JP4525109B2 - Reversible recording medium and recording method using the same - Google Patents

Description

  The present invention relates to a reversible recording medium for recording a desired image and various data, and a recording method using the same.

In recent years, the necessity of rewritable recording technology has been strongly recognized from the viewpoint of the global environment.
With the progress of computer network technology, communication technology, OA equipment, recording media, storage media, etc., paperless is progressing in offices and homes.

  Under such circumstances, as an example of a display medium that replaces printed matter, a recording medium capable of recording and erasing information by heat has become a residual amount due to the spread of various prepaid cards, point cards, credit cards, IC cards, etc. And other recorded information, etc., are being put into practical use for visualization and readability, and are also being put into practical use for copying machines and printers.

Various proposals have heretofore been made regarding the recording medium as described above and a recording method using the same.
For example, a leuco dye type, that is, a recording medium having a recording layer in which a leuco dye which is a color developing compound in a resin base material and a developer / color-reducing agent are dispersed, and a recording method using the same are proposed. This has the advantage that contrast and visibility are better than those of the low molecular weight dispersion type because it utilizes the color of the leuco dye itself.

Applying the color development principle as described above, separating a plurality of recording layers using leuco dyes, using a heat-sensitive recording medium having a structure in which layers are formed in an independent state, irradiating a laser beam and performing arbitrary conversion by light-to-heat conversion There is a disclosure relating to a technique for heating only the recording layer to develop a color (for example, see Patent Document 1).
According to this method, only an arbitrary recording layer can be colored by the effect of wavelength selectivity of the layer containing the light-heat conversion material.

JP 2001-1645 A

  However, in the technique disclosed in Patent Document 1, the light-to-heat conversion layer (laser light absorption layer) is formed by adhering a light absorbing material dissolved in an organic solvent without containing a binder. However, such a light-heat conversion layer has a drawback that the display accuracy is deteriorated because it absorbs laser light in an extremely wide wavelength region.

  In addition, the laser light absorption layer formed by such a method has light absorption even in the visible range, and there is a problem that the transparency of the recording layer deteriorates in the erased state, leading to deterioration in recording accuracy. is doing.

  In order to obtain a reversible recording medium that solves these problems, the chemical structure is strictly controlled and the wavelength of the recording laser light is strictly controlled in order to select the optimum light absorption characteristics for the light-to-heat conversion material. You will have to choose.

  However, the light-to-heat conversion material optimized to deal with the above problem inevitably has a limited chemical structure, so the types of light-to-heat conversion material that can be applied are very limited, and synthesis is also possible. The problem is that the process is also complicated.

  In addition, light-to-heat conversion materials generally have low durability against light. Particularly when mixed with a color forming material for recording, the function deteriorates due to decomposition over time, and repeated recording and erasing many times. If this is done, there is a practical problem that the color development and decoloring properties deteriorate significantly. From such a point, an improvement regarding the temporal stability of the light-heat conversion material has been desired.

  Therefore, in the present invention, in view of the problems of the prior art as described above, there are few restrictions on the chemical structure, many light-to-heat conversion materials can be applied, good color development, excellent contrast, and color cast. A reversible recording medium that has no image problems, has practically no image stability, has excellent light resistance, and can maintain excellent color reproducibility over a long period of time, and a recording method using the same It was decided to.

In the present invention, in the surface direction of the support substrate, two or more rewritable layers are each separated and laminated through a heat insulating layer made of only a resin transparent to light from the visible region to the near infrared region, This rewritable layer has a light-to-heat conversion layer in which a light-to-heat conversion material that absorbs near-infrared rays in a specific wavelength region and generates heat, and a colorless and colored state depending on temperature changes. The recording layer containing the thermosensitive color-developing composition that reversibly changes in the resin is laminated, and the recording layers constituting the two or more rewritable layers have different color tones. A light-to-heat conversion material that generates heat by absorbing near infrared rays in different wavelength regions in the light-to-heat conversion layer constituting the two or more rewritable layers. Contains Is made, the said light in the rewritable layer - the resin constituting the heat conversion layer and a non-water-soluble resin, wherein the resin constituting the recording layer and the water-soluble resin, wherein the resin constituting the heat insulating layer a water-insoluble resin Thus, a reversible recording medium is provided in which the light-to-heat conversion layer and the recording layer adjacent to the light-to-heat conversion layer are present in a separated and independent state.

