JPH0712746B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more specifically, a colorless or slightly pale color and a leuco dye at room temperature, and a developer which reacts with the leuco dye to develop a color. The present invention relates to an improvement in a thermosensitive recording material in which a thermosensitive coloring layer containing as a coloring component is provided on a support.

[Prior art]

Recently, various recording materials have been researched, developed, and put into practical use in the information recording field in response to social demands such as diversification and increase of information, resource saving, and pollution-free. (1) A color image is recorded only by heating and a complicated developing process is not necessary. (2) Recording can be performed using a relatively simple and compact device, and the obtained recording material is easy to handle. Maintenance costs are low, and (3) paper is often used as a support, in which case not only the cost of the support is low, but the feel of the obtained recording material is close to plain paper. Because of its advantages, it is widely used in the fields of computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimiles, vending machines, and thermal copying.

The heat-sensitive recording material is usually produced by coating a substrate such as paper, synthetic paper or synthetic resin film with a heat-sensitive color-forming layer liquid containing a color-forming component capable of causing a color-forming reaction by heating and drying. A color image is recorded on the heat-sensitive recording material thus obtained by heating it with a hot pen or a thermal head. A conventional example of such a heat-sensitive recording material is, for example, Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-1403.
The heat-sensitive recording material disclosed in Japanese Patent No. 9 is cited, but such a conventional heat-sensitive recording material has a low thermal response, for example, and a sufficient color density cannot be obtained during high-speed recording. Then, as a method for improving such a defect with a material, for example, Japanese Patent Laid-Open No.
-38424 discloses acetamide, stearamide, m
Nitrogen-containing compounds such as nitroaniline and phthalic acid dinitrile, acetoacetic anilide in JP-A-52-106748, and N, N-diphenylamine derivatives, benzamide derivatives, carbazole in JP-A-53-11036. Derivative
JP-A-53-39139 discloses alkylated biphenyls,
Biphenyl alkane is disclosed in JP-A-56-144193 as p.
-A method of increasing the speed and increasing the sensitivity by containing each of the oxybenzoic acid ester derivatives is disclosed, and among them, the most effective method is to use the p-oxybenzoic acid ester derivative as a color developer. Was known.

Further, as other methods, it is generally known that the dispersed particle diameter of the leuco dye or the developer is made fine, or the smoothness of the surface of the thermosensitive coloring layer is increased, but only the above materials, There is a limit in the above manufacturing method alone. Moreover, in recent years, there has been a growing demand for higher speed recording in the facsimile field, higher density in low-temperature environments, and smaller device size.
Along with this, higher sensitivity of thermal recording materials is required.

In order to meet these requirements, it is difficult to achieve the desired high sensitivity only by the above method, and as a method for solving these, for example, a leuco dye originally having a high melting point is mixed with a low melting point fusible substance. A method of forming a melt (eutectic) and containing it in the thermosensitive coloring layer is disclosed.

For example, JP-A-53-48751 discloses an example in which a heat-fusible substance at 60 ° C. to 200 ° C. is contained in one of a colorless dye and a color developing agent, and JP-A-56-164890. In JP-A No. 59-22792, a leuco dye or a coloring agent is used in a heat-fusible substance having a melting point of 60 to 200 ° C. in JP-A-59-22792. There is disclosed an example in which is melted and sprayed from a nozzle to form fine particles to improve sensitivity.

However, among these mixed melts, those containing a fusible substance in the leuco dye (mixed) are melted and melted with extremely low heat energy, so that a highly sensitive heat-sensitive recording material is provided. Since the mixed and fused leuco dye is amorphous, it is extremely difficult to obtain a heat-sensitive recording material having extremely high activity and a large fogging of the coating solution for the thermosensitive coloring layer, and a white background. Further, even if fingerprints or the like are attached to the background portion, there is a drawback that the portion develops color.

〔Purpose〕

In view of the present situation, the present invention overcomes the above-mentioned drawbacks of the prior art and provides a heat-sensitive recording material having higher sensitivity (higher dynamic color development sensitivity) and less background fog than those conventionally known. Especially.

