JP2002019292A - Heat reversible recording medium and record displaying method thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat reversible recording medium, which has a longer use-life than ever and a favorable contrast between a recording part and a non-recording part. SOLUTION: This heat reversible recording medium is equipped with a recording layer 14, in which the recording and elimination of information can be reversibly executed through the application of heat and the controlling of cooling conditions. On the surface 14b opposite to the recognizing surface 14a of the recording layer, a hard coating layer 18 is formed. The surface of the hard coating layer is a heat applying surface 18a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoreversible recording medium capable of repeatedly recording and erasing information by controlling heat application conditions, and a method for recording and displaying information on the medium.

[0002]

2. Description of the Related Art In recent years, research on thermoreversible recording media has been actively conducted. The reason is that the medium can be used repeatedly, which is preferable from the viewpoint of protection of the global environment.

As an example of a thermoreversible recording medium, there is a medium having a structure in which a recording layer containing a resin binder and an organic low-molecular substance dispersed in the resin binder is provided on a support. As another example, there is a medium having a structure in which a recording layer containing a color former and a developer or a developer is provided on a support. The former is called a light scattering type, and the latter is called a coloring type.

[0004] A light scattering type medium is disclosed, for example, in Document 1 (Japanese Patent Application Laid-Open No. 63-39377). This medium performs recording and erasing by reversibly changing the transparency of the recording layer by controlling the applied thermal energy.

On the other hand, a coloring type medium is disclosed, for example, in Document 2 (Japanese Patent Laid-Open No. 2-188293). In this medium, recording and erasing are performed by utilizing the phenomenon that the color-reducing agent becomes a color developer or a color-reducing agent depending on the heat application condition. An amphoteric compound having an acidic group for forming a leuco dye and a basic group for decoloring the formed leuco dye is used as the developer. The coloring and decoloring are controlled by giving priority to the action of one of the groups by the applied thermal energy. Leuco dyes are exclusively used as color formers.
The main reasons are that the leuco dye undergoes a reversible structural change in response to the above-described action of the color-reducing agent to become a colored compound or a colorless leuco body. This is because it is suitable as a practical material exhibiting a white color.

As a color-forming medium, a medium having a recording layer containing an electron-donating color-forming compound and an electron-accepting compound has been proposed.

The recording (coloring) and erasing (erasing) of this medium are performed by heating a portion of the medium on which recording is performed.
The electron donating color forming compound and the electron accepting compound are brought into a molten state. Thereby, charge transfer occurs from the electron-donating color-forming compound to the electron-accepting compound. The electron transfer changes the structure of the electron-donating color-forming compound to form a colored compound and develop color. Next, by slowly cooling the mixture of the two in a molten state, the two are solidified while separating into an electron-donating color-forming compound phase and an electron-accepting compound phase. At the time of this phase separation, the colored compound receives electrons again from the electron accepting compound, returns to the structure of the electron donating color former before coloring, and loses color.
Further, when the mixture in the molten state is rapidly cooled, no phase separation occurs and the mixture is solidified while maintaining the mixed state. For this reason,
Charge transfer from the colored compound to the electron-accepting compound does not occur, and the colored state is maintained.

[0008]

The light-scattering and color-developing thermoreversible recording media as described above require thermal energy when recording and erasing information. For example, a thermal head is often used as a means for applying the heat energy to the medium. The thermal head is used in direct contact with the recording portion of the medium. Therefore, the medium portion of the thermal head that contacts the high temperature portion is easily damaged by heat and friction. Therefore, in order to prevent the medium from being destroyed due to such damage, a hard coat layer mainly made of an ultraviolet curable resin is provided on the surface (viewing surface) of the medium.

However, particularly in the case of a coloring type medium, the temperature of the medium reaches a high temperature of 150 to 200 ° C. during recording. The accompanying damage of the medium surface due to the heat and friction is very large. For example, even if a hard coat layer is provided, a scratch is formed on the surface of the hard coat layer by repeatedly performing recording and erasing.
Then, since the light is scattered at the scratched portion, the recorded image becomes difficult to see. Therefore, the service life of the medium is currently short.

[0010] Leuco dyes used in color-forming media are destroyed by high-energy photons such as ultraviolet rays contained in light. As a result, discoloration occurs on the background of the medium, and as a result, there is a problem that the contrast between the recorded portion and the non-recorded portion is reduced.

