JP2003186143A - Multicolor image display method and multicolor image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical rewritable multicolor image display method which uses photochromic compounds and light sources for irradiation having high practicability and can easily control color tones and a multicolor image display device using the method. <P>SOLUTION: An image display medium (1) containing ≥2 kinds of the photochromic compounds varying in the maximal absorption wavelengths in a color development state is irradiated with two kinds of UV light (I) and (II) varying in wavelengths respectively by an UV LED array (4) and a UV lamp (5) to develop the colors of all kinds of the photochromic compounds contained in the medium and thereafter the respective predetermined regions are irradiated with the visible light of the wavelength regions corresponding to the respective maximal absorption wavelengths by LED arrays (6) and (7) to selectively decolor the respective photochromic compounds, to form images. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image display method and a multicolor image display device, and more particularly to a multicolor image display method and a multicolor image display capable of repeating writing and erasing of a color image by light irradiation. The present invention relates to a display device.

[0002]

2. Description of the Related Art There have been some studies on a rewritable image display medium using a photochromic compound which causes a reversible color change upon irradiation with light. However, it is practical that a full color image can be reversibly displayed many times. There are still no examples that have proposed a multicolor image display method. As a means for forming a color image using a photochromic compound,
For example, in Japanese Patent Laid-Open No. 5-271649, 254 nm
Of three photochromic diarylethene compounds that emit yellow-orange when irradiated with ultraviolet light of 313, red when irradiated with ultraviolet light of 313 nm, and blue-violet when irradiated with ultraviolet light of 365 nm, and irradiate the corresponding ultraviolet light Has been done. Three primary colors (blue, green, red, or yellow, magenta, cyan) to form a full-color image
It is necessary to control at least three kinds of photochromic compounds that emit light with light, but there are two problems in the above technique.

One is a problem regarding material properties of the photochromic compound, and it is necessary to collect compounds that absorb three different kinds of ultraviolet rays and further develop three primary colors. Even in the above technology, full colors cannot be displayed because blue, yellow and the like are not colored. Also,
In order to put it into practical use, it is necessary to consider not only color development characteristics but also repeated durability, heat and humidity stability, and it is very difficult to develop a material that satisfies all of these.
The second is regarding the irradiation light source. Although a high-pressure mercury lamp is used as an irradiation light source in the embodiment of the above technique, it is necessary to write with a small and highly directional light source such as a semiconductor laser (LD) or a light emitting diode (LED) in order to form an image pattern. Is. In this case, it is difficult to develop LDs and LEDs in the ultraviolet region, and at this stage LEDs of 372 nm
Is partially commercialized, and the 342 nm LED is only in the development stage. Therefore, it is very difficult to develop three types of short wavelength LDs and LEDs of about 300 nm in the ultraviolet region, and the image display method based on the use of these light sources is not practical.

In Japanese Patent Application Laid-Open No. 7-199401, a mixture of three kinds of photochromic fulgide compounds showing yellow, magenta and cyan in a colored state is described as 36
A method has been proposed in which all types of photochromic compounds are colored with 6 nm ultraviolet light and then selectively decolorized with white light passed through a color positive film. With this technology,
Although there is an advantage that there is only one type of ultraviolet light, 3
Since three types of photochromic compounds having almost the same sensitivity are required in the vicinity of 66 nm, it is not easy to control the color tone and it is difficult to develop the material. Further, the compounds shown in the examples have a maximum durability of 30 times, which is not practical.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned situation and problems of the prior art. The problem is written by using an existing photochromic compound and a highly practical light source. Storage stability of image information,
An object of the present invention is to provide a rewritable multicolor image display method and a multicolor image display device which are excellent in durability against repeated writing / erasing.

[0006]

In order to solve the above-mentioned problems, the present invention according to claim 1 provides a supporting substrate with a photosensitive layer containing two or more kinds of photochromic compounds having different maximum absorption wavelengths in a colored state. The formed image display medium is irradiated with two kinds of ultraviolet light having different wavelengths to cause all kinds of photochromic compounds contained in the photosensitive layer to develop color, and then the maximum absorption wavelength of each colored photochromic compound. In the multicolor image display method, visible light in a wavelength range corresponding to is irradiated to a predetermined area to selectively erase each photochromic compound to form an image.

