JP4476201B2 - Image display medium and image forming method - Google Patents

Description

  The present invention relates to an image display medium and an image forming method, and more particularly to a multicolor image display medium and a multicolor image forming method, and more particularly, to an image display medium and an image forming method capable of repeatedly forming an image by light irradiation. The present invention relates to a multicolor image display medium and a multicolor image forming method.

  Although proposals have been made for rewritable display media using photochromic compounds that exhibit reversible color changes upon light irradiation, proposals for practical display media and methods that can rewrite color images many times have not been made yet. I can't find it.

  As a method of forming a color image using a photochromic compound, three types of photochromic diarylethene compounds that produce yellow-orange by 254 nm ultraviolet light irradiation, red by 313 nm ultraviolet light irradiation, and blue-violet by 365 nm ultraviolet light irradiation are mixed. And the method of irradiating the ultraviolet light of each wavelength is proposed (for example, refer patent document 1). In order to form a full-color image, it is necessary to control the extinction / color development of three or more photochromic compounds that develop the three primary colors (blue, green, red or yellow, magenta, cyan) with light. It is necessary to be able to select whether or not each material is colored according to the three types of ultraviolet light wavelength range, that is, three or more types of photochromic compounds that do not overlap in the absorption band in the ultraviolet region are required. Although the three primary colors must be exhibited in the state, no such compound system is actually found. For practical use, it is necessary to consider not only the color development characteristics but also the repeated durability and heat / humidity stability, and it is very difficult to develop a material satisfying all of these.

  In addition, each photochromic is irradiated by irradiating white light through a color positive film after coloring all photochromic compounds with 366 nm ultraviolet light against three kinds of photochromic fulgide compounds showing yellow, magenta and cyan in a colored state. A method for obtaining a color image by selectively erasing the functional fulgide compound as necessary has been proposed (see, for example, Patent Document 2). Although this method has the advantage that only one type of ultraviolet light source can be used, it requires a color positive film for the image to be formed, and it is not practical to prepare it each time. Not suitable for use in image output. Regarding these and other related proposals, that is, proposals concerning rewritable display media and methods using photochromic compounds, no practical ones for color images have been found yet.

  In view of such circumstances and problems, the present inventors have previously developed an image display medium in which a photosensitive layer containing a plurality of photochromic compounds having different maximum absorption wavelengths in a colored state is formed on a support substrate. Several proposals have been made regarding a method and an apparatus for easily and repeatedly forming a color image (see, for example, Patent Document 3 and Patent Document 4). Among these proposals are a time for forming an image, an image after formation, and the like. There have also been proposals for further improvements in the color retention of the. That is, in image formation, all types of photochromic compounds contained in the photosensitive layer are developed by irradiation with ultraviolet light, and then visible light in a wavelength region corresponding to the maximum absorption wavelength of each of the developed photochromic compounds is respectively given in a predetermined range. There is a method of forming a multicolor image by irradiating an area and selectively erasing each photochromic compound. However, this method often requires a relatively long time for the decoloring process using visible light. From this point of view, it is desirable to use a photochromic compound having a high decoloring sensitivity. From the viewpoint of color retention when being observed with a photochromic compound, it is desired to use a photochromic compound with low decolorization sensitivity. As described above, the two problems of shortening the image formation time and securing the color retention of the formed image require conflicting characteristics with respect to the decolorization sensitivity of the photochromic compound, and are more preferable in consideration of the two problems. In order to improve it, it was necessary to have a technology for controlling the decolorization sensitivity, which temporarily increased the decolorization sensitivity of the photochromic compound only when forming an image and decreased the decolorization sensitivity after image formation. .

In contrast, the present inventors have found a technique for switching the decolorization sensitivity of the photochromic compound by switching the interaction between the photochromic compound and the electron-accepting compound with a simple heat treatment, and the above-described image display medium and image forming method described above. As a result of technical studies, the interaction between the photochromic compound and the electron-accepting compound, which is an important element, is sometimes used in other media components such as a binder material. Has been found to be potentially adversely affected by
JP 05-271649 A JP 07-199401 A JP 2002-37944 A JP 2002-117934 A

  Accordingly, the present invention has been made in view of the above, and in forming a high-definition and high-quality multicolor (color) image on a rewritable image display medium by light irradiation, the image forming time is shortened and the formed image is formed. It is an object of the present invention to provide an image display medium and an image forming method capable of ensuring color retention, and more specifically, for this purpose, the decoloring sensitivity of the decoloring process in image formation is reduced. It is an object of the present invention to provide an image display medium and an image forming method that can be switched.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have been able to obtain new knowledge and have completed the present invention.

That is, the invention described in claim 1 is an image display medium in which a photosensitive layer containing at least three kinds of microcapsules containing at least a photochromic compound and an electron accepting compound is formed on a support substrate, wherein the three kinds of microcapsules are formed. The combination of the photochromic compound and the electron-accepting compound in the capsule is 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) -2-trifluoromethylethylidene] -3- Isopropylidene succinic acid-Np-dimethylaminophenylimide and p- (octadecylthio) phenol, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) ethylidene] -3-isopropylidene Ridensuccinic acid-Np-dimethylaminophenylimide and docosylsulfonic acid And 2- [1- (2,5-dimethyl-1-p-dimethylaminophenyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide and 2-octadecylglutaric acid an image display medium, characterized in that there.

The invention according to claim 2, wherein the photosensitive layer is an image display medium according to claim 1, characterized in that it consists of at least microcapsules and a binder material.

The invention according to claim 13 is the image display medium according to claim 1 or 2 , wherein an infrared absorbing dye is contained in the microcapsule.

According to a fourth aspect of the present invention, the photosensitive layer comprises at least a microcapsule, a binder material, and an infrared absorbing dye, and the binder material in the photosensitive layer is 0.1 to 100 times the microcapsule by weight. an image display medium according to claim 1 or 2, characterized in.

Invention of claim 5, further wherein the on between the photosensitive layer supporting substrate or the photosensitive layer, any one of claims 1 to 4, characterized by providing a heating layer comprising an infrared absorbing dye It is an image display medium as described in above.

A sixth aspect of the present invention is the image display medium according to any one of the first to fifth aspects, wherein a protective layer is provided on a surface of the photosensitive layer or the heat generating layer.

According to a seventh aspect of the present invention, there is provided at least ultraviolet light for the image display medium according to any one of the first to fifth aspects and the image display medium having a protective layer formed on the surface of the photosensitive layer or the heat generating layer. A step of coloring the photochromic compound contained in the photosensitive layer by irradiation, a step of heating to a temperature higher than the melting temperature of the electron-accepting compound, and visible light in a wavelength region corresponding to the maximum absorption wavelength of the colored photochromic compound The image forming method is characterized in that a step of irradiating and decoloring and a step of heating to a temperature not higher than the melting temperature of the electron-accepting compound are performed.

The invention according to claim 8, claim 7 heating method with respect to the image display medium and image display medium to form a protective layer on the surface thereof the photosensitive layer or the heat generating layer is characterized in that infrared light radiation The image forming method described in 1.

The invention according to claim 9, the image display medium and image display medium to form a protective layer on the surface thereof the photosensitive layer or heat generating layer according to any one of claims 1 to 5, at least ultraviolet light The process of coloring all types of photochromic compounds contained in the photosensitive layer by irradiation, the process of heating to a temperature higher than the melting temperature of the electron-accepting compound, and the visible in the wavelength range corresponding to the maximum absorption wavelength of each colored photochromic compound An image forming method comprising performing a step of selectively erasing each photochromic compound by irradiating a predetermined region with light and a step of heating to a temperature lower than the melting temperature of the electron-accepting compound.

A tenth aspect of the present invention is the image forming method according to the ninth aspect, wherein the heating method is infrared light irradiation.

  According to the present invention, the erasing sensitivity can be reversibly changed, the image forming time can be shortened, and the rewritable image display medium and the image forming method by light irradiation that can ensure the color retention of the formed image, particularly multicolor. An image display medium and a multicolor image forming method can be provided.

  Hereinafter, embodiments of the thermal recording medium of the present invention will be described.

  Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims of the present invention.

  First, a basic mechanism of an image display medium in which a photosensitive layer containing a photochromic compound is formed on a substrate and a method for forming a color image by light irradiation on the image display medium will be described.

  The image display medium used here is produced by forming a photosensitive layer containing two or more kinds of photochromic compounds on a supporting substrate having different maximum absorption wavelengths in the colored state, that is, different colors recognized in the colored state. . In this, after coloring all kinds of photochromic compounds contained in the photosensitive layer by ultraviolet light irradiation, the wavelength range corresponding to the visible absorption band of each colored photochromic compound (wavelength range near the maximum absorption wavelength) A desired color image is obtained by irradiating each predetermined region with light and selectively decoloring a corresponding specific photochromic compound (see FIG. 1).

