JP5356975B2 - Water discoloration sheet and method for producing the same - Google Patents

Description

  The present invention relates to a water color-changing sheet using a water-containing color-changing pigment that is opaque in a dry state but transparent in a water-containing state, and a method for producing the same.

  Conventionally, a toy using a water discolorable sheet having a discoloration layer containing such a water-containing discoloration pigment has been provided by using a compound that is opaque in a dry state but changes transparently when it contains water (water discoloration discoloration pigment). Yes. This toy consists of the water discoloring sheet and an applicator in the form of a writing instrument that can cause a pen tip or the like to absorb a liquid such as water, and the surface of the water discoloring sheet can be written with the applicator. When drawing, the water-containing part of the surface of the water-coloring sheet is changed in color tone until it dries, so that writing and drawing can be enjoyed.

  As the color changing layer containing the water-containing color changing pigment of such a water color changing sheet, for example, in Patent Document 1, a low refractive index pigment, in particular, fine particle silicic acid (wet method fine particle silicic acid) produced by a wet method is dispersed in a binder resin. A porous layer fixed in a state is disclosed.

JP 2001-104661 A

  However, for example, when the wet method fine particle silicic acid used in Patent Document 1 is used as the water-containing discoloration pigment, the dispersibility in water is poor, so that an amount necessary for producing an appropriate color difference is blended. Requires a dispersant such as a styrene acrylic copolymer, which has been a factor in increasing costs.

Furthermore, wet method fine particle silicic acid has a mesopore structure with a relatively large pore volume forming a porous material, and the wet method fine particle silicic acid having an average particle diameter of 4.5 to 100 μm generally has a BET specific surface area value. In particular, it is about 190 to 700 m ² / g. For this reason, when a colored component such as a colored pigment is further added to the porous layer (discolored layer), the colored component that is present in the vicinity of the pores is taken in, so the colored component may not be fixed by the binder. . For this reason, the coloring component which is not fixed in the water-containing state flows out. As a result, the floor on which the water discoloring sheet is laid becomes a factor, and the color of the porous layer (discoloring layer) gradually becomes light. There was a problem in durability as a product.

  As a means for solving the above-mentioned problems, the water color-changing sheet of the present invention has the most important feature that boehmite is used as a pigment (water-containing color-changing pigment) used in a color-changing layer that changes in color shade when water is contained. To do.

  That is, the present invention provides a water discoloration sheet that changes color when it contains water, comprising at least a discoloration layer in which a water discoloration pigment is fixed in a dispersed state with a binder, and a support that supports the discoloration layer. A water discolorable sheet characterized by containing boehmite as a pigment.

  Furthermore, the water color-changing sheet having the above characteristics can be a water color-changing sheet in which a colorant layer containing a colored colorant is provided between the support and the color-change layer. Further, a colored pigment can be further added to the color changing layer, or the resin component of the binder of the color changing layer can be dyed with a colored dye.

  According to the water discolorable sheet of the present invention, the use of boehmite as the water-containing color-changing pigment of the color-changing layer makes it possible to sufficiently change the color tone between the dry state and the water-containing state, that is, the color difference (ΔE). Furthermore, since boehmite has a good dispersibility in water, even when a high concentration of a water-containing discoloration pigment is blended, a special dispersant can be dispensed with. Thereby, effective cost reduction is achieved.

  In addition to boehmite as a water-containing discoloration pigment in the discoloration layer, by adding calcium carbonate as a secondary component, the ink for producing the discoloration layer (white base) is given spinnability. In addition, since the continuous printability is improved, it is possible to obtain a water discolorable sheet having a smooth surface while improving mass productivity. In addition, by using calcium carbonate, which is an inexpensive material, in a blending ratio within a predetermined range, it is possible to reduce the cost as a whole without deteriorating the color difference ΔE as the water discoloring sheet.

