JPH11170710A - Reversible thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent printing characteristics from being deteriorated after carrying and use for a long period of time by a method wherein a solid organic acid being solid at a coloring temperature in recording on a reversible thermal recording layer is contained in a protective layer of a reversible thermal recording medium. SOLUTION: A reflection layer 2 consisting of a metal deposit layer, a reversible thermal recording layer 3 and a protective layer 4 are successively laminated on a surface of a sheetlike substrate consisting of a suitable material such as polyethylene terephthalate. The protective layer 4 is made to contain a solid organic acid being solid at a coloring temperature in recording on the reversible thermal recording layer 3, and formed of an abrasion resistant and heat resistant material being thermoplastic resin of cellulose series resin, urethane series resin, polyester series resin, etc. Thereby, even after coming in contact with ammonia brought about from sweat or the like in carrying and use, an initial texture density and a coloring density can be maintained, coloring performance is also not deteriorated, and practicability of the reversible thermal recording medium can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible writing method in which desired characters, numbers, symbols, patterns, etc. (hereinafter referred to as "characters, etc.") can be reversibly written by changing the transparency by changing the temperature. For thermosensitive recording media, especially mobile phones,
The present invention relates to a reversible thermosensitive recording medium improved so that printing characteristics do not deteriorate during use.

[0002]

2. Description of the Related Art In a reversible thermosensitive recording medium, a reversible thermosensitive recording layer formed by using a reversible thermosensitive recording material changes from a transparent state according to the temperature when heat is applied from the outside. Change its light transmittance in the range up to the cloudy state,
Since it has the property of maintaining that state after cooling, characters and the like can be written in a rewritable manner. Usually, characters and the like that are made cloudy are written on a transparent background. Such a reversible thermosensitive recording material is disclosed, for example, in JP-A-63-39.
378, JP-A-63-130380, JP-A-2-1
No. 363 is known.

[0003] These known reversible thermosensitive recording paints are basically composed of three components: (1) a resin base material, (2) an organic low-molecular substance, and (3) an organic solvent. Generally, a vinyl chloride-vinyl acetate copolymer is used as the resin base material. As organic low-molecular substances, fatty acids having about 16 to 24 carbon atoms, such as stearic acid or behenic acid, are often used. The organic solvent is capable of dissolving the resin base material and the organic low molecular weight substance, and is generally a tetrahydrofuran (T
HF) is used.

A protective layer is provided for protecting the surface of the reversible thermosensitive recording layer. This protective layer, cellulose resin, urethane-based resin, polyester-based resin, vinyl-based resin, epoxy-based resin, paint composed of a material with good wear resistance and heat resistance such as acrylic resin, or these resins, A phthalic acid ester, a fatty acid ester, a phosphoric acid ester, etc. as a plasticizer, or a low molecular polyethylene, oleyl amide, stearyl amide, silicone or the like added for imparting lubricity is applied to a desired thickness, and this is applied. It is formed by drying.

[0005] A protective layer is also known which uses an ultraviolet-curable resin coating material and is cured by irradiating ultraviolet rays after application (see, for example, JP-A-5-92658). Further, Japanese Patent Application Laid-Open No. 5-8543 proposes adding a hydrotalcite compound to a protective layer made of an ultraviolet-curable resin for the purpose of preventing adhesion of scum to a thermal head.

Depending on the type of solvent contained in the UV-curable resin coating for forming the protective layer, the solvent may penetrate the reversible thermosensitive recording layer and adversely affect its performance. An intermediate layer may be provided between the recording layer and the thermosensitive recording layer.

[0007]

However, the conventional reversible thermosensitive recording medium as described above has predetermined printing characteristics at the beginning, but the printing characteristics gradually decrease during carrying and use. There is a significant defect in that little or no printing can be made within a relatively short period of time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive recording medium improved so that the printing characteristics are not deteriorated even after being used for a long time.

[0009]

Means for Solving the Problems The present inventor has proposed a portable telephone,
As a result of examining the deterioration of printing characteristics during use,
The present inventors have found that the cause is mainly due to ammonia contained in sweat and the like transferred to the recording surface of the reversible thermosensitive recording medium due to contact with the skin, and have completed the present invention.

