JP3321940B2 - 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 and a color erasing / decoloring agent which reacts with the leuco dye to form or decolor. 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 and a color erasing / decoloring agent which reacts with the leuco dye to form or erase a color, for example, by controlling a cooling rate after heating, to form a colored state or an erased state. Can be changed to a color state. A 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. Examples of such a reversible thermosensitive medium include I
S &T's 9th International
Congress on Advances in
NIP Technologies, 413 (199
No. 3) discloses a reversible thermosensitive recording medium comprising a leuco dye and an acidic compound having a long-chain alkyl group.

[0003]

However, in these conventional reversible thermosensitive recording media, the sensitivity of coloring and erasing, the stability of coloring and erasing, the contrast of coloring and erasing, the coloring density, the repetition characteristics, the durability, etc. Was not sufficiently satisfied.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the recording layer comprising a leuco dye and a polycyclic phenolic compound having a specific skeleton as a color developer has been developed. The inventor has found that the reversible thermosensitive recording medium sufficiently satisfies required characteristics such as sensitivity of coloring and erasing, contrast of coloring and erasing, coloring density, repetition characteristics, and durability, and has reached the present invention. That is, the object of the present invention is to
An object of the present invention is to provide a reversible thermosensitive recording medium which is excellent in practicality such as coloring and erasing sensitivity, coloring and erasing contrast, and repetition characteristics. Thus, an object of the present invention is to provide a reversible thermosensitive recording medium comprising a recording layer containing a leuco dye and a color developing / decoloring agent which reacts with the leuco dye to form or decolor, wherein the color developing / developing agent has the following general formula: Equation (1)

[0005]

Embedded image

X represents a direct bond or a divalent organic residue,
R represents a monovalent organic residue. Where ring A is a benzene ring
X is -C when ring B is an aromatic hydrocarbon ring
(R ′) = C (R ″) — CONH— (wherein R ′ and
R ″ represents a hydrogen atom or a lower alkyl group. Group other than)
And R has no aliphatic hydrocarbon group having 6 or more carbon atoms.
It is a monovalent organic residue. This is easily achieved by a reversible thermosensitive recording medium characterized by being a polycyclic phenolic compound represented by the formula (1). Hereinafter, the present invention will be described in detail. The reversible thermosensitive recording medium of the present invention comprises a recording layer containing a leuco dye and a specific skeleton developing / decoloring agent which reacts with the leuco dye to form or decolor.

The reversible thermosensitive recording medium of the present invention maintains a color-developed state by being heated and colored, and then rapidly cooled.
After color development, the color can be changed to a decolored state by slow cooling. As the heating means, any means may be used, but a thermal head, a heat roller, a hot stamp and the like can be used. In order to maintain the color-developed state after the color development, heating is performed for a very short time with a thermal head, or when heated by other means, the color is developed and then rapidly cooled by contacting a low-temperature object or the like. It can be done by doing. In order to change to the decolored state, heating can be performed for a relatively long time on the order of seconds using a heat roller, a hot stamp, or the like, and then the heat source is removed, and then the material is gradually cooled by allowing it to cool. The leuco dye in the reversible thermosensitive recording medium of the present invention is not particularly limited,
For example, fluorans, diarylphthalides, polycarbinols, leuco auramines, acyl auramines, aryl auramines, rhodamine β-lactams,
Examples include indolines and spiropyrans.

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 agent in the reversible thermosensitive recording medium of the present invention reacts with the leuco dye to repeat coloring or erasing, and is represented by the general formula (1):
It has a structure in which a hydrocarbon residue having a hydroxyl group and a hydrocarbon residue having a monovalent organic residue are directly bonded or bonded by a divalent organic residue. In the general formula (1),

[0010]

Embedded image

Examples include alkyl groups such as methyl group, ethyl group and propyl group, alkoxy groups such as methoxy group, ethoxy group and propoxy group, fluorine atom, chloro element, halogen atom such as bromo atom and iodo atom, and hydroxyl group. .

[0012]

Embedded image

Alkyl groups such as methyl group, ethyl group and propyl group, alkoxy groups such as methoxy group, ethoxy group and propoxy group, fluorine atom, chloro atom, bromo atom,
Examples include a halogen atom such as an iodine atom.

X represents a direct bond or a divalent organic residue. Is not particularly limited as divalent organic residues _{but, -OCH 2 -, - CH 2} O - ,, NHCH 2 -,
_{-CH 2 CH 2 -, - OCO} -, - COO -, - CON
H- or -NHCO- indicates, R represents, -R ^1, -O
R ¹ , -NHR ¹ , -OCOR ¹ , -COOR ¹ , -C
ONHR ¹ , —NHCOR ¹ , —OCOOR ¹ or —N
HCOOR ¹ (R ¹ is an alkyl group having 1 to 23 carbon atoms,
Represents a cyclohexyl group or a phenyl group, each of which may be substituted with a halogen atom, a hydroxyl group, an alkyl group, an alkoxy group or an alkoxyalkoxy group. ) Is particularly preferred.

The substituent R ¹ is ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, tridecyl, pentadecyl, Represents an alkyl group having 1 to 23 carbon atoms such as a stearyl group, a cyclohexyl group or a phenyl group. The alkyl group has 1 to 1 carbon atoms.
It is preferably 5. The alkyl group, cyclohexyl group, and phenyl group each may have a substituent, and examples of the substituent include a fluorine atom, a chlorine atom, a bromo atom, a halogen atom such as an iodo atom, a hydroxyl group, and a methoxy group. Ethoxy group, butoxy group, hexyloxy group, octyloxy group, methoxyethoxy group, ethoxyethoxy group, ethoxyethoxyethoxy group and other alkoxy groups or alkoxyalkoxy groups. Here, the ring A is a benzene ring,
When B is an aromatic hydrocarbon ring, X is -C (R ') =
C (R ″) — CONH— (wherein R ′ and R ″ are hydrogen atoms
And a lower or lower alkyl group. ), R ¹
Is an alkyl group having 5 or less carbon atoms. Hereinafter, typical examples of the compound represented by the general formula (1) will be given, but the compounds used in the present invention are not limited to these specific examples unless they exceed the gist thereof.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

Embedded image More specifically, the developing / decoloring agent of the general formula (1) includes the compounds shown in Table 2 below.

[0022]

[Table 6]

[0023]

[Table 7]

[0024]

[Table 8]

[0025]

[Table 9]

[0026]

[Table 10]

[0027]

[Table 11]

In the reversible thermosensitive recording medium of the present invention,
To the leuco dye and developer / decolorant described in detail above, a polymer is appropriately added, heated and melted, applied to a support, and dried to form a recording layer. , A polymer or the like is dissolved or dispersed in water, an organic solvent or a mixed solvent thereof, coated on a support, and dried to form a recording layer.

As the polymer, for example, polyethylene,
Poly (meth) acrylates such as methyl poly (meth) acrylate, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, addition polymers of vinyl compounds such as polyvinyl fluoride and vinyl compounds, polyvinylidene chloride, polyvinylidene fluoride , Vinylidene cyanide,
Copolymer of vinyl compound or fluorine compound such as vinyldene fluoride / trifluoroethylene copolymer, vinylidene fluoride / tetrafluoroethylene copolymer, vinylidene cyanide / vinyl acetate copolymer, polytrifluoroethylene, polytetrafluoroethylene Compounds containing fluorine such as ethylene and polyhexafluoropropylene, polyamides such as nylon 6, nylon 66, polyimides, polyurethanes, polypeptides, polyesters such as polyethylene terephthalate, polyethers such as polycarbonate, polyoxymethylene, polyethylene oxide and polypropylene oxide, and epoxy Resin, polyvinyl alcohol, polyvinyl butyral, ethyl cellulose, cellulose acetate, polystyrene and the like can be mentioned.

Examples of the organic solvent to be 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 and the decoloring agent is 20: 1 to 1
It is common to use 1:20 (weight ratio), 5: 1
１ ： 1: 10 is preferred. In addition, a developer / decomposer + leuco dye:
The polymer is generally used at a ratio of 20: 1 to 1:20 (weight ratio), preferably 10: 1 to 1: 5.
Further, the ratio of solid content (developing agent + leuco dye or developing agent + leuco dye + polymer) in water or an organic medium is 5 to 5.
It is generally selected from the range of 60% by weight, with 10-40% being preferred. As the support used in the present invention, 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.
On the reversible thermosensitive recording medium of the present invention, the heat resistance of the recording layer,
In order to improve durability such as abrasion resistance, thermoplastic resin or
A protective layer made of an ultraviolet curable resin may be provided. 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 may be added to the protective layer. In addition, dyes or pigments for coloring, such as additives for improving light resistance, sensitizers for sharpening color development and erasing, inorganic or organic pigments for improving durability, fillers, etc. A tackifier or the like may be directly added to the recording layer.

[0031]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 0.05 g of crystal violet lactone was mixed with 0.15 g of p- (trans-4-n-propylcyclohexyl) phenol, sandwiched between cover glasses to a thickness of 7 μm, and heated. It developed a blue color. Further, when the mixture was rapidly cooled to 0 ° C. (contacted with ice water), a clear blue color was maintained. Also, without quenching, 2
When left at 5 ° C. and cooled slowly, the clear blue color disappeared and the color changed to almost colorless. The reflection density of MACBETH TR9
When measured at 27, the reflection density in the blue color development state is:
It was 2.83. The decolored state after slow cooling was 0.30. When coloring and erasing were repeated 20 times, similar coloring and erasing were confirmed.

Example 2 0.05 g of the crystal violet lactone of Example 1
In place of 3-diethylamino-6-methyl-7-anilinofluoran, 0.05 g of p- (trans-4-
Instead of 0.15 g of n-propylcyclohexyl) phenol, 0.15 g of 4- (4-n-octyloxyphenyl) phenol was used, and the others were treated in the same manner as in Example 1. , The color changes to black,
The color was erased when the color was erased. The reflection densities of coloring and decoloring were 2.78 and 0.32, respectively. Further, coloring and decoloring were repeated 20 times, and coloring and decoloring were confirmed.

Example 3 In the same manner as in Example 1 except that 0.15 g of each of the following color erasing agents was used instead of 0.15 g of p- (trans-4-n-propylcyclohexyl) phenol in Example 1. After processing, the color was developed in the same manner as in Example 1, and the color was changed to blue, and the color was erased when the color was erased. The respective reflection densities of color development and decoloration in each case are shown in Table 3 below.

[0034]

[Table 12]

Example 4 0.25 g of crystal violet lactone and 0.75 g of p- (trans-4-n-propylcyclohexyl) phenol were mixed with a vinyl chloride-vinyl acetate copolymer (400 × 150 ml, manufactured by Zeon Corporation). Was added to a solution containing 1 g of methyl ethyl ketone containing 0.25 g and 4 g of toluene, and treated with a paint shaker for 1 hour to prepare a dispersion. Using a wire bar, 7 g of this solution was placed on a 100 μm thick milk-white polyethylene terephthalate sheet.
/ M ² and dried to prepare a reversible thermosensitive recording paper. The recording paper thus produced was heated at 115 ° C. in the same manner as in Example 1 to develop a color, and further erased in the same manner. The reflection densities for coloring and decoloring are respectively 1.
2,0.13. When the printing operation and the erasing operation were repeated 20 times, similar coloring and erasing were confirmed.

COMPARATIVE EXAMPLE 1 0.75 g of N-lauroyl-p-amino-phenol was used in place of 0.75 g of p- (trans-4-n-propylcyclohexyl) phenol in Example 4, and the others were the same as in Example 4. In the same manner as described above, a reversible thermosensitive recording paper was prepared. When color was formed on this thermosensitive recording paper under the same conditions as in Example 4, the reflection density of the color formation was 0.3, and the color formation sensitivity was poor.

Example 5 In place of 0.75 g of p- (trans-4-n-propylcyclohexyl) phenol of Example 4, Table 3 of Example 3 A reversible thermosensitive recording paper was prepared by using 0.75 g of the compound of No. 5 and treating in the same manner as in Example 4 except for the above. The recording paper produced in this manner was applied to a thermal head (TH-PMD manufactured by Okura Electric Co., Ltd., printing conditions: applied power 0.14 W).
/ Dot, pulse width 14 ms ON / OFF), a clear blue printed image was obtained. The measured reflection density was 1.10. The reflection density after leaving at room temperature (25 ° C.) for 1 hour was 1.10, indicating that it had good memory properties. Next, the printed image was erased by pressing for 1 second with a hot stamp heated to 120 ° C. The measured reflection density was 0.40. When printing and erasing operations were repeated 20 times, similar printing and erasing were confirmed.

Comparative Example 2 Comparative Example 1 Using the reversible thermosensitive recording paper prepared, Example 5
The printing operation was performed in the same manner as described above. The reflection density of color development was 0.94. The reflection density after leaving at room temperature (25 ° C.) for 1 hour was 0.36, and the color was considerably erased and the memory property was insufficient.

[0039]

The reversible thermosensitive recording medium obtained according to the present invention is capable of developing color by heat. In particular, the coloring density, the stability of coloring and erasing, the contrast of coloring and erasing, the coloring density, the repetition characteristics, It has good durability and is useful for applications such as display media for cards such as prepaid cards, OA paper, displays, and electronic blackboards.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-210954 (JP, A) JP-A-6-278361 (JP, A) JP-A-6-270540 (JP, A) JP-A-6-270540 171225 (JP, A) JP-A-6-344673 (JP, A) JP-A-6-344672 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5 / 34

Claims (3)

(57) [Claims] 1. A reversible thermosensitive recording medium comprising a recording layer containing a leuco dye and a color erasing / decoloring agent which reacts with the leuco dye to form or decolor, wherein the color erasing / decoloring agent is represented by the following general formula (1): Formula 1 X represents a direct bond or a divalent organic residue, and R represents a monovalent organic residue. Here, ring A is a benzene ring and ring B
Is an aromatic hydrocarbon ring, X is -C (R ') = C
(R ″) — CONH— (wherein R ′ and R ″ are hydrogen atoms
Or a lower alkyl group. ), R is charcoal
Monovalent organic residue having no aliphatic hydrocarbon group with a prime number of 6 or more
Group. A reversible thermosensitive recording medium, which is a polycyclic phenolic compound represented by the following formula: 2. A reversible thermosensitive recording medium comprising a recording layer containing a leuco dye and a color developing / decoloring agent which reacts with the leuco dye to form or decolor, wherein the color developing / developing agent is represented by the following general formula (1): Formula 2 X represents a direct bond or a divalent organic residue, and R represents a monovalent organic residue. Here, both ring A and ring B are aromatic carbonized.
In the case of a hydrogen ring, X is -C (R ') = C (R ")-C
ONH- (wherein R ′ and R ″ are a hydrogen atom or lower
Represents a kill group. ), And R is a group having 6 or more carbon atoms.
Is an organic residue of monovalent no aliphatic hydrocarbon group. )
A reversible thermosensitive recording medium characterized by being a polycyclic phenolic compound represented by the formula: 3. The compound of the formula (1) The expressed, -X- is a direct bond, -OCH ₂ -, - CH _{2
O-, NHCH 2 -, - CH} 2 CH 2 -, - OCO -, -
COO-, -CONH- or -NHCO-;
^{Is, -R 1, -OR 1, -NHR} 1, -OCOR 1, -CO
OR ¹ , -CONHR ¹ , -NHCOR ¹ , -OCOO
R ¹ , —NHCOOR ¹ (R ¹ represents an alkyl group having 1 to 23 carbon atoms, a cyclohexyl group or a phenyl group, each of which is a halogen atom, a hydroxyl group, an alkyl group,
It may be substituted with an alkoxy group or an alkoxyalkoxy group. 3. The reversible thermosensitive recording medium according to claim 1, wherein the recording medium is a polycyclic phenolic compound represented by the following formula: