JPH05155131A - Reversible thermal recording material and magnetic card - Google Patents

Abstract

(57) [Summary] [Structure] The reversible thermosensitive recording material of the present invention is a reversible thermosensitive recording material in which a thermosensitive recording layer containing a resin base material and an organic low molecular weight substance is provided on a substrate. An ultraviolet absorber is incorporated in the layer, or an ultraviolet absorber is provided on the heat-sensitive recording layer. [Effect] The reversible thermosensitive recording material of the present invention retains a wide transparent temperature region even after storage and is easily erased by a thermal head. Suitable for magnetic cards.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible heat-sensitive recording material capable of reversibly repeatedly forming and erasing an image based on a temperature change. The present invention also relates to a magnetic card using this reversible thermosensitive recording material.

[0002]

2. Description of the Related Art In recent years, the use of thermal recording materials has been rapidly expanding with the spread of thermal heads. In particular, in prepaid cards that are rapidly becoming popular in the fields of communication, transportation, distribution, etc., magnetic information is often displayed on the card as visible information. Such magnetic cards are widely used as highway cards, JR orange cards, or prepaid cards for department stores, supermarkets, and the like.

However, the area in which visible information can be displayed on such a magnetic card is limited, and in the case of a high-priced prepaid card, the information may not be displayed completely when the balance is added. .. In such a case, a new card is usually reissued to deal with the problem, resulting in an increase in cost.

In order to solve such a problem, it is preferable to use a reversible recording material capable of recording / erasing a plurality of times in the same area. With such materials, old information can be erased and new information can be displayed.
There is no need to reissue a new card because it cannot be displayed.

Heretofore, as a heat-sensitive recording material capable of reversibly recording and erasing such information, a high-grade material in a resin base material such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester or polyamide. One having a heat-sensitive recording layer in which an organic low molecular weight substance such as alcohol or higher fatty acid is dispersed has been proposed (JP-A-54-119377).
JP-A-55-154198 and JP-A-2-13
63, etc.).

The formation and erasure of images with such materials is
It utilizes the reversible change in transparency of the thermosensitive recording layer depending on the temperature. That is, this recording material has a certain temperature (t ₁
~t ₁ ') the shows the transparent state (where t ₁ <t _1'), also shows the opaque state at a temperature (t ₁ ') or more. As a heating method for the recording layer, particularly when the recording layer is provided on the magnetic card,
A thermal head is preferred. That is, by making the initial state transparent and applying a temperature equal to or higher than the thermal head (t ₁ ′), the portion becomes clouded and characters and patterns are recorded. Alternatively, the initial state may be changed to a cloudy state, and the portion may be made transparent by recording the temperature (t _{1 to} t ₁ ′) with a thermal head for recording. In these erase, in the former case (t ₁ ~t ₁ '), the latter (t _1') or more temperature heat roll, may be added, such as by a thermal head.

[0007]

However, such a heat-sensitive recording material has a problem in storage stability even though it has excellent initial recording-erasing characteristics, and it has a problem of long-term storage, especially under a fluorescent lamp. When stored, the transparent temperature region becomes narrow, making it difficult to erase the record.

An object of the present invention is to provide a reversible thermosensitive recording material containing a resin base material containing an organic low molecule as a main component, wherein the reversible thermosensitive recording material has no deterioration in recording-erasing characteristics even after long-term storage. It is to provide a magnetic card using this.

[0009]

Means for Solving the Problems As a result of various studies to solve the above-mentioned problems, the present inventors have found that the transparentization temperature range can be maintained for a long period of time by using an ultraviolet absorber. The present invention has been completed by obtaining knowledge.

That is, the present invention is a reversible thermosensitive recording material in which a thermosensitive recording layer containing a resin base material and an organic low molecular weight substance is provided on a substrate, and whether an ultraviolet absorber is blended in the thermosensitive recording layer. Alternatively, the present invention provides a reversible thermosensitive recording material in which an ultraviolet absorbing layer is provided on the thermosensitive recording layer.

The thermosensitive recording layer of the recording material of the present invention can repeatedly record and erase information even after long-term storage,
Visual recording can be performed on the heat-sensitive recording layer by using a heating recording device such as a thermal head. In addition, it is possible to easily rewrite and rewrite the information by using the same device to erase and re-record.

