JP3382728B2 - Thermosensitive coloring ink and thermosensitive coloring film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel heat-sensitive recording material suitable for recording images, characters and the like by heat, and more specifically, for example, a prepaid card capable of withstanding high temperatures, a hot water boilable label, and other high temperatures. Recording paper used under high humidity,
The present invention relates to a thermosensitive coloring ink and a thermosensitive coloring film that exhibit excellent heat resistance and water resistance when heat-recorded on a process control card or the like.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material is prepared by dispersing a color former such as white leuco dye and a color developer having a phenolic hydroxyl group (for example, bisphenol A) in a binder, and dispersing the binder in paper, plastic film or the like. It is prepared by coating and drying on a substrate. The heat-sensitive recording material obtained in this way develops color when heated by a thermal head or a hot pen, and characters and image recording easily appear.Therefore, as a component of a facsimile or a thermal printer, data communication, computer, etc. It is widely used in a wide range of fields such as terminals, other labels, tickets, and commuter passes.

However, the conventional heat-sensitive recording materials using leuco dyes have an ambient temperature of 80 because the fog in the non-image area and the discoloration phenomenon such as fading and disappearance of the image area occur in a temperature range of about 80.degree. It has a drawback that it cannot be used in applications where the temperature exceeds ℃. Therefore, for example, if you store a parking ticket or a ticket that uses thermal paper, a prepaid card, etc. in a car parked in the hot summer of midsummer,
The above-mentioned discoloration phenomenon may occur, making it unusable.
Also, the heat sterilization process in food factories is carried out by boiling water to sterilize boiling water, but since ordinary heat-sensitive paper and heat-sensitive films use water-soluble resins, they lack water resistance and heat resistance to withstand boiling water sterilization. It becomes impossible to use.

[0004]

Therefore, excellent heat resistance that does not cause the above-mentioned discoloration phenomenon at an ambient temperature of 80 ° C. or more, stable water resistance even with hot water treatment, and color storage stability. It is desired to develop a heat sensitive recording material.

[0005] Since the present invention also <br/> been developed along the demands of the, and it is an object without causing the discoloration phenomenon in an atmosphere of high temperature and humidity exceeding 100 ° C., thermal Provides a thermosensitive coloring ink and a thermosensitive coloring film with a high coloring density, which has stable heat resistance and water resistance without causing the fog phenomenon in the non-colored area to be generated even when the water treatment is applied. To do.

[0006]

The heat-sensitive color-forming ink according to the present invention for achieving the above object comprises a phenolic compound and a leuco dye which reacts with the phenolic compound under heating to develop a color and is dispersed in a vehicle. In the solvent-based thermosensitive coloring ink having the composition
And having a melting range of 60 ° C. to 250 DEG ° C. all SANYO not dissolve in water, the vehicle is also an acrylic resin
It is a resin containing a rubber-based resin, Nafute down hydrocarbons及
Dissolved in a mixed hydrocarbon solvent containing aromatic and aromatic hydrocarbons
The structural feature is that it is understood .

Further, the thermosensitive coloring film of the present invention is supported by
A constitutional feature is that a protective layer of a resin coat layer containing magnesium oxide is formed on the upper surface of a thermosensitive color forming ink layer formed by applying the thermosensitive color forming ink on the surface of a base material. .

The phenolic compound constituting the thermosensitive color-forming ink of the present invention is selected from those having a melting point in the range of 160 to 250 ° C. and no solubility in water. Leuco dyes and phenolic compounds develop color when the phenolic compound melts above the melting point and reacts with the leuco dye, but generally the melting point of the phenolic compound is the sensitizer, ultraviolet absorber, antioxidant used in combination. , The lubricant, the type of leuco dye, and the like interact with each other to lower the melting temperature. The actual melting temperature is 10 to 60 ° C. lower than the inherent melting point of the melting temperature, and the melting occurs at the same time. Further, a phenolic compound having a solubility in warm water adversely affects the background fog phenomenon after boiling with hot water, and therefore it is necessary to select a phenolic compound insoluble in water.

