JP5524751B2 - Water discoloration sheet - Google Patents

Description

The present invention is opaque in the dry state relates to water-discoloring sheet using water discoloration pigment changes transparent hydrous state.

  Conventionally, a drawing sheet or a sheet using a water-coloring sheet having a color-changing layer containing a water-containing color-changing pigment using a compound (water-colored color-changing pigment) that is opaque in a dry state but changes transparently when water is contained. Toys such as drawing boards are provided. This toy consists of the water discoloring sheet and an applicator in the form of a writing instrument in which, for example, a pen tip is filled with a liquid such as water, and when the surface of the water discoloring sheet is written or drawn with the applicator, Until the water-containing portion of the surface of the water-coloring sheet is dried, the color tone is changed, so that writing or 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. However, the wet process fine particulate silicic acid is expensive as a material, and therefore has been a factor of high cost. On the other hand, calcium carbonate has been known as an inexpensive water-containing discoloration pigment (for example, Patent Document 2).

  However, although calcium carbonate is a water-containing discoloration pigment, since the color difference ΔE between the liquid absorption state and the dry state is not so large, calcium carbonate has not been used as an actual product.

JP 2001-104661 A

Japanese Utility Model Publication No. 49-130913

  Accordingly, an object of the present invention is to provide a water discolorable sheet having a sufficiently large color difference ΔE between the liquid absorption state and the dry state even when inexpensive calcium carbonate is used as the main component as the water-containing discoloration pigment.

  With respect to the above problems, the present inventors have incorporated a predetermined amount of boehmite in addition to calcium carbonate as a pigment (water-containing discoloration pigment) used in a discoloration layer that changes in color shade when water is contained, thereby absorbing liquid. The present inventors have found that the color difference ΔE between the state and the dry state is improved, and have reached the present invention.

  That is, in the water discolorable sheet of the present invention, the water discolorable sheet comprising at least a discoloration layer in which a water discolorable pigment is fixed in a dispersed state with a binder, and a support that supports the discoloration layer, The main feature is that it contains calcium carbonate and boehmite, and the blending ratio of the calcium carbonate is 50 wt% or more and 95 wt% or less with respect to the total amount of the water-containing discoloration pigment.

  Furthermore, the blending ratio of the boehmite is 5% by weight or more and less than 50% by weight with respect to the total amount of the water-containing discoloration pigment. It is preferable to contain the following urea.

  According to the water-discoloring sheet of the present invention, calcium carbonate is the main component as the water-containing color-changing pigment of the color-changing layer, and boehmite is used as a secondary component, so that the water-containing color-changing pigment is calcium carbonate alone. Thus, it was found that the color difference ΔE between the liquid absorption state and the dry state of the discolored layer becomes large.

  In addition, according to the water discoloring sheet of the present invention, effective cost reduction can be achieved while maintaining other performances such as wear resistance.

[Configuration overview]
The water color-changing sheet of the present invention is constituted by providing a color-changing layer on which a water-containing color-changing pigment containing calcium carbonate as a main component and boehmite as a secondary component is fixed to a binder resin in a dispersed state on a support. Is done. A water impervious body may be provided on the back surface of the support. Moreover, in order to make the change at the time of water containing clear, the said discoloration layer or the said support body can also be colored, and the coloring material layer containing a coloring agent may be provided between the said discoloration layer and the said support body. .

(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. Examples of the water-containing color changing pigment include silicic acid, aluminum silicate, aluminum oxide, magnesium carbonate, calcium carbonate, boehmite and the like. In the present invention, calcium carbonate and boehmite are particularly used as the essential components as the water-containing discoloration pigment.

[Calcium carbonate]
In the present invention, the water-containing color-changing pigment dispersed and fixed to the color-changing layer uses calcium carbonate, which is an inexpensive material, as a main component to reduce the cost of the water-color-changing sheet. That is, the calcium carbonate content is 50% by weight to 95% by weight, preferably 55% by weight to 90% by weight, based on the total amount of the water-containing color changing pigment. A cost merit is not acquired as the mixing | blending of calcium carbonate is less than 50 weight%.

