JPS6216986B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive coloring ink composition, and more particularly to a heat-sensitive coloring ink composition that enables gravure printing by using a vehicle consisting of a combination of a specific solvent and a resin. In recent years, thermosensitive color recording methods have been widely used in printing by thermal printers used as computer terminals, thermal pen recorders for various medical devices such as electrocardiograms,
It is widely applied in the field of information equipment, such as recording by printers of industrial measuring instruments or recording by heat-sensitive facsimiles. 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 a thermosensitive coloring system, a dispersed 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. It is thought that one of the two melts or sublimates and comes into close contact with the other, causing a reaction and color development. Therefore, the solvent and resin that make up the vehicle for dispersing the phenolic compound (color developer) and leuco dye (color former) (hereinafter sometimes collectively referred to as the "heat-sensitizing agent") include the following, respectively. Such characteristics are required. (b) It must be inert and non-soluble to heat-sensitive agents in order to provide a colorless ink and dispersion layer when no heat is applied. (b) Add a certain degree of viscosity to the heat-sensitive agent (color former and color developer) to separate them from each other. Furthermore, since the formed heat-sensitive layer is subjected to heating by the thermal head and usually additional sliding force, the vehicle must provide a tough film. In order to meet the above requirements, vehicles have conventionally mostly been prepared by dissolving water-soluble polymer compounds such as polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, starch, and polyacrylamide in water. is used.
However, there are several problems with using such vehicles, as follows. That is, first of all, since a water-soluble polymer is used, the formed heat-sensitive layer has poor water resistance and cannot withstand long-term storage. In addition, the heat-sensitive layer that has absorbed moisture has a remarkable thermal softening property, becomes sticky when heated, and adheres to the thermal head of the terminal, significantly impairing running performance, making stable printing and image recording impossible. As a method of improving this, there is an example of adding isobutylene-maleic anhydride copolymer, dialdehyde starch, etc. to the vehicle (Japanese Patent Laid-Open No. 1040/1983). However, in this case as well, although the film performance of the formed heat-sensitive layer is certainly improved, it is difficult to overcome the drawbacks associated with the use of an aqueous solvent as described below. That is, the second disadvantage of using an aqueous vehicle as described above is that since water is used as a solvent, drying is slow in the coating process for forming a heat-sensitive layer, resulting in extremely low work efficiency. Thirdly, it is difficult to obtain a uniform dispersion system of leuco dye in an aqueous vehicle, and increasing the resin concentration may cause thickening and gelling phenomena, while increasing the water content to reduce the viscosity may cause sedimentation and separation. This results in the inability to apply uniformly. As a result, the heat-sensitive layer formed on the support has extremely undesirable finishes such as mottling, swimming, and matte finish, and density unevenness occurs in the colored image during heat-sensing, making it impossible to obtain a clear recorded pattern. It is also known that when thin paper is used as a support, a non-aqueous vehicle containing terpene resin, petroleum resin, cyclic rubber, etc. dissolved in a petroleum solvent can be applied to prevent the paper from expanding, contracting, and wrinkling during coating. (Special Publication No. 14533, Showa 50). However, according to the research conducted by the present inventors, the use of such a non-aqueous vehicle does not essentially solve the drawbacks associated with the use of the aqueous vehicle described above, and on the contrary, as a support gives worse results than when using an aqueous vehicle. That is, ordinary petroleum solvents have a low ability to dissolve the binder resin, and depending on the petroleum resin etc. dissolved therein, good film properties cannot be obtained. Also, petroleum, which has a dissolving power, dissolves leuco dyes and develops color, causing a fogging phenomenon. For this reason,
The printing effect is poor, clear heat-sensitive recording cannot be obtained, and when the heat-sensitive layer is rubbed with a thermal head, a lot of residue adheres, making it unusable. In particular, the range of what is normally called petroleum is wide, petroleum ether (BP 20-60℃ pentane, hexane)
Ligroin, light naphtha (BP60-120℃ hexane,
Heptane), gasoline (BP 40-205℃), kerosene (BP 175-325℃), gas oil (BP 275℃ or higher), etc. These chain hydrocarbons have low solubility and are not suitable as vehicles. It is. Generally, some industrial gasolines contain naphthenic fractions due to the properties of the crude petroleum, but these have a wide boiling point range (40 to 205°C), and what is called naphthenic petroleum contains benzene, toluene, xylene, etc. It is said that aromatic hydrocarbons can account for as much as 40%. Therefore, these mixed components are unsuitable because they dissolve the heat-sensitive coloring agent and develop color. As mentioned above, the vehicle used in conventional heat-sensitive coloring ink compositions may be aqueous or non-aqueous;
It did not have good dispersion properties 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 applying the composition onto a support using a roll coater or an air knife. However, considering the actual demand, it is not enough to just paint the heat-sensitive coloring layer solidly, and there are many cases where pattern printing is required. Furthermore, it is not preferable to coat unnecessary parts in order to save resources. In view of the above-mentioned circumstances, the present inventors have arrived at the present invention as a result of intensive research in search of a thermosensitive coloring ink composition capable of pattern printing by gravure printing. When applying thermochromic ink compositions by gravure printing, the vehicle has, in addition to the above-mentioned properties, in particular non-reactivity with the thermosensitizer, better dispersion properties of the thermosensitizer and compatibility with both thick and thin thermal heads. It is necessary to provide a strong coating that can withstand the sliding of the substrate, to have good fluidity, excellent printability, and to quickly evaporate and dry after printing. As a result of research conducted by the present inventors, it was discovered that a vehicle that satisfies all of the above-mentioned properties can be obtained by combining a specific resin and a specific solvent. That is, the thermosensitive coloring ink composition of the present invention is a thermosensitive coloring ink composition in which a phenolic compound and a leuco dye that develops color by reacting with the phenolic compound under heating are dispersed in a vehicle, wherein the vehicle has a boiling point of 50 It is characterized by being formed by dissolving a vinyltoluene copolymer resin or a rosin ester resin in a naphthenic hydrocarbon or solvent at a temperature of ~150°C. The present invention will be explained in more detail below. The phenolic compound and leuco dye used in the present invention are known per se. That is, in this specification, a phenolic compound means a compound having a phenolic hydroxyl group, and includes phenol, o-
Cresol, p-cresol, p-ethylphenol, tert-butylphenol, 2,6-
ditertiarybutyl-4-methylphenol,
Nonylphenol, dodecylphenol, styrenated phenol, 2,2'-methylene-bis(4-
methyl-6-tert-butylphenol),
α-naphthol, β-naphthol, hydroquinone monomethyl ether, guaiacol, eugenol, p-chlorophenol, p-bromophenol, o-bromophenol, o-chlorophenol, 2,4,6-trichlorophenol, o-
phenylphenol, p-phenylphenol,
p-(p-chlorophenyl)phenol, o-
(o-chlorophenyl)phenol, salicylic acid, methyl p-oxybenzoate, ethyl p-oxybenzoate, propyl p-oxybenzoate, p-
Butyl oxybenzoate, octyl p-oxybenzoate, dodecyl p-oxybenzoate, catechol, hydroquinone, resorcinol, 3-methylcatechol, 3-isopropylcatechol, p-tert-butylcatechol, 2,5-ditertiarybutyl Hydroquinone, 4,4'-methylene diphenol, bisphenol A, 1,2-dioxynaphthalene, 2,3-dioxynaphthalene, chlorcatechol, bromocatechol, 2,4-dihydroxybenzophenone, phenolphthalein, o-Cresolphthalein, methyl protocatechuate, ethyl protocatechuate, propyl protocatechuate, octyl protocatechuate, dodecyl protocatechuate, pyrogallol, oxyhydroquinone, phloroglucin, 2,
4,6-trioxymethylbenzene, 2,3,4
-trioxyethylbenzene, gallic acid, methyl gallate, ethyl gallate, propyl gallate,
Butyl gallate, hexyl gallate, octyl gallate, dodecyl gallate, cetyl gallate, stearyl gallate, 2,3,5-trioxynaphthalene, tannic acid, phenolic resin, and the like can be used. Leuco dyes include triphenylmethane-based dyes such as crystal violet lactone and malachite green lactone; fluoran-based dyes such as 1,2-benz-6-diethylaminofluorane;
Auramine dyes such as benzoyl auramine; other phenothiazine dyes; and leuco dyes such as spiropyran dyes are used. The vehicle-forming solvent used in the present invention is a naphthenic hydrocarbon having a boiling point of 50 to 150°C, preferably 80 to 140°C. boiling point