For this reason, there has been a demand for a thermoreversible recording medium having a longer service life and a good contrast between a recorded portion and a non-recorded portion. In addition, there has been a demand for a method of recording and displaying on a thermoreversible recording medium that can reduce damage to the medium as compared with the related art.

[0012]

Therefore, the thermoreversible recording medium of the present invention has a recording layer in which information is recorded and erased reversibly by controlling the application of heat and cooling conditions. Then, a hard coat layer is formed on the surface of the recording layer opposite to the viewing surface. Then, the surface of the hard coat layer is used as a heat application surface.

With such a configuration, even if recording and erasing are repeatedly performed on the medium, damage such as a scratch due to the application of heat does not occur on the viewing surface side. Therefore, there is no possibility that the scratches generated on the visual recognition surface are scattered by the light and the recorded image becomes difficult to see. Therefore, the number of times of recording and erasing of information on the medium can be increased more than before. This means that the life of the medium has been extended.

Conventionally, the background of the recording layer is colorless or light-colored. Therefore, when the recording is viewed from the viewing surface side, the color of the recording portion on the surface opposite to the viewing surface has a complementary color relationship or a complementary color relationship. A coloring layer or coloring member of a similar color is provided. As a result, the background of the recording layer is transparent, so that the recording is displayed on the base of the color of the colored layer.

In practicing the present invention, it is preferable that the hard coat layer formed on the surface of the recording layer opposite to the viewing surface has a transmittance of light having a wavelength of 550 nm of 20% or less. .

As described above, the wavelength of 550 n
Since the transmittance of m light is 20% or less, that is, the hard coat layer having high visible light shielding property is provided, the hard coat layer plays the role of the colored layer. This eliminates the need for preparing a colored layer or a colored member, so that the cost of the thermoreversible recording medium can be reduced.

Further, according to a preferred embodiment of the thermoreversible recording medium of the present invention, it is preferable that an ultraviolet absorbing layer is provided at least on the viewing surface side of the recording layer.

Since the thermoreversible recording medium of the present invention is a reflection type display, it is irradiated with light on the viewing surface when used.
Here, an ultraviolet absorbing layer is provided on the viewing surface side.
Since this ultraviolet absorbing layer absorbs ultraviolet light contained in light, it is possible to prevent or suppress the incidence of ultraviolet light on the recording layer. Accordingly, when the material constituting the recording layer includes a material such as a leuco dye, which is destroyed by high-energy photons, it is possible to reduce the destruction of the material by ultraviolet rays as compared with the related art. it can.
In addition, with respect to the leuco dye, it is possible to prevent or suppress the discoloration of the background of the recording layer particularly caused by being destroyed by ultraviolet rays. Therefore, the recording part and the non-recording part (background)
, A contrast ratio sufficient for practical use can be obtained.

Further, in the medium of the present invention, the visible surface side on which the ultraviolet absorbing layer is provided is not a heat application surface. When the ultraviolet absorbing layer is provided on the heat application surface side, the thickness of the ultraviolet absorbing layer must be limited in consideration of the heat conduction efficiency during recording. However, in the medium of the present invention, since the ultraviolet absorbing layer is provided on the viewing surface to which no heat is applied, the thickness can be made sufficiently large. As a result, a desired ultraviolet absorption efficiency according to the design can be obtained.

Further, in the medium of the present invention, it is possible to provide an ultraviolet absorbing layer not only on the viewing surface but also on the surface opposite to the viewing surface. Since the surface on the opposite side of the viewing surface is a heat application surface, the thickness of the ultraviolet absorbing layer provided on this surface is limited as described above, but the ultraviolet absorbing layer is provided on both sides of the viewing surface side and the opposite side of the viewing surface. By providing the layer, the ultraviolet light transmitted through the ultraviolet absorbing layer on the viewing surface side and incident on the recording layer can be absorbed by the ultraviolet absorbing layer on the side opposite to the viewing surface without being reflected and scattered. Thereby, the destruction of the material constituting the recording layer can be further suppressed.

Further, the present invention is applicable to a thermoreversible recording medium of a recording system in which information is recorded and erased reversibly by controlling heat application and cooling conditions. As such a medium, a light scattering type thermoreversible recording material in which a recording layer is composed of a thermoreversible recording material including a matrix material such as vinyl chloride vinyl acetate and a low-molecular organic material such as a carboxylic acid having a long-chain alkyl. Recording medium, wherein the recording layer is formed of a thermoreversible recording material containing a color former and a color-reducing agent, or the recording layer is made of a heat containing an electron-donating color-forming compound and an electron-accepting compound. A coloring type medium composed of a reversible recording material is exemplified.

Further, according to the method of displaying information recorded on the thermoreversible recording medium of the present invention, the recording is performed by using a heating recording device from the surface of the recording layer opposite to the viewing surface. A mirror image of the information is formed on the layer, and this mirror image is displayed on the viewing surface side as a real image of the information.

According to this method, since information is recorded on the surface opposite to the viewing surface, there is no possibility that the viewing surface is damaged by the heating recording device. Therefore,
When displaying recorded information, even if light is applied to the viewing surface side, the light is not scattered and the recorded information is not difficult to see, so the number of times of recording and erasing information on the medium can be increased. . Therefore, the life of the thermoreversible recording medium can be made longer than before.

Further, by providing a hard coat layer on the side of the recording layer opposite to the viewing surface, damage due to the heating recording device can be further reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the shapes, sizes, and arrangements of the components so that the present invention can be understood, and thus the present invention is not limited to the illustrated examples.

FIGS. 1 to 3 are each a structural diagram showing an example of the structure of the thermoreversible recording medium of the present invention, and are schematically shown by cutaways in sectional views.

FIG. 1 is a sectional view showing a thermoreversible recording medium 10 of a first configuration example. Medium 1 of the first configuration example
Numeral 0 includes a support 12, a recording layer 14 provided on the support 12, and a hard coat layer 18 provided on the recording layer 14 with a barrier layer 16 interposed therebetween.

The viewing surface 14a of the recording layer 14 of the medium 10
Is the support 12 side. The hard coat layer 18 is formed on a surface 14b opposite to the viewing surface 14a. The surface 18a of the hard coat layer 18 is used as a heat application surface. Therefore, a heating recording device such as a thermal head is brought into contact with the heat application surface 18a. Then, a mirror image of information to be displayed is formed on the recording layer 14 by applying heat by the heating recording device. As a result, desired recording information can be visually recognized as a real image from the viewing surface 14a side opposite to the heat application surface 18a.

Here, in the first configuration example, the hard coat layer 18 is a colorless transparent or a pale colored transparent which is usually used. Therefore, in order to view the information recorded on the recording layer 14 from the viewing surface 14a side, for example, as shown in FIG. 1, a colored layer 20 colored white or a colored paper (plate) is formed on the hard coat layer 18. The display medium 22 is formed in contact with the surface 18a. As a result, the recorded information is clearly displayed from the viewing surface 14a side.

The support 12 can be made of various materials depending on the use of the thermoreversible recording medium. When a thermoreversible card is realized with this medium, the support is preferably made of a film made of any suitable material, for example, a resin film. In the present invention, the support is transparent because the viewing surface is on the support side. Therefore, for example, it is preferable to use a transparent PET film.

The recording layer 14 is a layer containing a thermoreversible recording material. In this thermoreversible recording material, a recorded portion of information, that is, a written portion is opaque, and a non-recorded portion of information, that is, a non-written portion is transparent. As such a thermoreversible recording material, for example, a material containing a matrix material and an organic low-molecular substance can be used.
Thereby, a light scattering type medium can be formed. Further, as the thermoreversible recording material, for example, a material containing a color former and a color-reducing agent may be used. Thereby, a coloring type medium can be formed. As the thermoreversible recording material, it is particularly preferable to use a material containing an electron-donating color-forming compound and an electron-accepting compound.

As the electron-donating color-forming compound, a fluoran or phthalide leuco dye having a lactone ring in the molecular structure can be used.

The leuco dye is selected according to how many colors of the record to be formed on the medium. Although detailed distinctions by color are omitted here, specific examples of leuco dyes include crystal violet lactone (CVL), 3,3-bis (1-ethyl-2-methylindol-3-yl), and 3- ( 4-
Diethylamino-2-ethoxyphenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-dibutylamino-6-methyl-7-anilinofluoran, 2- (2-chloroanilino) -6-diethylaminofluoran, 2- (2 -Chloroanilino)
-6-dibutylaminofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 2-anilino-3-methyl-6- (N-ethylisopentylamino)
Fluoran, 3-cyclohexylmethylamino-6-methyl-7-anilinofluoran, 3-benzylethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran , 3
Various dyes such as -methylpropylamino-6-methyl-7-anilinofluoran and 3-diethylamino-6-methyl-7-xylidinofluoran can be mentioned.

The electron-accepting compound is not limited to these, but it is preferable to use a phenolic color developing material having an alkyl group having 10 or more carbon atoms or N-alkylamide-carbamic acid. .

Further, as the additive, one or more additives for improving the characteristics of the medium, for example, the coloring and erasing characteristics can be used.

As a binder for dispersing each of the above-described electron-donating color-forming compound, electron-accepting compound, and additives to be added as required, a water-soluble binder is often used. . A typical example of the binder is an aqueous polyvinyl alcohol solution. The polyvinyl alcohol includes a type having a different fighting degree and a type having a functional group such as a carboxyl group in a side chain. As examples of commercially available polyvinyl alcohol, KL318 (trade name) manufactured by Kuraray Co., Ltd. and T-330H (trade name) manufactured by Nippon Gosei Kogyo Co., Ltd. can be used.

The concentration of the aqueous polyvinyl alcohol solution varies depending on the purpose of use of the thermoreversible recording medium.
0.1 to 50% by weight can be used. The aqueous polyvinyl alcohol solution in which the thermoreversible recording material and the additives are dispersed is used as a coating solution for forming a recording layer. For this reason, the viscosity of the aqueous polyvinyl alcohol solution is several to several in consideration of ease of use as a coating solution.
It is preferable to adjust to several hundred cps (center poise). In adjusting the viscosity of the coating solution, cellulose may be contained in the coating solution as a viscosity adjusting agent. In order to prepare a coating solution having the above viscosity, the concentration of polyvinyl alcohol is preferably set to 1 to 10% by weight.

Note that a binder material soluble in an organic solvent may be used depending on the type of the thermoreversible recording material and the additive used. For example, resins such as vinyl chloride-vinyl acetate copolymers and polyvinyl acetal can be used.

The barrier layer is preferably made of a transparent material, for example, polyvinyl alcohol, cellulose or acrylic resin. Further, as the coloring layer 20, an opaque colored paper, a colored plate, a colored film, or the like can be used.

FIG. 2 is a sectional view showing a thermoreversible recording medium 30 according to a second embodiment of the present invention. In this configuration example, similarly to the first configuration example, the support 12, the recording layer 14 provided on the support 12, and the hard coat layer provided on the recording layer 14 via the barrier layer 16. 24 are provided. Then, the surface 24 of the hard coat layer 24
a is the heat application surface, and the support 12 side of the recording layer 14 is the visible surface 14a.

In the second configuration example, the wavelength is 550 nm
Hard coat layer whose light transmittance is 20% or less
24 are provided. Such a hard coat layer
Examples of the material to be formed include epoxy acrylate and
TiO to urethane acrylate _TwoAnd BaSO_FourDispersed
It is preferable to use a material. Thereby, the hard coat layer 2
4 can enhance the visible light shielding property,
When viewing recorded information from the 14a side, the colored layer
No display medium is formed on the surface 24a of the
However, the recorded information can be displayed clearly.

FIGS. 3A and 3B are cross-sectional views showing a thermoreversible recording medium 40 according to a third embodiment of the present invention.

In this configuration example, a support 12, a recording layer 14 provided on the support 12, and a hard coat layer 24 provided on the recording layer 14 via a barrier layer 16 are provided. I have. Further, an ultraviolet absorbing layer 26 is provided on the viewing surface 14a side of the recording layer 14, that is, on the side 12a of the support 12 opposite to the side on which the recording layer 14 is provided.

As a material constituting the ultraviolet absorbing layer 26, for example, 2-hydroxy-4- (methacryloyloxyethoxy) benzophenone, benzophenone, triazole, hindered amine or the like may be used as a transparent material having excellent ultraviolet absorbing properties. it can.

Since the medium 40 is a reflection type display, the medium 40 is irradiated with light from the viewing surface 14a side when used. In this configuration example, since the ultraviolet ray absorbing layer 26 is provided on the viewing surface 14a side, the ultraviolet ray included in the irradiation light can be absorbed, and the incidence of the ultraviolet ray on the recording layer 14 can be suppressed. This can prevent or suppress the material in the recording layer 14 from being destroyed by the ultraviolet rays.

As shown in FIG. 3B, the recording layer 1
The ultraviolet absorbing layer 28 may be provided not only on the visible surface 14a side but also on the surface 14b opposite to the visible surface 14a. Thereby, the ultraviolet rays transmitted through the ultraviolet absorbing layer 26 on the viewing surface 14a side and incident on the recording layer 14 are absorbed by the ultraviolet absorbing layer 28 provided on the opposite side of the viewing surface 14a without being reflected and scattered. Can be done.

