JP3348477B2 - 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 decolor, and a polymer is heated, for example, by 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 necessary 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 method comprising applying a composition containing a leuco dye, a developing / decoloring agent which reacts with the leuco dye to repeatedly form or erase a color and a polymer on a support. In the medium, the developer is 1-amino-5-naphtho.
, 1-amino-6-naphthol and 2-amino-7
-A compound selected from the group consisting of naphthol
Easily achieved by a reversible thermosensitive recording medium characterized by
It is.

[0007]

[0008]

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 / erasing agent in the reversible thermosensitive recording medium of the present invention reacts with the leuco dye to repeat coloring or erasing, and comprises 1-amino-5-naphthol, 1-amino-5-naphthol,
-Amino-6-naphthol and 2-amino-7-naphthol
A compound selected from the group consisting of

[0012]

[0013]

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 lactone was added to 6 g of a toluene solution of 11% polymethyl methacrylate (Mitsubishi Rayon BR-80) (hereinafter abbreviated as PMMA), treated with a paint shaker for 1 hour, and dispersed. A liquid was prepared. Further, 1.5 g of 1-amino-7-naphthol was added to 6 g of the 11% PMMA toluene solution, and 1 g of the solution was added using a paint shaker.
A time treatment was performed to prepare a dispersion.

Next, 1 g of the former dispersion was added to 1 g of the latter dispersion.
4 g were mixed to prepare a coating solution. This solution was applied to a 100 μm thick milk-white polyethylene terephthalate sheet 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 is applied to a thermal head (TH-PMD printing conditions 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 with TR927 manufactured by MACBETH, 2.
It was 15 (0.26 before the test). The reflection density after leaving at room temperature (25 ° C.) for 1 hour was 2.08, indicating that the device had good memory properties.

Next, the printed image was erased by pressing for 1 second with a hot stamp heated to 70 ° C. The measured reflection density was 0.57. 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 m-aminophenol was used in place of 1.5 g of 1-amino-7-naphthol, and the others were treated in the same manner as in Example 1 to obtain reversible thermosensitive recording. 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 developed. The reflection density of color development was 1.50, lower than that of Example 1 (0.11 before the test). Further, the reflection density after leaving at room temperature (25 ° C.) for 1 hour was 0.31, and the color was considerably erased and the memory property was insufficient.

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-anilinofluoran was replaced by 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 treating in the same manner as in Example 1 except for the above. 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. After leaving for 1 hour at the time of color development and room temperature (25 ° C), the reflection densities of the decolorization were 2.11, respectively.
They were 2.10 and 0.50 (0.20 before the test). Further, printing and erasing were repeated to confirm color development and erasing.

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 2-amino-7-naphthol instead of 1.5 g
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 color developing operation was performed, the color became red, and when the color erasing operation was performed, the color was erased. After leaving the color developing room temperature (25 ° C.) for 1 hour, the reflection densities of the decolorization were 2.01, 1.98 and 0.49, respectively (0.21 before the test). Further, printing and erasing were repeated to confirm color development and erasing.

[0025]

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 the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A reversible thermosensitive recording medium comprising a support and a composition containing a leuco dye, a color developing / erasing agent which repeats coloring or decoloring by reacting with the leuco dye, and a polymer. The decoloring agent is 1-amino-5-naphthol,
1-amino-6-naphthol and 2-amino-7-naph
A reversible thermosensitive recording medium , which is a compound selected from the group consisting of tolls.