That is, the present invention comprises a reversible thermosensitive recording layer which reversibly repeats a transparent state and a cloudy state by heating, and a protective layer for protecting the reversible thermosensitive recording layer, wherein the protective layer comprises: The reversible thermosensitive recording layer contains a solid organic acid which is a solid at a color development temperature during recording.

The present invention further provides a reversible thermosensitive recording layer which reversibly alternates between a transparent state and a cloudy state by heating, a protective layer for protecting the reversible thermosensitive recording layer, the reversible thermosensitive recording layer and the protective layer. And an intermediate layer provided between the protective layer and the intermediate layer.
The reversible thermosensitive recording layer contains a solid organic acid which is a solid at a color development temperature during recording.

The intermediate layer is provided with an intermediate layer between the protective layer and the reversible thermosensitive recording layer in order to protect the reversible thermosensitive recording layer from a solvent or the like contained in a paint for forming the protective layer. .

In the reversible thermosensitive recording medium thus configured, even if sweat or the like adheres to the surface of the reversible thermosensitive recording medium due to contact with a finger, the ammonia contained in the reversible thermosensitive recording medium is removed by the protective layer and / or Since it is converted to an ammonium salt by the reaction with the solid organic acid contained in the intermediate layer, it effectively prevents ammonia from penetrating into the protective layer or the reversible thermosensitive recording layer provided below the intermediate layer. As a result, the printing characteristics are not degraded during carrying and use.

When an intermediate layer is provided, it is not necessary to consider the influence of the solvent on the reversible thermosensitive recording layer.
The degree of freedom in selecting a paint for forming the protective layer is increased.

[0015]

FIG. 1 shows a reversible thermosensitive recording medium according to a first embodiment of the present invention. This reversible thermosensitive recording medium is basically composed of a sheet-like base material 1 made of a suitable material such as polyethylene terephthalate, a reflective layer 2 made of a metal deposition layer, a reversible thermosensitive recording layer 3 and a protective layer. 4 are sequentially laminated. For printing of characters and the like, a thermal head is brought into contact with the surface of the protective layer 4 and heat is partially applied in a pattern corresponding to the characters and the like to be printed, so that the reversible thermosensitive recording layer 3 has a color development temperature of, for example, 12 ° C.
This is done by heating to 0 ° C. With this heating,
The reversible thermosensitive recording layer 2 becomes cloudy, and a desired display appears due to the contrast between the reversible thermosensitive recording layer 2 and the unheated transparent portion.
Also, when erasing once printed characters, etc.,
By heating to an erasing temperature slightly lower than the printing temperature, the cloudy portion is made transparent again.

Further, in the reversible thermosensitive recording medium according to the second embodiment of the present invention shown in FIG.
An intermediate layer 5 is provided between the protective layer 4 and the protective layer 4.

In the present invention, the protective layer 4 and the intermediate layer 5
Either one or both contains a solid organic acid that is solid at the color development temperature during recording on the reversible thermosensitive recording layer 3.

As the substrate 1, a transparent synthetic resin sheet such as an epoxy resin, polyvinyl chloride, and polycarbonate can be used in addition to a polyethylene terephthalate resin sheet.

As the reflection layer 2, a metal such as aluminum, silver, chromium, nickel and gold is vacuum-deposited.
A metal thin film formed using a film formation technique such as ion plating and sputtering can be used.

The reversible thermosensitive recording layer 3 provided on the reflective layer 2 is coated with a resin base material and a coating material in which an organic low-molecular substance is dissolved in an organic solvent, and is applied and dried by an appropriate application means such as a wire bar. Then, for example, it is provided with a thickness of about 5 μm.

As the resin base material, a material having good transparency, excellent mechanical strength, and good film forming property is preferable. Specific examples thereof include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. , Polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, polyester resin, polyamide resin, acrylic resin, silicone resin,
UV-curable resins in which acrylic acid or methacrylic acid are ester-bonded to a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, and the like. Of these, particularly preferred are vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, polyester resin, vinyl chloride-vinyl acetate- An ultraviolet-curable resin in which acrylic acid or methacrylic acid is ester-bonded to a vinyl alcohol copolymer corresponds to this.

