JP3307014B2 - Reversible thermosensitive recording medium - Google Patents

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 color erasing / decoloring agent which reacts with the leuco dye to form or erase a color, and a polymer. Particularly, the present invention relates to a reversible thermosensitive recording medium having good color contrast, color density, repetition characteristics, durability and the like.

[0002]

2. Description of the Related Art A reversible thermosensitive recording medium comprising a leuco dye, a developer / decolorant which reacts with the leuco dye to form or erase a color, and a polymer is heated, for example, with a thermal head for a very short time. The reaction of the developing / decoloring agent as an acid takes precedence to form a color. This color development state is turned on by a hot stamp or the like.
By heating the Dar for a relatively long time, the reaction as a base becomes dominant and the color is erased.

This reversible thermosensitive recording medium is capable of developing and erasing colors by heat, and is expected to be used in many applications such as display media for cards such as prepaid cards, OA paper, displays and electronic blackboards. I have. 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 developing / erasing agent (Japanese Patent Laid-Open No. 2-188294) has been proposed.

[0004]

However, these reversible thermosensitive recording media sufficiently satisfy the required characteristics such as sensitivity of coloring and erasing, contrast of coloring and erasing, coloring density, repetition characteristics and durability. It wasn't.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to overcome such difficulties and to obtain an excellent reversible thermosensitive recording medium. By containing a specific colorant / decolorant having a naphthalene skeleton and a polymer that repeats, the sensitivity of color development / decoloration, contrast of color development / decoloration, color density, repetition characteristics,
They have found that the required characteristics such as durability are sufficiently satisfied, and have reached the present invention.

That is, an object of the present invention is to provide a reversible thermosensitive recording medium which is excellent in practicality such as color developing / erasing sensitivity, color developing / erasing contrast, and repetition characteristics. Thus, an object of the present invention is to provide a reversible thermosensitive recording comprising applying a composition containing a leuco dye, a developing / decoloring agent which reacts with the leuco dye and repeatedly develops or decolors and a polymer to a support. In the medium, the developer may be represented by the following general formula (1)

[0007]

Embedded image

(Wherein R ¹ , R ² and R ³ are each
And a hydrogen atom and a carbon number of 1 to 23 which may have a substituent.
An alkyl group or an aryl group which may have a substituent
And at least one of R ¹ , R ² and R ³
Is a group other than a hydrogen atom, and m represents 2 or 3. )
Which is easily achieved by a reversible thermosensitive recording medium characterized by being a naphthoic acid amine salt represented by the formula:

Hereinafter, the present invention will be described in detail. The leuco dye in the reversible thermosensitive recording medium of the present invention is not particularly limited, but, for example, fluorans, diarylphthalides, polycarbinols, leuco auramines, acyl auramines, aryl auramines, Lodamin B lactams, indolines, spiropyrans and the like.

Specific examples of these compounds include crystal violet lactone, malachite green lactone, 3-diethylamino-6-methylfluoran,
Diethylamino-6-methyl-7-chlorofluoran,
3-diethylamino-7-methoxyfluoran, 3-diethylamino-6-benzyloxyfluoran, 3-diethylamino-7-chlorofluoran, 2- (2-chlorophenylamino) -6-diethylaminofluoran,
2- (2-fluorophenylamino) -6-di-n-butylaminofluoran, 3-diethylamino-7-cyclohexylaminofluoran, 3-diethylamino-5
-Methyl-7-t-butylfluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-butylanilinofluoran, 3-cyclohexyl-6 Chlorofluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) -fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-pyrrolidino-7-cyclohexylaminofluoran, 3- N-methylcyclohexylamino-6-methyl-7-anilinofluoran,
3-N-ethylbenzylamino-6-methyl-7-anilinofluoran, 1,2-benzo-6-diethylaminofluoran, Michlerhydrol, crystal violet carbinol, malachite green carbinol,
N- (2,3-dichlorophenyl) leuco auramine,
N-benzyl auramine, N-acetyl auramine, N
Phenyl auramine, rhodamine B lactam, N,
3,3-trimethylindolinobenzspiropyran and the like can be mentioned.

The developing and erasing colorant in the reversible thermosensitive recording medium of the present invention is one which repeats color development or decoloration by reacting with the leuco dye, and comprises a naphthoic acid amine salt represented by the general formula (1). Is raised.

In the present invention, the amine in the naphthoic acid amine salt 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) each represent 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, An alkyl group which may have a substituent having 1 to 23 carbon atoms such as a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a pentadecyl group, and a stearyl group (for the substituent, a fluorine atom, Halogen atoms such as chloro, bromo and iodo atoms; phenyl, 3-methylphenyl, 4-methylphenyl, 4-butylphenyl, 4-butoxyphenyl, 4-octyl, 4-octyloxy , A 4-chlorophenyl group, a 4-bromophenyl group, a 3-iodophenyl group and the like, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms Or a phenyl group optionally substituted with a halogen atom; a methoxy group,
Ethoxy, butoxy, hexyloxy, octyloxy, methoxyethoxy, ethoxyethoxy,
An alkoxy group such as an ethoxyethoxyethoxy group or an alkoxyalkoxy group can be exemplified. An aryl such as a phenyl group which may have a substituent (as the substituent, an alkoxy group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen atom) or a naphthyl group; And the like.

Any of R ¹ , R ² and R ³ may be linked to each other to form a ring. Examples of these include piperidine which may be substituted with an alkyl group such as piperidine, 4-methylpiperidine, N-methylpiperidine, 2,6-dimethylpiperidine; morpholine,
-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 quinidine.

The naphthalene compound of the present invention may be prepared in advance, or separately added to a coating solution.
Salt may be used in the coating solution. As the polymer in the reversible thermosensitive recording medium of the present invention, specifically, polyethylene, poly (meth) acrylates such as poly (meth) acrylate, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, Vinyl compounds such as polyvinyl fluoride and addition polymers of vinyl compounds, polyvinylidene chloride, polyvinylidene fluoride, vinylidene cyanide, vinylidene fluoride / trifluoroethylene copolymer, vinylidene fluoride / tetrafluoroethylene copolymer, cyanidation Vinyl compound such as vinylidene / vinyl acetate copolymer or copolymer of fluorine compound, compound containing fluorine such as polytrifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene, nylon 6,
Polyamides such as nylon 66, polyimides, polyurethanes, polypeptides, polyesters such as polyethylene terephthalate, polycarbonates, polyoxymethylene,
Polyethers such as polyethylene oxide and polypropylene oxide, epoxy resins, polyvinyl alcohol, polyvinyl butyral, ethyl cellulose, cellulose acetate
And polystyrene.

When using the reversible thermosensitive recording medium of the present invention, the reversible thermosensitive recording medium is dissolved in water or an organic solvent or dispersed in water or an organic solvent. The recording layer can be formed by dissolving the polymer, applying the polymer on a support, and drying. 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 use ratio of the leuco dye to the developer / decolorant is generally 1:10 to 10: 1 (weight ratio), preferably 1: 1 to 1: 6. The ratio of (developing colorant + leuco dye): polymer used is 5: 1 to 1: 5.
(Weight ratio), generally 2: 1
１ ： 1: 2. The proportion of solids (developing 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. In addition, as a coating method, a known coating method such as a screen, a gravure, a bar, and a roll coating can be appropriately used. In order to improve the heat resistance and the friction 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. In order to improve the durability, an inorganic or organic pigment, a filler or the like may be added to the protective layer.

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

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

[0020]

Next, the present invention will be described in detail with reference to Examples and Comparative Examples.
The present invention is not limited to the following Examples and Comparative Examples. Example 1 1.5 g of crystal violet was polymethyl methacrylate (Mitsubishi Rayon BR-80) having a concentration of 11% (hereinafter referred to as PMMA).
) And treated with a paint shaker for 1 hour to prepare a dispersion. Furthermore, 3,5-
Stearylamine dihydroxy-2-naphthoate 1.5g
Was added to 6 g of the above 11% PMMA toluene solution, and the mixture was treated with a paint shaker for 1 hour to prepare a dispersion. Subsequently, 1 g of the former dispersion was mixed with 4 g of the latter dispersion to prepare a coating liquid.

The solution was applied to a 100 μm thick milky white polyethylene terephthalate sheet using a wire bar at 7 g / m ^2.
And dried to produce a reversible thermosensitive recording paper. When the recording paper thus produced was printed using a thermal head (TH-PMD printing conditions manufactured by Okura Electric Co., Ltd .: applied power 0.12 W / dot, pulse width 14 ms ON / OFF), a clear blue printed image was obtained. . The reflection density was measured by MACBETH T
It was 1.44 when measured with R927 (0.1 before the test).
Five). Next, the printed image was erased by pressing for 1 second with a hot stamp heated to 70 ° C. When the reflection density was measured, it was 0.
It was 21. When the printing operation and the erasing operation were repeated 20 times, the same printing and erasing were performed, and it was confirmed that the medium was a reversible thermosensitive recording medium.

Comparative Example 1 In Example 1, 1.5 g of dodecylamine gallate was used in place of 1.5 g of stearylamine 3,5-dihydroxy-2-naphthoate, and the other conditions were the same as in Example 1. By processing, a reversible thermosensitive recording paper was prepared. An attempt was made to print on the thermosensitive recording paper with a thermal head under the same conditions as in Example 1, but no color was formed and printing was not possible.

Example 2 In place of 1.5 g of the crystal violet lactone of Example 1, 1.5 g of 3-diethylamino-6-methyl-7-anilinofluorane was added to stearylamine 3,5-dihydroxy-2-naphthoate. 1.5 g of 1,4-dihydroxy-2-naphthoic acid hexadecylamine salt was used in place of 1.5 g, and the same treatment as in Example 1 was carried out except that 1.5 g of a reversible thermosensitive recording paper was produced. When the color developing operation was performed in the same manner as in Example 1, the color was developed to black, and when the color erasing operation was performed, the color was erased. The reflection densities of the developed and erased colors were 1.40 and 0.17, respectively (0.15 before the test). Further, printing and erasing were repeated to confirm color development and erasing.

Comparative Example 2 In place of 1.5 g of hexadecylamine 1,4-dihydroxy-2-naphthoate in Example 2, 1.5 g of hexadecylamine gallate was used. Similarly, a reversible thermosensitive recording paper was produced. Example for this thermal recording paper
Thermal printing was attempted under the same conditions as in No. 1, but no color was formed and printing was not possible.

Example 3 In place of 1.5 g of the crystal violet lactone of Example 1, 1,2-benzo-6-diethylaminofluoran
1.5 g of 3,7-dihydroxy-2-naphthoic acid heptadecylamine salt was used instead of 1.5 g of 3,5-dihydroxy-2-naphthoic acid stearylamine salt. This was processed to produce a reversible thermosensitive recording paper. When the color developing operation was performed in the same manner as in Example 1, the color became red, and when the color erasing operation was performed, the color was erased. The reflection densities of the developed and erased colors were 1.38 and 0.19, respectively (0.18 before the test). Further, printing and erasing were repeated to confirm color development and erasing.

Comparative Example 3 In place of 1.5 g of heptadecylamine 3,7-dihydroxy-2-naphthoate in Example 3, 1.5 g of heptadecylamine gallate was used. Similarly, a reversible thermosensitive recording paper was produced. Example for this thermal recording paper
Thermal printing was attempted under the same conditions as in No. 1, but no color was formed and printing was not possible.

Example 4 Instead of 1.5 g of 3,5-dihydroxy-2-naphthoic acid stearylamine salt of Example 1, 5,6,7-trihydroxy-2-
A reversible thermosensitive recording paper was prepared in the same manner as in Example 1, except that 1.5 g of didecylamine naphthoate was used. When the color developing operation was performed in the same manner as in Example 1, the color was developed to blue, and when the color erasing operation was performed, the color was erased. The reflection densities of the developed and erased colors were 1.65 and 0.21 respectively (0.19 before the test). Furthermore,
Printing and erasing were repeated to confirm the coloring and erasing.

Example 5 In place of 1.5 g of the crystal violet lactone of Example 1, 1.5 g of 3-diethylamino-6-methyl-7-anilinofluorane was added with stearylamine 3,5-dihydroxy-2-naphthoate. A reversible thermosensitive recording paper was prepared in the same manner as in Example 1, except that 1.7 g of 3,5-dihydroxy-2-naphthoic acid p-octylaniline salt was used instead of 1.5 g. When the color developing operation was performed in the same manner as in Example 1, the color was developed to black, and when the color erasing operation was performed, the color was erased. Further, printing and erasing were repeated to confirm color development and erasing.

Example 6 Instead of 1.5 g of the crystal violet lactone of Example 1, 1,2-benzo-6-diethylaminofluoran
1.5 g, 1.7 g of 3,5-dihydroxy-2-naphthoic acid 2-phenylethylamine salt was used in place of 1.5 g of 3,5-dihydroxy-2-naphthoic acid stearylamine salt, and the other conditions were the same as in Example 1. To produce a reversible thermosensitive recording paper. When the color developing operation was performed in the same manner as in Example 1, the color became red, and when the color erasing operation was performed, the color was erased. Further, printing and erasing were repeated to confirm color development and erasing.

Example 7 Instead of 1.5 g of the crystal violet lactone of Example 1, 3-diethylamino-5-methylfluoran 1.
5 g was replaced with 1.5 g of 3,5-dihydroxy-2-naphthoic acid stearylamine salt, 1.7 g of 3,5-dihydroxy-2-naphthoic acid dimethyltetradecylamine salt. This was processed to produce a reversible thermosensitive recording paper. When the color developing operation was performed in the same manner as in Example 1, the color was developed to orange, and when the color erasing operation was performed, the color was erased. Further, printing and erasing were repeated to confirm color development and erasing.

[0031]

The reversible thermosensitive recording medium obtained according to the present invention has particularly good color erasing sensitivity, color erasing can be performed with low energy, good repetition characteristics, and a card such as a pay-per-read card. It is useful for applications such as display media, OA paper, displays, and electronic blackboards.

────────────────────────────────────────────────── ─── Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (2)

(57) [Claims] 1. A reversible thermosensitive recording medium comprising a support and a composition containing a leuco dye, a color developing / decoloring agent which reacts with the leuco dye and repeats coloring or decoloring, and a polymer. The decoloring agent has the following general formula (1) : (Wherein R ¹ , R ² and R ³ are each a hydrogen atom,
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 is a hydrogen atom
And m represents 2 or 3. )
A reversible thermosensitive recording medium, which is an amine salt of phthoic acid . 2. The amine having a total carbon number of 8 or more.
The reversible thermosensitive recording medium according to claim 1, wherein: