied to the electronic devicevia the cushioning portion at the time of impact application and time will be described with reference to. In the graphs shown in, the vertical axes represent acceleration G of the external force applied to the electronic device, and the horizontal axes represent time t. The time t is an elapsed time from when the electronic devicestarts to be applied with the external force. The relationship between the acceleration G of the external force applied to the electronic deviceand the time t when the electronic deviceis dropped from a predetermined height in a state where the cushioning portion is interposed between the electronic deviceand a floor surface is shown. When dropping onto the floor surface, the electronic devicereceives a compressive force as an external force from the cushioning portion. Therefore, in the electronic device, acceleration according to the compressive force is generated. The cushioning portion is the first cushioning portion, the second cushioning portion, and the composite cushioning portion.

shows the relationship between the acceleration G of the external force applied to the electronic deviceat the time of dropping and the time t when the cushioning portion is the corrugated cardboard material constituting the first cushioning portion.shows the relationship between the acceleration G of the external force applied to the electronic deviceat the time of dropping and the time t when the cushioning portion is the foamed resin material constituting the second cushioning portion.shows the relationship between the acceleration G of the external force applied to the electronic deviceat the time of dropping and the time t when the cushioning portion is the composite cushioning portion. Each graph also shows the relationship between the external force applied to the electronic deviceat the time of impact application and time. The external force applied to the electronic deviceat the time of impact application depends on the mass of the electronic device. When the mass of the electronic deviceis the same, the waveform of each graph also indicates the relationship between the external force applied to the electronic deviceand time. Note thatassumes that the following state occurs when electronic deviceis dropped from a predetermined height in a state where first cushioning portionis interposed between electronic deviceand the floor surface. That is, it is assumed that the electronic devicestops before all of the plurality of corrugated cardboard sheetsA constituting the first cushioning portionare compressed and crushed.

As shown in, the types of waveforms of the graphs of the first cushioning portionand the second cushioning portionare different. The waveform of the graph of the first cushioning portionis a trapezoidal wave. The waveform of the graph of the second cushioning portionis a half-sine wave. That is, the first cushioning portionincludes a material whose waveform is a trapezoidal wave. The second cushioning portionincludes a material whose waveform is a half-sine wave. In the present embodiment, the first cushioning portionincludes a corrugated cardboard material as a material whose waveform is a trapezoidal wave. The second cushioning portionincludes a foamed resin material as a material whose waveform is a half-sine wave. The waveform of the corrugated cardboard material becomes a trapezoidal wave because the change rate of the stress σ with respect to the strain ε is substantially 0 (zero) in the plastic region PA in the stress-strain diagram shown in. The waveform of the foamed resin material becomes a half-sine wave because the change rate of the stress σ with respect to the strain ε takes on a positive value in the plastic region PA in the stress-strain diagram shown in.

The trapezoidal wave that is the waveform of the graph of the corrugated cardboard material is a composite wave in which a plurality of half-sine waves having different frequencies are superimposed. When this trapezoidal wave includes the same frequency as the natural frequency of the electronic device, the electronic deviceresonates. In this case, the electronic deviceis applied with a large impact. The natural vibration of the electronic devicevaries depending on the type of the electronic deviceto be packaged. Therefore, in order to provide the cushioning materialhaving versatility, it is required not to resonate any type of electronic device.

The graph of the composite cushioning portionshown inincludes a half-sine wave. No trapezoidal wave is included. For this reason, the electronic deviceis less likely to resonate when dropping onto the floor surface via the cushioning portion(composite cushioning portion).

A corrugated cardboard material made of paper is vulnerable to humidity. Paper decreases its strength when it absorbs moisture. That is, in the stress-strain diagram shown in, the maximum stress σof the corrugated cardboard material that has absorbed moisture decreases. Even when the strength of the corrugated cardboard material decreases due to the influence of humidity, in order to ensure a necessary cushioning force, the thickness of the corrugated cardboard material is made thicker than a value required at the time of drying. This leads to an increase in the thickness of the cushioning portionand consequently an increase in the size of the packaged item.

On the other hand, the cushioning portionof the present embodiment is partially occupied by a water-resistant foamed resin material. Therefore, it is possible to thin the first cushioning portionmade of a corrugated cardboard material according to the proportion occupied by the foamed resin material in the composite cushioning portion. Therefore, even if the thickness of the thinned corrugated cardboard is added with the thickness of the corrugated cardboard by a proportion in consideration of the influence of humidity, it is possible to thin the thickness of the first cushioning portionconstituting the composite cushioning portionas compared with the case where the cushioning portionis constituted by the corrugated cardboard alone. Therefore, it is possible to thin the cushioning portionincluding the composite cushioning portion.