〔Constitution〕

According to the present invention, a normally colorless or slightly pale leuco dye, and a thermosensitive recording material having a thermosensitive color-forming layer containing as a main component a developer that develops the color of the leuco dye on a support, As at least a part of the leuco dye,
There is provided a heat-sensitive recording material characterized by using a leuco dye in a crystalline state obtained by subjecting a mixed melt of a melting point of 70 to 130 ° C. to a heat-fusible substance to a heat treatment.

The mixture of the leuco dye and the heat-fusible substance having a melting point of 70 to 130 ° C as referred to in the present invention can be prepared by the following method.

A method in which a leuco dye and a heat-fusible substance are mixed, heated and melted, made compatible, and then cooled to obtain a solid mixture.

A leuco dye and a heat-fusible substance are mixed, heated and melted to make them compatible, and then emulsified and dispersed in warm water containing a protective colloid, a surfactant, etc., and the emulsified dispersion is cooled to mix. Method for preparing a melt dispersion.

The leuco dye and the heat-fusible substance are dissolved in an organic solvent that dissolves both (eg acetone), and the solution is dropped into both non-solvents (eg water) to precipitate and then both solvents are volatilized. A method of making a mixed melt solid.

After mixing the leuco dye and the heat-fusible substance and making them compatible with each other by the method, etc., the mixture is sprayed in the air with a spray dryer or in water containing protective colloids to obtain mixed melt particles or mixed particles. Method for preparing a melt dispersion.

To the mixed melt or the mixed melt prepared by these methods, a protective colloid, a surfactant and the like are added, and the mixture is pulverized and dispersed in a water system to a desired particle size to prepare a mixed melt dispersion. At this stage, at least the leuco dye is in an amorphous state, and if a heat-sensitive coating liquid is prepared by mixing with a separately prepared developer dispersion liquid, the fog of the liquid is severe and a heat-sensitive recording material having a white background cannot be obtained.

In general, a leuco dye has a high activity, since a solid obtained by heating and melting and then cooling is amorphous. On the other hand, the above melting point
There are various substances such as higher fatty acid amides, aromatic hydrocarbons, phenyl benzoate derivatives, and terephthalate ester derivatives as heat-fusible substances at 70 to 130 ° C. These are melted by heating and cooling. Is hard to become amorphous. Therefore, if the mixture of the leuco dye and the heat-fusible substance has a low ratio of the heat-fusible substance, the mixture is amorphous, but if the ratio of the heat-fusible substance increases, the mixture becomes amorphous. The melt, the leuco dye shows amorphous,
A certain proportion of the heat fusible material is microcrystalline. As the heat-fusible substance, in addition to the above-mentioned ones, various substances generally used in the decomposition of this type of heat-sensitive recording material are used.

The inventors of the present invention thermally treat this mixed melt dispersion to microcrystallize the leuco dye, which is amorphous in the mixed melt, and then prepare a heat-sensitive coating liquid to prevent fog of the liquid. It was found that a heat-sensitive recording material having a white background can be obtained by using this heat-sensitive coating liquid. The term "thermochemical treatment" as used herein means to prepare a dispersion liquid of a mixed melt and then keep it at a constant temperature (for example, 15 to 50 ° C.), whereby a leuco dye in an amorphous state can be obtained. It begins to crystallize. The time to keep the temperature constant depends on the composition and additives, so it cannot be said unequivocally, but generally the higher the temperature, the shorter the time. Generally, the aging temperature is preferably 50 ° C. or lower, and if it exceeds 50 ° C., the dispersed particles are fused and coarsen, and the sensitivity is lowered, which is not preferable.

Whether the leuco dye in the dispersion liquid of the above-mentioned leuco dye and the heat-fusible substance is amorphous or in a crystalline state can be clearly observed by the X-ray diffraction measurement of this mixture. .

The leuco dyes used in the present invention may be used alone or as a mixture of two or more, and as such leuco dyes,
What is applied to this type of heat-sensitive material is arbitrarily applied, and, for example, leuco compounds of dyes such as triphenylmethane type, fluorane type, phenothiazine type, auramine type and spiropyran type are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p- Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3- Diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6 -Bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) Fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) ) -5-Methyl-7- (N, N
-Dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrolispirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolispirane, 3- (2'-hydroxy) -4'-Dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl)
Phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane and the like.

