JP2012247769A - Image forming medium, and image display device and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming medium for simply forming a high quality image by using a liquid such as water without needing ink or the like, and maintains the formed image for a certain sufficient time period; and an image display device and an image forming method using the same.SOLUTION: The image forming medium includes a color layer, and a transparent variable diffusion layer having gels for holding white particles and the liquid. In the transparent variable diffusion layer, the light diffusion property changes when the gels hold the liquid so that the transparency is enhanced comparing with before the gels holding the liquid. The image display device includes the image forming medium, image forming means that supplies the liquid to the image forming medium, and a light source that radiates light to the image forming medium.

Description

  The present invention relates to an image forming medium capable of easily and repeatedly forming an image using a liquid such as water, and an image display apparatus and an image forming method using the same.

2. Description of the Related Art Conventionally, an advertisement message or a bulletin board is printed on paper, plastic board, etc. and displayed by handwriting in the outdoors, transportation, stores, public facilities, and the like. However, in these methods, it is necessary to install the printed material by attaching it manually. In addition, there is a handy signboard, etc., but it takes too much time to display by hand, it is difficult to identify because it is not a well-defined font, and to display images such as photos, print it once on paper etc. After reworking, it takes troublesome work such as pasting. There are light-emitting bulletins and displays that use light-emitting elements (lamps, LEDs), etc. electronically, but it is necessary to continue to control lamps (including LEDs and light-emitting pixels) and display pixels while displaying images. Therefore, the device configuration becomes complicated, and the cost increases and the power consumption increases.
On the other hand, by allowing a liquid mainly composed of water to adhere to the image forming medium, and improving the translucency of the portion where the liquid adheres in the image forming medium, the base layer in the portion can be seen through There has been proposed a water pen paper that can form an image and can be erased by evaporation of the liquid and can be used repeatedly (see Patent Documents 1 to 3). In addition, an image forming method capable of repetitive image formation and a method for forming a color image by using this brush paper in combination with an ink jet image display device have been proposed (see Patent Documents 4 to 5).

  However, in these cases, there is a problem that the liquid is quickly evaporated from the brush paper and the recorded image cannot be held for a sufficient time. For this reason, it has been proposed to add a water-soluble organic solvent or the like to the water pen paper for the purpose of improving image retention (see Patent Document 6). On the other hand, the present applicant has also proposed an image forming method in which an ink jet image display device is used in combination with a sheet that develops or decolors on the same principle as that of the water brush paper (see Patent Document 7). However, even in these cases, there is a problem that the image retention can be achieved only for about 1 to 2 hours, and it cannot be said that the image quality is sufficient.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention does not require ink or the like, can easily and repeatedly form images with good image quality using a liquid such as water, and can form an image of transmitted light for a sufficient period of time. An object of the present invention is to provide a forming medium, and an image display device and an image forming method using the same.

  As a result of intensive studies by the present inventors in order to solve the above problems, the following knowledge was obtained. That is, the white particles and the gel are included by applying a liquid such as water used for forming an image to the image forming medium including the transparent scattering variable layer including the white particles and the gel capable of holding the liquid. This is a finding that the translucency of the transparent scattering variable layer is improved, light can be transmitted only for a sufficient period of time, and the colored layer can be easily visually recognized.

This invention is based on the said knowledge by this inventor, and as a means for solving the said subject, it is as follows. That is,
<1> A colored layer and a transparent scattering variable layer including a gel capable of holding white particles and a liquid. The transparent scattering variable layer has a light scattering property that is changed when the gel holds the liquid. Thus, the translucent property is improved as compared with that before the gel holds the liquid.
In the image forming medium according to <1>, when a liquid is applied to the gel that can hold the liquid contained in the transparent scattering variable layer, the liquid is held in the transparent scattering variable layer. Then, the translucency of the transparent scattering variable layer is improved (the optical transparency of the transparent scattering variable layer is improved). As a result, before the liquid is applied, the colored layer that has not been seen through can be seen through, and an image is formed (developed) by the colored layer that has been seen through. At this time, since the liquid is held in the transparent scattering variable layer for a sufficient period of time, the formed (developed) image can also be visually recognized for a sufficient period of time. The formed image disappears as the liquid gradually evaporates from the transparent scattering variable layer after a sufficiently long time has passed. For this reason, the image forming medium is capable of repetitive image formation, forms an image that does not need to be stored, and is suitably used for a meeting or the like, thereby improving the security of information.
<2> The transparent scattering variable layer is the image forming medium according to <1>, wherein white particles are dispersed in a gel.
In the image forming medium according to <2>, the gel contained in the transparent scattering variable layer contains the white particles. In the state where the transparent scattering variable layer is dried, light scattering occurs in the white particles dispersed in the transparent scattering variable layer, resulting in opaqueness (white). Then, after the liquid is absorbed by the transparent scattering variable layer, the white particles are covered with the liquid so that the space between the particles is filled with the liquid, thereby reducing the scattered light and increasing the translucency. Then, the colored layer positioned behind the transparent scattering variable layer that has become transparent becomes visible, and an image is formed (developed).
<3> The image forming medium according to any one of <1> to <2>, wherein the transparent scattering variable layer includes a white particle-containing layer including white particles and a gel layer including a gel.
In the image forming medium according to <3>, before the liquid is applied, the refractive index difference between the white particle-containing layer and the gel layer included in the transparent scattering variable layer is large. As a result of the light incident on the gel layer being scattered by the white particle-containing layer, the gel layer is clouded. However, after the liquid is applied, the difference in refractive index between the gel layer containing (holding) the liquid and the white particle-containing layer is smaller than before containing (holding) the liquid. The light incident on the gel layer is less likely to be scattered by the white particle-containing layer, so that the light transmittance of the gel layer is improved and becomes transparent. Then, the colored layer positioned behind the transparent gel layer and the white particle-containing layer can be visually recognized, and an image having excellent contrast between the background and the image forming portion is formed (developed).
<4> The image forming medium according to any one of <1> to <3>, wherein the liquid is water and the gel is a hydrogel.
In the image forming medium according to <4>, when the gel contained in the transparent scattering variable layer is the hydrogel and water is applied to the transparent scattering variable layer, the liquid is the transparent It is hydrated (bonded) in the scattering variable layer (hydrated with the polymer molecules forming the transparent scattering variable layer) and held in the transparent scattering variable layer. Then, the translucency of the transparent scattering variable layer is improved (the optical transparency of the transparent scattering variable layer is improved). As a result, before the liquid is applied, the colored layer that has not been seen through can be seen through, and an image is formed (developed) by the colored layer that has been seen through. At this time, the liquid is hydrated (bonded) in the transparent scattering variable layer (hydrated with the polymer molecules forming the hydrogel), and is retained in the transparent scattering variable layer for a sufficient period of time, The formed (developed) image is also visible for a sufficient period of time. The formed image is lost as the water gradually evaporates from the transparent scattering variable layer after a sufficient period of time has passed. For this reason, the image forming medium is capable of repeated image formation, and is preferably used for a meeting or the like by forming an image that does not need to be saved, thereby improving information security (confidentiality, secret management). obtain. Further, since the liquid used for image formation is water, an image is formed at a low cost with a low environmental load, safety, excellent handleability.
<5> The image forming medium according to any one of <1> to <4>, wherein the gel has a temperature-responsive polymer.
In the image forming medium according to <5>, since the gel included in the transparent scattering variable layer includes a temperature-responsive polymer, the image forming medium is subjected to temperature change (exposed to temperature change). ) And the liquid is removed from the transparent scattering variable layer easily and with high sensitivity. For this reason, the formed image can be erased reliably and efficiently in a short time, and the security of information (confidentiality and secret management) can be further improved.
<6> The image forming medium according to any one of <1> to <5>, wherein a water repellent layer is provided on the outermost surface.
The image forming medium according to <6> has the water repellent layer on the outermost surface. For this reason, as a result of suppressing bleeding of the transparent scattering variable layer, the resolution of the image is improved, and an image with small characters or the like is formed (developed) so as to be visible.
<7> The image forming medium according to any one of <1> to <6>, wherein the gel further includes a moisturizing material.
In the image forming medium according to <7>, since the gel contained in the transparent scattering variable layer contains a moisturizing material, the applied liquid is reliably held in the transparent scattering variable layer for a sufficient period of time. Thus, a longer image holding time is realized.
<8> The image forming medium according to any one of <1> to <7>, wherein the colored layer has translucency.
In the image forming medium described in <8>, since the colored layer has translucency by displaying light from the back side of the image forming medium, a light emitting image with transmitted light is formed. .

