JPS6129589A - Thermosensitive recording material - Google Patents

Abstract

PURPOSE:To obtain thermal recording material having no coat fogging and high image stability by using a specific complex of zinc thiocyanate as a developer in a thermal recording material using leuco dye and also containing an organic filler in a color-forming layer. CONSTITUTION:1-5pts.wt. of complex of zinc thiocyanate expressed by the formula (R represents an organic ligand which can form a complex by bonding with a zinc ion through a heteroatom, for instance, 2, methoxy pyridine and imiazole and K 2 or 4) is used with 1pt.wt. of triphenyl methane, lacton or fluoran leuco compounds. To the above mixture, organic fillers such as urea/formalin resin, starch and styrene/methacrylic acid copolymer are added. Further, a coating liquid prepared with usual bonding agent and auxiliary additive component properly added is applied to a support such as paper, synthetic paper, plastic film, etc. and then is dried to form a thermal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material on which an image is recorded by heating with a thermal head or the like, and particularly relates to a heat-sensitive recording material with excellent image stability.

[Prior art]

In recent years, various recording methods have been researched, developed, and put into practical use in the field of information recording in response to social demands such as the diversification and increase of information, resource saving, labor saving, and non-pollution. The heat-sensitive recording method using heat-sensitive recording materials has the following features: ■) A colored image is recorded simply by heating, eliminating the need for a complicated development process; ■) It is possible to record images using a simple and compact device, and (1) Paper can be used as a support, so not only is the cost of the support low, but the feel of the resulting recording sheet is also good. Because of its advantages such as being similar to plain paper, it has been put to practical use in computer output, medical measurement recorders, facsimiles, printers, PO3 bells, tickets for vending machines, etc. The heat-sensitive recording material used in such a recording method includes a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring as a color former on a support, and an organic acid or phenol as a color developer that develops color when heated. A type with a heat-sensitive coloring layer containing an acidic substance such as a chemical compound (Special Publication No. 43-4160,
No. 45-14039, etc.) are publicly known. However, in the case of this type of leuco-based heat-sensitive recording material, the stability of recorded images is poor, and for example, when it comes into contact with oils or plasticizers such as dioctyl phthalate contained in plastic films,
There is a drawback that the recorded image is easily discolored.

Conventionally, in order to improve the stability of recorded images, for example, a thermosensitive coloring layer containing a large amount of water-resistant and chemical-resistant resin, a thermosensitive coloring layer containing a resin that hardens by heat or light,
Alternatively, a method has been proposed in which a resin protective layer is formed on the surface to protect the heat-sensitive coloring layer from the effects of chemicals and water, but this method has the problems of complicating processing, lowering thermal sensitivity, and increasing cost. have

, Also 1. JP-A-59-11286 discloses the use of a thiocyanate metal complex as a color developer. However, when this color developer is used, the resulting heat-sensitive recording material has problems such as sticking, adhesion of residue, etc., and poor matching with the thermal head.

〔the purpose〕

The present inventor has overcome the above-mentioned drawbacks of conventional leuco-based heat-sensitive recording materials and has developed a highly stable product that does not discolor the image area even when it comes into contact with oils, plasticizers, etc. As a result of extensive research, the inventors have discovered that the purpose can be achieved by using the zinc thiocyanate complex represented by the general formula (1) in combination with an organic filler, and have completed the present invention. .

It is an object of the present invention to provide a heat-sensitive recording material which is free from background fog and has excellent image stability without decoloring of colored areas even when in contact with oils, plasticizers and the like.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, the color developer has the general formula % formula % () (wherein R is (indicates an organic ligand capable of bonding with zinc ions to form a complex through a heteroatom, where k is 2 or 4) is used, and an organic filler is used in the thermosensitive coloring layer. Provided is a heat-sensitive recording material characterized by containing the following.

