JP7794658B2 - Water-colored body, Water-colored body set - Google Patents

Description

The present invention relates to a water-discoloring body and a water-discoloring body set. More specifically, it relates to a water-discoloring body and a water-discoloring body set that includes a water-discoloring sheet and a cover member that delays the disappearance of the water-discoloring image formed on the water-discoloring sheet.

Conventionally, a water-discoloring body has been disclosed in which a porous layer in which a low refractive index pigment that is opaque in a non-water-absorbing state and becomes transparent in a water-absorbing state is dispersed and fixed in a binder resin is disposed on a colored layer. A water-discoloring material set has also been disclosed in which the water-discoloring image is formed by applying water with a writing or stamping tool or a finger, and then immediately after the water-discoloring image is formed, the water-discoloring image is covered with a cover member, thereby extending the maintenance time of the water-discoloring image (see, for example, Patent Document 1).
The water-color changing material set can prolong the time for which the water-color changing image is maintained, and can satisfy the practicality of toys and educational tools.

Japanese Patent Application Laid-Open No. 2002-254547

The present invention aims to provide a hydrochromic material and a hydrochromic material set that can extend the retention time of the hydrochromic image formed on this type of hydrochromic material and also allows confirmation of whether the hydrochromic image has been formed in a balanced manner.

The present invention provides a water-discoloring sheet comprising, as an upper layer of a colored layer, a porous layer in which a low refractive index pigment is fixed in a dispersed state in a binder resin, and a transparent cover member that covers a water-discoloring image formed on the surface of the porous layer by adhesion of water, thereby suppressing drying of the water and delaying disappearance of the water-discoloring image, and the underside of the transparent cover member has at least three or more dot-like convex portions that contact the surface of the water-discoloring sheet and maintain a non-contact state between the surface of the water-discoloring sheet and the transparent cover member, and are arranged in a non-linear pattern, the convex portions having a height of 0.4 mm to 12.0 mm, the surface area (s) of the convex portions visible from the upper surface of the transparent cover member and the height (h) of the convex portions satisfy the following formula (1), the area occupied by the convex portions visible from the upper surface of the transparent cover member is 10% or less of the surface area of the upper surface of the transparent cover member, and the transparent cover member is provided with character frames for the characters to be formed on the water -discoloring sheet . Alternatively, the present invention is directed to a water-discoloring sheet comprising, as an upper layer of a colored layer, a porous layer in which a low-refractive index pigment is dispersed and fixed in a binder resin; a transparent cover member that covers the water-discoloring image formed on the surface of the porous layer by the adhesion of water, thereby inhibiting the drying of the water and delaying the disappearance of the water-discoloring image; and a transparent frame sheet provided with character frames for characters to be formed on the water-discoloring sheet, wherein the underside of the transparent cover member has at least three or more dot-like convex portions that contact the surface of the water-discoloring sheet and are arranged in a non-linear manner to keep the surface of the water-discoloring sheet and the transparent cover member out of contact, the convex portions having a height of 0.4 mm to 12.0 mm, the surface area (s) of the convex portions visible from the top surface of the transparent cover member and the height (h) of the convex portions satisfy the following formula (1), and the water-discoloring body is such that the area occupied by the convex portions visible from the top surface of the transparent cover member is 10% or less of the surface area of the top surface of the transparent cover member .
1.0≦s/h≦ 400 (1)
Further requirements include that the convex portions are transparent, that the convex portions are white, that the tips of the convex portions are curved, that the transparent cover member is flexible and that there are three or more convex portions per 100 ^cm2 , that the transparent cover member has one end attached to the water-discoloring sheet and the other end as a free end and is attached to the water-discoloring sheet so as to be able to be opened and closed freely, that it consists of a plurality of the water-discoloring sheets and a plurality of the transparent cover members, that it consists of a plurality of the water-discoloring sheets, a plurality of the transparent cover members and a plurality of the transparent frame sheets , and that the dot-like convex portions are arranged in a checkerboard pattern .
Furthermore, the present invention requires a water-discoloring body set including the water-discoloring body and a water-attaching tool for forming a water-discoloring image.

The present invention provides a water-color changing object and water-color changing object set that satisfies marketability and practicality as a toy or educational tool by covering the water-color changing object with a cover member immediately after applying water to it using a writing or stamping tool, fingers, etc., and then easily extending the duration for which the water-color changing image remains. It also allows the user to check whether the water-color changing image has been formed in a balanced manner.

1 is a top view showing a water-chromatic body according to an embodiment of the present invention; FIG. 2 is a longitudinal cross-sectional view of the water-changing body of FIG. 1. FIG. 10 is a top view showing a water-chromatic body according to another embodiment of the present invention. FIG. 4 is a longitudinal cross-sectional view of the water-changing body of FIG. 3 . FIG. 2 is a longitudinal cross-sectional view showing a water-chromatic body of a reference example . FIG. 10 is a longitudinal cross-sectional view showing another reference example of a water-color changing body. 1 is a top view of a water-changing body set according to an embodiment of the present invention. FIG.

The water-discoloring sheet has a porous layer formed on the colored layer, in which a low refractive index pigment is fixed in a dispersed state in a binder resin.
The support itself may also serve as the colored layer, but it is preferable to provide a colored layer (including an image of any shape) on the surface of the support.
The support may be made of paper, synthetic paper, fabric such as woven fabric, knitted fabric, braided fabric, or nonwoven fabric, natural or synthetic leather, plastic, glass, ceramics, metal, wood, stone, etc. The support is preferably flat, but may also be uneven.
The colored layer provided on the surface of the support is formed from a binder resin containing a colorant.
Examples of the colorant include general dyes, general pigments, fluorescent dyes, fluorescent pigments, and metallic luster pigments.
The colorant is contained in a vehicle containing a binder resin as a binder, and the ink or paint is applied to a support, and then the volatile components are dried to form a colored layer.
Examples of the binder resin include urethane resins, nylon resins, vinyl acetate resins, acrylic ester resins, acrylic ester copolymer resins, acrylic polyol resins, vinyl chloride-vinyl acetate copolymer resins, maleic acid resins, polyester resins, styrene resins, styrene copolymer resins, polyethylene resins, polycarbonate resins, epoxy resins, styrene-butadiene copolymer resins, acrylonitrile-butadiene copolymer resins, methyl methacrylate-butadiene copolymer resins, butadiene resins, chloroprene resins, melamine resins, and emulsions of each of the above resins, casein, starch, cellulose derivatives, polyvinyl alcohol, urea resins, and phenolic resins.
The colored layer is formed on the support by a printing means such as process printing, screen printing, offset printing, gravure printing, coater, pad printing, inkjet printing, or transfer printing, or by a brush coating, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, or dip coating.
Alternatively, a transfer layer can be formed by first applying an ink or paint contained in a vehicle containing a colorant and a binder resin as a binder onto another substrate, and then transferring the transfer layer onto the support to form a colored layer.
Furthermore, when the support has transparency, a colored layer can be provided on the back surface of the support (the surface on which the porous layer is not provided).

