JPH0491172A - Radiation-curable thermocolor ink and thermocolor plastic card coated therewith - Google Patents

Abstract

PURPOSE:To obtain the subject ink having excellent storage stability and exhibiting good printability to plastic sheet by dispersing a phenolic compound and a leuco dye in a vehicle produced by dissolving a radiation-curable resin in a specific solvent. CONSTITUTION:The objective radiation-curable thermocolor ink is produced by (1) dissolving a radiation-curable resin such as polyester resin or polyether resin in a solvent composed mainly of a mixture of an aliphatic hydrocarbon (e.g. a rubber solvent) and/or a naphthenic hydrocarbon (e.g. cyclopentane) and/or an aromatic hydrocarbon (e.g. trichloroethylene) to obtain a vehicle (A) and (2) dissolving (B) a phenolic compound such as tert-butylphenol and (C) a leuco dye developing color when heated together with the component B (e.g. crystal violet lactone) in the vehicle A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive coloring ink, and more particularly to a method for achieving good printing, especially on plastic sheets, by using a vehicle consisting of a combination of a specific solvent and a resin. %5 for heat-sensitive coloring ink and heat-sensitive plastic cards
There are 7 things.

[Prior Art] In recent years, thermosensitive color recording methods have been used for printing by thermal printers used as terminals for electronic computers, by thermal pen recorders for various medical devices such as electrocardiograms, by printers for industrial measuring instruments, or by thermal facsimiles. It is widely applied in the field of information equipment.

In addition, as one of the heat-sensitive coloring ink compositions used for such purposes, a heat-sensitive agent consisting of a phenolic compound and a leuco dye that develops color by reacting with the phenolic compound under heating, and a support using these agents. It is known to consist of a vehicle for adhering to.

In such heat-sensitive coloring systems, a dispersed printing ink layer is provided by dispersing a phenolic compound and a leuco dye in a vehicle in the form of fine particles and coating them on a support. At the bottom, at least one of the two melts or sublimates and comes into close contact with the other, causing a reaction and color development.

Therefore, the phenolic compound (color developer) and the leuco dye (color former) E may be collectively referred to as "thermal sensitizer" hereinafter. ] The following properties are required of the solvent and resin that constitute the vehicle for dispersing.

1. At room temperature, the vehicle must be inert and non-soluble with respect to the heat-sensitive agent in order to maintain stability of the colorless ink before use and the dispersed printing ink layer after use.

■To separate the heat sensitive agent (color former and color developer) from each other,
The vehicle must have a certain high viscosity.

(2) The heat-sensitive coloring layer formed after printing is subjected to sliding friction by the high-temperature thermal head, so the vehicle must form a tough film even at high temperatures.

Conventionally, in order to meet the above requirements, the vehicle used is mostly a water-soluble polymer compound such as polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, starch, or polyacrylamide dissolved in water. ing.

[Problems to be Solved by the Invention] However, using such a water-soluble vehicle has the following drawbacks.

That is, first, in order to use a water-soluble polymer for @l,
The formed heat-sensitive layer has poor water resistance and may cause moisture to spill or
Cannot withstand long-term storage when humidity is high.

In addition, the moisture-absorbed heat-sensitive layer is easily softened by heat, becomes sticky when heated, and the thermal head of the terminal sticks to it, impeding running performance, resulting in the disadvantage that stable printing and image recording cannot be performed.

As a method to improve this, a method has been used in which an inbutylene-maleic anhydride copolymer, dialdehyde starch, etc. are added to the vehicle (Japanese Patent Laid-Open No. 1040/1983).

However, although this method certainly improves the film performance of the heat-sensitive layer formed, it has the disadvantage that the coating process for forming the heat-sensitive layer takes a long time to dry, resulting in extremely low work efficiency because water is used as a solvent. be.

In addition, it is difficult to obtain a uniform dispersion system of leuco paint in an aqueous vehicle, and increasing the resin concentration may result in thickening or gelation, while increasing the water content to reduce viscosity may cause sedimentation. Uniform coating will not be possible. As a result, the heat-sensitive layer formed on the support has mottling, smearing, matte, etc., resulting in an unfavorable appearance and uneven density in the heat-sensitive colored image, making it difficult to record clearly. I can't find a pattern.