Further, as the developer used in the present invention, various electron-accepting substances that react with the leuco dye when heated to develop a color thereof are applied, and specific examples thereof include phenols as shown below. Examples thereof include organic substances, organic or inorganic acidic substances, and their esters and salts.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol, 4,4′-isopropylidenebis (2-chloro) Phenol), 4,4 ′
-Isopropylidene bis (2,6-dibromophenol), 4,4'-isopropylidene bis (2,6-dichlorophenol), 4,4'-isopropylidene bis (2-methylphenol), 4,4'- Isopropylidene bis (2,6-
Dimethylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, 3,5-xylenol,
Thymol, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol,
Phloroglysin, phloroglysin carboxylic acid, 4-tert
-Octylcatechol, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, Propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, p-hydroxybenzoic acid-
p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-
2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2
-Hydroxy-6-naphthoate zinc, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone, bis- (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, 3,5-di Zinc -tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid and the like.

In the present invention, in order to bond and support the leuco dye mixture and the color developer on a support, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, starch and its derivatives, and methoxy. Cellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer,
Acrylic amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. In addition to polymer, polyvinyl acetate,
Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutylmethacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, etc. Latex or the like can be used.

Further, in the present invention, together with the leuco dye mixture and the color developer, if necessary, further auxiliary components commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant,
A heat-fusible substance (or lubricant) or the like can be used in combination.
In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, etc. , Urea-
Organic fine powders such as formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used. Examples of the heat-fusible substance include, for example, higher fatty acid or its ester, amide or metal salt, Various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-epoxy-dialkyl hexahydrophthalates, higher ketones, other heat-fusible organic compounds, etc. One having a melting point of about 50 to 200 ° C. can be mentioned.

The heat-sensitive recording material of the present invention is prepared, for example, by mixing a mixture of a leuco dye and a heat-fusible substance prepared as described above, and a developer and a dispersion of its additive at a predetermined ratio. It is manufactured by preparing a heat-sensitive coating liquid, coating it on a suitable support such as paper, synthetic paper, plastic film, and drying.

〔effect〕

The heat-sensitive recording material of the present invention comprises a leuco dye and a melting point of 70 to 130 ° C.
Since it is mixed with the heat-fusible substance and the leuco dye is finely crystallized by the thermal treatment, it has an effect that the dynamic color development sensitivity is high and the background is white.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

The parts and% shown below are based on weight.

Example 1 3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluorane and m-terphenyl were mixed 1: 1 and heated to 150-160 ° C in a glass beaker to melt / melt and then cooled to obtain a mixed-melt solid. Was crushed with a Henschel mixer to obtain a fine powder.

Next, a mixture having the following composition was pulverized and dispersed in a sand grinder for 3 to 4 hours to prepare solutions A and B.

[Liquid A]

3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluoran and m-terphenyl 1: 1 melt mixture powder 300 parts 10% aqueous solution of polyvinyl alcohol 300〃 sodium dioctyl sulfosuccinate 2〃 water 398〃 [liquid B] benzyl p-hydroxybenzoate 120 Part Tetrabrom bisphenol A 30〃 calcium carbonate 120〃 stearic acid Zn 30〃 10% polyvinyl alcohol aqueous solution 300〃 water 400〃 where the water of the liquid A is volatilized and the mixed powder is pulverized and dispersed X As a result of line diffraction measurement, a diffraction peak of m-terphenyl was confirmed, but 3- (N-methyl-
The peak of N-cyclohexyl) amino-6-methyl-7-anilinofluorane was not confirmed, and it was confirmed to be amorphous.

Next, in a container that can seal the liquid A, place it in an environment of 30 ° C.
It was left to stand and matured. X-ray diffraction measurement was performed on the mixed melt in the liquid A that had been aged in the same manner as above.
A diffraction peak of-(N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane appeared, and it was confirmed that the state changed from amorphous to crystalline.

Next, the aged solution A and the solution B are used in a weight ratio of A:
A heat-sensitive coating liquid was prepared by mixing and stirring so that B = 1: 5.
Further, a mixture having the following composition was dispersed in a sand grinder for 30 minutes to prepare a coating liquid C for undercoat.

