JPH05124383A - Reversible thermosensitive recording material and magnetic card - Google Patents

Abstract

PURPOSE:To eliminate deterioration in repeating use and of recording/deleting property in preservation by providing a base material with a reversible thermosensitive recording layer containing resin matrix and organic low molecular material as principal components and phenolic antioxidant mixed therewith. CONSTITUTION:Prtedetermined quantities of resin matrix, organic low molecular material and phenolic antioxidant are dissolved in a solution such as tetrahydrofuran so as to prepare coating liquid for a thermosensitive recording layer. A top of a base material such as glass plate, metallic plate, paper, and plastic film is coated with the coating liquid and dried so as to form a reversible thermosensible recording layer, and a reversible thermosensible recording material is obtained. As the resin matrix to be used, resin having a glass transition point of 80 deg.C or above, for example, polyvinyl chloride and vinyl chloridevinyl acetate copolymer are suitable. As the organic low molecular material, palmitic acid, stearic acid, and eicosane are suitable. As the phenolic antioxidant, 2, 6-di-t-butyl-p-cresol is suitable.

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 for highway cards, prepaid cards for department stores, supermarkets, JR Orange cards, and the like.

However, the area where the visible information can be displayed is limited, and in the case of a high-priced prepaid card, the information may not be able to be displayed 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. When such a material is used, old information is erased and new information is displayed, so that the information cannot be displayed and there is no need to reissue a new card.

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 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'),
Further, at a temperature (t ₁ ′) or higher, a cloudy state is exhibited. As a method for heating the recording layer, a thermal head is preferable especially when the recording layer is provided on the magnetic card. 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, even if such a heat-sensitive recording material is excellent in the initial recording-erasing property, the transparent temperature region is often narrowed by repeated use, which makes it difficult to erase the recording. May be.

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, and a reversible feeling which does not deteriorate in recording-erasing characteristics even during repeated use or storage. To provide a thermal recording material.

[0009]

DISCLOSURE OF THE INVENTION As a result of various studies to solve the above-mentioned problems, the present inventors have found that a phenolic antioxidant is effective in preventing deterioration of recording-erasing characteristics. After that, the present invention was completed.

That is, the present invention is a reversible thermosensitive recording material in which a reversible thermosensitive recording layer containing a resin base material and an organic low molecular weight substance is provided on a substrate, wherein the phenolic antioxidant is contained in the thermosensitive recording layer. The present invention provides a reversible thermosensitive recording material containing

The thermosensitive recording layer of the recording material of the present invention can record and erase information over and over again, and a thermal recording device such as a thermal head is used to perform visual recording on the thermosensitive recording layer. be able to. 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.
When the amount of sulfide is less than the above range, the transparent temperature range does not expand, while when it is more than the above range, the contrast remarkably decreases.

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 present invention, the reversible thermosensitive recording material further contains a phenolic antioxidant in addition to the above components. The addition of the phenolic antioxidant maintains a wide transparent temperature range even after repeated use. Examples of such antioxidant include 2,6-di-t-butyl-p
-Cresol, butylated hydroxyanisole, 2,6
-Di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and other monophenolic compounds; 2,2'-methylene-bis- (4 -Methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-t-
Butylphenol), 4,4'-thiobis- (3-methyl-
6-t-butylphenol), 4,4′-butylidene-bis- (3-methyl-6-t-butylphenol) and other bisphenol-based compounds; 1,1,3-tris- (2-methyl-4-)
Hydroxy-5-t-butylphenyl) butane, 1,3,
5-Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4) '-Hydroxyphenyl) propionate] methane, bis [3,
Polymeric phenols such as 3′-bis- (4′-hydroxy-3′-t-butylphenyl) butyric acid] glycol ester may be used.

These antioxidants may be used alone or in combination of two or more kinds. Further, in order to sufficiently bring out the effect, it may be used in combination with a secondary antioxidant and, if necessary, in combination with a stabilizer such as an organic tin compound, a metal soap, a lead-based inorganic salt.

These antioxidants are used in an amount of 0.01 to 30 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the resin base material.
Add 0 parts by weight. The content of the antioxidant is 0.0
When the amount is less than 1 part by weight, deterioration of repetitive characteristics of recording and erasing cannot be sufficiently prevented, while when the compounding amount of the antioxidant exceeds 30 parts by weight, white turbidity is lowered and visibility is deteriorated.

The reversible thermosensitive recording layer may further contain various additives such as lubricants, antistatic agents, plasticizers, dispersants, surfactants and inorganic or organic fillers, if necessary. You may.

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 selected. 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 it is generally preferably 1 to 50 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.

Further, in order to make it easier 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. Further, an overcoat layer may be provided to protect the reversible thermosensitive recording layer from heat and pressure generated by a heating device such as a thermal head. Such overcoat layers include silicone-based, acrylic-based, fluorine-based,
Urethane-based organic substances, or SiO ₂ , Si
Inorganic substances such as O, MgO, ZnO, TiO ₂ , Al ₂ O ₃ and 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.