If it is below 50°C, it dries quickly and the viscosity increases due to evaporation of the solvent, causing problems on the machine such as plate jams and making it impossible to print uniformly. Furthermore, if the boiling point exceeds 150°C, drying will be slow and printing speed will not increase, resulting in uneven printing such as mottling and satin finish. Furthermore, due to insufficient drying, solvent remains in the heat-sensitive layer, resulting in extremely undesirable phenomena such as blocking. As a representative of such naphthenic hydrocarbons,
Cyclopentane, methylcyclopentane, 1,1
- or 1,3-dimethylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, 1,2,4-trimethylcyclohexane, and the like. 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 naphthenic hydrocarbon described above alone. However, 40% (weight%) based on the total amount.
Paraffinic hydrocarbons such as hexane, heptane, octane, nonane, and their isomers up to (the same applies hereinafter); or chlorine-containing hydrocarbons such as trichlorethylene, perchlorethylene, diethylene chloride, etc. up to 5% based on the total amount can also be used in combination with naphthenic hydrocarbons. If the amount of paraffin mixed in exceeds 40%, the resin will lose its dissolving power, causing gelation and separation, which will worsen the printing effect. That is, mottling, satiny, etc. occur. Moreover, if the chlorine content exceeds 5%, it is undesirable from the viewpoint of odor and hygiene, so it is necessary to avoid using a large amount. If aromatic hydrocarbon, alcohol, ketone, or ester solvents are mixed, the leuco dye will be dissolved and so-called dissolution coloring will occur, so these components cannot be used together. The vehicle of the present invention is obtained by dissolving a vinyltoluene copolymer resin or a rosin ester resin in the above-mentioned solvent at room temperature or while heating to 60°C. Vinyltoluene copolymer means a copolymer containing vinyltoluene as one of the copolymerization components, and includes vinyltoluene-butadiene copolymer resins (for example, Gutdeyer's Priorite VT and Priorite VTL), vinyl Contains toluene-acrylate copolymer resins (eg, Priorite VTAC, Priorite OMS manufactured by Gutdeyer). Rhodiene ester resins include rosin-modified phenolic resin (for example, Tamanol 361 manufactured by Arakawa Chemical Co., Ltd.), polymerized rhodicypentaerythritol ester (for example, Pentaline C manufactured by Hercules Co., Ltd.), and pentaerythritol ester of dimeritscresic acid (for example, Pentaline K manufactured by Hercules Co., Ltd.). is included. Softening point of vinyltoluene-butadiene copolymer: 130-165
℃ (molecular weight 50,000 to 200,000) or a rosin ester resin having a softening point of 130 to 190℃ is suitable. As a vehicle resin, the resin body is uncolored and has excellent transparency, has excellent weather resistance and chemical resistance, does not cause discoloration due to oxidation during long-term storage, and has excellent heat resistance and water resistance. The above-mentioned resins are particularly suitable in these respects. Among them, vinyltoluene/butadiene copolymer resin is the most suitable. In addition to these resins, cyclized rubber can also be used in combination. In the vehicle of the present invention, auxiliary components are added in the range of 1 to 99% of the solvent and 1 to 50% of the resin, but basically 1 to 5%, to adjust the film characteristics of the heat-sensitive recording layer. It is also possible to do so. The above-mentioned phenolic compound and leuco dye are kneaded into the thus obtained vehicle using a dispersing machine such as a sand mill, ball mill, attritor, or shot mill to obtain respective dispersions. The thermal ink composition of the present invention is obtained by mixing in a mixing device. In the composition, the concentration of the phenolic compound and the leuco dye can be adjusted arbitrarily within the range of 2 to 50% depending on the required color density. The ink composition of the present invention may be 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,
Inorganic fillers such as silicon oxide; waxes such as paraffin wax, polyethylene wax, carnauba wax, microcrystalline wax, and amide wax that are solid at room temperature as auxiliary agents; phthalate esters, citric acid esters, adipic esters, etc. A plasticizer; and an anionic, nonionic or cationic surfactant can also be added. The thermosensitive coloring ink composition of the present invention can be coated onto a support such as paper, plastic film, or fiber sheet using a roll coater, reverse coater, or the like as in the past.