[C liquid]

Polystyrene 40% Dispersion 750 parts 10% Polyvinyl alcohol aqueous solution 200〃 Water 50〃 Next, the above-mentioned C solution is dried on 52g / m ^{2 high-} quality paper and the coating amount is 4g / m
^An undercoat paper was prepared by adjusting with a wire bar and applying so that it became ² . The above-mentioned heat-sensitive coating solution was applied onto this by adjusting with a wire bar so that the applied amount of the leuco paint after drying was 0.5 g / m ² . Then, apply this coated paper to a smoothness of 70
A thermosensitive recording material of the present invention was prepared by calendering for 0 to 1500 seconds.

Comparative Example 1 A thermosensitive recording material of Comparative Example 1 was prepared in the same manner as Example 1 except that the liquid A was not subjected to aging treatment.

Example 2 3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluorane (45 g) and p-benzylbiphenyl (45 g) were mixed and placed in a glass beaker at 150-160 ° C.
It was heated up to melt and melted.

Separately, 90 g of a 10% aqueous solution of polyvinyl alcohol, 5 g of a polycarboxylic acid type surfactant, 0.6 g of sodium dioctylsulfosuccinate and 115 g of water were mixed and heated to 85 to 95 ° C in a hot water bath. While stirring the warm water containing this polyvinyl alcohol with a high-speed disper, the above-mentioned molten solution of leuco dye and p-benzylbiphenyl was rapidly added, sufficiently emulsified, and then cooled. This emulsified dispersion was dispersed in a sand grinder for 3 hours to prepare a mixed melt dispersion A'solution.

Next, the liquid A'was left for 20 hours at 40 ° C in a container capable of being hermetically sealed for aging treatment. When X-ray diffraction measurement was performed on the mixed melt in the A'solution and the aged A'solution, it was confirmed that the leuco dye of the former mixed melt was amorphous and the latter was changed to crystal. .

The heat-sensitive coating liquid was prepared by mixing and stirring the aged solution A'and the solution B shown in Example 1 at A ': B = 1: 5, and otherwise in the same manner as in Example 1 A thermosensitive recording material was prepared.

Comparative Example 2 A mixture having the following composition was pulverized and dispersed in a sand grinder for 3 to 4 hours to prepare an A ″ liquid.

[A "liquid]

3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilifluoran 150 parts p-benzylbiphenyl 150 parts 10% aqueous solution of polyvinyl alcohol 300 〃 sodium dioctylsulfosuccinate 2 〃 water 398 〃 Next, the solution A ″ and the solution B shown in Example 1 were added. A ″
A heat-sensitive coating liquid was prepared by mixing and stirring so that the liquid: B liquid = 1: 5, and the heat-sensitive recording material of Comparative Example 2 was prepared in the same manner as in Example 1.

The above thermal recording materials were tested according to the following test methods for dynamic color development sensitivity and background density.

(1) Dynamic color development sensitivity ... Matsushita Electronics Co., Ltd., thermal printing experiment device with thin film head, head power 0.45 W / dot, 1 line recording time 20 ms / l, scanning line density 8 × 3.85 dots / pulse width 0.4, 0.6, 0.8, 1.0, 1.2me under mm condition
Each line of 80 lines was printed with c, and the print density was measured with a Macbeth densitometer RD-514 (filter-W-106).

(2) Background density: Measured with a Macbeth densitometer RD-514 (filter wratten-106).

As can be seen from Table-1, the heat-sensitive recording material of the present invention has a higher sensitivity than the unmelted material (Comparative Example 2), and uses a leuco dye mixed material in an amorphous state without aging treatment. It was confirmed that the background color was extremely white compared with that of Comparative Example 1 (Comparative Example 1).

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or slightly pale leuco dye and a developer for coloring the leuco dye under heat as main components. A melting point of 70 as at least part of the leuco dye
A heat-sensitive recording material characterized by using a leuco dye in a crystalline state obtained by subjecting a mixed material of a heat-fusible substance at a temperature of up to 130 ° C to a heat treatment.