JPH07172071A - Reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To form a thermal recording layer all or partly to a transparent state by setting an erasing temperature by forming the layer by laminating a plurality of thermal recording layers having different clarifying temperature ranges. CONSTITUTION:A thermal recording layer 12 obtained by laminating first and second thermal recording layers 12A and 12B having different clarifying temperature ranges in which a transparent state and an emulsified state are reversibly changed depending upon a temperature is provided on a support sheet 10. A protective layer 14 having heat resistance is provided on the layer 12. As a resin material for forming part of the layer 12, thermoplastic resin having near refractive index to that of organic molecular substance and no compatibility to the substance, excellent mechanical strength, film forming capacity and excellent transparency is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable reversible thermosensitive recording medium provided with a thermosensitive recording layer in which transparency and cloudiness change reversibly depending on temperature, and particularly, transparency temperature regions are different from each other. The present invention relates to a reversible thermosensitive recording medium in which a plurality of thermosensitive recording layers are laminated and the thermosensitive recording layers can be brought into a transparent state or a partially transparent state by setting an erasing temperature.

[0002]

2. Description of the Related Art In recent years, cards such as magnetic recording media in which machine-readable information is recorded have been remarkably developed, and have been used in many fields.

In this type of card, a magnetic recording layer is provided on a card base and information is recorded on this magnetic recording layer. The magnetically recorded information is invisible to the naked eye, but higher security is required for these cards.For example, as an identification function for determining the authenticity of the card outside the magnetic recording site. , A magnetic or non-magnetic visible recording medium is arranged, or a magnetic recording layer of the magnetic recording portion is formed with a concealing layer so that the magnetic recording contents cannot be easily read from the outside. .

By the way, in recent years, in addition to recording fixed information, identification information or variable information on the magnetic recording layer, it is also possible to record visible information on the card surface at the time of use for the convenience of the card owner. To be held,
In particular, in the case of price-reducing pre-baid cards such as various types of PVC cards, PET cards, paper cards, synthetic paper cards, etc., when the number of times of use is unreasonable, even if there is a remaining amount, the printing area disappears and it cannot be used. Due to the fact that it is difficult to print small letters or the like, update records such as the balance have not been adopted.

Therefore, the remaining balance, the frequency, etc. are roughly notified by drilling or the like. For this reason, there is a problem in that it is impossible to know the usage history and the accurate balance.

On the other hand, recently, a rewritable reversible thermosensitive recording card has been proposed which has a thermosensitive recording layer on one surface of which a transparent state and a cloudy state reversibly change depending on temperature. .

However, in a reversible thermosensitive recording medium having such a thermosensitive recording layer, the image becomes transparent at a certain temperature, and therefore information that is not usually desired to be erased (for example, information such as name and member number) is required. Even, there is a problem that it is erased.

[0008]

As described above, in the conventional reversible thermosensitive recording medium, there is a problem in that even information that is not normally desired to be erased is erased.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to reversibly rewrite information that is normally desired to be erased, and is necessary for information that is not usually desired to be erased. An object of the present invention is to provide an extremely reliable reversible thermosensitive recording medium that can be rewritten only occasionally.

[0010]

In order to achieve the above object, first, in the invention according to claim 1, the transparency and the cloudiness reversibly change on at least one of the supports depending on the temperature. In a reversible thermosensitive recording medium provided with a thermosensitive recording layer, the thermosensitive recording layer is formed by laminating a plurality of thermosensitive recording layers having mutually different transparentization temperature regions.

According to the second aspect of the invention, in the reversible thermosensitive recording medium, a thermosensitive recording layer in which transparency and cloudiness are reversibly changed depending on temperature is provided on at least one side of the support. The heat-sensitive recording layer is composed of a first heat-sensitive recording layer having a wide transparentization temperature region and a transparentization temperature region narrower than that of the first heat-sensitive recording layer and having a maximum clearing temperature substantially equal to that of the first heat-sensitive recording layer. It is constructed by laminating a second thermosensitive recording layer at a temperature.