  Further, by using crystalline boehmite or non-porous calcium carbonate as the water-containing color changing pigment of the color changing layer, even when a color pigment is further mixed in the color changing layer, the color pigment is firmly fixed by the binder, Colored pigments hardly flow out when containing water. Since such a configuration has become practical, color variations can be imparted to the surface of a water-changing sheet that was only white when the surface was dry.

[Configuration overview]
The water discolorable sheet of the present invention is a discoloration in which a water-containing discoloration pigment containing boehmite (usually in particulate form) or a water-containing discoloration pigment containing boehmite and calcium carbonate is fixed to a binder resin in a dispersed state on a support. Constructed by providing layers. Moreover, the structure which provides the coloring agent layer containing a coloring component between the said support body and the said discoloration layer may be sufficient. Moreover, you may further provide the mixed layer mentioned later between the said colorant layer and the said discoloration layer. Alternatively, a color pigment other than white may be blended in the discoloration layer to give a color variation. The fact that the configuration can be realized is also an advantage of the present invention. Moreover, it can also be set as the structure which dye | stained the binder of the said color-change layer with colored dyes other than white, and provided the color variation to this color-change layer.

(Water-containing discoloration pigment)
The water-containing discoloration pigment referred to in the present invention is a pigment whose color tone changes between a dry state and a water-containing state. Generally, it is a concealing white color in a dry state and changes in transparency in a water-containing state. In the present invention, boehmite is used as an essential component as a water-containing discoloration pigment. Examples of water-containing discoloration pigments other than boehmite include silicic acid such as the above-mentioned wet method fine particle silicic acid, aluminum silicate, aluminum oxide, calcium carbonate and the like. In the water discolorable sheet of the present invention, it is preferable that the water-containing color changing pigment is composed only of boehmite. However, a water-containing color changing pigment other than boehmite is used with boehmite as a main component (50% by weight or more based on the total water-containing color changing pigment). It can also be mixed and used as a secondary component. In particular, when boehmite was used as a main component as a water-containing discoloration pigment, it was found that compatibility with calcium carbonate was particularly good as a secondary component.

[Boehmite]
Boehmite used in the present invention is a kind of natural mineral contained in bauxite and is also called boehmite. The composition formula (structural formula) is represented by Al ₂ O ₃ .H ₂ O or γ-AlOOH. In this respect, the composition is different from that of aluminum hydroxide represented by Al ₂ O ₃ .3H ₂ O or Al (OH) ₃ .

The specific surface area of boehmite used in the present invention is not particularly limited, but it is preferably 0.5 to 100 m ² / g in terms of BET value. If the BET value is larger or smaller than this range, the color difference (ΔE) between the dry state and the water-containing state tends to be small, which is not preferable. The bulk density of boehmite is not particularly limited, but is preferably 0.1 to 0.5 g / cm ³ .

  The boehmite used in the water discoloring sheet of the present invention can be obtained from commercially available boehmite powder series manufactured by Daimei Kogyo Co., Ltd., or Cerasur series manufactured by Kawai Lime Industry.

[Calcium carbonate]
As the water-containing discoloration pigment dispersed and fixed in the discoloration layer, calcium carbonate is preferably used as a secondary component together with boehmite as a main component. When calcium carbonate is used alone as a water-containing discoloration pigment, the color difference ΔE between the water-containing state and the dry state is small, and a practical water-discoloring sheet cannot be obtained. However, it has been found that when boehmite is the main component and calcium carbonate is used as a secondary component, the excellent color change of boehmite is hardly inhibited. Moreover, since calcium carbonate is an inexpensive material, by using it in a blending ratio within a predetermined range, it is possible to reduce the cost while maintaining the performance as a water discoloring sheet.

