JP2010066315A - Rewritable paper, method for producing the same and color image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive rewritable paper which can be repeatedly used many times and in which fixability and color developing property of a photochromic material are good. <P>SOLUTION: The rewritable paper is surface-coated with the inorganic photochromic material composed of a metallic salt, which develops a color upon irradiation with ultraviolet rays and is decolored upon irradiation with visible light or infrared light or upon heating. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rewritable paper, a method for producing the rewritable paper, and a method for forming a color image on the rewritable paper, and more particularly, to a rewritable paper that can be used repeatedly at a low cost and a method for producing the rewritable paper.

  Conventionally, rewritable paper using a photochromic phenomenon in which a photochromic compound is irradiated with light to cause color development or decoloration is known (see, for example, Patent Documents 1 and 2). These rewritable papers are obtained by coating the surface with a photochromic material, and various organic compounds are used as the photochromic material.

  However, such an organic photochromic material has a drawback that it tends to deteriorate due to repeated coloring and erasing, and the coloring density is lowered or it cannot be completely erased. In addition, organic photochromic materials need to go through a number of steps to synthesize them, and use expensive raw materials, resulting in high prices and limited use as products.

  On the other hand, a photochromic article using an inorganic photochromic material is also known (see, for example, Patent Document 3). By using an inorganic photochromic material in this way, a certain degree of effect can be expected with respect to the durability of the material. However, since the photochromic material described in Patent Document 3 contains expensive silver, its use is considerably limited. It must be a thing.

In addition, the conventional rewritable paper has to use a dedicated print medium. Such a dedicated print medium needs to be purchased separately and is usually expensive. Therefore, it is desired that the dedicated print medium can be used more simply as necessary.
JP 2007-226159 A JP 2003-312064 A JP 2000-212553 A

  The present invention has been made under the circumstances described above, is rewritable paper that is inexpensive and can be repeatedly used many times, and has good fixability and color developability of a photochromic material, a manufacturing method thereof, and a color image on the rewritable paper An object is to provide a forming method.

  In order to solve the above-mentioned problems, the first aspect of the present invention provides an inorganic photochromic material made of a metal salt, which develops color when irradiated with ultraviolet rays and disappears when irradiated with visible light or infrared light, or heated. A rewritable paper characterized by being coated is provided.

  The second aspect of the present invention is a first inorganic photochromic material that develops a magenta color when irradiated with ultraviolet light, and disappears when irradiated with visible or infrared light, or heated, and develops a cyan color when irradiated with ultraviolet light. In addition, a second inorganic photochromic material that loses color when irradiated or heated by visible light or infrared light, and develops a yellow color when irradiated by ultraviolet light, and disappears when irradiated or heated by visible light or infrared light. A color rewritable paper characterized in that the surface is coated with a third inorganic photochromic material.

  In this color rewritable paper, the first inorganic photochromic material is potassium chloride and / or hackmanite, the second inorganic photochromic material is potassium bromide and / or sodium bromide, and the third inorganic photochromic material is used. The material can be sodium nitrate.

  The third aspect of the present invention is a first inorganic photochromic material that develops a magenta color when irradiated with ultraviolet light, and disappears when irradiated with visible light or infrared light, or heated, and develops a cyan color when irradiated with ultraviolet light. The second inorganic photochromic material that disappears when irradiated or heated with visible light or infrared light, develops a yellow color when irradiated with ultraviolet light, and disappears when irradiated or heated with visible light or infrared light. The surface is coated with a third inorganic photochromic material and a fourth inorganic photochromic material that develops a black color when irradiated with ultraviolet light and disappears when irradiated with visible light or infrared light, or heated. Provide full color rewritable paper.

  In this color rewritable paper, the first inorganic photochromic material is potassium chloride and / or hackmanite, the second inorganic photochromic material is potassium bromide and / or sodium bromide, and the third inorganic photochromic material is used. The material may be sodium nitrate, and the fourth inorganic photochromic material may be at least one selected from the group consisting of sodium chloride, sodium sulfate, and a tungsten oxide-titanium oxide composite.