Further, in the invention according to claim 4, in the reversible thermosensitive recording medium according to claim 1 or 2, the metal reflective layer is formed on the support.

Furthermore, in the invention according to claim 5, in the reversible thermosensitive recording medium according to any one of claims 1, 2 and 3, heat resistance is provided on the thermosensitive recording layer. A protective layer having is provided.

Here, in particular, information to be normally erased is within a transparent temperature region of the heat-sensitive recording layer having a wide transparent temperature region,
And information that is erased at a temperature outside the transparency temperature region of the heat-sensitive recording layer in a narrow transparency temperature region, and information that normally does not want to be erased much, in the transparency temperature region of the heat-sensitive recording layer of the wide transparency temperature region, The erasing temperature is set so that the erasing is performed at a temperature within the transparentizing temperature region of the thermosensitive recording layer in the narrow transparentizing temperature region.

[0015]

Therefore, in the reversible thermosensitive recording medium of the present invention, a plurality of thermosensitive recordings having different transparency temperature regions in which transparency and cloudiness are reversibly changed depending on temperature on at least one side of the support. By having the thermosensitive recording layer formed by stacking layers, two state transition temperatures T ₁ and T ₂ (provided that T ₁ <T ₂ ) are present at a temperature higher than the specific temperature T ₀ near room temperature.

Therefore, when the heat-sensitive recording layer of the reversible heat-sensitive recording medium is heated to a temperature of T ₂ or higher and then held and then cooled to a temperature of the specific temperature T ₀ or lower, the heat-sensitive recording layer becomes cloudy and its light scattering property. Is increased and the maximum light blocking state is achieved.

In addition, the heat-sensitive recording layer in the cloudy state is T
_When it is heated to a temperature lower than T ₂ at a temperature of ₁ or higher, and held and then cooled to a temperature of T ₀ or lower, its light scattering property is reduced and the state becomes transparent again.

Further, under the temperature condition of the specific temperature T ₀ or lower, the maximum light shielding state and the transparent state of the thermosensitive recording layer can be stably maintained, and these states can be reversibly changed. By setting one of the states as the base state, the state can be differentiated from the other state, and the recording medium can be used as a rewritable recording medium.

As described above, in the reversible thermosensitive recording medium of the present invention, depending on the setting of the erasing temperature, the thermosensitive recording layer is completely transparent or partially transparent, and the information to be normally erased can be reversibly rewritten. You can do it, and you can rewrite information that you don't usually want to delete much when necessary.

[0020]

EXAMPLES The reversible thermosensitive recording medium of the present invention utilizes the reversible change of transparent white turbidity, and the principle of the transparent state and the white turbid state can be considered as follows.

Transparent white turbidity is a change in light transmission due to a change in crystalline state (becomes polycrystal). In a transparent state, an organic low molecular substance dispersed in a resin matrix transmits light. It looks transparent.

In the cloudy state, it is considered that the organic low molecular weight substance dispersed in the resin matrix scatters light due to the change of the crystalline state and appears white.

That is, according to the present invention, a heat-sensitive recording layer comprising a plurality of heat-sensitive recording layers each having different transparency temperature regions in which transparency and white turbidity reversibly change depending on temperature is laminated on at least one side of the support. By having the recording layer, the two state transition temperatures T are increased to a temperature higher than the specific temperature T ₀ near room temperature.
_{By having 1} and T ₂ (provided that T ₁ <T ₂ ), the maximum light-shielding state and transparent state of the thermosensitive recording layer can be stably maintained under a temperature condition below a specific temperature T ₀ near room temperature,
In addition, these states are reversibly changed and one of the states is set as the base state so that the state can be differentiated from the other state and the recording medium can be used as a rewritable recording medium.

An embodiment of the present invention based on the above concept will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a structural example of a reversible thermosensitive recording medium according to the present invention.

That is, as shown in FIG. 1, the reversible thermosensitive recording medium of the present embodiment is transparentized on the support sheet 10 in which the transparent state and the cloudy state reversibly change depending on the temperature. A first heat-sensitive recording layer 12A having different temperature regions,
Thermal recording layer 12 formed by laminating second thermal recording layer 12B
And a heat-resistant protective layer 14 is provided on the heat-sensitive recording layer 12.