The present invention according to claim 2 is characterized in that at least one of the two types of ultraviolet light is applied to the entire surface of the image display portion of the image display medium. Image display method. The present invention according to claim 3 provides the multicolor image display method according to claim 1, characterized in that the two types of ultraviolet light are applied only to predetermined regions. The present invention according to claim 4 is characterized in that the photosensitive layer has a maximum absorption wavelength of 400 nm or more in a coloring state.
A photochromic compound in the range of less than 00 nm,
4. The multicolor image display method according to claim 1, further comprising a photochromic compound in the range of 500 nm or more and less than 600 nm and a photochromic compound in the range of 600 nm or more and less than 700 nm. . The present invention according to claim 5 provides the multicolor image display method according to any one of claims 1 to 4, wherein the protective layer is formed on the surface of the photosensitive layer.

The present invention according to claim 6 provides the multicolor image display method according to any one of claims 1 to 5, characterized in that the irradiation intensity or irradiation time of the ultraviolet light is controlled. The present invention according to claim 7 provides the multicolor image display method according to any one of claims 1 to 6, wherein the irradiation intensity or irradiation time of visible light is controlled. The present invention according to claim 8 includes the step of irradiating the entire surface of the image display portion of the image display medium with white light.
The multicolor image display method described in any one of 1 to 7.

According to a ninth aspect of the present invention, the visible light source comprises a white light source and an optical filter, and the multicolor image display method according to any one of the first to eighth aspects. To do. The present invention according to claim 10 provides the multicolor image display method according to any one of claims 1 to 8, wherein the visible light source is a plurality of types of light emitting elements having different emission wavelengths. . The present invention according to claim 11 comprises a linear ultraviolet light source and a visible light source,
A multicolor image display device, wherein an image is formed by using the multicolor image forming method according to any one of claims 1 to 10 while relatively moving the image display medium and the light source.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In order to form a full-color image, at least three types of photochromic compounds corresponding to the three primary colors must be controlled by light, but in the present invention, the ultraviolet light source used for color development corresponds to the absorption wavelength of at least one type of photochromic compound. The ultraviolet light (I) and the ultraviolet light (II) corresponding to the absorption wavelength of the remaining photochromic compound are shared. An example of the structure of the image display medium used in the present invention is shown in FIG. In FIG. 1, a photochromic compound (X) that develops cyan by absorbing ultraviolet light (I) and a photochromic compound (Y) that develops magenta and yellow by absorbing ultraviolet light (II), respectively ( And Z) are layered to form a photosensitive layer. The image display medium is
It is composed of a photosensitive layer and a support substrate that supports the photosensitive layer. As a multicolor image display method for displaying a full-color image on the image display medium, the following three methods will be mainly described in the present invention.

First, as shown in FIG. 2, UV light (I) and (II) are used to irradiate the entire surface of the image display portion of the image display medium with a lamp light source so that all kinds of photochromic compounds are irradiated. This is a method in which after color development, three kinds of semiconductor lasers (LD) or light emitting diodes (LEDs) in the visible range corresponding to each color are selectively erased. The entire surface is black when all types of photochromic compounds are colored. Here, in order to decolorize cyan, irradiation with visible light having a wavelength of 600 nm or more and less than 700 nm, preferably visible light in the vicinity of 650 nm may be applied. Similarly, for erasing magenta, visible light having a wavelength of 500 nm or more and less than 600 nm, preferably visible light having a wavelength of around 550 nm, may be irradiated, and for erasing yellow, visible light having a wavelength of 400 nm or more and less than 500 nm may be used. light,
Irradiation with visible light in the vicinity of 450 nm is preferable.
As a method for selectively erasing by using LD and LED, for example, a method of performing on / off control while scanning a laser beam with a rotating mirror, or a method of arranging LEDs arranged in an array according to an image signal is used. A method of performing on / off control by means of the like may be considered, but any method may be used.

As a light source for irradiating the ultraviolet light, a mercury lamp, a xenon lamp or the like may be combined with an optical filter to extract the ultraviolet light in a desired wavelength range for use.
You may use the light emitting element which emits light of a specific wavelength range, such as LED and LD. For example, in the case of manufacturing a display device in which a light source system for writing / erasing is made as compact as possible, a light emitting element such as an LED is preferable, and further, light emission capable of controlling on / off of irradiation for each minute region. You may comprise the light source array which formed the surface in succession.