  A fourth aspect of the present invention uses a toner containing an inorganic photochromic material made of a metal salt as a colorant, which develops color when irradiated with ultraviolet rays, and disappears when irradiated with visible light or infrared light, or heated. Provided is a method for producing a rewritable paper, wherein a solid image is formed by an electrophotographic process.

  In the fifth aspect of the present invention, the above-described rewritable paper is irradiated with ultraviolet rays to develop all colors, and then sequentially irradiated with visible light corresponding to each color according to the image pattern, A method for forming a color image on a rewritable paper is provided.

  In this color image forming method, an excimer UV lamp can be used as an ultraviolet light source.

  According to the present invention, there is provided a rewritable paper that is inexpensive and can be repeatedly used many times and has good fixability and color developability of a photochromic material, and a method for producing the rewritable paper.

  Hereinafter, embodiments of the present invention will be described.

  The rewritable paper according to an embodiment of the present invention is coated on the surface with an inorganic photochromic material made of a metal salt, which develops color when irradiated with ultraviolet rays, and disappears when irradiated with visible light or infrared light, or when heated. Features.

  Examples of inorganic photochromic materials used for such rewritable paper include various metal salts and metal oxides having photochromic properties. Examples of such inorganic photochromic materials include potassium chloride, potassium bromide, sodium bromide, sodium nitrate, sodium chloride, sodium sulfate, and tungsten oxide-titanium oxide composites. As shown below, specific colors are developed by irradiation with ultraviolet rays, and are erased by irradiation with visible light corresponding to each color, irradiation with infrared rays of a predetermined energy, or heating.

  Of the above inorganic photochromic materials, potassium chloride and / or hackmanite develops a magenta color, potassium bromide and / or sodium bromide develops a cyan color, and sodium nitrate develops a yellow color when irradiated with ultraviolet rays. At least one selected from the group consisting of sodium chloride, sodium sulfate, and a tungsten oxide-titanium oxide composite develops a black color.

  Those coated with one of these inorganic photochromic materials on the surface of the substrate can be colored in each color by irradiating ultraviolet rays in a predetermined image pattern to form an image of each color. . Since this image is erased by irradiation with visible light corresponding to each color, infrared irradiation with a predetermined energy, or heating, the image can be repeatedly used for image formation. In addition, inorganic photochromic materials are less expensive than organic photochromic materials, have durability, and can withstand repeated use.

  As the substrate on which the inorganic photochromic material is coated, paper, a plastic sheet such as PET, or the like can be used. Further, as the ultraviolet ray, one having a wavelength of 366 nm, for example, irradiated from an ultraviolet lamp can be used. Irradiation with infrared rays uses an infrared lamp, and heating can be performed by contact with a heating element.

  In addition, the above inorganic photochromic materials mixed with magenta, cyan, yellow, and the like coated on a single substrate, Furthermore, the thing coated with the mixture of what develops black can be used as a color rewritable paper. Alternatively, it is also possible to provide a multilayer structure by stacking layers of inorganic photochromic materials instead of as a mixture.

  Using such a color rewritable paper, a color image can be obtained by a process as shown in FIG.

  First, the color rewritable paper 1 is conveyed from the paper feeding unit A to the coloring unit B. In the coloring portion B, an ultraviolet light source, for example, a xenon excimer UV lamp 2 is arranged. When the entire surface of the color rewritable paper 1 is irradiated with ultraviolet rays from the xenon excimer UV lamp 2, all of the photochromic material is colored and becomes black.

  Next, the color rewritable paper 1 whose entire surface is colored black is conveyed to the decoloring section C. In the decoloring part C, a visible light corresponding to each color or an infrared ray having an energy specific to each color is irradiated in a pattern corresponding to the image pattern, or a thermal energy specific to each color is applied. Heating is performed sequentially for each color. As a result, each color is erased, and as a result, a color image can be obtained.

  As the visible light corresponding to each color of the pattern according to the image pattern, for example, red (R) which is a complementary color of cyan, green (G) which is a complementary color of magenta, and blue (which is a complementary color of yellow) B) can be used. These visible lights can be obtained by irradiating white light from the light source 3 through the color positive film 4.