The heat-sensitive recording material of the present invention contains a leuco dye, a color developer represented by the general formula (1), and an organic filler as essential components in the heat-sensitive coloring layer. The general formula (
In 1), the organic ligand represented by R includes colorless neutral monodentate or polydentate ligands. Specific examples of such organic ligands include those shown below.

2-methoxypyridineimidazole 1-methylimidazole 4-methylbenzylamine antipyrine 1-vinylimidazole 1,3-dimethyl-imidapurine-2-thione In addition, examples of the organic filler used in the present invention include urea-formalin resin, starch, Examples include fine powders of styrene-methacrylic acid copolymer, polystyrene resin, and the like.

In addition to the above-mentioned organic fillers, inorganic fillers such as calcium carbonate, silica gel, aluminum hydroxide, clay, and talc are conventionally known as fillers used in heat-sensitive recording materials.

However, such an inorganic filler can be treated with the general formula (
It has been found that when used in combination with the color developer shown in I), the density of recorded images obtained by thermal printing decreases, which is not preferable. However, it was unexpectedly discovered that when the color developer represented by the general formula (1) is used together with an organic filler, head matching properties can be improved without a decrease in image density. Ta. Although the reason for this is not clear, it is thought that when an inorganic filler is used, its metal component causes an exchange reaction with the metal of the color developer.

As the leuco dye used in the present invention, those normally applied to this type of heat-sensitive material can be arbitrarily applied.
For example, leuco compounds such as triphenylmethane, lactone, fluoran, and benzofuran are preferably used. Specific examples of leuco dyes include those shown below.

Crystal violet lactone, malachite green lactone, 3-diethylamino-6-methyl-7-chlorofluoran, 3-(N-ethyl-p-tolyluidino)-6-methyl-
7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilinofluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-(dinorbutylamino)-7-(o-chloroanilino)fluoran.

3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-(isoamyl-N''-ethylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methylfluorane, 3-Cyclohexylamino-6-chlorofluorane The above leuco dyes may be used alone or in a mixture or in a stack of two or more.In the present invention, the thiocyanide of general formula (1) is used. The color developer consisting of an acid zinc complex is generally used in an amount of 1 to 5 parts by weight per 1 part by weight of the leuco dye.

In the heat-sensitive color forming layer of the present invention, as a color developer, it is possible to use the zinc thiocyanate complex represented by the general formula (1%) in combination with an ordinary color developer, for example, a phenolic substance. , does not contradict the spirit of the present invention.

Note that in the heat-sensitive coloring layer of the present invention, various commonly used binders may be used as appropriate for bonding and supporting on the support, such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinylpyrrolidone. , polyacrylamide, polyacrylic acid, starch, gelatin, etc., or water-based emulsion materials such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as the binder. I can do it.

Further, in the present invention, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as surfactants, thermofusible substances, lubricants, etc., may be used in combination.

Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts, as well as various waxes,
Condensate of aromatic carboxylic acid and amine, benzoic acid phenyl ester, higher linear glycol, 3,4-epoxy-
Examples include dialkyl hexahydrophthalate, higher ketones, and other heat-fusible organic compounds having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention can be produced by, for example, applying a coating liquid for forming a heat-sensitive layer containing the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying it.
It is used in various recording fields, especially for PO5 thermal labels and heat-sensitive tickets, which often come into contact with oils and fats and plasticizers.

〔effect〕

According to the present invention, by using a complex of zinc thiocyanate represented by the general formula (I) as a color developer for leuco dyes and incorporating an organic filler into the heat-sensitive coloring layer, A heat-sensitive recording material with excellent properties can be obtained.

(1) The compound of the general formula (1) can be easily synthesized in high yield, with high purity, and therefore there is no problem in obtaining raw materials, so a heat-sensitive material can be obtained at a relatively low cost.

(2) It has excellent color development suitable for high-speed recording, and
Even if it comes into contact with oils, plasticizers, etc., the colored area will not fade, and the recorded image will be highly stable.