In addition, when paper is used as a support, terpene resin,
It is also known to apply a non-aqueous vehicle in which a petroleum resin, annular rubber, or the like is dissolved in a petroleum solvent to prevent paper from expanding, contracting, and wrinkling during coating (Japanese Patent Publication No. 14533/1982).

However, the use of such a non-aqueous vehicle does not essentially solve the drawbacks associated with the use of an aqueous vehicle as described above, and on the contrary, unless paper is used as a support as described above, the use of an aqueous vehicle is gives worse results than when using .

Ordinary aliphatic petroleum solvents have a low ability to dissolve binder resins, and some petroleum resins that are easily soluble in petroleum solvents do not provide good film properties for printed films. Furthermore, aromatic petroleum solvents with dissolving power dissolve leuco dyes and develop color, resulting in a fogging phenomenon. For this reason, the printing effect is poor and clear thermal recording cannot be obtained, and moreover, when the thermal head slides on the thermal layer, there is a large amount of adhered residue, making it unusable.

Usually, what we call petroleum has a wide range, and petroleum ether (
BP20-60℃ pentane, hexane), ligroin, light naphtha (BP60-120℃ hexane, heptane)
, gasoline (BP40-205℃), kerosene (BP175)
~325°C), gas oil (BP 275°C or higher), etc. Such chain hydrocarbons have low solubility and are insufficient as vehicles. In addition, industrial gasoline generally contains naphthenic fractions depending on the properties of the crude oil, but these have a boiling point range of 40 to 250℃.
) What is widely referred to as 7-tene petroleum is benzene,
It contains aromatic hydrocarbons such as toluene and xylene, and is said to have a high content of up to 40% by weight.

Therefore, the combination of solvent and resin used in the vehicle of the heat-sensitive coloring ink must be selected with sufficient consideration given to its solubility and the strength of the film formed.

Vehicles used in heat-sensitive coloring ink compositions as described above, whether aqueous or non-aqueous, do not have good dispersion and film properties.

For this reason, conventional thermosensitive coloring ink compositions have been used in a manner that provides a uniform thermosensitive coloring layer over the entire surface by coating the composition onto a support using a roll coater or an air knife. However, considering the actual demand, the heat-sensitive coloring layer is
There is no need for solid coating, and pattern printing is often necessary, and from an economic standpoint, it is not desirable to coat unnecessary areas.

In order to solve these problems, a phenolic compound and a leuco dye that develops color by reacting with the phenolic compound under heating are dispersed in a vehicle as a heat-sensitive coloring ink composition that can be used for pattern printing using gravure printing, etc. A thermosensitive coloring ink composition has been proposed in which the vehicle is a combination of a vinyltoluene copolymer resin or a rosin ester resin dissolved in a naphthenic hydrocarbon solvent with a boiling point of 50 to 150°C. (Special Publication No. 16986/1986).

However, although this ink exhibits good printability on paper, it has the disadvantage of poor printability on plastic sheets or films.

Currently, prepaid cards such as telephone cards, ticket cards, and video rental cards are
A balance display such as the remaining amount or the number of valid balances is shown by making a bunch of holes at a predetermined position on the card. In this type of punch hole method, the exact value is not known and the punch waste is likely to clog the machine and cause a malfunction, so recently, thermal coloring cards that display the balance using a thermal method have started to be used.

Synthetic paper or plastic sheets are usually used as materials for such prepayment cards because of their high durability.

The heat-sensitive coloring ink using the vinyl toluene resin vehicle has poor adhesion to plastic sheets, so it cannot be used for such plastic cards.

The vehicle for heat-sensitive coloring ink used for plastic cards such as prepaid cards has the adhesive properties described above.
In addition to being non-reactive with the heat-sensitive agent, it is necessary to have extremely good dispersion properties for the heat-sensitive agent, and in addition, because it is used repeatedly, it is perfect for the sliding friction of the high-temperature thermal head even if it is thick or thin. It is necessary to provide a strong film that can withstand high temperatures, as well as to have good fluidity, excellent printability, and rapid evaporation drying after printing. Furthermore, since it comes into contact with the high temperature part of a thermal pen or thermal head during recording, it is required to have heat resistance to prevent thermal deterioration due to printing.

As a result of intensive research, the present inventors have found that the above-mentioned good printability and strong film properties on plastic sheets can be achieved by using a radiation-curable resin alone or in combination with a weakly solvent-soluble resin as the vehicle resin. The present invention was completed by combining this resin with a specific soluble solvent that is compatible with this resin.

[Means for Solving the Problems] That is, the present invention provides a heat-sensitive coloring ink composition comprising a phenolic compound and a leuco dye that develops color by reacting with the phenolic compound under heating, dispersed in a vehicle. However, radiation-curable resins are used alone or in combination with acrylic resins, petroleum resins, rosin resins, rubber resins, and vinyltoluene resins that are soluble in weak solvents, mainly aliphatic hydrocarbons and/or naphthenes. Provided is a heat-sensitive coloring ink, characterized in that it is dissolved in a solvent consisting of one type or a combination of two or more of aromatic hydrocarbons and/or aromatic hydrocarbons, and a heat-sensitive coloring plastic card coated with this ink. It is something to do.

The present invention will be explained in detail below.

All known combinations of phenolic compounds and leuco dyes can be suitably used in the present invention.

That is, the phenolic compound used in the present invention refers to a compound having a phenolic hydroxyl group, for example,
Phenol, 0-cresol, p-cresol, p-ethylphenol, tert-butylphenol, 21
6-ditertiary-butyl-4-methylphenol, nonylphenol, dodecylphenol, styrenated phenol, 2,2'-methylene-bis(4-methyl-6-
tertiary-butylphenol), α-naphthol, β
-Sa7tol, hydroquinone methyl ether, guaiacol, eugenol, p-chlorophenol, p
-bromophenol, 0-bromophenol, 0-chlorophenol, 2.4.6-triclocphenol, 0
-Phenylphenol, p-7xylphenolyl)phenol, 0-(0-chlorophenyl)phenol, salicylic acid, ethyl p-oxybenzoate, ethyl p-oxybenzoate, zulovir p-oxybenzoate, p
-Butyl oxybenzoate, octyl p-oxybenzoate, dobnol p-oxybenzoate, catechol, hydroquinone, resolun, 3-methylcatechol, 3,-isopropylcatechol, p-tert-butylcatechol, 2,5-ditertiary- butylhydroquinone, 4,
4'-methylene diphenol, bisphenol A, 1.
2-Dioxynaphthalene, 2.3-dioxynaphthalene, chlorcatechol, bromocatechol, 2.4-dihydroxybenzophenone, phenolphthalein, 0-
Cresol 7-thalein, methyl protocatechuate, ethyl protocatechuate, propyl protocatechuate, octyl protocatechuate, dodecyl protocatechuate, pyrogallol, oxyhydroquinone, 70-glucine, 2,4.6-)lyoxymethylbenzene, 2,
3.4-h lyoxyethylbenzene gallic acid, methyl gallate, ethyl gallate, propyl gallate, butyl gallate, hexyl gallate, octyl gallate, dodecyl gallate, cetyl gallate, stearyl gallate, 2
, 3.5-) dioxynaphthalene, tannic acid phenolic resin, phenylbis(4-hydroxyphenyl)methane, 4.4'=(phenylethylidene)bisphenol, 4.4''-[1.4-722lenebis (1-methylethylidene)copisphenol, 4.4'-dihydroxydiphenyl ether, 4.4'-ethylidenebisphenol, l,4-bis(hydroxycumyl)benzene, 4
, 4'-[1.3-7enylenebis(1-methylethylidene)]copisphenol 2,6-cyhydroxynaphthalene, a,a'tr-)lis(4-hydroxyphenyl)-1,3,5-tri Isopropylbenzene, 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenol, 4,4'-(1
-methylpropylidene)bispheno-4,4,4'-cyclohexylidenebisphenol, 4,4'-(i-methylpentylidene)bisphenol, 4,4'-(phenylmethylene)bisphenol, 2,2'- Methylenebis(4-tert-butylphenol), methylenediphenol, 2.2′=methylenebis(4-methylphenol), 4.4″-methylene-bisresorcinol,
Impropylidene-di-resorcinol, diphenylbis(4-hydroxyphenyl)methane, and the like can be used.