The resin base material used in the reversible thermosensitive recording layer of the recording material of the present invention forms a layer in which organic low molecular weight substances are uniformly dispersed and held, and greatly affects the transparency at maximum transparency.
Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film forming property. As such a resin, a resin having a glass transition point (Tg) of 80 ° C. or higher is preferable. For example, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-acrylate copolymer, and other vinyl chloride-based copolymers; polyvinylidene chloride, vinylidene chloride- Vinyl chloride copolymers, vinylidene chloride copolymers such as vinylidene chloride-acrylonitrile copolymers; polyvinyl acetal resins such as polyesters, polyamides, polyvinyl formal, polyvinyl butyral, polyacrylates, polymethacrylates, acrylate-methacrylate copolymers Acrylic resin such as; silicone resin, polystyrene, styrene-butadiene copolymer, polyarylate, polycarbonate, polysulfone, aromatic polyamide, phenoxy type resin, cellulose resin, or other thermoplastic resin And other thermosetting resins. These base material resins may be used alone or in combination of two or more.

As the organic low molecular weight substance to be blended in the heat-sensitive recording layer, at least one higher fatty acid, particularly at least one higher fatty acid having 16 or more carbon atoms is used. Specific examples of the higher fatty acid having 16 or more carbon atoms include palmitic acid, margaric acid, stearic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, behenic acid, lignoceric acid, pentacosanoic acid, cerotic acid, heptacosanoic acid, montanic acid, Triacontanoic acid, nonacosanoic acid, mericinic acid, 2-hexadecenoic acid, trans-3-hexadecenoic acid, 2-heptadecenoic acid, trans-2-octadecenoic acid, cis-2-octadecanoic acid, trans-4-octadecenoic acid, cis- 6-octadecenoic acid, elaidic acid,
Vacenic acid, trans-gondoinic acid, erucic acid, brassic acid, ceracoleic acid, trans-ceracoleic acid,
Trans-8, trans-10-octadecadienoic acid,
Linoelaidic acid, α-eleostearic acid, β-eleostearic acid, pseudoeleostearic acid, 12,
20-heneicosadienoic acid and the like can be mentioned. You may use these individually or in mixture of 2 or more types.

As the organic low molecular weight substance, the above higher fatty acid may be further represented by the general formula: HOOC (CH ₂ ) _m —S— (CH ₂ ) _n C.
OOH [in the formula, m and n are each independently an integer of 1 to 5]
It is preferable to use a mixture of sulfides represented by
By combining this sulfide with a higher fatty acid having 16 or more carbon atoms, it is possible to shift the clearing temperature region to the high temperature side and expand the region width. Specific examples of the sulfide include (1,1′-dicarboxy) dimethyl sulfide,
(2,2'-dicarboxy) diethyl sulfide [thiodipropionic acid], (3,3'-dicarboxy) dipropyl sulfide, (1,2'-dicarboxy) methylethyl sulfide, (1,3'- Dicarboxy) methyl propyl sulfide, (1,4'-dicarboxy) methyl butyl sulfide, (2,3'-dicarboxy) ethyl propyl sulfide, (2,4'-dicarboxy) ethyl butyl sulfide, (5,5 Examples include ′ -dicarboxy) dipentyl sulfide, and thiodipropionic acid is particularly preferable. You may use these individually or in mixture of 2 or more types.

The mixing ratio of the higher fatty acid and the sulfide such as thiodipropionic acid is 90:10 to 1 by weight.
It is 0:90, preferably 90:10 to 30:70, and more preferably 85:15 to 50:50. When the amount of sulfide is less than the above range, the transparent temperature range is not sufficiently widened, while when it is more than the above range, the contrast is lowered.

The mixing ratio of the organic low molecular weight substance and the resin base material in the heat-sensitive recording layer is preferably about 50 to 1600 parts by weight of the resin base material with respect to 100 parts by weight of the organic low molecular weight substance.
Particularly preferred is 100 to 500 parts by weight. When the amount of the base material is less than 50 parts by weight, it becomes difficult to form a film in which the organic low molecular weight substance is stably retained in the base material. On the other hand, when the amount of the base material exceeds 1600 parts by weight, the amount of the organic low molecular weight substance that becomes cloudy is small, and thus the written recorded information cannot be clearly read, which is not preferable as a recording material.
In addition, the organic low molecular weight substance is uniformly dispersed in the base material,
Moreover, it is preferable that they are sufficiently fixed, and they may be partially compatible with the base material.