Further, in the thermoreversible recording media of the second configuration example shown in FIG. 2 and the third configuration example shown in FIG.
For the components denoted by the same reference numerals as in FIG. 1, it is preferable to use the same materials as those described in the description of the first configuration example.

[0048]

Next, the thermoreversible recording medium of the present invention will be described with reference to more specific examples. The materials used and numerical conditions used in the following description are merely examples within the scope of the present invention. Therefore, the present invention is not limited only to these materials and numerical conditions.

<First Embodiment> As the first embodiment, the first configuration example shown in FIG. 1 will be described more specifically.

The thermoreversible recording medium 10 has a support 12
And a recording layer 14 provided on the support 12, and a hard coat layer 18 provided on the recording layer 14 via a barrier layer 16.

Such a medium is manufactured, for example, as follows.

In this example, first, a coating liquid containing a thermoreversible recording material as a material of the recording layer 14 is prepared. A polyvinyl alcohol is prepared as a binder. As polyvinyl alcohol, KL manufactured by Kuraray Co., Ltd.
-318 (trade name) is used. 15 parts by weight of this polyvinyl alcohol is dissolved in 985 parts by weight of pure water over 3 hours. This dissolving operation is performed while heating the sample to 80 ° C. After dissolving, it is cooled to room temperature to obtain an aqueous polyvinyl alcohol solution.

On the other hand, as a black electron-donating color-forming compound, 3-diethylamino-6 which is a kind of leuco dye is used.
-Methyl-7-anilinofluoran (3-Diethylamino-6
-methyl-7-anilinofluoran) and 30 parts by weight of parahydroxy-n-nonadecananilide (the following formula (1)), which is a phenolic developer, as an electron-accepting compound, in the same container. Put in. And these are heated and melted at a temperature of 150 ° C. by a water bath for 10 hours,
These eutectics are obtained. The eutectic is cooled to room temperature. The solid thus obtained is crushed into a coarse powder having a size suitable for being put into a crusher (here, a ball mill). Put this coarse powder and the aqueous polyvinyl alcohol solution prepared above in a ball mill,
By grinding for 15 hours, a coating liquid for forming a recording layer is obtained.

[0054]

Embedded image

Next, the thickness of the support 12 is 100
The above coating solution is applied onto a μm transparent PET (polyethylene terephthalate) film by a bar coater so that the film thickness after drying is about 5 μm. The recording layer 14 is obtained by heating and drying this coating film at a temperature of 60 ° C. for 30 minutes using a circulating hot air dryer (see FIG. 1).

Next, a barrier layer 16 is formed on the recording layer 14.

The above-prepared polyvinyl alcohol is applied by a bar coater onto the recording layer 14 so that the dry film thickness becomes about 1 μm. This coating film is heated and dried at a temperature of 80 ° C. for 5 minutes with a circulating hot air dryer,
The barrier layer 16 is obtained.

Thereafter, a hard coat layer 18 is provided on the barrier layer 16. In this example, the hard coat layer 18 is formed of the urethane acrylate layer 1 which is often used in the past.
8 is assumed. Therefore, a coating solution of urethane acrylate is prepared in the same manner as in the prior art, and this coating solution is applied on the barrier layer 16 by a bar coater so that the dry film thickness is about 4 μm. This coating film is circulated for 60
Heat drying at a temperature of ° C. for 3 minutes. Thereafter, the surface of the dried coating film is irradiated with ultraviolet rays at an irradiation amount of 200 mJ / cm ² to cure the coating film and form the hard coat layer 18.
Get.

The wavelength 55 of the hard coat layer 18
The transmittance of the light of 0 nm is 80%.

Thus, the thermoreversible recording medium 10 of the first embodiment is obtained (FIG. 1).

Next, information is recorded on the obtained medium 10 using a heating recording device. Here, as the heating recording device, 200 dpi (dot per inch, but 1
The inch is 2.54 cm. By applying heat to the surface 18a of the hard coat layer 18 under the condition of an applied energy of 0.38 mJ using a thermal head having a resolution of (1), the recording layer 14 is colored to form a mirror image of information.

Thereafter, the surface 18a of the hard coat layer 18
Is brought into contact with a white colored film 20 to obtain a display medium 22.