Examples of leuco dyes include triphenylmethane-based dyes such as crystal violet lactone and malachite green lactone; fluoran-based dyes such as 1,2-benz-6-dinithylaminofluorane; auramine-based dyes such as N-benzoyl auramine; and other phenothiazines. Leuco dyes such as phenoxidine series; triphenylmethane hetthalide series; indolylphthalide series; rhodamine lactam series; diphenylmethane series: chromenoindole series; and spiropyran series are used.

The radiation-curable resin composition used in the present invention is a known material and consists of a radiation-curable resin and, if necessary, a photopolymerization initiator and other arbitrary components.

Typical examples of radiation-curable resins include relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, which have radically polymerizable unsaturated double bonds in their molecular structures,
Prepolymers such as acrylates and methacrylates of polyfunctional compounds such as polyhydric alcohols, and monofunctional and polyfunctional compounds such as ethyl (meth)acrylate, ethylhexyl (meth)acrylate, and styrene N-vinylpyrrolidone as reactive diluents. Functional additives 1 For example, polymethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, di Contains pentaerythritol hexa(meth)acrylate etc.
These components may be used alone or in mixtures.

In addition, the photopolymerization initiator required when using ultraviolet rays as radiation is a compound that generates free radicals due to the energy of ultraviolet rays, such as benzoin alkyl ethers, α-aziroxime esters, acetophenones, benzophenones, benzyl ketals,
Compounds such as ketone-amines are preferably used, and the amount added is usually 1 to 8 parts by weight per 100 parts by weight of the radiation-curable resin.

The ratio of the radiation curable composition to the heat-sensitive coloring ink component in the vehicle is preferably 5 to 100% by weight, preferably 10 to 50% by weight.

In addition, resin components used in combination with radiation-curable resin include acrylic resin, vinyltoluene resin, cyclic rubber,
Examples include ethyl cellulose, rosin, petroleum resin, EUA, chlorinated polyolefin resin, and phenol resin.

The solvent for the vehicle used in the present invention is mainly composed of one or a combination of two or more of aliphatic hydrocarbons, hexathenic hydrocarbons, and/or aromatic hydrocarbons, and aromatic hydrocarbons. A hydrocarbon content of 50% by weight or less, preferably 20% by weight or less can be suitably used.

The hydrocarbon solvent used here has an initial boiling point of 35°C and an ending point of 17°C.
Those having a distillation property of 0°C are suitable, and preferably those having an initial boiling point of 50°C and an end point of 120°C can be used.

If the initial boiling point of the solvent used is below 35°C, the viscosity of the vehicle will increase due to evaporation, causing on-machine troubles such as plate jams, making it impossible to perform uniform printing.

If the end point of the solvent exceeds 150° C., drying is slow and printing speed is not increased, resulting in uneven printing such as mottling and matte finish. Furthermore, due to insufficient drying, solvent remains in the heat-sensitive layer, resulting in extremely undesirable phenomena such as blocking.

The aliphatic hydrocarbons used in the present invention include industrial volatile oil,
For example, rubber volatile oil, extracted volatile oil, benzine and 1-gravisol, etc. can be suitably used.

On the other hand, naphthenic hydrocarbons can be used as solvents in the vehicles of the invention.

Specific examples of such 7-tene hydrocarbons include cyclopentane, methylcyclopenkune, 1,1- or 1,3-dimethylcyclopentane, cyclohexane,
Methylcyclohexane, ethylcyclohexane, 1,2
．． Examples include 4-trimethylcyclohexane. Among them, cyclohexane and ethylcyclohexane are the most desirable solvents.

In the present invention, two or more of the above hydrocarbons can also be used in combination.