  The coating of the inorganic photochromic material on the substrate surface can be performed by various methods as shown below, and is not particularly limited.

  (1) A method in which a solution obtained by dissolving an inorganic photochromic material in a solvent is applied to the substrate surface and dried to remove the solvent. In this case, in order to prevent the photochromic material from peeling off from the substrate surface, it is desirable to coat a resin film on the coated surface.

  (2) A method of dispersing a kneaded material obtained by kneading inorganic photochromic material powder with a binder resin such as polyester resin in a solvent, coating the suspension on the surface of the substrate, and drying to remove the solvent .

  (3) A method in which the kneaded material obtained in the method (2) is stretched to form a film and is attached to the substrate surface.

  (4) The inorganic photochromic material powder is kneaded with a toner material such as a binder resin such as a polyester resin, a charge control agent, and a release agent, the kneaded product is pulverized and classified, and externally added as necessary. An agent is added to obtain a toner. A method of forming a solid image on a substrate using an electrophotographic printer using this toner.

  Among the above methods, the method (4) is most preferable from the viewpoints of the fixing property of the inorganic photochromic material to the substrate surface and the coloring property.

Examples Hereinafter, various examples of the present invention will be shown to describe the present invention more specifically.

  Five types of rewritable paper samples (Examples 1 to 5) were produced as follows.

Example 1
Potassium bromide, potassium chloride, and sodium nitrate were dissolved in water, and the aqueous solution was coated on the surface of a white PET film. After drying the water, a transparent PET film was pasted on the coating surface to prepare a rewritable paper (Sample 1).

Example 2
Powders of potassium bromide, potassium chloride, and sodium nitrate were kneaded with a polyester resin by a twin screw extrusion kneader. The obtained kneaded material was dispersed in a THF solvent, and the obtained suspension was coated on a white PET film. THF was dried to obtain a rewritable paper (Sample 2)
Example 3
The kneaded material prepared in the same manner as Sample 2 was stretched to form a film, and the obtained film was attached to a white PET film to obtain a rewritable paper (Sample 3).

Example 4
Potassium bromide, potassium chloride and sodium nitrate powders, polyester resin for toner, charge control agent for toner (LR-147: manufactured by Nippon Carlit Co., Ltd.), wax for toner (carnauba wax: manufactured by Hiroyuki Kato) And kneaded by a twin screw extrusion kneader. The obtained kneaded material was pulverized by an airflow pulverizer and classified so that the center particle size (volume conversion D50) was 9 μm, and then silica was externally added in a mixer to form a toner. The obtained toner was developed as a solid image on a white PET film by an electrophotographic printer (N5300 manufactured by Casio Computer Co., Ltd.) to obtain a rewritable paper (Sample 4).

Example 5
The same toner as Sample 4 was developed on paper to obtain a paper rewritable paper (Sample 5).

  With respect to Samples 1 to 5 obtained as described above, the performance of the rewritable paper was evaluated as follows for the fixability of the photochromic material to the substrate surface and the color developability. Fixing was performed visually, and color development was performed by observing the color development state of a color image formed using a drawing apparatus.

  As shown in FIG. 1, as a drawing apparatus, a paper feeding unit A that conveys rewritable paper, a color forming unit B that irradiates rewritable paper with ultraviolet rays, a visible light is irradiated according to an image pattern, and the color of the irradiated light What was comprised by the decoloring part C which decolored was used. The xenon excimer UV lamp 2 was used as the ultraviolet light source of the color forming part A.

  First, the rewritable paper sent from the paper feeding unit A is irradiated with ultraviolet rays in the color developing unit B, and all the photochromic material is colored (becomes black). Next, in the decoloring part C, according to an image pattern, the visible light of a predetermined color was irradiated, and the color of the irradiated light of the irradiated photochromic material was erased. As a result, a color image excluding the erased color was formed.

The above evaluation results are shown in the following table.

  From the above table, Samples 1 and 2 according to Examples 1 and 2 had slightly poor fixability of the photochromic material on the substrate, and phenomena such as detachment from the substrate were observed. Further, Samples 1 and 3 according to Examples 1 and 3 were slightly colored in a colored state, and the photochromic material was not uniformly dispersed. Sample 4 according to Example 4 was in a good state with good fixability of the photochromic material and uniform color development. In addition, Sample 5 according to Example 5 in which a photochromic material was coated on paper instead of a PET film also had good fixability and color developability.