As a light source for irradiating visible light, a lamp having a structure in which an optical filter is combined with a white light source may be used, or a light emitting element such as an LED or LD which emits light in a specific wavelength range may be used. Good. For example, in the case of manufacturing a display device in which a light source system for writing / erasing is made as compact as possible, a light emitting element such as an LED is preferable, and further, light emission capable of controlling on / off of irradiation for each minute region. You may comprise the light source array which formed the surface in succession. In particular, in the case of irradiating only a desired area, the irradiation of each light emitting surface of the light source array is turned on / off while the light source array and the image display medium having the photosensitive layer formed on the supporting substrate are relatively moved. It can also be done by controlling the off. As described above, according to the present invention, since it is possible to display a multicolor image only by irradiating light, the energy used is smaller than that in the heat-sensitive method, and it is possible to form an image with higher resolution than that in the electric field method. Furthermore, since many photochromic compounds can be used, the method is a multicolor image display method that is stable to heat and humidity and has durability against repetition.

Second, as shown in FIG. 3, by using an ultraviolet LD and an LED as the ultraviolet light (I), cyan is selectively colored, and the ultraviolet light (II) is a lamp light source over the entire image display portion. By irradiating, the entire color of magenta and yellow is developed, and then 2 corresponding to magenta and yellow.
This is a method of selectively erasing with a LD or LED in the visible region of a type. This is because it is not necessary to irradiate at least one of the two types of ultraviolet light as a light source of the ultraviolet light in units of fine spots corresponding to the pixel size, so that the structure of the light source element is easy and the cost is reduced. It is advantageous.

Thirdly, as shown in FIG. 4, by irradiating both ultraviolet light (I) and (II) with an ultraviolet LD and an LED, a collective portion of cyan and magenta and yellow is selectively colored, After that, the magenta and yellow coloring portions are selectively erased by two types of visible region LDs and LEDs corresponding to the respective colors. In particular, the second and third methods do not require full-color development once, so they are useful in terms of reducing energy consumption and writing time when displaying images with many white areas such as text documents. is there.

In any of the above methods, the multicolor image display method of the present invention using two kinds of ultraviolet light sources having different wavelengths and visible light solves the problems of the prior art. First, as compared with a multicolor image display method using three types of ultraviolet light, the present invention has an advantage that only two types of ultraviolet light are required. Looking at the development trend of ultraviolet light sources, ultraviolet LD, L
It is considered very difficult to develop three types of EDs with different wavelengths (at least the wavelengths must be apart from each other by several tens of nm in order to avoid overlapping of absorption bands).
It is fully possible to develop only two types of ultraviolet LD and LED. Since the LDs and LEDs in the visible range have been put to practical use in small size and high output, a device having two kinds of wavelengths of ultraviolet light is highly practical.

Next, as compared with the method using one ultraviolet light and three kinds of visible light, there is an advantage that many photochromic compounds can be used. The absorption wavelength of the existing photochromic compound in the decolored state is in the range of less than 350 nm and mainly in the range of 350 nm or more and less than 400 nm, but one ultraviolet light (for example, 36 nm) is used.
In the case of 6 nm or 313 nm), only one of these compounds can be used. However, in the present invention using two kinds of ultraviolet light, both of them can be used, so that the range of selection of the photochromic compound is widened. Practical use of photochromic compounds has many problems such as thermal stability and repeated durability, but by selecting from a wide range of compounds, compounds having a molecular structure that can overcome these problems can be used. Typical photochromic compounds include spiropyran,
Examples include spirooxazine, fulgide, diarylethene and the like.

The photosensitive layer used in the present invention comprises a photochromic compound having a maximum absorption wavelength in the colored state of 400 nm to less than 500 nm, and a photochromic compound having a maximum absorption wavelength in the colored state of 500 nm to less than 600 nm. It contains all photochromic compounds having a maximum absorption wavelength in the colored state of 600 nm or more and less than 700 nm. The colors recognized in the color-developed state of each photochromic compound substantially correspond to yellow, magenta, and cyan, respectively, and these three primary colors are formed. It is preferable that these photochromic compounds have no overlap of absorption bands in their respective visible regions.