The first heat-sensitive recording layer 12A has a wide transparentization temperature region, and the second heat-sensitive recording layer 12A has a second transparent region.
The heat-sensitive recording layer 12B has a clearing temperature region narrower than that of the first heat-sensitive recording layer 12A and has a maximum clearing temperature substantially equal to that of the first heat-sensitive recording layer 12A. A first thermosensitive recording layer 12 having a wide transparentization temperature region
Information which is erased at a temperature within the transparency temperature region of A and outside the transparency temperature region of the second thermosensitive recording layer 12B in the narrow transparency temperature region, and which is usually not desired to be erased is a wide transparency temperature region. The second heat-sensitive recording layer 12 in the transparent temperature range of the first heat-sensitive recording layer 12A in the area and in the narrow clear temperature range.
The erasing temperature is set so that the erasing is performed at a temperature within the transparentizing temperature region of B.

Here, the base material of the support sheet 10 is, for example, a synthetic resin such as a polyvinyl chloride seed for a card used in an ID card or a credit card, or a polyester sheet for a card used in a prepaid card. Sheets, paper, etc. can be used.

On the other hand, as a resin material forming a part of the heat-sensitive recording layer 12, the organic low-molecular substance has a refractive index similar to that of the organic material and is incompatible with each other, and has excellent mechanical strength and film-forming ability. A thermoplastic resin having good transparency can be used.

Examples of the resin include polyester resins such as saturated copolyester, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-acetic acid. Vinyl-maleic acid copolymers, vinyl chloride copolymers such as vinyl chloride-acrylate copolymers, polyvinylidene chloride resins, vinylidene chloride-vinyl chloride copolymers,
There are vinylidene chloride copolymers such as vinylidene chloride-acrylonitrile copolymers, polyamide resins, silicone resins, polyacrylate or polymethacrylate resins, and copolymers thereof. These are used alone or in combination with 2
Although more than one kind can be mixed and applied, the invention is not limited thereto.

Examples of the organic low molecular weight substance dispersed in the heat-sensitive recording layer 12 include fatty acids, fatty acid derivatives, and alicyclic organic acids. More specifically, saturated or unsaturated ones, or carboxylic acid,
Alternatively, these include esters, amides and the like.

Specific examples of the saturated fatty acids include undecanoic acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotonin. Acid, montanic acid, melissic acid, etc. are mentioned.

Specific examples of the unsaturated fatty acids include oleic acid, elaidic acid, linoleic acid, sorbic acid and stearolic acid.

The fatty acid, the fatty acid derivative, or the alicyclic organic acid is not limited to these, and one kind or a mixture of two or more kinds thereof may be applied. .

Here, as the composition of the first heat-sensitive recording layer 12A having a wide transparent temperature range to be used, the organic low molecular weight substance has many low melting points, and the resin having low Tg is used. . As for the composition of the heat-sensitive recording layer 12B having the second narrow transparentization temperature region, many organic low molecular weight substances having a high melting point and a resin having a high Tg are used. By doing so, it becomes easy to make a difference in the transparentization temperature region.

On the other hand, the heat-resistant protective layer 14 does not deform with the energy of about 0.3 mJ / dot of the thermal head, and the gloss does not change.

Examples of materials for the heat-resistant protective layer 14 include nitrocellulose, hydroxycellulose, carboxymethyllose, polyvinyl alcohol,
Styrene-maleic acid copolymer, polyester resin, A
BS resin or the like can be used.

Further, a thermosetting resin, an ultraviolet curing resin,
A curable resin such as an electron beam curable resin can also be used.

The protective layer 14 has a thickness of 1 to 5 μm.
m is suitable.

Further, the protective layer 14 may contain a lubricant such as wax in order to improve the sliding property with the thermal head and ensure the smooth running of the thermal head.

Next, FIG. 2 is a cross-sectional view showing another structural example of the reversible thermosensitive recording medium according to the present invention. The same elements as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Now, only different parts will be described.