As the vehicle solvent used in the present invention, it is preferable to use the above-mentioned aliphatic hydrocarbons and/or naphthenic hydrocarbons. However, up to 20% by weight of aromatic hydrocarbons based on the total amount, or chlorine-containing hydrocarbons such as trichlorethylene, perchlorethylene, diethylene chloride, etc., up to 5% by weight based on the total amount can also be used together.

When the amount of aromatic hydrocarbon solvent mixed exceeds 20% by weight,
This is undesirable because it dissolves the leuco dye and causes so-called dissolution coloring.

Moreover, if the chlorine-containing hydrocarbon exceeds 5% by weight, it is unfavorable in terms of odor and hygiene, and therefore cannot be used in large amounts.

The vehicle of the present invention consists of 50 to 99% by weight of the above-mentioned solvent and 1 to 50% by weight of the above-mentioned copolymer resin, but an auxiliary component is separately added within the range of 1 to 5% by weight based on the total amount. It is also possible to adjust the film characteristics of the heat-sensitive recording layer.

The thermosensitive coloring ink of the present invention is prepared by placing the phenolic compound and the leuco dye in separate containers, adding the vehicle obtained above, and kneading the mixture using a dispersing machine such as a sand mill, ball mill, attritor, or shot mill. death,
After each dispersion is obtained, the two are combined and further mixed using a conventional mixing device such as a propeller mixer, thereby producing the dispersion. In the production of this heat-sensitive coloring ink, the concentration of the phenolic compound and the leuco dye in the composition can be adjusted arbitrarily within the range of 2 to 50% by weight, depending on the required coloring density.

The radiation-curable heat-sensitive coloring ink of the present invention is prepared according to a conventional method and, if necessary, a coloring agent such as a pigment or dye, calcium carbonate, precipitated barium sulfate, alumina, acid clay, silica gel, clay magnesium carbonate, oxidized clay, etc. Inorganic fillers such as silicon, waxes that are solid at room temperature as auxiliaries such as paraffin wax, polyethylene wax, carnauba wax, microcrystalline wax, amide wax, plasticizers such as phthalate esters, citric acid esters, adipic esters, etc. Anionic, nonionic or cationic surfactants can also be added.

The radiation-curable thermosensitive coloring ink of the present invention can be applied onto a support such as a plastic film, fiber sheet, or paper by a conventional coating method using a roll coater, reverse coater, doctor coater, etc. , is characterized in that the heat-sensitive recording layer can be formed by printing using a gravure printing method.

In particular, when used for private cards, synthetic paper or plastic films, such as resin sheets of polyester, polyamide, polypropylene, polycarbonate, polyvinyl chloride, etc., can be used.

In addition, letterpress printing, 7-lexo printing, and silk screen printing are also possible. For use in such printing applications,
The viscosity of the radiation-curable thermosensitive coloring ink of the present invention is 1 to 50.
It is preferable to set it in the range of 0 poise. Further, the heat-sensitive recording layer is usually formed as a film having a thickness of 0.5 to 10 9 /m' on a dry weight basis.

The heat-sensitive recording layer printed or coated in this way has a
Color develops sharply at a temperature of 250°C.

Clear print or images can be produced using the terminal's thermal head, thermal pen, etc.

[Example] The present invention will be explained in more detail with reference to Examples.

Example 1 Ink No., 1 milbase composition Fluorane leuco dye [manufactured by ODB Yamamoto Kitamoto Kasei] 20 parts by weight Acrylic resin [Dyanal BR102, manufactured by Mitsubishi Rayon Co., Ltd.] 10 parts by weight cyclohexane
20 parts by weight Toluene 20 parts by weight 7
0 parts by weight The above millbase was prepared and dispersed for 1 hour using a disperser using glass beads. The dispersed base ink was further subjected to letdown using the following formulation to obtain ink No. 1.

Ink No. 1 Composition Ink No. 1 Base 70 parts by weight Polyester acrylate prepolymer 101 parts by weight Trimethylolpropane triacrylate 10 parts by weight Benzoin isobutyl ether 1 part by weight Toluene
9 parts by weight 100 parts by weight Ink No. 2 Composition Bisphenol A Acrylic resin [manufactured by Dyana Mitsubishi Rayon Co., Ltd.] Ncrohexane toluene 20 parts by weight BR102, 10 parts by weight 50 parts by weight 20 parts by weight 1 part by weight The above blending ratio The prepared ink No. 2 base was dispersed for 1 hour using a dispersion machine using glass beads, and ink No. 1
I got 2.

These inks No. 1 and No. 2 were mixed at a weight ratio of 1:1 and stirred with a propeller mixer to obtain a radiation-curable thermosensitive coloring ink.

This radiation-curable heat-sensitive coloring ink was applied solidly to a milky white polyester film (250 μ) using gravure printing method I to a dry state of about 5 g/m, and then a high-pressure mercury lamp with an output of 80 W/m was applied for 2 seconds. irradiation to obtain a thermosensitive color recording film. For gravure printing, cyclohexane is used as a diluting solvent, and the ink viscosity is adjusted to 15% using a Zahn cup #3 (manufactured by Rigosha).
The time was adjusted to ~20 seconds.

This heat-sensitive white film developed a black color when heated, and exhibited the following color development characteristics. (A Macbeth reflection densitometer was used for optical density measurement.) A thermal line printer (Matsushita Electronic Components Co., Ltd.) was also used.
A clear black colored image was obtained by printing with an applied voltage of 22 V, an applied time of 1.0 m5 ec, and a head resistance of 1125 Ω. In continuous printing tests, only traces of printing remained on the thermal head, and it is superior in terms of low adhesion to the head and blocking compared to water-soluble resins, especially under high temperature and high humidity conditions. Its practical superiority was remarkable.

Example 2 Ink No. 1 composition Fluorane leuco dye [NC-R.

Made by Odugaya Chemical Co., Ltd.] 20 parts by weight cyclic rubber
20 parts by weight Pentaerythritol tetraacrylate 10 parts by weight Gravisol 301 μ parts Ethylcyclohexane 20 parts by weight ioo parts by weight Ink No. 2 Composition Bisphenol A 20 parts by weight Cyclic rubber
20 parts by weight Pentaerythritol tetraacrylate Loll parts Gravisol 301jL parts Ethylcyclohexane 20 parts by weight 100 parts by weight Ink No. 1 and Ink No. 2 prepared with the above formulation
were each dispersed for 1 hour using a disperser using glass beads. These Ink No. 1 and Ink No. 2 were mixed at a weight ratio of 1:2 and stirred with a propeller mixer to obtain a radiation-curable thermosensitive coloring ink.

This radiation-curable heat-sensitive coloring ink was partially coated on a milky white polyester film (250μ) using a gravure printing method so that it had a dry area of about 59/m', and then 5M
Rad electron beam irradiation was performed to obtain a thermosensitive color recording film.

Gravure printing uses gravure printing as a diluting solvent,
Adjust the ink viscosity to 15~ with Zahn Cup #3 (manufactured by Rigosha)
I adjusted it so that it was 20 seconds.

This heat-sensitive white film develops a red color when heated.

Example 3 Ink No. 11 Composition Triphenylmethane leuco dye 20 parts by weight Epoxy acrylate prepolymer 20 parts by weight Hexanediol diacrylate 10 parts by weight Benzyl dimethyl ketal 1 part by weight Toluene
25 parts by weight cyclohexane
24 parts by weight 100 parts by weight Ink No. 12 Composition Bisphenol A 20 parts by weight Epoxy acrylate prepolymer 20 parts by weight Hexanediol diacrylate 10 parts by weight Benzyl dimethyl ketal 1 part by weight Toluene
25 parts by weight cyclohexane
24 parts by weight 100 parts by weight Ink No. 001 and Ink No. 12 prepared with the above formulation
were each dispersed for 1 hour using a disperser using glass beads. These inks N011 and No. 2 were mixed in a weight ratio of 1:
The mixture was mixed in a ratio of 2 parts and stirred with a propeller mixer to obtain a radiation-curable heat-sensitive coloring ink.

This radiation-curable heat-sensitive coloring ink was coated on a milky white polyester film (188μ) using a gravure printing method to a dry area of approximately 5 y/m'', and then dried.
A cured coating film was obtained by irradiating for 2 seconds with a high-pressure mercury lamp with an output of 80 W/m.

Comparative Example 1 The same operation as in Example 2 was carried out according to the indicated formulation, using a vinyltoluene copolymer vehicle (heating residue: 51.2% by weight) in place of the cyclic rubber and pentaerythritortetraacrylate in Example 2. Ta.

Comparative Example 2 Polyester acrylate prepolymer in Example 1 Using aromatic petroleum resin vehicle (heating residue 50.1% by weight) in place of trimethylolpropane triacrylate and benzoin isobutyl ether, Example 1 was prepared according to the indicated formulation. performed the same operation.

The formulations and Macbeth reflection density test results of the above Examples and Comparative Examples are shown in Table 1, and the test results of the ink suitability, printing suitability, and recording suitability of the radiation-curable thermosensitive coloring ink are shown in Table 2.

The test methods for ink suitability etc. shown in Table 2 were carried out as follows.

・Storage stability The state of the ink was observed after being left at room temperature for three months.

1. Sedimentation degree 2. Gel generation 3. Observe the occurrence of discoloration and make a comprehensive evaluation Indicated by ○, △, and X ・PET adhesion Adhesion after PET film printing Judgment was made by cellophane tape peeling test.

A 1 mm square cut was made in the shape of a grid, cellophane tape was applied, and this was peeled off, and the amount adhered to the cellophane tape was evaluated.

・On-press stability: Observe and judge the ink condition during gravure printing.
.

1. Separation 2. Gelation 3.Drying property determined by comprehensive evaluation by observing discoloration Judgment was made based on the amount of residual solvent in the ink during printing.

- Blocking resistance PET during printing [The state of the paper was observed and judged by the presence or absence of blocking.

・Film strength A scratch test was conducted on the coated product after printing to judge it.

・Printer Appropriate printers were used to print, and the conditions of the following items were observed and an overall evaluation was made.

1. Head dirt 2. Printing, coloring state/print storage stability Storage stability after the printing test was comprehensively evaluated by observing the following items.

1. Light resistance 2, oil resistance 3, heat resistance 4, water resistance [Effects of the invention] The radiation-curable heat-sensitive coloring ink of the present invention has good printability on plastic sheets and is stable in storage in the ink state. Thermosensitive color-forming plastics such as prepaid cards, which have excellent durability and stability of the printed film after printing at room temperature, and have high film strength against sliding friction of high-temperature thermal heads, and in particular, have little film deterioration due to high-energy printing. It can be suitably used for cards.

The heat-sensitive coloring plastic card coated with the ink of the present invention has the advantage of clearly displaying the balance and being highly durable for repeated use.

Patent applicant: Dainichiseika Industrial Co., Ltd.

Claims (1)

[Scope of Claims] 1. A heat-sensitive coloring ink composition comprising a phenolic compound and a leuco dye that reacts with the phenolic compound under heating to form a color, dispersed in a vehicle, wherein the vehicle mainly contains a radiation-curable resin. Aliphatic hydrocarbons and/or
Or a thermosensitive coloring ink, characterized in that it is dissolved in a solvent consisting of one or a mixture of naphthenic hydrocarbons and/or aromatic hydrocarbons. 2 The vehicle is a radiation-curable resin and a combination of one or more of petroleum resin, acrylic resin, rubber resin, vinyl toluene resin, and rosin resin, and is mainly aliphatic carbonized. Hydrogen and/or one or two naphthenic hydrocarbons and/or aromatic hydrocarbons
A thermosensitive coloring ink characterized by being dissolved in a solvent consisting of a mixed system of more than one species. 3. The heat-sensitive coloring ink according to claim 1 or 2, wherein the radiation-curable resin is a low-molecular-weight resin having a radically polymerizable unsaturated bond in its molecular structure. 4. A heat-sensitive coloring plastic card coated with the ink according to claim 1, 2 or 3.