A water-discoloring sheet can be obtained by laminating a porous layer on the colored layer, in which a low refractive index pigment is fixed in a dispersed state by a binder resin.
The porous layer is a layer in which a low refractive index pigment is fixed together with a binder resin in a dispersed state, and is a layer whose transparency differs between a dry state and a liquid-absorbing state.
Examples of the low refractive index pigment include silicic acid and its salts, baryte powder, barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, talc, alumina white, and magnesium carbonate, which have a refractive index in the range of 1.4 to 1.8 and exhibit good transparency when absorbing water.
Examples of the salt of silicic acid include aluminum silicate, potassium aluminum silicate, sodium aluminum silicate, calcium aluminum silicate, potassium silicate, calcium silicate, sodium calcium silicate, sodium silicate, magnesium silicate, and potassium magnesium silicate.
A preferred example of a low refractive index pigment is silica.
Two or more of the low refractive index pigments can also be used in combination.
The particle size of the low refractive index pigment is not particularly limited, but is preferably 0.03 to 10.0 μm.
The silicic acid may be silicic acid produced by a dry method, but silicic acid produced by a wet method (hereinafter referred to as wet-method silicic acid) is particularly effective. In this regard, silicic acid is produced as amorphous silicic acid, and depending on the production method, it can be roughly divided into dry-method silicic acid (hereinafter referred to as dry-method silicic acid) which uses a gas phase reaction such as thermal decomposition of silicon halide such as silicon tetrachloride, and wet-method silicic acid which uses a liquid phase reaction such as decomposition with an acid such as sodium silicate. The dry-method silicic acid and the wet-method silicic acid have different structures, and the dry-method silicic acid forms a three-dimensional structure in which silicic acid is tightly bonded, while the wet-method silicic acid has a so-called two-dimensional structure in which silicic acid is condensed to form a long molecular arrangement.
Therefore, since the molecular structure is coarser than that of the dry process silica, when wet process silica is applied to a porous layer, it is presumed that the system will have better diffused reflection of light in a dry state and greater hiding power in the normal state than a system using dry process silica.
Furthermore, since the porous layer is capable of absorbing water, wet-process silica has more hydroxyl groups present as silanol groups on the particle surface than dry-process silica, and is therefore more hydrophilic, and is therefore preferably used.
In order to adjust the hiding power of the porous layer in its normal state and the transparency in its liquid-absorbed state, other low refractive index pigments may be used in combination with the wet-process silica.

The amount of the low refractive index pigment in the porous layer depends on properties such as particle size, specific surface area, and oil absorption, but in order to satisfy both hiding power in the normal state and transparency in the liquid-absorbed state, the coating amount is preferably 1 to 50 g/ ^m2 , and more preferably 5 to 50 g/ ^m2 . If it is less than 1 g/ ^m2 , it is difficult to obtain sufficient hiding power in the normal state, and if it exceeds 50 g/ ^m2 , it is difficult to obtain sufficient transparency when liquid is absorbed.
The low refractive index pigment is dispersed in a vehicle containing a binder resin as a binding agent, and after coating on a support, the volatile components are dried to form a porous layer.
Examples of the binder resin include urethane resins, nylon resins, vinyl acetate resins, acrylic ester resins, acrylic ester copolymer resins, acrylic polyol resins, vinyl chloride-vinyl acetate copolymer resins, maleic acid resins, polyester resins, styrene resins, styrene copolymer resins, polyethylene resins, polycarbonate resins, epoxy resins, styrene-butadiene copolymer resins, acrylonitrile-butadiene copolymer resins, methyl methacrylate-butadiene copolymer resins, butadiene resins, chloroprene resins, melamine resins, and emulsions of each of the above resins, casein, starch, cellulose derivatives, polyvinyl alcohol, urea resins, and phenolic resins.
The mixing ratio of the low refractive index pigment to the binder resin depends on the type and properties of the low refractive index pigment, but is preferably 0.5 to 2 parts by mass, more preferably 0.8 to 1.5 parts by mass, of binder resin solids per 1 part by mass of the low refractive index pigment. If the binder resin solids per 1 part by mass of the low refractive index pigment is less than 0.5 parts by mass, it is difficult to obtain a practical coating strength for the porous layer, and if it exceeds 2 parts by mass, water permeability into the porous layer is easily impaired.
The porous layer has a smaller binder resin to colorant ratio than a general coating film, making it difficult to obtain sufficient film strength. Therefore, in order to improve abrasion resistance, it is effective to use a nylon resin or a urethane-based resin among the binder resins.
The urethane resin may be a polyester urethane resin, a polycarbonate urethane resin, a polyether urethane resin, etc., and two or more of these may be used in combination. Alternatively, a urethane emulsion resin in which the resin is emulsified and dispersed in water, or a colloidal dispersion type (ionomer type) urethane resin in which the ionic urethane resin (urethane ionomer) itself emulsifies without the need for an emulsifier due to the ionic group of the urethane resin itself, and is dissolved or dispersed in water, may also be used.
The urethane resin may be either an aqueous urethane resin or an oil-based urethane resin, but an aqueous urethane resin, particularly an urethane emulsion resin or a colloidal dispersion type urethane resin, is preferably used.
The urethane-based resin can be used alone, or can be used in combination with other binder resins depending on the performance required for the film. When a binder resin other than a urethane-based resin is used in combination, in order to obtain practical film strength, it is preferable that the urethane-based resin be contained in the binder resin of the porous layer in an amount of 30% or more in terms of solid content mass ratio.
Among the binder resins, if the binder resin is crosslinkable, the strength of the film can be further improved by adding an optional crosslinking agent to crosslink the binder resin.
The binder resins have different affinities with water, and by combining these, it is possible to adjust the time and degree of penetration into the porous layer and the rate of drying after penetration. Furthermore, the adjustment can be controlled by adding a dispersant or surfactant as appropriate.

The porous layer can be formed on the colored layer by printing methods such as screen printing, offset printing, gravure printing, coater printing, pad printing, and transfer printing, as well as by brush coating, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, and dip coating.