<9> The image forming medium according to <8>, an image forming unit that forms an image with liquid from the front side of the image forming medium, and a light source that irradiates light from the back side of the image forming medium. An image display device characterized by comprising the image display device.
In the image display device according to <9>, when the image forming unit applies a liquid to the image forming medium, the liquid is brought into contact like an image to be formed. Then, the liquid is held in the gel included in the transparent scattering variable layer, and the translucency is improved as compared to before the liquid is held in the gel of the transparent scattering variable layer (the transparent scattering variable layer). Light transmittance is improved). As a result, before the liquid is applied, the colored layer in the image forming medium that cannot be seen through can be seen through. The image forming medium including the transparent scattering variable layer with improved translucency is irradiated with light from the light source to the back side of the image forming medium, so that the liquid contacts the image forming medium and sees through. Light passes through the colored layer that has become possible. Then, an image of the colored layer that can be seen through is formed (developed) on the surface of the image forming medium by the transmitted light, and is visible from the surface of the image forming medium. At this time, since the liquid is held in the transparent scattering variable layer for a sufficient period of time, the formed (developed) image can also be visually recognized for a sufficient period of time. The image forming medium does not require a complicated device such as a liquid crystal display or an electric bulletin board, is easy to handle, and can be manufactured at low cost.
<10> The image display device according to <9>, further including an image erasing unit including a heating unit configured to heat the image forming medium and volatilize a liquid.
In the image display device according to <10>, in the image erasing unit, the image forming medium on which an image is formed is heated by the heating unit, and the liquid held on the image forming medium is volatilized. The image is erased. For this reason, repetitive image formation is efficiently realized.

  According to the present invention, it is possible to solve the above-mentioned problems in the prior art, and it is possible to easily and repeatedly form a good image quality using a liquid such as water without using ink or the like. It is possible to provide an image forming medium that can be held for a certain period of time, and a simple and rewritable image display device and an image forming method using the image forming medium.

FIG. 1 is a schematic explanatory view for explaining one embodiment (ink jet system) of an image display apparatus using the image forming medium of the present invention. FIG. 2A is a schematic cross-sectional view for explaining an example of a layer configuration of an image forming medium having a laminated structure in which a white particle-containing layer and a gel layer are laminated in the transparent scattering variable layer. FIG. 2B is a schematic cross-sectional view for explaining an example of a layer configuration of an image forming medium having a single-layer structure in which the white particles are dispersed in the gel in the transparent scattering variable layer. FIG. 2C is a schematic cross-sectional view for explaining an example of an image forming medium having a color filter in the colored layer. 2D is a schematic cross-sectional view for explaining an example of an enlarged view of the color filter in FIG. 2C. FIG. 3 is a schematic explanatory diagram for explaining an example of an image display apparatus having a heat source as an image erasing unit in the image display apparatus of FIG.

(Image forming medium)
The image forming medium of the present invention has a colored layer and a transparent scattering variable layer containing a gel capable of holding white particles and a liquid, and further selected as necessary, as appropriate, such as a water repellent layer. It may have a layer.

-Colored layer-
There is no restriction | limiting in particular as said colored layer, Although it can select suitably according to the objective, For example, what contains the coloring agent in the base material etc. are mentioned suitably. The colored layer may be non-translucent or translucent, and is preferably translucent in that the image forming medium can be made transmissive. Furthermore, the translucency of the colored layer is preferably a haze value of 60% or more when measured with a haze meter.

--Base material--
There is no restriction | limiting in particular as a material of the said base material, Although it can select suitably according to the objective, For example, paper, resin, rubber | gum, a metal, etc. are mentioned. Among these, from the viewpoints of low cost, moldability, handleability, and the like, a resin is preferable.
There is no restriction | limiting in particular as said resin, According to the objective, it can select suitably, Any of curable resins, such as a thermoplastic resin, a thermosetting resin, and a photocurable resin, for example, polyethylene From polyesters such as terephthalate (PET) and polybutylene terephthalate (PBT), polyolefins such as polyethylene (PE) and polypropylene (PP), acrylic resins such as polymethyl methacrylate, vinyl resins such as vinyl chloride, polycarbonates, epoxy resins, etc. A transparent plastic film is preferably mentioned.

--Colorant--
There is no restriction | limiting in particular as said coloring agent, According to the objective, it can select suitably, For example, a pigment, dye, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, those which are uniformly dispersed or diffused in the base material alone are preferable, but those which are uniformly dispersed or dissolved in the base material by using a dispersant or the like may be used.
In addition, the said coloring agent can be provided in the said base material by mixing in the material of the said base material, disperse | distributing thru | or melt | dissolving and spreading | diffusion, when shape | molding the said base material. As a result, the base material has a color caused by the colorant and is formed as a colored layer (colored layer).

--Method of applying colorant--
A pre-colored base material can be used by kneading a pigment, a dye, or the like as a colorant to the plastic as the base material, but there is a method of applying the colorant to the surface of the base material.
The method for imparting the colorant to the surface of the substrate is not particularly limited and can be appropriately selected from known methods. For example, conventionally known relief printing, planographic printing, intaglio printing, Examples thereof include printing methods such as stencil printing, offset printing, gravure printing, ink jet printing, electrophotographic printing, and screen printing, and patterning methods such as photoresist and etching. Among these, a colored layer can be suitably formed by forming a colored pattern on the surface of a transparent plastic film using the method described in Japanese Patent Application Laid-Open No. 2008-20559 by the present applicant.

--- Pigment ---
There is no restriction | limiting in particular as said pigment, According to the objective, it can select suitably, A hydrophilic pigment, a lipophilic pigment (hydrophobic pigment), etc. are mentioned.
The dispersion may be in the form of secondary particles (aggregated particles), but from the viewpoint of reducing image quality unevenness, it is as fine as possible (primary particles or secondary particles having a small particle size). Dispersion at is preferred.

  There is no restriction | limiting in particular as a color of the said pigment, According to the objective, it can select suitably, A color pigment, a black pigment, etc. are mentioned. Examples of the color pigment include a yellow pigment, a magenta pigment, a cyan pigment, and other pigments.

Examples of the black pigment include carbon blacks, metal oxides, and organic pigments.
Examples of the carbon blacks include furnace black, lamp black, acetylene black, channel black, carbon black (CI pigment black 7 and the like), and the like.
Examples of the metal oxide include copper oxide, iron oxide (CI Pigment Black 11 and the like), titanium oxide, and the like.
Examples of the organic pigment include aniline black (CI pigment black 1).

Examples of the yellow pigment include C.I. I. Pigment Yellow 1 (Fast Yellow G), 2, 3, 12 (Disazo Yellow AAA), 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55 73, 74, 75, 81, 83 (disazo yellow HR), 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, and the like.
Examples of the magenta pigment include C.I. I. Pigment Red 1, 2, 3, 5, 7, 9, 12, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 1 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B) (Ca)), 48: 3 (permanent red 2B (Sr)), 48: 4 (permanent red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (brilliant carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 92, 97, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (dimethylquinacridone), 123, 146, 149, 166, 168, 170, 172, 175, 176, 178, 179, 180 184,185,190,192,193,202,209,215,216,217,219,220,223,226,227,228,238,240,254,255,272, and the like.
Examples of the cyan pigment include C.I. I. Pigment Blue 1, 2, 3, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 22, 56, 60, 63, 64, Bat Blue 4, Bat Blue 60, and the like.
Examples of other pigments include C.I. I. Pigment red 177, 194, 224, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment violet 3, 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment green 7, 36, and the like.

--- Dye ---
There is no restriction | limiting in particular as said dye, According to the objective, it can select suitably, For example, water-soluble dye, water-dispersible dye, oil-soluble dye, etc. are mentioned.

Examples of the acid dye and the food dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 289, C.I. I. Acid Blue 9, 29, 45, 92, 249, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, C.I. I. Food Yellow 3, 4, C.I. I. Food Red 7, 9, 14, C.I. I. Food black 1, 2, etc. are mentioned.
Examples of the direct dye include C.I. I. Direct yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144, C.I. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227, C.I. I. Direct Orange 26, 29, 62, 102, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202, C.I. I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 and the like.
Examples of the basic dye include C.I. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91, C.I. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112, C.I. I. Basic blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93, 105, 117, 120, 122, 124, 129, 137, 141, 147, 155, C.I. I. Basic black 2, 8, etc. are mentioned.
Examples of the reactive dye include C.I. I. Reactive Black 3, 4, 7, 11, 12, 17, C.I. I. Reactive Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67, C.I. I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97, C.I. I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95, and the like.

--- Colored layer shape, etc .--
There is no restriction | limiting in particular as a shape of the said colored layer, According to the objective, it can select suitably, For example, a sheet form, a film form, etc. are mentioned.
There is no restriction | limiting in particular as a structure of the said colored layer, According to the objective, it can select suitably, For example, a single layer structure, a laminated structure, etc. are mentioned.
The size of the colored layer is not particularly limited and may be appropriately selected depending on the purpose. For example, the colored layer may be a small size such as a widely used paper or a large size. .
Although there is no restriction | limiting in particular as thickness of the said colored layer, It can select suitably in consideration of a use, durability, visibility, etc.

-Transparent scattering variable layer-
The transparent scattering variable layer includes the gel capable of holding the white particles and the liquid.
In the transparent scattering variable layer, when the gel is dried, light scattering occurs at the interface of the white particles, and the transparent scattering variable layer becomes opaque (white). Then, after the liquid is absorbed by the gel, the liquid is covered with the liquid around the white particles, thereby reducing the scattered light and increasing the translucency.
The transparent scattering variable layer may be located in direct contact with the colored layer, or may be located in indirect contact with the colored layer via the other layer.

