JP2003186424A - Reversible image display medium and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rewriting type reversible image display medium and an image display method which make it possible to easily control the color tone of a full-color image. <P>SOLUTION: The reversible image display medium (1) is used which has two or more kinds of photochromic compound groups, having different absorption wavelength bands in a coloring state, formed on a white base substrate in regular array pattern. The medium (1) contains all of the photochromic compound groups: a group having a 450 to <550 nm maximum absorption wavelength in a coloring state, a group having a 550 to <650 nm maximum absorption wavelength in a coloring state, and a group having 400 to <500 nm and 600 to <700 nm maximum absorption wavelengths of its two or more absorption bands in a coloring state. <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 reversible image display medium, and more particularly to an image display medium and an image display method capable of reversible multicolor image formation by light irradiation.

[0002]

2. Description of the Related Art As the consumption of paper in offices has increased, research has been actively conducted on a reversible image display medium and an image display method capable of repeatedly recording and erasing images as a medium replacing paper. For example, a heat-sensitive reversible image display medium that is composed of a mixture of a polymer compound and a higher fatty acid such as oleic acid, becomes transparent when heated to a specific temperature, and becomes cloudy when heated to another temperature is put into practical use. Has been done. Further, it is composed of a composition containing a leuco dye and a color developer, and when the leuco dye and the color developer are temporarily heated to a temperature higher than the melting temperature to cause various colors to develop due to the structure of the leuco dye, the melting temperature A heat-sensitive reversible image display medium has been put into practical use, which is decolored by separating the leuco dye and the color developer by reheating to a lower temperature. However, all of the above-mentioned reversible image display media are monochrome displays, and there are no practical examples of reversible image display media capable of color display.

As a reversible image display medium capable of color display, for example, in JP-A-7-81235, a shielding layer capable of reversibly changing between a transparent state and an opaque state by heating is used and three primary colors (red, A shielding layer, which is a mixture of a high molecular compound and an organic low molecular substance, is formed on a supporting substrate that is separately coated with green, blue, or yellow, magenta, and cyan), and the image portion is made transparent by heat. Thus, a rewritable simple color image display medium for displaying the color of the supporting substrate is disclosed.

Further, in Japanese Patent Application Laid-Open No. 8-58245,
A variable transmission layer capable of reversibly controlling a transparent state and a light scattering state by heating is formed on a support substrate coated with three primary colors, and the image portion is made to be in a transmission state by heat, thereby forming a support substrate. A rewritable information recording sheet and recording system that displays colors is disclosed.

Further, in Japanese Patent Application Laid-Open No. 8-80682,
A variable transmission layer capable of reversibly controlling the transparent state and the light scattering state by heating is formed on a support substrate coated with three primary colors, and the image portion is heated by exposing it to light of a specific wavelength. However, a color rewritable recording medium and a recording method for displaying the color of the supporting substrate are disclosed.

In each of the above-mentioned JP-A-7-81235, JP-A-8-58245, JP-A-8-80682, etc., a transparent state is formed by heating on a support substrate which is preliminarily coated in three primary colors. Disclosed is a reversible image display medium having a heat-sensitive layer controllable in a cloudy state. However, since the transparent state of the heat-sensitive layer is not completely transparent, the color of the supporting substrate displayed has a low coloring density,
The image contrast is not clear. In addition, the white turbid state does not completely scatter light, and the reflectance is low, so that it does not reach the whiteness of the paper.

Therefore, in JP-A-9-160511, a magnetic particle layer whose orientation state is changed by heating and magnetic application is formed on a pattern forming layer in which black, yellow, magenta, and cyan are arranged, and an image portion is formed. Disclosed is a magnetic recording body that displays the color of a pattern forming layer by bringing the layer into a transparent state by heating and applying a magnetic field, and a recording method thereof.

Further, in Japanese Patent No. 2976111, polymer liquid crystals having different glass transition temperatures and isotropic phase transition temperatures, each of which is colored in three primary colors, are arranged in a pattern on a supporting substrate and rapidly cooled from the isotropic phase transition temperature or higher. Disclosed is a color image forming medium, a color image forming method, and a color image forming apparatus, in which the polymer liquid crystal has a fixed light transmission state and the polymer liquid crystal has a fixed light scattering state when slowly cooled.

In the above-mentioned Japanese Patent Laid-Open No. 9-160511, a magnetic particle layer is used instead of the heat-sensitive layer, and Patent Document 2
In the 976111 technology, polymer liquid crystals colored in three primary colors are used, but the contrast between the transparent state and the light scattering state is still poor, and it is difficult to form a high quality image.

In Japanese Patent No. 3080122, red,
A display recording medium, a display recording method, and a display recording device, which form images by stacking polymer cholesteric liquid crystals that selectively reflect green and blue respectively and changing the alignment state of the polymer cholesteric liquid crystals by applying an electric field and heating, are provided. Disclosure.

Similarly, in Japanese Unexamined Patent Publication No. 11-149088, a plurality of cholesteric liquid crystals that selectively reflect different colors in visible light are laminated, an image is written by applying an electric field from the outside, and a memory effect of the cholesteric liquid crystals is obtained. , A display storage medium capable of holding a color display screen without an electric field, an image writing method, and an image writing apparatus are disclosed.

