Method for producing paper-containing three-dimensional structure

Abstract

The purpose of the present invention is to provide a method of manufacturing a novel three-dimensional structure that uses an origami technique and that has high practical utility. This method, for manufacturing a paper-containing three-dimensional structure configured by folding a paper-containing sheet that is formed from paper or that has paper as the primary component, involves a step (A) in which, by permeating the paper-containing sheet with water from one side thereof, an area of the paper-containing sheet having a water concentration gradient in the thickness direction is made into one or more paper-containing sheets, and a step (B) in which, by drying the paper-containing sheet in a state having the aforementioned water concentration gradient, the paper-containing sheet automatically folds in the area having said water concentration gradient.

Description

[Technical field]

[0001] The present invention relates to a method for producing a paper-containing three-dimensional structure. [Background technology]

[0002] Origami technology has the advantage of being able to create a variety of three-dimensional structures by folding a single sheet of paper, and by devising folding patterns, it is possible to repeatedly use the functions of unfolding and storing, and it is possible to create structures with relatively high mechanical strength, so it is expected to be applied in a variety of fields. For example, origami technology can be expected to be applied to the manufacture of three-dimensional electronic devices, the manufacture of lightweight and inexpensive shock-absorbing materials, and space-saving by folding sheets.

[0003] In this context, autonomous paper folding technology, in which paper is made to bend by itself by applying some kind of external force to the paper, has attracted attention, and this type of technology is sometimes referred to as "self-folding." It is expected that the development of such autonomous paper folding technology will greatly advance the utilization of the above-mentioned properties of origami.

[0004] Previously, a folding technique that uses a material that responds to an external stimulus placed on the paper to autonomously fold the paper has been reported, using the response of the material when a stimulus is applied, such as an electric current or heat. However, such folding techniques require the supply of some kind of energy, such as electric current or heat, which may limit the environments in which they can be used. In addition, the paper must be modified with special materials, which increases costs.

[0005] As a method capable of solving such problems, a method has been disclosed in which an aqueous solution containing 2-propanol is ejected onto paper using an inkjet printer and then dried (see Non-Patent Document 1). This method has the advantage of being highly practical, since it does not require the supply of energy such as electric current or heat to the paper, and there is no need to modify the paper with a special material. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Hiroki Shigemune, Shingo Maeda, Yusuke Hara, and Shuji Hashimoto. “Design of paper mechatronics:Towards a fully printed robot” Proceedings of 2014 IEEE / RSJ International Conference on Intelligent Robots and Systems(IROS 2014) Summary of the Invention [Problem to be solved by the invention]

[0007] The method disclosed in Non-Patent Document 1 is useful in that it can solve the problems of other methods, but further improvements are required for application to a practical manufacturing method for three-dimensional structures. Furthermore, the usefulness of such folding technology will be further enhanced if it can be applied not only to paper but also to composite paper that combines paper with other materials.

[0008] An object of the present invention is to provide a novel, highly practical method for producing a three-dimensional structure using origami techniques. [Means for solving the problem]

[0009] The present invention provides a method for producing a paper-containing three-dimensional structure formed by folding a paper-containing sheet made of paper or containing paper as a main component, the method comprising: a step (A) of permeating water into the paper-containing sheet from one side thereof to create one or more regions in the paper-containing sheet having a water concentration gradient in the thickness direction of the paper-containing sheet; and a step (B) of drying the paper-containing sheet in a state having the water concentration gradient, thereby autonomously folding the paper-containing sheet at the region that had the water concentration gradient, in which step (A) comprises adhering water or an aqueous solution containing water as the only solvent component and a solute having a hydration parameter of 0.5 to 20.0 at 5 mass % or less at room temperature to the one side of the paper-containing sheet, and permeating the water or the water in the aqueous solution adhered to the one side into the paper-containing sheet.

[0010] In the method for producing a paper-containing three-dimensional structure of the present invention, in the step (B), it is preferable to autonomously fold the paper-containing sheet with the side having the higher water concentration facing inward. In the method for producing a paper-containing three-dimensional structure of the present invention, in the step (A), the amount of water to be permeated into the paper-containing sheet is set to 1.0×10 -12 ~10g / mm 3 It is preferable to set the above. In the method for producing a paper-containing three-dimensional structure of the present invention, in the step (A), it is preferable to form the site having the water concentration gradient in the form of a solid line or a dotted line in the paper-containing sheet.

[0011] In the method for producing a paper-containing three-dimensional structure of the present invention, in the step (B), the paper-containing sheet having the water concentration gradient is heated at a temperature of −273.15 to 1.0×10 5 It is preferable to dry the film under conditions of 0° C. and a relative humidity of 0 to 100%. In the method for producing a paper-containing three-dimensional structure of the present invention, it is preferable to create, in the step (A), two or more regions having a water concentration gradient in which the water permeation amounts are different from each other in the surface direction of the paper-containing sheet. In the method for producing a paper-containing three-dimensional structure of the present invention, in step (A), two or more different aqueous solutions may be separately applied to different regions of the paper-containing sheet, thereby creating two or more regions in the surface direction of the paper-containing sheet that have different water concentration gradients and different amounts of water permeated therethrough. In the method for producing a paper-containing three-dimensional structure of the present invention, the two or more aqueous solutions may all have different hydration parameters for the solutes. Effect of the Invention

[0012] According to the present invention, a novel, highly practical method for producing a three-dimensional structure is provided using origami techniques. [Brief description of the drawings]

[0013] [Figure 1A] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (A) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 1B] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (A) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 1C] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (A) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (A) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 3A] FIG. 2 is a plan view showing a schematic example of the shape of a portion having a water concentration gradient formed in a paper-containing sheet in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 3B]FIG. 2 is a plan view showing a schematic example of the shape of a portion having a water concentration gradient formed in a paper-containing sheet in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 3C] FIG. 2 is a plan view showing a schematic example of the shape of a portion having a water concentration gradient formed in a paper-containing sheet in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 3D] FIG. 2 is a plan view showing a schematic example of the shape of a portion having a water concentration gradient formed in a paper-containing sheet in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view showing a schematic example of a paper-containing sheet having a water concentration gradient and regions with different amounts of water penetration produced in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 5A] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (B) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 5B] FIG. 2 is a cross-sectional view for illustrating a schematic example of step (B) in the method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 6A] FIG. 4 is a schematic diagram for explaining a method for measuring the bending angle of a paper-containing sheet. [Figure 6B] FIG. 4 is a schematic diagram for explaining a method for measuring the bending angle of a paper-containing sheet. [Figure 7A] FIG. 1 is a perspective view showing an example of a paper-containing sheet used in a method for producing a paper-containing three-dimensional structure according to an embodiment of the present invention, and a target paper-containing three-dimensional structure. [Figure 7B] FIG. 1 is a perspective view showing an example of a paper-containing sheet used in a method for producing a paper-containing three-dimensional structure according to an embodiment of the present invention, and a target paper-containing three-dimensional structure. [Figure 7C] FIG. 1 is a perspective view showing an example of a paper-containing sheet used in a method for producing a paper-containing three-dimensional structure according to an embodiment of the present invention, and a target paper-containing three-dimensional structure. [Figure 8]FIG. 2 is a plan view showing a schematic diagram of another example of a paper-containing sheet used in a method for producing a paper-containing three-dimensional structure according to an embodiment of the present invention. [Figure 9A] FIG. 11 is a cross-sectional view showing another example of a paper-containing sheet having a region with a water concentration gradient and the desired paper-containing three-dimensional structure in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 9B] FIG. 11 is a cross-sectional view showing another example of a paper-containing sheet having a region with a water concentration gradient and the desired paper-containing three-dimensional structure in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 10A] FIG. 11 is a cross-sectional view showing another example of a paper-containing sheet having a region with a water concentration gradient and the desired paper-containing three-dimensional structure in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 10B] FIG. 11 is a cross-sectional view showing another example of a paper-containing sheet having a region with a water concentration gradient and the desired paper-containing three-dimensional structure in a method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention. [Figure 11] 2 is a plan view showing the paper-containing sheet after step (A) in Example 1. FIG. [Figure 12] 4 is a graph showing the measurement results of the folding angle of the paper-containing sheet after carrying out step (B) in Example 1. [Figure 13] 1 is a graph showing the measurement results of the bending angle of the paper-containing sheet measured in Example 1, together with the normalized ink ejection amount. [Figure 14] 1 is a graph showing an example of the measurement results of the angle of a bent portion of a paper-containing three-dimensional structure in Example 1. [Figure 15] FIG. 1 is a schematic diagram for explaining a paper-containing three-dimensional structure and a manufacturing process thereof in Example 2. [Figure 16] FIG. 11 is a schematic diagram for explaining a paper-containing three-dimensional structure and its manufacturing process in Example 3. [Figure 17] FIG. 11 is a schematic diagram for explaining a paper-containing three-dimensional structure and its manufacturing process in Example 4. [Figure 18] FIG. 11 is a schematic diagram for explaining a paper-containing three-dimensional structure and its manufacturing process in Example 5. [Figure 19] FIG. 11 is a schematic diagram for explaining the paper-containing three-dimensional structure and its manufacturing process in Example 6. [Figure 20] 1 shows imaging data of the paper-containing three-dimensional structure produced in Example 7. [Figure 21] 1 is a graph showing the relationship between the concentration of an aqueous electrolyte solution and the ease of expansion of a paper-containing sheet when the aqueous electrolyte solution is allowed to permeate the paper-containing sheet in Test Example 1. [Figure 22] 11 is a graph showing the relationship between the concentration of an aqueous electrolyte solution and the ease of drying of a paper-containing sheet when the aqueous electrolyte solution is allowed to permeate into the paper-containing sheet in Test Example 2. [Diagram 23] 13 is a graph showing the relationship between the type of electrolyte and the ease with which a paper-containing sheet expands when an aqueous electrolyte solution is permeated into the paper-containing sheet in Test Example 3. [Figure 24] 13 is a graph showing the relationship between the type of electrolyte and the ease of drying of a paper-containing sheet when an aqueous electrolyte solution is permeated into the paper-containing sheet in Test Example 4. [Diagram 25] 13 is a graph showing the relationship between the concentration of an aqueous electrolyte solution and the bending angle of a paper-containing sheet when the aqueous electrolyte solution is permeated into the paper-containing sheet in Example 8. [Figure 26] 13 is a graph showing the relationship between the concentration of an electrolyte aqueous solution, the width of the permeated area, and the bending angle of the paper-containing sheet when the electrolyte aqueous solution is permeated into the paper-containing sheet in Example 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <<Method of manufacturing paper-containing three-dimensional structures>> A method for producing a paper-containing three-dimensional structure according to one embodiment of the present invention is a method for producing a paper-containing three-dimensional structure formed by folding a paper-containing sheet made of paper or containing paper as a main component, the method comprising: a step (A) of creating one or more regions on the paper-containing sheet having a water concentration gradient in the thickness direction of the paper-containing sheet by permeating water into one side of the paper-containing sheet; and a step (B) of drying the paper-containing sheet in a state having the water concentration gradient, thereby autonomously folding the paper-containing sheet at the region that had the water concentration gradient.

