JPH0776174A - Reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal recording medium in which developing and decoloring contrast, developing density, repeated characteristics, durability, etc., are excellent by incorporating developing and decoloring agent containing leuco dye and specific naphthalene skeleton for repeatedly developing or decoloring in reaction with the dye and polymer. CONSTITUTION:A reversible thermal recording medium is formed by coating a support with composition containing leuco dye, developing and decoloring agent for repeatedly developing or decoloring in reaction with the dye and polymer. The agent is naphthalene compound containing at least one hydroxyl group and one group of carboxylic acid amino salt represented by at least one formula (wherein R<1>-R<3> are H, 1-23C alkyl group which may have a substituent or an aryl group which may have a substituent and at least one of R<1>-R<3> is a group except H) as a substituent. As a result, the medium which has excellent developing and decoloring sensitivity, can develop or decolor with low energy and has excellent repeating characteristics can be obtained.

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 comprising a leuco dye, a developer and a decoloring agent which develops or decolors by reacting with the leuco dye and a polymer. In particular, the present invention relates to a reversible thermosensitive recording medium having good contrast in color development / erasing, color density, repeatability, durability and the like.

[0002]

2. Description of the Related Art A reversible thermosensitive recording medium comprising a polymer and a leuco dye and a developer / decolorizer which develops or decolors by reacting with the leuco dye is heated, for example, with a thermal head for a very short time. , The reaction of the developer and decolorizer as an acid takes precedence, and color is developed. This color development status can
By heating the dare for a relatively long time, the reaction as a base becomes dominant and the color disappears.

This reversible thermosensitive recording medium is capable of coloring and erasing by heat, and is expected to be used in many applications such as card type display media such as prepaid cards, OA paper, displays and electronic blackboards. There is. For example, as such a reversible heat-sensitive medium, a system using a leuco dye, a polymer, and an amine salt of gallic acid as a color-developing agent (JP-A-2-188294) has been proposed.

[0004]

However, these reversible thermosensitive recording media sufficiently satisfy the necessary characteristics such as the sensitivity of color development / decoloration, the contrast of color development / decoloration, color development density, repetitive characteristics and durability. I couldn't say that.

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies to overcome such difficulties and obtain an excellent reversible thermosensitive recording medium. As a result, a leuco dye, which reacts with the leuco dye to develop or decolorize. By containing a color developer / decolorizer having a specific naphthalene skeleton and a polymer, the sensitivity of color development / decoloration, contrast of color development / decoloration, color density, repetitive characteristics,
The present invention has been completed by finding that the required characteristics such as durability are sufficiently satisfied.

That is, an object of the present invention is to provide a reversible thermosensitive recording medium which is excellent in practicability in terms of color development / erasing sensitivity, color development / contrast contrast, repeating characteristics and the like. Therefore, the object of the present invention is to provide a reversible thermosensitive recording obtained by coating a support with a composition containing a leuco dye, a decoloring agent that reacts with the leuco dye to repeatedly develop or decolor, and a polymer. In the medium, the developer / decolorizer has at least one hydroxyl group and at least one of the following general formula (1):

[0007]

[Chemical 3]

(In the formula, R ¹ , R ² and R ³ are each a hydrogen atom or an optionally substituted carbon atom having 1 to 23 carbon atoms.
Of Alkyl group or aryl group which may have a substituent, and at least one of R ¹ , R ² and R ³ represents a group other than a hydrogen atom. ), Which is a naphthalene compound having a carboxylic acid amine salt group as a substituent, is easily achieved by a reversible thermosensitive recording medium.

The present invention will be described in detail below. The leuco dye in the reversible thermosensitive recording medium of the present invention is not particularly limited, for example, fluoranes, diarylphthalides, polycarbinols, leuco auramines, acyl auramines, aryl auramines, Examples include rhodamine B lactams, indolines, spiropyrans and the like.

Specific examples of these compounds include crystal violet lactone, malachite green lactone, 3-diethylamino-6-methylfluorane, and 3-diethylamino-6-methylfluorane.
Diethylamino-6-methyl-7-chlorofluorane,
3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 3-diethylamino-7-chlorofluorane, 2- (2-chlorophenylamino) -6-diethylaminofluorane,
2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5
-Methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexyl-6- Chlorofluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) -fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3- N-methylcyclohexylamino-6-methyl-7-anilinofluorane,
3-N-ethylbenzylamino-6-methyl-7-anilinofluorane, 1,2-benzo-6-diethylaminofluorane, Michler hydrol, crystal violet carbinol, malachite green carbinol,
N- (2,3-dichlorophenyl) leukoauramine,
N-benzyl auramine, N-acetyl auramine, N
-Phenyl auramine, rhodamine B lactam, N,
3,3-Trimethylindolinobenz spiropyran and the like can be mentioned.

The developer and decolorizer in the reversible thermosensitive recording medium of the present invention is a compound which reacts with the leuco dye to repeatedly develop or decolor, and has at least one hydroxyl group in the naphthalene ring and at least one of the above general formulas. It is a naphthalene-based compound having an amino group represented by (1) as a substituent. Examples of the naphthalene compound in the present invention include:
Although not particularly limited, preferred examples include aminonaphthol compounds represented by the above general formula (2).