Similarly, in Japanese Patent Laid-Open No. 11-24027, a recording material composed of a cholesteric liquid crystal compound having a molecular weight of 2000 or less and a glass transition temperature of 35 ° C. or more or a mixture thereof is laminated and rapidly cooled from the cholesteric liquid crystal state. Discloses a rewritable color image recording medium and an image forming method using the rewritable color image recording medium, in which the reflected color can be stored at room temperature for a long period of time and can be repeatedly recorded by returning to a liquid crystal state.

The above-mentioned Japanese Patent No. 3080122, Japanese Patent Laid-Open Nos. 11-149088 and 11-24027, etc. disclose techniques utilizing the selective reflection characteristics of cholesteric liquid crystals. However, when the selective reflection color of the cholesteric liquid crystal is used, it is difficult to make the base color white because the black light absorption layer must be provided under the liquid crystal layer.
Therefore, although high image quality is possible, it is not a medium suitable for use as a substitute for paper.

Further, in JP-A-2000-35598, a dispersion medium colored in each of the three primary colors and a white electrophoretic element or magnetophoretic element are enclosed in a microcapsule, and the element is applied by applying an electric field or a magnetic field. Run,
A reversible image display medium for displaying a color image is disclosed. In the above technique, the electrophoretic element or the magnetophoretic element is moved to the surface to display the white color by hiding the colored dispersion medium, but a problem such as the colored dispersion medium remaining in the gap between the electrophoretic elements occurs. It is difficult to make the entire surface of the reversible image display medium completely white, and it is not suitable for use as a substitute for paper.

As described above, the conventionally proposed reversible image display medium capable of color display cannot show white as a background color having a reflection characteristic equivalent to that of paper. As it is said that people who are accustomed to the white color of paper routinely work with an image display medium having a lower reflectance than paper as an alternative, their eyes are tired and work efficiency decreases, so the whiteness of the background color is is important.

In order to show white as a background color, a reversible layer which reversibly changes between a completely transparent state and a colored state may be formed on a paper or a white substrate having a reflection characteristic equivalent to paper. . Examples of the material that reversibly changes between a completely transparent state and a colored state include a photochromic compound that causes a reversible color change by light irradiation. Although there have been some studies on color display media using a photochromic compound, there is still no example that proposes a practical technique for displaying a full-color image.

As a technique for forming and displaying a color image using a photochromic compound, for example, Japanese Patent Application Laid-Open No. 5-2 is known.
Japanese Patent No. 71649 discloses yellow-orange with 254 nm ultraviolet light.
A technique is disclosed in which three types of photochromic diarylethene compounds that emit red light with 313 nm ultraviolet light and blue-violet light with 365 nm ultraviolet light are mixed, and the corresponding ultraviolet light is irradiated.

In order to form a full-color image, at least three types of photochromic compounds that emit three primary colors (red, green, blue, or yellow, magenta, and cyan) must be controlled by light. Then 2
There are two problems. One is the material properties of photochromic compounds, and it is necessary to collect compounds that absorb three different types of ultraviolet rays and further develop three primary colors. Even in the above technology, since blue, yellow, etc. are not colored, a full-color image cannot be displayed. 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 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 there. In this case, it is very difficult to develop three types of short wavelength LDs and LEDs of 350 nm or less in the ultraviolet region, and the display technology based on the use of three types of ultraviolet light sources is not practical.

In Japanese Patent Laid-Open No. 7-199401, a mixture of three kinds of photochromic fulgide compounds showing yellow, magenta, and cyan in a colored state is used.
A technique is disclosed in which all kinds of photochromic compounds are colored with a 6 nm ultraviolet lamp, and then visible light in a wavelength range corresponding to the maximum absorption wavelength of each colored photochromic compound is irradiated to selectively decolor. . The above technique has the advantage that there is only one type of ultraviolet light, but has a major problem in the process of selectively erasing a specific type of photochromic compound. That is, since the absorption spectrum of the organic compound is broad, for example, the absorption spectrum of the photochromic compound that develops yellow and the absorption spectrum of the photochromic compound that develops magenta have a certain degree of overlap, and when the former is erased, the latter also becomes Not a little disappears. Therefore, it is not easy to control the color tone.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned situation and problems of the prior art, and its problem is a rewritable full-color that has a white background color and can be a substitute for paper. An object of the present invention is to provide a reversible image display medium for images, and an image display method and an image display device for forming an image using a light source having high practicality for the reversible image display medium.

[0021]

In order to solve the above problems, the present invention as set forth in claim 1, wherein two or more kinds of photochromic compound groups having different absorption wavelength bands in a colored state are regularly arranged on a supporting substrate. A reversible image display medium characterized by being formed in an array pattern. The present invention according to claim 2 provides the reversible image display medium according to claim 1, wherein the support substrate is white. The present invention according to claim 3 has a maximum absorption wavelength of 45 in the coloring state.
A photochromic compound group in the range of 0 nm or more and less than 550 nm and a maximum absorption wavelength of 550 in the coloring state.
has a photochromic compound group in the range of 1 nm or more and less than 650 nm and two or more absorption wavelength bands in a colored state, and the maximum absorption wavelength of two of the absorption wavelength bands is 40
0 nm or more and less than 500 nm and 600 nm or more and 700 n
3. The reversible image display medium according to claim 1, which contains all of the photochromic compound group in the range of less than m. A fourth aspect of the present invention is the reversible image display medium according to any one of the first to third aspects, which comprises a photochromic compound group having an absorption wavelength band in a colored state in the entire visible region.

The present invention according to claim 5 is characterized in that the regular arrangement pattern of the photochromic compound group formed on the supporting substrate is a stripe shape.
The reversible image display medium according to any one of 1 to 4.
The present invention according to claim 6 is the reversible image display medium according to any one of claims 1 to 5, wherein a protective layer is formed on the surface of the reversible image display medium.

According to a seventh aspect of the present invention, by irradiating the reversible image display medium according to any one of the first to sixth aspects with ultraviolet light, the photochromic compound group in a predetermined region is colored. The image display method is characterized by forming an image. The present invention according to claim 8 provides a reversible image display medium according to any one of claims 1 to 6 in which at least all kinds of photochromic compound groups are contained by irradiating the entire surface with ultraviolet light. An image display method is characterized in that an image is formed by performing a step of developing a color and a step of erasing a predetermined photochromic compound group by irradiating visible light.

The present invention according to claim 9 provides the image display method according to claim 7 or 8, characterized in that the irradiation intensity or irradiation time of light is controlled. The present invention according to claim 10 includes the step of irradiating the entire surface of the reversible image display medium with white light, and the image display method according to any one of claims 7 to 9. The present invention according to claim 11 has an invisible pattern on a reversible image display medium,
The image display method according to claim 7, wherein the image is formed after detecting the position of the invisible pattern. The present invention according to claim 12 is characterized in that a part of the reversible image display medium is irradiated with ultraviolet light, and an image is formed after detecting a color change of a light receiving part. Image display method.

According to a thirteenth aspect of the present invention, a linear light source is provided, and the image display method according to any one of the seventh to tenth aspects is used while the reversible image display medium and the light source are relatively moved. An image forming apparatus characterized by forming an image. According to a fourteenth aspect of the present invention, there is provided an image forming apparatus including a laser light source and a rotating mirror, and forming an image using the image display method according to any one of the seventh to tenth aspects.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The reversible image display medium of the present invention is characterized in that two or more kinds of photochromic compound groups having different absorption wavelength bands in a colored state are formed on a supporting substrate in a regular array pattern. Here, the photochromic compound group may be one kind of photochromic compound or a mixture of plural kinds of photochromic compounds. Further, the photochromic compound may be dispersed in a resin such as an acrylic resin, vinyl chloride resin, polyester resin, polyamide resin, polyolefin resin or urethane resin. The photochromic compound may be encapsulated in microcapsules. Further, each photochromic compound group may have a single layer structure containing a mixture of all kinds of photochromic compounds forming the group, or may have a laminated structure in which layers each containing each photochromic compound are stacked.

Typical photochromic compounds include thermoreversible compounds such as spiropyran and spirooxazine and heat irreversible compounds such as fulgide and diarylethene, but any kind of compound may be used. A plurality of types may be mixed.
However, the heat irreversible compound is more preferable from the viewpoint of retaining the recorded image. The absorption wavelength band of the photochromic compound group in the decolored state is preferably 410 nm or less. In addition, it is preferable that the maximum absorption wavelength of each photochromic compound in the decolored state is 350 nm or more and 410 nm or less.

As a method of forming the photochromic compound group in a regular array pattern, general methods such as a method of forming each kind by photolithography, screen printing, offset printing, gravure printing, pad printing, flexographic printing, etc. Examples of the method include a method of applying with a printing means, an inkjet method, a vapor deposition method, etc., but any method may be used. For example, in the photolithography method,
A photoresist containing one kind of photochromic compound group is arranged and fixed in a predetermined pattern by a series of photolithography processes of coating, drying, exposing and developing. Subsequently, similarly using a photoresist containing a different type of photochromic compound group, repeating to arrange and fix the photochromic compound group in a predetermined pattern,
A patterned reversible image display medium can be formed. Examples of photoresists used for these are negative resists containing a photopolymerization initiator such as benzophenones and anthraquinones in an acrylate resin, and positive photoresists containing an esterified product of o-quinonediazide in a novolak phenolic resin. Can be mentioned,
It is not particularly limited.

Another feature of the reversible image display medium of the present invention is that the surface of the supporting substrate is white. Since the photochromic compound group used in the present invention is almost transparent in the decolored state, the surface of the supporting substrate becomes a base color. Therefore, by using paper or a white substrate having a reflection characteristic equivalent to that of paper as the supporting substrate, a reversible image display medium having a white background color can be obtained. As a substrate material other than paper, a material in which a white pigment is dispersed in a resin such as a polymer may be used.

In order to display a color image, three kinds of photochromic compound groups corresponding to the three primary colors of red, green and blue may be periodically finely arrayed on the supporting substrate. When displaying each of the three primary colors, only the photochromic compound group corresponding to that color needs to be developed. For displaying yellow, for example, the photochromic compound group corresponding to red and green may be developed. It is possible to display gray by coloring all three colors.