[0015] According to the method for producing a paper-containing three-dimensional structure of the present embodiment, a paper-containing three-dimensional structure can be produced practically and efficiently using a paper-containing sheet without using special materials or requiring the supply of energy to the paper-containing sheet.

[0016] The present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show essential parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. 1A to 1C are cross-sectional views for illustrating a schematic example of step (A) in the method for producing a paper-containing three-dimensional structure of the present embodiment.

[0017] <Process (A)> In the step (A), water is allowed to permeate the paper-containing sheet from one side thereof. For this purpose, for example, as shown in FIG. 1A, water 9 is applied to one side 1a of the paper-containing sheet 1. At this time, by applying an appropriate amount of water 9, which is not an excessive amount, to one side 1a of the paper-containing sheet 1 in consideration of the thickness T1 of the paper-containing sheet 1, the water 9 can be allowed to permeate the paper-containing sheet 1 from one side 1a thereof as shown in FIG. 1B or FIG. 1C. FIG. 1B shows a state in which the paper-containing sheet 1 is warped so that one side 1a thereof is convex, and typically, after passing through such a state, the warp is eliminated as shown in FIG. 1C.

[0018] As shown in Figure 1B, the reason that the paper-containing sheet 1 warps is that as water 9 permeates from one side 1a to the other side 1b of the paper-containing sheet 1, the concentration of water 9 becomes higher (the content is greater) on one side 1a of the paper-containing sheet 1 than on the other side 1b, causing the one side 1a of the paper-containing sheet 1 to expand. As the difference in the concentration of water 9 decreases over time, the effect of the expansion of the paper-containing sheet 1 is alleviated, and the warping of the paper-containing sheet 1 is eliminated as shown in Figure 1C.

[0019] The paper-containing sheet 1 is a sheet made of paper (that is, a paper sheet) or a sheet containing paper as a main component, and contains cellulose as a main component.

[0020] An example of the sheet made of paper (paper sheet) is tracing paper.

[0021] A paper-based sheet contains paper and other ingredients in addition to the paper. The other components can be arbitrarily selected depending on the purpose within a range that does not impair the effects of the present invention. More specifically, examples of the other components include resins and silica gel.

[0022] The other components contained in the sheet containing paper as a main component may be one type only, or two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily.

[0023] In a sheet whose main component is paper, the ratio of the content of the other components to the total mass of the sheet ([amount of the other components in the sheet whose main component is paper (parts by mass)] / [total mass of the sheet whose main component is paper (parts by mass)]×100) is preferably 40% by mass or less, and may be, for example, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. When the ratio is less than the upper limit, the paper-containing sheet can be folded more efficiently than 1. On the other hand, the ratio may be more than 0% by mass, for example, 1% by mass or more. The higher the lower limit of the ratio, the higher the effect obtained by including the other components.

[0024] The paper-containing sheet (sheet made of paper, sheet mainly composed of paper) 1 may be one layer (single layer) or may be two or more layers. When the paper-containing sheet is made of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited.

[0025] In this specification, "multiple layers may be the same or different from one another" means "all layers may be the same, all layers may be different, or only some layers may be the same", and further, "multiple layers are different from one another" means "at least one of the constituent materials and thicknesses of each layer is different from one another".

[0026] The thickness T1 of the paper-containing sheet 1 can be selected arbitrarily depending on the purpose. -6 ~1,0×10 4 It is preferable that T1 is in the range of 1 to 1000 μm, and more preferable that it is in the range of 1 to 1000 μm. When T1 is in this range, the paper-containing sheet 1 can be folded with higher accuracy. Here, "thickness of the paper-containing sheet" means the thickness of the entire paper-containing sheet, and for example, the thickness of a paper-containing sheet consisting of multiple layers means the total thickness of all layers that make up the paper-containing sheet.

[0027] The shape of the paper-containing sheet 1 is not particularly limited as long as it is in the form of a sheet, and can be arbitrarily selected depending on the structure of the intended paper-containing three-dimensional structure. These shapes and structures will be described in detail later.

[0028] The water 9 can be attached (discharged) as droplets onto one surface 1a of the paper-containing sheet 1 by, for example, inkjet printing or the like.

[0029] In step (A), the amount of water 9 to be permeated into the paper-containing sheet 1 (adherent amount) is not particularly limited as long as it does not impair the effects of the present invention. -12 ~10g / mm 3 It is preferable to set the value to 1.0×10 -6 ~1g / mm 3 By setting the amount of water 9 to be permeated per unit volume of the paper-containing sheet 1 within this range, the paper-containing sheet 1 can be folded more efficiently.

[0030] In step (A), water 9 is permeated into the paper-containing sheet 1 from one surface 1a thereof to create one or more regions 11 in the paper-containing sheet 1 that have a concentration gradient of water 9 in the thickness T1 direction of the paper-containing sheet 1, as shown in Figure 1B or 1C. For convenience, only one region 11 with a water concentration gradient is shown in Figure 1.

[0031] In this specification, the paper-containing sheet has a water concentration gradient in its thickness direction means that the paper-containing sheet has regions with different water contents (water concentrations) per unit volume in the direction connecting both sides of the paper-containing sheet at the shortest distance. Figures 1B and 1C show a state in which the water 9 content of the paper-containing sheet 1 gradually decreases from one side 1a to the other side 1b of the paper-containing sheet 1. In this embodiment, the amount of water 9 in the paper-containing sheet 1 usually decreases in this way in the direction of penetration of the water 9, that is, in the direction from the side of the paper-containing sheet 1 to which the water 9 is attached (the one side 1a) to the opposite side (the one side 1b). However, what is shown here is an example of the change in the amount of water 9 in the paper-containing sheet 1. In step (A), such a water concentration gradient can be easily formed by attaching an appropriate but not excessive amount of water 9 to one side 1a of the paper-containing sheet 1, taking into account the thickness T1 of the paper-containing sheet 1.

[0032] In Figures 1B and 1C, the water 9 that has been permeated into the paper-containing sheet 1 does not reach the other side 1b of the paper-containing sheet 1. However, in step (A), if a concentration gradient of the water 9 occurs as described above, the water 9 that has been permeated into the paper-containing sheet 1 may reach the other side 1b of the paper-containing sheet 1, for example, as shown in Figure 2. In FIG. 2 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.

[0033] In step (A), one or more sites 11 having such a water concentration gradient are created in the paper-containing sheet 1 . The area 11 having a water concentration gradient is created at a location where it is desired to fold the paper-containing sheet 1. For example, when the paper-containing sheet 1 is viewed in plan from above the one surface 1a side, the shape, size, and number of the area 11 having a water concentration gradient are determined according to the intended paper-containing three-dimensional structure.

[0034] 3A to 3D are plan views each showing a schematic example of the shape of the region 11 having a water concentration gradient, when the paper-containing sheet 1 is viewed from above the one surface 1a side in a plan view.

[0035] 3A, the area 11 having the water concentration gradient is formed linearly in a direction parallel to the one surface 1a of the paper-containing sheet 1 (in other words, the surface direction). That is, the area 11 having the water concentration gradient shown here is provided as a continuous line in a direction parallel to the one surface 1a of the paper-containing sheet 1.

[0036] In Fig. 3B, the region 11 having a water concentration gradient is formed in the shape of a dotted line in a direction parallel to the one surface 1a of the paper-containing sheet 1. That is, the region 11 having a water concentration gradient shown here is formed by individual localized regions (regions shown by dots in Fig. 3B) having a water concentration gradient being adjacent to each other and intermittently connected to each other in a direction parallel to the one surface 1a of the paper-containing sheet 1. In this embodiment, when the localized regions having a water concentration gradient are thus arranged adjacent to each other and form some shape as a whole, they may be treated as one "region having a water concentration gradient."

[0037] In Fig. 3C, the region 11 having a water concentration gradient is formed in the shape of a dashed line in a direction parallel to the one surface 1a of the paper-containing sheet 1. The region 11 having a water concentration gradient shown here is the same as the region 11 having a water concentration gradient shown in Fig. 3B, except that some of the individual local regions have different shapes.

[0038] 3D, the region 11 having a water concentration gradient is formed as a solid line in a direction parallel to the one surface 1a of the paper-containing sheet 1, and is further formed as a dotted line continuing from one end of the solid line. Here, of the region 11 having a water concentration gradient, the solid line region is given the reference symbol 111, and the dotted line region is given the reference symbol 112.

[0039] In this embodiment, the portion having a water concentration gradient may be formed by combining different shapes or patterns in this manner. In FIG. 3D, two types of shapes or patterns are combined, but in this embodiment, three or more types of shapes or patterns may be combined to form one region having a water concentration gradient.