[0009] The melting point is in the range of 160 ~ 250 ℃,
Preferable examples of water-insoluble phenolic compounds include a, a ′, a ″ -tris-4-hydroxyphenyl-
1,2,3-Trisisopropylbenzene (mp189 ℃), 4,4'-
(1-phenylethylidene) bisphenol (mp 188 ℃),
Examples thereof include 3,4-dihydroxyphenyl-p-toluyl sulfone.

Other than this, a melting point of 160 to 250 which is effective
Examples of the phenolic compound at ℃ are the following substances for each melting point level. First, as a phenolic compound having a melting point in the range of 160 to 170 ° C., 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bis (2,6-dimethylphenol) 4,4 ''-(Phenylmethyl) bisphenol, 4,
4 '-(1-Methylethylidene) bis-2,6-dimethylphenol, 4,4'-(p-phenylenediisopropylidene) bis (2,6
-Xylenol), 4,4'-cyclopentylidenebisphenol, 4,4'-cyclohexylidenebis (2-cyclohexylphenol), 4,4 '-(1-methylethylidene) bis (2
-Cyclohexylphenol), 4-benzyloxyphenyl-4'-hydroxyphenylsulfone, 4,4'-cyclohexylidenebis (2-t-butylphenol), 5,5 '-(1,1-cyclohexylidene) bis (1,1-biphenyl) -2-ol,
2,2 '-[(2-hydroxyphenyl) methylene] bis (3,5-
Dimethylphenol) and the like.

Examples of phenol compounds having a melting point in the range of 170 to 180 ° C. are 2,2'-bis (4-t-octylphenol) sulfoxide, 4,4 '-(dimethylsilylene) bisphenol, 4,4'- Examples include methylenebis (2,6-dimethylphenol).

Examples of phenolic compounds having a melting point in the range of 180 to 190 ° C. are 4,4′-cyclohexylidene bisphenol, bis (2,5-dimethyl-4-hydroxyphenyl) sulfide, 4,4 ′-( 1-phenylethylidene) bisphenol, α, α ', α "-tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 4,4', 4" -ethylidenetris (2-methylphenol), Examples thereof include p-aminophenol and 4,4 ′-(α-methylbenzylidene) bisphenol.

Phenol compounds having a melting point in the range of 190 to 200 ° C. include 4,4'-cyclohexylidenebis (3-methylphenol), 4,4'-p-phenylenediisopropylidene) bisphenol, 3 , 3'- difluoro [1,
1'-biphenyl] -4,4'-diol, 4,4 '-[(3-hydroxyphenyl) methylene] bis [2,6-dimethylphenol, 3,3', 4,4 '-[1,4 -Phenylenebis (1-methylethylidene)] bisbenzenediol and the like.

Further, as a phenolic compound having a melting point in the range of 200 to 250 ° C., 2,2 '-[(4-hydroxyphenyl) methylene] bis [3,5-dimethylphenol]
, 4,4 '-[(2-Hydroxyphenyl) methylene] bis [2-
Cyclohexyl-5-methylphenol], 4,4 '-(3,4-
Dihydroxybenzylidene) bis-2,6-dimethylphenol, 4,4 ', 4 "-methylidenebisphenol and the like can be mentioned.

As the leuco dye which reacts with the above-mentioned phenolic compound under heating to form a color, a high molecular weight leuco dye of the usual fluoran leuco dye is particularly effective for the purpose of improving the storage stability. Specifically, 2,2-bis {4- [6 '-(N-
Cyclohexyl-N-methylamino) -3'-methylspiro
[Phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane [Showa Denko KK, "Papyrole SD-12"
0 "]. In addition, even a general fluoran-based leuco dye has a melting point of 160 to 250 ° C,
If a developer which is insoluble in water is used together, the fog phenomenon can be further suppressed.

[0016] These phenolic compounds and leuco dye shall be the solvent type heat-sensitive coloring ink composition is dispersed in the vehicle. Vehicle is at least acrylic resin or rubber
It includes a system resin, also containing other resin used together if necessary
A than those of these resin components dissolved in a solvent is used.

[0017] The acrylic resin or rubber resin Ru used known ones. As a reactive diluent for acrylic resin
Is a monofunctional monomer such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, N-vinylpyrrolidone, for example, polymethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, polyethylene glycol di (meth). Examples thereof include acrylate, hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and dipentathrithritol hexa (meth) acrylate . Acrylic resin or rubber tree
The fat is added to the vehicle in an amount of up to 80% by weight, preferably in the range of 5 to 30% by weight, based on the heat-sensitive color-forming ink component.

As means for curing the acrylic resin,
When radiation is used and ultraviolet rays are used as the radiation, it is preferable to add a photopolymerization initiator that generates a free radical by the energy of the ultraviolet rays. Examples of this type of photopolymerization initiator include benzoyl alkyl ethers, α-acyloxime esters, acetophenones, benzophenones, benzyl ketals and ketones.
Compounds such as amines are preferably used, and the addition amount thereof is usually set in the range of 1 to 8 parts by weight with respect to 100 parts by weight of the acrylic resin .

The resin component used in combination with acrylic resin or a rubber-based resin, petroleum resin, bi Nirutoruen resins, styrene resins, rosin resin, any one of olefin resin or two or more are preferred However, it is also possible to use ethyl cellulose, ethylene vinyl acetate, phenol resin, or the like.

As the solvent in which the above resins are dissolved to form a vehicle, one or a mixture of two or more of aliphatic hydrocarbons, naphthene hydrocarbons or aromatic hydrocarbons is mainly used. As the aliphatic hydrocarbon, for example, industrial volatile oil such as rubber volatile oil, extracted volatile oil, benzine K and gravizole are preferably used. Specific examples of naphthene-based hydrocarbons include cyclopentane, methylcyclopentane, 1,1- or 1,3-dimethylcyclopentane,
Examples thereof include cyclohexane, methylcyclohexane, ethylcyclohexane, 1,2,4-trimethylcyclohexane and the like. Of these, methylcyclohexane, ethylcyclohexane, and toluene are the most suitable solvents. When the mixed system is used, the content of aromatic hydrocarbons is 50% by weight or less,
It is preferably 20% by weight or less. When the content of aromatic hydrocarbon exceeds 50% by weight, the leuco dye is dissolved,
This is not preferable because it causes so-called dissolution color development.

As these hydrocarbon solvents, those having a distillation property of an initial boiling point of 35 ° C. and an end point of 170 ° C. are suitable, and those having an initial boiling point of 50 ° C. and an end point of 120 ° C. are preferable. If the initial boiling point is less than 35 ° C, the viscosity of the vehicle will increase due to evaporation, causing troubles such as plate clogging, making it difficult to perform uniform printing. If the end point exceeds 170 ° C, drying will be slow. Printing speed decreases, uneven printing such as spot ring (mottling) and satin finish occurs, and solvent remains in the heat-sensitive layer to cause blocking due to insufficient drying, causing various inconvenient phenomena. .

The composition of the vehicle is 50 to 50% by weight of the hydrocarbon solvent.
It is composed by dissolving 1 to 50% by weight of a resin component in 99% by weight, but in order to adjust the film characteristics of the heat-sensitive recording layer separately, an auxiliary component within the range of 1 to 5% by weight with respect to the total amount thereof Can also be added.

In the thermosensitive color-forming ink of the present invention, a phenolic compound and a leuco dye are put in separate containers, and a vehicle is added to the container, and a wet machine using a disperser such as a sand mill, a ball mill, an attritor or a shot mill is used. After the respective dispersions are obtained by kneading, both can be combined and further mixed by a mixing device such as a propeller mixer. In this process stage, the content of phenolic compound and leuco dye is
Each can be arbitrarily adjusted within the concentration range of 2 to 50% by weight with respect to all the composition components in accordance with the required color density. The viscosity of the resulting heat-sensitive color-forming ink is preferably in the final range of 1 to 100 poise.