  Further, when the above color image was formed 50 times and the durability was repeatedly examined, no deterioration of the photochromic material was observed in any of the samples.

  On the other hand, the repeated durability of a rewritable paper (however, dissolved in THF) according to a comparative example in which a spiropyran-based organic photochromic material (CAS-No 13433-31-3) was prepared in the same manner as Sample 1 was examined. However, the color density was less than half of the initial color density. That is, the inorganic photochromic material was recognized to be superior to the organic type in terms of durability.

  From the above results, it was found that by using an inorganic photochromic material, a rewritable paper having good performance can be produced without using an expensive material such as an organic photochromic material. Also, regarding the durability, it was found that inorganic photochromic materials are superior to organic photochromic materials.

  In addition, as in Samples 4 and 5, it was found that a rewritable paper having good fixability and color developability can be easily produced by producing a rewritable paper by an electrophotographic method.

  In the above embodiment, the printer for creating the rewritable paper and the drawing device for evaluating the color development of the rewritable paper are used separately. However, by providing two functions in one device, the rewritable paper is provided. The three functions of paper creation, drawing on rewritable paper, and color printer can be performed by a single device.

It is a schematic diagram which shows the process of obtaining the color image which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color rewritable paper, 2 ... Excimer UV lamp, 3 ... White light source, 4 ... Color positive film.

Claims (8)

  A rewritable paper characterized in that the surface is coated with an inorganic photochromic material made of a metal salt, which develops color when irradiated with ultraviolet rays, and disappears when irradiated with visible light or infrared light, or when heated.   A first inorganic photochromic material that develops a magenta color when irradiated with ultraviolet light, and is irradiated with visible or infrared light, or disappears when heated, and develops a cyan color when irradiated with ultraviolet light, and emits visible or infrared light. A second inorganic photochromic material that disappears when irradiated or heated, and a third inorganic photochromic material that develops yellow when irradiated with ultraviolet light and disappears when irradiated or heated with visible light or infrared light Color rewritable paper that is coated on the surface.   The first inorganic photochromic material is potassium chloride and / or hackmanite, the second inorganic photochromic material is potassium bromide and / or sodium bromide, and the third inorganic photochromic material is sodium nitrate. The color rewritable paper according to claim 2, wherein   A first inorganic photochromic material that develops a magenta color when irradiated with ultraviolet light, and is irradiated with visible or infrared light, or disappears when heated, and develops a cyan color when irradiated with ultraviolet light, and emits visible or infrared light. A second inorganic photochromic material that disappears when irradiated or heated; a third inorganic photochromic material that develops yellow when irradiated with ultraviolet light; and that disappears when irradiated or heated with visible or infrared light; and A full-color rewritable paper characterized in that the surface is coated with a fourth inorganic photochromic material that develops black color when irradiated with ultraviolet light, and is irradiated with visible light or infrared light, or decolored when heated.   The first inorganic photochromic material is potassium chloride and / or hackmanite, the second inorganic photochromic material is potassium bromide and / or sodium bromide, and the third inorganic photochromic material is sodium nitrate. 5. The full color according to claim 4, wherein the fourth inorganic photochromic material is at least one selected from the group consisting of sodium chloride, sodium sulfate, and a tungsten oxide-titanium oxide composite. Rewritable paper.   A solid image is formed on a substrate by an electrophotographic process using a toner containing an inorganic photochromic material made of a metal salt as a colorant, which develops color when irradiated with ultraviolet rays, or disappears when irradiated with visible or infrared light, or when heated. A method for producing a rewritable paper, characterized in that it is formed.   By irradiating the rewritable paper according to any one of claims 1 to 5 with ultraviolet rays to develop all colors, and then sequentially irradiating visible light corresponding to each color according to the image pattern, A method of forming a color image on rewritable paper.   8. The color image forming method according to claim 7, wherein an excimer UV lamp is used as an ultraviolet light source.

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