As a result, a real image of black information is clearly displayed on the white background from the viewing surface 14a side, that is, from the support 12 side. The reflection density of the recording unit at this time is set to Macb.
Obtained by measuring the black base optical density using an eth (Macbeth) optical densitometer.

As a result, the reflection density was 1.3 and the background density was 0.11.

Thus, in the thermoreversible recording medium 10 of the first embodiment, the thermal head comes into contact with the surface 14b opposite to the viewing surface 14a.
There is no danger of scratches and dirt on the viewing surface 14a due to contact with the thermal head. Therefore, even if the medium 10 is used repeatedly, scattering of light due to scratches and dirt on the side of the viewing surface 14a can be significantly prevented or suppressed as compared with the related art, so that the service life can be made longer than before. .

<Second Embodiment> As a second embodiment, in a thermoreversible recording medium having the same configuration as that of the first embodiment,
A medium in which the visible light shielding property of the hard coat layer is enhanced will be described.

Hereinafter, points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

FIG. 2 is an explanatory diagram of a second configuration example of the present invention, and is a configuration diagram of a medium according to the second embodiment. This medium 30 has a structure in which a recording layer 14, a barrier layer 16, and a hard coat layer 24 are laminated on a support 12 in this order.

This medium is used in the same manner as in the first embodiment.
A recording layer 14 is formed on a transparent PET film having a thickness of 100 μm as a support 12, and then a barrier layer 16 is formed.

Next, visible light shielding is performed on the barrier layer 16.
The hard coat layer 24 having high properties is formed. Here,
Dissolve oxyacrylate in toluene as solvent
Form an epoxy acrylate solution. To this solution, add
TiO with a uniform particle size of 0.3 μm _TwoAt a concentration of 30% by weight
Disperse. After this, add ethyl acetate to the solution
Is adjusted to be 700 to 800 cps.

Thereafter, the obtained solution is coated on the barrier layer 16 by a screen printing method so that the dry film thickness becomes 3 μm. Thereafter, the coating film is heated and dried at 60 ° C. for 3 minutes using a circulating hot air dryer. afterwards,
By irradiating the surface of the dried coating film with ultraviolet rays at a dose of 200 mJ / cm ² , the coating film is cured. Thereby, the hard coat layer 24 is obtained.

As described above, the thermoreversible recording medium 30 of the second embodiment is obtained (FIG. 2).

Here, the transmittance of the obtained medium 30 was measured by irradiating visible light having a wavelength of 550 nm from the support 12 side to be 5%. Therefore, the wavelength of 550 nm
It was confirmed that the transmittance of the light was 20% or less, that is, the hard coat layer 24 having low visible light transmittance was formed.

Next, in the same manner as in the first embodiment, information is recorded on the obtained medium 30 by using a heating recording device. In this example, the same thermal head as in the first example was used, and heat was applied under the condition of an applied energy of 0.4 mJ.

As a result, in this example, the hard coat layer 24
Has a high visible light shielding property, the background seen from the viewing surface 14a side is white. Then, black recording information is clearly displayed on the white background. At this time, the reflection density of the recording portion was 1.2, and the density of the background was 0.10.

Thus, the visible light shielding property of the hard coat layer 24 is increased, so that the hard coat layer 24
Plays a role of a colored layer for whitening the background seen from the viewing surface 14a side. Therefore, it is not necessary to bring the colored layer into contact with the surface of the hard coat layer during display.
Therefore, the cost for the colored layer (or colored paper (plate)) can be reduced.

Also in this embodiment, since the thermal head contacts the opposite side of the viewing surface 14a, the
There is no possibility that damage will occur on the 4a side. Therefore, it is possible to increase the number of times of recording and erasing of information more than before. Therefore, the service life of the medium can be extended.

<Third Embodiment> As a third embodiment, an example in which an ultraviolet absorbing layer is provided on a thermoreversible recording medium having the same configuration as that of the second embodiment will be described.

Hereinafter, points different from the first and second embodiments will be described, and detailed description of the same points will be omitted.

FIGS. 3A and 3B are explanatory diagrams of the configuration of the medium 40 according to the third embodiment of the present invention, and are diagrams illustrating the configuration of the medium 40 according to the third embodiment.

The medium 40 has a structure in which the recording layer 14, the barrier layer 16 and the hard coat layer 24 are laminated on the support 12 in this order. And in this example,
Further, an ultraviolet absorbing layer 26 is provided on the side 12a of the support 12 opposite to the side on which the recording layer 14 is provided (FIG. 3A).