  More specifically, the fact that the maximum absorption wavelength in the colored state is different means that the recognized “color” is different, and this maximum absorption wavelength is set according to the “color” to be used for display. The type of the photochromic compound may be set corresponding to the number of “colors” to be used for display. A photochromic compound having a maximum absorption wavelength in the range of 400 nm to less than 500 nm, a photochromic compound having a maximum absorption wavelength in the range of 500 nm to less than 600 nm, and a maximum absorption wavelength in the color development state of from 600 nm to less than 700 nm If the photosensitive layer is composed of all of the photochromic compounds in the range, the “colors” recognized in the colored state correspond to approximately yellow, magenta and cyan, respectively, and these constitute the three primary colors, For example, by adjusting the degree of decoloration of each photochromic compound in the visible light irradiation step, it is possible to control the density of “color” obtained by each photochromic compound, so the color display range is wide by the image display method described above. Multicolor display is possible.

  The above describes the case where an image is formed on an image display medium composed of a photosensitive layer containing two or more types of photochromic compounds having different maximum absorption wavelengths in a colored state. When an image display medium consisting of a photosensitive layer containing only one type of photochromic compound is targeted, a so-called monochrome image having a single color hue and a different density is formed. The basic method of forming an image by controlling the degree of color development of the photochromic compound contained is the same as in the case of forming a color image described above.

  Photochromic compounds to be included in the photosensitive layer include photochromic compounds such as thermally irreversible fulgide compounds, diarylethene compounds, thermoreversible spiropyran compounds, spirooxazine compounds, etc. It is preferable to use a thermally irreversible compound from the viewpoint of the thermal stability of the film, that is, it is very difficult to change from the colored state to the decolored state unless irradiated with light.

  In the present invention, a fulgide compound is used in particular, but the fulgide compound is likely to change its decolorization sensitivity due to its structure or interaction with other substances from the relationship between its structure and decoloration sensitivity. Excellent in terms.

  In addition to the photochromic compound, the material constituting the photosensitive layer includes a binder material, but does not adversely affect the photochromic function of the photochromic compound, and is compatible with the photochromic compound and can be formed into a film. It is preferable to use a resin material having excellent transparency after curing. Examples of such a material include polystyrene, polyester, polymethyl methacrylate, vinyl chloride-vinylidene chloride copolymer, polyvinyl chloride, polyvinylidene chloride, and polyvinyl acetate.

  Examples of the material for the support substrate include transparent materials such as polyethylene terephthalate, polyethersulfone, and polycarbonate, and opaque materials such as paper.

  As a method for forming the photosensitive layer, a vapor deposition method may be mentioned in addition to the coating method, but the coating method is simple, and both the photochromic compound and the binder material are dissolved in a solvent, and a method such as a printing method or a spin coating method is used. The film may be formed by coating and drying. The photosensitive layer may be a single layer obtained by uniformly mixing all the photochromic compounds that develop each “color” together with the binder material, or a plurality of layers may be formed by laminating layers composed of each photochromic compound and the binder material.

  The present invention is based on the above-described problem, that is, “image formation time” based on an image display medium having a photosensitive layer containing a photochromic compound described above formed on a substrate and a method for forming an image by light irradiation on the image display medium. This was obtained as a result of studying the control of the decolorization sensitivity to achieve both “shortening” and “ensuring color retention of the formed image”.

  Next, the configuration of the present invention will be described in more detail.

  An image display medium characterized by the present invention is an image display medium in which a photosensitive layer containing microcapsules containing <1> at least a photochromic compound and an electron accepting compound is formed on a support substrate, wherein the photochromic compound is It is a fulgide compound having two or more structures represented by the following general formula (I) in the molecule, the electron-accepting compound is a Lewis acid compound, and the carbon number of the long chain structure site excluding the Lewis acid site is 12 That's it.

（ただし、Ｒ_０１およびＲ_０２は水素または脂肪族基を表わす）
また、本発明の別の特徴として、＜２＞上述のような画像表示媒体に対し、少なくとも紫外光照射によって感光層に含有されるフォトクロミック化合物を発色させる工程、電子受容性化合物の溶融温度以上の温度に加熱する工程、発色したフォトクロミック化合物の極大吸収波長に対応した波長域の可視光を所定の領域に照射して消色する工程、および電子受容性化合物の溶融温度以下の温度に加熱する工程を施すことである。

(However, R ₀₁ and R ₀₂ represent hydrogen or an aliphatic group)
Further, as another feature of the present invention, <2> a step of developing a color of a photochromic compound contained in the photosensitive layer by irradiation with ultraviolet light on the image display medium as described above, a temperature equal to or higher than a melting temperature of the electron-accepting compound A step of heating to a temperature, a step of irradiating a predetermined region with visible light in a wavelength region corresponding to the maximum absorption wavelength of the colored photochromic compound, and a step of heating to a temperature below the melting temperature of the electron-accepting compound It is to give.

  This makes it possible to control the decolorization sensitivity, that is, to temporarily increase the decolorization sensitivity of the photochromic compound only when forming an image, and to decrease the decolorization sensitivity after image formation. Explained.

  That is, the decolorization sensitivity of the photochromic compound is directly dependent on the decolorization reaction quantum yield (φCE), and handling the change in decolorization sensitivity is almost the same as dealing with the change in φCE. Hereinafter, it is described that the change in φCE is a change in the decolorization sensitivity.

  The decolorization sensitivity of the fulgide-based compound varies greatly depending on the general properties (IX) and (X) and the electronic properties (electron donating property / accepting property) based on the chemical structure of the aromatic ring moiety described later in the description of these equations. Specifically, when the electron donating property of the aromatic ring portion is large, the decoloring sensitivity is small, and when the electron donating property is small, the decoloring sensitivity is large. The decolorization sensitivity of a compound having a specific structure can change depending on the electronic properties of the medium surrounding the molecule. In other words, the electronic properties of the aromatic ring moiety apparently change due to the interaction with the medium, and if the degree of interaction between the electron accepting moiety in the medium and the aromatic ring moiety of the fulgide compound increases, The electron donating property of the aromatic ring portion is decreased and the decolorization sensitivity is increased. Conversely, if the degree of the interaction decreases, the electron donating property of the aromatic ring portion increases and the decolorization sensitivity decreases. Therefore, the decolorization sensitivity can be controlled by controlling the degree of the interaction. As a result of intensive research on the control of the degree of interaction between the electron accepting site in the medium and the aromatic ring site of the fulgide compound, the present inventors have found that the fulgide compound is a fulgimide compound, and the general formula is included in the molecule. In the present invention, it is found that the electronic properties can be changed greatly when two or more structures represented by (I) are provided, and as a result, effective decolorization sensitivity can be controlled. It has come.

Regarding the decolorization sensitivity of the diarylethene compound, the chemical structure of the site containing the general formula (XI) and two 5-membered rings to be described later in the description of this formula and R ₂ , R ₃ , R ₅ and R ₆ , respectively. Depending on the electronic properties (electron donating property / accepting property), the structure having a larger electron donating property at these sites has a lower decoloring sensitivity, and the structure having a lower electron donating property has a higher decoloring sensitivity. And even for a diarylethene compound of a specific structure, the electronic properties of the aforementioned sites apparently change due to the electronic properties of the medium surrounding the molecule, and the interaction with the electron accepting sites in the media If the degree of is increased, the electron donating property of the aforementioned portion is decreased and the decoloring sensitivity is increased. On the other hand, if the degree of the interaction is reduced, the electron donating property of the aforementioned portion is increased and the decolorization sensitivity is decreased. Therefore, the decolorization sensitivity can be controlled by controlling the degree of the interaction.

  The decolorization sensitivity can be controlled by performing the process described in <2> on the image display medium having the structure described in <1>.

  This can be explained as follows.

  Taking the fulgide compound as an example, the fulgide compound in the photosensitive layer of the image display medium is colored by irradiation with ultraviolet light. Thereafter, the photosensitive layer is temporarily heated to a temperature (I) equal to or higher than the melting temperature of the electron-accepting compound, thereby forming a state in which the electron-accepting compound is regularly gathered to some extent. It stabilizes in a state where the base part has a close interaction with the aromatic ring part of the fulgide-based compound (hereinafter, this state is referred to as “state A”). This is a state in which the decolorization sensitivity is high. In this state, by performing the decoloring step by visible light irradiation, the decoloring step is performed with a small amount of energy, that is, in a short time, and the image formation is completed. Thereafter, the photosensitive layer is temporarily heated to a temperature (II) that is not higher than the melting temperature of the electron-accepting compound (by being temporarily heated to a temperature not lower than the melting temperature of the electron-accepting compound and gradually cooled). The acid group sites of the electron-accepting compound are closely gathered and stabilized with a small interaction with the aromatic ring site of the fulgide-based compound (hereinafter, this state is referred to as “state B”) Call). This is a state in which the decolorization sensitivity is low, and therefore, it is difficult for the color to be erased by illumination light or the like, and the formed image has high color retention.