In the thermosensitive color-forming ink having the above composition, if necessary, a conventional inorganic filler such as magnesium oxide, calcium carbonate, precipitable barium sulfate, alumina, silica, clay, magnesium carbonate or silicon carbide, and an auxiliary agent are further added. As the wax, waxes such as paraffin wax, carnauba wax, microcrystalline wax, and amide wax which are solid at room temperature can be added. In particular, magnesium oxide is a preferable additive component because it has a high thermal conductivity and heat energy is quickly transferred.

The thermosensitive coloring film according to the present invention is produced by applying the above thermosensitive coloring ink to the surface of a supporting substrate such as paper, fiber sheet or resin base to form a thermosensitive recording layer. The coating method is gravure coater, roll
Known means such as a coater, a die coater, a knife coater, and silk screen printing can be applied. The thermosensitive recording layer usually has a dry weight of 0.5 to 10 g / m ^2.
Formed as a film.

On the upper surface of the thermosensitive recording layer formed on the surface of the supporting substrate, it is preferable to provide a protective layer for the resin coating layer with a topcoat varnish. As the resin component used for this protective layer, acrylic resin, vinyltoluene resin, styrene resin, cyclic rubber, ethyl cellulose, rosin, petroleum resin, ethylene vinyl acetate, chlorinated polyolefin resin, phenol resin, olefin resin, etc. As the solvent, one kind or two or more kinds of hydrocarbon-based solvents mainly containing aliphatic hydrocarbons, naphthene-based hydrocarbons and aromatic hydrocarbons, which are similar to those used in the heat-sensitive color-forming ink, can be used. . Magnesium oxide having a high thermal conductivity is preferably added to the protective layer in order to quickly and efficiently transfer heat to the heat-sensitive recording layer that develops color at high temperature. At the same time calcium carbonate, precipitated barium sulfate, alumina,
Although inorganic fillers such as silica, clay, magnesium carbonate, and silicon carbide may be used in combination, the heat transfer effect at the time of adding magnesium oxide cannot be obtained by themselves. Further, waxes such as paraffin wax, carnauba wax, microcrystalline wax, amide wax, fluorosilicone, etc. which are solid at room temperature, oils such as silicone oil, fluorinated oil, etc. can be added as auxiliary agents.

The top coat varnish has a viscosity of 0.5 to 10 poise and is applied to the upper surface of the heat-sensitive recording layer by means of, for example, a gravure coater, a roll coater, a die coater, a knife coater, silk screen printing, etc. Usually 0.1
It is formed as a film of ~ 5 g / m ² .

In the thermosensitive recording layer formed on the thermosensitive coloring ink and the thermosensitive coloring film according to the present invention, the high molecular weight leuco dye and the phenol compound used in combination have a melting point of 1
Since it has physical properties insoluble in water at 60 to 250 ° C,
The color-developed heat-sensitive recording layer is extremely stable in a high temperature atmosphere near 100 ° C., and at the same time retains sufficient water resistance against hot water. Therefore, the formed thermosensitive coloring film is a thermal head of a computer-terminal, a thermal pen,
Clear markings or images can be made visible by marking with a laser and the discoloration phenomenon does not occur for a long period of time.

[0029]

In the conventional heat-sensitive recording material using the combination of the leuco dye and the phenol compound, the melting point of the phenol compound used is around 80 ° C., so that the coloring sensitivity is relatively low such as that of a facsimile or word processor paper. Although it is well suited to the usage conditions by thermal transfer in the temperature range, it becomes unstable under the conditions where the ambient temperature exceeds 80 ° C, and a discoloration phenomenon occurs. Further, in these applications, in order to increase the sensitivity, in many cases, it is designed to develop a black color at 80 ° C. or lower by using a sensitizer having a low melting point together,
The heat resistance is extremely poor. Further, a phenolic compound or a sensitizer having a low melting point has high solubility in an organic solvent, and when used in combination with a leuco dye, fog occurs in a non-recorded portion. There is a problem in terms of water resistance.

