JPH10315513A - Initialization method of color reversible thermosensitive recording medium - Google Patents

Abstract

(57) [Problem] To provide a method of initializing a color reversible thermosensitive recording medium capable of improving printing durability. A reversible thermosensitive recording layer having a reversible thermosensitive recording layer capable of erasing display contents displayed by heating by applying heating or erasing energy to a temperature higher than an erasing temperature. In the method for initializing the recording medium, the coloring type reversible thermosensitive recording medium is heated to a temperature equal to or higher than the erasing temperature or heated by applying energy equal to or more than the erasing energy, and the printing density of the coloring type reversible thermosensitive recording medium is saturated. A heating step of lowering the heating temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for initializing a coloring type reversible thermosensitive recording medium, and more particularly to a method for heating a display content displayed by heating to a temperature higher than an erasing temperature or applying an erasing energy to the content. The present invention relates to a method for initializing a coloring type reversible thermosensitive recording medium having an erasable recording layer.

[0002]

2. Description of the Related Art In various recording media such as an ID card and a prepaid card, a thermosensitive recording is performed for displaying a balance and the like in addition to a magnetic recording, for example. This thermosensitive recording is widely used because it does not require development, has high print density and is inexpensive. As an application of such a thermal recording technique, for example, there is a thermal recording type recording medium. In recent years, there has been a color reversible thermosensitive recording medium provided with a reversible thermosensitive recording layer so that information can be reversibly displayed.

In the above-described color reversible thermosensitive recording medium, a reversible thermosensitive recording layer containing a leuco dye and a color-reducing agent as main components is provided on one surface of a substrate. The color is developed or erased by heating with a thermal head or the like, and desired characters and the like are displayed.

However, since the reversible thermosensitive recording layer for performing such reversible thermosensitive recording is vulnerable to physical stress, it is necessary to protect the surface thereof.

Therefore, in order to protect the surface of the reversible thermosensitive recording layer and to provide heat resistance and smoothness, a protective layer is usually provided on the surface of the reversible thermosensitive recording layer. By providing such a protective layer, display by heat (hereinafter, also simply referred to as printing) and durability when repeating erasure (repetition durability) are improved.

On the other hand, as a printing method on a color-forming reversible thermosensitive recording medium, so-called saturated printing is performed in order to obtain a stable printing density.

The term "saturated printing" means that printing is performed by applying a printing energy exceeding a printing energy at which a printing density on a coloring type reversible thermosensitive recording medium is saturated to a thermal head. This is a commonly used printing method because it is possible to suppress poor coloring due to deviation of printing conditions such as an increase in the distance between the card and the thermal head due to adhesion or the like.

[0008]

However, the durability of the surface of the color reversible thermosensitive recording medium against physical stress is improved by providing the above-mentioned protective layer on the color reversible thermosensitive recording medium. However, internal durability cannot be improved.

Therefore, since the internal durability of the color reversible thermosensitive recording medium cannot be improved, the composition of the reversible thermosensitive recording layer can be increased by heating and pressurizing when printing and erasing by heat. Ingredients migrate, and a non-uniform distribution of the composition components occurs in the reversible thermosensitive recording layer.As a result, after repeated printing and erasing, the print density may decrease and the erase density may increase. It has been difficult to prevent this decrease in print density and increase in erase density in a color-forming reversible thermosensitive recording medium.

As described above, in the color-forming reversible thermosensitive recording medium, the printing energy must be low in order to suppress the deterioration of the coating film such as the reversible thermosensitive recording layer and the protective layer when printing and erasing are repeated. Although preferable, in the conventional color-forming reversible thermosensitive recording medium, when saturated printing is performed to obtain a stable printing density, it is difficult to suppress the printing energy to be low, and therefore, it is possible to suppress the deterioration of the coating film. However, there is a problem that it is impossible to prevent a decrease in print density and an increase in erase density.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a method for initializing a color reversible thermosensitive recording medium capable of improving the durability of the repeated printing and erasing.