In order to develop red, a photochromic compound group having a maximum absorption wavelength in the colored state in the range of 450 nm to less than 550 nm may be used.
Similarly, in order to develop blue, a group of photochromic compounds whose maximum absorption wavelength in the developed state is in the range of 550 nm or more and less than 650 nm, and to develop green have two or more absorption bands in the developed state. , The maximum absorption wavelength of two absorption bands is 400 nm or more 5
A photochromic compound group in the range of less than 00 nm and 600 nm or more and less than 700 nm may be used.

The maximum absorption wavelength in the colored state is 450 n
Examples of the photochromic compound in the range of m or more and less than 550 nm include “2- [1- (2,5-dimethyl-3-furyl) ethylidene] -3- (3-pentanilidene) succinic anhydride”, “2 -[1- (2,5-Dimethyl-3-furyl) ethylidene] -3-isopropylidenesuccinic acid N-benzylimide "," 2- [1- (5-
Methyl-2-p-dimethylaminophenyl-4-oxazolyl) ethylidene] -3-isopropylidene succinic anhydride "and the like.

The maximum absorption wavelength in the colored state is 550n
As the photochromic compound in the range of m or more and less than 650 nm, for example, “2- [1- (2-methyl-5)
-Diethylaminostyryl-3-thienyl) methylidene] -3-isopropylidene succinic anhydride "," 2-
[2,6-Dimethyl-3- (p-dimethylaminostyryl) -5-styrylbenzylidene] -3-isopropylidene succinic anhydride "," 2- [1- (2,5-dimethyl-1-phenyl- 3-pyrrolyl) ethylidene] -3-
“Isopropylidene succinic anhydride” and the like.

The maximum absorption wavelength in the colored state is 400 n
Examples of the photochromic compound in the range of m or more and less than 500 nm and 600 nm or more and less than 700 nm include, for example, “2- [1- (1,2-dimethyl-3- (5-dimethylaminoindolyl)) ethylidene] -3-isopropyi. "Ridene succinic anhydride", "1,2-bis- [5-
(1,3-Benzodithiol-2-yridenylmethyl)
2-Methylthien-3-yl] -perfluorocyclopentene "and the like.

Further, as described above, a color image can be displayed by finely arranging the photochromic compound groups capable of developing the three primary colors of red, green and blue, but in the state where all the photochromic compound groups are colored. It is gray and it is difficult to display black with high color density. Therefore, it is effective to add a photochromic compound group that develops black to the array pattern. When displaying black, the photochromic compound group that develops black may be developed. Since there is no photochromic compound that develops black alone, the black display portion may be provided with an absorption wavelength band in the entire visible region by mixing a plurality of photochromic compounds having different absorption wavelength bands. FIG. 1 shows a configuration example of the reversible image display medium of the present invention. As in this example, red (R), green (G), blue (B) black (K)
It is possible to display in color by finely arranging.

The arrangement of the photochromic compounds in the reversible image display medium of the present invention may be any pattern, but it is preferable that the photochromic compounds have a stripe shape. FIG. 2 shows an example in which four types of photochromic compound groups corresponding to red (R), green (G), blue (B), and black (K) are finely arranged in a stripe pattern. In this example, the area D1 represents one pixel. Red, green, blue, and black are evenly present in one pixel, and color display can be performed by appropriately coloring each color portion. Since the stripe-shaped array may be formed by linearly forming each photochromic compound group, a fine pattern can be easily formed in any method such as a photolithography method, a printing method, and an inkjet method. Further, at the time of light irradiation, by making the relative movement direction of the light source element and the reversible image display medium the same as the stripe direction, variation in relative movement speed between the light source element and the reversible image display medium or irradiation in the light source element. Even if the irradiation position is deviated due to the timing deviation of 1), the possibility that it will lead to the color misregistration is reduced.

A protective layer may be formed on the surface of the reversible image display medium of the present invention. The cause of the photodegradation of the photochromic compound is the bonding of oxygen during the photochemical reaction, and the durability is improved if the atmosphere is shielded by the protective layer. Needless to say, the mechanical shock from the outside is reduced by the protective layer. As a material for the protective layer, a transparent resin such as polyvinyl alcohol, polycarbonate, or acrylic resin is desirable. Further, as a film forming method, a vacuum vapor deposition method, a coating method, a spin coating method,
A dipping method or a cast method can be used.

As an image display method for displaying a multicolor image pattern using the reversible image display medium of the present invention, LD, L
The best method is to sequentially irradiate a high-output and highly directional light source such as an ED according to a desired image pattern. Since the photochromic compound group is patterned in advance in the reversible image display medium, a desired color can be obtained by irradiating a specific position (coordinate) with light. The following two methods are mainly mentioned as specific writing methods.

The first writing method is a method in which a photochromic compound group in a specific region is colored using an ultraviolet LD, an ultraviolet LED or the like. An example of the writing method is shown in FIG. The ultraviolet light in the present invention refers to light having a maximum emission wavelength of 410 nm or less including the near ultraviolet region. For a reversible image display medium that is in a completely erased state,
For example, when a part of the red (R) region is irradiated with ultraviolet light, only that part is colored and red is displayed. Similarly, when a part of the green (G) region is irradiated with ultraviolet light, only that part is colored and green is displayed. Therefore, a multicolor image can be formed by irradiating a specific region with ultraviolet light according to a desired image pattern. Most of the existing photochromic compounds have an absorption band between 350 nm and 410 nm in the decolored state, so only one type of UV light source is required, and some of the UV L
D, UV LED can be used.