--- Shape of transparent scattering variable layer, etc .--
There is no restriction | limiting in particular as a shape of the said transparent scattering variable layer, According to the objective, it can select suitably, For example, a sheet form, a film form, etc. are mentioned.
The structure of the transparent scattering variable layer is not particularly limited and may be appropriately selected depending on the purpose. For example, a single-layer structure in which the white particles are dispersed in the gel, a white color containing the white particles A laminated structure formed by laminating a particle-containing layer and a gel layer containing the gel is mentioned. Further, the number of the transparent scattering variable layers may be one or two or more.
The size of the transparent scattering variable layer is not particularly limited and may be appropriately selected depending on the purpose.For example, the transparent scattering variable layer may be a small size such as a widely used paper or a large size. Also good. In the image forming medium of the present invention, the portion where the transparent scattering variable layer is formed is an image forming region.
Although there is no restriction | limiting in particular as total thickness of the said transparent scattering variable layer, It can select suitably in consideration of a use, durability, visibility, etc.

--Method of forming transparent scattering variable layer--
The method for forming the transparent scattering variable layer is not particularly limited and can be appropriately selected from known methods. Specific examples include a method of applying the transparent scattering variable layer solution. .
Examples of the coating method include spray coating, roller coating, brush coating, spin coating, bar coating, and curtain coating.

--Gel--
The gel capable of holding the liquid contained in the transparent scattering variable layer absorbs the liquid applied at the time of image formation and holds it for a certain period of time. As long as the colored layer located behind can be visually recognized, there is no particular limitation, and it can be appropriately selected according to the purpose.
In addition, there is no restriction | limiting in particular as said liquid, According to the objective, it can select suitably, For example, an aqueous solvent (aqueous solvent), an oil-type solvent (hydrophobic organic solvent), etc. are mentioned. These may be used alone or in combination of two or more. Among these, the aqueous solvent (aqueous solvent) is preferable from the viewpoints of low environmental impact, high safety, handling properties, cost, and the like. There is no restriction | limiting in particular as said aqueous medium (aqueous solvent), According to the objective, it can select suitably, For example, water, a hydrophilic organic solvent, etc. are mentioned. Examples of the hydrophilic organic solvent include alcohols such as ethanol. Among these, water, ethylene glycol, propylene glycol and 1,3 butanediol are preferable. Of these, water is particularly preferable.

  The gel has a three-dimensional network structure matrix structure in which polymer chains forming the gel interact with each other. Examples of the interaction between the polymer chains include physical interaction and chemical interaction. Examples of the physical interaction include Coulomb force, van der Waals force, intermolecular force, hydrogen bond, and ionic bond. Examples of the chemical interaction include chemical bonds such as covalent bonds and coordinate bonds.

The material of the gel is not particularly limited and can be appropriately selected. However, the gel is not only simply absorbed when the image is formed, but the liquid is used for a sufficient period of time during use. From the standpoint of retention, a network-forming polymer is particularly preferred.
The gel formed by the network structure-forming polymer not only simply absorbs the liquid applied when forming an image, but can also hold the liquid for a sufficient period of time during use. Function as. In the present invention, the gel is particularly preferably the hydrogel.

  The hydrogel can be formed, for example, by crosslinking polymer chains by physical crosslinking, chemical crosslinking, or the like. For example, polymers composed of polymerizable monomers such as acrylic acid and methacrylic acid having a carboxyl group as a functional group, and salts thereof (for example, sodium salt, potassium salt, triethanolamine salt, etc.), and sulfonic acid group as a functional group Polymers composed of polymerizable monomers such as t-butylacrylamide sulfonic acid and salts thereof (for example, sodium salt, potassium salt, etc.), alginic acid, xanthan gum, etc., for example, aluminum hydroxide, potassium alum, sulfuric acid as a crosslinking agent Aluminum, aluminum glycinate, aluminum acetate, aluminum oxide, aluminum metasilicate, magnesium chloride, calcium hydroxide, calcium carbonate, magnesium metasilicate magnesium aluminate, polyethyleneimine, polyethylene glycol diglycy Luether, triglycidyl isocyanurate, etc. can be added and heated as necessary to form the hydrogel by crosslinking, and the pH can be adjusted to the optimum for the action of the crosslinking agent. For the purpose of ensuring, the hydrogel may be formed using various organic acids and inorganic acids such as tartaric acid, lactic acid, citric acid and hydrochloric acid as a pH adjuster. Moreover, the said hydrogel can also be formed by bridge | crosslinking polyvinyl alcohol etc. with boric acid etc., or crosslinking | crosslinking by intermolecular force, such as agar and gelatin, and a hydrogen bond. By performing polymerization with heat, light, etc., the hydrogel can be formed by polymerizing a polymerizable monomer, a crosslinking agent, a polymerization initiator, other components, and the like. Moreover, the said hydrogel can also be formed by irradiating a polymer aqueous solution with a radiation, an electron beam, etc., and making it bridge | crosslink.

  The network structure is not particularly limited and may be appropriately selected depending on the purpose. For example, (i) “IPN (interpenetrating polymer network (IPN) formed by intruding different types of crosslinked polymer networks into each other” Interpenetrating polymer network)) ”, (ii)“ semi-IPN ”formed by entanglement of a linear polymer chain and a crosslinked polymer network structure, and the like. The gel (the hydrogel) may have the IPN structure or the semi-IPN alone, or may have both the IPN structure and the semi-IPN structure.

Specific examples of the network structure may be 1) the IPN structure and / or the semi-IPN structure formed by crosslinking polymers and / or non-crosslinked polymers obtained by polymerizing monomers, and 2) The semi-IPN structure obtained by adding a non-crosslinked water-soluble polymer chain such as polyvinyl alcohol, polyacrylic acid, sodium polyacrylate, polyvinylpyrrolidone or the like when the monomer is polymerized may be used.
Further, as a specific example of the network structure, as described in JP 2008-163055 A, a double network gel in which a rigid and brittle gel and a flexible and highly stretchable gel have an IPN structure, As described in JP 2007-204527 A, a gel in which a water-swellable clay mineral is introduced as a crosslinking point, and a gel in which a pulley effect is introduced at the crosslinking point, such as polyrotaxane gel (International Publication WO2008 / 108411 Pamphlet) And a gel into which a homogeneous cross-linked structure is introduced, such as Tetra-PEG gel (International Publication WO2007 / 083522 pamphlet).

<Polymerizable monomer>
The polymerizable monomer is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include monomers capable of forming the crosslinked polymer or the non-crosslinked polymer and capable of undergoing a polymerization reaction. Monomers that can form responsive polymers are preferred.
Examples of the polymerizable monomer include N-alkyl substituted (meth) acrylamide derivatives, N, N-dialkyl substituted (meth) acrylamide derivatives, (meth) acrylamide derivatives having a cyclic group, vinyl ether derivatives, and (meth) acrylic acid poly. Examples include alkylene glycol, alkoxy polyalkylene glycol (meth) acrylate alkoxylated with an alkyl group having 1 to 3 carbon atoms, and other monomers. These may be used individually by 1 type and may use 2 or more types together.

Examples of the N-alkyl-substituted (meth) acrylamide derivative include N-ethylacrylamide, Nn-propylacrylamide, Nn-propylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, and N-cyclopropyl. Examples include acrylamide, N-cyclopropylmethacrylamide, N-ethoxyethylacrylamide, N-ethoxyethylmethacrylamide, N-tetrahydrofurfurylacrylamide, N-tetrahydrofurfurylmethacrylamide, and the like.
Examples of the N, N-dialkyl-substituted (meth) acrylamide derivative include N, N-dimethyl (meth) acrylamide, N, N-ethylmethylacrylamide, N, N-diethylacrylamide, and the like.
Examples of the (meth) acrylamide derivative having a cyclic group include 1- (1-oxo-2-propenyl) -pyrrolidine, 1- (1-oxo-2-propenyl) -piperidine, 4- (1- Oxo-2-propenyl) -formoline, 1- (1-oxo-2-methyl-2-propenyl) -pyrrolidine, 1- (1-oxo-2-methyl-2-propenyl) -piperidine, 4- ( 1-oxo-2-methyl-2-propenyl) -formoline, and the like.
Examples of the vinyl ether derivative include methyl vinyl ether.

  Among these polymerizable monomers, the temperature-responsive polymer can be formed, ionization is possible, and the N-alkyl-substituted (meth) group is excellent in terms of cost, handleability, safety, and practical performance. Acrylamide derivatives are preferred, and among the N-alkyl-substituted (meth) acrylamide derivatives, Nn-propylacrylamide, Nn-propylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-ethoxyethylacrylamide, N-ethoxyethyl methacrylamide, N-tetrahydrofurfuryl acrylamide, N-tetrahydrofurfuryl methacrylamide, and the like are more preferable, and N-isopropyl (meth) acrylamide is particularly preferable.

Examples of the polyalkylene glycol (meth) acrylate include 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, acrylic acid, methacrylic acid, N-isopropylacrylamide, vinylpyridine, hydroxyethyl acrylate, vinyl acetate, and dimethylsiloxane. , Styrene, methyl methacrylate, trifluoroethyl acrylate, styrene sulfonic acid, dimethylacrylamide, (meth) acrylamide, hydroxyethyl (meth) acrylate, polyalkylene glycol, polyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate -Polypropylene glycol, etc.
Examples of the (meth) acrylic acid alkoxypolyalkylene glycol alkoxylated with an alkyl group having 1 to 3 carbon atoms include, for example, (meth) acrylic acid methoxypolyethylene glycol, (meth) acrylic acid methoxypolyethylene glycol-polypropylene glycol, ( Examples include methacrylic acid ethoxypolyethylene glycol, (meth) acrylic acid ethoxypolyethylene glycol-polypropylene glycol, and the like.

Examples of the other monomer include (meth) acrylic acid phenoxypolyethylene glycol, (meth) acrylic acid phenoxypolyethylene glycol-polypropylene glycol, and the like. Moreover, carboxylic acids having a vinyl group, phosphoric acids, (meth) acrylic acid dialkylaminoalkyl compounds, dialkylaminoalkyl (meth) acrylamide compounds, salts and the like can be mentioned.
Examples of the carboxylic acid having a vinyl group include sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, (meth) acrylic acid, and the like. Is mentioned.
Examples of the phosphoric acids include vinyl phosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, and the like.
Examples of the dialkylaminoalkyl compound (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, and the like.
Examples of the dialkylaminoalkyl (meth) acrylamide compound include dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth) acrylamide.
Examples of the salts include dimethylaminoethyl methyl chloride (meth) acrylate, dimethylaminoethyl ethyl chloride (meth) acrylate, dimethylaminoethyl ethyl sulfate (meth) acrylate, and dimethylamino (meth) acrylate. Ethyl methyl phosphate, (meth) acrylic acid dimethylaminoethyl ethyl phosphate, (meth) acrylic acid diethylaminoethyl methyl chloride salt, (meth) acrylic acid diethylaminoethyl ethyl chloride salt, (meth) acrylic acid diethylaminoethyl dimethylamino Ethylethyl sulfate, (meth) acrylic acid diethylaminoethyl methyl phosphate, (meth) acrylic acid diethylaminoethyl ethyl phosphate, dimethylaminopropyl (meth) acrylamide methyl chloride salt, dimethyl Ruaminopropyl (meth) acrylamide ethyl chloride salt or dimethylaminopropyl (meth) acrylamide ethyl sulfate, dimethylaminopropyl (meth) acrylamide methyl phosphate, dimethylaminopropyl (meth) acrylamide ethyl phosphate, etc. .
Furthermore, as the other monomer, for example, 2,2,2-trifluoroethyl methyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 1H, 1H, 9H-hexadecafluorononimethacrylate, 2,2,2-trifluoroethyl acrylate, 2,3,4,5,6-pentafluorostyrene, vinylidene fluoride, etc., and (meth) Methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Hexyl acrylate, dodecyl (meth) acrylate, (meth) acrylate Examples include cetyl sulfate, stearyl (meth) acrylate, styrene, vinyl carbazole, vinyl chloride, acrylonitrile, and linear water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, sodium polyacrylate, and carboxymethyl cellulose. And polysaccharides such as gellan, hyaluronic acid, carrageenan, chitin or alginic acid, or proteins such as gelatin and collagen.

<Crosslinking agent>
There is no restriction | limiting in particular as said crosslinking agent, According to the objective, it can select suitably, For example, it functions as a polymerizable monomer which has two or more carbon-carbon double bonds which have polymerizability in a molecule | numerator, and a polyfunctional crosslinking point Suitable nanoclays are preferred.
The polymerizable monomer having two or more carbon-carbon double bonds having polymerizable properties in the molecule is not particularly limited and may be appropriately selected depending on the intended purpose. For example, N, N′-methylenebisacrylamide, N, N′-methylenebismethacrylamide, N, N′-ethylenebisacrylamide, N, N′-ethylenebismethacrylamide, 1,2-diacrylamideethylene glycol, di (tripoly) acrylate, di (tripoly) methacrylate, Etc.
The nanoclay that can function as the polyfunctional crosslinking point is not particularly limited and may be appropriately selected depending on the intended purpose. From the viewpoint of increasing the strength of the gel particles, for example, an inorganic layered compound is used. Preferably mentioned. There is no restriction | limiting in particular as said inorganic layered compound, Although it can select suitably according to the objective, For example, a water swelling clay mineral etc. are mentioned especially suitably. Examples of the water-swellable clay mineral include hectorite, smectite, montmorillolite, perovskite, and the like. Among these, hectorite is preferable in that the gel can be easily strengthened.

  There is no restriction | limiting in particular as content or addition amount of the said crosslinking agent, According to the objective, it can select suitably, The intensity | strength of a gel can be adjusted to a desired grade with this content thru | or addition amount.

<Polymerization initiator>
There is no restriction | limiting in particular as said polymerization initiator, According to the objective, it can select suitably, For example, a photoinitiator, a thermal polymerization initiator, a redox polymerization initiator etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the photopolymerization initiator include azo initiators and acetophenone initiators. The polymerization initiator is not particularly limited as long as it is cleaved by irradiation with radiation such as visible light, ultraviolet light, electron beam, gamma ray, and the like to generate radicals. For example, α-hydroxyketone, α-aminoketone, Preferred examples include benzylmethyl ketal, bisacylphosphine oxide, metallocene, α-ketoglutaric acid and the like. Specific examples thereof include azoisobutyronitrile, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 1- [4- (2-hydroxy Ethoxy) -phenyl] -2-hydroxy-2-methyl-propan-1-one, 2-hydroxy-1- {4-[-(2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2 -Methyl-propan-1-one, 2-methyl-1-[(methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -Butan-1-one, and the like.
Examples of the thermal polymerization initiator include azo polymerization initiators such as azobiscyanovaleric acid and azobisamidinopropane dihydrochloride.
Examples of the redox polymerization initiator include reducing agents such as ferrous sulfate, pyrosulfite, and tetramethylethylenediamine and hydrogen peroxide, peroxodisulfate, potassium persulfate, potassium peroxodisulfate, ammonium peroxopersulfate, and the like. And peroxides.

  There is no restriction | limiting in particular as content or addition amount of the said polymerization initiator, According to the objective, it can select suitably, The intensity | strength of a gel can be adjusted to a desired grade with this content or addition amount.

In the present invention, the transparent scattering variable layer is capable of absorbing the liquid applied during image formation, and capable of leaking the liquid to the outside when subjected to an external stimulus. It is more preferable from the viewpoint of information security (confidentiality, secret management), etc., that the image can be erased at a desired timing, especially if the liquid can be leaked to the outside when subjected to an external stimulus. There is no restriction | limiting, According to the objective, it can select suitably.
The external stimulus is applied from the outside to the image forming medium at a desired timing at which the formed image is desired to be erased.
Examples of the external stimulus include temperature change due to temperature rise or fall, pressure change due to pressure increase or pressure decrease, light irradiation with ultraviolet rays, electric field application, and the like.

When the external stimulus is applied, the gel changes in the state of the polymer formed. By utilizing this change, the liquid can be leaked from the transparent scattering variable layer. Such a change is, for example, that the polymer undergoes phase transition and volume shrinks, or its skeleton or structure collapses or deforms, and varies depending on external stimuli. For example, when the external stimulus is a temperature change, a change in conformation, a change in the interaction between polymers, a phase transition, etc. can be mentioned. When the external stimulus is a light irradiation, structural change, isomerization, Excitation state change, generation of local heat, bond formation / cleavage, phase transition, etc. are mentioned, and when external stimulus is pressure change, bond cleavage, conformation change, phase transition, etc. are mentioned, In the case where the external stimulus is an electric field application, a change in the transmittance of a neutral / charged substance, an electrostatic action, a charge change, a phase transition, and the like can be given.
Hereinafter, the case where the change is “phase transition (phase change)” will be described in more detail. That is, the transparent scattering variable layer is subjected to the external stimulus of at least one of temperature change, pressure change, light irradiation, and electric field application, and a phase transition (phase change) from the first gel state to the second gel state. Then, the liquid leaks out.
There is no restriction | limiting in particular as phase transition (phase change) from said 1st gel state to said 2nd gel state, According to the objective, it can select suitably, For example, the said transparent scattering variable layer is formed. Examples include a phase transition from a state in which the polymer has a random coil-like structure (first gel state) to a state in which the polymer has a globule-like structure (second gel state).
In this case, the hydrogel can be suitably used as the gel and absorbs and holds the water applied when an image is formed, and the external scattering layer is formed on the transparent scattering variable layer in the image forming medium. By applying the stimulus, it is preferable in that the image formed on the image forming medium can be erased at a desired timing.
As the external stimulus at this time, a temperature change due to a temperature rise is preferable in that an image can be easily erased. When the temperature change is used, the hydrogel has the temperature-responsive polymer. It is preferable to contain.
In this case, when the temperature stimulus by raising or lowering the temperature is applied as the external stimulus to the transparent scattering variable layer, the temperature-responsive polymer contained in the transparent scattering variable layer is temperature-responsive, and the transparent scattering variable layer is From the first gel state (the polymer forming the transparent scattering variable layer has a random coil-like structure) to the second gel state (the polymer forming the transparent scattering variable layer has a globule-like structure) This causes a phase transition (phase change).
In this case, as the transparent scattering variable layer, an image can be formed and held if the transparent scattering variable layer is in a state of being contained or retained (held) in the transparent scattering variable layer (first gel state). it can. After the phase transition to the second gel state by the temperature stimulation and the liquid leaks, the liquid leaks from the globule-shaped transparent scattering variable layer, and the image is erased. Further, by dropping / writing the liquid on the transparent scattering variable layer based on the image information, the globule-like transparent scattering variable layer can be phase-shifted again into a random coil shape to repeatedly form an image.

--- Temperature responsive polymer ---
When the temperature-responsive polymer is subjected to a temperature change due to temperature rise or temperature drop, which is the external stimulus, a phase transition (phase change) phenomenon occurs in response thereto. There are temperatures that can respond to temperature changes. The temperature is referred to as “Lower Critical Solution temperature (LCST)”. That is, when the temperature-responsive polymer is subjected to an external stimulus of a temperature change from a temperature lower than the lower critical solution temperature to a temperature higher than the lower critical solution temperature, a phase transition phenomenon occurs.

The lower critical solution temperature of the temperature-responsive polymer is not particularly limited and may be appropriately selected depending on the intended purpose. From the viewpoint of handleability, transportability, etc., for example, 40 ° C. to 150 ° C. Preferably, from the viewpoint of reducing the thermal energy applied when the liquid leaks to the outside, 40 ° C to 80 ° C is more preferable, and 50 ° C to 70 ° C is particularly preferable.
The temperature behavior of the temperature-responsive polymer having the lower critical solution temperature is, for example, visual observation, volume shrinkage (rate), weight loss (rate), turbidity measurement, calorimetry, nuclear magnetic resonance, fluorescence, light scattering. , Neutron scattering, and the like.

When the temperature-responsive polymer reaches a temperature equal to or higher than the lower critical solution temperature, a phase transition phenomenon occurs in response thereto.
Due to the phase transition phenomenon, at a temperature lower than the lower critical solution temperature, a polymer chain in the temperature-responsive polymer is bonded to the liquid (for example, hydrated) in the transparent scattering variable layer to hold the liquid. When the state reaches a temperature equal to or higher than the lower critical solution temperature, the bond (hydration) is released, and the polymer chains in the temperature-responsive polymer and / or the polymer chains of various polymers forming the transparent scattering variable layer Hydrophobic bonds (aggregation) frequently occur, and as a result, the liquid that has been bonded (hydrated) leaks (dehydrated or dehydrated) from the transparent scattering variable layer. In other words, at a temperature lower than the lower critical solution temperature, for example, due to strong interaction (hydration) between a hydrophilic group such as an amide group and water, the polymer chain dissolves and forms a random coiled conformation. Take. However, as the water temperature rises, dehydration occurs in the hydrophobic part as the hydrogen bond between the hydrophilic group such as the amide group and water becomes unstable, and the polymer chain contracts to become a globule. Furthermore, the polymer chains taking the globule form associate with each other by hydrophobic interaction, and macroscopic phase separation occurs. That is, the polymer chain discontinuously transitions from a coiled state (hydrated state) to a globule state (aggregated state) with the lower critical solution temperature as a boundary.

  Specific examples of the temperature-responsive polymer include (1) a cross-linked product of polyalkyl-substituted acrylamide such as poly-N-isopropylacrylamide, (2) alkyl-substituted acrylamide, acrylic acid and its metal salt, acrylamide, and alkyl acrylate ester. And (3) a crosslinked product of polyvinyl methyl ether, (4) a crosslinked product of an alkyl-substituted cellulose derivative such as methylcellulose, ethylcellulose, and hydroxypropylcellulose. These may be used individually by 1 type and may use 2 or more types together. Among these, a cross-linked product of polyalkyl-substituted acrylamide is preferable in that it can be ionized and has excellent flexibility in temperature response control, cost, handleability, safety, and practical performance. A cross-linked product of (NIPAM) is more preferable.

The temperature-responsive polymer includes the polymerizable monomer as a monomer unit, and examples thereof include a homopolymer and a copolymer of the polymerizable monomer. The content of the polymerizable monomer in the temperature-responsive polymer is not particularly limited as long as the temperature-responsive polymer exhibits a desired thermal response and can exhibit the phase transition phenomenon. You can choose.
The method for confirming (analyzing) the presence of the temperature-responsive polymer is not particularly limited and may be appropriately selected from known methods. For example, chromatographic methods such as GC and LC, GC-MS, LC -MS, MALDI-TOF-MS and other mass spectrometry methods, thermogravimetric-differential thermal simultaneous measurement (TG-DTA), DSC, TG-TMA and other thermal analysis methods. By these methods, the temperature-responsive polymer can be qualitatively analyzed or quantitatively analyzed.

  The method for adjusting the lower critical solution temperature (LCST) of the temperature-responsive polymer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, (A) Japan Packaging Society Vol. 13 No. 1 (2004), an ionizing agent such as sodium acrylate is added, (B) Chen, Y. et al. Sone, M .; Fuchise, K .; Sakai, R .; Kakuchi, R .; Duan, Q .; Sun, J .; Narumi, A .; Satoh, T .; Kakuchi, T .; , Structural effect of a series of block co-polymers constraining of poly (N-isopropylene hydride thyrethyramide). Funct. Polym. 69 (7), 463-469, (2009), and a method of introducing a substituent at the molecular end.

--- Gel layer--
The shape, structure, size, thickness, etc. of the gel layer when the transparent scattering variable layer has a laminated structure in which the white particle-containing layer containing the white particles and the gel layer containing the gel are laminated. Can be appropriately selected according to the purpose. The method for forming the gel layer is not particularly limited and may be appropriately selected from known methods. Specifically, the gel material is dissolved to prepare a gel layer solution. Examples of the method include a method of gelling after applying the layer solution.
Examples of the coating method include spray coating, roller coating, brush coating, spin coating, bar coating, and curtain coating.

-Method of gelation-
Examples of the gelation method include a method of cross-linking polymer chains by a known cross-linking method such as physical cross-linking and chemical cross-linking. For example, polymerizable such as acrylic acid and methacrylic acid having a carboxyl group as a functional group. Polymers composed of monomers and salts thereof (for example, sodium salts, potassium salts, triethanolamine salts, etc.), polymers composed of polymerizable monomers such as t-butylacrylamide sulfonic acid having a sulfonic acid group as a functional group, and the like (Eg, sodium salt, potassium salt, etc.), alginic acid, xanthan gum, etc., for example, aluminum hydroxide, potassium alum, aluminum sulfate, aluminum glycinate, aluminum acetate, aluminum oxide, aluminum metasilicate, magnesium chloride, Hydroxy hydroxide Adding calcium, calcium carbonate, magnesium aluminate metasilicate, polyethyleneimine, polyethylene glycol diglycidyl ether, triglycidyl isocyanurate, etc., if necessary, it can be crosslinked and gelled, For the purpose of adjusting the pH optimum for the action of the cross-linking agent and ensuring more reliable cross-linking, various organic acids and inorganic acids such as tartaric acid, lactic acid, citric acid and hydrochloric acid may be used as a pH adjusting agent for gelation. Good. It can also be gelled by cross-linking polyvinyl alcohol or the like with boric acid or the like, or cross-linking by intermolecular force such as agar or gelatin, hydrogen bonding or the like. By polymerizing with heat, light or the like, the polymerizable monomer, the crosslinking agent, the polymerization initiator, other components, and the like can be gelled by polymerization reaction. Moreover, it can also be made to gelatinize by irradiating a polymer aqueous solution with a radiation, an electron beam, etc., and making it bridge | crosslink.

--White particles--
When the gel is dried, the white particles are scattered by light at the particle interface, and become opaque (white). Then, after the liquid is absorbed by the gel, the liquid is covered around the white particles so that the space between the particles is filled with the liquid, thereby reducing scattered light and increasing translucency.
There is no restriction | limiting in particular as whiteness of the said white particle, Although it can select suitably according to the objective, From the viewpoint of enlarging contrast and improving visibility, it is preferable that the said whiteness is high. Specifically, the Hunter whiteness is preferably 70% or more.
There is no restriction | limiting in particular as a particle size of the said white particle, Although it can select suitably according to the objective, For example, 300 nm-50 micrometers are preferable.
The white particles are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include known white powders and white particles such as talc, mica, kaolin, sericite, and silica. , Silica sand, calcium carbonate, tribasic calcium phosphate, calcium pyrophosphate, titanium oxide, cellulose powder, acrylic and styrene resin particles, and the like. These may be used individually by 1 type and may use 2 or more types together. In addition, there is no restriction | limiting in particular as content in the said transparent scattering variable layer of the said white particle, According to the objective, it can select suitably.