The maximum absorption wavelength in the colored state is 400 n
Examples of the diarylethene compound having a photochromic property in the range of m to less than 500 nm include, for example,
1,2-bis (2-phenyl-4-trifluoromethylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene, dimethyl 2,3-di (2-methylbenzothienyl) maleate, 1,2-bis (5-ethoxy-2-methylthiazole) -3,3,4,4,5,5
-Hexafluorocyclopentene, etc. The maximum absorption wavelength in the colored state is 500 nm or more and 600 n
As the diarylethene compound having a photochromic property in the range of less than m, for example, 1- (3- (2-
Methyl-6- (2- (4-methoxyphenyl) ethynyl) benzothienyl))-2- (3- (2,4-dimethyl-5- (2- (4-methoxyphenyl) ethynyl) thienyl))-3 , 3,4,4,5,5-hexafluorocyclopentene, 1,2-bis (5-methyl-2-phenylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene, 1- (1,2-dimethyl-3-
Indolyl) -2- (2-methyl-3-benzothienyl) -3,3,4,4,5,5-hexafluorocyclopentene, and the like. Examples of the diarylethene compound having a photochromic property in which the maximum absorption wavelength in the colored state is 600 nm or more and less than 700 nm include, for example, 1- (5-methoxy-1,2-dimethyl-
3-indolyl) -2- (5-cyano-2,4-dimethyl-3-thienyl) -3,3,4,4,5,5-hexafluorocyclopentene, 1- (5-methoxy-1,2)
-Dimethyl-3-indolyl) -2- (6-carboxyl-2-methyl-3-benzothienyl) -3,3,4
4,5,5-hexafluorocyclopentene, 1- (6
-Cyano-2-methyl-3-benzothienyl) -2-
(5-Methoxy-1,2-dimethyl-3-indolyl)
-3,3,4,4,5,5-hexafluorocyclopentene, and the like.

The photosensitive layer used in the present invention may be a photochromic compound only, but the maximum absorption wavelength in the color-developed state is greatly different. Therefore, these photochromic compounds recognized almost as yellow, magenta, and cyan may be uniformly mixed at a predetermined mixing ratio to form a single-layer photosensitive layer together with the binder material. A plurality of photosensitive layers may be formed by laminating photosensitive layers made of a binder material. It may also be dispersed in a resin such as an acrylic resin, vinyl chloride resin, polyester resin, polyamide resin, polyolefin resin or urethane resin. Moreover, although the example of FIG. 1 has a laminated structure, the photochromic compounds may be mixed. Also,
The photochromic compound may be encapsulated in microcapsules. Further, the photosensitive layer is preferably formed on a white supporting substrate. The support substrate is preferably a thin film such as paper or film, but is not limited to this.

As a method for forming the photosensitive layer, a vapor deposition method may be used in addition to the coating method. The coating method is simple and the printing method and the spin coating method are prepared by dissolving both the photochromic compound and the binder material in a solvent. It may be applied by a method such as the above and dried to form a film. The photosensitive layer may be either a single layer or a plurality of layers, but when forming a plurality of layers, it is preferable to form a separation layer between the layers so that adjacent layers are not mixed. The separation layer can be formed by applying a film-forming solution using a solvent that does not dissolve the binder material and the photochromic compound in the photosensitive layer.

A protective layer may be formed on the surface of the photosensitive layer used in the present invention. The cause of the deterioration of the photochromic compound is the bonding of oxygen during the photochemical reaction. If the atmosphere is shielded by the protective layer, the durability is repeatedly improved. As a material for the protective layer, a transparent resin such as polyvinyl alcohol, polycarbonate, or acrylic resin is desirable. Further, examples of the film forming method include a vacuum vapor deposition method, a coating method, a spin coating method, a dipping method and a casting method.

In order to display a full-color image, it is necessary to develop an intermediate color. The color change of the photochromic compound is determined by the number of photo-reacted molecules, and the number of photo-reacted molecules corresponds to the number of photons in the irradiation light, so the color density can be easily adjusted by changing the irradiation light intensity or irradiation time. . The color density in the colored state may be changed by changing the intensity of the ultraviolet light or the irradiation time, or the color density may be changed by adjusting the coloring degree by changing the intensity of the visible light or the irradiation time. . Of course, both may be combined.