The second method is to irradiate the entire surface of the image display section with an ultraviolet lamp to develop a color of all kinds of photochromic compounds contained therein, and then to emit LD, LED in the visible range.
It is a method of selectively erasing the photochromic compound group in a specific region by using, for example. An example of the writing method is shown in FIG. By irradiating the reversible image display medium, which is in a completely decolored state, with an ultraviolet lamp, the entire surface is colored. Then, for example, when a part of the blue (B) region is irradiated with visible light, only that part is erased. Similarly, when a part of the black (K) region is irradiated with visible light, only that part is erased and an image is formed. In the present invention, since each photochromic compound group is patterned in advance, when, for example, blue (B) is erased, part of black (K) is not erased at the same time. Since each color can be erased independently, color tone control can be easily performed. As for the visible range LD and LED used for decoloring, plural kinds corresponding to the absorption wavelength band of each photochromic compound group may be used individually,
Use of a white LED or the like is useful as common decolorizing light.

Further, in order to display a full-color image, it is necessary to develop a halftone. The color density of a photochromic compound is determined by the number of photoreacted molecules, which corresponds to the number of photons in irradiation light. Therefore, the irradiation amount can be adjusted by changing the irradiation light intensity or irradiation time.
The color density can be easily adjusted, and a full-color image can be displayed.

Further, the photochromic compound which has been colored by irradiation with ultraviolet light returns to the decolorized state by irradiation with white light. Therefore, when the white light is applied to the entire display portion of the reversible image display medium, the formed image is erased. Further, when the ultraviolet light is irradiated again, the color is developed, so that the image display can be repeated.

In the image display method of the present invention, color misregistration occurs unless the region in the reversible image display medium to be colored is accurately irradiated with light. In particular, when the photochromic compound group is formed in a fine array, there is a possibility that a completely different color may be developed even if the light-irradiated region is slightly shifted. Furthermore, when the support substrate of the reversible image display medium is paper or a thin film, the pattern formation pattern of each photochromic compound also expands and contracts due to the expansion and contraction of the film, and it is possible that light irradiation cannot be performed accurately. Therefore, in order to reduce the occurrence of the color shift, it is an effective means to detect the degree of expansion and contraction of the arrangement pattern of the photochromic compound group immediately before light irradiation, and perform light irradiation based on the information. . As the coordinate detecting means, there are the following two methods.

First, an invisible pattern whose position information can be optically detected is previously formed on a part of the reversible image display medium, and the position of the pattern is read to detect the degree of expansion and contraction. Is the way. It is desirable that the invisible pattern is made of a material that absorbs only infrared light. It is possible to specify the position by irradiating the whole or part of the reversible image display medium with light corresponding to the absorption band and detecting the reflected light. it can. Since the invisible pattern has no particular influence on the image display, the shape, size, number, and arrangement position of the patterns may be appropriately selected.

The second method is to irradiate a part of the reversible image display medium with ultraviolet rays and detect the color change of the part. Visible light with low intensity may be used for detection, and reflected light may be detected. The irradiation position can be corrected by comparing the obtained information with the arrangement pattern of the photochromic compound group stored in advance in the writing device. The color-changed portion may be left as it is or may be erased by using visible light as long as it has an appropriate size that does not hinder the image display. The size of the part that changes color,
The number and arrangement position may be appropriately selected.

When an image display device is manufactured by using the 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, miniaturization, and low cost, the method of installing the light source in a line and writing while moving the reversible image display medium and the light source relatively, or the pulsed light from the LD It is considered more preferable to synchronize the rotation mirror with the rotation mirror and write for each pixel. 5 to 9 show configuration examples of the respective writing devices.

FIG. 5 is a plan view showing an example of the image display device, and FIG. 6 is a side view of FIG. In the image display device of FIGS. 5 and 6, the reversible image display medium (1) is conveyed by the roller (2). After whitening the display surface of the reversible image display medium (1) with white light (3), the ultraviolet LED array (4) irradiates light according to the desired image pattern. On the reversible image display medium (1), photochromic compound groups that develop red, green, blue, and black are arranged in stripes.

In the image display device shown in FIG. 7, the reversible image display medium (1) is conveyed by rollers (2). First, all kinds of photochromic compound groups are colored by an ultraviolet lamp (5). The color-developed reversible image display medium (1) is selectively erased by the white LED array (6) to display a desired image pattern. In the reversible image display medium (1), photochromic compound groups that develop red, green, blue and black are arranged in a stripe pattern.

In the image display device of FIG. 8, a plurality of invisible marks (7) made of an infrared absorbing compound are provided on the reversible image display medium (1). First, while the reversible image display medium (1) is being conveyed by the roller (2), the distance between the invisible marks (7) is detected by the infrared laser (8) and the infrared detector (9), and the reversible image display medium (1) is detected. ) Calculate the amount of expansion and contraction. Next, the reversible image display medium (1) is returned to the initial position by rotating the roller (2) in the reverse direction,
After returning to a white paper state with white light (3), the ultraviolet LED array (4) irradiates light according to a desired image pattern while correcting the expansion and contraction amount. Alternatively, as shown in FIG. 9, coordinates may be detected by utilizing reflected light of ultraviolet light applied to a part (D2) of the image area to prevent color misregistration.