In the reversible thermosensitive recording material of the present invention, an ultraviolet absorber is mixed in the resin base material, or an ultraviolet absorbing layer containing the ultraviolet absorber is provided on the thermal recording material layer. Due to these, a good transparent temperature region is maintained even after long-term storage under a fluorescent lamp or the like.

Examples of the ultraviolet absorber incorporated in the resin base material or in the ultraviolet absorbing layer include phenyl salicylate, p-tret-butylphenyl salicylate, p-
Salicylic acid type UV absorbers such as octylphenyl salicylate; Benzophenone type UV absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone; 2- (2 '-Hydroxy-5'
-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) -benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'methylphenyl) -5- Benzotriazole type UV absorbers such as chlorobenzotriazole; cyanoacrylate type UV absorbers such as 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate Is mentioned. These may be used alone or 2
You may use together more than one kind.

When these ultraviolet absorbers are added to the resin base material, the blending amount thereof is 0.01 to 20 parts by weight, preferably 0.01 to 10 parts by weight, based on 100 parts by weight of the resin base material. If the amount is less than 0.01 parts by weight, sufficient storage stability cannot be obtained. On the other hand, when the blending amount exceeds 20 parts by weight, the white turbidity of the heat-sensitive recording layer is lowered and the visibility is deteriorated.

Further, nickel bis (octylphenyl) sulfide, so as to obtain a sufficient ultraviolet absorbing effect,
(2,2'-thiobis (4-tert-octylphenolate))-n-butylamine nickel, nickel complex-3,5-di-tert-butyl-4-hydroxybenzyl phosphoric acid monoethylate, nickel dibutyldithioca -Bamate, benzoate type quencher,
A light stabilizer such as hindered amine may be used in combination.

In the reversible thermosensitive recording layer, a lubricant, an antistatic agent, a plasticizer, a dispersant, a surfactant, a heat-melting resin, an antioxidant, an inorganic or organic filler may be added, if necessary. You may mix | blend various additives, such as an agent.

The solvent used for forming the heat-sensitive recording layer may be variously selected depending on the types of the base material and the organic low molecular weight substance, and examples thereof include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, Examples thereof include benzene.
In the thermosensitive recording layer obtained not only when the dispersion liquid is used but also when the solution is used, the organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state.

In order to form a heat-sensitive recording layer using each of the above components, generally, a solution in which two components of a resin base material and an organic low molecular weight substance are dissolved is prepared, or at least one of the organic low molecular weight substances is prepared. A solution of the resin base material is prepared using a solvent that does not dissolve the above, the organic low molecular weight substance is dispersed in the form of fine particles, and a dispersion liquid in which a high boiling point solvent is dissolved is prepared. These are applied on a substrate such as plastic, glass plate, metal plate, paper, cloth, etc. and dried to form a heat-sensitive recording layer.

The thickness of the heat-sensitive recording layer varies depending on the use, but is generally 1 to 50 μm, preferably 1 to 30 μm. If the thickness of the heat-sensitive recording layer is thicker than this, heat from the thermal head or the like is less likely to be transferred, and if it is less than 1 μm, the contrast (white turbidity) is lowered, which is not preferable. There is no such limitation when using a heating method other than the thermal head.

On the other hand, when an ultraviolet absorbing layer containing an ultraviolet absorbent is provided on the heat-sensitive recording layer, a base material having excellent transparency and good compatibility with the ultraviolet absorbent is used. Examples of such a material include vinyl acetate resin, formal resin, butyral resin, polyvinyl alcohol, soluble polyamide resin, polyacrylamide,
Examples thereof include polyacrylic acid and polymethacrylic acid. These base materials for the ultraviolet absorbing layer may be used alone or in combination of two or more.

The blending amount of the UV absorber is adjusted so that the UV blocking rate of the UV absorbing layer is 70% or more, preferably 80% or more. If the UV blocking rate is lower than 70%, sufficient storage stability cannot be obtained. The ultraviolet stabilizer may be used alone or in combination of two or more kinds, as in the case of being blended in the heat-sensitive recording layer. Further, the light stabilizer may be used in combination. Also, if necessary, a lubricant, an antistatic agent, a plasticizer,
In addition to the dispersant and the surfactant, additives such as an inorganic or organic filler may be added.