[0012]

According to the first aspect of the present invention,
It contains a leuco dye and a color-developing agent as main components, and can at least erase the display contents displayed by being colored by heating, by applying heat or erasing energy above the erasing temperature and heating. After the production of a coloring type reversible thermosensitive recording medium having a reversible thermosensitive recording layer,
In an initialization method performed prior to the first recording, the coloring-type reversible thermosensitive recording medium is heated to a temperature equal to or higher than the erasing temperature or by applying energy equal to or more than the erasing energy to heat the recording medium. The method is characterized by having a heating step of reducing printing energy at which the printing density of the thermal recording medium is saturated.

Therefore, according to the present invention, by heating the coloring type reversible thermosensitive recording medium in advance to a temperature higher than the erasing temperature or applying an energy higher than the erasing energy to heat the printing medium, the printing density is saturated. Energy,
The stress applied to the coloring type reversible thermosensitive recording medium when performing saturated printing on the coloring type reversible thermosensitive recording medium can be reduced as compared with the coloring type reversible thermosensitive recording medium when such heating is not performed. Therefore, the durability of the color reversible thermosensitive recording medium for repeated printing and erasing can be significantly improved.

According to a second aspect of the present invention, in the first aspect, the heating step is a step of heating with a hot plate, an erasing bar, an infrared oven, or a hot air oven.

Therefore, according to the present invention, the effect of the invention described in claim 1 is obtained, and the heating step is a heating step using a hot plate, an erasing bar, an infrared oven, or a hot air oven. Since the reversible thermosensitive recording layer is not unnecessarily colored in the forming step, there is no need for a step of erasing unnecessary coloring, and the reversible thermosensitive recording medium can be used as it is.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for initializing a coloring type reversible thermosensitive recording medium according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment of a coloring type reversible thermosensitive recording medium to which the method for initializing a coloring type reversible thermosensitive recording medium according to the present invention is applied. This color-forming reversible thermosensitive recording medium has a structure in which a reversible thermosensitive recording layer 14 and a protective layer 18 are sequentially laminated on a substrate 12 as shown in FIG.

The substrate 12 is made of, for example, polyethylene terephthalate (PET), polyacetate, polystyrene (P
S), an epoxy resin, a synthetic resin sheet such as polyvinyl chloride (PVC) and polycarbonate (PC) or a synthetic paper can be used. The thickness of the substrate 12 is usually 1
It is about 00 to 300 μm.

The reversible thermosensitive recording layer 14 is composed of, for example, a leuco dye, a developer and a binder, and a binder resin.
This layer is a layer that repeats color development / decoloration reversibly by heat. Leuco dyes are generally referred to as colorless or pale color electron-donating dye precursors. Further, the color-reducing agent is called an electron-accepting compound, which causes a reversible color change in the dye precursor due to a difference in cooling rate after heating, and is an aliphatic hydrocarbon group having 6 or more carbon atoms. At least one
A phenolic compound or a phthalic acid compound having one or an amphoteric compound having a phenolic hydroxyl group and an amino group is used.

Next, the color-reducing agent according to the present invention comprises N-
(P-hydroxyphenyl) -N'-n-octadecylthiourea, N- (p-hydroxyphenyl) -N'-n
-Octadecyl urea, N- (p-hydroxyphenyl)
-N'-n-octadecylthioamide, 4'-octadecaneanilide, 2-octadecylterephthalic acid, N-octadecyl (p-hydroxyphenyl) amide, N-
(P-hydroxybenzoyl) -N-octadecanoylamine, N- [3- (p-hydroxyphenyl) propiono] -N'-octadecanohydretide, N-[(p-
[Hydroxyphenyl) methyl] -n-octadecylamide, N-[(p-hydroxyphenyl) methyl] -n-
Octadecyl urea, N-[(p-hydroxyphenyl)
Methyl] -N'-n-octadecyl oxamide and the like.

The leuco dyes include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluoran, and 2- (2-chlorophenylamine)- Diethylaminofluoran, 2- (2-
Fluorophenylamino) -6-diethylaminofluoran, 2- (2-fluorophenylamino) -6-di-
n-butylaminofluoran, 3-diethylamino-7
-Cyclohexylaminofluoran, 3-diethylamino-5-methyl-7-t-butylfluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7-p-butylanilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) -fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-pyrrolidino-7-cyclohexylaminofluoran, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluoran, 3-N-ethyl Pentylamino-6-methyl-7-anilinofluoran and the like can be mentioned.

The leuco dyes may be used alone or as a mixture of two or more.

Examples of the binder resin include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / Water-soluble polymers such as acrylate / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacryl Latexes such as acid esters, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer and the like can be mentioned. The binder resins may be used alone or in combination of two or more.

In the coloring type reversible thermosensitive recording medium, coloring can be achieved by performing rapid cooling following heating.
It is sufficient that the cooling rate after heating is low in order to erase the color. For example, when heating with a suitable heat source (thermal head, laser beam, hot roll, hot stamp, high frequency heating, radiant heat from infrared oven, hot air oven, etc.) for a relatively long time,
Since not only the recording layer but also the support and the like are heated, the cooling rate is low and the phase is in a phase separated state (decolored state). On the other hand, after being heated by an appropriate method, the color can be developed by rapidly cooling by pressing a low-temperature metal block or the like. In addition, when heating is performed for a very short time using a thermal head, laser light, or the like, cooling (solidification) starts immediately after the completion of heating, so that a colored state can be developed. Therefore, even if the same heating temperature and / or the same heat source is used, the color development state and the decoloration state can be arbitrarily developed by controlling the cooling rate.

Here, the reversible thermosensitive recording layer 14 is 3 to 10
It is formed to a thickness of μm.

The protective layer 18 can be made of an ultraviolet-curable resin, and may contain a porous filler such as silica or diatomaceous earth powder.

Next, a method of initializing the color-forming reversible thermosensitive recording medium according to the present invention will be described. In the present invention, the coloring type reversible thermosensitive recording medium is heated in advance at an erasing temperature or higher to be described later or by applying energy equal to or more than erasing energy. This is because when the color-forming reversible thermosensitive recording medium is manufactured, the structure in which the leuco dye and the color-reducing agent are dispersed in the reversible thermosensitive recording layer 14 in a fine particle state is changed by heating the leuco dye and the color-reducing agent. By making the structure in a state of being mixed in a molecular state, it is possible to reduce the minimum required printing energy for saturating the printing density, that is, the minimum saturated printing energy. The step of heating the color reversible thermosensitive recording medium to a temperature equal to or higher than the erasing temperature or applying energy equal to or higher than the erasing energy in advance is referred to as an initialization step. This initialization step may be performed once prior to the first recording after the production of the color reversible thermosensitive recording medium, and can be performed irrespective of the elapsed time after the production. Further, when performing the initialization step, the coloring type reversible thermosensitive recording medium may be in any form such as a form punched into a card, a sheet before punching into a card, a form wound on a roll, and the like. In the present invention, the coloring type reversible thermosensitive recording medium includes any of these forms.

By this initialization step, the printing energy at the time of performing saturated printing can be reduced, so that the damage of the coating film can be reduced and the durability of repeated printing and erasing can be improved.

Further, the heating in the initialization step may be performed by using a hot plate,
The heating is preferably performed using an erasing bar, an infrared oven, or a hot air oven. This means that the reversible thermosensitive recording layer is not unnecessarily colored by the initialization step, and the color developing type reversible thermosensitive recording medium can be used as it is.

However, the coloring type reversible thermosensitive recording medium to which the method for initializing a coloring type reversible thermosensitive recording medium according to the present invention is applied is limited to the coloring type reversible thermosensitive recording medium having a structure as shown in FIG. However, various extensions are possible without departing from the spirit of the present invention. For example,
In addition to the layers shown in FIG. 1, a magnetic recording layer, an intermediate layer, and the like may be provided.

[0031]

Next, the composition of the color-forming reversible thermosensitive recording medium when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is applied to specific examples, and the change in the characteristics thereof will be described. This will be described with reference to the drawings.

The structure of the color-forming reversible thermosensitive recording medium used in the following examples is the same as the structure of the color-forming reversible thermosensitive recording medium shown in FIG. The composition shown below is used for each layer.

First, as the base material 12, white polyethylene terephthalate (PET) having a thickness of 188 μm is used.
A reversible thermosensitive recording layer 14 is provided on the substrate 12, and a protective layer 18 made of a UV-curable paint is formed thereon.

The reversible thermosensitive recording layer 14 has the following composition. 1 part by weight of leuco dye (3-diethylamino-6-methyl-7-anilinofluoran, trade name ODB manufactured by Yamamoto Kasei Co., Ltd.) 3 parts by weight of color reducing agent (N- (4-hydroxyphenyl) -N′-) n-octadecyl urea, JP-A-6-210954) Thermoplastic resin 3 parts by weight (acrylic resin, manufactured by Mitsubishi Rayon Co., Ltd., product name: Dianal BR-80) UV-curable resin 1 part by weight (BASF Co., Ltd. product) LAROMER LR8864) 0.05 parts by weight of photopolymerization initiator (trade name: Darocur 1173 manufactured by Ciba Geigy) 50 parts by weight of solvent (MEK: toluene = 1: 1)

The material mixed with the above composition was dispersed by a paint shaker for 1 hour to obtain a coating, applied with a wire bar, dried (80 ° C., 5 minutes), and cured by irradiating ultraviolet rays ( A reversible thermosensitive recording layer 14 having a thickness of 160 W / cm, 30 m / min, 1 pass) and a dry film thickness of 6 μm was formed.

The protective layer 18 has the following composition. UV curable paint 100 parts by weight (Dai Nippon Ink & Chemicals, Inc. product name Unidick 17-806, solid content 80%) Porous filler 5 parts by weight (Silica, Fuji Silysia Chemical Ltd. product name Sylysia 436) 150 parts by weight of solvent (MEK: toluene = 1: 1)

The material mixed with the above composition was dispersed in a paint shaker for 10 minutes to obtain a coating, applied with a wire bar, dried (80 ° C., 1 minute), and cured by irradiating ultraviolet rays ( 160 W / cm, 30 m / min, 1 pass), and the protective layer 18 was formed to a dry film thickness of 2 μm.

Next, the change in the characteristics of the color-forming reversible thermosensitive recording medium when the method for initializing the color-forming reversible thermosensitive recording medium according to the present invention is applied to the above embodiment will be described with reference to the drawings. .

First, FIG. 2 shows the static erasing characteristics when the coloring type reversible thermosensitive recording medium formed by the above composition is heated by a hot plate. 2, the horizontal axis indicates the hot plate temperature (° C.), and the vertical axis indicates the optical reflection density (OD).
Graph 1 is a graph showing the optical reflection density when printing was performed using a thermal head having a dot density of 8 dots / mm at a printing energy of 0.50 mJ / dot, and then the printing was erased with a hot plate.

Here, the heating by the hot plate is performed by pressing 1 kg /
The heating was performed under the conditions of cm ² and a pressing time of 3 seconds.

As shown in FIG. 2, in the case of erasure by the hot plate after printing by the thermal head shown in graph 1, the optical reflection density sharply decreases when the temperature of the hot plate exceeds 70 ° C. , About 105 ° C. (temperature T1), the print is completely erased. This temperature T1 is the erasing temperature. In the above-described initialization method for the color-forming reversible thermosensitive recording medium, the temperature at which the color-forming reversible thermosensitive recording medium is heated is preferably at least this temperature (T1). However, after the temperature exceeded about 140 ° C. (temperature T2), the concentration slightly increased. This indicates a color change of the coloring type reversible thermosensitive recording medium due to decomposition of a dye or the like rather than printing. Therefore, the upper limit of the heating temperature of the coloring type reversible thermosensitive recording medium is preferably about the decomposition temperature indicated by the temperature T2 in order to prevent discoloration of the coloring type reversible thermosensitive recording medium.

In this embodiment, the minimum temperature T1 for heating the color-forming reversible thermosensitive recording medium and the decomposition temperature T2, which is the upper limit of the heating temperature of the color-forming reversible thermosensitive recording medium, are defined as follows. About 105 ° C and about 140 respectively
However, the present invention does not limit the temperatures T1 and T2 to such temperatures, and if the structure of the color-forming reversible thermosensitive recording medium changes, these temperatures also change accordingly.

Next, FIG. 3 shows the behavior of a thermal printer when the method for initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied to a color-forming reversible thermosensitive recording medium and when it is not applied. 3 is a graph showing a difference between a target printing and an erasing characteristic. In this figure, the horizontal axis represents the printing energy (m
J / dot), and the vertical axis indicates the optical reflection density (OD). However, in the present embodiment, the heating temperature at the time of performing the initialization in the initialization method of the coloring type reversible thermosensitive recording medium according to the present invention was set to the above-mentioned temperature T1 (105 ° C.), and the heating was performed using a hot plate.

In FIG. 3, a graph 2 is a graph showing the printing characteristics of the color-forming reversible thermosensitive recording medium when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is not applied. Graph 3 is a graph showing the erasing characteristics of the color reversible thermosensitive recording medium when the method of initializing the color reversible thermosensitive recording medium according to the present invention is not applied, and Graph 4 is related to the present invention. FIG. 5 is a graph showing the printing characteristics of the color-forming reversible thermosensitive recording medium when the method of initializing the color-forming reversible thermosensitive recording medium is applied, and graph 5 shows the initialization of the color-forming reversible thermosensitive recording medium according to the present invention. 6 is a graph showing the erasing characteristics of a coloring type reversible thermosensitive recording medium when the method is applied.

In FIG. 3, the energy E3 indicates the erasing energy used when erasing a print.
0.26 (mJ / dot). Energy E
Reference numeral 4 denotes a minimum saturation printing energy of the color-forming reversible thermosensitive recording medium when the method for initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied, and 0.44 (mJ / dot).
It has become. Energy E5 represents the lowest saturation printing energy of the color-forming reversible thermosensitive recording medium when the initialization method of the color-forming reversible thermosensitive recording medium according to the present invention is not applied, and is 0.50 (mJ / dot). Has become.

Therefore, the minimum saturation printing energy E5 of the color-forming reversible thermosensitive recording medium when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is not applied, and the color-forming reversible thermosensitive recording medium according to the present invention. The difference from the lowest saturation printing energy E4 of the coloring type reversible thermosensitive recording medium when the initialization method of the thermal recording medium is applied, E5-E4 is 0.06 (mJ /
dot), and it can be seen that when the method for initializing the color-forming reversible thermosensitive recording medium according to the present invention is applied, the minimum saturation printing energy is reduced by this energy difference.

Next, FIG. 4 shows the repetition durability of printing and erasing when the method of initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied to a color-forming reversible thermosensitive recording medium and when it is not applied. 3 shows a graph showing the difference between the two. In this figure, the abscissa indicates the number of recycles (times) of printing and erasing, and the ordinate indicates the optical reflection density (OD).

In FIG. 4, a graph 6 is a graph showing a change in print density when the method for initializing a color reversible thermosensitive recording medium according to the present invention is applied, and a graph 7 is shown.
Is a graph showing a change in print density when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is not applied, and Graph 8 is a graph showing the change in the color-forming reversible thermosensitive recording medium according to the present invention. FIG. 9 is a graph showing a change in print density when the initialization method is not applied, and a graph 9 shows a change in print density when the initialization method for the color-forming reversible thermosensitive recording medium according to the present invention is applied. It is a graph.

Here, when the initialization shown in the graph 6 is performed, the saturation printing energy is 0.44 m.
Printing was performed with J / dot and the initialization shown in Graph 7 was not performed, and the saturated printing energy was set at 0.50 mJ / dot.

When the initialization shown in the graphs 8 and 9 is not performed and when the initialization is performed, the erasing energy is 0.26 mJ / d.
performed as ot.

As shown in FIG. 4, the print density (Graph 7) and the erase density (Graph 8) when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is not applied are as follows. Each time the number of recycles increases, the number decreases and increases, and especially when the number of recycles exceeds 150, the number sharply decreases and increases. This indicates that the reversible thermosensitive recording layer 14 is deteriorated because the saturated printing is performed with a high saturated printing energy (0.50 mJ / dot).

On the other hand, the printing density (Graph 6) and the erasing density (Graph 9) when the method of initializing the color-forming reversible thermosensitive recording medium according to the present invention is applied, The print density and the erase density hardly change. This indicates that the reversible thermosensitive recording layer 14 did not deteriorate because the saturated printing was performed with a low saturated printing energy (0.44 mJ / dot).

Therefore, as shown in this example, when the method for initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied, the method for initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied. The minimum saturation printing energy can be reduced as compared with the case where no is applied (FIG. 3),
The durability of the color reversible thermosensitive recording medium after repeated printing and erasing is improved, and after performing printing and erasing many times,
A decrease in print density and an increase in erase density can be suppressed (FIG. 4). When initialization is performed by a thermal head instead of a hot plate, the coloring type reversible thermosensitive recording medium may be heated by applying energy equal to or higher than the above-described erasing energy E3 to the recording medium. When the reversible thermosensitive recording layer develops color, erasing may be performed by applying erasing energy E3.

[0054]

As is apparent from the above description, according to the present invention, the coloring type reversible thermosensitive recording medium is heated in advance to a temperature higher than the erasing temperature or by applying energy higher than the erasing energy. Since the temperature at which the print density of the coloring type reversible thermosensitive recording medium is saturated is lowered, the saturation printing temperature (saturation printing energy) at the time of performing saturated printing can be suppressed to be low. Provided is a method for initializing a color reversible thermosensitive recording medium capable of preventing a decrease in print density and an increase in erase density after performing printing and erasing many times because the durability of the medium is improved. can do.

Further, since the heating step is performed by a hot plate, an erasing bar, an infrared oven or a hot air oven, a method for initializing a color-reversible thermosensitive recording medium capable of suppressing unnecessary color development is provided. can do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a coloring type reversible thermosensitive recording medium to which a method for initializing a coloring type reversible thermosensitive recording medium according to the present invention is applied.

FIG. 2 is a graph showing static erasure characteristics of the color-forming reversible thermosensitive recording medium shown in FIG.

FIG. 3 shows a case where a method of initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied and a case where it is not applied.
4 is a graph showing dynamic printing and erasing characteristics.

FIG. 4 shows a case where a method of initializing a color-forming reversible thermosensitive recording medium according to the present invention is applied, and a case where the method is not applied.
9 is a graph showing a density change after repeatedly performing printing and erasing.

[Explanation of symbols]

 12 base material 14 reversible thermosensitive recording layer 18 protective layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Morinaka 4- 14-12 Koishikawa Bunkyo-ku, Tokyo Kyodo Printing Co., Ltd.

Claims (2)

[Claims] 1. A display containing a leuco dye and a color-reducing agent as main components, and at least erasing display contents displayed by heating to develop a color or applying an erasing energy above an erasing temperature. A reversible thermosensitive recording layer having a reversible thermosensitive recording layer capable of performing, after the production of a coloring reversible thermosensitive recording medium, an initialization method performed prior to the first recording; A coloring or reversible heat-sensitive recording medium, wherein a heating step of reducing the printing energy at which the printing density of the coloring-type reversible thermosensitive recording medium saturates is performed by heating at a temperature equal to or higher than the heating or erasing energy or more. Initializing method for thermosensitive recording medium. 2. The method according to claim 1, wherein the heating step is a step of heating with a hot plate, an erasing bar, an infrared oven, or a hot air oven.