FIG. 10 shows a method in which the pulsed light from the ultraviolet LD (10) and the rotating mirror (11) are synchronized and writing is performed for each pixel in consideration of high resolution, high speed writing, downsizing, and low cost. It is a figure which shows the image display apparatus. Figure 1
At 0, the reversible image display medium (1) is conveyed by the rollers (2). The reversible image display medium (1) which has been made into a white paper state with the white light (3) is scanned with the pulsed light of the ultraviolet LD (10) by the rotating mirror (11) and irradiated through the mirror (12). To display the image pattern.

(Example 1) The photochromic compound is a fulgide-based photochromic compound, 2-
[1- (2,5-dimethyl-3-furyl) ethylidene]
-3- (3-Pentanilidene) succinic anhydride [hereinafter P
Abbreviated as C1], 2- [1- (2-methyl-5-diethylaminostyryl-3-thienyl) methylidene] -3-
Isopropylidene succinic anhydride [abbreviated as PC2 below]
And were used. When the absorption spectra of these photochromic compounds were measured, the absorption wavelength band before light irradiation was P
Both C1 and PC2 were 300 nm or more and 380 nm or less, and both were colorless. When PC1 and PC2 were irradiated with a 366 nm bright line of a high-pressure mercury lamp, the maximum absorption wavelength of PC1 was 500 nm, which was red. Also, PC
The maximum absorption wavelength of No. 2 was 595 nm, which was blue. P
10 wt% each of C1 and PC2 was dispersed in a resist solution, and a white polyethylene terephthalate substrate (length 5 cm, width 2 cm, thickness 100 μm) was formed by photolithography.
A reversible image display medium was prepared by forming a pattern of PC1 on the right half (m) and a pattern of PC2 on the left half of m).

Example 2 When the reversible image display medium of Example 1 was used and a part of PC1 was irradiated with an ultraviolet LED having a wavelength of 380 nm, the irradiated part turned from white to red. Similarly, when a part of PC2 was irradiated with an ultraviolet LED, the irradiated part changed from white to blue.

(Example 3) When the reversible image display medium of Example 1 was used and the whole surface of the medium was irradiated with a 366 nm bright line of a high-pressure mercury lamp, PC1 part exhibited red color and PC2 part exhibited blue color. When 1 part of PC was irradiated with a white LED, the irradiated part changed from red to white again. Similarly, when the white LED was irradiated to the PC 2 part, the irradiated part returned from blue to white.

Example 4 As a photochromic compound, 2- [1] which is a fulgide type photochromic compound
-(1,2-Dimethyl-3- (5-dimethylaminoindolyl)) ethylidene] -3-isopropylidene succinic anhydride [hereinafter abbreviated as PC3] was used. When the absorption spectrum of PC3 was measured, the absorption wavelength band before light irradiation was 3
It was 00 nm or more and 410 nm or less. When PC3 was irradiated with a 366 nm bright line of a high pressure mercury lamp, 673 nm
And showed a maximum absorption wavelength at 450 nm and turned green. Further, 2- [1] which is a fulgide-based photochromic compound showing yellow, magenta, and cyan in a colored state, respectively.
-(5-Methyl-2-phenyl-4-oxazolyl) ethylidene] -3-isopropylidene succinic anhydride, 2
-[1- (2-Cyano-1,5-dimethyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic anhydride, 2- [1- (1,2,5-trimethyl-3-pyrrolyl) ethylidene ] A photochromic compound group [hereinafter abbreviated as PC4] mixed with -3-isopropylidene succinic anhydride was used. When the absorption spectrum of PC4 was measured, the absorption wavelength band before light irradiation was 300 nm or more and 410 n or more.
It was m or less. When PC4 was irradiated with a 366 nm bright line of a high pressure mercury lamp, it showed a black color.

PC1, PC2 and PC shown in the first embodiment
10% by weight of 3 and PC4 were dispersed in a resist solution, and a white polyethylene terephthalate substrate (length 2 cm, width 2 cm, thickness 100 μm) was formed by photolithography.
In m), a striped pattern was formed in the order of PC1, PC2, PC3, and PC4. Pitch width is about 220 μm
(Line width 200 μm, space 20 μm). Then, a thin film of polyvinyl alcohol (2 μm) was applied as a protective film on the surface of the reversible image display medium.

Example 5 When the reversible image display medium of Example 4 was used and a part of PC1 was irradiated with an ultraviolet LED condensed by a lens, the irradiated part turned from white to red. Similarly, when a part of PC2 was irradiated with an ultraviolet LED, the irradiated part changed from white to blue. Similarly, when a part of PC3 was irradiated with an ultraviolet LED, the irradiated part changed from white to green. Similarly, when a part of PC4 was irradiated with an ultraviolet LED, the irradiated part changed from white to black.

Example 6 When the reversible image display medium of Example 4 was used and an ultraviolet LED was irradiated on a portion extending over both the adjacent PC1 and PC2, reddish purple was observed on the irradiated portion. When the red-purple part was observed under a microscope, red and blue were mixed.

(Example 7) When the reversible image display medium of Example 4 was used and an ultraviolet LED was irradiated to a portion extending over both the adjacent PC2 and PC3, a deep blue color was observed in the irradiated portion. When the indigo part was observed under a microscope, blue and green were mixed.

(Embodiment 8) Using the reversible image display medium of Embodiment 4, the ultraviolet LED condensed by the lens was irradiated on a part of PC3 and a part of PC1 close to the irradiation part. A yellow part was observed. When this yellow part was observed under a microscope, green and red were mixed.

(Embodiment 9) When the reversible image display medium of Embodiment 4 was used and an ultraviolet LED was irradiated on a portion extending over adjacent PC1, PC2 and PC3, a gray color was observed on the irradiated portion. When the gray portion was observed under a microscope, red, blue, and green were mixed.

(Embodiment 10) When the reversible image display medium of Example 4 was used and a 366 nm bright line of a high pressure mercury lamp was applied to the entire surface of the medium, PC1, PC2, PC3 and PC4 also developed color, and the reversible image display medium was black. Was presented. Then P
When white LEDs were irradiated to the entire area of C1 and PC4, the entire surface of the medium became indigo. When this state was observed with a microscope, blue and green were mixed.

(Example 11) When the reversible image display medium of Example 4 was used and the whole surface of the medium was irradiated with a 366 nm bright line of a high pressure mercury lamp, PC1, PC2, PC3 and PC4 also developed a color, and the reversible image display medium was black. Was presented. Then P
When the white LED was irradiated to the entire area of C2 and PC4, the entire surface of the medium became yellow. When this state was observed under a microscope, red and green were mixed.

(Example 12) Using the reversible image display medium of Example 4, when a 366 nm bright line of a high-pressure mercury lamp was irradiated on the entire surface of the medium, PC1, PC2, PC3, PC4 also developed color, and the reversible image display medium was black. Was presented. Then P
When the white LEDs were irradiated to the entire area of C3 and PC4, the entire surface of the medium became magenta. When this state was observed with a microscope, red and blue were mixed.

Example 13 When the reversible image display medium of Example 4 was used and an ultraviolet LED condensed by a lens was irradiated on a part of PC1 with half the intensity of Example 5, Example 5 was obtained.
Compared with, the color was less and the color became light red. Similarly, when a portion of PC2 was irradiated with an ultraviolet LED at half the intensity of Example 5, the irradiated portion changed from white to light blue. Similarly, an ultraviolet LED is provided on a part of the PC 3 with half the intensity of the fifth embodiment.
When irradiated with, the irradiated part changed from white to light green.
Similarly, an ultraviolet L light was applied to a part of PC4 with half the intensity of Example 5.
When irradiated with ED, the irradiated part turned from white to gray.

Example 14 When the reversible image display medium of Example 4 was used and an ultraviolet LED condensed by a lens was irradiated on a part of PC 1 in half the time of Example 5, Example 5
Compared with, the color was less and the color became light red. Similarly, when a part of PC2 was irradiated with an ultraviolet LED for half the time of Example 5, the irradiated part changed from white to light blue. Similarly, an ultraviolet LED was applied to a part of PC3 in half the time of Example 5.
When irradiated with, the irradiated part changed from white to light green.
Similarly, in a half time of Example 5, a part of PC4 was exposed to ultraviolet L
When irradiated with ED, the irradiated part turned from white to gray.

(Example 15) When the white light of a halogen lamp was applied to the entire surface of the reversible image display medium with respect to the image patterns formed in Examples 5 to 14, all the image patterns were erased and returned to white. When light irradiation was performed again under the same conditions as in Examples 5-14, the same color as in Examples 5-14 was exhibited. The color tone of the color development did not change even after repeating 300 times under normal temperature and normal humidity.

Example 16 A reversible image display medium in which a protective film was not formed on the surface after forming a stripe pattern by the same method as in Example 4 was prepared. (Example 17) When the reversible image display medium of Example 16 was used and light irradiation was carried out under the same conditions as in Example 15, it was observed that the color tone at the time of color development was reduced after repeating about 100 times.

Example 18 A reversible image display medium was produced in the same manner as in Example 4. Then, an invisible mark of an infrared absorber made of ytterbium oxide crystal was laminated on the PC1 portion of the reversible image display medium. (Example 19) For the reversible image display medium of Example 18, the light of the infrared LD having a wavelength of 830 nm condensed by the lens was 85 ° in the vertical direction of the medium.
The reflected light was detected with a photodiode. When the infrared LD and the photodiode were moved relative to the reversible image display medium, the reflected light was attenuated at regular intervals, and the coordinate position of the PC1 part could be confirmed.

Example 20 With respect to the reversible image display medium of Example 4, an ultraviolet LED was irradiated only in the area D2 in FIG. 9 to develop a color. Next, blue LED, green LED, red L
The light from the ED was irradiated from an angle of 85 °, and the reflected light was detected by a photodiode. When the LEDs and the photodiodes are moved relative to the reversible image display medium, the reflected light is attenuated at regular intervals, and PC1, P
The coordinate positions of C2, PC3, and PC4 could be confirmed.

[0070]

As described above, claim 1 or 2
According to the present invention described in 1 above, by forming two or more kinds of photochromic compound groups having different absorption wavelength bands in a colored state in a regular array pattern on a white supporting substrate, a high image quality as a substitute for paper can be obtained. Moreover, a rewritable reversible image display medium can be provided. According to the present invention of claim 3, the three primary colors (red, green,
According to the present invention as set forth in claim 4, black having a high color density can be obtained, so that a reversible image display medium capable of color display faithful to an image signal can be provided. .