In the recording method of the present invention, two or more rewritable layers are separated and laminated in the surface direction of the support substrate via a heat insulating layer made of only a resin transparent to light from the visible region to the near infrared region, respectively. The rewritable layer is composed of a light-heat conversion layer in which a light-heat conversion material that absorbs near infrared rays in a specific wavelength region and generates heat, and a colorless / colored two-state according to a temperature change. And a recording layer containing a heat-sensitive color-developing composition that reversibly changes in the resin, and the recording layers constituting the two or more rewritable layers are different from each other. A light-to-heat conversion that contains a heat-sensitive color-forming composition that develops a color tone, and that generates heat by absorbing near infrared rays in different wavelength regions in the light-to-heat conversion layer constituting the two or more rewritable layers. Including material Is made, the said light in the rewritable layer - the resin constituting the heat conversion layer and a non-water-soluble resin, wherein the resin constituting the recording layer and the water-soluble resin, wherein the resin constituting the heat insulating layer a water-insoluble resin Thus, the light-to-heat conversion layer and the recording layer adjacent to the light-to-heat conversion layer are arbitrarily selected using a reversible recording medium in which the light-to-heat conversion layer and the recording layer adjacent to the light-to-heat conversion layer exist in a separated and independent state. Recording or erasing is performed by irradiating near-infrared rays having the above-mentioned wavelength.

According to the present invention, when a rewritable layer is formed by laminating a light-heat conversion layer containing a light-heat conversion material and a recording layer containing a thermosensitive color-forming composition, the material constituting these layers The light-to-heat conversion layer and the resin constituting the recording layer are selected so as not to be compatible with each other so that they are separated and independent from each other, and a heat insulating layer is provided between the rewritable layers, and the adjacent rewritable layers. By providing the light-heat conversion layer of one rewritable layer and the recording layer of the other rewritable layer so that the resins constituting them are not compatible with each other , the light resistance of the light-heat conversion material It is possible to reliably avoid the deterioration of the image quality, and even when the color conversion is repeatedly performed, the recording image quality equivalent to the initial value can be maintained for a long time.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the examples shown below.
In the following, a reversible recording medium having a structure in which three rewritable layers are formed will be described as an example. However, the present invention is not limited to this example, and for example, only a single color or two colors is used. It may be capable of coloring, and can be applied to any structure as long as one or more rewritable layers are formed.

FIG. 1 shows a schematic sectional view of an example of the reversible recording medium of the present invention.

The reversible recording medium 10 includes first to third light-to-heat conversion layers 11 to 13 and first to third recording layers 14 to 16 in the surface direction of the support substrate 1. The rewritable layers 31 to 33 are laminated via the heat insulating layers 17 and 18, and the protective layer 19 is formed as the uppermost layer. Hereinafter, each layer will be described in detail.

As the support substrate 1, a conventionally known material can be appropriately used as long as the material has excellent heat resistance and high dimensional stability in the planar direction. For example, it can be appropriately selected from polymer materials such as polyester and hard vinyl chloride, glass materials, metal materials such as stainless steel, and materials such as paper.
However, in cases other than transmission applications such as overhead projectors, the support substrate 1 is visible in white or metallic color in order to improve the visibility when recording is performed on the finally obtained reversible recording medium 10. It is preferable to form with a material having high reflectance to light.

  The first to third light-to-heat conversion layers 11 to 13 each comprise a light-to-heat conversion composition comprising a light-to-heat conversion material, a resin polymer, and various additives that generate heat by absorbing light in different wavelength ranges. It shall be comprised by.

  Light-to-heat conversion material avoids color development in the erased state and prevents color fogging to improve recording sensitivity. Therefore, it uses dyes that have almost no absorption in the visible wavelength range and a narrow absorption band as the main component. It shall be applied in a state where it is uniformly dissolved in a resin binder using a predetermined solvent.