Furthermore, a colorant may be added to the porous layer to color the porous layer in a dry state.
Examples of the colorant include general dyes, general pigments, fluorescent dyes, fluorescent pigments, metallic luster pigments, reversible thermochromic compositions, reversible thermochromic microcapsule pigments encapsulating a reversible thermochromic composition, photochromic compositions, and photochromic microcapsule pigments encapsulating a photochromic composition. When fluorescent colorants such as fluorescent dyes and fluorescent pigments are used, the clarity of the color change is excellent. When photochromic colorants such as thermochromic colorants such as reversible thermochromic compositions and reversible thermochromic microcapsule pigments encapsulating a reversible thermochromic composition are used, a variety of changes can be imparted.
The reversible thermochromic composition preferably contains three components: an electron-donating organic color-forming compound, an electron-accepting compound, and an organic compound medium that reversibly induces a color-forming reaction.
As the photochromic composition, photochromic compounds such as spirooxazine compounds, spiropyran compounds, diarylethene compounds, etc. are preferably used.

The surface of the porous layer of the water-discoloring sheet is provided with a transparent cover member that covers the water-discoloring image formed by the adhesion of water to the surface of the porous layer, inhibits the water from drying, and delays the disappearance of the water-discoloring image.
The transparent substrate forming the transparent cover member only needs to have a transparency sufficient to allow the water discoloration image to be seen through, and may be made of a plastic sheet material, a plastic molded body, or glass.
A transparent, colored substrate may also be used.
The underside of the transparent cover member (transparent base material) can be kept in a non-contact state between the surface of the water-color-changing sheet and the transparent cover member, and at least three or more convex portions that contact the surface of the water-color-changing sheet can be arranged in a non-linear pattern.
The convex portions form a space between the porous layer and the transparent cover member, and also prevent the contours of the water-discolored image from becoming blurred and unclear, which would occur if the transparent cover member came into contact with the porous image and water in the image diffused to areas where no image was formed.
By arranging the protrusions in a non-linear pattern at at least three locations, contact between the transparent cover member and the porous layer can be prevented.
Furthermore, by having the convex portions have a height of 0.4 mm to 12.0 mm, preferably 0.5 mm to 10.0 mm, the space between the porous layer and the transparent cover member can inhibit the drying of water, thereby improving the function of delaying the disappearance of the water-discolored image.
If the height of the convex portions is less than 0.4 mm, the water-discoloring image formed on the water-discoloring sheet is likely to come into contact with the transparent cover member, resulting in significant bleeding of the water-discoloring image and deformation of the image.If the height of the convex portions is more than 12.0 mm, the effect of suppressing water drying is difficult to exhibit, and it is difficult to extend the duration of the water-discoloring image.
Furthermore, when the height is changed from 0.4 mm to 12.0 mm, 0.4 mm is the longest length of time the water discoloration image is maintained, so by setting the height of the convex part, the time the water discoloration image is maintained can be adjusted.
Furthermore, by making the surface area (s) of the convex portions visible from the top surface of the transparent cover member and the height (h) of the convex portions satisfy the following formula (1), the visibility of the water-discolored image visible through the transparent cover member is not hindered by the convex portions, and the function of delaying the disappearance of the water-discolored image can be achieved.
1.0≦s/h≦ 400 (1)
If s/h is less than 1.0, the shape of the convex portions will be acute-angled, which will easily damage the porous layer and require careful handling.If s/h is more than 400 , the surface area of the convex portions visible from the top surface of the transparent cover member will be large, which will easily hinder the visibility of the water-discolored image.
Furthermore, the area occupied by the convex portions visible from the upper surface of the cover member is 10.0% or less of the surface area of the upper surface of the cover member, so that the visibility of the water discoloration image can be prevented from being obstructed by the convex portions.
The convex portions are preferably transparent, and when the porous layer is white, they preferably exhibit a white color, so that the convex portions can be prevented from interfering with the visibility of the water-discolored image.
The curved tip of the convex portion makes it difficult for the porous layer to be damaged, prevents the porous layer from peeling off, and makes it easy for even small children to handle.
Furthermore, since the transparent cover member is flexible, it can be easily covered and peeled off, and by providing three or more, preferably four or more, convex portions ^per 100 cm2, it is possible to suitably avoid contact with the water-discolored image during use.
Furthermore, by attaching one end of the transparent cover body to the water-discoloring sheet and leaving the other end as a free end so that it can be opened and closed freely on the water-discoloring sheet, convenience can be improved by allowing the water-discoloring image to be covered quickly and easily after it is formed.
Furthermore, by making the water-discoloring body consist of a plurality of water-discoloring sheets and a plurality of transparent cover members, a water-discoloring image can be formed on another water- discoloring sheet before the water-discoloring image dries, so that the desired image can be formed quickly.
The number of the water-coloring sheets and the number of the transparent cover members may be the same, or the number of the transparent cover members may be fewer.
Furthermore, a water-color changing body consisting of a plurality of water-color changing sheets and a single transparent cover member can also achieve the same effect.
Furthermore, by making the water-discoloring body consist of a plurality of water-discoloring sheets, a plurality of transparent cover members, and a plurality of transparent frame sheets, as described below, a water-discoloring image can be formed on another water -discoloring sheet before the water-discoloring image dries, thereby enabling the desired image to be formed quickly.
The number of the water-discoloring sheets, the number of transparent cover members, and the number of transparent frame sheets may be the same, or the number of transparent cover members and transparent frame sheets may be fewer than the number of water-discoloring sheets.
Furthermore, a water-color changing body consisting of a plurality of water-color changing sheets, a single transparent cover member, and a single transparent frame sheet can also achieve the same effect.

Furthermore, the transparent cover member has a peripheral portion on the underside of the cover member that is in close contact with the surface of the water-discoloring sheet, and the inner peripheral portion has a void portion that keeps it out of contact with the surface of the water-discoloring sheet, thereby covering the water-discoloring image formed by the adhesion of water to the surface of the porous layer, preventing the water from drying, and delaying the disappearance of the water-discoloring image.
The height of the void portion is 0.4 mm to 12.0 mm, preferably 0.5 mm to 10.0 mm, so that the space between the porous layer and the transparent cover member can suppress drying of water, thereby improving the function of delaying disappearance of the water-discolored image.
If the height is less than 0.4 mm, the water-discoloring image formed on the water-discoloring sheet is likely to come into contact with the transparent cover member, resulting in significant bleeding of the water-discoloring image and deformation of the image.If the height is more than 12.0 mm, it is difficult to achieve the effect of suppressing the drying of water, and it is difficult to extend the duration of the water-discoloring image.

