JP4149180B2 - Reversible thermosensitive recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound, and can control the formation of a color image and erase it by controlling thermal energy. The present invention relates to a reversible thermosensitive recording medium.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, heat-sensitive recording media using a color developing reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. It is used in printers such as facsimiles, word processors, and scientific instruments. However, any of these conventional recording media in practical use has irreversible color development, and once recorded images cannot be erased and used repeatedly.
[0003]
On the other hand, according to the patent publication, a recording medium capable of reversibly developing and decoloring has also been proposed. For example, Japanese Patent Application Laid-Open No. 60-193691 using a combination of gallic acid and phloroglucinol as a developer. Japanese Laid-Open Patent Publication No. 61-237684, which uses a compound such as phenolphthalein or thymolphthalein as a developer, and Japanese Unexamined Patent Publication No. Sho-63 containing a homogeneous solution of a color former, a developer and a carboxylic acid ester in the recording layer 62-138556, JP-A-62-138568 and JP-A-62-140881, JP-A-63-173684 using an ascorbic acid derivative as a developer, and bis (hydroxyphenyl) as a developer JP-A-2-188293, JP-A-2-188294 and the like using a salt of acetic acid or gallic acid and a higher aliphatic amine are disclosed. There.
[0004]
Furthermore, the present inventors previously used an organic phosphoric acid compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer in Japanese Patent Application Laid-Open No. 5-124360, and developed this color. By combining with the leuco dye, which is an agent, color development and decoloration can be easily performed under heating and cooling conditions, and the color development and decoloration state can be stably maintained at room temperature. In addition, a reversible thermosensitive coloring composition capable of repeating coloring and decoloring and a reversible thermosensitive recording medium using the same in a recording layer have been proposed. Thereafter, use of a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group has been proposed (see Japanese Patent Application Laid-Open No. 6-210954).
[0005]
A reversible thermosensitive recording medium produced using these materials can be developed with a thermal head, erased with a hot stamp, etc., and repeatedly developed / decolored.
[0006]
[Problems to be solved by the invention]
However, in recent years, there has been a demand for shortening the rewriting time of a recording medium and further erasing an image using a thermal head, and these reversible thermosensitive recording media cannot cope with erasing at a high speed.
[0007]
In addition, in order to improve the erasability at high speed, there is a problem that the heat-resistant storage stability is lowered by lowering the erasing temperature, and a reversible thermosensitive recording medium having both high-speed erasability and heat-resistant storability It has not been provided.
[0008]
The present invention has was made in view of the above, excellent erasability at a high speed, and to provide an excellent reversible thermosensitive recording medium in the heat-resistant storage stability.
[0009]
[Means for solving the problems]
The invention according to claim 1 of the present invention uses an electron-donating color-forming compound and an electron-accepting compound on a support, and relatively develops color depending on at least one of a heating temperature and a cooling rate after heating. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermosensitive composition capable of forming a state, the main feature is that a compound of the following formula (1) is used in the reversible thermosensitive recording layer. And
[Chemical 2]
(R represents a hydrocarbon group having 8 or more carbon atoms which may have a substituent, and n represents an integer of 1 to 12)
[0010]
That is, when the present inventors conducted various studies on the high-speed erasability of the reversible thermosensitive recording medium, it was found that the high-speed erasability of the recording medium is improved by using the compound of the above formula (1) . .
[0011]
Although the detailed reason is not clear, in the aggregate structure composed of the leuco dye and developer that form a colored state and the compound represented by the above formula (1) of the present invention, these compounds have three long chains at the ends. Since the end of the alkyl group spreads in a plane, it is considered that the color developing structure formed by the developer and the leuco dye is likely to be destroyed in the color developing state. In a relatively low temperature region, the aggregation structure is stabilized by the aggregation force of the central isocyanuric ring, and it is considered that the density of the color image and the heat-resistant storage stability are maintained at a high level.
[0012]
The invention according to claim 2 of the present invention is mainly characterized by a reversible thermosensitive recording medium in which R is a chain hydrocarbon group.
[0013]
That is, R in the formula (1) represents a saturated or unsaturated hydrocarbon group having 8 or more carbon atoms, and this hydrocarbon group may have a substituent, but preferably a chain hydrocarbon group is In particular, a chain hydrocarbon group having 12 to 22 carbon atoms is preferably used.