As the light-to-heat conversion material as described above, phthalocyanine dyes, cyanine dyes, metal complex dyes, diimmonium dyes, etc., which are generally used as infrared absorbing dyes having no absorption in the visible wavelength range, can be used. Cyanine dyes are preferred.
Cyanine dyes have little absorption in the visible range and sharp absorption in the near infrared range. Since the absorption maximum wavelength varies depending on the structure, it is possible to select one suitable for the laser wavelength used for recording.

  Examples of the resin binder for dispersing the dye as the light-to-heat conversion material include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, and polyester. , Aromatic polyester, polyurethane, polycarbonate, polymethacrylate, acrylic acid copolymer, maleic acid copolymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, gelatin, starch, etc., UV curable Examples thereof include a resin and a thermosetting resin.

Moreover, you may add various additives, such as a ultraviolet absorber and a singlet oxygen quencher, to the light-heat conversion layers 11-13 as needed.
The singlet oxygen quencher contains at least one selected from the group consisting of conjugated polyenes, transition metal complexes, hindered amines, amines, aminium salts, and iminium salts.
The addition amount of these singlet oxygen quenching agents is preferably about 0.05 to 4 times by weight with respect to the light-to-heat conversion material constituting the light-to-heat conversion layer. More preferably, it is 1 to 2 times.

  The film thicknesses of the first to third light-heat conversion layers 11 to 13 are preferably about 0.05 to 10 μm, and more preferably about 0.1 to 5 μm. If these film thicknesses are too thick, a sufficient color density cannot be obtained. Conversely, if the film thickness is too thin, the dye as the light-heat conversion material cannot be sufficiently dissolved.

Next, the first to third recording layers 14 to 16 will be described.
The first to third recording layers 14 to 16 are formed of a material capable of forming a stable color-decoloring state (colored state and transparent state) by controlling the heat state, and this is repeated. It shall be possible to record and erase.

  Each of the first to third recording layers 14 to 16 includes at least a color developing compound having an electron donating property, such as a leuco dye, and a thermosensitive coloring composition composed of a developing / color-reducing agent having a predetermined electron accepting property. Suppose that it is formed in a state of being uniformly dissolved in a resin binder using a predetermined solvent.

The first to third recording layers 14 to 16 are formed using a predetermined leuco dye corresponding to a desired color in each, and for example, the first to third recording layers 14 to 16 emit three primary colors. In this way, a full color image can be formed as the entire reversible recording medium 10.
As the leuco dye, an existing thermal paper dye or the like can be applied.
As the developer / color-reducing agent, organic acids having a long-chain alkyl group conventionally used in these (JP-A-5-124360, JP-A-7-108761, JP-A-7-188294, JP-A-7-238294 2001-105733, JP-A-2001-113829, etc.) can be applied.

Examples of the resin binder for forming the first to third recording layers 14 to 16 include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, modified cellulose, acetal resin, butyral resin, polystyrene, and styrene. Copolymer, phenoxy resin, polyester, aromatic polyester, polyether resin, polyurethane, polycarbonate, polyacrylate ester, polymethacrylate ester, acrylic acid copolymer, maleic acid polymer, polyvinyl alcohol, modified polyvinyl Examples include alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, starch and the like.
In addition, you may use together various additives, such as a ultraviolet absorber, for the 1st-3rd recording layers 14-16 as needed.

The first to third recording layers 14 to 16 are prepared by dissolving or dispersing the leuco dye, the developing / color-reducing agent, and various additives in the resin binder using a solvent. It can form into a film by apply | coating to the formation surface.
The first to third recording layers 14 to 16 are desirably formed to a thickness of about 1 to 50 μm, and more preferably about 2 to 20 μm. If these film thicknesses are too thin, a sufficient color density cannot be obtained. Conversely, if the film thickness is too thick, the heat capacity of the layer becomes too large, and the color development and decoloring properties deteriorate, or the thermal conductivity deteriorates. This is because the translucency is lowered.