The thickness of the ultraviolet absorbing layer is preferably 5 μm or less, more preferably 3 μm or less. If the thickness exceeds 5 μm, the thermal conductivity to the heat-sensitive recording layer decreases, which is not preferable for recording / erasing. Such an ultraviolet absorbing layer is formed by a known method by preparing a solution of an alcohol solvent such as methanol, ethanol or isopropyl alcohol. Since an alcohol solvent is used, it does not attack the heat-sensitive layer containing a vinyl chloride-vinyl acetate copolymer or the like as a base material. The solution concentration is 1 to 50% by weight
Is preferred.

Further, in order to make it easy to confirm the recorded contents of the recording layer (improvement of visibility), a colored layer or a metal reflective layer of Al, Ag, Sn or the like may be provided below the reversible thermosensitive recording layer. Good. Furthermore, it prevents deterioration of the reversible thermosensitive recording layer due to heat and pressure of a heating device such as a thermal head during recording and erasing, dents during erasing, and sticking during recording.
In order to improve recyclability, an overcoat layer may be provided on the heat sensitive layer or the ultraviolet absorbing layer. Examples of such an overcoat layer include organic materials such as silicone-based, acrylic-based, fluorine-based, epoxy-based, urethane-based, or SiO ₂ , SiO, MgO, ZnO, TiO ₂ ,
An inorganic substance such as Al ₂ O ₃ , AlN or Ta ₂ O ₅ may be used. Further, a thermosetting resin, an electron beam curable resin, or an ultraviolet curable resin may be used as the overcoat layer.

Such an overcoat layer can be formed by a conventionally known coating method or a vacuum deposition method, and in the case of an organic substance, the thickness is 0.1 to 5.0 μm, preferably 0.5 to 3 μm. Is. If the thickness is smaller than this, the effect of overcoating is small, while if it is larger than this, the contrast is deteriorated and both are not preferable. When an organic material is used for the overcoat layer, the resin base material or organic low-molecular weight material of the heat-sensitive recording layer may be dissolved and the recyclability may be reduced or disappeared depending on the selection of the organic material or the solvent. In such a case, it is preferable to provide an anchor coat layer between the thermal recording layer and the overcoat layer. When an organic material is used as the overcoat layer, fine powder such as organic beads or inorganic substances may be added to prevent sticking. When using an inorganic substance for the overcoat layer, if the overcoat layer is too thick (1.
0 μm or more) There is a risk of cracking.

The reversible recording material of the present invention is particularly preferably applied to a magnetic card. In this case, the reversible thermosensitive recording layer may be provided on the magnetic layer of the card or on the opposite surface. Further, it may be provided on the entire surface of the card or a part thereof. In providing such a magnetic card with the material of the present invention, an undercoat layer may be interposed, if necessary, in order to improve the adhesion to the substrate. In order to further improve the visibility, a colored layer or Al, under the reversible thermosensitive recording layer,
You may provide a metal reflective layer, such as Ag and Sn.

Magnetic cards having such a reversible heat-sensitive recording layer include various prepaid cards used in highway cards, department stores, supermarkets, JR orange cards,
It can be used widely such as stored fair cards.

[0032]

EXAMPLES Next, the heat-sensitive recording material of the present invention will be described more specifically with reference to examples. In the following, "parts" means "parts by weight".

Example 1 Composition Compounding amount Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts (2,2′-dicarboxy) diethyl sulfide 3 parts (Thiodipropionic acid) Vinyl chloride-vinyl acetate copolymer 25 parts (manufactured by UCC, VYHH) 1,3-pentadiene polymer 2 parts benzophenone-based UV absorber 0.25 part (2,2'-dihydroxy-4-methoxybenzophenone) tetrahydrofuran 120 parts Was applied onto a polyethylene terephthalate film (thickness 100 μm) so as to have a dry film thickness of 15 μm to obtain a heat-sensitive recording layer. Further, as an overcoat layer, 50 parts of an acrylic UV curable resin (BR-370 manufactured by Asahi Denka) and 5 parts of methanol
0 parts of the coating solution was applied to a dry thickness of 2 μm, and UV irradiation (500 mJ) was performed to cure it.

Example 2 In Example 1, a hindered amine light stabilizer (bis) was added to the compounding liquid for the heat-sensitive recording layer.
A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that 0.25 part of (2,2,6,6-tetramethyl-4-piperidyl) sebacate) was added. Table 1 shows the results evaluated in the same manner as above.

[Example 3] A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the blending amount of the benzophenone ultraviolet absorber was changed to 2 parts. Table 1 shows the results evaluated in the same manner as above.