[0040] In step (A), it is preferable to form the area 11 having a water concentration gradient in the form of a solid line or a dotted line in the paper-containing sheet 1. In this way, a so-called origami-style paper-containing three-dimensional structure having creases can be easily manufactured as a paper-containing three-dimensional structure.

[0041] In the step (A), when the area 11 having a water concentration gradient is formed in the paper-containing sheet 1 in the form of a solid line, a dotted line, or the like, the line width is 1.0×10 -6 ~1.0×10 9 μm, and preferably 1.0×10 -3 ~1.0×10 6 More preferably, the thickness is 1.0 to 1.0 × 10 5 It is more preferable that the line width is in this range. When the line width is in this range, the paper-containing sheet 1 can be folded autonomously more efficiently.

[0042] In step (A), when the portion having a water concentration gradient is linear, the line width may change over time. In this embodiment, unless otherwise specified, the line width means a constant value of the line width when the line width does not change over time, and means a maximum value of the line width when the line width changes over time. For example, as shown in Fig. 1B, when the line width is maximum when the paper-containing sheet 1 is warped, it is preferable that the line width W1 shown in Fig. 1B is within the above-mentioned numerical range. On the other hand, as shown in Fig. 1C, when the line width is maximum when the paper-containing sheet 1 is not warped, it is preferable that the line width W1 shown in Fig. 1C is within the above-mentioned numerical range. The line width can be measured, for example, by looking down on the paper-containing sheet 1 from above the one surface 1a side in a plan view.

[0043] In step (A), two or more regions having a water concentration gradient, in which the amount of water 9 permeated differs from each other, may be produced in a direction parallel to the one surface 1a of the paper-containing sheet 1 (in other words, the surface direction). Fig. 4 is a cross-sectional view that shows a schematic diagram of an example of a paper-containing sheet 1 produced with a first region 12 and a second region 13 having a greater amount of water permeated than the first region 12 as regions having such a water concentration gradient.

[0044] The only difference between the first region 12 having a water concentration gradient and the second region 13 having a water concentration gradient is the amount of water 9 that permeates therethrough, and these regions are otherwise the same. In this way, by creating regions (the first region 12 and the second region 13) with different amounts of water 9 permeated, it is possible to differentiate the folding speeds at these regions in step (B) described below based on the difference in the amount of water 9 permeated. By thus differentiating the folding speeds, it is possible to manufacture paper-containing three-dimensional structures with more complex shapes. Furthermore, it is possible to manufacture paper-containing three-dimensional structures with different folding angles at these regions.

[0045] The first region 12 and the second region 13 having a water concentration gradient can both have the same form as the region 11 having a water concentration gradient described above.

[0046] The first region 12 and the second region 13 having a water concentration gradient can be created by mutually changing the amount of water 9 that is attached to one surface 1a of the paper-containing sheet 1.

[0047] When applying water 9 to one side 1a of paper-containing sheet 1, an aqueous solution (not shown) may be used. That is, water in an aqueous solution may be applied to one side 1a of paper-containing sheet 1 as water 9. In this case, water 9 can be allowed to permeate paper-containing sheet 1 in the same manner as when water alone is used. In this case, solutes in the aqueous solution may also permeate paper-containing sheet 1. In this specification, water and aqueous solutions are sometimes collectively referred to as "aqueous medium."

[0048] Examples of the solute in the aqueous solution include electrolytes such as salts, dyes, and the like. The aqueous solution may contain only one type of solute, or two or more types. When there are two or more types, the combination and ratio of the solutes can be arbitrarily selected depending on the purpose.

[0049] The concentration of components other than water that are liquid at room temperature in the aqueous solution is preferably as low as possible, and is, for example, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. In this specification, "room temperature" means a temperature that is neither particularly cooled nor heated, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0050] In this embodiment, by adhering the aqueous solution, the majority of which is water, or water alone as the solvent component, to the paper-containing sheet 1, the paper-containing sheet 1 can be folded autonomously faster and at a larger folding angle.

[0051] For example, the above-mentioned Non-Patent Document 1 discloses a technology for autonomously folding a paper sheet using an aqueous solution containing 2-propanol, which contains water and 2-propanol in a mass ratio of "water:2-propanol = 90:10". However, although lower alcohols such as 2-propanol are well miscible with water, they do not have the effect of autonomously folding a paper-containing sheet, or even if they do, their effect is significantly inferior to that of water. Therefore, when compared at the same amount, when the above-mentioned aqueous solution containing 2-propanol is used, the autonomous folding of the paper-containing sheet is slower and the folding angle remains small than when the above-mentioned aqueous solution containing most of the solvent component is water or when only water is used as the solvent component. That is, the method for producing the paper-containing three-dimensional structure of the present embodiment is significantly effective in that the paper-containing sheet can be autonomously folded at a faster speed and at a larger folding angle than in the past.

[0052] In step (A), when an aqueous solution containing an additive is applied to one surface 1a of the paper-containing sheet 1, two types of aqueous solutions having different concentrations of the additive may be applied separately to different areas of the paper-containing sheet 1.

[0053] In step (A), when an aqueous solution is used and the water in the aqueous solution is applied as the water 9 to one surface 1a of the paper-containing sheet 1, two different aqueous solutions may be applied separately to different regions of the paper-containing sheet 1. In this way, it is possible to create regions (the first region 12 and the second region 13) in the paper-containing sheet 1 that have different amounts of water 9 permeated in a direction parallel to the one surface 1a of the paper-containing sheet 1 (in other words, the surface direction).

[0054] The solutes in the two aqueous solutions used to prepare the first region 12 and the second region 13 having a water concentration gradient may be the same or different. That is, these two types of aqueous solutions may contain the same solute but the solute concentrations are different from each other, may contain different solutes but the solute concentrations are different from each other, or may contain different solutes but the solute concentrations are the same from each other. When either or both of these two types of aqueous solutions contain two or more types of salts, the above-mentioned salt concentration refers to the total concentration of all the salts contained therein.

[0055] For example, when two aqueous solutions having the same type of solute but different solute concentrations are applied to the one surface 1a of the paper-containing sheet 1 in equal amounts, the amounts of water 9 in the applied aqueous solutions are different, and therefore the amounts of water 9 in these aqueous solutions that permeate into the paper-containing sheet 1 are different from each other. The lower the concentration of the solute in the aqueous solution, the greater the amount of water 9 in the aqueous solution that permeates into the paper-containing sheet 1 tends to be. In this case, the permeation speed of the water 9 into the paper-containing sheet 1 also differs between these aqueous solutions. The lower the concentration of the solute in the aqueous solution, the greater the permeation speed of the water 9 tends to be.

[0056] Also, for example, when two kinds of aqueous solutions having different types of solutes and the same solute concentration (M) are attached to the one surface 1a of the paper-containing sheet 1 in the same amount, if the hydration parameters of these solutes are different from each other, the amount of water 9 in these aqueous solutions that penetrates into the paper-containing sheet 1 will be different from each other. This is because the amount of water molecules that hydrate the solute will be different due to the difference in the hydration parameters of the solutes, and the ease of penetration of the water 9 into the paper-containing sheet 1 (water penetration speed) will be different. Usually, the smaller the hydration parameter of the solute, the smaller the amount of water molecules that hydrate the solute, and the easier it is for the water 9 to penetrate into the paper-containing sheet 1, and the more the amount of water 9 in the aqueous solution that penetrates into the paper-containing sheet 1 tends to be. In this case, the penetration speed of the water 9 into the paper-containing sheet 1 also differs between these aqueous solutions. The smaller the hydration parameter of the solute, the faster the penetration speed of the water 9 tends to be.

[0057] In this way, by using two different aqueous solutions, or by using water and an aqueous solution in combination, the permeation speed and amount of water 9 into the paper-containing sheet 1 can be adjusted, and the first region 12 and the second region 13 can be easily produced.

[0058] The solute is not particularly limited as long as it is water-soluble (in other words, capable of being hydrated), and can be arbitrarily selected. The aqueous solution is preferably neutral.

[0059] Of the solutes, the salt may be either an organic salt or an inorganic salt, but is preferably an inorganic salt. Examples of the inorganic salt include chlorides of alkali metals such as lithium chloride (LiCl, hydration parameter: 7.1), sodium chloride (NaCl, hydration parameter: 3.5), potassium chloride (KCl, hydration parameter: 1.9), and rubidium chloride (RbCl, hydration parameter: 1.2); bromides of alkali metals such as lithium iodide (LiI, hydration parameter: 9.0), sodium iodide (NaI, hydration parameter: 5.5), potassium iodide (KI, hydration parameter: 2.5), rubidium iodide (RbI, hydration parameter: 0.6); bromides of alkali metals such as magnesium chloride (MgCl2, hydration parameter: 13.7), potassium chloride (K ... Group 2 metal chlorides such as calcium (CaCl2, hydration parameter: 12.0) and strontium chloride (SrCl2, hydration parameter: 10.7); Group 2 metal bromides such as magnesium bromide (MgBr2, hydration parameter: 17.0), calcium bromide (CaBr2, hydration parameter: 14.6), and strontium bromide (SrBr2, hydration parameter: 12.7); magnesium iodide (MgI2, hydration parameter: 19.0), Examples of the iodides include iodides of Group 2 metals such as calcium iodide (CaI2, hydration parameter: 17.0) and strontium iodide (SrI2, hydration parameter: 15.5); and chlorides of transition metals such as manganese chloride (MnCl2, hydration parameter: 11.0), ferrous chloride (FeCl2, hydration parameter: 12.0), cobalt chloride (CoCl2, hydration parameter: 13.0), and nickel chloride (NiCl2, hydration parameter: 13.0).

[0060] The solute preferably has a hydration parameter of 0.5 to 20.0 in terms of availability and suitability for use, for example.

[0061] In order to facilitate the penetration of water 9 in an aqueous solution into the paper-containing sheet 1, a solute having a hydration parameter of, for example, 0.5 to 9 can be selected. In order to somewhat suppress the penetration of the water 9 in the aqueous solution into the paper-containing sheet 1, a solute having a hydration parameter of 15 to 20, for example, can be selected.

[0062] The concentration of the solute in the aqueous solution is not particularly limited as long as it is equal to or lower than the saturated concentration. The concentration of the solute in the aqueous solution may be, for example, 1 to 20 M. When the concentration is 1 to 7 M, the step (A) and the step (B) described below can be carried out more stably.

[0063] Here, the case has been described in which a first region 12 having a water concentration gradient and a second region 13 having a water concentration gradient are prepared by using two different aqueous solutions, but the types of different aqueous solutions used in this embodiment can be arbitrarily selected depending on the number of regions having a water concentration gradient to be prepared, each of which has a different amount of water 9 penetrating therein, and may be three or more types. That is, in step (A), two or more different aqueous solutions may be separately applied to different regions of the paper-containing sheet, thereby creating two or more regions in the surface direction of the paper-containing sheet that have water concentration gradients with different amounts of water penetration. In this case, for example, the two or more aqueous solutions may all have different hydration parameters for the solutes.

[0064] In step (A), the pressure of the environment when the water 9 is applied to the paper-containing sheet 1 and allowed to permeate is 0 to 1.0×10 12 Pa is preferably 1.0×10 2 ~1.0×10 9 Pa is more preferably 1.0×10 6 ~1.0×10 7 It is more preferable that the pressure is 0.1 Pa, and may be normal pressure (atmospheric pressure), for example. Under such pressure conditions, the water 9 can be more effectively permeated into the paper-containing sheet 1.

[0065] In the step (A), the temperature at which water 9 is applied to and permeated into the paper-containing sheet 1 is -273.15 to 1.0 × 10 5 °C, and is preferably -10 to 1.0 × 10 3 °C, more preferably 1.0 × 10 -12 It is more preferable that the temperature is from 10 to 35° C., for example. Under such temperature conditions, the water 9 can be permeated into the paper-containing sheet 1 more satisfactorily.

[0066] In step (A), the relative humidity when the water 9 is applied to and permeated into the paper-containing sheet 1 is preferably 0 to 100%, more preferably 10 to 80%, and may be, for example, any of 20 to 65% and 20 to 40%. Under such relative humidity conditions, the water 9 can be more effectively permeated into the paper-containing sheet 1.

[0067] In step (A), the time for permeating the water 9 from the application to the paper-containing sheet 1 can be set arbitrarily depending on other conditions at this time, and is not particularly limited. For example, the time may be within 100,000 minutes.

[0068] In step (A), it is preferable to set two or more selected from the group consisting of the pressure, temperature, relative humidity and time of the environment when water 9 is adhered to the paper-containing sheet 1 and then allowed to penetrate to the above-mentioned conditions, and all of the pressure, temperature, relative humidity and time of the environment when water 9 is adhered to the paper-containing sheet 1 and then allowed to penetrate may be set to the above-mentioned conditions. For example, in step (A), when water 9 is applied to the paper-containing sheet 1 and then permeated, these steps are performed under normal pressure and at a temperature of −273.15 to 1.0×10 5 For example, it may be performed under normal pressure, at a temperature of 10 to 35° C., and at a relative humidity of 20 to 65%, however, this is only one example of the preferred conditions for adhesion and penetration of water 9.

[0069] <Process (B)> After the step (A), the paper-containing sheet having the water concentration gradient is dried in the step (B). As a result, for example, as shown in Fig. 5A, the paper-containing sheet 1 begins to bend so that one surface 1a becomes concave in the area 11 having the water concentration gradient, and as the drying (in other words, the removal of water 9) progresses, the bending angle increases, and when the drying is completed, for example, as shown in Fig. 5B, the intended paper-containing three-dimensional structure 10 is formed. In this embodiment, by drying the paper-containing sheet 1 having a water concentration gradient (in other words, having an area 11 having a water concentration gradient), the paper-containing sheet 1 is caused to autonomously fold at the area 11' that previously had the water concentration gradient.

[0070] In the paper-containing sheet 1, cellulose molecules are initially bonded to each other by hydrogen bonds. When water 9 is permeated into the paper-containing sheet 1 in step (A), one surface 1a side expands as explained above, but in the paper-containing sheet 1, the water molecules break the hydrogen bonds between the cellulose molecules, resulting in a state in which the water molecules are interposed between the cellulose molecules, and it is presumed that intermolecular bonds of cellulose molecule-water molecule-cellulose molecule are formed. On the other hand, the paper-containing sheet 1 is manufactured in a state in which distortion has been generated by an external force due to its manufacturing method. When step (B) is performed on such a paper-containing sheet 1, as the water 9 in the paper-containing sheet 1 is reduced by drying, the cellulose molecules in the paper-containing sheet 1 are again bonded to each other by hydrogen bonds. At this time, the paper-containing sheet 1 is in a stable state in which the distortion is reduced or eliminated compared to the initial state, and it is presumed that it shrinks more than before the water 9 penetrated. It is presumed that the contraction force generated at this time causes the paper-containing sheet 1 to bend autonomously at the portion 11' that had the water concentration gradient, as shown in FIG. 5B.

[0071] In step (B), the paper-containing sheet 1 is folded autonomously with the side having a higher concentration of water 9 (i.e., one side 1a) facing inward (i.e., the other side 1b facing outward) out of both sides of the paper-containing sheet 1 (i.e., one side 1a and the other side 1b).

[0072] When a paper-containing sheet is folded autonomously, the folded portion does not necessarily have a clear crease, and the surface of the folded portion is often curved. The folding angle of the paper-containing sheet can be easily measured when the folded portion has a clear crease, but when the folded portion has a curved surface, it is difficult to measure it by the same method as when there is a crease. In such a case, the folding angle of the paper-containing sheet can be measured by the following method. Figures 6A to 6B are schematic diagrams for explaining a method of measuring the folding angle of the paper-containing sheet in such a case, where Figure 6A is a plan view showing the paper-containing sheet before folding, and Figure 6B is a front view showing the paper-containing sheet after folding (i.e., the paper-containing three-dimensional structure).

[0073] The paper-containing sheet 8 shown in FIG. 6A is cut to a width W 81 In the paper-containing sheet 8, a linear (thick) portion 81 having a water concentration gradient is formed. 81 In the width direction (in other words, the width direction of the paper-containing sheet 8), the area to the right of the area 81 having the water concentration gradient is the first area 802, and the area to the left of the area 81 is the second area 803. 802 and the width W of the second portion 803 803 is W 802 ≧W 803 This is in a relationship.

[0074] Consider the case where the paper-containing sheet 8 is autonomously folded in step (B) to form a paper-containing three-dimensional structure 80 as shown in FIG. 6B. In the paper-containing three-dimensional structure 80 (paper-containing sheet 8), in a portion 81' that had a water concentration gradient, one surface 8a is a concave curved surface (the other surface 8b is convex).

[0075] Here, in the first portion 802 of the paper-containing sheet 8, from the boundary with the portion 81′ having the water concentration gradient, ½W 81 A line segment is extended in the same direction as the surface direction of the first portion 802 for the length of , and its tip is defined as an imaginary end portion P1. The end of the first portion 802 opposite the side of the portion 81' that had a water concentration gradient is designated as a first end P2, and the end of the second portion 803 opposite the side of the portion 81' that had a water concentration gradient is designated as a second end P3. In FIG. 6B, the imaginary end P1, the first end P2, and the second end P3 are shown with black dots for the sake of convenience in order to make them easier to understand.

[0076] In this case, an extension line segment is created by further extending the line segment connecting the first end P2 and the imaginary end P1 beyond the imaginary end P1, and the angle θ1 (°) between the extension of this extension line segment and the line segment connecting the second end P3 and the imaginary end P1 is adopted as the bending angle of the paper-containing sheet 8. θ1 normally satisfies the condition 0°<θ1<180°, and here, the case where θ1>90° is illustrated. On the other hand, the angle θ2 (°) between the line segment connecting the first end P2 and the imaginary end P1 and the line segment connecting the second end P3 and the imaginary end P1 is the angle of the bent portion of the paper-containing three-dimensional structure 80, and is synonymous with 180-θ1 (°). θ2 also normally satisfies the condition 0°<θ2<180°, and here, the case where θ2<90° is illustrated.

[0077] In step (B), the pressure for drying the paper-containing sheet 1 is 0 to 1.0 × 10 12 Pa is preferably 1.0×10 2 ~1.0×10 9 Pa is more preferably 1.0×10 6 ~1.0×10 7 It is more preferable that the pressure is 1 Pa, and for example, the pressure may be normal pressure (atmospheric pressure). By drying the paper-containing sheet 1 under such pressure, the paper-containing sheet 1 can be folded autonomously more efficiently.

[0078] In step (B), the temperature (drying temperature) when drying the paper-containing sheet 1 is -273.15 to 1.0 × 10 5 °C, and is preferably -10 to 1.0 × 10 3 °C, more preferably 1.0 × 10 -12 It is more preferable that the temperature is in the range of 100° C. to 100° C., and may be, for example, 20 to 70° C. By drying the paper-containing sheet 1 under such temperature conditions, the paper-containing sheet 1 can be folded autonomously more efficiently.

[0079] In step (B), the relative humidity when drying the paper-containing sheet 1 is preferably 0 to 100%, more preferably 10 to 80%, and may be, for example, any of 20 to 65% and 20 to 40%. By drying the paper-containing sheet 1 under such relative humidity conditions, the paper-containing sheet 1 can be folded autonomously more efficiently.

[0080] In step (B), the time for drying the paper-containing sheet 1 (drying time) can be set arbitrarily depending on other conditions during drying, and is not particularly limited. For example, the time for drying the paper-containing sheet 1 is 1.0×10 30 It may be within minutes, it may be within 100,000 minutes, or it may be within 10,000 minutes.

[0081] In step (B), it is preferable to set two or more selected from the group consisting of pressure, temperature, relative humidity and time when drying the paper-containing sheet 1 to the above-mentioned conditions, and all of the pressure, temperature, relative humidity and time when drying the paper-containing sheet 1 may be set to the above-mentioned conditions. For example, in step (B), the paper-containing sheet 1 having a water concentration gradient is heated at a temperature of −273.15 to 1.0×10 5For example, it may be dried under normal pressure at a temperature of 20 to 70° C. and a relative humidity of 20 to 65%. However, this is just one example of the preferred drying conditions for the paper-containing sheet 1.

[0082] Step (B) may start, for example, with the paper-containing sheet 1 in a warped state as shown in FIG. 1B, or with the paper-containing sheet 1 in an unwarped state as shown in FIG. 1C. In this embodiment, if the environmental conditions (pressure, temperature, relative humidity, etc.) in which the paper-containing sheet 1 is placed after step (A) are not artificially changed to dry the sheet (i.e., the sheet is left as is), then step (B) can be considered to have started when a decrease in the amount of water 9 in the paper-containing sheet 1 can be clearly confirmed. Also, for example, if the environmental conditions in which the paper-containing sheet 1 is placed after step (A) are artificially changed to dry the sheet, then step (B) can be considered to have started when the conditions are changed. The reduction in the amount of water 9 in the paper-containing sheet 1 can be confirmed, for example, by measuring the mass of the paper-containing sheet 1 into which the water 9 has permeated.

[0083] In step (A), two or more different aqueous solutions are separately applied to different regions of the paper-containing sheet 1 to create two or more regions in the surface direction of the paper-containing sheet 1, each having a concentration gradient of water 9 with different amounts of water 9 penetrating therethrough.In this case, in step (B), a difference can be created in the autonomous bending pattern of the paper-containing sheet 1 between the two or more regions depending on the method of using the two or more aqueous solutions.

[0084] For example, as explained above, in step (A), when water 9 is permeated into the paper-containing sheet 1, the two or more regions are created by adjusting the concentration of the solute in the aqueous solution or the type of solute, and then step (B) is performed, whereby it is possible to create a difference in the angle or speed of the autonomous folding of the paper-containing sheet 1 between the two or more regions.

[0085] In this way, by using two or more different aqueous solutions, or a total of two or more types of water and aqueous solutions, it is possible to more easily form two or more autonomously bending regions in different modes in the paper-containing sheet 1.

[0086] ◎Shape of paper-containing sheet The shape of the paper-containing sheet can be selected arbitrarily depending on the structure of the intended paper-containing three-dimensional structure. 7A to 7C are perspective views each showing a schematic example of a paper-containing sheet used in this embodiment and a target paper-containing three-dimensional structure.

[0087] The paper-containing sheet 2 shown in FIG. 7A has a cross shape with one of its two sides being longer. When the paper-containing sheet 2 is regarded as a joint of six square sheets of the same size, step (A) is performed on the paper-containing sheet 2, and regions 21, 22, 23, 24, and 25 having a water concentration gradient can be created in the regions corresponding to the joints of these square sheets, as shown in Fig. 7B. At this time, these regions 21, 22, 23, 24, and 25 having a water concentration gradient can all be created by permeating water from the same side of the paper-containing sheet 2, i.e., from one side 2a. Next, by carrying out step (B), the paper-containing sheet 2 is autonomously folded towards the one surface 2a at the sites 21', 22', 23', 24' and 25' that previously had the water concentration gradient. In this manner, a cubic paper-containing three-dimensional structure 20 can be produced as shown in FIG. 7C.

[0088] FIG. 8 is a plan view that illustrates another example of the paper-containing sheet used in the method for producing a paper-containing three-dimensional structure of the present embodiment. The paper-containing sheet 200 shown here corresponds to the paper-containing sheet 2 shown in Figure 7A, in which arc-shaped cutout portions 29 corresponding to approximately 3 / 4 of the circumference are provided at the four corners where the outer periphery forms an angle of 90°, and arc-shaped cutout portions 28 corresponding to approximately 1 / 2 of the circumference are provided on the linear outer periphery at two points that can be regarded as the joints of the two square sheets mentioned above. In this way, the paper-containing sheet 200 has cutouts (four cutouts 29 and two cutouts 28) at locations on its outer periphery that overlap with the intended folding locations, making it easier to fold autonomously in step (B) than the paper-containing sheet 2 shown in Fig. 7A. By performing step (B) using the paper-containing sheet 200, a substantially cubic paper-containing three-dimensional structure can be manufactured.

[0089] ◎Variations The method for producing a paper-containing three-dimensional structure of this embodiment is not limited to the above-mentioned aspects, and some of the configurations may be changed, deleted, or added without departing from the spirit of the present invention.

[0090] For example, up to this point, we have described the case where, when creating multiple areas with a water concentration gradient on a paper-containing sheet, all of the areas with a water concentration gradient are created on the same side (the one side) of the paper-containing sheet. However, in this embodiment, one or more areas with a water concentration gradient may be created on each of both sides (the one side and the other side) of the paper-containing sheet.

[0091] 9A and 9B are cross-sectional views that typically show other examples of a paper-containing sheet in which a portion having a water concentration gradient has been produced, and a target paper-containing three-dimensional structure in this embodiment. The paper-containing sheet 3 shown in Figure 9A has a rectangular planar shape, and by performing step (A), regions 31 having a linear water concentration gradient are created in two locations on one surface 3a, and regions 32 having a linear water concentration gradient are created in three locations on the other surface 3b. Next, by carrying out step (B), the paper-containing sheet 3 is autonomously folded toward the one surface 3a at the portion 31' that had the water concentration gradient, and is autonomously folded toward the other surface 3b at the portion 32' that had the water concentration gradient. In this manner, a corrugated paper-containing three-dimensional structure 30 can be produced as shown in FIG. 9B.

[0092] Up to this point, we have described a case in which a portion of the paper-containing sheet having a water concentration gradient is created as a single independent line, and the flat paper-containing sheet is autonomously folded linearly along this portion. However, in this embodiment, the arrangement of the portion of the paper-containing sheet having a water concentration gradient and the method of autonomously folding the paper-containing sheet are not limited to this.

[0093] 10A and 10B are cross-sectional views that typically show other examples of a paper-containing sheet in which a portion having a water concentration gradient has been produced, and a target paper-containing three-dimensional structure in this embodiment. 10A has a rectangular planar shape, and by carrying out step (A), a large number of linear regions 41 having a water concentration gradient are formed parallel to one another with small gaps on one surface 4a of the paper-containing sheet 4. In contrast, no regions having a water concentration gradient are formed on the other surface 4b of the paper-containing sheet 4.

[0094] Next, by carrying out the step (B), the paper-containing sheet 4 is autonomously folded towards the one surface 4a at the portion 41' that had the water concentration gradient. As a result of the above, the paper-containing sheet 4 has the same number of regions 41' that had a water concentration gradient as the regions 41 that have a water concentration gradient, so that a semi-cylindrical paper-containing three-dimensional structure 40 can be produced, as shown in Figure 10B.

[0095] In addition, since the folding angle of the paper-containing sheet 4 can be adjusted by adjusting the amount of water permeation into the paper-containing sheet 4 or the width of the region 41 having a water concentration gradient, it is possible to form the paper-containing three-dimensional structure 40 into a shape other than a semi-cylindrical shape. For example, by increasing the amount of water permeation or widening the width of the region 41 having a water concentration gradient compared to the case of Fig. 10B, it is possible to manufacture a cylindrical paper-containing three-dimensional structure or a paper-containing three-dimensional structure wound into a roll.

[0096] Up to this point, generally, the areas in the paper-containing sheet that have a water concentration gradient have been shown to have a linear shape, but as long as a water concentration gradient can be formed, the shape of the area that has a water concentration gradient may be, for example, any filled shape that has a surface area that is clearly larger than that of a line (for example, a polygon, a circle, an ellipse, an irregular shape that does not fall into any of these categories, and a composite shape that combines one or more of these shapes).

[0097] The method for producing a paper-containing three-dimensional structure of this embodiment differs from conventional methods in that it does not require the supply of energy such as electric current or heat to the paper-containing sheet, and there is no need to modify the paper with special materials, and therefore has the advantage of being highly practical. Furthermore, the method for producing the paper-containing three-dimensional structure of the present embodiment has the advantage that the paper-containing sheet can be autonomously folded at a faster speed and at a larger folding angle than conventional methods.

[0098] Taking advantage of these characteristics, the manufacturing method of this embodiment is useful for applications such as the manufacture of three-dimensional electronic devices, the manufacture of shock-absorbing materials, and the folding of sheets. EXAMPLES

[0099] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples.

[0100] In this specification, the unit of concentration "M" means "mol / L."

[0101] [Example 1] <<Manufacturing of paper-containing three-dimensional structures (investigation of the bending angle of paper-containing sheets when the amount of water attached to the paper-containing sheets is changed)>> <Measurement of thickness of paper-containing sheet> Seven types of A4 size (210mm x 297mm) tracing paper (hereinafter referred to as "TP1", "TP2", "TP3", "TP4", "TP5", "TP6", and "TP7") were prepared as paper-containing sheets. The thickness of each tracing paper (TP1-TP7) was measured at two randomly selected points using a micrometer under conditions of 24°C temperature and 52% relative humidity. This thickness measurement was performed on 10 sheets of each type of tracing paper, and the average of the 20 measurements was calculated for each of the seven types of tracing paper, which was used as the thickness of the tracing paper. The results are shown in Table 1.

[0102] [Table 1]

[0103] <Production of paper-containing three-dimensional structure> A test piece measuring 95 mm in length and 65 mm in width (hereinafter referred to as the "TP1 test piece") was cut out from TP1, and this TP1 test piece was stored in a storage facility where the relative humidity was maintained at 30% to stabilize the condition of the TP1 test piece. Next, the TP1 test piece was taken out of the storage, and the TP1 test piece was attached and fixed to the center of the surface of the A4 size paper using a re-peelable spray glue. Then, under conditions of a temperature of 24°C and a relative humidity of 47%, an inkjet printer was used to adjust the black print density to five levels of 20%, 40%, 60%, 80%, and 100% by setting the discharge amount of the water-based black ink to five levels of 0.0017g, 0.0043g, 0.0093g, 0.0172g, and 0.0314g, and inkjet printing was performed on the TP1 test piece after the above fixation for each level of the discharge amount of the black ink, as shown in FIG. 11 (step (A)). FIG. 11 is a plan view showing the paper-containing sheet (TP1 test piece after printing with black ink) after the step (A) in this embodiment.

[0104] Next, the printed TP1 test piece was left to stand for 10 seconds under conditions of a temperature of 24° C. and a relative humidity of 47%, thereby allowing the black ink to penetrate into the TP1 test piece. Next, the TP1 test piece was immediately peeled off from the A4 size paper on which it was fixed, and the peeled TP1 test piece was left to stand for about 5 minutes on a thermoplate whose temperature was adjusted to 60°C in an environment of 30% relative humidity, thereby drying the TP1 test piece and folding it autonomously (step (B)). At this time, the TP1 test piece was placed on the thermoplate so that the surface opposite to the printed surface of the TP1 test piece faced the thermoplate. Before the drying was completed, the autonomous folding of the TP1 test piece had already stopped.

[0105] All steps up to this point were carried out under normal pressure.

[0106] The bending angle (θ1) of the thus obtained TP1 test piece (paper-containing three-dimensional structure) after bending was measured by the method described with reference to Figures 6A and 6B. At this time, image data of the TP1 test piece after bending was obtained, and the bending angle (θ1) was measured using this image data and software. The results are shown in Table 2 and FIG.

[0107] Furthermore, the bending angle (θ1) of each of the TP2, TP3, TP4, TP5, TP6 and TP7 test specimens was measured in the same manner as for the TP1 test specimen, except that TP2 to TP7 were used instead of TP1. The results are shown in Table 2 and Fig. 12. Note that in Fig. 12, the results for the TP4 test piece, the TP5 test piece, and the TP6 test piece are omitted.

[0108] [Table 2]

[0109] As is clear from Table 2 and Figure 12, when comparing the ink ejection amount at the same level, the thicker the tracing paper, the smaller the bending angle tends to be, and this tendency is more pronounced when the ink ejection amount is above a certain level (e.g., 0.0093 g or more). In addition, the change in the bending angle with the change in the ink ejection amount tends to be more gradual for thicker tracing paper. Furthermore, when the thickness of the tracing paper was 89 μm or less (i.e., TP4 test specimen, TP5 test specimen, TP6 test specimen, and TP7 test specimen), the specimens tended to bend more easily.

[0110] The thickness of each test piece from TP1 to TP7 corresponds to the test piece number, and i (i is an integer between 1 and 7), the volume V of the printing area in the test piece i is expressed by the following formula: V i =10×95×h i (mm 3 ) It is calculated as follows. The ink ejection amount m is the volume V of the printing target area. i The normalized ink ejection amount M is calculated by the following formula: M=m / V i (g / mm 3 ) It is calculated as follows. FIG. 13 shows a graph in which the results obtained above (angle of bending) are plotted for each normalized ink ejection amount.

[0111] As is clear from Fig. 13, it was confirmed that the bending angles were generally close when the tracing paper had a thickness of 97 μm or less (i.e., TP3 test piece, TP4 test piece, TP5 test piece, TP6 test piece, and TP7 test piece). This meant that if the tracing paper was relatively thin, about 97 μm or less, it was easy to achieve the desired bending angle regardless of its thickness.

[0112] FIG. 14 shows the relationship between the ink ejection amount and the angle (θ2=180−θ1(°)) of the bent portion of the obtained paper-containing three-dimensional structure in the TP3 test piece.

[0113] <<Manufacturing of paper-containing three-dimensional structures>> [Example 2] Using tracing paper (thickness 89.2 μm, size 105 mm×148 mm) as the paper-containing sheet and ion-exchanged water as the aqueous medium, a roughly cubic paper-containing three-dimensional structure was produced as shown in FIG. In Figure 15, the thin solid line in the left-hand figure indicates the cut portion of the tracing paper, and the thick solid line in the central figure indicates the portion of the tracing paper where the aqueous medium was ejected by the inkjet printing method. The figure on the right-hand side shows imaging data of the produced paper-containing three-dimensional structure.

[0114] In step (A), the aqueous medium was discharged (attached) to tracing paper under conditions of a temperature of 22°C and a relative humidity of 54%. The amount of aqueous medium discharged to the tracing paper (which is synonymous with the amount of water to be infiltrated; the same applies below) was 0.000140823 g / mm 3 The line width of the solid line was 6 mm. When the tracing paper was permeated with water, the temperature and relative humidity were the same as those when the aqueous medium was ejected, and the time was 300 seconds. In step (B), the tracing paper was dried for 10 minutes at a temperature of 22° C. and a relative humidity of 54%. Before the drying was completed, the tracing paper had already stopped folding autonomously. All steps up to this point were carried out under normal pressure.

[0115] [Example 3] Using tracing paper (thickness 89.2 μm, size 210 mm×297 mm) as the paper-containing sheet and ion-exchanged water as the aqueous medium, a roughly spherical paper-containing three-dimensional structure was produced as shown in FIG. In Figure 16, the thin solid line in the left-hand figure indicates the cut portion of the tracing paper, and the solid line in the central figure indicates the portion of the tracing paper where the aqueous medium was ejected by the inkjet printing method, and the figure on the right-hand side shows the imaging data of the produced paper-containing three-dimensional structure.

[0116] In step (A), the aqueous medium was discharged (attached) to the tracing paper under conditions of a temperature of 22° C. and a relative humidity of 54%. The amount of the aqueous medium discharged to the tracing paper was 0.000140823 g / mm 3 When the tracing paper was permeated with water, the temperature and relative humidity were the same as when the aqueous medium was discharged, and the time was 300 seconds. In step (B), the tracing paper was dried under conditions of a temperature of 22°C, a relative humidity of 54%, and a time of 30 minutes. Before the drying was completed, the tracing paper had already stopped folding autonomously. All steps up to this point were carried out under normal pressure.

[0117] [Example 4] Using tracing paper (thickness 89.2 μm, size 210 mm×297 mm) as the paper-containing sheet and ion-exchanged water as the aqueous medium, a soccer ball-shaped paper-containing three-dimensional structure was produced as shown in FIG. In Figure 17, the thin solid line in the left-hand figure indicates the cut portion of the tracing paper, and the thick solid line in the central figure indicates the portion of the tracing paper where the aqueous medium was ejected by the inkjet printing method. The figure on the right-hand side shows imaging data of the produced paper-containing three-dimensional structure.

[0118] In step (A), the aqueous medium was discharged (attached) to the tracing paper under conditions of a temperature of 22° C. and a relative humidity of 54%. The amount of the aqueous medium discharged to the tracing paper was 0.000140823 g / mm 3 The line width of the solid line was 5 mm. When the tracing paper was permeated with water, the temperature and relative humidity were the same as those when the aqueous medium was ejected, and the time was 300 seconds. In step (B), the tracing paper was dried for 30 minutes at a temperature of 22° C. and a relative humidity of 54%. Before the drying was completed, the tracing paper had already stopped folding autonomously. All steps up to this point were carried out under normal pressure.

[0119] [Example 5] Using tracing paper (thickness 89.2 μm, size 210 mm×297 mm) as the paper-containing sheet and ion-exchanged water as the aqueous medium, a paper-containing three-dimensional structure in the shape of a paper airplane was produced as shown in FIG. In Figure 18, the thin solid lines in the left-hand figure indicate the cut areas of the tracing paper, and the thick solid lines in the two central figures indicate the areas where the aqueous medium was ejected on both sides of the tracing paper using the inkjet printing method. The figure on the right-hand side shows image data of the produced paper-containing three-dimensional structure.

[0120] In step (A), the aqueous medium was discharged (attached) to the tracing paper under conditions of a temperature of 22° C. and a relative humidity of 54%. The amount of the aqueous medium discharged to the tracing paper was 0.000140823 g / mm 3The line width of the solid line was 7 mm and 15 mm. When the tracing paper was permeated with water, the temperature and relative humidity were the same as when the aqueous medium was ejected, and the time was 300 seconds. In step (B), the tracing paper was dried for 30 minutes at a temperature of 22° C. and a relative humidity of 54%. Before the drying was completed, the tracing paper had already stopped folding autonomously. All steps up to this point were carried out under normal pressure.

[0121] [Example 6] Using tracing paper (thickness 89.2 μm, size 40 mm × 50 mm) as the paper-containing sheet and ion-exchanged water as the aqueous medium, a three-dimensional wiring board having an approximately cylindrical shape and silver wiring on its convex surface, as shown in Figure 19, was produced as a paper-containing three-dimensional structure. More specifically, an ink composition containing silver nanoparticles was ejected using an inkjet printer onto one side of the tracing paper before folding to form a printed pattern corresponding to the print data shown in Figure 19, and then this printed pattern was dried by heating at 60°C to form silver wiring on the tracing paper.

[0122] Next, step (A) was carried out. That is, an aqueous medium was discharged using an inkjet printer onto the other side (the side opposite to the side on which the silver wiring was formed) of the tracing paper on which the silver wiring had already been formed, using ion-exchanged water as the aqueous medium, so as to obtain the print data shown in FIG. 19. At this time, the aqueous medium was discharged (attached) onto the tracing paper under conditions of a temperature of 24°C and a relative humidity of 48%. The amount of aqueous medium discharged onto the tracing paper was 0.000140823 g / mm 3The line width of the solid line was 8 mm. The inkjet printer used for ejecting the ink composition containing silver nanoparticles was used as it was. The aqueous medium was filled in a cartridge different from the cartridge filled with the ink composition. When water was permeated into the tracing paper, the temperature and relative humidity were the same as when the aqueous medium was ejected, and the time was 300 seconds.

[0123] Next, step (B) was carried out. That is, the tracing paper soaked in water was dried at a temperature of 24°C, a relative humidity of 48%, and for 30 minutes. Before the drying was completed, the tracing paper had already stopped folding autonomously.

[0124] All steps up to this point were carried out under normal pressure.

[0125] As described above, by using one inkjet printer, a three-dimensional wiring board could be produced in a simplified manner without mutual interference between the ink composition and the aqueous medium.

[0126] [Example 7] A wearable device having an approximately cylindrical shape with silver wiring provided on its convex surface, as shown in Figure 20, was produced as a paper-containing three-dimensional structure in the same manner as in Example 6, except that the printing pattern of the ink composition containing silver nanoparticles and the aqueous medium was changed.

[0127] [Test Example 1] <<Confirmation of the relationship between the concentration of the electrolyte aqueous solution and the ease of expansion of the paper-containing sheet when the electrolyte aqueous solution is permeated into the paper-containing sheet>> Aqueous solutions of lithium chloride (LiCl) were prepared with concentrations of 0 M, 3 M, 6 M, 9 M, 12 M, 15 M, and 18 M. In this test example and the following test examples and examples, an aqueous electrolyte solution with a concentration of 0 M means water. Tracing paper (thickness 125 μm, size 15 mm×15 mm) was used as the paper-containing sheet, and this tracing paper was immersed separately in each of the lithium chloride aqueous solutions obtained above. Next, at t seconds after the start of immersion (0 < t ≤ 1800), using a microscope (Olympus "SZX16"), the tracing paper during this immersion was observed from directly above its surface, and the length L of the tracing paper in the direction orthogonal to the longitudinal direction of the cellulose fibers constituting the tracing paper (hereinafter referred to as the "direction orthogonal to the fiber longitudinal direction") was measured. t (mm). Next, the length L0 (= 15 mm) of the tracing paper in the direction orthogonal to the fiber longitudinal direction before immersion in the lithium chloride aqueous solution and L t were used to calculate the ratio LR of the length of the tracing paper in the direction orthogonal to the fiber longitudinal direction before and after immersion in the lithium chloride aqueous solution using the following formula: LR = L t / L0 was calculated. At this time, black dots were printed in advance at both ends of the tracing paper in the direction orthogonal to the fiber longitudinal direction before immersion in the lithium chloride aqueous solution, the interval between these dots was measured, and this measured value was taken as L0 or L t . The above measurements and calculations were repeated three times, and the average value was adopted as the official data. The results are shown in Fig. 21.

[0128] As is clear from Fig. 21, when the concentration of the lithium chloride aqueous solution is 0 M, that is, in the case of water, the tracing paper swells the fastest. In the range where the concentration of the lithium chloride aqueous solution is 0 to 9 M, the lower the concentration, the faster the tracing paper swells. When the concentration is 9 M and 12 M, LR becomes less than 1 during the course of time, which is because the tracing paper during immersion curled. When the concentration is 12 M, LR remained less than 1 from the middle of the course of time, but it was推测 that LR would exceed 1 if the immersion time was extended beyond 1800 seconds. When the concentration is 15 M and 18 M, LR is approximately 1 and almost unchanged, that is, approximately L tAlthough it was L0, when the immersion time was extended beyond 1800 seconds, although it took longer than when the concentration was 12M, LR could be greater than 1, similar to the case when the concentration was 12M. Thus, it was found that the lower the concentration of the lithium chloride aqueous solution, the faster the tracing paper swelled. It was推测 that this was because the smaller the amount (mol) of lithium chloride in the lithium chloride aqueous solution, the smaller the amount of water molecules that hydrated the lithium chloride, making it easier for water to penetrate the tracing paper.

[0129] The above results indicated that when using an electrolyte aqueous solution to permeate water into a paper-containing sheet, by adjusting the concentration of the electrolyte aqueous solution, the permeation rate and permeation amount of water into the paper-containing sheet could be adjusted. Furthermore, it was shown that by drying the paper-containing sheet, it was possible to cause a difference in the self-folding angle of the paper-containing sheet.

[0130] [Test Example 2] [Confirmation of the relationship between the concentration of the electrolyte aqueous solution and the ease of drying of the paper-containing sheet when the electrolyte aqueous solution permeates the paper-containing sheet] Aqueous solutions of lithium chloride (LiCl) with concentrations of 0M, 3M, 6M, 9M, 12M, 15M, and 18M were prepared. Tracing paper (thickness 125 μm, size 40 mm × 40 mm) was used as the paper-containing sheet, and this tracing paper was immersed separately in each of the lithium chloride aqueous solutions obtained above. Then, immediately after 1800 seconds (30 minutes) had elapsed since the start of immersion, the tracing paper was taken out of the lithium chloride aqueous solution. And starting from 50 seconds later, under the conditions of a temperature of 20 - 22°C and a relative humidity of 53 - 55%, using an electronic balance (「GH-252」manufactured by A&D), the amount of water in this tracing paper was measured. This measurement was carried out until 12000 seconds (200 minutes) had elapsed after placing the tracing paper on the electronic balance. And the measured value M of the amount of water in the tracing paper t seconds after the start of measurement (0 < t ≦ 12000) tUsing the measured value M0 of the amount of water in the tracing paper at the start of the measurement, the drying rate DR of the tracing paper is calculated using the following formula: DR=M t / M0 The results are shown in Figure 22.

[0131] As is clear from FIG. 22, when the concentration of the lithium chloride aqueous solution was 0M, i.e., water, the tracing paper dried the fastest, and in the range of 0-6M lithium chloride aqueous solution, the lower the concentration, the faster the tracing paper dried. When the concentration was 9-18M, the DR exceeded 1 over time. This was presumed to be because lithium chloride is hygroscopic, and therefore drying did not proceed in the electronic balance, but moisture absorption proceeded instead. In this range of lithium chloride aqueous solution concentration (9-18M), the higher the concentration, the faster the moisture absorption. Thus, when the concentration of the lithium chloride aqueous solution was low, the tracing paper tended to dry faster as the concentration was lower. This was presumably because the smaller the amount (mol) of lithium chloride in the tracing paper, the smaller the amount of water molecules that hydrate the lithium chloride in the tracing paper, making it easier for water to evaporate from the tracing paper.

[0132] The above results showed that when water is permeated into the paper-containing sheet using an aqueous electrolyte solution, the drying speed of the paper-containing sheet can be adjusted by adjusting the concentration of the aqueous electrolyte solution. Furthermore, it was shown that it is possible to cause a difference in the progress of the autonomous folding of the paper-containing sheet.

[0133] [Test Example 3] <<Confirmation of the relationship between the type of electrolyte aqueous solution and the ease of expansion of the paper-containing sheet when the electrolyte aqueous solution is permeated into the paper-containing sheet>> An aqueous potassium chloride (KCl) solution with a concentration of 4 M, an aqueous sodium bromide (NaBr) solution with a concentration of 4 M, and an aqueous lithium chloride (LiCl) solution with a concentration of 4 M were prepared, and water was further prepared. The hydration parameters of these electrolytes are as follows, respectively. Potassium chloride (KCl): 1.9 Sodium bromide (NaBr): 4.2 Lithium chloride (LiCl): 7.1

[0134] Tracing paper (thickness 125 μm, size 15 mm × 15 mm) was used as the paper-containing sheet, and this tracing paper was immersed separately in the three aqueous solutions and water obtained above. Next, at t seconds after the start of immersion (0 < t ≤ 5), using a microscope (Olympus "SZX16"), the tracing paper during this immersion was observed from directly above its surface, and the length L t (mm) of the tracing paper in the direction perpendicular to the fiber length direction was measured. Next, the length L0 (= 15 mm) of the tracing paper in the direction perpendicular to the fiber length direction before immersion in the aqueous solution or water, L5 (L when t = 5 t ), and L other than L5 t were used to calculate the expansion rate ER of the tracing paper during immersion in the aqueous solution or water using the following formula: ER = (L0 - L t ) / (L0 - L5) was calculated. At this time, black dots were printed in advance at both ends in the direction perpendicular to the fiber length direction of the tracing paper before immersion in the aqueous solution or water, and the interval between these dots was measured, and this measured value was taken as L0, L t or L5. The results are shown in Fig. 23.

[0135] As is clear from Figure 23, the tracing paper swelled the fastest in water. In the three electrolyte aqueous solutions, the tracing paper swelled faster in the order of decreasing hydration parameters of the electrolytes, that is, the potassium chloride aqueous solution, the sodium bromide aqueous solution, and the lithium chloride aqueous solution. Thus, in the case of an electrolyte aqueous solution, the tracing paper tended to swell faster as the hydration parameter of the electrolyte decreased. This was presumably because the smaller the hydration parameter of the electrolyte, the fewer the amount of water molecules that hydrate the electrolyte, making it easier for water to penetrate the tracing paper.

[0136] The above results showed that when water is permeated into a paper-containing sheet using an aqueous electrolyte solution, the permeation rate and amount of water into the paper-containing sheet can be adjusted by adjusting the type of electrolyte. Furthermore, it was shown that it is possible to cause a difference in the autonomous folding angle of the paper-containing sheet by drying the paper-containing sheet.

[0137] [Test Example 4] <<Confirmation of the relationship between the type of electrolyte aqueous solution and the ease of drying of the paper-containing sheet when the electrolyte aqueous solution is permeated into the paper-containing sheet>> A 4M potassium bromide (KBr) aqueous solution, a 4M sodium bromide (NaBr) aqueous solution, a 4M lithium chloride (LiCl) aqueous solution, and a 4M calcium chloride (CaCl2) aqueous solution were prepared, and water was also prepared. The hydration parameters of these electrolytes are as follows: Potassium bromide (KBr): 2.1 Sodium bromide (NaBr): 4.2 Lithium chloride (LiCl): 7.1 Calcium chloride (CaCl2): 12

[0138] Tracing paper (thickness 125 μm, size 40 mm×40 mm) was used as the paper-containing sheet, and this tracing paper was immersed separately in the four aqueous solutions obtained above and in water. Next, immediately after 1800 seconds (30 minutes) from the start of immersion, the tracing paper was removed from these four aqueous solutions or water. After another 50 seconds, the amount of water in the tracing paper was measured using an electronic balance (A&D Co., Ltd., "GH-252") under conditions of a temperature of 20-22°C and a relative humidity of 48-51%. This measurement was continued until 12000 seconds (200 minutes) had elapsed since the tracing paper was placed on the electronic balance. The drying rate DR of the tracing paper was calculated in the same manner as in Test Example 2. The results are shown in FIG. 24.

[0139] As is clear from Figure 24, the tracing paper dried fastest in the case of water. Among the four electrolyte aqueous solutions, the tracing paper dried fastest in the order of decreasing hydration parameters of the electrolyte, that is, potassium bromide (KBr) aqueous solution, sodium bromide (NaBr) aqueous solution, lithium chloride (LiCl) aqueous solution, and calcium chloride (CaCl2) aqueous solution. Thus, in the case of an electrolyte aqueous solution, the smaller the hydration parameter of the electrolyte, the faster the tracing paper tends to dry. This is presumably because the smaller the hydration parameter of the electrolyte, the fewer the amount of water molecules that hydrate the electrolyte in the tracing paper, making it easier for water to evaporate from the tracing paper.

[0140] The above results showed that the drying speed of the paper-containing sheet can be adjusted by adjusting the type of electrolyte when water is permeated into the paper-containing sheet using an aqueous electrolyte solution. Furthermore, it was shown that it is possible to cause differences in the progress of the autonomous folding of the paper-containing sheet.

[0141] [Example 8] <<Confirmation of the relationship between the concentration of the electrolyte aqueous solution and the bending angle of the paper-containing sheet when the electrolyte aqueous solution is permeated into the paper-containing sheet>> Aqueous solutions of lithium chloride (LiCl) with concentrations of 0M, 6M, 12M and 18M were prepared. Tracing paper (60μm thick, 65mm×95mm in size) was used as the paper-containing sheet, and the tracing paper was attached and fixed to the center of the surface of the A4 size paper using a removable spray adhesive. Then, under conditions of a temperature of 20-22°C and a relative humidity of 49-53%, each of the lithium chloride aqueous solutions obtained above was printed separately on the tracing paper using an inkjet printer (step (A)). At this time, a thick line of 15mm width was printed along the short side direction at the center of the longitudinal direction of the tracing paper. Next, the printed tracing paper was peeled off from the A4 size paper to which it was fixed, and placed in an airtight container and left to stand. In this state, the tracing paper was dried and folded autonomously (step (B)). During this time, the relative humidity in the airtight container was adjusted to 55-60%. The bending angle of the tracing paper during this time (θ1 in FIG. 6B) (°) was measured. The results are shown in FIG. 25.

[0142] As is clear from FIG. 25, when the concentration of the lithium chloride aqueous solution was 0M, that is, water, the tracing paper bent the fastest, and when the concentration was 6M, the tracing paper bent the slowest. When the concentration was 12M and 18M, the tracing paper bent faster than when the concentration was 6M, and when the concentration was 18M, the tracing paper bent faster than when the concentration was 12M. This is presumed to be because lithium chloride has hygroscopicity, and especially when the concentration was 12M and 18M, the tracing paper absorbed moisture during its drying. That is, it was presumed that, in the range of the concentration of 0 to 6M, the lower the concentration, the faster the tracing paper bent.

[0143] The above results showed that when using an aqueous electrolyte solution to infiltrate water into a paper-containing sheet, it is possible to create differences in the speed at which the paper-containing sheet autonomously folds by adjusting the concentration of the aqueous electrolyte solution.

[0144] [Example 9] <<Confirmation of the relationship between the concentration of the electrolyte aqueous solution, the width of the area penetrated, and the bending angle of the paper-containing sheet when the electrolyte aqueous solution is penetrated into the paper-containing sheet>> Aqueous solutions of lithium chloride (LiCl) with concentrations of 0M, 6M, 12M and 18M were prepared. Tracing paper (60 μm thick, 65 mm×95 mm in size) was used as the paper-containing sheet, and the tracing paper was attached and fixed to the center of the surface of the A4-sized paper using a removable spray adhesive. Then, under conditions of a temperature of 20 to 22° C. and a relative humidity of 58 to 62%, each of the lithium chloride aqueous solutions obtained above was printed separately on the tracing paper using an inkjet printer (step (A)). At this time, thick lines with widths d of 1 mm, 3 mm, 5 mm, and 7 mm were printed in the center of the longitudinal direction of the tracing paper along the lateral direction. Next, the printed tracing paper was peeled off from the A4 size paper to which it was fixed, and placed in an airtight container and left to stand. In this state, the tracing paper was dried for two days and folded autonomously (step (B)). During this time, the relative humidity in the airtight container was adjusted to 64%. The bending angle of the tracing paper during this time (θ1 in FIG. 6B) (°) was measured. The results are shown in FIG. 26.

[0145] As is clear from FIG. 26, when the width d (printing area) is the same, the bending angle of the tracing paper is larger when the concentration of the lithium chloride aqueous solution is 0M, i.e., water, than when the concentration is 6M. When the concentration is 12M and 18M, the bending angle of the tracing paper is larger than when the concentration is 0M, and when the concentration is 18M, the bending angle of the tracing paper is larger than when the concentration is 12M. This is presumed to be because lithium chloride is hygroscopic, and the tracing paper absorbs moisture during drying, especially when the concentration is 12M and 18M. That is, when the width d is the same, in the range of 0 to 6M, the lower the concentration, the larger the bending angle of the tracing paper tends to be. On the other hand, when the concentration of the lithium chloride aqueous solution was the same, the wider the width d, the larger the bending angle of the tracing paper.

[0146] The above results showed that when water is permeated into a paper-containing sheet using an electrolyte aqueous solution, it is possible to create differences in the autonomous folding angle of the paper-containing sheet by adjusting the width of the permeated area. [Industrial Applicability]

[0147] The present invention can be used in all fields where origami techniques can be applied, including the manufacture of three-dimensional electronic devices, the manufacture of shock-absorbing materials, and the folding of sheets. [Explanation of symbols]

[0148] 1,2,3,4,8,200...Paper-containing sheet 1a, 2a, 3a, 4a...One side of paper-containing sheet 1b, 3b, 4b...other side of paper-containing sheet 11, 21, 22, 23, 24, 25, 31, 32, 41, 81...Areas with water concentration gradient in paper-containing sheets 12: A portion of the paper-containing sheet having a water concentration gradient (first portion) 13....A portion of the paper-containing sheet having a water concentration gradient (second portion) 111: Area of ​​paper-containing sheet with water concentration gradient (solid line area) 112: Area of ​​paper-containing sheet with water concentration gradient (dotted area) 11', 21', 22', 23', 24', 25', 31', 32', 41', 81': Areas with water concentration gradient of paper-containing sheet 9...Water 10,20,30,40,80...Paper-containing three-dimensional structure T1: Thickness of the paper-containing sheet

Claims

1. A method for producing a paper-containing three-dimensional structure, which is formed by folding a paper-containing sheet made of paper or containing paper as a main component, comprising: A step (A) of permeating water into the paper-containing sheet from one side thereof to create one or more regions in the paper-containing sheet having a water concentration gradient in a thickness direction of the paper-containing sheet; (B) a step of drying the paper-containing sheet in a state having the water concentration gradient, thereby autonomously folding the paper-containing sheet at the portion where the water concentration gradient was present; In the step (A), water or an aqueous solution containing a solute having a hydration parameter of 0.5 to 20.0 at room temperature and at a solvent content of 5% by mass or less, and comprising water alone, is applied to one side of the paper-containing sheet, and the water or the water in the aqueous solution applied to the one side is allowed to permeate the paper-containing sheet.

2. The method for producing a paper-containing three-dimensional structure according to claim 1 , wherein in the step (B), the paper-containing sheet is autonomously folded with the surface having the higher water concentration facing inward.

3. In the step (A), the amount of water to be permeated into the paper-containing sheet is set to 1.0×10 －１２ ~10g / mm ３ The method for producing the paper-containing three-dimensional structure according to claim 1 or 2,

4. The method for producing a paper-containing three-dimensional structure according to any one of claims 1 to 3, wherein in the step (A), the area having the water concentration gradient is formed in the paper-containing sheet in the form of a solid line or a dotted line.

5. In the step (B), the paper-containing sheet having the water concentration gradient is heated to a temperature of −273.15 to 1.0×10 under normal pressure. ５ The method for producing the paper-containing three-dimensional structure according to any one of claims 1 to 4, wherein the paper is dried under conditions of 0°C and a relative humidity of 0 to 100%.

6. The method for producing a paper-containing three-dimensional structure according to any one of claims 1 to 5, wherein in the step (A), two or more regions having a water concentration gradient in which the water penetration amount is different from each other are produced in the surface direction of the paper-containing sheet.

7. 7. The method for producing a paper-containing three-dimensional structure according to claim 6, wherein in the step (A), two or more different aqueous solutions are separately applied to different regions of the paper-containing sheet, thereby creating two or more regions in the surface direction of the paper-containing sheet having a water concentration gradient in which the water penetration amounts are different from each other.

8. The method for producing a paper-containing three-dimensional structure according to claim 7 , wherein the two or more aqueous solutions have solutes with hydration parameters all different from each other.

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