The first to third light-heat conversion layers 11 to 13 and the first to third recording layers 14 to 16 are combined to form the first to third rewritable layers 31 to 33, respectively. These rewritable layers 31 to 33 include a recording layer containing reversible thermosensitive coloring compositions having different coloring hues, and a light-to-heat conversion material that generates heat by absorbing near infrared light in different wavelength ranges. It shall consist of the light-heat conversion layer containing.
Note that the light-to-heat conversion layer and the recording layer constituting the rewritable layers 31 to 33 may be switched in the stacking order based on the support substrate 1.

  In the present invention, the light-heat conversion layers 11 to 13 and the recording layers 14 to 16 constituting the rewritable layers 31 to 33 and the recording layers 14 to 16 are particularly selected so that the resins constituting them are not compatible with each other. It shall be made to exist in a separated and independent state.

For example, a light-heat conversion layer is formed by applying a water-soluble resin, a recording layer is formed by applying a water-insoluble resin, and these are combined, or a light-heat conversion layer is applied by applying a water-insoluble resin. Forming a recording layer by applying a water-soluble resin and combining them, applying a water-insoluble resin to form a light-to-heat conversion layer, and applying an ultraviolet curable resin to form a recording layer. Form and combine these, apply a water-insoluble resin to form a light-to-heat conversion layer, apply a thermosetting resin to form a recording layer and combine them, or apply a thermosetting resin Then, a light-heat conversion layer can be formed, a water-insoluble resin can be applied to form a recording layer, and these can be combined.
Note that the present invention is not limited to the above combinations, and the water-soluble resin, the water-insoluble resin, the thermosetting resin, and the ultraviolet curable resin are not compatible with each other in the resins constituting the adjacent layers. It can be appropriately selected and used.

It is desirable to form heat-insulating layers 17 and 18 that are transparent to near infrared light to be irradiated between the rewritable layer 31 and the rewritable layer 32 and between the rewritable layer 32 and the rewritable layer 33.
This avoids conduction of heat between adjacent rewritable layers during recording, and an effect of preventing the occurrence of so-called color fogging can be obtained.
Further, by forming the heat insulating layers 17 and 18, in the recording layer and the light-to-heat conversion layer (for example, the first recording layer 14 and the second light-to-heat conversion layer 12 in FIG. 1) in the adjacent rewritable layer. It becomes easy to prevent the resins constituting them from being compatible with each other, and they can be reliably separated and formed independently.

The heat insulation layers 17 and 18 can be formed using a conventionally known translucent resin material. For example, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate ester, polymethacrylate ester , Acrylic acid copolymer, maleic acid polymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, starch and the like. Various additives such as ultraviolet absorbers may be used in combination in the heat insulating layers 17 and 18 as necessary.
Further, a light-transmitting inorganic film may be applied to the heat insulating layers 17 and 18. For example, it is preferable to apply porous silica, alumina, titania, carbon, or a composite thereof to reduce thermal conductivity. These can be formed by a sol-gel method capable of forming a film from a liquid layer.

  The heat insulating layers 17 and 18 are preferably about 2 to 100 μm in thickness, and more preferably about 40 to 50 μm. If the film thickness of the heat insulating layer is too thin, sufficient heat insulating effect cannot be obtained, and if the film thickness is too thick, the thermal conductivity deteriorates when the entire recording medium is uniformly heated in the recording method to be described later, or translucency This is because of a decrease.

Next, the protective layer 19 will be described.
The protective layer 19 can be formed using a conventionally known ultraviolet curable resin or thermosetting resin, and the film thickness is preferably about 0.5 to 50 μm.
If the protective layer 19 is too thin, a sufficient protective effect cannot be obtained. If the protective layer 19 is too thick, the thermal conductivity deteriorates or the translucency decreases when the entire recording medium described later is uniformly heated.

Next, the recording principle using the reversible recording medium of the present invention will be described.
In the following, a method for recording and erasing using the reversible recording medium 10 having the structure in which the three rewritable layers 31 to 33 shown in FIG. 1 are formed will be described. However, the present invention is not limited to this, and a reversible recording medium in which one or more rewritable layers are formed and which can generate only a single color or two colors can be similarly applied.

  First, the entire surface is heated at a temperature at which each recording layer is decolored, for example, at a temperature of about 120 ° C., and the first to third recording layers 14 to 16 are previously decolored. That is, in this state, it is assumed that the color of the support substrate 1 is exposed. Next, an arbitrary part of the reversible recording medium 10 is irradiated with infrared light having an arbitrarily selected wavelength and output by a semiconductor laser or the like.

  For example, when the first recording layer 14 is colored, infrared light near the absorption peak wavelength (λmax1) of the light-heat conversion material contained in the first light-heat conversion layer 11 is used as the first recording layer. 14 irradiates the first light-heat conversion layer 11 with energy that reaches the color development temperature to generate heat, and causes a color development reaction between the electron-donating color-forming compound and the electron-accepting developer / color-reducing agent, Color the irradiated area.

Similarly, for the second recording layer 15 and the third recording layer 16, the absorption peak wavelengths of the light-heat conversion materials contained in the second and third light-heat conversion layers 12, 13 respectively. Laser light in the vicinity of (wavelengths λmax2, λmax3) is irradiated to the second and third light-to-heat conversion layers with an energy sufficient for the corresponding recording layer to reach the color development temperature to generate heat, and the irradiated portion is colored.
In this way, an arbitrary portion of the reversible recording medium 10 can be developed in a desired hue. At this time, all hues can be recorded by using the same number of laser light sources having different oscillation wavelength bands as the number of recording layers including the light-heat conversion material.

  Furthermore, by irradiating the same position of the reversible recording medium 10 with laser beams having a plurality of wavelengths, a mixed color of corresponding colored hues can be obtained. At this time, the color tone of the mixed color can be displayed by adjusting the energy of the irradiated laser beam. That is, if each recording layer is set to develop yellow, cyan, and magenta, a full-color image and various types of information can be recorded on any part of the reversible recording medium 10 by using the above method. Can do.

  Further, in the recording layer that has been colored as described above, the recording information and the image can be obtained by heating uniformly to a temperature at which the first to third recording layers 14 to 16 are decolored, for example, 120 ° C. It can be erased and repeated recording can be performed.

Hereinafter, the present invention will be described with reference to specific examples and comparative examples.
First, paints 1 to 6 were prepared by combining the resins, solvents, and light-heat conversion materials shown in Table 1 below.
In addition, the leuco dye, developer / color reducing agent, resin, solvent, and light-heat conversion material shown in Table 2 below are mixed in an appropriate combination, pulverized to 0.3 μm or less with a paint conditioner, and paints 7 to 14 Was made.

Chemical formulas (1) to (3) corresponding to the leuco dyes of formulas 1 to 3 shown in Table 2 are shown below.
In the formula, Et represents an ethyl group, Me represents a methyl group, and n represents normal.

  The chemical formula (4) corresponding to the developer / subtractant of formula 4 shown in Table 2 is shown below.

Chemical formulas (5) to (8) corresponding to the light-to-heat conversion materials (near infrared absorbing dyes) of Formulas 5 to 8 shown in Tables 1 and 2 are shown below.
Me represents a methyl group.

Next, as shown in Table 3 below, a predetermined one of the paints shown in Tables 1 and 2 above was applied on a white polyethylene terephthalate support substrate having a thickness of 500 μm, and Examples 1 to 4 were compared. Sample media of Examples 1-5 were made.
In addition, each layer was formed into a film by apply | coating a coating material with a wire bar and making it dry.
However, the protective layer was formed using an ultraviolet curable resin.

Further, among the paints shown in Tables 1 and 2, predetermined ones were sequentially applied and laminated on a transparent PET film supporting substrate having a thickness of 100 μm, and Examples 5 and 6 and Comparative Examples 6 and 7 were formed. A sample of was prepared. In addition, the said Example 1, 4-6 is a reference example.
Then, each optical characteristic was evaluated about the samples of Examples 1-6 produced as mentioned above, and Comparative Examples 1-7.

[Evaluation method of optical characteristics]
First, the reflection density (OD) of the background of the sample produced as described above was measured with a Macbeth densitometer.
Subsequently, for each recording layer constituting the sample, the absorbance of the recording layer alone at the wavelength of the laser beam used for recording was measured, and the absorption curve was measured with a spectrophotometer. As a result, it was confirmed that the absorbance of the recording layer alone of all the recording layers at the wavelength of the laser beam used for recording was about 1.0 to 1.1.
For the absorption curve, one recording layer was prepared in the same manner as the sample preparation, and when a photothermal conversion layer was provided, a sample in which one recording layer was laminated on one light-heat conversion layer, It formed on the transparent PET film for a light absorbency measurement, and evaluated using this.

[Evaluation of storage stability of light-to-heat conversion material]
Using the samples of Examples 5 and 6 and Comparative Examples 6 and 7 produced as described above, the storability of the light-heat conversion material was evaluated.
In this, first, in the initial state, the absorption curve of the light-to-heat conversion material is measured by a spectrophotometer to measure the maximum value, and then the light source is set to a white fluorescent lamp using a light resistance tester. Then, after conducting a storage test in which light irradiation is performed under conditions of 500000 lx for 8 hours, similarly, the absorption curve of the light-to-heat conversion material is measured by the spectrophotometer, and the maximum value is measured. Went.
Moreover, the preservability of the light-heat conversion material was evaluated using the sample media of Example 1, Example 4, Comparative Example 1, and Comparative Example 5.
In this, first, the reflection density (OD) of the background in the initial state was measured, and the reflection density when recording was performed by irradiating with laser light. In this case, scanning was performed while irradiating a semiconductor laser beam having a predetermined oscillation center wavelength under the conditions of a spot shape of 30 μm × 200 μm and an output of 450 mW. Scanning conditions were evaluated by a Macbeth densitometer on the reflection density of a solid image recorded by scanning in the direction of the axis of the spot shape of 200 μm at a speed of 5.4 m / s and a scanning interval of 15 μm.
Furthermore, after performing a storage test in which the light source is a white fluorescent lamp and light irradiation is performed under conditions of 500000 lx for 8 hours, the reflection density (OD) of the background is measured in the same manner. Further, the reflection density was measured when recording was performed by irradiating a laser beam. The recording conditions are the same as above.

[Laser recording evaluation]
Using the samples of Examples 1 to 4 and Comparative Examples 1 to 5 produced as described above, the semiconductor laser was irradiated under the following conditions, and the recording line width and the evaluation of the reflection density of solid image recording were evaluated. Went.
In this case, scanning was performed while irradiating semiconductor laser light having oscillation center wavelengths of 800 nm, 860 nm, and 940 nm under the conditions of a spot shape of 30 μm × 200 μm and an output of 450 mW. The scanning conditions are: CMY (cyan, magenta, yellow) of solid images recorded by scanning at a speed of 5.4 m / s and a scanning interval of 15 μm in the direction of the axis of the spot shape of 200 μm, and the reflection density of each solid image. The total was evaluated.
Next, a 120 ° C. hot stamp was pressed for 1 second to erase the image.
The recording and erasing operations described above are repeated 100 times, and the solid image when the 100th recording is performed, the CMY (cyan, magenta, yellow) when the erasing is performed for the 100th time, and the respective reflection densities are Macbeth densities. The total was evaluated.

〔Evaluation results〕
Table 4 below shows the evaluation results of the storage characteristics of the light-heat conversion materials in the samples of Examples 5 and 6 and Comparative Examples 6 and 7.
Table 5 below shows changes in the laser recording evaluation before and after the storage test in the samples of Example 1, Example 4, Comparative Example 1, and Comparative Example 5. In Example 1 and Comparative Example 1, recording was performed with a laser beam having a wavelength of 940 nm to produce a cyan color, and in Example 4 and Comparative Example 5, recording was performed with a laser beam having a wavelength of 800 nm to cause a yellow color to be compared. went.
Table 6 below shows the results of initial laser recording evaluation in the samples of Examples 1 to 4 and Comparative Examples 1 to 5, and Table 7 below repeats the recording and erasing operations 100 times. The solid image when recording was performed and the CMY reflection density when erasing was performed for the 100th time are shown.

As shown in Table 4 above, in Examples 5 and 6, even after the light irradiation test (storage test), the absorbance of the light-to-heat conversion material does not change greatly, good characteristics are maintained, and high storage is achieved. It was confirmed that it has sex.
On the other hand, in Comparative Example 6, since the light-heat conversion material and the coloring dye were mixed in one layer, the light-heat conversion material was greatly deteriorated. After the light irradiation test (storage test), the light absorption characteristics were remarkably increased. Deteriorated.
Further, in Comparative Example 7, since the mixing of the resin occurred between the adjacent light-heat conversion layer and the recording layer, the light absorption characteristics deteriorated significantly after the light irradiation test (storage test). .

As shown in Table 5 above, in Examples 1 and 4, good color development was obtained even after the light irradiation test (storage test).
On the other hand, in Comparative Example 1, since the light-heat conversion material and the coloring dye were mixed in one layer, the light-heat conversion material was greatly deteriorated. After the light irradiation test (storage test), the light absorption characteristics were remarkably increased. Deteriorated, and sufficient color development was not obtained.
Further, in Comparative Example 5, since the resin was mixed between the adjacent light-heat conversion layer and the recording layer, the light absorption characteristics deteriorated remarkably after the light irradiation test (storage test). A sufficient color developability could not be obtained.

  From the above, in the samples of Examples 1 and 4 to 6 having the configuration of the present invention, the storage characteristics of the light-heat conversion material can be maintained high, and good color development can be obtained even after the storage test. I was able to confirm that.

As shown in Table 6 above, in Examples 1 to 4, good yellow, magenta, and cyan colors were obtained when recording was performed using laser beams having oscillation center wavelengths of 800, 860, and 940 nm. Also, no color cast occurred. When a plurality of laser beams were irradiated at the same time, a corresponding intermediate color was obtained with a clear color.
Further, after recording with laser light, all images could be erased by bringing a hot stamp at 120 ° C. into contact for 1 second, and the transparency after erasure was good.
Further, when the laser beam was irradiated, the recording could be further repeated, and the color tone after the repeated recording was very clear.

Further, as shown in Table 7 above, in Examples 1 to 4, good yellow, magenta and cyan colors were obtained and no color fogging occurred even after 100 times of recording and erasing were repeated.
Further, the reflection density after disappearance when the 120 ° C. hot stamp was contacted for 1 second was very small, and almost all images could be erased.

On the other hand, in Comparative Examples 1 to 5, as shown in Table 6 above, when recording was performed using each laser beam having an oscillation center wavelength of 800, 860, and 940 nm, good yellow, magenta, Cyan color was obtained and no color cast occurred. Moreover, when a plurality of laser beams were irradiated at the same time, a corresponding intermediate color was obtained.
However, as shown in Table 7 above, after repeating recording and erasing 100 times, the color developability of yellow, magenta and cyan was remarkably lowered. In addition, there was unerased residue when a 120 ° C. hot stamp was contacted for 1 second, and all images could not be erased.

  As is clear from the above-described results, according to the present invention, the light-to-heat conversion comprising the light-to-heat conversion material that generates heat by absorbing near-infrared light in a specific wavelength region in the surface direction of the support substrate. A resin constituting a light-heat conversion layer in a reversible recording medium comprising a layer and a recording layer containing a reversible thermosensitive coloring composition that reversibly changes between a colorless and colored state in response to heat However, it is incompatible with the resin in the recording layer existing around it, and these are separated and independent so that the storage stability of the light-to-heat conversion material can be improved, and repeated recording and erasing It has been found that image degradation can be effectively avoided even when performing.

1 is a schematic cross-sectional view of an example of a reversible recording medium of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Support substrate, 10 ... Reversible recording medium, 11 ... 1st light-heat conversion layer, 12 ... 2nd light-heat conversion layer, 13 ... 3rd light-heat conversion layer, 14 ... 1st recording layer, 15 ... 2nd recording layer, 16 ... 3rd recording layer, 17, 18 ... heat insulation layer, 19 ... protective layer, 31 ... 1st rewritable layer, 32 …… Second rewritable layer, 33 …… Third rewritable layer

Claims (5)

In the surface direction of the support substrate, two or more rewritable layers are separated and laminated through a heat insulating layer made of only a resin transparent to light from the visible range to the near infrared range,
The rewritable layer is
A light-to-heat conversion layer in which a light-to-heat conversion material that generates heat by absorbing near infrared rays in a specific wavelength region is contained in the resin;
A recording layer in which a heat-sensitive color-developing composition that reversibly changes two states of colorless and colored according to a temperature change is contained in the resin,
It has a structure formed by stacking,
The recording layer constituting the two or more rewritable layers contains a thermosensitive coloring composition that develops colors different from each other,
In the recording layer, a heat-sensitive color-forming composition comprising a color-forming compound having electron donating properties and a developer / color-reducing agent having electron accepting properties is contained in a resin, and the color-forming compound, By the reversible reaction between the developer and the color reducing agent, the recording layer is reversibly changed into two states of colorless and colored,
The light-to-heat conversion layer constituting the two or more rewritable layers contains a light-to-heat conversion material that generates heat by absorbing near infrared rays in different wavelength regions,
The resin constituting the light-heat conversion layer in the rewritable layer is a water-insoluble resin, the resin constituting the recording layer is a water-soluble resin,
The resin constituting the heat insulating layer is a water-insoluble resin,
Thereby, the light-heat conversion layer and the recording layer adjacent to the light-heat conversion layer exist in a separated and independent state ,
The color developing compound is
Leuco dye that develops cyan

Or
Leuco dye that develops color on magenta

Or
Leuco dye that develops yellow color

And
The developer / color-reducing agent is

And
The light-to-heat conversion material is

Or

Or

A reversible recording medium.   2. The reversible recording medium according to claim 1, wherein the two or more rewritable layers are respectively laminated in the order of the light-heat conversion layer and the recording layer from the support substrate side. The reversible recording medium according to claim 1, wherein the light-heat conversion layer contains a singlet oxygen quenching agent. In the surface direction of the support substrate, two or more rewritable layers are separated and laminated through a heat insulating layer made of only a resin transparent to light from the visible range to the near infrared range,
The rewritable layer is
A light-to-heat conversion layer in which a light-to-heat conversion material that generates heat by absorbing near infrared rays in a specific wavelength region is contained in the resin;
A recording layer in which a heat-sensitive color-developing composition that reversibly changes two states of colorless and colored according to a temperature change is contained in the resin,
It has a structure formed by stacking,
The recording layer constituting the two or more rewritable layers contains a thermosensitive coloring composition that develops colors different from each other,
In the recording layer, a heat-sensitive color-forming composition comprising a color-forming compound having an electron donating property and a developer / color-reducing agent having an electron accepting property is contained in a resin, and the color-forming compound, By the reversible reaction between the developer and the color reducing agent, the recording layer is reversibly changed into two states of colorless and colored,
The light-to-heat conversion layer constituting the two or more rewritable layers contains a light-to-heat conversion material that generates heat by absorbing near infrared rays in different wavelength regions,
The resin constituting the light-heat conversion layer in the rewritable layer is a water-insoluble resin, the resin constituting the recording layer is a water-soluble resin,
The resin constituting the heat insulating layer is a water-insoluble resin,
Thereby, the light-heat conversion layer and the recording layer adjacent to the light-heat conversion layer exist in a separated and independent state,
The color developing compound is
Leuco dye that develops cyan

Or
Leuco dye that develops color on magenta

Or
Leuco dye that develops yellow color

And
The developer / color-reducing agent is

And
The light-to-heat conversion material is

Or

Or

Using a reversible recording medium
A recording method for a reversible recording medium in which recording or erasing is performed by irradiating a laser beam having an oscillation center wavelength of 800 nm, 860 nm or 940 nm. The reversible recording medium recording method according to claim 4, wherein the two or more rewritable layers are laminated in the order of the light-heat conversion layer and the recording layer from the support substrate side.

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