〔Example〕

Examples of the present invention are shown below.

Example 1 A mixture having the following composition was separately ground for 2 days using a magnetic ball mill and dispersed to obtain (A) solution, CB) solution, (
C) Solution was prepared.

[A) Liquid 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilitofluorane 20 parts by weight 10% hydroxyethyl cellulose aqueous solution 20 Water 6
0 u (B) Liquid omidazole complex of zinc thiocyanate 20 parts by weight 5% aqueous solution of methylcellulose 20 1/water
60
(C) Fine powder of liquid urea-formalin condensation resin 20 parts by weight 10%
Polyvinyl alcohol aqueous solution 10 water
60 Using solutions [A] to [C] obtained as above, a heat-sensitive coloring layer solution having the following composition was prepared, and this was prepared with a reference basis weight of 50 g/rr?
After coating and drying on high-quality paper at a dry coating amount of 4 to 5 g/rrf to form a heat-sensitive coloring layer, further adjust the coating so that the surface smoothness is 500 to 600 seconds in Bekk smoothness.
Calendering was performed to prepare a heat-sensitive recording material (a) of the present invention.

Thermosensitive coloring layer solution (A) 10 parts by weight [B) solution 30 (C) solution 30 20% alkaline aqueous solution of isobutylene-anofomaleic acid copolymer 10 parts by weight Example 2 [C] of Example 1 Heat-sensitive recording material (b) was prepared in the same manner as in Example 1 except that the following CD) liquid was used instead of the liquid.
It was created.

(D) Liquid styrene-methacrylic acid copolymer 20 parts by weight Resin fine powder 10% polyvinyl alcohol aqueous solution 10 // Water 6 o
Comparative Example 1 Thermal recording material (C) was prepared in the same manner as in Example 1 except that the following liquid (E) was used instead of liquid [C] in Example 1.
It was created.

[E) Liquid calcium carbonate 20 parts by weight 10%
Polyvinyl alcohol aqueous solution 10 II water
6 o 〃
Comparison/Comparative Example 2 Heat-sensitive recording material (d) was prepared in the same manner as in Example 1 except that the following liquid (F) was used instead of the CB) liquid in Example 1.
It was created.

(Fl liquid bisphenol A 20 parts by weight 10% aqueous solution of hydroxyethyl cellulose 20 〃 Water 6
0 Comparative Example 3 A thermosensitive recording material (e) was prepared in the same manner as in Example 1, except that liquid (G) having the following formulation was used instead of liquid (B) in Example 1.

CG) Liquid P-Hydroxybenzoic acid benzyl ester 20 parts by weight 10% aqueous solution of hydroxyethyl cellulose 20 Water 60
〃Heat-sensitive recording materials (a) to (e) obtained as above
) was printed at 150° C. using a thermal gradient tester (manufactured by Toyo Seiki) at a pressure of 2 kg and a contact time of 1 second. For the heat-sensitive materials (a) to (e), 4CI11 squares were cut out and thinly coated with cottonseed oil, centering on the printed area.

Next, the sample was printed in a flesh-like manner and cut out using polyvinyl chloride film (Polywrap V - manufactured by Shin-Etsu Polymer Co., Ltd.)
After applying a load of 500 g/c+Il for 24 hours, the sample was taken out and the density of the colored area was measured using a Macbeth densitometer (RD-514) and compared with the density before the test.

The results are shown in Table-1.

Table 1 From the above, the heat-sensitive recording material of the present invention has a high color density;
It can be seen that it is a heat-sensitive recording material with extremely high image stability, without the disadvantage of decoloring of the colored portion due to contact with oils, plasticizers, etc.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, the color developer may be of the general formula, (R)kZn(SCN)_2(I) (Formula (wherein, R represents an organic ligand capable of bonding with zinc ions to form a complex via a heteroatom, and k represents 2 or 4). A heat-sensitive recording material characterized by containing an organic filler therein.