The image created by the multicolor image display method of the present invention can be easily rewritten by irradiating it with ultraviolet light and visible light again. Irradiation is easy. By irradiating all wavelengths in the visible region with white light at once, all the photochromic compounds in the colored state become decolorized bodies and become blank.

In the display method of the present invention, visible light in a plurality of wavelength ranges is used. As the light source, a combination of a white light source and an optical filter for extracting each wavelength or a plurality of types of light emitting elements having a specific emission wavelength range are used. It is possible to do either. When a white light source and an optical filter for extracting each wavelength are used, there is an advantage that the wavelength can be easily adjusted depending on the forming conditions of the optical filter and the like.
When a plurality of types of light emitting elements having a specific emission wavelength range are used, there are advantages that light utilization efficiency is high and energy consumption can be reduced.

When a multicolor image display device is manufactured using the multicolor image display method of the present invention, various configurations can be considered depending on the type and number of light sources, and may be appropriately selected according to the application. . However, considering high resolution, high speed writing, downsizing, and low cost, it is considered more preferable to install each light source in a line and write while moving the image display medium and the light source relatively. 5 and 6
Shows a configuration example of the multicolor image display device. 5 is a side view and FIG. 6 is a plan view. In this example, the image display medium (1) is conveyed by a plurality of conveying rollers (2). After whitening the image display portion of the image display medium (1) with white light (3), the cyan portion is written according to the image pattern by the ultraviolet LED array (4) of ultraviolet light (I). Then, magenta and yellow are entirely developed by an ultraviolet lamp (5) of ultraviolet light (II). After that, the LED array (6) which is visible light of 550 nm and the L which is visible light of 450 nm
With the ED array (7), magenta and yellow are erased according to the image pattern, and a full-color image is formed.

[0027]

EXAMPLES Example 1 As photochromic compounds, 1,2-bis (5-ethoxy-2-methylthiazole) hexafluorocyclopentene [hereinafter abbreviated as PC1], which is a diarylethene compound, 1,2-bis (3- (2-Methyl-6- (2- (4-methoxyphenyl) ethynyl) benzothienyl))-3,3,4,4
5,5-hexafluorocyclopentene [hereinafter abbreviated as PC2], 1- (6- (2- (4-dimethylaminophenyl) -1-ethenyl) -2-methyl-3-benzothionyl) -2-((5 -(2- (4-cyanophenyl) -1
-Ethenyl))-2,4-dimethyl-3-thienyl)-
3,3,4,4,5,5-hexafluorocyclopentene [hereinafter abbreviated as PC3] was used. When the absorption spectra of these photochromic compounds were measured, the maximum absorption wavelength before light irradiation was 330 nm for PC1 and 3 for PC2.
00 nm and PC3 were 370 nm, and both were colorless. When PC1 and PC2 were irradiated with a 313 nm bright line of a high pressure mercury lamp, the maximum absorption wavelength of PC1 was 475 n.
m, indicating a yellow color. The maximum absorption wavelength of PC2 was 565 nm, which was reddish purple. When PC3 was irradiated with a 366 nm bright line of a high-pressure mercury lamp, the maximum absorption wavelength of PC3 was 632 nm, which was blue.

10 mg of PC1 is replaced with 100 m of polystyrene
It was dissolved in toluene together with g and blade-coated on a supporting substrate (thickness 100 μm) made of white polyethylene terephthalate. Similarly, dissolve PC2 and PC3 together with polystyrene in toluene, and place PC2 on the PC1 layer.
2. Furthermore, PC3 was laminated on it, and the photosensitive layer was produced. The thickness of the photosensitive layer formed by laminating three layers was about 30 μm.
313 nm and 366 nm of high pressure mercury lamp on the entire surface of this photosensitive layer
When each of the bright lines is irradiated for several tens of seconds, PC1 to P
All layers of C3 developed color showing a dark gray color. Next, when a part of the photosensitive layer was irradiated with an LED of 468 nm for several seconds, the irradiated part became bluish purple. Next, another part of the photosensitive layer was irradiated with an LED of 560 nm for several seconds, and the irradiated part became green. In addition, 660n on another part of the photosensitive layer
When the LED of m was irradiated for several seconds, the irradiated part became pale red.