  In the step of temporarily heating to a temperature (I) equal to or higher than the melting temperature of the electron-accepting compound to obtain the state A, when the melting temperature of the fulgide-based compound is higher than the melting temperature of the electron-accepting compound, It is preferable to heat to a temperature equal to or higher than the melting temperature of the fulgide compound, but it should be higher than the melting temperature of the electron-accepting compound. It is preferable to rapidly cool after heating. When cooling slowly, the probability of changing to state B increases. This is because the heating temperature region for obtaining the state B exists in a region lower than the heating temperature region for obtaining the state A. Therefore, the state B can be obtained by heating the photosensitive layer in the state A to a specific temperature region. Temporarily heating to a temperature (I) equal to or higher than the melting temperature of the electron-accepting compound to obtain the state A, and temporarily to a temperature (II) below the melting temperature of the electron-accepting compound to obtain the state B The heating temperature in the step of heating is appropriately set according to the type and combination of the fulgide compound, the electron accepting compound and the binder to be used.

  Examples of fulgide compounds used in the present invention include fulgide compounds represented by general formula (IX) and fulgimide compounds represented by general formula (X), and compounds having these compounds in the structure and exhibiting photochromic properties. It is done.

（式中、Ｒ_１１、Ｒ_１２、Ｒ_１３、Ｒ_１４はそれぞれ独立して、水素、アルキル基、アルコキシ基、芳香環、複素芳香環などであり、Ｒ_１１、Ｒ_１２、Ｒ_１３、Ｒ_１４のうち少なくとも一つは芳香環あるいは複素芳香環を含む構造とする。）

(In the formula, R ₁₁ , R ₁₂ , R ₁₃ , and R ₁₄ are each independently hydrogen, an alkyl group, an alkoxy group, an aromatic ring, a heteroaromatic ring, and the like, and R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄₎ At least one of them has a structure containing an aromatic ring or a heteroaromatic ring.)

（式中、Ｒ_１５、Ｒ_１６、Ｒ_１７、Ｒ_１８およびＲ_１９はおよびそれぞれ独立して、水素、アルキル基、アルコキシ基、芳香環、複素芳香環などであり、Ｒ_１５、Ｒ_１６、Ｒ_１７、Ｒ_１８のうち少なくとも一つは芳香環あるいは複素芳香環を含む構造とする。）
本発明において用いられるジアリールエテン系化合物としては、一般式（ＩＶ）で示す化合物を始めとして、これらの化合物を構造中に含みフォトクロミック性を示す化合物が挙げられる。

Wherein R ₁₅ , R ₁₆ , R ₁₇ , R ₁₈ and R ₁₉ are each independently hydrogen, an alkyl group, an alkoxy group, an aromatic ring, a heteroaromatic ring, and the like, and R ₁₅ , R ₁₆ , R _At least one of ₁₇ and R ₁₈ has a structure containing an aromatic ring or a heteroaromatic ring.)
Examples of the diarylethene compound used in the present invention include compounds having a photochromic property including these compounds in the structure, including the compound represented by the general formula (IV).

（式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５およびＲ_６はそれぞれ独立して、水素、アルキル基、アルコキシ基、芳香環、複素芳香環などである。またＸおよびＹはそれぞれ独立して酸素、硫黄、あるいは窒素であり、窒素の場合はさらに水素、アルキル基、アルコキシ基、芳香環、複素芳香環などが結合しているものである。）
本発明において用いられる電子受容性化合物としては、基本的に分子内に、フルギド系化合物の芳香環部位と相互作用して芳香環部位の電子的性状に変化を与えうる構造であるルイス酸と、分子間の凝集力をコントロールする脂肪族基などを含む炭素数１２以上の長鎖構造を合わせ持つ化合物である。脂肪族基は、直鎖状または分枝状のアルキル基、アルケニル基が包含され、ハロゲン、アルコキシ基、エステル基等の置換基を有していてもよい。

(Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently hydrogen, an alkyl group, an alkoxy group, an aromatic ring, a heteroaromatic ring, etc., and X and Y are Each independently represents oxygen, sulfur, or nitrogen. In the case of nitrogen, hydrogen, an alkyl group, an alkoxy group, an aromatic ring, a heteroaromatic ring, and the like are further bonded.)
The electron-accepting compound used in the present invention is basically a Lewis acid that has a structure that can interact with the aromatic ring moiety of the fulgide-based compound and change the electronic properties of the aromatic ring moiety in the molecule. It is a compound having a long chain structure having 12 or more carbon atoms and containing an aliphatic group that controls intermolecular cohesion. The aliphatic group includes a linear or branched alkyl group or alkenyl group, and may have a substituent such as a halogen, an alkoxy group, or an ester group.

  As the phosphonic acid compound in the present invention, a compound represented by the following general formula (II) is used.

（式中、Ｒ_１は脂肪族基などを含む炭素数１２以上の長鎖構造を表わす。）
一般式（ＩＩ）で表わされる有機リン酸化合物の具体例としては、たとえば以下のものが挙げられる。

(In the formula, R ₁ represents a long chain structure having 12 or more carbon atoms including an aliphatic group.)
Specific examples of the organic phosphoric acid compound represented by the general formula (II) include the following.

  Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

  In addition, as the aliphatic carboxylic acid compound in the present invention, an α-hydroxy aliphatic carboxylic acid compound represented by the following general formula (III) is used.

（式中、Ｒ_２は脂肪族基などを含む炭素数１２以上の長鎖構造を表わす。）
一般式（ＩＩＩ）で表わされるα−ヒドロキシ脂肪族カルボン酸化合物としては、たとえば以下のものが挙げられる。

(In the formula, R ₂ represents a long chain structure having 12 or more carbon atoms including an aliphatic group.)
Examples of the α-hydroxy aliphatic carboxylic acid compound represented by the general formula (III) include the following.

  α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid , Α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

  In addition, the aliphatic carboxylic acid compound in the present invention is a carboxylic acid compound having a long chain structure having 12 or more carbon atoms including an aliphatic group substituted with a halogen element, and at least at the α-position or β-position carbon thereof. Those having a halogen element are used. Specific examples of such compounds include the following. Specific examples of such compounds include the following.

  2-bromohexadecanoic acid, 2-bromoheptadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid, 2-bromodocosanoic acid, 2-bromotetracosanoic acid, 3-bromooctadecanoic acid, 3-bromoeicosanoic acid 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodo Hexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluorooctadecanoic acid and the like.

  Further, the aliphatic carboxylic acid compound in the present invention is a carboxylic acid compound having a long chain structure having 12 or more carbon atoms including an aliphatic group having an oxo group in the carbon chain, and at least the α-position, β-position or Those in which the carbon at the γ-position is an oxo group are used. Specific examples of such compounds include the following.

  2-oxododecanoic acid, 2-oxotetradecanoic acid, 2-oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxotetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3-oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxooctadecanoic acid, 4-oxodocosanoic acid and the like.

  In addition, as the aliphatic carboxylic acid compound in the present invention, a dibasic acid represented by the following general formula (IV) is used.

（式中、Ｒ_３は脂肪族基などを含む炭素数１２以上の長鎖構造を表わし、Ｘは酸素原子またはイオウ原子を表わし、Ｘが酸素原子の場合はｎは１、またＸがイオウ原子の場合はｎは１または２を表わす。）
一般式（ＩＶ）で表わされる二塩基酸の具体例としては、たとえば、以下のものが挙げられる。

(In the formula, R ₃ represents a long chain structure having 12 or more carbon atoms including an aliphatic group, X represents an oxygen atom or a sulfur atom, n represents 1 when X is an oxygen atom, and X represents a sulfur atom. In the case of n, n represents 1 or 2.)
Specific examples of the dibasic acid represented by the general formula (IV) include the following.

  2- (dodecyloxy) succinic acid, 2- (tetradecyloxy) succinic acid, 2- (hexadecyloxy) succinic acid, 2- (octadecyloxy) succinic acid, 2- (eicosyloxy) succinic acid, 2- (Docosyloxy) succinic acid, 2- (tetracosyloxy) succinic acid, 2- (dodecylthio) succinic acid, 2- (tetradecylthio) succinic acid, 2- (hexadecyloxy) succinic acid, 2- (octadecylthio) ) Succinic acid, 2- (eicosylthio) succinic acid, 2- (docosylthio) succinic acid, 2- (tetracosylthio) succinic acid, 2- (dodecyldithio) succinic acid, 2- (tetradecyldithio) succinic acid, 2 -(Hexadecyldithio) succinic acid, 2- (octadecyldithio) succinic acid, 2- (eicosyldithio) succinic acid, 2- (docosyldithio) Succinic acid, 2- (tetracosyl dithio) like succinic acid.

  In addition, as the aliphatic carboxylic acid compound in the present invention, a dibasic acid represented by the following general formula (V) is used.

（式中、Ｒ_４、Ｒ_５、Ｒ_６は水素又は脂肪族基を表わし、このうち少なくとも１つは脂肪族基などを含む炭素数１２以上の長鎖構造である。）
一般式（Ｖ）で表わされる二塩基酸の具体例としては、たとえば以下のものが挙げられる。

(In the formula, R ₄ , R ₅ and R ₆ represent hydrogen or an aliphatic group, and at least one of them is a long chain structure having 12 or more carbon atoms including an aliphatic group.)
Specific examples of the dibasic acid represented by the general formula (V) include the following.