By providing the transparent cover member with a frame for letters, etc. to be formed on the water -discoloring sheet , or by providing the transparent cover member with a transparent frame sheet on which the frame for letters, etc. to be formed on the water -discoloring sheet is formed by means of printing or the like, it is possible to visually confirm whether the water-discoloring image has been properly formed within the frame, and to confirm whether the water-discoloring image has been formed in a well-balanced manner.
The size, shape, color, line width and line type of the character frame formed on the transparent cover member are not particularly limited.
The transparent frame sheet on which the character frame is provided is made of a plastic sheet material, a plastic molded body, or glass, and the character frame can be provided by means of printing or the like.
The characters may be hiragana, katakana, kanji, alphanumeric characters, and various symbols.
The surface of the transparent cover member or the surface of the transparent frame sheet has minute irregularities and is non-glossy, so that it is possible to prevent light from being reflected on the surface and impairing the visibility of the water-discolored image.
In addition, erasable writing implements such as whiteboard markers containing wipeable ink or writing implements containing ink that fades with water can be used to write on the surface of the transparent cover member or the surface of the transparent frame sheet to trace the water-discolored image or write other letters or marks.

As a means for applying water to the water-discoloring sheet, a hand or finger may be wetted with water and brought into contact with the sheet, or a water application tool may be used.
Examples of the water application tool include water guns, sprayers, writing or application tools with a brush tip or fiber pen body at the tip, writing or application tools that store water in a container and have a fiber body or brush that discharges the water from the container, stamping tools, etc.
A writing implement or applicator using a plastic porous body or processed fiber body having continuous pores as a pen tip member as the water adhesion implement can easily form a written image and has improved practicality.
In addition, a water-color changing object set can be constructed by combining the water-adhering tool and the water-color changing object, and can be used as a teaching tool set or a drawing toy set.
Examples of the water-adhering device include writing implements and stamping implements. The writing implements can be a writing brush, a continuous-pore plastic body, felt, a resin-processed or fused fiber body, a plastic body with capillary gaps in the internal axial direction, or other such components that can be used alone, but a more practical writing implement is one in which the component is attached to the barrel as a pen tip and is configured to be able to extract water contained in the barrel.
The stamping tool may be a stamping material made of a plastic porous body, a plastic molded body with a roughened stamping surface that is water-wettable, or a rotary stamp in which the above-mentioned component is attached to the outer periphery of a wheel-shaped rotating body.

Examples are shown below, but the present invention is not limited to these examples. In the examples, "parts" refers to parts by mass.
Example 1 (see Figures 1 and 2)
Preparation of Water-Discoloring Material A colored layer 4 was formed on a support 3 made of white synthetic paper by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of blue pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30% by weight, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid printed over the entire surface to form a porous layer 5, and a water-discoloring sheet 2 measuring 220 mm x 320 mm was obtained.
Next, a transparent substrate 7 was formed on the underside of a plate-shaped molded article made of transparent hard ABS resin with a thickness of 1.0 mm and dimensions of 200 mm x 300 mm. Three convex portions 8 made of transparent ABS resin with a diameter of 10 mm and a height of 1.0 mm and a curved tip were provided at positions corresponding to the vertices of an isosceles triangle, and a character frame 9 consisting of four rectangles was formed on the upper surface of the plate-shaped molded article using black printing ink, thereby obtaining a transparent cover member 6.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 78.5 ^mm2 , the height (h) of the convex portion was 1.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 78.5.
Furthermore, the surface area of the upper surface of the transparent cover member was 600 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 2.36 ^cm2 , and the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.39%.
A water-coloring body 1 comprising the water-coloring sheet 2 and the transparent cover member 6 was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, a blue water-discoloring image was formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discolored image was formed on the water-discolored sheet by writing with a writing pen containing water, and the transparent cover member was placed on the water-discolored sheet on which the water-discolored image had been formed so that the tips of the convex portions were in contact with the surface of the water-discolored sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, since the transparent cover member is provided with a frame for the letters, it is possible to visually confirm whether the water-discolored image is properly formed within the frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Next, when the transparent cover member was removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and the sheet returned to its original state. This phenomenon could be repeated many times.

Example 2 (see Figures 3 and 4)
Preparation of Water-Discoloring Material A colored layer 4 was formed on a support 3 made of white synthetic paper with a polyester nonwoven fabric provided thereon by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of black pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30% by weight, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid-printed over the entire surface to form a porous layer 5, and a water-discoloring sheet 2 measuring 280 mm x 380 mm was obtained.
Next, 48 convex portions 8 made of white polyurethane resin, each having a diameter of 3 mm and a height of 1.2 mm and a curved hemispherical shape with a curved tip, were arranged in a checkerboard pattern at equal intervals of 47 mm on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 253 mm x 353 mm as the transparent substrate 7, to obtain a transparent cover member 6.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 7.07 ^mm2 , the height (h) of the convex portion was 1.2 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 5.89.
Furthermore, the surface area of the upper surface of the transparent cover member was 893.09 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 3.39 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.38%, and the number of convex portions per 100 ^cm2 was 5.37.
Furthermore, a transparent base material 71 was a flexible polyester transparent sheet having a thickness of 50 μm and a size of 233 mm x 333 mm, and a character frame 9 consisting of six rectangles was printed on the underside of the sheet using black printing ink to obtain a transparent frame sheet 10.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was impregnated with water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discolored sheet, the water-discolored image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized, returning to a completely white water-discolored sheet. This phenomenon could be repeated many times.
Furthermore, since the transparent cover member and the transparent frame sheet are flexible, the water-discoloring body can be rolled up and carried around, and is therefore highly portable.

