JP2002274035A - Reversible heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible heat sensitive recording medium, which has a high color developing density and, in addition, is favorable in erasability and, at the same time, excellent in storage stability. SOLUTION: In the provided reversible heat sensitive recording medium having a reversible heat sensitive recording layer including a reversible heat sensitive composition, which at least consists of an electron donable compound and an electron acceptable compound so as to present relatively color developing state by the differences between their heating temperatures and/or between their cooling speeds after heating, a compound represented by general formula (1) is included as a color developing and decoloring controlling agent, in formula (1), R1 and R3 respectively and independently represent 6-22C chain-like hydrocarbon radicals having an unsaturated bonding or a hydroxyl group and R2 represents a 2-12C chain-like hydrocarbon radical or an aromatic hydrocarbon radical.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium, and more particularly, to a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound. The present invention relates to a reversible thermosensitive recording medium capable of forming and erasing a color image by controlling heat energy.

[0002]

2. Description of the Related Art Conventionally, an electron-donating color-forming compound (hereinafter, referred to as an electron-donating color-forming compound) has been proposed.
Thermal recording media utilizing a color development reaction between a color former or a leuco dye) and an electron-accepting compound (hereinafter sometimes referred to as a developer) are known, and include facsimile, word processor, and scientific measurement. Widely used for printers such as printers. However, these conventional recording media that have been put into practical use all have irreversible color development, and it is impossible to erase an image once recorded and use it repeatedly.

On the other hand, a recording medium capable of reversibly developing and decoloring has also been proposed. For example, a recording medium using a combination of gallic acid and phloroglucinol as a color developer (Japanese Patent Application Laid-Open No. 60-193691). Japanese Patent Application Laid-Open No. 61-237684), a recording layer containing a homogeneous solution of a color former, a developer, and a carboxylic acid ester in a recording layer. (Japanese Patent Application Laid-Open No. 62-138556,
138568 and JP-A-62-140881), those using an ascorbic acid derivative as a color developer (JP-A-63-173684), and bis (hydroxyphenyl) acetic acid or gallic acid as a color developer. Those using salts with aliphatic amines (JP-A-2-188293 and JP-A-2-188294) are known.

[0004] Further, the applicant of the present invention disclosed in Japanese Patent Laid-Open No. 5-124.
In JP-A-360, an organic phosphoric acid compound having a long-chain aliphatic hydrocarbon group, an aliphatic carboxylic acid compound or a phenol compound is used as a color developer, and a color is formed by combining this with a leuco dye as a color former. Decolorization can be easily performed by heating and cooling conditions, and its color development state and color erasure state can be stably maintained at room temperature, and reversible heat sensitivity that can repeat color development and color erasure A color forming composition and a reversible thermosensitive recording medium using the same in a recording layer were proposed. After that, it has been proposed to use a compound having a specific structure as a phenol compound having a long-chain aliphatic hydrocarbon group (Japanese Patent Application Laid-Open No. 6-210954).

A reversible thermosensitive recording medium manufactured using these materials can be colored by a thermal head or erased by a hot stamp or the like, and can be repeatedly colored and decolored. However, in these recording media, those having a high color density and a stable color image have poor color erasability and have a high temperature region at which sufficient color erasure is performed, and those having a low color erasure temperature region. And the image density is low and the stability of the image portion is poor.

[0006]

SUMMARY OF THE INVENTION The present invention solves such a conventional problem and provides a reversible thermosensitive recording medium having a high coloring density, good erasability, and excellent storage stability. The task is to do so.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies focusing on a coloring / decoloring controlling agent, and as a result, have completed the present invention.

That is, according to the present invention, on a support,
A reversible thermosensitive recording layer comprising a reversible thermosensitive composition comprising at least an electron donating compound and an electron accepting compound and capable of exhibiting a relatively colored state due to a difference in heating temperature and / or cooling rate after heating. In the formed reversible thermosensitive recording medium, a compound represented by the following general formula (1) is contained in the reversible thermosensitive recording layer as a coloring / decoloring control agent. Is provided.