--White particle-containing layer--
When the transparent scattering variable layer has a laminated structure in which the white particle-containing layer containing the white particles and the gel layer containing the gel are laminated, the white particle-containing layer is used when forming an image. For the purpose of increasing the change in light transmittance (translucency) of the gel layer before and after absorption of the applied liquid and increasing the contrast with the background of the formed image to improve the visibility, the colored layer And the gel layer, or between the gel layer and the water repellent layer, and the former case is more preferable.
Examples of the white particles contained in the white particle-containing layer include those described above, and the shape, structure, size, thickness, and the like of the white particle-containing layer can be appropriately selected depending on the purpose.

In the present invention, it is preferable that the transparent scattering variable layer contains a humectant from the viewpoint of improving the liquid holding ability of the gel.
There is no restriction | limiting in particular as said moisturizer, According to the objective, it can select suitably, For example, water-soluble polymer, polysaccharide, polyhydric alcohol, protein, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the water-soluble polymer include polyvinyl alcohol, polyacrylic acid, sodium polyacrylate, polyacrylamide, carboxymethyl cellulose, and hydroxyethyl cellulose.
Examples of the polysaccharide include gellan, hyaluronic acid, carrageenan, guar gum, xanthan gum, chitin, and alginic acid.
Examples of the polyhydric alcohol include ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin, diglycerin, and polyglycerin.
Examples of the protein include gelatin and collagen.
Of these humectants, polymer compounds such as water-soluble polymers, polysaccharides, and proteins can be used as the network structure-forming polymer to form the transparent scattering variable layer.

-Other layers-
There is no restriction | limiting in particular as said other layer, Although it can select suitably according to the objective, For example, a water repellent layer etc. are mentioned suitably.

-Water repellent layer-
The water repellent layer is disposed on the outermost surface of the image forming medium, that is, the surface to which the liquid used during image formation is applied, for the purpose of preventing bleeding of the liquid applied when forming an image. Preferably it is done.
The material of the water repellent layer is not particularly limited as long as it has a water repellent effect, and can be appropriately selected according to the purpose. For example, a fluorine resin, a fluorine surfactant, a fluorine monomolecule , Fluorocarbon silane coupling agents, silicone resins, silicone monomolecular films, silicone surfactants, silicone silane coupling agents, alkyl silane coupling agents, and the like. These may be used individually by 1 type and may use 2 or more types together.
The shape, structure, size, thickness and the like of the water repellent layer can be appropriately selected depending on the purpose. The water repellent layer can be formed by dissolving the material in a known solvent to form a coating solution, coating the coating solution by a known coating method, and drying. Examples of the coating method include a spray coating method, a roller coating method, a brush coating method, a spin coating method, a bar coating method, and a curtain coating method.

-Aspect of layer structure-
Examples of the layer configuration in the image forming medium of the present invention include (1) an aspect having the colored layer and the transparent scattering variable layer in this order, and (2) the colored layer, the transparent scattering variable layer, and the repellent layer. The aspect which has a water layer in this order, etc. are mentioned suitably.

-Manufacturing method, usage-
The image forming medium of the present invention can be produced by sequentially laminating the respective layers according to a known method.
In the image forming medium of the present invention, the liquid is applied to the gel contained in the transparent scattering variable layer in the image forming medium in an image-like manner to be formed, and the liquid is absorbed by the transparent scattering variable layer. , The image can be formed (developed) on the image forming medium. In the image forming medium on which the image is formed, an image can be held while the transparent scattering variable layer holds the liquid, but the liquid volatilizes from the transparent scattering variable layer, and the transparent scattering The image is erased after the variable layer no longer holds the liquid. The liquid is applied to the transparent scattering variable layer of the image forming medium again in an image-like manner (imagewise) to be formed on the image forming medium after the image is erased, and the liquid is changed to the transparent scattering variable. An image can be formed (developed) on the image forming medium by absorbing and holding the layer. For this reason, the image forming medium of the present invention can be repeatedly formed and can be used as a rewritable medium. In the image forming medium of the present invention, since the transparent scattering variable layer for holding the liquid contains the hydrogel, the liquid holding ability is a water-soluble polymer used in a conventional recording medium by water printing. Unlike the above, it can correspond to a sufficient time during use. Therefore, there is no problem that the formed image is gradually erased during use. In addition, since the bleeding can be suppressed by providing the water repellent layer, even if an image such as a small character is formed, it is excellent in visibility and can be easily read. In addition, the transparent scattering variable layer has the temperature-responsive polymer, and when exposed to a temperature change due to a temperature rise as the external stimulus, the transparent scattering variable layer sharply responds to the external stimulus to cause dehydration. Since the formed image can be erased at a desired timing, information security (confidentiality, secret management) can be further improved.
The method for applying the liquid to the transparent scattering variable layer is not particularly limited and may be appropriately selected depending on the purpose. For example, it may be manual (handwriting or the like) or may be determined by an apparatus or the like. It may be automatic. There is no restriction | limiting in particular as said apparatus, Although it can select suitably according to the objective, For example, an inkjet apparatus etc. are mentioned suitably. When the ink jet apparatus is used, characters and the like can be printed and images can be formed by discharging the liquid instead of ink from the nozzle head.
The image forming medium of the present invention can be particularly preferably used for the following image display apparatus of the present invention.

(Image display device)
The image display device of the present invention includes an image forming unit and a light source that emits light from the side opposite to the viewer side (back side), and further includes other units such as an image erasing unit.

-Image forming means-
The image forming unit is a unit that forms an image by bringing the liquid into contact with the image forming medium in which a colored layer is translucent among the image forming medium in the present invention.
The contact method is not particularly limited and may be appropriately selected depending on the purpose. For example, the contact method may be manual (handwriting or the like), or may be automatic by an apparatus or the like. There is no restriction | limiting in particular as said apparatus, Although it can select suitably according to the objective, For example, an inkjet apparatus etc. are mentioned suitably. When the ink jet apparatus is used, characters and the like can be printed and images can be formed by discharging the liquid instead of ink from the nozzle head. In the present invention, it is preferable that the contact is performed by liquid droplet ejection using a nozzle head in that a desired image can be easily and efficiently formed.

-Light source-
The light source is an image formed by the image forming unit by irradiating light from the opposite side (back side) to the viewer side in the image forming medium in which the colored layer of the image forming medium is translucent. Is visible on the viewer side (front side) by the transmitted light.
There is no restriction | limiting in particular as said light source, According to the objective, it can select suitably. The positional relationship between the light source and each layer in the image forming medium is in the order of the colored layer, the transparent scattering variable layer, and the water repellent layer from the light source side.

-Other means-
There is no restriction | limiting in particular as said other means, According to the objective, it can select suitably, For example, an image erasing means etc. are mentioned suitably.

-Image erasing means-
The image erasing unit includes the heating unit that volatilizes the liquid by heating the image forming medium after image formation by the image forming unit, and further supplies the liquid to the entire surface of the image forming medium. A liquid supply unit may be provided.
There is no restriction | limiting in particular as the heating method of the said heating part, According to the objective, it can select suitably, For example, a contact system, a non-contact system, etc. are mentioned.
As the contact-type heating method of the heating unit, for example, a method using a heated or heatable member such as a thermal head, a heating roller, or a heating sheet can be preferably cited.
As the non-contact type heating method of the heating unit, for example, a method using a means such as a heater or a fan is preferably exemplified.
There is no restriction | limiting in particular about conditions, such as the temperature of said heating of the said heating part, and time, According to the objective, it can select suitably.
The supply method of the liquid supply unit is not particularly limited and can be appropriately selected depending on the purpose. For example, spray coating method, roller coating method, brush coating method, spin coating method, bar coating method, Curtain coating method, etc. As the roller coating method, for example, supply by a coating roller is preferably exemplified.
When an ink jet apparatus is used as the image forming unit, the nozzle head may be used as a liquid supply unit, or a separate nozzle head may be provided and used as the liquid supply unit.

-Specific example-
Here, a specific example of the image forming method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic explanatory view for explaining an embodiment (ink jet system) of an image forming method using the image forming medium of the present invention.
An image display device 11 illustrated in FIG. 1 includes an image forming unit (image recording unit) 100 as an image forming unit, an image forming medium (image forming sheet) 400, and the image forming medium (image forming sheet) 400. It has a drum 200 to be conveyed, a transparent window 300 for displaying the formed image, and a light source 800 that makes the formed image visible.

  The image forming unit (image recording unit) 100 forms (records) an image on the image forming medium (image forming sheet) 400 by an ink jet recording method. In the image forming unit (image recording unit) 100, ejection is performed as a liquid supply unit for supplying water W as the liquid necessary for forming an image to the image forming medium (image forming sheet) 400. A tank 120 serving as a liquid storage unit connected to each of the heads 110, a discharge amount control unit 130 serving as a liquid supply amount control unit, and an image information input device 140 for inputting information on an image to be formed are provided. The tank 120 contains water W. The discharge head 110 includes one or more discharge ports for discharging the water W stored in the tank 120. Further, the ejection head 110 can be reciprocated in a direction (sheet width direction) orthogonal to the rotation direction of the image forming medium (image forming sheet) 400 by a driving source (not shown).