(Comparative Example 1) After a photosensitive layer was prepared using the same photochromic compound as in Example 1, the entire surface of the photosensitive layer was irradiated with only 313 nm ultraviolet light of a high pressure mercury lamp for several tens of seconds. Although color was developed, PC3 hardly developed color and turned red.

(Example 2) After a photosensitive layer was prepared by using the same photochromic compound as in Example 1, a part of the photosensitive layer was irradiated with an ultraviolet LED of 372 nm for several tens of seconds, and only PC3 developed a color and turned blue. became. Then 313
When the whole surface of the photosensitive layer was irradiated with a high-pressure mercury lamp of nm, the blue part was dark gray and the other parts were red. Further, when a part of the red part was irradiated with an LED of 468 nm, the part turned reddish purple. (Example 3) After a photosensitive layer was prepared using the same photochromic compound as in Example 1, 372 was formed on a part of the photosensitive layer.
When it was irradiated with an LED of nm, only PC3 developed a color and became blue. When another portion of the photosensitive layer was irradiated with a He-Cd laser (325 nm), a red color was obtained.
Furthermore, when a part of the red part was irradiated with an LED of 560 nm, it turned yellow.

Example 4 After a photosensitive layer was prepared using the same photochromic compound as in Example 1, a part of the photosensitive layer was irradiated with an LED of 372 nm at half the intensity of Example 3 for the same time. Compared to Example 3, the color change was small and the color became light blue. (Example 5) After a photosensitive layer was prepared using the same photochromic compound as in Example 1, He- was formed on a part of the photosensitive layer.
When it was irradiated with a Cd laser (325 nm), it showed a red color. Further, when a 560 nm LED was applied to a part of the red portion at an intensity half that of Example 3 for the same time, there was less color change as compared with Example 3, and the color changed to pale red. (Embodiment 6) The photosensitive layer having the color changed in each of Embodiments 1 to 40
When a xenon lamp having a wavelength of 0 nm or more was irradiated for several seconds, all the compounds became decolored and the white polyethylene terephthalate supporting substrate became white. The white polyethylene terephthalate substrate became white.

(Example 7) Several 372 nm LEDs were arranged in a line. At this time, the four sides of each LED were covered with reflecting mirrors so that the light beams of the LEDs did not interfere with each other. Similarly, several 468 nm and 560 nm LEDs are lined up to form 372 nm, 468 nm and 560 nm.
We arranged them in parallel in the order of. Furthermore, a fluorescent tube (313 nm) was placed in front of the 372 nm LED. After a photosensitive layer was prepared using the same photochromic compound as in Example 1, the photosensitive layer was slowly conveyed from the fluorescent tube side at several mm / sec, and each light source was turned on / off at regular intervals. As a result, the irradiated light source caused a color change in each part of the photosensitive layer, and yellow, blue, and dark gray color display was possible.

[0033]

As described above, according to the present invention as set forth in claim 1, since it is possible to display a multicolor image only by irradiating light, the energy consumption is smaller than that in the heat-sensitive system.
In addition, it enables high-resolution image formation compared to the electric field method, and since many photochromic compounds can be used, it is a multicolor image that can be used with an image display medium that is stable to heat and humidity and has repeated durability. A display method can be provided. Further, according to the present invention as set forth in claim 2, since it is not necessary to irradiate at least one of the two types of ultraviolet light as a light source in a fine spot unit corresponding to a pixel size, the light source element It is possible to provide a multicolor image display method which is easy in construction and advantageous in terms of cost. Further, according to the present invention described in claim 3, it is not necessary to perform light irradiation (writing processing) on a portion corresponding to white (colorless) on the image signal, and only a portion other than white is selectively selected. Although light irradiation is performed, in the case of targeting an image in which the white part occupies most, a multicolor image display method capable of reducing writing energy and writing time can be provided.