[Boehmite]
In the present invention, as the water-containing discoloration pigment dispersed and fixed in the discoloration layer, the calcium carbonate is a main component and boehmite is used as a secondary component. A water discolorable sheet having a sufficiently large color difference ΔE between the liquid-absorbing state and the dry state can be obtained by blending the secondary component, that is, boehmite at less than 50% by weight with respect to the total amount of the water-containing discoloration pigment. The minimum of the preferable compounding quantity of the boehmite which can exhibit this effect effectively is 5 weight%. On the other hand, when boehmite is blended in an amount exceeding 50% by weight, surface wear with time of the water-discoloring sheet is likely to proceed, and the surface tends to be damaged during writing and drawing, which is not preferable. A more preferable content ratio is 10% by weight or more and less than 45% by weight.

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.

[Other water-containing discoloration pigments]
In the water discolorable sheet of the present invention, a water-containing discoloration pigment other than calcium carbonate and boehmite can be blended within the range of the blending ratio of the calcium carbonate, preferably within the range of the suitable blending ratio of the boehmite. . Specific examples of the water-containing color changing pigment include the above-described silicic acid, aluminum silicate, aluminum oxide, and magnesium carbonate.

[Coloring ingredients]
The water discolorable sheet of the present invention is colored by a method such as coloring the support as a base, providing a colorant layer between the discoloration layer and the following support, or coloring the discoloration layer itself. You may go. Coloring components such as colored pigments and colored dyes (pigments and dyes having colors other than white) can be used for coloring. As the colored coloring component, various kinds such as known dyes and pigments can be used without limitation. Specifically, the blue product name “POLYMO NAVY BLUE NT-231 ECO” (manufactured by Kiwa Chemical Industry Co., Ltd.) and the green product name “Ryudye-w Green F2G” (manufactured by Dainippon Ink & Chemicals, Inc.) The product name “Lumikol” series (manufactured by Nippon Fluorescent Chemical Co., Ltd.), which is a fluorescent color, 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 a colorant, a 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. Of these, acrylic resins or acrylic-vinyl acetate resin emulsions are preferred. Further, a curing agent can be added to the resin emulsion.

  The preferred concentration of the resin emulsion used in 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 2.3 wt% or more and 36 wt%. It is preferable to set it as follows, and it is more preferable to set it as 4.6 to 27 weight%. If the solid content concentration of the resin emulsion is less than 2.3% 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 hiding power of the discoloration layer is inferior, and the discoloration speed after applying water to the discoloration layer is slow.

〔urea〕
The discoloration layer preferably contains urea. By containing urea in the discoloration layer, the moisture retention of the discoloration layer is improved, thereby increasing the discoloration speed of the discoloration layer to which water has been applied during writing or drawing. The urea content is not particularly limited, but is preferably 0.5 to 20% by weight, more preferably 1 to 10% by weight, based on the total components of the color changing layer. If the content is less than 0.5% by weight, the effect of increasing the discoloration speed hardly appears. On the other hand, when the content ratio exceeds 20% by weight, it is difficult to uniformly disperse urea in the discoloration layer.

[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 order to fix the water-containing color changing pigment to the binder resin in a dispersed state, and preferably prepare a color-changing layer further containing urea by the above printing method, the water-containing color changing pigment and the binder resin, and further urea, if necessary, A preparation ink containing a polyether-modified polydimethylsiloxane for improving the color component and the discoloration layer fixing property of the water-containing discoloration pigment, that is, a discoloration layer forming ink is prepared. In order to realize good printing, it is preferable to add a wetting agent, an antifoaming agent, a thickener, a viscosity modifier, and the like to the ink for preparation. If necessary, surfactants, film-forming aids, preservatives, water retention agents, plasticizers, dispersants and the like can be added.

[Viscosity modifier]
As the viscosity modifier, a polyurethane-based viscosity modifier is preferable. Specific examples of polyurethane-based viscosity modifiers include “RM-2020NPR” and “Adecanol UH” series manufactured by ADEKA Corporation, and “PRIMAL” series manufactured by Rohm and Haas. "RM-5000", "RM-6000", "RM-7", "RM-5", trade names "BERMODOL" manufactured by Akzo Nobel
PUR ”series. 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. Examples of such solid components include water-colored pigments, solids in resin emulsions, and pigments used when a pigment is used as a colorant in the case of coloring a color-change layer.

[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 .

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 .

[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. Among these, polyester is preferable because it has a good compatibility with calcium carbonate used as a water-containing color changing pigment and strongly holds the color changing layer. A support colored in color (other than white) can also be used.