Example 3
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 253 mm x 353 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 3 mm in diameter and 0.6 mm in height and with a curved hemispherical tip, were provided at equal intervals of 47 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 7.07 ^mm2 , the height (h) of the convex portion was 0.5 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 14.14.
Furthermore, the surface area of the upper surface of the transparent cover member was 893.09 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 3.39 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.38%, and the number of convex portions per 100 ^cm2 was 5.37.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 253 mm x 353 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and returned to its original state. This phenomenon could be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 4
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 262 mm x 362 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 12 mm in diameter and 5.0 mm in height and having a curved hemispherical tip, were provided at equal intervals of 38 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 113.04 ^mm2 , the height (h) of the convex portion was 5.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 22.61.
Furthermore, the surface area of the upper surface of the transparent cover member was 948.44 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 54.26 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 5.72%, and the number of convex portions per 100 ^cm2 was 5.06.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 262 mm x 362 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 20 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and returned to its original state. This phenomenon could be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 5
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 15 mm in diameter and 7.0 mm in height and with a curved hemispherical tip, were provided at equal intervals of 35 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 176.63 ^mm2 , the height (h) of the convex portion was 7.0 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 25.23.
Furthermore, the surface area of the upper surface of the transparent cover member was 967.25 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 84.78 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 8.77%, and the number of convex portions per 100 ^cm2 was 4.96.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 15 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and returned to its original state. This phenomenon could be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 6
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 15 mm in diameter and 10.0 mm in height and with a curved hemispherical tip, were provided at equal intervals of 35 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 176.63 ^mm2 , the height (h) of the convex portion was 10.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 17.66.
Furthermore, the surface area of the upper surface of the transparent cover member was 967.25 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 84.78 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 8.77%, and the number of convex portions per 100 ^cm2 was 4.96.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 10 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member are removed from the water-discoloring sheet, the water-discoloring image gradually disappears as the water evaporates, and after 10 minutes the image has completely disappeared and returned to its original state. This phenomenon can be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 7
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 15 mm in diameter and 0.5 mm in height and with a curved hemispherical tip, were provided at equal intervals of 35 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 176.63 ^mm2 , the height (h) of the convex portion was 0.5 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 353.33.
Furthermore, the surface area of the upper surface of the transparent cover member was 967.25 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 84.78 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 8.77%, and the number of convex portions per 100 ^cm2 was 4.96.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A transparent cover member and a transparent frame sheet were attached to one end of the water-coloring sheet, and the other end was left as a free end to obtain a water-coloring body.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member are removed from the water-discoloring sheet, the water-discoloring image gradually disappears as the water evaporates, and after 10 minutes the image has completely disappeared and returned to its original state. This phenomenon can be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 8
Preparation of Water-Colored Material A water-colored sheet was obtained in the same manner as in Example 2.
Next, 48 convex portions made of white soft SEBS resin, each having a diameter of 5 mm and a height of 10.0 mm and a curved tip, were provided in a grid pattern at equal intervals of 45 mm on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 255 mm x 355 mm as a transparent substrate, to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 19.63 ^mm2 , the height (h) of the convex portion was 10.0 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 1.96.
Furthermore, the surface area of the upper surface of the transparent cover member was 905.25 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 9.42 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 1.04%, and the number of convex portions per 100 ^cm2 was 5.30.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A transparent cover member and a transparent frame sheet were attached to one end of the water-coloring sheet, and the other end was left as a free end to obtain a water-coloring body.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was dipped in water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 10 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member are removed from the water-discoloring sheet, the water-discoloring image gradually disappears as the water evaporates, and after 10 minutes the image has completely disappeared and returned to its original state. This phenomenon can be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 9
A porous layer was formed on a support made of red polyester satin fabric with a basis weight of 130 g/ ^m² by solid printing using a white screen printing ink prepared by uniformly mixing and stirring 15 parts of wet-processed fine particle silica (trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.), 50 parts of an aqueous urethane resin (trade name: Hydran AP-10, polyester-based urethane resin, solids content 30 wt%, manufactured by Dainippon Ink and Chemicals, Inc.) as a binder resin, 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent. A water-discoloring sheet measuring 310 mm x 410 mm was obtained by solid printing on the entire surface of the support.
Next, a transparent sheet made of flexible soft PVC, 200 μm thick and 310 mm x 410 mm in size, was used as a transparent substrate. On the underside of the sheet, 63 convex portions made of transparent soft PVC resin, each having a diameter of 10 mm and a height of 3.0 mm and a curved hemispherical tip, were provided at intervals of 40 mm to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 78.5 ^mm2 , the height (h) of the convex portion was 3.0 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 26.17.
Furthermore, the surface area of the upper surface of the transparent cover member was 1,271 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 49.46 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 3.9%, and the number of convex portions per 100 ^cm2 was 4.95.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 100 μm and dimensions of 300 mm x 400 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A transparent cover member and a transparent frame sheet were attached to one end of the water-coloring sheet, and the other end was left as a free end to obtain a water-coloring body.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush containing water in the tip, red water-discolored images (letters) could be formed.
The water-discolored image was maintained for 3 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a writing brush containing water in the tip, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 20 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member are removed from the water-discoloring sheet, the water-discoloring image gradually disappears as the water evaporates, and after 10 minutes the image has completely disappeared and returned to its original state. This phenomenon can be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 10
Preparation of Water-Color Changing Material A water-color changing sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 253 mm x 353 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin, each 3 mm in diameter and 0.4 mm in height and with a curved hemispherical tip, were provided at equal intervals of 47 mm in a checkerboard pattern to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 7.07 ^mm2 , the height (h) of the convex portion was 0.4 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 17.68.
Furthermore, the surface area of the upper surface of the transparent cover member was 893.09 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 3.39 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.38%, and the number of convex portions per 100 ^cm2 was 5.37.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 260 mm x 360 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A transparent cover member and a transparent frame sheet were attached to one end of the water-coloring sheet, and the other end was left as a free end to obtain a water-coloring body.

The water-discolored sheet was normally white, but when a writing brush with the tip dipped in water was used to write on the porous layer, black water-discolored images (numbers) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member. Although a portion of the water-discolored image came into contact with the transparent cover member and caused slight bleeding, this did not pose a practical problem and the clear water-discolored image was maintained.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and returned to its original state. This phenomenon could be repeated many times.
Furthermore, since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Example 11
Preparation of Water-Color Changing Material A water-color changing sheet was obtained in the same manner as in Example 2.
Next, a transparent polyester sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm was used as a transparent substrate. On the underside of the sheet, 48 convex portions made of white polyurethane resin with a diameter of 15 mm, a height of 12.0 mm and a curved tip were provided in a checkerboard pattern at equal intervals of 35 mm to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 176.63 ^mm2 , the height (h) of the convex portion was 12.0 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 14.72.
Furthermore, the surface area of the upper surface of the transparent cover member was 967.25 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 84.78 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 8.77%, and the number of convex portions per 100 ^cm2 was 4.96.
Furthermore, a transparent frame sheet consisting of six squares was printed on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 265 mm x 365 mm as a transparent substrate using black printing ink to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, a transparent cover member, and a transparent frame sheet was obtained.

The water-discoloring sheet was normally white, but when a writing brush with the tip dipped in water was used to write on the porous layer, a black water-discoloring image (symbol) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, so the clear water-discolored image was maintained for 7 minutes in an environment of 25°C and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
The water-discolored image gradually disappeared as the water evaporated, and after 15 minutes the entire sheet returned to a white color.
This phenomenon can be repeated many times.
Since the transparent frame sheet and the transparent cover member are flexible, the water-color changing body can be rolled up and carried around, and is therefore highly portable.