In the medium 40, a recording layer 14 is formed on a transparent PET film having a thickness of 100 μm as a support 12 and then a barrier layer 16 is formed in the same manner as in the first embodiment. Thereafter, a hard coat layer 24 having a high visible light shielding property is formed on the barrier layer 16 in the same manner as in the second embodiment.
To form

Next, in this embodiment, the transparent PET film 12 has a side 12 opposite to the side on which the recording layer 14 is provided.
The ultraviolet absorbing layer 26 is formed on the surface a. In this example,
As a UV absorber, a commercially available UV manufactured by BASF
A-635L (trade name) is used. This UVA-635
L is 2-hydroxy-4- (methacryloyloxyethoxy) benzophenone in which benzophenone is bonded to a methyl methacrylate copolymer. This ultraviolet absorbent is dissolved in toluene and ethyl acetate as a solvent to form a coating solution, and the coating solution is dried with a bar coater so that the dried PET film has a thickness of 20 μm.
The film 12 is applied to the surface 12a opposite to the side on which the recording layer 14 is provided. This coating film is heated and dried at a temperature of 70 ° C. for 5 minutes using a circulating hot air dryer, whereby an ultraviolet absorbing layer 26 is obtained.

Thus, the medium 40 of the third embodiment is obtained (FIG. 3A).

In the thermoreversible recording medium 40 of the present invention, when recording is performed and this recording is displayed, reflection type display in which light is applied to the medium 40 from the viewing surface 14a side is performed. Therefore,
Since the ultraviolet absorbing layer 26 as thick as 20 μm is provided on the viewing surface 14a side as in this embodiment, the ultraviolet light included in the light applied to the medium 40 is absorbed by the ultraviolet absorbing layer 26, and the recording is performed. It can be prevented from being incident on the layer. Since the ultraviolet absorbing layer 26 is provided on the side of the viewing surface 14a to which no heat is applied, there is no limitation on the thickness for ensuring good heat conduction efficiency. Therefore, it can be formed sufficiently thick.

The thermoreversible recording material constituting the recording layer 14 of this embodiment contains a leuco dye. Leuco dyes are destroyed by high energy photons such as ultraviolet light. If the leuco dye is destroyed, the color may develop and discolor the background. In this embodiment, since the ultraviolet ray can be sufficiently absorbed by the ultraviolet ray absorbing layer 26 provided on the viewing surface 14a side, the ultraviolet ray incident on the recording layer 14 is drastically reduced. For this reason, there is almost no possibility of discoloration of the background. Therefore, it is possible to provide the medium 40 having a good contrast between the recording portion and the non-recording portion (background).

Further, similarly to the first and second embodiments,
Since damage occurring on the viewing surface 14a side due to the thermal head can be prevented, the medium 40 having a longer service life than before can be obtained.

<Modification of Third Embodiment> The ultraviolet absorbing layer described in the third embodiment may be provided not only on the viewing surface side of the recording layer but also on the surface opposite to the viewing surface. it can.

FIG. 3B shows the visual recognition surface 14 a of the recording layer 14.
FIG. 4 is a diagram showing a configuration in which ultraviolet absorbing layers 26 and 28 are provided on a surface 14b opposite to the viewing surface 14a, respectively.

The recording layer 14 and the barrier layer 1 are formed on the support 12.
6, second ultraviolet absorbing layer 28, and hard coat layer 2
4 are stacked in this order. A thick (20 μm thick) first ultraviolet absorbing layer 26 is provided on the surface of the support 12 opposite to the side on which the recording layer 14 is provided.

Second ultraviolet absorbing layer 2 on barrier layer 16
The formation of 8 is performed by, for example, applying the coating solution of the ultraviolet absorbent prepared in the third embodiment by a bar coater, and then performing heating and drying with a circulating hot air drier.

However, the surface 14b opposite to the viewing surface 14a
Since is the side to which heat is applied, the thickness of the second ultraviolet absorbing layer 28 is limited to 5 μm or less in consideration of the heat conduction efficiency of the heating recording device.

Therefore, in this modification, the second ultraviolet absorbing layer 28 is formed to have a thickness of 3 μm.

With such a configuration, the ultraviolet light transmitted through the first ultraviolet absorbing layer 26 on the viewing surface 14a side and incident on the recording layer 14 is not reflected and scattered, and the second ultraviolet absorbing layer 28 Can be absorbed. Thereby, destruction of the material (especially leuco dye) constituting the recording layer 14 can be further suppressed.