[0009]

Embedded image [In formula (1), R ₁ and R ₃ each independently represent a chain hydrocarbon group having 6 to 22 carbon atoms having an unsaturated bond or a hydroxyl group, and R ₂ represents a chain hydrocarbon group having 2 to 12 carbon atoms. A group or an aromatic hydrocarbon group. ]

In the present invention, the following (i) to (i)
The reversible thermosensitive recording medium described in v) is included. (I) A reversible thermosensitive recording medium having a thermoreversible recording section and an information recording section. (Ii) the information recording unit is a magnetic recording layer or an integrated circuit (IC)
Reversible thermosensitive recording medium. (Iii) A reversible thermosensitive recording medium having a card-like shape. (Iv) A reversible thermosensitive recording medium having a roll shape.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various studies on stabilization of a color-developed image and lowering of a decoloring temperature, and found that an unsaturated bond or a hydroxyl group is contained in a chain hydrocarbon group. By doing so, it was found that the erasability at a relatively low temperature was improved. Although the detailed reason is not clear, a leuco dye and a color developer that form a color-developing state are represented by the following general formula (1)
Since the aggregated structure composed of the coloring and decoloring control agent represented by the formula has the effect of weakening the interaction between the dye and the developer when transitioning to the decoloring state, the decoloring is rapid at the decoloration start temperature or higher. It is thought to happen. Further, it is considered that the concentration is high due to the hydrogen bond formed by the two amide groups to form a stable color-developed aggregated structure.

[0012]

Embedded image [In formula (1), R ₁ and R ₃ each independently represent a chain hydrocarbon group having 6 to 22 carbon atoms having an unsaturated bond or a hydroxyl group, and R ₂ represents a chain hydrocarbon group having 2 to 12 carbon atoms. A group or an aromatic hydrocarbon group. ]

R ₁ and R ₃ in the general formula (1) are a hydrocarbon group having 6 to 22 carbon atoms having an unsaturated bond or a hydroxyl group. Preferred structures of the hydrocarbon group having an unsaturated bond include those represented by the following formulas (2) to (4).

Embedded image CH ₃ (CH ₂ ) nCH （CH (CH ₂ ) m- (2)

Embedded image CH ₃ (CH ₂ ) nCH ＝ CH (CH ₂ ) mCH ＝ CH (CH ₂ ) lCH- (3)

CH ₂ = CH (CH ₂ ) k- (4) In this case, n, m, l and k in the formula are numbers satisfying the above carbon number. The position of the hydroxyl group may be at the terminal or at the middle of the hydrocarbon group.

R ₂ is a chain hydrocarbon group or an aromatic group having 2 to 12 carbon atoms, and preferable structures include those represented by the following formulas (5) to (7).

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Embedded image In the formulas (5) and (7), o represents an integer of 2 to 12, and p and q each represent 1 or 2.

Specific examples of the coloring / decoloring controlling agent used in the present invention are shown below, but are not necessarily limited thereto.

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As the leuco dye used in the present invention, one or more compounds used in this type of reversible thermosensitive recording medium can be used. For example, phthalide compounds, azaphthalide compounds, fluoran compounds and the like can be used.
Known dye precursors can be mentioned.

As a representative example of the color developer used in the recording layer, for example, JP-A-5-124360
JP, JP-A-6-210954 and JP-A-10-210
For example, those used in the recording layer described in JP-A-95175 and the like can be mentioned. The developer used here has a structure having a color developing ability to develop a leuco dye in a molecule, for example, a phenolic hydroxyl group, a carboxylic acid group, a phosphate group, and a structure for controlling the cohesion between molecules, for example, And compounds having one or more structures in which long-chain hydrocarbon groups are linked. In the connecting part,
A divalent or higher valent linking group containing a hetero atom may be interposed, and the same linking group and / or aromatic group may be contained in the long-chain hydrocarbon group. Specific examples of such a reversible developer include, for example, JP-A-9-29056.
No. 3, JP-A-11-188969.

A reversible recording layer using these leuco dyes and a developer develops and decolors in the process shown in FIG.
When the initial decolored state (A) is heated, the leuco dye and the developer melt and mix at a temperature of T1 or higher to form a color (B), and when this state is rapidly cooled, the color development state is fixed. When the color development state (C) is heated, the color is erased at a temperature T2 lower than the color development temperature. Thus, the recording layer can be recorded and erased by controlling the heating temperature and the cooling rate after heating.

