JPH05311092A - Printing ink for thermal recording paper - Google Patents

Abstract

PURPOSE:To provide an excellent printing ink for thermal recording paper free from the problems of shortage in density otherwise occurring in printing and collapse of ink particles. CONSTITUTION:The ink is one containing a colorant and a resin varnish, wherein an organic solvent which can dissolve the color former and/or the color developer is contained in an amount of 0.01-10wt.% based on the ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing ink for thermal paper, and more particularly, it does not have the problem of insufficient density which may occur when printing on thermal paper, and does not cause the problem of so-called crushing of the ink. It relates to printing ink for thermal paper.

[0002]

2. Description of the Related Art In recent years, thermal paper has been used in various fields such as telephone facsimiles, bar code paper, tickets for automatic ticket vending and automatic ticketing systems, tickets such as commuter tickets, and the like. Such a thermal paper is formed by dispersing base material, color former (leuco dye) and developer (phenolic acidic substance) in the form of fine crystals (fine particles) in a binder, and coating the base paper with the color former. One or both of the color-developing agent and the color-developing agent in the color-developing layer are melted by heat and brought into contact with each other to cause a color-developing reaction.

Today, thermal paper has a wide variety of applications, and depending on the application, printing may be performed on the thermal paper in advance by letterpress printing or offset printing before color development by the thermal recording system. For such printing, conventionally, a printing ink mainly composed of a colorant which is a pigment, a resin varnish which is a vehicle, an ink solvent for a mineral oil fraction and an additive such as a drying aid has been mainly used. It was

[0004]

However, when printing on thermal paper with the above conventional printing ink, due to problems such as affinity of the ink with the thermal paper, ink due to insufficient density or insufficient wetting of the thermal paper surface of the thermal paper. Crushing was often a problem. Therefore, an object of the present invention is to provide an excellent printing ink for thermal paper, which does not have the problem of insufficient density that may occur during printing on thermal paper, and does not cause the problem of ink crushing.

[0005]

In order to achieve the above-mentioned object, a printing ink for thermal paper containing a colorant and a resin varnish of the present invention is an organic solvent capable of dissolving a color forming layer in the thermal paper. It is characterized by containing 0.01 to 10% by weight.

[0006]

The coloring layer of the thermal paper, especially the coloring agent or developer in the coloring layer, or an organic solvent capable of dissolving both of them, is contained in the ink so that the color of the ink and the solvent are generated on the printing surface. Combined with the coloring of the thermal paper
Color density increases. Therefore, for example, when black ink is used as the printing ink for the thermal paper, the black density of the black ink and the black color development of the thermal paper are combined to obtain higher density black. Further, the addition of the above organic solvent improves the wettability of the ink to the coloring layer of the thermal paper,
This will improve the collapse.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The colorant used in the present invention may be an inorganic pigment, an organic pigment or a dye used in conventional printing inks, and any conventionally known pigment may be used as it is as a colorant for the thermal paper printing ink of the present invention. Can be used. The amount of the ink used may be the same as that of the conventionally known printing ink, for example, the printing ink 10
A ratio of about 10 to 40 parts by weight with respect to 0 parts by weight is general.

As the varnish resin, conventionally known natural or synthetic drying oils or semi-drying oils can be used. For example, the natural fats and oils are linseed oil, eucalyptus deer oil, soybean oil, safflower oil, cinnamon oil. Oil, Japanese millet oil, sunflower oil, eno oil, hemp oil, tall oil, sesame oil, wheat germ oil, corn oil, rapeseed oil, rice bran oil, dehydrated castor oil, cottonseed oil, squid oil, fish oil, whale oil, and various modifications thereof. As the synthetic varnish resin, for example, a rosin-modified phenol resin is mainly used, and other petroleum resins (aromatic type, aliphatic type, aromatic / aliphatic copolymer type), Examples include alkyd resins.

As the ink solvent for the mineral oil fraction, conventionally known paraffin type, isoparaffin type, naphthene type, alpha-olefin type and the like have a boiling point range of 20.
The thing of 0-400 degreeC can be used.