[0014]
Examples of preferable structures of R are listed in Table 1, but are not particularly limited thereto. (In Table 1, m is any one of 1 to 3, and n, n ′, and n ″ represent an integer of 0 or more, but the total number of carbons in each structure is 8 or more.)
[0015]
[Table 1]
Of these, a chain hydrocarbon group is particularly preferred.
[0016]
Specific examples of the compound represented by the formula (1) used in the present invention are listed in Table 2 below. However, the present invention is not limited to these.
[0017]
[Table 2]
[0018]
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, known dye precursors such as phthalide compounds, azaphthalide compounds, and fluorane compounds. It is.
[0019]
Further, as a developer used in the recording layer, representative examples thereof include those described in JP-A-5-124360, JP-A-6-210554, JP-A-10-95175, and the like. is there. The developer used here is a structure having a color developing ability for developing a leuco dye in the molecule, such as a phenolic hydroxyl group, a carboxylic acid group, or a phosphate group, and a structure that controls the cohesion between molecules, such as a long It is a compound having one or more structures in which chain hydrocarbon groups are linked. The linking moiety may be via a divalent or higher valent linking group containing a hetero atom, 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 are disclosed in, for example, JP-A-9-290563 and JP-A-11-188969.
[0020]
The reversible recording layer using these leuco dye and developer develops and decolors by the process shown in FIG. When the initial decolored state (A) is heated, the leuco dye and the developer are melted and mixed at a temperature of T1 or higher (B), and when this state is rapidly cooled, the colored 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, and when it is cooled, the color erased state is the same as the initial state. Thus, the recording layer can be erased by controlling the heating temperature and the cooling rate after heating. Printing with this recording layer provides high contrast and excellent image quality. Further, it is excellent in storage stability and repeated durability of printing and erasing, and is particularly suitable as a 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 way as normal heat-sensitive recording, and erasing can be performed with a temperature-controlled heating roller, a heating element such as a ceramic heater, and a thermal head. It can be used with a small and simple rewrite recording device.
[0021]
In the reversible thermosensitive recording medium of the present invention, the leuco dye, the developer and the compound represented by the above formula (1) form a recording layer together with the resin. The resin used at this time is only required to be able to bind these materials on the support, and conventionally known resins are widely used. Among them, in order to improve durability during repetition, a resin that can be cured by heat, ultraviolet light, electron beam, 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. .
[0022]
In the present invention, an under layer, a protective layer, a back layer, and the like may be provided for improving color development sensitivity, durability, light resistance, and the like. Inorganic fillers, ultraviolet absorbers, lubricants, color pigments, and the like can be used.
[0023]
As a support for the reversible thermosensitive recording medium of the present invention, it is sufficient that the recording layer can be held, and paper, synthetic paper, PET film, and the like are preferably used. Moreover, you may affix and use on another through these support bodies.
[0024]
The invention according to claim 3 of the present invention is mainly characterized in that the reversible thermosensitive recording medium has a thermoreversible recording section and an information storage section.
[0025]
That is, by providing both the thermoreversible recording unit and the information recording unit having the reversible thermosensitive recording medium of the present invention using the compound of the formula (1) , the information stored in the information storage unit is thermally reversible. By displaying on the recording unit, information can be confirmed without a special device, and convenience is improved.
[0026]
The invention according to claim 4 of the present invention mainly has a reversible thermosensitive recording medium in which the information storage section is a magnetic recording layer or an IC.
[0027]
The main feature of the fifth aspect of the present invention is that the reversible thermosensitive recording medium is processed into a card shape or a sheet shape.
[0028]
The main feature of the invention described in claim 6 is that the reversible thermosensitive recording medium is used in the form of a roll.
[0029]
That is, these can be processed into a shape according to the application, and processed into a card shape, a sheet shape, a roll shape, and the like. Examples of products processed into cards include applications for prepaid cards, point cards, and credit cards, and those processed into sheets are printed when processed into general document sizes such as A4 size. By using the / erasing device, not only test printing but also temporary output such as circulation documents and conference materials can be widely used. Furthermore, what was processed into the roll shape can be used for a display board, a bulletin board, or an electronic blackboard by incorporating in a device having a printing / erasing section. Such a display device can be preferably used in a clean room or the like because it does not generate dust or dust.
[0030]
The seventh aspect of the present invention is mainly characterized in that the reversible thermosensitive recording medium has a print portion.
[0033]
【Example】
The following examples further illustrate the present invention. In the examples, “parts” and “%” are based on weight.
[0034]
(Example 1)
[Create recording layer]
1) 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts 2) developer of the following structure 10 parts
3) 4 parts of the compound with the following structure
4) A 15% tetrahydrofuran (THF) solution of acrylic polyol resin 170 parts
The composition was pulverized and dispersed to a mean 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 stirred well to prepare a recording layer coating solution.
[0036]
The recording layer coating solution having the above composition was applied on a white polyester film having a thickness of 250 μm using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to obtain a recording film having a thickness of about 8.0 μm. A layer was provided.
[0037]
[Create protection layer]
[0038]
The above composition was thoroughly dissolved and stirred to prepare a protective layer coating solution. The protective layer coating solution having the above composition was applied onto the recording layer using a wire bar, dried at 90 ° C. for 1 minute, and then passed through an ultraviolet lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min. After curing, a protective layer having a thickness of 3 μm was provided, and the reversible thermosensitive recording medium of the present invention was produced.
[0039]
(Example 2) except that the compound of Example 1 was replaced with a compound of the following structure was prepared a reversible thermosensitive recording medium in the same manner as in Example 1.
[0040]
[Chemical formula 5]
[0041]
Comparative Example 1 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the compound in Example 1 was omitted.
[0042]
Was prepared (Comparative Example 2) a reversible thermosensitive recording medium in the same manner as in except that the compound in Example 1 was changed to the compounds of the following examples 1.
[Chemical 6]
[0043]
Test 1 The color density produced was recorded on a recording medium manufactured by Okura Electric Co., Ltd. with 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.
[0044]
Test 2 The color image obtained in the unerased density test 1 was erased with a thermal tilt tester manufactured by Toyo Seiki Co., Ltd. at 130 ° C. for 1.0 second to test the density and background density of the image after erasing. Measurement was performed in the same manner as in 1. Next, the unerased density was calculated from the following formula.
Unerased density = (Density of image area after erasure)-(Background density)
[0045]
Test 3 The color image obtained in the heat-resistant storage stability test 1 was stored in an environment at 60 ° C. for 24 hours, and then the image density was measured using a Macbeth densitometer to determine the residual ratio (%) of the color image density. .
[0046]
The above results are shown in Table 3.
[0047]
[Table 3]
[0048]
【The invention's effect】
According to the present invention described above, various excellent effects can be obtained, such as being able to obtain a reversible thermosensitive recording medium excellent in high-speed erasability and excellent in heat-resistant storage stability.
[Brief description of the drawings]
FIG. 1 is a graph showing color development / decolorization characteristics of a reversible thermosensitive recording medium of the present invention.

Claims (7)

A reversible thermosensitive composition capable of forming a relatively colored state by using at least one of a heating temperature and a cooling rate after heating, using an electron-donating color-forming compound and an electron-accepting compound on a support. A reversible thermosensitive recording medium having a reversible thermosensitive recording layer, wherein the compound of the following formula (1) is used in the reversible thermosensitive recording layer.
(R represents a hydrocarbon group having 8 or more carbon atoms which may have a substituent, and n represents an integer of 1 to 12) 2. The reversible thermosensitive recording medium according to claim 1, wherein R is a chain hydrocarbon group. The reversible thermosensitive recording medium according to claim 1 or 2, wherein the reversible thermosensitive recording medium has a thermoreversible recording section and an information storage section. 4. The reversible thermosensitive recording material according to claim 3, wherein the information storage unit is a magnetic recording layer or an IC. 5. The reversible thermosensitive recording medium according to claim 1, wherein the reversible thermosensitive recording medium is processed into a card shape or a sheet shape. The reversible thermosensitive recording medium according to claim 1, 2, 3, or 4, wherein the reversible thermosensitive recording medium is used in a roll shape. The reversible thermosensitive recording medium according to claim 1, 2, 3, 4, 5, or 6, wherein the reversible thermosensitive recording medium has a printed portion.