Printing with this recording layer has high contrast and excellent image quality. Further, it has excellent storage stability and durability against repeated printing and erasure, and is particularly suitable as the rewritable recording medium for documents of the present invention. Printing on a reversible recording medium using this recording layer can be performed with a thermal head in the same manner as ordinary thermal recording, and erasing is performed by a heating element such as a temperature-controlled heat roller, a ceramic heater, and a thermal head. Therefore, it can be used as a small and simple rewriting recording device.

In the reversible thermosensitive recording medium of the present invention,
The leuco dye, the color developer and the coloring / decoloring control agent form a recording layer together with the resin. The resin used at this time only needs to be able to bind these materials on the support, and conventionally known resins are widely used. Above all, in order to improve the durability at the time of repetition, a resin curable by heat, ultraviolet rays, electron beams or the like is preferably used, and a thermosetting resin using an isocyanate compound or the like as a crosslinking agent is particularly preferably used.

In the present invention, an under layer, a protective layer, a back layer and the like may be provided in order to improve the color sensitivity, the durability, and the light resistance. Organic and inorganic fillers, ultraviolet absorbers, lubricants, coloring pigments and the like can be used together with the resin. As a support of the reversible thermosensitive recording medium of the present invention, it is sufficient that the recording layer can be retained, and preferably, paper, synthetic paper, PET film or the like is used. Further, it may be used by attaching it to another material via these supports.

By providing both the thermoreversible recording section and the information recording section having the reversible thermosensitive recording medium of the present invention using the coloring / decoloring control agent represented by the general formula (1), the information recording section is provided. By displaying the information recorded in the thermoreversible recording section on the information, the information can be confirmed without using a special device, and the convenience is improved. As the recording unit used at that time, a magnetic recording layer, an IC recording unit, or the like is preferably used.

Further, these can be processed into a shape according to the use, and are processed into a card shape, a sheet shape, a roll shape and the like. The one processed into a card shape is applied to a prepaid card, a point card, and even a credit card, and the one processed into a sheet is processed into a general document size such as an A4 size. In this case, by using a printing / erasing device, it can be widely used not only for trial printing but also for temporary output such as circulation documents and conference materials. Further, the material processed into a roll shape can be used for a display board, a bulletin board, or an electronic blackboard by being incorporated in a device having a printing and erasing section. Such a display device can be preferably used in a clean room or the like because there is no generation of dust, dust, and the like.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. The “parts” and “%” are based on weight.

Example 1 [Preparation of Recording Layer] 1) 2 parts of 2-anilino-3-methyl-6-dibutylaminofluoran 2) 8 parts of a developer having the following structure

Embedded image 3) Color-decoloring control agent having the following structure: 4 parts

Embedded image 5) 150 parts of a 15% solution of acrylic polyol resin in tetrahydrofuran (THF)

The above composition was pulverized and dispersed to an average particle size of about 1 μm using a ball mill. 20 parts of Coronate HL (adduct type hexamethylene diisocyanate, 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. was added to the obtained dispersion, and the mixture was sufficiently stirred to prepare a recording layer coating liquid. The recording layer coating solution having the above composition was applied on a 188 μm-thick polyester film using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to obtain a film thickness of about 8.0 μm. Was provided.

[Preparation of Protective Layer] 1) Urethane acrylate-based UV-curable resin (C7-157 manufactured by Dainippon Ink and Chemicals, Inc.) 15 parts 2) Ethyl acetate 85 parts

The above composition was sufficiently dissolved and stirred to prepare a coating solution for the protective layer. The protective layer coating solution having the above composition was applied on the recording layer using a wire bar, dried at 90 ° C. for 1 minute, and then transferred under an ultraviolet lamp having an irradiation energy of 80 W / cm at a transport speed of 9 m / min. Hardens to a film thickness of 3
A protective layer having a thickness of μm was provided to produce a reversible thermosensitive recording medium.

Comparative Example 1 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the coloring / decoloring control agent was omitted.

Comparative Example 2 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following coloring / decoloring control agent was replaced by the following compound.

Embedded image

[Test 1] Coloring Density The prepared recording medium was printed by a thermal printing apparatus manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec, and the obtained image was measured by Macbeth densitometer RD-914. It was measured.

[Test 2] Density of remaining image The color image obtained in Test 1 was erased at 120 ° C. for 1 second using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd. And background density were measured in the same manner as in Test 1. Next, the remaining density was calculated from the following equation.

[Equation 1] remaining erase density = (density of image portion after erase)
-(Background density) The results are shown in Table 1.

[0033]

[Table 1]

Example 2 [Preparation of recording layer] 1) 2 parts of 2-anilino-3-methyl-6-dibutylaminofluoran 2) 8 parts of a developer having the following structure

Embedded image 3) Color-decoloring control agent having the following structure: 3 parts

Embedded image 5) 150 parts of a 15% solution of acrylic polyol resin in tetrahydrofuran (THF)

The above composition was pulverized and dispersed using a ball mill to an average particle size of about 1 μm. 20 parts of Coronate HL (adduct type hexamethylene diisocyanate, 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. was added to the obtained dispersion, and the mixture was sufficiently stirred to prepare a recording layer coating liquid. The recording layer coating solution having the above composition was applied on a white polyester film having a thickness of 188 μm using a wire bar.
After drying for 60 minutes, the recording layer was heated at 60 ° C. for 24 hours to form a recording layer having a thickness of about 8.0 μm.

[Preparation of Protective Layer] 1) Urethane acrylate UV curable resin (C7-157 manufactured by Dainippon Ink and Chemicals, Inc.) 15 parts 2) Ethyl acetate 85 parts

The above composition was sufficiently dissolved and stirred to prepare a coating solution for the protective layer. The protective layer coating solution having the above composition was applied on the recording layer using a wire bar, dried at 90 ° C. for 1 minute, and then under an ultraviolet lamp having an irradiation energy of 80 W / cm at a transport speed of 90 m / min. Then, a protective layer having a thickness of 3 μm was provided to prepare a reversible thermosensitive recording medium.

Comparative Example 3 A reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that the coloring / decoloring control agent was omitted.

Comparative Example 4 A reversible thermosensitive recording medium was prepared in the same manner as in Example 2, except that the following coloring / decoloring control agent was replaced by the following compound.

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[Test 3] Coloring density The prepared recording medium was printed with a thermal printing device manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec, and the obtained image was measured with a Macbeth densitometer RD-914. It was measured.

[0041]

[Test 4] Unerased density The color image obtained in Test 3 was erased with a thermal gradient tester manufactured by Toyo Seiki Co., Ltd. at 120 ° C. for 1 second. Was measured in the same manner as in Test 1. Next, the remaining density was calculated from the following equation.

## EQU2 ## Remaining erase density = (density of image portion after erasure)
-(Background density) The results are shown in Table 2.

[0042]

[Table 2]

[0043]

According to the present invention, there is provided a reversible thermosensitive recording medium having a high color density, good erasability, and excellent storage stability, which greatly contributes to the field of thermal recording. It is.

[Brief description of the drawings]

FIG. 1 is a diagram showing color development and decoloration characteristics of a reversible thermosensitive recording medium of the present invention.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Shibuya 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H026 AA09 DD43 DD53 FF01 FF25

Claims (5)

[Claims] 1. A reversible thermosensitive composition comprising at least an electron-donating compound and an electron-accepting compound on a support, which can exhibit a relatively colored state due to a difference in heating temperature and / or cooling rate after heating. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a substance, the following general formula (1)
A reversible thermosensitive recording medium characterized by containing a compound represented by the formula: Embedded image [In formula (1), R ₁ and R ₃ each independently represent a chain hydrocarbon group having 6 to 22 carbon atoms having an unsaturated bond or a hydroxyl group, and R ₂ represents a chain hydrocarbon group having 2 to 12 carbon atoms. A group or an aromatic hydrocarbon group. ] 2. The reversible thermosensitive recording medium according to claim 1, comprising a thermoreversible recording section and an information recording section. 3. The reversible thermosensitive recording medium according to claim 2, wherein the information recording section is a magnetic recording layer or an integrated circuit (IC). 4. The reversible thermosensitive recording medium according to claim 1, which has a card-like shape. 5. The reversible thermosensitive recording medium according to claim 1, wherein the recording medium has a roll shape.