That is, as shown in FIG. 2, the reversible thermosensitive recording medium of this embodiment has the support sheet 10 shown in FIG.
The metal reflective layer 11 is provided between the heat sensitive recording layer 12 and the heat sensitive recording layer 12.

Here, the metal reflection layer 11 can be formed by vapor-depositing a metal such as aluminum, tin, silver, magnesium, chromium, nickel or gold.

Next, a method of using the reversible thermosensitive recording medium of the present embodiment having the above-mentioned structure will be described.

The reversible thermosensitive recording medium of this embodiment utilizes the reversible change of transparent white turbidity, and the principle of the transparent state and the white turbid state can be considered as follows.

That is, the transparent white turbidity is such that the light transmittance changes due to the change of the crystalline state (becomes polycrystal). In the transparent state, the organic low molecular weight substance dispersed in the resin matrix emits light. It looks transparent by being transparent. Further, in the cloudy state, it is considered that the organic low molecular weight substance dispersed in the resin matrix scatters light due to the change of the crystalline state and appears white.

Specifically, in the reversible thermosensitive recording medium of this embodiment, the property that the light absorption characteristic (light scattering property) of the thermosensitive recording layer 12 reversibly changes depending on temperature is skillfully utilized. Is configured.

That is, the thermosensitive recording layer 12 has two state transition temperatures T at a temperature higher than the specific temperature T ₀ near room temperature.
₁ and T ₂ (provided that T ₁ <T ₂ ), the heat-sensitive recording layer of the reversible heat-sensitive recording medium is heated to a temperature of T ₂ or higher, and after being held, cooled to a temperature of a specific temperature T ₀ or lower. Then, the heat-sensitive recording layer becomes cloudy, its light scattering property increases, and the maximum light shielding state is achieved (printing).

In addition, the heat-sensitive recording layer in the cloudy state is T
_{When the material} is heated to a temperature of less than T ₂ at a temperature of ₁ or more, and held and then cooled to a temperature of T ₀ or less, its light scattering property is reduced and the state becomes transparent again (erasing).

Further, under the temperature condition of the specific temperature T ₀ or lower, the maximum light shielding state and the transparent state of the thermosensitive recording layer can be stably maintained, and these states can be reversibly changed. By setting one of the states as the base state, the state can be differentiated from the other state, and the recording medium can be used as a rewritable recording medium.

Next, a more specific example of the reversible thermosensitive recording medium of this embodiment will be described.

(Specific Example) The second heat-sensitive recording layer 12B was prepared by mixing 8 parts by weight of lignoceric acid, 1 part by weight of sebacic acid, 6 parts by weight of vinyl chloride / vinyl acetate copolymer resin, 30 parts by weight of tetrahydrofuran, and 10 parts by weight of toluene. And coating the support sheet 10 with this coating material and drying it to obtain a plastic film or sheet, or a plastic having a metal reflective layer 11 of aluminum, tin, silver, magnesium, chromium, nickel, gold or the like. A reversible thermosensitive recording medium was obtained on a film, sheet or paper.

Specific examples of the plastic film or sheet include materials having excellent heat resistance, transparency and mechanical strength such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate and polyparabanic acid.

Next, as the first thermosensitive recording layer 12A, 7 parts by weight of stearic acid, 2 parts by weight of sebacic acid, 6 parts by weight of vinyl chloride / vinyl acetate copolymer resin, 30 parts by weight of tetrahydrofuran, and 10 parts by weight of toluene were mixed to prepare a paint. This coating is applied to the second thermosensitive recording layer 12
A reversible thermosensitive recording card was prepared by applying the coating on B and applying a drying treatment, and then forming a protective layer 14.

The reversible thermosensitive recording card produced as described above forms image information of necessary items at a temperature of K ₅ or higher, as shown in FIG.

Next, when rewriting the one in which the amount and points are printed, only this portion is erased at the temperature of K ₂ ,
Printing is performed again at a temperature of K ₅ or higher to form image information.

This process is repeated several times, and when the number of times the reversible thermosensitive recording card has been used is finished, all the image information is erased at the temperature of K ₄ , and the image information of the following necessary items is formed.

FIG. 3 is a characteristic diagram showing an example of the relationship between the heating temperature and the reflection density in this case.

In the example of FIG. 3, within the temperature range in which the density changes rapidly with respect to temperature, that is, in the range K _{1 to} K ₅ for _one recording layer, and the range K ₁ for the other recording layer.
The areas of _{3 to} K ₄ are referred to as transparentization temperature areas.
Incidentally, the outside of the transparentization temperature region is referred to as a whitening temperature region.

As described above, in the reversible thermosensitive recording medium of this embodiment, the metal reflection layer 11 is provided on the support sheet 10 if necessary, and the metal reflection layer 11 is provided on the metal reflection layer 11 depending on the temperature. The first heat-sensitive recording layer 12A and the second heat-sensitive recording layer 12A, which have reversibly changed transparent and cloudy states and have different transparentization temperature regions.
The heat-sensitive recording layer 12 is formed by laminating the heat-sensitive recording layer 12B, and a heat-resistant protective layer 14 is further provided on the heat-sensitive recording layer 12 to form the first heat-sensitive recording layer 12A.
The transparent temperature range is wide, and the second thermal recording layer 12B has a transparent temperature range narrower than that of the first thermal recording layer 12A and the maximum transparent temperature is substantially the same as that of the first thermal recording layer 12A. The information to be erased normally is within the transparency temperature range of the first heat-sensitive recording layer 12A in the wide transparency temperature region and the transparency of the second heat-sensitive recording layer 12B in the narrow transparency temperature region. Information to be erased at a temperature outside the temperature range of transparency, and usually not to be erased so much, is within the temperature range of transparency of the first heat-sensitive recording layer 12A of the wide temperature range of transparency and the information of the second temperature range of the narrow temperature range. The erasing temperature is set so that the erasing is performed at a temperature within the transparentization temperature region of the second thermosensitive recording layer 12B.

Therefore, since two heat-sensitive recording layers having different transparentization temperature regions are formed, depending on the setting of the erasing temperature,
The thermosensitive recording layer 12 becomes completely transparent or partially transparent,
Information that is normally desired to be erased can be reversibly rewritten, and information that is normally not desired to be erased can be rewritten only when necessary.

As a result, when the heat-sensitive recording layer 12 of the reversible heat-sensitive recording medium is heated to a temperature of T ₂ or higher, held and then cooled to a temperature of T ₀ or lower, the heat-sensitive recording layer becomes cloudy and its light-scattering property. Is increased to a maximum light-shielding state, and the heat-sensitive recording layer in the cloudy state is heated to a temperature lower than T ₂ at a temperature of T ₁ or higher, held and then cooled to a temperature of T ₀ or lower, the light scattering occurs. It becomes less transparent and becomes transparent again,
Further, under the temperature condition of T ₀ or less, the thermosensitive recording layer 12
Since the maximum shaded state and transparent state of can be stably maintained, and these states can be reversibly changed,
By setting one of the states to the base state, the state can be differentiated from the other state and the recording medium can be used as a rewritable recording medium.

The present invention is not limited to the above embodiment, but can be implemented in the same manner as described below.

(A) In the above embodiment, the support sheet 10 is used.
The case where the thermosensitive recording layer 12, the (metal reflective layer 11), and the protective layer 14 are provided on one of the upper sides has been described, but the present invention is not limited to this, and the thermal recording layer 12 and the thermosensitive recording layer 12 may be provided on both sides of the support sheet 10.
The (metal reflective layer 11) and the protective layer 14 may be provided.

(B) In each of the above embodiments, the protective layer 14
Is not an essential element of the present invention and may be provided as needed.

(C) In the above embodiments, the case where the reversible thermosensitive recording medium of the present invention is applied to an information recording card has been described, but the present invention is not limited to this, and the present invention can be similarly applied. It is a thing.