  Dodecyl succinic acid, tridecyl succinic acid, tetradecyl succinic acid, pentadecyl succinic acid, octadecyl succinic acid, eicosyl succinic acid, docosyl succinic acid, 2,3-dihexadecyl succinic acid, 2,3-dioctadecyl succinic acid, 2-methyl-3 -Dodecyl succinic acid, 2-methyl-3-tetradecyl succinic acid, 2-methyl-3-hexadecyl succinic acid, 2-methyl-3-dodecyl succinic acid, 2-ethyl-3-dodecyl succinic acid, 2-propyl-3 -Dodecyl succinic acid, 2-octyl-3-hexadecyl succinic acid, 2-tetradecyl-3-octadecyl succinic acid and the like.

  In addition, as the aliphatic carboxylic acid compound in the present invention, a dibasic acid represented by the following general formula (VI) is used.

（式中、Ｒ_７、Ｒ_８は水素又は脂肪族基を表わし、このうち少なくとも１つは脂肪族基などを含む炭素数１２以上の長鎖構造である。）
一般式（ＶＩ）で表わされる二塩基酸の具体例としては、たとえば以下のものが挙げられる。

(Wherein R ₇ and R ₈ represent hydrogen or an aliphatic group, and at least one of them is a long chain structure having 12 or more carbon atoms including an aliphatic group.)
Specific examples of the dibasic acid represented by the general formula (VI) include the following.

  Dodecylmalonic acid, tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didodecylmalonic acid, ditetradecylmalonic acid, dihexadecylmalonic acid, di Octadecylmalonic acid, dieicosylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, methyleicosylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosyl Silmalonic acid, ethyltetracosylmalonic acid, etc.

  In addition, as the aliphatic carboxylic acid compound in the present invention, a dibasic acid represented by the following general formula (VII) is used.

（式中、Ｒ_９は脂肪族基などを含む炭素数１２以上の長鎖構造を表わし、ｎは０または１を表わし、ｍは１、２または３を表わし、ｎが０の場合、ｍは２または３であり、ｎが１の場合はｍは１または２を表わす。）
一般式（ＶＩＩ）で表わされる二塩基酸の具体例としては、たとえば以下のものが挙げられる。

Wherein R ₉ represents a long chain structure having 12 or more carbon atoms including an aliphatic group, n represents 0 or 1, m represents 1, 2 or 3, and when n is 0, m is 2 or 3, and when n is 1, m represents 1 or 2.)
Specific examples of the dibasic acid represented by the general formula (VII) include the following.

  2-dodecyl glutaric acid, 2-hexadecyl glutaric acid, 2-octadecyl glutaric acid, 2-eicosyl glutaric acid, 2-docosyl glutaric acid, 2-dodecyl adipic acid, 2-pentadecyl adipic acid, 2-octadecyl adipine Acid, 2-eicosyl adipic acid, 2-docosyl adipic acid and the like.

  Moreover, as a phenol compound in this invention, the compound represented by the following general formula (VIII) is used.

（式中、Ｒ_１０は脂肪族基などを含む炭素数１２以上の長鎖構造を表わし、Ｙは−Ｓ−、−Ｏ−、−ＣＯＮＨ−又は−ＣＯＯ−を表わし、ｎは１乃至３の整数を表わす。）
一般式（ＶＩＩＩ）で表わされるフェノール化合物の具体例としては、たとえば以下のものが挙げられる。

(Wherein R ₁₀ represents a long chain structure having 12 or more carbon atoms including an aliphatic group, Y represents —S—, —O—, —CONH— or —COO—, and n represents 1 to 3) Represents an integer.)
Specific examples of the phenol compound represented by formula (VIII) include the following.

  p- (dodecylthio) phenol, p- (tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (eicosylthio) phenol, p- (docosylthio) phenol, p- (tetracosi) Ruthio) phenol, p- (dodecyloxy) phenol, p- (tetradecyloxy) phenol, p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy) phenol, p- ( Docosyloxy) phenol, p- (tetracosyloxy) phenol, p-dodecylcarbamoylphenol, p-tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol, p-octadecylcarbamoylphenol, p-eicosi Carbamoyl phenol, p- de waist carbamoyl phenol, p- tetracosyl carbamoyl phenol, gallic acid hexadecyl ester, gallic acid octadecyl ester, gallic acid eicosyl ester, gallic acid docosyl esters, such as gallic acid tetracosyl esters.

  As a method for forming a microcapsule containing the above-mentioned fulgide compound and an electron accepting compound, conventional well-known methods such as an interfacial polymerization method, an in-situ polymerization method, and a coacervation method may be used. For example, it can be formed by the following procedure.

  Capsule shell (film) -forming material, and a surfactant, protective colloid, pH adjuster, electrolyte, and a solution prepared by dissolving the above-mentioned fulgide compound and electron accepting compound in a hot melt or common solvent. Is added to water or an organic solvent containing, etc., and emulsified or dispersed by high-speed stirring to form fine particles of a desired size, and a shell is formed at the interface between the fine particles and water or the organic solvent by a general method as described above. What is necessary is just to form. Examples of the shell forming material include polymer compounds such as polyurea, polyamide, polyester, polyurethane, epoxy resin, urea resin, melamine resin, gelatin, ethyl cellulose, polystyrene, and polyvinyl acetate. Moreover, after forming the shell (film), for example, melamine resin, urea resin, epoxy resin, aldehyde compound, isocyanate compound or the like may be used for crosslinking. By crosslinking, the shell can be made stronger and the heat resistance can be improved. Further, the surface is made of gum arabic, gelatin, polyvinyl pyrrolidone, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyacrylic acid soda, polyacrylic acid amide, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer. If it coat | covers with hydrophilic polymer compounds, such as, a shell will become still stronger.

  The size of the microcapsules is preferably about 0.1 to 50 μm.

  The mixing ratio of the fulgide-based compound and the electron-accepting compound may not be unconditional because the appropriate mixing ratio may vary depending on the combination of materials used, but the fulgide-based compound: 5 to 30% by mass, the electron-accepting compound : When mixing in the range of 20 to 80% by mass, preferable results are often obtained.

  By microencapsulating in this way, the influence of other medium components that can alienate the interaction between the fulgide compound and the electron accepting compound is eliminated, and the interaction between the two compounds can be reliably controlled, As a result, reliable reversible switching of the decolorization sensitivity of the image display medium can be performed.

  Examples of the material for the support substrate include transparent materials such as polyethylene terephthalate, polyethersulfone, and polycarbonate, and materials colored white or other colors, and opaque materials such as paper.

  After removing unnecessary water or organic solvent, the microcapsules obtained as described above are further heated or decompressed as necessary to remove the solvent in the microcapsules and dispersed in an appropriate dispersion medium. For example, the photosensitive layer can be formed by placing on a support substrate by a method similar to a coating method such as a printing method, a spin coating method, or a blade method.

  As a light source for irradiating ultraviolet light, a mercury lamp or a xenon lamp may be used in combination with an optical filter to extract ultraviolet light in a desired wavelength range, or light emission that emits light in a specific wavelength range such as an LED or LD. An element may be used.

  As a light source for irradiating visible light, lamps having a configuration in which an optical filter is combined with a white light source may be used, or a light emitting element that emits light in a specific wavelength region such as an LED or an LD may be used. In the case of irradiating only a desired area, for example, a light source array formed by continuously arranging light emitting surfaces that can be controlled on / off for each minute area, and an image display in which a photosensitive layer is formed on a support substrate This can also be achieved by controlling on / off of irradiation of each light emitting surface of the light source array while relatively moving the medium.

  As the heating means, conventional heaters such as a heat roller, a thermal head, a halogen heater, a ceramic heater, and a quartz tube heater can be used. The heating temperature of the heaters and the proximity distance to the image display medium The heating temperature and the heating time of the photosensitive layer of the image display medium can be adjusted according to the conditions such as the contact time and the contact pressure and the time.

  Another feature of the present invention is that the photosensitive layer comprises at least microcapsules and a binder material. As the binder material, it is preferable to use a resin material that can be formed into a film and has excellent transparency after curing. Examples of such a material include polystyrene, polyester, polycarbonate, polymethyl methacrylate, vinyl chloride-vinylidene chloride copolymer, polyvinyl chloride, polyvinylidene chloride, and polyvinyl acetate. In addition, phenoxy resin, aromatic polyester, phenol resin, epoxy resin, and the like can be used. The microcapsules can be dispersed in a solution obtained by dissolving such a binder material in an appropriate solvent, and can be formed on the supporting substrate by a coating method such as a printing method, a spin coating method, or a blade method. As a result, adhesion between the microcapsules and between the microcapsules and the support substrate is improved, and a photosensitive layer having a high physical strength as a film and an image display medium can be obtained.

  Furthermore, another feature of the present invention is that an infrared absorbing dye is contained in the microcapsule. And it is another feature of the present invention to perform heat treatment by infrared light irradiation.

  In the above <1> and <2>, the step of temporarily heating to a temperature (I) equal to or higher than the melting temperature of the electron-accepting compound in order to obtain the state A; In the step of temporarily heating to a temperature (II) lower than the melting temperature, when an infrared absorbing dye is contained in the aforementioned microcapsule, the infrared contained in the microcapsule is irradiated by irradiating infrared light. This is possible because the absorbing dye generates heat. Since the infrared absorbing dye is present in the microcapsule together with the fulgide-based compound and the electron accepting compound, efficient heat treatment is possible due to the heat generated by the infrared absorbing dye.