[Coloring ingredients]
In the present invention, when a discoloration layer or a colorant layer or mixed layer described later is provided, these layers are colored with a coloring component such as a colored pigment / colored dye (a pigment or dye having a color other than white). You can also. As the colored coloring component, various kinds such as known dyes and pigments are used without limitation. For example, blue product name “POLYMO NAVY BLYE NT-231 ECO” (manufactured by Kiwa Chemical Industry Co., Ltd.), green product name “Ryudye-w Green F2G” (manufactured by Dainippon Ink & Chemicals, Inc.), fluorescent color The product name “Lumikol” series (manufactured by Nippon Fluorescent Chemical Co., Ltd.) can be mentioned. In a mode in which a colorant is added to the color changing layer, when a colored pigment is used as the colorant, it can be fixed in a dispersed state using the following binder together with the water-containing color changing pigment. On the other hand, when a colored dye is used as the colorant, the resin component of the following binder can be dyed in advance.

〔binder〕
As the binder used in the present invention, a resin emulsion capable of fixing the water-containing color changing pigment or a colored pigment as a coloring component therewith in a dispersed state can be suitably used. Specifically, urethane resin, nylon resin, vinyl acetate resin, acrylic ester resin, acrylic ester copolymer resin, acrylic polyol resin, vinyl chloride-vinyl acetate copolymer resin, maleic resin, polyester resin, styrene resin Styrene copolymer resin, polyethylene resin, polycarbonate resin, epoxy resin, styrene-butadiene copolymer resin, acrylonitrile-butadiene copolymer resin, methyl methacrylate-butadiene copolymer resin, butadiene resin, chloroprene resin, melamine resin, and each of the above Examples include resin emulsions, caseins, starches, cellulose derivatives, polyvinyl alcohol, urea resins, and phenol resins.

  In particular, it has been found that acrylic resins or acrylic-vinyl acetate resin emulsions have good dispersibility with the boehmite or boehmite + calcium carbonate system and can be suitably used. Specifically, the product name “Movinyl DM772” manufactured by Nippon Synthetic Chemical Industry Co., Ltd. and the product name “PRIMAL” series manufactured by Rohm and Haas can be mentioned.

  Further, a curing agent can be added to the resin emulsion.

  The preferred concentration of the resin emulsion used for the binder depends on the properties of the dispersed particles to be dispersed, that is, the water-containing discolored pigment and the colored pigment, but the resin emulsion solid content concentration is 2.25 to 36% by weight. It is more preferable that the content be 4.5 to 27% by weight. When the solid content concentration of the resin emulsion is less than 2.25% by weight, the dispersed particles are settled and the fixing property is deteriorated. On the other hand, when the resin emulsion solid content concentration exceeds 36% by weight, the printability is poor when the color change layer is laminated on the support by printing.

[Lamination method]
Examples of means for forming a discoloration layer or a colorant layer and a discoloration layer thereon on the support include screen printing such as silk printing, offset printing, gravure printing, coater, tampo printing, and transfer. Known means such as printing means, brush coating, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, and dip coating can be appropriately used.

[Ink for production]
In the above printing, in order to produce a discolored layer or the like by the above printing, it is required to impart spinnability to the producing ink. The spinnability is a property related to the stickiness of the ink. If the ink has insufficient spinnability, the ink is not easily applied to the base, it is easy to repel, and a printed surface with unevenness like a mottled pattern tends to be formed. In the present invention, a viscosity modifier is further added in order to impart moderate spinnability to the preparation ink, and the total of solid components contained in the preparation ink is 35% by weight or more based on the total amount of the preparation ink. It is preferable that

[Viscosity modifier]
In the present invention using boehmite as the water-containing discoloration pigment, it has been found that a polyurethane-based viscosity modifier is preferable as the viscosity modifier. Specific examples of the polyurethane-based viscosity modifier include “RM-2020NPR” in the product name “ADEKA NOL UH” series manufactured by ADEKA Corporation, and the product name “PRIMAL” series manufactured by Rohm and Haas. “RM-5000”, “RM-6000”, “RM-7”, “RM-5”, trade name “BERMODOLPUR” series manufactured by Akzo Nobel, and the like can be mentioned. Of these, the “Adecanol UH” series is the most suitable.