(D) In the above embodiment, the heat-sensitive recording layer 12 has a two-layer structure in which the first heat-sensitive recording layer 12A and the second heat-sensitive recording layer 12B are laminated, but the present invention is not limited to this. First, the heat-sensitive recording layer 12 is composed of three layers (or a plurality of layers of more than that), and the heat-sensitive recording layer has a wide transparentizing temperature region, the heat-sensitive recording layer having a narrow transparentizing temperature region, and the heat-sensitive recording layer having a narrower transparentizing temperature region. It is also possible to stack recording layers and erase information at each temperature.

(E) In the above embodiment, when the thermosensitive recording layer 12 having a two-layer structure and transparent temperature regions different from each other is formed and is erased at the temperature of only the information to be erased and all the information is to be erased, A method of performing the erasing work twice may be adopted.

In addition, the present invention can be variously modified and implemented within the scope of the invention.

[0070]

As described above, according to the present invention, a reversible thermosensitive recording medium comprising a thermosensitive recording layer on which at least one of the support is reversibly changed transparent and cloudy depending on temperature. In the above, the heat-sensitive recording layer is formed by laminating a plurality of heat-sensitive recording layers having different transparentization temperature regions, and information normally desired to be erased is within a transparentization temperature region of the heat-sensitive recording layer in a wide transparency temperature region. Information that is erased at a temperature outside the transparency temperature range of the heat-sensitive recording layer in a narrow transparency temperature region, and information that is not normally desired to be erased, is in the transparency temperature region of the heat-sensitive recording layer in the wide transparency temperature region. Moreover, since the erasing temperature is set so that the erasing is performed at the temperature within the transparentizing temperature region of the thermosensitive recording layer in the narrow transparentizing temperature region, the information to be normally erased can be reversibly rewritten, and Usually less erased It can provide an extremely reliable reversible thermosensitive recording medium capable of rewriting only when needed for information not want.

[Brief description of drawings]

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

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

FIG. 3 is a characteristic diagram showing an example of the relationship between temperature and density in the reversible thermosensitive recording medium of the example.

[Explanation of symbols]

10 ... Support, 11 ... Metal reflective layer, 12 ... Thermal recording layer,
12A ... 1st thermosensitive recording layer, 12B ... 2nd thermosensitive recording layer, 14 ... protective layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06K 19/06 G06K 19/00 E

Claims (5)

[Claims] 1. A reversible thermosensitive recording medium comprising a thermosensitive recording layer, on which transparency and cloudiness change reversibly depending on temperature, provided on at least one side of the support. A reversible thermosensitive recording medium comprising a plurality of thermosensitive recording layers each having a different area laminated. 2. A reversible thermosensitive recording medium comprising a thermosensitive recording layer on which at least one of transparent and transparent layers reversibly changes depending on temperature, the thermosensitive recording layer comprising a transparentizing temperature. A first heat-sensitive recording layer having a wide area, and a second heat-sensitive layer having a clearing temperature region narrower than that of the first heat-sensitive recording layer and having a maximum clearing temperature substantially equal to that of the first heat-sensitive recording layer. A reversible thermosensitive recording medium comprising a recording layer laminated. 3. The reversible thermosensitive recording medium according to claim 1 or 2, wherein the information to be normally erased is within a transparent temperature range of a thermal recording layer having a wide transparent temperature range and a narrow transparent temperature range. The information that is erased at a temperature outside the transparency temperature range of the heat-sensitive recording layer in the activation temperature region, and normally is not desired to be erased, is within the transparency temperature region of the heat-sensitive recording layer in the wide transparency temperature region and is narrowly transparent. A reversible thermosensitive recording medium, wherein the erasing temperature is set so that the erasing is performed at a temperature within the transparentizing temperature region of the thermosensitive recording layer in the aging temperature region. 4. The reversible thermosensitive recording medium according to claim 1 or 2, wherein a metal reflective layer is formed on the support. 5. The reversible thermosensitive recording medium according to claim 1, wherein the thermosensitive recording layer is provided with a heat-resistant protective layer. A reversible thermosensitive recording medium characterized by: