JP4420840B2 - Confidential information display medium - Google Patents

Description

  The present invention relates to an information recording medium using a photochromic compound that is decolored by visible light as a recording layer, particularly a confidential information display medium, a method of manufacturing the confidential information display medium, and display of confidential information using the confidential information display medium. About the system.

JP 2001-171235 A (Patent Document 1), JP 2001-171236 A (Patent Document 2), and JP 2001-171237 A (Patent Document 3) include a photochromic compound contained in a thermal transfer ribbon. There is described a sheet having secret information printed on a postcard or card by a thermal printer, which is transparent at the time of printing, and which is colored by irradiating ultraviolet rays when viewed.
In Japanese Patent Laid-Open No. 05-262086 (Patent Document 4), two or more different meaningful images sharing a display space are formed in the same plane so as to form a “ground” region as a whole. Latent image by printing pixels by photochromic color material etc. which are located in similar hue circle and have different optical reflection characteristics from each other, or latent image by specific regular polygon printing pixels, and any shape There is described a display body characterized by having a multi-element image configured as a visible image by the print pixels.
Further, there is a technique regarding a medium in which a first recording layer that emits light or colors when irradiated with ultraviolet light and a second recording layer that is made of a photochromic material that changes to ultraviolet non-transparent when irradiated with ultraviolet light (for example, Patent Document 5). (See JP 2000-348156 A).
In this method, information can be viewed by exposing the second recording layer on a pattern, irradiating it with ultraviolet rays using the mask as a mask, and causing the first recording layer to emit light and develop color. However, this method also requires an ultraviolet light source for the recipient to read the information, and it is generally considered difficult to spread.

In addition, Japanese Patent Application No. 2003-359895 (Patent Document 6) relating to our development has a recording layer containing a thermally irreversible photochromic compound on at least a part of the substrate, and further information on the recording layer. A confidential information display medium characterized by having a means for concealing the information is proposed.
Currently, security requirements for information are increasing, and security management of printed information is very important. If the printed document information is inadvertently left on the desk or the like, there is a possibility that other people can see the information. Furthermore, when destroying information, the only way to erase it is to burn it. It is possible to repair even by shredding. To incinerate, it is usual to go from the trash can to the incinerator through many processes, and there is a possibility that information can be seen by a third party.

As the above countermeasure, we previously proposed a confidential information display medium having a recording layer containing a thermally irreversible photochromic compound on at least a part of the substrate in Japanese Patent Application No. 2003-359895. As a feature of this medium, information is not directly printed as in the technique described in Patent Document 1, but the recording layer is basically solid. When recording information on this recording layer, a method of displaying information by partially coloring the photochromic recording layer by partially irradiating the entire surface of the decolored medium, or irradiating the entire surface with ultraviolet rays. There are two types of methods of displaying information by partially erasing the photochromic recording layer by partially irradiating visible light after the entire surface is colored.
According to this method, since the photochromic layer itself is solid-coated, the displayed information can be erased by irradiating the entire surface with ultraviolet light or irradiating visible light after the information is displayed. There is a merit that I do not know what information was before. In addition, since there is no need for shredder or incineration, it is a very useful method for sensitive information.
However, in the case of a particularly sensitive document such as a company or a national top secret, the following problems are concerned with the method that we previously proposed in the specification of Japanese Patent Application No. 2003-359895.

  Photochromic compounds are characterized by being colored by irradiation with ultraviolet light and decoloring by irradiation with visible light. However, when changing from a colored state to a decolored state, and when changing from a decolored state to a colored state, It is characterized by accompanying shape change. That is, since the wavelength of light absorbed by the molecules changes due to the shape change, light in the visible region is absorbed (colored state) or light in the visible region is transmitted (decolored state).

  The above coloring state and decoloring state are two stable states, but it changes to another substance under the influence of moisture, oxygen, etc., or from the coloring state to the decoloring state (or from the decoloring state to the coloring state). When changing the shape of a molecule, it may change to another substance with a certain probability. When the photochromic compound is changed to another substance, no coloring reaction or decoloring reaction due to light occurs, and a color peculiar to the changed substance is exhibited. The changed substance-specific color may have visible light absorption (colored) or may not have visible light absorption (not colored).

  For example, it changes to another substance under the influence of moisture or oxygen in the colored state, or changes to another substance when the molecular shape changes from the colored state to the decolored state, and the changed substance is colored. In this case, after displaying information on the recording layer, even if visible light is irradiated on the entire surface, the changed substance is colored, so the trace of the displayed information remains, and what information is displayed before erasing it. It becomes clear whether there was.