  The content of the viscosity modifier is not particularly limited, but is preferably 0.5 to 30% by weight (solid content concentration of 0.2 to 10% by weight) with respect to the total amount of ink for preparation, % By weight (solid content concentration of 0.3 to 7% by weight) is more preferable. If the solid content concentration of the viscosity modifier is less than 0.2% by weight, the effect of imparting spinnability by the viscosity modifier hardly appears. On the other hand, when the solid content concentration exceeds 10% by weight, the fluidity of the ink for preparation is lost, and printing becomes difficult.

[Ratio of solid components]
In the ink for preparation, a solid component is contained in a binder, a viscosity modifier, and the like as well as a water-containing discoloration pigment as a component thereof. A solid component is a component which remains after completely removing water and other solvent components. In the present invention, the total of the solid components contained in the preparation ink is preferably 35% by weight or more based on the total amount of the preparation ink. This is because when the total of the solid components is less than 35% by weight, it becomes difficult to impart appropriate spinnability to the ink for preparation, and printing unevenness is likely to occur on the coated surface (discolored layer surface). Furthermore, the total of the solid components contained in the preparation ink is more preferably less than 60% by weight with respect to the total amount of the preparation ink. This is because if the total of the solid components exceeds 60% by weight, plate clogging is likely to occur in the printing mesh and the defect rate increases.

[Discoloration layer]
The coating amount for forming the color changing layer in the present invention depends on the material of the support on which it is applied, and is not particularly limited. However, it is suitable depending on whether the colored layer is mixed with a colored component, or the colored layer is not mixed with the colored layer and a separate colorant layer is provided or the support itself is colored. The amount of application varies. First, in a mode in which a colored component is not blended in the discoloration layer, the coating amount is preferably 5 to 50 g / m ² . If the coating amount exceeds 50 g / m ² , the color of the lower colorant layer or the colored support becomes difficult to see even in a water-containing state, and the change when water is applied becomes difficult to understand. A more preferable coating amount is 10 to 20 g / m ² . In the examples of the present specification, a coating solution for preparing a discolored layer (preparation ink) to which a colored colorant is not added may be referred to as a white base.

Moreover, in the aspect which mix | blends a colored coloring component with a discoloration layer with the water discoloration sheet | seat of this invention, the color difference ((DELTA) E) when water-containing becomes large, so that the thickness of this coloring layer is thickened. The coating amount for forming the discoloration layer containing the colorant is not particularly limited, but it is preferably 5 g / m ² or more, more preferably 20 g / m ² or more, in order to clarify the change in shading. is there. When the coating amount is less than 5 g / m ² , not only the difference in color tone is reduced, but the underlying support may be transparent from the surface. On the other hand, if the coating amount is too large, it becomes difficult to form a discolored layer by a simple method such as silk printing, and therefore it is 200 g / m ² or less, more preferably 100 g / m ² or less. The most preferable coating amount is 30 to 50 g / m ² .

  The discoloration layer is usually provided as the outermost surface layer of the water discoloration sheet, but a transparent coating protective layer that allows water to pass therethrough can be further provided as the outermost surface.

(Colorant layer)
In the case where the colored layer is not added to the color changing layer in the water color changing sheet of the present invention, it is preferable to provide a colorant layer between the color changing layer and the support. The colorant layer can be formed by dispersing a colored component such as a colored pigment with the binder, or the resin component of the binder can be dyed with a colored dye. Alternatively, it can be formed using an ink containing a vehicle. The coating amount when forming the colorant layer is not particularly limited as long as it does not impair the flexibility of the water discoloring sheet.