[Water impermeate]
The water discolorable sheet has flexibility such that water does not penetrate into the back surface (opposite surface opposite to the discoloration layer side) of the support, such as a softening plastic such as polyolefin resin or ethylene vinyl acetate resin. A water impervious material made of a material may be appropriately attached or laminated. The water-impermeable material may be in the form of a sheet, or may have a suitable thickness such as a foam. By providing such a water impermeant, even when the water discolorable 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].

(Abrasion resistance evaluation)
About the surface of the water-color-change sheet | seat obtained by the below-mentioned Example and comparative example, the applicator filled with water was repeated 500 times in the same location on the conditions of angle 65 degrees, load 50g, and 7 cm / sec. The pen tip of the applicator is a shell made of nylon with a diameter of 4.5 mm, and the applicator size is 99 × 15 mm (15 mm triangle on each side). The writing instrument was replenished with enough water to keep the nib fully filled with water during repeated writing. After completion of writing, the area ratio of the shaved surface in the state of the surface after writing was calculated and evaluated as follows.
○: X = 0
Δ: 0 <X ≦ 50
×: 50 <X
(X: Area ratio of scraped surface (%))

[Examples 1 to 3, Comparative Examples 1 to 4]
In the blending amounts shown in Table 1, wetting agents, preservatives, antifoaming agents, viscosity modifiers, urea and thickeners were stirred and mixed with a dissolver, and then applied to a three-roll mill. The base emulsion was prepared by vacuum stirring with the resin emulsion. A water-containing discoloration pigment (shown as “discoloration pigment” in the table) was added to the base liquid at a blending ratio shown in Table 1 and stirred, to prepare an ink for preparation. A 120-mesh screen with a coating amount of 15 g / m ² using a blue polyester (L ^* = 35.9, a ^* = 38.7, b ^* = − 67.9) polyester fabric as a support. It apply | coated by the printing method and the coating film was dried at room temperature for 1 day, and the water-color-change sheet | seat of Examples 1-3 and Comparative Examples 1-5 was obtained.

  The obtained water discoloration sheets of Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to color difference (ΔE) evaluation and abrasion resistance evaluation by the above-described methods. The results are shown in Table 1.

Specific compound names, trade names, and manufacturers of the components listed in Table 1 are as follows.
Calcium carbonate: “Minor calcium carbonate” (Omi Chemical Industries)
Boehmite "Boehmite C06" (Daiming Industry)
Resin emulsion: Acrylic emulsion “Movinyl DM772”, solid content 46% (Nippon GOHSEI Wetting agent: Propylene glycol Preservative: Dithio-2,2-bis (benzmethylamide) “Tencil P” (Arch Chemical Japan)
Antifoaming agent: Foam-breaking polymer "BYK-012" (BIC Chemie Japan)
Thickener: Hydroxyethyl cellulose Viscosity modifier: Urethane-modified viscosity modifier "Adecanol UH-420", solid content 30% (ADEKA)
Polyether-modified polydimethylsiloxane "BYK-345" (BIC Chemie Japan)

  In Examples 1 to 3 in which the calcium carbonate blending ratio with respect to the total water-containing discoloration pigment is within the predetermined range, it was found that any water discoloration sheet is excellent in abrasion resistance. On the other hand, it turns out that it is inferior in the surface of the color difference (DELTA) E of the liquid absorption state of a color-change layer and a dry state rather than the water-color-change sheet | seat of Examples 1-3 as it is the calcium carbonate single system like the comparative example 3. FIG. Further, as in Comparative Examples 1, 2, and 4, the boehmite blending ratio is equal to or greater than the calcium carbonate blending ratio, and as the boehmite blending ratio is further increased, there is no problem in terms of the color difference ΔE, but abrasion resistance. It turns out that it is inferior.

  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 (3)

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,
Containing calcium carbonate and boehmite as the water-containing discoloration pigment,
The water color-changing sheet, wherein a blending ratio of the calcium carbonate is 50% by weight to 95% by weight with respect to the total amount of the water-containing color changing pigment.   The water discolorable sheet according to claim 1, wherein a blending ratio of the boehmite is 5% by weight or more and less than 50% by weight with respect to the total amount of the water-containing discoloration pigment.   The water discoloring sheet according to claim 1 or 2, wherein the discoloring layer further contains 0.5 wt% or more and 20 wt% or less of urea with respect to all components of the discoloring layer.