In addition to being able to be coated by a normal coating method using a doctor coater or the like, the heat-sensitive recording layer can be formed by printing using a gravure method. In addition, letterpress, flexographic, and silk screen printing methods are also available. For use in such printing applications, the viscosity of the heat-sensitive coloring ink composition of the present invention is preferably in the range of 1 to 500 poise. Further, the heat-sensitive recording layer is usually formed as a film having a weight of 0.5 to 10 g/m ² on a dry weight basis. The heat-sensitive recording layer of the heat-sensitive recording material thus obtained is
Color develops rapidly at temperatures between 60 and 250°C.
Therefore, a clear print or image can be provided by transferring thermal energy using a terminal device's thermal head, thermal pen, or the like. As described above, the heat-sensitive coloring ink composition of the present invention has excellent storage stability at room temperature or storage stability after coating, and is particularly excellent in printability such as dispersibility and film-forming properties. Therefore, the heat-sensitive recording layer, which particularly requires film toughness, can be formed not only as a solid print layer by conventional coating but also as a pattern print layer by gravure printing or the like. Furthermore, the resulting heat-sensitive recording layer is formed as a smooth film with no unevenness such as mottling, swimming, or matte finish, and has excellent water resistance and
It has excellent heat resistance and low stickiness, so it hardly contaminates the thermal head. Hereinafter, the present invention will be explained in more detail with reference to Examples. [Example 1] Ink No. 1 Fluoran leuco dye 20 parts (PSD-170, manufactured by Nisso Kako Co., Ltd.) Vinyl toluene butadiene resin 15 parts (Priolite VT, manufactured by Gutdeyer Co., Ltd.) Softening point 155-165°C Molecular weight 152000 Ethylcyclohexane 65 parts Ink No. 2 Bisphenol A 20 parts Vinyl toluene butadiene resin 15 parts (Priolite VT, manufactured by Gutdeyer) Silica 3 parts Ethylcyclohexane 62 parts Ink No. 1 and Ink No. 2 each contain glass beads. The mixture was dispersed for 1 hour using a stirrer. Ink No. 1 and Ink No. 2 were mixed at a weight ratio of 1:5 and stirred with a propeller mixer to obtain a thermosensitive coloring ink. This thermosensitive coloring ink was applied all over by a gravure printing method to obtain a thermosensitive coloring recording paper having a dry coating weight of about 4g/m ² on a high-quality paper with a basis weight of 50g/m ² . In gravure printing, ethylcyclohexane was used as an ink diluent, and the viscosity was adjusted to 10 to 12 seconds using Zahn Cup #4 (manufactured by Rigosha). The printed matter was obtained without any unevenness such as a satin finish. This thermosensitive color recording paper turns black when heated.
It showed the following color development characteristics. (A Macbeth reflection densitometer was used for optical density measurement.)

[Table] Furthermore, thermal printer (thermal head KH)
-40, manufactured by Toyo Dengu Co., Ltd., applied voltage 15V, application time
30m sec) to obtain a clear black image.
Continuous printing tests showed that there was no printing residue adhering to the thermal head, and recording paper that uses a water-based binder, especially under high temperature and high humidity conditions, was prone to problems such as sticking to the head and poor running performance due to curling of the paper. Its practical superiority from the rainy season to summer was remarkable. Next, a comparison was made with the use of a non-claimed oil vehicle. The inks were prepared by changing either or both of the resin and solvent in the composition of Ink No. 1 and Ink No. 2 of Example 1, and the recording paper was
It was created in the same manner as in the example.