[0095]

As is clear from the above description, according to the thermoreversible recording medium 10 of the present invention, the recording layer 14 in which information is recorded and erased reversibly by controlling the application of heat and the cooling condition. The hard coat layer 18 is provided on a surface 14b of the recording layer 14 opposite to the viewing surface 14a.
Is formed, and the surface of the hard coat layer 18 is the heat application surface 18a. With such a configuration, even if information recording and erasing are repeatedly performed on the medium 10, damage such as a scratch due to heat application does not occur on the viewing surface 14a side. Therefore, there is no possibility that the scratches generated on the viewing surface 14a side are scattered by the light and the recorded image becomes difficult to see. Therefore, the number of times of recording and erasing information on the medium 10 can be increased more than before. This means that the life of the medium 10 has been further extended.

The method of displaying a record on the thermoreversible recording medium 10 according to the present invention uses the visual recognition surface 14 of the recording layer 14.
A mirror image of the information is recorded on the recording layer from the surface 14b opposite to the surface a using a heating recording device, and the recorded information is displayed on the viewing surface 14a side. According to this method, information is recorded on the surface 14b opposite to the visual recognition surface 14a.
There is no risk that the 4a side will be damaged. Therefore,
When displaying a record, even if light is applied to the viewing surface 14a, the light is not scattered and the recorded information is not difficult to see. Therefore, the number of times of recording and erasing on the medium 10 can be increased. . Therefore, the life of the thermoreversible recording medium 10 can be made longer than before.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first configuration example of a thermoreversible recording medium of the present invention, and is a configuration diagram provided for explaining a first embodiment.

FIG. 2 is a schematic diagram showing a second configuration example of the thermoreversible recording medium of the present invention, and is a configuration diagram provided for explanation of a second embodiment.

FIG. 3A shows a third example of the thermoreversible recording medium of the present invention.
FIG. 9 is a schematic diagram showing a configuration example of the third embodiment, and is a configuration diagram provided for describing a third embodiment. (B) is a configuration diagram showing a modification of the third embodiment.

[Explanation of symbols]

 10, 30, 40: thermoreversible recording medium (medium) 12: support (transparent PET film) 12a side opposite to the side provided with recording layer 14: recording layer 14a: visible surface 14b: surface on opposite side 16: barrier layer 18, 24: hard coat layer 18a, 24a: heat applied surface (surface) 20: colored layer (colored paper, colored plate, colored film) 22: display medium 26: ultraviolet absorbing layer (first ultraviolet absorbing layer) Layer) 28: UV absorbing layer (second UV absorbing layer)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41M 5/26 102 F term (Reference) 2H026 AA07 AA09 AA28 BB02 BB21 DD45 DD46 DD48 DD55 DD58 EE05 FF11 FF17 GG10 2H111 HA07 HA18 HA23 HA35

Claims (7)

[Claims] 1. A thermoreversible recording medium having a recording layer in which information is recorded and erased reversibly by controlling heat application and cooling conditions, wherein the recording layer has a surface opposite to a viewing surface. A thermoreversible recording medium having a hard coat layer formed thereon, wherein the surface of the hard coat layer is a surface to which heat is applied. 2. The thermoreversible recording medium according to claim 1, wherein the hard coat layer is a layer having a visible light shielding property having a transmittance of light having a wavelength of 550 nm of 20% or less. Thermoreversible recording medium. 3. The thermoreversible recording medium according to claim 1, wherein an ultraviolet absorbing layer is provided at least on the viewing surface side of the recording layer. 4. The thermoreversible recording medium according to claim 1, wherein the recording layer is made of a thermoreversible recording material containing a matrix material and an organic low-molecular substance. A thermoreversible recording medium characterized by the following. 5. The thermoreversible recording medium according to claim 1, wherein the recording layer is made of a thermoreversible recording material containing a color former and a developer. Characteristic thermoreversible recording medium. 6. The thermoreversible recording medium according to claim 1, wherein the recording layer is a thermoreversible recording material containing an electron-donating color-forming compound and an electron-accepting compound. A thermoreversible recording medium characterized by being constituted. 7. A method for recording and displaying information on a thermoreversible recording medium by applying heat to a recording layer, comprising: A method for recording and displaying on a thermoreversible recording medium, wherein a mirror image of the information is formed on the recording layer using a heating recording device, and the mirror image is displayed on the viewing surface as a real image of the information.