Reference Example 1 (see Figure 5)
Preparation of Water-Discoloring Material A colored layer 4 was formed on a support 3 made of white synthetic paper by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of blue pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30 wt%, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a porous layer 5, which was solid-printed over the entire surface using a white screen printing ink, and a water-discoloring sheet measuring 220 mm x 320 mm was obtained.
Next, a transparent cover member was obtained as a transparent substrate 7, made of a transparent hard ABS resin with a thickness of 1.0 mm and dimensions of 200 mm x 300 mm, the peripheral edge of the lower surface being in close contact with the surface of the water-discoloring sheet, and the inner peripheral edge having a 5 mm high gap that keeps it out of contact with the surface of the water-discoloring sheet, and having a letter frame consisting of four rectangles on the upper surface.
A water-coloring body comprising the water-coloring sheet and the transparent cover member was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, blue water-discoloring images (letters) were formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a writing implement filled with water, and a transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed.
The water discoloration image could be clearly maintained through the transparent cover member.
Furthermore, since the transparent cover member is provided with a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Next, when the transparent cover member was removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and the sheet returned to its original state. This phenomenon could be repeated many times.

Reference Example 2 (see Figure 6)
Preparation of Water-Discoloring Material A colored layer 4 was formed on a support 3 made of white synthetic paper by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of blue pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30 wt%, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a porous layer 5, which was solid-printed over the entire surface using a white screen printing ink, and a water-discoloring sheet measuring 220 mm x 320 mm was obtained.
Furthermore, a transparent cover member was obtained as a transparent substrate 7, made of a transparent hard ABS resin with a thickness of 1.0 mm and dimensions of 200 mm x 300 mm, the peripheral edge of the underside of which is in close contact with the surface of the water-discoloring sheet, and the inner peripheral edge has a 10 mm high gap that keeps it out of contact with the surface of the water-discoloring sheet.
Furthermore, a transparent base material 71 was prepared by forming a character frame 9 consisting of four rectangles on the underside of a flexible polyester transparent sheet having a thickness of 50 μm and a size of 200 mm x 300 mm using black printing ink, thereby obtaining a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, blue water-discoloring images (numbers) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a writing implement filled with water, and a transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed.
The water discoloration image could be clearly maintained through the transparent cover member.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and returned to its original state. This phenomenon could be repeated many times.

Example 14
Preparation of a hydrochromic body set (see Figure 7)
A water-coloring object set 12 was obtained by combining the water-coloring object 1 of Example 1 with a water-adhering tool 11 (a writing element containing water).
The water-discoloring body set can form a water-discoloring image on the water-discoloring sheet using a water-adhering tool, and by placing a transparent cover member on it as in Example 1, the water-discoloring image can be clearly seen through the transparent cover member, and the convex portion prevents the transparent cover member from coming into contact with the water-discoloring image, allowing the clear water-discoloring image to be maintained for a long time.
Furthermore, since the transparent cover member is provided with a frame for the letters, it is possible to visually confirm whether the water-discolored image is properly formed within the frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, each of the water-coloring products of Examples 2 to 11 was combined with a water-adhering tool (a writing tool containing water) to obtain a water-coloring product set.
The water-discoloring body set can be used to form a water-discoloring image on the water-discoloring sheet using a water-adhering tool, and by placing a transparent cover member on it as in Examples 2 to 11, the water-discoloring image can be clearly seen through the transparent cover member, and the convex portion prevents the transparent cover member from coming into contact with the water-discoloring image, allowing the clear water-discoloring image to be maintained for a long time.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
In addition, the water-coloring product of Example 12 was combined with a water-adhering tool (a writing tool containing water) to obtain a water-coloring product set.
The water-discoloring body set can be used to form a water-discoloring image on the water-discoloring sheet using a water-adhering tool, and by placing a transparent cover member on it as in Example 12, the water-discoloring image can be clearly seen through the transparent cover member, and the gap prevents the transparent cover member from coming into contact with the water-discoloring image, allowing the clear water-discoloring image to be maintained for a long time.
Furthermore, since the transparent cover member is provided with a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
In addition, the water-coloring product of Example 13 was combined with a water-adhering tool (a writing tool containing water) to obtain a water-coloring product set.
The water-discoloring body set can be used to form a water-discoloring image on the water-discoloring sheet using a water-adhering tool, and by placing a transparent cover member on it as in Example 13, the water-discoloring image can be clearly seen through the transparent cover member, and the gap prevents the transparent cover member from coming into contact with the water-discoloring image, allowing the clear water-discoloring image to be maintained for a long time.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.

Example 15
Preparation of Water-Discoloring Material A colored layer was formed on a support made of white synthetic paper by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of blue pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30% by weight, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid printed over the entire surface to form a porous layer, and a water-discoloring sheet measuring 220 mm x 320 mm was obtained.
Next, a transparent substrate was prepared by forming three convex portions made of transparent ABS resin with a diameter of 10 mm and a height of 1.0 mm at positions corresponding to the vertices of an isosceles triangle on the underside of a plate-shaped molded article made of transparent rigid acrylonitrile resin, the upper surface of which had a thickness of 1.0 mm and dimensions of 200 mm x 300 mm and had fine irregularities and was non-glossy. Four rectangular letter frames were then formed on the upper surface of the plate-shaped molded article using black printing ink to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 78.5 ^mm2 , the height (h) of the convex portion was 1.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 78.5.
Furthermore, the surface area of the upper surface of the transparent cover member was 600 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 2.36 ^cm2 , and the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.39%.
A water-coloring body comprising the water-coloring sheet and the transparent cover member was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, a blue water-discoloring image was formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discolored image was formed on the water-discolored sheet by writing with a writing pen containing water, and the transparent cover member was placed on the water-discolored sheet on which the water-discolored image had been formed so that the tips of the convex portions were in contact with the surface of the water-discolored sheet.
The water-discolored image could be seen more clearly through the transparent cover member without light being reflected on the surface of the transparent cover member to hinder visibility, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, allowing the clear water-discolored image to be maintained.
Furthermore, when a photograph was taken indoors with the transparent cover member in place, the lighting fixture was not reflected in the photograph, and a clear image of the discolored water was captured.
Furthermore, since the transparent cover member is provided with a frame for the letters, it is possible to visually confirm whether the water-discolored image is properly formed within the frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Next, when the transparent cover member was removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and the sheet returned to its original state. This phenomenon could be repeated many times.
Furthermore, by combining the water-discoloring body with an erasable writing implement (whiteboard marker), it was possible to write on the surface of the transparent cover member with the whiteboard marker to point out and grade the unskilled areas of the water-discoloring image. Also, the marker marks could be easily removed by rubbing the surface of the transparent cover member with a dry cloth or whiteboard eraser.

Example 16
Preparation of Water-Discoloring Material A colored layer was formed on a support made of white synthetic paper by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of blue pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30 wt%, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid printed over the entire surface to form a porous layer, and three water-discoloring sheets each measuring 220 mm x 320 mm were obtained.
Next, a plate-shaped molded article made of transparent hard ABS resin with a thickness of 1.0 mm and dimensions of 200 mm x 300 mm was used as the transparent substrate. On the underside of the molded article, three convex portions made of transparent ABS resin with a diameter of 10 mm and a height of 1.0 mm and a curved tip were provided at positions corresponding to the vertices of an isosceles triangle. On the upper surface of the molded article, four rectangular letter frames were provided using black printing ink to obtain transparent cover members (2 sheets).
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 78.5 ^mm2 , the height (h) of the convex portion was 1.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 78.5.
Furthermore, the surface area of the upper surface of the transparent cover member was 600 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 2.36 ^cm2 , and the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.39%.
A water-coloring body comprising the water-coloring sheets (3 sheets) and the transparent cover members (2 sheets) was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, a blue water-discoloring image was formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discolored image was formed on the water-discolored sheet by writing with a writing pen containing water, and the transparent cover member was placed on the water-discolored sheet on which the water-discolored image had been formed so that the tips of the convex portions were in contact with the surface of the water-discolored sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, since the transparent cover member is provided with a frame for the letters, it is possible to visually confirm whether the water-discolored image is properly formed within the frame, and to confirm whether the water-discolored image is well-balanced.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Next, when the transparent cover member was removed from the water-discoloring sheet, the water-discoloring image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized and the sheet returned to its original state. This phenomenon could be repeated many times.
Furthermore, after removing the transparent cover member from the water-discoloring sheet, a water-discoloring image was formed on another water-discoloring sheet and the transparent cover member was placed on it before the sheet completely faded and returned to its original state, thereby enabling rapid image formation.

Example 17
Preparation of Water-Discoloring Material A colored layer was formed on a support consisting of white synthetic paper with a polyester nonwoven fabric provided thereon by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of black pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30% by weight, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid-printed over the entire surface to form a porous layer, and a water-discoloring sheet measuring 280 mm x 380 mm was obtained.
Next, a transparent polyester transparent sheet having a thickness of 50 μm and dimensions of 253 mm x 353 mm was used as a transparent substrate, and 48 convex portions made of white polyurethane resin, each 3 mm in diameter and 1.2 mm in height, and having a curved hemispherical tip, were arranged in a checkerboard pattern at equal intervals of 47 mm to obtain a transparent cover member.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 7.07 ^mm2 , the height (h) of the convex portion was 1.2 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 5.89.
Furthermore, the surface area of the upper surface of the transparent cover member was 893.09 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 3.39 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.38%, and the number of convex portions per 100 ^cm2 was 5.37.
Furthermore, a transparent substrate was prepared by forming a letter frame consisting of six rectangles on the underside of a polyester transparent sheet having a thickness of 50 μm, a size of 233 mm x 333 mm, and a top surface with fine irregularities, making it non-glossy and flexible, using black printing ink, to obtain a transparent frame sheet.
A water-coloring body comprising the water-coloring sheet, the transparent cover member, and the transparent frame sheet was obtained.

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was impregnated with water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, the water-discolored image can be seen more clearly through the transparent frame sheet without light being reflected on the surface of the transparent frame sheet, which would hinder visibility.In addition, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image has been properly formed within the character frame, and to confirm whether the water-discolored image has been formed in a well-balanced manner.
Furthermore, when a photograph was taken indoors with a transparent frame sheet placed on top, no light fixtures were reflected in the photograph, and a clear image of the discolored water could be captured.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discolored sheet, the water-discolored image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized, returning to a completely white water-discolored sheet. This phenomenon could be repeated many times.
Furthermore, since the transparent cover member and the transparent frame sheet are flexible, the water-discoloring body can be rolled up and carried around, and is therefore highly portable.

Example 18
Preparation of Water-Discoloring Material A colored layer was formed on a support consisting of white synthetic paper with a polyester nonwoven fabric provided thereon by screen printing using a 180-mesh screen stencil, using a screen printing ink prepared by uniformly mixing and stirring 5 parts of black pigment, 50 parts of acrylic ester emulsion (solid content 50% by weight), 0.2 parts of silicone-based antifoaming agent, 3 parts of thickener, 2 parts of wetting agent, 1 part of leveling agent, 10 parts of water, and 2.5 parts of epoxy-based crosslinking agent. Next, on the colored layer, 15 parts of particulate silicic acid produced by a wet method [trade name: Nipsil E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.], 50 parts of an aqueous urethane resin as a binder resin [trade name: Hydran AP-10, polyester-based urethane resin, solid content 30 wt%, manufactured by Dainippon Ink and Chemicals, Inc.], 30 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of an aqueous ink thickener, 1 part of ethylene glycol, and 2 parts of an epoxy-based crosslinking agent were uniformly mixed and stirred to form a white screen printing ink, which was then solid printed over the entire surface to form a porous layer, and three water-discoloring sheets measuring 280 mm x 380 mm were obtained.
Next, 48 convex portions made of white polyurethane resin, each 3 mm in diameter and 1.2 mm in height and with a curved hemispherical tip, were arranged in a checkerboard pattern at equal intervals of 47 mm on the underside of a flexible polyester transparent sheet 50 μm thick and 253 mm x 353 mm in size as a transparent substrate, to obtain transparent cover members (2 sheets).
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 7.07 ^mm2 , the height (h) of the convex portion was 1.2 mm, and the ratio of the surface area (s) of the convex portion to the height (h) of the convex portion was 5.89.
Furthermore, the surface area of the upper surface of the transparent cover member was 893.09 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 3.39 ^cm2 , the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.38%, and the number of convex portions per 100 ^cm2 was 5.37.
Furthermore, a flexible polyester transparent sheet having a thickness of 50 μm and dimensions of 233 mm x 333 mm was used as a transparent substrate, and six rectangular letter frames were printed on the underside of the sheet using black printing ink to obtain two transparent frame sheets.
A water-coloring body was obtained comprising the water-coloring sheets (3 sheets), the transparent cover members (2 sheets), and the transparent frame sheets (2 sheets).

The water-discolored sheet was normally white, but when writing was done on the porous layer with a writing brush whose tip was impregnated with water, black water-discolored images (letters) could be formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discoloring image was formed on the water-discoloring sheet by writing with a brush whose tip was dipped in water, and the transparent cover member was placed on the water-discoloring sheet on which the water-discoloring image had been formed so that the tip of the convex portion was in contact with the surface of the water-discoloring sheet.
The water-discolored image was clearly visible through the transparent cover member, and the convex portions prevented the transparent cover member from coming into contact with the water-discolored image, thereby enabling the water-discolored image to be maintained clearly.
Furthermore, the water discoloration image maintained the same shape as the water discoloration image immediately after writing even after being left to stand for 30 minutes in an environment of 25° C. and 65% RH.
Furthermore, when the transparent frame sheet is placed on the transparent cover member, since the transparent frame sheet has a character frame, it is possible to visually confirm whether the water-discolored image is properly formed within the character frame, and to confirm whether the water-discolored image is well-balanced.
Next, when the transparent frame sheet and transparent cover member were removed from the water-discolored sheet, the water-discolored image gradually disappeared as the water evaporated, and after 10 minutes the image was completely decolorized, returning to a completely white water-discolored sheet. This phenomenon could be repeated many times.
Furthermore, since the transparent cover member and the transparent frame sheet are flexible, the water-discoloring body can be rolled up and carried around, and is therefore highly portable.
Furthermore, after removing the transparent cover member and transparent frame sheet from the water-discoloring sheet, a water-discoloring image was formed on another water-discoloring sheet and the transparent cover member and transparent frame sheet were placed on top before the sheet completely faded and returned to its original state, allowing for rapid image formation.

Comparative Example 1
Preparation of Water-Colored Material A water -colored sheet was obtained in the same manner as in Example 1.
Next, a transparent cover member was obtained by providing two conical convex portions made of transparent ABS resin with a diameter of 10 mm and a height of 1.0 mm and a curved tip on the underside of a plate-shaped molded product made of transparent hard ABS resin with a thickness of 1.0 mm and a size of 200 mm x 300 mm as a transparent substrate.
The surface area (s) of the convex portion visible from the top surface of the transparent cover member was 78.5 ^mm2 , the height (h) of the convex portion was 1.0 mm, and the surface area (s) of the convex portion/height (h) of the convex portion was 78.5.
Furthermore, the surface area of the upper surface of the transparent cover member was 600 ^cm2 , the area occupied by the convex portions visible from the upper surface of the transparent cover member was 2.36 ^cm2 , and the ratio of the area occupied by the convex portions visible from the upper surface of the transparent cover member to the surface area of the upper surface of the transparent cover member was 0.39%.
A water-coloring body comprising the water-coloring sheet and the transparent cover member was obtained.

The water-discoloring sheet was normally white, but when a writing tool containing water was used to write on the porous layer, a blue water-discoloring image was formed.
The water-discolored image was maintained for 5 minutes in an environment of 25°C and 65% RH, but gradually disappeared as the water evaporated, and after 10 minutes the entire sheet returned to a white water-discolored sheet. This phenomenon could be repeated many times.
Next, a water-discolored image was formed on the water-discolored sheet by writing with a writing pen containing water, and the transparent cover member was placed on the water-discolored sheet on which the water-discolored image had been formed so that the tips of the convex portions were in contact with the surface of the water-discolored sheet.
The water-discolored image could be seen through the transparent cover member, but there were some areas where the transparent cover member and the water-discolored image came into contact with each other, causing bleeding of the water-discolored image.
Furthermore, when the water-discolored image is left in an environment of 25°C and 65% RH, differences arise in the distance between the transparent cover member and the water-discolored image, which results in differences in the time it takes for the water-discolored image to fade, making it impossible to maintain a uniform water-discolored image.

DESCRIPTION OF SYMBOLS 1 Water-color changing body 2 Water-color changing sheet 3 Support 4 Colored layer 5 Porous layer 6 Transparent cover member 7, 71 Transparent substrate 8 Convex portion 9 Letter frame 10 Transparent frame sheet 11 Void portion 12 Water-adhering tool 13 Water-color changing body set

Claims (11)

The water-discoloring sheet comprises a porous layer, formed on an upper layer of a colored layer, in which a low-refractive index pigment is dispersed and fixed in a binder resin; and a transparent cover member that covers the water-discoloring image formed on the surface of the porous layer by the adhesion of water, thereby inhibiting the drying of the water and delaying the disappearance of the water-discoloring image. The underside of the transparent cover member has at least three or more dot-like protrusions that contact the water-discoloring sheet surface and maintain the water-discoloring sheet surface in a non-linear arrangement, and the protrusions have a height of 0.4 mm to 12.0 mm. The surface area (s) of the protrusions visible from the top surface of the transparent cover member and the height (h) of the protrusions satisfy the following formula (1): the surface area (s) of the protrusions visible from the top surface of the transparent cover member and the height (h) of the protrusions occupy 10% or less of the surface area of the top surface of the transparent cover member. The transparent cover member is provided with character frames for the characters to be formed on the water- discoloring sheet .
1.0≦s/h≦400 (1) The water-discoloring body comprises a water-discoloring sheet provided with a porous layer on top of a colored layer, in which a low-refractive index pigment is dispersed and fixed in a binder resin; a transparent cover member that covers the water-discoloring image formed on the surface of the porous layer by the adhesion of water, thereby suppressing the drying of the water and delaying the disappearance of the water-discoloring image; and a transparent frame sheet provided with character frames for characters to be formed on the water -discoloring sheet . The underside of the transparent cover member has at least three or more dot-like protrusions that contact the surface of the water-discoloring sheet and are arranged in a non-linear manner, maintaining the surface of the water-discoloring sheet and the transparent cover member in a non-contact state. The protrusions have a height of 0.4 mm to 12.0 mm, and the surface area (s) of the protrusions as viewed from the top surface of the transparent cover member and the height (h) of the protrusions satisfy the following formula (1), and the area occupied by the protrusions as viewed from the top surface of the transparent cover member is 10% or less of the surface area of the top surface of the transparent cover member .
1.0≦s/h≦400 (1) 3. The water-chromatic body according to claim 1, wherein the convex portions are transparent. 3. The water-chromatic body according to claim 1, wherein the convex portions are white. The water-chromatic body according to any one of claims 1 to 4, wherein the tips of the convex portions are curved. The transparent cover member is flexible, and the protrusion is 100 cm ² The hydrochromic body according to any one of claims 1 to 5, having three or more per molecule. 7. The water-coloring body according to claim 1, wherein the transparent cover member has one end attached to the water-coloring sheet and the other end left as a free end, and is provided on the water-coloring sheet so as to be openable and closable. The water-coloring object according to any one of claims 1 to 7, comprising a plurality of the water-coloring sheets and a plurality of the transparent cover members. 3. The water-coloring body according to claim 2, comprising a plurality of said water-coloring sheets, a plurality of said transparent cover members, and a plurality of said transparent frame sheets. 3. The hydrochromic material according to claim 1, wherein the dot-like protrusions are arranged in a grid pattern. A water-chromatic object set comprising the water-chromatic object according to any one of claims 1 to 10 and a water-attaching tool for forming a water-chromatic image.