  Even if the changed substance is not colored, it is not impossible to detect the position of the changed substance in the recording layer by using the latest analytical instrument for examining the molecular structure. Therefore, even when the changed substance is not colored, there is a possibility that what information was present before erasing is revealed.

JP 2001-171235 A JP 2001-171236 A JP 2001-171237 A Japanese Patent Laid-Open No. 05-262086 JP 2000-348156 A Japanese Patent Application No. 2003-359895 Specification

  The present invention has been made in view of the above-described state of the art and problems, and it is an object of the present invention to provide a confidential information display medium in which traces of information are less likely to remain after the displayed confidential information is erased.

That is, the above-mentioned problem is (1) of the present invention having a recording layer containing a thermally irreversible photochromic compound that develops color by irradiation with ultraviolet light and disappears by irradiation with visible light on at least a part of the substrate . An information display medium used as a display medium for confidential information , in which an arbitrary shape pattern is recorded / erased on the recording layer before confidential information is recorded on the recording layer, and the arbitrary shape pattern is erased Later, this is solved by a “confidential information display medium characterized in that traces of the pattern of the arbitrary shape exist in the recording layer ”.

  Further, the present invention can be solved by (2) “the confidential information display medium according to item (1), wherein the pattern of the arbitrary shape does not have a periodic structure”.

  Further, the present invention can be solved by (3) “the confidential information display medium according to item (2), wherein the pattern of the arbitrary shape is different among a plurality of media”.

Further, (4) “a step of forming a recording layer containing a thermally irreversible photochromic compound that develops color by irradiation with ultraviolet rays and is erased by irradiation with visible light on at least a part of the substrate, formed recording layer” A method of manufacturing a confidential information display medium, comprising: a step of recording an arbitrary shape pattern on the recording layer; and a step of erasing the arbitrary shape pattern recorded on the recording layer and causing traces of the arbitrary shape pattern to exist ” It is solved by.

Furthermore, (5) “a step of generating a random arbitrary-shaped pattern of the present invention, the generated random arbitrary-shaped pattern is formed on at least a part of the substrate, and is colored by irradiation with ultraviolet rays. It includes a step of recording on a recording layer containing a thermally irreversible photochromic compound that is erased by irradiation, a step of erasing an arbitrary shape pattern recorded on the recording layer , and causing a trace of the arbitrary shape pattern to exist. The method of manufacturing a confidential information display medium.

Furthermore, the invention is solved by (6) “a confidential information display system using the confidential information display medium according to any one of (1) to ( 3 )”.

(Claim 1)
When a medium having a recording layer containing a photochromic compound on at least a part of a substrate is used as a display medium for confidential information, a pattern having an arbitrary shape is formed on the recording layer before the confidential information is recorded on the medium. Even if there is a trace of erasure of confidential information when the confidential information is erased by being recorded and erased, it overlaps with the trace of erasure of the pattern of arbitrary shape, so the content of the confidential information can be determined The confidentiality is improved.
(Claim 2)
Since the pattern having an arbitrary shape does not have a periodic structure, since it is impossible to determine the trace of erasure of confidential information except for the trace of erasure of the periodic pattern, the confidentiality is further improved.
(Claim 3)
By making the pattern of arbitrary shape different between multiple media, it becomes impossible to determine the trace of erasure of confidential information except for the trace of erasure common to multiple media, thus improving the confidentiality. .

Hereinafter, the present invention will be described in detail and specifically.
A configuration example of the confidential information display medium of the present invention is shown in FIG. In the confidential information display medium of the present invention, a recording layer containing a photochromic compound is formed on the entire surface or a part of a substrate, and a medium having a recording layer containing a photochromic compound is formed on at least a part of the substrate. When used as a display medium, a pattern having an arbitrary shape is recorded / erased on a recording layer before confidential information is recorded on the medium.
As a result, when confidential information is erased, even if the trace of confidential information is erased, it overlaps with the trace of erase of an arbitrarily shaped pattern, so the content of the confidential information cannot be determined. In this respect, the present invention is basically different from the conventional one that remains thin even when characters are erased as shown in FIGS. 2 and 3 and there is a risk that the recorded information can be read. is doing.

As the photochromic compound used in the present invention, the following materials can be listed.
A photochromic compound is a compound that changes from a decolored body to a colored body when irradiated with ultraviolet light, and becomes decolored when irradiated with visible light. Photochromic compounds include thermoreversible photochromic compounds and thermally irreversible photochromic compounds. The former is a compound having the property that the color former is thermally decolored, and the latter is a compound in which the color former is thermally stable and can be decolored only by irradiation with visible light. Typical thermoreversible photochromic compounds include spiropyran, spirooxazine, azobenzene, and the like, and these color formers become decolorized in a few seconds to several days in the dark at room temperature. Typical heat irreversible photochromic compounds include fulgide and diarylethene.