Furthermore, according to the present invention as defined in claim 4, the three primary colors of color display can be obtained by changing the wavelength of the irradiation light, so that the three primary colors of the color display can be set at predetermined positions on the image display medium according to the image signal. By irradiating light of a predetermined wavelength, it is possible to provide a multicolor image display method capable of multicolor display. Further, according to the present invention described in claim 5,
By forming a protective layer, due to moisture and specific gas,
It is possible to reduce the adverse effect on the color development of the compound constituting the photosensitive layer, improve the durability, and provide a multicolor image display method capable of highly reliable multicolor display. Further, according to the present invention of claim 6 or 7, since the degree of color development can be adjusted by controlling the irradiation intensity or irradiation time of the light source, it is necessary and sufficient for the color density required in the image to be displayed. Provided is a multicolor image display method capable of producing various colors, reducing the degree of decolorization by irradiation with visible light, reducing energy consumption, and being advantageous in repeated durability of coloring and decoloring of materials. be able to.

Further, according to the present invention of claim 8, a white light source is provided in addition to a visible light source of each wavelength for selectively erasing each photochromic material, and a white light is provided on the entire display portion. By adding the step of irradiating light,
It is possible to provide a multicolor image display method capable of erasing all displayed images in a short time. Furthermore, according to the present invention of claim 9, a white light source and an optical filter constitute a visible light source for selectively erasing each photochromic material. As a result, it is possible to provide a multicolor image display device in which the wavelength can be easily adjusted. Further, according to the present invention as set forth in claim 10, since a light emitting element having a specific emission wavelength range is used as a visible light source and a light absorbing member such as an optical filter is not used, the light utilization efficiency is high and the consumption is high. A multicolor image display device capable of reducing energy can be provided. Furthermore, according to the present invention of claim 11, it is possible to write and erase a high resolution image in a short time.
A rewritable multicolor image display device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a photosensitive layer according to the present invention.

FIG. 2 is a diagram showing an example of a multicolor image display method of the present invention.

FIG. 3 is a diagram showing an example of a multicolor image display method of the present invention.

FIG. 4 is a diagram showing an example of a multicolor image display method of the present invention.

FIG. 5 is a side view showing an example of a multicolor image display device of the present invention.

FIG. 6 is a plan view of the multicolor image display device of FIG.

[Explanation of symbols]

1 Image display medium 2 Conveyor rollers 3 white light 4 UV LED array 5 UV lamp 6 LED array (550 nm) 7 LED array (450 nm)

Claims (11)

[Claims] 1. An image display medium comprising a support substrate and a photosensitive layer containing two or more types of photochromic compounds having different maximum absorption wavelengths in a color-developed state is irradiated with two types of ultraviolet light having different wavelengths. , After coloring all kinds of photochromic compounds contained in the photosensitive layer, irradiating visible light in the wavelength region corresponding to the maximum absorption wavelength of each colored photochromic compound to a predetermined region, respectively. A multicolor image display method characterized in that an image is formed by selectively erasing. 2. The multicolor image display method according to claim 1, wherein at least one of the two types of ultraviolet light is applied to the entire surface of the image display portion of the image display medium. 3. The multicolor image display method according to claim 1, wherein the two types of ultraviolet light are applied only to predetermined areas. 4. The photosensitive layer has a maximum absorption wavelength of 400 nm or more and 500 in a coloring state.
a photochromic compound in the range of less than nm, 50
4. The multicolor image display method according to claim 1, further comprising a photochromic compound in the range of 0 nm to less than 600 nm and a photochromic compound in the range of 600 nm to less than 700 nm. 5. The multicolor image display method according to claim 1, wherein the protective layer is formed on the surface of the photosensitive layer. 6. The multicolor image display method according to claim 1, wherein the irradiation intensity or irradiation time of the ultraviolet light is controlled. 7. The multicolor image display method according to claim 1, wherein the irradiation intensity or irradiation time of visible light is controlled. 8. The multicolor image display method according to claim 1, further comprising the step of irradiating the entire surface of the image display portion of the image display medium with white light. 9. The visible light source comprises a white light source and an optical filter.
The method for displaying a multicolor image according to any one of 1. 10. The multicolor image display method according to claim 1, wherein the visible light source is a plurality of types of light emitting elements having different emission wavelengths. 11. The multicolor image forming method according to claim 1, further comprising a line-shaped ultraviolet light source and a visible light source, wherein the image display medium and the light source are relatively moved. A multicolor image display device characterized in that an image is formed by using.