In the present invention, a color-developing agent in thermal paper (for example, triphenylmethane / phthalide type, phenothiazine type, spirodipyran type, indinospiropyran type, yellow orange, vermilion red, dark green or black fluorane type, rhodamine lactam type or A colorless dye such as a leuco auramine-based dye), and a developer (for example, t-butylphenol,
Bisphenol A, 2,2-bis (4-hydroxyphenyl) -n-peptane, 4-phenylphenol, 4,
Examples of the organic solvent capable of dissolving either one or both of 4-cyclohexylidenephenol and other phenolic acidic substances) include alcohols such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, toluene, o. -Xylene, m-xylene,
Hydrocarbons such as ethylbenzene and alkylbenzene, ethers such as ethyl ether, isopropyl ether and methylphenyl ether, ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl-n-propyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate. And the like. Here, when using an alcohol having a low boiling point or a high volatility, it may be used in a state of being contained in a water-absorbent resin in advance.

In the present invention, the organic solvent is contained in the ink in an amount of 0.01 to 10% by weight, preferably 0.5 to 2% by weight. If this content exceeds 10% by weight, the organic solvent will attack the rubber roller during printing,
On the other hand, if it is less than 0.01% by weight, the effect of the present invention cannot be obtained.

The printing ink for thermal paper of the present invention contains, in addition to the above-mentioned compounding agents, waxes such as paraffin wax, polyethylene wax, microcrystalline wax and Teflon wax, cobalt, manganese, cerium, zirconium, lead, iron, zinc, Copper, vanadium, barium, calcium and other polyvalent metals such as naphthenic acid, octylic acid, resin acids, oil-soluble carboxylic acids such as tall oil fatty acids, resin acid salt dryers, leveling improvers, thickeners, etc. , Anti-skinning agents, and other conventionally known additives can be used in usual amounts. The method for producing the printing ink for thermal paper of the present invention as described above may be a conventionally known method.

[0013]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts are based on weight. Example 1 33 parts of rosin-modified phenolic resin (Tamanol 354: manufactured by Arakawa Chemical Co., Ltd.), 33 parts of vegetable oil, 32 parts of ink solvent (No. 6 solvent: manufactured by Nippon Oil Co., Ltd.),
2 parts of a chelating agent (Al-CH-50: manufactured by Kawaken Fine Chemicals Co., Ltd.) was heated and dissolved to obtain a varnish.

31 parts of this varnish, 35 parts of vegetable oil, carbon black (MA-8 carbon: Mitsubishi Kasei Co., Ltd.)
17 parts) and 11 parts of extender pigment (calcium carbonate),
0.8 parts of a dryer and 5.2 parts of No. 6 solvent were mixed and kneaded with a triple roll to prepare a printing ink as a comparative example. Then, the printing ink 100 as this comparative example
The following organic solvents were added to the parts to prepare the inks of Examples 1-5. The printing density and the collapsing property when printing on thermal paper using these inks were evaluated. The density was measured by using a Coser 61J (manufactured by Coser) for the color-developed product developed by the RI tester. Further, the crushability was visually evaluated. The results obtained are as follows. Regarding the crushability, the wettability with respect to the thermal paper was good, and the one which did not cause unevenness of ink sticking was good, the other one was bad, and the middle thereof was normal.

Organic solvent (part) Concentration Crushability Comparative example-1.00 Poor Example 1 Methanol (0.5) 1.20 Normal Example 2 Toluene (0.5) 1.30 Good Example 3 Diethyl ether ( 0.5) 1.30 Good Example 4 Methyl ethyl ketone (0.5) 1.30 Good Example 5 Ethyl acetate (0.5) 1.30 Good As is clear from the above evaluation results, printing of all the examples The ink has a higher density and improved crushability than the inks of Comparative Examples.

[0016]

As described above, the printing ink for thermal paper of the present invention contains the organic solvent capable of dissolving the color former and / or the developer in the thermal paper in an amount of 0.01-10.
By including it in a weight percentage, the problem of insufficient density that occurs when printing on thermal paper and the problem of crushing are solved at the same time, and good printing becomes possible.

Claims (4)

[Claims] 1. A printing ink for thermal paper, comprising a colorant and a resin varnish, wherein the ink contains 0.01 to 10% by weight of an organic solvent capable of dissolving the color forming layer in the thermal paper. Printing ink for thermal paper. 2. The printing ink for thermal paper according to claim 1, wherein the printing ink for thermal paper is black ink. 3. The printing ink for thermal paper according to claim 1, wherein the organic solvent dissolves the color former and / or the developer in the color forming layer. 4. The printing ink for thermal paper according to claim 1, wherein the organic solvent is contained in the ink in an amount of 0.5 to 2% by weight.