While the image forming medium (image forming sheet) 400 that can be rotated in a roll shape by a pair of drums 200 is guided by the drum 200 on the opposite side (back side) of the image forming surface to the viewer, the ejection head 110. When the ink is transported to the image forming portion (liquid ejection region) facing the surface, water (water droplets) W is ejected from the ejection head 110, and image forming processing is performed. At this time, the discharge head 110 is moved in the sheet width direction, and water W is appropriately discharged from the discharge port of the discharge head 110 into droplets. As a result, on the image forming surface of the image forming medium (image forming sheet) 400, the light transmittance (translucency) of the transparent scattering variable layer in the portion to which water has adhered has changed and water has not adhered. The colored layer located behind is improved through comparison with the transparent scattering variable layer and developed (formed). The light source 800 irradiates the light L from the side opposite to the viewer side (back side), thereby displaying the image formed on the image forming medium by light emission and making it visible. Although not shown in the drawing, a tank that separately stores normal ink-jet ink colors and a discharge head that discharges the ink-jet ink stored therein may be further provided, and semi-permanent on the image forming medium (image forming sheet) 400. An image can also be formed.
The discharge amount control unit 130 controls the number of droplets that are ejected from the discharge head 110 onto one dot on the image forming medium (image forming sheet) 400 to change the amount of water W applied by the discharge head 110. .

2A to 2D are schematic cross-sectional views for explaining an example of the layer configuration of the image forming medium of the present invention.
In the image forming medium 400A of FIG. 2A, a colored layer 411, a white particle-containing layer 412a, a gel layer 412b, and a water repellent layer 413 are laminated in this order. The laminated structure of the white particle-containing layer 412a and the gel layer 412b is a transparent scattering variable layer 412.
2B, the base material 421, the colored layer 422, the transparent scattering variable layer 423 in which the white particles are dispersed in the gel, and the water repellent layer 424 are arranged in this order. Are stacked.
Further, in the image forming medium 400C of FIG. 2C, the base material 431, the RGB pattern 432, the transparent scattering variable layer 433 in which the white particles are dispersed in the gel, and the water repellent layer 434 are arranged in this order. Are stacked.
2D shows the details of the RGB pattern shown in FIG. 2C. In the RGB pattern, the R pattern 432a, which is the primary color of light, is red, the G pattern 432b is green, and the B pattern 432c is blue. Consists of. In the present invention, it is preferable that the RGB pattern is arranged on the image forming medium so that the RGB pattern corresponds to one pixel.
When the water W discharged from an image display device such as an ink jet recording system lands on the water repellent layers 413, 424 and 434 on the image forming media (image forming sheets) 400A, 400B and 400C, a high contact angle is obtained. And permeates in the vertical direction of the sheet without spreading in the horizontal direction on the uppermost surface of the sheet. When the water W permeates, the transparent scattering variable layers 412, 423, and 433 become transparent, so that the colored layer becomes visible and an image is formed (developed). By the transparent scattering variable layer, the image is held for a sufficient period of time during use.

FIG. 3 is a schematic explanatory view for explaining an embodiment (ink jet system) of the image display device including the image erasing step using the image forming medium.
In the image display device 12 illustrated in FIG. 3, an image erasing heat source 600 is incorporated in the image display device 11.
For example, the image erasing heat source 600 is arranged on the upstream side in the transport direction of the image forming medium (image forming sheet) 400 with respect to the image forming unit (image recording unit) 100. As a result, after the image formed on the image forming medium (image forming sheet) 400 on which an image is formed with water W is erased by the image erasing heat source 600, the image forming unit (image recording unit) 100 continues to It is possible to form a continuous image by forming a new image. Therefore, the process waits until the image forming medium (image forming sheet) 400 can be reused, that is, the water retained in the gel layer in the image forming medium (image forming sheet) 400 volatilizes naturally and the image is erased. There is no need to wait.
However, in the image erasing process by the image erasing heat source 600, the image forming medium (image forming sheet) 400 is heated. Therefore, even if a new image is formed with water immediately after the image erasing process, the image is generated by the residual heat. There is a possibility that the time that can be maintained is shorter than in normal image formation. Therefore, in this case, for example, the rotation of the coloring sheet after erasing the image is controlled by a roll and the heat is removed by, for example, stocking in the housing for a while, and then the image is printed on the image forming medium (image forming sheet) 400. It is preferable to form (record). Here, for example, only the heating means is shown as the image erasing heat source 600, but air blowing may be used, or an image may be erased by using both heating and air blowing.

According to the image display device of the present invention using the image forming medium of the present invention, water imparted to the image forming medium at the time of image formation is held in the transparent scattering variable layer in the image forming medium. Since the transparent scattering variable layer has a three-dimensional network structure (three-dimensional matrix structure), the water is held in the three-dimensional network structure, and evaporation in a short time is effectively suppressed. . Therefore, water retention capacity and film (layer) strength are higher than conventional water-based image-forming sheets formed by simply using non-crosslinked polyhydric alcohols, water-soluble polymers, polysaccharides, etc. as moisturizing materials. Thus, high performance can be realized.
In addition, when the image forming medium is provided with a white particle-containing layer in which white particles having high whiteness are dispersed, or the white particles are dispersed in the gel (the hydrogel), the contrast of the formed image is improved. Can do. As a result, it is possible to solve the conventional problem of the visibility reduction in the image forming sheet due to water. Furthermore, in a sheet such as normal water brush paper, there is a problem that the adhered water diffuses in the lateral direction on the surface and the image blurs. However, by providing a water repellent layer on the outermost surface, the landed water Lateral diffusion is effectively suppressed, and water diffuses in the thickness direction. As a result, lateral bleeding is prevented and a high-definition image is formed.

In addition, by appropriately adjusting the composition of the gel (the hydrogel) (water-soluble polymer, moisturizing material, etc.), the water-holding power of the transparent scattering variable layer can be controlled as desired, and images can be obtained for several hours at room temperature. It is also possible to hold the image, and after that, the image is erased naturally and erased. In some cases, by heating the image forming medium on which the image has been formed, evaporation of water held in the transparent scattering variable layer can be promoted, and decoloration can be realized in a short time. Further, by applying the liquid to the entire surface of the image forming medium on which the image has been formed, the image formed on the image forming medium can be made invisible in a short time.
Furthermore, by including the temperature-responsive polymer (N-isopropylacrylamide, etc.) in the transparent scattering variable layer, the decoloring temperature and decoloring speed can be controlled by utilizing the dehydration phenomenon at the phase transition (layer change). It can be controlled as desired, and information security (confidentiality, secret management) can be improved. Then, as described above, the image display device is provided with water containing means, and by applying this water to the image forming medium of the present invention, image formation is automatically performed only with water, and the light emission display is performed. Since it is possible, the environmental load can be significantly reduced at low cost.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
In order to form a pixel composed of an RGB pattern on a transparent PET film having a thickness of 100 μm, a width of 30 cm, and a length of 100 cm, a red coloring ink, a green coloring ink, and a blue coloring ink are used. A colored layer (transparent colored sheet) 1 in which the pixels were formed on the transparent PET film was obtained using an apparatus described in Japanese Unexamined Patent Application Publication No. 2008-20559.
The liquid for the transparent scattering variable layer 1 was weighed in the blending amounts shown in Table 1 below, and then dissolved and dispersed with a ball mill. A tartaric acid aqueous solution (30% by mass) was prepared, and the liquid for the transparent scattering variable layer 1 and the tartaric acid aqueous solution (30% by mass) were mixed at a mass ratio of 9: 1, and then the applicator on the colored layer (transparent colored sheet) 1 The film was coated to a thickness of 250 μm.
The transparent scattering variable layer 1 was allowed to stand for 24 hours in a saturated water vapor pressure atmosphere at 20 ° C., gelled, and then dried in a vacuum dryer at 60 ° C. for 12 hours.
Next, the water-repellent layer 1 was formed by spray-coating a fluororesin water-repellent agent (manufactured by Fluoro Technology; FS1010TH-2.0) on the transparent scattering variable layer 1.
Thus, an image forming medium (image medium sheet) of Example 1 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 1, and the water repellent layer 1 were laminated in this order was produced.

(Example 2)
In Example 1, except that glycerin 40 g of the liquid for transparent scattering variable layer 1 was changed to 2-pyrrolidone 50 g, wet silica was changed to kaolin, and the amount of water was changed from 608 g to 598 g, respectively, The transparent scattering variable layer 2 of Example 2 was produced.
Next, a fluororesin water repellent (Fluoro Technology, FS1010TH-2.0) was spray coated on the transparent scattering variable layer 2 to form a water repellent layer 1.
Thus, an image forming medium (image medium sheet) of Example 2 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 2, and the water repellent layer 1 were laminated in this order was produced.

(Example 3)
In Example 1, the transparent scattering variable layer 3 of Example 3 was prepared in the same manner as in Example 1 except that the amount of ethanol was changed from 100 g to 140 g without adding glycerin to the transparent scattering variable layer 1 solution. Produced.
Next, the water-repellent layer 1 was formed by spray coating a fluororesin water-repellent agent (manufactured by Fluoro Technology; FS1010TH-2.0) on the transparent scattering variable layer 3.
As described above, an image forming medium (image medium sheet) of Example 3 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 3, and the water repellent layer 1 were laminated in this order was produced.

Example 4
The white particle dispersion solution was mixed and stirred at the blending amount shown in Table 2 below, and then coated on the colored layer (transparent colored sheet) 1 so as to have a thickness of 150 μm using an applicator. The coated sheet was dried and cured at 130 ° C. for 5 minutes to prepare a white particle-containing layer (white particle layer sheet) 1 in a dry state.
A solution for gel layer 1 was prepared in the amount shown in Table 3 below. After the gel layer 1 solution and the tartaric acid aqueous solution 30% by mass were mixed at a weight ratio of 9: 1, the mixture was applied on the white particle-containing layer (white particle layer sheet) 1 to a thickness of 150 μm using an applicator. Worked.
The gel layer 1 is allowed to stand in a saturated water vapor pressure atmosphere at 20 ° C. for 24 hours to be gelled, and then dried in a vacuum dryer at 60 ° C. for 12 hours, whereby the white particle-containing layer (white particle layer sheet) 1 The transparent scattering variable layer 4 having a laminated structure of the gel layer 1 was formed.
Next, a fluororesin water repellent (Fluoro Technology, FS1010TH-2.0) was spray coated on the transparent scattering variable layer 4 to form the water repellent layer 1.
Thus, an image forming medium (image medium sheet) of Example 4 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 4, and the water repellent layer 1 were laminated in this order was produced.

(Example 5)
In Example 4, the image forming medium of Example 5 was produced in the same manner as in Example 4 except that the fluororesin water repellent was not spray coated.

(Example 6)
After weighing raw materials other than APS and TEMED at the blending amounts shown in Table 4 below in a nitrogen atmosphere, the particles are dispersed with a ball mill, and then APS and TEMED are mixed and stirred in the dispersion at the blending ratio shown in Table 4. Thus, a liquid for the transparent scattering variable layer 5 was prepared. On the colored layer (transparent colored sheet) 1, it applied so that thickness might be set to 250 micrometers using an applicator.
In addition, the alphabetic symbol of Table 4 shows the following compounds.
NIPAM: N-isopropylacrylamide MBAAm: N, N′-methylenebisacrylamide APS: ammonium persulfate TEMED: tetramethylethylenediamine The transparent scattering variable layer 5 is allowed to stand in a nitrogen atmosphere at 20 ° C. and saturated water vapor pressure for 24 hours to gel. And then dried in a vacuum dryer at 60 ° C. for 12 hours.
Next, a fluororesin water repellent (Fluoro Technology, FS1010TH-0.5) was spray coated on the transparent scattering variable layer 5 to form a water repellent layer 2.
Thus, an image forming medium (image medium sheet) of Example 6 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 5, and the water repellent layer 2 were laminated in this order was produced.

(Example 7)
The same as Example 6 except that 50 g of glycerin (100% by mass) was added to the liquid for transparent scattering variable layer 5 described in Example 6 and 12 g of TEMED (100% by mass) was changed to 116 g of TEMED (10% by mass). Thus, the transparent scattering variable layer 6 of Example 7 was produced.
Next, the water-repellent layer 2 was formed by spray coating a fluororesin water-repellent agent (manufactured by Fluoro Technology; FS1010TH-0.5) on the transparent scattering variable layer 6.
Thus, an image forming medium (image medium sheet) of Example 7 in which the colored layer (transparent colored sheet) 1, the transparent scattering variable layer 6, and the water repellent layer 2 were laminated in this order was produced.

(Example 8)
The liquid for gel layer 2 was produced with the compounding quantity shown in following Table 5 under nitrogen atmosphere. Then, it coated so that thickness might be set to 150 micrometers using the applicator on the white particle content layer (white particle layer sheet | seat) 1. FIG.
The gel layer 2 was allowed to stand for 24 hours in a nitrogen atmosphere at 20 ° C. and saturated water vapor pressure, gelled, and then dried in a vacuum dryer at 60 ° C. for 12 hours.
Next, a water repellent layer 2 was formed by spray coating a fluororesin water repellent (Fluoro Technology, Inc .; FS1010TH-0.5).
Thus, an image forming medium (image medium sheet) of Example 8 in which the colored layer (transparent colored sheet) 1, the white particle-containing layer 1, the gel layer 2, and the water repellent layer 2 are laminated in this order is produced. did.

(Comparative Example 1)
The white particle-containing layer (white particle layer sheet) 1 in Example 4 was used as the image forming medium (image medium sheet) of Comparative Example 1.

(Comparative Example 2)
On the white particle containing layer (white particle layer sheet) 1 used in Comparative Example 1, a fluororesin water repellent (Fluoro Technology Co., Ltd .; FS1010TH-0.5) was spray coated to form a water repellent layer 3. .
Thus, an image forming medium (image medium sheet) of Comparative Example 2 in which the white particle-containing layer (white particle layer sheet) 1 and the water repellent layer 2 were laminated in this order was produced.

<Evaluation>
The image forming media of each example and comparative example are incorporated in the apparatus shown in FIG. 1, and as the image information, the characters of the MS MS font “轟” in RGB are 3 lines with 6 points and 10 characters, and 3 characters with 8 points and 10 characters. Repeatedly input three lines with 10 characters, 10 characters, and while transporting the image forming medium, water is ejected from the inkjet head to the image forming medium, an image is formed, and the light source is turned on to display light. It was.
As described above, the obtained images were evaluated according to the following criteria. The results are shown in Table 6.

-Record retention-
Characters of 10 points can be distinguished after 24 hours ... ◎
Characters of 10 points can be identified after 12 hours ...
Characters of 10 points can be distinguished after 6 hours ... △
Cannot distinguish 10-point characters after 10 minutes
-Contrast, resolution-
6 point characters can be identified after 5 minutes from image formation ...
Only 8 characters or more can be identified after 5 minutes from image formation ...
Characters of 8 points or more cannot be distinguished after 5 minutes from image formation.

-Image erasing ability-
After the image formation, the image forming medium was heated using the image erasing heat source shown in FIG. 3, and the time until the image information was erased was measured.

In addition, after the formed image was decolored, the same image was formed again 50 times or more. However, the light emitting display medium (image forming medium) in the example is not inferior to the first formed image and is good and clear. Image reproducibility was observed in repeated image formation.
From Table 6, in the case of the image forming medium of the present invention, the image recording retention, contrast and resolution were improved. On the other hand, as in the comparative example, only the white particle-containing layer (white particle layer sheet) without the hydrogel layer has no record retention and is also on the white particle-containing layer (white particle layer sheet). By providing a water repellent layer, the contrast and resolution in a short time were improved, but there was almost no record retention. In addition, as in Examples 4 and 5, when the hydrogel layer was provided on the white particle layer, the record retention was improved, but the contrast and resolution were somewhat insufficient. Moreover, in Example 5, compared with Example 4, since it did not have a water-repellent layer, it was difficult to distinguish characters.
As described above, according to the present invention, it is possible to provide an image forming medium that can improve image quality such as record retention, contrast, and resolution, reduce cost, and reduce environmental burden.

100 Image forming unit (image recording unit)
110 Discharge head (Discharge nozzle)
DESCRIPTION OF SYMBOLS 120 Tank 130 Discharge amount control part 140 Image information input device
200 Drum 300 Window 400 Image forming medium (image forming sheet)
411 Colored layer 412a White particle-containing layer 412b Gel layer 412 Transparent scattering variable layer 413 Water repellent layer 421 Base material 422 Colored layer 423 Transparent scattering variable layer 424 Water repellent layer 431 Base material 432 RGB pattern 433 Transparent scattering variable layer 434 Water repellent layer G image W water 432a R pattern 432b G pattern 432c B pattern 600 Image erasing heat source 800 Light source L Light

Japanese Patent Publication No. 50-5097 Japanese Patent No. 4499269 Japanese Patent No. 3801619 Japanese Patent Laid-Open No. 9-16103 Japanese Patent Laid-Open No. 9-15726 Japanese Patent Laid-Open No. 9-40901 JP 2009-96074 A

Claims (10)

  A colored layer and a transparent scattering variable layer containing a gel capable of holding white particles and a liquid, and the transparent scattering variable layer has a light scattering property changed by the gel holding the liquid, An image forming medium characterized in that translucency is improved as compared with that before a gel holds a liquid.   The image forming medium according to claim 1, wherein the transparent scattering variable layer includes the white particles dispersed in the gel.   The image forming medium according to claim 1, wherein the transparent scattering variable layer includes a white particle-containing layer including the white particles and a gel layer including the gel.   The image forming medium according to claim 1, wherein the liquid is water and the gel is a hydrogel.   The image forming medium according to claim 1, wherein the gel has a temperature-responsive polymer.   The image forming medium according to claim 1, wherein a water repellent layer is provided on the outermost surface.   The image forming medium according to claim 1, wherein the transparent scattering variable layer further contains a moisturizing material.   The image forming medium according to claim 1, wherein the colored layer has translucency.   9. The image forming medium according to claim 8, an image forming unit that forms an image with a liquid from a viewer side on the image forming medium, and light from a side opposite to the viewer side with respect to the image forming medium. An image display device comprising: a light source that irradiates a light source. The image display device according to claim 9, further comprising an image erasing unit having a heating unit that heats the image forming medium and volatilizes the liquid.