  As the infrared absorbing dye, naphthalocyanine dyes, cyanine dyes, metal complex dyes and the like having absorption in the infrared region of 700 nm or more can be used.

  The mixing ratio of the fulgide-based compound, the electron-accepting compound, and the infrared-absorbing dye may not be unconditionally different depending on the combination of the materials used, but the fulgide-based compound: 5-30% by mass Electron accepting compounds: 20 to 80% by mass, infrared absorbing dyes: When mixed in the range of 5 to 30% by mass, preferable results are often obtained.

  As a light source for irradiating infrared light, a light source having a configuration combining an infrared lamp and an optical filter for cutting light in an unnecessary wavelength range may be used, or light in a specific wavelength range such as an LED or LD. A light-emitting element that emits light may be used. When irradiating the entire surface of the image display medium, a light source having a large irradiation size may be used, a light source element may be arranged in an array, or an appropriate optical system may be used to adjust to a predetermined irradiation size. In addition, when irradiating a minute specific portion of the image display medium, it may be similarly adjusted to a predetermined irradiation size using an appropriate optical system. The heating temperature of the photosensitive layer can be controlled by adjusting the irradiation intensity and irradiation time of the infrared light.

  Another feature of the present invention is that the photosensitive layer comprises at least microcapsules, a binder material, and an infrared absorbing dye. When the photosensitive layer is composed of at least microcapsules and a binder material, the microcapsules are dispersed in a solution in which the binder material is dissolved in an appropriate solvent, and applied to the support substrate by a coating method such as a printing method, a spin coating method, or a blade method. It has been explained that a film-like photosensitive layer intervening in a state where the binder material is filled between the microcapsules and between the microcapsules and the support substrate can be obtained by forming the film on the substrate. By dissolving both the outer absorbing dye in an appropriate solvent, a photosensitive layer in which the infrared absorbing dye is uniformly dispersed in the binder material portion can be obtained. Infrared absorbing dye is contained in the binder material portion, not in the microcapsules, and the degree of freedom in forming the microcapsules is great. The binder material in the photosensitive layer is preferably 0.1 to 100 times the microcapsule by weight.

  Irradiation with infrared light makes it possible to perform a heating process such as a mechanism including an infrared absorbing dye in a microcapsule and heating by infrared light irradiation.

  Another feature of the present invention is that a heat generating layer containing an infrared absorbing dye is provided between the photosensitive layer and the support substrate or on the photosensitive layer. The formation method of the microcapsule and the formation method of the photosensitive layer using the binder material are the same as the case where the photosensitive layer is composed of at least the microcapsule and the binder material, and on the support substrate on which the heat generating layer containing the infrared absorbing dye is formed in advance. A photosensitive layer may be formed on the substrate, or a similar heat generating layer may be formed after the photosensitive layer is formed on the support substrate. The heat generating layer may be formed by coating the infrared absorbing dye with an appropriate binder material in an appropriate solvent. Irradiation with infrared light makes it possible to perform the heating step in the same manner as the mechanism including the infrared absorbing dye in the microcapsule and heating by infrared light irradiation.

  Another feature of the present invention is that two or more kinds of fulgide compounds having different maximum absorption wavelengths in a colored state are used as the photochromic compound.

  And for such an image display medium, at least a step of coloring all kinds of fulgide compounds contained in the photosensitive layer by irradiation with ultraviolet light, a step of heating to a temperature higher than the melting temperature of the electron-accepting compound, and coloring A process of selectively erasing each fulgide compound by irradiating a predetermined region with visible light in a wavelength region corresponding to the maximum absorption wavelength of each fulgide compound, and a temperature lower than the melting temperature of the electron accepting compound It is also one of the features of the present invention to perform a heating step. Another feature of the present invention is that an image display medium having a photosensitive layer containing an infrared absorbing dye or a heat generating layer is subjected to a heat treatment by infrared light irradiation.

  For an image display medium having a photosensitive layer containing a fulgide compound and an electron accepting compound formed on a support substrate, an image is formed by controlling the decolorization sensitivity, that is, only temporarily when forming an image. The basic method for increasing the decolorization sensitivity of a compound and decreasing the decolorization sensitivity after image formation has been described above. However, it is sensitive to two or more types of fulgide-based compounds having different maximum absorption wavelengths in a colored state. Even in the case of performing multicolor display by forming a layer and performing the above-described steps, it is possible to form an image by controlling the decolorization sensitivity in the same manner.

  The difference in the maximum absorption wavelength in the colored state means that the color to be recognized is different, but this maximum absorption wavelength may be set according to the color to be used for display. The type may be set corresponding to the number of colors to be used for display.

  Another feature of the present invention is that the photochromic compound (A) has a maximum absorption wavelength in a colored state of from 400 nm to less than 500 nm, and a photochromic compound having a maximum absorption wavelength in a colored state of from 500 nm to less than 600 nm ( B) and a photochromic compound (C) having a maximum absorption wavelength in a colored state in the range of 600 nm or more and less than 700 nm are all contained in the photosensitive layer.

  The colors recognized in the colored state of each photochromic compound are substantially equivalent to yellow, magenta, and cyan, respectively, and these constitute three primary colors. Further, for example, the degree of decoloration of each photochromic compound in the visible light irradiation step By adjusting, it is possible to control the density of the color obtained by each photochromic compound, so that the above-described image display method enables multicolor display with a wide color reproduction range. When the same region of the image display medium is irradiated with visible light in a plurality of wavelength regions after the color development step, the irradiation may be performed simultaneously or sequentially. Moreover, when irradiating sequentially separately, the order of the wavelength to irradiate may be arbitrary.

  Examples of the photochromic compound (A) include 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) -2-trifluoromethylethylidene] -3-isopropylidene succinic acid-Np. -Dimethylaminophenylimide, 2- [1- (5-methyl-3-p-dimethylaminophenyl-4-isoxazolyl) -2-trifluoromethylethylidene] -3-isopropylidene succinic acid-Np-dimethylamino Phenylimide, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-thiazolyl) -2-trifluoromethylethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, Etc.

  Examples of the photochromic compound (B) include 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-thiazolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, 2- [1- (5-methyl 2-p-dimethylaminostyryl-4-oxazolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, 2- [1- (5-methyl- (4-p-dimethylaminophenyl) ) Budadien-1-yl) -4-oxazolyl] ethylidene] -3-isopropylidene succinic acid-Np-dimethyl Le aminophenyl imide, and the like.

  Examples of the photochromic compound (C) include 2- [1- (2,5-dimethyl-1-p-dimethylaminophenyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenyl. Imido, 2- [1- (5-methyl-2-p-dimethylaminophenyl-1-phenyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, 2- [ 1- (1,2-dimethyl-5-dimethylamino-3-indolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, 2- [2,6-dimethyl-3,5- Bis (p-dimethylaminostyryl) benzylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide, And the like.

  Furthermore, another feature of the present invention is that a microcapsule containing only (A) as a photochromic compound, a microcapsule containing only (B) as a photochromic compound, and a microcapsule containing only (C) as a photochromic compound. It consists of

  When forming a photosensitive layer with microcapsules as described above using multiple types of fulgide compounds, all fulgide compounds and electron-accepting compounds are present in the same microcapsule in a uniform state. . In that case, the decoloring sensitivity change behavior based on the interaction between the acidic group site of the electron-accepting compound and the aromatic ring site of the fulgide-based compound may vary depending on the electronic properties of the aromatic ring site of each fulgide-based compound. That is, since a common electron accepting compound is used, if the electron donating property of the aromatic ring site of each fulgide compound is different, the degree of change in decoloring sensitivity may be different for each fulgide compound.

  To avoid this and use multiple fulgide compounds with different electronic properties at the aromatic ring site, and to adjust the degree of change in decolorization sensitivity as described above, or the degree of change in decolorization sensitivity for each fulgide compound To select an electron-accepting compound so that an appropriate degree of interaction can be obtained for each fulgide compound, that is, the number of types of microcapsules is the same as the type of fulgide compound. It is possible to form a photosensitive layer using all of them. As one guideline for selection of fulgide-based compounds and electron-accepting compounds in consideration of the degree of interaction, the electron-donating property of the aromatic ring portion of the fulgide-based compound and the electron-accepting property of the acidic group portion of the electron-accepting compound are large. Can be mentioned. There is a tendency that the greater the both, the greater the degree of change in decoloring sensitivity, and the smaller both, the smaller the degree of change in decoloring sensitivity.

  Furthermore, another feature of the present invention is that a protective layer is provided on the surface of the photosensitive layer or the heat generating layer.

  As the material for the protective layer, silicone resin, acrylic resin, PVA (polyvinyl alcohol), or the like is preferably used because of its high transparency and high hardness. By forming the protective layer, the photosensitive layer can reduce adverse effects on the reaction related to the expression of necessary functions of the compound constituting the photosensitive layer due to moisture, specific gas, etc., and also from mechanical damage. Effectively protected to improve durability.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not restrict | limited at all by these Examples. In the following, parts and% are based on weight.