(Mixed layer)
In the water discolorable sheet of the present invention, in the configuration in which the colorant layer and the color change layer are provided, a mixed layer can be further provided between the colorant layer and the color change layer. That is, (back surface) support / colorant layer / mixed layer / discolored layer (front surface) containing no colored coloring component can also be used. The mixed layer includes a colored coloring component and a water-containing color changing pigment dispersed and fixed by a binder. When the colored coloring component is a colored pigment, it can be dispersed and fixed by the binder together with the water-containing discolored pigment, and when the colored coloring component is a colored dye, the resin component of the binder can be dyed. The blending ratio of the coloring component contained in the mixed layer is smaller than the blending ratio of the coloring component contained in the colorant layer, and the blending ratio of the water-containing color changing pigment contained in the mixing layer is that of the water-containing color changing pigment contained in the color changing layer. It is effective to make it smaller than the blending ratio.

  Further, the mixed layer may be a plurality of layers. In this case, it is preferable to increase the blending ratio of the colored coloring component in the mixed layer closer to the colorant layer and to increase the blending ratio of the water-containing discoloration pigment in the mixed layer closer to the color changing layer. When the mixed layer is provided, the preferable coating range is preferably such that the total coating amount of the thickness of the color changing layer and the mixed layer is within the range of the preferable coating amount of the color changing layer when the above-described colored coloring component is not blended. . Such a mixed layer can be produced by the same method as the above-described method of laminating the color changing layer and the colorant layer.

[Other ingredients]
In addition to the components described above, the discoloration layer, the colorant layer, and the mixed layer may include a surfactant, a wetting agent, a moisturizing agent, a film forming aid, an antiseptic, an antifoaming agent, a water retaining agent, and a plasticizer, respectively. Agents, thickeners and the like can be added as appropriate. The present invention is characterized by the use of boehmite which is excellent in water dispersibility without adding a dispersant, but this does not prohibit the incorporation of the dispersant into the discoloration layer.

[Support]
The water discolorable sheet support of the present invention is not particularly limited as long as a discoloration layer or the like can be laminated on the surface thereof by a method such as printing, but a woven fabric such as polyester, a knitted fabric, a nonwoven fabric, silk, etc. In addition to these fabrics, paper materials subjected to water resistance treatment can be suitably used. In the present invention, the colored layer is not included in the discoloration layer, and the support itself is colored with the colored component without providing the colorant layer, or a support having a color other than white can be used. .

[Water impervious sheet]
Further, a water impervious sheet made of a flexible material that does not allow water to permeate, such as a polyolefin-based resin or a softened plastic such as ethylene vinyl acetate resin, on the back surface (the surface opposite to the color changing layer side) of the support. May be attached or laminated. By providing such a water-impermeable sheet, even when the water-coloring sheet of the present invention is laid on a floor or the like, the floor will not be soiled with written water.

(Color difference evaluation)
About the water-color-change sheet | seat of each application quantity obtained by each following Example and the comparative example, the color tone change was evaluated by the color difference ((DELTA) E) of a surface dry state and a water-containing state. The CIE1978 (L ^* a ^* b ^* ) color system defined by JIS Z8729 was used for the measurement of the color difference. Note that L ^* indicates the brightness (brightness) of the color, and the chromaticness index a ^* b ^* indicates the saturation. As the color difference measuring device, a micro color difference meter “CR-241” (manufactured by Konica Minolta Sensing Co., Ltd.) was used. The measurement procedure is as follows.
1. Adjust the viewfinder diopter of the microscope.
2. The measurement diameter is set to 1.8 mm.
3. In the color specification mode Lab, calibration is performed with a white calibration plate.
4). Confirm the position without dirt and measure (L ^* a ^* b ^* ) on the surface of the water discolorable sheet in a dry state. This is defined as (L ₁ a ₁ b ₁ ).
5. Write a line with a width of about 2.0 mm with a pen containing water (apply water), and measure the (L ^* a ^* b ^* ) on the surface of the water-changing sheet before the surface is dry (within 5 seconds). To do. This is defined as (L ₂ a ₂ b ₂ ).
6). The color difference ΔE is obtained from the obtained measured value by the following formula [Equation 1].