  As a method for recording information on the confidential information display medium of the present invention, the recording layer is exposed to ultraviolet light of a desired image pattern (for example, characters), so that only the exposed portion undergoes a color reaction, and a corresponding image is obtained. Are formed in the recording layer. Further, in order to erase the information, it is only necessary to irradiate the recording layer with intense visible light, for example, to bring it closer to a desk lamp or the like. Although it depends on the material and the power of the light source, it can be erased in several seconds to several tens of seconds. Further, even if the recording layer is left under an indoor fluorescent lamp, it is naturally erased. Although it depends on the material, it can be erased in several tens of minutes to several hours under a fluorescent lamp in a general office (about 700 lx).

  As an ultraviolet light source and a writing method for recording information on the confidential information display medium of the present invention, a method of scanning an ultraviolet laser, a method of arranging ultraviolet LED chips side by side and emitting light sequentially, light from an ultraviolet lamp light source and a liquid crystal shutter, etc. There are methods such as combining modulation elements, but any method may be used.

The substrate used for the confidential information display medium of the present invention may have any form depending on the application.
The photochromic compound contained in the recording layer of the confidential information display medium of the present invention may be one kind or plural kinds.
When a plurality of types of photochromic compounds are used, if each compound develops a different color, it becomes a more useful confidential information display medium.

  For example, if three types of photochromic compounds that develop yellow, magenta, and cyan are mixed and colored simultaneously, black can be obtained, and a confidential information display medium with excellent visibility can be obtained. Further, if three types of photochromic compounds that develop yellow, magenta, and cyan are individually developed, full color recording is possible, and the utility value is expanded.

  Examples of thermally irreversible photochromic compounds that develop yellow color include “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-methylthiazol) -3,3,4,4,5,5-hexafluoro Cyclopentene "," 2- [1- (3,5-dimethyl-4-isoxazolyl) ethylidene] -3-isopropylidene succinic anhydride "," 2- [1- (5-methyl-2-phenyl-4-] Oxazolyl) ethylidene] -3-isopropylidene succinic anhydride "," 2- [1- (2-phenyl-5-methyl-4-oxazolyl) stearylidene] -3-isopropyl Ridenkohaku acid anhydride "and the like.

  Moreover, as a heat irreversible photochromic compound which develops magenta, for example, “1,2-bis (3- (2-methyl-6- (2- (4-methoxyphenyl) ethynyl) benzothienyl))-3, 3,4,4,5,5-hexafluorocyclopentene "," 1,2-bis (5-methyl-2-phenylthiazol) -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”, “2- [1 -(2,5-dimethyl-1-phenylpyrazolyl) ethylidene] -3-isopropylidene succinic anhydride "," 2- [1- (3-methoxy-5-methyl-1-phenyl-4-pyrazolyl) ethylidene " 3-isopropylidene succinic anhydride ", and the like" 2- [1- (2-methyl-5-styryl-3-thienyl) ethylidene] -3-isopropylidene succinic anhydride ".

  Further, as a heat irreversible photochromic compound that develops cyan, 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 "," 2- [1- (1,2,5-trimethyl-3-pyrrolyl) ethylidene] -3- Isopropylidenkoha Acid anhydride "," 2- [2,6-dimethyl-3,5-bis (p-dimethylaminostyryl) benzylidene] -3-isopropylidene succinic anhydride ", 1,2-bis (2-methyl- 5-phenyl-3-thienyl) -3,3,4,4,5,5-perfluorocyclopentene and the like.

  The photochromic compound in the recording layer may be dispersed in a resin such as an acrylic resin, a vinyl chloride resin, a polyester resin, a polyamide resin, a polyolefin resin, or a urethane resin, or encapsulated in a microcapsule. Also good.

  To perform full-color display using a confidential information display medium containing a photochromic compound that develops yellow, magenta, and cyan on the recording layer, first color the yellow, magenta, and cyan coloring compounds, and then color The best method is to selectively decolorize each photochromic compound by irradiating a desired region with visible light in a wavelength region corresponding to the maximum absorption wavelength of each photochromic compound.

  The confidential information display medium of the present invention may be discarded after use, but can also be used repeatedly. A photochromic compound repeatedly forms a colored body and a decolored body by light irradiation. Therefore, once the recorded information is erased by visible light irradiation, it can be used again and again by irradiating the desired range with ultraviolet light. For example, a white light source may be installed in the information recording apparatus, and the recording layer may be irradiated with ultraviolet light after first irradiating the entire recording layer.