( Reference Example 1 )
As a photochromic compound, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide (hereinafter referred to as PC2) And docosylphosphonic acid (melting temperature 108 ° C.) was used as the electron-accepting compound. 1 part by weight of PC2 and 9 parts by weight of docosylphosphonic acid were dissolved in tetrahydrofuran, added to a protective colloid aqueous solution, and emulsified by stirring at high speed. After adding sodium carbonate to adjust the pH to 9, urea-formaldehyde prepolymer is added, and acetic acid is further added to adjust the pH to 4. Then, the prepolymer is polymerized at the dispersion interface by reacting at 60 ° C. A film of urea-formaldehyde resin was formed, and microcapsules having a particle size of about 5 μm were obtained. This dispersion was applied onto a quartz substrate with a blade to form a film in which microcapsules were arranged, and dried under reduced pressure. When this was heated at 80 ° C. temporarily by heating with a heater and the absorption spectrum was measured, an absorption band was observed in the range of 300 nm to less than 400 nm having a maximum absorption wavelength at 325 nm, and it was colorless. When this was irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, magenta was developed, and the maximum absorption wavelength of the absorption spectrum was 521 nm. When this was heated at 170 ° C. temporarily by heating with a heater, the hue changed reddish, and the maximum absorption wavelength of the absorption spectrum was 485 nm.

  When this was also heat-treated temporarily at 80 ° C., the hue returned to magenta, and the maximum absorption wavelength of the absorption spectrum was 521 nm.

  A film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (188 μm), and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

The photosensitive layer of this image display medium is temporarily heated to 80 ° C. by heating with a heater, irradiated with 366 nm ultraviolet light to saturate the color reaction, and then visible light with a center wavelength of 520 nm and a half-value width of 10 nm is emitted with an illuminance of 1 mW. In the process of irradiating at / cm ² and saturating the decoloring reaction, the change in the reflection spectrum due to the irradiation time (that is, the irradiation energy) is evaluated (see FIG. 2). The irradiation energy required to obtain the change was found to be about 5025 mJ / cm ² (see FIG. 3). The energy thus obtained was defined as decolorization energy and used as an index of decolorization sensitivity.

Next, after irradiating the photosensitive layer of the image display medium with 366 nm ultraviolet light again to saturate the color reaction, it was temporarily heated to 170 ° C., and then visible light having a center wavelength of 480 nm and a half width of 10 nm was applied. Irradiation with an illuminance of 1 mW / cm ² was performed to determine the decoloring energy in the same manner, and it was 25 mJ / cm ² . Furthermore, the photosensitive layer of this image display medium is irradiated with 366 nm ultraviolet light to saturate the coloring reaction, and then temporarily heat-treated this time to 80 ° C., and then visible light having a center wavelength of 520 nm and a half-value width of 10 nm is illuminated with an intensity of 1 mW. It was determined decoloring energy in the same manner and irradiated at / cm ^2, and 5025mJ / cm ^2.

( Reference Example 2 )
PC2 was used as the photochromic compound, and docosylphosphonic acid was used as the electron-accepting compound. 1 part by weight of PC2 and 9 parts by weight of docosylphosphonic acid were dissolved in tetrahydrofuran, added to an aqueous solution containing a surfactant, and emulsified by stirring at high speed. This is put into an aqueous solution containing a melamine-formaldehyde prepolymer, further adjusted to pH 4.5 by adding acetic acid, and then reacted at 70 ° C. while stirring at low speed to polymerize the prepolymer at the interface of the dispersion. Then, a melamine-formaldehyde resin film was formed, and microcapsules having a particle size of about 3 μm were obtained. Microcapsules were taken out from this dispersion, dried under reduced pressure, dispersed in a polycarbonate solution, and applied onto a quartz substrate with a blade to form a microcapsule film using polycarbonate as a binder. When this was heated at 80 ° C. temporarily by heating with a heater and the absorption spectrum was measured, an absorption band was observed in the range of 300 nm to less than 400 nm having a maximum absorption wavelength at 320 nm, and it was colorless. When this was irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, magenta was developed, and the maximum absorption wavelength of the absorption spectrum was 521 nm. When this was heated at 170 ° C. temporarily by heating with a heater, the hue changed reddish, and the maximum absorption wavelength of the absorption spectrum was 486 nm.

  When this was also heat-treated temporarily at 80 ° C., the hue returned to magenta, and the maximum absorption wavelength of the absorption spectrum was 521 nm.

  A film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (188 μm), and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

The image display medium was processed in the same manner as in Reference Example 1 to determine the decoloring energy. The decolorization energy after the heat treatment at 80 ° C. was about 4850 mJ / cm ² , and the decoloration energy after the heat treatment at 170 ° C. was about 22 mJ / cm ² .

( Reference Example 3 )
PC2 was used as the photochromic compound, and docosylphosphonic acid was used as the electron-accepting compound. 1 part by weight of PC2 and 9 parts by weight of docosylphosphonic acid are dissolved in tetrahydrofuran, mixed with an aqueous gelatin solution and an aqueous gum arabic solution, heated to 50 ° C., and added with an aqueous sodium hydroxide solution to adjust the pH to 9 In addition to what was adjusted to, it was emulsified by stirring at high speed. Further, the pH was gradually lowered to 4 to precipitate a concentrated gelatin / gum arabic solution at the dispersion interface, then the temperature was lowered to gel the film, and an aqueous glutaraldehyde solution was added to cure. Thus, microcapsules having a particle size of about 5 μm and gelatin-gum arabic as a wall material were obtained.

  Microcapsules were taken out from this dispersion, dried under reduced pressure, dispersed in a polycarbonate solution, and applied onto a quartz substrate with a blade to form a microcapsule film using polycarbonate as a binder. When this was heated at 80 ° C. temporarily by heating with a heater and the absorption spectrum was measured, an absorption band was observed in the range of 300 nm to less than 400 nm having a maximum absorption wavelength at 325 nm, and it was colorless. When this was irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, magenta was developed, and the maximum absorption wavelength of the absorption spectrum was 521 nm. When this was heated at 170 ° C. temporarily by heating with a heater, the hue changed reddish, and the maximum absorption wavelength of the absorption spectrum was 486 nm.

  When this was also heat-treated temporarily at 80 ° C., the hue returned to magenta, and the maximum absorption wavelength of the absorption spectrum was 521 nm.

  A film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (188 μm), and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

The image display medium was processed in the same manner as in Reference Example 1 to determine the decoloring energy. The decoloring energy after the heat treatment temporarily at 80 ° C. was about 5230 mJ / cm ² , and the decolorization energy after the heat treatment temporarily at 170 ° C. was about 26 mJ / cm ² .

( Reference Example 4 )
PC2 was used as the photochromic compound, docosylphosphonic acid was used as the electron accepting compound, and metal complex dye: Mitsui Chemicals PA-1006 (hereinafter referred to as D1) was used as the infrared absorbing dye. 1 part by weight of PC2, 9 parts by weight of docosylphosphonic acid and 1 part by weight of D1 were dissolved in tetrahydrofuran, added to a protective colloid aqueous solution, and emulsified by stirring at high speed. After adding sodium carbonate to adjust the pH to 9, urea-formaldehyde prepolymer is added, and acetic acid is further added to adjust the pH to 4. Then, the prepolymer is polymerized at the dispersion interface by reacting at 60 ° C. A film of urea-formaldehyde resin was formed, and microcapsules having a particle size of about 5 μm were obtained. Microcapsules were taken out from this dispersion, dried under reduced pressure, dispersed in a polycarbonate solution, and applied onto a quartz substrate with a blade to form a microcapsule film using polycarbonate as a binder. This was irradiated with infrared light and temporarily heat-treated at 80 ° C., and the absorption spectrum was measured. As a result, an absorption band was observed in the range of 300 nm to less than 400 nm having a maximum absorption wavelength at 325 nm, and it was colorless. It was. When this was irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, magenta was developed, and the maximum absorption wavelength of the absorption spectrum was 521 nm. When this was irradiated with infrared light and heat-treated at 170 ° C. temporarily, the hue changed reddish, and the maximum absorption wavelength of the absorption spectrum was 486 nm.

  When this was also heat-treated temporarily at 80 ° C., the hue returned to magenta, and the maximum absorption wavelength of the absorption spectrum was 521 nm.

  A film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (188 μm), and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

The image display medium was processed in the same manner as in Reference Example 1 to determine the decoloring energy. However, the heat treatment was performed by infrared light irradiation. The decoloring energy after heat treatment at 80 ° C. temporarily by infrared light irradiation is about 5010 mJ / cm ² , and the decoloring energy after heat treatment at 170 ° C. temporarily by infrared light irradiation is about 25 mJ. / cm ² .

( Reference Example 5 )
Microcapsules were produced in the same manner as in Reference Example 1 . Next, D1 was added to the polycarbonate solution only in the same weight part as the polycarbonate, and the microcapsules were dispersed therein and applied onto a quartz substrate with a blade to form a microcapsule film using polycarbonate and D1 as a binder. This was irradiated with infrared light and temporarily heat-treated at 80 ° C., and the absorption spectrum was measured. As a result, an absorption band was observed in the range of 300 nm to less than 400 nm having a maximum absorption wavelength at 325 nm, and it was colorless. It was. When this was irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, magenta was developed, and the maximum absorption wavelength of the absorption spectrum was 521 nm. When this was irradiated with infrared light and heat-treated at 170 ° C. temporarily, the hue changed reddish, and the maximum absorption wavelength of the absorption spectrum was 486 nm.

  When this was also heat-treated temporarily at 80 ° C., the hue returned to magenta, and the maximum absorption wavelength of the absorption spectrum was 521 nm.

  A film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (188 μm), and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

The image display medium was processed in the same manner as in Reference Example 4 to determine the decoloring energy. The decolorization energy after temporarily heat-treating to 80 ° C. was about 5142 mJ / cm ² , and the decolorization energy after temporarily heat-treating to 170 ° C. was about 25 mJ / cm ² .

( Reference Example 6 )
An image display medium similar to that of Reference Example 2 was produced. However, before forming the protective layer on the photosensitive layer, a coating solution in which 1 part by weight of D1, 6 parts by weight of polycarbonate was dissolved in 50 parts by weight of tetrahydrofuran was applied to form a 5 μm heating layer, A protective layer was formed thereon. The image display medium was processed in the same manner as in Example 4 to determine the decoloring energy. The decolorizing energy after the heat treatment temporarily at 80 ° C. was about 4960 mJ / cm ² , and the decoloring energy after the heat treatment temporarily at 170 ° C. was about 22 mJ / cm ² .

( Reference Example 7 )
As a photochromic compound, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) -2-trifluoromethylethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide (Hereinafter referred to as PC1), PC2, 2- [1- (2,5-dimethyl-1-p-dimethylaminophenyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenyl An imide (hereinafter referred to as PC3) was used, D1 was used as an infrared absorbing dye, and docosylphosphonic acid was used as an electron-accepting compound.

PC1 and PC3 were used as photochromic compounds, and in the same manner as in Reference Example 5 , a microcapsule film using polycarbonate and D1 as a binder was formed on a quartz substrate. When these were irradiated with infrared light and heat-treated temporarily at 80 ° C. and the absorption spectra were measured, the microcapsule films produced using PC1 and PC3 had a maximum absorption wavelength of 338 nm and 357 nm, respectively. Absorption bands were observed in the range of ˜400 nm, and all were colorless. When these were irradiated with ultraviolet light of 366 nm extracted from a high-pressure mercury lamp, the microcapsule films produced using PC1 and PC3 developed yellow and cyan, respectively, and the maximum absorption wavelengths of the absorption spectra were 458 nm and 663 nm, respectively. It was. When these were irradiated with infrared light and heat-treated temporarily at 170 ° C., the hues of both changed, and the maximum absorption wavelengths of the absorption spectra were 427 nm and 623 nm, respectively. When these were again irradiated with infrared light and temporarily heat-treated at 80 ° C., the hue returned to the original, and the maximum absorption wavelengths of the absorption spectrum were 458 nm and 663 nm, respectively.

Depressurize the microcapsules containing PC1 and docosylphosphonic acid, the microcapsules containing PC3 and docosylphosphonic acid, and the microcapsules containing PC2 and docosylphosphonic acid produced in the same manner as in Reference Example 5 3 parts of microcapsules by weight, 1 part by weight of D1, and 6 parts by weight of polycarbonate dissolved in 40 parts by weight of tetrahydrofuran were coated with a white PET (polyethylene terephthalate) substrate (188 μm). ) To form an 8 μm microcapsule film, and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

When the photosensitive layer of this image display medium was irradiated with infrared light and temporarily heat-treated at 80 ° C., and irradiated with 366 nm ultraviolet light, all of PC1, PC2 and PC3 were colored and black. Further, when this was irradiated with white light, the photosensitive layer became colorless and transparent again, so that the image display medium was recognized as white. This image display medium was again irradiated with 366 nm ultraviolet light to develop a color, and then a part thereof was irradiated with visible light having a center wavelength of 450 nm and a half-value width of 10 nm. Exhibited a blue color. When another portion was irradiated with visible light having a center wavelength of 520 nm and a half-value width of 10 nm, PC2 was selectively decolored and the irradiated portion was green. When another portion was irradiated with visible light having a center wavelength of 660 nm and a half-value width of 10 nm, PC3 was selectively decolored and the irradiated portion was red. In the non-irradiated portion of the visible light, the visible light having the three wavelength distributions described above was used, and the decoloring energies of PC1, PC2, and PC3 were determined in the same manner as in Reference Example 1, and 4158 mJ / cm ² and 5260 mJ / cm, respectively. ² and 4753 mJ / cm ² .

Next, the photosensitive layer of this image display medium is irradiated again with 366 nm ultraviolet light to saturate the color reaction, then irradiated with infrared light and temporarily heated to 170 ° C., and then the center wavelength is 420 nm. When the decoloring energies of PC1, PC2, and PC3 were similarly determined using visible light of 480 nm and 620 nm, they were 20 mJ / cm ² , 25 mJ / cm ² , and 23 mJ / cm ² , respectively. Furthermore, after irradiating the photosensitive layer of this image display medium with 366 nm ultraviolet light to saturate the coloring reaction, and then irradiating with infrared light, this heat treatment is temporarily performed at 80 ° C. Were found to be 4158 mJ / cm ² , 5260 mJ / cm ² and 4753 mJ / cm ² , respectively.

  As a result, it was confirmed that the decolorization energy of each photochromic compound can be reversibly changed greatly by the infrared light irradiation treatment even in an image display medium having a photosensitive layer composed of microcapsules each containing three kinds of photochromic compounds. It was.

( Reference Example 8 )
1 part by weight of PC1, 1 part by weight of PC2, 1 part by weight of PC3 and 27 parts by weight of docosylphosphonic acid were dissolved in tetrahydrofuran, added to the protective colloid aqueous solution, and emulsified by stirring at high speed. After adding sodium carbonate to adjust the pH to 9, urea-formaldehyde prepolymer is added, and acetic acid is further added to adjust the pH to 4. Then, the prepolymer is polymerized at the dispersion interface by reacting at 60 ° C. A film of urea-formaldehyde resin was formed, and microcapsules having a particle size of about 5 μm were obtained. A microcapsule was taken out from this dispersion, dried under reduced pressure, and a coating solution in which 3 parts by weight of microcapsules, 1 part by weight of D1, and 6 parts by weight of polycarbonate were dissolved in 40 parts by weight of tetrahydrofuran was added to white PET ( A polyethylene terephthalate) substrate (188 μm) was applied to form an 8 μm microcapsule film, and a PVA film (2 μm) was further formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

When the photosensitive layer of this image display medium was irradiated with infrared light and temporarily heat-treated at 80 ° C., and irradiated with 366 nm ultraviolet light, all of PC1, PC2 and PC3 were colored and black. Further, when this was irradiated with white light, the photosensitive layer became colorless and transparent again, so that the image display medium was recognized as white. This image display medium was again irradiated with 366 nm ultraviolet light to develop a color, and then a part thereof was irradiated with visible light having a center wavelength of 450 nm and a half-value width of 10 nm. Exhibited a blue color. When another portion was irradiated with visible light having a center wavelength of 520 nm and a half-value width of 10 nm, PC2 was selectively decolored and the irradiated portion was green. When another portion was irradiated with visible light having a center wavelength of 660 nm and a half-value width of 10 nm, PC3 was selectively decolored and the irradiated portion was red. In the visible light non-irradiated portion, the visible light having the above-mentioned three wavelength distributions was used, and the decoloring energies of PC1, PC2, and PC3 were determined in the same manner as in Reference Example 1 , and found to be 4283 mJ / cm ² and 5298 mJ / cm, respectively. ² and 4781 mJ / cm ² .

Next, the photosensitive layer of this image display medium is irradiated again with 366 nm ultraviolet light to saturate the color reaction, then irradiated with infrared light and temporarily heated to 170 ° C., and then the center wavelength is 420 nm. When the decoloring energies of PC1, PC2, and PC3 were similarly determined using visible light of 480 nm and 620 nm, they were 21 mJ / cm ² , 26 mJ / cm ² , and 24 mJ / cm ² , respectively. Furthermore, after irradiating the photosensitive layer of this image display medium with 366 nm ultraviolet light to saturate the coloring reaction, and then irradiating with infrared light, this heat treatment is temporarily performed at 80 ° C. Were found to be 4283 mJ / cm ² , 5298 mJ / cm ² and 4781 mJ / cm ² , respectively.

  As a result, it was confirmed that the decolorization energy of each photochromic compound can be reversibly changed greatly by the infrared light irradiation treatment even in an image display medium having a photosensitive layer of microcapsules containing three kinds of photochromic compounds. .

Example 9
1 part by weight of PC2, 9 parts by weight of docosylphosphonic acid and 1 part by weight of D1 were dissolved in tetrahydrofuran, added to a protective colloid aqueous solution, and emulsified by stirring at high speed. After adding sodium carbonate to adjust the pH to 9, urea-formaldehyde prepolymer is added, and acetic acid is further added to adjust the pH to 4. Then, the prepolymer is polymerized at the dispersion interface by reacting at 60 ° C. A film of urea-formaldehyde resin was formed, and microcapsules having a particle size of about 5 μm were obtained.

  Next, microcapsules were prepared in the same manner as described above using PC1 instead of PC2 and p- (octadecylthio) phenol instead of docosylphosphonic acid.

  Furthermore, microcapsules were produced in the same manner as described above using PC3 instead of PC2 and 2-octadecylglutaric acid instead of docosylphosphonic acid.

  Microcapsules were taken out from these dispersions, dried under reduced pressure, and the three were mixed in equal amounts to form a microcapsule film using polycarbonate as a binder on a white PET (polyethylene terephthalate) substrate (188 μm), Further, a PVA film (2 μm) was formed as a protective layer. Since the photosensitive layer thus formed was colorless and the color of the substrate was white, the produced image display medium was recognized as white by an observer.

When the photosensitive layer of this image display medium was irradiated with infrared light and temporarily heat-treated at 80 ° C., and irradiated with 366 nm ultraviolet light, all of PC1, PC2 and PC3 were colored and black. Further, when this was irradiated with white light, the photosensitive layer became colorless and transparent again, so that the image display medium was recognized as white. This image display medium was again irradiated with 366 nm ultraviolet light to develop a color, and then a part thereof was irradiated with visible light having a center wavelength of 450 nm and a half-value width of 10 nm. Exhibited a blue color. When another portion was irradiated with visible light having a center wavelength of 520 nm and a half-value width of 10 nm, PC2 was selectively decolored and the irradiated portion was green. When another portion was irradiated with visible light having a center wavelength of 660 nm and a half-value width of 10 nm, PC3 was selectively decolored and the irradiated portion was red. In the visible light non-irradiated portion, the visible light of the above-mentioned three wavelength distributions was used and the decoloring energies of PC1, PC2, and PC3 were obtained in the same manner as in Reference Example 1, and 4271 mJ / cm ² and 5237 mJ / cm, respectively. ² and 4830 mJ / cm ² .

Next, the photosensitive layer of this image display medium is irradiated again with 366 nm ultraviolet light to saturate the color reaction, then irradiated with infrared light and temporarily heated to 170 ° C., and then the center wavelength is 420 nm. , 480 nm, was determined visible PC1 in the same manner by using a light, PC2, PC3 decoloring energy of 620 nm, were respectively ^{24mJ / cm 2, 25mJ / cm} 2, 25mJ / cm 2. Furthermore, after irradiating the photosensitive layer of this image display medium with 366 nm ultraviolet light to saturate the coloring reaction, and then irradiating with infrared light, this heat treatment is temporarily performed at 80 ° C. Were 4271 mJ / cm ² , 5237 mJ / cm ² and 4830 mJ / cm ² , respectively.

  As a result, by forming a photosensitive layer using different electron-accepting compounds for the three types of photochromic compounds, it is possible to make adjustments such that the respective decolorization sensitivities are substantially equal, as in this example. It was confirmed that

Therefore, the present invention eliminates the influence of other medium components that can alienate the interaction between the specific fulgimide compound and the electron-accepting compound by adopting the configuration of claim 1 or 2. The interaction of the compounds can be controlled, and as a result, an image display medium capable of reversible switching of the decolorization sensitivity can be obtained.
Further, with the configuration of the present invention, an image display medium capable of multicolor display and reversible control of decolorization sensitivity can be obtained.
In addition, with the configuration of the present invention, it is possible to express colors in a wide hue range, and reversible control of the decolorization sensitivity is possible, and it is possible to achieve both shortening of the image formation time and ensuring color retention of the formed image. It becomes possible.
Moreover, by setting it as the structure of this invention, adjustment of the change degree of a decoloring sensitivity is attained for every fulgide type compound to be used.

Further, the present invention has the structure of claim 2 to improve the adhesion between the microcapsules and between the microcapsules and the support substrate, and to obtain a photosensitive layer having a high physical strength as a film, and an image display medium. It is done.

Further, the present invention is to provide a structure according to claim 3, the image display medium reversible control is possible of the erasing sensitivity only in the light irradiation treatment is obtained. In addition, since the infrared absorbing dye is present in the microcapsule together with the fulgide compound and the electron accepting compound, efficient heat treatment can be performed by the heat generation of the infrared absorbing dye.

Further, the present invention is to provide a structure according to claim 4, the image display medium reversible control is possible of the erasing sensitivity only in the light irradiation treatment is obtained. There are few restrictions on the formation of microcapsules and the degree of freedom is large.

Further, the present invention is to provide a structure according to claim 5, the image display medium reversible control is possible of the erasing sensitivity only in the light irradiation treatment is obtained. There are few restrictions on the formation of microcapsules and the formation of the photosensitive layer, and the degree of freedom is large.

Further, according to the present invention, the durability as an image display medium is improved physically and chemically by adopting the structure of claim 6 .

Further, according to the present invention, the decoloring sensitivity can be reversibly controlled by adopting the structure of claim 7 , and both shortening of the image forming time and securing of color retention of the formed image can be achieved.

Further, according to the present invention, the configuration according to claim 8 enables reversible control of the decolorization sensitivity only by the light irradiation process, and it is possible to achieve both shortening of the image forming time and securing the color retention of the formed image. Become.

Further, according to the present invention, it is possible to perform multi-color display and reversible control of the decolorization sensitivity by adopting the configuration of claim 9 , and it is possible to achieve both shortening of the image forming time and ensuring the color retention of the formed image. Is possible.

Further, according to the present invention, it is possible to perform multicolor display by using the structure of claim 10 and to enable reversible control of the decolorization sensitivity only by the light irradiation process, thereby shortening the image forming time and coloring the formed image. It is possible to ensure both retention.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

It is a figure for demonstrating the mechanism of the selective deletion of the specific photosensitive layer by the visible light wavelength of the photosensitive layer containing a photochromic compound. It is a figure which shows the reflection spectrum change accompanying visible light irradiation time. It is a graph which shows the change of the reflectance in a bottom wavelength.

Claims (10)

An image display medium in which a photosensitive layer containing at least three kinds of microcapsules containing a photochromic compound and an electron accepting compound is formed on a support substrate,
The combination of the photochromic compound and the electron accepting compound in the three types of microcapsules is 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) -2-trifluoromethyl, respectively. Ethylidene] -3-isopropylidene succinic acid-Np-dimethylaminophenylimide and p- (octadecylthio) phenol, 2- [1- (5-methyl-2-p-dimethylaminophenyl-4-oxazolyl) ethylidene ] -3-Isopropylidene succinic acid-Np-dimethylaminophenylimide and docosylsulfonic acid, and 2- [1- (2,5-dimethyl-1-p-dimethylaminophenyl-3-pyrrolyl) ethylidene] -3-Isopropylidene succinic acid-Np-dimethylaminophenylimide and 2-octane The image display medium, which is a Deshirugurutaru acid. The image display medium according to claim 1 , wherein the photosensitive layer comprises at least microcapsules and a binder material. The image display medium according to claim 1 or 2, characterized in that contains an infrared-absorbing dye in said microcapsules. The photosensitive layer is composed of at least microcapsules and a binder material and an infrared absorbing dye, a binder material in the photosensitive layer is characterized by a 0.1 to 100 fold of the microcapsules by weight according to claim 1 or 2 The image display medium described in 1. Further, the on between the photosensitive layer supporting substrate or the photosensitive layer, the image display medium according to any one of claims 1 to 4, characterized by providing a heating layer comprising an infrared absorbing dye. The photosensitive layer or the image display medium according to any one of claims 1 to 5, characterized in that a protective layer on the surface of the heat generating layer. The photochromic contained in the photosensitive layer by at least ultraviolet irradiation to the image display medium according to any one of claims 1 to 5 and an image display medium having a protective layer formed on the surface of the photosensitive layer or the heat generating layer. A step of coloring the compound, a step of heating to a temperature equal to or higher than the melting temperature of the electron-accepting compound, a step of irradiating a predetermined region with visible light in a wavelength region corresponding to the maximum absorption wavelength of the colored photochromic compound, and decoloring. And an image forming method comprising a step of heating to a temperature not higher than the melting temperature of the electron-accepting compound. 8. The image forming method according to claim 7 , wherein the heating method for the image display medium and the image display medium having a protective layer formed on the surface of the photosensitive layer or the heat generating layer is infrared light irradiation. The image display medium according to any one of claims 1 to 5 and an image display medium having a protective layer formed on the surface of the photosensitive layer or the heat-generating layer, all contained in the photosensitive layer by at least ultraviolet light irradiation. A step of coloring various types of photochromic compounds, a step of heating to a temperature higher than the melting temperature of the electron-accepting compound, and irradiating a predetermined region with visible light in a wavelength region corresponding to the maximum absorption wavelength of each colored photochromic compound. And a step of selectively decoloring each photochromic compound and a step of heating to a temperature not higher than the melting temperature of the electron-accepting compound. The image forming method according to claim 9 , wherein the heating method is infrared light irradiation.

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