[Colored pigment runoff evaluation]
About the example (Example 7, Comparative Examples 9 and 10) which added the colored pigment to the discoloration layer, the colored pigment outflow evaluation was performed in the following procedure. First, filter paper is placed on the surface of the discolored layer, and the filter paper is moved 5 cm while rubbing with a load of 1 kg applied to the filter paper. The following evaluation is performed according to the coloring state of the filter paper after the test.
○: Coloring on the filter paper is not observed. Or it is so slight that there is no practical problem.
X: Coloring on the filter paper is clearly observed.

[Evaluation of stringiness]
For Examples 8 to 13, the spinnability was evaluated. First, the obtained white base was filled in a container having a depth of 1.2 cm or more to a certain extent, and then the upper surface of the filled container was flattened with a painting knife. Next, above the container, a glass rod having a diameter of 5 mm is set in a bending strength tensile tester “STA-1150” (manufactured by Orientec). When a glass rod is inserted 1 cm into the filled white base and then pulled up at 500 mm / min., The white base attached to the bottom of the glass rod grows as the glass rod is pulled up. When the glass rod is further lifted, the stretched white base is torn off. The distance H to the position of the bottom surface of the glass rod when the white base was torn off was measured on the basis of the position when the bottom surface of the glass rod was in contact with the white base to evaluate the spinnability.

[Printability evaluation]
The obtained white base was printed on a substrate with a 120 mesh and a squeegee at an angle of 65 °, and the printability was evaluated according to the following criteria.

(A. Number of surface spots)
The printed surface (discolored layer surface) was observed, and the number of spots found visually was counted.

(B. Plate jam)
◯: No plate clogging occurs in any of the five printings.
(Triangle | delta): Plate printing may be clogged several times among 5 times of printing, and printing may not be performed.
X: Clogging occurred every time out of 5 printings, and printing was not possible.

[Examples 1 to 5, Comparative Example 1]
A wetting agent, preservative, antifoaming agent, moisturizing agent, viscosity modifier, and leveling agent are mixed with a dissolver in the amount shown in Table 1, and then a resin emulsion and a thickener are added in the amount shown in Table 1. In addition, the base liquid was prepared by applying to a three-roll mill. To this base solution, a water-containing discoloration pigment (boehmite, calcium carbonate) was added in the amount shown in Table 1 applied to a roll and stirred to prepare a white base. This white base was applied by a screen printing method of 100 mesh at a coating amount of 15 g / m ² using a light blue synthetic paper “OPA (registered trademark) MDP” (manufactured by Nippon Paper Industries Co., Ltd.) coated with acrylic varnish. The membrane was dried at room temperature for 1 day to obtain water discoloring sheets of Examples 1 to 5 and Comparative Example 1.

  The obtained water discolorable sheets of Examples 1 to 5 and Comparative Example 1 were subjected to color difference (ΔE) evaluation by the above method. The results are shown in Table 1.

[Comparative Examples 2 and 3]
Compounds other than boehmite and calcium carbonate were used as water-containing discoloration pigments. In Comparative Example 2, silicic acid was used as the water-containing color-changing material, and in Comparative Example 3, aluminum silicate was used as the water-coloring material. A wetting agent, preservative, antifoaming agent, moisturizing agent, viscosity modifier, and leveling agent are mixed with a dissolver in the amount shown in Table 2, and then a resin emulsion and a thickener are added in the amount shown in Table 2. In addition, the base liquid was prepared by applying to a three-roll mill. To this base solution, a water-containing discoloration pigment was added in the amount shown in Table 2 applied to a roll and stirred to prepare a white base. An attempt was made to apply this white base by a screen printing method of 100 mesh at a coating amount of 15 g / m ² using a light blue synthetic paper “OPA (registered trademark) MDP” (manufactured by Nippon Paper Industries Co., Ltd.) coated with acrylic varnish. However, since the white base was gelled, printing could not be performed.

[Comparative Examples 4 and 5]
Since Comparative Examples 2 and 3 could not be produced due to white-based gelation, Comparative Examples 4 and 5 were prepared by reducing the amount of the water-containing color changing material used in Comparative Examples 2 and 3. In Comparative Example 4, silicic acid was used as the water-containing color changing material, and in Comparative Example 5, aluminum silicate was used as the water color changing material. In other respects, the water-discoloring sheets of Comparative Examples 4 and 5 were obtained in the same manner as in the amounts shown in Table 2, Examples 1 to 5 and Comparative Example 1.

  The water color changing sheets of Comparative Examples 4 and 5 were evaluated for color difference (ΔE) by the above method. The results are shown in Table 2. It can be seen that the water color-changing sheets of Comparative Examples 3 and 4 have a small color difference (ΔE) and a small change in color tone between the dry state and the water-containing state as compared with the water-coloring sheet of Examples.

[Comparative Examples 6-8]
Since Comparative Examples 1 and 2 could not be produced due to white-based gelation, Comparative Examples 6 and 7 were obtained by further adding a dispersant. The dispersant was added together with a wetting agent, preservative, antifoaming agent, humectant, viscosity modifier, and leveling agent, and stirred and mixed with a dissolver. In Comparative Example 6, silicic acid was used as the water-containing color-changing material, and in Comparative Example 7, aluminum silicate was used as the water-coloring material. Further, a system using aluminum oxide as a water-containing color changing material was set as Comparative Example 8. Others were the compounding amounts shown in Table 2, and water discolorable sheets of Comparative Examples 6 to 8 were obtained in the same procedure as in Examples 1 to 5 and Comparative Example 1.

  The water color changing sheets of Comparative Examples 6 to 8 were evaluated for color difference (ΔE) by the above method. The results are shown in Table 2. The color difference (ΔE) of the water-changing sheets of Comparative Examples 6 and 7 is about the same as that of the Example (Comparative Example 7) or slightly inferior (Comparative Example 6), but styrene acrylic copolymer is used as a dispersant. As a result, the cost was high. It can be seen that the water discolorable sheet of Comparative Example 8 has a small color difference (ΔE) and a small color change between the dry state and the water-containing state.

Example 6
A wetting agent, preservative, antifoaming agent, moisturizing agent, viscosity modifier, and leveling agent are mixed with a dissolver in the amount shown in Table 3, and then a resin emulsion and a thickener are added in the amount shown in Table 3. In addition, the base liquid was prepared by applying to a three-roll mill. To this base solution, a water-containing discoloration pigment (boehmite, calcium carbonate) was added in the amount shown in Table 3 applied to a roll and stirred to prepare a white base. On the other hand, a colorant layer containing a colored pigment was provided on the surface of a white polyester fabric as a support by a screen printing method. The white base was applied on the colorant at a coating amount of 15 g / m ² by a 100-mesh screen printing method, and the coating film was dried at room temperature for 1 day to obtain a water discoloring sheet of Example 6. The obtained water discolorable sheet was subjected to color difference (ΔE) evaluation by the above method. The results are shown in Table 3.

[Example 7, Comparative Examples 9 and 10]
A wetting agent, preservative, antifoaming agent, moisturizing agent, viscosity modifier, and leveling agent are mixed with a dissolver in the amount shown in Table 3, and then a resin emulsion and a thickener are added in the amount shown in Table 3. In addition, the base liquid was prepared by applying to a three-roll mill. To this base solution, the water-containing discolored pigment and the colored pigment were added in the amounts shown in Table 3 applied to a roll and stirred to prepare a white base. The white base was applied by a screen printing method of 100 mesh at a coating amount of 15 g / m ² using a white polyester fabric as a support, and the coating film was dried at room temperature for 1 day. Example 7, Comparative Example 9, Ten water discoloring sheets were obtained.

  The water discoloring sheets of Example 7 and Comparative Examples 9 and 10 were evaluated for color difference (ΔE) by the above method, and color pigment outflow evaluation was also performed. The results are shown in Table 3. In Comparative Example 9 in which silicic acid was used as the water-containing discoloration pigment, the outflow of the colored pigment was clearly generated, so that it was found that the durability due to use was lacking.

[Examples 8 to 14]
The wetting agent, preservative, antifoaming agent, moisturizing agent, viscosity modifier, and leveling agent are mixed with a dissolver in the amount shown in Table 4, and then the resin emulsion and thickener are added in the amount shown in Table 3. In addition, the base liquid was prepared by applying to a three-roll mill. To this base solution, the water-containing discoloration pigment was added in the amount shown in Table 4 applied to a roll and stirred to obtain white bases of Examples 8 to 14.

  In Example 11 in which the blending ratio of the viscosity modifier is small and Example 13 in which the solid content ratio of the resin emulsion is small, the spinnability is insufficient and there is no plate clogging during printing, but there are many spots on the coated surface. It was apparent that printing unevenness occurred on the surface of the discolored layer. In Example 12 in which the viscosity modifier was excessively blended and Example 14 in which the resin emulsion had a large solid content ratio, the spinnability was sufficient and the properties of the printed discoloration layer were good. Clogging may occur and the defect rate increased.

  The water-color-changing sheet of the present invention can be used in applications such as toys as a drawing sheet that can be used repeatedly, together with an applicator in the form of a writing instrument that allows a pen tip or the like to absorb a liquid such as water. Since the liquid used for writing is water, such a toy has little dirt after use as compared to a drawing sheet using colored ink or the like, and is particularly suitable as a toy for infants.

Claims (12)

In the water discolorable sheet comprising at least a discoloration layer in which a water-containing discoloration pigment is fixed in a dispersed state with a binder, and a support that supports the discoloration layer,
A water color-changing sheet comprising boehmite as the water-containing color changing pigment.   The water color-changing sheet according to claim 1, wherein the water-containing color changing pigment of the color changing layer comprises boehmite.   The water color-changing sheet according to claim 1, wherein the color-changing layer further contains calcium carbonate as a water-containing color changing pigment. The water discoloration sheet according to any one of claims 1 to 3, wherein the boehmite has a BET value of 0.5 to 100 m ² / g. The water color-changing sheet according to any one of claims 1 to ³ , wherein the boehmite has a bulk density of 0.1 to 0.5 g / cm ³ .   The water discoloring sheet according to claim 1, wherein the discoloring layer further contains a colored pigment.   The water discolorable sheet according to any one of claims 1 to 6, wherein the resin component of the binder of the discoloration layer is colored with a colored dye.   The water color-changing sheet according to any one of claims 1 to 6, wherein a colorant layer containing a colored component is provided between the support and the color-changing layer.   Provided between the color changing layer and the colorant layer is a mixed layer in which a water-containing color changing pigment is fixed in a dispersed state together with a colored coloring component, and the mixing ratio of the water-containing color changing pigment contained in the mixed layer is The water discolorable sheet according to claim 8, wherein the blending ratio of the coloring component is smaller than the blending ratio in the color changing layer and the blending ratio of the coloring component is smaller than the blending ratio in the colorant layer.   The water discoloration sheet according to any one of claims 1 to 9, wherein the discoloration layer further contains a polyurethane viscosity modifier as a viscosity modifier. The water discolorable sheet according to claim 10, comprising a step of forming the discolored layer by printing using a preparation ink containing boehmite, a binder, a polyurethane viscosity modifier, and water as a water-containing discoloration pigment. A method,
A method for producing a water discolorable sheet, wherein the solid content in the preparation ink is 35% by weight or more based on the total amount of the preparation ink.   The method for producing a water discolorable sheet according to claim 11, wherein the solid content in the preparation ink is 60% by weight or less based on the total amount of the preparation ink.