The reversible recording material of the present invention is 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.

Magnetic cards having such a reversible thermosensitive 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.

[0027]

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 Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer 25 parts (UCC, VYHH) Aliphatic hydrocarbon Resin 2 parts (Nippon Zeon Co., Quintone B170) Hindered phenolic substances 0.7 parts (Sumitomo Chemical Co., GA80) Organic sulfur compounds 0.35 parts (Sumitomo Chemical Co., TP-D) Tetrahydrofuran 120 parts

A solution of the above composition was applied to a polyethylene terephthalate film (thickness 100 μm) using an applicator.
m) to give a dry film thickness of 15 μm to provide a reversible thermosensitive recording layer. The heat-sensitive recording material thus obtained was
C. × 1 minute) − (80 ° C. × 1 minute) was repeated for 20 cycles. After the test, the transparent temperature range of the material was measured by a static thermal coloring device (Okura Electric Co., Ltd.).
It was evaluated by measuring the optical density with a Macbeth densitometer RD-920 on a standard black plate.

Example 2 Composition Composition Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer 25 parts (UCC, VYHH) Aliphatic hydrocarbon Resin 2 parts (Nippon Zeon Co., Quintone B170) Hindered phenolic substances 0.04 parts (Sumitomo Chemical Co., GA80) Organic sulfur compounds 0.02 parts (Sumitomo Chemical Co., TP-D) HALS substances 0 .04 parts (Sumitomo Chemical Co., Ltd., TM-061) Tetrahydrofuran 120 parts A thermal recording material was prepared in the same manner as in Example 1 except that the solution having the above composition was used. The results of the same evaluation are shown in Table 1.
Shown in.

Example 3 Composition Composition Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer 25 parts (UCC, VYHH) Aliphatic hydrocarbon Resin 2 parts (Nippon Zeon Co., Quintone B170) Hindered phenolic substances 0.04 parts (Sumitomo Chemical Co., GM) Organic sulfur compounds 0.02 parts (Sumitomo Chemical Co., TP-D) HALS substances 0 .04 parts (Sumitomo Chemical Co., Ltd., TM-061) Tetrahydrofuran 120 parts A thermal recording material was prepared in the same manner as in Example 1 except that the solution having the above composition was used. The results of the same evaluation are shown in Table 1.
Shown in.

Example 4 Composition Compounding amount Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer 25 parts (UCC, VYHH) Aliphatic hydrocarbon Resin 2 parts (Nippon Zeon Co., Quintone B170) Hindered phenolic substances 0.04 parts (Sumitomo Chemical Co., MDP-S) Organic sulfur compounds 0.02 parts (Sumitomo Chemical Co., TP-D) HALS Substance 0.04 parts (TM-061, manufactured by Sumitomo Chemical Co., Ltd.) Tetrahydrofuran 120 parts A thermosensitive recording material was prepared in the same manner as in Example 1 except that the solution having the above composition was used. The results of the same evaluation are shown in Table 1.
Shown in.

[Comparative Example 1] Composition Blend amount Behenic acid (C ₂₁ H ₄₃ COOH) 7 parts Thiodipropionic acid 3 parts Vinyl chloride-vinyl acetate copolymer 25 parts (UCC, VYHH) Aliphatic hydrocarbon Resin 2 parts (Nippon Zeon Co., Quintone B170) Epoxy antioxidant 0.2 parts (Sakai Chemical Co., ERL-4221) Tetrahydrofuran 120 parts Heat sensitive in the same manner as in Example 1 except that the solution having the above composition was used. A recording material was prepared. The results of the same evaluation are shown in Table 1.
Shown in.

[Comparative Example 2] A thermosensitive recording material was prepared in the same manner as in Example 1 except that no antioxidant was used. The results of the same evaluation are shown in Table 1.

Table 1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Transparent temperature range (℃) Initial period After recycling ━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 31.7 23.7 〃 2 32.3 20.4 〃 3 26. 4 23.2 〃 4 30.2 21.5 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Comparative Example 1 6.4 3.2 〃 2 31.3 15.0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0036]

The reversible thermosensitive recording material of the present invention retains a wide transparent temperature region of 20 ° C. or more after repeated recording and erasing, and is easily erased by a thermal head and has good storage stability.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G06K 19/06 G11B 5/80 7303-5D 8623-5L G06K 19/00 B (72) Inventor Shinagawa Takae Shimohozumi 1-2-2, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (3)

[Claims] 1. A reversible thermosensitive recording material comprising a base material and a reversible thermosensitive recording layer containing a resin base material and an organic low molecular weight substance, wherein a phenolic antioxidant is blended in the thermosensitive recording layer. Reversible thermosensitive recording material. 2. A magnetic card in which the reversible thermosensitive recording material according to claim 1 is provided on a magnetic card member. 3. The magnetic card according to claim 2, 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.