As the organic low molecular weight substances, alkanols,
Alkanediol, halogenalkanol or halogenalkanediol, alkylamine, alkane, alkene, alkyne, halogenalkane, halogenalkene, halogenalkyne, cycloalkane, cycloalkene, cycloalkyne, saturated or unsaturated mono- or dicarboxylic acid or ester thereof, Amides or ammonium salts, saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts, acrylic carboxylic acids or their esters, amides or ammonium salts, halogen acrylic carboxylic acids or their esters, amides or ammonium Salts, thioalcohols, thiocarboxylic acids or their esters, amides or ammonium salts, thioalcohol carboxylic esters, etc. In, and the number of carbon atoms from 10 to 40,
The molecular weight is 100 to 700. Particularly preferred are higher fatty acids such as lauric acid, palmitic acid, stearic acid, arachiic acid, and behenic acid having a melting point in the range of 50 to 150 ° C., or esters, amides, or ammonium salts thereof.

The mixing ratio between the resin and the organic low-molecular substance is as follows:
5 parts by weight of organic low molecular weight substance to 100 parts by weight of resin
Those in the range of 200 parts are preferred, and 10 parts to 100 parts.
The part is more preferable.

The reversible thermosensitive recording layer 3 has a glass transition point (Tg) lower than that of the resin base material, preferably a low glass transition point having a glass transition point of 50 ° C. or less, in order to extend the range of transparency. A resin (hereinafter, referred to as “low Tg resin”) can be contained as needed. As such a resin, it is preferable to use an acrylic resin, a polyester resin, or a polyamide resin.

The protective layer 4 protects the surface of the card, and is made of, for example, a thermoplastic resin such as a cellulose resin, a urethane resin, a polyester resin, a vinyl resin, an epoxy resin, and an acrylic resin. It is formed of a material having good wear resistance and heat resistance, such as a thermosetting resin or an ultraviolet-curing resin. These resins include:
Phthalate esters, fatty acid esters, phosphate esters, and the like can be added as plasticizers, and low molecular polyethylene, oleyl amide, stearyl amide, silicone, and the like can be added as those that impart lubricity. The thickness of this protective layer 13 is, for example, 10 μm
Hereinafter, it is preferably about 1 to 5 μm.

The intermediate layer 5, like the resin base material used for the reversible thermosensitive recording layer 3, preferably has good transparency, excellent mechanical strength and good film-forming properties. Specific examples thereof include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. , Polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, polyester resin,
Polyamide resin, acrylic resin, silicone resin, and the like are included. Of these, particularly preferred are vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-
Maleic acid copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, and polyester resins are applicable. The thickness of the intermediate layer 5 is, for example, 10 μm or less, preferably about 1 to 5 μm.

In the present invention, in the reversible thermosensitive recording medium according to the first embodiment shown in FIG. 1, the protective layer 4 contains a solid organic acid.

In the reversible thermosensitive recording medium according to the second embodiment shown in FIG. 2, the intermediate layer 5 contains a solid organic acid. In this case, the protective layer 4 may or may not contain a solid organic acid.

That is, in the reversible thermosensitive recording medium of the present invention, the protective layer 4 and / or the intermediate layer 5 contain a solid organic acid.

In the reversible thermosensitive recording medium of the present invention, if sweat or the like adheres to the surface of the protective layer 4 while being carried or used,
The ammonia 5 contained therein gradually penetrates into the protective layer 4, and this ammonia reacts with the solid organic acid contained in the protective layer 4 and / or the intermediate layer 5 to generally form Is captured as an ammonium salt and does not reach the reversible thermosensitive recording layer 3 thereunder. When the solid organic acid is not contained in the protective layer 4 but is contained only in the intermediate layer 5, ammonia is contained in the protective layer 4.
Is trapped in the intermediate layer 5 similarly.

Therefore, the reversible thermosensitive recording layer 3 does not deteriorate due to contact with ammonia, and the initial printing characteristics can be maintained for a long period of time. This effect is maintained until all the solid organic acids contained in the protective layer 4 and / or the intermediate layer 5 react with ammonia to form ammonium salts.

The solid organic acid used in the present invention is:
It is necessary that the color of the reversible thermosensitive recording layer 3 be solid. When a solid organic acid that melts at this temperature is used, the liquefied organic acid may float on the surface of the protective layer 4 during printing, and the organic acid contained in the intermediate layer may have a low melting point. During film formation, the film may float on the surface of the intermediate layer, and the adhesion to the protective layer may be reduced.

Solid organic acids suitable for the purpose of the present invention include higher fatty acids, dibasic acids, phenols, and derivatives thereof having a melting point higher than the coloring temperature of the reversible thermosensitive recording layer.

The higher fatty acid and its derivative have an alkyl group having 6 or more carbon atoms, and the methylene group at any position thereof is an amide group, a urea group, a thioamide group, an oxalic acid diamide group, a diacylamine, a diacylhydrazine, or the like. And the like.

Specific examples of the dibasic acid include dodecane diacid (melting point 128 ° C.), 1,14-tetradecamethylene dicarboxylic acid (melting point 125 ° C.), 1,16-hexadecamethylene dicarboxylic acid (melting point 125 ° C.) 1,18-octadecamethylenedicarboxylic acid (melting point 125 ° C.), 1,20
-Eicosamethylene dicarboxylic acid (melting point 126 ° C) and the like.

Examples of preferred phenols include:
2,2-bis (4′-hydroxydiphenyl) propane (melting point 156 ° C.), bis (4′-hydroxyphenyl)
Sulfone and the like.

The formation of such a protective layer containing a solid organic acid can be carried out by the usual thermoplastic resin for forming a protective layer,
A thermosetting resin, or a UV curable resin, a solid organic acid is blended in a desired ratio, and coating such as gravure coating, knife edge coating, die coating, or offset printing, printing such as screen printing, etc. Can be done in a way. Among these, an ultraviolet curable resin is preferred because the resulting coating film has excellent hardness and is easy to form.

When an ultraviolet-curable resin is used, for example, an acrylic, epoxy, or polyester-based ultraviolet-curable resin is dissolved in an appropriate solvent, and a solid organic acid is added thereto. After coating on a desired thickness and drying, it is cured by ultraviolet irradiation.

The amount of the solid organic acid added to the protective layer and / or the intermediate layer is not particularly limited. However, when the organic acid is added to the protective layer, it does not impair its strength and has a sufficient ammonia absorbing effect. In order to obtain, resin: solid organic acid =
A range of 1: 0.05 to 1: 0.5 (weight ratio of solid content) is appropriate. If there is too much solid organic acid, the film strength will decrease,
In addition, when an ultraviolet curable resin is used, there is a case where the curing by irradiation with ultraviolet light is hindered. On the other hand, when the amount of the solid organic acid is too small, the ability to absorb alkali such as ammonia cannot be sufficiently obtained. However, it goes without saying that the amount of addition varies depending on the number of hydroxyl groups of the solid organic acid. The above range is also appropriate when a solid organic acid is added to the intermediate layer.

[0040]

EXAMPLES Examples of the present invention will be described below together with comparative examples outside the scope of the present invention. In Examples and Comparative Examples, all “parts” represent parts by weight.

Example 1 A reflective layer composed of an aluminum vapor-deposited layer was provided on the surface of a substrate composed of a polyethylene terephthalate sheet having a thickness of about 188 μm, and a reversible thermosensitive recording paint having the following composition was coated on the reflective layer. Coating to a dry film thickness of about 6 μm by coating, 13
After drying at 0 ° C. for 1 minute, a reversible thermosensitive recording layer was formed.

Dodecane diacid 1 part by weight 1,18-octadecamethylene dicarboxylate distearyl 5 parts by weight Vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbite Co., Ltd., trade name “VYHH”) 3 parts by weight Low Tg resin (Tg) = -38 ° C, acrylic resin, manufactured by Toa Gosei Chemical Co., Ltd., trade name “S-2040”, solid content: 30%) 10 parts by weight Tetrahydrofuran 133 parts by weight On the reversible thermosensitive recording layer formed here, the following composition Was applied by bar coating to form a protective layer.

UV-curable paint (manufactured by Dainippon Ink and Chemicals, trade name “C3-374”, solid content: 75%) 80 parts by weight Toluene 160 parts by weight 2,2-bis (4′-human peroxyphenyl) phenyl (melting point) (156 ° C.) 12 parts by weight This UV-curable resin paint is applied by bar coating to a thickness so as to have a dry film thickness of about 2 μm.
After drying at ℃ for 1 minute, UV irradiation (160W / cm, 30m
/ Min) and cured.

Thus, a reversible thermosensitive recording medium having the structure shown in FIG. 1 was obtained.

Example 2 The procedure of Example 1 was repeated, except that the addition amount of 2,2-bis (4'-hydroxyphenyl) propane, a solid organic acid, was changed to 3 parts by weight. A thermal recording medium was produced.

Example 3 The procedure of Example 1 was repeated, except that the addition amount of 2,2-bis (4'-hydroxyphenyl) propane, which was a solid organic acid, was changed to 30 parts by weight. A thermal recording medium was produced.

Example 4 The procedure of Example 1 was repeated, except that the addition amount of 2,2-bis (4'-hydroxyphenyl) propane, a solid organic acid, was changed to 12 parts by weight. A thermal recording medium was produced.

Example 5 In Example 1, bis (4′-hydroxyphenyl) sulfone (melting point: 249 ° C.) was used in place of 2,2-bis (4′-hydroxyphenyl) propane, which is a solid organic acid. A reversible thermosensitive recording medium was prepared in the same manner except that the parts by weight were added.

Example 6 Example 1 was repeated except that 12 parts by weight of dodecane diacid (melting point 128 ° C.) was added in place of 2,2-bis (4′-hydroxyphenyl) propane as a solid organic acid. Was operated in the same manner to produce a reversible thermosensitive recording medium.

(Comparative Example 1) The procedure of Example 1 was repeated, except that a UV-curable resin coating material to which no solid organic acid, 2,2-bis (4'-hydroxyphenyl) propane was added, was used. A thermosensitive recording medium was produced.

Comparative Example 2 In Example 1, 2,2-
Instead of bis (4'-hydroxyphenyl) propane,
A reversible thermosensitive recording medium was prepared in the same manner except that 12 parts by weight of stearic acid (melting point 69 ° C.) was added.

The reversible thermosensitive recording media produced in each of the above Examples and Comparative Examples were subjected to a sweat resistance test and then a printing test.

In the sweat resistance test, an artificial sweat solution (JIS L 08) was used.
48B method, alkaline) was prepared, and the test reversible thermosensitive recording medium was immersed in this artificial sweat solution at room temperature for 24 hours, then pulled up, washed with distilled water, and dried.

The printing test was performed using the test reversible thermosensitive recording medium.
Before and after the sweat resistance test on the body, manufactured by Toyo Seiki Seisakusho
1 kg / hot plate at 120 ° C.
cm ^TwoPressure for 3 seconds, reversible heat sensitivity
The recording layer is colored, and the density of the colored portion and the color
The density of the unexposed background is compared with the optical reflection density manufactured by Macbeth.
Performed by measuring using a degree meter "RD918"
Was.

For each of the test reversible thermosensitive recording media, color was formed in the as-produced state, and the color density was measured. Then, a sweat resistance test was performed, and then the color density of the same portion was measured. Changes were observed. At the same time, measure the background density in the state as it was produced, perform a sweat resistance test, measure the background density, then color the background density measurement site, measure the color density, and change the background density. And the change in the coloring performance was observed. The obtained measurement results are summarized in Table 1 below.

[0056]

[Table 1] Example 7 A reflective layer composed of an aluminum vapor-deposited layer was provided on the surface of a substrate composed of a polyethylene terephthalate sheet having a thickness of about 188 μm, and a reversible thermosensitive recording paint having the following composition was dried by bar coating. It was applied to a thickness of about 6 μm and dried at 130 ° C. for 1 minute.

Dodecanedioic acid 1 part by weight 1,18-otatadecamethylene dicarboxylate distearyl 5 parts by weight Vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbite Co., Ltd., trade name “VYHH”) 3 parts by weight Low Tg resin ( Tg = −38 ° C., acrylic resin, manufactured by Toa Gosei Chemical Co., Ltd., trade name “S-2040”, solid content 30%) 10 parts by weight Tetrahydrofuran 133 parts by weight On the reversible thermosensitive recording layer formed here, Composition Vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbait Co., Ltd., trade name "VYHH") 10 parts by weight 2,2-bis (4'-hydroxyphenyl) propane 2 parts by weight Methyl ethyl ketone 24 parts by weight Toluene 24 parts by weight By bar coating, 130
Drying at 1 ° C. for 1 minute formed an intermediate layer having a dry film thickness of 2 μm.