The thermosensitive color-forming ink and the thermosensitive color-forming film provided by the present invention are composed by selecting a phenolic compound having a melting point of 160 to 250 ° C. as a developer for developing the color of the leuco dye. The reaction color point is in the temperature range of 160 ° C. or higher. Therefore, 100 ℃
Even in a high temperature atmosphere exceeding the range, there is no fading or disappearance of the color-developed recording portion, and no fog phenomenon occurs in the non-recorded portion. In addition to this excellent heat resistance, it also has sufficient water resistance, and a stable recording state is maintained even in the application of hot water treatment.

[0031]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. A Macbeth reflection densitometer was used to measure the color density in each example (color density is an OD value).

Example 1 (1) Preparation of Leuco Dye Ink Component: A leuco dye and a vehicle component were blended in a composition ratio shown in Table 1 to prepare a mill base, which was dispersed by a paint shaker. The processing conditions of the paint shaker are 100 g of mill base and 20 mm diameter glass beads 20.
It was set to 0 g and a dispersion time of 1 hour.

[0033]

[Table 1]

To the ink base No. 1 obtained by the dispersion treatment, components were further added at the compounding ratio shown in Table 2 and let down to prepare a leuco dye ink component.

[0035]

[Table 2]

(2) Preparation of Phenolic Compound Ink Component: Phenolic compound and vehicle component were blended in a composition ratio shown in Table 3 to prepare a mill base, which was subjected to dispersion treatment in the same manner as the above leuco dye system. Subsequently, ink base No. 2 was blended with the components in the ratio shown in Table 4 and red-down was performed to prepare an ink component of a phenolic compound.

[0037]

[Table 3]

[0038]

[Table 4]

(3) Preparation of thermosensitive color-forming ink: The above-mentioned leuco dye-based components and phenolic compound-based components are mixed in a weight ratio of 1: 2, and the mixture is stirred by a propeller mixer to be a radiation-curable solvent-based thermosensitive ink. A coloring ink was prepared.

(4) Preparation of thermosensitive coloring film: The obtained thermosensitive coloring ink was applied to a polyester film (thickness: 50 μm) by a gravure printing method and dried to about 5
A thermosensitive recording layer of g / m ² was formed. Then output 80W / m
The high-pressure mercury lamp of No. 2 was irradiated for 2 seconds to prepare a thermosensitive coloring film. Furthermore, in order to protect the formed thermosensitive recording layer, the components shown in Table 5 were used in a dispersing machine in which glass beads were placed.
Disperse for 0 minutes, and after dispersion, top coat varnish prepared to 100 parts by weight with toluene is solidly coated on the thermosensitive color recording film by a gravure printing method so as to be about 2 g / m ^{2 in a} dry state, and dried to coat the resin. Layers were formed.

[0041]

[Table 5]

(5) Evaluation of thermosensitive coloring film: When the above thermosensitive coloring film was heated, it developed a black color and the coloring characteristics shown in Table 6 were obtained.

[0043]

[Table 6]

A thermal line printer (manufactured by Matsushita Electronic Parts Co., Ltd.) was used to apply a voltage of 22 V, an application time of 2.0 msec, and a head resistance of 1184 Ω. As a result, a clear black color image was obtained. This black colored image showed no phenomenon of discoloration or disappearance even when exposed to a temperature atmosphere of 100 ° C. In the continuous print test, no print residue was attached to the thermal head and sticking did not occur.

Next, with respect to the above-mentioned color-developed product and the one printed on a commercially available thermal film, the color-developing density after immersing in boiling water for 3 minutes was measured, and the results are shown in Table 7. From the results in Table 7, the product of the present invention showed a small degree of decrease in color density even after immersion, and stable performance was recognized. Measurement is no longer possible.

[0046]

[Table 7]

Example 2 (1) Preparation of Leuco Dye Ink Component: A leuco dye and a vehicle component were blended in a composition ratio shown in Table 8 to prepare a mill base, which was subjected to dispersion treatment with a paint shaker. The processing conditions of the paint shaker were the same as in Example 1.

[0048]

[Table 8]

To the ink base No. 3 obtained by the dispersion treatment, further components were added at the compounding ratio shown in Table 9 and let down to prepare a leuco dye ink component.

[0050]

[Table 9]

(2) Preparation of Phenolic Compound Ink Component: A phenol compound and a vehicle component were blended in a composition ratio shown in Table 10 to prepare a mill base, which was subjected to dispersion treatment in the same manner as the leuco dye system. Subsequently, the ink base No. 4 was blended with the components in the ratio shown in Table 11 and red-down was performed to prepare an ink component of a phenolic compound.

[0052]

[Table 10]

[0053]

[Table 11]

It was mixed at a ratio of 2, Solvent type thermosensitive coloring ink by stirring with a propeller mixer: The above leuco dye component and the phenolic compound based component in a weight ratio 1: [0054] (3) Preparation of thermosensitive coloring ink Prepared.

(4) Preparation of thermosensitive coloring film: The obtained thermosensitive coloring ink was applied to synthetic paper [Yupo FPG80 manufactured by Oji Yuka Synthetic Paper Co., Ltd.] by a gravure printing method,
Form a thermosensitive recording layer of about 5 g / m ^{2 in} a dry state and
And dried for 10 seconds to prepare a thermosensitive coloring film. Further, in order to protect the formed thermosensitive recording layer, the components shown in Table 12 were dispersed for 30 minutes using a disperser containing glass beads, and after dispersion, 100 parts by weight of the prepared top coat varnish was used for thermosensitive color recording. A solid coating was applied on the film by a gravure printing method to a dry state of about 2 g / m ^2, and the film was dried.

[0056]

[Table 12]

(5) Evaluation of thermosensitive coloring film: When the above thermosensitive coloring film was heated, it developed a black color and the coloring characteristics shown in Table 13 were obtained.

[0058]

[Table 13]

As a result of printing with a thermal line printer under the same conditions as in Example 1, a clear black colored image was obtained, and this black colored image showed fading and erasing even when exposed to a temperature atmosphere of 100 ° C. No discoloration phenomenon was observed. In the continuous print test, no print residue was attached to the thermal head and sticking did not occur.

Next, with respect to the above-described color-developed product and the one printed on a commercially available thermal film (Yupobase), the color-developing density after immersion in boiling water for 3 minutes was measured, and the results are shown in Table 14. From the results in Table 14, the products of the present invention showed a small degree of decrease in color density even after immersion, and stable performance was recognized. Measurement is no longer possible.

[0061]

[Table 14]

Comparative Example 1 Of the component composition of the base ink No. 2 of Example 1, a phenolic compound was added to 4-{[4- (1-methylethoxy) phenyl] sulfonyl} phenol [Nippon Soda ( Co., Ltd., D-8], and the other component systems and processing conditions were all the same as in Example 1 to prepare a thermosensitive color forming film provided with a protective layer. The coloring characteristics when the thermosensitive coloring film was heated to give a black color were as shown in Table 15. Further, as a result of printing this thermosensitive coloring film with a thermal line printer under the same conditions as in Example 1, a clear black colored image was obtained, but when exposed to a temperature atmosphere of 100 ° C., the colored image faded and unrecorded. Fog occurred on the part. Further, Table 16 shows the results of immersion treatment in boiling water for 3 minutes under the same conditions as in Example 1.

[0063]

[Table 15]

[0064]

[Table 16]

From the above results, it is understood that the heat-sensitive color-forming ink and the heat-sensitive color-forming film of Comparative Example 1 are inferior in heat resistance and water resistance as compared with Example 1.

Comparative Example 2 Of the component composition of the base ink No. 4 of Example 2, the phenolic compound was replaced with bisphenol A having a melting point of 153 ° C., and the other component systems and treatment conditions were all the same as in Example 2 for protection. A thermosensitive coloring film provided with layers was produced.
Table 17 shows the color-developing characteristics when the thermosensitive color-developing film was heated to develop a black color. Further, as a result of printing this thermosensitive coloring film with a thermal line printer under the same conditions as in Example 1, a clear black colored image was obtained,
When exposed to a temperature atmosphere of 100 ° C., the color-developed image faded and fog occurred in the non-recorded area. Further, Table 18 shows the results of immersion treatment in boiling water for 3 minutes under the same conditions as in Example 1.

[0067]

[Table 17]

[0068]

[Table 18]

From the above evaluation results, it was confirmed that the heat-sensitive color-forming ink and the heat-sensitive color-forming film of Comparative Example 2 were inferior in heat resistance and water resistance as compared with Example 2.

Example 3 Magnesium oxide added to the protective layer of the thermosensitive color developing film in Example 1 was replaced with silica having a low thermal conductivity [Sylysia 350 manufactured by Fuji Silysia Chemical Ltd.], and other topcoat component systems and treatments were carried out. A thermosensitive coloring film was obtained under the same conditions as in Example 1. Table 19 shows the relationship between the applied energy and the color density when the obtained thermosensitive color developing film was printed. Table 19 also shows the relationship between the applied energy and the color density of the thermosensitive color developing film and the general thermosensitive paper obtained in Example 1.

[0071]

[Table 19]

From the results shown in Table 19, it can be seen that the thermosensitive color developing film of Example 3 is inferior in color developing characteristics to those of Example 1 and general thermal paper. Further, when Example 1 is compared with general thermal paper, Example 1 shows higher final color density in the normal printing energy range.

[0073]

As described above, according to the present invention, by selecting a phenolic compound having a melting point of 160 to 250 ° C. and no solubility in water as a developer, 160
It is possible to provide a thermosensitive color-forming ink that develops color at a temperature of not less than 0 ° C. and does not fade or disappear even when exposed to an atmosphere of about 100 ° C. and has excellent heat resistance. Further, the thermosensitive color forming film obtained by coating the supporting base material with the thermosensitive color forming ink is extremely stable without causing fog at an ambient temperature of about 100 ° C. Especially when a resin coat layer containing magnesium oxide is formed as a protective layer, the heat required for color development is efficiently transferred to the heat-sensitive layer, so that good color density can be obtained with energy equivalent to normal printing conditions. Becomes

Further, the thermosensitive color-forming ink and film of the present invention show excellent water resistance, and in addition to heat resistance, even if boiled in hot water, the density decrease in the printed recording area and the fog phenomenon in the non-printed area are extremely high. It is slight and the recorded part does not come off. Therefore, a label or the like using the thermosensitive color developing film of the present invention can be stably stored for a long period under high temperature and high humidity conditions.

Front Page Continuation (72) Inventor Masanobu Masanobu 1-7-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Within Dainichi Seika Kogyo Co., Ltd. (56) Reference JP-A-5-32050 (JP, A) JP-A 4-339691 (JP, A) JP-A-2-190391 (JP, A) JP-A-59-174389 (JP, A) JP-A-1-301770 (JP, A) International Publication 96/262 (WO, A1) ) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/28-5/34 G09D 11/00

Claims (2)

(57) [Claims] 1. A solvent-sensitive color developing ink of phenolic compounds and by dispersing the leuco dyes coloring in response to under heating and the phenolic compound in the vehicle composition, wherein the phenolic compound is 160 ° C. to 250 DEG ° C. It has a melting point range of and is insoluble in water,
The vehicle contains an acrylic resin or a rubber resin.
Naphthenic hydrocarbons and aromatic hydrocarbons
Dissolved in a mixed hydrocarbon solvent containing
The content of the aromatic hydrocarbon in the ink is 50
A thermosensitive color-forming ink characterized in that the content is less than or equal to% . 2. A protective layer of a resin coating layer containing magnesium oxide is formed on the upper surface of a thermosensitive color forming ink layer formed by applying the thermosensitive color forming ink of claim 1 on the surface of a supporting substrate. A thermosensitive coloring film characterized by.