Example 4 A benzotriazole-based ultraviolet absorber (2-
Example 2 except that 0.25 parts of (2'-hydroxy-5'-t-octylphenyl) -benzotriazole) were used.
A reversible thermosensitive recording material was prepared in the same manner as in. Table 1 shows the results evaluated in the same manner as above.

[Example 5] The same as Example 1 except that a magnetic sheet having an Al film of 500 Å (angstrom) provided on the back surface of the magnetic surface by a vacuum deposition method was used in place of polyethylene terephthalate in Example 1. A reversible thermosensitive recording material was obtained. Table 1 shows the results evaluated in the same manner as above.

Example 6 Composition Compounding amount Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts (2,2′-dicarboxy) diethyl sulfide 3 parts [Thiodipropionic acid] Vinyl chloride-vinyl acetate copolymer 25 parts (manufactured by UCC, VYHH) 1,3-pentadiene polymer 2 parts Tetrahydrofuran 120 parts A solution having the above composition was applied in the same manner as in Example 1 to obtain a thermosensitive recording layer. On the heat-sensitive recording layer, 0.5 part of a benzophenone-based UV absorber (2,2-dihydroxy-4-methoxybenzophenone) as a UV absorbing layer, vinyl acetate resin 25
Coating solution consisting of 75 parts of methanol and 75 parts of methanol to a dry thickness of 1 μm
It was applied so as to have a thickness of m (UV blocking rate 93.7%).
Further, an overcoat layer was provided on this ultraviolet absorbing layer in the same manner as in Example 1. Table 1 shows the results evaluated in the same manner as above.

[Comparative Example 1] A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that no ultraviolet absorber was used. Table 1 shows the results evaluated in the same manner as above.

The reversible thermosensitive recording materials obtained in Examples 1 to 6 and Comparative Example 1 were subjected to a storage test (5000 LUX-10).
The sample before and after the irradiation was evaluated by the following method. The results are shown in Table 1.

Optical density: A cloudy image area and an image erasing transparent area were placed on a standard blackboard and measured with a Macbeth RD-920 densitometer (manufactured by Macbeth).

Transparent temperature range: 50 ° C. to 1 for each recording material
After heating stepwise by ° C, it was cooled to room temperature and the above optical density was measured. At this time, the temperature at which the optical density was 1.20 or more was set as the transparent temperature region.

Table 1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━ Transparent temperature range (℃) ───────────── ───────── After the initial test ━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 67.5 ■ 85.3 (17.8) 70.2 ■ 90.1 (19.9) 〃 2 67.3 ■ 89.5 (22.2) 68.0 ■ 90.0 (20.0) 〃 3 67.0 ■ 90.1 (23.1) 67.2 ■ 90.3 (23.1) 〃 4 67.7 ■ 88.0 (20.3) 67.2 ■ 90.4 (23.2) 〃 5 70.0 ■ 86.7 (16.7) 70.1 ■ 86.0 (15.9) 〃 6 68.0 ■ 86.5 (18.5) 69.6 ■ 87.5 (17.9) ━━━━━━━━━━━━━━━━━━━━━━━━ ━━━ Comparative example 1 67.5 ■ 88.2 (20.7) 69.3 ■ 78.9 (6.9) ━━━━━━━━━━━━━━━━━━━━━━━━━━━ Note: In parentheses Indicates the temperature range.

[0044]

INDUSTRIAL APPLICABILITY The reversible thermosensitive recording material of the present invention has an initial transparent temperature range even under poor storage conditions, has good erasability by a thermal head, and is excellent in storage stability. ..

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G11C 13/00 2116-5L 8623-5L G06K 19/00 C

Claims (4)

[Claims] 1. A reversible heat-sensitive recording material comprising a base material and a heat-sensitive recording layer containing a resin base material and an organic low-molecular substance, wherein the heat-sensitive recording layer contains an ultraviolet absorber. Reversible thermosensitive recording material. 2. A reversible thermosensitive recording material comprising a base material and a thermosensitive recording layer containing a resin base material and an organic low molecular weight substance, wherein an ultraviolet absorbing layer is provided on the thermosensitive recording layer. And a reversible thermosensitive recording material. 3. A magnetic card in which the reversible thermosensitive recording material according to claim 1 or 2 is provided on a magnetic card member. 4. The magnetic card according to claim 3, wherein the heat-sensitive recording material is provided on the magnetic recording layer side or a part or the whole surface on the opposite side of the magnetic recording layer.