KR20050103044A - Multicolor recording medium, recording method using the same and recording device - Google Patents

Abstract

Provide a record carrier. The recording medium includes a substrate having an upper surface and a lower surface, a photosensitive layer and at least two layers of thermochromic layers. The thermochromic layers of the two layers may be a first thermochromic layer and a second thermochromic layer that express colors at different temperatures.

Description

Multicolor recording medium, multicolor recording medium, recording method using the same and recording device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor recording medium, and more particularly, to a multicolor recording medium having a coloring layer, a recording method and a recording apparatus using the same.

The multicolor recording method is widely used due to the advantage that the user can collect, edit and output the desired image unlike the silver-colored photograph. Such multicolor recording methods include a sublimation method using a sublimation thermal transfer film, a laser beam printing method using color toner, a color inkjet method using an ink cartridge, and the like. However, these methods have a disadvantage in that the consumables of the recording device such as film, toner, ink and the like must be continuously replaced in addition to the recording medium.

On the contrary, attention has been paid to a multicolor recording medium in which a recording layer is provided in the recording medium so that the recording device can be used semi-permanently without having to replace consumables.

U. S. Patent No. 6297840 discloses a recording paper and a recording apparatus having a thermochromic layer of yellow, magenta and cyan having different thermal sensitivities. Such a recording device adopts a method of fixing the already expressed color by applying ultraviolet rays after the first and second color expressions, respectively, to prevent additional color expression of the already expressed color during the second and third color expressions. have. However, such a recording apparatus has a disadvantage in that it is somewhat complicated because it requires one thermal head and two ultraviolet light sources having different maximum wavelength bands.

On the other hand, US Patent No. 5667949 discloses a recording paper having thermochromic layers of yellow, magenta and cyan. The thermochromic layers include an infrared absorber that converts an infrared light source into heat. Therefore, the apparatus using such recording paper has a disadvantage that it is also somewhat complicated because it requires three infrared laser light sources having different wavelength bands.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and to provide a multicolor recording medium, a recording method and a recording device using the same, which can be used in a relatively simple recording device without requiring any consumables other than the recording medium.

In order to achieve the above technical problem, a recording medium is provided as an aspect of the present invention. The recording medium includes a substrate having an upper surface and a lower surface, a photosensitive layer and at least two layers of thermochromic layers.

The thermochromic layers of the two layers may be a first thermochromic layer and a second thermochromic layer that express colors at different temperatures. Further, the first thermochromic layer and the second thermochromic layer are sequentially stacked on the upper surface of the substrate, the first thermochromic layer expresses color at a low temperature, and the second thermochromic layer is colored at high temperature. It is preferable to express. Thus, each of the colors can be expressed in the first and second thermochromic layers by using one thermal head operating at low and high temperatures.

The chromophoric layers may be stacked on an upper surface of the substrate. In this case, an undercoat layer may be interposed between the substrate and the substrate. A protective layer may be stacked on the color layer stacked on the top of the color layers. The back coating layer may be laminated on the lower surface of the substrate. The thermochromic layers of the two layers may be a first thermochromic layer and a second thermochromic layer, and the photochromic layer may be interposed between the first thermochromic layer and the second thermochromic layer. At this time, between the first thermochromic layer and the photosensitive layer; And a first intermediate layer and a second intermediate layer, respectively, between the photosensitive layer and the second photosensitive layer.

Meanwhile, at least one of the color layers may be stacked on the bottom surface of the substrate, and the remaining color layer (s) may be stacked on the top surface of the substrate. In this case, between the substrate and the color layer laminated on the upper surface of the substrate; And a first undercoating layer and a second undercoating layer may be interposed between the color development layer and the base material laminated on the lower surface of the base material. A protective layer may be stacked on the color layer stacked on the top of the color layer on the upper surface of the substrate. An opaque reflective layer and a back coating layer may be sequentially stacked on the color development layer on the lower surface of the substrate. Further, the photosensitive layer may be stacked on the lower surface of the substrate, and the two layers of thermochromic layers may be stacked on the upper surface of the substrate. In this case, the thermochromic layers of the two layers are a first thermochromic layer and a second thermochromic layer that express colors at different temperatures, and the first thermochromic layer and the second thermochromic layer are upper surfaces of the substrate. Can be stacked on top of one another. An intermediate layer may be interposed between the first thermochromic layer and the second thermochromic layer.

As another aspect of the present invention, there is provided a recording apparatus using the above-described recording medium. The recording apparatus includes a light source for irradiating light to the recording medium to express color in the photochromic layer of the recording medium and a heat head for transferring color to the recording medium to express color in the thermochromic layer of the recording medium. In this way, a relatively simple device that does not require any consumables other than the recording medium can be implemented. The thermal head may have a mode of operating at high temperatures and a mode of operating at low temperatures. The thermal head may have a mode of operating for a short time at high temperature and a mode of operating for a long time at low temperature. Thus, one thermal head can be used to develop thermochromic layers that express color at different temperatures.

As another aspect of the present invention, there is provided a recording method for recording an image on the above-described recording medium. In the recording method, a recording medium having one layer of photosensitive chromophores and at least two layers of thermochromic layers expressing different colors is fed, and the color is expressed on the photochromic layer by irradiating light to the recording medium. And expressing color in the thermochromic layer by applying heat to the recording medium. The thermochromic layers are a first thermochromic layer that develops at a low temperature and a second thermochromic layer that develops at a high temperature. By expressing a color in the layer and applying low temperature heat to the recording medium, it is possible to provide a color in the first thermochromic layer. Furthermore, the first thermochromic layer is farther away from the heat head than the second thermochromic layer, and expressing color in the second thermochromic layer is performed by applying high temperature heat to the recording medium for a short time. In addition, expressing color in the first thermochromic layer is preferably performed by applying low temperature heat to the recording medium for a long time.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms.

1 is a cross-sectional view showing a multicolor recording medium according to an embodiment of the present invention.

Referring to FIG. 1, the multicolor recording medium according to the present embodiment includes a substrate 100 having an upper surface and a lower surface. The substrate 100 may be used as long as it is used in a conventional recording medium, and may be, for example, paper, films, paper and film, synthetic or photo paper (aka baryta). More specifically, the papers include white paper, computerized paper, imitation paper, single-sided or double-sided art paper, cast coated paper, and the like, and the films include one of transparent, translucent, polyester-based, polycarbonate-based, cellulose-acetate-based, and polyethylene-based films. Or there is an opaque plastic film, and the paper and the film is laminated on one side or both sides of polyethylene or polypropylene. The base 100 has a thickness of 15 to 350 μm so as to be easy to handle and to prevent bending when forming a coating layer thereon. However, it is not limited thereto.

At least three chromophoric layers 131, 133, and 135 are disposed on an upper surface of the substrate 100. The coloring layers 131, 133, and 135 are layers expressing different colors. One layer is a photosensitive layer, and at least two layers are thermochromic layers. Thereby, the image can be recorded by a relatively simple recording device composed of one thermal head capable of expressing color in the thermochromic layer and one light source capable of expressing color in the photosensitive layer. .

Preferably, the thermochromic layers are formed of a first thermochromic layer and a second thermochromic layer capable of expressing color at different temperatures. In this case, the photochromic layer, the first and the second photochromic layer may exhibit yellow, magenta, and cyan colors, respectively, regardless of their order. In addition, the lamination order of the photosensitive layer and the first and second photosensitive layers is not particularly limited. However, preferably, the first thermochromic layer 131 and the second thermochromic layer 135 are sequentially stacked on the substrate 100. In this case, the first thermochromic layer 131 may be a layer expressing color at a low temperature, and the second thermochromic layer 135 may be a layer expressing color at a high temperature. Accordingly, each color may be expressed in the thermochromic layers 131 and 135 by using one heat head. More specifically, when the heat head is operated for a short time at a high temperature, color may be expressed in the second thermochromic layer 135 close to the heat head, while the operating time is short, and thus, the first thermochromic layer 131 may be transferred to the first thermochromic layer 131. Heat transfer is suppressed. However, when the thermal head is operated at a low temperature for a long time, the second thermochromic layer 135, which is colored at a high temperature, does not develop color, but due to a long operation time, the first thermochromic layer far from the thermal head may be formed. Heat transfer to 131) is sufficient to allow for color development.

Furthermore, the photosensitive layer 133 may be interposed between the first photosensitive layer 131 and the second photosensitive layer 135. Thus, when the heat head is operated for a short time, heat transfer between the first thermochromic layer 131 and the second thermochromic layer 135 is suppressed to prevent unwanted color development of the first thermochromic layer 131. Can be.

The thermochromic layer may include a coloring material that is directly or indirectly colored by heat from the heat head. The material which is directly colored by the heat may be a coloring material in which the structure of the material itself changes at a specific temperature, a coloring material in which the crystallinity is changed, or a coloring material in which the living group is released. In addition, the material indirectly developed by the heat may be a mixture of a developer and a color precusor, or a mixture of a microcapsule and a color precursor having a developer or a coupler. The developer is activated at a specific temperature to generate an acid and the like, and the color precursor refers to a material that reacts with the generated acid to develop color. In addition, the microcapsule is preferably formed of a material in which the transmittance of the developer, the coupler or the color precursor is changed at a specific temperature. The color precursor may be a leuco dye. Furthermore, the leuco dye may be lactone, fluorane, phenothiazine, triarylpyridine leuco dye. In addition, the developer may be an organic acidic material.

The photosensitive layer may include a coloring material that is directly or indirectly colored by light energy emitted from a light source. The material directly developed by the light energy may be a color developed by changing the structure of the material itself at a specific wavelength, crystallinity, self-coupling, or falling out of the living group. Can be. In addition, the material indirectly developed by the light energy is a mixture of a photo-thermal conversion agent and a thermochromic material, a mixture of a developer and a color precusor, or a developer or a coupler. It may be a mixture of microcapsules and color precursor having. The developer is activated at a specific wavelength to generate an acid and the like, and the color precursor refers to a material that reacts with and develops the generated acid. In addition, the microcapsules are formed of a material whose transmittance of the developer, the coupler or the color precursor is changed at a specific wavelength.

The thermochromic layer and the photochromic layer may further include a resin constituting the layer. The resin can be, for example, polyvinyl chloride, polystyrene, polyester, polyurethane, polycarbonate, polyacrylate or polyvinyl alcohol.

An intermediate layer may be interposed between the coloring layers. As described above, when the coloring layers are stacked in the order of the first thermal coloring layer 131, the photosensitive coloring layer 133, and the second thermal coloring layer 135, the first thermal coloring layer 131. ) And the first intermediate layer 141 may be interposed between the photosensitive layer 133, and the second intermediate layer 143 may be interposed between the photosensitive layer 133 and the second photosensitive layer 135. have. The intermediate layer may prevent the expressed color from spreading after the color is expressed in the color developing layer adjacent thereto. In addition, the intermediate layer also serves to prevent damage to the first layer formed when the adjacent chromophores are coated using similar organic solvents. Furthermore, when the intermediate layer is interposed between the thermochromic layers, unwanted color development can be suppressed by facilitating thermal separation of the thermochromic layers adjacent to the intermediate layer.

An undercoat layer 121 may be interposed between the base material 100 and the color light emitting layer stacked on the lowermost of the color light emitting layers, that is, the first thermal color light emitting layer 131. The undercoat layer 121 may improve the coating property of the substrate 100 and the adhesion between the substrate 100 and the coloring layer when the coloring layer is coated. In addition, the undercoat layer 121 may prevent the expressed color from spreading to the substrate 100 when the color is expressed in the chromophoric layer. The thickness of the undercoat layer 121 may be 0.5 to 4㎛, but is not limited thereto.

The protective layer 150 may be stacked on the color development layer, that is, the second thermal color development layer 135, which is stacked on the top of the color development layers. The protective layer 150 is a layer in direct contact with the heat head and should have heat stability. In addition, the protective layer 150 protects the coloring layer, and also serves to adjust the gloss of the surface of the recording medium. The protective layer 150 may be formed in a single layer or a multilayer structure as necessary. For example, the protective layer 50 may be formed in a single layer structure containing an ultraviolet absorber or the like in order to prevent a change in color due to ultraviolet exposure in the storage process after recording an image on a recording medium. Alternatively, an ultraviolet filter layer may be further stacked on the protective layer, and an adhesive layer may be added between the protective layer and the ultraviolet filter layer when the ultraviolet filter layer is not formed by a coating method but is formed using a laminating method. .

The back coating layer 170 may be laminated on the bottom surface of the substrate 100. The back coating layer 170 is a layer for improving the paper feedability when applied to the anti-curling of the recording medium or the recording device. However, when the substrate 100 is of the same type as the photo paper, it may already be included in the substrate 100.

Forming the lower coating layer 121, the color development layers 131, 133, 135, the intermediate layers 141, 143, the protective layer 150 and the back coating layer 170 is a layer of a recording medium When forming, it can be carried out using a commonly used method. For example, in the group consisting of air knife coating, vari-bar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, slot die coating, gravure coating and comma coating Each layer can be formed by applying and drying using one method selected. Alternatively, a method of applying and drying various layers using die coating or the like may be used. The protective layer 150 and / or the back coating layer 170 may be formed using a lamination method using laminating.

2 is a cross-sectional view showing a multi-color recording medium according to another embodiment of the present invention. In the multi-color recording medium according to the present embodiment, unlike the multi-color recording medium according to the above-described embodiment, the color layer is located on both sides of the substrate.

Referring to FIG. 2, the multicolor recording medium according to the present embodiment includes a substrate 200 having an upper surface and a lower surface. The base material 200 is a transparent material, it is preferable that the film. Such films include polyester-based, polycarbonate-based, cellulose-acetate-based, and polyethylene-based films. The base 200 has a thickness of 15 to 350 μm so as to be easy to handle and to prevent bending when forming a coating layer thereon. However, it is not limited thereto.

At least one layer of the chrominance layer is stacked on the bottom surface of the substrate 200, and the remaining chrominance layer (s) is stacked on the top surface of the substrate 200. One of the color layers 231, 233, and 235 is a photochromic layer, and at least two layers are thermochromic layers. Thereby, the image can be recorded by a relatively simple recording device composed of one thermal head capable of expressing color in the thermochromic layer and one light source capable of expressing color in the photosensitive layer. .

Preferably, the thermochromic layers are formed of a first thermochromic layer and a second thermochromic layer which express colors at different temperatures. In this case, the photochromic layer, the first and the second photochromic layer may exhibit yellow, magenta, and cyan colors, respectively, regardless of their order. The stacking order or stacking position of the photosensitive layer and the first and second photosensitive layers is not particularly limited. However, preferably, the first thermochromic layer 231 and the second thermochromic layer 235 are sequentially stacked on the upper surface of the substrate 200. In this case, the first thermochromic layer 231 may be a layer expressing color at a low temperature, and the second thermochromic layer 235 may be a layer expressing color at a high temperature. Thus, each color may be expressed in the thermochromic layers 231 and 235 by using one heat head. In more detail, when the heat head is operated for a short time at a high temperature, color can be expressed in the second heat-sensitive layer 235 close to the heat head, while the operating time is short, and thus the first heat-colored layer 231 can be transferred to the first heat-colored layer 231. Heat transfer is suppressed. However, when the thermal head is operated at a low temperature for a long time, the second thermochromic layer 235, which is colored at a high temperature, does not develop color, but due to a long operation time, the first thermochromic layer far from the thermal head may be formed. 231) can provide sufficient heat transfer and thereby develop color.

Preferably, the photosensitive layer 233 is stacked on the bottom surface of the substrate 200. Accordingly, when the photosensitive layer 233 is somewhat poor in durability, such as heat resistance, or easily oxidized by a material in the outside air, that is, when the gas resistance (or chemical resistance) is weak, the substrate 200 It can be protected by being located on the lower surface of the

For the description of the thermochromic layer and the material constituting the photochromic layer, reference will be made to the corresponding parts of the above-described embodiment.

An intermediate layer 240 may be interposed between the color layers, that is, between the first thermal color layer 231 and the photosensitive layer 233. The intermediate layer 240 may prevent the expressed color from spreading after the color is expressed in the color developing layer adjacent thereto. In addition, the intermediate layer 240 may serve to prevent damage to the first formed layer when the adjacent color developing layers are coated using similar organic solvents. In addition, the intermediate layer 240 may suppress unwanted color development by facilitating thermal separation of the thermochromic layers 231 and 235 adjacent thereto when the heat head is operated for a short time.

A first undercoating layer 221 may be interposed between the first thermochromic layer 231 and the base material 200, that is, the lowermost of the color layers stacked on the upper surface. In addition, a second undercoat layer 223 may be interposed between the photochromic layer 233 and the substrate 200 that are stacked on the lower surface. The undercoat layers 221 and 223 serve to improve the coating property on the substrate 100 and the adhesion between the substrate 200 and the coloring layer when the coloring layer is coated. In addition, the undercoating layers 221 and 223 may prevent the expressed color from spreading to the substrate 200 when the color is expressed in the coloring layer. The thickness of the undercoat layers 221 and 223 may be 0.5 to 4 μm, but is not limited thereto.

The protective layer 250 may be stacked on the chromophore layer stacked on the top of the chromophore layer stacked on the upper surface, that is, the second thermochromic layer 235. A backside coating layer 270 may be stacked on the bottom of the color developing layer, that is, on the photosensitive layer 233. Detailed description of the protective layer 250 and the back coating layer 270 will be referred to the above-described embodiment.

An opaque reflective layer 260 may be stacked on the light emitting layer on the lower surface, that is, on the photosensitive layer 233. Preferably, the opaque reflective layer 260 and the back coating layer 270 are sequentially stacked on the color developing layer on the lower surface, that is, on the photosensitive layer 233. The opaque reflective layer 260 reflects the light transmitted through the transparent substrate 200 so that the image recorded on the recording medium can only be seen from the upper surface of the substrate. The opaque reflective layer 260 may be made of titanium oxide.

Forming the undercoat layers 121 and 123, the color developing layers 231, 233, and 235, the intermediate layer 240, the protective layer 250, the opaque reflective layer 260, and the back coating layer 270. Reference is made to the above-described embodiment.

3 is a schematic cross-sectional view showing a recording apparatus according to another embodiment of the present invention.

Referring to FIG. 3, one column head 320 and one light source 330 are positioned on the support 300. The thermal head 320 preferably operates in two modes, a mode of operation at high temperatures and a mode of operation at low temperatures. More preferably, the thermal head 320 operates for a short time during the high temperature operation, and operates for a long time during the low temperature operation. In addition, the light source 330 may be a light source that emits a laser beam in an appropriate wavelength range.

The multi-color recording medium 310 according to the embodiment of the present invention is supplied onto the support 300. The multicolor recording medium 310 may be the recording medium described with reference to FIG. 1 or 2. More specifically, the multicolor recording medium 310 includes a substrate, a photosensitive chromophoric layer, and at least two layers of thermochromic layers. Furthermore, the thermochromic layers may be formed of a first thermochromic layer and a second thermochromic layer that express different colors. As shown in the above-described embodiment, the thermochromic layer close to the thermal head 320, that is, the second thermochromic layer (135 in FIG. 1 and 235 in FIG. 2) is thermally colored away from the thermal head 320. It is preferable to include a material that is colored at a higher temperature than the layer, that is, the first thermochromic layer (131 in FIG. 1 and 231 in FIG. 2).

Subsequently, light is irradiated from the light source onto the first area of the recording medium 310 supplied onto the support 300. At this time, the photosensitive layer of the recording medium 310 may be formed by reacting directly or indirectly by the light.

Subsequently, the thermal head 320 is in contact with the first area or the second area of the recording medium 310, and the thermal head 320 operates for a short time at a high temperature. At this time, the coloring material in the second thermochromic layer (135 of FIG. 1, 235 of FIG. 2) reacts with the high temperature heat applied from the thermal head 320, whereby the portion in contact with the thermal head 320 On the other hand, the first thermochromic layer (131 of FIG. 1 and 231 of FIG. 2) does not have sufficient heat transfer from the heat head 320.

Subsequently, the thermal head 320 is in contact with the first area, the second area or the third area of the recording medium 310, and the thermal head 320 is operated at a low temperature for a long time. At this time, the second thermochromic layer (135 of FIG. 1, 235 of FIG. 2) is not supplied with a high temperature heat for color development, so that color development is suppressed, whereas the first thermochromic layer (131, FIG. 1, 231 of FIG. 2 is provided with heat from the heat head 320 for a long time, so that heat is sufficiently transferred, and thus, a portion in contact with the heat head may be colored.

The photochromic layer and the first and second thermochromic layers may be layers capable of expressing yellow, magenta, and cyan colors, respectively, regardless of the order. In this case, the recording medium may be applied to the recording apparatus and the recording method. A full color image can be displayed by this.

As described above, according to the present invention, a relatively simple recording device having one column head and one light source and a recording medium applicable thereto can be obtained.

1 is a cross-sectional view illustrating a multicolor recording medium and a method of manufacturing the same according to an embodiment of the present invention.

2 is a cross-sectional view illustrating a multicolor recording medium and a method of manufacturing the same according to another embodiment of the present invention.

3 is a cross-sectional view illustrating a recording apparatus and a recording method using a multi-color recording medium according to another embodiment of the present invention.

(Explanation of symbols for main parts of drawing)

131, 133, 135, 231, 233, 235: thermal or photosensitive layer

320: heat head 330: light source

Claims (24)

A substrate having an upper surface and a lower surface; One layer of photosensitive layer; And And a thermochromic layer of at least two layers. The method of claim 1, And the at least two layers of thermochromic layers are a first thermochromic layer and a second thermochromic layer which express colors at different temperatures. The method of claim 2, The first thermochromic layer and the second thermochromic layer are sequentially stacked on the upper surface of the substrate, the first thermochromic layer is a layer expressing color at a low temperature, and the second thermochromic layer is colored at a high temperature. Multi-color recording medium, characterized in that the layer to express. The method of claim 1, And the coloring layers are stacked on the upper surface of the substrate. The method of claim 4, wherein And a undercoat layer interposed between the substrate and the substrate. The method of claim 4, wherein And a protective layer stacked on the top layer of the color layers. The method of claim 4, wherein And a backside coating layer laminated on the bottom surface of the substrate. The method of claim 4, wherein The at least two layers of thermochromic layers are a first thermochromic layer and a second thermochromic layer which express colors at different temperatures, The photochromic layer is a multi-color recording medium, characterized in that interposed between the first photochromic layer and the second photochromic layer. The method of claim 8, And a second intermediate layer interposed between the first thermochromic layer and the photosensitive layer, and a second intermediate layer interposed between the photosensitive layer and the second photosensitive layer. The method of claim 1, And at least one of the color developing layers is laminated on the bottom surface of the substrate, and the remaining color layer (s) is stacked on the top surface of the substrate. The method of claim 10, And a second undercoat layer interposed between the chromophore layer laminated on the substrate upper surface and the substrate, and the first undercoat layer interposed between the substrate, and the chromophoric layer laminated on the substrate lower surface and the substrate. Multicolor recording media. The method of claim 10, And a protective layer laminated on the color development layer stacked on the top of the color development layer on the upper surface of the substrate. The method of claim 10, And a backside coating layer laminated on the color development layer on the bottom surface of the substrate. The method of claim 10, And an opaque reflective layer stacked on the chromophoric layer on the lower surface of the substrate. The method of claim 10, And a opaque reflective layer and a back coating layer sequentially stacked on the chromophoric layer on the lower surface of the substrate. The method of claim 10, The photosensitive layer is laminated on the lower surface of the substrate, And the at least two layers of thermochromic layers are stacked on an upper surface of the substrate. The method of claim 16, The thermochromic layers are a first thermochromic layer and a second thermochromic layer which express colors at different temperatures, And the first thermochromic layer and the second thermochromic layer are sequentially stacked on the upper surface of the substrate. The method of claim 17, And a middle layer interposed between the first thermochromic layer and the second thermochromic layer. A light source for irradiating light to the recording medium to express color in the photosensitive layer of the recording medium; And a heat head which transfers heat to the recording medium to express color in the thermochromic layer of the recording medium. The method of claim 19, And the thermal head has a mode of operating at a high temperature and a mode of operating at a low temperature. The method of claim 20, And the thermal head operates for a short time during high temperature operation and for a long time during low temperature operation. A recording medium is provided which has one layer of photosensitive layers and at least two layers of thermochromic layers expressing different colors, By applying heat to the recording medium, the color is expressed in the thermochromic layer, And expressing a color in the photosensitive layer by irradiating light onto the recording medium. The method of claim 22, The thermochromic layers are a first thermochromic layer that develops at low temperature and a second thermochromic layer that develops at high temperature, Expressing color to the thermochromic layer expresses color to the second thermochromic layer by imparting high temperature heat to the recording medium, and imparting color to the first thermochromic layer by imparting low temperature heat to the recording medium. A recording method comprising the expression. The method of claim 23, wherein The first thermochromic layer is farther from the thermal head than the second thermochromic layer, Expressing color to the second thermochromic layer is performed by applying high temperature heat to the recording medium for a short time, and expressing color to the first thermochromic layer is performed by applying low temperature heat to the recording medium for a long time. Recording method characterized in that.