Next, a coating having the following composition was applied on the intermediate layer by bar coating to form a protective layer.

UV-curable paint (manufactured by Dainippon Ink and Chemicals, trade name “C3-374”, solid content: 75%) 80 parts by weight Toluene 160 parts by weight Coating to a thickness of about 2 μm, 130
After drying at ℃ for 1 minute, UV irradiation (160W / cm, 30m
/ Min) and cured.

Thus, a reversible thermosensitive recording medium having the structure shown in FIG. 2 was obtained.

(Example 8) In Example 7, the protective layer was made of an ultraviolet-curable paint (manufactured by Dainippon Ink and Chemicals, trade name "C3-374", solid content: 75%) 80 parts by weight Toluene 160 parts by weight 2, The operation shown in FIG. 2 was repeated in the same manner as described above except that a protective layer containing a solid organic acid was formed using a coating composition having a composition of 12 parts by weight of 2-bis (4′-human peroxyphenyl) fluorobenzene (melting point: 156 ° C.). Was obtained.

(Comparative Example 3) The procedure of Example 7 was repeated, except that 2,2-bis (4'-hydroxyphenyl) propane was not added as a paint for forming the intermediate layer. A reversible thermosensitive recording medium having the structure of No. 2 was obtained.

Comparative Example 4 In Example 7, 2 parts by weight of stearic acid (melting point 69 ° C.) was used in place of 2,2-bis (4′-hydroxyphenyl) propane as a coating material for forming an intermediate layer. The same operation was performed except that was added,
A reversible thermosensitive recording medium having the structure shown in FIG. 2 was obtained.

The reversible thermosensitive recording media obtained in Examples 7 and 8 and Comparative Examples 3 and 4 were subjected to the same test as described above, and the results shown in Table 2 below were obtained.

[0065]

[Table 2] As is clear from the results shown in Tables 1 and 2, in the reversible thermosensitive recording medium of the present invention, both the background density and the color density are small even after the sweat resistance test, and the color development performance after the sweat resistance test is excellent. Was.

In contrast, in each of the comparative examples, both the color density and the background density deteriorated after the sweat resistance test.
In Comparative Example 2, the organic acid contained in the protective layer was lifted up, and when the hot plate was pressed, the coloring property was poor and the practicality was poor. Further, in Examples 7, 8 and Comparative Example 4, JISK54
When the adhesion test between the intermediate layer and the protective layer was performed in accordance with the cross-cut tape method specified in 00, the comparative example 4 did not show any peeled portions in Examples 7 and 8. Peeled parts were found.

[0067]

As described above, the reversible thermosensitive recording medium of the present invention has the same coloring performance as the conventional reversible thermosensitive recording medium containing no solid organic acid even in the initial state. Maintains the initial background density and color density even after contact with ammonia caused by sweat, etc. during carrying and use, and exhibits the characteristics that color development performance does not deteriorate, greatly improving the practicality of reversible thermosensitive recording media. Improve.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a reversible thermosensitive recording medium according to an embodiment of the present invention.

FIG. 2 is a partial longitudinal sectional view of a reversible thermosensitive recording medium according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Reflective layer 3 Reversible thermosensitive recording layer 4 Protective layer 5 Intermediate layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Minoru Fujita 4-14-12 Koishikawa Bunkyo-ku, Tokyo Kyodo Printing Co., Ltd.

Claims (3)

[Claims] 1. A reversible thermosensitive recording layer that reversibly switches between a transparent state and a cloudy state by heating, and a protective layer that protects the reversible thermosensitive recording layer, wherein the protective layer is formed of the reversible thermosensitive recording layer. A reversible thermosensitive recording medium comprising a solid organic acid which is a solid at a coloring temperature at the time of recording on a layer. 2. A reversible thermosensitive recording layer that reversibly switches between a transparent state and a cloudy state by heating, a protective layer for protecting the reversible thermosensitive recording layer, and a protective layer between the reversible thermosensitive recording layer and the protective layer. Provided, wherein at least one of the protective layer and the intermediate layer contains a solid organic acid that is solid at a coloration temperature during recording on the reversible thermosensitive recording layer. Reversible thermosensitive recording medium. 3. The reversible thermosensitive recording medium according to claim 1, wherein the solid organic acid is selected from the group consisting of higher fatty acids, dibasic acids, and phenols.