  A protective layer can be formed on the surface of the recording layer of the confidential information display medium of the present invention. As a cause of photodegradation of the photochromic compound, oxygen bonding during a photochemical reaction and the like can be mentioned. If the atmosphere is blocked by a protective layer, repeated durability is improved.

Example 1
1,2-bis (2-methyl-5-phenyl-3-thienyl) -3,3,4,4,5,5-perfluorocyclopentene (hereinafter abbreviated as PC1) was used as the photochromic compound. The maximum absorption wavelength of the chromophore of PC1 was 600 nm, indicating blue. Further, the absorption band of the decolored material was 400 nm or less and was transparent.
PC1 was dispersed in polystyrene by 10% by weight and spin-coated on a white polyethylene terephthalate substrate (thickness: 188 μm) to produce a recording layer.

(Example 2)
When the sample produced in Example 1 was irradiated with a pattern having an arbitrary shape on the recording layer for 10 seconds using ultraviolet light having a main wavelength of 365 nm (intensity 10 mW / cm ² ), the irradiated portion was colored blue. Thereafter, the color was allowed to stand for about 2 weeks and left in a dark place. After that, the pattern of the arbitrary shape was erased. As a result, a slight blue trace of the pattern of the arbitrary shape was visually confirmed.
After that, a character information pattern that is meaningful as information, not an arbitrary shape, was irradiated for 10 seconds using ultraviolet light with a main wavelength of 365 nm (intensity 10 mW / cm ² ) to display character information, and then developed for about 2 weeks. When the above pattern of character information was erased after leaving it in the dark, the traces of color disappeared, but the traces of the pattern of arbitrary shape overlapped with the traces of character information, and what character information was recorded. It was not possible to determine.
FIG. 4 shows an example of a state in which an arbitrary pattern is previously erased and erased on the medium of the present invention. FIG. 5 shows an example of a normal state in which characters are recorded on the medium of the present invention. Show.

(Comparative Example 1)
When the sample produced in Example 1 was irradiated with a character information pattern on the recording layer for 10 seconds using ultraviolet light (intensity: 10 mW / cm ² ) having a main wavelength of 365 nm, the irradiated portion was colored blue. After that, the color information pattern was erased after leaving it in a dark place for about 2 weeks. After that, the blue trace of the text information pattern was slightly visible, and any text information was recorded. It was possible to determine if it was.

It is a figure showing the structural example of the confidential information display medium in this invention. It is a figure which shows an example of a prior art. It is a figure which shows the example at the time of erasing a character with the medium of the prior art shown in FIG. It is a figure which shows the example of the medium in this invention. It is a figure which shows the state which recorded the character on the medium of this invention. It is a figure which shows the example at the time of erasing the character with the medium of this invention shown in FIG.

Claims (6)

At least part of the substrate has a recording layer containing a thermally irreversible photochromic compound that develops color by irradiation with ultraviolet light and disappears by irradiation with visible light, and before confidential information is recorded on the recording layer, An information display medium used as a confidential information display medium in which an arbitrary-shaped pattern is recorded / erased on the recording layer , and after erasing the arbitrary-shaped pattern, traces of the arbitrary-shaped pattern are recorded on the recording layer Confidential information display medium characterized in that it exists .   The confidential information display medium according to claim 1, wherein the pattern having an arbitrary shape does not have a periodic structure.   The confidential information display medium according to claim 2, wherein the pattern of the arbitrary shape is different among a plurality of media. A step of forming a recording layer containing a thermally irreversible photochromic compound that develops color by irradiation with ultraviolet rays and is erased by irradiation with visible light on at least a part of the substrate, and a step of recording a pattern of an arbitrary shape on the formed recording layer A method for producing a confidential information display medium, comprising: erasing an arbitrary-shaped pattern recorded on the recording layer and causing traces of the arbitrary-shaped pattern to exist . A process for generating a random arbitrary-shaped pattern, a thermally irreversible photochromic compound in which the generated random arbitrary-shaped pattern is formed on at least a part of a substrate, develops color by irradiation with ultraviolet light, and discolors by irradiation with visible light A method for manufacturing a confidential information display medium, comprising: a step of recording on a recording layer including: a step of erasing a pattern having an arbitrary shape recorded on the recording layer and causing a trace of the pattern of the arbitrary shape to exist . Display system of confidential information, which comprises using the confidential information display medium according to any one of claims 1 to 3.

Images