Further, according to the present invention as defined in claim 5, by forming the arrangement pattern of the photochromic compound group into a stripe shape, the pattern formation can be easily performed and the color shift in the line direction can be reduced. It is possible to provide an inexpensive and highly reliable reversible image display medium. Furthermore, according to the present invention described in claim 6, since the deterioration of the reversible image display medium is prevented, a reversible image display medium having improved durability and high reliability can be provided.

Further, according to the invention of claim 7 or 8, two or more kinds of photochromic compound groups having different absorption wavelength bands in a colored state are formed in a regular array pattern on a white support substrate. By using the reversible image display medium, it is possible to provide an image display method capable of easily controlling multicolor display with a simple configuration. Further, according to the present invention described in claim 9, it is possible to provide an image display method capable of gradation display by adjusting the color density for each color by controlling the irradiation amount of light.
Furthermore, according to the present invention of claim 10, by adding a step of irradiating the entire display portion of the reversible image display medium with white light, a multicolor image display capable of efficiently rewriting an image. A method can be provided.

Further, according to the present invention of claim 11 or 12, by detecting the position information and the degree of expansion and contraction of the reversible image display medium before writing, a multicolor image display method without color misregistration. Can be provided.

Further, according to the present invention as set forth in claim 13 or 14, it is possible to provide an image display device capable of writing a high resolution image in a short time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a reversible image display medium of the present invention.

FIG. 2 is a plan view showing an example of an array of photochromic compound groups according to the present invention.

FIG. 3 is a diagram showing an example of an image writing method according to the present invention.

FIG. 4 is a diagram showing an example of an image writing method according to the present invention.

FIG. 5 is a plan view showing an example of an image display device of a method for selectively developing a color of a photochromic compound group.

FIG. 6 is a side view of FIG.

FIG. 7 is a plan view showing an example of an image display device in a method of selectively erasing after photochromic compound group color development.

FIG. 8 is a plan view showing an example of an image display device in which an invisible mark is added to a reversible image display medium.

FIG. 9 is a diagram showing an example in which coordinates are detected using reflected light of ultraviolet light.

FIG. 10 is a plan view showing a writing device of a writing method for each pixel.

[Explanation of symbols]

1 Reversible image display medium Two rollers 3 white light 4 UV LED array 5 UV lamp 6 White LED array 7 Invisible mark 8 infrared laser 9 Infrared detector 10 UV LD 11 rotating mirror 12 mirror R red G Green B blue K black D1 1 pixel area D2 coordinate detection area

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H123 AA00 AA08 AA09 AA12 AA19                       CA00 CA22                 5C080 AA18 BB10 CC03 DD21 EE30                       JJ06                 5C094 AA08 AA31 BA12 BA52 CA19                       CA24 FA01 FB01 GA01 JA11

Claims (14)

[Claims] 1. A different absorption wavelength band in a colored state 2
A reversible image display medium, comprising a group of photochromic compounds of at least one kind formed on a supporting substrate in a regular array pattern. 2. The reversible image display medium according to claim 1, wherein the supporting substrate is white. 3. The maximum absorption wavelength in the colored state is 450.
and a photochromic compound group in the range of not less than 550 nm and less than 550 nm, and a maximum absorption wavelength in the coloring state of not less than 550 nm and not more than 650
It has a photochromic compound group in the range of less than nm and two or more absorption wavelength bands in the coloring state, and the maximum absorption wavelength of two of the absorption wavelength bands is 400 nm or more.
And a photochromic compound group in the range of less than 00 nm and 600 nm or more and less than 700 nm.
The reversible image display medium described in 1. 4. The reversible image display medium according to claim 1, wherein the reversible image display medium comprises a photochromic compound group having an absorption wavelength band in a colored state in the entire visible region. 5. The reversible image display medium according to claim 1, wherein the regular arrangement pattern of the photochromic compound group formed on the supporting substrate is a stripe shape. 6. The reversible image display medium according to claim 1, wherein a protective layer is formed on the surface of the reversible image display medium. 7. A photochromic compound group in a predetermined region is colored by irradiating the reversible image display medium according to claim 1 with ultraviolet light to form an image. Characteristic image display method. 8. A step of causing at least the entire surface of the reversible image display medium according to any one of claims 1 to 6 to be irradiated with ultraviolet light so as to develop a color of all kinds of photochromic compound groups contained therein. And a step of erasing a predetermined photochromic compound group by irradiating with visible light, and forming an image by performing an image display method. 9. The image display method according to claim 7, wherein the irradiation intensity or irradiation time of light is controlled. 10. The image display method according to claim 7, further comprising the step of irradiating the entire surface of the reversible image display medium with white light. 11. The image display method according to claim 7, wherein the reversible image display medium has an invisible pattern, and the image is formed after detecting the position of the invisible pattern. 12. The image display method according to claim 7, wherein a part of the reversible image display medium is irradiated with ultraviolet light, and an image is formed after detecting a color change of the light receiving portion. 13. A line-shaped light source is provided, and an image is formed by using the image display method according to claim 7 while relatively moving the reversible image display medium and the light source. Image forming apparatus. 14. An image forming apparatus comprising a laser light source and a rotating mirror, and forming an image using the image display method according to claim 7.