In the present invention, the amine in the naphthalene compound represented by the general formula (1) is a primary, secondary or tertiary amine. R ¹ , R ² and R ^{3 in the} general formulas (1) and (2) are each a hydrogen atom; a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, 2-ethylhexyl group, nonyl group, decyl group, dodecyl group, tridecyl group, pentadecyl group, alkyl group which may have a substituent having 1 to 23 carbon atoms such as stearyl group (as a substituent, a fluorine atom, Halogen atom such as chloro atom, bromo atom, iodo atom; phenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-butylphenyl group, 4-butoxyphenyl group, 4-octyl group, 4-octyloxy group , 4-chlorophenyl group, 4-bromophenyl group, 3-iodophenyl group, and other C1-10 alkyl groups, C1-10 alkoxy groups Or a phenyl group which may be substituted with a halogen atom; a methoxy group,
Ethoxy group, butoxy group, hexyloxy group, octyloxy group, methoxyethoxy group, ethoxyethoxy group,
Examples thereof include an alkoxy group such as an ethoxyethoxyethoxy group and an alkoxyalkoxy group. ); A phenyl group which may have a substituent (the substituent includes an alkoxy group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen atom) or an aryl such as a naphthyl group. Groups and the like.

Further, any of R ¹ , R ² and R ³ may be connected to each other to form a ring. Examples of these include piperidine, 4-methylpiperidine, N-methylpiperidine, 2,6-dimethylpiperidine and the like, which may be substituted with an alkyl group; morpholine, 3
-Methylmorpholine, N-methylmorpholine, 2,6
-Morpholine which may be substituted with an alkyl group such as dimethylmorpholine and 3,5-diethylmorpholine; pyrrolidine which may be substituted with an alkyl group such as pyrrolidine and N-methylpyrrolidine; and quinicridine.

The naphthalene compound of the present invention may be prepared in advance, or it may be added separately to the coating solution.
Salt may be added in the coating liquid. As the polymer in the reversible thermosensitive recording medium of the present invention, specifically, polyethylene, poly (meth) acrylic acid ester such as poly (meth) acrylic acid methyl ester, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, Vinyl compounds such as polyvinyl fluoride, addition polymers of vinyl compounds, polyvinylidene chloride, polyvinylidene fluoride, vinylidene cyanide, vinylidene fluoride / trifluoroethylene copolymers, vinylidene fluoride / tetrafluoroethylene copolymers, cyanide Vinylidene / vinyl acetate copolymer, vinyl compound or fluorine compound copolymer, fluorine-containing compound such as polytrifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene, nylon 6,
Polyamide such as nylon 66, polyamide, polyimide, polyurethane, polypeptide, polyethylene terephthalate, polycarbonate, polyoxymethylene,
Polyethylene oxide, polypropylene oxide and other polyethers, epoxy resins, polyvinyl alcohol, polyvinyl butyral, ethyl cellulose, acetate cellulose
Examples thereof include polystyrene and polystyrene.

When the reversible thermosensitive recording medium of the present invention is used, it is placed in a system in which the leuco dye and the developer / decolorizer detailed above are dissolved or dispersed in water or an organic solvent. A recording layer can be prepared by dissolving a polymer, coating it on a support and drying it. Examples of the organic solvent used include aromatic solvents such as toluene and xylene, alcohol solvents such as isopropyl alcohol, and ketone solvents such as methyl isobutyl ketone and methyl ethyl ketone.

The ratio of the leuco dye to the decoloring agent used is generally 1:10 to 10: 1 (weight ratio), preferably 1: 1 to 1: 6. Also, the ratio of (developing / decoloring agent + leuco dye): polymer is 5: 1 to 1: 5.
(Weight ratio) is generally used, preferably 2: 1
~ 1: 2. The proportion of solids (developing / decoloring agent + leuco dye + polymer) in water or an organic medium is generally 5 to 60% by weight, preferably 10 to 40% by weight.

The support used in the present invention is not particularly limited, but for example, paper, synthetic paper, plastic film and the like can be used. As a coating method, a known coating method such as screen, gravure, bar, roll coating can be appropriately used. In order to improve durability such as heat resistance and abrasion resistance of the reversible thermosensitive recording medium of the present invention, a protective layer made of a thermoplastic resin or an ultraviolet curable resin can be provided on the recording layer. Inorganic or organic pigments, fillers and the like may be added to the protective layer in order to improve durability.

Further, in order to improve light resistance, an ultraviolet absorber, an infrared absorber or the like can be added to the protective layer. In addition, an additive for improving this light resistance,
A sensitizer for sharpening coloring and decoloring, an inorganic or organic pigment for improving durability, a filler, etc., a dye or pigment for coloring, a thickener, etc. are directly added to the recording layer. May be.

Although heat is used for image formation or image erasing of the present invention, a thermal head, a heat roller, a hot stamp or the like can be used as the method.

[0020]

EXAMPLES Next, the present invention will be described in detail with reference to Examples and Comparative Examples.
The present invention is not limited to the examples and comparative examples below. Example 1 1.5 g of crystal violet lactone was added to 6 g of a toluene solution of polymethacrylic acid methyl acrylate (Mitsubishi Rayon BR-80) (hereinafter abbreviated as PMMA) having a concentration of 11%, and treated with a paint shaker for 1 hour to disperse. A liquid was prepared. Furthermore, 1.5 g of 1-amino-7-naphthol was added to 6 g of the toluene solution of 11% PMMA, and the mixture was mixed with a paint shaker.
It was treated for a period of time to prepare a dispersion liquid.

Then, 1 g of the dispersion liquid of the former is added to the dispersion liquid of the latter.
A coating liquid was prepared by mixing 4 g. This solution was coated on a milky-white polyethylene terephthalate sheet having a thickness of 100 μm using a wire bar so as to be 7 g / m ² and dried to prepare a reversible thermosensitive recording paper. The recording paper produced in this manner was used as a thermal head (TH-PMD printing condition manufactured by Okura Electric Co., Ltd .:
When printing was performed using an applied power of 0.14 W / dot and a pulse width of 14 ms ON / OFF), a clear blue printed image was obtained. When the reflection density was measured by TR927 manufactured by MACBETH, 2.
It was 15 (0.26 before the test). The reflection density after standing at room temperature (25 ° C.) for 1 hour was 2.08, indicating good memory properties.

Then, the printed image was erased by pressing with a hot stamp heated to 70 ° C. for 1 second. The reflection density was measured and found to be 0.57. When the printing operation and the erasing operation were repeated 20 times, the same printing and erasing were possible, and it was confirmed that the recording medium was a reversible thermosensitive recording medium. Comparative Example 1 In Example 1, 1.5 g of m-aminophenol was used in place of 1.5 g of 1-amino-7-naphthol, and the same process as in Example 1 was repeated except that reversible thermosensitive recording was performed. Paper was made. When printing was performed on this thermosensitive recording paper with a thermal head under the same conditions as in Example 1, a blue color was formed. The color reflection density was 1.50, which was lower than that in Example 1 (0.11 before the test). In addition, the reflection density after standing at room temperature (25 ° C.) for 1 hour was 0.31, which was considerably decolored and the memory property was insufficient.

Example 2 Instead of 1.5 g of crystal violet lactone of Example 1, 1.5 g of 3-diethylamino-6-methyl-7-anilinofluorane was used instead of 1.5 g of 1-amino-7-naphthol. A reversible thermosensitive recording paper was prepared by using 1.5 g of -amino-6-naphthol and the same treatment as in Example 1 except for the above. In the same manner as in Example 1, when a color developing operation was performed, a black color was produced, and when a color erasing operation was performed, the color was erased. After leaving for 1 hour at color development and room temperature (25 ° C), the respective reflection densities of decolorization are 2.11.
The values were 2.10 and 0.50 (0.20 before the test). Further, printing and erasing were repeated to confirm coloring and erasing.

Example 3 Instead of 1.5 g of crystal violet lactone of Example 1, 1,2-benzo-6-diethylaminofluorane was used.
1.5 g of 2-amino-7-naphthol in place of 1.5 g of 2-
A reversible thermosensitive recording paper was prepared in the same manner as in Example 1 except that 1.5 g of amino-5-naphthol was used. Example 1
Similarly, when the coloring operation was performed, the color was red, and when the erasing operation was performed, the color was erased. After standing for 1 hour at room temperature (25 ° C), the reflection densities of the decolored products were 2.01, 1.98 and 0.49 (0.21 before the test), respectively. Further, printing and erasing were repeated to confirm coloring and decoloring.

[0025]

INDUSTRIAL APPLICABILITY The reversible thermosensitive recording medium obtained by the present invention has particularly good coloring and decoloring sensitivity, can be colored and decolored by low energy, and has good repetitive characteristics, and it is a card such as a paid card. It is useful for various kinds of display media, office paper, displays and electronic blackboards.

Claims (2)

[Claims] 1. A reversible thermosensitive recording medium prepared by coating a support with a composition containing a leuco dye, a decoloring agent that reacts with the leuco dye to repeatedly develop or decolor, and a polymer. The decolorizer has at least one hydroxyl group and at least one of the following general formula (1): (In the formula, R ¹ , R ² and R ³ are each a hydrogen atom,
Represents an alkyl group having 1 to 23 carbon atoms which may have a substituent or an aryl group which may have a substituent, and at least one of R ¹ , R ² and R ³ , Represents a group other than a hydrogen atom. ) A reversible thermosensitive recording medium, which is a naphthalene compound having a carboxylic acid amine salt group as a substituent. 2. The naphthalene compound according to claim 1 is represented by the following general formula (2): (In the formula, R ¹ , R ² and R ³ are each a hydrogen atom,
Represents an alkyl group having 1 to 23 carbon atoms which may have a substituent or an aryl group which may have a substituent, and at least one of R ¹ , R ² and R ³ , It represents a group other than a hydrogen atom, and m represents an integer of 1 to 3. The reversible thermosensitive recording medium according to claim 1, which is an aminonaphthol compound represented by the formula (1).