【table】

[Example 2]

Ink No. 1 Fluorane leuco dye 20 parts (TH106, manufactured by Hodogaya Chemical Co., Ltd.) Polymerized rosin pentaerythritol ester 20 parts (Pentaline C, manufactured by Hercules Co., Ltd. Softening point: 133°C) Ethylcyclohexane 60 parts Ink No. 2 Bisphenol A 20 parts Polymerized rosin Pentaerythritol ester 20 parts (Pentaline C, manufactured by Hercules) Ethylcyclohexane 60 parts Ink No. 1 and Ink No. 2 were each obtained by dispersing for 1 hour in a stirrer containing glass beads. . Ink No. 1 and Ink No. 2 were mixed at a weight ratio of 3:10 and stirred with a propeller mixer to obtain a thermosensitive coloring ink. This heat-sensitive coloring ink is printed using the gravure printing method.
Partially applied to 70 g/m ² continuous slip paper. At the same time, ruled lines were printed on this continuous form using regular black ink. The amount of heat-sensitive coloring ink applied is approximately 5g/dry state.
It was ^m2 . The continuous slip paper containing this heat-sensitive coloring part was printed using a thermal printer PU1800 (manufactured by Olivetei Co., Ltd.) to obtain a clear black image. The thermosensitive coloring characteristics are as shown below.The background density of the colored area was low and close to white, so the pattern of the colored area was inconspicuous and could be handled without any discomfort from ordinary slip paper. Temperature to obtain a density of 0.8: 110℃ Background density: 0.08 Paper density: 0.06 Maximum color density: 1.30 Also, the paper does not wrinkle or curl even under high humidity, and has excellent dimensional accuracy during manufacturing and positional accuracy during recording. It was hot. [Example 3] Ink No. 1 Fluoran leuco dye 20 parts (PSD-HR manufactured by Nisso Kako Co., Ltd.) Vinyl toluene butadiene resin 10 parts (Priolite VT, manufactured by Gutdeyer Co., Ltd.) Cyclized rubber 5 parts (Thermolite N Seiko Kagaku Co., Ltd.) Ethylcyclohexane 65 parts Ink No. 2 Bisphenol A 20 parts Vinyltoluene-butadiene resin 10 parts (Priolite VT, Gutdeyer Co., Ltd.) Cyclized rubber 5 parts Polyethylene wax 3 parts (AF wax, BASF Co., Ltd.) Ethylcyclohexane 62 parts Ink No. 1 and Ink No. 2 were each obtained by dispersing for 1 hour in a stirrer containing glass beads. Ink No. 1 and Ink No. 2 were mixed at a weight ratio of 1:5 and stirred with a propeller mixer to obtain a thermosensitive coloring ink. This heat-sensitive coloring ink was printed using a printing plate made with a gradation pattern (photographic pattern) using a gravure printing method to obtain a colorless photographic print. This colorless photographic print was heated with an iron and turned into a vermilion-red pattern with good gradation reproduction. In addition, ink was prepared using each leuco dye shown in the table below instead of the fluoran-based leuco dye (PSD-HR, manufactured by Shin Nisso Kako Co., Ltd.) in the composition of Ink No. 1. Each of these inks and Ink No. 2 were mixed at a ratio of 1:5 (weight ratio) and stirred with a propeller mixer to obtain each heat-sensitive coloring ink.
Using these thermosensitive coloring inks, multicolored colorless photographic prints were obtained using a gravure printing method. This colorless photographic print was heated with an iron and turned into a multicolored pattern with good gradation reproduction.

【table】

【table】

Claims (1)

[Claims] 1. A thermosensitive 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 is a naphthenic hydrocarbon solvent with a boiling point of 50 to 150°C, A heat-sensitive coloring ink composition characterized by being formed by dissolving a vinyltoluene copolymer resin or a rosin ester resin.